g.Al23 A\^3
mtI}eCttpoflrttigork
College of ^ijpsictanst anb ^urgeong
ILibrarp
Digitized by the Internet Archive
in 2010 with funding from
Columbia University Libraries
http://www.archive.org/details/morrisshumananaOOmorr
MORRIS'S
TEEATISE ON ANATOMY
FIFTH EDITION
CONTRIBUTORS TO FIFTH EDITION
CHARLES R. BARDEEN, University
of Wisconsin.
ELIOT R CLARK, Johns Hopkins
University.
IRVING HARDESTY, Tulane Uni-
versity of Louisiana.
C. M. JACKSON, University of Min-
nesota.
F. W. JONES, London School of Medi-
cine for Women.
ABRAM T. KERR, Cornell University.
J. PLAYFAIR McMURRICH, Uni-
versity of Toronto.
JOHN MORLEY, Manchester Univer-
sity.
H. D. SENIOR, University and Belle-
vue Hospital Medical College., N. Y.
R. J. TERRY, Washington University,
St. Louis.
PETER THOMPSON, University of
Birriiingham.
DAVID WATERSTON, King's Col-
lege, London.
For arrangement of subjects and authors see page v.
THIS WORK IS ALSO PUBLISHED IN FIVE PARTS AS FOLLOWS:
PART I. Morphogenesis. Osteology. Articulations. Index. $L50.
PART II. Muscles. Blood-Vascular System. Lymphatic System. Index.
$2.50.
PART III. Nervous System. Special Sense Organs. Index. $2.00.
PART IV. Digestive System. Respiratory System. Skin, Mammary and Duct-
less Glands. Urogenital System. Index. $L50.
PART V. Clinical and Topographical Anatomy. Index. $1.50.
MOEEIS'S
HUMAN ANATOMY
A COMPLETE SYSTEMATIC TREATISE
BY ENGLISH AND AMERICAN AUTHORS
EDITED BY
• C. M. JACKSON, M. S., M. D.
PROFESSOR AND DIRECTOR OF THE DEPARTMENT OF ANATOMY
UNIVERSITT OF MINNESOTA
ELEVEN HUNDRED AND EIGHTY TWO ILLUSTRATIONS
THREE HUNDRED AND FIFTY EIGHT PRINTED IN COLOURS
FIFTH EDITION, REVISED AND LARGELY REWRITTEN
PHILADELPHIA
P. BLAKISTON'S SON & CO,
1012 WALNUT STREET
Copyright, 1914, by P. Blakiston's Son & Co.
hi 4
. YORK- PA
AREANGEMENT OF SUBJECTS AND AUTHORS
The names of the more recent of those who wrote or revised articles for
previous editions have been retained in the following list in order that due credit
should be given them for the work done and for their share in the great success
which Morris's "Anatomy" has achieved.
MORPHOGENESIS. Revised and largely rewritten for the fifth edition by
C. M. Jackson, M.S., M.D., Professor of Anatomy in the University of Minne-
sota. Originally written by J. Playfair McMurrich, A.M., Ph.D., Professor of
Anatomy, University of Toronto.
OSTEOLOGY. Revised for the third, fourth and fifth editions by Peter
Thompson, M.D., Professor of Anatomy, University of Birmingham; Member
of Anatomical Society of Great Britain. This article was originally written by Sir
John Bland Sutton, F.R.C.S.
ARTICULATIONS. Revised for the fifth edition by Frederic Wood Jones,
D.Sc, M.B., B.S. (Lond.), M.R.C.S., L.R.C.P., Head of the Department of
Anatomy and Lecturer in the London School of Medicine for Women. Originally
written by Su- Henry Morris, A.M., M.B.
MUSCLES. Rewritten and revised for the fourth and fifth editions by
Charles R. Bardeen, A.B., M.D., Professor of Anatomy in the University of
Wisconsin; Member Association of American Anatomists; Member of Editorial
Board of "American Journal of Anatomy."
BLOOD-VASCULAR SYSTEM. Revised and in part rewritten by Harold
D. Senior, M.B., F.R.C.S., Professor of Anatomy, University and Bellevue Hos-
pital Medical College. The section on Blood-vessels was formerly revised by
Florence R. Sabin, B.S., M.D., Associate Professor of Anatomy, Johns Hopkins
University.
LYMPHATIC SYSTEM. Revised and partly rewritten for the fifth edition
by Eliot R. Clark, A.B., M.D., Associate in Anatomy, Johns Hopkins Uni-
versity. Revised for previous edition by Florence R. Sabin, B.S., M.D.
NERVOUS SYSTEM. Revised and largely rewritten for the fourth and fifth
editions by Irving Hardesty, A.B., Ph.D., Professor of Anatomy, Tulane
University, Louisiana; Member Association of American Anatomists.
SPECIAL SENSE ORGANS. Revised for the fifth edition by David
Waterston, M.A., M.D., F.R.C.S., Professor of Anatomy in the University of
London. In the earlier edition, the Ear, Nose, Tongue were revised by Abram
T. Kerr, B.S., M.D.
DIGESTIVE SYSTEM. Revised and largely rewritten for the fifth edition
by C. M. Jackson, M.S., M.D., Professor of Anatomy, LTniversity of Minnesota.
Revised for the fourth edition by G. Carl Huber, M.D.
vi ARRANGEMENT OF SUBJECTS AND AUTHORS
RESPIRATORY SYSTEM. Revised for the fourth and fifth editions by
R. J. Terry, A.B., M.D., Professor of Anatomy, Washington University, St.
Louis; Member Association of American Anatomists.
UROGENITAL SYSTEM. Revised for the fourth and fifth editions by
J. Playfair McMurrich, A.M., Ph.D., Professor of Anatomy, University of
Toronto; Member Association of American Anatomists.
THE SKIN AND MAMMARY GLAND; THE DUCTLESS GLANDS.
By Abram T. Kerr, B.S., M.D., Professor of Anatomy, Cornell University;
Member Association of American Anatomists, etc. The article on the Ductless
Glands was originally written by G. Carl Huber, M.D.
CLINICAL AND TOPOGRAPHICAL ANATOMY. By John Morley,
Ch.M., F.R.C.S., Honorary Surgeon, Ancoats Hospital, Manchester, and
Lecturer in Clinical Anatomy, Manchester University. Originally written by
W. H. A. Jacobson, F.R.C.S.
EDITOR'S PREFACE TO THE FIFTH EDITION
One criticism upon most of the current text-books of human anatomy is that
they are too extensive for the beginner. Much precious time is wasted by him in
floundering through a mass of details which obscure the fundamental facts. And
yet it is important to have these details conveniently accessible for both present
and future reference. To meet this difficulty, the attempt is made in this edition
to discriminate systematically in the use of sizes of type. The larger type is used
for the more fundamental facts, which should be mastered first, and the smaller
type for details. While it has been found difficult to apply this principle uni-
formly through the various sections, it is hoped that the plan, even though but
imperfectly realized, will prove useful to the beginner.
In the illustrations of the bones, as heretofore, the origins of muscles are in-
dicated by red lines, the insertions by blue lines, and the attachments of ligaments
by dotted black lines.
While the authors of the present edition are for the most part the same as in
the previous edition, a few changes have been made as noted under the preceding
section, "Arrangement of Subjects and Authors." Owing to the retirement
of the distinguished originator and former editor of this work. Sir Henry Morris,
and of Professor McMurrich as co-editor, the responsibility for the general
supervision of the fifth revision has fallen to the present editor.
Each author is alone responsible for the subject-matter of the article following
his name. Care has been exercised on the part of the editor, however, to make
the whole uniform, complete and systematic.
As to nomenclature, the Anglicised form of the BNA has been continued,
excepting those cases where the Latin form is adopted into English (e. g., most of
the muscles), and rare cases where the BNA term seems undesirable. As a rule,
the Anglicised form where first used is followed by the BNA Latin term in
brackets, except where the two are practically identical. For convenience of refer-
ence, some of the commoner synonyms of the old nomenclature are also added in
parenthesis.
The previous edition of Morris's Anatomy was the first general text-book of
anatomy in English to adopt the BNA. During the past few years the merit of
this system of nomenclature has become so widely recognized that it is now very
generally accepted among the English-speaking nations. Lack of space forbids
the enumeration here of the many advantages of this system, not the least of which
is the reduction of some 30,000 anatomical terms (including synonyms) to 5000.
The comparatively few defects of the BNA will doubtless be remedied by revision
(preferably through the International Anatomical Congress). For a full
discussion of the BNA system, with complete Hst of the Latin terms and English
equivalents, the reader is referred to the excellent work on the BNA by Professor
L. F. Barker, of Johns Hopkins University.
In addition to the bibliographical references scattered throughout the text, a
brief list is given at the close of each section. These brief lists of carefully selected
references are intended merely as a guide to put the student "on track" of the
original literature.
viii EDITOR'S PREFACE TO THE FIFTH EDITION
In addition to a thorough revision of the various sections, there has also been
a rearrangement of a part of the subject matter in the present edition. The Teeth
have been transferred from the section on Osteology to the Digestive System.
The Tongue and Nose are transferred to the Digestive System and Respiratory
System, respectively, excepting those portions forming the organs of Taste and
Smell, which have been retained in the section on Special Sense Organs. The
Pelvic Outlet has been discontinued as a separate section, the subject matter
being divided between Musculature and Clinical and Topographical Anatomy.
The Ductless Glands have been included in the section with the Skin and Mam-
mary Glands.
Due credit has been given throughout the book wherever illustrations have
been taken, or modified, from other works. Special acknowledgment should be
made of our indebtedness to the works of Toldt, Rauber-Kopsch, Poirier and
Charpy, Henle and Spalteholz.
The number of figures in the present edition has been increased about one
hundred and sixty and in addition many of the older figures have been improved
or replaced. For the generosity of the publishers in this connection, and for the
hearty cooperation of the contributors in the revision of the various sections, the
editor desires to express his deep indebtedness. Valuable assistance has been
rendered by Mr. Walter E. Camp in the reading of proof and preparation of
the index.
C. M. Jackson.
Minneapolis.
CONTENTS
Introduction.
By C. M. Jackson, M.S., M.D.
SECTION I
MORPHOGENESIS
By C. M. Jackson, M.S., M.D.
Segmentation of the Ovum 9
Embryonic Disc and Derivatives 10
Metamerism 15 '
Branchiomerism 16
Viscera and Limbs 18
Prenatal Growth 22
Variability 25
References 25
SECTION II
OSTEOLOGY
By Peter Thompson, M.D.
The Skeleton 27
I. The Axial Skeleton 29
A. The Vertebral Column 29
The Cervical Vertebrae 31
The Thoracic Vertebrae 36
The Lumbar Vertebrae 37
The Sacrum 39
The Coccygeal Vertebrae 42
The Vertebral Column as a
Whole 43
B. Bones of the Skull 51
The Occipital 51
The Parietal 57
The Frontal 59
The Sphenoid 62
The Sphenoidal Conchae 67
The Epipteric and Wormian
Bones 68
The Temporal Bone 68
The Tympanum 77
The Osseous Labyrinth 80
The Ethmoid 81
The Inferior Nasal Concha. . . 84
The Lacrimal Bone 85
The Vomer 85
The Nasal Bones 86
The Maxilla or Upper Jaw ... 87
The Palate Bone 91
The Zygomatic or Malar Bone 93
The Mandible or Lower Jaw. . 95
The Hyoid Bone 99
The Skull as a Whole 100
The Orbits 109
The Nasal Fossa 110
The Interior of the Skull 112
The Morphology of the Skull . 117
The Skull at Birth 120
C. The Thorax 126
The Ribs 126
The Sternum 132
The Thorax as a Whole 138
The Appendicular Skeleton 139
A, Bones of the Upper Extremity. 139
The Clavicle 139
The Scapula 141
The Humerus 146
The Radius 152
The Ulna 165
The Carpus 159
The Metacarpals 164
The Phalanges 167
B. Bones of the Lower Extremity . . 169
The Coxal Bone 169
The Pelvis 175
The Femur or Thigh Bone... 178
The Patella 184
The Tibia 185
The Fibula 189
The Tarsus 191
The Metatarsus 200
The Phalanges 203
The Bones of the Foot 205
Homology of the Bones of the
Extremities 206
References 209
CONTENTS
SECTION III
THE ARTICULATIONS
By F. W. Jones, D. Sc, M. B., M. R. C. S., L. R. C. P.
Constituents of an Articulation 211
Classifioation of Articulations 212
Development and Morphology 213
Movements of Joints 214
Articulations of the Skull 215
Mandibular Articulation 215
Ligaments and Joints between the
Skull and Vertebral Column 218
Articulations of Atlas with Occiput. . 218
Articulations between Atlas and Epis-
tropheus 220
Ligaments uniting the Occiput and
Epistropheus 223
Articulations of the Trunk 224
1. The Articulations of the Verte-
bral Column 225
a. The Bodies of the Verte-
brffi 225
6. The Articular Processes . . 228
c. The Lamina 229
d. The Spinous Processes . . . 229
e. The Transverse Processes 231
2. Sacro-vertebral Articulations. 232
3. Articulations of the Pelvis. . . . 234
4. Articulations of the Ribs with
the Vertebrfe 241
5. Articulations at the Front of
the Thorax 244
Movements of the Thorax 247
The Articulations of the Upper Ex-
tremity 248
PAGE
1. Sterno-costo-olavicular Articu-
lation 248
2. Scapulo-clavioular Union .... 250
3. Shoulder-joint 253
4. Elbow-joint 258
5. Union of Radius with Ulna. . 261
6. Radio-carpal Articulation. . . . 265
7. Carpal Joints 268
8. Carpo-metacarpal Joints 272
9. Intermetacarpal Articulations. 273
10. Metacarpo-phalangeal Joints. 274
11. Interphalangeal Articulations. 276
The Articulations of the Lower Limb . . . 276
1. Hip-joint 276
2. Knee-joint 284
3. Tibio-fibular Union 295
4. Ankle-joint 297
5. Tarsal Joints 301
a. The Talo-calcaneal Union.. 301
b. Articulations of Anterior
Part of Tarsus 303
c. Medio-tarsal or Trans-
verse Tarsal Joints 305
6. Tarso-metatarsal Articulations 307
7. Intermetatarsal Articulations. 309
8. Metatarso-phalangeal Articu-
lations 310
9. Interphalangeal Joints 310
References 311
SECTION IV
THE MUSCULATURE
By C. R. Bardeen, A.B., M.D.
General Remarks on Muscles 313
Muscle Fasciae 313
Gross Structure 314
Finer Structure of Muscles 315
Tendons 317
Synovial Bursse 318
Synovial Sheaths 318
Nerves and Vessels 318
Nomenclature 319
Variation 320
Physiology 320
I. Musculature of the Head and Neck
and Shoulder Girdle 323
Physiological and Morphological. . 323
1. Facialis Musculature 329
2. Cranio-mandibular Muscula-
ture 338
3. Supra-hyoid Musculature.... 343
4. Muscles of the Tongue 345
5. Superficial Shoulder Girdle
Musculature 347
6. Infrahyoid Muscles 350
7. Scalene Musculature 353
8. Prevertebral Musculature .... 355
9. Anterior and Lateral Inter-
transverse Muscles 356
10. Deep Musculature of the
Shoulder Girdle 356
II. Musculature of the Upper Limb. . 360
A. Musculature of the Shoulder. . 363
B. Pectoral Muscles and Axillary
Fascia 370
C. Musculature of the Arm 374
1. Dorsal or Extensor Group. . 377
2. Ventral or Flexor Group .... 379
D. Musculature of the Forearm
and Hand 383
1. Dorsal-Radial Division 387
a. Superficial Layer 387
6. Deep Layer 392
2. Ulno-Volar Division 395
a. First Layer 395
6. Second Layer 399
c. Third Layer 401
d. Fourth Layer 402
3. Musculature of the Hand... 403
III. Spinal Musculature 410
A. Superficial Lateral Dorsal Sj's-
tem 414
B. Deep Lateral Dorsal Muscles. 417
C. Superficial Medial Dorsal Sys-
tem 417
CONTENTS
PAGE
D. Deep Medial Dorsal System . . 417
E. Suboccipital Muscles 419
IV. Thoracic-abdominal Musculature. 422
A. Ventral Division 430
B. Lateral Division 431
1. Serratus Group 431 j
2. External Oblique Group.... 432
3. Internal Oblique Group 433
4. Transverse Group 434
C. Lumbar Muscle 436
D. Diaphragm 436
V. Musculature of the Pelvic Outlet. 439
A. Muscles of the Pelvic Dia- '•
phragm, Coccyx and Anus. . 448
B. Muscles of the Urogenital
Diaphragm 449 '
C. External Genital Muscles 450 ,
VI. Musculature of the Lower Limb . . 452
A. Musculature of the Hip 454 i
1. Ilio-femoral Musculature. . . 454 i
a. Anterior Group 455 i
b. Posterior Group 457
2. Ischio-pubo-femoral Muscu-
lature of the Hip 463
B. Musculature of the Thigh 464
1. Anterior Group 468
2. Medial (Adductor) Group. . 471
3. Posterior (Hamstring)
Group 474
C. Musculature of the Leg 477
1. Muscles of the Front of the
Leg 480
2. Lateral Musculature of the
Leg 483
3. Musculature of the Back of
the Leg 484
D. Muscles of the Foot 491
1. Muscle of the Dorsum of
the Foot 492
2. Muscles of the Sole 493
Muscles Grouped According to Function 500
References 506
SECTION V
BLOOD-VASCULAR SYSTEM
By Harold D. Senior, M.B., M.D.
A. The Heart and Pericardium 508
1. The Heart 508
Exterior of the Heart 509
Atrial Portion 511
Atrio- Ventricular Valves 515
Ventricular Portion 516
Semilunar Valves 517
Architecture of the Heart 518
Vessels and Nerves 519
2. The Pericardium 522
3. Surface Relations 523
4. Morphogenesis 523
B. The Arteries and Veins 527
1. Pulmonary Arteries and Veins. . . 528
2. The Systemic Arteries 529
The Aorta 529
Innominate Artery 532
Branches 532
Common Carotid Arteries 533
E.xternal Carotid Artery 536
Branches 536
Internal Carotid Artery 549
Branches 552
Subclavian Artery 556
Branches 658
Axillary Ai-tery 569
Branches 570
Brachial Artery 573
Branches 575
Ulnar Artery 576
Branches 577
Superficial Volar Arch 582
Branches 582
Radial Artery 582
Branches 583
Deep Volar Arch 586
Branches 586
Descending or Thoracic Aorta. . 586
Visceral Branches 588
Parietal Branches 588
Abdominal Aorta 590
Parietal Branches 592
Visceral Branches 593
Terminal Branches 603
Middle Sacral Artery 603
Common Iliac Arteries 603
Hypogastric Artery 605-
Parietal Branches 606
Visceral Branches 609
External Iliac Artery 614
Branches 614
Femoral Artery 616
Branches 618
PopUteal Artery 621
Branches 622
Posterior Tibial Artery 624
Branches 626
Lateral Plantar Artery 627
Branches 628
Medial Plantar Artery 629
Branches 629
Anterior Tibial Artery 629
Branches 630
Dorsahs Pedis Artery 632
Branches 632
Morphogenesis and Variations
of the Arteries 633
a. Arteries of the Head and
Trunk 6.33
6. Arteries of the Extremities 639
The Systemic Veins 640
Veins Emptying into the Vena
Cava Superior 641
Veins of the Head and Neck 642
Superficial Veins of the Head
and Neck 643
Deep Veins of the Head and
Neck 648
Veins of the Thorax 662
Superficial Veins of the Thorax. 662
Deep Veins of the Thorax 662
Veins of the Upper Extremity. . . 667
Superficial Veins of Upper Ex-
tremity 667
Deep Vems of Upper Extremity 670
Veins Emptying into the Vena
Cava Inferior 672
Portal Vein and its Tributaries. 675
Common lUao Veins 679
Hypogastric Vein 679
CONTENTS
PAG£
External Iliae Vein 683
Superficial Veins of Abdominal
Wall 683
Veins of the Lower Extremity. . . 683
Superficial Veins of Lower Ex-
tremity 684
Deep Veins of Lower Extremity 686
Morphogenesis and Variations of
the Veins 690
PAGE
a. Vena Cava Superior and
Tributaries 690
b. Vena Cava Inferior and
Tributaries 693
c. Portal System 694
The Foetal Circulation 695
References 696
SECTION VI
THE LYMPHATIC SYSTEM
By Eliot R. Claek, A.B., M.D.
I . General Anatomy of the Lymphatic
System 697
1. Lymphatic Capillaries 697
2. Lymphatic Vessels 702
3. Lymphoid Organs 704
4. Development of the Lym-
phatic System 706
II. Special Anatomy of the Lymphatic
System 709
A. Lymphatics of the Head and
Neck 709
1. Superficial Nodes of Head and
Neck 709
2. Lymphatic Vessels of the Face 712
3. Deep Lymphatic Nodes of the
Head and Neck 714
4. Deep Lymphatic Vessels of
the Head and Neck 714
B. Lymphatics of the Upper Ex-
tremity 719
1. Lymphatic Nodes of the Up-
per Extremity 719
2. Lymphatic Vessels of the Up-
per Extremity 721
C. Lymphatics of the Thorax 723
1. Superficial Lymphatic Vessels
of the Thorax 723
2. Lymphatic Nodes of the
Thorax 724
3. Deep Lymphatics of the Tho-
rax 725
Thoracic Duct 726
Right Collecting Ducts 728
Deep Lymphatic Vessels 728
D. Lymphatics of Abdomen and
Pelvis 730
1. Lymphatic Nodes of the Ab-
domen and Pelvis 730
2. Lymphatic Vessels of the Ab-
dominal WaUs 733
3. Visceral Lymphatic Vessels of
the Abdomen and Pelvis . . . 733
Lymphatics of Alimentary
Tract 733
Lymphatics of Excretory Or-
gans 737
Lymphatics of Reproductive
Organs 742
E. Lymphatics of the Lower Ex-
tremity 746
1. Lymphatic Nodes of the
Lower Extremity 746
2. Lymphatic Vessels of the
Lower Extremity 748
References 750
SECTION VII
THE NERVOUS SYSTEM
5y Irving Hardestt, A.B., Ph.D.
General Considerations 751
Central Nervous System 770
I. Spinal Cord 771
External Morphology 771
Internal Structure 775
II. Brain or Encephalon 792
General Topography 793
Rhombencephalon 799
1. Medulla Oblongata 799
2. Pons VaroUi 804
3. Cerebellum 804
Cerebrum 833
1. Mesencephalon (Mid-brain). 833
2. Prosencephalon (Fore-brain) 843
A. Diencephalon(Inter-brain) 843
B. Telencephalon (End-brain) 847
III. General Summary of Principal
Conduction Paths of Nervous
System 895
IV. Meninges 908
The Peripheral Nervous System 924
I. Cranial Nerves 927
Olfactory Nerves 929
Optic Nerves 930
Oculo-motor Nerves 931
Trochlear Nerves 933
Abducens Nerves 934
Trigeminal Nerves 934
Masticator Nerves 942
Facial Nerves 943
Glosso-palatine Nerves 946
Vestibular Nerves 949
Cochlear Nerves 950
Glosso-pharyngeal Nerves 951
Hypoglossal Nerves 952
Vagus Nerves 954
Spinal Accessory Nerves 958
Gangliated Cephalic Plexus 959
II. Spinal Nerves 964
A. Posterior Primary Divisions. . . 970
CONTENTS
xiu
1. Cervical Nerves 971
2. Thoracic Nerves 971
3. Lumbar Nerves 973
4. Sacral Nerves 973
B. Anterior Primary Divisions .... 973
1. Cervical Nerves 974
Cervical Plexus 974
Brachial Plexus 980
2. Thoracic Nerves 994
3. Lumbar Nerves 996
Lumbo-sacral Plexus 996
Lumbar Plexus 998
Lumbo-sacral Trunk 1005
4. Sacral Nerves 1006
Sacral Plexus 1006
Pudendal Plexus 1016
Coccygeal Plexus. . 1018
III. Distribution of the Cutaneous
Branches 1018
Cutaneous Areas of Scalp 1018
Cutaneous Areas of Face 1018
PAGE
Cutaneous Areas of Neck 1019
Cutaneous Areas of Trunk 1020
Cutaneous Areas of Limbs 1020
The Sympathetic System 1026
Sympathetic Trunks 1032
Cephalic and Cervical Portions of the
Sympathetic Trunk 1033
1. Superior Cervical Ganglion 1035
2. Middle Cervical GangUon 1036
3. Inferior Cervical Ganghon 1036
Thoracic Portion of Sympathetic
Trunk 1037
Lumbar Portion of Sympathetic
Trunk 1039
Sacral Portion of Sympathetic Trunk. 1040
Great Prevertebral Plexuses 1040
1. Cardiac Plexus 1041
2. CcEliac Plexus 1043
3. Hypogastric Plexus 1045
References 1047
SECTION VIII
SPECIAL SENSE ORGANS
By David Waterston, M.A., M.D., F.R.C.S.
General Considerations 1049
I. Olfactory Organ 1049
II. Organ of Taste 1051
III. The Eye 1051
General Surface View 1052
Examination of Eyeball 1055
Cavity of Orbit 1066
General Arrangement 1066
Optic Nerve 1073
Blood-vessels and Nerves of
Orbit 1074
Eyelids 1076
Lacrimal Apparatus 1079
Development of the Eye 1080
The Ear 1082
External Ear 1082
Middle Ear 1086
Internal Ear 1092
Development of the Ear 1096
References 1098
SECTION IX
THE DIGESTIVE SYSTEM
By. C. M. Jackson, M.S., M.D.
The Mouth 1100
The Lips and Cheeks 1102
The Palate 1104
The Tongue 1106
The Salivary Glands 1113
The Teeth 1117
The Pharynx 1128
The (Esophagus 1138
The Abdomen 1142
The Peritoneum 1145
The Stomach 1151
The Small Intestine 1161
The Duodenum 1161
The Jejunum and Ileum 1165
The Large Intestine 1170
The Liver 1180
The Bile Passages 1186
The Pancreas 1192
References 1197
SECTION X
THE RESPIRATORY SYSTEM
By R. J. Terry, A.B., M.D.
The Nose 1200
The Larynx 1209
Cartilages of Larynx. . 1209
Joints and Membranes of Larynx. . . 1213
Muscles of Larynx 1218
Cavity of Larynx and Mucosa 1220
The Trachea and Bronchi 1225
The Lungs 1228
The Thoracic Cavitv, 1235
The Pleura; .' 1236
Mediastinal Septum 1239
References 1240
CONTENTS
SECTION XI
UROGENITAL SYSTEM
By J. Playpair McMubeich, A.M., Ph.D.
PAGE
The Urinary Apparatus 1241
The Kidneys 1241
The Ureters 1247
The Urinary Bladder 1249
The Male Reproductive Organs 1253
The Testes and Their Appendages. . . 1254
The Scrotum 1254
The Testes and Epididymis 1255
The Ductus Deferentes and Seminal
Vesicles 1257
The Spermatic Cord 1259
The Penis 1260
The Male Urethra 1262
PAGE
The Prostate 1264
The Bulbo-urethral Glands 1265
The Female Reproductive Organs 1265
The Ovaries 1268
The Tuba; Uterinas 1269
The Uterus 1271
The Vagina 1274
Female External Genitalia and Ure-
thra 1276
Development of the Reproductive Or-
gans 1278
References 1280
SECTION XII
THE SKIN, MAMMARY AND DUCTLESS GLANDS
By Abeam T. Kerr, B.S., M.D.
The Skin 1281
Appendages of the Skin 1290
Hairs 1290
Nails 1293
Cutaneous Glands 1296
Mammary Glands 1299
The Ductless Glands 1306
The Spleen 1306
The Thyreoid Gland 1312
Parathyreoid Glands 1318
Thymus 1319
Suprarenal Glands 1323
Glomus Caroticum 1327
Aortic Paraganglia 1329
Glomus Coccygeum 1329
References 1329
SECTION XIII
CLINICAL AND TOPOGRAPHICAL ANATOMY
By John Morley, Ch.M., F.R.C.S.
The Head 1331
The Cranium 1333
The Bony Sinuses 1335
Cranio-cerebral Topography 1338
The Hypophysis Cerebri 1342
The Face 1342
The Orbit and Eye 1346
The Mouth 1349
The Nose 1352
The Neck 1354
The Thorax 1363
The Abdomen 1370
The Pelvis 1382
Male Pelvis 1382
Female Pelvis 1391
Hernia 1394
Inguinal Hernia 1394
Femoral Hernia 1398
Umbilical Hernia 1402
The Back 1403
The Upper Extremity 1409
The Shoulder and Arm 1409
The Elbow 1417
The Forearm 1419
The Wrist and Hand 1424
The Lower Extremity 1434
The Hip and Thigh 1434
The Knee 1444
Popliteal Space 1451
The Leg 1453
The Ankle 1459
The Foot 1464
Arches of the Foot 1468
Index 1471
INTRODUCTION
By C. M. JACKSON, M.S., M.D.
PROFESSOR OP ANATOMY, TJNrVEHSITT OP MINNESOTA.
ANATOMY, as the term is usually employed, denotes the study of the
/-\ structure of the human body. Properly, however, it has a much wider
-^-*- significance, including within its scope not man alone, but all animal forms,
and, indeed, plant forms as well; so that, when its application is limited to man,
it should be qualified by the adjective human. Human Anatomy, then, is the
study of the structure of the human body, and stands in contrast to, or rather in
correlation with. Human Physiology, which treats of the functions of the human
body, the two sciences, Anatomy and Physiology, including the complete study
of man's organization and functional activities.
In the early history of the sciences these terms sufficed for all practical needs,
but as knowledge grew, specialization of necessity resulted and new terms were
from time to time introduced to designate special lines of anatomical inquiry.
With the improvement of the microscope a new field of anatomy was opened up
and the science of Histology came into existence, assuming control over that
portion of Anatomy which dealt with the minuter details of structure. So, too,
the study of the development of the various organs gradually assumed the
dignity of a more or less independent study known as Embryology, and the study
of the structural changes due to disease was included in the science of Pathology;
so that the term Anatomy is sometimes limited to the study of the macroscopic
structure of normal adult organisms.
It is clear, however, that the lines of separation between Anatomy, Histology,
Embryology, and Pathology are entirely arbitrary. Microscopic anatomy
necessarily grades ofi' into macroscopic anatomy; the development of an organism
is a progressive process and the later embryonic or foetal stages shade gradually
into the adult; and structural anomalies lead insensibly from the normal to the
pathological domains. Furthermore it is found that in its individual develop-
ment the organism passes through stages corresponding to those of its ancestry
in evolution; in other words, Ontogeny repeats Phylogeny. A comprehensive
study of Anatomy must therefore include more or less of the other sciences, and
since an appreciation of the significance of structural details can only be obtained
by combining the studies of Anatomy, including Histology and Embryology,
and since, further, much light may be thrown on the significance of embryological
stages by comparative studies, Anatomy, Embryology, and Comparative Anatomy
form a triumvirate of sciences by which the structure of an organism, the signi-
ficance of that structure, and the laws which determine it are elucidated. For
this combination it is convenient to have a single term, and that which is used is
Morphology, a word meaning literally the science of form.
In morphological comparisons, the term liomology denotes similarity of structure, due to a
common origin in the evolution of organs or parts; while analogy denotes merely physiological
correspondence in function. Thus the arm of man and the wing of a bird are homologous, but
not analogous, structures; on the other hand, the wing of a bird and the wing of an insect are
analgous, but not homologous. Serial homology refers to oorresp ending parts in successive
segments of the body.
Nomenclature. — Formerly there was much confusion in the anatomical
nomenclature, due to the multiphcity of names and the lack of uniformity in
using them. Various names were applied to the same organs and great diversity
of usage prevailed, not only between various countries, but also even among
authors of the same country. Recently, however, a great improvement has been
made by the general adoption of an international sj^stem of anatomical nomen-
2 INTRODUCTION
clature. This system was first adopted by the German Anatomical Society at a
meeting in Basel, in 1895, and is hence called the Basel Nomina Anatomica, or
briefly, the BNA. The BNA provides each term in Latin form, which is es-
pecially desirable for international usage. Each nation, however, is expected to
translate the terms into its own language, wherever it is deemed preferable for
everyday usage. Thus in the present work the Anglicised form of the BNA is
generally used. Where not identical, however, the Latin form is added once for
each term in a place convenient for reference, and is designated by enclosure in
brackets [ ]. Where necessary the older terms have also been added as synonyms.
The Commission by whom the BNA was prepared included eminent anatomists represent-
ing various European nations. The work of the Commission was very thorough and careful,
and extended through a period of six years. Among the guiding principles in the difficult task
of selecting the most suitable terms were the following: (1) Each part should have one name
only. (2) The names should be as short and simple as possible. (3) Related structures
should have similar names. (4) Adjectives should be in opposing pairs. A few exceptions
were found necessary, however.
On account of its obvious merits, the BNA system has been generally adopted throughout
the civilised world, and the results are very satisfactory. Comparatively few new terms have
been thereby introduced, over 4000 of the 4500 names in the BNA corresponding almost exactly
to older terms already in use by the Enghsh-speaking nations. Certain minor defects in the
system have been criticised; but these are outweighed by the advantages of this uniform
system.
Abbreviations. — Certain frequently used words in the BNA are abbreviated as follows:
a., arteria (plural, aa., arterise); b., bursa; g., ganglion; gl., glandula; lig., ligamentum (plural,
ligg., ligamenta); m., musculus (plural, mm., muscuU); n., nervus (plural, nn., nervi); oss.,
ossis (or ossium); proc, processus; r., ramus (plural, rr., rami); v., vena (plural, vv., venae).
Terms of position and direction. — The exact meaning of certain fundamental
terms used in anatomical description must be clearly understood and kept in
mind. In defining these terms, it is supposed that the human body is in an
upright position, with arms at the sides and palms to the front.
The three fundamental planes of the body are the sagittal, the transverse and
the frontal. The vertical plane through the longitudinal axis of the trunk,
dividing the body into right and left halves, is the median or mid-sagittal plane;
and any plane parallel to this is a sagittal plane. Any vertical plane at right
angles to a sagittal plane, and dividing the body into front and rear portions is a
frontal (or coronal) plane. A plane across the body at right angles to sagittal and
coronal planes is a transverse or horizontal plane.
Terms pertaining to the front of the body are anterior or ventral; to the rear,
'posterior or dorsal] upper is designated as superior or cranial] and lower as inferior
or caudal.
The term medial means nearer the mid-sagittal plane, and lateral, further from
that plane. These terms should be carefully distinguished from internal (inner)
and external (outer), which were formerly synonymous with them. Internal, as
now used (BNA), means deeper, i. e., nearer the central axis of the body or part;
while external refers to structures more superficial in position. Proximal, in
describing a limb, refers to position nearer the trunk; while distal refers to a more
peripheral position.
'Adverbial forms are also employed, e. g., anteriorly or ventrally (forward, before); poster-
iorly or dorsally (backward, behind); superiorly or cranially (upward, above); and inferiorly or
caudally (downward, below).
It should also be noted that the terms ventral, dorsal, cranial and caudal are independent of
the body posture, and therefore apply equally weU to corresponding surfaces of vertebrates in
general with horizontal body axis. On this account these terms are preferable, and wiU doubt-
less ultimately supplant the terms anterior, posterior, superior and inferior.
The discrimination in the use of several similar terms of the BNA should also receive atten-
tion. Thus medianus (median) refers to the median plane. Medialis (medial) means nearer
the median plane and is opposed to lateral, as above stated. Medius (middle) is used to desig-
nate a position between anterior and posterior, or between internal and external. Between
medialis and lateralis, however, the term intermedius is used. Finally, transversalis means trans-
verse to the body axis; transversus, transverse to an organ or part; and iransversarius, pertaining
to some other structure which is transverse.
Parts of the body. — The primary divisions of the human body (fig. 1) are the
head, neck, trunk and extremities. The head [caput] includes cranium and face
[facies]. The neck [coUum] connects head and trunk. The trunk [truncus]
includes thorax, abdomen, and pelvis. The upper extremity [extremitas superior]
includes arm [brachium], forearm [antibrachium], and hand [man us]. The
INTRODUCTION
lower extremity [extremitas inferior] includes thigh [femur], leg [crus], and foot
[pes].
Each of the parts mentioned has further subdivisions, as indicated in fig. 1.
The cranium includes : crown [vertex] ; hack of the head [occiput] ; frontal region
[sinciput], including forehead [frons]; temples [tempora]; ears [aures], including
auricles [auriculfe].
Pig. 1. — Parts op the Human Body. A, Posterior view. B, Anterior view.
ERTEXl
EYE [OCULUS]
^EAR [AURIS]
NOSE [NASUS]
MOUTH [OS]
The face includes the regions of the eye [oculus], nose [nasus], and mouth [os],
the subdivisions of which will be given later under the appropriate sections.
The thorax includes: hreast [pectus]; mammary gland [mamma]; and thoracic
cavity [cavum thoracis]. The hack [dorsum] includes the vertebral column
[columna vertebralis]. The abdomen includes: navel [umbilicus] ; ^awfc [latus];
groin [inguen]; loin [lumbus]; and the abdominal cavity [cavum abdominis]. The
pelvis includes: "pelvic cavity [cavum pelvis]; genital organs [organa genitalia],
4 INTRODUCTION
buttocks [nates], separated by a cleft [crena ani] at the anus. The hip [coxa]
connects the pelvis with the lower extremity.
In the lower extremity, the thigh is joined to the leg by the knee [genu]. The
foot includes: heel [calx]; sole [planta]; instep [tarsus]; metatarsus; and five toes
[digiti I-V], including the great toe [hallux] and little toe [digitus minimus].
The upper extremity is joined to the thorax by the shoulder. The arm is
joined to the forearm at the elboiv [cubitus]. The hand includes: wrist [carpus];
Fig. 2. — Section of the Epidehmi.s of a Finger, prom a Human Embryo of 10.2 cm.
metacarpus, with palm [vola or palma] and back [dorsum manus]. The five
fingers [digiti I-V] include: thumb [pollex], index finger [index]; middle finger
[digitus medius]; ring finger [digitus annularis] and little finger [digitus minimus].
Organ-systems. — Each of the various parts of the body above outlined is
composed of various organs, and the groups of related organs make up organ-
systems.
The various organ-systems are treated as special branches of descriptive
anatomy. The study of the bones is called osteology; of the ligaments and joints,
Fig. 3. — Diagram op a Typical Cell. (Szymonowicz.)
'Granules
Nuclear membrane ^
Nuclear fluid'
Interfibrillar substanc
"Fibrillar substance
-~^ — Microsome
syndesmology for arthrology); of the vessels, angiology; of the muscles, myology; of
the nervous system, neurology; and of the viscera, splanchnology. Further subdivi-
sions are also made. The viscera, for example, include the digestive tract,
respiratory tract, urogenital tract, etc.
Tissues and cells. — The body, as above stated, has various parts, each of which may be
subdivided into its component systems and organs. A further analysis reveals a continued
series of structm'al units of gradually decreasing complexity. Thus each organ is found to con-
sist of a number of tissues (epithehal, connective, muscular or nervous). Finally, each tissue is
composed of a group of similar units called cells (figs. 2, 3) which are the ultimate structural units
INTRODUCTION 5
of the body. The body may therefore be regarded as composed of myriads of cell units, organ-
ized into units of gradually increasing complexity, very much as a social community is composed
of individuals organized into trades, municipalities, etc.
Most of the individual tissues can be recognized by their gross appearance. In fact, the
principal tissues were first demonstrated by Bichat through skilful dissection, maceration, etc.,
and without the aid of the microscope. The cellular structure of the tissues was later discovered
by Schwann in 1839.
Each cell (fig. 3) is composed of a material called ■protoplasm, a viscid substance variable in
appearance and exceedingly complex in chemical composition. It readily breaks down into sim-
pler chemical compounds, whereby energy (chiefly in the form of heat and mechanical energy) is
liberated. It has also the power of absorbing nutritive material to build up and replace what
was lost. Its decomposition results from stimuli of various kinds, and hence it is said to be
irritable. The mechanical energy which it liberates is manifested by its contractihty, especially
in the muscle cells. It excretes the waste products produced by its decomposition. Each cell
has the power, under favourable conditions, of reproducing itself by division. Protoplasm pre-
sents, in short, all the forms of activity manifested by the body as a whole; and, indeed, the ac-
tivities of the body are the sum of the activities of its constituent cells.
In the protoplasm of each cell is a specially differentiated portion, the nucleus (fig. 3). The
nucleus plays an important part in regulating the activities of the cytoplasm, the general proto-
plasm of the cell body. The nucleus differs from the cytoplasm both structurally and chem-
ically, and contains a very important substance, chromat^in, which during cell division is aggre-
gated into a definite number of masses called chromosomes. The cytoplasm of actively growing
cells also contains the archoplasm and centrosome, structures of importance in the process of cell
division. Further details concerning the cells and tissues may be found in the text-books of
cytology and histology.
In earher days Human Anatomy was almost entirely a descriptive science, but little atten-
tion being paid to the significance of structure, except in so far as it could be correlated with
physiological phenomena as they were at the time understood. In recent years attention has
been largely paid to the morphology of the human body and much valuable information as to
the meaning of the structure and relations of the various organs has resulted. Since the form
and structure of the body are the final result of a series of complicated developmental changes,
the science of Embryology has greatly contributed to our present knowledge of human Mor-
phology; and, accordingly, a brief sketch of some of the more important phases of morphogenesis
will form a fitting introduction to the study of the adult.
References. — General: For looking up the literature upon any anatomical
topic, the best guide is the " Jahresbericht ueber die Fortschritte der Anatomie
und Entwicldungsgeschichte," which contains classified titles and brief abstracts
of the more important papers in gross anatomy, histology and embryology.
Other useful aids are the "Zentralblatt fuer normale Anatomie," the "Index
Medicus" and the catalogue of the Surgeon Genera 's Library of the War Dep't.
(Washington, D. C). The latter two contain titles only, but cover the whole
field of medicine. The "Concilium Bibliographicum" also provides a conveni-
ent card-index system of references for the biological sciences, including
Anatomy.
For nomenclature: His, Archiv f. Anat., 1895 (BNA system); Barker, Ana-
tomical Nomenclature. Cells and tissues: Wilson, The Cell; Hertwig, Zelle und
Gewebe (also English transl.) ; Sehaefer, Microscopic Anatomy (in Quain's
Anatomy, 11th ed.) ; Heidenhain, Plasma und Zelle.
SECTION 1
MOEPHOGENESIS
Revised for the Fifth Edition
By C. M. JACKSON, M.S., M.D.
PROFESSOR OF ANATOMY IN THE tJNIVERaiTY OF MIN
CHANGE is a fundamental characteristic of all living things. The human
body during its life cycle accordingly passes through various phases of form
and structure. In the earliest embryonic phases of development the
changes are very rapid, decreasing in rapidity during the later foetal stages, but
continuing at a diminishing rate throughout infancy, childhood and youth up to
the adult. Following the acme of maturity, changes continue which lead
gradually to senescence and final death of the body.
This cycle of change in the body depends upon similar changes in its various component
organs, each having its own characteristic hfe cycle. In a few of the organs this cycle is very
short, as in some of the organs of the embryo (e. g., mesonephros). Other organs persist only
during childhood (e. g., thymus); while the majority continue, with varying degrees of change,
throughout postnatal life. The final death of the body is due to the breakdown of some of the
essential organs.
A further analysis reveals the fact that the characteristic life cycles of the organs depend
ultimately upon similar changes in their constituent tissues and cells. Every ceU has a definite
life cycle, an early period characterised by rapid and vigourous changes, later periods of differen-
tiation and maturity, followed by stages of degeneration and death. This cycle of cell changes
has been designated by Minot as cytomorphosis.
Growth. — Associated with the process of cell differentiation (cytomorphosis), and even
more important as a factor in the morphogenesis of the body, is the process of growth. The
developmental changes in form and structure of the body are due largely to the unequal growth
of its various parts. Growth, like other changes in the body and its parts, depends ultimately
upon the characteristics of the constituent cells.
Fig. 4. — The Ovum op a New-bohn Child, with Follicle Cells. (After Mertens.)
Nucleus
The cell changes during growth may be grouped under two heads. The first, or growth
proper, involves merely the enlargement (hypertrophy) of the individual cells and intercellular
products. The second includes the muUiplication (hyperplasia) of the cells, which is accom-
plished by mitotic division. Cell division is necessary in ceU growth, for otherwise the cell
would soon reach a size where its surface (for nutritive, respiratory and excretory purposes)
would be inadequate for its mass. In general, however, cell division is most active in the earher
embryonic periods, during which the cells remain small. Later, cell division diminishes or
ceases, and growth is due chiefly to enlargement of the cells already present. It is also during
the later period, when the cells have ceased rapid division, that the process of cell differentiation
and tissue formation is most marked.
The principle of the ratio of surface to mass often apphes to the growing organs as well as to
the individual cells. To maintain the necessary ratio, the surface area is increased by the for-
mation, through localised unequal growth, of projections (e. g., villi or folds) or invaginations
(e. g., glands) from surfaces. Innumerable modifications of this principle occur throughout the
process of morphogenesis.
7
8 MORPHOGENESIS
Fig. 5. — Ovum fkom Ovaey of a Woman Thibtt Years of Age. cr, corona radiata.
n, nucleus, y, yolk, p, clear protoplasmic zone, ps, perivitelline space, zp, zona pellucida.
(McMurrich's Embryology, from Nagel.)
zp
%
;>s
vJ
^
~ii^\
Fig. 6. — Stages of Segmentation in the Ovum of the Mouse, x, polar body.
(McMurrich's Embryology, from Sobotta.)
SEGMENTATION OF THE OVUM
9
While the present work deals primarily with the adult human organism in the
stage of maturity, reference is made also to its changes according to age. Although
these changes for the various systems of organs are described under the ap-
propriate sections, it is desirable to consider first some of the more fundamental
features pertaining to the body as a whole. This apphes particularly to the
earlier embryonic period, which includes the more general phases of morpho-
genesis. No attempt will be made to describe fully the process of development,
the details of which are to be found in text-books of embryology.
Segmentation of the ovum. — The human body, like all living organisms, arises
from a single cell, the egg-cell or ovum. An early stage in the development of the
ovum is shown in fig. 4, and a later stage, approaching maturity, in fig. 5. The
mature human ovum is about 0.2 mm. in diameter. In the uterine (Tallopian)
tube, the fertilised ovum undergoes segmentation, the various stages of which are
represented in figs. 6 and 7.
Fig. 7. — Diagram of Section
through a mammalian ovum at the
Morula Stage.
Fig. 8. — Diagram of Section of
A Mammalian Ovum Showing the
Inner Cell Mass.
fi
0~
^ ., J'\ ^ ^
i —
A^;
\;^-:^
('**-• -t^
While the processes of maturation, fertilisation and segmentation have not as yet been ob-
served in the human ovum, the evidence of comparative anatomy makes it very prolDable that in
all essential respects these processes are like those found in other mammals. As a result of the
successive divisions of the ovum in segmentation, a spherical mass of cells, the morula (fig. 7) is
formed. In this mass, an excentric cavity forms (fig. 8) whereby the mass is transformed into a
hollow vesicle. The wall of this vesicle is probably formed throughout the greater part of its
extent by a single layer of cejls; but at one point of the circumference there is a group of cells
termed the inner cell mass (fig. 8). Probably about this time the ovum enters the uterine cavity,
and through the activity of the outer layer of ceUs {trophoblasi) becomes embedded in the uterine
mucosa.
Formation of the embryonic disc and germ layers. — -In the earliest human
embryos which have been described, development has already proceeded beyond
Fig. 9. — Diagram Showing the Relations of the Germ Layers in an Early EimRYO.
Ac, amniotic cavity, lined by ectoderm. D, yolk-sac, lined by endoderm (En). Me, Me',
mesoderm, C, extra,-embryonic calom. B, chorion. T, trophoblast. (McMurrich.)
the stage represented by fig. 8, and has reached that of fig. 9. Within the inner
cell mass, two cavities have appeared. The more superficial fac) is the amniotic
10
MORPHOGENESIS
■cavity; the deeper (D) is the cavity of the yolk-sac; while between them is a
plate of cells forming the embryonic disc. The embryonic disc (figs. 9 and 10)
contains three layers of cells, — the fundamental germ layers, — ectoderm (Ec),
endoderm (En), &n.A mesoderm.
The germ layers of the embryonic disc are of prime importance in the development of the
body. From the ectoderm, which hes next to the amniotic cavity and represents the upper
(later outer) germ layer, are derived the epidermis and the entire nervous system. From the
■endoderm, which hes next to the yolk-sac, and represents the lower (later inner) germ layer, is
derived the epithehal lining of the digestive mucosa and its derivatives. From the mesoderm, or
middle germ layer, is differentiated the remainder of the body, including the skeletal and sup-
porting tissues, vascular system, muscle and most of the urogenital organs.
The germ layers also extend beyond the embryonic disc, as shown in figs. 9 and 10. The
yolk-sac is made up of a lining of endoderm and an outer layer of mesoderm. The amnion, which
Fig. 10. — Diagram op Section of a Mammalian Ovum showing the Embryonic Disc,
Amniotic Cavity and the Germ Layers.
Endoderm
later becomes separated from the chorion, is composed of mesoderm lined by endoderm. The
outer cell layers form the chorion, which likewise shows two layers, the outermost of which
(trophoblast) is ectoderm, the inner, mesoderm. In fig. 10 the chorion is beginning to send out
root-like projections (villi) which invade the uterine mucosa.
It is thus noteworthy that of the cells']derived from the ovum relatively only a few — those of
the embryonic disc — enter directly into the formation of the body. The yolk-sac, a rudimentary
organ of phylogenetic significance, is later chiefly absorbed, although the proximal portion may
enter slightly into the formation of the intestinal wall. The amnion is a protective membrane,
while the chorion forms the foetal part of the placenta.
Development of the embryonic disc. — When first formed, the surface of the
embryonic disc shows no trace of differentiation. A slightly later but still
comparatively early stage in its development is shown in fig. 11. It is here
Fig. 11.- — Model Showing the Embryonic Disc from an Embryo 1.17 mm. In Length.
Viewed from above and laterally, the roof of the amniotic cavity having been removed, n,
primitive pit (neurenteric canal), pg, primitive groove, mg, neural groove, b, body-stalk.
(McMurrich. from Frassi.)
viewed from above, the amnion having been removed. The disc is an elliptical
plate, whose long axis represents the mid-line of the embryo. Near the center
is a small rounded depression, the primitive pit. Extending backward (toward the
tail end of the embryo) from this is a dark line, the 'primitive streak, corresponding
to a groove, the primitive groove. Extending forward from the primitive pit is an
indistinct wide shallow groove, the neural groove.
At an earlier stage, the primitive streak extends further forward, possibly to the anterior end
of the embryonic disc (Spee). The primitive streak and groove probably con-espond to the
TOPOGRAPHY OF THE EMBRYONIC DISC
11
fused lips of a primitive blastopore. They represent a centre of proliferation from which the
mesoderm is budded off from the ectoderm and spreads out to form the middle germ layer of the
embryonic disc.
At the anterior end of the primitive streak this proliferation extends forward as a plate of
cells, the so-called 'head process.' The axial portion of this process is the anlage of the rtoto-
chord, the embryonic skeletal axis. It contains a canal, which opens into the primitive pit.
The notochordal anlage soon fuses with the underlyiag endoderm, and its canal forms the
transient neurenteric canal.
In the mid-line anterior to the primitive streak there appears the shallow neural groove
(fig. 11), corresponding to a thickened plate of ectodermic cells, the neural plate. The neural
groove is slightly forked at its posterior extremity, in the region of the primiiive node (Hensen's
node), which forms the dorsal lip of the primitive pit. As development proceeds, the neural
plate extends posteriorly, and the primitive pit is accordingly shifted backward, the correspond-
ing part of the primitive groove being converted into 'head process.' The primitive streak thus
becomes progressively shortened (cf. figs. 11 and 13).
Fig. 12. — Topogkapht of the Embryonic Disc. Diagram op Relations at the Length
OF ABOUT 1 MM. ng, neural groove, pn, primitive node, pp, primitive pit. U, upper limb.
L, lower limb.
Topography of the embryonic disc. — Although only slight signs of differentia-
tion are visible in the embryonic disc at the stage shown in fig. 11, it is already
possible to map out more or less definite areas corresponding to all the various
regions of the future body, as shown in fig. 12.
Beginning anteriorly, the head region is relatively enormous in size, occupying at this
time the entire portion in front of the primitive pit and forming about half of the entire disc.
The cervical, thoracic, lumbar and sacro-coccygeal regions appear successively smaller, ap-
proaching the posterior end ('tail bud') of the primitive streak. It is also a striking fact
that the future dorsal region of the body wall, corresponding to the central portion of the disc,
along each side of the mid-line, is now larger than the ventro-lateral regions, which occupy a
relatively narrow area around the periphery of the disc.
12
MORPHOGENESIS
The topography of the germinal areas in the embryonic disc shown in fig. 12 is based partly
upon a study of the succeeding stages of development, and partly upon the results of experi-
ments upon the germinal disc in lower forms, especially in the chick (Assheton, Peebles, Kopsch).
Law of developmental direction. — In the relative size of the various embryonic
areas is foreshadowed what may be termed the law of direction in development.
In general it is found that development (including growth and differentiation) in
Fig. 13. — Human Embryo 1.54 mm. long. Viewed from above, the roof of the amniotic
cavity having been removed. (Minot, after Graf Spee.)
Neurenteric canal
Primitive groove
Body-stalk
Chorion with villi
the long axis of the body appears first in the head region and progresses toward
the tail region. Similarly in the transverse plane development begins in the
mid-dorsal region and progresses latero-ventrally (in the limbs, proximo-distally).
These principles are of great importance in morphogenesis.
Fig. 14. — Diagrams Showing the Constriction of the Embryo prom the Yolk-sac.
A and C, longitudinal sections; B and D, corresponding cross-sections. (McMurrich.)
The law of developmental direction is also probably of phylogenetic significance. The
cranio-caudal direction of development is in accordance with the theory that the head is the most
primitive portion of the body, and hence precocious in development. The trunk is perhaps a
secondary acquisition, hence arising as an extension of the primitive head region.
DERIVATION OF BODY TUBE FROM EMBRYONIC DISC 13
The dorso-ventral direction of development, together with the plate-hke form of the embry-
onic disc, has a different phylogenetio significance. Both are probably inherited from an ances-
tral type with a yolk-laden ovum. In such an ovum, with the meroblastic type of segmentatien,
the flattened embryonic disc gradually spreads from the dorsal surface in a ventral direction
around the underlying yolk-mass.
Derivation of body tube from embryonic disc. — ^The primary result of the
precocious growth in the dorsal region of the embryonic disc is the conversion of
the disc into the body tube, curved ventrally in its long axis (fig. 14).
Fig. 15. — ■Portion op Cross Section of the Embryo shown in Fig. 13. ch, notochord.
ct, somatic mesoderm, df, splanchnic mesoderm, g, junction of extra-embryonic somatic and
splanchnic mesoderm, ek, ectoderm, en, endoderm. me, embryonic mesoderm. /, neural
groove, p, beginning of embryonic coelom (pericardial cavity). (Minot, after Graf Spee.)
As a result of the more rapid expansion of the germ layers (especially the ectoderm) near
the mid-line, the dorsal surface of the embryonic disc in general becomes convex, with a depres-
sion laterally (where growth is less rapid) forming a groove at the line of attachment of the am-
nion (figs. 11,12, 13, 14 B). The unequal growth in the germ layers is clearly evident in the cross
section shown in fig. 15. By a continuation of this process, the margins of the embryonic disc
become still further depressed and finally folded in ventrally so as to transform the disc into a
tube (fig. 14 D). Similarly, by a more rapid expansion of the dorsal layer of the disc in the lon-
gitudinal axis, the head and tail ends of the disc are folded and tucked in ventrally, and the
primitive body tube is thus correspondingly curved in its long axis (figs. 14 A, 14 C).
Fig. 16. — Model op Human Embryo 1.8 mm. Long. Viewed from above, the roof of the
amniotic cavity having veen removed. Near the caudal end of the neural groove, the primitive
pit (opening of neurenteric canal) is visible. The primitive somites are appearing in the occip-
ital region, the fourth corresponding to the boundary between head and neck. (McMurrich,
from Keibel and Elze.)
The embryonic disc is thus converted into a tube composed of an outer layer of ectoderm,
a middle layer of mesoderm and an inner layer of endoderm. The yolk-sac now presents an
expanded yolk-vesicle fined by endoderm which is still continuous through the constricted yolk-
stalk with the endoderm lining the primitive enteric cavity (fig. 14 C). The enteric cavity (or
archenteron) has a bhnd tubular prolongation (fore gut) into the head region, and another (hind
gut) into the tail region. From the latter a slender diverticulum, the allantois, extends into the
body stalk (later the umbiUcal cord). The allantois is an organ of phylogenetic importance,
with which the urinary bladder is later connected.
Formation of the neural tube. — The principle of unequal growth applies to the
formation not only of the body as a whole, but also of its constituent parts.
Thus the anlage of the nervous system arises from the ectoderm as a wide groove
14 MORPHOGENESIS
whose edges (neural ridges) by local growth are folded upward so as to meet in
the mid-line where they fuse, thus transforming the groove into the neural tube
(fi*gs. 11, 12, 13, 15, 16, 17, 18).
The closure begins, not at the anterior end (as might be expected from the general law of
cranio-oaudal development), but in the cervical region, extending forward into the brain region,
and backward along the spinal cord. Thus the extreme ends (anterior and posterior neuropores)
are the last to close.
The precocious and energetic growth of the neural anlage is largely responsible for the ven-
tral flexure of the embryonic body axis, especially in the head region, where the flexures of the
brain are very conspicuous (figs. 22, 26).
With the closure of the neural tube dorsally and of the aUmentary canal ventraUy the human
embryo assumes the typical vertebrate form. The cyhndrioal body wall now encloses two tubes
(neural and enteric) with the longitudinal axis (notochord) between them (figs. 18, 24).
After the embryonic disc has been transformed into a tube, the body of the human embryo
in cross section appears not circular but elongated dorso-ventrally. This is the typical form for
vertebrates with horizontal body axis. In later foetal stages, the body becomes more rounded in
cross section, and finally, with the assumption of the erect posture in postnatal life, becomes
decidedly flattened dorso-ventrally (figs. 20, 21).
Fia. 17. — A HoMAN Embryo 2.5 mm. in Length. (After Kollmann.)
Mesodermic somite
Medullary canal
Development of the mesoderm. — The mesodermic layer on each side of the
notochord in the embryonic disc develops in two divisions. The medial (or
dorsal) divisions form a series of hollow segments, the somites (figs. 16, 17, 18).
The lateral (later ventral) divisions each spht into an upper (outer) or somatic layer
and a lower (inner) or visceral layer. When the embryonic disc becomes folded,
the corresponding somatic and visceral layers unite ventrally and enclose between
them the common cmlom or primitive body cavity (fig. 18).
(As previously noted, the mesoderm arises chiefly from the lateral portions of the 'head
process.' A comparatively early stage before the appearance of the somites is shown m cross
section in fig. 15. The somites appear first in the occipital region, and rapidly differentiate
successively in the cranio-oaudal direction (figs. 16, 17, 22). In embryos 7 or 8 mm. in length,
about 40 somites may be distinguished, 3 to 5 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral
and 5 or 6 coccygeal (in the rudimentary tail region).
The cmlom or body cavity is unsegmented. Two.primitive pericardial cavities appear sepa-
DEVELOPMENT OF THE SOMITES
15-
rate at first, but soon fuse and unite with the general coelom. Later the general ccelom becomes
secondarily divided into the permanent pericardial, pleural and peritoneal cavities.
The outer layer of the lateral mesodermic division forms the somatic or parietal layer of the
peritoneum, etc. The inner layer forms the visceral or splanchnic layer, and develops not only
the serous membrane, but also the muscular and connective tissue of the walls of the alimentarj'
canal and its derivatives.
Development of the somites. Metamerism. — The appearance of the somites
marks the beginning of nietdmerism, the arrangement of the body in successive
Fig. 18. — Diagram of a Cross Section op a Human Embryo.
Spinal cord
Mesodermic somite
Intermediate cell i
^'",,.
Ventral mesoderm, visceral layer
/^^'SlLl^V entral mesoderm,
somatic layer
segments or metameres. Each somite develops a primitive muscle segment,
myotome, and a skeletal segment, sclerotome (figs. 18, 19). Moreover, the cor-
responding nerves and .blood-vessels likewise assume a metameric arrangement.
This metamerism persists (more or less modified) in the adult neck and trunk.
The differentiation of the somites is illustrated by figs. 18 and 19. The medial wall of each
somite forms the sclerotome. Its cells migrate to form the corresponding vertebra, rib, etc., as
Fig. 19. — Diagrams Illustrating the History of the Mesoderm. M, myotome, dM,
dorsal portion of myotome. vM, ventral portion of myotome. SC, sclerotome, gr, genital
ridge. PFd, Wolffian duct. iSm, somatic layer of mesoderm, bto, visceral layer of mesoderm.
mr, membrana reuniens. I, intestine. A'', neural tube. (MoMurrich.)
well as the mesenchyme forming the various connective tissues in this region. The remainder of
the somite forms the myotome, from which the voluntary musculature of the trunk, the neck and
(in part) the head is derived. The dorsal portions of the myotomes develop the muscle in the
dorsal region of the trunk, while the ventral portions extend ventralward to form the muscula-
ture of the latero-ventral body walls (figs. 19, 20, 21, 23).
At the junction of the dorsal and ventral divisions of the mesoblast is a group ofJceUs called
the intermediate cell mass. This mass becomes segmented (corresponding to the somites) and
16
MORPHOGENESIS
each segment, or nephrotome, gives rise to a portion of tlie mesonephros, the provisional kidney.
Other cells of the mass become mesenchyme, which is converted into blood-vessels, connective
tissue, etc.
As development proceeds, the metamerism of the muscles and arteries becomes more or less
obscured, but that of the vertebrfe and nerves is fully retained even in the adult. In the case of
the muscle plates, from which all the voluntary musculature of the trunk is derived, great modi-
fications occur. Extensive fusion of successive plates occurs, the intervening connective tissue
disappearing more or less completely; associated with this fusion there is longitudinal and tan-
gential splitting of the somites to form individual muscles; and portions of some of the plates may
wander far from their original position. But notwithstanding these complicated changes, in-
dications of the primary metameric arrangement of the muscle plates are abundant, and even in
the most e.xtreme cases of modification the developmental history of a muscle can be determined
by means of its nerve supply. For the fibres derived from each plate will usually retain, up
matter what changes of independence or position they may undergo, the innervation by their
originally corresponding segmental nerve; so that the occurence in the lumbar region of the body
of muscle-fibres (the diaphragm) supplied by nerve-fibres from a cervical nerve is evidence that
the muscle-fibres have been derived from a cervical mesodermic somite and have subsequently
migrated to the position they finally occupy.
As regards the arteries, they arise primarily from a longitudinal stem, the aorta, in a strictly
segmental manner, each metamere having distributed to it two pairs of arteries and a single
median one (fig. 20). One pair of arteries supplies the body wall, and these retain very distinctly
their original metameric arrangement; the other pair passes to the paired viscera, such as the
lungs, kidneys, ovaries (or testes), so many of the pairs disappearing, however, that their meta-
meric arrangement is not very evident in the adult. The unpaired vessels supply the digestive
tract and its unpaired appendages, such as the liver and pancreas, and undergo great modifica-
tions, those of the lower thoracic and lumbar regions becoming reduced by fusion and degenera-
tion to three main trunks.
Fig. 20. — Diagram of a Transvehsb Section through the Abdominal Region.
DORSAL MUSCLES
, =99aiv
DORSAL MUSCLES
.\
HYPOSK.ELETAL
MUSCLE
VERTEBR.o,
X_/
— PERITONEUM
\ PARIETAL LAYER
X.
Branchiomerism. — Throughout the trunk and neck regions, then, a funda-
mental metameric plan underlies and determines the arrangement of many parts.
In the head there is also evident a primary arrangement of the parts in succession;
but this arrangement appears to be somewhat different from that of the trunk in
that it involves the ventral instead of the dorsal mesoderm and is associated with
the occurrence of branchial arches rather than with true mesodermic somites.
It is consequently termed branchiomerism.
Not but that there are also indications of metamerism in the head, the muscles of the orbit,
and the majority of the extrinsic muscles of the tongue, together with the nerves supplying
these muscles, being apparently metameric structures, but the metamerism of this region of the
body is largely overshadowed by the branchiomerism.
If an embryo of about the fifth week of development (fig. 22) be examined, there will be
observed on the surface of the body in the pharyngeal region three or four linear depressions,
DEVELOPMENT OF THE SOMITES
17
and sections will show that similar and corresponding grooves also occur upon the inner surface
of the pharyngeal wall. These are the branchial grooves, and since they are four in number
(with a rudimentary fifth) in the human embryo, they mark off five branchial (or visceral) arches,
the first of which hes between the oral depression and the first branchial groove, while the fifth
is situated behind the fourth groove. These branchial arches are so named because they repre-
sent the arches which (excepting the first) support the gills (branchise) in the lower vertebrates,
the grooves representing the branchial slits, even although they do not become perforated in
the human embryo.
Each branchiomere consists of an axial skeletal structure, of muscles which act on this skel-
eton, of a nerve which supphes the muscles and the neighbouring integument and mucous mem-
brane, and of an artery which carries blood to all these structures. The arches, however, do
npt in the human embryo retain their original branchial function, but undergo extensive modi-
fications, becoming adapted to various functions and showing less in the adult of their originally
simple arrangement than do the metameres. Nevertheless no matter what modifications the
musculature of any arch may undergo, it will retain its original innervation and, to a large
extent, its relations to the skeletal elements of its arch; and even the arteries in their distribu-
tion show clear indications of being arranged in correspondence to the various arches.
Fig. 21. — Diagram of a Transverse Section through the Thoracic Region.
(The pleura is represented in blue and the pericardium in red.)
With respect to the fate of the various structures pertaining to each branchial arch, their
general arrangement in the adult body may be stated in the following table: —
Arch
Relations of the Branchial Arches in the Adult
Skeleton Muscles
First arch Mandible, malleus and
' incus.
Second arch Hyoid (lesser cornu),
I styloid process and
stapes.
Third arch ! Hyoid (greater cornu), .
Masticatory, mylohoid and di-
gastric (ant.), tensor tympani.
Stylohyoid, digastric (post.),
muscles of expression, stape-
dius.
Pharyngeal
Nerve
Trigeminus.
Facialis.
Glossopharyn-
geus.
Fourth and fifth Thyreoid cartilage ; Pharyngeal and laryngeal 1 Vagus.
arches. ! ,
» Branchial grooves. — Of the external branchial grooves, the first (lying between mandibular
and hyoid arches) becomes deepened to form the external auditory meatus, the margins becom-
ing elevated to form the auricle (fig. 26). The region corresponding to the second, third and
fourth external grooves becomes depressed, forming the sinus cervicalis, which soon closes up
and disappears.
The internal branchial grooves or pouches communicate with the pharjTigeal cavity and are
18
MORPHOGENESIS
lined with endoderm. The first internal groove becomes transformed into the auditory (Eu-
stachian) lube, tympanic cavity, etc. The second internal groove persists in part as the fossa of
the palatine tonsil. The third and fourth grooves are probably represented in part by the
vallecula and recessus piriformis, detached portions of their lining endoderm giving rise to the
thymus, parathyreoid glands, etc. The rudimentary fifth groove is said to give rise to the
ultimobranchial body, a structure of uncertain significance (fig. 27).
Development of the face, — -The facial region is at first relatively small. It includes the
sense organs (eye, ear, nose) and mouth region. Some of the more important developmental
features may be briefly mentioned. In an embryo of the sixth week (fig. 28) the wide mouth
aperture is seen to be bounded below (posteriorly) by the lower (mandibular) portion of the
Fig. 22. — Htjman Embryo of 4.2 mm., Showing Three Branchial Grooves.
(After His.)
tory vesicle
Branchial grooves
Mesodermic somite
first arch, laterally^by the upper (maxillary) process of the first arch. Above it is bounded by a
median plate, the nasal process, which on either side forms a protuberance, the globular process.
Lateral to the globular process is a rounded depression, the nasal pit. The maxillary process
extends forward and fuses with the globular process to form the upper jaw region (failure to
unite resulting in the malformation known as 'hare-lip'). The nose is at first broad, due to
the width of the nasal process, which later becomes the nasal septum (fig. 29). The nasal pits
deepen and later acquire openings into the primitive mouth cavity.
The viscera. — The structures so far considered belong, for the most part, to
the body wall; it remains to consider the general plan of arrangement of the
viscera. It has been pointed out that the body may be regarded as a cylinder
enclosing two tubes, one of which constitutes the central nervous system and the
THE VISCERA
19
other the digestive tract. The latter may be regarded as being primarily a
straight tube traversing lengthwise the body cavity enclosed by the body wall
(figs. 18, 20). The layers of both the visceral and somatic plates which im-
FiG. 23. — Sagittal Section Showing the Primitive Pericardial and Ccelomic Com-
munication, Septum Transversum, Liver, etc., in a Human Embryo op 3 mm. (After
KoUmann, from a model by His.)
Truncus aortse
_ Mesocardium posterius
Pericardial cavity .
Anterior wall of
pericardium
Septum transversum and floor
of pericardium
Venous trunk of the heart
Mesocardium laterale
Ductus Cuvieri
v. umbilicalis
v. omphalo-mesenterica
Ccelomic communication
Peritoneal cavity
mediately enclose the body cavity become transformed into a characteristic
pleuro-peritoneal membrane. Near the mid-dorsal line, a vertical double plate
of peritoneum extends ventrally connecting the somatic (parietal) and visceral
layers of peritoneum, and constituting what is termed the mesentery (fig. 20).
Fig. 24. — Diagram Illustrating the Recession of the JDiaphragm (Septum Trans-
versum) IN the Human Embryo. On the right are indicated the vertebral levels; on the
left, the position of the septum transversum in a series of embryos from 2 mm. (XII) to
24 mm. (VI) in length, pp, pleuro-peritoneal cavity. (Mall.)
'MtJuJ^
_ As development proceeds the digestive tract grows in length more rapidly than the cavity
which contains it, and so gradually becomes thrown into numerous coils in the abdominal
region, these changes leading to numerous modifications of the original arrangement of the mes-
entery. These will be described later on in the section on the digestive system. Several out-
growths also arise from the primitive digestive tract, to form important organs, such as the lungs,
20
MORPHOGENESIS
the liver, the pancreas and the urinary bladder; and, with the exception of the bladder, each
of^these becomes completely invested by primitive peritoneum. In the case of the liver this
original condition is practically retained, but the investment of the pancreas later becomes a
partial one on account of the modifications which ensue in the mesentery. The bladder has
only a portion of its surface in contact with the peritoneum, but the investment of the lungs
remains complete, each lung, indeed, appropriating to itself the entire visceral layer' of its half
of the thorax, with the exception of a small ventral portion which forms the investment of the
heart. Furthermore, the cavities which surround each of the three organs named, the two lungs
and the heart, become completely separated from one another; and since each investment con-
sists of a visceral and a parietal layer, each of the organs is enclosed within a double-waUed
sac, which in the case of each lung forms its pleura, while that of the heart is known as the
pericardium. The spaces which occur within the thorax between the pleurte of the two sides
are known as the mediastina, which include the heart, oesophagus, etc. (fig 21).
Tn addition to the viscera mentioned there are some organs, such as the spleen and genito-
urinary organs, which are developments of the mesoderm, the spleen arising in the mesentery
which passes to the stomach and the genito-urinary organs primarily from the intermediate
cell mass. The morphogeny of these structures and also of the vascular system, nervous system,
and sense organs will be considered later in connection with their structure.
Fig. 25. — Diagram op a Cross Section of the Embetonic Body and Limb. (McMurrich,
after Kollman.)
Dorsal (posterior) division of
spinal nerre
Ventral (anterior) division of
spinal nerve
Dorsal limb mus-
culature
Peritoneal cavity -
Recession of the diaphragm and heart. — In the early stages of development
the heart is situated far forward, in what will eventually be the pharyngeal
region (figs. 12, 17). Just behind (caudal to) the heart, between it and the yolk-
sac, is a plate of connective tissue, the septum transversum, which serves for the
passage of large veins from the body wall to the heart (figs. 17, 23). This septum
together with certain accessory structures eventually gives rise to the diaphragm,
which becomes a complete partition separating the thoracic and abdominal por-
tions of the body cavity.
The diaphragm and heart are therefore originally situated far above (cranial to) their
final position and recede in the course of development, producing an elongation of the vessels
and nerves associated with them and forcing downward such organs as the stomach and liver
(fig. 24). The chief factor in this displacement is probably the ventral head flexion and the
precocious growth and expansion of the organs in the head region. The effects of this recession
are especially noticeable in the nerves, these passing to the various organs concerned arising
from a much higher level than that occupied by the organs. The nerve to the diaphragm, for
instance, comes from the fourth cervical segment, those passing to the cardiac and pulmonary
plexuses from the cervical region, and those to the plexus in relation with the stomach, liver
and adjacent organs from the thoracic region. The blood-vessels, however, may shift their
origins from the main trunks by successive anastomotic roots, so that in general they keep pace
with the viscera in the migration caudalward.
The limbs. — Each limb at its first appearance (fig. 22) is a flat, plate-like
outgrowth from the side of the body, and consists of an axial mass (blastema) of
mesodermic tissue from which the limb skeleton will develop, and, surrounding
this, a layer, also of mesodermic tissue, from which the muscles and blood-vessels
will arise. It is as yet uncertain whether the muscle blastema is derived from the
myotomes (as in lower vertebrates) or whether it develops from the mesenchyme.
THE LIMBS
21
Fig. 26.
-Lateral View of a Human Embryo 18 mm. Long, Showing the Development op
THE Extremities. M, mandibular arch.
Fig. 27. — Diagram to Show the Derivatives op the Branchial Clefts. le, lie, Ille,
IVe, Ve, external branchial grooves, li, Hi, llli, IVi, Yi, internal branchial grooves. Tons.,
palatine tonsil. Ep III, Ep IV, epithelial bodies. Ub, ultimobranchial body. Th.^ 'thyreoid
D.th. gl., ductus thyreoglossus. (Modified rom Keibel and Mall.)
Ub. ^_^
Thymus
22
MORPHOGENESIS
As the muscles become differentiated, nerves grow to ttiem from a definite
number of spinal segments (fig. 25).
At first each limb plate is so placed that one of its surfaces looks dorsally and the other ven-
trally, and one border (that corresponding to the thumb or great toe) is anterior (i. e., cranial)
and the other posterior (caudal). Later, however, each limb becomes bent caudally through
about ninety degrees, so that the limbs whose long axes were at first at right angles to the long
axis of the body come to he parallel to that axis. In addition there occurs a rotation of each
fore-limb in such a manner that the thumb turns latero-dorsally, while in the lower Umb the
direction of the movement is exactly the opposite, the great toe turning ventro-medially. As
a result there is an apparent reversal of the surfaces in the two limbs, the flexor muscles of the
arm reaching on the surface which is directed anteriorly, while in the lower limb the corre-
sponding muscles occupy the posterior surface. The dorsum of the foot and the great toe side
correspond respectively to the back and thumb side of the hand, the tibia corresponds to the
radius and the fibula to the ulna. The limb anlage soon becomes divided into three primary
segments. The distal segment (hand or foot) is a flattened rounded disc, in which the digits
soon appear (fig. 26). The proximal portion forms the forearm or leg and the arm or thigh.
In general, the extremities follow the law of cranio-caudal and dorso-ventral (proximo-distal)
development.
Fig. 28A. — Face of Human Embryo of
ABOUT 8 MM. (His.)
"^Tasal fossa
Lateral nasal process
^lobular process
Maxillary process
Mandibular process
Fig. 28B. — Face of Human Embryo
AT Stage Slightly Later than 28A.
(After Kallius.)
Nasal fossa
Lateral nasal
process
Globular process
Maxillary process
Prenatal Growth in Length and Weight
Age in
lunar
Crown-rump or
sitting height
Crown-heel or
standing height
Weight at end of
month, grams
Ratio of increase
to weight at be-
months
(Mall), cm.
(Mall), cm.
ginning of month
0
(diameter of ovum
= 0.2 mm.)
(Ovum = 0.000004 g.)
I
0.25
0.25
0.004
999.0
II
2.5
3.0
2.0
499.0
III
6.8
9.8
24.0
11.0
IV
12.1
18.0
120.0
4.0
V
16.7
25.0
330.0
1.75
VI
21.0
31.5
600.0
0.82
VII
24.5
37.1
1000.0
0.67
VIII
28.4
42.5
1600.0
O.BO
IX
31.6
47.0
2400.0
0.50
*x
33.6
50.0
3200.0
0.33
Prenatal growth. — The prenatal growth of the human body in length and weight is indi-
cated in the preceding table. According to Hasse, the age of the foetus may be estimated from
its total length as follows. Before the fifth month, the square of the age in (lunar) months gives
the length in centimetres. After this, the age in months multiphed by five gives the length.
This gives approximate results, except for the first month.
While the growth in absolute weight increases from month to month, it is important to note
that the real (relative) growth rate rapidly diminishes. The ovum increases in weight during
the first month about 1000 times, or 100,000 per cent, (not including the extra-embryonic
structures). This rate diminishes rapidly, however, so that the increase during the last foetal
month is only about 33 per cent.
The continuation of growth in length and weight during the postnatal period is shown in
the following chart (fig. 30).
The following chart is based upon data from Camerer (1-5 yrs.). Porter (6-17 yrs.), and
Roberts (18-20 yrs.), showing the average postnatal growth in height and weight by sexes.
The average height at birth is about 50 cm. (20 inches) ; weight, about 3200 g. (7 pounds). The
male is slightly heavier and taller than the female, except during the acceleration at the period
* 270 days (Mall).
PRENATAL GROWTH
23
Fig. 29. — Face op a Human Embryo after Completion of the Upper Jaw. (McMurrich
from His.)
Fig. 30. — Chart Showing Average Postnatal Growth in Height and Weight.
^
^
-X-
^'
Heig
tit in
Cen
timet
ers
•
;^
Male
F<
male
,.-«*'
^
J'*^
^
^
/
■"^
<^
^'
/
....
y^'
****
A
^j
-''
V
^
>{^
/'
J
/'
,''
/
,
f
,''^
y
/
_y
^
«>
/
^
^
i^'
\
k^eig-}
it ii
iKik
igrai
IS
<<'
'i^'
r
Male
Fe
nale
g-".
<i^-
^
J"
-i^
/
r
8 9 10 II 12 13 W 15 16 17
"Years of age
24
MORPHOGENESIS
of puberty. Puberty occurs earlier in the female, so that between the ages of 12 and 15 the
girls exceed the boys in average height and weight. With the exception of this period of accel-
eration, the (relative) growth rate in general diminishes steadily from birth, and has practically
ceased at 20 years. The average height at this time is about 160 cm. (5 ft., 3 in.) in the female,
and 170 cm. (5 ft., 7 in.) in the male; average weight, about 56 kilograms (126 lbs.) in the female,
and 65 kilograms (146 lbs.) in the male. Under favourable conditions, growth in height may con-
tinue slowly up to about 25 years, and in weight even longer; but in old age there is a slight
decrease in both height and weight.
The following measurements (from Holt, "Diseases of Infancy and Childhood"
may be taken as a normal average standard of growth during the first three
years. The weights are taken without clothing. The height is taken by plac-
ing the baby on a perfectly flat surface like a table, and having some one hold
the child's knee down so that he hes out straight, then taking a tape-measure
and measuring from the top of his head to the bottom of his foot, holding the
tape line absolutely straight. The chest is measured by means of a tape line
passed directly over the nipples around the child's body and midway between
full inspiration and full expiration. The head measurement is taken directly
around the circumference of the head, over the forehead and occipital bone.
Weight,
pounds
Height,
inches
Chest,
inches
Head,
inches
Birth ;
6 months . .
12 months .
18 months .
2 Years . . .
3 Years . . .
7.56
7.16
16.0
15.5
20.5
19.8
22.8
22.0
26.5
25.5
31.2
30.0
20.6
20.5
25.4
25.0
29.0
28.7
30.0
29.7
32.5
32.5
35.0
35.0
13.4
13.0
16.5
16.1
18.0
17.4
18.5
18.0
19.0
18.5
20.1
19.8
13.9
13.5
17.0
16.6
18.0
17.6
18.5
18.0
18.9
18.6
19.3
19.0
Relative growth of the parts. — The growth of the body is not uniform in the
various parts, and changes in proportions therefore occur during development, as
Fig. 31. — Figures Illustrating the Changes in Proportion During Prenatal and
Postnatal Growth. (Stratz.)
shown in fig. 31. It will be noted that the changes are in accordance with the
law of developmental direction previously explained, the growth impulse passing
along the body in a cranio-caudal direction.
The head is therefore largest in the earlier stages, forming about half the body, decreasing
to 25 per cent, in the newborn, and to 7 or 8 per cent, of the body in the adult. The upper
limbs increase to about 10 per cent, of the body at birth, maintaining thereafter about the same
relative size. The trunk as a whole remains of about the same relative size (about 45 per cent.).
VARIABILITY 25
although the thoracic portion reaches its maximum in the earher stages, and the pelvic portion
not until adult life. The loiver limbs, Uke the pelvis, develop slowly, forming about 20 per cent,
of the body at birth and reaching 35 per cent, in the adult.
Relative growth of the systems. — There is also a marked difference in the relative growth
of the various systems. Data for the skin and skeleton are somewhat scanty and unsatis-
factory. The musculature, however, is relatively small in the embryo, increasing to about 25
per cent, of the body in the newborn, and to 40 or 45 per cent, in the adult. The visceral group
(including brain and spinal cord), on the other hand, is relatively largest in the early embryo,
decreasing from about 35 per cent, of the body to about 24 per cent, in the newborn and to about
10 per cent, in the adult.
Relative growth of the organs. — While in general, the individual organs follow the course
of relative growth of the visceral group, each organ has its own characteristic course of growth.
As a rule, after its appearance in the embryo, each organ increases more or less rapidly to its
maximum relative size, after which, although increasing in absolute size, it decreases in relative
size through subsequent prenatal and postnatal life up to the adult.
Thus the brain in the embryo of the second month forms more than 20 per cent, of the body,
but steadily declines to about 13 or 14 per cent, in the newborn, and about 2 per cent, in the
adult. The spinal cord and eyeballs have a similar course of growth. The heai-t declines from
about 5 per cent, of the body in the embryo of the second month to about .75 per cent, in the
newborn and .46 per cent, in the adult. The liver decreases from a maximum of nearly 10 per
cent, in the thh-d month to 5 per cent, in the newborn and 2.7 per cent in the adult. The supra-
renal glands decrease from about .46 per cent, of the body in the third month to .23 per cent,
in the newborn and .01 per cent, in the adult. The lungs decrease from 3.3 per cent, in the
fourth month to about 2 per cent, of the body at birth and 1 per cent, (bloodless weight) in
the adult. The kidneys reach a maximum of about 1 per cent, of the body toward the end of the-
fcetal period, decreasing to about .46 per cent, in the adult. The thymus, thyroid, spleen and
alimentary canal likewise reach their maximum slowly, being probably relatively largest about
the time of birth. The ovary and testis, however, appear to be relatively largest during the
prenatal period.
Variability. — It must be borne in mind that all statements concerning struc-
ture refer to the average or norin, and are always subject to variation. This is.
therefore a topic of importance to students of anatomy. Variations are classified
as either germinal or somatic.
Germinal variations are due to fundamental differences in the germ plasm, and are trans-
mitted by heredity. These include many of the characters whereby one individual differs from
another. Variations according to sex are included under this class. Variations inherited from,
more or less remote ancestors are termed atavistic or reversional.
Somatic variations, or 'acquired characters,' are due to environmental influences, such
as nutrition, temperature, shelter, disease, training, etc. While somatic variations may be
very great, they do not affect the germ plasm and are not transmitted by heredity.
In many cases it is exceedingly difficult to distinguish germinal from somatic variations
Size, for example, may be due to either or both. Moreover, somatic variations may be pro-
duced at any time after the fertilisation of the ovum. Very slight environmental changes are
sometimes sufficient to produce a marked effect upon the dehcately balanced mechanism of
the developing embryo. Malformations and pathological conditions are thus often to be
explained. As to the extent of variability, some characters are much more variable than others.
Height, for exahiple, is less variable than weight. Moreover, variability differs in the various
parts and organs. In general, the head and head organs are less variable than the remainder
of the body. The skeleton and musculature appear less variable than the integument and
viscera.
Details concerning variations and methods for their measurement may be found in works
on genetics and biometrical statistics.
'Reieiences.—Embnjology: Keibel and Mall, Human Embryology (2 vols.);
Bryce, Quain's Anatomy, 11th ed., vol. 1 ; Minot, Laboratory Text-book of Embry-
ology; McMurrich, Development of the Human Body. Growth: Minot, Age,
Growth, and Death; Jackson, Amer. Jour. Anat., vol. 9; Anat. Record, vol. 3.
Heredity: Davenport, Heredity and Eugenics; Walter, Genetics. Biometry:
Davenport, Statistical Methods; Yule, Theory of Statistics.
I
S E C T I O N 1 1
OSTEOLOGY
Revised for the Fifth Edition
By peter THOMPSON, M.D.,
PROFESSOR OF ANATOMY IN THE UNIVEIlSITr OF BIRMINQHAM; EXAMINER IN ANATOMY, THE HNIVERSITY
[^CAMBRIDGE; FORMERLY EXAMINER IN ANATOMY FOR THE UNIVERSITIES OF LOMDON, ABERDEEN, MANC
DUBLIN AND FOR THE CONJOINT BOARD OF ENGLAND
i
THE SKELETON
THE skeleton forms the solid framework of the body, and is composed of
bones, and in certain parts, of pieces of cartilage. The various bones and
cartilages are united by means of ligaments, and are so arranged as to
give the body definite shape, protect from injury the more important delicate
organs, and afford attachment to the muscles by which the various movements are
accomplished.
In its widest acceptance, the term skeleton includes all parts of the framework, whether
internal or external, and as in many of the lower animals there are, in addition to the deeper
osseous parts, hardened structures associated with the integument, it is convenient to refer to
the two groups as endoskeleton and exoskeleton or dermal skeleton, respectively. All verte-
brate— i. e., back-boned — animals ])o,sscss an endoskeleton, and many of them a well-developed
exoskeleton also, but in maniiiials, the highest group of vertebrates, the external skeleton, when
it exists, plays a relatively subordinate part. In most of the invertebrates the endoskeleton is
absent and the dermal skeleton alone is found.
In man by far the greater part of the endoskeleton is formed of bone, a tissue of definite
chemical composition, being formed mainly of a gelatine basis strongly impregnated with lime
salts.
The number of bones in the skeleton varies at different ages, some, which are
originally quite independent, becoming united as age advances. They are ar-
ranged in an axial set, which includes the vertebral column, the skull, the ribs,
and the sternum, and an appendicular set, belonging to the limbs. The following
table shows the number of bones usually distinct in middle Hfe, excluding the
auditory ossicles: —
Bones.
. . , f The vertebral column 26
™' , , The skull 23
bueieton ^ r^j^^ ^.-^^^ ^^^ sternum 25
Appendicular / The upper Umbs 64
Skeleton \ The lower limbs 62
Total 200
Several of the skull bones are compound, i. e., in the immature skeleton they consist of
separate elements which ultimately unite to form a single bone. In order to comprehend the
nature of such bones it is advantageous to study them in the various stages through which
they pass in the process of development in the foetus and the cliild.'
It follows, therefore, that to appreciate the morphology of the skeleton — i. e., the history
of the osteological units of which it is composed — the osteogenesis or mode of development of
the bones must be studied, as well as their topography or position.
Some bones arise by ossification in membrane, others in cartilage. In the embryo, many
portions of the skeleton are represented by cartilage which may become infiltrated by lime salts
— calcification. This earthy material is taken up and redeposited in a regular manner-
ossification. Portions of the original cartilage persist at the articular ends of bones, and, in
27
I
28 THE SKELETON
young bones, at the epiphysial lines, i. e., the lines of junction of the main part of a bone with the
extremities or epiphyses. Long bones increase in length at the epiphysial cartilages, and increase
in thickness by ossification of the deeper layers of the investing membrane or periosteum.
These processes — intracartilaginous and intramembranous ossification — proceed concurrently
in the limb-bones of a young and growing mammal.
There is no bone in the human skeleton which, though pre-formed in cartilage, is perfected
in this tissue. The ossification is completed in membrane. On the other hand, there are nu-
merous instances in the skull, of bones the ossification of which begins in, and is perfected by, the
intramembranous method. Ossification in a few instances commences in membrane, but later
invades tracts of cartilage; occasionally the process begins in the perichondrium and remains
restricted to it, never invading the underlying cartilage, which gradually disappears as the result
of continued pressure exerted upon it by the growing bone. The vomer and nasal bones are
the best examples of this mode of development. Further details of development and ossification
are included in the description of each bone.
The limb-bones differ in several important particulars from those of the skull. Some of
the long bones have many centres of ossification, but these have not the same significance as
those of the skull. It is convenient to group the centres into two sets, primary and secondary.
The primary nucleus of a long bone appears quite early in f cetal life, and the main part (shaft)
thus formed is called the diaphysis. In only three instances does a secondary centre appear
before birth, e. g., the lower end of the femur, the head of the tibia, and occasionally the head of
the humerus. Many primary ossific nuclei appear after birth, e. g., those for the carpal bones, the
cuneiform and navicular bones of the foot, the coracoid process of the scapula, and for the third,
fourth, and fifth pieces of the sternum.
When a bone ossifies from one nucleus only, this nucleus may appear before or after birth.
Examples: the talus (astragalus) at the seventh month of foetal life, and the lesser multangular
(trapezoid) at the eighth year. When a bone possesses one or more secondary centres, the pri-
mary nucleus, as a rule, appears early. Examples: the femur, humerus, phalanges, and the
calcaneus.
Secondary centres which remain for a time distinct from the main portion of a bone are
termed epiphyses. An epiphysis may arise from a single nucleus, as is the case at the lower end
of the femur, or from several, as at the upper end of the humerus. Prominences about the ends
of long bones may be capped by separate epiphyses, as illustrated at the upper end of the femur.
According to Professor F. G. Parsons, there are at least three kinds of epiphyses: — (1)
Those which appear at the articular ends of long bones, which, since they transmit the weight
of the body from bone to bone, may be termed pressure epiphyses. (2) Those which appear as
knob-like processes, where important muscles are attached to bones; and as these are concerned
with the pull of muscles, they may be described as traction epiphyses. (3) The third kind
includes those epiphyses which represent parts of the skeleton at one time of functional import-
ance but which, having lost their function, have now become fused with neighbouring bones and
only appear as separate ossifications in early life. These may be termed atavistic epiphyses
and include such epiphyses as the tuberosity of the ischium, the representative of the
hypoischium of reptiles.
The epiphyses of bones seem to follow certain rules, thus: —
1. Those epiphyses whose centres of ossification appear last are the first to unite with the
shaft. There is one exception, however, to this statement, viz., the upper end of the fibula,
which is the last to unite with the shaft, although its centre appears two years after that for the
lower end. This may perhaps be accounted for by the rudimentary nature of the proximal end
of the fibula in man and many other mammals.
2. The epiphysis toward which the nutrient artery is directed is the first to be united with
the shaft. It is also found that while the increase in length of the long bones takes place at the
epiphysiai cartilages, the growth takes place more rapidly and is continued for a longer period at
the end where the epiphysis is the last to unite. It follows, therefore, that the shifting of the
investing periosteum, which results from these two factors, leads to obliquity of the vascular
canal by drawing the proximal portion of the nutrient artery toward the more rapidly growing
end. Moreover, when a bone has only one epiphysis, the nutrient artery will be directed toward
the extremity which has no epiphysis.
3. The centres of ossification appear earliest in those epiphyses which bear the largest
relative proportion to the shafts of the bones to which they belong.
4. When an epiphysis ossifies from more than one centre, the various nuclei coalesce before
the shaft and epiphysis consolidate, e. g., the upper end of the humerus.
On section, the shaft of a f cetal long bone is seen to be occupied by red marrow lodged in
bony cells which do not present any definite arrangement. In an adult the central portion of
the shaft is filled with fat or marrow held together by a deUcate reticulum of connective tissue,
whence the space is known as the medullary cavity. The expanded ends of the bones contain a
network of cancellous tissue, the intervals being filled with red marrow. This cancellous tissue
differs from that of the foetal bone in being arranged in a definite manner according to the direc-
tion of pressure exerted by the weight of the body, and the tension produced by the muscles.
The arrangement of the cancelli in consequence of the mechanical conditions to which bones are
subject is noticed in the description of a vertebra, the femur, and the humerus.
Bones are divisible into four classes: — long, short, flat, and irregular. The long bones,
found chiefly in the limbs, form a system of levers sustaining the weight of the trunk and provid-
ing the means of locomotion. The short bones, illustrated by those of the carpus and tarsus,
are found mainly where compactness, elasticity, and Umited motion are the principal require-
ments. Flat bones confer protection or provide broad surfaces for muscular attachment, as
in the case of the cranial bones and the shoulder-blade. Lastly, the irregular or mixed bones
constitute a group of peculiar form, often very complex, which cannot be included under either
of the preceding heads. These are the vertebrae, sacrum, coccyx, and many of the bones of the
skull.
THE VERTEBRAL COLUMN
29
The shafts ot long bones at the time of birth are mainly cylindrical and free from ridges.
The majority of the lines and ridges so conspicuous on the shafts of long bones in adults are due
to the ossification of muscle-attachments. The more developed the muscles, the better marked
the ridges become.
The surfaces of bones are variously modified by environing conditions. Pressure at the
•extremities causes enlargement, and movement renders them smooth. The two causes combined
produce an articular surface. When rounded and supported upon a constricted portion of bone,
-an articular surface is termed a head, sometimes a condyle ; when depressed, a glenoid fossa.
Blunt, non-articular processes are called tuberosities; smaller ones, tubercles; sharp projections,
spines. Slightly elevated ridges of bones are crests; when narrow and pronounced, lines and
Fig. 32. — The Tibia and Fibula in Section to show the Epiphyses.
Centre of ossification of epiphysis
Epiphysial line
i
Shaft of fibula
Shaft of tibia in section
Epiphysis of tibia
{J_ Epiphysis of fibula
"borders. A shallow depression is a fossa; when narrow and deep, a groove; a perforation is
usually called a foramen.
In addition to these, other terms are employed which do not require any e.xplanation, such
as canal, notch or incisura, sulcus or furrow, and the like.
/. THE AXIAL SKELETON
A. THE VERTEBRAL COLUMN
The vertebral column [columna vertebralis] consists of a series of bones called
vertebrae, closely connected by means of fibrous and elastic structures, which
allow of a certain but limited amount' of motion between them. In the young
30 THE SKELETON
subject the vertebrse are thirty-three in number. Of these, the upper twenty-
four remain separate throughout life, and are distinguished as movable or true
vertebrae. The succeeding five vertebrae become consolidated in the adult to form
one mass, called the sacrum, and at the terminal part of the column are four rudi-
mentary vertebrae, which also tend to become united as age advances, to form the
coccyx. The lower nine vertebrae thus lose their mobihty as individual bones,
and are accordingly known as the fixed or false vertebrae. Of the true vertebrae,
the first seven are called cervical [cervicales], the succeeding twelve thoracic
[thoracales] or dorsal, and the remaining five lumbar [lumbales].
Although the vertebrae of the different regions of the coliunn differ markedly
in many respects, each vertebra is constructed on a common plan, which is more
or less modified in different regions to meet special requirements. The essential
characters are well seen in the vertebrae near the middle of the thoracic region, and
it will be advantageous to commence the study of the vertebral structures with
one selected from this region.
Description of a thoracic vertebra (figs. 33, 34). — The vertebra consists of two
essential parts — a body in front and an arch behind.
Fia. 33. — -A Thoracic Vertebra. (Side view.)
Superior costal pit for head of i
Superior articular process
Pedicle (root of
Transverse process
Inferior costal pit for
head of rib
Inferior articular process
-Spinous process
The body [corpus vertebrae] or centrum is a soUd disc of bone, somewhat
heart-shaped, deeper behind than in front, slightly concave on its superior and in-
ferior surfaces, and wider transversely than antero-posteriorly. The upper and
lower surfaces are rough' for the intervertebral discs which are interposed between
the bodies of the vertebrae, and the margins are slightly lipped. The circum-
ference of the body is concave from above downward in front, convex fron side to
side, and perforated by numerous vascular foramina. Posteriorly it is concave
from side to side and presents one or two large foramina for the exit of veins from
the cancellous tissue. On each side of the body, at the place where it joins the
arch, are two costal pits (superior and inferior) [fovea costalis superior; inferior]
placed at the upper and lower borders, and when two vertebrae are superimposed,
the adjacent costal pits form a complete articular pit for the head of a rib. The
superior and inferior costal pits were formerly designated as " demi-f acets. "
The arch [arcus vertebrae] is formed by two pedicles and two laminae, and
supports seven processes — one spinous, two transverse, and four articular. The
pedicles or roots of the vertebral arch [radices arcus vertebrae] are two short, con-
stricted columns of bone, projecting horizontally backward from the posterior sur-
face of the body. The concavities on the upper and lower borders of each pedicle,
of which the lower is much the deeper, are named vertebral notches [incisurae], and
when two vertebrae are in position, the notches are converted into intervertebral
foramina for the transmission of the spinal nerves and blood-vessels.
The laminae are two broad plates of bone which connect the spinous process
with the roots (pedicles) and complete the arch posteriorly. The superior border
and the lower part of the anterior surface of each lamina is rough for the insertion of
the ligamenta flava. The upper part of the anterior surface is smooth where it
forms the posterior boundary of the vertebral canal. When articulated, the
THE CERVICAL VERTEBRA 31
laminse in the thoracic region are imbricated or sloped, one pair over the other,
somewhat like tiles on a roof.
The spinous process [processus spinosus], long and three-sided, projects back-
ward and downward from the centre of the arch and terminates in a slight tubercle.
It gives attachment by its prominent borders to the interspinous ligaments and by
its free extremity to the supraspinous ligament. It serves mainly as a process for
muscular attachment.
The transverse processes [processus transversus] are two in number and extend
laterally from the arch at the junction of the pedicles and laminse. They are long,
thick, backwardly directed columns of bone terminating in a clubbed extremity,
on each of which is a costal pit for articulation with the tubercle of a rib. The
transverse processes, in addition to supporting the ribs, afford powerful leverage
to muscles.
The articular processes, two superior and two inferior, project upward and
downward opposite the attachments of the transverse processes. The superior
are flat and bear facets or surfaces [facies articulares superiores] which are directed
Fig. 34. — A Thoracic Vertebra.
Lamina
Costal pit for tubercle of rib
i
Pedicle (root of arch)
Costal pit for head of rib
Transverse process
upward, backward, and laterally, and are situated a little in advance of the inferior,
the facets of which [facies articulares inferiores] are oval, concave, and directed
downward, forward, and medially.
The vertebral foramen is bounded anteriorly by the body, posteriorly and on
each side by the arch. It is nearly circular, and is smaller than in the cervical or
the lumbar region. When the vertebrae are articulated, the series of rings con-
stitute the spinal or vertebral canal [canalis vertebralis],^in which is lodged the
spinal cord.
THE CERVICAL VERTEBRA
A typical cervical vertebra (from the third to the sixth inclusive) presents the
following characteristics (fig. 35) : — The body is smaller than in other regions of
the column and is of oval shape with the long axis transverse. The lateral mar-
gins of the upper surface are raised into prominent lips, so that the surface is
concave from side to side; it is also sloped downward in front. The inferior sur-
face, on the contrary, projects downward in front and is rounded off at the sides
to receive the corresponding lips of the adjacent vertebra. It is concave antero-
posteriorly and convex in an opposite direction.
The roots (pedicles) are directed laterally and backward and spring from the
body about midway between the upper and lower borders. The superior and
inferior notches are nearly equal in depth, but the inferior are usually somewhat
deeper. The laminse are long, narrow, and slender. The spinous process is
short and bifid at the free extremity.
32
THE SKELETON
Articular processes. — Both the superior and inferior articular processes are
situated at the junction of the root with the lamina and they form the upper and
lower extremities of a small column of bone. The articular surfaces are oblique
and nearly flat, the superior looking backward and upward, and the inferior
forward and downward.
The transverse process presents near its base a round costo-transverse foramen
[foramen transversarium] for the transmission of the vertebral artery, vein, and a
plexus of sympathetic nerves. Moreover, each process is deeply grooved above
for a spinal nerve, and is bifid at its free extremity, terminating in two tubercles —
anterior and posterior. The costo-transverse foramen is very characteristic of a
cervical vertebra. It is bounded medially by the pedicle, posteriorly by the
transverse process (which corresponds to the transverse process of a thoracic
vertebra), anteriorly by the costal process (which corresponds to the rib in the
thoracic region), and laterally by the costo-transverse lamella. The latter is a
bar of bone joining the two processes and directed obliquely upward and forward
in the upper vertebrae and horizontally in the lower. The vertebral foramen is
triangular with rounded angles, and is larger than in the thoracic or lumbra
vertebrae.
Fig. 35. — A Cervical Vertebra.
Costal process
Costo-transverse foramen
Transverse process
Superior articular process
Inferior articular process
Lamina
Spinous process
gvPedicle (root of arch)
Peculiar cervical vertebrae. — The various cervical vertebrae possess distinguishing features,
though, with the exception of the first, second, and seventh, which are so different as to necessi-
tate separate descriptions, these are largely confined to the direction of the costo-transverse
lamella, and the size and level of the anterior and posterior tubercles. In the third the anterior
tubercle is higher than the posterior and the costo-transverse lamella is obhque; in the fourth the
anterior tubercle is elongated vertically, so that its lower end is nearly on a level with the
posterior, though the lamella still remains oblique. In the fifth and sixth they are nearly on
the same level, but in the latter the anterior tubercle is markedly developed to form the carotid
tubercle.
The Atlas or First Cervical Vertebra
This vertebra (fig. 36) is remarkable in that it has neither body nor spinous
process. It has the form of an irregular ring, and consists of two thick portions,
the lateral masses, united in front and behind by bony arches. The anterior
arch joins the lateral masses in front and constitutes about one-fifth of the entire
circumference of the ring. On its anterior surface it presents a tubercle for the
attachment of the longus colli muscle and the anterior longitudinal ligament,
and on its posterior surface a circular facet [fovea dentis] for articulation with
the odontoid process [dens] of the axis. The upper and lower borders serve for
the attachment of ligaments uniting the atlas to the occipital bone and axis
respectively.
The lateral masses are thick and strong, supporting the articular processes above and below
and extending laterally into the transverse processes. The superior articular surfaces are
elongated, deeply concave, and converge in front. Directed upward and mediaOy they receive
the condyles of the occipital bone, and occasionally each presents two oval facets united by an
isthmus. The inferior articular surfaces are circular and almost flat; they are directed down-
ward and medially and articulate with the axis. The articular processes, like the superior
articular processes of the axis, differ from those of other vertebrte in being situated in front of
the places of exit of the spinal nerves.
Between the upper and lower articular surfaces on the inside of the ring are two smooth
rounded tubercles, one on each side, to which the transverse ligament is attached. This liga-
THE CERVICAL VERTEBRA
33
ment divides the interior of the ring into a smaller anterior part for the dens of the axis, and a
larger posterior part, corresponding to the foramina of other vertebrae, for the spinal cord and
its membranes.
The transverse processes are large and extend farther outward than those of the vertebrae
immediately below. They are flattened from above downward and each is perforated by a large
costo-transverse foramen; the extremity is not bifid, but, on the contrary, is broad and rough
for the attachment of numerous muscles. The posterior arch unites the lateral masses behind
and forms about two-fifths of the entire circumference. It presents in the rniddle line a rough
elevation or tubercle representing a rudimentary spinous process. At its junction with the
lateral mass on the superior surface is a deep groove, the sulcus arteriee vertebralis, which
Fig. 36. — The First Cervical Vertebra or Atlas.
Anterior tubercle
Superior articular process
Costal process
Costo-transverse foramen
Transverse process
Groove for vertebral artery-
Posterior tuberclt
i
lodges the vertebral artery and the sub-occipital (first spinal) nerve. The groove corresponds
to the superior notches of other vertebrae and occasionally it is converted into a foramen by a
bony arch — the ossified oblique ligament of the atlas. A similar but much shallower notch is
present on the inferior surface of the posterior arch, and, with a corresponding notch on the
axis, forms an intervertebral foramen for the exit of the second spinal nerve. The upper and
lower surfaces of the areh afford attachment to Ugaments uniting the atlas to the occipital
bone and the axis.
The atlas gives attachment to the following muscles: —
Anterior arch Longus colli.
Posterior arch Rectus capitis posterior minor.
Transverse (process Rectus capitis anterior (minor), "rectus"'capitis lateralis,
obliquus capitis inferior, obliquus capitis superior,
splenius cervicis, levator scapulae, and intertransver-
sarii, anterior and posterior.
Fig. 37. — The Epistropheus or Axis.
Odontoid process (dens)
Groove for transverse ligament -
Lamina
Facet for atlas
Superior articular process
Costo-transverse foramen
Body
Costal process
Spinous process Inferior articular process
The Epistropheus (Axis)
The epistropheus (axis) (fig. 37) is the thickest and strongest of the bones of
this region, and is so named from forming a pivot on which the atlas rotates,
carrying the head. It is easily recognised by the rounded dens (odontoid process)
which surmounts the upper surface of the body. This process, which represents
the displaced body of the atlas, is large, blunt, and tooth-Uke, and bears on its
anterior surface an oval facet for articulation with the anterior arch of the atlas;
posteriorly it presents a smooth groove which receives the transverse ligament.
To the apex a thin narrow fibrous band (the apical dental ligament) is attached,
and on each side of the apex is a rough surface for the attachment of the alar
34
THE SKELETON
ligaments which connect it with the occipital bone. The enlarged part of the
process is sometimes termed the head, and the constricted basal part the neck.
The inferior surface of the body resembles that of the succeeding vertebrae and
is concave from front to back and slightly convex from side to side. Its anterior
surface is marked by a median ridge separating two lateral depressions for the
insertion of the longus colli.
The roots (pedicles) are stout and broad; the laminae are thick and prismatic; the spinous
process is large and strong, deeply concave on its under surface, and markedly bifid; the trans-
verse processes are small, not bifurcated and not grooved. The costo-transverse foramen is
directed very obliquely upward and laterally and the costal process is larger than the transverse.
Fig. 38. — The Cervical Vertebra. (Anterior view.)
Anterior tubercle of atlas to which
the longus colli is inserted
Rectus capitis anterior
The upper oblique
portion of longus
colli
The upper oblique
portion of longus
colli and insertion
of inferior oblique
portion
This and the three suc-
ceeding processes give
origin to the longus
capitis and insertion
to the scalenus an-
terior
Origin of vertical portion of the longus colli;
its insertion is into the second, third, and fourth vertebrae
The superior articular surfaces are oval, and directed upward and laterally for articulation
with the atlas. They are remarkable in being supported partly by the body, and partly by the
pedicles, and in being situated in front of the superior notches. The inferior articular surfaces
are similar in form and position to those of the succeeding vertebrae.
The axis gives attachment to the following muscles: —
Body Longus coUi.
Spinous process Obliquus capitis inferior, rectus capitis posterior major
semispinalis cervicis, interspinales, multifidus.
Transverse process Splenius cervicis, intertransversarii, levator scapulae,
longissimus (transversahs) cervicis, scalenus medius.
The Seventh Cervical Vertebra
Situated at the junction of the cervical and thoracic regions of the vertebral
column, the seventh cervical vertebra (figs. 38, 39) may be described as a transi-
tional vertebra — i. e., possessing certain features characteristic of both regions.
The spinous process is longer than that of any of the other cervical vertebrae.
It is not bifurcated, but ends in a broad tubercle projecting beneath the skin,
THE CERVICAL VERTEBRAE
35
whence the name vertebra prominens has been applied to this bone. The trans-
verse process is massive; the costal element of the process is very small, but, on
the other hand, the posterior or vertebral part of the process is large and becom-
ing more like the transverse process of a thoracic vertebra.
The costo-transverse foramen is the smallest of the series and may be absent. It does not,
as a rule, transmit the vertebral artery, but frequently gives passage to a vein. Occasionally
the costal process is segmented off and constitutes a cervical rib. The body sometimes bears
on each side near the lower border a costal pit for the head of the first rib. When this is present,
there is usually a well-developed cervical rib.
Fig. 39. — The Cervical Vertebra. (Posterior view.)
Rectus capitis posterior minor
Superior oblique
■ oblique
Rectus capitis posterior major
(the pointer crosses the or-
igin of the inferior oblique)
Semispinalis cervicis-
Semispinalis cervicis.
Longissimus cervicis
Iliocostalis cervicis
Semispinal:
Levator costse (origin)
Iliocostalis dorsi (insertion)
Interspinales
Interspinales
Trapezius
Rhomboideus minor
Serratus posterior superior
Splenius
Semispinalis capitis
Transverse process
of atlas
Levator scapulae
(origin)
Splenius cervicis
(.insertion)
Levator scapulse
-pie ■
Scalenus medius
(insertion)
Levator scapulae
'Splenius cervicis
Scalenus medius
Semispinalis capitis
Levator scapulae
Sple ■
(sometimes)
Scalenus medius
i
Scalenus medius
Scalenus posterior
spinalis and lon-
gissimus capitis
Multifidus
medius
posterior
spinalis and lon-
gissimus capitis
Multifidus
Scalenus medius '
Scalenus posterior
Semispinalis and lon-
gissimus capitis
Multifidus spinas
(The large surface isfor
the multifidus)
Multifidus (and to each
spinous process as
high as the second)
The seventh cervical vertebra gives attachment to the following muscles: —
Body Longus coUi.
Spinous process Trapezius, rhomboideus minor, serratus posterior supe-
rior, splenius capitis, multifidus, interspinales, semi-
spinalis dorsi.
Transverse process Intertransversarii, levator costse, scalenus posterior,
iliocostahs dorsi (musculus accessorius), scalenus me-
dius, semispinalis capitis (complexus).
Articular process Multifidus, longissimus capitis (trachelomastoid).
The cervical vertebrae exhibit great variation in regard to the extremities of their spinous
processes. As a rule among Europeans, the second, third, fourth, and fifth vertebrae possess
bifid spines. The sixth and seventh exhibit a tendency to bifurcate, their tips presenting two
small lateral tubercles; sometimes the sixth has a bifid spine, and more rarely the seventh pre-
86
THE SKELETON
sents the same condition. Occasionally all the cervical spines, with the exception of the second,
are non-bifid, and even in the axis the bifurcation is not extensive. In the lower races of men
the cervical spines are relatively shorter and more stunted than in Europeans generally and,
as a rule, are simple. The only cervical vertebra which presents a bifid spine in all races is the
axis; even this may be non-bifid in the Negro, and occasionally in the European. (Owen,
Turner, Cunningham.)
The laminae of the lower cervical vertebrae frequently present posteriorly distinct tubercles
from which fasciculi of the muUifidus muscle arise. They are usually confined to the sixth
and seventh vertebrae, but are fairly frequent on the fifth, and are occasionally seen on the
fourth.
Fig. 40. — Peculiar Thoracic Vertebra.
An entire costal pit
above a half-pit
below. In shape the
body resembles that
of a cervical vertebra
Jsually a ha If-pit
above (sometimes 't
has a half-pit below)
Usually an entire pit
above . Occasionally
this pit is incomplete
The pit on the trans-
verse process is usu-
ally small
An entire pit above,
no pit on transverse
process which is tri-
partite; body large
Inferior articular pro-
cesses turn lateral-
ward as in a lumbar
vertebra
THE THORACIC VERTEBRA
The general characters of the thoracic (or dorsal) vertebrae have already
been considered. Their most distinguishing features are the pits on the trans-
verse processes and sides of the bodies for the tubercles and heads of the ribs
respectively.
Peculiar thoracic vertebrae. — Several vertebrae in this series differ from the
typical example. The exceptional ones are — the first, ninth, tenth, eleventh, and
twelfth (fig. 40). .
THE LUMBAR VERTEBRM
37
The first thoracic vertebra is a transitional vertebra. The body in its general
conformation approaches very closely the seventh cervical, in that the greatest
diameter is transverse, its upper surface is concave from side to side, and its lateral
margins bear two prominent lips. On each side is an entire pit, close to the upper
border, for the head of the first rib, and a very small pit (inferior costal pit) below
for the head of the second rib. The spinous process is thick, strong, almost hori-
zontal and usually more prominent than that of the seventh cervical, an important
point to remember when counting the spines in the living subject. Occasionally
the transverse process is perforated near the root.
The ninth has superior costal pits, and usually no inferior; when the inferior
pits are present, this vertebra is not exceptional.
The tenth usually has an entire costal pit at its upper border, on each side, but
occasionally only a superior costal pit. It has no lower pits and the pits on the
transverse processes are usually small.
The eleventh has a large body resembling a lumbar vertebra. The pits are on
the pedicles and they are complete and of large size. The transverse processes are
short, show evidence of becoming broken up into three parts, and have no pits for
the tubercles of the eleventh pair of ribs.
In many mammals, the spines of the anterior vertebrae are directed backward, and those
of the posterior directed forward, whilst in the centre of the column there is usually one spine
vertical. The latter is called the anti-clinal vertebra, and indicates the point at which the
thoracic begin to assume the characters of lumbar vertebrae. In man the eleventh thoracic is
the anti-cUnal vertebra.
The twelfth resembles in general characters the eleventh, but may be distin-
guished from it by the articular surfaces on the inferior articular processes being
convex and turned laterally as in the lumbar vertebrfe. The transverse process
is rudimentary and tripartite, presenting for examination three tubercles, superior,
inferior, and lateral, which correspond respectively to the mammillary, accessory,
and transverse processes of the lumbar vertebra. There is one complete pit on
the root (pedicle) for the head of the twelfth rib.
A pecuUarity, more frequent in the thoracic and lumbar than in the cervical and sacral
regions of the column, is the existence of a half-vertebra. Such specimens have a wedge-shaped
half-centrum, to which are attached a lamina, a transverse, superior, and inferior articular, and
half a spinous process. As a rule, a half-vertebra is ankylosed to the vertebrae above and below.
THE LUMBAR VERTEBRAE
The lumbar vertebrae (figs. 41, 42) are distinguished by their large size and by
the absence of costal articular surfaces.
The body is somewhat reniform, with the greatest diameter transverse, flat
above and below, and generally slightly deeper in front than behind. The roots
Fig. 41. — A Lumbar Vertebra.
(Side view.)
-Superior articular process
Mammillary process
Transverse process
Accessory process
Inferior articular process
(pedicles) are strong and directed straight backward, and the lower vertebral
notches are deep and large. The laminae are shorter and thicker than those of
the thoracic or cervical vertebrae, and the vertebral foramen is triangular, wider
than in the thoracic, but smaller than in the cervical region. The spinous process,
38
THE SKELETON
thick, broad, and somewhat quadrilateral, projects horizontally backward. It is
thicker below than above and terminates in a rough posterior edge. The articular
processes are thick and strong. The superior articular surface is concave and
directed backward and medially; the inferior is convex and looks forward and
laterally. The superior pair are more widely separated than the inferior pair and
embrace the inferior articular processes of the vertebra above. The posterior
margin of each superior articular process is surmounted by the mammillary
process or tubercle (metapophysis) which corresponds to the superior tubercle
of the transverse process of the last thoracic vertebra. In man. the mammillary
tubercles are rudimentary, but in some animals they attain large proportions, as
in the kangaroo and armadillo. The transverse processes are long, slender,
somewhat spatula-shaped, compressed from before backward, and directed
laterally and a little backward. They are longest in the third vertebra and dimin-
ish in the fourth, second, and fifth, in this order, to the first, in which they are
shortest of all. Their extremities are in series with the lateral tubercles of the
transverse processes of the twelfth thoracic vertebra and also with the ribs.
With the latter the so-called transverse processes in the lumbar region are homol-
ogous, and hence they are sometimes called the costal processes. Occasionally
the costal element differentiates and becomes a well-developed lumbar rib.
Fig. 42. — A Ltjmbar Vertebra.
(Showing the compound nature of the transverse process. Upper view.)
Mammillary process.
Accessory process
or tip of the true
transverse pro-
cess
Costal element
Behind the base of each transverse or costal process is a small eminence, directed down-
ward, which corresponds with the inferior tubercle of the lower thoracic transverse process,
and with the transverse processes of the thoracic vertebrae above, and is named the accessory
process (anapophysis). The accessory process represents the tip of the partially suppressed
true transverse process of a lumbar vertebra. It is well developed in some of the lower animals,
as in the dog and cat.
Each of the five lumbar vertebrae is readily recognized. The body of the first
is deeper behind than in front; the body of the second is equal in depth in front
and behind; the bodies of the third, fourth, and fifth are deeper in front than
behind, but the third has long transverse processes and the inferior articular
processes are not widely separated. The fourth has shorter transverse processes
and the inferior articular processes are placed more widely apart. The fifth
lumbar vertebra deviates in some of its features so widely from the other members
of the series that special prominence must now be given them.
The fifth lumbar vertebra is massive, and the body is much thicker in front
THE SACRUM
39
than behind in consequence of being bevelled off to form with the sacrum the sacro-
vertebral angle. The transverse processes are short, thick, conical, and spring
from the body as well as from the roots of the arch. They are very strong for the
attachment of the ilio-lumbar ligaments. The spinous process is smaller than
that of any of the other lumbar vertebrse; the laminae project into the vertebral
foramen on each side; and the roots are stout and flattened from above down-
ward. The inferior articular processes are separated to such a degree as to be
wider apart than the superior, and they articulate with the first sacral vertebra.
The roots of the arch in this vertebra are liable to a remarkable deviation from the condi-
tions found in other parts of the spine. The peculiarity consists of a complete solution in the
continuity of the arch immediately behind the superior articular processes. In such speci-
mens the anterior part consists of the body carrying the roots, transverse and superior articu-
lar processes; whilst the posterior segment is composed of the laminae, spine, and inferior articu-
lar processes. The posterior segment of the ring of this vertebra may even consist of two pieces.
There is reason to believe that this abnormality of the fifth lumbar vertebra occurs in five per
cent, of aU subjects examined. Sir William Turner, in his report on the human skeletons in
the Challenger Reports, found seven examples among thirty skeletons examined. The skeletons
in which this occurred were: — a Malay, an Andamanese, a Chinese, two Bushmen, an Eskimo,
and a Negro. Turner has also seen it in the skeleton of a Sandwich Islander. A similar con-
dition is occasionally met with either unilaterally or bilaterally in the thoracic vertebrae.
THE SACRUM
The five sacral vertebrse (figs. 43, 44) are united in the adult to form the os
sacrum, a large, curved, triangular bone, firmly wedged between the innominate
bones, and completing, together with the coccyx, the posterior boundary of the
Fig. 43. — The Sacrum and Coccyx. (Anterior view.)
Inferior lateral
angle
minor (or small) pelvis. Of the five vertebrae which compose the sacrum the
uppermost is the largest, the succeeding ones become rapidly smaller, and the fifth
is quite rudimentary. In the erect posture the sacrum lies obliquely, being di-
rected from above downward and backward, and forms with the last lumbar
vertebra an anterior projection known as the promontory. The sacrum presents
for examination a pelvic and a dorsal surface, two lateral margins, a base, and
an apex.
Surfaces. — The pelvic surface, directed downward and forward, is smooth,
concave from above downward and slightly from side to side. It is crossed in the
40
THE SKELETON
middle by four transverse ridges [lineae transversee] which represent the ossified
intervertebral discs and separate the bodies of the five sacral vertebrae. Of the
bodies, the first and second are nearly equal in size and are larger than the third,
fourth, and fifth, which, in vertical depth, are also nearly equal to each other. At
the extremities of the transverse ridges on each side are four openings, called the
anterior sacral foramina, which correspond to the intervertebral foramina in other
regions of the column, and transmit the anterior divisions of the first four sacral
nerves ; they are also traversed by branches of the lateral sacral arteries. The fora-
mina are separated by wide processes, representing the costal processes of the
vertebrae, which unite laterally to form the lateral portion (or mass) [pars lateralis].
The latter is grooved for the sacral nerves, and rough opposite the second, third,
and fourth sacral vertebrae, for the origin of the piriformis muscle. The lateral
part of the fifth sacral vertebra gives insertion to fibres of the coccygeus.
. The dorsal surface is strongly convex and rough. The middle line is occu-
pied by four eminences representing the somewhat suppressed spinous processes.
Of these the first is the largest, the second and third may be confluent, and the
fourth is often absent. The processes are united to form an irregular ridge or
The Sacrum. (Posterior view.)
Articular process
Auricular surface
Articular process'
Transverse process
Sacral foramen-
Multifidus
Sacro-spinalis
Gluteus maximus
Notch for fifth sacral
crest [crista sacralis media]. The bone on each side of the spines is slightly
hollowed and is formed by the united laminae. In the fourth sometimes, but
always in the fifth, the laminae fail to meet in the middle line, leaving a gap
[hiatus sacralis] at the termination of the spinal canal, the lateral margins of which
are prolonged downward as the sacral cornua. They represent the lower articular
processes of the fifth sacral vertebra and give attachment to the posterior sacro-
coccygeal ligaments. Lateral to the laminae is a second series of small eminences
which represent the articular and mammillary processes of the vertebrae above.
The first pair are large for the last lumbar vertebra, the second and third are small,
and the fourth and fifth are inconspicuous. Together they form a pair of irregular
ridges [cristae sacrales articulares].
Immediately lateral to the articular processes are the posterior sacral fora-
mina, four on each side; they are smaller than the anterior, and give exit to the
posterior primary divisions of the first four sacral nerves. Lateral to the fora^
mina on each side are five elevations representing the transverse processes. The
first pair, situated at the junction of the posterior surface with the base, are large
and conspicuous, and serve all for the attachment of ligaments and muscles.
THE SACRUM
41
Together they form on each side of the sacrum an irregular ridge [crista saoralis lateralis].
The space between the spinous and transverse processes presents a shallow concavity known as
the sacral groove, continuous above with the vertebral groove of the movable part of the
column, and, like it, lodging the multifidus muscle. Bridging across the groove and attached
to the sacral spines medially, and to the lower and back part of the sacrum laterally, is the flat
tendon of origin of the sacro-spinalis {erector spince) . The gluteus maximus takes origin from the
back of the lower two pieces of the sacrum.
The base or upper surface of the sacrum bears considerable resemblance to the
upper surface of the fifth lumbar vertebra. It presents in the middle the body, of
a reniform shape, posterior to which is the upper end of the sacral canal bounded
by two laminae. On each side of the canal are two articular processes bearing;well-
marked mammillary tubercles. The conjoined transverse and costal processes
form on each side a broad surface, the wing or ala of the sacrum, continuous with
the iliac fossa of the hip bone, and giving attachment to a few fibres of the iliacus.
Fig. 45. — Left Lateral View op Sacrum and Coccyx.
The lateral margins. — It has already been noted that the lateral portion of
the sacrum is the part lateral to the foramina. It is broad and thick above,
where it forms the ala, but narrowed below. The lateral aspect of the upper
part presents in front a broad irregular surface, covered in the recent state with
fibro-cartilage, which articulates with the ilium and is known as the auricular
surface. It is bounded posteriorly by some rough depressions for the attachment
of the posterior sacro-iliac ligaments. Below the auricular surface, the lateral
margin is rough for the sacro-tuberous (greater) and sacro-spinous (lesser sacro-
sciatic) ligaments, and terminates in the projection known as the inferior lateral
angle. Immediately below the angle is a notch, converted into a foramen by the
transverse process of the first coccygeal vertebra, and a ligament connecting this
with the inferior lateral angle of the sacrum. Through this foramen passes" the
anterior branch of the fifth sacral nerve.
The apex is directed downward and forward and is formed by the inferior
aspect of the body of the fifth sacral vertebra. It is transversely oval and
42
THE SKELETON
articulates by means of an intervertebral disc with the coccyx. In advanced
life the apex of the sacrum becomes united to the coccyx by bone.
The sacral canal is the continuation of the spinal canal through the sacrum.
Like the bone, it is curved and triangular in form at the base and flattened toward
the apex. It terminates at the hiatus sacralis between the sacral cornua, where
the laminse of the fourth and fifth sacral vertebrae are incomplete. The canal
opens on the surface by the anterior and posterior sacral foramina and lodges the
lower branches of the cauda equina, the filum terminale, and the lower extremity
of the dura and arachnoid. The sub-dural and sub-arachnoid spaces extend
downward within the canal as far as the body of the third sacral vertebra.
Differences in the two sexes. — The sacrum of the female is usually broader in proportion
to its length, much less curved, and directed more obliquely backward than in the male. The
curvature of the female sacrum belongs chiefly to the lower part of the bone, whereas in the
male it is equally distributed over its whole length; but the curvature is subject to considerable
variation in different skeletons.
Fig. 46. — Base of Sacrum.
Spinous process— j^fjf^ij
cular process
Lamina
Sacral canal
Racial differences. — The human sacrum is characterised by its great breadth in comparison
with its length, though in the lower races it is relatively longer than in the higher. The propor-
tion is expressed by the sacral index = . — — rr ' The average sacral index in the British
male is 112, in the female 116. Sacra in which the index is above 100 are plaiyhieric, as in
Europeans; those under 100 are dolichohieric, as in most of the black races (Sir W. Turner).
Fig. 47. — The Coccyx. A. Posterior view; B. Anterior view.
A. B.
THE COCCYGEAL VERTEBRiE
The four coccygeal vertebrae are united in the adult to form the coccyx [os
coccygis] (fig. 47). While four is the usual number of these rudimentary vertebrse,
occasionally there are five, and rarely three. In middle life the first piece is
usually separate, and the original division of the remaining portion of the coccyx
THE VERTEBRAL COLUMN AS A WHOLE 43
into three parts is indicated by transverse grooves. In advanced life the pieces
of the coccyx, having previously united to form one bone, may also become
joined to the sacrum.
The first piece of the coccyx is much broader than the others. It consists of a body,
transverse processes, and rudiments of a neural arch. The body presents on its upper surface
an oval facet for articulation with the apex of the sacrum. On each side of the body a trans-
verse process projects laterally and is joined either by ligament or bone to the inferior lateral
angle of the sacrum, forming a foramen for the anterior division of the fifth sacral nerve. From
the posterior surface of the body two long coccygeal cornua project upward and are connected to
the sacral cornua by the posterior saero-coccygeal ligaments, enclosing on each side an aperture
— the last intervertebral foramen — for the exit of the fifth sacral nerve. The coccygeal cornua
represent the roots and superior articular processes of the first coccygeal vertebra.
The second piece of the coccyx is much smaller than the first, and consists of a body,
traces of transverse processes, and a neural arch, in the form of slight tubercles at the sides and
on the posterior aspect of the body.
The third and fourth pieces of the coccyx, smaller than the second piece, are mere nodules
of bone, corresponding solely to vertebral bodies.
The anterior surface of the coccyx gives attachment to the anterior sacro-coccygeal ligament
and near the tip to the levator ani; it is in relation with the posterior surface of the rectum.
The posterior surface of the coccyx is convex, and the upper three pieces afford attachment
to the gluteus maximus on each side, and the last piece to the coccygeal portion of the sphincter
ani externus.
The lateral margins are thin, and receive parts of the sacro-seiatio ligaments, of the
coccygei muscles, and of the levatores ani.
THE VERTEBRAL COLUMN AS A WHOLE
The vertebral column (fig. 48) is the central axis of the skeleton and is situated in the
median line at the posterior aspect of the trunk. Superiorly it supports the skull; laterally it
gives attachment to the ribs, through which it receives the weight of the upper limbs, and
inferiorly it is supported by the hip bones, by which the weight of the trunk is transmitted to
the lower limbs. Its length varies in different skeletons, but on an average it measures about
70 cm. (28 in.) in the male and about 2.5 cm. (1 in.) less in the female. To the entire length the
cervical region contributes 12.5 cm. (5 in.), the thoracic 27.5 cm. (11 in.), the lumbar 17.5 cm.
(7 in.), and the sacro-coccygeal portion the remaining 12.5 cm. (5 in.). The vertebral column
presents a series of curvatures, four when viewed in profile and one when viewed from the front
or back. The former are directed alternately forward and backward, and are named, from the
regions of the column in which they occur, cervical, thoracic, lumbar, and sacral. The fifth
curve is lateral, being in most cases directed toward the right side.
The cervical, thoracic and lumbar curvatures pass imperceptibly into one another, but at
the junction of the last lumbar vertebra with the sacrum a well-marked angle occurs, known as
the sacro-vertebral or lumbo-sacral angle, with the result that the promontory of the sacrum
overhangs the cavity of the minor (small) pelvis and forms a portion of the superior aperture of
the small pelvis.
The thoracic and sacral curves have their concavities directed forward and are developed
during intra-uterine life. They are in obvious relation to two great cavities of the trunk,
thoracic and pelvic, and may be regarded as primary or accommodation curves, for the thoracic
and pelvic viscera. The thoracic curve extends from the second to the twelfth thoracic vertebra
and the sacral curve coincides with the sacrum and coccyx.
The cervical and lumbar curves have their convexities directed forward, and are developed
during the first year after birth. They are essentially curves of compensation, necessary for
the maintenance of the upright posture, and are brought about by modifications in the shape
of the intervertebral discs. The cervical curve is formed about the third month, or as soon as
the infant can sit upright. The great pecuharity of the curve is that it is never consolidated,
being present when the body is placed in the erect position and obliterated by bending the head
down upon the chest. The lumbar curve is developed about the end of the first year or when the
child begins to walk, but is not consolidated until adult life. (Symington.) The cervical curve
extends from the atlas to the second thoracic vertebra, and the lumbar curve from the twelfth
thoracic to the promontory of the sacrum.
The lateral curve is situated in the upper thoracic region, and when directed to the right is
probably associated with the greater use made of the right hand. This curve, however, is
particularly liable to modification in different occupations and in different races.
Viewed from the front, the vertebral column presents a series of pyramids due to the
successive increase and decrease in size of the bodies. These become broader from the axis to
the first thoracic vertebra and then decrease to the fourth thoracic. The first pyramid therefore
includes all the cervical vertebrae except the atlas, and has the apex directed upward and its
base downward, whilst the second is inverted and formed by the first four thoracic vertebrae.
The third pyramid, much the longest, is the result of the increase in size from the fourth thoracic
to the fifth lumbar vertebra, and the fourth, which is inverted, is produced by the rapid contrae- ■
tion of the sacral and coccygeal vertebriE.
Viewed from behind, the spinous processes project in the middle Hne, and the transverse
processes as two lateral rows. Of the spines, those of the axis, seventh cervical, first thoracic,
and the lumbar vertebrae appear most prominent. On each side is the vertebral groove, the
floor of which is formed in the cervical and lumbar regions by the laminae and articular processes,
44
THE SKELETON
Fig. 48. — Vertebral Column. (Lateral; view.) '
Atlas ^«&a^^T
Epistropheus "-
Vertebra prominens .
Vff
iin
OSSIFICATION OF VERTEBRA
45
and in the thoracic region, by the laminae and transverse processes. The transverse processes
project laterally for a considerable distance in the atlas, first thoracic, and the middle of
the lumbar series; they are shortest in the third cervical and the twelfth thoracic.
In the lateral view, the intervertebral foramina appear oval in shape, and are small in the
cervical, larger in the thoracic, and largest in the lumbar region.
Structure o£ a vertebra. — The bodies of the vertebrae are largely composed of cancellous
tissue, with a thin outer covering of compact tissue. In a vertical section through the centrum
Fig. 49. — A Divided Thoracic Vertebra. (After Turner-.)
the fibres of the cancellous tissue are seen to be arranged vertically and horizontally, the vertical
fibres being curved with their concavities directed toward the centre of the bone. The hori-
zontal fibres are slightly curved parallel with the upper and lower surfaces, and have their con-
vexities toward the centre of the bone. They are not so well defined as the vertical set.
(Wagstaffe.)
Ossification. — The vertebrae in general. — The ossification of each vertebra takes place
in cartilage from three primary and five secondary centres. The three primary centres
Fig. 50. — A Vertebral Centrum in Section to Show the Pressure Curves.
appear, one in the^body and two in the arch, about the seventh week of intra-uterine life.
In the thoracic region the nucleus for the body appears first, but in the cervical region it is pre-
ceded by the centres for the arch. The nucleus for the body soon becomes bilobed, and this
condition is sometimes so pronounced as to give rise to the appearance of two distinct nuclei.
Indeed, the nucleus is very rarely double and the two parts of the body may remain separate
throughout life (fig. 49). The bilateral character of the nucleus is further emphasised by the
occasional formation of half-vertebrje. The lateral centres are deposited near the bases of the
Fig. 51. — A Vertebra at Birth.
Neuro-central suture
Centrum or body
Superior articular processes and give rise to the roots, laminae, articular, and the greater
parts of the tran8.verse and spinous processes.
At birth a typical vertebra consists of three osseous pieces — a body and two lateral masses,
which constitute the arch, the parts being joined together by hyahne cartilage. The line of
union of the lateral portion with the body is known as the neuro-ceniral suture, and is not actually
obliterated for several years after birth. In the thoracic region the central ossification does not
pass beyond the point with which the head of the rib articulates, and leaves a portion of the bodj'
on each side formed from the lateral ossification. A thoracic vertebra at the fifth year shows
46
THE SKELETON
that the pits for the heads of the ribs are situated behind the neuro-central suture, which is
directed obhquely backward and medially. The laminae unite during the first year after birth;
and by the gradual extension of ossification into the various processes, the vertebrae have at-
tained almost their full size by the time of puberty. Subsequently the secondary centres
appear in the cartilaginous extremities of the spinous and transverse processes, and in the carti-
FiQ. 52.-
-Cervical Vertebra showing the Epiphysial Plate on the Upper Surface op
THE Body.
lage on the upper and lower surfaces of the bodies, forming in each vertebra two annular plates,
thickest at the circumference and gradually thinning toward the central deficiency. The
epiphyses appear from the fifteenth to the twentieth year and join with the vertebra by the
twenty-fifth year.
Fig. 53. — Lumbar Vertebra at the Eighteenth Year with Secondary Centres.
Epiphysial plate or disc
Mammillary tubercle
Transverse process
Spinous process
Epiphysial plate
In several vertebrae the mode of ossification differs from the account given above — in some
cases considerably — and necessitates separate consideration.
Atlas. — The lateral portions and posterior arch are formed from two centres of ossification,
which correspond to the lateral centres of other vertebrae and appear about the seventh week.
Fig. 54. — Upper Thoracic Vertebra with an Epiphysial Plate Removed and Drawn at
the Side.
The plate shows the characteristic deficiency in the centre. (Natural size.)
The anterior arch is ossified from one centre, which, however, does not appear until a few months
after birth. Union of the lateral parts occurs posteriorly in the third year, being sometimes
preceded by the appearance of a secondary centre of ossification in the intervening cartilage,
and the union of the lateral parts with the anterior arch occurs about the sixth year.
EPISTROPHEUS
47
Epistropheus. — The arch, and the processes associated with it, are formed from two lateral
centres which appear, like those in the other vertebras, about the seventh week. The common
piece of cartilage which precedes the body and dens is ossified from four (or five) centres, one
(or two) for the body of the axis, in the fourth month, two, laterally disposed, for the dens, a
Fig. 55. — Immature Atlas. (Third year.)
few weeks later, and one, for the apex of the dens, in the second year. The two collateral centres
for the main part of the dens soon coalesce, so that at birth the axis consists of four osseous pieces
— two lateral portions which constitute the arch, the body, and the dens, surmounted by a
piece of cartilage. During the third or fourth year the dens joins with the body, the line of
i
Fig.
Suspensory ligament
Nucleus for tip of odontoid dens-
Lateral centres for odontoid dens'
)iphysial plate or disC'
Pedicle
■Development of the Epistkopheus.
Centrum or body.
Epiphysial plate
union being indicated even in advanced life by a small disc of cartilage, and the arch unites in
front and behind about the same time or a little later. The apical nucleus of the dens, which
represents an epiphysis, joins the main part about the twelfth year and in the seventeenth year
Fig. 57.-
-The Epistropheus at Four Years op Age, showing the Size and Extent of
the Dens. (Natural size.)
an epiphysial plate appears for the lower surface of the body. There are also rudiments,
adjoining the cartilaginous disc, of the upper epiphysial plate of the body.
Cervical vertebrse. — In the cervical vertebrae the lateral centres form a larger share of the
body than in the vertebrae of other regions, and the neuro-central suture runs almost in a sag-
FiG. 58. — The Epistropheus (prom an Adult) in Sagittal Section.
Dens (odontoid process)
Cartilage representing the inter-
vertebral disc between the dens
and the body of the epistropheus
Body of epistropheus
ittal direction. The sixth, seventh, and even the fifth have additional centres which appear
before birth for the anterior or costal divisions of the transverse processes. In the other cer-
vical vertebrae the costal processes are ossified by extension of the lateral nuclei. The costal
processes of the seventh cervical sometimes remain separate, constituting cervical ribs.
48
THE SKELETON
Lumbar vertebrae. — In the lumbar vertebrEe the neuro-oentral suture is almost transverse,
and to the usual number of centres of ossification, two other epiphyses for the mammillary
tubercles are added, the centres appearing about puberty. The transverse process of the first
lumbar vertebra is occasionally developed from an independent centre.
The fifth lumbar exhibits in some cases a special mode of ossification in the arch. Instead
of two centres, there are four — one on each side for the root, transverse process, and supe-
FiG. 59. — An Immature Cervical Vertebra.
Neuro-central suture
rior articular process, and another on each side for the lamina, inferior articular process, and the
lateral half of the spinous process (fig. 60). There may be failure of union of roots with the
laminae or of the laminae with one another.
Sacral vertebree. — The sacrum ossifies from thirty-five centres, which may be classified as
follows ; — In each of the five vertebrae there are three primary nuclei — one for the body and two
for the arch; in each of the first three the costal element of the lateral mass on each side is
Fig. 60. — Ossification of the Fifth Lumbar Vertebra.
Neuro-central suture.
Centrum^
formed from a separate nucleus; associated with each body are two epiphysial plates; and on
each lateral margin are two irregular epiphyses, one for the auricular surface and another for
the rough edge below.
The centres for the bodies appear about the eighth or ninth week and for the vertebral
arches about the sixth month. The arches join the bodies at difi'erent times in the different
Fig. 61. — Sacrum at Birth to show Centres op Ossification. (Enlarged one-third.)
Ossific centre in the body of first sacral vertebra.
Beneath this are seen in succession the centres in the
bodies of the second, third, fourth, and fifth vertebras
Ossific centres in the lateral mass^ \ yi^\
vertebrae, ranging from the second year below, to the fifth or sixth year above, and union of the
laminae takes place behind some years later, from about the ninth to the fifteenth year.
The centres for the costal elements appear outside the anterior sacral foramina, from the
fifth to the seventh month, and these unite with the bodies somewhat later than the arches.
The centres for the epiphysial plates appear about the fifteenth year, and for the auricular
epiphyses and the edges below, from the eighteenth to the twentieth year.
COCCYGEAL VERTEBRA
49
Consolidation begins soon after puberty by fusion of the costal processes, and this is followed
by ossification from below upward in the intervertebral discs, resulting in the union of the
adjacent bodies and the epiphysial plates, the ossific union of the first and second being com-
pleted by the twenty-fifth year or a little later. The marginal epiphyses are also united to the
Fig. 62.-
-Thb Sacrum at Four Years of Age (B). The Figure at the Top (A) Shows
THE Base Drawn from Above. (Three-fourths natural size.)
icle and transverse proces
Cartilage
Costal process
Cartilage
i
Cartilage covering lateral mass
Cartilaginous disc
Ossification in first piece of coccyx
sacrum by the twenty-fifth year. Even in advanced life intervertebral discs persist in the
more central parts of the bone and can be well seen in sections.
Coccygeal vertebrae. — The coccygeal vertebrae are cartilaginous at birth and each is usually
ossified from a single centre, though there may be two for the first piece. Ossification be-
gins soon after birth in the first segment, and in the second from the fifth to the tenth year.
Fig. 63. — Sacrum at about Twenty-two Years. (Three-fifths'natural size.)
Epiphysial plate on the upper surface of body of first sacral vertebra
Lateral epiphyses appear at eighteen
( years and join at twenty-five
The centres for the third and fourth segments appear just before, and after, puberty respec-
tively. As age advances the various pieces become united with each other, the three lower
uniting before middle life and the upper somewhat later. In advanced life the coccyx maj' join
with the sacrum, the union occurring earUer and more frequently in the male than in the female.
50
THE SKELETON
The Serial Morphology of the Vertebrae
Although at first sight many of the vertebrae exhibit peculiarities, nevertheless a study
of the mode by which they develop, and their variations, indicates the aerial homology of> the
constituent parts of the vertebrae in each region of the column.
The body (centrum) of the vertebra is that part which immediately surrounds the noto-
chord. This part is present in all the vertebrae of man, but the centrum of the atlas is disso-
ciated from its arch, and ankylosed to the body of the epistropheus. The reasons for regard-
FiG. 64. — Morphology of the Tkansverse and Articular Processes.
Cervical vertebra
Transverse process
Costo-transverse foramen
Transverse process
Costo-transverse foramen
Neuro-central suture
Rib
.Transverse process
Lumbar rib
Sacral vertebra
Netiro-central suture
Costal process
ing the dens as the body of the atlas are these: In the embryo the notochord passes through
it on its way to the base of the cranium. Between the dens and the body of the axis there is
a swelling of the notochord in the early embryo as in other intervertebral regions. This swell-
ing is later indicated by a small intervertebral disc hidden in the bone, but persistent even in
old age. Moreover, the dens ossifies from primary centres, and in chelonians it remains as a
separate ossicle throughout life; in Ornithorhynchus it remains distinct for a long time, and it
has been found separate even in an adult man. Lastly, in man and many mammals, an epi-
BONES OF THE SKULL 51
physial plate develops between it and the body of the axis. The anterior arch of the atlas
represents a cartilaginous hypochordal bar, which is present in the early stages of development
of the vertebrae, but disappears in all but the atlas in the ossification of the body.
The arches and spinous processes are easily recognised throughout the various parts of the
column in which complete vertebrae are present.
The articular processes or zygapophyses are of no morphological value, and do not require
consideration here.
•The transverse processes offer more difficulty. They occur in the simplest form in the tho-
racic series. Here they articulate with the tubercles of the ribs, whence the term tubercular
processes or diapophyses has been given them (the place of articulation of the head of the rib
with the vertebra is the capitular process or parapophysis), and the transverse process and the
neck of the rib enclose an arterial foramen named the costo-transverse foramen. In the cer-
vical region the costal element (pleur apophysis) and the transverse process are fused together,
and the conjoint proce.ss thus formed is pierced by the costo-transverse foramen. The com-
pound nature of the process is indicated by the fact that the anterior or costal processes in the
lower cervical vertebrte arise from additional centres and occasionally retain their independence
as cervical ribs, and in Sauropsida (birds and reptiles) these processes are represented by free
ribs. In the lumbar region, the compound nature of the transverse process is further marked.
The true transverse process is greatly suppressed, and its extremity is indicated by the accessory
tubercle. Anterior to this in the adult vertebrae a group of holes represents the costo-transverse
foramen, and the portion in front of this is the costal element. Occasionally it persists as an
independent ossicle, the lumbar rib.
In the sacral series the costal elements are coalesced in the first three vertebrae to form the
greater portion of the lateral portion for articulation with the ilium, the costo-transverse fora-
mina being completely obscured. In rare instances the first sacral vertebra will articulate with
the ilium on one side, but remain free on the other, and under such conditions the free process
exactly resembles the elongated transverse process of a lumbar vertebra. The first three sacral
vertebrae which develop costal processes for articulation with the ilium are termed true sacral
vertebrae, while the fourth and fifth are termed pseudo-sacral. A glance at fig. 64 will show the
homology of the various parts of a vertebra from the cervical, thoracic, lumbar, and sacral
regions.
B. BONES OF THE SKULL
The skull is the expanded upper portion of the axial skeleton and is supported
on the summit of the vertebral column. It consists of the cranium, a strong bony
case enclosing the brain and made up of eight bones — viz., occipital, tvs^o parietal,
frontal, two temporal, sphenoid, ethmoid; and the bones of the face, surrounding
the mouth and nose, and forming with the cranium the orbital cavity for the
reception of the eye. The bones of the face are fourteen in number — viz., two
maxillae, two zygomatic {malar), two nasal, two lacrimal, two palate, two inferior
conchoe {turbinates), the mandible, and the vomer. All the bones enumerated
above, with the exception of the mandible, are united by suture and are therefore
immovable. The proportion between the facial and cranial parts of the skull
varies at different periods of life, being in the adult about one (facial) to two
(cranial), and in' the new-born infant about one to eight. A group of movable
bones, comprising the hyoid, suspended from the basilar surface of the cranium,
and three small bones, the incus, malleus, and stapes, situated in the middle ear or
tympanic cavity, is also included in the enumeration of the bones of the skull.
According to the BNA nomenclature, the term cranium is used in a wider sense as synony-
mous with skull, and is subdivided into cranium cerebrate (cranium in the narrower sense) and
cranium viscerate (facial skeleton). In the BNA, seven bones above listed with the facial, —
two inferior conchae, two lacrimal, two nasal and the vomer — are classed with the cranium
cerebrate.
THE OCCIPITAL
The occipital bone [os occipitale] (fig. 65) is situated at the posterior and
inferior part of the cranium. In general form it is flattened and trapezoid in
shape, curved upon itself so that one surface is convex and directed backward
and somewhat downward, while the other is concave and looks in the opposite
direction. It is pierced in its lower and front part by a large aperture, the foramen
magnum, by which the vertebral canal communicates with the cavity of the
cranium.
The occipital bone is divisible into four parts, basilar, squamous, and two
condylar, so arranged around the foramen magnum that the basilar part lies in
front, the condylar parts on either side, and the squamous part above and behind.
52
THE SKELETON
Speaking generally, this division corresponds to the four separate parts of which the bone
consists at the time of birth (fig. 69), known as the basi-occipital, supra-occipital, and ex-
occipital. In early life these parts fuse together, the lines of junction of the supra-occipital and
ex-occipitals extending lateralward from the posterior margin of the foramen magnum, and
those of the ex-occipitals and basi-occipital passing through the condyles near their anterior
extremities. It must be noted, however, that the upper portion of the squamous part represents
an additional bone, the interparietal.
The squamous part [squama occipitalis] (supra-occipital and interparietal)
presents on its convex posterior surface, and midway between the superior angle
and the posterior margin of the foramen magnum, a prominent tubercle known
as the external occipital protuberance, from which a vertical ridge — the external
occipital crest — runs downward and forward as far as the foramen. The pro-
tuberance and crest give attachment to the ligamentum nuchse.
Fig. 65. — The Occipital. (External view.)
External occipital protuberance
Trapezius
Semispinalis capitis
Area covered by
scalp
Rectus capitis anterior
Longus capitis
'Attachment of superior constrictor of
pharynx to pharyngeal tubercle
Arching lateralward on each side from the external occipital protuberance
toward the lateral angle of the bone is a semicircular ridge, the superior nuchal
line [linea nuchce superior], which divides the surface into two parts — an upper
[planum occipitale] and a lower [planum nuchale]. Above this line, a second less
distinctly marked ridge — the highest nuchal line [linea nuchse suprema] — is
usually seen. It is the most curved of the three lines on this surface and gives
attachment to the epicranial aproneuosis and to a few fibres of the occipitalis
muscle. Between the superior and highest curved lines is a narrow crescentic
area in which the bone is smoother and denser than the rest of the surface, whilst
the part of the bone above the hnea suprema is convex and covered by the scalp.
The lower part of the surface is ver.y uneven and subdivided into an upper
and a lower area by the inferior nuchal line, which runs laterally from the middle
of the crest to the jugular process.
THE OCCIPITAL BONE
53
The curved lines and the areas thus mapped out between and below them give attachment
to several muscles. To the superior nuchal line are attached, medially the trapezius, and
laterally the occipitalis and sterno-cleido-mastoid; the area between the superior and inferior
curved lines receives the semispinalis capitis (complexus) medially, and splenius capitis and
ohliquus capitis superior laterally; the inferior nuchal line and the area below it afford insertion
to the rectus capitis posterior minor and major.
The anterior or cerebral surface is deeply concave and marked by two grooved
ridges which cross one another and divide the surface into four fossse of which
the two upper, triangular in form, lodge the occipital lobes of the cerebrum, and
the two lower, more quadrilateral in outline, the lobes of the cerebellum. The
vertical ridge extends from the superior angle to the foramen magnum and the
transverse ridge from one lateral angle to the other, the point of intersection being
indicated by the internal occipital protuberance [eminentia cruciata]. The
Fig. 66. — -Occipital Bone, Cerebral Stjefacb.
Superior angle
Cerebral fossa
Groove for transverse sinus
Lateral angle
Cerebellar fossa
Groove for transverse smus
Jugular process
For petrosal
i
upper part of the vertical ridge is grooved [sulcus sagittalis] for the superior
sagittal {longitudinal) sinus and gives attachment, by its margins, to the falx
cerebri; the lower part is sharp and known as the internal occipital crest, and
affords attachment to the falx cerebelli. Approaching the foramen magnum
the ridge divides, and the two parts become lost upon its margin. The angle
of divergence sometimes presents a shallow fossa for the extremity of the vermis
of the cerebellum, and is called the vermiform fossa. The two parts of the
transverse ridge are deeply grooved [sulcus transversus] for the transverse
{lateral) sinuses, and the margins of the groove give attachment to the tentorium
cerebelli. To one side of the internal occipital protuberance is a wide space,
where the vertical groove is continued into one of the lateral grooves (more
frequently the right), and this is termed the torcular Herophili; it is sometimes
exactly in the middle line.
The squamous portion has three angles and four borders. The superior angle
forming the summit of the bone is received into the space formed by the union of
the two parietals. The lateral angles are ver}' obtuse and correspond in situatio n
with the lateral ends of the transverse ridges. Above the lateral angle on each
side the margin is deeply serrated, forming the lambdoid or superior border
which extends to the superior angle and articulates with the posterior border of
the parietal in the lambdoid suture. The mastoid or inferior border extends
54 THE SKELETON
from the lateral angle to the jugular process and articulates with the mastoid
portion of the temporal.
The condylar or lateral portions [partes laterales] (ex-occipitals) form the
lateral boundaries of the foramen magnum and bear the condyles on their in-
ferior surfaces. The condyles are two convex oval processes of bone with smooth
articular surfaces, covered with cartilage in the recent state, for the superior
articular processes of the atlas. They converge in front, and are somewhat
everted. Their margins give attachment to the capsular ligaments of the
occipito-atlantal joints and on the medial side of each is a prominent tubercle
for the alar (lateral odontoid) ligament. The anterior extremities of the condyles
extend beyond the ex-occipitals on the basi-occipital portion of the bone. The
hypoglossal (anterior condyloid) foramen or canal [canalis hypoglossi] perforates
the bone at the base of the condyle, and is directed from the interior of the
cranium, just above the foramen magnum, forward and laterally; it transmits
the hypoglossal nerve and a twig of the ascending pharyngeal artery.
The foramen is sometimes double, being divided by a delicate spicule of bone. Above the
canal is a smooth convexity known as the tuberculum jugulare sometimes marked by an oblique
groove for the ninth, tenth and eleventh cranial nerves. Posterior to each condyle is a pit, the
Fig. 67. — Cerebral Surface of the Occipital, Showing an Occasional Disposition of
THE Channels.
Vermiforin fossa
Condylar foramen
Hypoglossal foramen.
condylar fossa, which receives the hinder edge of the superior articular process of the atlas when
the head is extended. The floor of the depression is occasionally perforated by the condylar
(posterior condyloid) canal or foramen [canalis condyloideus], which transmits a vein from the
transverse sinus. Projecting laterally opposite the condyle is a quadi'ilateral portion of bone
known as the jugular process, the extremity of which is rough for articulation with the jugular
facet on the petrous portion of the temporal bone. Up to twenty-five years the bones are united
here by means of cartilage; about this age ossification of the cartilage takes place, and the jugular
process thus becomes fused with the petrosal. Its anterior border is deeply notched to form the
posterior boundary of the jugular foramen, and the notch is directly continuous with a groove
on the upper surface which lodges the termination of the transverse sinus. In or near the groove
is seen the inner opening of the condylar foramen. The lower surface of the process gives
attachment to the rectus capitis lateralis and the oblique occipito-atlantal ligament. Occa-
sionally the mastoid air cells extend into this process and rarely a process of bone, representing
the paramastoid process of many mammals, projects downward from its under aspect and may
be so long as to join or articulate with the transverse process of the atlas.
The basilar portion (basi-occipital) is a quadrilateral plate of bone projecting
forward and upward in front of the foramen magnum. Its superior surface
presents a deep groove — the basilar groove [chvus]; it supports the medulla
oblongata and gives attachment to the tectorial membrane (occipito-axial
ligament). The lower surface presents in the middle line a small elevation
known as the pharyngeal tubercle for the attachment of the fibrous raphe of the
pharynx, and immediately in front of the tubercle there is frequently a shallow
THE OCCIPITAL BONE
55
fossa — the scaphoid fossa — which originally received the primitive anterior
extremity of the foregut.
On each side of the middle line are impressions for the insertions of the longus capitis (rectus
capitis anterior major) and rectus capitis anterior (minor), the impression for the latter being
Fig. 68. — The Foramen Magnum at the Sixth Year.
Condylar foramen
Ex-occipital portion of the
condyle, J
Hypoglossal foramen.
Basi-occipital portion' I of
the condyle
i
Basi-occipitaj
nearer to the condyle, and near the foramen magnum this surface gives attachment to the
anterior occipito-atlantal ligament. Anteriorly the basilar process articulates by synchondrosis
with the body of the sphenoid up to twenty years of age, after which there is complete bony
union. Posteriorly it presents a smooth rounded border forming the anterior boundary of
the foramen magnum. It gives attachment to the apical odontoid ligament, and above this
Fig. 69. — The Occipital at Birth. (Anterior view.)
Interparietal portion (develops in'
membrane)
The interparietal and supra-occipital
portions form the squamous portion
of the adult
Supra-occipital portion (develops in
cartilage)
to the ascending portion of the crucial ligament. In the occipital bone at the sixth year the
lateral extremities of this border are enlarged to form the basilar portion of the condyles. The
lateral borders are rough below for articulation with the petrous portion of the temporal bones,
but above, on either side of the basilar groove, is a half-groove, which, with a similar half -groove
on the petrous portion of the temporal bone, lodges the inferior petrosal sinus.
56
THE SKELETON
The foramen magnum is oval in shape, with its long axis in a sagittal direc-
tion. It transmits the medulla oblongata and its membranes, the accessory
nerves (spinal portions) , the vertebral arteries, the anterior and posterior spinal
Fia. 70. — The Occipital with a Separate Interparietal.
arteries, and the tectorial membrane (occipito-axial ligament). It is widest
behind, where it transmits the medulla, and is narrower in front, where it is
encroached upon by the condyles.
Fig. 71. — Skull showing a Pre-inteeparietal Bone (P.I.)-
Occasionally a facet is present on the anterior margin, forming a third occipital condyle for
articulation with the dens. Between the condyles and behind the margin of the foramen mag-
num the posterior occipito-atlantal ligament obtains attachment.
Blood-supply. — The occipital bone receives its blood-supply from the occipital, posterior
auricular, middle meningeal, vertebral and the ascending pharyngeal arteries.
Articulations. — The occipital bone is connected by suture with the two parietals, the two
temporals, and the sphenoid; the condyles articulate with the atlas, and exceptionally the occip-
ital articulates with the dens of the epistropheus by means of the third occipital condyle.
THE PARIETAL BONE 57
Ossification. — The occipital bone develops in four pieces. The squamous portion is ossi-
fied from four centres, arranged in two pairs, which appear about the eighth week. The
upper pair are deposited m membrane, and this part of the squamous portion represents the
interparietal bone of many animals. The lower oair, deposited in cartilage, form the true
supra-ocoipital element, and the four parts quickly coalesce near the situation of the future
occipital protuberance. For many weeks two deep lateral fissures separate the interparietal
and supraoccipital portions, and a membranous space extending from the centre of the squamous
portion to the foramen magnum partially separates the lateral portions of the supra-occipital.
This space is occupied later by a spicule of bone, and is of interest as being the opening through
which the form of hernia of the brain and its rneninges, known as occipital meningocele or en-
cephalocele, occurs. The basi-occipital and the two ex-occipitals are ossified each from a single
nucleus which appears in cartilage from the eighth to the tenth week.
At birth the Ijone consists of four parts united by strips of cartilage, and in the squamous
portion fissures running in from the upper and lateral angles are still noticeable. The osseous
union of the squamous and ex-occipital is completed in the fifth year, and that of the ex-
occipitals with the basi-occipital before the seventh year. Up to the twentieth year the basi-
occipital is united to the body of the sphenoid by an intervening piece of cartilage, but about
that date ossific union begins and is completed in the course of two or three years. Occasionally
the interparietal portion remains separate throughout Ufe (fig. 70), forming what has been
termed the inca hone, or it may be represented by numerous detached ossicles or Wormian
bones. In some cases a large Wormian bone, named the pre-interparietal, is found, partly
replacing the interparietal bone (fig. 71). A pre-interparietal bone is found in some mammals,
and it has occasionally been observed in the human foetal skull. In fig. 71 the bone is seen in
an adult human skull — a distinctly rare condition.
I
THE PARIETAL
The two parietal bones (figs. 72, 73), interposed between the frontal before
and the occipital behind, form a large portion of the roof and sides of the cranium.
Each parietal bone [os parietale] is quadrilateral in form, convex externally,
concave internally, and each presents for examination two surfaces, four borders,
and four angles.
The parietal surface is smooth and is crossed, just below the middle, by two
curved lines known as the temporal lines. The superior line gives attachment
to the temporal fascia; the lower, frequently the better marked, limits the origin
of the temporal muscle; whilst the narrow part of the surface enclosed between
them is smooth and more poHshed than the rest. Immediately above the ridges
is the most convex part of the bone, termed the parietal eminence [tuber parietale],
best marked in young bones, and indicating the point where ossification com-
menced. Of the two divisions on the parietal surface marked off by the temporal
lines, the upper is covered by the scalp, and the lower, somewhat striated, ait'ords
attachment to the temporal muscle. Close to the upper border and near to the
occipital angle is a small opening — the parietal foramen — which transmits a vein
to the superior sagittal {longitudinal) sinus.
The cerebral surface is marked with depressions corresponding to the cerebral
convolutions and by numerous deep furrows, running upward and backward
from the sphenoidal angle and the lower border, for the middle meningeal vessels
(sinus and artery). A shallow depression running close to the superior border
forms, with the one of the opposite side, a channel for the superior sagittal sinus,
at the side of which are small irregular pits for the Pacchionian bodies; the pits
are usually present in adult skulls, but are best marked in those of old persons.
The margins of the groove for the superior sagittal sinus give attachment to the
falx cerebri.
Borders. — The sagittal or superior border, the longest and thickest, is deeply
serrated to articulate with the opposite parietal, with which it forms the sagittal
suture. The frontal or anterior border articulates with the frontal to form the
coronal suture. It is deeply serrated and bevelled, so that it is overlapped by the
frontal above, but overlaps the edge of that bone below. The occipital or
posterior border articulates with the occipital to form the lambdoid suture, and
resembles the superior and anterior in being markedly serrated. The squamosal
or inferior border is divided into three portions : — the anterior, thin and bevelled,
is overlapped by the tip of the great wing of the sphenoid; the middle portion,
arched and also bevelled, is overlapped by the squamous part of the tempora,l;
and the posterior portion, thick and serrated, articulates with the mastoid
portion of the temporal bone.
Angles. — The frontal or anterior superior, almost a right angle, occupies that
part of the bone which at birth is membranous and forms part of the anterior
58
THE SKELETON
fontanelle. The sphenoidal or anterior inferior angle is thin and prolonged
downward to articulate with the tip of the great wing of the sphenoid. Its inner
surface is marked by a deep groove, sometimes converted into a canal for a short
Fig. 72. — The Left Parietal. (Outer surface.)
Sagittal border Parietal foramen
Portion covered by
Superior temporal line
Inferior temporal line
For temporal muscle,
and forms part of
the temporal fossa
Sphenoidal angle'
Fig. 73. — The Left Parietal. (Inner surface.)
Parietal foramen Groove for superior sagittal sinus Depressions for Pacchionian bodies
Groove for transverse
Grooves for middle meningeal artery
distance, for the middle meningeal vessels (chiefly for the sinus). The occipital
or posterior superior angle is obtuse and occupies that part which during foetal
life enters into formation of the posterior fontanelle. The mastoid or posterior
THE FRONTAL BONE
59
inferior angle is thick and articulates with the mastoid portion of the temporal
bone. Its inner surface presents a shallow groove which lodges a part of the
transverse (lateral) sinus.
Blood-supply. — The parietal bone receives its blood-supply from the middle meningeal,
occipital, and supra-orbital arteries.
Articulations. — The parietal articulates with the occipital, frontal, sphenoid, temporal,
its fellow of the opposite side, and the epipterio bone when present. Occasionally the temporal
and epipteric bones exclude the parietal from articulation with the great wing of the sphenoid.
Ossification. — The parietal ossifies from a single nucleus which appears in the outer layer
of the membranous wall of the skull about the seventh week. The ossification radiates in
such a way as to leave a cleft at the upper part of the bone in front of the occipital angle, the
Fig. 74. — Unusual Form op Pabietal Exhibiting a Horizontal Suture Separating the
Bone into Two Pif.ces, Upper and Lower.
^f^^^^^^^sy^m
cleft of the two side forming a lozenge-shaped space across the sagittal suture known as the sag-
ittal fontanelle. This is usually closed about the fifth month of intra-uterine life, but traces may
sometimes be recognised at the time of birth, and the parietal foramina are to be regarded as
remains of the cleft. According to Dr. A. W. W. Lea, a well-developed sagittal fontanelle is
present in 4 . 4 per cent, of infants at birth. In such cases it closes within the first two months
of life, but at times it may remain open for at least eight months after birth and possibly longer.
Rarely the parietal bone is composed of two pieces (fig. 74), one above the other, and
separated by an antero-posterior suture (sub-sagittal suture), more or less parallel with the
sagittal suture. In such cases the parietal is ossified from two centres of ossification.
THE FRONTAL
The frontal bone [os frontale] closes the cranium in front and is situated above
the skeleton of the face. It consists of two portions — a frontal {vertical) portion
[squama frontalis], forming the convexity of the forehead, and an orbital {hori-
zontal) portion, which enters into formation of the roof of each orbit.
Frontal {vertical) portion. — The frontal surface is smooth and convex, and
usually presents in the middle line above the root of the nose some traces of the
suture which in young subjects traverses the bone from the upper to the lower
part. This suture, known as the frontal or metopic suture, indicates the line of
junction of the two lateral halves of which the bone consists at the time of birth;
in the adult the suture is usually obliterated except at its lowest part. On each
side is a rounded elevation, the frontal eminence [tuber frontale], very prominent
in young bones, below which is a shallow groove, the sulcus transversus, separat-
ing the frontal eminence from the superciliary arch. The latter forms an arched
pi^ojection above the margin of the orbit and corresponds to an air-cavity within
the bone known as the frontal sinus; it gives attachment to the orbicularis oculi
and the corrugator muscles. The ridges of the two sides converge toward the
'
60
THE SKELETON
median line, but are separated by a smooth surface called the glabella (nasal
eminence). Below the arch the bone presents a sharp curved margin, the supra-
orbital border, forming the upper boundary of the circumference of the orbit and
separating the frontal from the orbital portion of the bone. At the junction of
its medial and intermediate third is a notch, sometimes converted into a foramen,
and known as the supra-orbital notch or foramen ; it transmits the supra-orbital
nerve, artery, and vein, and at the bottom of the notch is a small opening for
a vein of the diploe which terminates in the supra-orbital. Sometimes, a second
less marked notch is present, medial to the supra-orbital, and known as the
frontal notch; it transmits one of the divisions of the supra-orbital nerve. The
extremities of the supra-orbital border are directed downward and form the
medial and zygomatic (lateral angular) processes. The prominent zygomatic proc-
ess articulates with the zygomatic bone and receives superiorly two well-marked
lines which converge somewhat as they curve downward and forward across the
bone. These are the superior and inferior temporal lines, continuous with the
Fig. 75. — The Frontal. (Anterior view.)
'Temporal line
Supra-orbital notch
Zygomatic process
temporal lines on the parietal bone, the upper giving attachment to the temporal
fascia and the lower to the temporal muscle. Behind the lines is a slight con-
cavity which forms part of the fioor of the temporal fossa and gives origin to the
temporal muscle. The medial angular processes articulate with the lacrimals
and form the lateral limits of the nasal notch, bounded in front by a rough,
semilunar surface which articulates with the upper ends of the nasal bones and
the frontal (nasal) processes of the maxillae.
In the concavity of the notch hes the nasal portion of the frontal, which projects somewhat
beneath the nasal bones and the nasal processes of the maxillfe. It is divisible into three parts:
— a median frontal (nasal) spine, which descends in the nasal septum between the crest of the
nasal bones in front and the vertical plate of the ethmoid behind, and, on the posterior
aspect of the process, two alee, one on either side of the median ridge from which the frontal
(nasal) spine is continued. Each ala forms a small grooved surface which enters into the
formation of the roof of the nasal fossa.
The cerebral surface presents in the middle line a vertical groove — the sagittal
sulcus — which descends from the middle of the upper margin and lodges the
superior sagittal (longitudinal) sinus. Below, the groove is succeeded by the
frontal crest, which terminates near the lower margin at a small notch, converted
into a foramen by articulation with the ethmoid.
THE FRONTAL BONE
61
The foramen is called the foramen caecum, and is generally closed below, but sometimes
transmits a vein from the nasal fossje to the superior sagittal (longitudinal) sinus. The frontal
crest serves for the attachment of the anterior part of the falx cerebri. On each side of the
middle line the bone is deeply concave, presentino: depressions for the cerebral convolutions
and numerous small furrows which, running medially from the lateral margin, lodge branches of
the middle meningeal vessels. At the upper part of the surface, on either side of the frontal
sulcus, are some depressions for Pacchionian bodies.
The horizontal portion consists of two somewhat triangular plates of bone
called the orbital plates, which, separated from one another by the ethmoidal
Fig. 76. — The Frontal Bone. (Inferior view.)
Frontal spine
Articulation with nasal
bone
Articulation with max-
illa ^<Jitf^'^- - '^^fst&i^li l«Ktf\ iillillllWIIIIiillli
Trochlear fossa
Lacrimal fossa
Orbital surface
ulation with
papyracea
of ethmoid
Articulation with
zygomatic
Articulation with
greater wing of
sphenoid
Articulation with
lesser wing of
sphenoid
{
Ethmoidal notch
notch [incisura ethmoidalis], form the greater part of the roof of each orbit. When
the bones are articulated, the notch is filled up by the cribriform plate of the
ethmoid, and the half -cells on the upper surface of the lateral mass of the ethmoid
are completed by, the depressions or half -cells which occupy the irregular margins
of the notch. Traversing these edges transversely are two grooves which com-
plete, with the ethmoid, the anterior and posterior ethmoidal canals. The
anterior transmits the anterior ethmoidal nerve and vessels; the posterior trans-
mits the posterior ethmoidal nerve and vessels, and both canals open on the
medial wall of the orbit. Farther forward, on either side of the nasal spine, are
the openings of the frontal sinuses, two irregular cavities which extend within
Fig. 77. — The Frontal Bone at Birth.
the bone for a variable distance and give rise to the superciliary arches (ridges) .
Each is lined by mucous membrane and communicates with the nasal fossa by
means of a passage called the infundibulum.
The inferior surface of each orbital plate, smooth and concave, presents im-
mediately behind the lateral angular process the lacrimal fossa, for the lacrimal
gland. Close to the medial angular process is a depression called the trochlear
fossa [fovea trochlearis], which gives attachment to the cartilaginous pulley for
the superior oblique muscle. The superior surface of each plate is convex and
strongly marked by eminences and depressions for the convolutions on the orbital
surface of the cerebrum.
62
THE SKELETON
Borders. — The articular border of the frontal portion (parietal margin) forms a little more
than a semicircle. It is thick, strongly serrated, and bevelled so as to overlap the parietal
above and to be overlapped by the edge of that bone below. The border is continued inferiorly
into a triangular rough surface on either side, which articulates with the great wing of the sphe-
noid. The posterior border of the orbital portion is thin and articulated with the lesser wing
of the sphenoid.
Blood-supply. — The blood-vessels for the supply of the vertical portion are derived
from the frontal and supra-orbital arteries, which enter on the outer surface, and from the
middle and small meningeal, which enter on the cerebral surface. The horizontal portion
receives branches from the ethmoidal, and other branches of the ophthalmic, as well as from
the meningeal.
Articulations. — The frontal articulates with the parietal, sphenoid, ethmoid, lacrimal,
zygomatic (malar), maxilla, and nasal bones. Also, with the epipteric bones when present,
and occasionally with the squamous portion of the temporal, and with the sphenoidal concha
when it reaches the orbit.
Fig. 78. — Unusually Large Frontal Sinuses.
Ossification. — The frontal is ossified from two nuclei deposited in the outer layer of the
membranous wall of the cranium, in the situations ultimately known as the frontal eminences.
These nuclei appear about the eighth week, and ossification spreads quickly through the mem-
brane. At birth the bones are quite distinct, but subsequently they articulate with each other
in the median line to form the metopie suture. In the majority of cases the suture is obliter-
ated by osseous union, which commences about the second year, though in a few cases the
bones remain distinct throughout life.
After the two halves of the bone have united, osseous material is deposited at the lower
end of the metopie suture to form the frontal spine, which is one of the distinguishing features
of the human frontal bone. The spine appears about the twelfth year, and soon consolidates
with the frontal bone above. Accessory nuclei are sometimes seen between this bone and the
lacrimal and may persist as Wormian ossicles.
The frontal sinuses appear about the seventh year as prolongations upward from the hiatus
semilunaris and increase in size up to old age. As they grow they extend in three directions,
viz., upward, laterally, and backward along the orbital roof. A bony septum, usually com-
plete, separates the sinuses of the two sides, and they are larger in the male than in the female.
The supercihary arches are not altogether reliable guides as to the size of the sinuses, since
examples are seen in which the arches are low and the sinuses large. In fig. 78 an example
of unusually large sinuses is figured, illustrating the extension upward, laterally, and backward.
THE SPHENOID
The sphenoid [os sphenoidale] (figs. 79, 80, 81, 82) is situated in the base of
the skull and takes part in the formation of the floor of the anterior, middle, and
posterior cranial fossae, of the temporal and nasal fossae, and of the cavity of the
orbit. It is very irregular in shape and is described as consisting of a central
part or body, two pairs of lateral expansions called the great and small wings,
and a pair of processes which project downward, called the pterygoid processes.
The body, irregularly cuboidal in shape, is hollowed out into two large cavities
known as the sphenoidal sinuses, separated by a thin sphenoidal septum and
opening in front by two large apertures into the nasal fossae. The superior sur-
THE SPHENOID
63
face presents the following points for examination: In front is seen a prominent
spine, the ethmoidal spine, which articulates with the hinder edge of the cribri-
form plate of the ethmoid. The sm-face behind this is smooth and frequently
presents two longitudinal grooves, one on either side of the median line, for the
olfactory bulbs; it is limited posteriorly by a ridge, the limbus sphenoidalis,
which forms the anterior border of the narrow transverse optic groove [sulcus
chiasmatis], above and behind which lies the optic commissure. The groove
terminates on each side in the optic foramen, which perforates the root of the
small wing and transmits the optic nerve and the ophthalmic artery. Behind the
optic groove is the tuberculum sellae, indicating the line of junction of the two
parts of which the body is formed (pre- and post-sphenoid); and still further
back, a deep depression, the hypophyseal fossa [sella turcica], which lodges the
hypophysis cerebri. The floor of the fossa presents numerous foramina for
blood-vessels, and at birth the superior orifice of a narrow passage called the
basi-pharyngeal canal opens on the tuberculum. The posterior boundary of the
fossa is formed by a quadrilateral plate of bone, the dorsum sellae (dorsum
Fig. 79. — The Sphenoid, from Above.
Optic groove Ethmoidal spine . ....
Optic Tuberculum sellse Superior orbital fissure
Articulation
with frontal
Articulation
with parietal
Cerebral surface
of great wing
Foramen rotundum
Foramen Vesalii
Foramen spinosum
Carotid groove
Posterior petrosal process
Dorsum sellae
Posterior clinoid process
ephippii), the posterior surface of which is sloped in continuation mth the basilar
groove of the occipital bone. The superior angles of the plate are surmounted
by the posterior clinoid processes, which give attachment to the tentorium cere-
belli and the interclinoid ligaments. Below the clinoid process, on each side of
the dorsum sellffi (sometimes at the suture between the sphenoid and apex of
petrosal), a notch is seen, converted into a foramen by the dura mater, for the
passage of the sixth cranial nerve, and at the inferior angle the posterior petrosal
process, which articulates with the apex of the petrous portion of the temporal
bone, forming the inner boundary of the foramen lacerum. The dorsum sellse
is slightly concave posteriorly (the clivus) and supports the pons Varolii and the
basilar artery.
The inferior surface presents in the middle line a prominent ridge known as
the rostrum, which is received into a deep depression between the alee of the
vomer. On each side is the vaginal process of the medial pterygoid plate,
directed horizontally and medially, which, with the alee of the vomer, covers the
greater part of this surface. The remainder is rough and clothed by the mucous
membrane of the roof of the pharynx.
The anterior surface is divided into two lateral halves by the sphenoidal
crest, a vertical ridge of bone continuous above with the ethmoidal spine, below
with the rostrum, and articulating in front with the perpendicular plate of the
ethmoid. The surface on each side presents a rough lateral margin for articula-
tion with the lateral mass of the ethmoid and the orbital process of the palate
bone. Elsewhere it is smooth, and enters into the formation of the roof of the
64
THE SKELETON
nasal fossae, presenting superiorly the irregular apertures of the sphenoidal
sinuses.
The body is not hollowed until after the sixth year, but from that time the sinuses increase
in size as age advances. Except for the apertures just mentioned, they are closed below and
in front by the two sphenoidal conchse (turbinate bones), originally distinct, but in the adult
usually incorporated with the sphenoid.
The posterior surface is united to the basilar process of the occipital, up to
the twentieth year, by a disc of hyaline cartilage forming a synchondrosis, but
afterward this becomes ossified and the two bones then form one piece.
Fig. 80. — The Left Half of the Sphenoid.
Anterior clinoid process
Middle clinoid process
Posterior clinoid process
Spine of sphenoid
Lateral pterygoid plate-
Hamular process of medial pterygoid platt
Ethmoidal spine
— -The limbus
Optic groove
Tuberculum sella
Dorsum sellee
The lateral surface of the body gives attachment to the two wings, and its
fore part is free where it forms the medial boundary of the superior orbital fissure and
the posterior part of the medial wall of the orbit. Above the line of attachment
of the great wing is a broad groove which lodges the internal carotid artery and
the cavernous sinus, called the carotid groove. It is deepest where it curves behind
the root of the process, and this part is bounded along its lateral margin by a
slender ridge of bone named the lingula, which projects backward in the angle
between the body and the great wing.
Fig. 81. — The Sphenoid. (Anterior view.)
Orbital surface (the pointer"^
crosses the zygomatic
border)
Lateral pterygoid plate
Pterygoid notch,
Hamular process-
Pterygo-palatine groove
The small or orbital wings [alse parvse] are two thin, triangular plates of bone
extending nearly horizontally and laterally on a level with the front part of the
upper surface of the body. Each arises medially by two processes or roots, the
upper thin and flat, the lower thick and rounded.
Near the junction of the lower root with the body is a small tubercle for the attachment of
the common tendon of three ocular muscles — viz., the superior, medial, and upper head of
lateral rectus — and between the two roots is the optic foramen. The lateral extremity, slender
and pointed, approaches the great wing, but, as a rule, does not actually touch it. The supe-
rior surface, smooth and slightly concave, forms the posterior part of the anterior fossa of the
cranium. The inferior surface constitutes a portion of the roof of each orbit and overhangs
THE SPHENOID 65
the superior orbital (or sphenoidal) fissure, the elongated opening between the small and great
wings. The anterior border is serrated for articulation with the orbital plate of the frontal,
and the posterior border, smooth and rounded, is received into the Sylvian fissure of the cere-
brum. Moreover, the posterior border forms the boundary between the anterior and middle
cranial fossse and is prolonged at its medial extremity to form the anterior clinoid process,
which gives attachment to the tentorium cerebelli and the interclinoid ligaments. Between
the tuberoulum sellse and the anterior chnoid process is a semicircular notch which represents
the termination of the carotid groOve. It is sometimes converted into a foramen, the carotico-
clinoid foramen, by a spicule of bone which bridges across from the anterior clinoid to the middle
clinoid process; the latter is a small tubercle frequently seen on each side, in front of the hypo-
physeal fossa, and slightly posterior to the tuberculum sellse; the foramen transmits the internal
carotid artery, and the spicule of bone which may complete the foramen is formed by ossi-
fication of the carotioo-clinoid ligament.
The great or temporal wings [alse magnse], arising from the lateral surface of
the body, extend laterally and then upward and forward. The posterior part
is placed horizontally and projects backward into the angle between the squamous
and petrous portions of the temporal bone. From the under aspect of its pointed
extremity the spine, which is grooved medially by the chorda tympani nerve
(Lucas), projects downward. The spine serves for the attachment of the spheno-
mandibular ligament and a few fibres of the tensor veli -palatini. Each wing
presents for examination four surfaces and four borders.
Fig. 82. — Right Half op Sphenoid. (Anterior view.)
Temporal surface
Ridge which forms the upper bound-
ary of the inferior orbital fissure
Ext. pterygoid muscU
Sphenoidal crest
Sphenoidal sinus
The cerebral or superior surface is smooth and concave. It enters into the
formation of the middle cranial fossa, supports the temporo-sphenoidal lobe of
the cerebrum, and presents several foramina. At the anterior and medial
part is the foramen rotundum for the second division of the fifth nerve, and
behind and lateral to it, near the posterior margin of the great wing, is the large
foramen ovale, transmitting the third division of the fifth, the small meningeal
artery, and an emissary vein from the cavernous sinus.
Behind and lateral to the foramen ovale is the small circular foramen spinosum, sometimes
incomplete, for the passage of the middle meningeal vessels, and the recurrent branch of the
third division of the fifth. Between the foramen ovale and the foramen rotundum is the incon-
stant foramen Vesalii, which transmits a small emissary vein from the cavernous sinus; and on
the plate of bone, behind and medial to the foramen ovale (spheno-petrosal lamina), a minute
canal is occasionally seen — the canaliculus innominatus — -through which the small superficial
petrosal nerve escapes from the skull. When the canaliculus is absent, the nerve passes through
the foramen ovale.
The anterior surface looks medially and forward and consists of two divisions —
a quadrilateral or orbital surface, which forms the chief part of the lateral wall of
the orbit, and a smaller, inferior or spheno-maxillary surface, situated above the
pterygoid process and perforated by the foramen rotundum; this inferior part
forms the posterior wall of the pterygo-palatine fossa.
The lateral or squamo-zygomatic surface is divided by a prominent infra-
temporal ridge into a superior portion, which forms part of the temporal fossa and
affords attachment to the temporal muscle, and an inferior part, which looks
downward into the zygomatic fossa and gives attachment to the external pterygoid
muscle; the inferior part joins the lateral surface of the lateral pterygoid plate,
and presents the inferior orifices of the foramen ovale, foramen spinosum, and
foramen of Vesalius.
66 THE SKELETON
Borders. — The posterior border extends from the body to the spine. By its lateral third it
articulates with the petrous portion of the temporal bone, whilst the medial two-thirds form the
anterior boimdary of the foramen laoerum. The squamosal border is serrated behind and
bevelled in front for articulation with the squamous portion of the temporal bone, whilst its
upper extremity, or summit, is bevelled on its inner aspect, for the anterior inferior angle of the
parietal. Immediately in front of the upper extremity is a rough, triangular, sutural area for
the frontal, the sides of which are formed by the upper margins of the superior, anterior, and
lateral surfaces respectively. The zygomatic or anterior border separates the orbital and tem-
poral surfaces and articulates with the zygomatic, and by its lower angle, in many skulls, also
with the maxilla. Below the anterior border is a short horizontal ridge, non-articular, which
separates the spheno-maxillary and zygomatic surfaces. Above and medially, where the orbital
and cerebral surfaces meet, is the sharp medial border, which forms the lower boundarj' of the
superior orbital fissure, serving for the passage of the third, fourth, three branches of the first
division of the fifth, and the sixth cranial nerves, the orbital branch of the middle meningeal
artery, a recurrent branch from the lacrimal artery, some twigs from the cavernous plexus of
the sympathetic, and one or two ophthalmic veins. Near the middle of the border is a small
tubercle for the origin of the lower head of the lateral rectus muscle.
The pterygoid processes project downward from the junction of the bodj' and
the great wings. Each consists of two plates, one shorter and broader, the lateral
pterygoid plate [lamina lateralis], the other longer and narrower, the medial
pterygoid plate [lamina medialis]. They are united in front, but diverge behind
so as to enclose between them the pterygoid fossa in which lie the internal "pterygoid
and tensor palati muscles. The lateral pterygoid plate is turned a httle laterally
and by its lateral surface, which looks into the zygomatic fossa, affords attach-
ment to the ezteimal pterygoid muscle, whilst from its medial surface the internal
pterygoid takes origin.
The posterior border of the lateral pterygoid plate frequently presents one or more bony
projections, which represent ossified parts of the pterygo-spinous ligaments, and occasionally
one may extend across to the spine and complete the bony boundary of the pterygo-
spinous foramen. The medial pterygoid plate is prolonged below into a slender, hook-like or
hamular process, smooth on the under aspect for the tendon of the tensor palati, which plays
round it. Superiorly, the medial plate extends medially on the under surface of the body,
forming the vaginal process, which articulates with the ala of the vomer and the sphenoidal
process of the palate. The vaginal process presents, on the under surface, a small groove
which, with the sphenoidal process of the palate, forms the pharyngeal canal for the trans-
mission of branches of the spheno-palatine vessels and ganglion. The medial surface of
the medial pterygoid plate forms part of the lateral boundary of the nasal fossa, and the
lateral surface, the medial boundary of the pterygoid fossa. The posterior border presents
superiorly a well-marked prominence, the pterygoid tubercle, above and to the lateral side
of which is the posterior orifice of the pterygoid canal. The latter pierces the bone in the
sagittal direction at the root of the medial pterygoid plate and transmits the Vidian vessels
and nerve. Some distance below the tubercle is a projection, called the processus tubarius,
which supports the cartilage of the tuba auditiva (Eustachian tube). From the lower third
of the posterior border and from the hamular process, the superior constrictor of the pharynx
takes origin, and from the depression known as the scaphoid fossa, situated in the upper part
of the recess between the two pterygoid plates, the tensor palati arises.
Fig. 83. — The Sphenoid at Birth.
Pterygoid canal
In front, the two plates are joined above, but diverge below, leaving a gap —
the pterygoid notch — occupied, in the articulated skull, by the pyramidal process
of the palate. Superiorly, they form a triangular surface which looks into the
pterygo-palatine fossa and presents the anterior orifice of the pterygoid canal.
The anterior border of the medial pterygoid plate articulates with the posterior
border of the vertical plate of the palate.
Blood-supply. — The sphenoid is supplied by branches of the middle and small meningeal
arteries, the deep temporal and other branches of the internal maxillary artery — viz., the
Vidian and spheno-palatine. The body of the bone also receives twigs from the internal carotid.
Articulations. — The sphenoid articulates with all the bones of the cranium — viz., occipital,
THE SPHENOIDAL CONCHM
67
parietal, frontal, ethmoid, temporal, and sphenoidal conohfe. Also with the palate, vomer,
zygomatic, epipteric bone when present, and occasionally with the maxilla.
Ossification.^The sphenoid is divided, up to the seventh or eighth month of intra-uterine
life, into an anterior or pre-sphenoid portion, including the part of the bddy in front of the tub-
erculum sellai and the small wings, and a post-sphenoid portion, the part behind the tuberculum
sellae including the hypophyseaf fossa and the great wings. The two portions of the body join
together before birth, but in many animals the division is persistent throughout life.
The pre-sphenoid portion ossifies in cartilage from four centres, one of which gives rise to
each lesser wing (orbito-sphenoid) and a pair to the body of the pre-sphenoid.
In the formation of the post-sphenoidal portion both cartilage and membrane bone partici-
pate, the pterygoid plates being formed in membrane, while the rest of the portion, together
with the hamular process, ossifies from cartilage. (Fawoett.) At about the eighth week a
Fig. 84. — The Jugum Sphenoidale.
centre appears at the base of each greater wing (ali-sphenoid), and at about the same time a
pair of centres appear in the body (basi-sphenoid) and later one in each hngula (sphenotic).
The medial pterygoid plates are pre-formed in cartilage, in which a centre appears for the
hamular process, but the rest of the plate is formed from membrane bone which invests the
cartilage. The lateral plate is formed in membrane and a considerable part of the greater
wing is also membranous in origin (see epipteric bone).
At birth the bone consists of three pieces. The median piece includes the basi-sphenoid
and Hngulse, conjoined with the pre-sphenoid, carrying the orbito-sphenoids.
The two lateral pieces are the ali-sphenoids, carrying the medial pterygoid plates. The
dorsum sellae is cartilaginous. A canal, known as the basi-pharyngeal canal, extends into the
Pig. 85. — The Inferior Surface op Pre-sphenoid at the Sixth Year.
Pre-sphenoid
Pterygo-palatine groove
~ Vidian canal
Vaginal process
body from the sella turcica and sometimes reaches its under surface. It contains a process
of dura mater, and represents the remains of the canal in the base of the cranium, through
which the diverticulum of Rathke extended upward to form part of the hypophysis.
The great wings are joined to the lingulae by cartilage, but in the course of the first year
bony union takes place. About the same time the orbito-sphenoids meet and fuse in the mid-
dle line to form the jugum sphenoidale, which thus excludes the anterior part of the pre-sphenoid
from the cranial cavity. For some years the body of the pre-sphenoid is broad and rounded
inferiorly (fig. 85). The posterior clinoid processes chondrify separately, a fact which throws
some hght on the occasional absence of these processes.
THE SPHENOIDAL CONCHA
The sphenoidal conchEe (or turbinate bones; bones of Bertin) (figs. 86, 87) may be obtained
as distinct ossicles about the fifth year, and resemble in shape two hollow cones flattened in
three planes. At this date each is wedged in between the under surface of the pre-sphenoid
and the orbital and sphenoidal processes of the palate bone, with the apex of the cone directed
backward as far as the vaginal process of the medial pterygoid plate. Of its three surfaces,
the lateral is in relation with the pterygo-palatine fossa, and occasionally extends upward be-
tween the sphenoid and the lamina papyracea of the ethmoid, to appear on the medial wall of
the orbit (fig. 105). The inferior surface forms the upper boundary of the spheno-palatine
foramen and enters into formation of the posterior part of the roof of the nasal fossa. The
68 THE SKELETON
superior surface lies flattened against the under surface of the pre-sphenoid, whilst the base of
the cone is in contact with the lateral mass of the ethmoid.
The deposits of earthy matter from which the sphenoidal conchae are formed appear at the
fifth month. At birth each forms a small triangular lamina in the peiichondrium of the ethmo-
vomerine plate near its junction with the presphenoid, and partially encloses a small recess from
the mucous membrane of the nose, which becomes the sphenoidal sinus. By the third year the
bone has surrounded the sinus, forming an osseous capsule, conical in shape, the circular orifice
which represents the base becoming the sphenoidal foramen. As the cavity enlarges the
medial wall is absorbed, and the medial wall of the sinus is then formed by the pre-sphenoid.
Fig. 86. — The Sphenoidal Concha at the Sixth Year.
The bones are subsequently ankylosed in many skulls with the ethmoid, whence they are often
regarded as parts of that bone. More frequently they fuse with the pre-sphenoid, and less
frequently with the palate bones. After the twelfth year they can rarely be separated from the
skull without damage. In many disarticulated skulls they are so broken up that a portion is
found on the sphenoid, fragments on the palate bones, and the remainder attached to the
ethmoid. Sometimes, even in old skulls, they are represented by a very thin triangular plate
on each side of the rostrum of the sphenoid (fig. 87).
Fig. 87. — The Sphenoidal Conch.s: from an Old Skull.
Sphenoidal concha
Rostrum of sphenoid
THE EPIPTERIC AND WORMIAN BONES
The epipterics are scale-like bones which occupy the antero-lateral fontanelles-
Each epipteric bone is wedged between the squamo-zygomatic portion of the
temporal, frontal, great wing of sphenoid, and the parietal, and is present in most
skulls between the second and fifteenth year. After that date it may persist as a
separate ossicle, or unite with the sphenoid, the frontal, or the squamo-zygomatic.
The epipteric bone is pre-formed in membrane, and appears as a series of bony
granules in the course of the first year.
The Wormian or sutural bones [ossa suturarum] are small, irregularly shaped
ossicles, often found in the sutures of the cranium, especially those in relation with
the parietal bones. They sometimes occur in great numbers; as many as a
hundred have been counted in one skull. They are rarely present in the sutures
of the face.
THE TEMPORAL BONE
The temporal bone [os temporale], situated at the side and the base of the
cranium, contains the organ of hearing and articulates with the lower jaw. It is
usually divided into three parts — viz., the squamous portion, forming the anterior
and superior part of the bone, thin and expanded and prolonged externally into
the zygomatic process; the mastoid portion, the thick conical posterior part,
behind the external aperture of the ear; and a pyramidal projection named the
petrous portion, situated in a plane below and to the medial side of the two parts
already mentioned, and forming part of the base of the skull.
When it is considered in reference to its mode of development, the temporal bone is found
to be built up of three parts (figs. 88, 89, 90), which, however, do not altogether correspond to
the arbitrary divisions of the adult bone. The three parts are named squamosal, petrosal,
THE TEMPORAL BONE
69
and tympanic, and a knowledge of their arrangement in the early stages of growth greatly
faciHtates the study of the fully formed bone.
The more important division of the temporal bone is the petrous portion. It
is pyramidal in shape, and contains the essential part of the organ of hearing,
Fig. 88. — -The Temporal Bone at Birth. Fig.
-Temporal Bone at Birth.
(Inner view.)
i
Hiatus canalis facialis
Floccular fossa
A.qu£eductus vestibuli
Internal auditory
meatus
Fig. 90. — The Temporal Bone at Birth. (Outer view.)
Post-glenoid tubercle
Petro-tympanic fissure
Tympanic annulus
Petro- squamous suture
Petrosal
Stylo-mastoid foramen
Tympano-byal
Carotid canal
Fig. 91. — Right Temporal Bone at about Six Years.
The tympanic plate has been separated and drawn below. A portion of the post-auditory
process of the squamosal has been removed to show the mastoid antrum.
Position of lateral semicircular canal
Mastoid antrum
Mastoid process
Fenestra cocbleaa
Fenestra vestibuli
Canal for tensor tympani
Promontory
>y Carotid canal
Non-ossified area of tbe
tympanic plate
around which it is developed as a cartilaginous capsule. This is known as the
periotic capsule or petrosal element, and its base abuts on the outer aspect of the
70
THE SKELETON
cranium, where it forms a large part of the so-called mastoid portion of the
temporal bone. Besides containing the internal ear, it bears on its cranial side a
foramen for the seventh and eighth cranial nerves (internal auditory meatus),
and on its outer side two openings — the fenestra vestibuli and fenestra cochleae
(fig. 91). The squamosal is a superadded element and is formed as a membrane
bone in the lateral wall of the cranium. It is especially developed in man in
consequence of the large size of the brain, and forms the squamous division of the
adult bone, and by a triangular shaped process which is prolonged behind the
aperture of the ear it also contributes to the formation of the mastoid portion.
It is obvious, therefore, that the mastoid is not an independent element, but
belongs in part to the petrous, and in part to the squamous. The tympanic
portion, also superadded, is a ring of bone developed in connection with the
external auditory meatus, and eventually forms a plate constituting part of the
bony wall of this passage. These three parts are easily separable at birth, but
eventually become firmly united to form a single bone which affords little trace
of its complex origin. Lastly a process of bone, developed in the second visceral
arch, coalesces with the under surface of the temporal bone and forms the styloid
process.
Fig. 92. — The Left Temporal Bone. (Outer view.)
Zygomatic process
Tympanic plati
Stylo-pharyngeus
Stylo-hyoid
Stylo-glossus
Styloid process Mastoid process
The squamous portion [squama temporalis] is flat, scale-like, thin, and trans-
lucent. It is attached almost at right angles to the petrous portion, forms part
of the side wall of the skull and is limited above by an uneven border which
describes about two-thirds of a circle. The outer surface is smooth, slightly
convex near the middle, and forms part of the temporal fossa. Above the
external auditory meatus it presents a nearly vertical groove for the middle
temporal artery. Connected with its lower part is a narrow projecting bar of
bone known as the zygomatic process. At its base the process is broad, directed
lateralljr, and flattened from above downward. It soon, however, becomes
twisted on itself and runs forward, almost parallel with the squamous portion.
This part is much narrower and compressed laterally so as to present medial
and lateral surfaces with upper and lower margins. The lateral surface is sub-
cutaneous; the medial looks toward the temporal fossa and gives origin to the
masseter muscle. The lower border is concave and rough for fibres of the same
muscle, whilst the upper border, thin and prolonged further forward than the
lower, receives the temporal fascia. The extremity of the process is serrated for
articulation with the zygomatic bone. At its base the zygomatic process presents
three roots — anterior, middle, and posterior.
THE TEMPORAL BONE
71
The anterior, continuous with the lower border, is short, broad, convex, and directed
medially' to terminate in the articular tubercle, which is covered with cartilage in the recent
state, for articulation with the condyle of the lower jaw. The middle root, sometimes very
prominent, forms the post-glenoid process. It separates the articular portion of the man-
dibular fossa from the external auditory meatus and is situated immediately in front of the
petro-tympanic (Glaserian) fissure. The posterior root, prolonged from the upper border, is
strongly marked and extends backward as a ridge above the external auditory meatus. It is
called the temporal ridge (supra-mastoid crest), and marks the arbitrary line of division be-
tween the squamous and mastoid portions of the adult bone. It forms part of the posterior
boundary of the temporal fossa, from which, as well as from the ridge, fibres of the temporal
muscle arise. Where the anterior root joins the zygomatic process is a slight tubercle — the
preglenoid tubercle — for the attachment of the temporo-mandibular ligament, and between the
anterior and middle roots is a deep oval depression, forming the part of the mandibular fossa
for the condyle of the lower jaw. The mandibular fossa is a considerable hollow, bounded in
front by the articular tubercle and behind by the tympanic plate which separates it from the
external auditory meatus. It is divided into two parts by a narrow slit — the petro-tympanic
(Glaserian) fissure. The anterior part [facies articularis], which belongs to the squamous
portion, is articular, and, like the articular tubercle, is coated with cartilage. The posterior
Fig. 93. — The Left Temporal Bone. (Seen from the inner side and above.)
Squaipous portion
Meningeal groove
{
Zygomatic process
Eminentia arcuata
Sigmoid groove
Mastoid foramen
Masseter
Hiatus canalis facialis
Internal auditory meatus
Aquasductus vestibuli
Fossa subarcuata
Mastoid process Aquaeductus cochleaE
Stylo-pharyngeus
Styloid process
part, formed by the tympanic plate, is non-articular and lodges a lobe of the parotid gland.
Immediately in front of the articular tubercle is a small triangular surface which enters into
the formation of the roof of the zygomatic fossa.
The inner or cerebral surface of the squamous portion is marked by furrows for the con-
volutions of the brain and grooves for the middle meningeal vessels. At the upper part of the
surface the inner table is deficient and the outer table is prolonged some distance upward,
forming a thin scale, with the bevelled surface looking inward to overlap the corresponding
edge of the parietal. Anteriorly the border is thicker, serrated, and slightly bevelled on the
outer side for articulation with the posterior border of the great wing of the sphenoid. Pos-
teriorly it joins the rough serrated margin of the mastoid portion to form the parietal notch.
The line separating the squamous from the petrous portion is indicated at the lower part of
the inner surface by a narrow cleft, the internal petro-squamous suture, the appearance of
which varies in different bones according to the degree of persistence of the original line of
division.
The mastoid portion [pars mastoidea] is rough and convex. It is bounded
above by the temporal ridge and the parieto-mastoid suture; in front, by the
external auditory meatus and the tympano-mastoid fissure; and behind, by the
suture between the mastoid and occipital. As already pointed out, it is formed
by the squamous portion in front and by the base of the petrosal behind, the
line of junction of the two component parts being indicated on the outer surface
by the external petro-squamous suture (squamo-mastoid). The appearance of
the suture varies, being in some bones scarcely distinguishable, in others, a series
72 THE SKELETON
of irregular depressions, whilst occasionally it is present as a well-marked fissure
(fig. 92) directed obliquely downward and forward. The mastoid portion is
prolonged downward behind the external acoustic meatus into a nipple-shaped
projection, the mastoid process, the tip of which points forward as well as down-
ward. The process is marked, on its medial surface, by a deep groove, the
mastoid notch (digastric fossa), for the origin of the digastric muscle, and
again medially by the occipital groove for the occipital artery.
The outer surface is perforated by numerous foramina, one, of large size, being usually
situated near the posterior border and called the mastoid foramen. It transmits a vein to the
transverse (lateral) sinus and the mastoid branch of the occipital artery. The mastoid portion
gives attachment externally to the auricularis posterior (retrahens aurem) and occipitalis, and,
along with the mastoid process, to the sterno-mastoid, splenius capitis, and longissimus capitis
{trachelo-mastoid) . Projecting from the postero-superior margin of the external auditory
meatus there is frequently a small tubercle — the supra-meatal spine — behind which the surface
is depressed to form the mastoid (supra-meatal) fossa.
The inner surface of the mastoid portion presents a deep curved sigmoid
groove, in which is lodged a part of the transverse sinus ; the mastoid foramen is
seen opening into the groove. The interior of the mastoid portion, in the adult,
is usually occupied by cavities lined by mucous membrane and known as the
mastoid air-cells (fig. 97). These open into a small chamber — the mastoid
antrum — which communicates with the upper part of the tympanic cavity. The
mastoid cells are arranged in three groups: (1) antero-superior, (2) middle, and
(3) apical. The [apical cells, situated at the apex of the mastoid process, are
small and usually contain marrow.
Borders. — -The superior border is broad and rough for articulation with the hinder part of
the inferior border of the parietal bone. The posterior border, very uneven and serrated,
articulates with the inferior border of the occipital bone, extending from the lateral angle to
the jugular process.
The petrous portion [pars petrosa; pyramis] is a pyramid of very dense bone
presenting for examination a base, an apex, three (or four) surfaces, and three (or
four) borders or angles. Two sides of the pyramid look into the cranial cavity,
the posterior into the posterior cranial fossa, and the anterior into the middle
cranial fossa. The inferior surface appears on the under surface of the cranium .
The medial and posterior walls of the tympanic cavity in the temporal bone
are sometimes described as a fourth side of the pyramid. The base forms a part
of the lateral surface of the cranium; the apex is placed medially.
The posterior surface of the pyramid is triangular in form, bounded above by
the superior angle and below by the posterior angle Near the middle is an
obliquely directed foramen [porus acusticus internus] leading into a short canal — ■
the internal auditory meatus — at the bottom of which is a plate of bone, pierced
by numerous foramina, and known as the lamina cribrosa. The canal transmits
the facial and auditory nerves, the pars intermedia, and the internal auditory
artery. The bottom of the internal auditory meatus can be most advantageously
studied in a temporal bone at about the time of birth, when the canal is shallow
and the openings relatively wide.
The fundus of the meatus is divided by a transverse ridge of bone, the transverse crest, into a
superior and inferior fossa. Of these, the superior is the smaller, and presents anteriorly the
beginning of the facial canal (aqueduct of Fallopius), which transmits the seventh nerve. The
rest of the surface above the crest is dotted with small foramina (the superior vestibular area)
which transmit nerve-twigs to the recessus elliptious (fovea hemielliptica) and the ampuUae
of the superior and lateral semicircular canals (vestibular division of the auditory nerve).
Below the crest there are two depressions and an opening. Of these, an anterior curled tract
(the spiral cribriform tract) with a central foramen (foramen oentrale cochleare) marks the
base of the cochlea; the central foramen indicates the orifice of the canal of the modiolus,
and the smaller foramina transmit the cochlear twigs of the auditory nerve. The posterior
opening (foramen singulare) is for the nerve to the ampulla of the posterior semicircular
canal. The middle depression (inferior vestibular area) is dotted with minute foramina for
the nerve-twigs to the saccule, which is lodged in the recessus sphsericus (fovea hemisphaeri-
ca). The inferior fossa is subdivided by a low vertical crest. The fossa in front of the crest
is the fossula cochlearis, and the recess behind it is the fossula vestibularis.
Behind and lateral to the meatus is a narrow fissure, the aquseductus vestibuli, covered by
a scale of bone. In the fissure lies the ductus endolymphaticus, a small arteriole and venule,
and a process of connective tissue which unites the dura mater to the sheath of the internal
ear. Occasionally a bristle can be passed through it into the vestibule. Near the upper
margin, and opposite a point about midway between the meatus and the aqueduct of the vesti-
THE TEMPORAL BONE 73
bule, is an irregular opening, the fossa subarcuata, the remains of the floccular fossa, a con-
spicuous depression in the foetal bone. In the adult the depression usually lodges a process of
dura mater and transmits a small vein, though in some bones it is almost obhterated.
.The anterior surface of the pyramid, sloping downward and forward, forms
the back part of the floor of the middle fossa of the cranium.
Upon the anterior surface of the pyramid will be found the following points of interest,
proceeding from the apex toward the base of the pyramid: — (1) a shallow trigeminal im-
pression for the semilunar (Gasserian) ganglion of the trigeminal nerve; (2) two small grooves
running backward and laterally toward two small foramina overhung by a thin osseous lip, the
larger and medial of which, known as the hiatus canalis facialis, transmits the great superfi-
cial petrosal nerve and the petrosal branch of the middle meningeal artery, whilst the smaller
and lateral foramen is for the small superficial petrosal nerve; (3) behind and lateral to these
is an eminence — the eminentia arcuata — best seen in young bones, corresponding to the su-
perior semicircular canal in the interior; (4) still more laterally is a thin transulcent plate of
bone, roofing in the tympanic cavity, and named the tegmen tympani.
Fig. 94. — The Foramina in the Fundtts of the Left Internal Auditory Meatus op a
Child at Birth (y). (Diagrammatic.)
Superior fossa
Superior cribriform area
Foramen singulare
Entrance to the facial canal
- Transverse crest
Middle cribriform area \j,'^ j^^^g\ Orifice of the canal of the modiolus
Spiral cribriform tract
The inferior or basilar surface of the pyramid is very irregular. At the apex
it is rough, quadrilateral, and gives attachment to the tensor tympani, levator
veil palatini, and the pharyngeal aponeurosis. Behind this are seen the large
circular orifice of the carotid canal for the transmission of the carotid artery and
a plexus of sympathetic nerves, and on the same level, near the posterior border,
a small three-sided depression, the canaliculus cochleae, which transmits a small
vein from the cochlea to the internal jugular. Behind these two openings is the
large elliptical jugular fossa which forms the anterior and lateral part of the
bony wall of the jugular foramen, in which is contained a dilatation on the
commencement of the internal jugular vein; on the lateral wall of the jugular
fossa is a minute foramen, the mastoid canaliculus, for the entrance of the
auricular branch of the vagus (Arnold's nerve) into the interior of the bone.
Between the inferior aperture of the carotid canal and the jugular fossa is the
sharp carotid ridge, on which is a small depression, the fossula petrosa, and at the
bottom of this a minute opening, the tympanic canaliculus, for the tympanic
branch of the glosso-pharyngeal or Jacobson's nerve, and the small tympanic
branch from the ascending pharyngeal artery. Behind the fossa is the rough
jugular surface for articulation with the jugular process of the occipital bone, on
the lateral side of which is the prominent cylindrical spur known as the styloid
process with the stylo-mastoid foramen at its base. The facial nerve, and
sometimes the auricular branch of the vagus, leave the skull, and the stylo-mas-
toid artery enters it by this foramen. Running backward from the foramen are
the mastoid and occipital grooves already described.
The tympanic surface of the pyramid, forming the medial and posterior
walls [paries labyrinthica] of the tympanic cavity, is shown by removing the
tympanic plate (fig. 91). It presents near the base an excavation, known as the
tympanic or mastoid antrum, covered by the triangular part of the squamous
below and behind the temporal line. The opening of the antrum into the
tympanic cavity is situated immediately above the fenestra vestibuli, an oval-
shaped opening which receives the base of the stapes; below the fenestra vestibuli
is a convex projection or promontory, marked by grooves for the tympanic plexus
of nerves and containing the commencement of the first turn of the cochlea.
In the lower and posterior part of the promontory is the fenestra cochlesB, closed
in the recent state by the secondary membrane of the tj^mpanum. Running
downward and forward from the front of the fenestra vestibuli is a thin curved
plate of bone [septum canalis musculotubarii], separating two grooves converted
74
THE SKELETON
into canals by the overlying tympanic plate. The lower is the groove for the
Eustachian tube [semicanalis tubse audi tivse], the communicating passage between
the tympanum and the pharynx ; the upper is the semicanalis m. tensoris tympani,
and the lateral apertures of both canals are visible in the retiring angle, b-etween
the petrous and squamous portions of the bone.
The apex of the pyramid is truncated and presents the medial opening of the
carotid canal. The latter commences on the inferior surface, and, after ascending
for a short distance, turns forward and medially, tunnelling the bone as far as
the apex, and finally opens into the upper part of the foramen lacerum formed
between the temporal and sphenoid bones. One or two minute openings in the
wall of the carotid canal, known as the carotico -tympanic canaliculi, transmit
communicating twigs between the carotid and tympanic plexuses. The upper
part of the apex is joined by cartilage to the posterior petrosal process of the
sphenoid.
The base is the part of the pyramid which appears laterally at the side of
the cranium and takes part in the formation of the mastoid portion. It is
described with that chvision of the bone.
Fig. 95. — The Left Temporal Bone. (Inferior view.)
Carotid canal-
Tensor tympani
Levator veil palatini'
Carotid canal
Tympanic canaliculus
Canalicul
Mastoid canaliculus
Jugular fossa
Jugular surface
Zygomatic process
Masseter
Articular tubercle
Mandibular fossa
■Petro-tympanic fissure
Tympanic plate
Styloid process
Stylo-pharyngeus
Tympano-mastoid fissure
Stylo-mastoid foramen
Mastoid process
Digastric
Occipital groove
Angles. — The superior angle (border) of the pyramid is the longest and separates the pos-
terior from the anterior surface. It is grooved for the superior petrosal sinus, gives attachment
to the tentorium cerebelli, and presents near the apex a semilunar notch upon which the fifth
cranial nerve lies. Near its medial end there is often a small projection for the attachment
of the petro-sphenoid.al ligament, which arches over the inferior petrosal sinus and the sixth
nerve. The posterior angle separates the posterior from the inferior surface, and when ar-
ticulated with the occipital, forms the groove for the inferior petrosal sinus, and completes the
jugular foramen formed by the temporal in front and on the lateral side, and by the occipital
behind and on the medial side. The jugular foramen is divisible into three compartments: an
anterior for the inferior petrosal sinus, a middle for the glossopharyngeal, vagus and accessory
cranial nerves, and a posterior for the internal jugular vein and some meningeal branches
from the occipital and ascending pharyngeal arteries. The anterior angle is the shortest
and consists of two parts, one joined to the squamous in the petro-squamous suture and a
small free part internally which articulates with the sphenoid. A fourth or inferior border may
be distinguished, which runs along the line of junction with the tympanic plate and is continued
on to the rough area below the apex.
THE TEMPORAL BONE 75
The tympanic portion [pars tympanica] is quadrilateral in form, hollowed out
above and behind, and nearly flat, or somewhat concave, in front and below. It
forms the whole of the anterior and inferior walls, and part of the posterior wall,
of the external auditory meatus, and is separated behind from the mastoid
process by the tympano-mastoid (auricular) fissure through which the auricular
branch of the vagus in some cases leaves the bone.
In front it is separated by the petro-tympanic fissure from the squamous portion. Through
the petro-tympanio fissure the tympanic branch of the internal maxillary artery and the so-
called laxator tympani pass. The processus graoihs of the malleus is lodged within it, and a
narrow subdivision at its inner end, known as the canal of Huguier, transmits the chorda
tympani nerve. The tympanic part presents for examination two surfaces and four borders.
The antero-inferior surface, directed downward and forward, lodges part of the parotid
gland. Near the middle it is usually very thin, and sometimes presents a small foramen (the
foramen of Huschke), which represents a non-ossified portion of the plate. The postero-
superior surface looks into the external auditory meatus and tympanic cavity, and at its medial
end is a narrow groove, the sulcus tympanicus, deficient above, which receives the membrana
tympani.
The lateral border is rough and everted, forming the external auditory process for the
attachment of the cartilage of the pinna; the superior border enters into the formation of the
petro-tympanic fissure; the inferior border is uneven and prolonged into the vaginal process
[vagina processus styloideil which surrounds the lateral aspect of the base of the styloid process
and gives attachment to the front part of the fascial sheath of the carotid vessels; the medial
border, short and irregular, lies immediately below and to the lateral side of the opening of the
Eustachian tube, and becomes continuous with the rough quadrilateral area on the inferior
aspect of the apex.
The external auditory meatus is formed partly by the tympanic and partly
by the squamous portion. It is an elliptical bony tube leading into the tym-
panum, the extrance of which is bounded throughout the greater part of its
circumference by the external auditory process of the tympanic plate. Above,
the entrance is limited by the temporal ridge or posterior root of the zygomatic
process.
The styloid process is a slender, cylindrical spur of bone fused with the
inferior aspect of the temporal immediately in front of the stylo-mastoid foramen.
It consists of two parts, basal (tympano-hyal), which in the adult lies under cover
of the tympanic plate, and a projecting portion (stylo-hyal) , which varies in length
from five to fifty millimetres. When short, it is hidden by the vaginal process,
but, on the other hand, it may reach to the hyoid bone. The projecting portion
gives attachment to three muscles and two ligaments.
The slylo-pharyngeus arises near the base from the medial and slightly from the posterior
aspect; the slylo-hyoid from the posterior and lateral aspect near the middle; and the slylo-
glossus from the front near the tip. The tip is continuoiis with the stylo-hyoid ligament, which
runs down to the lesser cornu of the hyoid bone. A band of fibrous tissue — the stylo-mandibular
ligament — passes from the process below the origin of the stylo-glossus to the angle of the lower
jaw.
Blood-supply. — The arteries supplying the temporal bone are derived from various sources.
The chief are: —
Stylo-mastoid from posterior auricular: it enters the stylo-mastoid foramen.
Anterior tympanic from internal maxillary: it passes through the petro-tympanic fissure.
Superficial petrosal from middle meningeal: transmitted by the hiatus canalis facialis.
Carotieo-tympanic from internal carotid whilst in the carotid canal.
Internal auditory from the basilar: it enters the internal auditory meatus, and is distributed
to the cochlea and vestibule.
Other less important twigs are furnished by the middle meningeal, the meningeal branches
of the occipital, and by the ascending pharyngeal artery. The squamous portion is supplied,
on its internal surface, by the middle meningeal, and externally by the branches of the deep
temporal from the internal maxillary.
Articulations. — The temporal bone articulates with the occipital, parietal, sphenoid,
zygomatic, and, by a movable joint, with the mandible. Occasionally the squamous portion
presents a process which articulates with the frontal. A fronto -squamosal suture is common
in the skulls of the lower races of men, and is normal in the skulls of the chimpanzee, gorilla,
and gibbon.
Ossification. — Of the three parts which constitute the temporal bone at birth, the squa-
mosal and tympanic develop in membrane and the petrosal in cartilage. The squamosal is
formed from one centre, which appears as early as the eighth week, and ossification extends
into the zygomatic process, which grows concurrently with the squamosal. At first the tym-
panic border is nearly straight, but soon assumes its characteristic horseshoe shape. At birth
the post-glenoid tubercle is conspicuous, and at the hinder end of the squamosal there is a pro-
cess which comes into relation with the mastoid antrum The centre for the tympanic ele-
ment appears about the twelfth week. At birth it forms an incomplete ring, open above, and
slightly ankylosed to the lower border of the squamosal. The anterior extremity terminates
76
THE SKELETON
in a small irregular process, and the medial aspect presents, in the lower half of its circumfer-
ence, a groove for the reception of the tympanic membrane.
Up to the middle of the fifth month the periotio capsule is cartilaginous; it then ossifies
so rapidly that by the end of the sixth month its chief portion is converted into porous bone.
The ossifio material is deposited in four centres, or groups of centres, named according to
their relation to the ear-capsule in its embryonic position.
The nuclei are deposited in the following order; —
1. The opisthotic appears at the end of the fifth month. The osseous material is seen first
on the promontory, and it quickly surrounds the fenestra cochleae from above downward, and
forms the floor of the vestibule, the lower part of the fenestra vestibuli, and the internal au-
ditory meatus; it also invests the cochlea. Subsequently a plate of bone arises from it to sur-
round the internal carotid artery and form the floor of the tympanum.
2. The prootic nucleus is deposited behind the internal auditory meatus near the medial
limb of the superior semicircular canal. It covers in a part of the cochlea, the vestibule, and
the internal auditory meatus, completes the fenestra vestibuli, and invests the superior semi-
circular canal.
3. The pterotic nucleus ossifies the tegmen tympani and covers in the lateral semicircular
canal; the ossific matter is first deposited over the lateral limb of this canal.
4. The epiotic, often double, is the last to appear, and is first seen at the most posterior
part of the posterior semicircular canal.
At birth the bone is of loose and open texture, thus offering a striking contrast to the dense
and ivory-like petrosal of the adult. It also differs from the adult bone in several other par-
ticulars. The floccular fossa is widely open and conspicuous. VoltoUni has pointed out that
a small canal leads from the floor of the floccular fossa and opens posteriorly on the mastoid
surface of the bone; it may open in the mastoid antrum. The hiatus canalis facialis is unclosed
Fig. 96. — -Temporal Bone at the Sixth Year.
External auditory meatus
Non-ossified area of the tympanic plate
Petro-tympamc fissure
Wormian bone in
parietal notch
and the tympanum is filled with gelatinous connective tissue. The mastoid process is not
developed, and the jugular fossa is a shallow depression.
After birth the parts grow rapidly. The tympanum becomes permeated with air, the var-
ious elements fuse, and the tympanic annulus grows rapidly and forms the tympanic plate.
Development of the tympanic plate takes place by an outgrowth of bone from the lateral
aspect of the tympanic annulus. This outgro\vth takes place most rapidly from the tubercles
or spines at its upper extremities, and in consequence of the slow growth of the lower segment a
deep notch is formed; gradually the tubercles coalesce, lateral to the notch, so as to enclose a
foramen which persists until puberty, and sometimes even in the adult. In most skuUs a cleft
capable of receiving the nail remains between the tympanic element and the mastoid process;
this is the tympano-mastoid fissure. The anterior portion of the tympanic plate forms with
the inferior border of the squamosal a cleft known as the petro-tympanic fissure, which is sub-
sequently encroached upon by the growth of the petrosal. As the tympanic plate increases in
size it joins the lateral wall of the carotid canal and presents a prominent lower edge, known as
the vaginal process (sheath of the styloid).
The mastoid process becomes distinct about the first year, coincident with the obliteration
of the petro-squamous suture, and increases in thickness by deposit from the periosteum.
According to most writers, the process becomes pneumatic about the time of puberty, but
it has been shown by Young and Milligan that the mastoid air-cells develop at a much
earlier period than is usually supposed. These writers have described specimens in which the
air-cells were present, as small pit-like diverticula from the mastoid antrum, in a nine months'
foetus and in an infant one year old. In old skulls the air-cells may extend into the jugular
process of the occipital bone.
At birth the mastoid antrum is relatively large and bounded laterally by a thin plate of
bone belonging to the squamosal (post-auditory process). As the mastoid increases in thick-
ness the antrum comes to lie at a greater depth from the surface and becomes relatively smaller.
THE TYMPANUM
77
The styloid process is ossified in cartilage from two centres, one of which appears at the
base in the tympano-hyal before birth. This soon joins with the temporal bone, and in the
second year a centre appears for the stylo-hyal, which, however, remains very small until pu-
berty. In the adult it usually becomes firmly united with the tympano-hyal, but it may remain
permanently separate.
THE TYMPANUM
The tympanum (middle ear) includes a cavity [cavum tympani] of irregular
form in the temporal bone, situated over the jugular fossa, between the petrous
portion medially and the tympanic and squamous portions laterally. When fully
developed, it is completely surrounded by bone except where it communicates
with the external auditory meatus, and presents for examination six walls —
lateral, medial, posterior, anterior, superior (roof), and inferior (floor). The
lateral and medial wails are flat, but the remainder are curved, so that they run
into adjoining surfaces, without their limits being sharply indicated.
The roof or tegmen tympani [paries tegmentalis] is a translucent plate of bone, forming
part of the superior surface of the petrous portion and separating the tympanum from the
middle fossa of the skull. The floor [paries jugularis] is the plate of bone which forms the roof
of the jugular fossa.
The medial wall [paries labyrinthica] is formed by the tympanic surface of the petrous
portion. In the angle between it and the roof is a horizontal ridge which extends backward as
far as the posterior wall and then turns downward in the angle between the medial and posterior
walls. This is the facial (Fallopian) canal, and is occupied by the facial nerve. The other
features of this surface — viz., the fenestra vestibuli, the fenestra cochleae, and the promontory
— have previously been described with the anterior surface of the petrous portion of the temporal
bone.
The posterior wall [paries mastoidea] of the tympanum is also formed by the anterior
surface of the petrous portion. At the superior and lateral angle of this wall an opening
Fig. 97. — The Medial Wall of the Tympanum.
Carotid canal
Tensor tympani
Groove for Eustacliian.
tube
Levator veli palatini'
Canal for small deep.
petrosal nerve
Stylo pharyngeus
Stylo-hyoxd
Stylo gl(
Lateral semicircular
canal
Mastoid antrum
Facial canal
Canal for chorda tympani
Stylo-mastoid foramen
leads into the mastoid antrum. Immediately below this opening there is a small hoUow cone,
the pyramidal eminence, the cavity of which is continuous with the descending limb of the
facial canal. The cavity is occupied by the stapedius and the tendon of the muscle emerges
at the apex. One or more bony spicules often connect the apex of the pyramid with the
promontory.
The roof and floor converge toward the anterior extremity of the tympanum, which is, in
consequence, very low; it is occupied by two semicanals, the lower for the Eustachian tube, the
upper for the tensor tympani muscle. These channels are sometimes described together as the
canalis musculo-tubarius. In carefully prepared bones the upper semicanal is a small hori-
zontal hollow cone (anterior pyramid), 12 mm. in length; the apex is just in front of the fenestra
vestibuli, and is perforated to permit the passage of the tendon of the muscle. As a rule, the
thin walls of the canal are damaged, and represented merely by a thin ridge of bone. The
posterior portion of this ridge projects into the tympanum, and is known as the processus
cochleariformis. The thin septum between the semicanal for the tensor tympani and the
tube is pierced by a minute opening which transmits the small deep petrosal nerve.
The lateral wall [paries membranaeea] is occupied mainly by the external auditor}' meatus.
This opening is closed in the recent state by the tympanic membrane. The rim of bone to
which the membrane is attached is incomplete above, and the defect is known as the tympanic
notch (notch of Rivinus). Anterior to this notch, in the angle between the squamous portion
and the tympanic plate, is the petro-tympanic (Glaserian) fissure, and the small passage
which transmits the chorda tympani nerve, known as the canal of Huguier.
Up to this point the description of the middle ear conforms to that in general usage. But
Young and Milligan have laid stress on the fact that the middle ear is really a cleft, named
by them the "middle-ear cleft," which intervenes between the periotic capsule, on the one hand,
and the squamo-zygomatic and tympanic elements of the temporal bone on the other. This
cleft, as development proceeds, gives rise to three cavities: — -(1) the mastoid antrum; (2)
78
THE SKELETON
tympanum; and (3) the Eustachian tube. They point out that "the cleft is primarily con-
tinuous, and however much it may be altered in shape and modified in parts to form these three
cavities, that continuity is never lost." It will be clear that the mastoid antrum, according to
this view, is not an outgrowth from the tympanum, but is simply the lateral end of the middle-
ear cleft.
The tympanic cavity may be divided into three parts. The part below the
level of the superior margin of the external auditory meatus is the tympanum
proper ; the portion above this level is the epitympanic recess or attic ; it receives
the head of the malleus, the body of the incus, and leads posteriorly into the
recess known as the mastoid antrum. The third part is the downward extension
known as the hypotympanic recess.
The tympanic or mastoid antrum. — The air-cells which in the adult are found in the
interior of the mastoid portion of the temporal bone open into a small cavity termed the
mastoid antrum. This is an air-chamber, communicating with the attic of the tympanum,
and separated from the middle cranial fossa by the posterior portion of the tegmen tympani.
The floor is formed by the mastoid portion of the petrosal, and the lateral wall by the squamosal,
below the temporal ridge. In children the outer wall is exceedingly thin, but in the adult it ia
of considerable thickness. The lateral semicircular canal projects into the antrum on its
Fig. 98."
-Temporal Bone at Birth Dissected prom above and behind to show the Semi-
circular Canals and the Mastoid Antrum. (Enlarged \.)
Opening into tympanura
Superior semicircular canal
Mastoid antrum
'Lateral semicircular canal
Posterior semicircular canal
medial wall, and is very conspicuous in the foetus. Immediately below and in front of the
canal is the facial nerve, contained in the facial canal.
The mastoid antrum has somewhat the form of the bulb of a retort (Thane and Godlee)
compressed laterally, and opening by its narrowed neck into the attic or epitympanic recess.
Its dimensions vary at different periods of hfe. It is well developed at birth, attains its maxi-
mum size about the third year, and diminishes somewhat up to adult life. In the adult the
plate of bone which forms the lateral wall of the antrum is 12 to 18 mm. (| to J in.) in thickness,
whereas at bu-th it is about 1.8 mm. (j^ in.) or less. The deposition of bone laterally occurs,
therefore, at average rate of nearly 1 mm. a year in thickness. In the adult the antrum ia
about 12 mm. (i in.) from front to back, 9 mm. (f in.) from above downward, and 4.5 mm.
(j^V in.) from side to side.
A canal occasionally leads from the mastoid antrum through the petrous bone to open in
the recess which indicates the position of the fioecular fossa; it is termed the petro-mastoid
canal. (Gruber.)
The facial (Fallopian) canal. — This canal begins at the anterior angle of the superior fossa
of the internal auditory meatus, and passes forward and laterally above the vestibular portion
of the internal ear for a distance of 1.5-2.0 mm. At the lateral end of this portion of its course
it becomes dilated to accommodate the geniculate ganglion, and then turns abruptly back-
ward and runs in a horizontal ridge on the medial wall of the tympanurn, lying in the angle
between it and the tegmen tympani, immediately above the fenestra vestibuli, and extending
as far backward as the entrance to the mastoid antrum. Here it comes into contact with the
inferior aspect of the projection formed by the lateral semicircular canal, and then turns verti-
cally downward, running in the angle between the medial and posterior walls of the tympanum
to terminate at the stylo-mastoid foramen.
The canal is traversed by the facial nerve. Numerous openings exist in the walls of this
passage. At its abrupt bend, or genu, the greater and smaller superficial petrosal nerves escape
from, and a branch from the middle meningeal artery enters, the canal, and in the vertical part
of its course the cavity of the pyramid opens into it. There is also a small orifice by which the
auricular branch of the vagus joins the facial, and near its termination the iter chordae posterius
for the chorda tympani nerve leads from it into the tympanum.
THE SMALL BONES OF THE TYMPANUM
79
The small bones of the tympanum. — These bones, the malleus, incus and
stapes, are contained in the upper part of the tympanic cavity. Together they
form a jointed column of bone connecting the membrana tympani with the
fenestra vestibuli.
The malleus. — This is the most external of the iiuditory ossicles, and hes in relation with the
tympanic membrane. Its upper portion, or head, is lodged in the epitympanic recess. It is
of rounded shape, and presents posteriorly an elliptical depression for articulation with the
incus. Below the head is a constricted portion or neck, from which three processes diverge.
The largest is the handle or manubrium, which is slightly twisted and flattened. It forms an
obtuse angle with the head of the bone, and lies between the membrana tympani and the
mucous membrane covering its inner surface. The tensor tympani tendon is inserted into the
manubrium near its junction with the neck on the medial side.
Fig. 99. — The Bones of the Ear. (Modified from Henle.)
Fossa for incus
Posterior crus
■Head of malle
Lateral process
Anterior process
Articular surface for malleus
Lenticular process
The anterior process (processus gracilis or Folii) is a long, slender, dehoate spiculum of bone
(rarely seen of full length except in the fcetus), projecting nearly at right angles to the anterior
aspect of the neck, and extending obliquely downward. It lies in the petro-tympanic fissure,
and in the adult usually becomes converted into connective tissue, except a small basal stump.
The lateral process is a conical projection from the lateral aspect of the base of the manu-
brium. Its apex is connected to the upper part of the tympanic membrane, and its base receives
the lateral ligament of the malleus. The malleus also gives attachment to a superior hgament
and an anterior ligament, the latter of which was formerly described as the laxator tymipani
muscle.
The incus. — This bone is situated between the malleus externally and the stapes internaUy.
It presents for examination a body and two processes. The body is deeply excavated anteriorly
for the reception of the head of the malleus. The short process projects backward, and is
connected by means of ligamentous fibres to the posterior wall of the tympanum, near the
entrance to the mastoid antrum. The long process is slender, and directed downward and in-
ward, and lies parallel with the manubrium of the maUeus. On the medial aspect of the distal
extremity of this process is the lenticular process (orbicular tubercle), separate in early life, but
80
THE SKELETON
subsequently joined to the process by a narrow neck. Its free surface articulates with the head
of the stapes.
The stapes is the innermost ossicle. It has a head directed horizontally outward, capped
at its outer extremity by a disc resembling the head of the radius. The cup-shaped depression
receives the lenticular process of the incus. The base occupies the fenestra vestibuli, and like
this opening, the inferior border is straight, and the superior curved. The base is connected
with the head by means of two crura, and a narrow piece of bone called the neck. Of the two
crura, the anterior is the shorter and straighter. The crura with the base form a stirrup-shaped
arch, of which the irmer margin presents a groove for the reception of the membrane stretched
across the hollow of the stapes. In the early embryo this hollow is traversed by the stapedial
artery. The neck is very short, and receives on its posterior border the tendon of the stapedius
muscle.
Development. — The tympanic cavity represents the upper extremity of the first endodermal
branchial groove, which becomes converted into a blind pouch, the communication of which
with the pharyngeal cavity is the tuba auditiva (Eustachian tube). The thin membrane which
separates the endodermal from the ectodermal groove becomes the tympanic membrane, and
it is from the upper extremities of the axial skeletons of the first and second branchial arches,
which bound the groove anteriorly and posteriorly, that the auditory ossicles are formed, the
malleus and incus belonging to the first arch and the stapes to the second (Reichert). The
ossicles consequently lie originally in the walls of the cavity, but they are surrounded by a loose
spongy tissue, which, on the entrance of air into the cavity, becomes compressed, allowing the
cavity to enfold the ossicles. These therefore are enclosed within an epithelium which is con-
tinuous medially with that lining the posterior tympanic wall, and laterally with that lining
the internal surface of the tympanic membrane.
The mastoid cells are outgrowths of the cavity into the adjacent bone, and are therefore
lined with an epithelium continuous with that of the cavity.
THE OSSEOUS LABYRINTH
The osseous labyrinth [labyrinthus osseus] (fig. 100) is a complex cavity
hollowed out of the petrous portion of the temporal bone and containing the
membranous labyrinth, the essential part of the organ of hearing. It is in-
completely divided into three parts, named the vestibule, the semicircular canals,
and the cochlea.
Fig. 100. — The Left Osseous L.\byrinth. (After Henle. From a cast.)
Superior semicircular caaal
Lateral semicircular canal
Posterior semicircular canal
Fenestra cochleae Fenestra vestibul:
The vestibule. — This is an oval chamber situated between the base of the internal auditory
meatus and the medial wall of the tympanum, with which it communicates by way of the
fenestra vestibuh. Anteriorly, the vestibule leads into the cochlea, and posteriorly it receives
the extremities of the semicircular canals. It measures about 3 mm. transversely, and is some-
what longer antero-posteriorly.
Its medial wall presents at the anterior part a circular depression, the spherical recess
(fovea. hemispherica), which is perforated for the passage of nerve-twigs. This recess is sepa-
rated by a vertical ridge (the crista vestibuli) from the vestibular orifice of the aquseductus
Fig. 101. — The Cochlea in S.agittal Section. (After Henle.)
Internal auditory meritus
The spiral canal
vestibuli, which passes obhquely backward to open on the posterior surface of the petrosal.
The roof contains an oval depression — the elliptical recess (fovea hemielUptioa).
The semicircular canals are three in number. Arranged in different planes, each forms
about two-thirds of a circle. One extremity of each canal is dilated to form an ampulla. _
The superior canal lies transversely to the long axis of the petrosal, and is nearly vertical;
i
THE ETHMOID 81
its highest limb makes a projection on the superior surface of the bone. The ampulla is at the
lateral end; the medial end opens into the vestibule conjointly with the superior limb of the
posterior canal.
The posterior canal is nearly vertical and lies in a plane nearly parallel to the posterior sur-
face of the petrosal. It is the longest of the three; its upper extremity joins the medial hmb
of the superior canal, and opens in common with it into the vestibule. The lower is the ampul-
lated end.
The lateral canal is placed horizontally and arches laterally; its lateral limb forms a
prominence in the mastoid antrum. This canal is the shortest; its ampulla is at the lateral end
near the fenestra vestibuli.
The cochlea. — This is a cone-shaped cavity lying with its base upon the internal auditory
meatus, and the apex directed forward and laterally. It measures about five millimetres in
length, and the diameter of its base is about the same. The centre of this cavity is occupied by
a column of bone — the modiolus — around which a canal is wound in a spiral manner, making
about two and a half turns. This is the spiral canal of the cochlea; its first turn is the largest
and forms a bulging, the promontory, on the medial wall of the tympanum.
Projecting into the canal throughout its entire length there is a horizontal, shelf-like lamella,
the lamina spiralis, which terminates at the apex of the cochlea in a hook-like process, the
hamulus. The free edge of the lamina spiralis gives attachment to the membranous cochlea,
a canal having in section the form of a triangle whose base is attached to the lateral wall of the
spiral canal. By this the spiral canal is divided into a portion above the lamina spiralis, termed
the scaia vestibuli, which communicates at its lower end with the osseous vestibule, and a portion
below, termed the scala tympani, which abuts at its lower end upon the fenestra cochlea. The
two scalae communicate at the apex of the cochlea by the helicotrema. Near the commencement
of the scala tympani, and close to the fenestra rotunda, is the cochlear orifice of the canaliculus
cochlese (ductus perilymphaticus). In the adult this opens below, near the middle of the pos-
terior border of the petrous bone, and transmits a small vein from the cochlea to the jugular
fossa.
Measurements of the principal parts connected with the auditory organs: —
Internal auditory meatus Length of anterior wall, 13-14 mm.
Length of posterior waU, 6.7 mm.
External auditory meatus 14^16 mm. (Gruber.)
Tympanum Length, 13 mm.
Height in centre of cavity, 15 mm.
Width opposite the membrana tympani, 2 mm.
Width opposite the tubal orifice, 3-4 mm. (Von Troltsch.)
The capsule of the osseous labyrinth is in length 22 mm. (Schwalbe.)
Superior semicircular canal measures along its convexity 20 mm.
The posterior semicircular canal measures along its convexity 22 mm.
The lateral semicircular canal measures along its convexity 15 mm.
The canal is in diameter 1.5 mm. (Huschke.)
The ampulla of the canal, 2.5 mm.
Development. — The membranous internal ear arises in the embryo as a depression of the
ectoderm of the surface of the head opposite the fifth neuromere of the hind-brain and later
becomes a sac-like cavity, the otocyst, which separates from its original ectodermal connec-
tions and sinks deeply into the subjacent mesoderm, a part of which becomes incorporated with
it. The rest of the mesodermal tissue which surrounds the otocyst becomes later the petrous
portion of the temporal bone, the perilymph and the internal periosteal layer; the osseous
labyrinth is therefore merely the portions of the petrous which enclose the cavity occupied by
the membranous internal ear.
THE ETHMOID
The ethmoid [os ethmoidale] is a bone of delicate texture, situated at the an-
terior part of the base of the cranium (figs. 102, 103, 104). Projecting downward
from between the orbital plates of the frontal, it enters into the formation of the
orbital and nasal fossae. It is cubical in form, and its extreme lightness and
delicacy are due to an arrangement of very thin plates of bone surrounding
irregular spaces known as air-cells. The ethmoid consists of four parts: the hori-
zontal or cribriform plate, the ethmoidal labyrinth on each side, and a perpen-
dicular plate.
The cribriform plate [lamina cribrosa] forms part of the anterior cranial fossa,
and is received into the ethmoidal notch of the frontal bone. It presents on its
upper surface, in the median line, the intra-cranial portion of the perpendicular
plate, known as the crista galli, a thick, vertical, triangular process with the high-
est point in front, and a sloping border behind which gives attachment to the f alx
cerebri. The anterior border is short and in its lower part broadens out to form
two alar processes which articulate with the frontal bone and complete the
foramen caecum. The ci'ista galli is continuous behind with a median ridge,
and on each side of the middle line is a groove which lodges the olfactory bulb.
82
THE SKELETON
The cribriform plate is pierced, on each side, by numerous foramina, arranged in two or
three rows, which transmit the filaments of the olfactory nerves descending from the bulb.
Those in the middle of the groove are few and are simple perforations, through which pass the
nerves to the roof of the nose; the medial and lateral series are more numerous and constitute
the upper ends of small canals, which subdivide as they course downward to the upper parts
of the septum and the lateral wall of the nasal fossa. At the front part of the cribriform plate
is a narrow longitudinal sht, on each side of the crista gaUi, which transmits the anterior eth-
moidal (nasal) branch of the ophthalmic division of the fifth nerve. The posterior border
articulates with the ethmoidal spine of the sphenoid.
Fig.
102. — Section through the Nasal Fossa to show the Mesethmoid
(Lamina Perpendiculaeis).
Crest of sphenoid
-palatine nerve:
Crest of maxilla
The perpendicular plate (mesethmoid) [lamina perpendicularis is directly
continuous with the crista galli on the under aspect of the cribriform plate, so
that the two plates cross each other at right angles. The larger part of the
perpendicular plate is below the point of intersection and forms the upper third
of the septum of the nose. It is quadrangular in form with unequal sides.
Fig. 103. — The Ethmoid. (Lateral view.)
-Crista galli
Anterior ethmoidal groove — -
Uncinate process
Inferior nasal concha
Jt'osterior ethmoidal groove
' -|- Lamina papyracea
Sphenoidal concha
Middle nasal concha
The anterior border articulates with the spine of the frontal and the crest of the nasal bones.
The inferior border articulates in front with the septal cartilage of the nose and behind with the
anterior margin of the vomer. The posterior margin is very thin and articulates with the crest
of the sphenoid. This plate, which is generally deflected a little to one side, presents above a
number of grooves and minute canals which lead from the inner set of foramina in the cribri-
form plate and transmit the olfactory nerves to the septum.
The labyrinth (lateral mass) is oblong in shape and suspended from the under
aspect of the lateral part of the cribriform plate. It consists of two scroll-like
THE ETHMOID
83
pieces of bone, the superior and middle nasal conchse (turbinate bones), and
encloses numerous irregularly shaped spaces, known as the ethmoidal cells.
These are arranged in three sets — anterior, middle, and posterior ethmoidal cells
— and, in the recent state, are lined with prolongations of the nasal mucous
membrane. Laterally the labyrinth presents a thin, smooth, quadrilateral plate
of bone — the lamina papyracea (os planum) — which closes in the middle and
posterior ethmoidal cells and forms a large part of the medial wall of the orbit.
By its anterior border it articulates with the lacrimal, and by its posterior border with the
sphenoid; the inferior border articulates with the medial margin of the orbital plate of the
maxilla and the orbital process of the palate bone, whilst the superior border articulates with
the horizontal plate of the frontal. Two notches in the superior border lead into grooves
running horizontally across the lateral mass to the cribriform plate, which complete, with the
frontal bone, the ethmoidal canals. The anterior canal transmits the anterior ethmoidal ves-
sels and (nasal) nerve; the posterior transmits the posterior ethmoidal vessels and nerve.
Fig.
104. — Section THRonGH the Nasal Fossa to show the Labyrinth of .the Ethmoid.
It shows also the lateral wall of the left nasal fossa.
Superior nasal concha
Probe in sphenoidal foran
Sphenoidal sinus
Sella turcica
{
Superior meatus
Spheno-palatine
foramen
Uncinate process of ethmoid
Medial pterygoid plate
Palate bone
Probe in posterior palatine canal
Agger nasi
Lacrimal bone
Lower end of bristle
in middle meatus
Middle meatus
Inferior nasal
concha
Probe at lower end
of naso-lacrimal
canal where it
opens into inferior
meatus
Incisive canal
At the lower part of the lateral surface is a deep groove, which belongs to
the middle meatus of the nose, and is bounded below by the thick curved margin
of the inferior nasal concha. Anteriorly the middle meatus receives the in-
fundibulum, a sinuous passage which descends from the frontal sinus through the
anterior part of the labyrinth. The anterior ethmoidal cells open into the lower
part of the infundibulum, and in this way communicate with the nose, whereas
the middle ethmoidal cells open directly into the middle or horizontal part of the
meatus. In front of the lamina papyracea are seen a few broken cells, which
extend under, and are completed by, the lacrimal bone and the frontal process
of the maxilla; from this part of the labyrinth an irregular lamina, known as the
uncinate process, projects downward and backward. The uncinate process
articulates with the ethmoidal process of the inferior nasal concha and forms a
small part of the medial wall of the maxillary sinus.
Medially the labyrinth takes part in the formation of the lateral wall of the
nasal fossa, and presents the superior and middle nasal conchae (turbinate
processes), continuous anteriorly, but separated behind by a space directed for-
ward from the posterior margin. This channel is the superior meatus of the nose
and communicates with the posterior ethmoidal cells. The conchse are covered
84
THE SKELETON
in the recent state with mucous membrane and present numerous foramina for
blood-vessels and, above, grooves for twigs of the olfactory nerves. Each
concha has an attached upper border and a free, slightly convoluted, lower
border, and in the case of the middle concha, the lower margin has already been
noticed on the outer aspect, where it overhangs the middle meatus of the nose.
The posterior extremity of the labyrinth articulates with the anterior surface
of the body of the sphenoid and is commonly united with the sphenoidal concha.
A rounded prominence on the lateral wall of the middle meatus is known as the bulla
ethmoidalis. Antero-inferior to the bulla is a large semilunar depression [hiatus semilunaris]
which corresponds to the lower aperture of the infundibulum.
Man}' of the ethmoidal cells are imperfect and are completed by adjacent bones. Those
along the superior edge of the lateral mass are the fronto-ethmoidal; those at the anterior
border, usually two in number, are known as lacrimo-ethmoidal. Those along the lower
edge of the lamina papyraoea are the maxillo-ethmoidal; and posteriorly, are the spheno-
ethmoidal, completed by the sphenoidal concha, and a palate -ethmoidal cell. The anterior
extremity presents one or two incomplete cells closed by the nasal process of the maxilla.
Blood-supply. — The ethmoid receives its blood-supply from the anterior and posterior
ethmoidal arteries and from the spheno-palatine branch of the internal maxillary.
Articulations. — With the frontal, sphenoid, two palate bones, two nasals, vomer, two
inferior nasal conchae, two sphenoidal oonohse, two maxills, and two lacrimal bones. The
posterior surface of each labyrinth is in relation with the sphenoid on each side of the crest and
rostrum, and helps to close in the sphenoidal sinus.
Ossification. — The ethmoid has three centres of ossification. Of these, a nucleus appears
in the fourth month of intra-uterine hfe in each labyrinth, first in the lamina papyraoea and
afterward extending into the middle concha. At birth each lateral portion is represented by
two scroll-like bones, very delicate and covered with irregular depressions, which give it a worm-
eaten appearance. Six months after birth a nucleus appears in the ethmo-vomerine cartilage lor
the vertical plate which gradually extends into the crista galU, and the cribriform plate is formed
by ossification extending laterally from this centre, and medially from the labyrinth. The
three parts coalesce to form one piece in the fifth or sixth year.
The ethmoid.al cells make their appearance about the third year, and gradually invade
the labyrinths. In many places there is so much absorption of bone that the cells perforate
the ethmoid in situations where it is overlapped by other bones. Along the lower border, near
its articulation with the maxilla, the absorption leads to the partial detachment of a narrow
strip known as the uncinate process. Sometimes a second but smaller hook-like process is
formed, above and anterior to this, so fragile that it is difficult to preserve it in disarticulated
bones. The relations of the uncinate process are best studied by removing the lateral wall of
the maxillary sinus.
THE INFERIOR NASAL CONCHA
The inferior nasal concha (inferior turbinate) (fig. 105) is a slender, scroll-Hke
lamina, attached by its upper margin to the lateral wall of the nasal fossa, and
hanging into the cavity in such a way as to separate the middle from the inferior
Fig. 105. — The Inferior Concha, Adult Sphenoidal Turbinate, and Lacrimal Bones.
The crest of lacrimal
Tensor tarsi
The orbital surface
Lacrimal groove
Hamular process,
Conchal process
The lacrimal process
The ethmoidal process
The maxillary process
Middle nasal concha
meatus of the nose. It may be regarded as a dismemberment of the ethmoidal
labyrinth, with which it is closely related. It presents for examination two
surfaces, two borders, and two extremities.
The lateral surface is concave, looks toward the lateral wall of the nasal fossa,
THE LACRIMAL 85
and is overhung by the maxillary process. The medial surface is convex, pitted
with depressions, and grooved for vessels, which, for the most part, run longi-
tudinally. The superior or attached border articulates in front with the conchal
crest of the maxilla, then ascends to form the lacrimal process, which articulates
with the lacrimal bone and forms part of the wall of the lacrimal canal. Behind
this, it is turned downward to form the maxillary process, already mentioned,
which overhangs the orifice of the maxillary sinus and serves to fix the bone firmly
to the lateral wall of the nasal fossa. The projection behind the maxillary process
is the ethmoidal process, joined in the articulated skull with the uncinate process
of the ethmoid across the opening of the maxillary sinus. Posteriorly the upper
border articulates with the conchal crest of the palate. The inferior border
is free, rounded, and somewhat thickened. The anterior extremity is blunt and
flattened, and broader than the posterior extremity, which is elongated, narrow,
and pointed.
Articulations. — With the maxilla, lacrimal, palate, and ethmoid.
Ossification. — The inferior nasal conotia is ossified in cartilage from a single nucleus which
appears in the fifth month of intra-uterine life. At birth it is a relatively large bone and filla
up the lower part of the nasal fossa.
THE LACRIMAL
The lacrimal bone [os lacrimale] (fig. 105) is extremely thin and delicate,
quadrilateral in shape, and situated at the anterior part of the medial wall of the
orbit. It is the smallest of the facial bones.
The orbital surface is divided by a vertical ridge, the posterior lacrimal
crest, into two unequal portions. The anterior, smaller portion is deeply grooved
to form the lacrimal groove, which lodges the lacrimal sac and forms the com-
mencement of the canal for the naso-lacrimal duct. The portion behind the
ridge is smooth, and forms part of the medial wall of the orbit. The ridge gives
origin to the orbicularis oculi (pars lacrimalis) muscle and ends below in a hook-like
process, the lacrimal hamulus, which curves forward to articulate with the lacrimal
tubercle of the maxilla and completes the superior orifice of the naso-lacrimal
canal. The medial surface is in relation with the two anterior cells of the ethmoid
(lacrimo-ethmoidal), forms part of the infundibulum, and inferiorly looks into
the middle meatus of the nose. The superior border is short, and articulates
with the medial angular process of the frontal. The inferior border posterior to
the crest joins the medial edge of the orbital plate of the maxilla. The narrow
piece, anterior to the ridge, is prolonged downward as the descending process
to join the lacrimal process of the inferior nasal concha. The anterior border
articulates with the posterior border of the frontal process of the maxilla and the
posterior border with the lamina papyracea of the ethmoid.
The vessels of the lacrimal bone are derived from the infra-orbital, dorsal nasal branch of
the ophthalmic, and anterior ethmoidal arteries.
Articulations. — The lacrimal articulates with the ethmoid, maxilla, frontal, and inferior
nasal concha.
Ossification. — This bone arises in the membrane overlying the cartilage of the fronto-nasal
plate, and in its mode of ossification is very variable. As a rule, it is formed from a single
nucleus which appears in the third or fourth month of intra-uterine life. Not infrequently, the
hamulus is a separate element, and occasionally the bone is divided by a horizontal cleft, a pro-
cess of the lamina papyracea projecting between the two halves to join the frontal process of
the maxilla. More rarely the bone is represented by a group of detached ossicles resembling
Wormian bones.
The hamular process is regarded as representing the remains of the facial part of the
lacrimal seen in lower animals.
THE VOMER
The vomer (fig. 106) (ploughshare bone) is an unpaired flat bone, which lies
in the median plane and forms the lower part of the nasal septum. It is thin and
irregularly quadrilateral in form, and is usually bent somewhat to one side,
though the deflection rarely involves the posterior margin. Each lateral surface
is covered in the recent state by the mucous membrane of the nasal cavity, and is
traversed by a narrow but well-marked groove, which lodges the naso-palatine
nerve from the spheno-palatine ganglion.
i
86
THE SKELETON
The superior border, by far the thickest part of the bone, is expanded laterally
into two alse. The groove between them receives the rostrum of the sphenoid,
and the margin of each ala comes into contact with the sphenoidal process of the
palate and the vaginal process of the medial pterygoid plate. The inferior border
is uneven and lies in the groove formed by the crests of the maxillary and palate
bones of the two sides. The anterior border slopes downward and forward and is
grooved below for the septal cartilage of the nose; above it is united with the
perpendicular plate of the ethmoid. The posterior border, smooth, rounded, and
covered by mucus membrane, separates the posterior nares. The anterior and
inferior borders meet at the anterior extremity of the bone which forms a short
vertical ridge behind the incisor crest of the maxillae. From near the anterior
extremity, a small projection passes downward between the incisive foramina.
Fig. 106.— The Vomer. (Side view.)
Anterior border
-palatine nerve
Groove for septal cartilage — ^^^f\^
Inferior border
Blood-supply. — The arterial supply of the vomer is derived from the anterior and posterior
ethmoidal and the spheno-palatine arteries. Branches are also derived from the posterior
palatine through the foramen incisivum.
Ossification. — The vomer is ossified from two centres which appear about the eighth week
in the membrane investing the ethmo-vomerine cartilage. The two lamellae unite below during
the third month and form a shallow bony trough in which the cartilage lies. In the process
of growth the lamells extend upward and forward and gradually fuse to form a rectangular
plate of bone, the cartilage enclosed between them undergoing absorption at the same time.
The alae on the superior margin and the groove in front are evidence of the original bilaminar
condition.
THE NASAL
The nasal (figs. 107 and 108) are two small oblong bones situated at the upper
part of the face and forming the bridge of the nose. Each bone is thicker and
narrower above, thinner and broader below, and presents for examination two
surfaces and four borders.
Fig. 107. — The Left Nasal Bone,
Facial Surface.
Superior borde
Medial border
Lateral border-
Inferior border'
Fig. 108. — The Left Nasal Bone,
Nasal Surface.
Medial border
The facial surface is concave from above downward, convex from side to side,
and near the centre is perforated by a small foramen, which transmits a small
tributary to the facial vein. The posterior or nasal surface, covered in the recent
state by mucous membrane, is concave laterally, and traversed by a longitudinal
groove [sulcus ethmoidalis] for the anterior ethmoidal branch of the ophthalmic
division of the fifth nerve. The short superior border is thick and serrated for
articulation with the medial part of the nasal notch of the frontal. The inferior
border is thin, and serves for the attachment of the lateral nasal cartilage. It
is notched for the external nasal branch of the anterior ethmoidal nerve. The
nasal bones of the two sides are united by their medial borders, forming the inter-
nasal suture. The contiguous borders are prolonged backward to form a crest
which rests on the frontal spine and the anterior border of the perpendicular
plate of the ethmoid. The lateral border articulates with the frontal process
of the maxilla.
THE MAXILLA 87
Blood-supply. — Arteries are supplied to this bone by the nasal branch of the ophthalmic,
the frontal, the angular, and the anterior ethmoidal arteries.
Articulations. — With the frontal, maxilla, ethmoid, and its fellow of the opposite side.
Ossification. — Each nasal bone is developed from a single centre which appears about the
eighth week in the membrane overlying the fronto-nasal cartilage. The cartilage, which is
continuous with the ethmoid cartilage above and the lateral cartilage of the nose below, sub-
sequently undergoes absorption as a result of the pressure caused by the expanding bone. A.t
birth the nasal bones are nearly as wide as they are long, whereas in the adult the length is
three times greater than the width.
THE MAXILLA
The maxilla or upper jaw-bone (figs. 109, 110, 111) is one of the largest and
most important of the bones of the face. It supports the maxillary teeth and
takes part in the formation of the orbit, the hard palate, and the nasal fossa.
It is divisible into a body and four processes, of which two — the frontal and
zygomatic — belong to the upper part, and the palatine and alveolar to the lower
part of the bone.
The body is somewhat pyramidal in shape and hollowed by a large cavity
known as the sinus maxillaris (antrum of Highmore) , lined by mucous membrane
in the recent state, and opening at the base of the pyramid into the nasal cavity,
the zygomatic process forming the apex. The anterior (or facial) surface
looks forward and outward and is marked at its lower part by a series of eminences
which indicate the positions of the fangs of the teeth. The eminence produced
by the fang of the canine tooth is very prominent and separates two fossa.
That on the medial side is the incisive fossa, and gives origin to the alar and
transverse portions of the nasalis, and just above the socket of the lateral incisor
tooth, to a slip of the orbicularis oris; on the lateral side is the canine fossa, from
which the caninus {levator anguli oris) arises. Above the canine fossa, and close
to the margin of the orbit, is the infra-orbital foramen, through which the terminal
branches of the infra-orbital nerve and vessels emerge, and from the ridge im-
mediately above the foramen the quadratus labii superioris takes origin. The
medial margin of the anterior surface is deeply concave, forming the nasal notch,
and is prolonged below into the anterior nasal spine.
A ridge of bone extending upward from the socket of the first molar tooth
separates the anterior from the infratemporal (zygomatic) surface. This latter
surface is convex and presents near the middle the orifices of the posterior
alveolar canals, transmitting the posterior alveolar vessels and nerves. The
posterior inferior angle, known as the tuberosity [tuber maxillare], is rough and is
most prominent after eruption of the wisdom tooth. It gives attachment to a
few fibres of the internal pterygoid muscle and articulates with the tuberosity of
the palate.
The orbital surface [planum orbitale] is smooth, irregularly triangular, and
forms the greater part of the floor of the orbit.
Anteriorly, it is rounded and reaches the orbital circumference for a short distance at the
root of^the nasal process; lateraUy is the rough surface for the zygomatic bone. The posterior
border, smooth and rounded, forms the inferior boundary of the inferior orbital fissure. The
medial border is nearly straight and presents behind the frontal process, a smooth rounded
angle forming part of the circumference of the orbital orifice of the naso-lacrimal canal, and a
notch which receives the lacrimal bone. The rest of the medial border is rough for articulation
with the lamina papyracea of the ethmoid and orbital process of the palate bone.
The orbital surface is traversed by the infra-orbital groove, which, com-
mencing at the posterior border, deepens as it passes forward and finally becomes
closed in to form the infra-orbital canal. It transmits the second division of the
fifth nerve and the infra-orbital vessels and terminates on the anterior surface
immediately below the margin of the orbit. From the infra-orbital, other canals
— the anterior and middle alveolar — run downward in the wall of the antrum and
transmit the anterior and middle alveolar vessels and nerves. Lateral to the
commencement of the lacrimal canal is a shallow depression for the origin of
the inferior oblique.
The nasal surface takes part in the formation of the lateral wall of the nasal
fossa. It presents a large irregular aperture which leads into the antrum and,
immediately in front of this, the lacrimal groove, directed downward, backward,
and laterally into the inferior meatus of the nose. The groove is converted
(
THE SKELETON
into a canal by the lacrimal and inferior nasal concha and transmits the naso-
lacrimal duct.
In front of the groove is a smooth surface crossed obhquely by a ridge, the concbal crest,
for articulation with the inferior nasal concha. The surface below the crest is smooth, concave,
and belongs to the inferior meatus; the surface above the crest extends on to the lower part of
the frontal process and forms the wall of the atrium of the middle meatus. Behind the open-
ing of the antrum the surface is rough for articulation with the vertical plate of the palate
bone, and crossing it obliquely is a smooth groove converted by the ipalate into the pterygo-
palatine canal for the passage of the (descending) palatine nerves and the descending palatine
artery.
Fig. 109. — The Left Maxilla. (Outer view.)
Infra-orbital foramen-
Nasal notch.
Canine fossa'
al spine
Canin
eminence
Border of inferior orbital fissure
For sphenoid
Zygomatic surface
Zygomatic process
Posterior alveolar canals
W , It /J -Tuberosity
The frontal process, somewhat triangular in shape, rises vertically from the
angle of the maxilla. Its lateral surface is continuous with the anterior surface
of the body, and gives attachment to the orbicularis oculi, the medial palpebral
ligament and the quadratus labii superioris {caput angular e). The medial sur-
face forms part of the lateral boundary of the nasal fossa and is crossed obliquely
by a low ridge, known as the agger nasi, limiting the atrium of the middle meatus.
The hinder part of this surface rests on the anterior extremity of the labyrinth of the eth-
moid and completes the maxillo-ethmoidal cells. The superior border articulates with the
frontal; the anterior border articulates with the nasal bone; the posterior border is thick and
vertically grooved, in continuation with the lacrimal groove, and lodges the lacrimal sac.
The medial margin of the groove articulates with the lacrimal bone, and the junction of its
lateral margin with the orbital surface is indicated by the lacrimal tubercle.
Fig. 110. — The Left Maxilla. (Inner view.)
'Frontal process
Posterior palatine groove
Palatine process
The zygomatic process, rough and triangular, forms the summit of the
prominent ridge of bone separating the anterior and infratemporal surfaces. It
articulates above with the zygomatic, and from its inferior angle a few fibres of
the masseter take origin. The anterior and posterior surfaces are continuous
with the anterior and infratemporal surfaces of the body.
The palatine process projects horizontally from the medial surface and, with
the corresponding process of the opposite side, forms about three-fourths of the
hard palate. The superior surface is smooth, concave from side to side, and
THE MAXILLA 89
constitutes the larger part of the floor of the nasal fossa. The inferior surface is
vaulted, rough, and perforated with foramina for nutrient vessels. Near its
lateral margin is a longitudinal groove for the transmission of the vessels and
nerves which issue at the posterior palatine canal and course along the lower
aspect of the palate. When the bones of the two sides are placed in apposition, a
large orifice may be seen in the middle line immediately behind the incisor teeth.
This is the incisive foramen, at the bottom of whjch are four foramina. Two are
small and arranged one behind the other exactly in the meso-palatine suture.
These are the foramina of Scarpa and transmit the naso-palatine nerves, the left
Fig. 111. — Section op Maxilla to show the Floor op the Maxillary Antrum.
(Reduced J.)
(
passing through the anterior and the right through the posterior aperture. The
lateral and larger orifices are the foramina of Stenson, representing the lower
apertures of two passages by which the nose communicates with the mouth ; they
transmit some terminal branches of the descending palatine artery to the nasal
fossae, and lodge recesses of the nasal mucous membrane and remnants of
Jacobson's organs.
Fig. 112. — Maxilla and Zygomatic Bone, to show Muscular Attachments.
Inferior oblique
(Poirier.)
Quadrate muscle,
zygomatic head
Orbicularis oculi
Quadrate muscle,
angular head
Dilator narisposterii
Nasalis (alar portion)
Running laterally from the incisive foramen to the space between the second incisor and
canine tooth, an indistinct suture may sometimes be seen, indicating the hne of junction of the
maxillary and pre-maxillary portions of the bone. The premaxilla or incisive bone is the part
which bears the incisor teeth and in some animals exists tliroughout life as an independent
element. The posterior border of the palate process is rough and serrated for articulation with
90
THE SKELETON
the horizontal plate of the palate bone which completes the hard palate. The medial border
joins with its fellow to form the nasal crest upon wliich the vomer is received. The more
elevated anterior portion of this border is known as the incisor crest, and is continued forward
into the anterior nasal spine. The septal cartilage of the nose rests on its summit and the anterior
extremity of the vomer lies immediately behind it. At the side of the incisor crest is seen the
upper aperture of the canal leading from the nose to the mouth (Stenson's canal), which in its
course downward becomes a groove by a deficiency of its medial wall. Thus when the two bones
are articulated a canal is formed (incisive) with the lower ends of two canals opening into it.
The alevolar process is crescentic in shape, spongy in texture, and presents
cavities [alveoli dentales] in which the upper teeth are lodged. When complete
there are eight tooth-cavities (alveoli), with wide mouths, gradually narrowing
as they pass into the substance of the bone, and forming exact impressions of the
corresponding fangs of the teeth. The pit for the canine tooth is the deepest;
those for the molars are the widest, and present subdivisions. Along the lateral
aspect of the alveolar process the buccinator arises as far forward as the first molar
tooth.
The maxillary sinus or antrtma of Highmore, as the air-chamber occupying
the body of the bone is called, is somewhat pyramidal in shape, the base being
represented by the nasal or medial surface, and the apex corresponding to the
zygomatic process. In addition it has four walls: the superior is formed by the
orbital plate, and the inferior by the alveolar ridge. The anterior wall corre-
sponds to the anterior surface of the maxilla, and the posterior is formed by the
infratemporal surface. The medial boundary or base presents a very irregular
Fig. 113. — The Maxilla at Birth.
Premaxillary portion
Inferior view
orifice at its posterior part; this is partially filled in by the vertical plate of the
palate bone, the uncinate process of the ethmoid, the maxillary process of the
inferior nasal concha, and a small portion of the lacr'mal bone. Even when these
bones are in their relative positions, the orifice is very irregular in shape, and
requires the mucous membrane to form the definite rounded aperture (or apertures,
for they are often multiple) known as the opening of the sinus through which
the cavity communicates with the middle meatus of the nose.
The cavity of the sinus varies considerably in size and shape. In the young, it is small and
the walls are thick: as life advances it enlarges at the expense of its walls, and in old age they are
often extremely thin, so that occasionally the cavity extends even into the substance of the
zygomatic bone. The floor of the sinus is usually very uneven, due to prominences corre-
sponding to the roots of the molar teeth. In most oases the bone separating the teeth from
the sinus is very thin, and in some cases the roots project into it. The teeth which come into
closest relationship with the sinus are the first and second molars, but the sockets of any of
the teeth lodged in the maxilla may, under diseased conditions, communicate with it. As a
rule, the cavity of the sinus is single, but occasionally specimens are seen in which it is divided
by bony septa into chambers, and it is not uncommon to find recesses separated by bony
processes. The roof of the sinus presents near its anterior aspect what appears to be a thick
rib of bone; this is hollow and corresponds to the infra-orbital canal.
The most satisfactory method of studying the relation of the bones closing in the base of
the antrum is to cut away the lateral wall of the cavity (see fig. 128).
Blood-supply. — The maxilla is a very vascular bone and its arteries are numerous and
large. They are derived from the infra-orbital, alveolar, descending palatine, spheno-pala-
tine, ethmoidal, frontal, nasal, and facial vessels.
Articulations. — With the frontal, nasal, lacrimal, ethmoid, palate, vomer, zygomatic,
inferior nasal concha and its fellow of the opposite side. Occasionally it articulates with the
great wing, and the pterygoid process, of the sphenoid.
THE PALATE BONE
91
Ossification. — The maxilla is developed from several centres which are deposited in mem-
brane during the second month of intrauterine life. Several pieces are formed which speedily
fuse, so that at birth, with the exception of the incisor fissure separating the maxilla from the
premaxiUa, there is no trace of the composite character of the bone. The centres of ossification
comprise — (1) the malar, which gives rise to the portion of bone outside the infra-orbital canal;
(2) the maxillary, from which the greater part of the body and the frontal process are developed;
(3) the palatine, forming the hinder three-fourths of the palatal process and adjoining part
of the nasal wall; (-1) the premaxiilary, giving rise to the independent premaxiUary bone (os
incisivum), which lodges the incisor teeth and completes the anterior fourth of the hard palate.
In the early stages of growth the premaxiUa may consist of two pieces arising from two centres
of ossification which AJbrecht has named as follows: — the endognathion, or medial division for
Fig. 114. — Maxilla at the end op the First Dentition in both op which the Sutures
BETWEEN Maxilla and Premaxilla, and between the two Parts op the Prbmaxilla,
ARE seen.
£ndo-mesognathic suture
Meso-exognatliic suture
{
the central incisor, and the mesognathion, or lateral division for the lateral incisor; the rest
of the maxilla is named the exognathion; (5) the prepalatine, corresponding to the infra-vomerine
centre of Rambaud and Renault, forms a portion of bone interposed between the premaxiUary
in front and the palatine process behind. It gives rise to a part of the nasal surface and com-
pletes the medial waU of the incisive canal.
At birth the sinus is narrow from side to side and does not extend laterally to any appre-
ciable extent between the orbit and the alveoli of the teeth. During the early years of life it
graduaUy enlarges, but does not attain its fuU growth untU after the period of the second
dentition.
THE PALATE
The palate bone [os palatinum] (figs. 115, 116) forms the posterior part of the
hard palate, the medial wall of the nasal fossa between the maxilla and the
medial pterygoid plate, and, by its orbital process, the hinder part of the floor
of the orbit. It is somewhat L-shaped and presents for examination a horizontal
part and a perpendicular part; at their point of junction is the pyramidal process,
and surmounting the top of the vertical plate are the orbital and sphenoidal
processes, separated by the spheno-palatine notch.
The horizontal part resembles the palatine process ofthe maxilla, but is much
shorter. The superior surface is smooth, concave from side to side, and forms
the back part of the floor of the nasal fossa; the inferior surface completes the
hard palate behind and presents near its prosterior border a transverse ridge
which gives attachment to the tensor veli 'palatini muscle.
The anterior border is rough for articulation with the palatine process of the maxiUa; the
posterior is free, curved, and sharp, giving attachment to the soft palate. MediaUy it is thick
and broad for articulation with its fellow of the opposite side, forming a continuation of the
crest of the palatal processes of the maxiUae and supporting the vomer. The posterior extremity
of the crest is the posterior nasal spine, from which the azygos uvulce arises. LateraUy, at its
junction with the perpendicular part, it is grooved by the lower end of the pterygo-palatine
canal.
The perpendicular part is longer and thinner than the horizontal plate. The
lateral surface is in relation with the maxilla and is divided into two parts by
92
THE SKELETON
a vertical groove which forms with the maxilla the pterygo -palatine canal for
the transmission of the anterior palatine nerve and the descending palatine
artery. The part of the surface in front of the groove articulates with the nasal
surface of the maxilla and overlaps the orifice of the antrum by the maxillary
process, a variable projection on the anterior border. Behind the groove the
surface is rough for articulation with the maxilla below and the medial pterygoid
plate above.
Fig. 115. — Palate Bone (Left). (Medial view.)
Sphenoidal process.
-palatine notcli (when
complete in the palate
bone, it is due to ankylosis with
sphenoidal concha)
Orbital process (ethmoidal surfaced
Superior meatus
■Ethmoidal crest
Middle meatus
Conchal crest
Inferior meatus
The medial or nasal surface presents two nearly horizontal ridges separating
three shallow depressions. Of the depressions, the lower forms part of the inferior
meatus of the nose, and the limiting ridge or conchal (inferior turbinate) crest
articulates with the inferior nasal concha. Above this is the depression forming
part of the middle meatus, and the ridge or ethmoidal (superior turbinate) crest,
constituting its upper boundary, articulates with the middle nasal concha.
Fig. 116. — Palate Bone. (Posterior view.)
Orbital surface
Zygomatic surface
Spheno-palatine foramen (usually a
notch)
Groove for external pterygoid-
Groove for pterygoid fo
Groove for internal pterygoid
Tuberosity-
Orbital process
Sphenoidal process
The upper groove is narrower and deeper than the other two and forms a large part of the
superior meatus of the nose. The anterior border of the vertical plate is thin and bears the
maxillary process, a tongue-like piece of bone, which e.xtends over the opening of the maxillary
sinus from behind. This border is continuous above with the orbital process. The posterior
border is rough and articulates with the anterior border of the medial pterygoid plate. It is
continuous superiorly with the sphenoidal process.
The pyramidal process or tuberosity fits into the notch between the lower extremities of
the pterygoid plates and presents posteriorly three grooves. The middle, smooth and concave,
completes the pterygoid fossa, and gives origin to a few fibres of the internal -pterygoid; the
medial and lateral grooves are rough for articulation with the anterior border of the correspond-
ing pterygoid plate. Inferiorly, close to its junction with the horizontal plate, are the openings
of the greater palatine and smaller palatine canals, of which the latter are the smaller and less
constant; they transmit the palatine nerves. Medially the pyramidal process gives origin to a
few fibres of the superior constrictor of the pharynx, and laterally a small part appears in the
zygomatic fossa between the tuberosity of the maxilla and the pterj'goid process of the sphenoid.
The sphenoidal process, the smaller of the two processes surmounting the vertical part,
curves upward and medially and presents three surfaces and two borders. The superior sur-
face is in contact with the body of the sphenoid, and the top of the medial pterygoid plate, where
it completes the pharyngeal canal. The medial or inferior surface forms part of the lateral
THE ZYGOMATIC BONE 93
wall and roof of the nasal fossa, and at its medial end tounhes the ala of the vomer. The
lateral surface looks forward and laterally into the pterygo-palatine (spheno-maxillary) fossa.
Of the two border3,the posterior is thin and articulates with the medial pterygoid plate; the
anterior border forms the posterior boundary of the spheno-palatine foramen.
The orbital process is somewhat pyramidal in shape, and presents for examination five
surfaces, three of which — the posterior, anterior, and medial — are articular and the rest non-
articular. The posterior or sphenoidal surface is small and joins the anterior surface of the
body of the sphenoid; the medial or ethmoidal articulates with the labyrinth of the ethmoid;
and the anterior or maxillary, which is continuous with the lateral surface of the perpendicular
part, is joined with the maxilla. Of the two non-articular surfaces, the superior or orbital,
directed upward and laterally, is slightly concave, and forms the posterior angle of the floor
of the orbit; the lateral or zygomatic, smooth and directed lateral, looks into the pterygo-
palatine (spheno-maxillary) and zygomatic fossse, and forms the anterior boundary of the
spheno-palatine foramen. The process is usually hollow and the cavity completes one of the
posterior ethmoidal cells or communicates with the sphenoidal sinus.
Fig. 117. — Maxilla and Palate Bones showing how the Inpha-okbital Groove
Runs Outwakd almost at Right Angles phom the Neighbourhood op the Spheno-
palatine Foramen on the Back of the Maxilla and the Orbital Process op the
Palate. Posterior View. (E. Fawcett.)
.Infra-orbital groove
Between the orbital and sphenoidal processes is the spheno-palatine notch, converted by
the body of the sphenoid, into a complete foramen. It leads from the pterygo-palatine fossa
into the back part of the nasal cavity close to its roof, and transmits the medial branches from
the spheno-palatine ganglion and the spheno-palatine vessels.
Blood-supply. — The palate bone receives branches from the descending palatine and the
spheno-palatine arteries.
Articulations. — With the sphenoid, maxilla, vomer, inferior nasal concha, ethmoid, and its
fellow of the opposite side.
Ossification. — The palate is ossified in membrane from a single centre which appears about
the eighth week at the angle between the horizontal and perpendicular parts. At birth the
two parts are nearly equal in length, but as the nasal fossae increase in vertical depth, the
perpendicular part is lengthened until it becomes about twice as long as the horizontal part.
THE ZYGOMATIC
The zygomatic [os zygomaticum] or malar bone (fig. 118) forms the promi-
nence known as the cheek and joins the zygomatic process of the temporal with the
maxilla. It is quadrangular in form with the angles directed vertically and
horizontally. The malar (or external) surface is convex and presents one or two
small orifices for the transmission of the zygomatico-facial nerves and vessels.
It is largely covered by the orbicularis oculi and near the middle is slightly ele-
vated to form the malar tuberosity, which gives origin to the zygomaticus and
zygomatic head of quadrate muscle of upper lip.
The temporal (or internal) surface is concave and looks into the temporal
and infratemporal fossae; it is excluded from the orbit by a prominent curved plate
94
THE SKELETON
of bone, the orbital process, which forms the anterior boundary of the temporal
fossa. The upper part gives origin to a few fibres of the temporal muscle, while
at the lower part is a large rough area for articulation with the zygomatic process
of the maxilla.
The orbital process is placed at right angles to the remaining part of the bone
and forms the anterior portion of the lateral wall of the orbit. On the orbital
Fig. 118. — The Left Ztgoma.tic Bone.
A, the malar surface. B, the temporal and orbital surfaces.
Frontal process
Frontal process
Orbital border
Malar canal
Processus marginalis Temporal —
Temporal border Temporal border
Zygomatic process
Infra-
orbital
process
Intraorbital head ^'^
of quadrate muscle X-^
Maxillary
border
Zygomatic head
of quadrate muscle
Zygomaticus
Masseter
Malar tubercle
Malar tubercle
surface of the process are seen the foramina of two zygomatico -orbital canals,
which transmit the zygomatico-facial and zygomatico-temporal branches of the
zygomatic branch of the fifth, together with two small arteries from the lacri-
mal. In some cases, however, the canal is single at its commencement on the
orbital plate and bifurcates as it traverses the bone. The rough free edge of the
Fig. 119. — Skull showing the Right Malar Bone DrviDED into Two Parts by a Hori-
zontal Suture. (From a specimen in the Museum of University College, London.)
process articulates above with the zygomatic border of the great wing of the
sphenoid, and below with the maxilla. When the orbital process is large, it
excludes the great wing of the sphenoid from articulation with the maxilla,
and the border then presents near the middle a short, non-serrated portion
THE MANDIBLE 95
which closes the anterior extremity of the inferior orbital (spheno-maxillary)
fissure.
All the four angles of the zygomatic bone have distinguishing featm-es. The superior,
forming the fronto-sphenoidal process, is the most prominent, and is serrated for articulation
with the zygomatic process of the frontal; the anterior or infra-orbital process, sharp and
pointed, articulates with the maxilla and occasionally forms the superior boundary of the infra-
orbital foramen; the posterior or temporal process is blunt and serrated rnainly on its medial
aspect for articulation with the zygomatic process of the temporal; the inferior angle, blunt
and rounded, is known as the malar tubercle.
Of the four borders, the orbital is the longest and extends from the fronto-sphenoidal to the
infra-orbital process. It is thick, rounded, and forms more than one-third of the circumference
of the orbit; the temporal border, extending from the fronto-sphenoidal to the temporal process,
is sinuously curved and gives attachment to the temporal fascia. Near the frontal .angle is
usually seen a sHght elevation, the processus marginalis, to which a strong shp of the fascia is
attached; the masseteric border, thick and rough, completes the lower edge of the zygomatic
arch and gives origin to the anterior fibres of the masseler; the maxillary border, rough and eon-
cave, is connected by suture with the maxilla, and near the margin of the orbit gives origin to
the infra-orbital head of the guadratus Inbii svperioris.
Blood-supply. — The arteries of the zygomatic are derived from the ^infra-orbital, lacrimal,
transverse facial, and deep temporal arteries.
Articulations. — With the maxilla, frontal, temporal, and sphenoid.
Ossification. — The zygomatic is ossified in membrane from three centres which appear in
the eighth week of intra-uterine life. The three pieces, which have received the names of ■pre-
violar, poslmalar, and hypnmalar, unite .about the fifth month. Occasionally the primary nuclei
fail to coalesce, and the bone is then represented in the adult by two or three portions sepa-
rated by sutures. In those cases in which the premalar and postmalar unite and the hypo-
malar remains distinct, the suture is horizontal; if the independent portion is the premalar,
then the suture is vertical. The bipartite zygomatic has been observed in skulls obtained from
at least a dozen different races of mankind, but because of the greater frequency in which it
occurs in the crania of the Japanese (seven per cent.), the name of o.« Japonicum has been
given to it.
THE MANDIBLE
The mandible [mandibula] or lower jaw-bone (figs. 120, 121) is the largest and
strongest bone of the face. It supports the mandibular teeth, and by means of a
pair of condyles, moves on the skull at the mandibular fossse of the temporal
bones. It consists of a horizontal portion — the body- — strongly curved, so as to
somewhat resemble in shape a horseshoe, from the ends of which two branches
or rami ascend almost at right angles.
The body is marked in the middle line in front by a faint groove which in-
dicates the symphysis or place of union of the two originally separate halves
of the bone. This ends below in the elevation of the chin known as the mental
protuberance, the lowest part of which is slightly depressed in the centre and
raised on each side to form the mental tubercle. Each half of the mandible
presents two surfaces and two borders. On the lateral surface, at the side of
the symphysis, and below the incisor teeth, is a shallow depression, the incisor
fossa, from which the vientalis and the incisivus labii inferioris muscle arise; and
more laterally, opposite the second bicuspid tooth, and midway between the
upper and lower margins, is the mental foramen, which transmits the mental
nerve and vessels. Below the foramen is the oblique line, extending backward
and upward from the mental tubercle to the anterior border of the rairius; it
divides the body into an upper or alveolar part and a lower or basilar part, and
affords attachment to the quadratus labii inferioris and the triangularis oris.
The medial surface presents at the back of the symphysis four small pro-
jections, called the mental spine (genial tubercles). These are usually arranged
in two pairs, one above the other; the upper comprising a pair of prominent
spines, gives origin to the genio-glossi, and the lower, represented in some bones
by a median ridge or only a slight roughness, gives origin to the genio-hyoid muscles.
At the side of the symphysis near the inferior margin is an oval depression, the
digastric fossa, for the insertion of the digastric muscle. Commencing below
the mental spine, and extending upward and backward to the ramus, is the
mylo-hyoid line, which becomes more prominent as it approaches ,the alveolar
border; it gives attachment along its whole length to the mylo-hyoid muscle,
at its posterior fifth to the superior constrictor of the pharynx, and at the pos-
terior extremity to the pterygo-mandibular raphe. Above this line at the side
of the symphysis is a smooth depression [fovea sublingualis] for the sublingual
gland, and below it, farther back, is another for the submaxillary gland.
96
THE SKELETON
The alveolar part or superior border is hollowed out into eight sockets or
alveoli. These are conical in shape and form an exact counterpart of the roots-
of the teeth which they contain. From the lateral aspect of the alveolar process,
as far forward as the first molar tooth, the buccinator muscle takes origin.
The base or inferior border is thick and rounded. In the anterior part of its
extent it gives attachment to the platysma, and near its junction with the ramus
is a groove for the external maxillary artery which here turns upward into the face.
The ramus is thinner than the body and quadrilateral in shape. The lateral
surface is flat, gives insertion to the masseter, and at the lower part is marked by
several oblique ridges for the attachment of tendinous bundles in the substance
of the muscle. The medial surface presents near the middle the mandibular
(inferior dental) foramen, leading into the mandibular (inferior dental) canal
which traverses the bone and terminates at the mental foramen on the lateral
surface of the body. From the canal, which in its posterior two-thirds is nearer to
the medial, and in its anterior third nearer to the lateral, surface of the mandible,
Fig. 120.^The Mandible. (Lateral view.)
Coronoid
Temporal process
Mandibular
notch External pterygoid
Plat\ sma
Triangularis' oris Groove for external maxillary artery
External oblique line
a series of small channels pass upward to the sockets of the posterior teeth and
transmit branches of the inferior alveolar (dental) vessels and nerve; in front of
the mental foramen a continuation of the canal extends forward and conveys the
vessels and nerves to the canine and incisor teeth. The mandibular foramen is
bounded medially by a sharp margin forming the lingula (mandibular spine),
which gives attachment to the spheno-mandibular ligament.
The posterior margin of the. lingula is notched. This notch forms the
commencement of a groove, the mylo-hyoid groove [sulcus mylohyoideus],
which runs obliquely downward and forward and lodges the mylo-hyoid nerve
and artery, and, in the embryo, Meckel's cartilage. Behind the spine is a rough
area for the insertion of the internal pterygoid muscle.
The posterior border of the ramus is thick and rounded, and in meeting the
inferior border of the ramus forms the angle of the jaw, which is rough, obtuse,
usually everted, and about 122° in the adult; the angle gives attachment to the
stylo-mandibular ligament. The inferior border is thick, rounded, and continu-
ous with the base. The anterior border is continuous with the oblique line,
whilst the upper border presents two processes separated by a deep concavity, the
mandibular (sigmoid) notch. Of the processes, the anterior is the coronoid; the
posterior, the condylar.
THE MANDIBLE
97
The condylar process consists of the condyle [capitulum mandibulse] and the
narrowed portion by which it is supported, the neck. The condyle is oval in
shape, with its long axis transverse to the upper border of the ramus, but oblique
with regard to the median axis of the sicull, so that the lateral extremity, which
presents the condylar tubercle for the temporo-mandibular ligament of the
temporo-mandibular articulation, is a little more forward than the medial ex-
tremity. The convex surface of the condyle is covered with cartilage in the recent
Fig. 121. — The Mandible. (Medial view.)
Lin^ula
Mandibular
foramen
Spheno-mandib-
ular ligament
Superior
constnctor
Mylo-hyoid
groove
Internal
pterygoid
Stylo-mandibular
ligament
^ > " tii { — Groove for sub-
lingual gland
Genio-glossus
Genio-hyoid
Digastric
Mylo-hyoid Groove for submaxillary gland
Mylo-hyoid line
state, and rests in the mandibular fossa; the neck is flattened from before back-
ward, and presents, in front, a depression [fovea pterygoidea] for the insertion
of the external pterygoid muscle.
The coronoid process, flattened and triangular, is continued upward from the
anterior part of the ramus. The lateral surface is smooth and gives insertion
to the temporal and masseter muscles; the medial surface is marked by a ridge
which descends from the tip and becomes continuous with the posterior part of
the mylo-hyoid line. On the medial surface, as well as on the tip of the coronoid
Fig 122 — Mandiblb showing Relations op Meckel's Cartilage in Human Fcetus op
8 CM. Cbown-Rump Length. (After KoUmann, Handatlas der Entwickelungsgeschichte.)
Groove for teeth
Meckel's cartilage
AnniUus tym-
panicus
process, the temporal muscle is inserted. The mandibular notch, the deep semi-
lunar excavation separating the coronoid from the condylar process, is crossed
by the masseteric nerve and vessels.
Blood-supply. — Compared with other bones, the superficial parts of the mandible are not
so freely supplied with blood. The chief artery is the inferior alveolar which runs in the man-
dibular canal, and hence, as the bone is exposed to injury and sometimes actually laid bare in
its alveolar portion, it often necroses, especially if the artery is involved at the same time.
7
98 THE SKELETON
Ossification. — The mandible is mainly formed by ossification in the fibrous tissue investing
the cartilage of the first branchial arch or Meckel's cartilage, although a small portion of the
cartilage itself is directly converted into bone.
It is now generally admitted that the lower jaw is developed in membrane as a single skel-
etal element. The centre of ossification appears in the outer aspect of Meckel's cartilage and
gives rise to the bony plate known as the dentary. This plate extends forward right up to the
middle line in front, and from it a shelf grows upward for the support of the tooth germs.
Fig. 123. — The Mandible at Birth.
Meckel's cartilage lies below and medial to the dentary plate, and the inferior alveolar nerve
passes forward between the two structures. Meckel's cartilage itself takes some small part in
the formation of the lower jaw. Ossification from the primary nucleus invades the cartilage
at a point opposite the interval between the first and second tooth germs, and the resulting
bone contributes to the formation of the alveolar margin opposite these two teeth. Behind
this point the cartilage atrophies except in so far as it helps to form the spheno-mandibular
ligament and the malleus and incus. Behind the symphysis the anterior extremity of the
cartilage does not enter into the formation of the jaw, but it usually persists throughout foetal
Fig. 124. — The Skull op a Woman Eighty-three Years Old, to show the Changes in
THE Mandible and Maxilla
life as one or two small, rounded, cartilaginous masses. Occasionally they become ossified
and give rise to accessory ossicles in this situation. The lamella of bone situated on the medial
side of Meckel's cartilage, corresponding to the distinct splenial element in some animals, arises
in man as an extension from the dentary element.
In connection with the condylar and coronoid processes, cartilaginous masses are developed.
These do not, however, indicate separate elements, but are adaptations to the growth of the
lower jaw. 'They are ossified by an extension from the surrounding membrane bone.
THE HYOID BONE
The process of ossification of the lower jaw commences very early, between the sixth and
eighth week, and proceeds rapidly, so that by the fourth month the various parts are formed.
Age-changes. — At birth the mandible is represented by two nearly horizontal troughs of
bone, lodging unerilpted teeth, and joined at the symphysis by fibrous tissue. The body
is mainly alveolar, the basal part being but little developed; the condyle and the upper edge
of the symphysis are nearly on a level; the mental foramen is nearer the lower than the upper
margin, and the angle is about 175°. The inferior alveolar nerve lies in a shallow groove
between the spleuial and dentary plates.
During the first year osseous union of the two halves takes place from below upward, but
is not complete until the second year. After the first dentition, the ramus forms with the body
of the mandible an angle of about 140°, and the mental foramen is situated midway between
the upper and lower borders of the bone opposite the second milk-molar. In the adult, the
angle formed by the ramus and body is nearer to a right angle, and the mental foramen is oppo-
site the second bicuspid, so that its relative position remains unaltered after the first dentition.
In old age, after the fall of the teeth, the alveolar margin is absorbed, the angle formed by the
ramus and body is again increased, and the mental foramen approaches the alveolar margin.
In a young and vigorous adult the mandible is, with the exception of the petrous portion of the
temporal, the densest bone in the skeleton; in old age it becomes exceedingly porous, and often
so soft that it may easily be broken.
(
THE HYOID BONE
The hyoid bone [os hyoideum] or os linguae (fig. 125), situated in the anterior
part of the neck between the chin and the thyreoid cartilage, supports the tongue
and gives attachment to numerous muscles. It is suspended from the lower
extremities of the styloid processes of the temporal bones by two slender bands
known as the stylo-hyoid ligaments, and is divisible into a body and two pairs of
processes, the greater and lesser cornua.
The body, constituting the central portion of the bone, is transversely placed
and quadrilateral in form. It is compressed from before backward and lies
obliquely so that the anterior surface looks upward and forward and the posterior
surface in the opposite direction.
The anterior surface is convex and divided by a horizontal ridge into a superior
and an inferior portion. Frequently it also presents a vertical ridge crossing the
former at right angles, and just above the point of intersection is the glosso-hyal
Fig. 125. — The Hyoid Bone. A, Male, B, Female (Natural Size)
process, the vestige of a well-developed process in this situation in the hyoid
bone of some of the lower animals (reptiles and the horse). In this way four
spaces or depressions for muscular attachments are marked off, two on either
side of the middle line. The posterior surface is deeply concave and separated
from the epiglottis by the thyreo-hyoid membrane, and by some loose areolar
tissue. The membrane passes upward from the thyreoid cartilage to be attached
to the superior border, and interposed between it and the concavit.y on the
back of the body is a small synovial bursa. The inferior border, thicker than
the upper, gives insertion to muscles. The lateral borders are partly in relation
with the greater cornua, \vith which they are connected, up to middle life, by
synchondrosis, but after this period, usually by bone.
100
THE SKELETON
The greater cornua projects upward and backward from the sides of the body.
They are flattened from above downward, thicker near their origin, and terminate
posteriorly in a rounded tubercle to which the thyreo-hyoid ligament is attached.
The lesser cornua are small conical processes projecting upward and back-
ward opposite the lines of junction between the body and the greater cornua,
and by their apices give attachment to the stylo-hyoid ligaments; they are
connected to the body by fibrous tissue. Professor Parsons has shown that a
joint with a synovial cavity is common between the smaller and geater cornua.
The lesser cornua are sometimes partly or even completely cartilaginous in the
adult.
Fig. 126. — Hyoid Bone Enlarged to show Muscular Attachments. (After
F. G. Parsons.)
Greater cornu'
Attachment to
digastric tendon
Hyo-glossus
The muscles attached to each half of the hyoid bone may be enumerated as follows: —
Body Genio-hyoid, genio-glossus, mylo-hyoid, sterno-hyoid, omo-hyoid, stylo-
hyoid, thyreo-hyoid and hyo-glossus.
Greater cornu Thyreo-hyoid, middle constrictor, hyo-glossus, and digastric.
Lesser cornu Chondro-glossus, and middle constrictor.
Ossification. — In the early months of intra-uterine life the hyoid bone is composed of
hyahne cartilage and is directly continuous with the styloid processes of the temporal bones.
Ossification takes place from six centres, of which two appear in the central piece of cartilage,
one on either side of the middle line, either just before or just after birth; soon after their
appearance, however, they coalesce to form the body of the bone (basi-hyal). The centre for
each of the greater cornua (thyreo-hyals) appears just about the time of birth, and for each
of the lesser cornua (oerato-hyals) some years after birth, even as late as puberty. (F. G.
Parsons.) The greater cornua and the body unite in middle life; the lesser cornua rarely anky-
lose with the body and only in advanced age. Professor Parsons has shown, however, that the
lesser cornua more frequently unite with the greater cornua.
THE SKULL AS A WHOLE
The skull, formed by the union of the cranial and facial bones already de-
scribed, may now be considered as a whole. Taking a general view, it is spheroidal
in shape, smooth above, compressed from side to side, flattened and uneven
below, and divisible into six regions : a superior region or vertex, a posterior or
occipital region, an anterior or frontal region, an inferior region or base, and two
lateral regions.
(1) The Superior Region
Viewed from above {norma verticalis) the skull presents an oval outline with
the broader end behind, and includes the frontal, parietals, and the interparietal
portion of the occipital. In a skull of average width the zygomatic arches are
visible, but in very broad skulls they are obscured.
THE SKULL AS A WHOLE 101
The sutures of the vertex are : —
The metopic, which is, in most skulls, merely a median fissure in the frontal bone just
above the glabella; occasionally it involves the whole length of the bone. It is due to the
persistence of the fissure normally separating the two halves of the bone in the infant.
The sagittal is situated between the two parietals, and extends from the bregma to the
lambda.
The coronal lies between the frontal and parietals, and extends from pterion to pterion.
The lambdoid is formed by the parietals and interparietal portion of the occipital. It
extends from asterion to asterion.
The occipital suture is only present when the interparietal exists as a separate element
(figs. 70 and 71).
The more important points are: —
The bregma, which indicates the situation of the frontal (gi-eater) fontanelle, and marks
the confluence of the coronal, the sagittal, and, when present, the metopic sutures.
The lambda, where the sagittal enters the lambdoid suture; it marks the situation of the
occipital (lesser) fontanelle.
The obelion, a little anterior to the lambda, is usually indicated by a median or two lateral
foramina.
(2) The Posterior Region
Viewed from behind {norma occipitalis) the skull is somewhat pentagonal in
form. Of the five angles, the superior or median is situated in the line of the
sagittal suture; the two upper lateral angles coincide with the parietal eminences
and the two lower with the mastoid processes of the temporal bones. Of the
sides, four are somewhat rounded, and one, forming the basal line, running
between the mastoid processes, is flattened.
The centre is occupied by the lambda, and radiating from this point are three sutures,
the sagittal, and the two parts of the lambdoid. Each half of the lambdoid suture bifurcates
at the mastoid portion of the temporal bone, the two divisions constituting the parieto-mastoid
and occipito-mastoid sutures; the point of bifurcation is known as the asterion.
In the lower part of the view is seen the external occipital protuberance (inion), the occipital
crest, and the thi-ee pairs of nuchal lines, which give it a rough and uneven appearance. The
occipital point is the point of the occiput furthest from the glabella in the median plane. It
is situated above the external occipital protuberance.
(3) The Lateral Region
The lateral region (norma lateralis) (fig. 127) is somewhat triangular in shape,
being bounded above by a line extending from the zygomatic process of the
frontal, along the temporal line to the lateral extremity of the superior nuchal line
of the occipital bone; this forms the base of the triangle. The two sides are
represented by lines drawn from the extremities of the base to the angle of the
jaw. It is divisible into two portions, one in front, the other behind, the emi-
nentia articularis [tuberculum articulare]. The posterior portion presents, in a
horizontal line from behind forward, the mastoid portion of the temporal, with
its process and foramen, the external auditory meatus, the centre of which is
known as the atiricular point, the mandibular fossa, and the condyle of the mandible.
In the anterior portion are three fossaj, (a) temporal, (b) infratemporal, (c)
pterygo-palatine (spheno-maxillary), and two fissures, the inferior orbital (spheno-
maxillary) and pterygo-palatine.
(a) The temporal fossa, somewhat semilunar in shape, is bounded above and behind by the
temporal line, in front by the frontal, zygomatic, and great wing of sphenoid, and laterally by
the zygomatic arch, by which it is separated superficially from the infratemporal fossa; more
deeply the infratemporal ridge separates the two fossae.
The fossa is formed by parts of five bones, the zygomatic, temporal, parietal, frontal,
great wing of sphenoid, and is traversed by six sutures, coronal, spheno-zygomatic, sphcno-
sc(uamosal, spheno-parietal, squamosal, and spheno-frontal. The point where the temporal
ridge is crossed by the coronal suture is the stephanion, and the region where the frontal,
sphenoid, temporal, and parietal meet is the pterion. The latter is frequently occupied in the
adult by the epipteric bone.
The temporal fossa is concave in front, convex behind, filled by the temporal muscle, and
roofed in by a strong glistening aponeurosis, the temporal fascia, which serves to bind down
the muscle.
(b) The infratemporal fossa (zygomatic fossa), irregular in shape, is situated below and
to the medial side of the zj'goma, covered in part by the ramus of the mandible. It is bounded
in front by the lower part of the medial surface of the zygomatic, and by the infratemporal
surface of the maxilla, on which are seen the orifices of the posterior superior alveolar canals;
behind by the posterior border of the lateral pterygoid plate, the spine of the sphenoid, and the
articular tubercle; above by the infratemporal ridge, a small part of the squamous portion of
102
THE SKELETON
the temporal, the great wing of the sphenoid perforated by the foramen ovale and foramen
spinosum; helow by the alveolar border of the maxilla; laterally by the ramus of the mandible
and the zygoma formed by zygomatic and temporal; medially by the lateral pterygoid plate, a
line from which to the spine of the sphenoid separates the infratemporal fossa from the base of
the skull. It contains the lower part of the temporal muscle and the coronoid process of the
mandible, the external and internal pterygoids, the internal maxillary vessels, and the mandibular
division of the fifth nerve with numerous branches. At its upper and medial part are seen the
inferior orbital and pterygo-palatine fissures.
The inferior orbital (or spheno-maxillary) fissure is horizontal in position, and lies between
the maxQla and the great wing of the sphenoid; laterally it is usually completed by the zygo-
matic, though in some cases the sphenoid joins the maxilla, and in this way excludes the zygo-
matic bone from the fissure; medially it is terminated by the infratemporal surface of the orbital
process of the palate bone. Through this fissure the orbit communicates with the pterygo-
palatine (spheno-maxillary), infratemporal, and temporal fossae. It transmits the infra-
orbital nerve and vessels, the zygomatic nerve, ascending branches from the spheno-palatine
ganglion to the orbit, and a communicating vein from the ophthalmic to the pterygoid plexus.
Fig. 127.^The Skull. (Norma lateralis.)
The pterygo-palatine (pterygo-maxillary) fissure forms a right angle with the inferior
orbital fissure and is situated between the maxilla and the anterior border of the pterygoid
process of the sphenoid. At its lower angle, where the two lips of the fissure approximate, the
lateral pterj'goid plate occasionally articulates with the maxilla, but they are usually separated
by' a thin portion of the pyramidal process of the palate. The pterygo-palatine fissure, which
serves to connect the infratemporal fossa with the pterygo-palatine fossa, is bounded medially
by the perpendicular part of the palate; it transmits branches of the internal maxillary artery,
and the corresponding veins, to and from the pterygo-palatine fossa.
(c) The pterygo-palatine (spheno-maxillary) fossa is a small space, of the form of
an inverted pyramid, situated at the angle of junction of the inferior orbital (spheno-maxil-
lary) with the pterygo-palatine (pterygo-maxillary) fissure, below the apex of the orbit. It is
bounded infroid by the infratemporal surface of the maxilla; behind, by the base of the pterygoid
process and the lower part of the anterior surface of the great wing of the sphenoid; medially
by the perpendicular part of the palate with its orbital and sphenoidal processes; above by the
lower surface of the body of the sphenoid. Three fissures terminate in it — viz., the superior
orbital, pterygo-palatine, and inferior orbital; through the superior orbital fissuje it communi-
cates with the cranium, through the pterygo-palatine fissure with the infratemporal fossa,
through the inferior orbital fissure with the orbit, and throagh the spheno-palatine foramen
on the medial wall it communicates with the upper and back part of the nasal fossa. In-
THE SKULL AS A WHOLE
103
eluding the spheno-palatine foramen sL\ foramina open into the fossa. Of these, three are on
the posterior wall: enumerated from without inward, and from above downward, they are the
foramen rotundum, the pterygoid (Vidian) canal, and the pharyngeal (pterygo-palatine)
canal. The apex of the pyramid leads below into the pterygo-palatine canal and the accessory
palatine canals which branch from it; and anteriorly is the orifice of the infra-orbital canal.
The fossa contains the spheno-palatine ganglion, the maxillary nerve, and the terminal part of
the internal maxillary artery, and the various foramina and canals in relation with the fossa
serve for the transmission of the numerous branches which these vessels and nerves give off.
Fig. 128. — A Section of the Skull, showing the Medial Wall of the Orbit, the Medial
Wall of the Antrum, and the Pterygo-palatine Fossa.
Frontal sinus
Frontal process of maxilla ~7
Lacrimal -—
Lacrimal canal
Orifice of antrum
Inferior nasal concha
Palate bone
Anterior nasal spine
Anterior ethmoid canal
Posterior ethmoid canal
Spheno-palatine foramen
Pterygoid canal, leading into the
pterygo-palatine fossa
Sphenoid
Lateral pterygoid plate
(4) Inferior Region or External Base of Skull
The external base of the skull {norma basilaris) (figs. 130, 131) extends from
the incisor teeth to the occipital protuberance, and is bounded on each side by
the alveolar arch, the zygomatic, the zygoma, the temporal, and the superior
nuchal line of the occipital bone. It is very uneven and, excluding the lower
jaw, divisible into three portions: (a) anterior, (b) middle or subcranial, and (c)
posterior or suboccipital.
Fig. 129. — Hard Palate of a Child Five Years Old.
Palate bonet^
L^f'Cc ^ Palate process of maxilla
Greater palatine foramen
Lesser palatine foramen
(a) The anterior division consists of the hard palate, the alveolar arch, and
the choanse (posterior nares).
When the skull is inverted, the hard palate stands at a higher level than the
rest, and is bounded anteriorly and laterally by the alveolar ridges containing the
teeth. The bones appearing in the intermediate space are the premaxillary and
palatine portions of the maxillse and the horizontal parts of the palate bones.
104
THE SKELETON
Fig 130 — The Skull (Norma basilaris.)
Tensor veli palatini
Azygos uvulee
Superior constrictor
Internal pterygoid
Tensor veli palatini
Tensor tympani
Levator veli palatini
Longus capitis
Superior constrictor
Rectus capitis anterior
Anterior longitudinal ligament of spine
Vertical part of crucial ligament
Alar ligament
Articular capsule
Posterior occipito-atlantal membrane
Superior oblique
Rectus capitis posterior major
Rectus capitis posterior minor
f- - Ligamentum nuchse
Trapezius
THE SKULL AS A WHOLE
105
Fig. 131. — The Skull. (Norma basilaris.)
Scarpa^s foramen
Stenson's foramen
Scarpa's foramen
: fossa
Palatine groove
Posterior palatine foramen
Spine of the palate bone
Hamular process
VO\ER
Sphenoidal process of palate bone
Foramen lacerum
Pharyngeal tubercle
Carotid canal
Tubercle for alar ligament
Condylar foramen'
External occipital crest
External occipital protuberance
106
THE SKELETON
They are rough for the attachment of the muco-periosteum, and near the posterior
margin is the ridge for the fibrous expansion of the tensor veli 'palatini. The fol-
lowing points are readily recognised (fig. 129) : —
The meso-palatine suture commences at the alveolar point, traverses the incisive fossa, and
terminates at the posterior nasal spine.
The transverse palatine suture, between the palate bones and palatine processes of the
maxiUae.
In young skulls the incisive sutures, and behind the incisor teeth four small openings
known aS the gubemacular canals (see figs. 114 and 129).
The incisive fossa containing the termination of four canals: two small orifices, foramina of
Fig. 1.32. — The Skull. (Norma facialis.)
Quadratus lahii superions
(zygomatic head)
Orbicularis oculi
Quadratus labii superioris
(ancular head)
Quadratus labii superiosis
(infraorbital head)
Nasalis (transverse
portion)
Nasalis (alar portion)
Orbicularis oris
Scarpa, situated one behind the other in the meso-palatine suture; and two larger openings,
the foramina of Stenson. The foramina of Scarpa transmit the naso-palatine nerves, and those
of Stenson are in relation (embryonic) with the organs of Jacobson.
At the posterior angles of the hard palate are the greater palatine foramina, through which
the descending palatine vessels and the anterior palatine nerves emerge on to the palate; a thin
lip of bone separates them from the lesser palatine foramen in the tuberosity of the palate bone
on each side, for the posterior palatine nerve.
The hamular process of the medial pterygoid plate is the most posterior limit of the hard
palate.
At the posterior extremity of each alveolar ridge is the tuberosity of the maxilla, and between
it and the palate bone is a foramen (variable in size and sometimes absent), the middle palatine
foramen, for the middle palatine nerve. This foramen is often included under the lesser pala-
tine foramina (BNA).
THE SKULL AS A WHOLE
107
Behind the hard palate are the choanae (posterior nares), separated from each other by the
vomer. Each is bounded laterally by the medial pterygoid plate; below by the horizontal
plate of the palate bone; above by the under surface of the body of the sphenoid, with the ala
of the vomer and a portion of the sphenoidal process of the palate bone.
Lateral to the choanae there is on each side a vertical fossa lying between the pterygoid
plates. It extends upward to the under surface of the great wings of the sphenoid; it is com-
pleted anteriorly by the coalescence of the pterygoid plates and below by the pyramidal process
of the palate bone. It contains the following points of interest: —
An elongated furrow, the scaphoid fossa, for the tensor veli palatini muscle and the carti-
lage of the Eustachian tube.
The general cavity of the pterygoid fossa which lodges the tensor veli palatini and internal
pterygoid muscles.
Fig. 133. — ^The Skuli,. (Norma facialis.)
Ophryoa
Superciliary arch
Glabella
Nasion
Nasal (piriform)
apertxire
Subnasal point
Canine fossa
Canine eminence
Alveolar point
(
Frequently there is a notch in the lateral pterygoid plate close beside the foramen ovale.
The posterior termination of the pterygoid (Vidian) canal.
If a line be drawn across the base of the skull from one preglenoid tubercle to
the other, it will fall immediately behind the lateral pterygoid plate and bisect
the foramen spinosum on each side. A second transverse line, drawn across the
opisthion or posterior margin of the foramen magnum, will fall behind the
mastoid processes. The space between these arbitrary lines may be called the
subcranial region; that behind the second hne, the suboccipital region.
(b) The subcranial region is separated from the infratemporal fossa by a line
drawn from the posterior margin of the lateral pterygoid plate to the spine of the
108 THE SKELETON
sphenoid. It is formed by the inferior surface of the basilar process of the
occipital and the body of the sphenoid, the petrous portion of the temporal bone,
a small piece of the squamosal portion, the posterior part of the great wing of the
sphenoid, and the condylar portions of the occipital bone. It presents the
following points for examination (Figs. 95, 131): —
The pharyngeal tubercle.
The foramen magnum and the occipital condyles. The most anterior point of the foramen
is termed the basion, and the most posterior point the opisthion.
On each side will be seen: — The hypoglossal foramen for the hypoglossal nerve and a men-
ingeal branch of the ascending pharyngeal artery.
The condylar fossa with the condylar foramen (this foramen is not constant).
The under aspect of the jugular process, from which the rectus capitis lateralis takes origin.
The foramen lacerum and the orifice of the pterygoid (Vidian) canal.
The canalis musculo -tubarius for the tensor tympani muscle and Eustachian tube.
The carotid canal.
The quadrilateral area for the origin of the levator veli palatini and tensor tympani muscles.
The canaliculus cochleae, or ductus perilymphaticus.
The jugular foramen and fossa for the glosso-pharyngeal, vagus, and spinal accessory
nerves, the internal jugular vein, and a meningeal branch of the ascending pharyngeal artery.
The tympanic canaliculus for Jacobson's nerve (tympanic branch of glossopharyngeal).
The spine of the sphenoid; this is sometimes fifteen miUimetres in length.
The mandibular fossa with the petro-tympanic fissure. This lodges the anterior process
of the malleus, the tympanic twig of the internal maxillary artery. A small passage beside
it, the canal of Huguier, conducts the chorda tympani nerve from the tympanum.
The external auditory meatus.
The auricular or tympano-mastoid fissure.
The tympanic plate and vaginal process.
The styloid process.
The stylo -mastoid foramen for the stylo-mastoid artery and the exit of the facial nerve
and, in some cases, the auricular branch of the vagus.
The mastoid process with the digastric and occipital grooves.
(c) The suboccipital region is largely formed by the tabular portion of the
occipital bone with its ridges and areas for muscular attachment. Laterally a
small part of the mastoid portion of the temporal is seen, pierced by a small
foramen, of variable size, the mastoid foramen, which transmits a vein from the
transverse (lateral) sinus and a meningeal branch of the occipital artery.
(5) The Anterior Region
The anterior region {norma facialis) (figs. 132, 133) comprises the anterior
end of the cranium or forehead, and the skeleton of the face; also the cavities
known as the orbits, formed by the junction of the two parts of this region, and
the nasal fossae, situated on either side of the septum of the nose.
The upper part or forehead, narrowest between the temporal crests about
half an inch above the zygomatic processes of the frontal, presents at this level
the two transverse sulci ; above are the frontal eminences, below the superciliary
arches, and still lower the supra-orbital margins, interrupted near their medial
ends by the supra-orbital notches.
Below the forehead are the openings of the orbits, bounded laterally by the
zygomatic bones constituting the prominences of the cheeks, and between them
the bridge of the nose, formed by the nasal bones and the frontal processes of the
maxillae. Below the nasal bones is the apertura piriformis or anterior nasal
aperture, leading into the nasal fossse. The teeth form a conspicuous feature
in this view of the skull, the outline of which is completed below by the mandible.
The bones entering into formation of the norma facialis are: — the frontal, nasals, lacrimals,
orbital surfaces of the small and the great wings, and a portion of the body of the sphenoid,
the laminas papjrraceoB of the ethmoids, the orbital processes of the palate bones, the zygomatics,
maxillse, inferior nasal conchae, and the mandible.
The sutures are numerous, and for the most part unimportant: —
The transverse sutiu-e (fig. 133) extends from one zygomatic process of the frontal to the
other. The upper part of the suture is formed by the frontal bone; below are the zygomatic,
great and small wings of the sphenoid, lamina papyracea, lacrimal, maxillary, and nasal bones.
A portion of this complex suture, lying between the sphenoidal and frontal bones, appears in
the anterior cranial fossa.
Other fissures are the internasal, naso-maxillary, inter-maxillary and zygomatioo-maxillary.
The small sutures seen in the orbit are described with that cavity.
The foramina are: — the supra-orbital, infra-orbital, optic, zygomatico-facial, and mental;
the naso-lacrimal canal; the ethmoidal canals; and the inferior and superior orbital fissures.
THE ORBITS
109
The following points may also be noticed: —
The glabella, a smooth space between the converging superciliary arches.
The ophryon, the most anterior point of the metopic suture.
The nasion, the middle of the naso-frontal sutui'e.
The subnasal point, the middle of the inferior border of the pyriform aperture at the base
of the nasal spine.
The alveolar point, the centre of the anterior margin of the upper alveolar arch.
THE ORBITS
The orbits [orbitse] (fig. 134) are two cavities of pyramidal shape, with their
bases directed forward and laterally and their apices backward and medially;
their medial walls are nearly parallel, but their lateral walls diverge so as to be
nearly at right angles to each other. Each cavity forms a socket for the eyeball
and the muscles, nerves, and vessels associated with it.
Seven bones enter into formation of its walls, viz., the frontal, zygomatic,
sphenoid, ethmoid, lacrimal, palate, and maxilla; but as three of these — the
frontal, sphenoid, and ethmoid — are single median bones which form parts of
each cavity, there are only eleven bones represented in the two orbits. Each
orbit presents for examination four walls, a circumference or base, and an apex.
The superior wall or roof, vaulted and smooth, is formed mainly by the orbital plate of the
frontal and is completed posteriorly by the small wing of the sphenoid. At the lateral angle
it presents the lacrimal fossa for the lacrimal gland, and at the medial angle a depression or a
spine for the puOey of the superior oblique muscle.
Fig. 134. — The Medial Wall of the Orbit.
Frontal process of maxilla / V
T.arrimfll- /—
Lacrimal canal
Orifice of antrum
Inferior nasal concha
Palate b(
Anterior nasal spine
Anterior ethmoid canal
Posterior ethmoid canal
Optic foramen
Lamina papyracea of ethmoid
\ r^Spheno-palatine foramen
?^— ^Pterygoid canal, leading into the
^^^ pterygo -palatine fossa
Sphenoid
External pterygoid plate
The inferior wall or floor is directed upward and laterally and is not so large as the roof.
It is formed by the orbital plate of the maxilla, the orbital process of the zygomatic, and the
orbital process of the palate bone. At its medial angle it presents the naso-laorimal canal, and
near this, a depression for the origin of the inferior oblique muscle. It is marked near the middle
by a furrow for the infra-orbital artery and the second division of the fifth nerve, terminating
anteriorly in the infra-orbital canal, through which the nerve and artery emerge on the face.
Near the commencement of the canal a narrow passage, the anterior alveolar canal, runs for-
ward and downward in the anterior wall of the antrum, transmitting nerves and vessels to the
incisor and canine teeth.
The lateral wall, directed forward and medially, is formed by the orbital surface of the
great wing of the sphenoid, and the zygomatic. Between it and the roof, near the apex, is the
superior orbital (sphenoidal) fissure, by means of which the third, fourth, ophthalmic division
of the fifth, and sixth nerves enter the orbit from the cranial cavity; it also transmits some
filaments from the cavernous plexus of the sympathetic, the orbital branch of the middle men-
ingeal artery, recurrent branches of the lacrimal artery, and an ophthalmic vein. The lower
margin of the fissure presents near the middle a small tubercle, from which the inferior head of
the lateral rectus muscle arises. Between the lateral wall and the floor, near the apex, is the
inferior orbital (spheno-maxiUary) fissure, tlu-ough which the second division of the fifth and
the infra-orbital vessels pass from the pterygo-palatine fossa to enter the infra-orbital groove.
At the anterior margin of the fissure the sphenoid occasionally articulates with the maxilla, but
no
THE SKELETON
the two are usually separated by the orbital plate of the zygomatic, and on the latter are seen
the orifices of the zygomatico-temporal and zygomatico-facial canals, which traverse the
zygomatic bone. The commencement of the zygomatico-temporal canal is sometimes seen in
the spheno-zygomatic sutm-e connecting the sphenoid and zygomatic bones.
The medial wall, narrow and nearly vertical, is formed from before backward by the
frontal process of the maxilla, the lacrimal, the lamina papyracea of the ethmoid, and the
body of the sphenoid. At the junction of the medial wall with the roof, and in the suture
between the ethmoid and frontal, are seen the orifices of the anterior and posterior ethmoidal
canals, the anterior, transmitting the anterior ethmoidal vessels and nerve; and the posterior,
the posterior vessels and nerve. Anteriorly is the lacrimal groove for the lacrimal sac, and
behind this the lacrimal crest, from which the tensor tarsi arises. The medial wall, which is
the smallest of the four, is traversed by three vertical sutures: — one between the frontal process
of the maxilla and the lacrimal, a second between lacrimal and lamina papyracea, and a third
between the lamina papyracea and the sphenoid. Occasionally the sphenoidal concha appears
in the orbit between the ethmoid and the body of the sphenoid.
The apex of each orbit corresponds to the optic foramen, a circular orifice which transmits
the optic nerve and ophthalmic artery. The base or circumference is quadrilateral in form
and is bounded by the frontal bone above, the frontal process of the maxilla and the medial
angular process of the frontal on the medial side, the zygomatic bone and the zygomatic process
of the frontal on the lateral side, and by the zygomatic and the body of the maxilla below.
The following points may also be noted: — The suture between the zygomatic process of the
frontal bone and the zygomatic; the supra-orbital notch (sometimes a complete foramen);
the sutiu'e between the frontal bone and the frontal process of the maxilla; and in the lower
segment, the zygomatico-maxillary suture.
The orbit communicates with the cranial cavity by the optic foramen and superior orbital
fissure; with the nasal fossa, by means of the naso-lacrimal canal; with the zygomatic and
ptery go-palatine fossae, by the inferior orbital fissure. In addition to these large openings, the
orbit has five other foramina — the infra-orbital, zygomatico-orbital, and the anterior and
posterior ethmoidal canals — opening into it or leading from it.
The following muscles arise within the orbit : — the four recti, the -tuperior oblique, and
levator palpebrce superioris, near the apex; the inferior oblique on the floor of the orbit lateral
to the naso-lacrimal canal; and the tensor tarsi from the lacrimal crest. The margins of the
inferior orbital fissure give attachment to the orhitalis muscle.
THE NASAL FOSS^
The nasal fossae (figs. 135, 136) are two irregular cavities situated on each
side of a median vertical septum. They open in front by the piriform aperture
and communicate behind with the pharynx by the choanse. They are somewhat .
Fig. 135. — Section through the Nasal Fossa to show the Septum. Left Half, with
Septum looking toward Right Nasal Fossa.
Crest of sphenoid—^
';4
Groove for naso-palatine nerve
Crest of maxilla
oblong in transverse section, and extend vertically from the anterior part of the
base of the cranium above to the superior surface of the hard palate below.
Their transverse extent is very limited, especially in the upper part. Each fossa
presents for examination a roof, floor, medial and lateral walls, and communicates
with the sinuses of the frontal, sphenoid, maxilla, and ethmoid bones.
THE NASAL FOSSAE
111
The roof is horizontal in the middle, but sloped downward in front and behind. The
anterior slope is formed by the posterior surface of the nasal bone and the nasal process of the
frontal; the horizontal portion corresponds to the cribriform plate of the ethmoid and the sphe-
noidal concha; the posterior slope is formed by the inferior surface of the body of the sphenoid,
the ala of the vomer, and a small portion of the sphenoidal process of the palate. The sphe-
noidal sinus opens at the upper and back part of the roof into the spheno-ethmoidal recess,
above the superior meatus.
The floor is concave from side to side, and in the transverse diameter wider than the roof.
It is formed mainly by the palatine process of the maxilla and completed posteriorly by the hori-
zontal part of the palate bone. Near its anterior extremity, close to the septum, is the incisive
canal.
The septum or medial waO is formed by the perpendicular plate of the ethmoid, the vomer,
the rostrum of the sphenoid, the crest of the nasal bones, the frontal spine, and the rnedian
crest formed by the apposition of the palatine processes of the maxilte and the horizontal
parts of the palate bones. The anterior border has a triangular outline limited above by the
perpendicular plate of the ethmoid and below by the vomer, and in the recent state the defi-
ciency is filled up by the septal cartilage of the nose. The posterior border is formed by the
Fig. 136.-
-Section throctgh the Nasal Fossa to show the Lateral Wall with
THE Meatuses.
Superior nasal concha
Probe in sphenoidal foramen
Sphenoidal sinus
Sella turcica
Superior meatus
Spheno-palatine
Uncinate process of ethmoid
Internal pterygoid plate
Palate bone
Probe in posterior palatine canal
Probe in naso-
lachrymal canal
Frontal sinus
Agger nasi
?r — Lachrymal bone
■*■ Lower end of bristle
in middle meatus
Middle meatus
r nasal
concha
Probe at lower end
of naso-lachrymal
canal where it
opens into inferior
meatus
Incisive canal
pharyngeal edge of the vomer, which separates the two choanaj. The septum, which is usually
deflected from the middle line to one side or the other, is occasionally perforated, and in some
cases a strip of cartilage, continuous with the triangular cartilage, extends backward between
the vomer and perpendicular plate of the ethmoid (posterior or sphenoidal process).
The lateral wall is the most extensive and the most comphcated on account of the forma-
tion of the meatuses of the nose. It is formed by the frontal process and the medial surface of
the maxilla, the lacrimal, the superior and inferior conchse of the ethmoid, the inferior nasal
concha, the vertical part of the palate bone, and the medial surface of the medial pterygoid
plate. The three conchae, which project medially, overhang the three recesses known as the
meatuses of the nose. The superior meatus, the shortest of the three, is situated between the
superior and middle nasal conch®, and into it open the orifice of the posterior ethmoidal cells
and the spheno-palatine foramen. The middle meatus lies between the middle and inferior
conchse. At its fore part it communicates with the frontal sinus by means of the infundibulum,
and near the middle with the maxillary sinus (antrum); the communication with the sinus is
very irregular and sometimes represented by more than one opening (fig. 136). Two sets of
ethmoidal cells — the middle and anterior — also open into the middle meatus, the anterior in
common with the infundibulum, the middle on an elevation known as the bulla ethmoidalis.
The inferior meatus, longer than either of the preceding, is situated between the inferior nasal
concha and the floor of the fossa, and presents, near the anterior part, the lower orifice of the
canal for the naso-lacrimal duct.
112
THE SKELETON
The nasal fossae open on the face by means of the apertura piriformis, a heart-shaped or
piriform opening whose long axis is vertical and whose broad end is below. The orifice is
bounded above by the lower borders of the nasal bones, laterally by the maxillae, inferiorly
by the premaxillary portions of the maxiUae, and in the recent state the orifice is divided by the
septal cartilage. Below, where the lateral margins slope inward to meet in the middle line,
is the anterior nasal spine.
The choanae (posterior nares) are bounded superiorly by the alae of the vomer, the sphe-
noidal processes of the palate, and the inferior surface of the body of the sphenoid; laterally
by the lateral pterygoid plates; and inferiorly by the posterior edge of the horizontal plates of
the palate bones. They are separated from each other by the posterior border of the vomer.
The nasal fossae communicate with all the more important fossae and the air-sinuses of the
skull. By means of the foramina in the roof they are in connection with the cranial cavity;
Fig. 137. — The Choan^. Veiwed from behind.
Pharyngeal canals
Pterygoid canal
Foramen ovale
Scaphoid fossa
Pterygoid fossa
Lateral pterygoid plate
Tuberosity of palate bone
Medial pterygoid plate
Hamular process
by the infundibulum each fossa is in communication with the frontal and anterior ethmoidal
cells; the posterior ethmoidal cells open into the superior meatuses and the sphenoidal sinuses
into the recesses above; the spheno-palatine foramina connect them with the pterygo-palatine
fossae, and by means of an irregular orifice in each lateral wall they communicate with the max-
illary sinuses. The canals for the naso-lacrimal ducts connect them with the orbits,Jand the
incisive canals with the oral cavity.
THE INTERIOR OF THE SKULL
In order to study the interior of the skull it is necessary to make sections in
three directions — sagittal, coronal, and horizontal. This enables the student to
examine the various points with facility, and displays the great proportion the
brain cavity bears to the rest of the skull. The sagittal section (fig. 138) should
be made slightly to one side of the median line, in order to preserve the nasal
septum. The black line (fig. 138) drawn from the basion (anterior margin of
the foramen magnum) to the gonion (the anterior extremity of the sphenoid)
represents the basi-cranial axis ; whilst the line drawn from the gonion to the
subnasal point lies in the basi-facial axis. These two axes form an angle termed
the cranio -facial, which is useful in making comparative measurements of crania.
A line prolonged vertically upward from the basion will strike the bregma. This
is the basi-bregmatic axis, and gives the greatest height of the cranial cavity.
A line drawn from the ophryon to the occipital point indicates the greatest length
of the cranium.
Near its middle, the cranial cavity is encroached upon by the petrous portion
of the temporal bone on each side; the walls are channelled vertically by narrow
grooves for the middle and small meningeal vessels, and toward the base and at
the vertex are broader furrows for the venous sinuses.
The coronal section is most instructive when made in the basi-bregmatic
axis. The section will pass through the petrous poition on each side in such a
way as to traverse the external auditory passage and expose the tympanum and
vestibule, and will also partially traverse the internal auditory meatus. Such
THE INTERIOR OF THE SKULL
113
a section will divide the parietal bones slightly posterior to the parietal eminences,
and a line drawn transversely across the section at the mid-point will give the
greatest transverse measurement of the cranial cavity. A skull divided in this
way facilitates the examination of the parts about the choanse (posterior nares) .
The horizontal section (figs. 139, 140) of the skull should be made through a
line extending from the ophiyon to the occipital point, passing laterally a few
millimetres above the pterion on each side. It is of great advantage to study the
various parts on the floor of the cranial cavity in a second skull in which the dura
mater and its various processes have not been removed.
The floor [basis cranii interna] of the cranial cavity presents three irregular
depressions termed the anterior, middle, and posterior fossse (figs. 139 and 140).
The Anterior Cranial Fossa. — The floor of this fossa is on a higher level
than the rest of the cranial floor. It is formed by the horizontal plate of the
frontal bone, the cribriform plate of the ethmoid, and the lesser wings of the
Fig. 138. — The Skull in Sagittal Section.
Bregma
Ophryon
sphenoid, which meet and exclude the body of the sphenoid from the anterior
fossa. The free margins of the lesser wings and the anterior margin of the optic
groove mark the limits of this fossa posteriorly. The central portion is depressed
on each side of the crista galli, presents the numerous apertures of the cribriform
plate, and takes part in the formation of the roof of the nasal fossse; laterally,
the floor of the anterior cranial fossa is convex; it forms the roof of the orbits,
and is marked by irregular furrows. It supports the frontal lobes of the cerebrum.
The sutures traversing the floor of the fossa are the fronto-ethmoidal, forming
three sides of a rectangle, that portion of the transverse facial suture which tra-
verses the roof of the orbit, and the ethmo-sphenoidal suture, the centre of which
corresponds to the gonion. The other points of interest in the fossa are:^
A groove for the superior sagittal sinus.
The foramen caecum which frequently transmits a small vein to the nasal cavity.
The crista galli. •
The ethmoidal fissure for the anterior ethmoida,l branch of the fifth nerve.
The cranial orifice of the anterior ethmoidal canal, transmitting the anterior ethmoidal
branch of the fifth nerve, and a meningeal branch of the anterior ethmoidal artery.
The cranial orifice of the posterior ethmoidal canal, transmitting a meningeal branch of the
posterior ethmoidal artery.
The ethmoidal spine of the sphenoid.
Furrows for meningeal vessels.
114
THE SKELETON
Fig. 139. — The Skull in Horizontal Section.
Ethmoidal fissure for anterior eth-
Ethmoidal foramina for olfactory
nerve
Ethmoid
Optic foramen (for
optic nerve)
Foramen ovale (third divis
trigeminus
Notch for abducens nerve
Interior auditory meatus (facial
and auditory nerves)
Jugular foramen (glosso-^ haryngeal
vagus and accessary nerves)
Hypoglossal foramen (hypoglossal nervo
THE INTERIOR OF THE SKULL
115
Fig. 140. — The Skull in Horizontal Section.
Frontal bo
Ridge for falx cerebri
Crista galli
Anterior fossa
Cribriform plate
Lesser wing of sphenoid
The limbus
Optic groove-
Pituitary fossa-
Dorsum sellae.
Petro-sphenoidal proces
Internal occipital crest
Internal occipital protuberance
Foramen magnum
116 THE SKELETON
The Middle Cranial Fossa, situated on a lower level than the anterior,
consists of a central and two lateral portions. In front it is limited by the posterior
borders of the lesser wings of the sphenoid and the anterior margin of the optic
groove, behind by the dorsum sellse and the upper angle of the petrous portion
of both temporal bones. Laterally it is bounded on each side by the squamous
portion of the temporal, the great wing of the sphenoid, and the parietal bone,
whilst the floor is formed by the body and great wings of the sphenoid and the
anterior surface of the petrous portion of the temporals. It contains the follow-
ing sutures: — spheno-parietal, petro-sphenoidal, squamo-sphenoidal, squamous,
and a part of the transverse suture. The central portion of the fossa presents
from before backward :
The optic groove, above and behind which is the optic chiasma.
The optic foramen on each side, transmitting the optic nerve and ophthalmic artery.
The tuberculum sellae, indicating the hne of junction of pre- and post-sphenoid elements.
The anterior clinoid processes.
The fossa hypophyseos or sella turcica, with the middle clinoid processes, and grooves for
the internal carotid arteries. The dorsum sellse, with the posterior clinoid processes, and
notches for the sixth pair of cranial nerves.
The central portion is in direct relation with the parts of the brain within the circle of
Willis.
The lateral portions are of considerable depth and marked by numerous elevations and
depressions corresponding to the convolutions of the temporal lobes of the brain, and by grooves
for the branches of the middle and small meningeal vessels. The following foramina are seen
on each side: —
The superior orbital (sphenoidal) fissure, leading into the orbit and transmitting the third,
fom-th, three branches of the ophthalmic division of the fifth and sixth cranial nerves, some
filaments from the cavernous plexus of the sympathetic, an ophthalmic vein, the orbital branch
of the middle meningeal, and a recurrent branch of the lacrimal artery.
The foramen rotundum, for the passage of the second division of the fifth nerve into the
pterygo-palatine fossa.
The foramen ovale, which transmits the third division of the fifth nerve with its motor
root (mandibular nerve), the small meningeal artery, and the small superficial petrosal nerve.
The foramen Vesalii (not always present) for a small vein.
The foramen spinosum, for the middle meningeal artery and its venae comitantes; also the
N. spinosus.
The foramen lacerum is the irregular aperture between the body and great wing of the
sphenoid, and the apex of the petrous portion of the temporal. In the recent state it is closed
below by a layer of fibro-cartilage which is perforated by the Vidian nerve, a meningeal branch
of the ascending pharynge.<!l artery, and an emissary vein. The carotid canal opens on its
lateral wall and the pterygoid (Vidian) canal in front.
On the anterior surface of the petrous portion of the temporal bone are seen: —
A depression which lodges the semilunar (Gasserian) ganglion.
The hiatus canalis facialis for the great superficial petrosal nerve and the petrosal branch
of the middle meningeal artery.
The accessory hiatus for the small superficial petrosal nerve.
A minute foramen for the external superficial petrosal nerve.
The eminentia arcuata, formed by the superior semicircular canal.
Anterior and slightly lateral to the eminentia arcuata the bone is exceedingly thin and
translucent, forming the roof of the tympanum (tegmen tympani). When the dura mater is
in situ, the depression lodging the semilunar ganglion is converted into a foramen, traversed by
the fifth nerve, and in the same way the notch on the side of the dorsum sellae is converted into
a foramen for the sixth nerve. In many skulls the middle clinoid process is prolonged toward
the anterior clinoid process, with which it may be joined to complete a foramen for the internal
carotid artery. The grooves for the middle meningeal vessels are sometimes converted into
canals or tunnels for a short distance, especially in old skulls. The bones most deeply marked
are the squamous portion of temporal, the great wing of the sphenoid, and the parietal.
The Posterior Cranial Fossa is the deepest and largest of the series. It is
bounded in front by the dorsum sellse of the sphenoid and on each side by the
superior border of the petrosal, and the mastoid portion of the temporal bone, the
posterior inferior angle of the parietal, and the groove on the occipital bone for
the transverse sinus; each of the bones mentioned takes part in the formation of
its floor.
In the recent state the fossa lodges the cerebellum, pons, and medulla, and is
roofed in by the tentorium cerebelli, a tent-like process of the dura mater attached
to the ridges limiting the fossa above. It communicates with the general cranial
cavity by means of the foramen ovale of Pacchionius, a large opening bounded
in front by the clivus (basilar groove) and behind by the anterior free edge of the
tentorium.
THE MORPHOLOGY OF THE SKULL 117
The posterior fossa is marlced by several sutures, viz., petro-occipital, occipito-mastoid,
parieto-mastoid, and in young skulls the basilar (occipito-sphenoidal). In addition, the follow-
ing points may be noted: —
The clivus, extending from the dorsum selte to the anterior margin of the foramen magnum,
and in relation with the basilar artery, the pons, the medulla, the sixth nerves, and the basilar
sinus.
The foramen magnum, occupied in the recent state by the lower end of the medujla oblon-
gata and its membranes, the vertebral, anterior spinal and posterior spinal arteries, the accessory
(eleventh) cranial nerves, and the tectorial membrane.
The hypoglossal canal (foramen) , sometimes divided by a spicule of bone into two divisions,
for the two parts of the hypoglossal nerve and a meningeal branch of the ascending pharyngeal
artery.
The internal occipital crest, behind the foramen magnum, for the attachment of the falx
cerebelli. It sometimes presents a depression known as the vermiform fossa.
The internal auditory meatus, for the seventh and eighth cranial nerves, the pars inter-
media, and the internal auditory vessels.
The jugular foramen (foramen laoerum posterius), somewhat pyriform in shape, and divis-
ible into three compartments. The anterior division, placed somewhat medially, transmits
the inferior petrosal sinus and is sometimes completely separated by an iutra-jugular process of
bone; the middle division transmits three cranial nerves, the ninth, tenth, and eleventh; and, in
the posterior division, placed somewhat laterally, the transverse sinus becomes continuous with the
internal jugular vein. A meningeal branch of the ascending pharyngeal or occipital artery
enters the cranium through this division of the foramen.
The termination of the groove for the transverse sinus with the internal orifice of the mas-
toid foramen.
The aquseductus vestibuli and the fossa subarcuata, on the posterior surface of the petrous
portion of the temporal.
The cranium of an average European has a capacity of 1450 c.c. The circumference, taken
in a plane passing through the ophryon in front, the occipital point behind, and the pterion at
the side, is 52 cm. The length from the ophryon to the occipital point is 17 cm., and the width
between the parietals at the level of the zygomata is 12.5 cm. The proportion of the greatest
width to the length is known as the cephalic index, i. e., index of breadth. A skull with an aver-
age cephalic index is mesaticephalic. When the index is above the average, it is brachycephalic
(short and broad), and when below the average, dolichocephalic (long and narrow). The height
from the basion to the bregma is nearly the same as the width at the level of the zygomata.
The cranio-facial angle is about 96°.
THE MORPHOLOGY OF THE SKULL
In man the skull during development passes thi-ough three stages. At first the brain vesi-
cles are enclosed in a sac of indifferent tissue which ultimately becomes tough and fibrous to form
the membranous cranium. This, in turn, is partly converted into the membrane or roof bones
of the cranium, whilst the remainder is represented in the adult by the dura mater. At the
sides and base of the membranous cranium, however, cartilage is deposited, chondro -cranium,
in which, as well as in the membranous tracts, osseous tissue appears in due course. Eventually,
as osseous box is formed, consisting of membrane bones and cartilage bones intricately
interwoven.
A study of the skull in the chondral stage is very instructive. It consists of two parts:
(1) The skull proper and (2) the appendicular elements.
(1) The skull proper consists of three regions: —
(a) The notochordal region, which ultimately gives rise to the chief parts of the occipital
bone and a part of the sphenoid. It is named notochordal because the notochord runs
in it as far as the anterior extremity, i. e., the level of the fossa hypophyseos (sella turcica.)
(6) Anterior to the notochordal is the trabecular region, from which the remainder of the
sphenoid is developed.
(c) The most anterior part of the prechordal portion of the base is the ethmo-vomerine
region, from which the nasal septum and its cartilages arise. These thi-ee parts continue
forward the line of the vertebral a.xis, and constitute a cranio-facial axis terminating, in
front, in the premaxilk;. Finally, wedged in on each side, between the notochordal and
trabecular regions, is the complicated periotic capsule.
The chondro-cranium at the thii-d month presents the following parts. Seen from above,
the cartilage extends from the cranial base to a spot midway between the base and the vertex,
shading off indefinitely on the membranous wall. The oval masses on each side are the periotic
cartilages, in which the fossae subarouatEe are conspicuous objects. Each periotic cartilage is
joined to the sphenoid by a strip, termed the sphenotic cartilage, which usually persists in the
adult skuU. The cartilage for the orbito-sphcnoid (the small wing) is co-extensive with the
aU-sphenoid, and forms part of the lateral wall of the skuU. The snout-like appearance of the
anterior part of the skull is caused bj' thefronto-nasal plate. On each side of the ethmo-vomerine
plate, near its anterior termination, are two small concave pieces of cartilage for Jacobson's
organs. They are sometimes referred to as the ploughshare cartilages, owing to their shape.
Further details are given in fig. 141.
(2) The appendicular elements of the skull are a number of cartilaginous rods surrounding
the visceral cavity — i. e., nose, mouth, and pharymx — which undergo a remarkable metamor-
phosis, and are represented in the adult by the ear bones, the styloid process, and the hyoid bone.
118
THE SKELETON
Fig. 141. — Model of the Chondro-cranium of a Human Fcetus 8 cm. in Length.
Cartilage in Blue. Viewed from Above. (After O. Hertwig.)
Crista galli
Lamina cribrosa
Ala orbitalis
Foramen opticum
Ala temporalis
Sella turcica
Dorsum sellas
Facial nerve and canal
Auditory capsule
Foramen magnum
Tectum synoticum
Fig. 142. — An Enlarged Portion of the Same Model of the Chondro-cranium as Shown
IN Fig. 141. Viewed From the Right Side, Showing the Skeleton of the Auditory
Region. Cartilage in Blue. (After O. Hertwig.)
Facial nerve
Pars mastoidea
— Pars petrosa
Styloid process
J
THE MORPHOLOGY OF THE SKULL 119
Metamorphosis of the Branchial or Visceral Bars
These rods of cartilage are named, f om before backward, the mandibular, hyoid, and
thyreoid bars. They may with care be easily dissected in the foetus between the third and fourth
months. Their metamorphosis is as follows: — •
The two extremities of the mandibular bar (cartilago Meckehi) ossify; the distal end ulti-
mately forms a portion of the mandible near to the symphysis (see p. 98); the pro.ximal end
ossffies as the malleus and incus. The intermediate portion disappears; the only vestige is a
band of fibrous tissue, the spheno-mandibular ligament, extending from the spine of the sphenoid
to the spine of the mandible.
In the connective tissue surrounding the bar there appear, however, ossifications, one of
which invests the bar to form the dentary plate; while a second, situated more proximally, forms
the tympanic bone.
The hyoid bar fuses distaUy with the thyreoid bar, and forms part of the hyoid bone. Its
proximal end becomes the stapes, the tympano-hyal portion of the styloid process (fused with
the petro-mastoid), and the stylo-hyal or free portion of the process. The succeeding portion
(epl-hyal segment) is represented in the adult by the stylo-hyoid ligament, and the lowest seg-
ment, or cerato-hyal, by the small cornu of the hyoid.
The thyreoid bar forms the great cornu of the hyoid bone (thyreo-hyal). The body of the
hyoid (basi-hyal) is regarded as representing the fused ventral ends of the hyoidean and thy-
reoidean arches.
In addition to these structures ossifications occur in the connective tissue of the maxillary
process, a structure which may be regarded as forming the anterior part of the first branchial
arch, and in the fronto-nasal process. The ossifications in the maxillary process give rise to
the pterygoid (medial pterygoid process of the sphenoid), the palate, the maxiUa, and the
zygomatic, while that in the fronto-nasal process forms the premaxilla.
The bony elements of the head may therefore be arranged, according to their origin, in the
following table: —
I. Basilar Bones Developed in the Cartilaginous Cranium
Basi-occipital Basilar portion of the occipital bone.
Exoccipitals Condylar parts of the occipital bone.
Supra-occipital Lower part of the squamous portion of the occipital.
Pre-s^ henoW^ } Constituting the body of the sphenoid.
Ali-sphenoids Greater wings and lateral pterygoid plates.
Orbito-sphenoids Lesser wings.
Petro-mastoids Petrous and mastoid portions (excepting post-auditory
processes) of the temporal bones.
II. Roof Bones Developed in the Membranous Cranium
Squamosals Squamous portions of temporals.
Parietals The two parietal bones.
Frontals United to form a median frontal bone.
Interparietal Upper part of squamous portion of occipital.
Epipterics The epipteric bones.
III. Bones of the Nasal Region
Mesethmoid Vertical plate of ethmoid developed in the cartilage of the
cranio-facial axis.
Ethmo-turbinals Superior and inferior conchal processes of ethmoid.
Maxillo-turbinals The inferior nasal conohaj.
Cribriform lamina Cribriform plate of ethmoid.
These elements are developed in the cartilage of the lateral nasal process.
Sphenoidal turbinals Sphenoidal conchse. These are derivatives of the ethmo-
turbinals.
Lacrimals The lacrimal bones 1 Developed in the membrane over
Nasals The nasal bones J the lateral nasal process.
Vomer The vomer. Ossified in the membrane investing the carti-
lage of the cranio-facial axis.
IV. Facial Bones
MaxillEe The maxillse 1 Developed in the connective tissue
Zygomatics The zygomatic bones / of the maxillary process.
Premaxillae The incisor parts of the maxilLe. Formed at the anterior
extremity of the cranio-facial axis in the tissue of the
fronto-nasal process (proc. globulares).
120 THE SKELETON
V. AppENDicnLAR Elements (Bones of the Visceral Arches)
(A) Cartilaginous
Malleus, Incus, and
Stapes The ossicula auditus.
Mento-Meckelian portion
of the lower jaw Small part on either side near to the symphysis menti.
Tympano-hyals and Stylo-
hyals Styloid processes of the temporal bones.
Epihyals Stylo-hyoid ligaments.
Cerato-hyals Lesser cornua of hyoid bone.
Thyreo-hyals Greater cornua of hyoid bone.
Basi-hyals Body of hyoid bone.
(B) Membranous
Mandible The lower jaw excluding a small portion near symphysis.
Tympanies The tympanic plates.
Pterygoids The medial pterygoid plates.
Palatals The palate bones.
The Skull at Birth
The skull at birth presents, when compared with the adult skull, several important and
interesting features. Its peculiarities may be considered under three headings: — The pecuhar-
ities of the fcetal skuU as a whole; the construction of the individual bones; the remnants of
the chondral skull.
(1) The General Characters of the Fcetal Skull
l-The most striking featm'es of the skull at birth are, its relatively large size in comparison
with the body, and the predominance of the cranial over the facial portion of the skull (8_to 1) ;
the latter is, in fact, very smaU.
Fig. 143. — The Cranium at Birth. (Viewed from above.)
\
\
The frontal and parietal eminences are large and conspicuous; the sutures are absent; the
adjacent margins of the bones of the vault are separated by septa of fibrous tissue continuous
with the dura mater internally and the pericranium externally; hence it is difficult to separate
the roof bones from the underlying dura mater, each being lodged, as it were, in a dense mem-
branous sac. The bones of the vault consist of a single layer without any diploe, and their
cranial surfaces present no digital impressions. Six membranous spaces e.xist, named fonta-
neUes: two are median, the frontal [fonticulus frontalis; major] being anterior and the occipital
[fonticulus occipitahs; minor] posterior. Two exist on each side, termed anterior [fonticulus
sphenoidalis] and posterior [fonticulus mastoideiis] lateral fontanelles. Each angle of the pari-
etal bones is in relation with a fontanelle. The anterior fontanelle is lozenge-shaped, the poste-
rior triangular. The lateral fontanelles are nregular in outUne. The lateral fontanelles close
soon after birth; the occipital fontanelle closes in the first year, and the frontal during the second
year.
THE MORPHOLOGY OF THE SKULL
121
Turning to the base of the skull, the most striking points are the absence of the mastoid
processes, and the large angle which the pterygoid plates form with the skull-base, whereas in
the adult it is almost a right angle. The base of the skull is relatively short, and the lower
border of the mental symphysis is on a level with the occipital condyles.
The facial skeleton is relatively smaU in consequence of the small size of the nasal fossae,
the small size of the maxiUary sinus, and the rudimentary condition of the alveolar borders
Fig. 144. — The Cranium at Birth. (Lateral view.)
of the maxiUse and mandible; the nasal fossce are as wide as they are high, and are almost fiUed
with the conchje.
Growth takes place rapidly in the first seven years after birth. There is a second period
of rapid growth at puberty, when the air sinuses develop, and this affects especially the face
and frontal portion of the cranium.
Fig. 145. — The Cranium at Birth in Sagittal Section. (Sphenoidal concha
indicated by a *)
(2) The Peculiarity o/ Individual Bones at Birth
The occipital bone consists of four distinct parts, which have already been described.
Compared with the adult bone, the following are the most important points of distinction: — ■
There is no pharyngeal tubercle or jugular process ; the squamous portion presents two deep
fissures separating the interparietal from the supra-occipital portion and extending medially
122
THE SKELETON
as far as the occipital protuberance. The grooves for the transverse (lateral) sinuses are
absent.
The sphenoid in a macerated foetal skuU falls into three pieces: (1) united pre- and post-
sphenoids, orbito-sphenoids, and lingulse, and (2 and 3) the ali-sphenoids. The pre-sphe-
noid is quite solid and connected with the ethmo-vomerine cartilage, and presents no traces of
the air sinuses which occupy this part in the adult skull. The pre-sphenoid by its upper surface
forms part of the anterior cranial fossa, from which it is subsequently excluded by the growth
of the orbito-sphenoids. The optic foramina are large and triangular in shape. The lingulae
Fig. 146.— The Occipital at Birth.
Interparietal portion (develops in — ^'
membrane)
The interparietal and supra-occipital
portions form the squamous portion
of the adult
Supra-occipital portion (develops
cartilage)
stand out from the basi-sphenoid as two lateral buttresses, and at the tuberculum sellse is the
basi-pharyngeal canal, which in the recent bone is occupied by fibrous tissue. The dorsum
sellae is still cartilaginous. The ali-sphenoids with the pterygoid processes are separated^from
the rest of the bone by cartilage. The foramen rotundum is complete, but the future foramen
ovale is merely a deep notch in the posterior border of the great wing, and there is no foramen
spinosum. The pterygoid processes are short, and each medial pterygoid plate presents a broad
surface for articulation with the lingula. The pterygoid canal is a groove between the medial
pterygoid plate, the lingula, and great wing.
Fig. 147. — The Sphenoid at Birth.
Pterygoid canal Lingula
The temporal bone at birth consists of three elements, the petrosal, squamosal, and tym-
panic. The petrosal presents a large and conspicuous floccular fossa; the hiatus Fallopii is
a shallow bay lodging the geniculate gangUon of the facial nerve. There is a relatively large
mastoid antrum, but no mastoid process. The styloid process is unossified, but the tympano-
hyal may be detected as a minute rounded nodule of bone near the stylo-mastoid foramen.
The squamosal has a very shallow mandibular fossa and a relatively large post-glenoid
tubercle. The posterior part of the inferior border is prolonged downward into an uncinate
process {post-auditory process) which closes the mastoid antrum laterally.
THE MORPHOLOGY OF THE SKULL
123
The tympanic bone or annulus is a delicate, horseshoe-shaped ossicle, attached by its ante-
rior and posterior extremities to the inferior border of the squamosal
The ear -bones are chiefly of interest from their size, for they are as large at birth as in the
adult. The anterior process (Fohan process) may be 2 cm. in length.
Fig. 149. — Temporal Bone at Bibth.
Fig 148. — The Temporal Bone at Birth. (Medial view.)
Squamosal
Hiatus canalis facialis
Floccular fossa
Aquseductus vestibuU
Internal auditory
meatus
Post-glenoid tubercle
Petro-tympanic fi
Tympanic annulus
(Lateral view.)
Petro-squamous suture
Petrosal
Stylo-mastoid foramen
Tympano-hyal
•Carotid canal
The frontal 'consists of two bones separated by a median vertical (metopic) suture. The
frontal eminence is very pronounced, but the superciliary arche=i and frontal sinuses are wanting.
The frontal spine, which later becomes one of the most conspicuous features of this bone, is
absent. There is no temporal line. gil
Fig. 151. — The Frontal Bone at Birth.
The parietal is simply a quadrilateral lamina of bone, concave on its inner and convex on
the outer surface. The parietal eminence, which indicates the spot in which the ossification of
the bone commenced, is large and prominent. The grooves for blood-sinuses, as in other cranial
124
THE SKELETON
bones, are absent. Each angle of the parietal is in relation with a fontanelle. As in the adult,
the anterior inferior angle of the bone is prolonged downward toward the aU-sphenoid.
The ethmoid consists of two lateral portions separated by the still cartilaginous ethmo-
vomerine plate. The ethmoid cells are represented by shallow depressions, and the uncinate
process is undeveloped.
The sphenoidal conchae are two small triangular pieces of bone lying in the perichondrium
on each side of the ethmo-vomerine plate near its junction with the pre-sphenoid. (Indicated
by the * in fig. 145.)
The maxilla presents the following characters: — The incisive suture is visible on the palatine
aspect of the bone. The alveolar border presents five sockets for teeth. The infra-orbital
Fig.
152. — The Maxilla at Birth.
Premaxillary portion
Inferior view.
Medial view.
foramen communicates with the floor of the orbit by a deep fissure; this fissure sometimes per-
sists in the adult. The sinus is a shallow depression.
The mandible at birth consists of two halves united by fibrous tissue in the fine of the future
symphysis. Each half is a bony trough lodging teeth. The trough is divided by thin osseous
partitions into five compartments: of these, the fifth is the largest, and is often subdivided by
a ridge of bone. The floor is traversed by a furrow as far forward as the fourth socket (that
for the first milk molar), where it turns outward at the mental foramen. This furrow lodges
the inferior alveolar nerve and artery, which enter by the large mandibular foramen. The con-
dyle is on a level with the upper border of the anterior extremity of the bone.
The palate bones differ mainly from those in the adult in that the vertical and horizontal
plates are of the same length; thus the nasal fossae in the foetus are as wide as they are high,
whereas in the adult the height of each nasal fossa greatly exceeds the width.
Concerning the remaining bones little need be said. The vomer is a delicate trough of
bone for the reception of the inferior border of the ethmo-vomerine plate; its inferior border,
Fig. 153. — The Mandible at Bikth.
which rests upon the hard palate, is broad, and the bone presents quite a different appearance
from that in the adult. The nasal bones are short and broad; the zygomatics and inferior
conchae are relatively very large; and the lacrimals are thin, frail, and dehoate lamellae.
The hyoid consists of five parts. There is a median nucleus for the basi-hyal, and one on
each side for the greater cornua (thyreo-hyals). The lesser oornua are cartilaginous.
(3) Remnants of the Cartilaginous Cranium
It has aheady been pointed out that at an early date the base of the skull and the face are
represented by hyahne cartilage, which for the most part is replaced by bone before birth.
Even at birth remnants of this primitive chondral skull are abundant. In the cranium, carti-
laginous tracts exist between the various portions of the occipital bone, as well as at the line of
THE MORPHOLOGY OF THE SKULL 125
junction of the occipital with the petrosal and sphenoid. The dorsum sellae is entirely carti-
laginous at birth, and the last portion of this cartilage disappears with the ankylosis of the
basi-occipital and basi-sphenoid about the twentieth year. A strip of cartilage unites the ali-
sphenoids with the hngulae, and for at least a year after bu-th this cartilage is continuous with
that which throughout life occupies the foramen lacerum. A strip of cartilage exists along the
posterior border of the orbito-sphenoid, and not unfrequently extends lateralward to the
pterion. In the adult skull it is replaced by ligamentous tissue.
The ethmo-vomerine plate is entkely cartilaginous, and near the end of the nose supports
the lateral nasal cartilages, remnants of the fronto-nasal plate. The fate of the ethmo-vomerine
plate is instructive. The upper part is ossified to form the mesethmoid; the lower part atro-
phies from the pressure exerted by the vomer; the anterior end remains as the septal cartilage.
The lateral snout-like extremities of the fronto-nasal plate persist as the lateral cartilages of the
Among the appendicular elements of the skull, the styloid process and a large portion of the
hyoid are cartilaginous at birth.
The Nerve-foramina of the Skull
The various foramina and canals in the skull which give passage to nerves may be arranged
in two groups, primary and secondary. Primary foramina indicate the spots where the nerves
leave the general cavity of the dura mater, and as this membrane indicates the limit of the
primitive cranium, a cranial nerve, in a morphological sense, becomes extra-cranial at the point
where it pierces this membrane. In consequence of the complicated and extraordinary modifica-
tions the vertebrate skull has undergone, many nerves traverse, in the adult skull, bony tunnels
and canals which are not represented in the less complex skulls of low vertebrates, such as
sharks and rays. To such foramina and canals the terms secondary or adventitious may be
Nerve-foramina are further interesting in that they occupy sutm-es, or indicate the points
of union of two or more ossific centres. To this rule the foramen rotundum is the only excep-
tion in the human skull.
The Primary Foramina
1. Foramen magnum. — This is bounded by four distinct centres, the supra-, basi-, and
two ex-ocoipitals. It transmits the accessory (eleventh) pair of cranial nerves, the vertebral
arteries and their anterior and posterior spinal branches, the medulla oblongata and its mem-
branes, and the membrana tectoria.
2. The hypoglossal. — At birth this is a deep notch in the anterior extremity of the ex-
ocoipital, and becomes a complete foramen when the basi- and ex-occipitals fuse. Occasionally
it may be complete in the ex-occipital, but it indicates accurately the line of union of these two
elements of the occipital bone. It transmits the hypoglossal nerve, the meningeal branch of the
ascending pharyngeal artery, and its venae comitantes.
3. Jugular foramen. — This occupies the petro-occipital suture, and is formed by the basi-
and ex-occipital in conjunction with the petrosal. It transmits the glosso-pharyngeal, vagus,
and accessory nerves, a meningeal branch of the ascending pharyngeal artery, and receives the
transverse and inferior petrosal sinuses.
4. Auditory. — This marks the point of confluence of the groups of centres termed pro-otic
and opisthotic. It transmits the facial and auditory nerves, the pars intermedia, and the au-
ditory twig of the basilar artery.
5. Trigeminal. — This is only a foramen when the dura mater is present in the skull. It
is a notch at the apex of the petrosal converted into a foramenby the tentorium. The main
trunk of the trigeminal nerve, with the small motor root (masticator nerve), traverses it.
6. Petro-sphenoidal. — This is a notch between the side of the dorsum sellae and apex of
the petrosal which becomes converted into a foramen by dura mater.
7. Optic. — This foramen is formed by the confluence of the orbito- and pre-sphenoidal
centres. It opens into the orbit and transmits the optic nerve and ophthalmic artery.
The Secondary Nerve -foramina
Foramina transmitting the various subdivisions of the trigeminal nerve. — The primary
foramen of exit for the trigeminal nerve is formed partly of bone and partly of membrane at
the apex of the petrosal. The three divisions of the nerve issue through secondary foramina.
(a) The superior orbital (sphenoidal) fissure is an elongated chink, bounded above by
the orbital wing and below by the great wing of the sphenoid, medially by the body of the
sphenoid, and laterally by the frontal. It opens into the orbit, and transmits the third, fourth,
first (ophthalmic) division of the trigeminal and abducens nerves, also the ophthalmic vein or
veins.
(6) The foramen rotundum is the only exception to the ru,le relating to the formation of
nerve-foramina; it is probably a segment of the superior orbital fissure. The foramen is really
a canal running from the middle cranial fossa to the pterygo-palatine fossa, and transmits the
second or maxillary division of the trigeminal.
(c) The foramen ovale at birth is a gap in the hinder border of the great wing (ali-sphe-
noid) of the sphenoid, and is converted into a foramen by the petrosal; subsequently it becomes
complete in the sphenoid. It transmits the thii'd or mandibular division of the trigeminal and
the small or motor root, the small superficial petrosal nerve (which occasionally passes thi-ough
a separate foramen), and the small meningeal artery with its venae comitantes.
126 THE SKELETON
The ethmoidal canals. — These commence in the suture between the lamina papyracea and
the frontal bone, and traverse the space between the upper surface of the lateral mass of the
ethmoid and the horizontal plate of the frontal, to emerge on the cribriform plate; they are
situated outside the dura mater. The anterior foramen transmits the anterior ethmoidal
branch of the ophthalmic, which subsequently gains the nasal cavity by passing through the
ethmoidal fissure by the side of the crista galli.
The infra-orbital canal indicates the line of confluence of the maxillary and malar centres
of the maxilla; occasionaOy it is completed by the zygomatic; rarely it is incomplete above,
and communicates by a narrow fissure with the orbit. It lodges the infra-orbital nerve and
artery.
The zygomatico-temporal foramen is situated in the suture between the zygomatic and
the greater wing of the sphenoid (ali-sphenoid) ; it transmits the temporal branch of the zygo-
matic nerve and a branch of the lacrimal artery. In the adult this foramen may be wholly
confined to the zygomatic bone.
The zygomatico -facial canals traverse the zygomatic bone, and indicate the line of con-
fluence of the two chief centres for this bone. The facial twigs of the zygomatic nerve issue
from them accompanied by arterial twigs.
The spheno-palatine foramen is a deep groove between the orbital and sphenoidal pro-
cesses of the palate bone, converted into a foramen by the sphenoidal concha. It is traversed
by the naso-palatine nerve and artery as they enter the nasal from the pterygo-palatine fossa.
Scarpa's foramina are two minute openings in the meso-palatine suture where it is in
relation with the incisive fossa. They are traversed by the naso-palatine nerves.
The pharyngeal foramen is situated between the sphenoidal process of the palate bone,
the medial pterygoid plate of the sphenoid, and the sphenoidal concha. The pharyngeal
branch of the spheno-palatine ganghon and a branch of the spheno-palatine artery pass
through it.
The pterygoid (Vidian) canal is trumpet-shaped: the narrower end is situated in the foramen
lacerum; the broader orifice opens on the posterior wall of the pteryo-palatine fossa. The canal
is 10 mm. long; in the fcetal skull it is a chink between the base of the medial pterygoid plate,
the ah-sphenoid, and the lingula of the sphenoid. The canal is traversed by the Vidian branch
of the spheno-palatine ganglion and the Vidian artery.
The posterior (greater) palatine canal is a passage left between the maxilla, the vertical
plate and tuberosity of the palate bone and the medial pterygoid plate; it commences on the
hard palate by the greater palatine foramen. The descending palatine nerve and artery trav-
erse this canal. Several foramina open from it. In the suture between the vertical plate of the
palate bone and the maxilla, two small openings allow minute nerves to issue for the middle and
inferior nasal conchae. In the fissures between the tuberosities of the palate and maxillee, and
the pterygoid plates, the posterior and middle palatine nerves issue. These are sometimes called
the posterior and middle (smaller) palatine canals.
The mandibular or inferior dental canal runs in the mandible between the dentary and
Meckel's cartilage of the mandible. The posterior orifice of the canal is the mandibular (infe-
rior dental) foramen; the anterior orifice is the mental foramen. The inferior alveolar nerve
and artery enter the canal at its posterior orifice; the mental foramen allows the mental nerve
to escape from the canal accompanied by the mental artery.
Foramina transmitting the facial nerve and its branches. — The main trunk of the facial
enters the internal auditory meatus and traverses the facial canal. In the early embryo the
nerve lies on the petrosal, and is not covered in with bone until the fifth month of foetal life.
The terminal orifice, the stylo-mastoid foramen, is situated between the tympanic, tympano-
hyal, and epiotic elements of the complex temporal bone.
The 'iter chorda posterius' is a chink between the squamosal and the tympanic elements,
and allows the chorda tympani nerve to enter the tympanum. The fissure of exit for this nerve
is the subdivision of the petro-tympanic fissure termed the canal of Huguier, or 'iter chordae
anterius.' The petro-tympanic fissure lies between the tympanic plate and the squamosal.
It transmits the tympanic branch of the internal maxillary artery, and lodges the anterior proc-
ess of the malleus.
The inferior orbital (spheno-maxillary) fissure is situated between the posterior border
of the orbital plate of the maxilla and a smooth ridge on the orbital surface of the great wing
of the sphenoid. It transmits the superior maxillary division (second) of the fifth nerve, the
zygomatic nerve, branches of the spheno-palatine ganglion to the orbit, and a communicating
vein from the ophthalmic to the pterygoid plexus.
C. THE THORAX
The thorax is a bony cage formed by the thoracic vertebrte already described,
the ribs with their costal cartilages, and the sternum.
THE RIBS
The ribs [costse] (figs. 154, 155) twelve in number on each side, constitute a
series of narrow, flattened bones, extending from the sides of the thoracic vertebrae
toward the median line on the anterior aspect of the trunk. The anterior ends
of the first seven pairs are connected, by means of their costal cartilages, with the
sides of the sternum, and on this account the first seven ribs on each side are
THE RIBS 127
termed true or sternal ribs. The remaining five pairs, known as false or asternal
ribs, may be arranged in two sets: — one, including the eighth, ninth, and tenth
ribs, in which the cartilages of the anterior extremities are connected together,
and the other, including the eleventh and twelfth, in which the anterior extremi-
ties, tipped with cartilage, are free. The eleventh and twelfth are known, in
consequence, as the floating ribs. Thus, the first seven are vertebro -sternal;
the eighth, ninth, and tenth, vertebro -chondral; the eleventh and twelfth,
vertebral ribs.
The ribs increase in length from the first to the seventh, and decrease from the
seventh to the twelfth. They also vary in their direction, the upper ones being
less oblique than the lower. The obliquity is greatest at the ninth rib and gradu-
ally decreases from the ninth to the twelfth.
Typical characters of a rib (fig. 154). — The seventh is regarded as the most
typical rib. It presents for examination a vertebral extremity or head; a narrow
portion or neck; a sternal extremity; and an intermediate portion, the body or
shaft.
The head [capitulum costse] presents an articular surface made up of two
articular facets separated by a horizontal crest [crista capituh]. The crest is
connected by an interarticular ligament with an intervertebral disc, and the facets
articulate with the costal pits on the sides of the bodies of two vertebrae (sixth and
seventh) . As a rule, the lower facet is the larger, and articulates with the thoracic
vertebra, to which the rib corresponds in number. This is the primary facet, and
is the one represented in those ribs which possess only a single facet on the rib-head.
The anterior margin is lipped for the attachment of the radiate ligament.
The neck [coUum costae] is that portion of the rib extending from the head to
the tubercle. It is flattened from before backward and the posterior surface is
in relation with the transverse process of the lower of the two vertebrae with which
the head articulates; it forms the anterior boundary of the costo-transverse fora-
men, and is rough where it is attached to the neck (middle costo-transverse)
ligament. The anterior surface is flat and smooth. The superior border of the
neck, continuous with the corresponding border of the shaft, presents a rough
crest [crista colli] for the anterior costo-transverse ligament. The inferior bor-
der of the neck is rounded and continuous with the ridge of the costal groove.
This difference in the relation of the neck, to the upper and lower borders of the
rib-shaft, is useful in determining to which side a rib belongs.
The tubercle, situated behind at the junction of the neck with the shaft, con-
sists of an upper and lateral part, rough for the attachment of the posterior costo-
transverse ligament, and a lower and medial part, bearing a facet for articulation
with a pit near the tip of the transverse process. The tubercle projects
below the lower edge of the rib to form a crest, marking the beginning of the costal
groove.
The body is strongly curved and presents for examination two surfaces and
two borders. At first the curve is in the same plane as the neck, but it quickly
turns forward at a spot on the posterior surface of the shaft known as the angle,
where it gives attachment to the ilio-costalis muscle and some of its subdivisions.
The rib has also a second or upward curve, beginning at the angle. These curves
are expressed by describing the main curve as disposed around a vertical, and the
second or upward curve around a second transverse axis.
When a rib, except the first, second, and twelfth, is laid with its lower border upon the table,
the rib-head rises and the rib touches the table at two places, viz., at the anterior end, and in the
neighbourhood of the angle.
Besides the two curves now described, the rib is slightly twisted on itself, so that the sur-
faces which look medially and laterally behind are placed obhquely in front and look downward
as well as medially, and upward as well as laterally.
The external sui-face of the rib is convex, and gives attachment to muscles. Near its an-
terior extremity it forms a somewhat abrupt curve, indicated by a ridge on the bone, which gives
attachment to the serratus anterior (niagnus) muscle, and is sometimes called the anterior
angle.
The internal surface is concave and presents near its inferior border the
costal groove [sulcus costae]. The groove is best marked near the angle, and
gradually becomes shallower toward the anterior extremity of the rib, where it
is finally lost; it lodges the intercostal vessels and nerve. The ridge limiting the
128
THE SKELETON
groove above is continuous with the inferior border of the neck of the rib, and
gives attachment to the internal intercostal muscle.
The superior border is rounded, and affords attachment to the internal and
external intercostal muscles. The inferior border commences abruptly near the
angle, and gives attachment to the external intercostal muscle.
The sternal end of the shaft is cupped for the reception of the costal cartilage.
Fig. 154. — The Seventh Rib of the Left Side. (Seen from below.)
Tubercle
Costal groove
sternal end for costal
cartilage
Blood-supply. — -The ribs are very vascular and derive numerous branches from the inter-
costal arteries. The branches in the shaft run toward the vertebral end, whilst those in the
head and neck run, as a rule, toward the shaft. In the neighbourhood of the tuberosity the
vessels do not seem to have any constant arrangement.
Peculiar ribs (figs. 155, 156). — Several of the ribs present certain pecuUarities and differ
in many particulars from the general description given above. These are the first, second, tenth,
eleventh, and twelfth.
The first rib is the broadest, flattest, strongest, shortest, and most curved of all the series.
It is not twisted, and is so placed that its superior sm-face looks forward as well as upward, and
its inferior surface backward as well as downward. The head is small, and as a rule is furnished
THE RIBS
129
with only one articular facet. The neck, longer than that of most of the ribs, is slender and
rounded. The tubercle is large and prominent. The shaft lies for its whole extent nearly in
one plane, has no angle, and is curved in one du'eotion only, i. e., around a vertical axis. The su-
perior surface presents two shallow grooves, separated near the inner border by a rough surface
(scalene tubercle or tubercle of Lisfranc) for the scalenus anterior muscle. The groove in
front of this surface is for the subclavian vein, and the groove behind it is for the subclavian
artery and a nerve trunl;; passing to the brachial plexus. Between the groove for the artery and
the tubercle is a rough surface for the insertion of the scalenus medius, and between the groove
and the outer margin is an area for the origin of the serratus anterior {magnus). The inferior
surface is uniformly flat and lacks a subcostal groove. By the lateral portion, which is rough,
it gives attachment to the internal intercostal muscle; the remainder of the inferior surface is in
relation to pleura and lung. The lateral border is thick and rounded, and gives attachment
to the external intercostal muscle, whilst the medial border, thin, sharp, and concave, receives
the attachment of the fascia (Sibson's) covering the dome of the plem-a. The anterior extrem-
ity is thick and broad, and its upper margin, as well as the cartilage to which it is joined, afford
attachment to the costo-olavicular ligament and the subclavius muscle. The costal cartilage
of this rib is du-ectly united to the manubrium sterni, and occasionally the cartilage and the
adjoining part of the anterior extremity of the rib are replaced by fibrous tissue.
Fig. 155. — Fikst and Second Ribs. (Viewed from above.)
Scalenus anterior"
lOve for subclavian
vein
Levator costEe
Ilio-costalis d(
(insertion)
Ilio-costali
(origin)
Serratus posteri
superior
(insertion)
Scalenus posteri
External intercostals
The rib derives its nutrition mainly from the superior intercostal branch of the subclavian
artery.
The second rib'is much longer than the first, and although like it in being strongly curved
round a vertical axis, in its form and general characters there is a closer resemblance to the
ribs lower down in the series. The head is round and presents two facets, the costal groove is
present, though faintly marked, and an angle is situated near the tubercle. The specially dis-
tinguishing featm-e of the rib, however, is a well-marked tuberosity on its outer surface some-
what near the middle, for the origin of a part of the first digitation, and the whole of the second
digitation of the serratus anterior {magnus). Between the tuberosity and the tubercle the outer
surface is smooth and rounded and gives attachment to the scaletius posterior, the serratus
posterior superior, the ilio-costalis cervicis {cervicalis ascendens), and the ilio-costalis dorsi (acces-
sorius) . The internal sm-face is smooth and in relation to the pleura. The borders give attach-
ment to the intercostal muscles, the upper, to those of the first space, the lower, to those of the
second. The shaft of the second rib is not twisted on its own axis, so that both ends can he fiat
on the table. The second rib receives vessels from the superior intercostal branch of the
subclavian artery and the first aortic intercostal.
The tenth rib is distinguished by a single facet on the head for articulation with the body
of the tenth thoracic vertebra. Occasionally there are two facets, in which case the rib articu-
lates also with the ninth thoracic vertebra. The tenth rib, like the ribs immediately above, is
long, curved, presents a deep costal groove, a well-marked tuberosity and an angle. It may
9
130
THE SKELETON
be noted, however, that the distance between the tubercle and the angle in this rib is greater
than in the ribs above. Speaking generally, the distance between these points increases from
above downward — a disposition which is useful in at once determining if any given rib belongs
to the upper or lower end of the series.
The eleventh rib is peculiar in that it has a single facet on the head, a feebly marked angle
some distance from the head, a shallow costal groove, no tubercle, and no neck. The tubercle
is sometimes represented by a slight elevation or roughness without any articular facet. The
anterior extremity is pointed.
The twelfth rib has a large head furnished with one facet for articulation with the root
(pedicle) of the tweUth thoracic vertebra. The shaft is narrow and extremely variable in length
(3 to 20 cm.). It is usually somewhat longer than the first rib, but it may be shorter. There
is no tubercle, no angle, no neck, no costal groove. The anterior extremity is pointed. Poste-
riorly, the upper border is smooth and somewhat rounded; the lower border is sharp and
rough.
The costal cartilages are bars of hyaline cartilage attached to the anterior extremities of the
ribs, and may be regarded as representing unossified epiphyses. Like the shaft of a rib, each
cartilage has an outer and inner surface. The outer surfaces give origin and insertion to large
muscles, and the inner surfaces, from the second to the sixth inclusive, are in relation with the
transversus thoracis {triangularis sterni) . The upper and lower borders serve for the attachment
of the internal intercostal muscles. The upper seven cartilages, and occasionally the eighth,
are connected with the sternum. Of these, the first fuses with the manubrium sterni and the
remaining six are received into small articular concavities, and retained by means of ligaments.
Fig. 156. — The Vertebral Ends of Tenth, Eleventh, and Twelfth Ribs.
Angle
Single facet (sometimes
two facets are present)
Single facet (this rib has
an angle, but no tuber-
osity and no neck)
Single facet (this rib has
neither tuberosity, angle,
nor neck)
xn
The cartilages of the vertebro-ohondral ribs are united to one another and to the seventh costal
cartilage by ligaments (sometimes by short vertical bars of cartilage), while those of the verte-
bral ribs form no such attachment, but lie between the abdominal muscles. The inner surfaces
of the lower six costal cartilages afford attachment to the diaphragrn and the transversalis muscle.
Each of the second, third, fourth, and fifth costal cartilages articulates with the side of the
sternum, at a point corresponding to the junction of two sternebrse. The sixth and seventh
(and eighth when this reaches the sternum) are arranged irregularly. As a rule, the sixth lies
in a recess at the side of the fifth sternebra; the seventh corresponds to the line of junction of
the meso- and metasternum; and the eighth articulates with the metasternum (see figs. 158,
161).
Blood-supply. — The costal cartilages derive their blood-supply from the terminal twigs of
the aortic intercostals and from the internal mammary arteries.
Ossification. — At the eighth week of intra-uterine life the ribs are cartilaginous. About
this date a nucleus appears near the angle of each rib, and spreads with great rapidity along'the
shaft, and by the fourth month reaches as far as the costal cartilage. At this date the length of
rib-shaft bears the same proportion to that of the costal cartilage as in adult life. Whilst the
ribs are in a cartilaginous condition, the first eight reach to the side of the sternum, and even
after ossification has taken place, the costal cartilage of the eighth rib, in many instances, retains
its articulation with the sternum up to as late as the eighth month (fig. 158). This relationship
may persist through life, but usually the cartilage retrogresses, and is replaced by ligamentous
tissue. About the fifteenth year a secondary centre appears for the head of each rib, and a
little later one makes its appearance for the tubercle, except in the eleventh and tweKth ribs.
Frequently epiphyses are developed on both parts of the tubercle (see figs. 159 and 160). The
THE RIBS
131
epiphyses fuse with the ribs about the twenty-third year. The rib-shaft increases in length
mainly at its line of junction with the costal cartilage.
Variations in the Number and Shape of the Ribs
The ribs may be increased in number by addition either at the cervical or lumbar end of the
series, but it is extremely rare to find an additional rib or pair of ribs in both the cervical and
lumbar regions in the same subject.
Fig. 157. — RtB at Puberty.
The cartilaginous siiaft commences to
ossify at the eighth week of intra-
uterine life
Fig. 158. — The Thorax at the Eighth FfETAL Month.
(On the left side eight cartilages reach the sternum.)
Cervical ribs are fairly common; as a rule, they are of small size and rarely extend more than
a few millimeters beyond the extremity of the transverse process (see p. 35). Rarely
they exceed such insignificant proportions and reach as far as the sternum; between these two
extremes many varieties occur. In one case Tui'ner was able to make a thorough dissection of
a specimen in which a complete cervical rib existed. Its head articulated with the body of the
132 THE SKELETON
seventh cervical vertebra and had a radiate ligament. The tubercle was well developed, and
articulated with the transverse process. The costal cartilage blended with that of the first
thoracic rib, and gave attachment to the costo-clavicular ligament. Between it and the first
thoracic rib there was a well-marked intercostal space occupied by intercostal muscles. It
received the attachment of the scalenus anterior and meditis muscles, and it was crossed by the
subclavian artery and vein. The nerves of the intercostal space were supplied by the eighth
cervical and first thoracic. The artery of the space was derived from the dee)] cervical, which,
with the superioi intercostal, arose from the root of the vertebral. The head of the first thoracic
rib in this specimen articulated with the seventh cervical, as well as with the first thoracic
vertebra. An interesting; fact is also recorded in the careful account of this specimen. There
was no movable twelfth thoracic rib on the same side as this well-developed cervical rib, and the
twelfth thoracic vertebra had mammillary and accessory processes, and a strong elongated
costal process, and was in linear series with the lumbar transverse processes.
Fig. 159. — Posterioe Pohtion op the Sixth Rro in the Fifteenth Year.
(After Toldt.)
Epiphysis of non-articular portion of the tubercle
Epiphysis of head
Articular facet
Gruber and Turner, from a careful and elaborpte study of this question, summarise the varia-
tions in the cervical rib thus: — It may be very short and possess only a bead, neck, and tubercle.
When it extends beyond the transverse process, its shaft may end freely or join the first thoracic
rib: this union may be effected by bone, cartilage, or ligament. In very rare instances it may
have a costal cartilage and join the manubrium of the sternum. Net unfrequently a process,
or eminence, exists on the first thoracic rib at the spot where it articulates with a cervical rib.
Lumbar ribs are of less significance than cervical ribs and rarely attain a great length.
Their presence is easily accounted for, as they are the differentiated costal elements of the trans-
verse processes. They are never so complete as the cervical ribs, and articulate only with
the transverse processes; the head never reaches as far as the body of the vertebra, and there is
no neck or tubercle. An extra levator costce muscle is associated with a lumbar rib.
Fig. 160. — Posterior Portion of the Sixth Rib in the Eighteenth Year.
(After Toldt.)
Non-articular portion of tubercle
Epiphysis of head
Epiphysis of the articular facet of the tubercle
Not the least interesting variation of a rib is that known as the bicipital rib. This condition
is seen exclusively in connection with the first thoracic rib. The vertebral end consists of two
Hmbs which lie in different transverse planes. These bicipital ribs have been especially studied
in whales and man. This abnormality is due to the fusion of two ribs, either of a cervical rib
with the shaft of the first thoracic; or the more common form, the fusion of the first and second
true ribs.
Among unusual variations of ribs should be mentioned the replacement of the costal carti-
lage and a portion of the rib-shaft by fibrous tissue, a process which occurs normally in the case
of the eighth rib during its development.
Sometimes the shafts of two or more ribs may become united by small quadrilateral plates
of bone extending across the intercostal spaces.
THE STERNUM
The sternum (figs. 161, 162) is a flat, oblong plate of bone, situated in the
anterior wall of the thorax, and divisible into three parts, called respectively — (1)'
the manubrium sterni (presternum), (2) the gladiolus (mesosternum), constitut-
fng the body of the bone, and (3) the xiphoid (or ensiform) process (metasternura).
In the young subject it consists of six pieces or segment (sternebrae) . Of these,
the first remains separate throughout life and forms the manubrium; the sue-
THE STERNUM 133
ceeding four segments fuse together, forming the body ; whilst the lowest segment,
also distinct until middle life, is represented by the xiphoid process.
In its natural position the sternum is inclined obliquely from above downward and forward,
and corresponds in length to the spine from the third to the ninth thoracic vertebra. It is not
of equal width throughout, being broader above at the manubrium and narrow at the junction
of this piece with the body. Toward the lower part of the body the sternum again widens, and
then suddenly contracts at its junction with the xiphoid process which constitutes the narrowest
part.
The manubrium or first piece of the sternum forms the broadest and thickest
part of the bone, and is of a somewhat triangular form with the base directed up-
ward and the apex downward. It presents for examination two surfaces and four
borders. The anterior surface [planum sternale] is largely subcutaneous. It is
slightly convex and directed obhquely upward and forward, is smooth and
gives origin on each side to the sternal head of the sterno-mastoid and the pedoralis
major. The posterior surface, almost flat, and directed downward and backward,
affords origin near the lateral margins on each side; to the sterno-hyoid muscle
above and the sterno-thyreoid muscle below. Of the four borders, the superior
is the longest and much the thickest. In the middle is a curved, non-articular
depression, called the jugular (interclavicular) notch, to which the fibres of the
interclavicular ligament are attached, and at either end is an oval articular
surface [incisura clavicularis], somewhat saddle-shaped and directed upward,
backward, and lateral^ for the reception of the medial end of the clavicle. The
circumference of the articular surface gives attachment to the sterno-clavicular
ligaments. The lateral borders slope from above downward and medially and
each presents an irregular surface above for the first costal cartilage and a small
facet below, which, with an adjoining facet on the body, forms a notch for the
second costal cartilage. The two articular surfaces are separated by a narrow
curved edge in relation with the internal intercostal muscle of the first space. The
lower border is thick and short and presents an oval rough surface which articu-
lates with the upper border of the body, forming the sternal S3aichondrosis.
The two opposed surfaces are separated by a fibro-cartilaginous disc, which may,
however, become partially ossified in advanced age, and at the position of the
joint there is usually an angle — the angle of the sternum — which can be felt as a
transverse ridge beneath the skin. This is useful in locating the position of the
second rib in the living subject.
The body (gladiolus) or second piece of the sternum is longer, narrower, and
thinner than the manubrium. It is widest opposite the notches for the fifth
costal cartilages and becomes narrower above and below. The anterior surface
is flat, directed upward and forward, and marked by three transverse elevations
which indicate the lines of junction of its four component parts. It gives attach-
ment on each side to fibres of the pectoralis major, and occasionally presents a
foramen — the sternal foramen — situated at the junction of the third and fourth
pieces of the bone. The posterior surface is slightly concave, marked by lines
corresponding to those on the anterior surface, and below gives attachment on
each side to fibres of the transversus thoracis {triangularis sterni). The lateral
borders present four whole notches [incisure costse] and two half-notches on
each side, which articulate with the costal cartilages of the second to the seventh
ribs inclusive; the two half-notches are completed by corresponding notches on
the manubrium and the xiphoid process. Between the articular depressions the
lateral border is curved and in relation to the internal intercostal muscles.
In order to appreciate the nature of these articular notches, it is advantageous to study
the sternum in a young subject. Each typical sternebra presents four angles at each of which is
a demi-notch. Between every two sternebrae there is an intersternebral disc so that when in
position, each notch for a costal cartilage is formed by a sternebra above and below and an inter-
sternebral disc in the middle, thus repeating the relation of the rib-head to the vertebral centre.
Later in life these fuse more or less together, except in the case of the first and second sternebrae,
which usually remain separate to the end of life. The first (pre-sternum) is the most modified
of all the sternebrae, and differs from them in the fact that the costal cartilage of the first rib
is continuous with it, and in fact that it supports the clavicles. Occasionally a rounded pisi-
form bone is seen on each side, medial to the articular notch for the clavicle; these are the
supra-sternal bones.
The superior border of the sternal body presents an oval facet for articulation
(synchondrosis) with the manubrium. The inferior border is short and articu-
134
THE SKELETON
lated with the xiphoid process, forming the meso-metasternal joint, the two
opposed surfaces being separated by a layer of cartilage so long as they are not
united by bone.
The xiphoid (ensiform) process is the thin, elongated process projecting
downward between the cartilages of the seventh ribs. It is the least developed
Fig. 161. — The Sternum. (Anterior view.)
Jugular notch
Clavicular notch
For first costal cartilage
Xiphoid foramen'
Sterno-mastoid
Pectoralis major
Body or mesostetnum
Rectus abdominis
metasternum
part of the sternum and is subject to many variations in form, being sometimes
pointed, broad and thin, occasionally bifid or perforated by a foramen, and some-
times bent forward, backward, or deflected to one side. In structure it is carti-
laginous in early life, partially ossified in the adult, but in old age it tends to be-
come ossified throughout and to fuse with the body.
The anterior surface of the xiphoid process gives attachment to a few fibres of the rectus
ahdominis muscle and the chondro-xiphoid ligament, the posterior surface to the sternal fibres
of the diaphragm, and the lowest fibres of the transversus thoracis {triangularis sterni), whilst
THE STERNUM
135
the lateral margins receive the aponeuroses of the abdominal muscles. Its tip is directly con-r
tinuous with the linea alba.
Differences according to sex. — The sternum differs somewhat in the two sexes. The female
sternum is relatively shorter, the diminution being almost confined to the body. In the male
the body is more than twice as long as the manubrium, whereas in the female it is usually less
than twice the length of the first piece.
Fig. 162. — The Stbhnttm. (Posterior view.)
Clavicular notch
Sterno-hyoid
Sterno-thyreoid
Transversus thoracis
For first costal cartilage
Second
Diaphragm
Structurally the sternum is composed of cancellous tissue covered with an outer layer of
compact tissue. Its arterial supply is derived mainly from the sternal and perforating branches
of the internal mammary.
Development of the sternum. — -The osseous sternum is preceded by a continuous or non-
segmented central sternal cartilage formed in the following way When the cartilaginous ribs
first appear in the embryo, their anterior or ventral ends fuse together on either side of the mid-
dle fine. For some time a median fissure is present, bordered by two sagittaUy directed strips
of cartilage with each of which at first nine ribs are joined. As development proceeds the two
strips come into contact in the middle line and fuse from before backward to form a median
sternal cartilage. The eighth cartilage generally loses its sternal attachment, although in some
cases it remains permanently articulated with the side of the ensiform process. The ninth
136
THE SKELETON
costal cartilage becomes subdivided, one part remaining attached to the sternum and forming the
xiphoid process, whilst the end still continuous with the rib acquires a new attachment to the
eighth cartilage. The ends adherent to the sternum may remain separate and give rise to a
bifid xiphoid process, though much more frequently they unite, leaving a small foramen.
At first, therefore, the sternum and costal cartilages are continuous. A joint soon forms
between the presternum and mesosternum, and others between the costal cartilages and the
sternum (except in the case of the first) quickly follow. The division of the mesosternum into
segments is a still later formation and arises during the process of ossification.
Fig. 163. — Posteeior Surface of the Manubrium (Pre-sternum), with Sternal Ends
OF Clavicles and the First Costal Cartilages.
Sterno-hyoid Sterno-thyreoid
On the other hand, a view has been advanced by Professor A. M. Paterson that the sternum
is not a bilateral structure, but is laid down, as shown in human sterna of the third month, as a
simple median band of hyahne cartilage, in complete fusion with the costal cartilages on each
side and presenting no differentiation of its component parts. From a study of the earliest
stages of the development of the sternum, its comparative anatomy and structure, Professor
Paterson has, moreover, brought forward evidence which indicates its independence in the first
instance of costal elements and its genetic association with the shoulder girdle.
Ossification. — The ossification of the sternutn is slow and irregular. The process begins
in the presternum (manubrium) by a single centre about the sixth month of intra-uterine life,
though occasionally other accessory centres are superadded.
Fig. 164. — Two Stages in the Formation of the Cartilaginous Sternum. (After Huge.)
The mesosternum (body) usually ossifies from seven centres. The upper segment ossifies
from a single median nucleus about the eighth month, and below this, three pairs of ossific
nuclei appear, which may remain for a long time separate. Of these, two parrs for the second
and third segments are visible at birth, and those for the lower segment make their appearance
toward the end of the first year. The various lateral centres unite in pairs, so that at the sixth
year the sternum consists of six sternebra3, the lowest (metasternum) being cartilaginous.
Very often, however, there are only four centres of ossification in the gladiolus, as shown in
fig. 165. Gradually the four pieces representing the mesosternum fuse with one another, and
THE STERNUM
137
Fig. 165. — Ossification of the Sternum.
A, common arrangement of the ossific centres. B, showing accessory centre in the manubrium
sterni, and bilateral centres in the second, third, and fourth pieces of the body.
Single centre for each
of the four pieces of
the body
Single centre f^ -_^
xiphoid process ^*^.
Accessory centre
Single centre for first
piece of body
Bilateral centres for
second, third, and
fourth pieces of body
Single centre for
xiphoid process
Fig. 166.— The Thorax. (Front view.)
Superior thoracic aperture
' >False ribs
138
THE SKELETON
at twenty-five they form a single piece, but exhibit, even in advanced hfe, traces of their original
separation. A sternal foramen is usually the result of non-union across the middle line or a
defect of ossification.
The metasternum is always imperfectly ossified, and does not join with the mesosternum
till after middle life. The presternum and mesosternum rarely fuse. The dates given above
for the various nuclei, and for the union of the various segments, are merely approximate, hence
the sternum affords very uncertain data as to age.
Abnormalities of the Sternum. — The mode of development of the sternum as described
above is of importance in connection with some deviations to which it is occasionally subject.
In rare instances the two lateral halves fail to unite, giving rise to the anomaly of a completely
cleft sternum. The union of the two halves may occur in the region of the manubrium and fail
below, whilst in other cases the upper and lower parts have fused but remain separate in the
middle. The clefts are in many instances so small as not to be of any moment, and are not
even recognised until the skeleton is prepared. In a few individuals, however, they have been
so extensive as to allow the pulsation of the heart to be perceptible to the hand, and even to
the eye, through the skin covering the defect in the bone.
A common variation in the sternum is asymmetry of the costal cartilages. Instead of cor-
responding, the cartilages may articulate with the sternum in an alternating manner. The
cause of this asymmetry is not known.
THE THORAX AS A WHOLE
The bony thorax (fig. 166) is somewhat conical in shape, deeper behind than in front
and compressed antero-posteriorly, so that in the adult it measures less in the sagittal than in
the transverse axis. The posterior wall, formed by the thoracic vertebrae and the ribs as far
Fig. 167.-
-The Thorax. (Posterior view.) The scapulae are drawn from an X-ray
photograph of a man 33 years old.
outward as their angles, is convex from above downward, and the backward curve of the ribs
produces on each side of the vertebrae a deep furrow, the costo-vertebral groove, in which the
sacro-spinalis (erector spinoe) muscle and its subdivisions are lodged. The anterior wall is formed
by the sternum and costal cartilages. It is slightly convex and inchned forward in its lower
part, forming an angle of about 20° with the vertical plane. The lateral walls are formed by
the ribs from the angles to the costal cartilages. The top of the thorax presents an elUp-
tical aperture, the superior thoracic aperture, which measures on an average 12.5 centimetres (5
THE CLAVICLE 139
inches) transversely and 6.2 centimetres (2J inches) in its sagittal axis. It is bounded by the
first thoracic vertebra behind, the upper margin of the manubrium sterni in front, and the first
rib on each side. As the upper margin of the manubrium sterni is oftenest on a level with
the disc between the second and third thoracic vertebrae, it follows that the plane of the open-
ing is directed obliquely upward and forward. The angle of the sternum {angulus Ludovici) is
usually opposite the body of the fifth thoracic vertebra and the xiphi-sternal junction corre-
sponds to the disc between the ninth and tenth thoracic vertebrae. The lower aperture of the
thorax is very irregular, and is formed by the twelfth thoracic vertebra behind, the twelfth ribs
laterally, and in front by two curved lines, ascending one on either side from the last rib, along
the costal margin to the lower border of the gladiolus. The two borders form the costal arch,
which in the median line below the sternum forms the infrasternal angle. From this angle the
xiphoid process projects downward. The intervals between the ribs are the intercostal spaces,
and are eleven in number on each side.
The ratio of the sagittal and the transverse diameter of the thorax forms the thoracic index,
which is higher in the female and in children, in whom the thorax is more rounded. In the
embryo, the index is very much higher, the sagittal diameter being greater than the transverse.
In the early embryo, the index is nearly 200; at birth it is about 90. In the adults it_ varies
from 70 to 75, averaging 2 or 3 per cent, lower in the male than in the female. It is also
lower in the negro than in the white race. (Rodes, Zeitschr. f. Morph. u. Anthrop., Bd. 9.)
//. THE APPENDICULAR SKELETON
A. BONES OF THE UPPER EXTREMITY
The bones of the upper extremity may be arranged in four groups correspond-
ing to the division of the limb into four segments. In the shoulder are the
clavicle and the scapula, which together constitute the pectoral or shoulder girdle;
in the arm is the humerus; in the forearm are the radius and ulna; and in the hand
the carpus, the metacarpus, and the phalanges.
THE CLAVICLE
The clavicle [clavicula] or collar bone (figs. 168, 169) is situated immediately
above the first rib and extends from the upper border of the manubrium sterni,
laterally and backward to the acromion process of the scapula. It connects the
upper limb with the trunk, and is so arranged that whilst the medial end rests on
the sterniun and first costal cartilage, the lateral end is associated with the scapula
in all its movements, supporting it firmly in its various positions and preventing it
from falling inward on the thorax.
The clavicle is a long bone, and when viewed from the front presents a double
curvature, so that it somewhat resembles in shape the italic letter /. The medial
curve, convex forward, extends over two-thirds of the length of the bone; the
lateral, concave forward, is smaller and confined to the lateral part. For descrip-
tive purposes the clavicle may be divided into a medial prismatic portion, a
lateral flattened portion, and two extremities.
Prismatic portion. — The medial two-thirds of the bone, extending from the
sternal extremity to a point opposite the coracoid process of the scapula, has the
form of a triangular prism. This portion, however, is subject to considerable
variations of form, being more cylindrical in ill-developed specimens and be-
coming almost quadrangular when associated with great muscular development.
In a typical specimen it is marked by three borders separating three surfaces.
Of these, the anterior surface is convex and divided near the sternal end by a
prominent ridge into two parts, a lower, giving origin to the clavicular portion of
the pectoralis major; an upper, for the clavicular portion of the sterno-cleido-
mastoid. Near the middle of the shaft the ridge disappears, the surface is smooth,
and is covered by the platysma myoides. Occasionally this surface is pierced by a
small canal, transmitting a cutaneous nerve from the cervical plexus. The
posterior surface is concave, forming an arch over the brachial plexus and the
subclavian artery, broadest medially and smooth in its whole extent. It
gives origin near the sternal extremity to a part of the sterno-hyoid and occasion-
ally to a few fibres of the sterno-thyreoid. Somewhere near the middle of this
surface is a small foramen, directed laterally, for the chief nutrient artery of the
bone, derived from the transverse scapular (suprascapular) artery. Sometimes the
140
THE SKELETON
foramen is situated on the inferior surface of the bone, in the subclavian groove.
On the inferior surface near the sternal end is a rough area, the costal tuberosity,
about three-quarters of an inch in length, for the attachment of the costo-
clavicular ligament, by which the clavicle is fixed to the first rib. More laterally
is a longitudinal groove for the subclavius, bordered by two lips, to which the sheath
of the muscle is attached. To the posterior of the two lips the layer of deep cer-
vical fascia which binds down the posterior belly of the omo-hyoid to the clavicle
is also attached.
Of the three borders, the superior separates the anterior and posterior surfaces. Be-
ginning at the sternal end, it is well-marked, becomes rounded and indistinct in the middle,
whilst laterally it is continuous with the posterior border of the outer third. The posterior
border separates the inferior and posterior surfaces and forms the posterior lip of the subclavian
Fig. 168. — The Left Clavicle.
Anterior
(Superior surface.)
Pectoralis major
Epiphysial line
groove. It begins at the costal tuberosity and can be traced laterally as far as the coracoid
tubercle, an eminence on the under aspect of the bone near the junction of prismatic and flat-
tened portions. The anterior border is continuous with the anterior border of the flattened
portion and separates the anterior and inferior surfaces. Medially, it forms the lower boundary
of the elliptical area for the origin of the pecloralis major, and approaches the posterior border.
Near the middle of the bone it coincides with the anterior lip of the subclavian groove.
Flattened portion. — The lateral third of the bone, extending from a point
opposite the coracoid process of the scapula to the acromial extremity, is flat-
Oblique
line for
Articular trapezoid
capsule ligament
Fig. 169. — The Left Clavicle.
Posterior
Coracoid
tubercle for
conoid ligament Subclavius
(Inferior surface.)
Costo -clavicular
ligament and
sterno-
hyoid Sterno-thyreoid (occasional)
Facet for first
•costal cartilage
sternal facet
Acromial facet
tened from above downward and presents two surfaces and two borders. The
superior surface is rough and looks directly upward and gives attachment to the
trapezius behind and the deltoid in front; between the two areas the surface is
subcutaneous. On the inferior surface, near the posterior border, is a rough
elevation, the coracoid (conoid) tubercle ; it overhangs the coracoid process and
gives attachment to the conoid ligament. From the coracoid tubercle, a promi-
nent ridge, the trapezoid or oblique line, runs laterally and forward to near
the lateral end of the bone. To it the trapezoid ligament is attached. The
conoid and trapezoid ligaments are the two parts of the coraco-clavicular liga-
ment which binds the clavicle down to the coracoid process.
The anterior border is sharp, gives origin to the deltoid muscle, and frequently presents
near the junction of the flattened and prismatic portions a projection known as the deltoid
tubercle. The posterior border is thick and rounded, and receives the insertion of the upper
fibres of the trapezius.
THE SCAPULA 141
Extremities. — The sternal extremity of the clavicle presents a triangular
articular surface, directed medially, downward, and a little forward, slightly
concave from before backward and convex from above downward, which articu-
lates with a facet on the upper border of the manubrium sterni through an
interposed interarticular fibro-cartilage.
Of the three angles, one is above and two below. The postero-inferior angle is prolonged
backward, and so renders this surface considerably larger than that with which it articulates;
the superior angle receives the attachment of the upper part of the fibro-cartilage. The lower
part of the surface is continuous with a facet on the under aspect of the bone, medial to the
costal tuberosity, for the first costal cartilage. The circumference of the extremity is rough,
and gives attachment to the interclavicular ligament above and the anterior and posterior
sterno-clavicular ligaments in front and behind.
The acromial extremity presents a smooth, oval, articular facet, flattened or
convex, directed shghtly downward for the acromion; its border is rough, for the
attachment of the capsule of the acromio-clavicular joint.
Structure. — The clavicle consists e.\ternally of a compact layer of bone, much thicker in
the middle and thinning out gradually toward the two extremities. There is no true medullary
Fig. 170. — The Sternal Ends op Two Clavicles with Epiphyses.
A, right clavicle from below and behind. B, left clavicle from below and behind.
(From Royal College of Surgeons Museum.)
Sternal epiphyses
cavity, for the interior is occupied from end to end by cancellous tissue, the amount in the vari-
ous parts of the bone being in inverse proportion to the thickness of the outer compact shell
Ossification. — From observations made by F. P. Mall, D. C. L. Fitzwilliams, and E. Faw-
cett it seems almost certain that there are two centres of ossification of the shaft of the clavicle,
at the juncture of the middle and lateral thirds. They appear very early, about the fifth week
of embryonic life, and rapidly fuse. The ossific process extends medially and laterally along the
shaft toward the medial and lateral extremities, respectively. About the eighteenth year a
secondary centre appears at the sternal end and forms a small epiphysis which joins the shaft
about the twenty-fifth year.
THE SCAPULA
The scapula (figs. 171, 172) is a large flat bone, triangular in shape, situated
on the dorsal aspect of the thorax, between the levels of the second and seventh
ribs. Attached to the trunk by means of the clavicle and various muscles it
articulates with the lateral end of the clavicle at the acromio-clavicular joint,
and with the humerus at the shoulder-joint. The greater part of the bone con-
sists of a triangular plate known as the body, from which two processes are
prolonged: one anterior in position, is the coracoid; the other, posterior in posi-
tion, is the spine, which is continued laterally into the acromion.
The body presents for examination two surfaces, three borders, and three
angles. The costal (anterior) surface, or venter, looks considerably medialward,
is deeply concave, forming the subscapular fossa, and marked by several oblique
lines which commence at the posterior border and pass obliquely upward and
laterally; these lines or ridges divide the surface into several shallow grooves,
from which the suhscapularis takes origin, whilst the ridges give attachment to
the tendinous intersections of that muscle. The lateral third of the surface is
smooth and overlapped by the subscapularis, whilst medially are two small flat
areas in front of the upper and lower angles respectively, but excluded from the
subscapular fossa by. fairly definite lines and joined by a ridge which runs close
to the vertebral border. The ridge and its terminal areas serve for the insertion
of the serratus anterior {magnus).
The dorsal (posterior) surface is generally convex and divided by a prominent
plate of bone — the spine — into two unequal parts. The hollow above the spine
is the supraspinous fossa and lodges the supraspinatus muscle. The part below
142
THE SKELETON
the spine is the infraspinous fossa; it is three times as large as the supraspinous
fossa, is alternately concave and convex, and gives origin to the infraspinatus.
The muscle is attached to its medial three-fourths and covers the lateral fourth,
without taking origin from it.
The infraspinous fossa does not extend as far as tlie axillary border, but is limited laterally
by a ridge — the oblique hne— Which runs from the glenoid cavity — the large articular surface
for the head of the humerus — downward and backward to join the posterior border a short dis-
tance above the inferior angle. Tliis line, which gives attachment to a stout aponeurosis, cuts
ofi an elongated surface, narrow above for the origin of the teres minor, and crossed near its
middle by a groove for the circumflex (dorsal) artery of the scapula; below, the surface is broader
for the origin of the teres major and occasionally a few fibres of the latissimus dorsi. The two
areas are separated by a line which gives attachment to an aponeurotic septum situated
between the two teres muscles.
Fig. 171. — The Left Scapula. (Dorsal surface.)
Coraco-acromial ligament Omo-hyoid and the superior transverse ligament
Superior angle
Rhomboideus
major
Teres ma jo
The supra- and infraspinous fossa communicate through the great scapular
notch at the lateral border of the spine, and through the notch the suprascapular
nerve and transverse scapular artery are transmitted from one fossa to the other.
Borders. — The three borders of the scapula are named superior, vertebral,
and axillary. The superior is short and thin and extends from the upper angle
to the coracoid process. Laterally it presents a deep depression, the scapular
notch, to the extremities of which the superior transverse ligament is attached.
Not infrequently the notch is replaced by a scapular foramen, and it is interesting to note
that a bony foramen occurs normally in some animals, notably the great ant-eater (Myrmeco-
phaga jubata). The notch or foramen transmits the suprascapular nerve, whilst the transverse
scapular artery usually passes over the ligament. From the adjacent margins of the notch and
from the ligament the posterior belly of the omo-hyoid takes origin.
THE SCAPULA
143
The vertebral border (sometimes called the base) is the longest, and extends
from the upper or medial to the lower angle of the bone. It is divisible into three
parts, to each of which a muscle is attached: an upper portion, extending from
the medial (superior) angle to the spine, for the insertion of the levator scapulae;
a middle portion, opposite the smooth triangular area at the commencement
of the spine, for the rhomhoideus minor; and the lowest and longest portion,
extending below this as far as the inferior angle, for the rhomhoideus major,
the attachment of which takes place through the medium of a fibrous arch.
The axillary border is the thickest, and extends from the lower margin of
the glenoid cavity to the inferior angle of the bone. Near its junction with the
glenoid cavity there is a rough surface, about 2.5 cm. (1 in.) in length the in-
fraglenoid tubercle, from which the long head of the triceps arises, and below
Fig. 172. — The Left Scapula. (Ventral surface.)
Trapezoid ligament Pectoralis minor
Scapular notch Conoid lig
Serratus anten
Coraco-acromial
ligament
Biceps and coraco-
brachialis
Clavicular facet
Glenoid fossa
Articular capsule
Triceps (middle or long head)
the tubercle is the groove for the circumflex (dorsal) artery of the scapula.
The upper two-thirds of the border is deeply grooved on the ventral aspect and
gives origin to a considerable part of the subscapidaris.
Angles. — The three angles are named medial, inferior, and lateral.
The medial (or superior) angle, forming the highest part of the body, is thin, smooth, and
either rounded or approximating a right angle. It is formed by the junction of the superior
and vertebral borders and gives insertion to a few fibres of the levator scapula. The inferior
angle, constituting the lowest part of the body, is thick, rounded, and rough. It is formed by
the junction of axillary and vertebral borders, gives origin to the teres major, and is crossed
liorizontally by the upper part of the lalissimus dorsi, the latter occasionally receiving from it
a small slip of fleshy fibres.
The lateral angle forms the expanded portion of the bone known as the head,
bearing the glenoid cavity, and supported by a somewhat constricted neck. The
144 THE SKELETON
glenoid cavity is a wide, shallow, pyriform, articular surface for the head of the
humerus, directed forward and laterally, with the apex above and the broad end
below. Its margin is raised, and affords attachment to the glenoid ligament,
which deepens its concavity. The margin is not, however, of equal prominence
throughout, being somewhat defective where it is overarched by the acromion,
notched anteriorly, and emphasised above to form a small eminence, the supra-
glenoid tubercle, for the attachment of the long head of the biceps.
The circumference and adjoining part of the neck give attachment to the articular capsule
of the shoulder-joint, and the anterior border to the three accessory ligaments of the capsule,
known as the superior, middle, and inferior gleno-humeral folds. The superior fold (Flood's
ligament) is attached above the notch near the upper end; of the two remaining folds, which
together constitute Schlemm's ligament, the middle is attached immediately above the notch
and the inferior below the notch. In the recent state the glenoid fossa is covered with hyaline
cartilage. The neck is more prominent behind than before and below than above, where it
supports the coracoid process. It is not separated by any definite boundary from the body.
Processes. — The spine is a strong, triangular plate of bone attached obliquely
to the dorsum of the scapula and directed backward and upward. Its apex is
situated at the vertebral border; the base, corresponding to the middle of the neck,
is free, concave, and gives attachment to the inferior transverse ligament, which
arches over the transverse scapular (suprascapular) vessels and suprascapular
nerve. Of the two borders, one is joined to the body, whilst the other is free,
forming a prominent subcutaneous crest. The latter commences at the vertebral
border, in a smooth triangular area, over which the tendon of the trapezius glides,
usually without the intervention of a bursa, as it passes to its insertion into a
small tubercle on the crest beyond. Further laterally, this border is rough, and
presents two lips — a superior for the insertion of the trapezius and an inferior for
the origin of the deltoid. Laterally the crest is continued into the acromion.
The spine has two sm-faces, the superior, which also looks medialward and
forward, is concave, contributes to the formation of the supraspinous fossa, and
gives origin to the supraspinatus muscle; the inferior surface, also slightly concave,
is directed lateralward and backward, forms part of the infraspinous fossa, and
affords origin to the infraspinatus muscle. On both surfaces are one or more
prominent vascular foramina.
The acromion, a process overhanging the glenoid cavity, springs from the
angle formed by the junction of the crest with the base of the spine. Somewhat
crescentic in shape, it forms the summit of the shoulder and is compressed from
above downward so as to present for examination two surfaces, two borders, and
two extremities.
The posterior part sometimes terminates laterally in a prominent acromial angle (meta-
cromion) and the process then assumes a more or less triangular form. Of the two extremities,
the posterior is continuous with the spine, whilst the anterior forms the free tip. The upper
surface, directed upward, backward, and slightly lateralward, is rough and convex, and affords
origin at its lateral part to a portion of the deltoid; the remaining part of this surface is sub-
cutaneous. The lower surface, directed downward, forward, and slightly medialward, is con-
cave and smooth. The medial border, continuous with the upper lip of the crest, presents,
from behind forward, an area for the insertion of the trapezius; a small, oval, concave articular
facet for the lateral end of the clavicle, the edges of which are rough for the acromio-clavioular
ligaments; and, beyond this, the anterior extremity or tip, to which is attached the apex of the
coraco-acromial ligament. The lateral border, continuous with the inferior lip. of the crest, is
thick, convex, and presents three or four tubercles with intervening depressions; from the
tubercles the tendinous septa in the acromial part of the deltoid arise, and from the depressions,
some fleshy fibres of the same muscle.
Projecting upward from the neck of the scapula is the coracoid process, bent
finger-like,' pointing forward and laterally. It consists of two parts, ascending
and horizontal, arranged at almost a right angle to each other.
The ascending part arises by a wide root, extends upward and medially for a short distance,
and is compressed from before backward; it is continuous above with the horizontal part and
below with the neck of the scapula; the lateral border lies above the glenoid cavity and gives
attachment to the coraco-humeral ligament; the medial border, which forms the lateral boundary
of the scapular notch, gives attachment to the conoid ligament above and the transverse liga-
ment below. Its anterior and posterior surfaces are in relation with the subscapularis and
supraspinatus respectively. The horizontal part of the process runs forward and lateralward; it
is compressed from above downward so as to present two borders, two surfaces, and a free
extremity. The medial border gives insertion along its anterior half to the pectoralis minor and
nearer the base to the oosto-coracoid membrane; the lateral border is rough for the coraco-
acromial and coraco-humeral ligaments ;_the upper surface is irregular and gives insertion in
THE SCAPULA
145
front to the ■pectoralis minor, and behind to the trapezoid ligament; the inferior surface is smooth
and directed toward the glenoid cavity, which it overhangs; the free extremity or apex gives
origin to the conjoined coraco-brachialis and short head of the biceps.
The greater part of the body of the scapula and the central parts of the spinous process
are thin and transparent. The coracoid and acromion processes, the crest of the spine and in-
ferior angle, the head, neck, and axillary border, are thick and opaque. The young bone consists
of two layers of compact tissue with an intervening cancellous layer, but in the transparent
parts of the adult bone the middle layer has disappeared. The vascular foramina on the costal
surface transmit twigs from the subscapular and transverse scapular (suprascapular) arteries;
those in the infraspinous fossa, twigs from the circumflex (dorsal) and transverse scapular
(suprascapular) arteries, the latter also giving off vessels which enter the foramina in the supra-
spinous fossa. The acromion is supplied by branches from the thoraco-acromial (acromio-
thoracic) artery.
The line of attachment of the spinous process to the dorsum of the scapula is known as the
morphological axis, and the obtuse angle in the subscapular fossa opposite the spine as the
Fig. 173. — Ossification op the Scapula.
The right Scapula at the twelfth year, showing the
subcoracoid element (a little larger than half
the natural size, i. e. ^).
Acromial cartilage
Subcoracoid element
The Scapula at the third year,
showing the caracoid element. (Anterior view.)
Tee Scapula at birth. (Anterior view.)
A
B
subscapular angle. From the axis three plates of bone radiate as from a centre, the prescapula
forward, the mesoscapula laterally, and the postscapula backward, being named in accordance
with the long axis of the body in the horizontal position. In the human subject the postscapula
is greatly developed, and this is associated with the freedom and versatility of movement
possessed by the upper limb.
Ossification. — The scapula is ossified from nine centres. Of these, two (for the body of the
scapula and the coracoid) may be considered as primary, and the remainder as secondary.
The centre for the body appears in a plate of cartilage near the neck of the scapula about the
eighth week of intra-uterine life, and quickly forms a triangular plate of bone, from which the
spine appears as a slight ridge about the middle of the third month. At birth the glenoid fossa
and part of the scapular neck, the acromion and coracoid processes, the vertebral border and
inferior angle, are cartilaginous. During the first year a nucleus appears for the coracoid, and
at the tenth year a second centre appears for the base of the coracoid and the upper part of the
glenoid cavity (subcoracoid, fig. 173).
During the fifteenth year the coracoid unites with the scapula, and about this time the other
secondary centres appear. Two nuclei are deposited in the acromial cartilage, and fuse to form
the acromion, which joins the spine at the twentieth year. The union of spine and acromion
may be fibrous, hence the latter is sometimes found separate in macerated specimens. The
cartilage along the vertebral border ossifies from two centres, one in the middle, and another at
the inferior angle. A thin lamina is added along the upper surface of the coracoid process and
146
THE SKELETON
occasionally another at the margin of the glenoid cavity. These epiphyses join by the twenty-
fifth year.
The occurrence of a special primary centre for the coracoid process is of morphological im-
portance in that the process is the representative of what in the lower vertebrates is a distinct
coracoid hone. This primarily takes part in the formation of the glenoid cavity and extends
medially to articulate with the sternum. In man and all the higher mammals only the lateral
portion of the bone persists.
THE HUMERUS
The^humerus (figs. 174, 175, 176) is the longest and largest bone of the upper
limb, and extends from the shoulder above, where it articulates with the scapula.
Fig. 174. — The Left Humerxts. (Anterior view.)
Subscapularis-
Latissimus dorsi-
Teres major
-Intertubercular groove
Pectoralis major
Coraco-brachialis -
-Brachio-radialis
' carpi radialis longus
iiKl
Pronator teres-
Fexor carpi radialis .
Palmaris longus
Flexor digitorum sublimis
Flexor carpi ulnaris
I Extensor carpi radialis brevis
J Extensor digitorum communis
F Extensor digiti quinti proprius
Extensor carpi ulnaris
Supinator
to the elbow [cubitus] below, where it articulates with the two bones of the fore-
arm [anti-brachium]. It is divisible into a shaft and two extremities; the upper
extremity includes the head [caput], neck [collum], and two tuberosities — great
and small; the lower extremity includes the articular surface ^\dth the surmounting
fossae in front and behind, and the two epicondyles.
THE HUMERUS
147
Upper extremity. — The head forms a nearly hemispherical articular surface,
cartilage-clad in the recent state and directed upward, medially, and backward
toward the glenoid cavity. Below the head the bone is rough and somewhat
constricted, constituting the anatomical neck, best marked superiorly, where it
forms a groove separating the articular surface from the two tuberosities. The
circumference of the neck gives attachment to the capsule of the shoulder-joint
and the gleno-humeral folds, the upper of which is received into a depression near
the top of the intertubercular (bicipital) groove. The lowest part of the capsule
Fig. 175. — The Left HuMERtrs. (Posterior view.)
Articular capsule
Infraspinatus
Triceps (lateral head)-
Groove for radial nerve-
Triceps (medial bead)-
Articular capsule
1 fossa-
Lateral epicondyle
Anconeus and radial collateral ligament
-Medial epicondyle
descends upon the humerus some distance from the articular margin. Laterally
and in front of the head are the two tuberosities, separated by a deep furrow. The
greater tuberosity [tuberculum majus], lateral in position and reaching higher than
the lesser tuberosity [tuberculum minus}, is marked by three facets for the
insertion of muscles: an upper one for the supraspinatus, a middle for the in-
148
THE SKELETON
fraspinatiis, and a lower for the teres minor. The lesser tuberosity is situated in
front of the head and is the more prominent of the two ; it receives the insertion of
the subscapularis. The furrow between the tuberosities lodges the long tendon
of the biceps and forms the commencement of the intertubercular (bicipital)
groove, which extends downward along the shaft of the humerus. Between the
tuberosities the transverse humeral ligament converts the upper end of the groove
into a canal. In addition to the long tendon of the biceps and its tube of synovial
Fig. 176. — The Left Humerus with a Suphacondyloid Process and some Irregular
Muscle Attachments. (Anterior view.)
Lesser tuberosity_
Subscapula
Capsular ligament-
brevis (Rotator_
- Greater tuberosity
-Transverse humeral ligament
-Fourth head of biceps
Intertubercular groove-
Coraco-brachialis-
-Rough surface for deltoid
Third head of biceps-
. The lateral condylar ridge
Pronator teres-
Medial epicondyle
Ulnar collateral ligament ~
Trochlea -
-Radial fossa
^"I'i- Lateral epicondyle
ip- Capitulum
membrane, the groove transmits a branch of the anterior circumflex artery.
Immediately below the two tuberosities the bone becomes contracted and forms
the surgical neck.
The shaft or body [corpus humeri] is somewhat cylindrical above, flattened
and prismatic below. Three borders and three surfaces may be recognised.
Borders. — The anterior border commences above at the greater tuberosity,
and its upper part, forming the crest of this tuberosity [crista tuberculi majoris],
THE HUMERUS 149
receives the pectoralis major. In the middle of the shaft it is rough and prominent
and gives insertion to fibres of the deltoid; below it is smooth and rounded, giviiig
origin to fibres of the brachialis, and finally it passes along lateral to the coronoid
fossa to become continuous with the ridge separating the capitulum and trochlea.
It separates the antero-medial from the antero-lateral surface. The lateral
margin extends from the lower and posterior part of the greater tuberosity to the
lateral epicondyle. Smooth and indistinct above, it gives attachment to the
teres minor and the lateral head of the triceps; it is interrupted in the middle by
the groove for the radial nerve (musculo-spiral groove), but the lower third
becomes prominent and curved laterally to form the lateral supracondylar
ridge, which affords origin in front to the brachio-radialis and the extensor carpi
radialis longus; behind to the medial head of the triceps, and between these
muscles in front and behind to the lateral intermuscular septum. It separates
the antero-lateral from the posterior surface. The medial border commences
at the lesser tuberosity, forming its crest which receives the insertion of the
teres major, and continuing downward to the medial epicondyle. Near the
middle of the shaft it forms a ridge for the insertion of the coraco-brachialis and
presents a foramen for the nutrient artery, directed downward toward the
elbow-joint. Below it forms a distinct medial supracondylar ridge, curved
medially, which gives origin to the brachialis in front, the medial head of the
triceps behind, and the medial intermuscular septum in the interval between
the muscles. This border separates the antero-medial from the posterior surface.
Fig. 177. — A Diagram showing Prbssuee and Tension Curves in the Head
OF THE Humerus. (After Wagstaffe.)
Surfaces. — The antero-lateral surface is smooth above, rough in the middle,
forming a large impression for the insertion of the deltoid, below which is the
termination of the groove for the radial nerve. The lower part of the surface
gives origin to the lateral part of the brachialis. The antero-medial surface is
narrow above, where it forms the floor of the intertubercular (bicipital) groove,
and receives the insertion of the latissimus dor si. Near the junction of the upper
and middle thirds of the bone the groove, gradually becoming shallower, widens
out and, with the exception of a rough impression near the middle of the shaft
for the coraco-brachialis, the remaining part of the antero-medial surface is flat
and smooth, and gives origin to the brachialis.
Occasionally, a prominent spine of bone, the supracondylar process, projects downward
from the medial border about 5 cm. (2 in.) above the medial epicondyle, to which it is joined by
a band of fibrous tissue. Through' the ring thus formed, which corresponds to the supracon-
dylar foraman in many of the lower animals, the median nerve and brachial artery are trans-
mitted, though in some cases it is occupied by the nerve alone. The process gives origin to the
pronator teres, and may afford insertion to a persistent lower part of the coraco-brachialis.
The posterior surface is obliquely divided by a broad shallow groove, which
runs in a spiral direction from behind downward and forward and transmits the
radial (musculo-spiral) nerve and the profunda artery. The lateral part of the
surface above the groove gives attachment to the lateral head, and the part
below the groove, to the medial head of the triceps.
The lower extremity of the humerus is flattened from before backward, and
terminates below in a sloping articular surface, subdivided by a low ridge into the
150
THE SKELETON
trochlea and the capitulum. The trochlea is the pulley-hke surface which extends
over the end of the bone for articulation with the semilunar notch (great sigmoid
cavity) of the ulna. It is constricted in the centre and expanded laterally to form
two prominent edges, the medial of which is thicker, descends lower, and forms a
marked projection; the lateral edge is narrow and corresponds to the interval
between the ulna and radius. Above the trochlea are two fossae : on the anterior
surface is the coronoid fossa, an oval pit which receives the coronoid process of
Fig. 178.-
-ossification of the humerus ; the figure also shows the relations of the
Epiphysial and Capsular Lines
nites with the shaft at the twentieth
year. The upper epiphysis is
formed by the union of the nucleus-
for the head, greater tuberosity,
and that for the lesser tuberosity.
These form a common epiphysis
before uniting with the shaft
Capsular line^
Shaft begins to ossify in the eighth
week of intra-uterine life
1
r#^
Capsular line
Nucleus for the medial epicondyle i
appears at fifth, fuses at ***" '
eighteenth year
Nucleus for trochlea appears at the -
tenth year
Nucleus for lateral epicondyle ap-
pears at fourteenth year
_ Nucleus for capitulum appears in the
third year
The centres for the radial epicondyle,
trochlea, and capitulum unite to-
gether and form an epiphysis which
fuses with the shaft at the seven-
teenth year
the ulna when the forearm is flexed; on the posterior aspect is the olecranon fossa,
a deep hollow for the reception of the anterior extremity of the olecranon in exten-
sion of the forearm. These fossae are usually separated by a thin, translucent
plate of bone, sometimes merely by fibrous tissue, so that in macerated specimens
a perforation, the supratrochlear foramen, exists. The capitulum, or radial head,
is much smaller than the trochlea, somewhat globular in shape, and limited to
the anterior and inferior surfaces of the extremity. It articulates with the con-
THE HUMERUS 151
cavity on the summit of the radius. The radial fossa is a slight depression on the
front of the bone, immediately above the capitulum, which receives the anterior
edge of the head of the radius in complete flexion of the forearm, whilst between
the capitulum and the trochlea is a shallow groove occupied by the medial margin
of the head of the radius.
In the recent state the inferior articular surface is covered with cartilage, the fossae are lined
by synovial membrane, and their margins give attachment to the capsule of the elbow-joint.
Projecting on either side from the lower end of the humerus are the two epicondyles. The
medial one is large and by far the more prominent of the two, rough in front and below, smooth
behind, where there is a shallow groove for the ulnar nerve. The rough area serves for origin
of the pronator teres above, the common tendon of origin of the flexor carpi radialis, palmaris
longus, flexor digitorum sublimis and flexor carpi ulnaris in the middle, and the ulnar collateral
ligament below. The lateral epicondyle is flat and irregular. Above, it gives attachment to a
common tendon of origin of the extensor carpi radialis brevis, extensor digitorum communis,
extensor quinti digiti proprius, extensor carpi ulnaris, and supinator; to a depression near the outer
margin of the capitulum, the radial collateral ligament is attached, and from an area below and
behind, the anconeus takes origin.
Architecture. — The interior of the shaft of the humerus is hollowed out by a large medullary
canal, whereas the extremities are composed of cancellated tissue invested by a thin compact
layer. The arrangement of the cancellous tissue at the upper end of the humerus is shown
in fig. 177. The lamellae converge to the axis of the bone and form a series of superimposed
arches which reach upward as far as the epiphysial line. In the epiphyses the spongy tissue
forms a fine network, the lamellae resulting from "pressure" being directed at right angles to
the articular surface of the head and to the great tuberosity.
Blood-supply. — The foramina which cluster round the circumference of the head and tuber-
osities transmit branches from the transverse scapular (suprascapular) and anterior and pos-
terior circumflex arteries. At the top of the intertubercular groove is a large nutrient foramen
Fig. 179. — The Head of the Humebus at the Sixth Year. (In section.)
The centre for the head appears
during the first year; it is some-
times present at birth
The centre for the greater tuberosity
appears in the third year
for a branch of the anterior circumflex artery which supplies^the head. The nutrient artery of
the shaft is derived from the brachial, and in many cases, an additional branch, derived from the
profunda artery, enters the foramen in the groove for the radial nerve (musculo-spiral groove) .
The lower extremity is nourished by branches derived from the profunda (superior profunda) ,
the superior and inferior ulnar collateral (inferior profunda and anastomotic), and the recurrent
branches of the radial, ulnar, and interosseous arteries.
Ossification. — The humerus is ossified from one primary centre (diaphysial) and six second-
ary centres (epiphysial). The centre for the shaft appears about the eighth week of intra-
uterine life and grows very rapidly. At birth only the two extremities are cartilaginous, and
these ossify in the following manner: Single centres appear for the head in the first year, for
the greater tuberosity in the third year, and for the lesser tuberosity in the fifth year, though
sometimes the latter ossifies by an extension from the greater tuberosity. These three nuclei
coalesce at six years to form a single epiphysis, which joins the shaft about the twentieth year.
The inferior extremity ossifies from four centres: one for the capitulum appears in the third
year, a second for the medial epicondyle in the fifth year, a third for the trochlea in the tenth
year, and a fourth for the lateral epicondyle in the fourteenth year. The nuclei for the capitu-
lum, trochlea, and lateral epicondyle coalesce to form a single epiphysis which joins the shaft
in the seventeenth year. The nucleus of the medial epicondyle joins the shaft independently
at the age of eighteen years.
A study of the upper end of the humeral shaft before its union with the epiphysis is of interest
in relation to what is known as the neck of the humerus. The term neck is appUed to three
parts of this bone. The anatomical neck is the constriction to which the articular capsule is
mainly attached, and its position is accurately indicated by the groove which Ues internal to
the tuberosities. The upper extremity of the humeral shaft, before its union with the epiphysis ,
terminates in a low three-sided pyramid, the surfaces of which are separated from one another
by ridges. The medial of these three surfaces underlies the head of the bone, and the two
lateral surfaces underhe the tuberosities. The part supporting the head constitutes the morpho-
logical neck of the humerus, whilst the surgical neck is the indefinite area below the tuberosities
where the bone is liable to fracture.
152
THE SKELETON
THE RADIUS
The radius (figs. 180-185) is the lateral and shorter of the two bones of the
forearm. Above, it articulates with the humerus; below, with the carpus; and
on the medial side with the ulna. It presents for examination a shaft and two
extremities.
The upper extremity, smaller than the lower, includes the head, neck, and
tuberosity. The head [capitulum], covered with cartilage in the recent state, i&
a circular disc forming the expanded, articular end of the bone. Superiorly it
presents the capitular depression [fovea capituli] for the reception of the capitulum
Fig. 180. — The Left Ulna and Radius. (Antero-medial view.)
Articular capsule" ^^*- %;^
Ulnar collateral ligament^
Tubercle for the flexor digitorum sublimis —
Ulnar collateral ligament —
Brachialis —
Pronator teres (lesser head) —
Flexor pollicis longus (accessory head) —
Interosseous membrane.
Flexor digitorU|BU profundu
"'Semilunar notch
^Head of radius
"Neck of radius
"Lower Umit of annular ligament
-Oblique ligament
- Tuberosity
"Oblique ligament
-Supinator
Flexor sublimis digitorum
ObUque line
Radius
■ Pronator teres
Flexor pollicis longus
Pronator quadratus .
Anterior radio-ulnar ligament-
Ulnar collateral ligament'
Pronator quadratus
Interarticular fibro-cartilage
Brachio-radialis
Radial collateral ligament
Anterior radio-carpal ligament
of the humerus; its circumference [circumferentia articularis], deeper on the
medial aspect, articulates with the radial notch (lesser sigmoid cavity) of the ulna,
and is narrow elsewhere for the annular ligament by which it is embraced. Below
the head is a short cylindrical portion of bone, somewhat constricted, and known
as the neck. The upper part is surrounded by the hgament which embraces the
head, and below this it gives insertion antero-laterally to the supinator. Below
the neck, at the antero-medial aspect of the bone, is an oval eminence, the radial
tuberosity, divisible into two parts: a rough posterior portion for the insertion of
THE RADIUS
153
the tendon of the biceps, and a smooth anterior surface in relation with a bursa
which is situated between the tendon and the tuberosity.
The body [corpus radii] or shaft is somewhat prismatic in form, gradually in-
creasing in size from the upper to the lower end, and slightly curved so as to be
concave toward the ulna. Three borders and three surfaces may be recognised.
Of the borders, the medial or interosseous crest [crista interossea] is best marked.
Commencing at the posterior edge of the tuberosity, its first part is round and in-
distinct, and receives the attachment of the oblique cord of the radius; it is con-
FiG. 181. — The Left Ulna and Radius. (Postero-lateral view.)
Triceps -yjy^^^
Articular capsule ^^mMi Olecranon
Subcutaneous surface
Lower limit of annular ligament "
Abductor pollicis longus-
Extensor pollicis brevis-
-Abductor pollicis longus
An aponeurosis is attached to this
border from which the flexor and
extensor carpi ulnaris, and flexor
digitorum profundus arise
- Extensor polHcis longus
Ulna
-Extensor indicis proprius
Grooves for abductor longus and ex-
tensor pollicis hrevis
For extensor carpi radialis longus^
and brevis ~~
Extensor pollicis longus-
-Ettensor quinti digiti proprius
-iiixtensor carpi ulnaris
^Ulnar collateral ligament
Extensor digitorum communis and Posterior Posterior radio-ulnar ligament
extensor indicis proprius radio-carpal
ligament
tinned as a sharp ridge which divides near the lower extremity to become continu-
ous with the anterior and posterior margins^of the ulnar notch (sigmoid cavity).
The prominent ridge and the posterior of the two lower lines give attachment to
the interosseous membrane, whilst the triangular surface above the ulnar notch
receives a part of the pronator quadratus. The interosseous crest separates the
volar from the dorsal surface. The volar border [margo volaris] runs from the
tuberosity obliquely downward to the lateral side of the bone and then descends
vertically to the anterior border of the styloid process. The upper third, consti-
154
THE SKELETON
tuting the oblique line of the radius, gives origin to the radial head of the flexor
digitorum suhlimis, limits the insertion of the supinator above, and the origin
of the flexor pollicis longus below. The volar border separates the volar from
the lateral surface. The dorsal border extends from the back of the tuberosity to
the prominent middle tubercle on the posterior aspect of the lower extremity.
Separating the lateral from the dorsal surface, it is well marked in the middle
third, but becomes indistinct above and below.
Surfaces. — The volar (or anterior) surface is narrow and concave above; broad,
flat, and smooth below. The upper two-thirds is occupied chiefly by the flexor
pollicis longus and a little less than the lower third by the pronator quadratus. Near
Fig. 182. — Articulae Facets on the Lower End op Left Radius and Ulna.
Posterior
For naviculi
For Iunat(
styloid process of ulna
Head of ulna : it articulates with
the interarticular fibro-cartilage
of the wrist-joint
the junction of the upper and middle thirds of the volar surface is the nutrient fora-
men, directed upward toward the proximal end of the bone. It transmits a
branch of the volar interosseous artery. The lateral surface is rounded above
and affords insertion to the supinator; marked near the middle by a rough, low,
vertical ridge for the pronator teres; smooth below, where the tendons of the exten-
sor carpi radialis longus and brevis lie upon it, and where it is crossed by the
abductor pollicis longus and extensor pollicis brevis. The dorsal (or posterior)
surface, smooth and rounded above, is covered by the supinator; grooved longi-
tudinally in the middle third for the abductor pollicis longus and the extensor pollicis
Fig. 183. — Dorsal View op the Lower End op the Radius and Ulna.
Insertion of brachio -radialis
Abductor pollicis longus and
ext. pollicis brevis i
Extensor carpi radialis longus |
and brevis r
Tubercle for posterior annular- — p-j
ligament fcii^
Extensor pollicis longus \\j
styloid process
Ext. digitorum communis and
extensor indicis proprius
Extensor quinti digiti proprius
lies in the groove between the
radius and ulna
Extensor carpi ulnaris
Styloid process
brevis; the lower third is broad, rounded, and covered by tendons. The line which
forms the upper limit of the impression for the abductor pollicis longus is known
as the posterior oblique line.
The lower extremity of the radius is quadrilateral; its carpal surface [facies
articularis carpea] is articular and divided by a ridge into a medial quadrilateral
portion, concave for articulation with the lunate bone; and a lateral triangular
portion, extending onto the styloid process for articulation with the navicular
(scaphoid) bone. The medial surface, also articular, presents the ulnar notch
(sigmoid cavity) for the reception of the rounded margin of the head of the ulna.
To the border separating the ulnar and carpal articular surfaces the base of the
THE ULNA
155
articular disc is attached, and to the anterior and posterior borders, the anterior
and posterior radio-ulnar ligaments respectively. The anterior surface is raised
into a prominent area for the anterior ligament of the wrist-joint. The lateral
surface is represented by the styloid process, a blunt pyramidal eminence, to the
base of which the hrachio-radialis is inserted, whilst the tip serves for the attach-
ment of the radial (external) collateral ligament of the wrist. Its lateral surface
is marked by two shallow furrows for the tendons of the abductor pollicis longus
and extensor pollicis brevis. The posterior surface is convex, and marked by three
prominent ridges separating three furrows. The posterior annular ligament is
attached to these ridges, thus forming with the bone a series of tunnels for the
passage of tendons.
The most lateral is broad, shallow, and frequently subdivided by a low ridge. The lateral
subdivision is for the extensor carpi radialis longus, the medial for the extensor carpi radialis
brevis The middle groove is narrow and deep for the tendon of the extensor pollicis longus.
The most medial is shallow and transmits the extensor indicts proprius, the extensor digitorum
communis, the dorsal branch of the interosseous artery, and the dorsal interosseous nerve.
When the radius and ulna are articulated, an additional groove is formed for the tendon of the
extensor quinti digiti proprius.
Ossification. — The radius is ossified from a centre which appears in the middle of the shaft
in the eighth week of intra-uterine hfe and from two epiphysial centres which appear after birth.
The nucleus for the lower end appears in the second year, and that for the upper end, which
forms simply the disc-shaped head, in the fifth year. The head unites with the shaft at the
seventeenth year, whilst the inferior epiphysis and the shaft join about the twentieth year.
THE ULNA
The ulna (figs. 180, 181, 189) is a long, prismatic bone, thicker above than
below, on the medial side of the forearm and parallel with the radius, which it
Fig. 184. — Upper End of Left Ulna. (Lateral view.)
Olecranon-
Semilunar notch
Coronoid process
Annular ligament
Flexor digitorum profundu
Radial notch
Oblique ligament iPilI) HI S Supinator
Interosseous membn
exceeds in length by the extent of the olecranon process. It articulates at the
upper end with the humerus, at the lower end indirectly \vith the carpus, and on
the lateral side with the radius. It is divisible into a shaft and two extremities.
The upper extremity is of irregular shape and forms the thickest and strongest
part of the bone. The superior articular surface is concave from above dowTiward,
convex from side to side, and transversely constricted near the middle. It belongs
156
THE SKELETON
partly to the olecranon, the thick upward projection from the shaft, and partly
to the coronoid process, whicli projects horizontally forward from the front of the
ulna. This semilunar excavation forms the semilunar notch (greater sigmoid
cavity) and articulates with the trochlear surface of the humerus. The olecranon
is the large curved eminence forming the highest part of the bone.
The superior surface of the olecranon, uneven and somewhat quadrilateral in shape, receives
behind, where there is a rough impression, the insertion of the triceps, and along the anterior
margin the articular capsule of the elbow-joint. The posterior surface, smooth and triangular
in outline, is separated from the skin by a bursa. The anterior surface, covered with cartilage
in the recent state, is dii'ected downward and forward, and its margins give attachment to the
articular capsule of the elbow-joint. This surface, as already noticed, forms the upper and back
part of the semilunar notch. On the medial surface of the olecranon is a tubercle for the origin
of the ulnar head of the flexor carpi ulnaris, and in front of this a fasciculus of the ulnar collateral
ligament of the elbow-joint is attached to the bone; the lateral surface is rough, concave, and
gives insertion to a part of the anconeus. The extremity of the olecranon lies during extension
of the elbow in the olecranon fossa of the humerus.
Fig. 185. — Ossification of the Radius and Ulna; the Figure also shows the Relations
OP THE Epiphysial and Capsular Lines.
Appears at the fifth year ; fuses at the
seventeenth year
Appears at the second year; fuses at
the twentieth year
The coronoid process, forming the lower and anterior part of the semilunar
notch, has a superior articular surface continuous with the anterior surface of the
olecranon, and, like it, covered with cartilage. The inferior aspect is rough and
concave, and gives insertion to the brachialis.
It is continuous with the volar surface of the shaft, and near the junction of the two is a
rough eminence, named the tuberosity of the ulna, which receives the attachment of the obhque
cord of the radius and the insertion of the brachialis. The medial side presents above a smooth
tubercle for the origin of the ulnar portion of the flexor digitorum suhlimis, and a ridge below
for the lesser head of the pronator teres and the rounded accessory bundle of the flexor pollicis
longus, whilst immediately behind the subhmis tubercle there is a triangular depressed surface
for the upper fibres of the flexor digitorum profundus.
THE ULNA
157
On the lateral surface is the radial notch (lesser sigmoid cavity), an oblong
articular surface which articulates with the circumference of the head of the radius,
the anterior and posterior margins of which afford attachment to the annular
ligament and the radial collateral ligament of the elbow-joint. In flexion of the
elbow the tip of the process is received into the coronoid fossa of the humerus.
The body [corpus ulnae] or shaft throughout the greater part of its extent is
three-sided, but tapers toward the lower extremity, where it becomes smooth and
rounded. It has three borders and three surfaces. Of the three borders, the
lateral, the interosseous crest, is best marked. In the middle three-fifths of the
shaft it is sharp and prominent, but becomes indistinct below; above it is contin-
ued by two lines which pass to the anterior and posterior extremities of the radial
notch and enclose a depressed triangular area (bicipital hollow), the fore part of
which lodges the tuberosity of the radius and the insertion of the biceps tendon
during pronation of the hand, while from the posterior part the supinator takes
origin. The interosseous crest separates the volar from the dorsal surface and
gives attachment by the lower four-fifths of its extent to the interosseous mem-
brane. The volar border is directly continuous with the medial edge of the rough
surface for the brachialis and terminates inferiorly in front of the styloid process.
Fig. 186. — Upper End of Ulna Showing Two Epiphyses. (E. Faweett.)
" Beak centre
Scale on summit of olecranon
t^^WMwk 1
Semilunar notch
Throughout the greater part of its extent it is smooth and rounded, and affords
origin to the flexor digitorum profundus and the pronator quadratus. It separates
the volar from the medial surface. The dorsal border commences above at the
apex of the triangular subcutaneous area on the back of the olecranon, and takes a
sinuous course to the back part of the styloid process. The upper three-fourths
gives attachment to an aponeurosis common to three muscles, viz., the flexor and
extensor carpi ulnaris and the. flexor digitorum profundus. This Isorder separates
the medial from the dorsal surface.
Surfaces. — The volar (or anterior) surface is grooved in the upper three-
fourths of its extent for the origin of the flexor digitorum profundus, narrow and
convex below, for the origin of the pronator quadratus. The upper limit of the
area for the latter muscle is sometimes indicated by an oblique line — the pronator
ridge. Near the junction of the upper and middle thirds of the anterior surface is
the nutrient foramen, directed upward toward the proximal end of the bone. It
transmits a branch of the volar interosseous artery. The medial surface, smooth
and rounded, gives attachment, on the upper two-thirds, to the flexor digitorwn
profundus, whereas the lower third is subcutaneous. The dorsal (or posterior)
surface, directed laterally as well as backward, presents at its upper part the
oblique line of the ulna running from the posterior extremity of the radial notch
to the dorsal border.
158
THE SKELETON
The oblique line gives attachment to a few fibres of the supinator and marks off the posterior
surface into two unequal parts. That above the hne, much the smaDer of the two, receives the
insertion of the anconeus. The more extensive part below is subdivided by a vertical ridge
into a medial portion, smooth, and covered by the extensor carpi ulnaris, and a lateral portion
which gives origin to three muscles, viz., the abductor pollicis longus, the extensor pollicis longus
and the extensor indicis proprius, from above downward.
The lower extremity of the uhia is of small size and consists of two parts, the
head and the styloid process, separated from each other on the inferior surface by a
groove into which the apex of the articular disc is inserted. That part of the head
adjacent to the groove is semilunar in shape and plays upon the articular disc
which thus excludes the ulna from the radio-carpal or wrist-joint. The margin of
the head is also semilunar, and is received into the ulnar notch of the radius. The
styloid process projects from the medial and back part of the bone, and appears
as a continuation of the dorsal border. To its rounded summit the ulnar collateral
ligament of the wrist-joint is attached, and its dorsal surface is grooved for the
passage of the tendon of the extensor carpi ulnaris. Immediately above the
articular margin of the head the anterior and posterior radio-ulnar ligaments are
attached in front and behind.
Fig. 187. — The Left Radius and Ulna in Pronation. (Anterior view.)
Ossification. — The ulna is ossified from three centres. The primary nucleus appears near
the middle of the shaft in the eighth week of intra-uterine life. At birth the inferior extremity
and the greater portion of the olecranon are cartilaginous. The "nucleus for the lower end ap-
pears during the fourth year and the epiphysis joins with the shaft from the eighteenth to the
twentieth year. The greater part of the olecranon is ossified from the shaft, but an epiphysis
is subsequently formed from a nucleus which appears in the tenth year.
The epiphysis varies in size, and may be either scale-like and form a thin plate on the sum-
mit, or involve the upper fourth of the olecranon and the corresponding articular surface. In
the latter case the epiphysis is probably composed of two parts fused together: (1) The scale
on the summit of the olecranon process, and (2) the beak centre which enters into the formation
of the upper end of the semilunar notch (see fig. 186). The epiphysis unites to the shaft in the
sixteenth or seventeenth year.
THE CARPUS
159
THE CARPUS
The carpus (figs. 188, 189) consists of eight bones, arranged in two rows, four
bones in each row. Enumerated from the radial to the ulnar side, the bones of
the proximal row are named navicular (scaphoid), lunate (semilunar), triquetral
(cuneiform), and pisiform; those of the distal row, greater multangular (trape-
zium), lesser multangular (trapezoid), capitate (os magnum), and hamate
(unciform) .
When the bones of the carpus are articulated, they form a mass somewhat quad-
rangular in outline, wider below than above, and with the long diameter trans-
verse. The dorsal surface is convex and the volar surface concave from side to
side. The concavity is increased by four prominences, which project forward, one
Fig. 188. — Bones of the Left Hand. (Dorsal surface.)
Lunate
Extensor carpi
radialis longus
Extensor carpi,
radialis brevis
Extensor digitorum communis
Extensor digitorum communis
Third, ungual, or terminal phalanx
from each extremity of each row. On the radial side are the tuberosity of the
navicular and the ridge of the greater multangular; on the ulnar side, the pisiform
and the hook of the hamate. Stretched transversely between these prominences,
in the recent state, is the transverse carpal ligament forming a canal for the passage
of the flexor tendons and the median nerve into the palm of the hand. The proxi-
mal border of the carpus is convex and articulates with the distal end of the
radius and the articular disc. The pisiform, however, takes no share in this ar-
ticulation, being attached to the volar surface of the triquetral. The distal border
forms an undulating articular surface for the bases of the metacarpal bones. The
160
THE SKELETON
line of articulation between the two rows of the carpus is concavo-convex from side
to side, the lateral part of the navicular being received into the concavity formed
by the greater multangular, lesser multangular, and capitate, and the capitate
and hamate into that formed by the navicular, lunate, and triquetral bones.
Fig. 189. — -Bones of the Left Hand. (Volar surface.)
Adductor poUicis obliquus Abductor polUcis brevis
Flexor carpi ulnaris
Abductor digiti
quinti
Flexor brevis and
opponens digiti
quinti
Flexor carpi ulnaris
Adductor pollicis
transversus
Opponens digiti
quinti
Opponens and flexor brevis pollicis
Occasional insertion into greater
multangular
Abductor pollicis longus
carpi radialis
ep head of flexor pollicis brevis
(ist volar interosseus)
Opponens pollicis
iexor brevis and
abductor poUicis
Abductor pollicis and
ist volar interosseus
Abductor and
flexor brevis
digiti quinti
The individual carpal bones have several points of resemblance. Each bone
(excepting the pisiform) has six surfaces, of which the anterior or volar and poste-
rior or dorsal are rough for the attachment of ligaments, the volar surface being
the broader in the proximal row, the dorsal surface in the distal row. The supe-
rior and inferior surfaces are articular, the former being generally convex and the
latter concave. The lateral surfaces, when in contact with adjacent bones, are
also articular, but otherwise rough for the attachment of ligaments. Further,
the whole of the carpus is cartilaginous at birth and each bone is ossified from a
single centre.
The Navicular
The navicular [os naviculare] or scaphoid (fig. 190) is the largest bone of the
proximal row, and so disposed that its long axis runs obhquely downward and
lateralward.
The superior surface is convex and somewhat triangular in shape for articulation with the •
lateral facet on the distal end of the radius. The inferior surface, smooth and convex, is divided
THE CARPUS
161
into two parts by a ridge running from before backward. The lateral part articulates with the
greater multangular, the medial with the lesser multangular. The volar surface, rough and con-
cave above, is elevated below into a prominent tubercle for the attachment of the transverse
carpal ligament and the abductor pollicis brevis. The dorsal surface is narrow, being reduced
Fig. 190. — The Left Naviculae
For lunate
For ligament
For greater multangular
For lesser multangular-
to a groove running the whole length of the bone; it is rough and serves for the attachment
of the dorsal radio-carpal ligament. The medial surface is occupied by two articular facets,
of which the upper is crescentio in shape for the lunate bone, whilst the lower is deeply concave
for the reception of the head of the capitate. The lateral surface is narrow and rough for the
attachment of the radial collateral ligament of the wTist-joint.
Articulations. — With the radius above, greater and lesser multangular below, lunate and
capitate medially.
The Lunate
The lunate [os luuatum] or semilunar (fig. 191), placed in the middle of the
proximal row of the carpus, is markedly crescentic in outline.
The superior surface is smooth and oonve.x and articulates with the medial of the two facets
on the distal end of the radius. The inferior surface presents a deep concavity divided into two
parts by a line running from before backward. Of these, the lateral and larger articulates with
the capitate; the medial and smaller with the hamate. The volar surface is large and convex,
Fig. 191. — The Left Lunate.
For triquetral-
the dorsal surface narrow and flat, and both are rough for the attachment of ligaments. The
medial surface is marked by a smooth quadrilateral facet for the base of the triquetral. The
lateral surface forms a narrow crescentic articular surface for the lunate.
Articulations. — With the radius above, capitate and hamate below, navicular laterally
and triquetral medially.
The Triquetral
The triquetral [os triquetrum] or cuneiform (fig. 192) is pyramidal in shape
and placed obliquely, so that its base looks upward and laterallj^ and the apex
downward and medially.
Fig. 192. — The Left Triquetral.
For lunate "
For pisiform
For hamate
The superior surface presents laterally near the base a small, convex articular facet which
plays upon the articular disc interposed between it and the distal end of the ulna, and medially
a rough non-articular portion for ligaments. The inferior surface forms a large, triangular
undulating facet for articulation with the hamate. The volar surface can be readily recognised
by the conspicuous oval facet near the apex for the pisiform bone. The dorsal surface is rough
for the attachment of ligaments. The medial and lateral surfaces are represented by the base
and the apex of the pyramid. The base is marked by a flat quadrilateral facet for the lunate.
The apex forms the lowest part of the bone and is roughened for the attachment of the ulnar
collateral ligament of the WTist.
Articulations. — With the pisiform in front, lunate laterally, hamate below, articular disc
above.
162 THE SKELETON
The Pisiform
The pisiform [os pisiform e] (fig. 193), the smallest of the carpal bones, is in
many of its characters a complete contrast to the rest of the series. It deviates
from the general type in its shape, size, position, use, and development. Forming
a rounded bony nodule with the long axis directed vertically, it is situated on a
plane in front of the oth^r bones of the carpus.
Fig. 193. — The Left Pisiform.
For triquetral-
On the dorsal surface is a single articular facet for the triquetral which reaches to the upper
end of the bone, but leaves a free non-articular portion below. The volar surface, rough and
rounded, gives attachment to the transverse carpal ligament, the flexor carpi ulnaris, the ab-
ductor quinti digiti, the piso-metacarpal and the piso-hamate ligaments. The median and lateral
surfaces are also rough and the lateral presents a shallow groove for the ulnar artery. It is
usually considered that the pisiform is a sesamoid bone developed in the tendon of the ^ea;or
carpi ulnaris, though by some writers it is regarded as part of a rudimentary digit.
The Greater Multangular
The greater multangular [os multangulum ma jus] or trapezium (fig. 194),
situated between the navicular and first metacarpal, is oblong in form with the
lower angle prolonged downward and medially.
Fig. 194. — The Left Greater Multangular.
-The ridge
For navicular
For lesser multangular
For second metacarpal
■Groove for flexor carpi radialis
'For first metacarpal
The superior surface is concave and directed upward and medially for articulation with the
lateral of the two facets on the distal surface of the navicular, and on the inferior surface is a
saddle-shaped facet for the base of the first metacarpal. The volar surface presents a prominent
ridge with a deep groove on its medial side which transmits the tendon of the^exor carpi radialis.
The ridge gives attachment to the transverse carpal ligament, the abductor pollicis brevis, the
opponens pollicis, and occasionally a tendinous slip of insertion of the abductor pollicis longus.
The dorsal and lateral surfaces are rough for ligaments. The medial surface is divided into
two parts by a horizontal ridge. The upper and larger portion is concave and articulates with
the lesser multangular; the lower — a small flat facet on the projecting lower angle — articulates
with the base of the second metarcarpal.
Articulations. — With the navicular above, first metacarpal below, the lesser multangular
and second metacarpal on the medial side.
The Lesser Multangular
The lesser multangular [os multangulum minus] or trapezoid (fig. 195), the
smallest of the bones in the distal row, is somewhat wedge-shaped, with the
broader end dorsally and the narrow end ventrally.
Fig. 195. — The Left Lesser Multangular.
Volar surface.
For greater multangular
For second metacarpal
The superior surface is marked by a small, quadrilateral, concave facet, for the media
of the two facets on the lower surface of the navicular. The inferior surface is convex from side
to side and concave from before backward, forming a saddle-shaped articular surface for the
base of the second metacarpal. Of the volar and dorsal surfaces, the former is narrow and rough.
THE CARPUS
163
the latter broad and rounded, constituting the widest sui-face of the bone, and both are rough
for the attachment of ligaments. The lateral surface slopes downward and medially and is
convex for articulation with the corresponding sm-face of the greater multangular. On the
medial surface in front is a smooth flat facet for the capitate; elsewhere it is rough for ligaments.
Articulations. — With the navicular above, second metacarpal below, greater multangular
laterally, and the capitate medially.
The Capitate
The capitate [os capitatum] or os magnum (fig. 196) is the largest bone of the
carpus. Situated in the centre of the wrist, the upper expanded portion, globular
in shape and known as the head, is received into the concavity formed above by
the navicular and lunate. The cubical portion below forms the body, whilst the
intermediate constricted part is distinguished as the neck.
For lunati
For navicular'
Fig. 196. — The Left Capitate.
tacarpal
Of the six surfaces, the superior is smooth and convex, elongated from before backward
for articulation with the concavity of the lunate bone. The inferior surface is divided into
three unequal parts by two ridges. The middle portion, much the larger, articulates with the
base of the third metacarpal; the lateral, narrow and concave, looks lateral as well as downward
to articulate with the second metacarpal, whilst the medial portion is a small facet, placed on the
projecting angle of the bone dorsally, for the fom'th metacarpal bone. The volar surface is
convex and rough, giving origin to fibres of the oblique adductor pollicis; the dorsal surface is
broad and deeply concave. Thelateral surface presents, from above downward: — (1) a smooth
convex sm-face, forming the outer aspect of the head, with the superior surface of which it is
continuous, for articulation with the navicular; (2) a groove representing the neck, indented
for hgaments; (3) a small facet, flat and smooth, for articulation with the lesser multangular.
Behind this facet is a rough area for attachment of an interosseous ligament. The medial
surface has extending along its whole hinder margin an oblong articular surface for the hamate;
the lower part of this smooth area sometimes forms a detached facet. The volar part of the
surface is rough for an interosseous ligament.
Articulations. — With the lunate and navicular above, second, third, and fourth meta-
carpals below, lesser multangular laterally, and hamate medially.
The Hamate
The hamate [os hamatum] or unciform (fig. 197) is a large wedge-shaped bone,
bearing a hook-like process, situated between the capitate and triquetral, with
the base directed downward and resting on the two medial metacarpals.
Fig. 197. — The Left Hamate.
Hamulus—
Fifth metacarpal-
Fourth metacarpal-
The apex of the wedge forms the narrow superior surface, directed upward and laterally
for articulation with the lunate. The inferior surface or base is divided bj' a ridge into two
(juadrilateral facets for the fourth and fifth metacarpal bones. The volar svu-face is triangular
in outline and presents at its lower part a prominent hamulus (unciform process), a hook-like
eminence, projecting forward and curved toward the carpal canal. It is flattened from side
to side so as to present two surfaces, two borders, and a free extremity. To the latter the trans-
verse carpal ligament and the flexor carpi ulnaris (by means of the piso-hamate ligament) are
attached, whilst the medial surface affords origin to the flexor brcvis and the opponens digili quinli.
The lateral surface is concave and in relation to the flexor tendons. The dorsal surface is
triangular and rough for ligaments. The lateral surface has extending along its upper and
164
THE SKELETON
hinder edges a long flat surface, wider above than below, for articulation with the capitate.
In front of this articular facet the surface is rough for the attachment of an interosseous liga-
ment. The medial surface is oblong and undulating, i. e., concavo-conve.x from base to apex,
for articulation with the triquetral.
Articulations. — With the triquetral, lunate, capitate, and the fourth and fifth metacarpal
bones.
Ossification of the Carpal Bones
Capitate first year
Hamate second year
Triquetral third year
Lunate fourth year
Greater multangular fifth year
Navicular sixth }rear
Lesser multangular eighth year
Pisiform twelfth year
Additional carpal elements are occasionally met with. The os centrale occurs normally in the
carpus of many mammals, and in the human fcetus of two months it is present as a small carti-
laginous nodule which soon becomes fused with the cartilage of the navicular. Failure of
fusion, with subsequent ossification of the nodule, leads to the formation of an os centrale in
the human carpus which is then found on the dorsal aspect, between the navicular, capitate,
and lesser multangular. In most individuals, however, it coalesces with the navicular or under-
goes suppression.
An additional centre of ossification, leading to the formation of an accessory carpal element,
occasionally appears in connection with the greater multangular and the hamate. An accessory
element {os Vesalianum) also occurs occasionally in the angle between the hamate and the fifth
metacarpal, and others occur between the second and third metacarpals and the lesser multan-
gular and capitate.
THE METACARPALS
The metacarpus (figs. 188, 189) consists of a series of five cylindrical bones
[ossa metacarpalia], well described as 'long bones in miniature.' Articulated
with the carpus above, they descend, slightly diverging from each other, to sup-
port the fingers, and are numbered from the lateral to the medial side. With
the exception of the first, which in some respects resembles a phalanx, they con-
form to a general type.
A typical metacarpal bone presents for examination a shaft and two extrem-
ities. The body or shaft is prismatic and curved so as to be slightly convex
toward the back of the hand. Of the three surfaces, two are lateral in position,
Fig. 198. — The First (Left) Metacarpal.
separated in the middle part of the shaft by a prominent palmar ridge, and con-
cave for the attachment of interosseous muscles. The third or dorsal surface
presents for examination a large, smooth, triangular area with the base below and
apex above, covered in the recent state by the extensor tendons of the fingers, and
two sloping areas, near the carpal extremity, also for interosseous muscles. The
triangular area is bounded by two hnes, which commence below in two dorsal
tubercles, and, passing upward, converge to form a median ridge situated be-
tween the sloping areas on either side. A little above or below the middle of the
shaft, and near the volar border, is the medullary foramen, entering the bone
obliquely upward. The base or carpal extremity, broader behind than in front,
is quadrilateral, and both palmar and dorsal surfaces are rough tor hgaments; it
articulates above with the carpus and on each side with the adjacent metacarpal
bones. The head [capitulum] or digital extremity presents a large rounded ar-
ticular surface, extending further on the palmar than on the dorsal aspect, for
THE METACARPALS
165
articulation with the base of the first phalanx. The volar surface is grooved for
the flexor tendons and raised on each side into an articular eminence. On each
side of the head is a prominent tubercle, and immediately in front of this a well-
marked fossa, to both of which the collateral hgament of the metacarpo-phalangeal
joint is attached.
Fig. 199. — The Second (Left) Metacarpal.
For greater multangular
I h
For third metacarpal
■For capitate
The second is the longest of all the metacarpal bones, and the third, fourth,
and fifth successively decrease in length. The several metacarpals possess dis-
tinctive characters by which they are readily identified.
The first metacarpal (fig. 198) is the shortest and widest of the series. Diverging from the
carpus more widely than any of the others the palmar surface is directed medially and marked
Fig. 200. — The Third (Left) Metacarp.^.l.
For second metacarpal
For fourth metacarpal
Styloid process
bj' a ridge placed nearer to the medial border. The lateral portion of the surface slopes gently
to the lateral border and gives attachment to the opponens poUicis; the medial portion, the
smaller of the two, slopes more abruptly to the medial border, is in relation to the deep head of
the flexor pollicis brevis, and presents the nutrient foramen, directed downward toward the
head of the bone and transmitting a branch of the arteria princeps poUicis. The dorsal
surface, wide and flattened, is in relation to the tendons of the extensor poUicis longus and brevis.
166
THE SKELETON
The base presents a saddle-shaped articular surface for the greater multangular, prolonged in
front into a thin process. There are no lateral facets, but laterally a small tubercle receives
the insertion of the abductor pollicis longus. Medially is a rough area from which fibres of the
inner head of the flexor pollicis brevis take origin. The margin of the articular surface gives
attachment to the articular capsule of the carpo-metacarpal joint. The inferior extremity or
head is rounded and articular, for the base of the first phalanx; the greatest diameter is from
side to side and the surface is less convex than the corresponding surface of the other metacarpal
bones. On the volar surface it presents two articular eminences corresponding to the two
sesamoid bones of the thumb. Of the two margins, the medial gives origin to the lateral
head of the first dorsal interosseous, the lateral receives fibres of insertion of the opponens pollicis.
Fig. 201. — The Fouhth (Left) Metacarpal.
For third metacarpal
For capitate
For fifth metacarpal
The second metacarpal (fig. 199). — The distinctive features of the four remaining meta-
carpals are almost exclusively confined to the carpal extremities. The second is easily recog-
nised by its deeply cleft base. The terminal surface presents three articular facets, arranged
as follows, from lateral to medial border : — (1) a small oval facet for the greater multangular; (2)
a hollow for the lesser multangular; and (3) an elongated ridge for the capitate. The dorsal
surface is rough for the insertions of the extensor carpi radialis longus and a part of the extensor
carpi radialis brevis; the palmar surface receives the insertion of the flexor carpi radialis and
gives origin to a few fibres of the oblique adductor pollicis. The lateral aspect of the extremity
is rough and non-articular; the medial surface bears a bilobed facet for the third metacarpal.
Fig. 202. — The Fifth (Left) Metacarpal.
Fourth metacarpal'
The shaft of the second metacarpal gives attachment to three interosseous muscles, and the
nutrient foramen, directed upward on the ulnar side, transmits a branch of the second volar
metacarpal artery.
The third metacarpal (fig. 200) is distinguished by the prominent styloid process projecting
upward from the lateral and posterior angle of the base. Immediately below it, on the dorsal
surface, is a rough impression for the extensor carpi radialis brevis. The carpal surface is
concave behind and convex in front, and articulates with the middle of the three facets on the
inferior surface of the capitate. On the lateral side is a bilobed articular facet for the second
metacarpal, and on the medial side two small oval facets for the fourth metacarpal. The volar
a.spect of the base is rough and gives attachment to fibres of the oblique adductor pollicis and
THE PHALANGES
167
sometimes a slip of insertion of the flexor carpi radialis. The shaft of the third metacarpal
serves for the origin of the transverse adductor pollicis and two interosseous muscles. The
nutrient foramen is directed upward on the radial side and transmits a branch of the second
volar metacarpal artery.
The fourth metacarpal (fig. 201) has a small base. The carpal surface presents two facets:
a medial, large and flat, for articulation with the hamate, and a small facet, at the lateral and
posterior angle, for the capitate. On the lateral side are two small oval facets for the correspond-
ing surfaces on the third metacarpal and a single concave facet on the medial side for the fifth
metacarpal. The shaft of the fourth metacarpal gives attachment to three interosseous muscles,
and the nutrient foramen, directed upward on the radial side, transmits a branch of the third
volar metacarpal artery.
The fifth metacarpal (fig. 202) is distinguished by a semilunar facet on the lateral side of
the base for the fourth metacarpal, and a rounded tubercle on the medial side for the extensor
carpi ulnaris, in place of the usual medial facet. The carpal surface is saddle-shaped for the
hamate; the palmar surface is rough for ligaments including the piso-metacarpal prolongation
from the flexor carpi ulnaris. The dorsal surface of the shaft presents an oblique line separating
a lateral concave portion for the fourth dorsal interosseous muscle from a smooth medial por-
tion covered by the extensor tendons of the little finger. The palmar surface gives attachment
laterally to the third palmar interosseous muscle and medially to the opponens digili quinti. The
nutrient foramen is directed upward on the radial side and transmits a branch of the fourth
volar metacarpal artery.
THE PHALANGES
The phalanges (fig. 203) are the bones of the fingers, and number in all fourteen.
Each finger consists of three phalanges distinguished as first or proximal, second
Fig. 203. — The Phalanges op the Third Digit op the Hand. (Dorsal view.)
[The arrows indicate the direction of the nutrient canals.]
Third terminal or ungual phalanx
Second phalanx
or middle, and third or distal. In the thumb, the second phalanx is wanting.
Arranged in horizontal rows, the phalanges of each row resemble one another
and differ from those of the other two rows. In all the phalanges the nutrient
canal is directed downward, toward the distal extremity.
First phalanx, — The shaft of a phalanx from the first row is flat on the palmar surface,
smooth and rounded on the dorsal surface, i. e., semi-cyUndrical in shape. The borders of the
palmar surface are rough for the attachment of the sheaths of the flexor tendons. The base
or metacarpal extremity presents a single concave articular surface, oval in shape, for the
168
THE SKELETON
convex head of the metacarpal bone. The distal extremity forms a pulley-like surface, grooved
in the centre and elevated at each side to form two miniature condyles, for articulation with
the base of a second phalanx.
Second phalanx. — The second phalanges are four in number and are shorter than those of
the first row, which they closely resemble in form. They are distinguished, however, by the
articular surface on the proximal extremity, which presents two shallow depressions, separated
by a ridge and corresponding to the two condyles of the first phalanx. The distal end for the
base of the third phalanx is trochlear or pulley-like, but smaller than that of the first phalanx.
The palmar surface of the shaft presents on each side an impressionSfor the tendon of the flexor
digitorum sublimis, and the dorsal aspect of the base is marked by a projection for the insertion
of the extensor digitorum communis.
Third phalanx. — A third phalanx is readily recognised by its small size. The proximal
end is identical in shape with that of a second phalanx, and bears a depression in front for the
tendon of the flexor digitorum profundus. The free, flattened and expanded distal extremity
presents on its palmar surface a rough semilunar elevation for the support of the pulp of the
finger. The somewhat horseshoe-shaped free extremity is known as the ungual tuberosity
[tuberositas unguicularis], and the bone is accordingly referred to as the ungual phalanx.
Ossification of. the Metacarpus and Phalanges
Each of the metacarpal bones and phalanges is ossified from a primary centre for the greater
part of the bone, and from one epiphysial centre. The primary nucleus appears from the eighth
to the tenth week of intra-uterine life. In four metacarpal bones the epiphysis is distal, whilst
Fig. 204. — Ossification of the Metacarpals and Phalanges.
Appears in th
Consolidates i
year
Epiphysis for base-
Metacarpal of thum^
Epiphysis for head
1 Appear in the third, and con-
J soiidate in the twentieth year
Appear between the third and
fifth year. Consolidate in
the eighteenth year
in the first metacarpal bone, and in all the phalanges, it is proximal. The epiphysial nuclei
appear from the third to the fifth year and are united to their respective shafts about the twen-
tieth year. In many cases the first metacarpal has two epiphyses, one for the base in the third
year and an additional one for the head in the seventh year, but the latter is never so large as
in the other metacarpal bones. The third metacarpal occasionally has an additional nucleus
for the prominent styloid process which may remain distinct and form a styloid bone, and traces
of a proximal epiphysis have been observed in the second metacarpal bone. In many of the
Cetacea (whales, dolphins, and porpoises) and in the seal, epiphyses are found at both ends of
the metacarpal bones and phalanges (Flower).
The ossification of a terminal phalanx is peculiar. Like the other phalanges, it has a pri-
mary nucleus and a secondary nucleus for an epiphysis. But whereas in other phalanges the
primary centre appears in the middle of the shaft, in the case of the distal phalanges the earthy
matter is deposited in the free extremity.
Sesamoid Bones
The sesamoid bones are small and rounded and occur imbedded in certain tendons where
they exert a considerable amount of pressure on subjacent bony structures. In the hand five
sesamoid bones are of almost constant occurrence, namely, two over the metacarpo-phalangeal
joint of the thumb in the tendons of the flexor pollicis brevis, one over the interphalangeal joint
of the thumb, and one over the metacarpo-phalangeal joints of the second and fifth fingers.
THE COXAL BONE 169
Occasionally sesamoids occur over the metacarpo-phalangeal joint of the third and fourth digits,
and an additional one may occur over that of the fifth.
Very rarely a sesamoid is developed in the tendon of the biceps over the tuberosity of the
radius.
B. THE BONES OF THE LOWER EXTREMITY
The bones of the lower extremity may be arranged in four groups correspond-
ing to the division of the limb into the hip, thigh, leg, and foot. In the hip is the
coxal or hip-bone, which constitutes the pelvic girdle [cingulum extremitatis
inferioris], and contributes to the formation of the pelvis; in the thigh is the femur;
in the leg, the tibia and fibula, and in the foot the tarsus, metatarsus, and phalanges.
Associated with the lower end of the femur is a large sesamoid bone, the patella
or knee-cap.
THE COXAL BONE
The coxal (innominate) bone or hip-bone [os coxse] (figs. 205, 206) is a large,
irregularly shaped bone articulated behind 'with the sacrum, and in front with its
fellow of the opposite side, the two bones forming the anterior and side walls of
the pelvis. The coxal bone consists of three parts, named ilium, ischium, and
pubis, which, though separate in early life, are firmly united in the adult. The
three parts meet together and form the acetabulum (or cotyloid fossa), a large,
cup-like socket situated near the middle of the lateral surface of the bone for
articulation with the head of the femur.
The ilium [os ilium] is the upper expanded portion of the bone, and by its
inferior extremity forms the upper two-fifths of the acetabulum. It presents for
examination three borders and two surfaces.
Borders. — When viewed from above, the thick crest [crista iliaca] or superior
border is curved somewhat like the letter /, being concave medially in front and
concave laterally behind. Its anterior extremity forms the anterior superior
iliac spine, which gives attachment to the inguinal (Poupart's) ligament and the
sartorius; the posterior extremity forms the posterior superior iliac spine and
affords attachment to the sacro-tuberous (great sacro-sciatic) ligament, the pos-
terior sacro-iliac ligament, and the multifidus. The crest is narrow in the middle,
thick at its extremities, and may be divided into an inner lip, an outer lip, and an
intermediate line. About two and a half inches from the anterior superior spine
is a prominent tubercle on its external lip.
The external lip of the crest gives attachment in front to the tensor fascia latw; along its
whole length, to the fascia lata; along its anterior half to the external oblique; and behind this,
for about an inch, to the latissimus dorsi. The anterior two-thirds of the intermediate line
gives origin to the internal oblique. The internal lip gives origin, by its anterior two-thirds, to
the iransversus; behind this is a small area for the quadratus lumborum, and the remainder
is occupied by the sacro-spinalis (erector spince). The internal lip, in the anterior two-thirds,
also serves for the attachment of the iliac fascia.
The anterior border of the ilium extends from the anterior superior iliac spine
to the margin of the acetabulum. Below the spine is a prominent notch from
which fibres of the sartorius arise, and this is succeeded by the anterior inferior
iliac spine, smaller and less prominent than the superior, to which the straight
head of the rectus and the ilio-femoral ligament are attached. On the medial side
of the anterior inferior spine is a broad, shallow groove for the ilio-psoas as it
passes from the abdomen into the thigh, limited below by the ilio-pectineal
eminence, which indicates the point of union of the ilium and pubis.
The posterior border of the ilium presents the posterior superior iliac spine,
and below this, a shallow notch terminating in the posterior inferior iliac spine
which corresponds to the posterior extremity of the auricular surface and gives
attachment to a portion of the sacro-tuberous (great sacro-sciatic) hgament.
Below the spine the posterior border of the ilium forms the upper limit of the
greater sciatic notch.
Surfaces. — The external surface or dorsum is concave behind, convex in front,
limited above by the thick superior border or crest, and traversed by three gluteal
lines.
170
THE SKELETON
The posterior gluteal line commences at the crest about two inches from the posterior
superior iliac spine and curves downward to the upper margin of the greater sciatic notch.
The space included between this ridge and the crest affords origin at its upper part to the
gluteus maximus, and at its lower part, to a few fibres of the piriformis, while the intermediate
portion is smooth and free from muscular attachment. The anterior gluteal line begins at
the crest, one inch behind its anterior superior iliac spine, and curves across the dorsum to
terminate near the lower end of the superior line, at the upper margin of the greater sciatic
notch. The surface of bone between this line and the crest is for the origin of the gluteus
medius. The inferior gluteal line commences at the notch immediately below the anterior
Fig. 205."
Insertion of external oblique
Internal oblique
Tensor fasicEe latee
Sartorius
-The Left Coxal or Hip-bone. (Lateral view.)
Posterior limit of external oblique
Latissimus dorsi
Crest of ilium
Posterior
superior iliac
spine
•informis
Posterior inferior
iliac spine
Greater sciatic (ilio-sci-
atic) notch
Pectineus
Rectus
abd
Pyramidali
Adducto
longu
Adducto
brevi
Descending ramus of
pubis
Gracilis
Ramus of ischium Obturator externus
superior iliac spine and terminates posteriorly at the front part of the greater sciatic notch-
The space between the anterior and inferior gluteal lines, with the exception of a small area
adjacent to the anterior end of the spine for the tensor fasciw latce, gives origin to the gluteus
minimus. Between the inferior gluteal line and the margin of the acetabulum the surface
affords attachment to the capsule of the hip-joint, and on a rough area (sometimes a depression)
toward its anterior part, to the reflected tendon of the rectus femoris.
The internal surface presents in front a smooth concave portion termed the
iliac fossa, which lodges the iliacus muscle. The fossa is limited below by linea
arcuata, the iliac portion of the terminal (iho-pectineal) line. This is a rounded
border separating the fossa from a portion of the internal surface below the line,
which gives attachment to the obturator internus and enters into the formation of
the minor (true) pelvis. Behind the iliac fossa the bone is uneven and presents
THE COXAL BONE
171
an auricular surface, covered with cartilage in the recent state, for articulation
with the lateral aspect of the upper portion of the sacrum; above the auricular
surface are some depressions for the posterior sacro-iliac ligaments and a rough
area reaching as high as the crest, from which parts of the sacro-spinalis {erector
spince) and vmltifidus take origin. The rough surface above the auricular facet is
known as the tuberosity of the ilium.
The ischium [os ischii] consists of a body, a tuberosity, and a ramus. The
body, which has somewhat the form of a triangular pyramid, enters superiorly into
Fig. 206. — The Left Coxal or Hip-bone. (Medial aspect.)
Quadratus lumborum
Transversus muscle and
iliac fasica
Auricular surface
Ant. inf. spine of ilium
Symphysial surface
Levator ani
Junction of pubis Cms penis and Sphincter Arcuate
and ischium Ischio- urethra ligament
cavernosas membranacese
the formation of the acetabulum, to which it contributes a little more than two-
fifths, and forms the chief part of the non-articular portion or floor. The inner
surface forms part of the minor (true) pelvis and gives origin to the obturator in -
ternus. It is continuous with the ilium a little below the terminal (ilio-pectineal)
line, and with the pubis in front, the line of junction with the latter being fre-
quently indicated in the adult bone by a rough line extending from the ilio-pec-
tineal eminence to the margin of the obturator foramen. The outer surface in
eludes the portion of the acetabulum formed by the ischium. The posterior sur-
face is broad and bounded laterally by the margin of the acetabulum and behind
172 THE SKELETON
by the posterior border. The capsule of the hip-j oint is attached to the lateral part
and the -pirijorniis, the great sciatic and posterior cutaneous nerves, the inferior
gluteal (sciatic) artery, and the nerve to the quadratus femoris lie on the surface
as they leave the pelvis. Inferiorly this surface is limited by the obturator groove,
which receives the posterior fleshy border of the obturator externus when the thigh
is flexed. Of the three borders, the external, forming the prominent rim of the
acetabulum, separates the posterior from the external surface and gives attach-
ment to the glenoid lip. The inner border is sharp and forms the lateral
boundary of the obturator foramen. The posterior border is continuous with the
posterior border of the ilium, with which it joins to complete the margin of the
great sciatic notch [incisura ischiadica major]. The notch is converted into a
foramen by the sacro-spinous (small sacro-sciatic) ligament, and transmits the
piriformis muscle, the gluteal vessels, the superior and inferior gluteal nerves, the
sciatic and posterior cutaneous nerves, the internal pudic vessels and nerve, and
the nerves to the obturator internus and quadratus femoris. Below the notch is
the prominent ischial spine, which gives attachment internally to the coccygeus
and levator ani, externally to the gemellus superior, and at the tip to the sacro-
spinous ligament. Below the spine is the small sciatic notch [incisura ischiadica
minor], covered in the recent state with cartilage, and converted into a foramen by
the sacro-tuberous (great sacro-sciatic) ligament. It transmits the tendon of the
obturator internus, its nerve of supply, and the internal pudic vessels and nerve.
The rami form the flattened part of the ischium which runs first downward,
then upward, forward and medially from the tuberosity toward the inferior
ramus of the pubis, with which it is continuous. The rami together form an L-
shaped structure with an upper vertical ramus [ramus superior] and a lower
horizontal ramus [ramus inferior]. The outer surface of the rami gives origin to
the adductor magyius and obturator externus; the inner surface, forming part of the
anterior wall of the pelvis, receives the crus penis (or clitoridis) and the ischio-
cavernosus, and gives origin to a part of the obturator internus. Of the two borders,
the upper is thin and sharp, and forms part of the boundary of the obturator
foramen; the lower is rough and corresponds to the inferior ramus. It is some-
what everted and gives attachment to the fascia of Colles, and the transversus
perinei. To a ridge immediately above the impression for the cms penis (or
clitoridis) and the ischio-cavernosus , the urogenital trigone (triangular ligament)
is attached. The posterior and inferior aspect of the superior ramus is an ex-
panded area forming the tuberosity [tuber ischiadicum].
The tuberosity is that portion of the ischium which supports the body in the sitting posture.
It forms a rough, thick eminence continuous with the inferior border of the infeiior ramus,
and is marked by an oblique line separating two impressions, an upper and lateral for the
semimembranosus, and a lower and medial for the common tendon of the biceps and semitendi-
nosus, while the lower part is markedly uneven and gives origin to the adductor magnus. The
upper border gives origin to the inferior gemellus; the inner border, sharp and. prominent, re-
ceives the sacro-tuberous (great sacro-sciatic) ligament, while the surface of the tuberosity
immediately in front is in relation with the internal pudic vessels and nerve. The outer
border gives origin to the quadratus femoris.
The pubis [os pubis] consists of a body and two rami — superior and inferior.
The body is somewhat quadrilateral in shape and presents for examination two
surfaces and three borders. The anterior surface looks downward, forward and
slightly outward, and gives origin to the adductor longus, the adductor brevis, the
obturator externus, and the gracilis. The posterior surface is smooth, looks into
the pelvis, and affords origin to the levator ani, the obturator internus, and the pubo-
prostatic ligaments. The upper border or crest of the body is rough and presents
laterally a prominent bony point, known as the tubercle [tuberculum pubicum]
or spine, for the attachment of the inguinal (Poupart's) ligament. The upper
border extends from the pubic tubercle medialward to the upper end of the
symphysis, with which it forms the angle of the pubis. The upper border is a
short horizontal ridge, which gives attachment to the rectus abdominis and pyram-
idalis. The medial border is oval in shape, rough, and articular, forming with
the bone of the opposite side the symphysis pubis [facies symphyseos]. The
lateral border is sharp and forms part of the boundary of the obturator foramen.
The inferior ramus, like the inferior ramus of the ischium, with which it is
continuous, is thin and flattened. To its anterior surface are attached the
THE COXAL BONE
173
adductor hrevis, adductor magnus, and obturator externus. The posterior surface
is smooth and gives attachment to the crus penis or clitoridis, the sphincter urethrce
(urogenitalis) , the obturator internus, and the urogenital trigone (triangular liga-
ment). The lateral border forms part of the circumference of the obturator
foramen, and the medial border forms part of the pubic arch and gives attach-
ment to the gracilis.
The superior ramus extends from the body of the pubis to the ilium, forming
by its lateral extremity the anterior one-fifth of the articular surface of the acetab-
ulum. It is prismatic in shape and increases in size as it passes laterally. Above
it presents a sharp ridge, the pecten or pubic portion of the terminal (ilio-pectineal)
line continuous with the iliac portion at the ilio-pectineal eminence, and affording
Fig. 207. — An Immature Coxal (Innominate) Bone, showing a Cotyloid Bone.
Tha cotyloid bone
attachment to the conjoined tendon [falx aponeurotica inguinalis], the lacunar
(Gimbernat's) hgament, the reflected inguinal ligament (fascia triangularis),
and the pubic portion of the fascia lata; the ihac portion of the terminal (ilio-
pectineal) line gives attachment to the psoas minor, the iliac fascia, and the pelvic
fascia. Immediately in front of the pubic portion of the line is the pectineal
surface; it gives origin at its posterior part to the pectineus, and is limited below
by the obturator crest, which extends from the pubic tubercle to the acetabular
notch. The inferior surface of the ascending ramus forms the upper boundary
of the obturator foramen and presents a deep groove [sulcus obturatorius] for the
passage of the obturator vessels and nerve. The posterior surface is smooth,
forms part of the anterior wall of the pelvic cavity, and gives attachment to a
few fibres of the obturator internus.
According to the BNA, the body [corpus ossis pubis] is the portion corresponding to the
acetabulum. The remainder of the bone is described as consisting of the ramus superior and
the ramus inferior, which meet at the symphysis. Thus the divisions according to the BNA
are different from those in the description above given.
The acetabulum is a circular depression in which the head of the femur is
lodged and consists of an articular and a non-articular portion. The articular
portion is circumferential and semilunar in shape [facies lunata], with the defi-
ciency in the lower segment. One-fifth of the acetabulum is formed bj^ the pubis,
two-fifths by the ischium, and the remaining two-fifths are formed by the ilium.
In rare instances the pubis may be excluded by a fourth element, the cotyloid
bone. The non-articular portion [fossa acetabuli] is formed mainly by the
ischium, and is continuous below with the margin of the obturator foramen.
The articular portion presents a lateral rim to which the glenoid lip is
attached, and a medial margin to which the synovial membrane which excludes
174
THE SKELETON
the ligamentum teres from the synovial cavity is connected. The opposite
extremities of the articular lunate surface which limit the acetabular notch are
united by the transverse ligament, and through the acetabular foramen thus
formed a nerve and vessels enter the joint.
The obturator (thyreoid) foramen is sHuated between the ischium and pubis.
Its margins are thin, and serve for the attachment of the obturator membrane.
At the upper and posterior angle it is deeply grooved for the passage of the obtu-
rator vessels and nerve.
Fig. 208. — The Pelvis of a Fcetus at Birth, to show the Three Portions of the
CoxAL Bones.
The nucleus for the pubis appears
bout the end of the fourth month
3 nucleus for the ischium appears
Q the third month
Blood-supply. — The chief vascular foramina of the coxal bone are found where the bone is
thickest. On the inner surface, the ilium receives twigs from the ilio-lumbar, deep circumflex
iliac, and obturator arteries, by foramina near the crest, in the iliac fossa, and below the terminal
line near the greater sciatic notch. On the outer surface the chief foramina are found below
the inferior gluteal line and the nutrient vessels are derived from the gluteal arteries. The
ischium receives nutrient vessels from the obturator, internal and external circumflex arteries,
and the largest foramina are situated between the acetabulum and the ischial tuberosity. The
pubis is supplied by twigs from the obturator, internal and external circumflex arteries, and
from the pubic branches of the common femoral artery.
Fig. 209. — Coxal or Hip-bone, showing Secondary Centres.
Appears at fifteen. Unites at twenty-
Appears at fifteen. Unites at twenty.
Appears at fifteen. Fuses at twenty
Fuses at twenty
Ossification. — The cartilaginous representative of the hip-bone consists of three distinct
portions, an iliac, an ischiatic, and a pubic portion; the iliac and ischiatio portions first unite
and later the pubic portion, so that eventually there is found a single cartilaginous mass. Early
in the second month a centre of ossification appears above the acetabulum for the ilium. A
little later a second nucleus appears below the cavity for the ischium, and this is followed in
the fourth month by a deposit in the pubic portion of the cartilage. At birth, the three nuclei
THE PELVIS
175
are of considerable size, but are surrounded by relatively wide tracts of cartilage; ossification
has, however, extended into the margin of the acetabulum. In the eighth j^ear the rami of the
pubis and ischium become united by bone, and in the tweKth year the triradiate cartilage which
separates the three segments of the bone in the acetabulum begins to ossify from several centres.
Of these, one is more constant than the others and is known as the acetabular nucleus. The
triangular piece of bone to which it gives rise is regarded as the representative of the cotyloid
or acetabular bone, constantly present in a few mammals. It is situated at the medial part of
the acetabulum and is of such a size as to exclude entirely the pubis from the cavity. With
this bone, however, it eventually fuses, and afterward becomes joined with the ilium and
Fig. 210. — Coxal or Hip-bone (Inner Surface) at the Eighth Year.
ischium, so that by the eighteenth or twentieth year the several parts of the acetabulum have
become united. In the fifteenth year other centres appear in the cartilage of the crest of the
ilium, the anterior inferior iliac spine, the tuberosity of the ischium, and the pubic pecten. The
epiphyses fuse with the main bone about the twentieth year. The fibrous tissue connected
with the tubercle of the pubis represents the epipubio bones of marsupials.
THE PELVIS
The pelvis (figs. 211, 212, 213, 214) is composed of four bones: the two coxal
or hip-bones, the sacrum, and the coccyx. The hip-bones form the lateral and
anterior boundaries, meeting each other in front to form the pubic symphysis
[symphysis ossium pubis]; posteriorly they are separated by the sacrum. The
interior of the pelvis is divided into the major and minor pelvic cavity.
The major (or false) pelvis is that part of the cavity which lies above the ter-
minal (ihopectineal) lines and between the iliac fossse. This part belongs really to
the abdomen, and is in relation with the hypogastric and iliac regions.
The minor (or true) pelvis is situated below the terminal (ilio-pectineal) lines.
The upper circumference, known as the superior aperture (inlet or brim) of the
pelvis, is bounded anteriorly by the tubercle and pecten of the pubis on each side,
posteriorly by the anterior margin of the base of the sacrum, and laterally by the
terminal lines. The inlet in normal pelves is heart-shaped, being obtusely pointed
in front; posteriorly it is encroached upon by the promontory of the sacrum. It
has three principal diameters; of these, the antero-posterior, called the conjugate
diameter [conjugata], is measured from the sacro-vertebral angle to the symphj^sis.
The transverse diameter represents the greatest width of the pelvic cavity. The
oblique diameter is measured from the sacro-iliac synchondrosis of one side to the
ilio-pectineal eminence of the other.
The cavity of the minor (true) pelvis is bounded in front by the pubes, behind
bjr the sacrum and coccj^x, and laterally by a smooth wall of bone formed in part
by the ilium and in part by the ischium. The cavity is shallow in front, where it
is formed by the pubes, and is deepest posteriorly.
176
THE SKELETON
The inferior aperture, or outlet, of the minor pelvis is verj' irregular, and en-
croached upon by three bony pi'ocesses: the posterior process is the coccyx, and
the two lateral processes are the ischial tuberosities. They separate three notches.
The anterior notch is the pubic arch, and is bounded on each side by the conjoined
rami of the pubes and ischium. Each of the two remaining gaps, bounded by the
Fig. 211.— The Male Pelvis.
ischium anteriorly, the sacrum and coccjrx posteriorly, and the ilium above, cor-
responds to the greater and lesser sciatic notches. These are converted into
foramina bj^ the sacro-tuberous (great sacro-sciatic) and sacro-spinous (small
sacro-sciatic) ligaments.
The position of the pelvis. — In the erect position of the skeleton the plane of the pelvic
inlet forms an angle with the horizontal plane, which varies in indi%dduals from 50° to 60°.
212. — The Female Pelvis.
The base of the sacrum in an average pelvis lies nearly ten centimetres (four inches) above the
upper margin of the symphysis pubis.
The axis of the pelvis.— This is an imaginary curved line drawn through the minor pelvis
at right angles to the planes of the inlet, cavity, "and outlet through then central points.
As the posterior wall, formed by sacrum and coccyx, is nearly five inches long and concave,
and the anterior waU at the symphysis pubis one one and a half to two inches long, it follows
that the axis must be cm-ved.
THE PELVIS
177
The average measurements of the diameters of the minor pehas in the three planes are
given below: —
Inlet...
Cavit}' .
Outlet .
Conjugate or
axtero-posterior.
a inches (10.6 cm.)
4i " (11.8 cm.)
3f " (9.0 cm.)
Oblique.
o inches (12.5 cm.)
5i " (13.0 cm.)
4i " (11.2 cm.)
Thaxsverse.
5t inches (13.0 cm.)
4J " (11.8 cm.)
4i " (10.6 cm.)
Fig. 213. — M.^le Pewis. (Lateral view.)
Fig. 214. — Female PEL-\as. (Lateral view.)
There is, however, a difference between the sexes, the diameters of the male pelvis in
general averaging slighth- less, and those of the female sUghtly greater than the figures above
given.
Differences according to sex. — There is a marked difference in the size and form of the
male and female pelvis, the pecularities of the latter being necessary to qualify it for its func-
tions in partm-ition. The various points of divergence may be tabulated as follows: —
M.\.LE.
Bones heavier and rougher.
Ilia less vertical.
Iliac fossEB deeper.
Major pehds relatively wider.
Minor pelvis deeper.
" " narrower.
Superior aperture move heart-shaped.
Symphysis deeper.
Tuberosities of ischia inflexed.
Pubic angle narrow and pointed.
Margins of ischio-pubic rami more everted.
Obturator foramen oval.
Sacrum narrower and more curved.
Capacity of minor pelvis less.
Female.
Bones more slender.
Ilia more vertical.
Iliac fossae shallower.
Major pelvis relatively narro'srer.
Minor pelvis shallower.
" " wider.
Superior aperture more oval.
Symphj'sis shallower.
Tuberosities of ischia everted.
Pubic arch wider and more rounded.
Margins of ischio-pubic rami less everted.
Obturator foramen triangular.
Sacrum wider and less curved.
Capacity of minor pelvis greater.
The sexual characters of the pelvis as shown by A. Thomson are manifest as early as the
fourth month of fcetal life.
Quite recently attention has been drawn by D. Derry to some special points in which the
OS coxaj differ in the two sexes, and two figures are shown here in which one of these points is
clearly brought out. It will be seen that the great sciatic notch is larger in the female, and
that the sacrum projects less forward at its apex. Moreover the facies auricularis is smaller
whilst below and in front of this surface, the sulcus preauricularis, a depression for the attach-
ment of the ligamenta sacroiliaca anteriora, is usualh- more pronounced.
In comparison with the pelves of lower animals, which, speaking generally, are elongated
and narrow, the human pelvis is characterised by its breadth, shallowness, and great capacity.
Differences are also to be recognised in the form of the pelvis in the various races of mankind, the
most important being the relation of the antero-posterior to the transverse diameter, measured
at the inlet. This is expressed bj' the pelmc index = —^^-^r.
transverse diameter
In the average European male the index is about 80; in the lower races of mankind, 90 to 95.
Pelves with an index below 90 are platypellic, from 90 to 95 are mesatipellic, and above 95
dolichopellic. (Sir WiUiam Turner.)
178 THE SKELETON
THE FEMUR
The femur or thigh bone (figs. 215, 216) is the largest and longest bone in the
skeleton, and transmits the entire weight of the trunk from the hip to the tibia.
In the erect posture it inclines from above downward and medially, approaching
at the lower extremity its fellow of the opposite side, but separated from it above
by the width of the true pelvis. It presents for examination a superior extremity,
including the head, neck, and two trochanters, an inferior extremity, expanded
laterally into two condyles, and a shaft.
The upper extremity is surmounted by a smooth, globular portion called the
head, forming more than half a sphere, directed upward and medially for articu-
lation with the acetabulum. With the exception of a small rough depression, the
fovea, for the ligamentum teres, a little below and behind the centre of the head,
. its surface is covered with cartilage in the recent state. The head is connected
with the shaft by the neck, a stout rectangular column of bone which forms with
the shaft, in the adult, an angle of about 125*. Its anterior surface is in the same
plane with the front aspect of the shaft, but is marked off from it by a ridge to
which the capsule of the hip-joint is attached. The ridge, which commences at
the great trochanter in a small prominence, or tubercle, extends obliquely down-
ward, and winding to the back of the femur, passes by the lesser trochanter and
becomes continuous with the medial lip of the linea aspera, on the posterior aspect
of the shaft. This ridge forms the intertrochanteric line or spiral line of the femur.
The intertrochanteric line receives the bands of the ilio-femoral thickening of the
capsule of the hip-joint. The posterior surface of the neck is smooth and concave
and its medial two-thirds is enclosed in the capsule of the hip-joint. The superior
border of the neck, perforated by large nutrient foramina, is short and thick, and
runs downward to the great trochanter. The inferior border, longer and narrower
than the superior, curves downward to terminate at the lesser trochanter.
The trochanters are the prominences which afford attachment to the rotator
muscles of the thigh; they are two in number — great and lesser.
The great trochanter is a thick, quadrilateral process surmounting the junction
of the neck with the shaft, and presents for examination two surfaces and four
borders. The lateral surface is broad, rough, and continuous with the lateral
surface of the shaft. It is marked by a diagonal ridge running from the postero-
superior to the antero-inferior angle, which receives the insertion of the gluteus
medius. The ridge divides the surface into two triangular areas : an upper, cov-
ered by the gluteus medius, and occasionally separated from it by a bursa, and a
lower, covered by a bursa to permit the free gliding of the tendon of the gluteus
maximus. Of the medial surface the lower and anterior portion is joined with
the rest of the bone; the upper and posterior portion is free, concave, and presents
a deep depression, the trochanteric or digital fossa, which receives the tendon of
the obturator externus. The fore part of the surface is marked by an impression
for the insertion of the obturator internus and two gemelli.
Of the four borders, the superior, thick and free, presents near the centre an oval mark for
the insertion of the -piriformis; the anterior border, broad and irregular, receives the gluteus
minimus; the posterior border, thick and rounded, is continuous with the intertrochanteric
crest, the prominent ridge uniting the two trochanters behind. Above the middle of this line is
an elevation, termed the tubercle of the quadratus, for the attachment of the upper part of the
quadralus femoris. The inferior border corresponds with the line of junction of the base of
the trochanter with the shaft; it is marked by a prominent ridge for the origin of the upper part
of the vastus lateralis.
The lesser trochanter is a conical eminence projecting medially from the poste-
rior and mecUal aspect of the bone, where the neck is continuous with the shaft.
Its summit is rough and gives attachment to the tendon of the ilio-psoas. The
fibres of the iliacus extend beyond the trochanter and are inserted into the surface
of the shaft immediately below.
The body or shaft of the femur is almost cylindrical, but is slightly flattened in
front and strengthened behind by a projecting longitudinal ridge, the linea aspera,
for the origin and insertion of muscles. The linea aspera extends along the middle
third of the shaft and presents a medial lip and a lateral lip separated by a narrow
interval. When followed into the upper third of the shaft, the three parts diverge.
The lateral lip becomes continuous with the gluteal tuberosity and ends at the
base of the great trochanter. The ridge affords insertion to the gluteus maximus,
THE FEMUR
179
Fig. 215. — The Left Femur. (Anterior view.)
Greater trochanter
Superior cervical tubercl
Adductor tubercl
Adductor magnu;
Capsular line — ^
Piriformis
Obturator internus and gemelli
Gluteus minimus
Vastus lateralis
Fibular collateral ligament
Popliteus
Literal condyle
180
THE SKELETON
Fro. 216. — The Left Femur. (Posterior view.)
Obturator externus
. Fovea for ligamentum teres
Gluteus medius
-^'^
Quadratus femoris
Capsule
-Intertrochanteric crest
Vastus lateralis -
Gluteal tuberosity
Gluteus maximus |r~
-Psoas
-Lesser trochante
-Iliacus
-Pectineus
-Adductor brevis
Adductor magnus
Lateral lip of the Hnea aspera
Biceps
Vastus laterahs -
Vastus intermedn
Intervening space of the linea aspera
"Adductor longus
Vastus medialis
"Medial lip of the linea aspera
. Nutrient foramen
- For femoral artery
Plantaris _
Gastrocnemius-
Anterior crucial ligament-
Intercondylar fossa-
l«
pCapsule
-Tibial collateral ligament
Lateral condyle
Posterior crucial ligament
' Medial condyle
THE FEMUR
181
and when very prominent is termed the third trochanter. The medial Hp curves
medialward below the lesser trochanter, where it becomes continuous with the
intertrochanteric line; the intervening portion bifurcates and is continued upward
as two lines, one of which ends at the small trochanter, and receives some
fibres of the iliacus, whilst the other is the linea pectinea and marks the insertion
of the pectineus muscle.
Toward the lower third of the shaft the medial and lateral lips of the linea
aspera again diverge, and are prolonged to the condyles by the medial and lateral
supra-condylar lines, enclosing between them a triangular surface of bone, the
popliteal surface [planum popliteum] of the femur, which forms the upper part of
the floor of the popliteal space. The lateral line is the more prominent and ter-
minates below in the lateral epicondyle. The medial one is interrupted above,
where the femoral vessels are in relation with the bone, better marked below,
where it terminates in the adductor tubercle, a small sharp projection at the sum-
mit of the medial epicondyle, which affords attachment to the tendon of the ad-
ductor magnus.
Fig. 217. — A Diagram to show the Pressure and Tension Curves of the Femur.
(After Wagstaffe.)
Near the centre of the linea aspera is the foramen for the medullary artery, directed upward
toward the head of the bone.
From the medial lip of the linea aspera and the lower part of the int-ertrochanteric line
arises the vastus medialis (internus), and from the lateral lip and the side of the gluteal ridge
arises the vastus lateralis (externus). The adductor magnus is inserted into the medial lip of
the linea aspera, from the medial side of the gluteal tuberosity above, and the medial supra-
condylar line below. Between the adductor magnus and vastus medialis (internus) four muscles
are attached: the pectineus and iliacus above, then the adductor brevis, and lowest of all, the
adductor longus. Above, in the interval between the adductor magnus and the vastus lateralis
(externus), the gluteus maximus is inserted; in the interval lower down is the short head of
the biceps, taking origin from the lower two-thirds of the lateral] lip of the linea aspera and the
upper two-thirds of the lateral supra-condylar line. On the popliteal surface of the bone, just
above the condyles, are two rough areas from which fibres of the two heads of the gastrocnemius
take origin. Above the area for the lateral head of the gastrocnemius is a slight roughness for
the plantaris.
For purposes of description it is convenient to regard the shaft of the femur as
presenting anterior, medial, and lateral surfaces, although definite borders separat-
ing the surfaces from one another do not exist. All three surfaces are smooth
and the anterior is not separated from the lateral by ridges of any kind. In the
middle third of the shaft the medial and lateral surfaces approach one another
behind, being separated by the linea aspera.
182
THE SKELETON
The shaft is overlapped on its medial side by the vastus medialis (internus) , and
on its lateral side by tlie vastus lateralis (externus). The upper three-fourths of
the anterior and lateral surfaces afford origin to the vastus intermedius (crureus),
and the lower fourth of the anterior surface, to the articularis genu (sub-crureus) .
The medial surface is free from muscular attachment.
Fig. 218. — Transverse Section op Shaft of
Femtjr to show the Medttllary Cavity.
Fig. 219. — Section of Upper End of Femur
to show the Calcar Femorale.
Lateral lip Linea aspera Medial Up
. Nutrient canal
Lateral surface
Medial surf ace
Anterior surface
Fig. 220. — The Femur at Birth.
The lower extremity presents two cartilage-covered eminences or condyles,
separated behind by the intercondyloid fossa. The lateral condyle is wider
than its fellow and more prominent anteriorly; the medial condyle is narrower,
more prominent, and longer, to compensate for the obliquity of the shaft. When
the femur is in the natural position, the inferior surfaces of the condyles are on the
THE FEMUR
183
same plane, and almost parallel, for articulation with the upper surfaces on the
head of the tibia. The two condyles are continuous in front, forming a smooth
trochlear surface [facies patellaris] for articulation with the patella. This surface
presents a median vertical groove and two convexities, the lateral of which is
wider, more prominent, and prolonged farther upward. The patellar surface is
faintly marked off from the tibial articular surfaces by two irregular grooves,
best seen while the lower end is still coated with cartilage. The lateral groove
commences on the medial margin of the lateral condyle near the front of the
intercondylar fossa, and extends obliquely forward to the lateral margin of the
bone. The general direction of the medial groove is from front to back, turning
medially in front and extending backward as a faint ridge which marks off from the
Fig. 221. — The Left Femur at the Twentieth Year. (Posterior view ,)
The figure shows the relations of the epiphysial and capsular lines.
Appears in the firsts and fuses in the
nineteenth year
the f ourth, and unites
the e ighteenth year
Appears in the fourteenth, and unite
in the seventeenth year
Appears early in the ninth month of,
intra-uterine life, and unites at
the twentieth year
rest of the medial condyle a narrow semilunar facet for articulation with the
medial perpendicular facet of the patella in extreme flexion. The grooves receive
the semilunar menisci in the extended position of the joint. The tibial surfaces
are almost parallel except in front, where the medial turns laterally to become
continuous with the patellar surface.
The opposed surfaces of the two condyles form the boundaries of the inter-
condylar fossa and give attachment to the crucial ligaments which are lodged
within it. The posterior crucial ligament is attached to the fore part of the lateral
surface of the medial condyle and the anterior crucial ligament to the back part of
the medial surface of the lateral condyle. The two remaining surfaces of the
condyles are broad and convex, and each presents an epicondyle (tuberosity) for
the attachment of lateral ligaments. The medial epicondyle, the larger of the
two, is surmounted by the adductor tubercle, behind which is an impression for
184
THE SKELETON
the medial head of the gastrocnemius on the upper aspect of the condyle; below
and behind the lateral epicondyle is a deep groove which receives the tendon of
the popliteus muscle when the knee is flexed, and its anterior end terminates in
a pit from which the tendon takes origin. Above the lateral epicondyle is a
rough impression for the lateral head of the gastrocnemius.
The interior of the shaft of the femur is hollowed out by a large medullary canal, and the
extremities are composed of cancellated tissue invested by a thin compact la3'er. The arrange-
ment of the cancelli in the upper end of the bone forms a good illustration of the effect produced
by the mechanical conditions to which bones are subject. In the upper end of the bone the
cancellous tissue is arranged in divergent curves. One system springs from the lower part of
the neck and upper end of the shaft medially and spreads into the great trochanter ('pressure
lamellae'). A second system springs from the lateral part of the shaft and arches upward into
the neck and head ('tension lamelte'), crossing the former almost at right angles. A second set
of pressure lamellae springs from the lower thick wall of the neck, and extends into the upper
part of the head to end perpendicularly in the articular surface mainly along the lines of greatest
pressure. A nearly vertical plate of compact tissue (calcar femorale) projects into the neck
of the bone from the inferior cervical tubercle toward the great trochanter. This is placed in
the line through which the weight of the body falls, and adds to the stability of the neck of the
bone; it is said to be liable to absorption in old age. In the lower end of the bone the vertical
and horizontal fibres are so disposed as to form a rectangular meshwork.
Blood-supply. — The head and neck of the femur receive branches from the inferior gluteal,
obturator, and circumflex arteries, and the trochanters from the circumflex arteries. The
nutrient vessel of the shaft is derived from either the second or third perforating artery, or
there may be two nutrient vessels arising usually from the first and third perforating. The
vessels of the inferior extremity arise from the articular branches of the popliteal and the
anastomotic branch of the femoral (supremagenu).
Ossification. — The femur is ossified from one primary centre for the shaft and from four
epiphysial centres. The shaft begins to ossify in the seventh week of intra-uterine life. Early
in the ninth month a nucleus appears for the lower extremity. During the first year the nucleus
for the head of the bone is visible, and in the fourth year that for the trochanter major. The
centre for the lesser trochanter appears about the thirteenth or fourteenth year. The lesser
trochanter joins the shaft at the seventeenth, the great trochanter at the eighteenth, the head
about the nineteenth, and the lower extremity at the twentieth year.
The neck of the femur is an apophysis, or outgrowth from the shaft. The line of fusion of
the condylar epiphysis with the shaft passes through the adductor tubercle.
The morphological relation of the patellar facet to the tibial portions of the condyles is
worthy of notice. In a few mammals, such as the ox, this facet remains separated from the
condyles by a furrow of rough bone,
The angle which the neck of the femur forms with the shaft at birth measures, on an average,
160°. In the adult it varies from 110° to 140°; hence the angle decreases greatly during the
period of growth. When once growth is completed, the angle, as a rule, remains fixed.
(Humphry.)
THE PATELLA
The patella (fig. 222) or knee-pan, situated in front of the knee-joint, is a sesa-
moid bone, triangular in shape, developed in the tendon of the quadriceps femoris.
Its anterior surface, marked by numerous longitudinal striae, is slightly convex, and
Fig. 222.-
Anterior surface
-The Left Patella.
perforated by small openings which transmit nutrient vessels to the interior of the
bone. It is covered in the recent state by a few fibres prolonged from the com-
mon tendon of insertion (supra-patellar tendon) of the quadriceps femoris, into the
ligamentum patellae (infra-patellar tendon), and is separated from the skin by one
THE TIBIA 185
or more bursse. The posterior surface is largely articular, covered with cartilage
in the recent state, and divided by a slightly marked vertical ridge, corresponding
to the groove on the trochlear surface of the femur, into a lateral larger portion
for the lateral condyle, and a medial smaller portion for the medial condyle.
Close to the medial edge a faint vertical ridge sometimes marks off a narrow articu-
lar facet, for the lateral margin of the medial condyle of the femur in extreme
flexion of the leg. Below the articular surface is a rough, non-articular depression,
giving attachment to the ligamentum patellae, and separated by a mass of fat from
the head of the tibia.
The base or superior border is broad, sloped from behind downward and for-
ward, and affords attachment, except near the posterior margin, to the common
Fig. 223. — The Superior Border or Base of the Left Patella.
Anterior surface
tendon of the quadriceps. The borders, thinner than the base, converge to the
apex below, and receive parts of the two vasti muscles. The apex forms a blunt
point directed downward, and gives attachment to the ligamentum patellae, by
which the patella is attached to the tibia.
Structurally the patella consists of dense cancellous tissue covered by a thin compact layer,
and it receives nutrient vessels from the articular branch of the suprema genu (anastomotic),
the anterior tibial recurrent, and the inferior articular branches of the popliteal.
Ossification. — The cartilaginous deposit in the tendon of the quadriceps muscle takes place
in the fourth month of intra-uterine life. Ossification begins from a single centre during the
third year, and is completed about the age of puberty.
THE TIBIA
The tibia (figs. 224, 225) or shin-bone is situated at the front and medial side
of the leg and nearly parallel with the fibula. Excepting the femur, it is the
largest bone in the skeleton, and alone transmits the weight of the trunk to the
foot. It articulates above with the femur, below \vith the tarsus, and laterally
with the fibula. It is divisible into two extremities and a shaft.
The upper extremity (or head) consists of two lateral eminences, or condyles.
Their superior articular surfaces receive the condyles of the femur, the articular
parts being separated by a non-articular interval, to which ligaments are attached.
The medial articular surface is oval in shape and concave for the medial condyle
of the femur. The lateral articular surface is smaller, somewhat circular in shape,
and presents an almost plane surface for the lateral condyle. The peripheral
portion of each articular surface is overlaid by a fibro-cartilaginous meniscus of
semilunar shape, connected with the margins of the condyles by bands of fibrous
tissue termed coronary ligaments. Each semilunar meniscus is attached firmly
to the rough interval separating the articular surfaces. This interval is broad
and depressed in front, the anterior intercondyloid fossa, where it affords attach-
ment to the anterior extremities of the medial and lateral menisci and the anterior
crucial ligament; elevated in the middle to form the intercondyloid eminence or
spine of the tibia, a prominent eminence, presenting at its summit two compressed
intercondyloid tubercles, on to which the condylar articular surfaces are prolonged ;
the posterior aspect of the base of the eminence affords attachment to the posterior
extremities of the lateral and medial semilunar menisci, and limits a deejj notch,
inclined toward the medial condyle, known as the posterior intercondyloid fossa
or popliteal notch. It separates the condyles on the posterior aspect of the head
and gives attachment to the posterior crucial ligament, and part of the posterior
ligament of the knee-joint. Anteriorly, the two condyles are confluent, and form
a somewhat flattened surface of triangular outline, the apex of which forms the
tuberosity of the tibia. The tuberosity is divisible into two parts. The upper
186
THE SKELETON.
part, rounded and smooth, receives the attachment of the ligamentum patellse.
The lower part is rough, and into its lateral edges prolongations of the ligamentum
patella are inserted. A prominent bursa intervenes between the ligament and
the anterior aspect of the upper extremity of the bone.
Fig. 224. — -The Left Tibia and Fibitla. (Anterior view.)
Intercondyloid eminence
Medial meniscus
Coronary ligament
Anterior crucial ligament-
Medial condyle
Tibial collateral ligament
Ligamentum patellge
Gracilis
Sartorius
border of crest of the tibi
Medial surface of tibia,
Interosseous membrane-
Anterior ligament of ankle-joint
Deltoid ligament-
Medial malleolus-
Lateral meniscus
Capsule
Lateral condyle
Biceps and the anterior
tibio-fibular ligament
Fibular collateral ligament
Extensor digitorum longus
Peroneus longus
Peroneus brevis
Extensor digitorum longus
Peroneal surfa.ce of fibula
Extensor surface of fibula
Extensor hallucis longus
Peroneus tertius
Subcutaneous portion
Anterior tibio-fibular ligament
Lateral malleolus
Anterior talo-fibular ligament
The medial condyle is less prominent though more extensive than the lateral, and near the
posterior part of its circumference is a deep horizontal groove for the attachment of the
central portion of the semimembranosus tendon. The margins of this groove, and the surface
THE TIBIA
187
of bone below, give attachment to the tibial (internal) lateral ligament of the knee. On the
under aspect of the lateral condyle is a rounded articular facet for the head of the fibula, flat
and nearly circular in outline, directed downward, backward, and laterally. The circumfer-
ence of the facet is rough and gives attachment to the ligaments of the superior tibio-fibular
joint, while above and in front of the facet, at the junction of the anterior and lateral surfaces
Fig. 225. — The Left Tibia and Fibula. (Posterior view.)
Posterior intercondyloid notch
Lateral meniscus ^^__^ ~f^ 1 iV^-= ^ Medial meniscus
Capsule 3(f*^*«io«.» ^* '*!>uui»--i^'ir^ Capsule
Posterior crucial ligament V^g,; • ■■ vyf^in. kT vJ
j^pgx ^ \' ^.L-w ^ J£Buff'*'w**>Kk*^ 'Semimembranosus
Posterior tibio-fibular ligament'
Flexor hallucis longus-
Flexor surface of fibula
Nutrient foramen'
Peroneus brevis
Posterior tibio-fibular ligament'
Groove for flexor hallucis longus-
Posterior talo-fibular ligament
Calcaneo-fibular ligament
Nutrient foramen
flexor digitorum longus
Groove for tibialis posterior
and flexor digitorum longus
Deltoid ligament
Posterior ligament of ankle-joint
of the condyle, is a ridge for the ilio-tibial band. A slip from the tendon of the biceps and parts
of the extensor longus digitorum and peroneus longus muscles are attached to the head below
the ilio-tibial band.
188
THE SKELETON
The shaft or body [corpus] of the tibia, thick and prismatic above, becomes
thinner as it descends for about two-thirds of its length, and then gradually ex-
pands toward its lower extremity. It presents for examination three borders and
three surfaces. The anterior border is very prominent and known as the anterior
crest of the tibia. It commences above on the lateral edge of the tuberosity and
terminates below at the anterior margin of the medial malleolus. It runs a some-
what sinuous course, and gives attachment to the deep fascia of the leg. The
medial border extends from the back of the medial condyle to the posterior margin
of the medial malleolus, and affords attachment above, for about three inches, to
Fig. 226. — The Tibia and Fibula at the Sixteenth Yeae.
The figure shows the relations of the epiphysial and capsular lines.
apsule
.Appears at birth; unites at twenty-
one : but union is sometimes delayed
to twenty-five
Appears at the fourth year; unites at
twenty -four
Capsule
Appears at the
twenty
cond year; unites at
the tibial (internal) lateral ligament of the knee-joint and in the middle third, to
the soleus. The interosseous crest or lateral border, thin and prominent, gives
attachment to the interosseous membrane. It commences in front of the fibular
facet, on the upper extremity, and toward its termination bifurcates to enclose a
triangular area for the attachment of the interosseous ligament uniting the lower
ends of the tibia and fibula.
The medial surface is bounded by the medial margin and the anterior crest; it
is broad above, where it receives the insertions of the sartorius, gracilis, and semi-
tendinosus; convex and subcutaneous in the remainder of its extent. The lateral
surface lies between the crest of the tibia and the interosseous crest. The upper
two-thirds presents a hollow for the origin of the tibialis anterior; the rest of the
THE FIBULA 189
surface is convex and covered by the extensor tendons and the anterior tibial
vessels. The posterior surface is limited by the interosseous crest and the medial
border. The upper part is crossed obliquely by a rough popliteal line, extending
from the fibular facet on the lateral condyle to the medial border, a little above the
middle of the bone.
The popliteal line gives origin to the soleus and attachment to the popliteal fascia, while
the triangular surface above is occupied by the popliieus muscle. Descending along the
posterior surface from near the middle of the popliteal line is a vertical ridge, well marked at
its commencement, but gradually becoming indistinct below. The portion of the surface
between the ridge and the medial border gives origin to the flexor digilorum longus; the lateral
and narrower part, between the ridge and the interosseous border, to fibres of the tibialis
posterior. The lower third of the posterior surface is covered by flexor tendons and the posterior
tibial vessels. Immediately below the popliteal line and near the interosseous border is the large
medullary foramen directed obliquely downward.
The lower extremity, much smaller than the upper, is quadrilateral in shape
and presents a strong process called the medial malleolus, projecting downward
from its medial side. The anterior surface of the lower extremity is smooth and
rounded above, where it is covered by the extensor tendons, rough and depressed
below for the attachment of the anterior ligament of the ankle-joint. It some-
times bears a facet for articulation with the neck of the talus (astragalus) . (A.
Thomson.) The posterior surface is rough and is marked by two grooves. The
medial and deeper of the two encroaches on the malleolus, and receives the tendons
of the tibialis posterior and flexor digitorum longus; the lateral, very shallow and
sometimes indistinct, is for the tendon of the flexor hallucis longus. The lateral sur-
face is triangular and hollowed for the reception of the lower end of the fibula and
rough for the interosseous ligament which unites the two bones, except near the
lower border, where there is usually a narrow surface, elongated from before back-
ward, covered with cartilage in the recent state for articulation with the fibula.
The lines in front of and behind the triangular surface afford attachment to the
anterior and posterior ligaments of the inferior tibio-fibular articulation. The
medial surface, prolonged downward on the medial malleolus, is rough, convex,
and subcutaneous. The lateral surface of this process is smooth and articulates
with the facet on the medial side of the talus (astragalus). Its lower border is
notched, and from the notch, as well as from the tip and anterior border, the fibres
of the deltoid Hgament of the ankle-joint descend. The inferior or terminal
surface, by which the tibia articulates with the talus, is of quadrilateral form,
concave from before backward, wider in front than behind, and laterally than
medially where it is continuous with the lateral surface of the malleolus.
The occasional facet on the anterior siu'face of the lower extremity of the tibia is a pressure
facet, produced by extreme flexion of the ankle joint. It is therefore sometimes designated as
the squatting facet." (See fig. 333.)
Blood-supply. — The tibia is a very vascular bone. The nutrient artery of the shaft is
furnished by the posterior tibial, and is the largest of its kind in the body. The head of the
bone receives numerous branches from the inferior articular arteries of the popliteal and the
recurrent branches of the anterior and posterior tibial. The lower extremity receives twigs
from the posterior and anterior tibial, the peroneal, and the medial malleolar arteries.
Ossification. — The tibia is ossified from one principal centre for the shaft, which appears
in the eighth week of intra-uterine life, and two epiphyses, the centres for which appear in the
cartilaginous head of the bone toward the end of the ninth month, and in the lower extremity
during the second year. The latter unites with the shaft at eighteen, but the union of the head
with the shaft does not take place until the twenty-first year, and it may even be delayed until
twenty-five. The upper part of the tubercle of the tibia is ossified from the upper epiphysis,
and the lower part from the diaphysis.
THE FIBULA
The fibula (figs. 224, 225) is situated on the lateral side of the leg and, in
proportion to its length is the most slender of all the long bones. It is placed
nearly parallel to the tibia with which it is connected above and below. In man
it is a rudimentary bone and bears none of the weight of the trunk, but is retained
on account of the muscles to which it gives origin and its participation in the
formation of the ankle-joint. Like other long bones, it is divisible into a shaft
and two extremities.
The head [capitulum fibulae], or upper extremity, is a rounded prominence.
Its upper surface presents laterally a rough eminence for the attachment of the
190 THE SKELETON
biceps tendon and the fibular (long external) collateral ligament of the knee-joint,
medially it presents a round or oval facet [fades articularis capituli], directed
upward, forward, and medially, for articulation with the lateral condyle (tuber-
osity) of the tibia. The margin of the facet gives attachment to the articular
capsule of the superior tibio-fibular articulation. Posteriorly, the head rises into
a pointed apex (styloid process), which affords attachment to the short lateral
ligament of the knee-joint, and on the lateral side, to part of the biceps tendon.
The posterior aspect of the head gives attachment to the soleus, the lateral aspect, extend-
ing also in front of the eminence for the biceps, to the peroneus longus; from the anterior aspect
fibres of the extensor digiiorum longus arise, whilst the medial side lies adjacent to tlie tibia.
The shaft [corpus fibulse], in its upper three-fourths, is quadrangular, possessing
four borders and four surfaces, whereas its lower fourth is flattened from side to
side, so as to be somewhat triangular. The borders and surfaces vary exceed-
ingly so that their description is difficult. The anterior crest (or antero-lateral
border) commences in front of the head and terminates below by dividing to
enclose a subcutaneous surface, triangular in shape, immediately above the
Fig. 227. — The Upper End of the Left Flbtjla to show Musculae and Ligamentous
Attachments X 2. (G. J. Jenkins.)
Fibular collateral ligament
Biceps ^ V^^^^^^^- 9 JBt — Capsule of superior tibio-
^ ' fibular joint
Styloid process
Posterior superior tibio-
fibular ligament
lateral malleolus. It gives attachment to a septum separating the extensor
muscles in front from the peronei muscles on the lateral aspect. The interosseous
crest (or antero-medial border), so named from giving attachment to the interos-
seous membrane, also commences in front of the head, close to the anterior crest,
and terminates below by dividing to enclose a rough triangular area immediately
above the facet for the talus {astragalus) ; this area gives attachment to the inferior
interosseous ligament, and may present at its lower end a narrow facet for articula-
tion with the tibia. The medial crest (or postero-medial border), sometimes
described as the oblique line of the fibula, commences at the medial side of the
head and terminates below by joining the interosseous crest, in the lower fourth
of the shaft. It gives attachment to an aponeurosis separating the tibialis
posterior from the soleus and flexor hallucis longus. The lateral crest (or postero-
lateral border) runs from the back of the head to the medial border of the peroneal
groove on the back of the lower extremity; it gives attachment to the fascia sepa-
rating the peronei from the flexor muscles.
The anterior or extensor surface is the interval between the interosseous and
anterior crests. In the upper third it is extremely narrow, but broadens out
below, where it is slightly grooved longitudinally. It affords origin to three
muscles : laterally, in the upper two-thirds, to the extensor digitorum longus, and, in
the lower third, to the peroneals tertius; medially, in the middle third, also to the
extensor hallucis longus. The medial surface, situated between the interosseous
and medial crests, is narrow above and below, and broadest in the middle. It
is grooved and sometimes crossed obliquely by a prominent ridge, the secondary
oblique line of the fibula; the surface gives origin to the tibialis posterior, and the
ridge to a tendinous septum in the substance of the muscle. The posterior surface
THE TARSUS 191
is the interval between the medial and lateral crests, and is somewhat twisted so
as to look backward above and medially below. It serves, in its upper third, for
the origin of the soleus, and in its lower two-thirds for the flexor hallucis longus.
Near the middle of the surface is the medullary foramen, directed downward
toward the ankle. The lateral surface, situated between the anterior and lateral
crests, is also somewhat twisted, looking laterally above and backward below,
where it is continuous with the groove on the back of the lateral malleolus.
The surface is often deeply grooved and is occupied by the peroneus longus in the
upper two-thirds and by the peroneus brevis in the lower two-thirds.
The lateral malleolus or lower extremity is pyramidal in form, somewhat
flattened from side to side, and joined by its base to the shaft. It is longer, more
prominent, and descends lower than the medial malleolus. Its lateral surface is
convex, subcutaneous, and continuous with the triangular subcutaneous surface
on the shaft, immediately above. The medial surface is divided into an anterior
and upper area [facies articularis malleoli], triangular in outline and convex from
above downward for articulation with the lateral side of the talus (astragalus), and
a lower and posterior excavated area, the digital fossa, in which are attached the
transverse iriferior tibio-fibular ligament and the posterior talo-fibular (posterior
fasciculus of the external lateral) ligament of the ankle. The anterior border is
rough and gives attachment to the anterior talo-fibular (anterior fasciculus of the
external lateral) ligament of the ankle, and the anterior inferior tibio-fibular liga-
ment. The posterior border is grooved for the peronei tendons, and near its
upper part gives attachment to the posterior inferior tibio-fibular ligament. The
apex or summit of the process affords attachment to the calcaneo-fibular (middle
fasciculus of the external lateral) ligament of the ankle.
Blood-supply. — The shaft of the fibula receives its nutrient artery from the peroneal
branch of the posterior tibial. The head is nourished by branches from the inferior lateral
articular branch of the popliteal artery, and the lateral malleolus is supplied mainly by the
peroneal, and its perforating and malleolar branches.
Ossification. — The shaft of the fibula commences to ossify in the eighth week of intra-
uterine life. A nucleus appears for the lower extremity in the second year, and one in the upper
extremity during the fourth or fifth year. The lower extremity fuses with the shaft about
twenty, but the upper extremity remains separate until the twenty-second year or even later.
It is interesting, in connection with the times of appearance of the two epiphyses of the
fibula, to note that the ossification of the lower epiphysis is contrary to the general rule — viz.,
that the epiphysis toward which the nutrient artery is directed is the last to undergo ossification.
This is perhaps explained by the rudimentary nature of the upper extremit}'. In birds the head
of the bone is large and enters into the formation of the knee-joint; and in human embryos,
during the second month, the fibula is quite close up to the femur.
The human fibula is characterised by the length of its malleolus, for in no other vertebrate
does this process descend so far below the level of the tibial malleolus. On the other hand, in
the majority of mammals the tibial descends to a lower level than the fibular malleolus. In
the human embryo of the third month, the lateral is equal in length to the medial malleolus.
At the fifth month the lateral malleolus exceeds the medial by 1.5 mm.; at birth, the lateral
malleolus is still longer; and by the second year it assumes its adult proportion.
THE TARSUS
The tarsal bones [ossa tarsi] (figs. 228, 229) are grouped in two rows: — a
proximal row, consisting of the talus and calcaneus, and a distal row, consisting
of four bones which, enumerated from tibial side, are the first, second, and third
cuneiform bones and the cuboid. Interposed between the two I'ows on the tibial
side of the foot is a single bone, the navicular ; on the fibular side the proximal and
distal rows come into contact.
Compared with the carpus, the tarsal bones present fewer common characters,
and greater diversity of size and form, in consequence of the modifications for sup-
porting the weight of the trunk. On each, however, six surfaces can generally be
recognised, articular when in contact with neighbouring bones, elsewhere sub-
cutaneous or rough for the attachment of ligaments. As regards ossification, they
correspond in the main with that of the bones of the carpus. Each tarsal bone is
ossified from a single centre, but the calcaneus has, in addition, an epiphysis for a
large part of its posterior extremity, and the talus, an occasional centre for the os
trigonum.
192
THE SKELETON
The Talus
The talus (or astragalus) (figs. 230, 231) is, next to the calcaneus, the largest
of the bones of the tarsus. Above it supports the tibia, below it rests on the cal-
caneus, at the sides it articulates with the two malleoli, and in front it is received
into the navicular. For descriptive purposes, it may be divided into a head, neck,
and body.
Fig. 228. — The Left Foot. (Superior surface.)
Tendo Achill
Extensor digitorum brevis
Peroneus brevis
Peroneus tertius
Metatarsus
|\ [I First phalanx
Second phalam
l.h Third phalanx
Extensor digitorum longus
The body is somewhat quadrilateral in shape. The upper surface presents a broad, smooth
surface for the tibia, slightly concave from side to side, convex from before backward, and
wider in front than behind. "The diminution in width posteriorly is associated with an obliquity
of the lateral margin, which is directed medially as well as backward and downward. The
inferior surface is occupied by a transversely disposed oblong facet [taoies articularis calcanea
THE TARSUS
193
posterior], deeply concave from side to side, which articulates with a corresponding surface
on the calcaneus. Of the malleolar sm-faces, the lateral is almost entirely occupied by a large
triangular facet, broad above, where it is continuous with the superior surface, concave from
above downward, for articulation with the lateral malleolus; on the medial malleolar surface
is a pyriform facet continuous with the superior surface, broad in front and narrow behind,
which articulates with the medial malleolus. Below this facet the medial surface is rough for
the attachment of the deep fibres of the deltoid (internal lateral) ligament of the ankle. The
Fig. 229. — The Left Foot. (Plantar surface.)
Abductor digiti quinti
Abductor ossis metatarsi quiati
Quadratus plantae (lateral head)
Flexor hallucis brevis
Abductor ossis metatarsi quinti
Flexor brevis digiti quinti
Adductor hallucis
Third plantar interosseous
Second plantar interosseous
First plantar interosseou
Flexor brevis digiti quinti
Abductor digiti quinti
Third plantar interosseous
Second plantarinterosseous'
First plantar interosseouE.
Flexor digitorum brevis.
Flexor digitorum longus
Abductor hallucis
Flexor digitorumi brevis
Quadratus plantce (medial head)
Tibiahs posterior
Tibialis anterior
Peroneus longus
Abductor hallucis
Flexor hallucis brevis
(medial) portion)
Flexor hallucis brevis
(lateral) portion)
Adductor hallucis
Transversus pedis
Flexor hallucis longus
superior surface and the two malleolar surfaces together constitute the trochlea. The poste-
rior Surface is of small extent and marked by a groove which lodges the tendon of the flexor
hallucis longus. Bounding the groove on either side are two tubercles, of which the
lateral [processus posterior tali] is usually the more prominent, for attachment of the posterior
talo-fibular ligament of the ankle-joint; the medial tubercle gives attachment to the medial
talo-calcaneal ligament. Continuous, with the anterior aspect of the body is the neck, a con-
194
THE SKELETON
strioted part of the bone supporting the head. Above it is rough, and perforated by numerous
vascular foramina. Below, it presents a deep groove [sulcus tali], directed from behind forward
and lateralward. When the talus is articulated with the calcaneus, this furrow is converted
into a canal [sinus tarsi] in which is lodged the interosseous talo-calcaneal ligament. The head
is the rounded anterior end of the bone, and its large articular surface is divisible into three
parts: in front, a smooth, oval convex area, directed downward and forward for the navicular
bone; below, an elongated facet, convex from front to back, for articulation with the sustentacu-
lum taJi of the calcaneus; and between these, is a small facet which rests on the calcaneo-
FiG. 230. — The Left Talus. (Plantar view.)
Groove for the flexor hallucis longus
For calcaneus
■For the sustentaculum tall
For the calcaneo-navicular (or the
spring) ligament
For navicular
navicular ligament, separated from it by the synovial membrane of the talo-calcaneo-navicular
joint.
Articulations. — The talus articulates with four bones and two ligaments. Above and
medially with the tibia, below with the calcajieus, in front with the navicular, laterally with the
fibula. The head articulates with the calcaneo-navicular ligament and the lateral border of
the superior surface, at its posterior part, with the transverse ligament of the inferior tibio-
fibular joint.
The talus is a very vascular bone and is nourished by the dorsalis pedis artery and its tarsal
branch. It gives attachment to no muscles.
Fig. 231. — A Talus with the Os Trigonum.
Os trigonum
Ossification. — The talus is ossified from one, occasionallj* from two, nuclei. The principal
centre for this bone appears in the middle of the cartilaginous talus at the seventh month of
intra-uterine life. The additional centre is deposited in the posterior portion of the bone, and
forms the lateral posterior tubercle which may remain separate from the rest of the bone and
form the os trigonum. At birth, the talus presents some important peculiarities in the disposi-
tion of the articular facet on the tibial side of its body, and in the obliquity of its neck. If, in the
adult talus, a line be drawn through the middle of the superior trochlear surface parallel with
its medial border, and a second line be drawn along the lateral side of the neck of the bone so as
to intersect the first, the angle formed by these two lines will express the obliquity of the neck
of the bone. This in the adult varies greatly, but the average may be taken as 10°. In the
THE TARSUS
195
foetus at birth the angle averages 35°, whilst in a young orang it measures 45°. In the normal
adult talus the articular surface on the tibial side is limited to the body of the bone. In the
foetal talus it extends for some distane on to the neck, and sometimes reaches almost as far
forward as the navicular facet on the head of the bone. This disposition of the medial malleolar
facet is a characteristic feature of the talus in the chimpanzee and the orang. It is related to
the inverted position of the foot which is found in the human foetus almost up to the period of
birth, and is of interest to the surgeon in connection with some varieties of club-foot. (Shattock
and Parker.)
The Calcaneus
The calcaneus (or os calcis) (figs. 232, 233) is the largest and strongest bone of
the foot. It is of an elongated form, flattened from side to side, and expanded at
its posterior extremity, which projects downward and backward to form the heel.
It presents six surfaces, superior, inferior lateral, medial, anterior and posterior.
The superior surface presents in the middle a large, oval, convex, articular facet for the
under aspect of the body of the talus. In front of the facet the bone is marked by a deep
Fig. 232. — The Left Calcaneus. (Dorsal view.)
Media] process
Calcaneal groove'
Peroneal tubercle
Facet for talus
depression, the floor of which is rough for the attachment of ligaments, especially the talo-
calcaneal, and the origin of the extensor digitorum hrevis muscle; when the calcaneus and talus
are articulated, this portion of the bone forms the floor of a cavity called the sinus tarsi. Medi-
ally, the upper surface of the bone presents a well-marked process, the sustentaculum tali,
furnished with an elongated concave facet, occasionally divided into two, for articulation with
the under aspect of the head of the talus. The posterior part of the upper surface is non-
articular, convex from side to side, and in relation with a mass of fat placed in front of the
tendo Aohillis.
The inferior surface is narrow, rough, uneven, and ends posteriorly in two processes: the
medial is the larger and broader, the lateral is narrower but prominent. The medial process
affords origin to the abductor hallucis, the flexor digitorum brevis, and the abductor digiti quinti;
the last muscle also arises from the lateral process and from the ridge of bone between. The
rough surface in front of the tubercles gives attachment to the long plantar ligament (calcaneo-
cuboid) and the lateral head of the quadratus plantoe. Near its anterior end this surface forms
a rounded eminence, the anterior tubercle, from which (as well as from the shallow groove in
front) the plantar (short) calcaneo-cuboid ligament arises. (According to the BNA nomen-
clature, the medial and lateral processes belong to the tuber calcanei or the posterior extremity
of the bone.)
The lateral surface is broad, flat, and slightly convex. It represents near the middle a small
eminence for the calcaneo-fibular ligament of the ankle-joint. Below and in front of this is a
well-marked tubercle — the trochlear process [processus trochlearis] (or peroneal tubercle),
separating two grooves, the upper for the peroneus brevis and the lower for the peroneiis longus.
The medial surface is deeply concave, the hollow being increased by the prominent medial
process behind and the overhanging sustentaculum tali in front. The latter forms a promi-
nence of bone projecting horizontally, concave and articular above, grooved below for the
tendon of the flexor hallucis longus, and giving attachment to a slip of the tendon of the tibialis
posterior, the inferior calcaneo-navicular ligament, and some fibres of the deltoid ligament of
the ankle-joint. The hollow below the process receives the plantar vessels and nerves and its
lower part gives attachment to the medial head of the quadratus planice.
196
THE SKELETON
The anterior surface is somewhat quadrilateral in outline with rounded angles, and presents
a saddle-shaped articular surface for the cuboid.
The posterior surface is oval in shape, rough, and convex. It is divided into three parts: —
an upper, smooth and separated by a bursa from the tendo Aohillis; a middle part giving
attachment to the tendo Achillis and the plantaris, and a lower part in relation to the skin and
fat of the heel. The expanded posterior extremity of the bone is known as the tuber calcanei.
Articulations. — The calcaneus articulates with two bones, the talus above and the cuboid
in front.
Blood-supply. — The calcaneus is nourished by numerous branches from the posterior tibial
and the medial and lateral malleolar arteries. They enter the bone chiefly on the inferior
and medial surfaces.
Fig. 233. — The Calcaneus at the Fifteenth Year, showing the Epiphysis.
Appears at the tenth, and unites at the sixteenth year
Ossification. — The primary nucleus appears in the sixth month of intra-uterine life. The
epiphysis, for its posterior extremity, begins to be ossified in the tenth year and is united to
the body of the bone by the sixteenth year. It may extend over the whole of the posterior
surface, as shown in fig. 233, or over the lower two-thirds only, leaving a part above in relation
to the bursa beneath the tendo Achillis, which is formed from the primary nucleus. The
medial and lateral processes are formed by the epiphysis.
The Naviculae
The navicular [os naviculare pedis] (figs. 234, 235) is oval in shape, flattened
from before backward, and situated between the talus behind and the three
cuneiform bones in front. It is characterised by a large oval, concave, articular
Fig. 234. — The Left Navicular. (Anterior view.)
For first cuneiform'
Medial border
Tuberosity
■For second cuneiform
Lateral border
■For third cuneiform
facet on the posterior surface, which receives the head of the talus; a broad, rough,
rounded eminence on the medial surface, named the tuberosity of the navicular,
the lower part of which projects downward and gives insertion to the tendon of
Fig. 235. — The Left Navicular, showing a Facet for the Cuboid.
For first cuneif'
For second cuneiform
■For third cuneiform
For cuboid
the tibialis posterior; and an oblong-shaped anterior surface, convex and chvided
by two vertical ridges into three facets which articulate with the three cuneiform
bones. The superior (dorsal) surface is rough, convex, and slopes downward to
THE TARSUS 197
the tuberosity; the inferior (plantar) surface is irregular and rough for the attach-
ment of the inferior cAlcaneo-navicular ligament, and the lateral surface is rough
and sometimes presents a small articular surface for the cuboid.
Articulations. — With the talus behind, with the three cuneiform bones in
front, and occasionally with the cuboid on its lateral aspect.
Ossification. — The nucleus for the navicular appears in the course of the fourth year. The
tuberosity of the navicular, into which the tibialis posterior acquires its main insertion, occasion-
ally develops separately, and sometimes remains distinct from the rest of the bone.
The Cuneiform Bones
Of the three cuneiform bones, the first is the largest, the second is the smallest,
and the third intermediate in size. They are wedge-shaped bones placed between
the navicular and the first, second and third metatarsal bones. Posteriorly, the
ends of the bones lie in the same transverse line, but in front, the first and third
project farther forward than the second, and form the sides of a deep recess into
which the base of the second metatarsal bone is received.
Fig. 236. — The Left First Cuneiform. (Medial surface.)
For first metatarsal
The first cuneiform [os cuneiforme primum] (figs. 236, 237) is distinguished by its large
size and by the fact that when articulated, the base of the wedge is directed downward and the
apex upward. The posterior surface is concave and pyritorm for articulation with the medial
facet on the anterior surface of the navicular. The anterior surface forms a reniform articular
facet for the base of the first metatarsal. The medial surface is rough, and presents an oblique
groove for the tendon of the tibialis anterior; this groove is limited inferiorly by an oval facet
into which a portion of the tendon is inserted. The lateral surface is concave and presents along
its superior and posterior borders a reversed L-shaped facet for articulation with the second
cuneiform, and, at its anterior extremity, with the second metatarsal. Anteriorly it is rough
for ligaments. The inferior surface is rough for the insertion of the peroneus longus, tibialis
anterior, and (usually) the tibialis posterior. The superior surface is the narrow part of the
wedge and is directed upward.
FiQ 237. — The Left First Cuneiform. (Lateral aspect.)
For second metatarsal
For second cuneiform
Articulations. — With the navicular behind, second cuneiform and second metatarsal on
its lateral side, and first metatarsal in front.
Ossification. — From a single nucleus which appears in the course of the third year.
The second cuneiform [os cuneiforme secundum] (figs. 238, 239) is placed with the broad
extremity upward and the narrow end downward, and is readily recognised by its nearly
square base. The posterior surface, triangular and concave, articulates with the middle facet
on the anterior surface of tlie navicular. The anterior surface, also triangular, but narrower
than the posterior surface, articulates with the base of the second metatarsal. The medial
surface has a reversed L-shaped facet running along its superior and posterior margins for
articulation with the corresponding facet on the first cuneiform, and is rough elsewhere for the
198
THE SKELETON
attachment of ligaments. On the lateial surface near its posterior border is a vertical facet,
sometimes bilobed, for the third cuneiform, and occasionally a second facet at the anterior
inferior angle. The superior surface forms the square-cut base of the wedge and is rough for
the attachment of ligaments. The inferior surface is sharp and rough for ligaments and a slip
of the tendon of the tibialis posterior.
Fig. 238. — The Left Second Cuneiform. (Medial sm-face.)
For first cuneiform
For second metatarsal
Articulations. — With the navicular behind, second metatarsal in front, third cuneiform on
the lateral side, and first cuneiform on the medial side.
Ossification. — From a single nucleus which appears in the fourth year.
The third cuneiform bone (figs. 240, 241) also placed with the broad end directed upward
and the narrow end downward, is distinguished by the oblong shape of its base. Like the
Fig. 239. — The Left Second Cuneiform. (Lateral surface.)
-For third cuneiform
For navicular
jional facet for third cuneiform
second cuneiform, the posterior surface presents a triangular facet for the navicular; and the
anterior surface a triangular facet, longer and narrower, for the third metatarsal. The medial
surface has a large facet extending along the posterior border for the second cuneiform, and
along the anterior border a narrow irregular facet for the lateral side of the base of the second
metatarsal. Occasionally, a small facet is present near the anterior inferior angle for the second
Fig. 240. — The Left Third Cuneiform (Medial surface.)
For second cuneiform -
For navicular
Foi second metatarsal. The circular
facet near the inferior angle is for
the second cuneiform
cuneiform. The lateral surface has a large distinctive facet near its posterior superior angle
for the cuboid, and at the anterior superior angle there is usually a small facet for the medial
side of the base of the fourth metatarsal. The superior surface, oblong in shape, is rough for
ligaments, and the inferior, forming a rounded margin, receives a slip of the tibialis posterior
and gives origin to a few fibres of the^e:!;or hallucis brevis.
Fig. 241. — The Left Third Cuneiform. (Lateral surface.)
T^ z ..t- 1. 4. , i T. =^ ^1 i^-rt-t-i — For cuboid
For fourth metatarsal i v,.^ -«i i , >• i
For third metatarsal
Articulations. — With the navicular behind, third metartarsal in front, cuboid and fourth
metatarsal on the lateral side, .second cuneiform and second metatarsal on the me'dial side.
Ossification. — A single nucleus appears in the course of the first year.
THE TARSUS 199
The Cxiboid
The cuboid (figs. 242, 243, 244), irregularly cubical in shape, is placed on the
lateral aspect of the foot, forming a continuous line with the calcaneus and the
fourth and fifth metatarsals.
Its posterior surface is somewhat quadrangular with rounded angles and presents a saddle-
shaped articular surface for the calcaneus. Its lower and medial angle is somew-hat prolonged
backward beneath the sustentaculum tali (calcaneal process of the cuboid), an arrangement to
oppose the upward or outward movement of the bone. This process occasionally terminates
Fig. 242. — The Left Cdboid. (Medial view.)
For third cuneiform j|^iq5\-J — J'''', 'A — For fourth metatarsal
For calcaneus
Groove for tendon of the per
longus "■ ■- -
in a rounded facet which plays on the head of the talus lateral to the facet for the calcaneo
navicular ligament. The anterior surface is smaller and divided by a vertical ridge into two
articular facets, a lateral for the base of the fifth, and a medial for the base of the fourth meta-
tarsal. The superior surface is rough, non-articular, and directed obliquely upward. The
inferior surface presents a prSminent ridge for the attachment of the long plantar (calcaneo-
cuboid) ligament, in front of which is a deep groove — the peroneal groove — running obliquely
forward and medially and lodging the tendon of the peroneiis longus. The ridge terminates
laterally in an eminence, the tuberosity of the cuboid, on which there is usually a facet for a
sesamoid bone of the tendon contained in the groove. The part of the surface behind the ridge
is rough for the attachment of the plantar (short) calcaneo-cuboid ligament, a slip of the tibialis
posterior, and a few fibres of the flexor hallucis hrevis.
Fig. 243.-
-The Left Cuboid. (Medial view.)
For third cuneiform
For calcaneus
-fSpTM
For navicular (occasional)
"z/^vA .^^v-^'Il
Groove for tendon of the peroneus_
longus
^^^^
The medial surface presents, near its middle and upper part, an oval facet for articulation
with the third cuneiform bone (fig. 242); behind this, a second facet for the navicular is fre-
quently seen (fig. 243). Generally the two facets are confluent and then form an elliptical
surface (fig. 244). The remainder of this surface is rough for the attachment of strong inter-
osseous ligaments.
The lateral surface, the smallest and narrowest of all the surfaces, presents a deep notch
which leads into the peroneal groove.
Articulations. — With the calcaneus behind, fourth and fifth metatarsals in front, third
cuneiform and frequently the navicular on the medial side; occasionally also the talus.
Fig. 244. — The Left CtTBOiD. (Medial view.)
For third cuneiform
For navicular
Ossification. — The cuboid is ossified from a single nucleus which appears about the time
of birth.
Accessory tarsal elements. — As in the carpus, a number of additional elements may
occur in the tarsus. The most frequent of these is the os trigonum, which has already been
noticed. Ne.\t in frequency is an additional first cuneiform, resulting from the ossification of
the plantar half of that bone independently of the dorsal half, so that the bone is represented
by a plantar and a dorsal first cuneiform. Other additional elements may occasionally occur
at the upper posterior angle of the sustentaculum tali; at the anterior superior angle of the cal-
caneus, between that bone and the navicular; in the angle between the first cuneiform and the
first and second metatarsals; and in the fibular angle between the fifth metatarsal and the
cuboid (os Vesalianum).
200
THE SKELETON
The fibular portion of the navicular is sometimes united to the cuboid and quite separate
from the rest of the navicular, the cuboid in such eases articulating with the talus. This con-
dition suggests the recognition of the fibular portion of the navicular as a distinct accessory
tarsal element, the cuboides secundarium, though it has not yet been observed as an inde-
pendent bone in the human foot.
THE METATARSUS
The metatarsus [ossa metatarsalia] consists of a series of five somewhat
cylindrical bones. Articulated with the tarsus behind, they extend forward,
nearly parallel with each other, to their anterior extremities, which articulate
with the toes, and are numbered according to their position from great toe to small
toe. Like the corresponding bones in the hand, each presents for examination a
three-sided shaft, a proximal extremity termed the base, and a distal extremity or
head. The shaft tapers gradually from the base to the head, and is slightly
curved longitudinally so as to be convex on the dorsal and concave on the plantar
aspect.
A typical metatarsal bone. — The shaft [corpus] is compressed laterally and
presents for examination three borders and three surfaces. The two borders, dis-
tinguished as medial and lateral, are sharp and commence behind, one on each side
of the dorsal aspect of the tarsal extremity, and, gradually approaching in the
middle of the shaft, separate at the anterior end to terminate in the corresponding
Fig. 245. — The First (Left) Metatarsal.
For peroneus longus
Facet for second meta-
tarsal (occasional)
tubercles. The inferior border is thick and rounded and extends from the under
aspect of the tarsal extremity to near the anterior end of the bone, where it bi-
furcates, the two divisions terminating in the articular eminences on the plantar
aspect of the head. Of the three surfaces, the dorsal is narrow in the middle and
wider at either end. It is directed upward and is in relation -with the extensor
tendons. The medial and lateral surfaces, more extensive than the dorsal,
corresponding with the interosseous spaces, are separated above, but meet to-
gether at the inferior border; they afford origin to the interosseous muscles. The
base is wedge-shaped, articulating by its terminal surface with the tarsus, and on
each side with the adjacent metatarsal bones. The dorsal and plantar surfaces
are rough for the attachment of ligaments. The head presents a semicircular
articular surface for the base of the first jjhalanx, and on each side a depression,
surmounted by a tubercle, for the attachment of the lateral ligaments of the
metatarso-phalangeal joint. The inferior surface of the head is grooved for the
passage of the flexor tendons and is bounded by two eminences continuous with
the terminal articular surface.
The several metatarsals possess distinctive characters by which they can be
readily recognised.
THE METATARSUS
201
The first metatarsal (fig. 245) is the most modified of all the metatarsal bones, and deviates
widely from the general description given above. It is the shortest, the thickest, the strongest,
and most massive of the series. The base presents a large reniform, slightly concave facet
for the first cuneiform and projects downward into the sole to form the tuberosity, a rough
eminence into which the peroneus longus and a slip of the tibialis anterior are inserted. A little
Fig. 246. — The Second (Left) Metatarsal.
Medial side
An occasional facet for the first
metatarsal /
First cuneiform —
Facets for third metatarsal
Facets for third cuneiform
above the tuberosity, on its lateral side, there is occasionally a shallow, but easily recognised
facet, for articulation with the base of the second metatarsal. The head is marked on the plan-
tar surface by two deep grooves, separated by a ridge, in which the two sesamoid bones of the
flexor hallucis brevis glide. The shaft is markedly prismatic. The dorsal surface is smooth,
broad, and convex, directed obliquely upward; the plantar surface is concave longitudinally
Fig. 247 — The Third (Left) Metatarsal.
Facets for second metatarsal
Facets for second metatarsal
Facet for fourth metatarsal
and covered by the flexor hallucis longus and brevis, whilst the lateral surface is triangular in
outline, almost vertical, and in relation with the first dorsal interosseous and adductor hallucis
obliquus. A few fibres of the medial head of the fii'st dorsal interosseous occasionally arise from
the hinder part of the surface adjoining the base, or from the border separating the lateral from
the dorsal surface. Somewhere near the middle of the shaft, and on its fibular side, is the
nutrient foramen, directed toward the head of the bone.
202
THE SKELETON
The second metatarsal (fig. 246) is the longest of the series. Its base is prolonged back-
ward to occupy the space between the first and third cuneiform, and accordingly it is marlced
by facets for articulation with each of these bones. The tarsal surface is triangular in outline,
with the base above and apex below, and articulates with the second cuneiform bone. On the
tibial side of the base, near the upper angle, is a small facet for the first cuneiform, and occa-
FiG. 248. — The Fourth (Left) Metatarsal.
Facet for third metatarsal
Facet for third metatarsal
Facet for third cuneiform
- Facet for fifth metatarsal
sionally another for the first metatarsal a little lower down. The fibular side of the base pre-
sents an upper and a lower facet, separated by a non-articular depression, and each facet is
divided by a vertical ridge into two, thus making four in all. The two posterior facets articu-
late with the third cuneiform and the two anterior with the third metatarsal. The base gives
attachment to a slip of the tibialis posterior and the adductor hallucis obliquus, whilst from the
Fig. 249. — The Fjfth (Left) Metatarsal.
Tibial
Medial side
Fourth metatarsal
Fibular
lateral side
shaft the first and second dorsal interosseous muscles take origin. The nutrient foramen is
situated on the fibular side of the shaft near the middle and is directed toward the base of the
bone.
The third metatarsal (fig. 247), a little shorter than the second, articulates by the tri-
angular surface of its base with the third cuneiform. On the medial side are two small facets,
one below the other, for the second metatarsal, and on the lateral side, a single large facet for
the fourth metatarsal. The base gives attachment to a slip of the tibialis posterior and the
adductor hallucis obliquus, and from the shaft three interosseous muscles take origin. The
nutrient foramen is situated on the tibial side of the shaft and is directed toward the base.
THE PHALANGES
203
The fourth metatarsal (fig. 248), smaller in size than the preceding, is distinguished by
the quadrilateral facet on the base, for the cuboid. The medial side presents a large facet
•divided by a ridge into an anterior portion for articulation with the third metatarsal and a,
posterior portion for the third cuneiform. Occasionally the cuneiform part of the facet is
wanting. On the lateral side of the base is a single facet for articulation with the fifth
metatarsal.
The fifth metatarsal (fig. 249), is shorter than the fourth, but longer than the first. It is
recognised by the large nipple-shaped process, known as the tuberosity, which projects on the
lateral side of the base. It constitutes the hindmost part of the bone and gives insertion to
the -peroneus brevis on the dorsal aspect, and flexor brevis digili quinli and the occasional
■abduclor ossis metatarsi quinli on the plantar aspect. The fifth metatarsal articulates behind
by an obliquely directed triangular facet with the cuboid, and on the medial side with the
fourth metatarsal. The plantar aspect of the base is marked by a shallow groove which
lodges the tendon of the abductor digili quinli, and the dorsal surface, continuous with the
superior surface of the shaft, receives the insertion of the peroneus terlius. The head is small
and turned somewhat laterally in consequence of the curvature of the shaft in the same
direction. The shaft differs from that of any of the other metatarsals in being compressed
from above downward, instead of from side to side, so as to present superior, inferior, and
medial surfaces. It gives origin to the lateral head of the fourth dorsal interosseous and the
third plantar interosseous muscles. The nutrient foramen is situated on its tibial side and is
directed toward the base.
Ossification. — Each metatarsal ossifies from two centres. The primary nucleus for the
shaft appears in the eighth week of embryonic life in the middle of the cartilaginous metatarsal.
At birth, each extremity is represented by cartilage, and that at the proximal end is ossified by
extension from the primary nucleus', except in the case of the first metatarsal. For this, a
nucleus appears in the third year.
The distal ends of the four lateral metatarsals are ossified by secondary nuclei which make
their appearance about the third year. Very frequently an epiphysis is found at the distal end
of the first metatarsal as well as at its base. The shafts and epiphyses consolidate at the twen-
tieth year. The sesamoids belonging to the flexor hallucis brevis begin to ossify about the fifth
year.
THE PHALANGES
The phalanges (fig. 250) are the bones of the toes, and number in all fourteen.
Except the great toe, each consists of three phalanges, distinguished as first
(proximal), second and third (distal) ; in the great toe the second phalanx is absent.
Fig. 250. — The Phalanges of the Middle Toe.
5?1
There is thus a similarity as regards number and general arrangement with the
phalanges of the fingers. With the exception of the phalanges of the great toe,
which are larger than those of the thumb, the bones of the toes are smaller and
more rudimentary than the corresponding bones of the fingers. In all the pha-
langes, the nutrient foramen is directed toward the distal extremity.
The phalanges of the first row are constricted in the middle and expanded at either ex-
tremity. The shafts are narrow and laterally compressed, rounded on the dorsal and concave
204
THE SKELETON
on the plantar aspects. The base of each presents a single oval concave facet for the convex
head of the corresponding metatarsal, whilst the head forms a pulley-like surface [trochlea
phalangis], grooved in the centre and elevated on each side for the second phalanx.
The phalanges of the second row are stunted, insignificant bones. Their shafts, besides
being much shorter, are flatter than those of the first row. The bases have two depressions,
separated by a vertical ridge, and the heads present trochlear surfaces for the ungual phalanges.
The third, or ungual phalanges are easily recognised. The bases articulate with the second
phalanges; the shafts are expanded, forming the ungual tuberosities which support the nails,
and their plantar surfaces are rough where they come into relation with the pulp of the digits.
The muscles attached to the various phalanges may be tabulated thus: —
The first phalanx of the hallux gives insertion to the flexor haUucis brevis; abductor halluois;
adductor hallucis transversus and obliquus; extensor digitorum brevis.
The first phalanx of second toe : The first and second dorsal interosseous.
The first phalanx of third toe : Thii'd dorsal interosseous; first plantar interosseous.
The first phalanx of fourth toe : Second plantar interosseous; fourth dorsal interosseous.
The first phalanx of fifth toe: Third plantar interosseous; flexor digiti quinti brevis; and
abductor digiti quinti.
The terminal phalanx of hallux: Flexor hallucis longus; extensor hallucis longus.
Fig. 251. — A Longitudinal Section of the Bones of the Lower Limb at Birth.
The centre for the lower extremity of
the femur appears early in the
ninth month
The centre for the upper end of the
tibia appears about a week before
The centre for the navicular appears in the fourth year
For the first cuneiform appears in the third year
First phalanx of hallux
Second phalanx of hallux
The second phalanges of the remaining toes : Dorsal expansion of the extensor tendons,
including extensor digitorum longus, extensor digitorum brevis (except in the case of the fifth
toe), and expansions from the interossei and lumbricales.
The third phalanges : Flexor digitorum longus; dorsal expansion of the extensor tendon
with the associated muscles.
Ossification, — Like the corresponding bones of the fingers, the phalanges of the toes ossify
from a primary and a secondary nucleus. In each, the centre for the shaft appears during the
eighth or ninth week of embryonic life. The secondai-y centre forms a scale-like epiphysis for
the proximal end between the fourth and eighth years, and union takes place in the eighteenth
or nineteenth year — i. e., earlier than the corresponding epiphj'ses in the fingers. The primary
centres for the third phalanges appear at the distal extremities of the bones.
Sesamoid Bones
In the foot a pah- of sesamoid bones is constant over the metatarso-phalangeal joint of the
great toe in the tendons of the flexor hallucis brevis. One sometimes occurs over the inter-
phalangeal joint of the same toe and over the metatarso-phalangeal joints of the second and
fifth and rarely of the third and fourth toes.
BONES OF THE FOOT AS A WHOLE
205
A sesamoid also occurs in the tendon of the peroneus longus, where it glides over the groove
in the cuboid; another may be found, especially in later life, in the tendon of the tibialis anterior
over the first cuneiform bone, and another in the tendon of the tibialis posterior over the medial
surface of the head of the talus. Further a sesamoid, the fabella, sometimes occurs in the
lateral head of the gastrocnemius, and another may be found in the tendon of the ilio-psoas
over the pubis.
BONES OF THE FOOT AS A WHOLE
Although the foot is constructed on the same general plan as the hand, there
is a marked difference in its architecture to qualify it for the different functions
which it is called upon to perform. When in the erect posture, the foot forms a
firm basis of support for the rest of the body, and the bones are arranged in an
elliptical arch, supported on two pillars, a posterior or calcaneal pillar and an
Fig. 252. — The Secondary Ossific Centres op the Foot.
The centre for the epiphysis for
calcaneus appears at the tenth year
consolidates at the sixteenth year
The centre for the epiphysis for the
metatarsal of the hallux appears at
the third year; consolidates at the
twentieth year
The centres for the base of the ter-
minal phalanges appear at sixth
year, and consolidate at the eight-
eenth year
The'centres for the heads of the metatarsals
appear'atlthelthird year, and consoUdate at the twentieth year
anterior or metatarsal pillar. It is convenient, however, to regard the anterior
part of the arch as consisting of two segments, corresponding to the medial and
lateral borders of the foot respectively. The medial segment is made up of the
three metatarsal bones, the three cuneiform, the navicular, and talus; the lateral
segment is made up of the fourth and fifth metatarsal bones, the cuboid, and the
calcaneus, and both segments are supported behind on a common calcaneal pillar.
The division corresponds to a difference in function of the two longitudinal arches.
Both are intimately concerned in ordinarj- locomotion. In addition, the medial,
characterised by its great curvature and remarkable elasticitj^, sustains the more
violent concussions in jumping and similar actions, whereas the lateral, less curved,
more rigid, and less elastic arch forms, with the pillars in front and behind, a
firm basis of support in the upright posture.
Both arches are completed and maintained by strong ligaments and tendons.
The weakest part is the joint between the talus and navicular bone, and special
206
THE SKELETON
provision is accordingly made, by the addition of a strong calcaneo-navicular liga-
ment, for the support of the head of the talus. This ligament is in turn supported
by its union with the deltoid ligament of the ankle, and by the tendon of the
tibialis posterior which passes beneath it to its insertion.
Besides being arched longitudinally, the foot presents a transverse arch formed
by the metatarsal bones in front and the distal row of the tarsus behind. It is
produced by the marked elevation of the central portion of the medial longitudinal
arch above the ground, whereas the lateral longitudinal arch is much less raised,
and at its anterior end becomes almost horizontal. Both the longitudinal and
transverse arches serve the double purpose of increasing the strength and elasticity
of the foot and of providing a hollow in which the muscles, nerves, and vessels of
the sole may lie protected from pressure.
Homology of the Bones of the Limbs
That there is a general correspondence in the plan of construction of the two extremities is
apparent to a superficial observer, and this becomes more marked when a detailed examination
of the individual bones, their forms and relations, their embryonic and adult peculiarities, is
systematically carried out. In each limb there are four segments, the shoulder girdle corre-
sponding to the pelvic girdle, the arm to the thigh, the forearm to the leg, and the hand to the
foot. These parts have been variously modified, in adaptation to the different functions of the
two limbs, particularly as regards the deviations or changes from what is regarded as their primi-
FiG. 253.-
Subscapular fo
-Diagrammatic Representation op the Bones op the Two Limbs, to
SHOW Homologous Parts. (Modified from Flower.)
Iniiaspinous fossa
Great trochanti
^^'
'^V.
tive position, and as a knowledge of these changes is essential to a clear understanding of the
homologous bones, it will be advantageous to refer briefly to the relations of the limbs in the
earliest stages of development.
The limbs first appear as flattened, bud-like outgrowths from the sides of the trunk. Each
presents a dorsal or extensor surface, and a ventral or flexor surface, as well as two borders,
an anterior, or cephalic, directed toward the head end of the embryo, and a posterior or caudal,
du-ected toward the tail end. In reference to the axis of the limb itself, the borders have
been called pre-axial and post-axial, respectively. When, somewhat later, the various divisions
of the limb make their appearance, it is seen that the gi-eater tuberosity, the lateral epicondyle,
the radius, and the thumb he on the pre-axial border of the anterior extremity, and the small
trochanter, the medial condyle, the tibia, and the great toe on the pre-axial border of the
posterior extremity. Further on the post-axial border of the anterior extremity are seen the
lesser tuberosity, the medial epicondyle, the ulna, and little finger, whilst on the corresponding
border of the posterior limb are the great trochanter, the lateral condyle, the fibula, and the
little toe. The parts now enumerated on the corresponding borders of the two limbs must
therefore be regarded as serially homologous (fig. 253).
HOMOLOGY OF THE BONES OF THE LIMBS 207
It is necessary to trace next the further changes which take place in the segments of the limbs
up to the time when they assume their permanent positions. They may be arranged in stages
as follows: —
(1) Each segment of the limb is bent upon the one above it. The humerus and femur
remain unchanged. The forearm segment, however, is bent so that the ventral surface looks
medially and the dorsal surface laterally. Moreover, the joints between these segments — i. e.,
elbow and knee — form marked projections. The terminal segments (hand and foot) are bent
in the opposite direction to the middle one, so that the primitive position is retained, and the
ends of the digits directed laterally. It will be noticed that in this series of changes the relations
of the pre-axial and post-axial borders of the limbs remain as before.
(2) This stage consists in a rotation of the whole limb from the proximal end, though in an
exactly opposite direction in each case. The anterior extremity is rotated backward so that the
humerus lies parallel with the trunk; the elbow is directed toward the caudal end, the pre-axial
(radial) border becomes lateral, and the post-axial border medial. The ends of the digits point
backward. The posterior extremity undergoes a rotation forward to the same extent, so that
the femur is also nearly parallel with the trunk; the knee is directed toward the head end, the
pre-axial (tibial) border becomes medial, and the post-axial border lateral. The tibia and
fibula are parallel, the ends of the digits are directed forward, the gi-eat toe is on the pre-axial
and the Uttle toe on the post-axial border of the Umb, and in this position the posterior extremity
remains, the changes being finally completed by the extension of the Hmb at the hip-joint as the
body attains its full development.
(3) This stage affects the anterior extremity alone and consists in a rotation of the radius,
carrying the hand round the ulna so that the digits are brought round from the back to the front
of the limb, and in many animals the maOus is thus placed permanently in the prone position.
But in man, in whom the capacity for pronation and supination is highly developed, the hand
can assume either position at will. In his case the final change is the extension which takes place
at the shoulder-joint with the assumption of the upright posture, the limb dropping loosely at
the side of the body, and being endowed with the greatest freedom of movement.
Homological comparison of —
I. The shoulder and pelvic girdles. — Primarily the lateral half of each girdle consists
of a curved bar or rod of cartilage placed at right angles to the longitudinal axis of the trunk and
divisible into a dorsal segment, and a ventral segment, the point of division corresponding
to the place of articulation with the limb-stalk — i. e., the glenoid and acetabular cavities. In
the fore-limb the dorsal segment is the scapula, and the ventral segment the coracoid, whilst
in the hind-hmb the dorsal segment is the iUum and the ventral segment the ischium and
pubis.
The dorsal segments of the two girdles — i. e., scapula and ihum — are accordingly regarded
as homologous bones, the chief difference being that whereas the scapula is free from articulation
with the vertebral column, the ilium is firmly jointed to the rib elements (lateral mass) of the
sacrum. But the correspondence is not quite so clear with regard to the ventral segments. In
the primitive condition the coracoid articulates with the side of the sternum, an arrangement
which persists throughout hfe in certain animals, such as reptiles and Ornithorhynchus. But in
aU the higher mammals it undergoes reduction, withdrawing from the side of the sternum, and
eventually forming a more or less rudimentary process attached to the scapula. In the more
generahsed form of shoulder girdle the ventral bar is double, consisting of coracoid and pre-
coracoid elements, the latter being situated in front and almost parallel with the coracoid. The
pre-coracoid in mammals is largely replaced by the development over it of the clavicle, a dermal
or membranous splint-bone which eventually invades the underlying cartilage. Parts, however,
remain distinct and form the sternal epiphysis of the clavicle, the inter-articular cartilage
between it and the sternum, the supra-sternal bones, and the inconstant inter-articular cartilage
in the acromio-clavicular joint.
It has already been noticed that in the hip girdle the ventral segment also consists of two
elements, the pubis and ischium. Both take part in the formation of the acetabular cavity, and
the pubis meets in the ventral median line the corresponding segment of the opposite side.
It is generally agreed that the coracoid and ischium are homologous structures. The pubic
portion of the ventral segment appears to correspond most closely with the pre-coracoid element
of reptiles, so that there is no true homologue of the clavicle in the pelvis. If, however, the
clavicle corresponds to the reptilian pre-coracoid, as believed by many anatomists, it then be-
comes the representative of the pubis,
From a consideration of the condition in oranio-cleido-dysostosis, Mr. FitzwiUiams has
put forward the following views regarding the homology of the shoulder girdle: — Coracoid bar
is represented by (a) medial two-thu'ds of clavicle; (b) coraco-clavicular ligaments; and (c)
sub-coracoid centre of coracoid process. The clavicula, a membranous bone, is represented
by the lateral third of adult clavicle. The pre-coracoid bar is represented by: — (a) the coracoid
process (less the sub-coracoid centre) ; and (b) the costo-coracoid ligament. The epi-coracoid
is represented by the meniscus of the sterno-clavicular joint.
Moreover, it is possible to establish a comparison between the individual parts of the ilium
and scapula. A reference to fig. 253 shows that both the scapula and ilium may be resolved into
three-sided prismatic rods, each of which has thi-ee surfaces and three borders. In the primitive
position of the limb one surface — the internal — is turned toward the vertebral column, the
remaining surfaces are external, and named -pre-axial and post-axial, corresponding to the borders
of the limb. The borders separating the internal from the external surfaces are antero-internal
(terminating in the acromion or pubis) and postero-internal (terminating in the coracoid or
ischium). The two external surfaces are separated by a ridge, terminating below at the upper
margin of the glenoid cavity or acetabulum (glenoid and cotyloid borders).
The primitive arrangement is lost by the marked growth of the borders of the rods leading
to the formation of fossae and by the rotation of each rod, the scapula laterally and the ihum
medially, in association with the rotation which takes place in the free part of the limb, so that
208
THE SKELETON
the inner surface of the one comes to correspond with the outer surface of the other. It results
that the primitive vertebral surface of the scapula is now the pre-scapular or supraspinous
fossa, and the corresponding surface in the ilium is the sacral, which, on account of its close con-
nection with the vertebral column, undergoes but little change in position. Further, the primi-
tive pre-axial surfaces are the infraspinous fossa and the iliac fossa, which accordingly are to
be regarded as homologous, as well as the two post-axial surfaces, the subscapular fossa and the
dorsum ilii. The correspondence between the various parts of the scapula and ilium is shown
in the appended table (after Flower).
I. Surfaces •
II. Borders:
ScAPUIiA
Supraspinous fossa.
Infraspinous fossa.
Subscapular fossa.
Axillary or glenoid.
Spine.
Superior or coracoid.
Base.
Primitive
Arrangement
Vertebral.
Pre-axial.
Post-axial.
External.
Antero-internal.
Postero-internal.
Dorsal extremity.
Ilium
Sacral surface.
Iliac fossa.
Gluteal surface.
Cotyloid or anterior
border.
Terminal line.
Posterior border.
Crest of ilium.
II. Bones of the arm and thigh, forearm, and leg. — It has already been pointed out in
describing the deviation of the limbs from the primitive position that the humerus corresponds
to the femur, the radius to the tibia, and the ulna to the fibula; also that in consequence of the
rotation backward of the fore-limb, and forward of the hind-limb, the lateral side of the humerus
corresponds with the medial aide of the femur, the radial border of the forearm to the tibial
border of the leg, and the ulnar (border of the forearm) to the fibular border of the leg. The
corresponding parts are tabulated below: —
Fore-Limb
Humerus
Greater tuberosity
Lesser tuberosity
Lateral epicondyle and capitulum
Medial epicondyle and trochlea
Radius
Ulna
Not represented
Hind-Limb
Femur
Lesser Trochanter
Great Trochanter
Medial Condyle
Lateral Condyle
Tibia
Fibula
Patella
III. Bones of the hand and foot. — It is obvious that the carpus and tarsus, the meta-
carpus and metatarsus, and the various digits, commencing at the thumb, in the hand, and at
the great toe, in the foot, are serially homologous.
Fig. 254. — Dorsal Surface of the Right Manus of a Water-tortoise, Chelydra serpentina.
("After Gegenhaur.l
In order to trace the correspondence between the various elements of the carpus and tarsus
it is convenient to refer in the first place to the primitive type of hand and foot as found in the
water-tortoise and the lizard (fig. 254). In each segment nine elements may be recognised,
arranged in a proximal row of three, named respectively radiate or tibiale, intermedium, and
ulnare, or flbulare, a distal row of five carpalia, or tarsalia, numbered from one to five, commenc-
ing at the pre-axial border, and between the two rows an os cenlrale.
In man the carpus is derived from the typical form in the following manner: The radiale
forms the navicular, intermedium the lunate, and the ulnare, the triquetral; carpale I forms
the greater multangular, oarpale II the lesser multangular, carpale III the capitate, whilst car-
paha IV and V coalesce to form the hamate. The os centrale is present in the human carpus
at an early stage, but in the second month it joins the navicular. It is occasionally separate —
a normal arrangement in most of the primates.
HOMOLOGY OF THE BONES OF THE LIMBS
209
In the tarsus, the tibiale and intermedium coalesce to form the talus, and the fibulare
becomes the calcaneus. It is interesting to note that although in the human subject there are
three bones in the first row of the carpus and two in the first row of the tarsus, in carnivores the
navicular and lunate are united to form a naviculo-lunate bone — the homologue of the talus.
In the human tarsus the intermedium occasionally remains distinct as the os trigonum.
Tarsale I forms the first cuneiform, tarsale 11 the second cuneiform, tarsale III the third
cuneiform, and tarsale IV and V are joined to form the cuboid. The os centrale forms the
navicular.
In addition to the carpal and tarsal elements enumerated above, brief mention must now
be made of the sesamoid bones of the two segments, which are regarded by many anatomists
as vestiges of suppressed digits. In the hand are the ulnar and radial sesamoids, the ulnar
being represented by the pisiform and the radial probably by the tuberosity of the navicular.
(In the mole and other aUied species with fossorial habits, the radial sesamoid is greatly de-
veloped to form a sickle-shaped bone which has received the name of os falciforme.)
The corresponding structures in the foot are the tibial and fibular sesamoids, the tibial
being most nearly represented by the tuberosity of the navicular and the fibular by the tuber
of the calcaneus.
Table Showing the HoMOLOGOtis Bones op the Carpus and Tarsus.
in Quain's Anatomy.)
[After G. D. Thane
Carpus
Priaiitive Names
Tarsus
> Calcaneus
I Talus
> Navicular
First cuneiform
Second cuneiform
Third cuneiform
} Cuboid
References. — ^For the development of the skeleton, consult the bibliography
in Bardeen's article in Keibel and Mall's ' Human Embryology,' Vol. 1. For
further references concerning the adult structure and morphology of the skeleton,
the sections on osteology in the larger works on human anatomy by Quain, von
Bardeleben, Rauber-Kopsch. Poirier-Charpy, etc., should be consulted. Refer-
ences to the most recent literature may be found in Schwalbe's Jahresbericht,
the Index Medicus, and in the various anatomical journals.
Triquetral
Ulnare
Fibulare
Pisiform
Ulnar sesamoid
Fibular sesamoid
Lunate
Intermedium
Intermedium
■ Radiale
Tibiale
Navicular
Radial sesamoid
Tibial sesamoid
Centrale
Centrale
Greater multangular
Carpale I
Tarsale I
Lesser multangular
II
II
Capitate
" III
" III
Hamate
r " IV
( " V
" IV
V
I
SECTION III
THE ARTICULATIONS
Revised for the Fifth Edition
By FREDERIC WOOD JONES, D.Sc, M.B., B.S.(Lond.), M.R.C.S.,L.R.C.P.
HEAD OF THE DEPARTMENT OF ANATOMY AND LECTURER IN THE LONDON SCHOOL OP MEDICINE FOR WOMEN.
THE CONSTITUENTS OF AN ARTICULATION
THE section devoted to the Articulations or Joints deals with the union of the
various and dissimilar parts of the human skeleton. The followiing struc-
tures enter into the formation of joints.
Bones constitute the basis of most joints. The long bones articulate by their
ends, the flat by their edges, and the short at various parts on their surfaces. The
articular ends are usually expanded, and are composed of cancellous tissue, sur-
rounded by a dense and strong shell of compact tissue.
This shell has no Haversian canals (the vessels of the cancellous tissue turn back and do
not perforate it), or large lacunae, and no canaliculi, and is thus well adapted to bear pressure.
This "osteoid" layer may represent in part calcified cartilage rather than true bone.
The cartilage which covers the articular ends of the bones is called articular,
and is of the hyaline variety. It is firmly implanted on the bone by one surface,
while the other is smooth, polished, and free, thus reducing friction to a minimum,
while its slight elasticity tends to break jars. It ends abruptly at the edge of the
articulation, and is thickest over the areas of greatest pressure.
Another form of cartilage, the white fibrous, is also found in joints: —
(i) As inlerarlicular cartilage in diarthrodial joints — viz., in the knee, mandibular,
sterno-clavicular, radio-carpal, and occasionally in the acromio-clavicular joint. It is interposed
between the ends of the bones, partially or completely dividing the synovial cavity into two.
It serves to adjust dissimilar bony surfaces, adding to the security of, while it increases the
extent of motion at, the joint; it also acts as a buffer to break shocks.
(ii) As circumferential or marginal iibro-cartilages, which serve to deepen the sockets
for the reception of the heads of bones — e. g., the glenoid ligaments of the shoulder and hip.
Another form of marginal plate is seen in the accessory volar ligaments of the fingers
and toes, which deepen the articulations of the phalanges and add to their security.
(iii) As connecting fibro-cartilage. The more pliant and elastic is the more cellular form,
and is found in the intervertebral discs; while the less yielding and more fibrous form is seen in
the sacro-iliac and pubic articulations, where there is little or no movement.
The ligaments which bind the bones together are strong bands of white fibrous
tissue, forming a more or less perfect capsule [capsula articularis], round the articu-
lation. They are pliant but inextensile, varying in shape, strength, and thick-
ness according to the kind of articulation into which they enter. They are closely
connected with the periosteum of the bones they unite. In some cases — as the
ligamenta flava which unite parts not in contact — they are formed of j'ellow
elastic tissue.
The synovial membrane [stratum synoviale] lines the interior of the fibrous
ligaments, thus excluding them, as well as the cushions or pads of fatty tissue
situate within and the tendons which perforate the fibrous capsule, from the
articular cavity. It is a thin, delicate membrane, frequently forming folds and
fringes which project into the cavity of the joint; or, as in the knee, stretches across
the cavity, forming a so-called synovial ligament. In these folds are often found
pads of fatty tissue, which fill up interstices, and form soft cushions between the
contiguous bones. The amount of fat that is normally present within a joint
varies greatly. It is an old observation that although there is always fat in the hip-
211
I
212 THE ARTICULATIONS
and knee-joints, there is usually none within the shoulder-joint. Sometimes
these fringes become villous and pedunculated, and cause pain on movement of
the joints. They contain fibro-fatty tissue, with an isolated cartilage cell or two.
The synovial membrane is well supplied with blood, especially near the margins of
the articular cartilages and in the fringes. It secretes a thick, glairy fluid like
white of egg, called synovia, which lubricates the joint. Another variety of
synovial membrane is seen in the bursas, which are interposed between various
moving surfaces. In some instances bursas in the neighbourhood of a joint may
communicate with the synovial cavity of that joint.
CLASSIFICATION OF ARTICULATIONS
Joints may be classified: — (a) From an anatomical point of view, with regard
to the substances and the arrangement of the substances by which the constituent
parts are united. (6) From a physiological standpoint, with regard to the greater
or smaller mobility at the seat of union, (c) From a physical standpoint, either
the shapes of the portions in contact being mainly considered or the axes round
which movement can occur. Or again (d) a combination of the preceding methods
may be adopted, and this is the plan most generally followed. None of the classi-
fications hitherto used is quite satisfactory, but perhaps, on the whole, that
suggested by Prof. Alex. Macalister is the least open to objection, and therefore
with slight modification it is utilised here.
There are three chief groups of joints: —
1. Synarthroses. In joints of this class the bones are united by fibrous tissue.
2. Synchondroses. Or joints in which the uniting substance intervening be-
tween the bones is cartilage.
3. Diarthroses. The constituent parts of joints of this class are (a) two or more
bones each covered by articular hyaline cartilage ; (6) a fibrous capsule uniting the
bones, and (c) a synovial membrane which lines the fibrous capsule and covers
any part of bone enclosed in the capsule and not covered with articular cartilage.
An interarticular plate of cartilage may or may not be present.
Synarthroses. —
(a) Sutures or immovable joints, in which the' fibrous tissue between the bones is too
small in amount to allow movement.
(1) Harmonic. The edges of the bones are comparatively smooth and are in even
apposition, e. g., vertical plate of palate and maxilla.
(2) Squamous. The margin of one bone overlaps the other, e. g., temporal and
parietal.
(3) Serrate. The opposed edges interlock by processes tapering to a point.
(4) Dentate. The opposed edges are dovetailed, e. g., occipital and parietal.
(5) Limbous. The opposed edges alternately overlap, e. g., parietal and frontal.
(6) Schindylesis. A ridge or flattened process is received into a corresponding
socket, e. g., rostrum of sphenoid and vomer.
(7) Gotnphosis. A peg-like process is lodged in a corresponding socket, e. g., the
fangs of the teeth.
(6) Syndesmoses. Movable joints in which the fibrous tissue between bones or carti-
lages is sufficiently lax to allow movement between the connected parts, e. g.,
thyreo-hyoid membrane. Interosseous membranes of forearm and leg.
2. Synchondroses. — In all synchondroses a certain amount of movement is possible, and
they are often called amphiarthroses.
(1) True synchondroses. The cartilage connecting the bones is the remains of the bar
in which the bones were ossified, e. g., occipito-sphenoidal joint.
(2) False synchondroses. The plate of cartilage intervening between and connecting
the bones is fibro-cartilage and is not part of the cartilage in which the bones were
ossified, but is developed separately, e. g., intervertebral joint and pubic sym-
physis. The articular end of each bone may be covered with hyaUne cartilage
and there may be a more or less well-marked cavity in the intervening plate of
fibro-cartilage.
3. Diarthroses. — In diarthrodial joints the surfaces in contact may be equal and similar
or unequal and dissimilar. In the former case the joints are homomorphic; in the
latter, heteromorphic.
(A) HomomorTphic.
(a) Plane or arlhrodial. Flat surfaces, admitting gliding movement, e. g.,
intercarpal and acromio-clavicular joints.
(6) Ephippial. Saddle-shaped surfaces placed at right angles to each other, ad-
mitting free movement in all directions, e. g., metacarpo-phalangeal joint
of thumb.
DEVELOPMENT OF JOINTS
213
(B) Heteromorphic.
(a) Enarlhrodial. Ball-and-socket, allowing the most free movement, e. g., hip-
and shoulder-joints.
(6) Condylarlhroses. The convex surface is ellipsoidal, and fits into a corresponding
concavity, e. g., wrist and metacarpo-phalangeal joints,
(c) Ginglymi. One surface consists of two conjoined condyles or of a segment of
a cone or cylinder, and the opposite surface has a reciprocal contour. In these
joints movement is only permitted round one axis, which may be transverse;
e. g., elbow, ankle; or it may be vertical, in which case the joint is trochoid;
e. g., odontoid process of axis with atlas, radius with ulna.
Such a classification should be considered as being purely academic and the student must
always remember that it is not enough to discuss a joint by assigning it to a particular class in
any scheme; for he must be familiar with the actual conditions present in every joint. No
classification, however perfect, must be taken as final, and each joint should be studied as a
separate thing altogether apart from any general systematic arrangement.
DEVELOPMENT AND MORPHOLOGY OF JOINTS
The arrangement of the various parts which constitute an articulation is best appreciated
by a study of the development of the various types of joints. In this way it is easy to recog-
nise a primitive condition typical of each class; but it must be remembered that various modi-
fications take place during growth, that these modifications vary in the individual joints, and
produce adult departures from the primitive arrangement which are peculiar to each joint and
which must be studied separately.
In the case of bones ossifying in membrane the articulation will be a suture, the ossifications
from neighbouring centres extending until they practically come into contact.
Fig. 255. — Development of Joints
A. Stage in which primary embryonic tissue separates the developing cartilages.
B. Primary embryonic tissue transformed into cartilage (synchondrosis), or fibrous connec-
tive tissue (syndesmosis).
C. Degeneration of embryonic tissue with production of a joint cavity (diarthrosis).
tWith cartOage bones the articulation may be either a syndesmosis, a synchondrosis, or a
diarthrosis. The embryonic tissue in which the cartilage is to develop is at first continuous;
centres of chondrification, corresponding in number to the bony elements which are destined to
be formed, appearing in it. As the chondrifications approach each other a small portion of the
primary embryonic tissue persists between them (fig. 255), and it is the subsequent fate of
this intermediate tissue that determines the nature of the articulation.
(1) When the ossification of the cartilage occurs to form the articulating bones, the inter-
mediate tissue may undergo transformation into cartilage (fig. 255), a synchondrosis being
thus produced. (2) Or the intermediate tissue may be converted into fibrous connective-tissue
I
214 THE ARTICULATIONS
(fig. 255), the result being a syndesmosis. (3) Or, finally, the central portion of the inter-
mediate tissue may degenerate, so that an articular cavity is produced, the peripheral portions
being converted into connective tissue, forming a sleeve-like capsule surrounding the cavity,
continuous at either extremity with the periosteum of the articulating bones (fig. 255). This
is the articular capsule, and the connective-tissue cells arranging themselves in a layer upon
its inner surface give rise to a synovial membrane. As the result of these processes a diarthrosis
is produced, and from its mode of formation it is clear that the cavity of such an articulation is
completely closed.
In a typical diarthrosis there is therefore a ligamentous capsule which entirely encloses the
joint cavity, which is continuous with the periosteum of the bones entering into the articulation
but which is not attached to nor reflected onto the cartilaginous ends of the bones which consti-
tute the articulating surfaces. Such a capsule constitutes the primitive bond between the articu-
lating bones and furnishes a complete lubricating bag in which these smooth cartilaginous
ends gKde over one another. This primitive capsule, however, becomes modified in most adult
joints, (1) by unequal development of various parts of the capsule; and (2) by the more or less
complete incorporation of other structures which are developmentaUy separate from the capsule.
Under the first heading come specially thickened bands which may be so distinctly marked off
from the rest of the capsule as to be named as separate hgaments (e. g., the temporo-mandibular
ligament of the mandibular joint). Again certain thickened bands of capsule may, with
alteration of joint contour, take up anatomical positions which are apparently separated from
the rest of the capsule; advanced examples of this process are, in all probability, seen in the
ligamentum teres of the hip-joint and the crucial ligaments of the knee. Under the second
heading comes a series of ligaments derived from a gi'eat variety of soirrces; the most common
origin being from the divorced or rearranged tendons of the muscles around the joint.
Muscles arising from, or inserted into, bones in the immediate vicinity of a joint tend to
become metamorphosed into tendon near their attachments, and a comprehensive study of
myology in low vertebrate forms indicates that there is associated with this tissue-change a
tendency for the muscle to alter its point of attachment; hence a muscle originally inserted below
a joint may eventually come to have its insertion above the joint. In the same way, a muscle
arising above a joint may, as a result of altered environment, shift its origin to some point below
the joint. To this change of position the term migration of muscles has been applied. In
many instances a portion of the muscle equivalent to the distance between the original and the
acquired attachment persists as a fibrous band and fulfils the function of a Ugament. This is well
seen in the knee-joint, where the tibial collateral ligament is derived from the adductor magnus,
this muscle having shifted its insertion from the tibia to the femur. In the same way the
fibular collateral ligament represents the tendon of the peroneus longus, which has migrated
from the femur to the head of the fibula.
Among other ligaments derived in a similar way from muscles may be mentioned the sacra-
tuberous ligament. This was originally the tendon of origin of the biceps femoris. (H. Morris,
Med. Times and Gazette, 1877, p. 361.) The sacro-spinous is derived from the fibrous retro-
gression of portions of the coccygeus. The sacro-coccygeal ligaments represent the muscles
which lift, depress, and wag the tail in those mammals furnished with such an appendage;
indeed, these ligaments are occasionally replaced by muscle-tissue.
The coraco-humeral ligament is derived from the original tendon of insertion of the pectorahs
minor, and not unfrequently the muscle is inserted into the lesser tuberosity of the humerus, the
ligament being then replaced by the tendon of the muscle. The coraco-clavicular, rhomboid, and
gleno-humeral ligaments are probably derived from modifications of the subclavius muscle.
Other anatomical structures besides muscles may, when degenerated or functionally
altered, form the basis of ligaments in connection with joints. The spheno-mandibular ligament
is the fibrous remnant of the cartilaginous mandibular bar.
The pulpy substance in the centre of each interoertebral disc is derived from the notochord;
the apical ligament passing from the tip of the dens to the anterior margin of the foramen
magnum is a remnant of the sheath of the notochord, and indicates its position as it passed
from the vertebral column into the base of the cranium. The transverse ligament of the atlas
(as pointed out by Professor Cleland) is a persistent and functional form of the posterior conjugal
ligament uniting the rib-heads in seals and many other mammals, whilst the interosseous
ligament of the head of a rib in man is the feeble representative of this structure in the thoracic
region of the spine. The ligamentum conjugate costarum was described by Mayer in 1834
(Mtiller's Archiv fiir Anatomie). According to Luschka's account of this ligament it would
seem as though the posterior superior fibres of the capsule of the costo-central joint represented
it in man, rather than the interosseous ligament.
THE MOVEMENTS OF JOINTS
The movements which may take place at a joint are either gliding, angular,
rotatory, or circumductorJ^
The gliding motion is the simplest, and is common to aU diarthrodial joints; it consists of a
simple sliding of the apposed surfaces of the bones upon one another, without angular or rotatory
motion. It is the only kind of motion permitted in the carpal and tarsal joints, and in those
between the articular processes of the vertebne.
The angular motion is more elaborate, and increases or diminishes the angle between difi'er-
ent parts. There are four varieties, viz., flexion and extension, which bend or straighten the
various joints, and take place in a forward and backward direction (in a perfect hinge-joint this
is the only motion permitted) ; and adduction and abduction, which, except in the case of the fin-
gers.and toes, signifies an approach to, or deviation from, the median plane of the body. In the
ARTICULATIONS OF THE SKULL 215
case of the hand, the line to or from which adduction and abduction are made is drawn through
the middle finger, while in the foot it is through the second toe.
Rotation is the revolution of a bone about its own axis without much change of position.
It is only seen in enarthrodial and trochoidal joints. The knee also permits of slight rotation in
certain positions, which is a distinctive feature of this articulation.
Circumduction is the movement compounded of the four angular movements in quick
succession, by which the moving bone describes a cone, the proximal end of the bone forming the
apex, while the distal end describes the base of the cone. It is seen in the hip and shoulder, as
well as in the carpo-metacarpal joint of the thumb, which thus approximates to the ball-and-
socket joint.
In some situations where a variety of motion is required, strength, security, and celerity
are obtained by the combination of two or more joints, each allowing a different class of action,
as in the case of the wrist, the ankle, and the head with the spine. Many of the long muscles,
which pass over two or more joints, act on all, so tending to co-ordinate their movements and
enabhng them to be produced with the least expenditure of power. Muscles also act as elastic
ligaments to the joints; and when acting as such, are diiJusers and combiners, not producers
of movement; the short muscles producing movement, the long diffusing it, and thus allowing
the short muscles to act on more than one joint.
Muscles are so disposed at their attachments near the joints as never to strain the Uga-
ments by tending to pull the bones apart, but, on the contrary, they add to the security of the
joint by bracing the bones firmly together during their action.
The articulations may be divided for convenience of description into those: 1 .
of the Skull; 2. of the Trunk; 3. of the Upper Limb; and 4. of the Lower Limb.
THE ARTICULATIONS OF THE SKULL
The movable articulations of the skull comprise (1) the mandibular; and (2)
those between the skull and the vertebral column, namely (a) between the occiput
and atlas ; (6) between the atlas and epistropheus (axis) ; and (c) the ligaments
which connect the occiput and epistropheus.
The union of the atlas and epistropheus is described in this section because,
(1) there is often a direct communication between the synovial cavity of the trans-
verse epistrophic and the occipito-atlantal joints; (2) the rotatory movements of
the head take place around the dens (odontoid process) ; and (3) important liga-
ments from the dens pass over the atlas to the occiput.
(1) THE MANDIBULAR ARTICULATION
Class. — Diarthrosis. Subdivision. — Condylarthrosis.
The parts entering into the formation of this joint (figs. 256, 257) are: — the
anterior portion of the mandibular fossa and glenoid ridge (eminentia articularis)
of the temporal bone above, and the condyle of the lower jaw below. Both are
covered with articular cartilage, which extends over the front of the glenoid ridge
to facilitate the play of the interarticular cartilage. The ligaments which unite
the bones are:
1. Articular capsule. 3. Spheno-mandibular.
2. Articular disc. 4. Stylo-mandibular.
The articular capsule is often described as consisting of four portions, anterior,
posterior, lateral and medial, which are, however, continuous with one another
around the articulation.
1. The anterior portion consists of a few stray fibres connected with the anterior margin
of the articular disc, and attached below to the anterior edge of the condyle, and above to the
front of the articular eminence. Some fibres of insertion of the external pterygoid pass between
them to be inserted into the margin of the articular disc.
2. The posterior portion is attached above, just in front of the petro-tympanic {Glaserian)
fissure, and is inserted into the back of the jaw just below its neck.
3. The lateral portion or temporo-mandibular (external lateral) ligament (fig. 256) is the
strongest part of the capsule. It is broader above, where it is attached to the lower edge of
the zygoma in nearly its whole length, as well as to the tubercle at thu point where the two
roots of the zygoma meet. It is inoUned downward and backward, to be inserted into the
condyle and neck of the mandible laterally. Its fibres diminish in obliquity and strength from
before backward, those coming from the tubercle being short and nearly vertical.
4. The medial portion (or short internal lateral ligament) (fig. 257) consists of well-defined
fibres, having a broad attachment, above to the lateral side of the spine of the sphenoid and
medial edge of the mandibular fossa; and below, a narrow insertion to the medial side of the neck
216
THE ARTICULATIONS
of the condyle. Fatty and cellular tissue separate it from the spheno-mandibular ligament
which is medial to it.
The articular disc (fig. 258) is an oval plate of fibro-cartilage interposed between
and adapted to the two articular surfaces. It is thinner at the centre than at the
circumference, and is thicker behind, where it covers the thin bone at the bottom
of the mandibular fossa which separates it from the dura mater, than in front,
where it covers the articular eminence.
Fig. 256. — Lateral View op the Mandebtjlar Joint.
I
Temporo mandibular
ligament
mandibular ligament
Fig. 257. — Medial View of the Mandibijlar Joint.
Stylo-hyoid,
ligament
Its inferior surface is concave and fits on to the condyle of the lower jaw; while its superior
surface is concavo-convex from before backward, and is in contact with the articular surface
of the temporal bone. It divides the joint into two separate synovial cavities, but is occasion-
ally perforated in the centre, and thus allows them to communicate. It is connected with the
articular capsule at its circumference, and has some fibres of the exiernallpterygoid muscle
inserted into its anterior margin.
There are usually two synovial membranes (fig. 258), the superior being the
larger and looser, passing down from the margin of the articular surface above, to
the upper surface of the articular disc below; the lower and smaller one passes
THE MANDIBULAR JOINT
217
from the articular disc above to the condyle of the jaw below, extending somewhat
further down behind than in front. When the disc is perforated, the two sacs
communicate.
The spheno-mandibular ligament (long internal lateral) (fig. 257) is a thm,
loose band, situated some little distance from the joint. It is attached above to
the spine of the sphenoid and contiguous part of the temporal bone, and is inserted
into the lingula of the lower jaw.
It covers the upper end of the mylo-hyoid groove, and is here pierced by the mylo-hyoid
nerve. Its origin is a little medial to, and immediately behind, the origin of the medial por-
tion of the capsule. It is separated from the joint and ramus of the jaw by the external ■ptery-
goid muscle, the internal maxillary artery and vein, the inferior alveolar {dental) nerve and
artery, the auriculo-temporal nerve, and the middle meningeal artery. It is really the fibrous
remnant of a part of the mandibular (Meckelian) bar.
The stylo -mandibular ligament (stylo-maxillary) (figs. 256 and 257) is a
process of the deep cervical fascia extending from near the tip of the styloid proc-
ess to the angle and posterior border of the ramus of the jaw, between the masseter
and internal ■pterygoid muscles. It separates the parotid from the submaxillary
gland, and gives origin to some fibres of the st^ylo-glossus muscle.
Fig. 258. — Sagittal Section through the Condyle op Jaw to show the Two Synqviai.
Sacs and the Articular Disc.
Articular disc -l^j^ftr •rr _^ r
Section through condyle^ — -> — i-4-
Posterior portion of -ji/lTiN u
capsule \»4T^^
Spheno-mandibular hgament
Stylo-mandibular hgament
The arterial supply of the mandibular joint is derived from the'temporal, middle meningeal
and ascending pharyngeal arteries, and from the latter by its branches to the Eustachian tube.
The nerves are derived from the masseteric and auriculo-temporal.
Movements. — The chief movement of this joint is of (i) a ginglymoid or hinge character,
accompanied by a slight gliding action, as in opening or shutting the mouth. In the opening
movement the condyle turns like a hinge on the articular disc, while at the same time the ar-
ticular disc, together with the condyle, glides forward so as to rise upon the eminentia articularis,
reaching as far as the anterior edge of the eminence, which is coated with articular cartilage
to receive it; but the condyle never reaches quite so far as the summit of the eminence. Should
the condyle, however, by excessive movement (as in a convulsive yawn), glide over the summit,
it slips into the zygomatic fossa, the mandible is dislocated, and the posterior portion of the
capsule is torn. In the shutting movement the condyle revolves back again, and the articular
disc glides back, carrying the condyle with it. This combination of the hinge and gUding
motions gives a tearing as well as a cutting action to the incisor teeth, without any extra muscu-
lar exertion.
There is (ii) a horizontal gliding action in an antero-posterior direction, by which the lower
teeth are thrust forward and drawn back again: this takes place almost entirely in the upper
compartment, because of the closer connection of the articular disc with the condyle than with
the squamosal bone, and also because of the insertion of the external pterygoid into both bone
and cartilage. In these two sets of movements the joints of both sides are simultaneously and
similarly engaged.
The third form of movement is called (iii) the oblique rotatory, and is that by which the
grinding and chewing actions are performed. It consists in a rotation of the cond3'le about
I
218 THE ARTICULATIONS
the vertical axis of its neck in the lower compartment, while the cartilage glides obUquely for-
ward and inward on one side, and backward and inward on the other, upon the articular surface
of the squamosal bones, each side acting alternately. If the symphysis be simply moved from
the centre to one side and back again, and not from side to side as in grinding, the condyle of
that side moves round the vertical axis of its neck, and the opposite condyle and cartilage ghde
forward and inward upon the mandibular fossa. But in the ordinary grinding movement, one
condyle advances and the other recedes, and then the first recedes while the other advances,
slight rotation taking place in each joint meanwhile.
Relations. — The chief relations are: Behind, and overlapping the lateral side, the parotid
gland. Laterally, the superficial temporal artery. Medially, the internal maxillary artery
and auriculo-temporal nerve. In front, the nerve to the masseter muscle.
Muscles acting on the joint. — Elevators of the mandible. — temporals, masseters, int.
pterygoids.
Depressors. — -Mylo-hyoids, digastrics, genio-hyoid, muscles connecting the hyoid bone to
lower points. Ext. pterygoids. The weight of the jaw.
Protractors. — Ext. pterygoids, superficial layer of masseters, anterior fibres of temporals.
Retractors. — Posterior fibres of temporals, slightly by the int. pterygoids and deep layer of
the masseters.
(2) THE LIGAMENTS AND JOINTS BETWEEN THE SKULL AND
VERTEBRAL COLUMN, AND BETWEEN THE ATLAS AND
EPISTROPHEUS
(a) The Articulation of the Atlas with the Occiput
Class. — Diarthrosis. Subdivision. — Double Condylarthrosis.
This articulation [articulatio atlanto-occipitalis] consists of a pair of joints
symmetrically situated on either side of the middle line. The parts entering into
their formation are the cup-shaped superior articular processes of the atlas and
the condyles of the occipital bone. They are united by the following ligaments : —
1. Anterior atlanto-occipital. 3. Two articular capsules.
2. Posterior atlanto-occipital. 4. Two anterior oblique.
The anterior atlanto-occipital ligament [membrana atlanto-occipitalis anterior]
(fig. 259) is less than an inch (about 2 cm.) wide, and is composed of densely
woven fibres, most of which radiate slightly lateralward as they ascend from the
front surface and upper margin of the anterior arch of the atlas to the anterior
border of the foramen magnum; it is continuous at the sides with the articular
capsules, the fibres of which overlap its edges, and take an opposite direction
medially and upward.
The central fibres ascend vertically from the anterior tubercle of the atlas to the pharyn-
geal tubercle on the occipital bone; they are thicker than the lateral fibres, and are continuous
below with the superficial part of the anterior atlanto-epistrophic ligarnent, and through it
with the anterior longitudinal ligament of the vertebral column. It is in relation, in front,
with the recti capitis anteriores; and behind, with the apical dental or suspensory ligament.
The posterior atlanto-occipital ligament (fig. 260) is broader, more mem-
branous, and not so strong as the anterior. It extends from the posterior surface
and upper border of the posterior arch of the atlas to the posterior margin of the
foramen magnum from condyle to condyle; being incomplete on either side for the
passage of the vertebral artery into, and suboccipital nerve out of, the canal. It is
somewhat thickened in the middle line by fibres, which pass from the posterior
tubercle of the atlas to the lower end of the occipital crest.
It is not tightly stretched between the bones, nor does it limit their movements; it corre-
sponds with the position of the ligamenta flava, but has no elastic tissue in its composition.
It is in relation in front with the dura mater, which is firmly attached to it; and behind with the
recti capitis posteriores minores, and enters into the floor of the suboccipital triangle. Its
lateral margins, which do not reach the occipital bone but terminate on the posterior end of
the superior articular processes of the atlas, form the so-called oblique ligaments of the atlas.
The lateral margins of these ligaments are free and they form the posterior boundaries of the
apertures through which the vertebral arteries enter and the suboccipital nerves leave the
vertebral canal.
The atlanto-occipital articular capsules (figs. 259 and 260) are very distinct
and strongly marked, except on the medial side, where they are thin and formed
only of short membranous fibres. They are lax, and do not add much to the
security of the joint.
ARTICULATION OF ATLAS WITH OCCIPUT
219
In front, the capsule descends upon the atlas, to be attached, some distance below the
articular margin, to the front surface of the lateral mass and to the base of the transverse proc-
ess ; these fibres take an obUque course upward and medialward, overlapping the anterior atlan to-
occipital. At the sides and behind, the capsule is attached above to the margins of the occipital
condyles; below, it skirts the medial edge of the foramen for the vertebral artery, and behind
is attached to the prominent tubercle overhanging the groove for that vessel; these latter fibres
are strengthened by a band running obliqviely upward and medialward to the posterior margin
of the foramen magnum.
The anterior oblique or lateral occipito-atlantal ligament is an accessory
band which strengthens the capsule laterally (fig. 259). It is an oblique, thick
band of fibres, sometimes quite separate and distinct from the rest, passing
upward and medialward from the upper surface of the transverse process beyond
the costo-transverse foramen to the jugular process of the occipital bone.
The synovial membrane of these joints occasionally communicates with the
synovial sac between the dens (odontoid process) and the transverse ligament.
The arterial supply is derived from twigs of the vertebral, and occasionally from twigs
from the meningeal branches of the ascending pharyngeal.
Fig. 259. — Anteriok View of the Upper End of the Vertebral Column.
Continuation of
tiie anterior
longitudinal
ligament of
Atlanto- V ,/^ '^' A ' ' ' /K H_ '^ 'he vertebral
occipital" ^~\ ^ /y^^a 1%"'K ^ I column
articular ^j; \ i '<ii£l^a L£ZZZ. »X , , Anterior atlanto-
capsule N^\ Z5 I *■' / ' occipital liga-
ment
The anterior oblique or — , ,,
lateral occipitoatlantal ////
ligament
Atlanto-epistroph: _ ^
articular capsule ]^ /^ ii]i\'J~, I ^ J^ ''*
Articular capsules of arti-
cular processes between
axis and the third, the
third and fourth, and
the fourth and fifth cer-
vical vertebrae
Anterior atlanto-
-^■* epistrophic ligament
Short vertebral
ligament
Anterior longitudinal
*^ ligament
The nerve-supply comes from the anterior division of the suboccipital nerve.
Movements. — By the symmetrical and bilateral arrangement of these joints, security and
strength are gained at the expense of a very small amount of actual articular surface; the basis
of support and the area of action being equal to the width between the most distant borders
of the joint.
The principal movement permitted at these joints is of a ginglymoid character, producing
flexion and extension upon a transverse axis drawn across the condyles at their slightly con-
stricted parts.
In flexion, the forehead and chin drop, and what is called the nodding movement is made;
in extension, the chin is elevated and the forehead recedes.
There is also a slight amount of gliding movement, either directly lateral, the lateral edge
of one condyle sinking a little within the lateral edge of the socket of the atlas, and that of the
opposite condyle projecting to a corresponding degree. The head is thus tilted to one side, and
it is even possible that the weight of the skull may be borne almost entuely on one joint, the
articular surfaces of the other being thrown out of contact.
Or the movement may be obliquely lateral, when the lower side of the head will be a trifle
220
THE ARTICULATIONS
in advance of the elevated side. In this motion, which takes place on the antero-posterior axis,
one condyle advances slightly and approaches the middle line, while the other recedes. This is
of the nature of rotation, though there is no true rotation round a vertical axis possible between
the occiput and atlas.
These lateral movements are checked by the alar ligaments and the lateral part of the
capsules; extension is checked by the anterior atlanto-oocipital and anterior oblique ligaments,
and flexion by the posterior part of the capsule and the tectorial membrane.
Muscles acting upon the occipito-atlantal joint. — Flexion whereby the chin is approxi-
mated toward the sternum is produced by the weight of the anterior part of the head and by
all muscles which are attached to the hyoid bone or to the bones of the skuU in front of a trans-
verse axis between the two condyles. These muscles take their fixed point below either from
the vertebral columir, the sternum, or the bones of the shoulder girdle. Before those connected
with the mandible can act that bone must be fixed by the muscles of mastication which, there-
fore, also take part in the movements. It must be noted that the sterno-mastoid muscles are
powerful flexors, although a part of their insertion is behind the transverse axis between the
two condyles.
Extension is due to the action of muscles or portions of muscles inserted into the skull
behind the transverse axis above mentioned, and connected below either with the vertebral
column, shoulder girdle, or sternum.
Lateral movement is produced by the anterior and posterior groups of muscles on the same
side acting simultaneously and aided by the rectus capitis lateralis of that side.
I
Fig. 260. — Median Sagittal Section of Yektebral Column showing Ligaments.
Transverse ligament
Inner part of capsular ligament of
atlanto-occipital joint
Posterior atlanto-occipital
ligament
Descending portion of crucial
ligament
Posterior atlanto-epistrophic
ligament
Interspinous ligament
Ligamentum flavum
-Apical dental ligament
Anterior atlanto-occipital
\\ ligament
\_ Atlanto-dental synovial
(b) The Articulations between the Atlas and Epistropheus (Axis).
1. The Lateral Atlanto-epistrophic Joints.
2 . The Central Atlanto-epistrophic Joint or
The Atlanto-dental.
Class. — Diarthrosis.
Subdivision. — Arthrodia.
Class. — Diarthrosis.
\ Subdivision. — Trochoides.
The bones that enter into the formation of the lateral joints are the inferior
articular processes of the atlas and the superior of the epistropheus (axis); the
central joint is formed by the dens (odontoid process) articulating in front with
the atlas, and behind with the transverse ligament.
ATLANTO-EPISTROPHIC JOINTS
221
The ligaments which unite the epistropheus and atlas are : —
1. The anterior atlanto-epistrophic. 3. Two articular capsules (for lateral
joints).
2. The posterior atlanto-epistrophic. 4. The transverse ligament.
5. The atlanto-dental articular capsule.
The anterior atlanto-epistrophic ligament (figs. 259 and 260) is a narrow but
strong membrane filling up the interval between the lateral joints. It is attached
above to the front surface and lower border of the anterior arch of the atlas, and
below to the transverse ridge on the front of the body of the epistropheus. Its
fibres are vertical, and are thickened in the median line by a dense band which is
a continuation upward of the anterior longitudinal ligament of the vertebral
column.
This band is fixed above to the anterior tubercle of the atlas, where it becomes continuous
with the central part of the anterior atlanto-oocipital ligament (fig. 259) ; it is sometimes sepa-
rated by an interval from the deeper ligament, and is often described as the superficial atlanto-
epistrophic ligament. It is in relation with the longus colli muscle.
The posterior atlanto-epistrophic ligament (fig. 260) is a deeper, but thinner
and looser membrane than the anterior. It extends from the posterior root of the
transverse process of one side to that of the other, projecting laterally beyond
the posterior part of the capsules which are connected with it. It is attached
above to the posterior surface and lower edge of the posterior arch of the atlas,
and below to the superior edge of the laminae of the epistropheus on their dorsal
aspect.
It is denser and stronger in the median line, and has a layer of elastic tissue on its anterior
surface like the ligamenta flava, to which it corresponds in position. It is connected in front
with the dura mater; behind, it is in relation with the inferior oblique muscles, and is perforated
at each side by the second cervical nerve.
1. The Lateral Atlanto-epistrophic Joints are provided with short,
ligamentous fibres, forming ari:icular capsules (fig. 259), which completely sur-
round the lateral articular facets. Lateral to the canal they are attached some
little distance from the articular margins, extending along the roots of the
Pig. 261. — Horizontal Section through the Lateral Masses of the Atlas and the
Top of the Dens (Odontoid Process).
Atlanto-dental
synovial sac
Transverse dental
synovial sac
Atlanto-dental
articular capsule
Transverse
ligament
Posterior longitud-
inal ligament and
tectorial membrane
transverse processes of the epistropheus nearly to the tips, but between the roots
they skirt the medial edge of the costo-transverse foramina. They are strength-
ened in front and behind by the atlanto-epistrophic hgaments.
Medially each capsule is thinner, and attached close to the articular mai'gins, being strength-
ened behind by a strong band of slightly oblique fibres passing upward along the lateral edge of
the tectorial membrane from the body of the epistropheus to the lateral mass of the atlas behind
the transverse ligament; some of these fibres pass on, thickening and blending with the atlanto-
oocipital capsule, to be inserted into the margin of the foramen magnum. This band is some-
times called the accessory band (fig. 263).
There is a synovial membrane for each joint.
2. The Central Atlanto-epistrophic Joint, although usually described as
one, is composed of two articulations, which are quite separate from one another :
>
222 THE ARTICULATIONS
an anterior between the dens and the arch of the atlas, and a posterior between
the dens and the transverse hgament.
The transverse ligament (figs. 260, 261, and 263) is one of the most important
structures in the body, for on its integrity and that of the alar ligaments our
lives largely depend. It is a thick and very strong band, as dense and closely
woven as fibro-cartilage, about a quarter of an inch (6 mm.) deep at the sides,
and somewhat more in the middle line. Attached at each end to a tubercle on
the inner side of the lateral mass of the atlas, it crosses the ring of this bone in a
curved manner, so as to have the concavity forward; thus dividing the ring into
a smaller anterior portion for the dens and a larger posterior part for the spinal
cord and its membranes, and the spinal accessory nerves.
It is flattened from before backward, being smooth in front, and covered by synovial mem-
brane to allow it to glide freely over the posterior facet of the dens. Where it is attached to the
atlas it is smooth and well rounded off to provide an easy floor of communication between the
transverso-dental and occipito-atlantal joints.
To its posterior surface is added, in the middle line, a strong fasciculus of
vertical fibres, passing upward from the root of the dens to the basilar border of
the foramen magnum on its cranial aspect. Some of these fibres are derived
from the transverse ligament. These vertical fibres give the transverse liga-
ment a cruciform appearance; hence the name, the crucial ligament (figs. 260
and 263) applied to the whole.
The atlanto-dental articular capsule (fig. 261) is a tough, loose membrane,
completely surrounding the apposed articular surfaces of the atlas and dens.
At the dens it blends above with the front of the alar and central occipito-odontoid liga-
ments, and arises also along the sides of the articular facet as far as the neck of the dens; the
fibres are thick, and blend with the capsules of the lateral joint. At the atlas they are attached
to the non-articular part of the anterior arch in front of the tubercles for the transverse liga-
ment, blending, above and below the borders of the bone, with the anterior atlanto-occipital
and atlanto-epistrophic ligaments, as well as with the medial portion of the articular capsules.
It holds the dens to the anterior arch of the atlas after aU the other ligaments have been divided.
The synovial membranes (figs. 260 and 261) are two in number: — one for the
joint between the dens and atlas; and another (transverso-dental) for that
between the transverse ligament and the dens. This last often communicates
with the atlanto-occipital articulations; it is closed in by membranous tissue
between the borders of the transverse ligament and the margin of the facet on
the dens, and is separated from the front sac by the atlanto-dental articular
capsule.
The arterial supply is from the vertebral artery, aiid the nerve-supply from the loop between
the first and second cervical nerves.
Movements. — The chief and characteristic movement at these joints is the rotation, in a
nearly horizontal plane, of the collar formed by the atlas and transverse ligament, round the
dens as a pivot, which is extensive enough to allow of an all-round view without twisting the
trunk. Partly on account of its ligamentous attachments, and partly on account of the shape
of the articular siirfaces, the cranium must be carried with the atlas in these movements. The
rotation is checked by the ligaments passing from the dens to the occiput (alar ligarnents), and
also by the atlanto-epistrophic. Owing to the fact that the facets of both atlas and epistropheus,
which enter into the formation of the lateral atlanto-epistrophic articulations, are convex from
before backward, and have the articular cartilage thicker in the centre than at the circumfer-
ence, the motion is not quite horizontal but slightly curvilinear. In the erect position, with the
face looking directly forward, the most convex portions of the articular surfaces are alone in
contact, there being a considerable interval between the edges; dm-ing rotation, therefore, the
prominent portions of the condyles of the atlas descend upon those of the epistropheus, dimin-
ishing the space between the bones, slackening the ligaments, and thus increasing the amount of
rotation, without sacrificing the security of the joint in the central position.
Besides rotation, forward and backward movements and some lateral flexion are permitted
between the atlas and epistropheus, even to a greater extent than in most of the other vertebral
joints.
The muscles acting upon the atlanto-epistrophic joints. — The muscles capable of producing
rotation at the atlanto-epistrophic joints are those which take origin from near the mesial plane
either in front or behind and which are attached above either to the atlas or the skull, lateral
to the atlanto-epistrophic joints. When the muscles which lie at the back of the joint on one
side act they will turn the head to the same side and will be aided by the muscles in front on the
opposite side. If the muscles in front and behind on the same side act simultaneously, they will
pull down the head to that side and will be aided by muscles which pass more or less vertically
from the transverse process of the atlas to points below.
LIGAMENTS OF OCCIPUT AND EPISTROPHEUS
223
(c) The Ligaments uniting the Occiput and Epistropheus
The following ligaments unite bones not in contact, and are to be seen from
the interior of the canal after removing the posterior arches of the epistropheus
and atlas and posterior ring of the foramen magnum : —
1. The tectorial membrane.
2. The crucial ligament.
3. Two alar (or check) ligaments.
4. The apical dental ligament.
The tectorial membrane (occipito-cervical hgament) (figs. 261, 262, and 263)
consists of a very strong band of fibres, connected below to the upper part of
the body of the third vertebra and lower part of the body of the epistropheus
as far as the root of the dens. It is narrow below, but widens out as it ascends,
to be fastened to the basilar groove of the occiput. Laterally, it is connected
with the accessory fibres of the atlanto-epistrophic capsule. It is really only
the upward prolongation of the deep stratum of the posterior longitudinal
ligament, the superficial fibres of which run on to the occipital bone without
touching the epistropheus, thus giving rise to two strata. It is in relation in
front with the crucial ligament.
Fig. 262. — The Superficial Layer of the Posteeioe Longitudinal Vertebral Liga-
ment HAS BEEN Removed to show its Deep oh Short Fibres. These Deep Fibres
FORM the Tectorial Membrane. Viewed from behind.
$/ Membrana tectoria, i. e.^
the deep stratum of the
posterior longitudinal
vertebral hgament
Transverse process of atlas
The crucial ligament has been already described (see p. 222).
The alar (or check) ligaments (figs. 260 and 263) are two strong rounded
cords, which extend from the sides of the apex of the dens, transversely lateral-
ward to the medial edge of the anterior portion of the occipital condyles.
They are to be seen immediately above the upper border of the transverse ligament, which
they cross obliquely owing to its forward curve at its attachments to the atlas. Some of their
fibres occasionally run across the middle line from one alar ligament to the other. At the dens
they are connected with the atlan to-dental capsule, and at the condyles they strengthen the
atlanto-occipital articular capsule.
The apical dental or suspensory ligament (figs. 260 and 263) consists of a
slender band of fibres ascending from the summit of the dens to the lower surface
of the occipital bone, close to the foramen magnum. It is best seen from the
front, after removing the anterior atlanto-occipital ligament, or from behind by
drawing aside the crucial ligament.
224
THE ARTICULATIONS
The apical ligament is tightened by extension and relaxed by flexion or nodding; the alar
ligaments not only limit the rotatory movements of the head and atlas upon the epistropheus,
but by binding the occiput to the pivot, round which rotation occurs, they steady the head
and prevent its undue lateral inclination upon the vertebral column. (See Transverse
Ligament, p. 222.)
By experiments, it has been proved that the head, when placed so that the orbits look a
little upward, is poised upon the occipital condyles in a line drawn a little in front of their
middle; the amount of elevation varies slightly in different cases, but the balance is always to
be obtained in the human body — it is one of the characteristics of the human figm'e. It serves
to maintain the head erect without undue muscular effort, or a strong ligamentum nuchse
and prominent dorsal spines such as are seen in the lower animals. Disturb this balance, and
let the muscles cease to act, the head will either drop forward or backward according as the
centre of gravity is in front or behind the balance line. The ligaments which pass over the dens
to the occiput are not quite tight when the head is erect, and only become so when the head is
flexed; if this were not so, no flexion would be allowed; thus, muscular action, and not liga-
mentous tension, is employed to steady the head in the erect position. It is through the com-
bination of the joints of the atlas and epistrophaus, and occiput and epistropheus (consisting of
two paii-s of joints placed symmetrically on either side of the median line, while through the
median line there passes a pivot, also with a pair of joints), that the head enjoys such freedom
and celerity of action, remarkable strength, and almost absolute security against violence,
which could only be obtained by a ball-and socket joint; but the ordinary ball-and-socket
joints are too prone to dislocations by even moderate twists to be reliable enough when the
life of the individual depends on the perfection of the articulation: hence the importance
of this combination of joints.
>
Fig. 263. — Coronal Section of the Vertebral Column and the Occipital Bone
TO SHOW Ligaments.
(The tectorial membrane (1), though shown as a distinct stratum, is really the deeper part of
the posterior longitudmal ligament (2) The upper ends have been reflected
upward the lower downward Viewed from behind.)
Vertical portion of crucial
ligament
Apical dental ligament
Accessory ^ band of atlanto
epistropbic capsules
Atlanto -epistrophic joint
Tectorial membrane
Posterior longitudinal ligament
THE ARTICULATIONS OF THE TRUNK
These may be divided into the following sets: —
1. Those of the vertebral column. Joints and ligaments connecting:
(a) The bodies.
{h) The articular processes.
(c) The laminae.
2. Vertebral column with the pelvis.
3. Pelvis.
(d) The spinous processes.
(e) The transverse processes.
(o) Sacro-iliac
(b) Sacro-coccygeal.
(c) Intercoccygeal.
(d) Symphysis pubis.
'ARTICULATIONS OF VERTEBRAL COLUMN 225
4. Ribs with the vertebral column.
5. The articulations at the front of the thorax.
(a) Costal cartilages with the sternum.
(6) Costal cartilages with the ribs.
(c) Sternal.
(d) Certain costal cartilages with each other.
1. THE ARTICULATIONS OF THE VERTEBRAL COLUMN
There are two distinct sets of articulations in the vertebral column : —
(a) Those between the bodies and intervertebral discs which form synchon-
droses and which are amphiarthrodial as regards movement.
(6) Those between the articular processes which form arthrodial joints.
The ligaments which unite the various parts may also be divided into two
sets, viz. — immediate, or those that bind together parts which are in contact;
and intermediate, or those that bind together parts which are not in contact.
Immediate.
(a) Those between the bodies and discs.
(6) Those between the articular processes.
Intermediate.
(c) Those between the laminae.
(d) Those between the spinous processes.
(e) Those between the transverse processes.
Fig. 264. — Horizontal Section through an Intervektebbal Fibro-cartilage and
THE Corresponding Ribs.
Fibrous ring of intervertebral
fibro-cartilage
Tubercular ligament
(a) The Aeticxtlations of the Bodies of the Vertebra
Class. — False Synchondrosis.
The ligaments which unite the bodies of the vertebrae are : —
Intervertebral fibro-cartilages.
Short lateral ligaments.
Anterior longitudinal.
Posterior longitudinal.
The intervertebral fibro-cartilages (figs. 260 and 264) are tough, but elastic
and compressible discs of composite structure, which serve as the chief bond of
union between the vertebrae. They are twenty-three in number, and are inter-
posed between the bodies of all the vertebrae from the epistropheus to the sacrum
(figs. 260 and 271). Similar discs are found between the segments of the sacrum
and coccyx in the younger stages of life, but they undergo ossification at their
surfaces and often throughout their whole extent.
226
THE ARTICULATIONS
Each disc is composed of two portions — a circumferential laminar, and a central pulpy
portion; the former tightly surrounds and braces in the latter, and forms somewhat more than
half the disc. The fibrous ring [annulus fibrosus] or laminar portion consists of alternating
layers of fibrous tissue and fibro-oartilage; the component fibres of these layers are firmly con-
nected with two vertebriE, those of one passing obliquely down and to the right, those of the
next down and to the left, malving an X -shaped arrangement of the alterriate layers. A few
of the superficial lamellie project beyond the edges of the bodies, their fibres being connected
with the edges of the anterior and lateral surfaces; and some do not completely siu-round the
rest, but terminate at the intervertebral foramina, so that on horizontal section the circum-
ferential portion is seen to be thinner posteriorly. The more" central lamellae are incomplete,
less firm, and not so distinct as the rest; and as they near the pulp they gradually assume its
characters, becoming more fibro-cartilaginous and less fibrous, and have cartilage cells in their
structure.
The pulpy nucleus [nucleus pulposus] or central portion is situated somewhat behind the
centre of the disc, forming a baU of very elastic and tightly compressed material, which bulges
freely when the confining pressure of the laminar portion is removed by either horizontal or
vertical section. Thus, it has a constant tendency to spring out of its confinement in the
direction of least resistance, and constitutes a pivot round which the bodies of the vertebrae
can twist, tilt, or incline. It is yellowish in colour, and is composed of fine white and elastic
Fig. 265. — The Anterior Longitudinal Ligament, the Radiate, the Interarticular,
AND THE Anterior Costo-transverse Ligaments.
The interarticular ligament
The anterior costo-
transverse ligaments
The radiate ligament
fibres amidst which are ordinary connective-tissue cells, and pecuhar cells of various sizes which
contain one or more nuclei. Together with the most central laminee, it is separated from im-
mediate contact with the bone by a thin plate of articular cartilage. The central pulp of the
intervertebral substance is the persistent part of the notochord.
The intervertebral substances vary in shape with the bodies of the vertebrae they unite,
and are widest and thickest in the lumbar region. In the cervical and lumbar regions they are
thicker in front than behind, and cause, the convexity forward of the cervical, and increase that
of the lumbar; the curve in the thoracic region, almost entirely due to the shape of the bodies,
is, however, somewhat increased by the discs. Without the discs the column loses a quarter
of its length, and assumes a curve with the concavity forward, most marked a little below the
mid-thoracic region. Such is the curve of old age, which is due to the shrinking and drying
up of the intervertebral substances. The disc between the epistropheus and third cervical is
the thinnest of all (fig. 260) ; that between the fifth lumbar and sacrum is the thickest, and is
much thicker in front than behind (fig. 271). The intervertebral discs are in relation, in front
with the anterior longitudinal ligament; behind, with the posterior longitudinal ligament;
laterally, with the short lateral; and in the thoracic region, with the interarticular and radiate
ligaments.
In the cervical region lateral diarthrodial joints are placed one on each side of the inter-
vertebral discs. They are of small extent and are confined to the intervals between the promi-
nent lateral lips of the upper surface of the body below and the bevelled lateral edges of the lower
surface of the body above. Situated in front of the issuing spinal nerves and between those
parts of the bodies formed from the neural arches, they are homologous with the joints between
the atlas and epistropheus, and between the atlas and occipital bone.
VERTEBRAL LIGAMENTS
227
The anterior longitudinal ligament (figs. 259 and 265) commences as a narrow
band attached to the inferior surface of the occipital bone in the median line,
just in front of the atlanto-occipital Ugament, of which it forms the thickened
central portion. Attached firmly to the tubercle of the atlas, it passes down as
the central portion of the atlanto-epistrophic ligament, in the mid-line, to the
front of the body of the epistropheus. It now begins to widen out as it descends,
until it is nearly two inches (5 cm.) wide in the lumbar region. Below, it is fixed
to the upper segment of the sacrum, becoming lost in periosteum about the
middle of that bone; but is again distinguishable in front of the sacro-coccygeal
joint, as the anterior sacro-coccygeal ligament.
Its structure is bright, pearly-white, and gUstening. Its lateral borders are separated
from the lateral bands by clefts through which blood-vessels pass; they are frequently indistinct
and are best marked in the thoracic region. It is thickest in the thoracic region, and thicker in
the lumbar than the cervical. It is firmly connected with the bodies of the vertebra, and is
composed of longitudinal fibres, of which the superficial extend over several, while the deeper
pass over only two or three vertebrae. It is connected with the tendinous expansion of the pre-
vertebral muscles in the cervical, and the crura of the diaphragm are closely attached to it in
the lumbar region.
Fig. 266. — Posterior Longitudinal Ligament. (Thoracic region.)
(Pedicles cut through, and posterior arches of vertebrae removed.)
The posterior longitudinal ligament (figs. 263, 266, 267, and 274) extends
from the occipital bone to the coccyx. It is wider above than below, and com-
mences by a broad attachment to the cranial surface of the basi-occipital. In the
cervical region it is of nearly uniform width, and extends completely across the
bodies of the vertebrae, upon which it rests quite flat. It does, however, extend
slightly further laterally on each side opposite the intervertebral discs. In the
thoracic and lumbar regions it is distinctly dentated, being broader over the inter-
vertebral substances and the edges of the bones than over the middle of the
bodies, where it is a narrow band stretched over the bones without resting on
them, the anterior internal vertebral venous plexus being interposed. The
narrow median portion consists of longitudinal fibres, some of which are super-
ficial and pass over several vertebrae; and others are deeper, and extend only from
one vertebra to the next but one below.
The dentated or broader portions (fig. 267) are formed by oblique fibres which, springing
from the bodies near the intervertebral foramina, take a curved course downward and back-
228
THE ARTICULATIONS
ward over an intervertebral fibro-cartilage, and reach the narrow portion of the ligament on the
centre of the vertebra next below; they then diverge to pass over another intervertebral dies
to end on the body of the vertebra beyond, near the intervertebral notch. They thus pass
over two discs and three vertebrae. Deeper still are other fibres thickening these expansions
of the longitudinal hgament, and extending from one bone to the next.
The last well-marked expansion is situated between the first two segments of the sacrum:
'below this, the ligament becomes a deUcate central band with rudimentary expansions, being
more pronounced again over the sacro-coccygeal joint, and losing itself in the ligamentous
tissue at the back of the coccyx. The dura mater is tightly attached to it at the margin of the
foramen magnum and behind the bodies of the upper cervical vertebrae, but is separated from
it in the rest of its extent by loose cellular tissue which becomes condensed in the sacral region
to form the sacro-dural ligament. The filum terminale becomes blended with it at the lower
part of the sacrum and back of the coccyx.
Fig. 267. — Postbbior Longitudinal Ligament. (Lumbar region.)
Median band
Expanded lateral portion
The lateral (or short) vertebral ligaments (fig. 265) consist of numerous short
fibres situated between the anterior and posterior longitudinal ligaments, and
passing from one vertebra over the intervertebral disc, to which it is firmly
adherent, to the next vertebra below.
The more superficial fibres are more or less vertical, but the deeper decussate and have a
crucial arrangement. They are connected with the deep surface of the anterior longitudinal
ligament, and so tie it to the edges of the bodies of the vertebrae and to the intervertebral discs.
They blend behind with the expansions of the posterior longitudinal ligament, and so complete
the casing round each amphiarthrodial joint. In the thoracic region, they overlie the radiate
ligament, and in the lumbar they radiate toward the transverse processes. In the cervical
region they are less well marked.
(b) The Ligaments Connecting the Articular Processes
Class. — Diarthrosis. Subdivision. — Arthrodia.
The articular capsules (fig. 259) which unite these processes are composed
partly of yellow elastic tissue and partly of white fibrous tissue. In the cervical
region only the medial side of the capsule is formed by the ligamenta flava, which
in the thoracic and lumbar regions, however, extend anteriorly to the margins
of the intervertebral foramina.
The part formed of white fibrous tissue consists of short, well-marked fibres, which in the
cervical region pass obhquely downward and forward over the joint, between the articular proc-
VERTEBRAL LIGAMENTS
229
esses and the posterior roots of the transverse processes of two contiguous vertebra. In the
thoracic region the fibres are shorter, and vertical in direction, and are attached to the bases
of the transverse processes; in the lumbar, they are obhquely transverse. The articular
capsules in the cervical region are the most lax, those in the lumbar region are rather tighter,
and those in the thoracic region are the tightest.
There is one s3movial membrane to each capsule.
(c) The Ligaments uniting the Lamina
The ligamenta flava (fig. 268) are thick plates of closely woven yellow elastic
tissue, interposed between the laminae of two adjacent vertebrae. The first con-
nects the epistropheus with the third cervical, and the last the fifth lumbar with
Fig. 268.-
Canal.
-Ligamenta Flava in the Lumbar Region, seen from within the Vertebral
Portion of ligamentu
flavum removed to
show the articular
cavity
Ligamentum flavum
the sacrum. Each ligament extends from the medial and posterior edge of the
intervertebral foramen on one side to a corresponding point on the other ; above,
it is attached close to the inner margin of the inferior articular process and to a
well-marked ridge on the inner surface of the laminae as far as the root of the
spine; below, it is fixed close to the inner margin of the superior articular process
and to the dorsal aspect of the upper edge of the laminae.
Thus each ligamentum flavum, besides filling up the interlaminar space, enters into the
formation of two articular capsules; they do so to a greater extent in the thoracic and lumbar
regions than in the cervical, where the articular processes are placed wider apart. When seen
from the front after removing the bodies of the vertebrae, they are concave from side to side,
but convex from above downward; they make a more decided transverse curve than the arches
between which they are placed. This concavity is more marked in the thoracic, and still more
in the lumbar region than in the cervical; in the lumbar region the hgamenta flava extend a
short distance between the roots of the spinous process, blending with the interspinous ligament,
and making a median sulcus when seen from the front; there is, however, no separation between
the two parts. In the cervical region, where the spines are bifid, there is a median fissure in the
yellow tissue which is filled up by fibro-areolar tissue. The ligaments are thickest and strongest
in the lumbar region; narrow but strong in the thoracic; thinner, broader, and more membranous
in the cervical region.
(d) The Ligaments connecting the Spinous Processes
These include supraspinous ligament, interspinous ligaments, and the liga-
mentum nuchae.
230
THE ARTICULATIONS
The supraspinous ligament (fig. 270) extends without interruption as a
well-marked band of longitudinal fibres along the tips of the spines of the vertebrae
fromthat of the seventh cervical downward till it ends on the median sacral crest.
Fig. 269. — Side View op Ligamentum Nuch^.
Ligamentum auchs
First iuterspinalis muscle'
Fig. 270. —The Interspinous and Supraspinous Ligaments in the Lumbar Region.
-The interspinous ligament
jttJ — The supraspinous ligament
Its more superiioial fibres are much longer than the deep. The deeper fibres pass over
adjacent spines only, while the superficial overlie several. It is connected laterally with the
aponeurotic structures of the back; indeed, in the lumbar region, where it is well marked, it
VERTEBRAL LIGAMENTS 231
appears to result from the interweaving of the tendinous fibres of the several muscles which are
attached to the tips of the spinous processes. In the dorsal region it is a round slender cord
which is put on the stretch in flexion and relaxed in extension of the back.
The ligamentum nuchse, or the posterior cervical ligament (fig. 269), is the
continuation in the neck of the supraspinous ligament, from which, however, it
differs considerably. It is a slender vertical septum of an elongated triangular
form, extending from the seventh cervical vertebra to the external protuberance
and the crest of the occipital bone. Its anterior border is firmly attached to the
tips of the spines of all the cervical vertebrte, including the posterior tubercle of
the atlas, as well as to the occiput. Its posterior border gives origin to the
trapezii, with the tendinous fibres of which muscle it blends. Its lateral, tri-
angular surfaces afford numerous points of attachment for the posterior muscles
of the head and neck.
In man it is rudimentary, and consists of elastic and white fibrous tissues. As seen in the
horse, elephant, ox, and other pronograde mammals, it is a great and important elastic ligament,
which even reaches along the thoracic part of the spinal column. In these animals it serves
to support the head and neck, which otherwise from their own weight would hang down. Its
rudimentary state in man is the direct consequence of his erect position.
The interspinous ligaments (fig. 270) are thin membranous structures which
extend between the spines, and are connected with the ligamenta flava in front,
and the supraspinous ligament behind.
The fibres pass obliquely from the root of one spine to the tip of the next; they thus decus-
sate. They are best marked in the lumbar region, and are replaced by the well-developed
inierspinales muscles in the cervical region.
(e) The Ligaments connecting the Transverse Processes
The intertransverse ligaments are but poorly developed.
In the thoracic region they form small rounded bundles, and in the lumbar they are flat
membranous bands, unimportant as bonds of union. They consist of fibres passing between
the apices of the transverse processes. In the cervical region they are replaced by the inter-
transversarii muscles.
The arterial supply for the column comes from twigs of the vertebral, ascending pharyn-
geal, ascending cervical, superior and aortic intercostals, lumbar, iUo-lumbar, and lateral sacral.
The nerve-supply comes from the spinal nerves of each region.
Movements. — The vertebral column is so formed of a number of bones and intervertebral
discs as to serve many purposes. It is the axis of the skeleton; upon it the skull is supported;
and with it the cavities of the trunk and the limbs are connected, As a fixed column it is capable
of bearing great weight, and, through the elastic intervertebral substances, of resisting and
breaking the transmission of shocks. Moreover, it is flexible. Now, the range of movements
of the column as a whole is very considerable; but the movements between any two vertebrae
are slight, so that motions of the spine may take place without any change in the shape of the
column, and without any marked disturbance in the relative positions of the vertebrae. It is
about the pulpy part of the intervertebral discs, which form a central elastic pivot or ball, upon
which the middle of the vertebras rest, that these movements take place.
The amount of motion is everywhere limited by the common vertebral Ugaments, but it
depends partly upon the width of the bodies of the vertebrae, and partly upon the depth of the
discs, so that in the loins, where the bodies are large and wide, and the discs very thick, free
motion is permitted; in the cervical region, though the discs are thinner, yet, as the bodies are
smaller, almost equally free motion is allowed. As the ball-Uke pulpy part of the intervertebral
disc is the centre of movement of each vertebra, it is obvious that the motion would be of a
rolUng character in any direction but for the articular processes, wtiich serve also to give steadi-
ness to the column and to assist in bearing the superincumbent weight. Were it not for these
processes, the column, instead of being steady, endowed with the capacity of movement by
muscular agency, would be tottering, requiring muscles to steady it. The influence of the
articular processes in limiting the direction of incUnation will appear from a study of the
movements in the three regions of the spine.
In the neck all movements are permitted and are free, except between the second and third
cervical vertebrje, where they are slight, owing to the shallow intervertebral disc and the great
prolongation of the anterior hp of the inferior surface of the body of the epistropheus, which
checks forward flexion considerably. On the whole, however, extension and lateral inclination
are more free and extensive in this than in any other region of the column, whilst flexion is more
limited than in the lumbar region. Rotatory movements are also free, but take place, on ac-
count of the position and inclination of the articular facets, not, as in the thoracic region, round
a vertical axis, but round an oblique axis, the articular process of one side gliding upward and
forward and that of the opposite side downward and backward.
In the thoracic region, especially near its middle, antero-posterior flexion and extension
are very slight; and, as the concavity of the curve here is forward, the flat and nearly vertical
surfaces of the articular processes prevent anything like sliding in a curvilinear manner of the
232 THE ARTICULATIONS
one set of processes over the sharp upper edges of the other, which would be necessary for
forward flexion. A fair amount of lateral inclination would be permitted but for the impedi-
ment offered by the ribs; while the position and direction of the articular processes allows rota-
tion round a vertical axis which passes through the centres of the bodies of the vertebrae. This
rotation is not very great, and is freer in the upper than in the lower part of the thoracic
region.
In the lumbar region, extension and flexion are very free, especially between the third and
fourth and fourth and fifth vertebrae, where the lumbar curve is sharpest; lateral inclination
is also very free between these same vertebrae. It has been stated that the shape and position
of the articular processes of the lumbar and the lower two or three dorsal are such as to prevent
any rotation in these regions; but, owing to the fact that the inferior articular processes are not
tightly embraced by the superior, so that the two sets of articular processes are not in contact
on both sides of the bodies at the same time, there is always some space in which horizontal
motion can occur round an axis drawn through the central part of the bodies and interverte-
bral discs, but it is very slight. Thus, the motions are most free in those regions of the column
which have a convex curve forward, due to the shape of the intervertebral discs, where there
are no bony waOs surrounding solid viscera, where the spinal canal is largest and its contents
are less firmly attached, and where the pedicles and articular processes are more nearly on a
transverse level with the posterior surface of the bodies of the vertebrae.
Nor must the uses of the ligamenta flava be forgotten: these useful structures — (1) com-
plete the roofing-in of the vertebral canal, and yet at the same time permit an ever-changing
variation in the width of the interlaminar spaces in flexion and extension; (2) they also restore
the articulating surfaces to their normal position with regard to each other after movements
of the column; (3) and by forming the medial portion of each articular capsule, they take the
place of muscle in preventing it from being nipped between the articular surfaces during
movement.
Muscles which take part in the movements of the vertebral column. — Flexors : When acting
with their fellows of the opposite side. Rectus abdominis, infra-hyoid muscles (slightly)
sterno-mastoid, external oblique, internal obHque, intercostals, scalenus anterior, psoas
major and minor, longus colli, longus capitis (rectus capitis anterior major).
Extensors : When acting with their fellows of the opposite side. Sacro-spinalis, quadratus
lumborum, semispinalis, multifidus, rotatores, interspinales, serrati posteriores, the splenius,
and with the scapula fixed the levator scapulae and the upper fibres of the trapezius.
Muscles which help to incline the column to their own side. — Sacro-spinaUs, quadratus
lumborum, semispinalis, multifidus, the intercostals helping to fix the ribs, the external and
internal oblique muscles, levatores costarum, serrati posteriores, the scalenes, splenius cervicis,
longus coUi (oblique part), rotatores, intertransversales, psoas, and with the scapula fixed the
levator scapulae and the upper and lower fibres of the trapezius.
Muscles which rotate the column and turn the body to their own side. — Splenius cervicis,
internal oblique (the ribs being fixed), serratus posterior inferior, and with the scapula fixed
the lower fibres of the trapezius.
Muscles which rotate the column and turn the body to the opposite side. — Multifidus,
semispinalis, external oblique, the lower oblique fibres of the longus colli, and with the scapula
and humerus fixed the latissimus dorsi and trapezius.
2. THE SACRO-VERTEBRAL ARTICULATIONS
(a) Class. — False Synchondrosis.
(b) Class. — Diarthrosis. Subdivision. — Arihrodia.
As in the intervertebral articulations, so in the union of the first portion of the
sacrum with the last lumbar vertebra, there are two sets of joints — viz. (a) a
synchondrosis, between the bodies and intervertebral disc; and (6) a pair of
arthrodial joints, between the articular processes. The union is effected by the
following ligaments, which are common to the vertebral column: — (i) anterior,
and (ii) posterior longitudinal; (iii) lateral or short vertebral; (iv) capsular; (v)
ligamenta flava; (vi) supraspinous and (vii) interspinous ligaments. Two
special accessory ligaments on either side, viz., the sacro-lumbar and the ilio-
lumbar, connect the pelvis with the fourth and fifth lumbar vertebrae.
The sacro-lumbar ligament (fig. 271) is strong, and triangular in shape. Its
apex is above and medial, being attached to the whole of the lower border and
front surface of the transverse process of the fifth liunbar vertebra, as well as to
the pedicle and body. It is intimately blended with the ilio-lumbar ligament.
Below, it has a wide, fan-shaped attachment, extending from the edge of the ilio-
lumbar ligament forward to the brim of the true pelvis; blending with the perios-
teum on the base of the sacrum and in the iliac fossa, and with the superior sacro-
iliac ligament.
By its sharp medial border it Umits laterally the foramen for the last lumbar nerve. It is
pierced by two large foramina, which transmit arteries to the saoro-iliac synchondrosis. This
ligament is in series with the intertransverse ligaments of the spinal column. It is sometimes
described as a part of the ilio-lumbar ligament.
SACRO-VERTEBRAL ARTICULATIONS
233
The ilio-lumbar ligament (fig. 271) is a strong, dense, triangular ligament
connecting the fourth and fifth lumbar vertebrae with the iliac crest.
It springs from the front surface of the transverse process of the fifth lumbar vertebra as
far as the body, by a strong fasciculus from the posterior surface of the process near the tip,
and also from the front surface and lower edge of the transverse process and pedicle of the fourth
lumbar vertebra, as far medialward as the body. Between these two lumbar vertebrae it is
inseparable from the intertransverse hgament.
At its origin from the transverse process of the fifth lumbar vertebra it is closely inter-
woven with the sacro-lumbar ligament, and some of its iibres spread downward on to the body
of the fifth vertebra, while others ascend to the disc above. At the pelvis it is attached to the
inner lip of the crest of the ilium for about two inches (5 cm.) . The highest fibres at the column
form the upper edge of the ligament at the pelvis, those which come from the posterior portion
of the transverse process of the fifth lumbar vertebra forming the lower, while the fibres from
the front of the same process pass nearly horizontally lateralward. Near the column the surfaces
Fig. 271. — Anterior View of the Ligaments between Vertebra and Pelvis.
anterior primary branch of fourth
Foramen for last
lumbar nerve
Intervertebral disc
between last lum-
bar and first sacral
vertebrae
The ilio-lumbar
ligament
The sacro-luml
ligament
Superior sacro-
ligament
Anterior sacro-
ligament
Sacro-tuberous
ligament
Sacro-spinous ligament
look directly backward and forward, but at the ilium the ligament gets somewhat twisted, so
that the posterior surface looks a little upward, and the anterior looks a Mttle downward.
The anterior surface forms part of the posterior boundary of the major (false) pelvis, and over-
lies the upper part of the posterior sacro-iliao ligament; the posterior surface forms part of the
floor of the spinal groove, and gives origin to the mullifidus muscle. Of the borders, the upper
is oblique, has the anterior lamella of the lumbar fascia attached to it, and gives origin to the
quadralus lumborum; the lower is horizontal, and is adjacent to the upper edge of the sacro-
lumbar ligament; while the medial is crescentic, and forms the lateral boundary of a foramen
through which the fourth lumbar nerve passes.
The arterial supply is very free, and comes from the last lumbar, ilio-lumbar, and lateral
sacral.
The nerve-supply is from the sympathetic, as well as from twigs from the fourth and fifth
lumbar nerves.
Movements. — The angle formed by the sacrum with the spinal column is called the sacro-
vertebral angle. The pelvic inclination does not depend entirely upon this angle, but in great
part upon the obUquity of the co.xal (innominate) bones to the sacrum, so that in males in whom
the average pelvic obliquity is a Uttle greater, the average sacro-vertebral angle is considerably
less than in females.
The sacro-vertebral angle in the male shows that there is a greater and more sudden change
in direction at the sacro-vertebral union than in the female. A part of this change in direction
is due to the greater thickness in the anterior part of the intervertebral fibro-cartilage between
the last lumbar vertebra and the sacrum. Owing to the greater thickness of the intervertebral
234 THE ARTICULATIONS
disc here than elsewhere, the movements permitted at this joint are very free, being freer than
those between any two lumbar vertebrEe. As the diameter of the two contiguous bones is less
in the sagittal than in the frontal plane, the forward and backward motions are much freer than
those from side to side. The backward and forward motions take place every time the sitting
is exchanged for the standing position, and the standing for the sitting posture; in rising, the
back is extended on the sacrum at the sacro-lumbar union; in sitting down it is flexed.
The articular processes provide for the ghding movement incidental to the extension,
flexion, and lateral movements; they also allow some horizontal movement, necessary for the
rotation of the vertebral column on the pelvis, or pelvis on the column. The inferior articular
processes of the fifth differ considerably from the inferior processes in the rest of the lumbar
vertebrae, and in direction they resemble somewhat those of the cervical vertebrae; while the su-
perior articular processes of the sacrum differ in a similar degree from the superior processes of
the lumbar vertebrae. This difference allows for the freer rotation which occurs at this joint.
The sacro-vertebral angle averages 117° in the male, and 130° in the female; while the
pelvic incKnation averages 155° in the male, and 150° in the female.
As already stated, the movements at the sacro-vertebral joint are the same as those in other
parts of the spinal column, but more extensive, and the muscles which produce the movements
are those mentioned in the preceding groups which cross the plane of the articulation.
3. THE ARTICULATIONS OF THE PELVIS
This group may again be subdivided into — -
(a) The sacro-iliac.
(6) The sacro-coccygeal.
(c) The intercoccygeal.
(d) The symphysis pubis.
(a) The Sacro-iliac Articulation and Sacro-sciatic Ligaments
Class. — Diarthrosis. Subdivision. — Arthrodia.
It is now generally admitted that the sacro-iliac joint is a diarthrosis, the
articular surface of each bone being covered with a layer of cartilage, whilst the
cavity of the joint is a narrow cleft and the capsule is extremely thick posteriorly.
The cartilage on the sacrum is much thicker than that on the ilium and the
cartilages are sometimes bound together here and there by fibrous strands.
The different character of the joint in the two sexes should be noted. Briefly,
the female joint has strong ligamentous bonds with but little bony apposition,
while the male joint gains its strength by virtue of extensive areas of bony
contact and a slighter development of ligaments. This difference is, of course,
a physiological one; for some laxity of the joint is demanded during pregnancy
and labour. The bones which enter into the joint are the sacrum and ilium,
and they are bound together by the following ligaments: —
Anterior sacro-iliac. Superior sacro-iliac.
Posterior sacro-iliac. Inferior sacro-iliac.
Interosseous.
The anterior sacro-iliac ligament (figs. 271 and 272) consists of well-marked
glistening fibres which pass above into the superior, and below into the inferior,
ligaments. It extends from the first three bones of the sacrum to the ilium
between the brim of the pelvis minor and the great sciatic notch, blending with the
periosteum of the sacrum and ilium as it passes away from the united edges of
the bones.
The superior sacro-iliac ligament (figs. 271 and 272) extends across the
upper margins of the joint, from the ala of the sacrum to the iliac fossa, being
well marked along the brim of the pelvis, where it is thickened by some closely
packed fibres. Behind, it is far stronger, especially beneath the transverse process
of the fifth lumbar vertebra. This ligament is connected with the strong sacro-
lumbar ligament, which spreads lateralward and forward over the joint to reach
the iliac fossa and terminal line. By some authors it is described as a part of the
ilio-lumbar ligament.
The posterior sacro-iliac ligament is extremely strong and consists essentially
of two sets of fibres, deep and superficial. The deep fibres (short posterior sacro-
iliac ligament) pass downward and medialward from the rough area of the
PELVIC ARTICULATIONS
235
ilium behind the auricular surface to the back of the lateral mass of the sacrum,
both lateral to and between the upper foramina and to the upper sacral articular
process, and the area between it and the first sacral foramen. The deepest fibres
of this group constitute the so-called interosseous ligament. The more superficial
fibres (long posterior sacro-iliac ligament) are oblique or vertical, and pass from
the posterior superior iliac spine to the second, third, and fourth tubercles on
the back of the sacrum, a more or less well-defined band which goes to the third
and fourth sacral tubercles being called sometimes the oblique saero-iliac band
and sometimes the long straight band.
The inferior sacro-iliac ligament (fig. 272) is covered behind by the upper
end of the sacro-tuberous ligament; it consists of strong fibres extending from
the lateral border of the sacrum below the articular facet to the posterior iliac
spines; some of the fibres are attached to the deep surface of the ilium and join
the interosseous ligament.
Fig. 272. — Median Sagittal Section op the Pelvis, Showing Ligaments.
Anterior sacro-iliac liga-
ment
Inferior sacro-iliac liga-
ment
Sacro-spinous ligament
Sacro-tuberous ligament
i
The interosseous ligament is the strongest of all, and consists of fibres of
different lengths passing in various directions between the two bones. Imme-
diately above the interspinous notch of the ilium the fibres of this ligament are
very strong, and form an open network, in the interstices of which is a quantity
of fat in which the articular vessels ramify.
Tlie ear-shaped cartilaginous plate, which unites the bones firmly, is accu-
rately applied to the auricular surfaces of the sacrum and ilium. It is about
one-twelfth of an inch (2 mm.) thick in the centre, but becomes thinner toward
the edges. Though closely adherent to the bones, it tears away from one entirely,
or from both partially, on the application of violence, sometimes breaking irregu-
larly so that the greater portion remains connected with one bone, leaving the
other bone rough and bare. It is usually one mass, and is only occasionally
formed of two plates with a synovial cavity between them.
Because of the occasional presence of a more or less extensive synovial ca^dty within the
fibro-cartilage, and also of a synovial lining to the Ugaments passing in front and behind the
articulation, the term 'diarthro-amphiarthrosis' has been given to this joint, and also to the
sympliysis pubis. Testut mentions certain folds of sjiiovial membrane filling up gaps which
here and there occur at the margin of the fibro-cartilage but they are not usually seen.
The sacro-tuberous (great sciatic) ligament (figs. 271, 272, and 273) is at-
tached above to the posterior extremity of the crest of the ilium and the lateral
aspect of the posterior iliac spines. From this attachment some of its fibres
236
THE ARTICULATIONS
pass downwai'd and backward to be attached to the lateral borders and posterior
surfaces of the lower three sacral vertebrae and upper two segments of the coccyx;
while others, after passing for a certain distance backward, curve forward and
downward to the ischium, forming the anterior free margin of the ligament
where it limits posteriorly the sciatic foramina. These fibres are joined by others
which arise from the posterior surfaces of the lower three sacral vertebrse and
upper pieces of the coccyx. At the ischium it is fixed to the medial border of the
tuberosity, and sends a thin sharp process upward along the ramus of the
ischium which is called the falciform process (fig. 273), and is a prolongation of
the posterior edge of the ligament.
A great many fibres pass on directly into the tendon of the biceps muscle, so that traction
on this muscle braces up the whole ligament, and the coccyx is thus made to move on the sacrum.
The ligament may not unfairly be described as a tendinous expansion of the muscle, whereby
its action is extended and a more advantageous leverage given. It is broad and flat at its
attached ends, but narrower and thicker in the centre, looking like two triangular expansions-
Fig. 273. — Sacro-tuberous and Sacro-spinous Ligaments. (Posterior view.)
Falciform process of sacro-tuberous
ligament
joined by a flat band, the larger triangle being at the ilium, and the smaller at the ischium^
The fibres of the ligament are twisted upon its axis at the narrow part, so that some of the-
superior fibres pass to the lower border.
The posterior surface gives origin to the gluteus maximus muscle, and on it ramify the loop;
from the posterior branches of the sacral nerves; its anterior surface is closely connected at its
origin ,with the sacro-spinous ligament, and some fibres of the piriformis muscle arise from its
below the obturator internus passes out of the pelvis under its cover, and the internal pudic
vessels and nerve pass in. At the ilium, its posterior edge is continuous with the vertebra,
aponeurosis; while to the anterior edge is attached the thick fascia covering the gluteus mediusl
The obturator fascia is attached to its falciform edge. It is pierced by the coccygeal branches of
the inferior gluteal {sciatic) artery and the inferior clunial {perforating cutaneous) nerve from the
second and third sacral.
The sacro-spinous (small sciatic) ligament (figs. 271, 272, and 273) is tri-
angular and thin, springing by a broad base from the lateral border of the sacrum
and coccyx, from the front of the sacrum both above and below the level of the
fourth sacral foramen, and from the coccyx nearly as far as its tip. By its apex
it is attached to the front surface and the borders of the ischial spine as far out-
ward as its base. Its fibres decussate so that the lower ones at the coccyx be-
come the highest at the ischial spine; muscular fibres are often seen intermingled
with the ligamentous.
The sacro-spinous ligament is situated in front of the sacro-tuberous Hgament, with which
it is closely connected at the sacrum, and separates the greater from the lesser sciatic foramen.
SACRO-COCCYGEAL ARTICULATION
237
Its front surface gives attachment to the coccygeus muscle, which overlies it. Behind, it is
connected with, and hidden by, the sacro-tuberous ligament, so that only the lateral inch or
less (2 cm.) and a small part of its attachment to the coccyx can be seen; the internal pudic
nerve also passes over the posterior surface.
The arterial supply of the sacro-Uiac joint comes from the superior gluteal, ilio-lumbar, and
lateral sacral.
The nerve-supply is from the superior gluteal, sacral plexus, and external twigs of the
posterior divisions of the first and second sacral nerves.
Movements. — Recent investigations have shown that in spite of the interlocking of the
articular surfaces and the strong ligaments connecting the bones together a slight amount of
movement, both a gUding and rotatory, does occur at the sacro-iliac joint. The gliding move-
ment is both up and down, and forward and backward, and the latter is associated with a slight
rotation round a transverse axis which passes through the upper tubercles on the back of the
sacrum. The movement is but small in extent, nevertheless as the base of the sacrum moves
Fig. 274. — Ligaments connecting Sacrum and Coccyx posteriorly.
Superficial part of
the supraspinous
ligament, turned
Deep part of the su-
praspinous ligament
turned up
Lateral sacro-coccygeaL
ligament
The deep posterior sacro-
cocygeal ligament, or the
lower end of the poste-
rior longitudinal liga-
ment
The superficial posterior
sacro-coccygeal 1 i g a -
ment connecting the
cornus of the sacrum
and coccyx, cut and
turned down
downward and forward the conjugate (antero-posterior) diameter of the pelvic inlet is diminished
and at the same time, as the coccyx moves up and back, the conjugate diameter of the outlet
is increased. This rotatory movement is limited principally by the sacro-sciatic (sacro-
tuberous and sacro-spinous) Ugaments which prevent any extensive upward and backward
movement of the coccyx and lower part of the sacrum.
Downward displacement of the sacrum when the body is in the sitting posture is prevented
not only by the surrounding hgaments, but also by the wedge-like character of the sacrum,
which is broader above than below. Downward and forward displacement of the sacrum in
the erect posture is prevented by the ligaments and more particularly by the posterior sacro-
iliac bands, while backward displacement would be hindered by the breadth of the anterior as
contrasted with the posterior part of the sacrum as well as by the anterior ligaments.
Relations. — The sacro-ihac joint is in relation above with psoas and iUaous. In front it
is in relation at its upper part with the hypogastric vessels and obturator nerve, and at its
lower part with the piriformis muscle.
(b) The Sacro-coccygeal Articulation
Class. — False Synchondrosis.
The last piece of the sacrum and first piece of the coccyx enter into this union
[symphysis sacrococcygea] and are bound together by the following ligaments : —
Anterior sacro-coccygeal. Deep posterior sacro-coccygeal.
Superficial posterior sacro-coccygeal. Lateral sacro-coccygeal.
Intervertebral substance.
238 THE ARTICULATIONS
The intervertebral fibro -cartilage is a small oval disc, three-quarters of an
inch (about 2 cm.) wide, and a little less from before backward, closely con-
nected with the surrounding ligaments. It resembles the other discs in struc-
ture, but is softer and more jelly-like, though the laminse of the fibrous portion
are well marked.
The anterior sacro-coccygeal ligament is a prolongation of the glistening
fibrous structure on the front of the sacrima. It is really the lower extremity of
the anterior longitudinal ligament, which is thicker over this joint than over
the central part of either of the bones.
The posterior sacro-coccygeal ligament (fig. 274) is divided into two layers
of which one (the deep) is a direct continuation of the posterior longitudinal
ligament of the column, consisting of a narrow band of closely packed fibres,
which become blended at the lower border of the first segment of the coccyx
with the filum terminate and deep posterior ligament.
The superficial layer of the posterior sacro-coccygeal ligament (or supra-
cornual ligament), (fig. 274) is the prolongation of the supraspinous which be-
comes inseparably blended with the aponeurosis of the sacro-spinalis (erector
spince) opposite the laminse of the third sacral vertebra, and is thus prolonged
downward upon the back of the coccyx, passing over and roofing in the lower
end of the spinal canal where the laminge are deficient.
The median fibres (the supraspinous ligament) extend over the back of the coccyx to its
tip, blending with the deep fibres of the posterior sacro-coccygeal ligament and filum terminale;
the deeper fibres run across from the stunted laminae on one side to the next below on the oppo-
site side, and from the sacral cornua on one side to the coccygeal on the opposite, some passing
between the two cornua of the same side, and bridging the aperture through which the fifth
sacral nerve passes. Its posterior surface gives origin to the gluteus inaximus muscle.
The lateral sacro-coccygeal or intertransverse ligament (fig. 274) is merely a quantity of
fibrous tissue which passes from the transverse process of the coccyx to the lateral edge of the
sacrum below its angle. It is connected with the saerosciatic ligaments at their attachments,
and the fifth sacral nerve escapes behind it. It is perforated by twigs from the lateral sacral
artery and the coccygeal nerve.
The arterial supply of the sacro-coccygeal joint is from the lateral sacral and middle sacral
arteries.
The nerves come from the fourth and fifth sacral and coccygeal nerves.
The movements permitted at this joint are of a simple forward and backward, or hinge-
like character. In the act of defecation, the bone is pushed back by the faecal mass, and, in
parturition, by the foetus; but this backward movement is controlled by the upward and forward
puU of the levator ani and Qoccygeus. The external sphincter also tends to puU the coccyx
forward.
(c) Intercoccygeal Joints
The several segments of the coccyx are held together by the anterior and
posterior longitudinal ligaments, which completely cover the bony nodules on
their anterior and posterior aspects. Laterally, the sacro-sciatic ligaments,
being attached to nearly the whole length of the coccyx, serve to connect them.
Between the first and second pieces of the coccyx there is a very perfect amphiar-
throdial joint, with a well-marked intervertebral substance.
Movements. — But Uttle movement occurs as a rule at the sacro-coccygeal and inter-
coccygeal joints, but when the head of the child is passing through the pelyic outlet at birth,
the tip of the coccyx is displaced backward, it may be to the extent of one inch.
(d) The Symphysis Pubis
Class. — False Synchondrosis.
The bones entering into this joint are the pubic portions of the hip-bones.
This joint is shorter and broader in the female than in the male. The ligaments,
which completely surround the articulation, are : —
Superior. Anterior.
Arcuate. Posterior.
Interpubic cartilage.
The superior ligament (figs. 275 and 276) is a well-marked stratum of yellowish
fibres which extends lateralward along the crest of the pubis on each side, blending
in the middle line with the interosseous cartilage.
SYMPHYSIS PUBIS
23&
It is continuous in front with the deep traverse fibres of the anterior ligament, and be-
hind with the posterior ligament. It gives origin to the rectus abdominis tendon.
The posterior ligament (fig. 277) is slight, and, excepting above and below,
consists of little more than thickened periosteum.
Near the uipper part is a band of strong fibres, reaching the whole width of the pubic bones,
and continuous with the thickened periosteal fibres along the terminal line. Below, many of the
upper and superficial fibres of the arcuate ligament ascend over the back of the joint, and
interlace across the median line with fibres from the opposite side nearly as high as the middle
of the symphysis.
Fig. 275. — Anteeiob View of the Symphysis Pubis (Male), showing the Decussation
OF THE Fibres of the Anterior Ligament.
Superior pubic ligament
X
Arcuate ligament
The anterior ligament (figs. 275 and 276) is thick and strong, and is closely
connected with the fascial covering of the muscles arising from the body of the
pubis. It consists of several strata of thick, decussating fibres of different de-
grees of obliquity, the superficial being the most oblique, and extending lowest
over the joint.
The most superficial descending fibres extend from the upper border of the pubis, cross
others from the opposite side about the middle of the symphysis, and are attached to the ramus
of the opposite bone. The most superficial ascending fibres come from the arcuate ligament,
Fig. 276. — Anterior View of the Symphysis Pubis (Female), showing greater Width
between the Bones.
Superior pubic ligament
Arcuate ligament
arch upward,"and decussate with other fibres across the middle line, and are lost on the oppo-
site side beneath the descending set. There is another deeper set of descending fibres which
arise below the angle, but do not descend so far as the superficial; and a deeper set of ascending,
which decussate, and reach higher than the superficial set, and are connected with the arcuate
ligament. Some few transverse fibres pass from side to side, especially above and below^the
points of decussation.
The arcuate (inferior or subpubic) ligament (figs. 275, 276, and 277) is a
thick, arch-like band of closety packed fibres which fills up the angle between the
pubic rami, and forms a smooth, rounded summit to the pubic arch. On section,
it is yellowish in colour and three-eighths of an inch (1 cm.) thick in the middle
line; it is inseparably connected with the interpubic cartilage.
240
THE ARTICULATIONS
Both on the front and back aspects of the joint it gives off decussating fibres, which, by their
interlacement over the anterior and posterior ligaments of the symphysis, add very materi-
ally to its security. In fact, the ligament may be said to split superiorly into two layers, one
passing over the front, and the other over the back, of the articulation.
The interpubic fibro -cartilage varies in thickness in different subjects, but
is thicker in the female than in the male. It is thicker in front than behind,
and projects beyond the edges of the bones, especially posteriorly (see fig. 277),
blending intimately with the ligaments at its margins. It is sometimes uninter-
ruptedly woven throughout, but at others has an elongated narrow fissure,
partially dividing the cartilage into two plates, with a little fluid in the interspace
Fig. 277. — Posterior View of the Symphysis Pubis, showing the Decussation op the
Fibres prom the Arcuate Ligament.
Arcuate ligament
(fig. 278). This is situated toward the upper and posterior aspects, but does
not usually reach either; it generally extends about half the length of the
cartilage.
When this cavity is large, especially if it reaches or approaches very near to the circumfer-
ence of the cartilage (which, however, it very rarely does), it is thought by some anatomists
that it more nearly resembles a diarthrodial than an amphiarthrodial joint, and it is then classed
with the sacro-Uiac joint under similar conditions, as 'diarthroamphiarthrosis.' The interos-
seous cartilage is intimately adherent to the layer of hyaline qartUage which covers the medial
surface of each pubic bone; the osseous surface is ridged to give a firmer attachment; and, on
forcing the bones apart, it does not frequently spht into two plates, but is torn from the bone
on one side or the other.
Fig. 278. — Section of Symphysis to show the Synovial Cavity.
The arterial supply of the interpubic joint is from twigs of the internal pudic, pubic branches
of the obturator and epigastric, and ascending branches of the internal circumflex and super-
ficial external pudic.
The nerve-supply has not been satisfactorily made out, but it probably comes, m part,
from the internal pudic and in part from the ilio-hypogastric and Uio-inguinal.
The movements amount only to a slight yielding of the cartilage; neithermuscular force
nor extrinsic forces produce any appreciable movement in the ordinary condition. Occasion-
ally, as the result of child-bearing, the joint becomes unnaturally loose, and then waMng and
standing are painfully unsteady. It is known that, during pregnancy and parturition, the
COSTO-VERTEBRAL ARTICULATIONS
241
symphyseal cartilage becomes softer and more vascular, so as to permit the temporary enlarge-
ment of the pelvis; but it must be remembered that the fibres of the obhque muscles decussate
and thus, during labour, while they force the head of the fcetus down, they strengthen the joint
by bracing the bones more tightly together.
Relations. — The interpubic joint is in relation above with the Unea alba. Behind with
the prostate and the anterior border of the bladder. In front with the suspensory ligament
of the penis or chtoris and below with the dorsal vein of the penis or clitoris and the upper
border of the urogenital trigone (triangular ligament).
4. THE COSTO-VERTEBRAL ARTICULATIONS
These consist of two sets, viz. : — ■
(a) The capitular (costo-central) : i. e., the articulation of the head of the rib
with the vertebrae.
(6) The costo-transverse, or the articulation of the tubercle (of each of the
first ten ribs) with the transverse process of the lower of the two vertebree, with
which the head of the rib articulates: i.e., the one bearing its own number, as
the first rib with the first thoracic vertebra, the second rib with the second thoracic
vertebra, and so on.
Fig. 279. — -The Capsular Ligaments op the Costo-vertebral Joints.
Capsular ligament of
capitular joint
(a) The Capitular (Costo-central) Articulation
Class. — Diarthrosis. Subdivision. — Condylarthrosis.
It is a very perfect joint, into the formation of which the head of the rib and
two vertebrae, with the intervertebral disc between them, enter. In the case of
the first, tenth, eleventh, and twelfth ribs, it is formed by the head of the rib
articulating with a single vertebra.
The ligaments are : —
Articular capsule.
Interarticular.
Radiate.
The articular capsule (fig. 279) consists of short, strong, woolly fibres, com-
pletely surrounding the joint, which are attached to the bones and intervertebral
substances, a little beyond their articular margins.
At its upper part it reaches through the intervertebral foramen toward the back of the
bodies of the vertebrae, being strengthened here by fibres which at intervals connect the anterior
with the posterior longitudinal ligaments. The lower fibres extend downward nearly to the
demi-faoet (costal pit) of the rib below; behind, it is continuous with the neck ligament, and
in front is overlaid by the radiate.
The interarticular ligament (fig. 280) consists of short, strong fibres, closely
interwoven with the outermost ring of the intervertebral disc, and attached to
the transverse ridge separating the articular facets on the head of the rib. It
completely divides the articulations into two parts, but does not brace the rib
tightly to the spine, being loose enough to allow a moderate amount of rotation
242
THE ARTICULATIONS
on its own axis. There is no interarticular ligament in the costo-vertebral joints
of the first, tenth, eleventh, and twelfth ribs.
The radiate (or stellate) ligament, a thickening of the anterior part of the
capsule (figs. 280 and 281), is the most striking of all, and consists of bright,
pearly-white fibres attached to the anterior surface, and upper and lower borders
of the neck of the rib, a little way beyond the articular facet; from this they
radiate upward, forward, and downward, so as to form a continuous layer of
distinct and sharply defined fibres.
The middle fibres run straight forward to be attached to the intervertebral disc; the upper
ascend to the lower half of the lateral surface of the vertebra above, and the lower descend to
the upper half of the vertebra below. The radiate ligament is overlapped on the vertebral
bodies by the lateral (short) vertebral ligaments.
In the case of the first, tenth, eleventh, and twelfth ribs, each of which articulates with one
vertebra, the ligament is not quite so distinctly radiate, but even in these the ascending fibres
reach the vertebra above that with which the rib articulates.
Fig. 280. — Showing the Anterior Longitudinal Ligament, and the Connection op the
Ribs with the Vertebra.
The interarticular ligament
The costo-transverse ligaments
^ — The radiate ligament
The synovial membranes (fig. 281) consist of two closed sacs which do not
communicate: one above, and the other below, the interarticular ligament. In
the case of the first, tenth, eleventh, and twelfth articulations, there is but one
synovial membrane, as these joints have no interarticular ligament.
The arterial supply is from the intercostal arteries, the twigs piercing the radiate and
capsular ligaments.
The nerve -supply comes from the anterior primary branches of the intercostal nerves.
These joints approach most nearly in their movements to the condylarthroses.
The movements are ginglymoid in character, consisting of a slight degree of elevation and
depression around an obliquely horizontal axis corresponding with the interarticular ligament;
there is also a slight amount of forward and backward gliding; and a slight degree of screwing or
rotatory movement is also possible . There is a considerable difference in the degree of mobility of
the different ribs, for while the first rib is almost immobile except in a very deep inspiration,
the mobility of the others increases from the second to the last; the two floating ribs being the
most mobile of all. The head of the rib is the most fixed point of the costal arch, and upon
it the whole arch rotates; the interarticular ligament allows only a very limited amount of
flexion and extension (i. e., elevation and depression), and of gliding. Gliding is checked by
the radiate ligament.
In inspiration, the rib is elevated, and glides forward in its socket, too great elevation
being checked not only by the ligaments, but also by the overhanging upper edge of the cavity
itself. In expiration, the rib is depressed, and glides backward in its cavity.
COSTO-TRANSVERSE ARTICULATIONS
243
(6) The Costo-transvehse Articulation
Class. — Diarthrosis.
Subdivision. — Arthrodia.
This joint is formed by the tubercle of the rib articulating with the anterior
part of the tip of the transverse process. The eleventh and twelfth ribs are
devoid of these joints, for the tubercles of these ribs are absent, and the transverse
processes of the eleventh and twelfth thoracic vertebrae are rudimentary.
The ligaments of the union are :-
Articular capsule.
Neck ligament.
Tubercular ligament.
Costo-transverse ligaments.
The articular capsule (figs. 279 and 281) forms a thin, loose, fibrous envelope to
the synovial membrane. Its fibres are attached to the bones just beyond the
articular margins, and are thickest below, where they are not strengthened by
any other structure. It is connected medially with the neck ligament, above
with the costo-transverse, and laterally with the tubercular (posterior costo-
transverse) ligaments. The eleventh and twelfth ribs are unprovided with costo-
transverse capsules.
Fig. 281. — Horizontal Section through the Inteevertebeal Disc and Ribs.
Fibrous ring of intervertebral
fibro-cartilage
Radiate ligament
i
Costo-transverse synovial sac
Tubercular ligament
The neck ligament [lig. colli costae] (middle costo-transverse, or interosseous
ligament) (fig. 281), consists of short fibres passing between the back of the neck
of the rib and front of the transverse process, with which the tubercle articulates.
It extends from the capsule of the capitular joint to that of the costo-transverse.
It is best seen on horizontal section through the bones. In the eleventh and
twelfth ribs this ligament is rudimentary.
The tubercular ligament (posterior costo-transverse) (fig. 281) is a short but
thick, strong, and broad ligament, which extends laterally and upward from the
extremity of the transverse process to the non-articular surface of the tubercle
of the corresponding rib. The eleventh and twelfth ribs have no posterior
ligament.
The (superior) costo-transverse ligament (fig. 280) is a strong, broad band of
fibres which ascends laterally from the crest on the upper border of the neck
of the rib, to the lower border of the transverse process above. A few scattered
posterior fibres pass upward and medially from the neck to the transverse process.
The costo-transverse ligament is subdivided into a stronger anterior portion
(anterior costo-transverse ligament) best seen from the front (fig. 280) , and a
weaker posterior portion (posterior costo-transverse ligament). Its medial
border bounds the foramen through which the posterior branches of the inter-
costal vessels and nerves pass. To the lateral border is attached the thin aponeu-
I
244 THE ARTICULATIONS
rosis covering the external intercostals. Its anterior surface is in relation with the
intercostal vessels and nerve; the posterior with the longissimus dor si. The
first rib has no (superior) costo-transverse ligament.
The synovial membrane (fig. 281) is a single sac.
The arterial and nerve supplies come from the posterior branches of the intercostal arteries
and nerves.
The movements which take place at these joints are limited to a gliding of the tubercle of
the rib upon the transverse process. The exact position of the facet on the transverse process
varies slightly from above downward, being placed higher on the processes of the lower vertebrae.
The plane of movement in most of the costo-transverse joints is inclined upward and backward
in inspiration, and downward and forward in expiration. The point round which these move-
ments occur is the head of the rib, so that the tubercle of the rib gUdes upon the transverse
process in the circumference of a circle, the centre of which is at the capitular joint.
5. THE ARTICULATIONS AT THE FRONT OF THE THORAX
These may be divided into four sets, viz.: — ■
(a) The intersternal joints, or the union of the several parts of the sternum
with one another.
(6) The costo -chondral joints, or the union of the ribs with their costal
cartilages.
(c) The chondro-stemal joints, or the junction of the costal cartilages with
the sternum.
(d) The interchondral joints, or the union of five costal cartilages (sixth,
seventh, eighth, ninth, and tenth) with one another.
(a) The Intersternal Joints
The sternum being composed, in the adult, of three distinct pieces — the
manubrium, body, and the xiphoid process — has two articulations, viz., the
superior, which unites the manubrium with the body (gladiolus), and the inferior,
which unites the body with the xiphoid.
1. The Superior Intersternal Articulation
Class. — False Synchondrosis.
The lower border of the manubrium and the upper border of the body of the
sternum present oval-shaped, fiat surfaces, with their long axes transverse, and
covered with a thin layer of hyaline cartilage. An interosseous fibro-cartilage
is interposed between the bony surfaces: it corresponds exactly in shape and
intimately adheres to them. At each lateral border this fibro-cartilage enters
into the formation of the second chondro-sternal articulation (fig. 282).
In consistence it varies, being in some oases uniform throughout, in others softer in the
centre than at the circumference, and in others again an oval-shaped synovial cavity is found
toward its anterior part. When such a cavity exists in the fibro-cartilage this joint has a
remote resemblance to the diarthroses, and is classed, with the sacro-iliac joint and the symphy-
sis pubis under similar conditions, as 'diarthro-amphiarthrosis.'
The periosteum passes uninterruptedly over the joint from one segment of the sternum to
the other, forming a kind of capsular ligament [membrana sterni]. This capsule is strength-
ened, especially on its pos'erior aspect, by longitudinal ligamentous fibres as well as by the
radiating and decussating fibres of the chondro-sternal ligaments.
In some instances the fibro-cartilage is replaced by short bundles of fibrous tissue which
unite the cartilage-coated articular bony sm'faces.
2. The Inferior Intersternal Articulation
Class. — False Synchondrosis.
The gladiolus is joined to the xiphoid cartilage by a thick investing mem-
brane, by anterior and posterior longitudinal fibres, and by radiating fibres of the
sixth and seventh chondro-sternal ligaments. The costo-xiphoid ligament also
connects the xiphoid with the anterior surface of the sixth and seventh costal
cartilages, and thus indirectly with the gladiolus; and some fine fibro-areolar
tissue also connects the xiphoid with the back of the seventh costal cartilage.
STERNO-COSTAL ARTICULATIONS 245
The junction of the xiphoid with the sternum is on a level somewhat posterior to the junc-
tion of the seventh costal cartilage with the sternum. The union is a synchondrosis, each bone
being covered by hyahne cartilage which is connected with the intervening fibro-cartilage plate.
(b) The Costo-chondral Joints
Class. — Synarthrosis.
The extremity of the costal cartilage is received into a cup-shaped depression
at the end of the rib, which is somewhat larger than the cartilage. The two are
joined together by the continuity of the investing membranes, the periosteum of
the rib being continuous with the perichondrium of the cartilage.
(c) The Steeno-costal Articulations
Class. — Diarthrosis. Subdivision — Ginglymus.
These articulations are between the lateral borders of the sternum and the
ends of the costal cartilages. The union of the first rib with the sternum is
synchondrodial, and therefore forms an exception to the others. From the second
to the seventh inclusive, the articulations have the following ligaments, which
together form a complete capsule: —
Radiate (anterior) sterno-costal. Superior sterno-costal.
Posterior sterno-costal. Inferior sterno-costal.
The radiate (anterior) sterno-costal ligament (fig. 282) is a triangular band
composed of strong fibres which cover the medial half-inch of the front of the
costal cartilage, and radiate upward and downward upon the front of the sternum.
Some of the fibres decussate across the middle line with fibres of the opposite
ligament. At its upper and lower borders it is in contact with the superior and
inferior ligaments respectively.
The posterior sterno-costal ligament consists of little more than a thickening
of the fibrous envelopes of the bone and cartilage, the joint being completed
behind by a continuity of perichondrium with periostemn.
The superior and inferior ligaments are strong, well-marked bands, which
pass from the upper and lower borders respectively of the costal cartilage to the
lateral edges of the sternum. The sixth and seventh cartilages are so close that
the superior ligament of the seventh is blended ^^^th the inferior of the sixth rib.
Deeper than the fibres of these ligaments are short fibres passing from the margins of the
sternal facets to the edges of the facets on the cartilages; they are most distinct in the front
and lower part of the joint, and may encroach so much upon the synovial cavity as to reduce
it to a very small size, or almost obliterate it. This occurs mostly in the case of the sixth and
seventh joints, especially the latter.
The interarticular ligament (fig. 282) is by no means constant, but is usually
present in the second joint on one, if not on both sides of the same subject. It
consists of a strong transverse bundle of fibres passing from the ridge on the facet
on the cartilage to the fibrous substance between the manubrium and body;
sometimes the upper part of the synovial cavity is partially or entirely obliterated
by short, fine, ligamentous fibres.
The costo-xiphoid ligament (fig. 282) is a strong flat band of fibres passing
obliquely upward and laterally from the front surface of the xiphoid cartilage to
the anterior surface of the sternal end of the seventh costal cartilage, and most
frequently to that of the sixth also.
Synovial membranes. — -The union of the first cartilage with the sternum being synchondro-
dial, it has no synovial membrane; the second has usually two, separated by the interarticular
Ugament. The rest usually have one synovial membrane, which may occasionally be subdivided
into two (fig. 2S2).
The arterial supply is derived from perforating branches of the internal mammary; and
the nerves come from the anterior branches of the interoostals.
Movements. — -Excepting the first, the chondro-sternal joints are ginglymoid, but the
motion of which they are capable is verj' limited. It consists of a hinge-like action in two direc-
tions: first, there is a slight amount of elevation and depression which takes place round a
transverse axis, and, secondly, there is some forward and backward movement round an ob-
liquely vertical axis. In inspiration the cartilage is elevated, the lowest part of its articular
facet is pressed into the sternal socket, and the sternum is thrust forward so that the upper
i
246
THE ARTICULATIONS
aad front edges of the articular surfaces separate a little; in expiration the reverse movement
takes place. Thus the two extremities of the costal arches move in their respective sockets in
opposite directions.
This difference results necessarily from the fact that the costal arch moves upon the verte-
bral column, and, having been elevated, it in its turn raises the sternum by pushing at upward
and forward.
The costo-.xiphoid ligament tends to prevent the xiphoid cartilage from being drawn back-
ward by the action of the diaphragm.
Fig. 282. — The Articulation at the Front of the Thorax.
(Left side, showing ligaments, right side, the synovial cavities.)
For clavicle and first rib
The plate of fibre- - -,^.3
cartilage betW' ^^" ' '^
manubriuDi i
body
^^Radiate sterno-
costal ligameat
(d) The Interchondral Articulations
Class. — Diarthrosis. Subdivision. — Arthrodia.
A little in front of the point where the costal cartilages bend upward toward
the median line the sixth is united with the seventh, the seventh with the eighth,
the eighth with the ninth, and the ninth with the tenth.
At this point each of the cartilages from the sixth to the ninth inclusive is deeper than
elsewhere, owing to the projection downward from its lower edge of a broad blunt process,
which comes into contact with the cartilage next below. Each of the apposed surfaces is smooth.
MOVEMENTS OF THE THORAX
247
and they are connected at their margins by ligamentous tissue, which forms a complete capsule
for the articulation, and is hned by a synovial membrane (fig. 282). The largest of these cavi-
ties is between the seventh and eighth; those between the eighth and ninth, and ninth and tenth,
are smaller, and are not free to play upon each other in the whole of their extent, being held
together by ligamentous tissue at theii' anterior margins. Sometimes this fibrous tissue com-
pletely obliterates the synovial cavity.
The arteries are derived from the musoulo-phrenio, and the nerves from the intercostals.
Movements. — -By means of the costal cartilages and interchondral joints, strength with
elasticity is given to the wall of the trunk at a part where the cartilages are the only firm struc-
tures in its composition; while a slight gliding movement is permitted between the costal carti-
lages themselves, which takes place round an axis corresponding to the long axis of the cartilages.
By this means, the outward projection of the lower part of the thoracic wall is increased by deep
inspiration.
MOVEMENTS OF THE THORAX AS A WHOLE
Before describing these movements as a <vhole, it must be premised that there are somt
few modifications in the movements of certain ribs resulting from their shape. Thus the firs
rib (and to a less extent the second also), which is flat on its upper and lower surfaces, revolves
on a transverse axis drawn through the oosto-vertebral and costo-transverse joints. During
inspiration and expiration, the anterior extremities of the first pair of costal arches play up and
down, the tubercles and the heads of the ribs acting in a hinge-like manner, the latter having
also a sHght screwing motion. By this movement the anterior ends of the costal arches are
simply raised or depressed, and the sternum pushed a little forward; it may be likened to the
movement of a pump-handle, as in fig. 283, a, b.
The movements of the other ribs, particularly in the mid-region of the thorax, are more
complex, for, besides the elevation of the anterior extremities, the bodies and angles of the
Fig. 283. — Diagram op Axis op Rib-movement. (After Kirkes.)
ribs rise nearly as much as the extremities themselves. In this'movement the tubercles of the
ribs glide upward and backward in inspiration, and downward and forward in expiration; and
the movement may be likened to that of a bucket handle, as in fig. 283, A, B.
During inspiration, the cavity of the thorax is increased in every direction. The antero-
posterior diameter is increased by the thrusting forward of the sternum, caused by the eleva-
tion of the costal cartilages and fore part of the ribs, whereby they are brought to nearly the
same level as the heads of the ribs. The transverse diameter is increased: (i) Behind, by the
elevation of the middle part of the ribs; for when at rest the mid-part of the rib is on a lower
level than either the costo-vertebral or chondro-sternal articulations. Owing to this obUquity
the transverse diameter is increased when the rib is raised, and the increase is proportionate
to the degree of obliquity, (ii) By the eversion of the lower border of the costal arch, which
tuTns outward as the arch is raised, (iii) The transverse diameter is increased in front by the
abduction of the anterior extremity of the rib at the same time as it is elevated and thrust
forward.
The increase in the vertical diameter of the thorax is due to the elevation of the ribs, espe-
cially the upper ones, and the consequent widening of the intercostal spaces; but the chief
increase in this direction is due to the descent of the diaphragm.
The greatest increase both in the antero-posterior and transverse diameters takes place
where the ribs are longest, most oblique, and most curved at theu' angles, and where the bulkiest
part of the lung is enclosed. This is on a level with the sixth, seventh, and eighth ribs.
At the lower part of the thorax, where the ribs have no relation to the lungs, and do not
affect respiration directly by their movements, it is important that the costal arches should
be thrown well outward in order to counteract the compression of the abdominal viscera by the
contraction of the diaphragm.
By widening and steadying the lower part of the thorax during inspiration, the attachments
ofjthe muscular fibres of the diaphi-agm are widened, and their power increased.
Muscles which take part in the movements of inspiration. — (a) Ordinary inspiration; The
scalenes, serratus posterior superior, the external and internal (?) intercostals, the diaphragm;
the quadratus lumborum and serratus posterior inferior fixing the lower ribs, possibly the poste-
rior fibres of the external oblique also helping to fix the lower ribs, (b) Extraordinary inspira-
tion: The superior extremities are raised and fixed. The cervical part of the vertebral column
and the head are extended, and in addition to the muscles of ordinary inspiration, the following
>
248 THE ARTICULATIONS
muscles also come into play: The pectoralis minor, the muscles which extend the head and the
cervical part of the vertebral column, the sterno-mastoid and the supra- and infra-hyoid mus-
cles, the lower fibres of the pectoralis major, some of the lower fibres of the serratus anterior, and,
when the clavicle is fixed, the subclavius.
Expiration is produced by the elasticity of the lungs and the weight of the thorax, aided
by the elastic reaction and contraction of the external and internal oblique muscles, the recti
and pyramidales, the transversus abdominis, and the levatores ani and coccygei. In forcible
expiration all muscles which depress the ribs and reduce the dimensions of the abdomen are
thrown into action. The internal interoostals probably tend to contract the thorax, excepting,
the parts between the costal cartilages, which tend to expand the thorax.
THE ARTICULATIONS OF THE UPPER EXTREMITY
The articulations of the upper extremity are the following: —
1. The stemo-costo -clavicular.
2. The scapulo-clavicular union.
3. The shoulder-joint.
4. The elbow-joint.
5. The radio-ulnar union.
6. The radio-carpal or wrist-joint.
7. The carpal joints.
8. The carpo-metacarpal joints.
9. The intermetacarpal joints.
10. The metacarpo-phalangeal joints.
11. The interphalangeal joints.
1. THE STERNO-COSTO-CLAVICULAR ARTICULATION
Class. — Diarthrosis. Subdivision. — Condylarthrosis.
At this joint the large medial end of the clavicle is united to the superior angle
of the manubrium sterni, the first costal cartilage also assisting to support the
clavicle. It is the only joint between the upper extremity and the trunk, and
takes part in all the movements of the upper limb. Looking at the bones, one
would say that they were in no waj^ adapted to articulate with one another, and
yet they assist in constructing a joint of security, strength, and importance.
The bones are nowhere in actual contact, being completely separated by an
articular disc. The interval between the joints of the two sides varies from one
inch to an inch and a half (2.5-4 cm.). The ligaments of this joint are: —
(1) Articular capsule. (3) Articular disc.
(2) Interclavicular. (4) Costo-clavicular.
The articular capsule (fig. 284) consists of fibres, having varying directions
and being of various strength and thickness, which completely surround the
articulation, and are firmly connected with the edges of the interarticular fibro-
cartilage.
The fibres at the back of the joint, sometimes styled the posterior stemo-clavicular liga-
ment, are stronger than those in front or below, and consist of two sets: a superficial, passing
upward and laterally from the manubrium sterni, to the projecting posterior edge of the end of
the clavicle, a few being prolonged onward upon the posterior surface of the bone. A deeper
set of fibres, especiallj^ thick and numerous below the clavicle, connect the interarticular car-
tilage with the clavicle and with the sternum, but do not extend from one bone to the other.
The fibres in front, the anterior sterno -clavicular ligament, are well marked, but more lax and
less tough than the posterior, and are overlaid by the tendinous sternal origin of the sterno-
mastoid, the fibres of which run parallel to those of the ligament. They extend obliquely up-
ward and laterally from the margin of the sternal facet to the anterior surface of the clavicle
some little distance from the articular margin. The fibres which cover in the joint below are
short, woolly, and consist more of fibro-areolar tissue than true fibrous tissue; they extend from
the upper border of the first costal cartilage to the lower border of the clavicle just lateral to
the articular margin, and fill up the gap between it and the costo-clavicular ligament. The
superior portion consists of short tough fibres passing from the sternum to the articular disc;
and of others welding the fibro-cartilage to the upper edge of the clavicle, onlj' a few of them
passing from the clavicle direct to the sternum.
The interclavicular ligament (fig. 284) is a strong, concave band, materially
strengthening the superior portion of the capsule. It is nearly a quarter of an
STERNO-COSTO CLAVICULAR JOINT
249
inch (6 mm.) deep with the concavity upward, its upper border tapering to a
narrow, almost sharp edge. It is connected with the posterior superior angle of
the sternal extremity of each clavicle, and with the fibres which weld the inter-
articular cartilage to the clavicle; and then passes across from clavicle to clavicle
along the posterior aspect of the upper border of the manubrium sterni. The
lowest fibres are attached to the sternum, and join the posterior fibres of the
capsule of each joint. In the middle line, between the ligament and the sternum,
there is an aperture for the passage of a small artery and vein.
In addition to the interclavicular ligament Mr. Carwardine ("Journal of Anatomy and
Physiology," vol. 7, new series, p. 232) has described a special band of the upper portion of the
sterno-clavioular capsule which he proposes to name the 'suprasternal hgament.' It descends
from the upper border of the sternal end of the clavicle to the upper border of the sternum, and
is of special importance as it encloses the suprasternal bones, when these rudiments are present.
The costo -clavicular or rhomboid ligament (fig. 284) is a strong dense band,
composed of fine fibres massed together into a membranous structure. It
extends from the upper (medial) border of the first costal cartilage (and rib),
Fig. 284.^Posteeior View op the Stbrno-costo-claviculak Joint.
upward, backward, and distinctly laterally to the costal tuberosity on the under
surface of the medial extremity of the clavicle, to which it is attached just lateral
to the lower part of the capsule. Frequently some of the lateral fibres pass up-
ward and medially behind the rest, and give the appearance of decussating. It
is from half to three-quarters of an inch (1.5-2 cm.) broad.
The articular disc (fig. 285) is a flattened disc of nearly the same size and
outline as the medial articular end of the clavicle, which it fairly accurately
fits. It is attached above to the upper border of the posterior edge of the clavicle ;
and below to the cartilage of the first rib at its union with the sternum, where it
assists in forming the socket for the clavicle. At its circumference it is connected
with the articular capsule, and this connection is very strong behind, and still
stronger above, where it is blended with the interclavicular ligament.
It is usually thinnest below, where it is connected with the costal cartilage. It varies in
thickness in different parts, sometimes being thinner in the centre than at the circumference
sometimes the reverse, and is occasionally perforated in the centre. It divides the joint into
two compartments.
There are two synovial membranes (fig. 285) ; a lateral one, which is reflected
from the clavicle and capsule over the lateral aspect of the disc and is looser
than the medial one; the medial is reflected from the sternum over the medial
side of the articular disc, costal cartilage, and capsule. Occasionally a communi-
cation takes place between them.
The arterial supply is derived from branches — (1) from the internal mammary; (2) from
the superior thoracic branch of the axillary; (3) twigs of a muscular branch often arising from
the subclavian artery pass over the interclavicular notch; (4) twigs of the transverse scapular
(suprascapular) artery.
The nerve-supply is derived from the nerve to the subclavius and sternal descending branch
of the cervical plexus.
250
THE ARTICULATIONS
Relations. — In front of the joint is the sternal head of the sterno-mastoid. Behind it are
the sterno-hyoid and sterno-thyreoid muscles. Still further back, on the right side, are the
innominate and internal mammary arteries, and, on the left side, the left common carotid, the
left subclavian, and the internal mammary arteries. Above and behind, between the sterno-
mastoid and s terno-hyoid muscles, the anterior jugular vein passes back and laterally toward the
posterior triangle.
The movements permitted at this joint are various though limited, owing to the capsular
ligament being moderately tense in every position of the clavicle. Motion takes place in
nearly every direction — viz., upward, downward, forward, backward, and in a circumductory
manner. The upward and downward motions occur between the clavicle and the articular
disc; during elevation of the arm the upper edge of the clavicle with its attached articular disc
is pressed into the sternal socket, and the lower edge gUdes away from the disc; during depression
of the limb, the lower edge of the clavicle presses on to the disc, while the rest of the articular
surface of the clavicle inclines laterally, bringing with it to a slight degree the upper edge of
the articular disc. These movements occur on an antero-posterior axis drawn through the
outer compartment of the joint. The forward and backward motions take place between the
articular disc and sternum, the clavicle with the disc gUding backward upon the sternum when
the shoulder is brought forward, and forward when the shoulder is forced backward; these
movements odcur round an axis drawn nearly vertically through the sternal socket.
FiQ. 285. — Anterior View of Stbrno-costo-clavicular Joint, with Section
SHOWING Cavities opened on the Right Side.
Interclavicular ligament
Joint between ster-
num and second cos-
tal cartilage
The articular disc serves materially to bind the bones together, and to prevent the media
and upward displacements of the clavicle. It also forms an elastic lauffer which tends to break
shocks. The capsule, by being moderately tight, tends to limit movements in all directions,
while the interclavicular ligament is a safeguard against upward displacement during depression
of the arm. Tlie costo-clavicular ligament prevents dislocation upward during elevation of the
arm, and resists displacements backward.
Muscles which move the clavicle at the sterno-clavicular joint. — Elevators. — Trapezius,
clavicular part of sterno-mastoid, levator scapulae, omo-hyoid, rhomboids.
Depressors. — Subclavius, pectoraUs minor, lower fibres of trapezius and serratus anterior
(magnus). Depression is aided by the weight of the upper extremity.
Protractors. — PectoraUs major and minor. Serratus anterior (magnus).
-Latissimus dorsi, trapezius.
2. THE SCAPULO-CLAVICULAR UNION
The scapula is connected with the clavicle by a synovial joint with its liga-
ments at the acromio-clavicular articulation; and also by a set of ligaments pass-
ing between the coracoid process and the clavicle. So that we have to consider —
(a) The acromio-clavicular articulation.
lb) The cor aco -clavicular ligaments.
(c) The proper scapular ligaments are also best described in this section —
viz., the coraco-acromial and transverse.
COROCO-CLAVICULAR UNION 251
(a) The Acromio-claviculae Joint
Class. — Diarthrosis. Subdivision. — Arthrodia.
The acromio-clavicular joint is surrounded by an articular capsule and fre-
quently contains an articular disc.
The articular capsule (figs. 287 and 290) completely surrounds the articular
margins, and is composed of strong, coarse fibres arranged in parallel fasciculi,
of fairly uniform thickness, which are attached to the borders as well as the
surfaces of the bones. It is somewhat lax in all positions of the joint, so that the
clavicle is not tightly braced to the acromion. The fibres extend three-quarters
of an inch (2 cm.) along the clavicle posteriorly, but only a quarter of an inch
(6 mm.) anteriorly. Superiorly, they are attached to an oblique line joining
these two points, while inferiorly they reach to the ridge for the trapezoid liga-
ment with which they blend.
At the acromion they extend half way across the upper and lower surfaces, but at the
anterior and posterior limits of the joint they are attached close to the articular facet. The
anterior fibres become blended with the insertion of the eoraco-acromial ligament. The
fibres are strengthened above by the aponeuroses of the trapezius and deltoid muscles; and all
run from the acromion to the clavicle medially and backward.
The articular disc is occasionally present, but is usually imperfect, only oc-
cupying the upper part of the joint; it may completely divide the joint into two
cavities, or be perforated in the centre. It is usually thicker at the edge than
in the centre, and some of the fibres of the articular capsule are blended with its
edges.
The synovial membrane lining the joint is occasionally either partially or
entirely divided into two by the articular disc.
Relations. — Superiorly skin and fascia and the tendinous intersection between the deltoid
and the trapezius. Inferiorly, the eoraco-acromial ligament and supraspinatus. Anteriorly,
part of the origin of the deltoid. Posteriorly, part of the insertion of the trapezius.
Movements. — A certain amount of gliding movement occurs at this joint, but the most
important movement is a rotation of the scapula whereby the glenoid cavity is turned forward
and upward, or downward. As these movements occur the inferior angle of the scapula moves
forward as the glenoid cavity turns upward and the superior angle recedes.
The forward movement of the inferior angle is produced mainly by the inferior fibres of
the serratus anterior (magnus), aided by the inferior fibres of the trapezius, and it is by this
movement that the arm is raised above the level of the shoulder forward.
The reverse movement is produced mainly by the rhomboideus major aided by the latissimus
dorsi.
(6) The Coraco-clavicular Union
The coraco-clavicular ligament (figs. 286, 287, and 290) consists of two parts,
the conoid and the trapezoid ligaments.
The conoid ligament is the medial and posterior portion, and passes upward
and laterally from the coracoid process to the clavicle.
It is a very strong and coarsely fasciculated band of triangular shape, the apex being
fixed to the medial and posterior edge of the root of the coracoid process just in front of the
scapular notch, some fibres joining the transverse ligament. Its base is at the clavicle, where
it widens out, to be attached to the posterior edge of the inferior surface, as well as to the cora-
coid tubercle. It is easily separated from the trapezoid, without being absolutely distinct. A
small bursa often exists between it and the coracoid process; medially, some of the fibres of the
subclavius muscle are often attached to it.
The trapezoid ligament is the anterior and lateral portion of the coraco-
clavicular ligament. It is a strong, flat, quadrilateral plane of closely woven
fibres, the surfaces of which look upward and medially toward the clavicle, and
downward and laterally over the upper surface of the coracoid process.
At the coracoid it is attached for about an inch (2.5 cm.) to a rough ridge which runs
forward from the angle, along the anterior border of the process. At the clavicle it is attached
to the oblique ridge which runs laterally and forward from the coracoid tubercle, reaching as
far as, and blending with the inferior part of the acromio-clavicular ligament. Its anterior
edge is free, and overlies the eoraco-acromial Ugament; the posterior edge is shorter than the
anterior, and is in contact with the posterior and lateral portion of the conoid hgament.
The arterial supply is derived from the transverse scapular (suprascapular), acromial
branches of the thoraco-acromial, and the anterior circumflex.
The nerve-supply is derived from the suprascapular and axillary (circumflex) nerves.
252
THE ARTICULATIONS
Movements. — In the movements of the shoulder girdle, the scapula moves upon the lateral
end of the clavicle, and the clavicle, in turn, carried by the uniting Ugaments, moves upon the
sternum; so that the entire scapula moves in the arc of a circle whose centre is at the sterno-
clavicular joint, and whose radius is the clavicle. The scapula, in moving upon the clavicle,
also moves upon the thorax forward and backward, upward and downward, and also in a rota^
tory direction upon an axis drawn at right angles to the centre of the bone. Throughout these
movements the inferior angle and base of the scapula are kept in contact with the ribs by the
Fig. 286.— Anterior View op Shoulder, showing also Coraco-clavicular and
cohaco-acromial ligaments.
Conoid ligament
Superior transverse scapular ligament t
Coraco-acromial ligament
>
Short head of biceps
'Subscapular tendon
Capsule of shoulde
Long tendon of biceps
latissimus dorsi, which straps down the former, and the rhomboids and serratus anterior {magnus),
which brace down the latter. The glenoid cavity could not have preserved its obUquely
forward direction had there been no acromio-clavicular joint, but would have shifted round a
vertical axis, and thus the shoulder would have pointed medialward when the scapula was
advanced, and lateralward when it was drawn backward. By means of the acromio-clavicular
joint, the scapula can be forcibly advanced upon the thorax, the glenoid cavity all the time
keeping its face duly forward. Thus the muscles of the shoulder and forearm can be with
advantage combined, as, for example, in giving a direct blow. The acromio-clavicular joint
also permits the lower angle of the scapula to be retained in contact with the chest wall during
the rising and faUing of the shoulder, the scapula turning in a hinge-like manner round the
horizontal axis of the joint.
There are no actions in which the scapula moves on a fixed clavicle, or the clavicle ona
fixed scapula; the two bones, bound together by their connecting ligament, must move in
unison.
(c) The Phoper Scapular Ligaments
There are three proper ligaments of the scapula, which pass
portions of the bone, viz. —
Coraco-acromial. Superior transverse.
Inferior transverse.
The coraco-acromial ligament (figs. 286 and 290) is a flat, triangular band
with a broad base, attached to the lateral border of the coracoid process, and a
blunt apex which is fixed to the tip of the acromion. It is made up of two broad
marginal bands, and a smaller and thinner intervening portion. The anterior
band, which arises from the anterior portion of the coracoid process, is the
stronger, and some of its marginal fibres can often be traced into the short head
of the biceps, which can then make tense this edge of the ligament. The pos-
terior band, coming from the posterior part of the coracoid process, is also strong.
between different
THE SHOULDER-JOINT
253
The intermediate part, of variable extent, is thin and membranous, containing
but few ligamentous fibres; it is often incomplete near the coracoid process,
leaving a small gap (fig. 286).
The superior surface of the ligament looks upward and a little forward, and is covered by
the deltoid muscle; the inferior looks downward and a little backward, and is separated from
the capsule of the shoulder-joint by a bursa and the tendons of the supraspinatus and sub-
scapularis muscles. At the coracoid process it overlies the coraco-humeral ligament. It is
barely one-third of an inch (8 mm.) above the capsule of the shoulder, and in the undissected
state there is scarcely a quarter of an inch (6 mm.) interval. The anterior band projects over
the centre of the head of the humerus, and is continued into a tough fascia under the deltoid;
the posterior band is continuous with the fascia over the supraspinatus muscle. It binds the
Fig. 287. — Posterior View of the Shoulder-joint, showing also the Acromio-ola-
vicuLAR Joint and the Special Ligaments or the Scapula.
Superior transverse ligament
Conoid ligament
Acromio-clavicular
ligament
Tendon of infra
spinatus and
teres minor
Inferior transverse
ligament
Capsule of shoulder
two processes firmly together, and so strengthens each; it holds the deltoid off the capsule of
the shoulder, and protects the joint from slight injuries directed downward and backward
against it.
The superior transverse (coracoid, or suprascapular) ligament (figs. 286,
287, and 288) is a small triangular band of fibrous tissue, the surfaces of which
look forward and backward; and its edges, which are thin and sharp, are turned
upward and downward. It continues the superior border of the scapula, bridging
over the scapular notch.
It is broader medially, where it springs from the upper border of the scapula on its dorsal
surface; and narrow laterally, where it is attached to the base of the coracoid process; some of
its fibres are inserted under the edge of the trapezoid ligament, and others pass upward with
the conoid to reach the clavicle. The transverse scapular {suprascapular) artery passes over it,
and the suprascapular nerve beneath it. Medially, some fibres of the omo-hyoid muscle arise
from it.
The inferior transverse (spino-glenoid) ligament (fig. 287) reaches from the lateral
border of the spine of the scapula to the margin of the glenoid cavity, and so forms a foramen
under which the transverse scapular (suprascapular) vessels and suprascapular nerve gain the
infraspinous fossa. It is usually a weak membranous structure with but few ligamentous
fibres.
3. THE SHOULDER-JOINT
Class. — Diarthrosis. Subdivision. — Enarthrodia.
The shoulder [articulatio humeri] is one of the most perfect and most movable
254
THE ARTICULATIONS
of joints, the large upper end of the humerus playing upon the shallow glenoid
cavity. Like the hip, it is a ball-and-socket joint. It is retained in position
much less by ligaments than by muscles, and, owing to the looseness of its cap-
sule, as well as to all the other conditions of its construction and position, it is
exceedingly liable to be displaced; on the other hand, it is sheltered from violence
by the two projecting processes — the acromion and coracoid.
The ligaments of the shoulder-joint are: — -
Articular capsule.
Gleno-humeral.
Coraco-humeral.
Glenoid:
The articular capsule (figs. 286, 287, and 288) is a loose sac, insufficient in
itself to maintain the bones in contact. It consists of fairly distinct but not
coarse fibres, closely woven together, and directed, some straight, others ob-
liquely, between the two bones, a few circular ones being interwoven amongst
them. At the scapula, it is fixed on the dorsal aspect to the prominent rough
Fig. 288. — Vertical Section through the Shoulder-joint to show the Gleno-humeral
Ligament.
(The joint is opened from behind.)
Supraspinatus muscle
Subacromial bursa
Tendon of biceps with
gleno-humeral liga-
Articular capsule
Superior trans-
verse ligament
Glenoid ligament (lip)
Articular capsule
surface around the margin of the glenoid cavity, reaching as far as the neck of
the bone. Superiorly, it is attached to the root of the coracoid process; an-
teriorly, to the ventral surface, at a variable distance from the articular margin,
often reaching half an inch (12 mm.) upon the neck of the bone, and thus allow-
ing the formation of a pouch; it may not, however, extend for more than a
quarter of an inch (6 mm.) beyond the articular margin; inferiorly, it blends with
the origin of the long head of the triceps. At the humerus, the superior half is
fixed to the anatomical neck, sending a prolongation downward between the two
tuberosities which attenuates as it descends, and covers the transverse hmneral
ligament. The lower half of the capsule descends upon the hmnerus further
from the articular margin, some of the deeper fibres being reflected upward so
as to be attached close to the articular edge, thus forming a kind of fibrous in-
vestment for the neck of the humerus. This ligament is more uniform in thickness
than that of the hip.
Gleno-humeral bands of the capsule (figs. 288 and 289) . — There are three
accessory bands, known as the superior, middle and inferior gleno-humeral bands,
which project toward the interior of the joint from the fore part of the capsule
and are consequently best seen when the joint is opened from behind.
The middle band reaches from the anterior margin of the glenoid cavity along the lower
border of the subscapularis tendon to the lower border of the lesser tuberosity, and the inferior
band from the inferior part of the glenoid cavity to the inferior part of the neck of the humerus.
THE SHOULDER-JOINT 255
The superior band, known also as the gleno -humeral ligament, runs from the edge of the glenoid
cavity at the root of the coracoid process, just medial to the origin of the long tendon of the
biceps, and, passing laterally and downward at an acute angle to the tendon, for which it forms
a slight groove or sulcus, is fixed to a depression, the fovea capitis humeri, above the lesser
tuberosity of the humerus. It is a thin, ribbon-hke band, of which the superior surface is
attached to the capsule, while the inferior is free and turned toward the joint. In the foetus
it is often, and in the adult occasionally, quite free from the capsule, and may be as thick as
the long tendon of the biceps (fig. 289).
The tendons of the supra- and infraspinatus, teres minor, and subscapularis muscles
strengthen and support the capsule, especially near their points of insertion, and can be with
difficulty dissected off from it. The long head of the triceps supports and strengthens the
capsule below. The capsule also receives an upward sUp from the pectoralis major. The
supraspinatus often sends a shp into the capsule from its upper edge (fig. 288).
The coraco-humeral ligament (fig. 290) is a strong broad band, which is
attached above to the lateral edge of the root and horizontal limb of the coracoid
process nearly as far as the tip. From this origin it is directed backward along
the line of the biceps tendon to blend with the capsule, and is inserted into
the greater tuberosity of the humerus.
Seen from the back, it looks like an uninterrupted continuation of the capsule, while from
the front it looks like a fan-shaped prolongation from it overlying the rest of the ligament. At
its origin there is sometimes a bursa between it and the capsule.
The glenoid ligament or lip [labrum glenoidale] (figs. 288 and 292) is a narrow
rim of dense fibro-cartilage, which surrounds the edge of the glenoid socket and
deepens it. It is about a quarter of an inch (6 mm.) wide above and below, but
less at its sides. Its peripheral edge is inseparably welded, near the bone, with
Fig. 289. — Fcbtal Shoulder-joint, showing the Glbno-humeeal Ligament, and also the
Short Head op the Biceps, being continuous wtith the Coraco-acromial Ligament.
Short tendon of biceps running
-Long tendon of biceps
nto'anterior ba'nd'of coraco- | " iiiBS//^''\i\\\\)/ H/'^ — Gleno-humeral ligament
acromial Ugament I , |,«!#^^ ILlUW^Iil^ Capsule of shoulder, turned back
the articular capsule. Its structure is almost entirely fibrous, with but few
cartilage cells intermixed. At the upper part of the fossa the biceps tendon is
prolonged into the glenoid ligament, the tendon usually dividing and sending
fibres right and left into the ligament, which may wind round nearly the whole
circumference of the socket. It may, however, send fibres into one side only,
usually into the lateral.
The articular cartilage covering the glenoid fossa is thicker at the circumfer-
ence than in the centre, thus tending to deepen the cavity. It is usually thickest
at the lower part of the fossa; over the head of the humerus the cartilage is thickest
at and below the centre.
The synovial membrane lines the glenoid ligament, and is then refiected over
the capsule as far as its attachment to the humerus, from which it ascends as
far as the edge of the articular cartilage. The tendon of the biceps receives a
long tubular sheath, which is continuous with the synovial membrane, both at
its attached extremity and at the bicipital groove, but is free in the rest of its
extent. The synovial cavity almost always communicates with the bursa under
the subscapularis, and sometimes with one under the infraspinatus muscle.
It also sends a pouch-like prolongation beneath the coracoid process when the fibrous
capsule is attached wide of the margin of the glenoid fossa. A few fringes are seen near the
edge of the glenoid cavity, and there is often one which runs down the medial edge of the
biceps tendon, extending slightly below it and making a slight groove for the tendon to lie in.
256
THE ARTICULATIONS
The transverse humeral Ugament (fig. 290) is so closely connected with the
capsule of the shoulder that, although it is a proper hgament of the humerus, it
may well be described here. It is a strong band of fibrous tissue, which extends
Fig. 290. — Lateral View of the Shoulder-joint, showing the Coraco-humbral and
Transverse Humeral Ligaments.
Capsule of the acromio-cla-
vicular joint
Coraco-acromial ligament
Coraco-humeral ligament
-Transverse humeral ligament
Tendon of biceps
Fig. 291. — The Upper Extremity or the Humerus, Anterior View, to Show the Rela-
tion OF THE Articular Capsule of the Shoulder-joint (in red) to the Epiphysial Line.
between the two tuberosities, roofing in the intertubercular (bicipital) groove. It
is covered by a thin expansion of the capsule. It is limited to the portion of the
bone above the line of the epiphysis.
THE SHOULDER-JOINT
257
Relations. — -The following muscles are in contact with the capsule of the shoulder-joint.
In front, the subscapularis; above, the supraspinatus; above and behind, the infraspinatus;
behind, the teres minor; below, the long head of the triceps and the teres major. In the interval
between the subscapularis and the supraspinatus the subacromial bursa is close to the capsule
and occasionally its cavity communicates with the cavity of the joint.
The axillary (circumflex) nerve and posterior circumfle.x artery pass beneath the capsule
in the intei'val between the long head of the triceps, the humerus, and the teres major. When
the arm is abducted, the long head of the triceps and the teres major are drawn into closer rela- ,
tion with the capsule and help to prevent dislocation of the humerus.
The axillary vessels, the great nerves of the axilla, the short head of the biceps, and the
coraco-brachialis are separated from the joint by the subscapularis, whilst the deltoid forms a
kind of cap, which extends from the front to the back over the more immediate relations.
The arterial supply is derived from the transverse scapular (suprascapular), anterior and
posterior circumflex, subscapular, circumflex scapular (dorsalis scapulae), and a branch from the
second portion of the axiUary artery.
The nerve-supply is derived from the suprascapular, by branches in both fossse; and from
the axillary (circumflex) and subscapular nerves.
The movements of the shoulder-joint consist of flexion, extension, adduction, abduction,
rotation and circumduction.
Flexion is the swinging forward, extension the swinging backward, of the humerus; abduc-
tion is the raising of the arm from, and adduction depression of the arm to, the side. In flexion
and extension the head of the humerus moves upon the centre of the glenoid fossa round an
Fig. 292. — Biceps Tendon, Bifukcating and Blending on each Side with the Glenoid
Ligament.
Tendon of biceps-
Tendon of biceps blended with glenoid,
ligament
oblique line corresponding to the axis of the head and neck of the humerus, flexion being more
free than extension, and in extreme flexion the scapula follows the head of the humerus, so as
to keep the articular surfaces in apposition. In extension the scapula moves much less, if
at all.
In abduction and adduction the scapula is fixed, and the humerus roUs up and down upon
the glenoid fossa; during abduction the head descends until it projects beyond the lower edge
of the glenoid cavity, and the greater tuberosity impinges against the arch of the acromion;
during adduction, the head of the humerus ascends in its socket, the arm at length reaches the
side, and the capsule is completely relaxed.
In circumduction, the humerus, by passing quickly through these movements, describes
a cone, whose apex is at the shoulder-joint, and the base at the distal extremity of the bone
or hmb.
Rotation takes place round a vertical axis drawn through the extremities of the humerus
from the centre of the head to the inner condyle; in rotation forward (that is, medialward) the
head of the bone rolls back in the socket as the great tuberosity and shaft are turned forward;
in rotation backward (that is, lateral ward) the head of the bone glides forward, and the tuber-
osity and shaft of the humerus are turned backward, i. e., lateralward.
Great freedom of movement is permitted at the shoulder, and this is increased by the
mobility of the scapula. Restraint is scarcely exercised at all upon the movements of the
shoulder by the ligaments, but chiefly by the muscles of the joint.
In abduction, the lower part of the capsule is somewhat, and in extreme abduction con-
siderably, tightened; and in rotation medialward and lateralward, the upper part of the capsule
is made tense, as is also, in the latter movement, the coraco-humeral ligament.
The movements of abduction and extension have a most decided and definite resistance
offered to them other than by muscles and ligaments, for the greater tuberosity of the humerus,
by striking against the acromion process and coraco-acromial ligament, stops short any further
advance of the bone in these directions, and thus abduction ceases altogether as soon as the arm
258 THE ARTICULATIONS
is raised to a right angle with the trunk, and extension shortly after the humerus passes the Hne
of the trunk.
Further elevation of the arm beyond the right angle, in the abducted or extended position,
is effected by the rotation of the scapula round its own axis by the action of the trapezius and
serratus anterior muscles upon the sterno-clavioular and acromio-clavicular joints respectively.
The acromion and coracoid process, together with the coraco-acromial ligament, form an
arch, which is separated by a bursa and the tendon of the supraspinatus from the capsule of
the shoulder. Beneath this arch the movements of the joint take place, and against it the head
and tuberosities are pressed when the weight of the trunk is supported by the arms; the greater
tuberosity and the upper part of the shaft impinge upon it when abduction and extension are
carried to their fullest extent.
No description of the shoulder-joint would be complete without a short notice of the peculiar
relation which the biceps tendon bears to the joint. It passes over the head of the humerus a
little to the medial side of its summit, and lies free within the capsule, surrounded only by a
tubular process of synovial membrane. It is fiat, with the surfaces looking upward and down-
ward, until it reaches the intertubercular (bicipital) groove, when it assumes a rounded form.
It strengthens the articulation along the same course as the coraco-humeral hgament, and tends
to prevent the head of the humerus from being pulled upward too'.forcibly against the inferior
surface of the acromion. It also serves the purpose of a ligament by steadying the head of the
humerus in various movements of the arm and forearm, and to this end is let into a groove at
the upper end of the bone, from which it cannot escape on account of the abutting tuberosities
and the strong transverse humeral ligament which binds it down. Further, it acts Uke the four
shoulder muscles which pass over the capsule, to keep the head of the humerus against the glen-
oid socket; and, moreover, it resists the tendency of the pecloralis major and latissimus dorsi
muscles, in certain actions when the arm is away from the side of the body, to pull the head of
the humerus below the lower edge of the cavity.
Muscles which act upon the shoulder-joint.- — Flexors or protractors. — Deltoid (anterior
fibres), peotoralis major (clavicular fibres), coraco-brachiahs, biceps (short head),Eubscapularis
(upper fibres).
Extensors or retractors. — ^Latissimus dorsi, deltoid (posterior fibres), teres major, teres minor,
infraspinatus (lower fibres).
[Abductors. — Deltoid, supraspinatus, biceps (longhead).
Adductors. — Pectorahs major, latissimus dorsi, subscapularis, infraspinatus, teres major,
teres minor, coraco-brachiahs, biceps (short head), triceps (lower head).
Medial rotators. — Pectoralis major, latissimus dorsi, teres major, subscapularis, deltoid
(anterior fibres).
Lateral rotators. — Deltoid (posterior fibres), infraspinatus, teres minor.
Circumductors. — The above groups acting consecutively.
4. THE ELBOW-JOINT
Class. — Diarthrosis. Subdivision. — Ginglymus.
The elbow [articulatio cubiti] is a complete hinge, and, unlike the knee,
depends for its security and strength upon the configuration of its bones rather
than on the number, strength, or arrangement of its ligaments. The bones
composing it are the lower end of the humerus above, and the upper ends of the
radius and ulna below; the articular surface of the humerus being received
partly within the semilunar notch (great sigmoid cavity) of the ulna, and partly
upon the cup-shaped area (fovea) of the radial head. The ligaments form one
large and capacious capsule [capsula articularis], which, by blending with the
annular ligament, and then passing on to be attached to the neck of the radius,
embraces the elbow and the superior radio-ulnar joints, uniting them into one.
Laterally, it is considerably strengthened by superadded fibres arising from the
epicondyles of the humerus and inseparably connected with the capsule. For
convenience of description it will be spoken of as consisting of four portions:- —
Anterior. Medial.
Posterior. Lateral.
The anterior portion (fig. 293) is attached to the front of the humerus above
the articular surface and coronoid fossa, in an inverted V-shaped manner, to two
very faintly marked ridges which start from the front of the medial and lateral
epicondyles, and meet a variable distance above the coronoid fossa. Below, it is
fixed, just beyond the articular margin, to the front of the coronoid process and it
is intimately blended with the front of the annular ligament, a few fibres passing
on to the neck of the radius.
It varies in strength and thickness, being sometimes so thin as barely to cover the syriovial
membrane; at others, thick and strong, and formed of coarse decussating fibres, the majority
of which descend from the medial side laterally to the radius.
THE ELBOW-JOINT
259
The posterior portion (fig. 294), thin and membranous, is attached superiorly
to the humerus, in much the same inverted V-shaped way as the anterior; ascend-
ing from the medial epicondyle, along the medial side of the olecranon fossa
nearly to the top; then, crossing the bottom of the fossa, it descends on the lateral
side, skirting the lateral margin of the trochlear surface, and turns laterally along
the posterior edge of the capitulum. Inferiorly, it is attached to a slight groove
Fig. 293. — Medial View of the Elbow-joint.
Anterior ligament
Ulnar collateral-
ligament
Annular ligament
— Tendon ot biceps
Oblique ligament
Upper edge of in-
terosseous mem-
brane
along the superior and lateral surfaces of the olecranon, and the rough surface of
the ulna just beyond the radial notch, and to the annular ligament, a few fibres
passing on to the neck of the radius.
It is composed of decussating fibres, most of which pass vertically or obliquely downward, a
few taking a transverse course at the summit of the olecranon fossa where the ligament is usually
thinnest.
Fig. 294. — Lateral View of the Elbow-joint.
Annular ligament
■Radial collateral ligment
■Posterior ligament
The medial portion, the ubiar collateral ligament (fig. 293), is thicker, stronger,
and denser than either the anterior or posterior portions. It is triangular in
form, its apex being attached to the anterior and under aspect of the medial
epicondyle, and to the condyloid edge of the groove between the trochlea and the
condyle. The fibres radiate downward from this attachment, the anterior
passing forward to be fixed to the rough overhanging medial edge of the coronoid
260
THE ARTICULATIONS
process ; the middle descend less obliquely to a ridge running between the coronoid
and olecranon processes, while the posterior pass obliquely backward to the
medial edge of the olecranon just beyond the articular margin.
Fig. 295. — Lower Extremity of the Humerus, to show the Relation of the Articu-
lar Capsule of the Elbow-joint (in red) to the Epiphysial Lines.
Fig. 296. — The Upper Extremity of the Ulna, to show the Relation of the Articu-
lar Capsule of the Elbow-joint (in red) to the Epiphysial Lines.
An oblique band (the oblique ligament of Sir Astley Cooper) connects the margin of the
olecranon process with the margin of the coronoid process. It lies superficial to the posterior
fibres of the ulnar collateral ligament. The anterior fibres are the thickest, strongest, and most
pronounced.
RADIO-ULNAB JOINTS 26L
The lateral portion, the radial collateral ligament (fig. 294), is attached above
to the lower part of the lateral epicondyle, and from this the fibres radiate to
their attachment into the lateral side of the annular ligament, a few fibres being
prolonged to reach the neck of the radius. The anterior fibres reach further
forward than the posterior do behind. It is strong and well-marked, but less
so than the medial portion.
The synovial membrane lines the whole of the capsule, and extends into the
superior radio-ulnar joint, lining the annular ligament.
Outside the synovial membrane, but inside the capsule, are often seen some pads of fatty
tissue; one is situated on the medial side at the base of the olecranon, another is seen on the
lateral side projecting into the cavity between the radius and ulna; this latter, with a fold of
synovial membrane opposite the front of the lateral hp of the trochlea, suggests the division of
the joint into two parts — one medially for the ulna, and another laterally for the radius.
There are also pads of fatty tissue at the bottom of the olecranon and coronoid fossas, and at
the tip of the olecranon process.
The arterial supply is derived from each of the vessels forming the free anastomosis around
the elbow, and there is also a special branch to the front and lateral side of the joint, from the
brachial artery, and the arterial branch to the brachialis also feeds the front of the joint.
The nerve-supply comes chiefly from the musculo-cutaneous; the ulnar, median, and radial
(musculo-spiral) also give fUaments to the joint.
Relations. — In front of the joint, and in immediate relation with the capsule, are the
brachiahs, the superficial and deep branches of the radial (musculo-spiral) nerve, the radial re-
current artery, and the brachio-radiahs. The brachial artery, the median nerve, and the pro-
nator teres are separated from the capsule by the brachiahs. Directly behind the capsule
are the triceps, the anconeus, and the posterior interosseous recurrent artery. On the medial
side are the ulnar nerve, the superior ulnar collateral (posterior ulnar recurrent) artery, and the
upper parts of the flexor carpi ulnaris and flexor digitorum subhmis. On the lateral side lie
the extensor carpi radiahs longus and the upper part of the common tendon of origin of the
superficial extensors of the wrist and fingers.
The movements permitted at the elbow are those of a true hinge joint, viz., flexion and
extension. These movements are oblique, so that the forearm is inclined medially in flexion,
and laterally in extension ; they are limited by the contact respectively of the coronoid and ole-
cranon processes of the ulna with their corresponding fossae on the humerus, and their extent is
determined by the relative proportion between the length of the processes and depth of the
fossae which receive them, rather than by the tension of the ligaments, or the bulk of the soft
parts over them. The anterior and posterior portions of the capsule, together with the corres-
ponding portions of the collateral ligament, are not put on the stretch during flexion and exten-
sion; but, although they may assist in checking the velocity, and thus prevent undue force of
impact, they do not control or determine the extent of these movements. The limit of exten-
sion is reached when the ulna is nearly in a straight line with the humerus; and the limit of
flexion when the ulna describes an angle of from 30° to 40° with the humerus.
The obliquity of these movements is due to the lateral inclination of the upper and back
part of the trochlear surface, and the greater prominence of the medial lip of the trochlea below;
thus the plane of motion is directed from behind forward and medially, and carries the hand
toward the middle third of the clavicle. The obliquity of the joint, the twist of the shaft of
the humerus, and the backward direction of its head, all tend to bring the hand toward the mid-
line of the body, under the immediate observation of the eye, whether for defence, employment,
or nourishment. This is in striking contrast to the lower limb, where the direction of the foot
diverges from the median axis of the trunk, thus preventing awkwardness in locomotion. In
flexion and e.xtension, the cup-like depression of the radial head glides upon the capitulum, and
the medial margin of the radial head travels in the groove between the capitulum and the
trochlea. This allows the radius to rotate upon the humerus while following the ulna in all
its movements. In full extension and supination, the head of the radius is barely in contact
with the inferior surface of the capitulum, and projects so much backward that its posterior
margin can be felt as a prominence at the back of the elbow. In full flexion the anterior edge
of the radial head is received into, and checked against, the depression above the capitulum ;
while in mid-flexion the cup-like depression is fairly received upon the capitulum, and in this
position, the radius being more completely steadied by the humerus than in any other, pro-
nation and supination take place most perfectly.
Muscles which act upon the elbow-joint. — Flexors. — Brachialis, biceps, brachio-radialis,
pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum sublimis, flexor carpi
ulnaris.
Extensors. — Triceps, anconeus, and the muscles which spring from the lateral epico ndyle
5. THE UNION OF THE RADIUS WITH THE ULNA
The radius is firmly united to the ulna by two joints, and an intermediate
fibrous union, viz. : — •
(a) The superior radio-ulnar — whereat the head of the radius rotates within
the radial notch and annular ligament.
(b) The union of the shafts — the mid radio-ulnar union.
(c) The inferior radio-ulnar — whereat the lower end of the radius rolls round
the head of the ulna.
262
THE ARTICULATIONS
. (a) The Superior Radio-ulnar Joint
Class. — Diarthrosis. Subdivision. — Trochoides.
The bones which enter into this joint (which is often included with the elbow-
joint) are, the ulna by its radial notch and the radius by the smooth vertical border
or rim on its head. There is but one ligament special to the joint, viz.: —
Annular.
The annular ligament consists of bands of strong fibres, somewhat thicker
than the capsule of the elbow-joint, which encircle the head of the radius, re-
taining it against the side of the ulna. The bulk of these fibres forms about three-
fourths of a circle, and they are attached to the anterior and posterior margins
of the radial notch; some few are continued round below the radial notch, and
form a complete ligamentous circle.
The ligament is inseparably connected along its upper edge and lateral (i. e., its non-
articular) surface with the anterior, posterior, and lateral portions of the capsule of the elbow,
a few of the fibres of these portions, especially of the lateral, descending to be attached to the
necli of the radius. The lower part of the articulation is covered in anteriorly, posteriorly, and
laterally by a thin independent membranous layer, which passes from the lower edge of the
annular ligament to the neck of the radius, strengthened on the lateral side by those fibres
passing down from the capsule. They are loose enough to allow the bone to rotate upon its
Fig. 297. — Annular Ligament.
(The head of the radius removed to show the membranous connection of this ligament
with the radius.)
Capsule of elbow-joint
CusMon of fatty tissue
Membranous tissue joining the an-
nular ligament to the neck of the
radius
Radius
Annular ligament
own axis (fig. 297). Medially and below the cavity is closed in by a loose membrane, the liga-
mentum quadratum, which passes from the lower border of the radial notch to the neck of the
radius.
The synovial membrane is the same as that of the elbow-joint, and, after
lining the annular ligament, passes on to the neck of the radius, and thence up to
the lower margin of the articular cartilage.
The arterial and nerve -supply are the same as those to the lateral part of the elbow-joint.
Relations. — Behind lies the anconeus and in front the lateral border of the brachiaUs.
(b) The Mid Radio-ulnar Union
Class. — Synarthrosis. Subdivision. — Syndesmosis.
There are two interosseous ligaments which pass betweeen the shafts of the
bones and unite them firmly together, viz. : —
Oblique cord. Interosseous membrane.
The oblique cord [chorda obliqua] (figs. 293 and 298) is a fairly strong, narrow
band, which passes from the lower end of the rough lateral border of the coronoid
RADIO-ULNAR JOINTS
263
process, downward and laterally to be attached to the posterior edge of the
lower end of the tuberosity of the radius and the vertical ridge running from it
to the medial border of the bone.
Some of its fibres blend with the fibres of insertion of the biceps tendon; behind, it is in
close contact with the supinator; below, a thin membrane passes off from it to the upper edge
of the interosseous membrane; the posterior interosseous vessels pass in the space between it
and the interosseous membrane; occasionally a slip is continued into the annular ligament of the
superior radio-ulnar articulation (see fig. 298).
The interosseous membrane (fig. 293) is attached to the ulna at the lowest
part of the ridge in front of the depression for the supinator, and along the whole
length of the interosseous border as far as the inferior radio-ulnar articulation,
approaching the front of the bone in the lower part of its attachment. To the
radius it is attached along the interosseous border, from an inch (2.5 cm.) below
the tuberosity to the ulnar notch for the lower end of the ulna.
It is strongest and broadest in the centre, where the fibres are dense and closely packed ;
it is also well marked beneath the pronator quadratus, and thickens considerably at the lower end,
forming a strong band of union between the two bones. Its fibres pass chiefly downward
and medially, from the radius to the ulna, though some take the opposite direction; at the lower
end some are transverse. On the posterior surface are one or two bands, which pass downward
and laterally from the ulna to the radius, and frequently there is a strong bundle as large as the
Fig. 298. — Upper Portions of Left Ulna and Radius, to show an Occasional Slip prom
THE Oblique Cohd to the Lower Part op the Annular Ligament. This condition is
present in the spider monkey (Ateles), which has no external thumb but only rudimentary
bones of one.
(From a dissection by Mr. W. Pearson, Royal CoUege of Surgeons, England.)
Annular ligament
Occasional slip from oblique cord
to annular ligament
Oblique cord
oblique cord; this, which may be called the inferior oblique ligament (fig. 303), stretches from
the ulna, an inch and a half above its lower extremity, downward and laterally to the ridge
above and behind the ulnar notch of the radius.
At its attachment to the bones, the interosseous membrane blends with the periosteum.
Its upper border is connected with the oblique cord by a thin membrane, which is pierced by
the posterior interosseous vessels; and the lower border, which stretches across between the two
bones just above the inferior radio-ulnar articulation, assists in completing the capsule of that
joint. Its anterior surface is iii relation with the flexor digitorum profundus and flexor pollids
longus in the upper three-quarters, the lower fourth being in relation with the pronator quadratus.
The anterior interosseous vessels and nerve descend along the middle of the membrane, the
artery being bound down to it. About an inch from the lower end it is pierced by the anterior
interosseous artery. The posterior surface is in relation with the supinator, abductor pollids
longus (extensor ossis metacarpi pollids), extensor pollids longus and brevis, and the extensor
indids proprius; at its lower part, also with the posterior branch of the anterior interosseous
artery, and the deep branch of the radial nerve (posterior interosseous).
(c) The Inferior Radio-xjlnar Joint
Class. — Diarthrosis. Subdivision. — Trochoides.
This is, in one respect, the reverse of the superior; for the radius, instead of
presenting a circular head to rotate upon the facet on the ulna, presents a concave
facet which rolls round the ulna. The articulation may be said to consist of two
264
THE ARTICULATIONS
parts at right angles to each other; one between the radius and ulna, and the
other between the ulna and the articular disc (triangular fibro-cartilage) .
Anterior radio-ulnar.
The ligaments are:
Articular disc.
Posterior radio-ulnar.
The articular disc (triangular fibro-cartilage) (figs. 303 and 304) assists the
radius in forming an arch under which is received the first row of carpal bones.
Its base is attached to the margin of the radius, separating the ulnar notch from
the articular surface for the carpus, while its apex is fixed to the fossa at the base
of the styloid process of the ulna. It gradually and uniformly diminishes in
width from base to apex, becoming rounded where it is fixed to the ulna; it is
joined by fibres of the ulnar collateral ligament of the wrist.
The articular disc is about three-eighths of an inch (1 cm.) wide, and the same from base to
apex; thicker at the circumference than in the centre; smooth and concave above to adapt
Fig. 299. — ^Lower Extremities op the Radius and Ulna to Show the Relation op
THE Articulab Capsule OP THE Wrist Joint (In red) to the Epiphysial Lines. Note the
upward extension of the membrana saccLformis.
itself to the ulna, and smooth and slightly concave below to fit over the triquetral bone. Its
anterior and posterior borders are united to the anterior and posterior radio-ulnar and radio-
carpal ligaments. It is the most important structure in the inferior radio-carpal articulation,
as it is a very firm bond of union between the lower ends of the bones, and serves to hmit their
movements upon one another more than any other structure in either the upper or lower radio-
ulnar joints. Its structure is fibrous at the circumference, while in the centre there is a prepon-
derance of cells. It differs from all other fibro-cartilages in entering into two distinct articula-
tions; and separates entirely the synovial membrane of the radio-ulnar joint from that of the
wrist.
The lower end of the interosseous membrane extends between the ulna and
radius immediately above their points of contact. Transverse fibres between the
two bones form a sort of arch above the concave articular facet of the radius, and,
joining the anterior and posterior radio-ulnar ligaments, complete the articular
capsule of the inferior radio-ulnar joint. The ligaments represent merely
thickenings of the capsule.
The anterior radio-ulnar ligament (fig. 300) is attached by one end to the anterior edge
of the ulnar notch of the radius, and by the other to the rough bone above the articular surface
of the ulna as far mediaDy as the notch, as well as into the anterior margin of the trianguar
cartOage from base to apex.
The posterior radio-ulnar ligament (fig. 301) is similarly attached to the posterior margin
of the ulnar notch at one end, and at the other to the rough bone above the articular surface of
the extremity of the ulna as far medially as the groove for the extensor carpi ulnaris, with the
sheath of which it is connected, as well as into the whole length of the posterior margin of the
articular disc. Both the radio-ulnar ligaments consist of thin, almost scattered, fibres.
THE WRIST-JOINT 265
The synovial membrane, sometimes called the membrana sacciformis, is
large and loose in proportion to the size of the joint. It is not onty interposed
between the radial and ulnar articular surfaces, but lines the terminal articular
surface of the ulna and the upper surface of the articular disc.
The arterial supply is derived from the volar interosseous artery and branches of the
volar carpal rate.
The nerve-supply comes from the volar interosseous of the median, and the deep branch
of the radial (posterior interosseous).
Relations. — Behind hes the tendon of the extensor digiti quinti proprius and in front the
flexor digitorum profundus.
The movements of the radius. — The upper end of the radius rotates upon an axis drawn
through its own head and neck within the coUar formed b}' the radial notch and the annular
ligament, while the lower end, retained in position by the articular disc, rolls round the
head of the ulna. This rotation is called pronation, when the radius from a position nearly
parallel to the ulna turns medialward so as to lie obliquely across it; and supination, when the
radius turns back again, so as to uncross and lie nearly parallel with the ulna. In these move-
ments the radius carries with it the hand, which rotates on an axis passing along the ulnar side
of the hand; thus, the hand when pronated hes with its dorsum upward, as in playing the
piano, whUe when supinated, the palm lies upward — the attitude of a beggar asking alms.
Ward thus expresses the relations of the two extremities of the radius in pronation and supina-
tion: 'The head of the radius is so disposed in relation to the sigmoid cavitj' (ulnar notch) at
the lower end that the axis of the former if prolonged falls upon the centre of the circle of which
the latter is a segment;' the axis thus passes through the lower end of the ulna at a point at
which the articular disc is attached, and if prolonged further, passes through the ring finger.
Thus the radius describes, in rotating, a blunt-pointed cone whose apex is the centre of the radial
head, and whose base is at the wrist; partial rotation of the bone being unaccompanied by anj'
hinge-like or antero-posterior motion of its head, and pronation and supination occurring with-
out disturbance to the parallelism of the bones at the superior radio-ulnar joint. Associated
with this rotation in the ordinary way, there is some rotation of the humero-ulnar shaft, which
causes lateral shifting of the hand from side to side; thus, with pronation there is some abduc-
tion, and with supination some adduction combined, so that the hand can keep on the same
superficies in both pronation and supination. The power of supination in man is much greater
than pronation, owing to the immense power and leverage obtained by the cm-ve of the radius,
and bj' the attachment of the biceps tendon to the back of the tuberosity. For this reason all
our screw-driving and boring tools are made to be used bj- supination movements.
In the undissected state, the amount of rotation it is possible to obtain is about 135°, so
that neither the palm nor the fore part of the lower end of the radius can be turned completely
in opposite directions; j-et in the hving subject this amount can be greatly increased by rotation
of the humero-ulnar shaft at the shoulder-joint.
Pronation is checked in the living subject by (a) the posterior inferior radio-ulnar ligament,
which is strengthened by the connection of the sheath of the extensor tendons with it; (b) the
lowermost fibres of the interosseous membrane; (c) the back part of the ulnar collateral and
adjacent fibres of the posterior hgament of the wrist, and (d) the meeting of the soft parts on
the front of the forearm.
Supination is checked mainly (a) by the medial ulnar collateral ligaments of the wrist, but
partly also by (b) the oblique cord; (c) the anterior inferior radio-ulnar hgament, and (d) the
lowest fibres of the interosseous membrane.
The interosseous membrane serves, from the direction of its fibres downward and medially
from the radius to the ulna, to transmit the weight of the body from the ulna to the radius in
the extended position of the elbow, as in pushing forward with the arms extended, or in support-
ing one's own weight on the hands, the ulna being in intimate contact with the humerus, but
not at all with the carpus; whOe the area of contact of the radius with the humerus is small,
and that of the radius with the carpus large. Hence the weight transmitted bj' the ulna is
communicated to the radius by the tightening of the interosseous membrane. Conversely, in
falls upon the hand with the arm extended, the interosseous membrane acts as a sUng to break
the violence of the shock, and prevents the whole force of the impact from expending itself
directly upon the capitulum.
Muscles which act upon the radio-ulnar joints.— Pronators. — Pronator teres, pronator
quadratus, flexor carpi radiahs, palmaris longus.
Supinators. — Biceps, supinator, extensor poUicis longus.
The brachio-radialis is chiefly a flexor of the elbow-joint, but it takes part in the initiation
of the movement of supination when the hand is fully pronated and of pronation when the hand
is fully supinated.
6. THE RADIO-CARP.\L OR WRIST-JOINT
Class. — Diarthrosis. Subdivision. — Condylarthrosis.
The wrist-joint is formed by the imion of the radius and articular disc above,
articulating -^vith the navicular, lunate, and triquetral bones below; the ulna
being excluded by the intervention of the articular disc. The radius and disc
together present a smooth surface, slightly concave both from before backward,
and from side to side, whilst the three bones of the carpus present a smooth,
266
THE ARTICULATIONS
convex surface, made uniformly even by the interosseous ligaments which bind
them together.
The capsule of the wrist-joint has been usually described as four separate liga-
ments, and it will be convenient for the sake of a complete description to follow
this method; but it must be understood that these four portions are continuous
around the joint, extending from styloid process to styloid process on both its
aspects.
The four portions are : —
Volar radio-carpal.
Dorsal radio-carpal.
Ulnar collateral.
Radial collateral.
The volar (or anterior) radio-carpal (fig. 300) is a thick strong ligament, at-
tached superiorly to the radius immediately above the anterior margin of the
terminal articular facet, to the curved ridge at the root of the styloid process of
the radius, and to the anterior margin of the articular disc, blending with some
fibres of the capsule of the inferior radio-ulnar joint. It passes downward and
in a medial direction to be attached to both rows of carpal bones, especially the
second, and to the volar intercarpal ligament.
Fig. 300.- — Anterior View op Wrist.
Ulnar radio-ulnar
ligament
Ulnar collateral liga-
ment of wrist
Flexor carpi ulnaris
Volar radio-carpal
ligament
Tendon of flexor carpi
radialis
Capsular ligament of first
carpo-metacarpal joint
The strongest and most oblique fibres arise from the root of the styloid process of the radius,
and pass obhquely over the navicular, with which only a few fibres are connected, to be inserted
into the lunate, capitate, and triquetral bones. Another set, less oblique, passes from the margin
of the facet for the lUnate to be attached to the adjacent parts of the capitate, hamate, and tri-
quetral bones. Between the two sets of fibres, small vessels pass into the joint.
The dorsal (or posterior) radio-carpal ligament (fig. 301) is attached above
to the dorsal edge of the lower end of the radius, the back of the styloid process,
and the posterior margin of the fibro-cartilage. It passes downward and in a
medial direction to be connected with the first row of the carpal bones, chiefly
with the lunate and triquetral, and the dorsal intercarpal ligament. This
ligament is thin and membranous.
It is strengthened by (i) strong fibres passing from the back of the articular disc where
they are blended with the posterior inferior radio-ulnar ligament, and, from the edge of the radius
just behind the ulnar notch, to the triquetral bone; (ii) from the ridge and groove for the extensor
pollicis longus to the back of the lunate and triquetral bones; and (iii) from the groove for the
radial e.xtensors to the back of the navicular and lunate. It is in relation with, and strengthened
by, the extensor tendons which pass over it.
The ulnar collateral ligament (fig. 301) is fan-shaped, with its apex above, at
the styloid process of the ulna, to which it is attached on all sides, blending with
THE WRIST-JOINT
267
the apex of the articular disc. Some of the fibres pass forward and laterally to
the base of the pisiform bone and to the medial part of the upper border of the
transverse carpal ligament, where it is attached to the pisiform bone; they form
a thick, rounded fasciculus on the front of the wrist. Other fibres descend
vertically to the medial side of the triquetral bone, and others again laterally to
the dorsal surface of the triquetral. The tendon of the extensor carpi ulnaris is
posterior to, and passes over, part of the fibres of the ligament.
The radial collateral ligament (fig. 300) consists of fibres which radiate from
the fore part and tip of the styloid process of the radius. Some pass downward
and medially, in front, to the navicular and adjacent edge of the capitate; some
downward, a little forward and medially, to the tubercle of the navicular and
ridge of the greater multangular; and others downward and laterally to the
rough dorsal surface of the navicular.
The fibres of this ligament are not so long and strong, nor do they radiate so much as those
of the ulnar collateral ligament. It is in relation with the radial artery, and the abductor pollicis
longus {extensor ossis metacarpi pollicis) and extensor pollicis brevis, the artery separating the
tendons from the ligament.
Fig. 301. — Posterior View op Whist.
Dorsal radio-carpal ligament
Posterior radio-ulnar ligament
Ulnar collateral ligament of
wrist
The synovial membrane is extensive, but does not usually communicate with
the synovial membrane of the inferior radio-ulnar joint, being shut out by the
articular disc. It is also excluded, in almost every instance, from that of
the carpal joints by the interosseous ligaments between the first row of carpal
bones. The styloid process of the radius is cartilage-covered medially, and
forms part of the articular cavity, while that of the ulna does not.
The arterial supply is derived from the anterior and posterior carpal rami, the dorsal
division of the volar interosseous, and from twigs direct from the radial and ulnar arteries.
The nerve -supply is derived from the ulnar and median in front, and the deep branch of
the radial (posterior interosseous) behind.
Relations. — In front of the radio-carpal joint are the tendons of the flexor muscles of the
wrist and fingers, the synovial sheaths associated with thern, the radial and ulnar arteries, and
the median and ulnar nerves.
Behind the joint are the majority of the tendons of the extensor muscles of the wrist and
fingers, with their synovial sheaths, the terminal part of the anterior and posterior interosseous
arteries, and the deep branch of the radial nerve (posterior interosseous). On the radial side
lie the tendons of the abductor pollicis longus {extensor ossis metacarpi pollicis) and the extensor
pollicis brevis. On the ulnar side the joint is subcutaneous and it is crossed by the dorsal
cutaneous branch of the ulnar nerve.
Movements. — The wrist is a condyloid joint, the carpus forming the condyle. It allows
of movements upon a transverse axis, i. e., flexion and extension; and around an antero-pos-
terior axis, i. e., abduction and adduction; together with a combination of these in quick succes-
268
THE ARTICULATIONS
sion — oiroumduction. Lacking only rotation on a vertical axis, it thus possesses most of the
movements of a ball-and-socket joint, without the weakness and liability to dislocation which
are peculiar to these joints. This deficiency of rotation is compensated for by the movements
of the radius at the radio-ulnar joints, viz., supination and pronation. Its strength depends
chiefly upon the number of tendons which pass over it, and the close connection which exists
between the fibrous tissue of their sheaths and the capsule of the wrist; also upon the proximity
of the medio-carpal and carpo-metacarpal joints, which permits shocks and jars to be shared
and distributed between them; another source of strength is the absence of any long bone on the
distal side of the joint. In flexion and extension the carpus rolls backward and forward, respec-
tively, beneath the arch formed by the radius and articular disc; flexion being limited by the
dorsal ligament and dorsal portions of the collateral; extension by the volar, and volar portions
of the collateral ligaments. In adduction and abduction the carpal bones ghde from the ulnar
to the radial side and from the radial to the ulnar side, respectively. Abduction is more limited
than adduction, and is checked by the ulnar collateral hgament and by contact of the styloid
process of the radius with the greater multangular; adduction is checked by the radial collateral
ligament alone. One reason for adduction being more free than abduction is that the ulna does
Fig. 302. — Front of Wrist with Transverse Carpal Ligament.
ulnar collateral ligament of
wrist with slip to annu-
lar ligament
Pisiform-
Transverse carpal ligament'
Volar radio-carpal ligament
not reach so low down as the radius, and the yielding articular disc allows of greater movement
upward of the ulnar end of the carpus. In circumduction the hand moves so as to describe a
cone, the apex of which is at the wrist. These movements are made more easy and extensive
by the slight gliding of the carpal bones upon one another, and the comparatively free motion
at the medio-carpal joint. The oblique direction of the fibres of the collateral hgaments pre-
vents any rotation at the radio-carpal joint, while it permits considerable freedom of abduction
and adduction.
Muscles which act upon the radio-carpal joint. — Flexors. — The flexors of the carpus and
the long flexors of the fingers and the thumb, and the pahnaris longus. Extensors. — The exten-
sors of the carpus and fingers. Abductors. — Extensor carpi radialis longus, the abductor pol-
licis longus (extensor ossis metacarpi poUicis. Adductors. — Flexor carpi ulnaris, extensor carpi
ulnaris.
7. THE CARPAL JOINTS
The joints of the carpus may be subdivided into — •
(a) The joints of the first row.
(6) The joints of the second row.
(c) The medio-carpal, or junction of the two rows with each other.
THE CARPAL JOINTS
269
(a) The Joints of the First Row of Carpal Bones
Class. — Diarthrosis. Subdivision. — Arthrodia.
The bones of the first row, the pisiform excepted, are united by two sets of
ligaments and two interosseous fibro-cartilages.
Dorsal.
Volar.
Interosseous.
The two dorsal intercarpal ligaments extend transversely between the bones, and connect
the navicular with the lunate, and the lunate with the triquetral. Their posterior siu-faces are
in contact with the posterior ligament of the -nTist.
The two volar intercarpal ligaments extend nearly transversely between the bones connect-
ing the navicular with the lunate, and the lunate with the triquetral. They are Wronger than
the dorsal ligaments, and are placed beneath the anterior ligament of the wrist.
The two interosseous intercarpal ligaments (fig. 304) are interposed between the navicular
and lunate, and the lunate and triquetral bones, reaching from the dorsal to the volar surfaces.
Fig. 303. — Posterior View op the Wrist, with Capsule cut to show Articular Surfaces,
'll^^ — ^J Lower end of interosseous ligament
Inferior oblique ligament
Articular disc
Band of posterior ligament of wrist
i^ujH .,,,,, n^ .. V >,i|i left to keep bones in situ
Transverse dorsal ligament v*w».«™/ ^
/ Tendon flexor carpi ulnaris
and being connected with the dorsal and volar ligaments. They are narrow fibro-cartilages
which extend between small portions only of the osseous surfaces. They help to form the
convex carpal surface of the radio-carpal joint, and are somewhat wedge-shaped, their bases
being toward the wrist, and their thin edges between the adjacent articular surfaces of the bones.
The synovial membrane is a prolongation from that of the medio-oarpal joint.
The arterial and nerve-supplies are the same as for the medio-carpal joint.
The Joint of the Pisiform Bone with the Triquetral
This is an arthrodial joint which has a loose fibrous capsule attached to both
the pisiform and triquetral bones just beyond the margins of their articular
surfaces.
It is lined by a separate synovial membrane. Two strong rounded or flattened bands pass
downward from the pisiform, one to the process of the hamate [Ug. pisohamatum], and the
other [Ug. pisometacarpeum] to the bases of the third to fifth metacarpals; these are regarded as
prolongations of the tendon of the flexor carpi ulnaris, and the pisiform bone may be looked
upon in the light of a sesamoid bone developed in that tendon.
(b) The Joints of the Second Row of Carpal Bones
Class. — Diarthrosis. Subdivision. — Arthrodia.
The four bones of this row are united by three dorsal, three palmar, and three
interosseous ligaments.
270 THE ARTICULATIONS
The three dorsal ligaments (fig. 303) extend transversely and connect the greater with the
lesser multangular, the lesser multangular with the capitate, and the capitate with the hamate.
The three volar ligaments are stronger than the dorsal, and are deeply placed beneath the
mass of flexor tendons; they extend transversely between the bones in a similar manner to the
dorsal ligaments.
Three interosseous ligaments connect the bones of the lower row of the carpus together.
Two are connected with the capitate, one uniting it with the hamate (fig. 304) and the other
binding it to the lesser multangular. The third Mgament joins the greater and lesser multangular.
The synovial membrane is a prolongation of that lining the medio-carpal joint.
The arterial and nerve -supplies are the same as for the medio-carpal joint.
(c) The Medio-carpal Joint, or the Union op the Two Rows of the Carpus
WITH EACH other
(I) Class. — Diarthrosis. Subdivision. — Arthrodia.
(II) Class.- — Diarthrosis. Subdivision. — Condylarthrosis.
The inferior surfaces of the bones of the first row are adapted to the superior
articular surfaces of the bones of the second row. The line of this articulation is
concavo-convex from side to side, and is sometimes described as having the course
of a Roman S placed horizontally, co , a resemblance by no means strained, (i)
The lateral part of the first row consists of the navicular alone; it is convex, and
bears the greater and lesser multangulars. (ii) Then follows a transversely
elongated socket formed by the medial part of the navicular, the lunate, and
triquetral, into which are received — (a) the head of the capitate, which articulates
with the navicular and lunate; (6) the upper and lateral angle of the hamate, which
articulates with the navicular; and (c) the upper convex portion of the medial
surface of the hamate, which articulates with the lateral and concave portion of
the inferior surface of the triquetral, (iii) The medial part of the inferior sur-
face of the triquetral bone is convex, and turned a little backward to fit into the
lower portion of the medial surface of the hamate, which is a little concave and
turned forward to receive it. The central part, which forms a socket for the capi-
tate and hamate, has somewhat the character of a condyloid joint, the capitate
and hamate being the condyle, to fit into the cavity formed by the navicular,
lunate, and triquetral; the other portions are typically arthrodial. The liga-
ments are: — (1) radiate or anterior medio-carpal; (2) posterior medio-carpal;
(3) transverse dorsal.
The radiate, anterior or volar medio-carpal is a ligament of considerable strength, consisting
mostly of fibres which radiate from the capitate to the navicular, lunate, and triquetral; some
few fibres connect the greater and lesser multangular with the navicular, and others pass between
the hamate and triquetral. It is covered over and thickened by fibrous tissue derived from the
sheaths of the flexor tendons and the fibres of origin of the small muscles of the thumb and httle
finger.
The posterior or dorsal medio-carpal ligament, consists of fibres passing obliquely from the
bones of the first row to those of the second. It is stronger on the ulnar side than on the radial,
but is not so strong as the volar ligament.
The transverse dorsal ligament (fig. 303) is an additional band, well marked and often of
considerable strength, which passes across the head of the capitate from the navicular to the
triquetral bone; besides binding down the head of the capitate, it serves to fix the upper and lat-
eral angle of the hamate in the socket formed by the first row.
The dorsal ligaments, like the volar, are strengthened by a quantity of fibrous tissue belong-
ing to the sheaths of the extensor tendons, and by an extension of some of the fibres of the capsule
of the wrist. There are no proper collateral medio-carpal hgaments; they are but prolongations
of the collateral ligaments of the wrist.
The synovial membrane (fig. 304) of the carpus is common to all the joints of the carpus,
and extends to the bases of the four medial metacarpal bones. Thus, besides hning the inter- or
medio-carpal joint, it sends two processes upward between the three bones of the first row, and
thi'ee downward between the contiguous surfaces of the lesser and greater multangular, the lesser
multangular and capitate, and capitate and hamate. From these latter, prolongations extend
to the four medial carpo-metacarpal joints and the three intermetacarpal joints.
The arterial supply is derived from — (a) the volar and dorsal carpal rami of the radial
and ulnar arteries; (b) the carpal branch of the volar interosseous; (c) the recurrent branches
from the deep palmar arch. The terminal twigs of the volar and dorsal interosseous arteries
supply the joint on its dorsal aspect.
The nerve -supply comes from the ulnar on the ulnar side, the median on the radial side, and
the deep branch of the radial (posterior interosseous) behind.
Relations. — The relations of this joint are practically the same as those of the radio-carpal
joint, except that the flexor carpi ulnaris does not cross the front, the ulnar artery is separated
THE CARPAL JOINTS
271
from it by the transverse carpal ligament, and the radial artery passes across its lateral border
instead of in front.
The movements of the carpal articulations between bones of the same row are very hmited
and consist only of slight gliding upon one another; but, slight as they are, they give elasticity
to the carpus to break the jars and shocks which result from blows or falls upon the hand.
The movements of one row of bones upon the other at the medio-carpal joint are more
extensive, especially in the direction of flexion and extension, so that the hand enjoys a greater
range of these movements than is permitted at the wrist-joint alone. At the wrist, extension is
more free than flexion; but this is balanced by the greater freedom of flexion than of extension
at the medio-carpal joint, and by flexion at the carpo-metacarpal joint, so that on the whole- the
range of flexion of the hand is greater than that of extension.
Fig. 304. — Synovial Membranes of Wri&t Hand, and Fingers.
Synovial sac of the wrist-joint
Synovial sac of the carpus
Synovial sac, occasionally
separate, for the fourth
and fifth metacarpal bones
.Synovial sac of the carpo-meta-
carpal joint of the thumb
Collateral ligaments of the metacarpo-
pha angeal and interphalangeal
A slight amount of side to side motion accompanied by a limited degree of rotation also
takes place; this rotation consists in the head of the capitate and the superior and lateral angle
of the hamate bone rotating in the socket formed by the three bones of the upper row, and in^a
gliding forward and backward of the greater and lesser multangular upon the navicular.
In addition to the ligaments, the undulating outUne and the variety of shapes of the apposed
facets render this joint very secure.
Bearing in mind the mobility of this medio-carpal joint and of the carpo-metacarpal, we see
at once the reason for the radial and ulnar flexors and extensors of the carpus being prolonged
down to their insertion into the base of the metacarpus, for they produce the combined effect
of motion at each of the three transverse articulations: — (1) at the wrist; (2) at the medio-carpal;
(3) at the carpo-metacarpal joints.
Muscles which act upon the mid-carpal joint. — The muscles which act upon this joint are
the same as those which act upon the radio-carpal joint, except the flexor carpi ulnaris, which is
inserted into the pisiform bone.
272 THE ARTICULATIONS
8. THE CARPO-METACARPAL JOINTS
These may be divided into two sets, namely: —
(a) The carpo-metacarpal joints of the four medial fingers.
(6) The carpo-metacarpal joints of the thumb.
The inferior surfaces of the bones of the second row of the carpus present a
composite surface for the four medial metacarpal bones ; the greater multangular
presents in addition a distinct and separate saddle-shaped surface for the base of
the metacarpal bone of the thumb.
(a) The Four Medial Carpo-metacarpal Joints
Class. — Diarthrosis. Subdivision. — Arthrodia.
These joints exist between the greater and lesser multangular, capitate, and
hamate bones above, and the four medial metacarpal bones below. The liga-
ments which unite them are, dorsal, volar, and interosseous.
The dorsal ligaments (fig. 303). — Three dorsal ligaments pass to the second metacarpal
bone: one from each of the carpal bones with which it articulates, viz., the greater and lesser
multangular, and capitate. Two dorsal bands pass from the capitate to the third metacarpal
bone. Two dorsal bands pass to the fourth bone: viz., one from the hamate, and another from
the capitate; the latter is sometimes wanting. The fifth bone has only one band passing to it
from the hamate.
The volar ligaments (fig. 300). — One strong band passes from the second metacarpal bone
to the greater multangular medial to the ridge for the transverse carpal ligament; it is covered
by the sheath of the flexor carpi radialis.
Three bands pass from the third metacarpal: one laterally to the greater multangular, a
middle one upward to the capitate, and a third medially over the fourth to reach the fifth meta-
carpal and the hamate bones.
One ligament connects the fourth bone to the hamate.
One ligament connects the fifth bone to the hamate, the fibres extending medially, and con-
necting the dorsal and volar ligaments. The ligament to the fifth bone is strengthened in front
by the prolonged fibres of the flexor carpi ulnaris and the strong medial sUp of the ligament of
the third metacarpal bone; and posteriorly, by the tendon of the extensor carpi ulnaris.
The interosseous ligament (fig. 304) is Hmited to one part of the articulation, and consists
of short fibres connecting the contiguous angles of the hamate and capitate with the third and
fourth metacarpal bones toward their volar aspect. There is, however, a thick strong ligament
connecting the edge of the greater multangular with the lateral border of the base of the second
metacarpal bone; it helps to separate the carpo-metacarpal joint of the thumb from the common
carpo-metacarpal joint, and to close in the radial side of the latter joint.
The synovial membrane is a continuation of the medio-carpal joint; occasionally there is
a separate membrane between the hamate and fourth and fifth metacarpal bones (fig. 304) ;
while that between the fourth and capitate is lined by the synovial sac of the common joint.
The arteries to the four medial carpo-metacarpal joints are as follows: —
(1) For the index finger: twigs are supphed by the trunk of the radial on the dorsal and volar
aspects, and by the dorsal and volar metacarpal branches.
(2) For the middle finger: the first dorsal metacarpal by the branch which passes upward
to join the dorsal carpal arch, and a branch from the deep volar arch which joins the volar carpal
arch.
(3) For the ring finger: the deep volar arch and recurrent twigs from the second dorsal
metacarpal in the same manner as for the middle finger.
(4) For the little finger: the ulnar and its deep branch; also twigs from the second dorsal
metacarpal.
The nerves are supplied to these joints by the deep volar branch of the ulnar, the deep branch
of the radial (posterior interosseous), and the median.
Relations. — In front of the four medial carpo-metacarpal joints are the flexors of the
fingers with their synovial sheath. The flexor carpi radialis crossing in front of the lateral part
of the joint and the fibres of the oblique adductor poUicis which spring from the capitate and
lesser multangular are also anterior relations. Behind the joints are the extensors of the wrist
and fingers with their synovial sheaths and the dorsal metacarpal arteries. At the lateral border
of the joints between the index and lesser multangular hes the radial artery.
The movements permitted at these joints, though slight, serve to increase those of the
medio-carpal and wrist-joints. The joint between the fifth metacarpal and the hamate bones
approaches somewhat in shape and mobihty the first carpo-metacarpal joint; it has a greater
range of flexion and extension, but its side to side movement is nearly as limited as that of the
three other metacarpal bones; the process of the hamate bone hrnits its flexion. Motion toward
the ulnar side is checked by the strong palmar band which unites the base of the fifth meta-
carpal to the base of the third, and the strong transverse ligament at the head of the bones.
The mobility of the second, third, and fourth metacarpal bones is very limited, and consists
almost entirely of a slight gliding upon the carpal bones, i. e., flexion and extension; that of the
third and fourth bones is extremely slight, as there is no long flexor attached to either; but,
INTERMETACARPAL JOINTS 273
owing to the close connection of the bases of the metacarpal bones, the radial and ulnar flexors
and extensors of the carpus act on all by their pull on the particular bone into which they are
inserted.
Abduction, or movement toward the radial side, is prevented by the impaction of the second
bone against the greater multangular; a little adduction is permitted, and is favoured by the
slope given to the hamate and fifth metacarpal bones.
There is also a slight gliding between the fourth and fifth bones, when the concavity they
present toward the palm is deepened to form the 'cup of Diogenes.'
Muscles which act upon the four medial carpo-metacarpal joints are the flexors and ex-
tensors of the wrist and fingers, except the flexor carpi ulnaris.
(6) The Carpo-metacarpal Joint of the Thumb
Class. — Diarthrosis. Subdivision. — Saddle-shaped Arthrodia.
The bones entering into this joint are the base of the first metacarpal and the
greater multangular. The first metacarpal bone diverges from the other four,
contrasting very strongly with the position of the great toe. It is due to this
divergence that the thumb is able to be opposed to each and all the fingers.
The ligament which unites the bones is the
Articular capsule.
The articular capsule (figs. 300 and 301) consists of fibres which pass from
the margin of the articular facet on the greater multangular, to the margin of
the articular facet at the base of the first metacarpal bone.
The fibres are stronger on the dorsal than on the palmar aspect. They are not tense
enough to hold the bones in close contact, so that while they restrict they do not prevent motion
in any direction. The medial fibres are stronger than the lateral.
The synovial membrane is lax, and distinct from the other synovial membranes of the
carpus.
The arteries of the carpo-metacarpal joint of the thumb are derived from the trunk of the
radial, the first volar metacarpal, and the dorsahs pollicis.
The nerves are supplied by the branches of the median to the thumb.
Relations. — Behind are the long and short extensor tendons of the thumb, and behind
and laterally the tendon of the abductor pollicis longus (extensor ossis metacarpi pollicis).
The tendon of the flexor pollicis longus is in front and fibres of the flexor pollicis brevis and op-
ponens pollicis muscles are also anterior relations. To the medial side is the radial artery as
it passes forward into the palm of the hand.
The movements of this joint are regulated by the shape of the articular surfaces, rather
than by the ligaments, and consist of flexion, extension, abduction, adduction, and circum-
duction, but not rotation. In flexion and extension the metacarpal bone slides to and fro upon
the multangular; in abduction and adduction it slides from side to side or, more correctly, re-
volves upon the antero-posterior axis of the joint. The power of opposing the thumb to any
of the fingers is due to the forward and medial obliquity of its flexion movement, which is by
far its most extensive motion. Abduction is very free, while adduction is limited on account
of the proximity of the second metacarpal bone. The movement of the greater multangular
upon the rest of the carpus somewhat increases the range of all the movements of the thumb.
Muscles which act upon the carpo-metacarpal joint of the thumb. — Flexors. — Flexor
pollicis brevis, flexor pollicis longus, opponens pollicis. Extensors. — Extensores pollicis brevis
and longus and abductor pollicis longus. Ahduclors. — Abductores pollicis longus and brevis.
Adductors. — The transverse and oblique adductor pollicis, opponens, fii'st dorsal interosseous.
Muscles "producing opposition. — Opponens, flexor brevis, oblique adductor.
9. THE INTERMETACARPAL ARTICULATIONS
Class. — Diarthrosis. ■ Subdivision. — Arthrodia.
The metacarpal of the thumb is not connected with any other metacarpal
bone. The second, third, fourth, and fifth metacarpal bones are in actual
contact at their bases, and are held firmly together by the following ligaments
(in addition to the articular capsule) : —
Dorsal. Volar.
Interosseous hgaments.
The dorsal ligaments (fig. 302) are layers of variable thickness of strong, short fibres, which
pass transversely from bone to bone, filUng up the m-egularities on the dorsal surfaces.
The volar ligaments are transverse layers of hgamentous tissue passing from bone to bone;
they cannot be well differentiated from the other ligaments and fibrous tissue covering the bones.
The interosseous ligaments (fig. 304) pass between the apposed surfaces of the bones, and
are attached to the distal sides of the articular facets, so as to close in the synovial cavities on
274
THE ARTICULATIONS
this aspect; where there are two articular facets, the fibres extend upward between them nearly
as far as their carpal facets. That between the fourth and fifth is the weakest.
The synovial membrane is prolonged downward from the common carpal sac.
The arteries to the intermetacarpal joints are twigs from the volar and dorsal metacarpal
arteries; the twigs pass upward between the interosseous muscles.
The nerves are derived from the ulnar and the deep branch of radial (posterior interosseous).
The Union of the Heads of the Metacarpal Bones
The distal extremities of these bones are connected together on their palmar aspects by
what is called the transverse ligament [lig. capitulorum]. This consists of three short bands
of fibrous tissue, which unite the second and third, third and fourth, and the fourth and fifth
bones. They are rather more than 6 mm. (J in.) deep, and rather less in width, and limit the
distance to which the metacarpal bones can be separated. They are continuous above with the
fascia covering the interosseous muscles; below, they are connected with the subcutaneous
tissue of the web of the hand. They are on a level with the front surface of the bones, and are
blended on either side with the edges of the glenoid hgament in front, with the lateral Ligaments
Fig. 305. — Anterior and Posterior Views of Ligaments of the Fingers.
Transverse ligament
between the heads
■ of the metacarpal
! bones
_ Accessory volar ligament
-Collateral ligament
Areolar tissue .
capsule
Collateral ligament -
noid ligament
-Collateral ligament
-Flexor tendon
Areolar tissue
capsule
Collateral ligament — ^
Extensor tendon
-Flexor tendon
of the metacarpo-phalangeal joint, and also with the sheaths of the tendons. In front, a lum-
brical muscle passes with the digital arteries and nerves; while behind, the interossei muscles
pass to their insertions.
10. THE METACARPO-PHALANGEAL JOINTS
(a) The Metacarpo-phalangeal Joints of the Four Medial Fingers
Class.- — Diarthrosis. Subdivision. — Condylarihrosis.
In these joints the cup-shaped extremity of the base of the first phalanx fits
on to the rounded head of the metacarpal bone, and is united by the following
ligaments (in addition to the articular capsule) : —
Collateral.
Volar accessory.
The volar accessory (or glenoid) ligament (fig. 305) is a fibro-cartilaginous plate which
seems more intended to increase the depth of the phalangeal articular facet in front, than to
unite the two bones. It is much more firmly attached to the margin of the phalanx than to the
metacarpal bone, being only loosely connected with the palmar surface of the latter by some
loose areolar tissue which covers in the synovial membrane, here prolonged some little distance
upon the surface of the bone. At the sides, it is connected with the collateral ligaments and the
METACARPO-PHALANGEAL JOINTS 275
transverse metacarpal ligament. It corresponds to the sesamoid bones of the thumb; a sesa-
moid bone sometimes exists at the medial border of the joint of the little finger.
The collateral ligaments (304 and 305) are strong and firmly connect the bones with one
another; each is attached above to the corresponding tubercle, and to a depression in front
of the tubercle, of the metacarpal bone. From this point the fibres spread widely as they de-
scend on either side of the base of the phalanx; the anterior fibres are connected with the glenoid
ligament; the posterior blend with the tendinous expansion at the back of the joint.
The joint is covered in posteriorly by the expansion of the extensor tendon, and some loose
areolar tissue passing from its under surface to the bones (fig. 305).
The synovial membrane is loose and capacious, and invests the inner surface of the liga-
ments which connect the bones.
The arteries come from the digital or volar metacarpal vessels of the deep arch.
The nerves are derived from the digital branches, or from twigs of the branches of the ulnar
to the interosseous muscles.
Relations. — I. The metacarpo-phalangeal joints of the middle three digits. In front,
the tendons of the flexor profundus and flexor subhmis digitorum. On the radial side, a lum-
brical, an interosseous muscle, and digital nerves and vessels; on the ulnar side, an interosseous
muscle and digital vessels and nerves. Behind, the common extensor tendon and in the case
of the index digit the tendon of the extensor indicis.
II. The metacarpo-phalangeal joint of the little finger. In front, the flexor quinti digiti
brevis and the tendons of the flexor profundus and subhmis digitorum muscle which go to
this digit. Behind, the extensor digiti quinti to a slip of the extensor digitorum communis
sometimes. On the radial side, a lumbrical, the third palmar interosseous muscle, digital ves-
sels and nerves. On the ulnar side, digital vessels and nerves.
The movements permitted at these joints are flexion, extension, abduction, adduction, and
circumduction. Flexion is the most free of all and may be continued until the phak nx is at
a right angle with the metacarpal bone. It is on this account that the articular surface of the
head of the bone is prolonged so much further on the palmar aspect, and that the synovial
membrane is here so loose and ample. Extension is the most limited of the movements, and can
only be carried to a little beyond the straight line. Abduction and adduction are fairlj' free,
but not so free as flexion. Flexion is associated with adduction, and extension with abduction.
This may be proved by opening the hand, when the fingers involuntarily separate as they
extend, while in closing the fist they come together again. The free abduction, adduction, and
circumduction which are permitted at these joints are due to the fact that the long axes of the
articular facets are at right angles to one another.
Muscles acting on the middle three digits. — Flexors. — Flexor digitorum profundus, flexor
digitorum sublimis. Extensors. — Extensor digitorum communis and on the index digit the
extensor indicis. Abductors. — Dorsal interossei. Adductors. — Volar interossei.
Muscles acting on the metacarpo-phalangeal joint of the little finger. — Flexors. — Flexor
quinti digiti brevis, flexor digitorum sublimis, flexor digitorum profundus. Extensors. — Exten-
sor digitorum communis, extensor quinti digiti. Abductor. — Abductor quinti digiti. Adductor.
— Third volar interosseous.
(6) The Metacarpo-phalangeal Joint of the Thumb
Class. — Diarthrosis. Subdivision. — Condylarthrosis.
The head of the metacarpal bone of the thumb differs considerably from the
corresponding ends of the metacarpal bones of the fingers. It is less convex, wider
from side to side, the palmar edge of the articular surface is raised and irregular,
and here on either side of the median line are the two facets for the sesamoid
bones. The base of the first phalanx of the thumb, too, is more like the base of
the second phalanx of one of the other fingers. The ligaments are : —
Collateral. Dorsal.
Articular capsule.
The collateral ligaments are short, strong bands of fibres, which radiate from depressions
on either side of the head of the metacarpal bone to the base of the first phalan.x and sesamoid
bones. As they descend they pass a little forward, so that the gi'eater number are inserted in"
front of the centre of motion.
The dorsal ligament consists of scattered fibres which pass across the joint from one col-
lateral Ugament to the other, completing the articular capsule and protecting the synovial sac.
The sesamoid bones are two in number, situated on either side of the middle fine, and con-
nected together by strong transverse fibres which form the floor of the groove for the long
flexor tendon; they are connected with the base of the phalanx and head of the metacarpal bone
by strong fibres. Anteriorly they give attachment to the short muscles of the thumb, and pos-
teriorly are smooth for the purpose of gliding over the facets. The collateral ligaments are partly
inserted into their sides.
The arteries and nerves come from the digital branches of the thumb.
Relations. — Of the metacarpo-phalangeal joint of the thumb: In front and externally
abductor poUicis brevis and superficial head of flexor poUicis brevis. In front and medially
oblique and transverse adductors and deep head of flexor poUicis brevis. Directly in front
flexor pollicis longus and terminal branches of first volar metacarpal artery. Behind, extensor
pollicis brevis and longus tendons. On either side, the dorsal digital vessels and the digital
nerves.
276 THE ARTICULATIONS
The movements are chiefly flexion and extension, very little side to side movement being
permitted, and that only when the joint is slightly bent. Thus this joint more nearly approaches
the simple hinge character than the corresponding articulations of the fingers. The thumb
gets its freedom of motion at the carpo-metacarpal joint; the fingers get theirs at the meta-
carpo-phalangeal, but they are not endowed with so much freedom as the thumb enjoys.
Muscles which act upon the metacarpo-phalangeal joint of the thumb. — Flexors. — Flexor
poUicis brevis, flexor pollicis longus. Extensors. — Extensor poUicis brevis, extensor pollicis
longus.
11. THE INTERPHALANGEAL ARTICULATIONS
Class. — Diarthrosis. Subdivision. — Ginglymus .
The ligaments which unite the phalanges of the thumb and of the fingers are
(in addition to the articular capsule) : —
Accessory volar. Collateral.
The accessory volar (or glenoid) ligament (fig. 305), sometimes called the sesamoid body,
is very firmly connected with the base of the distal bone, and loosely, by means of fibro-areolar
tissue, with the head of the proximal one. It blends with the collateral ligaments at the sides,
and over it pass the flexor tendons. Occasionally a sesamoid bone is developed in the cartilage
of the interphalangeal joint of the thumb.
The collateral ligaments (figs. 304 and 305) are strong bands which are attached to the rough
depressions on the sides of the upper phalanx, and to the projecting margins of the lower phalanx
of each joint. They are tense in every position, and entirely prevent any side to side motion;
they are connected posteriorly with the expansion of the extensor tendon.
Dorsally (fig. 305) the joint is covered in by the deep surface of the extensor tendon, and a
little fibro-areolar tissue extends from the tendon, and thickens the posterior portion of the
synovial sac, completing the articular capsule.
The synovial membrane is loose and ample, and extends upward a little way along the shaft
of the pro.ximal bone.
The arteries and nerves come from their respective digital branches.
The relations of the interphalangeal joints are the flexor and extensor tendons and the
digital vessels and nerves.
The movements are limited to flexion and extension. Flexion is more free, and can be
continued till one bone is at a right angle to the other, and is most free at the junction of the
first and second bones; the second phalanx can be flexed on the first through 110° to 115° when
the latter is not flexed. The greater freedom of flexion is due to the greater extent of the articu-
lar surface in front of the heads of the proximal bones, and to the direction of the flbres of the
collateral hgaments, which pass a little forward to their insertion into the distal bone.
The muscles which act upon the interphalangeal joints are the extensors and flexors of
the digits.
THE ARTICULATIONS OF THE LOWER LIMB
The articulations of the lower limb are the following : —
1. The hip-joint.
2. The knee-joint.
3. The tibio-fibular union.
4. The ankle-joint.
5. The tarsal joints.
6. The tarso -metatarsal joints.
7. The intermetatarsal joints.
8. The metatarso-phalangeal joints.
9. The interphalangeal joints.
1. THE HIP-JOINT
Class. — Diarthrosis. Subdivision. — Enarthrodia.
The hip is the most typical example of a ball-and-socket joint in the body, the
round liead of the femur being received into the cup-shaped cavity of the acetab-
ulum. Both articular surfaces are coated with cartilage, that covering the head
of the femur being thicker above where it has to bear the weight of the body, and
thinning out to a mere edge below; the pit for the ligamentum teres is the only
part uncoated, but the cartilage is somewhat heaped up around its margin.
Covering the acetabulum, the cartilage is horseshoe-shaped, and thicker above
than below, being deficient over the depression at the bottom of the acetabulum,
THE HIP-JOINT
277
where a mass of fatty tissue — the so-called synovial or Haversian gland — is
lodged.
The ligaments of the joint are: —
Articular capsule. Ligamentum teres.
Transverse. . Glenoid lip.
The articular capsule is one of the strongest ligaments in the body. It is
large and somewhat loose, so that in every position of the body some portion of it
is relaxed. At the pelvis it is attached, superiorly, to the base of the anterior
inferior iliac spine; curving backward, it becomes blended with the deep surface
of the reflected tendon of the rectus Jemoris; posteriorly, it is attached a few
millimetres from the acetabular rim ; and below, to the upper edge of the groove
between the acetabulum and tuberosity of the ischium. Thus it reaches the
Fig. 306. — Anterior View of the Articitlar Capsule op the Hip-joint.
■Tendon of rectus pulled up
Tendino-trochanteric band passing between rectus
and vastus lateralis
Placed on the weak spot of capsule, which is some-
times perforated to allow the bursa under psoas to
communicate with joint
Ilio-f emoral ligament
■Pubo-capsular ligament
transverse ligament, being firmly blended with its outer surface, and frequently
sends fibres beyond the notch to blend with the obturator membrane. Anteriorly
it is attached to the pubis near the obturator notch, to the ilio-pectineal eminence
and thence backward to the base of the inferior iliac spine.
A thin strong stratum is given off from its superficial aspect behind; this extends beneath
the gluteus minimus and small rotators, to be attached above to the dorsum of the ihum higher
than the reflected tendon of the rectus, and posteriorly to the ilium and ischium nearly as far
as the sciatic notch. As this expansion passes over the long tendon of the rectus, the tendon
may be described as being in part contained within the substance of the capsule.
At the femur, the capsule is fixed to the anterior portion of the upper border
of the great trochanter and to the cervical tubercle. Thence it runs down,
the intertrochanteric line as far as the medial border of the femur, where it is on a level
with the lower part of the lesser trochanter. It then runs upward and backward
along an oblique line about 1.6 cm. (f in.) in front of the lesser trochanter, and con-
tinues its ascent along the back of the neck nearly parallel to the intertrochanteric
crest, and from 12 to 16 mm. (| to f in.) above it; finally, it passes along the medial
side of the trochanteric fossa to reach the anterior superior angle of the great
trochanter.
278
THE ARTICULATIONS
On laying open the capsule, some of the deeper fibres are seen reflected upward along the
neck of the femur, to be attached much nearer the head: these are the retinacula. One corre-
sponds to the upper, and another to the lower, part of the intertrochanteric line; a third is seen
at the upper and back part of the neck. They form flat bands,which lie on the femoral neck.
Superadded to the capsule, and considerably strengthening it, are three auxil-
iary bands, whose fibres are intimately blended with, and in fact form part of,
the capsule, viz., the ilio-femoral, ischio-capsular, and pubo-capsular ligaments.
The ilio-femoral ligament (fig. 306) is the longest, widest, and strongest of the bands.
It is of triangular shape, with the apex attached above to a curved line on the iUum immediately
below and behind the anterior inferior spine, and its base below to the anterior edge of the
greater trochanter and to the spiral line as far as the medial border of the shaft. The highest or
most lateral fibres are coarse, almost straight, and shorter than the rest; the most medial fibres
are also thick and strong, but obhque. This varying obliquity of the fibres, and their accumula-
tion at the borders, explain why this band has been described as the Y-shaped ligament; but it
Fig. 307. — Upper Extremity of the Femur (Anterior View), to snow the Relation
OP THE Articular Capsule op the Hip-joint (in red) to the Epiphysial Lines.
should be noted that the Y is inverted. About the centre of its base, near the femoral attach-
ment, is an aperture transmitting an articular twig from the ascending branch of the external
circumflex artery.
The ischio-capsular ligament (fig. 308) is formed of very strong fibres attached all along
the upper border of the groove for the external obturator, and to the ischial margin of the ace-
tabulum above the groove. The highest of these incline a little upward as they pass laterally
to be fixed to the greater trochanter in front of the insertion of the piriformis tendon, while the
other fibres curve more and more upward as they pass laterally to their insertion at the inner
side of the trochanteric fossa, blending with the insertion of the external rotator tendons. When
the joint is in flexion, these fibres pass in nearly straight lines to their femoral attachment, and
spread out uniformly over the head of the femur; but in extension they wind over the back of
the femur in a zonular manner [zona orbicularis], embracing the posterior aspect of the neck
of the femur.
The pubo-capsular (pectineo-femoral) band (fig. 306) is a distinct but narrow set of fibres
which are individually less marked than the fibres of the other two bands; they are fixed above
to the obturator crest and to the anterior border of the iUo-pectineal eminence, reaching as far
down as the pubic end of the acetabular notch. Below, they reach the neck of the femur, and
are fixed above and behind the lowermost fibres of the iho-femoral band, with which they blend.
THE HIP'JOINT
279
In thickness and strength the capsule varies greatly; thus, if two lines be
drawn, one from the anterior inferior spine to the medial border of the femur near
the lesser trochanter, and the other from the anterior part of the groove for the
Fig. 308. — Posterior View of the Articular Capsule of the Hip-joint.
The reflected tendon of the
rectus and the triangular ilio-
trochanteric ' band
Ischio-capsular ligament
This is placed on the weak portion
of the capsule
Fig. 309. — Section through the Hip-joint, showing the Glenoid Lip, Ligamentum
Teres, and Retinacula.
Ligamentum teres.
The upper line is
placed on the fem-
oral, the lower on
the ischial, attach-
ment
Articular capsule
Reflected fibres of
capsule (retin-
acula)
Reflected fibres
of capsule
external obturator to the trochanteric fossa, all the ligament between these lines
on the lateral and upper aspects of the joint is very thick and strong, while that
below and to the medial side, except at the narrow pubo-capsular ligament, is
280
THE ARTICULATIONS
thin and weak, so that the head of the bone can be seen through it. The capsule
is thickest in the course of the iho-femoral ligament, toward the lateral part of
which it measures over 6 mm. (J in.). Between the ilio-femoral and ischio-cap-
sular ligaments the capsule is very strong, and with it here, near the acetabulum,
is incorporated the reflected tendon of the rectus, and here also a triangular band
of fibres runs downward and forward to be attached by a narrow insertion to
the ridge on the front border of the greater trochanter near the gluteus minimus
(the ilio-trochanteric band) (fig. 308).
The capsule is strengthened also at this point by a strong band from the under surface of
the gluteus minimus, and by the tendino-trochanteric band which passes down from the reflected
tendon of the rectus to the vastus lateralis (externus) (fig. 306). This is closely blended with
the capsule near the lateral edge of the ilio-femoral Ugament.
The thinnest part of the capsule is between the pubo-capsular and ilio-femoral
ligaments; this is sometimes perforated, allowing the bursa under the psoas to
communicate with the joint. The capsule is also very thin at its attachment to
the back of the femoral neck, and again opposite the acetabular notch.
Pig. 310.-
-Hip-joint after Dividing the Aeticulab Capsule and Disarticulating the
Femur.
Articular capsule, cut
Glenoid lip
Articular capsule
Ligamentum teres
Articular capsule
The ligamentum teres (figs. 309 and 310) is an interarticular flat band which
extends from the acetabular fossa to the head of the femur, and is usually about
3.7 cm. (1| in.) long. It has two bony attachments, one on either side of the
acetabular notch immediately below the articular cartilage, while intermediate
fibres spring from the lower surface of the transverse ligament. The ischial
portion is the stronger, and has several of its fibres arising outside the cavity,
below and in connection with the origin of the transverse ligament, where it is
also continuous with the capsule and periosteum of the ischium. At the femur
it is fixed to the front part of the depression on the head, and to the cartilage round
the margin of the depression.
It is covered by a prolongation of synovial membrane, which also covers the cushion of fat
in the recess of the acetabulum; the portion of the membrane reflected over the fatty tissue does
not cling closely to the round hgament, but forms a triangular fold, the apex of which is at the
femur.
The transverse ligament (fig. 311) passes across the acetabular notch and
converts it into a foramen; it supports part of the glenoid fibro-cartilage, and is
connected with the ligamentum teres and the capsule. It is composed of decus-
sating fibres, which arise from the margin of the acetabulum on either side of
the notch, those coming from the pubis being more superficial, and passing to form
THE HIP-JOINT
281
the deep part of the ligament at the ischium, while those superficial at the ischium
are deep at the pubis. It thus completes the rim of the acetabulum.
The glenoid lip (cotyloid fibro-cartilage) (figs. 309 and 310) is a yellowish-
white structure, which deepens the acetabulum by surmounting its margin. It
Fig. 311.-
-PoETiONS OP Ischium and Pubis, showing the Acetabular Notch and the
LiGAMENTUM TeBES ATTACHED OUTSIDE THE ACETABULUM.
Transverse ligament
^>^^^
Transverse ligament
Ligamentum teres at-
tached to ischium out-
side the acetabulum
varies in strength and thickness, but is stronger at its iliac and ischial portions
than elsewhere. Its base is broad and fixed to the bony rim as well as to the
articular cartilage of the acetabulum on the inner, and the periosteum on the
outer, side of it, and blends inseparably with the transverse ligament which
supports it over the acetabular notch.
Fig. 312. — The Uppek Extremity op the Femur (Posterior View), to show the Rela-
tion OP the Articular Capsule op the Hip-joint (in red) to the Epiphysial Lines.
Its free margin is thin; on section it is somewhat lunated, having its outer surface convex and
its articular face concave and very smooth in adaptation to the head of the bone, which it
tightly embraces a little beyond its greatest circumference. It somewhat contracts the aper-
ture of the acetabulum, and retains the head of the femur within its grasp after division of the
muscles and capsular hgament. It is covered on both aspects by synovial membrane.
282
THE ARTICULATIONS
The synovial membrane lines the capsule and both surfaces of the glenoid
lip, and passes over the border of the acetabulum to reach and cover the fatty
cushion it contains. The part covering the fatty cushion is unusually thick, and
is attached round the edges of the rough bony surface on which the cushion rests.
The membrane is loosely reflected off this on to the ligamentum teres, along
which it is prolonged to the head of the femur; thus the fibres of the round liga-
ment are shut out from the joint cavity. From the capsule the synovial mem-
brane is also reflected below on to the neck of the femur, whence it passes over
the retinacula to the margin of the articular cartilage. A fold of synovial mem-
brane on the under aspect of the neck often conveys to the head of the femur a
branch of an artery — generally a branch of the medial circumflex.
The arterial supply comes from — (a) the transverse branches of the medial and lateral
circumflex arteries; (6) the lateral branch of the obturator sends a branch through the acetabular
notch beneath the transverse ligament, which ramifies in the fat at the bottom of the ace-
tabulum, and travels down the round ligament to the head of the femur; (c) the inferior branch of
the deep division of the superior gluteal; and (d) the inferior gluteal (sciatic) arteries. The
branch from the obturator to the ligamentum teres is sometimes very large when the branch
from the medial circumflex does not also supply the hgament.
The superior and inferior gluteal send several branches through the innominate attachment
Fig. 313. — ^Ligamentum Teres, lax in Flexion.
of the articular capsule: these anastomose freely beneath the capsule around the outer aspect
of the acetabulum, and supply some branches to enter the bone, and others which enter the
substance of the glenoid lip. There is quite an arterial crescent upon the posterior and postero-
superior portions of the acetabulum; but no vessels are to be seen on the inner aspect of the
glenoid lip.
The nerve-supply comes from — (a) femoral (anterior crural), (6) anterior division of the
obtm-ator, (c) the accessory obturator, and (d) the sacral plexus, by a twig from the nerve to
the quadratus femoris, or from the upper part of the great sciatic, or from the lower part of the
sacral plexus.
Relations. — In front and in contact with the capsule are the psoas bursa, the tendinous
part of the psoas magnus, and the Uiacus. StiU more anteriorly and not in contact are the
femoral artery, the femoral (anterior crural) nerve, the rectus femoris, the sartorius, and the
tensor fasciae latse.
Above and in close relation with the capsule are the piriformis, the obturator internus and
the gemelli, and the reflected head of the rectus femoris, whilst more superficially lie the gluteus
minimus and medius.
Behind and in close relation with the capsule are the obturator externus, the gemeUi and
obturator internus, and the piriformis. More superficially he the quadratus femoris, the sciatic
nerves, and the gluteus maximus.
Below the obturator externus, the pectineus, and the medial circumflex artery are in close
relation with the capsule.
The movements. — The hip-joint, like the shoulder, is a ball-and-socket joint, but with a
much more complete socket and a corresponding limitation of movement. Each variety of
movement is permitted, viz., flexion, extension, abduction, adduction, circumduction, and rota-
tion; and any two or more of these movements not being antagonistic can be combined, i. e.,
flexion or extension associated with abduction or adduction can be combined with rotation in
or out.
THE HIP-JOINT
283
It results from the obliquity of tne neck of the femur that the movements of the head in
the acetabulum are always more or less of a rotatory character. This is more especially the case
during flexion and extension, and two results follow from it. First, the bearing surfaces of the
femur and acetabulum preserve their apposition to each other, so that the amount of articular
surface of the head in the acetabulum does not sensibly diminish pari passu with the transit of
the joint from the extended to the flexed position, as would necessarily be the case if the move-
ment of the femoral head, like that of the thigh itself, was simply angular, instead of rotatory
and angular. Secondly, as rotation of the head can continue until the ligaments are tight with-
out being checked by contact of the neck of the thigh bone with the rim of the acetabulum,
flexion of the thigh so far as the joint is concerned is practically unlimited. Flexion is the most
important, most frequent, and most extensive movement, and in the dissected limb, before the
ligaments are disturbed, can be carried to 160°, and is then checked by the lower fibres of the
ischio-capsular ligament. In the living subject simple flexion can continue until checked by the
contact of the soft parts at the groin, if the knee be bent; if the knee be straight, flexion of the
hip is checked in most persons by the hamstring muscles at nearly a right angle. This is very
evident on trying to touch the ground with the fingers without bending the knees, the chief strain
being felt at the popliteal space. This is due to the shortness of the] hamstrings. Extension
is limited by the ilio-femoral ligament.
Fig. 314. — ^Ligamentum Teres, vekt lax in Complete Extension.
Abduction and lateral rotation can be performed freely in every position of flexion and
extension — abduction being limited by the pubo-capsular hgament; lateral rotation by the
ilio-femoral Ugament, especially its medial portion, during extension; but by the lateral portion,
as well as by the ligamentum teres, during flexion.
Adduction is very limited in the extended thigh on account of the contact with the opposite
limb. In the slightly flexed position adduction is more free than in extension, and is then limited
by the lateral fibres of the ilio-femoral band and the superior portion of the capsule. In flexion
the range is still greater, and limited by the ischio-capsular hgament, the hgamentum teres being
also rendered nearly tight. Medial rotation in the extended position is limited by the lower
fibres of the ilio-femoral ligament; and in flexion by the ischio-capsular ligament and the portion
of the capsule between it and the ilio-femoral band.
The ilio-femoral band also prevents the tendency of the trunk to roU backward on the thigh
bones in the erect posture, and so does away with the necessity for muscular power for this pur-
pose; it is put on stretch in the stand-at-ease position.
The ligamentum teres is of little use in resisting violence or in imparting strength to the
joint. It assists in checking lateral rotation, and adduction during flexion. A ligament can
only be of use when it is tight, and it was found by trephining the bottom of the acetabulum,
removing the fat, and threading a piece of whipcord round the ligament, that the ligament was
slack in simple flexion, and very loose in complete extension, but that its most slack condition
was in abduction. It is tightest in flexion combined with adduction and lateral rotation and
almost as tight in flexion with lateral rotation alone, and in flexion with adduction alone (flgs.
313-315).
Muscles which act upon the hip-joint. — Flexors. — The psoas and iliacus, the rectus femoris,
the pectineus, the adductors, the sartorius, the tensor fasciae latse, and the gluteus medius.
284
THE ARTICULATIONS
Fig. 315. — Ligamentum Teres, drawn Tight in I'lexion Combined with Lateral
Rotation and Adduction.
Extensors. — The gluteus maximus, the posterior fibres of the glutei medius and miQimus, the
biceps, the semitendinosus, the semimembranosus, and the ischial fibres of the adductor magnus;
also (slightly) the piriformis, obturator internusand gemelli. Abductors. — Gluteus maximus
(upper fibres), tensor fasciae latae, gluteus medius, gluteus minimus, and, when the joint is
flexed, the pii-iformis, obturator internus, the gemelli, and the sartorius also become abductors.
Adductors. — Adduotores magnus, longus, brevis, and minimus, semitendinosus, biceps^ the
gracilis, the peotineus, the quadratus femoris, and the lower fibres of the gluteus maxunus.
Medial rotators. — Psoas (slightly), adductor magnus, semimembranosus, the anterior fibres
of the gluteus medius and minimus, and the tensor fascise latae. Lateral rotators. — Gluteus
maximus, posterior fibres of gluteus medius and minimus, the adductors, obturator extemus,
quadratus femoris, obturator internus, the gemelli, and the piriformis when the joint is extended.
2. THE KNEE-JOINT
Class. — Diarthrosis.
Subdivision. — Ginglymus.
The knee is the largest joint in the body. It is rightly described as a gingly-
moid joint, but there is also an arthrodial element; for, in addition to flexion and
extension, there is a sliding backward and forward of the tibia upon the femoral
condyles, as well as slight rotation round a vertical axis. It is one of the most
superficial, and, as far as adaptation of the bony surfaces goes, one of the weakest
joints, for in no position are the bones in more than partial contact. Its strength
lies in the number, size, and arrangement of the ligaments, and the powerful
muscles and fascial expansions which pass over the articulation and enable it to
withstand the leverage of the two longest bones in the bodj\ It may be said'to
consist of two articulations with a common synovial membrane — the patello-
femoral and the tibio-femoral, the latter being double. It is composed of the
condyles and trochlear surface of the femur, the condyles of the tibia, and the
patella, united by the following ligaments, which may be divided into an external
and internal set: —
External
(1) Fibrous expansion of the extensors.
(2) Articular capsule.
(3) Oblique popliteal ligament.
(4) Fibular collateral.
(5) Tibial collateral.
(6) Ligamentum patellae
Internal
(1) Anterior crucial.
(2) Posterior crucial.
(3) Medial meniscus.
(4) Lateral meniscus.
(5) Coronary.
(6) Transverse.
THE KNEE-JOINT
285
External Ligaments
Superficial to the fibrous expansion of the quadriceps extensor tendons the
fascia lata of the thigh covers the front and sides of the knee-joint.
The deep fascia of the thigh, as it descends to its attachment to the tuberosity and oblique
lines of the tibia, not only overhes but blends with the fibrous expansion of the extensor tendons.
The oblique lines of the tibia curve upward and backward from the tuberosity on each side
to the postero-lateral part of the condyles. The process of fascia attached to the lateral ridge
of the tibia and to the head of the fibula descends from the tensor fascise latas and is very thick
and strong. It is firmly blended with the tendinous fibres of the vastus laterahs. The fascia
lata, on the medial side of the patella, besides being attached to the medial oblique ridge of the
tibia, sends some longitudinal fibres lower down to become blended with the fibrous expansion
of the sartorius. The fascia is much thinner on the medial side of the patella than on the lateral,
and blends much less with the tendon of the vastus niedialis than the lateral part of the fascia
does with the vastus lateralis. A thin layer of the fascia lata in the form of transverse or aroi-
form fibres passes over the front of the joint. These fibres are speciaUy well marked over the
ligamentum patellae, and blend here with the central portion of the quadriceps extensor fibres.
Fig. 316. — The Lower Extremity of the Femur (Posterior View), to show the Rela-
tion OP the Articular Capsule of the Knee-joint (in red) to the Epiphysial Line.
The fibrous expansion of the extensor tendons consists — (1) of a central
portion, densely thick and strong, 3.7 cm. (1| in.) broad, which is inserted into
the anterior two-thirds of the upper border of the patella, many of its superficial
fibres passing over the subcutaneous surface of the bone into the ligamentum
patellfe; (2) of two side portions thinner, but strong.
The side portions are inserted into the patella along its upper border on either side of the
central portion and also into its medial and lateral borders, nearer the anterior than the posterior
surface, as low down as the attachment of the ligamentum patellar; passing thence along the
sides of the ligamentum patelte to the tibia, they are attached to the obhque lines which extend
from the tuberosity to the medial and lateral condyles, and reach as far as the tibial and fibular
collateral ligaments. On the lateral side, the fibres blend with the ilio-tibial band of the fascia
lata, and on the medial they extend below the oblique line to blend with the periosteum of the
shaft. Thus there is a large hood spread over the whole of the front of the joint, investing the
patella, and reaching from the sides of the ligamentum pateUse to the collateral ligaments, at-
tached below to the tibia, and separated everywhere from the synovial membrane by a layer
■of fatty tissue.
The ligamentum patellae (fig. 320) is the continuation in line of the central
portion of the conjoined tendon, some fibres of which are prolonged over the front
286
THE ARTICULATIONS
of the patella into the ligament. It is an extremely strong, flat band, attached
above to the lower border of the patella; below, it is fixed to the lower part of the
tuberosity and upper part of the crest of the tibia, somewhat obliquely, being
prolonged downward further on the lateral side, so that this border is fully 2.5
cm. (1 in.) longer than the medial, which measures 6.7 cm. {2\ in.) in length.
Behind, it is in contact with a mass of fat which separates it from the synovial
membrane, and a small bursa intervenes between it and the head of the tibia.
In front, a large bursa separates it from the subcutaneous tissue, and at the sides
it is continuous with the fibrous expansion of the extensors.
The tibial (internal) collateral ligament (fig. 317) is a strong, flat band, which
extends from the depression on the tubercle on the medial side of the medial
Fig. 317. — Posterior View op the Knee-joint.
Plantaris
Lateral head of gastrocnemius
Fibular collateral ligament
anterior portion
Posterior part of fibular
collateral ligament
Tendon of popliteus
Tendon of biceps
Superior posterior tibio-
fibular ligament
Tendon of adductor magaus
Medial head of gastrocnemius
Tendon of semimembra-
nosus with its slip to
thicken the oblique pop-
liteal ligament
Tibial collateral ligament
epicondyle of the femur, to the medial border and medial surface of the shaft of
the tibia, 3.7 cm. (1| in.) below the condyle. It is 8.7 cm. (3| in.) long, well
defined anteriorly, where it blends with the expansion of the conjoined extensor
tendons; but not so well defined posteriorly, where it merges into the oblique
popliteal ligament.
Some of the lower fibres blend with the descending portion of the semimembranosus tendon.
Its deep surface is firmly adherent to the edge of the medial meniscus and coronary ligament,
while part of the semimembranosus tendon and inferior medial articular vessels and nerve pass
between it and the bone. Superficially, a bursa separates it from the tendons of the gracilis
and semitendinosus muscles and from the aponeurosis of the sartorius muscle.
The fibular (external) collateral ligament (fig. 317) consists of two portions:
the anterior, which is the longer and better marked, is a strong, rounded cord,
about 5 cm. (2 in.) long, attached above to the tubercle on the lateral side of the
lateral epicondyle of the femur, just below and in front of the origin of the lateral
head of the gastrocnemius, whilst the tendon of the popliteus arises from the
groove below and in front of it. Below, it is fixed to the middle of the lateral
surface of the head of the fibula, 1.25 cm. (J) in. or more anterior to the apex.
Superficially is the tendon of the biceps, which sphts to embrace its lower extremity; while
beneath it pass the popliteus tendon in its sheath, and the inferior lateral articular vessels and nerve.
THE KNEE-JOINT
287
Some fibres of the peroneus longus occasionally arise from the lower end of the ligament. The
posterior portion is 8 mm. (\ in.) behind the anterior. It is broader and less defined; fixed below
to the apex of the fibula, it inclines upward and somewhat backward, and ties down the popliteus
against the lateral condyle of the tibia, blending beneath the lateral head of the gastrocnemius
with the oblique popliteal ligament of the knee, of which it is really a portion.
The oblique popliteal ligament or ligamentum Winslowii (fig. 317) is a broad
dense structure of interlacing fibres, with large orifices for vessels and nerves.
It is attached above to the femur close to the articular margins of the condyles,
stretching across the upper margin of the intercondyloid fossa, to which it is
connected by fibro-fatty tissue; it thus reaches across from the tibial to the
fibular collateral ligaments. Below, it is fixed to the border of the lateral condyle
of the tibia, to the bone just below the posterior intercondyloid notch, and to the
shaft of the tibia below the medial condyle, blending with the descending slip of
the semimembranosus and tibial collateral ligament.
Superficially, an oblique fasciculus from the semimembranosus runs across the centre, passing
upward and laterally from near the back part of the medial condyle of the tibia to the lateral
Fig. 318. — The Lower Extremity op the Femur (Anterior View) to show the Rela-
tion OP THE Articular Capsule op the Knee-joint (in red) to the Epiphysial Line.
epicondyle of the femur, where it joins the lateral head of the gastrocnemius, a sesamoid plate
being sometimes developed at the point of junction. This slip greatly strengthens the oblique
pophteal ligament, of which, if not the chief constituent, it is at least a very important part.
Its deep surface is closely connected with the semilunar menisci (especially the medial) and
coronary ligaments, and in the interval between the cartilages with the posterior crucial ligament
and fibro-fatty tissue within the joint. Superficially it forms part of the floor of the popHteal
space. A special band, the arcuate ligament, is sometimes found extending from the lateral
epicondyle to the oblique ligament.
The articular capsule (fig. 319) is thin but strong, covering the synovial
membrane, and looking like a loose sac. It is attached to the femur near the
articular margin on the medial side, but further away on the lateral; it passes
beneath the fibular collateral ligament to join the sheath of the popliteus. Medi-
ally it joins the tibial collateral ligament. Below, it is fixed to the upper as well
as the medial and lateral borders of the patella and the anterior border of the
head of the tibia. It is strengthened superficially between the femur and patella
by an expansion from the articularis genu {suh-crureus) and is separated from
288
THE ARTICULATIONS
the fibrous expansion of the extensor tendon by a layer of fatty tissue. The
synovial membrane lines its deep surface, and holds it against the borders of the
semilunar menisci; it is also attached to the coronary ligaments.
Internal Ligaments
The anterior crucial ligament (figs. 319 and 320) is strong and cord-like. It
is attached to the medial half of the fossa in front of the intercondyloid eminence
of the tibia, and to the lateral border of the medial articular facet as far back as
the medial intercondyloid tubercle. It passes upward, backward, and laterally
to the back part of the medial surface of the lateral condyle of the femur. To
Fig. 319. — Anterior View of the Internal Ligaments op the Knee-joint.
Aperture leading into the
bursa beneath the quadri '
ceps extensor
Attachment of articular,
capsule to femur
Posterior crucial ligament
Medial meniscus
Transverse ligament
Coronary ligament
Anterior crucial ligament'
Lateral
Coronary ligament
the tibia, it is fixed behind the anterior extremity of the medial semilunar menis-
cus. Behind and to the lateral side it has the anterior extremity of the lateral
meniscus, a few fibres of which blend with the lateral edge of the ligament.
Its anterior fibres at the tibial end are strongest and longest; being fixed highest on the
femur; while the posterior, springing from the intercondyloid eminence, are shorter and more
oblique. Near the spine, a slip is sometimes given off to the posterior crucial hgament.
The posterior crucial ligament (fig. 319, 320, and 322) is stronger and less
oblique than the anterior. It is fixed below to the greater portion of the fossa
behind the intercondyloid eminence of the tibia, especially the lateral and pos-
terior portion, and then medially along the posterior intercondyloid fossa; being
joined by fibres which arise between the intercondyloid tubercles, it ascends
to the anterior part of the lateral surface of the medial condyle of the femur,
having a wide crescentic attachment 1.5 cm. (f in.) in extent just above the
articular surface.
Behind, it is connected at the tibia directly with the posterior Ugament, and a little higher
up by means of a quantity of interposed areolar tissue. In front it rests upon the posterior
THE KNEE-JOINT
289
horn of the medial semilunar meniscus, and receives a large slip from the lateral meniscus,
which ascends along it, either in front or behind, to the femur; higher up in front it is connected
with the anterior crucial hgament.
Until they rise above the intercondyloid eminence of the tibia the two crucial ligaments
are closely bound together, so that no interspace exists between their tibial attachments and
the point of decussation; the only space between them is therefore a v-shaped one correspond-
ing to the upper half of their x-shaped arrangement, and this is a mere chink in the undissected
state, and can be seen from the front only, owing to the fatty tissue beneath the synovial mem-
brane which sm-rounds their femoral attachment.
The interarticular menisci or semilunar fibro-cartilages (figs. 319 and 320)
are two crescentic discs resting upon tlie circumferential portions of the articular
facets of the tibia, and moving with the tibia upon the femur. They some-
what deepen the tibial articular surfaces, and are dense and compact in structure,
becoming looser and more fibrous near their extremities, where they are firmly
fixed in front of and behind the intercondyloid eminence of the tibia. The
circumferential border of each is convex, thick, and somewhat loosely attached to
the borders of the condyles of the tibia by the coronary ligaments and the re-
flexion of the synovial membrane. The inner border is concave, thin, and free.
Half an inch (1.3 cm.) broad at the widest part, they taper somewhat toward their
Fig. 320. — Strtjctuhes lying on the Head op the Tibia. (Right knee.)
Ligamentum pateUee yiTTTiTT nt J'ili]
Transverse ligament
Lateral meniscus
Anterior crucial ligament
Medial meniscus — W- \
Posterior crucial ligament
Tendon of biceps
Fibulai* collateral
ligament
extremities, and cover rather less than two-thirds of the articular facets of the
tibia. Their upper surfaces are slightly concave, and fit on to the femoral
condyles, while the lower are flat and rest on the head of the tibia; both surfaces
are smooth and covered by synovial membrane.
The lateral meniscus (fig. 320) is nearly circular in form and less firmly fixed than the
medial, and consequently slides more freely upon the tibia. Its anterior cornu is attached to a
narrow depression along the lateral articular facet, just in front of the lateral intercondyloid
tubercle of the tibia, close to, and on the lateral side of, the anterior crucial hgament; a small slip
from the cornu is often fixed to the tibia in front of the crucial ligament. The posterior
cornu is firmly attached to the tibia behind the lateral intercondyloid tubercle, blending with the
posterior crucial ligament, and giving off a well-marked fasciculus, which runs up along the
anterior border of the ligament to be attached to the femur (ligament of Wrisberg). It also
sends a narrow slip into the back part of the anterior crucial ligament. Its outer border is
grooved toward its posterior part by the popliteus tendon, which is held to it by fibrous tissue
and synovial membrane, and separates it from the fibular collateral hgament. From its anterior
border is given off the transverse hgament.
The medial meniscus (fig. 320) is a segment of a larger circle than the lateral, and has an
outline more oval than cuxular. Its anterior cornu is wide, and has a broad and oblique attach-
ment to the anterior margin of the head of the tibia. It reaches from the margin of the condyle
toward the middle of the fossa in front of the intercondyloid eminence, being altogether in front
of the anterior crucial ligament. The posterior cornu is firmly fixed by a broad insertion in an
antero-posterior line along the medial side of the posterior intercondyloid fossa, from the medial
tubercle to the posterior margin of the head of the tibia. Its convex border is connected with
the tibial collateral ligament and the seviimeinhrmiosus tendon.
The transverse ligament (figs. 319 and 320) is a rounded, slender, short cord,
which extends from the convex border of the lateral meniscus to the concave
border or anterior cornu of the medial, near which it is sometimes attached to the
bone. It is an accessory band of the lateral meniscus, and is situated beneath
the synovial membrane.
290
THE ARTICULATIONS
The coronary ligaments (fig. 319) connect the margins of the semilunar
discs with the head of the tibia. The lateral is much more lax than the medial,
permitting the lateral disc to change its position more freely than the medial.
They are not in reality separate structures, but consist of fibres of the several
surrounding ligaments of the knee-joint which become attached to the margins
of the discs as they pass over them.
The synovial membrane (fig. 324) of the knee forms the largest synovial sac
in the body. Bulging upward from the patella, it follows the capsule of the joint
into a large cul-de-sac beneath the tendon of the extensor muscles on the front of
the femur. It reaches some distance beyond the articular surface of the bone, and
communicates very frequently with a large bursa interposed between the tendon
and the femur above the line of attachment of the articular capsule. After
investing the circumference of the lower end of the femur, it is reflected upon the
Fig. 321. — The Uppee Extremity of the Tibia (Anterior View), to show the Rela-
tion OP THE Articular Capsule op the Knee-joint (in red) to the Epiphysial Line.
fibrous envelope of the joint formed by the capsular, posterior, and collateral
ligaments.
The synovial membrane covers a great portion of the crucial ligaments, but leaves uncovered
the back of the posterior crucial where the latter is connected with the posterior hgament, and
the lower part of both crucial ligaments where they are united. Thus the hgaments are com-
pletely shut out of the synovial cavity. Along the fibrous envelope the synovial membrane is
conducted down to the semilunar menisci, over both surfaces of which it passes, and is reflected
off the under surface on to the coronary ligaments, and thence down to the head of the tibia,
around the circumference of which it extends a short way. It dips down between the external
meniscus and the head of the tibia as low as the superior tibio-fibular ligament, reaching inward
nearly as far as the intercondyloid notch, and forming a bursa for the play of the popliteal
tendon.
At the back of the joint two pouches are prolonged beneath the muscles, one on each side
between the condyle of the femur and the origin of the gastrocnemius. Large processes of syno-
vial membrane also project into the joint, and being occupied by fat serve as padding to fill up
spaces. The chief of these processes, the patellar synovial fold (ligamentum mucosum) (figs.
322 and 324), springs from the infrapatellar fatty mass. This so-called ligament is the central
portion of the large process of synovial membrane, of which the alar folds form the free margins.
It extends from the fatty mass, below the patella, backward and upward to the intercondyloid
notch of the femur, where it is attached in front of the anterior crucial, and lateral to the poste-
rior crucial ligament. Near the femur it is thin and transparent, consisting of a double fold of
synovial membrane, but near the patella it contains some fatty tissue. Its anterior or upper
edge ia free, and fully 2.6 cm. (an inch) long; the posterior or lower edge is half the length, and
is attached to the crucial ligaments above, but is free below.
THE KNEE-JOINT
291
Passing backward from the capsule on each side of the patella is a prominent crescentic
fold formed by reduplications of the synovial membrane — these are the alar folds (fig. 3?2).
Their free margins are concave and thin, and are lost below in the patellar fold. There is a
slight fossa above and another below each Ligament.
Fig. 322.— Anterior View of the Knee-joint, showing the Stnoviai, Ligaments.
(Anterior portion of capsule with the extensor tendon thrown downward.)
Posterior crucial ligament
Synovial pouch under tendon
quadriceps femoris
Fig. 323. — The Upper Extremity op the Tibia (Posterior View), to show the Relation
OF THE Articular Capsule op the Knee-joint (in red) to the Epiphysial Line.
The arterial supply is derived from the art. genu suprema (anastomotica) ; the superior ajid
inferior medial and lateral articular; the medial articular; the descending branch of the lateral
circumflex; the anterior recurrent branch from the anterior tibial; and the posterior tibial
recurrent.
292
THE ARTICULATIONS
The nerve-supply comes from the great sciatic, femoral, and obturator sources. The
great sciatic pves off the tibial and common peroneal; the tibial sends tAvo, sometimes three
bi'anches — one with the medial articular artery; one with the inferior medial, and sometimes
one with the superior medial articular artery; the common peroneal gives a branch which accom-
panies the superior, and another which accompanies the inferior articular artery, and a recurrent
branch which follows the course of the anterior recm-rent branch of the anterior tibial artery.
The femoral sends an articular branch from the nerve to the vastus lateralis; a second from the
nerve to the vastus mediaiis; and sometimes a third from that to the vastus intermedins. Thus
there are three articular twigs to the knee derived from the muscular branches of the femoral.
The obturator by its deep division sends a branch through the adductor magnus on to the pop-
liteal artery, which enters the joint posteriorly.
Fig. 324. — Sagittal Section of the Knee-joint.
(The bones are somewhat drawn apart.)
Fatty tissue
Opening in synovial mem-
brane behind crucial
ligament leading into
inner half of joint
Synovial membrane re-
flectedoff crucialligaments
Cut end of anterior crucial
ligament
Posterior crucial ligament
Oblique popliteal ligament
Muscular fibres of quadriceps
femoris
(,. Extension of synovial sac of knee
I \\\ upon femur
\V.\\ .Tendon of quadriceps femoris,
'H\
l\^ forming fibrous capsule of joint
Patella
Pre-patellar bursa
Condyle of femur
^medial)
Patellar synovial fold
Fatty tissue between
ligamentum patellas
and synovial sac
Bursa beneath ligamentum
patellas
Relations. — Anteriorly and at the sides the knee-joint is merely covered and protectedlby
skin, fascia, and the tendinous expansions of the quadriceps extensor muscle. Laterally and
posteriorly it is crossed by the biceps tendon. Medially and posteriorly lie the sartorius and
the tendons of the gracilis and seinitendinosus muscles. Posteriorly it is in relation with the
popliteal vessels and nerves, the semimembranosus, the two heads of the gastrocnemius, and the
plantaris. The tendon of the popliteus pierces the capsule behind and medial to the biceps
tendon.
The movements which occur at the knee-joint are flexion and extension, with some slight
amount of rotation in the bent position. These movements are not so simple as the correspond-
ing ones at the elbow, for the knee is not a simple hinge joint. The movements of rotation
instead of occurring between tibia and fibula, as between radius and ulna, are movements of the
tibia with the fibula upon the condyles of the femur.
The knee differs from a true hinge joint, like the elbow or ankle, in the following par-
ticulars:—
1. The points of contact of the femur with the tibia are constantly changing. Thus, in
THE KNEE-JOINT
293
the flexed position, the posterior part of the articular surface of the tibia is in contact with the
rounded bacli part of the femoral condyles; in the semiflexed position the middle parts of the
tibial facets Articulate with the anterior rounded part of the condyles; while in the fully extended
position the anterior and middle parts of the tibial facets are in contact with the anterior flat-
tened portion of the condyles. So with the patella: in extreme flexion the medial articular facet
rests on the lateral part of the medial condyle of the femur; in flexion the upper pair of facets
rests on the lower part of the trochlear surface of the femur; in mid-flexion the middle pan-
rests on the middle of the trochlear surface; while in extension the lower pair of facets on the
patella rests on the upper portion of the trochlear surface of the femur.
Fig. 325. — The Collateral Ligaments op the Knee in Flexion and Extension.
This difference may be described as the shifting of the points of contact of the articular
surface.
2. It differs from a true hinge in that, in passing from a state of extension to one of flexion,
the tibia does not revolve round a single transverse axis drawn through the lower end of the
femur, as the ulna does round the lower end of the humerus. The articular surface of the
tibia slides forward in e.xtension and backward in flexion; thus the axis round which the tibia
revolves upon the femur is a shifting one, as is seen by reference to fig. 325, B, C, D.
3. Another point of difference is that extension is accompanied by lateral rotation, and
flexion by medial rotation. This rotation occurs round a vertical axis drawn through the middle
of the lateral condyle of the femur and the lateral condyle of the tibia, and is most marked at
the termination of extension and at the commencement of flexion. This rotation of the leg at
the knee is a true rotation about a vertical axis, and thus differs from the obliquity of the flexion
294
THE ARTICULATIONS
and extension movements at the elbow wMcIi is due to the oblique direction of the articular
surfaices of the bones.
4. The antero-posterior spiral curve of the femoral condyles is such that the anterior part
is an arc of a greater circle than the posterior; hence certain ligaments which are tightened during
Fig. 326. — Section op Knee, showing Crucial Ligaments in Extension.
Anterior crucial ligament
Intercondyloid eminence of tibia
Transverse ligament
Slip from lateral meniscus to femur
(ligament of Wrisberg)
Posterior crucial ligament
Latetal meniscus
Coronary ligament
Anterior tibio-fibular ligament
extension are relaxed during flexion, and thereby a considerable amount of rotatory movement
is- permitted in the flexed position. The axis of this rotation is vertical, and passes through the
medial intercondyloid tubercle of the tibia, so that the lateral condyle moves in the arc of a
larger circle than does the medial, and is therefore required to move more freely and easily;
Fig. 327. — Crucial Ligaments in Flexion.
Posterior crucial
Anterior crucial
Medial meniscus
Transverse ligament
Slip from lateral cartilage to femur
Lateral meniscus
Coronary ligament
Anterior tibio-fibular ligament
hence the shape of the lateral articular facet and the loose connection of the lateral meniscus
which is adapted to it.
In extension, all the ligaments are on the stretch with the exception of the ligamentum
patellae and front of the capsule. Extension is checked by both the crucial ligaments and the
cSlateral ligaments (figs. 325, A, B, and 326).
THE KNEE-JOINT 295
In flexion the ligamentum patellae and anterior portion of the capsule are on the stretch;
so also is the posterior crucial in extreme flexion, though it is not quite tight in the semiflexed
state of the joint. All the other ligaments are relaxed (fig. 325, C, D), although the relaxation
of the anterior crucial ligament is slight in extreme flexion (fig. 327). Flexion is only checked
during hfe by the contact of the soft parts, i. e., the calf with the back of the thigh.
Rotation medially is checked by the anterior crucial ligament; the collateral ligaments
being loose.
Rotation laterally is checked by the collateral Ugaments; the crucial hgaments have no
controlling effect on it, as they are untwisted by it.
Sliding movements are checked by the crucial and collateral ligaments — sliding forward
especially by the anterior, and sliding backward by the posterior crucial.
Muscles which act upon the knee-joint. — Flexors. — Biceps, semimembranosus, semiten-
dinosus, sartorius, gastrocnemius, plantaris, and pophteus. Extensor. — Quadriceps extensor.
Medial Bolators. — Sartorius, gracilis, semitendinosus, semimembranosus, popliteus. Lateral
Rotator. — Biceps.
3. THE TIBIO-FIBULAR UNION
The fibula is connected with the tibia throughout its length by an interosseous
membrane, and at the upper and lower extremities by means of two joints.
Very little movement is permitted between the two bones.
(a) The superior tibio-fibular joint.
(6) The middle tibio-fibular union.
(c) The inferior tibio-fibular joint.
(a) The Superior Tibio-fibular Joint
Class. — Diarthrosis. Subdivision. — Arthrodia.
The superior tibio-fibular joint is about 6 mm. (J in.) below, and quite distinct
from, the knee at its upper and anterior part; but at its posterior and superior
aspect, where the border of the lateral condyle of the tibia is bevelled by the pop-
liteus muscle, the joint is in the closest proximity to the bursa beneath the tendon
of that muscle, and is only separated from the knee-joint by a thin septum of
areolar tissue. There is often a communication between the synovial cavities of
the two joints. The ligaments uniting the bones are: —
Articular capsule. Anterior tibio-fibular.
Posterior tibio-fibular.
The articular capsule is a well-marked fibro-areolar structure; it is attached
close round the articular margins of the tibia and fibula. In front it is shut off
completely from the knee-joint by the capsule of the knee and the coronary liga-
ment; but behind, it is often very thin, and may communicate with the bursa
under the pophteus tendon.
The anterior tibio-fibular (capitular) ligament (fig. 326) consists of a few fibres
which pass upward and medially from the fibula to the tibia. It lies beneath the
anterior portion of the tendon of the biceps.
The posterior tibio-fibular (capitular) ligament (fig. 317) consists of a few fibres
which pass upward and medially between the adjacent bones, from the head of
the fibula to the lateral condyle of the tibia.
The superior interosseous ligament consists of a mass of dense yellow fibroareolar tissue,
binding the opposed surfaces of the bones together for 2 cm. (f in.) below the articular facets.
It is continuous with the interosseous membrane along the tibia.
The biceps tendon is divided by the fibular collateral ligament of the knee; of the two
divisions the anterior is by far the stronger, and is inserted into the lateral condyle of the tibia
as well as to the front of the head of the fibula, and thus the muscle, acting on both bones, tends
to brace them more tightly together; indeed, it holds the bones strongly together after all other
connections have been severed.
The synovial membrane which lines the joint sometimes communicates with the knee-joint
through the bursa beneath the popliteus tendon.
The arterial supply is from the inferior lateral articular and recurrent tibial arteries.
The nerve-supply is from the inferior lateral articular, and also from the recurrent branch
of the common peroneal.
Relations. — In front, the upper ends of the tibialis anterior, the extensor digitorum longus,
and the peroneus longus. Behind, the tendon of the popliteus overlapped by the lateral head
of the gastrocnemius. Laterally, the biceps tendon and the common peroneal nerve. Below
and medially, the anterior tibial vessels.
The movements are but slight, and consist merely of a gliding of the two bones upon each
other. The joint is so constructed that the fibula gives some support to the tibia in transmitting
296
THE ARTICULATIONS
the weight to the foot. The articular facet of the tibia overhangs, and is received upon the
articular facet of the head of the fibula in an oblique plane. This joint allows of slight yielding
of the lateral malleolus during flexion and extension of the ankle-joint, the whole fibula gUding
slightly upward in flexion, and downward in extension, of the anlde.
(6) The Middle Tibio-fibular Union
Class. — Synarthrosis.
Subdivision. — Syndesmosis.
The interosseous membrane is attached along the lateral border of the tibia
and the interosseous border of the fibula. It is deficient above for about 2.5 cm.
(1 in.) or more, measured from the under aspect of the superior joint. Its upper
border is concave, and over it pass the anterior tibial vessels.
The membrane consists of a thin aponeurotic and translucent lamina, formed of oblique
fine fibres, some of which run from the tibia to the fibula, and some from the fibula to the tibia,
but all are inchned downward. They are best marked at their attachment to the bones, and
gradually grow denser and thicker as they approach the inferior interosseous ligament. The
Fig. 328. — Lower Ends op Left Tebia and Fibula, showing the Ligaments. The synovial
fold between these bones has been removed to show the transverse ligament forming part
of the capsule of the joint, and the deeper fibres of the anterior lateral malleolar hgament
which come into contact with the talus.
(From a dissection by Mr. W. Pearson, of the Royal College of Surgeons' Museum.)
Deltoid ligament
Anterior lateral malle-
_ / olar ligament
Lateral ligament
Transverse ligament
Posterior lateral malle-
olar ligament
chief use of the membrane is to afford a surface for the origin of muscles. It is continuous below
with the inferior interosseous ligament.
In front of the interosseous membrane lie the tibialis anterior, the extensor digitorum longus,
the extensor hallucis longus, and the anterior tibial vessels and nerves. Behind it is in relation
with the tibialis posterior, the flexor hallucis longus, and the peroneal artery.
(c) The Inferior Tibio-fibular Articulation
Class. — Diarihrosis. Subdivision. — Arthrodia.
This junction is formed by the lower ends of the tibia and fibula. The rough
triangular surface on each of these bones formed by the bifurcation of their
interosseous lines is closely and firmly united by the inferior interosseous liga-
ment. The fibula is in actual contact with the tibia by an articular facet, which
is small in size, crescentic in shape, and continuous with the articular facet of
the malleolus.
The ligaments which unite the bones are: — •
1. Anterior lateral malleolar ligament.
2. Posterior lateral malleolar ligament.
3. Transverse ligament.
4. Inferior interosseous ligament.
The anterior lateral malleolar ligament (anterior inferior tibio-fibular liga-
ment) (figs. 328 and 334) is a strong triangular band about 2 cm. (f in.) wide,
and is attached to the lower extremity of the tibia at its anterior and lateral
angle, close to the margin of the facet for the talus and passes downward and
THE ANKLE-JOINT 297
laterally to the anterior border and contiguous surface of the lower end of the
fibula, some fibres passing along the edge nearly as far as the origin of the anterior
talo-fibular ligament.
The fibres increase in length from above downward. In front it is in relation with the
peroneus tertius and deep fascia of the leg, and gives origin to fibres of the anterior Kgament of
the ankle-joint. Behind, it Lies in contact with the interosseous Ugament, and comes into con-
tact with the articxilar surface of the talus (see figs. 328 and 329).
The posterior lateral malleolar ligament (figs. 328 and 334) is very similar
to the anterior, extending from the posterior and lateral angle of the lower end
of the tibia downward and laterally to the lowest 1.5 cm. (| in.) of the border
separating the medial from the posterior surface of the shaft of the fibula, and to
the upper part of the posterior border of the lateral malleolus. It is in relation
in front with the interosseous ligament; below, it touches the transverse ligament.
The inferior interosseous ligament is a dense mass of short, felt-like fibres, passing trans-
versely between and firmly uniting the opposed rough triangular surfaces at the lower ends of the
Fig. 329. — Right Ankle-joint, showing the Ligaments.
(From dissection by Mr. W. Pearson, of the Royal College of Surgeons' Museum.)
Superficial fibres of anterior
lateral malleolar ligament
Deep fibres of anterior lateral.
malleolar Ugament
Anterior talo-fibular ligament —
Posterior talo-fibular ligament —
Calcaneo-fibular ligament —
Deltoid ligament
tibia and fibula, except for 1 cm. (f in.) at the extremity, where there is a synovial cavity. It
extends from the anterior to the posterior lateral malleolar hgaments, reaching upward 4 cm.
(l-J- in.) in front, but only half this height behind.
The transverse ligament (fig. 331) is a strong rounded band, attached to nearly the whole
length of the inferior border of the posterior svu-face of the tibia, just above the articular facet
for the talus. It then inclines a little forward and downward, to be attached to the medial
surface of the lateral malleolus, just above the fossa, and into the upper part of the fossa itself.
The synovial membrane is continuous with that of the ankle-joint; it projects upward
between the bones beyond their articular facets as high as the inferior interosseous ligament.
The nerve-supply is the same as that of the ankle-joint; the arterial supply is from the
peroneal and the anterior peroneal, and sometimes from the anterior tibial, or its lateral malleolar
branch.
Relations. — In front of the inferior tibio-fibular joint are the anterior peroneal artery and
the tendon of the peroneus tertius, and behind it are the posterior peroneal artery and the pad
of fat which Ues La front of the tendo Achillis.
The movement permitted at this joint is a mere gliding, chiefly in an upward and downward
direction, of the fibula on the tibia. The bones are firmly braced together and yet form a slightly
yielding arch, thus allowing a slight side to side expansion during extreme flexion, when the
broad part of the talus is brought under the arch, by the upward gliding of the fibula on the
tibia. To this end the direction of the fibres of the lateral malleolar ligaments is downward
from tibia to fibula. This mechanical arrangement secures perfect contact of the articular
surfaces of the ankle-joint in all positions of the foot.
4. THE ANKLE-JOINT
Class. — Diarthrosis. Subdivision. — Ginglymus.
The ankle [articulatio talo-cruralis] is a perfect ginglymus or hinge joint.
The bones which enter into its formation are: the lower extremity and medial
malleolus of the tibia, and the lateral malleolus of the fibula, above; and the upper
298
THE ARTICULATIONS
and lateral articular surfaces of the talus (astragalus) below,
(supplementing the articular capsule) uniting the bones are: —
The ligaments
Anterior.
Posterior.
Deltoid.
Lateral ligament.
The anterior ligament (fig. 334) is a thin, membranous structure, which
completes the capsule in front of the joint. It is attached above to the anterior
border of the medial malleolus, to a crest of bone just above the transverse groove
at the lower end of the tibia, to the anterior lateral malleolar ligament, and to the
anterior border of the lateral malleolus. Below, it is attached to the rough upper
surface of the neck of the talus (astragalus). Medially it is thicker, and is fixed
to the talus close to the facet for the medial malleolus, being continuous with the
deltoid ligament, and passing forward to blend with the talo-navicular ligament.
Laterally it is attached to the talus, just below and in front of the angle between
the superior and lateral facets, close to their edges, and joins the anterior talo-
fibular ligament.
It is in relation, in front with the tibialis anterior muscle, the anterior tibial vessels and nerve,
the extensor tendons 0/ the toes, and the peroneus tertius; and behind with a mass of fat and syno-
vial membrane.
Fig. 330. — Medial View of the Ankle and the Tarsus, showing the Groove for the
Tendon of the Tibialis Posterior.
Plantar calcaneo-cuboid ligament Long plantar ligament
The posterior ligament (fig. 331) is a very thin and disconnected membranous
structure, connected above with the lateral malleolus, medial to the peroneal
groove; to the posterior margin of the lower end of the tibia lateral to the groove
for the tibialis posterior; and to the posterior lateral malleolar ligament. Below,
it is attached to the posterior surface of the talus from the deltoid to the lateral
ligaments. The passage of the flexor hallucis longus tendon over the back of
the joint serves the purpose of a much stronger posterior ligament.
The deltoid ligament (fig. 330) is attached superiorly to the medial malleolus
along its lower border, and to its anterior surface superficial to the anterior liga-
ment; some very strong fibres are fixed to the notch in the lower border of the
malleolus, and, getting attachment below to the rough depression on the medial
side of the talus, form a deep portion to the ligament. The ligament radiates;
the posterior fibres are short, and incline a little backward to be fixed to the rough
medial surface of the talus, close to the superior articular facet, and into the
THE ANKLE-JOINT
299
tubercle to the medial side of the flexor hallucis longus groove. The fibres next
in front are numerous and form a thick and strong mass, filling up the rough
depression on the medial surface of the talus, whilst some pass over the talo-
calcaneal joint to the upper and medial border of the sustentaculum tali. The
fibres which are connected above with the anterior surface of the malleolus pass
downward and somewhat forward to be attached to the navicular and to the
margin of the calcaneo-navicular ligament.
The lateral ligament (figs. 329 and 334) consists of three distinct slips (fas-
ciculi). The anterior talc -fibular ligament (anterior fasciculus), is ribbon-like
and passes from the anterior border of the lateral malleolus near the tip to the
rough surface of the talus in front of the lateral facet, and overhanging the sinus
pedis. The calcaneo -fibular ligament (middle fasciculus) , is a strong roundish
bundle, which extends downward and somewhat backward from the anterior
border of the lateral malleolus close to the attachment of the anterior fasciculus,
and from the lateral surface of the malleolus, just in front of the apex, to a tuber-
cle on the middle of the lateral surface of the calcaneum. The posterior talo-
FiG. 331. — Ligaments seen from the Back of the Ankle-joint.
Posterior ligament of ankle-joim
Posterior part of the deltoid
ligament
Transverse ligament of inferior
tibio-fibular joint
Posterior talo-fibular ligament
Calcaneo-fibular ligament
fibular ligament (posterior fasciculus), is almost horizontal; it is a strong, thick
band attached at one end to the posterior border of the malleolus, and slightly to the
fossa on the medial surface; and at the other end to the talus, behind the articular
facet for the fibula, as well as to a tubercle on the lateral side of the groove for
the flexor hallucis longus.
The middle fasciculus is covered by the tendons of the peronei longus and brevis; and in
extension, the posterior fasciculus is received into the pit on the medial surface of the lateral
malleolus.
The synovial membrane is very extensive. Besides lining the ligaments of
the ankle, it extends upward between the tibia and fibula, forming a short cul-
de-sac as far as the interosseous ligament. Upon the anterior and posterior liga-
ments it is very loose, and extends beyond the limits of the articulation. It is
said to contain more synovia than any other joint.
The nerve -supply is from the saphenous, posterior tibial, and the lateral division of the
anterior tibial.
300
THE ARTICULATIONS
The arterial supply comes from the anterior tibial, the anterior peroneal, the lateral malleolar,
the posterior tibial, and posterior peroneal.
Relations. — In front and in contact with the anterior hgament, from medial to lateral
aspects, are the tendons of the tibiahs anterior, the tendon of the extensor haUucis longus, the
anterior tibial vessels, the anterior tibial nerve, the tendons of the extensor digitorum longus,
and the tendon of the peroneus tertius. To the medial side of the tibiahs anterior and to the
lateral side of the peroneus tertius the joint is subcutaneous anteriorly. Behind and laterally
are the tendons of the peroneus longus and brevis. Behind and medially, from medial to
lateral side, are the tendon of the tibialis posterior, the tendon of the flexor digitorum longus,
the posterior tibial vessels, the posterior tibial nerve, and the tendon of the flexor hallucis longus.
Directly behind is a pad of fat which intervenes between the tendo Achillis and the joint.
Below and on the lateral side, crossing the middle fasciculus of the lateral ligament, are the
tendons of the peroneus longus and brevis. Below and on the medial side, crossing the deltoid
ligament, are the tendons of the tibialis posterior and the flexor digitorum longus.
Movements. — This being a true hinge joint, flexion and extension are the only movements
of which it is capable, there being no side to side motion, except in extreme extension, when the
narrowest part of the talus is thrust forward into the widest part of the tibio-fibular arch.
Fig. 332. — Tne Lower Extremity op the Tibia (Anterior view), to Show the Relation
OP the Articular Capsule op the Ankle-joint (in red) to the Epiphysial Line.
In flexion the talus is tightly embraced by the malleoli, and side to side movement is impossible.
Flexion of the ankle-joint is hmited by: — (i) nearly the whole of the fibres of the deltoid ligament,
none but the most anterior being relaxed; (ii) the posterior and middle portions of the lateral liga-
ment, especially the posterior; (iii) the posterior ligament of the ankle. It is also hmited by the
neck of the talus abutting on the edge of the tibia.
In most European ankle-joints the anterior edge of the lower end of the tibia is kept from
actual contact with the neck of the talus in positions of extreme flexion by the intervention of a
pad of fat situated beneath the anterior extension of the anterior hgament. In races which
adopt a squatting posture, however, an actual articulation may be developed between these two
bony surfaces, a facet being present both upon the anterior margin of the tibia and upon the neck
of the talus. These facets are known as "squatting facets" (fig. 333, A) and are of common
occurrence in ancient bones and in the bones of modern oriental people.
Extension of the ankle-joint is limited by: — (i) the anterior fibres of the deltoid ligament;
(ii) the anterior and middle portions of the lateral hgament; (ui) the medial and stronger fibres
of the anterior hgament. It is also limited by the posterior portion of the talus meeting with the
tibia. Thus the middle portion of the lateral ligament is always on the stretch, owing to its
obliquely backward direction, whereby it hmits flexion; and its attachment to the fibula in front
of the malleolar apex, whereby it prevents over-extension as soon as the foot begins to twist
THE TARSAL JOINTS
301
medialward. .This medial twisting, or adduction of the foot, is partly due to the greater pos-
terior length of the medial border of the superior articular surface of the talus, and to the less
proportionate height posteriorly of the lateral border of that surface, but chiefly to the side to
side movement in the talo-calcaneal joints. Fle.xion and extension take place round a transverse
axis drawn through the body of the talus. The movement is not in a direct antero-posterior
plane, but on a plane inclined forward and laterally from the middle of the astragalus to the
intermetatarsal joint of the second and third toes.
Muscles which act on the ankle-joint. — Flexors. — Tibialis anterior, extensor hallucis longus,
extensor digitorum longus, peroneus tertius. Extensors. — Tibialis posterior, flexor digitorum
longus, flexor hallucis longus, peroneus longus, peroneus brevis, soleus, gastrocnemius, plantaris.
Fig. 333. — Anterior Aspect of the Lower Extremity op the Tibia.
In A, the articular surface is prolonged upward in front, forming a "squatting facet" which
articulates with a corresponding facet on the neck of the talus. In B (the usual condition) the
articular surface is confined to the lower aspect of the bone.
5. THE TARSAL JOINTS
These may be divided into the following sub-groups : —
(a) The talo-calcaneal union.
(b) The articulations of the anterior portion of the tarsus.
(c) The medio-tarsal joint.
(a) The Talo-calcaneal Union
There are two joints which enter into this union — viz., an anterior and a
posterior.
(i) The Posterior Talo-calcaneal Joint
Class. — Diarthrosis. Subdivision. — Arthrodia.
'. The calcaneus articulates with the talus by two joints, the anterior and
posterior: the former communicates with the medio-tarsal; the posterior is
separate and complete in itself. At the latter joint the two bones are united by
an articular capsule with the following ligaments: —
Interosseous.
Posterior talo-calcaneal.
Lateral talo-calcaneal.
Medial talo-calcaneal.
The interosseous ligament (figs. 334 and 335) is a strong band connecting
the apposed surfaces of the calcaneus and talus along their oblique grooves. It
is composed of several vertical laminae of fibres, with some fatty tissue in between.
302 THE ARTICULATIONS
It is better marked, deeper, and broader laterally. Strong laminse extend from the rough
inferior and lateral sm-faces of the neck of the talus to the rough superior surface of the calcaneus
anteriorly, forming the posterior boundary of the anterior talo-caloaneal joint; these have been
described as the anterior (interosseous) ligament. The posterior lamina extend from the roof
of the sinus pedis to the calcaneus immediately in front of the lateral facet, thus forming the
anterior part of the capsule of the posterior joint.
The lateral talo-calcaneal ligament (fig. 334) extends from the groove just below and in
front of the lateral articular facet of the talus, to the calcaneus some little distance from the articu-
lar margin. Its fibres are nearly parallel with those of the calcaneo-fibular ligament of the
ankle, which passes over it and adds to its strength. It fiUs up the interval between the calcaneo-
fibular and anterior talo-fibular ligaments, a considerable bundle of its fibres blending with the
anterior border of the calcaneo-fibular.
The posterior talo-calcaneal ligament passes from the lateral tubercle of the talus and lower
edge of the groove for the flexor haUucis longus to the calcaneus, a variable distance from the
articular margin.
The medial talo-calcaneal ligament includes two portions. The first is a narrow band of
well-marked fibres passing obliquely downward and forward from the medial tubercle of the
talus, just behind the medial end of the sinus tarsi, to the calcaneus behind the sustentaculum
tali, thus completing the floor of the groove for the flexor hallucis longus tendon. The second
portion, which is often considered a separate ligament, is described below with the anterior
talo-calcaneal joint.
The synovial sac is distinct from any other.
The nerve-supply is from the posterior tibial or one of its plantar branches.
The arteries are, a branch from the posterior tibial, which enters at the medial end of the
sinus pedis; and twigs from the tarsal, lateral malleolar, and the peroneal, which enter at the
lateral end of the sinus.
(ii) The Anterior Talo-calcaneal Joint
Class. — Diarthrosis. Subdivision. — Arthrodia.
This joint is formed by the anterior facet on the upper surface of the calcaneus
and the facets on the lower surface of the neck and head of the talus; it is bounded
on the sides and behind by ligaments, and communicates anteriorly with the
talo-navicular joint. The ligaments are: —
Interosseous. Medial talo-calcaneal.
Lateral calcaneo-navicular.
The interosseous ligament by its anterior laminae limits this joint posteriorly. It has been
already described.
The medial talo-calcaneal ligament (second portion; see above) consists of short fibres at-
tached above to the medial surface of the neck of the talus, and below to the upper edge of the
free border of the sustentaculum tali, blending posteriorly with the medial extremityof the inter-
osseous ligament, and anteriorly with the upper border of the plantar calcaneo-navicular liga-
ment. It is strengthened by the deltoid ligament, the anterior fibres of which are also attached
to the plantar calcaneo-navicular ligament.
The lateral calcaneo-navicular (figs. 334 and 335) limits this, as well as the talo-navicular
joint, on the lateral side. It is a strong, well-marked band, extending from thorough upper sur-
face of the calcaneus, lateral to the anterior facet, to a slight groove on the lateral surface of
the navicular near the posterior margin. It blends below with the plantar calcaneo-navicular,
and above with the talo-navicular ligament. Its fibres run obliquely forward and medially.
The deltoid ligament and middle fasciculus of the lateral ligament of the ankle-joint also add
to the security of these two joints, and assist in limiting movements between the bones by pass-
ing over the talus to the calcaneus.
The synovial membrane is the same as that of the talo-navicular joint. The arteries and
nerves are derived from the same sources as those of the medio-tarsal joints.
The movements of which these two joints are capable are adduction and abduction, with
some amount of rotation. Adduction, or inclination of the sole medialward, is combined with
some medial rotation of the toes, and some lateral rotation of the heel; while abduction, or in-
clination of the foot lateralward, is associated with turning of the toes laterally and the heel
medially. Thus the variety and the range of movements of the foot on the leg, which at the ankle
are almost limited to flexion and extension, are increased. The cuboid moves with the calca-
neus, while the navicular revolves on the head of the talus.
In walking, the heel is first placed on the ground; the foot is slightly adducted; but as the
body swings forward, first the latei-al then the medial toes touch the ground, the talus presses
against the navicular and sinks upon the plantar calcaneo-navicular ligament; the foot then
becomes slightly abducted. When the foot is firmly placed on the ground, the weight is trans-
mitted to it obliquely downward and medially, so that if the ligaments between the calcaneus
and talus did not check abduction, medial displacement of the talus from the tibio-fibular arch
would only be prevented by the tendons passing round the medial ankle (especially the tibialis
posterior). If the ligaments be too weak to limit abduction, the weight of the body increases it,
and forces the medial malleolus and talus downward and medially, giving rise to flat foot.
The advantages of the obhquity and pecuUar arrangement of the posterior talo-
calcaneal articulation are seen in walking: — (i) for the posterior facet of the calcaneus receives
THE TARSAL JOINTS
303
the whole weight of the body when the heel is first placed on the ground; (ii) by the upward
pressure of this facet against the talus it transfers the weight to the ball of the toes as the heel
is raised, the posterior edge of the sustentaculum tali and the anterior and lateral part of the
upper surface of the calcaneus preventing the talus from being displaced too far forward by
the superincumbent weight; and (iii) the calcaneus serves to suspend the talus when, with the
heel raised by muscular action, the other foot is being swung forward.
Fig 334 — ^Lateral View of the Ligaments op the Foot and Ankle.
Posterior lateral malleolar
ligament
Anterior lateral malleolar bgament
Anterior (mterosseous) talo-
calcaneal ligament
Lateral calcaneo navic
ular ligament
Posterior talo-fibular ligament
JJorsal cuboideo navicular \
ligament I
Medial calcaneo-cuboid Dorsal Lateral Calcaneo-fibular ligament
calcaneo- talo-
cuboid calcaneal
ligament
(b) The Articulations of the Anterior Part of the Tarsus
These include (i) the cuboideo-navicular; (ii) cuneo-navicular; (iii) inter-
cuneiform; and (iv) cuneo-cuboid joints.
(i) The Cuboideo-navicular Union
Class. — Diarthrosis. Subdivision. — A rthrodia .
The joint cavity is only occasionally present and this joint is often included
in the transverse tarsal.
The ligaments which unite the cuboid and navicular are: —
Dorsal.
Plantar.
Interosseous.
The dorsal cuboideo-navicular ligament (fig. 334) runs forward and laterally from the
lateral end of the dorsal surface of the navicular to the middle third of the medial border of the
cuboid on its dorsal aspect, passing over the posterior lateral angle of the third cuneiform bone.
It is wider laterally.
The plantar cuboideo-navicular ligament is a well-marked strong band, which runs forward
and laterally, from the plantar surface of the navicular to the depression on the medial siurface
of the cuboid, and slightly into the plantar surface just below it.
The interosseous cuboideo-navicular ligament is a strong band which passes between the
apposed surfaces of these bones from the dorsal to the plantar ligaments. Some of its posterior
fibres reach the plantar surface of the foot behind the cuboideo-navicular ligament, and radiate
laterally and backward over the medial border of the cuboid to blend with the anterior ex-
tremity of the plantar calcaneo-cuboid ligament.
304 THE ARTICULATIONS
(ii) The Cuneo-navicular Articulation
Class. — Diarthrosis. Subdivision. — Arthrodia.
The ligaments uniting tlie navicular with the three cuneiform bones are : —
Dorsal. Plantar.
Medial.
The dorsal cuneo-navicular ligament is very strong, and stretches as a continuous structure
on the dorsal surface of the navicular, between the tubercle of the navicular on the medial side,
and the dorsal cuboideo-navicular ligament laterally, passing forward and a little laterally to
the dorsal surfaces of the three cuneiform bones.
The medial cuneo-navicular ligament is a very strong thick band which connects the tuber-
cle of the navicular with the medial surface of the first cuneiform bone. It is continuous
with the dorsal and plantar ligaments. Its lower border touches the tendon of the tibialis
posterior.
The plantar cuneo-navicular ligament forms, like the dorsal, a continuous structure ex-
tending between the plantar surfaces of the bones. Its fibres pass forward and laterally. It
is in relation below with the tendon of the tibialis posterior.
It must be noticed that the expanded tendon of insertion of the tibialis posterior, and the
ligaments uniting the navicular with the cuboid and cuneiform bones, pass forward and later-
aUy, while the peroneus longus tendon and the ligaments uniting the first and second rows of
bones, except the medial half of the dorsal talo-navicular ligaments, pass forward and medially.
This arrangement is admirably adapted to preserve the arches of the foot, and especially the
transverse arch. Had these tendons and ligaments run directly forward, all the strain on the
transverse arch would have fallen on the interosseous ligaments, but as it is, the arch is braced
up by the above-mentioned structures.
(iii) The Intercuneiform and (iv) The Cuneo-cuboid A^'ticulations
Class. — Diarthrosis. Subdivision — Arthrodia.
The uniting ligaments of these bones are divided into three sets : —
Dorsal. Plantar.
Interosseous.
The dorsal ligaments are three in number, two, the dorsal intercuneiform, connecting the
three cuneiform bones, and a thhd, the dorsal cuneo-cuboid, uniting the third cuneiform with
the cuboid. They pass between the contiguous margins of the bones, and are blended behind
with the dorsal ligaments of the cuboideo-navicular and cuneo-navicular joints.
The plantar ligaments are two in number: a very strong one, the plantar intercuneiform,
passes laterally and forward from the lateral side of the base of the first cuneiform to the apex
of the second cuneiform, winding somewhat to its lateral side. The second, the plantar cuneo-
cuboid, connects the apex of the third cuneiform with the anterior half of the medial surface of
the cuboid along its plantar border, joining with the plantar cuboideo-navicular hgament
behind.
The interosseous ligaments are three in number. They are strong and deep masses of
ligamentous tissue which connect the second cuneiform with the first and third cuneiform bones,
and the third cuneiform with the cuboid; occupying all the non-articular portions of the apposed
surfaces of the bones. The ligaments extend the whole vertical depth between the second cunei-
form and the third, and the third cuneiform and the cuboid, and blend with the dorsal and
plantar ligaments; they are situated in front of the articular facets, and completely shut off
the synovial cavity behind from that in front. The hgament between the first and second cunei-
form bones occupies the inferior and anterior two-thirds of the apposed surfaces, and does not
generally extend high enough to separate the synovial cavity of the anterior tarsal joint from that
of the second and third metatarsal and cuneiform bones. If it does extend to the dorsal sur-
face, it divides the facets completely from one another, making a seventh synovial sac in the
foot.
The synovial cavity will be described later on.
The arterial supply is from the metatarsal and plantar arteries.
The nerves are derived from the deep peroneal and medial and lateral plantar.
The movement permitted in these joints is very limited, and exists only for the purpose of
adding to the general pliancy and elasticity of the tarsus without allowing any sensible
alteration in the position of the dilferent parts of the foot, as the medio-tarsal and talo-cal-
caneal joints do. It is simply a gUding motion, and either deepens or widens the transverse
arch. The third cuneiform being wedged in between the others is less movable, and so forms
a pivot upon which the rest can move. The movement is more produced by the weight of
the body than by direct muscular action; and of the muscles attached to this part of the
tarsus, all deepen the arch save the tibiahs anterior, which pulls the first cuneiform up, and
so tends to widen it.
THE TARSAL JOINTS
305
(c) The Tbansverse Tarsal Joints
The articulations of the anterior and posterior portions of the tarsus, although
in the same transverse line, consist of two separate joints, viz., (i) a medial, the
talo-navicular, which communicates with the anterior talo-calcaneal articulation;
and (ii) a lateral, the calcaneo-cuboid, which is complete in itself. The move-
ments of the anterior upon the posterior portions of the foot take place at these
joints simultaneously. It will be most convenient to deal with the joints sepa-
rately as regards the ligaments; while the arteries, nerves, and movements will
be considered together.
(i) The Talo-navicular Articulation
Class. — Diarthrosis. Subdivision. — Enarthrodia.
This is the only ball-and-socket joint in the tarsus. It communicates with
the anterior talo-calcaneal articulation, and two of the ligaments which close it in
do not touch the talus, but pass from the calcaneus to the navicular. The uniting
ligaments include, in addition to the articular capsule, the following: —
Lateral calcaneo-navicular.
Plantar calcaneo-navicular
Talo-navicular.
The lateral calcaneo-navicular has been already described (p. 302).
The plantar calcaneo-navicular ligament (figs. 335 and 336) is an exceedingly dense, thick
plate of fibro-elastio tissue. It extends from the sustentaculum tali and the under surface of
the calcaneus in front of a ridge curving laterally to the anterior tubercle of that bone, to the
Fig. 335. — View of the Foot from above, with the Talus removed to show the Plantar
AND Lateral Calcaneo-navicular Ligamenti?
Dorsal cuboideo-navicular ligament
Dorsal calcaneo-cuboid ligament'
Medial calcaneo-cuboid ligament*
Lateral calcaneo-navicular ligament'
Plantar calcaneo-navicular
ligament
Tendon of tibialis posterior
Cut edge of interosseous ligament'
whole width of the inferior surface of the navicular, and also to the medial surface of the navicular
behind the tubercle. Medially it is blended with the anterior portion of the deltoid ligament of
the ankle, and laterally with the lower border of the lateral calcaneo-navicular hgament. It
is thickest along the medial border. Its upper surface loses the well-marked fibrous appear-
ance which the ligament has in the sole, and becomes smooth and faceted. In contact
with the under surface of the ligament the tendon of the libialis posterior passes, giving consider-
able support to the head of the talus by assisting the power and protecting the spring of the
ligament. The fibres of the ligament run forward and mediaUy. On account of its elasticity it
is sometimes termed the spring ligament.
306
THE ARTICULATIONS
The talo -navicular ligament is a broad, thin, but well-marked layer of fibres which passes
from the dorsal and lateral surfaces of the neck of the talus to the whole length of the dorsal
surface of the navicular. Many of the fibres converge to their insertion on the navicular. The
fibres low down on the lateral side blend a little way from their origin with the upper edge of
the lateral calcaneo-navicular ligament, and then pass forward and medially to the navicular;
those next above pass obliquely and with a distinct twist over the upper and lateral side of the
head of the talus to the centre of the dorsum of the navicular, overlapping fibres from the medial
side of the talus as well as some from the anterior ligament of the ankle-joint.
Synovial membrane. — The talo-navicular is lined by the same synovial membrane as the
anterior talo-calcaneal joint.
(ii) The Calcaneo-cuboid Articulation -
Class. — Diarthrosis.
Subdivision. — Saddle-shaped Arthrodia.
The ligaments which are supplementary to the articular capsule and unite
the bones forming the outer part of the medio-tarsal joint are: —
Medial calcaneo-cuboid.
Long plantar.
Dorsal calcaneo-cuboid.
Plantar calcaneo-cuboid.
The medial calcaneo-cuboid ligament (fig. 335) is a strong band of fibres attached to the
calcaneus along the medial jiiirt ol' the non-articular ridge above the articular facet for the cuboid,
and also to the upper part of tlie medial surface close to the articular margin, and passes forward
to be attached to the depression on the medial surface of the cuboid, and also to the rough angle
Fig. 336. — Ligaments op the Sole of the Left Foot.
Long plantar ligament
Tendon of peroneuslongus
Groove for flexor hallucis longus
Plantar calcaneo-navicular ligament
_U ^Plantar calcaneo-cuboid
(short plantar) ligament
' "A — Tubercle of navicular
"".if
Medial cuneiform
Insertion of peroneus longus
between the medial and inferior surfaces. At the calcaneus this ligament is closely connected
with the lateral calcaneo-navicular Mgament. Toward the sole it is connected with the plantar
calcaneo-cuboid ligament, and superiorly with the dorsal calcaneo-cuboid.
The dorsal calcaneo-cuboid (fig. 335) is attached to the dorsal surfaces of the two bones,
extending low down laterally to blend with the lateral part of the plantar calcaneo-cuboid
ligament. Over the medial half, or more, the ligament stretches some distance beyond the mar-
gins of the articular surfaces, reaching well forward upon the cuboid to be attached about
midway between its anterior and posterior borders; but toward the lateral side, the ligament
is much shorter, and is attached to the cuboid behind its tubercle.
TARSO-METATARSAL JOINTS 307
The long plantar ligament (fig. 336) is a strong, dense band of fibres which is attached pos-
teriorly to the whole of the inferior surface of the calcaneus between the posterior tubercles and
the rounded eminence (the anterior tubercle) at the anterior end of the bone. Most of its fibres
pass directly forward, and are fixed to the lateral two-thirds or more of the oblique ridge behind
the peroneal groove on the cuboid, while some pass further forward and medially, expanding
into a broad layer, and are inserted into the bases of the second, thu-d, fourth, and medial half
of the fifth metatarsal bones. This anterior expanded portion completes the canal for the
peroneus hiugiiK tvndnn, and from its under surface arise the oblique adductor hallucis and the
flexor quinii iliijili lircris muscles.
The plantar calcaneo-cuboid (short plantar) (fig. 336) is attached to the rounded eminence
(anterior tubercle) at the anterior end of the under surface of the calcaneus, and to the bone in
front of it, and then takes an oblique course forward and medially, and is attached to the whole
of the depressed inferior surface of the cuboid behind the oblique ridge, except its lateral angle.
It is strongest near its lateral edge, and is formed by dense strong fibres.
The synovial membrane is distinct from that of any other tarsal joint.
The arterial supply of the medio-tarsal joints is from the anterior tibial, from the tarsal
and metatarsal branches of the dorsalis pedis, and from the plantar arteries.
The nerve-supply of the medio-tarsal joints is from the lateral division of the deep
peroneal, and occasionally from the superficial peroneal or lateral plantar.
Relations. — On the dorsal aspect of the mid-tarsal joint lie the tendons of the tibialis
anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius, the muscular
part of the extensor digitorum brevis, the dorsalis pedis artery, and the anterior tibial nerve.
On its plantar aspect are the tendons of the flexor digitorum longus and hallucis longus, quadratus
plantse (accessorius), and the medial and lateral plantar vessels and nerves. It is crossed later-
ally by the tendons of the peroneus longus and brevis and medially by the tendon of the tibialis
posterior.
The movements which take place at the medio-tarsal joints are mainly flexion and extension,
with superadded side-to-side and rotatory movements. Flexion at these joints is simultaneous
with extension of the ankle, and vice versa. Flexion and extension do not take place upon a
transverse, but round an oblique, axis which passes from the medial to the lateral side, and some-
what backward and downward through the talus and calcaneus.
Combined with flexion and extension is also some rotatory motion round an antero-posterior
axis which turns the medial or lateral border of the foot upward. There is also a fail' amount
of side-to-side motion whereby the foot can be inclined medially (i. e., adducted) or laterally
(i. e., abducted).
These movements of the medio-tarsal joint occur in conjunction with those of the ankle'
a,nd talo-calcaneal joints. Rotation at the talo-calcaneal joint is, however, round a vertical
axis in a horizontal plane, and so turns the toes medially or laterally; whereas at the medio-
tarsal union the axis is antero-posterior and the medial or lateral edge of the foot is turned up-
ward. Gliding at the talo-calcaneal joint elevates or depresses the edge of the foot, while at
the medio-tarsal it adducts or abducts the toes without altering the relative position of the cal-
caneus to the talus.
Thus flexion at the medio-tarsal joint is associated with adduction and medial rotation
of the foot, occurring simultaneously with extension of the ankle; and extension at the medio-
tarsal joint is associated with abduction and lateral rotation, occurring simultaneously with
flexion of the ankle.
Flexion and medial rotation are far more free than extension and lateral rotation, which
latter movements are arrested by the ligaments of the sole as soon as the foot is brought into the
position in which it rests on the ground.
Although the talo-navicular is a baU-and-socket joint, yet, owing to the union of the
navicular with the cuboid, its movements are limited by the shape of the calcaneo-cuboid joint;
this latter being concavo-convex from above downward, prevents rotation round a vertical axis,
and also any side-to-side motion except in a direction obliquely downward and mediaUy, and
upward and laterally. This is also the direction of freest movement at the talo-navicular joint.
Movement is also limited by the ligamentous union of the calcaneus with the navicular. The
twisting movement of the foot, such as turning it upon its medial or lateral edge, and the increase
or diminution of the arch, take place at the tarsal joints, especially the medio-tarsal and talo-
calcaneal articulations. Here too those changes occur which, owing to paralysis of some mus-
cles or contraction of others, result in talipes equino-varus, or valgus.
Muscles which act on the mid-tarsal joint. — Medial rotators. — Tibialis anterior and posterior
acting simultaneously; they are aided by the flexor digitorum longus and flexor hallucis longus.
Lateral rotators. — The peronei longus, brevis, and tertius, acting simultaneously. They are
aided by the extensor digitorum longus.
6. THE TARSO-METATARSAL ARTICULATIONS
There may be said to be three articulations between the tarsus and metatarsus,
viz. : —
(a) The medial, bet'ween the first cuneiform and first metatarsal bones.
(6) The intermediate, between the three cuneiform and second and third
metatarsal bones.
(c) The lateral, or cubo-metatarsal, between the cuboid and fourth and fifth
metatarsal bones.
308 THE ARTICULATIONS
(a) The Medial Taeso-metatarsal Joint
Class. — Diarthrosis. Subdivision. — Arthrodia.
A complete articular capsule unites the first metatarsal with the first cunei-
form, the fibres of which are very thick on the inferior and medial aspects; those
on the lateral side pass from behind forward in the interval between the interos-
seous ligaments which connect the two bones forming this joint with the second
metatarsal. The ligament on the plantar aspect is by far the strongest, and
blends at the cuneiform bone with the cuneo-navicular ligament.
(6) The Intermediate Taeso-metatarsal Joint
Class. — Diarthrosis. Subdivision. — Arthrodia.
Into this union there enter the three cuneiform and second and third meta-
tarsal bones, which are bound together by the following ligaments (supplementary
to the articular capsule) : dorsal, plantar, interosseous.
The dorsal ligaments. — 1. Some short fibres cross obliquely from the lateral edge of the
first cuneiform bone to the medial border of the base of the second metatarsal bone; they take
the place of a dorsal metatarsal hgament, which is wanting between the first and second meta-
tarsal bones.
2. Between the second cuneiform and the base of the second metatarsal bone some fibres
run directly forward.
3. The third cuneiform is connected with (1) the lateral corner of the second metatarsal
bone by a narrow band passing obliquely medially; (2) with the third metatarsal by fibres
passing directly forward; and (3) with the fourth metatarsal by a short band passing obUquely
laterally to the medial edge of its base.
The plantar ligaments. — A strong hgament unites the first cuneiform and the bases of the
second and third metatarsal bones. The tibialis posterior is inserted into these bones close
beside it. Other slender ligaments connect the second cuneiform with the second, and the third
cuneiform with the third metatarsal bones.
The interosseous ligaments. — (1) A strong broad interosseous hgament extends between
the lateral surface of the first cuneiform and the medial surface of the base of the second meta-
tarsal bone. It is attached to both bones below and in front of the articular facets, and sepa-
rates the intermediate [from the medial tarso-metatarsal joint. (2) A second band is attached
behind to a fossa on the anterior and lateral edge of the third cuneiform and to the interosseous
ligament between it and the cuboid, and passes horizontally forward to be attached to the whole
depth of the fourth metatarsal bone behind its medial facet, and to the opposed surfaces of the
third and fourth below the articular facets upon their sides. It separates the middle tarso-
metatarsal, and intermetatarsal between the third and fourth bones, from the oubo-metatarsal
joint. It is more firmly connected with the third bone than with the fourth. (3) A slender
ligament composed only of a few fibres often passes from a small tubercle on the medial and an-
terior edge of the third cuneiform to a groove on the lateral edge of the second metatarsal bone
between the two facets upon then- sides.
The synovial membrane is prolonged forward from that of the naviculari-cuneiform and
inter-cuneiform articulations.
The arteries for the tarso-metatarsal joints are derived: — (1) for the medial, from the dor-
saUs pedis and medial plantar; (2) for the rest, twigs from the arcuate and deep plantar arch.
The nerve-supply comes from the deep peroneal and plantar nerves.
The movements permitted at these joints are flexion and extension of the metatarsus on
the tarsus; and at the medial and lateral divisions, slight adduction and abduction. In the
lateral, the side-to-side motion is freer than in the medial joint, and freest between the fifth
metatarsal bone and the cuboid. In the medial joint, flexion is combined with sUght abduction
and extension with abduction.
There is also a little gliding, which aflows the transverse arch to be increased or diminished
in depth; the medial and lateral two bones sliding downward, and the two middle a little
upward, when the arch is increased; and vice versa when the arch is flattened.
(c) The Lateral or Cubo-metatarsal Joint
Class. — Diarthrosis. Subdivision. — Arthrodia.
The bones comprising this joint are the fourth and fifth metatarsal and the
anterior surface of the cuboid, firmly connected on all sides by the articular cap-
sule, strengthened by the following ligaments: —
Dorsal. Plantar. Interosseous.
The plantar cubo-metatarsal ligament is a broad, well-marked ligament, which extends
from the cuboid behind to the bases of the fourth and fifth metatarsal bones in front. It is
INTERMETATARSAL JOINTS
309
continuous along the groove at the base of the fifth metatarsal bone with the dorsal ligament,
and as it passes round the lateral border of the foot it is somewhat thickened, and may be de-
scribed as the lateral cubo-metatarsal ligament. On its medial side it joins the interosseous
ligaments, thus completing the capsule below. It is not a thick structure, and to see it the long
plantar ligament, the peroneus longus, and lateral slip of the tibialis posterior must be removed;
the attachment of these structures to the fourth and fifth metatarsal bones considerably assists
to unite them with the tarsus.
The dorsal cubo-metatarsal ligament is composed of fibres which pass obliquely outward
and forward from the cuboid to the bases of the fourth and fifth metatarsal bones. They com-
plete the capsule above, and are continuous laterally with the lateral cubo-metatarsal hgament.
The interosseous ligament shuts off the cubo-metatarsal from the middle tarso-metatarsal
joint. It is attached to the third cuneiform behind, and to the whole depth of the fourth meta-
tarsal behind its medial facet, and to the apposed surfaces of the third and fourth bones below
their articular facets. It is continuous below with the plantar ligament.
The synovial membrane is separate from the other synovial sacs of the tarsus, and is con-
tinued between the fourth and fifth metatarsal bones.
Relations. — The line of the tarso-metatarsal joints is crossed dorsally by the tendons of
the long and short extensor muscles of the toes and the tendon of the peroneus tertius. On
the plantar aspect it is in relation with the obUque adductor of the great toe, the short flexor
of the great toe, the lateral plantar artery, and the tendon of the peroneus longus. Its medial
end is subcutaneous except that it is crossed, near the plantar surface, by a slip of the tendon
of the tibialis anterior, and its lateral end is crossed by the tendon of the peroneus brevis.
Fig. 337. — Section to show the Synovial Cavities op the Foot.
7. THE INTERMETATARSAL ARTICULATIONS
Class. — Diarthrosis.
Sub division. — A rthrodia .
The bases of the metatarsal bones are firmly held in position by dorsal, plantar,
and interosseous ligaments, supplementing the articular capsules. The first
occasionally articulates by means of a distinct facet with the second metatarsal
(figs. 245 and 246).
The dorsal ligaments are broad, membranous bands passing between the four lateral toes
on their dorsal aspect; but in place of one between the first and second metatarsal bones, a
ligament extends from the first cuneiform to the base of the second metatarsal bone.
The plantar ligaments are strong, thick, well-marked ligaments which connect the bones on
their plantar aspect.
The interosseous ligaments are three in number, very strong, and are situated at the points
of union of the shaft with the bases of the bones, and fill up the sulci on their sides. They limit
the synovial cavities in front of the synovial facets.
The common synovial membrane of the tarsus extends between .the second and third, and
third and fourth bones; that of the cubo-metatarsal joint extending between the fourth and fifth.
The arterial and nerve-supply is the same as for the tarso-metatarsal joints.
The movements consist merely of gliding, so as to allow the raising or widening of the
transverse arch. Considerable flexibihty and elasticity are thus given to the anterior part of
the foot, enabling it to become moulded to the irregularities of the ground.
The Union of the Heads of the Metatarsal Bones
The heads of the metatarsal bones are connected on their plantar aspect by
the transverse ligament [Ligg. capitulorum transversa], consisting of four bands
310 THE ARTICULATIONS
. of fibres passing transversely from bone to bone, blending witli the fibro-cartilagi-
nous or sesamoid plates of the metatarso-phalangeal joints, and the sheaths of the
flexor tendons where they are connected witli the fibro-cartilages. It differs
from the corresponding ligament in the hand by having a band from the first to
the second metatarsal bone.
8. THE METATARSO-PHALANGEAL ARTICULATIONS
(0) The Metatarso-phalangeal Joints op the Four Lateral Toes
Class. — Diarthrosis. Subdivision. — Condylarthrosis.
These joints are formed by the concave proximal ends of the first phalanges
articulating with the rounded heads of the metatarsal bones, and united by
articular capsules strengthened by the following ligaments: —
Collateral. Dorsal. Plantar accessory.
The two collateral ligaments are strong bands passing from a ridge on each side of the head
of the metatarsal bone to the sides of the proximal end of the first phalanx, and also to the sides
of the sesamoid plate which unites the two bones on their plantar surfaces. On the dorsal
aspect they are united liy the dorsal ligament.
The dorsal ligament consists of loose fine fibres of areolo-fibrous tissue, extending between
the collateral ligaments, thus completing a capsule. It is connected by fine fibres to the \inder
surface of the extensor tendons, which pass over and considerably strengthen this portion of the
capsule.
The plantar accessory ligament or sesamoid plate helps to deepen the shallow facet of the
phalanx for the head of the metatarsal bone, and corresponds to the accessory volar ligament of
the fingers. It is firmly connected to the collateral Ugaments and the transverse ligament, and
is grooved inferiorly where the flexor tendons pass over it. It serves to prevent dorsal disloca-
tion of the phalanx.
The second metatarso-phalangeal joint is 6 mm. (J in.) in front of both the first and third
metatarso-phalangeal joints.
The third metatarso-phalangeal joint is 6 mm. (J in.) in front of the foui-th, and the fourth
9 mm. (I in.) in front of the fifth.
The head of the fifth metatarsal is in line with the neck of the fourth.
Thus the lateral side of the longitudinal arch of the foot is shorter than the medial, it is
also distinctly shallower.
(b) The Metatarso-phalangeal Joint of the Great Toe
The metatarso-phalangeal joint of the great toe differs from the rest in the
folloTftdng particulars : —
(1) The bones are on a larger scale, and the articular surfaces are more extensive.
(2) There are two grooves on the plantar surface of the metatarsal bone, one on each side
of the median hne, for the sesamoid bones.
(3) The sesamoid bones replace the accessory plantar ligament (sesamoid plate). They
are two small hemispherical bones developed in the tendons of the flexor hallucis brevis, convex
below, but flat above where they play in grooves on the head of the metatarsal bone; they are
united by a strong transverse hgamentous band, which is smooth below and forms part of the
channel along which the long flexor tendon plays. They are firmly united to the base of the
phalanx by strong short fibres, but to the metatarsal bone they are joined by somewhat looser
fibres. At the sides they are connected with the collateral ligaments and the sheath of the flexor
tendon. They provide shifting leverage for the flexor hallucis brevis as well as for the flexor
hallucis longus.
The arteries come from the digital and metatarsal branches ; and the nerves from the cuta-
neous digital, or from small twigs of the nerves to the interossei muscles.
The movements permitted are: flexion, extension, abduction, adduction, and circumduction.
Flexion is more free than extension, and is limited by the extensor tendons and dorsal liga-
ments; extension is limited by the flexor tendons, the plantar fibres of the collateral ligaments,
and the sesamoid plates. The side-to-side motion is possible from the shape of the bony surfaces,
but is very limited, being most marked in the great toe. It is limited by the collateral ligaments
and sesamoid plates.
9. THE INTERPHALANGEAL JOINTS
Class. — Diarthrosis. Subdivision. — Ginglymus.
The articulations between the first and second and second and third phalanges
of the toes are similar to those of the fingers, with this important difference, that
INTERPHALANGEAL JOINTS 311
the bones are smaller and the joints, especially between the second and third
phalanges, are often ankylosed. The ligaments which unite them include, in
addition to the articular capsule : —
Collateral. Dorsal. Accessory plantar.
The two collateral ligaments are well marked, and pass on each side of the joints from a
little rough depression on the head of the proximal, to a rough border on the side of the base of
the distal phalanx of the joint.
The dorsal ligament is thin and membranous, and extends across the joint from one col-
lateral ligament to the other beneath the extensor tendon, with the deep surface of which it is
connected and by which it is strengthened.
The accessory plantar ligament covers in the joint on the plantar surface. It is a fibro-
cartilaginous plate, connected at the sides with the collateral hgaments, and with the bones by
short ligamentous fibres; the plantar surface is smooth, and grooved for the flexor tendons.
The arteries and nerves are derived from the corresponding digital branches.
The only movements permitted at these joints are flexion and extension.
At the interphalangeal joint of the great toe there is very frequently a small sesamoid bone
which plays on the plantar surface of the first phalanx, in the same way as the sesamoid bones
of the metatarso-phalangeal joint play upon the plantar surface of the head of the metatarsal
bone.
Relations of the muscles acting on the metatarso-phalangeal and interphalangeal joints
of the foot. — If the student will refer to the accounts given of the relations of the corresponding
joints in the hand and of the actions of the muscles upon those joints, and if he contrasts and
compares the muscles of the hand with those of the foot, he will readily be able to construct
tables of the relations of the metatarso-phalangeal and interphalangeal joints of the foot, and
tables of the muscles acting upon the joints.
References. — A complete bibliography for the joints is given in the "Hand-
buch der Anatomie und Mechanik der Gelenke," by Professor Rudolf Tick (in von
Bardeleben's Handbuch der Anatomie). References are also given in the larger
works on human anatomy by Quain, Rauber-Kopsch, Poirier-Charpy, etc.
References to the most recent literature may be found in Schwalbe's Jahres-
bericht, the Index Medicus and the various anatomical journals.
SECTION IV
THE MUSCULATURE
Revised fob the Fifth Edition
By C. R. BARDEEN, A.B., M.D.
PROFESSOR OF ANATOMY IN THE UNIVERSITT OF WISCON SIN
MUSCLES, the movements of which are under the control of the will, almost
completely envelope the skeletal framework of the body; close in the oral,
abdominal, and pelvic cavities; separate the thoracic from the abdominal
cavity; surround the pharynx and the upper portion of the cesophagus; and are
found connected with the eye, ear, larynx, and other organs. They constitute
about two-fifths to three-sevenths of the weight of the body.
In this section an account is given of the gross anatomy of the musculature
attached to the skeleton and the skin, with the exception of certain of the
muscles which are more conveniently treated in connection with the organs to
which they are appended. Thus, the muscles of the eye, the ear, the pharynx,
the larynx, and the intrinsic muscles of the tongue are described in the sections
devoted to those structures.
Relations to the skin. — Beneath the skin is a sheet of connective tissue, the
tela subcutanea. In this, in some regions of the body (the head, neck, and palm),
thin, flat, subcutaneous muscles are embedded. Superficial muscles of this kind
constitute a panniculus carnosus, much more extensive in the lower mammals than
in man. The tela subcutanea is separated from the more deeply seated muscu-
latiu-e by areolar tissue, which, in most places, is loose in texture over the muscles.
In some regions, as over the upper part of the back, the tela subcutanea is firmly
united to the underlying musculature and is less freely movable. In the tela sub-
cutanea more or less fat is usually embedded. This constitutes the panniculus
adiposus, which varies greatly in thickness in different parts of the body. As a
rule, it is much more developed over muscles than over those regions where bone
and joints lie beneath the skin. From the tela subcutanea of the eyelids, penis,
and scrotum fat is absent. The deeper layer of the tela subcutanea is more or less
free from fat, and in it run the main trunks of the cutaneous nerves and vessels.
In some regions, as over the lower part of the abdomen, one or more fibrous mem-
branes are differentiated in this deeper layer.
To the tela subcutanea the term superficial fascia has been commonly applied, but since
this leads to a confusion with the superficial fascia; which immediately invest the muscles, it
seems better to restrict the term fascia to the membranes connected with the muscular system,
and to use the term tela subcutanea for the layer of connective tissue which underlies the skin
and is continuous over the whole surface of the body.
In several places where the skin overlies bony prominences well-marked
synovial bursse, or sacs (bursae mucosae), are developed in the tela subcutanea.
Since the skin and the subcutaneous tissue must be removed in order to study
the muscles of various regions, the tela subcutanea and subcutaneous bm-sse may
be conveniently described in connection with the muscles, and brief references will,
therefore, be made to them in connection with the musculature of various regions.
Muscle fasciae. — The musculature of the body, with the exception of some of
the subcutaneous muscles, is ensheathed by fibrous tissue, which, in certain regions
forms distinct membranes, while in other regions it is delicate and not clearly to be
distinguished from the superficial connective tissue of the muscles, the perimy-
313
I
314 THE MUSCULATURE
sium externum. The membranes, or muscle fasciae, are united to various parts
of the skeleton, eitlaer directly or by means of intermuscular septa, and, where
strong, keep the underlying musculature in place. In some regions they are united
to the muscles; in others they are separated from the underlying musculature by
loose areolar tissue, which allows free movement between the surface of the mus-
cles and the overlying fascia. The best example of a strong fascia of this nature
is that which envelopes the extensor muscles of the thigh. Where the fasciee are
well developed, the main bundles of constituent fibres take a course directly or
obliquely transverse to the direction of the underlying muscles. They may be
composed of several successive layers of fibrous tissue, the fibres of one layer tak-
ing a different direction from those of the next layer.
The function of the fascicS is the mechanical one of restraining or modifying muscle action.
The direction of the main component fibre-bundles indicates the direction of the greatest stress
to which the fascia? are subjected. Indirectly the fasciae promote the circulation of the blood
and lymph in places where the vessels lie between the contracting muscles and the overlying
fascia.
Intermuscular septa. — Muscle fasciae enclose not only the external layer
of the musculature of the body, but also the various groups of more deeply
seated muscles. In addition, between the individual muscles, and between the
different layers and groups of muscles, there intervenes a greater or less amount of
connective tissue, sometimes loose in texture, sometimes dense in structure. In
these intermuscular septa run the chief nerves and blood-vessels of the region in
which the musculature lies.
Gross structure of the muscles. — The muscles are composed of bundles of red-
dish fibres surrounded by a greater or less extent of white and glistening connective
tissue. They are attached by prolongations of this tissue in the form of tendons
or aponeuroses usually to the bony skeleton, but also in places to cartilages, as in
the thorax and larynx; to the skin, as in the face; to mucous membranes, as in the
tongue and cheeks; to the tendons of other muscles, as in the case of the lumbrical
muscles; to muscle fasciae, as in the case of the oblique and transverse muscles of
the abdomen; and to other structures, as, for instance, to the eyeball.
The fleshy portion of the muscle is called the belly. The belly is usually
attached at one extremity to a portion of the skeleton or to some other structure
which serves as a support for its action on the structures to which its other ex-
tremity is attached. The attachment to the more fixed part is called the origin of
the muscle; the attachment to the structure chiefly acted on is called the insertion.
Thus the origin of the biceps muscle, the chief flexor of the forearm at the elbow,
is from the scapula; the insertion is into the radius and into the fascia of the fore-
arm. The part of the muscle attached to the origin is called the head of the mus-
cle. The part attached to the insertion is sometimes called the tail, but this term
is much less frequently used than the former.
The muscles vary greatly in size and form. Thus the stapedius muscle of the
middle ear is a slender little structure, only a few millimetres long, while the glu-
teus maximus muscle of the hip is a large, rhomboid structure often several centi-
metres thick and with a surface area of over 500 square centimetres. The length
of a muscle from origin to insertion may be much less than the width of the muscle,
as in the intercostal muscles; or much greater than the width, as in most of the
long muscles of the limbs. The thickness of a muscle is usually less than the width
— so much so in some instances that the muscle is described as flat, sheet-like, or
ribbon-like; while in other instances the belly is cylindrical. In flat muscles the
general outline is usually quadrilateral or triangular. In triangular muscles in
most instances one angle of the triangle marks the insertion of the muscle, while
the opposite side marks the origin. In cylindrical muscles the belly usually has a
somewhat fusiform shape, and grows smaller both toward the origin and the in-
sertion of the muscle.
Some muscles are divided by tendons transverse to the long axis of the muscle.
When one such tendon exists, the muscle is called digastric (fig. 348) ; when sev-
eral, polygastric, e. g., rectus abdominis (fig. 388).
Two muscle masses with separate origins may have a common insertion. Such
muscles are usually designated bicipital muscles (biceps muscles of the arm and
thigh). Other muscles have three heads (the triceps muscle of the arm) or four
(the quadriceps muscle of the thigh). In the latter case special names are given
FINER STRUCTURE OF MUSCLES 315
to the four parts or muscles which constitute the quadriceps as a whole. In ad-
dition to these comparatively simple compound muscles there are others in which
the various component fasciculi and the tendons of origin and insertion are numer-
ous and complexly interrelated. The intrinsic muscles of the back offer good
illustrations of muscles of this nature.
In addition to muscles with distinct regions of origin and insertion, there are a
few voluntary muscles which surround hollow viscera or their orifices and have a
circular or tube-like form (sphincter muscles, voluntary muscles of the oesophagus,
■etc.).
Number of muscles. — A logical constancy does not appear always to have been
followed in the commonly accepted division of the musculature into muscles indi-
vidually designated. Most of the muscles are symmetrically placed in pairs, one
on each side of the body. Authors not only vary in the extent to which they carry
the subdivisions of the musculature on each side of the body into individual
muscles, but also in describing muscles placed near the median line either as single
muscles with bilateral halves or as paired muscles. In addition some muscles are
not constantly present, and there are differences of opinion as to which of these less
constant muscles should be classed with the normal musculature. The BNA
recognises 347 paired and two unpaired skeletal muscles, and 47 paired and two
unpaired muscles belonging to the visceral system and organs of special sense.
Of the skeletal muscles the head has 25 paired and one unpaired; the neck 16
paired; the back 112 paired; the thorax 52 paired, one unpaired; the abdomen and
pelvis 8 paired; the upper extremity, 52 paired; the lower extremity, 62 paired
(Eisler).
Finer structure of muscles. — While no attempt can be made here to describe in detail the
finer microscopic features of muscle structure, some of the more general features of muscle
architecture may be briefly mentioned.
The contractile cells of voluntary muscle are long, slender, multinucleated 'fibres,' the pro-
toplasm of which exhibits both cross and longitudinal striation. The longitudinal striation
is due to the presence of fibrils situated in the sarcoplasma. The cross striation is due to alter-
nate segments of singly and doubly refracting substance in these fibrils. The length of these
fibres in the human body varies from a few millimetres to sixteen centimetres or more, and the
thickness from ten to eighty microns. Each muscle-fibre is surrounded by an especially differ-
entiated sheath, the sarcolemma. Outside of this is a layer of delicate connective tissue, the
perimysium internum or endomysium, the fibres of which are in part inserted into the sarco-
lemma. This connective tissue, which is especially developed at the ends of the fibres, serves to
.attach them either directly to the structures on which the muscle acts or to the skeletal frame-
work of the muscle.
In the simplest mammalian muscles the muscle-fibres take a parallel course from tendon to
tendon, and are not definitely bound into secondary groups. An example may be seen in fig.
338, a, which represents two segments of the rectus abdominis muscle of a mouse. More often,
however, the individual fibres do not run the entu-e distance from tendon to tendon, but instead
. they interdigitate, and the interdigitating fibres are bound up into secondary and tertiary
anastomosing fibre-bundles by connective tissue, in which there is usually a considerable amount
of elastic tissue. Fig. 338, b, represents diagrammatically this interdigitation of fibre-bundles as
seen in the abdominal musculature of one of the larger mammals.
In most of the flat muscles of the body the fibre-bundles either take a nearly parallel course
from tendon to tendon or they converge from the tendon of origin toward the tendon of insertion
(see fig. 338, c-e). The gi-eater the distance from tendon to tendon, the more marked is the
interdigitation of the constituent fibre-bundles.
In elongated muscles the tendons of origin and insertion may either arise near the extremities
of the muscle or may extend for a considerable distance on the surface or within the substance of
the muscle. In the former case the belly of the muscle is composed of bundles of interdigitating
fibres which take a course parallel with the long axis of the muscle. This is shown diagi'ammatic-
ally in fig. 338, f. An example may be seen in the sartorius muscle of the thigh (fig. 411).
When the tendons extend far on the surface or within the substance of the muscle, the con-
stituent fibre-bundles take a course oblique to the long axis of the muscle. When they take a
course from a tendon of origin on one side toward a tendon of insertion on the other, the muscle
is called unipenniform (see fig. 338, g, and the extensor digitorum longus, fig. 415). In other
instances the fibre-bundles converge from two sides toward a central tendon. Such a muscle
is called bipenniform (see fig. 338, h, and the flexor hallucis longus, fig. 416). When there
are several tendons in the muscle between which the fibre-bundles run obliquely, the muscle
is called multipenniform. In fusiform muscles the tendons usually either embrace the ex-
tremity of the muscle like a hollow cone, or they extend far on the surface or within the sub-
stance of the muscle. In such muscles the fibre-bundles take a curved course from one tendon
to the other. The bundles which arise highest on one tendon are inserted highest on the other,
and the fibre-bundles of lowest origin have the lowest insertion. This structm-e is diagram-
matically shown in fig. 338, i. A good example may be found in the rectus femoris muscle
(fig. 411).
Many other arrangements of the fibre-bundles are found, and the arrangements here shown
may be variously combined. In most muscles the architecture is decidedly complex. In the
316
THE MUSCULATURE
more complex muscles dense connective-tissue septa, or intramuscular fasciae, serve to separate
different regions of the muscle from one another. In general there are groups of muscle fibre-
bundles surrounded by a greater amount of connective tissue, or perimysium internum, than that
surrounding the individual fibre-bundles, and the latter are surrounded by a denser connective
Fig. 338. — Diagrammatic Outlines to Illustrate Various Types op Muscle Archi-
tecture AND THE Relations of the Main Nerve Branches to the Fibre-bundles op
THE Muscle.
a. Two segments of the rectus abdominis muscle of a small mammal, b. Portion of sheet-like
muscle with two nerve-branches and intramuscular nerve plexus, c. Typical quadrilateral
muscle with nerve passing across the muscle about midway between the tendons, d and e.
Two triangular muscles with different types of innervation, f. Long ribbon-like muscle
with interdigitating fibre-bundles, g. Unipenniforra muscle, h. Bipenniform muscle,
i. Typical fusiform muscle. The main intramuscular nerve-branches are distributed to the
fibre-bundles about midway between their origins and insertions, n. nerve.
>
V
tissue than that surrounding the component muscle-fibres. The muscles are surrounded exter-
nally by a more or less dense sheet of connective tissue called the perimysium externum, or
epimysium, which is continuous with the connective tissue within the muscle, the perimysium
internum. In the following pages 'muscle fibre-bundle' is used to denote small groups of
muscle-fibres, 'fasciculus' to denote large, more or less isolated, groups of fibre-bundles.
Embryonic development of muscles. — The voluntary muscles are of mesodermal origin.
The muscles of the trunk arise chiefly from the myotomes, those of the head and limbs chiefly
from the mesenchyme in these regions. New muscle fibres are formed mainly before birth.
After birth, growth of muscles depends on growth of individual muscle fibres.
TENDONS 317
Tendons. — Muscles vary not only in general form and in the relations of the
constituent fibre-bundles to the intrinsic skeletal framework, but also in the mode
of attachment to the parts on which they act. In many instances the fibre-bun-
dles impinge, perpendicularly or obliquely, directly upon a bone or cartilage.
The tendinous tissue arising from the fibre-bundles of the muscle here is attached
to the periosteum or perichondrium or to the bone directly. A broad attachment
is thus offered the muscle. Instances of this mode of attachment may be seen in the
attachment of the intercostal muscles and of many of the muscles attached to the
shoulder and hip girdles.
In the case of most thin, flat muscles the muscle is continued at one or both
extremities into thin, tendinous sheets called aponeuroses, composed of connective
tissue. Well-marked instances may be seen in the transverse muscle of the abdo-
men (fig. 390), and the trapezius and latissimus dorsi muscles of the back (fig. 355) .
The extent of development of these aponeuroses is generally inversely proportional
to the development of the muscle — the more extensively developed the muscle is
in a given individual, the less extensive the aponeurotic sheet.*
Most muscles are continue,d at one or both extremities into dense, tendinous
bands which may be comparatively short and thick, like the tendon of Achilles
(fig. 413) , or very long and narrow, like the tendon of the palmaris longus (fig. 370) .
In this latter case the tendon represents in part the remnants of musculattu-e
more highly developed in the lower vertebrates. In most instances, however,
the tendons are structures specifically differentiated for definite functions and are
composed of bundles of parallel connective-tissue fibrils held together by an inter-
lacing fibrous-tissue framework. The tendons usually contain a relatively small
amount of elastic tissue.
The tendons are attached to the skeleton early in embryonic development.
As the bones enlarge the tendons become in part incorporated in the substance of
the bone and ossified.
In some tendons sesamoid bones are developed in the neighbourhood of joints
over which the tendons pass. Examples of these are the patella at the knee-joint
(fig. 412) and the sesamoid bones of the thumb and great toe.
Where muscles or tendons closely envelope a joint, there is usually formed a
close union between the connective tissue of the capsule of the joint and that of the
muscle or the tendon. Special bands may develop in the direction of the pull
of the muscle (lig. popliteum obhquum).
Where tendons run for some distance across or beneath a fascia, they are
usually either bound to the fascia by a special investment, as near the wrist and
knee (fig. 366 and fig. 414), or are fused with the fascia, as in the case of the ilio-
tibial band. Fibrous tracts in the fascia may indicate stress under muscle con-
traction (the lacertus fibrosus of the fascia of the forearm) .
Often in broad aponeurotic attachments of muscles there is formed in the ten-
don near the attachment a fibrous archway [arcus tendineus] for the passage of
blood-vessels, nerves, muscles, or tendons. The tendinous arch is either fastened
at both ends to the bone, or at one end it is connected with'a joint capsule or other
membrane. The dorsal attachment of the diaphragm (fig. 391) and that of the
adductor magnus to the femur (fig. 409) offer good examples of tendon arches.
In digastric and polygastric muscles the transverse tendons which separate
the bellies are often composed of narrow, incomplete bands of fibrous tissue.
Such a transverse band is called an inscriptio tendinea (see Rectus Abdominis
Muscle, fig. 388).
Tendon sheaths. — The tendons are held in place by sheaths composed of dense
connective tissue. These sheaths vary in different regions. In the most com-
plete form they confine tendons in osseous grooves which they convert into osteo-
fibrous canals on the flexor surface of the digits. The sheath is here called a
vagina fibrosa tendinis. It is strengthened by tendinous bands (vaginal liga-
ments). In other regions special dense bands or ligaments, retinacula tendinum,
confine a series of tendons in place, as at the ankle (fig. 417), or fasciae may be
modified for this purpose, as at the back of the wrist (fig. 366) . A tendinous loop,
* The terms fascia and aponeurosis are often loosely and interchangeably used. It seems
best to make a distinction by restricting the term fascia to membranous sheets of investment,
and aponeurosis to broad tendons. The latter may, however, be inserted into and form a part
of the former.
>
318 THE MUSCULATURE
annulus fibrosus, may hold a tendon in place, as, for instance, the trochlea of the
tendon of the superior oblique muscle of the eye.
Synovial bursas [bursae mucosae]. — Where there is freedom of action between
muscles and tendons and the surrounding parts, there intervenes a loose connective
tissue. In regions where the pressure is great or considerable friction would re-
sult were these conditions retained, there are developed special cavities with
smooth surfaces and containing fluid. Most of these bursas are developed from
the intervening connective tissue at a period in embryonic life preceding muscular
activity, but special bursas may later be developed as the result of unusual pressure
or muscular activity after birth. An instance of a bursa lying in a region of fric-
tion may be seen in the bur?a intervening between the tendinous posterior surface
of the ilio-psoas muscle and the ilio-femoral ligament. As an instance of a bursa
lying in a region of intermittent pressure may be cited that between the tendon of
Achilles and the calcaneus.
Most synovial burste intervene between a tendon and a bone, a tendon and a
ligament, or between two tendons (subtendinous bursse mucosae). Others lie be-
tween two muscles, a muscle and some skeletal part, or between a muscle and a
tendon (submuscular bursae mucosae) ; or below a fascia (subfascial bursae mu-
cosas). Subcutaneous bm-sse have been referred to in connection with the tela
subcutanea (see p. 313). Most bursas are developed near joints. The bursae may
so expand during active life that they come to communicate with other bursae or
with a neighbouring joint cavity.
Synovial sheaths [vaginae mucosae tendinum]. — Synovial sheaths are developed
about tendons where the latter are confined in osteo-fibrous canals, as in the
fingers. The wall of the canal and the enclosed tendon, or tendons, are each
covered by a smooth membrane which at the extremities of the canal is reflected
from the wall to the tendon. Between the membrane covering the tendon and
that lining the canal is a sjaiovial cavity. An interesting feature of these tendon-
sheaths is the presence of mesotendons, delicate bands of vascular connective
tissue which run in places from the osseous groove to the tendon and carrj^ blood-
vessels and nerves.
Trochlese. — Where a tendon passes at an angle about a bone, the tissue in the groove in
which the tendon runs frequently is composed of hj'aUne cartilage instead of bone. An example
may be seen in the trochlear process of the calcaneus.
Nerves. — To each muscle of the body a nerve containing motor and sensory
fibres is distributed. A few muscles receive two or more nerves. Sherrington has
estimated that in the muscle-nerves of the cat two-fifths of the fibres are sensory
and thi-ee-fifths motor.
The muscles of the liead and in part those of the neck are supplied by branches
of the cranial nerves. The intrinsic muscles of the neck, back, thorax, and abdo-
men are supplied by branches which arise fairljr directty from the spinal nerves.
The muscles of the limbs are supplied by branches from nerve-trunks which arise
from plexuses formed by the spinal nerves in the regions near which the limbs
are attached.
The main nerve-trunks lie beneath the superficial muscles. They usually run in the
intermuscular septa which separate the deeper groups of muscles from one another and from
the superficial muscles. The nerve-branches which enter a given muscle usually pass in where
the larger intramuscular septa approach the surface of the muscle, and then ramify tlu-ough
the perimysium internum, the smaller branches being distributed in the finer layers of connective
tissue which surround and separate the primary muscle fibre-bundles, to the constituent muscle-
fibres of which terminal branches are given. Special sensory end organs are distributed chiefly
in the large intramuscular septa, in the tendons and in the muscles near the tendons. Simple
sensory endings are found on the muscle fibres.
The size of a nerve supplying a muscle is not proportional to the size of the latter, but
rather to the comple.xity of movements in which the muscle plays a part.
Muscles receive then- nerve supply early in development. During later development the
muscle may wander a considerable distance from its place of origin and carry its nerve with it.
The diaphragm, innervated by cervical nerves, is a good example.
The distribution of the motor nerves varies according to the architectm-e of the muscle, but
in general it appears that the nerves are so distributed as to carry the main branches of distri-
bution most directly to the middle of the constituent fibre-bundles. This is seen most clearly in
muscles with comparatively short fibre-bundles, where the individual muscle-fibres run nearly
or quite the entire distance from tendon to tendon (fig. 338 a, c, d, e, g, h, and i). When the
distance is long, a marked plexiform arrangement is found (fig'. 338, b andf). To each muscle
NOMENCLATURE 319
fibre there is distributed a terminal nerve-fibre which passes through the sarcolemma and ends
in a motor end organ (muscle plate) . Occasionally there are two such nerve-fibres to one muscle-
fibre.
Vessels. — The muscles are richly supplied with blood. In many instances the
larger blood-vessels accompany the larger nerve-trunks as they enter the muscle,
and their primary branches are distributed in the larger intramuscular septa.
Often, however, the main blood-vessels approach a muscle from a direction dif-
ferent from that taken by the nerves. Each muscle has, however, its own blood
supply. There is little anastomosis between the blood-vessels of a muscle and
those of a neighbouring structure, but the anastomosis between the vessels within
the muscle is exceedingly rich. Veins, as a rule, accompany all but the smallest
arteries within the muscle. The veins are richly supplied with valves, so that
muscle contraction promotes the flow of blood through the muscle. Rich cap-
illary plexuses sm-round the muscle-fibres. The capillaries are of unusually
small diameter.
During contraction, the blood is forced from the muscles; during expansion
it rushes in through dilated arteries which furnish five or six times as much
blood to muscles during exercise as that supplied to them during rest.
The connective-tissue sheaths, the larger intramuscular septa, and the tendons
of muscles are richly supplied vnih. lymphatics. There are no lymphatics within
the muscle bundles or in small muscles.
Nomenclature. — The names of the various muscles and their classification are
less satisfactory than is desirable. The muscular system was first carefully
studied in the human body, and names based sometimes upon the shape, structure,
size, or position, at other times upon the supposed function or other associated
facts, were applied to the muscles found in various regions. Sometimes two or
more names were applied to a muscle to indicate several of these factors. Thus
trapezius and triangularis indicate the shape of the corresponding muscles; biceps
or triceps indicates the origin by two or three heads; rectus, obliquus, and irans-
versus represent the direction taken by a muscle or its constituent fibre-bundles;
viagnus and minimus indicate size; sublimis (superficial) and profundus (deep)
represent the relative positions occupied; sterno-cleido-mastoid indicates structures
to which the muscle is attached; flexor and extensor indicate function; and sar-
torius indicates that the corresponding muscle was supposed to be of use to tailors.
Since careful study has been devoted to the comparative anatomy of the muscles in
various vertebrates, it has become apparent that a simple and more consistent nomenclature
applicable to corresponding muscles found in various animals would be of great value. A
satisfactory nomenclature of this sort has not, however, as yet been devised and adopted in
comparative anatomy, and the established usage of the terms now familiarly apphed to the
muscles of the human body makes it seem improbable that even if such a system were devised
for comparative anatomy it could be brought into extensive use in human anatomy. For
many of the muscles in the human body various synonyms have been in use in different countries.
The Anatomical Congress assembled at Basel in 1895, to simpUf}' the nomenclature of human
anatomy, adopted in large part the terms in familiar use in England and America. In the
following pages the terms approved by the Congress wiU be employed, but where they differ
materially from those previously in use, the synonym wUl be given in parentheses.
Classification. — The muscles are usually treated strictly according to the region of the body
in which they are found. This method of consideration is still of value in a dissector's guide and
in text-books of topographical anatomy. But in studying the muscles scientifically it is of
importance also to consider them in their more fundamental genetic relationships to one another
and to the nervous system. Embryology and comparative anatomy have proved of the greatest
value in revealing these relationships. Studies of this nature have revealed well-marked rela-
tionships in the adult human musculature which are of practical as well as scientific importance
The voluntary musculature may be broadly divided into that of the skeletal axis, the limbs, and
the visceral orifices. The musculature of each of these divisions has a different and in general
simpler form in the lower than in the higher vertebrates, and in the embryos of the higher
vertebrates than in the adult. The musculature of the spinal region of the body axis of fishes,
the tailed amphibia, and all vertebrate embryos is metamerically segmented; that is, it is divided
along the axis of the body into a series of components corresponding with the segmentation of
the vertebral column. Although marked alterations take place in the subsequent ontogenetic
differentiation in higher vertebrates, traces of this primitive segmentation are still to be found
in the adult; in man, for instance, in the intercostal muscles and the segments of the rectus ab-
dominis. In the region of the head conditions are complex, owing to the concurrent presence
of muscles which primitively correspond in nature with the segmental spinal musculature, and
muscles non-segmental in character, which surround the visceral orfices. This also is true of
the anus and external genitalia, where, however, the conditions are simpler. Embrj'ology and
comparative anatomy have done much to clear up puzzling features in both regions.
■ The muscles of the hmbs are metamerically arranged in no adult vertebrate. In some of the
lower forms a series of axial muscle segments, myotomes, fm-nishes material from which the
320 THE MUSCULATURE
musculature of the limbs is differentiated. In the mammals this appears not to be the case, and
the muscles are differentiated from the non-segmental tissue of the hmb-buds.
Where mammalian musculature is primitively segmental, each segment becomes associated
with a corresponding spinal nerve or, in the head, with a nerve which corresponds in series with a
spinal nerve. Even when subsequent differentiation brings about marlied alterations in the
axial musculature, the nerves maintain to a considerable degree a segmental distribution.
Into each of the limbs, where the intrinsic musculature is at no time segmental, there extends
during embryonic development a series of segmental spinal nerves, so that in them, as in the
region of the body axis, a certain segmentation in the nerve-supply can be made out in the adult.
That part of the limb nearest the head in early embryonic development has its muscles supplied
by the most cranial, that part nearest the caudal extremity of the body by the most caudal,
of the nerves which supply the hmb musculature. There is here, however, considerable over-
lapping of the segmental areas.
Variation. — In man some variation in the arrangement of the muscles is met
with in every individual, and often marked deviations from the normal conditions
are found. The muscles vary in their mode of origin or insertion, and in the ex-
tent to which muscles of a given group are fused with one another or to which the
chief parts of a complex muscle are isolated from one another. Some muscles,
like the palmaris longus and the plantaris, are frequently entirely absent, and
other muscles generally absent are frequently present.
In addition to these frequent variations there are others so rare that many authors prefer
to speak of them as anomalies rather than variations. Sometimes muscles may be found
doubled by longitudinal division, or two or more muscles normally present may be fused into
a single indivisible muscle. Occasionally there occur muscles constantly present in some of
the lower animals, but normally not met with in the human body (anomalies of reversion or of
convergence). In such instances the muscle may be normally represented by a tendon or fascia.
At times the anomalies are supposed to be not a reversion to an ancestral condition, but a dis-
tinct step in advance. This, however, is difficult to prove. At other times no phylogenetic
relation is apparent, and the anomaly is looked upon as a monstrous sport or as the result of
somepathological condition.
The nerve-supply of the muscles is of value in the study of muscle variations.
There is, however, not infrequent variation in the nerves with relation to the
supply of the muscles.
Physiology. — From the standpoint of morphology the muscles are grouped
according to their intimate relations to one another and to the peripheral nerves,
relations, as noted above, that are made more clear by a study of comparative
anatomy and embryology. From the physiological aspect a different grouping of
the muscles is required, because muscles belonging morphologically in one group
may have different physiological functions in the animal body. The chief features
of the mechanical action of muscles may be briefly considered here.
Most muscles act on the bones as levers. In physics three types of levers
are recognised In levers of the first type (fig. 339, I) the fulcrum (F) lies be-
tween the place where power (P) is exerted on the lever and the point of resist-
ance or load (L) . Levers of this kind are frequently met with in the body.
A good example is seen in the attachment of the skull to the vertebral column.
The fulcrum lies at the region of attachment; the weight of the skull tends to
bend the head forward, while the force exerted by the dorsal muscles of the
neck serve to keep the head upright or to bend it back.
In levers of the second class (fig. 339 II) the point on which power is exerted
moves through a greater distance than the point of resistance. Speed of move-
ment is thus sacrificed to power. Levers of this type are exceedingly rare in
the animal body. An example in the human body is the foot when the body is
raised on the toes.
In levers of the third class (fig. 339, III) the point on which force is exerted
moves a less distance than the point of resistance. Power is thus sacrificed to
speed. This is the common form of leverage found in the body. A good ex-
ample is found in the action of the muscles which flex the forearm on the arm.
The region in which the biceps and brachialis are attached is but a short dis-
tance from the elbow-joint or fulcrum, while the hand may be looked upon as
the region of resistance to the force exerted. A movement of the point P
through a short distance will cause L to move through a great distance.
The more the angle between a muscle or its tendon and the bone on which it acts approaches
a right angle, the greater is the power of movement exerted by the muscle. The arm in fig. 339,
III, is in the position of greatest advantage for the action of the biceps on the forearm. All
boys know that it is easier to 'chin' oneself after the arm is partly bent than when hanging
PHYSIOLOGY
321
straight from a bar. Many of the muscles run nearly parallel with the parts on which they act,
but the tendons before their attachment are usually either carried over a bony prominence or
some fascia or hgament acts as a pulley so that tlie tendon is inserted at an oblique angle.
At other times a process for the attachment of the tendon projects from the bone and causes
the force of the contracting muscle to be more advantageously exerted on the bone. It may,
of course, readily be seen that the greater the distance of the attachment of a muscle from the
joint over which it acts, the greater will be the power exerted by the muscle.
In considering the movements of the body, it is convenient to recognise two
groups, simple and complex. To the former, which alone can be considered in
a text-book of anatomy, belong such movements as flexion, extension, adduc-
tion, rotation, etc., while to the latter belong those associated movements which
give rise to changes in the positions of the body as a whole or of extensive
regions of the body.
In flexion the extremities of the trunk or limbs or special portions of these
regions are bent near to one another; in extension the reverse movement is
brought about. The parts are straightened or even bent beyond the straight
position (over-extension).
Fig. 339. — Thbee Diagrams (after Testut) to Illustrate Different Types of Levers in
THEIR Relations to the Mechanical Action of the Muscles.
m
In abduction transverse movements are made, a part being bent away from
the median line of the body or limb; in adduction the reverse movement is
brought about.
In rotation a part is turned on its longitudinal axis. The rotation of the
femur at the hip-joint is called medial rotation when the toes are turned medial-
ward, lateral rotation when the toes are turned lateralward. Rotation at the
shoulder-joint is called medial when the thumb is turned forward and medial-
ward toward the body, lateral when the reverse movement takes place. These
movements are also carried out at the elbow-joint, but here medial rotation is
called pronation, lateral rotation, supination. Fick prefers these terms also for
the rotation at other joints as at the shoulder, hip and knee.
At the shoulder- joint the swinging of the arm toward the back is called exten-
sion; toward the front, flexion; and from the side, abduction. Moving the arm
toward the mid-dorsal or mid-ventral line is called adduction.
Taking the body as a whole the musculature may be divided into two main
divisions, an ex-pander division and a, contractor division. In general the extensors,
abductors and lateral rotators expand, the flexors, adductors and medial rota-
tors contract.
In the most expanded condition the head and spine are extended or even sUghtly hyper-
extended (flexed dorsally), and the limbs project laterally from the body with the backs of the
hands and feet facing dorsalward, the palms and soles ventral ward, and the digits spread out.
In the fully formed human body it is not possible to put the lower extremity in the completely
expanded position, although it is in this position early in embryonic development. As develop-
ment proceeds the lower extremity is adducted and rotated medialward and the girdle is so fixed
that full abduction becomes no longer possible. In many of the lower vertebrates full abduction
is possible throughout life in the lower extremities just as it is throughout life in the upper
extremities in man. Full extension of the spinal column in man is also hindered in the thoracic
region by the thorax, and in the sacro-coccygeal region by the osseous union of the vertebrae
with one another as well as by the attachment of the hip girdles. The lumbar region in man is
in a condition of permanent hyper-extension.
322 THE MUSCULATURE
In the fully contracted condition the head and spinal column are strongly flexed, and the
digits are adducted, the various segments of the Hmbs are flexed and the Umbs are adducted,
flexed and rotated medialward toward the middle of the trunk. The body approaches a ball
in form. It is the position taken by a gymnast when turning a somerset in the air, and is in
marked contrast to the fuUy expanded condition which would be assumed could man fly Mke a
bat or glide Uke a flying squirrel.
In general, the muscles which tend to put the body or a part of the body into the
expanded position form a distinct group as contrasted with those which tend to put the body
into the contracted position. The chief musculature which extends the head and trunk lies
dorso-lateral to the spinal column and is supplied by the dorsal divisions of the spinal nerves.
The chief musculature which flexes the head and trunk lies ventro-lateral to the spinal column
and is supplied by ventro-lateral divisions of the spinal nerves. The chief muscles which
abduct, extend and rotate the limbs lateralward arise during embryonic development on the
dorsal sides of the limb buds and are innervated by branches from the dorsal sides of the brachial
and lumbo-sacral nerve plexus. The chief muscles which flex, adduct and rotate the Hmbs
medialward arise on the ventral sides of the Umb buds and are supphed by nerves which arise
from the ventral sides of the hmb plexuses. To these general rules there are some exceptions,
the most marked of which is at the hip-joint where rotation of the girdle has brought about a
condition in which the primitive action of the flexor and extensor groups is partly reversed. The
chief flexors (the ilio-psoas and rectus femoris) belong to the dorsal division and some of the chief
extensors (the hamstring muscles) belong to the ventral division. At the ankle-joint the ex-
ception is more apparent than real. What is usually called flexion at the ankle-joint is really
hyper-extension and the reverse movement is the nearest we can come to real flexion. In
the extremelj' contracted position of the body as a whole the feet are extended (flexed plantar-
ward) at the ankle-joint.
Muscles which produce a movement in a common direction are called
S3aiergists, while those whose contraction produces opposite movements are
called antagonists; e. g., the flexors and extensors are antagonists. In the
actual working of the muscular system, however, when a set of muscles is
contracting to produce a movement, the antagonists also contract to a .;ertain
degree. The movement is the result of nerve /^impulses^ sent simultaneously to
all the muscles which act on the part moved. |
The relation of the internal architecture of a muscle to the movements to which its contrac-
tion gives rise is a complex subject, the details of which cannot be entered into here. In general
it may be said that when the fibre-bundles run directly from one attachment to the other, as in
fig. 338, a and f, the force exerted by the contraction of the individual muscle-fibres is most
efficiently utilised and the extent of the movement varies directly as the length of the fibres,
while the force exerted varies directly with the number of the fibres.
In muscles of the types indicated in fig. 338, g, h, i, a certain amount of the extent of move-
ment and of the force exerted by the contraction of the individual fibres is not effectively
exerted on the parts moved by the muscles, as may be seen by applying to this action the laws
of the parallelogram of forces. In such muscles, however, the great number of short muscle-
fibres composing them makes possible the exertion of great power with some loss of speed of
contraction in the muscle as a whole.
The direction of the movements which result from muscular contraction is in large part
determined by the shape of the articular surfaces, none of which are to be looked upon as simple
fulcra, but instead, during a given movement, the fulcrum shifts from one region to another of
the joint.
In different muscles the extent of contraction of the constituent fibre-bundles during
activity varies considerably. While usually the length of the contracted fibre-bundles is
half that of those in the extended state, the amount of shortening in some muscles is only 25
to 35 per cent.
Functional activity is necessary for the fuU development or for the maintenance of develop-
ment in muscles. Muscles atrophy if their nerve supply is injured or if they are passively
prevented from contracting.
Order of treatment. — The muscles and fascia are here treated in the following
order : — (1) those of the head and neck and shoulder girdle (p. 323) ; (2) those of the
upper extremity (p. 360); (3) those of the back (p. 410); (4) those of the thorax
and abdomen (p. 422); (5) those of the pelvic outlet (p. 439); (6) those of the
lower extremity (p. 452). The reason for taking up the musculature in the order
named is, that during embryonic development musculature belonging primitively
to the head comes to overlap that of the neck; that of the neck spreads over the
region of the back and thorax, and becomes attached to the shoulder girdle;
that of the arm extends over the region of the thorax, abdomen, and back; that
of the back partially over the region of the thorax; while that of the abdomen
enters into intimate relation with the pelvic girdle. So far as practicable the
musculature of these various regions will be taken up according to fundamental
morphological relationships.
Since a morphological grouping of the muscles does not accord perfectly with
a physiological grouping, there is given at the end of this section a table showing
what muscles are concerned in performing the simpler voluntary movements.
HEAD, NECK AND SHOULDER GIRDLE
323
The topographical relations of the muscles in various regions of the body are
illustrated in the series of cross-sections given for each region.
Tables illustrating the relations of the central nervous system and the per-
ipheral nerves to the muscles are given in the section on the nervous system
(Section VI).
Fig. 340.— Human Embryo (Le) 42 mm. Long. (After His.)
Auditory sac
Branchial clefts
Upper limb
First thoracic myotome
Sixth thoracic myoton
First Ijimbar myotome
I. MUSCULATURE OF THE HEAD, NECK AND
SHOULDER GIRDLE
PHYSIOLOGICAL AND MORPHOLOGICAL ASPECTS
The head, situated at the anterior end of the trunk in bilaterally symmetrical
animals, is primitively that part of the body first brought into contact with new
surroundings as the animal moves forward. We therefore find developed here
the most highly differentiated organs of .special sense, those of vision, hearing,
and smell, through which the animal is put in touch with an environment more or
less removed from immediate contact with the body. In connection with these
324 THE MUSCULATURE
organs of special sense, the brain is developed. In most animals the head also
is the chief organ for the prehension of food and for attack and defense. The
neck is a part of the trunk differentiated to give freedom to the movements of the
head. The forelimbs, relatively unimportant as the forefins in the fishes, become
important organs of locomotion in the land animals. In the fishes there is no
true neck, but the forefins are developed at the sides of the cervical part of the
trunk. In the higher vertebrates the forelimbs are also first differentiated at the
sides of the cervical region (fig. 340) but, as embryonic development goes on, they
shift caudalward to the sides of the cranial (anterior) part of the thorax. The
cervical region is thus left free for movement but the musculature and nerves of
the upper extremity remain intimately related to it.
In man, with the assumption of the erect posture, the head no longer has to
bear the brunt of the new surroundings as the body moves forward. There is,
however, a distinct advantage in having those organs of special sense, which put
the individual into touch with the more distant parts of the environment, situated
high above the ground, and a motile neck is of great value in directing the
organs of special sense toward various parts of the environment. The develop-
ment of the superior extremities as organs for the prehension of food and as
organs of attack and defense reduces the value of the head for these purposes, but
still leaves it the important functions of the reception of food and air and the
preparation of food for gastric and intestinal digestion. The head, furthermore,
assumes a new and most important function as an organ for the expression of the
emotions and of speech.
The expression of the emotions, such as anger, fear, affection and the like,*
is brought about largely through the action of flat, subcutaneous "facialis"
muscles which underlie most of the skin of the face and head and extend down
under that of the neck (figs. 341 and 344). They also line the mucous membrane
of the lips and cheeks. Most of them arise from the surface of the skull and are
inserted into the skin, which they pull in various directions causing it to become
smooth or twinkled, according to the direction of the pull. The various muscles
are grouped about the buccal, nasal and aural orifices and about the orbit of the
eye. Some of the fibre-bundles are arranged so as to constrict the orifices, others
radiate out so as to dilate them.
The chief groups of muscles of the head and neck, in addition to the facialis
group just mentioned, are the muscles of the orbit and middle ear, the muscles
used in mastication and swallowing (cranio-mandibular, supra- and infrahyoid
groups, muscles of the tongue, soft palate and pharj^nx), the muscles of the
larynx, and the ventral and dorsal groups of muscles which lie in the region of
neck, extend over the thorax and move the head, neck and shoulder girdle. A
brief summary of these groups will be given before proceeding to a more
detailed account.
Facialis group. — The muscles are especially well developed about the mouth, a
sphincter muscle {orbicularis oris) serving to close, the radiating muscles to open the lips
{quadratus labii superioris and inferioris), to pull the corners ot the mouth in various directions,
as, for instance, upward to express bitterness {caninus) or pleasure {zygomaticus) , or lateral-
ward and downward to express grief or pain (risorius, triangularis, plalysma) or to protrude the
lips as in pouting {mentalis and incisive muscles). The buccinator, which radiates out from the
corner of the mouth and hues the mucous membrane of the cheek, is used in mastication and
whisthng.
About the orbit and in the eyelids a circulai- musculature {orbicularis oculi) is broadly
developed. It is usedto close the eyes, and to contract the skin about the orbit. Associated
with the orbicularis are muscles which produce perpendicular furrows in the skin of the fore-
head above the nose (procerus, corrugator). The skin is drawn upward from the orbit and
horizontal furrows are caused in the skin ot the forehead by muscles attached to the scalp
(epicranius). Two of these muscles, the occipitales, arise one on each side from the occipital
bone and are attached to an aponeurosis which lies beneath the scalp to which it is firmly
united. Two of the muscles, the frontales, extend one on each side from this aponein-osis to the
skin above the eyebrows.
About the nasal orifices there are weak constrictors (alar part of the nasalis, depressor aloe
nasi) and dilators (dilator naris anterior and posterior, transverse part of the nasalis, angular
head of the quadratus labii superioris). From the ear (auricle) three flat muscles radiate,
one backward (auricularis posterior), one upward (auricularis superior) and one forward
(auricularis anterior). These muscles are seldom functionally developed. They pull the
auricle in their respective directions. They may be looked upon as (primitively) dilators
of the aural orifice. On the cartilage of the auricle are several rudimentary " intrinsic " muscles
which may be looked upon as remnants of a constrictor of this orifice.
*See Darwin: The Expression of the Emotions in Man and Animals.
GROUPS OF MUSCLES 325
In the orbital cavity there are six muscles which are attached to and move the
eyeball and one muscle (the levator palpehroe superioris) which extends into and raises the
upper lid (fig. 341) . Of the muscles which move the eyebaU five arise hke the levator of the lid,
from the back of the orbit. Four of these, the rectus muscles, are inserted respectively into the
superior, inferior, medial and lateral sides of the eyeball and direct the pupil upward,
downward, medialward and lateralward. One, the superior oblique, sends a tendon through
a loop at the upper, front part of the nasal side of the orbit and thence to the upper surface
of the eyeball. Another muscle, the mferior oblique, arises from the nasal side of the front of
the lower part of the orbit and is attached to the lower part of the eyebaU. The obUque
muscles prevent the rectus muscles from rotating the eyeball. These muscles are supphed
by the third, fourth and sixth cranial nerves. They are described in the section on the eye, p.
1067. In the middle ear are two small muscles (the tensor tympani and the stapedius) attached
respectively to the malleus and stapes and supplied by fifth and seventh cranial nerves. They
are described in the section on the ear, p. 1091.
Mastication and swallowing. — The complex musculature used in biting, masticating and
swallowing food is used also in speech in conjunction with the muscles of the larynx and the lips.
The two movable bones of the skull concerned with these functions are the mandible and the hyoid
bone. The mandible articulates with the skull on each side, just in front of the external audi-
tory meatus. The hyoid bone is connected on each side by the stylo-hyoid ligament with the
styloid process of the temporal bone, which descends just behind the external auditory meatus.
A powerful group of muscles, the cranio -mandibular muscles (figs. 344, 345, 346, 347 c), or
muscles of mastication, arise from the temporal fossa {temporal muscle), the zygomatic arch
[masseter muscle) and the pterygoid process (external and internal pterygoid muscles) and are
inserted into the coronoid process of the mandible [temporal muscle), the outer side of the
ramus {masseter muscle), the inner side of the ramus {internal pterygoid), and into the condyle
of the jaw {external pterygoid). These muscles raise the jaw, move it forward and from side
to side, and are used in biting and chewing the food. They are innervated by the fifth cranial
(masticator) nerve.
Another less powerful group of muscles, the suprahyoid group (fig. 348), is divisible into
two subdivisions, hyo-mandibular which extends in front between the hyoid bone and the
ramus of the jaw (anterior belly of the digastric, genio-hyoid, mylo-hyoid) and a hyo-temporal
group which extends between the hyoid bone and the temporal bone back of the external audi-
tory meatus {stylo-hyoid, posterior belly of the digastric). Two of the hyo-mandibular muscles
(the anterior belly of the digastric and the mylo-hyoid) are innervated by the trigeminal; the
genio-hyoid by the hypoglossal nerve. The two hyo-temporal muscles (posterior belly
of the digastric and stylo-hyoid) are innervated by the facial nerve. Morphologically
therefore, as indicated by this innervation, the muscles of this group are diverse. Physiolog-
ically they are closely united. The group, acting as a whole, elevates the hyoid bone and with
this the larynx and the tongue. If, however, the hyoid bone be fixed by contraction of the
neck muscles (infrahyoid muscles) attached to its lower border, the suprahyoid muscles act
as antagonists of the cranio-mandibular muscles and depress the jaw. The hyo-mandibular
muscles form, together with the tongue, the muscular floor of the mouth. When acting with
the hyo-temporal muscles they help the tongue to pass food into the pharynx. When acting
alone the hyo-mandibular muscles draw forward the hyoid bone and with it the base of the tongue
and the larynx and thus open the passage from the pharynx into the oesophagus. The two
hyo-temporal muscles, acting in conjunction with the middle and inferior constrictors of the
pharynx, draw the hyoid bone and larynx backward, as well as upward, and thus constrict the
pharynx while giving free passa'_e for air from the naso-pharynx into the larynx. The chief
functions of the suprahyoid group are, therefore, to play a part in deglutition and respiration.
Closely associated with the muscles of the suprahyoid group in the performance of
these important functions are the muscles of the tongue, the pharynx and the soft palate.
The bulk of the tongue (fig. 349) is made up of muscles which have their origin on each side from
the inner surface of the front part of the mandible {genio-glossus) , the hyoid bone {hyo-glossus
and chondro-glossus) and the styloid process of the temporal bone {stylo-glossus) . Muscles
also connect the tongue with the palate (glosso-palatinus) and with the pharynx {glosso-pharyn-
geus). These muscles, together with intrinsic longitudinal, transverse and perpendicular
fibre-bundles, enable the tongue to perform the complex activities associated with mastication
and swallowing and with speech. During mastication the tongue passes the food from side to
side between the teeth. When the food has been masticated the tongue forms a bolus of it
and then this is passed into the pharynx by a sudden elevation of the dorsum of the tongue
produced in part by the muscles of the tongue, in part by the suprahyoid group of muscles.
The muscles of the tongue are described on p. 345.
The pharynx is the dilated upper part of the alimentary canal into which open the Eus-
tachian tubes, the nasal passages, the mouth and the larynx. The walls of the side and back
of the pharynx are composed mainly of muscular tissue. The chief muscles are three " con-
strictor " muscles on each side, a superior, a middle and an inferior, and an elevator and dilator,
the stylO'pharyngeus (fig. 894). The three constrictor muscles are attached to the median
raphe* which extends in front of the spinal column from the base of the occipital bone to the
sixth cervical vertebra. The superior constrictor muscle is attached to the pterygoid process,
the pterygo-mandibular ligament, the mandible and the side of the root of the tongue (fig. 343) ;
the middle constrictor to the hyoid bone ; and the inferior constrictor to the larynx. These muscles
constrict the pharyngeal orifice and thus force food into the oesophagus. The stylo-pharyngeal
muscle, which extends from the styloid process into the lateral wall of the pharynx, serves to
* The attachments to the raphe are usually spoken of as the insertions, those to the bones
in front as the origins of these muscles. The raphe is, however, a more fixed structure than
most of the structm'es to which the constrictors are attached in front.
326 THE MUSCULATURE
elevate and dilate the pharynx and elevate the larynx. The muscles of the pharynx are de-
scribed on page 1134.
The orifices of the various passages into the pharynx are dilated or constricted by muscular
action. The orifices of the nasal passages, the Eustachian tubes, and the mouth are controlled
mainly by the musculature of the soft palate and pharynx. The orifice of the larynx is con-
trolled by special muscles which act in conjunction with those of the suprahyoid group, the
tongue, and the pharynx.
The soft palate is a muscular partition which is continued backward from the hard palate
between the buccal cavity and the naso-pharyngeal orifice and then bends downward between
the back part of the mouth and the nasal part of the pharynx, terminating in a median pro-
jection, the uvula. Above, on each side, back of the fold of tissue {plica salpingo-palatinus)
which descends from the ventral border of the orifice of the Eustachian tube and which marks
laterally the passage from the nose into the pharynx, there is a muscle,- the levator veli palatini
(fig. 343~>. This arises from the petrous portion of the temporal bone and from the Eustachian
tube descends to the middle of the side of the soft palate and then spreads out broadly on its
dorsal side. The muscle from each side interdigitates to some extent with that of the other
side. These muscles raise the soft palate toward the upper part of the posterior wall of the naso-
pharynx and thus shut off the nose from the buccal portion of the pharynx during deglutition.
The sides of this portion of the pharynx are, meanwhile, constricted by the superior constrictors
of the pharynx and by the pharyno-palatinus muscles described below. Contraction of the
levator veli palatini tends to cause folds of tissue to close firmly the opening of the Eustachian
tube. This is counteracted by the tensor veli palatini muscles (fig. 343). One of these arises
on each side from the pterygoid region of the sphenoid bone, and is inserted into the anterior
part of the soft palate by a tendon which passes beneath the hamular process of the pterygoid
process. Contraction of this pair of muscles flattens the anterior part of the soft palate and
exerts a traction which dilates the orifice of the Eustachian tube. Most authorities state that
the Eustachian tube is thus opened each time we swaUow. As air is admitted into the middle
ear the tensor tympani muscle contracts so as to prevent too sudden an effect on the ear drum
(Jonnesco.)
Dorsal to the fibres of the elevator of the palate in the soft palate next the median line on
each side there extends from the hard palate into the uvula a small muscle, the muscle of the
uvula, which lifts the tip of this and shortens the soft palate from front to back thus enlarging
the opening from the mouth into the pharynx. On each side of the uvula the posterior edge of
the soft palate is continued backward and downward into a fold, the arcus pharyngo-palatinus,
which contains a muscle, the pharyngo-palatinus (fig. 865). This arises from the soft palate,
gasses downward and backward on the inner side of the lateral wall of the pharynx and divides
iato two fasciculi, one of which is attached to the larynx, the other to the median raphe. The
muscle constricts the pharynx at the junction between the nasal and buccal portions and elevates
the larynx. As the bolus of food is passed from the dorsum of the tongue into the pharynx
the bucco-pharyngeal opening is dilated by the contraction of the elevators of the palate and
uvular muscles and the opening into the naso-pharynx is closed not only by the soft palate
being raised against the posterior wall of the naso-pharynx but also by the lateral folds raised
on each side by the pharyngo-palatinus against the uvula. Meanwhile the larynx is raised by
the pharyngo-palatinus and the stylo-pharyngeus, as well as by the suprahyoid muscles, and
carried forward by the hyo-mandibular subdivision of the latter muscles so that the opening
from the pharynx into the cesophagus is dilated for the passage of food. At the same time the
opening into the larynx is constricted from above, the larynx being carried forward beneath the
tongue so that the epiglottis slants somewhat backward. This backward slant is aided by the
constriction of the thjTeo-hyoid muscle which raises the thyreoid cartilage toward the hyoid
bone and by the stylo-glossus muscle whioh pulls the tongue backward over the larynx. The
opening into the larynx is constricted at the sides and behind by the contraction of muscles
which run in the aryepiglottic folds and by the thyreo-arytenoid and transverse arytenoid
muscles. At the end of deglutition the larynx is puUed back from beneath the base of the
tongue by the middle and inferior constrictors of the pharynx and the opening is again dilated.
The buccal cavity may be shut off from the pharynx by the action of the muscles which pass
in the glosso-palatal folds from the soft palate to the mouth in front of the tonsils. These
glosso-palatal muscles elevate the folds in which they he, depress the soft palate, and, if the
dorsum of the tongue be raised, shut oft' the buccal cavity. The muscles of the soft palate are
described on p. 1134.
The uvular muscle, the levator veU palaini, the glosso-palatinus and the pharyngo-
palatinus muscles are supphed by the pharyngeal plexus. The tensor veU palatini is sup-
plied by the mandibular division of the fifth nerve. The pharyngeal muscles are supplied
by the glosso-pharyngeal, the vagus, and the spinal accessory cranial nerves.
The larynx lies in the neck, but since the intrinsic muscles of the larynx from the standpoint
of embryology and comparative anatomy belong with the musculature of the head, it is con-
venient to refer to them briefly here rather than to treat of them with the intrinsic muscles of the
neck. A full description of the laryngeal muscles is given in the section on the larynx (fig. 981) .
They develop from tissue which corresponds with that which in fishes gives rise to the muscles
of the gills and are innervated by the nerves which in the fishes innervate the gills, the tenth
pair (vagus) of cranial nerves. The movements of the laryngeal cartilages are such as to
approximate or draw apart the vocal cords and to loosen or make them tense. The approxi-
mation of the vocal cords is produced by the rotation medialward of the vocal processes of the
arytenoid cartilages brought about by the lateral crico-arytcnoid and transverse arytenoid
muscles. The drawing apart of the vocal cords is produced by the posterior crico-arytenoids.
The vocal cords are made long, thin and tense by the crico-thyreoid. They are shortened and
thickened by the thyreo-arytenoid (externus) and the vocalis. The inferior laryngeal branch of
GROUPS OF MUSCLES 327
the vagus supplies all the muscles but the crioo-thyreoid. This is supplied by the superior
laryngeal branch of the vagus.
Metamerism. — The muscles thus far considered are essentially visceral muscles, although
all are composed of striated muscle cells and all are more or less directly under the control of
the will. From the morphological standpoint the muscles of the orbit, the tensor tympani,
the muscles of mastication, the hyo-mandibular muscles and the muscles of the tongue have
been grouped with the ordinary voluntary skeletal muscles while the facialis musculatm'e, the
stapedius, the hyo-temporal muscles and the muscles of the soft palate, pharyn.x and larynx
are looked upon as of a more purely visceral origin. A primitive characteristic of the voluntary
skeletal muscles is metameric segmentation. This is maintained through life in the trunk
musculature of fishes and of tailed amphibia and is passed through as a temporary stage in
aU the higher vertebrates. The embryonic segmented muscles are caDed myotomes (see fig.
340). In some regions the metamerism is retained throughout life even in the higher forms,
as, for instance, in the intercostal muscles and the intertransverse muscles. But for the most
part the primitive metamerism is so lost during the differentiation of the definitive trunk
musculature that only traces of it remain here and there as, for instance, in the segments of the
rectus abdominis muscle. In the lower forms the myotomes give rise during embryonic
development to material utilized in the formation of the limb musculature, but even in the
fishes all traces of trunk metamerism are lost in the differentiated limb musculature and in the
higher forms, as in man, the limb musculature appears to differentiate directly from the un-
segmented tissue in the hmb-buds. In the head the musculature is differentiated directly, as
in the limbs, without undergoing a preliminary metameric or myotomic stage. Attempts
have been made to show that in primitive forms the cranial voluntary skeletal musculature, in
the narrower morphological sense mentioned above, passes through a metameric stage com-
parable with the myotomic metamerism of the trunk. This attempt has been partially success-
ful as regards the development of the muscles of the eye in some of the lower forms. There
is also good evidence that the spinal region of the skull and associated structures represent a
part of the metameric trunk fused with a more primitive head so that the musculature of the
tongue and the hyo-mandibular muscles belongs morphologically with the primitively metameric
trunk musculature. The rest of the cranial musculature gives little evidence of a primitive
metameric segmentation and hence is probably to be classed morphologically with the unseg-
mented visceral musculature.
Of the muscles of the neck, the most superficial, the platysma (fig. 341), is a subcutaneous
muscle belonging to the facialis group of the head from which it grows down during embryonic
development. It is supplied by the seventh cranial (facial) nerve. It extends from the corner
of the mouth and the side of the mandible over the clavicle. It depresses the corner of the
mouth, wrinkles up the skin of the neck and aids the circulation by reUeving pressure on the
uiiderlying veins.
Beneath the platysma there lies a layer composed of two flat muscles (fig. 344) which
extend from the base of the skull behind the ear to the shoulder girdle. One of these muscles,
the sterno-cleido-mastoid, arises in front from the sternum and clavicle and is inserted into the
m.istoid process of the temporal bone and the skull behind this. The other, the trapezius, arises
from the base of the skull, and from the ligamentum nuohfe and vertebral spines of the cervical
and thoracic regions, and is inserted into the spine of the scapula, the acromion and the lateral
third of the clavicle. These two muscles constitute the superficial shoulder -girdle musculature.
They extend the head, bend it toward the same side and rotate it toward the opposite side.
The sterno-cleido-mastoid and the upper part of the trapezius raise the shoulder girdle and
thorax and hence are of use in forced inspiration. The trapezius draws the scapula toward the
spine and rotates the inferior angle of the scapula lateralward. The lower part of the trapezius
acting alone draws the scapula downward and dorsalward while rotating the inferior angle
lateralward. The trapezius is therefore used when the arm is raised high or carried backward.
The two muscles of this group are innervated partly by the spinal accessory, and partly by the
ventral divisions of the second, third and fourth cranial nerves. They represent in part
musculature which in the lower vertebrates is associated with the visceral musculature of the
gills (hence the innervation by the spinal accessory, a derivative of the vagus nerve) and in
part metameric musculature of the second, third, and fourth cervical segments. During
embryonic development this musculature therefore spreads out widely from its origin, the upper
cervical region. The lower part of the trapezius varies greatly in the extent of its development
caudalward. It may reach only half way down the thoracic region or it may extend into the
lumbar region. The deeper musculature of the neck is derived from the cervical myotomes.
The primitive segmental musculature of the neck, hke that of the whole trunk, becomes
divided at an early embryonic stage into two divisions, a dorsal, supplied by the dorsal divisions
of the spinal nerves, and a ventro-lateral supplied by the ventral divisions. The trapezius,
although it covers the intrinsic dorsal musculature of the cervical region, insofar as it is of
cervical origin, belongs to the ventro-lateral musculature and is derived, apparently, from the
first three cervical myotomes. There is also a deeper layer of muscles attached to the shoulder
girdle which arise from the ventro-lateral divisions of the lower five or six cervical myotomes
but which, with one exception, the levator scapulm (fig. 353), wander over the thorax during
embryonic development. This group is described below as the deep shoulder-girdle muscula-
ture. The rest of the muscles derived from the ventro-lateral divisions of the cervical myo-
tomes are divisible into three gi'oups, the infra-hyoid, the scalene and the prevertebral.
The infra-hyoid group hes at the front of the neck, superficial to the larynx and trachea
(fig. 348), and is composed of four flat muscles, the sterno-hyoid, sterno-thyreoid, thyreo-hyoid
and omo-hyoid (scapulo-hyoid), the names of which indicate the origin and insertion. The
chief function of this group of muscles is to depress the hyoid bone, the larynx and the as-
sociated structures. When the supra-hyoid group of muscles contracts at the same time, the
infra-hyoid muscles help to depress the lower jaw, or if this in turn is fixed by the cranio-man-
dibular group, to flex the head. The muscles of this group are derived from the ventral portions
328 THE MUSCULATURE
of the first three cervical myotomes and are innervated by the first three cervical nerves through
the ansa hypoglossi. The primitive segmental origin of these muscles is frequently indicated
by transverse tendons (inscriptiones tendineae). They correspond morphologically with the
rectus abdominis musculature.
The scalene group (fig. 352) lies at the side of the neck and extends to the first and
second ribs from the transverse processes of the lower six cervical vertebrae. The muscles of this
group bend the neck toward the side, or if the neck be fixed, elevate the thorax. They come
from the lateral parts of the ventro-lateral divisions of the lower five cervical myotomes and are
innervated by the lower five cervical nerves. They correspond morphologically with the
intercostal and with the lateral abdominal musculature.
The prevertebral group lies back of the pharynx and oesophagus and in front of the bodies
and transverse processes of the cervical veitebrae. The muscles of this gi-oup arise not only
from the transverse processes and bodies of the cervical vertebrae, but also in part from the
bodies of the first three thoracic vertebrae and are inserted in part into the cervical vertebrae
(?or!(/MS coiM) and in part into the base of the occipital bone {longus capitis). This musculature
flexes the neck and the head. When acting on one side it rotates the head toward the same
side. It is innervated by the first six cervical nerves.
The deep shoulder-girdle musculature. — This becomes differentiated from the ven-
tro-lateral divisions of the lowei five or six cervical myotomes. Like the muscles of the
superficial layer those of the deeper layer spread out widely from their origin. There are four
muscles in the deeper group, all of which become attached to the dorsal border of the scapula.
Of these, one, the levator scapulce (fig. 353), remains in the cervical region, extending from
the upper cervical transverse processes to the medial angle of the scapula. Two, the rhomboids
(fig. 353), extend over the intrinsic dorsal musculature and are attached to the upper thoracic
and lower cervical vertebral spines; while the fourth, the serratus anterior (fig. 354), extends
over the side of the upper part of the thorax beneath the scapula and is attached to the first
nine ribs. These muscles all, however, through their innervation, reveal in the adult their
primitive cervical origin. They are supplied by branches from the third to the seventh cervical
nerves. The levator scapulae elevates the scapula, the rhomboid muscles retract it and the serratus
anterior draws it forward. The levator and rhomboid muscles rotate the shoulder girdle so
as to depress the shoulder, the serratus anterior, like the trapezius, rotates it so as to raise
the shoulder. The two former muscles are an aid in extending the arm, the latter in flexing
and abducting it. When the group, as a whole, contracts action is exerted on the ribs so that
the group is of use in forced inspiration.
The intrinsic dorsal musculature of the neck, innervated by the dorsal divisions of the
cervical nerves, is separated from the scalene muscles by the levator scapula. Dorsally it is
covered by the trapezius and the rhomboid muscles. It is to be looked upon as a specialized
portion of the system of intrinsic dorsal muscles which extend from the sacrum to the base of
the skull on each side of the vertebral column. The primary function of this muscle system
is to extend and to rotate the spine and the skuU. In the thoracic region three main subdivi-
sions may be recognised, a lateral, the ilio-costal; an intermediate, the longissimus; and a medial,
the transverse-spinal group (fig. 381). In the cervical region these three groups may hkewise
be recognised and, in addition, there is a superficial group, the splenius (fig. 380) , not represented
in the lower thoracic region. The splenius arises from the upper thoracic and lower cervicla
spines and is inserted into the transverse processes of the upper cervical vertebrae and into the
mastoid processes of the temporal bone and the neighbouring part of the occipital. It acts with
the sterno-cleido-mastoid, by which it is crossed near the head, in extending the head, bending
it toward the side, but tends to rotate it toward the same side instead of toward the opposite
side. Laterally beneath the splenius the ilio-costalis cervicis extends from the upper part
of the thorax to the transverse processes of the sixth to the fourth cervical vertebrae, and the
longissimus cervicis and capitis extend from the same region to the transverse processes of the
mid-cervical vertebrae and to the mastoid process of the temporal bone (fig. 381). These
muscles likewise extend and bend the head and neck laterally and rotate it toward the same
side. Medially on each side the strong semispinalis capitis (fig. 381), arises from the upper
thoracic and the lower cervical vertebrae, spreads out and is inserted into the squamous portion
of the occipital bone. It is a powerful extensor of the head. Beneath it numerous fasciculi
extend from the transverse proceses to the spines of the cervical vertebrae. These fascicuh,
the more superficial of which are the Ion', est, constitute the Scmispinales cervicis, muliifidus,
and roiatores muscles. They extend and rotate the neck.
Between the successive spines and the transverse process there are short muscles (inler-
spinales, intertransversares) . The rectus capitis anterior and the rectus capitis lateralis between
the transverse process of the atlas and the lateral part of the occipital belong with the latter
series.
Between the base of the skull behind and the first two vertebrae there are four deep-seated
specialized muscles which constitute the suboccipital group (fig. 382). The rectus capitis
posterior major and minor spread out respectively from the spines of the atlas and epistropheus
and are inserted beneath the inferior nuchal line of the occipital. The obliquvs capitis inferior
arises from the spine of the epistropheus and is inserted into the transverse process of the
atlas; the obliquvs capitis superior arises from this and is inserted into the lateral part of the
inferior nuchal line of the occipital. These muscles extend and rotate the head. A detailed de-
scription of the intrinsic muscles of the back is given on page 410.
The muscle fasciae in the head and neck are well developed in connection with most of
the groups of muscles except the facialis group and are described in detail in connection with
each of these groups. In the head we may here call attention merely to the dense temporal
fascia which covers over the temporal fossa and hides from view the temporal muscle. In
the neck the fasciae are of considerable practical importance. It is convenient to think of them
as divisible into several layers although the various layers fuse to some extent. The external
layer (fig. 350) may be looked upon as completely ensheathing the neck and as dividing on each
FACIALIS MUSCULATURE 329
side into two layers which ensheath the sterno-cleido-mastoid and trapezius muscles. As a
free fascia it is attached to the lower jaw, to the clavicle and sternum, and to the hyoid bone
which divides it into a submaxillary and an infra-hyoid portion. It is connected with the fibrous
sheath of the parotid and submaxillary glands. The middle layer of cervical fascia is composed
of two laminae, one extending between the sterno-hyoid and omo-hyoid and another more deli-
cate one beneath this, ensheathing the thyreo-hyoid and sterno-thyreoid muscles and fused with
the fibrous sheath which encloses the carotid artery, internal jugular vein and the vagus nerve.
The deeper muscles of the side and front of the neck and the intrinsic muscles of the back of
the neck are hkewise ensheathed by muscle fasciae.
Of the various groups of muscles mentioned above, some, for the sake of con-
venience, are treated in connection with the organs to which they belong. Thus
the muscles of the eye and ear are taken up in Section VIII; those of the palate,
pharynx and larynx in Sections IX and X; the deep dorsal musculature of the
neck will be taken up in the section on the intrinsic muscles of the back, p. 410,
The remaining groups of muscles will be taken up in the following order: —
1. The facial group p. 329.
2. The cranio-mandibular group p. 338.
3. The supra-hyoid musculature p. 343.
4. The muscles of the tongue p. 345.
5. The superficial shoulder-girdle musculature p. 347.
6. The infra-hyoid musculature p. 350.
7. The scalene musculature p. 353.
8. The prevertebral musculature p. 355.
9. Anterior and lateral intertransverse muscles p. 356. ■
10. Deep musculature of the shoulder girdle p. 356.*
1. THE FACIALIS MUSCULATURE
(Figs. 341, 344)
The muscles of this group are intimately connected with the scalp, with the
skin of the face and neck, and with the mucous membrane lining the lips and the
cheeks. Most of the muscles have an osseous origin and a cutaneous insertion,
but there are exceptions. Both origin and insertion may be cutaneous, or the
attachment may be to an aponeurosis instead of directly to the skin. The
deeper musculature about the mouth is attached to the mucous membrane.
The muscles are composed of interdigitating muscle-fibres which are grouped
in bundles that take a nearly parallel or slightly converging course and give rise
to thin muscle-sheets. The extent of development of the various muscles of the
group and their independence varies greatly in different individuals.
The region from which the facial musculature originates in the embryo is, in the main at
least, that of the hyoid arch immediately below the ear. From here the musculature spreads
with the development of the facial nerve, dorsally to the occipital region behind the ear, distally
over the neck, ventrally over the face, and upward toward the eye, forehead, and the side of
the skull. The course of the development is indicated by the branches of the facial nerve. A
somewhat similar phylogenetic development is indicated by conditions found in the inferior
mammals and lower vertebrates. According to Ruge and Gegenbam-, the facial musculature
is to be looked upon as derived from two muscle-sheets, of which in man the deeper has dis-
appeared in the region of the neck while it is differentiated into the deeper facial muscles in the
region of the head. The deeper layer of transverse fibres in the neck, the sphincter colli, is found
in several of the mammals. The complex development of the facial muscles in man is char-
acteristic of the human species, and is associated with the use of these muscles as a means of
expression of the emotions, a physiological function superadded to the primitive function of
opening and closing visceral orifices. There is much individual variation in the differentiation
of the muscles.
Fasciae. — The skin of the head and neck is, in most regions, firmly fused with the tela
subcutanea. This is composed of a dense fibrous tissue united by a looser areolar tissue to the
underlying structures. But a slight amount of fat is embedded in the subcutaneous ti.ssue of
the scalp, forehead, and nose. Considerable fat may be embedded in the region of the cheeks,
the back of the neck, and the under surface of the chin (double chin). The constantly repeated
action of various muscles of the facialis group usually results by middle Hfe in the production
of permanent wrinkles due to alterations in the structure of the tela subcutanea and the cutis.
The subcutaneous muscles of the cranial vault and the neck are invested with fascial
membranes. That covering the cranial musculature externally is firmly fused to the subcutane-
* The pectoral muscles and the latissimus dorsi, which extend from the skeleton of the hmb
to the front and side of the thorax and the lower part of the back, arise from the hmb-bud during
embryonic development, are innervated through the brachial plexus, and wiU, therefore, be taken
up in considering the intrinsic musculature of the upper Imrb, p. 360.
330
THE MUSCULATURE
ous tissue of the scalp. That covering the subcutaneous muscle of the neck is less firmly fused
with the subcutaneous tissue. In the facial region the more superficial muscles are so closely
embedded in the subcutaneous tissue that no distinct fasciae intervening between the muscles
and the skin can, as a rule, be distinguished. Of the deeper muscles of the facialis group, the
buccinator alone possesses a distinct fascia. This muscle lies upon the mucous membrane of the
lateral wall of the mouth, and is covered externally by a fascia continued into the fascia investing
the superior constrictor of the pharynx.
Bursse. — Bursa subcutanea prementalis. Between the periosteum at the tip of the chin
and the overlying tissue. Bursa subcutanea prominentias laryngese. In front of the junction
of the right and left laminae of the thyreoid cartilage.
Fig. 341.^The Superficial Muscles of the Head and Neck.
Orbicularis oculi
Procerus
Quadr. labii sup
caput angulare
Nasalis, pars transversa
Dilator naris anterior-,
Dilator naris posterior^
Quadr. labii sup.
caput infraorbitale
Caput zygomaticum
Orbicularis oris
Quadratus labii infenoris
Triangularis
Auricularis
superior
MUSCLES
The muscles of the faciahs group may be conveniently subdivided as follows: —
(a) Cervical : the platysma. (&) Oral : the orbicularis oris and the incisivus
labii superioris and inferioris; the quadratus labii superioris and inferioris; the
caninus, zygomaticus, risorius, and triangularis; and the buccinator, (c)
Mental, (d) Nasal: the nasalis, depressor septi, and the dilatores naris. (e)
Periorbital: the orbicularis oculi, corrugator, and procerus. (/) Epicranial: the
frontalis and occipitalis, with the galea aponeurotica. (g) Auricular: anterior,
superior, and posterior. With these the temporalis superficialis is also described.
(o) CERVICAL MUSCLE
The platysma is a large, thin, quadrangular muscle which runs obliquely from
the chin, the corner of the mouth, and the lower part of the cheek across the
ORAL MUSCLES 331
mandible and the neck to the proximal part of the thorax and shoulder. The
muscles of each side interdigitate across the chin. A short distance below the
chin, in the neck, the ventral margins diverge (fig. 341).
Origin. — From the tela suboutanea by somewhat scattered bundles — (1) along a Une ex-
tending from the cartilage of the second rib to the acromion, and (2) along the dorsal margin of
the muscle.
Insertion. — Into — (1) the mental protuberance of the mandible and the inferior margin
of the mandible; and (2) into the skin of the lower part of the cheek and at the corner of the
mouth, where it fuses more or less with the quadratus labii inferioris and the orbicularis oris.
Nerve-supply. — The cervical branch (ramus colh) of the seventh cranial nerve forms beneath
the muscle a plexus to which the cutaneus colh nerve contributes sensory branches.
Relations. — The muscle is situated beneath the panniculus adiposus, to which in the neck it
is not very firmly attached. For the most part it is separated from the external layer of the
cervical fascia by loose areolar tissue. The main cutaneous rami of the cervical plexus and the
external jugular vein lie beneath the muscle.
Action. — It wrinkles up the skin of the neck, depresses the corner of the mouth, and thus
plays a part in expression of sadness, fright, and suffering. It aids the circulation by relieving
pressure on the underlying veins.
Variations. — Either the facial or the distal development of the muscle may be more exten-
sive than that described above. On the other hand, it ma.y be less developed than usual, and
rarely it is absent. Accessory shps have been seen going to the zygoma, the auricle, or the
mastoid process, etc., and to the clavicle and sternum. Rarely a deep transverse layer is found
in man.
Fig. 342. — Diagram to Illustkate the Architecture op the Orbicularis Oris.
(After T. D. Thane.)
Depressor septi nasi-^
Incisivus sup. ~
(b) ORAL MUSCLES
The muscles of the mouth belonging to the facialis system include several
intralabial muscles: — a sphincter, the orbicularis oris; a transverse, the com-
pressor labii; and four deep submucous muscles which pass from the sides of
the lips to the alveolar juga of the upper canine and lower lateral incisor teeth, the
incisivi labii superioris and inferioris. From each corner of the mouth there
radiate out several muscles; the caninus and zygomaticus upward to the maxilla
and zygomatic bone; the risorius lateral ward over the cheek; the platysma and
the triangularis downward over the side of the jaw; and the buccinator, lateral-
ward over the side of the oral cavity. From each of these fibre-bundles are
continued into the more peripheral and superficial portions of the orbicularis.
In addition to these muscles there are two retractors or quadrate muscles, one of
which, the quadratus labii superioris, extends from the upper lip medial to the
angle to the bridge of the nose, the lower margin of the orbit, and the zygo-
matic bone; while the other, the quadratus labii inferioris, extends from a corre-
sponding position in the lower lip to the side of the chin. The orbicularis oris,
compressor labii, and incisive muscles close the lips; the other muscles open them
and pull them in various directions. The buccinator, however, plays a part in the
closing of the mouth by offering support for the orbicularis.
Intralabial Muscles
The orbicularis oris (figs. 308, 341, 342, 343) is a complex muscle which surrounds the oral
orifice and forms the chief intrinsic musculature of the Ups. Immediately about the orifice,
and on the deep surface of the muscle, is a fairly well-defined sphincter, although at the corners
of the mouth the fibre-bundles of one hp cross those of the other and are inserted into the
mucosa, and to a less extent into the skin. In the mid-line the fibre-l^undles end partly in the
perimysium, partly in the skin. About this sphincter area and between its outer margin and
332 THE MUSCULATURE
the skin is a complex musculature comprised partly of fibre-bundles prolonged from the muscles
which radiate from the corners of the mouth. The more superficial portion of the muscle in
the upper Up is composed of fibre-bundles from the triangularis (depressor anguU oris), the more
superficial portion of that in the lower lip by fibre-bundles from the caninus (levator anguli oris).
These fibre-bundles form commissures at the angles of the mouth and extend toward the median
line, where many of them interdigitate with those of the opposite side, and are attached to the
skin of the lips. The deeper portions are partly formed by fibre-bundles prolonged from the
buccinator, the mandibular fibre-bundles of the latter muscle going mainly to the upper lip,
the maxillary fibre-bundles mainly to the lower hp. These fibre-bundles are attached chiefly
to the mucosa, near the corners of the mouth.
The compressor labii, or muscle of Klein, is composed of bundles of fibres which take a
course transverse to those of the orbicularis, and pass obhquely from the skin surrounding the
oral orifice toward the mucosa which bounds its inner margin. It is said to be best marked
in infants.
The incisivus labii superioris is a small muscle-bundle which passes from the alveolar jugum
of the upper canine tooth to the back of the orbicularis near the corner of the mouth.
The incisivus labii inferioris passes similarly from the alveolar jugum of the lower lateral
incisor tooth to the back of the orbicularis in the lower lip.
Nerve-supply. — These muscles are suppUed by the buccal branches of the facial nerve which
enter the orbicularis on the lateral border.
Relations. — The main mass of intrinsic musculature of the lips is placed slightly nearer the
mucosa than the skin. On its deep surface lie the labial arteries.
Action. — The orbicularis draws the upper lip downward, the lower lip upward. The
incisive muscles draw the corners of the lips medialward, and the compressor flattens the lips.
Together they serve to close the mouth. Acting separately they may draw different parts of
it in the directions indicated by their structure. The circumferential portion of the orbicularis
acting with the incisive muscles makes the lips protrude. The central portion of the orbicularis
draws the lips together, and when the buccinator also acts, draws them against the teeth. It
is this portion of the muscle that has chiefly to do with nutritive functions. The more peripheral
parts of the muscle are chiefly utilised in the expression of the emotions.
Retractors op the Lips or Quadrate Muscles
(Fig. 341)
The quadratus labii superioris is a thin, quadrangular muscle with three heads, all of
which are inserted into the skin and musculature of the upper lip.
The caput zygomaticum (zygomaticus minor) is long and slender and arises from the lower
part of the external surface of the zygomatic bone beneath the lower border of the palpebral
portion of the orbicularis oculi. It passes obliquely forward over the caninus and orbicularis
oris muscles, and extends to a cutaneous and muscular insertion in the upper hp medial to the
corner of the mouth. It lies medial to the zygomaticus.
The caput infraorbitale (levator labii superioris), a broad, flat muscle, arises from the infra-
orbital margin of the maxilla, where it is concealed by the orbicularis oculi. It extends obhquely
forward over the caninus and beneath the caput angulare to the skin and musculature of the
lateral half of the upper hp.
The caput angulare (levator labii superioris alseque nasi) arises from the root of the nose,
where it is fused with the frontalis. As it descends it divides into two fasciculi, one of which is
attached to the skin and the alar cartilage of the nose; the other passes obliquely downward
over the caput infraorbitale to the skin and musculature of the lateral half of the upper hp.
Nerve-supply. — The zygomatic ramus of the seventh nerve sends branches to enter the deep
surface of each of the divisions of the muscle.
Actions. — It raises the lateral hah of the upper lip and the wing of the nose. It is of value
in inspiration, serves to express the emotion of discontent, and comes into play in violent weep-
ing.
Variations. — The caput zygomaticum is often absent. It may be fused with the zygoma-
ticus (major). It may be doubled. Its origin may extend to neighbouring structures. The
other heads, though more stable, vary considerably, especiafly in the extent of their fusion with
neighbouring muscles.
The quadratus labii inferioris (depressor labii inferioris) is a thin, rhomboid muscle which
arises below the canine and bicuspid teeth from the base of the mandible, between the mental
protuberance and the mental foramen, and extends obhquely upward in a medial direction to the
orbicularis oris, through which its fibre-bundles pass. Its more medial fibres cross at their
insertion with those of the muscle of the other side. It is attached to the skin and mucosa of
the lower lip. It is essentially a part of the platysma, and is superficially united to the skin
except where covered by the triangularis (depressor anguh oris). It crosses the mental vessels
and nerves and a part of the mentalis (levator menti).
Nerve-supply. — The mandibular branch of the facial sends twigs into its deep surface near
the lateral border.
Action. — It draws down and everts the lower Up. It is an antagonist of the mentahs
(levator menti). It plays a part in the expression of terror, irony, great anger, and similar
emotions.
Muscles of the Angle of the Mouth
(Figs. 341, 342, 344, 345)
The caninus (levator anguli oris) is a flat, quadrilateral muscle which arises from the canine
fossa of the maxilla and runs beneath the quadratus (levator) labii superioris to the corner of
ORAL MUSCLES
333
the mouth, where it becomes attached to the skin and sends some fasciculi into the orbicularis of
the lower lip. Between the caninus and the quadratus labii superioris there is a certain amount
of fatty areolar tissue through which the infraorbital vessels and nerves run. Its deep surface
extends over the canine fossa, the buccinator muscle, and the mucosa of the Up. The external
maxillary (facial) artery passes over its inferior extremity.
The zygomaticus (z. major) is a long, ribbon-shaped muscle which arises by short tendinous
processes from the zygomatic bone near the temporal suture under cover of the orbicularis oculi.
It passes obliquely to the corner of the mouth, where it is attached to the skin and mucosa.
The body of the muscle is subcutaneous and is usually surrounded by fat. It crosses the
masseter and buccinator muscles and the anterior facial vein.
The risorius is a thin, triangular, subcutaneous muscle which extends across the middle of
the cheek and lies in a more superficial plane than the platysma, with which it is often fused. It
arises from the tela subcutanea above the parotid fascia. Its fibres converge across the masseter
muscle toward the angle of the mouth and are attached to the skin and mucosa in this vicinity.
It lies above the anterior facial vein and external maxillary artery.
The platysma has been described above.
The triangularis (depressor anguli oris) is a broad, flat, well-developed, subcutaneous muscle
which arises from the base and external surface of the body of the mandible below the canine,
bicuspid, and first molar teeth. From here its fibres converge toward the corner of the mouth,
where they are in part inserted into the skin and in part are continued into the orbicularis oris
of the upper hp. It overUes the buccinator and the quadratus (depressor) labii inferioris
muscles. Not infrequently (58 out of 92 bodies — LeDouble) some fascicuh are continued into
Fig. 343. (After Eisleh.) Buccinator Muscle and Ptertgomandibular Raphe,
as seen from the buccal side.
The alveolar processes of both jaws have been removed in the region of the molar teeth.
The soft palate and its muscles have been removed.
Auditory
(Eustachian)
.tube
Mylo-hyoid
Buccinator
Internal pterygoid
the neck as the transversus menti, a fibro-musoular band formed by the interdigitation of the
slips prolonged from each side below the chin and superficial to the platysma. Santorini
described the transversus menti as an independent though inconstant muscle. According to
Eisler the true transversus menti muscle is to be distinguished from aberrent slips of the tri-
angularis or of the platysma in this region. In one instance Eisler found a slender nerve
emerging through the platysma and passing to this muscle.
Nerue-supply. — The zygomatic branch of the seventh nerve supphes the canine (levator
anguli oris) and zygomatic (major) muscles. Branches enter the middle of the deep surface of
the latter muscle and the superficial surface of the former near its lateral border. The risorius
is suppUed by branches from the buccal rami of the seventh nerve, which enter its deep sur-
face. The triangularis (depressor anguh oris) is supplied by the buccal branch through branches
which enter its deep surface near the posterior margin.
Action. — The caninus (levator anguli oris) and zygomatic (z. major) muscles raise the corner
of the mouth, the former at the same time drawing it medially, the latter, laterally. The
caninus gives rise to expression of bitterness or menace. The zygomaticus is active in smihng or
laughing. When contracted greatly it elevates the cheek and the lower eyehd and produces
crow's-foot wrinkles at the corner of the eye. The risorius draws the angle of the mouth later-
ally. ^ In spite of its name it is not used to express pleasure, but instead gives rise to an expression
of pain. The triangularis (depressor anguli oris) depresses the corner of the mouth and draws
it laterally, giving rise to the expression of grief.
334 THE MUSCULATURE
Variations. — The risorius is very inconstant in its development, and in its relations to-
neighbouring muscles, and is not infrequently quite small. The zygomaticus is rarely absent
Its origin may extend to the temporal or masseteric fascias. It may be doubled throughout its
length or at one extremity. Frequently the triangularis is divided into three fasciculi.
The buccinator (fig. 343) arises from — (1) the molar portion of the alveolar process of the
maxilla; (2) the buccinator crest of the mandible, and (3) the pterygo-mandibular raphe of the
bucco-pharyngeal fascia. This narrow fibrous band, which separates the buccinator from the
superior constrictor of the pharynx, extends from the pterygoid hamulus to the buccinator crest
of the mandible. The fibre-bundles are divisible into four sets. The most cranial extend
directly into the orbicularis of the upper lip. The next pass through the commissure at the
corner of the lips into the orbicularis of the lower lip; the third through the commissure into the
orbicularis of the upper hp, and the fourth directly into the orbicularis of the lower lip. The
muscle is attached chiefly to the mucosa of the lips near the angle of the mouth. Some fibre-
bundles extend to the more medial portion of the mucosa and some through the orbicularis to
the skin.
Nerve-supply. — By the buccal branch of the facial nerve through filaments which enter the
posterior half of its outer surface.
Relations. — The muscle is covered externally by the thin bucco-pharyngeal fascia; internally
by the mucosa of the mouth. Above its outer surface lie the zygomatic (z. major), risorius, and
masseter muscles." Between the last and the buccinator lies a large pad of fat (the buccal fat
pad). The parotid duct passes forward over the muscle, and slightly in front of its centre
pierces it and passes into the mouth. It is crossed by the external maxillary (facial) artery and
anterior facial vein and by the buccal artery and nerve.
Actions. — It draws the corner of the mouth laterally, pulls the lips against the teeth, and
flattens the cheek. It is of use in mastication, swallowing, whistling, and blowing wind-
instruments.
Variations. — Occasionally it consists of two laminse, a condition found in many mammals.
It may be continuous in part with the superior constrictor of the pharynx, as in the cat.
(c) MENTAL MUSCLE
The mentalis (levator menti) (fig. 343) is a short, thick muscle which arises from the alveolar
jugum of the lower lateral incisor tooth and the neighbouring region of the mandible under
cover of the quadratus (depressor) labii inferioris and beneath the oral mucosa, where this is
reflected from the lips to the gums. It extends to the chin, where it is fused with the muscle
of the opposite side and is attached to the skin of the chin.
Nerve-supply. — The mandibular branch of the seventh nerve sends terminal twigs into this
muscle.
Actions. — It draws up the skin of the chin and thus indirectly causes the lower lip to pro-
trude. It is of use in articulation, in forcing bits of food from between the gums, and in the
expression of various emotions (muscle of pride) .
Variations. — It varies greatly in size and generally is fused with the platysma.
{d) NASAL MUSCLES
(Figs. 341 and 344)
Toward the nasal apertures several muscles converge. Those extending from
above elevate and dilate, those from below depress and contract, the nostrils.
To the former belongs the pars transversa of the nasalis (compressor naris), a
triangular muscle extending from the bridge of the nose to the naso-labial sulcus;
the caput angulare of the quadratus labii superioris (levator labii superioris
alaeque nasi), which arises from the root of the nose and sends a fasciculus to the
wing of the nose; and the dilatores naris, described below; to the latter, the
pars alaris of the nasalis (depressor alas nasi), which extends from the alveolar
juga of the upper lateral incisor and canine teeth to the dorsal margin of the
nostril; and the small depressor septi nasi.
The nasalis consists of two parts, the pars transversa and the pars alaris. The pars trans-
versa (compressor naris) is triangular. It lies on the side of the nose above the wing. Its
fibre-bundles arise from an aponeurosis which overlies the bridge of the nose, is adherent to the
skin, and is not closely attached to the underlying cartilage. From this aponeurosis the fibre-
bundles converge toward the back of the wing, where they are attached to the skin along the
fine which separates the wing from the cheek (naso-labial sulcus). Its insertion is covered by
the nasal proce.ss of the caput angulare (levator labii superioris alseque nasi) of the quadratus
labii superioris (p. 332), with which its fibres interdigitate. An attachment (origin) is also
described by many as taking place in the lower part of the canine fossa of the maxilla.
The pars alaris (depressor ala; nasi) (fig. 343), is a small quadrangular muscle situated below
the aperture of the nose, between this and the alveolar portion of the maxilla. It is covered by
the mucosa of the gum, by the orbicularis oris and the quadratus (levator) labii superioris, aad
laterally is fused with the pars transversa (compressor naris). It arises from the alveolar juga
of the lateral incisor and the canine teeth. Its fibre-bundles extend vertically to the skin of
the dorsal margin of the nostril, from the dorsal part of the cartilage of the wing to the septum
The depressor septi is a flat, triangular muscle which extends from the orbicularis oris to
the lower edge of the nasal septum. It may arise from the jugum alveolare of the medial
PERIORBITAL MUSCLES
335
The dilator naris posterior is a thin, triangular muscle which lies on the side of the wing
of the nose. It arises from the skin of the naso-labial groove and is attached to the inferior
border of the wing of the nose.
The dilator naris anterior is a very small, thin muscle which runs from the lower margin
of the cartilage at the front of the wing of the nose to the skin. It is not usually clearly marked.
Nerve-supply. — The muscles of this gi'oup are supphed by the infra-orbital and buccal
branches of the facial nerve.
Actions. — The transverse portion of the nasalis (compressor naris) acts with the angular
head (levator labii superioris alaeque nasi) of the quadratus labii superioris in drawing lateral-
FiG. 344. — The Deeper Muscles op the Face and Neck.
Procerus
Quadr. labii
sup. caput
angulare
Caput infra-
orbitale
Nasalis, pars
transversa
Cani
Depressor
septi nasi
Nasalis, pars
alaris
Orbicularis oris
Buccinator
Triangularis
Quadratus la-
bii inferions
M entails
Mylo-hyoid
Anterior belly
of digastric
- Temporal
_ Posterior belly
of digastric
' Splenius capitis
- Stylo-hyoid
Scalenus anterior
• '■ %\
ward and up the lateral margin of the wings of the nose, and gives rise to the expression of sen-
suaUty. (Poirier.) This accords with the electrical experiments of Duchenne. However,
acting in conjunction with the alar portion, the transverse portion of the nasalis may constrict
the nostrils. The alar portion (depressor alae nasi) of the nasalis and the depressor septi nasi
draw down the nostril. The former tends to contract it from side to side, the latter from front
to back, and at the same time to depress the tip of the nose. They play a part in the expression
of anger and of pain. The functions of the other muscles are indicated by then' names.
Variations. — The muscles of the nose vary considerably in extent of development, and one
or more may be absent. Authors differ considerably in their description of several of the
muscles. The anomalus is a longitudinal muscle strip occasionally found running from the
frontal process to the body of the maxilla near the lateral margin of the nasal aperture.
(e) PERIORBITAL MUSCLES
(Figs. 341, 344)
The muscles which encircle the orbit constrict the entrance of the orbit so as
to shut out light and protect the eye against foreign bodies. To these belong
336 THE MUSCULATURE
the orbicularis oculi, the corrugator, and the procerus. The orbicularis oculi is a
large, flat, elliptical muscle which lies in the eyelids and over the bone surrounding
the orbit. Three parts are recognised, a palpebral, an orbital and a lacrimal.
The quadrangular corrugator extends from the nasal portion of the frontal bone
to the skin of the middle half of the eyebrow; the narrow procerus (pyramidaHs
nasi) from the bridge of the nose to the skin at the root. The muscles which
have an antagonistic action are the levator palpebrse superioris and the epicranius.
The levator palpebrse is described in the chapter on the Eye (see Section VIII),
the epicranius in the following subsection.
The orbicularis oculi. — The palpebral portion arises from the ventral surface and margins
of the lateral portion of the medial palpebral hgament (tendo oculi), and from the covering of the
lacrimal sac. The fibre-bundles spread out as they pass into the eyelids and again are con-
centrated toward their insertion into the outer surface of the lateral palpebral ligament. Many
of the fibre-bundles interdigitate here without being inserted into the ligament. The muscle
in each eyelid lies between the tarsal plate and the skin, separated from both by loose tissue.
The superficial muscle-fibres nearest the margin of the hds constitute the ciliary muscle, or muscle
of Riolan. They are very small fibres and probably act on the eyelashes and Meibomian
glands.
The orbital portion arises by a superior origin from the medial palpebral ligament (tendo
ocuU), the nasal portion of the frontal bone, and the anterior lacrimal crest of the maxilla, and
by an inferior origin from the medial palpebral hgament and the medial portion of the inferior
rim of the orbit. The fibre-bundles form a flat ring which surrounds the orbit for a consider-
able distance, especially inferiorly. The muscle is adherent to the overlying skin. It hes over
the bones surrounding the margin of the orbit and over the attachments of several of the facial
muscles attached to these bones. With these muscles some of the fibre-bundles are usually
continuous.
The lacrimal portion (tensor tarsi or Horner's muscle) arises from the posterior lacrimal
crest of the lacrimal bone and passes down on the dorsal surface of the lacrimal sac and the
medial palpebral ligament (tendo oculi). It bifurcates and furnishes a fasciculus attached to
each tarsal plate. Some of the fibre-bundles surround the lacrimal canaliculi and some
surround the ducts of the tarsal glands and the roots of the eyelashes.
The corrugator arises from the frontal bone near the fronto-nasal suture. It extends
obliquely upward to be inserted into the skin of the middle half of the eyebrow. The fibre-
bundles of insertion interdigitate with those of the frontahs. The muscle hes relatively deep.
It is covered by the procerus (pyramidahs nasi), the frontalis, and the orbicularis. Under it
lie the supra-orbital vessels and nerves.
The procerus (p3rramidalis nasi) overlies the nasal bone. It arises from the lateral cartilage
of the nose through a fibrous membrane and also directly from the nasal bone, and is attached
to the skin over the root of the nose, where its fibres interdigitate with those of the frontalis.
The medial margins of the muscles on each side are more or less fused.
Nerve-supply. — The muscles of this group are supphed by temporal and infraorbital branches
of the facial nerve which enter the deep surfaces near the lateral margins.
Action. — The palpebral portion of the orbicularis closes the eyehds, of which the upper
moves more freely than the lower. It also serves to dilate the lacrimal sac and allow the
tears to flow away readily. The tensor tarsi probably contracts the sac and forces the tears
into the nose. The upper half of the orbital portion of the orbicularis contracts and depresses
the tissue overhanging the orbit, and stretches the skin of the forehead. The corrugator draws
the skin of the brow downward and medially, thus aiding the preceding muscle. It causes the
perpendicular furrows characteristic of frowning. The procerus (pyramidahs nasi) draws down
the skin of the forehead and wrinkles the skin across the root of the nose. The lower half of
the orbital portion of the orbicularis raises the skin of the cheek, causing the wrinkles seen to
radiate from the corner of the eye. The whole set of muscles comes into play in the forcible
closure of the eyes. In case of violent expiratory efforts, as in shouting, sneezing, coughing,
etc., the eye is thus usually forcibly closed. The pressure thus exerted on the eyeball prevents
a too violent flow of blood to the vessels of the eye. Pressure is thought at the same time to
be exerted on the lacrimal gland so as to cause the excessive flow of tears often experienced at
such times.
Variations. — The muscles of this group vary in extent and differentiation, and may be more
or less fused with one another or with neighbouring muscles. The orbital portion of the or-
bicularis, the corrugator, and the procerus have been found absent.
(/) THE EPICRANIAL MUSCULATURE
(Fig. 341)
The epicranius (occipito-frontalis) is formed of the two frontal muscles, which
lie on each side of the forehead, the two occipital muscles, which occupy corre-
sponding positions on the occipital bone, and of the epicranial aponeurosis, the
galea aponeurotica, which extends between these. The occipital muscles arise
from the supreme nuchal line and are inserted into the galea aponeurotica. The
frontal muscles arise from the latter and are inserted into the skin near the eye-
brows. The chief function of these muscles is to elevate the brows. The
AURICULAR MUSCLES 337
muscles and the intervening aponeurosis lie between two layers of fascia, the
external of which is fused to the skin, while the internal moves freely over the
periosteum, to which it is loosely attached. Hsemorrhages and abscesses
spread freely between the deep layer of fascia and the periosteum.
The frontalis is a large, thin muscle with convex upper and concave lower border. It arises
from the epicranial aponeurosis midway between the coronal suture and the orbital arch, and is
inserted into the skin of the eyebrow and of the root of the nose. The medial fibre-bundles take
a sagittal direction; the lateral converge obhquelj' toward the brow. The medial margins of
the muscles of each side are approximated near the attachment. The more medial fibre-bundles
are continuous with those of the procerus (pyramidahs nasi) and the angular portion (levator
labii superioris alasque nasi) of the quadratus labii superioris; the more lateral interlace with those
of the corrugator and orbicularis muscles. The branches of the vessels and nerves of the frontal
region pierce the muscle and are distributed between it and the skin.
The occipitalis, flat and quadrangular, lies on the occipital bone above the supreme nuchal
line. It rises by tendinous fibres from the lateral two-thirds of this line and from the posterior
part of the mastoid process of the temporal bone, and is inserted into the epicranial aponeurosis.
The medial fibre-bundles run sagitaUy, while the lateral run obliquely forward. The occipital
artery and nerve lie between the muscle and the skin. The lateral border of the muscle comes
in contact with the posterior auricular muscle. The muscles of each side are usually separated
by a strip of aponeurosis.
The galea aponeurotica (epicranial aponeurosis) is a fibrous membrane which extends be-
tween the occipital muscles and from them anteriorly to the frontal muscles. In the area be-
tween these two sets of muscles it is composed largely of sagitahy running fibres into which
coronal fibres radiate from the region of the muscles of the ear. Between the two occipital
muscles the aponeurosis is attached to the supreme nuchal line and external occipital protuber-
ance. Laterally the fascia covering it is continued as a special investment of the auricular
muscles, beyond which it is attached to the mastoid process, the zygoma, and to the external
cervical and the masseteric fasciae.
Nerve-supply. — The frontahs is suppUed by the temporal branches of the facial nerve, the
occipitalis by the posterior auricular branch. The branches enter the deep surface of each of
these muscles near its lateral border.
Action. — The occipitalis serves to draw back and to fix and make tense the epicranial ap-
oneurosis. The frontalis, with its aponeurotic extremity fixed, elevates the brows and throws
the skin of the forehead into transverse wrinkles as in the expression of attention, surprise, or
horror. When both muscles contract forcibly there is, in addition, a tendency to make the
hair stand on end because the hair-bulbs of the occipital region slant forward, those of the frontal
region backward. The frontalis when fixed below puUs the scalp forward.
Variations. — The ocoipitahs is occasionally absent, a condition normal in ruminants. The
muscles of the two sides may be fused in the median line (normal in dogs). It may be fused
with the posterior auricular. The frontalis is rarely missing. The frontalis may send shps
to the medial or lateral angles or the orbital arch of the frontal bone, to the nasal process of the
maxilla or to the nasal bone. The fibre-bundles of the frontalis may interdigitate across the
median line.
The transversus nuchas, or occipitaUs minor, is a small muscle, frequently present (27 per
cent., Le Double), which runs from the occipital protuberance toward the posterior auricular
muscle, with which it may be fused. It may He over or under the trapezius.
(g) AURICULAR MUSCLES
(Fig. 341)
The intrinsic muscles of the auricle are described in Section VIII. There are
three 'extrinsic^ auricular muscles which converge from regions anterior, superior,
and posterior to the auricle and are inserted into it.
The auricularis anterior (attrahens aurem) is a small, flat, triangular muscle which arises
between the two layers of the fascia of the galea aponem-otica, extends over the zygomatic arch,
and is attached to the ventral end of the helix. The fibre-bundles converge from the origin
toward a tendon of insertion. The area of origin of this muscle is often marked by a fibrous
band tangential to its component fibres. From this band muscle fibre-bundles radiate out
toward the frontal region of the skull. To the muscle formed of these radiating fibres the names
epicranio-temporalis (Henle), temporalis superficialis (Sappey) and auriculo-frontalis (Gegen-
baur) have been given.
The auricularis superior (attoDens aurem) is a large, tliin, triangurar muscle which, from
its tendinous insertion on the eminence of the triangular fossa of the ear, radiates upward into '
the fascia of the galea aponeurotica, between the layers of which it takes oigin near the temporal
ridge. It lies over the temporal fascia and the periosteum of the parietal bone.
The auricularis posterior (retrahens aurem) is a thin, band-like muscle which extends over
the insertion of the sterno-cleido-mastoid from the base of the mastoid process and the ap-
oneurosis of the sterno-cleido-mastoid muscle to the convexity of the concha, where it has a ten-
dinous insertion. It is usually composed of two fasciculi, and is contained between two layers
of fascia derived from the galea aponeurotica.
Nerve-supply. — The aiu-icularis anterior and superior are supphed by the temporal branch
of the facial, the auricularis superior and posterior by the posterior am-icular branch. The
twigs of supply run to the deep surface of the muscles.
338
THE MUSCULATURE
Relations. — The superficial ascending branch of the auriculo-temporal nerve usually runs
superficial to the anterior and superior auricular muscles. The superficial temporal vessels run
at first beneath these muscles and the lateral expansion of the galea aponeurotica, then between
the two fascial layers which enclose the muscles. Their branches of distribution finally come
to lie between the muscles and aponeurosis and the skin. The posterior auricular artery and
nerve usually run under cover of the auricularis posterior.
Action. — The anterior muscle is a protractor, the superior an elevator, and the posterior a
retractor of the ear, but usually in man they are inactive.
Variations. — These muscles vary much in development. The most constant of them is
the superior. The posterior frequently is increased in size and may be fused with the occipitalis,
which originally was probably an ear muscle. From the anterior muscle a special deep fasciculus
is occasionally isolated. Each of the muscles is occasionally, though rarely, absent, the anterior
most frequently. An inferior auricular muscle is very rarely found in man, though present in
many of the lower mammals. A slip of the posterior auricular may run beneath the ear to the
parotid fascia.
Fig. 345. — The Temporal Muscle.
2. CRANIO-MANDIBULAR MUSCULATURE
(Figs. 344, 345, 346, and 347)
The cranio-mandibular muscles, or muscles of mastication, pass from the base
of the skull to the lower jaw. They are represented in the selachians by a single
muscle mass, the adductor mandibulee (Gegenbaur), but in the higher vertebrates
this muscle mass becomes variously subdivided during embryonic development.
The muscles are innervated by the masticator nerve (motor root of the tri-
geminal cranial nerve, the nerve of the mandibular arch). In man four muscles
are recognised, the temporal, masseter, and internal and external pterygoids.
The temporal and masseter muscles are situated on the lateral sm-face of the
skull, partly under cover of muscles of the facialis group. The temporal muscle
(fig. 345), which resembles the quadrant of a circle, arises from the temporal
fossa and is inserted into the coronoid process of the mandible; the thick, quad-
rilateral masseter (fig. 344) muscle arises from the zygomatic arch and is in-
serted into the lateral surface of the ramus and angle of the mandible. The
pterygoids (fig. 346) are more deeply seated. The cone-shaped external pterygoid
arises from the lateral side of the pterygoid process and lower surface of the great
wing of the sphenoid and is inserted into the condyloid process of the mandible
and the capsule of the joint. The thick, quadrilateral internal pterygoid parallels
the masseter. It arises from the pterygoid fossa of the sphenoid and is inserted
into the inner side of the angle of the mandible. It will be noted that the tem-
FASCIJE
339
poral, masseter, and internal pterygoid muscles have approximately vertical axes
of contraction and adduet the lower jaw, while the external pterygoid- has an
approximately horizontal axis of contraction and draws the jaw forward and,
when acting on one side, toward the opposite side.
Fig. 346. — The Pterygoid Muscles.
External pterygoid
Internal pterygoid
FASCI.E
The temporal fascia arises from the temporal line of the frontal bone and from the superior
temporal line of the parietal and the periosteum immediately below this. It extends to the
zygomatic arch. In its inferior quarter the fascia divides into two lamellae, one of which passes
to the outer, the other to the inner, surface of the arch, but at the superior margin of the arch
these two lamelte are united by dense fibrous tissue. Between the two lamella? above the
arch hes a fatty areolar tissue in which the middle temporal artery often runs. The outer sur-
face of the fascia is covered by the superficial temporal and anterior and superior auricular
muscles, and by a thin layer of fascia from the galea aponeurotica, with which, toward the zygo-
matic arch, it becomes merged. The superficial temporal artery and auriculo-temporal nerve
cross it.
The masseteric fascia represents essentially a continuation of the temporal fascia from the
inferior margin of the zygomatic arch over the masseter muscle which it covers. It is less thick
than the temporal fascia, but is firm and strong. It is attached dorsally to the dorsal margin
of the mandible, mferiorly to the inferior margin, and ventrally to the body and to the ventral
majgin of the ramus and the coronoid process of the mandible. In part it extends over the fat
pad of the cheek to the buccinator fascia. The parotid gland, covered by the parotid extension
of the external cervical fascia, extends over the posterior portion of this fascia. The parotid
fascia becomes fused to its external surface at the anterior margin of the gland. Over it lie
the parotid duct, the transverse facial artery, branches of the facial nerve, the zygomaticus
(major), risorius, and platysma muscles.
The pterygoid muscles are each surrounded by a dehcate membrane. In addition an
mterpterygoid fascia separates the two muscles. This arises from the sphenoidal spine and
toUows the internal surface of the external pterygoid to the mandible. MediaUy it is attached
to the lateral lamella of the pterygoid process; posteriorly and laterally it presents a free margin
which forms with the neck of the mandibular condyle, an orifice for the passage of the internal
maxillary artery, the auriculo-temporal nerve, and several veins. Its posterior margin is
strengthened into the spheno-mandibular ligament, which runs from the spine of the sphenoid
to the lingula of the mandible.
The pharyngeal region is separated from the pterygoid by a dense membrane, the lateral
pharyngeal fascia. This extends from the depth of the pterygoid fossa to the prevertebral
tascia, a,nd separates the tensor veh palatini from the internal pterygoid muscle. It is attached
above along a Ime extending from the external margin of the carotid canal to the internal margin
ot the oval foramen.
i
340
THE MUSCULATURE
Fig. 347.
CRANIO-MANDIBULAR MUSCLES 341
The sigmoidal septum is a thin membrane which occupies the incisura mandibulae and sepa-
rates the masseter from the external pterygoid muscle.
MUSCLES
The temporalis (fig. 345). — Origin. — (1) From the whole of the temporal fossa, with the
exception of that part formed by the body and temporal process of the zygomatic (malar) bone;
and (2) from the fascia covering the fossa. Insertion is into the tip, dorsal and ventral borders,
and the whole internal surface of the coronoid process of the mandible and the ventral portion
of the medial surface of the ramus.
In structure, the muscle is thin near its superior margin, but becomes thick as its insertion
is approached. The fibre-bundles arising from the medial surface of the fossa and from the
fascia converge upon the medial and lateral surfaces and the margins of a thick, broad tendon
which begins very high in the muscle, becomes visible laterally some distance above the zygo-
matic arch, and is inserted into the tip, edges, and internal surface of the coronoid process. On
the ventral and dorsal margins of the tendon the insertion of fibre-bundles continues to the coro-
noid process, while medially the insertion of the fibre-bundles is continued on the medial surface
of the coronoid process and often on the ramus as far as the body of the bone.
Nerve-supply. — Usually three branches from the anterior branch of the mandibular division
of the fifth nerve curve upward over the temporal surface of the great wing of the sphenoid and
enter the deep surface of the muscle. The posterior and middle nerves pass above the external
pterygoid; the anterior, which springs from the buccinator nerve, passes between the two heads
of the external pterygoid before curving upward.
Relations. — The muscle is covered by the temporal fascia and the zygomatic arch. Below
the temporal fossa the pterygoid muscles and the buccinator lie medial to it. The temporal
fossa in front of the muscle is filled with a fatty areolar tissue and this also extends between the
muscle and the temporal fascia. Fatty tissue hkewise lies between the muscle and the buccina-
tor. Medial to the muscle run the deep temporal vessels and nerves, the buccinator nerve
and the spheno-mandibular ligament. The masseteric nerve passes lateralward behind and
below the tendon.
The masseter (fig. 343) is composed of two layers. The superficial layer arises by an apo-
neurosis from the anterior two-thirds of the lower border of the zygomatic (malar) bone. The
fibre-bundles arise from the deep surface of this aponeurosis and its tendinous prolongations
pass obliquely downward and backward, and are inserted into the lower half of the external
surface of the ramus, into the angle, and into the neighbouring portion of the body of the man-
FiG. 347.* — A AND B ARE Transvehsb Sections and C (after Testut), a Frontal Section
THROUGH the LeFT SiDE OF THE HeAD, IN THE REGIONS INDICATED IN THE DIAGRAM.
a and b in the diagram indicate the regions through which pass sections A and B, fig. 351; and
a', section A, fig. 357.
1. Adipose tissue. 2. Arteria temporalis superfioialis. 3. A. carotis externa. 4. A. car-
otis interna. 5a. A. maxillaris externa (facial). 56. A. maxillaris interna. 6. A. verte-
bralis. 7. Atlas. 8. Cerebellum. 9. Epistropheus (axis). 10. Fascia buccopharyngea.
11. F. cervicalis, a (superficial layer), 6, deep parotid process. 12. F. interpterygoidea.
13. F. masseterioa. 14. F. nuchie. 15. F. pharyngobasilaris. 16. F. pharyngis lateralis.
17. F. temporaHs. 18. Galea aponeurotica. 19. Glandula parotica. 20. Ligamentum stylo-
mandibularis. 21a. Mandible, capitulum; b, coronoid process. 22. Meatus acusticus
ext. 23. Medulla oblongata. 24. MeduUa spinalis (spinal cord). 25. Musculus auricu-
laris posterior (retractor auris). 26. M. buccinator. 27. M. caninus (levator anguli
oris). 28. M. constrictor pharyngis medius. 29. M. constrictor pharyngis superior. 30.
M. digastricus. 31. M. genio-glossus. 32. M. hyo-glossus. 33. M. incisivus labii
inferioris. 34. M. levator veli palatini. 35. M. longus capitis (rectus capitis anticus
major). 36. M. longissimus capitis (trachelo-mastoid). 37. M. longitudinalis inferior.
38. _M. masseter. 39. M. mylo-hyoideus. 40. M. nasalis (alar portion). 41. M.
obhquus ca,pitis inferior. 42. M. obUquus capitis superior. 43. M. pterygoideus externus
— a, superior fasciculus; 6, inferior fasciculus. 44. M. pterygoideus internus. 45. M.
quadratus (levator) labii superioris. 46. M. rectus capitis anterior (minor). 47. M.
rectus capitis posterior major. 48. M. rectus capitis posterior minor. 49. M. rectus
capitis laterahs. 50. M. semispinalis capitis (complexus). 51. M. splenius capitis.
52. M. sterno-cleido-mastoideus. 53. M. stylo-glossus. 54. M. stylo-hyoideus. 55.
M._ stylo-pharyngeus. 56. M. temporalis (a, fasciculus from zygoma). 57. M. tensor
veli palatini. 58. M. trapezius. 59. M. zygomaticus (major). 60. Nervus accessorius
(spinal accessory). 61. N. alveolaris inferior (dental). 62. N. alveolaris posterior superior
(dental). 63. N. auriculo-temporalis. 64. N. buccinatorius. 65. N. canalis pterygoidei
(Vidian nerve). 66. N. glosso-pharyngeus. 67. N. hypoglossus. 68. N. Ungualis.
69. N. mandibularis. 70. N. masseteric nerve. 71. N. maxillary nerve. 72. N. mylo-
hyoid nerve. 73. N. palatinus. 74. Sympathetic trunk. 75. N. temporalis profundus.
76. N. vagus. 77. Os occipitale — a, basilar portion; b, external protuberance. 78. Os
sphenoidale. 79. Os temporale — o, processus zygomaticus; b, tubercle. 80. Os zygo-
maticum (malar). 81. Pharyngeal orifice of tuba auditiva (Eustachian tube). 82.
Palatum durum (hard palate). 83. Pharynx — a, oral portion; b, nasal portion. 84.
Pharyngeal recess. 85. Sinus maxillaris (antrum of Highmore). 86. Sinus transversus
(lateral). 87. Tonsila palatina. 88. Uvula. 89. Vena facialis posterior (temporo-
maxillary). 90. V. jugularis interna.
* This and the following series of cross-sections are taken from a thin, not very muscular,
adult male. The fasciae are represented in most instances disproportionately thick.
342 THE MUSCULATURE
dible — the more anterior directly, the posterior by means of an aponeurosis. The deep layer
arises from the lower border and internal surface of the zygomatic arch. The fibre-bundles
pass neai'ly vertically downward, and are inserted upon the upper hah of the external surface
of the ramus. The origin and insertion are by tendinous bands, to which the fibre-bundles are
attached in a multipenniform manner. The two layers are fused near the origin and insertion
and in front. From the temporal surface of the zygomatic bone and the neighbouring part of
the deep layer of the temporal fascia there arises a fasciculus which is separated by a pad of
fat from the main body of the temporal muscle, and is inserted into the lateral sm-faoe of the
lower extremity of the tendon of the temporal muscle and into the ventro-lateral surface of the
tip of the coronoid process. This fasciculus, sometimes described as a part of the temporal
muscle, is innervated by the masseteric nerve.
Nerve-supply. — The branch arises in common with the posterior nerve to the temporal
muscle from the motor root of the trigeminal (the masticator nerve). It passes above the
external pterygoid, through the mandibular (sigmoid) notch, and enters the deep surface of
the muscle near the dorsal margin.
• I Relations. — It is covered by the masseteric fascia (see above). It lies upon the ramus of
the jaw and ventrally is separated by a pad of fat from the buccinator muscle. At the mandibu-
lar (sigmoid) notch the sigmoid septum separates it from the external pterygoid muscle.
The parotid gland partly overlaps its posterior border.
The pterygoideus externus (figs. 343-346) consists of two fasciculi. Each is thick and tri-
angular. The superior is flattened in a horizontal, the inferior in a vertical, plane. At their
origin they are separated by a narrow cleft. Near the insertion they become more or less fused.
The superior fasciculus arises by short tendinous processes from the infratemporal (pterygoid)
crest and from the neighbouring portion of the under surface of the great wing of the sphenoid.
Its fibre-bundles converge toward the insertion, which takes place by short tendinous processes
into — (1) the capsular ligament in front of the articular disc and (2) the upper third of the front
of the neck of the condyle. The inferior fasciculus is the larger. It arises by short tendinous
processes from the lateral surface of the lateral lamina of the pterygoid process, from the pyrami-
dal process of the palate bone, and from the adjacent portions of the maxillary tuberosity.
The fibre-bundles converge toward their insertion into a depression on the front of the neck of
the condyle.
Nerve-supply. — A branch from the masticator nerve (mot6r root of the trigerninus) ap-
proaches the muscle near the upper border of the medial surface of the superior fasciculus and
gives branches to both portions.
Relations. — It is partly covered by the maxillary fasciculus of the internal pterygoid and by
the temporal and masseter muscles. Medial to it lies the chief fasciculus of the internal ptery-
goid muscle. The masseteric and the posterior and middle temporal nerves usually pass above
the muscle, the anterior temporal and the buccinator nerves and frequently the internal maxil-
lary artery between the two fasciculi. The internal maxillary vessels usually pass below the
lower border of the muscle and across its external surface; and the auriculo-temporal, lingual,
and infei-ior alveolar (dental) nerves cross the deep surface of the muscle.
The pterygoideus internus (fig. 346). — Origin. — From (1) the pterygoid fossa, and (2) from
the maxillary tuberosity and the pyramidal process of the palatine, where these adjoin.
Structure and Insertion. — From the medial and lateral lamins of the pterygoid process
there ai-ise aponeuroses and from the palatine bone at the lower margin of the fossa, and from
the maxillary tuberosity and palatine bone in front of the external pterygoid, there arise short
tendons. From these aponeuroses and tendons and directly from the fossa the fibre-bundles
take a nearly parallel course downward, backward, and outward, and are inserted in part in a
multi-penniform manner into the lower half of the internal surface of the ramus of the mandible.
The insertion extends to the mylo-hyoid ridge. The muscle is divided at its origin into two
fascicuh by the distal margin of the external pterygoid.
Nerve-supply. — The internal pterygoid nerve arises from the back of the mandibular nerve
near the foramen ovale. It passes near or through the otic ganglion, and thence to the medial
surface of the muscle near the dorsal edge. Both the buccinator and lingual nerves are also
described as sending filaments to this muscle.
Relations. — Laterally the muscle is covered by the interpterygoid fascia and the spheno-
mandibular ligament, the external pterygoid, temporal, and masseter muscles, and the ramus
of the mandible. The inferior alveolar (dental) and Ungual nerves and the corresponding vessels
run across this surface. Medial to the muscle lie the lateral pharyngeal fascia, the tensor veh
palatini muscle, and the superior constrictor of the pharynx.
Action. — The muscles of this group adduct the lower jaw and serve to carry it forward and
backward and from side to side. The elevation is produced by the masseter, temporal, and
internal pterygoid muscles. The suprahyoid muscles and the external pterygoid are the feeble
antagonists. T?he forward movement of the jaw is produced by the simultaneous action of the
two external pterygoids (slightly by the superficial layer of the masseter, and the anterior
fibres of the temporal) while the inferior posterior portions of the temporal muscles carry the
jaw at the temporo-discoidal joint somewhat backward. Oblique lateral rotator}' movements
are produced chiefly by the action of one of the external pterygoids. The alternate action of
these two msucles associated with the elevating action of the other muscles of the group,
gives rise to the grinding movement of the molar teeth. Purely lateral movements of the jaw
may be produced by the internal pterygoids, acting alternately. Lord (Anat. Rec, vol. 7, p.
355, 1913) states that in ordinary opening of the mouth the external pterygoids pull the
articular discs and condyles forward while the jaw rotates about an axis passing through
the insertions of the stylo-mandibular ligaments.
Variations. — The temporal muscle may have a more extensive cranial origin than usual.
It may be formed of two superimposed layers. It may be more or less fused with the external
pterygoid, or send a fasciculus to the coronoid process. The masseter may be completely
SUPRAHYOID MUSCULATURE
343
divided into two fasciculi, a condition normal in many mammals. A special fasciculus may
arise from the temporo-mandibular articulation or from the zygomatic (malar) bone. Its
deepest fibres may be fused with the temporal muscle. The two fasciculi of the external
pterygoid may be distinct, as in the horse. It has been seen fused with the temporal and with
the digastric muscle. The internal pterygoid may send a fasciculus to the masseter. It may
give origin to the stylo-glossus. Inconstant fasoiouh (accessory pterygoids) extending from the
body of the sphenoid to the pterygoid process represent perhaps remnants of the muscles which
act on the movable pterygoids possessed by many inferior vertebrates.
3. SUPRAHYOID MUSCULATURE
(Fig. 348)
From the hyoid bone there extend to the base of the skull on each side four
muscles which form a fairly well-defined group. They are situated external to
Fig. 348. — Antebioe and Lateral Cervical Muscles.
stylo-glossus
Hyo-glossus
Mylo-hyoid
Anterior belly of_£j
digastric
Raphe of mylo-,
hyoid
Inferior constrictor
Anterior belly of omo-
hyoid
Sterno-hyoid
Sterno-thyreoid
Thyreo-hyoid
the musculature of the tongue and pharynx. They elevate the hyoid bone and
larynx and depress the mandible. The most superficial of the group is the
slender, fusiform stylo-hyoid, which arises from the styloid process of the temporal
bone and is inserted into the body of the hyoid. Immediately behind this is the
flattened posterior belly of the digastric, which extends from its origin in the
mastoid notch to a tendon that runs between two divisions of the tendon of the
stylo-hyoid and is attached to the hyoid bone by an aponeurotic process. From
the digastric tendon the flat, triangular anterior belly is continued to the back
of the ventral portion of the inferior margin of the mandible. Internal to this
anterior belly the thin, quadrangular mylo-hyoid arises from the inner surface of
the body of the mandible and is inserted into a median raphe extending from the
mandible to the hyoid. Still more internally the triangular genio-hyoid extends
from the hyoid to the mental spine of the mandible. The last two muscles form
the muscular floor of the mouth. The motor innervation of the posterior belly
344 THE MUSCULATURE
of the digastric and of the stylo-hyoid is from the seventh cranial nerve, the
sensory innervation probably from the glosso-pharyngeal cranial nerve. The
mylo-hyoid and the anterior belly of the digastric are supplied by the masticator
(fifth) cranial nerve; the genio-hyoid from the hypoglossal by a branch, the
fibres of which are possibly derived through anastomosis from the first cervical
nerve.
From the morpliological standpoint, therefore, the stylo-hyoid and the posterior belly of
the digastric belong to the faciahs group; the anterior belly of the digastric and the mylo-hyoid
to the group of mandibular muscles, and the genio-hyoid to the muscles of the tongue inner-
vated by the hypoglossal, or, if we consider the nerve-fibres of the nerve to the genio-hyoid as
derived from the first cervical nerve, to the same group as the infra-hyoid muscles. It is con-
venient, however, to follow the usual custom of considering these muscles as a suprahyoid group.
FASCIA
The muscles of this group he internal to that portion of the external cervical fascia which
extends above the hyoid bone. This fascia, which is described on p. 347, comes into contact
merely with the tendon, the anterior belly, and to a slight extent with the posterior belly of the
digastric muscle. Above the tendon it sends inward a process which curves down internal to
the tendon, and is inserted into the external surface of the hyoid bone. The individual muscles
of the group are covered by dehcate adherent membranes. An aponeurotic membrane usually
extends between the anterior bellies of the digastric muscles of each side.
MUSCLES
(Fig. 348)
The stylo-hyoideus. — Origin. — From the lateral and dorsal part of the base of the styloid
process by a rounded tendon which soon becomes a hollow cone to the internal surface of which
the fibre-bundles of the muscle are attached. Structure and Insertion. — The fibre-bundles are
inserted on both sides of a slender tendon which divides to let the tendon of the digastric pass
through and then is attached to the ventral surface of the body of the hyoid bone near its junc-
tion with the great cornu.
Nerve-su-pply. — From the facial nerve as it emerges from the stylo-mastoid foramen a small
twig is given off which enters the proximal third of the deep surface of the muscle. The glosso-
pharyngeal nerve also gives to it a small twig, probably sensory.
Relations. — It descends immediately in front of the posterior belly of the digastric. Ex-
ternally lie the parotid and submaxillary glands. Medially it crosses the internal and ex-ternal
carotid artery, the hypoglossal nerve, the stylo-pharyngeus muscle, the superior constrictor
of the pharynx, and the hyo-glossus muscle. The posterior auricular artery passes between it
and the posterior belly of the digastric and the external maxillary artery crosses over it.
The digastricus. — The posterior belly arises by tendinous processes from the mastoid
(digastric) notch of the temporal bone. The fibre-bundles form a ribbon-)ike belly which con-
verges on the intermediate tendon. This begins as a semiconical laminar process on the outer
surface of the muscle a short distance above the hyoid bone. The anterior belly arises by short
tendinous processes from the digastric fossa of the mandible. This attachment is often de-
scribed as an insertion. The fibres converge on both surfaces of the flattened anterior end of
the intermediate tendon. The intermediate tendon hes a variable distance above the hyoid
bone, usually less than a centimetre. It curves upward toward each belly of the muscle. It
is united to the outer surface of the body and to the base of the great cornu of the hyoid bone
by an aponeurotic expansion from its inferior margin. Other expansions are usually continued
into the interdigastric aponeurotic membrane. Occasionally the intermediate tendon of the
digastric is bound to the hyoid bone by a fibrous loop which allows the tendon free play.
Nerve-supply. — The facial nerve near the stylo-mastoid foramen gives off a branch which
enters the proximal third of the anterior margin of the muscle. From this a ramus may be
continued through the muscle to the glosso-pharyngeal nerve. The anterior belly is supplied
by a branch of the nerve to the mylo-hyoid muscle. This enters the middle of the lateral part
of the deep surface. Very rarely the vagus may supply the anterior belly, the hypoglossal,
the posterior belly.
Relations. — The posterior belly of the digastric lies internal to the mastoid process and
the longissimus capitis (trachelo-mastoid), splenius, and sterno-cleido-mastoid muscles. Pos-
teriorly near its origin are the rectus capitis lateralis and obliquus cap. sup. muscles, the occip-
ital artery and the spinal accessory nerve. It helps to form the deep wall of the cavity in which
the parotid gland is placed. Internally it crosses the origin of the styloid muscles, the carotid
arteries, the internal jugular vein, and the twelfth cranial nerve. The intermediate tendon
of insertion hes below the inferior margin of the submaxillary gland, and crosses the hyo-
glossus and mylo-hyoid muscles. The relations to the stylo-hyoid muscle have been described
above. The anterior belly lies on the mylo-hyoid and is covered by the external cervical fascia
and the platysma.
The mylo-hyoideus. — Origin. — From the mylo-hyoid ridge of the mandible. Structure
and Insertion. — Its fibre-bundles take an oblique course and are inserted into — (1) a median
raphe extending from the middle of the ventral surface of the hyoid bone nearly or quite to the
MUSCLES OF THE TONGUE 345
dorsal surface of the inferior margin of the mandible, and (2) into the ventral surface of the hyoid
bone. Some of the fibre-bundles may cross the median line. The muscles of the two sides
form a sheet with a downward convexity which lies between the inner surface of the body of
the mandible and the hyoid bone. On the diaphragm thus formed rests the tongue.
Nerve-supply. — From the mylo-hyoid branch of the inferior alveolar (dental) nerve several
filaments enter the under surface of the muscle.
Relations. — The mylo-hyoid muscle is covered externally by the submaxillary gland, the
anterior belly of the digastric, and the external cervical fascia. It is crossed by the submental
artery. With the genio-hyoid and the genio-glossus muscles it helps to bound a cornpartment
in which are lodged the sublingual gland, the duct of Wharton, and the deep portion of the
submaxillary gland. Its deep surface also faces the stylo-glossus and hyo-glossus muscles, the
lingual and hypoglossal nerves, and to a slight extent the buccal mucosa.
The genio-hyoideus (fig. 349). — Origin. — By short tendinous fibres from the mental spine
of the mandible. Structure and Insertion. — The fibre-bundles diverge and are inserted into the
ventral surface of the body of the hyoid bone. Usually a special fasciculus goes to the great
cornu of the hyoid bone.
Nerve-supply. — The hypoglossal nerve sends a filament to the middle third of the deep
surface of the muscle. The nerve-fibres are thought to be derived chiefly from the first
cervical nerve.
Relations. — It lies between the genio-glossus and mylo-hyoid muscles. It adjoins its
fellow of the opposite side and is often fused with it. Lateral to it he the subhngual and sub-
maxillary glands and the hypoglossal nerve.
Action. — The muscles of this group all elevate the hyoid bone and, through this, the larynx
and inferior part of the pharynx, and thus play a part in the act of swallowing. The stylo-
hyoid and posterior belly of the digastric serve also to draw the hyoid bone in a dorsal direction;
the ventral belly of the digastric and the genio-hyoid, in a ventral direction. The digastric,
genio-hyoid, and mylo-hyoid depress the mandible, when the hyoid bone is fixed. The
posterior belly of the digastric has a slight power to bend the head backward.
Variations. — The stylo-hyoid tendon frequently passes entirely in front of and less frequently
entirely behind the digastric muscle. Its insertion may be of greater extent than usual. A
special fasciculus to the lesser cornu is not very infrequent; more rarely one extends to the angle
of the jaw or to other regions. The muscle may arise from the petrous portion of the tem-
poral or from the occipital bone, as in some lower vertebrates. It may be doubled or absent,
or fused with the posterior belly of the digastric. The anterior belly of the digastric may be
missing; the posterior belly may be inserted into the angle of the jaw. The intermediate ten-
dons of the digastric of each side may be connected by a fibrous arch. The anterior bellies of
the muscles of each side may be united by a fasciculus or fused. The anterior belly is frequen tly
doubled. The posterior belly may be divided by a tendinous inscription. Fasciculi may pass
from either belly to neighbouring structures. The mylo-hyoid may not extend quite to the
hyoid bone. It may be more or less fused with neighbouring muscles. Rarely it is absent.
The genio-hyoid is frequently more or less fused with the muscles of the tongue or with the genio-
hyoid of the opposite side. A considerable number of infrequently found muscles have been
described superficial to the stylo-hyoid and digastric muscles. Most of them are innervated
by the glosso-pharyngeal nerve or by the facial nerve.
4. MUSCLES OF THE TONGUE
(Fig. 349)
The tongue is a flexible organ, composed chiefly of various muscles, some of
which lie entirely within its substance, while others extend to be attached to
neighbouring parts of the skeleton. To the former the term intrinsic, to the
latter the term extrinsic, is frequently applied. In this section the extrinsic
muscle will alone be taken up. The intrinsic muscles are described in the
section on the Digestive System. Certain pharyngeal and palatal muscles
which are continued into the tongue are described in connection ^vith the
pharynx. The extrinsic musculature of the tongue is concealed below by the
suprahyoid musculature and the sublingual gland. It is covered on the free
surface of the tongue by the mucosa.
The musculature of the tongue is supplied by the hypoglossal nerve, which is
in series with the motor roots of the spinal nerves. It is, primitively at least,
derived from the ventral portion of mj'^otomes in series with the spinal myotomes.
Four extrinsic muscles are recognised on each side. The stylo-glossus is a
slender muscle, which arises from the styloid process and is inserted into the side
of the tongue. It is cylindrical near its origin, flat and triangular near its inser-
tion. The thin, quadrilateral hyo-glossus arises from the body and great cornu
of the hyoid bone and is inserted into the dorsum of the tongue. The chondro-
glossus arises from the lesser cornu of the hyoid bone and joins the superior and
inferior longitudinal muscles of the tongue. The genio-glossus (genio-hyo-
glossus), which forms the main part of the body of the tongue, arises from the
mental spine of the mandible, from which the fibre-bundles radiate out toward the
whole length of the dorsum of the tongue and to the hj'oid bone.
346
THE MUSCULATURE
Under the mucous membrane of the tongue is a dense layer of fibrous tissue,
the lingual fascia. In the body of tlie tongue there is a sagittal septum linguae,
which separates the two genio-glossus muscles. A transverse fibrous lamella,
the hyo-glossal membrane, helps to unite the tongue to the hyoid bone. Delicate
membranes invest the free portions of the extrinsic muscles of the tongue.
MUSCLES
The stylo -glossus. — This arises from the front of the lower end of the styloid process of
the temporal bone and from the upper part of the stylo-mandibular ligament. Insertion. — It
runs obliquely downward, forward, and medially, with slightly diverging fibre-bundles, to the
lateral margin of the tongue, where it gives rise near the anterior pillar of the fauces to two
fasciculi. The larger, lateral, longitudinal fasciculus runs superficially along the lateral margin
of the tongue to the tip. The fibre-bundles are attached to the overlying mucosa and under-
lying musculature. The smaller, inferior, transverse fasciculus gives rise to diverging fibre-
bundles which pass medially through the hyo-glossus into the base of the tongue. The most
posterior of these diverging bundles may extend to the hyoid bone.
The hyo-glossus. — This arises from — (1) the lateral part of the ventral surface of the body
of the hyoid bone and (2) from the upper border of the great cornu. The fibre-bundles take a
nearly parallel course upward, diverging, however, slightly. Near the upper margin of the back
Fig. 349. — Side View op the Muscles op the Tongue.
>
Glosso-palatinus
Stylo-glossus
-hyoid
Anterior belly of -
digastric
part of the tongue they curve mcdianward and interlace with the intrinsic musculature of this
region. The dorsal fibre-bundles pass transversely, the middle obliquely, the ventral longi-
tudinally. They are inserted into the fibrous tissue which forms the skeletal framework of the
tongue.
The chondro-glossus is a small muscle which arises from the lesser cornu of the hyoid bone
and gives rise to fasciculi which join the longitudinalis inferior and the longitudinalis superior
of the tongue described in Section IX.
The genio-glossus. — This arises from the mental (genial) suine of the mandible partly
directly, partly by means of a short, triangular tendon. The more inferior fibre-bundles radiate
toward the tip of the tongue; the intermediate extend directly toward the dorsum of the tongue,
where they are inserted into the lingual fascia and skeletal framework. The inferior curve
back to be inserted on the median part of the superior border of the hyoid bone.
Nerve-supply. — Twigs from the hypoglossal nerve enter the lateral surfaces of the muscles
of this group.
Action. — The chief of the muscles, the genio-glossus, performs various services according to
the part which contracts. The anterior portion serves to withdraw the tongue into the mouth
and depress the tip; the middle portion to draw the base of the tongue forward, depress the
median portion of the tongue, and make the tongue protrude from the mouth; the inferior fibres
to elevate the hyoid bone and carry it forward. The stylo-glossus retracts the tongue, elevates
its margin, and raises the hyoid bone and base of the tongue. The hyo-glossus draws down the
sides of the tongue and is also a retractor. The chondro-glossus aids in both these movements.
Relations. — The main portion of the tongue is composed of the two genio-glossus muscles,
which are separated in the median line by the hngual septum. The genio-glossus is covered
inferiorly by the genio- hyoid and the mylo-hyoid muscles; along the lateral margin of the tongue
by the glosso-palatinus, the stylo-glossus, the longitudinalis inferior, and the glosso-pharyngeus
CERVICAL FASCIA 347
muscles; and posteriorly by the hyo-glossus, and the chondro-glossus. Below it forms a part of
the medial wall of the space in which the sublingual gland is lodged. Over the dorsum and tip
of the tongue it is covered by the mucosa. This likewise covers laterally, in the region of the
base of the tongue, the stylo-glossus, hyo-glossus, and the longitudinalis inferior. The lingual
artery runs between the hyo-glossus and the genio-glossus, and along the boundary between the
longitudinalis inferior and the genio-glossus to the tip of the tongue. The lingual vein, which
lies lateral to the hyo-glossus muscle, takes a similar although much more irregular course.
The glosso-pharyngeal nerve passes down medial to the stylo-glossus muscle to the root of the
tongue. The hngua! nerve passes along the lateral margin of the tongue external to the stylo-
glossus, hyo-glossus, and inferior longitudinal muscles. The hypoglossal nerve hes lateral to
the inferior portion of the hyo-glossus muscle and then sinks into the genio-glossus.
The hyo-glossus muscle is covered laterally below the free portion of the tongue by the mylo-
hyoid, digastric, and stylo-hyoxd muscles and by the deep part of the submaxillary gland.
Medially it covers in part the middle constrictor of the pharynx.
The stylo-glossus muscle above the tongue hes medial to the stylo-hyoid and the internal
pterygoid muscles and the parotid gland, and between the internal and external carotid arteries.
It lies lateral to the superior constrictor of the pharynx.
Variations. — The genio-glossus often sends a slip to the epiglottis (levator epiglottidis) .
It may send some bundles into the superior constrictor of the pharynx (genio-pharyngeus) or
to the stylo-hyoid hgament. Various parts of the muscle may be more or less, isolated. Of
these, a fasciculus from the mental (genial) spine to the tip of the tongue is the most frequent
(longitudinalis linguae inferior medius). The hyo-glossus exhibits considerable variation in
structure. Some authors consider the chondro-glossus but a portion of this muscle, while
Poirier considers it merely the origin of the longitudinalis inferior. The stylo-glossus may be
absent on one side or on both. Its origin varies considerably and may be from the angle of the
jaw. The muscle may be doubled.
5. SUPERFICIAL MUSCULATURE OF THE SHOULDER
GIRDLE AND THE EXTERNAL CERVICAL FASCIA
(Figs. 348, 355)
The stemo-cleido-mastoid is a strong, band-shaped muscle, bifurcated below,
which arises from the medial third of the clavicle and the front of the manubrium
and is inserted into the mastoid process of the temporal bone and the neigh-
bouring part of the occipital. The large, fiat, triangular trapezius arises from the
occipital bone and the spines of the cervical and thoracic vertebrae and is in-
serted into the lateral third of the clavicle and into the acromion and spine of
the scapula. The two muscles lie in a well defined layer of fascia which ensheaths
the neck beneath the platysma, the external cervical fascia. Both muscles bend
the head and neck toward the shoulder, rotate and extend the head, and raise
the shoulder. The sterno-cleido-mastoid also elevates the thorax and flexes
the neck.
These two superficially placed muscles represent differentiated portions of a musculature
found in elasmobranchs and in the amphibia and all higher vertebrates. In sharks this muscula-
ture is associated with the musculature of the branchial arches, and, hke them, is innervated
by the vagus nerve. In the higher vertebrates it is innervated by the vagus or by the spinal
accessory nerve, developed in connection with the vagus. To this innervation by a cranial
nerve, innervation by cervical nerves is added in those higher vertebrates in which the muscula-
ture is more extensively developed. In the human embryo the muscles migrate from their
origin in the upper lateral cervical region to the positions found in the adult.
FASCIA
The fascise of the neck and the relations of the muscles are shown in cross-section in figs.
347, and 351.
The tela subcutanea of the head and neck in the upper dorsal region is thick, fibrous, and
closely adherent to the underlying muscle fascia. Ventrally in the cervical region it contains
the platysma.
The external cervical fascia (fig. 350) lies beneath the subcutaneous tissue and the platysma,
completely invests the neck and extends cranialward over the parotid gland to the zygoma and
the masseteric fascia. The trapezius hes between two closely adherent lamince of the fascia.
From the ventral margin of the trapezius it is continued as a thin but strong membrane across
the posterior triangle of the neck, between this muscle and the sterno- cleido-mastoid, and is
attached below to the clavicle. It invests the sterno-cleido-mastoid with two adherent laminse
and extends from the ventral margin of this muscle across the anterior triangle to the mid-line
where it is continued into that of the opposite side. In this triangle the fascia is bound to the
hyoid bone, and is thus divided into a submaxillary and an infrahyoid portion. The infrahyoid
portion is simple and is attached below to the front of the manubrium. The submaxillary
portion is attached to the inferior margin of the mandible. It covers the submaxillary gland,
and along the inferior margin gives rise to a strong, membranous 'process which passes inward
below the gland and, after extending around the tendon of the digastric muscle, becomes united
348
THE MUSCULATURE
to the superior margin of the hyoid bone. This process ventrally becomes fused with the peri-
mysium of the ventral belly of the digastric. Dorsally it extends over the posterior end of the
submaxillary gland and becomes attached to the angle of the jaw. Here it is strengthened by
fibrous tissue which extends in from the ventral margin of the sterno-cleido-mastoid and serves
to separate the parotid from the submaxillary gland. This 'mandibular process' is continued
into the stylo-mandibular ligament.
Fig. 350. — Fascia op the Neck. (After Eisler.) The superficial fascia has been removed
in places in order to show the deeper fasciaj; the sterno-cleido-mastoid has been partly removed;
the submaxillary gland, almost wholly; the parotid gland, as far as the duct.
1. Submaxillary space. 2. Parotid space. 3. Sterno-cleido-mastoid. 4 Supra-clavicular
fossa. 5. Supra-sternal space. 6. External jugular vein. 7. Anterior jugular vein. 8. Median
colU vein. 9. N occipitaUs minor. 10. N. aurioularis magnus. 11. Deltoid. 12.^Proc.
coracoideus. 13, Fascia ooraco-clavieularis.
The parotid gland is enclosed between two laminae of the external cervical fascia. These
are continued over the gland from the fascial investment of the sterno-cleido-mastoid, and unite
ventrally to become fused to the masseteric fascia along the anterior margin of the gland.
They unite below the inferior margin of the gland, and are continued into the rnandibular process
mentioned above. The external layer, which is the thicker and stronger, is attached above
to the cartilage of the auditory canal and to the zygoma. The inner lamina is attached above
TRAPEZIUS 349
to the base of the temporal bone. It is incomplete and is more or less fused to the posterior
belly of the digastric muscle, the styloid process, and the muscles arising from this process.
Between the styloid process and the angle of the jaw this lamina is strengthened to form the
stylo-mandibular ligament.
In the back, beyond the spine of the scapula, the fascia arising from the investing adherent
fascial sheath of the trapezius muscle is continued laterally across the fascia investing the infra-
spinatus muscle, and becomes fused with the most superficial layer of this fascia and more
djstally with that of the latissimus dorsi muscle. Near this lateral line of fusion it is usually
closely adherent to the tela subcutanea.
MUSCLES
The sterno-cleido-mastoideus (fig. 348). — Origin. — By a medial (sternal) head from the
front of the manubrium and by a lateral (clavicular) head from the upper border of the median
third of the clavicle. Between the two origins there intervenes a triangular area covered by
the external cervical fascia. Its insertion is — (1) on the anterior border and outer surface of
the mastoid process, and (2) on the lateral half of the superior nuchal line of the occipital bone.
Structure. — The tendons are comparatively short, the longest being that on the anterior
surface of the sternal attachment. The fibre-bundles of the muscle take a nearly parallel
course from origin to insertion. Five fasciculi may be more or less clearly recognised. In a
superficial layer — (1) a superficial sterno-mastoid; (2) a sterno-occipital; and (3) a cleido-
occipital. In a deep layer — (4) a deep sterno-mastoid and (5) a cleido-mastoid.
Nerve-supply. — (1) From the spinal accessory nerve, which gives it branches during its
course through the deep portion of the muscle, and (2) by branches from the anterior primary
divisions of the second and third (?) cervical nerves. These branches enter the deep surface
of the upper half of the muscle.
Action. — To bend the head and neck toward the shoulder and rotate the head toward the
opposite side. When both muscles act, the neck is flexed toward the thorax and the chin is
raised; or, with fixed head, the sternum is raised, as in forced respiration. When the head is
bent back, the two muscles may further increase the hyperextension.
Relations. — The muscle and its sheath are covered externally by the tela subcutanea, which
here contains the platysma and the external jugular vein, as well as the superficial branches of
the cervical plexus. Beneath the muscle lie the sterno-hyoid, sterno-thyreoid, omo-hyoid.
levator scapuliE, scaleni, splenius, and digastric muscles, the cervical plexus, the common carotid
artery, internal jugular vein, and the vagus nerve. The spinal accessory nerve usually runs
through its deep cleido-mastoid portion.
Variations. — There is considerable variation in the extent of independence of the main
fasciculi of the muscle. In many of the lower animals the cleido-mastoid portion of the muscle
is quite distinct from the sterno-mastoid portion, and this condition is frequently found in
man. The cleido-occipital portion of the muscle is that most frequently absent (Wood found
it present in 37 out of 102 instances). The clavicular portion of the muscle varies greatly in
width. The sternal head has been seen to e.xtend as far as the attachment of the fifth rib.
Slips from the muscle may pass to various neighbouring structures. The main fascicuU of the
muscle may be doubled. Sometimes one or more tendinous inscriptions cross a part or the
whole of the superficial layer of the muscle.
The trapezius (fig. 355). — Origin. — By aflat aponeurosis from the superior nuchal fine and
external protuberance of the occipital bone, the ligamentum nuchte, and the vertebra! spines
and supraspinous ligament from the seventh cervical to the twelfth thoracic vertebra. The
aponeuroses of the right and left muscles are continuous across the middle fine. Between the
middle of the ligamentum nuchae and the second thoracic vertebra, the aponeuroses give rise
to an extensive quadrilateral tendinous area. At the distal extremity of the muscle they are
also weU developed.
Structure and Insertion. — The superior fibre-bundles pass obliquely downward, lateralward,
and forward to the postero-superior aspect of the lateral third of the clavicle; the middle fibre-
bundles, transversely to the medial edge of the acromion and the upper border of the spine of the
scapula; the lower fibre-bundles, obliquely upward and laterally to terminate thi'ough a flat,
triangular tendon on a tubercle at the medial end of the spine of the scapula.
Nerve-supply. — The external branch of the spinal accessory nerve descends for a distance
near the superior border of the trapezius muscle and then along the ventral surface. Soon it
gives rise to ascending branches for the superior portion of the muscle and descending branches
for the middle and inferior portions. The main branches of distribution run about midway
between the origin and insertion of the fibre-bundles. The branches from the second (?), third
and fourth cervical nerves anastomose with the trunk of the spinal accessory, sometimes as it
passes along the margin of the muscle, at other times within the substance of the upper portion
of the muscle.
Action. — When the whole muscle contracts, it draws the scapula toward the spine and
turns it so that the inferior angle points laterally, the lateral angle upward. In addition the
upper portion draws the point of the shoulder upward, and with the scapula fixed extends the
head, bends the neck toward the same side, and tm'ns the face to the opposite side. The lower
portion of the muscle tends to draw the scapula downward and inward and at the same time to
rotate the inferior angle of the scapula outward.
Relations. — It is covered merely by skin and fascia. It Ues external to the semispinahs,
splenii, rhomboidei, latissimus dorsi, levator scapute, supraspinatus, and a small portion of the
infraspinatus muscles.
Variations. — The lower limit of attachment of the muscle may be as high as the fourth
thoracic vertebra. The right and left muscles are seldom symmetrical. The upper attach-
ment may not extend to the skull. The clavicular attachment may be much more extensive
>
350 THE MUSCULATURE
than normal or may be missing. The attachments to the scapula show considerable variations.
Occasionally the cervical and thoracic portions are separate, a condition normal in many
mammals. VentraUy the trapezius may become continuous with the sterno-cleido-mastoid
in the neck, or send a fasciculus to it or to the sternum. Aberrant fasciculi are not infrequent.
Rarely a transverse tendinous inscription is found in the cervical or in the thoracic portion of
the muscle. Sometimes a fasciculus is sent into the deltoid. The innervation of either the
sterno-cleido-mastoid or the trapezius may be by cervical nerves only. The omo-cervicalis
{levator claviculce) is a fasciculus frequent in the lower mammals, but rarely found in man.
It usually extends from the acromial end of the clavicle to the atlas and axis, but may extend
to more distal cervical vertebrae. It is innervated by a ramus from the cervical branches to the
trapezius. The supra-clavicularis proprius is a muscle rarely found. It extends on the cranial
surface of the clavicle from the sternal to the acromial end and is innervated by the third cervical
nerve. It is said to make tense the superficial layer of the cervical fascia.
A bursa is often found between the base of the spine of the scapula and the tendon of inser-
tion of the thoracic portion of the trapezius. Another bursa is also frequently found between
the insertion of the transverse portion and the supraspinous fascia.
6. INFRAHYOID MUSCULATURE
(Figs. 348 and 351)
The four infrahyoid muscles constitute a well-defined group of muscles which
depress the hyoid bone, the larynx, and the associated structures. They lie
beneath the sterno-cleido-mastoid muscle and the external cervical fascia. Two
strata may be recognised. In the superficial stratum are comprised the omo-
hyoid, a narrow, ribbon-like digastric muscle which arises from the superior
margin of the scapula and is inserted into the hyoid bone; and the thin, quad-
rangular sterno-hyoid, which arises from the superior margin of the sternum and
the medial end of the clavicle and is inserted into the hyoid bone. Between
these two muscles is an aponeurotic membrane which constitutes the main part
of the middle layer of the cervical fascia, and represents possibly a retrograde
portion of a single muscle, of which the two above named are but the ventral and
dorsal margins. Beneath this superficial musculature the thin, quadrangular
thyreo-hyoid descends from the hyoid bone to the thyreoid cartilage, and the
ribbon-like stemo-thyreoid arises from the dorsal surface of the manubrium
and is inserted into the thyreoid cartilage.
All these muscles are supplied by branches from the ansa hypoglossi. The
nerve-fibres arise from the first three cervical nerves.
The muscles of this group are derived from the ventral portions of the ventro-lateral divi-
sions of the first three cervical myotomes, and correspond with the rectus abdominis muscle,
which is derived from the ventral portions of the eighth to the tweUth thoracic myotomes.
This musculature is characterised by metameric segmentation, which may be more or less ob-
scured, and by a general longitudinal direction taken by the component fibre-bundles. The
course of the fibres in the omo-hyoid may be looked upon as a secondary condition due to the
shifting laterally of the distal attachment of the muscle. Musculature of this nature is not
derived from the lower cervical and upper thoracic myotomes in man, but in some of the lower
vertebrates it forms a continuous ventral band. Even in man occasional traces of this ventral
musculature may, however, be seen as muscular and aponeurotic slips on the upper part of the
thoracic wail, above the ribs and the aponeurosis of the external intercostal muscles.
FASCIA
(Figs. 351 and 357)
The middle cervical fascia is composed of two laminae. Of these, the superficial, which
ensheaths the sterno-hyoid and omo-hyoid muscles and fills in the intervening area, is much the
stronger and better differentiated. The more delicate deep lamina ensheaths the thyreo-hyoid
and sterno-thyreoid muscles, and laterally extends out to become fused with the superficial
lamina. It is also more or less closely bound to the sheath which covers the internal jugular
vein, carotid artery, and vagus nerve.
The middle cervical fascia is attached above to the hyoid bone. Beyond the lateral edge
of the omo-hyoid it becomes fused with the deep lamina of the external layer of the cervical
fascia, beneath the sterno-cleido-mastoid. Posterior to this muscle it usually terminates along
the cranial margin of the omo-hyoid in the areolar tissue of the neck. Its distal attachment
takes place into the dorsal surface of the upper margin of the sternum, and from here a process
is sent over the left innominate vein to the pericardium. Lateral to the sternum the fascia is
attached for some distance to the inner margin of the clavicle, and gives rise to processes, one of
which extends to the fascia of the subclavius muscle, while the others pass on each side of the
subclavian vein to the first rib. Still more laterally the fascia is fused along the lower margin
of the scapular belly of the omo-hyoid to the underlying dense, fatty areolar tissue.
INFRA-HYOID MUSCLES 351
MUSCLES
(Figs. 348 and 351)
The sterno-hyoideus. — Origin. — From (1) the deep surface of the medial extremity of the
clavicle; (2) the costo-clavicular (rhomboid) ligament; and (3) the neighbouring part of the
sternum. The origin may extend to the cartilage of the first rib. Structure and insertion —
The fibre-bundles take a nearly parallel course upward. The muscle belly, however, contract,
slightly in width and increases slightly in thickness and slants somewhat toward the median
Hne. The insertion takes place directly upon the inferior margin of the body of the hyoid
lateral to the mid-line. Not infrequently a tendinous inscription near the junction of the middle
and inferior thirds more or less completely divides the muscle into two portions. A second
inscription is sometimes found at the level of the oblique line of the thyreoid cai'tilage. Nerve-
supply. — One or more branches from the ansa hypoglossi enter the lateral margin of the muscle.
Frequently one goes to the upper third, another to the lower third, of the muscle.
The omo-hyoideus. — Origin. — From the superior margin of the scapula near, and occa-
sionally also from, the superior transverse ligament of the scapula. Insertion. — The lower
border of the hyoid bone lateral to the sterno-hyoid muscle. Structure. — The inferior belly of
the muscle near its origin is thick and fleshy. It contracts as it passes ventrally across the
posterior triangle of the neck. Beneath the sterno-cleido-mastoid it is attached to a short ten-
don from which, as it bends upward toward the hj-oid bone, the superior belly takes origin and
thence expands toward the insertion. The tendon of attachment is short. The fibre-bundles
of both bellies take a nearly parallel course. The central tendon of the muscle is held in place
by a strong process in the middle layer of the cervical fascia. This process is attached to the
dorsal surface of the clavicle and to the first rib. Nerve-supply. — The superior belly is supphed
by a branch which enters its deep surface near the medial margin somewhat below the centre;
the inferior by a branch which enters the proximal third of its deep surface. These branches
arise from the ansa hypoglossi.
jjThe sterno-thyreoideus. — Origin. — Partly directly, partly by tendinous fibres, from — (1)
the dorsal surface of the manubrium from the middle line to the notch for the first rib; (2) the
dorsal surface of the cartilage of the first rib. Occasionally also from the back of the cartilage
of the second rib or from the clavicle. Structure and insertion. — The fibre-bundles take a nearly
parallel course upward and shghtly lateralward. The muscle is inserted by short tendinous
fibres into the oblique hne on the lamina of the thyreoid cartilage. A transverse tendinous
inscription near the upper border of the interclavicular hgament not infrequently divides the
belly of the muscle more or less completely into two parts. Sometimes a second transverse
inscription is found at the level of the lower margin of the thyreoid cartilage. Nerve-supply. —
By one or two branches from the ansa hypoglossi, which enter the ventral surface of the muscle
near the lateral margin. One branch usually goes to the upper, another to the lower, third of
the muscle.
The thyreo-hyoideus. — Origin. — From the oblique line on the lamina of the thyreoid
cartilage. Structure and insertion. — The fibre-bundles take a parallel course and are inserted
on the inferior margin of the lateral third of the body of the hyoid bone and the external surface
of the great cornu. Many fibre-bundles are continuous with those of the sterno-thyreoid.
Nerve-supply. — By a branch of the hypoglossal which enters the muscle near the middle of its
lateral border. The fibres are said to be derived from the first cervical nerve.
Action. — The sterno-hyoid and omo-hyoid depress the hyoid bone; the sterno-thyreoid
depresses the thyreoid cartilage; and the thyreoid-hyoid approximates the bone to the cartilage.
The omo-hyoid tends to draw the hyoid bone somewhat laterally. In this it is aided by the
posterior bell}' of the digastric and the stylo-hyoid and is opposed by the sterno-thyreoid
and thyreo-hyoid muscles, and the anterior belly of the digastric.
Relations. — The muscles of this group he beneath the external cervical fascia. The sterno-
cleido-mastoid muscle crosses the omo-hyoid, the sterno-hyoid, and sterno-thyreoid muscles.
The latter two'muscles extend for a distance behind the manubrium of the sternum. The omo-
hyoid is partly covered by the trapezius, crosses the scalene muscles, the brachial plexus, the
internal jugular vein, carotid artery, and the sterno-thyreoid and thyreo-hyoid muscles. The
sterno-hyoid extends over the sterno-thyreoid muscle, the thyreoid gland, crico-thyreoid
muscle, and the thyi'eoid cartilage. The sterno-thyreoid Ues over the innominate veui, the
trachea, and thyreoid gland. It is partly covered by the sterno-hyoid and omo-hyoid muscles.
The thyreo-hj'oid is largely covered by the omo-hyoid and sterno-hyoid muscles, and lies upon
the hyo-thyreoid membrane and the upper part of the thyreoid cartilage.
Variations. — The muscles vary in extent of development and may be more or less fused
with one another. The sternal attachment of the sterno-hyoid is more frequently absent than
the clavicular attachment. The region between the omo-hyoid and sterno-hyoid may be com-
posed of muscle instead of fascia. Each of the muscles may be longitudinally divided into two
distinct fascicuh, may send fascicuU to one another or to the middle layer of the cervical fascia,
or may have an abnormal origin or insertion. The omo-hyoid is the one of the group most
frequently absent. One of the bellies is much more frequently absent than both. The inter-
mediate tendon of the omo-hyoid may be reduced to a tendinous inscription or even disappear
entirely. The distal attachment maj' take place on the scapular spine, the acromion, the cora-
coid process, or even the first rib or clavicle. An extra fasciculus from the clavicle is found in
3 per cent, of instances. (Le Double.). Not very infrequently a muscle innervated by a
branch of the descendens hypoglossi is found extending from the sternum to the clavicle behind
the origin of the sterno-cleido-mastoid. It may also extend from the sternum or clavicle in
various directions upward toward the head.
352
THE MUSCULATURE
Fig. 351, A and B. — Tbansverse Sections Through the Left Side of the Neck and
Shoulder in the Regions indicated in the Diagram.
a and 6 in the diagram indicate sections A and B of fig. 347 (p. 340). a, that of section A, fig.
357 (p. 366).
41 63 35 5G 36 60 30 H 28 29
SCALENE MUSCLES 353
BURS^
The bursa m. sterno-hyoidei is in constantly found between the lower margin of the hyoid
bone and median hyo-thyreoid ligament and the sterno-hyoid muscle and external cervical
fascia. It is better developed in men than in women and is found either on each side of the
median line or fused in the median line.
The bursa m. thyreo-hyoidei is frequently found between the greater cornu of the hyoid
bone and hyo-thyreoid membrane and the thyreo-hyoid muscle.
7. SCALENE MUSCULATURE
(Figs. 348 and 352)
The three muscles which form this group constitute a triangular mass which
extends in front of the levator scapulae and intrinsic dorsal musculature and
behind the prevertebral musculature from the first two ribs to the transverse
processes of the cervical vertebrae. They cover laterally the apex of the pleural
cavity. They bend the neck and fix the first two ribs or raise the thorax. In
front lies the scalenus anterior, which extends from the first rib to the fourth to
skth vertebrae. Behind this the scalenus medius extends from the first rib to the
lower six vertebrae. The most dorsal of the group, the scalenus posterior,
extends from the second rib to the fifth and sixth vertebrae.
These muscles are supplied by direct branches of the cervical nerves. They are probably
derived from the lateral portions of the cervical myotomes. According to Gegenbaur, the two
more ventral are homologous with intercostal muscles, the dorsal with the levatores costarum.
It is to be noted, however, that the anterior muscle lies in front of the brachial plexus, i. e., in
a position similar to that of the subcostal musculature. The scalene musculature is morpho-
logically closely related to the deep shoulder-girdle musculature, p. 356.
FASCIA
(Figs. 351, 357)
From the front of the bodies of the cervical vertebrae the prevertebral fascia is continued
laterally over the longus colli and the scalene muscles, and extends dorsally into the fascia
covering the levator scapulae. Between the muscles fascial processes are sent in to become
attached to the cervical vertebras. Interiorly the fascia extends to the outer surface of the thorax.
MUSCLES
(Fig. 352)
The scalenus anterior. — This arises from the ventral part of the inferior border of the
transverse processes of the fourth, fifth, and sixth cervical vertebrae, usually also from the third,
rarely from the seventh, by means of long, slender tendinous processes. From each tendon
arises a fasciculus composed of nearly parallel fibre-bundles. The fasciculi soon fuse to form a
muscle belly which contracts somewhat toward the insertion. This takes place by means of
1. Arteria carotis communis. 2a. A. cervicalis profunda. 2b. A. cervicalis superficiaUs
3. A. thoracoacromialis (acromial branch). 4a. A. thyreoidea inferior. 4b. A. thyreoidea
superior. 5. A. transversa colli. 6. A. transversa scapulae. 7. A. vertebralis. 8. Bursa
m. subscapularis. 9. Cartilago arytenoidea. 10. Cartilago thyreoidea. 11. Clavicle.
12. Costa I. 13. Costa II. 14. Fascia cervicalis — a, superficial layer; b, middle layer.
15. Deep or prevertebral layer. 16. Fascia coraco clavicularis. 17. Fascia nuchas.
IS. Glandula thyreoidea. 19. Humerus. 20. Ligamentum coracohumerale. 21. Med-
ulla spinalis (spinal cord). 22. Musculus arytenoideus transversus. 23. M. biceps brachii,
tendon long head. 24. M. constrictor pharyngis inferior. 25. M. deltoideus. 26. M.
Uio-costalis. 27. M. infraspinatus. 28. M. levator scapulae. 29. M. longissimus capitis
(trachelo-mastoid). 30. M. longissimus cervicis. 31a. M. longus colli. 31b. M. longus
capitis (rectus capitis anticus major). 32. M. omo-hyoideus. 33. M. platysma. 34. M.
rhomboideus minor. 35. M. scalenus anterior. 36. M. scalenus medius. 37. M. semi'
spinalis capitis (oomplexus). 38. M. serratus anterior. 39. M. serratus posterior superior.
40. M. splenius. 41. M. sterno-cleido-mastoideus. 42. M. sterno-hyoideus. 43. M.
sterno-thyreoideus. 44. M. subclavius. 45. M. subscapularis; a, tendon. 46. M.
thyreo-arytenoideus (and vocalis). 47. M. thyreo-hyoideus. 48. M. transverso-spinales.
49. M. trapezius. 50. Nervous accessorius. 51. N. cervicalis IV. 52. N. laryngeus
inferior. 53. N. descendens hypoglossi. 54. Sympathetic trunk. 55. N. thoracaUs I.
56. N. vagus. 57. (Esophagus. 58. Plexus brachialis. 59. Scapula — a, glenoid cavity;
b, ooracoid process; c, spine. 60. Trachea. 61. Vena transversa colli. 62. V. jugularis
externa. 6.3. V. jugularis interna. 64. Vertebra cervicalis V. 65. Vertebra cervicalis
VII. 66. Vertebra thoracalis I, arch. 67. Vertebra thoracalis II — a, spine; b, transverse
process.
354
THE MUSCULATURE
a tendon which sends a fibrous lamina a short distance upward on the outer surface of the muscle.
The tendon is inserted into the scalene tubercle on the upper surface of the body of the first rib.
The scalenus medius. — This arises usually from the third to the seventh, sometimes from
aU seven or from merely the last four or five cervical vertebrrs. The origin takes place from the
posterior part of the lateral border of the transverse processes by means of a slender tendon from
each of the upper and directly by a muscular fasciculus from each of the lower vertebrae. The
.fasciculi become combined into a compact muscle belly which is inserted in a manner similar to
the scalenus anterior into the upper surface of the fu-st rib behind the subclavian groove. The
insertion usually extends to the second rib.
The scalenus posterior arises by short tendons from the posterior tubercles of the transverse
processes of the fifth and sixth cervical vertebrae. The origin may extend as high as the fourth
vertebra, or as low as the seventh. It is inserted by a short tendon into the lateral surface
of the second rib. Occasionally it extends to the third rib.
Fig. 352 — The Deep Ventral Muscles op the Neck.
Rectus capitis anterior
Rectus capitis lateralis
Orgin of tlie longus
capitis
Scalenus medius
Scalenus anterior
Scalenus posterior
Rectus capitis la-
teralis
Rectus capitis
anterior
Intertransversus
posterior
Nerve-supply. — The scalenus anterior is innervated by branches from the'fifth, sixth, and
seventh cervical nerves; the middle by the fourth, fifth, sixth, seventh, and eighth cervical
nerves; the posterior by the seventh or eighth nerves.
Action. — With the thorax fixed the scalene muscles bend the neck to the side and sUghtly
forward and turn it sUghtly toward the opposite side. With the neck fixed they serve to lift
the first two ribs and are of use in enforced inspiration. In quiet inspiration they serve to
fix the first two ribs.
Relations. — The longus colli lies medial to the scalenus anterior. DorsaUy the scalene
muscles; medially the pharynx, thyreoid gland, and trachea; ventro-lateraUy the sterno-cleido-
mastoid, infra-hyoid, and subclavius muscles and the clavicle bound a space filled with dense
fatty areolar tissue in which are contained the subclavian and carotid arteries, the subclavian
and internal jugular veins, the vagus, phrenic, and sympathetic nerves, and numerous smaller
blood-vessels and nerves. The main branches of the lower five cervical nerves pass laterally
between the scalenus anterior and medius. The subclavian artery passes behind, the sub-
clavian vein in front, of the attachment of the scalenus anterior. The scalenus medius above
and the scalenus posterior below enter into relations dorsally with the levator scapulae and the
intrinsic dorsal musculature, from which they are separated by fascial septa.
PREVERTEBRAL MUSCLES 355
Variations. — The scaleni present numerous variations in the extent of the costal and ver-
tebral attachments. The degree of fusion of the various fasciculi likewise varies so much that
diiferent authors have described varying numbers of muscles into which the scalenus mass
should be subdivided. A muscle frequently present is the scalenus minimus. This arises
from the anterior tubercle of the sixth or sixth and seventh cervical vertebrte, and is inserted
into the first rib behind the sulcus for the subclavian artery. It sends a process (Sibson's
fascia) to the pleural cupola and serves to make the pleura tense. Zuckerkandl found it in
22 out of 60 bodies on both sides; 12 times on the right side only, 9 times on the left. It is
innervated by the eighth cervical nerve. When absent, a ligamentous band takes its place.
An intertransversarius lateralis longus, may extend from the posterior tubercles of the 3-5
transverse processes to the tip of the seventh transverse process and divide the muscle fasciculi
near their origin into dorsal and ventral divisions.
8. THE PREVERTEBRAL MUSCULATURE
(Fig. 352)
This deep-seated musculature extends along tiie ventro-Iateral sm-faces of the
three upper thoracic and the cervical vertebrEe to the skull. It is composed of
two muscles. The longus colli arises from the bodies of the three thoracic and
from the bodies and transverse processes of the third to the sixth cervical verte-
brae, and is inserted into transverse processes and bodies of the cervical vertebrae.
The longus capitis (rectus capitis anterior major) arises from the transverse
processes of the fourth, fifth, and sixth cervical vertebrae, and is inserted into the
basilar process of the occipital bone. These muscles flex, abduct, and rotate
the head and neck. All of them are supplied by direct branches from the anterior
divisions of the cervical nerves. They are probably specialised from the ventro-
lateral portions of the cervical myotomes. Similar muscles are found in all
vertebrates with well-developed necks. The rectus capitis anterior (minor)
represents an anterior cervical intertransverse muscle.
FASCIA
(Figs. 351, 357)
The muscles are firmly bound to the vertebral column by the prevertebral fascia described
in connection with the scalene muscles and by the septa which extend in between the muscles
of this group and between them and the scalenus anterior.
MUSCLES
(Fig. 352)
The longus colli. — This muscle may be compared to a triangle, the base of which extends
from the anterior tubercle of the atlas to the body of the third thoracic vertebra and the apex
of which is the transverse process of the fifth cervical vertebra. The complex construction of
the muscle makes it advisable to consider it as divided into three parts.
The supero-lateral portion consists of fasciculi which arise from the anterior tubercles of
the transverse processes of the third, fourth, fifth, and sixth cervical vertebrse and from the body
of the third thoracic and become fused into a belly which is inserted into the anterior tubercle
of the atlas.
The median portion is formed of muscle fasciculi which arise from the antero-lateral p.irts
of the bodies of the first three thoracic vertebrae and the last three cervical vertebrae by tendin-
ous processes. These fasciculi fuse into a belly which terminates by three flat tendinous fas-
ciculi on the antero-lateral surfaces of the bodies of the second, third, and fourth cervical
vertebras.
The infero -lateral portion is applied to the inferior lateral surface of the median portion.
It arises from the lateral parts of the bodies of the first three thoracic vertebrae and is inserted
by tendinous processes into the transverse processes of the fifth and sixth cervical vertebrae.
Nerve-supply. — By branches from the second to sixth cervical nerves which send rami
to the various constituent fasciculi of the muscle.
The longus capitis (rectus capitis anterior major). — Origin. — By cylindrical tendons from
the tips of the anterior tubercles of the third, fourth fifth, and sixth cervical vertebras. The
tendons send up aponeurotic expansions on the outside of the fasciculi, which arise from them.
These fasciculi fuse into a dense muscular belly to which is usually added a fasciculus from the
longus colli. The insertion takes place into the impression on the inferior sui'face of the basilar
portion of the occipital bone, extending lateral to the pharyngeal tubercle outward and for-
ward. The insertion of the fibre-bundles from the third vertebra is direct; the other fibre-
bundles are inserted largely into a tendinous lamina which covers the middle of the ventral
surface of the muscle and from which, in turn, other fibre-bundles arise. It is an incomplete
digastric muscle. Nerve-supply. — The first, second, third, and fourth cervical nerves send
branches into the ventral surface of the muscle.
356 THE MUSCULATURE
Actions. — The longus colli serves to bend the neck forward; the supero-lateral portion, when
acting on one side only, serves slightly to bend the neck toward that side and to rotate it; the
infero-lateral portion serves especially to prevent hyperextension. The longus capitis bends the
head forward; one side acting alone rotates the head toward that side.
Variations. — There is considerable variation in the number of vertebrje to which the ten-
dons of origin and insertion of the longus colh and longus capitis may be attached and in the
extent of fusion of the different fasciculi composing them. There may be fusion with the scale-
nus anterior. The atlantico-hasilaris internus in 4 per cent, of cases extends from the anterior
tubercle of the atlas to the base of the skull.
9. ANTERIOR AND LATERAL INTERTRANSVERSE
MUSCLES
(Fig. 352)
The anterior intertransverse muscles extend successively between the anterior
tubercles of the cervical vertebrte. They lie in front of the anterior divisions of
the cervical nerves and are supplied by branches from these divisions. They
are usually more or less bound up with the insertions of the scalene and pre-
vertebral muscles into these tubercles. The muscle between the atlas and epi-
stropheus is frequently missing; when present, it passes in front of the lateral
articulation between these vertebrte. The rectus capitis anterior (minor) may
be considered a continuation of the series. The lowest muscle may extend
between the seventh cervical vertebra and the first rib. The lateral intertrans-
verse muscles lie immediately behind the ventral divisions of the spinal nerves and
lateral to the dorsal divisions and are supplied by branches from the ventral
divisions. The rectus capitis laterahs belongs to this series. The rectus capitis
anterior (minor) arises from the lateral mass of the atlas and is inserted into
the base of the occipital bone. The rectus capitis lateralis runs from the
transverse process of the atlas to the lateral part of the occipital. For the
posterior intertransverse muscles see p. 417.
The rectus capitis anterior (minor). — This arises from the upper surface of the lateral mass
of the atlas in front of the articular process and partly from the neighbouring transverse proc-
ess. From a tendon the fibre-bundles extend in a nearly parallel direction upward and medially
to be inserted on the inferior surface of the basilar portion of the occipital bone in front of the
condyle Nerve-supply. — From the first (and second) cervical nerves. Action. — The rectus
capitis anterior (minor) serve to bend the head forward and, when the muscles on one side
only are contracted, to rotate the head toward the same side.
Relations. — The muscles of this group are closely apphed to the vertebral column. Be-
tween the fascia covering them and the fascia surrounding the pharynx which lies in front is
a region in which merely a slight amount of loose areolar tissue is found. Dorso-mediaUy the
longus colli below and the longus capitis above help to bound the space in which the chief ves-
sels and nerves extend between the thorax and the head.
The rectus capitis lateralis (fig. 352). — Origin. — From the upper surface of the transverse
process of the atlas.
Structure and insertion. — The fibre-bundles give rise to a quadrilateral sheet which passes
upward to be inserted on the under surface of the pars lateralis of the occipital bone.
Nerve-supply. — The ventral branch of the suboccipital (first cervical) nerve gives twigs
to its ventral surface.
Action. — To flex the head laterally.
Relations. — In front lie the anterior primary division of the suboccipital nerve and the
internal jugular vein. Behind the muscle lie the superior oblique and the longissimus capitis
(trachelo-mastoid) muscles and the atlanto-occipital joint.
10. DEEP MUSCULATURE OF THE SHOULDER GIRDLE
(Figs. 348, 353, 354, 388)
To this group belong four muscles which arise in the lateral cervical region
during embryonic development and become secondarily attached to the vertebral
margin of the scapula. One of these muscles, the band-like levator scapulae
(fig. 353), remains in the cervical region. It extends beneath the sterno-cleido-
mastoid, the trapezius, and the intervening fascia from the transverse processes
of the first four cervical vertebrae to the medial angle of the scapula. A second,
the large, quadrilateral serratus anterior (magnus) (fig. 354), comes to lie beneath
the blade of the scapula and wanders with this to the thoracic region. It arises,
in the adult, from the first nine ribs and is inserted into the vertebral margin of
the scapula. The flat, quadrangular rhomboideus major and rhomboideus
DEEP SHOULDER MUSCLES
357
minor (fig. 353) arise from the spines of the last cervical and first four
or five thoracic vertebrae, pass obliquely downward across the deep dorsal
muscles beneath the trapezius and are inserted into the vertebral margin
of the scapula. The third to the seventh cervical nerves supply this set of
Fig. 353. — The Levator Scapul* and Rhomboidbi.
Semisplnalis capitis
Spleiiius capitis
Levator scapulae
Serratus posterior superior
Rhomboideus minor
Splenius cervicis
Rhomboideus major
Supraspinatusp""
Serratus posterior inferior
Obliquus internus'
muscles. The levator scapulae is supplied by the third and fourth cervical
nerves, the rhomboids by the fifth (dorsal scapular), the serratus anterior by
the fifth to the seventh (long thoracic nerve). The muscles of this group ele-
vate the scapula, rotate it, and draw it backward (rhomboidei) or forward
(serratus anterior). When all contract together they raise the thorax.
358
THE MUSCULATURE
The levator soapulse and the serratus anterior (magnus) are two differentiated parts of a
muscle which is a continous mass in many of the lower mammals. A muscle corresponding
to the rhomboideus is found in some of the reptiles and many of the higher vertebrates. In
some of the mammals it has a more extensive cervical attachment than in man.
FASCIiE
The fasciae investing these muscles are shown in cross-section in fig. 357.
The levator seapulEc is invested by fascial membranes, the external and stronger of which
is continued dorsaUy from the fascial investment of the scalene muscles. The thinner layer
on^its deep surface Hes next the fascial investment of the intrinsic muscles of the back. Cranial-
ward from the rhomboid muscles the fascial investment of the levator scapulse is fused dorsally
with the fascia covering the splenius cervicis. Where the dorsal margin of the levator comes
in contact with the rhomboideus minor, the fascia is continued over into the thin fascial mem-
FiQ. 354, — SERKATtrs Anterioh.
brane which invests both surfaces of the rhomboidei. Similarly the investing fascia of the leva-
tor is continued ventrally into the fascia investing both sm'faces of the serratus anterior (mag-
nus). Within the internal fascial investment of this group of muscles, near the insertion of
the levator, run the transversa coUi artery and the dorsal scapular nerve.
MUSCLES
The rhomboideus minor (fig. 353). — Origin. — ^Lower part of the ligamentum nuchse, the
spines of the seventh cervical and first thoracic vertebrae, and the intervening supraspinous Uga-
ment. Insertion. — Vertebral border of the scapula near the spine.
The rhomboideus major (fig. 353). — Origin. — Spines of the fii'st four or five thoracic ver-
tebrae. Insertion. — Vertebral border of the scapula opposite the infraspinous fossa.
Structure. — The two muscles are included between two adherent fascial layers which bridge
over the greater or less space that may intervene between them. The fibre-bundles take a
parallel course obliquely downward and lateralward from the vertebrae. From the vertebral
spines the muscles arise by an aponeurosis which varies in width. The attachment to the scap-
ula is by short tendinous processes. The attachment of the rhomboideus major is firmest to-
ward the inferior angle of the scapula.
Nerve-supply. — The dorsal scapular nerve, which usually arises chiefly from the fifth
cervical nerve, enters the superior margin of the rhomboideus minor and then courses distaUy
near the deep ventral surface of the two muscles and about midway between the tendons of
origin and insertion.
SERRATUS ANTERIOR 359
Action. — The two muscles draw the scapula upward and medialward toward the spine and
rotate it so as to depress the shoulder.
Relations. — Over the muscles lies the trapezius. Under them he the serratus posterior
superior and the splenius cervicis, the longissimus dorsi, the iho-costalis, serratus posterior
superior and external intercostal muscles. The descending ramus of the transversa ooUi
artery descends on the deep surface. Blood-vessels for the trapezius pass to this muscle between
the two rhomboids.
Variations. — There is much variation in the extent of the vertebral attachment. The
minor is frequently, the major occasionally, absent. The two rhomboids are frequently fused
with one another or may be divided into several distinct fascicuU. Frequently (SO per cent.,
Balli) a fasciculus extends obliquely on the deep surface of the R. major from the cranial part
of the origin to the distal part of the insertion. Shps may be sent to the latissimus dorsi or
the teres major. An accessory slip may pass between the trapezius and splenius muscles to
the occipital bone (occipito-scapularis). A muscle corresponding to this fasciculus is normally
found in many mammals.
The levator scapulae (figs. 353, 388). — Origin. — By short tendons from the dorsal tubercles
of the transverse processes of the first four cervical vertebras, between the attachments of the
splenius cervicis and scalenus medius muscles. The tendons from the third and fourth cervical
vertebrae are fused for a short distance with those of the longissimus cervicis. Structure and
insertion. — The fibres run in parallel bundles in a dorso-lateral direction downward to the ver-
tebral border of the scapula opposite the supraspinous fossa. The fibre-bundles are inserted
directly into the periosteum. As a rule, the flat fasciculi arising from the different vertebrae
are easily separated.
Nerve-supply. — By rami chiefly from the third and fourth cervical nerves. These rami enter
the ventral margin of the muscle and extend obhquely across the dorsal surface of the constituent
fascicuh about midway between the tendons of origin and insertion. Frequently anastomosing
branches pass between the nerves. The lowest fasciculus is usually supplied by branches from
the nerve to the rhomboid muscles (dorsal scapular).
Action. — Draws the scapula upward and tends to rotate it so that the inferior angle
approaches the spine. When the scapula is fixed, the muscle serves to bend the neck laterally
and slightly to rotate it toward the same side and extend it.
Relations. — Externally the sterno-cleido-mastoid and, in part, the splenius capitis cover it
above; the trapezius, below; and the external cervical fascia, its middle portion. Internally
lie the splenius cervicis, longissimus and ilioeostaUs cervicis (transversalis cervicis), and
serratus posterior superior muscles and the ramus descendens of the transversa colU artery.
In front lie the scalene muscles.
Variations. — The number of cervical vertebrae from which the muscle springs varies from
two to seven. The most constant are the slips of origin from the fii'st two vertebrae. The
muscle may send slips to the temporal or the occiptal bone or to the trapezius, the serratus
anterior (magnus), serratus posterior superior, and other muscles, or to the clavicle, first or
second rib, etc. Often the parts of the muscle running to each vertebra are separated for the
whole distance. A bundle of fibres that appears to be a detached shp of the levator scapulae
may run from the first two or from lower cervical vertebrae to the lateral end of the clavicle and
to the acromion. This represents the levator claviculae found normally in many vertebrates.
According to Le Double, it is innervated by a branch from the cervical branches to the trapezius
group.
The serratus anterior (magnus) (figs. 354, 388). — First Pari. — The origin is by two digita-
tions from the first and second ribs and from a fibrous arch uniting these two attachments.
The fibre-bundles converge to be inserted on an oval space on the costal surface of the scapula
near its medial angle. Second Part. — This arises by two or three digitations from the second,
third, and sometimes the fourth ribs. The fibre-bundles spread out into a thin sheet which is
inserted along the vertebral border of the scapula. Third Part. — This, the strongest part of the
muscle, arises by digitations from the fourth or fifth to the eighth or ninth ribs. The attach-
ments of the digitations are longest on the upper border of each rib. The interdigitate with the
attachments of the external oblique muscle of the abdomen. The fibre-bundles converge to be
inserted on the large oval space on the costal surface near the inferior angle of the scapula.
Nerve-supply. — From the proximal portions of the anterior divisions of the fifth, sixth,
seventh, and sometimes the eighth cervical nerves branches arise which fuse into the long
thoracic nerve. This nerve usually passes laterally through or behind the scalenus medius
muscle, courses along the outer surface of the serratus anterior midway between the origin and
insertion, and gives rise to numerous twigs to supply the various divisions. The fibres to the
upper portion come mainly from the fifth cervical nerve; those to the middle from the fifth
and sixth; and those to the lower from the sixth and seventh.
Action. — -The muscle holds the scapula against the thorax and draws it forward and later-
ally and, by its highly developed inferior portion, rotates the bone so as to raise the point of
the shoulder. It is of especial importance in abduction of the arm. It also aids, to a slight
degree, in forced inspiration.
Relations. — Superficial to the muscle lie the peotoralis major and minor, subscapularis,
teres major, and latissimus dorsi muscles, the subclavian and axillary vessels, and the brachial
plexus. Between the latissimus dorsi and pectoral muscles it is covered by skin and fascia
inferiorly, and superiorly by the fatty areolar tissue of the axiUary fossa. Under it he the ex-
ternal intercostal, serratus posterior superior, and the lower extremity of the scalenus medius
and posterior muscles.
Variations. — -The digitations may extend to the tenth or only to the seventh rib. The
muscle may be continuous with the levator scapulae as it is in the carnivora, or some of its
upper digitations may be wanting. Slips may be continued into neighbouring muscles. The
lower digitations may be partially replaced by digitations innervated by intercostal nerves.
360 THE MUSCULATURE
II. MUSCULATURE OF THE UPPER LIMB
The upper limbs in man, relieved of the function of locomotion which is their
chief office in most of the lower mammals, have become endowed with great
Fig. 355. — First Layer of Muscles of the Back.
Sterno-cleido-mastoid
Triceps
Rhomboideus major
Pectoralis major
Gluteus medius
Gluteus maximus
MUSCLES OF UPPER LIMB 361
freedom of movement which permits their developing many important functions.
Primitively of value in climbing, in seizing food, preparing it for eating and
carrying it to the mouth, in attack and defense, their importance has been greatly
increased through the invention and use of tools, at first simple but constantly
increasing in complexity. They are also used as a means of social expression, as
seen primitively in the shrugging of the shoulders, or in the varied movements of
the arms which accompany heated discourse, and as finally developed in the art of
writing. In order to understand the muscles which are called into play in the
performance of these varied functions it is necessary to consider the various types
of movement which take place at each of the joints. Since, however, most
muscles act on more than one joint and the different parts of a muscle may act
differently on the same joint, it is convenient to take up the muscles of each
region of the limb in groups, based not so much upon the action of the muscles on
any one joint as upon the development of the group and the innervation of
the muscles composing it.
Movement of the scapula is of essential importance in the movements of the arm. The
scapula is kept against the thorax by muscular attachments and atmospheric pressure, but it
may be moved forward, backward, upward, and downward, and may be rotated so that the
glenoid fossa, with which the head of the humerus articulates, is pointed forward when the arms
are carried forward, lateralward when the arms are abducted, upward when the arms are raised
high and somewhat downward when the arms are carried backward, thus greatly increasing the
extent of movement in these various directions. The acromio-clavicular, and sterno-clavieular
joints both allow hmited movements in various directions so that they resemble physiologically
limited ball and socket joints. The part played by the superficial and deep shoulder-girdle
muscles in the various movements has been described above, p. 356, in connection with these
groups of muscles. The action of these muscles is aided by the "pectoral muscles," (figs. 360,
388) and by the latissimus dorsi (fig. 355) described below. These muscles depress the scapula*
At the humero-scapular or shoulder-joint the arm may be carried outward or abducted,
bodyward or adducted, forward or flexed and backward or extended. The last is much more
hmited in degree than the other two. The arm may also be partially rotated at this joint.
These various movements are brought about by the scapulo-humeral muscles (figs. 355, 356, 363)
and by the latissimus dorsi (fig. 355) and the pectoralis major, (fig. 360) assisted by the muscles
of the arm which arise from the scapula. They are produced in association with the movements
of the scapula described above. At the ulno-humeral joint the movements are relatively
simple, consisting of flexion and extension. Extension is produced at the elbow by the dorsal
muscles of the arm (fig. 363), flexion is produced not only by the ventral muscles of the arm,
which are inserted into the radius and ulna (fig. 364), but also by the more superficial of both
the main groups of muscles of the forearm. The pronation of the forearm, whereby the palm is
turned downward, and supination, whereby it is turned upward, take place in the joints be-
tween the radius and ulna at each extremity and between the radius and the lower end of the
humerus. At the upper radio-ulnar joint the radius is turned on its long axis, at the lower
joint it is carried about the lower end of the ulna. Pronation is produced chiefly by muscles
belonging to the ulno-volar group of forearm muscles (fig. 370) ; supination is produced by the
biceps of the arm (fig. 364) in conjunction with some of the muscles of the radio-dorsal group
of the forearm (fig. 367). At the wrist joints (radio-carpal, intercarpal), the movements are
those of flexion, extension, radial abduction and ulnar abduction. Volar flexion takes place
chiefly at tlie radio-carpal joint, dorsal flaxion at the intercarpal joint (Frohse). Extension
is produced by those muscles of the radio-dorsal group of the forearm, which send tendons
to the wrist and digits, flexion by the corresponding muscles of the ulno-volar group, radial
abduction is produced by the radial carpal extensors (fig. 367), and flexor ulnar abduction
by the ulnar carpal extensor and flexor (fig. 370). The varied movements of the thumb
and fingers, flexion, extension, abduction, and adduction are produced partly by muscles of
the two chief groups of forearm muscles, partly by the intrinsic muscles of the hand. Of
chief interest here are the free movements of the metacarpal of the thumb and the hmited
movements of the other metacarpals, that of the little fingers being the most movable,
as seen in spreading or cupping the hand. In flexion and extension of the metacarpal
of the thumb the movement is such as to bring the thumb into opposition to the fingers. In the
metaoarpo-phalangeal joints those of the fingers admit of much greater freedom of movement,
flexion, extension, abduction, and adduction, than that of the thumb. The interphalangeal
joints are pure hinge joints and permit merely flexion and extension.
Divisions. — The muscles described in this section as the muscles of the upper
limb are all differentiated from the blastema of the embryonic limb bud. Most
of them are differentiated in connection with the skeleton of the limb and extend
between the various bones which compose it, but a few grow out from the limb
bud over the trunk and become secondarily attached at one extremity to the
trunk, while the other extremitj' remains attached to the skeleton of the limb.
Thus the pectoral muscles (fig. 360), extend from the limb bud over the front of
the thorax and the latissimus dorsi extends over the side and back of the trunk
* The upper sternal part of the pectoralis major, however, acting alone elevates the scapula,
and the glenoid fossa, the latissimus dorsi draws the scapula backward, tlie pectoral muscles
draw it forward.
362 . THE MUSCULATURE
as far as the iliac crest (fig. 355). The muscles of the limb may be divided into
two great divisions, a dorsal division, innervated by nerves arising from the back of
the brachial plexus (supra- and subscapular, axillary and radial nerves) and a
ventral division innervated by nerves arising from the front of the plexus (sub-
clavian, anterior thoracic, musculo-cutaneous, median and ulnar). The former,
which correspond with the musculature on the back of the shark's fin, are in the
main extensors; the latter, which correspond with the musculature on the front
of the shark's fin are in the main flexors. The bellies of the muscles of each
division are found in the region of the shoulder and thorax, the arm, the forearm,
and the hand.
The shoulder muscles belong to the dorsal division. They arise from the
lateral third of the clavicle and from both surfaces of the scapula and are inserted
into the upper part of the humerus. They include the deltoid (fig. 355), the chief
abductor of the arm; the supraspinatus, the infraspinatus and the teres minor
(fig. 363), all lateral rotators; the subscapularis (fig. 356), the chief medial rotator;
and the teres major (fig. 355) , a medial rotator and adductor. With these may
be classed the latissimus dorsi (a medial rotator, adductor and extensor) (fig.
355), which arises from the dorsolumbar fascia and the crest of the ilium and is
inserted into the upper part of the shaft of the humerus. These muscles are sup-
plied by the suprascapular, the subscapular, and the axillary nerves.
The pectoral group belongs to the ventral division. It includes the pedoralis
major (fig. 360) , a powerful flexor and adductor of the arm arising from the anterior
chest wall and inserted into the shaft of the humerus; the pectoralis minor (fig.
388), which arises from the chest wafl and is inserted into the coracoid process of
the scapula, and the subclavius (fig. 361), which extends from the first rib to the
clavicle. These muscles are supplied by the subclavian and the anterior thoracic
nerves.
In the arm the dorsal division is represented by the triceps and anconeus,
(fig. 363). The triceps arises from the scapula and the back of the humerus and is
inserted into the olecranon process of the ulna. The anconeus arises from the
radial epicondyle of the humerus and is inserted into the olecranon process. Both
muscles extend the forearm. The triceps also adducts the arm. They are
supplied by the radial nerve.
The ventral division is made up of the coraco-brachialis (fig. 365) ; the biceps
(fig. 364); and the brachialis (fig. 365). The coraco-brachialis (fig. 365), arises
from the tip of the coracoid process of the clavicle and is inserted into the shaft of
the humerus. It adducts and flexes the arm. The biceps (fig. 364), arises by a
short head from the coracoid process and by a long head from the scapula above
the glenoid fossa and is inserted into the radius and the fascia of the forearm. It
flexes and supinates the forearm. The long head is an abductor, the short head
an adductor and flexor of the arm. The brachialis (fig. 365), arises from the
lower part of the shaft of the humerus and is inserted into the ulna. It is a
flexor of the forearm.
The two main divisions of the musculature of the forearm give rise to the
prominences on each side of the elbow-joint. Their peculiar arrangement with
respect to the humerus is because in man, as in most tetrapods, the normal posi-
tion of the forearm is one of pronation and in this position the back of the forearm
is in line with the radial epicondyle, the front with the ulnar epicondyle. The
dorsal or extensor muscles, springing from the lower end of the humerus (fig. 367),
get the most direct purchase when attached to the radial epicondyle, and the
ventral or flexor muscles (fig. 370), the most direct purchase when attached to the
ulnar epicondyle. The two divisions of the musculature may therefore here be
designated the radio-dorsal and the ulno-volar or volar divisions. The main
bulk of the musculature is found in the upper part of the forearm. At the wrist
numerous tendons pass over to the wrist, palm and digits. This arrangement
facilitates movement of the hand.
The muscles of the dorsal division (figs. 367, 368, 369), are divisible into two
groups, a superficial and a deep group. Those of the superficial group arise
from the radial side of the lower end of the humerus and are inserted into the dorsal
end of the radius (brachio-radialis) , the radial and ulnar sides of the metacarpus
{extensor carpi radialis longus and b7-evis and extensor carpi ulnaris) and into the
backs of the digits {extensores digitorum) . The deeper muscles arise chiefly from
MUSCLES OF SHOULDER 363
the ulna and are inserted into the radius (supinator), the thumb (abductor pollicis
longus, extensor pollicis loncjus and brevis) and index-finger (extensor indicis pro-
prius, fig. 369) . All are supplied by the radial nerve. The chief function of the
brachio-radialis is to flex the forearm. The chief functions of the other muscles
are indicated by their names.
The volar musculature (figs. 370, 371, 372, 375) arises from the medial side
of the lower end of the humerus and from the front of the radius and ulna and is
divisible into four planes. The muscles of the most superficial plane, pronator
teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris, arise from the
humerus and are inserted respectively into the radius, the radial side of the meta-
carpus, the palmar fascia and the ulnar side of the metacarpus. In the second
layer the flexor digitorum sublimis arises from the humerus and the upper part of
the radius and ulna and sends tendons to the second row of phalanges of the fin-
gers. In the third layer the flexor digitorum profundus and flexor pollicis longus
arise from the radius and ulna and send tendons to the terminal row of phalanges.
In the fourth layer a single muscle, the pronator quadratus (fig. 377), extends in
the lower part of the forearm from the radius to the ulna. These muscles are
supplied mainly by branches of the median nerve but the ulnar nerve supplies
the flexor carpi ulnaris and a part of the flexor profundus digitorum. The chief
functions of these muscles are indicated bj^ their names.
In the hand (figs. 368, 375, 376, 377, 379) there are several sets of intrinsic
muscles. About the metacarpal of the thumb is grouped a set of muscles which
arise from the carpus and metacarpus and are inserted into the metacarpal and
first phalanx of the thumb (flexor brevis pollicis, opponens pollicis, abductor pollicis
brevis, adductor pollicis) . A similar set of muscles is grouped about the metacarpal
of the little finger (abductor digiti quinti, opponens digiti quinti, flexor brevis digiti
quinti) . These sets of muscles give rise respectively to the thenar and hypothenar
eminences. Between the metacarpals two sets of interosseous muscles arise; a
volar, adductor toward the middle finger and a dorsal, abductor group. They are
inserted into the sides of the bases of the first row of phalanges and into the
extensor tendons. They also flex the first row of phalanges and extend the other
two rows. From the tendons of the deep flexor muscle of the fingers, a series
of lumbrical muscles extends to the radial sides of the extensor tendons. They
flex the first row of phalanges and extend the other two. Over the thenar emi-
nence there is a subcutaneous muscle, the palmaris brevis. The muscles of the
hand are supplied by the ulnar nerve, with the exception of the two more radial
lumbricals and the abductor, opponens, and flexor brevis of the thumb, which are
supplied by the median nerve.
Fasciae. — The muscle fascise of the upper extremities are well developed. The deltoid
and latissimus dorsi are contained in a fascial sheet which extends between them. The deeper
muscles which arise from the scapula are covered by strong fascia. Of the pectoral muscles the
pectorahs major is covered by a delicate fascia, while the subclavius and pectoralis minor are
contained within the dense cosio-coracoid membrane (fig. 358) which extends into the fascia
covering the axillary fossa. The latter (fig. 359), is thin and is intimately fused to the tela
subcutanea. The muscles of the arm are enveloped in a cylindrical sheath which in the lower
half of the arm is united to the humerus by intermuscular septa.
In the forearm near the wrist and on the back of the hand the tela subcutanea contains
little fat. The antibrachial fascia forms a cylindrical enclosure for the muscles of the forearm.
Near the wrist it becomes strengthened dorsally to form the dorsal ligament of the carpus
(posterior annular ligament). This ligament converts the grooves on the back of the radius
into canals for the tendons of the extensors of the wrist and fingers. On the back of the hand
and fingers the fascia is intimately connected with these tendons. On the volar side near the
wrist the fascia is strengthened to form the volar hgament of the carpus. Beneath the ligament
hes the transverse hgament of the carpus which extends from the pisiform and hamate bones to
the tuberosities of the navicular and greater multangular bones. It completes an osteo-fibrous
canal for the tendons of the long flexors of the fingers. On the palm of the hand the fascia is
firmly bound to the bones by intermuscular septa, which separate the thenar and hypothenar
regions from a central palmar region. On the volar sides of the fingers the fascia forms the
vaginal ligaments of the flexor tendons.
A. MUSCULATURE OF THE SHOULDER
(Figs. 355, 356, 357, 363, 388)
The muscles belonging to this group are the deltoid, the teres minor, the infra-
and supraspinatus, the latissimus dorsi, the teres major, and the subscapularis.
364
THE MUSCULATURE
The deltoid (fig. 355) is a large, shield-shaped muscle which covers the shoulder.
It arises from the spine of the scapula, the acromion, and lateral third of the
clavicle and is inserted into the deltoid tubercle of the humerus. It abducts the
arm.
The teres minor, infra- and supraspinatus form a group of muscles (fig. 363)
which arise from the back of the scapula, pass over the capsule of the shoulder-
joint, to which their tendons are adherent, and, under cover of the deltoid, are
inserted into the top and the dorsal margin of the great tubercle of the humerus.
The band-like teres minor arises from the upper two-thirds of the axillary border
of the scapula, and has the lowest insertion on the tubercle. The triangular
infraspinatus (fig. 363) arises from the whole infraspinous fossa except the axillary
border, and is inserted above the teres minor. The pyramidal supraspinatus
(fig. 363) arises under cover of the trapezius from the supraspinous fossa, and
has the highest insertion on the tubercle. The teres minor, supraspinatus and
infraspinatus act as lateral rotators of the arm, the supraspinatus also as an
abductor.
The latissimus dorsi, the teres major, and the subscapularis form a group of
muscles attached to the lesser tubercle of the humerus and to the crest which
Fig. 356. — Front View of the Scapular Muscles.
Clavicle
Coracoid process
Supraspinatus
Deltoid
Coraco bracliialis and
sliort head of biceps
Pectoralis major
extends distally from this on the medial side of the intertubercular (bicipital)
groove. The latissimus dorsi (figs. 355, 356) is a large, flat, triangular muscle,
which arises from an aponeurosis covering the lumbar and the lower half of the
thoracic regions of the back and from the posterior part of the iliac crest, and is
inserted into the intertubercular (bicipital) groove. The teres major (figs.
355, 356) is a thick, ribbon-shaped muscle which arises from the dorsal surface of
the inferior angle of the scapula and is inserted behind the latissimus dorsi into
the distal two-thirds of the crest of the small tubercle of the humerus. The
subscapularis (fig. 355) is a thick, triangular muscle which extends from the
subscapular fossa to the small- tubercle of the humerus. These muscles adduct
the arm and rotate it medialward. The latissmus dorsi is also the chief extensor
of the arm.
Near their humeral attachments these two groups of muscles are separated
below by the long head of the triceps. The supraspinatus is separated from the
subscapularis by the base of the coracoid process and by the intertubercular
(bicipital) groove. The tendons of the latissimus dorsi, teres major, and sub-
scapularis are crossed ventrally by the main vessels and nerves of the arm and by
the short head of the biceps and the coraco-brachialis.
The supra- and infraspinatus muscles are supplied by the suprascapular nerve.
The deltoid and the teres minor are supplied by the axillary (circumflex). The
subscapularis, the teres major, and the latissimus dorsi are supplied by subscapular
nerves. That to the latissimus dorsi is called the dorsal thoracic nerve.
DELTOIDS us 365
The deltoid in many of the mammals and the lower vertebrates is represented by separate
scapulo-humeral and cleido-humeral portions. The cleido-mastoid in some mammals is con-
tinued into the deltoid. The teres minor, which is innervated by the same nerve, may be looked
upon as a derivative of the deltoid, although in man it is anatomically more intimately connected
with the infraspinatus. The teres major may be looked upon as a speciahsed portion of the
more primitive latissimus dorsi. The comparative anatomy of the shoulder muscles through-
out the vertebrate series is a somewhat intricate subject, owing to the great variations exhibited
in the form and attachment of the shoulder girdle.
The muscles of this group show more or less marked resemblances to certain muscles of the
lower limb. The deltoid and the teres minor probably represent the tensor fascise latEe, the glu-
teal fascia, and the upper part of the gluteus maximus; the latissimus dorsi and teres major,
the lower portion of the gluteus maximus; and the subscapularis, the gluteus medius and mini-
mus, and the piriformis. The subscapular and axillary nerves, which supply the arm muscles
mentioned, therefore represent in the main the nerves to the gluteal muscles, and the gluteal
branch of the posterior cutaneous nerve of the thigh. The infraspinatus muscle probably
represents the ihacus; the supraspinatus possibly the pectineus muscle of the lower limb.
FASCIA
(Figs. 351, 357, 359, 362)
The tela subcutanea covering the regions occupied by these muscles contains considerable
fat. In most regions it is not readily separable into two distinct layers. In the neighbourhood
of the shoulder-joint it is adherent to the underlyingmusculatureand the axillary fasciie. Over
the acromion there is a well-marked subcutaneous bursa, bursa subcutanea acromialis.
Muscle fasciae. — The deltoid and latissimus dorsi muscles are throughout the greater part
of their extent superficially placed. They are covered by an adherent fascial layer, which,
above, is attached to the clavicle and to the spine of the scapula. VentraUy it is continued over
and fuses with the fascia covering the pectoralis major, serratus anterior, and external oblique
muscles. On the back it extends as a thin sheet between the dorsal margin of the deltoid and
the upper margin of the latissimus dorsi, and is continued dorsaUy into the fascial investment
of the rhomboid muscles. The lateral fascial extension of the trapezius becomes fused to the
dorsal surface of this sheet. Toward the armpit the fascial investment of the deltoid and latiss-
imus dorsi muscles is continued into the axillary fascia, and on the back of the arm it is con-
tinued into the fascial investment of the triceps.
The supraspinatus muscle lies beneath the trapezius. It is covered by a dense adherent
fascial layer which is separated from the trapezius by loose connective tissue which usually
contains a considerable amount of fat.
The infraspinatus and the two teres muscles lie beneath the musculo-fascial layer composed
of the deltoid, the latissimus dorsi, and the fascial sheet described above. Each of the three
muscles has a special fascial investment which is bound to the scapula about the region of attach-
ment of the muscle to the bone. Where two of the muscles adjoin, their fasciae gives rise to
intermuscular septa. Septa of this nature are found between the infraspinatus and each of the
teres muscles, and between the teres minor and the teres major. The intermuscular septum
between the infraspinatus and teres minor muscles is often incomplete. The fascia covering
the teres major is so delicate as hardly to deserve the name, except near the origin of the muscle.
Near the spine the fascia covering the deep surface of the deltoid is often fused to that covering
the infraspinatus.
The subscapularis muscle is invested by a moderately dense fascia which is bound to the
scapula along the periphery of the attachment of the muscle. For a short distance this fascia
is fused with the fascial investment of the teres major near the origin of the latter muscle, so that
an intermuscular septum is formed. From the ventro-lateral margin of the fascia covering the
subscapularis muscle a sheet of fascia is continued below the axillary fascia into the fascia cover-
ing the serratus anterior (magnus).
MUSCLES
The deltoideus (figs. 355, 356, 360). — Origin. — Fleshy from the lateral border and upper
surface of the acromion and from the ventral border and upper surface of the lateral third of the
clavicle, and tendinous from the spine of the scapula. Some fibre-bundles also at times arise
from the deep fascia of the muscle where it overlies and is fused to the fascia of the infraspinatus
muscle near the spine.
Insertion. — Into the deltoid tuberosity of the humerus by a strong tendon arising from
numerous tendinous bands within the muscle (fig. 364).
Structure. — In structure the deltoid muscle is complex. Three portions may be recognised:
— a clavicular, an acromial, and a spinous. The first and last are composed of long fibre-bundles
which take a slightly converging course and are inserted by aponeurotic tendons respectively
on the front and back of the V-shaped area of insertion of the muscle. The acromial portion,
on the other hand, is multipenniform in composition. Four or five tendinous expansions descend
into the muscle from the acromion, and three up into the muscle from the tendon of insertion.
From the acromion and from the descending tendinous processes fibre-bundles run to be inserted
on the sides of the ascending processes and into the tendons of insertion of the clavicular and
spinous portions of the muscle.
N eroe-supply . — The axillary (circumflex) nerve passes across the costal surface of the
muscle near the tendon of insertion and gives off rami which enter lateral to the middle of the
muscle. The nerve fibres are derived from the (foiu-th), fifth, and sixth cervical nerves.
Action. — When the whole muscle contracts, the arm is abducted (raised lateralhO to a
366
THE MUSCULATURE
TERES MINOR 367
horizontal position. When the clavicular and acromial parts act, the arm is raised and flexed
(brought forward toward the chest). When the acromial and spinous parts act, the arm is
raised and extended (carried toward the back), but in this instance the arm is not brought to a
level with the shoulder-joint, but only about 45° from the hanging position. The inferior part
of the serratus anterior and the trapezius act in conjunction with the deltoid in abduction.
Abduction is greatest when the arm is rotated lateralward. The ventral portion rotates the
arm medially, the dorsal portion laterally. When the arm is fixed, the deltoid tends to carry
the inferior angle of the scapula toward the spinal column and away from the thorax.
Relations. — On its ventral border the deltoid is in contact with the pectoralis major muscle.
Near the clavicle the cephalic vein and a small artery pass between the two muscles. Its dorsal
border is continued into a dense fascial sheet which overlies the infraspinatus muscle. Its
tendon of insertion passes between the biceps and triceps muscles. The deltoid overhes the
coracoid process and upper extremity of the humerus, the coraco-olavicular and coraco-acromial
hgaments, and the insertions of the supraspinatus, infraspinatus, and teres minor muscles, the
origins of the biceps and coraco-brachiahs, and a part of the long and lateral heads of the triceps.
Beneath it run the posterior circumflex artery and axillary (circumflex) nerve.
Variations. — The clavicular portion is frequently separate from the rest of the muscle. The
three portions may be distinctly separate — a condition normal in some of the lower mammals.
The clavicular and acromial portions have been found missing. The deep portion of the muscle
may be separated as a distinct layer and inserted either into the capsule of the joint or into the
humerus. Accessory fasciculi may pass into the muscle from the fascia over the infraspinatus
and from the vertebral and axillary borders of the scapula. Not infrequently fasciculi are con-
tinued into the muscle from the trapezius — a condition normal in animals with ill-developed
clavicles. An accessory tendon of insertion may extend to the radial side of the forearm.
Bundles of fibres from the axillai'y border of the scapula have been seen to cross the deep sm^face
of the deltoid and be inserted into the deltoid fascia. The deltoid may be fused with neighbour-
ing muscles, the pectoralis major, trapezius, infraspinatus, brachialis, brachio-radiahs.
The teres minor (fig. 363). — Origin. — From the upper two-thirds of the axillary border of
the infraspinous fossa, and from the septa lying between it and the infraspinatus on the one
side and the teres major and subscapularis on the other. The origin is in part fleshy, in part
from an aponeurotic band on its ventral surface toward the subscapularis muscle.
Structure and insertion. — The fibre-bundles from this origin take a slightly converging course
toward a tendon of insertion which extends for some distance on the dorsal surface of the
muscle. The muscle is adherent to the capBule of the joint, and terminates on the inferior of
the three facets of the great tubercle of the humerus and the postero-lateral aspect of that
bone for two or three centimetres below the facet.
Nerve-supply. — From a branch of the axillary (circumflex) nerve which enters the muscle on
its lateral margin about midway between its extremities. A 'ganglion' is usually found upon
this nerve. A branch from the nerve to the teres major has also been reported. The nerve
fibres are derived from the fifth cervical nerve.
Action. — It acts conjointly with the infraspinatus to rotate the arm laterally. It is a
flexor when the arm is down and an extensor when it is abducted. It is also an adductor.
Relations. — The muscle is in part covered by the deltoid. Ventrally it enters into relations
with the long head of the triceps, the teres major, and the subscapularis. Superiorly, the cir-
cumflex (dorsal) scapular vessels run between it and the axillary border of the scapula.
Fig. 357. A and B. — Transverse Sections through the Left Shoulder in the Regions
INDICATED IN THE DIAGRAM.
In the neighbourhood of the brachial plexus in each section some of the adipose and lymphatic
tissue has been removed. In section B the fascia covering the apex of the axillary fossa
is thus revealed from above, a and 6 in the diagram indicate the regions through which
pass sections A and B, fig. 351 (p. 352); a' and b', the regions through which pass
sections A and B, fig. 362 (p. 375).
1. Aorta. 2. Arteria brachiaUs. 3. A. circumflexa scapulae (dorsahs scapulse). 4. A. carotis
communis. 5. A. mammaria interna. 6. A. subclavia. 7. A. thoracahs lateralis (long
thoracic). 8. Costa I. 9. Costa II. 10. Costa III. 11. Costa IV. 12. Costa V.
13. Costa VI. ' 14. Clavicle. 15. Fibrocartilago intervertebrahs (intervertebral disc).
16. Fascia axillaris. 17. Fascia cervicalis (superficial layer). 18. Middle layer. 19. F.
coraco-clavicularis. 20. F. lumbo-dorsahs. 21. Fascia of posterior serrati. 22. Humerus.
23. Medulla spinalis (spinal cord). 24. Musculus biceps — a, long head; 6, short head;
c, tendon of short head. 25. M. coraco-brachialis. 26. M. deltoideus. 27. M. infraspin-
atus. 28. M.iho-costahsdor^i (accessorius). 29.M.intercostalesexterni. 30. M.intercostales
interni. 31. M. latissimus dorsi, tendon. 32. M. levator costs. 33. M. longissimus dorsi.
34. M. longus oolU. 35. M. pectorahs major. 36. M. pectorahs minor. 37. M. platysma.
38. M. rhomboideus major. 39. M. scalenus anterior. 40a. M. serratus anterior. 406,
M. serratus posterior superior. 41. M. sterno-mastoideus. 42. M. cleido-mastoideus.
insertion. 43. M. sterno-hyoideus. 44. M. sterno-thyreoideus. 45. M. subclavius. 46.
M. subscapularis. 47. M. teres major. 48. M. teres minor. 49. M. trapezius. 50.
M. transverso-spinales. 51. M. triceps — a, long head; 6, lateral head. 52. Nervus axillaris
53. N. cutaneus antebrachii medialis (internal cutaneous). 54. a-e, Nn. intercostales
I-V. 55. N. medianus. 56. N. phrenicus. 57. N. musculocutaneus. 58. N. radiaUs
(musoulo-spiral). 59. N. recurrens. 60. N. subscapularis. 61. Sj'mpathetic trunk.
62. N. thoracalis anterior. 63. N. thoracalis longus. 64. N. thoracodorsaUs (long
subscapular). 65. N. ulnaris. 66. N. vagus. 67. CEsophagus. 68. Plexus brachialis —
a, lateral fasciculus; 6, medial; c, posterior. 69. Scapula. 70. Sternum. 71. Trachea.
72. Venae brachiales. 73. V. cephaUca. 74. V. jugularis anterior. 75. V. jugularis
inferior. 76. V. subclavia. 77. Vertebra I. 78. Vertebra II. 79. Vertebra III. 80.
Vertebra IV. 81. Vertebra V. 82. Vertebra VI.
368 THE MUSCULATURE
Variations. — Aside from its frequent fusion with the infraspinatus, there has also been
reported an isolation of a special fasciculus to the subtubercular attachment.
The infraspinatus (fig. 363). — Origin. — From the vertebral three-fourths of the infra-
spinous fossa, from the under surface of the spine, from the enveloping fascia and from inter-
muscular septa between it and the two teres muscles.
Structure and insertion. — The fibre-bundles converge toward the lateral angle of the scapula
to be attached to a deep-seated tendon which is adherent to the capsule of the joint and is
attached to the middle facet of the great tubercle. The fibre-bundles arising from the inferior
surface of the spine and the fascia near this form a distinct fasciculus which descends on and
covers the tendon of insertion.
Nerve-supply. — From the suprascapular nerve, which passes beneath the supraspinatus
muscle and enters the deep surface of the infraspinatus in the lateral part of the midde third
of its upper margin. From here rami spread out toward the vertebral border of the muscle
and toward the humeral insertion. The nerve fibres are derived from the fifth and sixth
cervical nerves.
Action. — This muscle is the chief lateral rotator of the arm, a movement that can be
carried through 90°. The upper part of the muscle is an abductor, the lower part an adductor
of the arm. The muscle is also a flexor.
Relations. — The deltoid and trapezius, and sometimes the latissimus dorsi muscles, cover
a portion of the dorsal surface. Over most of it extends the complex fascia described above.
Laterally it adjoins the teres minor and major muscles. Under the muscle he the transverse
(suprascapular) and circumflex (dorsal) scapular vessels.
Variations. — These are rare, aside from a greater or less independence of the bundles arising
from the spine and a greater or less complete fusion with the teres minor. A fasciculus has
been seen extending to the muscle from the deltoid.
The supraspinatus (fig. 363). — Origin. — Fleshy from the medial two-thirds of the supra-
spinous fossa and from the deep surface of the enveloping fascia near the vertebral end.
Structure and insertion. — The fibre-bundles converge upon a deep-seated tendon nearly to its
attachment into the highest of the three facets on the great tubercle of the humerus.
Nerve-supply. — Two branches from the suprascapular nerve enter the middle third of the
deep surface of the muscle. The nerve fibres are derived from the fifth cervical nerve.
Action. — It aids the deltoid in abducting the arm. It is also a weak lateral rotator and
flexor. It keeps the head of the humerus in place during abduction of the arm.
Relations. — The muscle is covered by the trapezius, the acromion, and the coraco-acromial
hgament. Beyond the base of the spine of the scapula it comes into contact with the infra-
spinatus muscle. Beneath the muscle pass the suprascapular nerve and transverse scapular
(suprascapular) vessels.
Variations. — The muscle shows slight variations. Its tendon may be fused with that of
the infraspinatus. Its belly may be reinforced by fibre-bundles from the coraco-acromial
ligament.
The latissimus dorsi (figs. 355, 356, 387, 388). — Origin. — (1) From an aponeurosis at-
tached to the spines and interspinous ligaments of the five or six last thoracic and the upper
lumbar vertebra, to the lumbo-dorsal fascia, and to the posterior third of the external lip of the
crest of the ilium; (2) from the external surface and upper margin of the last three or four ribs
by muscular slips which interdigitate with those of the external oblique. In the lumbar region
the aponeuroses of the right and left muscles are connected by fibrous fascicuh which cross the
mid-dorsal line above the supraspinous ligament.
Structure and insertion. — From this extensive area of the origin fibre-bundles converge
toward the tendon of insertion. In the region of the dorsal wall of the axillary fossa the muscle
is concentrated into a thick, ribbon-like band which winds about the teres major and passes to
the ventral surface of that muscle. As this takes place the fibre-bundles become apphed to each
surface of a flat tendon, which, after emerging from the muscle, is six to eight cm. long and three
to five cm. broad, and is inserted into the ventral side of the crest of the lesser tubercle of the
humerus and into the depth of the intertubercular (bicipital) groove immediately ventral to
the tendon of the teres major. With this it is more or less closely bound, although between
the tendons there lies a serous bursa. Some of the fasciculi of the tendon extend to the crest
of the greater tubercle. Frequently a tendon slip passes from the inferior margin of the ten-
don to the tendon on the posterior surface of the long head of the triceps or into the brachial
fascia (see lalissirno-condyloideus, p. 379).
Like the teres major, with which it is closely associated, the latissimus dorsi muscle under-
goes a torsion between its origin and its insertion, so that the dorsal surface of the muscle is
continued into the ventral surface of the tendon and the most cranially situated of the fibre-
bundles are most distally attached to the humerus, and vice versa. The muscle either directly
or through its fascial extension is often adherent to the inferior angle of the scapula.
Nerve-supply. — From the dorsal thoracic (long subscapular) nerve (from the sixth, seventh
and eighth cervical nerves) . This nerve, which may arise in conjunction with the axillai'y nerve,
passes to the deep surface of the muscle in the lower part of the axilla, and here gives rise to
rami which diverge as the muscle expands toward its tendons of origin. Though soon embedded
in the muscle substance, two main branches may be followed for a considerable distance near
the deep surface of the muscle. One usually extends near the lateral, the other near the supe-
rior, border of the muscle, and from these large rami pass into the intervening region. Branches
of the dorsal thoracic artery and vein accompany the nerve.
Action. — With the trunk fixed, the latissimus dorsi draws the raised arm down and back-
ward and rotates it medialward (swimming movement). When the arm is hanging by the side,
the action of the muscle is on the scapula. The upper third of the muscle draws the scapula
toward the spine, the inferior two-thirds depress the shoulder. When the humerus is fi^ed,
the latissimus serves to lift the trunk and pelvis forward, as in climbing. It also aids in forced
inspiration through its costal attachments.
BURSJE 369
^Relations. — The trapezius covers a small portion of the muscle in the mid-thoracic region
of the back. Over a large area it is subcutaneous, and its fascial investment is adherent to
the skin. As it winds about the teres major its tendon comes to lie behind the coraco-brachialis
muscle. The main nerves and vessels of the arm here pass across its ventral surface. The
muscle covers in part the rhomboideus major, the infraspinatus, teres major, serratus posterior
inferior, the lower ribs, the external intercostal muscles, the dorsal border of the external and
internal oblique muscles, and the lower dorsal part of the serratus anterior (magnus).
Variations. — It may show considerable variation in the extent of its fleshy portion and in
the attachment of its aponeurosis to the vertebral column, crest of the ilium, the ribs, and the
scapula. Its origin may be merely from the ribs. It maj' be divided into separate fasciculi.
Frequently a fasciculus arises from the inferior angle of the scapula. The muscle is often inti-
mately united to the teres major. For an account of the muscular slip which extends from the
latissimus dorsi across the axillary fossa to the tendon of the pectoralis major near the inter-
tubercular (bicipital) groove see the latter muscle (p. .374); and for the slip continued from the
tendon of the latissimus dorsi to the olecranon see the Triceps Muscle (p. .379).
The teres major (figs. 356, 388). — Origin. — Directly from the dorsal surface of the inferior
angle of the scapula and from the septa which lie between this muscle and the subscapularis,
teres minor, and infraspinatus muscles.
Insertion. — For about five or six cm. from the lower border of the small tubercle of the
humerus, along the medial lip of the intertubercular (bicipital) groove. ProximaUy the fibre-
bundles are attached directly to the tubercle; more distally the attachment is by means of a flat
tendon which extends for some distance on the dorsal surface of the muscle.
Structure. — The nearly paraOel fibre-bundles pass upward in a spiral direction so that the
muscle undergoes a torsion on its axis. The fibre-bundles which have the highest attachment
to the scapula have the lowest humeral attachment, and vice versa.
Nerue-supply. — By a branch of the lower subscapular nerve which enters the muscle near
the middle of its scapular border. The nerve fibres are derived from the fifth, sixth (and seventh)
cervical nerves.
Action. — It aids the latissimus dorsi in adducting the arm, and in some positions of the arm
acts as a medial rotator and as an extensor.
Relations. — Dorsally the muscle is covered by the latissimus dorsi and by the fascia which
extends from this muscle to the deltoid and rhomboid muscles. It is also crossed by the long
head of the triceps. Its lower border and ventral surface are largely covered by the latissimus
dorsi and its tendon. Its upper border helps to bound a triangular space the other sides of
which are the borders of the scapula and the humerus. In front lies the subscapularis, and
behind, the teres minor. Across this space passes the long head of the triceps. Lateral to this
head lie the humeral circumflex vessels and axillary (circumflex) nerve; and medial, the circum-
flex (dorsal) scapular artery.
Variations. — The teres major may be connected with the latissimus dorsi by a fasciculus,
or it may be fused with that muscle or its tendon. Slips have also been seen extending to the
triceps and into the fascia of the arm. The muscle is rarely absent.
The subscapularis (figs. 356, 388). — Origin. — The fibre-bundles spring — (1) directly and
by means of tendinous bands from the costal surface of the scapula, except near the neck and
at the upper and lower angles; and (2) from intermuscular septa between it and the teres major
and teres minor muscles.
Insertion. — The tendon of insertion as it passes over the capsule of the joint is intimately
bound to this. It is inserted into the lesser tubercle of the humerus and into the shaft im-
mediately below this.
Structure. — The fibre-bundles arising from the tendinous bands attached to the bone con-
verge upon several tendinous laminee which extend into the muscle from the tendon of insertion,
thus forming small pennif orm fasciculi. The fibre-bundles arising directly from the bone con-
verge toward the extremities of the tendinous lamina;, thus forming triangular bundles inter-
digitating with the penniform fasciculi. The fasciculus which arises highest on the axillary
border goes directly to the humerus.
Nerve-supTply. — By two or three subscapular branches from the back of the brachial plexus.
One or more of these may arise in association with the axillary (circumflex) nerve. From the
main nerves rami spread out to enter the ventral surface of the muscle near the junction of the
lateral and middle thirds. The nerve fibres come from the fifth and sixth cervical nerves.
Action. — It is the chief medial rotator of the arm. It strengthens the shoulder-joint by
drawing the humerus against the glenoid cavity. It is an extensor when the arm is at the side,
a flexor when the arm is abducted. The upper portion of the muscle, however, acts as a
flexor in both positions. The upper part acts as an abductor but when the arm is abducted the
muscle is an adductor.
Relations. — Ventrally it forms the greater part of the posterior wall of the axillary fossa,
and enters into relation with the serratus anterior (magnus) and the combined tendon of the
coraco-brachiaUs and biceps. On it lie the axillary vessels, the brachial plexus, and numerous
lymph-vessels and glands. At its lateral border lie the teres major, the humeral cu-cumflex
vessels, axillary (circumflex) nerve, and circumflex (dorsal) scapular vessels. Behind it he the
long head of the triceps and the teres minor muscle.
Variations. — It may be divided into several distinct segments. A fasciculus may be sent
to the tendon of the latissimus dorsi and another to the brachial fascia. The subscapularis
minor arises from the axillary border of the scapula and is inserted into the articular capsule
(capsular hgament) of the shoulder-joint or into the crest of the lesser tubercle of the humerus.
BURS^
B. subacromialis. — A large bursa, nearly constantly found, between the acromion and
coraco-acromial ligament and the insertion of the supraspinatus muscle and capsule of the joint.
370
THE MUSCULATURE
Processes extend over the greater and lesser tubercles.
B. supracoracoidea. — A bursa sometimes found between the coracoid process and the
clavicle and the deltoid muscle.
B. m. subscapularis. — Between the glenoid border of the scapula and the subscapularis
muscle. Communicates with the joint cavity. A small portion of this bursa may be isolated
adjacent to the base of the coracoid process (6. subcoracoidea) .
B. m. infraspinati. — Between the tendon of the infraspinatus and the capsule of the joint
or the great tubercle.
B. m. latissimi dorsi. — Constant between the tendons of the latissimus dorsi and the teres
major.
B. m. teretis majoris. — Under the insertion of the tendon of the teres major muscle.
B. PECTORAL MUSCLES AND AXILLARY FASCIA
(Pigs. 357, 358, 360, 361, 388)
The muscles belonging to this group are the pectoralis major, pectoralis
minor, and the subclavius. Of these, the largest and most superficial is the
Fig. 358. — Deep Fascia of the Breast. (After Eisler). The Pectoralis Major Has
Been in Large Part Removed. 1, Deltoid; .2, Pectoralis Major, Abdominal Past; 3,
Pectoralis. Minor; 4, Coraco-Brachialis.
triangular pectoralis'major (fig. 360), which arises from the second to the sixth
ribs, the sternum, and the medial half of the clavicle and is inserted into the crest
of the greater tubercle of the humerus (pectoral ridge). Its lateral margin adjoins
the ventral margin of the deltoid. Beneath this muscle the much smaller triangu-
lar pectoralis minor (fig. 388) extends from near the ends of the second, third,
fourth, and fifth ribs to the tip of the coracoid process, while the small subclavius
(fig. 361) extends from the first rib upward and lateralward to the clavicle.
The pectoral muscles and the subclavius play a part in forced inspiration.
The pectoralis major also serves to adduct and flex the arm- and rotate it
medialward.
Of the muscles included in this group, the two pectoral muscles are morphologically the most
closely related. They receive a nerve-supply from the same set of nerves, the anterior thoracic
With them the subclavius, which has a separate nerve of its own, is closely associated. Cor-
F ASCIIS
371
responding musculatui-e, although variously modified in different forms, is found tlii'oughout the
vertebrate series. In the lower forms it se"ems to be differentiated directly from the segmental
trunk musculature and secondarily attached to the shoulder girdle, like the superficial and deep
musculature of the shoulder girdle previously described. In man, however, the muscle mass
from which these muscles arise is at all times in intimate union with the skeleton of the upper
limb, and the nerves which supply it are in much more intimate union with the brachial plexus
than are those of the shoulder-girdle muscles. For these reasons the three muscles are classed
with the intrinsic muscles of the arm. They have no certain representatives in the lower hmb,
although the clavicular portion of the pectoralis major is considered by some to represent certain
adductor muscles of the thigh. Possibly they correspond in their embryonic origin with the
obturator internus group of the lower hmb.
In many of the mammals a subcutaneous muscle arises from the pectoral muscle mass and
extends over the axUla and the trunk. In man this musculature is frequently represented by
abnormal shps of muscles, of which the 'axillary arch' and possibly the 'sternalis' are representa-
tives. A list of some of the abnormal muscles which are innervated from the anterior thoracic
nerves and are evidently derivatives of the pectoral muscle mass is given at the end of this section
Fig. 359. — (After Eisler). Fascia of the Axillary Fossa.
FASCIiE
In the tela subcutanea of the pectoral region the mammary gland is embedded between
two layers which ensheath the gland and are connected by dense fibre-bands. To a greater
or less extent the platysma extends into the tela of this region from above the clavicle.
Muscle fasciae. — The pectorahs major is invested with a thin, adherent membrane, fascia
pectoralis, attached to the clavicle and the sternum and continued into the fascial invest-
ment of the external obUque, the serratus anterior (magnus), and the deltoid muscles,
and in to the axillary fascia. More important is the coraco-clavicular (costo-coracoid) fascia
fig. 358. This arises from two fascial sheets which invest the subclavius muscle and are at-
tached to the clavicle. From the inferior margin of this muscle the membrane is continued
to the superior margin of the pectoralis minor. Between the coracoid process and the first
costal cartilage it is strengthened to form the costo-coracoid ligament. Between this and the
pectorahs minor it is thin. At the superior margin of this muscle it again divides to form two
adherent fascial sheets, which, at the axillary margin of the muscle, once more unite to form a
fii'm membrane continued into the fascial investment of the coraco-brachiahs and short head of
the biceps and into the axiUai'y fascia. Above, dorsally, the membrane is adherent to the sheath
of the axillary vessels and nerves.
Axillary fascia (fig. 359). — The arm-pit, or axillary fossa, is a pyramidal space bounded
by the pectoralis major and minor and coraco-brachialis muscles in front; by the latissimus
372
THE MUSCULATURE
dorsi, teres major, and subsoapularis muscles behind; by the subscapularis muscle toward the
joint; and by the serratus anterior (magnus) toward the thoracic wall. In the groove between
the coraco-brachiaUs and the subscapularis and tendons of the latissimus dorsi and teres major
muscles run the main nerves and vessels of the arm. These are surrounded by a considerable
amount of connective tissue in which numerous blood- and lymph-vessels, lymph-nodes,
nerves, and masses of fat are embedded.
Fig. 360. — The Pectoralis Major and Deltoid.
Sterno-cleido-
mastoid
■Aponeurosis of external oblique
External intercostal
Over this connective tissue the fascia covering the musculature of the neighbouring portion
of the shoulder and thorax is continued into the fascia covering the musculature of the medial
side of the arm. Thus the fascia covering the pectoralis minor, the coraco-clavicular fascia,
strengthened by a reflection of the fascial investment of the pectorahs major and deltoid muscles-
is continued across the ventral margin of the arm-pit into the fascia which covers the coraco-
brachialis and biceps muscles in the arm. Similarly, dorsally, the fascia Covering the latissimus
dorsi and teres major is continued over the arm-pit into that covering the long head of the triceps
in the arm. The ventral is connected with the dorsal fascia by a thin membrane which is
adherent to the connective tissue filling the axillary space and to the subcutaneous tissue.
On the trunk this membrane, the fascia axillaris, becomes fused below the axillary fossa with
the fascia of the serratus anterior (magnus). In the arm it becomes fused with the fascia over
the biceps muscle. Owing to its adherence to the skin and the connective tissue of the axillary
fossa, investigators have dissected out and figured the axillary fascia in different ways.
MUSCLES
The pectoralis major (fig. 360). — Origin. — (1) From the medial half of the clavicle; (2)
from the side and front of the sternum as far as the sixth costal cartilage; (3) from the front of
the cartilages of the second to the sixth ribs; and (4) from the upper part of the aponeurosis of
the external oblique where this extends over the rectus abdominis muscle. The costal origin
may in part take place from the osseous extremities of the sixth and seventh ribs.
Insertion. — Crest of the greater tubercle (outer lip of the bicipital groove) of the humerus
from the tubercle to the insertion of the deltoid (fig. 174). Some of the tendon fibres are also
continued into the tendon of the deltoid and adjacent fibrous septa and into the fibrous lining
of the intertubercular sulcus.
Structure. — The muscle is divisible into a series of overlapping layers spread out hke a fan.
Of these, the clavicular portion forms the most cranial and superficial layer, and the portion of
the muscle springing from the aponeurosis of the external oblique, the most caudal and deepest
layer. This last layer has a special tendon, while the other layers are inserted into a combined
SUBCLAVIUS
373
tendon lying ventral to this. The two tendons are continuous at their distal margins. (W. H.
Lewis.)
Neroe-supply. — From the external and internal anterior thoracic nerves, branches of which
enter the sterno-costal portion of the muscle about midway between the tendons of origin
and insertion, and the clavicular portion in the proximal third. The nerve fibres are derived
from the (fifth), si.xth, seventh and eighth cervical and first thoracic nerves.
Action. — With the thorax fixed, the muscle adducts and flexes the arm and rotates it medial-
ward. The clavicular portion draws the arm forward, upward, and medialward; the sterno-
costal portion draws the arm downward, medialward, and forward. When the arm is pendent,
the upper portion elevates, the lower depresses, the shoulder. With the arm fixed, the muscle
draws the chest upward toward it. It is of value in forced inspii'ation.
Relations. — It lies over the coracoid process, the subclavius, pectoralis minor, intercostal,
and serratus anterior (magnus) muscles, the coraco-clavicular (costo-coracoid) fascia, and the
thoraco-aoromial vessels. It forms the main part of the ventral wall of the axillary fossa, and
laterally it enters into relation with the deltoid, biceps, and coraco-brachialis muscles.
Variations. — In considering variations the muscle may be looked upon as composed of
four portions — a clavicular, a sternal, a costal, and an abdominal, the last being that portion
which arises from the aponeurosis of the external obhque. These portions vary in the extent
of their attachments and in the degree of separation which they present. The abdominal por-
tion may extend to the umbilicus. Huntington considers this portion a derivative of the pan-
nicular muscle of the lower mammals. On the sternum the muscles of the two sides may de-
cussate across the middle line. The sterno-costa! portions of the muscle are more frequently
deficient or missing than the clavicular, but in rare cases the entire muscle is absent. The
clavicular portion of the muscle may be fused with the deltoid. The sterno-costal may extend
laterally to the latissimus dorsi. There may be an intimate fusion of the abdominal portion
with the rectus abdominis or the external oblique. Sometimes a slip may run from the pec-
toralis major to the biceps, the pectoralis minor, coracoid process, capsule of the joint, or
brachial fascia.
The pectoralis minor (fig. 388). — Origin. — By aponeurotic slips from the second, third,
fourth, and fifth ribs near the costal cartilages.
Fig. 361. — The Subclavius and the Upper Portion op the Serratus Anterior.
Serratus anterior
Structure and insertion. — The fibre-bundles converge upward and outward to a flattened
tendon which is attached to the medial border and upper surface of the coracoid process of
the scapula.
Nerve-supply. — From the internal anterior thoracic nerve which enters the upper part of
the middle third of the deep surface by several branches. Some of the branches extend through
to the pectoralis major. The nerve fibres arise from the seventh and eighth cervical nerves.
Action. — When the thorax is fixed, the pectoraUs minor pulls the scapula forward, the
lateral angle of the bone downward, and the inferior angle dorsalward and upward. When
the scapula is fixed, the muscle aids in forced inspiration.
Relations. — It is covered by the pectorahs major. Near its insertion the fibrous investment
of the chief nerves and vessels of the arm is adherent to its enveloping fascia.
Variations. — The origin may extend to the sixth rib or may be reduced to one or two ribs.
In the primates below man the insertion of the muscle takes place normally into the humerus.
In man its insertion may be continued (in more than 15 per cent, of bodies — Wood) over the
coracoid process to the coraco-acromial or coraco-humeral ligaments, to the tendon of the sub-
scapularis muscle, or to the great tubercle of the humerus. It may be divided into two super-
imposed fasciculi. Fasciculi may extend from the muscle to the subclavius or the pectoralis
major.
The subclavius (fig. 361). — Origin. — From a flat tendon attached to the fii-st rib and its
cartilage near their junction.
Structure and insertion. — The fibre-bundles arise in a penniform manner from the tendon
of origin which extends for some distance along the lower border of the muscle. They are
inserted in a groove which lies on the lower sm'face of the clavicle between the costal tuberosity
and the coracoid tuberosity. The medial fibre-bundles are inserted directly, the lateral by a
strong tendon.
Nerve-supply. — By a branch which arises usually from the fifth or fifth and sixth cervical
nerves and enters the middle of the back part of the muscle.
Action. — When the first rib is fixed, the subclavius depresses the clavicle and the point of
374 THE MUSCULATURE
the shoulder. When the clavicle is fixed, the muscle aids in forced inspiration. It also serves
to keep the clavicle against the sternum.
Relations. — It is concealed by the clavicle and peotorahs major muscle. Behind it lie the
subclavian vessels and the brachial plexus.
Variations. — It may be replaced by a ligament or by a peotoralis minimus muscle (see below).
It may be doubled or may be inserted into the coracoid process, ooraco-aoromial hgament, the
acromion, or the humerus. The subclavius posticus arises near the subolavius, passes backward
over the subclavian vessels and brachial plexus and is inserted into the cranial margin of the
scapula near the base of the coracoid process.
Abnormal Muscles of the Pectoral Group
The following muscles are usually innervated by the anterior thoracic nerves and are
probably generally abnormal derivatives of the pectoral mass. Frequently they represent
muscles normally found in lower mammals.
The sternalis. — A flat muscle somewhat frequently seen on the surface of the pectoralis
major, usually nearly parallel to the sternum. It arises from the sheath of the rectus and from
some of the costal cartilages (third to seventh) and terminates on the sterno-oleido-mastoid,
on the sternum, or on the fascia covering the pectoraUs major. When present on both sides,
the two muscles may be fused across the sternum. This muscle is found in 4 per cent, of
normal individuals and 48 per cent, of anencephalic monsters. (Eisler.) Rarely, corresponding
muscle slips have been found innervated by the intercostal nerves. These probably represent
remains of a thoracic 'rectus' muscle.
The pectoro-dorsalis (axillary arch). — This muscle in its most complete form extends from
the tendon of the pectoralis major over the axillary fossa to the tendon of the latissimus dorsi,
to the fascia covering the latissimus dorsi, to the teres major or even more distaUy. It may,
however, be more or less fused with either of the last two muscles mentioned, and it presents a
great variety of forms. It may extend from the latissimus dorsi to the brachial fascia over the
coraco-brachialis or biceps, to the long tendon of the biceps, to the axillary fascia, to the axillary
margin of the pectoralis minor, or to the coracoid process, etc. It is found in about 7 per cent,
of bodies. (Le Double.) When supplied from the anterior thoracic nerves, it probably rep-
resents a portion of the thoraco-humeral subcutaneous (pannicular) muscle of the lower
primates. It is also sometimes supplied by the medial brachial cutaneous or the intercosto-
brachial (humeral) nerve and frequently is partly or wholly supplied by the dorsal thoracic (long
subscapular) nerve. The part of the muscle supphed by the dorsal thoracic nerve is probably
derived from the latissimus dorsi musculature.
The costo-coracoideus. — A muscular slip which arises from one or more ribs or from the
aponeurosis of the external oblique between the pectoralis major and latissimus dorsi muscles,
and is inserted in the coracoid process.
The chondro-humeralis (epitrochlearis). — This is a slip which springs from one or two rib
cartilages or from the thoraco-abdominal fascia beneath the pectoralis major, or from its lower
border or tendon, and extends on the medial side of the arm to the intertubercular (bicipital)
groove, the brachial fascia, the intermuscular septum, or the medial epicondyle. It is found in
12 to 20 per cent, of bodies (Le Double), and occurs normally in many of the lower mammals.
The pectoralis minimus (sterno-chondro-scapularis). — From the cartilage of the first rib
and sternum to the coracoid process.
The sterno-clavicularis. — From the manubrium of the sternum to the clavicle between the
pectoralis major and the coraco-clavicular (costo-coracoid) fascia. In 2 per cent, to 3 per cent
of bodies. (Gruber.)
The scapulo-clavicularis. — From the coracoid process of the scapula to the outer third of
the clavicle.
The infra-clavicularis. — From above the clavicular part of the pectoralis major to the
fascia over the deltoid.
BURSiE
B. m. pectoralis majoris. — Between the tendon of insertion of the pectoralis major and
the long head of the biceps. Frequent.
C. MUSCULATURE OF THE ARM
(Figs. 355, 356, 362, 363, 364, 365, 367, 370, 372)
The muscles included in this section are the triceps and anconeus, coraco-
brachialis, biceps, and brachialis. The triceps and anconeus (fig. 363) constitute
a mass of musculature extending along the back of tlie arm from the scapula and
humerus to the olecranon of the ulna. The coraco-brachialis, biceps, and brachialis
(figs. 364, 365) constitute a similar mass of musculature extending along the front
of the arm from the scapula and the humerus to the humerus, and to the radius
and ulna near the elbow. In the upper half of the arm the two groups are
separated on the lateral side of the arm by the deltoid, pectoralis major, teres
minor, supra- and infraspinatus muscles, and by the greater tubercle of the
humerus. On the medial side they are separated the by chief nerves and blood-
MUSCLES OF THE ARM
375
Fig. 362, A-D. — Transverse Sections through the Left Arm in the Regions shown in
THE Diagram.
o and 6 in the diagram indicate the regions through which pass sections A and B, fig. 351
(p. 352); a' and b', the regions through which pass sections A and B, fig. 367 (p. 366); and
a" the region thi-ough which passes section A, fig. 366 (p. 385).
1. Arteria brachialis. 2. Bursa subcutanea olecrani. 3. Fascia brachiahs. 4. Humerus. 5.
Musculus anconeus. 6. M. biceps — a, long head; b, short head; c, tendon of insertion.
7. M. brachiahs. 8. M. brachio-radialis. 9. M. coraco-brachialis. 10. M. deltoideus.
11. M. e.xtensor carpi radiahs brevis. 12. M. extensor carpi radialis longus. 13 M.
extensor digitorum communis. 14. M. flexor carpi radialis. 15. M. flexor carpi ulnaris.. 16.
M. flexor digitorum subhmis. 17. M. flexor digitorum profundus. 18. M. palmaris
longus. 19. M. pronator teres. 20. M. triceps — a, lateral head; b, long head; c, medial
head. 21a. N. cutaneus antibrachii medialis (internal cutaneous). 216. N. cutaneus
antibrachii dorsalis. 22. N. musculo-cutaneus. 23. N. medianus. 24. N. radialis^a,
muscular branch. 25. N. ulnaris. 26. Lymphatic gland. 27. Olecranon. 28. Septum
intermusculare laterale. 29. Septum intermusculare^mediale. 30. Vena cephalica. 31.
V. basilica. 32. Vv. brachiales.
9 2,1'' 23 32.2,5 24°-
376
THE MUSCULATURE
MUSCLES OF THE ARM 377
vessels of the arm and by the tendons of the latissimus dorsi, teres major, and
subscapularis muscles. In the distal half of the arm they are separated medially
by the medial intermuscular septum (described below) and by the medial epicon-
dyle and the ulno-volar group of muscles of the forearm. On the lateral side
of the arm they are separated by the lateral intermuscular septum, by the
lateral epicondyle, and by the brachio-radialis and the extensor muscles of the
forearm which take origin from the lateral epicondyle.
FASCIA
The fasciae and the general relations of the muscles of the arm are shown in the cross-
sections in fig. 362.
The tela subcutanea of the arm is fairly well developed and contains a considerable amount
of fat, especially near the shoulder. It is but loosely bound to the muscle fascia, except near
the insertion of the deltoid, where the union may be more intimate.
Bursse. — B. subcutanea epicondyli lateralis. — Between the lateral epicondyle and the skin.
Rare. B. subcutanea epicondyli medialis. — Between the medial epicondyle and the skin.
Inconstant. B. subcutanea olecrani. — Between the olecranon process of the ulna and the
skin. Nearly constant.
The brachial fascia forms a cylindrical sheath about the muscles of the arm. It contains
circular and longitudinal fibres, the former being the better developed. The fascia is strong
over the dorsal muscles, especially near the two epicondyles of the humerus. Proximally the
fascia of the arm is continued into the axillary fascia and into the fascial investment of the pec-
toralis major, deltoid, and latissimus dorsi muscles; distally it is continued into the fascial
investment of the forearm. It is intimately bound to the epicondyles and to the dorsal surface
of the olecranon. It is separated by loose areolar tissue from the beUies of the muscles which it
covers. From the tendons of the deltoid, pectoralis major, teres major, and latissimus dorsi
muscles, however, fibrous bundles are continued into the brachial fascia. There are a number
of orifices in the fascia for the passage of nerves and blood-vessels. Of these, the largest is
that for the basilic vein and two or three large branches of the medial antibrachial (internal)
cutaneous nerve. This lies on the ulnar margin of the arm in the lower third. On the radial
margin lie the cephalic vein in a double fold of the fascia, orifices for branches of the musculo-
cutaneous nerve, and more dorsally orifices for branches of the radial. From the fascia septa
descend between the muscles which it invests. Of these septa, the most important are the medial
and lateral intermuscular septa, which separate the dorsal group of muscles from the ventral
in the distal half of the arm. The medial intermuscular septum is the stronger. It is attached
to the medial epicondyle and to the medial margin of the humerus proximal to this, It is
continued proximally into the tendon of insertion of the coraco-brachialis and the investing
fascia of this muscle. Into it longitudinal bundles of fibres descend from the tendon. It
separates the brachiaUs and pronator teres muscles from the medial head of the triceps. The
lateral intermuscular septum is attached to the lateral epicondyle and to the lateral margin
of the humerus. It is continued proximally into the dorsal surface of the tendon of insertion
of the deltoid muscle, and into the septa between the deltoid and the triceps. It separates
the triceps from the brachialis in the third quarter of the arm and from the brachio-radi-
alis and extensor carpi radialis longus in the distal quarter. The median nerve and brachial
vessels lie in front of the medial septum. The ulnar nerve and the superior ulnar collateral
(inferior profunda) artery are bound to its dorsal surface.
MUSCLES
1. Dorsal or Extensor Group
Two muscles are included in this group, the triceps brachii and the anconeus.
The triceps is a complex muscle in which proximally three heads, a long or scapu-
lar, a lateral humeral, and a medial humeral, may be distinguished. The long
head arises from the infraglenoid tuberosity of the scapula, the lateral head from
the humerus above and laterally to the groove for the radial nerve fmusculo-
spiral groove), the medial head from the lower half and medial margin of the
posterior surface of the humerus. Distally these heads fuse and are inserted
by a common tendon into the olecranon of the ulna. The anconeus lies chiefly
in the forearm, but physiologically and morphologically it belongs with the triceps,
and hence is described in connection with the muscles of the arm. It is a tri-
angular muscle, which arises from the lateral epicondyle and is inserted into the
olecranon and adjacent part of the shaft of the ulna. Both muscles are supplied
378
THE MUSCULATURE
by branches of the radial (musculo-spiral) nerve. They extend the forearm.
The long head is also an adductor of the arm.
The triceps, variously modified, is found in the amphibia and all higher vertebrates. The
anconeus is found in the prosimians and all higher forms. The triceps muscle is homologous
with the quadriceps of the thigh. The long head is equivalent to the rectus femoris. The
anconeus is not represented in the lower limb.
The triceps brachii (figs. 355, 356, 363). — The long head arises from the infraglenoid tuber-
osity of the scapula by a strong, broad tendon, some of the fibres of which are connected with
the inferior portion of the capsule of the shoulder-joint. The tendon soon divides into two
lamellse, which extend distally, one a short distance on the deep surface, the other much farther
Fig. 363. — Dorsal View op the Scapular Muscles and Triceps.
Supraspinatus
Infraspinatus
Teres minor
Long bead of triceps
Lateral head of triceps
Medial head of triceps
on the superficial surface of this head. The parallel fibre-bundles which arise from these
lamellae form a thick muscle-baud which twists upon itself so that the ventral surface at the
origin becomes dorso-medial at the insertion. At the insertion the long head becomes ap-
plied to an aponeurosis which extends upward from the main tendon of insertion of the triceps.
The fibre-bundles extend for some distance on the medial side of this tendon and terminate
about three-fourths of the way down the arm.
' The lateral head has a tendinous origin from the superior lateral portion of the posterior
surface of the humerus along a line extending from the insertion of the teres minor as far as the
groove for the radial (musoulo-spkal) nerve, and from the aponeurotic arch formed by the
lateral intermuscular septum as it crosses this groove. The constituent fibre-bundles descend,
the superior vertically, the inferior obliquely, to be inserted on the dorsal and ventral surfaces
of the proximo-lateral margin of the common tendon of insertion of the triceps.
The medial head has a fleshy origin from the posterior surface of the humerus below the
radial (musculo-spiral) groove and from the dorsal surfaces of the medial and lateral intermus-
cular septa. The greater part of the fibre-bundles arising from this extensive area are inserted
into the deep surface of the common tendon, but some extend directly to the olecranon and the
articular capsule of the elbow. The slip attached to the capsule is sometimes called the
subanconeus muscle.
FLEXORS OF THE ARM 379
Insertion. — The tendon of insertion of the triceps forms a flat band covering the dorsal
surface of the distal two-fifths of the muscle. It also extends proximally between the long and
lateral heads and on the deep surface of the former. This tendon is inserted into the olecranon
and laterally, by a prolongation over the anconeus, into the dorsal fascia of the forearm.
Neroe-supply. — From the radial (musculo-spiral) nerve. The branch to the long head arises
in the arm-pit and enters that margin of the muscle which is prolonged down from the lateral
edge of the tendon, but which, because of the torsion of the muscle, comes to he on the medial
side. The nerve usually enters through several rami about the middle of the free portion of the
long head. Somewhat more distally the radial nerve gives off a branch that enters, by two or
three branches, the proximal portion of the medial head. A similar branch is given to the
lateral head and other branches are given to the lateral and medial heads from that portion of
the radial (musculo-spiral) nerve lying in the radial (musculo-spiral) groove." The nerve fibres
arise from the sixth, seventh, and eighth cervical nerves.
Relations. — Near the shoulder the triceps is covered by the deltoid muscle. The long head
passes between the teres major and teres minor muscles. The circumflex (dorsal) scapular
vessels here pass medial, the circumflex humeral vessels and the axillary (circumflex) nerve
lateral, to this head. More distally the muscle lies beneath the brachial fascia. It covers the
radial groove of the humerus, in which run the radial (musculo-spiral) nerve and (superior) pro-
funda brachii artery. Ventro-lateral to the muscle he the deltoid, brachialis, brachio-radialis,
and extensor carpi radiaUs muscles; ventro-medial, the coraco-brachiahs, biceps, and brachialis
muscles.
Action. — It extends the forearm. The leverage is of such a nature that force is sacrificed
for speed of movement. The long head of the triceps also serves to extend and to adduct the
arm and to hold the head of the humerus in the glenoid cavity.
Variations. — The scapular attachment may extend for a considerable distance down the
axillary border of the scapula. Each of the heads may be more or less fused with neighbouring
muscles. Frequently a fourth head is found. This may arise from the humerus, from the
axillary margin of the scapula, from the capsule of the shoulder-joint, from the coracoid process,
or from the tendon of the latissimus dorsi.
The latissimo-condyloideus (dorso-epitrochlearis).^This muscle is found in about 5 per
cent, of bodies. When well developed, it extends from the tendon of the latissimus dorsi to the
brachial fascia, the triceps muscle, the shaft of the humerus, the lateral epicondyle, the olec-
ranon, or the fascia of the forearm. It is innervated by a branch of the radial (musculo-spiral)
nerve. It is a muscle normally present in some one of the forms above mentioned or in some
similar form, in a large number of the inferior mammals. In the human body it is normally
represented by a fascial slip from the tendon of the latissimus to the long head of the triceps or
the brachial fascia.
The anconeus. — Origin. — By a short narrow tendon from the distal part of the back of the
lateral epicondyle and the adjacent part of the capsular hgament of the elbow-joint.
Structure and insertion. — The tendon of origin is prolonged on the deep surface and lateral
border of the muscle. From this the fibre-bundles spread, the proximal transversely, the more
distal obliquely, to be inserted into the radial side of the olecranon and an adjacent impres-
sion on the shaft of the ulna. Its superior fibre-bundles are usually continuous with those of
the medial head of the triceps.
Nerve-supply. — By a long branch which arises in the radial (musculo-spiral) groove from the
radial (musculo-spiral) nerve, passes through the medial head of the triceps, to which it gives
branches, and enters the proximal border of the anconeus. The nerve fibres arise from the
seventh and eighth cervical nerves.
Action. — It aids the triceps in extending the forearm and draws the ulna laterally in prona-
tion of the hand.
Relations. — The muscle hes immediately beneath the antibrachial fascia. It extends over
the head of the supinator (brevis) and the elbow-joint and upper radio-ulnar joint.
Variations. — The extent of fusion of .the muscle with the medial head of the triceps varies
a good deal. It may also be fused with thfe extensor carpi ulnaris. It has been reported
missing.
P^P^*^ ^>>
B. intratendinea olecrani. — Within the tendon of the='triceps near its insertion. JVIore
frequent than the following: — - ,'
B. subtendinea olecrani. — Between the tendon of the trffeopS; and the olecranon and dorsal
ligament of the elbow-joint. Inconstant.
B. epicondyli medialis dorsalis. — Between the medial epicondyle, the edge of the triceps,
and the ulnar nerve. Rare. jiC-
B. m. anconei. — Between the tendon of origin of the muscle and the head of the raditi^'*
Frequent.
2. Ventral or Flexor Group
(Figs. 364, 365, 370, 372)
The muscles of this group are the coraco-brachialis, the biceps, and the brachi-
alis. The coraco-brachialis (fig. 365) is a band-like muscle which arises from
the coracoid process and is inserted into the middle third of the shaft of the
humerus. The biceps (fig. 364) arises by two heads: a short head, closely as-
sociated with the coraco-brachialis, fi"om the coracoid process; a long head, by an
380
THE MUSCULATURE
extended tendon, from the supraglenoid tuberosity of the scapula. The fusiform
belly whicli arises from the fusion of these two heads is inserted into the radius and
into the fascia of the forearm. The brachialis (fig. 365) extends under cover of
the biceps from the lower three-fifths of the shaft of the humerus to the coronoid
process of the ulna. The muscles of this group are supplied by the musculo-
cutaneous nerve. The brachialis also usually receives a branch from the radial
nerve. The coraco-brachialis and short head of the biceps flex and adduct the
arm at the shoulder; the biceps and brachialis flex the forearm at the elbow. The
long head of the biceps abducts the arm at the shoulder.
Fig. 364. — Superficial Muscles of the Front of the Ahm.
Pectoralis minor
Coraco-brachiali;
Long head of triceps
Tendons of insertion of _ pectoralis
major and deltoid
Lateral head of triceps
Medial head of triceps
Semilunar fascia
(lacertus fibrosus)
Extensor carpi radialis iongus
Brachio-radialis
The muscles of this group are found in most of the hmbed vertebrates. In many of the
lower forms the coraco-brachialis, which appears farther down in the vertebrate series than the
biceps, has a more extensive insertion than in man. It may extend to the ulna (lizards) and
may be subdivided into various muscles which correspond with the adductors of the thigh. The
biceps, the place of which is taken in the lower vertebrates by a coraco-radial muscle, in most
of the mammals presents two heads, the more lateral of which is attached by a tendon to the
scapula above the shoulder-joint. This long tendon of the biceps lies primitively outside the
capsule of the shoulder-joint, but in some of the higher mammals has come to lie within the
capsule. In the biceps four elements mayberecogni.sed; — a coraco-radial, coraco-ulnar, gleno-
radial, and gleno-ulnar. (Krause.) The development of these elements varies in different
mammals
CORA CO-BRA CHIALIS
381
The coraco-brachialis (fig. 365). — Origin. — (1) By a short tendon from the tip of the cora-
coid process of the scapula and (2) from the tendon of the short head of the biceps.
Insertion. — (1) By means of a strong tendon into the medial surface of the humerus im-
mediately proximal to the middle of the shaft, and (2) often above this also into an aponeurotic
band which e.xtends from the tendon along the medial margin of the humerus, arches over the
tendons of the latissimus dorsi and teres major, and is attached to the lesser tubercle of the
humerus. When the attachment to the tubercle does not take place, the band becomes closely
applied to the deep surface of the muscle.
Structure. — From the tendons of origin, which are usually closely associated, the fibre-
bundles take an oblique, nearly parallel, course and are attached to the aponeurotic band above
Fig. 365. — Deep Muscle.? of the Front of the Arm.
Pectoralis minor
Short head of biceps
Coraco-brachiahs
Long head of triceps
Medial head of triceps
Medial intermuscular septi
rLong head of biceps
— r~ — -Insertion of pectoralis major
Insertion of deltoid
J- Lateral part of brachialis
Insertion of biceps
mentioned and to both surfaces of the flat tendon of insertion. This extends high into the
muscle. The belly of the muscle usually shows some separation into a superficial and a deep
portion, between which runs the musculo-cutaneous nerve. When this separation is well
marked, the tendon of origin of the superior fasciculus may be distinct from that of the inferior
fasciculus and the short head of the biceps, and the tendon of insertion may give a separate
lamina to each fasciculus.
Nerve-supply. — A branch of the musculo-cutaneous nerve, or of the brachial plexus near
the origin of this nerve, enters the upper third of the medial border of the muscle, and passes
across the constituent fibre-bundles about midway between their attachments. The nerve
fibres arise from the sixth and seventh cervical nerves.
Action. — Adducts and flexes the arm at the shoulder and helps to keep the head of the
humerus in the glenoid fossa. When the arm has been rotated lateralward, it acts as a medial
rotator.
Relations. — The coraco-brachialis is largely covered by the deltoid and pectoralis major
muscles. Below the inferior border of the latter it becomes superficial. Near its origin it lies
382 THE MUSCULATURE
between the pectoralis minor and the subscapularis muscles. More distally it lies medial to the
humerus and in front of the chief brachial vessels and nerves. The musculo-cutaneous nerve
usually runs through it.
Variations. — The humeral insertion of the muscle varies considerably. According to Wood,
the coraco-braohialis consists primitively of three parts, which arise from the coraooid process
and are inserted respectively into the upper, the middle, and the distal part of the humerus
along the medial side. The superior division is most deeply, the inferior the most superficially,
placed. In man the muscle is composed of parts of the middle and inferior divisions. The
inferior division may be completely developed as far as the medial epicondyle. The superior
division of the muscle is occasionally found. Slips from the coraco-brachialis to the brachiahs
have been seen. Complete absence of the muscle has been recorded.
The biceps brachii (figs. 364, 370). — The short head arises by a flat tendon closely asso-
ciated with that of the coraco-brachialis from the coracoid process. From the dorso-medial
surface of this tendon the fibre-bundles descend nearly vertically, though increasing in num-
ber, toward their attachment to the tendon of insertion. The fibre-bundles which arise highest
on the tendon of origin are inserted highest on the tendon of insertion, while those which have
the lowest origin have the lowest insertion.
The long head arises from the supraglenoid tuberosity and from the glenoid ligament
by a long tendon (9 cm.) bifurcated at its origin. The tendon at first passes over the head
of the^humerus within the capsule of the joint, and then passes into the intertubercular (bicipital)
groove, which is covered by the capsule of the joint and an expansion from the tendon of the
pectoralis major. To this point the tendon is surrounded by the synovial membrane of the
joint. After emerging from this the tendon slowly expands and from its dorsal concave surface
arise fibre-bundles which, increasing in number, extend, somewhat obliquely, toward the ten-
don of insertion. As in case of the short head, here also the fibre-bundles which arise highest on
the tendon of origin have the highest insertion.
Insertion. — The tendon of insertion begins usually in the distal quarter of the arm as a
vertical septum between the two heads of the muscle. More distally this broadens out on each
side into a flattened aponeurosis. The fibre-bundles are inserted into the sides of the septum
and on each surface of the aponeurosis — those of the long head chiefly on the deep surface, those
of the short head chiefly on the superficial surface. The aponeurosis is continued into a strong,
flattened tendon which descends between the brachio-radialis and pronator teres muscles to be
inserted on the dorsal half of the bicipital tuberosity of the radius. From the medial border
of the tendon an aponeurotic expansion, the lacertus fibrosus (semilunar fascia), is continued
into the fascia of the ulnar side of the forearm.
Nerve-supply. — By a branch from the musculo-cutaneous nerve for each head. These
branches may be bound in a common trunk for some distance. They enter the deep surface of
the muscle in the proximal part of the middle third of each belly often by several rami. Usually
there is a distinct intramuscular fissure for the reception of the branches to each head and the
blood-vessels which accompany them. The nerve fibres come from the fifth and sixth cervical
nerves.
Action. — It is a chief flexor of the arm at the elbow and is also a supinator of the forearm.
This last action is most marked when the forearm is flexed and pronated. Both heads are
flexors and medial rotators of the arm at the shoulder. The long head is an abductor and
so also is the short head when the arm is greatly abducted, otherwise the short head is an
adductor.
Relations. — The tendons of origin are concealed by the pectoralis major and deltoid muscles.
Beyond this the muscle is covered by the fascia brachii. In the lower part of the ai-m it lies
upon the brachialis muscle. Upon the medial margin lie the coraco-brachialis muscle, the
brachial vessels, and the median nerve.
Variations. — Variations are frequent. The whole muscle or either head may be missing,
but such cases are rare. The long head may extend only to the bicipital groove. Frequently
the muscle is partially divided into the four primitive portions mentioned above. The two
heads may be separate from origin to insertion. There may be an accessory head (1 in 10
subjects — Le Double) which arises from the coracoid process, the capsule of the joint, the tendon
of the pectoralis major, or the shaft of the humerus near the insertion of the coraco-brachialis.
In most instances the origin takes place above the origin of the brachialis from the humerus.
Sometimes several accessory heads are seen. Marked vai-iation of insertion is less frequent,
but occasionally a supernumerary slip may go to the medial intermuscular septum or the medial
epicondyle. The fusion of the biceps with neighbouring muscles (pectoralis major and minor,
coraco-brachialis, brachialis, palmaris longus, pronator teres, brachio-radialis) by means of
tendinous or muscular slips has been frequently reported.
The brachialis (fig. 365). — Origin. — (1) From the distal three-fifths of the front of the
humerus, (2) from the medial intermuscular septum, and (3) from the lateral intermuscular
septum proximal to the heads of the brachio-radialis and extensor carpi radiaUs longus. Proxi-
mally it sends up a pointed process on the lateral side of the insertion of the deltoid and another
between the insertions of the deltoid and the coraco-braohiahs. Distally the area of origin
stops a little above the capitulum and the trochlea.
Structure and Insertion. — The fibre-bundles arise directly from this area of origin, except
near the insertion of the deltoid and on the medial margin, where tendinous bands are developed.
The fibre-bundles descend, the middle vertically, the medial obliquely lateralward, the lateral
still more obliquely medialward. The tendon of insertion appears on the dorsal side of the
lateral edge of the muscle in its lower fourth. Continuous with this stronger lateral portion of
the tendon more distally a thinner band appears upon the ventral surface of the muscle above
the joint. The tendon becomes thick as it passes distally, is closely united to the capsule of the
elbow-joint, and is attached to the ulnar tuberosity. In addition to the main tendon, some of
the deeper fibre-bundles of the muscle and some of those coming from the lateral intermuscular
septum are attached by short tendinous bands to the coronoid process.
MUSCLES OF FOREARM AND HAND 383
Neri/e-supply. — From the museulo-cutaneous nerve by a branch which enters the ventral
surface of the muscle near the junction of the upper and middle thirds of the medial border.
In addition the radial (musculo-spiral) nerve usually sends a small branch into the distal lateral
portion of the muscle. A branch from the median nerve frequently supplies the medial side of
the muscle near the elbow-joint (Frohse).
Action. — To flex the forearm.
Relations. — It lies behind the biceps, on each side of which it projects. The distal lateral
portion of the muscle is grooved by the brachio-radialis, which here is closely apphed to it.
The radial (musculo-spiral) nerve runs between these two muscles. On the medial side run the
brachial vessels and median nerve.
Variations. — It may be divided into two distinct heads continuous with the projections on
each side of the deltoid tuJjerosity. A great number of supernumerary slips have been recorded.
These may be attached to the radius, ulna, fascia of the forearm, capsule of the joint, brachio-
radialis, and extensor carpi radialis muscles. It may be partially fused with neighbouring
muscles. It has also been reported absent.
BURS^
B. m. coraco-brachialis. — Between the subscapularis muscle, the tendon of the coraco-
brachialis, and the coracoid process. Frequent.
B. bicipito-radialis. — Between the ventral half of the radial tuberosity and the tendon of
the biceps. Constant.
B. cubitalis interossea. — Between the tendon of the biceps and the ulna and the neighbour-
ing muscles. Frequent.
D. MUSCULATURE OF THE FOREARM AND HAND
(Figs. 366-379)
The muscles of the forearm arise in part from the humerus, in part from the
radius and ulna. Their bellies lie chiefly in the proximal half of the forearm.
They are divisible into two groups: — a radio-dorsal, composed of extensors of the
hand and fingers and supinators of the forearm; and an ulno-volar, composed of
flexors of the hand and fingers and pronators of the forearm. The brachio-
radialis, which belongs morphologically with the former group, is physiologically
a flexor of the forearm.
The two groups are separated on the medial side of the back of the forearm
by the dorsal margin of the ulna (figs. 366, 369). Ventrally they are separated
by the insertions of the biceps and brachialis and by an intermuscular septum
(figs. 366, 370).
In the hand, in addition to the tendons of the muscles of the forearm mentioned
above (fig. 376), there are several sets of intrinsic muscles. About the meta-
carpal of the thumb (figs. 375, 376, 377) is grouped a set of muscles which arise
from the carpus and metacarpus and are inserted into the metacarpal and first
phalanx of the thumb. A similar set of muscles is grouped about the metacarpal
of the little finger (figs. 375, 376). These sets of muscles give rise respectively
to the thenar and hypothenar eminences. Between the metacarpals lies a series
of dorsal and palmar interosseous muscles (figs. 377, 378, 379) which are inserted
into the first row of phalanges and into the extensor tendons. From the tendons
of the deep flexor of the fingers a series of lumbrical muscles passes to the radial
side of the extensor tendons (figs. 373, 375). These various muscles abduct,
adduct, flex, and extend the digits. In addition to these deeper skeletal muscles
of the hand there is a subcutaneous muscle over the hypothenar eminence (fig.
375). Of the muscles of the hand, all are supplied by the ulnar nerve except
most of those of the thumb and the two more radial lumbricals, which are
supplied by the median nerve.
An arrangement of the muscles of the forearm in which the dorsal extensor-supinator mus-
culture extends proximally on the radial side of the arm to the distal extremity of the humerus,
and the volar flexor-pronator musculature similarly on the ulnar side, is characteristic of all
limbed vertebrates and is associated with the pronate position of the forehmb characteristic of
quadrupeds. In ampliibia and reptiles the musculature terminates distaUy on the carpus and
in the aponeuroses of the hand. In the higher forms special tendons are differentiated for those
muscles of the forearm which act on the fingers. On the back of the hand in many vertebrates
short extensor muscles are found running from the carpus to the phalanges. On the volar
surface a complex musculature is found in all forms which have freely movable fingers. In
animals which walk on the ends of the fingers, especially in the hoofed animals, the intrinsic
musculature of the hand is greatly reduced. The phylogenetic development of the muscles of
384 THE MUSCULATURE
the forearm and hand is too complex a subject to be briefly summarised. The phylogeny of the
forearm flexors and the palmar musculature has been studied by McMurrich. In his papers a
summary of the hterature on the subject may be found.
FASCIA
The fasciae and the general relations of the musculature of the forearm and hand may be
followed in the cross-sections fig. 366.
The tela subcutanea contains a moderate amount of fat in the upper part of the forearm.
This grows less in amount as the wrist is approached. On the back of the hand it contains
little fat. In the palm and on the volar surface of the fingers a moderate amount of fat is
embedded between dense vertical bundles of fibres which unite the skin to the fascia. Except
on the volar surface of the hand and on the backs of the terminal phalanges, the tela is but
loosely united to the underlying fascia.
The bursa subcutanea olecrani lies over the dorsal surface of the olecranon. Subcutaneous
bursiE are also frequently found over the knuckles (b. subcutanese metacarpophalangeae
dorsales) and the proximal joints of the fingers (b. subcutanese digitorum dorsales).
The antibrachial fascia encloses the muscles of the forearm in a cylindrical sheath, composed
in the main of circular fibre-bundles, but strengthened by longitudinal and obhque bundles
extending in from the epicondyles of the humerus, the olecranon, the lacertus fibrosus of the bi-
ceps, and the tendon of the triceps. The fascia of the forearm is attached to the dorsal surface
of the olecranon and to the subcutaneous margin of the ulna. Above, it is continued into the
fascia of the arm; below, into the fascia of the hand. From the antibrachial fascia in the upper
half of the foreai-m a fibrous septum extends between the radio-dorsal and the ulno-volar
muscle group to the radius. In the radial septum below the elbow a branch of communica-
tion extends between the superficial and deep veins of the arm. That part of the fascia over-
lying the radio-dorsal group of muscles is much denser than that covering the volar group,
except where the latter is strengthened by the lacertus fibrosus. In addition to the main
radial septum other septa descend between the underlying muscles from the antibrachial
fascia. These septa are best marked near the attachment of the muscles to the humerus.
Here the fascia is firmly fused to the muscles.
Dorsally the antibrachial fascia is strengthened at the wrist by transverse fibres which
extend from the radius to the styloid process of the ulna, the triquetrum (cuneiform), and
pisiform, and give rise to the dorsal ligament of the carpus (posterior annular ligament). From
this ligament septa descend to the radius and ulna and convert the grooves in these bones into
osteo-fibrous canals which lodge the tendons of the various muscles extending to the wrist and
hand.
On the back of the hand there is spread a fascia composed of two thin fascial sheets between
which the extensor tendons are contained. Between the tendons these sheets are more or less
fused. On the backs of the fingers the fascia blends with the extensor tendons and.the associated
aponeurotic expansions from the interosseous and lumbrical muscles. Between the fingers
it is continued into the transverse fasciculi of the palmar aponeurosis. At the sides of the hand
the fascia is continued into the thenar and hypothenar fasciae. Each dorsal interosseous
muscle is covered by a special fascial membrane which is separated by loose tissue from the
fascia investing the e.xtensor tendons.
Fig. 366, A-H. — Transverse Sections through the Llpt Forearm and Hand.
H. Transverse section through the first phalanx of the middle finger, diagrammatic, with the
cavity of the synovial sheath of the flexor tendons distended.
The regions through which these sections pass are indicated in the diagram, c and d in the
diagram show the regions through which pass sections C and D, fig. 362 (p. 375).
1. Aponeurosis palmaris. 2. Arteria radialis. 3. A. ulnaris. 4. Bursa bicipito-radiahs. 5
Discus articularis. 6. Ligamentum carpale dorsale. 7. L. carpi transversum. 8. L.
carpi volare. 9. Fascia antibrachii. 10. Musculus abductor pollicis brevis. 11. M.
abductor pollicis longus — a, tendon. 12. M. abductor digiti quinti. 13. M. adductor
polhcis. 14. M. anconeus. 15. M. biceps, tendon. 16. M. brachialis, tendon. 17. M.
braohio-radialis — a, tendon. 18. M. extensor carpi radiahs brevis — a, tendon. 19. M.
extensor carpi radiahs longus — a, tendon. 20. M. extensor carpi ulnaris. 21. M. ex-
tensor digitorum communis — a, tendon for second finger; b, tendon for the third finger; c,
tendon for fourth finger; d, tendon for fifth finger; e, digital aponeurosis. 22. M. extensor
digiti quinti proprius. 23. M. extensor indicis proprius. 24. M. extensor polhcis brevis
— a, tendon. 25. M. extensor poUicis longus — a, tendon. 26. M. flexor carpi radialis —
a, tendon. 27. M. flexor carpi ulnaris — a, tendon. 28. M. flexor digitorum profundus —
a, tendon for second finger; b, tendon for third finger; c, tendon for fourth finger; d, tendon
for fifth finger. 29. M. flexor digitorum sublimis — a, tendon for second finger; b, tendon
for third finger; c, tendon for fourth finger; d. tendon for fifth finger. 30. M. flexor digiti
quinti brevis. 31. M. flexor pollicis brevis. 32. M. flexor pollicis longus — a, tendon.
33. M. interossei dorsales. 34. M. intero.ssei volares. 35. M. lumbricales. 36. M. op-
ponens polhcis. 37. M. opponens digiti quinti. 38. M. palmaris brevis. 39. M. palmaris
longus — a, tendon. 40. M. pronator quadratus. 41. M. pronator teres. 42. M. supi-
nator. 43. N. cutaneus antibrachii lateralis. 44. N. medianus. 45. N. radialis — a,
deep radial nerve; b, superficial radial nerve. 46. N. ulnaris. 47. Os capitatum
(magnum). 48. Os hamatum (unciform). 49. Os lunatum (semilunar). 50. Os meta-
carpal, I. 51. Os metacarpale, II. 52. Os metacarpale. III. 53. Os metacarpale, IV.
54. Os metacarpale, V. 55. Os multangulum majus (trapezium). 56. Os naviculare.
57. Ossa sesamoidea of fifth digit. 58. Radius. 59. Ulna. 60. Vagina fibrosa (tendon-
sheath) of the long digital flexors. 61. Vagina fibrosa (tendon-sheath) of the flexor
pollicis longus. 62. Vagina fibrosa (tendon-sheath in digit). 63. Vena cephalica.
MUSCLES OF FOREARM AND HAND
385
44 2 9
d
A
-~.
4^i
42 ^1 4-5»2a JO 9
H
386
THE MUSCULATURE
D
28° 28* 28' 2t2Z ai' 3f 2\^
F
RADIO-DORSAL DIVISION 387
On the volar side of the forearm for some distance above the wrist the tendons of the
flexor carpi radialis, tlie palmaris longus, and the flexor carpi ulnaris run between two layers of
the fascia. The fascia is much strengthened at the wrist by transverse fibres which give rise
to the volar ligament of the carpus. Beneath it hes the transverse ligament of the carpus
(anterior annular hgament). This dense band is broader than the volar ligament but like it
extends from the pisiform bone and the hamulus of the hamatura (unciform) to the tuberosity
of the navicular and the tuberosity of the greater multangular (trapezium). It serves to
complete an osteo-fibrous canal through which pa.ss the flexor tendons of the fingers. Between
the two ligaments which are partially fused with one another run the ulnar artery and nerve.
On the palm of the hand the ensheathing fascia presents three distinct areas — a central,
a lateral, and a medial.
The central portion, the palmar aponeurosis, is composed chiefly of bundles of fibrous
tissue which radiate superficially toward the fingers from the tendon of the palmaris longus or
from a corresponding region of the forearm fascia when this muscle is absent. Between these
bundles are others which arise from the transverse ligament. The deep surface of the fascia is
composed of a thin incomplete layer of transverse fibres which continue the transverse fibres of
the forearm fascia. Near the capitula of the metacarpals this layer becomes much stronger
and constitutes a ligamentous band (superficial transverse ligament of Poirier). Near the bases
of the digits bundles of transverse fibres (fasciculi transversi) lie in the webs of the fingers and
constitute an incomplete transverse ligament separated by a distinct interval from the super-
ficial transverse ligament.
From the palmar aponeurosis processes are sent in toward the deeper structures. Of these,
the most important are those continued into a fibrous sheath which surrounds the space con-
taining the long flexor tendons and the lumbrical muscles. This dense fibrous sheath is united
by fibrous processes to the third, fourth, and fifth metacarpals. As the flexor tendons diverge
and the ends of the metacarpals are approached, numerous processes descend from the palmar
aponeurosis to the transverse capitular ligament. These hold the tendons in place. On the
volar surface of the fingers the fascia serves to complete osteo-fibrous canals for the long flexor
tendons. The ventral surface of the first and second phalanges of each finger is slightly grooved.
The fascia is firmly united on each side to the margin of the groove, and over the groove forms
a semicyhndrical, strong, fibrous sheath, the vaginal ligament of the finger. This sheath is
strengthened by transverse bands over the bases of the first and second phalanges (annular
ligaments) and by cruciate bands over the shafts of the phalanges (cruciate ligaments). Over
the interphalangeal joints the sheath is thin, but is strengthened by crucial bands which permit
of freedom of motion.
The thenar fascia is a thin membrane covering the short muscles of the thumb. It is con-
tinued above into the fascia of the forearm, medially is fused with the tendon of the palmaris
longus and the palmar aponeurosis, and extends as a septum to be attached to the third meta-
carpal. Laterally it is attached to the first metacarpal and is continued into the dorsal fascia
of the hand. It is fused with an aponeurosis from the tendon of the abductor poUicis longus.
Distally it is continued into the vaginal ligament of the long flexor of the thumb. Superficially
it is closely adherent to the skin.
The hypothenar fascia invests the palmar muscles of the little finger. It is continued
from the ulnar margin of the fifth metacarpal over the muscles of the little finger to the palmar
aponeurosis, and, by means of a septum, to the radial side of the fifth metacarpal. Proximally,
it is attached to the hamatum (unciforn?^ and extends into the fascia of the forearm, distally,
it extends into the vaginal ligament of the tendon of the fifth digit.
A deeply seated suprametacarpal fascial layer, or deep palmar fascia, covers the inter-
osseous muscles and is attached to the volar surface of the metacarpal bones.
In addition to the fasciae mentioned, intermuscular septa serve to separate mjre or less
completely the various intrinsic muscles of the hand.
MUSCLES
1. Radio-Dorsal Division
The muscles of this group lie in two chief layers, a superficial and a deep.
a. Superficial Layer
(Figs. 367, 370, 371),
The muscles of this laj^er, closely associated at their origins, extend from the
radial .side of the distal end of the humerus to the distal extremity of the radius,
the carpus, and the fingers. They are divisible into a radial, an intermediate,
and an ulnar set.
Radial set. — To this belong three muscles, the brachio-radialis, extensor carpi
radialis longus and brevis. The brachio-radialis (fig. 370), a forearm flexor, is a
superficial fusiform muscle which arises from the lateral epicondylar ridge of the
humerus and is inserted into the base of the styloid process of the radius. The
extensor carpi radialis longus (fig. 371) is a narrow, fusiform muscle which extends
388 THE MUSCULATURE
along the radial margin of the forearm, partly under cover of the brachio-radialis.
It arises from the lateral epicondylar ridge of the humerus, and is inserted into
the second metacarpal bone. The extensor carpi radialis brevis (fig. 367) is a
band-like muscle more dorsally placed than the last at the radial side of the arm.
It arises from the lateral epicondyle and is inserted into the bases of the second
and third metacarpals. These muscles are supplied by branches of the radial
nerve which arise proximal to the passage of the deep radial (posterior inter-
osseous) through the supinator muscle. Distally this set of muscles is separated
from the intermediate set by the long abductor and the extensors of the thumb,
which pass from an origin under the latter set over the tendons of the radial
extensors to the thumb.
The intermediate set. — This consists of the thick, flattened extensor digitorum
communis and the slender extensor digiti quinti proprius (fig. 367). They arise
from the lateral epicondyle, and are inserted into the backs of the fingers.
The ulnar set consists of one muscle, the fusiform extensor carpi ulnaris,
which arises from the lateral epicondyle of the humerus and is inserted into the
back of the base of the fifth metacarpal.
The intermediate and ulnar sets of muscles are supplied by branches from the
ramus profundus of the radial nerve after this has passed through the supinator
muscle.
In the leg the lateral set of the superficial layer is represented by the tibialis anterior. The
intermediate set is represented by the long extensors of the toes. The single muscle which
constitutes the medial set is represented by the peroneal muscles.
The brachio-radialis (supinator radii longus) (figs. 367, 370). — Origin. — From the upper
two-thirds of the lateral epicondylar ridge of the humerus and from the front of the lateral
intermuscular septum.
Insertion. — Into the lateral side of the base of the styloid process of the radius.
Structure. — The constituent fibre-bundles arise directly from the septum and by short
tendinous bands from the epicondylar ridge, extend downward and ventrally, and terminate
in a penniform manner on a tendon which extends high on the deep surface of the muscle.
This tendon becomes free about the middle of the forearm as a broad, flat band. This be-
comes narrow as the tendon winds about the radius from the volar to the lateral surface.
Before its insertion it expands laterally and is connected with neighbouring ligaments. The free
surface of the muscle faces laterally at its origin, but, owing to the torsion, ventrally in the
forearm. The tendon, however, is turned again so that at the insertion it faces laterally once
more.
Nerve-supply. — From a branch of the radial nerve (musculo-spiral) which enters the
proximal third of the muscle on its deep surface. The nerve fibres arise from the fifth and sixth
cervical nerves.
Action. — To flex the forearm. This action is strongest when the forearm is pronated.
It acts as a supinator only when the arm is extended and pronated. It then serves to put the
arm in a state of semi-pronation. When the forearm is flexed, it acts as a pronator.
Relations. — The muscle is superficially placed on the ventro-lateral surface of the forearm.
Its tendon of insertion, however, is covered by the long abductor and the short extensor of the
thumb. Near its origin (fig. 367) it lies lateral to the brachialis. In the intervening tissue run
the radial nerve and the terminal branch of the profunda brachii artery. Dorsally and laterally
lieslthe medial head of the triceps. More distally the muscle overlies the extensor carpi radialis
longus. It crosses the supinator, pronator teres, and flexor pollicis longus muscles. Beneath
its medial edge lie the radial vessels and nerve.
Variations. — The humeral origin may extend half-way up the shaft. The radial insertion
may be as high as the middle of the shaft or descend to the lesser multangular, navicular, or
third metacarpal. In about 7 per cent, of bodies (Le Double) the tendon of insertion divides
into two or three slips which are inserted on the styloid process of the radius. Occasionally
the radial nerve passes between these slips. An accessory slip may pass to the fascia of the
forearm. The muscle may be doubled throughout its length and it may be missing. It may be
connected by accessory slips with neighbouring muscles, the deltoid, brachialis, long abductor of
the thumb, or long radial carpal extensor. The slip most frequently found goes to the brachiahs.
The extensor carpi radialis longus (figs. 367, 368, 371.) — Origin. — From the lower third
of the lateral epicondylar ridge, the lateral intermuscular septum, and from the front of the
tendons of the extensor carpi radialis brevis and the extensor communis digitorum which arise
from the lateral epicondyle.
Structure and insertion. — The fibre-bundles are inserted in a penniform manner on both
surfaces of a tendon which first appears on the lateral border of the deep surface of the muscle,
becomes free above the middle of the forearm, and descends, closely applied to the tendon of
the short radial carpal extensor, to the second compartment beneath the dorsal carpal ligament,
through which it passes to its insertion into the base of the second metacarpal near the radial
border. The outer surface of the muscle faces at first laterally, then ventrally.
Nerve-supply. — By one or two branches which arise from the radial (musculo-spiral) nerve
as it passes between the brachialis and brachio-radialis. The nerve enters the deep surface
of the muscle in the proximal third. The nerve fibres arise from the (fifth), sixth and seventh
cervical nerves.
Action. — To extend and abduct the hand. It steadies the wrist when the flexors act on
EXTENSOR CARPI RADIALIS BREVIS
389
the fingers. It is a flexor of the forearm; a supinator when the forearm is extended, a pronator
when it is flexed.
Relations. — It is covered by the brachio-radialis near the elbow. Below it becomes super-
ficial except where crossed by the tendons of the muscles of the thumb. (For the relations to
the short radial carpal extensor see below.)
Fig. 367. — Muscles of the Radial Side and the Back of tee Foeearm.
Brachlalis
Brachio-radialis
Extensor carpi radialis longus
Extensor digitorum communis
Extensor carpi radialis brevis
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Flexor carpi ulnaris
Extensor carpi ulnaris
Extensor digiti quinti propnus
Variaiions. — The humeral attachment may be more extensive than that indicated above.
The tendon of insertion may send a band to the third or to the fourth metacai'pal or to the mul-
tangulum majus (trapezium). The muscle may be fused, partly or completely, with the short
radial extensor. It may send a slip to the abductor pollicis longus or to some of the interossei.
The extensor carpi radialis brevis (figs. 367, 368). — Origin. — From a band which descends
on its deep surface from the common extensor tendon attached to the lateral epicondyle, from
the intermuscular septa surrounding its head, and from the radial collateral ligament of the
elbow-joint.
390
THE MUSCULATURE
Structure and insertion. — The fibre-bundles converge obliquely toward a tendon which
appears high up on the dorso-lateral surface of the muscle. Toward the lower third of the
forearm this tendon becomes a free, strong band closely apphed to the under surface of the
tendon of the long radial extensor, and with this passes through the second compartinent be-
neath the dorsal ligament of the carpus, diverging as it does so toward its insertion into the
back of the bases of the second and third metacarpal bones.
Fig. 368 — Tendons upon the Dobsum of the Hand.
Abductor poUicis longus
Extensor polUcis brevii
Dorsal carpal ligament
Extensor carpi ulnans
^^^ Extensor digitorum communis
Extensor digiti quinti
Extensor indicts proprius
Attachment of extensor
digitorum
to third phalanx
Nerve-supply. — A branch is supplied to the muscle from the deep radial (posterior interos-
seous) nerve before this enters the supinator (brevis). The branch enters the middle third of
the medial margin of the muscle by several rami. The nerve fibres arise from the (fifth),
sixth and seventh cervical nerves.
Action. — To extend the hand and, to a slight extent, to flex the forearm.
Relations. — In its proximal portion the muscle is placed with a medial surface toward
the common extensor, a deep toward the supinator (brevis) and pronator teres, and a dorso-
lateral toward the long radial extensor. More distally the muscle and its tendon become
flattened about the radius and partly covered by the long radial extensor and its tendon.
EXTENSOR CARPI ULNARIS 391
In the distal quarter of the forearm the tendons of these two muscles are crossed by the long
abductor and the short extensor of the thumb. Beneath the dorsal carpal ligament the tendon
of the short radial extensor is crossed by the tendon of the long extensor of the thumb.
Variations. — The tendon often sends no slip to the second metacarpal. Fusion of the two
radial extensors is frequent. The fused muscle may have from one to four tendons. The
extensor carpi radialis intermedius of Wood is a muscle which arises, rarely directly from the
humerus, but not infrequently as a slip from one or both radial extensors. It is inserted into
the second or third metacarpal bone or into both. The extensor carpi radialis accessorius is a
muscle which has an origin like the extensor intermedius, but which terminates on the base of
the metacarpal or first phalanx of the thumb, the short abductor of the thumb, or some neigh-
bouring structure.
The extensor digitorum communis (figs. 367, 368). — Origin. — From a tendon attached to
the lateral epicondyle, and from intermuscular septa which lie between the head of the muscle
and the short radial extensor, the extensor of the Uttle finger, and the supinator muscle.
Insertion. — By four tendons into the bases of the phalanges of the fingers.
Structure. — The fibre-bundles arise from the interior of the pyramidal case formed by the
tendon, the fascia, and intermuscular septa, and pass distally to converge on four tendons which
begin in the middle of the forearm, become free a little above the wrist, pass under the dorsal
carpal ligament in a groove common to them and the tendon of the extensor indicis proprius, and
diverge to the backs of the fingers. Opposite the metacarpo-phalangeal joint each tendon gives
rise on its under surface to a band which becomes attached to the base of the first phalanx of its
respective digit. The tendon is also closely bound to the joint by fibrous bands connected
with the palmar fascia. On the dorsum of the first phalanx the tendon expands and is bound
to an aponeurotic extension from the interosseous and lumbrical muscles. The tendon divides
into three bands. The middle band passes to the base of the second phalanx, the lateral bands
pass laterally around the joint to be inserted into the back of the base of the third phalanx.
The lateral bands are bound to the second joint by a thin layer of transverse and oblique fibres.
An obliquely transverse band usually passes from the tendon of the index to that of the
middle finger above the heads of the metacarpals. The tendon to the index finger is united to
the tendon of the extensor indicis proprius opposite the metacarpo-phalangeal articulation.
The tendon to the ring finger usually sends a slip to join the tendon of the middle finger. The
fourth tendon lies near that of the ring finger and divides into two shps, one of which joins the
tendon of the ring finger and one goes to the little finger to join the tendon of the extensor digiti
quinti proprius.
Nerve-supply. — From a branch which arises from the deep radial (posterior interosseous)
nerve as it emerges from the supinator (brevis) muscle. From this several twigs enter the deep
surface of the middle third of the belly. Often the nerve is bound up with the nerve to the
extensor of the little finger and the ulnar extensor. On the other hand, there may be several
separate branches to the muscle. The nerve fibres arise from the sixth, seventh, and eighth
cervical nerves.
Action. — The muscle extends the two terminal phalanges on the basal, the basal on the
metacarpus, and the hand at the wrist. The extensor action is strongest on the first phalanx.
The cross-bands between the tendons hinder ^Jie independent extension of the middle and ring
fingers, while the special extensors of the index and little fingers makes the movements of these
fingers freer. When the hand is abducted toward the radial side, the extensor muscles tend to
draw the fingers ulnarward. When the hand is abducted toward the ulnar side, the muscles
tend to draw the fingers toward the thumb. When the hand is in the mid-position the ring
finger and little finger are abducted and the index-finger is adducted. (Frohse.)
Relations. — It is superficially placed. Under it lie the deep muscles of the back of the
forearm, the interosseous vessels, and the deep radial (posterior interosseous) nerve. It lies
between the short radial carpal extensor and the extensor of the little finger.
Variations. — There is considerable variation in the extent of isolation of the parts going
to the various fingers. That to the index-finger is the one most frequently isolated. At times
the tendon to the index or httle finger may be wanting. More frequently one or more of the
tendons subdivides to be attached to two or more fingers or to the thumb. The connections
between the tendons on the back of the hand vary greatly.
The extensor digiti quinti proprius (extensor minimi digiti) (figs. 367, 368). — Origin. —
Chiefly from the septum between it and the common extensor, but also in part from the septum
between it and the extensor ulnaris and from the overlying fascia.
Structure and insertion. — The fibre-bundles descend in a narrow band which begins near
the neck of the radius. They are inserted into the side of a tendon which begins high on the
ulnar margin of the muscle. The most distal fibre-bundles extend nearly to the wrist-joint.
The tendon passes through the fifth compartment beneath the dorsal carpal ligament, and
extends on the back of the fifth metacarpal to the base of the first phalanx of the little finger,
where it is joined by a shp from the fourth tendon of the common extensor. The insertion of
the tendon is Uke that of the tendons of the common extensor.
Nerve-supply. — By a branch or branches from the deep radial (posterior interosseous), nerve.
The nerve filaments enter the middle third of the fleshy portion of the muscle on its deep
surface. The innervation of this muscle is intimately related to that of the preceding.
Action. — It acts as a portion of the common extensor, but, owing to its separation, in-
dependent movement of the Little finger is possible.
Relations. — It Ues between the common extensor and the ulnar extensor and upon the deep
muscles of the back of the forearm.
Variations. — Absence is not very frequent; blending with the common extensor is frequent.
Its tendon often divides into two or more slips. The belly may also be doubled. It may have
a supplementary origin from the ulna. A tendon shp to the ring-finger is frequently found.
The extensor carpi ulnaris (figs. 367, 368). — Origin. — By two heads: one from the inferior
dorsal portion of the epicondyle by an aponeurotic band attached below the tendon of the
392 THE MUSCULATURE
common extensor, from the enveloping fascia, and from the septa between it and the extensor
digitiquinti, anconeus, and supinator (brevis); the other from the proximal three-fourths of
the dorsal border of the ulna.
Structure and insertion. — The fibre-bundles descend in an osteo-fascial compartment
bounded by the dorsal surface of the ulna, the fascia of the forearm, the dense fascia overlying
the ulnar origin of the muscles of the thumb, and the origin of the extensor indicis. The tendon
commences high in the muscle and appears on the radial border of the middle third of the back
of its belly. The fibre-bundles are inserted in a penniform manner on the ulnar border and
deep surface of the tendon as far as the wrist. Here the tendon enters the sixth osteo-fibrous
canal beneath the dorsal carpal Ugament in a special groove on the outer side of the styloid
process of the ulna. It is inserted into the base of the fifth metacarpal.
Nerve-supply. — By a branch which arises from the deep radial (posterior interosseous) nerve
as this emerges from the supinator (brevis) muscle. Several filaments enter the deep surface
of the muscle in the middle third. The nerve fibres arise from the sixth, seventh and eighth
cervical nerves.
Action. — To extend and abduct the hand ulnarward.
Relations. — It occupies a superficial position on the ulnar side of the extensors of the fore-
arm. Beneath it he the deep muscles of the back of the forearm and the posterior surface of
the ulna.
Variations. — It may receive a slip from the triceps or be fused with the anconeus or with
the extensor of the little finger. More frequently it is doubled, partially or completely. An
accessory tendon may go to the first phalanx of the little finger, to the head of the fifth meta-
carpal, to the fourth metacarpal, to the extensor tendon of the little finger, or to the fascia over
the opponens digiti quinti. The muscle may be reduced to a fibrous band. The ulnaris digiti
quinti is a rare muscle arising from the dorsal surface of the ulna and inserted into the base of
the first phalanx of the httle finger. It may be represented by a fasciculus or an extra tendon
from the ulnar extensor.
b. Deep Layer
(Fig. 369)
The muscles of this group extend from the ulna to the radius, thumb, and index-
finger. They are the supinator, abductor pollicis longus, extensor pollicis longus
and brevis, and extensor indicis proprius. The supinator is a rhomboid muscle
which arises from the lateral epicondyle of the humerus and the supinator crest of
the ulna winds laterally around the radius and is inserted into its volar surface.
The abductor pollicis longus is a fusiform muscle which arises from the middle
third of the ulna, the interosseous membrane, and the radius, and is inserted
into the base of the first metacarpal. The extensor pollicis brevis arises from the
radius distal to the preceding muscle, and is inserted into the base of the first
phalanx of the thumb. The extensor pollicis longus is a narrow muscle which
arises from the middle third of the dorsal surface of the ulna and is inserted into
the base of the second phalanx of the thumb. The extensor indicis proprius is a
narrow, fusiform muscle arising from the shaft of the ulna and inserted into the
dorsal aponeurosis of the index-finger. These muscles are supplied from branches
of the deep radial (posterior interosseous) nerve while this is passing through or
after its exit from the supinator.
The extensor pollicis longus is represented by the extensor hallucis longus of the leg. The
abductor pollicis longus and extensor pol'icis brevis are represented by the abnormal abductor
hallucis longus and extensor primi internodii hallucis muscles, the rudiments of which are
perhaps normally present in the tibialis anterior. The supinator and the extensor indicis
muscles are not represented in the leg. On the other hand, the extensor digitorum brevis,
norma! in the foot, is only occasionally found on the back of the hand.
The supinator (brevis) (figs. 366, 369, 372). — Origin. — From (1) the inferior dorsal portion
of the lateral epicondyle by a tendinous band which is adherent to the deep surface of the
tendons of origin of the radial and common extensors and to the radial collateral ligament of
the joint; and (2) the ulna by a superficial aponeurosis and by fibre-bundles attached directly
to the depression below the radial notch and to the supinator crest.
Insertion. — The lateral and volar surfaces of the radius from the tuberosity to the attach-
ment of the pronator teres.
Structure. — From their origin the fibre-bundles descend spirally in a muscular sheet which
enwraps the radius (fig. 366). The attachment extends to the oblique Une. The muscle is
divided into a superficial and a deep plane by a septum in which the deep radial (posterior
interosseous) nerve runs. The radial attachments of these two portions are separated by an
osseous area into which no fibre-bundles are inserted. The fibre-bundles of the superficial layer
have a much more vertical course and are longer than those of the deep layer.
Nerve-supply. — By branches which arise from the deep radial (posterior interosseous)
nerve before it passes between the two layers of the supinator muscle. The nerve fibres arise
from the fifth, sixth, and seventh cervical nerves.
Action. — To supinate the forearm.
Relations. — The supinator is covered by the superficial group of extensor muscles above
described and by the anconeus.
ABDUCTOR POLLICIS LONGUS
393
' Variations. — The extent of separation of the muscles into two portions varies. Accessory
fasciculi of origin are not uncommon. These may spring from the annular ligament, tensor liga-
menti annularis anterior (5 per cent, or more of bodies — Le Double), the lateral epicondyle,
the tendon of the bi ceps, the tuberosity of the radius, etc. A sesamoid bone may lie in the
tendon of origin. The tensor ligamenti annularis posterior is a sUp generally present and
often independent of the supinator. It runs from the ulna behind the radial notch to the annular
ligament of the radio-ulnar joint.
The abductor polUcis longus (extensor ossis metacarpi poUicis) (fig. 369). — Origin. — From
(1) the lateral margin of the dorsal surface of the ulna in the proximal portion of the middle third.
Fig. 369. — The Deep Muscles of the Back of the Forearm.
Abductor pollicis longus
Extensor poUicis brevis
Extensor poUicis longus
Radial extensors
Flexor carpi ulnaris
Flexor digitorum profundus
Extensor indicis proprius
Extensor carpi ulnaris
and the adjacent interosseous membrane, (2) the dorsal surface of the radius distal and medial
to the attachment of the supinator, and (3) at times, from the septa lying between it and the
supinator, extensor carpi ulnaris, and extensor polUcis longus.
Structure and insertion. — The fibre-bundles from this extensive area of origin converge in
a bipenniform manner upon a tendon which appears as an aponeurosis on the deep surface of
the muscle about the middle of the forearm. The tendon as it descends becomes rounded.
The insertion of fibre-bundles continues nearly to the wrist. Here, together with the tendon
of the short extensor, it enters the first osteo-fibrous canal beneath the dorsal carpal ligament
upon the lateral surface of the distal extremity of the radius. Upon leaving this canal the
tendon extends to be inserted on the radial side of the base of the first metacarpal bone.
Nerve-supply. — By one or more branches from the deep radial (posterior interosseous) nerve
394 THE MUSCULATURE
after it has emerged from the supinator. The branches enter the muscle on the superficial
surface in the proximal third. The nerve fibres come from the sixth, seventh (and eighth)
cervical nerves.
Action. — It carries the first metacarpal radialward and forward. At the height of its
contraction it flexes and abducts the hand at the wrist.
Relations. — Near its origin the muscle is covered by the superficial extensors of the forearm.
More distally, accompanied by the short extensor, it passes radially, becomes superficial, and
crosses the tendons of the two radial carpal extensors.
Variations. — The muscle or its tendon may be doubled. An accessory tendon may be
applied to the multangulum majus (trapezium), the transverse ligament of the carpus, the
superficial muscles of the thenar eminence, or the first metacarpal. Of these, the attachment
to the short abductor and short flexor is the most frequent (7 out of 36 bodies — Wood). There
may be three or more tendons. The muscle may be fused with the short extensor.
The extensor poUicis brevis (fig. 369). — Origin. — From the distal part of the middle
third of the medial portion of the dorsal surface of the radius and from the neighbouring portion
of the interosseous membrane. Rarely its origin extends to the ulna.
Structure and insertion. — The fibre-bundles converge on a tendon which appears on the
radial border. The fibres are inserted as far as the dorsal carpal (posterior annular) ligament.
The tendon hes parallel to the ulnar side of that of the abductor poUicis longus, and, in close
connection with it, passes through the first compartment beneath the dorsal carpal ligament,
and crosses the metacarpo-phalangeal joint on the radial side of the long extensor tendon. It
is inserted on the base of the first phalanx of the thumb or into the capsule of the metacarpo-
phalangeal joint.
Nerve-supply. — From a branch derived from the deep radial (posterior interosseous) nerve.
This branch is usually given off in common with or near the nerve to the abductor pollicis
longus, and many traverse that muscle to reach the extensor pollicis brevis, which it enters in
the proximal third of its radial border. The nerve fibres come from the sixth, seventh (and
eighth) cervical nerves.
Action. — To extend the thumb at the metacarpo-phalangeal joint and to abduct the first
metacarpal. It likewise acts as a weak supinator of the forearm.
Relations. — It hes between the abductor pollicis longus and the extensor pollicis longus,
by which its origin is partly overlapped. In company with the former muscle it passes medially
from beneath the common extensor of the fingers and over the tendons of the radial carpal
extensors to reach its osteo-fibrous canal under the dorsal carpal hgament.
Variations. — The head of the mu3cle may be fused with the long abductor. Its tendon
of insertion may give rise to a sUp inserted on the first metacarpal (in 2 out of 85 bodies — Le
Double) or into the terminal phalanx. Its tendon is often united with that of the long extensor.
It may be fused with the long abductor of the thumb and has been found missing. It may be
doubled.
The extensor pollicis longus (fig. 369). — Origin. — From the middle third of the lateral
part of the dorsal surface of the ulna; from the neighbouring part of the interosseous membrane;
and from the septa between it and the extensor indicis proprius, and the extensor carpi ulnaris.
Structure and insertion. — The fibre-bundles converge in a bipenniform manner on the two
sides of a tendon which appears high on the dorsal surface of the muscle. They extend as far
as the dorsal carpal (posterior annular) hgament. The fusiform body of the muscle descends
somewhat obliquely on the dorsal surface of the forearm. The tendon enters the third osteo-
fibrous canal beneath the dorsal carpal (posterior annular) Hgament. On emerging from the
canal it passes very obliquely across the dorsal surface of the carpus, over the tendons of
the radial extensors, to the ulnar side of the first metacarpal. It passes along this and on the
dorsal surface of the first phalanx, expands to be inserted into the base of the second phalanx.
The aponeurosis of insertion receives tendinous slips from the short muscles of the volar surface
of the thumb.
Nerve-supply. — By a twig from the deep radial (posterior interosseous) nerve. The branch
gives rise to twigs which enter the proximal third of the radial border of the muscle. The
fibres arise from the sixth, seventh, and eighth cervical nerves.
Action. — To extend the second phalanx on the first, and this on the metacarpal. It also
draws the whole thumb when extended toward the second metacarpal. It may have a sUght
supinator action on the forearm.
Relations. — The head of the muscle is partly overlapped by the long abductor of the thumb.
It lies between this and the extensor pollicis brevis on one side, and the extensor indicis proprius
on the other. Over it lie the extensors of the fingers and the ulnar carpal extensor.
Variations. — The tendon may give a slip to the base of the first phalanx of the thumb,
to the dorsal carpal hgament, or to the index finger. It may receive an accessory slip from the
common extensor of the fingers or the short extensor of the thumb. It is frequently! doubled.
An additional extensor is found in about 6 per cent, of bodies between the extensor! of the index
finger and that of the thumb. It has a double tendon and insertion into both digits (extensor
communis pollicis et indicis).
The extensor indicis proprius (fig. 369). — Origin. — From the proximal part of the distal
third of the posterior surface of the ulna, medial and distal to that of the preceding muscle, from
the adjacent interosseous membrane, and from the septum between it and the extensor pollicis
longus.
Structure and insertion. — The fibre-bundles are inserted on a tendon which first appears on
the radial border of the muscle. The insertion of fibre-bundles extends nearly to the dorsal
carpal (posterior annular) ligament. Here the tendon passes beneath that of the extensor
of the little finger and enters the fourth osteo-fibrous canal beneath the lateral tendons of the
common extensor. It passes across the wrist beneath the tendon from the extensor communis
to the index finger, and is inserted on the ulnar side of this into the dorsal aponeurosis of the
index finger opposite the base of the first phalanx.
ULNO-VOLAR DIVISION 395
Nerve-supply. — By a twig from the deep radial (posterior interosseous) nerve. This twig
enters the proximal third of the radial border of the muscle. It frequently arises from a branch
to the extensor pollicis longus. The nerve fibres come from the sixth, seventh, eighth cervical
nerves.
Ac! ion. — To extend the first phalanx on the metacarpal. Like the common extensor
it has a limited action on the two terminal phalanges. It also adducts the index finger and is a
weak supinator of the forearm.
Relations. — It is covered by the superficial extensor group.
Variations. — These are frequent. It may be absent. There may be two heads, or the
muscle may be completely doubled. It may receive an accessory slip from the ulna or the
carpus. The tendon may give accessory slips to the middle finger, the ring finger, or the thumb.
The accessory tendon to the middle finger is the most frequent. The tendon to the index
finger may be inserted on the metacarpus.
Abnormal Muscles of the Back of the Wrist and Hand
The extensor medil digiti is a small muscle which arises from the ulna beneath the extensor
of the index finger, with which it is more or less fused. It sends a tendon to the extensor
aponeurosis of the middle finger or slips both to this finger and the index finger. It is present
in about 10 per cent, of bodies (Le Double).
The extensor digiti annularis is a muscle similar to the extensor medii digiti, but much
rarer .
The extensor digitorum brevis, which resembles the muscle of corresponding name on the
dorsum of the foot, may have from one to four fascicuU, but most frequently one. The most
common fasciculus is one which sends a tendon to the extensor tendon of the index finger. One
for the middle finger is nearly as frequent. Others are rare. A fasciculus for the thumb has not
been reported. (Le Double.) The fasciculi usually arise from the bones of the ulnar half of
the carpus — lunatum (semilunar), triquetrum (cuneiform), hamatum (unciform), and capitatum
(magnum), and from the dorsal ligaments uniting these bones. The tendons are inserted either
into the corresponding extensor tendons or into the metacarpals. The muscle is found in about
10 per cent, of bodies (Wood).
BurSjB
B. m. extensoris carpi radialis brevis. — Between the tendon and the base of the third
metacarpal.
B. m. abductoiis pollicis longi. — Between the tendons of the long and short radial extensors
and the tendons of the abductor pollicis longus and extensor pollicis brevis. Another bursa
lies beneath the tendon of insertion of the abductor.
B. intermetacarpo-phalangeae. — Between the laXeral surfaces of the heads of the meta-
carpal bones of neighbouring fingers dorsal to the transverse capitular ligament.
B. tendinum m. extensoris digitorum communis. — Small bursae are sometimes found beneath
the tendons to the index and little fingers near where they begin to diverge from the common
tendon.
B. m. extensoris carpi ulnaris. — A small bursa may be found under the tendon of origin
of this muscle.
B. m. supinatoris. — Between the supinator and the tendon of the extensor muscles.
B. m. extensoris pollicis longi. — Between the tendon and the first metacarpal.
Synovial Tendon-sheaths
Vagina tendinum mm. extensorum carpi radialium. — Synovial sheaths cover the tendons
of the two radial carpal extensors as they pass beneath the dorsal carpal (posterior annular)
ligament. In the adult these sheaths usually are more or less fused and communicate with the
sheath of the extensor pollicis longus where this crosses them.
Vagina tendinum mm. extensoiis digitorum communis et extensoris indicis. — A synovial
sheath surrounds the tendons of these muscles as they pass beneath the dorsal carpal (posterior
annular) ligament. This sheath extends for some distance on the tendons as they diverge.
Vagina tendinis m. extensoris digiti quinti. — A synovial sheath extends on the tendon of
this muscle from above the dorsal carpal (posterior annular) ligament to the base of the meta-
carpal.
Vagina tendinis m. extensoris carpi ulnaris. — This sheath commences above the carpal
(posterior annular) ligament and extends to the insertion of the tendon.
Vagina tendinum mm. abductoris pollicis longi et extensoris pollicis brevis. — The sheaths
which surround these two tendons beneath the dorsal carpal (posterior annular) Ugament
usually communicate freely.
Vagina tendinis m. extensoiis pollicis longi. — A long synovial sheath surrounds this
tendon. Where it crosses the tendons of the radial extensors, a communication is found with the
sheath of the latter.
2. Ulno-Volar Division
The muscles on the volar side of the forearm lie in four layers.
a. First Layer
(Fig. 370)
Of the four muscles of associated ulnar epicondylar origin which constitute
this layer the pronator teres is a strong, band-like muscle which is inserted into
396
THE MUSCULATURE
the lateral surface of the middle third of the shaft of the radius; the fusiform
flexor carpi radialis sends a tendon to the base of the second metacarpal; the
slender palmaris longus is inserted into the palmar fascia; and the medially
situated, fusiform flexor carpi ulnaris into the pisiform bone and the palmar
fascia. The pronator teres is the most powerful pronator of the forearm. When
Fig. 370. — Front of the Forearm First Laier of Muscles.
Pronator teres
Flexor carpi radialis —
Palmaris longus
Flexor carpi ulnaris
Flexor digitorum sublimis
Brachio-radialis
Flexor poUicis longus
the hand is slightly flexed the ulnar carpal flexor abducts ulnarward. When the
hand is greatly flexed lateral movement is difficult. The ulnar flexor is supplied
by the ulnar nerve, the other muscles by the median.
The pronator teres probably corresponds with the pophteus of the leg. The flexor carpi
radialis and flexor carpi ulnaris probably represent in the main the two heads of the gastroc-
nemius, and the palmaris longus, the plantaris.
The pronator teres (fig. 370}. — Origin. — By two heads: — (1) The humeral or chief head
arises by a tendon from the superior half of the ventral surface of the medial epioondyle and
directly from the overlying fascia and from the intermuscular septa between it and the medial
PRONATOR TERES
397
head of the triceps and the flexor carpi radialis. (2) The ulnar, deep or accessory, head arises
by an aponeurotic band attached to the inner border of the coronoid process medial to the
tendon of the brachialis. Between the humeral and ulnar heads is a fibrous arch beneath
which the median nerve passes.
Structure and insertion. — The fibre-bundles of the humeral head are inserted in a penniform
manner on a tendon which begins near the middle of the belly of the muscle on the superficial
Fig. 371. — Front of the Forearm: Second Layer op Muscles.
Muscles of first layer
Brachialis
Flexor digitorum subli:
Flexor carpi ulnans
Flexor carpi radialis
Palmaris longus
Brachio-radialis
Extensor carpi radialis longus
Supinator
Brachio-radialis
Flexor pollicis longus
Abductor pollicis longus
Extensor pollicis brevis
surface along the radial border. The tendon gradually becomes broader, winds about the volar
surface of the radius, and is inserted into the middle third of its lateral surface. The attach-
ment of fibre-bundles continues nearly to this insertion. The fibre-bundles of the ulnar head
form a slender fasciculus which is inserted into the radial side of the deep surface of the humeral
head.
Nerve-supply. — By a branch derived from the median nerve before it passes between the two
heads of the muscle. The nerve enters the proximal part of the middle third of the main belly
of the muscle on its deep surface near the radial border. The branch to the ulnar head usually
enters this portion of the muscle somewhat proximal to its fusion with the humeral head.
The nerve fibres arise from the sixth and seventh cervical nerves.
Action. — To pronate and flex the forearm.
398 THE MUSCULATURE
Relations. — The muscle is superficially placed. Near its origin it is covered by the lacertus
fibrosus of the biceps, and near its insertion by the radial vessels and nerve and the brachio-
radialis and radial extensor muscles. It is the most radial of the group of muscles under con-
sideration. The radial border helps to bound an angular space, the cubital fossa, in which lie
the brachial vessels, median nerve, and the tendon of the biceps. The median nerve passes
between its humeral and ulnar heads. The muscle overlies the supinator, the brachialis, and
the radial origin of the flexor digitorum sublimis muscles and the ulnar artery.
Variations. — Supplementary fasciculi may arise from the humerus, the medial intermuscular
septum of the arm, the flexor carpi radialis, the flexor sublimis, or the brachiahs muscles. The
two portions of the muscle may be distinct from origin to insertion. Either part of the muscle
may be doubled. The ulnar head may be absent. The radial insertion may be extensive.
Fasciculi may extend to the long flexor of the thumb. There may be a sesamoid bone in the
tendon of origin from the humerus.
The flexor carpi radialis (fig. 370). — Origin. — From (1) the common tendon attached
to the medial epicondyle; and (2) the septa between its head and the pronator teres, the flexor
sublimis, and the palmaris longus.
Structure and insertion. — The fibre-bundles descend to converge upon a tendon at first intra-
muscular, but which in the middle of the arm appears on the vblar surface of the muscle and soon
becomes free from the attachment of fibre-bundles. The fibre-bundles from the epicondyle
descend nearly vertically to the front and sides of the tendon, while those from the intermus-
cular septa take an oblique course to the deep surface of the tendon. The tendon is at first
flat, but soon becomes cylindrical, bound to the superficial muscle fascia, and enters the hand
through a special osteo-fibrous canal formed mainly by the groove in the os multangulum
majus (trapezium) and the transverse carpal (anterior annular) ligament. It is inserted into
the base of the second metacarpal. It usually also sends a tendon slip to the third.
Nerve-supply. — By a branch from the median nerve which divides into several twigs that
enter the muscle near the junction of its proximal and middle thirds on the deep surface. The
nerve usually arises near the elbow. The nerve fibres arise from the sixth, seventh (and eighth)
cervical nerves.
Action. — To flex the hand at the wrist. To a slight extent it may also act as a pronator
of the forearm and a flexor of the forearm on the arm.
Relations. — It is superficial except near its insertion. The belly of the muscle lies between
the pronator teres and the palmaris longus and upon the flexor digitorum sublimis. The tendon
of the muscle passes over the flexor poUicis longus, and near the wrist is a guide to the radial
artery, which here lies lateral to it. In the hand the tendon lies beneath the thenar muscles
and is crossed by the tendon of the long flexor of the thumb.
Variations. — It may receive a fasciculus from the brachiahs or biceps muscles or from the
radius or ulna. It may send tendon slips to the multangulum majus (trapezium), navicular,
the transverse carpal (anterior annular) hgament, or the fourth metacarpal. The insertion
may take place variously into these structures.
The palmaris longus (fig. 370). — Origin. — From the common tendon attached to the
medial epicondyle and from the surrounding intermuscular septa.
Structure and insertion. — The fibre-bundles take a nearly parallel course to a tendon which
appears high in the middle third of the forearm on the volar surface of the muscle. In the
middle of the forearm the attachment of fibre-bundles usually ceases, the tendon becomes
bound to the overlying fascia, and descends paraUel with that of the radial flexor. Near the
proximal border of the transverse carpal (anterior annular) ligament the tendon expands into
radiating bundles of fibres of which the medial and lateral are attached to the fascia over the
intrinsic muscles of the thumb and little finger, while the middle, much more developed, con-
stitute the chief portion of the palmar aponeurosis.
Nerve-supply. — From a branch which usually arises in company with the nerve to the
proximal part of the flexor sublimis. It frequently traverses the superficial fibres of the flexor
sublimis. The nerve enters the middle third of the muscle.
Action. — To flex the hand. It is also a weak flexor and pronator of the forearm.
Relations. — It is placed between the radial and ulnar flexors over the flexor sublimis.
In the distal part of the forearm the tendon lies over the median nerve.
Variations. — It is absent in 11.2 per cent, of instances (Le Double). It may be highly
developed or reduced to a tendinous band. The belly of the muscle may lie in the distal instead
of in the proximal part of the forearm. It may be digastric. It may be fused with neighbouring
muscles. It may arise from the medial intermuscular septum of the arm or from the lacertus
fibrosus, from the radius, from the coronoid process, from the radial or ulnar flexor, or from the
flexor sublimis muscles. The tendon may terminate in the fascia of the forearm, the thenar
eminence, the carpus, or the abductor of the thumb. The muscle may be partly or wholly
doubled.
The flexor carpi ulnaris (fig. 370). — Origin. — By two heads: — (1) the humeral head arises
from the common flexor tendon attached to the lower ventral part of the medial epicondyle
Fibre-bundles of this head are also attached to the surrounding intermuscular septa and the
deep fascia of the forearm. (2) The ulnar head arises by short tendinous fibres from the medial
side of the olecranon and by an aponeurotic band common to it and the flexor digitorum pro-
fundus from the upper two-thirds of the dorsal border of the ulna. Proximally the two heads
of the muscle are united by a fibrous arch extending from the olecranon to the medial epi-
condyle. Beneath this band pass the ulnar nerve and the dorsal recurrent ulnar artery. (See
Epitrochleo-olecranonis, p. 402.)
Structure and insertion. — The fibre-bundles of the humeral head descend nearly vertically,
those of the ulnar head obliquely distally in a radial direction. They are iiiserted in a penniform
manner on a tendon which appears in the proximal part of the middle third of the belly of the
muscle on the radial margin of the deep surface, and in the distal third of the forearm forms the
radial border of the muscle. On the ulnar side the insertion of fibre-bundles continues nearly
FLEXOR DIGITORUM SUBLIMIS 399
to the pisiform bone. The insertion of the tendon takes place chiefly into the pisifoi'in bone,
but from it tendinous bundles extend to the palmar aponeurosis, volar ligament of the carpus,
to the pisohamate ligament (pisi-unciform), and to the bases of the fifth, fourth, and third
metacarpals.
Nerve-supply. — From two or three branches of the ulnar nerve, the most pro.ximal of which
arises near the elbow-joint. These branches, which may arise by a single trunk, enter the deep
surface of the proximal third of the muscle and send long twigs distally across the middle third
of the constituent fibre-bundles. The nerve fibres arise from the seventh and eighth cervical
and first thoracic nerves.
Action. — To flex the hand and to abduct the hand ulnarward.
Relations. — It is superficially placed. Its aponeurotic origin is adherent to the fascia
of the forearm. It lies medial to the palmaris longus and flexor sublimis and upon the flexor
profundus. Beneath the muscle lies the ulnar nerve. The ulnar artery extends along the
radial border of the tendon near the wrist.
Variations. — These are rare. Slips from the tendon may pass to the metacarpo-phalangeal
articulation of the little finger. (See, however. Abnormal Muscles, p. 402.)
b. Second Layer
This is composed of one muscle, the flexor digitorum sublimis, which,
although in part covered by the muscles of the preceding layer, is in part super-
ficial. It arises from the medial epicondyle of the humerus, and from the radius
and the ulna, and sends tendons to the second row of phalanges of the fingers.
It corresponds probably with the soleus and the tendons of the flexor digitorum
brevis in the leg and foot.
The flexor digitorum sublimis (figs. 371, 373, 375). — Origin. — By two heads: the ulnar
or chief head arises (1) by the tendon common to it and the superficial group of muscles from
the medial epicondyle, and by short tendinous bands from the ventral surface of the epicondyle;
(2) from the ulnar collateral ligament of the elbow, the ulnar tuberosity, the medial border of
the coronoid process, and the inferior extremity of the tendon of the brachialis; and (3) from
the intermuscular septum between the flexor subhmis and the overlying muscles. The radial
head arises from an oblique line on the volar surface of Ijje radius, and from the middle third
of the anterior border.
Insertion. — Into the sides of the volar surface of the shafts of the second row of phalanges of
the fingers.
Structure. — The fibre-bundles of the ulnar head and the upper part of the radial head con-
verge, the ulnar fibre-bundles nearly vertically, the radial obliquely, to form a common belly
the deep surface of which on the ulnar side is backed by a dense tendinous band. On the radial
side of this a less dense membrane covers over an oval canal which passes distally along the
line of junction of the two heads and lodges the ulnar artery and the median nerve.
The fibre-bundles of the ulnar head form a superficial and a deep group. The superficial
portion near the middle of the forearm divides into a lateral and a medial division, the former
being inserted on a tendon that goes to the middle and the latter on one that goes to the ring
finger. The fibre-bundles of the radial head join with the lateral division of the superficial
layer of the ulnar head and are inserted on the tendon of the middle finger nearly as far as the
wrist. A small muscle fasciculus of the superficial portion of the ulnar head is usually united
by a tendon to the long flexor of the thumb.
The deep portion of the ulnar head about the middle of the forearm terminates in large part
on the volar surface of the dense tendinous band above mentioned. From this in turn two
muscle bellies arise. One of these is inserted in a bipenniform manner on a tendon going to
the index finger, the other on a tendon going to the little finger. A muscle fasciculus also usually
passes from the region of the tendon band to that portion of the superficial fasciculus which
terminates on the tendon of the ring finger.
The four tendons pass together through the carpal canal under the transverse carpal
(anterior annular) ligament, those to the middle and ring fingers lying at first superficial to the
other two. The tendons then diverge, and each tendon, together with and above a tendon of
the flexor profundus, passes over the metacarpo-phalangeal joint into an osteo-fibrous canal on
the palmar surface of the first phalanx of the finger for which it is destined. Here the tendon
becomes flattened about the round tendon of the flexor profundus. Opposite the middle of the
phalanx the tendon divides into two slips, between which the tendon of the flexor profundus
passes. The divided halves of the sublimis tendon fold about the profundus tendon so that their
lateral edges come to meet in the mid-line beneath this tendon opposite the phalangeal joint
(figs. 375, 376). They then again separate, extend distally, and are attached one on each side
into a ridge at the middle of the lateral border of the second phalanx. The tendons are also
attached by vincula tendinum, a ligamentum breve, between the tendon and the head of the
first phalanx and the joint, and a ligamentum longum, between the tendon and the volar surface
of the first phalanx.
Nerve-supply. — Before the median nerve passes between the two heads of the pronator
teres a branch arises which accompanies the nerve through the pronator and sends several
branches into the proximal third of the ulnar head of the muscle. As the median nerve passes
beneath the muscle, one or more branches are given to the radial head, and a long branch is given
to the fasciculus of the second and from this one to that of the fifth digit. Occasionally, the
median nerve in the distal third of the forearm gives rise to branches for these fasciculi. The
nerve fibres arise from the seventh and eighth cervical and first thoracic nerves.
Action. — Chiefly to flex the second phalanx of each finger on the first; secondarily, to flex
the fingers on the hand and the hand on the forearm.
400
THE MUSCULATURE
Relations. — The belly of the muscle is covered by the pronator teres, flexor carpi radialis,
and palmaris longus, but is superficial along a narrow strip between the flexor carpi ulnaris and
the palmaris longus, and on each side of the tendon of the flexor carpi radialis. The muscle
rests on the flexor pollieis longus and flexor digitorum profundus, the median nerve (see de-
scription given above) and ulnar vessels. The median nerve emerges from beneath the radial
border of the muscle in the lower third of the forearm. In the palm the tendons lie beneath the
Fig. 372. — Front of the Forearm: Third Later of Muscles.
Brachio-radialis
Muscles of the first and second ,^</J
layers \ li
Flexor digitorum profundus.
Pronator quadratus
Brachialis
Extensor carpi radialis longus
Supinator
■Flexor pollieis longus
■Brachio-radialis
■Abductor pollieis longus
■Extensor pollieis brevis
pahnar aponeurosis, the superficial palmar arch, and the branches of the median nerve, while
they lie in front of the tendons of the fle.xor profundus, with which they are closely associated
into a common bundle by loose fibrous tissue. The digital relations of the tendons are described
above.
Variations. — The whole muscle may be rendered digastric by a transverse tendon. A
fasciculus of the flexor sublimis may replace the palmaris longus or the two may coexist. A
fasciculus may terminate in the fascia of the forearm or in the transverse carpal ligament, the
palmar aponeurosis, etc. Various parts of the muscle may be absent or more independent than
usual. The extent of the radial attachment varies greatly and may be missing. A special
fasciculus may be received from the coronoid process of the ulna. A fasciculus may be sent to
the flexor profundus or to other muscles. There may be some fusion with neighbouring
muscles.
FLEXOR DIGITORUM PROFUNDUS 401
c. Third Layer
(Figs. 372-376)
The two muscles which constitute this layer may be looked upon as differen-
tiated from a single deep flexor muscle. The flexor digitorum profundus is a
strong, broad muscle which arises from the upper three-fourths of the volar surface
of the ulna and gives rise to tendons which are inserted into the bases of the third
row of phalanges of the fingers. The flexor pollicis longus, likewise broad and flat,
arises from the volar surface of the radius and is inserted into the base of the
second phalanx of the thumb. Both muscles are supplied by the median nerve
and the flexor profundus is also supplied by the ulnar nerve.
These muscles correspond to the flexor digitorum longus and the flexor hallu-
cis longus of the leg.
The flexor digitorum profundus (figs. 372-,376). — Origin. — (1) Through an aponeurotic
septum between it and the fiexor earpi ulnaris from the dorsal border of the ulna; (2) directly
from the proximal two-thirds of the medial surface and the proximal three-fourths of the volar
surface of the uhia and from the adjacent interosseous membrane; and (3) inconstantly, from a
small area on the radius below the bicipital tuberosity.
Structure and insertion. — The fibre-bundles descend nearly vertically and give rise to a
common belly which soon divides into four portions, each of which is attached about midway
down the forearm in a semipennif orm manner to the dorsal surface of a tendon. The attachment
of fibre-bundles continues nearly to the wrist. The digital divisions of the muscle vary in the
height to which they extend. That belonging to the index finger is usually the one most exten-
FiG. 373. — Insertions of the Tendons of the Muscles which act on the Fingee.
(After Toldt, Atlas of Human Anatomy, Rebman, London and New York.)
dOD of fiexor digitorum sublin
sively isolated, and that to the little finger is the next most so. The tendons pass side by side
under the transverse carpal (anterior annular) ligament, and then diverge to the bases of the
fingers. At the metacarpo-phalangeal joints, they enter the osteo-fibrous canals described
above (p. 387). On the volar surface of the first phalanx each tendon passes through the sht
in the subhmis tendon. The tendon then is continued over the second phalanx to the base of the
third. Vincula tendinum are described passing to the capsule of the second interphalangeal joint
(ligamentum breve) and to the tendon of the flexor subhmis (ligamentum longum). The
lumbrical muscles arise from the tendons while they are in the palm.
Nerve-supply. — The interosseous branch of the median nerve arises usually before the
nerve passes through the pronator teres and accompanies the main trunk. This branch as it
passes beneath the flexor sublimis gives off a branch (or two) from which several twigs spring.
These twigs enter the muscle near the radial border and pass in across the middle third of the
constituent fibre-bundles of the fasciculi to the index and middle fingers. The ulnar nerve near
the elbow gives rise to a branch which enters the volar surface of the muscle near the junction
of the proximal and middle thirds of that portion of the belly, giving tendons to the ring and
little fingers. There is some variation in the extent of the innervation by the branches of the
ulnar and those of the median nerve. To a greater or less extent through anastomosis their
territories overlap. The nerve fibres arise from the seventh and eighth cervical and first
thoracic nerves.
Action. — To flex the terminal phalanx of each finger on the second and the second on
the first, while that of the superficial flexor is to flex the second phalanx on the first. The
action of the two flexors on the first phalanx is somewhat more limited. The interosseous
muscles, aided by the lumbricals, are the chief flexors of the first row of phalanges. The flexor
profundus acts, though not powerfully, as a flexor of the wrist.
Relations. — The flexor profundus muscle lies beneath the flexor sublimis and the flexor carpi
ulnaris muscles, the median nerve, and the ulnar vessels and nerve. Under the muscle lie the
ulna, the interosseous membrane, and the pronator quadratus muscle. Under the transverse
carpal (anterior annular) ligament the tendons lie beneath those of the flexor sublimis in the
same synovial sac. In the palm the tendons with the associated lumbrical muscles lie upon the
interosseous muscles, the adductor of the thumb, and the deep palmar arch, and beneath the
flexor sublimis tendons. For the relations to the synovial bursse see p. 403.
402 THE MUSCULATURE
Variations. — There is considerable variation in the extent of the radial origin and in the
extent of the independence and fusion of the different fasciculi. In the prosimians a common
tendon extends as far as the hand. The division in the higher forms is associated with refine-
ment of movements of the fingers. One or more special fasciculi not infrequently join the
muscle from the flexor sublimis, the flexor pollicis longus, the medial epicondyle, or the ulna.
The accessorius ad flexorem digitorum profundum is a fasciculus which arises from the coro-
noid process of the ulna and sends a tendon to join the tendon of one of the fingers, most fre-
quently the middle or index. It is found in 20 per cent, of bodies.
The flexor pollicis longus (fig. 372). — Origin. — The attachment extends along the oblique
line and the ventral border of the radius from slightly below the bicipital tuberosity to within
5 cm. of the wrist. Medially it is continued into the interosseous membrane. Proximally the
tendon frequently extends to the distal radial margin of the coronoid process of the ulna and
gives rise to fibre-bundles connected with the muscle, as well as to a fasciculus of the flexor
profundus.
Structure and insertion. — The fibre-bundles descend obliquely to be inserted in a penni-
form manner on a tendon which begins high up on the volar surface near the ulnar border
of the muscle, and descends as a broad band which near the wrist becomes cyhndroid. The
insertion of fibres continues nearly to the point where the tendon passes under the transverse
carpal ligament. Here the tendon enters the carpal canal radial to the tendons of the flexor
profundus, and passes beneath the superficial head of the short flexor of the thumb, then between
the thumb sesamoids into the osteo-fibrous canal of the thumb, in which it is continued to the
base of the terminal phalanx.
Nerve-supply. — Usually from two branches of the volar interosseous ramus of the median
nerve. These enter the proximal half of tlie ulnar margin of the muscle. The nerve fibres
arise from the sixth, seventh (and eighth) cervical nerves.
Action. — It is a strong flexor of the second phalanx on the first and has less powerful action
. on the metacarpo-phalangeal joint and on the wrist.
Relations. — It lies beneath the flexor subhmis, the flexor carpi radialis and brachio-radialis
muscles, and the radial artery. Near the wrist it crosses over the insertion of the pronator
quadratus. In the hand the tendon runs beneath the opponens pollicis and the superficial head
of the flexor brevis, and across the deep head of the latter.
Variations. — It may be fused or united by fasciculi with the flexor profundus, the flexor
subhmis, or the pronator teres. It may be partially doubled, giving rise to an accessory ten-
don which extends to the index finger. The origin may extend to the medial epicondyle of
the humerus (epitrochlear bundle).
d. Fourth Layer
This layer consists of a single quadrilateral muscle which passes transversely
across the lower part of the forearm from the ulna to the radius. In the leg there
is no corresponding muscle.
The pronator quadratus (fig. 377). — Origin. — Medial side of the volar sm-face of the lower
fourth of the ulna.
Structure and insertion. — From the ulna a strong aponeurosis extends a third of the way
across the volar surface of the muscle. From this membrane and from the bone fibre-bundles
extend transversely to be inserted on the distal quarter of the volar surface of the radius and on
the triangular area above the ulnar notch. The deeper fibre-bundles which arise directly from
the ulna are inserted into the radius by means of an aponeurosis. The superficial and deep
portions of the muscle are often separated. The muscle is thicker distally than proximally.
Nerve-supply. — The volar interosseous nerve descends along the interosseous membrane,
passes behind the middle of the proximal margin of the muscle, and sends branches into its
deep surface. The nerve fibres arise from the (sixth), seventh and eighth cervical and first
thoracic nerves.
Action. — To pronate the forearm.
Relations. — The muscle lies immediately beneath the muscles of the third layer and upon
the radius and ulna, the interosseous membrane, and radio-ulnar joint. The radial artery and
ulnar nerve pass in front of it, the volar interosseous artery behind it.
Variations. — It may be missing or may extend further up the forearm than usual or down
upon the carpus. It may be triangular or divided into parts the fibre-bundles of which take
different directions. It may send fasciculi to the carpus or metacarpus or be fused with the
flexor carpi radialis brevis (see below).
Abnormal Muscles of the Volar Side of the Forearm and Wrist
The epitrochleo-olecranonis (anconeus internus). — A muscle fasciculus, distinct from
the distal margin of the triceps, which runs from the medial epicondyle to the olecranon over
the groove for the ulnar nerve, by a branch of which it is supplied. It takes the place of the
fibrous arch normally extending between the epicondylar and ulnar heads of the flexor carpi
ulnaris. It occurs in about 25 per cent, of bodies (Testut), and represents an adductor of the
olecranon of the lower mammals. Occasionally the medial head of the triceps may descend
over the ulnar groove, but this forms another type of muscle variation.
The flexor carpi ulnaris brevis (ulno-carpeus). — An abnormal muscle which arises from
the distal quarter of the volar surface of the ulna and is inserted into the hamatum (unciform),
the pisiform, the abductor of the little finger, or the superior extremity of the fifth metacarpal.
MUSCLES OF THE HAND
403
The unci-pisiformis. — A short, thick band of muscle which runs from the pisiform to the
tip of the hamulus of the os hamatum (unciform) parallel with the pisohamate (pisi-unciform)
ligament. It is innervated by the ulnar nerve.
The flexor carpi radialis brevis (radio-carpeus). — An abnormal muscle found in about 5 per
cent, of bodies (Le Double). It arises from the lateral or the volar surface of the distal half
of the radius. Some of the fibre-bundles may spring from the pronator quadratus, the fascia
of the forearm, or the ulna. It is inserted into the carpus or metacarpus, and occasionally even
into the first phalanx of the index finger, etc. It is supplied by a branch of the volar interosse-
ous nerve. It serves to flex the wrist. It is said to represent the tibialis posterior of the leg.
BURS^
B. m. flexoris carpi ulnaris. — Between the tendon of this muscle and the pisiform bone.
B. m. flexoris carpi radialis. — Between the tendon of this muscle and the tubercle of the
navicular bone.
Fig. 374. — Synovial Sheaths of the Tendons op the Long Flexors op the Fingers
A. Frequent type; B. normal type; C. foetal type. (After Poirier and Charpy.)
A bursa is often found between the tendon of the deep flexor of the index finger and the
carpus. This bursa is frequently in communication with the radial and ulnar tendon sheaths.
A bursa is also often found between the deep and superficial tendons of the index finger.
Synovial Tendon Sheaths
(Figs. 366 and 374)
Vagina tendinis m. flexoris carpi radialis. — About the tendon as it passes beneath the
transverse carpal ligament.
Vaginae tendinum mm. flexorum digitorum. — The osteo-fibrous canals of the digits are
lined by a synovial membrane which is reflected by means of a fold (oul-de-sac) to the^tendons at
each end and over the vincula tendinum, in which blood-vessels and nerves for the tendons are
contained. The synovial cavity of the first and usually that of the fifth digit communicate
with those of the palm.
In the wrist and palm two large synovial sacs may usually be recognized, although the
number may be raised to five or reduced to one.
The radial sac, vagina tendinis m. flexoris pollicis longi, surrounds the long flexor tendon
of the thumb in the wrist and palm and usually communicates with that of the thumb. In the
palm a well-marked mesotendon usually extends to the deep ulnar side of the tendon from the
parietal layer of the sheath.
The ulnar sac, vagina tendinum mm. flexorum communium, surrounds the tendons of the
long flexors of the fingers. It begins proximal to the transverse carpal ligament and extends
nearly or quite to the synovial sheath of the little finger on the ulnar side and on the radial
side to the centre of the palm.
3. Musculature of the Hand
(Figs. 366, 368, 375-379)
The intrinsic muscles of the hand are taken up in the following groups : —
a The subcutaneous muscle of the palm.
b The muscles of the little finger,
c The muscles of the thumb.
d The lumbrical muscles,
e The interosseous muscles.
404 THE MUSCULATURE
The ulnar nerve supplies the muscles of the little finger, the interossei, the
medial lumbrical muscles, and two of the muscles of the thumb; the median
nerve supplies most of the muscles of the thenar region and the lateral lumbrical
muscles.
(a) Subcutaneous Muscle
(Fig. 375)
The palmaris brevis is a small, trapezoid sheet situated between the hypothe-
nar fascia and the skin. It arises at the lateral edge of the palmar aponeurosis
from tendinous slips which may be traced through the aponeurosis to the navicular
and greater multangular. It is composed of nearly parallel fibre-bundles, and ex-
tends into the deep surface of the skin along the ulnar border of the palm. It is
generally taken to be a subcutaneous muscle like the superficial muscles of the
head and neck. It has, however, been suggested that it represents the remnants
of a short flexor of the digits corresponding with the flexor digitorum brevis of the
foot.
Nerve-supply. — The superficial branch of the palmar division of the ulnar nerve gives rise
to a twig which enters the deep surface of the muscle. The fibres come from the (seventh and)
eighth cervical and first thoracic nerves.
Action. — The action of the muscle is to draw the skin of the ulnar side of the hand toward
the centre of the palm. It is said that it thus helps to form a cup-shaped hollow when the hand
conveys fluid to the mouth. The contraction of the muscle by raising a ridge over the ulnar
nerve and artery when an object is grasped hard serves, according to Henle, to protect these
structures.
Variations. — It varies in size. In about 2 per cent, of bodies it is absent (Le Double).
It may send tendinous slips to the pisiform bone. (For a thenar subcutaneous muscle, see
variations of the abductor polhcis brevis.)
(h) Muscles of the Little Finger
(Figs. 375, 376, 377)
In the hypothenar eminence are three muscles, the abductor, the flexor brevis,
and the opponens digiti quinti. The abductor digit! quinti is a flat, fusiform
muscle which arises from the pisiform and is inserted into the ulnar border of the
first phalanx and into the dorsal aponeurosis through which it helps to flex the
first and extend the second and third phalanges of the little finger. The fusiform
flexor brevis arises from the hamatum (unciform) and adjacent part of the trans-
verse carpal (anterior annular) ligament and is inserted into the ulnar side of the
base of the first phalanx. The triangular opponens likewise arises from the hama-
tum (unciform) and the transverse (anterior annular) ligament. It is inserted
into the ulnar border and the head of the fifth metacarpal.
The abductor of the little finger corresponds with that of the little toe. A part of the oppo-
nens beneath the ulnar nerve corresponds with that of the little toe, while the more superficial
portion is unrepresented in the foot. The flexor brevis of the httle toe corresponds with a part
of the deep portion of the opponens of the little finger. The flexor brevis of the httle finger
is unrepresented in the foot. (Cunningham.)
The abductor digiti quinti (figs. 375, 376). — Origin.— Yrom the distal half of the pisiform,
the ligaments between this and the hamatum, the tendon of the flexor cai'pi ulnaris, and often
from the transverse carpal (anterior annular) ligament.
Structure and insertion. — The fibre-bundles descend vertically, at first increasing in number
and then concentrated, toward two short tendons one of which is inserted into the ulnar border
of the first phalanx of the little finger and the other into the aponeurosis of the extensor tendon
of the httle finger.
Nerve-suppbj. — From the deep palmar division of the ulnar nerve before it passes through
the opponens, or from the superficial palmar branch, arise one or more twigs which enter the
radia) side of the muscle on its deep sm'face in the proximal third. The nerve fibres arise from
the (seventh and) eighth cervical and fu'st thoracic nerves.
Action. — To abduct the little finger, flex the first phalanx, and extend the last two.
Relations. — It overlies the opponens and flexor brevis. Superficially it is covered by fascia
and the palmaris brevis muscle. Along the proximal part of its radial margin run the deep
palmar branches of the ulnar artery and nerve.
Variations. — It may be missing or doubled. It may be fused with the short flexor or
receive fasciculi from the palmaris longus, the ulnar flexor, the fascia of the forearm, etc.
The flexor digiti quinti brevis (figs. 376, 377). — Origin. — By a short tendon from the hook of
the hamatum (unciform) and from the adjacent parts of the transverse carpal (anterior annular)
ligament.
Structure and insertion. — The fibre-bundles take a nearly parallel com'se and are inserted
MUSCLES OF LITTLE FINGER
405
by a short tendon which is fused with that of the abductor and is inserted into the ulnar side of
the base of the first phalanx of the little finger. A sesamoid bone may lie in the tendon.
Nerve-supply. — A branch from the superficial or deep palmar division of the ulnar nerve
enters the deep surface of the muscle in its proximal half. The nerves to the abductor and flexor
may arise in common from the ulnar. The nerve fibres arise from the (seventh and) eighth
cervical and first thoracic nerves.
Fig. 375. — The Superficial Muscles of the Palm of the Hand.
Flexor carpi radialis
Abductor poUicis longus
Flexor digitorum'
profundus
Action. — To flex the first phalanx of the little finger. When it sends a tendon slip to the
aponeurosis of the extensor of the finger it helps to extend the two terminal phalanges.
Relations. — The muscle closely adjoins and is partly covered by the abductor. The pal-
maris brevis and the lateral volai' digital artery to the fifth finger lie superficial to it. Under it
lies the opponens.
Variations. — The muscle may be wanting or may be closelj' fused with the abductor or the
opponens. It may receive an accessory slip from the forearm fascia. It may give a tendon
sUp to the extensor aponeurosis or to the head of the fifth metacarpal.
The opponens digiti quinti (fig. 377). — Origin. — Partly tendinous, from the distal ulnar
border of the hook of the hamatum (unciform) and from the adjacent transverse carpal (anterior
annular) ligament.
406
THE MUSCULATURE
Structure and insertion. — The fibre-bundles diverge, the proximal short and horizontal, the
distal long and oblique, and are inserted on the whole of the ulnar border and on a part of the
head of the fifth metacarpal. Often the^musole is divisible into two portions between which the
ulnar nerve runs.
Nerve-supply. — Before the deep palmar branch passes through the muscle it gives rise to
a twig which enters its volar surface in the middle third near the ulnar margin. The nerve
fibres arise from the (seventh and) eighth cervical and first thoracic nerves.
Action. — To flex, adduct, and slightly rotate the fifth metacarpal; as, for example, in 'cup-
ping' the hand to drink from it.
Relations. — The opponens lies beneath the abductor and flexor brevis muscles. The deep
branches of the ulnar nerve and artery pass through the opponens near its carpal origin and
then under it extend into the palm.
Fig 376 — The Debpek Muscles op the Palm of the Hand.
Abductor poUicis longus
Flexor carpi radialis
Extensor polUcis brevis
Abductor pollicis brevis
Opponens pollicis
Flexor digitorum.^5^
profundu
Abductor pollicis
brevis
Flexor pollicis
brevis
Adductor pollicis
Variations. — -It may be fused with neighbouring muscles or receive accessory slips.
The tensor capsularis articulationis metacarpo-phalangei digiti quinti is a slender muscle
which arises from the ligaments which unite the pisiform to the hamatum, and is inserted into
the volar surface of the metacarpo-phalangeal joint of the little finger.
(c) Muscles of the Thumb
(Figs. 375, 376, 377)
In the therar region there are four muscles. Of these, the abductor pollicis
brevis is the most superficial. Then come the opponens pollicis and the short
flexor, and beneath the last the adductor pollicis. All are triangular in form.
The abductor pollicis brevis arises from the radial side of the volar surface of the
MUSCLES OF THE THUMB
407
carpus and is inserted into the radial side of the base of the first phalanx of the
thumb. The opponens is a thick muscle extending from the transverse carpal
(anterior annular) ligament to the radial side of the first metacarpal. The flexor
poUicis brevis arises by two heads, a "deep" and a "superficial" from the carpus
and is inserted into the radial side of the base of the first phalanx. The adduc-
tor poUicis arises from the carpus and the second and third metacarpals and is
inserted into the ulnar side of the first phalanx of the thumb. From the ten-
dons of insertion of the abductor and flexor brevis slips are continued into the
dorsal aponeurosis of the thumb so that they aid in extending the second
phalanx.
In the foot an opponens halluois occurs as an abnormal muscle. The abductor, flexor brevis
and adductor ot the thumb are represented by the corresponding muscles of the big toe, although
Fig. 377. — The Pronator Quadratus and Deep MtrscLEs op the Palm.
Pronator quadratus
Flexor carpi ulnarl
Abductor digiti V.
Abductor pollicis brevis
Deep head of flex-
or poUicis brevis
Opponens pollicis
I Volar inter-
osseous
Adductor pollicis,
oblique head
Fourth dorsal
interosseous
Third volar interosseous
Third dorsal interosseous
Second volar interosseous
Second dorsal interosseous
the last two muscles are not perfectly homologous in the hand and foot.
The abductor pollicis brevis (fig. 375). — Origin. — From the volar surface of the transverse
carpal (anterior annular) ligament, and from the greater multangular bone (trapezium). Also
often from the navicular bone and from a tendon slip of the long abductor.
Structure and insertion. — The fibre-bundles converge upon a flat tendon with two lamellae,
the deeper of which is inserted into the radial side of the base of the first phalanx of the thumb
and the superficial into the aponeurosis of the extensor poUicis longus.
Neroe-supply. — By a branch ot the first volar digital ramus of the median nerve. This
branch passes over or through the flexor brevis and enters the muscle on the volar surface in
the middle third near its ulnar border.
Action. — To abduct the thumb, flex the first phalanx, and extend the terminal phalanx.
Relations. — It lies beneath the thenar fascia lateral to the superficial head of the flexor
brevis and over the opponens. The superficial volar artery usually perforates the muscle.
Variations. — It may be wanting or may be divided into two divisions. The origin may
extend to the fascia of the forearm or styloid process of the radius. It may receive an accessory
slip from the long radial extensor, the opponens, or the short extensor of the thumb. A thenar
subcutaneous muscle is occasionally present. It is narrow, is closely associated with the short
abductor of the thumb, and extends from the radial side of the base of the first metacarpal into
the skin of the thenar eminence.
408 THE MUSCULATURE
The opponens poUicis (fig. 377). — Origin. — From the volar surface of the transverse carpa
(anterior annular) ligament and from the tubercle of the greater multangular bone (trapezium).
Structure and Insertion, — The fibre-bundles extend obliquely in a nearly parallel direction
to their insertioB along the -whole lateral border of the volar surface of the shaft and the head of
the first metacarpal.
Nerve-supply. — By a branch of the first volar digital ramus of the median nerve. This
branch passes over or through the superficial division of the flexor brevis near the origin of the
muscle. One or two twigs enter the deep surface of the proximal third of the opponens near
its ulnar border. The nerve fibres arise from the sixth and seventh cervical nerves.
Action. — To flex, adduct, and rotate medialward the first metacarpal bone. The volar
surface of the thumb is thus brought to face the volar surface of the other digits.
Relations. — It lies beneath the thenar fascia and the abductor brevis. The flexor brevis
overlies its ulnar border.
Variations. — It may be absent or it may be divided into two heads. It is usually more or
less fused with the short flexor.
The flexor poUicis brevis (figs. 376, 377). — The muscle is divided by the tendon of the
long flexor into a superficial and a deep portion. The superficial head arises from the greater
multangular bone (trapezium), the adjacent part of the transverse carpal (anterior annular)
ligament, and the tendon sheath of the flexor carpi radialis. The fibre-bundles descend closely
applied to the opponens, and terminate by a tendon which is attached to the lateral side of the
front of the base of the first phalanx. Over the joint a sesamoid bone lies in the tendon. The
deep head has a tendinous origin from the os multangulum minus (trapezoid) and the os capi-
tatum (magnum). The fibre-bundles take an oblique course, to be inserted into the tendon of
the superficial part. A muscle fasciculus which arises from the ulnar side of the base of the first
metacarpal and the neighbouring carpal ligaments and is inserted on the ulnar side of the base
of the first phalanx, is sometimes considered to be the deep head of the flexor brevis. It is
closely bound up with the carpal head of the adductor poUicis and they have a common tendon.
Some fibres of the medial division of the tendon may be traced into the aponeurosis of the exten-
sor tendon. It is probable that this portion of the muscle represents a first volar interosseous,
and it is so described later with the interosseous muscles. There is much dispute as to what
fascicuU should be included in the flexor brevis.
Nerve-supply. — The muscle is usually suppUed by twigs derived from a branch from the
first volar digital ramus of the median nerve as this branch passes through its substance, and
by twigs from the deep branch of the ulnar. Brookes found this supply in 19 out of 29 instances,
in 5 by the median alone, and in 5 by the ulnar alone. The nerve fibres come from the sixth
and seventh cervical nerves.
Action. — To flex, adduct, and rotate medialward the metacarpal of the thumb; flex the first
phalanx; and extend the second phalanx.
Relations. — Proximally the short flexor is grooved for the tendon of the long flexor, beneath
which more distally the deep head of the muscle passes laterally. The superficial portion of
the muscle lies beneath the skin. The ulnar border of the deep head is fused prOximaUy with
the adductor.
Variations. — The deep head may be absent. Either or both heads may be double. The
superficial head may be fused with the abductor brevis, and is usually more or less fused with
the opponens.
The adductor poUicis (fig. 377).- — Origin. — By two heads. The carpal or oblique head
arises from the deep carpal ligaments, the capitatum and the bases of the second and third
metacarpals; the metacarpal or transverse head, from the crest of the third metacarpal, from
the suprametacarpal fascia of the third interspace, and sometimes also from that of the fourth
interspace and from the capsules of the second, third, and fourth metacarpo-phalangeal articu-
lations.
Structure and insertion. — The fibre-bundles converge toward a tendon which is inserted
into the ulnar side of the front of the base of the first phalanx of the thumb. A sesamoid bone
lies in the tendon over the joint.
Nerve-supply. — One or more twigs from the deep palmar branch of the ulnar enter the middle
third of the muscle on its deep surface. There may also be an anastomosing branch from the
median nerve. The nerve fibres come from the sixth, seventh and eighth cervical and first
thoracic nerves.
Action. — To adduct and flex the first metacarpal and flex the first phalanx of the thumb.
When the thumb is in an extreme position of apposition, it acts as an abductor.
' Relations. — Superficial to the muscle lie some of the tendons of the deep flexor of the fingers
and the first two lumbrical muscles. It extends over the two more lateral intermetacarpal
spaces, and is in part subcutaneous on the dorsal surface. The deep palmar arch extends
between the two heads and beneath the oblique head. The oblique head of the muscle is closely
united to the first volar interosseous, so that the latter by some is considered a part of the
adductor.
Variations. — The extent of the attachments of origin of the muscle vary considerably.
The two heads of the muscle may be more or less completely separated from one another. Each
may be divided into separate fasciculi.
(d) Lumbrical Muscles
From the deep flexor tendons in the palm of the hand arise the lumbrical
muscles, four in number, which are attached by small tendons to the radial side of
the extensor tendons (figs. 373, 375). These lumbrical muscles have homologues
in the sole of the foot.
INTEROSSEOUS MUSCLES
409
The lumbricales (figs. 375, 376). — Origin. — The two lateral arise from the radial side of
the volar aspect of the first and second tendons of the flexor digitorum profundus; the two
medial arise from the adjacent sides of the second and third and third and fourth tendons.
Structure and insertion. — The fibre-bundles of each muscle arise directly from the flexor
tendons near the distal border of the transverse carpal (anterior annular) ligament. They
converge as far as the metacarpo-phalangeal joint, upon a small tendon which begins about the
middle of the muscle. The tendon passes out between the palmar aponeurosis and the trans-
verse capitular ligament, winds about the metacarpo-phalangeal joint, expands, and is attached
along the side of the first phalanx to the radial border of the tendon of the extensor digitorum
communis. . j- , , ,
NerBe-supply. — Branches from the median nerve enter the middle third of the radial border
of the first two or three lumbrical muscles. The last one or two are supplied by branches from
the deep volar branch of the ulnar nerve, which enter the middle third of the deep surface. The
third lumbrical and sometimes one or more of the others may receive a branch from both nerves.
The nerve fibres come from the eighth cervical and first thoracic nerves.
Action. — Together with the interosseous muscles they flex the basal phalanges on the meta-
carpal bones and extend the terminal and middle phalanges. They also adduct the fingers
toward the thumb.
Relations. — The muscles run between the tendons of the flexor profundus and beneath the
palmar aponeurosis. They lie upon the fascia covering the interosseous muscles, the capitular
ligaments, and the septum' over the adductor and deep head of the flexor pollicis brevis.
Variations. — These are very frequent, especially in case of the third and fourth. Each
may be doubled or missing. They may arise from the tendons of the flexor subhmis or from
the belly of the deep flexor. The first lumbrical may come from the tendon of the long flexor,
from the opponens, or the metacarpal of the thumb. The tendon of insertion may go to the
ulnar side of the base of the digit opposite that to which the tendon Is usually attached, or the
tendon may divide and go to the adjacent sides of two fingers. Kopsch has found that in 110
bodies all four lumbricals were inserted on the radial side of their respective digits in 39 per cent.
In 35 per cent, the first, second, and fourth were so inserted, while the third sent slips to the
adjacent sides of the middle and ring fingers. An accessory fasciculus has been found to arise
from the tendon of the flexor poUicis longus and go to the base of the index finger.
(e) Interosseous Muscles (figs. 377, 378, 379)
These muscles lie between the metacarpal bones and are covered dorsally and
ventrally by fasciae attached to the metacarpals. In each interspace are two mus-
cles, a dorsal and a palmaw The volar interossei are inserted into all the fingers
Fig. 378. — The Volar Interossei.
except the middle finger, and are adductors toward an axis passing through the
middle finger; the dorsal interossei are inserted into both sides of the middle finger
and into the radial side of the second and the ulnar side of the fourth finger, and
are abductors. All also serve as flexors of the first row of phalanges and extensors
of the second and third. In the foot the axis to and from which the interosseous
muscles adduct and abduct the toes passes through the second toe.
The interossei volares arise from the sides toward the middle finger and the front of the
shafts of the first, second, fourth, and fifth metacarpals. The first arises from near the base, the
410
THE MUSCULATURE
others from three-fourths of the shaft. The fibre-bundles of each muscle converge in a penni-
form manner upon a tendon which is inserted into the aponeurosis of the digital extensor tendon
and the base of the first phalanx on the middle finger side of the corresponding digit (see fig. 373).
The first volar interosseous is often described as a division of the flexor poUicis brevis or of the
adductor poOicis.
The interossei dorsales arise from the adjacent sides of the metacarpal bones in each inter-
space. On the sides nearest the middle finger they cover three-fourths of the bone, on the
opposite sides much less. The fibre-bundles converge in a bipenniform manner upon a tendon
which begins high in the muscle and is inserted into the aponeurosis of the extensor muscles
and the base of the first phalanx on each side of the middle finger, on the thumb side of the
index finger, and the ulnar side of the ring finger. The interosseous muscle in the first interspace
is thick and strong and forms with the adductor poUicis the fleshy web between the base of the
thumb and the palm.
Nerve-supply. — By branches of the deep palmar division of the ulnar nerve. As a rule, a
branch to each volar interosseous enters the proximal third of the muscle. To each dorsal inter-
osseous a branch is given which enters between the two heads. These branches may be variously
combined before entering the interosseous muscles. The nerve fibres arise from the eighth
cervical and first thoracic nerves.
Fig. 379. — The Dorsal Interossei
Action, — To move the fingers toward the radial and ulnar sides, to flex the first phalanx
and extend the second and third. The volar interossei move the fingers toward the median
axis, the dorsal from it.
Relations. — The volar interossei lie volarward from the dorsal interossei. The two sets
of muscles are bound in place by the dorsal and volar metacarpal fascise. The tendons pass out
on the dorsal side of the transverse capitular ligament and are closely apphed to the metacarpo-
phalangeal joints. The muscles of the first two interspaces lie immediately dorsal to the adduc-
tor of the thumb; the others dorsal to the flexor tendons.
Variations. — The tendon slip from an interosseous muscle to the base of the first phalanx
of a digit may be missing. This is more frequent in case of the volar than in that of the dorsal
interossei, and in the medial than the lateral muscles. Either a volar or a dorsal interosseous
muscle may be double or missing. Rarely the insertions of the interosseous muscles character-
istic of the foot (see p. 499) may be found in the hand.
III. SPINAL MUSCULATURE
(Figs. 380, 381, 382, 383)
The spinal (vertebral) column is of special interest as the segmented longitudi-
nal axial support of the body vsrhich has given rise to the term "vertebrates" as
applied to the class of animals of which man is the highest form. The segmenta-
tion in fishes permits the lateral movements of the body which are their chief
means of propulsion. In the land vertebrates, with the exception of snakes, the
limbs are developed as the chief organs of propulsion but flexibility of the column
SPINAL MUSCULATURE 411
is retained for the sake of freedom of movement. In man the spinal column, with
the exception of the sacral region, may be readily extended (bent backward) and
flexed (bent forward), abducted (bent to the side) and rotated. Freedom of
movement is greatest in the cervical and lumbar regions and is restricted by the
thorax in the thoracic region. The cervical region allows considerable flexion,
extension and rotation, but a more limited abduction. In the thoracic region
rotation and abduction are freer than flexion and extension. The lumbar region
is that in which the chief flexion and extension of the trunk takes place, but abduc-
tion and rotation are limited, especially the latter. In the isolated articulated
spinal column freedom of movement of the various parts depends chiefly upon the
thickness and elasticity of the intervertebral discs, upon the conformation of the
articulat processes, and upon the elasticity or arrangement of the various liga-
ments uniting the vertebrae. In the living body freedom of movement is further
restricted by the musculature and skeletal apparatus attached to the column.
There is much individual variation in the flexibility of the vertebral column.
The various movements ot the column are produced partly by muscles which act directly on
it and partly by muscles which act on it through the head, thorax or pelvis. Most of the muscles
which act on it directly belong to the intrinsic dorsal musculature; that is, to musculature which
is derived from the dorsal divisions of the myotomes and is innervated by the dorsal divisions
of the spinal nerves. This musculature extends from the sacrum to*the skull and is closely
applied on each side of the mid-dorsal line of the body to the backs of the vertebrae and the back
of the thorax (fig. 381). Its chief function is to extend the spinal column and head, hence the
old term applied to the superficial portion of this musculature "erector spinas. " During the
development of the body, muscles belonging to the ventro-lateral thoracic musculature and to
the upper extremity come to overlie in part the intrinsic dorsal musculature. The trapezius
and rhomboid muscles which cover it in the cervical and thoracic regions, and the latissimus
dorsi which covers it in the thoracic and lumbar regions belong to the shoulder girdle and arm
and have already been described, p. 360. The serratus posterior superior, which overlaps it
in the upper thoracic region, and the serratus posterior inferior, which overlaps it at the junction
of the thoracic and lumbar regions, are derived from the intercostal musculature which is de-
scribed below, p. 422 (fig. 380). All of these muscles are innervated by the ventro-lateral divi-
sions of the spinal nerves. The levatores costarum (fig. 380), which extend from the transverse
process of the thoracic vertebrae to the ribs, and which, in spite of their name, act chiefly on
the spinal column, are derived from the external intercostal musculature and are innervated by
the intercostal nerves.
Ventral to the spinal column and closely applied to it there are a few muscles, the chief
function of which is to flex the column. All are supplied by branches from the ventro-lateral
divisions of the spinal nerves. Of these the longissimus colli and longissimus capitis and scalene
muscles have been described in connection with the muscles of the neck, p. 353. In the thoracic
region there are no muscles of this type. In the lumbar region there are four muscles on each
side, the pillars of the diaphragm, fig. 391, the psoas minor, fig. 391, the psoas major, fig. 391,
and the quadralus lumborum, fig. 391. All of these muscles are flexors of the spine^ except the
quadratus, which is an extensor. The psoas major muscle is also a flexor of the thigh. Even
more powerful flexors of the column than those above mentioned are some of those which work
indirectly upon it through the leverage offered by the skull (sterno-cleido-mastoid described
above, p. 347), and the thorax (the ventro-lateral abdominal musculature).
Abduction and rotation of the spine are produced by contraction of muscles on one side
while the corresponding muscles on the other side are relaxed. See Table, p. 502.
In the present section we shall confine our attention to the intrinsic dorsal musculature,
leaving for consideration elsewhere the other musculature which acts on the vertebral column.
The intrinsic dorsal musculature is attached to the sacrum, to the ilium, to the
spines, transverse, and articular processes and laminae of the lumbar, thoracic, and
cervical vertebrae, to the backs of the ribs and to the base of the skull. Two great
longitudinal subdivisions may be recognised, a lateral, supplied by lateral branches
of the posterior divisions of the spinal nerves, and a medial, supplied by medial
branches. The lateral portion is further divisible into a superficial division, con-
sisting chiefly of systems of muscles extending laterally from the spines of the verte-
hv3d upward toward the transverse processes of the vertebrae, the ribs, and the
mastoid process of the skull; and a deep division, consisting of muscles which ex-
tend between successive transverse processes. The medial portion likewise con-
sists of two parts; a superficial medial composed of fasciculi extending from in-
ferior to superior spines, best developed in the dorsal region, and a deep portion
consisting mainly of muscle fasciculi which pass from the transverse processes up-
ward toward the spines of vertebrae situated more cranially. In the neck the more
superficial extend to the base of the skull. Between the base of the skull and the
first two vertebrae there are several specialised muscles. There is also frequently
present the rudimentary sacro-coccygeus posterior described on p. 448, which
represents an extension into the caudal region of the intrinsic dorsal musculature.
412 THE MUSCULATURE
The superficial lateral dorsal musculature consists of the splenius and the sacro-
spinalis. The splenius (fig. 380) is a flat, somewhat triangular muscle, which
extends from the cervical and upper thoracic spines to the upper cervical trans-
verse processes and to the mastoid process of the temporal bone and the neighbour-
ing part of the occipital. The sacro-spinalis (erector spinte) (fig. 381) is the name
given to a mass of musculature which takes its origin from the ihum, the sacrum,
and the lumbar spines. In the lumbar region this muscle divides into its two chief
portions, the ilio-costalis and the longissimus. The ilio-costalis (fig. 382) is
attached to the lumbar transverse processes and to the ribs near the angles, and is
continued upward by accessory fasciculi along the back of the thorax to the trans-
verse processes of the cervical vertebrae. The longissimus (fig. 382) extends up-
ward between the ilio-costalis and the spines of the lumbar and thoracic vertebree.
It is attached to the transverse processes of the lumbar and thoracic vertebrae and
to the ribs lateral to the transverse processes. It is continued to the transverse
processes of the cervical vertebrae and to the skull by accessory muscle slips.
The deep lateral dorsal musculature consists of the dorsal intertransverse
muscles. The intertransverse muscles are best developed in the cervical and lum-
bar regions. In the cervical region intertransverse muscles belonging to the dor-
sal musculature extend between the successive dorsal tubercles, while intertrans-
verse muscles belonging to the ventral musculature extend between the ventral
tubercles. The latter, as well as the rectus capitis anterior and rectus capitis
lateralis, which belong in the series, have been described above (p. 356). In the
lumbar region there are also two sets of intertransverse muscles, one belonging to
the ventral and one to the dorsal musculature.
The superficial medial dorsal musculature consists of the spinalis dorsi and
cervicis. The spinalis dorsi (fig. 381) is intimately fused with the longissimus. It
extends from the lower to the upper thoracic spines, and is derived from the medial
dorsal musculature. The inconstant spinalis cervicis, which extends from the
upper thoracic to the lower cervical spines, is likewise derived from the medial
dorsal musculature, but is less intimately related to the longissimus.
The deep medial dorsal musculature (fig. 383) lies in the groove between the
transverse processes and the spines of the sacral, lumbar, thoracic, and cer-
vical vertebrae. It extends from the sacrum to the skull, and is best developed in
the lumbar and cervical regions. It is subdivided into a vertebro-occipital muscle
(semispinalis capitis), a transverso-spinal group, and the interspinal muscles.
The semispinalis capitis (complexus) (fig. 381) arises from the transverse processes
of the third cervical to the sixth thoracic vertebrae and from the spines of the upper
thoracic vertebrae and is inserted into the base of the skull. The transverso-spinal
group (fig. 383) extends from the sacrum to the second cervical vertebra. It is
more or less artificially divisible into several layers. In the superficial layer, the
semispinalis dorsi et cervicis, which extends from the twelfth thoracic to the second
cervical vertebra, the constituent fasciculi extend from the transverse process of
one vertebra to the spine of a vertebra four to six segments above. In the middle
layer, the multifidus, the fasciculi extend over from two to four vertebrae. In the
deepest layer, the rotatores, the fasciculi extend to the ne.xt vertebra (short rotators)
or to the second vertebra above (long rotators). The interspinal muscles extend
between successive spines.
The muscles which pass from the first two vertebrae to the base of the skull
behind, or suboccipital muscles (fig. 382), consist of the rectus capitis posterior
minor, from the spine of the atlas to beneath the inferior nuchal line of the occip-
ital and rectus capitis posterior major, from the spine of the epistropheus (axis) to
beneath the inferior nuchal line, lateral to the preceding; of the obliquus capitis
inferior, from the spine of the epistropheus (axis) to the transverse process of the
atlas, and the obliquus capitis superior, from the transverse process of the atlas to
the base of the lateral part of the inferior nuchal line of the occipital above the
rectus major.
The primitive condition of the dorsal musculature is one of metameric segmentation. This
is characteristic of fishes, many amphibia, and of the embryos of all higher vertebrates. In
the tailless amphibia, however, a partial differentiation of the dorsal musculature takes place dur-
ing embryonic development, and in all higher forms a differentiation takes place which corre-
sponds in many ways to that described above for man. According to Favaro, the splenius is
differentiatied from the medial dorsal system, but its innervation should place it with the lateral
system. In the human embryo the dorsal segmental musculature extends into the tail region,
but afterward here undergoes retrograde metamorphosis.
FASCIA
413
The intrinsic musculature of the back serves to extend, bend from side to side, and to rotate
the spinal column and head. The muscles attached to the ribs depress the thorax.
Fig. 380. — The Third and Fourth Layers of the Muscles op the Back.
(Intrinsic Dorsal Musculature)
Semispinalis capitis
Splenius capitis
Splenius cervici
Serratus posterior superior
Lumbo-dorsal fascia
Serratus posterior inferior
Obliquus internus
Origin of latissimus dorsi
Seventh cervical vertebra
Twelfth thoracic vertebra
3 Fifth lumbar vertebra
FASCIA
The fasciae and the general relations of the muscles of the back may be followed in the cross-
sections shown in figs. 347, 351, 357, 384, and 407.
The tela subcutanea of the upper dorsal region has been described in connection with the
muscles of the shoulder girdle (p. 347). It is thick, fibrous, and adherent. In the lower dorsal
414 THE MUSCULATURE
region it is somewhat less compact, but is thicker and contains more fat. It is usually divisible
into two layers, of which the deeper is adherent to the lumbodorsal fascia.
The splenius (fig. 380) is enveloped in a thin, adherent fascial covering. The saoro-spinalis
is covered by a fascia, the fascia lumbo-dorsalis (fig. 380), which inferiorly is attached to the
iliac crest, the distal and lateral margins of the sacrum, and the sacral spines. In the lumbar
and thoracic regions it is attached medially to the vertebral spines. Laterally, in the lumbar
region, it is reflected around the muscle to its ventral surface, where a 'ventral' or 'deep'
layer forms an intermuscular septum (fig. 384) between the quadratus lumborum and the sacro-
spinalis. This intermuscular septum (fig. 383) extends from the twelfth rib to the iliac crest
and the ilio-lumbar ligament, and is attached medially to the transverse processes of the lumbar
vertebra, from which fibre-bands extend laterally into it. It is strengthened above by fibre-
bundles which pass from the first and second lumbar vertebrce to the twelfth rib (lumbo-costal
ligament). (For the relation of the abdominal muscles to this fascia see p. 328.)
In the thoracic region (fig. 384) the lumbo-dorsal fascia is attached to the ribs lateral to
the iho-costal muscle. In the cervical region (fig. 351) the fascia is continued into the inter-
muscular septa which surround the muscles of this group in the neck.
The transversospinal muscles are covered throughout their extent by a fascial membrane
which serves to separate them from the longissimus in the sacral, lumbar, and thoracic regions.
In the dorsal region of the neck (figs. 347, 351, 357) the muscles are covered on each surface
by adherent fascial sheets, fascia nuchas, and are arranged in several concentric layers, each
of which is separated from its neighbour's by dense fatty areolar tissue. The deepest of the
layers is formed by the muscles of the transverso-spinal group. This is covered by a dense mem-
brane, and is separated from the semispinalis capitis (complexus) by a thick layer of areolar
tissue containing the chief blood-vessels and nerves of the neck. The semispinalis capitis
(complexus) is covered on each surface by a more delicate adherent membrane, and is separated
from the splenius by loose tissue. The splenius has a somewhat denser adherent fascial cover-
ing into which the fascia of the levator scapulse is continued. Separated from this by areolar
tissue lies the trapezius. The cervical and thoracic portions of the semispinalis are separated
by delicate membranous septa from the semispinalis capitis (complexus), the levator scapute,
and the splenius. The muscles of each side are separated in the dorsal median plane by the
dense ligamentum nuchae, into which the various cervical septa and fasciie extend. The sub-
occipital muscles are covered by fascial sheaths which are so fused as to constitute a special
fascia for these muscles. Distally this is continued into the fascia of the transversospinal
muscles.
MUSCLES
A. Superficial Lateral Dorsal System
The splenius (fig. 380). — The two parts of which this muscle is composed may be separately
considered.
The splenius cervicis. — Origin. — By a narrow aponeurotic band from the spinous processes
and the supraspinous ligament of the third to the sixth thoracic vertebrae.
Structure and insertion. — The fibre-bundles extend upward and laterally and give rise to a
flat muscle sheet from which fascicuh arise that are inserted by short tendinous processes on the
posterior tubercles of the transverse processes of the first two or three cervical vertebrae. The
processes are often united with those of the levator scapula? and the longissimus cervicis.
The splenius capitis. — Origin. — Froin the ligamentum nuchae in the region of the third
to the seventh cervical vertebrae and from the spinous processes and the supraspinous ligament
of the first two to five thoracic vertebrae.
Structure and insertion. — The fibre-bundles form a sheet which continues cranialward
that of the splenius cervicis. The fibre-bundles converge somewhat and are inserted by a
short, broad, thick tendon into — (1) the back, the side, and the tip of the mastoid process below
the sterno-cleido-mastoid muscle, and (2) into the neighbouring part of the occipital bone.
Relations. — The splenius lies dorsal to the semispinalis capitis (complexus) and to the
cervical (transversalis cervicis) and the cranial (trachelo-mastoid) portions of the longissimus
and the cervical portion (cervicalis ascendens) of the ilio-costalis and to the levator scapulae, and
is partly covered by the trapezius, sterno-cleido-mastoid, serratus posterior superior, and the
rhomboids. In the triangle bounded by the trapezius, sterno-cleido-mastoid, and the levator
scapulae it is subcutaneous.
Nerve-supply. — The lateral branches of the posterior divisions of the second, third and fourth
(sometimes also of the first, the fifth and the sixth) cervical nerves give off rami which enter the
deep surface of the muscle.
Action. — To incline and rotate the head and neck toward the side on which the muscle is
placed. When both muscles act, the head and neck are extended.
Variations. — The extent of separation and of fusion of the two muscles varies. Absence
of either muscle is rare. The splenius capitis may be divided into mastoid and occipital portions.
The attachment of the muscle also varies somewhat. Occasionally the spinal origin of the
splenius may extend to the cranial end of the ligamentum nuchae. The origin may extend later-
ally over the fascia covering the deeper dorsal muscles. An accessory slip, the splenius cervicis
accessorius, separated from the main muscle by the tendon of the serratus posterior superior,
is frequently (8 per cent, of instances, LeDouble) found to run from the lower cervical or upper
thoracic vertebrae to the transverse process of the atlas.
The sacro -spinalis (erector spinas). — Origin. — (1) From a strong aponeurosis attached to
the spines of the lumbar, and the sacral vertebrae, to the ligament passing from the sacrum to the
coccyx, to the lateral sacral crest, the sacro-tuberous ligament, the long posterior sacro-ihac
ligament, and to the dorsal fifth of the iliac crest; (2) directly from the iliac crest in front of
and lateral to the attachment of the aponeurosis; and (3) from the short posterior sacro-iliac
MUSCLES OF THE BACK
415
ligaments. The aponeurosis covers the muscles of the sacral region and is there united to
the overlying fascia by more or less dense areolar tissue. Opposite the iliac crest fibre-bundles
begin to take origin from the lateral margin of the dorsal surface as well as from the deep or
Fig. 381. — The Fifth Layer of the Muscles of the Back.
Semispinalis capitis
Longissimus capitis
Longissimus cervicis
Ilio-costalis cervicis
Longissimus dorsi
Ilio-costalis dorsi
Spinalis dur i —
nio-costalis lumborum
Obliquus internus-
SacrospinaliS'
Seventh cervical vertebra
Twelfth thoracic vertebra
Fifth, lumbar vertebra
ventral surface of the aponeurosis of origin, and gradually the line of dorsal attachment extends
medially until, in the lower thoracic region, the tendon becomes completely embedded in the
muscle-fasciculi which take their origin from it. The aponeurosis, which is the strongest in
the lower lumbar region, is composed chiefly of fibres which take a direction upward and some-
what lateralward.
416 THE MUSCULATURE
In the lower lumbar region the sacro-spinalis (erector spinae) muscle begins to show a
distinct division into its two chief component parts, the ilio-costalis and the longissimus.
The parts of which the ilio-costalis and longissimus are composed will be taken up separately.
The ilio-costalis lumborum (figs. 381, 382). — Origin. — (1) Chiefly from the back of the
sacrospinal aponeurosis, medial to and cranialward from the iliac crest, and (2) from the iliac
crest directly. The deep medial surface of the muscle is closely united in the lumbar region
to the longissimus.
Structure and insertion. — From the mass of fibre-bundles which compose the muscle, fas-
ciculi are given off which are attached chiefly by tendinous slips to — (l)the tips of the transverce
processes of the lumbar vertebrse; (2) the fibrous processes which extend lateralward from the
tips of the transverse processes of the upper lumbar vertebrte into the anterior layer of the lumbo-
dorsal fascia; (3) the inferior margin of the last six or seven ribs near the angles. The inser-
tions into the lumbo-dorsal fascia and the twelfth rib are usually fleshy. The portions attached
to the lumbar vertebrse are by some considered to belong to the longissimus (Eisler).
Relations. — The muscle lies on the lateral margin of the longissimus and upon the ribs and
the external intercostal and levatores costarum muscles, and under the axio-appendicular
muscles described above.
The ilio-costalis dorsi (accessorius). — Origin. — By fleshy fasciculi from the superior borders
of the lower seven ribs medial to the angles.
Structure and insertion. — The slips of origin lie beneath the preceding portion of the muscle,
pass medial to and partly fuse with it, and give rise to a belly from which tendinous shps extend
to be inserted into the upper seven ribs near their angles and to the transverse process of the
seventh cervical vertebra.
Relations. — The muscle Ues upon the ribs and the external intercostal muscles lateral to the
longissimus.
The ilio-costalis cervicis (cervicalis ascendens). — Origin. — By fleshy shps from the upper
borders near the angles of the seventh to the third (sometimes to the second or first) ribs.
Structure and insertion. — The slips of origin are covered by the slips of insertion of the dorsal
portion (accessorius). They emerge medial to them and give rise to a fleshy beUy from which
tendons pass to the backs of the transverse processes of the sixth to the fourth cervical vertebrse.
Relations. — The scalenus posterior hes in front, the levator scapulse at the side, and the
splenius and longissimus (transversalis) cervicis medial to this muscle.
A bursa is frequently found between the muscle and the tubercle of the first rib.
The longissimus dorsi (figs. 381, 382). — Origin. — (1) From the deep surface of the sacro-
spinal aponeurosis; (2) from the short posterior sacro-iliac ligaments; and (3) through accessory
slips which arise from the transverse processes of the first two lumbar and the last five or six
thoracic vertebrse. In the lumbar region it is fused dorso-laterally with the ilio-costalis.
Structure and insertion. — From the muscle mass arise fasciculi which are inserted partly
directly, partly by means of tendons, into — (1) the lower border of the back of the transverse
processes of the lumbar vertebrse and the inferior margins of the ribs lateral to the tubercles; and
(2) the accessory tubercles of the lumbar and the tips and inferior margins of the transverse
processes of the thoracic vertebra. The attachment to the first rib is usually wanting. The
attachment to the first five ribs may fail. The medial attachments seldom extend to the first
vertebra.
Relations. — The lateral margin of the muscle is covered by the ilio-costahs. Medially it
overlies the transverso-spinal muscles. The lateral branches of the dorsal veins, arteries, and
nerves pass mainly in the fibrous tissue which separates the longissimus from the ilio-costalis,
the medial branches chiefly between the longissimus and the transverso-spinal muscles. The
relations to the axio-appendicular muscles and to the dorsal fascia have been pointed out above.
Ventrally it lies upon the intertransverse muscles, the external intercostals, and the levatores
costarum.
The longissimus cervicis (transversalis cervicis). — Origin. — By tendinous slips from the
transverse processes of the first four to six thoracic vertebrse.
Structure and insertion. — The fasciculi which arise from these slips give rise to a muscle belly
from which tendons of insertion extend to the posterior tubercles of the transverse processes of
the mid-cervical (second to sixth) vertebrse.
Relations. — This muscle lies between the longissimus dorsi and capitis with which it is to
some extent fused and the ilio-costahs dorsi (accessorius) and cervicis (cervicalis ascendens)
muscles.
The longissimus capitis (trachelo-mastoid). — Origin. — By tendinous slips from the trans-
verse processes of the first three or four thoracic vertebrse and the articular processes of the last
four cervical.
Structure and insertion. — The muscle fasciculi arising from these tendons form a belly which
is united to the mastoid process by a short tendon. A tendinous inscription often crosses the
muscle.
Relations. — It lies ventral to the splenius capitis, lateral to the semispinalis capitis (com-
plexus) and medial to the longissimus cervicis (cervicalis ascendens).
Nerve-supply of the sacro-spinalis. — From the lateral branches of the posterior divisions of
the spinal nerves. The exact distribution of these branches is too complex to be treated here.
The nerves for the ilio-costalis arise from the eighth cervical to the first lumbar, those for the
longissimus from the first cervical to the fifth lumbar.
Action of the sacro-spinalis. — The sacro-spinalis serves, when acting on one side, to bend
the spinal column toward that side, and when acting on both sides, to extend the spinal column.
The cranial portions of the muscle serve to inchne the head toward the same side, and when
both muscles act they serve to extend the head. The ilio-costalis muscle has the greatest power
for producing lateral inclination. The ilio-costalis lumborum depresses the ribs, while the
ilio-costalis cervicis (cervicalis ascendens) may aid in elevating them. The spinahs muscle
serves merely as an extensor.
MUSCLES OF THE BACK 417
Variations of the sacro-spinalis. — The slips of origin and insertion of the various parts of
this muscle and the extent of fusion of the various parts vary greatly. Statistical data from
which the most frequent conditions might be determined are wanting. Tendinous inscriptions
may extend across the longissimus cervicis and other parts of the sacro-spinaUs.
B. Deep Lateral Dorsal System
The intertransversarii. — These are vertical bands composed of short bundles which pass
between the transverse processes of the cervical, lumbar, and the lower thoracic vertebrae.
(a) Ceroical (fig. 349). — Ventral, lateral and dorsal muscles are found in the cervical region.
The ventral and lateral muscles run between the ventral tubercles and tips of the transverse
processes of the vertebrae, are homologous with the intercostal muscles, are supplied by branches
from the anterior divisions of the corresponding spinal nerves, and have been described above
(p. 356). The dorsal muscles run between the dorsal tubercles and belong to the intrinsic
dorsal musculature. They are supplied by the lateral branches of the posterior divisions of the
cervical nerves.* The three sets of muscles are, however, more or less fused. The first pair
of muscles extends between the atlas and axis, the lowest passes to the transverse process of the
first thoracic vertebra, or to the first rib close to this. The obliquus capitis superior (described
later) belongs, however, to the posterior set of muscles, the rectus capitis laigralis (p. 356) to
the lateral set. The vertebral artery runs vertically between each pair of muscles above the
sixth, and the anterior division of each cervical nerve passes laterally between the artery and the
dorsal muscle in each space, and then out between the ventral and lateral muscles. The pos-
terior division of each cervical nerve passes medial to each dorsal muscle.
(b) Thoracic. — Small muscle f ascicuh may extend between the transverse processes of the
thoracic vertebrae and between the last thoracic and first lumbar. They are most frequent in
the upper and lower thoracic regions. Often they are replaced by tendinous bands. In the
second interspace the insertion may extend to the rib near the transverse process. The inner-
vation is from the lateral branches of the posterior divisions of the spinal nerves.
(c) Lumbar (fig. 383). — In the lumbar region there is a lateral set of muscles connecting
the adjacent margins of the transverse processes and a medial connecting the mammary tubercle
of one vertebra to the mammary or the accessory tubercle of the vertebra next above. They
extend between each two of the five lumbar vertebrae and sometimes also to the first sacral.
They lie between the sacrospinalis and psoas muscles. The medial muscles are supplied by
the lateral branches of the posterior divisions of the spinal nerves. The lateral muscles are
supplied by branches from the junction between the two divisions of the corresponding spinal
nerves. These branches probably belong to the anterior divisions.
Action. — The intertransverse muscles bend the spinal column laterally, and when acting
on both sides, make it rigid.
Variations. — The number of intertransverse spaces occupied by the muscles varies, espe-
cially in the thoracic region. They may be doubled or extend over more than one interspace.
C. Superficial Medial Dorsal System
The spinalis dorsi. — Origin. — By tendinous bands from the tips of the two upper lumbar
and the last two thoracic spines.
Structure and insertion. — From the deep surface of the tendinous bands there arises a long
slender muscle belly which is fused laterally with the longissimus dorsi. It is attached by
tendinous processes to the spines of the upper thoracic vertebrae, usually the second or third to
the ninth.
Nerve-supply. — From the medial divisions of the sixth to ninth thoracic nerves.
The spinalis cervicis. — A muscle of inconstant development which arises from the spines
of the two upper thoracic and two lower cervical vertebrae and extends to the spines of the second
to the fourth cervical vertebrae. The nerve supply is from the dorsal divisions of the lower cer-
vical nerves.
Action. — To extend the vertebral column.
Variation. — There is great variation in the development of the spinaUs muscles. Similar
fasciculi are sometimes found in the lumbar region and in the cervical region sometimes extend
to the skull.
D. Deep Medial Dorsal System
1. Vertebro-occipital Muscle
The semispinalis capitis (complexus) (fig. 381). — This muscle is usually separated from the
semispinalis muscles of the back and neck by a well-marked septum and has a distinctive
structure.
Origin. — (1) By long tendinous fasciculi from the tips of the transverse processes of the
upper five or six thoracic vertebrae and of the seventh cervical vertebra; (2) by short fleshy
processes from the articular processes and bases of the transverse processes of the third to the
sixth cervical vertebrae; and (3) by delicate fleshy fasciculi from the spinous processes of the
upper thoracic vertebrae.
Structure and insertion. — The sUghtly diverging fibre-bundles form a long, flat belly which
is inserted, partly by means of an aponeurosis which covers the muscle laterally, into the lower
* According to Lickley, both sets of cervical intertransverse muscles are supphed by the
anterior divisions of the spinal nerves.
418
THE MUSCULATURE
surface of the squamous portion of the occipital, between the superior and inferior nuchal hnes.
There is often a transverse tendinous inscription across the muscle opposite the sixth cervical
vertebra, and less frequently one between the upper and middle thirds of the muscle. These
Fig. 382. — The Fifth Layer of the Muscles of the Back, after separating the Longis-
SIMUS AND IlIO-COSTALIS DIVISIONS.
Obliquus superior
Rectus capitis posterior major
Obliquus capitis inferior —
Longissimus capitis
Longissimus cervicis
Ilio-costalis cervicis
Ilio-costalis dorsi
Ilio-costalis lumborum
Insertion of ilio-costalis upon lum-
bar transverse processes
Rectus capitis posterior
Seventh cervical vertebra
— Longissimus dorsi
Twelfth thoracic vertebra
Fifth lumbar vertebra
Sacrospinalis
are best marked in the medial portion of the muscle, which comes from the thoracic vertebra
and is sometimes separately designated as the spinalis capitis {hiventer cervicis).
Nerve-supply. — It is suppUed chiefly by the medial branches of the posterior divisions of the
first four or five cervical nerves. The muscle also gets some twigs from the lateral branches.
SUBOCCIPITAL MUSCLES 419
Relations. — It lies dorso-lateral to the suboccipital muscles and to the semispinalis cervieis.
From this latter it is separated by a septum containing the descending branch of the occipital
artery, the deep cervical artery, and the medial dorsal branches of the cervical nerves. It is
covered laterally by the longissimus capitis (trachelo-mastoid), and dorsally by the splenius,
and above the upper margin of the splenius by the trapezius.
Action. — To extend the head and to inchne it slightly toward the same side.
Variations. — The origin of the muscle may extend to the eighth thoracic vertebra or merely
to the first thoracic. It may be fused with the longissimus (transversahs) cervieis. A special
fasciculus may run beneath the muscle from the upper thoracic vertebrse to the head. The ori-
gin from the spinous processes of the thoracic vertebrse is not constant. The part of the muscle
arising from this origin may be looked upon as a spinalis capitis.
2. Transversospinal Muscles
The semispinalis dorsi et cervieis (fig. 383). — This superficial transverso-spinal muscle sheet
extends from the twelfth thoracic to the second cervical vertebra. The fasciciili which compose
it arise by short tendons from the backs of the transverse processes, and are inserted by short
tendons into the spines.
The semispinalis dorsi. — Origin. — From the sixth to the tenth or twelfth thoracic vertebrae.
Insertion. — The upper four to six thoracic and the last two cervical vertebrae. The fas-
cicuh extend over four to six vertebrae.
Nerve-supply. — Third to sixth thoracic.
The semispinalis cervieis. — Origin. — From the upper five or six thoracic vertebrse.
Insertion. — Into the fifth to the second cervical vertebrae. The fascicuU extend over four
. to five vertebrae.
Nerve-supply. — Third to sixth cervical.
Relations. — This muscle lies beneath the longissimus dorsi and the semispinalis capitis
(complexus) and over the following musculature.
Variations. — A semispinalis lumborum is a muscle rarely found extending from the lumbar
to the lower thoracic vertebras.
The multifidus (fig. 383). — This second layer of transverso-spinal musculature extends from
the sacrum to the second cervical vertebra. It is best developed in the lumbar region and least
so in the thoracic.
Origin. — (1) From the groove on the back of the sacrum between the spines and the ar-
ticular elevations, from the dorsal sacro-iliao ligaments, from the dorsal end of the Uiac crest, and
from the deep surface of the aponeurosis of the sacrospinal muscle; (2) from the mammary and
accessory processes of the lumbar vertebrae; (3) from the backs of the transverse processes of the
thoracic vertebrae; and (4) from the articular processes of the fourth to the seventh cervical
vertebrae and the back of the transverse process of the seventh.
Insertion. — Spinous processes of the lumbar, thoracic, and lower six cervical vertebrae.
Structure. — The more superficial fasciculi arise by short tendinous processes, the deeper
ones directly. The more superficial fasciculi extend to the fourthor fifth vertebra above, the
middle to the third, and the deepest to the second above.
The rotatores. — These, the third layer of transverso-spinal muscles, extend from the sa-
crum to the second cervical vertebra. They are composed of short fleshy fascicuh which ex-
tend to the second vertebra above (rotatores longi) and to the first above {rotatores breves). The
fasciculi arise from the back and upper borders of the transverse processes or their homologues,
and are inserted into the laminae of the preceding vertebrae. They are best developed in the
thoracic region. Some authors consider the rotatores breves confined to the thoracic region.
In the cervical region the fascicuU usually run from articulai- processes to the bases of the spines,
in the lumbar region from the mammary processes to the caudal margin of the laminae of the
arches.
3. The Interspinal Muscles
The interspinales consist of short fasciculi which extend from the upper surface of the spiae
of each vertebra near its tip to the lower surface of the spine of the vertebra above. In the
neck the muscles lie in pairs between the bifid extremities of the vertebrae. In the lumbar
region they form broad bands attached to the whole length of the spinous processes and are
separated by the interspinous hgaments. In the thoracic region they usually are undeveloped.
Nerve-supply of medial dorsal muscles. — These are all supplied by the medial branches
of the posterior divisions of the spinal nerves.
Action of medial dorsal muscles. — These muscles extend the spinal column when acting on
both sides. When acting on one side, they produce a movement of rotation toward the opposite
side.
E. StTBOCCiPiTAL Muscles
(Figs. 382, 383)
The rectus capitis posterior major. — Origin. — From the upper surface of the spine of the
epistropheus.
Structure and insertion. — The muscle-fibres diverge to form a broad triangular band which
is inserted into the lateral half of the inferior nuchal line of the occipital bone and the area
below it. Its insertion is immediately below that of the obliquus superior.
The rectus capitis posterior minor. — Origin. — From the upper part of the side of the posterior
tubercle of the atlas.
420
THE MUSCULATURE
Structure and insertion.— The fibre-bundles diverge to form a flat, triangular sheet inserted
below the medial third of the inferior nuchal line of the occipital bone on the mfenor surface ot
the squama occipitalis. .^ , , „ ^-^ -j c 4.1. ■ e
The obliquus capitis inferior.— Origrm.— From the upper part of the side ot the spme 01
the epistropheus (axis). , ., , ,, , . 1 • ■ ^ j 1.
Structure and i«se»«io?i.— The fibre-bundles form a fusiform beUy which is inserted by a
short tendon into the lower part of the tip of the transverse process of the atlas.
Fig. 383. — The Tkansverso-spinalis.
Obliquus capitis superior
Rectus capitis posterior major
Obliquus capitis inferior mi
Multifidus spinsE'
Semispmalis cerviciS'
Ilio-costalr
Longissimus dorsi.
Levator costee
Longissimus dorsi-
Ilio-costalii
Obliquus internuS'
Seventh cervical vertebra
Semispinalis dorsi
Twelfth thoracic vertebra
Fifth lumbar vertebra
Multifidus
The obliquus capitis superior.— Onffiw.— From the back of the upper part of the trans-
verse process of the atlas. n ^ ^ ■ 1 ^ .„„i„ ,-r.
Structure and insertion.— The fibre-bundles diverge to form a flat, triangular muscle in-
serted into the lateral third of the inferior nuchal line of the occipital bone, and above the lateral
part of the insertion of the rectus capitis posterior major.
MUSCLES OF THE BODY WALL
421
Fig. 384, A and B. — Sections through the Left Side op the Trunk in the Regions shown
IN THE Diagram.
The muscles of the body wall have been sUghtly pulled apart in order to reveal the relations
of muscles, fasciae, and aponeuroses, a and 6 in the diagram indicate sections A and B,
fig. 351 (p. 352); a- and 6^, sections A and B, fig. 357 (p. 366); a^" and 6', sections A and B,
fig. 407 (p. 458):
1. Aorta. 2. Arteria mammaria interna. 3. Costa VI — a, cartilage. 4. Costa VII — a,
cartilage. 5. Costa VIII. 6. Costa IX. 7. Costa X. 8. Costa XI. 9. Descending
colon. 10. Diaphragm — a, costal portion; b, lumbar portion; c, sternal portion; d, cen-
trum tendineum. 11. Fascia lumbodorsalis — a, anterior layer; b, posterior layer. 12.
Fascia transversalis. 13. Flexura colica sinstra (splenic flexure). 14. Kidney. 15.
Liver. 16. Linea alba. 17. Musculi intercostales externi — a, ligament. 18. Mm.
intercostales interni. 19. M. iho-costalis. 20. M. latissimus dorsi. * 21. M. levator costee.
22. M. longissimus dorsi. 23. M. obUquus abdominis externus. 24. M. obhquus
abdominis internus. 25. M. psoas major. 26. M. quadratus lumborum. 27. M. rectus
abdominis. 28. M. serratus posterior inferior. 29. M. subcostalis. 30. M. transversus
thoracis. 31. M. transversus abdominis. 32. Mm. transverso-spinales. 33. M. trape-
zius. 34. Nervus lumbalis I. 35. N. thoracalis VI. 36. N. thoracalis VII. 37. N.
thoracalis VIII. 38. N. thoracahs IX. 39. N. thoracalis X. 40. N. thoracaUs XI.
41. N. thoracalis XII. 42. Sympathetic trunk — a, great splanchnic nerve. 43. Omen-
tum majus. 44. CEsophagus. 45. Scarpa's fascia. 46. Spleen. 47. Stomach. 48.
Ureter. 49. Vertebra lumbalis II. 50. Vert, lumbalis III. 51. Vert, thoracalis X.
4 36181723 5 371817
142 14 49 48 2534 SO 47 32
422 THE MUSCULATURE
Nerve-supply.- — These muscles are all supplied by the posterior branch of the suboccipital
(first cervical) nerve. The branch to the two rectus muscles passes across the dorsal surface
of the major rectus and supphes branches to the middle of the dorsal surface of each muscle.
The branch to the superior oblique muscle enters the middle of the medial margin, that to
the inferior oblique about the middle of its superior margin. The inferior oblique and major
rectus muscles usually, the other muscles occasionally, receive branches from the second cervical
nerve.
Relations. — The two oblique muscles with the rectus major serve to bound a small tri-
angular space, the suboccipital triangle, through which pass the dorsal division of the sub-
occipital nerve and the vertebral artery. The two minor recti lie on the atlanto-occipital
membrane in the upper part of the space bounded by the major recti. The muscles are covered
medially by the semispinalis capitis (complexus), laterally by the longissimus and splenius
capitis. In front of the two oblique muscles and the major rectus runs the vertebral artery.
The great occipital nerve runs between the semispinalis capitis (complexus) and the inferior
oblique and the two recti in a dense fatty connective tissue containing the extensive sub-
occipital venous plexus.
Action. — The rectus muscles and the superior oblique draw the head backward. The
rectus major and the inferior obUque, when acting on one side, rotate the face toward that side.
Variations. — Each of these muscles may be doubled by longitudinal division. Accessory
sUps may connect the two recti with the semispinahs capitis. The atlanto -mastoid is a small
muscle frequently found. It passes from the transverse process of the atlas to the mastoid
process.
IV. THE THORACIC-ABDOMINAL MUSCULATURE
The thoracic and abdominal viscera are contained within cavities, the ventro-
lateral walls of which may be contracted and expanded by muscular action. The
skeletal support for the intrinsic musculature of these walls consists of the ribs,
the sternum and the vertebral column and the pelvis. The intrinsic musculature
in the thoracic walls is situated chiefly between the ribs {intercostal muscles, figs.
385, 386) while in the region of the abdomen it extends in broad sheets from the
lower part of the thorax to the pelvis (the quadratus lumborum and the external
and internal oblique, transverse, and reciws muscles, figs. 387, 388, 390, 406). Be-
tween the two cavities, attached to the lower part of the thorax and to the lumbar
vertebrae lies the dome-shaped diaphragm (fig. 391). The thoracic cavity ex-
tends on each side slightly above the first rib. The abdominal cavity extends
downward and backward into the pelvis, as the pelvic cavity.
The function of the intercostal muscles is to expand and contract the thoracic cavity for
the sake of respiration. The shape of the ribs and their articulations with the vertebrae are
such that a slight rotation of the neck of each rib will cause the shaft to swing outward and up-
ward or in the reverse direction. The costal cartilages are elastic enough to permit this move-
ment, and at the same time are strong enough to make the thorax an effective skeletal apparatus.
Ninety joints are called into play in the movements of the thorax (24 between the heads of
the ribs and the vertebrte, 20 between the tuberosities and the transverse processes of the ver-
tebras, 24 between the ribs and costal cartilages, 14 between the costal cartilages and the sternum,
6 between the costal cartilages and 2 intrasternal). When the shafts of ribs are swung outward
and upward the thorax is enlarged in the antero-posterior and transverse axes. In the adult
when standing the sternum may be raised nearly 3 cm., and protruded 1 cm. The cartilages
of the lower ribs may be raised 4 to 5 cm. The side of the thorax at the level of the second
rib may be protruded 3 cm., and at the level of the eighth rib nearly as far. This extent of
movement, however, is found only in forced respiration. In ordinary quiet respiration it is
far less, the sternum being raised merely 3 or 4 mm. and protruded 2 mm., and the thorax is
enlarged at the side merely 5 mm. (R. Fick). The chief muscles used in quiet inspiration are
the external intercostals and the intercartOaginous parts of the internal intercostals.
During inspiration the diaphragm contracts so that the thoracic cavity is further enlarged
perpendicularly. The extent of movement of the upper part of the diaphragm is estimated by
R. Fick at from 14-3 cm.
The ventro-lateral abdominal muscles contract the thoracic cavity by depressing the
thorax and by pushing the diaphragm upward. They directly contract the abdominal cavity.
Contraction of the abdominal cavity is of aid in defecation and parturition. The abdominal
muscles are also of value in flexion, abduction, and rotation of the vertebral column and pelvis.
The thorax, with its intrinsic musculature, is in large part covered by the musculature
which extends from the tnmk to the shoulder girdle and arm; dorsally by the trapezius and
rhomboids, ventrally by the pectoral muscles, and laterally by the serratus anterior and the
latissimus dorsi, as well as by the scapula and the muscles which pass from it to the humerus.
The upper extremity on each side is largely supported from the spine by the trapezius, rhomboid
and levator scapulae muscles but it none the less exerts some pressure on the thorax and inter-
feres to some extent with respiration. If the girdle and arm are fixed or raised the muscles
which pass from them to the thorax are an aid in forced inspiration. Advantage of this is
taken when in artificial respiration the arms are raised so as to hft the ribs through traction
by the latissimus dorsi, the pectoralis muscles and the subclavius. Some of the muscles of the
neck, especially the scalene muscles and the sterno-cleido-mastoid, are Ukewise of value in forced
inspiration.
THORACIC-ABDOMINAL MUSCLES 423
Expiration is produced not only by the part ofthe internal intercostals which lie between the
bony ribs, and by the abdominal muscles, but also by the lumbar ilio-costales and by the quad-
ratus lumborum.
The intrinsic muscles of the thorax and abdomen are derived from the twelve
thoracic myotomes and the first one or two lumbar and are innervated by the
corresponding nerves, while the musculature of the shoulder girdle and arm which
covers the intrinsic muscles of the thorax is of cervical origin an d is innervated
by cervical nerves. The diaphragm is likewise of cervical origin and is innervated
by the phrenic nerve from the cervical plexus. .,
The intrinsic muscles of the back extend over the thoracic musculature (ex-
ternal intercostals and levators of the ribs, fig. 383) and in turn are in part covered
by muscles which extend dorsally from the thoracic region (posterior serrate
muscles, fig. 380).
The intrinsic thoracic-abdominal muscles are composed laterally of three layers
of sheet-like muscles.
In the external layer the fibre bundles run downward and ventralward. This
layer is represented in- the thoracic region by the external intercostal muscles, the
levators of the ribs and the posterior serrate muscles. The fibre-bundles of the
external intercostals (fig. 385), extend between each pair of ribs but between the
costal cartilages are replaced by fibrous tissue, the external intercostal ligaments.
The levatores costarum (fig. 383), extend from the transverse process of one
vertebra to the rib which articulates with the next vertebra below and in some
instances the fibre bundles are continued to the second rib below.
The serratus posterior superior and inferior (fig. 380) , are derivatives of the
external oblique which during development wander in part over the intrinsic
dorsal musculature. The superior serrate arises from the spines of the last two
cervical and first two thoracic vertebrae and is inserted into the second to the
fifth ribs. The inferior serrate muscle arises from the spines of the last two tho-
racic and first two lumbar spines and is inserted into the last four ribs. The fibre-
bundles of this muscles therefore take a direction opposite to that of the other
muscles of the group. The muscles aid in inspiration. In the abdominal region
the external layer is represented by the external oblique muscle (fig. 387). This
arises by digitations from the last seven ribs and is inserted into the crest of the
ilium and by means of a broad flat aponeurosis into the Hnea alba in the mid-
ventral fine and into the inguinal Hgament below. The external intercostal,
levatores costarum, and posterior serrate muscles are innervated from branches
which arise near the tubercles of the ribs. The external oblique muscles are inner-
vated by branches which in large part arise in conjunction with or from the lateral
branches of the anterior divisions of the last seven thoracic nerves and frequently
also by branches from the ilio-hypogastric.
The middle layer of the lateral thoraco-abdominal musculature is composed of
fibre-bundles which run downward and backward obliquely across the fibre-bundles
of the external layer. In the thoracic region it is represented by the internal
intercostal and subcostal muscles. The internal intercostal (fig. 385) muscles lie
between the costal cartilages and between the ribs as far dorsalward as the angles,
beyond which they are replaced by membranous tissue and by the subcostal
muscles. The latter, instead of extending from one rib to the next rib below, ex-
tend to the second or third rib below. They are best developed in the lower part
of the thoracic cavity. In the abdominal region the middle layer is represented by
the internal oblique muscle (fig. 388) . This arises from the lumbo-dorsal fascia,
the crest of the ilium and the inguinal ligament and is inserted into the sheath of
the rectus abdominis muscle and into the inferior margins of the ventral extremi-
ties of the three lower ribs. The aponeurosis, which helps to form the sheath of
the rectus, divides in the upper abdominal region into two layers, one of which
passes in front and the other of which passes behind the rectus to be inserted into
the linea alba in the mid-ventral line. In the lower third of the ventral abdominal
wall both layers pass in front of the rectus. The fibre-bundles which compose the
internal obUque muscles do not all follow the usual course of the fibre-bundles of
this layer. At the level of the iliac crest they pass nearly transversely across the
body and below here they slant downward and forward. Just above the in-
guinal ligament and medial to its centre the internal oblique muscle is continuous
with the thin cremaster muscle (fig. 389), which is prolonged over the spermatic
cord and the tunica vaginalis of the testis and epididymis in the male and over the
424 THE MUSCULATURE
ligamentum teres in the female. The cremaster muscle is attached laterally
to the inguinal ligament, medially to the outer layer of the sheath of the rectus
near the insertion of the latter.
The inner layer of the thoraco-abdominal musculature is composed of fibre
bundles which take a course transversely across the body. In the thoracic region
it is represented by the transversus thoracis (fig. 386) , a slightly developed muscle
which arises from the costal cartilages of the third to sixth ribs and is inserted into
the lower part of the sternum and into the xiphoid process. In the upper portion
of the muscle the fibre-bundles extend obliquely downward and forward instead of
transversely. In the abdomen this layer is represented by the transversus
abdominis (fig. 390) which arises from the cartilages of the lower seven ribs, from
the lumbo-dorsal fascia, the iliac crest and lateral part of the inguinal ligament and
is inserted into the linea alba by means of an aponeurosis which lies behind the
rectus in the upper two-thirds of the ventral wall of the abdomen and in front in
the lower third. It is intimately fused with the aponeurosis of the internal
oblique.
The main trunks of the anterior divisions of the last five or six thoracic nerves
give rise to branches which supply the muscles both of the middle and inner layers
of the lateral thoraco-abdominal musculature. In the abdominal region these
trunks run in the main between the two layers. Some muscular branches are
usually also supplied from the ilio-hypogastric and ilio-inguinal nerves. In the
thoracic region the intercostal nerves run external to the subcostal muscles,
through the substance of the costal part of the internal intercostal muscles, and
internal to the parts of the internal intercostals which lie between the costal
cartilages. Eisler includes the subcostal muscles and that part of the internal
intercostals which lies internal to the nerve trunk, with the inner rather than with
the middle layer of the thoracic musculature.
The ventral part of the muscular thoraco-abdominal wall is represented by a
single muscle on each side, the rectus abdominis muscle, except just above the
symphysis pubis where the rudimentary pyramidalis is usually found. The rec-
tus abdominis muscle (fig. 388), is a band-like muscle which arises from the ventral
surfaces of the fifth to the seventh costal cartilages and from the xiphoid process
and is inserted into the superior ramus of the pubis. It is ensheathed by the ap-
oneuroses of the lateral abdominal musculature described above. The component
fibre-bundles run nearly parallel with the mid-sagittal line. Transverse inscrip-
tions partially divide the muscles into segments. It is innervated by the last six
or seven thoracic nerves. The pyramidalis (fig. 388) is a small muscle which
arises from the superior pubic ramus and is inserted into the linea alba for about a
third of the distance to the umbilicus.
The lateral intertransverse muscles of the lumbar region described on p. 417
probably belong to the ventro-lateral musculature of the trunk. The nerves
supplying them come from the junction between the posterior and anterior
divisions of the spinal nerves.
The inguinal (Poupart's) ligament and the inguinal canal, described in detail
below, are of considerable practical interest because of the frequency of hernias
in this region. In the quadrupeds the pressure of the weight of the abdominal
viscera centres toward the umbilicus while in man it centres toward the ventral
part of the line of attachment of the abdominal wall to the pelvis. The lower
margin of the aponeurosis of the external oblique muscle is here strengthened to
form the inguinal (Poupart's) ligament which extends from the anterior superior
iliac spine to the pubic tubercle. Near the latter it is reflected (curves medial-
ward) to the pubic crest forming the triangular lacunar ligament (Gimbernart's).
The medial half of the inguinal ligament helps to bound a slit-hke space, inguinal
canal through which in the male the spermatic cord passes to the scrotum, and in
the female, the round ligament passes to the labium majus. This canal begins on
the inner side at the (internal) abdominal ring, which is situated above and medial
to the centre of the inguinal ligament. The canal, which is about 4 cm. long,
extends medialward and downward to the subcutaneous (external abdominal)
ring, a slit-like opening in the aponeurosis of the external oblique just above the
inguinal ligament. The canal is bounded ventrally by the aponeurosis of the ex-
FASGIM 425
ternal oblique and the cremaster muscle, below by the reflected portion of the in-
guinal ligament, dorsally by the transversalis fascia and above by the transversus,
internal oblique, and cremaster muscles.
The quadratus lumborum (fig. 406), which extends from the twelfth rib to the
ilium and ilio-lumbar ligament, is supplied by direct branches of the lumbar nerves
in series with the nerves supplying the musculature of the abdominal wall. It
will, therefore, be taken up with the intrinsic thoraco-abdominal muscles. It
depresses the thorax and abducts and extends the spine. The psoas- muscle, on
on the other hand, which also lies at the back of the abdominal cavity, represents
an extension of the intrinsic musculature of the limb to the spinal column (see
p. 455).
The diaphragm (fig. 391), a dome-shaped muscle which is attached to the distal
margin of the thorax and to the upper lumbar vertebrae, and separates the thoracic
and abdominal cavities, arises in the embryo in the region of the neck, and main-
tains cervical relations through its innervation by the phrenic nerves, which spring
one on each side usually from the third to fifth cervical nerves. It does not belong
morphologically with the other muscles considered in this section, but is here
included because of its physiological and anatomical relations and the convenience
of treating it in connection with the intrinsic thoraco-abdominal muscles. A
diaphragm completely separating the thoracic from the abdominal cavities is
found only in the mammals. The central portion of the diaphragm is an aponeu-
rosis or central tendon with a convex ventral and concave dorsal margin. Into
this tendon is inserted the musculature which arises on each side from the xiphoid
cartilage, the cartilages and tips of the last six or seven ribs and by means of three
crura from the sides of the first four lumbar vertebras.
In fishes and tailed amphibians the musculature of the body wall is composed of meta-
merically segmented musculature. In all higher vertebrates it is hkewise at an early embryonic
stage segmental, being composed of the ventro-lateral portions of the myotomes. The ventral
ends of the myotomes give rise to a ventral longitudinal muscle which runs on each side of the
body next the mid-hne in front, and retains more or less of the primitive segmentation. The
rectus abdominis and the infrahyoid muscles represent this system in man. Very frequently
traces of the system may also be seen on the upper thoracic wall in the form of slerider muscular
and aponeurotic slips. The rectus muscle in man is usually developed from the last seven tho-
racic myotomes. The pyramidalis becomes spht ofT from its lower end. The lateral part of
the ventro-lateral portions of the thoracic myotomes usually gives rise to several strata of mus-
cles which vary somewhat in different vertebrates, although quite similar among the mammals.
In man the twelve thoracic and first two lumbar myotomes give rise to the lateral musculature
of the thoraco-abdominal wall.
The quadratus lumborum represents the ventro-lateral portions of the lumbar myotomes
with the exception of that portion of the first two which enter into the lateral abdominal mus-
culature and of the fifth, which probably undergoes retrograde metamorphosis.
It will be noted that the abdominal wall is composed of musculature which has an origin
chiefly from the thoracic myotomes. At an early stage of embryonic development both the
thoracic and the abdominal viscera are covered by a non-muscular membrane. The myotomes
extend into this from the thoracic region, and as the musculature is differentiated, it approaches
the median fine in front and extends distally to the pelvis. Owing to the rotation of the limbs
the abdominal musculature is stretched ventrally over an area corresponding to the lumbar
and sacra! regions dorsally. The last part of the thoraco-abdominal wall to be furnished with
musculature is that about the umbilicus. Occasionally the process fails to be completed in this
region.
Each spinal nerve suppUes primarily the musculature derived from the myotome which lay
caudal to it, and at first the musculature lies wholly superficial to the nerves. With subsequent
differentiation the metamerism is somewhat obscured by anastomosis of nerves and fusion of
myotomes; and a part of the internal oblique layer and all the transverse layer of the lateral
musculature comes to he on the inner side of the main nerve-trunks.
FASCIA
The fasciae and the topographical relations of the thoraco-abdominal muscles may be fol-
lowed in the sections shown in figs. 357, 384, and 407.
Tela subcutanea. — As mentioned above, most of the intrinsic thoracic musculature is cov-
ered by other muscles, while the superficial layer of the abdominal musculature is subcutaneous.
A panniculus adiposus, Camper's fascia, in which much fat may be deposited is usualh' easily
distinguishable, especially in the lower part of the ventral wall of the abdomen, from a membran-
ous fascial sheet which is loosely attached to the underlying fascial envelopment of the muscles.
To this membrane has been applied the term Scarpa's fascia. Near the groin it is separated
from the panniculus adiposus by blood-vessels and lymphatic glands. It is closely bound to the
linea alba between the two rectus muscles, to the fibrous structures in front of the pubic bone,
to the fascia lata below the inguinal ligament, and to the crest of the ihum.
Over the scrotum of the male and vulva of the female both layers of the tela subcutanea are
continued. In the male the fat of the more superficial layer disappears and the two layers
426
THE MUSCULATURE
blend with the fundiform (suspensory) hgament and fascia of the penis and the dartos and sep-
tum of the scrotum.
Muscle fascias and sheaths. — The posterior serrate muscles (fig. 380) are enveloped by two
adherent layers of an aponeurotic sheet that extends as a single membrane between them and is
attached lateralward to the ribs and medialward to the spines of the thoracic vertebrae. The
membrane between the muscles may represent the rudiment of a primitive continuous muscle
such as is found in some lower vertebrates. This membrane may usually be easily separated
from the aponeurosis of the latissimus dorsi on its superficial surface and the lumbo-dorsal
fascia beneath.
The intercostal muscles are covered by delicate, adherent membranes on each surface.
The e.xternal intercostal muscles are continued as aponeurotic bands between thCjCostal cartil-
ages. These serve here as fasciae for the internal intercostals.
Fig. 385. — The Intercostal Muscles.
The external obhque muscle is covered externally by a dense, adherent membrane and in-
ternally by a more delicate membrane except where the muscle is attached to the ribs or fused
with the external intercostal muscles. VentraUy and distally these membrau'es are fused be-
yond the fleshy portion of the muscle to the broad aponeurosis that serves to ensheath the rectus
muscle and cover the lower part of the abdominal wall (fig. 389). Dorsally i,he membranes
are in part attached to the ribs and in part are fused to form a membrane whioh becomes ad-
herent to the deep surface of the latissimus dorsi in the thoracic region and to th(3 lumbo-dorsal
fascia in the lumbar region.
The internal oblique muscle and the transversus abdominis have similar membranous
coverings which are fused to the aponeuroses of origin and insertion of these njusoles. The
membranes on the muscles are, however, much more delicate than that of the extt;rnal obhque.
More or less fusion between the two muscles with disappearance of the membrfj,nes covering
the opposing surfaces takes place, especially in the lower part of the abdominal wall. The super-
ficial muscle fasciae of the external oblique and the fasciae of the internal oblique iire continued
into the thin cremasteric fascia which covers the cremasteric muscle, spermatic corci and testis.
The diaphragm is covered on each surface by a more or less weD-marked adherent membrane.
The transversalis fascia is a thin membrane which lies external to the peritoneum of the ab-
dominal wall. It covers the peritoneal surface of the transversus muscle and its aponeurosis.
Ventrally it is continued across the median line internal to the rectus abdominis. In the lum-
bar region the fascia divides at the lateral margin of the quadratus lumborum (fig. 384), one
lamina of it passing dorsal to this muscle to be attached to the lumbo-dorsal fascia. The other
lamina extends over the ventral surface of the quadratus and becomes fused with the psoas
fascia. Proximally the transversalis fascia becomes fused with the fascial mernbrane adherent
FASCIA
427
to the diaphragm. In the region of the ihac fossa the transversalis fascia is reflected from the
transversus muscle to the ilio-psoas fascia, with which it usually becomes fused. Sometimes,
however, it may be traced as a very delicate membrane over the iliac artery and vein. As
these vessels pass below the inguinal ligament a process from the transversalis fascia is usually
reflected into their sheath.
The sheath of the rectus (figs. 384, 407) is formed externally in the upper portion of its
extent by the aponeurosis of the external oblique which fuses distal to the costal margin with
the external layer of the aponeurosis of the internal oblique. In the lower portion of the abdo-
men this fusion takes place nearer the linea alba than in the upper portion. In the lewer third
of its extent the rectus is covered ventrally by the fused aponeuroses of the two oblique muscles
conjoined with that of the transversus. Internally the rectus is covered in the upper two-thirds
of the abdomen by the inner layer of the aponeurosis of the internal oblique conjoined with that
of the transversus and by the transversalis fascia. In the lower thkd of the abdomen the ap-
oneurosis of the internal obhque, together with that of the transversus, passes in front of the
rectus, leaving the rectus in this portion of its abdominal surface covered merely by the trans-
versahs fascia and the peritoneum. The line which marks the lower limit of the dorsal ensheath-
ment of the rectus by the aponeurosis of the transversus muscle is called the linea semicircularis,
Fig. 386. — The Muscles attached to the Back op the Sternum.
Sterno-hyoid
Stemo-thyreoid
Transversus abdominis
or fold of Douglas. Between the transversalis fascia and the rectus just above the pubis
there is a space filled with loose connective tissue or with fat.
The pyramidalis lies beneath the ventral layer of the sheath of the rectus. From the latter
it is sometimes separated by a distinct fascial layer.
Between the rectus muscles of each side the investing aponeuroses are firmly united into
a dense tendinous band, the linea alba (fig. 389). This is broadest opposite the umbilicus.
Above this it gradually grows narrower toward the xiphoid process to the ventral surface of
which it is attached. From the tip of the xiphoid process it is often separated by a bursa.
Toward the symphysis pubis it extends as a narrow line. Just above the symphysis it divides
to be attached on each side to the tubercle (spine) of the pubis. Behind it broadens into the
adminiculum linem alboe which is attached on each side to the pubis. The linea alba is composed
mainly of the interlacing of the fibres which pass into it from the aponeurotic sheaths of the
rectus abdominis. From it and Scarpa's fascia, a few centimetres above the symphysis, there
arises a broad elastic band, the fundiform ligament (superficial suspensory ligament) of the penis,
which sends a fasciculus on each side of the penis. Below the penis these fasciculi unite.* At
the umbilicus there is a circular opening encircled by dense fibrous tissue and filled with a thick
connective tissue, extending from the tela subcutanea to the subserosa.
* Alex. Hagenton has shown that the linea alba varies much in width. It is relatively wide
in fat people and in foetuses.
428
THE MUSCULATURE
The ventral layer of the lumbo-dorsal fascia and its relations to the abdominal muscles also
merit attention. This lies between the intrinsic dorsal musculature and the quadratus lum-
borum muscle and extends from the twelfth rib to the ilio-lumbar ligament. It is strengthened
by the lumbo-costal ligament, which extends between the transverse processes of the first and
Fig. 387. — Superficial Musculature op Abdomen and Thigh.
Pectoralis major
)rigin of pectoralis
major from aponeu-
rosis of obliquus ex-
ternus
Obliciuus externus
Linea semilunaris
Tensor fasciae latae
Ilio-tibial band
Trapezius
Serratus anterior
Latissimus dorsi
Gluteus maximum
Tendon of biceps
second lumbar vertebras and the twelfth rib, and by fibrous processes which extend into it
from the transverse processes of the lumbar vertebras to which it is attached. With the lateral
margin of this ventral layer the dorsal layer of the lumbo-dorsal fascia is fused. The dorsal
aponeurosis of the transversus muscle is united to the lumbo-dorsal fascia at the line of junction
of the ventral and dorsal layers. The internal oblique muscle, covered externally by a
fascia continued dorsally from the external obhque, arises in part from the dorsal layer of the
lumbo-dorsal fascia near the junction of the two layers.
INGUINAL LIGAMENT
429
The inguinal ligament (Poupart's ligament) (figs. 387, 389, 390) is a strong band which
extends along the distal margin of the aponeurosis of the external oblique from the anterior
superior iliac spine to the pubic tubercle. Internally the iliac fascia is fused to it. Distally
the fascia lata of the thigh is attached to it. The deeper lateral abdominal muscles m part
Fig. 388. — The Pectoralis Minor, Obliquus Internus, Ptramidalis, and Rectus
Abdominis.
Subscapularis
Pectoralis minor
Latissimus dorsi
Pectoralis major
Teres major
Obliquus internus
Pyramidalis
Falx inguinalis
arise from it. Medially near the attachment of the hgament to the pubic tubercle (spine)
diverging fibres are given otT which pass inward and upward to the pecten (crest) of the pubis
and give rise to the triangular lacunar ligament (Gimbernat's ligament). This is fused with the
fascia of the peotineus muscle and bounds the femoral ring. Above the inguinal ligament near
its medial extremity lies the external opening of the inguinal canal, the subcutaneous (external)
430 THE MUSCULATURE
inguinal ring [annulus inguinalis subcutaneus]. This opening is formed by the diverging of
the lower medial fibres which compose the aponeuroiss of the external oblique muscle. The supe-
rior fibres form the upper boundary, superior crus, of the ring and pass to the front of the sym-
physis pubis. The inferior fibres form the inferior boundary, inferior crus, of the ring and pass
to the pubic tubercle (spine). Between these two fibre bands intercrural (intercolumnar)
fibres arch about the lateral boundary of the ring and serve to strengthen the anterior and infe-
rior walls of the inguinal canal. Some of the fibres of the superior crus, intermingled with other
fibres cross to the opposite side of the body and are inserted into the tubercle (spine) and
crest of the pubis and into the superior crus of the opposite side. The structure thus formed
is called the reflected inguinal ligament (CoUes's ligament, or triangular fascia).
Inguinal canal [canalis inguinalis]. — This term is apphed to the slit in the lower margin of
the abdominal wall through which, in the male, the spermatic cord passes, and in the female, the
hgamentum teres. It is not a true canal. The inner end begins at the (internal) abdominal
ring [annulus inguinalis abdominahs]. This is situated just above and slightly medial to the
middle of the inguinal (Poupart's) ligament. Below the hgament in this region lies the femoral
canal through which the femoral vessels pass into the thigh. The (internal) abdominal ring
is covered by the peritoneum and the transversalis fascia. The latter here sends a shallow
funnel-like extension outward to be attached to the spermatic cord. The base of this funnel-
Hke depression toward the inguinal (Poupart's) ligament is formed by a thickened band of
tissue, the tractus ilio-pubicus. Medially and laterally the bundles of fibrous tissue which con-
stitute this tract spread out fan-like, medially over the sheath of the rectus and toward
the pubis, lateraUy over the transversus muscle and toward the crest of the ilium. The trans-
verse abdominal muscle arises from the inguinal ligament nearly as far as the lateral margin of
the abdominal ring. The fibre-bundles of this portion of the muscle course ventralward above
the base of the funnel mentioned above and are inserted by tendons forming a more or less
complete aponeurosis, the "conjoined tendon" [falx inguinalis], common to it and the internal
obhque into the ventral sheath of the rectus abdominis muscle, into the tubercle, crest and
pecten of the pubis and sometimes into the pectineal fascia or the lacunar (Gimbernat's)
ligament. Tendinous bands from the transversahs muscle curve downward medial to the
(internal) abdominal ring and help to strengthen the transversalis fascia here. These bands
constitute the interfoveolar ligament [ligamentum interfoveolare, Hesselbachij. The fibrous
bands constituting this ligament are attached to the lacunar ligament and the pectineal fascia.
From the internal ring the spermatic cord (or in the female the hgamentum teres) passes
downward and forward in a space (inguinal canal) about 4 cm. long and then through the sub-
cutaneous (external abdominal) ring which has been described in connection with the inguinal
ligament. The ventral wall of the inguinal canal is composed of the aponeurosis of the external
oblique, the intercrural fibres, and the cremaster muscle. Laterally it is also covered by the
caudal portions of the internal oblique and transversus muscles. The caudal wall or floor of
the space is formed chiefly by the lacunar (Gimbernat's) hgament and laterally also by the iho-
pubic tract. Cranialward the lateral part of the space is covered by the transversus and internal
oblique muscles, the medial part by the cremaster muscle. The dorsal (internal) wall is formed
mainly by the transversalis fascia. IMedially the lacunar (Gimbernat's) ligament and the con-
joined tendon (falx inguinahs), when this is well developed, help to form the dorsal wall.
Lateral to these structures the dorsal wall is thinner but may be strengthened by a well developed
ilio-pubic tract. Near the (internal) abdominal ring it is strengthened by the interfoveolar
ligament, and sometimes by muscle slips (interfoveolar muscle).
Abdominal fossae in the inguinal region. — The hernias so frequent in this region make a
special study of the inner surface of the abdominal wall of considerable practical importance.
Medial to the abdominal (internal) inguinal ring the inferior internal epigastric vessels give rise
to a shght fold (plica epigasirica) which slants medialward and upward toward the rectus muscle.
From the lateral margin of the tendon of insertion of the rectus muscle upward toward the
umbilicus over the obliterated umbilical artery there extends a better marked fold, the plica
umbilicalis lateralis. Lateral to the plica epigastrica lies the fovea inguinalis lateralis, with the
internal inguinal ring. Between the phca epigastrica and the phca umbihcalis laterahs lies the
fovea inguinalis medialis. In the latter region the fascia transversalis which here forms the
inner wall of the inguinal canal is strengthened by two longitudinal fibrous bands belonging to
the aponeurosis of the transversalis muscle and described above, the hgament interfoveolare
at the medial side of the (internal) abdominal ring, and the falx inguinalis (conjoined tendon)
lateral to the rectus muscle. These bands vary in width. When they are narrow the part of
the internal wall of the inguinal canal covered merely by the thin transversalis fascia and the
peritoneum is relatively large and, since this region hes behind the subcutaneous (external
abdominal) ring, opportunity is offered for direct inguinal hernia.
JVIUSCLES
A. Ventral Division
The rectus abdominis (fig. 388). — Origin — Ventral surface of the fifth to seventh costal
cartilages, the xiphoid process, and the costo-xiphoid ligament.
- Insertion. — The upper border of the body of the pubis and the ventral surface of the
symphysis.
Structure. — The muscle is long, flat, and somewhat triangular in form. Cranialward it is
broad and thin; caudalward it becomes thicker as it converges toward the insertion. The
fibre-bundles of the muscle have a longitudinal course. It is crossed by several incomplete,
zigzag, transverse tendinous bands, inscriptiones tendinese, better developed on the ventral
than on the dorsal surface of the muscle and intimately united to the ventral sheath of the rectus.
One of these, corresponding segmentally to the tenth rib, is usually situated opposite the um-
SERRATUS MUSCLES 431
bilicus. Another, corresponding to the ninth rib, is situated midway between this and the lower
margin of the thoracic wall, and one corresponding to the seventh rib is found at the level of the
xiphoid process. Between this and the one corresponding to the ninth rib an additional inscrip-
tion is frequently found. Below the umbilicus an inscription corresponding with the eleventh
rib is often found (30 per cent.). In these inscriptions many of the fibre-bundles have their
origin and insertion. The thoracic attachments take place by means of band-like fascicuU
which extend upward from the highest inscription, the fibre-bundles of these fasciculi being
inserted by short tendinous bands. The pubic attachment of the muscle takes place by a*
short, thick tendon, usually divisible into two portions, of which the broader, lateral portion is
inserted into a rough area extending from the pubic tubercle (spine) to the symphysis, while the
more slender medial portion is attached to the fascise in front of the symphysis pubis, where its
fibres interdigitate with those of the opposite side. In addition to the attachments mentioned,
some of the fibre-bundles are attached to the sheath of the rectus and many, after interdigitating,
terminate in the intramuscular framework.
Nerve-supply. — The anterior branches of the six or seven lowermost intercostal nerves
enter the deep surface of the muscle neai^its lateral edge. The cutaneous branches pass
obliquely through its substance, while the muscular branches give rise to an intramuscular
plexus. As a rule, the chief ventral branch of the tenth thoracic nerve enters the substance
of the muscle slightly below the umbilical transverse inscription. The branches of the eleventh
and twelfth nerves enter at a lower level. The main branch of the ninth nerve enters slightly
below the preumbilical inscription; the eighth nerve, between this and the lower margin of
the thorax. Either the sixth or seventh nerve may supply the fascicuh of origin. In addition
to the main branches other smaller branches of the nerves of the abdominal wall are also usually
distributed to the muscle. Each segment, either directly or through intramuscular plexuses,
has a supply from more than one spinal nerve.
Action. — To depress the thorax and flex the spinal column. When the thorax is fixed the
rectus serves to flex the pelvis upon the trunk.
Relations. — It lies between the transversalis fascia and the tela subcutanea and is ensheathed
by the aponeuroses of the lateral abdominal muscles, as above described. The epigastric artery
runs on its deep surface.
Variations. — The rectus muscle varies in the number of its tendinous inscriptions and in
the extent of its thoracic attachment. It may extend farther than usual on the thorax. Fre-
quently aponeurotic slips or slips of muscle on the upper part of the thorax indicate a more
primitive condition in which the muscle extended to the neck. Absence of a part or the whole
of the muscle has been noted. The muscles of the two sides may be separated by a considerable
interval in the neighbourhood of the umbiUcus. The muscle is relatively thicker in men than
in women..
The pyramidalis (fig. 388). — Origin. — Upper border of the body of the pubis.
Structure and insertion. — The fibre-bundles extend toward and are inserted into the hnea
alba for about a third of the distance to the umbilicus, and give rise to a flat, triangular belly.
Nerve-supply. — Usually through a branch of the twelfth thoracic, which may extend into
the muscle through the rectus abdominis. Not infrequently a special branch extends into the
muscle from the iho-hypogastric or ilio-inguinal or, rarely, from the genito-femoral.
Action. — -To draw down the hnea alba in the median line.
Relations. — It hes between two lamina; of the anterior layer of the sheath of the rectus.
Variations. — It is missing in about 16 per cent, of instances (Le Double). Dwight has
found it absent in 81 out of 450 males and in 60 out of 223 females dissected at the Harvard
Medical School. It may extend upward to the umbilicus or be but very shghtly developed.
It may be double. In many of the mammals it is missing. It is well developed in the marsu-
pials and monotremes.
B. Lateral Division
1. Serratus Group (fig. 380)
The serratus posterior superior. — Origin. — By a broad, thin aponeurosis from the liga-
mentum nuchfe and the spines of the last one or two cervical and the first two or three thoracic
vertebrae. •
Structure and insertion. — The fibre-bundles take a nearly parallel course downward and
lateralward and give rise to a flat belly which ends by four fasciculi on the upper margin of
the second to the fifth ribs, lateral to the ilio-costahs.
Neroe-supply. — Through branches from the first four intercostal nerves. These nerves
give rise to a plexus which passes across the deep surface of the muscle in the middle third be-
tween the tendons of origin and insertion.
Action.— To elevate the ribs to which the muscle is attached, and through them to enlarge
the thorax.
Relations. — It lies upon the wall of the thorax and the intrinsic dorsal musculature and
beneath the levator scapulae, rhomboids, serratus anterior, and trapezius. Its fascicuh extend
on the ribs to those of the serratus anterior (magnus).
The serratus posterior inferior. — Origin. — Through an aponeurosis, fused medially and
inferiorly with the lumbo-dorsal fascia, from the last two or three thoracic and first two or three
lumbar spines.
Structure and insertion. — From the aponeurosis arise four flat bands which are successively
attached to the inferior margins of the last four ribs, lateral to the iho-costalis.
Nerve-supply. — From the ninth to eleventh intercostal nerves arise branches which form a
plexus that extends across the deep surface of the muscle in the middle third between the ten-
dons of origin and insertion.
Action. — To depress and draw outward the four lower ribs and through them to enlai'ge
432 THE MUSCULATURE
the thorax. Together with the serratus posterior superior and the connecting aponeurotic
fascia it aids in keeping the intrinsic dorsal muscles in place.
Relations. — It lies upon the intrinsic dorsal musculature, the lower dorsal part of the
thorax, and the lumbo-dorsal fascia, and beneath the latissimus dorsi, the trapezius, and their
aponeuroses.
Variations. — The fasciculi of both muscles vary in number and may be replaced by ap-
oneurotic slips. Aberrant muscle fasciculi, supracostales posteriores, may be found in the fascia
which connects the two muscles. In several of the lower mammals the two muscles are nor-
mally continuous.
2. External Oblique Group
The intercostales extern! (fig. 385). — These muscles extend in the intercostal spaces from
the tubercles of the ribs to the costal cartilagess. The intermediate muscles do not, however,
often quite reach the cartilages. The first intercostal muscle may extend to the sternum. The
others are continued through the intercostal region by thin aponeuroses, the external inter-
costal ligaments, the fibres of which have a direction corresponding to that of the muscle fibre-
bundles. Dorsally the muscles are fused with the levatores, and ventrally the lower seven
muscles are more or less fused with the corresponding fasciculi of the external oblique.
Origin. — From the lower margin of each rib external to the costal sulcus.
Structure and insertion. — The fibre-bundles take a parallel course obliquely forward and
downward to the upper margin of the next rib. The proximal fibre-bundles are more obhque
than the distal, and the muscles are best developed in the dorsal part of the intercostal spaces.
Nerve-supply. — By several branches from the corresponding intercostal nerves.
Action. — To elevate the ribs and enlarge the thorax.
Relations. — They are covered externally by the pectoral muscles, the serratus anterior,
and serrati posteriores, the levatores costarum, the sacro-spinalis (erector spinae), and the
external obhque muscles. Internally they are separated by a slight amount of loose tissue from
the internal intercostals, the membranes which continue these muscles medially, and from the
subcostal muscles.
Variations. — When the twelfth''rib is very small or is lacking, the eleventh intercostal
muscle may be missing. When there is a supernumerary cervical or thirteenth thoracic rib,
there may be an extra external intercostal muscle. Next to the first intercostal, the fourth
most frequently reaches the sternum.
The levatores costarum (fig. 383). — These consist of a series of flat, triangular muscles,
each of which arises from the tip and inferior margin of a transverse process and extends later-
ally with diverging fibre-bundles to be inserted into the dorsal surface of the rib below, from
the tubercle to the angle. The fb'st extends from the transverse process of the seventh cervical
vertebra to the first rib. They increase successively in size from this to the last, which is at-
tached to the twelfth rib. Those arising from the transverse processes of the eighth to the elev-
enth thoracic vertebrse send their more medial fibre-bundles across the rib below to join the
lateral margin of the succeeding muscle (levatores longi). The levatores costarum are closely
united to the external intercostals and are innervated by the 'ntercostal nerves which pass for-
ward in the corresponding intercostal spaces. The first muscle is innervated by the eighth
cervical nerve.
Action. — To bend laterally and extend the spinal column.
Relations. — They are covered dorsally by the longissimus dorsi and the ilio-costahs.
Variations. — The first levator may be continued into the scalenus posterior. When greatly
developed, the series of levators forms a serrate muscle.
■ The obliquus abdominis externus (fig. 387). — Origin. — By eight fleshy digitations from
the external surface of the lower eight ribs immediately lateral to where they join the cartilages.
The fu'st five slips interdigitate with the serratus anterior (magnus), the last three with the
latissimus dorsi.
Insertion. — (1) By a strong aponeurosis which extends over the rectus to the hnea alba,
where the more superficial fibres interdigitate across the median line, and to the inguinal (Pou-
part's) ligament; and (2) directly into the outer hp of the crest of the ilium. The aponeurosis
over the rectus is usually partly fused with the aponeurosis of the internal obhque.
Structure. — The fibre-bundles which compose the flat fasciculi of origin diverge shghtly
as they pass forward and downward, and by fusion of their edges give rise to a flat sheet of
muscle. The fasciculus taking origin from the fifth rib passes nearly directly ventrally, but
the succeeding fasciculi incline somewhat downward, those from the seventh to the ninth ribs
showing the greatest downward inclination. The lower margin of the fasciculus which arises from
the seventh rib terminates opposite the umbilicus, that from the ninth rib extends toward the
anterior superior spine of the ilium, and those from the last three ribs descend to the ihac crest.
The first two fasciculi extend over the lateral margin of the rectus, the next two to its lateral
edge. The fourth and fifth usually terminate along a line extending ventrally from the anterior
superior iliac spine toward the rectus.
Nerve-supply. — The external oblique is supplied by rami from the lateral branches of the
lower seven intercostal nerves and usually from the ilio-hypogastric as well. The rami of the
first two or three nerves usually extend on the external surface of the muscle, while the others
extend on the deep surface of the muscle as the cutaneous branches are passing through it to-
ward the skin. The nerves of the external oblique take a more transverse direction than the
fasciculi of the muscle. Thus the branch from the tenth intercostal nerve extends toward the
umbilicus and that of the twelfth toward a point midway between the umbilicus and the sym-
physis pubis. The nerves have a segmental distribution corresponding with the primitive
segmental condition of the muscle.
Action. — (1) To compress the abdomen; (2) to depress the thorax; (3) to flex the spinal
INTERNAL OBLIQUE GROUP
433
column; and (4) to rotate the column toward the opposite side. With the thorax fixed it
serves to flex and rotate the pelvis.
Relations. — It lies superficial to the lower ventro-lateral margin of the thorax and the
internal oblique muscle. It is partly covered by the latissimus dorsi muscle behind. Other-
wise it is subcutaneous. •
Variations. — It may have a more or less extensive origin from the ribs. Broad fasciculi
not infrequently are separated by loose tissue from the main belly of the muscle either on its
deep or superficial surface. Occasionally tendinous inscriptions are found. These transverse
inscriptions are constant in many of the smaller mammals. The supracostalis anterior is a
rare fasciculus sometimes found on the upper portion of the thoracic wall. It is usually suppUed
by branches of the upper thoracic nerves and seems to be a continuation upward of the external
oblique muscle. In some prosimians the external oblique extends normally to the first or sec-
ond rib.
3. Internal Oblique Group
The intercostales interni (figs. 385, 386, 388). — These extend in the intercostal spaces from
the angles of the ribs to the sternal ends of the spaces. The upper and lower muscles are usually
continued dorsally slightly beyond the angles of the ribs, while the intermediate muscles fre-
quently do not quite reach them. Dorso-medially the internal intercostals are continued in
Aponeurosis
of obliquus
externus Ky'l
Spermatic cord~^
Origin of
cremaster
Ligament'
reflexum
Origi
cremaster
xum h
n of 4
Inguinal ligament
the form of thin fascial sheets across the inner surface of the external intercostals and become
fused with the subcostals.
Origin. — Near the angles of the ribs they arise from the internal lip of the costal sulcus.
More ventraUy they arise mainly from the external lip of the sulcus, but also in part from the
internal lip.
Structure and insertion. — The fibre-bundles take a parallel course downward and dorsal-
ward to the upper margin of the rib below. They are less obliquely placed than those of the
external intercostals. The muscles are thicker in front and grow thinner dorsaUy. They con-
tain less fibrous tissue than the e.xternal intercostals.
Nerve-supply. — From numerous branches of the corresponding intercostal nerves.
Action. — Investigators disagree as to the functions. It is probable that the portions of
the muscles between the ribs serve to contract, those between the costal cartilages to expand,
the thorax.
Relations. — Between the ribs they are covered by the external intercostal muscles and be-
tween the costal cartilages by the external intercostal ligaments. Between the internal and
external muscles there is some loose areolar tissue. Proximally, for a short distance, the inter-
costal nerve in each interspace runs between the external and internal intercostal muscles, but
more distally it runs first in the substance of and then on the internal surface of the internal
intercostal. Eisler distinguishes that portion of the internal intercostal muscle which lies
external to the nerve as the intercostalis intermedius, that which lies internal as the true in-
ternal intercostal. The terminal branches of the fii'st six nerves, however, pass through the
muscle on their way to the skin, while the last six pass beneath the inferior margin of the thorax.
Internal to the internal intercostal muscles lie the transversus (triangularis sterni) and sub-
434 THE MUSCULATURE
costal muscles, the diaphragm, and the pleural membranes. The more distal internal inter-
costal muscles are continuous with the internal obUque and the subcostal muscles.
Variations. — The tenth and eleventh internal intercostal muscles normally are but sHghtly
developed and often may be wanting. The internal intercostals of the first three spaces may
extend to the vertebrae.
The subcostales (fig. 385). — These muscles are due to an extension over two or more inter-
costal spaces of those fibre-bundles of the internal intercostal muscles which lie in the proximal
part of the interspaces. They arise near the angles of the ribs, and are usually well developed
only in the lower part of the thorax. The component fibre-bundles keep the general direction
of the internal intercostals, but they converge toward the tendons of insertion, which are at-
tached in each case to the second or third rib below, between the angle and the neck.
Nerve-supply. — The main nerve of supply for each muscle comes from the intercostal nerve
running below the rib from which the muscle takes origin.
Action. — To depress the ribs and contract the thorax.
Relations. — They lie on the inner side of the internal and external intercostals and the ribs,
and are covered by the pleural membranes.
Variations. — They vary much in development. Next to the lower fasciculi, the fasciculi
in the cranial part of the thorax are those usually best developed.
The obliquus abdominis internus (fig. 388). — Origin. — From the lumbo-dorsal fascia the
intermediate lip of the ventral two-thirds of the iliac crest, and the lateral half of the inguinal
Structure and insertion. — From the origin the fibre-bundles radiate forward in a flat sheet.
The most dorsal extend to the lower three ribs, where they become continuous with the internal
intercostals. The rest extend toward the lateral margin of the rectus, the upper ones toward
the xiphoid process, the intermediate toward the umbilicus, the lower ones somewhat obhquely
downward across the lower part of the abdomen. The fibre-bundles which extend toward the
rectus terminate in an aponeurosis which in its upper two-thirds divides into two layers, one
of which passes in front of and the other behind the rectus muscle to the linea alba. In the
lower third the aponeurosis passes as a single membrane in front of the rectus. In the neigh-
bourhood of the subcutaneous inguinal (external abdominal) ring the muscle is continued into
the cremaster. Medial to the ring some fasciouh are attached to the tubercle of the pubis
and to the symphysis.
Nerve-supply. — From branches of the last three intercostal and the ilio-hypogastric, ilio-
inguinal and genito-femoral (?) nerves as these pass between this muscle and the transversus.
Action. — To depress the thorax, flex the vertebral column, and bend and rotate it toward
the side on which the muscle is placed. When the thora.x is fixed, the muscle serves to flex and
rotate the pelvis.
Relations. — It hes between the external obhque and the transversus. The trigonum lum-
bale (triangle of Petit) is an area, variable in size, between the posterior margin of the external
obUque, the lateral margin of the latissimus dorsi, and the crest of the ihum. In this area the
internal obhque is subcutaneous.
Variations. — The attachments and the extent of development of the fleshy part of the
muscle vary considerably. Occasionally tendinous inscriptions are found in the muscle which
indicate a primitive segmental condition.
The cremaster (fig. 389). — The cremaster muscle is found well developed only in the male.
It represents an extension of the lower border of the internal obhque muscle and possibly also
of the transverse over the testis and spermatic cord.
Origin. — (1) Lateral, thick and fleshy, from about the middle of the upper border of the
inguinal hgament, and (2) medial, thin and tendinous, from the sheath of the rectus muscle and
the tubercle (spine) of the pubis.
Structure. — The lateral head is apphed to the lateral side, the medial head to the medial side,
of the spermatic cord. Both pass with this through the subcutaneous (external abdominal)
ring of the inguinal canal and become spread in loops over the testis. Ensheathing the muscle
and between the somewhat scattered fibre-bundles which compose it, there extends a thin,
membranous layer of connective tissue, the cremasteric (Cowper's) fascia.
Nerve-supply. — The genital nerve (external spermatic), usually joined by a ramus from the
inguinal nerve, gives rise to branches which spread over the muscle.
Action. — To lift the testis toward the subcutaneous inguinal (external abdominal) ring.
Relations. — It is covered by the aponeurosis of the external oblique, the cremasteric fascia,
the dartos, and the skin. It covers the spermatic cord and the testis.
Variations. — In the female the muscle is represented by a few fasciculi on the round hga-
ment. It may arise whoUy from the transversalis fascia or be somewhat fused with the trans-
versus muscle. The latter condition is espeoiaUy frequent in muscular individuals.
4. Transversus Group
The transversus thoracis (triangularis sterni) (fig. 386). — Origin. — By aponeurotic bands
from the dorsal surface of the lower half of the body of the sternum and the xiphoid process.
Structure and insertion. — The muscle is composed of several flat, thin fasciculi, partly
fibrous, more or less isolated, which are inserted by aponeurotic bands into the dorsal surface
of the cartilages of the second or third to the sixth ribs, and occasionally also into the tips of
the bony portions of the ribs. The lower fasciculus is closely related to the cranial margin of
the transversus abdominis.
Nerve-supply. — By rami from the ventral portions of the second to the sixth intercostal
nerves. These nerves give rise to a longitudinal plexus across the deep surface of the muscle
near the middle of the constituent fasciculi.
TRANSVERSUS ABDOMINIS
435
Action. — To depress the ribs in expiration.
Relations. — The sternum, the costal cartilages, internal intercostal muscles, and the internal
mammary vessels lie in front and the pleura and pericardium behind the muscle.
Variations. — It is an exceedingly variable muscle, both in the extent of its attachments
and in the development of the individual fasciouh. The fasciculi vary in number from one to
six. With this muscle Eisler would class the subcostal muscles and those portions of the internal
intercostal muscles which lie internal to the intercostal nerves.
The transversus abdominis (figs. 386, 390). — Origin. — Directly from — (1) the inner side
of the cartilages of the lower six ribs by dentations which interdigitate with the attachments of
the diaphragm; (2) the internal lip of the iliac crest and lateral half of the inguinal ligament;
and (3) through an aponeurosis from the lumbo-dorsal fascia.
Structure and insertion. — The fibre-bundles give rise to a broad, thin belly and take a nearly
transverse course across the inner side of the abdominal wall. The most distal fibres, however,
are inclined obliquely toward the pubis. The fleshy portion of the muscle terminates in a
strong aponeurosis along a curved line, which extends above well under the rectus and emerges
Fig. 390.-
-Teansversus Abdominis and Sheath op Rectus.
External intercostal — fe
Internal intercostal
Transversus abdomims
Rectus abdominis — %C"
Iliacus
Transversalis fascia
Falx inguinalis
Inguinal ligament
Lacunar ligament
Serratus anterior
lateral to the rectus opposite the umbilicus, whence it extends toward the middle of the inguinal
ligament. In the upper two-thirds of the abdomen the aponeurosis extends behind the rectus
to the linea alba and fuses with the inner lamina of that of the internal oblique. In the lower
third of the abdomen it extends in front of the rectus to the hnea alba, and is here also fused
with the aponeurosis of the internal obhque. Some of the fibres are continued into the aponeu-
rosis of the muscle of the opposite side. The lower attachment of the muscle is somewhat
more complex. The fibre-bundles here bend around the spermatic cord, on the medial side of
which they are spread out to be attached to the lacunar (Gimbernat's) ligament and pectineal
fascia, the pubis, and the sheath of the rectus. The attachment to the lacunar ligament and
pectineal fascia takes place by means of an aponeurotic band, the more lateral fibres of which
are dense and curve below the spermatic cord to the lacunar hgament and the pectineal fascia
below this. This band is caOed the interfoveolar ligament. It is composed partly of bundles of
fibres prolonged from the aponeurosis of the opposite transversus, and bounds the abdominal ring
medially and below. Medially the transversus is united to the upper part of the os pubis, and
to the sheath of the rectus by an aponeurotic band, the falx inguinalis (conjoined tendon).
Between the interfoveolar ligament and the falx inguinalis the transversalis fascia forms the
posterior wall of the inguinal canal. In this area a detached band of muscle-fibres is sometimes
found. This is called the musciilus interfoveolaris.
Nerve-supply. — The transversus is supphed with nerves by the last five or six thoracic and
436
THE MUSCULATURE
the ilio-hypogastric, inguinal and genito-femoral nerves as these course forward between this
muscle and the internal oblique.
Action. — The chief function is to compress the abdominal viscera. Through the portions
extending between the lower margins of the thorax on each side it serves to contract the thorax
and so may aid in expiration.
Relations. — It lies on the inner side of the lower ribs, the internal oblique and rectus muscles,
and is covered on the deep surface by the transversalis fascia.
Variations. — It is very rarely absent. It shows considerable variation in the extent of its
development. The pubo-peritonealis is a similar muscle which may pass from the pubic crest
to the transversus near the umbilicus. The pubo-transversalis is a small muscle which may
extend from the superior ramus of the pubis to the transversalis fascia near the abdominal
inguinal ring. The tensor laminae posterioris vaginae musculi recti abdominis, essentially like
the preceding, may e.xtend from the inguinal ligament to the rectus sheath on the deep surface
of the rectus muscle near the umbilicus. The tensor laminae posterioris vaginae musculi
recti et fasciae transversalis abdominis likewise extends from the transversalis fascia near the
abdominal inguinal ring to the fold of Douglas.
C. LuMBAE Muscle
The quadratus lumborum (fig. 406). — Origin. — From — (1) the internallip of the iliac crest
near the junction of the middle and dorsal thirds, and the iliolumbar ligament; (2) the transverse
processes of the three or four lower lumbar vertebra; and (3) the lumbo-dorsal fascia.
Fig. 391. — Diaphkagm.
(£ sophagus
Left division
of tendon
Costal origin
Left crus
Lateral lumbo-
costal arch
Transverse pro-
cess of second
lumbar vertebra
Fourth lumbar
vertebra
Structure and insertion. — From the origins there arises a complex quadrangular muscle
belly from which spring the fasiouli of termination. These extend to — (1) the transverse
processes of the upper three or four lumbar vertebrae; (2) to the fibre-bands which extend out
laterally in the lumbar fascia from the transverse processes; and (3) to the medial part of the
lower border of the twelfth rib.
Nerve-supply. — Through du-eot branches from the first three or four lumbar nerves.
Action. — It serves primarily to produce lateral flexion of the spinal column. When both
muscles act together, they produce extension of the column. The muscle also serves to depress
and fix the twelfth rib.
Relations. — It rests posteriorly on the lumbo-dorsal fascia and the transverse processes of
the lumbar vertebrae. Its medial edge is partly covered by the psoas. In front of it also he
the kidney, the intestines, and the lumbar arteries and nerves. It is ensheathed by membranes
continued over each surface from the transversalis fascia. Of these, the anterior is the better
marked and is called the lumbar fascia.
Variations. — There is much individual variation in the internal structure of the muscle and
in its attachments. Its insertion may e.xtend to the eleventh rib.
The psoas major and minor belong essentially to the^musculature of the lower limb and are
there described (p. 455).
D. The Diaphragm
The diaphragm (figs. 386, 391). — This dome-shaped musculo-membranous sheet has, when
seen from above, something of the outline of a kidney. It consists of a pair of muscles which
arise one on each side from the thoracic wall and are inserted into a central tendon. Lateral
THE DIAPHRAGM
437
to the tendon the diaphragm projects higher into the thoracic cavity than in the central area.
On the right, in moderate expiration, it extends in adults to the height of the medial extremity
of the fifth rib, and on the left to the fifth interspace.
Origin. — On each side from — (1) the lower border' and back of the .xiphoid process and the
adjacent aponeurosis of the transversus abdominis or from the tendinous arch extending from
the tip of the xiphoid process to the cartilages of the fifth and sixth ribs, {sternal portion) ; (2)
the lower border and inner surfaces of the cartilages of the seventh and eighth ribs, the cartilages
and osseous extremity of the ninth rib and the osseous extremities of the last three ribs [costal
portion); and (3) from the lumbar vertebrae (lumbar portion). The lumbar portion is divided
somewhat irregularly into three crura, between which pass blood-vessels and nerves.
The lateral crus arises from the lateral surface of the bodies of the first two lumbar vertebrae
and from fibrous thickenings of the fascia over the psoas and quadratus lumborum muscles.
Of these, one, the medial lumbo-costal arch (internal arcuate Ugament), extends from the body
of the second lumbar vertebra to the transverse process of the same vertebra; the other, the
lateral lumbo-costal arch (external arcuate hgament), extends from the tip of the transverse
Fig. 392.-
-The Perineal Muscles in the Female.
Pubis
Vagina
Superficial layer of
urogenital trigone
Sphincter ani exter-
nus profundus
Pubo-coccygeus
Ilio-coccygeus
Sphincter ani exter-
nus subcutaneus
Sphincter ani exter-
nus superficialis
Coccyx
process of the second lumbar vertebra to the twelfth rib. The lateral crus is only inconstantly
attached to this. The intermediate crus arises from the ventro-lateral surface of the body of
the second lumbar vertebra from the sides of the bodies of the first two lumbar vertebrae and
from the intervening discs. The medial crus arises from the front of the bodies of the third and
the fourth lumbar vertebrae. On the left side it usually extends only to the third vertebra,
and it does not always extend to the fourth on the right. The extremity and medial margin
of this crus are tendinous, the lateral portion fleshy. On the second, third, and fourth, and the
lower part of the first lumbar vertebrae the medial crus of each side is separated from its fellow
by the hiatus aorticus (for the aorta and thoracic duct). Over the first lumbar vertebra they
are fused by a process which extends from the right crus into the lower ventral sm'face of the
left. Above here the right crus may be divided into two parts, one of which, fused with the
left crus, passes on the left of the hiatus oesophageus, while the other passes on the right. Some-
times the hiatus oesophageus lies between the right and left crura. Frequently the left crus gives
off a slip which passes to the ventral surface of the right below the hiatus.
The costal portion arises by a series of dentations which do not correspond perfectly in
number with the ribs. Some costal cartilages have two dentations attached to them. It
interdigitates with the transversus abdominis but in part arises from tendinous arches which
bridge the origin of the transversus in the last three interspaces.
Slructiire and insertion. — The central tendon has somewhat the shape of a trifoliate leaf,
438
THE MUSCULATURE
the place of the stem being taken by the region occupied by the vertebral column, one leaflet
lying on each side of this and one in front. The ventral part is usually placed somewhat to the
left and is more or less completely fused with the left leaflet. Between the ventral and the right
leaflets there is a large opening through which passes the inferior vena cava, the foramen venae
cavae. The leaflets are fused in front and behind this.
Fig. 393.— Ventr.4l Coccygeal Muscles (After Eisler.)— 1. M. sacrococcygeus anterior.
2. M. coccygeus. 3. M. piriformis. 4. M. obturator internus' 5. Fascia iUaca, above the ilio-
psoas. 6. Fibrocartilago intervertebralis lumbosacralis. 7. Ventral trunk of first sacral nerve.
8. Sacral plexus.
The fleshy portion of the muscle is composed of fibre-bundles which pass at first nearly
vertically upward and then arch over to be attached to the margins of the central tendon. The
sternal portion of the muscle is the shortest. It is often separated from the costal portion by a
small space through which the superior epigastric vessels pass.
Nerve-supply. — From the phrenic nerves, one of which arises on each side from the third to
the fifth cervical nerves. Each nerve penetrates the diaphragm lateral to the central tendon
and breaks up into an extensive plexus on the inferior surface of the muscle. Some of the lower
intercostal nerves also contribute to the sensory innervation of the margin of the muscle and pos-
sibly also slightly to the motor innervation. The sympathetic nerves furnish fibres for the
blood-vessels.
Action. — To enlarge the thoracic cavity and thus cause inspiration. According to R. Fick,
however, the diaphragm plays a less important part in inspiration than is usuaUv assumed for
it. The middle part of the central tendon is united to the pericardium and through this to
the cervical fascia, and is, therefore, not very movable. In the contraction of the muscle it is
the dorsal and lateral portions which in the main are flattened. The diaphragm aids in defeca-
tion, parturition and vomiting, by the pressure it exerts on the abdominal viscera. It also
acts as a constrictor of the oesophagus.
Relations. — Above lie the heart and the lungs; below he the Uver, stomach, duodenum,
pancreas, spleen, kidneys, and suprarenal bodies.
Variations. — The sternal portion of the muscle is frequently absent. Infrequently the
diaphragm is incompletely developed dorsally on the left side. This condition is rarer on the
right side. The extent of the various insertions of the diaphragm shows considerable individual
differences. The vertebral portion of the muscle may be slightly fused with the psoas or with the
quadi-atus lumborum. Some fusion of the ventral portion of the muscle with the transversus
MUSCLES OF PELVIC OUTLET
439
thoracis has also been seen. Small fasciculi may pass to neighbouring structures : the oesophagus,
stomach, liver, mesentery, etc. Muscle fasciculi are frequently found in the central tendon.
V. MUSCULATURE OF THE PELVIC OUTLET
In order to understand the musculature of the pelvic outlet it is necessary first
to consider briefly the structure of the pelvis. It is bounded laterally and in front
by the ilium below the terminal (ilio-pectineal) line, the ischium and the pubis, and
by the obturator membrane and the sacro-spinous (small sciatic), sacro-tuberous
(great sciatic) and the interpubic hgaments. The pubis, ischium and the obturator
membrane are covered by the obturator internus muscle (figs. 392, 401) which here
takes its origin and which converges toward and passes through the lesser sciatic
notch on its way to its insertion on the great trochanter of the femur. The piri-
formis muscle (figs. 393, 396), which arises from the sides of the pelvic surface of
Fig. 394. — The Male Perineum. (Modiiied from Hirschfeld and LeveiUd.)
Bulbo-cavernosus
Superficial layer of uro-genital trigone
Iscliio-cavernosus
Muscles of thigh
Posterior femoral cutaneous ner
Perineal nerve
Inferior haemorrhoidal nerve
Cutaneous branch of fourth sacral
Gluteus maximus
Tuberosity of ischium
Sacro-tube
Levator ani
Superficial transversus perinei
Sphincter ani
the sacrum, from the posterior border of the great sciatic notch and the neighbour-
ing part of the sacro-tuberous (great sciatic) ligament nearly fills up the great
sciatic notch on its way to its insertion on the great trochanter. The walls of the
pelvis are thus padded by muscles which belong to the limb. The muscles are
covered by fascia best developed over the obturator internus muscle as the
obturator fascia. The gluteus maximus muscle (figs. 392, 394, 400, 401), which
arises from the back of the ilium, the sacrum, and the coccj^x, and is inserted into
the femur and the fascia of the thigh overlaps to some extent the sacro-tuberous
ligament, and in the standing position the tuberosity of the ischium so that its
lower margin forms an accessory boundar}' to the pelvic outlet.
440
THE MUSCULATURE
The outlet of the pelvis thus bounded by bone, ligaments and by muscles be-
longing to the lower extremity presents two triangles (figs. 392, 394), an anterior or
urogenital triangle, with the base between the two ischial tuberosities and the apex
below the symphysis pubis, and a posterior or rectal with the base between the
ischial tuberosities and the apex at the coccyx which projects into it here. The
outlet is closed by a special musculature divisible into three groups of muscles and
fascia; those of the pelvic diaphragm and anus, those of the urogenital diaphragm,
and those of the external genitalia.
The pelvic diaphragm [diaphragma pelvis] extends from the upper part of the
pelvic surface of the pubis and ischium to the rectum which passes through it to be
surrounded by the external sphincter. The urogenital trigone or urogenital dia-
phragm [diaphragma urogenitale] lies between the ischio-pubic rami superficial to
the pelvic diaphragm and surrounds the membranous urethra and in the female
also the vagina. The external genital muscles lie superficial to the trigone.
The muscles of the pelvic diaphragm are two in number on each side, the coccy-
geus, and the levator ani (figs. 395, 396, 397). The coccygeus arises from the
; Fig. 395. — The Pelvic Diaphragm in the Female, fkom below and behind.
ischial spine and is inserted into the lateral margin of the lower sacral and the
upper coccygeal vertebrae. It is closely applied to the pelvic surface of the sacro-
spinous (small sciatic) ligament. In so far as it is active it flexes and abducts the
coccyx.
The levator ani arises (figs. 395, 396, 397) from the inner side of the pubis,
along a line extending laterally from the inferior margin of the symphysis to the
obturator canal, and from the obturator fascia along a line, the arcus tendineus,
extending from the pubis to the spine of the ischium. The levator ani is inserted
into the median raphe back of the anus, the ano-coccygeal raphe, into the tip and
sides of the coccyx and into an aponeurosis, which is attached to the anterior
sacrococcygeal ligament. It is divisible into three portions, a pubo-coccygeal, an
iliococcygeal, and a pubo-rectal. The levator ani muscles of the two sides are sepa-
rated by a slit which extends from the rectum to the symphysis pubis and in which
in the male lie the lower part of the prostate, and the membranous urethra (fig.
396), and in the female the vagina and urethra (fig. 395). Back of the rectum
some of the fibre-bundles from the muscles of the two sides interdigitate, while
ISCHIO-RECTAL FOSSA
441
others terminate in the ano-coccygeal raphe. A few fibre-bundles also inter-
digitate across the median line, in front of the rectum (pubo-coccygeal, fig. 395)
and some are inserted into the walls of the rectum. The levator ani and coccygeal
muscles of the two sides form a funnel-shaped muscular support for the pelvic
viscera (fig. 399). When the abdomino-thoracic diaphragm contracts, as during
inspiration, the pressure on the viscera is transmitted to the pelvic diaphragm
which resists the pressure and elevates the viscera when the abdomino-thoracic
diaphragm relaxes. The levator ani muscle also constricts the rectum and pulls
it forward and in the female constricts the vagina from side to side.
As it passes through the pelvic diaphragm, the rectum for about two and a
half centimetres is surrounded by a special external sphincter muscle ffigs.
393, 394, 397), divisible into three concentric layers as described below. This
muscle, especially differentiated from the primitive sphincter of the cloaca,
Fig. 396. — ^Lateral View of Muscles of the Flooh op the Pelvis.
(A portion of the ischial and pubic bones sawn away.)
Aperture for superior
gluteal vessels and
nerve
Sacrum
Aperture for inferior
gluteal and pudic
vessels and nerve
and sciatic nerve
Ischial spine
Coccyx
Coccygeus
Hindmost fibres of
levator ani
White line farcus
tendineus") of
levator ani
serves to close the rectum. It is supplemented by a sphincter of smooth muscle
which lies immediately beneath the mucous membrane of the anus. It is attached
behind to the coccygeus, and in front to the central tendon of the perineum
described below.
The lateral origin of the levator ani, as above described and as shown in figs.
396 and 399, is considerably above the osseous and muscular margin of the pelvic
outlet. The muscles of each side converge toward the post-anal region so that a
space is left between the lateral wall of the pelvis, and the levator ani and external
sphincter (fig. 399). This space, the ischio-rectal fossa, is filled with fat (fig. 400,
401, 402). It is deepened laterally by the lower margin of the gluteus maxim us
muscle (fig. 400). In the fascial canal (Alcock's canal) in the lateral wall of the
442
THE MUSCULATURE
fossa run the internal pudic vessels and nerves (fig. 401). Above the pelvic
diaphragm in the median part of the pelvic cavity are found the bladder, the
ampulla of the rectum, and the prostate gland (in the male) or the vagina and
uterus (in the female). Laterally on each side there is a subperitoneal space, filled
with connective tissue and containing blood-vessels and nerves (fig. 402) . Fasciae
invest each surface of the pelvic diaphragm {diaphragmatic fascia) and extend
about the viscera [endo-pelvic fascia) .
Fig. 397.-
-SAGITT.4.L Section op the Pelvis to Show the Pelvic Diaphragm and External
Sphincter Ani.
Tendinous aponeu-
of pubo-
coccygeus
Raphe formed by
iho-coccygei
Sphincter recti
Sphincter ani ext. profundus
Sphincter ani externus subcutaneus
The muscular apparatus of the anterior or urogenital triangle of the pelvic
outlet is much more complicated than that of the posterior or rectal triangle just
described. We have seen that between the levator ani muscles of each side in
front of the rectum there is a slit which extends to the symphysis pubis and that
through it, the lower part of the prostate and the urethra extend in the male, the
urethra and the vagina in the female. Between the ischio-pubic rami there is
stretched a triangular muscular and fibrous membrane, which likewise surrounds
these urogenital ducts and which serves to strengthen the pelvic wall in this
region. This structure is known as the urogenital trigone (figs. 398, 400, 403).
The musculature within it, called by Holl the accessorj^ or urogenital diaphragm,
includes two muscles (fig. 398), the sphincter urogenitalis (urethraj) and the deep
transverse perineal muscle. The sphincter embraces the urethra and associated
structures. The component fibre-bundles arise chiefly from the fibrous tissue in
the angle beneath the symphysis pubis, but partly also from the descending pubic
rami. They pass analward and medialward on each side of the urethra and then
partly interdigitate across the median line, partly terminate in a median raphe.
Some fibre-bundles embrace in the male the lower part of the prostate and
Cowper's gland. In the female the fibre-bundles of the sphincter partly terminate
in the wall of the vagina. Some of them are continued downward on each side of
the vagina and interdigitate with fibre-bundles from the deep transverse perineal
muscle. The deep transverse perineal muscle (fig. 398) arises on each side from
the ischio-pubic ramus. It constitutes a flat band of muscle, the fibre-bundles of
B ULBO-CA VERNOS US
443
which in part interdigitate across the median line, and in part are inserted into a
median raphe.
The musculature of the urogenital diaphragm is enclosed between two well
marked fasciallayers (fig. 400, 403), the deep (superior) and superficial (inferior)
layers of the urogenital trigone (triangular ligament). The anterior margins of
the two fascial layers are fused to form the transverse ligament of the pelvis
which extends between the inferior pubic rami, beneath the dorsal nerves and
veins of the penis (clitoris). At the anal margin of the musculature these two
layers are also fused with one another. The deep layer of the urogenital trigone
forms the floor of the anterior recess of the ischio-rectal fossa (fig. 400).
Superficial to the urogenital trigone lie the external genitalia (figs. 392, 394).
Voluntary muscle is here found in connection with the crura of the penis (clitoris)
and the bulb of the penis (vestibule). Although the musculature in the two sexes
is fundamentally similar, neverthel^gs, owing to the differences in the structure of
the genitalia in the two sexes, it is convenient to take up first the external genital
musculature in the male and then that in the female.
Fig. 398. — Muscles between the Two Layers of the Urogenital Trigone (Male.)
Corpus cavernosum
Dorsal vein of
penis
Transverse liga-
ment of pelvis
Urethra, sur-
rounded by
sphincter
Transversus urethra
Transversus perinei profundus
In the male the crus penis, the posterior part of the corpus cavernosum, is
relatively large. It lies in the groove between the ischio-pubic ramus and the
urogenital trigone (fig. 398), to the former of which it is firmly united. It is
enwrapped on its free medial surface by the ischio-cavernosus muscle (erector
penis) (figs. 398, 402). The fibre-bundles of this muscle arise from the ischial
tuberosity and from the ischio-pubic ramus on each side of the attachment of the
crus. It is inserted into the medial and ventral surfaces of the crus near the
attachment of the suspensory ligament. Some of the fibre-bundles may fre-
quently be traced to the dorsal surface of the root of the penis (levator penis
muscle).
The corpus spongiosum [corpus cavernosum urethrae] terminates posteriorly
in the bulb which lies on the urogenital trigone between the two crura (figs. 394,
402). It is united to the superficial layer of the trigone (fig. 402). It is envel-
oped by the bulbo-cavernosus muscle, composed of right and left halves united by
a median raphe on the superficial surface of the bulb (fig. 394). Each half con-
sists of several superimposed laj^ers of fibre-bundles described below. The
component fibre-bundles arise from the superficial layer of the urogenital trigone,
from fibrous tissue on the dorsum of the bulb in the angle between the two crura,
from the lateral surface of the corpus cavernosum penis in front of the ischio-
cavernosus and from the dorsal surface of the penis. It is inserted into a tendi-
nous structure situated in front of the anus, the central tendon of the perineum,
444
THE MUSCULATURE
and into the median raphe on the free surface of the bulb. By its contraction the
bulbo-cavernosus forces semen or urine from the bulbous part of the urethra.
The superficial transverse muscle of the perineum (figs. 392, 394) arises on
each side from the ascending ramus of the ischium and is inserted into the central
tendon of the perineum. It is frequently weakly developed. It acts with the
deep transverse perineal muscle in fixing the perineum and thus offering support
for the action of otiier muscles.
In the female (fig. 392) the ischio-cavernosus does not differ markedly from that
in the male although usually it is smaller. The superficial transverse muscles are,
on the other hand, usually relatively better developed. The central tendon of
the perineum is likewise usually better developed in women and is more elastic, a
characteristic of value in childbirth.
The chief difference in the musculature in the two sexes is found in the
bulbo-cavernosus (fig. 392) . This, in the female, arises from the back of the clitoris,
the corpus cavernosum and the trigone. It covers the outer side of the bulb of
the vestibule and the gland of Bartholin. It is inserted into the central tendon of
the perineum. The chief function of the pair of muscles is to constrict the vagina.
The external genital muscles are covered by a deep layer of the tela subcutanea,
Fig. 399. — Diagram to show the Fascia op the Pelvis in Section. (After HoU.)
Endo-
pelvic
fascia
Ischio-rectal fossa
Colles' fascia, which is firmly fused with the two layers of the urogenital trigone
at the anal margin of the latter.
MORPHOLOGICAL REMARKS
While the shoulder-girdle and the muscles which extend from this and from the trunk to the
upper extremity are superficially placed with respect to the trunk, and do not interrupt the trunk
musculature the reverse is true of the hip-girdle and the musculature of the lower extremity.
The hip-girdle is firmly united to the spinal column at the sacrum. The muscles which arise
from the trunk and are attached to the lower limbs are few in number compared with those of
the upper extremity and, unhke the latter, are deeply placed. Thus the psoas major muscle
(fig. 406) arises on each side of the lumbar region of the spinal column at the back of the ab-
dominal cavity and is inserted into the femur and the piriformis (fig. 406) arises from the front
of the sacrum at the back of the pelvic cavity and is inserted into the great trochanter of the
femur. The skeleton and musculature of the lower extremity, furthermore, markedly inter-
fere with the continuity of the trunk musculature which in the lower vertebrates and in the hu-
man embryo may be followed continuously to the caudal end. The interruption is much less
marked behind than in front. The intrinsic dorsal spinal musculature extends well down over
the back of the sacrum, but on the back of the lower end of the sacrum and on the back of the
coccyx there is found merely the inconstant sacro-coccygeus posterior. Of the ventro-lateral
musculature the musculature of the abdominal wall, as is indicated by its innervation, is de-
rived from the lower thoracic and the first one or two lumbar myotomes; thequadratus lum-
borum, at the back of the abdominal cavity (fig. 406), from the first three or four lumbar myo-
FASCIA
445
tomes. Beyond here there is an interruption until we come to the musculature of the pelvic
outlet which, in part, may be looked vipon as modified trunk musculature belonging to the last
three sacral myotomes. The intervening region is "cut out" for the reception of the base of the
lower extremity.
It is of interest to note that more and more of the ventro-lateral wall of the trunk is "cut
out" as the mid-ventral line is approached. Thus while the quadratus lumborum behind
represents spinal segments as far caudal as the third or fourth lumbar, the rectus abdominis
in front represents segments merely as far caudal as the twelfth thoracic. Similarly while the
Fig. 400. — Sagittal Section" through the Urogenital Trigone and Ischio-rbctal Fossa
TO the Left op the Middle Line. (Diagrammatic.)
Obturator fascia
Subperitoneal tissue
Fascia transversalis
f Os pubis
Obturator internus
Fascia lata of thigh
Muscles of thigh
Nerves
Sacro-tuberous ligament
Sacro-spinous ligament
Gluteus
Levator ani with its fascia
Ischio-rectal fossa
Deep perineal interspace
with sphincter urethree,
etc.
Superficial fascia of
urogenital trigone
coccygeus at the back part of the pelvic outlet represents the third and fourth sacral segments,
the levator ani at the front represents chiefly the fourth.
The musculature which in the tailed mammals is used to move the tail as well as to wall off
the pelvic cavity and close rectal and urogenital openings, in man is modified whoUy for the latter
functions. It constitutes the pelvic diaphragm.
The musculature of the urogenital diaphragm of the external genitalia and anus in man is
differentiated from the primitive sphincter of the cloaca.
FASCI.E
The tela subcutanea in the male perineal region contains many bundles of smooth muscle
fibres continuous with and similar to the dartos of the scrotum (corrugator cutis ani). At the
sides where it passes over the lower margin of the gluteus maximus it contains a large amount of
fat, but in the dorsal region over the coccyx and sacrum, as in the mid-perineal region, the fat
is limited in amount. In the labia majora of the female perineum there is much fat in the tela
subcutanea.
The ischio-rectal fossa (figs. 401, 402) is bounded laterally by the obturator internus muscle
and fascia, the tuberosity of the ischium and the ischio-pubic ramus, medially by the levator ani
and coccygeus muscles and fasoise, ventraUy by the dorsal aspect of the urogenital trigone and
dorsaUy by the gluteus maximus muscle. An anterior recess extends forward well toward the
body of the pubis between the levator ani, the ischio-pubic ramus and the urogenital trigone.
A posterior recess may likewise be traced backward covered by the lower edge of the gluteus
maximus (figs. 400, 401). The fossa is filled with loose fatty tissue continuous with that of
the tela subcutanea. Through it pass the hemorrhoidal, and long and short perineal branches
of the pudic artery and nerve. The main trunks of these vessels and nerves lie in a special
fascial compartment (Alcook's canal) in the lateral wall (fig. 401).
The external genital organs are covered by a special deep layer of the tela subcutanea, the
superficial perineal (CoUes') fascia (fig. 402). This is attached on each side to the lower margin
of the ischio-pubic ramus and to the ischial tuberosity. At the posterior margin of the superficial
transverse perineal muscle it fuses with the two fascial layers of the trigone. It is adherent to
the central tendon of the perineum and to the raphe of the bulb. Anteriorly it is continuous
with the deep layer of the tela subcutanea covering the scrotum, the penis, and the lower part
of the abdominal wall. In rupture of the urethra urine is prevented, by the attachments of the
tela, from getting further back than the posterior edge of the trigone, but anteriorly it may
extend to the surface of the abdomen. Here it may extend upward for a considerable distance,
but it is kept from the thighs by the attachment of the deep laj'er of the tela subcutanea (Scarpa's
fascia) to the inguinal ligament. Beneath the superficial perineal fascia are found the crura of
446
THE MUSCULATURE
the penis and their muscles, the bulb of the corpus spongiosum and its muscles, the superficial
transverse perinei muscles, and the perineal vessels and nerves (fig. 402).
Muscle fasGise. — The muscles of the urogenital diaphragm, the urogenital (urethral) sphincter
and the transversus perinei profundus, are contained between two fascia layers which constitute
the superficial (inferior) and deep (superior) layers of the urogenital trigone (the superficial
or inferior and the deep or superior layers of the triangular ligament).
Fig. 401. — Section showing the Ischio-bectal Fossa in its Relations to the Pelvic
Viscera.
Symphysis pubis
Pubo-prostatic ligaments
Prostatic plexus
Prostate
Capsule of prostate formed by
endopelvic fascia
Fat
Rectum invested by er.do-
pelvic fascia
'ith its fasciae
Obturator internu
Internal pudic vessels and /%// ^r*
nervesin obturator fascia ^"g,/ 'g'*"4^o,''i^bft
Tuber ischii / ^^"«*-\ \1
Ischio-rectal fossa with its an- I '•UOr*^ r vt
teriorand posterior recesses
The superficial (inferior) layer (figs. 392, 394, 400, 402, 403) which lies between the external
genitalia and the urogenital diaphi-agm, is composed of strong bands of fibrous tissue which extend
■ transversely across the subpubic arch and are attached to a ridge on the ischio-pubic rami. It
is separated from the arcuate (subpubic) ligament by a mass of fibrous tissue through which the
dorsal veins and nerves of the penis (clitoris) run, and in which there is a venous plexus.
Fig. 402. — Vertical Frontal Section of the Pelvis, showing Fascia.
(Modified from Braune.)
Tendinous arch
Subperitoneal fat
Obturator internus
/ ij'fjf ^^S7~ Ischio-rectal fascia
^^^~- Os innominatum
Endopelvic fascia and
prostatic sheath
^v^'sT Obturator fascia
— Obturator membrane
Levator am
Prostate
Colli cuius seminalis
Bulbo-cavernosus
with its fa;
Integument o£-
peri
Ischio-rectal fossa
Superior layer of
trigone
Deep transversus
perinei
Inferior layer of uro-
genital trigone
Muscles of thigh
Ischio-cavernosus
Muscles of thigh
Beneath this tissue a fibrous band, the transverse ligament of the pubis, extends between the
descending pubic rami. This represents a region of fusion of the deep and superficial layers of
the fascia of the trigone. Posterior to the deep transverse muscle the two layers are likewise
fused. The superficial layer is better developed in the front than in the back part of the space.
It is pierced by the urethra (about 3 cm. below the symphysis) by the ducts of the bulbo-urethral
PELVIC FASCIA
447
(Cowper's) glands, the arteries of the bulb, and the dorsal nerves and arteries of the penis.
In the female it is pierced by the vagina as well as by the structures mentioned above.
Beneath the superficial layer of the fascia of the trigone, in addition to the muscles of the
urogenital diaphragm, there are found the membranous uretlira, the bulbo-urethral glands
(Cowper's), the internal pudic arteries and the pudic nerves (in part).
The dee-p (superior) layer of the urogenital trigone (figs. 400, 402, 403) lies between the muscles
of the urogenital diaphragm and the ischio-rectal fossa and levator ani. It may be looked upon
as a continuation of the obturator fascia across the pubic arch. Posterior to the deep transverse
perineal muscle it fuses with the superficial layer of the fascia of the urogenital trigone. In
this region in the male it fuses with a fascial membrane, the prostaiico-perineal fascia, which
extends upward between the rectum and prostate, and is attached to the posterior wall of the
latter. In the female it is fused with the fibrous tissue which lies between the vagina and the
rectum.
The muscle fasciae of the pelvis (figs. 399, 400, 401, 402, 407, B) have been described in
various ways by different authors. They may be subdivided into parietal and diaphragmatic.
Fig. 403. — Diagram of the Supehpicial and Deep Layers op the Urogenital Trigone.
Arcuate ligament
Apertures for dorsal artery and
nerve of the penis
Crus penis
Aperture for deep artery of penis
Superficial layer of urogenital
trigone
Ischio-cavernosus
Aperture for artery. &__. ,
to bulb M&
Urethral aperture
Aperture for bulbo
Apertures for peri
neal vessels and
nerve
Tela subcutanea of,
perineum turned
backwards
Aperture for dorsal vein of the penis
1 nerve
Superficial layer of urogenital
trigone (reflected)
Dorsal artery of penis
Deep layer of urO'
genital trigone
Deep artery of
penis
Artery to bulb
Position of bulbo-ure-
thral gland
Internal pudic artery
Junction of urogen-
ital trigone with
tela subcutanea of
The parietal fasciae (fig. 399) cover the muscles which extend from the interior of the pelvis
to the thigh (the obturator internus and piriformis muscles). Above, the fascia on each side
is attached to the linea terminalis and is continuous with the fascia transversalis and the iliac
fascia. It is attached to the margins of the greater and lesser sciatic notches and to the ischio-
pubic ramus and the body of the pubis. Between the ischio-pubic rami it is stretched across
the subpubic arch and forms the superior or deep layer of the urogenital trigone described above.
The portion of parietal pelvic fascia over the obturator internus muscle is called the obturator
fascia.
The diaphragmatic pelvic fasciae cover both surfaces of the pelvic diaphragm and are re-
flected upon the viscera. The fascia; covering the two surfaces of the levator ani are attached
to the parietal (obturator) fascia along the line of origin of the muscle.
The line of attachment of the levator ani divides the obturator fascia into two parts (fig.
399), a pelvic part above the line of attachment, covered by peritoneum, and an ischio-rectal
part below the line of attachment. The latter bounds the lateral wall of the ischio-rectal fossa.
The former part is much the thicker. It consists morphologically of two fused membranes, the
obturator fascia proper and the aponeurosis of the ilio-coccygeal portion of the levator ani,
which although usually fused with the obturator fascia, may frequentlj' be traced to the term-
inal (ilio-pectineal) line from which in tailed mammals this portion of the levator takes origin.
The two layers of fascia also become continuous at the medial margin of the muscle where this
faces the urogenital passage (fig. 399). Posteriorly, the inner layer fuses with the tendinous
insertion of the pubo-coocygeus portion of the muscle and the fasciae of the muscles of each side
are continuous. It also fuses with a fascia covering the coccygeus muscle.
The thin perineal layer of the levator fascia behind the rectum fuses with that of the opposite
side and is attached to the coccyx and the ano-coccygeal raphe. About the anus it helps to
form a covering for the external sphincter. Ventrally it is attached to the ischio-pubic rami.
It forms the medial wall of the ischio-rectal fossa.
Endo-pelvic fascia (figs. 401, 402), — The peritoneum is reflected from the pelvic wall onto
the viscera much higher up than the level at which the viscera are attached to the pelvic dia-
phragm. Between the pelvic fascia covering the deep surface of the pelvic diaphragm (levator
ani and coccygeus muscles) and the peritoneum there is thus left a space, subperitoneal space
(fig. 467 B). In the median plane in this region in the male are found the bladder, prostate,
seminal vesicles, the ureter and ductus deferens in their course near the bladder, and the am-
pulla of the rectum. In the female we find here the bladder, the vagina, the uterus, and the am-
pulla of the rectum. Between these medially placed viscera and the lateral wall of the pelvis
448 THE MUSCULATURE
there is an irregularly shaped space, cavum pelvis subperitoneale, bounded above by peritoneum,
below by the fascia covering the pelvic diaphragm and filled with connective tissue of varying
density. The tissue in this space in the female is continuous with that between the two per-
itoneal surfaces of the broad ligament. Between the viscera in the subperitoneal region and
about their walls tlie connective tissue is more or less definitely condensed into membranes
which constitute the endopelvio fascia, variously described by different authors. The fascia
covering the pelvic diaphragm, especiaOy that on the deep surface, is fused to the endopelvic
fascia where the viscera pass through the pelvic diaphragm. In the connective tissue of the
subperitoneal space are found the hypogastric artery and vein and their chief branches, and
various visceral nerves. The subperitoneal space above the pelvic diaphragm is to be compared
with the subcutaneous space below the pelvic diaphragm known as the ischio-rectal fossa and
described above.
MUSCLES
A. Muscles of the Pelvic Diaphragm, Coccyx, and Anus
The coccygeus (figs. 393, 396, 397, 400). — Origin. — From the ischial spine and the neigh-
bouring margin of the great sciatic notch. Structure and insertion. — The fibre-bundles diverge
to be inserted partly directly, partly by means of an aponeurosis, into the lateral margin of the
fourth and fifth sacral vertebrse and of the coccyx. Usually the muscle is composed in consider-
able part of tendinous connective tissue, especially on the dorsal side of the cranial portion, and
the ventral side of the caudal portion.
Nerve-supply. — From the pudendal plexus several small nerves enter the cranial margin
and pelvic surface of the muscle. They arise usually from the third and fourth sacral nerves.
Action. — Insofar as the muscle is active it flexes and abducts the coccyx.
Relations. — Ventrally the muscle bounds the pelvic cavity, from which it is separated by
the pelvic fascia, beneath which runs the nerve to the levator ani muscle. The dorsal surface
is partly covered by the sacro-spinous (lesser sciatic) ligament and helps to bound the ischio-
rectal fossa (posterior recess).
Variations. — The muscle varies greatly in the extent of its fleshy development. It may be
doubled. It may be partially fused with the levator ani. Occasionally it is absent.
The sacro-coccygeus anterior (fig. 393). — This inconstant muscle, when well developed,
arises from the sides of the fourth and fifth sacral and from the front of the fii'st coccygeal ver-
tebra and from the sacro-spinous ligament. The short fibre-bundles which compose it make up
a somewhat irregular beDy which is inserted into the anterior sacro-coccygeal ligament and into
the second to fourth coccygeal vertebrse dorsal to the insertion of the levator ani. The innerva-
tion is from the fourth and fifth sacral nerves.
The sacrococcygeus posterior is an inconstant muscle consisting of a few muscle bundles
which extend from the dorsal surface of the lower sacral vertebrae or from the posterior Oiac
spine to the dorsal surface of the coccyx. It hes beneath the superficial layer of the sacro-
tuberous (great sciatic) ligament.
The levator ani (figs. 392, 394, 395, 396, 399, 401) is divisible into three portions, the iUo-
coccygeus, the pubo-coccygeus and the pubo-rectahs.
The ilio-coccygeus (fig. 397) arises from the ischial portion of the arcus tendinous (white
line). This extends from the iscliial spine and posterior part of the arcuate line to the superior
ramus of the pubis near the obturator canal, curving downward for a variable distance below
the obturator canal. The constituent fibre-bundles form a muscular sheet which is inserted
into the side of the coccyx and into the median raphe (ano-coccygeal) which extends from the
tip of the coccyx to the rectum. Many fibre-bundles cross the median hne.
The pubo-coccygeus (figs. 395, 397) arises from the inner surface of the os pubis, along
a line extending from the lower margin of the symphysis pubis to the obturator canal, and from
the arcus tendineus as far backward as the origin of the ilio-coccygeus. The fibre-bundles
form a sheet of muscle which passes backward, downward, and medialward past the urogenital
organs and the rectum on each side and is inserted by means of an aponeiu:osis into the anterior
sacro-coccygeal hgament. Back of the rectum some of the fibre-bundles of the muscle sheets
of each side interdigitate across the median line. Some of the more superficial fibres are in-
serted into the deep part of the ano-coccygeal raphe. Some of the fibre-bundles which arise
nearest the symphysis are inserted on each side into the rectum. The pubo-coccygeus lies to
some extent on the pelvic surface of the insertion of the ilio-coccygeus.
The pubo-rectalis (fig. 395) arises (a) from the body and descending ramus of the pubis
beneath the origin of the pubo-coccygeus, (b) from the neighbom'ing part of the obturator fascia
and (c) from the fascia covering the pelvic surface of the urogenital trigone. The fibre-bundles
form a thick band on each side of the rectum behind which those of each side are inserted into
the ano-coccygeal raphe. Many fibre-bundles may be traced into the muscle of the opposite
side. Some of the more superficial fibre-bundles are reflected medialward in front of rectum
and may be followed into the superficial transverse perineal muscle, others may be followed into
the sphincter ani externus, or even to the skin.
Nerve-supply. — By a special nerve which arises usually from the fourth sacral, runs across
the pelvic surface of the muscle and gives a special branch to each portion.
Action. — To flex the coccyx, raise the anus and constrict the rectum. It resists the down-
ward pressure which the thoraco-abdominal diaphragm exerts on the viscera during inspiration.
Relations. — Between the right and left muscles in front lie the m-ethra and the lower part
of the prostate in the male, the urethra and vagina in the female. In the triangle between the
ischio-pubic rami of each side lies the urogenital diaphragm separated from the pubo-rectal part
of the muscle by the deep layer of the trigone from which some of the fibres of the latter arise.
Back of the iirogenital diaphragm the muscle helps to bound the ischio-rectal fossa.
UROGENITAL DIAPHRAGM 449
Variations. — The muscle shows great individual variation in structure which causes it to
be variously described by different authors.
The sphincter ani externus (figs. 392, 394, 396, 397, 399) is made up of bundles of muscle
fibres which surround the anus for nearly two centimetres. It is elliptical in form. Behind
the anus the fibre-bundles of each side in part interdigitate, forming a ring. They are attached
to the skin, and in part are attached through a tendon, the ligamentum ano-coccygeum, to the
back of the coccyx. In front of the anus the fibre-bundles also in part interdigitate with one
another, in part are inserted into the skin and in part interdigitate with the fibre-bundles of the
transverse perineal and bulbo-cavernosus muscles. At the point where these muscles meet,
about two and a half centimetres in front of the anus, there may be a visible mass of fibrous
tissue, the central tendon of the -perineum, but this is not always distinct. It is usually better de-
veloped in the female than in the male perineum. The external sphincter is divisible into three
portions, a subcutaneus, a superficial and a deep (fig. 397). The thi-ee parts are connected by
fibre-bundles, and are not always distinct. The subcutaneous division is small and immediately
encircles the anal orifice. The superficial division lies external to the subcutaneous ring and de-
scends further toward the rectum. It is shown in figs. 392, 394. It is the only part attached
to the coccyx. In front it is attached to the central tendon of the perineum, but some fibres
are continued into the bulbo-cavernosus. The deep portion forms a heavy ring above the rec-
tum beneath the superficial part. It is distinctly, though not completely, separated from the
pubo-rectal portion of the levator ani by fascial tissue containing the inferior haemorrhoidal
vessels. Some of the fibre-bundles of the deep portion may be traced in front of the anus
across the mid-line to the ascending ramus of the opposite side and form part of the superficial
transverse perineal muscle.
Nerve-supply. — From the inferior haemorrhoidal branches of the pudendal (internal pudic)
and frequently also by a perineal branch from the fourth sacral.
Action. — To keep the anus closed.
Relations. — Externally it is surrounded by the fat of the ischio-rectal fossa, internally near
the skin it surrounds the sphincter ani internus, composed of smooth muscle, deeper it lies
next the mucous membrane, for a distance of two centimetres from the skin.
Variations. — The muscle shows considerable individual variation in structure.
The recto-coccygeus or muscle of Treitz, is a triangular bundle of smooth muscle fibres.
The origin of the muscle is from the second and third coccygeal vertebrse. It is inserted by
its apex into the posterior wall of the rectum and the perirectal fascia. It retracts and elevates
the rectum.
B. Muscles of the Urogenital Diaphragm
The urogenital diaphragm is composed of two closely united muscles, the deep transverse
perineal muscle and the urogenital sphincter.
The transversus perinei profundus (fig. 398) is a flat muscle which arises from the inner side
of the inferior ischial ramus and is inserted into the median raphe. Many of the fibre-bundles
interdigitate with those of the opposite side and some may be followed into the external sphinc-
ter of the anus and into the urogenital spincter and other perineal muscles.
Nerve-supply. — By the perineal branch of the pudendal (internal pudic).
Action. — The pair of muscles draw back and fix the central tendon of the perineum and thus
give firm support for the action of the urogenital sphincter.
Relations. — The inferior surface is separated (often incompletely) by the inferior layer of
the urogenital trigone from the superficial transverse perineal muscle. The superior surface
is covered by the deep layer of the urogenital trigone, into which the superficial layer is reflected
about the anal margin of the muscle.
Variations. — The muscle is variable in structure and may be absent. (It is more frequently
absent in the female than in the male.)
The sphincter urogenitalis differs in the male and female owing to the passage of the vagina
through the perineum in the latter. In each sex it is convenient to consider the muscle as
divided into two parts, a peri-urethral and an infra-urethral (vaginal).
In the male (fig. 398) the peri-urethral part, the m. sphincter urethros memhranacece is com-
posed of fibre-bundles which are circularly placed about the membraneous urethra. The more
external fibre-bundles are attached to the crura of the penis near their junction, to the trans-
verse ligament of the pubis and to the fasciae of the trigone. Some of them partially ensheath
the lower part of the prostate, and others envelop the bulbo-urethral (Cowper's) glands. Some
of the fibre-bundles take a longitudinal course along the urethra. Bundles of smooth muscle
fibres are intermingled with the striated, and the fibrous framework of the musculature is marked
by the large amount of elastic tissue which it contains. The infra-urethral part, the m. trans-
versus urethrce, is closely associated with the urethral part. The fibre-bundles arise on each side
from the inferior ramus of the pubis. They pass for the greater part beneath the urethra and
interdigitate with that of the opposite side or are inserted into a median raphe. A few fibre-
bundles may pass above instead of below the urethra. The transverse urethral muscle, first
described by Guthrie (On the anatomy and diseases of the neck of the bladder, London, 1834)
is inconstant. Its existence as a normal constituent of the male perineal musculature has been
disputed by Delbet (Poirier and Charpy) and others.
In the female the peri-urethral part, .•sphincter urethrce, differs in no essential respects from
the corresponding muscle in the male. Some of the fibre-bundles form a true sphincter about
the uretlu-a. The infra-urethral part, on the other hand, seems to vary gi'eatly in different indi-
viduals so that the descriptions given by different authors are somewhat contradictory. It is
better developed in women who have not borne children than in those who have. It may be
looked upon as composed of two portions, a m. transversus vagina and an m. constrictor vagince.
450
THE MUSCULATURE
The iransversus vagince arises from the ischio-pubic rami and is inserted into the lateral wall of
the vagina. Some of the fibre-bundles pass above and some below the vagina. This muscle
corresponds with the transversus urethrce of the male but is, apparently, seldom fully developed.
The m. constrictor vagince, on the other hand, seems to be more constant. It is composed of
fibre-bundles which embrace the lateral wall of the vagina and are inserted above into the peri-
urethral framework, below into the raphe between the two deep transverse perineal muscles.
Some of the fibre-bundles are attached to the vaginal waU. Some interdigitate With the sphinc-
ter urethrae, others with the deep transverse perineal muscle and with the transversus vaginse.
Nerve-supply. — By a branch from the perineal nerve.
Action. — To compress or close the urethra and in the male to compress the prostate and
Cowper's glands, in the female to compress the vagina and BarthoUn's glands.
Relations. — On the pelvic side it is separated from the levator ani by the deep layer of the
urogenital trigone, and on the perineal side it is separated from the superficial muscles by the
superficial layer of the trigone. Toward the anus it is closely associated with the deep trans-
verse perineal muscle. Venous plexuses are well developed near the sphincter urethral in both
sexes, but especially in the female.
Fig. 404. — Buibo-cavernostjs in the Male.
The two halves have been reflected from the median raphe, and the bulb turned downward after
division of the corpus spongiosum. (The isohio-bulbosus is not present on the right side.)
Corpus cavernosum penis
Median aponeurosi:
Cut surface of corpus
cavernosum urethra
Corpus cavernosum urethrse
(corpus spongiosum)
Constrictor radicis penis
Ischio-bulbosus
Compressor bulbi proprius
Variations. — It has already been pointed out that there is considerable variation in the
muscles composing urogenital sphincter. Occasionally a rudimentary ischio-puhicus is found
arising from the ischio-pubic ramus and terminating in a tendon which unites with that of the
opposite side beneath the dorsal vein of the penis (clitoris). The tendon may be present as
the transverse ligament of the pelvis when the muscle itseH is absent. It represents the com-
pressor of the dorsal vein found in lower mammals.
C. External Genital Muscles
The bulbo-cavernosus (figs. 394, 404) in the male ensheaths the bulb. The fibre-bundles
arise from the dense tissue covering the corpus cavernosum at the root of the penis and from the
subpubic connective tissue dorsal to the bulbar part of the urethra and are inserted into its median
raphe on the ventral side of the bulb and into the central tendon of the perineum. Several
parts may be more or less clearly distinguished.
1. The constrictor radicis penis arises usually from the lateral surface of the corpus caver-
nosum penis at the base of the penis, but may arise from the under surface or from the dorsal
surface, or even from the suspensory ligament of the penis. The fibre-bundles pass obliquely
backward and medialward and are inserted into the median raphe on the perineal surface of the
bulb.
2. The compressor bulbi proprius arises (1) from a strong fibrous aponeurosis situated
between the corpus spongiosum and the united crura of the penis and firmly adherent to the
former, and (2) from the superficial layer of the trigone. The fibre-bundles ensheath the bulb
aim are inserted into the posterior part of the median raphe and into the central tendon of the
ISCHIO-CA VERNOS US
451
perineum. To a greater or less extent, depending on the development of the two muscles, the
compressor covers the more posterior part of the constrictor.
3. The compressor hemisphcerium bulbi arises from a tendon common to the muscles of the
two sides on the dorsum of the bulbous part of the uretlira near the membranous part. The
fibre-bundles embrace the hemisphere of the bulb and are inserted into the median raphe. This
muscle is covered by the preceding. It not only compresses the bulb, but also is a sphincter
of the urethra.
4. The ischio-bulbosus is placed by Holl in this group. It arises from the pelvic surface of
the tuberosity and of the inferior ramus of the ischium and when well developed is inserted into
the median raphe, superficial to the compressor bulbi proprius or the constrictor radicis pro-
prius. Frequently, however, it does not extend over the bulb but is inserted into the inferior
surface of the corpus cavernosum. It is more frequently absent than present. (See fig. 404.)
Nerve-supply. — The perineal division of the pudic nerve sends several branches to the bulbo-
cavernosus.
Action. — It compresses the bulb and at the same time the bulbous portion of the urethra.
The turgescence of the penis is thus increased and urine or semen is expelled from this portion
of the urethra.
Relations. — It lies beneath the skin and subcutaneous tissue.
Variations. — The muscle is variable in structure as is indicated by the different descriptions
given by different authors. The compressor vence dorsalis described by Houston is composed of
Fig. 405. — Diagrammatic Representation op the Perineal Structures in the Female.
Iscbio-pubic arch
Bulbo-cavernosus
covering bulbus
vestibuli
Inferior layer of urO'
genital trigone
Glans clitoridis with
prepuce
Pars intermedia
Mucous membrane of
vestibule
Urethral orifice
Bulbus vestibuli
External sphincter ani
a few fasciculi which arise from the sheath of the corpus spongiosum, and from the median
raphe and are united to those of the opposite side by a tendon which passes over the dorsal vein.
The hulbo-cavernosus (sphincter vagince) (fig. 392, 405) in the female arises (1) from fibrous
tissue dorsal to the clitoris, (2) from the tunica fibrosa of the corpus cavernosum and from the
superficial layer of the urogenital trigone in the angle between the crura of the ohtoris. The
fibre-bundles form a band of tissue about two centimetres wide at the side of the vagina and are
inserted into the posterior part of the superficial (inferior) layer of the trigonum and into the
central tendon of the perineum where some of the fibre-bundles interdigitate with those of other
muscles attached here. The fibre-bundles arising from the back of the clitoris correspond with
those of the constrictor radicis penis in the male. The other fibre-bundles correspond with those
of the compressor bulbi proprius in the male.
Nerve-supply. — From the perineal division of the pudic.
Action. — To compress the vagina.
Relations. — It covers the bulb of the vestibule and the great vestibular gland (Bartholin's).
It is covered by skin and superficial fascia.
The ischio-cavernosus (figs. 398, 405) (erector penis or clitoridis) arises from the pelvic
surface of the tuberosity and inferior ramus of the ischium, back and on each side of the attach-
ment of the crus. The fibre-bundles form a thin sheet which is spread over the crus into the
medial and inferior surfaces of which it is inserted near the symphysis pubis. It is better devel-
oped in the male than in the female.
Nerve-supply. — By branches of the perineal nerve.
Action. — By constricting the crus to maintain turgescence of the penis or chtoris.
Relations. — Superficially it is covered by skin and subcutaneous tissue. Laterally it lies
next the ischio-pubic ramus. Medially it bounds a space lying between the crus and the bulb
and filled with fat.
452 THE MUSCULATURE
Variations. — The muscle in the male is much larger than in the female. Some of the more
anterior fibre-bundles may extend to the dorsal surface of the penis (chtoris) and form a 'puho-
cavernosus or levator penis muscle.
The transversus perinei superficialis (figs. 392, 394, 405) arises from the inferior ischial
ramus. The fibre-bundles extend in front of the rectum superficial to the deep transverse mus-
cle and are inserted into the central tendon of the perineum. Some cross to the opposite side.
Some of the fibre-bundles are continuous with those of the external sphincter or of the pubo-
rectalis of the opposite side.
Action. — It acts with the deep transverse muscle in fixing the central part of the perineum.
Nerve-supply. — By a branch _from the perineal division of the pudic.
Variations. — It is frequently absent or poorly developed.
VI. THE MUSCULATURE OF THE LOWER LIMB
The lower limbs are used chiefly for the support and propulsion of the body.
Variety of movement is subordinated to strength and precision. In contrast with
the upper limbs, which perform a vast variety of complex movements under
conscious control, the lower limbs are called upon to perform chiefly the relatively
simple movements which are used in walking or running, without our paying much
attention to them.
The contrast between the two extremities is best marked in the girdles, the relations of
which to the trunk have already been described, p. 444. The shoulder girdle is constantly
called upon for movements in various directions which increase the freedom of action of the whole
extremity. The sterno-clavicular and acromio-clavicular joints are movable so that the scapula
can be carried in various directions over the thorax. The bones of the hip-girdle on each side,
on the other hand, are ossified into a single hip-bone (os innominatum). The two hip-bones are
almost immovably united to one another in front by the symphysis pubis and behind each is
united to the sacrum by a joint which, although a diarthrosis, likewise permits but sUght move-
ment. The sacrum in turn is composed of vertebrre firmly ossified together. The pelvis,
composed of the two hip-bones and the sacrum forms a strong support for the trunk. Such
movements as it makes are due chiefly to the lumbo-sacral joint and to a less extent to the joints
between the lumbar vertebrae. These joints permit the pelvis, in a limited manner, to be flexed
and extended, abducted, adducted, and rotated. Flexion is produced by the rectus and the
oblique muscles of the abdomen (fig. 387) and by the psoas muscles (fig. 406), extension is pro-
duced by the quadratus lumborum (fig. 406) and the sacrospinahs (fig. 381). Rotation and
abduction are produced when these muscles act on one side only. The weight of the body in
the sitting posture is transmitted through the sacrum and hip-bones to the ischial tuberosities.
In this position the pelvis is flexed. The weight of the body in the standing position is trans-
mitted to the femora through the acetabulum on each side. In this position the pelvis is ex-
tended. In walking the pelvis is rotated forward toward the limb that is being advanced.
The hip-joint is a true ball-and-socket joint, but freedom of movement is greatly limited
by the powerful musculature which surrounds it, as well as by the ligaments. Movements
here, however, are freer than at the shoulder-joint, if the shoulder girdle be left out of considera-
tion. At the hip-joint the most frequent and most free movements are those of flexion and
extension, the main movements in'walking or running; but abduction, adduction, circumduction,
and rotation are of the greatest importance in balancing the body.
At the knee-joint the main movements are also those of flexion and extension and the mus-
culature is so arranged that the chief flexors of the knee which lie at the back of the thigh are
extensors of the hip (fig. 408) while the extensor musculature of the knee which lies at the front
of the thigh flexes the hip (fig. 411). Flexion of the hip, however, through the action of gravity
on the foot passively brings about flexion at the knee, while flexion of the knee likewise passively
brings about flexion of the hip, since the flexed knee tends to swing forward. These passive
movements, due to gravity, are of importance in walking. The gastrocnemius (fig. 413), the
most powerful extensor of the ankle-joint, is also a powerful flexor of the knee-joint. At the
knee-joint, in addition to flexion and extension, some rotation is possible, best marked when
the knee is flexed. This rotation is of value in walking over rough ground in that it helps
to accommodate the foot to the ground. It is also of value in sitting on a flat surface. Whfle
there is thus some rotation at the knee-joint not found at the elbow-joint, the free movement
of the radius about the ulna which accompanies pronation and supination in the forearm, is
unrepresented in the leg where the fibula is firmly united to the tibia at each end.
The joint between the bones of the leg and the tarsus permits merely of flexion and exten-
sion in contrast to the wrist-joint which also permits of adduction and abduction. Flexion
and extension are also more limited iit the ankle than at the wrist. On the other hand, the
movements of inversion and eversion which take place in the intertarsal joints are not needed
in the wrist because of the pronation and supination of the forearm. Inversion and eversion
of the foot are of value in walking on rough ground.
The movements of the toes resemble those of the fingers except that they are, in most
individuals, far more restricted. The greatest restriction is seen at -the joint between the
metatarsal of the big toe and the tarsus, as compared with that between the metatarsal of the
thumb and the carpus.
The musculature of the inferior extremity, like that of the superior, can be
divided according to its development and innervation into two great subdivisions
MUSCLES OF LOWER LIMB 453
which correspond with the musculature on the dorsal and ventral sides of the
(shark's fin. The dorsal musculature is supplied by nerve branches which arise
from the back of the lumbo-dorsal plexus ("femoral, gluteal, and peroneal nerves),
the ventral musculature by branches which arise from the front of the plexus
obturator and tibial nerves). Owing, however, to the rotation which the limb
makes during embryonic development, the musculature which primitively lies on
the dorsal side of the limb-bud comes to lie on the front and lateral side of the
extremity and the musculature of the ventral side of the limb-bud comes to lie
on the back and medial side of the extremity or in the sole of the foot. The side
of the limb which primitively was toward the head becomes the medial side
of the limb, and that which faced caudalward comes to lie laterally. While
this makes the primitive relations of the musculature of the limb at first somewhat
confusing, it is possible to approximate these primitive conditions by abducting
the limb and rotating it so that the sole of the foot faces forward. An under-
standing of the innervation of the limb is thus greatly facilitated.
In the region of the hip the musculature of the dorsal division is that which
arises from the spinal column and ilium and is inserted into the upper part of the
femur and into the fascia of the thigh. It includes the chief flexor of the thigh,
the ilio-psoas (fig. 406), and the most powerful extensor, the gluteus maximus
(fig. 413), as well as several important rotators and abductors, gluteus medius and
minimus, piriformis and tensor fascice latce (fig. 408) . The ilio-psoas is innervated
by nerves from the back of the lumbar, the other muscles by nerves from the back
of the sacral plexus. The musculature of the ventral division arises from the
pubis and ischium, is inserted into the femur near the great trochanter and serves
to adduct the thigh and rotate it lateralward, obturator internus, gemelli, quadratus
femoris (fig. 408) and obturator externus (fig. 406). The obturator externus is
innervated by the obturator nerve from the front of the lumbar plexus, the other
muscles by special branches from the front of the sacral plexus.
In the thigh there are three well-marked groups of muscles, an anterior or
extensor group (fig. 411), a medial or adductor group (fig. 411), and a posterior or
flexor group (fig. 408). The anterior group belongs to the primitive dorsal
division, the other two groups to the ventral division.
The muscles of the anterior group (fig. 411) the sartorius and quadriceps arise
from the ilium and the shaft of the femur and are inserted into the tibia. The
quadriceps flexes the thigh and extends the leg. The sartorius flexes both the
thigh and the leg and rotates the former lateralward, the latter medialward.
They are innervated by the femoral nerve. The muscles of the medial group
(fig. 411), gracilis, pectineus, adductor brevis, longus, and magnus, arise from the
pubis and the inferior ramus of the ischium and are inserted into the shaft of the
femur. They adduct and fiex the thigh. They are innervated by the obturator
nerve. The adductor magnus gets part of its nerve-supply from the sciatic.
The pectineus usually gets all or most of its supply from the femoral. The rea-
sons for including it in this group are given below. The posterior group (fig. 408)
consists of the semitendinosus and semimembranosus, which arise from the ischial
tuberosity, and of the biceps, one head of which also arises from the ischial tuber-
osity while the other arises from the shaft of the femur. The semimembranosus
and semitendinosus are inserted into the tibia, the biceps into the fibula. They
are innervated by branches of the sciatic. They extend the thigh and flex the
knee. The semitendinosus rotates the leg medialward, the biceps lateralward.
In the leg there are also three groups of muscles, an anterior, a lateral and a
posterior. The two former belong to the dorsal division and are innervated by
the peroneal nerve. The last belongs to the ventral division and is innervated by
the tibial nerve. The muscles of the anterior group (fig. 415), the tibialis anterior,
extensor digitorum longus, peroneus tertius and extensor hallucis longus, arise from
the tibia and fibula and are inserted into first and fifth metatarsals and into the
two distal rows of phalanges. They flex the ankle and extend the toes. The
extensor digitorum longus and peroneus tertius evert the foot. The muscles of
the lateral group (fig. 415), the peroneus longus and brevis, arise from the fibula,
send tendons behind the lateral malleolus and are inserted respectively into the
first and the fifth metatarsals. Thej^ extend and evert the foot. The posterior
group (figs. 413, 416) may be separated into two subdivisions, a superficial and a
deep. The superficial subdivision (fig. 413) consists of the gastrocnemius, which
454 THE MUSCULATURE
arises from the two epicondyles of the femur, and the soleus which arises from the
tibia and fibula. These powerful extensors of the ankle are inserted by means of
the tendon of Achilles into the calcaneus. The gastrocnemius is a flexor of the
knee as well as an extensor of the ankle. A rudimentary muscle, the plantaris,
arises near the lateral head of the gastrocnemius and is inserted into the fibrous
tissue of the heel.
The deep group ("fig. 416) consists of one muscle, the popliteus, a medial
rotator and flexor of the leg, which arises from the lateral condyle of the femur and
is inserted into the tibia; and of three muscles, the ^exor digitorum longus, flexor
hallucis longus and tibialis posterior, which arise from the tibia and fibula, send
tendons behind the medial malleolus and are inserted into the plantar surface of
the tarsus and into the terminal phalanges of the toes. They invert the foot and
fiex the toes.
In the foot one muscle on the dorsum represents the primitive dorsal division,
the extensor digitorum brevis (fig. 418), supplied by a branch from the peroneal
nerve. On the other hand the primitive ventral division is well represented in
the sole of the foot, not only by the muscles associated with the long flexor tendons,
quadratus plantae, lumbricales (fig. 420), but also by the short flexor of the toes
(fig. 419), by the special musculature of the big and little toes (fig. 421) and by the
interosseous muscles (fig. 422). The flexor digitorum brevis (fig. 419), the most
superficial of these muscles, arises from the calcaneus and is inserted into the
second row of phalanges of the four more lateral toes. The quadratus plantce
arises from the calcaneus and is inserted into the tendon of the long extensor of
the toes. It makes the action of the tendon on the digits more direct. The four
lumbrical muscles run from this tendon to the medial sides of the four lateral toes.
They flex the digits. Of the intrinsic muscles of the great toe (figs. 419, 421),
the abductor arises from the calcaneus; the flexor brevis from the cuneiform
bones; and the adductor, by one head from the long plantar ligament, by the other
from the capsules of the metatarso-phalangeal joints. All are inserted into the
base of the first phalanx. Of the muscles of the little toe (figs. 419-421), the abduc-
tor arises from the calcaneus, the flexor and opponens from the cuboid. The two
former are attached to the base of the first phalanx, the last to the fifth metatarsal.
The interosseous muscles which arise between the metatarsals are so arranged
that the three plantar abduct and the four dorsal adduct the four lateral toes to
and from an axis passing through the second toe. The muscles of the sole of the
foot which send tendons to the sides of the bases of the first row of phalanges help
to flex the digits on the metatarsals and to extend the toes at the first row of inter-
phalangeal joints. These are much less effective extensors of the phalanges than
are the corresponding muscles of the hand and, unlike the latter, seem, in most
individuals, to exert but little extensor action on the third row of phalanges.
The muscles of the sole of the foot are supplied by the lateral and medial plantar
branches of the tibial nerve.
The muscle fasciae of the inferior extremity are well developed. The fascia lata, which
•encloses the musculature of the back of the hip and the musculature of the thigh, is especially
strong on the lateral side where it includes the longitudinal bundles of fibres which compose
the iho-tibial band. From the fascia lata strong intermuscular septa extend on each side of the
quadriceps group of muscles to the femur. Medially beneath the sartorius muscle (fig. 410),
septa help to bound Hunter's canal in which lies the femoral artery on its way to the pophteal
space behind the knee. In the leg there is hkewise a strong cylindrical fascial sheath which
encloses the musculature and sends septa on each side of the peroneal group to the fibula. A
transverse septum also separates the deep from the superficial muscles of the calf. The fascia
of .the leg is especially well developed near the anlde where it helps to hold in place the tendons
which pass from the muscles of the leg into the foot. Muscle fasciae are well developed both on
the dorsum and in the sole of the foot.
A. MUSCULATURE OF THE HIP
1. Ilio-Femoeal Musculature
The ihac blade divides these muscles into an anterior group (ilio-psoas),
supplied by nerves from the lumbar plexus, and a posterior group (the gluteal
muscles, piriformis, and tensor fasciae latse, supplied by nerves from the sacral
plexus.
MUSCLES OF HIP 455
In most of the limbed vertebrates these two groups of muscles are represented, but they
present marked specific variations in the different forms. Primitively, the iliacus group lies
on the proximal portion of the lateral surface of the iUum.
(a) Anterior Grottp
■ (Figs. 406, 411)
The fan-shaped iliacus muscle arises from the iliac fossa. The fusiform psoas
major muscle arises from the sides of the last thoracic and of the lumbar vertebrae
and extends along the medial margin of the iliacus muscle. The two muscles are
inserted by a common tendon into the lesser trochanter of the femur. Together
they constitute the ilio-psoas muscle. The small, flat, fusiform psoas minor lies
on the medial surface of the psoas major and extends from the twelfth thoracic
vertebra to the ilio-pectineal eminence. The ilio-psoas flexes the thigh at the hip
and the pelvis on the trunk. The psoas minor aids in flexing the pelvis.
The ilio-psoas muscle arises in the human embryo from a blastema which at first surrounds
the femoral nerve and later extends proximally over the ihum (iliacus) and toward the lumbar
vertebrae (psoas). The iliacus is phylogenetically the more primitive. In the shoulder it is
probably represented by the infraspinatus. The psoas minor is much better developed in many
of the lower mammals than in man.
FASCIA
The fasciae and the relations of these muscles are shown in figs. 384 and 407.
The iUac and psoas muscles are covered by a dense fascia which is but sHghtly adherent
to the underlying muscles. It is best developed in the pelvic region, where it extends from the
iliac crest and ilio-lumbar ligament to the iliac portion of the linea arcuata and is called the iliac
fascia. Superiorly it is continued over the psoas muscle as the psoas fascia and is attached
medially to the sacrum and the lumbar region of the spinal column. Laterahj' it unites with
the lumbar fascia and superiorlj' it is strengthened to form the medial lumbo-cosfal arch (fig.
391). Infiriorly the ilio-pectineal fascia extends over the iUo-psoas muscle to its femoral inser-
tion. It is firmly united on each side of the muscle to the capsule of the hip-joint and to the
femur. As it passes beneath the inguinal ligament it is united to this by tendinous processes.
Beyond the ligament it is less dense than in the pelvic region.
MUSCLES
The psoas major (figs. 406, 411). — Origin. — (1) By a series of thick fascicuh from the inter-
vertebral discs between the tweKth thoracic and the fifth lumbar vertebra, from the adjacent
parts of the bodies of these vertebrae and from tendinous arches which bridge over the middle
of the sides of the first four lumbar vertebrae ; and (2) by a series of more slender fascicuh from
the lower borders and ventral surfaces of the transverse processes of the lumbar vertebrae.
Structure and insertion. — From these origins parallel fibre-bundles descend nearly vertically
and give rise to a fusiform muscle which hes at the side of the vertebral bodies and extends along
the border of the true pelvis toward its insertion. A tendon arises deep in the muscle near
the last lumbar vertebra, and becomes free on its dorso-lateral surface slightly above the inguinal
(Poupart's) ligament. On the medial side the attachment of fibre-bundles continues to the
insertion of the muscle into the small trochanter. The Uiacus muscle is attached to the lateral
side of the tendon from near the ilio-pectineal eminence downward.
Nerve-supply. — Delicate branches pass into the psoas muscle from the trunks which unite
to form the femoral (anterior crural) nerve, i. e., from the fourth, third, second, and often the
first lumbar nerves.
The iliacus (figs. 406, 411). — Origin. — (1) From the iliac crest, the ilio-lumbar hgament,
and the greater part of the iliac fossa, the anterior sacro-iliac ligaments, and often from the
sacrum, and (2) from the ventral border of the ilium between the two anterior spines.
Structure and insertion. — From these areas of origin the fibre-bundles pass to be inserted —
(1) in a penniform manner on the lateral surface of the tendon which emerges from the psoas
above the inguinal (Poupart's) ligament, and (2) directly on the femur immediately distal to the
small trochanter. The lateral portion of the muscle arise from the ventral border of the ilium
and is adherent to the direct tendon of the rectus femoris and the capsule of the hip-joint. It is
sometimes more or less isolated (m. iliacus minor, ilio-capsulo-trochantericus, etc.).
Nerve-supply. — Nerve branches, often united in a plexiform manner, arise from the femoral
(anterior crural) nerve and pass across the surface of the Uiacus muscle about midway between
the crest of the ilium and the combined iUo-psoas tendon. Special nerve branches are usually
likewise distributed from the main trunk of the femoral nerve to the fleshy portion of the muscle
which extends over the acetabulum and the head of the femur.
Relations. — The psoas major lies lateral to the lumbar vertebrae and in front of the quad-
ratus lumborum and intertransverse muscles. The psoas minor passes downward across its ventral
surface. Both psoas muscles are crossed by the crura of the diaphragm. The kidney with its
adipose capsule lies lateral to them opposite the first two lumbar vertebriB. For the rest, their
fascia is covered ventro-laterally by retro-intestinal and retro-peritoneal tissue in which the
vena cava inferior runs in front of them on the right side, the inferior mesenteric vein in front
of them on the left side, and the ureter, the spermatic or ovarian, and the renal and colic vessels
on each side. The external iliac artery lies medial to the psoas major in the pelvis, and beyond
the inguinal (Poupart's) ligament the femoral artery hes ventral to it. The lumbar plexus arises
456
THE MUSCULATURE
between its origins from the vertebral bodies and discs and those from the transverse processes.
The nerves springing from the lumbar plexus take courses subject to much individual variation
through the muscle on the way to their destinations. Fasciculi of the muscle may thus be
separated by the femoral (anterior crural) nerve or other branches of the lumbar plexus.
The iliacus muscle in the region of the pelvis is covered by retro-peritoneal fat. The psoas
muscle crosses its medial margin and from between the two muscles the femoral nerve usuaUy
emerges to pass into the thigh above the iliacus. Beyond the inguinal ligament the iliacus lies
in front of the capsule of the hip-joint and the straight tendon of the rectus femoris, and is
crossed by the sartorius.
Fig. 406 — Pscis, Iliacus, and Quadratus Lumborum.
Quadratus lumborum
■Quadratus lumborum
Action. — The ilio-psoas is a powerful flexor of the thigh at the hip and a weak medial
rotator and adductor. It also serves to flex the lumbar region of the spine.
Variations. — The psoas muscle may be separated from the Uiacus as far as the femoral
insertion. The part of the psoas arising from the distal lumbar vertebrae may form a distinct
muscle. Slips may pass from the psoas major to the psoas minor. A separate lamina of the
iliacus muscle may be attached to the iliac fascia. From the anterior inferior iliac spine a small
muscle slip may run to the intertrochanteric line or the ilio-femoral ligament. To this slip the
term iliacus minor has been applied as well as to the larger fasciculus mentioned above.
The psoas minor (fig. 406). — Origin. — From the twelfth thoracic and first lumbar vertebrae
and the intervening disc.
Structure and insertion. — The fibre-bundles pass to be attached as far as the level of the fifth
lumbar vertebra to a flat tendon which appears about the mid-lumbar region and is inserted
into the ilio-pectineal eminence. It is intimately united to the iUac fascia.
Nerve-supply. — The branch to the psoas minor arises usually from the first and second lum-
bar nerves, often in company with the genito-femoral (genito-crural).
Action. — To flex the pelvis.
Relations. — It is closely applied to the ventral surface of the psoas major.
Variations. — The muscle is inconstant in development and is frequently absent. Gruber
has found it absent on both sides in 183 out of 450 bodies, on one side in 69.
BuRS^
B. iliopectinea. — A large bursa between the ilio-psoas muscle, the ilio-pectineal eminence,
and the capsule of the hip-joint. B. iliaca subtendinea. — A small bursa between the tendon
of insertion of the ilio-psoas and the lesser trochanter.
FASCIAE 457
(6) Posterior Group
(Figs. 387, 407, 408, 413)
The muscles of this group arise from the ilium and sacrum, cover the dorso-
lateral surface of the hip, and are inserted into the great trochanter and shaft
of the femur and into the iho-tibial band. They lie in three planes. In the first
layer (fig. 387) are the flat, quadrilateral tensor fasciae latae, which arises from
the front of the crest of the ilium and is inserted into the ilio-tibial band, and the
thick, rhomboid gluteus maximus, which arises from the dorsal portion of the
ihac ala, the lumbo-dorsal fascia, the sacrum and coccyx, and the sacro-tuberous
(great sacro-sciatic) ligament, and is inserted in part into the ilio-tibial bandand
in part into the back of the upper part of the shaft of the femur. The ilio-tibial
band is a flat tendon which descends, closely fused with the fascia lata, to the
lateral side of the upper extremity of the tibia. In the second layer (fig. 408)
are the flat, thick, triangular gluteus medius and the 'pear-shaped' piriformis
The former arises from the upper and back part of the outer surface of the ala of
the ilium, the latter from the ventral surface of the sacrum and the posterior
border of the great sciatic notch. Both are inserted into the top of the great
trochanter. The third layer (fig. 409) is composed of the triangular gluteus
minimus, which arises from the inferior ventral portion of the outer surface of
the ala of the ilium, and is inserted into the front of the great trochanter of the
femur.
The muscles of this group extend, flex, abduct, and rotate the thigh at the hip.
The gluteus maximus and medius are in part extensors, the gluteus minimus
and the tensor fasciae latae are flexors of the hip-joint. All the muscles serve to
abduct, the gluteus maximus acting thus when the hip is flexed. When the thigh
is extended the lower part of the gluteus maximus is an adductor. The gluteus
maximus and posterior part of the gluteus medius and the piriformis act as
lateral, the anterior part of the gluteus medius, the gluteus minimus, and the
tensor fasciae latae as medial, rotators. The gluteus maximus and the tensor
fasciae latae through the iho-tibial band keep the extended knee-joint firna.
The gluteus maximus is supphed by the inferior gluteal nerve, the piriformis
by special nerves, and the other muscles of the group by the superior gluteal
nerve. All these nerves arise from the upper part of the back of the sacral
plexus.
The gluteus medius, gluteus minimus, and piriformis form a group of muscles which in the
embryo have a common origin and are more or less fused in the adult. The gluteus maximus
arises in two distinct, though associated, portions, and the tensor fasciae latae as another^ dis-
tinct portion. The two muscles, however, are probably to be considered as parts of a primitive
caudo-pelvo-tibial musculature, while the gluteus medius group is represented in the lower forms
by an iho-femoral musculature. The former group is often closely associated with the extensor
muscles of the thigh in the lower forms (frog), and in some of the lower mammals extends its
insertion to the plantar fascia (ornithorhynchus). In the arm this group is perhaps represented
by the deltoid, the latissimus dorsi, and the teres major, while the gluteus medius group is
represented by the subscapularis.
FASCIA
The tela subcutanea of the gluteal region is very thick, contains much fat, and is often
divisible into two layers, of which the deeper is closely adherent to the fascia lata and through
this to the gluteus maximus. Over the great trochanter a subcutaneous bursa is usually found
(bursa trochanterica subcutanea).
Muscle fascia. — The muscles of the hip and thigh are enclosed in a dense fascia, the fascia
lata (figs. 387, 407). This arises from the tuber isohii, the sacro-tuberous (great sacro-sciatic)
ligament, the back of the sacrum and the coccyx, the crest of the iUum, the inguinal (Poupart's)
ligament, and the pubic and ischial rami, and extends to the tibia and the fascia covering the
muscles of the leg. It is composed mainly of bundles of fibres running transversely to the long
axis of the limb. In the region of the gluteal groove it is strengthened by a transverse fibrous
band which arises from the tuberosity of the ischium and arches upward over the lower border
of the gluteus maximus muscle.
In the region of the hip the fascia lata invests both surfaces of the tensor fasciae latae and
the gluteus maximus, and is closely bound to these muscles through intramuscular septa.
Between these two muscles the fascia covers the fascia of the gluteus medius, to which it is
adherent near the ihac crest, but from which it is sejjarated by loose tissue more distally. Anter-
iorly the fascia is fused with the IMo-pectineal fascia and the inguinal (Poupart's) ligament.
458
THE MUSCULATURE
More distally the tendons of the tensor fasciae latse and of the superficial portion of the
gluteus maximus become incorporated with the deep surface of the fascia lata and give rise to
the ilio -tibial band [tractus iliotibialis].
Fig. 407, A and B. — Tbansveesb Sections through the Left Side of the Pelvis in the
Regions Indicated in the Diagram.
C. Section through the muscles of the left inguinal region parallel to the inguinal (Poupart's)
ligament (after Spalteholz). h in the diagram indicates Section B, fig. 384, p. 421; a'
and h' indicate sections A and B, fig. 410, p. 465. (For legends, see p. 459.)
The gluteus medius and minimus muscles are invested by adherent fascial sheets which,
ventrally between the two muscles, may be combined into an intermuscular septum or be so
shghtly developed that the muscles are fused. The fascial sheet covering the gluteus medius
toward the iliac crest is fused with the deep surface of the fascia lata. This fusion results in the
formation of septa between the gluteus medius and the gluteus maximus and tensor fasciae latae.
GLUTEUS MAXIM US 459
The piriformis in the pelvic cavity is covered on the anterior surface by a special slightly
developed fascia. This fascia also covers the pelvic surface of the sacral plexus. Outside the
pelvis the piriformis is covered by an adherent membrane which usually is separated by loose
tissue from the surrounding structures.
MUSCLES
I. First Layer
The tensor fascise latae (figs. 387, 411). — Origin. — (1) By a tendinous band from the external
lip of the iliac crest, and the upper part of the notch between the anterior superior and anterior
inferior spines of the ilium, and (2) from the septum between it and the gluteus medius.
Structure and insertion. — The nearly parallel fibre-bundles pass distally and laterally and are
united to tendon fasciculi which become incorporated with the ilio-tibial band (traotus ilio-
tibiaUs) about one-third of the way down the thigh.
Nerve-supply. — The superior gluteal nerve sends a branch through the ventral margin of
the gluteus minimus to terminate in the middle third of the deep surface of the tensor fasciae
latae near its dorsal border.
Action. — To rotate medially, flex, and abduct the thigh, and to make tense the fascia lata.
Relations. — It lies over the gluteus medius, the proximal part of the rectus femoris, and the
vastus laterahs.
Variations. — It may be divided into two parts, one rising from the anterior superior spine,
the other from the iliac crest. Accessory slips may arise from the inguinal ligament, the crest
of the ilium, or the fascia over the lower part of the abdominal wall. Union of the muscle with
the gluteus maximus has been observed, thus making a muscle much resembling the deltoid of
the shoulder. By some the fascia lata between the tensor and the gluteus maximus is considered
an atrophied part of a deltoid of the hip.
The gluteus maximus (figs. 387, 413). — Origin. — (1) From the dorsal fifth of the outer lip
of the iliac crest, the outer surface of the ilium dorsal to the posterior gluteal line, the lumbo-
dorsal fascia between the posterior superior spine of the ilium, and the side of the sacrum, and
(2) from the lateral portions of the fourth and fifth sacral and the coccygeal vertebrae and from
the back of the sacro-tuberous (great sacro-sciatic) ligament.
Insertion. — Into (1) the ilio-tibial band; (2) the gluteal tuberosity of the femur and the
adjacent part of the tendinous origin of the vastus lateralis (fig. 407).
Structure. — The large fibre-bundles of which the muscle is composed take a somewhat
parallel course from origin to insertion. From the areas of origin and the enveloping fascia
fibrous bands extend into the muscle. The belly is divisible into two portions, a superficial and
a deep. The division may be much more clearly recognised in the embryo than in the adult.
The superficial portion is the larger, and includes all of that part of the muscle which springs
from the ilium and the more superficial portion of that arising from the sacrum and the upper
part of the coccyx. The deep portion includes that part of the muscle attached to the side of
the sacrum and the coccyx, and to the sacro-tuberous ligament. The superficial portion and
some of the fibre-bundles of the deep portion terminate in the iho-tibial band along a line
extending from the great trochanter to the end of the upper third of the femur. The deep por-
tion is inserted chiefly by a flat tendon into the gluteal tuberosity, and also directly into the
adjacent portion of the origin of the vastus lateralis.
Nerve-supply. — Two branches (inferior gluteal) arising from the sacral plexus either separately
or united, are usually given to the muscle. One of these curves anteriorly across the deep
surface of the proximal superficial portion of the muscle in the middle third between the tendons
1. Acetabulum. 2. Annulus femoralis. 3. Annulus inguinalis subcutaneous (ext. abdominal
ring). 4. Arteria femorahs. 4a. A. profunda femoris. 46. A. ciroumflexa femoris medialis.
5. A. glutea inferior. 6. A. hypogastrica (internal iliac). 7. A. ihaca externa. 8. A.
pudena interna (pudic) . 9. Bursa iho-peotinea. 10. B. trochanterica m. glutaei maximi.
11. Eminentia iliopectinea. 12. Fascia iliaca. 13. F. ilio-pectinea. 14. F. lata — a, iho-
tibial band. 15. F. obturatoria. 16. F. pectinea. 17. F. transversahs. 18. Femur — a,
trochanter major; b, trochanter minor. 19. Funiculus spermaticus (spermatic cord).
20. — Lacuna vasorum. 21. Ligamentum ilio-femorale. 22. L. inguinale (Poupart's
ligament). 23. L. lacunare (Gimbernat's). 24. L. saoro-tuberosum (great sciatic). 25.
Musoulus adductor brevis. 26. M. adductor longus. 27. M. coccygeus. 28. M. gemel-
lus inferior. 29. M. gluteus maximus. 30. M. gluteus medius. 31. M. gluteus
minimus. 32. M. iliopsoas — a, psoas; 6. iliacus. 33. M. levator ani. 34. M.
obliquus abdominis externus, aponeurosis. 35. M. obhquus abdominis internus.
36. M. obturator externus. 37. M. obturator internus. 38. M. pectineus. 39. M.
quadratus femoris. 40. M. rectus femoris. 41. iVI. sartorius. 42. M. tensor fasciaj
latae. 43. M. transversus abdominis. 44. M. transverso-spinales (multifidus). 45. M.
vastus lateralis. 46. N. cutaneus femoris anterior (middle cutaneous). 47. N. cutaneous
femoris posterior (small sciatic). 48. N. femoralis (anterior crural). 49. N. gluteus
superior. 50. N. ischiadicus (great sciatic) — a, peronaeus communis (external popliteal) ;
6, tibialis (internal popliteal). 51. N. obturatorius. 52. N. pudendus. 53. N. sacralis
I. 54. N. sacralis II. 55. N. saphenus. 56. Os ilium^a, spina anterior superior; 6,
spina anterior inferior. 57. Os ischium. 58. Os pubis — a, spina (tubercle). 59. Pros-
tata. 60. Truncus lumbo-saeralis. 61. Vena femoralis. 62. V. saphena magna. 63.
V. iliaca e.xterna. 64. V. hypogastrica (internal iliac). 65. Vertebra sacralis I. 66.
Vertebra sacralis II.
460
THE MUSCULATURE
of origin and insertion, the other descends to enter the middle third of the distal deep portion
of the muscle.
Action. — It is the most powerful extensor of the thigh. It also serves slightly to rotate the
limb lateralward and to make tense the fascia lata, and through the iho-tibial band to keep the
extended knee-joint steady. When the thigh is extended the major part of the muscle is an
adductor but the upper part is a weak abductor. The whole muscle is an abductor when the
thigh is flexed. It is brought powerfully into play in cUmbing and in walking up hiU.
Fig. 408. — The Lateral Rotators and the Hamstring Muscles.
Gluteus mediu
Piriformi
Gemellus superior]
Gemellus infer:
Quadratus femoris
Obturator internus
Gluteus maximus
Vastus lateralis
Biceps
Vastus intermedius
Short head of biceps
Plantaris
Gastrocnemius
Semi-membranosus
Sartorius
Semi-tendinosus
Relations. — It is covered by the fatty superficial tissue of the buttock. It extends over the
posterior portion of the ilium, the lateral surface of the sacrum and coccyx, the sacro-tuberoua
ligament, and the great trochanter. It covers the tuber of the ischium in the standing but not
in the sitting position. Immediately beneath the muscle lie portions of the gluteus medius,
piriformis, obturator internus, gemelH, quadratus femoris, obturator externus, and hamstring
muscles, and of the gluteal vessels and nerves and the sciatic nerve.
Variations. — Few anomahes are recorded. The deep distal portion of the muscle may be
more isolated than normal in the adult. A special coccygeo-femoral muscle may run from the
coccyx to the Unea aspera, or from the sacro-tuberous ligament to the fascia of the leg. A
GLUTEUS MINIMUS 461
special fasciculus, the ischio-femoralis, may arise from the tuberosity of the ischium and become
inserted into the lower border of the muscle near the great trochanter. The sacral, ischial, or
coccygeal origin may be lacking, or the origin of the muscle may be from the sacrum only.
II. Second Layer
The muscles of this layer are the gluteus medius and the piriformis.
The gluteus medius (fig. 408). — Origin. — From (1) the ventral three-fourths of the ihac
crest, and the outer surface of the ilium between the anterior and posterior gluteal hnes and (2)
the investing fascia.
Structure and insertion. — The fibre-bundles converge upon both surfaces of a broad tendon
nearly to its insertion on an oblong impression on the postero-superior angle and the external
surface of the great trochanter. The more posterior fibre-bundles of the superficial stratum
of the ventral portion of the muscle cross obliquely those of the deeper dorsal portion near
the tendon of insertion. From the tendon an aponeurotic extension is usually continued into
the tendon of the vastus lateraUs.
Nerve-supply. — From the superior gluteal nerve a branch passes to the dorsal portion of the
muscle and one or more twigs of the branch to the tensor f ascise latse enter the ventral portion of
the muscle. The branches enter the middle third of the muscle between its tendons of origin
and insertion. The nerve-fibres arise usually from the fourth and fifth lumbar and first sacral
nerves. The branch to the dorsal portion of the muscle has a lower spinal origin than
those to the ventral portion.
Action. — To abduct the thigh. The anterior portion of the muscle is a flexor and a medial
rotator, the posterior a lateral rotator and an extensor. When the muscle acts as a whole, it is
a medial rotator.
Relations. — Upon the muscle lie the tensor fasciae latas and gluteus maximus muscles and the
fascia lata; beneath it lie the gluteus minimus muscle, the superior gluteal nerve and vessels,
and the great trochanter.
Variations. — It may be divided into two distinct portions, or it may be fused with the
piriformis or the gluteus minimus or botli. A special fasciculus may extend to the superior
portion of the great trochanter.
The piriformis (fig. 408). — Origin. — From (1) the lateral part of the ventral surface of the
second, third, and fourth sacral vertebrae; (2) the posterior border of the great sciatic notch;
and (3) the deep surface of the sacro-tuberous (great sacro-sciatic) ligament near the sacrum.
Structure and insertion. — The fibre-bundles converge upon a tendon which is inserted upon
the anterior and inner portion of the upper border of the great trochanter. The insertion of
fibre-bundles continues nearly to the great trochanter. An accessory shp of insertion may pass
to the gluteus minimus.
Nerve-supply. — From a nerve which arises either directly from the first or second sacral
nerve or from a loop between them. The nerve enters the deep surface of the muscle in its
middle third. There may be two or more nerves.
Action. — It is an extensor, abductor, and lateral rotator of the thigh. It causes medial rota-
tion when the hip is flexed.
Relations. — Its ventral surface faces the sacral plexus, the rectum, and the hip-joint. It is
covered dorsaUy by the gluteus maximus. It hes between the gluteus medius and the superior
gemellus. Between the piriformis and the superior gemellus the sciatic nerve usually passes
into the thigh. The superior gluteal nerve and vessels pass dorsall}' above its superior margin;
the inferior nerve and vessels beneath its inferior margin.
Variations. — It is rarely absent. The origin may extend to the first sacral or to the fifth
sacral vertebra and the coccyx. It may be fused with the gluteus medius or minimus or more
rarely with the superior gemellus. Its tendon of insertion may be fused with that of the gluteus
medius or the obturator internus. In about 20 per cent, of bodies it is divided partly or com-
pletely into two portions, between which the sciatic nerve or its peroneal (external popliteal)
division usually passes. Rarely the tibial instead of the peroneal portion may pass between the
two fascicuh, or the muscle may be divided into three or more fasciculi, between which the
branches of the sciatic nerve pass.
III. Third Layer
The gluteus minimus (fig. 409). — Origin. — From the outer surface of the ilium between
the anterior and inferior gluteal lines; (2) from the septum between it and the gluteus medius
near the anterior superior ihac spine; and (3) from the capsule of the hip-joint.
Structure and insertion. — The fibre-bundles converge upon a tendon which appears on the
middle of the ventral border and gradually spreads over the lateral surface. The muscle is
thickest in front, where it is usually bound by an intermuscular septum to the gluteus medius.
The tendon is inserted into the ventral surface of the great trochanter of the femur.
Nerve-supply. — From twigs of the branch of the superior gluteal nerve which goes to the
tensor fasciae latae. These twigs enter the middle third of the muscle as the tensor branch passe.i
across it.
Action. — -To abduct the thigh and rotate it medialward. The anterior part of the muscle
is a flexor, the posterior an extensor.
Relations. — It is covered by the gluteus medius and piriformis muscles. Beneath it lie the
inferior part of the iliac ala, the hip-joint (to the capsular ligament of which it is bound), and the
direct tendon of the rectus femoris muscle.
Variations. — It may be fused with the gluteus medius or the piriformis. It vaay send a
slip to the fascia lata or the vastus lateralis. It may be divided into two distinct divisions,
462
THE MUSCULATURE
an anterior and a posterior. Very frequently from the anterior margin of the muscle a special
fasciculus is more or less isolated (the scansorius, invertor femoris, small anterior gluteal, etc.).
The accessorius of the gluteus minimus is a small muscle fasciculus which may lie under cover
of the gluteus minimus and extend to be inserted into the capsule of the hip-joifit.
BuRS^
B. ischiadica m. glutei maximi. — A small inconstant bursa between the tuber ischii and
the gluteus maximus muscle. B. trochanterica m. glutei maximi. — A large bursa constantly
Fig. 409 — The Deep Muscles of the Back op the Thigh.
Gluteus minimus-
Obturator externus
Gluteus maximus
Vastus lateral!
Short head of biceps
Vastus intermedius-
Tendon of biceps-
Obturator internus
Adductor magnus
Vastus medialis
present between the fascial tendon of the gluteus maximus and the posterior lateral surface
of the great trochanter and the origin of the vastus lateralis muscle. B. gluteofemorales. —
Two or three small burste on each side of the tendon of attachment of the gluteus maximus to
the femur. B. trochanterica m. glutei medii anterior. — A small bursa constantly present
between the tendon of the gluteus medius muscle and the lateral surface of the great trochanter.
B. trochanterica m. glutei medii posterior. — A small bursa frequently present between the
tendons of the piriformis and the gluteus medius. B. trochanterica m. glutei minimi. — A
fairly large bursa generally present between the margin of the great trochanter and the tendon
of this muscle. B. m. piriformis. — A small bursa frequently present between the tendons of
the piriformis and superior gemellus muscles and the femur.
OBTURATOR INTERNUS 463
2. ISCHIO-PUBO-FEMORAL MUSCULATURE OF THE HiP
The muscles belonging to this group (the obturator internus, the two gemelli,
the quadratus femoris and the obturator externus, extend from the pubis and
ischium across the back of the hip-joint to the great trochanter and the neigh-
bouring part of the shaft of the femur. They are powerful lateral rotators of
the thigh. The obturator internus (fig. 409), a large, flat, triangular muscle,
arises from the pelvic surface of the innominate bone and from the obturator
membrane. At the lesser sciatic notch its tendon is joined by the two gemelli
(fig. 408), one of which arises on each side from the bony projections which make
the notch, and the combined tendon is inserted into the trochanteric (digital)
fossa. The quadratus femoris (fig. 408) passes from the tuber of the ischium to
the femur behind and below the great trochanter. These muscles are supplied
by special nerves which arise from the front of the sacral plexus and enter the
deep surfaces of the muscles. A fifth muscle, attached to the greater trochanter
and associated with this group, the obturator externus, is differentiated near the
adductor muscles of the thigh and is supplied by a branch from the obturator
nerve. It arises from the outer surface of the bones bounding the ventral two-
thirds of the obturator foramen and is inserted by a tendon into the trochanteric
(digital) fossa.
These muscles seem to have no certain representatives in the arm, where the shoulder-ioint
is entirely ensheathed by the dorsal musculature. It is possible that the pectoral group has a
corresponding embryonic origin. The group is represented, with marked variations, in the lower
extremities of amphibia and aU higher vertebrates.
FASCIA
Within the pelvis the obturator internus hes on the obturator membrane. It is covered
by the obturator fascia, which is attached to the body of the pubis, to the iliac portion of the
arcuate line, to tlie ventral margin of the great sciatic notch, to the ischial spine, to the sacro-
tuberous (great sacro-sciatic) ligament, and with the falciform process of that Ugament, to the
ischial and pubic rami. Near the upper part of the obturator foramen the fascia instead of being
attached to bone is reflected over the muscle and attached to the obturator membrane. It here
helps to bound the canal for the obtiu-ator vessels and nerve. The upper part of the fascia lies
beneath the pelvic peritoneum and the levator ani. The lower part forms the outer boundary of
the ischio-rectal fossa. The fascia is continued as a thin, adherent membrane over the obturator
internus and the gemellus muscles to their attachment. The quadratus femoris is invested by
a thin adherent fascial sheet.
MUSCLES
The obturator internus (fig. 409). — Origin. — From (1) the pelvic surface of the pubic rami
near the obturator foramen; (2) the pelvic surface of the iscliium between the foramen and the
great sciatic notch; (3) the deep surface of the obturator internus fascia; (4) the fibrous arch
which bounds the canal for tlie obturator vessels and nerve; and (5) the pelvic surface of the
obturator membrane except in the lower part.
Structure and insertion. — From this extensive area of origin the fibre-bundles converge
toward the lesser sciatic notch and become applied to the broad tendon of insertion. At the
notch the muscle curves laterally and extends outward and upward to its insertion into the fore
part of the trochanteric fossa of the femur. The tendon is formed of five or six bands which
begin high in the muscle and converge into a common tendon situated on the deep surface
of the muscle as the latter curves about the ischium. The tendon bands at first throw the ten-
don into folds which run in ridges in the fibro-cartilage which lines the notch. The attachment
of fibre-bundles continues upon the dorsal surface of the tendon to half way between the lesser
sciatic notch and the great trochanter.
Nerve-supply. — A special nerve to the obturator internus arises from the front of the sacral
plexus, usually from the lumbo-sacral cord and the first and second sacral nerves. This nerve
passes lateral to the sacro-spinous (lesser sciatic) ligament, then re-enters the pelvis through
the lesser sciatic notch and sends out branches of distribution on the pelvic surface of the obtu-
rator internus.
Action. — This muscle with its two companions, the gemelli, is a powerful lateral rotator
of the thigh. It is also an extensor and abductor when the thigh is bent at a right angle.
Relations. — The chief pelvic relations have been described in connection with the obturator
fascia which completely covers the medial surface of the muscle. The muscle passes out be-
tween the two sacro-ischial (sacro-sciatic) ligaments. Outside the pelvis the gemellus muscles
run on each side of the tendon, which is here closely applied to the capsule of the joint. Dorsal
to it lie the gluteus maximus, the sacro-tuberous (great sacro-sciatic) ligament, the inferior
gluteal (sciatic) vessels, and the sciatic and posterior cutaneous nerves. The nerve of the quad-
ratus femoris runs beneath the obturator internus and gemellus muscles.
Variations. — It varies in the extent of its insertions. It may be divided into two parts,
464 THE M USC ULA T URE
a pubic and an ischial. Fasciculi may be sent to the postero-inferior part of the ilio-pectineal
eminence, the tendon of the psoas minor, the tuber ischii, the sacro-tuberous (great sacro-sciatic)
ligament, the ischial spine, etc.
The gemellus superior (fig. 408). — Origin. — From the outer surface of the ischial spine
and the neighbouring edge of the lesser sciatic notch.
Structure and insertion. — The fibre-bundles encircle the upper border and ventral aspect of
the tendon of the obturator internus. They are inserted into the upper border of this tendon,
and sometimes also into the trochanteric fossa.
Nerve-supply. — From a small nerve which arises either directly from the plexus or as a
branch of the nerve to the obturator internus or of that to the quadratus femoris. This nerve
usually enters the deep surface of the muscle near the junction of its ischial and middle thirds.
Action. — It is essentially a part of the obturator internus.
Relations. — It hes between the piriformis and the tendon of the obturator internus. Proxi-
mally it adjoins its fellow beneath this tendon; distally, the two gemeUi enclose the tendon in a
musculo-tendinous sheath.
Variations. — It may be wanting or may have a more extensive origin than usual. It
may be joined to the piriformis or to the gluteus minimus or be joined more closely than usual
to the obturator tendon.
The gemellus inferior. — Origin. — From the upper part of the inner border of the tuberosity
of the ischium, the sacro-tuberous (great sacro-sciatic) ligament and from the neighbouring edge
of the lesser sciatic notch.
Structure and insertion. — The fibre-bundles converge upon the inferior border of the tendon
of the obturator internus, and are inserted by tendon-fibres into this or into the great trochanter
below the obturator internus tendon.
Nerve-supply. — From a branch of the nerve to the quadratus femoris. This branch enters
the deep sm-face of the muscle near the junction of the ischial with the middle third.
Action. — -It is essentially a part of the obturator internus.
Relations.— \t lies between the quadratus femoris and the tendon of the obturator internus.
Variations. — It is rarely absent. It may be joined to the quadratus femoris. It is fre-
quently closely bound up with the obturator internus. It may be doubled.
The quadratus femoris (fig. 408) .^rOrijin. — From the upper part of the outer border of the
tuber of the ischium.
Structure and insertion. — The fibre-bundles take a nearly parallel course and are inserted
into the vertical ridge which terminates above on the inferior dorsal angle of the great trochanter.
Nerve-supply. — ^From a nerve which arises usually from the lumbo-sacral cord and the first
sacral nerve and passes under the gemelli and the tendon of the obturator internus. The nerve
enters the deep surface of the muscle near the junction of the ischial and middle thirds.
Action. — It is a powerful lateral rotator and a weak adductor of the thigh.
Relations. — -It is covered by the gluteus maximus. Between this muscle and the quadratus
femoris runs the sciatic nerve. The obturator externus muscle lies in front. The inferior
gemellus extends along its superior border. The adductor minimus adjoins it distally.
Variations. — It is absent in from 1 to 2 per cent, of instances. (Schwalbe and Pfitzner.)
It may be double near its femoral insertion. It may be fused with the inferior gemellus or the
adductor magnus. It may send a fasciculus to the semimembranosus.
The obturator externus (figs. 407, 409). — Origin. — From the lateral surface of the pubic
and ischial rami, where they bound the obturator foramen, and from the surface of the obtu-
rator membrane.
Structure and insertion. — ^Often the muscle is distally divided into three fasciculi, a superior
from the superior pubic ramus, a middle from the inferior pubic ramus and the obturator mem-
brane, and an inferior from the ischium. The fibre-bundles converge upon a tendon which is at
first deeply buried, then appears on the lateral surface of the muscle and is continued as a
rounded tendon over the capsule of the joint to its insertion into the dorsal part of the trochan-
teric fossa.
Nerve-supply. — -The obturator nerve gives rise, usually in the obturator canal, to a branch
which bifurcates to enter the superior border and ventral surface of the muscle in its middle
third.
Action. — It is a powerful lateral rotator of the thigh and is also a weak adductor.
Relations. — It is covered by the pectineus, the ilio-psoas, and the adductor magnus muscles
in front, and by the quadratus femoris behind near its insertion. It covers over the obturator
membrane. The obturator nerve passes either above the muscle or through its upper portion.
Variations. — The reported variations are few. It may be joined by a slip from the ad-
ductor brevis.
BURS^
B. m. obturatoris interni. — A fairly large bursa constantly present between the tendon of
the obturator internus muscle and the lesser sciatic notch. It may extend on each side be-
neath the gemellus muscles. B. m. quadrati femoris. — A small bursa frequently found between
this muscle and the small trochanter. B. m. obturatoris externi. — A bursa is sometimundes of
between the tendon of this muscle and the capsule of the joint.
B. MUSCLES OF THE THIGH
In the thigh three groups of muscles may be recognised, an anterior or ex-
tensor (figs. 411, 412), a medial or adductor (figs. 409, 411, 412), and a posterior,
flexor or hamstring group (figs. 408, 413).
MUSCLES OF THIGH
465
Fig. 410, A-D. — Transverse Sections through the Left Thigh in the Regions indicated
IN the Diagram.
466 THE MUSCULATURE
In the proximal part of the thigh the anterior group of muscles is separated
from the medial group by the ilio-psoas muscle (fig. 411) and by the femoral
blood-vessels and nerve, and from the posterior group by the gluteus maximus
(fig. 413). More distally it is separated from the medial group by the medial
intermuscular septum and from the posterior by the lateral intermuscular septum
(see p. 468). The medial and posterior groups are closely associated. The
adductor magnus belongs ontogenetically to both.
The three groups of muscles, with numerous modifications, are represented in the thighs
of amphibia and all higher vertebrates. In the human arm they are likewise represented, the
adductor group in a much reduced form by the coraco-brachialis. The quadriceps is represented
by the triceps in the arm, the long head of the triceps corresponding with the rectus femoris.
The hamstring muscles are represented by the biceps and the braohiahs.
FASCIA
The fascise and the relations of the musculature of the thigh may be followed in the cross-
sections figs. 407, 410, 414.
The tela subcutanea of the thigh varies considerably in thickness in different regions,
but is well developed throughout and contains a considerable amount of fat. Over the front
of the thigh, especially in the upper medial region, one or more deeper membranous layers
may usually be separated from the superficial adipose layer. Between the former and the
latter are situated the inguinal lymphatic nodes and the saphenous vein. The deepest layer
near the inguinal (Poupart's) Ugament is fused with the fascia lata (see below). Medially it
is attached to the pubic arch. Thus fluids beneath the tela subcutanea of the abdomen and
perineum do not readily pass into the region of the thigh.
Over the lower half of the patella a 'subcutaneous bursa (b. praepatellaris subcutanea) is
found. Another is usually found over the upper end of the patellar ligament (b. infrapatellaris
subcutanea).
The muscles of the thigh are enclosed in a dense fascial sheet, the fascia lata (figs. 387, 410).
The gluteal portion of this and the ilio-tibial band have already been described (p. 457). The
ventral portion of the fascia, composed chiefly of transverse fibres, is a dense, fibrous membrane.
Above it is attached to the inguinal Hgament from the anterior superior spine to the pubic
tubercle. Below it extends over the knee, where it is united to the capsule of the joint and is
strengthened by expansions from the vastus lateraUs and mediahs. Between the front of the
patella and the fascia is a bursa (b. praspatellaris subfascialis). Above the knee the fascia is
strengthened by an arciform process which extends obliquely distally across the fascia from the
ilio-tibial band to the capsule of the knee. This gives rise to a fold in the skin when the leg is
extended and the muscles are not tense. Over the medial and posterior regions of the thigh
the fascia is less dense. It extends from the body and inferior ramus of the pubis, the inferior
ramus and tuber of the ischium, and the sacro-tuberous ligament into the fascia of the back
of the leg. Above the popUteal space it is strengthened by a transverse band of fibres. Near
the knee the tendons of the quadriceps, sartorius, gracihs, and semitendinosus become bound
to the fascia by membranous laminse.
The relations of the fascia lata to the inguinal ligament and the iliac fascia are somewhat
complex. The fascia of the ilio-psoas muscle extends over the muscle to its femoral insertion.
Above the inguinal ligament this fascia is called the fascia iliaca; below the ligament, the fascia
ilio-pectinea. This fascia is firmly united to the lateral extremity of the inguinal ligament.
The pectineus muscle is likewise invested with a fascial membrane which extends over the
muscle from the pubis to the femur and is fused laterally with that of the ilio-psoas. This
combined fascia is firmly bound between the two muscles to the ilio-pectineal eminence. The
ilio-pectineal fascia divides the space beneath the inguinal ligament into a lateral lacuna
musculorum, which contains the iUo-psoas muscle and the femoral (anterior crural) nerve, and
a medial lacuna vasorum, which contains the femoral artery and vein. Medial to the vein
is the femoral ring, bounded medially by the lacunar (Gimbernat's) ligament. This is closed
off from the abdominal cavity by a septum derived from the transversahs fascia, the femoral
septum, but offers passage for lymph-vessels.
a and 6 in the diagram indicate the regions through which pass sections A and B, fig. 407 (p. 458) ;
1. Arteria circumflexa femoris lateralis. 2. A. circumflexa femoris medialis. 3. A. fem-
oraUs. 4. A. femoralis profunda. 5. A. glutea inferior (sciatic). 6. A. poplitea. 7. Bursa
praepatellaris subfascialis. 8. Adductor (Hunter's) canal. 9. Fascia lata. 10. Femur — a,
distal extremity. 11. Funiculus spermaticus (spermatic cord). 12. Musculus adductor
brevis. 13. M. adductor longus. 14. M. adductor magnus. 15. M. biceps femoris — a,
long head; b, tendon of origin; c, short head. 16. M. gastrocnemius — a, lateral head; b, medial
head. 17. M. gluteus maximus. 18. M. gracihs — a, tendon. 19. M. rectus femoris — a,
tendon. 20. M. sartorius. 21. M. semimembranosus — a, tendon. 22. M. semitendinosus
• — a, tendon. 23. M. sphincter ani. 24. M. vastus intermedins (orureus) — a, tendon. 25.
M. vastus lateralis — a, tendon. 26. M. vastus medialis — a, tendon. 27. Nervus cutaneous
femoris anterior. 28. N. cutaneous femoris posterior (small sciatic). 29. N. gluteus inferior.
30. N. obturatorius — a, superficial branch; b, deep branch. 31. N. peroneus communis
(external popliteal). 32. N. saphenus (great saphenous). 33. N. tibialis (internal pophteal).
34. Patella. 35. Septum intermusculare laterale. 36. Septum intermusculare mediale. 37.
Tractus iliotibialis (ilio-tibial band). 38. Vena femoralis. 39. Vena poplitea. 40. V.
saphena magna (great saphenous vein).
FASCIA
467
Beyond the inguinal ligament the fasciae of the ilio-psoas and pectineal muscles line a
triangular space, the ilio-pectineal fossa,* through which run the femoral vessels (fig. 407).
The sartorius muscle partly overlies the distal lateral margin of this fossa. The fascia lata is
here reflected from the surface of the sartorius to the ilio-psoas fascia, and becomes fused with
it. From the medial margin of the sartorius a process of the fascia is continued over the lateral
and upper part of the fossa, and is attached to the inguinal and lacunar (Gimbernat's) liga-
FiG. 411. — Muscles of the Front op the Thigh.
Adductor brevis.
Adductor longus
Adductor magnus
Vastus medians
Tendon of sartorius'
Gluteus medius
Gluteus minimus
Tensor fascia latat
Rectus femoris
Ilio-tibial band
Vastus lateralis
Ligamentum patellse
ments (fig. 389). Over the lower extremity of the fossa a process is continued medially into
the pectineal fascia. On the medial margin of the fossa the fascia lata is continued directly
into the pectineal fascia. The lateral concave margin of the fascia overlying the fossa is called
the falciform margin; the upper extremity of this, the superior cornu; the distal extremity, the
inferior cornu. The oval space bounded by the margo falciformis is called the fossa ovalis
(saphenous opening). This is covered by the fascia cribrosa, which some consider a deep layer
* This lies within Scarpa's Iriangle [trigonum femorale], a space bounded by the inguinal
(Poupart's) ligament and the sartorius and long adductor muscles.
468 THE MUSCULATURE
of the tela suboutanea and others a portion of the fascia lata. This fascia cribrosa contains
many openings for the passage of blood-vessels and lymphatics. The space which lies medial
to the femoral vessels between the femoral ring and the fossa ovahs is called the femoral canal
(crural canal).
From the fascia intermuscular septa descend in between the underlying muscles. Of
these, the medial and lateral intermuscular septa are the best marked (fig. 410).
The lateral intermuscular septum separates the extensor muscles from the hamstring
group. It extends from the tendon of the gluteus maximus to the lateral epicondyle. It is
composed chiefly of longitudinal fibres and is thickest distaUy. The vastus lateraUs is united
to its ventro-lateral surface; the short head of the biceps, to its dorso-medial surface.
It will be noted that this septum serves to divide primarily ventral from primarQy dorsal
musculature, with the exception of the short head of the biceps, which, though primarily dorsal,
occupies a position, perhaps secondarily acquhed, with the primarily ventral muscles.
The medial intermuscular septum serves to divide the anterior extensor from the medial
adductor musculature. It is perhaps simplest in the region immediately distal to the ilio-
pectineal fossa (fig. 410 B). Here a well-marked septum may be seen extending to the femur
between the sartorius and quadriceps on the one side, and the adductor longus and brevis on
the other. The septum here, next the muscles, has on each side a membranous lamina. Be-
tween the two laminae there is a looser tissue in which run blood-vessels and nerves. A fibrous
membrane extends between the rectus and sartorius to the septum.
More distally the sartorius comes to overlie the septum (fig. 410 C). The sheath of the
sartorius on the lateral margin becomes fused with the fascia of the vastus mediahs, and on
the medial margin to a membrane that covers the ventral surfaces of the adductor longus and
magnus. Beneath the sartorius and between the adductor longus and the vastus medialis is a
triangular space bounded by the sheaths of these muscles, and fiUed with a loose areolar tissue
in which run the chief blood-vessels of the thigh. This space, first described by John Hunter,
is known as Hunter's canal, or the adductor canal. Still more distally the vessels with their
surrounding fibrous tissue pass through the hiatus tendinous, between the long tendon of the
adductor magnus and the femur, to the back of the thigh. The septum here passes behind the
posterior surface of the vastus medialis to the femur.
MUSCLES
1. The Anterior Group
(Figs. 411, 412)
This group, which forms a semi-conical mass pointed upward, is composed of
the quadriceps femoris and the sartorius muscles, innervated by the femoral
nerve.
The sartorius is a long, ribbon-like muscle which arises from the anterior
superior spine of the ilium and extends along the medial margin of the quadriceps,
passing obliquely across the upper part of the thigh, and then descending to the
dorse-medial side of the knee, whence its tendon curves forward to be inserted
into the ventro-medial surface of the superior extremity of the tibia.
The quadriceps femoris is composed of four muscles differentiated from a com-
mon embr3'onic origin. Of these, the rectus femoris, which arises from the
ventro-lateral margin of the ilium by two tendons, is the most superficial and
the most completely differentiated. The vastus lateralis, which arises from the
superior e.xtremity of the ventral surface of the shaft of the femur and from the
lateral lip of the linea aspera; the vastus medialis, which arises from the medial
lip of the linea aspera and from the intertrochanteric line; and the vastus inter-
medius (crureus), which arises between these two and beneath the rectus from the
surface of the femur, are less distinctly differentiated from one another. The
vastus intermedius and vastus laterahs are partly fused at the insertion, the
intermedins and medialis at their origins. From the four muscles arises a tendon
which is inserted into the tuberosity of the tibia. In this tendon, which is
closely applied to the capsule of the knee-joint, lies a sesamoid bone, the patella.
The sartorius and the rectus flex the thigh; the quadriceps extends
the leg; the sartorius flexes the leg and rotates the thigh lateralward and the
leg medialward.
In the embryo the sartorius has an origin distinct from that of the quadriceps. In the
anthropoid apes it is much more developed than in man.
In addition to supplying the muscles of this group, the femoral nerve also gives branches
to the iliaous muscle (p. 4.55) and the pectineus muscle (p. 472).
The sartorius (fig. 411). — Origin. — From the anterior superior spine of the iUum and the
area immediately below this.
Insertion. — Into the medial surface of the tibia near the tuberosity and into the neighbour-
ing fascia of the leg.
SARTORIUS
469
Structure. — The muscle arises by short tendinous strands. The fibre-bundles take a nearly
parallel course. The component muscle-fibres are said to be the longest in the body. Near the
medial epicondyle of the femur the tendon of insertion makes its appearance on the deep as-
pect of the muscle. On the superficial surface of the tendon the muscle-fibres are inserted
as far as the distal margin of the knee-joint. From there the tendon turns forward to its
insertion.
Nerve-supply. — Usually two branches enter the deep surface of the proximal third of the
sartorius. One or both of them may be bound up with an anterior cutaneous nerve passing
Fig. 412. — The Deep Muscles of the Front op the Thigh.
Obturator externus
Adductor longu:
Adductor magnu£
Adductor longus
Vastus intermedius
Vastus mediali!
Rectus femoris
Ligamentum patellae
Rectus tendon
Gluteus medius
[— Gluteus minimus
Adductor brevis
Vastus lateralis
Biceps
Ilio-tibial band
through the muscle. The first of the branches is distributed chiefly to the lateral and proximal,
the second to the medial and distal, portions of the muscle. Within the muscle is a complex
plexus.
Action. — (1) To flex the thigh at the hip, abduct and rotate it lateralward; (2) to flex the leg
and rotate it slightly medialward; (3) to make tense the medial part of the fascia lata.
Relations. — The sartorius lies in a fascial canal bounded by the fascia lata and by inter-
muscular septa which descend from this. It crosses the rectus femoris, ilio-psoas, the adductor
d70 THE MUSCULATURE
longus and magnus, and the vastus medialis muscles, the femoral vessels and nerve, and the
knee-joint. At its insertion its tendon covers the gracilis and semitendinosus.
Variations. — It may arise from the inguinal ligament or be inserted into the fascia lata,
the medial epicondyle, or the capsule of the knee-joint. It may be longitudinally divided into
two parts. The tendon of the secondary slip is in such instances usuaOy attached to the capsule
of the knee-joint, but sometimes is attached to the fascia over the vastus medialis or to the
anterior wall of the adductor canal. More frequently the muscle is partly divided proximally
or distaUy. The secondary tendon of origin may arise from the anterior inferior spine, the
ilio-pectineal eminence, etc. The muscle is very rarely absent. It may be crossed by a ten-
dinous inscription, or more rarely it is rendered digastric by an intervening tendon.
The quadriceps femoris (figs. 411, 412). — This, as pointed out above, is composed of the
rectus femoris and the vastus lateralis, intermedins, and medialis.
The rectus femoris (fig. 411). — Origin. — By two tendons. The anterior 'straight' tendon
is attached to the anterior inferior spine of the ilium; the posterior 'reflected' tendon to the
postero-superior surface of the rim of the acetabulum. The two tendons unite so as to form
a small arch above the capsule of the joint.
Structure and insertion. — From this arch an aponeurotic expansion descends upon the front
of the muscle nearly to the middle of the thigh. This expansion is broad above, becomes
narrower as it descends, and is continued a short distance as a narrow intramuscular tendon
after it disappears from the surface. The tendon of insertion begins on the back of the muscle
above the middle of the thigh, expands into a broad aponeurosis, and finally becomes a strong
band which is inserted into the proximal border of the patella. The fibre-bundles pass in a bi-
penniform manner from the back and sides of the tendon of origin to the front and sides of the
tendon of insertion.
Nerve-swpply. — As a rule, two branches enter the muscle. One of these enters the deep
surface of the muscle in its upper fourth, and is distributed mainly to the proximal part of the
lateral half. The other enters the medial margin of the muscle near the junction of the proxi-
mal and middle thirds, and is distributed chiefly to the medial half and distal portion of the
muscle.
The vastus lateralis (vastus externus) (fig. 412). — Origin. — From — (1) the shaft of the
femur along the antero-inferior margin of the great trochanter and in front of the gluteal tuber-
osity; and (2) the lateral intermuscular septum along the upper half of the linea aspera.
Insertion. — By a flat tendon into — (1) the proximo-lateral border of the patella; and (2) the
front of the lateral condyle of the tibia and the fascia of the leg.
Structure. — The fibre-bundles arise partly from the bone, partly from an aponeurosis which
covers the proximal two-thirds of the muscle, and from the lateral intermuscular septum. They
take a parallel course distally in a ventro-medial direction, and are inserted into an aponeurosis
which lies on the deep surface of the muscle and receives fibres until within a few centimetres
of the patella. Ventrally this aponeurosis fuses with the rectus tendon, laterally with that of
the vastus medialis, and dorsally it receives some of the fibre-bundles of the vastus intermedins.
Commonly the muscle is distinctly divisible for the greater part of its course into two sheets,
a superficial and a deep. The deep sheet is often subdivided into two laminae.
NerBe-supply. — Usually there are three nerves, one of which, accompanied by blood-vessels,
runs on the inner surface of the superficial sheet midway between the tendons of origin and
insertion, the second between the two laminae of the deep layer, and the third passes through
the innermost lamina to be distributed in part to the vastus intermedins (crureus) muscle.
The vastus medialis (vastus internus) (fig. 412). — Origin. — From the whole extent of the
medial lip of the linea aspera and from the distal half of the intertrochanteric line. The origin
takes place by means of an aponeurosis which is adherent to the tendons of insertion of the
adductor muscles.
Structure and insertion. — The fibre-bundles arise from the deep surface of this aponeurosis
and are inserted on the medial surface and margin of a tendon which begins on the deep surface
of the muscle about its middle near the lateral margin. On the distal lateral border of the
muscle it is inserted into the medial half of the proximal margin of the patella and into the
medial condyle of the tibia and the fascia of the leg. For some distance near the knee the
lateral margin of the tendon is united to those of the vastus intermedins (crureus), lateralis
(externus) and the rectus.
Nerve-supply. — The nerve to this muscle descends on its medial surface, often bound up
with the saphenous nerve for a part of its course. It gives off successive branches and finally
sinks into the muscle substance. These branches enter about midway between the origin and
insertion of the fibre-bundles of the muscle.
The vastus intermedins (crureus) (figs. 409, 412). — Origin. — From (1) the distal half of the
lateral margin of the linea aspera and its lateral bifurcation; (2) the antero-lateral siu'face of the
shaft of the femur. Between the origin of the vastus intermedins (crureus) and that of the
vastus medialis the shaft of the femui' is free from muscle attachment.
Structure and insertion. — On the ventral surface of the muscle lies an aponeurosis which
extends from its proximal fourth to the proximal margin of the patella. The fibre-bundles of
the muscle are inserted into the deep surface of this and into the deep surface of the aponeurosis
of insertion of the vastus lateralis. The proximal fibre-bundles descend vertically, the medial
and lateral, especially the latter, obliquely to their insertion. Medially the tendon is more or
less fused with that of the vastus medialis, and laterally with that of the vastus lateralis. The
muscle is composed of muscle lamelto superimposed concentrically about the shaft of the femur.
The deepest, most distal of these is called the articularis genu (subcrureus). The fibre-bundles
of this layer are inserted into the capsule of the joint or into the superior margin of the pateUa.
Nerve-supply. — Several branches are usually distributed to this muscle. To the lateral
region a branch from the nerve to the vastus lateralis is usually given; to the middle of the
muscle another branch descends from the femoral (anterior crural) nerve; to the medial portion
there extend several twigs from the nerve to the vastus medialis.
ADDUCTOR MUSCLES 471
Tendon of the quadriceps. — The quadriceps tendon may be more or less distinctly divided
into layers, of which the superficial layer belongs to the rectus, the deep to the vastus inter-
medins, and the intermediate to the vastus lateralis and medialis. Some of the more superficial
fibres of the tendons of the two vasti, however, cross in front of the rectus tendon. The com-
bined tendon of the quadriceps is in part attached to the superior and lateral margins of the
patella, and in part extends over the patella into the patellar ligament. A part of the tendon
fibres of the vastus laterahs and medialis run on each side of the patella to the ventral surface of
the condyles of the tibia. These form the retinacula patellse mediate and laterale. The medial
is the broader and better developed. With the retinacula are included bundles of fibres which
run from the epicondyles to the patella and into which some muscle fibre-bundles are inserted.
From the apex of the patella to the tuberosity of the tibia the quadriceps tendon is continued
as the patellar ligament (fig. 415).
Nerve-supply. — The relations of the branches of distribution to the various parts of the
muscle have been pointed out above in connection with each head. The general relations of
these branches of the femoral nerve are as follows: — From the femoral nerve near the proximal
end of the vastus medialis the branches for the vastus lateralis, vastus intermedins (crureus), and
rectus pass distally and laterally between the rectus and vastus intermedins (crureus) to be
distributed to the muscles named, while the chief nerve for the vastus mediahs descends on the
medial side of this muscle in company with the saphenous nerve. The branches to the vastus
lateralis and intermedins are commonly bound up in a single nerve-trunk for some distance.
The branches to the rectus are usually bound up with this trunk for a shorter distance. The
nerve to the vastus medialis may be united to this trunk for a slight distance, but more
frequently it is more or less bound up with the saphenous nerve.
Action. — The quadriceps is the extensor of the leg. The rectus femoris also flexes the thigh
at the hip and is a weak abductor of the thigh. The articularis genu makes tense the capsule
of the knee-joint.
Relations. — The quadriceps is covered ventrally immediately by the fascia lata. The
sartorius runs along its medial margin; the tensor fasciee latse lies over the proximal quarter
of its lateral surface. Dorsal to the vastus lateralis lie the gluteus maximus and biceps; dorso-
medial to the vastus medialis, the three adductor muscles and the semimembranosus. Next
the vastus medialis lies the adductor canal with the femoral vessels and the saphenous nerve.
Variations. — The variations of this muscle, aside from a greater or less fusion of its parts,
are not marked. The attachment of the rectus femoris to the anterior inferior spine, which
takes place in the embryo later than its insertion above the acetabulum, may be wanting. On
the other hand, this tendon may extend to the anterior superior spine. Occasionally the deep
reflected tendon may be wanting. The rectus accessorius is a fasciculus rarely found, which
arises by a tendon from the rim of the acetabulum and is inserted into the ventral edge of the
vastus lateralis. It is innervated by a twig from the branch to the rectus.
BURS^
B. m. recti femoris (superior). — A small bursa between the deep tendon of the rectus
femoris and the edge of the acetabulum. Rare. B. m. recti femoris (inferior). — Between
the tendon of the rectus and the combined tendon of the vastus lateralis and medialis. Oc-
casional. B. praepatellaris subtendinea. — A bursa between the tendon of the quadriceps
and the periosteum of the patella. Of the three prepatellar bursK — the subcutaneous, sub-
fascial, and subtendinous — as a rule only one occurs. When two or three exist, they usually
communicate freely with one another. B. suprapatellaris. — A bursa between the anterior
surface of the lower end of the femur and the tendon of the quadriceps. It usually communi-
cates with the joint cavity. B. infrapatellaris profunda. — A bursa between the patellar liga-
ment and the tibia. It seldom communicates with the joint cavity. B. m. sartorii propria.
— A bursa, fairly large, between the tendon of the sartorius and the tendons of the semitendi-
nosus and gracilis muscles. This usually communicates with the bursa anserina (see p. 474).
2. The Medial (Adductor) Group
(Figs. 409, 411, 412)
To this group of muscles belong the gracilis, the pectineus, the adductors brevis,
longus, and magnus, and the obturator externus. The most superficial of the
group is the gracilis (figs. 408, 411). This ribbon-shaped muscle arises from the
inferior pubic and ischial rami, extends along the medial side of the thigh, and
gives rise to a tendon which curves forward from behind the medial condyle of
the femur to be inserted under the tendon of the sartorius into the medial side of
the upper extremity of the tibia. The quadrilateral pectineus arises from the
body and superior ramus of the pubis; the triangular adductor longus from the
superior ramus medial to this (fig. 411). The pectineus is inserted into the
pectineal line of the femur; the adductor longus into the middle third of the linea
aspera. The triangular adductor brevis (fig. 412) arises from the inferior pubic
ramus below the adductor longus. It is inserted into the pectineal line and the
upper third of the linea aspera. The large, triangular adductor magnus (figs.
409, 412) arises from the inferior ramus and the tuber of the ischium and is
472 THE MUSCULATURE
inserted behind the short and long adductors into the whole length of the linea
aspera, and by a special tendon into the adductor tubercle of the femur. The
deepest muscle of the group, the obturator externus, which arises from the outer
surface of the bones bounding the ventral two-thirds of the obturator foramen,
and is inserted by a tendon into the trochanteric (digital) fossa, has been described
in connection with the ischio-pubo-femoral muscles of the hip.
All the muscles of this group adduct the thigh. The gracilis, obturator ex-
ternus, adductor brevis and the lower part of the adductor magnus (when the
thigh is extended) rotate it lateralward. The pectineus, adductor longus, and
the adductor magnus rotate it medialward. Those attached to the pubis flex
the thigh. The gracilis flexes the leg and rotates it medialward. The inferior
part of the adductor magnus extends the thigh.
The muscles of this group are supplied by the obturator nerve, except the
pectineus, which usually gets its whole supply from the femoral (anterior crural)
nerve, and the adductor magnus, which gets a part of its supply from the sciatic
nerve.
In embryonic development the pectineus arises in close conjunction with the obturator
group, and in the adult it may get the wliole or a part of its nerve-supply from the obturator
nerve or from the accessory obturator nerve. In the lower mammals the nerve-supply may
come from the femoral (anterior crural) or the obturator nerve or from both. It is not certain
whether the innervation from the femoral nerve indicates that the muscle belongs phylo-
genetically, if not ontogenetically, with the primitive dorsal musculature of the limb. By
some it is considered to be derived in part from the primitive dorsal, in part from the primitive
ventral, musculature. The adductor magnus arises in the embryo as two distinct portions, one
connected with the flexor group of muscles, the other with the adductor group. These two
portions later become fused. Primitively the sciatic portion of the adductor magnus and the
semimembranosus constitute a single medial flexor muscle.
The gracilis (figs. 408, 411). — Origin. — By a flat tendon from the medial margin of the
inferior ramus of the pubis and the pubic extremity of the inferior ramus of the ischium.
Structure and insertion. — The nearly parallel fibre-bundles which arise between two laminse
of the tendon form a thin band of muscle which is narrower and thicker distaUy than proximally.
They are inserted on a tendon which begins as an aponeurosis on the posterior border and medial
surface of the muscle in the distal third of the thigh, becomes free as a rounded cord a little
proximal to the medial condyle of the femur, runs behind the condyle, and then turns forward
to be inserted by an expanded process into the tibia below the medial condyle.
Nerve-supply. — The nerve enters the deep surface of the muscle near the junction of the
superior and middle thirds.
Action. — To adduct, flex and (sUghtly) rotate the thigh lateralward, and flex the leg.
With the knee flexed, it acts as a medial rotator of the leg.
Relations. — It occupies a position beneath the fascia lata and superficial to the adductor
brevis, longus, and magnus muscles. DistaUy the sartorius lies in front, the semimembranosus
behind. Its tendon crosses the tibial collateral Ugament of the knee-joint and the tendons
of the semitendinosus and the semimembranosus, and is overlapped by that of the sartorius.
Variations. — The pubic Origin of the muscle may be much reduced or may be double.
Its tendon of insertion may give rise to an accessory fasciculus which extends distaUy in the
leg. In some of the apes the tendon descends normally much farther down the leg than in man.
The pectineus (fig. 411.) — Origin. — (1) From the peoten (crest) of the os pubis, the bone
in front of this, and the pectineal fascia near this origin; and (2) from the anterior margin of
the obturator sulcus and from the pubo-capsular hgament. Laterally the two areas of origin
are usually separated by most of the superior surface of the body of the pubis. Medially _they
come together.
Structure and insertion. — From each area of origin a separate lamina arises. The fibre-
bundles of each layer take a nearly parallel course and terminate between two tendinous lameUfe
which fuse to be inserted into the upper half of the pectineal line behind the small trochanter.
The fibre-bundles of the superficial layer cross those of the deep slightly obliquely. The muscle
faces ventraUy at its origin, laterally at its insertion.
Nerve-supply. — From a branch of the femoral (anterior crural) nerve, which passes behind
the femoral artery and vein and through the pectineal fascia to enter the ventral surface of the
muscle. It may also be supplied by the accessory obturator nerve, when present, or by a branch
from the obturator. When both the femoral (anterior crura!) and obturator nerves supply this
muscle, the femoral supphes the superficial, the obturator, the deep lamina (Paterson).
Action. — To flex and adduct the thigh (as in crossing the legs).
Relations. — It is covered by the pectineal fascia, lies between the ilio-psoas and the adductor
longus muscles, and crosses the obturator externus and adductor brevis muscles. The medial
circumflex artery runs between it and the ilio-psoas, the deep femoral artery between it and the
adductor longus.
Variations. — The extent of the division of the pectineus into superficial and deep portions
varies considerably. It may also be divided into a lateral and a medial division. Often the
pectineus is fused with the adductor longus. It may receive an accessory fasciculus from the
capsule of the hip-joint, the iliacus muscle, the obturator externus, or the adductor brevis
muscles, or the small trochanter. It may send a fasciculus to the sartorius.
The adductor longus (fig. 411). — Origin. — From the medial corner of the superior ramus
ADDUCTOR LONGUS
473
of the pubis by a strong tendon which extends for some distance on the medial border of the
Structure and insertion. — From this tendon the fibre-bundles diverge toward then- insertion.
Fig. 413. — Superficial Muscles op the Back of the Thigh and Leg.
Gluteus medius-
Fascial insertion of gluteus maximus"
-Gluteus maximus
"Semi-membranosus
Vastus lateralis-
Gastrocnemius-
"Semi-tendinosus
"Gracilis
-Tendon of semi-membranosus
Peroneus longus"
-Flexor digitorum longus
■'Tendo Achillis
This takes place between two lamellae of a short tendon attached to the middle third of the linea
aspera. The tendon is usually fused to the medial intermuscular septum and sends an expansion
to the long tendon of the adductor magnus.
474 THE MUSCULATURE
Nerve-supply. — A branch from the anterior division of the main obturator trunk gives off
several twigs which enter the middle third of the deep surface of the muscle. Occasionally a
small branch from the femoral (anterior crural) nerve enters the muscle. This is probably
sensory in nature.
Action. — To adduct and flex the thigh, and rotate it medialward.
Relations. — The sartorius, the vastus medialis, and the femoral vessels he antero-lateral
to it. Behind it lie the adductor brevis and adductor magnus muscles. Between these and
the longus run the profunda vessels. Its lateral border touches the pectineus above, but is
separated from it toward the insertion.
Variations. — It may be fused with the other adductors, including the pectineus. It may
be doubled. The femoral insertion may extend to the medial epioondyle.
The adductor brevis (fig. 412). — Origin. — From the medial part of the outer surface of the
inferior ramus of the pubis directly, and by means of short tendinous processes or a short flat
tendon.
Structure and insertion. — From their origin the fibre-bundles diverge into a sheet which is
inserted by short tendinous bands into the distal two-thirds of the pectineal line and the upper
third of the hnea aspera. The muscle is more or less completely divided into two fasoiouU near
its insertion. The place of division is near where the intertrochanteric fine curves away from
the linea aspera.
Nerve-supply. — Usually from the anterior but also sometimes from the posterior branch
of the main obturator trunk. The rami enter the middle third of the muscle near the proximal
border.
Action. — It is chiefly an adductor and to a less extent a flexor and a lateral rotator of the
thigh.
Relations. — In front he the pectineus and adductor longus; behind, the obturator externus
quadratus femoris and adductor magnus. It is crossed by the profunda artery. The first
perforating artery passes usually between the two fasciouh of the insertion.
Variations. — It may be fused with other members of the group. It may be divided com-
pletely into two fasciculi, rarely into three.
The adductor magnus (figs. 409, 412). — The origin of this muscle begins on the inferior
ramus of the pubis posterior to the origins of the adductor brevis and gracilis muscles. From
here it extends backward along the inferior margin of the ventro-lateral surface of the ischium
to the tuberosity. The muscle in passing from this curved origin to its extensive femoral in-
sertion presents posteriorly a longitudinal groove in which rest the hamstring muscles. The
adductor magnus is composed of three superimposed fasciculi, of which the first is frequently
fairly distinct and is called the'.adductor minimus, while the other two are normally fused, but
are occasionally distinct.
The superior fasciculus (adductor minimus) arises directly from the inferior rami of the
pubis and ischium. From here the fibres diverge to form a thin sheet inserted by tendinous
bands to the medial side of the gluteal ridge and the superior part of the hnea aspera. The
middle fasciculus arises dii'ectly from the inferior margin of the ventro-lateral surface of the
inferior ramus and the tuber of the ischium, and from a tendon which descends along the dorso-
medial margin of the muscle from the tuber ischti. The fibre-bundles diverge to be inserted
between the lamellae of a narrow flat tendon attached to the distal three-fourths of the linea
aspera. This tendon is pierced by the perforating vessels. The inferior fasciculus arises
dorsal to and in common with the middle fasciculus. The fibre-bundles converge toward a
strong tendon which begins in the distal third of the -thigh and is'inserted into a tubercle at the
distal end of the medial supracondylar ridge.
Nerve-supply. — The chief nerve-supply is from the posterior ramus of the obturator.
This enters by one or more branches the proximal portion of the ventral surface of the muscle
about midway between its pubic and femoral attachments. It also receives a branch from
the sciatic which enters the dorsal surface of the muscle in the middle third of the thigh. To
the adductor minimus a branch may be sent from the nerve to the quadratus femoris.
Action. — It is the strongest of the adductors. The superior and middle fasciculi rotate
the thigh medialward and flex it; the inferior rotate it lateralward when the thigh is extended,
but medialward when the thigh is flexed. The latter also extend the thigh.
Relations. — In front are the pectineus, the short and long adductor and the vastus medialis
muscles, and the profunda artery. Behind lie the hamstring muscles and the gluteus maximus.
Medially lies the gracilis muscle. The femoral and perforating arteries pass through its attach-
ment to the shaft of the femur.
Variations. — The divisions of the muscle may be more or less distinct. It may be partly
fused or exchange fasciculi with neighbouring muscles — the semimembranosus, quadratus
femoris, adductor brevis, and adductor longus.
BxmsM
B. m. pectinei. — A small bursa frequently present between this muscle and the iUo-psoas
and small trochanter. B. anserina. — A fairly large bursa which lies between the tendons of
the sartorius, gracUis, and semitendinosus muscles and the tibial collateral hgament of the knee-
joint. (See also B. M. Sartorii Propria, p. 471.)
3. The Posterior (Hamstring) Group
(Figs. 408, 413)
The muscles of this group are the semitendinosus, semimembranosus, and
biceps. They flex the leg and extend and adduct the thigh. The semitendinosus
HAMSTRING GROUP 475
and semimembranosus rotate the thigh and the leg medialward; the biceps,
lateralward. The semitendinosus and the long head of the biceps constitute a
superficial layer; the semimembranosus and the short head of the biceps a deep
layer. The semitendinosus and the long head of the biceps arise by a common
tendon from the tuber of the ischium. The somewhat fusiform semitendinosus
gives rise to a tendon in the lower half of the thigh. The tendon curves forward
behind the knee to be inserted under that of the sartorius into the medial side of
the tibia. The penniform short head of the biceps arises from the linea aspera
in the lower part of the thigh, and is inserted, together with the fusiform long
head, into a tendon that passes over the lateral side of the knee and is attached
to the head of the fibula. The semimembranosus arises from the tuber ischii
through a long, flat, triangular tendon. The belly of the muscle increases in
thickness toward the knee. It is inserted by a strong tendon on the back of the
medial condyle of the tibia. From the tendons of all the hamstring muscles
expansions are sent into the crural fascia.
The muscles of this group are all supplied by the tibial portion of the sciatic,
except the short head of the biceps, which is suppUed from the peroneal portion.
The femoral head of the biceps is characteristic of the anthropoid apes and man. In many-
mammals its place is taken by a slender muscle, the tenuissimus, which extends from the caudal
vertebraj, the sacro-tuberous (great sacro-sciatic) ligament, or the gluteal fascia to the fascia
of the back of the leg. In some forms this muscle is broad instead of slender. According to
Testut, the long head of the biceps may be looked upon as arising by two fasciculi, one primi-
tively attached to the posterior part of the ihum, the other to the caudal vertebrse or coccyx.
The sacro-tulserous (great sacro-sciatic) ligament represents the reduced upper portion of this
muscle. In the foetus the origin of the muscle extends higher on the sacro-tuberous Ugament
than in the adult. In many of the lower mammals the origins of the semimembranosus and
semitendinosus take place in part from the sacro-caudal vertebras.
In the mammals below man the insertion of the biceps, gracilis, and semitendinosus takes
place chiefly into the fascia of the back of the leg, and extends more distally than in man. This
insertion of these flexor muscles is associated with a permanent position of flexion of the leg at the
knee. In the human embryo likewise these muscles are inserted more distally than in the adult.
In the lower primates the semimembranosus is chiefly a medial rotator of the leg.
Biceps femoris (Figs. 408, 413). — Long head. — Origin. — From a tendon common to it and
the semitendinosus. This tendon arises from the more medial of the two facets on the back of
the tuber of the ischium and from the sacro-tuberous (great sacro-sciatic) ligament. It is
continued for a third of the distance to the knee as a septum between the biceps and the semi-
tendinosus, and for a short distance as. an aponeurotic sheath on the deep surface of the biceps.
Structure and insertion. — The fibre-bundles begin to arise from the tendon some distance
from the ischium. They form a thick fusiform belly which is inserted into the deep surface of
a tendon that begins laterally on the back of the muscle about the middle of the thigh. The
insertion of the fibre-bundles of the long head continues on the medial margin of the deep surface
of the tendon nearly as far as the lateral condyle of the femur.
Short head. — Origin. — By short tendinous fibres from the lateral lip of the linea aspera of
the femur from the middle of the shaft to the bifurcation of this line, the proximal two-thirds
of the supracondylar ridge, and the lateral intermuscular septum.
Structure and insertion. — ^The fibre-bundles take a nearly parallel course, to be inserted on
the deep surface of the common tendon of insertion. The most distal fibres are inserted nearly
to the skeletal attachment of the tendon. The tendon is inserted into the superior extremity
of the head of the fibula, into the lateral condyle of the tibia, and into the fascia of the leg.
Nerve-supply. — Commonly two branches are given to the long head of the biceps. One
of these branches is given off proximal to the ischium, and enters the 'proximal third of the deep
surface of the muscle. The other is given off more distally and usually enters the middle third.
Either or both branches may be doubled or the two may be combined for some distance in a
common trunk. The nerve-fibres arise usually from the first, second, and third sacral nerves.
The branch to the short head arises from the peroneal (external pophteal) portion of the sciatic
nerve about the middle of the thigh. It enters the posterior surface near the lateral margin of
the muscle, and passes distaUy across the muscle bundles about midway between the tendons of
origin and insertion. The nerve-fibres come chiefly from the fifth lumbar, first and second
sacral nerves.
Action. — To extend and adduct the thigh and flex the leg. The short head acts only on the
leg. The long head acts as a lateral rotator of the thigh, and of the leg when flexed.
Relations. — The upper extremity of the muscle is covered by the gluteus maximus. Below
this the long head and tendon of insertion lie beneath the fascia lata and overhe the short head.
Ventral to the muscle lie the tendon of origin of the semimembranosus, the adductor magnus
and vastus lateralis muscles, and the lateral head of the gastrocnemius. The medial border is
in contact with the semitendinosus and semimembranosus. Distally it forms the upper lateral
border of the pophteal space. The sciatic nerve runs between it and the adductor magnus.
Variations. — The short head is rarely absent. It may be more isolated from the long
head than usual, and at times has a separate tendon of insertion. It may itself be divided into
two distinct laminae. Its origin may take place higher up on the femur than usual or from the
fascia lata. Variations of this sort suggest the tenuissimus muscle of some of the lower mammals
476 THE MUSCULATURE
(see above). The long head of the biceps may receive accessory fasciculi from the coccyx,
sacrum, sacro-tuberous (great sacro-sciatic) ligament, tuber of the ischium, or the deep surface
of the gluteus maximus. These fasciculi suggest the iliac and sacro-coccygeal origin of the
muscle found in lower vertebrates (see above). Inferiorly, a muscle fasciculus may take
the place of the fibrous prolongations from the tendon of the biceps into the sural fascia (the
tensores fasciae suralis). This may extend to the tendon of Achilles. The long head may
have a tendinous inscription similar to that of the semitendinosus.
The semitendinosus (figs. 408, 413). — Origin. — Partly from a medio-dorsal facet on the
distal margin of the tuber of the ischium by direct implantation of the fibre-bundles, and
partly from the medial surface of the tendon common to it and the long head of the biceps.
Structure and insertion. — The fibre-bundles spread out to form a flat, fusiform belly which,
about the middle of the thigh, again contracts toward the tendon of insertion. This begins on
the medial margin and dorsal surface of the muscle, becomes free from the muscle slightly above
the medial condyle of the femur, passes behind this and curves forward to be inserted by a trian-
gular expansion into the proximal part of the medial surface of the tibia behind and distal to
the insertion of the gracilis. An aponeurotic expansion is continued into the fascia of the leg.
About the middle of the muscle a narrow irregular tendinous inscription more or less completely
divides the belly into proximal and distal divisions.
Nerve-supply. — To the muscle two nerves are commonly given. One arises from the sciatic
nerve or directly from the plexus, proximal to the tuber of the ischium, sometimes in com-
pany with a branch to the long head of the biceps. It enters the middle third of the deep surface
of the proximal portion of the muscle. The other branch arises from the sciatic nerve, usually
distal to the ischial tuber, sometimes in common with a nerve to the biceps or the semimem-
branosus. It enters about the middle of the deep surface of the distal half of the muscle.
Either or both branches may be represented by two nerves. The nerve fibres of the first
branch arise chiefly from the first and second sacral nerves, those of the second from the fifth
lumbar and first sacral nerves.
Action. — To extend and adduct the thigh and rotate it medialward and to flex the leg,
and with knee flexed, to rotate the leg medialward.
Relations. — It is covered by the gluteus maximus and fascia lata; on the lateral side lies
the biceps; and in front, the semimembranosus and adductor magnus.
Variations. — It may be completely separated from the biceps at its origin. It may be
fused with neighbom'ing muscles. There may be two tendinous inscriptions. It may have a
femoral head (a condition characteristic of many birds). A muscle fasciculus may extend from
the body of the muscle to the fascia of the back of the leg.
The semimembranosus (fig. 408). — Origin. — By a long, flat tendon which lies beneath the
proximal half of the semitendinosus, and which arises from the more lateral of the two facets
on the back of the tuber of the ischium, between the tendons of the biceps and the quadratus
femoris. The tendon is at first adherent to the tendon of the adductor magnus in front and
to that of the biceps and semitendinosus behind. It descends to the middle of the muscle.
Structure and insertion. — From both surfaces of the medial side and distal extremity
of the tendon of origin fibre-bundles arise which take an oblique course to their insertion on the
aponeurosis of the tendon of insertion. This appears on the deep surface and medial margin
of the muscle opposite the end of the tendon of origin and descends on the medial side and deep
surface of the muscle. Near the back of the medial condyle of the femur the insertion of muscle-
fibres ceases and the tendon is inserted directly on the back of the medial condyle of the tibia,
and by aponeurotic expansions into the capsule of the joint, into the lateral condyle of the femur,
into the tibial collateral ligament, and into the fascia of the pophteus muscle.
Nerve-supply. — By several branches from the sciatic nerve, which usually arise from a
common trunk in company with the branches to the adductor magnus. These branches enter
the deep surface of the muscle about midway between the origin and insertion of the constituent
fibre-bundles.
Action. — To flex the leg and rotate it medialward and to extend and adduct the thigh and
rotate it medialward.
Relations. — It is covered by the gluteus maximus, the long head of the biceps, the semi-
tendinosus, and the fascia lata. It lies dorsal to the quadratus femoris, the adductor magnus,
and the knee-joint.
Variations. — It may be fused with the semitendinosus or the adductor magnus. It may
be doubled. Its tendons may have a more extensive attachment than usual. The extent of
the belly of the muscle varies con.siderably. A muscle fasciculus may be sent into the popUteal
space. An extra head may arise from the ischial spine.
BURS^
B. m. bicipitis femoris superior. — A fair-sized bursa which frequently lies between the
tendon of origin of the long head of the biceps and semitendinosus and the tendon of the semi-
membranosus and the ischial tuber. B. m. bicipitis femoris inferior. — A small bursa which
separates the tendon of insertion from the fibular collateral ligament of the knee-joint. B. m.
bicipitis gastrocnemialis. — A bm-sa infrequently found between the tendon of the biceps and
the tendons of origin of the lateral head of the gastrocnemius and the plantaris muscles. B.
m. semimembranosus. — This is a large double bursa constantly present. One part extends
between the semimembranosus, the medial head of the gastrocnemius, and the knee-joint.
With the cavity of the joint it frequently communicates. The other part extends between the
tendon of the semimembranosus and the medial condyle of the tibia.
MUSCLES OF LEG 477
C. MUSCULATURE OF THE LEG
(Figs. 413-422)
The musculature of the leg arises in part from the distal end of the femur,
but in the main from the tibia and fibula. The muscle-bellies are best developed
in the proximal half of the leg, where they give rise to the ' calf behind and to less
well-marked ventral and lateral protrusions. Toward the ankle the muscle-
bellies give way to tendons which attach the muscles of the leg to the skeleton of
the foot.
The musculature is divisible into an anterior, a lateral and a posterior group of
muscles. The anterior and lateral groups are separated from one another by an
intermuscular septum. The antero-lateral groups are separated from the pos-
terior group by the tibia and fibula, the interosseous membrane, and by an
intermuscular septum which extends from the lateral margin of the shaft of the
fibula to the fascia enveloping the leg. Medially the separation is well marked
by the broad medial surface of the tibia. Laterally the line of division is not so
clearly marked externally. In the proximal part of the leg the dorsal musculature
protrudes somewhat ventrally; in the distal part the lateral musculature passes
dorsal to the lower end of the fibula. The posterior group is divided by a trans-
verse septum into superficial and deep divisions.
While in the forearm the extensor-supinator muscles extend proximally on the radial side
of the arm to the humerus, and the flexor-pronator muscles on the ulnar side, in the leg both
of the corresponding sets of muscles extend primitively on the fibular side of the leg to the femur.
In the higher vertebrates the superficial layer of the flexor musculature of the leg takes origin
from both sides of the distal extremity of the femur, and the origin of the extensor musculature
ceases to extend to the femur. The crural musculatiu'e is primitively inserted into the bones of
the leg, the tarsus, and the aponeuroses of the foot. On the extensor side of the leg the muscula-
ture ultimately becomes attached wholly to the foot by means of tendons differentiated, in part
at least, from the dorsal aponeurosis. The lateral portion of the extensor musculature, which
primitively extends from the femur to the fibula, in the higher vertebrates extends from the
fibula to the tarsus and metatarsus (peroneal musculature). On the flexor side of the leg the
more superficial musculature maintains a tarsal attachment through the tendon of Achilles.
The deeper musculature in part extends from the femur and fibula to the tibia, in part arises
from the fibula and tibia, and is inserted into the metatarsus and the digits through tendons
differentiated from the plantar aponeuroses. The musculature of the sole of the foot is highly
developed in five-toed vertebrates, but in those which walk on the toes, and especially in hoofed
animals, it is very greatly reduced.
FASCIiE OF THE LEG
The tela subcutanea of the leg contains a considerable amount of fat where it overlies the
muscles, but less where it overhes the bones and joints. Subcutaneous bursas are found over
the tuberosity of the tibia (b. subcutanea tuberositatis tibiae) and over each of the malleoU
(b. subcutanea malleoli medialis et lateralis). Over the dorsum of the foot the tela contains
comparatively little fat, but on the sole of the foot and plantar surface of the toes it contains
much fat interposed between dense fibrous tissue. The b. subcutanea calcanea hes beneath
the tuber calcanei.
The crural fascia, or external layer of fascia of the leg, extends from the knee to the ankle.
It forms an enveloping cone-Hke sheath for the muscles and is adherent to the periosteum of
the medial surface of the tibia. It is formed of transverse, oblique, and longitudinal fibres
and is thickest in front.
Ventrally the fascia of the thigh, to which the tendons of the quadriceps, sartorius, graciUs,
semitendinosus, and biceps muscles and the ilio-tibial band are closely united, becomes attached
with these tendons to the tibia and fibula. From these attachments, therefore, the fascia of
the front of the leg may be said to arise. Into it extend processes from the tendons men-
tioned. DorsaUy the fascia of the thigh is continued uninterruptedly into that of the leg.
Distally the crural fascia is attached to the two malleoli and to the posterior surface of the
calcaneus.
In the proximal part of the leg in front the underlying muscles in part take origin from the
fascia; in other places the fascia is separated from the underlying muscles by loose tissue.
From the fascia two main intermuscular septa arise. One, the anterior intermuscular
septum, extends between the extensor digitorum longus and peroneal muscles to the anterior
crest of the fibula; the other, the posterior intermuscular septum, between the peroneal muscles
and the soleus to the lateral crest of the fibula. These septa separate compartments for the
anterior, lateral, and posterior groups of muscles.
As the heads of the gastrocnemius pass over the back of the knee they are held in place by a
special deep lamina of the fascia lata, which distally becomes fused with the crural fascia (fig.
414 A).
478
THE MUSCULATURE
Fig. 414, A-F. — TransybbseISections thhough the Left Leg in the Regions shown in
THE Diagram.
d In the diagram indicates'the region through which passes section D, fig. 410 (p. 465) ; a', 6', c',
d', the regions through which pass sections A, B, C, D, fig. 417 (p. 488).
1. Arteria peronea. 2. A. pophtea. 3. A. tibialis anterior. 4. A. tibialis posterior. 5
Bursa anserina. 6. Bursa m. sartorii propria. 7. Fascia cruralis. 8. Fibula. 9
Ligamentum crurale transversum. 10. Lig. patellse. 11. Membrana interossea. 12
Musculus biceps femoris — tendon. 13. M. e.xtensor digitorum longus — a, tendon. 14. M
extensor hallucis longus. 15. M. flexor digitorum longus. 16. M. flexor hallucis longus
17. M. gastrocnemius — a, lateral head; b, medial head. 18. M. graciUs, tendon. 19
M. peroneus brevis. 20. M. peroneus longus — a, tendon. 21. M. peroneus tertius,
22. M. plantaris — a, tendon. 23. M. pophteus. 24. M. sartorius, tendon. 25. M
I semimembranosus, tendon. 26. M. semitendinosus, tendon. 27. M. soleus — a, fasciculus
accessorius. 28. M. tibialis anterior — a, tendon. 29. M. tibialis posterior — a, tendon.
30. N. cutaneus surse lateralis. 31. N. cutaneus surse medialis. 32. N. peroneus
communis (external pophteal). 33. N. peroneus profundus (anterior tibial). 34. N. pero-
neus superficiales (musculo-cutaneus) . 35. N. plantaris laterahs (external plantar). 36.
N. plantaris medialis (internal plantar). 37. N. suralis (external saphenous). 38. N.
tibialis (posterior tibial). 39. Septum intermusculare (anterior). 40. S. intermusculare
(posterior). 41. S. surse transversum. 42. Tendo Achilhs (calcanei). 43. Tibia. 44.
Vena saphena magna. 45. V. saphena parva.
FASCIA
479
I The semimembranosus has a special fascial investment which, on the back of the_knee
becomes bound on each side of the muscle and its tendon to the capsule of the joint. This
fascia extends into a transverse septal membrane which is continued over the deep muscles of
the back of the leg to the ankle. It is united on one side to the tibia, on the other to the fibula.
Proximally the fibres are continued into it from the tendon of the semimembranosus. Over
the back of the tibia the septum is interrupted by the attachment of the soleus to the pophteal
line. Beyond the tibial origin of the soleus it is fused on the medial side of the flexor digitorum
longus to the crural fascia.
In addition to the two intermuscular septa and the longitudinal transverse septum, other
septa serve to separate the individual muscles of the different groups.
Above the ankle the fascia is enforced by bands of tissue so that ligaments are formed
which -serve to retain in position the various tendons which pass from the leg into the foot.
The transverse crural ligament (upper part of anterior annular ligament) (fig. 415) lies
on the front of the lower part of the leg above the ankle. It is composed of fascia strengthened
by transverse bundles which pass from the medial side of the tibia to the ventral margin of the
fibula. From its deep surface a strong, broad septum descends to the tibia and divides the
underlying space into two osteo-fibrous canals, a medial for the tibialis anterior and a lateral
for the long extensor muscles. The lateral compartment is further subdivided by a sUghtly
marked septum into a medial division for the extensor hallucis longus and a lateral for the ex-
tensor digitorum longus and the peroneus tertius.
The cruciate ligament (lower part of anterior annular ligament) (fig. 415) serves to hold
the tendons of the anterior muscle group in place as they pass to the dorsum of the foot. In
part it is formed by a dense fibrous band lying in the fascia over the ankle, in part of a liga-
ment which passes from the bones of the ankle to the deep surface of this band. The superficial
band is V-shaped. It arises from the lateral surface of the body of the calcaneus and passes
across the dorsum of the foot, one arm of the V going to the medial malleolus, the other to the
side of the foot, where it terminates in the fascia over the first cuneiform bone. The apex of
the V lies over the tendons of the extensor digitorum longus and peroneus tertius muscles.
The distal arm extends over the tendons of the extensor hallucis longus and tibialis anterior
480 THE MUSCULATURE
muscles. The proximal arm passes over the tendon of the extensor hallucis longus and then
divides into two layers, between which the tendon of the tibialis anterior passes. The deeper
ligament mentioned above arises from deep within the tarsal sinus, some of its fibres even
from the sustentaculum tali. It then passes forward and medially beneath the long extensor
tendons, and divides into two parts, one of which curves about the medial margin of the ten-
don of the extensor digitorum longus, the other about the extensor hallucis longus tendon to
the under surface of the proximal arm of the V-shaped band.
The peroneal retinacula are strengthened regions in the fascia which serve to hold the
tendons of the peroneal muscles in place. The superior extends from the lateral malleolus into
the fascia on the back of the leg, and to the lateral surface of the calcaneus. The inferior
overlies the tendons on the lateral surface of the calcaneus, and is attached to this bone on
each side of them. Between the tendons it sends a septum to the bone. It is connected with
the superficial layer of the cruciate ligament.
The laciniate ligament (internal annular) (fig. 416) is found on the medial side of the ankle.
Here the fascia is strengthened by fibre-bands which form a well-marked ligament that holds
in place the tendons of the deep dorsal cruro-pedal muscles. This ligament extends from the
dorsal and distal margins of the medial malleolus to the calcaneus. It is closely bound to the
tibia and the talo-tibial (tibio-astragaloid) ligament until the tendon of the tibialis posterior is
reached. It passes over this and becomes bound to the bony structures on the posterior
margin of the tendon. From tjiis attachment two layers, a deep and a superficial, extend
backward. The superficial layer extends to the tuber calcanei, and is connected superiorly
with the crural fascia. The deep layer, which represents a continuation distally of the trans-
verse septum, extends over the tendons of the flexor digitorum longus and flexor hallucis longus
to the medial surface of the calcaneus, and is closely united to the underlying bone on each
side of these tendons, thus giving rise to osteo-fibrous canals.
MUSCLES
1. Muscles of thf Front of the Leg
(Figs. 415, 418)
The anterior musculature of the leg consists of four muscles, the tibialis
anterior, extensor digitorum longus, peroneus tertius, and extensor hallucis
longus. The tibialis anterior has a quadrangular prismatic belly which arises
from the lateral side of the tibia and adjacent interosseous membrane in the
proximal half of the leg. The tendon passes over the front of the tibia to the
first metatarsal. The extensor digitorum longus is a transversely flattened,
fusiform muscle, which arises from the superior extremity of the tibia, the anterior
crest of the fibula, and the adjacent interosseous membrane, and gives rise to a
tendon which passes over the front of the distal extremity of the tibia and sends
tendons to the two terminal phalanges of the four more lateral toes. The
peroneus tertius represents a more or less completely differentiated portion of
the preceding muscle. Its tendon passes laterally through the same osteo-
fibrous canal in the same synovial sheath and terminates on the fifth metatarsal.
The extensor hallucis longus is a narrow muscle which arises from the distal half
of the medial surface of the fibula and the interosseous membrane. Its tendon
extends over the ankle to the great toe. The tendons of these muscles are held
in place by the transverse and cruciate ligaments described above.
All the muscles of this group flex the foot. The extensors extend the toes; the
peroneus tertius and the extensor digitorum longus evert the foot. The nerve
supply is from the deep peroneal (anterior tibial) nerve.
The tibialis anterior is represented in the arm probably by the braohio-radialis and the two
radial extensors; the extensor digitorum longus by the extensor digitorum communis and
extensor digiti quinti proprius; and the extensor hallucis longus by the extensor poUicis longus.
Two abnormal muscles not infrequently found, the abductor hallucis longus and extensor primi
internodii hallucis, represent probably the corresponding normal muscles of the hand.
The tibialis anterior (fig. 415). — Origin. — From the distal surface of the lateral condyle
of the tibia, and the lateral surface of the proximal half of the shaft of the tibia, the adjacent
interosseous membrane, the overlying fascia near the condyle (tuberosity) of the tibia, and the
intermuscular septum between it and the extensor digitorum longus.
Structure. — Bipenniform. The fibre-bundles converge upon a flat tendon which begins
high in the muscle and emerges on the anterior margin of the muscle about the middle of the leg.
On the deep surface the implantation of fibre-bundles continues to the transverse crural (anterior
annular) ligament.
Insertion. — The tendon passes over the front of the tibia to the medial side of the foot,
where it is inserted into the medial surface of the first cuneiform and the base of the first
metatarsal.
Nerve-supply. — As a rule, a branch from the common peroneal (external popUteal) nerve
enters the proximal portion of the muscle by several twigs, and another from the deep peroneal
(anterior tibial) enters near the middle of the belly on the lateral edge.
EXTENSOR DIGITORUM LONGUS
481
Relations. — In the proximal half of the leg the extensor digitorum longus hes lateral to it;
and between the two muscles, the anterior tibial artery and vein. It is covered by the crural
fascia and rests on the interosseous membrane. Distally it lies over the extensor hallueis
longus. The tendon passes in special compartments beneath the transverse and the cruciate
(anterior annular) hgaments.
Fig. 415. — The Muscles of the Front of the Leg.
ill J
Ligamentum patellae
Gastrocnemius
Extensor hallueis longus
Transverse crural ligament
Dorsal interossei
Peroneus longus
Tibialis anterior
Peroneus tertius
Extensor digitorum longus
Peroneus tertius
Cruciate ligament
Extensor digitorium brevis
f^' u^^*^°^°^ digitorum longus (fig. 4:1 5). —Grig 171. —From the lateral condyle of the
tibia, the anterior crest (surface) of the fibula, the intermuscular membrane between it and
the tibiahs anterior, the lateral margin of the interosseous membrane, the septum between
it and the peroneus longus, and the fascia of the leg near the tibial origin.
Structure. — Penniform. The fibre-bundles converge upon the posterior surface of a tendon
which begins at the middle of the leg. The implantation of fibres continues nearly to the
482 THE MUSC ULA T URE
ankle. Usually at the distal margin of the transverse (anterior annular) Hgament the tendon
divides into two parts which pass between the two layers of the cruciate (lower part of an-
terior annular) ligament, and then each divides again into two parts, thus giving rise to four
slips, one for each of the four lateral toes.
Insertion. — Each tendon on the dorsal surface of the toe to which it goes divides into three
fasciculi: an intermediate, which is attached to the dorsum of the base of the second phalanx;
and two lateral, which converge to the dorsum of the base of the third phalanx. The margins
of the tendon are also bound by fibrous tissue to the sides of the back of the first phalanx.
Nerve-supply. — Most frequently two branches of the deep peroneal (anterior tibial) enter
the deep surface of the muscle, one near its tibial origin, one about the centre of the belly.
Relations. — In the proximal half of the leg it lies on the interosseous membrane, and beneath
the fascia of the leg, and adjoins medially the tibialis anterior, laterally the peroneus longus.
DistaUy it lies over the extensor hallucis longus and adjoins laterally the peroneus brevis. The
tendon passes beneath the transverse crural and the superficial layer of the cruciate (anterior
annular) ligaments and over the extensor digitorum brevis muscle. The superficial peroneal
(musculo-cutaneous) nerve runs in the septum between it and the peroneal muscles; the anterior
tibial artery and deep peroneal nerve pass beneath the head of the muscle, and then between
it and the tibialis anterior.
The peroneus tertius (fig. 415). — Origin. — From the distal third of the medial surface
of the fibula, the neighbouring interosseous membrane, and the anterior intermuscular septum.
Structure. — It is essentially a fasciculus of the extensor digitorum longus, from which it is
seldom completely differentiated. The fibre-bundles descend obliquely forward to be inserted
In a penniform manner on a tendon which runs along the lateral margin of the tendons of the
extensor digitorum. The attachment of fibre-bundles continues to the cruciate ligament (lower
part of anterior annular ligament).
Insertion. — On the base of the fifth metatarsal and often also on the base of the fourth.
Nerve-supply. — The more distal nerve to the extensor digitorum continues into this muscle.
Relations. — It lies lateral to the extensor digitorum longus. Its tendon passes into the foot
beneath the transverse crural and the superficial layer of the cruciate hgament in the same
compartments with those of the extensor longus.
The extensor hallucis longus (fig. 415). — Origin.- — From the middle two-fo\irths of the
medial surface of the fibula near the interosseous crest, and from the distal half of the interos-
seous membrane.
Structure. — Penniform. The fibre-bundles are attached as far as the cruciate ligament
to the back and sides of a tendon which begins on the antero-medial margin of the distal
third of the muscle.
Insertion. — On the base of the second phalanx of the big toe. On the back of the first
phalanx the margins of the tendon are attached to the bone by bands of fibres.
Nerve-supply. — As a rule, a branch from the deep peroneal (anterior tibial) nerve enters
the deep surface of the muscle near the junction of the upper and middle thirds, and passes
distally across the middle of the obliquely running muscle fibre-bundles.
Relations. — It lies on the distal half of the interosseous membrane, partly covered by the
extensor digitorum longus and the tibiaUs anterior muscles. Its tendon passes over the front
of the distal extremity of the tibia and the medial side of the dorsum of the foot and is held in
place by the transverse and cruciate ligaments and by a strengthening band in the fascia over
the base of the first metatarsal. In the distal part of the leg the anterior tibial artery and the
deep peroneal (anterior tibial) nerve pass beneath the muscle to enter the foot on the lateral
side of its tendon.
Actions. — The muscles of this group all flex the ankle. The tibiahs anterior and extensor
hallucis longus evert the foot at the talo-calcaneo-navicular joints, and invert it at the talo-
navicular, calcaneo-cuboid joints. In certain positions the tibialis anterior may, however,
invert the foot at these joints. The peroneus tertius and the long extensor evert the foot.
The force of the extensor hallucis longus is exerted powerfully on the first phalanx and weakly
on the second. The short muscles of the big toe aid in extending the second phalanx. The
extensor digitorum longus extends the first phalanx of each toe powerfully, but exerts less
force on the second and third. The lumbrical muscles assist in extending the last two phalanges.
Variations. — The origin of the tibialis anterior may extend to the femur. Its tendon of
insertion may give accessory slips to the cuneiforms, metatarsals, and phalanges. ^ More rarely
its belly is divided into two portions, one of which sends a tendon to the first cuneiform and one
to the first metatarsal. A slip, the tensor fascise dorsalis pedis (Wood), may pass to the dorsal
fascia of the foot. Another, the tibio -astragalus anticus (Gruber), to the talus (astragalus)
or calcaneus. The bellies or the tendons of the extensor hallucis and extensor digitorum may
be more or less completely fused, or tendon slips may pass from the tendon of one muscle to that
of the other. Tendon slips may pass to the metatarsal bones or from the tendon of one toe to
that of a neighbouring toe. The tendon to each toe may be doubled. The belly of the extensor
digitorum longus may be more or less completely subdivided to correspond with the tendons
to individual toes. The peroneus tertius is frequently fused with the long extensor. It may
be doubled. More often its tendon may bifurcate or trifurcate and be inserted into the extensor
tendons of the fifth toe or into the fourth or third metatarsal. It is absent in about 8.5 per cent,
of bodies (Le Double).
Abnormal Muscles. — The abductor hallucis longus is rarely found as a completely in-
dependent muscle. It usually arises as a fasciculus of the e.xtensor digitorum longus, extensor
hallucis longus, or the tibialis anterior. It is inserted into the base of the first metatarsal. The
extensor primi internodii hallucis (extensor hallucis brevis) has an origin similar to that of the
long abductor above described. It is inserted into the dorsum of the base of the first phalanx
of the big toe. It is not to be confounded with that portion of the extensor digitorum brevis
connected with the great toe and also sometimes called the extensor hallucis brevis.
PERONEI MUSCLES 483
BnRSiE
B. subtendinea m. tibialis anterioris. — A small bursa between the medial surface of the
first cuneiform bone and the tendon of the tibialis anterior. B. subtendinea m. extensoris
hallucis longi. — A small bursa beneath the tendon near the tarso-metatarsal articulation. It
may communicate with the synovial sheath of the tendon. B. sinus tarsi. — A large bursa in
the sinus tarsi and on the lateral surface of the neck of the talus (astragalus) beneath the tendons
of the extensor digitorum longus and the fibrous bands between the talo-calcaneal and the
cruciate ligaments. It extends back to the talo-crural, forward to the talo-navioular joint,
and may communicate with the joint cavity of the latter.
Synovial Tendon-sheaths
Vagina tendinis m. tibialis anterioris. — This sheath surrounds the tendon from above
the transverse crural ligament to the talo-navicular joint. Vagina tendinis m. extensoris
hallucis longi. — The sheath begins above the proximal arm of the cruciate ligament, and
ends near the tarso-metatarsal joint beneath a band-Uke thickening of the dorsal fascia of the
foot. Vagina tendinum m. extensoris digitorum longi. — This sheath surrounds the tendons
of the long digital extensor and the peroneus tertius from above the cruciate ligament to the
middle of the third cuneiform bone.
2. Lateral Musculature op the Leg
(Figs. 416, 422)
The lateral muscles consist of the peroneus longus and the peroneus brevis.
They extend and evert the foot. The thick prismatic belly of the peroneus longus
arises from the proximal half of the lateral surface of the fibula and from neigh-
bouring structures, while the smaller belly of the peroneus brevis arises from the
middle third of the lateral surface of this bone. The peroneus longus partly
covers the peroneus brevis. The tendons of the two muscles pass behind the
lateral malleolus, held in place by special retinacula (p. 480). There the tendon
of the peroneus longus lies at first lateral to and then crosses behind that of the
peroneus brevis and curves about the lateral side of the calcaneus and across the
sole of the foot closely applied to the cuboid and to the tarso-metatarsal articula-
tions, and terminates on the base of the first metatarsal. The tendon of the
peroneus brevis terminates on the lateral side of the foot at the base of the fifth
metatarsal. The nerve supply is from the superficial peroneal (musculo-cuta-
neous) nerve.
The two muscles are probably represented in the arm by the extensor carpi ulnaris. In
some of the lower animals the head of the peroneus longus extends to the femur. The fibular
collateral ligament of the knee-joint probably represents in man the femoral head of the
peroneus longus.
The peroneus longus (figs. 416, 422). — Origin. — Anterior head: tendinous from the anterior
tibio-fibular ligament, the neighbouring part of the lateral condyle of the tibia, and the head of
the fibula; fleshy from the proximal third of the anterior intermuscular septum and the crural
fascia near the tibia. Posterior head : fleshy from the proximal half of the lateral surf ace^of the
shaft of the fibula and from the posterior intermuscular septum.
Structure. — Bipenniform. The fibre-bundles converge upon a tendon which begins high in
the muscle. The constituent fibre-bundles of the anterior head are long and take a nearly
vertical course. The fibre-bundles of the posterior head take a more obhque course and their
attachment extends more distally on the tendon. The tendon emerges on the surface of the
muscle in the distal half of the leg. The fibre-bundles of the posterior head extend to within
a few centimetres of the lateral malleolus. The tendon passes through the retro-malleolar
groove, passes across the lateral face of the calcaneus, to and through the peroneal groove of
the cuboid, and crosses the second and third tarso-metatarsal joints. Where the tendon enters
the groove in the cuboid it contains a fibro-cartilaginous nodule which may become a sesamoid
bone.
Insertion. — On the inferior surface of the first cuneiform and on the supero-lateral border
and base of the first metatarsal. From the region of the fibro-cartilaginous nodule above men-
tioned a fibrous slip is usually sent to the base of the fifth metatarsal.
Nerve-supply. — Most commonly the peroneal (external pophteal) nerve before dividing
gives off two branches. One of these enters the deep surface of the middle third of the anterior
head, the other passes across the middle third of the constituent bundles of the posterior head.
The latter branch may arise from the superficial peroneal (musculo-cutaneous) nerve, and it
may extend to supply the peroneus brevis.
The peroneus brevis (fig. 416). — Origin. — From the middle third of the lateral surface
of the fibula; (2) from the septa which separate it from the anterior and posterior groups
of muscles.
Structure. — Penniform. The fibre-bundles converge upon a tendon which begins high in
the muscle and becomes visible on the lateral surface of the distal half of the belly. Behind the
lateral malleolus the tendon becomes free, then passes forward below the malleolus and, across
the calcaneus and cuboid.
484 THE MUSCULATURE
Insertion. — Into the tip of the tuberosity of the fifth metatarsal.
Nerve-supply. — The nerve arises from the superficial peroneal (musculo-cutaneous) nerve,
or from a branch to the peroneus longus. It enters the proximal margin of the muscle and
passes distally across its constituent fibre-bundles.
Relations. — The peroneal muscles in the leg are contained in a compartment bounded by
the anterior and posterior intermuscular septa, by the fibula, and by the fascia of the leg. The
peroneus longus to a considerable degree overlies the peroneus brevis. Beneath the upper part
of the peroneus longus the peroneal (external popliteal) nerve bifurcates into its two chief
branches. The deep peroneal (anterior tibial) nerve passes medially beneath the anterior head
of the muscle. The superficial peroneal (musculo-cutaneous) nerve extends in the interval
between the areas of the attachment of the two heads of the peroneus longus, and along the an-
terior margin of the peroneus brevis to the anterior intermuscular septum, through which it
passes to its superficial distribution. The tendon of the peroneus longus at first lies lateral to
and slightly overlaps that of the peroneus brevis. Toward the tip of the malleolus it lies almost
directly posterior to this tendon. On the lateral surface of the calcaneus the tendon of the
brevis lies superior to that of the longus, from which it is separated by a bony spine, the processus
trochlearis of the calcaneus. The tendon of the longus is separated from the deep surface of the
abductor of the little toe, and is held in place in the groove in the cuboid by the long plantar
ligament.
Action. — The peroneus brevis everts the foot. The peroneus longus extends, abducts, and
everts the foot, and supports the arch of the foot. The peroneus brevis also extends the foot
when this is greatly flexed.
Variations. — The two peroneal muscles may be more or less fused. The origin of the
peroneus longus may extend to the femur. The two heads of origin may be fused. Its tendon
of insertion may send slips to the second, third, and rarely to the fourth and fifth metatarsals.
The tendon may be united to that of the tibialis posterior (12 out of 45 bodies — Picou). Sesa-
moid cartilages or bones are occasionally found in the retro-malleolar and calcaneal portions of
the tendon. The tendon of the peroneus brevis may send a slip to the second or third phalanx
or to the head of the metatarsal of the fifth toe, to its extensor tendon, or to the cuboid. It may
also send a fasciculus to the fourth metatarsal or the extensor tendon of the fourth toe.
Accessory peroneals. — Poirier considers these all varieties of a muscle which in its simplest
form arises from the distal fourth of the fibula and is inserted by a tendon into the fifth toe. A
corresponding muscle is normally found in many of the monkeys (peroneus digiti quinti). In
man in one form or another it is a frequent anomaly. It may be so fused with the peroneus
brevis that only its tendon of insertion is apparent. It may appear as a special muscle fasciculus
of the peroneus longus or brevis. It may be merely a tendinous band, or it may be tendinous
at origin and insertion, with an intermediate belly. Instead of being attached to the fifth toe,
it may be inserted into the fifth metatarsal, the cuboid, the tendon of the peroneus longus, the
calcaneus, lateral malleolus, or posterior talo-fibular hgament.
Synovial Tendon-sheaths
Vagina tendinum peroneorum communis. — There is a double sheath for the tendons of
the peroneal muscles as they pass back of the lateral malleolus. From this region of union the
sheath sends processes along each tendon proximally above the malleolus and distally over the
lateral surface of the calcaneus. This process on the tendon of the peroneus longus often
communicates with the following sheath. Vagina tendinis m. peronaei longi plantaris. —
This sheath begins in the peroneal groove of the cuboid and ends near the medial border of the
long plantar hgament.
3. Musculature of the Back op the Leg
a. Superficial Group (fig. 413)
To this group belong the gastrocnemius, soleus, and plantaris muscles. They
extend the foot and flex the leg. The two ovoid heads of the gastrocnemius arise
one on each side from above the condyles of the femur, extend about to the middle
of the back of the leg, and are inserted into the posterior surface of the tendon of
Achilles, and through this into the back of the calcaneus. The broad, flat, ovoid
soleus arises beneath the gastrocnemius from the tibia and fibula, and is in-
serted into the deep surface of the tendon of Achilles as far as the ankle. The
two heads of the gastrocnemius and the soleus constitute the triceps surag. The
plantaris is a slender muscle which passes along the medial margin of the lateral
head of the gastrocnemius and beneath the medial head, where it gives rise to a
slender tendon that runs between the gastrocnemius and soleus and along the
medial margin of the tendon of Achilles to the fatty fibrous tissue of the heel.
The nerve-supply is from the tibial nerve.
The muscles of this group have a common embryonic origin, and are first differentiated
on the fibular side of the leg, whence they extend over the posterior tibial vessels and nerve to
their medial attachments. The gastrocnemius corresponds with the flexor carpi radialis and
ulnaris, the plantaris with .the palmaris longus, the soleus with a portion of the flexor digitorum
PLANTARIS 485
sublimis of the forearm. In many of the monkeys and in the prosimians the plantaris is much
more developed than in man.
The gastrocnemius (fig. 413). — Medial head. — Origin. — From a facet on the back of the
medial condyle of the femur above the articular surface, from an area on the back of the femur
superior and lateral to this, and from the femoral margin of the capsule of the knee-joint.
Lateral head. — Origin. — From a facet on the proximal portion of the postero-lateral surface
of the lateral condyle of the femur and from a rough area situated more medially and at a
greater distance from the joint.
Structure and insertion. — The heads of the gastrocnemius are similar in structure. From the
condylar facets there descend aponeurotic bands, one oh the medial margin and the medial side
of the posterior surface of the medial head, the other on the lateral margin and the lateral side
of the posterior surface of the lateral head. These bands descend about two-thirds of the way
down the muscle. In the tendon of the lateral head a sesamoid bone is frequently found. The
fibre-bundles of the muscle pass obhquely from the supracondylar areas of origin and from the
deep surface of the aponeurosis on each side to the tendon of insertion. This tendon begins as
a septum between the two heads, and as a lamina on the deep surface of each head. The septum
and laminae soon fuse with the broad aponeurosis which covers the dorsal surface of the soleus.
The attachment of fibre-bundles continues to about the middle of the back of the leg. The
attachment of the medial head extends more distaUy than that of the lateral head. As a rule,
the medial head is also the broader and thicker of the two.
The soleus. — Origin. — (1) By a fibular head from the back of the head and the proximal
third of the posterior surface of the shaft of the fibula, and from the intermuscular septum
between it and the peroneus longus; and (2) by a tibial head from the transverse septum over the
distal margin of the pophteus, from the popliteal line, and from the middle third of the medial
border of the tibia.
Structure and insertion.'- — From the fibular and tibial origins arise broad aponeuroses which
unite proximally on the deep surface of the muscle so as to form a fibrous arch over the pos-
terior tibial vessels and nerves. DistaUy they diverge and become more narrow, but the fibular
aponeurosis is continued on the fibular side and the tibial aponeurosis on the tibial side of
the muscle as far as the distal quarter of the leg. The main portion of the belly of the muscle
is formed by fibre-bundles which arise from the posterior surface of these aponeuroses and
pass obliquely to be inserted in a bipenniform manner on the deep surface of the tendon of
Achilles. This tendon begins as a broad aponeurosis which covers the greater part of the
posterior surface of the muscle, and gradually converges into a heavy fibrous band that is in-
serted into the calcaneus. The bundles of fibres of the tendon take a slightly spiral course.
Those on the posterior surface run from the medial margin toward the lateral surface of the
calcaneus; those on the anterior surface in a reverse direction. The attachment of the fibre-
bundles continues to within a short distance of the heel. A few of the fibre-bundles arise
directly from the fibula and the posterior intermuscular septum. On the deep surface of the
belly of the muscle there is an accessory fasciculus which is formed by fibre-bundles that spring
on each side from the anterior surface of the aponeuroses of origin of the muscle and have a
bipenniform insertion on each side of a thin, obUque tendinous lamina which inferiorly becomes
united to the deep surface of the tendon of Achilles.
The plantaris (fig. 413). — This muscle arises from the distal part of the lateral line of
bifurcation of the Unea aspera, in close association with the lateral head of the gastrocnemius.
The fibre-bundles give rise to a flat, short, fusiform belly, and are united to a narrow tendon
which extends along the medial edge of the tendon of Achilles to the lateral part of the dorsal
surface of the calcaneus, where it terminates in the neighbouring fibrous tissue.
Nerve-supply. — From the tibial (internal pophteal) part of the sciatic nerve in the popliteal
space nerves arise for each head of the gastrocnemius. Each nerve enters the middle third of the
deep surface of the head near the proximal margin. The nerve-supply for the soleus is from two
sources. One nerve arises in the pophteal space, often in company with the nerve to the lateral
head of the gastrocnemius. It enters the posterior surface of the muscle near the proximal
border and divides into two branches, one for each head of the muscle. The tibial (posterior
tibial) nerve gives rise to a branch which, about half-way down the leg, enters the deep surface
of the muscle and furnishes branches for the deep portion of the muscle on each side. The
nerve-supply of the plantaris is by a branch from the tibial (internal popliteal) portion of
the sciatic. This arises in the popliteal space and enters the deep surface of the muscle.
Relations. — The semimembranosus winds about the medial margin of the medial head of
the gastrocnemius to its deep surface. The biceps passes to the lateral side of the lateral head
of the gastrocnemius, and the plantaris along its mecUal margin. The semimembranosus and
biceps above, the medial head of the gastrocnemius and the plantaris below, bound the ponUteal
space. The peroneal (external popliteal) nerve passes from the popliteal space obliquely across
the plantaris and the lateral head of the gastrocnemius. The medial sural (short saphenous)
nerve and the small saphenous vein pass between the heads of the gastrocnemius to the surface
and thence to the lateral side of the ankle. From the peroneal (external pophteal) nerve in the
popliteal space the lateral sural (communicans peronei) nerve extends distaUy over the calf.
The (posterior) tibial nerve and posterior tibial artery and vein run between the two heads of the
gastrocnemius, and then beneath the soleus to the medial side of the ankle. In the region of the
tendon of Achilles a considerable space filled with fatty tissue intervenes between the tendon
and the transverse septum.
Action. — The contraction of the triceps surte produces extension, adduction, and inversion
of the foot. The gastrocnemius is also a flexor of the leg. The plantaris has no known function
in man. In some animals it is an extensor of the plantar fascia.
Variations. — There is considerable variation in the extent of the separation of the different
parts of the triceps sura;. The tendons of the three heads may be separate nearly to the heel.
Either or both heads of the gastrocnemius or the soleus may be doubled. A shp from the biceps
486 THE MUSCULATURE
or semimembranosus, from the linea aspera, or popliteal space may join the triceps and give
rise to a quadriceps surse. On the other hand, one of the heads of the gastrocnemius or the
tibial head of the soleus may be missing. A supernumerary fasciculus may extend from the
deep surface of the soleus to the calcaneus. The plantaris is exceedingly variable in origin,
structure, and insertion. The origin may be from the capsule of the knee-joint, the fascia of the
leg, or from the tibia. Its tendon may terminate at almost any part of its course in neighbouring
structures. It may be represented by a fibrous band. It is absent in about 7 per cent, of
instances (Le Double).
BURS^
B. m. gastrocnemii lateralis. — A bursa is often found between the tendon of the lateral
head of the gastrocnemius and the capsule of the joint. It may communicate with the joint
cavity. B. m. gastrocnemii mediaUs. — A bursa usually hes between the tendon of origin of
the medial head of the gastrocnemius, the condyle of the humerus, and the capsule of the joint.
Another bursa (b. m. semimembranosi) extends between the semimembranosus and the medial
head of the gastrocnemius muscle. The two bursaj frequently communicate with one another
and with the joint. B. tendinis calcanei. — This lies between the tendon of AchiUes and the
upper part of the back of the calcaneus. Between the back of the tendon and the crural fascia
another bursa is frequently present.
h. Deep Group
The deep posterior musculature is separated from the superficial by the trans-
verse septum described above (p. 479). The muscles covered by this septal fascia
are the popliteus, the flexor digitorum longus, the flexor hallucis longus, and
the tibialis posterior. An intermuscular septum between the popliteus and the
tibialis posterior, and the attachment of the soleus to the popliteal line on the
back of the tibia serve to separate the popliteus from the other deep posterior
muscles which lie distal to this region and send tendons into the sole of the foot
The deep posterior musculature may thus be considered as divided into a proximal
femoro-tibial and a distal cruro-pedal group. Both sets of muscles are supplied
by branches of the tibial nerve.
Femoro-tibial Muscle
The popliteus (fig. 416). — A triangular muscle which arises from an ovoid
facet at the inferior extremity of the groove on the outer side of the lateral condyle
of the femur and is inserted into the proximal lip of the popliteal line of the tibia
and the surface of the shaft of the tibia proximal to this. It rotates the leg
medialward and flexes it.
Structure. — From the origin a broad tendon ghdes over the condyle within the capsule of
the joint, then over the lateral fibro-cartilage and through a groove on the back of the tibio-fibu-
lar articulation. From both surfaces of this tendon, fibre-bundles diverge toward the area of
insertion. The tendon is more or less intimately united to several structures with which it
comes in contact about the joint. Rarely it contains a sesamoid bone. The fibres of insertion
terminate in part in the fascia covering the muscle. The pophteus is homologous with the
pronator teres of the arm, or, according to some investigators, with the deep portion of that
muscle.
Nerve-supply. — -A nerve which arises either independently or in conjunction with that to
the posterior tibial muscle enters the popliteus near the middle of its distal edge. Sometimes
a branch from the chief nerve to the knee-joint enters the proximal edge of the muscle.
Action. — To flex and rotate the leg medially.
Relations. — The popliteus lies within a compartment bounded by the transverse septum,
the capsules of the knee and superior tibio-fibular joints, the back of the tibia, and a septum
extending to the pophteal line (see above). On the transverse septum run the popliteal vessels
and the tibial nerve. The proximal margin of the soleus overlaps the distal margin of the
popliteus. The synovial membrane of the knee-joint sends a prolongation between its tendon
and the back of the lateral condyle of the tibia.
Variations. — It is rarely absent. An accessory head may arise from the medial side of
the lateral condyle or from some neighbouring structure. The fibulo-tibialis (peroneo-tibiaUs)
is a small muscle found by Gruber in one body in seven. It arises from the medial side of the
head of the fibula and is inserted into the posterior surface of the tibia beneath the popliteus.
Cruro-pedal Muscles (figs. 416, 420)
Of the three muscles of this group, the flexor digitorum longus lies on the
tibial side of the leg, the flexor hallucis longus on the fibular side, and the tibialis
posterior upon the interosseous membrane, partly covered by the other two
CRURO-PEDAL MUSCLES
487
muscles, beneath the former of which it crosses, distally, to the tibial side of the
leg. Septa separate the flexor muscles from the tibialis. The tendons of the
three muscles pass behind the medial malleolus, held in place by the transverse
septum and the deep layer of the laciniate (internal annular) ligament. They lie
Fig. 416. — The Deep Muscles op the Back of the Leg.
Lateral head of gastrocnemius t-r- ? *«) i , I t~^/ J
y-^-\ — Medial head of gastrocnemius
Peroneus longus
Flexor hallucis longus
Peroneus brevis
Tendon of semi-membranosus
Tibialis posterior
Flexor digitorum longus
Tibialis posterior
Laciniate ligament
Tendo Achillis
in compartments divided by septa which descend to the tibia. The compart-
ment for the tibialis posterior is the most medial. It is partly overlapped by
that for the flexor digitorum. At the ankle the tendon of the tibialis passes
above, the tendon of the flexor digitorum medial to, and that of the flexor hallucis
below, the sustentaculum tall, each in a separate osteo-fibrous canal bounded
488
THE MUSCULATURE
Fig. 417. A-D. — Transverse Sections through the Foot in the Regions Shown in the
Diagram.
/in the diagram indicates the region through which passes section F, fig. 414 (p. 478).
1. Arteria peronea. 2. A. plantaris mediaUs (internal). 3. A. plantaris lateralis (external).
4. A. tibiahs anterior. 5. Aponeurosis plantaris. 6. Calcaneus. 7. Fascia pedis dorsalis.
8. F. plantaris — a, lateral; b, intermediate; c, medial. 9. Ligamentum cruciatum (anterior
annular). 10. L. laciniatum (internal annular). 11. Malleolus lateralis (external). 12.
Malleolus medialis (internal). 13. Musculus abductor hallucis — a, tendon. 14. M.
abductor quinti digiti — a, insertion. 15. M. adductor hallucis — a, oblique head, origin;
b, transverse head. 16. M. extensor digitorum brevis — a, tendons. 17. M. extensor digi-
torum longus, tendons. 18. M. extensor hallucis longus, tendon. 19. M. flexor digitorum
brevis — a, tendon. 20. M. flexor digiti quinti brevis — a, tendon. 21. M. flexor digitorum
longus, tendon. 22. M. flexor hallucis brevis tendon. 23. M. flexor hallucis longus.
24. M. interossei dorsales. 25. M. interossei plantares. 26. M. lumbricales. 27. M.
peroneus brevis. 28. M. peroneus longus. 29. M. peroneus tertius — a, tendon. 30.
M. planaris, tendon. 31. M. quadratus plantae. 32. M. tibialis anterior, tendon. 33.
M. tibialis posterior, tendon. 34. Nervus peroneus profundus. 35. N. peronsus superficialis
(musculo-cutaneous). 36. N. plantaris medialis (internal). 37. N. plantaris laterahs
(external). 38. N. surahs (external saphenous) . 39. Os cuneiform I, 40. Os cuneiform
III. 41. Os cuboid. 42. Osmetacarpalel. 43. Os metacarpalell. 44. Os metacarpale
III. 45. Os metacarpale IV. 46. Os metacarpale V. 47. Os naviculare. 48. Ossa
sesamoidea. 49. Os talus (astragalus). 50. Tendo Achillis 51. Retinacula mm.
peroneorum. 52. Septum intermusculare laterale. 53. S. intermusculare mediale. 54.
Vena saphena magna.
FLEXOR DIGITORUM LONGUS
29 17
externally by the laciniate (internal annular) ligament. In the sole the tendon of
the long flexor of the big toe passes under (deeper than) the tendon of the flexor
digitorum, to which it gives a slip, and is inserted into the terminal phalanx of
the big toe. The tendon of the long flexor of the toes passes obliquely across the
sole, is joined by the quadratus plantae (flexor accessorius), and gives rise to a
tendon for the terminal phalanx of each of the four lateral toes. From these
tendons the lumbrical muscles arise. The tibialis posterior has an extensive
insertion on the plantar surface of the tarsus.
The long flexors act chiefly on the toes. Together with the tibialis posterior
they invert and extend the foot.
The long flexors of the toes probably represent the flexor profundus and the flexor polhcis
longus of the forearm. The tendons of the deep flexors of the forearm do not, however, cross
like those of the long flexors of the toes. In the lower mammals there is much variation in the
toes to which the tibial and fibular flexors are distributed. The tibiahs posterior has no certain
representative in the forearm. The rare ulno-carpeus may represent it.
The flexor digitorum longus (figs. 416, 420). — Origin. — From the popUteal line, the medial
side of the second quarter of the dorsal surface of the tibia, the fibrous septum between the
muscle and the tibiahs posterior, and the fascia covering its proximal extremity.
Structure and insertion. — From these areas of origin the fibre-bundles run obUquely to be
inserted in a penniform manner on a tendon which begins in the proximal quarter of the
muscle as a narrow septum, and more distally becomes a strong band on the medial margin.
The insertion of the fibre-bundles continues nearly to the medial maUeolus. From here the
tendon passes behind the medial malleolus, dorso-lateral to the tendon of the tibiahs posterior,
crosses the posterior talo-tibial ligament, and passes along the medial margin of the sustenta-
culum tali into the sole of the foot. Here it crosses the tendon of the flexor hallucis longus,
from which it receives a tendinous slip, and divides into four parts, which pass to the second to
the fifth toes. Each tendon is bound to the phalanges of the toe to which it passes by a fibrous
sheath. Superficial to it in the sheath lies a tendon of the flexor digitorum brevis, which the
490 THE MUSCULATURE
, flexor longus tendon perforates as it passes to the base of the terminal phalanx. The tendon
is connected, like those of the fingers, by vincula tendinum, to the phalanges of the toes.
Nerve-supply. — From the tibial (posterior tibial) nerve a branch arises, often in company
with nerves to some other or others of the muscles of this group. The nerve divides into two
branches, one of which passes to the lateral side of the muscle, where it extends along near the
middle of the fibre-bundles of that side, while the other branch passes along near the middle
of the fibre-bundles of the medial side of the muscle.
Relations. — In the proximal half of the leg it lies on the tibia, in the distal half on the
posterior tibial muscle. Between it and the flexor hallucis lie the posterior tibial vessels and
nerve. Near the ankle the plantar vessels and nerves cross the tendon of the muscle, separated
from it by the deep layer of the laciniate (internal annular) ligament. In the upper two-thirds
of its extent it is covered by the triceps surte. In the lower third of the leg it emerges medial to
the soleus and the tendon of Achilles. The relations of its tendon at the ankle have been de-
scribed above. The tendon Ues beneath the origin of the abductor hallucis muscle and in the
sole is covered by the flexor digitorum brevis, crosses the tendon of the long flexor and the
oblique adductor of the big toe and the interosseous muscles, is joined by the quadratus plantse
(flexor accessorius), and gives origin to the lumbrical muscles.
The flexor hallucis longus (figs. 416, 420). — Origin. — From the distal two-thirds of the
posterior surface of the fibula, the septa between it and the tibialis posterior and peroneal
muscles, and the fascia above its proximal extremity.
Structure and insertion. — The fibre-bundles converge upon a tendon which begins in the
second quarter of the muscle, within its substance, and emerges upon the postero-medial margin
in its distal half. The insertion of the fibre-bundles continues to the end of the tibia. From
here the tendon passes over the dorsal talo-tibial (tibio-astragaloid) ligament, and through the
groove on the posterior surface of the talus and the under surface of the sustentaculum tali,
where it lies on the fibular side of the tendon of the flexor digitorum longus. It then crosses
the deep surface of this tendon, to which it gives a slip, passes over the plantar surface of the
medial head of the flexor hallucis brevis, and between the sesamoid bones of this muscle into
the osteo-fibrous canal on the plantar surface of the big toe. It is inserted into the base of
the terminal phalanx of the big toe.
Nerve-supply. — The nerve arises from the tibial (posterior tibial) nerve, often in company
with the nerve to the flexor digitorum longus or the other muscles of the group. It runs
along the deep surface of the muscle and sends twigs into the middle third of its constituent
fibre-bundles. Sometimes two nerves are furnished to the muscle.
Relations. — It hes on the fibular side of the distal two-thirds of the leg. ProximaUy it
diverges from the preceding muscle so as to disclose the tibiahs posterior, which is more deeply
situated. Between it and the tibialis posterior he the peroneal vessels. Distally its tibial
margin approaches the flexor digitorum longus, but between them lie the posterior tibial vessels
and nerve. Lateral to it lie the peroneal muscles. It is covered in the leg by the soleus. In
the distal part of the leg its tendon hes medial to the tendon of Achilles. On entering the foot
the tendon crosses beneath the abductor hallucis muscle and the lateral plantar vessels and
nerve. The other relations of the tendon have been described above.
The tibialis posterior (figs. 416, 422). — Origin. — From — (1) the lateral half of the distal
margin of the popliteal line and the middle third of the posterior surface of the tibia; (2) the
medial side of the head and of that part of the body of the fibula next the interosseous mem-
brane in the proximal two-thirds; (3) from the whole of the proximal and the lateral portion of
the distal part of the posterior surface of the interosseous membrane; and (4) from the septa
between its proximal portion and the long flexor muscles.
Structure. — From this extensive area of origin the fibre-bundles converge upon a tendon
which is at first deep seated within the muscle-belly, but about the middle of the leg emerges
on the medial margin of the muscle. The fibular portion of the muscle is much more extensive
than the tibial. The proximal fibres take a nearly perpendicular, the most distal (from
the fibula) a nearly transverse, course. The insertion of fibres stops a little proximal to
the medial malleolus. The tendon then extends to the medial side of the tendon of the long
flexor of the toes, passes through the groove on the back of the malleolus, across the medial
talo-tibial (tibio-astragaloid) ligament, and above the sustentaculum tali to the sole.
Insertion. — The tendon divides into two chief divisions, a deep and a superficial. (1)
The deep portion becomes attached chiefly to the tubercle of the navicular bone, and usually
in part also to the first cuneiform. (2) The superficial spreads out to be attached chiefly to the
third cuneiform and the base of the fourth metatarsal, but also in part to the second cuneiform,
to the capsule of the naviculo-cuneiform joint, to the sulcus of the cuboid, and usually also to
the origin of the short flexor of the big toe and the base of the second metatarsal. Shps may,
however, also be given to other structures. A sesamoid bone is usuaUy found in the tendon
either near the calcaneo-navicular hgament or the navicular bone.
Nerve-supply. — The nerve arises from the tibial (posterior tibial) in company often with
branches to the other muscles of the group. It enters the posterior surface of the muscle in its
proximal third, and gives off one or two branches for the tibial fasciculus. The main trunk
descends across the middle third of the fasciculi arising from the fibula.
Relations. — The muscle covers the posterior surface of the interosseous membrane, and
extends distally over the posterior surface of the tibia beneath the flexor digitorum longus. It
is covered proximally by the soleus, distally by the two long digital flexors. The posterior
tibial and peroneal arteries and the tibial (posterior tibial) nerve run upon its posterior surface.
The tendon in the sole is under cover of the origin of the plantar muscles of the big toe.
Action. — The tibialis posterior adducts the foot and slightly inverts it. The flexor digi-
torum longus flexes the terminal phalanx on the second and the second on the first, and at the
height of its contraction the first on the metatarsals. It also rotates medially to some extent
the ends of the fourth and fifth toes, and inverts the foot. The flexor haUucis longus flexes
MUSCLES OF FOOT 491
the second phalanx of the big toe on the first, and, less energetically, the first on the metatarsal.
It also inverts the foot. All three muscles extend the foot. The flexor haUucis is the strongest
of the three in this respect.
Variations. — The muscles of the group may be more or less fused with one another or be
united by fascicuh. This is especially common between the two flexors of the toes. The
individual muscles vary in development. The flexor digitorum longus may be more or less
divided into separate fasciculi for the individual toes. The slip from the flexor haUucis longus
to the flexor digitorum longus varies greatly in extent, but usually passes mainly to the second
and third toes, more rarely to the second, third, and fourth, and very rarely to the fifth. In
most of the apes the tibial flexor (flexor digitorum) sends tendons to the second and fifth, the
fibular flexor (flexor haUucis) to the first, third, and fourth toes. This condition is also some-
times found in man. A slip may pass from the tendon of the flexor digitorum to that of the
flexor haUucis longus. There may be a sesamoid bone in the tendon of the flexor haUucis
longus as it passes over the talus (astragalus) and calcaneus. The tibiahs posterior may be
doubled. Aberrant fasciculi may arise from various regions on the back of the leg and join any
one of the three muscles of the group.
Abnormal muscles. — The soleus accessorius. — Arises by a tendon from the head of the fibula
beneath the soleus. It is usually a slender muscle inserted into the medial surface of cal-
caneus. The tibialis secundus (tensor of capsule of ankle-joint). — A smaU muscle which
arises from the tibia beneath the flexor digitorum and is inserted into the capsule of the ankle-
joint. The fibulo-calcaneus medialis (peroneo-oalcaneus internus of MacAlister, flexor
accessorius long. dig. long., etc.). — A fasciculus which arises from the lower third of the body of
the fibula and gives rise to a tendon which passes beneath the laciniate hgament to the quadratus
plantse or to the tendon of the flexor digitorum longus.
BURS^
B. subtendinea m. tibialis posterioris. — A smaU bursa between the navicular fibro-cartilage
and the tendon.
Synovial Tendon-sheaths
Vagina m. flexoris digitorum longi. — The tendon is surrounded by a synovial sheath
from the back of the medial malleolus to where it crosses the tendon of the flexor haUucis longus
below the navicular bone. It may communicate with the sheath of the tibialis anterior or with
that of the flexor haUucis longus. Vaginae tendinum digitales. — The tendons of the long
flexor, together with those of the short flexor, are surrounded by synovial sheaths from the
heads of the metatarsals to the insertions of the tendons. In structure these resemble those
of the fingers. Vagina m. flexoris haUucis longi. — The tendon is surrounded by a sheath
from the back of the medial malleolus to the crossing of the tendon of the flexor digitorum
longus. Another sheath surrounds the tendon from the middle of the first metatarsal to its
insertion. Vagina m. tibialis posterioris. — The tendon is surrounded by a synovial sheath ex-
tending from a region proximal to the medial malleolus to the insertion of the tendon.
D. MUSCULATURE OF THE FOOT
On the dorsum of the foot there is a muscle not represented in the hand, the
extensor digitorum brevis (fig. 418). In the sole of the foot there is a highly
developed musculature which may be subdivided into the flexor digitorum brevis
(fig. 419); the muscles connected with the long extensor of the toes, quadratus
plantse and lumbricales (fig. 420); the intrinsic muscles of the great toe, (figs.
419, 421); the intrinsic muscles of the little toe (figs. 419, 421); and the inter-
osseous muscles (fig. 422). These muscles abduct and adduct the toes, flex them
at the metacarpophalangeal joints and flex and extend them at the first row of
interphalangeal joints. On the second row of interphalangeal joints they seem
to exert relatively little action. All the movements, excepting flexion, are weak
in most individuals. The extensor digitorum brevis is innervated by the deep
peroneal (anterior tibial) nerve. The muscles of the sole of the foot are all
innervated by the lateral (external) plantar, except the flexor digitorum brevis,
the most medial of the lumbrical muscles, and the abductor and flexor brevis of
the great toe, which are innervated by the medial (internal) plantar.
FASCIiE
Tela subcutanea. — Over the dorsum of the foot the tela subcutanea contains Uttle fat. On
the sole of the foot and the plantar surface of the toes it contains much fat embedded in
dense fibrous tissue.
Muscle fasciae. — Over the dorsum of the foot a fascial membrane extends from the
cruciate ligament mentioned above to the toes, where it is continued as fibrous sheaths for
the extensor tendons. Laterally and mediaUy it is continued into the plantar fascia. Where
492 THE MUSCULATURE
it overlies skeletal structures it becomes adherent to them. In the main this fascial sheet is
thin. Over the base of the first metatarsal it is strengthened by a band which runs from the
medial side of this bone over the extensor tendons of the big toe to the base of the second
metatarsal. The extensor digitorum brevis is covered by an adherent fascial sheet. The
dorsal surface of each dorsal interosseous muscle is likewise covered by an adherent membrane.
The plantar surface of the foot is invested by a fascia in which three distinct regions may
be observed, a central, a lateral, and a medial. The central region is greatly thickened by
bands of fibrous tissue, the plantar aponeurosis, which diverge toward the toes from the medial
half of the tuber calcanei. These bands become distinct from one another as the toes are
approached, and each finally terminates partly in the skin over the head of the corresponding
metatarsal and in the digital sheath of the flexor tendons. Some of the fibres are continued
into the transverse capitular ligaments, the others extend through near the metatarsophalangeal
articulation to the dorsum of the foot. Broader, thicker bands go to the three middle toes
than to the big and little toes. At the margins of this central area some fibres radiate into
the fascia of the lateral and medial area, some extend lateraUy into the skin, and some sink
into the intermuscular septa described below. Near the toes well-marked transverse bundles
of fibres may be seen between the digital bands. The central area of the plantar fascia is not
densely adherent to the skin.
The digital sheaths of the flexor tendons of the toes correspond essentially with those
previously described (p.' 387) for the fingers.
The medial plantar fascia is thin and adherent to the skin. It extends between the central
plantar and the dorsal fascia over the intrinsic muscles of the big toe. The lateral plantar
fascia is thick and well developed near the heel, thin as the little toe is approached. A dense
band, the calcaneo -metatarsal ligament, strengthens it between the calcaneus and the tuberosity
of the fifth metatarsal.
At the junction of the lateral with the central region of the plantar fascia the lateral inter-
muscular septum sinks in to be attached to the first cuneiform, the navicular and the tendon
of the posterior tibial. A similar medial intermuscular septum sinks in between the medial and
central regions of the plantar fascia and is attached to the long plantar hgament, the tendon
sheath of the peroneus longus and the base of the fifth metatarsal. The fascia of each of these
regions in considerable part extends into these septa instead of becoming continuous across them.
The sole is thus divided into three great fascial compartments by these septa, a lateral, a
central, and a medial. In the lateral fie the intrinsic pedal muscles of the little toe; in the
medial, the abductor and the flexor brevis of the big toe and the distal end of the tendon of
the flexor hallucis longus. The central compartment is subdivided by transverse septa into
several sub-compartments. In the most superficial compartment lies the flexor digitorum
brevis; in the second, the tendons of the flexor digitorum longus and its associated muscles,
the quadratus plantse (flexor accessorius) and the lumbrical muscles; in the third, the adductor
muscles of the big toe; and in the fourth, the interosseous muscles.
The first two sub-compartments are most clearly marked in the region of the tarsus.
Distally they become merged by the disappearance of the intervening transverse septum, and
longitudinaUy subdivided by fibrous septa which serve to make a complete sheath over each
digit for the flexor tendons. The sheath over the adductor muscle of the big toe is a thin mem-
brane continued laterally from the medial intermuscular septum. Where the two heads of the
adductor muscle advance upon their tendon of insertion, the medial septum has no skeletal at-
tachment, so that the adductor sub-compartment of the middle fascial compartment com-
municates freely with the medial compartment. Over the cuneiform bones the tendon of
the flexor hallucis longus passes from the long flexor region of the middle compartment into
the medial compartment. Here the medial intermuscular septum divides into two layers,
which form a sheath for the tendon as it passes to the plantar surface of the flexor hallucis
brevis.
MUSCLES
1. Muscle of the Dorsum of the Foot
The extensor digitorum brevis (fig. 418). — This muscle is broad and thin,
lies beneath the tendons of the long extensor muscle on the tarsus, lateral to the
navicular and the head of the talus, and sends tendons to the four more medial
toes. It arises from the calcaneus. Its nerve-supply is from the deep peroneal.
Origin. — From the lateral and superior surfaces of the body of the calcaneus and from the
apex of the cruciate hgament.
Structure and insertion. — The fibre-bundles arise directly from the hgament, and by short
tendinous bands from the bone. As they extend distally they become grouped into four beUies.
Those of the most medial and largest beUy, the extensor hallucis brevis, become inserted in a
bipenniform manner on the lateral and medial margins of a tendon which begins opposite the
cuboid. The insertion of fibre-bundles continues to the base of the first metatarsal. The in-
sertion of the fibre-bundles of the other belUes, which are seldom so distinctly isolated as the
first, takes place in a penniform manner into their respective tendons, but the exact mode of
attachment is subject to great individual variations. The tendon of the first digit is inserted
mainly into the middle of the back of the base of the first phalanx, but it is often also united
to the tendon of the long extensor. The other three tendons are fused with the lateral margins
of the corresponding tendons of the long extensor near the bases of the three middle digits.
They also usually give shps to the bases of the first phalanges of the corresponding toes.
MUSCLES OF THE SOLE
493
Nerve-stipply. — The deep peroneal (anterior tibial) nerve, which, accompanied by the
anterior tibial artery, passes beneath the medial beUy of the muscle, gives off a branch which
passes transversely across the middle of the deep surface of the muscle and sends twigs into it.
Relaiions. — It lies on the lateral side of the tarsus, beneath the long extensor tendons of the
toes. The relations of its tendons have been described above.
Action. — It aids the long extensors in extending the first phalanx of each of the four medial
digits. It has but a limited action on the second and third phalanges. It serves also to pull
the ends of the toes to which its tendons go toward the little toe.
Fig. 418. — The Muscle of the Dorsum of the Foot.
Transverse crural ligament
Extensor digitorum longus — -f— ::^ ^
Extensor digitorum brevis
Extensor hallucis longus
Peroneus brev
Cruciate ligament
Peroneus tertius
Flexor digit! V brevis
Variations. — The muscle shows great variation in development. Rarely the whole muscle,
more frequently one or more of its digital divisions, may be missing. On the other hand, it may
be more highly developed than usual. Accessory fasoicuh vary greatly in origin and termi-
nation. Most frequently their tendons go to a metacarpo-phalangeal articulation or to the
second or the fifth toe.
2. Muscles of the Sole of the Foot
a. Flexor Digitorum Brevis (fig. 419)
The flexor digitorum brevis, the most superficially placed of the plantar
muscles, lies in the mid-plantar region beneath the plantar fascia and over the
tendons of the long flexor of the toes and its associated muscles. It arises from
the calcaneus, and has a flat, elongated belly, which toward the middle of the sole
is prolonged into four processes, each of which has a special tendon that is inserted
into the second phalanx of one of the four lateral toes. The tendons of the muscle
correspond to those of the flexor sublimis in the palm. The belly of the flexor
494
THE MUSCULATURE
The nerve supply is from
sublimis is supposed to be represented by the soleus.
the medial (internal) plantar.
Origin. — From (1) the medial process of the tuber calcanei; (2) the posterior third of the
plantar aponeurosis; and (3) the medial and lateral intermuscular septa.
Structure. — The constituent fibre-bundles pass distally in a compact mass. The tendons
of insertion begin within the muscle substance, and as the fibre-bundles become inserted on
them, the separate fascicuh become more and more distinct. The fascicuU for the second and
third toes are larger and arise more superficially than those for the fourth and fifth toes. The
fasciculus for the fifth toe is often very small, and its tendon takes an obhque course to the
insertion.
Insertion. — The tendons of the short flexor pass superficial to those of the long flexor into
the osteo-fibrous canals on the flexor surface of the digits. Upon the first phalanx of each toe
the tendon of the short flexor divides and forms an, opening (chiasma tendinis) through which
Fig. 419. — First Layer op the Muscles of the Sole
Abductor digiti V
Flexor digiti V brevis>
Tendon of flexor digitorumlongus
Flexor digitorum brevis
Abductor hallucis
Flexor hallucis longus
Flexor hallucis brevis
First lumbrical
Tendon of adductor hallucis
^-i-W...!.^
the tendon of the long flexor passes, while the tendon of the short flexor becomes attached to the
base of the second phalanx. The arrangement is essentially Uke that described at length for
the flexors of the fingers (p. 401).
Nerve-supply. — From the medial plantar nerve by a branch which enters the middle third
of the deep surface near the medial margin of the muscle.
Action. — It is a strong flexor of the second row of phalanges.
Relations. — The short flexor is sejiarated from the abductors of the big toe and little toe
by strong intermuscular septa (p. 492), and from the long flexor tendons and the quadratus
plantaj (flexor accessorius) by a transverse septum in which the lateral plantar vessels and
nerve cross the foot. In its distal two-thirds it is separated from the plantar fascia by loose
tissue.
Variations.— The muscle shows a tendency toward reduction, one or more of its fasciculi
being frequently absent, and occasionally the whole muscle. The fasciculus for the fifth toe
is absent in about 20 per cent, of bodies (Le Double). When a fasciculus is absent, its tendon is
usually replaced by an accessory tendon from the long flexor. The muscle or its tendons may
be more or less fused to the tendons of the flexor digitorum longus.
MUSCLES OF GREAT TOE 495
b. Muscles Attached to the Tendons op the Flexor Digitoeum
LoNGUs (fig. 420)
The muscles belonging in this group are the quadratus plantae (flexor ac-
cessorius), a flat, quadrangular, bicipital muscle which runs from the medial and
plantar surface of the body of the calcaneus to the dorso-lateral margin and deep
surface of the long flexor tendon; and the lumbrlcales, four slender bipinnate
muscles which run from the medial sides of the digital slips of the tendon to the
medial sides of the four more lateral toes. The quadratus aids the long flexor
muscle; the lumbricales extend the last two phalanges and flex the first phalanx
of each of the digits to which they pass. The lumbrical muscles correspond to
those of the hand. The quadratus is not there represented. The nerve-supply
is from the lateral (external) plantar nerve except that for the first lumbrical
muscle which gets its supply from the medial (internal) plantar.
The quadratus plantae (flexor accessorius) (fig. 420). — This muscle arises by two heads-
The lateral head springs by an elongated tendon from the calcaneus in front of the lateral
process of the tuber, and from the lateral margin of the long plantar hgament. The medial head
arises directly from the medial surface of the body of the calcaneus as far back as the medial
process of the tuber calcanei, and from neighbouring hgaments.
Structure and insertion. — The two heads are separated at their origin by a short triangular
space. They soon fuse to form a single beUy, but the fibre-bundles of each head in the main
are separately inserted. Those from the lateral head diverge to be attached to the lateral
margin of the flexor tendon. Those from the medial head are inserted on a tendon that begins
on the medial margin and deep surface of this head, becomes broader, and is inserted as a
flat aponeurosis on the deep surface of the flexor tendon. There are great individual varia-
tions in the structure of this muscle. The flbres of either part may be inserted with those of
the other part.
Nerve-supply. — From a branch of the lateral plantar nerve which passes obliquely across
the superficial surface of the muscle parallel with the tendon of the flexor digitorum longus. _
Relations. — The muscle Ues in a fascial compartment with the long flexor tendons. This
compartment is bounded on each side by intermuscular septa, deeply by the tarsus, and plantar-
ward by a septum which intervenes between it and the flexor digitorum brevis, and in which the
lateral plantar nerve and vessels cross to the lateral side of the foot.
Action. — It assists the long flexor tendon in flexing the toes. It makes the direction of
traction on the toes parallel with the long axis of the foot.
Variations. — It is frequently reduced in size. The lateral head is not infrequently missing,
the medial head or the whole muscle much more rarely. The mode of attachment to the tendon
varies. It may be inserted in part or wholly into the long flexor of the great toe. It may
receive, in about one body in twenty (Wood), an accessory slip of origin from the fibula, one of
the muscles of the leg, the fascia of the leg or foot, or the medial surface of the calcaneus, etc.
The lumbricales. — The three lateral muscles arise from the contiguous sides of the digital
tendon-slips of the flexor digitorum longus in the angles of division. The first lumbrical arises
on the medial margin of the tendon to the second toe. The fibre-bundles of each muscle con-
verge on both sides of a tendon which becomes free near the metatarso-phalangeal joint and is
attached to the medial side of the first phalanx of the toe to which the muscle belongs. A tendi-
nous expansion is sent into the aponeurosis of the extensor muscle.
Nerve-supply. — The three lateral lumbrical muscles are most frequently supplied by
branches of the deep ramus of the lateral plantar nerve, the medial by the first common plantar
digital branch of the medial plantar nerve. The latter nerve may supply the two more medial
muscles or the more medial muscles may receive a double supply. The branches of the lateral
plantar nerve enter the deep surfaces of the muscles in the middle third. The branches of the
medial plantar enter the medial borders of the muscles near the junction of the proximal and
middle thirds.
Relations. — The lumbrical muscles lie in a plane with the long flexor tendons deeper than
the flexor brevis tendons and superficial to the adductor hallucis. The deep branches of the
lateral plantar nerve and vessels pass across their deep surface; superficial branches of both
plantar nerves across the superficial surface.
Action. — To extend the last two phalanges of the toes and to flex the first.
Variations. — One or more of the muscles may be absent. Sometimes a muscle is doubled.
This is more frequently the case with the third and fourth muscles. The first may arise
wholly from the tendon of the posterior tibial muscle or from this and the Ions flexor of the
big toe. The third lumbrical may arise from the flexor digitorum brevis. The second and
fourth lumbricals may be inserted into the tendons of the flexor digitorum brevis.
c. Intrinsic Muscles of the Great Toe (figs. 419-421)
These muscles are the abductor, flexor brevis, and adductor. Of the three
muscles, the first two lie in the medial fascial compartment, while the last lies in
the middle compartment covered by the flexor digitorum longus and its associated
muscles.
496
THE MUSCULATURE
The abductor hallucis (fig. 419), the largest and most superficial of these
muscles, lies on the border of the sole medial to the short flexor muscle. It passes
from|the calcaneus across the tendons of the long flexor muscles, and is inserted
into the medial side of the base of the first phalanx of the great toe and into the
medial side of the long extensor tendon. It is partly fused to the medial belly of
the flexor hallucis brevis. The flexor hallucis brevis (fig. 421) is a bicaudal
muscle which lies over the first metatarsal. It arises in the region of the cune-
iform bones and is inserted on each side of the base of the first phalanx. Between
Fig. 420. — Second Layer of the Muscles op the Sole.
Origin of abductor digit! V
Part of abductor digiti V
Flexor digiti V \<\
Abductor digiti V
Lumbricales
Flexor digitorum brevis
Abductor hallucis
Quadratus plantEe
Flexor digitorum longus
Flexor hallucis longus
Flexor hallucis brevis
Adductor hallucis
Abductor hallucis
Tendon of flexor digitorum brevis
its two bellies and insertions runs the tendon of the long flexor of the great toe.
Proximally and medially the flexor brevis is crossed by the abductor hallucis.
Its tendons are fused with those of the abductor and the oblique head of the ad-
ductor. The adductor hallucis (fig. 421) is composed of two distinct heads, an
oblique and a transverse. The oblique head extends from the long plantar liga-
ment under cover of the tendons of the flexor digitorum longus and the lumbrical
muscles to the lateral side of the base of the first phalanx of the great toe. Its
tendon of insertion is joined by the transverse head, which arises from the capsules
of the third to the fifth metatarso-phalangeal joints. Beneath the adductor lie
the more medial interosseous muscles.
These muscles perform not only the functions indicated by their names, but
also extend the second phalanx. They correspond fairly well with those of the
thumb. The opponens is not normally present in the foot. The nerve supply for
the adductor is from the lateral (external) plantar nerve; that for the other muscles
is from the medial (internal) plantar.
The abductor hallucis (fig. 419). — Origin. — From (1) the medial process of the tuber
calcanei; (2) the deep surface of the neighbouring plantar fascia; (3) the laoiniate (internal
FLEXOR HALLUCIS BREVIS
497
annular) ligament; (4) the septum between the muscle and the flexor digitorum brevis; and
(5) a fibrous arch which extends on the deep surface of the muscle over the plantar vessels and
nerves and the long flexor tendons from the calcaneus to the navicular bone.
Structure. — From the medial process of the tuber calcanei a tendinous band passes to the
deep, lateral side of the muscle. Numerous tendinous bands arise from the other areas of origin.
The fibre-bundles arise from these tendons and directly from the fibrous arch. They are
attached in a penniform manner to numerous tendinous slips which extend far up in the muscle.
These slips become graduahy fused into a tendon which appears on the superficial plantar aspect
of the muscle. Opposite the distal half of the first metatarsal bone the tendon leaves the
belly of the muscle and becomes closely bound to the medial belly of the flexor hallucis brevis.
Fig. 421. — Third Layer of the Muscles op the Sole.
Part of abductor digiti V
Flexor digiti V brevi:
Tendon of flexor digitorum longus.
Flexor hallucis longus
Flexor digitorum longus
Tibialis posterior
Flexor hallucis brevis
Adductor hallucis (caputobliquum)
Insertion. — In conjunction with the tendon of the medial belly of the flexor brevis into the
base of the first phalanx. It usually sends an expansion to the extensor tendon.
Nerve-supply. — A branch from the medial plantar nerve usually enters near the middle of
the lateral border of the muscle.
Relations. — It is covered by the plantar fascia and is separated from the muscles of the
median compartment by the medial intermuscular septum. It crosses the tendons of the tibialis
anterior, tibiahs posterior, flexor digitorum longus, and flexor hallucis longus muscles and the
plantar vessels and nerves.
The flexor hallucis brevis (fig. 421). — Origin. — From a tendon attached to the first (in-
ternal), second and third cuneiform bones. The more lateral of its fibres are continued into
the plantar calcaneo-cuboid Ugament and the more medial into the expansion of the tendon of
the posterior tibial muscle.
Structure and insertion. — The fibre-bundles give rise to two belHes, a medial and a lateral.
Those of the medial belly pass obUquely medially to be inserted into the tendon of the abductor
hallucis, and by a short tendon fused with this into the medial side of the plantar surface of the
base of the first phalanx. This tendon contains a sesamoid bone. Those of the lateral converge
upon the tendon of the oblique head of the adductor, and the two muscles are inserted by a
common tendon, which contains a sesamoid bone, into the lateral side of the plantar surface
of the base of the first phalanx.
498 THE MUSCULATURE
Nerve-suy-ply. — A branch from the medial plantar (or first plantar digital) nerve divides over
the plantar surface of the muscle and gives a twig to each belly near the middle third. Rarely
the lateral belly may receive a branch from the lateral plantar nerve.
Relations. — The abductor halluois covers it medially; the tendon of the flexor hallucis
longus passes between its two heads. Branches of the medial plantar vessels and nerve lie
on its superficial surface.
The adductor hallucis (fig. 421). — The oblique head. — Origin. — From (1) the tuberosity
of the cuboid and the sheath over the tendon of the peroneus longus muscle; (2) the plantar
calcaneo-cuboid hgament; (3) the third cuneiform; (4) the bases of the second and third meta-
tarsals and (5) a fi^brous arch which extends from the plantar calcaneo-cuboid Ugament to the
interosseous fascia.
Structure and insertion. — From short tendon-slips the fibre-bundles pass forward to form a
thick, fusiform belly which is attached in a bipeuniform manner to a flat tendon. The tendon
begins about the middle of the plantar surface of the muscle and is inserted in common with that
of the flexor brevis into the lateral side of the plantar surface of the base of the first phalanx,
and by a sUp into the aponeurosis of the long e.xtensor muscle on the back of the big toe.
Nerve-supply. — A branch from the deep ramus of the lateral plantar nerve enters the middle
third of the lateral border of the muscle on its deep surface.
The transverse head arises from the joint-capsules of the third, fourth, and fifth metatarso-
phalangeal joints and from the transverse capitular hgaments.
Structure and insertion. — Of the three fasciculi, that to the little toe Hes nearest the heel,
that to the middle toe the most distally. The fibre-bundfes take a nearly parallel course to be
attached to tendon-shps which are fused into a common tendon that sphts and passes on each
side of the tendon of the obUque head and is inserted into the sheath of the tendon of the long
flexor of the great toe (Leboucq).
Nerve-supply. — A branch from the deep ramus of the lateral plantar nerve enters the middle
third of the deep surface of the muscle.
Relations. — The adductor hallucis is crossed superflciaUy by the tendons of the flexor
digitorum longus and by the lumbrical muscles. On its deep surface he the interosseous muscles,
and the deep plantar vessels and nerves.
Action. — The actions of the muscles of this group are indicated by the names of the individ-
ual muscles. The abductor and the obhque head of the adductor are also flexors of the first
phalanx. All the muscles of the group aid in extending the second phalanx. The transverse
head of the adductor serves to draw together the heads of the metatarsals after they have been
separated by the weight of the body during the tread.
Variations. — The extent of fusion of the abductor and adductor with the two heads of the
short flexor varies considerably. The' abductor may receive an accessory fasciculus from the
medial border of the foot. Either the adductor or the flexor brevis may send a tendon to the
base of the first phalanx or to the short flexor tendon of the second toe. The adductor shows
frequent variations in relation to its metatarsal attachments, owing to the fact that originally
a fasciculus from the body of the second (and third) metatarsal was probably normally present
and the transverse head was more developed (Leboucq). The opponens hallucis is a fasciculus
occasionally found which extends from the short flexor or the medial intermuscular septum to
the body of the first metatarsal. This muscle is normal in some monkeys. An adductor digiti
secundi has been seen to arise from various sources and become attached to the lateral side of
the plantar sm-face of the base of the first phalanx of the second toe. This muscle may be fused
with the oblique adductor. A corresponding muscle is found normally in some apes, and in
some of the lower animals there is a special adductor for each toe.
d. Intrinsic Muscles of the Little Toe (figs. 419-421)
In this group belong three muscles, an abductor, a flexor and an opponens.
The largest of these, the abductor digiti quinti (fig. 419), extends superficially over
the lateral margin of the foot from the lateral side of the tuber calcanei to the
base of the little toe. The flexor digiti quinti brevis (fig. 421) is a small, flat
muscle ,which lies on the plantar surface of the fifth metatarsal. The opponens
is a small muscle lying lateral to this. The two, which are often fused, arise from
the cuboid. The flexor brevis is inserted into the plantar side of the base of the
first phalanx of the little toe. The opponens is inserted into the lateral surface
of the metatarsal. The abductor corresponds with the abductor of the little
finger. The opponens and flexor brevis correspond probably with the deep
part of the opponens of the little finger. The nerve supply is from the lateral
plantar nerve.
The abductor digiti quinti (fig. 419). — -Origin. — From (1) the lateral process of the tuber
calcanei and the lateral and plantar surface of the body of the bone in front of this; (2) the lateral
intermuscular septum; (3) the deep surface of the lateral plantar fascia, including the fibrous
band extending from the calcaneus to the lateral side of the base of the fifth metatarsal bone.
Structure. — The fibre-bundles run obhquely to a flat tendon of insertion. This begins within
the muscle near the calcaneo-cuboid joint, soon emerges on the medial side of the deep surface,
and becomes free near the metatarso-phalangeal joint. Considerable individual variation in
structure is found.
Insertion.- — On the lateral surface of the first phalanx of the httle toe and the metatarso-
phalangeal capsule. Often a shp is sent to the extensor tendon. While usually the muscle
INTEROSSEUS MUSCLES 499
glides over the tuberosity of the fifth metatarsal, it frequently sends a second fasciculus to be
attached to this bone (abductor ossis metatarsi quinti) . A special fasciculus from the tuberosity
often constitutes the lateral margin of the muscle.
Nerve-supply. — The nerve arises from the lateral plantar. It may be distributed either
near the deep or the superficial surface of the muscle. The former appears to be the case when
the muscle is slightly developed. The chief intramuscular branches then extend across the
middle third of the constituent fibre-bundles near the deep surface. In case the calcaneo-meta-
tarsal bundles are well developed, the nerve enters the proximal margin of the muscle and its
chief branches extend across the middle third of the more superficial muscle-bundles, finally
terminating in the distal margin of the muscle.
Relations. — It is ensheathed by the plantar fascia and the lateral intermuscular septum.
It lies superficial to the quadratus plantoe (flexor accessorius), the opponens and flexor Ijrevis
of the Mttle toe, the long plantar hgament, and the tendon of the peroneus longus muscle.
The flexor digiti quinti brevis (fig. 421). — Origin. — From the sheath of the peroneus longus,
the tuberosity of the cuboid, and (3) the base of the fifth metatarsal.
Structure and insertion. — The fibre-bundles take a nearly parallel course, although the belly
is slightly fusiform. They are attached by short tendinous bands to the base of the first
phalanx of the little toe, the capsule of the corresponding joint, and the aponeurosis on the
dorsal surface of the toe.
Nerve-supply. — A branch of the superficial ramus of the lateral plantar nerve sends twigs
to the middle third of the plantar surface of this and the following muscle.
Relations. — It is covered medially by the plantar fascia, laterally by the abductor of the
fifth toe. Medially it lies superficial to the third plantar interosseous muscle.
The opponens digiti quinti. — This muscle arises from the sheath of the peroneus longus
and the tuberosity of the cuboid by a slender tendon which passes over the tuberosity of the
fifth metatarsal and gives rise to fibre-bundles which are inserted on the lateral surface of the
fifth metatarsal.
Nerve-supply. — From branches of the nerve to the flexor brevis.
Relations. — It is covered by the abductor of the fifth toe.
Actions. — The abductor and flexor brevis abduct the little toe and flex the first phalanx.
They act as extensors of the second phalanx. The opponens serves to draw the little toe medi-
ally in a plantar direction.
Variations. — The muscles of this group may be more or less completely fused. The abduc-
tor, in addition to the variations mentioned above, may send tendons to the third and fourth
metatarsals. The opponens is frequently missing. The abductor accessorius digiti quinti is
a rare muscle which arises from the lateral process of the tuber of the calcaneus and is inserted
into the lateral surface of the base of the first phalanx of the httle toe.
e. The Interosseous Muscles (fig. 422)
Two groups of interosseous muscles are recognised, a dorsal and a plantar.
The dorsal are the larger and fill the interspaces. The first two are inserted into
each side of the base of the first phalanx of the second toe; the third and fourth
into the lateral sides of the bases of the first phalanges of the third and fourth toes.
The plantar interossei lie on the medial side of the ventral surfaces of the third,
fourth, and fifth metatarsals, and are inserted each on the medial side of the base
of the first phalanx of the corresponding toe. In the hand the axis about which
the interosseous muscles are arranged passes through the middle finger, in the foot
through the second toe. The nerve-supply is from the lateral plantar nerve.
The interossei dorsales. — Each of the three lateral dorsal interosseous muscles arises from
— (1) the sides of the shaft and the plantar surface of the bases of the metatarsal bones bounding
the space in which it lies; (2) from the fascia covering it dorsally; and (3) from fibrous prolonga-
tions from the long plantar hgament. The first has a similar origin except that it is attached
medially to the base of the first metatarsal and to a fibrous arch extending from the base to the
head.
Structure. — The component fibre-bundles of each muscle are inserted bipinnately on a ten-
don which begins high in the muscle and becomes free near the metatarso-phalangeal joint.
Insertion. — The first and second on each side of the base of the first phalanx of the second
toe. The third and fourth on the lateral side of the bases of the proximal phalanges of the third
and fourth toes. Each tendon is adherent to the capsule of the neighbouring joint. They
send no well marked processes to the extensor tendons, as do those of the hand.
The interossei plantares. — Each plantar interosseus arises — (1) from the proximal third
of the medial plantar surface of the shaft and from the base of the metatarsal on which it Ues;
and (2) from expansions of the long plantar hgament.
Structure and insertion. — The obliquely placed fibre-bundles are longer than those of the
dorsal interossei, and are inserted in a tendon which hes near the medial border of the muscle,
becomes free near the metatarso-phalangeal joint, and is inserted into a tubercle on the medial
side of the base of the first phalanx of the digit to which it goes.
Nerve-supply. — From the deep branch of the lateral plantar nerve several rami are given
ofi for the interossei. The nerve of each muscle enters the plantar surface in the proximal
third. The interosseous muscles of the foiirth interspace, however, are usually supplied by a
branch from the superficial ramus of the lateral plantar nerve.
500
THE MUSCULATURE
Relations. — -The interosseous muscles are covered on the plantar surface by a thin fascia
on which the deep branches of the lateral plantar nerve and vessels run. The first dorsal inter-
osseous adjoins mediaOy the flexor hallucis brevis and laterally on the plantar surface of the
second metatarsal, adjoins the second dorsal interosseous. Dorsal and plantar interossei then
alternate across the plantar surface of the foot until the fifth metatarsal is reached. Here the
third plantar interosseous adjoins the flexor brevis of the little toe.
Fig. 422. — Fourth Layer op the Muscles op the Sole.
Peroneus longus
Plantar interossei
Dorsal interossei
Action. — The chief axis of the foot may be taken to extend through the second toe. The
dorsal interosseous muscles abduct — pull the digits to which they are attached away from this
axis; the plantar interosseous muscles adduct — pull the digits toward the axis. The interossei
all flex the first row of phalanges.
Variations. — The second dorsal interosseous may have no attachment to the third
metatarsal.
BURS^
B. intermetatarsophalangeae. — Four bursse between the neighbouring sides of the heads of
the metatarsal bones and dorsal to the transverse capitular ligaments. B. mm. lumbricalium.
— Between the ends of the tendons of the lumbrioal muscles and the transverse capitular hga-
ments. The three medial are more constant than the lateral.
For other bursas in the foot, see pp. 483 and 491.
MUSCLES GROUPED ACCORDING TO- FUNCTION
The exact functions of many of the muscles have not yet been decisively determined.
Anatomical studies, the construction of mechanical models, the electrical stimulation of the
musculature, and observation of the muscular activities of normal individuals and of individuals
in whom given muscles or sets of muscles are absent or paralysed, have all proved valuable
methods of investigation, but each method has its drawbacks, and knowledge of the part actu-
ally played by individual muscles in the normal activities of the body is as yet merely approxi-
FUNCTIONS OF MUSCLES 501
mate. Owing to the influence of gravity, the relations of other muscles to the skeleton, and
similar factors, a given muscle may perform functions which would not be deduced from a simple
study of the relations of the muscle to the skeleton. Thus the ihacus serves to flex not only the
hip, but also the knee, and the hamstring muscles may flex the hip while flexing the knee. The
functions ascribed to various muscles in the following tables, although an attempt has been
made to base them upon the more recent work on the action of the muscles, must be taken to
be merely approximately correct. So far as possible the muscles are given in order of their
power in effecting the various movements. In this we have utilized chiefly the work of R. Fiok:
"Anatomie und Mechanik der Gelenke unter Berticksichtigung der bewegenden Muskeln"
in von Bardeleben's Handbuch der Anatomie des Menschen.
(In this table have been included not only the voluntary muscles, described in the preceding
section, but also several described in other parts of the book.
1. Facial muscles.
These serve essentially to contract the various visceral orifices of the head or to retract
the tissue surrounding them.
Ear.
Retractors: auricularis anterior, superior, and posterior.
Orbit.
(a) Retractor: Epicranius (occipito-frontalis). The levator palpebrse
superioris, innervated by the third cranial nerve, serves to
raise the upper lid of the eye.
(6) Contractors: orbicularis oculi, corrugator, and procerus.
Nasal orifice.
(o) Dilators: angular head of the quadratus labii superioris, transverse
portion of the nasahs, and the dilatores naris.
(6) Contractors: pars alaris of the nasalis and the depressor septi nasi.
Oral orifice.
(a) Retractors:
Upward: zygomaticus, quadratus labii superioris, caninus.
Lateralward: zygomaticus, risorius, platysma, triangularis, bucci-
nator.
Downward: triangularis, quadratus labii inferioris, platysma.
(6) Contractors: orbicularis oris, compressor labii, incisivus labii inferioris
and superioris.
(c) Protractors of the lips : incisivus labii inferioris and superioris, mentalis.
2. Muscles acting on the eyeball (see Section on Eye).
To adduct the pupil: rectus medialis.
To abduct the pupil: rectus lateralis.
To direct the pupil upward: rectus superior, in association with the obhquus
inferior.
To direct the pupil downward: rectus inferior, in association with the obliquus
superior.
3. Muscles acting on the lower jaw.
(a) To raise it: masseter, temporal, internal pterygoid.
(6) To lower it: external pterygoid, digastric, mylo-hyoid, genio-hyoid, and the
infrahyoid muscles. The weight of the jaw also plays a part in
this movement.
(c) To protract it: external pterygoid, internal pterygoid, masseter and the ante-
rior part of the temporal.
(d) To retract it: the inferior dorsal portion of the temporal and the digastric.
(e) To produce lateral movements: the external pterygoid acting on one side
rotates the chin and carries the jaw toward the opposite side.
The rotation may be aided by the digastric of the opposite
side. The masseter draws it slightly toward the side on which
the muscle lies. This action of the masseter is counterbalanced
by the internal pterygoid (Riegner).
4. Muscles acting on the hyoid bone.
(a) To elevate it: digastric, stylo-hyoid, stylo-glossus, mylo-hyoid, genio-hyoid,
genio-glossus, hyo-glossus, and the middle constrictor of the
pharynx.
(6) To depress it: thyreo-hyoid, sterno-hyoid, omohyoid, sterno-thyreoid.
(c) To protract it: genio-glossus (inferior portion), genio-hyoid, anterior belly of
digastric, and the mylo-hyoid.
(d) To retract it: posterior belly of digastric, stylo-hyoid, and the middle con-
strictor of the pharynx.
5. Muscles acting on the larynx (see Section IX).
(o) To elevate it: thyreo-hyoid, stylo-pharyngeus, pharyngo-palatinus, the in-
ferior constrictor of the pharynx, and the elevators of the hj'oid
bone.
(6) To depress it: sterno-thyreoid, sterno-hyoid, and omo-hyoid.
(c) To approximate the vocal cords: crico-arytenoideus lateralis; vocalis;
thjTeo-arytenoideus, arytenoideus transversus.
(d) To make the vocal cord tense: crico-thj'reoideus.
(e) To widen the rima glottidis: crico-arytenoideus posterior.
(/) To shorten and thicken the vocal cords: thyreo-arytenoideus (externus),
vocalis.
502 THE MUSCULATURE
(g) To constrict the aditus and vestibule of the larynx: aryepiglotticus,
thyreo-arytenoideus.
(h) To widen the aditus and vestibule of the larynx: thyreo-epiglottideus
6. IMuscles acting on the tongue (see Section IX).
(o) To elevate it: stylo-glossus (especially along the sides), glosso-palatinus,
glosso-pharyngeus, and the elevators of the hyoid bone.
(6) To depress it: genio-glossus (in the centre), hyogiossus (at the sides),
chondroglossus, and the depressors of the hyoid bone.
(c) To protrude it: geniq-glossus (middle and inferior portions).
(d) To retract it: genio-glossus (anterior portion), stylo-glossus, chondro-
(e) To shorten it and make it bulge upwards: longitudinalis superior and
inferior.
(/) To narrow it and make it bulge upwards: transversus Unguse.
(g) To flatten it: verticalis linguse.
When the muscles work symmetrically, these movements are symmetrical; when they
do not work symmetrically, the tongue is moved from side to
side, rotated, etc.
7. Muscles acting on the palate and pharynx (see Section IX).
(a) To narrow the pharyngeal opening of the tuba auditiva (Eustachian tube) :
levator veli palatini.
(6) To widen the isthmus of the tuba: levator veli palatini.
(c) To open the tube: tensor veli palatini, pharyngo-palatinus.
(d) To raise and shorten the uvula: m. uvulae.
(e) To depress the soft palate: glosso-palatinus, pharyngo-palatinus.
(f) To make tense the soft palate: tensor veli palatini.
(g) To lift the soft palate: levator veli palatini.
(h) To approximate the glosso-palatine arches (anterior pillars of the fauces):
glosso-palatinus.
(i) To approximate the pharyngo-palatine arches (posterior pillars of the
fauces): pharyngo-palatinus, superior constrictor of the
pharynx.
{j) To constrict the pharynx: superior, middle, and inferior constrictors.
(k) To widen the pharynx: stjdo-pharyngeus and the muscles which protract
the hyoid bone.
(I) To elevate the pharynx: stylo-pharyngeus, pharyngo-palatinus.
8. Muscles acting on the head.
(a) To flex it: the supra- and infrahyoid muscles, rectus capitis anterior, longus
capitis, rectus capitis lateralis.
(6) To extend it: sterno-cleido-mastoid, trapezius, splenius capitis, longissimus
capitis, semispinalis capitis, obliquus capitis superior, rectus
capitis posterior major and minor. When the hyoid bone and
lower jaw are fixed by contraction of the hyomandibular and
infrahyoid muscles, the posterior beUy of the digastric aids the
extensors of the head in opening the mouth.
(c) To bend it laterally: sterno-cleido-mastoid, rectus capitis lateralis, splenius
capitis, longissimus capitis, semispinalis capitis, obliquus
capitis superior.
(d) To rotate it: sterno-cleido-mastoid, trapezius, splenius capitis, longissimus
capitis, semispinalis capitis, obhquus capitis superior and in-
ferior, rectus capitis posterior major.
9. Muscles acting on the spinal column.
(o) To flex it: sterno-cleido-mastoid, longus colli, longus capitis, psoas major
and minor, scaleni, rectus abdominis, obhquus abdominis
externus and internus, the crura of the diaphragm, levator ani,
and the coccj'geus. .
(6) To extend it: splenius capitis, splenius cervicis, spinahs, sacro-spinaHs,
semispinalis dorsi, cervicis and capitis, multifidus, rotatores,
interspinales, intertransversarii, levatores costarum, quadratus
lumborum.
(c) To bent it laterally and extend it: quadratus lumborvim, splenius, iliocostalis,
longissimus dorsi, cervicis and capitis, semispinales, multi-
fidus, rotatores, levatores costarum, intertransversarii.
(d) To bend it laterally and flex it: scalene, sterno-cleido-mastoid, obliquus
abdominis externus and internus, intercostales, psoas major
and minor.
When the arm and shoulder girdle are fixed the trapezius,
levator scapulae, latissimus dorsi and rhomboids aid abduction.
(e) To rotate it to the right: r. internal oblique, 1. external oblique, r. splenius,
1. sterno-cleido-mastoid, r. longissimus capitis, r. ilio-costalis,
1. semispinahs, 1. multifidus, 1. rotatores (except the lumbar) ,
longus colli (r. above, 1. below), 1. serratus anterior and rhom-
boids, r. levatores costarum.
FUNCTIONS OF MUSCLES 503
10. Muscles of respiration.
Quiet inspiration: the external intercostals, interoartilaginous parts of internal
interoostals, diaphragm.
Enforced inspiration: in addition to the muscles mentioned above, the scaleni,
sterno-cleido-mastoid, serratus posterior superior and inferior,
rhomboids, serratus anterior, latissimus dorsi, subclavius,
pectoralis major and minor, and the extensors of the spinal
column, the trapezius and the levator scapuli.
Quiet expiration: interosseous pai'ts of internal intercostals, subcostales, and
transversus thoracis.
Enforced expu-ation: in addition to the muscles mentioned above, the abdominal
muscles, ilio-costalis lumborum and dorsi, longissimus dorsi,
and the quadratus lumborum.
The chief muscles of respiration are the intercostals; the diaphragm plays a minor
part (Fick).
11. Muscles acting on the abdomen.
(a) Constriction of the abdominal cavity: obliquus abdominis externus and
internus, the transversus and rectus abdominis, and the dia-
phragm, levator ani, and coccygeus.
(6) Reduction of pressure in the abdominal cavity: the muscles of inspiration,
with the exception of the diaphragm, serve to lessen the com-
pression of the abdominal viscera.
12. Action of the muscles of the perineal region.
(a) To close anal canal: sphincter ani externus.
(&) To constrict the anal portion of the rectum: levator ani (pubo-coccygeal
portion).
(c) To constrict the bulbus urethrae and the corpus cavernosum urethrse (corpus
spongiosum) : bulbo-cavernosus.
(d) To elevate the prostate gland: levator ani.
(e) To constrict the vagina: bulbo-cavernosus, levator ani (pubo-coccygeal por-
tion), constrictor vaginse.
(f) To cause erection of penis and clitoris: ischio-cavernosus, bulbo-cavernosus,
and sphincter urethrae membranaceaj.
(g) To compress the urethra and the bulbo-urethral (Cowper's) or the great ves-
tibular (Bartholin's) gland: sphincter urethrae membranaceae
and the transversus perinei profundus.
(h) To support and Uft the pelvic floor : levator ani, coccygeus, transversus perinei
profundus and superficialis.
13. Muscles acting on the shoulder-girdle.
The two joints acted upon are the sterno-clavicular and the acromio-clavicular.
The movements produced consist in lifting and lowering the
scapula, carrying it forward and backward and rotating it.
(o) Elevation: trapezius (upper portion), levator scapulae, sterno-cleido-mastoid,
rhomboidei, pectoralis major (upper sternal part), serratus
anterior (middle portion), omo-hyoid.
(6) Depression: trapezius (lower portion), pectoralis major (lower portion),
pectoralis minor, subclavius, latissimus dorsi, serratus anterior
(lower part). The weight of the limb is likewise a factor.
(c) Forward movement: serratus anterior, pectorales major and minor.
(d) Backward movement: trapezius, rhomboidei, latissimus dorsi.
(e) Rotation:
Associated with abduction of the arm : serratus anterior" (inferior
portion), trapezius.
Associated with adduction of the arm: rhomboidei, pectoralis major
(pectoral portion), latissimus dorsi, pectoralis minor, levator
scapulae.
14. Muscles acting on the arm at the shoulder-joint.
(o) To flex it,
When the arm is at the side: pectoralis major (upper part), deltoid (anterior
part), short head of biceps, coracobrachialis, infraspinatus,
long head of biceps, teres minor, subscapularis (upper part),
supraspinatus.
When the arm is abducted 60°: pectoralis major, deltoid, subscapularis,
short head of biceps, coracobrachialis, long head of biceps,
infraspinatus, supraspinatus.
The movement is aided by the trapezius and the serratus anterior.
(6) To extend it,
When the arm is at the side: latissimus dorsi, deltoid (posterior part), teres
major, subscapularis (lower part), triceps.
When the arm is abducted 60°: latissimus dorsi, deltoid, teres major, triceps,
teres minor.
The upper and middle portions of the trapezius and the levator scapulae play
an important part in extension of the arm.
(c) To abduct it,
When the arm is at the side: deltoid, supraspinatus, long head of biceps,
subscapularis, infraspinatus (upper part).
When the arm is abducted 60°: deltoid, supraspinatus, infraspinatus (upper
part), long head of biceps, short head of biceps.
504 THE MUSCULATURE
The siibscapularis is an adductor when the arm is abducted. The inferior
part of the serratus anterior and the trapezius are important
in abduction of the arm.
(d) To adduct it,
When the arm is at the side: pectoralis major, latissimus dorsi, deltoid (pos-
terior and anterior parts), teres major, triceps, coraoobrachialis,
short head of biceps, teres minor, infraspinatus.
When the arm is abducted: pectoralis major, latissimus dorsi, teres major,
triceps, subscapularis, deltoid (dorsal and ventral parts),
coracobrachialis.
(e) To rotate it lateral ward (supinate).
When the arm is at the side: infraspinatus (upper part), the dorsal part of
the deltoid, teres minor, supraspinatus.
When the arm is abducted 60°: teres minor, infraspinatus, deltoid (dorsal
part), coracobrachialis.
(/) To rotate it medialwai-d (pronate).
With the arm at the side: latissimus dorsi, pectoralis major, subscapularis,
deltoid (ventral part), long head of biceps, teres major, short
head of biceps.
With the arm abducted 60°: latissimus dorsi, pectoralis major, subscapularis,
teres major, deltoid (ventral part).
When the arms are raised high the power of rotation at the shoulder becomes
slight.
15. Muscles acting on the forearm at the elbow-joint (arranged according to R. Fick).
(a) Fle-xion at elbow.
Forearm supinated: brachialis, long head of biceps, short head of biceps,
brachio-radialis, pronator teres, extensor carpi radiahs longus,
flexor carpi radialis, extensor carpi radialis brevis, palmaris
longus.
Forearm in mid-position or pronated: brachiaUs, long head of biceps, short
head of biceps, brachio-radialis, extensor carpi radialis longus,
pronator teres, flexor carpi radialis, extensor carpi radialis
brevis, palmaris longus.
(6) Extension at elbow: triceps (lateral, medial, and long heads), anconeus.
(c) Pronation of forearm.
Forearm extended: flexor carpi radiahs, pronator teres, pronator quadratus,
palmaris longus.
Forearm at right angles: pronator teres, flexor carpi radiahs, brachio-radialis,
pronator quadratus, extensor carpi radialis longus, palmaris
longus.
Forearm flexed: pronator teres, brachio-radiahs, flexor carpi radialis, pro-
nator quadratus, extensor carpi radiahs longus, palmaris
longus.
{d) Supination.
Forearm extended: short head of biceps, supinator, long head of biceps,
brachio-radiahs, extensor carpi radialis longus, abductor
poUicis longus, extensor pollicis brevis, extensor pollicis longus,
extensor indicis proprius.
Forearm at right angles: short head of biceps, long head of biceps, supina-
tor, abductor poUicis longus, extensor polhcis brevis, brachio-
radialis (in pronation), extensor pollicis longus, extensor
indicis proprius.
Forearm flexed: short head of biceps, long head of biceps, supinator, ab-
ductor pollicis longus, extensor polhcis brevis, extensor pollicis
longus, extensor indicis proprius.
16. Muscles acting on the hand at the wrist (arranged according to R. Fick).
(o) To flex it: flexor digitorum sublimis, flexor digitorum profundus, flexor
carpi ulnaris, flexor pollicis longus, flexor carpi radialis, ab-
ductor pollicis longus, palmaris longus.
(6) To extend it: extensor digitorum communis, extensor carpi ulnaris, extensor
carpi radialis longus and brevis, extensor indicis proprius,
extensor pollicis longus.
(c) Radial abduction: extensor carpi radialis longus, extensor carpi radialis
brevis, abductor pollicis longus, flexor carpi radialis, extensor
indicis proprius, extensor pollicis longus, extensor polhcis brevis.
(d) Ulnar abduction: extensor carpi ulnaris, flexor carpi ulnaris.
17. Muscles acting on the palm :
(a) To_flex the ulnar side: opponens, long and short flexors of the little finger.
(h) To extend the ulnar side: extensor carpi ulnaris, extensor digiti quinti.
(c) To adduct the ulnar side: third volar interosseous.
{d) To abduct the ulnar side: abductor digiti quinti.
For action on the radial side see " muscles adting on the thumb." Move-
ments of the second, third and fourth metacarpals are produced
by the long flexors and the dorsal interosseous muscles.
18. Muscles acting on the thumb.
(a) To oppose the thumb: adductor, opponens, flexor brevis, flexor longus, ad-
ductor brevis.
(6) To repose the thumb: long abductor, short extensor.
FUNCTIONS OF MUSCLES 505
(c) To flex all joints: flexor poUicis longus; the carpo-metacarpal and metacarpo-
phalangeal joints; flexor brevis, the adductors, abductor brevis;
thecarpo-metacarpaljoints: opponens poUicis, abductor longus.
(d) To extend: all joints, extensor pollicis longus; the carpo-metacarpal and
metacarpo-phalangeal joints, extensor poUicis brevis; the inter-
phalangeal joint, abductor brevis, flexor brevis.
(e) To adduct: the adductor, flexor brevis, opponens, first dorsal interosseous,
extensor longus.
(/) To abduct: the long and short abductors.
19. Muscles acting on the fingers.
(a) To flex: all the joints, flexor digitorum profundus; all but the last, flexor digito-
rum subhmis; the metacarpo-phalangeal joint only, flexor
digiti quinti brevis, the lumbrieales, and interossei.
(6) To extend the fingers: extensor digitorum communis, extensor indicis pro-
prius, extensor digiti quinti proprius; to extend the two inter-
phalangeal joints: the lumbrieales, interossei, and frequently the
flexor digiti quinti brevis.
(c) To abduct from the axis passing through the centre of the middle finger:
dorsal interossei, first two lumbrieales, abductor digiti quinti,
the long extensor of the fingers.
(d) To adduct toward this axis : volar interossei, last two lumbrieales, opponens
and flexor digiti quinti brevis.
20. Muscles acting on the pelvis.
(o) To flex it: rectus abdominis, obliquus abdominis externus and internus,
psoas major and minor.
(6) To extend it: sacro-spinalis, multifidus, latissimus dorsi and quadratus
lumborum.
(c) To bend it laterally and rotate it: abdominal muscles, quadratus lumbo-
rum, psoas muscles, and latissimus dorsi acting on one side.
21. Muscles acting on the thigh at the hip-joint (arranged according to R. Fiok).
(a) To flex it: ilio-psoas, rectus femoris, adductor longus, adductor brevis,
obturator externus, tensor fasciae latae, pectineus, sartorius,
gluteus minimus, adductor magnus (upper part), gracilis,
quadratus femoris.
(6) To extend it: gluteus maximus, adductor magnus (posterior lower part),
biceps, semitendinosus, semimembranosus, gluteus medius,
piriformis, obturator internus.
(c) To adduct it: adductor magnus, gluteus maximus, adductor brevis, adductor
longus, quadratus femoris, obturator externus, gracilis, ad-
ductor magnus (upper part), pectineus, biceps, semitendinosus,
obturator internus and gemelU, semimembranosus.
(d) To abduct it: gluteus medius and minimus, the piriformis, rectus femoris,
tensor fasciiB latte, sartorius; and when the hip is flexed, the
gluteus maximus, obturator internus, and gemeUi.
(e) To rotate it medialward: gluteus medius (anterior portion), gluteus minimus,
ilio-psoas, adductor magnus (upper part), pectineus, adductor
longus, semitendinosus, semimembranosus, tensor fasciae
latae.
(/) To rotate it lateralward: gluteus maximus, quadratus femoris, obturator
internus, piriformis, rectus femoris, adductor brevis, adductor
magnus (lower part), biceps, sartorius, obturator externus
gracilis, gluteus medius (posterior part).
22. Muscles acting on the leg at the knee-joint (arranged according to R. Fick).
(o) To flex it: semimembranosus, semitendinosus, biceps, gastrocnemius,
gracilis, sartorius, popHteus.
(6) To extend it: quadriceps femoris (the tensor fasciae latae and gluteus maxi-
mus through the ilio-tibial band keep the extended leg fixed).
(c) To rotate it medialward (when flexed): semimembranosus, semitendinosus,
sartorius, popliteus, gracilis.
(d) To rotate it lateralward (when flexed) : biceps, tensor fasciae latae.
23. Muscles acting on the foot at the ankle-joint (arranged according to R. Fick).
(a) To flex it: tibialis anterior, extensor digitorum longus, peroneus tertius,
extensor hallucis longus.
(6) To extend it: gastrocnemius, soleus, flexor hallucis longus, peroneus longus,
tibialis posterior, flexor digitorum longus, peroneus brevis.
(c) To Invert the foot at the inferior articulation of the talus (art. talo-calcanea
and talo-calcaneo-navicularis) : gastrocnemius, soleus, tibialis
posterior, flexor hallucis longus, flexor digitorum longus, tibialis
anterior.
(d) To evert the foot at the inferior articulation of the talus : peroneus longus,
peroneus brevis, extensor digitorum longus, peroneus tertius,
extensor hallucis longus, tibialis anterior.
(e) To invert the foot at Chopart's (talo-navicular-calcaneo-cuboid) joint:
tibialis anterior, tibiaUs posterior, flexor digitorvmi longus,
flexor hallucis longus, extensor hallucis longus.
(J) To evert the foot at Chopart's joint: peroneus longus, peroneus brevis,
extensor digitorum longus, peroneus tertius.
506 THE MUSCULATURE
24. Muscles acting on the toes (arranged according to R. Fick).
(a) To flex: all the joints, flexor hallucis longus, quadrat us plantse, and flexor
digitorum longus; the first interphalangeal and the metatarso-
phalangeal joints of the four lateral toes, flexor digitorum
brevis; the metacarpo-phalangeal joints, the lumbricales,
interossei, abductor hallucis, adductor hallucis (oblique head),
flexor hallucis brevis, abductor digiti quinti, flexor digiti
quinti brevis.
(6) To extend; all joints, extensor digitorum longus, extensor hallucis longus,
extensor digitorum brevis; the interphalangeal joints, the
lumbricales, and the adductors and abductors of the big and
little toes.
(c) To abduct from an axis passing through the second toe; abductor hallucis,
dorsal interossei, abductor digiti quinti, first lumbrical.
(d) To adduot toward this axis : adductores hallucis, plantar interossei, three more
lateral lumbricals.
(e) To draw together the ends of the metatarsals : the transverse head of the ad-
ductor of the big toe.
References. — For development of the muscular system, consult the list given by
W. H. Lewis, Development of the Muscular System, in Keibel and Mall's Human
Embryology; for variations: Le Double, Traite cles variations du systeme
musculaire de I'homme; for action of muscles: R. Fick, Handbuch der Anatomic
und Mechanik der Gelenke unter Berticksichtigung der bewegenden Muskeln,
in von Bardeleben's Handbuch, and H. Strasser, Lehrbuch der Muskel und
Gelenkmechanik; for the extremities: Frohse und Frankel, Die Muskeln des
menschlichen Armes und Beines, in von Bardeleben's Handbuch; for the head
and trunk: Eisler, Die Muskeln des Stammes, in von Bardeleben's Handbuch;
for the pelvis: Holl, Die Muskeln und Fascien des Beckenausganges. Further
references to the literature upon the muscular system may be found in Poirier-
Charpy's Traite d'anatomie humaine.
SECTION V
THE BLOOD- VASCULAR SYSTEM
Revised for the Fifth Edition
By H. D. senior, M.B., F.R.C.S.
PROFESSOR OF ANATOMY, NEW YORK UNIVERSITY
THE organs of circulation consist of a system of tubes or vessels which during
life are filled with fluid constantly moving in one direction. The major
portion of the system is concerned with the continuous distribution of blood
throughout the body and is called the haemal or blood-vascular system. A
circumscribed part of the hismal circulation is differentiated into a rhythmically
contracting propulsory organ called the heart. The minor portion of the system
is called the lymphatic system. The lymphatic vessels convey fluid, the lymph,
from the tissues to the haemal system.
The essential functions of the blood-vascular system are performed by the
smallest of all the blood-vessels, the capillaries [vasa capillaria], which form a
network pervading practically all the tissues of the body. Blood is carried to and
from the capillaries by larger vessels called the arteries and veins respectively.
The heart receives blood from the veins and propels it, in turn, into the arteries.
One of the primary functions of the blood is the transmission of oxygen from the atmosphere
to the tissues. In order to do this the blood must of necessity pass through the respiratory
organ before being deUvered to the body at large. In gill-breathing vertebrates, the blood,
having received oxygen in its passage through the giUs, passes on directly to the tissues._ The
entire circuit is here accomplished by a single continuous chain of vessels in which capillaries
occur twice, once in the gills and again in the organs and tissues in general. In man, as in other
higher vertebrates, lungs assume the function of the gills. Having received oxygen in the lungs
the blood is returned again to the heart before being redistributed throughout the body.
There are thus in man two separate circuits or systems of blood-vessels, one traversing the lungs
and a second ramifying throughout the body. The former is known as the pulmonary circula-
tion; the latter as the systemic. Each has its own arteries, capillaries and veins; the heart is
common to both. From the time of birth the heart is longitudinally divided into right and left
halves, each of which contains its own independent stream of blood. The blood entering the
left side of the heart has issued from the pulmonary circulation and is driven into the systemic;
that in the right side, having traversed the systemic circuit, is returned again to the lungs.
The heart and blood-vessels have a continuous lining of flattened cells called endothelium ;
the hsemal system is, therefore, a closed circuit.* The main thickness of the heart,_ arteries
and veins consists of additional tissue developed around the endothelial lining. It is due to
this tissue that the blood is continuously delivered to and withdrawn from the capillaries under
suitable pressure and velocity. The heart is mainly composed of rhythmically contracting
muscle and its valves are so arranged that the contained blood is driven intermittently in one
direction only. The walls of the largest arteries are formed to a great extent of elastic tissue,
and, being constantly under tension from within, are instrumental in converting the stream,
intermittently received from the heart, into a continuous flow. The walls of the medium sized
to smallest arteries are mainly muscular. The smallest arteries are microscopic in size and
known as arterioles [arteriote]. The muscular arteries are capable of general or local alterations
of calibre regulated by the nervous system; they are thus largely concerned in the maintenance
of the blood pressure and in the regulation of the volume of blood entering given localities
under varying conditions. The veins have much thinner walls than the arteries; the blood in
them is under low tension upon which they e.xercise little or no control.
When an artery divides, the combined calibre of its branches is greater than that of the
vessel itself. Since the arteries divide repeatedly the bed of the blood-stream increases in
proportion as the vessels diminish in size. The rate of increase, slow at first, becomes enormous
in the arterioles. Conversely, the bed of flow undergoes contraction as the heart is approached
from the venous side. The velocity of flow in the capillaries must necessarily be much lower
* In the spleen and bone marrow the blood-channels intermediate between the arteries and
veins are possible exceptions to this statement, but the essential conditions here are still imper-
fectly understood.
507
508 THE BLOOD-VASCULAR SYSTEM
than in the great arteries and veins. From the relative slowness of the blood flow in the sys-
temic capillaries, it has been estimated that then- total bed is eight hundred times greater than
the bed of the main arterial stem.
Variations in the course and arrangement of the adult arteries and veins, originally studied
by the surgeon for utihtarian purposes only, now furnish one of the most stimulating fields for
anatomical research. Text-books can provide, at best, catalogues of the arrangement commonly
found in the adult body and of the most ordinary variations. That no text-book description
can fit any individual case in all particulars, and that unusual distribution of vessels does not
necessarily shorten hfe are among the earhest lessons learned in the anatomical laboratory.
The adult vascular pattern is derived from a symmetrical arrangement in the early embryo
of which scarcely a trace remains. The intervening changes are so numerous and profound that
the general uniformity of vascular distribution Ln different individuals is more remarkable
than the occurrence of occasional wide variations from the usual type.
In early stages of development all vessels have a similar structure ; they consist, in fact, of
a single layer of endothehum. Some vessels, however, are larger than others; these act as
arteries or veins (according to the direction of flow) while the smaller channels perform the office
of capillaries. The early principal vessels do not necessarily persist, for many of these dwindle
or are lost. New channels are meanwhile in continuous process of formation and some of these
may, in turn, become main channels. It thus follows that the main vessels of the adult must
be looked upon rather as selected channels through a plexus of possible pathways, than as sepa-
rate entities which must necessarily conform to given rules of distribution and branching.
In time, no doubt, most of the commoner variations from the usual adult type wUl receive
a rational explanation; at present enough has been done to indicate the value of the embryo-
logical method. The Ust of v.ariations in the arteries and veins respectively is preceded by a
brief account of the morphogenesis of these vessels.
In the case of the heart anomalies frequently result in early death, so that subjects of devel-
opmental irregularities are seldom seen in the anatomical laboratory. The anomahes usually
consist in improper development of the septa which normally divide the heart and main ar-
terial trunk into their pulmonary and systemic halves. A short account of the morphogenesis
of the heart is appended to the description of the adult organ.
In the following section the heart and pericardium will first be considered
followed by the arteries and veins.
A. THE HEART AND PERICARDIUM
1. THE HEART
The heart [cor] is a hollow organ principally composed of muscle, the myo-
cardium. It is lined internally by endocardium which is continuous with the
intima of the blood-vessels. Externally, it is covered by the epicardium, a serous
membrane continuous with the serous Hning of the pericardium. The form of
the heart, when removed from the body without previous hardening, is that of a
fairly regular truncated cone. The base [basis cordis] is poorly circumscribed
but corresponds, in a general way, to the area occupied by the roots of the great
vessels and the portion of the heart-wall between them. The base of the heart
is held in position* chiefly by the great vessels, which are attached to the peri-
cardium; the remainder of the organ is capable of free movement within the
pericardial cavity.
The interior of the heart is longitudinally divided, into right and left cavities,
by a septum passing from base to apex. Each cavity is subdivided into an
atrium [atrium cordis] and a ventricle [ventriculus cordis], the former receiving
the ultimate venous trunks and the latter giving rise to the main arteries. Thus
the left atrium receives the four pulmonary veins, and the right atrium the
superior and inferior vena cava and the coronary sinus; the aorta issues from the
left ventricle and the pulmonary artery from the right. The ventricles, which
constitute the major portion of the heart, may be recognised by their very thick
walls. The atria have thinner walls and are less capacious than the ventricles;
projecting from each is a diverticulum or auricle [auricula cordis]. The auricles
(which receive their name from their resemblance to dog's ears) partially embrace
the roots of the pulmonary artery and aorta.
Orientation of the heart. — The apex of the heart [apex cordis] points forward,
to the left and downward. The base is directed backward, to the right and up-
ward. The longitudinal axis of the heart forms an angle of about 40° with the
horizontal plane and also with the median sagittal plane of the body.
* Not necessarily fixed, for during systole the base performs a greater excursion than does
the apex.
EXTERIOR OF THE HEART
509
The long axis of the heart is therefore slightly more horizontal than vertical, and slightly-
more antero-posterior than transverse. The atria are posterior to rather than above the ven-
tricles. To arrive approximately at the longitudinal axis, it is necessary to select the central
point of the base. By cutting the vessels short in several hearts, hardened by formalin before
removal, a point immediately to the left of the left lower pulmonary vein was selected in deter-
mining the data above given. A steel pin was passed through this point to the apex cordis, and
the angles controlled by frontal and transverse sections of the thorax. Mention of angular
measurements of the axis of the heart could be found only in the text-books of Testut and
Luschka; the former gives 40° to the horizontal plane, the latter 60° to the mid-sagittal.
Luschka's angle appear to be too large; but further investigation in this direction is desirable.
Fig. 423. — Steeno-costal Surface op the Heart.
Left subclavian artery
Left inferior thyreoid vein
Left innominate vein
Left superior intercostal vein
Vestige of left common cardinal
Left pulmonary artery
Vena cava superior
Conus arteriosus
Margo obtusus
Left ventricle
Incisura apicis cordis
Size and weight. — In the adult the heart measures about 12.5 cm. (5 in.) from base to apex,
8.7 cm. (31 in.) across where it is broadest, and 6.2 cm. (24 in.) at its thickest portion. In the
male its weight averages about 312 gm. (eleven ounces), and in the female about 255 gm.
(nine ounces). It increases both in size and weight up to advanced life, the increase being most
marked up to the age of twenty-nine years. The proportion of heart-weight to body-weight
is about 1:205 in the adult.
EXTERIOR OF THE HEART
In hearts which have been hardened by injection before removal from the
bod}^, the regularity of the heart-cone is disturbed by a well-marked triangular
facet, imparted by contact with the diaphragm. This facet is the diaphragmatic
surface [facies diaphragmatica], which is directed downward and slightlj- back-
ward (fig. 424). It ends abruptly along a sharp margin extending from the apex
510
THE BLOOD-VASCULAR SYSTEM
toward the right. This margin is the margo acutus (fig. 423) ; it separates the
diaphragmatic surface from the sternocostal surface. The other margin of the
diaphragmatic surface is more rounded and shades gradually into the very wide
margo obtusus (fig. 423), which passes almost insensibly into the sternocostal
surface. The convex sternocostal surface [facies sternocostalis] (fig. 423),
directed forward and somewhat upward and to the right, is triangular and bounded
below by the margo acutus. To the left it goes over into the margo obtusus
along a line extending from the apex of the heart to the root of the pulmonary
artery. The margo obtusus corresponds to the rounded left side of the left
ventricle.
The interventricular sulcus is a slightly marked groove indicating the separa-
tion of the ventricles upon the exterior of the heart. It lodges coronary blood-
vessels and a moderate quantity of fat which can be seen through the epicardium.
Fig. 424. — Base and Diaphragmatic Surface op the Heart. (After His.)
Left pulmonary ^
artery
Left superior pul-
monary vein
Left inferior pul-
monary vein
^Reflexion
of pericardium
Coronary sinus
■ Aorta
. Superior
vena cava
. Right pulmonary
artery
Margo obtusus
^
The anterior part of this groove, sulcus longitudinalis anterior, beginning poste-
riorly, runs obliquely over the upper part of the margo obtusus on to the sterno-
costal surface. Crossing the margo acutus to the right of the apex, it is continuous
with the sulcus longitudinalis posterior upon the diaphragmatic surface. The
diaphragmatic surface is formed about equally by the right and left ventricles,
and the sterno-costal surface mainly by the right. Where the longitudinal
sulcus crosses the margo acutus it produces a slight notch, the incisura (apicis)
cordis.
The atria are separated externally from the ventricles by the sulcus coronarius.
This is a horseshoe-shaped groove well marked below and laterally, and inter-
rupted above by the roots of the pulmonary artery and aorta. It lodges the
coronary sinus, smaller coronary vessels and fat.
ATRIAL PORTION
511
ATRIAL PORTION
The atrial portion of the heart is situated behind, and shghtly to the right of
and above, the ventricular portion. The separation between the right and left
atrium is not indicated behind except in distended hearts (such as that shown in
fig. 424) ; in these it is marked by a slight groove connecting the left sides of the
superior and inferior venae cavse. In front, the auricles are separated by the deep
notch which lodges the aorta and pulmonary artery. A slight groove on the
back of the right atrium which connects the right sides of the superior and
inferior vense cavse, is the sulcus terminalis (figs. 424, 425) . This represents the
right limit of what was, in the embryo, the sinus venosus. It also indicates that
the embryonic sinus venosus has become an integral part of the adult right
atrium. The superior and inferior cavae have each a nearly vertical direction
and join the posterior part of the right atrium above and below, respectively.
The coronary sinus runs downward, backward and to the right to join the lower
part of the right atrium anterior to the inferior vena cava. The four pulmonary
veins run nearly transversely and somewhat forward into the right and left sides
of the left atrium.
Fig. 425. — Atria Opened Posteriorly to show the Septum Atriorum.
Pulmonary artery
Aorta
Vena cava superior
Crista terminalis
I ^ ^^ Sulcus
terminalis
Limbus fossae
ovalis
(.section)
Vena cava inferior
Facies diaphragmatica
The interior of the atrial portion of the heart is divided into right and left
cavities by the septum atriorum. This septum is a composite structure, having
been developed (see morphogenesis of the heart) in two independent parts, each
forming an incomplete septum in itself. The two incomplete septa, however,
partly overlap one another so that, by the lateral fusion at the time of birth, they
together produce the impervious structure of the adult heart (fig. 425). Of
these septa, the first to be formed is the membranous septum [pars membranacea
septi atriorum]. Later there is formed to the right of this the muscular septum,
the margin of which forms, in the adult atrium, the greater part of the limbus
fossae ovalis. The margin of the membranous septum is recognizable as a fold
512
THE BLOOD-VASCULAR SYSTEM
of endocardium on the septal wall of the left atrium; it is called the valvula
foraminis ovjilis.
Posteriorly into the right atrium [atrium dextrum (fig. 425)], above and below,
respectively, open the superior and the inferior vena cava. Upon the septal
wall, immediately above the inferior cava is the fossa ovalis, a depression of
Fig. 426. — Section op the Ventricles in Systole and Diastole. (After Krehl.)
>
which the floor is formed by the membranous septum. Surrounding the fossa
ovalis except below (indeed producing the fossa) is the limbus fossae ovalis
which is continuous anteriorly and below with the valvula venae cavae (inferioris
Eustachii). Just anterior to the fossa ovalis is the orifice of the coronary sinus
guarded by the valvula sinus coronarii (Thebesii) (fig. 428). Leading from the
ATRIAL PORTION
513
front of the atrium forward and slightly downward and to the left is the ostium
venosum (right atrio-ventricular orifice) guarded by the tricuspid valve. Above
and behind this is the auricle, the exterior of which is in contact medially with the
root of the aorta. To the right of the superior and inferior caval orifices there is a
vertical ridge, the crista terminalis, which corresponds to the sulcus terminalis on
the exterior (figs. 425, 428).
The portion of the atrium medial to the crista is smooth and is called the sinus venarum;
in the embryo it is separated from the atrial cavity proper by the right and left sinus valves.
The crista terminalis marks the original line of attachment of the right sinus valve. The
valve itself has disappeared, except at the lower part where it persists as the caval and coronary
valves. These valves vary in size considerably in different specimens, and are frequently
nethke from numerous perforations.
The conversion of a portion of a single valve into two separate valves, which meet at an
acute angle, is brought about by an attachment between the sinus valve and an embryonic
structure called the sinus-septum. This septum is a ridge dividing the right horn of the sinus
venosus from the transverse portion of the sinus (the coronary of the adult) ; it probably con-
FiG. 427. — The Interiok op the Ventricles, Anteriok Half. (After His.)
ilmonary artery
Aortic semilunar
valves
Anterior papillary
of left vent.
Muscular ventricu-
lar seplum
'Opening into ventricle
'Conus arteriosus
Membranous ven-
■ tricular septum,
'Crista supra ven-
\ tricularis
■Papillary of conus
-Right ventricle
Anterior papillary
muscle
tributes somewhat to the formation of both the coronary and caval valves. The left sinus
valve usually disappeai's by blending with the septum atriorum on which it unites with the
limbus fossae ovalis; it ooeasionaUy remains partially separate in the adult.
The interior of the right auricle and of the portion of the atrium lateral to the
crista terminalis is thrown into ridges (musculi pectinati) by prominent bands of
the atrial myocardium. The musculi pectinati end abruptly by joining the
crista. The orifice of the superior cava has no valve and is directed downward
and somewhat forward; below it, on the posterior wall of the atrium, there has
been described a tubercle or ridge, the tuberculum intervenostun (Loweri).
Apart from the posterior circumference of the superior cava itself and the limbus fossae
ovalis, the hiunan heart appears to contain nothing in this region that could be described as a
tubercle. With regard to the segregation of the streams entering the foetal right atrium from
the superior and inferior cavae, respectively, in which the tubercle of Lower has been supposed
to participate, it is to be noted that the fossa ovalis is just above (almost within) the inferior
514
THE BLOOD-VASCULAR SYSTEM
caval orifice. Also that the caval opening and the fossal ovalis (containing the foetal foramen
ovale) are, in hearts well hardened before removal, situated in a distinct diverticulum to the
left of the remainder of the atrium. Between this diverticulum and the atrium proper, the
caval valve and the limbus fossa? ovalis form a prominent flange, better marked in the foetus
than the adult. Opening into the right atrium, particularly upon the septal and right lateral
walls, are numerous /orowiraa venarum minimarum (Thebesii).
The left atrium [a. sinistrum] (fig. 425) is to the left and somewhat posterior
to the right. It is behind the root of the aorta and its auricle is to the left of the
Fig. 428. — Interior of the Right Atrium and Ventricle.
The atrio-ventricvdar bundle is dissected out.
• Left common carotid artery
- Innominate artery
Vena cava superior
Reflexion 'of pericardium
Pulmonary artery
Ascending aorta
Left pulmonary valve
Conus arteriosus
Vena cava inferior
Part of posterior tricuspid cusp Posterior papillary
pulmonary root. Opening into it posteriorly on the right and left sides, re-
spectively, are the right and left upper and lower pulmonary veins. The valvula
foraminis ovalis forms a more or less distinct crescentic ridge on the septal wall
(fig. 425). This may not be attached to the limbus fossas ovalis, in which case
there is a communication between the two atria. Absence of lateral adhesion
between the two septa atriorum does not necessarily lead to admixture of arterial
and venous blood during life. The left ostium venosum (atrio-ventricular orifice)
ATRIO-VENTRICULAR VALVES
515
guarded by the mitral valve leads from the anterior part of the atrium forward and
shghtly downward and to the left. The interior of the left atrium is smooth ex-
cept in the auricle, in which musculi pectinati are well marked.
Fig. 429. — Left Ventricle and Part op the Atrium.
The aorta is opened through the anterior cusp of the mitral valve. The plainly visible left
limb of the atrio-ventricular bundle has been accentuated.
Aorta
Pulmonary artery
Apex of the left ventricle
ATRIO-VENTRICULAR VALVES
The atrio-ventricular valves (figs. 427, 428, 429, 431) are attached around the
venous ostia of the ventricles in such a way as to open freely into the ventricles,
but to prevent regurgitation of the blood into the atria during ventricular systole.
Each valve is continuous along its line of attachment, but its free edge is notched
so as to produce an irregular margin; some of the notches are so deep as to
partially divide the valve into cusps. The right atrio-ventricular valve is
commonly divided by three deep notches into three cusps; this valve is therefore
called the tricuspid [valvula tricuspidalis]. The left is similarly divided into two
cusps and is called the bicuspid [v. bicuspidalis] or mitral. The depth of the
notches, however, is very variable and there may be an increase or (more rarely)
a diminution in the number of cusps; the addition of small subsidiary cusps is
quite common. Each valve cusp is tied down to the papillary muscles [mm.
papillares] of the ventricle by chordae tendinese. The latter are fibrous cords,
generally branched, of varying thickness. The thinnest cords are attached to the
free margin of the cusp; those of intermediate thickness to the ventricular surface
a few millimetres from the margin, and the thickest to the ventricular surface
516 THE BLOOD-VASCULAR SYSTEM
near the attached margin. The valves are smooth and glistening on the atrial
aspect, but rough and fasciculated, from the attachment of the chordae, on the
ventricular. The cusps of the mitral valve are called anterior and posterior; those
of the tricuspid, anterior, posterior and medial. Each cusp receives chorda from
more than one papillary muscle and each papillary muscle sends chordse to more
than one cusp. The chordse tendinese of the mitral valve are thicker than those
of the tricuspid (figs. 428, 429).
VENTRICULAR PORTION
The ventricles form the greater portion of the heart. In the adult the relation
of the ventricles to one another is as follows. The left [ventriculus sinister]
has the form of a narrow cone, the apex of which is the apex of the heart. The
right ventricle [ventriculus dexter] is crescentic in section and appears to be
partially wrapped around the right or lower wall of the left ventricle which forms
the septum ventriculorum (fig. 426). The left ventricle forms the margo ob-
tusus of the heart, about half the diaphragmatic surface, and a shght part of the
sterno-costal surface. The right ventricle forms about half the diaphragmatic
surface and the major part of the sterno-costal surface; it takes no share in the
formation of the apex of the heart.
The interventricular septum [septum ventriculorum] is thick and muscular
except for a small area near the root of the aorta which is membranous [septum
membranaceum ventriculorum]. The latter can be seen from the left ventricle in
the angle between the attached edges of the right and posterior aortic valves
(fig. 429). The membranous septum is partly concealed from the right heart by
the medial cusp of the tricuspid valve which is attached to it near its upper part.
The portion of the membranous septum above the medial tricuspid cusp is
therefore atrio-ventricular, i. e., between the right atrium and left ventricle.
The membranous septum is the extreme lower part of the independent septum (s. aorticum)
which divides the aortic root from the pulmonary artery and conus arteriosus (and partially
subdivides, also, the right ventricle by separating the conus arteriosus from the remainder of
the ventricle). The relation of the part of the aortic septum between the conus arteriosus and
aortic root to the septum ventriculorum is beautifully shown by His, in fig. 427.
The greater part of the interior of the ventricles is thrown into ridges by myocardial
bundles of large size. These fasciculi [trabeculae cordis] either stand out in rehef only, or, by
being undermined, form bands covered except at either end by endotheUum. A careful exam-
ination of the endocardium of fresh hearts will reveal a plexiform network of Purkinje fibres.
These fibres, belonging to the atrio-ventricular conducting system, become very obvious when
the endocardium has been exposed to the air long enough to become partially dry.
The wall of the right ventricle [ventriculus dexter] (figs. 427, 428) is much
thicker than that of the atria, but less so than that of the left ventricle. The
upper and anterior part of the right ventricle is in relation posteriorly with the root
of the aorta. This portion of the ventricle is called the conus arteriosus and is
separated from the remainder of the right ventricle by a muscular spur which
extends from the back of the conus to the right venous ostium. The spur is the
crista supraventricularis ; its relation to the partition between the conus and
aorta, and to the septum membranaceum, shows that it is the free edge of the
embryonic aortic septum (see morphogenesis of the heart).
Two papillary muscles in the right ventricle are constant in position, the
large anterior papillary muscle, and the small papillary muscle of the conus
(Luschka). The anterior papillary is situated on the sterno-costal wall, near the
junction of this with the septal wall. The papillary of the conus is placed just
below the septal end of the crista supraventricularis. The posterior papillary
muscles form an irregular group springing from the diaphragmatic wall. Some
chordae tendinese stretch directly from the septal wall (with or without small
muscular elevations at their bases) to the medial cusp of the tricuspid valve. The
chordae tendinese from the anterior papillary go to the anterior and posterior
cusps; those from the conus papillary to the medial and anterior, and those from
the posterior papillary muscles to the medial and posterior cusps of the tricuspid
valve, respectively.
There is frequently a band of myocardium extending from the septal wall of the right ven-
tricle to the anterior papillary muscle near its middle. This is the moderator band, which
contains a part of the right limb of the atrio-ventricular bundle. If the moderator band joins
SEMILUNAR VALVES
517
the anterior papUlary near its base, as it frequently does, it is difficult to distinguish it from the
ordinary trabeoulae in this situation.
The term moderator band was originally applied to this bridge or band of muscle under the
impression that it prevented overdistention of the ventricle. Subsequent discovery of the
conducting system of the heart makes it plain that there is always a band conducting the right
limb of the atrio- ventricular bundle from the septum to the anterior papillary muscle. Whether
the band is isolated from the other trabecules, and therefore readily recognizable, appears
to depend somewhat upon the relation of the base of the papillary muscle to the septum
ventriculorum.
The wall of the left ventricle [veiitriculus sinister] (figs. 427, 429) is very
thick except at the extreme apex, and at the membranous septum. In the left
ventricle are two large papillary muscles, generally known as anterior and posterior;
both send chordae tendineae to each cusp of the mitral valve. On the septal wall
of the ventricle the left limb of the atrio-ventricular bundle can usually be seen
as a broad, flattened band beneath the endocardium. The band appears just
below the septum membranaceum and divides into strands which go to the two
papillary muscles. The strands in many places bridge across part of the ventricle
to reach the papillary muscles covered only by tubes of endocardium.
These bridging strands connecting the papillary muscles with the septum ventriculorum,
which were formerly called "false chordas tendinese," are exactly comparable to the moderator
band of the right ventricle which occasionally consists of atrio-ventricular bundle and endo-
cardium only.
SEMILUNAR VALVES
The semilunar valves [valvulse semilunares] guard the arterial ostia of the
ventricles. The aortic ostium is directed upward and slightly forward and to the
right; the pulmonary backward and slightly upward and to the left. Each valve,
of which there are three to each ostium, is a pocket-like fold of endocardium
strengthened by fibrous tissue (fig. 430) . The free edge of each valve is directed
away from the ventricle, so that excess of pressure within the great vessels brings
Fig. 430. — Intbrigh View of the Aortic Semilunar Valves.
Aortic sinus
Section of fibrous ring
Free edge of valve i
Nodulus Arantii
Lunula
the three valves of either ostium into mutual apposition. In the middle of the
free edge of each valve there is a small fibro-cartilaginous nodule; radiating from
this toward the entire fundus, and along the extreme free edge of the valve, are
fibrous thickenings. On either side of the nodule, between the thicker margin
and fundus, the valve is thin over a crescentic area called the lunula.
The aortic valves are called the right, left, and posterior; the pulmonary valves,
the right, left, and anterior.* The aortic semilunar valves are stronger than the
pulmonary; opposite them there are three dilatations in the aortic wall, the aortic
* The BNA names of the aortic and pulmonary valves are not based upon their relative
positions in the body. From transverse sections through the thorax (see any good atlas) it
may be seen that one aortic valve is anterior, one pulmonary valve posterior, and the other
aortic and pulmonary valves are right and left. If the removed heart is held so that the ven-
tricles are on the right and left of the septum, respectively, the valves take the positions indi-
cated by the BNA. The names given by the BNA to the valves, although conventional (Uke
many other terms of orientation applied to parts of the heart), are convenient, particularly from
a developmental standpoint.
518
THE BLOOD-VASCULAR SYSTEM
sinuses [sinus aortae] or sinuses of Valsalva. From the right and left sinuses the
right and left coronary arteries, respectively, arise.
After ventricular systole the increased pressure in the great vessels distends the valves with
blood. The noduli meet in the centre and the lunulas, coming into mutual contact, produce a
tri-radiate line of contact between the valves.
ARCHITECTURE OF THE MYOCARDIUM
In the adult heart the myocardium of the atria is separate from that of the ventricles.
There is, between the atria and ventricles, a fibrous partition, the upper and lower surfaces ol
which give attachment to the muscle fibres of these cavities, respectively.
The fibrous partition (fig. 431) is thickest in the triangle formed by the meeting of the aortic,
and right and left atrio-ventricular ostia. This interval is filled by a mass of fibrous tissue,
which in the angles between the aortic and the left atrio-ventricular ostium forms two thickened
triangular masses, the trigona fibrosa. The fibrous mass is continued to the pulmonary ostium
as the tendon of the conus. Below the point of junction of the trigona and the tendon of the
conus these structures blend with the septum membranaceum ventriculorum. The septum
membranaceum, tendon of the conus, and part of the trigona are derived from the aortic septum
(pp. 516, 527). The trigona give off laterally, on either side, atrio-ventricular rings which en-
circle the venous ostia and give attachment to the atrio-ventricular valves. There are also weak
Fig. 431. — Base op a Well Developed Heart showing the Coubse op the Superficial
Muscle Fibres.
From X to jX' around the front of the aorta indicates the course of the aortic septum.
(Mall, I nat. size.)
rings surrounding the pulmonary and aortic orifices; the aortic and left atrio-ventricular rings
being partly confluent. The rings surrounding the arterial and venous ostia axe the annuli
fibrosi.
The atrial musculature is attached to the trigona and atrio-ventricular rings only. The
superficial fibres are attached to both rings and either encircle both atria in one loop, or enter the
septum and form a figure 8. The deeper fibres are attached to one ring and encircle one atrium
only; some fibres encircle only the auricle.
The ventricular musculature is very complex and consists of numerous superimposed layers
distinguished from one another by the direction taken by the muscle fibres. In a general way,
the fibres of the deepest layer have a direction crossing those upon the surface of the same area
at a right angle. The intervening layers of fibres pass through all stages of obhquity.
Recent work upon the origin and distribution of the ventricular fibres has resulted in the
recognition of a certain uniformity of behavior, thus: —
1. AH fibres arise from, and are inserted into, the fibrous partition at the base. The at-
tachment may be directly to the trigona or annuli, or indirectly to them by means of the chordse
tendineae and atrio-ventricular valves.
2. The more superficial fibres (fig. 432) tend to encircle the entire heart, passing over the
longitudinal sulci. If they enter the septum they do so by passing into the vorte.x or whorl
at the apex of the left ventricle. These fibres have always a definite direction upon the sur-
face, i. e., from right to left upon the sterno-costal surface and from left to right on the dia-
phragmatic (fig. 431).
3. The deeper fibres all enter the septum in a direction oblique or perpendicular to its
longitudinal axis. In addition they completely encircle one or both ventricles forming, in the
latter case, double loops (fig. 433).
VESSELS AND NERVES OF THE HEART
519
During systole, as a result of this arrangement: — (1) The papillary muscles and the longi-
tudinal and antero-posterior axes of the ventricles are simultaneously shortened. (2) There is
a movement of torsion or "wringing" which I'educes the ventricular cavities to their minimum
dimensions.
Conducting system. — Although the ordinary myocardium of the atria is distinct from that
of the ventricles there is, at one place, a connection between them. This connection is by means
of a small band of muscle which differs histologically from ordinary heart muscle. It is known
as the atrio-ventricular bundle, and serves to transmit the atrial rhythm of contraction to the
ventricles.
The atrio-ventricular bundle begins in the septal wall of the atrium a short distance in
front of the coronary orifices (fig. 428). It has an e.xpanded free end, the atrio-ventricular node,
from which branches pass to be quickl}' lost in the atrial myocardium. The bundle passes
forward covered by endocardium and by one or two millimetres of mj'ocardium, and passes
beneath the medial cusp of the tricuspid valve. In passing from the atrium to the ventricle,
the bundle skirts the lower margin of the septum membranaceum. Immediately in front of the
septum membranaceum it divides into a left and right limb, of which the former pierces the
muscular interventricular septum . The right limb now passes beneath the crista supra ventricul-
aris and above the papillary muscle of the conus, giving off branches to the latter and to other
small papillaries on the septum (fig. 428). Bending somewhat toward the apex, it enters the
moderator band which conducts it to the large anterior papillary muscle. From here it passes
along one of the trabeculae connected with the sterno-oostal wall of the ventricle, or in the wall
itself, to reach the posterior papillary muscle or muscles. The right limb is compact and
rounded and in the intact heart is usually invisible except, sometimes near the root of the
moderator band or in the band itself.
The left limb of the bundle appears in the left ventricle a little below the septum mem-
branaceum. It is a wide band immediately beneath the endocardium, which cannot usually be
Fig. 432. — Diagram of one Anterior
AND ONE Posterior Superficial Bundle
OP Cardiac Muscle Fibres seen from
Behind. (After MacCallum.)
Fig. 433. — Diagram of a Deeper
Bundle of Muscle Fibres. (After
MacCallum.)
Conus arteriosus
Tendon of the conus
V ""^r^ «\ Right atrio-ven-
•^^ -3 ' ■■' x tncular ring
stripped off without injuring the bundle (fig. 429). It passes along the septal wall toward the
apex and divides into two parts, which again subdivide to be distributed to the anterior and the
posterior papillary muscles. The branches for the papillary muscles may reach them through
thick trabecula;, or they may form thin strands which, covered only by endocardium, bridge
from septum to papillary muscle.
In addition to the comparatively distinct branches to the papillary muscles of both ventricles,
the bundle gives off finer fibres which form a sub-endocardial plexus. This plexus, visible to the
naked eye (p. 516) is made up of fibres having a structure similar to those of the ventricular
portion of the bundle. The fibres were described by Purkinje as long ago as 1845,* but it was
not until 1906, thirteen years after the discovery of the bundle by W. His, Jr., that Tawaraf
recognised their significance.
There is another node of muscle having characters similar to that of the conducting system,
although not connected with it except by myocardium of the ordinary character. This is the
sinus-node which is situated at the upper end of the crista terminaUs of the right atrium. Una-
nimity is still lacking with regard to the physiological significance of this structure.
Vessels and Nerves of the Heart
The arteries. — The two coronary arteries arise from the right and left sinuses of the aorta.
The right coronary artery [a. coronaria dextraj passes forward between the pulmonary
artery and the right atrium, and then follows the right coronary sulcus to the diaphragmatic
surface of the heart (fig. 435), to anastomose with the left coronary artery. The posterior
descending branch [ramus descendens posterior] arises at the posterior longitudinal sulcus. It
* Arch. f. Anat., Physiol, u. wissenschafthche Medizin.
t Das Reitungssystem des Saiigertierherzens, Fischer, Jena, 1906.
520
THE BLOOD-VASCULAR SYSTEM
E asses in the furrow between the ventricles toward the apex, near which it anastomoses with
ranches derived from the left coronary artery. In this course the right coronary artery
supplies branches to the right atrium and roots of the pulmonary artery and aorta, as well as
one that descends near the margo acutus (right marginal), and a second (preventricular) to the
anterior wall of the right ventricle. It supplies both ventricles and the septum.
The left coronary artery [a. coronarius sinistra] passes for a short distance forward, between
the pulmonary artery and the left auricle, and then divides into two principal branches, one of
which runs in the anterior longitudinal sulcus to the apex of the heart, the anterior descending
branch [r. descendens anterior], around which it sends branches to anastomose with the right
coronary; whilst the other, the circumflex [ramus circumflexus], winds to the diaphragmatic
surface in the coronary groove, to anastomose with the corresponding twigs of the right artery.
In this course it gives off a branch which follows the margo obtusus (left marginal) as well as
smaller branches to the left atrium, both ventricles, and the commencement of the aorta and
pulmonary vessels.
Fig. 434. — Stebno-costal Surface of the Heart, showing its Arteries and Veins.
(After Spalteholz.)
Innominate artery
Left subclavian artery
Superior vena cava
Left common carotid artery
_ Pulmonary artery
Conus arteriosus
- Left auricle
Rightcoronary.
artery
Right ventricle
The cardiac or coronary veins accompany the coruuary arteries and return the blood from
the walls of the heart.
The great cardiac vein [v. cordis magna], (fig. 434) runs in the anterior longitudinal sulcus,
passing round the left side of the heart in the coronary sulcus to terminate in the commence-
ment of the coronary sinus. Its mouth is usually guarded by two valves, and it receives in its
course the posterior vein of the left ventricle, with other smaller veins from the left atrium and
ventricle, all of which are guarded by valves.
The middle cardiac vein (v. cordis media], sometimes the larger of the two chief veins, com-
municates with the foregoing at its commencement above the heart's apex. It ascends in the
posterior longitudinal groove, receiving blood from the ventricular walls, and joins the coronary
sinus through an orifice guarded by a single valve, close to its termination.
VESSELS AND NERVES OF THE HEART
521
The posterior vein of the left ventricle [v. post, ventriculi sinistri], lies upon the posterior
surface of the ventricle and, receiving branches from it, passes upward to terminate directly
in the coronary sinus.
The anterior cardiac veins [vv. cordis anteriores] consist of several small branches from the
front of the right ventricle, which vary in number and either open separately into the right
atrium or join the lesser cardiac vein (fig. 434).
The small cardiac vein [v. cordis parva] is a small vessel which receives branches from both
the right atrium and ventricle, and winds around the right side of the heart, in the coronary
sulcus, to terminate in the coronary sinus.
The coronary sinus [sinus coronarius] (fig. 435) may be regarded as a much dilated terminal
portion of the great cardiac vein. It is about 2.5 cm. (1 in.) in length, is covered by muscular
fibres from the atrium, and hes in the coronary sulcus below the base of the heart. Its cardiac
orifice, with the coronary (Thebesian) valve, has already been described. Besides the tributary
veins already named, a small oblique vein [v. obUqua atrii sinistri] of the left atrium may some-
FiG. 435. — Base and' Diaphragmatic Surface op the Heart, showing its Arteries and
Veins. (After Spalteholz.)
Kigtit pulmonary artery
Left pulmouary artery
Left atrium
Great cardiac
vein
Posterior
'vein of tlie
left ven-
tricle
Right pulmonary veins
Left ventricle-
Middle cardiac vein
. Posterior descending
branch of the right
coronary artery
Posterior longitudinal sulcus
times be traced, on the back of the left atrium, from the ligament of the left vena cava (Marshall)
to the sinus. This httle vein, which is not always pervious or easy of demonstration, never
possesses a valve at its orifice, and, Uke the coronary sinus, formed a part of the left superior
vena cava of earlyfoetal life.
The smallest cardiac veins [vv. cordis minima;] drain blood from septum and lateral walls
of the atria, particularly the right; also from the conus arteriosus. They open directly into the
right atrium.
Although anastomoses occur between the two coronary arteries, these are by no means
extensive, and are not sufficient to allow of the estabhshment of a satisfactory collateral cir-
culation in the case of the blocking of one coronary artery. Consequently such interference
with the cardiac circulation produces rapid pathological changes in the heart musculature,
provided it is sudden in occurrence. If the obhteration of the artery take place gradually,
however, some rehef may be afforded by the estabhshment of a collateral circulation through
the vense minimse, which open out from both the atrial and ventricular cavities and communicate
522
THE BLOOD-VASCULAR SYSTEM
with the finer branches of the cardiac veins, and also with the general capillary network in the
heart's walls.
The lymphatic vessels of the heart pass chiefly through the anterior mediastinal lymph-
nodes into the broncho-mediastinal trunk. (See Section VI.)
The cardiac nerves, derived from the vagus and the cervical sympathetic, descend into the
superior mediastinum, passing in front of and behind the arch of the aorta; they unite in the
formation of the superficial and deep cardiac plexuses. The superficial plexus lies above the
right pulmonary artery as the latter passes beneath the aortic arch. The deep plexus lies be-
tween the trachea and the arch of the aorta, above the bifurcation of the pulmonary trunk.
For the connections of the plexuses see section on Nervous System.
2. THE PERICARDIUM
The pericardium is a cone-shaped, fibro-serous sac which surrounds the heart
and contains a small amount of fluid [liquor pericardii]. Its apex is above at the
root of the great vessels, and its base below, adherent to the diaphragm. Its
connection with the diaphragm is in part to the central tendon and in part to the
muscle, especially on the left side. It consists of an outer fibrous layer and an
inner serous layer. The virtual space between the serous pericardium and the
epicardium is commonly called the pericardial cavity.
Fia. 436. — ^Lept Posteriok View of the Heart to show the Reflections of the Peri-
cardium.
Pulmonary artery
Left pulm. artery
Ligament of left
superior cava
Morgo obtusus
Coronary sinus
Vena cava inferior
The fibrous layer is strong and inelastic, made of interlacing fibres. Its connection with
the central tendon of the diaphragm is intimate, particularly in the region of the caval opening,
but elsewhere it is attached loosely by means of areolar tissue. Above, it is lost on the sheaths
of the great vessels, all of which receive distinct investments, with the single exception of the
inferior vena cava, which pierces it from below. The aorta, superior vena cava, the pulmonary
artery, and the four pulmonary veins, are all ensheathed in this manner. The pericardium is
connected above with the deep cervical fascia. Two variable bands of fibrous tissue, the
sterno-pericardial ligaments [ligg. sterno-pericardiaca], connect the front of the pericardium,
above and below, with the posterior surface of the sternum.
RELATIONS OF HEART AND PERICARDIUM 523
The serous layer is smooth and ghstening and consists of connective tissue, rich in elastic
fibres, covered by endotheUum. It lines the interior of the fibrous layer and is continuous with
the epicardium or serous covering of the heart. The reflexion of the serous layer from the heart
to the fibrous layer of the pericardium occurs at both the arterial and venous attachments of the
heart. At the arterial attachment a simple tube of epicardium is reflected along the pul-
monary artery and aorta. At the venous attachment the serous layer is reflected from the front
of the pulmonary veins on the left, and from the front of these and from the roots of the venae
cavae on the right. This reflexion is separated above from that around the aorta and pulmon-
ary artery (figs. 424, 436). Around the lower margin of the left lower pulmonary vein (fig. 436)
and the root of the inferior vena cava, this reflexion is continuous with an arched refle.xion from
the back of the atria (figs. 424, 436). The latter reflexion forms a pocket posterior to the atria
which is sometimes called the oblique sinus of the pericardium.
Between the reflexions of the epicardium at the arterial and venous attachments of the heart
there is a dorsal communication between the right and left sides of the pericardial cavity. This
is the transverse sinus of the pericardium [s. transversus pericardii]; it passes behind the aorta
and pulmonary artery and in front of the superior cava and left atrium.
During early embryonic life the sinus transversus is closed by the dorsal mesocardium
(see p. 527). The primitive ventral mesocardium, which divides the right and left sides of the
pericardial cavity ventrally, is lost very early.
The ligament of the left superior cava [lig. vense cavae sinistrse] (figs. 423, 436)
is a doubling of the serous layer which passes between the left pulmonary artery
above and the left superior pulmonary vein below. It contains, besides some
fatty and areolar tissue, the shrunken remains of the left superior vena cava.
It is usually connected above with the left superior intercostal vein by means of a
small tributary of the latter. Passing from its lower end to the left end of the
coronary sinus is the small vena obliqua atrii sinistri (oblique vein of Marshall).
The root of the left superior intercostal (and the adjacent part of the left innom-
inate) vein; the vein passing from the super or intercostal to the lig. venae
cavae sinistrse; the obhque vein of the left atrium, and the coronary sinus all
represent parts of the embryonic left vena cava superior.
Relations. — In front of the pericardium are found the thymus gland or its remains, areolar
tissue, the sterno-pericardial ligaments, the left transversus thoracis muscle, the internal
mammary vessels, the anterior margins of the pleural sac and' lungs, and the sternum. Later-
ally, it is overlapped by the lungs with their pleural sacs, and it is in contact with the phrenic
nerves and their accompanying vessels. Posteriorly, it is in relation with the cesophagus and
vagus nerves, the descending aorta, the thoracic duct and vena azygos, and the roots of the lungs.
Below it is separated by the diaphragm from the stomach and the left lobe of the fiver.
Vessels. — The arteries of the pericardium are derived from the pericardiac, oesophageal,
and bronchial branches of the thoracic aorta and from the internal mammary and phrenic
arteries.
RELATIONS OF THE HEART AND PERICARDIUM TO THE
THORACIC WALL
Heart (fig. 437 A and B). — The base of the heart corresponds posteriorly to the fifth,
to the ninth thoracic vertebra. Anteriorly the apex is in the fifth intercostal space, 7.5 to
S cm. (3 to 3i in.) from the medan line. The base (above) corresponds to a line (A) drawn
from a point 1 cm. (= in.) below the second left chondro-costal articulation, and 3 cm (Ij in.
from the median line, to another point (the same distance from the median line) 1 cm. above
the right third ehondro-sternal articulation. The marge acutus, or lower border corresponds
to a line (B) drawn from the apex through the xiphi-sternal articulation, to a point on
the sixth costal cartilage 2 cm. to the right of the median line. The right border of the heart
may be indicated approximately by a fine (shghtly convex to the right) joining the right ends
of A and B. The left border corresponds to a fine (slightly convex to the left) joining the left
end of A to the apex.
If a line be drawn from the upper margin of the left third ehondro-sternal articulation to the
right edge of the sternum in the fifth intercostal space, the upper end of the line wiU he over the
centre of the pulmonary ostium, and the lower two-thirds of it (approximateljO will overlie
the main axis of the tricuspid ostium. The aortic ostium is immediately to the left of the above
line with its centre at the left edge of the sternum opposite the third space. The mitral ostium
is very largely behind the third left interspace; its upper end is behind the third cartilage, its
lower behind the left margin of the sternum opposite the fourth cartilage and space.
Of the ostia of the heart, the pulmonary is nearest the anterior thoracic wall, the aortic is
slightly in advance of the mitral, and the tricuspid is the deepest of all.
The pericardium follows the heart closely. The upper end (apex) in the subject used in
preparing fig. 437 extended up, behind the sternum, to the lower margin of the first costal
cartilage on the right and the upper margin of the second on the left.
MORPHOGENESIS OF THE HEART AND PERICARDIUM
The heart is formed by the blending in the median fine of two longitudinal endothehal
tubes lying ventral to the fore-gut of the early embryo. Each tube is partially surrounded
laterally by the splanchnic mesoderm which forms a septum between the right and left sides of
524
THE BLOOD-VASCULAR SYSTEM
Fig. 437. — A, Telebobntgenogham of a Formalin Preparation or the Anterior
Thoracic Wall with the Heart, Pericardium and Diaphragm in situ. (Le Wald,
X i). B, Explanatory Outline Drawing, Traced from the Negative and Con-
trolled BY Stereoscopic Views.
The ostia have been accurately fitted with wire rings. P, pulmonary ostium; M, mitral;
T, tricuspid; aortic ostium is unlabelled; I- VII, right costal cartilages.
I
MORPHOGENESIS OF THE HEART AND PERICARDIUM
525
the ccelomic cavity. The blended endothehal tubes form the endocardium. The splanchnic
mesoderm in relation to the endocardium becomes the myoepicardium, and the double layer
connecting the heart dorsally and ventrally with the somatic mesoderm becomes the (temporary)
dorsal and ventral mesocardia. The somatic mesoderm of the heart region becomes the peri-
cardium.
The originally straight heart-tube grows rapidly and becomes tortuous on account of its
increasing length between the hmits assigned by its fixed arterial and venous ends. Its arterial
end is continued into the truncus arteriosus, which is later divided into the pulmonary artery
and the ascending aorta. Its venous end receives the vitehine and umbihcal veins, and, later
on, the common cardinals also. By the formation of a series of alternate bulgings and constric-
tions the heart becomes differentiated into the sinus venosus, atrium, ventricle and conus arte-
riosus, counting from the venous to the arterial end. These parts, after going through a process
of progressive differentiation and shifting (fig. 438) take up relative positions somewhat ap-
proaching those of the adult.
Fig. 438. — Models showing the Development of the Heart. (After His.)
Conus arteriosus Conus arteriosus
The sinus venosus hes on the dorsal wall of the atrium, and is composed of right and left
horns united by a transverse portion. The sinus is separated from the atrium by a sagitaUy
directed sHt-Uke opening, guarded by right and left lateral valves which project into the atrium.
The atrium is wide, being prolonged into a ventrally projecting pouch on either side, the future
right and left auricles. The ventricle is situated caudal and somewhat ventral to the atrium.
The right Umb of the common ventricle, which leads into the conus arteriosus, is the future
right ventricle; the left limb, connected with the atrium, is the future left ventricle. The
Fig. 439. — Sagittal Section throtjgh a Reconstrttction of the Heart of a 9 mm. Human
Embryo seen FROir the Left Side. (Tandler, X 75.)
Septum
=«''""1'"° Foramen ovale
Conus arteriosus-
Septum prinum
Sinus venosus
communication between the atrium and the ventricle, known as the atrial canal, is indicated
on the exterior by a constriction; its interior consists of a transversely placed slit. The conus
arteriosus is continued from the ventricle without obvious constriction and passes over into the
truncus arteriosus.
The sinus venosus early loses its bilateral symmetry owing to the rapid enlargement of the
right horn. This horn soon receives, through the proximal portion of the right vitelline vein
{inferior vena cayo), all the blood coming from the left vitelline and both umbihcal veins. The
right common cardinal also gains ascendency over the left and becomes the superior vena cava.
526
THE BLOOD-VASCULAR SYSTEM
The left horn and transverse part, now only draining the dwindling left common cardinal, (left
superior cava) and the coronary veins, become the coronary sinus. The right horn gradually
becomes absorbed into the right end of the atrial cavity until the superior and inferior cava;
and the coronary sinus acquire separate openings into that chamber. Between the opening
of the coronary sinus and that of the inferior cava there is a ridge, the sinus-septum (between
the right horn and transverse parts of the sinus), which becomes attached to the lower part
of the right sinus valve.
In the atrium a septum begins early to grow from the ventro-cephaUc wall of the atrium,
toward the atrial canal. As the interatrial communication around the edge of the septum
(ostium primum) is becoming narrow, a perforation occurs near the attached margin of the
septum (ostium secundum). This fii-st septum (septum primum) is incomplete because when
its edge reaches the atrial canal the atria stiU communicate through ostium secundum. To the
right of the septum primum another septum (s. secundum) is formed later; this never stretches
completely across the atrium and is rather a crescentic ridge than a true septum. Until the
free edges of the two septa overlap one another there is a direct passage leading from one side
of the atrium to the other; eventually they do overlap and the communication becomes
oblique but persists until birth. (For adult relations of septa, see p. 511.) The cavities
resulting from the division of the common atrium are the right and left atria of the adult.
The obUque channel connecting the atria (foramen ovale) is bounded on the right side by the
s. secundum the free edge of whicli forms the limbus fossae ovalis. The channel is bounded
on the left by the s. primum which slants into the left atrium. The free edge of the s.
primum becomes the valvula foraminis ovalis; the remainder, the membranous atrial septum of
the adult.'
Fig. 440. — Reconstkuction op the Heart of an 11 mm. Human Embryo viewed from
Below. (Mall, 50.)
The lower part of the ventricular portion has been cut off. Connective tissue septa colored
yellow. Ao, aorta; Ap, anterior papillary muscle; La, left atrium; Lo, left venous ostium; Lp,
large (anterior) papillary muscle of right ventricle; Mpm, medial papillary muscle; PP, pos-
terior papillary muscle; P, pulmonary artery; RA, right atrium.
i
The portion of the dorsal wall of the right atrium immediately adjoining the septa is derived
from the sinus venosus. Tliis part of the atrium (the sinus venarum) receives the great venous
openings. The left side of the left sinus-valve is attached to both septa and assists the septum
secundum in the formation of the limbus foraminis ovalis. The cephalic part of the right sinus-
valve disappears along the line of the (adult) crista ierminalis, which therefore hmits the right
portion of the right atrium derived from the sinus venosus. The caudal portion of this valve
persists as the inferior caval and coronary valves. These are drawn out of their original ahgn-
ment by the adhesion between the caudal part of the right sinus-valve and the sinus-septum.
The left atrium receives, through the dorsal mesocardium, the originally single pulmonary
vein. This common stem is absorbed into the atrial wall; later, the primitive right and left
tributaries are absorbed in a similar way, leaving the four pulmonary veins of the adult open-
ing separately into the left atrium. The area of the left atrium adjacent to the pulinonary
veins, therefore, is not part of the original atrial waU.
The ventricles are divided by a septum (s. musculare ventriculorum) growing from the caudal
wall of the common ventricular cavity toward the atrial canal. The canal moves to the right,
and the dorsal part of the septum blends with the dorsal lip of the canal. The free ventral
edge of the interventricular septum helps to bound the foramen through which blood from the left
ventricle must enter the right on its way to the conus arteriosus. The foramen persists until
(the free margin of the interventricular septum having been joined by the aortic septum) it
becomes the circumference of the aortic ostium.
THE ARTERIES AND VEINS 527
The aortic septum is a composite structure formed partly by a septum growing between tlie
fourth and sixth pairs of aortic arches, and partly by sweUings growing in the interior of the conus
and truncus arteriosus. When fully formed it extends spirally along the truncus and conus,
and enters the right half of the common ventricular cavity, where it joins the right side of the
free edge of the interventricular septum. The septum is arranged in such a way that the blood
from the left ventricle passes no longer through the right ventricle but along its own channel
{the aorta) through the conus and truncus to the first four pairs of aortic arches. The blood
from the right ventricle passes through the pulmonary division of the conus and truncus arterio-
sus, anterior and to the left of the aorta, into the sixth arches. Further differentiation brings
about the external separation of the aorta from the pulmonary artery, but their common cover-
ing of epicardium persists as such in the adult. The lower end of the aortic septum persists
in the adult as the septum membranaceum ventriculorum and the crista supraventricularis, the
relations of which to the septum musculare are well shown in fig. 428. During the formation
of the aortic septum four endocardial swelhngs appear at the distal part of the interior of the
conus. These are arranged as smaller and larger opposite pairs; the smaller and larger swellings,
therefore, alternating around the lumen. The larger pair of swellings assists (by partial
blending) in the formation of the aortic septum. When the septum is complete, half of each
of the larger sweUings is contained in the aorta and half of each in the pulmonary artery. One
of the smaller swelhngs remains in the aorta and one in the pulmonary artery, so that there are
now three sweUings in each vessel. Each of the six swellings becomes undermined to form
a semilunar valve of the adult.
The atrio-ventricular valves. — The interior of the ventricular cavity, which is at first
smooth, becomes undermined in an irregular way, to form a system of myocardial trabeculse.
The Ups of the transversely directed atrial canal become thickened into prominent anterior and
posterior endocardial cushions; these project into the ventricular cavity and become involved
in its myocardial trabecular system. The atrial canal, which has now moved to the right, be-
comes divided sagittaUy, into right and left venous osiia, by the septum primum. The inter-
ventricular septum joins the ventricular side of the posterior endocardial cushion. The anterior
and posterior endocardial cushions, where they blend with one another and with the septum
primum on the medial side of each venous ostium, form an atrio-ventricular valve-cusp on
either side, viz., the anterior cusp of the mitral in the left ostium, and the medial cusp of the
tricuspid in the right. The posterior cusp of the mitral and the anterior and posterior of the
tricuspid are formed later, partly, by lateral tubercles developing in either ostium, and partly
by undermining of the ostia from the ventricular side. The atrial musculature extends into the
atrio-ventricular valves and, until a late stage, is continuous with the trabecular system of the
ventricles. GraduaUy, however, this connection between atrial and ventricular musculature
is lost, leaving only the chordae tendinese connecting the papillary muscles with the valves
Muscle is found at the basal region of the valve-cusps in the adult, and occasionally persists in
the chordae tendinese.
The connection between the atrial and ventricular musculature is not confined to that
occurring by means of the valves and trabecular system. The original myocardial connection
between the atrial and ventricular portions of the heart remains complete until the embryo
has reached the length of about 11 mm. From that time on the epicardium begins to blend
with the fibrous annuh of the venous ostia. MeanwhUe the atrial musculature rapidly loses its
connection with that of the ventricles until they are connected in one place only, i. e., the site
of the atrio-vetitricular bundle.
The pericardial cavity is the original cephalic end of the intraembryonic ccelom. The
somatic mesoderm of the pericardial region forms the adult pericardium. The splanchnic
mesoderm persists only in the part which furnishes the myo-epicardium. The ventral and dorsal
mesocardia, both of which are formed by the splanchnic mesoderm, are, in the main, transitory.
The early disappearance of the ventral mesocardium unites the right and left sides of the peri-
cardial ccelom ventral to the heart. The dorsal mesocardium persists at the arterial and venous
ends of the heart only. The loss of the dorsal mesocardium between the latter points gives
rise to the sinus transversus pericardii of the adult.
During development, the heart and pericardium migrate from a point opposite the cephahc
end of the pharynx to one opposite the caudal end of the oesophagus; in fact, from the neck well
into the thorax. In the adult, instead of being at the cephahc end of the ccelom, the heart
and pericardium are contained between the right and left layers of the ventral mesentery of the
oesophagus; the pericardial pleura of the adult.
The cranio-caudal migration is evidenced in the adult by the course of the recurrent and of
the cardiac nerves, and also by the apparent migration of the vessels derived from some of
the dorsal segmental arteries.
B. THE ARTERIES AND VEINS
The arteries [arteriae], proportionately to their size, have much thicker walls
than the veins. After death they retain their natural form, but are contracted
and contain usually a small amount of pale clot. In a very general way the
thickness of wall is proportional to cahbre. Some arteries, however, are con-
stantly thicker or thinner than could be predicted from size alone.
The larger arteries usually take a direct course and branch dichotomously. In descriptive
anatomy if dichotomous branches are of nearly equal size it is common for each to take another
name; if one branch preponderates in size, it is apt to retain the name of the parent trunk
while the smaller is regarded as a collateral branch [vas coUaterale] . There are numerous
528 THE BLOOD-VASCULAR SYSTEM
exceptions to dichotomous branching; branches may run perpendicularly or recurrently to the
vessel from which they arise; or several branches may arise simultaneously.
There is less tendency to anastomosis between large or medium sized arteries than in veins
of corresponding magnitude. Anastomoses do occur, however, particularly in the form of
arches, such as the palpebral, plantar and volar arches, or the arches between the intestinal
arteries. This form of anastomosis is sometimes called inosculation. Between smaller arteries
anastomosis is usually free as in the case, for instance, of the articular retia. In some organs
anastomosis (excepting capillary) between neighbouring arteries can scarcely be said to exist
at all; the a. centralis retinae affords a good example of this, as do the arteries of the brain, spleen,
and kidney; such arteries are called terminal.
The larger arteries are supplied by vasa vasorum, frequently arising from their own recurrent
branches.
The veins [venae] have thin walls, and after death are either collapsed or
filled with clot or stained serum. They are characterized by the presence of
valves and frequent anastomoses.
Frequent anastomoses occur between veins of all sizes; plexuses are common, such, for
instance, those of the pelvis. Venm comitantes are veins which, usually in pairs, accompany
many arteries; they communicate with one another, around the artery, very freely. Veins
do not primitively accompany arteries. In the case of the extremities the primitive veins are
superficial. The deep veins of the hmbs are of later formation and to them the superficial
veins subsequently become tributary.
The veins from the stomach, spleen, pancreas and intestine are collected into a large trunk,
the portal vein. This does not open into the inferior vena cava directly, but breaks up into
numerous smaller vessels in the Hver. From these the blood is returned, through the hepatic
veins, to the inferior cava.
Many veins are provided with valves, the free borders of which are directed toward the heart.
In the small veins the valves are single; in the larger veins they are usually double, rarely treble.
Valves are much more numerous in the veins of infants than those of the adult, they seem to
disappear progressively with advancing age. The venous valves are most numerous in the
superficial veins, and in the deep veins of the extremities; in many veins of the head and neck
they occur only at their point of termination in a larger trunk.
The cranial venous sinuses are modified veins, consisting of intima only which lines channels
in the fibrous dura mater. The venous spaces in cavernous tissue, such as the corpora cavernosa,
may be looked upon as specially modified veins.
The larger veins, hke the arteries, have vasa vasorum.
The arteries and veins will be considered in the following order: 1, pulmonary
artery and veins; 2, the systemic arteries; and, 3, the systemic veins. At the
ends of the second and third divisions, the development and variations are
considered.
1. THE PULMONARY ARTERY AND VEINS
The pulmonary artery [a. pulmonahs] (fig. 441) passes from the right ventricle
to the lungs. It differs from all other arteries in the body in that it contains
venous blood. It arises as a short, thick trunk from the conus arteriosus of
the right ventricle, and, after a course of about 5 cm. (2 in.) within the pericar-
dium, divides into a right and a left branch. These branches pass to the, right
and the left lung respectively.
The trunk of the pulmonary artery at its origin is on a plane anterior to the
ascending aorta, and slightly overlaps that vessel. Thence it passes upward,
backward, and to the left, forming a slight curve around the front and left side of
the ascending portion of the aorta; and, having reached the concavity of the
aortic arch, on a plane posterior to the ascending aorta, it divides into its right
and left branches, which diverge from each other at an angle of about 130°.
The division of the pulmonary artery occurs immediately to the left of the second
left chondrosternal articulation.
In the foetus, the pulmonary artery continues its course upward, backward, and to the left
under the name of the ductus arteriosus (Botalli), and opens into the descending aorta just
below the origin of the left subclavian artery. After birth, that portion of the pulmonary
artery which extends to the aorta becomes obhterated, and remains merely as a fibrous cord,
the ligamentum arteriosum (fig. 436).
Relations. — In front, the trunk of the pulmonary artery is covered by the remains of the
thymus gland, and the pericardium. The artery Ues, at its commencement, behind the upper
margin of the third left chondro-sternal articulation. The right margin of the artery is behind
the second piece of sternum but the greater part of the vessel is behind the medial end of the
second intercostal space.
Behind, it lies successively upon the ascending aorta and the left atrium.
To the right are the ascending aorta, the right atrium, the right coronary artery, and the
cardiac nerves.
THE SYSTEMIC ARTERIES 529
To the left are the pericardium, the left pleura and lung, the left auricle, the left coronary
artery, and the cardiac nerves.
The right pulmonary artery [ramus dexter] longer than the left, passes almost
horizontally under the arch of the aorta to the root of the right lung, where it
divides, either directly or after repeated division, into three branches, one for
each lobe. These branches follow the course of the bronchi, dividing and sub-
dividing for the supply of the lobules of the lung. The terminal branches do
not anastomose with each other.
Relations. — In its course to the lung it has in front of it the ascending aorta, the superior
vena cava, the phrenic nerve, the anterior pulmonary plexus, and the reflexion of the pleura.
Behind are the right bronchus and the termination of the azygos vein. Above is the arch of
the aorta, and below are the left atrium and the upper right pulmonary vein.
At the root of the lung it has the right bronchus above and behind it; the pulmonary veins
below and in front. Crossing in front of it and the other structures forming the root of the lung
are the phrenic nerve and the anterior pulmonary plexus; behind are the azygos vein, the vagus
nerve, and the posterior pulmonary plexus.
The left pulmonary artery, shorter and slightly smaller than the right, passes
in front of the descending aorta to the root of the left lung, where it divides into
two branches for the supply of the upper and lower lobes respectively. These
divide and subdivide as on the right side.
Relations. — At the root of the lung it has the left bronchus behind and also below it, in
consequence of the more vertical direction taken by the left bronchus than by the right. Below
and in front are the pulmonary veins, while passing from the artery and the upper left pulmonary
vein is the hgament of the left superior cava. Crossing in front of it and the other structures
forming the root of.the lung are the phrenic nerve, the anterior pulmonary plexus, and the reflex-
ion of the left pleura; crossing behind, are the descending aorta, the left vagus nerve, and the
posterior pulmonary plexus.
The pulmonary veins [vv. pulmonales] (figs. 424, 441) return the aerated
blood from the lungs to the heart. They are usually four in number, superior
and inferior, of the right and left sides. Occasionally, however, there are three
pulmonary veins on the right side, the result of the vein from the middle lobe
of the right lung opening separately into the left atrium instead of joining as usual
the upper of the two right pulmonary veins. The relations of the pulmonary veins
to the pulmonary arteries and bronchi in the lungs- are given with the anatomy
of the lungs (Section X).
The pulmonary veins are about 15 mm. in length. In the pericardium the
right pulmonary veins [vv. pulmonales dextrse] both pass behind the superior
vena cava. The superior vein receives the vein from the right middle lobe and
runs below and in front of the right pulmonary artery.
The left pulmonary veins [vv. pulmonales sinistrse] enter the left atrium about
3 cm. in front of the veins of the right side. The superior vein is below the left
pulmonary artery.
2. THE SYSTEMIC ARTERIES
THE AORTA
The aorta (fig. 442) is the main systemic arterial trunk, and from it all the
systemic arteries are derived. It begins at the left ventricle of the heart, and
ascends near the anterior thoracic wall as high as the second right chondro-sternal
articulation [aorta ascendens]. It then turns backward and to the left forming
an arch [arcus aortas] which reaches the posterior thoracic wall at the left side of
the fourth thoracic vertebra. From here it runs downward along the vertebral
column [aorta descendens] through the thorax and abdomen and ends by dividing,
opposite the fourth lumbar vertebra, into the right and left common iliac arteries.
From the point of bifurcation a small vessel, the middle sacral, is continued down
the middle line in. front of the sacrum and coccyx. The midclle sacral represents
the sacral and coccygeal aorta.
The Ascending Aorta
The ascending aorta [aorta ascendens] (fig. 442) begins at the upper part of
the left ventricle, on a level with the third intercostal space, and ascends behind
I
530
THE BLOOD-VASCULAR SYSTEM
the sternum to the upper border of the right second chondrosternal articulation.
It measures about 5 to 5.5 cm. (2 to 2i in.), forming, as it ascends, a gentle curve
with its convexity to the right. It is enclosed for the greater part of its length in
the pericardium, being invested, together with the pulmonary artery, in a com-
mon sheath formed by the serous layer of that membrane. A dilatation known
as the bulbus aortse occurs immediately above the heart upon which are three
locaHzed bulgings, known as the aortic sinuses (sinuses of Valsalva); they are
placed, one to the right, one to the left, and one posteriorly. From the right and
eft are derived the coronary arteries of the heart. (See Heart.)
Fig. 441. — The Gkeat
(Modified from a dissection in St,
Internal jugular vein
Transverse cervical
artery
Transverse scapular
artery
Vessels of the Thorax.
Bartholomew's Hospital Museum.)
Inferior thyreoid ■
Right inferior laryn-
Right common carotid
artery
Subclavian vein'
Innominate artery
Left innominate vem
Phrenic nerve
Superior vena cava
Arch of aorta
Right bronchus
Branch of right pul-
monary artery
Branch of right pul-
monary vein
Right pulmonary
artery
Branch of right pul-
monary artery
Branch of right pul-
monary vein
Right coronary artery
Thoracic vertebra
Azygos vein
Intercostal veins
Intercostal arteries
--Thyreoid gland
Left internal jugular
vein
, Vagus nerve
Left common carotid
artery
Left inferior laryngeal
nerve
-Left subclavian artery
Left subclavian vein
Left internal mammary
vein
Left superior inter-
costal vein
Phrenic nerve
Vagus nerve
Recurrent nerve
Ligamentum arteri-
osum
Left pulmonary artery
Left pulmonary vein
Left bronchus
Branch of left pulmon-
ary artery
Pulmonary artery
Left pulmonary vein
Left coronary arteiy
Conus arteriosus
Thoracic duct
Thoracic aorta
Relations. — In front, it is overlapped at its commen-cement by the right auricle, conut
arteriosus and pulmonary artery. Higher up, as the pulmonary artery and auricle diverge, is
is separated from the manubrium by the pericardium, the remains of the thymus gland, and by
the loose tissue and fat in the superior mediastinum, and is here shghtly overlapped by the right
pleura and by the edge of the right lung in full inspiration. The root of the right coronary
artery is also in front.
Behind are the left atrium of the heart, the right pulmonary artery, the right bronchus,
and the anterior right deep cardiac nerves.
On the right side it is in contact, below with the right atrium, and above with the superior
vena cava.
On the left side are the pulmonary artery and the branches of the right superficial cardiac
nerves.
Branches. — The right and left coronary arteries have already been described (p. 519).
The Arch of the Aorta
The arch of the aorta [arcus aortse] (figs. 441, 442), extends in a gentle curve
upward, backward, and to the left, from the level of the upper border of the
THE ARCH OF THE AORTA
531
second right costal cartilage to the lower border of the fourth thoracic vertebra.
Attached to the concavity of the arch, just beyond the origin of the left sub-
clavian artery, is the ligamentum arteriosum (vestige of the dorsal part of the
left sixth arch). Between the left subclavian artery and the ligamentum arterio-
sum there is sometimes a definite constriction of the arch (isthmus aortse) situated
opposite the third thoracic vertebra. When the isthmus is well marked, it is
succeeded by a dilatation (aortic spindle) which begins in the neighbourhood of
the ligamentum arteriosum and passes over into the descending aorta. Passing
under the arch are the left bronchus, the right pulmonary artery, and the left
recurrent (inferior laryngeal) nerve. It measures about 4.5 cm. (14- in.).
Fig 442 — ^The Thoracic and Abdominal Aorta.
Right common carotid
artery
Right internal jugular
vein
Right lymphatic duct
Innominate artery
Right vagus nerve
Right innominate vein
Internal mammary vein
Trunk of the pericardiac
and thymic veins
Superior vena cava
Hemiazygos vein^ cross-
ing spine to enter vena
azygos
Inferior vena cava
Right inferior phrenic
artery
Cceliac artery
Right middle suprarenal
artery
Right internal spermatic
artery
Right spermatic vein
Left common carotid
artery
Left vagus nerve
Thoracic duct
Left innominate vein
Left subclavian artery
Left superior intercostal
Recurrent (laryngeal)
Accessory hemiazygos
vein
(Esophagus
Left upper azygos vein
(Esophageal branches
from aorta
Hemiazygos vein
Thoracic duct
Left inferior phrenic
artery
Left middle suprarenal
artery
Receptaculum chyli
Superior mesenteric
artery
Left ascending lumbar
Left internal spermatic
artery
Inferior mesenteric
artery
Relations. — In front and to the left, it is slightly overlapped by the right pleura and lung,
and to a greater extent by the left pleiu-a and lung. It is crossed in the following order from
right to left, by the left phrenic nerve, by the cardiac branches of the vagus nerve, the cardiac
braUches of the sympathetic nerve, by the left vagus nerve, and by the left superior intercostal
vein as it passes up to the left innominate vein.
Behind and to the right are the trachea, the oesophagus, the thoracic duct, the deep cardiac
plexus which is situated on the trachea just above its bif.urcation, and the left recurrent (inferior
laryngeal) nerve.
Above it are the three chief branches for the head, neck, and upper extremities, namely, the
innominate, the left carotid, and the left subclavian arteries, and the left innominate vein.
532
THE BLOOD-VASCULAR SYSTEM
Below it — that is, in its concavity — are the bifurcation of the pulmonary artery, the left
bronchus, the left recurrent (inferior laryngeal) nerve, the ligamentum arteriosum, the super-
ficial cardiac plexus, two or more bronchial lymphatic glands, and the reflexion of the
pericardium.
The branches of the aortic arch are: — the inDominate, the left common caro-
tid, and the left subclavian arteries. The innominate and left carotid arise close
together — indeed, so close that, when seen from the interior of the aorta, the
orifices appear merely separated by a thin septum. The left subclavian arises a
little less close to the left carotid.
THE INNOMINATE ARTERY
The innominate [a. anonyma] or brachio-cephalic artery (fig. 441), the largest
branch of the arch of the aorta, extends from near its commencement upward
and a little forward and to the right, as high as the upper limit of the right
sterno-clavicular joint where it bifurcates into the right common carotid and right
subclavian arteries. It lies obliquely in front of the trachea, and measures from
-3.7 to 5 cm. (1| to 2 in.).
Fig. 443. — -The Thykeoidea Ima. (After Henle.)
fiight carotid artery
Sight subclavian artery
Innominate artery
Superior vena cava
Left carotid artery
Left subclavian ai'tery
Pulmonary artery
Relations. — In front of the artery are the manubrium, the origins of the sterno-hyoid and
sterno-thyreoid muscles, the right sterno-clavicular joint, and the remains of the thymus gland.
The left innominate vein crosses the root of the vessel, and the inferior thyreoid and thyreoidea
ima veins descend obliquely over it to end in the left innominate vein. The inferior cervical
cardiac branches of the right vagus nerve pass in front of it on their way to the deep cardiac
plexus.
Behind, it hes on the trachea, crossing that tube obhquely from left to right, and coming
into contact above with the right pleura.
To the right side are the right innominate vein, the right vagus, and the pleura.
To the left side are the left common carotid, the remains of the thymus gland, the right
inferior thyreoid vein; and, higher, the trachea.
The branches of the innominate artery are: — (1) The right common carotid;
and (2) the right subclavian. These are terminal branches. There are usually
no collateral branches from this vessel, but at times the thyreoidea ima may arise
from it.
THE COMMON CAROTID ARTERY 533
The thyreoida ima artery, which occurs in about 10 per cent, of subjects, ascends on the
front of the trachea to the thyreoid gland. It may be large in which case it might complicate
the low operation of tracheotomy. It does not always arise from the innominate, but occa-
sionally from the arch of the aorta (fig. 443) or from the right common carotid.
THE COMMON CAROTID ARTERIES
The common carotid arteries [aa. carotides communes] pass up deeply from
the thorax on either side of the neck to about the level of the upper border of the
thyreoid cartilage, where they divide into the external and internal carotid
arteries. The external carotid supplies the structures at the upper part of the
front and side of the neck, the larynx, pharynx, tongue, face, the upper part of
the back of the neck, the structures in the pterygoid region, the scalp, and in
chief part the membranes of the brain. The internal carotid gives off no branch
in the neck, but enters the cranium and supplies the greater part of the brain, the
structures contained in the orbit, and portions of the membranes of the brain.
The common carotid artery on the right side arises from the bifurcation of the
innominate at the upper limit of the sterno-clavicular joint; on the left side from
the arch of the aorta a little to the left of the innominate artery, and on a plane
somewhat posterior to that vessel (fig. 441). The portion of the left common
carotid artery which extends from the arch of the aorta to the upper limit of the
sterno-clavicular articulation lies deeply in the chest, and requires a separate
description; but above the level of the sterno-clavicular joint the relations of the
right and left carotids are practically the same, and are given under the account
of the right common carotid.
THORACIC PORTION OF THE LEFT COMMON CAROTID ARTERY
Within the thorax the left common carotid is deeply placed behind the
manubrium of the sternum, and is overlapped by the left lung and pleura. It
arises from the middle of the aortic arch, close to the left side of the innominate
artery, and a little posterior to that vessel, and ascends obliquely in front of the
trachea to the left sterno-clavicular articulation, above which its relations are
similar to those of the right common carotid (fig. 442).
Relations. — In front, but at some httle distance, are the manubrium and the origins of the
left sterno-hyoid and sterno-thyreoid muscles, whilst in contact with it are the remains of the
thymus gland, and the loose connective tissue and fat of the superior mediastinum. Crossing
its root is the left innominate vein.
Behind, it lies successively upon the trachea the left recurrent (inferior laryngeal) nerve, the
oesophagus (which here inclines a little to the left), and the thoracic duct.
To its right side is the root of the innominate artery, and higher up are the trachea and the
inferior thyreoid veins.
To its left side, but on a posterior plane, are the left subclavian artery and the left vagus
nerve; and, shghtly overlapping it, the edge of the left pleura and lung.
THE COMMON CAROTID ARTERY IN THE NECK
The common carotid artery in the neck extends from the sterno-clavicular
articulation to the upper border of the thyreoid cartilage on a level with the fourth
cervical vertebra, where it divides into the external and internal carotid arteries.
A line drawn from the sterno-clavicular joint to the interval between the mastoid
process and the angle of the jaw would indicate its course. The artery is at first
deeply placed beneath the sterno-mastoid, sterno-hyoid, and sterno-thyreoid
muscles, and at the level of the top of the sternum is only 2 cm. (f in.) distant
from its fellow of the opposite side, and merely separated from it by the trachea.
As the carotid arteries run up the neck, however, they diverge in the form of a V
and become more superficial, though on a plane posterior to that in which they lie
at the root of the neck, and are separated from each other by the larynx and
pharynx. At their bifurcation they are about 6 cm. (2j in.) apart. The com-
mon carotid is contained in a sheath of fascia common to it and the internal
jugular vein and vagus nerve. The artery, vein, and nerve, however, are not in
contact, but separated from one another by fibrous septa, which divide the com-
mon sheath into three compartments: one for the artery, one for the vein, and one
534
THE BLOOD-VASCULAR SYSTEM
for the nerve. The vein, which is larger than the artery, lies to the lateral side,
and somewhat overlaps it. The vagus nerve lies behind and between the two
vessels. The artery on the right side measures about 9.5 cm. (3f in.) ; on the left
side, about 12 cm. (4J in.) in length.
Fig. 444. — The Collateral Circulation after Ligature op the Common Carotid and
Subclavian Arteries.
(A ligature is placed on the common carotid and on the third portion of the subclavian artery.)
Right anterior cerebral -
Internal carotid -
Right posterior cerebral -
Occipital
Descending branch of occipital
External carotid — ^■
Superficial branch of descending
occipital
Deep branch
Transverse cervical
Descending branch
Acromial branch.
Subscapular branch
Anterior circumflex
tnfraspinous branch
Posterior circum
flex
Lateral thorucli
Subscapular
Circumflex scapulai
Infrascapul:
Subscapular
Left anterior cerebral
Anterior communicating
Posterior communicating
Left posterior cerebral
Anterior spinal
Vertebral
External maxillary
Lingual
Superior thyreoid
.Inferior thyreoid
Common carotid
Thyreo- cervical trunk
Costo-cervical trunk
Innominate
Superior intercostal
^■T Left common carotid
-j Left subclavian
7 Superior thoracic
Internal mammary
Anterior intercostal
First aortic inter-
costal
Second aortic inter-
costal
■Anterior intercostal
Relations. — In front the artery is covered by the skin, superficial fascia, platysma, and
deep fascia, and is more or less overlapped by the sterno-mastoid muscle. At the lower part
of the neck it is covered in addition by the sterno-hyoid and sterno-thyreoid muscles, and is
crossed by the anterior jugular vein, and is often overlapped by the thyreoid gland. _ Opposite
the cricoid cartilage it is crossed obliquely by the onio-hyoid muscle, and, above this spot, by
the superior thyreoid vein, and the sterno-mastoid artery. Along the anterior border of the
sterno-mastoid there is a communicating vein between the facial and anterior jugular veins,
which, as it crosses the line of the carotid artery, is in danger of being wounded in the operation
THE COMMON CAROTID ARTERY
535
of tying the carotid. The ramus descendens n. hypoglossi generally descends in front of the
carotid sheath, being there joined by one or two communicating branches from the second and
third cervical nerves. At times this nerve runs within the sheath. There are usually two
lymphatic glands about the bifurcation of the artery. These are often found enlarged and
infiltrated in cancer of the lip and tongue.
Behind, the common carotid lies on the longus colli and scalenus anterior below, and longus
capitis (rectus capitis anterior major) above. Posterior to the artery, but in the same sheath,
is the vagus nerve; and posterior to the sheath, the cervical sympathetic and the cervical
Fig. 445. — Artebies or the Head and Neck. (After Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Transverse facial artery Supraorbital artery
^ -•^^'"'t^^^'^S^^^^^ /' Frontal artery
/ 0<=iS^r*^i^ / Dorsal nasal artery
Superficial temporal artery ^ ~^^-^T^S^ ' Infraorbital
— Angular artery
Superior labial artery
-^ At — Inferior labial artery
J
y Mental artery
- Submental artery
Glandular branches
External maxillary artery
Lingual artery
Auricular branch
Stylomastoid arterj
Posterior auricular artery ^ y
Descending branch of occipital artery
Splenius capitis muscle
Internal carotid artery
Transverse cervical artery
Trapezius muscle""
Ascending branch —
Descending branch —
Axillary artery
Acromial branch -^
Superior
Hyoid branch
Anterior branch I Vh/re'crd
Posteriorbranch artery
Thyreoid gland
Common carotid artery
Inferior thyreoid artery
Ascending cervical artery
Superficial cervical artery
Th3n:eocervical trunk
V Subclavian artery
^^ 'm^" Pleura
Internal mam-
"" mary artery
"-Transverse scap-
ular artery
Deltoid branch
I Pectoral branches
Thoracoacromial artery
cardiac branches of the sympathetic and vagus nerves. At the lower part of the neck the inferior
thyreoid artery courses obliquely behind the carotid, as does Hkewise the inferior (recurrent)
laryngeal nerve.
Medially, from below upward, are the trachea and oesophagus, with the inferior (recurrent)
laryngeal nerve in the groove between them, and the terminal branches of the inferior thyreoid
artery, the lateral lobe of the thyreoid gland, the cricoid cartilage, the thyreoid cartilage, and
the lower part of the pharynx. At the angle of bifurcation is the carotid gland [glomus caro-
ticumj.
Laterally are the internal jugular vein and the vagus nerve. On the right side, at the
root of the neck, the vein diverges somewhat from the artery, leaving a space in which the vagus
)
536 THE BLOOD-VASCULAR SYSTEM
nerve and vertebral artery are exposed. On the left side the vein approaches and somewhat
overlaps the artery, thus leaving no interval corresponding to that on the right side.
The cricoid cartilage is, as a rule, taken as the centre of the incision in the operation for
ligature of the common carotid artery. The incision is made in the line of the vessel parallel
to the anterior margin of the sterno-mastoid muscle. The omo-hyoid forms one of the chief
rallying points in the course of the operation for ligature of the artery above that muscle, the
usual situation. The artery is found beating at the angle formed by the omo-hyoid with the
sterno-mastoid.
Branches. — (1) External and (2) internal carotid arteries. The common
carotid gives off no lateral branch, and consequently does not diminish in size as it
runs up the neck. It is often a little swollen just below its bifurcation, a condition
that should not be mistaken for an aneurismal dilation.
The collateral circulation (fig. 444), after Hgature of the common carotid, is carried on
chiefly by the anastomosis of the internal carotid with the internal carotid of the opposite side
through the circle of Willis; by the vertebral with the opposite vertebral; by the inferior thy-
reoid with the superior thyreoid; by the deep cervical branch of the costo-cervical trunk (superior
intercostal) with the descending branch of the occipital; by the superior thyreoid, hngual,
external maxillary (facial), occipital, and temporal, with the corresponding arteries of the oppo-
site side, and by the ophthalmic with the angular. The anastomosis between the deep cervical
branch of the costo-cervical trunk with the descending branch of the occipital is an important
one; it is situated deeply at the back of the neck, and is to be found lying between the semi-
spinaUs capitis (complexus) and cervicis muscles.
THE EXTERNAL CAROTID ARTERY
The external carotid artery [a. carotis externa] (fig. 445), the smaller of the
two branches into which the common carotid divides at the upper border of the
thyreoid cartilage, is distributed to the anterior part of the neck, the face, and
the cranial region, including the skin, the bones, and the dura mater. It is
at first situated medial to the internal carotid; but as it ascends in the neck it
forms a gentle curve, with its convexity forward, and, running slightly backward
as well as upward, terminates opposite the neck of the mandible just below the
condyle, by dividing into the internal maxillary and superficial temporal arteries.
It here lies superficial to the internal carotid, from which it is separated by a
portion of the parotid gland. At its origin it is overlapped by the anterior margin
of the sterno-mastoid, and is covered by the superficial fascia, platysma, and deep
fascia. Higher up the neck it is deeply placed, passing beneath the stylo-hyoid
muscle, the posterior belly of the digastric muscle, and the hypoglossal nerve;
and finally becomes embedded in the parotid gland, where it divides into its
terminal branches. It is separated from the internal carotid artery posteriorly
by the stylo-pharyngeus and stylo-glossus muscles, the glosso-pharyngeal nerve,
the pharyngeal branch of the vagus nerve, a portion of the parotid gland, and the
stylo-hyoid ligament; or, if the styloid process is abnormaUy long, by that
process itself. It measures about 6.5 cm. (2| in.).
Relations. — In front, in addition to the skin, superficial fascia, platysma, and deep fascia,
it has the hypoglossal nerve, the hngual, common facial and posterior facial veins, the posterior
belly of the digastric and stylo-hyoid muscles, the superior cervical lymphatic glands, branches of
the facial nerve, and the parotid gland. The sterno-mastoid also overlaps it in the natural
state of the parts.
Behind, it is in relation with the internal carotid, from which it is separated by the stylo-
glossus and stylo-pharyngeus muscles, the glosso-pharyngeal nerve, the pharyngeal branch of
the vagus nerve, the stylo-hyoid hgament, and the parotid gland. The superior laryngeal nerve
crosses behind both the external and internal carotid arteries.
Medially, it is in relation with the hyoid bone, the pharyngeal wall, the ramus of the
mandible, the stylo-mandibular ligament which separates it from the submaxillary gland, and
the parotid gland.
Laterally, in the first part of its course, it is in contact with the internal carotid artery.
The branches of the external carotid are usually given off in the following
order, from below upward: —
1. Ascending pharyngeal.
2. Superior thyreoid.
3. Lingual.
4. External maxillary (facial).
5. Sternocleidomastoid.
6. Occipital.
7. Posterior auricular.
8. Superficial temporal.
9. Internal maxillary.
THE ASCENDING PHARYNGEAL ARTERY
537
1. THE ASCENDING PHARYNGEAL ARTERY
The ascending pharyngeal artery [a. pharyngea ascendens] (fig. 446) is usually
the first or second branch of the external carotid. Occasionally it comes off at
the bifurcation of the common carotid from the common carotid itself. It is a
long slender vessel which runs deeply seated up the neck to the base of the skull,
having the walls of the pharynx and the tonsil medially, the internal carotid
artery laterally, and the vertebral column, the longus capitis (rectus capitis
anterior major), and the sympathetic nerve posteriorly. In front it is crossed by
the stylo-glossus (fig. 446) and the stylo-pharyngeus muscles and the glosso-
pharyngeal nerve.
Branches of the Ascending Pharyngeal Artery
The branches of the ascending pharyngeal artery are small and variable.
They supply the longus and rectus capitis muscles, the upper cervical sympathetic
ganglion and adjacent lymph-nodes, as well as the pharynx, soft palate, ear,
cranial nerves, and meninges.
The pharyngeal branches [rami pharyngei] supply the superior and middle constrictor
muscles and the mucous membrane lining them. These vessels anastomose with branches
Fig. 446. — Scheme op Right Ascending Pharyngeal Abteey.
The internal carotid artery is hooked aside.
Meningeal branch passing
through lacerated foramen
Inferior tympanic branch
Meningeal branch passing
through jugular foramen
Meningeal branch passing
through hypoglossal canal
(Walsham.)
Stylo-pharyngeus
Glosso-pharyngeal nerve
Occipital artery
Longus capitis
Ascending pharyngeal
artery
Middle constrictor of
pharynx
Sympathetic nerve
Internal carotid artery
External carotid artery
Levator veli palatini
Palatine branch
Buccinator muscle
Superior constrictor of
pharynx
Pterygo-mandibular
raphe
Stylo-glossus
Ascending palatine
branch of ext.
maxillary artery
Tonsillar branch of ext. maxil-
lary artery
xillary artery
Lingual artery
Superior thyreoid artery
Common carotid artery
of the superior thyreoid. One branch (the palatine) passes over the upper edge of the superior
constrictor to the soft palate and its muscles. This branch follows a course similar to that taken
by the ascending palatine artery, and when the latter is small may take its place. It generally
gives off small twigs to the Eustachian tube and tonsil. The inferior tympanic artery [a.
tympanica inferior] accompanies the tympanic branch of the glosso-pharj'ngeal nerve through
the tympanic canaliculus into the tympanum, and anastomoses with the other tympanic arteries.
The posterior meningeal artery [a. meningea posterior] is distributed to the membranes of the
brain. Some twigs pass with the jugular vein through the jugular foramen into the cranium,
and supply the dura mater in the posterior fossa of the skull. Others occasionally reach the
same fossa through the hypoglossal (anterior condyloid) canal in company with the hji^oglossal
nerve; while others pass through the cartilage of the lacerated foramen and supply the middle
fossa of the skull.
538
THE BLOOD-VASCULAR SYSTEM
2. THE SUPERIOR THYREOID ARTERY
The superior thyreoid artery [a. thyreoidea superior] (figs. 445, 447) arises
from the front of the external carotid a little above the origin of that vessel, and,
coursing forward, medially, and then downward, in a tortuous manner, supplies
the depressor muscles of the hyoid bone, the larynx, the thyreoid gland, and the
lower part of the pharynx. The arterj' at first runs forward and a little upward,
just beneath the greater cornu of the hyoid bone. In this part of its course it
lies in the superior carotid triangle, and is quite superficial, being covered only
with the integument, fascia, and platysma. It next turns downward, and passes
beneath the omo-hyoid, sterno-hyoid, and sterno-thyreoid muscles, and ends at
the upper part of the thyreoid gland by breaking up into terminal glandular
branches. The superior thyreoid vein passes beneath the artery on its way to the
internal jugular vein. The superior thyreoid is the artery most commonly
divided in cases of suicidal wounds of the throat.
Branches of the Superior Thyreoid Artery
The named branches of the superior thyreoid artery are: — (1) The hyoid;
(2) the sterno-mastoid; (3) the superior laryngeal; (4) the crico-thyreoid; (5)
anterior; (6) posterior; and (7) glandular.
Fig. 447. — Scheme of Left Superior Thyreoid Artery. (Walsham.)
External maxillary artery
Hyoid branch of lingual
Superior laryngeal branch j- —
Crico-thyreoid branch
External carotid artery
Ascending pharyngeal artery
Internal carotid artery
Sterno-mastoid branch
Superior thyreoid artery
Common carotid artery
Inferior thyreoid artery
(1) The hyoid [ramus hyoideus] is usually a small twig which passes along the lower border
of the hyoid bone, lying on the thyreo-hyoid membrane under cover of the thyreo-hyoid and
sterno-hyoid muscles. It supplies the infra-hyoid bursa and the thjo-eo-hyoid muscle, and
anastomoses with its fellow of the opposite side, and with the hyoid branch of the lingual.
When the latter artery is small, the hyoid branch of the superior thyreoid is usually com-
paratively large, and vice versa.
(2) The sterno-mastoid [ramus sternocleidomastoideus] (fig. 447) courses downward and
backward across the carotid sheath, and entering the sterno-mastoid supphes the middle portion
of that muscle. It gives off slender twigs to the thyreo-hyoid, sterno-hyoid, and omo-hyoid
muscles, and the platysma and integuments covering it. At times the vessel arises directly
from the external carotid. It hes usually somewhere in the upper part of the incision for tying
the common carotid above the omo-hyoid muscle.
(3) The superior laryngeal [a. laryngea superior] (fig. 447) passes medially beneath the
BRANCHES OF THE LINGUAL ARTERY 539
thyreo-hyoid muscle, and, perforating the thyreo-hyoid membrane along with the internal
branch of the superior laryngeal nerve, suppUes the intrinsic muscles and mucous lining of the
larynx. Its further distribution within the larynx is given with the description of that organ.
This branch sometimes arises from the external carotid direct. It may enter the larynx by
passing through a foramen in the thyreoid cartUage.
(4) The crico -thyreoid [ramus cricothyreoideus] passes across the crico-thyreoid membrane
immediately beneath the lower border of the thyreoid cartilage. It anastomoses with its
fellow of the opposite side, and usually sends a small branch through the membrane into the
interior of the larynx. Occasionally a considerable twig descends over the cricoid cartilage
to enter the isthmus of the thyreoid gland. The crico-thyreoid has, however, frequently been
seen of comparatively large size — once as large as the radial, and crossing the membrane
obliquely. In order to avoid injuring the crico-thyreoid artery in the operation of laryngot-
omy, it is usual, if the operation has to be done in a hurry, to make the incision through the
crico-thyreoid membrane in a transverse direction, and as near to the cricoid cartilage as possible.
(5) The anterior branch [ramus anterior] is the terminal branch supplying the isthmus and
the neighbouring part of the lateral lobe of the thyreoid gland.
(6) The posterior branch [ramus posterior], the other terminal, supplies the posterior part
of the lateral lobe, and sends branches to the inferior constrictor of the pharynx and to the
oesophagus. It anastomoses with the ascending branches of the inferior thyreoid artery.
(7) The glandular branches [rami glandulares] are the ultimate twigs, arising from the ante-
rior and posterior terminal branches, for the supply of the thyreoid gland.
3. THE LINGUAL ARTERY
The lingual artery [a. lingualis] (fig. 448) arises from tiie front of the external
carotid, between the superior thyreoid and external maxillary (facial) arteries,
often as a common trunk with the latter vessel, and nearly opposite or a little
below the greater cornu of the hyoid bone. It may, for purposes of description,
be divided into three portions: the first, or oblique, extends from its origin to the
posterior edge of the hyo-glossus muscle; the second, or horizontal, lies beneath
the hyo-glossus; the third, or ascending, beneath the tongue. The first or
oblique portion is situated in the superior carotid triangle, and is superficial, being
covered merely by the integument, platysma, and deep fascia. Here it lies on
the middle constrictor muscle and superior laryngeal nerve. After ascending a
short distance, it curves downward and forward beneath the hypoglossal nerve,
and, in the second part of its course, runs horizontally along the upper border of
the hyoid bone, beneath the hyo-glossus, by which it is separated from the
hypoglossal nerve and its vena comitans, and the posterior belly of the digastric
and the stylo-hyoid muscles. In this part of its course it lies successively on the
middle constrictor of the pharj^nx and the genio-glossus muscle, and crosses a
small triangular space known as 'Lesser's triangle,' the sides of which are formed
by the tendons of the digastric, the base by the hypoglossal nerve, and the floor
by the hyo-glossus muscle, in which situation it is usually tied. In the third
part of its course it ascends tortuously, usually beneath the anterior margin of the
hyo-glossus, to the under surface of the tongue, and is thence continued to the
tip of that structure lying between the lingualis and the genio-glossus muscles.
From the anterior edge of the hyo-glossus to its termination it is only covered by
the mucous membrane of the under surface of the tongue. This part of the
vessel is sometimes called the ranine artery. The lingual artery is accompanied
by small vense comitantes.
Branches op the Lingital Artery
The named branches of the lingual artery are: — (1) The hyoid; (2) the dorsal
lingual; (3) the sublingual; and (4) the deep lingual (ranine).
(1) The hyoid branch [ramus hyoideus] (fig. 448) is a small vessel which arises from the first
part of the lingual, and courses along the upper border of the hyoid bone, superficial to the hyo-
glossus, but beneath the insertion of the posterior belly of the digastric and the stylo-hyoid.
It anastomoses with its fellow of the opposite side, and with the hyoid branch of the superior
thyreoid artery, and supphes the contiguous muscles.
(2) The dorsalis linguse (fig. 448) arises from the second portion of the Ungual artery,
usually under cover of the posterior edge of the h}'o-glossus muscle. It ascends to the back of
the dorsum of the tongue, and, dividing into branches, supplies the mucous membrane on each
side of the V formed by the vallate papillae. It also supplies the pillars of the fauces and the
tonsil, where it anastomoses with the other faucial and tonsillar arteries. Instead of a single
artery, as above described, there may be several small vessels running directly to the parts
mentioned. The artery anastomoses in the mucous membrane by very small branches with the
540
THE BLOOD VASCULAR-SYSTEM
vessel of the opposite side; but the anastomosis is so minute that when one Hngual artery is
injected the injection merely passes across to the opposite side at the tip of the tongue; and when
the tongue is divided accurately in the middle line, as in the removal of one-half of that organ,
practically no haemorrhage occurs.
(3) The sublingual artery [a. sublingualis] (fig. 448) usually comes off from the lingual at the
anterior margin of the hyo-glossus. It passes beneath the mylo-hyoid to the subhngual gland,
which it supplies, and finally it usually anastomoses with the submental artery, a branch of
the external maxillary (facial). It also supplies branches to the side of the tongue, and gives
off a terminal twig, which anastomoses beneath the mucous membrane of the floor of the mouth
(to which it also gives twigs) with the artery of the opposite side. The artery of the frgenum
is usually derived from this vessel (fig. 448).
(4) The deep lingual [a. profunda hnguai], the termination of the hngual, courses forward
beneath the mucous membrane, on the under surface of the tongue, to the tip. It lies lateral
to the genio-glossus, between that muscle and the inferior lingualis, and is accompanied by the
lingual vein and terminal branch of the lingual nerve. It follows a very tortuous course, so
that it is not stretched when the tongue is protruded. Branches are given off from it to the
contiguous muscles and mucous membrane. Near the tip of the tongue it communicates with
its fellow of the opposite side, as shown by the fact that when the lingual artery of one side is
injected, the injection fluid passes into the branches of the artery of the other side.
Fig. 448. — Scheme of the Right Lingual Artery.
Glosso-palatinus
Descending palatine
artery
Pharyngo -palatinus
Palatine tonsil
Ascending palatine
branch of external
maxillary
Tonsillar branch, of
dorsal lingual
Tonsillar branch of
external maxillary
Stylo -glossus
Dorsal lingual artery
Middle constrictor
Hypoglossal nerve
External maxillary
artery
Posteriorbelly of digas-
tric and stylohyoid
Hyoid branch of lingual
Sup. laryngeal n
Hyoid branch of sup
thyreoid
Internal carotid artery
Common carotid
(Walsh am.)
Deep lingual artery
Artery of frsenulum
Hyo-glossus
Subungual artery
Genio -hyoid
Anterior belly of
digastric
Submental artery
Superior thyreoid artery
4. THE EXTERNAL MAXILLARY (FACIAL) ARTERY
The external maxillary or facial artery [a. maxillaris externa] (fig. 449) arises
immediately above the lingual from- the fore part of the external carotid, at times
as a common trunk with the lingual. It courses forward and upward in a tortuous
manner to the mandible, and, passing over the body of this bone at the anterior
edge of the masseter muscle, winds obliquely upward and forward over the face
to the medial angle of the eye, where it anastomoses, under the name of the
angular artery, with the dorsal nasal branch of the ophthalmic. It is usually
divided into two portions — the cervical and the facial.
The cervical portion (fig. 449) ascends tortuously from its origin from the
external carotid upward and forward beneath the posterior belly of the digastric
and stylo-hyoid muscles, and usualty also beneath the hypoglossal nerve, and then,
making a turn, runs horizontally forward for a short way beneath the jaw, either
imbedded in or lying under the submaxillary gland. It has here the mylo-hyoid
and stylo-glossus beneath it. On leaving the cover of the gland it forms a loop
passing first downward and then upward over the lower border of the jaw imme-
diately in front of the masseter muscle, where it is superficial, being merely cov-
ered by the integument and platysma. Here it can be felt beating, and can be
readily compressed. In the above course it lies in the posterior part of the sub-
maxillary triangle, and, in addition to the structures already mentioned as cross-
ing it, is covered by the skin, superficial fascia, and platysma, and by one or two
submaxillary lymphatic nodes. The vein is separated from the artery by the
BRANCHES OF THE EXTERNAL MAXILLARY ARTERY 541
submaxillary gland, the posterior belly of the diagastric muscle, the stylo-hyoid
muscle, and the hypoglossal nerve.
The facial portion (fig. 449) of the external maxillary artery ascends tortuously
forward toward the angle of the mouth, passing under the platysma (risorius),
the zygomatic muscle, the zygomatic head of the quadratus labii superioris
(zygomaticus minor), and the zygomatic and buccal branches of the facial nerve.
It here lies upon the jaw and the buccinator muscle. Thence it courses upward by
the side of the nose toward the medial angle of the eye, passing over or under the
infraorbital and angular heads of the quadratus labii superioris, and under the
infraorbital branches of the facial nerve. It lies on the caninus (levator anguli
oris) and the infraorbital branches of the fifth nerve. The anterior facial vein
takes a straighter course than the external maxillary artery, is separated from it by
the zygomatic muscle, and lies lateral to it.
Branches of the External Maxillary Artery of the Neck
The branches of the external maxillary artery in the neck are: — (1) The
ascending palatine; (2) the tonsillar; (3) the glandular; (4) the submental.
(1) The ascending palatine [a. palatina ascendens] (figs. 448, 449) — the first branch of the
external maxillary, but often a distinct branch of the external carotid — ascends between the
internal and external carotids, and then between the stylo-glossus and stylo-pharyngeus mus-
cles, and on reaching the wall of the pharynx is continued upward between the superior constrictor
and internal pterygoid muscles toward the base of the skull as high as the levator veli palatini,
where it divides into two branches, a palatine and a tonsillar. One of these branches, the pala-
tine, passes with the levator veU palatini over the curved upper margin of the superior constrictor
to the soft palate, where it is distributed to the tissues constituting that structure, and anasto-
moses with its fellow of the opposite side and with the descending palatine branch of the internal
maxillary, and the ascending pharyngeal, which vessel often to a great extent supplies the place
of this artery. The other branch, the tonsillar, supplies the tonsil and the Eustachian tube,
anastomosing with the tonsillar branch of the external maxillary (facial) and ascending pharyn-
geal arteries. The ascending palatine artery supphes the muscles between which it runs on its
way to the palate.
(2) The tonsillar branch [ramus tonsillaris] (fig. 449) ascends between the stylo-glossus and
internal pterygoid muscles to the level of the tonsil, where it perforates the superior constrictor
muscle of the pharynx, and ends in the tonsil, anastomosing with the tonsillar branch of the
ascending palatine and with the other tonsillar arteries (fig. 448). It gives branches also to the
root of the tongue.
(3) The glandular branches [rami glandulares] are distributed to the submaxillary gland
as the artery is passing through or beneath that structure. A small twig from one of these
branches usually supplies the submaxillary (Wharton's) duct.
(4) The submental artery [a. submentahs] (fig. 449) comes off from the external maxillary
as the latter vessel lies under cover of the submaxillary gland, and, passing forward on the
mylo-hyoid muscle between the base of the jaw and the anterior belly of the digastricus, supphes
these structures and the overlying platysma and integuments. It anastomoses with the sub-
lingual artery. The external maxillary also supphes the adjacent muscles of the neck.
Branches of the External Maxillary Artery on the Face
From the lateral or concave side of the artery are given off branches which
supply the masseter muscle and anastomose with the masseteric and buccinator
branches of the internal maxillary artery, the transverse facial artery, and the
infraorbital arteries.
From the medial or convex side the following larger and named vessels are
given off : — (1) The inferior labial; (2) the superior labial; and (3) the angular.
(1) The inferior labial artery [a labiahs inferior] arises at the angle of the mouth and runs in
the under Up within the substance of the orbicularis oris, close to the mucous membrane. It
anastomoses with the artery of the other side. Frequently an additional branch passes from
the external maxillary to the lower lip.
(2) The superior labial artery [a. labialis superior] arising from the facial a httle higher
than the inferior, passes forward beneath the zygomaticus, and then, hke the inferior labial,
courses tortuously along the lower margin of the upper hp between the orbicularis oris and the
mucous membrane, about 1.2 cm. (i in.) from the junction of the mucous membrane and the
skin. It is usually larger than the inferior labial. It anastomoses with its fellow of the opposite
side, and gives off a small artery to the septum — arteria septi nasi. Compression of this vessel
will sometimes control hiemorrhage from the nose.
(3) The angular artery [a. angularis] (fig. 449) is the terminal branch of the external max-
illary. It supplies the nose and anastomoses at the medial angle of the eye with the dorsal nasal
branch of the ophthalmic. It is accompanied by the anterior descending vein from the scalp.
542
THE BLOOD-VASCULAR SYSTEM-
It lies to the medial side of the lacrimal sac and supphes that structure and the lower part of
the orbicularis oculi, beneath which a branch anastomoses with the infraorbital artery. The
situation of the artery to the medial side of the lacrimal sac should be borne in mind in opening
a lacrimal abscess.
Fig. 449. — Scheme of the Right External Maxillary Artery. (Walsham.)
Orbicularis oculi muscle
Transverse facial artery
Quad, labii sup.,
zygomatic head
Zygomaticus muscle
Buccinator muscle
Masseteric branch
Masseter muscle
Stylo-pharyngeus
muscle
Stylo-glossus muscle
Ascending palatine
branch
Tonsillar branch
External maxillary
artery
External carotid
artery
Posterior belly of
digastric muscle
Lingual artery
Frontal branch of ophthal-
mic artery
■Dorsal nasal branch of ophthal-
mic artery
Angular artery
Quad, labii sup.,
angular head
Infraorbital artery
Quad, labii sup.,
infraorbital head
i-at. nasal artery
Caninus muscle
.Artery of septum
Superior labial
artery
Risorius muscle
Inferior labial artery
Mental branch of inferior
alveolar artery
Quadratus labii inferioris
muscle
-Inferior labial artery
.Triangularis muscle
■Submental artery
.Branches to submaxillary
gland
Anterior belly of digastric muscle
Mylo-hyoid muscle
■Hyo glossus muscle
'Hypoglossal nerve
5. THE STERNOCLEIDOMASTOID
The sternocleidomastoid artery [a. sternocleidomastoidea] arises from the
posterior side of the external carotid at the point where the carotid is crossed by
the digastric muscle. It is distributed to the sternocleidomastoid muscle, and is
frequently represented by one of the muscular branches of the occipital artery.
6. THE OCCIPITAL ARTERY
The occipital artery [a. occipitalis] (fig. 450) is usually a vessel of considerable
size. It comes off from the posterior part of the external carotid opposite the
external maxillary (facial), or else a little higher than that vessel. It then winds
THE POSTERIOR AURICULAR ARTERY 543
upward and backward to the interval between the mastoid process of the temporal
bone and transverse process of the atlas, and, after running horizontally backward
in a groove on the mastoid portion of the temporal bone, again turns upward, and
ends by ramifying in the scalp over the back of the skull, extending as far forward
as the vertex.
The vessel may be divided into three parts — viz., that anterior to the sterno-
mastoid muscle; that beneath the sterno-mastoid; and that posterior to the
sterno-mastoid.
In the first part of its course the occipital artery is covered by the integuments and fascia,
and is more or less overlapped by the posterior belly of the digastric muscle, the parotid gland,
and posterior facial (temporo-maxillary) vein. It is crossed by the hypoglossal nerve as the
latter winds forward over the carotid vessels to reach the tongue. It successively crosses in
front of the internal carotid artery, the hypoglossal nerve, the vagus nerve, the internal jugular
vein, and tlie spinal accessory nerve.
In the second part of its course it sinks deeply beneath the digastric muscle into the interval
between the mastoid process of the temporal bone and the transverse process of the atlas. It
is here covered by the sterno-mastoid, splenius capitis, and longissimus capitis muscles and by
the origin of the digastric; and lies, first on the rectus capitis laterahs, which separates it from
the vertebral artery, then in a groove, the occipital groove, on the mastoid portion of the tem-
poral bone, and then on the insertion of the superior oblique muscle.
In the third part of its course it enters the triangular interval formed by the diverging borders
of the splenius capitis and the superior nuchal line of the occipital bone. Here it lies beneath
the integuments and the aponeurosis uniting the occipital attachments of the sterno-mastoid
and trapezius, and rests upon the semi-spinalis capitis (complexus) just before tlie insertion of
that muscle into the occipital bone. In company with the greater occipital nerve, it perforates
either this aponeurosis, or less often the posterior belly of the epicranius (occipito-frontaHs),
and follows roughly, but in a tortuous course, the line of the lamboid suture, lying between the
integument and the cranial aponeurosis. In the scalp it divides into several large branches,
which ramify over the back of the skull and reach as far forward as the vertex. They anasto-
mose with the corresponding branches of the opposite side, and with the posterior auricular
and the superficial temporal arteries.
Branches of the Occipital Arteey (Fig. 450)
The branches of the occipital artery are : — (1) The muscular; (2) the menin-
geal; (3) the auricular; C4) the mastoid; (5) the descending; (6) the occipital.
(1) The muscular branches [rami musculares] (fig. 450) supply the sternocleidomastoid and
adjacent muscles. One of these branches may take the place of the sterno-mastoid branch of
the external carotid. The hypoglossal nerve then, as a rule, loops round it instead of round the
occipital.
(2) The meningeal branches [rami meningei] (fig. 450), one or more in number, are long
slender vessels which leave the occipital artery as it crosses the internal jugular vein and, ascend-
ing along the vessel, pass with it through the jugular or hypoglossal foramen, and are distributed
to the dura mater lining the posterior fossa of the skull.
(3) The auricular branch [ramus auricularis] ascends over the mastoid process to the back
of the ear, and supphes the pinna and concha. It sometimes takes the place of the posterior
auricular artery (fig. 450).
(4) The mastoid branch [ramus mastoideus] is a small twig that passes into the skull through
the mastoid foramen, supplying the dura mater, the diploe, the walls of the transverse sinus,
and the mastoid cells.
(5) The descending or princeps cervicis [ramus descendens] (fig. 450), the largest of the
branches of the occipital, arises from that artery just before it emerges from beneath the splenius,
and, descending for a short distance between the splenius and semi-spinalis capitis (complexus),
divides into a superficial and a deep branch. The superficial branch perforates the splenius,
supplies branches to the trapezius, and anastomoses with the ascending branch of the transverse
cervical artery. The deep branch passes downward between the semi-spinahs capitis (com-
plexus) and colli, and anastomoses with the deep cervical branch of the costo-cervical trunk
and with branches of the vertebral. The anastomoses between the above-mentioned arteries
form important collateral channels after hgature of the common carotid and subclavian arteries
(fig. 444).
(6) The occipital or terminal branches [rami occipitales] (fig. 450), usually two in number,
named from their position medial and lateral, ramify over the scalp, and have already been
described. The medial branch generally gives off a twig which enters the parietal foramen
(parietal artery) and is distributed to the dura mater. The occipital artery may also give off
the stylo-mastoid, the posterior auricular, or the ascending pharyngeal arteries.
7. THE POSTERIOR AURICULAR ARTERY
The posterior auricular artery [a. auricularis posterior] (fig. 450) arises from
the posterior part of the external carotid artery, usually immediately above the
544
THE BLOOD-VASCULAR SYSTEM
posterior belly of the digastric, about the level of the tip of the styloid process.
Occasionally it arises under cover of the digastric, quite close to, or as a common
trunk with, or as a branch of, the occipital. It courses upward and backward in
the parotid gland to the notch between the margin of the external auditory meatus
and the mastoid process, where it divides into branches. In this course it rests
on the styloid process, crosses the spinal accessory nerve, and is crossed by the
facial nerve.
Fig. 450. — Scheme of Left Occipital and Posterior Auricular Arteries. (Walsham.)
Occipital branch of pos-
terior auricular
Parotid gland
Sterno -mastoid, cut
Auricular branch of
occipital
Post, auricular artery
Rectus capitis lateralis
Spinal accessory
Occipital artery
Internal jugular vein
Ext. maxillary artery ^
Hypoglossal n
Lingual artery
Vagus nerve
Superior thyreoid
Common carotid
^^ \IM/''^_
Lateral branch of
occipital
'" Medial branch of
occipital
■Semi-spinalis capitis
Descending branch of
occipital
■Superior oblique
Longissimus capitis, cut
Splenius capitis, cut
Meningeal branches
Sternocleidomastoid branch
of occipital
-Internal carotid
- Sterno-mastoid
- External carotid
- Trapezius
Branches of the Posterior Auricular Artery
The branches of the posterior auricular artery are: — (1) the stylo-mastoid; (2)
the auricular; (3) the occipital ffig. 450).
The posterior auricular also gives branches to the parotid gland and the adjacent muscles,
namely, the posterior belly of the digastric, the stylo-hyoid, and auricularis posterior (retrahens
aurem) .
(1) The stylo-mastoid artery [a. stylomastoidea] comes off from the posterior auricular
artery just before it reaches the notch between the margin of the external auditory meatus
and the mastoid process, and, following the facial nerve upward, enters the stylo-mastoid fora-
men in the temporal bone. In the facial canal (aqueduct of Fallopius) it gives off the following
named twigs: — (a) meatal, to the external auditory meatus; (6) mastoid [rami mastoidei], to
the mastoid cells and tympanic antrum; (c) stapedic [ramus stapedius], which runs forward to
the stapedius muscle; (d) posterior tympanic [a. tympanica posterior], which anastomoses with
the anterior tympanic branch of the internal maxillary, forming with it in the foetus a vascular
circle around the membrana tympani; (e) vestibular, to the vestibule and semicircular canals;
and (J) terminal, a small twig which leaves the facial canal (by the hiatus) with the great super-
ficial petrosal nerve, and anastomoses with the superior petrosal branch of the middle meningeal
artery.
(2) The auricular branch [ramus auricularis] passes upward behind the ear and beneath the
auricularis posterior (retrahens aurem), supplying the medial surface of the pinna and adjacent
THE INTERNAL MAXILLARY ARTERY 545
skin. It anastomoses with the posterior branch of the superficial temporal artery. The
branches to the pinna not only supply the back of that structure, but some perforate the
cartilage, and others turn over its free margin to supply the lateral surface; there they anasto-
mose with the anterior auricular branches from the temporal.
(3) The occipital branch [ramus ooeipitahs] passes upward and backward, crossing the
aponeurotic insertion of the sterno-mastoid muscle. It gives a branch to the posterior belly
of the epioranius (occipito-frontaHs), and anastomoses with the occipital artery.
8. THE SUPERFICIAL TEMPORAL ARTERY
The superficial temporal artery [a. temporalis superficialis] (fig. 445), is the
smaller of the two terminal divisions of the external carotid, though apparently
the direct continuation of that vessel. It arises opposite the neck of the man-
dible and, under cover of the parotid gland, passes upward in the interval be-
tween the condyle and the external auditory meatus to the zygoma, lying on the
capsule of the temporo-mandibular joint. Thence it ascends over the posterior
zygomatic root and the temporal aponeurosis for about 4 or 5 cm. (1| or 2 in.), and
there divides into frontal and parietal branches. It is surrounded by a dense
plexus of sympathetic nerves, and is accompanied by the auriculo-temporal nerve,
which lies beneath and generally a little behind it. It is crossed by the temporal
and zygomatic branches of the facial nerve, and by the auricularis anterior (attra-
hens aurem) muscle. As it crosses the zygoma it can be readily felt pulsating
immediately in front of the ear, and in this situation can be compressed against the
bone. It is here quite superficial, being merely covered by the integuments and a
delicate prolongation from the cervical fascia (fig. 445) .
Branches of the Superficial Temporal Artery
The branches of the superficial temporal artery are: — (1) The parotid; (2)
the transverse facial; (3) the anterior auricular; (4) the zygomatico-orbital;
(5) the middle temporal; (6) the frontal; (7) the parietal.
(1) The parotid branches [rami parotidei] are small twigs given off in the substance of the
parotid gland.
(2) The transverse facial [a. transversa faciei] is the largest branch of the temporal. It
sometimes arises from the external carotid as a common trunk with the temporal. It is at
first deeply seated in the substance of the parotid gland, but soon emerging from the upper part
of the anterior border of the gland known, courses transversely across the masseter muscle
about a finger's breadth below the zygoma. The parotid duct runs below it, and the zygomatic
(infraorbital) branches of the facial nerve above it. It supphes the parotid gland, the masseter
muscle, and the skin of the face, and anastomoses with the infraorbital, the buccal, and the ex-
ternal maxillary (facial) arteries.
(3) The anterior auricular branches [rami auriculares anteriores] are three or four in number
and supply the tragus, the pinna, and the lobule of the ear, and to some extent the external
auditory meatus.
(4) The zygomatico-orbital artery [a. zygomaticoorbitahs] (fig. 445), at times a branch of
the deep temporal, passes forward along the upper border of the zygoma, in the fat between
the superficial and deep layers of the temporal aponeurosis, and, after giving branches to the
orbicularis oculi, sends one or more twigs into the orbit through foramina in the zygomatic
(malar) bone to anastomose with the lacrimal and palpebral branches of the ophthalmic.
(5) The middle temporal artery [a. temporahs media] (fig. 453), arises just above the
zygoma, and, perforating the temporal aponeurosis and temporal muscle, ascends on the squa-
mous portion of the temporal bone, and anastomoses with the posterior deep temporal artery.
(6) The frontal or anterior terminal branch [ramus frontalis] ramifies tortuously in an up-
ward and forward direction over the front part of the skull. It hes first between the skin and
temporal fascia and then between the skin and epicranial aponeurosis. It supphes the anterior
belly of the epicranius (occipito-frontahs) and the orbicularis ocuh muscles, and anastomoses
with the supraorbital and frontal branches of the ophthalmic, and with the corresponding
artery of the opposite side. The secondary branches given off from this vessel to the scalp
run from before backward.
(7) The parietal or posterior terminal branch [ramus parietahs] ramifies on the side of the
head between the skin and temporal fascia. Its branches anastomose, in front with the anterior
terminal branch; behind, with the posterior auricular and occipital arteries; and above, across
the vertex of the skull, with the corresponding artery of the opposite side.
9. THE INTERNAL MAXILLARY ARTERY
The internal maxillary artery [a. maxillaris interna] (fig. 451) is the larger of
the two terminal divisions of the external carotid. It arises opposite the neck of
the mandible in the substance of the parotid gland, and, passing first between the
mandible and the spheno-mandibular ligament and then between the external
546
THE BLOOD-VASCULAR SYSTEM
and internal pterygoid muscles, sinks deeply into the pterygo-palatine (spheno-
maxillary) fossa, and there breaks up into its terminal branches. It is divided into
three portions: a mandibular, a pterygoid, and a pterygo-palatine.
(1) In the first part of its coixrse (the mandibular portion) the artery lies
between the neck of the mandible and the spheno-mandibular ligament, taking a
horizontal course forward, nearly parallel to and a httle below the auriculo-
temporal nerve and the external pterygoid muscle. It is here embedded in the
parotid gland, and usually crosses in front of the inferior alveolar (dental) nerve.
(2) In the second part of its course (the pterygoid portion) the artery may be
placed superficial or deep to the external pterygoid muscle. In the first case it
passes between the two pterygoid muscles and the ramus of the jaw, and then
turns upward over the lateral surface of the external pterygoid, medial to the tem-
poral muscle to gain the two heads of the external pterygoid, between which it
Fig. 451.' — Scheme of Left Internal Maxillary. (Walsham.)
Infraorbital artery and nerve
Spheno-palatine branch
Descending palatine branch
Naso-palatine branch
Artery of the pterygoid canal (Vidian)
Anterior deep temporal artery
External pterygoid branch
Orbital branch
Nasal branch--^
Anterior alveolar-/-
branch
Labial branch-
Posterior alve-,
olar branch
Alveolar branch-
Mental branch
Submental branch
Posterior deep temporal artery
Small meningeal
artery
Middle meningeal
artery
Temporal artery
Anterior tympanic
Deep auricular
branch
Auriculo-temporal
Masseteric branch
External carotid
artery
\Spheno-mandibu-
lar ligament
.Inferior alveolar
artery and nerve
Internal pterygoid branch
Mylo-hyoidean branch
sinks into the pterygo-palatine fossa. In the second case it passes medial to the
external pterygoid, and is covered by that muscle till it reaches the interval be-
tween its two heads, where it then often forms a projecting loop as it turns into the
pterygo-palatine fossa.
(3) In the third part of its course (the pterygo-palatine portion) the artery
lies in the pterygo-palatine fossa beneath the maxillary division of the fifth nerve
and in close relationship with the spheno-palatine (Meckel's) ganglion, and there
breaks up into its terminal branches.
Bhanches of the Internal Maxillary Artery
The branches of the internal maxillary artery are: —
(A) From the first part : — (1) The deep auricular; (2) the anterior tympanic;
(3) the middle meningeal; (4) the inferior alveolar (dental); (5) the accessory
meningeal (sometimes). All these vessels pass through bony or cartilaginous
canals.
FIRST PART OF THE INTERNAL MAXILLARY ARTERY 547
(B) From the second part : — fl) The masseteric; (2) the posterior deep tem-
poral; (3) the pterygoid; (4) the buccal; and (5) the anterior deep temporal.
All these branches supply muscles.
(C) From the third part: — (1) The posterior superior alveolar (dental); (2)
the infra-orbital; (3) the descending palatine; (4) the a. canalis pterygoidei or
Vidian; and (5) the spheno-palatine. All these branches pass through bony
canals.
Branches of the First Part of the Internal
Maxillary Artery
(1) The deep auricular artery [a. auricularis profunda] (fig. 451) passes upward in the sub-
stance of the parotid gland behind the capsule of the temporo-mandibular joint, and, perforating
the bony or cartilaginous wall of the external auditory meatus, supplies the skin of that passage
and the membrana tympani. It at times gives a branch to the joint as it passes behind the
temporo-mandibular articular capsule.
Fig. 452. — The Middle Meningeal Arteet within the Skull.
Middle meningeal artery
Anterior meningeal artery
(After Spalteholtz.)
Anterior etIi-_ V
moidal artery , ^^j^^
Posterior eth- / _>^*^w
moidal artery
' ■ .. ■ ■ Mastoid branch
.- ^^ of occipital artery
!r_^=;^ — Occipital artery
, • Internal jugular vein
, ^ Posterior auricular artery
\ Superficial temporal artery
, . Deep auricular artery
\ \ Anterior tympanic artery
Middle meningeal artery
Internal maxillary artery
Accessory meningeal branch
External pterygoid branch
Inferior alveolar artery
I Artery of the pterygoid canal (Vidian)
Posterior lateral ' Mylohyoid branch
nasal arteries , ,
Major palatine artery ' Spheno-palatine artery
Major and minor palatine arteries
(2) The anterior tympanic artery [a. tympanica anterior] is a long slender vessel, which runs
upward behind the condyle of the jaw to the petro-tympanic (Glaserian) fissure, through which
it passes to the interior of the tympanum. Here it supphes the fining membrane of that cavity
and anastomoses with the other tympanic arteries, forming with the posterior tympanic branch
of the stylo-mastoid artery a vascular circle around the membrana tympani. This circle is
more distinct in the foetus than in the adult.
(3) The middle meningeal artery [a. meningea media] is the largest branch of the internal
ma.xillary artery. It comes off from the vessel as it hes between the spheno-mandibular liga-
ment and the ramus of the jaw, and under cover of the external pterygoid passes directly up-
ward to the foramen spinosum, through which it enters the interior of the cranium. In this
part of its course it is crossed by the chorda tympani nerve; and just before it enters the foramen
is embraced by the two heads of origin of the auriculo-temporal nerve (fig. 451).
The trunk of the mandibular division of the fifth nerve, as it emerges from the foramen
ovale, lies in front of the artery. As the artery passes upward it is surrounded b3' filaments of
the sympathetic nerve, and is accompanied by two veins. On entering the skull it ramifies
between the bone and dura mater, supplying both structures. It at first ascends for a short
548 THE BLOOD-VASCULAR SYSTEM
distance in a groove on the greater wing of the sphenoid, and then divides into two branches, an
anterior and a posterior.
The anterior branch passes upward, in the groove on the greater wing of the sphenoid, on
to the parietal bone at its anterior and inferior angle; at this spot the groove becomes deepened
and often bridged over by a thin plate of bone, being converted for 6 to 12 mm. (j to I in.) or
more into a distinct canal. The situation of the artery is here indicated on the exterior of the
skull by a spot 3.7 cm. (Ij in.) behind, and about 2.5 cm. (1 in.) above, the zygomatic process
of the frontal bone. The anterior branch is continued along the anterior border of the parietal
bone nearly as far as the superior sagittal sinus, and gives off in its course, but especially poste-
riorly, large branches which ramify in an upward and backward direction in grooves on the pari-
etal bone (fig. 452).
The posterior branch passes backward over the squamous portion of the temporal bone;
and thence on to the parietal bone, behind the anterior branch. This branch and its collaterals
extend upward as far as the sagittal sinus, and backward as far as the transverse (lateral)
sinus.
In addition to its terminal anterior, and terminal posterior branches, the middle meningeal
gives off: — (a) Ganglionic branhecs to the semOunar (Gasserian) gangUon and its sheath of
dura mater, (b) A superficial petrosal branch [ramus petrosus superficiahs], which enters
the hiatus of the facial canal in company with the large superficial petrosal nerve and anasto-
moses with the terminal branch of the stylo-mastoid artery, (c) A superior tympanic artery
[a. tympanica superior], which enters the canal for the tensor tympani, and supplies that muscle.
(d) An orbital or lacrimal branch, which enters the orbit at the outermost part of the superior
orbital (sphenoidal) fissure, or sometimes through a minute foramen, just lateral to that
fissure, and anastomoses with the lacrimal branch of the ophthalmic, (e) Anastomotic or
perforating branches which pierce the greater wing of the sphenoid bone, and anastomose with
the deep temporal arteries.
(4) The inferior alveolar artery [a. alveolaris inferior] (fig. 451), arising from the internal
maxillary as it lies between the spheno-mandibular hgament and neck of the jaw, courses
downward to the mandibular foramen, which it enters in company with, and a little behind
and lateral to, the inferior alveolar nerve. It then passes along the canal in the interior of the
bone, giving off branches to the molar, premolar, and canine teeth. On reaching the mental
foramen it divides into two branches, the incisive and the mental. The incisive continues its
course in the bone, supplies branches to the incisor teeth, and anastomoses with the artery of
the opposite side. The mental branch [ramus mentahs] passes through the mental foramen in
company with the mental branch of the inferior alveolar (dental) nerve, and emerges on the chin
under cover of the quadratus labii inferioris. It anastomoses above with the inferior labial
(coronary), and below with the submental, and also with the inferior labial. Near its origin
the artery gives off (a) a lingual or gustatory branch, which accompanies and supplies the lingual
nerve, and ends in the mucous membrane of the mouth; and, just before it enters the man-
dibular (dental) foramen in the lower jaw, (6) a mylo-hyoidean branch [ramus mylohyoideus],
which accompanies the nerve of that name along the groove in the lower jaw, and, after supply-
ing the mylo-hyoid muscle, anastomoses with the subhngual and submental arteries.
(5) The accessory or small meningeal branch [ramus meningeus aocessoria] arises either
from the internal maxillary a little in front of the middle meningeal, or as a branch of the latter
vessel. It passes upward along the com'se of the mandibular division of the fifth nerve, and,
entering the skull through the foramen ovale, is distributed to the semilunar (Gasserian)
ganglion, and to the waUs of the cavernous sinus and the dura mater in the neighbourhood.
Branches op the Second Part of the Internal IMaxillary Artery
The branches of the second portion of the internal maxillary all supply muscles. They
are: — (1) The masseteric; (2) the posterior deep temporal; (3) the pterygoid; (4) the buccal;
and (5) the anterior deep temporal.
(1) The masseteric artery [a. masseterica] comes off from the internal maxillary as the latter
is passing from between the neck of the jaw and the spheno-mandibular ligament. It passes,
with the masseteric nerve tln-ough the mandibular (sigmoid) notch in the mandible and supplies
the masseter muscle. Some filaments perforate the muscle and anastomose with the transverse
facial and with the masseteric branches of the external maxillary (facial).
(2) The posterior deep temporal artery [a. temporalis profunda posterior] arises, as a rule,
from the internal maxillary in common with the masseteric for a little be3'ond that branch.
It passes upward beneath the temporal muscle in a slight groove on the anterior margin of
the squamous portion of the temporal bone, supplying the temporal muscle, the pericranium
and the external layer of the bone. It anastomoses with the other temporal arteries.
(3) The pterygoid branches [rami pterygoidei] are short trunks which pass into and supply
the internal and external pterygoid muscles.
(4) The buccal artery [a. buccinatoria] (fig. 451) courses forward and downward with the
buccal nerve to the buccinator muscle, lying in close contact with the medial side and anterior
margin of the tendon of the temporal muscle and coronoid process of the lower jaw. It supplies
the buccinator muscle and mucous membrane of the mouth, and anastomoses with the external
maxillary (facial), transverse facial, and infraorbital arteries.
(5) The anterior deep temporal artery [a. temporalis profunda anterior] ascends beneath the
temporal muscle in a slight groove on the greater wing of the sphenoid bone. It supplies the
muscle, pericranium, and subjacent bone, and gives off small branches which pass through
minute foramina in the zygomatic (malar) bone. Some of these last branches enter the orbit
and anastomose with the lacrimal artery; others emerge on the face and anastomose with the
transverse facial artery.
THE INTERNAL CAROTID ARTERY 549
Branches of the Third Part of the Internal Maxillary Artery
The branches of the third part of the internal maxillary artery, like those of the first part,
all pass through bony canals. They are the following: — (1) The posterior superior alveolar
(dental); (2) the infraorbital; (3) the descending palatine; (4) the artery of the pterygoid canal
(Vidian); and (5) the sphenopalatine.
(1) The posterior superior alveolar (dental) artery [a. alveolaris superior posterior] arises
from the internal maxiUary as the latter is passing into tlie pterygo-palatine (spheno-maxillary)
fossa, and descends in a tortuous manner in a gi'oove on the back of the body of the maxilla.
It gives off branches to the maxillary sinus, to the molar and premolar teeth, the gums, and to
the buccinator muscle.
(2) The infraorbital artery [a. infraorbitalis] arises from the internal maxillary, generally
as a common trunk with the posterior alveolar (dental). It passes forward and a little upward
through the pterygo-palatine (spheno-maxillary) fossa; then forward in company with the
infraorbital branch of the fifth nerve, first along the groove, and then tlirough the canal in the
orbital plate of the maxilla; and finally, emerging on the face at the infraorbital foramen,
under cover of the quadratus labii superioris, is distributed to the structures forming the upper
Up, the lower eyeUd, the lacrimal sac, and the side of the nose. It anastomoses with the
superior labial (coronary) and angular branches of the external maxillary (facial), with the
nasal and lacrimal branches of the ophthalmic, and with the transverse facial. It gives off
small branches supplying the fat of the orbit and the inferior rectus and inferior oblique muscles.
The anterior superior alveolar branch [a. alveolaris superior anterior] passes downward through
a groove in the anterior wall of the maxilla, together with the anterior alveolar branch of the
infraorbital nerve, and supplies branches to the incisor and canine teeth and the mucous
membrane of the maxillary sinus. It has also nasal branches which pass through the foramina
in the nasal process of the maxiUa.
(3) The descending palatine artery [a. palatina descendens] descends in the pterygo-
palatine canal with the anterior palatine branch of the spheno-palatine ganglion. On emerging
on the palate at the greater (posterior) palatine foramen, it divides into the following branches;
— (a) The major palatine artery [a. palatina major], which courses forward in the muco-perios-
teum at the junction of the hard palate with the alveolar process as far as the incisive (anterior
palatine) foramen, where it anastomoses with the spheno-palatine artery; and (b) minor
palatine arteries [aa. palatina; minores], which pass backward and downward into the soft
palate, contributing to the supply of that structure, and anastomosing with the ascending
palatine artery. After the operation for cleft palate, serious heemorrhage occasionally occurs
from the descending palatine artery. The foramen is situated a little behind, and medial
to, the last molar tooth, and almost immediately in front of the hamular process (fig. 452).
(4) The arteria canalis pterygoidei or Vidian artery is a long slender branch which passes
backward through the pterygoid (Vidian) canal in company with the nerve of tlie same name
into the cartilage of the lacerated foramen. It gives off branches which supply the roof of the
pharynx, and anastomose with the ascending pharyngeal and spheno-palatine arteries; also a
branch which is distributed to the Eustachian tube; and one which enters the tympanum, and
anatomoses with the other tympanic arteries.
(.5) The spheno-palatine [a. sphenopalatina], the terminal branch of the internal maxillary,
passes with the naso-palatine branch of the spheno-palatine ganglion from the pterygo-palatine
(spheno-maxillary) fossa into the nose through the spheno-palatine foramen. Crossing the
roof of the nose in the muco-periosteum, it passes on to the septum, and then runs forward and
downward in a groove on the vomer toward the incisive (anterior palatine) foramen, where it
anastomoses with the anterior palatine artery, which enters the nose through the lateral com-
partment of that foramen (the canal of Stenson). In this course it gives off branches to the roof
and contiguous portions of the pharynx, and to the sphenoidal cells. It has also posterior
lateral nasal branches [aa. nasales post, laterales], which ramify over the nasal conchse (tur-
binate bones) and lateral walls of the nose, and give twigs to the ethmoidal and frontal sinuses
and the Uning membrane of the maxillary sinus; and posterior septal branches [aa. nasales
post, septi], which run upward and forward, giving small twigs to the mucous membrane cover-
ing the upper part of the septum, and which pass through the cribriform plate of the ethmoid,
and anastomose with the ethmoidal arteries (perforating or meningeal branches).
THE INTERNAL CAROTID ARTERY
The internal carotid artery [a. carotis interna] (figs. 453 and 454) arises with
the external carotid at the bifurcation of the common carotid, opposite the upper
border of the thyreoid cartilage, on a level with the fourth cervical vertebra. It
is at first placed a little lateral to the external carotid, but as it ascends in the neck
the external carotid becomes more superficial and in front of the internal. The
internal carotid passes up the neck, in front of the transverse processes of the upper
cervical vertebrae, lying upon the longus capitis (rectus capitis ant. major), to the
carotid foramen, thence through the carotid canal in the petrous portion of the
temporal bone, making at first a forward and medial turn and then a second turn
upward, and enters the cranium through the foramen lacerum. It makes a sig-
moid curve on the side of the body of the sphenoid bone, and terminates, after
perforating the dura mater, by dividing opposite the anterior clinoid processes
{
550
THE BLOOD-VASCULAR SYSTEM
in the lateral fissure (fissure of Sylvius) j into the anterior and middle cerebral
arteries.
In its course up the neck it often forms one or more curves, especially in old
people. Between the internal and the external carotids, at their angle of diver-
gence, is situated the carotid body or gland [glomus caroticum].
The internal carotid is the continuation upward of the primitive dorsal aorta,
and supplies the greater part of the brain, the contents of the orbit, and parts of
the internal ear, forehead, and nose. It is divided into three portions: — (1) a
cervical; (2) a petrosal; and (3) an intracranial.
1. The Cervical Portion
Relations. — In the neck (fig. 453) the artery is at first comparatively superficial, having
in front of it, as it lies in the superior carotid triangle, the skin, superficial fascia, platysma and
Fig. 453. — The Carotid Arteries. (After Toldt, ''Atlas of Human Anatomy," Rebman Lon-
don and New York.)
Anterior deep temporal artery
Lacrimal gland
Posterior deep temporal artery Lateral palpebral arteries
Temporal muscle \ \ *, \
Supraorbital artery
Frontal artery
Dorsal nasal artery
Masseteric
artery
External
pterygoid
muscle
Middle tem-
poral artery
Middle men
ingeal artery "^-.^V
Superficial tern- \^
poral artery
Internal maxil- ,
lary artery - \
Inferior alveolar
artery
Spheno-mandibular
ligament
Stylomastoid artery
Inferior alveolar
Posterior auricular
artery
Mylohyoid branch.
Posterior belly of
digastric muscle
Internal pterygoid muscle
Lingual nerve
Buccinator artery
Occipital artery ''
External carotid artery
External maxillary artery
Sternocleidomastoid artery ,'
Lingual artery '' /''
Hyoglossus muscle'' ^
Hyothyreoid membrane ' /
Superior thyreoid artery ' /
Internal carotid artery
Posterior branch
Anterior branch
Common carotid artery
Thyreohyoid muscle
Infraorbital artery
Superior pos-
terior alve-
olar artery
Inferior labial
artery
~~^ Mylohyoid muscle
■-^External maxillary
artery
Submental artery
^ ThiiTreohyoid muscle
.^ Hyoid branch of the lingual artery
Superior laryngeal artery
Crico-thyreoid branch
Middle crico-thyreoid ligament
deep fascia, and the overlapping edge of the sterno-mastoid muscle. Higher up, as it sinksHDe-
neath the parotid gland, it becomes deeply placed, and is crossed by the posterior belly of the
digastric and stylo-hyoid muscles, the hypoglossal nerve, and the occipital and posterior auricu-
lar arteries; whilst still higher it is separated from the external carotid artery, which here gets
THE INTRACRANIAL PORTION
551
in front of it, by the stylo-glossus and stylo-pharyngeus muscles, the glosso-pharyngeal nerve,
the pharyngeal branch of the vagus nerve, and by the stylo-hyoid ligament.
Behind, it hes upon the longus capitis (rectus capitis anticus major), which separates it
from the transverse processes of the three upper cervical vertebrae, on the superior cervical
ganglion of the sympathetic nerve, and on the vagus nerve. Near the base of the skull, the
hypofilossal, vasus, glosso-pharyngeal, and spinal accessory nerves cross obhquely behind it,
separating it here from the internal jugular vein, which, as the artery is about to
enter the carotid canal, also forms one of its posterior relations.
On its lateral side are the internal jugular vein and vagus nerve.
On its medial side it is in relation with the pharynx, the superior constrictor muscle separat-
ing it from the tonsil. The ascending pharyngeal and ascending palatine arteries, and at the base
of the skull the Eustachian tube and levator palati muscles, are also medial to it.
2. Thf Petrosal Portion
The petrosal portion (fig. 454) is situated in the carotid canal in the petrous portion of the
temporal bone. It is here separated from the walls of the canal by a prolongation downward
of the dura mater. In this part of its course it first ascends in front of the tympanum and
cochlea of the internal ear; it then turns forward and medially, lying a little medial to and
behind the Eustachian tube, and enters the cranial cavity by turning upward through the fora-
FiG. 454. — The Internal Carotid Artert in the Canal.
Superficial petrosal branch
(After Spalteholz.)
Superior ophthalmic vein
Cavernous sinus
Superior
tympanic artery
Anterior tympanic
artery
_« Jugular fossa
— -Longus capitis muscle
Inferior tympanic artery
.^Internal carotid artery
Ascending pharyngeal
artery
men lacerum, lying upon the Ungula of the sphenoid bone. In this part of its course it is accom-
panied by the ascending branches from the superior cervical ganghon of the sympathetic.
These form a plexus about the artery, but are situated chiefly on its lateral side. It is also
surrounded by a number of small veins, which receive tributaries from the tympanum and open
into the cavernous sinus and internal jugular vein.
3. The Intracranial Portion
On entering the cranium through the foramen lacerum, the internal carotid first ascends
to reach the lateral part of the body of the sphenoid medial to the hngula. It then follows
the carotid sulcus forward and slightly downward along the medial waU of the cavernous smus
(fig. 454). Here it has the sixth nerve immediately lateral to it, and is covered by the hning
membrane of the sinus. Again turning upward, it pierces the dura mater on the medial side
of the anterior clinoid process, and, passes between the second and third nerves to the anterior
perforated substance. At the medial end of the lateral (Sylvian) fissure it pierces the arachnoid
and divides into its two terminal branches, the anterior and middle cerebral. As it hes in the
552 THE BLOOD-VASCULAR SYSTEM
foramen laoerum the artery is crossed on its lateral side by the great superficial petrosal nerve
as the latter goes to join the great deep petrosal from the carotid plexus to form the nerve of
the pterygoid, canal (Vidian).
Branches of the Internal Carotid Artery
The cervical portion gives off no branch. The petrosal portion gives off the
caroticotympanic. The branches of the intracranial portion are : — (2) ophthalmic ;
(3) posterior communicating; (4) chorioid; (5) anterior cerebral; (6) middle
erebral.
As the internal carotid artery lies on the medial side of the cavernois sinus, it also gives off
the following small branches — branches to the walls of the cavernous inus; to the pituitary body;
to the semilunar (Gasserian) ganglion; to the dura mater. These anastomose with anterior
branches of the middle meningeal.
1. THE CAROTICOTYMPANIC ARTERY
The caroticotympanic enters the tympanum through a small foramen in the
posterior wall of the carotid canal, and contributes its quota to the blood-supply of
that cavity. It anastomoses with the tympanic branches of the stylo-mastoid,
internal maxillary, and middle meningeal arteries.
2. THE OPHTHALMIC ARTERY
The ophthalmic artery (fig. 455) comes off from the internal carotid immedi-
ately below the anterior clinoid process just as the latter vessel is passing through
the dura matter. Entering the orbit through the optic foramen below and lateral
to theo ptic nerve, it at once perforates the sheath of dura mater which is prolonged
through the optic foramen on both artery and nerve. It then runs in a gentle
curve with a lateral convexity below the optic nerve and lateral rectus, being here
crossed by the naso-ciliary (nasal) nerve. Turning forward and upward, it
passes over the optic nerve, to its medial side. Thence it runs obHquely beneath
the superior rectus in front of the naso-ciliary (nasal) nerve under the lower border
of the superior oblique, but above the medial rectus, and continues its course under
the pulley for the superior oblique and reflected tendon of that muscle to the
medial palpebral region, where it divides into the frontal and nasal branches.
Branches of the Ophthalmic Artery
The branches of the ophthalmic artery are: — (1) the lacrimal; (2) the supra-
orbital; (3) the central artery of the retina; (4) the muscular; (5) the ciliary;
(6) the posterior ethmoidal; (7) the anterior ethmoidal; (8) the medial palpe-
bral; (9) the frontal; and (10) the dorsal nasal.
(1) The lacrimal artery [a. laorimalis], is usually the first and often the largest branch 9f
the ophthalmic. It arises between the superior and lateral rectus on the lateral side of the optic
nerve from the ophthalmic, soon after that vessel has entered the orbit. At times it is given
off from the ophthalmic outside the orbit, and then usually passes into that cavity through the
superior orbital (sphenoidal) fissure. It runs forward along the lateral waO of the orbit with
the lacrimal nerve, above the upper border of the lateral rectus, to the lacrimal gland, which
it supplies. In this course it furnishes the following branches: — (a) Recurrent, one or more
branches which pass backward through the superior orbital (sphenoidal) fissure, and anasto-
mose with the lacrimal branch of the middle meningeal artery. The anastomosis is sometimes
of large size, and then takes the chief share in the formation of the lacrimal artery, (b) Mus-
cular branches, distributed chiefly to the lateral rectus, (c) Zygomatic branches — small twigs,
which pass through the zygomatico-orbital (malar) canals, and anastomose with the orbital
branch of the middle temporal, and with the transverse facial on the cheek, (d) Lateral
palpebral arteries [aa. palpebrales laterales] which are distributed to the upper- and lower
eyelids and to the conjunctiva, (e) Ciliary. See Ciliary Arteries, page 553.
(2) The supraorbital artery [a. supraorbitaHs] usually arises from the ophthalmic as the latter
vessel is about to cross over the optic nerve. Passing upward to the medial side of the superior
rectus and levator palpebrse, it runs along the upper surface of the latter muscle with the
frontal nerve in the orbital fat, but beneath the periosteum, to the supraorbital notch. On
emerging on the forehead beneath the orbicularis ocuU, it divides into a superficial and deep
branch, the former ramifies between the skin and epicranius (occipito-frontahs), the latter
BRANCHES OF THE OPHTHALMIC ARTERY
553
between the epicranius and the pericranium. Both branches anastomose with the anterior
branches of the superficial temporal, the angular branch of the external maxillary (facial),
and the transverse facial artery. The branches of the supraorbital are: — (o) periosteal, to
the periosteum of the roof of the orbit; (6) muscular, to the levator palpebra; and superior rectus;
(c) diploic, given off as the artery is passing through the supraorbital notch and, entering a
minute foramen at the bottom of the notch, is distributed to the diploe and frontal sinuses;
(d) trochlear, to the pulley of the superior obhque; (e) palpebral, to the upper eyehd.
(3) The arteria centralis retinae, a small but constant branch, comes off from the oph-
thalmic close to the optic foramen, and, perforating the optic nerve about 6 mm. (\ in.) behind
the globe, runs forward in (the substance of the nerve) to the eyeball, supplying the retina.
Its further description is given in the section on the Eye.
(4) The muscular branches [rami musculares] are very variable in their origin and distri-
bution. They may be roughly divided into superior and inferior sets. The superior or smaller
set supply the superior oblique, the levator palpebra3, and superior rectus. The inferior pass
forward, between the optic nerve and the inferior rectus, supplying that muscle, the medial
rectus, and the inferior oblique. From the muscular branches are given off the anterior ciliary
arteries. (See Ciliary Arteries.)
(5) The ciliary arteries are divided into three sets: — The short posterior, the long posterior,
and the anterior, (i) The short posterior [aa. oiliares posteriores breves], five or six in number,
come off chiefly from the ophthalmic as it is crossing the optic nerve. They run forward about
Fig. 45.5. — The Left Ophtii.'vlmic Artery and Vein.
Supraorbital artery
Lacrimal gland
Superior rectus, cut — pr;
Eyeball
Lateral rectus
Lacrimal artery
Superior rectus, cut
Inferior ophthalmic
Superior ophthalmic
Optic nerve
Superior ophthalmic
Commencement of superior
ophthalmic vein
Reflected tendon of superior oblique
Ophthalmic artery
Anterior ethmoidal artery
Posterior ethmoidal artery
Ciliary arteries
Levator palpebrse, cut
Annulus communis (of Zinn)
Ophthalmic artery
Optic commissure
Internal carotid artery
the nerve, dividing into twelve or fifteen smaU vessels, which perforate the sclerotic around
the entrance of the optic nerve, and are distributed to the chorioid coat, (ii) The long posterior
ciUary arteries [aa. ciliares posteriores longte], usually two, sometimes three, in number, come off
from the ophthalmic on either side of the optic nerve, and run forward with the short ciliary to
the sclerotic. On piercing the sclerotic, they course forward, one on either side of the eyeball
between the sclerotic and the chorioid to the ciliary processes and iris. Their further distribu-
tion is given under the anatomy of the Eye. (iii) The anterior ciliary arteries [aa. ciliares an-
teriores] are derived from the muscular branches and from the lacrimal. They run to the globe
along the tendons of the recti, forming a zone of radiating vessels beneath the conjunctiva.
Some of them, the episcleral arteries [aa. episclerales] ; perforate the sclerotic about 6 mm.
(-f in.) behind the cornea, and supply the iris and ciUary processes. It is these vessels that are
enlarged and congested in iritis, forming the circumcorneal zone of redness so characteristic of
that disease. They then differ from the tortuous vessels of the conjunctiva in that they are
straight and parallel. The remainder constitute the anterior conjunctival arteries [aa. oon-
junctivales anteriores].
(6) The posterior ethmoidal artery [a. ethmoidalis posterior] (fig. 455) runs medially be-
tween the superior oblique and medial rectus, and, leaving the orbit by the posterior ethmoidal
canal, together with the posterior ethmoidal branch of the naso-ciliary (nasal) nerve, enters
the posterior ethmoidal cells, whence it passes through a transverse slit-hke aperture between
the sphenoid bone and cribriform plate of the ethmoid bone into the cranium. It gives off (a)
ethmoidal branches to the posterior ethmoidal cells; (6) meningeal branches to the dura mater
lining the cribriform plate; and (c) nasal branches, which pass through the cribriform plate to
(
\
554 THE BLOOD-VASCULAR SYSTEM
the superior meatus and upper spongy bones of the nose, and anastomose with the nasal branches
of the spheno-palatine artery (fig. 452).
(7) The anterior ethmoidal artery [a. ethmoidahs anterior] (fig. 452), a larger branch
than the posterior ethmoidal, arises in front of the latter, passes medially between the superior
obhque and medial rectus, and, leaving the orbit through the anterior ethmoidal canal, in com-
pany with the anterior ethmoidal nerve, enters the cranial cavity. After running a short dis-
tance beneath the dura mater on the cribriform plate of the ethmoidal bone, it passes into the
nose through the horizontal slit-hke aperture by the side of the crista gaUi. Its terminal
branch passes along the groove on the under surface of the nasal bone, and emerges on the nose
between the bone and lateral cartilage, terminating in the skin of that organ. It gives off the
following branches in its course: — (i) Ethmoidal, to the anterior ethmoidal cells; (ii) anterior
meningeal artery, [a. meningea anterior] to the dura mater of the anterior fossa; (iii) nasal,
to the middle meatus and anterior part of the nose; (iv) frontal, to the frontal sinuses; (v)
cutaneous, or terminal, to the skin of the nose.
(8) The medial palpebral arteries [aa. palpebrales mediales] arise either separately or by a
common trunk from the ophthalmic artery opposite the pulley for the superior obhque, just
as the latter vessel is about to divide into its terminal branches. They pass, one above and
one below, the medial palpebral hgament and then skirt along the upper and lower eyelids
respectively, near the free margin between the palpebral tarsi and the orbicularis muscle,
and form a superior and an inferior tarsal arch [arcus tarsus superior et inferior] by anastomosing
with the lateral palpebral branches of the lacrimal. The upper also anastomoses with the supra-
orbital artery and orbital branch of the temporal artery; the lower with the infraorbital, the
angular branch of the external maxillary (facial), and the transverse facial arteries. A branch
from the lower palpebral passes with the ductus nasolacrimalis as far as the inferior meatus.
Small twigs, the posterior conjunctival arteries [aa. conjunctivales posteriores], are also given
to the caruncula lacrimahs and conjunctiva.
(9) The frontal artery [a. frontalis], the upper of the terminal branches of the ophthalmic,
pierces the superior tarsus at the medial angle of the orbit, passes upward over the frontal bone
.beneath the orbicularis ocuh, supphes the structures in its neighbourhood, and anastomoses
with its feUow of the opposite side, with the supraorbital, and with the anterior division of the
superficial temporal artery.
(10) The dorsal nasal [a. dorsahs nasi], the lower of the terminal branches of the ophthalmic,
leaves the orbit at the medial angle by perforating the tarsus above the medial palpebral liga-
ment. It then descends along the dorsum of the nose, beneath the integuments, and anasto-
moses with the angular and lateral nasal branches of the external maxillary (facial). It gives
off a lacrimal branch as it crosses the lacrimal sac, and a transverse nasal branch as it crosses
the root of the nose; the latter vessel anastomoses with its fellow of the opposite side.
3. THE POSTERIOR COMMUNICATING ARTERY
The posterior communicating artery [a. communicans posterior] (fig. 456) is
given off from the internal carotid just before the division of that vessel into the
anterior and middle cerebral arteries; occasionally it arises from the middle cere-
bral itself.
It is as a rule a slender vessel which runs backward over the optic tract and pedunculus
cerebri along the side of the hippocampal gyrus to join the posterior cerebral. At times, how-
ever, it is of considerable size, and contributes chiefly to form the posterior cerebral, the portion
of the latter vessel between the basilar and posterior communicating being then as a rule reduced
to a mere rudiment. It gives off the following branches: — (a) the hippocampal, to the gyrus
of that name; and (6) the middle thalamic, to the optic thalamus.
4. THE CHORIOID ARTERY
The chorioid artery [a. chorioidea] is a small but constant vessel which arises
as a rule from the back part of the internal carotid just lateral to the origin of the
posterior communicating.
It passes backward on the optic tract and the pedunculus cerebri, at first lying parallel and
lateral to the posterior communicating artery. It then dips under the edge of the uncinate
gyrus and, entering the chorioid fissure at the lower end of the inferior cornu of the lateral
ventricle, ends in the chorioid plexus and supplies the hippocampus and fimbria.
5. THE ANTERIOR CEREBRAL ARTERY
The anterior cerebral artery [a. cerebri anterior] (figs. 456, 459), one of the
terminal branches into which the internal carotid divides in the lateral fissure
(fissure of Sylvius), supplies a part of the cortex of the frontal and parietal lobes
of the brain and a small part of the basal ganglia. It passes at first anteriorly and
medially across the anterior perforated substance between the olfactory and optic
nerves to the longitudinal fissure where it approaches its fellow of the opposite side
CIRCULUS ARTERIOSUS
555
and communicates with it by a short transverse trunk, about five mm. long, known
as the anterior communicating artery [a. communicans anterior] (fig. 456). On-
ward from this point it runs side by side with its fellow in the longitudinal fissure
round the genu of the corpus callosum; then, turning backward, it continues along
the upper surface of that commissure, and, after giving off large branches to the
frontal and parietal lobules, anastomoses with the posterior cerebral artery.
6. THE MIDDLE CEREBRAL ARTERY
The middle cerebral artery [a. cerebri media] (figs. 456, 460), the larger of the
terminal divisions of the internal carotid, supplies the basal ganglia and a part of
the cortex of the frontal and parietal lobes. It passes obliquely upward and
lateralward into the lateral (Sylvian) fissure, and opposite the insula divides into
cortical branches.
CiEcuLus Arteriosus
The four arteries which supply the brain, namely, the two internal carotid
arteries and the two vertebrals (which unite to form the basilar), form a remark-
FiG. 456. — -The Arteries of the Brain.
(The cerebellum has been out away on the left side to show the posterior part of the cere-
brum. From a preparation in the Museum of St. Bartholomew's Hospital.)
Anterior cerebral,
artery
Middle cerebral
artery
Internal carotid.
artery
Postero-median
perforating
Posterior cere-
bral artery
Superior cerebel-
lar artery
Anterior inferior
cerebellar artery
Vertebral artery
Anterior commu-
nicating artery
Antero-lateral
perforating
Chorioid
Posterior com-
municating artery
Posterior chorioid
Basilar artery
Hum, cut
Anterior spinal
artery
able anastomosis at the base of the brain known as the circle of Willis [circulus
arteriosus (WilHsi)]. This so-called circle, which has really the form of a heptagon,
is formed, in front, by the anterior communicating artery uniting the anterior
cerebral arteries of opposite sides; laterally, by the internal carotids and the
posterior communicating arteries stretching between these and the posterior
cerebrals; behind, by the two posterior cerebrals diverging from the bifurcation of
the basilar artery (fig. 456).
This free anastomosis between the two internal carotid and the two vertebral arteries
serves to ecjuaUse the flow of blood to the various portions of the brain; and, should one or more
of the arteries entering into the formation of the circle be temporarily or permanently obstructed,
it ensures a flow of blood to the otherwise deprived part through some of the collateral arteries.
Thus, if one carotid or one vertebral is obstructed, the parts suppHed by that vessel receive
their blood through the circle from the remaining pervious vessels. Indeed, one vertebral
artery alone has been found equal to the task of carrying sufBcient blood for the supply of the
>
556 THE BLOOD-VASCULAR SYSTEM
brain after ligature of both the carotids and the other vertebral artery. Further, the circle of
Willis is the only medium of communication between the ganglionic or central and the peripheral
or cortical branches of the cerebral arteries, and between the various ganglionic branches them-
selves. The ganglionic and the cortical branches form separate and distinct systems, and do
not anastomose with each other; and the ganglionic, moreover, are so-called end-vessels, and do
not anastomose with the neighbouring ganglionic branches. The three cerebral arteries,
anterior, middle, and posterior may be regarded as branches of the circle of Willis. (For details
concerning the distribution of the cerebral arteries see p. 562.)
THE SUBCLAVIAN ARTERY
The subclavian artery on the right side [a. subclavia dextra] arises at the bifur-
cation of the innominate opposite the upper limit of the right sterno-clavicular
articulation. On the left side it arises from the arch of the aorta, and, as far as the
medial border of the scalenus anterior, is situated deeply in the chest. The first
portion of the left subclavian artery is described separately.
Beyond the medial border of the scalenus anterior the artery has the same rela-
tions on both sides. It courses from this point beneath the clavicle in a slight
curve across the root of the neck to the lateral border of the first rib, there to end
in the axillary artery. Thus the course of the artery in the neck will be indicated
by a line drawn from the sterno-clavicular joint in a curve with its convexity
upward to the middle of the clavicle. The height to which the artery rises in the
neck varies. It is perhaps most commonly about 1.2 cm. (| in.) above the clavicle.
If the cm-ved line above mentioned is drawn to represent part of the circumference
of a circle having its center at a point on the lower margin of the clavicle 3.7 cm.
d^ in.) from the sternal end of that bone, the line of the artery will be sufficiently
well indicated for all practical purposes. In its course the artery arches over the
dome of the pleura and gains the groove on the upper surface of the first rib by
passing between the scalenus anterior and medius muscles. The artery is accom-
panied by the subclavian vein, the latter vessel lying in front of the scalenus
anterior, anterior to the artery, and on a slightly lower plane.
The subclavian artery is divided into three portions — as it lies medial to, pos-
terior to, or lateral to, the scalenus anterior muscle.
THE FIRST OR THORACIC PORTION OF THE LEFT
SUBCLAVIAN ARTERY
The left subclavian artery [a. subclavia sinistra] (fig. 457) arises from the left
end of the arch of the aorta. The first part of the left subclavian is consequently
longer than the first part of the right, which arises at the bifurcation of the
innominate artery. The artery at its origin is situated deeply in the thorax,
and as it arises from the aorta is on a plane posterior to and a little to the left of
the thoracic portion of the left common carotid. It first ascends almost vertically
out of the chest, and at the root of the neck curves laterally over the apex of the
left plem-a and lung to the interval between the anterior and middle scalene mus-
cles. Beyond the medial border of the scalenus anterior — that is, in the second
and third portions of its course — its relations are similar to those of the right sub-
clavian artery.
Relations. — In front it is covered by the left pleura and lung, whilst more superficial are
the sterno-thyreoid, sterno-hyoid, and sterno-mastoid muscles. It is crossed a Uttle above its
origin by the left innominate vein, and higher in the neck near the scalenus anterior by the
internal jugular, vertebral, and subclavian veins. The phrenic nerve crosses the artery imme-
diately medial to the scalenus anterior, and then descends parallel to it, but on an anterior plane,
to cross the arch of the aorta. The vagus nerve descends parallel to the artery between it and
the left common carotid, coming into contact with its anterior surface just before crossing the
arch of the aorta. The left cervical cardiac nerves of the sympathetic also descend in front of
it on their way to the cardiac plexus. The left ansa subclavia also loops in front of the subclavian
artery. The left common carotid is situated anteriorly and to its right. The thoracic duct
arches over the artery just medial to the scalenus anterior, to empty its contents into the
confluence of the internal jugular and subclavian veins (fig. 442).
Behind and somewhat medial to it are the oesophagus, thoracic duct, inferior cervical gang-
lion of the sympathetic, longus coUi muscle, and vertebral column. To some extent it is over-
lapped posteriorly by the left pleura and lung.
On its right side are the trachea and the inferior laryngeal nerve, and, higher up, the oesopha-
gus and thoracic duct.
On its left side are the left pleura and lung.
THE FIRST PORTION OF THE RIGHT SUBCLAVIAN ARTERY 557
Branches. — The vertebral, internal mammary^ and thyreo-cervical trunk
(thyreoid axis) usually arise from the first portion on the left side. (See p. 559.)
THE FIRST PORTION OF THE RIGHT SUBCLAVIAN ARTERY
The first portion of the right subclavian artery (fig. 457) extends from its origin
at the bifurcation of the innominate, behind the ui3per margin of the right sterno-
FiG. 457. — The Subclavian Artery. (After Toldt, "Atlas of Human Anatomy," Rebman,
London and New York.)
Medial palpebral arteries
Tarsal
. / Superior . /,
*^i Inferior s/yl/
Lateral palpebral arteries
Infra -orbital artery
Superior labial artery
Anterior auricular brancbes -^
Perforating branches of the
posterior auricular artery
Supra-orbital artery
Frontal artery
,Dorsal nasal artery
Zygomatico-orbital artery
Left naris
..^Frontal branch ) of the superficial
Parietal branch J temporal artery
Zygomatic muscle
Transverse facial artery
.. — "Superficial temporal artery
of the superior
thyreoid artery
Inferior labial artery
Mental artery --
Submental artery
,-. t J i. [ Internal
Carotid artery I j.^j^^^^,
Superior th3Teoid artery —
Levator scapulee muscle
Common cartoid artery A^^s '^f
Inferior thyreoid artery //^m^ ,« -^
Phrenic nerve
Vertebral artery
Transverse scapular
artery
Subclavian artery
Serratus anterior
muscle
Internal mammary _
artery (
Innominate artery""
Pericardico-phrenic —
artery _
vena dSerrT^M?* V-^^
Thymus- j:^m^'
Intercostal £
branches "^T^bm**- -«
Costal pleura -~-^ / S^^,
Perforating
branches
Anterior medi
astinal artery
Superior
phrenic ,
artery
Superio;
epigastric
artery
Musculo
phrenic
artery
clavicular joint, upward and laterally in a gentle curve over the apex of the right
lung and pleura to the medial border of the scalenus anterior. It measures about
3 cm, {\\ in.). In this course it ascends in the neck a variable distance above the
clavicle, but is so deeply placed, so surrounded by important structures, and gives
>
558 THE BLOOD-VASCULAR SYSTEM
off so many large branches, that it is now seldom or never selected for the applica-
tion of a ligature.
Relations. — In front it is covered by the integuments, the superficial fascia, the platysma,
the anterior layer of the deep fascia, the clavicular origin of the sterno-mastoid, the sterno-hyoid
and sterno-thyreoid muscles, and the deep cervical fascia. It is crossed by the commencement
of the innominate, by the internal jugular, and by the vertebral veins; and, in a medio-lateral
direction, by the vagus and phrenic nerves, and the superior cardiac branches of the sympathetic
nerve. A loop of the sympathetic nerve itself also crosses the artery, and forms with the trunk
of the S3'mpathetic a ring around the vessel known as the ansa subclavia (annulus of Vieussens).
Behind, but separated from the artery by a cellular interval, are the longus coUi muscle,
the transverse process of the seventh cervical or first thoracic vertebra, the main chain of the
sympathetic nerve, the inferior cardiac nerves, the recurrent laryngeal nerve, and the apex of the
right lung and pleura.
Below, it is in contact with the pleura and lung and the loop of the recurrent laryngeal
nerve, which winds round the artery from the vagus and ascends behind it to the larynx. The
subclavian vein is below the artery and on an anterior plane.
Branches. — The vertebral, internal mammary, superficial cervical, and thyreo-
cervical trunk (thyreoid axis) arise from this part of the vessel on the right side.
(See p. 559.) Not uncommonly a small aberrant artery also takes origin from this
portion of the artery and descends to the left behind the oesophagus to join a
branch of the aorta opposite the third or fourth thoracic vertebra. This vessel is
probably the remains of the right dorsal aorta.
THE SECOND PORTION OF THE SUBCLAVIAN ARTERY
The second portion of the subclavian artery lies behind the scalenus anterior
muscle. It measures about 2 cm. ff in.) in length and here reaches highest in the
neck. The subclavian vein is separated from the artery by the scalenus anterior,
and lies on a lower and anterior plane (fig. 463) .
Relations. — In front it is covered by the skin, superficial fascia, platysma, anterior layer
of deep fascia, the clavicular origin of the sterno-mastoid, posterior layer of deep fascia, and by
the scalenus anterior. The phrenic nerve — which, in consequence of its oblique course medially
downward, crosses a portion of both the first and second part of the subclavian — is separated
from the second portion by the scalenus anterior muscle, as is also the subclavian vein which
courses on a somewhat lower plane.
Behind the artery are the apex of the pleura and lung, and a portion of the scalenus medius;
also the scalenus minimus (partially or entirely fibrous, known as Sibson's fascia, see p. 355).
Above is the brachial plexus.
Below are the pleura and lung.
One branch only — the costo-cervical trunk (superior intercostal) — is, as a
rule, given off from this portion of the subclavian; occasionally the transverse
cervical or the descending branch of the transverse cervical (posterior scapular
artery) arises from it.
THE THIRD PORTION OF THE SUBCLAVIAN ARTERY
The third portion of the subclavian artery extends from the lateral margin of
the scalenus anterior muscle to the lateral border of the first rib. It is more super-
ficial than either the first or second portions; it is in relation with less important
structures, and as a rule gives off no branch, and for these reasons is the part
selected when practicable for the application of a ligature. It is the longest of
the three portions of the subclavian artery, and lies in a triangle — the subclavian
triangle — bounded by the sterno-mastoid, the omo-hyoid, and the clavicle (fig.
445).
Relations. — In front it is covered by skin, superficial fascia, platysma, supra-clavicular
nerves (descending superficial branches) of the cervical plexus; the anterior layer of deep
fascia which descends from the omo-hyoid to the clavicle; and the posterior layer of deep fascia
which descends from the omo-hyoid to the fu'st rib and passes over the scalenus anterior and
phrenic nerve. Between the two layers of fascia is a variable amount of cellular tissue and fat,
and running in this is the transverse scapular (supra-scapular) artery. The subclavian is crossed
by this artery unless the arm is drawn well downward. Close to the lateral margin of the
sterno-mastoid, the external jugular vein pierces the fascia, and crosses the subclavian artery
to open into the subclavian vein. As this vein hes between the two layers of fascia, it receives
on its lateral side the transverse scapular (supra-scapular), transverse cervical, and other veins
of the neck, which together form a plexus of large veins in front of the arterj'. The nerve to
the subclavius, and, when present, the accessory branch from this nerve to the phrenic, also
THE VERTEBRAL ARTERY 559
here cross in front of the artery. In very muscular subjects the clavicular head of the sterno-
mastoid may be larger than usual, and in such a case wiU form one of the coverings of the artery.
Behind, the artery is in contact with the scalenus medius, and with the lower trunk of the
brachial plexus.
Below, the artery rests in the posterior of the two grooves on the upper surface of the first
rib.
Above is the brachial plexus of nerves and the posterior beUy of the omo-hyoid muscle.
The trunk formed by the fifth and sixth cervical nerves is also above the artery, but on a some-
what anterior plane. It is close to the vessel, and has been mistaken for the artery in the appU-
cation of a Kgature.
As a rule there is no branch given off from the third portion of the subclavian.
At times, however, the transverse cervical or the descending branch of the
transverse cervical (posterior scapular artery) may arise from the third portion of
the subclavian instead of from the thyreo-cervical trunk (thyreoid axis) and from
the transverse cervical respectively, as here described.
There is considerable variation in the branches of the subclavian artery and
Bean (Am. Jour. Anat., Vol. 4, p. 303) has shown that the branches are arranged
in a different way on the two sides of the body. The usual form on the right side
is for the vertebral, internal mammary, the superficial cervical and the common
trunk of the inferior thjTeoid and transverse scapular arteries to arise from the
first part of the subclavian. In this case the ascending cervical is a branch of
the inferior thyreoid, while the transverse cervical and costo-cervical arise from
the second portion. There are no branches from the third portion. On the left
side the usual form is for the vertebral and internal mammary, and thyreo-cer-
vical trunk, to arise from the first part. The thyreo-cervical trunk divides into
inferior thyreoid, transverse scapular, and transverse cervical arteries; the super-
ficial cervical is absent, and the costo-cervical trunk arises from the first part.
There are three more types of origin of the branches; in one, the vertebral,
internal mammary, costo-cervical, and inferior thyreoid come from the first part,
while the transverse cervical arises from the second part, and the transverse
scapular comes either from the third part or the axillary artery; in the second,
the inferior thyreoid, transverse scapular and transverse cervical arise in a com-
mon stem from the first part; while in the third, which is the rarest form, the in-
ferior thyreoid and superficial cervical arteries come by a common trunk from
the first part, while the transverse scapular artery arises from the internal
mammary.
1. THE VERTEBRAL ARTERY
The vertebral artery [a. vertebralis] (fig. 458) the first, largest, and most con-
stant branch, arises from the upper and posterior part of the first portion of the
subclavian, on the right side, about 2 cm. (f in.) from the origin of the latter ves-
sel from the innominate, on the left side, from the most prominent part of the
arch of the subclavian, close to the medial edge of the scalenus anterior muscle. It
first ascends vertically to the foramen transversarium of the sixth cervical
vertebra, and, having passed through that foramen and those of the next succeed-
ing cervical vertebrae as high as the epistropheus (axis), it tmns laterally and
then ascends to reach the foramen in the transverse process of the atlas; after
passing through that foramen it turns backward behind the articular process,
lying in the groove on the posterior arch of the atlas. It next pierces the posterior
occipito-atlantoid membrane and the dura mater, and enters the cranium through
the foramen magnum. Here it passes upward, at first lying by the side of the
medulla, then in front of that structure, and terminates at the lower portion of the
pons by anastomosing with the vertebral of the opposite side to form the basilar.
The vertebral artery may be divided for purposes of description into four parts:
the first, or cervical, extending from its origin to the transverse process of the
sixth cervical vertebra; the second, or vertebral, situated in the foramina trans-
versaria; the third, or occipital, contained in the suboccipital triangle; and the
fourth, or intracranial, within the cranium.
The first or cervical portion. — The artery here lies between the scalenus anterior and longus
colli muscles. In front it is covered by the vertebral and internal jugular veins, and is crossed
by the inferior thyreoid artery, and on the left side, in addition, by the thoracic duct, which runs
over it medio-laterally. Behind, the artery hes on the transverse process of the seventh cervical
vertebra and the sympathetic nerve. To its medial side is the longus coUi. To its lateral
i
560
THE BLOOD-VASCULAR SYSTEM
side is the scalenus anterior. It gives off as a rule no branch in this part of its course. Occa-
sionally, however, a small branch passes into the foramen tranversarium of the seventh cervical
vertebra.
The second or vertebral portion. — As the artery passes through the foramina transversaria,
it is surriunded by a plexus of veins and by branches of the sympathetic nerve. The cervical
nerves lie behind it. Between the transverse processes it is in contact with the intertransverse
muscles.
The third or occipital portion. — The artery here hes in the suboccipital triangle, bounded
by the superior oblique, inferior oblique, and rectus capitis posterior major muscles. As it
winds round the groove on the atlas, it has the rectus capitis laterahs, the articular process,
and the posterior ocoipito-atlantoid membrane in front of it; the superior oblique, the rectus
capitis posterior major, and the semispinalis capitis (complexus) behind it. Separating it
from the arch of the atlas, is the first cervical or suboccipital nerve.
The fourth or intracranial portion extends from the aperture in the dura mater to the
lower border of the pons, where it pierces the arachnoid and unites with its fellow to form the
basilar artery. It here winds round from the side to the front of the medulla, lying in the
Fig. 458. — Scheme op the Left Veetebeal Aeteey. (Walsham.)
The internal jugular and vertebral veins are hooked aside to expose the artery.
Risht posterior cerebral
artery
Left posterior cerebral "
artery
Basilar artery "
Basilar part, occipital
Intracranial portion of verte
bral artery
Rectus capitis lateralis muscl
Second cervical nerve
Vertebral plexus of veins
Third cervical
Vertebral portion of vertebral
artery
Fourth cervical nerve
Vertebral plexus of veins
Fifth cervical nerve
Sixth cervical
Inferior thyreoid artery
Longus colli muscle
Cervical portion of vertebral
artery
Internal jugular vein, hooked a
little aside
Vertebral vein, cut
Subclavian artery
:ipital bone
Occipital portion of vertebral artery
Descending branch of occipital artery
Semispinalis colli muscle
Deep cervical artery
Scalenus anterior muscle, cut
Subclavian vein
vertebral groove on the basilar part of the occipital bone. In this course it passes beneath
the first process of the hgamentum denticulatum, and between the hypoglossal nerve in front,
and the anterior roots of the suboccipital nerve behind.
Branches of the Vertebral Artery
The first part of the vertebral artery gives no branches. The second and third
parts give off muscular branches to the semispinalis and posterior recti and oblique
muscles. The second part also gives off five or six, (1) Spinal branches. The
fourth part gives off the following: (2) Posterior meningeal; (3) posterior spinal;
(4) anterior spinal; and (5) posterior inferior cerebellar.
(1) The spinal branches [rami spinales] run through the intervertebral foramina into the
vertebral canal, and there divide into two branches: one of which ramifies on the ba,cks of
the bodies of the cervical vertebra;; while the other runs along the spinal nerves, supphes the
cord and its membranes, and anastomoses with the arteries above and below.
(2) The meningeal [ramus meningeus] is a small branch given off as the vertebral artery
pierces the dura mater to enter the cranium. It supplies the bone and dura mater of the
posterior fossa of the skull, and anastomoses with the posterior meningeal branches derived
from the occipital and ascending pharyngeal arteries. It gives branches to the falx cerebelli.
THE BASILAR ARTERY 561
(3) The posterior spinal artery [a. spinalis posterior] runs downward obliquely along the
side of the medulla to the back of the cord, down which it passes behind the roots of the spinal
nerves, being reinforced by spinal branches accompanying these nerves, in the neck, the thoracic,
and in the lumbar region. It can be traced as low as the end of the spinal cord.
(4) The anterior spinal artery [a. spinalis anterior] comes off from the vertebral a little
below its termination in the basilar artery. Descending with a medial slant in front of the
medulla, it unites on a level with the foramen magnum with its fellow of the opposite side.
The single vessel thus formed runs downward in front of the spinal cord beneath the pia mater
as far as the termination of the cord, being reinforced by the spinal branches on the way down.
The spinal arteiies are described in detail with the anatomy of the spinal cord.
(5) The posterior inferior cerebellar [a. cerebeUi inferior posterior] (fig. 456) — the largest
branch of the vertebral — arises from that vessel just before it joins its fellow to form the basilar
artery. At times it may come off from the basilar itself. It runs, at first laterally across
the restiform body between the origin of the vagus and hypoglossal nerves, and, descending
toward the vallecula, there divides into two branches, medial and lateral, (a) The medial
branch runs backward between the vermis and the lateral hemisphere of the cerebellum. It
supplies the vermis, and anastomoses with the artery of the opposite side, and with the superior
vermian of the superior cerebellar. (6) The lateral branch runs laterally and, ramifying over
the under surface of the cerebellar hemisphere, supplies its cortex and anastomoses along its
lateral margin with the superior cerebellar arteries.
From the undivided trunk of the posterior inferior cerebellar artery branches are given
to the medulla oblongata, supplying the chorioid plexus and the fourth ventricle.
THE BASILAR ARTERY
The basilar artery [a. basilaris] is formed by the confluence of the right and
left vertebral arteries, which meet at an acute angle at the lower border of the
pons. It runs forward and upward in a slight groove in the middle line of the
pons, and divides at the upper border of that structure at the level of the tentorial
notch into the two posterior cerebral arteries, which take part in the formation of
the circle of Willis (fig. 456) .
Branches of the Basilar Artery
The branches of the basilar artery are: — 1. Pontine; 2. internal auditory;
3. anterior inferior cerebellar; 4. superior cerebellar; 5. posterior cerebral.
(1) The pontine branches [rami ad pontem] are numerous small vessels which come off at
right angles on either side of the basilar artery, and, passing laterally over the pons, supply that
structure and adjacent parts of the brain.
(2) The internal auditory artery [a. auditiva interna], a long slender vessel, accompanies
the auditory nerve into the internal auditory meatus (fig 514). It here lies between the
facial and auditory nerves, and at the bottom of the meatus passes into the internal ear, and
anastomoses with the other auditory arteries. (See Internal Ear.)
(3) The anterior inferior cerebellar [a. cerebelU inferior anterior] arises from the basilar
soon after its origin, passes laterally and backward across the pons, and then over the brachium
pontis to the front part of the under surface of the cerebellum. It anastomoses with the
posterior inferior cerebellar artery (fig. 456).
(4) The superior cerebellar [a. cerebelli superior] comes off from the basilar immediately
behind its bifurcation into the posterior cerebral arteries. It courses laterally and backward
over the pons, in a curve roughly corresponding to that of the posterior cerebral artery, from
which it is separated by the third cranial nerve; but, soon sinking into the groove between the
pons and the pedunculus cerebri, it curves round the latter onto the upper surface of the
cerebellum, lying nearly parallel to the fourth nerve. Here it divides into two branches
medial and lateral, (o) The medial branch courses backward along the superior vermis, anas-
tomosing with its fellow of the opposite side, and, at the posterior notch of the cerebellum, with
the inferior vermian branch of the posterior inferior cerebellar artery. (6) The lateral runs
to the circumference of the cerebellum, anastomosing with the lateral branch of the inferior
posterior cerebellar artery.
Branches are given off from the main trunk of the superior cerebellar artery, or from its
medial branch to the anterior velum (valve of Vieussens), the corpora quadrigemina, the pineal
body, and the chorioid plexus.
(5). The posterior cerebral arteries [aa. cerebri posteriores] are the two terminal branches
into which the basilar bifurcates at the upper border of the pons, immediately behind the
posterior perforated substance. Each artery runs at fii'st laterally and a little forward across
the pedunculus cerebri immediately in front of the third nerve, which separates it from the
superior cerelsellar artery. After receiving the posterior communicating artery, which runs
backward from the internal carotid, the posterior cerebral turns backward onto the under surface
of the cerebral hemisphre, where it breaks up into branches for the supply of the temporal and
occipital lobes.
The branches of the posterior cerebral artery are described below in connection with those
of the other cerebral arteries.
562
THE BLOOD-VASCULAR SYSTEM
Distribution of the Cerebral Arteries
Although the brain receives its blood supply from two distinct sources, namely, from
the internal carotids and from the vertebrals, it is convenient to consider together the dis-
tribution of the various cerebral branches derived from these stems. The formation of the circulus
arteriosus (circle of Willis) and the origin of the anterior, middle and posterior cerebral arteries
has already been described (pp. 554, 561). The detailed distribution of these vessels will now
be considered. In general, their branches may be divided into central or ganglionic and per-
ipheral or cortical.
The anterior cerebral artery has but a hmited central distribution. It gives off a few
inconstant branches which enter the anterior perforated substance and supply the anterior end
of the caudate nucleus. One or two of these run to the corpus callosum and septum peUucidum.
The anterior communicating branch is a transverse trunk which connects the two arteries and
thereby completes the circulus arteriosus in front. It hes in front of the optic chiasm, and
varies considerably in length and size. It may give off some of the branches to the anterior
perforated substance. The cortical branches supply the gyrus rectus, the olfactory lobe and a
part of the orbital gyri on the ventral surface. On the medial surface branches supply the
cortex as far back as the parieto-occipital fissure. These branches are given off as the artery
Fig. 459. — The Arteries or the Mesial Surface op the Brain. (After Spalteholz.)
Sulcus cinguli Corpus callosum
Anterior cerebral
artery
Anterior communicating artery '
Internal carotid artery
I Posterior cerebral artery
Posterior communicating artery
curves around the corpus callosum and some of them curve over onto the lateral surface and
supply the superior and middle temporal convolutions. Branches from the anterior cerebral
artery also supply the corpus callosum (fig. 459).
The middle cerebral artery gives off most of the branches to the basal gangha and supplies
the greater part of the lateral surface of the brain. It runs through the lateral fissure (fissure
of Sylvius) (fig. 460). The branches of the middle cerebral include the following:
The central branches are: — (i) The caudate, two or three small branches, which arise from
the medial aspect of the artery and pass through the medial part of the floor of the lateral fissure
(fissure of Sylvius) to the head of the caudate nucleus, (ii) The antero -lateral are numerous
small arteries which pass through the anterior perforated substance and supply the caudate
nucleus (except its head), the internal capsule, and part of the optic thalamus, (iii) The
lenticulostriate, a larger branch of the antero-latera! set, passes through a separate aperture in
the lateral part of the anterior perforated substance, runs upward between the lenticular nucleus,
which it supplies, and the external capsule, perforates the internal capsule, and terminates in the
caudate nucleus. It has been so frequently found ruptured in apoplexy that it is called by
Charcot the 'artery of cerebral haemorrhages.' (iv) Sometimes a more or less distinct branch,
called lenticulo-optic, is distributed to the lateral and hinder portion of the lenticular nucleus
and the lateral portion of the optic thalamus.
The cortical branches come off opposite the insula. They supply the insula, the inferior
frontal gyri, the central gyri (anterior and posterior), the parietal lobules, superior and in-
ferior, the supra-marginal, angular, and superior temporal g}T:i.
The posterior cerebral give off both central and cortical branches. The central branches
are the postero-median, posterior chorioid, and the postero-lateral. The postero-median
THE CEREBRAL ARTERIES
563
enter the posterior perforated substance and supply the medial portion of the optic thalamus,
and the walls of the third ventricle; the posterior chorioid pass through the transverse fissure
to the tela chorioidea (velum interpositum) and chorioid plexus; the postero-lateral run to
the posterior part of the optic thalamus and give branches to the cerebral peduncles and the
corpora quadrigemina.
The cortical branches of the posterior cerebral supply the entire occipital lobe and all of the
temporal lobe except the superior temporal gj'rus (fig. 459).
In regard to the cerebral arteries in general it may be said that there is no anastomosis
between the cortical and central branches, the two forming distinct and separate systems.
The cortical may or may not anastomose with each other, but the communication between the
neighbouring cortical branches is seldom sufficient to maintain the nutrition of an area when
the vessel that normally supphes it is obstructed. The central branches are so-called end-
vessels and do not anastomose with each other. Hence obstruction of the middle cerebral
artery leads to softening of the area suppUed by its central branches, but not always to softening
of the region suppHed by its cortical branches. Indeed, the cortical region may escape com-
pletely, although the central area is irreparably disorganised. The gross anastomosis of the
posterior cerebral with the anterior cerebral arteries through the circulus arteriosus has already
been described. To sum up the distribution of the cerebral arteries, the branches of each are
divided into the central, or ganglionic and the peripheral or cortical. The central branches
arise at the commencement of the cerebral arteries about the cireulus arteriosus whilst the
cortical are derived chiefly from the termination of these vessels.
Fig. 460. — The Arteries of the Lateral Surface of the Brahst. (After Toldt,
Human Anatomy," Rebman, London and New York.)
Central sulcus (Rolandi)
' Atlas of
Branches of the anterior cerebral artery
Branches of the posterior
cerebral artery
Branches of the anterior cere
bral artery
Optic nerve
Branch of the posterior cerebral
artery
Middle cerebral artery
(A) The central branches are divided into four sets — two median and two lateral. 1.
The two median are — (1) The antero-median, which arise from the anterior cerebral and the
anterior communicating, and supply the fore end of the caudate nucleus, and (2) the postero-
median, which arise from the posterior cerebral and supply the medial part of the optic thalamus
and neighbouring wall of the third ventricle. 2. The two lateral are: — (1) The antero -lateral
arise from the middle cerebral, and, passing through the anterior perforated substance, supply
the lenticular nucleus, the posterior part of the caudate nucleus, the internal and external
capsules, and the lateral part of the optic thalamus. (2) The postero-lateral arise from the
posterior cerebral, and supply the hinder part of the optic thalamus, the pedunculus cerebri, and
the corpora quadrigemina.
(B) The cortical branches ramify in the pia mater, giving off branches to the cortical
substance, some of which extend through it to the underlying white substance.
It will be seen that the middle cerebral supphes the somaesthetic area of the cortex. It
also supphes the cortical auditory centre, and, in part, the higher visual centre. The anterior
cerebral supphes only a small part of the somtesthetic area, namely, the part of the leg centre
that occupies the paracentral lobule and the highest part of the anterior central gyrus. The
posterior cerebral supphes the visual path from the middle of the tract backward, and the half
vision centre in the occipital lobe. It supphes also the corpora quadrigemina and the sensory
part of the internal capsule.
The branches which supply the cerebellum and brain stem are given in connection with
the vertebrals on page 561.
564 THE BLOOD-VASCULAR SYSTEM
2. THE THYREOCERVICAL TRUNK
The thyreocervical trunk [truncus thyreocervicalis] or thyreoid axis arises from
the upper and front part of the subclavian artery, usually opposite the internal
mammary, and slightly medial to the scalenus anterior. It is a short thick trunk,
and divides almost immecUately into three radiating branches — namely, the
inferior thyreoid, the transverse scapular, and the transverse cervical (figs. 444,
457). This is the usual form only on the left side (see page 559). It may give off
also the ascending cervical.
THE INFERIOR THYREOID ARTERY
The inferior thyreoid artery [a. thyreoidea inferior] is the largest of the three
branches into which the thyreocervical trunk (thyreoid axis) divides, and may
arise in a common trunk with the transverse scapular, or as a branch of the sub-
clavian. It ascends tortuously passing medially in front of the vertebral artery,
the inferior laryngeal nerve and the longus colU muscle, and behind the common
carotid and the sympathetic nerve or its middle cervical ganglion, to the thyreoid
gland, where it anastomoses with the superior thyreoid artery and the artery of the
opposite side.
The branches of the inferior thyreoid artery are : — (1) Muscular; (2) oesophageal
and pharyngeal; (3) tracheal; (4) inferior laryngeal; (5) glandular; and (6) as-
cending cervical.
(1) The muscular branches supply the scalenus anterior, longus coUi, sternohyoid, sterno-
thyreoid, and omo-hyoid muscles, and the inferior constrictor muscle of the pharynx.
(2) The oesophageal and pharyngeal branches [rami oesophagei et pharyngei] of the inferior
thyreoid artery supply the oesophagus and pharynx and anastomose with the other arteries
supplying those structures.
(3) The tracheal branches [rami tracheales] ramify on the trachea, where they anastomose
with the tracheal branches of the superior thyreoid and bronchial arteries.
(4) The inferior laryngeal artery [a. laryngea inferior] passes along the trachea to the back
of the cricoid cartilage in company with the inferior laryngeal nerve. It enters the larynx
beneath the inferior constrictor. Its further distribution in that organ is described under
Larynx.
(5) The glandular branches [rami glandulares] supply the thsrreoid gland.
(6) The ascending cervical artery [a cervicalis ascendens] (figs. 444, 457) is given off from
the thyreocervical trunk or from the inferior thyreoid as that vessel is passing beneath the
carotid sheath. It ascends between the scalenus anterior and the longus capitis (rectus capitis
anterior major), lying parallel and medial to the phrenic nerve and behind the internal jugular
vein. It anastomoses with the vertebral, ascending pharyngeal, and occipital arteries, and
supphes branches to the deep muscles of the neck [rami musculares], to the spinal canal [rami
spiuales], and to the phrenic nerve. Two veins accompany the ascending cervical artery and
end in the innominate vein.
THE TRANSVERSE SCAPULAR ARTERY
The transverse scapular or suprascapular [a. transversa scapulae] artery passes
laterally across the root of the neck, lying first beneath the sterno-mastoid, and
then in the subclavian triangle behind the clavicle and subcalvius muscle. At
the lateral angle of this space it is joined by the suprascapular nerve, sinks
beneath the posterior belly of the omo-hyoid, and passes over the hgament bridg-
ing the scapular notch, the nerve passing through the notch (fig. 461). It then
ramifies in the supraspinous fossa of the scapula, and, winding downward round
the base of the spine over the neck of the scapula, enters the infraspinous fossa,
and terminates by anastomosing with the circumflex (dorsal) scapular artery,
and the descending branch of the transverse cervical (posterior scapular) artery.
As it lies under cover of the sterno-mastoid muscle, it crosses the phrenic nerve and the
scalenus anterior; and as it courses through the subclavian triangle, it is separated by the
cervical fascia which descends from the omo-hyoid to the first rib, from the subclavian artery
and brachial plexus of nerves. If this artery is seen in tying the subclavian it should not be
injured, as it is one of the chief vessels by which the collateral circulation is carried on after
ligature of the subclavian in the third part of its course. At the lateral part of the subclavian
triangle it is covered by the trapezius, and after passing over the transverse scapular Mgament
it pierces the supraspinous fascia and passes beneath the supra-spinatus muscle, ramifying
between it and the bone. In the infraspinous fossa it hes between the infra-spinatus and
the bone. The artery is accompanied by two veins.
THE TRANSVERSE CERVICAL ARTERY
565
The branches of the transverse scapular are: — (1) the nutrient, to the clavicle; (2) the
acromial [ramus acromialis] to the arterial rete or plexus on the acromial process, to reach
which it pierces the trapezius; (3) the articular, to the acromio-clavicular joint and shoulder-
joint; (4) the subscapular, given off as the artery is passing over the transverse scapular liga-
ment, descends to the subscapular fossa between the subscapularis and the bone, and anas-
tomoses with the infrascapular branch of the circumflex (dorsal) scapular artery, and with
the subscapular and transverse cervical arteries; (5) the supraspinous branches, which ramify
in the supraspinous fossa, and supply the supra-spinatus muscle and the periosteum, and the
nutrient artery to the bone; (6) the infraspinous branches, which ramify in a similar way in
the infraspinous fossa, giving off twigs to the infra-spinatus muscle, the periosteum, and the
bone.
Fig. 461. — Scheme of Anastomoses of the Right Scapular Arteries. (Walsham.)
Subscapular branch of transverse scapular artery
Supraspinous branch of transverse scapular artery
Descending branch
of transverse cer^
vical artery
Branch of inter
costal artery
Branch of inter-
costal artery
Continuation of de-
scending branch
of transverse cer-
vical artery
Transverse scapular artery
-. ^^y7 Acromial branch of
;^/ A thora CO -acromial
-Acromial rete
Subscapular branch of
transverse scapular
artery
Infraspinous branch of
transverse scapular
artery
Subscapular branch of
axillary artery
Circumflex scapular artery
branch of cir
apular artery
Dorsal thoracic branch o£
subscapular artery
THE TRANSVERSE CERVICAL ARTERY
The tranverse cervical artery [a. transversa colli], somewhat larger than the
transverse scapular (suprascapular), runs like the latter vessel laterally across the
root of the neck, but on a slightly higher transverse plane, and a little above the
clavicle. At its origin from the thyreo-cervical trunk (thyreoid axis) it lies under
the sterno-mastoid; on leaving the cover of this muscle, it crosses the upper part
of the subclavian triangle, lying here only beneath the platysma and cervical
fascia; further laterally, it passes beneath the anterior margin of the trapezius and
omo-hyoid muscle, and at the lateral margin of the levator scapulse divides into a
descending (posterior scapular) and an ascending (superficial cervical) branch.
In this course it crosses the phrenic nerve, the scalenus anterior, the brachial
plexus, and the scalenus medius. Sometimes it passes between the cords of the
brachial plexus.
The branches of the transverse cervical artery are: — (1) a descending
(posterior scapular) ; and (2) an ascending (or superficial) cervical. The descend-
ing branch occasionally arises from the third portion of the subclavian artery.
(1) The descending branch, or posterior scapular [ramus descendens] the apparent continua-
tion of the transverse cervical artery, begins at the lateral border of the levator scapula;, and,
continuing its course beneath this muscle to the upper and posterior angle of the scapula, turns
downward and skirts along the posterior border of the scapula, between the serratus anterior
566
THE BLOOD-VASCULAR SYSTEM
(magnus) in front and the levator seapulEe and rhomboideus minor and major behind, to the
inferior angle, where it anastomoses with the subscapular artery. It gives off the following
branches: — (a) Supraspinous, which ramifies between the supraspinous muscle and the trapezius,
and sends branches through the muscle into the fossa, to anastomose with the transverse
scapular artery. (6) Infraspinous branches, one or more of which enter the infraspinous
fossa, and anastomose with the circumflex (dorsal) scapular, (c) Subscapular branches, which
enter the subscapular fossa, and anstomose with the branches of the transverse scapular and
subscapular arteries, (d) Muscular branches, to the muscles between which it runs and to
the latissimus dorsi. These branches anastomose with the posterior divisions of the intercostal
arteries.
(2) The ascending branch or superficial cervical artery [r. asoendens], smaller than the
descending branch, ascends under the anterior margin of the trapezius, lying upon the levator
scapulae and splenius muscles. It supplies branches to the trapezius, levator scapulae, and
splenius muscles, and the posterior chain of lymphatic glands. It anastomoses with the
superficial branch of the descending branch of the occipital between the splenius and semi-
spinahs capitis (complexus) . It is accompanied by two veins. This artery may arise directly
from the thyreoid axis, or from the third part of the subclavian artery.
3. THE INTERNAL MAMMARY ARTERY
The internal mammary artery [a. mammaria interna] (figs. 457, 462) comes off
from the lower part of the first portion of the subclavian, usually opposite the
Fig. 462. — Scheme of the Right Internal Mammary Artery. (Walsham.)
_^ Common carotid artery
Phremc nerve
Subclavian artery
Subclavian vein, cut
Anterior intercostal branch
■ intercostal branch
Musculo-phrenic artery
Deep circumflex iliac artery
Internal jugular vein
Subclavian vein, cut
Scalenus anterior muscle
Sternum
Transversus thoracis muscle
Perforating branch
Superior epigastric artery
-Inferior epigastric artery
thyreo-cervical trunk (thyreoid axis), close to the medial edge of the scalenus
anterior, occasionally opposite the vertebral, or at a spot between these two ves-
sels. It descends with a slight inclination forward and medialward, under cover
of the clavicle, and enters the thorax behind the cartilage of the first rib, and
thence passes down behind the cartilages of the next succeeding ribs, about 1.2 cm.
(I in. ) from the lateral margin of the sternum, to the sixth interspace, where it
divides into the superior epigastric and musculo-phrenic. It is accompanied by
two veins, which unite into one trunk behind the first intercostal muscle; this
THE INTERNAL MAMMARY ARTERY 567
passes to the medial side of the artery into the corresponding vena innominata,
or occasionally on the right side into the vena cava superior direct. The artery
may be divided into two portions, the cervical and the thoracic.
The cervical portion is covered by the sterno-mastoid muscle, subclavian vein, and internal
jugular vein, and is crossed obliquely, in the latero-medial direction, by the phrenic nerve.
It rests upon the pleura and courses around the upper part of the innominate vein. There
is no branch from this part of the artery.
The thoracic portion lies behind the cartilages of the six upper ribs, and in the interspace
between the ribs has in front of it the pectoralis major and the internal intercostal muscles
and external intercostal hgaments. Behind, it is in contact above with the pleura, but it is
separated from it lower down by shps of the transversus thoracis (triangularis sterni). On
the left side, the artery between the fourth and sixth ribs may be said to be in the anterior
mediastinum, the pleura here forming a notch for the heart. In the first, second, and third
spaces the artery, if wounded, can be easily tied; but in the fourth space the operation is at-
tended with more difficulty. The remaining spaces are so narrow that a portion of the cartilage
would have to be removed to expose the vessel.
The branches of the internal mammary artery are: — (l) The pericardio-
phrenic; (2) the anterior mediastinal and thymic; (3) the bronchial; (4) the peri-
cardiac; (5) the sternal; (6) the anterior intercostals; (7) the perforating; (8) the
lateral costal; (9) the superior epigastric; and (10) the musculo-phrenic.
(1) The pericardio-phrenic artery [a. pericaridiophrenica], is a long slender vessel which
comes off from the internal mammary just after it has entered the chest, and descends with
the phrenic nerve, at first between the pleura and innominate vein; then (on the right side)
between the pleura and the vena cava superior ; and lastly, between the pleura and the pericardium
to the diaphragm, where it anastomoses with the other diaphragmatic arteries. It gives
branches both to the pleura and pericardium.
(2) The anterior mediastinal and thymic arteries [aa. mediastinales anteriores et thymicae]
come off irregularly from the internal mammary. They are of small size, and supply the con-
nective tissue, fat, and lymphatics in the superior and anterior mediastina and the remains of
the thymus gland.
(3) The bronchial branches [rami bronchiales] are often wanting. When present they are
supphed to the bronchi and the lower part of the trachea.
(4) The pericardiac branches are distributed to the anterior surface of the pericardium.
(5) The sternal branches [rami sternales] enter the nutrient foramina in the sternum, and
also supply the transversus thoracis (triangularis sterni).
(6) The anterior intercostal branches [rami intercostales] (figs. 463, 478) — two in each of
the five or six upper intercostal spaces — run laterally from the internal mammary artery,
along the lower border of the rib above and the upper border of the rib below, and anastomose
with the corresponding anterior and collateral branches of the aortic intercostals. Each pair
of branches sometimes arises by a common trunk from the internal mammary, which in this case
soon divides into an upper and a lower branch, as above described. They lie at first between
the internal intercostal muscles and the pleura; afterward between the external and internal
intercostal muscles. They supply the contiguous muscles, the pectoralis major, and the ribs.
(7) The perforating or anterior perforating branches [rami perforantes] — five or six in
number, one corresponding to each of the five or six upper spaces — come off from the front of
the internal mammary, between the superior and inferior anterior intercostals, and, perforating
the internal intercostal muscles, pass forward between the costal cartilages to the pectoralis
major, which they supply [rami musculares]. The terminal twigs perforate that muscle close
to ttie sternum, and are distributed to the integument [rami cutanei]. The second, third, and
fourth perforating supply the inner and deep surface of the mammary gland, and become
greatly enlarged during lactation [rami mammaria]. They frequently require ligation in
excision of the breast.
(8) The lateral costal branch [ramus costales lateralis] is given off close to the first rib, and
descends behind the ribs just external to the costal cartilages. It anastomoses with the upper
intercostal arteries. This vessel is often of insignificant size, or absent.
(9) The superior epigastric artery [a. epigastrica superior] (fig. 462), or medial terminal
branch of the internal mammary artery, leaves the thorax behind the seventh costal cartilage
by passing through the costo-xiphoid space in the diaphragm. It is the direct prolongation of
the internal mammary downward. In the abdomen it descends behind the rectus muscle,
between its posterior surface and its sheath, and, lower, entering the substance of the muscle,
anastomoses with the inferior epigastric, a branch of the external iliac. It gives off the following
small branches: — (o) The phrenic, to the diaphragm; (b) the xiphoid, which crosses in front of
the xiphoid cartilage, and anastomoses with the artery of the opposite side; (c) the cutaneous,
which perforate the anterior layer of the sheath of the rectus and supply the integuments;
(d) the muscular, to the rectus muscle, some of which perforate the rectus sheath laterally, and
are distributed to the obhque muscles; (e) the hepatic (on the right side only), which pass along
the falciform ligament to the liver, and anastomose with the hepatic artery; (/) the peritoneal,
which perforate the posterior layer of the sheath of the rectus, and ramify on the peritoneum.
(10) The musculo-phrenic artery [a. musculophrenica], or lateral terminal branch of the
internal mammary artery, skirts laterally and downward behind the costal cartilages of the
false ribs along the costal attachments of the diaphragm, which it perforates opposite the ninth
rib. It terminates, much reduced in size, at the tenth or eleventh intercostal space by anasto-
mosing with the ascending branch of the deep circumflex iUac artery. It gives off in its course
the following small branches: — (a) The phrenic for the supply of the diaphragm; (b) the an-
terior intercostals, two in number for each of the lower five or six intercostal spaces, are dis-
568
THE BLOOD-VASCULAR SYSTEM
tributed like those to the upper spaces, aheady described, and anastomose like them with the
corresponding anterior branches of the lower aortic intercostals; (c) the muscular for the supply
of the oblique muscles of the abdomen.
4. THE COSTO-CERVICAL TRUNK
The costo-cervical trunk [truncus costocervicalis] (figs. 444, 463) is a short
stem which arises usually from the back part of the second portion of the sub-
clavian artery, behind the scalenus anterior on the right side, but commonly
just medial to that muscle on the left side. Its course is upward and backward
above the dome of the pleura and then downward toward the thorax, before
entering which it divides into its two terminal branches.
The branches of the costo-cervical trunk are : — (1) the superior intercostal and
(2) the deep cervical.
(1) The superior intercostal [a. intercostahs suprema] (fig. 463) continues the direction of
the costo-cervical trunk, passing downward into the thorax in front of the neck of the first rib.
It sometimes terminates opposite the first intercostal space by becoming the first intercostal
artery. Usually, however, it is prolonged downward over the neck of the second rib and supplies
the second intercostal space in addition. It communicates with the highest aortic intercostal
artery. As it crosses the neck of the first rib the superior intercostal lies anterior (ventral)
to the first intercostal nerve and lateral to the superior thoracic ganghon of the sympathetic.
Fig. 463. — Scheme of the Right Costo-cervical Trunk. (Walsham.)
Scalenus anterior muscle
Deep cervical branchi
First thoracic nerve
First intercostal nerve.
Subclavian artery.
Second intercostal nerve
Anterior intercostal
artery
Third intercostal^
nerve
Anterior intercostal
artery
Internal mammary
artery
Intercostal vessels of,
third space
Sympathetic nerve
Costo-cervical trunk
Arteria aberrans
Arteria aberrans
Intercostal vessels of fourth space
The branches to the first and second intercostal spaces resemble in course and distribution
the succeeding intercostals derived from the thoracic aorta (see p. 588). Like the aortic inter-
costals they give off dorsal [rr. dorsales] and spinal branches [rr. spinalesj. An arteria aberrans,
when present, arises from the medial side of the right superior intercostal, or occasionally from
the right subclavian itself. It descends as a slender vessel into the thorax, passing downward
and medially behind the oesophagus as far as the third or fourth thoracic vertebra, where in
some cases it anastomoses with a similar slender branch arising from the aorta below the hga-
mentum arteriosum. This anastomosis represents the remains of the embryonic right
dorsal aortic arch, and it is by its occasional enlargement that the anomaly of the right sub-
clavian artery rising from the descending portion of the aortic arch occurs (see p. 637).
(2) The deep cervical artery [a. cervicahs profunda] passes directly backward, first between
the seventh and eighth cervical nerves, and then between the transverse process of the seventh
cervical vertebra and the neck of the first rib, having the body of the seventh cervical vertebra
to its medial side, and the intertransverse muscle to its lateral side. It then tm'ns upward
in the groove between the transverse and spinous processes of the cervical vertebrae lying upon
the semispinaUs colh. It is covered by the semispinahs capitis (complexus). Between these
muscles it anastomoses with the deep branch of the descending branch (princeps cervicis) of
the occipital artery. It gives off a spinal branch which enters the vertebral canal through
the intervertebral foramen with the eighth cervical nerve.
THE AXILLARY ARTERY
569
THE AXILLARY ARTERY
The term axillary is applied to that portion of the maia arterial stem of the
upper limb that passes through the axillary fossa. The axillary artery [a. axillaris]
(fig. 464) therefore is continuous -with the subclavian above and with the brachial
below. It extends from the lateral border of the first rib to the lower edge of the
teres major muscle, and has the shoulder-joint and the neck of the humerus to
its lateral side. When the arm is placed close to the side of the body, the artery
forms a gentle curve with its convexity upward; but when the arm is carried out
from the side at right angles to the trunk in the ordinary dissecting position, the
vessel takes a nearly straight course, which will then be indicated by a Hne drawn
from the middle of the clavicle to the groove on the medial side of the coraco-
brachialis and biceps muscles. The axillary artery is at first deeply placed
beneath the pectoral muscles, but in its lower third it is superficial, being covered
Fig. 464. — The Axillary Artery. (After Spalteholz.)
Axillary artery
Thoraco-acromial artery I .
I Axillary vein
Acromial branch I , J
Deltoid branch
Musculo-cutaneous j
Circumflex humeral artery
Coraco brachial muscle
Deltoid muscle
Pectorahs
major muscle
( ' Deltoid branch^ .
Median ! Ulnar nerve / / /
nerve I Brachial cutaneous/ ' /
Brachial vein and medial anti- / /
brachial nerves /
Axillary nerve /
Subscapular artery
Latissimus dorsi muscle '
Pectoralis minor muscle
'■< y^^ Pectoral branches
umflex scapular artery
Lateral thoracic artery
sal thoracic artery
only by the skin and the superficial fascia and deep fascia. It is divided into
three parts, first, second, and third, according as it lies respectively above,
beneath, or below the pectoralis minor.
The First Part of the Axillary Artery
The first part of the axillary artery extends from the lateral border of the first
rib to the upper border of the pectorahs minor. It measures about 2.5 cm. (1 in.)
in length.
Relations. — In front it is covered by the skin, superficial fascia, lower part of the platysma,
the deep fascia, the pectorahs major, the coraco-clavioular (costo-ooracoid) fascia, the sub-
clavius muscle and the clavicle when the arm hangs down by the side. The cephalic and
thoraco-acromial veins, the external anterior thoracic nerve, and the axillary lymphatic trunk,
cross over it. A layer of the deep cervical fascia which has passed under the clavicle also
descends in front of it.
570 THE BLOOD-VASCULAR SYSTEM
Behind, it rests upon the first intercostal space and first intercostal muscle, the first digita-
tion and sometimes a portion of the second digitation of the serratus anterior (magnus) muscle,
and a part of the second rib. The long thoracic nerve, on its way to the serratus anterior
muscle, passes behind it.
To its lateral side, and somewhat on a higher plane, are the cords of the brachial plexus.
To its medial side, and on a slightly anterior plane, is the axillary vein. The internal
anterior thoracic nerve courses between the vein and the artery.
The Second Part of the Axillary Artery
The second part of the axillary artery (fig. 464) lies beneath the pectoralis
minor deep in the axilla. It measures 3 cm. (a little more than 1 in.) in length.
Relations. — In front, in addition to the pectorahs minor, it is covered by the pectoralis
major and the integuments.
Behind, it is separated by a considerable interval, containing loose connective tissue and
fat, from the subscapularis muscle; whilst behind, and in contact with it, is the posterior cord
of the brachial plexus.
To the medial side, but separated from the artery by the medial cord of the brachial
plexus, is the axillary vein.
To the lateral side is the lateral cord of the brachial plexus, and at some little distance
the coracoid process.
It is thus seen that the second portion of the auxiliary artery is surrounded on three sides
by the cords of the brachial plexus — one behind, one medial, and one lateral.
The Third Part of the Axillary Artery
The third part of the axillary artery (fig. 464) extends from the lower border
of the pectoralis minor to the lower border of the teres major. Its upper half lies
deeply placed within the axilla, beneath the lower edge of the pectoralis major
muscle, but its lower half is in the arm external to the axilla, and is uncovered by
muscle. It measures about 7.5 cm. (3 in.) in length.
Relations. — In front it has, in addition to the skin and superficial fascia, the pectorahs
major above, and lower down the deep fascia of the arm. It is crossed obhquely by the medial
root of the median nerve and by the lateral brachial vena comitans.
Behind, it lies successively upon the subscapularis, the latissimus dorsi, and teres major
muscles. From the first-named muscle it is separated at first by a considerable mass of fat
and cellular tissue. The radial (musculo-spiral) and axillary (circumflex) nerves intervene
between the artery and the muscles.
On its lateral side it is separated from the bone by the coraco-brachialis, by which it is
partly overlapped, this muscle and the short head of the biceps serving as a guide to the artery
in hgature. For a part of its course it has also the musculo-cutaneous nerve and the lateral
root of the median nerve to its lateral side.
To its medial side it has the axillary vein, the ulnar nerve, the medial antibrachial (internal)
and brachial (lesser internal) cutaneous nerves, and the medial root of the median nerve.
The ulnar nerve is between the artery and the vein. The medial antibrachial (internal)
cutaneous nerve is a httle in front of the artery as well as medial to it.
Branches of the Axillary Artery
The branches of the axillary artery are exceedingly variable. In fig. 465 is
shown what Hitzrot has found the usual type, in which the second portion of
the artery has no named branches. The figure brings out the segmental relation
of the branches of the axillary artery to the chest wall and suggests how one of the
branches may supply the place of another. If the lateral thoracic arises directly
from the axillary, it is generally from the second part as described below. In
addition to the larger branches of the artery small twigs are supplied to the ser-
ratus anterior, coraco-brachialis, and subscapularis; also to the axillary lymph-
nodes.
The first part gives off. — ^(1) The superior thoracic; and (2) the thoraco-
acromial.
The second part gives off: — (3) The lateral thoracic.
The third part gives off: — (4) The subscapular; (5) the anterior humeral
circumflex; and (6) the posterior humeral circumflex.
Branches of the Axillary Artery
1. The superior thoracic [a. thoracalis suprema] is variously given off from the
axillary artery, usually either as a common trunk' with the next branch, the
THE AXILLARY ARTERY
571
thoraco-acromial, or a little above. It passes behind the axillary vein across the
first intercostal space, supplying the intercostal muscles and the upper portion
of the serratus anterior, and anastomoses with the intercostal arteries. At
times it sends a branch between the pectoralis major and minor, which then, as a
rule, more or less takes the place of the pectoral branch of the thoraco-acromial
(figs. 464 and 465).
2. The thoraco-acromial or acromio-thoracic axis [a. thoracoacromialis]
arises from the front part of the axillary just above the upper border of the
pectoralis minor. It is a short trunk, and, coming off from the front of the
artery, pierces the coraco-clavicular fascia, and then divides into three or four small
branches, named from their direction: — (a) the acromial; (b) the deltoid; (c) the
pectoral, and {d) the clavicular.
Fig. 46.5. — The Branches of the Axillary Artery. (After Hitzrot.)
The numbers 1-5 indicate the intercostal spaces.
Thoraco-acromial
Superior thoracic Clavicular branch
/M/,:^
Acromial branch
Pectoral branch
Deltoid branch
Anterior circumflex
humeral
Posterior circumflex
humeral
Branch to teres major
Branches to latissimus do
Branch to serratus anterior
(a) The acromial branch [r. acromiaUs] or branches pass laterally across the coracoid
process, frequently through the deltoid muscle, which they in part supply, to the acromion,
where they form, by anastomosing with the anterior and posterior circumflex and transverse
scapular (suprascapular) arteries, the so-called acromial rete, or plexus of vessels on the surface
of that process.
(6) The deltoid branch [r. deltoideus] runs downward with the cephalic vein in the interval
between the pectorahs major and the deltoid, and, supplying lateral ofTsets to these muscles
and the adjacent integument, anastomoses with the anterior and posterior circumflex humeral
arteries.
(c) The pectoral branch [r. pectorahs] passes between the pectorahs major and minor
muscles, both of which it supplies. In the female, one or more branches which perforate the
pectoralis major are often of large size, and supply the superimposed mammary gland.
(d) The clavicular branch passes upward beneath the clavicle, supphes the subclavius
muscle, and anastomoses with the transverse scapular artery.
3. The lateral thoracic artery [a. thoracalis lateralis] descends along the lower
border of the pectoralis minor, under cover of the pectoralis major, to the chest
wall. It supplies both pectoral muscles and the serratus anterior fmagnus),
sends branches around the lower border of the pectoralis major to the mammary
gland, and terminates in the intercostal muscles by anastomosing with the aortic
intercostals and the internal mammary. It also furnishes branches to the
lymph-nodes of the axillary fossa. The branches to the mammary gland in the
female are often of large size.
4. The subscapular artery [a. subscapularis] is the largest branch of the
axillary. It arises opposite the lower border of the subscapularis, and runs in a
572
THE BLOOD-VASCULAR SYSTEM
downward and medial direction along the anterior border of that muscle under
cover of the latissimus dorsi. It supplies the subscapularis, teres major, latissimus
dorsi, and serratus anterior (magnus) muscles, and gives branches to the nodes
in the axillary fossa. The course of this large vessel along the posterior border
of the axillary fossa should be remembered in opening abscesses in the fossa, and
in removing enlarged nodes from it. It is accompanied by two veins, which
usually unite and then receive the circumflex (dorsal) scapular vein, and open as
a single vein of large size either into the axillary or at the confluence of the medial
brachial vena comitans with the basilic vein.
About 2.5 or 3.7 cm. (1 or 1| in.) from its origin, the subscapular artery divides
into two end branches, (1) the circumflex (dorsal) scapular, and (2) the dorsal
thoracic.
Fig. 466. — The Anastomoses about the Scapula.
Subscapular branch of transverse scapular artery
Supraspinous branch of transverse scapular artery
Descending branch
of transverse cer-
vical artery
Transverse scapular artery
Acromial branch of
thoraco-acromial
Acromial rete
Subscapular branch of
transverse scapular
artery
Infraspinous branch of
transverse scapular
artery
Subscapular branch of
axillary artery
Circumflex scapular artery
Infrascapular branch of cir-
cumflex scapular artery
Branch of inter
costal artery
Branch of inter-
costal artery
Continuation of de-
scending branch
of transverse cer-
vical artery
(1) The circumflex scapular artery [a. circumflexa scapulae], or dorsal scapular, arising
from the subscapular, usually at the point above mentioned, passes backward through the trian-
gular space bounded by the subscapularis above, the teres major below, and the long head of
the triceps laterally, and then between the teres minor and the axiUary border of the scapula,
which it commonly grooves. It thus reaches the infraspinous fossa, where, under cover of
the infra-spinatus, it anastomoses with the transverse scapular (suprascapular) artery and the
descending branch of the transverse cervical (posterior scapular) (fig. 466). As it passes through
the triangular space, it gives off a ventral branch which ramifies between the subscapularis
and the bone, supplying branches to the subscapularis, to the scapula, and to the shoulder-
joint. A second branch is often given off near the triangular space and passes downward
between the teres major and teres minor, supplying both muscles (fig. 467).
(2) The dorsal thoracic artery [a. thoracodorsahs] continues in the course of the subscapular
as far as the angle of the scapula, where it anastomoses with the circumflex scapular, the
descending branch of the transverse cervical (posterior scapular), the lateral thoracic, and
intercostal arteries.
5. The anterior circumflex humeral artery [a. circumflexa humeri anterior],
usually quite a small vessel, comes off from the lateral side of the axillary artery,
generally opposite the posterior circumflex. It passes beneath the coraco-
brachialis and short and long heads of the biceps, winding transversely round the
front of the surgical neck of the humerus, across the intertubercular (bicipital)
groove, and anastomoses ^vith the posterior circumflex and thoraco-acromial
arteries. It gives off the following small branches:
THE BRACHIAL ARTERY
573
(o) The bicipital or ascending, which runs up the intertubercular groove to supply the long
tendon of the biceps and the shoulder-joint; and (h) a pectoral or descending branch, which
runs downward along the insertion of the pectorahs major, and supplies the tendon of that
muscle. The anterior circumflex artery, in consequence of its being close to the bone, is
sometimes difficult to secure in the operation for excision of the shoulder-joint.
6. The posterior circumflex humeral artery [a. circumflexa humeri posterior]
(fig. 467) arises from the posterior aspect of the axillary, just below the lower
border of the subscapularis muscle. It passes through the quadrilateral space,
bounded by the teres minor above, the latissimus dorsi and teres major below, the
humerus laterally, and the long head of the triceps medially, and, winding round
the back of the humerus beneath the deltoid, breaks up under cover of that muscle
into a leash of branches, which for the most part enter its substance. The axillary
(circumflex) nerve and two vense comitantes run with it. It anastomoses with
the anterior circumflex, the arteries on the acromion, and the profunda artery.
Fig. 467. — The Arteries of the SHOtiLDER. (After Spalteholz.)
Transverse cervical artery
Ascending branch 1 Superior transverse scapular Ugament
Descending branch ! ' ' Transverse scapular artery
—Acromion
^^_^ «„_^ -Acromial branch
/A '__'__ __ ; _'^. _ ^^
■Deltoid muscle
Infraspinatus muscle
CIrcumSex
scapular artery
Teres minor muscle i
Posterior circumflex
Teres major humeral artery
muscle
Triceps muscle (lateral head)
Triceps muscle (long head)
In addition to the leash of vessels to the deltoid, it gives off the following small branches:
— (a) nutrient, to the greater tuberosity of the humerus; (b) articular, to the back of the shoulder-
joint; (c) acromial, to the plexus on the acromion; and [d) muscular, to the teres minor and long
and short heads of the triceps. One or more of these branches to the triceps descend either
between the lateral and long head or in the substance of that muscle, to anastomose with an
ascending branch from the profunda artery. It is by means of this anastomosis that the
collateral circulation is chiefly carried on when the axillary or the brachial artery is tied between
the origins of the posterior circumflex and profunda arteries.
THE BRACHIAL ARTERY
The brachial artery [a. brachialis] (fig. 468), the continuation of the axillary,
extends from the lower border of the teres major to a little below the centre of the
crease at the bend of the elbow, where it divides, opposite the junction of the
head with the neck of the radius, into the radial and ulnar arteries. The artery
is situated at first medial 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 lies midway between the
two epicondyles. Hence, in controlling hiemorrhage, the artery should be com-
pressed laterally against the bone in its upper third, laterally and backward in its
middle third, and directly backward in its lower third. Throughout the greater
part of its course the artery is superficial, being merely overlapped slightly on
574
THE BLOOD^VASCULAR SYSTEM
its lateral side by the coraco-brachialis and biceps muscles; but at the bend of
the elbow it sinks deeply beneath the lacertus fibrosus of the biceps into the
triangular interval (antecubital space) bounded on either side by the brachio-
FiG. 468. — The Brachial Artery. (After Toldt, "Atlas of Human Anatomy" Rebman,
London and New York.)
Subscapular artery
Deltoid pectoral triangle
Thoraco- f Acromial branch
acromial ]
artery [ Deltoid branch
Axillary lymph-nodes
''y- Dorsal thoracic artery
Circumflex scapular
artery
Cutaneous branch— V
Coraco-brachiahs
Brachial artery -
Deltoid muscle — t
Lateral antibrachial cutaneous nerve f™"-^'
/ ^
Brachial artery
Lacertus fibrosus
Brachio-radialis muscle- — '
Radial recurrent artery-^
Cutaneous branches v.
|"~ Antibrachial fascia
radialis and pronator teres, and at its bifurcation is more or less under cover
of these muscles (fig. 469). The sheath of the brachial artery is closely incor-
porated with the fascia covering the biceps muscle, and it is for this reason that
in the operation for hgaturing the vessel is apt to be retracted with the muscle.
THE BRACHIAL ARTERY
575
A line drawn from the groove medial to the coraco-brachialis and biceps muscles
to midway between the epicondyles of the humerus will indicate its course. It
is accompanied by two veins which frequently communicate across the artery.
In addition to the branches named below the iDrachial artery gives off numerous
muscular branches and, occasionally, the nutrient artery to the humerus. The
muscular branches usualty come off from the lateral side of the artery; one in
particular, which supplies the biceps muscle, is frequently of large size.
Relations. — In front, the artery is covered by the integument and superficial and deep
fasciae, and at the bend of the elbow by the lacertus fibrosus of the biceps, and in muscular
subjects by the overlapping margins of the brachio-radialis and pronator teres. In the middle
third of the arm it is crossed obliquely from the lateral to the medial side by the median nerve,
and at the bend of the elbow by the median cubital vein, the bicipital fascia intervening (fig. 475).
Behind, it lies successively on the long head of the triceps (from which it is separated by
the radial (musculo-spiral) nerve and profunda artery), on the medial head of the triceps,
on the insertion of the ooraco-braohialis, and thence to its bifurcation on the brachiahs muscle.
Fig. 469. — The Brachial Ahteey at the Bend of the Elbow, Left Side, Front View.
(From a mounted specimen in the Anatomical Department of Trinity College, Dublin.)
Posterior branch of medial
antibracliial cutaneous
nerve
Anterior branch of medial
antibrachial cutaneous
nerve
Brachial artery
Branch to pronator teres
Lacertus fibrosus, cut
Pronator teres muscle
Median nerve
Ulnar artery
Superficial radial nerve
Radial recurrent artery and
deep radial nerve
Tendon of biceps
Musculo-cutaneous nerve
Brachio-radialis muscle
* — Radial artery
Lateral to the artery is the coraco-brachialis above, and the muscular belly of the biceps
below, both of which shghtly overlap the vessel, and at the bend of the elbow the tendon of
the biceps. The lateral vena comitans is also to its lateral side. The median nerve is in close
contact with the lateral side of the artery in the upper third of its course, but in the middle third
crosses the artery obliquely to gain the medial side.
Medial to the artery in the upper part of its course are the medial antibrachial (internal)
cutaneous and the ulnar nerves; the latter nerve, however, leaves the artery about the origin
of the ulnar collateral (inferior profunda) branch, to make, with that vessel, for the medial
epicondyle. Lower down, the medial antibrachial cutaneous nerve also leaves the artery,
by piercing the deep fascia. The median nerve is in close contact with the medial side of the
artery in its lower third and at the bend of the elbow. The basilic vein is superficial to it,
and a Uttle to its medial side in the greater part of its course, but separated from it by the deep
fascia. The medial vena comitans runs along its medial side.
Branches of the Brachial Artery
The branches of the brachial artery are: — (1) The profunda brachii; (2) the
superior ulnar collateral (inferior profunda); (3) the inferior ulnar collateral
576 THE BLOOD-VASCULAR SYSTEM
(anastomotica magna); and (4) the terminal branches — the radial and ulnar
arteries.
(1) The Profunda Artery
The profunda brachii (superior profunda) is the largest branch of the brachial.
It arises from the medial and hinder aspect of that artery, a Httle below the in-
ferior border of the tendon of the teres major. It at first lies to the medial side
of the brachial, but soon passes behind that vessel, and, sinking between the
medial and long heads of the triceps with the radial (musculo-spiral) nerve, curves
around the humerus in the groove for the nerve, lying in contact with the bone
between the medial and lateral heads of the triceps. On reaching the lateral
supracondyloid ridge of the humerus it perforates the lateral intermuscular
septum, and, continuing forward between the brachio-radialis and brachialis to
the front of the lateral epicondyle, ends by anastomosing with the radial re-
current artery (figs. 468 and 474).
It gives off the following branches: —
(a) The deltoid branch [r. deltoideus] which may also arise from the brachial itself or from
the superior ulnar collateral. It runs across the anterior surface of the humerus, under cover
of the coraco-brachialis and biceps, and suppUes the brachiahs and deltoid.
(6) The middle collateral artery [a. coUaterahs media] runs in the substance of the middle
head of the triceps as far as the elbow, where it terminates in the articular rete.
(c) The radial collateral artery [a. collateralis radialis] arises about the middle of the upper
arm, and runs behind the lateral intermuscular septum to the rete at the elbow-joint.
(d) A nutrient humeral artery [a. nutritia humeri], which may come from the brachial
itself or from a muscular branch, enters a canal in the humerus.
(2) The Superior Ulnar Collateral Artery
The superior ulnar collateral artery [a. collateralis ulnaris superior] (inferior
profunda) arises from the medial side of the brachial, usually about the level of
the insertion of the coraco-brachialis, at times as a common trunk with the
profunda. It passes with the ulnar nerve medially and downward through the
medial intermuscular septum, and then along the medial head of the triceps to the
back of the medial epicondyle, where, under cover of the deep fascia and the
origin of the flexor carpi ulnaris from the olecranon and medial epicondyle, it
enters into the anastomoses around the elbow-joint. It frequently supplies the
nutrient artery to the humerus. It gives branches to the triceps, to the elbow-
joint, and a branch which passes in front of the medial epicondyle to anastomose
with the anterior ulnar recurrent.
(3) The Inferior Ulnar Collateral Artery
The inferior ulnar collateral artery [a. collateralis ulnaris inferior] or anasto-
motica magna arises from the medial side of the brachial, about 5 cm. (2 in.) above
its bifurcation into the radial and ulnar arteries, and, running medially and down-
ward across the brachialis, divides into two branches, a posterior and an anterior.
The posterior pierces the medial intermuscular septum, winds round the medial
condyloid ridge of the humerus, and pierces the triceps, between which and the
bone it anastomoses with the articular branch of the profunda artery, and to a
lesser extent with the interosseous recurrent, forming an arterial arch or rete
around the upper border of the olecranon fossa. The anterior branch passes
medially and downward between the brachialis and pronator teres, and anas-
tomoses in front of the medial epicondyle, but beneath the pronator teres, with
the anterior ulnar recurrent. From this branch a small vessel passes down behind
the medial epicondyle to anastomose with the posterior ulnar recurrent and
superior ulnar collateral arteries (fig. 474).
THE ULNAR ARTERY
The ulnar artery [a. ulnaris] (fig. 470) the larger of the two terminal branches
of the brachial, begins opposite the lower border of the head of the radiusin the
middle fine of the forearm. Thence through the upper half of the forearm it runs
THE ULNAR ARTERY 677
beneath the pronator teres and superficial flexor muscles, and, having reached the
ulnar side of the arm about midway between the elbow and the wrist, it passes
directly downward, being merely overlapped by the flexor carpi ulnaris. Crossing
the transverse carpal (anterior annular) ligament immediately to the radial side
of the pisiform bone, it enters the palm, where it divides into two branches, which
enter respectively into the formation of the superficial and deep volar arches.
The artery is accompanied by two veins, which anastomose with each other by
frequent cross branches, and usually terminate in the brachial venae comitantes.
The ulnar nerve is at first some distance from the artery, but approaches the
vessel at the junction of its upper and middle thirds, and then lies close to its
medial or ulnar side. The course of the artery in the lower two-thirds of the
forearm is indicated by a line drawn from the front of the medial epicondyle to
the radial side of the pisiform bone; and in the upper third of the forearm by a
line drawn in a gentle curve with its convexity to the medial side from 2.5 cm.
(1 in.) below the centre of the bend of the elbow to a point in the former line at
the junction of its upper with its middle third. The artery throughout its course
is best reached through the interval between the flexor carpi ulnaris and the
flexor digitorum sublimis.
The relations of the artery will be given in detail in the forearm, and in the palm of the
hand.
The relations in the forearm are: —
In front. — In the upper half of the forearm the ulnar artery is deeply placed beneath the
pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor digitorum sublimis.
In the lower half it is comparatively superficial, being merely overlapped above by the tendon
of the flexor carpi ulnaris, whilst the last inch or so of the vessel is only covered as a rule by
the skin and superficial and deep fasciae. As the artery hes beneath the pronator teres, it is
crossed from the medial to the lateral side by the median nerve, the deep head of origin of the
muscle usually separating the nerve from the artery. The lower part of the artery is crossed
by the palmar cutaneous branch of the ulnar nerve.
Behind. — For about 2.5 cm. (1 in.) of its course the artery lies upon the brachialis; but
thence, as far as the transverse carpal (anterior annular) ligament, upon the flexor digitorum
profundus, which separates it above from the interosseous membrane and bone, and at the
wrist from the pronator quadratus. The artery is bound down to the flexor digitorum pro-
fundus by bands of fasciae.
To the lateral side in the lower two-thirds of its course is the flexor digitorum subMmis.
To the medial side in the lower two-thirds is the flexor carpi ulnaris, the guide to the
vessel. The ulnar nerve, as it enters the forearm from behind the medial epicondyle, is at first
some distance from the artery, being separated from it in its upper third by the flexor digitorum
subhmis, but in its lower two-thirds is in close contact with the vessel and on its ulnar side.
The branches of the ulnar artery in the forearm are: — 1. The ulnar recurrent
arteries. 2. The common interosseous. 3. Muscular. 4. Dorsal ulnar carpal.
5. Volar ulnar carpal.
1. The ulnar recurrent arteries [aa. recurrentes ulnares] are two, the volar, and dorsal.
The volar is a small branch which arises from the medial side of the ulnar artery, or the dorsal
ulnar recurrent, and, running between the lateral edge of the pronator teres and the brachiahs.
anastomoses in front of the medial epicondyle with the inferior and superior ulnar collaterals.
It supphes branches to the muscles between which it runs, and to the skin. The dorsal, larger
than the volar, comes'off from the medial side of the ulnar artery, either a little below the latter
branch, or else as a common trunk with it, and, passing between the flexores digitorum subhmis
and profundus, turns upward to the back of the medial epicondyle, where it Ues with the ulnar
nerve between the two heads of origin of the flexor carpi ulnaris. It supplies the contiguous
muscles — the flexor carpi ulnaris, the palmaris longus, and the flexores digitorum sublimis and
profundus — the elbow-joint, and the ulnar nerve, and anastomoses with the inferior and superior
ulnar collaterals, and with the interosseous recurrent forming the so-called rete olecrani.
2. The common interosseous artery [a. interossea communis] is a short thick
trunk 1.2 cm. (| in.) or so in length, which comes off from the lateral and back
part of the ulnar artery about 2.5 cm. ( 1 in.) from its origin, and just before
that artery is crossed by the median nerve. It passes backward and downward
between the flexor pollicis longus and the flexor digitorum profundus, toward the
triaagular interval bounded by the upper border of the interosseous membrane,
the oblique hgament, and the lateral border of the ulna, where it divides into the
volar and dorsal interosseous arteries.
(a) The volar interosseous artery [a. interossea volaris], smaller than the dorsal, but
apparently the direct continuation of the common trunk, courses downward in front of the
. interosseous membrane. It lies under cover of the overlapping edges of the flexor digitorum
profundus and flexor poUicis longus, to both of which muscles it supphes branches. At the
578
THE BLOOD-VASCULAR SYSTEM
upper border of the pronator quadratus it divides into two branches, an anterior terminal
and a posterior terminal (fig. 473).
The volar interosseous artery is accompanied by two veins and by the deep branch of the
median nerve which hes to its radial side. The artery is bound down to the interosseous
membrane by aponeurotic fibres.
Fig. 470. — The Volar Arteries of the Forearm and Hand. (After Toldt, "Atlas of
Human Anatomy/' Rebman, London and New York.)
Biceps brachii —
Inferior ulnar collateral artery —
Brachial artery —
Tendon of the biceps brachn —
Brachio-radiah:
Radial recurrent artery
Ulnar recurrent artery
Supinator
interosseous artery
f longus
Extensor carpi radialis ]
[ brevis
Flexor digitorum sublimis^-
Brachio -radialis
Flexor digitorum profundus 1
Median nerve
Pronator quadratus ^-.
Flexor carpi radiahs ' Ir- _
Radial artery — -vflfll
Superficial volar branch —
Transverse carpal ligament
Abductor brevis pollicis
Flexor brevis pollicis
Common volar digital arteries .e^^^-
Adductor pollicis — tj—/-'
First dorsal interosseii ' ^'j,
LumbricaIes-^--r.
Superior ulnar collateral artery
Medial intermuscular septum
Bracbialis
Median nerve
Pronator teres
Flexor carpi radialis
Palmaris longus
Ulnar artery
Flexor carpi ulnaris
Flexor profundus digitorun
Deep volar branches of ulnar artery
Superficial volar arch
Flexor digiti V brevis
Abductor digiti V
Proper volar digital arteries
The branches of the volar interosseous artery are: — (i) The median artery [a. mediana]
is a long slender vessel which arises from the volar interosseous immediately after the latter is
given off from the common trunk. It passes forward between the flexor digitorum profundus
and the flexor pollicis longus to the median nerve, with which it descends beneath the transverse
carpal (anterior annular) ligament into the palm, and when of large size sometimes enters into
the formation of the superficial palmar arch. At times the artery arises from the common
THE ULNAR ARTERY
579
interosseous before its division, (ii) The nutrient arteries of the radius and uhia are usually
derived from this vessel, (iii) The volar terminal division of the volar interosseous artery passes
either in front of or behind the pronator quadratus, but in either case in front of the interos-
seous membrane, and anastomoses with the volar carpal branches of the radial and ulnar
arteries, and with the recurrent branches from the deep volar arch, forming the so-called
volar carpal rete. (iv) The dorsal terminal, the larger division, pierces the interosseous mem-
brane, and continues its course downward behind the interosseous membrane, under cover of
the extensor muscles, to the back of the wrist, where it ends by anastomosing with the dorsal
Fig. 471. — The Back of the Left Forearm, with the Dorsal Interosseous Artery
AND Branches of the Radial at the Back of the Wrist.
(From a dissection in the Hunterian Museum.)
Articular branch of the profunda
Brachialis
Brachio-radialis, cut
Common extensor tendon
Supinator
Dorsal interosseous artery
Abductor pollicis longus
Brachio-radialis, cut
Extensor pollicis brevis
Dorsal carpal ligament
Extensor carpi radialis longus
Radial artery
First dorsal metacarpal artery
Extensor pollicis longus
First dorsal interosseous muscle
First dorsal metacarpal artery
Princeps pollicis artery
Dorsal digital artery
Rete over olecranon
Interosseous recurrent artery
Anconeus, cut
Extensor carpi ulnaris
Flexor carpi ulnaris
Origin of extensor pollicis longus and
indicis proprius
Dorsal branch of volar interosseous
artery
Interosseous membrane
Dorsal ulnar carpal artery
Extensor carpi radialis brevis
Dorsal radial carpal artery
Fourth dorsal metacarpal artery
Third dorsal metacarpal artery
Second dorsal metacarpal artery
carpal branches of the radial and ulnar arteries, forming the so-called dorsal carpal rete.
This branch anastomoses, as soon as it pierces the interosseous membrane, with the dorsal
interosseous artery.
(6) The dorsal interosseous artery [a. interossea dorsalis], the larger division of the com-
mon interosseous, turns backward through the triangular interval bounded by the interosseous
membrane below, the oblique hgament above, and the ulna on the medial side, and emerging
at the back of the forearm between the abductor pollicis longus and the supinator, under cover
of the superficial extensors of the forearm, descends between the superficial and the deep muscles,
crossing in this course the abductor polhcis longus, the extensor pollicis brevis, the extensor
pollicis longus, and the extensor indicis proprius (fig. 471). It anastomoses at the lower border
580
THE BLOOD-VASCULAR SYSTEM
of this muscle and just above the wrist joint, with the dorsal branch of the volar interosseous
which here, as above described, has perforated the interosseous membrane. It is separated
from the deep radial nerve at first by the radius and supinator, and on the back of the forearm
by the extensores polUcis longus and indicis proprius.
The chief branch of the dorsal interosseous artery, the interosseous recurrent artery [a.
interossea recurrens] arises from the dorsal interosseous as the latter emerges from beneath
the supinator. It runs upward between the anconeus and supinator, usually under cover
of the former, to the interval between the lateral epicondyle and the olecranon, where it anas-
tomoses with the profunda, inferior ulnar collateral, radial recurrent, and dorsal ulnar recurrent
arteries, and gives branches to the retiform plexus over the olecranon — the rete olecrani.
Fig. 472. — Anastomoses and Distribution of the Arteries of the Hand,
Volar interosseous -
Radial artery -
Volar radial carpal
Superficial volar
Dorsal radial carpal
Radial artery at wrist
First dorsal
metacarpal
Second dorsal
metacarpal
Princeps polUcis
First dorsal meta-
carpal (branch to
index)
Radialis indicis
Dorsal digital
Volar digital
First dorsal branch of volar digital
Second dorsal branch of volar digital
Anastomosis of volar digital arteries
about matrix of nail and pulp of
finger
Ulnar artery
Volar ulnar
carpal
Dorsal ulnar
carpal
Deep ulnar
Superficial arch
Carpal re-
current
Dorsal per-
forating
Volar meta-
carpals
Common volar
digitals
Dorsal meta-
carpals
Common volar
digital
3. The muscular branches [rami musculares] are numerous. * They supply
the deep and superficial flexors of the fingers, the flexor carpi radialis and ulnaris,
and the pronator radii teres.
4. The dorsal ulnar carpal [ramus carpeus dorsafis] comes off from the ulnar
artery a little above the transverse carpal (anterior annular) ligament, and,
winding medially round the end of the ulna or the ulnar collateral ligament of the
wrist, beneath the flexor carpi ulnaris, ramifies on the back of the carpus beneath
the extensor tendons. It forms by its anastomosis with the dorsal radial carpal,
with the dorsal terminal branch of the volar interosseous and with the dorsal
interosseous arteries a plexus or rete, the so-called dorsal carpal rete. The
branches given off from this plexus or arch are described with the dorsal carpal
branch of the radial artery.
THE ULNAR ARTERY
581
5. The volar ulnar carpal [ramus carpeus volaris] is a small branch given off
from the ulnar artery opposite the carpus. It passes beneath the flexor digitoruro
profundus to anastomose with the volar radial carpal, with terminal twigs of the
volar branch of the volar interosseous, and with recurrent branches from the
deep volar arch, forming an anastomotic arch across the front of the carpus — the
volar carpal arch or rete.
Fig. 473. — The Arteries op the Right Forearm and the Deep Volar Arch.
-Superior ulnar collateral
-Inferior ulnar collateral
Brachial artery -
Radial recurrent artery.
Brachio-radialis -
Flexor pollicis longus muscle -
-Brachialis muscle
- Volar ulnar recurrent
-Dorsal ulnar recurrent
-Volar interosseous artery
-Flexor carpi ulnaris
-Flexor digitorum profundus muscle
-Volar interosseous artery
Transverse carpal ligament, cut-
"Volar branch of ulnar artery, cut
"Deep volar arch
'H\ fe^^Vc—
Volar metacarpal arteries
Volar digital artery, cut short
Volar digital artery"
The Ulnar Artery at the Wrist
The ulnar artery at the wrist may be said to extend from the upper to the
lower border of the transverse carpal (anterior annular) ligament upon which
it rests. It here lies immediately to the radial side of the pisiform bone, and
to the ulnar side of the hook of the hamate (unciform), the two bones forming
for the vessel a protecting channel, which is further converted into a short canal
by the expansion of the flexor carpi ulnaris passing from the pisiform to the hook
of the hamate (unciform). The ulnar nerve in this situation is immediately to
the ulnar side of the artery.
582 THE BLOOD-VASCULAR SYSTEM
The Ulnae Artery in the Palm (Superficial Volar Arch)
The ulnar artery, on entering the palm, divides into two branches, the super-
ficial and deep.
The superficial branch (fig. 472) , the direct continuation of the vessel, anasto-
moses with the superficial volar, a branch of the radial, forming what is then
known as the superficial volar arch. After descending a short distance toward the
cleft between the fourth and fifth fingers, it turns toward the thumb, forming a
curve with its convexity toward the fingers and its concavity toward the muscles
of the thumb, and anastomoses opposite the cleft between the index and middle
fingers, at the junction of the upper with the middle third of the palm, with the
superficial volar branch of the radial artery to complete the arch. A line drawn
transversely across the palm on a level with the metacarpo-phalangeal joint of the
thumb will roughly indicate the situation of the arch.
Relations. — In front: in addition to the skin and superficial fascia, the vessel is crossed
successively, by the palmaris bevis, the palmar branch of the ulnar nerve, the palmar aponeuro-
sis and the palmar branch of the median nerve.
Behind, it rests successively upon the short muscles of the little finger, the digital branches
of the ulnar nerve, the flexor tendons, and the digital branches of the median nerve.
The branches of the superficial volar arch. In addition to small muscular
and cutaneous branches the superficial volar supplies: —
The common digital arteries [aa. digitales volares communes]. These, usually four in
number, arise from the conve.xity of the superficial arch and, running downward through the
palm, give off the digital arteries proper to both sides of the httle, ring, and middle fingers,
and the ulnar side of the index finger. The radial side of the index finger and the thumb are
supplied by the first volar metacarpal branch" of the radial artery.
The most ulnar of the common digital arteries passes distally over the muscles in the ulnar
border of the palm, and thence along the ulnar bordet of the httle finger. The remaining
arteries pass distaUy in the three ulnar intermetacarpal spaces to within about 6 mm. (j in.) of
the clefts between the fingers, where they divide into branches, the digital arteries proper
[aa. digitales volares proprise], which supply the sides of contiguous fingers.
As the common digital arteries pass through the palm, they lie between the flexor tendons,
on the digital nerves and lumbrical muscles, and beneath the palmar aponeurosis. Just before
bifurcating they pass under the transverse fasciculi, and are joined b}^ the volar metacarpal
branches from the deep volar arch (fig. 472). At this spot they also receive the volar perforating
branches from the dorsal metacarpal vessels. On the sides of the fingers the proper digital
arteries lie between the palmar and dorsal digital nerves. They anastomose by small branches,
forming an arch across the front of the bones on the proximal side of each interphalangeal joint.
They supply the flexor tendons and the integuments, and terminate in a plexiform manner
beneath the pulp of the finger and around the matrix of the nail. A dorsal digital branch is
given off to the back of the fingers about the level of the middle of the first phalanx, and a
second but smaller dorsal digital branch about the level of the middle of the second phalanx.
The deep branch of the ulnar artery, also called the communicating artery,
sinks deeply into the palm between the abductor and flexor quinti digiti brevis,
and joins the radial to form the deep volar arch. (See The Radial Artery.)
THE RADIAL ARTERY
The radial artery — the smaller of the two arteries into which the brachial
divides at the bend of the elbow — appears as the direct continuation of the
brachial. It runs, at first curving laterally, along the radial side of the forearm
as far as the styloid process, then, coiling over the radial collateral ligament and
the lateral and back part of the wrist, enters the palm of the hand from behind be-
tween the first and second metacarpal bones, and ends by anastomosing with the
deep branch of the ulnar to form the deep volar arch. Hence the artery is divisible
into three parts: that in the forearm, that at the wrist, and that in the palm of the
hand. The course of the artery is indicated by a line drawn from a point 2.5
cm. (1 in.) below the centre of the elbow to a point situated just medial to the
styloid process of the radius.
I. The Radial Artery in the Forearm
In its course through the forearm (fig. 470) the radial artery is found in the
most lateral of the intermuscular spaces, and it is only necessary to divide the.
THE RADIAL ARTERY
583
skin, superficial and deep fascia, to expose the vessel, and in addition in the upper
third to separate the brachio-radialis from the pronator teres.
Relations. — In front, the artery is at first overlapped by the brachio-radialis, but for the
rest of its course it is merely covered by the slcin, superficial and deep fascise, by some cutaneous
veins, and by cutaneous branches of the musculo-cutaneous nerve.
Behind, it lies successively from above downward on the tendon of the biceps, the supinator,
from which it is separated by a layer of fat, the insertion of the pronator teres, the radial origin
of the flexor digitorum sublimis, the flexor poUicis longus, the pronator quadratus, and the
volar surface of the lower end of the radius. It is in this last situation, where the artery Ues
upon the bone and can therefore be easily pressed against it, that the pulse is usually felt.
Fig. 474. — Diagram of the Relation of the Arteries of the Left Forearm to
THE Bones. (Walsham.)
Superior ulnar collateral artery
Brachial artery
Inferior ulnar collateral artery
Volar ulnar recurrent
Dorsal ulnar recurrent -
Ulnar artery
interosseous artery
Volar interbsseous artery
Volar ulnar carpal
Superficial branch of ulnar artery
(superficial volar arch)
L volar digital artery
Profunda artery
Lateral epicondyle
Articular branch of profunda artery
Radial recurrent artery
Interosseous recurrent artery
Radial artery
Oblique ligament
Interosseous membrane
Dorsal interosseous artery
Volar radial carpal
Radial artery of wrist
Superficial volar branch of radial
artery
Deep volar arch
On its lateral side it has, throughout the whole of its course, the braohio-radiahs muscle,
the guide to the artery in ligature, and the lateral vena comitans; in its middle third, the
superflcial radial nerve as well. In its lower third the superficial radial nerve is to its lateral
side, but separated from it by the brachio-radialis and fascia.
On its medial side, in the upper third is the pronator teres, in the lower third the tendon
of the flexor carpi radialis, and throughout the whole of its course the medial vena comitans.
The branches of the radial artery in the forearm are: — (1) The radial re-
current; (2) the muscular; (3) the volar radial carpal; (4) the superficial volar.
(1) The radial recurrent [a. recurrens radialis] usually arises from the lateral side of the
radial just below its origin from the brachial. It at first runs laterally on the supinator and then
divides into three chief branches (fig. 475). One of these continues laterally through the fibres
of the radial (musculo-spiral) nerve, or between the superficial (radial) and deep radial (posterior
interosseous) nerves when the radial (musculo-spiral) divides higher than usual, into the brachio-
radiaUs and extensor carpi radiahs longus and brevis, and anastomoses with the interosseous
recurrent. A second ascends between the brachiahs and braehio-radiahs, with the radial
584
THE BLOOD-VASCULAR SYSTEM
(musculo-spiral) nerve, and anastomoses with the profunda artery. A third descends with the
superficial radial nerve under cover of the brachio-radialis, supplying that muscle. The
radial recurrent also gives off branches to the elbow-joint.
(2) The muscular branches [rami musculares] come off irregularly to supply the contiguous
muscles on the lateral side of the forearm.
(3) The volar radial carpal branch [ramus carpeus volaris] arises from the rnedial side of the
radial artery about the level of the lower border of the pronator quadratus. It crosses the front
of the radius beneath the flexor muscles, and anastomoses with the volar carpal branch of the
ulnar, forming the volar carpal rete. This plexus is joined above by terminal twigs from the
volar interosseous artery, and below by recurrent branches from the deep volar arch. It sup-
plies branches to the lower end of the radius, and to the wrist and carpal joints.
(4) The superficial volar branch [ramus volaris superficialis] leaves the radial artery as the lat-
ter vessel is about to turn over the radial collateral ligament to the back of the wrist. It courses
forward over the short muscles of the ball of the thumb, and anastomoses with the superficial.
Fig. 475. — The Bend op the Elbow, Left Side.
(From a dissection by Dr. Alder Smith in the Museum of St. Bartholomew's Hospital.)
Median nerve
Posterior branch of in-
ferior ulnar collateral
Branches of medial
a nti -brachial
cutaneous nerve
Basilic vein
Brachialis
Volar branch of inferiori
ulnar collateral
Median antibrachial vein
Median cubital vein
Tendon of biceps
Lacertus fibrosus
Deep median vein
Ulnar artery
Pronator teres
Vena comitans of
brachial artery
Basilic vein
Brachialis
Cephalic vein
Brachial artery
Dorsal anti-
brachial cuta-
neous nerve
Radial n. and as-
cending branch
of radial recur-
rent artery
'Accessory ceph-
-~ alio vein
Cephalic vein
Ascending br. of
radial recurrent
Deep radial
nerve
Radial recurrent
artery
Brachio-radialis
Superficial
radial
nerve
branch of the ulnar artery to complete the superficial volar arch. It supplies small branches
to the muscles of the ball of the thumb, and frequently terminates in these muscles without
ioining the arch. Occasionally it passes beneath the abductor poUicis brevis.
II. The Eadial Artery at the Wrist
The radial artery at the wrist winds over the radial side of the carpus, under
the extensor tendons of the thumb, from a spot a little below and medial to the
styloid process of the radius to the base of the first interosseous space, where it
sinks between the two heads of the first dorsal interosseous muscle into the palm,
to form, by anastomosing with the deep branch of the ulnar artery, the deep volar
arch. A line drawn from 1.2 cm. (| in.) medial to the styloid process to the
base of the first interosseous space, which can be distinctly felt on the back of
the hand, will roughly indicate the course of the artery (fig. 476).
THE RADIAL ARTERY
585
Relations. — The artery is covered successively by the abductor poUicis longus and extensor
pollicis brevis, by branches of the superficial radial nerve and veins, and, just before it sinks
between the two heads of the interosseous muscle, by the tendon of the extensor pollicis longus.
The branches of the superficial radial nerve to the thumb and index finger cross it. It is at
first somewhat deeply placed beneath the first-mentioned extensor muscles of the thumb;
but subsequently it lies quite superficial, and can be felt pulsating in a fittle triangular depression
bounded on either side by the extensores pollicis longus and brevis, and above by the lower
end of the radius. The artery lies successively on the radial collateral ligament of the wrist, on
the navicular (scaphoid), the greater multangular (trapezium), the base of the first meta-
carpjal bone, and on the dorsal ligaments uniting these bones. It has usually with it two com-
panion veins, and a few branches of the musculo-cutaneous nerve.
Fig. 476. — The Radial Artery at the Wrist, Left Forearm.
(From a dissectionjn the Hunterian^Museum.)
Articular branch of the profunda
Brachialis
Brachio-radialis, cut
Common extensor tendon
Supinator
Dorsal interosseous artery
Abductor pollicis longus
Brachio-radialis, cut
Extensor pollicis brevis
Borsal carpal ligament
Extensor carpi radialis longus
Radial artery
First dorsal metacarpal artery
Extensor pollicis longus
First dorsal interosseous muscle
First dorsal metacarpal artery
Princeps pollicis artery
Dorsal digital artery
Triceps
Rete over olecranon
Interosseous recurrent artery
Anconeus, cut
Extensor carpi ulnaris
Flexor carpi ulnaris
Origin of extensor pollicis longus and
indicis proprius
Dorsal branch of volar interosseous
artery
Interosseous membrane
Dorsal ulnar carpal artery
Extensor carpi radialis brevis
Dorsal radial carpal artery
Fourth dorsal metacarpal artery
Third dorsal metacarpal artery
■^^^ — ' Second dorsal metacarpal artery
-(1) The dorsal radial
The branches of the radial artery at the wrist are:
carpal; (2) the first dorsal metacarpal,
(1) The dorsal radial carpal branch [ramus carpeus dorsaUs] arises from the radial as the
latter vessel passes under the abductor pollicis longus, and runs medially beneath the ex-
tensor carpi radiahs longus and brevis, and the extensor pollicis longus, across the dorsal surface
of the carpus, to anastomose with the dorsal ulnar carpal and with the terminal twigs of the
posterior branch of the volar interosseous artery. This anastomosis is called the dorsal carpal
586 THE BLOOD-VASCULAR SYSTEM
rete [rete carpi dorsale]. From this rete are given oif the second, third, and fourth dorsal
metacarpal arteries to the second, third, and fourth intermetacarpal spaces respectively. These
vessels run downward on the dorsal interosseous muscles as far as the flexure of the fingers, and
there divide into two branches (dorsal digital), which run along the sides of the contiguous
fingers on their dorsal aspect. Near their proximal ends they anastomose with the dorsal
perforating branches of the deep volar arch. Distally they are connected by volar perforating
branches with the digital arteries or the corresponding spaces. The branches which run along
the backs of the fingers anastomose with the dorsal branches of the first dorsal digital arteries
derived from the volar common digital vessels (fig. 476).
(2) The first dorsal metacarpal (figs. 472, 476) is given off by the radial shortly before it
passes between the two heads of the first dorsal interosseous muscle. It quickly divides into
two branches which supply the dorsal surface of the thumb and the radial side of the index-
finger toward its dorsal surface.
III. The Radial Artery in the Palm (Deep Volar Arch)
The radial artery enters the palm between the first and second metacarpal
bones at the base of the first interosseous space, by passing between the two
heads of the first dorsal interosseous muscle. It then runs medially between the
transverse and oblique heads of the adductor pollicis muscle and continuing its
course in a slight curve with the convexity forward, across the base of the meta-
carpal bones and interosseous muscles, it anastomoses with the deep branch
of the ulnar, forming the deep volar arch [arcus volaris profundus]. The arch
may be said to extend from the first interosseous space to the base of the meta-
carpal bone of the little finger, and is a finger's breadth nearer the wrist than the
superficial arch. It is covered by the superficial and deep fiexor tendons, by the
superficial head of the flexor pollicis brevis, and by part of the flexor quinti
digiti brevis. It is accompanied by the deep branch of the ulnar nerve, and two
small venae comitantes (figs. 472, 473).
The branches of the deep volar arch are: — (1) The princeps pollicis; (2) the
radialis indicis; (5) the volar metacarpals (three in number); (4) the recurrent
carpal; (3) the dorsal perforating. The first two are usually spoken of as coming
off from the radial artery in the palm; the last three from the deep volar arch.
(1) The arteria princeps pollicis arises from the radial artery as it enters the palm between
the two heads of the first dorsal interosseous muscle. It passes downward between the adductor
pollicis transversus and the first dorsal interosseous muscle, parallel to the metacarpal bone,
and between the two portions of the flexor polhcis brevis under cover of the flexor polUcis
longus. Opposite the metacarpo-phalangeal joint it usually divides into two branches, one
of which is distributed to each side of the thumb on its volar aspect. These vessels anasto-
mose with each other at the end of the thumb, like the other digital arteries.
(2) The arteria radialis indicis comes off from the radial artery a little lower than the former
vessel, or as a common trunk with it, and passes forward between the first dorsal interosseous
and adductor pollicis transversus, parallel to the radial side of the second metacarpal bone.
After emerging from beneath the adductor poUicis transversus it continues its course along the
radial side of the index-finger, on its volar aspect, as far as the tip, anastomosing in this course
with the digital artery on the opposite side of the finger in a way similar to that of the other
digital arteries. It frequently communicates, at the lower border of the adductor pollicis,
with the superficial volar arch and princeps pollicis. It gives off a dorsal branch, which anasto-
moses with the branch fron the fu-st dorsal metacarpal to the index finger.
(3) The volar metacarpal arteries [aa. metacarpex volares], three in number, come off from
the convexity of the deep arch, and, coursing downward in the centre of the second, third, and
fourth interosseous spaces on the interosseous muscles, terminate near the cleft of the fingers
by anastomosing with the digital arteries from the superficial arch. These vessels supply the
interosseous muscles and the bones, and the second, third, and fourth lumbricales.
(4) The recurrent branches come off from the concavity of the arch, and consist of two or
three small vessels which run upward toward the wrist, and anastomose with the volar branch
of the volar interosseous, and the volar radial and ulnar carpal arteries.
(5) The dorsal perforating brandies (rr. perforantes), which are usnally three in number,
pass from the arch directly through the second, third, and fourth interosseous spaces between
the two heads of the corresponding dorsal interosseous muscle, and join the proximal ends of
the first dorsal interosseous, and the second, third, and fourth dorsal metacarpal arteries re-
spectively.
THE THORACIC AORTA
The thoracic aorta [aorta thoracalis] (fig. 477) is the thoracic portion of the
aorta descendens. It extends from the termination of the aortic arch at the
lower border of the body of the fourth thoracic vertebra to the lower border of
the body of the twelfth thoracic vertebra, where it passes between the medial
THE THORACIC AORTA
587
crura of the diaphragm, and is thence continued under the name of the abdominal
aorta. It is at first situated a little to the left of the vertebral column, but as it
descends, approaches the front of the column, at the same time following the back-
ward curve of the spine, and at the diaphragm is almost in the middle line. It
lies in the posterior mediastinum, having the oesophagus at first a little to the
right of it, then in front of it, and just above the tenth thoracic vertebra, where
this tube pierces the diaphragm, a little to its left side.
Fig. 477. — The Arch of the Aorta, the Thoracic Aorta, and the Abdominal Aorta,
WITH THE Superior and Inferior Vena Cava and the Innominate and Azygos Veins.
Right common carotid
artery
Right internal jugular
Right lymphatic duct
Innominate artery
Right vagus nerve
Right innominate vein
Internal mammary vein
Trunk of the pericardiac
and thymic veins
Superior vena cava
Azygos vein
Hemiazygos vein, cross-
ing spine to enter vena
azygos
Inferior vena cava
Coeliac artery
Right middle suprarenal
artery
Right internal spermatic
artery
Right spermatic vein
Left common carotid
artery
Left vagus nerve
Thoracic duct
Left innominate vein
Left subclavian artery
Left superior intercostal
Recurrent (laryngeal;
nerve
Accessory hemiazygos
vein
(Esophagus
Left upper azygos vein
(Esophageal branches
from aorta
_^ Hemiazygos vein
Thoracic duct
Left inferior phrenic
artery
Left middle suprarenal
artery
Receptaculum chyH
Superior mesenteric
artery
Left ascending lumbar
Left internal spermatic
vessels
Relations. — In front it is crossed from above downward by the root of the left lung, by the
oesophagus, which separates it from the pericardium and heart, and by the diaphragm.
Behind, it hes upon the lower seven thoracic vertebrae, and is crossed obhquely opposite
the seventh or eighth thoracic vertebra by the the vena hemiazygos (azygos minor) and op-
posite the fifth or sixth vertebra by the accessory hemiazygos vein, or by one or more of the
intercostal veins.
On the right side it has, above, the oesophagus and vertebral column; lower down the
right pleura and lung. The vena azygos and thoracic duct also lie to the right, but on a some-
what posterior plane.
On the left side it has the left lung and pleura above, and the oesophagus below. The vena
hemiazygos and the accessory hemiazygos vein are also to the left, but on a posterior plane.
588 THE BLOOD-VASCULAR SYSTEM
Branches of the Thoracic Aorta
The branches of the thoracic aorta may be divided into the visceral and the
parietal. The visceral are: — (1) The pericardiac; (2) the bronchial; and (3) the
oesophageal. The parietal are: — (1) The intercostal; (2) the superior phrenic;
and (3) the arteria aberrans.
A. Visceral Branches
(1) The pericardiac branches [rami pericardiaci] — two or three small branches,
irregular in their origin, course, and distribution — pass to the posterior surface of
the pericardium to supply that structure, and anastomose with the other peri-
cardiac branches. They give small twigs to the posterior mediastinal glands.
(2) The bronchial arteries [aa. bronchiales] supply the bronchi and the lung
substance. They vary considerably in their origin, course, and distribution;
they are usually three in number — one on the right side, and two on the left.
(a) The right bronchial generally arises either from the first right aortic intercostal, or else
as a common trunk witli the left upper bronchial from the front of the aorta just below the level
of the bifurcation of the trachea. It passes laterally on the back of the right bronchus, and is
distributed to the bronchi and lung substance, (b) The left upper bronchial arises from the front
of the aorta just below the bifurcation of the trachea, or as a common trunk with the right
bronchial, (c) The left lower bronchial arises from the front of the aorta just below the level of
the left bronchus. Like the corresponding artery on the right side, the left bronchial arteries
run laterally on the left bronchus, and, after dividing and subdividing on the back of the bronchi,
supply the bronchi themselves and the lung substance. Small twigs are given off from the
bronchial arteries to the bronchial glands and to the oesophagus.
(3) The oesophageal arteries [aa. oesophageae], four or sometimes five in
number, arise at intervals from the front of the descending thoracic aorta, the
first coming off just below the left lower bronchial. They usually increase in
size from above downward, the upper coming off more toward the right side of
the aorta, the lower more toward the left side. They pass forward to the
oesophagus, supplying that tube and anastomosing with each other and with the
descending oesophageal branches of the inferior thyreoid above, and with the
ascending oesophageal branches of the phrenic and gastric arteries below, thus
forming a chain of anastomoses along the whole length of the tube.
B. Parietal Branches
(1) The intercostal arteries [aa. intercostal es], usually ten in number on each
side, supply the lower intercostal spaces, the two upper spaces (occasionally the
first only) being supplied from the costo-cervical trunk of the subclavian artery.
The lowest artery accompanies the twelfth thoracic nerve below the last rib and
is therefore called the subcostal artery. Its distribution is similar to that of the
lumbar arteries (p. 593) except that it commonly crosses the anterior surface,
rather than the posterior, of the quadratus lumborum.
The intercostals arise in pairs from the back part of the aorta, and at once
turning, the one to the right, the other to the left, wind backward over the
front and sides of the vertebral bodies to reach the intercostal spaces. In foetal life
these arteries run almost transversely backward, or even with a slight inclination
downward, to the intercostal spaces; but after the first year, in consequence of
the disproportionate growth of the aorta and vertebral column, the upper int-er-
costals have to ascend to reach their respective spaces.
The arteries in their course around the vertebrae differ on the two sides of the
body. On the right side the arteries — and especially the upper, in consequence
of the aorta lying a little to the left side of the spine in the upper part of its
course — are longer than the left. They wind over the front and right side of the
vertebrae, being crossed by the thoracic duct and vena azygos (major), and covered
by the right pleura and lung. The upper are also crossed by the oesophagus.
They give off small branches to the bodies of the vertebrae and anterior longi-
tudinal Hgament. On the left side, as the intercostals wind around the sides of
the bodies of the vertebrae, the lower are crossed by the vena hemiaz3rgos (azygos
minor), the two upper by the left superior intercostal vein, and the two next by
THE THORACIC AORTA
589
the accessory hemiazygos vein when this is present. They are all covered by
the left pleura and lung (fig. 478).
The branches of the intercostal arteries are: — (a) anterior, (b) posterior.
(a) The anterior branches [rami anteriores] at first cross the intercostal space obliquely, in
consequence of the downward direction of the ribs, toward the angle of the rib above, and
thence are continued forward in the costal groove, and anastomose with the superior branches
of the anterior intercostals from the internal mammary in the upper spaces, and from the
musculo-phrenic in the lower spaces. They he at first on the external intercostal muscles,
being covered in front by the pleura and lung, the endothoracic fascia, and the subcostal
muscles. Opposite the heads of the ribs they are crossed by the sympathetic nerve. At the
angle of the ribs they pass under cover of the internal intercostal muscles, and thence to their
termination he between the two intercostal muscles. Their situation in the midspace as far
as the angle of the rib should be remembered in performing paracentesis thoracis. To avoid
the risk of injuring the vessels, the puncture should not be made further back than the angle
of the ribs. They are accompanied by a nerve and vein, the vein lying above and the nerve
below, except in the upper spaces, where the artery, having to ascend to reach the space, at
first Mes below the nerve which runs more horizontally. The uppermost branch anastomoses
with the costo-oervical artery from the subclavian, and at times supplies almost entirely the
second intercostal space. The arteries to the tenth and eleventh spaces on reaching the end
Fig. 478. — Scheme op Intercostal Abtebt. (Walsham.)
Longissimus dorsi
Medial cutaneous branch
Semlspinalis dorsi and multifidus spinse
Prelaminar branch
Neural branch
Postcentral branch
Spinal cord
Anterior spinal artery
Lateral cutaneous branch
llio-costalls
Intercostal artery
Vena hemiazygos
Vena azygos
Thoracic duct
(Esophagus
Anterior intercostal
Internal mammary artery
Anterior cutaneous branch'
Posterior branch
Sympathetic
Collateral branch
Medial mammary
branch
^ Upper or main branch
of anterior intercostal
of their respective ribs pass between the abdominal muscles, and anastomose with the inf.
epigastric artery from the external ihac, and with the lumbar arteries from the abdominal
aorta. The artery beneath the twelfth rib anastomoses with the lumbar arteries and with
the external circumflex ihac.
Each anterior branch gives off the following: — (i) The collateral branch which comes off
near the angle of the rib and runs forward, between the external and internal intercostals,
along the upper border of the lower rib enclosing the space. It is smaller than the main anterior
branch and anastomoses with tlie lower anterior intercostal in each space, (ii) Muscular
branches [rami nmsculares] supply the intercostal, pectoral and abdominal muscles, (iii)
The lateral cutaneous branches [rami cutanei laterales], both pectoral and abdominal, run with
the corresponding branches of the intercostal nerves through the external intercostal and ser-
ratus anterior muscles. They then divide into anterior and -posterior branches which turn for-
ward and backward, respectively, to supply the integument. The anterior branches from the
third, fourth and fifth spaces supply lateral mammary branches [rr. mammarii laterales] to the
lateral region of the breast, (iv) Anterior cutaneous branches [rami cutanei anteriores]
pierce the external intercostal ligament and the pectorahs major just lateral to the sternum.
590 THE BLOOD-VASCULAR SYSTEM
They are distributed to the skin and give medial mammary branches [rr. mammarii mediales]
to the medial region of the breast.
(b) The posterior branches [rami posteriores]. — These large branches are given oil from the
intercostals opposite the quadrilateral space bounded by the transverse process of the vertebra
above, the neck of the rib below, the body of the vertebra medially, and the anterior costo-
transverse ligament laterally. Passing backward toward this space with the dorsal branch
of the corresponding intercostal nerve, they divide opposite the intervertebral foramen into a
muscular and a spinal branch, (i) The muscular branch [r. muscularis] passes backward
through the quadrilateral space, and soon subdivides into a medial and a lateral branch. The
former passes between the longissimus dorsi and iUo-costaUs, and, after supplying these muscles,
gives off medial cutaneous branches [rr. cutanei mediales]. The latter branch pierces the multi-
fidus spinas, and, emerging between the longissimus dorsi and semispinahs dorsi near the spinous
processes, gives off lateral cutaneous branches [rr. cutanei laterales]. It suppHes the muscles ■
in its course.
(ii) The spinal branch [r. spinalis] enters the intervertebral foramen with the spinal nerve
of the corresponding segment. The disposition of the spinal branch is similar to_ that of the
spinal branches entering the canalis vertebralis in other regions and may be described here: —
ARTERIES OF THE VERTEBRAL CANAL
Spinal arteries are derived from the vertebral, ascending cervical and costo-cervical arteries,
from the dorsal rami of the intercostal (fig. 478) and lumbar arteries, and from the ilio-lumbar
and lateral sacral arteries. The spinal branch in each case divides into three branches, post-
central, prelaminar and neural.
Each post-central branch divides on the lateral part of the posterior longitudinal ligament
into an ascending and a descending branch by which means a bilateral series of anastomosing
arches are formed throughout the length of the canal. From the concavities of the opposite
arches transverse connecting stems are formed which are again connected by a median longitu-
dinal channel.
The pre-laminar branches also divide and form an anastomosis in front of the laminse
and ligamenta flava. This is similar in character to the post-central, but much less regular.
The neural branches enter the dura mater and are usually small and end by supplying the
nerve roots. A variable number of these (5-10 on a side) are larger than the others and rein-
force the longitudinal anterior and posterior spinal arteries given off from the vertebrals within
the cranium. (For arteries of the spinal cord, see Section VII.)
(2) The superior phrenic arteries [aa. phrenicse superiores], are small twigs
coming off from the thoracic aorta immediately above the diaphragm. They are
distributed to the vertebral portion of the diaphragm on its upper surface.
(3) The arteria aberrans is a small twig which, arising from the thoracic
aorta near the right bronchial artery, passes upward and to the right behind the
oesophagus and trachea, and is occasionally found to anastomose on the oesophagus
with the arteria aberrans of the superior intercostal artery (see p. 568). It is
regarded as the remains of the right aortic dorsal stem (fig. 506).
(4) The mediastinal branches [rami mediastinales], numerous, but small, are
distributed to the pleura, and the vessels, nerves and lymph-nodes of the posterior
mediastinum.
THE ABDOMINAL AORTA
The abdominal aorta [aorta abdominalis] (fig. 479), the abdominal portion of
the descending aorta, begins at the aortic opening in the diaphragm opposite the
lower broder of the twelfth thoracic vertebra, and ends usually opposite the middle
of the body of the fourth lumbar vertebra by dividing into the right and left
common iliac arteries. It is at first centrally placed between the medial crura
of the diaphragm, but as it descends in front of the lumbar vertebrse it leaves the
middle line, and, at its bifurcation, lies a little to the left side of the spine.
The place at which the aorta bifurcates may be somewhat roughly indicated on the surface
of the abdomen by a point about 2.5 cm. (1 in.) below and a little to the left of the umbilicus.
The level of its bifurcation may be more accurately determined by drawing a straight line
across the front of the abdomen joining the highest points of the iliac crests.
The inferior vena cava, which accompanies the abdominal aorta, lies to its
right side. Below, the vein is in contact with the artery and on a somewhat
posterior plane; but above, it is separated from the aorta by the right medial crus
of the diaphragm, and, in consequence of the caval opening in the diaphragm
being placed further forward than the opening for the aorta, is on an anterior
plane.
THE ABDOMINAL AORTA
591
Relations. — In front, the aorta is successively crossed from above downward by the right
lobe of the liver, the cceHac (solar) plexus, the lesser omentum, the termination of the oesophagus
in the stomach, the ascending layer of the transverse meso-colon, the splenic vein or commence-
ment of the portal vein, the pancreas, the left renal vein, the third portion of the duodenum,
the mesentery, the aortic plexus of the sympathetic nerve, the internal spermatic or ovarian
arteries, the inferior mesenteric artery, the median lumbar lymphatic nodes and lymphatic
vessels, and the small intestines.
Of these structures the cceliac (solar) plexus, the aortic plexus, the splenic vein or the
commencement of the portal vein, the pancreas, the left renal vein, the duodenum, the lym-
phatics, the spermatic or ovarian arteries, and the peritoneal reflexions are in contact with the
aorta.
Behind, the aorta hes upon the bodies of the lumbar vertebrae and intervening intervertebral
cartilages, the anterior longitudinal ligament, the origin of the left medial crus of the diaphragm,
and the left lumbar veins.
Fig. 479. — The Abdominal Aorta and its Branches, with the Inferior Vena Cava and
ITS Tributaries.
Cystic arterj
Hepatic duct —
Cystic duct
Commoa duct
Portal vem_
Gastro-duodenal br __
Right gastric artery_
Hepatic artery^
Right suprarenal vein
Inferior suprarenal
artery
Renal artery
Renal vein
Vena cava inferior
Kidney
Right spermatic \
Right internal spermatic
artery
Quadratus lumborum
muscle
Right lumbar artery
and left lumbar vein
Ureteric branch of —
spermatic artery
Middle sacral vessels.
Left lobe of liver
(Esophagus
Left inferior phrenic
artery
Right inferior phrenic
artery
Superior suprarenal
Left gastric artery
Inferior suprarenal
Splenic artery
— — • Left phrenic vein
— — Left suprarenal vein
,. . \— Superior mesenteric
ir^., ^''"^
Kidney
Ureteric branch of renal
Left spermatic vein
Left internal spermatic
artery
Inferior mesenteric
artery
Ureteric branch of
spermatic
Ureteric branch of
common iliac
Common iliac artery
External iliac artery
Hypogastric artery
On the right side from above downward are the right medial crus of the diaphragm, the
great splanchnic nerve, the caudate lobe of the liver, tlie receptaculum chyU and beginning
of the thoracic duct (the two latter structures are on a posterior plane), the right coeHac (semi-
lunar) gangUon, and the inferior vena cava.
On the left side are the left medial crus of the diaphragm, the left splanchnic nerve, and
the left cocliac (semilunar) ganghon. The pancreas is also in contact with the aorta on the
left side, and the small intestines are separated from it only by peritoneum.
Branches of the Abdominal Aorta
The branches of the abdominal aorta usually arise in the following order from
above downward (figs. 479, 480) : — ■
(1) Right and left inferior phrenic; (2) coeliac; (3) right and left middle
suprarenal; (4) right and left first lumbar; (5) superior mesenteric; (6) right and
592
THE BLOOD-VASCULAR SYSTEM
left renal; (7) right and left internal spermatic; (8) right and left second lumbar;
(9) inferior mesenteric; (10) right and left third lumbar; (11) right and left fourth
lumbar; (12) right and left common iliac; (13) middle sacral.
The above branches may be divided into the parietal, the visceral, and the
terminal.
The parietal branches are distributed to the abdominal walls. They are the
right and left phrenics, and the four right and left lumbars.
The visceral branches supply the viscera. Three of these are given off singly
from the front of the aorta, namely, the cceliac, the superior mesenteric, and the
inferior mesenteric; and three are given off in pairs, namely, the two suprarenals,
the two renals, and the two spermatics.
The terminal branches are the middle sacral and the right and left common
iliac arteries.
Fig. 480. — Scheme of the Abdominal Aorta. (Walsham.)
Lesser nmpntnm^ *'*^
Pancreas
Left renal vein
Superior mesenteric
artery
Transverse meso-colon
Inferior part of
duodenum
Transverse colon
Mesentery
Small intestines
Great omentum'
Inferior mesenteric
artery
Thoracic duct
Cceliac artery
First lumbar vein
Cisterna chyli
Second lumbar vein
Peritoneum
Third lumbar vein
Fourth lumbar vein
A. The Parietal Branches of the Abdominal Aorta
1. THE INFERIOR PHRENIC ARTERIES
The inferior phrenic artery [a. phrenica inferior] usually arises from the aorta
as it passes between the medial crura of the diaphragm. At times it comes off
from the cceliac artery; or when it arises as two separate vessels, either the right
or left vessel may come from this artery, or from other of the upper branches of
the abdominal aorta.
The right phrenic passes (fig. 480) over the right medial crus of the diaphragm behind
the vena cava, and then upward and to the right between the central and right leaflets of the
central tendon of the muscle, where it divides into an anterior and a posterior branch. The
former courses anteriorly and medially and anastomoses with the anterior branch of the left
phrenic, with the musculo-phrenio branches of the internal mammary, and with the pericardio-
phrenic arteries; the latter passes posteriorly and laterally toward the ribs, and anastomoses
with the intercostal arteries. Besides the two terminal branches and branches for the supply
of the diaphragm itself the right phrenic gives off the right superior suprarenal [ramus supra-
renaUs superior], to the right suprarenal gland, as well as branches to the vena cava,- to the
hver, and to the pericardium.
The left phrenic crosses the left medial crus of the diaphragm behind the CESophagus,
and, like the right artery, divides into an anterior and posterior branch and gives off a left
suprarenal branch. The distribution and anastamoses are similar on the two sides.
THE LUMBAR ARTERIES 593
2. THE LUMBAR ARTERIES
The lumbar arteries [aa. lumbales] (fig. 479), usually eight in number, four on
each side, come off in pairs from the posterior aspect of the abdominal aorta,
opposite the bodies of the four upper lumbar vertebrae. A fifth pair of lumbar
arteries, generally of small size, frequently arises from the middle sacral artery
opposite the fifth lumbar vertebra. The lumbar arteries, which are rather longer
on the right than on the left side, in consequence of the aorta lying a little to the
left of the median line, wind more or less transversely around the bodies of the
vertebrae to the space between the transverse processes, where they give off each a
dorsal branch, and then, coursing forward between the abdominal muscles, termi-
nate, by anastomosing with the other arteries of the abdominal wall.
Relations. — As they wind around tlie bodies of the vertebra they pass beneath the chain of
the sympathetic nerve trunk, and the upper two beneath the crura of the diaphragm. The
right arteries also pass beneath the vena cava inferior, and the two upper on that side beneath
the receptaculum chyli. The arteries on both sides then dip beneath the tendinous arch thrown
across the sides of the bodies of tlie vertebrae by the psoas, and continue beneath this muscle
until they arrive at the interval between the transverse processes of the vertebrae and the
medial edge of the quadratus lumborum. While under cover of the psoas they are accompanied
by two slender filaments of the sympathetic nerve and by the lumbar veins. A httle anterior
to the transverse processes they are crossed by branches of the lumbar plexus, and here usually
cross in front of the ascending lumbar vein. They now pass behind the quadratus lumborum,
with the exception sometimes of the last, which ma}' pass in front of the muscle. At the lateral
edge of the quadratus they run between the transversus and the internal oblique, and then, after
perforating the internal oblique between the internal and external oblique. Finally, much
diminished in size, they enter the rectus, and give off one or more anterior cutaneous branches,
which accompany the last thoracic and the ilio-hypogastric nerves to the skin. They
anastomose with the lower intercostals, ilio-lumbar, deep ckcumflex iliac, and inf. epigastric
arteries.
The branches of the lumbar arteries are ; —
(a) Vertebral branches which supply the bodies of the vertebrae and their connecting
ligaments.
(6) Muscular branches to the psoas, quadratus lumborum, and obUque muscles of the
abdomen.
(c) The dorsal branch [r. dorsahs]. This is of large size, and passes backward in company
with the dorsal nerve between the transverse processes above and below, the intertransversalis
medially and the quadratus lumborum laterally, to the muscles of the back. On reaching the
interval between the longissimus dorsi and multifidus spinae, it divides into a lateral and a
medial branch. The former ends in the multifidus, the latter and larger supphes the sacro-
spinalis, and gives branches which accompany the termination of the dorsal nerves to the skin.
Just before the artery passes between the transverse processes it gives off a spinal branch fr.
spinalis], which accompanies the lumbar nerve through the intervertebral foramen into the
vertebral canal (see p. 590).
(d) Renal branches of small size pass forward in front of the quadratus lumborum to the
capsule of the kidney. They anastomose with the renal artery. A communication is thus
established between the renal arteries and the arteries supplying the lumbar region.
B. The Visceral Branches of the Abdominal Aorta
THE CCELIAC ARTERY
The coeliac artery [a. coeliaca] — or coeliac axis, as it is commonly called,
because it breaks up simultaneously into three branches which radiate from it
like the spokes of a wheel from the axle — is a short thick trunk given off from
the front of the aorta between the medial crura of the diaphragm a little below
the aortic opening. It passes horizontally forward above the upper margin
of the pancreas for about half an inch, and then breaks up into three branches
for the supply of the stomach, duodenum, spleen, pancreas, liver, and gall-
bladder (fig. 481).
Relations. — In front is the lesser omentum; behind, the aorta; above, the right lobe of the
liver; below, the pancreas; to the right, the right coeliac (semilunar) ganghon and caudate lobe
of the liver; to the left, the left cceliac (semilunar) ganglion and the cardiac end of the stomach.
It is closely surrounded by the dense coeliac (solar) ple.xus of sympathetic nerves.
Branches of the coeliac artery. — The ccehac artery divides into the left
gastric, the hepatic, and the splenic arteries.
1. The Left Gastric Artery
The left gastric [a. gastrica sinistra] (fig. 481), the smallest of the three
branches into which the coeliac artery divides, courses at first upward and to the
594
THE BLOOD-VASCULAR SYSTEl
left toward the cardiac end of the stomach, where it turns sharply round, and then,
following the lesser curvature of the stomach, descends from left to right toward
the pylorus. It anastomoses with the right gastric branch of the hepatic artery,
which has proceeded from the opposite direction, the two branches thus forming a
continuous arterial arch corresponding to the lesser curvature of the stomach.
The artery at first lies behind the posterior layer of the omental bursa of peritoneum
(fig. 480), but on reaching the cardiac end of the stomach it passes, between the layers of
peritoneum reflected from the diaphragm onto the oesophagus, into the lesser omentum in which
it then runs to its terminal anastomosis with the pyloric. It is surrounded by a plexus of
sympathetic nerves.
It supplies both surfaces of the stomach around the lesser curvature and gives off email
CBSophageal branches [rami oesophagei] which anastomose with the oesophageal branches
from the thoracic aorta.
Fig. 481. — -The Cceliac Artery and its Branches.
Abdominal aorta
Right medial crus of diaphragm
Cystic artery
Right inferior
phrenic artery
Hepatic duct
Cystic duct
Splenic artery
Common bile
duct
Right gastric v
artery "^
Gastro-duod-
enal artery
Superior pan-
creatico - du-
odenal artery
Head of ^
pancreas
Inferior pan-
creatico - du-
Left crus of diaphragm
(Esophageal branch
Coeliac artery
Left gastnc
artery Vasa brevia
odenal artery _^
Right gastro-
epiploic artery
2. The Hepatic Artery
Left gastro-epiploic artery
The hepatic artery [a. hepatica], the largest branch of the coeliac artery in the
foetus, but intermediate in the adult between the left gastric and the splenic,
comes off on the right side of the coeliac artery, and, winding upward and to the
right to the porta (portal fissure) of the liver, there breaks up into two chief
branches for the supply of the right and left lobes of that organ. It at first courses
forward and to the right along the upper border of the head of the pancreas, behind
the posterior layer of the peritoneal omental bursa, to the upper margin of the
duodenum, where it passes forward beneath the layer of peritoneum forming
the floor of the epiploic foramen (of Winslow). It thus runs between the two
layers of the lesser omentum, and ascends along with the hepatic duct which lies
to its right, and with the portal vein which lies behind it (figs. 480, 481).
The branches of the hepatic artery are: — (1) The right gastric; (2) thegastro-
duodenal; (3) the hepatic proper.
(1) The right gastric artery [a. gastrica dextra] comes off from the hepatic just
as the latter vessel enters the lesser omentum, and, descending between the two
layers of that fold of peritoneum to the pylorus, there turns to the left, and,
ascending from right to left, anastomoses along the lesser curvature of the
stomach, as already mentioned, with the left gastric artery, which descends
from the opposite direction.
(2) The gastro-duodenal artery [a. gastroduodenalis] arises from the hepatic
THE SPLENIC ARTERY 595
a little beyond the pyloric. It descends behind the superior portion of the
duodenum to the lower border of the pylorus, where it divides into the right
gastro -epiploic and the superior pancreatico-duodenal. It varies from 1.2 to
2.5 cm. (I to 1 in.) in length.
(a) The right gastro-epiploic artery [a. gastroepiploica dextra] passes from right to left
along the greater curvature of the stomach between the laj;ers of the great omentum, and
anastomoses with the left gastro-epiploic branch of the splenic. From this anastomotic arch
are given oS: — (i) Ascending or gastric branches, which supply the anterior and posterior
surfaces of the stomach, and anastomose with the descending gastric branches of the arteries
along the lesser curvature, (ii) Epiploic [rami epiploici] or omental branches — long slender
vessels which descend between the two anterior layers of the great omentum, and then, looping
upward, anastomose with similar slender branches given off from the middle and left colic,
and passing down in Uke manner between the two posterior layers of the great omentum.
(6) The superior pancreatico-duodenal [a. pancreaticoduodenaUs superior] — the smaller
division of the gastro-duodenal — arises from that vessel as it passes behind the first portion of
the duodenum, and courses downward behind the peritoneum, in the anterior groove between
the second portion of the duodenum and the pancreas, to anastomose with the inferior pan-
creatico-duodenal, a branch of the superior mesenteric. Both the inferior and superior pan-
creatico-duodenal give off duodenal [rami duodenales] and pancreatic branches [rami pancreatici]
to supply these organs.
(3) The hepatic artery proper [a. hepatica propria] is the continuation of the
hepatic after the gastro-duodenal has arisen. It ascends between the layers of
the lesser omentum, preserving the relations of the main artery to the portal vein
and common bile (and hepatic) duct, and divides, near the porta hepatis, into
right and left branches.
(a) The right branch [r. dexter], given off at the porta (portal fissure) of the liver, runs to the
right either behind the hepatic and cystic ducts, or between these strucures. At the right end
of the porta it divides into or more branches, which again subdivided as they enter the hver sub-
stance for the supply of the right lobe. As it crosses the cystic duct it gives off the cystic artery.
The cystic artery [a. cystica] courses forward and downward through the angle formed
by the union of the hepatic and cystic ducts, and just before it reaches the gall-bladder divides
into a superficial and deep branch. The former breaks up into a number of small vessels, which
ramify over the free surface of the gall-bladder beneath the peritoneal covering, and furnish
branches to the muscular and mucous coats. The deep branch ramifies between the gall-
bladder and the liver^ubstance, supplying each, and anastomosing with the superficial branch.
(b) The left branch [r. sinister], the smaller division of the hepatic artery, runs medialward
toward the left end of the porta hepatis, and, after giving off a distinct branch to the caudate
(Spigelian) lobe, enters the left lobe of the liver.
3. The Splenic Artery
The splenic artery [a. lienalis] — the largest branch of the cceliac artery —
arises from the left side of the termination of that vessel below the left gastric,
and passes along the upper border of the pancreas in a tortuous manner to the
spleen. It at first lies behind the ascending layer of the transverse meso-colon,
but on nearing the spleen enters the lieno-renal ligament, and there breaks up
into numerous branches, which enter the hilus and supply the organ. In this
course it crosses in front of the left medial crus of the diaphragm and the upper
end of the left kidney and is placed above the splenic vein.
The branches of the splenic artery are: — (1) The pancreatic; (2) the left
gastro-epiploic; (3) the vasa brevia; and (4) the terminal.
(1) The pancreatic branches (rami pancreatici) come off from the splenic at varying intervals
as that vessel courses along the upper margin of the pancreas. They enter and supply the
organ. One larger branch usually arises from the splenic about the junction of its middle
with its left third. Entering the pancreas obUquely, it runs from left to right, commonly above,
and a httle behtad, the pancreatic duct, whidh it supplies together with the substance of the
organ.
(2) The left gastro-epiploic [a. gastroepiploica sinistra] arises from the splenic near the
greater curvature and below the fundus of the stomach, and, passing between the anterior
layers of the great omentum, descends along the greater curvature of the stomach from left
to right, and anastomoses with the right gastro-epiploic. Like that vessel, it gives off ascend-
ing or gastric branches to the anterior and posterior surfaces of the stomach respectively, and
long slender descending epiploic or omental branches to the great omentum which anastomose
with like branches from the right and left colic arteries.
(3) The vasa brevia [aa. gastrics breves] come off from the splenic just before it divides into
its terminal branches, oftentimes from some of these terminal branches themselves. Passing
from between the folds of the Ueno-renal ligament into those of the gastro-henal, they thus
reach the fundus of the stomach, where, ramifying over both its anterior and posterior surfaces,
they anastomose with the left gastric and left gastro-epiploic arteries.
596
THE BLOOD-VASCULAR SYSTEM
(4) The splenic or terminal branches, five to eight or more in number, are given off from the
splenic as it lies in the lieno-renal ligament, and, entering the spleen at the hilum, are distributed
in the way mentioned in the description of that organ.
THE SUPERIOR MESENTERIC ARTERY
The superior mesenteric artery [a. mesenterica superior] is given off from the
front of the aorta a little below the cojliac, which it nearly equals in size; some-
times it forms a common trunk with the coehac. Lying at first behind the pan-
creas and splenic vein, it soon passes forward between the lower border of that
gland and the upper border of the inferior portion of the duodenum, and, crossing
in front of the duodenum, enters the mesentery, in which it runs from left to' right,
in the form of a curve with its convexity to the left, to the caecum, where it
anastomoses with its ileo-colic branch. Its vein Hes to its right side above, having
Fig. 482. — The Supekior Mesbntekic Artery and Vein.
(The colon is turned up, and the small intestines are drawn over to the left side.)
Middle colic
artery
Inferior pancre
atico-duodenal ^
artery
Right colic
artery \
Ileo-colic artery
Left colic artery
Superior mes-
enteric artery
previously crossed obhquely in front of the artery from left to right. It is sur-
rounded by the mesenteric plexus of nerves. The accessory portion of the head
of the pancreas dips in behind the vessel.
The branches of the superior mesenteric are, in their primitive order: —
(1) the inferior pancreatico-duodenal; (2) the intestinal arteries; (3) the ileo-
colic; (4) the right colic; and (5) the middle colic.
(1) The inferior pancreatico-duodenal [a. pancreatico duodenaUs inferior] arises either from
the superior mesenteric as that vessel emerges from the contiguous margins of the pancreas
and inferior part of the duodenum or from its first intestinal branch. Crossing behind the
superior mesenteric vein, it courses upward and to the right between the head of the pancreas
and the duodenum, and beneath the ascending layer of the transverse meso-colon, to anas-
tomose with the superior pancreatico-duodenal.
(2) The intestinal arteries [aa. intestinales] arise from the convex side of the superior
mesenteric, and, varying from twelve to sixteen in number, radiate in the mesentery, where
THE SUPERIOR MESENTERIC ARTERY
597
Fig. 483. — The Blood-vessels of the Ileo-c^cal Region. (From Kelly.)
(Arteries red, veins blue.) The peritoneal covering is removed so as to show the vessels more
clearly. Above and to the right are seen the cut ends of the ileo-cohc artery and vein. This
artery gives off a branch to the ascending colon and a posterior and anterior ctecal artery,
the latter descending through the ileo-colic fold. A short anastomosis connects the ileo-
cohc with the mesenteric. The artery of the vermiform process (appendix) is seen to
arise from the posterior cfecal artery, 2 cm. above the ileum. It passes behind the ileum
in the free border of the mesappendix and gives off five branches (long appendices have
8-12, short appendices, 2-3), which traverse the mesappendix at fairly regular intervals
in the direction of the hilus of the appendix, where they divide into anterior and posterior
branches. The branches in the me.sappendix are sometimes seen to anastomose, forming
loops of varying size. The terminal branch curves around the tip. The CEeco-appendicular
junction is supplied by a separate branch arising likewise from the posterior ileo-caecal trunk.
This branch may or may not anastomose with the proximal appendicular twig and while
in some cases it supplies only the caecum, in others, as in the present case, it sends a few
dehcate branches into the appendix. At the place where this caeco-appendicular artery
crosses the ileo-caecal fold it is seen to give off a dehcate recurrent twig to this structure.
Throughout their entire course the arteries are accompanied by veins.
598 THE BLOOD-VASCULAR SYSTEM
each divides into two branches, which inosculate with similar branches given oS from the
branch above and below. From the primary loops thus formed, secondary loops are derived
in Hke manner, and from these tertiary, and at times quaternary, or even quinary loops. From
the ultimate loops terminal jejunal and iliac branches [aa. jejunales et iliea;] pass on to the muscu-
lar coat of the gut. These terminal vessels bifurcate, the two branches encircling the intestine,
and thus forming with those above and below a series of vascular rings surrounding the small
intestine throughout its whole length. The first intestial artery anastomoses with the pancre-
atico-duodenal arteries, and the last (the continuation of the main artery) with the Ueo-coUc.
These branches of the superior mesenteric in their course to the intestine also supply the
mesentery and the mesenteric glands.
(3) The ileo-colic [a. ileocolica] descends behind the peritoneum toward the caecum, where
it divides into a cohc branch which tracks upward beneath the peritoneum to anastomose with
the descending branch of the right cohc; and into an ihac branch which passes between the
layers of the mesentery and anastomoses with the termination of the superior mesenteric
artery. Near the site of division the ileo-colic gives off anterior and posterior csecal branches.
From the latter of these arises a caeco-appendicular artery, to the caecum and root of the vermi-
form process, and a main appendicular artery [a. appendicularis] (fig. 483).
(4) The right colic [a. colica dextra] — sometimes given off as a common trunk either with
the middle colic or with the ileo-colic — passes to the right behind the peritoneum to the back
of the ascending colon, where it divides into an ascending branch, which anastomoses with the
descending branch of the middle cohc, and a descending branch which anastomoses with the
ascending or colic branch of the ileo-cohc.
(5) The middle colic [a. colica media], arising from the concavity of the superior mesenteric
a little below the pancreas, enters the transverse meso-colon, and divides into two branches —
one of which passes to the left and anastomoses with the ascending branch of the left colic;
the other, winding downward and to the right, anastomoses with the ascending branch of the
right colic.
THE RENAL ARTERIES
The renal arteries [aa. renales] come off one on each side of the abdominal
aorta, a little below the superior mesenteric and first lumbar arteries, on a level
with the first lumbar vertebra. They pass laterally across the crura of the
diaphragm to the kidneys, the right being on a slightly lower plane and somewhat
longer than the left, and passing behind the inferior vena cava. In front of each
is the corresponding renal vein, and behind, at the hilus of the kidney, is the com-
mencement of the ureter. Each artery as it enters the hilus usually divides into
three main stems, one of which passes toward the upper part of the pelvis, a second
to its middle portion, and a third to its lower. Each of these primary stems then
divides so that there result from seven to nine secondary branches, the majority
of which pass anterior to the pelvis, while the remainder are posterior to it (fig.
484). No anastomoses take place between the branches of the anterior and
posterior secondary stems and hence a longitudinal incision into the kidney along
its curved border, half way between the anterior and posterior calices, will cut
only terminal arteries.
The branches of the renal arteries are : —
(1) The inferior suprarenal [a. suprarenahs inferior] which ascends to the suprarenal body.
(2) The capsular or peri-renal branches to the capsule of the kidney and peri-renal fat.
(3) The ureteral branch to the upper end of the ureter.
THE MIDDLE SUPRARENAL ARTERIES
The middle suprarenal artery [a. suprarenahs media] comes off, one on each
side from the aorta, just above the first lumbar artery, and passes laterally to the
suprarenal body, across the medial crura of the diaphragm a little above the renal
arteries. In the foetus they equal the renals in size. In the adult they are much
smaller.
They anastomose with the superior and inferior suprarenal arteries from the
inferior phrenic and renal arteries respectively. For the distribution of the
suprarenal vessels within the suprarenal bodies, see Section XII.
THE INTERNAL SPERIVIATIC ARTERIES
The internal spermatic arteries [a. spermatica interna], (fig. 479), right and
left, come off from the front of the abdominal aorta. They diverge from each
other as they descend over the aorta and psoas muscle to the abdominal inguinal
(internal abdominal) ring, where they are joined by the ductus deferens, and, pass-
THE INTERNAL SPERMATIC ARTERIES
599
ing with it through the inguinal canal and out of the subcutaneous inguinal (ex-
ternal abdominal) ring, run downward into the scrotum in a tortuous course to the
testes. They terminate in branches to the epididymis and body of those organs.
Within the abdomen they lie beneath the peritoneum, and cross in their descent
over the ureters and distal ends of the external iliac arteries; the right being super-
FiG. 484. — A. The Renal Artery and the Distribution of its Branches in Relation
TO THE Pelvis. B. Transverse Section through the Middle op the Same Kidney.
(After Brodel, Johns Hopkins Hospital Bulletin.)
o, renal artery; a' and a", its anteiior and pubtenor branches, 6, branches to pyramids; c, line
of division between anterior and po&tenoi pyi imids The arrow and dotted Una indicate
the line of separation between tin fi lunn iK ot the anterior and posterior branches.
ficial to the vena cava, and behind the termination of the ileum; and the left
beneath the sigmoid colon. In the inguinal canal and in the scrotum the sper-
matic veins lie in front of the artery, and the ductus deferens lies behind it.
In the foetus these vessels pass in a transversely lateral direction to the testis,
which in early foetal life lies in the loin in front of the kidney; but as the testes
600 THE BLOOD-VASCULAR SYSTEM
Fig. 485. — The Vascular Trunks of iiii: Li>wi:k Ahimi.mf.x. (From l\f'lly, by Brodel.)
THE INTERNAL SPERMATIC ARTERIES
601
descend to the scrotum, the vessels become elongated, and are drawn with the
testis into the scrotum.
The branches of the internal spermatic artery are: — (1) Ureteral; (2) cre-
masteric; (3) epididymal; and (4) testicular.
(1) The ureteral are small branches given off to the ureter as the spermatic artery crosses
it. They anastomose with the other ureteral branches derived from the renal, common ihac,
and vesical arteries.
(2) The cremasteric are small branches given off to the cremaster muscle; they anastomose
with the cremasteric branch of the inf. epigastric.
Fig. 486. — The Ovakian Vessels. (After Clark.)
1
(3) The epididynal are distributed to the epididymic, and anastomose with the deferential
artery.
(4) The testicular arteries [aa. testiculares] are the terminal branches of the spermatic;
they perforate the tunica albuginea posteriorly, and are distributed to the body of the organ in
the way mentioned in the section on the Testis.
The e.xternal spermatic artery is a branch of the inferior epigastric artery (p. 614).
602
THE BLOOD-VASCULAR SYSTEM
THE OVARIAN ARTERIES
The ovarian arteries [aa. ovaricse], are the homologues of the internal sper-
matic arteries in the male, and correspond in their relations in the upper part of
their course. They diverge somewhat less, however, and, on reaching the level
of the common iliac artery, turn medialward over that vessel and descend tor-
tuously into the pelvis between the folds of the broad ligament to the ovaries.
In the broad hgament the ovarian artery lies below the Fallopian tube, and on
reaching the ovary turns backward and supplies that organ. In fig. 486 is shown
how the artery enters the hilus of the ovary and breaks up into_branches which
determine the lobules of the organ.
The branches of the ovarian arteries are: — (1) Ureteral; (2) tubal; (3) uterine;
and (4) ligamentous.
(1) The ureteral is distributed, as in the male, to the ureter.
F(2) The tubal suppKes the isthmus and ampulla of the tuba uterina (Fallopian tube) and
its fimbriated extremity.
(3) The uterine runs beneath the tuba uterina (Fallopian tube) to the uterus, supplying
the upper part of the fundus, and anastomosing with the uterine arteries from the hypogastric.
(4) The ligamentous is distributed to the round ligament, passing with that structure through
the inguinal canal, and anastomosing with the superficial external pudendal artery.
Like the spermatic, the ovarian arteries in the foetus come off at right angles to the aorta,
and pass transversely lateralward to the ovaries, which are formed, as are the testes, in the
right and left loin in front of the kidneys. They elongate as the ovaries descend into the pelvis.
During pregnancy these arteries undergo great enlargement.
THE INFERIOR MESENTERIC ARTERY
The inferior mesenteric artery [a. mesenterica inferior], smaller than the
superior, arises from the front of the abdominal aorta about 3.7 cm. (1| in.)
Fig. 487. — The Inferiob Missenteeic Artery and Vein.
(The colon is turned up, and the small intestines me drawn to the right side.)
Middle colic artery
Inferior pancreatico-
duodenal artery
Superior mesenteric
artery
Right colic artery
Abdominal aorta
Vena cava inferior
Right common iliac
artery
Middle sacral artery
and vein
Left colic artery
teric artery
Left colic artery
Inferior mesen-
teric artery
Sigmoid artery
Superior haemor-
rhoidal artery
above the bifurcation of that vessel. It runs obliquely downward and to the
left, behind the peritoneum, across the lower part of the abdominal aorta a,nd then
over the left psoas muscle and left common iliac artery. It descends into the
THE COMMON ILIAC ARTERIES 603
pelvis between the layers of the sigmoid meso-colon, and terminates on the rectum
in the superior hsemorrhoidal artery. It supplies the lower half of the large in-
testine. Its vein lies at first close to the left side, but soon passes upward on the
psoas, away from the artery, to end in the splenic vein (fig. 487).
The branches of the inferior mesenteric are: — (1) The left colic; (2) the
sigmoid; and (3) the superior haemorrhoidal.
(1) The left colic artery [a. colica sinistra] runs transversely to the left, beneath the peri-
toneum, and divides into two branches, one of which, entering the transverse meso-colon, as-
cends upward and to the right, to anastomose with the middle colic. The other descends, and,
entering the sigmoid meso-coion anastomoses with tlie ascending branch of the sigmoid artery.
The distribution of this artery, and of the next, to the colon is similar to that of the cofie
branches of the superior mesenteric, and does not require a separate description. (See pp.
597, 598.)
(2) The sigmoid artery [a. sigmoidea] runs downward and to the left over the psoas mus-
cle and, entering the sigmoid meso-colon, divides into two branches; the upper anastomosing
with the left cohc, the lower with the superior hemorrhoidal.
(3) The superior haemorrhoidal artery [a. hasmorrhoidaUs superior] is the continued trunk of
the inferior mesenteric. It descends into the pelvis, behind the rectum, between the layers of the
sigmoid meso-colon. On reaching the wall of the bowel it bifurcates, one branch proceeding on
either side of the gut, to within 10 or 12 cm. (4 or 5 in.) of the anus. Here each again divides,
and the branches, piercing the muscular coat, descend between that coat and the mucous mem-
brane, forming with each other, and with the middle haemorrhoidal arteries — derived from the
hypogastric (internal ihac) — a series of small vessels, running longitudinally to the rectum, and
parallel to each other as far as the level of the internal sphincter, where, by their anastomosis,
they form a series of loops around the lower part of the rectum.
C. The Terminal Branches of the Abdominal Aorta
THE MIDDLE SACRAL ARTERY
The middle sacral artery [a. sacralis media], is, anatomically, the continuation
of the aorta. The coccygeal glomerulus [glomus coccygeum], in which it ter-
minates, is believed to contain the rudiments of the caudal aorta. The artery
extends from the bifurcation of the aorta to the tip of the coccyx. As it passes
downward into the pelvis, it runs behind the left common iliac vein, the hypo-
gastric plexus of the sympathetic nerve, and the peritoneum. It lies successively
upon the intervertebral disc between the fourth and fifth lumbar vertebrse, the
fifth lumbar vertebra, the intervertebral disc between that vertebra and the
sacrum, and lower down upon the anterior surface of the sacrum and coccyx.
Branches. — The branches of the middle sacral artery are : —
(1) The lowest lumbar artery [a. lumbahs ima], which, when present, usually comes off from
the middle sacral artery. Each vessel of this pair runs laterally beneath the common ihac artery
and vein; and, after giving off a dorsal branch, ramifies over the lateral part of the sacrum, and
ends in the iliacus muscle by anastomosing with the circumflex Oiac artery. The dorsal branch
passes to the back between the last lumbar vertebra and the sacrum and ramifies in the gluteus
maxiraus, anastomosing with the lumbar arteries above, and the superior gluteal artery below.
(2) Lateral sacral branches, are usually four in number. They are serially homologous with
the intercostal and lumbar arteries given off by the aorta. They run laterally, and anastomose
with the lateral sacral branches of the hypogastric (internal iliac) artery. They give off small
spinal branches, which pass through the sacral foramina, and supply the sacral canal and back
of the sacrum.
(3) Rectal or haemorrhoidal branches pass forward beneath the peritoneum or in the sig-
moid meso-colon to the rectum, which they help to supply, and anastomose with the other
haemorrhoidal or rectal arteries.
THE COMMON ILIAC ARTERIES
The common iliac arteries [aa. iliacse communes] arise opposite the left side
of the middle of the body of the fourth lumbar vertebra, at the bifurcation of the
abdominal aorta, and, diverging from each other in the male at about an angle
of 60°, and in the female at an angle of 68°, terminate opposite the lumbo-sacral
articulation by bifurcating into the external iliac, which is continued along the
brim of the pelvis to the lower hmb, and into the hypogastric (internal iliac),
which passes through the superior aperture of the pelvis and descends into that
cavity (fig. 488).
The relations differ slightly on the two sides, and maj^ be considered separately.
604
■THE BLOOD-VASCULAR SYSTEM
Fig. 488. — The Relations of the Common
Anatomy," Rebman,
Internal jugular vein
Thyreoidea ima vein
Subclavian vein
Right innominate vein
Thymic veins //j/^
Superior vena cava
Iliac Arteries. (Alter Toldt, "Atlas of Human
London and New York.)
Thyreoid gland
., Left innominate vein
Internal mammary artery and
Suprarenal gland ^__ /"/
Superior
teric artery
Inferior vena cava
Spermati
Internal spermatic
artery
Common iliai
artery and vein ^
Anterior sacral, / ■"
plexus '"' 1^
Deep circumflex
iliac artery and ,
vein I
Inferior epigas- / N^'
trie artery and / \
vein '
External sper-
matic artery
Femoral artery
Femoral vein'
\
I
External puden- '"
dal veins ''
Anterior scrotal veins
Common tunica vaginali
THE HYPOGASTRIC ARTERY 605
The Right Common Iliac Artery
The right common iliac measures about 5 cm. (2 in.) in length, and is rather
longer than the left, in consequence of the aorta bifurcating a little to the left of
the median line.
Relations. — In front it is covered by the peritoneum, and is crossed by the right ureter a
little before its bifurcation, by the ovarian artery in the female, by the termination of the ileum,
by .the terminal branches of the superior mesenteric artery, and by branches of the sympathetic
nerve descending to the hypogastric plexus.
Behind, it hes on the right common iliac vein, the end of the left common ihac vein, and the
commencement of the inferior vena cava, which separate it from the fourth and fifth lumbar
vertebrae and their intervening disc, the psoas muscle, and the sympathetic nerve; whilst still
deeper in the groove between the fifth vertebra and the psoas are the lumbo-sacral trunk,
the obturator nerve, and the ilio-lumbar artery.
To the right side are the beginning of the inferior vena cava, the end of the right common
iliac vein, and the psoas muscle, which, however, is separated from the artery by the vena cava
inferior at its upper part.
To the left side are the right common iliac vein, the termination of the left common Uiac vein,
and the hypogastric plexus.
The Left Common Iliac Artery
The left common iliac artery, 4 cm. (14 in.) in length, is a little shorter and
thicker than the right.
Relations. — In front it is covered by the peritoneum, which separates it from the intestines,
and is crossed by the ureter, the ovarian artery in the female, branches of the sympathetic nerve
descending to the hypogastric plexus, the termination of the inferior mesenteric artery, the
sigmoid colon, and the sigmoid mesocolon.
Behind are the lower border of the body of the fourth lumbar vertebra, the disc between the
fourth and fifth lumbar vertebra, the body of the fifth lumbar vertebra, and the disc between it
and the sacrum. Crossing deeply behind the artery between the fifth lumbar vertebra and the
psoas, is the obturator nerve, the lumbo-sacral trunk, and the ilio-lumbar artery.
To the left side is the psoas muscle.
To the right side are the left common ihac vein, the hypogastric plexus, and the middle
sacral artery.
Collateral Circulation
The collateral circulation after obstruction or ligature of the common ihac artery is carried
on chiefly (fig. 497) by the anastomosis of the middle sacral with the lateral sacral; the internal
mammary with the epigastric; the lumbar arteries of the aorta with the iho-lumbar and deep
circumflex iliac; the pubic branch of the epigastric with the pubic branch of the obturator; the
posterior branches of the sacral arteries with the superior gluteal (gluteal) ; the superior hem-
orrhoidal from the inferior mesenteric, with the hfemorrhoidal branches of the hypogastric (in-
ternal iliac) and pudic; the ovarian arteries from the aorta with the uterine branches of the hy-
pogastric (internal iliac) ; and by the anastomosis across the middle line of the pubic branch of
the obturator with the like vessel of the opposite side; the lateral sacral with the opposite
lateral sacral; and the vesical, hemorrhoidal, uterine, and vaginal branches of the hypogastric
with the corresponding branches of the opposite hypogastric (internal iliac).
Branches of the Common Iliac Artery
The branches of the common iliac artery are: — (1) The hypogastric (internal
iliac); and (2) external iliac.
There are a few small, unimportant branches distributed to the peritoneum and subperi-
toneal fat. They anastomose with vessels given off from the lumbar, inferior phrenic, and renal
arteries, forming a subperitoneal arterial anastomosis. The ureter receives small insignificant
twigs as it crosses the artery. They anastomose with the ureteral arteries given off from the
internal spermatic above, and with those derived from the vesical arteries below.
THE HYPOGASTRIC ARTERY
The hypogastric or internal iliac artery [a. hypogastrica], arises at the bifur-
cation of the common iliac opposite the lumbo-sacral articulation. It descends
into the pelvis for about 3 cm. (1| in.) and then divides, opposite the upper
margin of the great sciatic foramen, into an anterior and a posterior division.
The anterior divisio?i commonly gives off the obturator, inferior gluteal, umbilical,
606
THE BLOOD-VASCULAR SYSTEM
inferior vesical, deferential, middle hsemorrhoidal, uterine fin the female), and
internal pudendal arteries. From the posterior division the ilio-lumbar, lateral
sacral, and superior gluteal arteries arise. These vessels are classified, for
description, as parietal and visceral.
In the adult the hypogastric is smaller than the external ihac; in the foetus it is much larger
and through it the foetal blood is returned to the placenta. The adult hypogastric and common
ihac arteries of either side represent the proximal portion of each of the embryonic umbilical
arteries. The remainder of the umbUical artery within the body is represented by the umbiMcal
branch of the hypogastric which runs to the navel. At birth, when the circulation in the um-
bihcal cord ceases, the lumen of the umbihcal branch of the hypogastric becomes obhterated
except a small channel which remains pervious as the superior vesical of tlie adult.
Relations. — Behind, the hypogastric artery rests on the termination of the external iliac
vein, the hypogastric vein, the medial margin of the psoas muscle, the lumbo-sacral trunk, the
obturator nerve, and the sacrum.
In front, it is covered by the peritoneum, and is crossed by the ureter.
Fig. 489. — The Htpogastbic Artery. (After Henle.)
ExternI iliac artery
Hypogastric artery
Deep circumflex,
iliac artery
Ilio-lumbar artery
Lateral sacral artery
Inferior epigastric,
artery
Ascending branch
^Internal pudic
artery
Internal ves-
ical artery
Hsemorrhoidal
artery
Coccygeus muscle
Bladder
Internal obturator muscle
The branches of the hypogastric artery may be divided into parietal and
visceral sets. The parietal branches are: — -(1) The ilio-lumbar; (2) the lateral
sacral; (3) the obturator; and (4) the gluteal arteries.
The visceral branches are: — (1) The umbilical; (2) the inferior vesical; (3)
the middle haemorrhoidal; (4) the uterine; and (5) the internal pudendal.
Parietal Branches of the Hypogastric Artery
1. THE ILIO-LUMBAR ARTERY
The ilio-lumbar artery [a. iliolumbalis] — a short vessel coming off from the
posterior part of the hypogastric artery — -runs upward and laterally beneath the ,
common iliac artery, first between the lumbo-sacral trunk and obturator nerve,
THE LATERAL SACRAL ARTERIES
607
and then between the psoas muscles and the vertebral column. On reaching the
superior aperture of the pelvis it divides into two branches, an iliac and a lumbar
(fig- 489).
The iliac branch [ramus iliaous] passes laterally beneath the psoas and the femoral (anterior
crural) nerve and, perforating the iUacus, ramifies in the iliac fossa between that muscle and the
bone. It supphes a nutrient artery to the bone, and then breaks up into several branches which
radiate from the parent trunk, upward toward the sacro-iUac synchondrosis, laterally toward
the crest of the Uium, downward toward the anterior superior spine, and medially toward the
pelvic cavity. The first anastomoses witli the last lumbar; the second with the external circum-
flex and gluteal; the third with the deep circumflex iUac from the external ihac; the fourth with
the Uiac branch of the obturator. The lumbar branch [ramus lumbalis] ascends beneath the
psoas, and, supplying that muscle and the quadratus lumborum, anastomoses with the last lum-
bar artery. It sends a spinal branch (ramus spinalis) into the vertebral canal through the inter-
vertebral foramen between the last lumbar vertebra and the sacrum; this branch anastomoses
with the other spinal arteries. The Qio-lumbar artery is serially homologous with the lumbar
arteries. Hence the similarity in its course and distribution.
2. THE LATERAL SACRAL ARTERIES
The lateral sacral artery [a. sacralis lateralis], commonly arises as two vessels
from the posterior division of the hypogastric. The superior artery, when two
Fig. 490. — The Gluteal Artehies. (After Toldt, "Atlas of Human Anatomy," Rebman,
London and New York.)
^ Glutaeus medius muscle
Inferior branch -
Superior brancli-
Superior gluteal artery -
Piriformis muscle-
Inferior gluteal artery —
Internal pudendal artery,
A. comitans nervi
ischiadici
Obturator fascia
Inferior h£e
rhoidal artery /
Sacro-tuberous ,'
ligament ~^
Perineal artery
Hedial circumflex
femoral artery
(deep branch)
■ Glutseus minimus muscle
^ Obturator internus muscle
/\
Biceps femoris muscle •
(long head)
Attachment of the ilio-
psoas muscle to the
trochanter minor
Adductor minimus muscle
First perforating artery
Adductor magnus muscle
Second perforating artery
are present, runs downward and medially to the first anterior sacral foramen,
through which it passes; and, after supplying the spinal membranes and anas-
tomosing with the other spinal arteries, passes through the first posterior sacral
08 THE BLOOD-VASCULAR SYSTEM
foramen, and is distributed to the skin over the back of the sacrum, there anas-
tomosing with branches of the superior and inferior gluteal arteries. The inferior
lateral sacral descends on the side of the sacrum, lateral to the sacral chain of the
sympathetic, and medial to the anterior sacral foramina, crossing in its course the
slips of origin of the piriformis muscle and the first anterior sacral nerve. On
reaching the coccyx it anastomoses in front of that bone with the middle sacral
artery, and with the inferior lateral sacral of the opposite side (fig. 489).
In this course it gives off: — Spinal branches [rami spinales], which enter the second, third
and fourth anterior sacral foramina, and, after supplying the spinal membranes and anastomos-
ing with each other, leave the spinal canal by the corresponding posterior sacral foramina, and
are distributed to the muscle and skin over the back of the sacrum; and rectal branches which
run forward to the rectum.
At times the lateral sacral arteries are exceedingly small, the spinal branches then coming
chiefly from the middle sacral. The anastomosing branches between the lateral sacral and
middle sacral are usually regarded as sacral arteries diminished in size, and serially homologous
with the lumbar and intercostal arteries.
3. THE OBTURATOR ARTERY
• The obturator artery [a. obturatoria], usually arises from the anterior division
of the hypogastric. It runs forward and downward a Httle below the brim of the
pelvis, having the obturator nerve above and the obturator vein below. It here
lies between the peritoneum and the endo-pelvic fascia, but later it passes through
the obturator canal, the aperture in the upper part of the obturator membrane.
In this course it is crossed by the ductus deferens. On emerging from the obturator
canal the artery divides into two branches, anterior and posterior, which wind
around the margin of the obturator foramen beneath the obturator externus
muscle.
The branches of the obturator artery are: — (1) The iliac or nutrient branch;
(2) a vesical branch; (3) the pubic branch; (4) the anterior, and (5) posterior
terminal branches.
(1) The iliac or nutrient branch ascends to the iliac fossa, passing between the iUacus
muscle and the bone. It suppUes a nutrient vessel to the ihum, and anastomoses with the
medial branch of the iliac division of the ilio-lumbar artery.
(2) The vesical branch or branches are smaU vessels which run in the lateral false ligament
of the bladder to that organ, where they anastomose with the other vesical arteries.
(3) The pubic branch [ramus pubicus] comes off from the obturator as that vessel is leaving
the pelvis by the obturator canal. It runs upward and medially behind the pubis, anastomosing
with its feUow of the opposite side of the body, and with the pubic branch of the inferior epi-
gastric artery. One of the anastomosing channels between the pubic branch of the obturator
and pubic branch of the inferior epigastric arteries is sometimes of large size, a fact of surgical
interest in that the enlarged vessel may then run around the medial side of the femoral ring
(pp. 615 and 636).
(4) The anterior branch [ramus anterior] runs around the medial margin of the obturator
foramen, and anastomoses with the posterior branch and with the medial circumflex artery. It
supplies branches to the obturator and adductor muscles.
(5) The posterior branch [ramus posterior] skirts the lateral margin of the obturator fora-
men, lying between the obturator externus and the obturator membrane. At the lower margin
of the foramen it divides into two branches. One branch continues its course around the lower
margin of the foramen, and anastomoses with the anterior branch of the obturator and with
the medial circumflex. The other branch turns laterally below the acetabulum, and ends in the
muscles arising from the tuberosity of the ischium. It anastomoses with the inferior gluteal
artery. This branch gives off a small twig, the acetabular artery [a. acetabuli], which passes
under the transverse Ugament into the hip-joint, where it suppUes the synovial membrane,
the hgamentum teres, and the fat in the fossa at the bottom of the acetabulum.
4. THE GLUTEAL ARTERIES
There are two gluteal arteries, the superior and inferior. The superior
gluteal artery [a. glutea superior], the largest branch of the posterior division of
the hypogastric comes off as a short, thick trunk from the lateral and back part
of that vessel, of which indeed it may be regarded as the continuation. Passing
backward between the first sacral nerve and the lumbo-sacral trunk through an
osseo-tendinous arch formed by the margin of the bone and the upper edge of the
endo-pelvic fascia, it leaves the pelvis through the great sciatic foramen above
the piriformis muscle in company with its vein and the superior gluteal nerve. At
its exit posteriorly from the great sciatic foramen it lies under cover of the gluteus
THE INFERIOR VESICAL ARTERY 609
maximus and beneath the superior gluteal vein, and in front of the superior
gluteal nerve. It here breaks up into two chief branches, a superficial and a
deep. Its emergence from the pelvis is indicated on the surface by a point
situated at the junction of the posterior with the middle third of a line drawn
from the anterior superior to the posterior superior spine of the ilium.
The branches of the superior gluteal artery are : —
(o) Within the pelvis, branches are distributed to the obturator internus, the
piriformis, the levator ani, the coccygeus, and the pelvic bones.
(h) External to the pelvis, the artery divides into a superior and an inferior
branch.
(i) The superior branch [ramus superior] breaks up into a number of large vessels for the
supply of the upper portion of the gluteus maximus, some of them piercing the muscle and supply-
ing the skin over it, and anastomosing with the posterior branches of the lateral sacral arteries;
whilst one of larger size, emerging from the muscle near the ihao crest, anastomoses with the
deep circumflex iliac artery. The lower branches to the muscle anastomose with branches of
the inferior gluteal (sciatic).
(ii) The inferior branch [ramus inferior] subdivides into two branches — One skirts along
the lane of origin of the gluteus minimus (fig. 490), between the gluteus medius and the bone,
and, emerging in front from beneath these muscles under cover of the tensor fascite lata:, anas-
tomoses with the ascending branch of the lateral circumflex and the deep circumflex iliac arter-
ies. The other passes forward between the gluteus medius and minimus, accompanied by the
branch to the tensor fasciae lata; of the inferior division of the superior gluteal nerve, toward the
greater trochanter, where it anastomoses with the ascending branch of the lateral circumflex.
It supphes branches to the contiguous muscles and to the hip-joint. The inferior branch before
its division gives off the external nutrient artery of the ilium.
The inferior gluteal [a. glutea inferior], is one of the terminal branches
of the anterior division of the hypogastric artery. It leaves the pelvis below the
piriformis muscle, and immediately breaks up into a number of diverging branches.
The largest enter the gluteus maximus muscle, where they anastomose with the
superior gluteal branches. Others pass to the hip-joint and the deep muscles
around it; a third group passes downward to the hamstring muscles and anas-
tomoses with the medial and lateral circumflex and first perforating; a fourth
slender branch, the sciatic artery [a. comitans n. ischiadici], accompanies the
sciatic nerve (fig. 490).
Visceral Branches of the Hypogastric Artery
1. THE UMBILICAL ARTERY
The umbilical artery in the fcetus is the continuation of the hypogastric.
Passing forward along the side of the pelvis, it runs beneath the lateral reflexion of
peritoneum from the bladder, where, after giving off one or more vesical branches,
it ceases to be pervious and passes on to the side and upper part of the bladder.
Thence it ascends in the lateral umbilical fold, as a fibrous cord [ligamentum
umbilicale laterale], to the umbilicus, where it is joined by its fellow of the
opposite side. As it lies lateral to the bladder it is crossed by the ductus deferens.
The branches of the umbilical artery are: — (1) Superior vesical arteries, the
lowest of which is sometimes called (2) the middle vesical artery (fig. 489).
The superior vesical arteries [aa. vesicales superiores] ramify over the upper surface of the
bladder, anastomosing with the artery of the opposite side and with the middle and inferior
vesical below. They give off the following branches: — (a) The urachal branches which pass
upward along the urachus. (h) The ureteric branches pass to the lower end of the ureter,
and anastomose with the other ureteric arteries, (c) The middle vesical may come off from
one of the superior vesicals or from the umbilical. It is distributed to the sides and base of the
bladder, and anastomoses with the other vesical arteries.
2. THE INFERIOR VESICAL ARTERY
The inferior vesical artery [a. vesicahs inferior] arises from the anterior
division of the hypogastric, frequently in common with the middle haemorrhoidal,
and passes downward and medially to the fundus of the bladder, where it breaks
up into branches which ramify over the lower part of the viscus. It gives off
branches to the prostate, which supply that organ and anastomose with the
arteries of the opposite side by means of descending arteries which pass through
610 THE BLOOD-VASCULAR SYSTEM
the prostatic plexus of veins, but outside the capsule of the prostate, and with the
inferior hsemorrhoidal branches of the internal pudic. At times one of these
prostatic branches is of large size, and supplies certain of the parts normally
supplied by the int. pudendal. It is then known as the accessory pudendal and
most commonly terminates as the dorsal artery of the penis.
The inferior vesical usually gives off the deferential, or artery of the ductus deferens [a.
deferentialis]. This vessel, which may come off from the superior vesical, divides, on the ductus
deferens, into an ascending and a descending branch. The ascending branch follows the ductus
through the inguinal canal to the testis, where it anastomoses with the internal spermatic artery.
The_ descending branch passes downward to the dilated portion of the ductus and vesiculse
seminales.
3. THE MIDDLE HEMORRHOIDAL ARTERY
The middle hsemorrhoidal artery [a. hsemorrhoidals media], variable in origin,
perhaps most commonly arises from the anterior division of the hypogastric
along with the inferior vesical. It runs medially to the side of the middle portion
of the rectum, dividing into branches which anastomose above with the superior
hsemorrhoidal derived from the inferior mesenteric, and below with the inferior
hsemorrhoidal derived from branches of the internal pudendal. Its corre-
sponding vein terminates in the inferior mesenteric vein. In the female it also
sends branches to the vagina.
4. THE UTERINE ARTERY
The uterine artery [a. uterina], arises from the anterior division of the hypo-
gastric close to or in conj unction with the middle hsemorrhoidal or inferior vesical.
It runs downward and medially through the pelvic connective tissue, crossing the
ureter about 12 mm. (| in.) from the cervix uteri. It then turns upward and
ascends in the parametrium between the layers of the broad ligament at the
side of the uterus in a coiled and tortuous manner, and, after giving off a number of
tortuous branches which ramify horizontally over the front and back of the uterus,
supplying its substance, anastomoses with the uterine branch of the ovarian
artery.
In addition to the branches to the uterus the branches of the uterine artery are: — (1)
Cervical. — This branch comes off from the uterine as the latter artery crosses the ureter to turn
upward on to the uterus. It is directed medially, and divides into three or four branches which
pass on to the cervix at right angles to it; one branch anastomosing with its fellow of the opposite
side in front and behind the neck, forming the so-caUed coronary artery of the cervix. (2)
Tubal [ramus tubarius]. — Tliis courses along the lower surface of the tuba uterina (FaUopian
tube) as far as its fimbriated extremity, and may also send a brancli to the ligamentum teres.
(3) Ovarian [ramus ovarii]. — This runs along the attached border of the ovary, sending branches
to that structure, and terminates by anastomosing widely with the ovarian artery. Usually
the vaginal artery also arises from tlie uterine. (4) The vaginal artery [a. vaginaUs] corresponds
to the inferior vesical artery of the male, and may arise directly from the hypogastric artery,
close to the origin of the uterine, or from the superior vesical. It passes medially, behind the
ureter, to the upper part of the vagina, and sends numerous branches to that structure and also
some iio the posterior part of the fundus of the bladder.
The branches to the vagina tend to anastomose with one another and with the cervical
branch of the uterine, to form a more or less perfect vertical stem in the median Une of the vagina,
both back and front. This stem is sometimes termed the azygos artery of the vagina. Branches
also pass to the vagina from the middle hsemorrhoidal artery.
5. THE INTERNAL PUDENDAL ARTERY
The internal pudendal (pudic) artery [a. pudenda interna] (figs. 492, 493, 494)
is one of the terminal branches of the anterior division of the hypogastric artery
(the inferior gluteal being the other) . It arises opposite the piriformis muscle and
accompanies the inferior gluteal downward to the lower border of the great
sciatic foramen. It leaves the pelvis between the piriformis and coccygeus and
winds over the ischial spine to enter the ischio-rectal fossa through the small
sciatic foramen. Running forward in the ischio-rectal fossa medial to the lower
part of the obturator internus it ends by dividing into the perineal artery and the
artery of the penis (or clitoris).
INTERNAL PUDENDAL ARTERY
611
Relations. — Within the -pelvis, the artery is anterior to the piriformis muscle and the sacral
plexus of nerves, and lateral to the inferior gluteal artery. It passes between the piriformis
and coccygeus, with the gluteal artery and pudendal nerve medial to it, and the nerve to the ob-
turator internus lateral. The sciatic and posterior femoral cutaneous (lesser sciatic) nerves
are still more lateral. On, the ischial spine the artery retains its relations to the pudendal nerve
(which often divides in this situation into its two terminal branches) and the nerve to the ob-
turator internus. It is accompanied by venae comitantes and covered by the gluteus maximus
muscle. In the ischio-rectal fossa the artery is placed on the lateral wall about 3.5 cm. (IJ in.)
above the tuberosity of the ischium. It is accompanied in a canal in the obtm-ator fascia
(Alcock's canal) by the dorsal nerve of the penis and the perineal nerve, which are respectively
above and below the artery.
The branches of the internal pudendal artery are: — (1) Small branches to the
gluteal region; (2) the inferior hsemorrhoidal arteries; and the terminal branches
(3) perineal; and (4) artery to the penis or clitoris.
612
THE BLOOD-VASCULAR SYSTEM
Fig. 492. — The Internal Pudendal Artery. (From Kelly, by Brodel.)
Dorsal artery of clitoris
Inferior hasmorrhoidal artery
Internal pudic artery
Sacro-spinous ligament
Fig. 493. — The Perineal and Hemorrhoidal Branches of the Internal Pudendal
Arteries. (From Kelly, by Brodel.)
INTERNAL PUDENDAL ARTERY
613
(1) The branches of the gluteal region are: (a) twigs to the gluteus maximus; (6) branches
accompanying the nerve to the obturator internus; (c) a sacral branch which pierces the sacro-
tuberous ligament, and anastomoses with the inferior gluteal artery.
(2) The inferior hemorrhoidal artery (a. haemorrhoidalis inferior] (figs, 493, 494) arises at
the posterior part of the ischio-rectal fossa and, perforating the obturator fascia, at once breaks
up into several branches. These, rumiing medially toward the anus, traverse the ischio-rectal
fat and supply the fascia, skin and the levator ani and external sphincter muscles. The in-
ferior hEemorrhoidal branches anastomose with those from the middle and superior hemor-
rhoidal, and from the gluteal and perineal arteries.
(3) The perineal artery [a. perinei] (figs. 493, 494), one of the terminal arieries of the in-
ternal pudendal, arises at the anterior part of the ischio-rectal fossa. It pierces the base of the
urogenital diaphragm (triangular hgament) anterior or posterior to the superficial transverse
perineal muscle, and enters the space deep to CoUes's fascia. Here it runs forward between the
ischio- and bulbo-cavernosus muscles to the scrotum or labium majus and divides into numer-
ous terminal branches. Immediately after piercing the diaphragm, the perineal artery gives
off a constant transverse perineal branch which runs toward the median Une along the super-
ficial transverse perineal muscle. The terminal branches of the perineal are the posterior
scrotal or labial arteries [aa. scrotales, or labiales posteriores] which ramify on the scrotum or
labia majora (according to sex) and anastomose with external pudendal arteries.
(4) The artery of the penis, or clitoris [a. penis or clitoridis] (figs. 493, 494) pierces the free
border of the urogenital diaphragm and runs forward between the layers of the diaphragm
with the dorsal nerve of the penis along the inferior ramus of the pubis. It traverses the fibres
of the deep transverse perineal muscle and of the sphincter of the membranous urethra and
Fig. 494. — The Arteries op the Male PERiN.ffi;uM.
On the right side CoUes's fascia has been turned back to show the perineal artery. On the
left side the perineal vessels have been cut away with the inferior layer of the urogenital dia-
phragm to show the artery of the penis.
Posterior sacral artery
Bulbo-cavernosus
CoUes's fascia, turned back
Dorsal artery of penis
Deep artery of penis
Ischio-cavernosus
Transverse perineal vessels
Cut edge of urogenital
diaphragm
Perineal nerve giving oB
transverse branch
Internal pudendal artery
Inferior hemorrhoidal
artery
Artery of bulb
Bulbo-urethral gland
Artery of the penis
Sacro-tuberous ligament
— Levator ani
External sphincter ani
Gluteus maximus
ends by dividing into deep and dorsal arteries of the penis, or clitoris, according to sex.
The branches of the artery of the penis (or clitoris) are: (a) The artery to the bulb; (b)
the uretliral artery; and (c) the terminal, deep artery of the penis or clitoris.
(a) The artery of the bulb [a. bullii urethras or vestibuli vaginas] takes a medial direction
through the fibres of the m. transversus perinei profundus. It then pierces the inferior fascia
of the urogenital diaphragm to reach the bulb, the erectile tissue of which it supplies, in either
sex. This vessel also suppUes branches to the bulbo-urethral gland (Cowperi) or the gland of
the vestibule (Bartholini).
The situation of the artery to the bulb should be remembered in performing the operation
of lateral lithotomy, particularly as it may arise far back. When the artery arises, as it occa-
sionally does, from the accessory pudendal it pierces the urogenital diaphragm further forward
and is out of danger in the ordinary low operation.
(6) The urethral artery [a. urethralisj.is a small branch which passes into the corpus spongi-
osum and anastomoses with branches from the artery of the bulb.
614 THE BLOOD-VASCULAR SYSTEM
(c) The deep artery of the penis or clitoris [a. profunda penis or clitoridis], larger in the male
sex, pierces the inferior layer of the urogenital diaphragm near the inferior ramus of the pubis.
It enters the crus of the penis (fig. 494) or clitoris, and is distributed in the corpus cavernosum
urethrae.
(d) The dorsal artery of the penis or clitoris [a. dorsalis penis or clitoridis] (figs. 492, 494),
perforates the inferior fascia of the urogenital diaphragm near its apex. The dorsal nerve is
lateral to the artery and both join the dorsal vein (which hes between the arteries of either side)
on the dorsum of the penis or clitoris. The artei-y is much larger in the male than the female;
in either sex it supphes the glans, corona, and prepuce and anastomoses with the external
pudendal artery.
THE EXTERNAL ILIAC ARTERY
The external iliac artery [a. iliaca externa] — the larger in the adult of the two
vessels into which the common iliac divides opposite the lumbo-sacral articulation
— extends along the superior aperture of the pelvis, lying upon the medial border
of the psoas muscle, to the lower margin of the inguinal ligament, where, midway
between the anterior superior spine of the ilium and the symphysis pubis, it passes
into the thigh, and takes the name of the femoral.
It measures 8.5 to 10 cm. (3| to 4 in.) in length. The course of the vessel is
indicated by a line drawn from 2.5 cm. (1 in.) below and a little to the left of the
umbilicus to a spot midway between the symphysis pubis and the anterior
superior spine of the ilium. If this line is divided into thirds, the lower two-thirds
indicate the situation of the external iliac, the upper third the common iliac. The
external iliac vein, the continuation upward of the femoral vein from the thigh,
lies to the medial side of the artery, but on a slightly lower plane, and, just before
its termination, gets a little behind the artery on the right side.
Relations. — In front, the artery together with the vein is covered by the parietal per-
itoneum descending from the abdomen into the pelvis, and by a layer of condensed subperitoneal
tissue (Abernethy's fascia). It is crossed by the termination of the ileum on the right side, and
by the sigmoid colon on the left. The external spermatic (genital) branch of the genito-
femoral (genito-crural) nerve runs obhquely over its lower third, and just before its termination
it is crossed transversely by the deep circumflex iliac vein. The internal spermatic or ovarian
vessels lie for a short distance on the lower part of the artery, and the ductus deferens in the male
curves over it to descend to the pelvis. It is sometimes crossed at its origin by the ureter. The
external iliac lymphatic nodes lie along the course of the artery. The commencement of its
inferior epigastric branch is also in front.
Behind. — At first the artery lies partly upon its own vein; lower down upon the medial
border of the psoas; and just before it passes through the lacuna vasorum, beneath Poupart's
ligament, upon the tendon of the psoas. The continuation of the ihac into the endo-pelvic fascia
is also below it.
To its medial side is the external iliac vein, the peritoneum, and the ductus deferens in the
male, or the ovarian vessels in the female.
To its lateral side is the psoas muscle and the iliac fascia.
The collateral circulation is carried on (fig. 497) when the external ihac is tied, by the anas-
tomosis of the iUo-lumbar and lumbar arteries with the circumflex ihac; the internal mammary
with the inferior epigastric; the obturator with the medial circumflex; the inferior gluteal with
the medial circumflex and superior perforating; the gluteal with the lateral circumflex; the
arteria comitans nervi ischiadici from the inferior gluteal, with the perforating branches of the
profunda; the external pudenal with the internal pudendal; the pubic branch of the obturator
with the pubic branch of the epigastric.
The branches of the external iliac artery are: — (1) The inferior epigastric; (2)
the deep circumflex iliac; and (3) several small and insignificant twigs to the
neighbouring psoas muscles and lymphatic gland.
(1) The Inferior Epigastric Artery
The inferior or deep epigastric artery [a. epigastrica inferior] (fig. 495) usually
comes off from the external iliac just above the inguinal (Poupart's) ligament.
Immediately after its origin, the ductus deferens in the male, and the round
ligament in the female, loop around it on their way to the pelvis. It here lies
medial to the abdominal inguinal (internal abdominal) ring, behind the inguinal
canal, and a little above and lateral tc the femoral ring. Thence it ascends with
a slightly medial direction passing above and to the lateral side of the subcu-
taneous inguinal (external abdominal) ring, lying between the fascia transversalis
and the peritoneum. Having pierced the fascia transversalis at this point, it
THE INFERIOR EPIGASTRIC ARTERY
615
passes in front of the linea semicircularis (Douglas' fold) and turns upward be-
tween the rectus and its sheath. Higher, it enters the substance of the muscle,
and anastomoses with the superior epigastric, descending in the rectus from the
internal mammary.
The situation of the artery between the two inguinal rings should be borne in
mind in the operation for strangulated inguinal hernia, and its near proximity to
the upper and lateral side of the femoral ring should not be forgotten in the
operation for femoral hernia. The arter3r is accompanied by two veins which
end in a single trunk before opening into the external iliac vein.
The branches of the inferior epigastric are small and include: — (a) The external spermatic
[a. spermatica externa], which runs with the ductus through the inguinal canal, supplies the
cremaster muscle, and anastomoses with the internal spermatic, external pudendal, and perineal
arteries. In the female a corresponding artery [a. hg. teretis uteri] accompanies the round liga-
FiG. 495. — The Inferior (Deep) Epigastric Artery. (From Kelly, by Brodel).
l^ectus A
" Ovarian vessels
External iliac
artery
^External iliac
ment of the uterus through the inguinal canal and anastomoses in a similar manner. (6) The
pubic [ramus pubicus], which passes below, or sometimes above, the femoral ring to the back
of the pubis, where it anastomoses with the pubic branch of the obturator. This branch,
though usually small, is occasionally considerably enlarged, when its exact course becomes of
great interest to the surgeon. Thus it may descend immediatelj' medial to the vein, and there-
fore lateral to the femoral ring, or it may course medially in front of the femoral ring and turn
downward either behind the os pubis or immediately behind the free edge of the lacunar (Gim-
bernat's) ligament, in which situation it would be exposed to injury in the operation for the re-
lief of a strangulated femoral hernia. In such cases the obturator may lose its connection with
the hypogastric and actually arise from the inferior epigastric. Very rarely the inferior epi-
gastric loses its connection with the external iUac and arises from the obturator. This abnormal
origin of the obturator is said to occur once in every three subjects and a half; but the abnormal
616 THE BLOOD-VASCULAR SYSTEM
artery only courses around the medial side of the ring — in which situation it is liable to injury
in the operation for femoral hernia — in exceptional cases. According to Langton (Holden's
'Anatomy'), the chances are about seventy to one against this occurring. But even when it
takes the abnormal course, it lies 3 mm. or so from the margin of the ring, and will probably
escape injury in the division of the stricture if several short notches are made in place of a single
and longer incision.
(2) The Deep Circumflex Iliac Artery
The deep circumflex iliac artery [a. circumflexa ilium profunda], arises from
the lateral side of the external iliac artery either opposite the epigastric or a little
below the origin of that vessel. It courses laterally just above the lower margin
of Poupart's ligament, lying between the fascia transversahs and the peritoneum,
or at times in a fibrous canal formed by the union of the fascia transversahs with
the iliac fascia. Near the anterior superior spine of the ihum, it perforates the
transversus, and then courses between that muscle and the internal oblique,
along and a little above the crest of the ilium. It finally gives off an ascending
branch, which anastomoses with the lumbar and lower intercostal arteries,, and
runs backward to anastomose with the ilio-lumbar artery. It is accompanied by
two veins. These unite into one trunk, which then crosses the external iliac artery
to join the external iliac vein.
The branches of the deep circumflex iliac artery are as follows: — (a) Muscular branches
which supply the psoas, iliacus, sartorius, tensor fasciae latse, and the oblique and transverse
muscles of the abdomen. One of these branches, larger than the rest, usually arises about
2.5 cm. (1 in.) behind the anterior superior spine of the ilium and ascends perpendicularly be-
tween the transversus muscle and the internal oblique. It has received no name but is impor-
tant to the surgeon, as it indicates the intermuscular plane between the two muscles. (6)
Cutaneous branches, which supply the skin over the course of the vessel, and anastomose
with the superficial circumflex ihac, the superior gluteal, and the ascending branch of the lateral
circumflex.
THE FEMORAL ARTERY
The femoral artery (fig. 496) is the continuation of the external iliac, and
extends from the lower border of Poupart's ligament, down the anterior and
medial aspect of the thigh, to the tendinous opening in the adductor magnus,
through which it passes into the popliteal space, and is then known as the pop-
liteal. The femoral artery is at first quite superficial, being merely covered by the
skin, and superficial and deep fascia; but, after thus passing abo.ut 13 cm. (5 in.)
downward through the space known as the femoral trigone (Scarpa's triangle),
it sinks at the apex of that triangle beneath the sartorius muscle, and thence
to its termination continues beneath the sartorius, coursing deeply between the
vastus medialis and adductor muscles in the space known as the adductor
(Hunter's) canal. It at first rests upon the brim of the pelvis and head of the
thigh bone, from which it is merely separated by the capsule of the hip-joint and
the tendon of the psoas. Here it can be readily compressed. Owing to the
obliquity of the neck of the femin- and the direct course taken by the artery, it
lies lower down on muscles only, at some little distance from the bone. At its
termination, in consequence of the shaft of the femur inclining toward the middle
line of the body, the artery lies close to the bone, but to the mechal side. The
course of the vessel when the thigh is slightly flexed and abducted — the position
in which the Hmb is placed when the vessel is hgatured — is indicated by a line
drawn from a spot midway between the anterior superior spine of the ilium and
the symphysis pubis to the adductor tubercle. When the thigh is in the extended
position and parallel to its fellow, the course of the artery will correspond to a hne
drawn from the spot above mentioned to the medial border of the patella.
About 4-5 cm. (li-2 in.) below the inguinal ligament the femoral artery gives
off a large branch called the profunda femoris. The portion of the artery proximal
to the origin of the profunda is sometimes called the common femoral, and the
continuation of the vessel the superficial femoral.
The superficial femoral varies in length according to the distance that the profunda is given
off from the common femoral below Poupart's ligament. As a rule, it measures 9 cm. (Ss in.),
the common 4 cm. (IJ in.). But the profunda may come off 5 cm. (2 in.) or more below Pou-
part's ligament, in which case the superficial femoral will be shorter to this extent; or it may
THE FEMORAL ARTERY
617
come off less than 3.7 cm. (IJ in.) below Poupart's Ugament, or even from the external ibac above
Poupart's ligament, when the superficial will be longer than normal. The practical point to
remember is that it is more usual to meet with a short than with a long common femoral and
that if the superficial femoral is tied at the apex of the femoral trigone— i. e., the spot where
the sartorius comes into contact with the adductor longus— there is nearly always a sufficient
Fig. 496.— The Femoral Artert. (After Toldt, "Atlas of Human Anatomy," Rebman
London and New York.)
Superficial epigastric artery-
Tensor of fascia lata
Femoral nerve.
Femoral artery.
Femoral vein
Sartonus.
Deep femoral artery-
(Ascending ,
branch
Descending,
branch
Fascia lata
First perforating artery-
Deep femoral artery
Vastus medialis
Femoral i
Saphenous nerve- t B.i
Femoral artery "
Rectus femons
Articular rate of the knee-
External spermatic artery
— Medial circumflex artery
Superficial branch
— Adductor brevis
Adductor longus
Gracilis
Ventral wall of adductor canal
Muscular branch
Saphenous nerve
Sartorius
Genu suprema artery
- Superior medial articular artery
Articular branch
Saphenous branch
length of that vessel above the ligature to ensm-e a firm internal clot and consequently, as far
as this point is concerned, a successful result.
The relations of the femoral artery in the femoral trigone.— In front, the femoral artery
(fig. 496) is covered by the skin, the superficial fascia, the iUac portion of the fascia lata, and the
lumbo-inguinal (crural) branch of the genito-femoral nerve. The superficial cu-cumflex ihao
vein, and sometimes the superficial epigastric vem, descend over the artery from the medial to
618 THE BLOOD-VASCULAR SYSTEM
the lateral side. Just above the sartorius, the artery is crossed by the most medial of the anterior
cutaneous branches of the femoral nerve. The fascia transversahs, which is continued down-
ward into the thigh beneath the inguinal ligament, is also in anterior relation, but it soons be-
comes indistinguishable from the sheath of the vessel.
Behind, the artery rests from above upon the tendon of the psoas muscle, which separates
it from the brim of the pelvis and capsule of the hip-joint; the pectineus, and adductor longus.
The artery is partially separated from the pectineus by the femoral vein and the profunda vein
and artery, and from the adductor longus by the femoral vein which is almost directly behind
the artery near the apex of the femoral trigone. The small nerve to the pectineus crosses
behind the artery to reach its medial side.
A similar prolongation to that derived from the fascia transversaUs in front, descends be-
hind the vessel from the iliac fascia; but this, lil^e the anterior prolongation or fascia, soon blends
with the sheath of the vessels.
To the medial side is the femoral vein. This is separated above from the artery, where
the two vessels he in the femoral sheath, by a thin fascial septum. Below, the vein is some-
what behind the artery.
To the lateral side. — Above, the common stem of the femoral (anterior crural) nerve ia
about 1 cm. (J in.) lateral to the artery. When the femoral nerve gives off its branches, the
saphenous nerve and the nerve to the vastus mediaUs accompany the artery on the lateral
side.
The adductor canal is the somewhat triangularly shaped space bounded by the vastus
medialis on the lateral side, the adductors longus and magnus posteriorly, and by an aponeurosis
thrown across from the adductors to the vastus medially and in front. Below, the canal
terminates at the tendinous opening in the adductor magnus; above, its Umit is less well defined,
as here the aponeurosis between the muscles becomes less tendinous, and gradually fades away
into the perimuscular fascia. The transverse direction of the fibres of the aponeurotic covering
at the lower two-thirds of the canal is characteristic, and serves as a raUying-point in tying the
artery in this part of its course. Lying superficial to the aponeurosis is the sartorius muscle.
The femoral artery, in the adductor (Hunter's) canal, has the following relations :■ —
In front, in addition to the skin, superficial and deep fascia, are the sartorius muscle and the
aponeurotic fibres of the canal. The saphenous nerve crosses in front of the artery from the
lateral to the medial side, lying in the wall of the canal.
Behind, the artery is in contact with the adductor longus, and just above the opening in
the adductor magnus, usually with the latter muscle.
The femoral vein lies behind the artery, but gets a httle lateral to it at the lower part of
the canal. It is here very firmly and closely attached to the artery, embracing it as it were on
its posterior and lateral aspect. Hence it is very hable to be punctured on ligaturing the artery
in this part of its course. Such an accident is best avoided by opening the sheath of the vessels
well to the medial side of the front of the artery, and by keeping the point of the aneurysm needle
closely applied to the vessel in passing it between the vein and the artery. There are some-
times two veins, which then more or less surround the artery.
To the lateral side are the vastus mediaUs, the nerve to the vastus medialis, and at the lower
part of the canal, the femoral vein.
Branches of the Femoral Artery
The branches of the femoral artery are: —
(1) The superficial epigastric; (2) the superficial circumflex iUac; (3) the
external pudendal; (4) the inguinal; (5) the profunda; (6) muscular branches;
and (7) the suprema genu (anastomotica magna).
(1) the superficial epigastric artery [a. epigastrica superficialis], comes_ off
from the femoral about 1.2 cm. (| in.) below the inguinal ligament. At its origin
it is beneath the fascia lata, but almost at once passes through this fascia, or else
through the fossa ovalis, and courses in an upward and slightly medial direction
in front of the external oblique muscle almost as far as the umbilicus.
It ends in numerous small twigs, which anastomose with the cutaneous branches from the
inferior epigastric and internal mammary. In its course it gives off small branches to the in-
guinal glands and to the sldn and superficial f ascifs. Running with it is the superficial epigastric
irein, which ends in the great saphenous just before the latter passes through the fossa ovalis
(saphenous opening).
(2) The superficial circumflex iliac artery [a. circumflexa ilium superficialis],
(fig. 496), usually smaller than the superficial epigastric, arises either in common
with that vessel, or else as a separate branch from the femoral. It passes laterally
over the ihacus, and, soon perforating the fascia lata a Httle to the lateral side of
the fossa ovalis, runs more or less parallel to the inguinal ligament about as far
as the crest of the ihum, where it ends in branches which anastomose with the
deep circumflex iliac artery.
In its course it gives off branches to the iliacus and sartorius muscles, to the inguinal glands,
and to the fascia and skin. Its companion vein ends in the great saphenous vein just before the
latter passes through the fossa ovaUs (saphenous opening).
BRANCHES OF THE FEMORAL ARTERY
619
(3) the external pudendal arteries [aa. pudendae externse], arise from the
medial side of the femoral. Some of them pass either through the fascia lata, or
Fig. 497. — To show the Anastomoses of the Arteries of the Lower Extremity.
(After Smith and Walsham.)
Inferior epigastric artery
Ilio-lumbar artery
Deep circumflex iliac artery
Superior gluteal artery
Common femoral artery
Profunda artery
Lateral circumflex artery
Crucial anastomosis '
Popliteal artery
Superior lateral articular
Anterior tibial artery
Inferior lateral articular -
Fibular collateral ligament ^ U^"
Tibial recurrent -
Peroneal artery -
Lateral anterior malleolar artery .
Perforating peroneal artery -
Posterior peroneal artery -
Lateral plantar artery
Abdominal aorta
Common iliac artery
Middle sacral artery
Hypogastric artery
External iliac artery
Obturator artery
Inferior gluteal artery
Internal pudendal artery
Medial circumflex artery
Superficial femoral artery
Perforating branches of profunda
Genu suprema
Terminal branch of profunda anasto-
mosing with popliteal
Superior medial Eirticular
Tibial collateral ligament
Inferior medial articular
Posterior tibial artery
Anterior msdial malleolar artery
lateral tarsal artery
Dorsalis pedis artery
Arcuate artery
through the fascia covering the fossa ovalis (saphenous opening) and cross the
spermatic cord in the malCj or round ligament in the female, to reach and supply
the integument above the pubes. One branch descends along the penis lateral
620 THE BLOOD-VASCULAR SYSTEM
to the dorsal artery, with which, and with the corresponding artery of the opposite
side, it anastomoses at the corona. In the female, this branch terminates in the
preputium clitoridis, anastomosing with the dorsal artery of the clitoris.
Other branches run medially beneath the deep fascia, across the pectineus and adductor
longus muscles, and, perforating the fascia close to the ramus of the pubis, supply the skin of the
scrotum or the labium majus, in the female [aa. scrotales or labiales anteriores] anastomosing
with the posterior scrotal or labial branches of the perineal artery. The external pudendal
supplies small twigs to the pectineus and adductor muscles. Its companion veins terminate as a
single trunk in the great saphenous.
(4) The inguinal branches [rami inguinales], a series of five or six small
branches arise a short distance below the inguinal Hgament. They supply the
subinguinal lymph-nodes, and the skin and muscles in this region.
(5) The profunda artery [a. profunda femoris] (figs. 496, 497), is the chief
nutrient vessel of the thigh. It is usually given off from the back and lateral
part of the common femoral, about 4 cm. (1| in.) below the inguinal fPoupart's)
ligament. At first it is a little lateral to the femoral, but as it runs downward and
backward it gets behind that artery and closer to the bone. On reaching the upper
border of the adductor longus muscle, it leaves the femoral, and, passing beneath
the muscle, pierces the adductor magnus. Finally, much reduced in size, it ends
in the hamstraing muscles, anastomosing with the third perforating and muscular
and articular branches of the popliteal.
Jlelations. — Behind, the artery Hes successively upon the iKacus, the pectineus, the adduc-
tor brevis, and adductor magnus muscles. In front, at first it is superficial, being merely covered
by the skin, superficial and deep fascise, and branches of the femoral (anterior crural) nerve; but
as it sinks behind the femoral artery, it has in front of it both the femoral and the profunda veins
and lower down the adductor longus muscle. Laterally is the femur at the angle of union of the
adductors longus and brevis. Medially is the pectineus at the upper part of its course.
Branches of the profunda. — The profunda gives off the following branches: —
(a) The lateral circumflex; (h) the medial circumflex; and (c) the three per-
forating. The termination of the artery is sometimes called the fourth perforating
branch.
(a) The lateral- circumflex [a circumflexa femoris laterahs] a short trunk, but the largest in
diameter of the branches of the artery, arises from the lateral side of the profunda as it hes on the
iUacus muscle, about 2 cm. (f in.) below the origin of that vessel from the femoral. It passes
in a transversely lateral direction over the iliacus, under the sartorius and rectus, and between the
branches of the femoral (anterior crural) nerve. In this course it gives off branches to the rectus
and vastus intermedins (crureus), and then divides into two chief sets of branches — ascending
and descending.
The ascending branch [ramus ascendeus] either breaks up at once into numerous branches
or it may arise as several vessels some of which are apt to come from the profunda itself or even
from the femoral. These run upward under the sartorius and tensor facise latse or laterally
under the rectus femoris. The highest branches reach the gluteus medius and minimus and
anastomose with the gluteal and deep circumflex ihac arteries; one branch runs beneath the
rectus femoris to the hip-joint, and the others cross the vastus intermedins and pierce the vastus
lateralis to anastomose with the first perforating and the medial circumflex.
The descending branches [rami descendentes] run directly downward along with the nerve
to the vastus laterahs muscle. They lie beneath the rectus muscle and on the vastus intermedins
(crureus) or vastus laterahs, some of them being j ust under cover of the anterior edge of the latter
muscle. They are distributed to the vastus lateralis, vastus intermedins, and rectus, one branch
usually running along the anterior border of the vastus laterahs as far as the knee-joint, where it
anastomoses with the superior lateral articular branch of the pophteal (fig. 499); another, enter-
ing the vastus intermedius, anastomoses with the termination of the profunda and with the genu
suprema (anastomotica magna).
(6) The medial circumflex artery [a. circumflexa femoris medialis] comes off from the back
and medial aspect of the profunda artery on about the same level as the lateral circumflex;
sometimes as a common trunk with that vessel. As it winds around the medial side of the femur
to reach the region of the trochanters, it lies successively, flrst, between the psoas and pectineus,
then between the obturator externus and adductor brevis; finaUy, between the adductor mag-
nus and quadratus femoris, where it anastomoses with the lateral circumflex, with the inferior
gluteal (sciatic), and with the superior perforating, forming the so-called crucial anastomosis.
While still in the femoral trgione it gives off a superficial branch [r. superfioialis] which runs in a
transversely medial direction to supply the pectineus adductor longus and brevis, and the
gracilis. The remainder of the artery is designated as the deep branch [r. profundus]. An
acetabular branch (r. acetabuli] courses upward beneath the tendon of the psoas, and enters the
hip-joint beneath the transverse ligament, and, together with the articular branch of the obtura-
tor, supplies the fatty tissue in the acetabulum, and sends branches to the synovial membrane.
The medial circumflex veins join the profunda vein.
(c) The perforating arteries of the profunda are so called because they perforate, in a more or
less regular manner from above downward, certain of the adductor muscles. They form a series
THE POPLITEAL ARTERY 621
of loops by anastomosing with one another (fig. 497), and with the superior gluteal, medial cir-
cumflex, and inferior gluteal arteries above, and with the muscular and articular branches of the
popliteal below. They are distributed chiefly to the hamstring muscles, but send twigs along
the lateral intermuscular septum to supply the integuments at the back and lateral parts of the
thigh. Other branches perforate the lateral intermuscular septum and the short head of the
biceps, and, entering the vastus intermedins (crureus) and vastus laterahs, anastomose with the
descending' branch of the lateral circumflex. All the perforating arteries, moreover, contribute
to reinforce the artery of the sciatic nerve, a branch of the inferior gluteal (sciatic) artery. They
are each accompanied by two veins which terminate in the profunda.
The first perforating artery [a. perforans prima] is given off from the profunda as that vessel
sinks beneath the adductor longus. It either pierces the adductor brevis, or else runs between
the pectineus and adductor brevis, and then passes through a small aponeurotic opening in the
adductor magnus close to the medial lip of the hnea aspera. In this course it supphes branches
to the adductors, and, after perforating the adductor magnus, is distributed to the lower part of
the gluteus maximus and the hamstring muscles, one branch commonly running upward beneath
the gluteus maximus to anastomose with the lateral circumflex, medial circumflex, and inferior
gluteal (sciatic) arteries, forming the crucial anastomosis at the junction of the neck of the femur
with the great trochanter (flg. 497). A second branch descends to anastomose with the ascend-
ing branch of the second perforating.
The second perforating artery [a. perforans secunda] which is given off from the profunda as
it lies behind the adductor longus, pierces the adductor brevis, and then passes through a second
aponeurotic opening in the adductor magnus a httle below that for the first perforating artery,
and also close to the linea aspera. It supplies the hamstring muscles, sends a branch upward to
anastomose with the descending branch of the first perforating, and another downward to anas-
tomose in hke manner with the ascending branch of the third perforating.
The third perforating artery [a. perforans tertia] also arises from the profunda as it hes under
the adductor longus, usually about the level of the lower border of the adductor brevis. It turns
beneath this border, and then, like the first and second perforating, passes through an aponeu-
rotic opening in the adductor magnus close to the linea aspera. It also supplies the hamstring
muscles, and divides into two branches, which anastomose above with the second perforating,
and below with the termination of the profunda.
Two nutrient arteries to the femur [aa. nutritiae femoris superior et inferior] arise from the
perforating arteries. The superior generally arises from the first perforating, the inferior
usually from the third.
(6) The muscular branches [rami musculares], of the femoral artery supply
the sartorius, the rectus, the vastus medialis, the vastus intermedius (crureus),
and the adductor muscles.
(7) The genu suprema (or anastomotica magna) arises from the front and
medial side of the femoral just before the latter perforates the adductor magnus
muscle, and almost immediately divides into branches, (a) saphenous, {h) muscu-
lar, and (c) articular. These branches may sometimes come off separately from
the femoral.
(a) The saphenous branch [a. saphena] pierces the aponeurotic covering of the adductor
canal, passes between the sartorius and gracilis muscles along with the saphenous nerve, and,
perforating the deep fascia, suppUes the skin of the upper and medial side of the leg and anasto-
moses with the inferior medial articular branch of the popUteal and the other vessels forming the
plexus or rete at the medial side of the knee. In its course it gives twigs to the lower part of the
sartorius and gracihs muscles.
(6) The muscular branches [rr. musculares] run downward in front of the adductor magnus
tendon, burrowing amongst the fibres of the vastus mediahs as far as the medial condyle. They
break up into numerous twigs which supply the lower ends of the vasti muscles and adductor
magnus. One branch runs laterally across the lower end of the femur to end in the vastus
laterahs.
(c) The articular branches [rr. articulares] come off from the saphenous and muscular
branches and enter the arterial rete on the medial and lateral sides of the knee. They anas-
tamose with the medial and lateral superior articular branches of the popHteal and the ante-
rior tibial recurrent and, Uke other vessels of the rete, supply branches to the joint.
THE POPLITEAL ARTERY
The popliteal artery [a. poplitea] (fig. 498) runs through the pophteal space or
ham. It is a continuation of the femoral, and extends from the aponeurotic
opening in the adductor magnus at the junction of the middle with the lower
third of the thigh to the lower border of the popliteus muscle, where it terminates
by dividing into the anterior and posterior tibial arteries. This division is on a
level with the lower border of the tuberosity of the tibia. As the artery passes
through the opening in the adductor magnus, it is accompanied by the pophteal
vein, and at times by the branch of the obturator nerve to the knee-joint. The
vein throughout is behind the artery, at first lying a little lateral to it, but as the
vessels pass through the popliteal space the vein crosses obliquely over the artery.
622 THE BLOOD-VASCULAR SYSTEM
and at the termination of the artery lies a little to its medial side. The tibial
(internal popliteal) nerve is superficial to both artery and vein. As it enters the
space it is well to the lateral side of the vessels, but as it descends it gradually
approaches them, crosses behind them, and at the lower part of the space lies to
their medial side. The artery in the whole of its course is deeply placed and
covered by a considerable amount of fat and cellular tissue.
Relations (fig. 498). — In front, the artery lies successively on the pophteal surface of the
femur (from which it is separated by a httle fat and sometimes one or two small glands); on the
posterior ligament of the knee; on the hinder edge of the articular surface of the head of the tibia;
and on the pophteus muscle. From the latter muscle it is separated by the expansion from the
semi-membranosus which covers the muscle, and is attached to the popUteal line on the tibia.
Behind, the artery is covered, above by the semi-membranosus; in the centre of the space by
the skin, superficial and deep fascia; and below, by the medial head of the gastrocnemius. The
Eopliteal vein is behind it in the whole of its course. The tibial (internal popliteal) nerve crosses
ehind it obUquely, from the lateral to the medial side, about the centre of the space. As the
artery divides into the anterior and posterior tibial, it is crossed by the aponeurotic arch of the
soleus which stretches between the tibial and fibular origins of that muscle.
To the medial side are the semi-membranosus above, and the medial head of the gastrocne-
mius and the tibial (internal pophteal) nerve below.
To the lateral side are the biceps and the tibial (internal popliteal) nerve above, and the
lateral head of the gastrocnemius and the plantaris below.
Branches of the Popliteal Artery
The branches of the popliteal include the following: — (1) the sural; (2) the
articular; and (3) the terminal.
(1) The sural arteries [aa. surales] arise irregularly from the popliteal and
supply the muscles of the calf, sending branches upward to the muscles bound-
ing the upper part of the popliteal space. From the sural arteries also arise
the superficial sural or cutaneous branches which pass downward between the
two heads of the gastrocnemius, and, perforating the deep fascia, supply the skin
and fascia of the calf. A branch, usually of moderate size, accompanies the small
saphenous vein, and is sometimes called the posterior saphenous artery.
(2) The articular, five in number, are divided into two superior (medial and
lateral), two inferior (medial and lateral), and the middle or azygos. The
superior and inferior come off transversely in pairs from either side of the popliteal,
the superior above, the inferior below the joint. Winding round the bones to
the front of the knee, they form — by anastomosing with each other and with the
genu suprema (anastomotica magna) , the termination of the profunda, the descend-
ing branch of the lateral circumflex, and the anterior tibial recurrent — a super-
ficial and deep arterial rete (fig. 499). The superficial anastomosis or rete lies
between the skin and fascia round about the patella (patellar rete), which it
supplies, the larger branches entering it from above. The deep anastomosis or
articular rete [rete articularis genu] lies on the surface of the bones around the
articular surfaces of the femur and tibia, supplying branches to the contiguous
bones and to the joints. The middle articular is a single short trunk coming
off from the deep surface of the popliteal artery. It at once passes through the
posterior ligament into the joint.
(o) The superior lateral articular artery [a. genu superior lateralis], the larger of the two
superior articular branches, runs in a lateral direction above the lateral head of the gastrocne-
mius, and, passing beneath the biceps and through the lateral intermuscular septum and vastus
lateralis, enters the substance of the vastus intermedins (erureus), and anastomoses, above with
the descending branch of the lateral circumflex, below with the inferior lateral articular, and
across the front of the femur with the superior medial articular, the genu suprema (anastomot-
ica magna), and termination of the profunda, forming with them, as already described, the
deep articular rete. Branches are given off to the patella, to the upper and lateral part of the
joint, to the bone, and to the contiguous muscles.
(6) The superior medial articular artery [a. genu superior mediaUs] (fig. 499) runs medially
just above the medial head of the gastrocnemius, beneath the semi-membranosus, and, after
perforating the tendon of the adductor magnus, enters the substance of the vastus medialis.
Here it anastomoses with the deep branch of the genu suprema (anastomotica magna) and ter-
mination of the profunda above, with the inferior medial articular below, and with the superior
lateral articular across the front of the femur. It supphes small branches to the contiguous
muscles, to the femur, to the patella, and to the joint.
(c) The inferior medial articular artery [a. genu inferior mediaUs], the larger of the two in-
ferior articular arteries, passes in an obliquely medial direction across the pophteus, below the
medial condyle (tuberosity) of the tibia and beneath the tibial collateral ligament to the front and
POPLITEAL ARTERY
623
medial side of the knee-joint. Here it anastomoses (fig. 499), above witli the superior medial
articular and the superficial branch of the genu suprema (anastomotica magna), and across the
front of the tibia with the inferior lateral articular. It supphes branches to the lower and medial
part of the joint.
(d) The inferior lateral articular artery [a. genu inferior lateralis] passes laterally above the
head of the fibula, along the tendon of the popliteus muscle, beneath the lateral head of the gas-
trocnemius, and then under the tendon of the biceps, and between the long and short fibular
Fig. 498. — Relations of the Popliteal Artery to Bones and Muscles, Left Side.
Superior lateral articular artery -
Fibular lateral ligament llj
IK
Inferior lateral articular artery {i-
Popliteus
Muscular branch to soleus
Soleus
Anterior tibial artery
Peroneus longus ■
Peroneal artery ■
Flexor hallucis longus
Cutaneous branch of peroneal artery
Peroneus brevis .
Continuation of peroneal artery
Superior medial articular artery
Popliteal artery
Posterior ligament of knee
■ Azygos articular artery
— 14 Semi-membranosus
Inferior medial articular artery
Muscular branch
. Tibialis posterior
■ Tibial nerve
Flexor digitorum longus
Posterior tibial artery
Tibialis posterior
Communicating brauch
Laciniate ligament
Internal calcaneal artery
collaterallligaments. Then winding to the front of the joint, it anastomoses above with the
superior lateral articular, below with the anterior tibial recurrent, and across the front of the
tibia with the inferior medial articular. It also supplies branches to the lateral and lower part
of the joint.
(e) The middle or azygos articular artery [a. genu media] arises from the deep surface of the
popliteal artery, and passes, with the articular branch of the obtiu*ator nerve, through the
624
THE BLOOD-VASCULAR SYSTEM
popliteal ligament, directly into the knee-joint, where it supplies the crucial ligaments, and the
patellar synovial and alar folds. It anastomoses with the intrinsic branches of the other articu-
lar arteries.
(3) The terminal branches of the popliteal are the posterior and the anterior
tibial arteries.
Fig. 499. — The Anastomosis about the Left Knee-joint. (Walsham.)
(Semi-diagrammatic. )
Deep branch of genu suprema
Superficial branch of genusuprema . .
Adductor magnus
Superior medial articular artery
piercing tendon of adductor
magnus
Tibial collateral ligament
Inferior medial articular artery
passing under tibial collateral
ligament
Posterior tibial artery
Descending branch of lateral
circum,flex artery
Superior lateral articular artery
passing through external inter-
muscular septum
Lateral epicondyle
Fibular collateral ligament
Inferior lateral articular artery
passing under fibular collateral
ligament
Anterior tibial recurrent artery
■~ Anterior tibial artery
THE POSTERIOR TIBIAL ARTERY
The posterior tibial artery [a. tibialis posterior] (fig. 500) , the larger of the
two branches into which the popliteal divides at the lower border of the popliteus
muscle, runs downward on the flexor aspect of the leg between the superficial
and deep muscles to the back of the medial malleolus. Midway between the tip
of the malleolus and the calcaneus, and under cover of the origin of the abductor
hallucis as it arises from the laciniate (internal annular) ligament, it divides into
the medial and lateral plantar arteries.
The artery is first situated midway between the tibia and fibula, and is deeply
placed beneath the muscles of the calf. As it passes downward it inclines to the
medial side and at the lower third of the leg is superficial, being only covered by
the skin and fasciae. At the ankle it lies beneath the laciniate ligament, and at its
bifurcation also beneath the abductor hallucis. A line drawn from the centre of
the popliteal space to a spot midway between the medial malleolus and point of
the heel will indicate its course. In addition to the branches named below it
supplies the muscles between which it passes, and the integument of the lower
medial region of the leg.
Relations. — Anteriorly, from above downward, it lies successively on the tibialis posterior,
the flexor digitorum longus, the posterior surface' of the tibia, and the deltoid ligament of the
ankle-joint.
Posteriorly, it is covered by the skin and fascia, the gastrocnemius and soleus, and the deep
or intermuscular fascia of the leg, by which it is tightly bound down to the underlying muscles.
It is crossed by the tibial nerve about 4 cm. (If in.) below its origin, after it has given off its
POSTERIOR TIBIAL ARTERY
625
peroneal branch; the nerve first lies on the medial, and for the rest of its course on the lateral
side of the vessel. It is accompanied by two veins, which send numerous anastomosing branches
across it. In the lower third of the leg the artery is superficial, being covered only by the skin
and^by the superficial and deep fascia?.
Fig. 500. — The Popliteal, the Posterior Tibial, and the Peroneal Arteries.
(After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Adductor magnus -
;nu suprema artery-
Vastus medialis -^ z:
Superior medial articular artery —
- Superior lateral articular artery
a Popliteal artery
Middle articular artery '^ ,
Semimembranosus — i
Inferior medial articular artery ~
Popliteal artery —
- Sural arteries
Collateral fibular ligament
Inferior lateral articular artery
Fibular branch
Anterior tibial artery
_,-Interosseous membrane
.^Tibial nutrient artery
Posterior tibial artery -
Flexor longus digitorum-
Flesor hallucis longus b
» Peroneal artery
-^ — ■ Fibtilar nutrient artery
> Flexor hallucis longus
Communicating branches , ~^,
I
Posterior tibial muscle'- ^«3(
Posterior medial malleolar artery- v^^nm^j
Flexor longus hallucis-
Communicating branches-
Tendo Achllli;
Medial calcanean branches tt/V^
aPeroneus brevis
- Perforating branch
^ Peroneus longus
- Posterior lateral malleolar artery
— Lateral calcanean branche
■•Calcanean rete
At the medial malleolus it lies beneath the laciniate (internal annular) ligament and abduc-
tor hallucis upon the deltoid ligament of the ankle-joint. Here it has the tibialis posterior
and flexor digitorum longus in front of it, and the tibial nerve and the flexor haUucis longus be-
hind and to its lateral side.
At times the tibial nerve divides higher than usual, when one branch lies on the medial side
of the artery and the other branch on the lateral side.
626 THE BLOOD-VASCULAR SYSTEM
The branches of the posterior tibial artery are: — (1) The fibular; (2) the
peroneal; (3) the tibial nutrient; (4) the communicating; (5) the posterior medial
malleolar; (6) the medial calcanean, and (7) the terminal, medial and lateral
plantar.
(1) The fibular or superior fibular branch [ramus fibularis], which frequently arises from the
beginning of the anterior tibial, runs upward and laterally toward the head of the fibula. It is
small and gives twigs to the soleus, peroneus longus, and extensor digitorum longus, and anasto-
moses with the inferior lateral articular and the lateral sural arteries.
(2) The peroneal artery [a. peronea] is a large vessel which (figs. 498, 500),
arises from the posterior tibial about 2.5 cm. (1 in.) below the lower border of the
popliteus muscle. At first forming a gentle curve convex laterally, it approaches
the fibula, and continues its course downward close to that bone as far as the lower
end of the interosseous membrane, where it gives off a large branch, the perforating
(anterior peroneal), and then, passing over the back of the inferior tibio-fibular
joint, terminates by breaking up into a network, which is distributed over the
back of the lateral malleolus and lateral surface of the calcaneus (figs. 500, 504).
It is accompanied b}^ two vense comitantes. Besides the named branches it
supplies twigs to the flexor hallucis longus, tibialis posterior, tibialis anterior,
peronei and soleus; also to the integument on the lateral side of the leg.
Relations. — At its upper part it is deeply placed between the tibialis posterior and soleus
muscles, and beneath the deep or intermuscular fascia. For the rest of its course to the ankle
it Ues beneath, or sometimes in the substance of, the flexor hallucis longus in the angle between
the fibula and interosseous membrane. After giving off the perforating branch, it is only cov-
ered, as it lies behind the tibio-fibular articulation, by the integuments and deep fascia, and in
this part of its course is sometimes called the posterior peroneal.
The branches of the peroneal artery are: — (a) The perforating (anterior
peroneal) ; (b) the fibular nutrient; (c) the communicating; (d) the lateral malleolar;
(e) the lateral calcanean; and (/) the terminal.
(o) The perforating (or anterior peroneal) branch [ramus perforans] arises from the front
of the peroneal artery at the lower part of the interosseous space, and, passing through the
interosseous membrane, runs downward over the front of the inferior tibio-fibular joint, beneath
the peroneus tertius, and supplies this muscle and the inferior tibio-fibular joint. It anasto-
moses with the tarsal, arcuate (metatarsal) and lateral malleolar branches of the anterior tibial
artery, and with the lateral plantar artery on the lateral side of the foot, forming a plexus over
the ankle (fig. 503).
(b) The fibular nutrient [a. nutritia fibula;] enters the nutrient foramen of the fibula.
(cj The communicating branch [ramus communicans] passes medially in front of the tendo
Achillis to anastomose with the communicating branch of the posterior tibial. The usual
situation of this communication is from 2.5 to 5 cm. (1 to 2 in.) above the ankle-joint.
(d) The lateral posterior malleolar artery [a. malleol.aris poster, lateralis] anastomoses on
the lateral malleolus with the anterior lateral malleolar of the anterior tibial artery to form the
lateral malleolar rete.
(e) The lateral calcaneal branches [rami calcanei laterales] come off from the peroneal below
the point at which the perforating is given off, and are distributed over the lateral surface of the
calcaneus.
(/) The terminal branch or posterior peroneal, the continuation of the peroneal artery,
anastomoses with the other arteries distributed to the lateral malleolus and heel.
(3) The tibial nutrient artery [a. nutritia tibiae], a vessel of large size, leaves the posterior
tibial at its upper part, pierces the tibialis posterior, and enters the nutrient foramen in the
upper third of the posterior surface of the tibia. In the interior of the bone it divides into two
branches: an ascending or smaller, which runs upward toward the head of the bone; and a de-
scending or larger, which courses downward toward the lower end. It gives off two or three
muscular twigs to the tibialis posterior before it enters the foramen. The nutrient artery of the
tibia is the largest nutrient artery of bone in the body, and is accompanied by a nerve given off
by the nerve to the popliteus.
(4) The communicating branch [ramus communicans] arises from the posterior tibial about
5 cm. (2 in.) above the medial malleolus, and, passing transversely across the tibia beneath
the flexor hallucis longus and tendo Achillis, anastomoses with the communicating branch of
the peroneal.
Frequently an inferior communicating branch between the posterior tibial and peroneal
arteries is hkewise present in the loose connective tissue beneath or behind the tendo Achillis.
(5) The posterior medial malleolar branch [ramus maUeolaris posterior medialis] divides
for distribution over the medial malleolus, anastomosing with the other arteries entering into
the medial malleolar rete [rete m.iUeolare mediale] which is formed over the portion of bone.
In its course to the malleolus it runs beneath the flexor digitorum longus and tibiaUs posterior
muscles.
(6) The medial calcanean branches [rami calcanei mediales] are distributed to the soft
parts over the medial side of the calcaneus. These branches come off from the posterior tibial
just before its bifurcation, and anastomose with the medial malleolar and pei'oneal arteries.
(7) The terminal branches are the lateral and medial plantar arteries.
ANTERIOR TIBIAL ARTERY
627
THE LATERAL PLANTAR ARTERY
The lateral plantar artery [a. plantaris lateralis] (figs. 501, 502) — the larger of
the two branches into which the posterior tibial divides beneath the laciniate
(internal annular) ligament — passes at first laterally and forward across the sole
of the foot to the base of the fifth metatarsal bone, where it bends medially, and
still running forward sinks deeply into the foot and terminates at the proximal end
of the first interosseous space by anastomosing with the deep plantar (com-
municating) branch of the dorsal artery of the foot. In its course to the fifth
metatarsal bone the artery runs in a more or less straight line obliquely across the
foot ; whilst its deep portion, extending from thefif th metatarsal bone to the proximal
Fig. 501. — The Plantar Arteries, Left Foot.
(From a dissection in the Museum of St. Bartholomew's Hospital.)
Lateral calcanean branch
Anastomosing branch of lateral
plantar
Abductor digiti quinti
— Medial calcane
Cutaneous branch of medial
plantar
Plantar aponeurosis, cut
Abductor hallucis
Anastomotic branch
Lateral plantar artery
Digital to lateral side of little toe
Lumbrical muscle
Fourth metatarsal
Third metatarsal
Second metatarsal
Anastomosis about interpha-
langeal joint
Dorsal branch of plantar digital
Anastomosis of plantar digital arteries
around matrix of nail and pulp of toe
Medial plantar artery
Flexor digitorum brevis
Superior branch of medial plantar
Flexor hallucis brevis
First plantar metatarsal artery
Plantar digital branch of first meta-
tarsal to toe
Plantar digital branch of first meta-
tarsal to medial side of great toe
Plantar digital branch of first meta-
tarsal to lateral side of great toe
end of the first interosseous space, forms a slight curve with the convexity forward,
and is known as the plantar arch. The plantar arch is comparable to the deep
volar arch formed by the deep branch of the ulnar anastomosing with the radial
through the first interosseous space. This homology is at times more complete
in that the deep plantar (communicating) branch of the dorsalis pedis, the
homologue of the radial in the upper limb, takes the chief share in forming the
arch. The lateral plantar artery is accompanied by two veins. The course of
the artery is indicated by a line drawn across the sole of the foot from a point
midway between the tip of the medial malleolus and the medial tubercle of the
calcaneus to the base of the fifth metatarsal bone, and thence to the lateral side
of the base of the first metatarsal.
The lateral plantar artery, besides the branches named below gives twigs to
supply the muscles between which it passes, and the tarsal joints. It also gives
628
THE BLOOD-VASCULAR SYSTEM
branches to the integument of the lateral side of the sole, some of which anasto-
mose with arteries on tlie lateral side of the dorsum.
Relations. — In the first part of its course from the medial malleolus to the base of the fifth
metatarsal bone, the artery is covered successively by the abductor hallucis and the flexor
digitorum brevis, by which it is separated from the plantar aponeurosis, and may be slightly
overlapped in muscular subjects by the abductor quinti digiti. As it approches the base of the
fifth metatarsal bone it Ues, as it turns medially before sinking into the foot, in the interspace
between the flexor digitorum brevis and the abductor quinti digiti, and is here covered only by the
skin and superficial fascia and the plantar aponeurosis. It hes upon the calcaneus, the quadratus
plantse (flexor accessorius), and the flexor digiti quinti brevis. It is accompanied by the lateral
plantar nerve, the smaller of the two divisions into which the tibial nerve divides. In this part
of its course it gives off small branches to the contiguous muscles and to the heel.
Fig. 502. — Plantae Arteries (Deep). (After Henle.)
Anterior perforating branch
First dorsal interosseous muscle
Metatarsal artery
Deep plantar b"°'=h\J^>«MMi ]l||, I m\miiii^-\^^^^''^ metatarsal artery
Plantar metatarsal artery
Perforating branch
Branch of the medial plantar artery
Abductor hallucis muscl
Tendon of the posterior tibial
muscle
Medial plantar artery
Tendons of the flexor
digitorum longus
Quadratus plant£e
Abductor of the fifth digit
Lateral plantar artery
tibial artery
In the second part of its course the artery, which is here known as the plantar arch [arcus
plantaris], sinks into the sole, and is covered, in addition to the skin, superficial fascia, plantar
aponeurosis, and flexor digitorum brevis by the tendons of the flexor digitorum longus, the
lumbricales, branches of the medial plantar nerve, and the adductor hallucis. It lies upon the
proximal ends of the second, third, and fourth metatarsal bones and the corresponding interos-
seous muscles.
The branches of the lateral plantar artery are: — (1) Perforating; and (2)
plantar metatarsal (digital).
(1) The perforating branches [rr. perforantes], three in numbers, ascend through the
proximal end of the second, third, and fourth spaces, between the two heads of the correspond-
ingly named dorsal interosseous muscles, and communicate with the proximal ends of the
first, second, and third dorsal metatarsal (interosseous) arteries (fig. 502).
(2) The plantar metatarsal arteries [aa. metatarsete plantares] are usually four in number,
and pass forward in the four intermetatarsal spaces, which are numbered from the medial side.
They rest upon the interosseous muscles of their spaces, and are at first under cover of the lum-
bricals, but as they approach the clefts of the toes each divides into two branches, the plantar
digital arteries [aa. digitales plantares], which supply the contiguous sides of the toes. The
plantar digital branch for the medial side of the great toe is usually given off by the first plantar
metatarsal; that for the lateral side of the Uttle toe is usually a separate branch from the lateral
end of the plantar arch.
ANTERIOR TIBIAL ARTERY 629
The plantar metatarsal arteries, immediately before they bifurcate, send to the dorsum of
the foot a perforating branch each to the corresponding dorsal metatarsal arteries. They
anastomose by many small twigs with the dorsal metatarsal arteries, which also run along the
sides of the metatarsal bones, but more toward the dorsal aspect. Immediately above each
phalangeal joint the plantar digital vessels communicate by cross branches, forming a rete for
the supply of the articular end of the phalanges and the contiguous joints. At the distal end
of the toes they also freely anastomose with each other, forming a rete beneath the pulp and
around the matrix of the nail. The metatarsal and digital arteries are each accompanied by
two small veins.
THE MEDIAL PLANTAR ARTERY
The medial plantar artery [a. plantaris medialis] (figs. 501, 502) — much the
smaller of the two divisions into which the posterior tibial divides, passes forward
along the medial side of the sole of the foot usually to the first interosseous space.
Here it ends by anastomosing either with the first plantar metatarsal artery
derived from the plantar arch, or with the branch given off by the first plantar
metatarsal to the medial side of the great toe.
Relations. — The artery is at first under cover of the abductor hallucis, but afterward Ues
in the interval between that muscle and the flexor digitorum brevis. It is covered by the skin
and superficial fascia, but not by the plantar aponeurosis, since it lies between the central and
medial portions of that structure.
The branches of the medial plantar are: — (1) The deep and (2) the superficial
branches.
(1) The deep branch [ramus profundus], which at once divides — or it may come off as
several branches — to supply the muscles, articulations,and integument of the medial side of the
sole. Some of these branches form an anastomosis aroundthe medial margin of the foot, with
branches of the dorsahs pedis.
(2) The superficial branch [ramus superficialis] breaks up into very small twigs which ac-
company the digital branches of the medial plantar nerves, and anastomose with the plantar
metatarsal arteries in the first, second, and third spaces. At times a twig from one of these
branches joins the lateral plantar artery to form a superficial plantar arch.
THE ANTERIOR TIBIAL ARTERY
The anterior tibial artery [a. tibialis anterior] fig. 503 — the smaller of the
two branches into which the popliteal artery divides at the lower border of the
popliteus muscle — at first courses forward between the two heads of origin of the
tibialis posterior, and, after passing between the tibia and fibula above the upper
part of the interosseous membrane, runs downward on the front and lateral aspect
of the leg, between the anterior muscles, as far as the front of the ankle-joint.
Below the joint it is known as the dorsalis pedis. The course of the vessel is
indicated by a line drawn from the front of the head of the fibula to a point mid-
way between the two malleoli.
The artery is accompanied by two veins which communicate with each other
at frequent intervals across it. It is also accompanied in the lower three-fourths
of its course by the deep pei'oneal nerve. The nerve, which winds round the head
of the fibula, and pierces the extensor digitorum longus, first comes into contact
with the lateral side of the artery about the upper third of the leg; in the middle
third it is a little in front of the artery, and in the lower third again lies to its
lateral side. In addition to the named branches the anterior tibial artery supplies
muscular twigs to the extensors of the toes and the tibiahs anterior.
Relations. — The artery at first Ues in the triangle formed by the two heads of the tibiahs
posterior and the popliteus muscle; and, as it passes above the interosseous membrane, it has
the tibia on one side and the fibula on the other. It is separated from the deep peroneal (ante-
rior tibial) nerve at its commencement by the neck of the fibula and the extensor digitorum
longus. This arrangement is homologous with that met with in the forearm in the case of the
posterior interosseous artery and deep radial (posterior interosseous) nerve.
Posteriorly in its course down the leg it lies in its upper two-thirds upon the interosseous
membrane, to which it is closely bound by fibrous bands; and in its lower tliird upon the front
of the tibia and the ankle-joint.
To its medial side along its upper two-thirds is the tibialis anterior muscle; but at the lower
third it is crossed by the tendon of the extensor hallucis longus and then for the rest of its
course has this tendon overlapping it or to its medial side.
On its lateral side it is in contact in its upper third with the extensor digitorum longus
muscle; in its middle third with the extensor hallucis longus; but, as this muscle crosses to
the medial side of the artery, the vessel usually for a very short part of its course comes again
630
THE BLOOD-VASCULAR SYSTEM
into contact with the extensor digitorum longus. At the upper and lower thirds of its course
on the front of the leg the artery has the deep peroneal (anterior tibial) nerve to its lateral side.
In front the artery is covered by the skin, superficial and deep fascia. In its upper two-
thirds it is deeply placed in the cellular interval between the tibiahs anterior on the medial
side and the extensor digitorum longus and extensor hallucis longus on its lateral side; and
in .its lower third it is crossed in the latero-medial direction by the tendon of the extensor
Fig. 503. — The Anterior Tibial Artery, Dorsal Artery op the Foot, and Perforatinq
(Anterior) Peroneal Artery, and their Branches, Left Side.
Superior medial articular artery
Inferior medial articular artery
Anterior tibial recurrent artery
Anterior tibial artery
Tibialis anterior muscle
Extensor hallucis longus'
Medial malleolar artery
Crucial ligament-
Dorsalis pedis artery.
Most medial tendon of extensor digi
torum brevis
Deep plantar branch'
First dorsal metatarsal artery
Superior lateral articular artery
— -Inferior lateral articular artery
^Extensor digitorum longus
Peroneus tertius
^ Perforating peroneal artery
Lateral malleolar artery
Peroneus brevis muscle
— Extensor digitorum brevis, cut
— Lateral tarsal artery
Arcuate artery
Dorsal metatarsal artery
hallucis longus, and lies beneath the cruciate (anterior annular) ligament of the ankle-joint
The deep peroneal nerve is usually in front of the artery in the middle third of the leg.
The branches of the anterior tibial artery are: — (1) The posterior tibial recur-
rent: (2) the anterior tibial recurrent; (3) the medial malleolar; and (4) the
DORSALIS PEDIS ARTERY
631
Fig. 504.^Scheme of the Distribution and Anastomoses op the Arteries of the Right
Foot. (Walsham.)
(The plantar arteries are shown in dotted outHne; the dorsal in solid red.)
Peroneal artery
Perforating peroneal branch
Lateral malleolar branch
Posterior peroneal artery
Dor sails pedis artery
Lateral plantar artery
Lateral tarsal branch
Lateral plantar artery
forming plantar arch r -|
Posterior perforating \\, |"^'
branches "^^^^5^^_ I "^
Plantar digital artery to
lateral side of Uttle toe
Second, third, and fourth
dorsal metatarsal ar-
teries given off from
arcuate artery
Second, third, and fourth
plantar metatarsal ar-
teries
Branch of third dorsal
metatarsal artery to
lateral side of little toe
Anterior tibial artery
Medial malleolar branch
Malleolar branch of pos-
terior tibial artery
Communicating branch
between posterior
tibial and peroneal
arteries
Medial plantar artery
Medial tarsal branch
■Arcuate artery
■Deep plantar artery
First dorsal metatarsal
First plantar metatarsal
artery
Dorsal digital branch of
first dorsal metatarsal
to medial side of great
632 THE BLOOD-VASCULAR SYSTEM
lateral malleolar. In addition, ten or twelve muscular branches are given off
irregularly to the adjacent muscles along the artery.
(1) The posterior tibial recurrent artery [a. recurrens tibialis posterior] is occasionally absent.
It ascends between the popliteus muscle and the popliteal ligament of the knee-joint, supplying
these structures and the superior tibio-fibular joint. It anastomoses with the inferior lateral
articular branch of the pophteal, and to a less extent with the inferior medial articular branch.
(2) The anterior tibial recurrent [a. recurrens tibiahs anterior] is given off from the anterior
tibial artery immediately after that vessel has passed above the interosseous membrane. It
winds tortuously through the substance of the tibialis anterior muscle, over the lateral condyle
(tuberosity) of the tibia close to the bone; and, perforating the deep fascia, ramifies on the lower
and lateral part of the capsule of the knee-joint. It anastomoses with the inferior and superior
lateral articular branches of the pophteal, with the descending branch of the lateral circumflex,
and somewhat less freely with the medial articular branches of the pophteal and with the genu
suprema (anastomotica magna). It gives off small branches to the tibialis anterior, the extensor
digitorum longus, the knee-joint, and the contiguous fascia and skin. It forms one of the col-
lateral cliannels by which the blood is carried to the hmb below in obstruction of the pophteal
artery (fig. 503).
(3) The medial malleolar [a. maUeolaris anterior medialisj, the smaller of the two malleolar
branches, arises from the lower part of the anterior tibial artery a httle higher than the lateral,
usually about the spot where the tendon of the extensor haUucis longus crosses the anterior
tibial artery. It winds over the medial malleolus, passing beneath the tibiaUs anterior, and
joins the medial malleolar rete anastomosing with branches from the posterior tibial artery.
(4) The lateral malleolar artery [a. maUeolaris anterior lateralis], larger than the medial,
arises from the lateral side of the anterior tibial artery, usually on a lower level than the medial
malleolar. It winds downward and laterally round the lateral malleolus, passing beneath the
extensor digitorum longus and peroneus tertius, and joins the lateral malleolar rete by anas-
tomosing with the perforating peroneal, the termination of the peroneal, and the lateral tarsal
branch of the dorsahs pedis (fig. 503).
The anastomosis between the lateral malleolar and perforating peroneal is sometimes of
considerable size, supplying the blood to the dorsal artery of the foot; the anterior tibial, then
much reduced in size, usually ends at the place of origin of the lateral malleolar.
THE DORSALIS PEDIS ARTERY
The dorsalis pedis artery [a. dorsalis pedis] (fig. 503) is a continuation of the
anterior tibial. It extends from the front of the ankle-joint to the proximal end
of the first interosseous space, where it ends, as the deep plantar branch, by joining
the lateral plantar artery to complete the plantar arch. It is accompanied by
two venae comitantes. The course of the artery is indicated by a fine drawn from
a point midway between the two malleoli to the proximal end of the first metatar-
sal space.
Relations. — Behind, the artery from above downward Ues successively on the talus (astrag-
alus), navicular, second cuneiform, and the base of the second metatarsal bones, and the hga-
ments uniting these bones. At times its course is a little more lateral, lying either partly on
the second cuneiform bone, or on the dorsal ligaments uniting the second cuneiform to the first
cuneiform. It is more or less bound down to the bones by aponeurotic fibres derived from the
deep fascia.
In front, the artery is covered by the crucial (anterior annular) hgament, sometimes by the
extensor hallucis longus, by the skin, the superficial and deep fascia, and, just before its termi-
nation, by the tendon of the extensor hallucis brevis. The angle formed by this tendon with the
extensor hallucis longus is the best guide to finding the artery in the process of Ugature (fig. 503).
To its lateral side is the most medial tendon of the extensor digitorum longus, and lower
down the tendon of the extensor hallucis brevis. The deep peroneal (anterior tibial) nerve is
also to its lateral side.
To its medial side is the extensor hallucis longus, except at times for about half an inch below,
where the tendon of the extensor haUucis brevis, having crossed the artery, may he between it
and this tendon.
The branches of the dorsalis pedis artery are: — (1) The tarsal; (2) the arcu-
ate; and (3) the deep plantar.
(1) The tarsal branches may be divided into (a) the lateral and (6) the medial, (a) The
lateral tarsal artery [a. tarsea lateraUs] runs laterally over the navicular and cuboid bones beneath
the extensor digitorum brevis. It supplies branches to that muscle, and to the bones and the
articulations between them, and anastomoses above with the lateral malleolar and perforating
(anterior) peroneal, below with the arcuate (metatarsal) and, over the lateral border of the foot,
with the anastomotic branches of the lateral plantar artery. (6) The medial tarsal arteries
[aa. tarseai raediales] consists of a few small branches which run over the medial side of the foot,
supplying the skin and articulations, and anastomose with the medial malleolar.
(2) The arcuate (metatarsal) artery Ja. arcuata] (figs. 503, 504) runs laterally across the
foot, in a shght curve with the convexity forward, over the bases of the metatarsal bones, and
beneath the e.xtensor tendons and the extensor digitorum brevis. At the lateral border of the
foot it anastomoses, with the lateral tarsal, and with branches of the lateral plantar.
MORPHOGENESIS OF THE ARTERIES 633
lYom the oonvexity of the arch it gives off four dorsal metatarsal (interosseous) arteries,
which run forward on the dorsal interosseous muscles in the centre of the four interosseous spaces
to the cleft of the toes, where they bifurcate for the supply of the contiguous sides of the toes.
The artery to the first space is large, and gives off the digital artery to the medial side of the great
toe. This vessel continues the direction of the dorsalis pedis and is commonly known as the
dorsalis hallucis artery. The most lateral of the interosseous branches gives off a small vessel
for the supply of the lateral side of the little toe. At the proximal end of the second, third, and
fourth interosseous spaces each artery receives a perforating branch from the lateral plantar
artery, and immediately before they bifurcate a second perforating artery through the distal
end of the interosseous space from the corresponding digital.
The dorsal digital arteries [aa. digitales dorsales], into which the dorsal metatarsal arteries
divide at the cleft of the toes, run along the side of each toe toward the dorsal aspect, anas-
tomosing with each other across the dorsum of the toes and by frequent branches with the
digital branches of the plantar metatarsal arteries, which also run along the sides of the toes,
but nearer the plantar surface. At the end of the toes they anastomose with each other around
the quick of the nail.
(3) The deep plantar branch [ramus plantaris profundus] comes off from the dorsaUs pedis
with the first dorsal metatarsal (into which arteries indeed the dorsalis pedis may be said to
divide). At the back of the first interosseous space it dips into the sole between the two heads
of the first dorsal interosseous muscle, and communicates with the termination of the lateral
plantar artery, completing the plantar arch, in a manner similar to that in which the radial
artery, passing through the first dorsal interosseous muscle in the hand, completes by anastomos-
ing with the ulnar the deep palmar arch.
MORPHOGENESIS AND VARIATIONS OF THE ARTERIES
A. ARTERIES OF THE HEAD AND TRUNK
1. MORPHOGENESIS
In conformity with the branchiomeric and metameric development of the head
and trunk (see p. 15) the arteries are developed in two sets, the branchiomeric
(aortic arches) and metameric (segmental arteries).
Fig. 505. — Model of the Pharynx and Aortic Arches op a Human Embryo 5 mm. Long.
(Tandler, X75.)
Second aortic arch
Dorsal aorta
Third aortic arch
Sixth aortic arch
(1) The system of aortic arches consists of five pairs of arteries which spring from the ven-
tral aorta, or aortoe, and pass around the pharynx in the branchial arches to join the paired
dorsal aorta;. Some of the arches are veiy transitory, but all those that give rise to permanent
vessels are present in embryos about five miUimetres in length. Fig. 505 shows their distri-
bution and rlations to the pharyngeal pouches at this stage; the arches which appear fifth in
order are regarded as the sixth because (like the sixth arches in lung-fish and amphibia) they give
634
THE BLOOD-VASCULAR SYSTEM
off the pulmonary arteries. The true fifth arches are probably not always developed, but when
they occur they are later in development, imperfect, and very transitory. The dorsal aortEe,
originally paired, are now united to form a single vessel as far forward as a place slightly caudal
to the sixth arches.
During the separation of the heart into right and left halves (p 526.), the primitive ventral
aorta is divided by the aortic septum into two vessels, the main pulmonary artery and the as-
cending aorta of the adult. The pulmonary trunk becomes connected with the sixth pair of
arches only; the other arches then communicate, by means of the aorta, with the left ventricle.
The further changes which occur in the arches to bring about the conditions found in the adult
are shown diagrammatioally in fig. 506. The right and left pulmonary arteries arise from the
corresponding sixth arches. The portion of the sixth arch dorsal to the pulmonary artery dis-
appears on the right, on the left it persists until birth as the ductus arteriosus (lig. arteriosum of
the adult). The fourth arch, including the short ventral stem between the fourth and sixth
arch, becomes the permanent aortic arch on the left side, and the innominate and proximal por-
tion of the subclavian upon the right. The dorsal longitudinal stem disappears on both sides
between the third and fourth arches, and on the right side from the sixth arch back to the un-
paired dorsal aorta. A trace of the latter portion of the right dorsal stem frequently persists in
the adult as a small vessel (a. aberrans) connecting the dorsal aorta, directly or indirectly, with
the right subclavian artery (p. 590). The ventral stems between the fourth and third arches
form the common carotids; those between the third and first become the external carotids. The
internal carotids are formed by the third arches and tlie dorsal stems between the third and first
arches. The first and second arches disappear early, contributing somewhat to the formation
of the branches of the internal and external carotids.
Fig. 506. — -Diageams showing the Method of Normal Development op the Aoetic
(Arches, and Indicating the Mechanism op Some Variations.)
The primitive aortic arches (1-6), and some of the cervical dorsal segmentals (V-VIII) are
shown in all the diagrams but numbered in Y only. X., abnormal: the aortic arch is on the
right; the left subclavian takes the dorsal course; the right vertebral arises direct from the
aortic arch. Y., normal; Z., abnormal: the right subclavian arises from the sixth cervical
dorsal segmental; the left from the sixth and seventh. A, ascending aorta; AA, aortic
arch; AD, dorsal 'aorta ; CC, common carotid; CE, external carotid; CI, internal carotid;
D, ductus arteriosus; IN, innominate; S, subclavian; T, costo-cervical; V, vertebral.
X
In early development the segmental arteries are caudally placed with regard to the aortic
arch vessels. As the latter, however, become shifted following the migration of the heart from
the neck into the thorax, the persistent seventh dorsal cervical segmental (subclavian) reaches
the neighbourhood of the sixth aortic arch.
Little is known of the share taken by the first and second aortic arches in the formation of the
branches of the internal and external carotid arteries. It has been shown by Tandler that the
internal maxillary is prirnarily a branch of the internal carotid, (the first and second arches tak-
ing a share in its formation). The primitive vessel is known as the stapedial since it passes be-
tween the crura of the developing stapes. It gives off supraorbital, infraorbital, and mandibular
branches; the latter two arising from the main artery by a common trunk. The common trunk
is later joined by a branch from the external carotid and, together with the supraorbital, becomes
the middle meningeal. An anastomosis between the supraorbital and the ophthalmic persists
80 that in the adult the anterior branch of the meningeal frequently takes a considerable share in
the blood-supply of the orbit. The stapedial trunk undergoes retrogression and is represented
in the adult by the carotico-tympanic of the internal carotid and by the superior tympanic of the
middle meningeal. The infraorbital branch of the stapedial becomes the second and third parts
of the internal maxillary and gives off branches accordingly. The mandibular branch becomes
the inferior alveolar of the adult.
(2) The segmental system (fig. 507) consists of arteries primarily arising from the aorta in
three longitudinal series, dorsal, lateral, and ventral on either side. The segmental arrange-
ment is much less perfect in the ventral and lateral groups than in the dorsal. So much so, in
fact, that the term segmental is used for the ventral and lateral groups rather as a matter
MORPHOGENESIS OF THE ARTERIES
635
of convenience than as indicating a strict numerical correspondence between segments and
The dorsal segmental arteries primarily supply the central nervous system but later give
off two sets of vessels to the body wall; these persist in the adult as the anterior and posterior
main branches of the intercostal and lumbar arteries. The remainder of each segmental artery is
represented in the adult by the spinal ramus which accompanies the corresponding nerve root
through the intervertebral foramen. The tendency to form intersegmental anastomoses
between these vessels (and their branches) gives rise to many of the important longitudinal stems
of adult anatomy. Thus, the spinal ramus gives rise to a pre- and postneural anastomosing
channel on either side, the (primarily paired) anterior and posterior spinal arteries. The anterior
branches have each a longitudinal precostal anastomosis, and, as they grow forward with the
developing body wall, their ends are connected to form the mammary anastomosis.
Between the posterior rami, a postoostal and a postvertebral anastomosis may be formed.
In addition, the anterior rami give off lateral and anterior perforating branches (fig. 507).
Two dorsal segmental arteries have been recognized in the occipital region, the first dis-
appears and the second, the hypoglossus artery, follows the hypoglossal nerve to the ventral sur-
face of the brain where it is connected with the termination of the internal carotid of its own side
by means of a longitudinal stem the a. vertebralis cerebralis. The hypoglossus artery, by shift-
ing forward to the third aortic arch, itself acquires a secondary origin from the internal carotid.
In the cervical region, the spinal ramus of segmental cervical I forms the third, or sub'
occipital, part of the vertebral artery. Cervical segmentals I to VI lose their connection with
the aorta and a postcostal anastomosis between them forms the second part of the same artery.
The first part of the vertebral is formed by the posterior ramus of cervical VI and its precostal
anastomosis with cervical VII (subclavian) (fig. 508).
Fig. 607. — Scheme of the Typical Arrangement of the Branches op the Aorta. (After
Quaim)
Longitudinal anastomoses: 1, precostal; 2, postcostal; 3 postvertebral; 4, preneural; 5, post-
neural; 6, mammary.
, Posterior branch
Anterior branch
Lateral perforating branch
Anterior perforating branch
The anterior ramus of cervical VII forms the entire first part of the subclavian on the left,
and the distal portion of it upon the right (see system of aortic arches). The second part of
the subclavian is formed by the lateral branch of the anterior ramus of cervical VII, while the
portion of the anterior ramus ventral to this becomes the root of the internal mammary. The
anterior ramus of cervical VIII disappears, but the pi'ecostal anastomosis connecting it with the
subclavian (cervical VII) persists to form the costo-cervical of the adult. The posterior ramus
of cervical VIII forms the root of the deep cervical, and, by a postvertebral anastomosis with
the other posterior cervical rami and with the occipital, forms the remainder of the deep cervical
and the descending branch of the occipital artery.
In the thoracic and lumbar regions, the embryonic conditions very largely persist (fig. 508).
The anterior rami of thoracic segmentals I and II, however, lose their connection with the
aorta and, by a precostal anastomosis with cervical VIII, become secondarily connected
(through the costo-cervical trunk) with the subclavian. The superior intercostal of the adult
is thus formed. The fifth lumbar segmental apparently joins the umbihcal artery (of the
ventral segmental series) to form the external ihac which, in the adult, provides the chief
arterial supply to the lower extremity. The inferior gluteal (sciatic), which is the primitive
artery of supply for the lower extremity, if it is segmental at all, belongs to the sacral region.
The free ends of the anterior rami of all the thoracic and the upper four lumbar segmentals
become united, as they grow out with the body wall, to form the longitudinal mammary
anastomosis (fig. 508). This anastomosis, by its connection with the anterior ramus of cervical
636 THE BLOOD-VASCULAR SYSTEM
yil (subclavian) and with the anterior ramus of lumbar V (external iliac), forms the
internal matnmary (with its superior epigastric branch) and the inferior {deep) epigastric
arteries of the adult.
In the sacral region, the adult shows evidence of segmental vessels in branches of the middle
and lateral sacral arteries; the latter probably representing a precostal anastomosis. Whether
the parietal branches may be derived directly from segmental sources, or whether they are vessels
of new formation, has not been determined embryologicaUy. The obturator would appear to
be segmentalifor it contributes a branch to the mammary anastomosis which persists in the adult
(pubic brandies of obturator and inferior epigastric). If the connecting branch with the inferior
epigastric is large, the obturator may lose its connection with the hypogastric, in which case the
latter is said to arise from the former, or from the external iliac,
One of the most interesting of the longitudinal anastomoses in connection with the dorsal
segmentals is the primitively bilateral preneural anastomosis extending ventral to the spinal
cord 'and connected, beyond the first spinal segment, with each internal carotid by means of the
right and left aa. cerebrales vertebrales. The hypoglossus artery (p. 635) having lost its con-
nection with the internal carotid, leaves the spinal ramus of cervical I (third part of the
subclavian) to take over the major share of the cerebral supply. A process of blending by anas-
FiG. 508. — Diagram to Show the Development of the Arteries or the Trunk prom the
Aortic Arches and Segmental Arteries.
The arteries which persist are black; those which degenerate are in outhne; those newly formed
are shaded. (After Mall.)
txternal Cl
Bulbus Arteriosus';
fulmooaryArleij '
SabclariaffArterCffs '
J)eep£plgastricAtterK.
femora t Artery ,^
Umbilical Artery,
tomosis now occurs resulting in the single basilar and anterior spinal arteries of the adult. The
posterior communicating, proximal portions of the posterior cerebrals, the fourth part of the vevte-
brals, and the right and left roots in the anterior spinals of the adult alone retain the primitive
arrangement and testify to the double nature of the original anastomosis. Asymmetry in the
vertebrals and other irregularities in the adult can usually be explained on developmental
grounds. The postneural anastomosis, which joins the preneural at about the first cervical seg-
ment, retains its bilaterality throughout to form tlie paired posterior spinal arteries of the adult.
The lateral segmental arteries take origin from the aorta in series, intermediate in position
between the dorsal and ventral segmentals. They reach their fullest development in embryos
of about 8 mm., when they extend from the seventh cervical to the twelfth thoracic segment and
supply the mesonephros. At this stage Broman found twenty arteries on each side, many of
which were non-segmental. As the suprarenals and gonads develop, they each receive branches
from several mesonephric arteries. The latter arteries now undergo rapid retrogression and
the suprarenal and gonadie branches are shifted caudally through the mesonephric series to
newly formed (non-segmental) arteries opposite the upper lumbar segments. Finally there
remain three suprarenal arteries opposite the twelfth thoracic and first and second lumbar
segments and a gonadie artery {ovarian or internal spermatic of the adult) opposite the third
lumbar segment. AU of these vessels now appear to be direct branches from the aorta. Of the
three suprarenal branches, the upper and lower each gives a large branch to the diaphragm and
kidney respectively and become the inferior phrenic and renal arteries of the adult. The middle
becomes the middle suprarenal of the adult. Felix puts a somewhat different interpretation upon
the origin of the vessels persisting in the lumbar region after the disappearance of the thoracic
mesonephric arteries. He finds in an embryo of 18 mm. nine arteries on either side, extending
from the ninth thoracic to the third lumbar segment, all of which he looks upon as mesonephric.
These he classifies into tlxree groups: — Cranial, which reach the mesonephros by passing dorsal
to the suprarenal; caudal which pass ventral to the suprarenal, and middle which pass through
it. Inasmuch as the arteries anastomose in the mesonephros there is great liability to variation
in the number and position of the stems which persist in the adult. The suprarenal arteries
VARIATIONS OF THE ARTERIES 637
are usually derived from the caudal group, the renals from the caudal or middle and the sper-
matics from the middle. When accessory renals or spermatics occur in the adult their place
of origin and course will generally indicate the group from which they are derived.
The ventral segmental arteries appear very early. In an embryo of seven somites (ca. 2
mm.) described by Dandy* there was a right and a left series of twelve arteries, each arising
from the still ununited dorsal aortce, the artery at the caudal end of each series being the um-
bihcal, and the remainder vitelline arteries. In an embryo of 4.9 mm. (35 somites) described
by IngaUst the originally paired viteUine arteries had united (as had the dorsal aortffi in part)
to form unpaired vessels. There were unpaired vessels as follows: one opposite the seventh
cervical segment (co^hac); five opposite the first four thoracic (omphalo-mesenterics, united
by a longitudinal anastomosis), and one vessel of doubtful significance opposite the fifth and
sixth thoracic segments. The paired umbiUoal arteries were opposite the first lumbar segment.
No other ventral arteries were present.
It has been found from more fully developed stages that the inferior mesenteric artei-y is
distinguishable at a stage of 8 mm. opposite the second lumbar segment. Also that the ventral
segmental vessels undergo a process of migration until they reach their definitive positions,
i. e., the coeliac opposite the twelfth thoracic segment, the superior mesenteric opposite the first,
the inferior mesenteric opposite the third, and the umbilicals opposite the fourth lumbar seg-
ments, respectively. The cesophageal arteries of the adult do not belong to this series; but
seem to be vessels of later formation.
The umbilical arteries, by means of secondary anastomosis, move laterally upon the aorta
so as to pass lateral to the Wolffian ducts instead of medial . The proximal portion of each um-
bilical artery becomes the common iliac of the adult; its continuation is represented by the hypo-
gastric and its umbilical branch. The external iliac appears to be derived from the dorsal seg-
mental artery of the fifth lumbar segment, and the parietal branches of the hypogastric
from corresponding sacral segmentals acquired by anastomosis. How such anastomoses be-
tween the umbihcals and the dorsal segmentals come about has not been ascertained.
2. VARIATIONS
Aorta and pulmonary artery. — The variations met with in the arch of the aorta are usually
to be explained as persistent foetal conditions, and are often associated with abnormahties of
the heart. Many of the variations are due to different modes of transformation of the primitive
system of aortic arches. Since the aorta and pulmonary artery develop from a common conus
and truncus arteriosus, irregular and imperfect development of the aortic septum may also
produce numerous variations.
It has been seen that at one stage of development two fourth arches, a right and a left, are
present, and such a condition is occasionally persistent in the adult. In such cases, owing
to the portion of the aorta derived from the bulbus arteriosus being directed upward and to
the right and the descending aorta lying in the left side of the vertebral column, the right arch
passes from right to left behind the oesophagus, which thus seems to perforate the aortic arch.
Another variation occasionally seen is the occurrence of an aortic arch curving to the right
instead of the left. This may be due to a persistence of the lower portion of the right dorsal
longitudinal stem and the disappearance of the left, as shown in fig. 506; or it may be associated
with a complete inversion of all the viscera, a situs inversus.
If the lower portion of the right dorsal longitudinal trunk should persist, and the part of it
which normally forms the proximal part of the right subclavian should disappear, the right
subclavian would arise from the descending portion of the aortic arch. It is to be noted
that in such cases the subclavian passes behind the oesophagus and below the right
inferior laryngeal nerve. Partial persistence of the lower portion of the right dorsal longitu-
dinal trunk is represented in the arteria aberrans (see p. 590).
Another group of variations is based on the persistence of the ductus arteriosus, which is
derived from the sixth aortic arch. With this group belong the cases in which the pulmonary
artery arises from the aorta; that is, where the blood of the pulmonary arteries passes from the
aorta through the ductus arteriosus.
Variations in the number and the position of the vessels arising from the arch are extremely
great, and many of these conditions are found normally in other mammals or birds. There may
be from one to six branches. The case of one branch is the normal in the horse. It involves the
fusion of the two aortic stems and the shortening of the fourth arch so that the left subclavian
joins with the common stem. The avian form with trto innominate arteries is extremely rare.
A more common form is the one found in most apes, in which the innominate and left carotid
form one branch ; in rare instances the three branches are the two subclavians and a general
carotid artery. When there are more than three branches the vertebral arteries are added, or
the extra branch may be the thyreoidea ima (fig. 443). The commonest form with four vessels
is the one in which the left vertebral arises between the left carotid and subclavian. A rarer
form is to be found when the order is right subclavian, right carotid, left carotid, and left sub-
clavian. Where there are five arteries, the extra ones are the right subclavian and left vertebral.
The case of six branches is due to the separate origin of both vertebrals and both subclavians.
The manner in which the vertebral artery may arise from the adult aortic arch is indicated
in fig. 506.
The innominate artery may be absent, or may give off additional branches (see Aokta).
It may be longer than usual and, bending to the left, ascend in front of the trachea (or more
rarely behind the trachea and oesophagus) to turn again to the right. The thyroidea ima has
been referred to (p. 532).
Carotid arteries. — The common carotid may be absent or bifurcate higher or lower than usual.
* Am. Journ. Anat., Vol. 10, 1910.
t Arch. f. mikr. Anat., Bd. 70, 1907.
638 THE BLOOD-VASCULAR SYSTEM
Itjmay not bifurcate at all, in which case the branches usually arising from the external car-
otid are derived from the common. The ascending pharyngeal and superior thyreoid occa-
sionally arise from an otherwise normal common carotid. Unusual origin ^of the common
carotids has been referred to (see Aorta).
Branches of the carotid arteries. — The superior thyreoid, lingual and external maxillary
sometimes have a common stem of origin. The superior thyreoid artery varies in size inversely
with the inferior. The external maxillary occasionally terminates in its submental branch.
In such cases the main supply of the face is taken over by an abnormally large dorsal nasal
branch of the ophthalmic, or transverse facial branch of the temporal artery. The occipital
sometimes arises from the internal carotid or from the ascending cervical. The ascending
pharyngeal is very variable in its place of origin from the external carotid, it may arise from the
common or internal.
Out of 447 arteries examined, the second portion of the internal maxillary passed lateral to
the external pterygoid muscle in 55 per cent., and medial to it in 45 per cent, of cases. When
medial to this muscle the internal maxillary sometimes passes medial to the inferior alveolar
and lingual nerves and occasionally between them. The variability in the course of this artery
appears to depend on a tendency to reduplication of the infraorbital branch of the stapedial
artery (p. 634) in the neighbourhood of the mandibular nerve. Such a condition was found
by Thyng in a 17 mm. human embryo. When the internal maxiUary passes medial to the ex-
ternal pterygoid there is often a parallel anastomosing channel between the posterior deep
temporal and buccal branches.
The ophthalmic artery may arise, wholly or in part, from the middle meningeal, or vice versa.
This is due to the anastomosis between the supraorbital branch of the stapedial and the oph-
thalmic in the embryo.
Subclavian artery. — Irregularities of origin have been referred to (see Aorta).
The branches of the subclavian artery are very variable in their place of origin (p. 559).
The vertebral may arise directly from the arch of the aorta (p. 537) or take an unusual course
in the neck. It may enter the foramen transversarium of the fourth or fifth cervical vertebra
instead of the sixth; this arises from substitution of an embryonic precostal anastomosis in these
segments for the usual postcostal. By a converse substitution it may enter the seventh. The
aa. transversa colli and scapulas vary inversely in size. The arteria aberrans connecting the right
subclavian with the dorsal aorta has been referred to (p. 634).
The thoracic aorta. — Transposition, and the arteria aberrans have been referred to above.
Branches of the thoracic aorta. — The intercostal arteries are hable to numerical variation,
evidently owing to the occurrence of precostal intersegmental anastomoses between the embry-
onic dorsal segmentals. A common longitudinal stem may even take over the vessels of both
sides. The anterior spinal artery usually shows lack of median symmetry which indicates the
bilaterality of its origin (p. 636). The arrangement of the bronchial arteries is hable to, much
variation; this has not received adequate explanation.
The abdominal aorta sometimes divides as low as the fifth lumbar vertebra, occasionally
higher than usual, depending upon the definitive position taken by the umbiUcal arteries (p.
637). Cases are on record of accessoiy pulmonary arteries arising by a single stem from the
abdommal aorta, which passes into the thorax along the oesophagus. The aorta and vena cava
inferior may be transposed either as a part of situs inversus or as an abnormality of the venous
system.
Branches of the abdominal aorta. — The lumbar arteries are subject to the same type of
variation as occurs in the intercostals. There may be a loop connecting the caeliac and superior
mesenteric arteries. Any or all of the branches of the coeUac may arise from the superior
mesenteric (coelio-mesenteric in the latter case) or directly from the aorta. The instabiUty of
the coeUac and superior mesenteric branches is favored by the rapid cranio-caudal migration
of the two trunks; intersegmental anastomosis, in some cases, may be a factor also. There is
very great variation in the number of branches given off by the superior mesenteric and in the
details of their arrangement. This is a natural result of the number of possible routes which
may be taken by the blood; these resemble, in their variety, those of an embryonic circulation.
The region of supply of the inferior mesenteric artery is sometimes taken over entirely or in part
(e. g., middle colic) by the superior mesenteric. An omphalo-mesenteric artery, in rare cases,
arises from the superior mesenteric or one of its branches. It passes to the navel and anasto-
moses with inferior epigastric and with the small arteries accompanying the round ligament of
the liver or the urachus.
Accessory renal arteries are very common; as many as six have been recorded. These
may arise from the aorta, middle sacral, inferior phrenic, middle suprarenal or internal spermatic.
According to Felix, these are to be regarded as persistent mesonephric arteries. Those arising
above the regular renal frequently enter the kidney dorsal to the hilum. Those below it are
more apt to be ventraUy placed.
Nearly all possible varieties of origin are met with in the inferior phrenic, middle supra-
renal, internal spermatic and accessory renal arteries which find explanation in the caudal migra-
tion of, and anastomosis between, the embryonic representatives of these vessels. The oc-
casional origin of the inferior phrenic from the coeUac (or its branches) or from the superior
mesenteric; of the internal spermatic or the middle suprarenal from the lumbar arteries, or
of an accessory renal from the inferior mesenteric must be taken as indicating embryom'c
anastomoses between the dorsal, lateral, or ventral segmental arteries, as the case may be.
The iliac and hypogastric arteries. — The length of the common iZiac depends upon the site of
aortic bifurcation (p. 590) ; also upon the site of division of the common iliac into external iliac
and hypogastric. If these spring directly from the aorta (as they do in rare cases) the common
iliac is absent. The trunk formed by the common iliac and hypogastric is the proximal portion
of the embryonic umbilical artery. The manner in which tliis takes over a dorsal segmental
artery (probably the fifth lumbar) to become the external iliac is not sufficiently undersood to
account for variations in this region.
VARIATIONS OF THE ARTERIES 639
The branches of the hypogastric artery show great variation in their origin, and there is
frequently no separation of the hj'pogastrio into anterior and posterior divisions. Rarely
the branches all take origin from the external iUao, in which case the hypogastric (as such)
is absent. The obturator artery may arise from the inferior epigastric, or vice versa (p. 615).
The arleria comitans n. ischiadici may be larger than usual and form a very pronounced anas-
tomosis with the popliteal. In rare cases the main blood-supply of the lower limb is thus
derived from the inferior gluteal which is the primitive embryonic condition (p. 640). .The
vesical and vaginal arteries are liable to variation in their relative areas of distribution. The
internal pudendal is sometimes small and maj' terminate as the perineal artery, in these cases
the urogenital region is supplied largely by the accessory pudendal (p. 610).
B. ARTERIES OF THE EXTREMITIES
1. MORPHOGENESIS
The arteries of the adult extremities represent surviving chaimels resulting from the
selection of a chosen path traversing the perineural arterial plexuses of the early embryonic
limb.
At present there is little unanimity of opinion as to whether the pattern of the developing
nerve trunks is specifically reproduced by the primitive arterial plexuses or whether the un-
doubted similarity between the two is of a more general nature. There occurs in either ex-
tremity one case in which an artery of fundamental importance follows a course practically
independent of nerve distribution. The volar interosseous, in the forearm, and the peroneal,
in the leg, are accompanied by insignificant nerves (n. to pronator quadratus, and n. to fie.xor
hallucis longus respectively) which, moreover, do not ex-tend the full length of the arteries in
question.
The blood of a developing limb, having traversed the proximal segment by means of the
arterial plexus around a single nerve, has the choice of several possible paths by which to
reach the digits. The selected channel becomes, for the time, the principal artery of the distal
segment. This presently gives way to a second favoured route, which may persist or again
give way to a third. Thus, finally, the adult arrangement is established. This process of
alternation is the cause of many of the commoner variations for, if it does not proceed to its
usual termination, a small vessel, commonly rated as a branch, may testify to its earher im-
portance by appearing as one of the chief vessels of the part.
In the upper extremity the blood first traverses the peri-median plexus (which becomes
later the axillo-brachial trunk) and flows to the digits mainly by the volar interosseous route.
Next the volar interosseous d-nandles in favour of the median. The median afterward relin-
quishes its function to the radial and ulnar.
In the lower extremity the main blood-flow at first follows the peri-sciatic plexus from
which it is dehvered to the digits chiefly by the peroneal artery. The peroneal artery passes
from the sole to the dorsum of the foot through the sinus pedis, and from here suppUes the digits.
The anterior and posterior tibial are at first small, the latter supplj-ing the plantar digital
arteries. At a stage of 10 millimetres the femoral artery is represented by a peri-saphenous
plexus which anastomoses with the peri-sciatic plexus near the knee. The peri-femoral plexus
rapidly consoUdates into the femoral and genu suprema arteries. The femoral later takes
over the pophleal as its direct continuation, and the origin of the genu suprema marks the
boundary between the femoral and ischiadic zones of the main trunk. Finally the peroneal
gives place to the anterior and posterior tibial arteries. The portion of the peroneal perforating
the tarsus disappears. In so doing it leaves the original termination of the peroneal artery
connected with the dorsalis pedis to become the arcuate branch of the latter.
2. VARIATIONS
The variations of the arteries of the upper extremity may be divided into two categories,
A certain number of them, particularly those occurring in the forearm and hand, are directly
traceable to the unusual persistence of one or more of the embryonic channels; or, when varia-
tion involves magnitude only, to reciprocal variations in the size of the normal vessels. The
commoner and more important variations of the arterial distribution, however, arise in a manner
much less susceptible to ready explanation. They depend, in fact, upon variations in the course
taken by the single or double route which, surviving from the intricacies of the peri-median
plexus, persists to maturity. These will be referred to later.
The volar interosseous artery maj' be unusually large. It may reinforce a deficient radia
or ulnar through the volar carpal arterj% or its dorsal carpal branch may join the radial at the
back of the wrist. In very rare cases the volar interosseous, together with a large ulnar artery,
replaces the radial altogether.
A large median artery may participate in the palmar supply of the fingers, either b}' joining
the superficial volar arch or (the arch being absent) by breaking directly into digital
branches. The median, when large, occasionally replaces the ulnar, verj' rarely the radial,
and frequently the superficial volar.
The superficial volar arch may be small, with compensation by the deep, or absent. In
the latter case the digital arteries may come directly from the ulnar and radial, ulnar and median
or median and radial. In the absence of the superficial volar, which is ver3- frequent, the super-
ficial arch is completed by the princeps pollicis or the volaris radiahs indicis.
640 THE BLOOD-VASCULAR SYSTEM
Cases are on record in which the ulnar artery, arising in the middle of the arm passes behind
the medial epicondyle to follow the nerve in the forearm as usual. The ulnar artery here
replaces the superior ulnar collateral and the ulnar recurrent. This anomaly is explained in a
striking way by the account given by de Vriese of the development of the vessels of the upper
extremity.
Several important variations in the distribution of the main vessels belong to the second
category. It is not uncommon for tioo arteries to arise from the primitive peri-median plexus
of the arm. In such cases one artery usuaUy takes a course dorsal to the median nerve, i. e.,
it is crossed medio-lateraUy by the medial head of the nerve and in the contrary direction by
the nerve itseh. Its course corresponds to that taken by the ordinary axiUo-brachial trunk;
it is known as the deep brachial artery. The other vessel takes a course ventral to the median,
nerve, and is known as the superficial brachial. The superficial brachial may join its com-
panion artery, at or above the elbow, or one of the forearm vessels arising from it. In either
case the superficial brachial is referred to as a "vas aberrans." Persistence of the superficial
brachial further operates as a frequent cause of abnormality in the forearm in that it is often
continued directly into one or moi-e of the chief arteries of the latter, the deep brachial taking
the remainder. This condition is classified as a high origin of the radial, ulnar, etc., as the case
may be.
There is another type of variation belonging to the same category. In this, one large
artery only occurs above the elbow which, instead of following the normal course of the brachial,
passes, entirely or in part, ventral to the median nerve. In the first case this vessel represents
the superficial brachial, the deep being absent. In the second it corresponds in its upper part
to the deep brachial and in its lower to the superficial, the two components varying in inverse
proportion.
E. MiiUer*, who has made a study of the variations belonging to this category, classifies
the abnormal artery occurring in cases of vas aberrans, of high origin of fore arm- vessels, and
of single abnormal brachial, according to the proportion of superficial brachial present in
any particular example, as a. brachialis superficialis superior media, inferior, or ima. In an
embryo of 11.7 milhmetres he found a system of arterial channels in relation with the median
nerve out of which any variation of this category might have been produced during further
development.
In cases in which the superficial brachial alone persists, the branches of the axillary (and
sometimes the profunda brachii and superior ulnar collateral) arise from a common (deep
brachial) trunk called the profunda axillaris. In cases in which the deep and superficial brachial
co-exist examples of continuation of the superficial brachial into the radial are rather common,
continuation into the ulnar less so. Continuation of the superficial brachial into the median,
interosseous, or of posterior interosseous arteries occasionally occur, but they are rare. In any
case of high origin a cross branch may connect the high vessel with the deep brachial in the
neighbourhood of the elbow. The ulnar artery when arising high is often superficial to the
forearm flexors (a fact which has not been explained on embryological grounds), the inter-
osseous arising from the radial.
The variations occurring in the arteries of the lower extremity are usually compensatory,
or due to persistence of alternative embryonic channels. The sciatic (inferior gluteal) very
rarely persists as the main artery of supply. In such cases the small femoral ends as the genu
suprema which then appears to be a branch of the profunda.
The profunda is irregular; its origin may occur anywhere between the inguinal Ugament
and a point four inches below it. The median or lateral circumflex may arise from the femoral.
The branches of the latter commonly arise separately from the profunda, or from the femoral.
The popliteal does not vary much in its point of division. High division is commoner than low,
but is never higher than the lower epiphyseal fine of the femur.
The anterior tibial may be small and only reach the middle or lower part of the leg. In
such cases an enlarged anterior peroneal may end as the dorsahs pedis, or the dorsal metatarsal
arteries may be supphed from the plantar arch. Cases in which the anterior peroneal supplies
the dorsum of the foot do not represent a dkect inheritance of the embryonic method by which
the peroneal artery performs this office. The embryonic route of the peroneal to the dorsum
of the foot is transtarsal. The anterior tibial artery may reach the extensor surface of the leg by
accompanying the peroneal nerve. This case, hke that of the ulnar artery passing around the
medial epicondyle, is interesting in connection with the work of de Vriese. ^ . c ■
The posterior tibial artery may be absent or small, the peroneal replacing it, or remforcmg
it by means of the ramus communicans. Absence of the peroneal has been recorded by Otto
and W. Krause, but these cases are explained by Barkow as being suppression of the posterior
tibial artery between the origin of the peroneal and the communicating branch (Quain).
The lateral plantar is sometimes very small, in which case the plantar arch may be supphed
by a large deep plantar. In rare cases there is a superficial plantar arch as in the embryo.
3. THE SYSTEMIC VEINS
The systemic veins are naturally divided into three groups — (1) the veins of
the heart; (2) the vena cava superior and its tributaries, namely the veins of the
head, neck, upper extremity, and thorax; and (3) the vena' cava inferior and its
tributaries, namely, the portal system, and the veins of the abdomen, pelvis, and
lower extremity.
* E. Miiller, Anat. Hefte, No. 22, 1903.
THE INNOMINATE VEINS 641
I. THE VEINS OF THE HEART
The veins of the heart have already been described (p. 520).
II. THE VENA CAVA SUPERIOR AND ITS TRIBUTARIES
THE VENA CAVA SUPERIOR
The vena cava superior (fig. 509) carries to the heart the blood returned from
the head and neck and upper extremities through the right and left innominate
veins, and from the walls of the thorax, either directly through the azygos vein,
or indirectly through the innominate veins. It is formed (fig. 509) by the con-
fluence of the right and left innominate veins behind the first right sterno-chondral
articulation. Descending from its origin in a gentle curve with its convexity to
the right and in a direction slightly backward behind the sternal end of the first
and second intercostal spaces and second costal cartilage, it terminates in the
right atrium of the heart on a level with the third right costal cartilage in front and
the seventh thoracic vertebra behind. It measures about 7 to 8 cm. (3 in.) in
length. A little more than its lower half (4 cm.) is contained within the pericar-
dium, the serous layer of that membrane being reflected obliquely over it imme-
diately below the spot where it is joined by the vena azygos, and on a lower
level than the reflexion of the pericardium on the aorta. The superior vena
cava contains no valves.
Relations. — In front, in addition to the first and second intercostal spaces and the second
costal cartilage, it is covered by the remains of the thymus gland, the intrathoracic fascia, and
the pericardium, and is overlapped by the right pleura and lung.
Behind (fig. 609) are the vena azygos (major), the right bronchus, the right pulmonary
artery, and the superior right pulmonary vein; and below, the fibrous layer of the pericardium.
The serous layer is reflected over the front and sides of the vessel, but not over its posterior
part.
To the right side are the right lung and pleura and the phrenic nei've.
To the left side are the innominate artery and the ascending aorta.
Tributaries. — In addition to the right and left innominate veins and the vena
azygos it receives small veins from the mediastinum and pericardium.
THE INNOMINATE VEINS
The innominate or brachio-cephalic veins [vv. anonymae] return the blood
from the head and neck and upper extremity. They are formed on each side by
the confluence of the internal jugular and subclavian veins behind the sternal
end of the clavicle. They terminate behind the first costal cartilage on the right
side by uniting to form the vena cava superior. The innominate veins have no
valves.
The right innominate vein [v. anonyma dextra] (fig. 509) measures about 2 to
3 cm. (1 to H in-) in length, and descends from its origin behind the sternal end
of the clavicle, very slightly forward and medially, along the right side of the sub-
clavian and innominate arteries, to its junction with the left vein behind the first
costal cartilage close to the sternum. It is superficial to the innominate artery.
Relations. — In front are the origins of the sterno-hyoid and sterno-thyreoid muscles,
the clavicle, the first costal cartilage, and the remains of the thymus gland.
Behind are the pleura and lung.
To the right are the right pleura and lung and the phrenic nerve.
To the left (fig. 509) are the right subclavian artery, the innominate artery, the right
vagus nerve, and the trachea.
The left innominate vein [v. anonyma sinistra] (fig. 509) measures 6 to 7.5 cm.
(2| to 3 in.) in length, and extends from its origin behind the sternal end of the
left clavicle obHqueljr across the three main branches of the arch of the aorta, to
unite with the right innominate vein behind the cartilage of the first rib close to
the sternum to form the vena cava superior. In this course it runs from left
to right with an inclination downward and slightly backward. A line drawn
obliquely across the upper half of the manubrium of the sternum, from the sterno-
642
THE BLOOD-VASCULAR SYSTEM
clavicular articulation on the left side to the lower border of the first costal carti-
lage at its junction with the sternum on the right side, will indicate its course.
The left innominate vein is on a level with the top of the sternum at birth.
Relations. — In front, in addition to the manubrium of the sternum, it has the origins of
the sterno-hyoid and sterno-thyreoid muscles, and the remains of the thymus gland, the sternal
end of the left clavicle, and the sterno-clavicular articulation.
Behind are the three chief arteries arising from the arch of the aorta, the trachea, and the
left phrenic and left vagus nerves.
Below it is the arch of the aorta.
Above it are the cervical fascia, the inferior thyreoid, and thyreoidea ima veins.
Tributaries. — In addition to the internal jugular and subclavian veins, by the
confluence of which the innominate veins are formed, each vein receives on its
upper aspect the vertebral, the deep cervical, and inferior thyreoid veins; and
Fig. 509.
(Modified
Internal jugular vein-
Transverse cervical
Transverse scapular
artery
Right recurrent nerve
Right common carotid
artery
Subclavian vein
Vagus nerve
Innominate artery *^
I*
Left innominate vein
Phrenic nerve
Superior vena cava
Arch of aorta
Right bronchus
Branch of right pul
monary artery
Branch of right pul
monary vein
Right pulmonary
artery
Branch of right pul-
monary artery
Branch of right pul
monary vein
Right coronary artery
Thoracic vertebra
Azygos vein
Intercostal veins
Intercostal arteries
— The Vena Cava Supeeior and the Innominate Veins.
from a dissection in St. Bartholomew's Hospital Museum.)
Inferior thyreoid '
-Thyreoid gland
Left internal jugular
Vagus nerve
Lett common carotid
artery
Left recurrent
nerve
Left subclavian artery
Left subclavian vein
Left internal mammary
Phrenic nerve
Vagus nerve
Recurrent nerve
Ligamentum arteri-
osum
Left pulmonary artery
Lett pulmonary vein
Left bronchus
Branch of left pulmon-
ary artery
Pulmonary artery
Lett pulmonary vein
Left coronary artery
Conns arteriosus
CEsophagus
Thoracic duct
Thoracic aorta
on its lower aspect the internal mammary vein. The left vein, moreover, is
joined by the thyreoidea ima, the left superior intercostal, and by the thymic,
tracheal, oesophageal, superior phrenic, anterior mediastinal, and pericardiac veins.
At the confluence of the internal jugular and subclavian veins on the right side
the three lymphatic trunks or the right lymphatic duct open; on the left side the
thoracic duct.
THE VEINS OF THE HEAD AND NECK
The veins of the head and neck may be divided for purposes of description into
the superficial, which return the blood from the external parts of the head and
SUPERFICIAL VEINS OF HEAD AND NECK
643
neck; and the deep, which return the blood from the deeper structures. All
the veins, whether superficial or deep, terminate in the internal jugular or sub-
clavian, or open directly into the innominate veins at the root of the neck.
Through the latter all the blood from the head and neck ultimately passes on its
way to the heart.
THE SUPERFICIAL VEINS OF THE HEAD AND NECK
The venous blood from the anterior part of the scalp and integument of the
face is returned, through the anterior and posterior facial veins, to the common
facial, a tributary of the internal jugular vein. From the posterior part of the
scalp and from the integument of the neck venous blood is returned, through the
external jugular and its tributaries, to the subclavian vein.
A. The Antehior Facial Vein
The anterior facial vein [v. facialis anterior] (fig. 510) begins a little below the
medial end of the eyebrow where it is formed by the union of the frontal and
Fig. 510. — The Supeepicial Veins of the Face and Scalp. (After Quain.)
Superficial tem-
poral
Nasal branch of
igular vein
Posterior facial
Posterior exter^
nal jugular vein"
External jugula:
Communicating
branch with an-
terior jugular
Anterior jugtUar
vein
Transverse scapular i
supraorbital veins. It descends near the medial angle of the orbit, and then by the
side of the nose to the cheek, which it crosses obliquely, to the anterior edge of the
massetpr muscle. Thence it passes through the digastric triangle to the upper
border of the hyoid bone, where it terminates in the common facial vein. In this
course it is reinforced by numerous collateral veins, and gradually increases in
size. It has, moreover, numerous communications with the deep veins. The
portion of this vein above the lower margin of the orbit is called the angular [v.
644 THE BLOOD-VASCULAR SYSTEM
angularis]. In the remainder of its course over the face and neck it is termed the
anterior facial vein.
The angular vein skirts around the medial margin of the orbit, lying with the angular
artery on the frontal (nasal) process of the maxillary bone slightly medial to the lacrimal
sac. Branches pass from the posterior part of the angular vein into the orbit to join the
ophthalmic.
The angular, the facial, and the ophthalmic veins contain no valves. The blood, therefore,
can' pass either forward from the ophthalmic into the angular, or backward through the facial
and angular into the ophthalmic, and so on to the cavernous and other venous sinuses of the
cranium. Hence in certain tumours in the orbit and cranium, the congestion of the angular
and facial veins; and the danger in facial carbuncle and anthrax of septic thrombi spreading
backward through the angular and ophthalmic veins to the cranial sinuses.
The anterior facial vein runs in a more or less direct line behind its corre-
sponding artery, the external maxillary (facial), which itself pursues a tortuous
course. It usually passes deep to the zygomatic muscle, the zygomatic head of the
quadratus labii superioris, and the risorius, but superficial to the other muscles.
At the anterior edge of the masseter it meets the external maxillary artery, lying
immediately posterior to it. In the neck it lies beneath the platysma and cer-
vical fascia, and is usually separated from the external maxillary artery by the
submaxillary gland and the stylo-hyoid and posterior belly of the digastric muscles,
below which it is joined by the posterior facial, to form the common facial vein.
Tributaries. — It receives, from above downward: — fa) the frontal vein; (b)
the supraorbital vein; (c) the superior palpebral veins; (d) the external nasal
veins; (e) the inferior palpebral veins; (f) the superior labial vein; (g) the inferior
labial vein; (h) the masseteric veins; (i) the anterior parotid veins; (j) the pala-
tine vein and (k) the submental vein.
(a) The frontal vein [v. frontalis] (fig. 510) begins about the level of the coronal suture in a
venous plexus which communicates with the anterior division of the temporal vein. Soon
forming a single trunk, it passes vertically downward over the frontal bone, a short distance
from the middle line and parallel to its feUow of the opposite side, to the medial end of the eye-
brow where it terminates in the angular vein.
(b) The supraorbital vein [v. supraorbitalis] begins over the frontal eminence by inter-
communication with the middle temporal vein. It receives tributaries from the forehead and
eyebrow, and, running obliquely, medially and downward, opens into the termination of the
frontal vein to form the angular. It communicates with the ophthalmic vein, and receives the
frontal vein of the diploe as the latter vein issues from the bone at the bottom of the supraorbital
notch.
(c) The superior palpebral veins [vv. palpebrales superiores] arise in the upper eyeMd and
open into the lateral side of the angular vein. They communicate with the middle temporal
vein.
(d) The external nasal veins [vv. nasales externae] form three or four stems on either side.
The upper veins run upward into the angular and the lower, from the ala, pass more hori-
zontally into the anterior facial vein.
(e) The inferior palpebral veins [vv. palpebrales inferiores] arise in the lower eyelid, and,
passing medially and downward over the cheek from which they receive tributaries, open into
the later.ll side of the anterior facial vein. They communicate with the infraorbital vein.
(f) Tlie superior labial vein [v. labialis superior] and (g) the inferior labial vein [v. labialis
inferior] arise from venous plexuses in the upper and lower lips. They run laterally to open
into the medial side of the facial vein.
(h) The masseteric veins [vv. masseterioae] and (i) the anterior parotid veins [vv. parotidae
anteriores], of small size, drain the cheek over the masseteric and parotid regions.
(j) The palatine vein [v. palatina] accompanies the ascending palatine or tonsillar artery
from the venous plexus about the tonsil and soft palate, and joins the anterior facial vein just
below the body of the mandible.
(k) The submental vein [v. submentalis] lies on the mylo-hyoid muscle superficial to the
submental artery. Running back in the submental triangle, it joins the anterior facial vein
just after the latter has passed over the body of the mandible. It communicates with the
anterior jugular vein.
Communications. — The tributaries of the anterior facial vein comrnunicate freely with
the anterior and middle temporal, ophthalmic, infraorbital and anterior jugular veins. The
main trunk has a large communicating branch with the pterygoid plexus. This vein, some-
times known as the deep facial, opens into the anterior facial Ijelow the zygomatic bone under
cover of the zygomaticus muscle.
B. The Posterior Facial Vein
The posterior facial (temporo-maxillary) vein [v. facialis posterior] is formed in
in the region of the root of the zygoma by the union of the superficial and
middle temporal veins. It passes downward behind the ramus of the mandible
POSTERIOR FACIAL VEIN
645
through the substance of the parotid gland— here lying lateral to the super-
ficial temporal and external carotid arteries. At the angle of the mandible it
runs medially and somewhat forward, and, passing either deep or superficial to
the stylo-hyoid and digastric muscles, joins the anterior facial to form the
common facial vein.
The tributaries received by the posterior facial vein are: — (a) the superficial
-The Veins of the Head, Neck, and Axilla. ^ (Aft^er Toldt, 'Atlas of Human
Anatomy," Rebman, London and New York.)
Frontal diploic veins
Supraorbital vein
Middle temporal vein
Superficial temporal artery
and vein
Articular mandibular veins ^^^/
Posterior facial veins
External nasal veins
Angular vein
Anterior facial vein
Submental vein
Occipital artery and
Hypoglossal nerve
''^ and venee comitans
Superior thyreoid
artery and vein
\ Superior laryngeal
, artery and vein
Circumflex hum- / Anterior \ 15, '
1 Posterior \ v;'
Circumflex scapular
Lateral thoracic artery and vein
temporal veins; (b) the middle temporal vein; (c) the transverse facial vein;
(d) the articular veins; fe) the posterior parotid veins; (f) the anterior auricular
veins; (g) the stylo-mastoid vein; and (h) the internal maxillary vein through
which occurs the principal drainage of the pterygoid plexus.
646 THE BLOOD-VASCULAR SYSTEM
_ (a) The superficial temporal vein [v. temporalis superficialis] returns the blood from the
parietal region of the scalp. It is formed by the union of an anterior and a posterior branch:
theformer communicates with the supraorbital and frontal veins; the latter with the posterior
auricular and occipital veins and the temporal vein of the opposite side. These branches lie
superficial to the corresponding branches of the superficial temporal artery, which they roughly
though not accurately follow. Like the artery, they lie between the skin and the cranial
aponeurosis, and descend over the temporal fascia to unite a Uttle above the zygoma, and just
in front of the auricle of the ear, to form the superficial temporal trunk. The vein thus formed
continues its course downward with the trunk of the temporal artery, and opposite the zygoma
is joined by the middle temporal vein to form the common temporal vein.
(b) The middle temporal vein [v. temporaUs media] corresponds with the orbital branch
of the temporal arterj', and communicates in front with the ophthalmic vein, the external
palpebral veins, and the infraorbital veins, and then runs backward between the layers of the
temporal fascia to join the superficial temporal vein. The middle temporal vein communicates
with the deep temporal veins, and through them with the pterygoid venous plexus.
(c) The transverse facial vein [v. transversa faciei] corresponds to the transverse facial
artery, (d) Articular veins [vv. articulares mandibute] form the plexus around the temporo-
mandibular joint; this plexus receives the tympanic veins [w. tympanicae), which, together
with its corresponding artery, passes through the petrotympanic fissure, (e) Posterior parotid
veins [w. parotidese posteriores] emerge from the substance of the parotid gland, (f) Anterior
auricular veins [w. auriculares anteriores], from the auricle of the ear. (g) Stylo-mastoid vein
[v. stylomastoidea] from the facial canal, (h) The internal maxallary vein accompanies the
first part of the internal maxillary artery. It begins at the posterior confluence of the veins
forming the pterygoid plexus, and passes backward between the stylo-mandibular ligament and
the neck of the mandible. It ends by joining the posterior facial vein.
The pterygoid plexus [plexus pterygoideus] is formed by the veins which correspond to the
branches of the internal maxillary artery. It is situated, partly on the medial surface of the
internal pterygoid muscle, and partly around the external pterygoid muscle. The veins
entering into this plexus are: — the two middle meningeal veins [w. meningeae mediae], which
accompany the artery of that name; the posterior superior alveolar (dental); the inferior alveolar
(dental); the masseteric; the buccal; the pterygoid veins from the pterygoid muscles; the deep
temporal veins [vv. temporales profundae], by which the plexus communicates with the temporal
plexus; the spheno -palatine vein; the infraorbital; the superior palatine; a branch of commu-
nication with the lower branch of the ophthalmic vein, which courses through the inferior
orbital (spheno-maxillary) fissure; and the rete foraminis ovalis and Vesalian vein, through
which the plexus communicates with the cavernous sinus. The plexus ends posteriorly in
the internal maxillary vein, which joins the posterior facial vein, and anteriorly in a com-
municating vessel (the deep facial vein), which passes forward and downward between the
buccinator and masseter muscles to join the anterior facial vein.
The above-mentioned veins, forming by their confluence the pterygoid plexus, correspond
in then- course so nearly with that of their companion arteries that a detaOed description is
not necessary. Although for convenience described with the superficial veins, they are all
deeply placed.
Near the angle of the mandible there is almost always a communicating branch between the
posterior facial and the external jugular veins. When large, this branch may drain the greater
part of the blood from the posterior facial.
C. The Common Facial Vein
The common facial vein [v. facialis communis] is a short thick stem contained
within the carotid triangle. It is formed, just below the angle of the mandible,
by the union of the anterior and posterior facial veins. It ends opposite the hyoid
bone, by opening into the internal jugular vein. In addition to the vessels which
form it, sometimes it receives the superior thyreoid, the pharyngeal, and the lin-
gual or the subHngual veins.
D. The External Jugular Vein
The external jugular vein [v. jugularis externa] (fig. 510) is formed by the con-
fluence of the posterior auricular and a short communicating trunlc from the
posterior facial near the angle of the mandible. It runs obliquely downward and
backward across the sterno-mastoid muscle to a point opposite the middle of the
clavicle, where it terminates as a rule in the subclavian vein. A line drawn from
a point midway between the mastoid process and angle of the jaw to the middle of
the clavicle will indicate its course. It is covered by the skin, superficial fascia,
and platysma, and is crossed by a few branches of the cervical plexus, the great
auricular nerve running parallel to it at the upper part of the neck. It is separated
from the sterno-mastoid by the anterior layer of the deep cervical fascia.
Just above the clavicle it perforates the cervical fascia, by which it is prevented from readily
collapsing, the fascia being attached to its walls. It then opens into the subclavian vein, oc-
casionally into the internal jugular, or into the confluence of the subclavian and internal jugular
THE EXTERNAL JUGULAR VEIN
647
veins. It contains a pair of valves about 2.5 to 5 cm. (1 to 2 in.) above the clavicle, and a
Becond'pair where it enters the subclavian vein. Neither of these valves is sufficient to prevent
the blood from regurgitating, or injections from passing from the larger vein into the external
jugular.
Tributaries and communications. — These include; — (a) The posterior auricular
vein; (b) the occipital vein; (c) a branch of communication with the posterior fa-
cial vein; (d) the posterior external jugular vein; (e) the transverse scapular vein;
and (f) the anterior jugular vein.
(a) The posterior auricular vein [v. auricularis posterior] begins in a venous plexus on the
posterior part of the parietal bone. This plexus communicates with the vein of the opposite
side across the sagittal suture, and with the posterior branch of the superficial temporal vein
in front, and with the occipital vein behind. It descends over the back part of the parietal
bone and the mastoid process of the temporal bone, lying with its artery behind the ear, and
joins a branch from the posterior facial vein to form the external jugular.
Fig. 512. — The Veins of the Face. (After Toldt, "Atlas of Human Anatomy," Rebman,
London and New York.)
Deep temporal veins
Infraorbital artery and i
Lateral lacuna of the superior sagittal sinus
Sphenoparietal sinus
Middle
temporal
vein
Articular man-
dibular veins
Superficial
temporal art* ry
Pterygoid
pi.
Internal
maxillary arter>
Inferior
alveolar nerve
Posterior facial vein ^
Inferior alveolar artery
and vein
Jugular
Common facial vein
(6) The occipital vein [v. occipitalis] begins at the back of the skuU in a venous plexus
which anastomoses with the posterior auricular and the posterior branch of the superficial
temporal veins. It passes downward over the occipital bone, and usually perforates the
trapezius with the occipital artery, to join a plexus drained by the deep crevical and vertebral
veins. It also communicates with the posterior auricular, and in many cases this forms the
chief path of drainage. One of its branches, usually the most lateral, receives a mastoid em-
issary vein [emissarium mastoideum] which issues through the mastoid foramen of the tem-
poral bone, and in this way forms a communication with the transverse sinus.
(c) The branch of communication with the posterior facial vein occurs a short distance below
the point at which the posterior facial receives the internal maxillary vein. It is very constant
and is placed immediately behind the angle of the mandible. Through it the external jugular
648 THE BLOOD-VASCULAR SYSTEM
usually receives a considerable proportion of the blood returning from the temporal and ptery-
goid regions.
(d) The posterior external jugular vein (fig. 512) descends from the upper and back part
of the neck, receiving small tributaries from the superficial structures and muscles. At times it
communicates with the occipital, or may appear as a continuation of that vein. It opens into
the external jugular as the latter vein is leaving the sterno-mastoid muscle.
(e) The transverse scapular vein [v. transversa scapulae] corresponds to the transverse
scapular (suprascapular) artery. If double, these venae comitantes usually form one trunk
before they open into the external jugular vein. They contain well-marked valves.
(/) The anterior jugular vein [v. jugularis anterior] begins below the chin by communicating
with the mental, submental, inferior labial, and inferior hyoid veins. It descends a little
lateral to the middle line, receiving branches from the superficial structures at the front and
side of the neck, and occasionally a branch from the larynx and thyreoid body. Just above
the clavicle it turns laterally, and, piercing the fascia, passes beneath the sterno-mastoid
muscle and opens into the external jugular vein just before the latter joins the subclavian; at
times it opens into the subclavian vein itself. In its course down the neck it communicates
with the external jugular; and, as it turns laterally beneath the sterno-mastoid, sends a branch
across the trachea, between the layers of cervical fascia, to join the anterior jugular of the
opposite side. This communicating vein, the jugular venous arch [arcus venosus juguli],
may open directly into the external jugular or into the internal jugular vein; occasionally one
or both ends may open into the subclavian or innominate vein. It may be divided in the
operation of tracheotomy, and is then often found greatly engorged with blood. Another
branch, often of considerable size, courses along the anterior margin of the sterno-mastoid and
joins the anterior facial vein. When the anterior jugular vein is large, the external jugular is
small, and vice versa. It is usually also of large size when the corresponding vein on the opposite
side is absent, as is frequently the case. It contains no valves.
THE DEEP VEINS OF THE HEAD AND NECK
The deep veins of the head and neck may be divided into: — (1) the veins of
the diploe; (2) the venous sinuses of the dura mater encephah; (3) the veins of
the brain; (4) the veins of the nasal cavities; (5) the veins of the ear; (6) the
veins of the orbit; (7) the veins of the pharynx and larynx; and (8) the deep veins
of the neck. The veins of the diploe terminate partly in the superficial veins
already described, partly in the venous sinuses of the cranium, and partly in the
deep veins of the neck. The venous sinuses open into the deep veins of the neck.
The veins of the brain terminate in the venous sinuses. The veins of the nasal
cavities terminate partly in the deep, and to some extent in the superficial veins.
The veins of the ear join both the superficial and deep veins and the venous sinuses.
The veins of the orbit terminate partly in the superficial veins, but chiefly in the
venous sinuses. The veins of the pharynx and larynx enter the deep veins of the
neck.
1. THE VEINS OF THE DIPLOE
The veins of the diploe [venae diploicse] (fig. 513) are contained in bony chan-
nels in the cancellous tissue between the external and internal laminae of the skull.
They are of comparatively large size, with very thin and imperfect walls, and form
numerous irregular communicating channels. They have no valves. They ter-
minate in four or five main and descending channels, which open, some outward
through the external cranial lamina into some of the superficial and deep veins of
the head and face, and some inward through the internal lamina into the venous
sinuses. They are divided into the frontal, anterior temporal, posterior temporal,
and occipital.
The frontal diploic veins are contained in the anterior part of the frontal bone. They
converge anteriorly to a single vein [v. diploica frontalis] which passes downward, perforates the
external table through a small aperture in the roof of the supraorbital notch, and terminates in
the supraorbital vein. They also communicate with the superior sagittal sinus.
The anterior temporal [v. diploica temporahs ant.] are contained in the posterior part of
the frontal and in the anterior part of the parietal bone. They pass downward, and end, partly
in the deep temporal veins by perforating the greater wing of the sphenoid bone, and partly
in the spheno-parietal sinus.
The posterior temporal [v. diploica temporalis post.] ramifies in the parietal bone, and,
coursing downward to the posterior inferior angle of that bone, passes either through a foramen
in its inner table, or through the mastoid foramen into the transverse sinus.
The occipital [v. diploica occipitalis] ramifies chiefly in the occipital bone, and opens into
the occipital vein or into the transverse sinus.
The diploic veins freely anastomose with one another in the adult; but in the foetus, before
the bones have united, each system of veins is distinct.
VENOUS SINUS OF THE DURA MATER
649
2. THE VENOUS SINUSES OF THE DURA MATER
The venous sinuses of the dura mater [sinus durse matris] are endothelially
lined blood-spaces, situated between the periosteal and meningeal layers of the
dura mater. They are the channels by which the blood is conve3red from the
cerebral veins, and from some of the veins of the meninges and diploe, into the
veins of the neck. The sinuses at the base of the skull also carry the chief part of
the blood from the orbit and eyeball to the jugular veins. At certain spots the
sinuses communicate with the superficial veins by small vessels known as the emis-
sary veins, which run through foramina in the cranial bones.
The venous sinuses are sixteen in number, six being median and unpaired, the
remaining ten consisting of five lateral pairs. The median sinuses are: — (1) the
superior sagittal; (2) the inferior sagittal; (.3) the straight; (4) the occipital; (5)
the circular; and (6) the basilar plexus. The lateral and paired sinuses are: — •
(7) the two transverse; (8) the two superior petrosal; (9) the two inferior petro-
sal; (10) the two cavernous; and (11) the two spheno-parietal. Occasionally
there are two additional sinuses, the two petro-squamous.
(1) The superior sagittal (or longitudinal) sinus [sinus sagittalis superior] (fig.
515) lies in the median groove on the inner surface of the cranium along the
attached margin of the falx cerebri. It extends from the foramen caecum to the
Fig. 513. — The Veins op the Diploe.
(From a specimen in St. Bartholomew's Hospital Museum.)
The occipital
diploic vein
The posterior
temporal diploic
internal occipital protuberance. It grooves from before backward the frontal
bone, the contiguous sagittal margins of the parietal bones, and the squamous por-
tion of the occipital bone In the foetus, and occasionally in the adult, it commu-
nicates (through the foramen caecum) with the nasal veins. It communicates
throughout life with each superficial temporal vein by means of a parietal emis-
sary vein [emissarium parietale] which passes through the parietal fora-
man. It is triangular on section, the base of the triangle corresponding "to the
bone. Crossing it are a number of fibrous bands known as the chords of Willis,
and projecting into it in places are the arachnoidal (Pacchionian) granulations.
The parts of the sinus into which the arachnoidal granulations project are irregu-
lar lateral diverticula from the main channel known as the lacimce laterales ffig.
517). In front the sinus is quite small, but it increases greatly in calibre as it
runs backward. It receives at intervals the superior cortical cerebral veins and
the veins from the falx. The former, for the most part, open into it in the direc-
tion opposite to that in which the blood is flowing in the sinus. They pass for
some distance in the walls of the sinus before opening into it. Posteriorly, at the
internal occipital protuberance, the superior sagittal sinus usually turns sharply to
650
THE BLOOD-VASCULAR SYSTEM
the right, and ends in the right transverse (lateral) sinus; the straight sinus then
usually terminates in the left transverse (lateral) sinus.
Occasionally, however, the superior sagittal sinus ends in the left transverse sinus, the
straight then passing into the right. At the angle of union between the superior sagittal
sinus and the transverse sinus into which it empties there is a dilation, the confluens sinuum
or torcular Herophih. At this point there is a communication between the right and left trans-
verse sinuses. In some cases the communication is so free that the blood from the sagittal
sinus flows almost equally into each transverse sinus. The confiuens may communicate with
the occipital vein through the occipital emissary vein [emissarium occipitale], which, when present
passes through a minute foramen in the occipital protuberance.
(2) The inferior sagittal (or longitudinal) sinus [sinus sagittalis inferior] (fig.
515) is situated at the free margin of the falx cerebri. Beginning about the
junction of the anterior with the middle third of the falx, it is continued backward
along the concave or lower margin of that process to the junction of the falx with
the tentorium, where it ends in the straight sinus. The sinus is cylindrical in
Fig. 514. — The Venous Sinuses.
(From a dissection by W. J. Walsham in St. Bartholomew's Hospital Museum.)
Meningeal branch of pos-
terior ethmoidal aitery
Middle meningeal
artery
Ophthalmic division of
trigeminus
Oculomotor nerve
Cavernous sinus
Trochlear nerve
Auditory & facial nerve!
Superior petrosal sinus
Inferior petrosal sinus
Petro-squamous sinus
Spinal accessory nerve
Sigmoid portion of
transverse sinus
Posterior meningeal
branch of vertebral
artery
Left marginal sinus
'\f'iV\ — Circular sinus
Left transverse sinus
Superior sagittal sinus
Carotid artery
-Abducens nerve
Basilar artery
Basilar plexus of
veins
Auditory artery
Vertebral artery
— Glosso - pharyngeal
—J and vagus nerves
I' / Anterior spinal
, artery
/_ Hypoglossal nerve
/ Spinal accessory
nerve
Right marginal sinus
Occipital sinus
Right transverse sinus
shape and of small size, and receives some of the inferior frontal veins of the brain,
some of the veins from the medial surface of the brain, and some of the veins of the
falx. .
(3) The straight sinus [sinus rectus] lies along the junction of the falx cerebri
with the tentorium cerebelli. It is formed by the union of the great cerebral vein
(of Galen) and the inferior sagittal sinus. It receives in its course branches from
the tentorium cerebelh and from the upper surface of the cerebellum. _ It runs
downward and backward to the internal occipital protuberance, where it ends in
the transverse sinus opposite to that joined by the superior sagittal sinus. On
section it is triangular in shape, with its apex upward.
(4) The occipital sinus [sinus occipitaHs] (fig. 514) ascends at the attached
margin of the falx cerebelli, along the lower half of the squamous portion of the
occipital bone from near the posterior margin of the foramen magnum to the
internal occipital protuberance. It usually begins in a right and a left branch,
known as the marginal sinuses. These proceed from the termination of each
VENOUS SINUSES OF THE DURA MATER
651
transverse sinus, run around the foramen magnum, where they communicate with
the venous vertebral retia, and unite at a variable distance from the internal oc-
cipital protuberance to form the single occipital sinus. Sometimes they re-
main separate as far as the occipital protuberance, then forming two occipital
sinuses. One of the two marginal sinuses may be much smaller than the other,
or be entirely absent. At the point where the marginal sinuses unite to form the
single occipital sinus, there is a communication with the venous vertebral retia.
The occipital sinus ends in the confluens sinuum. It receives in its course veins
from the tentorium cerebelli, and from the inferior surface of the cerebellum.
It communicates through the plexus of veins which surrounds the hypoglossal
nerve [rete canalis hypoglossi] in the hypoglossal (anterior condyloid) canal
with the vertebral vein and the longitudinal vertebral venous sinuses.
(5) The circular sinus [sinus circularis] (fig. 516) encircles the hypophysis
cerebri. It consists of the two cavernous sinuses and their communications across
Fig. 515. — The Venous Sinuses. (Longitudinal section.)
Abducens. aerve Oculomotor nerve
Superior sagit-
Vein of Galen
Middle
meningeal
artery
Internal
carotid artery
Superior
petrosal sinus
Fabr cerebell
Facial and auditory
nerves
Glossopharyngeal, vagus and
accessory
Hypoglosaal
Second cervical nerve
Ligamentum denticulatum
petrosal sinus
the median line by means of the anterior and posterior intercavernous sinuses.
The intercavernous sinuses are small and cross the median line in front of and
behind the hypophysis, respectively.
(6) The basilar plexus [plexus basilaris] is a venous plexus in the substance of
the dura mater over the basilar part of the occipital bone. It extends from
the cavernous sinus to the margin of the foramen magnum below. It communi-
cates laterally with the inferior petrosal sinus, and inferiorly with the internal
vertebral venous plexuses. One of the larger of the irregular venous channels
forming the plexus passes transversely from one inferior petrosal sinus to the
other. This venous plexus is serially homologous with the longitudinal vertebral
venous sinuses on the posterior surfaces of the bodies of the vertebrae.
(7) The transverse (or lateral) sinus [sinus transversus] (figs. 514, 516)
extends from the internal occipital protuberance to the jugular foramen. In
this course it lies in the groove (which has been named after it) along the squamous
portion of the occipital bone, the posterior inferior angle of the parietal bone, the
mastoid portion of the temporal bone, and the jugular process of the occipital
bone. It at first runs laterally and forward horizontally between the two layers
of the tentorium cerebelli, following the curve of the groove on the occipital and
on the mastoid angle of the parietal bone. On reaching the groove in the mas-
652 THE BLOOD-VASCULAR SYSTEM
1. toid portion of the temporal bone it leaves the tentorium and curves medially
|/ and downward and then forward over the jugular process of the occipital bone,
and ends in the posterior compartment of the jugular fossa in the superior bulb of
the internal jugular vein. The S-shaped part of the sinus which hes on the mas-
toid portion of the temporal and jugular portion of the occipital bone is sometimes
known as the sigmoid sinus. The transverse sinus receives the internal auditory
veins [vv. auditivse internfe] from the labyrinth, which emerge from the internal
auditory meatus. It also receives veins from the temporal lobe of the cerebrum,
some of the superior and inferior cerebellar veins, some of the veins of the medulla
and pons, the occipital, and the posterior temporal and occipital veins of the diploe.
At the point where it leaves the tentorium it drains the superior petrosal sinus
and, when present, the petro-squamous sinus. It communicates with the occip-
ital and vertebral veins through the mastoid and posterior condyloid foramina
by means of the mastoid and condyloid emissary veins. As the transverse sinus
lies between the layers of the tentorium it is on section prismatic in shape.
The sigmoid portion is semicylindrical.
The right transverse sinus is usually the larger and the direct continuation of the superior
sagittal sinus, and hence conveys the chief part of the blood from the cortical surface of the brain
and vault of the skull. The left transverse sinus is usually the smaller and the direct con-
tinuation of the straight sinus, and hence returns the chief part of the blood from the central
ganglia of the brain. The right and left sinuses communicate opposite the internal occipital
protuberance.
The relation of the lateral sinus to the outside of the skuU, especially to the mastoid process
of the temporal bone, is of importance with reference to the operations of trephining the
mastoid cells, opening the tympanum, and exposing the sinus itself, in septic thrombosis, etc.
The course of the sinus corresponds to a hne drawn from the external occipital protuberance
to the base of the mastoid process, or to the asterion, and thence over the back of the mastoid
process in a curved line toward its apex.
(8) The superior petrosal sinus [sinus petrosus superior] (figs. 514, 515)
runs at the attached margin of the tentorium cerebelli, along the upper border
of the petrous portion of the temporal bone. It connects the cavernous with the
transverse sinus. Leaving the lateral and back part of the cavernous sinus just
below the fourth nerve, it crosses the fifth nerve, and, after grooving the petrous
bone, ends in the transverse sinus as the latter turns downward on the mastoid
portion of the temporal bone. It receives veins from the temporal lobe of the
cerebrum, veins from the cerebellum, veins from the tympanum through the
squamo-petrosal fissure, and sometimes the anterior temporal veins of the diploe.
(9) The inferior petrosal sinus [sinus petrosus inferior] (figs. 514, 516) runs
along the line of the petro-occipital suture, and connects the cavernous sinus with
the commencement of the internal jugular vein. It is shorter than the superior
petrosal, but considerably wider. As it crosses the anterior compartment of the
jugular foramen, it separates the glosso-pharyngeal from the vagus and accessory
nerves. It receives veins from the inferior surface of the cerebellum, from the
medulla and pons, and from the internal ear. The last, the vein of the cochlear
canaliculus [v. canaliculi cochleae], issues through the canaliculus cochleae.
(10) The cavernous sinus [sinus cavernosus] (fig. 516) is an irregularly shaped
venous space situated between the meningeal and periosteal layers of the dura
mater on the side of the body of the sphenoid bone. It extends from the medial
end of the superior orbital (sphenoidal) fissure in front to the apex of the petrous
bone behind. Its lateral wall is the more distinct, and contains the third and
fourth nerves, and the ophthalmic division of the fifth nerve. The nerves take
the above-mentioned order from above downward, and in the medio-lateral direc-
tion. The internal carotid artery and the sixth nerve also pass through the sinus,
being separated from the blood by the endothelial lining. The right and left
cavernous sinuses communicate across the middle line with the opposite sinus in
front and behind the hypophysis cerebri as before mentioned.
The cavernous sinus is traversed by numerous trabeculae or fibrous bands, so that there is
no central space, but rather a number of endotheUal-lined irregular lacunar cavities commu-
nicating one another. Hence its name cavernous, from its resemblance to cavernous tissue.
In front it receives the ophthalmic vein, with which it is practically continuous, and just
above the third nerve the spheno-parietal sinus. Medially it communicates with the opposite
sinus, and posteriorly it ends in the superior and inferior petrosal sinuses. It also receives
veins from the inferior surface of the frontal lobe of the brain, and some of the middle cerebral
veins. Through the Vesahan vein, which runs in a minute foramen in the spinous process of
THE VEINS OF THE BRAIN
653
the sphenoid bone, the sinus communicates with the pterygoid plexus of veins; through the
venous plexus around the petrosal portion of the internal carotid [plexus venosus caroticus
internus], with the internal jugular vein; and through a venous rete which leaves the cranium
by the foramen ovale [rete foraminis ovalis] and by small veins passing through the foramen
lacerum medium, with the pterygoid and pharyngeal plexuses.
(11) The spheno-parietal sinus [sinus sphenoparietalis] runs in a slight groove
on the under surface of the lesser wing of the sphenoid bone. It originates in
one of the meningeal veins near the apex of the lesser wang, and, running roedially,
passes through the sphenoidal fold of dura mater above the third nerve into the
front part of the cavernous sinus. It generally receives the anterior temporal
veins from the diploe.
(
Fig. 516. — The Venous Sinttses at the Base of the Brain. The dura mater has not been
removed. (After Toldt, ''Atlas of Human Anatomy," Rebman, London and New York,)
Position of crista gall:
Circular sinus \
Circular sinus \
Process of dura in foramen cEecum
Eyeball
Ophthalmic vein
Connection
the rete foraminis
ovalis
Middle meningea:
artery
Internal carotid _
artery
Superior T>ulb of the __
internal jugular
vein
Transverse sinus
Mastoid vein
Vertebral artery
._- Maxillary nerve
-^ V^ ~ Facial nerve
■"Acoustic nerve
Vagus nerve
Accessory nerve
Fold of dura mater
Hypoglossal nerve
First spinal nerve
The petro-squamous sinus is occasionally present. It hes in a groove along the junction
of the petrous and squamous portions of the temporal bone. It opens posteriorly into the trans-
verse sinus at the spot where the latter enters on its sigmoid course. In front it sometimes,
though very rarely, passes through a foramen in the squamous portion of the temporal bone
between the mandibular fossa and the external auditory meatus into the temporal vein.
3. THE VEINS OF^THE BRAIN
The veins of the brain present the following peculiarities: — (a) They do not
accompany the cerebral arteries, (h) Ascending veins do not, as in other situ-
ations, run with descending arteries, but with ascending arteries, and vice versa.
(c) The deep veins do not freely communicate, {d) The veins have very thin
walls, no muscular coat, and no valves, ie) The veins opening into the sagittal,
and some of those opening into the transverse (lateral) sinus pour in their blood in
a direction opposite to the current in the sinuses, so impeding the flow in both
654
THE BLOOD-VASCULAR SYSTEM
vein and sinus. (/) The flow of blood in the sinuses is further retarded by the
trabeculfe stretching across their lumen, and in the sagittal sinus by the blood
having to ascend, when the body is erect, through the anterior half of its course.
The veins of the brain may be divided into the cerebral and the cerebellar.
Fig. 517.-
-The Veins of the Brain, Superior Surface. (After Toldt,
Anatomy," Rebman, London and New York.)
'Atlas of Human
Superior sagittal sinus
Lateral protrusion
(lacuna) of superior
sagittal sinus Un- \
jected)
— Superior cerebral veins
Lateral lacuna of su.*
perior sagittal sinus
(opened)
Arachnoidal
(Pacchionian)
Lateral lacuna of superior sagit-
(opened)
Venous orifice
The Cerebral Veins
The cerebral veins, like the cerebral arteries, may be divided into the cortical
and the central.
The cortical or superficial veins ramify on the surface of the brain and return
the blood from the cortical substance into the venous sinuses. The}^ lie for the
most part in the sulci between the gyri, but some pass over the gyri from one sulcus
to another. They consist of two sets : a superior and an inferior.
(1) The superior cerebral veins [vente cerebri superiores] (fig. 517), some eight to twelve in
number on each side, are formed by the union of branches from the convex and medial surfaces
of the cerebrum. Those from the convex surface pass medially and forward toward the
longitudinal fissure, where they are joined by the branches coming from the medial surface.
After receiving a sheath from the arachnoid, they enter obliquely into the superior sagittal
THE CEREBRAL VEINS
655
sinus, running for some distance in its walls. These veins freely communicate with each other,
thus differing from the cortical arteries. They also communicate with the inferior cortical
veins. They may be roughly divided into (a) frontal; (6) paracentral; (c) central; (d) occipital.
(2) The inferior cerebral veins [venec cerebri inferiores] (fig. 518), ramify on the base of
the hemisphere and the lower part of its lateral surface. Those on the inferior surface of the
frontal lobe pass, in part into the inferior sagittal sinus, and in part into the cavernous sinus.
Those on the temporal lobe enter in part into the superior petrosal sinus, and in part into the
transverse sinus, passing into the latter from before backward. A large vein from the occipital
lobe winds over the cerebral peduncle and joins the great cerebral vein (of Galen) just before
the latter enters the straight sinus. One of the inferior cortical veins is called the middle
cerebral vein [v. cerebri media] ; it runs in the lateral fissure (of Sylvius) and ends in the cavernous
sinus. This vein is sometimes called the superficial Sylvian vein. Another, the great anasto-
FiG. 518. — The Veins op t^e Brain, Inpehior Sttepace. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Roots of the superior
cerebral veins
Opening of the in-
f e r i 0 r cerebral
veins into the
transverse sinus
Inferior cerebellar veins
Opening of the superior sagittal sinus -"
into the right transverse sinus
Inferior cere-
^/ bral veins
Anterior external
spinal ^
Opening of the straight sinus into the
left transverse sinus
Occipital sinus
mosing vein of Trolard, a branch of the middle cerebral, estabhshes a communication between
the superior sagittal and cavernous sinuses by anastomosing with one of the superior cortical
veins. A second anastomotic vein, that of Labb6, is also a tributary of the middle cerebral,
and connects the veins over the temporal lobe with the transverse sinus.
A small inferior cerebral vein, the ophthalmomeningeal vein, estabhshes a communication
between the cerebral veins and those of the orbit. It communicates with the veins of the base
and is usually drained by the superior ophthalmic vein. It occasionally opens into the superior
petrosal sinus.
The central or deep (ganglionic) veins return blood from the internal parts of
the cerebrum, and converge to the great cerebral vein.
656
THE BLOOD-VASCULAR SYSTEM
Fig. 519. — The Veins of the Brain, Lateral Surface. (After Toldt, "Atlas of Human
Anatomy/' London and New York.)
Superior cerebral veins Dura mater
Lateral lacuna of the superior ^ r__^ »
sagittal sinus _ ^. ^y'7^^t0'^^mK~^ J^
Middle cerebral vein
Transverse sinus
Middle temporal vein
External carotid artery
Palatine vein
Internal pterygoid muscle
Posterior facial vein
Internal carotid artery
Hypoglossal nerve '
Internal jugular vein
^^^ ^f Internal maxillary artery
&g?"**5^<^ Vena comitans of hypo-
**-^ ■* glossal nerve
Submaxillary duct
External maxillary artery
;X ''^N^ Anterior facial vein
Y \ 2»B Lingual artery
Superior thyreoid vein
Superior oph
thalmic vein
Inferior oph-
thalmic vein
Pterygoid
plexus
Temporal
Fig. 520. — The Ophthalmic Veins. (After Quain.)
Posterior ciliary vein
Superior ophthalmic vein
Supraorbital vein
communicating
with nasofrontal
Frontal vein
Lacrimal gland
Maxillary sinus
•Anterior facial vein
THE VEINS OF THE EAR 657
(3) The internal cerebral veins [vv. cerebri internee] are two large venous trunks (the vense
Galeni) which leave the brain at the transverse fissure, that is, between the splenium of the
corpus callosum and the corpora quadrigemina. In this region they unite to form the great
cerebral vein [v. cerebri magna, Galeni], which opens into the anterior end of the straight
sinus. The internal cerebral veins are formed by the union of the chorioid vein with the vena
terminalis near the interventricular foramen. From this spot they run backward parallel to
each other, between the layers of the tela chorioidea, and terminate in the way above mentioned.
Tributaries of the internal cerebral veins. — In addition to the vena terminalis and the chori-
oidal, the internal cerebral veins also receive the basal vein, the veins of the thalmus, the
vein of the chorioid plexus of the third ventricle, and veins from the corpus callosum, the pineal
body, the corpora quadrigemina, and posterior horn of the lateral ventricle. The united
trunk, or great cerebral vein, receives veins from the upper surface of the cerebellum, and one of
the posterior inferior cerebral veins.
The chorioid vein [v. chorioidea] runs with the chorioid plexus. It begins in the inferior
cornu of the lateral ventricle, and ascends on the lateral side of the chorioid plexus along the
margin of the tela chorioidea to the interventricular foramen, where it unites with the vena
terminalis to form the internal cerebral vein. It receives tributaries from the hippocampus,
corpus callosum, and fornix.
The terminal vein (or vein of the corpus striatum) [v. terminalis], formed by veins from the
corpus striatum and thalamus, runs forward in the groove between those structures, passing
in its course beneath the stria terminalis, and joins the chorioid (choroid) vein at the inter-
ventricular foramen. Tributaries. — It receives, in addition to the veins from the corpus
striatum, thalamus and fornix, the vena septi pellucidi which receives blood from the septum
peUucidum, and anterior cornu of the lateral ventricle.
The basal vein [v. basalis], runs backward over the cerebral peduncle, and enters the
internal cerebral vein near the union of that vessel with the vein of the opposite side.
Tributaries. — A vein, the deep Sylvian, from the insula and surrounding convlutions; the
inferior striate veins from the corpus striatum, which they leave through the anterior perforated
substance; and the anterior cerebral veins from the front of the corpus callosum. It is also
joined by interpenduncular veins from the structures in the interpeduncular space; ventricular
veins from the inferior cornu of the lateral ventricle; and by mesencephalic veins from the
mid-brain.
The Cerebellar Veins
The cerebellar veins are divided into the superior and inferior.
The superior [vv. cerebeDi superiores] ramify on the upper surface of the cerebellum; some
of them run medially over the superior vermis to join the straight sinus and great cerebral
vein; others run laterally to the transverse and superior petrosal sinuses.
The inferior [vv. cerebeUi inferiores], larger than the superior, run, some forward and
laterally to the inferior petrosal and transverse sinuses, and others directly backward to the
occipital sinus.
The Veins of the Medulla and Pons
The veins from the medulla oblongata and the pons terminate in the inferior
petrosal and transverse sinuses.
4. THE VEINS OF THE NASAL CAVITIES
The venous plexuses on the inferior nasal concha (turbinate bone) and back
of the septum are described with the Nose. The veins leaving the nasal cavities
follow roughly the course of their corresponding arteries. Thus the spheno-
palatine veins pass through the spheno-palatine foramen into the pterygoid plexus;
the anterior and posterior ethmoidal veins join the ophthalmic. Small veins
accompany branches of the external maxillary artery through the nasal bones and
frontal processes of the maxillary bones, and end in the angular and anterior facial
veins; and other small veins pass from the nose anteriorly into the superior labial,
and thence to the anterior facial.
5. THE VEINS OF THE EAR
The veins from the external ear and external auditory meatus join the posterior
facial and posterior auricular veins. The veins from the tympanum open into
the superior petrosal sinus and posterior facial vein. The blood from the laby-
rinth flows chiefly through the internal auditory veins [vv. auditivse internse],
which lie with the internal auditory artery in the internal auditory meatus, and
enters the transverse or inferior petrosal sinus. Some of the blood from the laby-
rinth, however, passes through the vestibular vein which Hes in the aquseductus
658
THE BLOOD-VASCULAR SYSTEM
vestibuli, into the inferior petrosal sinus. Some also passes through the vena
canalicuU cochleae which traverses the canal of the same name and empties into
the commencement of the internal jugular vein.
6. THE VEINS OF THE ORBIT
The blood from the eyeball and orbit is returned by the superior ophthalmic
vein into the cavernous sinus. This vein and its tributaries have no valves, and
communicate with the frontal, supraorbital, inferior cerebral, and other veins.
Hence under certain conditions, as from pressure on the cavernous sinus, the blood
Fig. 521. — The Veins of the Orbit.
Supraorbital artery
Lacrimal gland
Superior rectus, cut
Eyeball
Lateral rectus
Lacrimal artery
Superior rectus, cut
Inferior ophthalmic vein
Superior ophthalmic vein
Optic nerve
Superior ophthalmic
^ Commencement of superior
H^l ophthalmic vein
Reflected tendon of superior
obUque
Ophthalmic artery
Anterior ethmoidal artery
Posterior ethmoidal artery
Ciliary arteries
Levator palpebrae, cut
Annulus communis of Zinn
Ophthalmic artery
Optic chiasma
Internal carotid artery
may flow in the contrary direction to the normal — i. e., from behind forward into
the frontal and supraorbital, and thence through the angular vein into the anterior
facial; or upward into the cerebral venous system. In this way pressure on the
retinal veins is quickly relieved, and little or no distension occurs in cases of
obstruction in the cavernous sinus.
The superior ophthalmic vein [v. ophthalmica superior] begins at the medial
angle of the eyelid by a free communication with the frontal, supraorbital, and
angular veins, and thence runs backward and laterally with the ophthalmic
artery across the optic nerve to the medial end of the superior orbital (sphenoidal)
fissure, where it is usually joined by the inferior ophthalmic vein. It then passes
backward between the two heads of the lateral rectus muscle below the sixth
nerve, leaves the orbit through the medial end of the superior orbital (sphenoidal)
fissure and enters the front part of the cavernous sinus. In this course it lies
anterior and superficial to the ophthalmic artery.
Tributaries. — (1) The naso-frontal vein; (2) the superior muscular veins; (3)
the veins of the lids and conjunctiva; (4) the ciliary veins; (5) the anterior and
posterior ethmoidal veins; (6) the lacrimal vein; (7) the central vein of the
retina; and (8) the inferior ophthalmic vein.
(1) The naso-frontal vein [v. naso-frontalis] begins by a free communication with the supra-
orbital vein and enters the orbit through the frontal notch or foramen. It frequently joins
the superior ophthalmic vein quite far back in the orbit (see fig. ,520).
(2) The muscular veins [vv. musculares] are derived from the levator palpebrse, superior
rectus, superior oblique, and medial rectus.
(3) The palpebral and conjunctival veins [vv. palpebrales; vv. conjunctivales ant. et post.],
both anterior and posterior, open into the superior ophthalmic.
(4) The ciliary veins, the veins of the eyeball, are divided into two sets. An anterior
[vv. cihares ant.] emerge from the eyeball with the anterior ciliary arteries, and open
THE INTERNAL JUGULAR VEIN 659
into the muscular veins returning the blood from the four recti. They form a circumcorneal
ring of episcleral veins [w. episclerales]. The posterior set, which drain the venae vorticosae,
leave the globe midway between the cornea and the entrance of the optic nerve. The latter
veins are four or five m number, the upper ending in the superior, the lower in the inferior
ophthalmic vein (fig. 520).
(5) The anterior and posterior ethmoidal veins [w. ethmoidales ant. et post.), correspond
in their course with the arteries of the same name. They enter the orbit through the anterior
and posterior ethmoidal foramina, and join either the ophthalmic direct, or one or other of
the superior muscular branches.
(6) The lacrimal vein [v. lacrimalis] retm-ns the blood from the lacrimal gland, and corre-
sponds in its course to the lacrimal artery.
(7) The central vein of the retina [v. centrahs retinse] runs with the central artery in the
optic nerve. It joins the superior ophthalmic at the back of the orbit.
(8) The inferior ophthalmic vein [v. ophthalmica inferior], smaller than the superior, is
formed near the front of the orbit by the confluence of the inferior muscular with the lower
posterior ciliary veins. It runs backward below the optic nerve, along the floor of the orbit,
and either joins the superior ophthalmic vein, or opens separately into the cavernous sinus.
A large communicating branch passes downward through the inferior orbital (spheno-maxillary)
fissure to join the pterygoid plexus of veins. It receives muscular twigs from the inferior and
lateral rectus and from the interior oblique, and some posteior ciliary veins.
7. THE VEINS OF THE PHARYNX AND LARYNX
The pharyngeal veins [vv. pharyngeee] are arranged in the form of a plexus,
between the constrictor muscles and the pharyngeal or prevertebral fascia. The
pharyngeal plexus receives branches from the mucous membrane, the pterygoid
canal [vv. canalis pterygoidei] from the soft palate, the Eustachian tube and the
anterior recti and longus colli muscles. Above, it communicates with the ptery-
goid plexus of veins; below it drains into the internal jugular vein.
The veins of the larynx end partly in the superior laryngeal vein [v. laryngea
superior], which opens into the internal jugular vein, and partly in the inferior
laryngeal vein [v. laryngea inferior], which terminates in the plexus thyroideus
impar. The laryngeal plexus of veins communicates with the pharyngeal plexus.
8. THE DEEP VEINS OF THE NECK
The deep veins of the neck include the internal jugular, vertebral, deep cervical,
erior thyreoid, thyreoidea ima, thymic, tracheal, and oesophageal veins.
The Internal Jugular Vein
The internal jugular vein [v. jugularis interna] begins at the jugular fossa, and
is the continuation of the transverse sinus. It passes down the neck, in company
first with the internal carotid artery and then with the common carotid artery,
to a point a little lateral to the sterno-clavicular articulation, where it joins the
subclavian to form the innominate vein. At its commencement in the larger,
posterior and lateral part of the jugular foramen, it is somewhat dilated, forming
the superior bulb of the jugular vein [bulbus v. jugularis superior] (fig. 522). This
dilated part of the internal jugular vein lies in the jugular fossa of the temporal
bone and is therefore in immediate relation to the floor of the tympanum. At
first the internal jugular lies in front of the rectus capitis lateralis, and behind the
internal carotid artery, from which it is separated by the hypoglossal, glosso-
pharyngeal, and vagus nerves, and by the carotid plexus of the sympathetic.
As it descends it passes gradually to the lateral side of the internal carotid, and re-
tains this relation as far as the upper border of the thyreoid cartilage. Thence it
runs to its termination along the lateral side of the common carotid artery, being
contained in the same sheath with it and the vagus nerve, but separated from
these structures by a distinct septum. The vein generally overlaps the artery in
front. About 2.5 cm. (1 in.) above its termination it contains a pair of imperfect
valves below which a second dilation usually occurs in the vein. This, the inferior
bulb [bulbus v. jugularis inferior], extends as low as the junction of the internal
jugular with the subclavian. It not infrequently receives the termination of the
external jugular vein.
Tributaries. — At the superior bulb the internal jugular vein receives the
inferior petrosal sinus; the vein of the cochlear canaliculus, and a meningeal
660
THE BLOOD-VASCULAR SYSTEM
vein; opposite the angle of the jaw, veins from the pharyngeal plexus, and often a
communicating branch from the external jugular vein; opposite the bifurcation of
the carotid it is joined by the common facial, and a little lower down by the
lingual, sternomastoid, and the superior thyreoid veins. At the level of the cricoid
cartilage by the middle thyreoid when this vein is present.
The inferior petrosal sinus is described with the other sinuses of the brain (p.
652) ; the pharyngeal plexus with the veins of the pharynx (see p. 659) ; and the
common facial vein with the superficial veins of the scalp and face (p. 646).
The lingual vein [v. lingualis], begins near the tip of the tongue, where it accompanies the
arteria profunda linguEe. It lies at first beneath the mucous membrane covering the under
surface of the tongue. It then passes backward medial to the hyo-glossus, and in company
with the lingual artery. After receiving the sublingual vein [v. sublingualis] and the dorsal
Fig. 522. — The Internal Jugular Vein. (After Henle).
Branches of the
anterior facial
vein
Superficial temporal vein
Styloglossus muscle
Sublingual gland
Hyoglossus muscle
Geniohyoid muscli
Sternohyoid muscle
Thyreohyoid muscle
Omohyoid muscle
Temporal vein
Stylopharyngeus
Pterygoid plexus
Superficial branches
^Styloglossus muscle
^Posterior facial vein
Pharyngeal vein
Stylohyoid muscle
Anterior facial i
Common facial vein
Superior thyreoid vein
Internal jugular vein
lingual veins [w. dorsales linguae], which roughly correspond to their respective arteries, it is
joined by the small v. comitans nervi hypoglossi which follows the upper border of the hypo-
glossal nerve. The trunk finally crosses the common carotid artery and opens into the internal
jugular vein. The lingual vein communicates with the pharyngeal veins and with tributariesof
the anterior facial. It occasionally terminates in the posterior or in the common facial vein.
The sternomastoid vein [v. sternocleidomastoidea] accompanies the artery of the same name and
empties into the internal jugular.
The superior thyreoid vein [v. thyreoidea superior] emerges from the upper part of the
thyreoid gland, in which it freely anastomoses with the other thyreoid veins. This anas-
tomosis, the plexus thyreoideus impar, occurs both in the substance of the organ and on its
surface beneath the capsule. The vein then passes upward and laterally into the interna]
jugular vein, crossing the common carotid artery in its course. At times it forms a common
trunk with the common facial vein. Its tributaries are the sterno-hyoid, sterno-thyreoid,
and thyreo-hyoid veins from the muscles bearing those names; and the crico-thyreoid and
superior laryngeal veins which correspond with the crico-thyreoid and superior laryngeal arteries
respectively. These require no special description.
THYMIC, TRACHEAL AND (ESOPHAGEAL VEINS 661
A separate vein frequently passes out from the capsule of the thyreoid gland near the lower
part of the lateral lobe, crosses the common carotid, and opens into the main superior thyreoid
vein or into the internal jugular vein a little below the cricoid cartilage. In the former case it
is regarded as part of the superior th3Teoid vein system ; in the latter it is generally known as the
middle, thyreoid vein.
The Vertebral Vein
The vertebral vein [v. vertebralis] does not accompany the vertebral artery in
its fourth stage, that is, within the skull, but begins in the posterior vertebral
venous plexus of the suboccipital triangle. It then enters the foramen in the
transverse process of the altas, and passes with the vertebral artery through the
foramina in the transverse processes of the cervical vertebrae, forming a plexus
around the artery. On leaving the transverse process of the sixth cervical verte-
bra it crosses in front of the subclavian artery and opens into the innominate vein.
It has one or two semilunar valves at its entrance into the innominate vein. In
the suboccipital triangle it communicates with the internal vertebral venous
plexuses, with the deep cervical, and occipital veins, and is joined by veins from
the recti and oblique muscles and the pericranium.
Tributaries. — -As it passes down the neck it receives (1) intervertebral veins, which issue
along with the cervical nerves, from the spinal canal; (2) tributaries from the anterior and
posterior vertebral venous plexus from the bodies of the cervical vertebrse and their transverse
processes; and (3) tributaries from the deep cervical muscles. Just before it terminates in the
innominate it is joined by (4) the anterior vertebral vein, a small vein which accompanies the
ascending cervical artery, and, sometimes, by the deep cervical vein.
The Deep Cervical Vein
The deep cervical vein [v. cervicahs profunda], larger than the vertebral,
passes down the neck posterior to the cervical transverse processes. It corre-
sponds to the deep cervical artery from which it is separated by the semispinalis
eervicis muscle.
It begins in the posterior vertebral venous plexus and receives tributaries from the deep
muscles of the neck. It communicates with, or enthely drains, the occipital vein by a branch
which perforates the trapezius muscle. The deep cervical vein then passes forward beneath
the transverse process of the seventh cervical vertebra to open into the innominate vein near
the vertebral, or into the latter near its termination. Its orifice is guarded by a pair of valves.
The Inferior Thyreoid and Thyreoidea Ima Veins
The inferior thyreoid veins [vv. thyreoidea inferiores] descend from the lower
part of the thyreoid gland obliquely lateralward to the innominate veins. The
right vein crosses the innominate arteiy just before its bifurcation, and ends in
the right innominate vein a little above the superior vena cava. It receives
inferior laryngeal veins and veins from the trachea, and has valves at its termina-
tion in the innominate. The left vein passes obliquely over the trachea behind
the sterno-thyreoid muscle, and opens into the left innominate vein. It also
receives laryngeal and tracheal veins, and sometimes the thyreoidea ima; it is
guarded by valves where it opens into the innominate trunk.
The thyreoidea ima vein [v. thyreoidea ima] is single and placed approximately
in the median line. It begins in the thj'reoid isthmus from the plexus thyreoideus
impar, runs downward upon the anterior surface of the trachea, and opens into
the left innominate vein or into the left inferior thja-eoid.
The Thymic, Tracheal and CEsophageal Veins
These small veins usually open into the left innominate vein. The thymic
veins [vv. thymicae], small in the adult, open into the left innominate or into the
inferior thyreoid or thyreoidea ima vein. The tracheal veins [vv. tracheales]
anastomose with the laryngeal and bronchial veins. The oesophageal veins
[vv. cesophagese] from the upper part of the oesophagus, anastomose with the
lower oesophageal veins and with the pharyngeal plexus.
662 THE BLOOD-VASCULAR SYSTEM
THE VEINS OF THE THORAX
THE SUPERFICIAL VEINS OF THE THORAX
The superficial veins of the front of the thorax can be seen in fig. 537. They
form a plexus over the entire chest which the portion over the mammary gland is
called the mammary plexus. The laterally placed lateral thoracic and costo-
axillary veins drain the mammary plexus and communicate with the thoraco-
epigastric vein. These three veins terminate in the axillary vein (p. 671). The
veins nearer the median line are drained by the internal mammary vein and its
anterior intercostal and superior epigastric tributaries. The veins over the entire
thorax are in free communication with the superficial veins of the abdominal wall
(p. 683).
THE DEEP VEINS OF THE THORAX
The deep veins of the thorax are: — the pulmonary veins, and the vena cava
superior and its innominate and other tributaries. Of these veins, the pulmonary,
the vena cava superior, and the innominate veins have already been described,
as have the tributaries of the latter arising in the neck.
The following veins are described below: — (1) The azygos and ascending
lumbar veins, which discharge their blood into the vena cava superior; (2) the
veins of the vertebral column, which are tributary to the azygos veins through the
intercostals; (3) the internal mammary veins, and (4) the superior phrenic, an-
terior mediastinal and pericardiac veins, all of which open into the innominate
veins.
I. THE AZYGOS AND ASCENDING LUMBAR VEINS
The azygos veins are longitudinal veins, the remnants of the posterior cardi-
nals, which are the main collecting trunks for the posterior part of the body in
the embryo. They lie along the sides of the thoracic vertebrae, and collect the
blood from the intercostal veins; they are the upward continuation of longitudinal
anastomotic trunks, the ascending lumbar veins which take origin in the abdomen.
The azygos veins are three in number, the azygos (azygos major) on the right side,
and the hemiazygos (azygos minor) and accessory hemiazygos (azygos tertia) on
the left.
The azygos vein [v. azygos] begins in the abdomen as a continuation .upward of
the ascending lumbar vein. Through this means it connects with the iliac veins
and it has also an anastomosis with the vena cava inferior which may become very
important in cases of obstruction of the vena cava. It runs up through the pos-
terior mediastinum on the right side of the front of the bodies of the thoracic
vertebrte as high as the fourth thoracic vertebra, in this part of its course lying to
the right of the aorta and thoracic duct; it then curves forward over the root of the
right lung, and opens into the vena cava superior immediately before the latter
pierces the pericardium.
It usually contains an imperfect pair of valves at the point where it turns for-
ward from the fourth thoracic vertebra to arch over the root of the lung; and still
more imperfect valves are found at varying intervals lower down the vein.
It receives the intercostal veins of the right side, except the first two or three.
These veins (usually excepting the first) are collected into a common trunk
before joining the azygos vein. It also receives the hemiazygos and accessory
hemiazygos, the right posterior bronchial vein, and small oesophageal and pos-
terior mediastinal veins.
The hemiazygos vein [v. hemiazygos] begins in the abdomen by communicat-
ing, like the azygos vein, with the ascending lumbar vein of its own side. It
courses up the posterior mediastinum to the left of the bodies of the lower thoracic
vertebrae as high as the eighth or ninth, where it turns obliquely to the right, and,
crossing in front of the vertebral column behind the aorta and the oesophagus,
opens into the vena azygos. In its course it crosses over three or four of the lower
left intercostal arteries, and is covered by the pleura.
AZYGOS AND ASCENDING LUMBAR VEINS
663
Tributaries. — (1) The lower four or five left intercostal veins; (2) the lower
end of the accessory hemiazygos vein (sometimes); (3) small left mediastinal
veins; and (4) the lower left oesophageal veins.
The accessory hemiazygos [v. azygos accessorial varies considerably in size,
position, and arrangement, and is often continuous with, or drained by, the left
superior intercostal vein. It hes in the posterior mediastinum by the left side of
the bodies of the fifth, sixth, and seventh or eighth thoracic vertebrae, and is more
Fig. 523. — The Superior and Inferior Ven^ Cav.e, the Innominate Veins,
\ND THE Azygos Veins
Right common carotid
.rtery
Right internal jugular -
Right lymphatic duct
Innominate artery
Right vagus nerve
Right innominate vein
Internal mammary vein
Trunk of the pericardiac
and thymic veins
Vena cava superior
Vena hemiazygos, cross-
ing to enter vena azygos
Hepatic veins
Right inferior phrenic
artery
Coeliac artery
iddle suprarenal
artery
Right
Right spermatic vein
Left common carotid
artery
Left vagus nerve
Thoracic duct
Left innominate vein
Left subclavian artery
Recurrent nerve
Accessory hemiazygos
CEsophagus
Accessory hemiazygos
vein
(Esophageal branches
from aorta
Vena hemiazygos
Thoracic duct
Left inferior phrenic
artery
Left middle suprarenal
artery
Cisterna chyli
Superior mesenteric
artery
Left ascending lumbar
or less vertical in direction. It communicates above with the left superior in-
tercostal vein, and below either joins the hemiazygos or passes obliquely across
the seventh or eighth thoracic vertebra to join the azygos vein. It crosses the
corresponding left intercostal arteries, and is covered by the pleura.
Tributaries. — (1) The fourth, fifth, sixth, seventh, and sometimes the eighth
intercostal veins; and (2) the left posterior bronchial vein.
The ascending lumbar vein [v. lumbalis ascendens] begins, on either side, in
the neighbourhood of the sacral promontory. It is here in free communication, by
664 • THE BLOOD-VASCULAR SYSTEM
means of the anterior sacral plexus, with the middle and lateral sacral veins, and
with the common iliac, hypogastric and ilio-lumbar veins. It ascends in front of
the lumbar transverse processes communicating with the lumbar veins, the vena
cava inferior and, usually, with the renal vein. The right vein enters the
thorax between the aorta and the right medial crus of the diaphragm, and is
continued upward as the vena azygos. The left vein pierces the left medial crus
and becomes the hemiazygos.
The intercostal veins [vv. intercostales]. — The intercostal veins are twelve in
number on each side, the last one being subcostal. They correspond to the inter-
costal arteries. There is one vein to each artery, the vein lying above the artery
whilst in the intercostal space. Each vein receives a dorsal tributary which
accompanies the posterior ramus of an intercostal artery between the transverse
process of the vertebrae and the neck of the rib. These dorsal branches not only
return the blood from the muscles of the back, but receive a spinal branch from
the vertebral venous plexuses. The intercostal veins also receive small tributaries
from the bodies of the vertebrae. The termination of the intercostal veins is
different on the two sides and also varies greatly in different individuals. The
intercostal vein from the first space on either side may join the superior inter-
costal vein, but commonly opens directly into the innominate or one of its tribu-
taries, most frequently the vertebral.
On the right side. — The second intercostal vein joins with the third or with the third and
fourth to form the right superior intercostal vein [v. intercostalis suprema dextra]. This vein
opens into the azygos vein as the latter is arching over the root of the right lung. The rest
join the azygos directly. The upper of these liave well-marked valves where they join the
azygos vein; in the lower veins these valves are imperfect. All the intercostal veins are pro-
vided with valves in their course between the muscles.
On the left side the second intercostal vein joins the third and fourth to form a single
trunk, the left superior intercostal vein [v. intercostalis suprema sinistra]. This vein passes
upward across the arch of the aorta and opens into the left innominate vein. The left superior
intercostal frequently communicates at its lower end with the accessory hemiazygos vein,
which is occasionally tributary to it. In most oases a small tributary runs up over the front
of the aortic arch to join the superior intercostal vein; it is a vestige of the left common cardinal
and from it a small fibrous cord can often be traced through the vestigial fold of the pericardium
to the oblique vein of the left atrium (p. 523).
The left fifth, sixth and seventh intercostal veins commonly open into the accessory
hemiazygos, and the eighth or ninth and succeeding veins into the hemiazygos. The method
of termination of the intercostal veins of the left side is subject to such variation that a normal
arrangement can scarcely be said to exist at all. The eighth may open directly into the azygos,
as may the seventh and ninth or even more of the veins; the hemiazygos and accessory hemi-
azygos being correspondingly reduced in size.
The posterior bronchial veins [vv. bronchiales posteriores] correspond to the bronchial
arteries, but do not return the whole of the blood carried to the lungs by those vessels — that
part which is distributed to the smaller bronchial tubes and the alveola; being brought back by
the pulmonary veins. The posterior bronchial veins issue from the lung substance behind the
structures forming the root of the lung. The right vein generally joins the vena azygos just
before the latter vein enters the superior vena cava. The left vein opens into accessory hemi-
azygos vein. The bronchial veins at the root of the lung receive smaU tributaries from the
bronchial glands, from the trachea, and from the posterior mediastinum.
The oesophageal veins [vv. oesophagefe] from the thoracic portion of the oesophagus end
in part in the vena azygos, and in part in the vena hemiazygos. They anastomose with the
upper oesophageal veins, and with the coronary vein.
The posterior mediastinal veins, small and numerous, open into the azygos and hemiazygos
veins.
2. THE VEINS OF THE VERTEBRAL COLUMN
The venous plexuses around and within the vertebral column extending from
the cranium to the coccyx may be divided into two categories: — (1) the external
and (2) the internal vertebral venous plexuses. The external plexuses consist
of two parts, the anterior vertebral venous plexuses situated on the anterior aspect
of the vertebral bodies and the posterior vertebral venous plexuses ramifying over
the posterior aspect of the vertebral arches, spines, and transverse processes.
The internal plexuses consist of two longitudinal venous sinuses situated between
the vertebrae and the posterior longitudinal ligament, and of two vertebral venous
retia placed immediately external to the dura mater. The sinuses of the internal
plexuses communicate freely with one another and with the internal retia and
external plexuses. They receive the external spinal veins and the basivertebral
veins from the bodies of the vertebrae. The venous circulation of the vertebral
VEINS OF THE VERTEBRAL COLUMN
665
column is drained by the vertebral, intercostal, lumbar and sacral veins either
directly or by means of (3) the intervertebral veins.
1. The external vertebral venous plexuses [plexus venosi vertebrales externi] include the
following :
(a) The anterior vertebral venous plexuses [plexus venosi vertebrales anteriores] (fig.
524) consist of small veins ramifying in front of the bodies of the vertebrae. These veins com-
municate with the basivertebral veins and are larger in the cervical region than elsewhere.
(6) The posterior vertebral venous plexuses [plexus venosi vertebrales posteriores] (fig.
524) are situated around the transverse, articular, spinous processes and laminae of the vertebrae.
Communications take place between the plexuses of each segment and with the veins of the
neighbouring muscles and integuments. Branches are also sent, through the ligamenta flava,
to the internal vertebral venous plexuses, and, between the transverse processes, to the inter-
vertebral veins.
2. The internal vertebral venous plexuses [plexus venosi vertebrales interni] (fig. 524) : —
(a) The two longitudinal vertebral sinuses [sinus vertebrales longitudinales] run through-
out the entire length of the vertebral canal. They are situated behind the bodies of the vertebrae
on either side, between the bone and the posterior longitudinal hgament. The sinuses have
Fig. 524. — The Veins op the Vertebral Column.
{
Mammillary process
Accessory
process or tip
of the true
transverse
process
Costal elem
Posterior transverse
branch
Ejrternal spinal veins
Intervertebral vei
Anterior transversi
Lumbar vein
Posterior vertebral
plexus
Basivertebral veins
ertebral plexu
extremely thin walls, and their interior is made irregular by numerous folds but no true valves
are present. The calibre of the longitudinal sinuses is reduced by constrictions opposite the
intervertebral discs; the consti'ictions alternating with dilatations opposite the vertebral bodies.
At each dilatation there occurs a cross communication between the longitudinal sinuses of
either side, and each receives a basivertebral vein from the corresponding vertebral body.
Opposite every intervertebral foramen and anterior sacral foramen each longitudinal sinus
is joined by the corresponding intervertebral vein. The longitudinal sinuses communicate
very freely with one another, and with the vertebral retia. At the foramen magnum they
communicate with the basilar plexus and, by means of the rate canalis hypoglossi, with the
internal jugular vein.
(6) The venous rete of the vertebrae [retia venosa vertebrarum] (fig. 524) extend from the
foramen magnum to the coccyx. They consist of two main retia situated posteriorly and
lateraOy to the dura between the latter and the vertebral arch. They communicate very
freely with one another across the median line; with the posterior external plexus by means
of twigs perforating the ligamenta flava; and with the longitudinal vertebral sinuses by means
of lateral branches. At the foramen magnum they communicate with the occipital sinus.
(c) The external spinal veins consist of two sets — anterior and posterior — which are drained
by means of veins following the nerve roots, into the internal vertebral venous plexus.
The anterior external spinal veins [w. spinales externa; anteriores] form a tortuous anas-
tomosing vessel in the region of the anterior median fissure.
The posterior external spinal ^•eins [vv. spinales externse posteriores], smaller than the an-
terior run longitudinally on the posterior surface of the cord.
The external spinal veins form a wide-meshed plexus in the pia mater which drains the
internal spinal veins [vv. spinales internae] (see Spinal Cord).
666
THE BLOOD-VASCULAR SYSTEM
{d) The basivertebral veins [vv. basivertebrales] (fig. 524) collect the blood from the
cancellous tissue of the bodies of the vertebra;, and consist of a tunica intima only. They take
a radial direction converging to the transverse vessels connecting the longitudinal vertebral
sinuses. They communicate with the anterior external plexus and with the intercostal veins.
3 The intevertebral veins [vv. intervetebrales] (fig. 524), emerge from each longitudinal
Fig. 525. — The Vertebral Venotts Plexuses. (After Henle.)
Occipital vein
Venous rete
Dura mater spinalis
sinus and pass out through the intervertebral or anterior sacral foramina. They open into the
vertebral, intercostal, lumbar or sacral veins according to region and receive numerous tribu-
taries from the anterior and posterior external vertebral venous plexuses. They are instru-
mental in draining the venous system of the vertebral column and spinal cord.
3. THE INTERNAL MAMMARY VEIN
The internal mammary vein [v. mammaria interna] is formed by the union of
the vena3 comitantes corresponding to the superior epigastric and musculo-phrenic
arteries. The right and left internal mammary veins pass upward, in company
with the corresponding arteries, to open into the right and left innominate
respectively.
Tributaries. — In addition to the superficial veins of the thorax, the internal
mammary veins receive the anterior intercostal, anterior bronchial and peri-
cardiac veins.
The superior epigastric vein [v. epigastrica superior] assists in the drainage of the subcu-
taneous abdominal veins [vv. subcutanCEe abdominis].
The anterior bronchial veins [w. bronchiales anteriores] arise in the bronchial walls and
communicate with the tracheal and posterior bronchial veins.
THE VEINS OF THE UPPER EXTREMITY 667
4. THE SUPERIOR PHRENIC, ANTERIOR MEDIASTINAL, AND
PERICARDIAC VEINS
The superior phrenic [vv. phreniese superiores], the anterior mediastinal [w mediastinales
anteriores], and pericardiac [w. pericardiacae] veins are small vessels, corresponding to the ar-
teries of those names. They pass over the arch of the aorta and open into the lower and an-
terior part of the left innominate.
THE VEINS OF THE UPPER EXTREMITY
The veins of the upper limb consist of two sets — a superficial and a deep.
The superficial veins ramify in the subcutaneous tissue above the deep fascia, and
they do not accompany arteries. The deep veins accompany the arteries, and
have practically the same relations as those vessels. The superficial and deep
veins communicate at frequent intervals through the intermuscular veins which
run between the muscles and perforate the deep fascia. Both sets of veins are
provided with valves, but the valves are more numerous in the deep than in the
superficial. There are usually valves where the deep veins join the superficial.
The superficial veins are larger than the deep, and take the greater share in
returning the blood.
I. THE SUPERFICIAL VEINS OF THE UPPER EXTREMITY
The superficial veins begin in two irregular plexuses, one in the palm and the
other on the back of the hand. The plexus in the palm is much finer, and com-
municates with the superficial volar veins of the fingers. The latter discharge
their blood into the dorsal venous rete by means of the veins of the folds between
the fingers, or the intercapitular veins [vv. intercapitulares] (fig. 426).
The veins of the back of the hand begin in a longitudinal plexus over the
fingers, and at the bases of the fingers the veins of the adjacent digits are con-
nected by digital venous arches [arcus venosi digitales], from which arise the
dorsal metacarpal veins [vv. metacarpese dorsales]; these form upon the back
of the hand a dorsal venous rete [rete venosum dorsale manus] (fig. 427).
Of the veins of the arm, two stand out prominently, the basilic and the
cephalic. Both of these arise from the veins of the back of the hand, curve
around to the volar surface of the forearm, and pass to the upper arm (fig. 426).
The basilic vein [v. basilica],* arises on the back of the hand from the ulnar
end of the dorsal venous rete, which usually forms an arch. It curves around the
ulnar side of the forearm to the volar surface and passes to the elbow and the
upper arm, where it lies in the median bicipital sulcus. It extends up to about
the middle third of the sulcus, and, piercing the brachial fascia, joins the brachial
vein.
The cephalic vein [v. cephalica],* begins at the radial end of the dorsal
venous rete or arch and curves around the radial border of the forearm to the
volar surface not far above the thumb. It passes to the elbow and the upper
arm, but, unlike the basilic, it maintains its superficial course up to the shoulder,
lying first in the lateral bicipital sulcus and then in the groove between the pec-
toralis major and the deltoid. Just below the clavicle it turns into the depth, and
empties into the axillary vein.
In the forearm plexus one or more longitudinal veins besides these are usually
distinct. One lateral to the cephalic is known as the accessory cephalic [v.
cephalica accessoria] (formerly the radial) vein; one near the centre is known
as the median antibrachial [v. mediana antibrachii], (formerly the anterior
ulnar) vein.
At the elbow there is usually an obhque connecting branch, the median
cubital vein [v. mediana cubiti] (formerly termed median basilic) which extends
*Tlie basilic vein here described corresponds to tlie posterior ulnar and basilic; the cephalic
corresponds to the median, median cephalic and cephalic of the older terminology employed
in English text-books. The BNA terminology has the gi-eat advantage that it can be readily
used to desci'ibed any form of venous pattern. The English terminology applies only to cases
in which the M-shaped arrangement occurs upon the volar surface of the elbow. Berry and
Newton find the latter arrangement in only 13 per cent, out of 300 cases examined.
668
THE BLOOD-VASCULAR SYSTEM
from the cephalic up to the basilic. In some cases this anastomosis is made by a
division of the median antibrachial into two branches, a median cephalic and
Fig. 526.-
-The Superficial Veins of the Akm and Forearm. (After Toldt, "Atlas of
Human Anatomy," Rebman, rondon and New York.)
Cephalic /
vein I
Conaecting branches
between the superfi-
cial and deep veins Brachial
fascia
Accessory
median cubital
(var;
Median cubital
— .- Intercapitular
veins Cephal:
vein
-Proper volar
--^ digital Connec-
veins tion
with deep
veins
Accessory
cephalic
Antibrachial
fascia
> Basilic vein
Note. — In the limb here represented the direct venous channel on the radial side of the
forearm, the accessory cephalic (formerly radial) vein, is continued directly into the cephalic
above the elbow. The cephalic in the forearm (formerly median) is mainly drained by the
basilic through the median antecubital. The vein opposite the bend of the elbow, which usu-
ally forms the segment of the cephalic formerly known as the median cephalic vein, is here a
small channel draining into an accessory median cubital. The basilic vein of the forearm
(formerly posterior ulnar) is represented by a plexus of small venous channels.
SUPERFICIAL VEINS OF THE ARM
669
median basilic. Occasionally the cephalic in the upper arm is reduced to a small
tributary, which takes the course of the cephalic in the forearm, but bends ulnar-
ward at the elbow to form the basilic. Numerous connections occur between the
deep and the superficial veins at the elbow.
The superficial plexus of veins in the upper arm consists of small vessels that
pass to the cephalic vein.
Fig. 527. — Veins op the Back op the Forearm. (After Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Cephalic vein
— Accessory median cubital vein
Median cubital vein
Subcutaneous venous /
network v.
Accessory cephalic vein
Basilic vein
Dorsal venous rete .
Digital venous arch
670
THE BLOOD-VASCULAR SYSTEM
II. THE DEEP VEINS OF THE UPPER EXTREMITY
The deep veins of the upper extremity accompany their corresponding
arteries. There are two veins to each artery below the level of the axilla, known
as the vense comitantes. The deep veins all contain numerous valves, and
Fig. 528. — Deep Veins of the Ahm and Axilla. (After Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Internal jugular vein
Transverse scapular vein / Transverse cervical artery
Axillary artery and vein \ m^^ / Transverse cervical vein
Anterior circumflex humeral artery and vem \ ^.^^^H^^^^L * External jugular vein
Subclavian vein
Jugular venous arch
Right innominate vein
Posterior cir< umflex
humeral artery and
Circumflex scapular vem
Biceps muscle
Basilic vein
Biceps muscle
Brachial veins
Ulnar nerve
Dorsal thoracic artery and vein
^Median cubital vein
L^^^^^Inferior ulnar collateral artery and vein
. v^Connection of radial with superficial veins
-Ulnar artery and veins
Radial artery and veins
communicate at frequent intervals through intermuscular veins with the super-
ficial vessels.
DEEP VEINS OF THE UPPER EXTREMITY 671
Beginning at the fingers, two minute proper volar digital veins [venae digitales
volares proprise], accompany each digital artery along the sides of the fingers,
and uniting at the cleft, form common volar digital veins [vv. digitales volares
communes], which join the vense comitantes of the arteries, forming the super-
ficial palmar arch. In like manner the veins accompanying the arteries forming
the deep arch receive tributaries, the volar metacarpal veins [vv. metacarpese
volares], corresponding to the branches of that arch. A superficial and a deep
volar venous arch [ arcus volaris venosi superficialis et profundus] are thus formed
accompanying the arterial arches. The venae comitantes from the ulnar side of
the superficial and deep arches unite at the spot where the ulnar artery divides
into the superficial and deep branch to form two ulniar venae comitantes [vv.
ulnares] ; whilst those on the radial side of the superficial and deep arch accompan}^
the superficial volar artery and the termination of the radial artery respectively,
and unite at the spot where the superficial volar is given off from the radial artery,
to form the radial venae comitantes [vv. radiales]. The ulnar and radial venae
comitantes thus formed course up the forearm with their respective arteries,
receiving numerous tributaries from the muscles amongst which they run, and
giving frequent communications to the superficial veins. They finally unite at
the bend of the elbow to form the brachial venas comitantes [vv. brachiales].
The ulnar venae comitantes receive, before joining the radial, the companion
veins of the interosseous arteries. At the bend of the elbow the deep veins are
connected with the basilic or with the median antibrachial vein by a short, thick
trunk (fig. 528).
The brachial venae comitantes accompany the brachial artery. At the lower
border of either the teres major or subscapularis muscle, the more medial vein
receives the more lateral and the basilic vein, to form a single axillary vein.
The venae comitantes of the arteries of the arm anastomose with one another
by frequent cross branches.
The axillary vein [v. axillaris], is formed by the junction of the medial brachial
vena comitans with the basilic vein at the lower border of either the teres major
or subscapularis muscle. It is a vessel of large size, conveying as it does nearly
the whole of the returned blood from the upper extremity. It accompanies the
axillary artery through the axillary fossa, lying to its medial side and, at the upper
part of the space, on a slightly posterior plane. At the lateral border of the first
rib it changes its name to the subclavian. It has one or two axillary lymphatic
nodes in close connection with it, and is liable, if care is not taken, to be wounded
in removing these glands. The vein contains a pair of valves, usually placed
near the lower border of the subscapularis muscle.
Tributaries : — (1) The subscapular veins which accompany the subscapular
artery; (2) the circumflex veins accompanying the circumflex arteries; (3) the
lateral thoracic vein [v. thoracalis lateralis] a large vein which accompanies
the lateral thoracic artery and receives numerous thoraco-epigastric veins [vv.
thoracoepigastricse] from the epigastric and lower thoracic regions; (4) the costo-
axillary veins [vv. costoaxillares] the radicles of which arise in the pectoral region
from the mammary plexus [plexus venosus mamillae] ; and (5) the cephalic vein.
The subclavian vein [v. subclavii] (fig. 528), is the continuation of the axillary.
It begins at the lateral border of the first rib, and terminates by joining the
internal jugular to form the innominate vein opposite the lateral end of the
sterno-clavicular articulation. It lies anterior to the subclavian artery and on a
lower plane, and is separated from the artery in the second part of its course
by the scalenus anterior muscle. The subclavian vein, just before it is joined by
the external jugular, contains a pair of valves.
Tributaries. — The subclavian vein receives the thoracoacromial vein near its
distal end, and the external jugular vein near the lateral border of the sterno-
mastoid muscle. The transverse cervical veins terminate in the subclavian near
the external jugular, or in the latter vein, or in a plexiform arrangement formed
between the transverse scapular, transverse cervical and external jugular veins.
The external jugular vein is described with the superficial veins of the head
and neck (p. 646).
The thoracoacromial vein [v. thoracoacromiahs], receiving tributaries cor-
responding to the branches of the artery of the same name, terminates near the
lateral border of the first rib.
672 THE BLOOD-VASCULAR SYSTEM
The transverse cervical veins [vv. transversae colli] receive tributaries cor-
responding in distribution to the branches of the transverse cervical artery.
They emerge from beneath the trapezius muscle, cross the posterior triangle, and
usually terminate in the subclavian vein. They usually terminate as a single vein
the orifice of which is guarded by a pair of valves. Occasionally the cephahc vein,
or a branch from the cephalic (the jugulo-cephalic), passes over the clavicle to the
subclavian.
III. THE VENA CAVA INFERIOR AND ITS TRIBUTARIES
All the veins of the abdomen, pelvis, and lower extremities, with the exception
of the superior epigastric (p. 666), and ascending lumbar vein (p. 521), which
join with the superior caval system, enter directly or indirectly into the vena
cava inferior. The veins corresponding to the parietal branches of the abdominal
aorta, except the middle sacral vein, open directly into the vena cava inferior;
the middle sacral vein only indirectly through the left common iliac vein. Of the
visceral veins corresponding to the visceral branches of the abdominal aorta,
those which return the blood from the stomach, intestines, pancreas, and the
spleen end in a common trunk called the portal vein.
The portal vein [vena portae] enters the liver and there breaks up into a net-
work of smaller vessels somewhat after the manner of an artery. This network
contains venous blood, and is moulded upon the tissue-elements of the organ
itself. The smaller vessels consist, like capillaries (from which they differ in
developmental history) of intima only; they are called sinusoids. The venous
blood is returned from the sinusoidal plexus by the hepatic veins which open into
the vena cava inferior as that vessel lies in the fossa venae ca,v£e of the liver.
Of the other visceral veins, both renals, the right suprarenal, and the right
spermatic or ovarian open directly into the vena cava inferior; whilst the left
suprarenal and left spermatic or ovarian are drained through the left renal.
Two of the superficial veins of the lower part of the anterior abdominal wall,
the superficial epigastric and superficial circumflex iliac, enter the great saphenous
vein; and two of the deep veins from the like situation, the inferior epigastric and
deep circumflex iliac, enter the external iliac vein. The blood in these vessels,
however, can flow upward as well as in the normally downward direction. In
obstruction of the vena cava inferior they become greatly enlarged, and form,
with the superior epigastric vein and with other superficial veins of the thorax
with which they anastomose, one of the chief channels for the return of the blood
from the lower limbs.
The veins of the pelvis, which receive the veins from the perinseum and gluteal
region, join the hypogastric vein.
THE VENA CAVA INFERIOR
The vena cava inferior (fig. 529) is the large vessel which returns the blood
from the lower extremities and the abdomen and pelvis. It is formed by the con-
fluence of the right and left common iliac veins opposite the body of the fifth
lumbar vertebra, ascends in front of the lumbar vertebrae to the right of the ab-
dominal aorta, passes through the caval opening in the diaphragm, and ends in
the lower and back part of the right atrium of the heart on a level with the lower
border of the ninth thoracic vertebra. At its origin it lies behind the right
common iliac artery on a plane posterior to the aorta, but as it ascends it passes
slightly forward and to the right, reaching a plane anterior to the aorta, and
becoming separated from that artery by the right medial crus of the diaphragm
and the caudate lobe of the liver. While in contact with the liver it lies in a
deep groove [fossa venae cavje] on the posterior surface of that organ, the groove
being often converted into a distinct canal by a thin portion of the hepatic sub-
stance bridging across it. As it passes through the diaphragm its walls are
attached to the tendinous margins of the caval opening, and are thus held apart
when the muscle contracts. On the thoracic side of the diaphragm it Hes for about
1.2 cm. (I in.) within the pericardium, the serous layer of that membrane being
reflected over it.
THE VENA CAVA INFERIOR
673
Relations. — In front it is covered by the peritoneum, and crossed by the right spermatic
artery, branches of the aortic plexus of the sympathetic, the transverse colon, the root of the
mesentery, the duodenum, the head of the pancreas, the portal vein, and the liver. The
median gi'oup of the lumbar lymphatic nodes are also in front of it below, and at its com-
mencement the right common iliac artery rests upon it.
Behind, it hes on the lumbar vertebrae, the right lumbar arteries, the right renal artery,
the right coehao (semilunar) ganglion, and the right medial crus of the diaphragm.
To the right are the peritoneum, liver, and psoas muscle.
To the left is the aorta, and higher up the right medial crus of the diaphragm.
Tributaries. — The vena cava inferior receives the following veins: — ■(!) the
renal veins; (2) the right suprarenal vein; (3) the right spermatic or the right
Fig. 529. — The Abdominal Aorta and Vena Cava Inferior.
i
Cystic artery
Hepatic duct
Cystic duct
Common bile duct
Portal vein
Gastro-duodenal br.
Right gastric arterj
Hepatic artery
Right suprarenal vein
Inferior suprarenal
artery
Renal artery
Renal vein
Vena cava inferior
Kidney
Right spermatic vein
Right internal sper-
matic artery
Quadratus lumborum
muscle
Right lumbar artery
and left lumbar vein
Ui eteric branch of
spermatic artery
Middle sacral vessels,
Left lobe of liver
(Esophagus
Left inferior phrenic
artery
Right inferior phrenic
artery
Superior suprarenal
Left gastric artery
Inferior suprarenal
Splenic artery
Left inferior phrenic vein
Left suprarenal vein
Superior mesenteric
artery
Kidney
Ureteric branch of renal
Left spermatic vein
Left internal spermatic
artery
Inferior mesenteric
artery
Ureteric branch of
spermatic
Ureteric branch of
common iliac
Common iUac artery
External iliac artery
Hypogastric artery
ovarian vein; (4) the lumbar veins; (5) the inferior phrenic veins; (6) the hepatic
veins; and (7) the right and left common iliac veins.
(1) The renal veins [vv. renales] (fig. 529) return the blood from the kidneys.
They are short but thick trunks, and open into the vena cava nearly at right
angles to that vessel. The vein on the left side, like the kidney, is a little higher
than on the right, and is also longer, in consequence of its having to cross the
aorta.
Each renal vein lies in front of its corresponding artery. The left vein crosses in front of
the aorta, just below the origin of the superior mesenteric artery. It is covered by the inferior
portion of the duodenum, and receives the left spermatic, or the left ovarian in the female,
and usually the left suprarenal, and sometimes the left phrenic. There are rudiments of valves
in each vein where it joins the vena cava. Those on the right side, however, are less well
marked.
(2) The suprarenal veins [vv. suprarenales] (fig. 529). — ^There is usually only one suprarenal
vein on each side to return the blood brought to the suprarenal body by the three suprarenal
arteries. On the right side the vein opens directly into the vena cava, above the opening of the
right renal vein. On the left side, it opens into the left renal.
674
THE BLOOD-VASCULAR SYSTEM
(3) The spermatic veins [vv. sperraaticaj] (fig. 529) retui-n the blood from the testis. They
begin by the confluence of small branches from the body of the testis and epididymis. As
they proceed up the spermatic cord, in front of the internal spermatic artery and ductus
deferens, they become dilated and plexiform, constituting the pampiniform plexus [plexus
pampiniformis] (fig. 541). After passing through the subcutaneous inguinal ring, the inguinal
canal, and the abdominal inguinal ring, the plexus communicates with the inferior epigastric
vein and is continued as two veins. Along with the artery the veins pass up beneath the
peritoneum, and on the left side also beneath the sigmoid colon, across the psoas muscle and
ureter. They receive small tributaries from the ureter and peritoneum, and proceed as a single
trunk, on the right side to the vena cava inferior, and on the left side to the left renal vein.
There are commonly a number of imperfect valves in the spermatic plexus and a perfect pair
at the termination of each spermatic vein. On the left side, however, the terminal valve may
be wanting.
Fig. 530. — The Veins op the Female Pelvis. (After Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Right common iliac artery and vein
Right external iliac artery
Left common iliac artery and vein Edge of the suspensory ligament /
Hypogastric artery and vein of the ovary , / /
Ovarian vein / — «^'
, Left external iliac artery and vein -^' ^
Sacrotu-
berous
ligament
Obturator in-
ternus muscle
Utero-vaginal plexus
; behind the bulbus vestibuli
The ovarian veins [vv. ovarica3[ begin at the plexus pampiniformis near the ovary,
between the layers of the broad ligament. This plexus is larger than in the male and com-
municates freely with the utero-vaginal plexus of veins, and with the plexus of veins which ex-
tends from the hilus of the ovary into the ovarian ligament (fig. 486). After passing from
between the layers of the broad Ugament, the plexus unites to form at first two and then a
single vessel, which accompanies the ovarian artery, following a course similar to that of the
spermatic veins in the male. The right ovarian veins open into the vena cava inferior, the left
into the left renal. They usually contain imperfect valves in their plexiform part, and a perfect
valve where they join the vena civa and renal vein respectively.
THE PORTAL VEIN 676
(4) The lumbar veins [vv. lumbales], four to five on either side accompany the lumbar
arteries and collect venous blood from the muscles of the back and abdomen. They terminate
by passing beneath the tendinous arches of the psoas major, along the sides of the lumbar
vertebrae, and opening into the vena cava inferior. The veins of the left side are longer than
those of the right and pass behind the aorta. Each vein receives a dorsal tributary corre-
sponding in distribution to the dorsal branch of the lumbar artery. Between the dorsal tribu-
taries and the posterior vertebral venous plexus there occurs a free communication. There
is also an anastomosis between the main lumbar veins and the anterior vertebral venous plexus
around the bodies and transverse processes of the lumbar vertebrae. By means of these
communications the intervertebral veins, the internal and external vertebral and spinal plexuses
are partly drained. In addition to these anastomoses the lumbar veins are connected with one
another and with common iliac, hypogastric, ilio-lumbar, renal, azygos and hemiazygos veins
by means of the ascending lumbar vein (p. 66.3).
(5) The inferior phrenic veins [v. phrenica inferior] follow the course of the inferior phrenic
arteries; the right opens into the vena cava direct; the left into the suprarenal, the left renal, or
the vena cava.
(6) The hepatic veins [vv. hepaticse], the largest tributaries of the vena cava, return the
blood from the liver. Commencing in the substance of the liver (see Liver), they converge as
they approach its posterior surface, and unite to form two or there large trunks, which open
into the vena cava as it lies in the fossa vense cavae. Some smaller vessels from the caudate
lobe, and other parts of the liver in the nighbourhood of the caval fossa, open directly into the
vena cava. The hepatic veins contain no valves, but, in consequence of opening obliquely
into the vena cava, a semilunar fold occurs at the lower magin of each orifice.
THE PORTAL VEIN
The veins corresponding to the inferior mesenteric, the superior mesenteric,
and to some of the branches of the coeliac artery, do not join the vena cava in-
ferior direct, but unite to form a common trunk — the portal vein.
This vein enters the liver, and breaks up in its substance into sinusoids
from which the blood is again ultimately collected by the hepatic veins, and carried
by them into the vena cava inferior. The terminal branches of the hepatic artery
also empty into the hepatic sinusoids, and their blood likewise finds its way
finally into the hepatic veins, and thence into the vena cava inferior. The portal
vein and its tributaries have no valves.
The portal vein [v. portae] (fig. 531), is a thick trunk 7 or 8 cm. (3 in.) in length.
It is formed behind the head of the pancreas, opposite the right side of the body
of the second lumbar vertebra, by the union of the superior mesenteric with the
splenic veins. It passes upward and to the right behind the superior part of the
duodenum, and then between the layers of the lesser omentum. In the latter
situation it passes in front of the foramen epiploicum and is accompanied by
the hepatic artery and the hepatic duct. Finally it enters the porta of the liver,
and there divides into a right and a left branch. In this course the hepatic artery
and the common bile duct are in front, the former to the left, the latter to the
right. It is surrounded by branches of the hepatic plexus of the sympathetic
nerve, and by numerous lymphatic vessels and some glands. The connective
tissue sheath enclosing these structures is called the fibrous capsule of Glisson
[capsula fibrosa, Glissoni]. Just before it divides it is somewhat dilated, the
dilated portion being called the sinus of the portal vein. The division into right
and left branches takes place toward the right end of the porta of the liver.
The right branch is shorter and thicker than the left, and supplies the right
lobe of the liver and a branch to the quadrate lobe. The left branch is longer and
smaller than the right, and supplies the left lobe, and gives a branch to the caudate
(Spigelian) and quadrate lobes. It is joined, as it crosses the left sagittal fossa,
by a fibrous cord, known as the ligamentum teres hepatis (obUterated vena
umbilicalis), and posteriorly by a second fibrous cord, the ligamentum venosum (ob-
lietrated ductus venosus). The position of the original course of the umbilical
vein across the left portal is marked, in. adult life, by a dilation of the latter
vein, called the umbilical recess.
Tributaries. — ^The pyloric, the coronary (gastric), the cystic, the superior
mesenteric, and the splenic.
The pyloric vein begins near the pylorus in the lesser curve of the stomach, and, running
from left to right with the right gastric artery, opens directly into the lower part of the portal
vein. It receives branches from the pancreas and duodenum.
The coronary vein [v. coronaria ventriculi] (fig. 533) runs with the left gastric artery at
first from right to left, among the lesser curvature of the stomach, toward the cardiac end, and
then, turning to the right, passes across the spine from left to right to end in the portal trunk a
676
THE BLOOD-VASCULAR SYSTEM
Fig. 531. — The Portal Vein. (From Kelly, by Brodel.)
TRIBUTARIES OF THE PORTAL VEIN
677
little higher than the pyloric vein. At the cardiac end of the stomach it receives small branches
from the oesophagus.
The cystic vein [v. cystica] (fig. 533) returns the blood from the gall-bladder. It usually
opens into the right branch of the portal vein.
The superior mesenteric vein [v. mesenterica superior] (fig. 534) begins in
tributaries whichi correspond witli the branches of the superior mesenteric artery.
It courses upward a little in front and to the right of the artery, passing with that
vessel from between the layers of the mesentery. It passes in front of the
inferior portion of the duodenum, and behind the pancreas, where it joins the
splenic vein to form the portal trunk (fig. 531).
Tributaries. — In addition to the tributaries corresponding to the branches of
the superior mesenteric artery — viz. the ileo-colica, colica dextra, colica media, and
vence intestinales (fig. 534) — it receives the right gastro-epiploic and the pan-
creatico-duodenal veins just before its termination in the portal vein.
The right gastro-epiploic vein [v. gastroepiploica dextra] (fig. 533) accompanies the artery
of that name. It runs from left to right along the greater curvature of the stomach, receiving
branches from the anterior and posterior surfaces of that viscus, and from the great omentum,
and, passing behind the superior portion of the duodenum, ends in the, superior mesenteric
vein just before that vessel joins the portal trunk.
Fig. 532. — The Portal Vein within the Lr^ee.
Ascending branch
(After Rex.)
Vena cava inferior'
Falci-
form
liga-
ment
Right main branch
Left Round
' branch lig.
Gall-bladder Trunk of por- Umbilical
tal vein recess
The pancreatio-duodenal veins [vv. pancreatico-duodenales] (fig. 531) run with the superior
and inferior pancreatico-duodenal arteries between the head of the pancreas and the second
portion of the duodenum. They receive pancreatic and duodenal veins [vv. pancreaticiE et
duodenales] and are collected into a single stem which follows the inferior pancreatico-duodenal
artery and ends in the superior mesenteric vein a little below the right gastro-epiploic vein.
.The splenic vein [v. lienalis] (fig. 531) issues as several large branches from
the hilus of the spleen. These soon unite to form a large trunk, which passes
across the aorta and spine in company with the splenic artery, below which it lies,
to join at nearly a right angle the superior mesenteric vein. In this course it lies
behind the pancreas; and at its union with the superior mesenteric to form the
vena portse in front of the vena cava inferior.
Tributaries. — It receives the short gastric veins [vv. gastricse breves], from the
fundus of the stomach, the left gastro-epiploic vein, and the inferior mesenteric
vein. As it lies in contact with the pancreas it receives some small pancreatic
veins [vv. pancreaticse].
The left gastro-epiploic vein [v. gastroepiploica sinistra] (fig. 533) accompanies the left
gastro-epiploic artery. It runs from right to left along the greater curvature of the stomach,
receives branches from the stomach and omentum, and opens into the commencement of the
splenic vein.
678
THE BLOOD-VASCULAR SYSTEM
The inferior mesenteric vein [v. mesenterica inferior] (fig. 531) begins at the
rectum as the superior hgemorrhoidal vein. This emerges from the hsemor-
rhoidal plexus in which it communicates freely with the middle and inferior
haemorrholdal veins. It passes out of the pelvis with the inferior mesenteric
artery; but, after receiving the sigmoid and left colic veins [vv. sigmoideee et
V. colica sinistra] which accompany the arteries of the same names, it leaves the
artery and runs upward on the psoas to the left of the aorta and behind the
peritoneum. On approaching the pancreas it turns medially, and passes obliquely
behind that gland to join the splenic vein just before the latter unites with the
superior mesenteric to form the vena portse.
Fig. 533.-
-The Veins of the Stomach and the Portal Vein.
(From a dissection by W. J. Walsham.)
Right branch of
portal vein
Hepatic artery
Hepatic artery
proper
Gastro-duodenal
branch of hepatic
artery
Pyloric vein
Right gastro-
epiploic vein'
Omental veins
Left branch or
portal ^
5 corres-
ponding to short
gastric arteries
Left gastric artery
Hepatic artery
The adult portal vein and its tributaries contain no valves, a circumstance which adversely
affects the circulation of blood within this system. The liability to excessive pressure in the
most dependent part of the portal system is evidenced by the great frequency of the condition
known as piles, due to dilatation of the veins of the internal hsemorrhoidal plexus. In earrly
life valves are present in the veins of the stomach and of the intestinal wall but these undergo
retrogression.
The accessory portal veins. — Since the blood returning from the abdominal portion of the
digestive tract and spleen must pass through the hepatic-capillaries before returning to the heart,
extensive obliteration of these capillaries, such as occurs in certain diseases of the liver, would
prevent the return of the portal blood to the heart were it not for anastomoses between tribu-
taries of the portal vein and those of the caval systems, constituting what have been termed
accessory portal veins. Some of the more important of these are — (1) between the branches of
the coronary vein of the stomach and the oesophageal veins which open into the vena azygos;
(2) between the parumbilical veins [vv. parumbilicales], which communicate with the portal
vein above and descend upon the ligamentum teres to the anterior abdominal wall to anastomose
with the superior and inferior epigastric and superior vesical veins; (3) between the superior
and middle hsemorrhoidal veins, the latter opening into the hypogastric, and (4) between a
wide-meshed retro-peritoneal plexus of veins which communicates with the portal vessels
over the posterior surface of the liver and the veins of the pancreas, duodenum and ascending
and descending colon on the portal side, and with the phrenic and azygos veins on the systemic.
THE HYPOGASTRIC VEIN
THE COMMON ILIAC VEINS
679
The common iliac veins [vv. iliacae communes], (fig. 536) are formed opposite
the sacro-iliac articulation by the confluence of the external iliac and hypo-
gastric (internal iliac) veins. They converge as they ascend, and unite oppo-
site the upper border of the fifth lumbar vertebra and a little to the right of the
median line to form the vena cava inferior.
Fig. 534. — The Superior Mesenteric Vein.
(The colon is turned up, and the small intestines are drawn over to the left side.)
Middle coin
artery
Inferior pancre
Left colic artery
Superior mes-
enteric artery
and vein
Ileo-colic artery
Vermiform
process
The right vein, shorter and more vertical in direction than the left, passes obliquely behind
the right common iliac artery to its lateral side, where it is joined by the left common iliac vein.
The left vein lies to the medial side of the left common iliac artery, and, after crossing in
front of the promontory of the sacrum and the fifth lumbar vertebra below the bifurcation of
the aorta, passes beneath the right common iliac artery to join the right vein and form the
vena cava inferior. The left vein may contain an imperfect valve.
Tributary. — The ilio-lumbar veins may enter the lower part of the common
iliac, or open into the hypogastric vein. The left vein receives the middle sacral
vein.
The middle sacral vein [v. sacralis media] opens usually as a single trunk
into the left common liiac vein. The venae comitantes which form it ascend on
either side of the middle sacral artery in front of the sacrum. They communicate
with the lateral sacral veins, forming the anterior sacral plexus [plexus sacralis
anterior] which receives the sacral intervertebral veins, and anastomoses freely
with the neighbouring lumbar and pelvic veins. Below, the middle sacral veins
communicate with the hsemorrhoidal veins.
THE HYPOGASTRIC VEIN
The hypogastric (internal iliac) vein [v. hypogastrica] (fig. 536) is formed by
the confluence of the veins (except the umbilical) corresponding to the branches
680
THE BLOOD-VASCULAR SYSTEM
of the hypogastric artery. It varies considerably in length, but is usually quite
a short trunk, extending from the upper part of the great sciatic foramen to the
sacro-liac articulation, where it joins the external iliac to form the common
iliac vein. It lies behind and a little medial to the hypogastric artery. It con-
tains no valve.
Tributaries. — The hypogastric vein receives directly or indirectly the following
vessels; the superior gluteal, ilio-lumbar, lateral sacral, obturator, inferior
Fig. 635. — The Inferior Mesenteric Vein.
(The colon is turned up, and the small intestines are drawn to the right side.)
Middle colic artery - —
Inferior pancreatico-
duodenal artery
Superior mesenteric
artery
Right coUc artery
Abdominal aorta
/ena cava inferior
Right common iliac
artery
Middle sacral artery
and vein
Left colic artery
Inferior mesen-
teric artery
Left colic artery
Inferior mesen-
teric artery
Sigmoid artery
Superior hasmor-
rhoidal artery
gluteal (sciatic), internal pudendal, and (in the female) the uterine veins; also
branches from the pudendal, vesical, and haemorrhoidal plexuses. The single
umbilical vein-^the vein corresponding to the right and left hypogastric arteries
and their continuation, the umbilical arteries — does not enter the pelvis, but,
leaving the umbihcal arteries at the navel, passes along the falciform ligament
to the liver. After birth it is converted into the hgamentum teres hepatis.
(See Portal Vein, p. 675.)
The superior gluteal veins [vv. glutete superiores] accompany the superior gluteal artery
and, passing through the upper part of the great sciatic foramen, open into the hypogastric
vein near its termination, either separately or as a single trunk.
The ilio-lumbar veins [vv. ilio lumbales] open into the hypogastric a little higher than the
superior gluteal. At times they join the common iliac vein.
The lateral sacral veins [vv. sacrales laterales] (fig. 536) join the superior gluteal or the
hypogastric at or about the same situation as the gluteal. They form with the middle sacral
veins a ple.xus in front of the sacrum, which receives tributaries from the sacral canal.
The obturator vein [v. obturatoria] (fig. 536), which lies below the obturator artery as it
crosses the side of the pelvis, opens into the front of the hypogastric vein a little below the su-
perior gluteal. Its branches correspond to those of the artery.
The inferior gluteal veins [vv. giuteae inferiores] accompany the inferior gluteal (sciatic)
artery, and, as a rule, unite to form a single trunk before joining the hypogastric a little below
the obturator vein.
All the above veins so closely follow the ramifications of their respective arteries that no
further special description of them is required. They all contain valves.
THE DORSAL VEIN OF THE PENIS
681
The internal pudendal vein [v. pudenda interna] (fig. 536) begins at tlie termination of the
deep veins of the penis [w. profundae penis] which issue from the corijus coavernosum penis with
the artery of that body. Tliese veins communicate with the dorsal vein at the root of the penis
In its course the internal pudendal vein runs with the internal pudendal artery, receiving
tributaries corresponding to the branches of that vessel. It. terminates in the lower part of the
hypogastric vein.
Fig. 536. — The Veins of the Pelvis, Male. (After Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Abdominal aorta
Ascending lumbar vein
External iliac artery and vein
Ductus deferens
Inferior gluteal vein
Internal pudendal artery and vein
Vems from pudendal plexus
Obturator fascia
Crus of the perns
L of the penis
Corpus cavernosun
Deep artery of penis
The dorsal vein of the penis [v. dorsalis penis] (fig. 536) begins in a plexus around the corona
glandis, then runs along the centre of the dorsum of the penis between the two dorsal arteries.
In this course it receives large tributaries from the interior of the organ, which, emerging for
the_ most part between the corpus cavernosum lu-ethrai and corpus cavernosum penis, wind
obliquely over the lateral surface of the latter structure to the dorsum of the penis to end in the
dorsal vein. At the root of the penis the dorsal vein communicates with the subcutaneous veins
of the dorsum of the penis and, leaving the arteries, passes straight backward between the two
layers of the fundiform (suspensory) ligament. It then goes between the subpubic linament
682
THE BLOOD-VASCULAR SYSTEM
and the upper part of the fascia of the urogenital diaphragm (fig. 542). Here it bifurcates,
each branch passing backward and downward to the pudendal plexus of veins. At times the
dorsal vein begins as two branches, which run between the dorsal arteries and only unite to form
a single trunk about 3.7 cm. (Ij in.) from the symphysis. After dividing into a right and a
left branch within the pelvis, each vessel generally communicates with the obturator vein by a
branch passing over the back of the pubis to the obturator foramen.
Fig. 537. — The SuBcrrTANEOus Arteries and Veins op the Anterior Body Wall.
(After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
venous net of the neck
Anterior jugular vein
Edge of superficial cervical fascia
Superficial cervical artery and vein
Cephalic vein opening into the deep
vein of neck (variation)
Subcutane
Arch of the jugular vein
Pectoral venous rete
Mammillary venous plexus
Connections with th
internal mammar
veins and with tht
perforating branches
of the internal mam-
mary arteries
Connections with the su-
perior epigastric veins
and chief branches of
the superior epigastric
arteries
Venous rete of the
umbilicus
Connections with the infer-
ior epigastric veins and>^.
the chief branches of the
inferior epigastric ar-
teries
Superficial epigastn
artery and veins
Superficial
iUac artery and vem
Superficial subingxii-
nal lymph-nodes
Subcutaneous dor^
sal vein of thi
penis
The pudendal plexus [plexus pudendalis] surrounds the prostate and the neck and fundus
of the bladder. It receives in front the right and left divisions of the dorsal veins of the penis,
and communicates with the posterior scrotal veins [vv. scrotales posteriores] and with the hasmor-
rhoidal plexus. The prostatic veins and the vesical plexus open into it, and it also communi-
cates with the internal pudendal vein. The veins forming the plexus are of large size, especially
in old men, in whom they often become varicose, and contain phleboliths, or vein-stones
VEINS OF THE LOWER EXTREMITY 683
The plexus is surrounded by a kind of capsule formed by the superior fascia of the pelvic
diaphragm. It terminates in a single stem on each side which opens into the hypogastric
vein.
In the female the smaller pudendal plexus surrounds the urethra and receives the dorsal
and deep veins of the clitoris [vv. dorsales et profunda clitoridis], veins from the vestibule, and
the posterior labial veins [w. labiales posteriores]. It communicates freely with the utero-
vaginal plexus and is drained by the hypogastric veins.
The vesical plexus [plexus vesicalis] surrounds the apex, the sides, and the anterior and
posterior surfaces of the bladder. It is situated between the muscular coat and the peritoneum,
and where the bladder is uncovered by peritoneum external to the muscular coat in the pelvic
cellular tissue. It opens into the pudendal plexus.
The utero-vaginal plexus [plexus uterovaginalis] connects with the haemorrhoidal, vesical,
and uterine plexuses. Its lower part drains thi'ough the internal pudendal veins and the
pudendal plexus, and its upper protion largely through the ovarian veins, and partly through
the uterine veins [vv. uterinae] to the hypogastric (fig. 530).
The hEemorrhoidal plexus [plexus haemorrhoidalis] surrounds the rectum, and is situated at
the lower part of that tube. It consists of two portions, one of which, the internal haemor-
rhoidal plexus, is situated between the muscular and mucous coats, while the other, the external
hsemorrhoidal plexus, rests upon the outer sui-face of the muscular coat. The veins of this
latter plexus terminate in the inferior, middle, and superior hsemorrhoidal veins. The inferior
[w. hiemorrhoidales inferiores] join the internal pudendal; the middle [v. haemorrhoidalis
media] accompanies the middle hsemorrhoidal artery and opens into the hypogastric and
superior haemorrhoidal veins; the superior (p. 678) forms the commencement of the inferior
mesenteric vein, and through this the blood gains the portal vein. None of these veins have
any valves, hence the enlargement of the inferior htcmorrhoidal veins, when the portal vein is
obstructed, as in cirrhosis of the liver. Through the haemorrhoidal veins a free communication
is established between the systemic and portal system of veins.
THE EXTERNAL ILIAC VEIN
The external iliac vein [v. iliaca externa] (fig. 536), is the upward continuation
of the femoral. Beginning at the lower border of the inguinal ligament, it
accompanies the external iliac artery medially upward along the brim of the mi-
nor pelvis, lying at first on the superior ramus of the pubis, and then on the psoas
major muscle. It terminates by joining the hypogastric vein behind the hypo-
gastric artery, opposite the lower border of the sacro-iliac articulation, to form
the common iliac vein. It lies at first medial to the external iliac artery, and on
the left side remains medial to the artery throughout its course. On the right
side, however, as it ascends, it gradually gets behind the artery. It contains one or
two valves.
In addition to the femoral, the external iliac receives the inferior epigastric
vein [v. epigastrica inferior] (fig. 536) and the deep circumflex iliac vein [v. cir-
cumflexa ilium profunda] (fig. 541), which accompany the arteries of the same
name.
THE SUPERFICIAL VEINS OF THE ABDOMINAL WALL
The plexus of superficial veins of the anterior abdominal wall is continuous
with that of the thorax (fig. 537). Its main channels are the superficial circumflex
ihac, the superficial epigastric, and the external pudendal, all of which open into
the great saphenous vein. These communicate, by means of subcutaneous
abdominal veins, with the superior epigastric vein, and, by means of the thoraco-
epigastric veins, with the lateral thoracic and costo-axillary. The superficial veins
communicate verj' freely with the deeper veins of the abdominal wall, and, by
means of parumbilical veins, they communicate to a slighter extent with the
portal system.
The superficial veins of the lumbar region form an abundant plexus which
drains through the dorsal and lateral perforating branches of the intercostal,
lumbar, and sacral veins.
THE VEINS OF THE LOWER EXTREMITY
The veins of the lower extremity are divided into the superficial and the deep.
The superficial veins lie in the subcutaneous tissue superficial to the deep fascia,
through which they receive numerous communicating branches from the deep
veins. They are collected chiefly into two main trunks, which, beginning on the
foot, extend upward, one, the great saphenous, lying antero-medially, and the
684 THE BLOOD-VASCULAR SYSTEM
other, the small saphenous, postero-laterally. The former finally joins the
femoral vein by passing through the deep fascia at the groin; the latter, the pop-
liteal by perforating the fascia at the ham. The deep veins, on the other hand,
accompany their corresponding arteries. All the veins of the lower limb have
valves which are more numerous than in the veins of the upper extremity and in
the deep than in the superficial veins.
I. THE SUPERFICIAL VEINS OF THE LOWER
EXTREMITY
The superficial veins of the lower limb begin in the plexuses of the foot. The
dorsal digital veins [vv. digitales pedis dorsales] collect blood from the dorsal
surfaces of the toes and unite in pairs, around each cleft, to form the dorsal
metatarsal veins [vv. metatarsese dorsales pedis]. The dorsal metatarsal veins, of
which the first and fifth are larger than the others, join the dorsal venous arch
[arcus venosus dorsalis pedis]. This arch is convex toward the toes and crosses
near the bases of the metatarsal bones. From the medial and lateral ends of the
arch the great and small saphenous veins, respectively, take origin. The area
of the dorsum of the foot contained between the arch and the two saphenous
veins is covered by the dorsal venous rate [rete venosum dorsale pedis] which
extends as high as the ankle-joint (fig. 539).
On the plantar surface the plantar digital veins [w. digitales plantares]
return the venous blood to the clefts of the toes and unite to form the common
digital veins [vv. digitales communes pedis]. The common digital veins join
freely with one another on the sole to form the plantar venous rete [rete venosum
plantare]. There are numerous communications between the superficial veins
of the dorsum and sole. These occur both in the clefts of the toes, by means of
the intercapitular veins [vv. intercapitulares], and around the margins of the
foot. Communications between the superficial and deep veins of the foot are
very free (fig. 540).
The great (or internal) saphenous vein [v. saphena magna] (fig. 538) com-
mences as the medial end of the dorsal venous arch, and, after receiving
branches from the sole which join it by turning over the medial border of the
foot, passes upward in front of the medial malleolus, and then obliquely up-
ward and backward about a finger's breadth from the posterior border of the
tibia in company with the saphenous nerve, which becomes superficial just be-
low the knee. Continuing its course upward, it passes behind the medial epi-
condyle, and then runs upward on the medial side of the front of the thigh to
about 3.7 cm. (li in.) below the inguinal Hgament, where it dips through the fossa
ovalis (saphenous opening) in the fascia lata, and ends in the femoral vein.
Tributaries. — In its course up the leg and thigh it receives numerous unnamed cutaneous
tributaries. As it passes up the thigh it often receives a large vein, the femoro-popliteal which
communicates with the small saphenous, and several of the cutaneous veins on the lateral part of
the thigh, and a second vein, the accessory saphenous [v. saphena accessorial, formed by the
union of the cutaneous veins from the medial and back part of the thigh (fig. 538). The great
saphenous vein contains from ten to twenty valves.
Immediately before entering the fossa ovalis the great saphenous vein receives the super-
ficial epigastric, superficial circumflex iliac, and external pudendal veins, though any of these
veins — or all of them — may pierce the fascia separately and enter the femoral vein.
The superficial epigastric vein [v. epigastrica superficialis] anastomoses with the superficial
abdominal, and parumbUical veins.
The superficial circumflex iliac vein [v. circumflex ilium superficiahs] anastomoses with the
thoraco-epigastric and the superficial circumflex iliac veins.
The external pudendal veins [vv. pudenda^ externaj] collect venous blood from the anterior
scrotal or labial veins, which anastomose with the posterior scrotal or labial veins, and from the
subcutaneous veins of the dorsum of the penis [vv. dorsales penis subcutanese].
The small saphenous vein [v. saphena parva] (fig. 539) begins at the lateral end
of the venous arch on the dorsum of the foot. After receiving branches from the
sole, which turn over the lateral border of the foot, it passes behind the lateral
malleolus, and then upward and, lying at first along the lateral side of the tendo
Achillis, afterward along the back of the calf, in company with the sural (short
saphenous) nerve, to about the lower part of the centre of the popliteal space,
where it perforates the deep fascia, and, sinking between the two heads of the
gastrocnemius, opens into the popliteal vein.
SUPERFICIAL VEINS OF THE LOWER LIMB
685
Tributaries.^As it passes up the calf between the superficial and deep fascia, it receives
numerous cutaneous veins from the heel, and the lateral side and back part of the leg, and
Fig. 538. — The Superficial Veins and Lymphatics of the Left Lower Limb.
(Walsham.)
Superficial epigastric vein
Lymphatics from penis and
scrotum
Femoral vein
Superficial femoral lymphatic
glands
External pudendal vein
Superficial lymphatics from
lateral wall of abdomen
Superficial lymphatics from
lower and anterior walls
of abdomen
Accessory saphenous vein.
Great saphenous vein'
Femoro-popliteal vein,
Medial malleolus'
Dorsal venous arch
Superficial inguinal lym-
phatic glands
Superficial circumflex
iliac vein
communicates at intervals, through transverse or intermuscular branches, with the deep veins
accompanying the peroneal artery. Just before perforating the deep fascia, it receives a large
descending branch, the vena femoropoplitea, from the lower and back part of the thigh. This
686 THE BLOOD-VASCULAR SYSTEM
communicates with a plexus of veins upon the posterior and lateral regions of the thigh and
with the great saphenous. In many cases the small saphenous vein is entirely drained, by means
of the femoro-popliteal, into the great saphenous. Under these circumstances the usual place
of termination of the small saphenous is marked by a small vein opening into the popliteal. A
small offshoot from the inferior sural branch of the popliteal artery accompanies this vein for a
Fig. 539. — The Veins op the Dorsum op the Foot. (After Toldt, "Atlas of Human Anat-
omy," Rebman, London and New York.)
Great saphenous vein
Anterior tibial muscle
Dorsal pedal artery and vein
Extensor hallucis longus tendon
Dorsal venous arch
Dorsal digital vein -
Anterior tibial artery
i=— Anterior tibial veins
^ Dorsal venous rete of foot
^Dorsal metatarsal arteries
-Dorsal metatarsal vein
Intercapitular veins
short distance down the back of the calf. The small saphenous vein contains from nine to
twelve valves.
II. THE DEEP VEINS OF THE LOWER EXTREMITY
The deep veins of the lower extremity accompany the arteries, and have
received corresponding names. From the foot to the knee there are two veins to
each artery. These veins run on either side of the corresponding artery, and com-
DEEP VEINS OF THE LOWER LIMB
687
municate at frequent intervals with each other across it. They are known as the
venae comitantes. From the knee upward there is a single main vein to each
artery, except at the back of the thigh and in the gluteal region, where there are
commonly two.
Fig. 540.-
-The Veins op the Sole of the Foot. (After Toldt, "Atlas of Human Anatom}','
Rebman, London and New York.)
Intercapitular veins
Posterior tibial veins
7 /
Posterior tibial muscle— -| t
Posterior tibial artery
Great saphenous vein —
Flexor digitorum ^^
longus tendon ^^V ^
- Plantar digital ^
.-i- Plantar venous arch
Lateral plantar artery
and accompanying
veins
Deep branch of the
medial plantar and
veins
Venous rete of the heel
Small saphenous vein
The veins of the foot and leg. — The deep veins of the foot become separated
from the superficial where the plantar metatarsal veins [vv. metatarsese plantares]
leave the plantar digital and intercapitular veins to accompany the plantar meta-
tarsal arteries. The plantar metataisal veins empty into the plantar venous arch
[arcus venosus plantaris] which accompanies the arterial plantar arch in the depth
of the sole. (fig. 540)
THE BLOOD-VASCULAR SYSTEM
The posterior tibial veins [vv. tibiales posteriores] drain the plantar venous
arch and the superficial rete (fig 542).
They follow the posterior tibial artery up the leg, receiving tributaries corresponding to
its branches, the largest of which are the peroneal veins [vv. peronefe]. They unite with the
anterior tibial vense comitantes at the lower border of the popliteus muscle.
The anterior tibial veins [vv. tibiales anteriores] begin in the dorsal venous rete
and accompany the anterior tibial artery up the leg receiving tributaries cor-
responding to branches of the artery.
Fig. 541. — The Femoral Vein. (After Toldt, "Atlas of Human Anatomy," Rebman, London
and New York.)
Deep circumflex iliac artery and v
Inferior epi-
gastric ar-
tery and vein
Fundiform ligament of penis
Vastus
medialis
Second per-
forating
artery
and
Adductor
longus
Tunica vaginalis
propria testis
Deep femoral artery and vein
They pass backward between the interosseous membrane and the tibia and fibula to unite
with the posterior tibial veins. The posterior and anterior tibial veins unite at the lower
border of the popliteus muscle to form the popliteal vein.
All these veins contain numerous valves, and communicate, by means of intermuscular
branches, with the superficial veins.
The popliteal vein [v. poplitea] (fig. 542), is formed by the confluence of the
venae comitantes of the anterior and posterior tibial arteries at the lower border
of the popliteus, and extends upward to the opening in the adductor magnus at
the junction of the middle and lower third of the thigh, where it changes its name
to femoral.
TEE POPLITEAL VEIN
It accompanies the popliteal artery, lying superficial to it in the whole of its course, and
tightly bound down to it by its fascial sheath. At the lower part of the space it is a little medial
to the artery, but, crossing the vessel obliquely as it ascends, lies a little lateral to it at the
upper part of the space. The tibial (internal popliteal) nerve lies superficial to the vein,
being lateral to it above, then posterior to it, and then a little to its medial side. The popliteal
vein contains two or three valves.
Fig. 542. — The Deep Veins of the Leg. (After Toldt, *' Atlas of Human Anatomy," Rebman.
London and New York.)
Semimenibraaosus .^
Semitendinosus
Popliteal artery
Medial sural artery and veins
Popliteal veins <->_-
Gastrocnemius (medial head)
Deep layer of the crural fascia -
Flexor digitorum longus
Posterior tibial artery and veins
Flexor hallucis longu:
- Popliteal vein
Lateral sural artery and veins
al artery and
Flexor digitorum longus -.
Posterior tibial
Posterior medial malleolar artery
Medial calcanean branches——-
Venous rete of the heel —
_ Peroneal artery and
Flexor hallucis longus
Posterior lateral malleolar artery and veins
Lateral calcanean branches and veins
The popliteal receives the small saphenous vein. It is also joined on its lateral and medial
sides by the accessory popliteal veins [vv. popliteoe accessorise] which form common trunks of
termination of the sural and articular veins of the respective sides. The medial vein receives
in addition, through a plexus extending as high as the opening in the adductor magnus, the veins
accompanying the a. genu suprema.
690 THE BLOOD-VASCULAR SYSTEM
The femoral vein [v. femoralis], the continuation of the popliteal upward,
extends from the tendinous opening in the adductor magnus to the inguinal
ligament. In this course its relations are similar to those of the femoral artery.
As the vein passes through the adductor canal, it lies behind and a little lateral
to the artery. At the apex of the femoral trigone (Scarpa's triangle) it is still
posterior to the artery, but gradually passes to the medial side as it ascends
through the trigone (fig. 541).
In the neighbourhood of the inguinal hgament the femoral vein hes on the same plane as
the artery from which it is separated by a delicate prolongation of the fascia stretching be-
tween the front and back layers of the femoral sheath. On the medial side the vein is sepa-
rated by a similar septum from the femoral canal. The femoral vein contains five pairs of
valves.
Tributaries. — The femoral vein receives (in addition to the great saphenous
vein, and, in some cases the superficial veins of the epigastrium and groin) the
profunda veins and a variable number of small femoral vense comitantes.
The profunda femoris veins [vv. profunda femoris) arise from the vense comitantes corre-
sponding to branches of the profunda femoris artery. The medial and lateral circumflex veins
[w. circumflex femoris mediales et laterales] collect blood from the muscles of the adductor
and lateral rotator regions. The perforating veins anastomose with femoro-popliteal and other
veins of the posterior femoral region, and with the circumflex and accessory popUteal veins.
They return blood from the femur and the adductor, hamstring and vasti muscles.
The venae comitantes, much smaller than the main femoral vein, accompany the femoral
artery on either side. They anastomose with one another, with the femoral, and often with the
popliteal vein. They terminate in the femoral a short distance above the profunda veins.
MORPHOGENESIS AND VARIATIONS OF THE VEINS
The veins of the adult human body tend to accompany the arteries; this tendency is more
pronounced in the trunk, neck, and extremities than in the cranium. Developmental history
shows that the primitive distribution of the veins of the trunk resembles that of the arteries
of the same region in its bilateral symmetry only. Also that the changes which modify the
primitive bilateral symmetry of the chief veins are not only more extensive but of a different
nature from those producing a similar effect upon the arteries. In both cases the main body-
vessels begin as a pan- of main longitudinal trunks and end as a main unpaired channel (or
channels in the case of the venous system) situated near the median plane of the body. In
the ease of the venous system the change results from wholesale destruction of the vessels on
the left of the body accompanied by enlargement of those upon the right. In the arterial
system destruction occurs to a much more limited extent; the definitive channel results mainly
from blending of the two primitive aortse.
The main venous channels of the cranium and extremities are primitively superficial;
in the cranium they remain so. In the extremities new veins are formed which follow the main
arteries; to these the more primitive channels become tributary.
The heart, as soon as it assumes the simple tubular form is found to receive four veins.
These, the two vitelline and two umbilical veins, enter the sinus venosus, a vitelline and an
umbilical vein on either side. The umbilical veins are lateral to the vitellines, and are paired
within the body only; they arise from the placenta, and traverse the belly-stalk as a single
trunk. The vitelline veins return blood from the yolk sac, and, at first, are independent
throughout.
At a later period two other pairs of veins arise for the venous drainage of the embryonic
body. They are the pre- and post-cardinals which drain the cephalic and caudal regions
respectively. The right pre-cardinal vein unites with the right post-cardinal to form the right
common cardinal (duct of Cuvier). The latter runs in a medial direction to join the sinus
venosus lateral to the right umbilical. On the left side the arrangement matches that on the
right to produce a primitively symmetrical pattern.
During development changes are brought about in the primitive veins which end in the
production of the adult venous system as follows: the common and pre-cardinals, together
with the subclavian veins and the cephalic ends of the post-cardinals, are transformed into the
vena cava superior and its larger tributaries. The remainder of the post-cardinal system is
instrumental in the production of the vena cava inferior and its tributaries. FinaUy the
intra-embryonic portions of the vitelline and umbilical veins participate in the formation of the
portal and hepatic systems of veins together with the proximal end of the vena cava inferior.
The following brief account of morphogenesis and variations is divided into three headings
(1) vena cava superior and its tributaries; (2) vena cava inferior and its tributaries, and (3)
the portal system.
A. THE VENA CAVA SUPERIOR AND ITS TRIBUTARIES
1. MORPHOGENESIS
The pre-cardinal veins at first return blood from the head only, but as the heart recedes
into the thorax the cardinal veins migrate with it. In so doing the common cardinals lag
somewhat behind and in consequence their direction, primitively transverse, approaches the Ion-
THE VENA CAVA SUPERIOR
691
gitudinal. The pre-cardinals, which have increased in relative length, now course symmet-
rically along the neck into the thorax. At a stage of 16 mm., the definitive subclavian vein has
migrated from the common to the pre-cardinal, which henceforth receives the main ven-
ous flow from the upper extremity as well as from the head. The symmetrical arrangement of
the cardinal veins is disturbed at a stage of about 18 mm., by the development of a transverse
connection between the right and left pre-cardinals (fig. 544). This connection, the left in-
nominate vein, arises, probably, by the development of cross-anastomoses uniting the lateral
veins draining the developing thymus and thyreoid glands. On the right side of the embryo
the veins of the adult are now recognisable as follows: — the vein (pre- and common cardinal)
extending from the left innominate to the heart becomes the vena cava superior. The pre-
cardinal, from the left innominate to the subclavian, becomes the right innominate. From
the subclavian to the cranium it becomes the internal jugular.
The vessel of the left side corresponding to the vena cava superior now rapidly diminishes
in size. It extends from the left innominate vein (the extreme left end of which corresponds in
its method of formation to the entire right innominate) to the right atrium. In so doing it
passes ventral to the aortic arch and the foot of the left lung, dorsal to the left artium, and
through part of the coronary sulcus.
Fig. 543. — Semidiagrammatic Reconstructions of the Cranial Venous System. (Mall.)
A, 4 Weeks; B, 5th Week; C, Beginning op 3rd Month; D, An Older Fcetus.
A.c.v; pre-cardinal vein; A.V., otic vesicle; Inf. Pet., inferior petrosal sinus; L., eye; O.V., superior
ophthalmic vein; S.L.S., superior sagittal sinus; S.P.S. sphenoparietal sinus; S.R., sinus
rectus; S.S., middle cerebral vein; T.H., confluens sinuum; V., semilunar ganglion; V.C.A.,
v. cerebralis anterior; V.J., internal jugular vein; V.C.L., v. capitis lateralis; V.O.M. or
sup. pet., v. cerebralis media and superior petrosal sinus; V.C.P. or L.S., v. cerebralis pos-
terior and transverse sinus.
The segmental veins draining the second, third and fourth intercostal spaces of the left side
open, by a common stem formed by the left pre-cardinal, into the left innominate. The cor-
responding segmental veins of the right side open, by a common stem, into the vena azygos. The
collecting stem, on either side, is the vena intercostais suprema. The method of origin of the
azygos, hemiazygos and accessory hemiazygos veins is treated with the inferior caval system.
Below the superior intercostal tributary, the left superior cava is lost to within a short distance
of the sinus venosus. Here its lower end persists as the oblique vein of the left atrium and the
left end of the coronary sinus. The former course of the left superior cava is often indicated in
the adult by a small fibrous cord, uniting the extremities of the persisting veins and passing
through the ligamentum v. cavoe sinistrae (p. 523).
Within the cranium the pre-cardinal veins are primitively in close contact with the brain
and medial to the semilunar, acustico-facial, glossopharyngeal and vagus ganglia. The portion
of each vein extending from the semilunar ganglion to the facial canal (its exit from the cranium)
early becomes involved in a process of anastomosis-migration which eventually places it lateral
to the ganglia and to the otocyst. The new vein formed in the latter situation is called the vena
capitis laterahs (fig. 543). The portion of the pre-cardinal vein which remains medial to the
semilunar ganglion persists as the adult cavernous sinus and receives a primitive vein (v. cerebralis
anterior) which drains the orbit and the mid- and forebrain. The forebrain tributaries of
692
THE BLOOD-VASCULAR SYSTEM
the right and left v. cerebralis anterior unite to from a median vein, the definitive superior
sagittal sinus, wliicli at first drains into the cavernous sinus. There are two other primitive
cerebral veins; the v. cerebralis media and v. cerebralis posterior. The first receives blood
from the cerebellar region and drains into the cavernous sinus. The second, the v. cerebralis
posterior, also receives blood from the hind-brain and, leaving the skull through the jugular fora-
men, joins the pre-cardinal (internal jugular) vein m the neck. Several changes occur from
now on (fig. 543) which bring about the definitive relations of the dural sinuses and transfer
the main venous exit from the stylomastoid to the jugular foramen. The right v. cerebralis
posterior joins the superior sagittal sinus and this becomes the right transverse sinus. The
left V. cerebralis posterior communicates with the junction of the superior sagittal and right
transverse sinuses (now the confluens sinuum) and becomes the left transverse sinus. The
confluens receives the sinus rectus, which forms its adult connections with the inferior petrosal
sinus and great cerebral vein. The v. cerebralis media joins the transverse sinus to become the
superior petrosal sinus. The latter forms a new (intracranial) means of drainage for the caver-
nous sinus and its tributaries. The original drainage channel of the cavernous sinus (v.
capitis lateralis), having been supplanted, disappears. The superior cerebral veins drain into
the superior sagittal sinus. The remaining portion of the interrupted v. cerebrah's anterior
drains the middle cerebral vein and spheno-parielal sinus. The inferior petrosal sinus arises
de novo.
In the upper extremity the venous drainage is at first superficial and opens into the post-
cardinal and umbilical veins. The ulnar limb of the loop-like early venous channel (marginal
vein) becomes the primitive ulnar vein, but does not open into the pre-cardinal until a stage later
than that of 10 millimetres. The primitive ulnar forms the basilic, part of the brachial, the
axillary, and subclavian veins. It receives the large thoraco-epigastric trunk. The cephalic
vein, which at first joins the external jugular, is of secondary formation. The venoe comitantes
are formed later still.
2. VARIATIONS
The great veins of the thorax may present variations from the normal as a result of absence
of the left innominate vein. In this case there are two superior cavse, not necessarily of equal
size, each of which receives an internal jugular and subclavian vein. Persistence of the left
Fig. 544. — The Transformation of the Postcardinal System of Veins, C representing
THE Adult. The Wolffian Body is Dotted. (Lewis.)
a.c, precardinal; as. 1., ascending lumbar; az., azygos; c, caudal; c.h., common hepatic;
c. il., common iliac; C.S., coronary sinus; d.C, common cardinal; g., spermatic or ovarian; h.,
hepatic; h.-az., hemiazygos; h.-az. ac, accessory hemiazygos (here draining into the intercostalis
suprema); i. j., internal jugular; l.c.i., left common iliac; 1. in., left innominate; m.s., middle
sacral; p.c, posterior cardinal; r., renal; r.a., renal anastomosis; r.c.i., right common iliac;
r. in., right innominate; s., suprarenal; s-c, subcardinal; s-cl., subclavian; s.l., sinusoids;
v.c.i., vena cava inferior; v.c.s., vena cava superior.
^i JL
vena cava superior without failure of the left innominate may occur in three classes of cases:
(a) In which both cavse are present, equal in size or asymmetrical, (b) In which the left cava
only occurs, associated with situs inversus, (c) In which the left cava only is present, without
situs inversus. The left vena cava superior, when present, crosses in front of the aortic arch and
THE VENA CAVA INFERIOR 693
enters the right atrium by way of the coronary sinus, collecting the coronary veins. Cases are •
on record of a left superior cava terminating in the left atrium.
The azygos weins.^Variations of these veins and of the intercostal veins have been dealt
with on pp. 663-664. For their morphogenesis, see under vena cava inferior.
The veins of the neck, face, and scalp. — These veins have so many variations in detail that
it is difficult, in the case of some veins, to assign their normal distribution. The external
jugular, for instance, is usually described in Enghsh text-books as a tributary of the subclavian
vein; it is assigned by the BNA to the internal jugular. It is frequently found to open into the
angle between the two, or, forming a plexus with its tributaries, drain into both. The origin
of the external jugular vein is also exceedingly variable. The external jugular may be small,
or absent, in which case the anterior jugular is large. The reverse may be the case since the
external jugular frequently receives the posterior, and sometimes the common facial. Fortu-
nately venous variations are not of prime surgical importance.
Veins of the cranium. — The venous sinuses of the dura mater are not subject to important
variations. Variations in the relative size of the transverse simises have been referred to on
p. 651. The petrosquamous sinus, occasionally present, is described on p. 653. The occipital
and inferior sagittal sinuses are frequently absent.
The cerebral veins are liable to great variation in detail: the great cerebral vein may be absent,
as a single trunk, in which case the internal cerebral veins open directly into the sinus rectus.
The middle cerebral vein may open into the sphenoparietal, or superior petrosal sinus or into the
basilar plexus.
Veins of the upper extremity. — The subclavian vein is occasionally posterior to the artery,
or spUts to enclose the latter and the anterior scalenus. Either case represents a partial re-
tention of the early condition in which the vein passes behind the brachial plexus. Variations
in the superficial veins have been referred to on p. 668. The question of the most common
distribution of these vessels has lately been fully reviewed by Berry and Newton. The cephalic
vein occasionally opens into the external jugular by persistence of the embryonic jugulo-cephahc
vein.
B. THE VENA CAVA INFERIOR AND ITS TRIBUTARIES
1. MORPHOGENESIS
The right and left post-cardinal veins (fig. 544) are at first symetrical in size and position.
Early in development each posterior cardinal vein becomes involved in the growth of the cor-
responding mesonephros, and the original venous channel is converted into a system of sinusoids.
In the sinusoidal circulation of each mesonephros two main longitudinal venous channels soon
make their appearance. One lies ventro-medial to the mesonephros and is called the sub-cardinal
vein. The other, which lies dorsal to the mesonephros, receives the segmental veins and is
frequently called the post-cardinal. Since the mesonephric segment of the post-cardinal vein
has obviously passed out of existence, the vein in question (unlabelled in fig. 544) wQl be here
distinguished as the dorsal trunk. The sub-cardinals communicate freely between themselves
and with the dorsal trunks, lie ventral to the mesonephric arteries, and are at first symmetrical.
The cephalic end of the right sub-cardinal now acquires a communication with the common
hepatic vein, thus providing a new means of drainage for the sub- and post-cardinal systems
(fig. 544) . The rapidly enlarging main venous channel resulting from this alternative niethod of
drainage follows the right dorsal trunk as far as the level of the permanent renal veins. It is
then transferred, by means to an anastomosing channel, to the right sub-cardinal and, through
this, to the common hepatic vein; it becomes the vena cava inferior. From now on the portions
of the sub-cardinal veins not participating in the formation of the cava dwindle rapidly. A
cross anastomosis between the right and left sub-cardinals persists as the portion of the adult
left renal vein which crosses ventral to the aorta. By means of it the remainder of the left
renal; thfe left internal spermatic and left suprarenal veins are connected with the vena cava.
The left lumbar and left common ihac veins are also transferred to the vena cava, probably by
direct anastomosis with the left post-cardinal vein. The vena cava inferior is at first lateral
to the right ureter, its transference to the medial side occurs through anastomosis.
The portion of the right posterior cardinal vein above the mesonephric region, together with
its continuation into the dorsal trunk, becomes the azygos vein (fig. 544). The corresponding
vessel upon the left side is transformed into the accessory hemiazygos and hemiazygos veins.
The hemiazygos vein is drained into the azygos by means of an anastomosing channel which
may also drain the accessory hemiazygos. The variability of the means of drainage of the
accessory hemiazygos vein, by means of anastomosing channels, is referred to onp. 663. The
ascending lumbar veins are anastomosing channels of new formation.
In the lower extremity, as in the upper, the original superficial plexus is gradually drained
by a loop-Uke marginal vein. The fibular limb of this loop, the primitive fibular vein, becomes
small saphenous; it follows the sciatic nerve and opens into the post-cardinal. The next vein to
be developed is the great saphenous; the small saphenous is transferred to this by an anastomos-
ing vein which is usually present in the adult — the femoropopliteal vein. The deep veins are
of later formation. The drainage of the small saphenous is usually taken over by the popliteal
vein.
2. VARIATIONS
In determining the probable embryonic cause of variations of the vena cava inferior the
possibility of abnormal persistence of the sub-cardinal veins must be remembered. The posi-
tion of transverse anastomoses with regard to the aorta is often the key to diagnosis. Instruc-
694
THE BLOOD-VASCULAR SYSTEM
tive cases of abnormalities of the vena cava inferior have recently been pubhshed by v. Alten
and by Neubei-ger (see References). Both articles contain bibUographies. The chief varia-
tions are as follows: —
(1) The inferior vena cava, in cases of transposition of the viscera, may he on the left side
of the aorta. (2) Without transposition it may also lie to the left of the aorta, crossing to the
right to gain the caval opening immediately below the diaphragm, or after receiving the left
renal vein. (3) It may be double, the left cava than usually passing across the aorta into the
right after receiving the left renal vein. A communication between the right and left veins in
the position of the normal left common iliac vein may or may not then exist. (4) The inferior
vena cava may be absent, the blood from the lower extremities passing by a large vein in the
position of the ascending lumbar and azygos veins through the diaphragm to open into the
superior vena cava. The hepatic veins then open directly into the right atrium through the
normal caval opening in the diaphragm. (5) The inferior vena cava may receive the left sper-
matic vein. (6) It may receive a left accessory renal vein passing behind the aorta, and into
this the usual tributaries of the left renal vein may open. (7) It may receive several accessory
renal veins; as many as seven on each side have been met with. (8) The lumbar veius may
enter it on one or both sides as a common trunk.
The variations in the veins of the lower extremity are for the most part unimportant.
They have been mentioned in the description of the corresponding veins.
3. THE PORTAL SYSTEM OF VEINS
The portal system arises by transformations in the vitelline and umbilical veins. The
proximal ends of the vitelline veins, where they lie between the umbilicals, are early enveloped
in, and invaded by, the growing liver. The columns of liver cells, while not penetrating the
endothelium, subject the vitelline veins to a process of fenestration by which the original channels
are subdivided into innumerable smaller vessels or sinusoids. The sinusoids arising from the
two vitelline veins intercommunicate to form one continuous network in which the vessels are
larger in the afferent (portal) and efferent (hepatic) areas than in the intermediate zone.
Fig. 545. — Sbmidiagrammatic Reconstructions of the Veins of the Liver, Ventral
Aspect (Mall). A, Embryo of 4.5 mm. Long; B, 4 mm. (more advanced than A); C, 7 mm.
d.v., ductus venosus; I., intestine; L., liver; m., superior mesenteric (continued as portal)
vein; r.a., ramus angularis; r. a'., right branch of portal vein; r.h.d., right hepatic vein;
r.h.s., left hepatic vein; r.u., recessus umbilicahs; u.v., left umbilical vein (the right
umbihcal vein is not labelled); v.o.m., vitelline veins.
The two umbilical veins now form communications with the portal area of the sinusoidal
network and eventually lose their original connections with the sinus venosus (fig. 545). The
fate of the umbilical veins differs on the two sides; the right degenerates, from the sinus venosus
to the common umbilical vein, and leaves the left to receive all the blood flowing from the pla-
centa. The left, having lost its connection with the sinus venosus, discharges its blood partly
into the portal sinusoidal zone, and partly, by means of the newly formed direct channel, the
ductus venosus, into the right vitelline (fig. 545).
The hepatic end of the right vitelline vein enlarges considerably, for the left vitelline loses
its original connection with the sinus venosus. It transmits blood both from the sinusoids
and from the ductus venosus to the sinus venosus, and is called the common hepatic.
The vitelline veins are not only connected within the liver, but their distal ends become
united upon the yolk-stalk to form a single trunk. A third communication between them is
effected by a transverse vessel passing dorsal to the duodenum. The portion of the right
vitelline below the transverse vessel disappears, as does the portion of the left between it and
the liver. A tortuous vitelline vein is thus produced which enters the liver by passing dorsal
to the intestine from left to right. This vessel is joined, to the left of the intestine, by the
superior mesenteric vein and, dorsal to it, by the splenic. When the portion of the vitelline
below the termination of the superior mesenteric finally disappears the vessel extending from
the splenic vein to the liver becomes the portal vein of the adult.
Important variations of the portal system are rarely found in the adult. The mechanism
of anomalies found in the embryo have been investigated by Begg (Anier. Jour. Anat., Vol. 13).
THE FCETAL CIRCULATION
695
FGETAL CIRCULATION
The changes which accompany the transformation of the foetal type of
circulation into that of the adult are initiated by the first inspiration. Prior. to
this act the functions of external respiration and digestion are performed by the
Fig. 546.^The Heart, with the Arch op the Aorta, the Pulmonary Artery, the
Ductus Arteriosus, and the Vessels concerned in the Fcetal Circulation.
(From a preparation of a fcetua in the Museum of St. Bartholomew's Hospital.)
Right innominate vein
Superior vena cava
Right pulmonary artery
Inferior vena
Left branch of portal vein
Ductus venosus
Arch of aorta
Ductus arteriosus
Left pulmonary
artery
Descending aorta
Umbilical vein
Portal vein
Right branch of,
portal vein
Umbilical
Umbilical arteries
Umbilical -artery
mesenteric vein
Inferior
senteric artery
eft common iliac
artery
Hypogastric artery
External iliac artery
mother; the foetal venous blood passing to the placenta through the umbilical
arteries and returning through the umbilical vein.
At the time of birth the right and left chambers of the heart communicate
only by means of an oblique passage between the overlapping atrial septa (p. 511) .
The pulmonary artery and descending aorta communicate by means of the
ductus arteriosus (p. 508).
696 THE BLOOD-VASCULAR SYSTEM
Arterial blood, transmitted from the placenta through the umbilical vein,
passes almost entirely by way of the ductus venosus to the vena cava inferior.
From here it passes through the right atrium; then, obliquely between the atrial
septa into the left atrium, from which it passes through the left ventricle and
into the ascending aorta. Escaping largely through the branches of the aortic
arch, it is distributed to the head and upper extremities, and returned to the vena
cava superior. Having reached the right atrium it passes, to the right of the
stream from the vena cava inferior fp. 513), through the atrio-ventricular ostium
into the right ventricle. The blood issuing from the right ventricle into the
pulmonary artery goes almost entirely (the lungs being functionless) into the
ductus arteriosus and so into the descending aorta. Having performed two
circuits, the blood returns to the placenta through the umbilical branches of the.
hypogastric arteries.
The two streams, arterial and semi-venous, cross one another in the right
atrium. The degree of intermixture, if any, which occurs in this cavity has been
the subject of much discussion; for literature and experimental evidence on this
point see Pohlmann, A. (Johns Hopkins Hosp. Bui., Vol. 18, 1907.)
When the lungs assume their function at birth the pressure in the left atrium
is suddenly raised by an inrush of blood. The overlapping atrial septa (primum
and secundum) are brought into lateral apposition and thus the blood entering
the right atrium finds but one exit — the atrio-ventricular ostium. Since the
vessels of the expanded lungs now transmit a greatly increased volume of blood,
the stream passing through the ductus venosus is diminished proportionately.
The blood traversing the aortic arch, released from the check exerted by the lateral
stream pouring from the ductus arteriosus, passes more readily into the descending
aorta; thus the adult equilibrium is established.
References for blood-vascular system. — A. Heart: (Development) Born,
Archiv f. mikr. Anat., Bd. 33, 1889; His, Anatomie menschl. Embryonen,
1880-85, Anatomie des menschl. Herzens, 1886; Tandler, in Keibel and Mall's
Human Embryology. (Morphology) MacCallum, Johns Hopkins Hospital
Reports, vol. 9, 1900; Mall, Amer. Jour. Anat., vol. 11, 1911, vol. 13, 1912;
(Atrio-ventricular bundle) Keith and Flack, Jour. Anat. and Physiol., vol. 41, 1907.
B. Arteries. (Development) Evans, in Keibel and Mall's Human Embryology;
(Pulmonary) Bremer, Anat. Rec, vol. 3, 1908; (Internal mammary) Mall, Johns
Hopkins Hospital Bui., 1898; (Cephalic) Tandler, Morph. Jahrb., Bd. 30, 1902;
(C celiac) Tandler, Anat. Hefte, Bd. 25, 1904; (Extremities) Miiller, Anat. Hefte,
Bd. 22, 1903; de Vriese, Arch, de Biol., T. 18, 1902; (Variations) Goppert,
Morph. Jahrb., Bd. 40, 1909; C. Veins. (Development) Davis, Amer. Jour.
Anat., vol. 10, 1910; (Brain) Mall, Amer. Jour. Anat., vol. 4, 1904; (Liver) Mall,
Amer. Jour. Anat., vol. 5, 1905; (Cervical) Lewis, F. T., Amer. Jour. Anat., vol.
9, 1909; (Upper extremity) Berry and Newton, Anat. Anz., Bd. 33, 1908; (Vena
cava inferior) Neuberger, Anat. Anz., Bd. 43, 1913; v. Alten (ibid): (Sinusoids)
Minot, Proc. Boston Soc. Nat. Hist., vol. 29, 1900.
S E C T 1 O N V [
THE LYMPHATIC SYSTEM
Revised for the Fifth Edition
By ELIOT R. CLARK, A.B., M.D.
ASSOCIATE IN ANATOMY, JOHNS HOPKINS MEDICAL SCHOOL
I. GENERAL ANATOMY OF THE LYMPHATIC SYSTEM
THE blood-vascular system has, as a part of its function, the collection of
substances from the various tissues of the body which are to be conducted
to the other tissues. In carrying on this function it is assisted by a second
system of collecting vessels, the lymphatics.
This second system resembles the blood-vascular system in many ways, but differs markedly
in others. Like the tslood-vascular system, it is made up of minute endothehal-Uned capillaries,
where the absorption of substances occurs, and of larger conducting vessels. It differs from the
blood-vascular system' in two important particulars. While the blood-vascular system is pro-
vided with a pumping'mechanism by which its fluid content is driven through a complete circuit
from the heart, through artery, capillary, vein and back to the heart, the lymphatics merely
conduct fluid from, the capillaries to the larger vessels, which eventually empty their contents
into the large veins of the neck. The second important difference between the two systems is
found in the presence, along the course of the lymphatic vessels, of glands or nodes (fig. 553)
[lymphoglandulee] in which the vessels branch out into lymph capillaries. These are lined, as are
the absorbing capillaries, with a single layer of endothehal cells, thus permitting an interchange
of substances between the contents of the lymph capillaries and the lymphoid tissue around
them.
Our present knowledge does not permit an exact statement of the complete extent of the
lymphatic system. While, in a general way, the lymphatics may be said to be present where-
ever blood-capillaries occur, there are certain tissues where lymphatics have not been definitely
demonstrated.
The general constitution of the lymphatic system will be considered under
three heads — (1) the capillaries, (2) the collecting vessels and (3) the lymphoid
organs.
I. THE LYMPHATIC CAPILLARIES
The lymphatic capillary, like the blood-capillary, is the portion of the lymph-
atic system which is chiefly concerned in the specific function of this system. In
the blood-capillaries, where the blood is separated from the outside tissues by a
single layer of flat endothehal cells, there occurs the interchange of fluid substances
and of cells, while the heart, arteries and veins serve to transport the blood, modi-
fied in the capillaries, to other parts of the body. Similarly in the lymphatic
system, it is in the capillaries, both those most peripheral and those in the lymph
nodes, where the absorption and interchange of fluid substances and of cells takes
place. Consequently it becomes of prime importance to obtain a clear under-
standing of the structure of the lymphatic capillaries, their relation to the other
tissues, and their mode of functioning. At the outset, however, it must be
admitted that our knowledge on this subject is far from complete.
Historical. — Previous to the development of microscopic anatomy, in the middle third of the
19th century, there was no accm-ate knowledge of such small structures as the lymphatic capil-
lary. In order to explain the absorption of substances by the lymphatics, as well as the passage
of substances from the blood-vessels through the tissues, various theories were invented. Promi-
nent among such theories was that of the "vasa serosa," of H. Boerhaave and other 18th century
anatomists and physiologists, which was perhaps most elaborately developed by Bichat, 1801-03.
According to this theory there are two sets of minute vessels, too small for the passage of cellu-
lar elements. The one set leads from the blood-capillaries onto the various surfaces of the body
and into the loose spaces in the tissues — the "exhalants. " The other set leads from the body
surfaces (including the serous cavities) and the loose spaces in the tissues to the lymphatics —
the "inhalants" or " absorbants, " which take in fluids by a sucking action.
697
698 THE LYMPHATIC SYSTEM
This theory was somewhat shaken by the discovery of Magendie, in the first decade of the
19th century, that absorption may take place by the veins, as well as the lymphatics, and by the
criticism of early 19th centmy anatomists who developed the teohnio of injection of lymphatics
to a high point.
Our present conception of the lymphatic capilJaries may be said to have started with
KoUiker who, in 1846, saw, with the aid of the microscope, the lymphatic capillaries in the trans-
parent tails of living frog larvae. He found them to be definite structures made up of a thin
wall, from which projected fine-pointed processes, and in which were nuclei. Like Schwann
who, in 1837, had studied the blood-capillaries in the tail of the frog larva, he erroneously sup-
posed that the fine processes of the lymphatic capillaries were continuous with similar proc-
esses of the surrounding connective-tissue cells. Since, according to the conception current at
the time, cells were thought to be hollow structures, with a membranous wall and fluid content,
it was concluded that the mode of transmission of fluid from blood to lymphatic capillary took
place through canaliculi inside these cells. This conception was elaborated by Virchow, in his
CeUular-Pathologie.
In 1862 von Recklinghausen by means of the silver nitrate staining method discovered that
the lymphatic vessels are lined with an endothelium made up of flattened cells whose outlines
show as fine dark Knes after this treatment. Again, however, as a result of the eagerness to find
open passages through the tissues from blood to lymphatic capillary, an erroneous interpretation
was made, von Recklinghausen held that the unstained parts outside the lymph vessels rep-
resent a system ofj irregularly shaped lymph-canaliculi ("Saftkanalchen") which are in open
communication on the one hand with the blood-capiUaries, and on the other with the lymphatics
This conclusion has since been disproved by numerous investigators.
In a second series of observations, von Recklinghausen brought evidence in favor of open
communications between the lymphatics and the peritoneal cavity. He watched, under the
microscope, the passage into lymphatics, through minute openings, of milk, placed on a portion of
the central tendon of the diaphragm. These minute openings he termed "stomata. " Cohn-
heim described similar though smaller openings in blood-capillaries, and His described them in
other lymphatic capillaries. Arnold termed the openings in the vessels "stigmata," as dis-
tinguished from the openings into the peritoneal cavity, or "stomata."
With the advent into microscopical technic of the various dyes for staining cell-nuclei and
protoplasm, and the more precise methods for making histological studies, the endothelial wall
of the lymphatic capillary has been definitely established, although much remains to be learned
concerning the differences between the lymphatics of the various tissues.
Moreover, recent investigators have failed to find open connections between the lumen of
the lymphatic vessel and the tissue outside. Kolossow failed to find the "stomata" of von
Recklinghausen and the "stigmata" of Cohnheim, His and Arnold. The "stomata" have been
carefully studied by a number of other recent investigators. All agree in finding a complete
endothelial lining for the lymphatic capillaries lying underneath the peritoneum and pleura,
with no openings or "stomata." Careful studies of the lymphatic capillaries in the transparent
tails of living frog larvae, which may be clearly seen with the higher magnifications of the micro-
scope, show that the endothelial lining of these capillaries is complete, with no trace of an open-
ing into the spaces in the tissue outside (E. R. Clark).
Form. — The shape of the lymphatic capillaries has been found to vary enormously in the
different parts of the body, where they have been studied. In general they form richly anas-
tomosing plexuses, from which may extend cul-de-sacs, which end bUndly. Such cul-de-sacs
are especially noticeable in the dermal papillae, in the filiform papillse of the tongue, and in the
intestmal villi. The plexuses are often present in two layers — a superficial and a deep. The
vessels of the superficial plexus are of smaller calibre than those of the deep. These two sets
of plexuses are particularly well seen in the skin and the gastro-intestinal tract. In relation
to the blood-capiUaries, the lymphatic capillaries are generally the more deeply placed.
In cahbre, unlike the comparatively uniform diameter of blood-capillaries, the lymphatics
vary enormously. In the same capillary a very narrow part may be succeeded by a very wide
one (figs. 547, 548). Teichmann found lymphatic capillaries varying in diameter from a few
thousandths of a millimetre to one millimetre. In the capsule of the spleen of the cow some meas-
ured more than 1.5 mm.! The capillaries are without valves.
Activity. — That the lymphatic endothelium is not exclusively a passive membrane has been
shown by Clark in studies on the lymphatics in the transparent tails of living frog larvae. The
lymphatics here are seen to send out protoplasmic processes which, somewhat like an amoeba,
actively take into the interior of the lymphatic red blood-cells accidentally forced from the
blood-capiUaries into the tissue-spaces.
The mode of passage of leucocytes into or out of the lymphatics offers no such difiiculties
as that of the fluids, for they are able, through their power of amoeboid movement, to pass
independently through the endothelium — a process first directly observed by Cohnheim.
1. The Extent and Chabacter of Lymphatic Capillaries
The skin over the entire surface of the body is richly provided with lymphatic capiUariea.
They form two sets of plexuses in the dermis, a superficial and a deep. The superficial set sends
out bhnd cul-de-sacs into the dermal papillae. The richest skin plexuses are found in the
scrotum, the palms of the hand and palmar side of the fingers and in the soles of the feet and
plantar side of the toes. In the loose subcutaneous fascia, according to Teichmann, there are
present only the larger collecting vessels, with no lymphatic capillaries. Lymphatic capillaries
of the scrotum are shown in Fig. 547.
The conjuntiva, both the sclerotic and corneal, is supplied with a rich plexus of capillaries,
which are narrower in the corneal than in the sclerotic portion. At the corneal border the
LYMPHATIC CAPILLARIES 699
capillaries form a fairly regular ring which has been called by Teichmann a ciroulus lymphaticus.
At the various orifices of the body, the skin plexuses go over into the mucous plexuses,
forming anastomoses with them. Tiiroughout the entire alimentary tract, including the nasal
cavities, the lymphatic capillaries form extensive plexuses which are in many places divided
into a superficial plexus in the mucosa and a deeper plexus in the submucosa. In portions pro-
vided with a peritoneal covering, there is a third rich subserous plexus. In the tongue and the
small intestine the plexus in the mucosa sends out blind cul-de-sacs; in the tongue into the
filiform papilla?; in the small intestine into the villi. Where muscle is present along the ali-
mentary tract, the lymphatics pass between the muscle bundles, but form no plexuses around
them.
The lining of the tracheal and bronchial passages is supplied with a double plexus of lym-
phatic capillaries, a mucous and a submucous set, which vary in richness according to the loose-
ness of the tissue. In the smaller bronchi but a single layer of capillaries is present, and, ac-
cording to Miller, no capillaries are present around the air cells. Plexuses surround the pul-
FiG. 547. — The Lymphatics of the Scrotum. (After Teichmann.) Showing the transition
of the capillaries to the vessels with valves (o, a, a).
monary arteries and veins. Under the pleura lie rich plexuses which connect with the deeper
lymphatics around the veins only in places where the veins reach the surface of the lung.
Concerning the arrangement of the lymphatic capillaries in the glands derived from the
alimentary tract much remains to be learned.
The salivary glands have been recently studied anew by Aagaard, who has found lymphatic
capillaries accompanying the blood-vessels into the interior of the lobules, and forming here
irregular plexuses.
The thyreoid gland contains lymphatic plexuses which lie in relation to the colloid-con-
taining alveoli. Direct connection between the lymphatics and the alveoli has lately been
described by Matzunaga, but this observation needs verification. The lymphatics are apparently
concerned in the absorption of the colloidal secretion, for traces of it have been found in the
lymphatics draining the gland.
Concerning the lymphatics of the parathyreoids nothing is known.
The course of the lymphatics draining the thymus has been recently described, but the
nature of the capillaries in this gland is unknown.
The lymphatic capillaries of the liver are of great importance, for the lymph which flows
from this organ forms a very considerable part of the total lymph which is collected into the
thoracic duct. And yet very little is definitely knowm about the natm'e and distribution of the
lymphatic capillaries in the interior of the organ. In the capsule there is a rich plexus, lying
under the peritoneum, in which very large widenings have been described (called bj^ Teichmann
"Lymphbehalter"). In the interior rich plexuses surround the branches of the hepatic artery
and portal vein (fig. 549), and plexuses have been described accompanying the branches of the
portal vein into the lobules.
The linings of the large bile-ducts and the gall-bladder are provided with a submucous network
of lymphatics (Sudler and Clermont). The gall-bladder has also a rich subserous plexus.
Concerning the lymphatic capillaries of the pancreas Bartels notes briefly that they form
richly branched plexuses in the interlobular connective tissues, which surround larger or smaller
parts of whole lobules, not the single gland elements.
The mucous lining of the genito-urinary tract, wherever- it has been carefully studied
700
THE LYMPHATIC SYSTEM
has been found provided with plexuses of lymphatics. In the bladder they form a rich plexus of
irregular capillaries which lie immediately under the almost intraepithelial blood-capiUaries.
They connect, through the muscular layer, with a subserous plexus. The lymphatic plexus of the
urethra anastomoses \vith the capillaries of the base of the bladder, and in the male with those of
the glans penis. The lymphatic capillaries of the ductus deferens and of the seminal vesicles have
not been studied. In the prostate (Camineti) the lymphatics form rich plexuses surrounding the
glands, which connect with a very wide meshed subcapsular plexus, surrounding the entire
gland.
In the testis there is a rich superficial plexus, lying directly beneath the tunica albuginea.
Concerning the deep lymphatics of the testis there has been much dispute. Ludwig and Thomsa
Fig. 548. — Surface View and Section of Lymph-nodes op the Intestine. A. Solitary
folhcle. B. Pej'er's patch. (After Teiohmann.)
found the lymphatic capillaries going over into lacunse, without endothelium. This has been
disputed by Tommasi and Gerster, who find, in the septa, capillaries with endothelial wall,
which they consider the beginnings of the lymphatics.
In the female, lymphatic plexuses have been found in the mucosa of vagina and hymen,
anastomosing with those of the vulva. In the uterus, capillaries in the mucosa are very difficult
to demonstrate. Definite lymphatics, however, have been found passing through the mus-
cularis, and under the peritoneum a rich subserous plexus of capillaries is present. In the preg-
nant uterus these subserous capillaries are much distended (Schick). The Fallopian tubes are
provided v?itb lymphatics, but they have not been carefully described.
LYMPHATIC CAPILLARIES
701
The ovary has a rich superficial lymphatic plexus. In the iaterior of the gland, according
to His, the capUlaries form networks in the connective- tissue framework. In the tunica externa
of the follicles there is a rich plexus.
The kidney has two sets of lymphatics, a superficial, capsular set, and a deep set. The cap-
sular set is divided into two layers, one lying directly beneath the peritoneum made up of a wide
meshed plexus, and the other in the fibrous capsule of the kidney, with finer capillaries and
narrower meshes, which anastomose with the deeper capillaries. The lymphatic capillaries of
the kidney parenchyma have recently been described by Kumita. He found rich plexuses in
both cortex and medulla, surrounding the straight and convoluted tubules, the loops of Henle
and the collecting tubules. He also found a plexus surrounding and accompanying the blood-
vessels into the interior of the glomeruli.
The lymphatic capillaries of the adrenal have also been described recently by Kumita.
His results agree with those of Stilling, who studied the lymphatics of the adrenal of horse, cow
and calf. Like the kidney, the adrenal possesses a superficial and a deep set. The superficial set
Fig. 549. — ^Lymphatic Plexus ahound the PortaljVein in"' an Adult Man. (After Teich-
mann.) Showing the supporting relation of the vein.
is in two layers, as in the kidney, the outer lying in the looser tissue around the adrenal and the
inner lying within and just under the capsule. The latter is made up of a rich lymphatic plexus,
which anastomoses with the capillaries of the parenchyma. The parenchymatous lymphatics
are present in the form of plexuses which surround the groups of cells.
In spite of numerous investigations, endothelial-lined lymphatics have not been definitely
found in the central nervous system, or in the peripheral nerves. The subarachnoid and similar
spaces, including the perineural spaces, do not form parts of the lymphatic system.
Rich plexuses of lymphatic capillaries are present in the tendons of muscles (Schweigger-
Seidel and Ludwig). In muscles, themselves, the question of the presence of lymphatics has
long been disputed, sometimes answered in the affirmative, more often in the negative. A re-
cent study by Aagaard, however, would seem to place beyond doubt the presence of lymphatic
capillaries in striated muscles. By long continued injection, he was able to find Ij'mphatics in the
intramuscular portions of the tendons, which extended out among the muscle fibres themselves.
He also found capillaries in the tongue musculature.
The heart is provided with a subpericardial plexus of lymphatic capillaries. A subendocardial
plexus has also been described (Sappey, Rainer). Bock has recently found that there is an ex-
tremely rich lymphatic network throughout the substance of the heart. According to his de-
scription, the lymphatic capillaries are more numerous than the blood-capillaries.
*~, kThe periosteum of bones is provided with a rich plexus of lymphatic capillaries. They are
present in 'several layers, of which the outermost form the richest plexus. Lymphatic capillaries
702 THE LYMPHATIC SYSTEM
have also been described accompanying the blood-vessels in the Haversian canals in bones
(Rauber, Schwalbe, Budge). Nothing is known concerning the lymphatics of the bone marrow.
Cartilage lacks both blood and lymphatic capillaries.
The capsular membranes of joints are richly provided with lymphatic capillaries (Tillmanns) .
They are arranged in two layers — an inner layer made up of a rich plexus of wide capillaries,
lying just outside the subendothelial blood-capillaries, and an outer layer, consisting of a rich
plexus in the subsynovial tissue. The lymphatic capillaries have no open connection with the
joint cavity.
The membranes suiTounding the pleural, pericardial and peritoneal cavities are richly sup-
plied with lymphatic capillaries, which form here thick plexuses outside the endotheUum. These
plexuses are usually described with the underlying organ, as the subserous lymphatic capillaries
of the intestine, etc. In the central tendon of the diaphragm the subperitoneal lymphatics are
extremely rich. They widen out here to form very large endotheUal-lined cavities which, in the
spaces between the connective-tissue bundles, lie directly in contact with the peritoneal
epithelium. The existence of open connections between these capillaries and the peritoneal and
pleural surfaces (the "stomata" of von Recklinghausen) has recently been disproven. The
capillaries on the two surfaces of the central tendon communicate freely with one another.
2. THE LYMPHATIC VESSELS
The lymph which enters the lymphatic capillaries passes over into collecting
vessels (ducts), which carry it through the lymph-glands (nodes) to the large veins
at the base of the neck. The lymph-vessels course in the loose subcutaneous
tissues, in the connective tissues between muscles and organs, often accompanying
the arteries and veins, sometimes forming networks around them. An idea of
their arrangement can be best obtained by glancing at the illustrations of the
lymphatics of special regions. In general they are made up of numerous long,
narrow vessels, rarely more than half or three-fourths of a millimetre in diameter,
which occasionally communicate with one another, and which radiate toward
groups of lymph-glands placed in certain definite regions. In the lymph-glands
the afferent lymph-vessels break up into capillaries, which again collect into
efferent vessels. Several of these efferents from each lymph-gland may pass to a
second lymph-gland, where they undergo a second widening into capillaries. In
this way the lymph, passing through one, two, three or more lymph-nodes in
succession, eventually reaches the thoracic duct, or one of the short ducts, all of
which empty into the large veins at the base of the neck. The thoracic duct,
which receives, at its lower end, the lymph from the lower half of the body, is the
only lymphatic vessel which attains any considerable size (four to six millimetres
in diameter) and is usually the only one large enough to be seen readily without
injection.
In structure the lymphatic vessels much resemble the veins. They possess an intima, a
media and an adventitia, although the line of demarcation between the different layers is not
sharp. In the thoracic duct, the endothelium of the intima is succeeded by a delicate layer of
fibres, mainly elastic; outside of this is the media, made up mainly of circular smooth muscle-
cells, interspersed with elastic and connective-tissue fibres; then follows a layer of coarse elastic
and connective-tissue fibres, which is succeeded by the adventitia, containing longitudinal and
transverse bundles of smooth muscle-ceUs, as well as blood-vessels and nerves. The other lym-
phatic vessels possess the three layers, which, however, toward the capillaries, grow thinner, and
eventually reach a stage in which, outside the endothehum, there are found only single musole-
ceUs, or muscle-ceUs in groups of two or three.
The lymphatic vessels are characterised by their great richness in valves, which are present
throughout their entire course, from their beginnings in the capillary region to their openings
into the veins of the neck. The valves are bi- or tri-cuspid, and are always arranged so as to
prevent the flow of lymph back to the capillaries. They thus aid indirectly in the movement of
the lymph, in that any external pressure on the vessels must always force the lymph onward.
Nerves of lymphatic vessels. — That the thoracic duct and the smaller lymphatic vessels are
provided with nerves has been shown by several observers. According to Kytmanoff (in dogs)
the nerves to the lymphatics are mainly non-medullated, and are both motor and sensory
They form four sets of plexuses — adventitial, supramuscular, intermuscular and subendotheUal.
Sensory nerve-endings (fig. 550) are found in adventitia and media, in the form of free-ending
threads, and bush-like endings. Motor endings are present in connection with the smooth
muscle cells of the media. In the intima there is a plexus of extremely fine varicose threads.
The physiological action of the nerves supplying the receptaculum chyli has been tested by
Camus and Gley who found in dogs a dilatation of the receptaculum as the result of electrical
stimulation of the splanchnic nerve.
Movement of the lymph. — It has been estimated (Ludwig) that the amount of lymph which
passes through the lymphatic ducts of a dog aggregates, during the twenty-four hours, one-third
the body-weight. In the thoracic duct the lymph is under a sufficient pressure to burst the duct
behind a ligature. In the absence of any especial propulsive organ, such as the heart for the
blood-circulation, what are the forces which move the lymph? There must be recognised pri-
mary and accessory forces. As accessory forces there are the movement of the muscles and the
LYMPHATIC VESSELS
703
general pressure of the organs on the lymph-ducts. Since these are provided with valves, all
preventing the lymph from flowing backward, any such pressure causes the lymph to move on-
ward. As accessory agents must also be reckoned the smooth muscle and elastic tissue which is
present in the walls of the lymph-vessels and in the lymph-gland. That these forces, however,
are not primary is shown by numerous facts. There is an active circulation in the lymphatics of
Fig. 650. — A. The Adventitial and SuPKA-MusctrLAR Nerve Plexuses, together with
Sensory Endings in the Thoracic Duct of a Dog. (Methylene-blue method.) B.
Nerve-fibres on the Endothelium op a Lymphatic Capillary of a Dog. (After
Kytmanoff.)
U^:^^^^ ^^^'\r^i*.I^ ~'^"'*J^
iXiatmrft'^-:^:
^■S53*K*^?.>S5„W^'^-
^
■/'
embryos long before valves develop. In many lower animals no valves develop save at the
entrance of the lymphatics to the veins. That neither valves nor muscular movements are es-
sential is shown by the fact that, in the tails of frog larvae, where no valves are present and
where the muscle movements have been completely paralysed by an anesthetic, the circular-
tion of lymph continues unchecked.
The primary cause, therefore, for the movement of lymph is to be sought in the capillary
region, in the force produced by the passage of lymph through the endothelial wall, whether this
704
THE LYMPHATIC SYSTEM
process be a filtration and diffusion — -in which case the causes would he in the pressure and mo-
lecular condition of the tissue fluid outside the lymphatic — or whether it be an active secretion
by the endothelium — in which case the driving force would be this secretory power of the
endothelium.
3. THE LYMPHOID ORGANS
Closely associated with the lymphatic capillaries and vessels is a group of
glandular structures known as lymphoid organs. They consist, essentially, of
groups of round lymphoid cells, lying in a meshwork of reticulum fibres, and hav-
ing often a definite relationship to the blood or lymph vessels.
The group of lymphoid organs includes, in addition to the lymph-glands
[lymphoglandulse] or lymph-nodes, which are particularly related to the lymphatic
vessels, the spleen, thymus and bone-marrow, which are also largely made up of
lymphoid tissue. The spleen and thymus, however, are considered separately
with the Ductless Glands.
Fig. 551.
-Diagram op a Ltmph-nodb. (After Toldt, "Atlas of Human Anatomy, "Rebman,
London and New York.)
Capsule
Medullary cords
Deep lymph vessels
Anastomosis between afiferent and efferent vessel
-^ Superficial
y lymph-paths
In their most simple form, the lymphoid organs form mere irregular accumulations or patches
of lymphoid cells, whioh^iave been termed lymphoid infiltrations. Such patches are frequent
in mucous membranes especially along the intestinal tract (fig. 549) and the air-passages in the
lungs.
Larger accumulations of lymphoid cells produce definite round nodules, which may occur
singly, as solitary follicles or in groups, as aggregated follicles (Peyer's patches) (fig. 548). In the
sohtary foLhcle the lymphoid ceSs are arranged concentrically, with a region in the centre where
the cells are less closely packed together. This is called the germinal centre, and contains
numerous cells undergoing mitotic division. The sohtary folhole contains blood-capiUaries.
Lymph-capiUaries, however, do not enter the follicle but form a rich plexus about it.
The lymph-glands or nodes (fig. 551) are larger lymphoid structures, which are developed
along the course of the lymph-vessels. They vary much in size, shape, and colour, and may occur
singly or in small or large groups. The size varies from the size of a pin-head to that of an oUve,
or larger. In skape'they may be spherical, oval, or flattened on one or more sides, according to
their relations to other organs. Each gland has an indentation or hilus, where the arteries
enter, and where the veins and efferent ducts emerge. Their colour depends upon position and
state of function. The glands along the respiratory tract are black, due to the presence of car-
bon granules. The mesenteric glands are milk-white during digestion, and other nodes are pale
and translucent when their sinuses are filled with fluid, and pink or even red when red-blood
LYMPHOID ORGANS
705
cells are present in the sinuses. The lymph-gland is made up of four distinct elements : lymphoid
elements, lymphatic capillaries, supporting structures, and blood-vessels.
The lymphoid elements (fiji. .551) are arranged as follicles and as cell-strings. The follicles
lie around the circumference of the gland, and form the cortex [substantia corticalis]. The cell-
strings or meduUary cords are irregular cords of cells which extend from the follicles through the
central or medullary portion [substantia medullaris] of the gland. The follicles and medullary
cords are made up, as are the solitary follicles, of round lymphoid cells.
Fig. 552.-
-SuRFACE View and Section op a Lymph-node showing the Peripheral and Cen-
tral, Sinuses. (After Teichmann.)
The lymphatic vessels (tig. 551) enter the lymph-gland as several vasa afferentia, and leave
it, at the hilus, as the vasa efferentia. The vasa afferentia spread out in the cortical portion
of the gland into an extremely rich plexus of wide capillaries which surround the follicles,
forming the peripheral sinus. The capillaries do not enter the follicle. This plexus continues,
around the foUicles, into the medullary portion where it forms again a rich plexus, the medullary
sinus, in the spaces around the meduUary cords (fig. 552). At the hilus the medullary capil-
laries collect into larger vessels and emerge as the vasa efferentia.
The supporting structures consist of a fibrous capsule surrounding the gland, from which
trabecula3 or septa pass in, around and between the foUicles and cords. From the septa, a
fine reticulum passes into the foUicles and cords, where it forms a rich dense meshwork, in the
interstices of which lie the Ij'mphoid cells. The capsule and trabeculse are made up of white
fibres, elastic fibres and smooth muscle-fibres.
i
706 THE LYMPHATIC SYSTEM
The blood-vessels, which enter and leave at the hilus, send branches into the follicles and
into ihe meduUary cords.
The enormous widening of the lymph-stream in the lymph-node from the vasa afferentia
to the capillaries — like a brook widening out into a pond — causes a very great diminution in
the rate of flow of the lymph. Thus there is present in the gland a very slowly moving stream
of lymph, which is separated from the lymphoid tissue outside by a single layer of flattened
endotheh'al cells. There is thus possible an easy interchange of substances, and an opportunity
for the passage, through the endothelium, of wandering cells. While the entire mode of func-
tioning of the lymph-gland is not clear, it is known that lymphocytes, formed here, enter the
lymph-stream, and that substances such as, for instance, carbon granules, or leucocytes laden
with bacteria, are checked in their course by the lymph-gland.
Arrangement. — The lymph-glands are so arranged throughout the body that
all the lymph which enters the lymphatic capillaries must pass through one or
more lymph-glands on its way to the veins.
It is possible that this rule may have exceptions, although none have yet been definitely
proved. Thus, some of the small lymphatics which join the thoracic duct may enter it without
having passed through a gland. Moreover, there is often found (fig. 551) a direct anastomosis
between an afferent and an efferent lymphatic vessel.
Most of the glands are collected in certain regions, where they form centers
toward which the lymphatic vessels radiate. Such groups are termed regional
glands. The glands forming such a group are connected with one another by
numerous anastomoses, which are termed lymphatic plexuses [plexus lymphatici].
In addition to the regional glands there are many isolated glands which lie along the
course of the lymph-vessels, and through which pass the vessels draining a much
more limited capillary area. Such glands are termed intercalated glands.
4. THE DEVELOPMENT OF THE LYMPHATIC SYSTEM
Our knowledge of the lymphatic system has been very greatly increased during the past
ten years by studies on its mode of development. Previous to 1902 nothing definite was known
about the primary development or the mode of growth of the lymphatic system. It was
concluded by some (Budge, GuUard and Saxer) that the lymphatics arise from undifferentiated
mesenchyme cells; Ranvier believed that they arise from veins by budding of the endothelium;
while Sala described them as arising partly from the mesenchyme and partly from venous
endothelium.
Regarding the mode of growth and spreading of the lymphatics, various theories were like-
wise held. Kolliker, His, Goethe and, later, Sala held that growth takes place by the suc-
cessive addition of mesenchyme cells; Langer, Rouget, and Ranvier maintained that growth
takes place by sprouting of the endothelium (fig. 553). S. Mayer thought that new lymphatics
are derived from transformed blood-capillaries.
Miss Sabin in 1902 gave the first clear picture of the mode of origin and growth of the
lymphatic system, and our present knowledge is largely based upon her discoveries. She
showed by injections of embryo pigs that the lymphatics of the skin appear first in four regions
of the body — two on each side at the base of the neck, and two in the inguinal region — in the
form of sacs which are connected with the veins. From these four regions the lymphatics
spread out step by step over the skin of the entire body, in the form of a richly anastomosing
capillary plexus. Since the publication of Miss Sabin's paper, numerous studies have been
made on the mode of development of lymphatics in many different animals, including man.
The results of these studies indicate that the lymphatic endothelium first appears in the form
of buddings-out from the veins in certain well-defined regions of the embryo. As to the exact
manner of this primary origin views differ. Miss Sabin, in her first paper, held that it arises
by budding from the veins. F. T. Lewis held that it is formed by the transformation of plexuses
of blood-capillaries. This view was accepted by Miss Sabin, and verified by Huntington and
McClure. Stromsten recuiTi'd to Sala's view that the first lymphatic endothehum arises in
part from venous endothelium, and in part from the mesenchyme cells. Hoyer and his pupila
find that the first lymphatics arise as buds from the veins. This has also been found (1912) by
E. R. and E. L. Clark in chick embryos.
Thus far six regions have been found, in which lymphatics develop from the veins — in the
neck, on each side, at the angle formed by the internal jugular and subclavian veins; in the pelvis,
on each side, along the iliac veins; and two unpaired sets in the region of the renal veins, one
ventral to the aorta, the mesenteric, and one dorsal to the aorta, retroperitoneal. In these
six regions the lymphatics soon coalesce to form large sacs, the jugular, iliac, mesenteric and
retroperitoneal. The sacs are later broken up into the primary sets of lymph-nodes. The
receptaculum chyli develops in the region of the retroperitoneal sac.
From these primary anlages derived from the veins the lymphatics spread out into the
various organs and tissues of the body. The cutaneous lymphatics spread out from the two
jugular and two iliac regions (Sabin), the lymphatics of the intestine from the mesenteric sac
(Heuer).
The method by which this extension of the primary lymphatics occurs is still in dispute,
but there seems to be conclusive evidence that it takes place by the sprouting of the endothehum
(fig. 553) ; that the endothehum of the lymphatics, derived from the veins, is a specific, inde-
pendent tissue, and that all new lymphatic endothehum is formed from lymphatic endothehum,
DEVELOPMENT OF THE LYMPHATICS
707
and not from blood-vessels or mesenchyme cells. This view is supported especially by the
work of Sabin, MacCaUum, Hoyer and his pupils and E. R. Clark.
On the other hand, F. T. Lewis has suggested that the spreading of lymphatics occurs
by the transformation of blood-vessels into lymphatics; while Huntington and McClure and
their pupils maintain that it occurs by the continued transformation of mesenchyme cells.
The lymphatics growing from the various primary centres meet and anastomose with
one another, and gradually lose aU connections with the veins save those at the base of the neck
Sylvester has found, however, that in South American monkeys the connections with the veins
in the region of the renal veins are maintained in the adult. Valves do not appear in the lym-
phatic vessels until quite late, in human embryos about 5 or 6 cm. long. (Sabin.)
The lymphatic nodes do not make their appearance until the system of vessels is well
established. They are at first represented by masses of lymphoid tissue in the meshes of a
lymphatic network. Later the lymphoid mass breaks up into smaller portions, into which
the blood-vessels and branches from the surrounding network penetrate; and each mass, together
Fig. 553. — The Speouting of Lymphatic Capillaries in the Pig. (After MacCaUum.)
The lymphatics are injected and the sprouts are both single cells and clumps of cells.
with the portions of the network surrounding it, becomes enclosed in a connective-tissue capsule.
The original lymphoid tissue becomes transformed into the medullary cords and cortical nodules
of the node, while the enclosing lymphatic capillaries form its peripheral lymph-sinus.
The earhest nodes appear in the places occupied by the primary Ij'mphatic plexuses or
sacs (Miss Sabin, F. T. Lewis, JoUy), and have been termed the "primary nodes" (Miss Sabin).
Secondary and tertiary sets of nodes develop later at places of confluence of many Ivmohatics
(cf. A. H. Clark.) • ^ f ^^
Regeneration and new growth of lymphatic vessels and glands. — While blood-vessels
are known to possess throughout life the capacity for regeneration and new growth, this process
in lymph-vessels has been very little studied. Yet enough has been learned from the work of
Coffin and Evans to justify the statement that lymphatic vessels also possess the capacityFfor
new growth. Evans made the interesting observation that lymphatic vessels grow into a tumor
of connective-tissue origin (a round-celled sarcoma), while they fail to grow into a tumor of
epithelial origin (an experimentally-produced peritoneal carcinoma in mice).
708
THE LYMPHATIC SYSTEM
The question as to whether lymph-glands may form anew is not yet entirely settled. The
study of the problem is extremely difficult, because very small lymph-nodes may be normally
present in a csrfcain region, yet they may escape observation untQ they become hypertrophied
under certain conditions. A. W. Meyer in a careful experimental study found no evidence of
new-formation of lymph glands. On the other hand, there is considerable evidence for the new-
formation of lymph-glands under pathological conditions.
The haemolymph nodes. — In addition to the ordinary lymph-nodes, there
occur along the course of certain veins small nodes which are either red or brown
in colour, according to their state of functional activity. These have been termed
haemolymph nodes. The red nodes closely resemble in structure an ordinary
lymph-node, except that the sinuses are filled with blood, while the brown nodes
show not blood, but blood pigment, both free in the sinuses and in the phagocytic
cells of the sinuses. In certain respects these nodes resemble the spleen, there
being a reduction of the medullary cords and an increase in the amount of the
sinuses, which resemble those of the spleen-pulp rather than the more open
lymphatic sinuses; and their trabeculae are also like those of the spleen in having
numerous smooth muscle-cells. Some of these hsemolymph nodes have lymphatic
Fig. 554. — A Developing H^moltmph Node.
Central blood-vessel
vessels, but whether, as in the spleen, these are limited to the capsule, or whether
they open into the blood-sinuses, making true hsemolymph nodes, is not yet clear.
A difficult point in connection with the structure of the hfemolymph nodes is the relation
of the blood-sinuses to the blood-vessels. The greater weight of evidence seems to favour
the view that the sinuses are connected with the veins rather than that the arteries open directly
into them, although one observer fails to find any connection between the blood-vessels and
the central sinus (Schumacher). In fig. 554 is shown a hsemolymph node in the neck of a pig
24.5 cm. long. This stage marks the first appearance of the hsemal node in the neck, and shows
the node in its simplest form, the foUicle and its peripheral blood-sinus (Miss Sabin).
There are wide variations in the distribution and number of the haemolymph nodes; indeed
sufficient observations have not yet been made to determine their complete distribution.
They have been divided into three groups, the prsevertebral, the renal, and the splenic. In
one subject, in which they were very numerous, they occurred at the root of the lung, near the
bronchi, and bronchial vessels, a few near the oesophagus, a continuous praevertebral chain in
the abdomen extending from the diaphragm to the upper two or three sacral vertebra, as well
as a few along the ccefiac axis and its branches, the superior mesenteric, renal, and iliac vessels
(Lewis).
Schumacher, from a study of lymph-glands and haemolymph glands of various stages,
concludes that the haemolymph glands are not to be considered as organs sui generis, but that
they represent rudimentary forms of ordinary lymph-glands, which have lost their connections
with the lymphatic vessels. Further investigations are needed to clear up this subject.
NODES OF THE HEAD AND NECK 709
II. SPECIAL ANATOMY OF THE LYMPHATIC SYSTEM
The lymphatic system will be considered by regions as follows: A, head and
neck; B, upper extremity; C, thorax; D, abdomen and pelvis; E, lower ex-
tremity.
A. THE LYMPHATICS OF THE HEAD AND NECK
The lymphatics of the head and neck may be divided into two sets. One set is
superficial, draining the entire skin sin-face, and has its nodes, for the most part,
in the neck, the principal group lying along the external jugular vein. The other
set is deeper and drains the mucous membrane of the upper part of the digestive
and respiratory tracts, together with the deep organs, such as the thyreoid gland
and the tendons of the muscles. The nodes of this set are deeply placed, being
situated along the carotid arteries, with outlying retro-pharyngeal nodes.
1. THE SUPERFICIAL NODES OF THE HEAD AND NECK
Lymph-nodes appear first in the neck in the process of development. In the
pig the first node to appear develops from the lymph heart, which is in the supra-
clavicular triangle behind the sterno-cleido-mastoid muscle. From here ducts
grow across the muscle and give rise to a chain of nodes along the external jugular
vein. This chain is to be considered as the main chain of superficial nodes in the
neck. From it lymphatic vessels grow over the back of the head, the side of the
head, the face, and the front of the neck, and in their course groups of secondary
nodes develop. The nodes of the main chain are known as the superficial cervical
nodes, and are from four to six in number. The secondary groups are — (1) the
occipital; (2) the posterior auricular; (3) the anterior auricular; (4) the parotid;
(5) the submaxillary, with the facial as a tertiary set, and (6) the submental.
1. The occipital nodes [lymphoglandulse occipitales]. — The lymphatics of the
skin of the back of the head collect into a few trunks that either empty into from
one to three small nodes near the occipital insertion of the semispinalis capitis
muscle, or pass by the secondary group and empty directly into the upper nodes
of the main superficial cervical chain (fig. 555).
2. The posterior auricular nodes [Igl. auriculares posteriores]. — A portion of
the temporal part of the scalp, together with the posterior surface of the ear, except
the lobule, and the posterior surface of the external auditory meatus, drain into
two small nodes on the insertion of the sterno-cleido-mastoid muscle. The effer-
ent vessels of these nodes pass to the upper part of the superficial cervical chain.
3. The anterior auricular nodes [Igl. auriculares anteriores] are few innumber —
from one to three — and are situated immediately in front of the tragus of the ear.
They receive vessels from the anterior surface of the auricle and the external audi-
tory meatus, from the integument of the temporal region and the lateral portion
of the eyelids. Their efferents pass to the parotid and superior deep cervical
nodes.
4. The parotid nodes. — The parotid group of nodes is considerably larger than
the two preceding, containing from ten to sixteen nodes, and the group drains a
more complex area. It receives vessels from the adjacent surface of the external
ear, the external auditory meatus, the skin of the temporal and frontal regions,
and the eyelids and nose. The deeper nodes of this set receive vessels from the
parotid gland.
In the embryo these nodes He in the pathway of the lymph- vessels that grow to the scalp;
many of these vessels, however, pass the parotid group and empty into the superficial cervical
chain. The nodes of the parotid group lie embedded in the substance of the parotid gland,
and their efferents pass to the submaxillary and the superior superficial and deep cervical nodes.
As "inferior auricular nodes" Bartels designates one or two small glands of the parotid
group which lie below the ear, and receive afferent vessels from the lower part of the ear.
5. The submaxillary [Igl. submaxillares] and facial [Igl. faciales profundae]
nodes. — The submaxillary (perhaps better "mandibular") group consists of a
i
710
THE LYMPHATIC SYSTEM
chain of from three to six nodes, resting on the submaxillary (salivary) gland,
along the inferior border of the mandible. They lie usually on the submaxillary
gland, but may extend from the insertion of the anterior belly of the digastric to
Fig. 555. — The Lymphatics of the Head and Neck. (After Toldt, "Atlas of Human
Anatomy " Rebman, London and New York )
Occipital lymph-nodes
Posterior auricular lymph-nodes
Superficial cervical lymph-nodes \
►
Axillary lymph-nodes
.i.„z:^^=^
the angle of the jaw. They are about the size of a pea, and the largest is near the
point where the external maxillary (facial) artery crosses the mandible. The sub-
maxillary nodes, together with the next group, the facial, drain a complex area,
THE FACIAL NODES
711
including not only skin, but mucous membrane. They receive lymph-vessels
from the nose, cheek, upper lip, the external part of the lower lip, together with
almost all those from the gums and teeth and from the anterior third of the lateral
portions of the tongue. In agreement with the fact that these nodes, though lying
superficially and draining the skin, drain also the mucous membrane, their vessels
empty not only into the superficial cervical chain, but also into the deep carotid
chain.
The facial nodes are evidently outlying nodes of the submaxillary group.
They are in two main sets — (1) the supra-maxillary set, which consists of from
one to thirteen nodes, resting on the mandible near the point where it is crossed
by the external maxillary (facial) artery. (2) The buccinator set, lying on the
Fig. 556. — Lymphatics or the Outer Nose and Face. (After Ktittner.)
Submax-
illary
node
line connecting the lower margin of the ear and the angle of the jaw. Of these
latter nodes, some lie near the point where the parotid duct perforates the buc-
cinator muscle; the others are farther forward, between the external maxillary
artery and the anterior facial vein. Additional nodes belonging to the group may
occur near the nose and in the suborbital region. These facial nodes receive affer-
ents from the outer surface of the nose, the lips, eyelids, cheek, temporal part of
the face, the mucosa of the mouth, the teeth of the upper jaw, the gums, the tonsils,
and the parotid gland. Their efferents pass to the submaxillary and parotid
nodes.
6. The submental nodes [Igl. submentales], usually two in number, lie in the
triangle bounded by the anterior bellies of the two digastric muscles and the hyoid
bone (fig. 559). They are usually near the median line, and drain the skin of the
chin, the skin and corresponding mucous membrane of the central part of the lower
712
THE LYMPHATIC SYSTEM
lip and jaw, the floor of the mouth, and the tip of the tongue. The efferent
vessels pass either to the submaxillary nodes or to the deep cervical chain.
2. THE LYMPHATIC VESSELS OF THE FACE
The different parts of the face and their lymphatic relation to these groups of
superficial nodes will now be considered.
The lymphatics of the scalp form a rich network in the neighbourhood of the
vertex, from which vessels pass in various directions. From the frontal region a
Fig 557. — Lymphatic Nodes and Vessels of the Ear, Eyelids, Nose and Lips. New-
born child. P, parotid. M, submaxillary gland. B, buccal fat ("sucking pad"). Supero-
lateral deep cervical lymph nodes are not labelled. (After Bartels.)
Ant. auricular
lymph nodes
Ant. submaxillary /'
lymph nodes
Middle submaxillary/
lymph nodes
Inferior submental lymph nodes (var )
Posterior submaxillary lymph nodes
number of ducts pass downward and backward to the parotid nodes; those from
the parietal and temporal regions pass to the anterior auricular, parotid, and pos-
terior auricular nodes; and those from the occipital region pass partly to the occi-
pital nodes and partly to the superior deep cervical group, while a single large
vessel descends along the posterior border of the sterno-mastoid muscle to ter-
minate in one of the inferior deep cervical nodes.
The lymphatics of the eyelids and conjunctiva. — The capillary plexus of the
eyelids and the conjunctiva is an abundant one, and at the free border of the
eyelids becomes extremely close. The lymphatics from the lateral three-fourths
of the lids pass to the anterior auricular and parotid groups of nodes, while those
from the medial one-fourth pass obliquely across the cheek with the facial vein to
terminate in the facial and submaxillary nodes (figs. 556, 557, 561).
The lymphatics of the nose. — The lymphatics of the nose (fig. 556) form a net-
work which is coarse at the root of the organ, but dense over the alar region.
The vessels run in three sets — (1) one set passing over the eye to the parotid nodes;
(2) a set passing under the eye to the same nodes; and (3) the most important
LYMPH-VESSELS OF THE FACE
713
group, consisting of from six to ten trunlts, passing to the facial and submaxillary
nodes. There are some anastomoses between the capillaries of the skin and those
of the mucous membrane of the nose.
Fig. 558. — The Facial Nodes. (After Buchbinder.)
ll
-Suborbital nodes
"Node of nasogenial fold
- Supra maxillary ]
' Inframaxillary n(
The lymphatics of theUps (fig. 559). — -The capillary plexuses of the skin and
mucous membrane are continuous at the free border of the lips. The vessels of
the upper lip, of which there are about four on each side, pass to the submaxillary
Fig. 559. — The Lymphatics op the Lips. Newborn child.
Dorendorf.)
(From Bartels after
Superior submental
lymph nodes
Ant. submaxillary lymph
Deep cervical lymph node
nodes. From the lower lip the trunks from near the angle of the mouth pass to
the submaxillary nodes, while those from the centre of the lip pass to the
submental nodes.
There are from two to four subcutaneous vessels and from two to three submucous vessels on
either side. The collecting trunks passing to the submaxillary nodes do not anastomose, and
714 THE LYMPHATIC SYSTEM
the same is true of the submucous vessels of the lower lip. The subcutaneous vessels, on the
other hand, passing to the submental nodes, anastomose freely, an important fact in connection
withthe extension of cancer of the lower lip.
The lymphatics of the auricle and external auditory meatus. — The lymphatic
plexus in the auricle, external auditory meatus, and the outer side of the tympanic
membrane is an abundant one. An anastomosis has been described between a
scanty plexus on the inner side of the tympanic membrane and the plexus on the
outside. The collecting vessels pass to three sets of nodes: — (1) those from the
external and internal surface of the auricle and the posterior part of the external
auditory meatus pass to the posterior auricular nodes; (2) those from the lobule,
the helix, a part of the concha and the outer portion of the external auditory mea-
tus pass to the inferior auricular and superficial cervical chain; some of the vessels
from the first and second areas also run to the deep cervical group; (3) an anterior
group from the tragus and part of the external auditory meatus consisting of from
four to six trunks, pass to the anterior auricular nodes, which are connected with
the parotid nodes.
3. THE DEEP LYMPHATIC NODES OF THE HEAD AND NECK
The deep cervical chain is the largest mass of nodes in the neck. It consists
of from fifteen to thirty nodes, which lie along the entire course of the carotid
artery and internal jugular vein. This chain receives vessels from all the super-
ficial nodes, also directly from the skin, as well as from the entire mucous mem-
brane of the respiratory and alimentary tracts in the head and neck. Thus it
drains both the superficial and the deep structures.
For convenience of description this long chain, though usually continuous, is
divided into two groups — (1) a superior group, lying above the level at which the
omo-hyoid muscle crosses the carotid artery, and (2) an inferior or supra-clavicular
group, lying below that level.
(1) The superior deep cervical nodes [Igl. cervicales profundae superiores]. —
This group of nodes extends from the tip of the mastoid process to the level at
which the omo-hyoid muscle crosses the common carotid artery. The dorsal and
smaller nodes of the chain lie on the splenius, levator scapulae, and scalene mus-
cles. They drain the skin of the back part of the head, both indirectly and
directly, and receive (1) efferents from the occipital and posterior auricular nodes,
(2) a large vessel from the skin of the occipital part of the scalp, (3) some trunks
from the auricle, and (4) cutaneous and muscular vessels from the neck.
The ventral nodes of the chain lie on the internal jugular vein. They drain
the face both directly and indirectly, as well as the deeper structures of the head
and neck. They show especially well in fig. 563 in connection with the tongue.
(2) The inferior deep cervical [Igl. cervicales profundse inferiores] or supra-
clavicular nodes lie in the supra-clavicular triangle. In the upper part of the tri-
angle the nodes rest on the splenius, the levator scapulae, and the scalene muscles,
while at the base of the triangle they are related to the subclavian artery and the
nerves of the brachial plexus. They drain a wide area, receiving vessels from the
head, neck, arm, and thoracic wall. They are connected with the superior deep
cervical chain, and receive afferents from the axillary nodes, and, in addition, they
receive vessels directly from the back of the scalp, from the skin of the arm, and
from the pectoral region. Thus it will be seen that a large part of the lymph
of the head and neck, as well as some from the arm and thorax, passes through
these nodes. Their efferents unite to form the jugular trunk, which ends at the
junction of the internal jugular and subclavian veins.
In the descriptions of the deep lymphatic vessels certain additional groups of
nodes will be considered, which may be regarded as outlying groups from the deep
cervical chain.
4. THE DEEP LYMPHATIC VESSELS OF THE HEAD AND NECK
The lymphatics of the brain. — It is now recognised that there are no lymph-
atics in the brain and cord, so that the function of absorption must be accom-
phshed by means of the veins. There is an abundant exudation of lymph around
the nervous system into the subdural space, which is connected with the central
LYMPHATICS OF THE MOUTH
715
canal of the nervous system, and which is to be considered as a zone in which the
tissue-spaces are especially large. Along the arteries of the brain the adventitia is
loose and open, possessing tissue-spaces which have received the confusing name of
perivascular lymphatics. It would be better to name them perivascular tissue-
spaces.
The lymphatics of the eye. — No lymphatic vessels have as yet been discovered
either in the eyeball or in the orbit. In both, however, there are abundant tissue-
spaces, the most noteworthy of the orbit being the interfascial space (space of
Tenon), which communicates by a space between the optic nerve and its sheath
with the subarachnoid spaces of the cranial cavity. In the eyeball the tissue-
spaces are abundant, even if the vitreous and aqueous chamber be omitted from
the category. Numerous spaces exist in the chorioid coat, especially in the lamina
supra-chorioidea, and in the sclerotic, both sets communicating by perivascular
spaces surrounding the venae vorticosae with the interfascial space. In the cornea
there are abundant lacunae, united by their anastomosing canaliculi, to form a
network of lymph-spaces which come into close relation with the conjunctival
lymphatics at the corneal margin.
Fig. 560. — The Deep Ceevical Chain (After Poirier.)
Mastoid node
Internal jugular chain
The conjunctiva, being a portion of the integument, does possess lymphatic
vessels ffig. 562), arranged in a double network whose collecting vessels accompany
those of the eyelids, and terminate with them in the submaxillary, anterior
auricular, and parotid nodes.
The Lymphatics of the Digestive Tract in the Head and Neck
The lymphatics of the gums. — ^The lymphatics from the mucous membrane
of the gums pass to the submaxillary nodes. The capillary plexus is abundant;
the collecting vessels arise from it on the inner surface of the gum, and pass
between the teeth to reach a common semicircular collecting vessel on the outer
surface. Lymphatics have recently been demonstrated in the pulp of the tooth
(Schweitzer).
The lymphatics of the tongue. — -There is a rich lymphatic plexus throughout
the entire extent of the submucosa of the tongue, but that portion lying in the
basal part of the tongue seems to be more or less independent of the rest. Accord-
ing to Aagaard the tongue muscles are provided with lymphatics which are drained
by the ducts of the submucosal plexuses. There are four groups of collecting
vessels — (1) apical; (2) marginal; (3) basal; and (4) central.
(1) The apical vessels are usually four in number, two on each side. One pair perforates
the mylo-hyoid muscle and ends in a supra-hyoid median node, while the other pair pass to
the deep cervical chain. The latter are long, slender vessels, which run along the frenum of
the tongue to the surface of the mylo-hyoid muscle, cross the hj'oid bone just behind the pulley
of the digastric, and then run downward in the neck to a node of the deep cervical chain, just
716
THE LYMPHATIC SYSTEM
above the omo-hyoid. It will be noted in fig. 563 that the most anterior vessels end in the
lowest nodes, while those from the back of the tongue end in higher nodes,
(2) The marginal vessels are from eight to twelve in number. They all pass to the superior
Fig. 561. — Lymphatics of the Head, Neck, and Axilla. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Lymph-vessels of the breasts
deep cervical nodes, a part of them passing external to the sublingual gland, while the larger
number pass internal to it. There is one large and constant node at the point where the digastric
muscle crosses the jugular vein, to which a large number of the vessels converge.
LYMPHATICS OF NASAL CAVITIES
111
(3) The hasal vessels are seven or eight in number, and drain the basal portion of the tongue.
Some end in the large node just mentioned, while others run backward close to the median
line, where they anastomose, as far as the glosso-epiglottidean fold, when they separate and
join the tonsillar vessels to pass outward to the superior deep cervical nodes.
(4) The central vessels, arising from the central portion of the tongue, pass backward in
the median line on the ventral surface of the tongue. They lie upon the mylo-hyoid muscle,
cross the hyoid bone, and end in the superior deep cervical chain.
The lymphatics of the palate. — The lymphatics from the palate pass to the
deep cervical chain. The trunks from the hard palate run in the submucosa as
far as the last molar tooth, where they pass in front of the anterior pillars of the
fauces and end in the superior deep cervical nodes beneath the digastric muscle.
In the soft palate the capillary plexus is very rich, reaching a maximum in the
uvula. From the inferior surface of the soft palate and the pillars of the fauces
vessels pass directly to the superior deep cervical chain, but some of the vessels
Fig. 562. — The Lymphatics of the Conjunctiva. (After Teichmann.)
from the upper surface of the soft palate run forward with the pharyngeal vessels
and end in the retro-pharyngeal nodes. It will be seen from fig. 564 that the retro-
pharyngeal nodes are simply outlying nodes from the deep cervical chain.
The lymphatics of the pharynx. — As has just been stated, there are certain
outlying nodes of the deep cervical chain which lie behind the phaiynx. They
receive some of the ducts from the submucosa of the roof of the pharynx, but many
of the pharyngeal vessels pass by these nodes and end directly in the superior deep
chain. The tonsil is especially rich in lymphatics, and its ducts, together with
those from the middle and inferior portions of the pharynx, end in the superior
deep cervical chain. The lymphatics of the Eustachian tube run to the lateral
retro-pharyngeal lymph-nodes or, passing these, to the deep cervical nodes.
The lymphatics of the nasal cavities. — The mucous membrane of the nose
contains a rich lymphatic plexus whose main ducts pass to the retro-pharyngeal
nodes. An anterior set, however, anastomoses with the subcutaneous vessels,
and through these their lymph is conveyed to the facial and submaxillary nodes.
The posterior vessels run either to the deep cervical chain or to the retro-pharyn-
geal nodes. Key and Retzius have shown that an injection of the Ij^mphatics of
the nose may be made by injecting the subarachnoid spaces at the base of the
718
THE LYMPHATIC SYSTEM
brain, although there is presumably no direct connection between the spaces and
the lymphatic vessels. The lymphatics of the nasal sinuses end in the retro-
pharyngeal nodes.
Fig. 563. — The Lymphatics of the Tongite. (Poirier and Charpy.)
Basal trunks
ir^-
. Marginal collecting trunks
/ with hypoglossal nerve
— Marginal trunk
V>___ ' Submen-
j^y' ^l^ '"" ^ ' tal node
"5^^-^- CoUecting
~ trunks frora
margin of
— tongue
Node inter-
calated in
these ducts
Vessel from margin of
tongue ending in in-
ternal jugular chain
_ ^""Intercalated node
Central vessel passing
to node above the
omo-hyoid
Inferior node of m
ternal jugular
chain (above omo
hyoid muscle)
>
] Collecting
f trunks from
tip of tongue
1 Retro-pharyngeal
J nodes
Intercalated node
CoUecting vessels of
pharynx to deep ;
cervical chain [
NODES OF THE UPPER LIMB 719
The lymphatics of the larynx. — The larynx is, for the most part, drained by
the deep cervical nodes, although its lymph may also pass through certain out-
lying nodes situated upon its ventral surface. The mucous membrane is divided
into two zones by the ventricular folds, the mucous membrane of these structures
possessing but a scanty lymphatic plexus. The vessels from the upper part of the
lar3'nx, four or five in number, pass to the nodes of the superior deep cervical chain,
situated near the digastric muscle; those from the lower part pass to the lower
nodes of the same chain, some even descending as far as the supra-clavicular nodes.
The lymphatics of the trachea pass, on each side, to the paratracheal and inferior
deep cervical nodes.
The lymphatics of the thyreoid body. — The lymphatics of the thyreoid body
pass either to the small nodes situated in front of the larynx and trachea, or to
nodes of the deep cervical chain, a part of them ascending and a part descending.
It will thus have been seen that the lymphatics of the mucous membrane of
the head and neck all end in the deep cervical chain of nodes or in the outlying
nodes from it. Some of the vessels pass by the outlying nodes, but since the nodes
of the chain are so closely connected, the lymph must pass through several nodes
before entering the veins. The main tonsils, the numerous lingual and pharyngeal
tonsils, together with small lymph-follicles in the submucosa of the respiratory
tract, represent lymph-nodes in the capillary zone.
B. THE LYMPHATICS OF THE UPPER EXTREMITY
1. THE LYMPHATIC NODES OF THE UPPER EXTREMITY
The lymph-nodes of the arm lie, for the most part, in the axilla, where thpre is
a large group of nodes which receive almost the entire drainage of the arm and
the thoracic wall. In addition, there is in the arm a set of outlying superficial
nodes, the superficial cubital (supra-trochlear) , while small isolated nodes are often
intercalated along the course of the deep lymphatic vessels which accompany the
radial, ulnar, anterior interosseus and brachial arteries, the cephalic vein, and the
deep cubital vessels.
(1) The antibrachial nodes are very small, pin-head sized nodes which are
intercalated along the deep lymphatics which accompany the radial, ulnar, ante-
rior and posterior interosseus arteries.
(2) The deep cubital nodes [Igl. cubitales profundse] are also very small
nodes, one or two in number, intercalated along the ducts, near the deep vessels
at the bend of the elbow.
(3) The superficial cubital node [Igl. cubitales superficiales] (or supratrochlear)
is situated three or four centimetres above the medial epicondyle of the humerus.
It lies in the superficial fascia on the medial side of the basilic vein near the place
where it passes through the deep fascia. It is usually single, but may be absent
or represented by a chain of from two to five nodes. Its eflerents follow the
basilic vein.
(4) The delto-pectoral nodes are very small intercalated nodes from one to
three in number, and are situated in the groove between the deltoid and pectoral
muscles. Their vessels follow the cephalic vein.
(5) The axillary nodes [Igl. axillares], from twelve to thirty-six in number,
may be divided into groups according to the areas which they drain (fig. 566).
In addition to the upper extremity, they receive lymphatic drainage from the
thoracic walls, including dorsal, lateral and ventral (mammary) regions.
(1) The subclavian group consists of four or five nodes, situated in the apex of the axillary
fossa. They receive the efferent vessels of all the other groups, and their efferent vessels in turn
unite to form a single trunk, the subclavian, which empties into the thoracic duct on the left
side and on the right side either into the vein directly or else after uniting with the jugular
trunk. (See pp. 726-728.)
(2) The central group. A little lower along the axillary artery is a group of three to five
nodes, which makes a second centre for the vessels of the other groups, and sends its efferents
to the subclavian group. It will be clear from the figure that the separation of groups 1 and 2
is arbitrary.
(3) The brachial group. — This consists of four or five nodes, and, as its position toward
the junction of the axillary and brachial arteries indicates, is the main station for the lymphatics
of the arm proper. It receives almost all the superficial and deep lymphatics of the arm, and
its efferents pass to the central and subclavian groups, although a few pass directly to the
720
THE LYMPHATIC SYSTEM
suprascapular group. Small, outlying nodes of this group may be intercalated along the
vessels following the brachial artery throughout its course.
(4) The subscapular group [Igl. subscapulares]. — In this group are six or seven nodes,
which follow the subscapular artery and its branch, the circumflex (dorsal) scapular. Belonging
Fig. 565. — The Lymphatics op the Uppeb Extremity. (After Toldt,
Anatomy," Rebman, London and New York.)
'Atlas of Human
Axillary lymph nodes —
to it there are usually two or three sjnall nodes on the dorsal surface of the scapula, in the
groove which separates the teres major and minor. This group receives vessels from the dorsal
surface of the thorax, aa well as from the arm, and its efferents pass to the brachial group.
(5) The anterior Jpeclmal'^group [Igl. peotorales]. — This group consists of four or five nodes
which lie along the lower border of the peetorahs major and drain the mammary gland and
front of the chest. Their efferent vessels pass to the central and subclavian groups.
LYMPH-VESSELS OF THE LOWER LIMB
721
(6) The posterior pectoral group [Igl. pectorales] consists of small nodes situated on the inner
wall of the axiUa, along the course of the long thoracic artery. They receive afferents from
the lateraljntegument of the thorax and drain into the nodes of the central group.
^[2. THE LYMPHATIC VESSELS OF THE UPPER EXTREMITY
The lymphatic vessels of the upper extremity are divided into two sets — -a
superficial and a deep set.
The superficial vessels. — The superficial lymphatic vessels of the arm course
in two layers, the one quite subcutaneous, the other next the deep fascia, with
frequent anastomoses between the two sets. The majority of these vessels
remain superficial throughout the arm, but some of them pass through the deep
fascia in the upper arm especially where the basilic vein pierces the deep fascia,
Fig. 566. — The Axillary Ltmph-nodbs. (After Poirier and Cuneo.)
Brachial group Central group
Nodes connect-
ing the central
and subscapu-
lar groups
Subscapular
group
Subclavian
?S^^ group
Vessel from the
mammary
gland
Anterior pec-
toral node
Vessel from the
mammary
gland
Collecting trunk
Subareolar
plexus
Vessel from
lateral
thoracic wall
Vessel passing
to internal
mammary
node
Collecting
vessels
Vessel passing
to internal
mammary
node
to join the deep lymphatics accompanying the brachial artery. The general
distribution of the superficial lymphatics and their relations with the lymph-
nodes are shown in figs. 565 and 567.
The capillary plexus is most dense in the palmar sm-faces of the fingers, where the meshes
are so fine that they can only be seen with a lens. On the dorsal surface of the fingers and hand
the plexus is less dense. From the plexus on the palmar side of the fingers vessels come together
at the base of the fingers where they pass dorsally to be joined by the dorsal vessels of the
finger. They now follow two rather distinct curves: (1) those from the thumb and index
finger and a part of the middle finger pass upward along the radial side of the forearm, com-se
medially over the lower part of the biceps muscle, and empty into the axillary lymph-nodes.
One or two vessels follow the cephalic vein and, after traversing the delto-peotoral node, pierce
the costo-eoracoid membrane to enter the subclavian nodes, or pass over the clavicle into the
inferior deep cervical nodes. (2) Those from the rest of the fingers course for a short stretch
on the dorsum of the forearm, when they turn toward the ulnar side, wind around to the volar
side and either continue superficially along the upper arm to the axillary nodes, or pass into
the superficial cubital node, or, joining the efferents from these nodes, pass through the deep
fascia to unite with the deep lymphatics. (3) A set of vessels from the palm of the hand passes
upward along the volar side of the forearm. Anastomoses are frequent between these groups of
lymphatic vessels, particularly in the cubital region.
It will thus be seen that the superficial cubital nodes receive lymph from the ulnar digits
and from the palm of the hand, but not from the thumb and forefinger.
The superficial lymphatics from the rest of the arm join these thi'ee main groups at various
levels.
The deep vessels. — ^The deep lymphatic vessels of the upper extremity drain
the joint capsules, periosteum, tendons, and (if the recent work of Aagaard is
722
THE LYMPHATIC SYSTEM
correct) the muscles. They collect into vessels which, in general, accompany the
arteries, in the forearm, the radial, ulnar, anterior and posterior interosseous, and
in the arm the brachial. Above the elbow they are joined by numerous super-
FiG. 567. — The Lymphatics op the Forearm. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Brachial fabcia
Brachial artery and veins
^Superficial lymphatic vessels
Superficial cubital lymph-nodes
Tendon of the biceps muscle
■^ Deep cubital lymph-nodes
Deep lymphatic vessels
AntibracMal fascia— -
■ Superficial lymphatic vessels
Lymph-vessels
of the hand fj / / i/ ^^ ^ ^
Lymph-vessels of the thumb *^
Lymph-vessels of the finger
Lymphatic network
--- Superficial volar arch
^--- Palmar aponeurosis
— Lymphatic network
Subcutaneous fat of the finger
ficiall lymphatic vessels including efferents from the superficial cubital nodes.
Along their course in the forearm are intercalated small nodes (pin-head size),
radial, ulnar, anterior and posterior interosseous (Mouchet) and deep cubital; and,
in the arm, small brachial intercalated nodes. The deep vessels in the main enter
the brachial group of axillary lymph-glands which lie behind the large vessels
LYMPHATICS OF THE MAMMARY GLAND 723
and nerves, the efferents from which nodes pass either into the lower deep cer-
vical lymph-nodes or directly into the subclavian trunk.
The lymphatics of the shoulder-joint have recently been described by Tananesco. He
finds a ring of lymphatics in the joint capsule, whose efferents, in the main, following the arteries,
run to the central and subclavian groups of axillary nodes.
C. THE LYMPHATICS OF THE THORAX
The lymphatics of the thorax will be considered under the following divisions:
the superficial vessels, the deep nodes, and the deep vessels.
1. THE SUPERFICIAL LYMPHATIC VESSELS OF THE THORAX
The superficial lymphatics of the thorax pass almost exclusively to the axillary
nodes, and may be regarded as forming three sets, a ventral, a lateral, and a
dorsal. The ventral set drains the thoracic integument, which extends form
the median line and the clavicle over to the lateral border of the chest, and includes
the vessels of the mammary gland, which will, however, be described separately.
The majority of the vessels from this area end in the anterior pectoral group of
axillary nodes, a few, which arise beneath the clavicle, passing to the supra-
clavicular nodes, and a few perforating the intercostal spaces and ending in the
chain of nodes along the internal mammary artery.
It has been shown that an injection into the subcutaneous plexus near the median line
passes to the opposite side, and that, in addition to the anastomosis between the networks of
the two sides of the thorax which this result manifests, there may also be a few collecting trunks
crossing the median line, and, furthermore, anastomoses occur between the superficial networks
of the anterior thoracic and abdominal walls. Thus while the main channel of lymphatic
drainage is through the axiUa, there are minor accessory channels to (1) the supraclavicular
nodes, (2) to the axilla of the opposite side, (3) to the internal mammary chain, and (4) in iso-
lated cases even to the inguinal nodes. These accessory channels may become more open in
cases of obstruction to the main channel.
The lateral set of superficial thoracic lymphatics is much less extensive than
the anterior, and its collecting vessels pass upward to open into the posterior
pectoral group of axillary nodes.
The dorsal set, which occupies the subcutaneous tissue of the dorsal thoracic
wall, sends its vessels to the subscapular group of axillary nodes.
The Lymphatics of the Mammary Gland (Figs 566, 568)
The lymphatic network over the peripheral portions of the mammary gland is
like that of the rest of the thoracic wall. In the areola, however, the capillaries
are far more abundant, forming a double subareolar plexus. The superficial
plexus is so dense that its meshes can be seen only with a lens. The deeper plexus
not only drains the superficial plexus, but receives the vessels from the mammary
gland itself, and from it arise two large trunks, one from the inferior and one from
the superior part of the plexus. These two vessels pass to one or two of the nodes
belonging to the anterior pectoral group of axillary nodes. In addition there may
be — (1) one or two vessels passing to the nodes along the axillary artery; (2) in
rare cases a vessel passing directly to the subclavian nodes. There is also a defi-
nite channel from the medial margin of the gland to the internal mammary nodes,
the ducts following the perforating branches of the internal mammary vessels,
and it may be noted that the crossed anastomosis and that with the abdominal
network, mentioned in connection with the superficial thoracic vessels, may, on
occasions, serve as channels for the mammarj^ drainage.
There is also clinical evidence indicating that lymphatic vessels from the
lower and medial aspect of the mammary gland may pass through the abdom-
inal wall in the angle between the xiphoid process and the costal cartilages,
establishing a communication with the lymphatics of the abdomen in the
diaphragmatic region.
Lymphatics of the thoracic muscles. — The recent studies of Aagaard make it probable
that muscles are provided with lymphatics. Whether his findings will be substantiated or
not, however, it is unquestioned that lymphatic vessels course through the pectoral muscles —
some passing to the axillary, others to the subclavian, and still others to the internal mammary
chain of nodes. This would suffice to explain the fact that cancer of the breast may extend
into and through the pectoral muscles.
724
THE LYMPHATIC SYSTEM
2. THE DEEP LYMPHATIC NODES OF THE THORAX
The lymphatic nodes of the thoracic cavity may be divided into the parietal
and the visceral. The parietal nodes are arranged in two sets, the internal
mammary chain and the intercostal nodes (fig. 570) . Along the internal mam-
mary artery are from four to sLx small nodes, [Igl. sternales] which receive ducts
from the anterior thoracic and the upper part of the abdominal walls, from the
anterior diaphragmatic nodes which drain the liver, and from the medial edge of
the mammary gland. The efferent vessels usually unite with the vessels of the
anterior mediastinal and bronchial nodes, to form the broncho-mediastinal trunk,
which may join the thoracic duct on the left and the jugular or subclavian trunk
on the right or may empty separately into the subclavian vein on both sides.
Fig. 568.-
-Lymphatics of the Subareolar Plexus of the Breast. (After Sappey.)
Vessels from network
Lobuleof gland,
uninjected
Subareolar
network
Vessel from , . (
network n ^
Lobule of gland
uninjected
Superficial *:i—
network
Vessels from network
The intercostal nodes [Igl. intercostales] lie along the intercostal vessels, near
the heads of the ribs. There are usually one or two in each space, and occasiona,lly
a node is placed where the perforating lateral artery is given off. They receive
afferents from the deeper part of the thoracic wall and costal pleura. Their
efferents enter the thoracic duct, those from the nodes of the lower four or five
interspaces uniting usually to form a common duct on each side, but more marked
on the left side, which descends to the receptaculum chyh.
The efferent lymph-vessels from the upper intercostal nodes often unite into common
trunks which drain several interspaces, and which may pass through a large gland near the
thoracic duct before emptying into it. Occasionally such collecting vessels from the right side
cross the mid-Une behind the aorta to reach a large gland to the left of the aorta.
The visceral nodes of the thorax are arranged in three groups : — ■
1. The anterior mediastinal nodes [Igl. mediastinales anteriores] are situated,
as their name indicates, in the anterior mediastinum, and are arranged in an upper
and a lower set. The upper set is situated upon the anterior surface of the arch
of the aorta, and consists of eight or ten nodes, which receive afferents from the
pericardium and the remains of the thymus gland. Their efferent vessels pass
upward to join the broncho-mediastinal trunk. The lower set consists of from
LYMPH-VESSELS OF THE THORAX
725
three to six nodes, situated in the lower part of the mediastinum. They receive
afferent ducts from the diaphragm, hence they are sometimes termed the dia-
phragmatic nodes, and also from the upper surface of the liver. Their efferents
pass upward to open into the upper anterior mediastinal nodes.
2. The posterior mediastinal nodes [Igl. mediastinales posteriores] eight or ten
in number, are situated along the thoracic aorta, and receive vessels from the medi-
astinal tissue and from the thoracic portion of the oesophagus. Their efferents
open directly into the thoracic duct.
3. The bronchial nodes [Igl. bronchiales] form an extensive group lying along
the sides of the lower part of the trachea, and along the bronchi as far as the hilus
Fig. 569. — The Tracheal and Bronchial Nodes. (Sukiennikow.)
Inferior laryngeal nerve
— Tracheal nodes
Trachea
Inierior laryngeal nerve
Tracheo-bronchial node
Bronchial nodes
Connecting chain
Pulmonary nodes
Pulmonary nodes
Connecting chain
Pulmonary nodes
of each lung, those lying in the hilus being termed the pulmonary nodes, and
others, according to their position, lateral tracheo-bronchial, inferior tracheo-
bronchial (nodes of the bifurcation) and tracheal (paratracheal). Thej'' receive
the drainage of the lower part of the trachea, the bronchi, the lungs, part of the
oesophagus, and, to a small extent, the heart. Thek efferent vessels unite with
those from the upper anterior mediastinal and internal mammarj^ nodes to form
the broncho-mediastinal trunk.
3. THE DEEP LYMPHATIC VESSELS OF THE THORAX
In following the deep lymphatics of the thorax the course of development will
be followed in describing first the thoracic duct and right lymphatic ducts,
second the parietal vessels, and third the visceral vessels.
726
THE LYMPHATIC SYSTEM
The Thoracic Duct
The thoracic duct [ductus thoracicus] (fig. 570), which is the main collecting
duct of the lymphatic system, extends from the second lumbar vertebra along
the spinal column and course of the aorta to the junction of the left internal jugular
and subclavian veins. It receives all the Ij^mphatics below the diaphragm, and
the deep lymphatics from the dorsal half of the chest wall; and also, when joined,
near its cephalic end, by the left broncho-mediastinal, subclavian and jugular
trunks, from the remainder of the left half of the body, above the diaphragm.
At the caudal end the duct is formed usually by the union of three collecting
ducts, one from each of the lumbar groups of nodes, and an unpaired intestinal
Fig. 570. — The Thokacic Duct. (After Toldt, "Atlas of Human Anatomy," Rebman,
London and New York.)
Thoracic duct
Internal jugular vein
Jugular trunk
Subclavian trunk
Subclavian vein
Right innominate vein — >^~.-^.n,^, .— ,.^^^^_^ — ^, ..
Axillary lymph -nodes
Intercostal lymph-nodes ■<!_/
—Thoracic duct
Crus of diaphragm
Lumbar trunks, right and
left "JY"^'
Lumbar lymphatic plexus —
Jf| — Hemiazygos vein
; Cisterna chyli (recepta
%X Intestinal trunks
\^ i\— =Lumbar nodes
trunk. At its origin then is usu ilh i dil i1( d poition known as the receptaculum
[cisterna chyli]. This usually endh opposite the bodj^ of the eleventh thoracic
vertebra, and from here on the duct is from 4 to 6 mm. in diameter, until near its
termination, where it is again wider.
In its cadual part, the duct lies dorsal to the aorta in the median line; it passes
through the aortic opening in the diaphragm, and then inclines to the right and
passes upward to about the fourth, fifth, or sixth thoracic vertebra, when it
bends to the left and passes, continuing upward, over the apex of the left lung
and the left subclavian artery, and in front of the root of the left vertebral artery
and vein, and then curves downward to open into the left subclavian vein, close
to its junction with the left internal jugular. The duct runs in the wall of the
vein a short distance before ending.
Variations. — There is a wide range of variation from this usual course. The duct is fre-
quently double throughout a part of its course, the two branches being connected by cross
anastomoses, and finally uniting into a single trunk before joining the veins. It may be
THE THORACIC DUCT
727
multiple, or a single trunk may pass in front of the aorta instead of behind. In a few instances
it has been found emptying into the right instead of the left subclavian vein. There is also a
wide range of variation in the height to which the duct ascends in the neck before curving down-
ward to the vein. As regards the termination of the thoracic duct, variations are also frequent;
it may bifurcate and end as two ducts. It often connects with the lowermost part of the
internal jugular, or the beginning of the innominate. According to Henle, there is one un-
doubted case reported of a thoracic duct ending in the azygos vein near the sixth thoracic
vertebra, the duct being obliterated above this point. At the terminal bend the thoracic
duct receives the jugular trunk from the neck; it may also receive the subclavian and the broncho-
mediastinal trunks, but it is more usual for these last two to open either separately or together
into the subclavian.
Variations are extremely numerous in the region of the receptaculum. Severa lobservers
state that, in the majority of cases in man, no definite receptaculum exists. Bartels found one
in only 25 per cent, of the cases studied. Instead, there is present a widening of each of the two
lumbar trunks, with several anastomoses between them (55 per cent., Bartels), or a widening
of these two stems without anastomosis (5 per cent.), or a much elongated widening arising
Pig. 571. — Abdominal Poetion of the Thoracic Duct. (Poirier and Cun6o.)
from the growing together of the two lumbar trunks (10 per cent.). In eases where the lumbar
trunks remain separate, the intestinal trunk joins the left one.
Development. — While the exact mode of its development is still in dispute, enough is
agreed upon by the various investigators to explain most of the variations in the thoracic duct.
In brief, it is known that the lymphatics start in the neck as a variable number of outgrowths
from the veins in the region of the junction between the later internal jugular and subclavian
veins. A variable number of these connections disappear, while the various combinations of
one, two, three or four which are retained furnish the numerous variations in number and
position of the ducts which empty into the vein in the adult. Thus the thoracic duct may
have one, two or even three openings into the veins, while the jugular, subclavian and broncho-
mediastinal trunks may join the thoracic duct or may enter the veins separately or in various
combinations.
It is also known that the upper part of the thoracic duct is at first bilateral, being formed
by outgrowths from the primary plexus, which meet in a common plexus around the aorta.
Normally the right portion of these connections disappears, so that the thoracic duct empties into
the left subclavian vein. In exceptional cases, where it opens into the right subclavian vein,
there have also been present variations in the large right arterial trunk. These conditions
in all probability at a certain stage in development produced a greater resistance to the lymph
stream in the left than in the right vessel causing it to become obliterated so that the right
instead of the left became the permanent ending of the duct.
728
THE LYMPHATIC SYSTEM
Most of the other variations — the frequent presence of longer or shorter doublings of the
duct with anastomoses between the two parts, the numerous variations in the region of the
receptaculum chyli — are easily explained by the fact that the duct and receptaculum pass
through a stage in development in which they form richly anastomosing plexuses around the
aorta.
The Right Tbbminal Collecting Ducts
On the right side the jugular, subclavian, and broncho-mediastinal trunks
usually open separately into the subclavian vein, the orifices of the first two
being near together. When the jugular and subclavian trunks unite, the com-
mon duct is termed the right lymphatic duct; this is a rare form, and it is still
more rare for the three ducts to unite to form a common stem (fig. 572). These
variations have the same explanation, embryologically, as was given for the
corresponding variations on the left side.
Fig. 572. — Tekminal Collecting Ducts on the Right Side. (Poirier and Cun^o.)
V)
Jugular trunk
Subclavian trunk
Node of internal mam
mary chain
Right lymphatic duct
Subclavian trunk
Right lymphatic duct
Broncho-mediastinal trunk
Node of internal mammary chain
The Deep Lymphatic Vessels
As with the nodes, the deep lymphatic vessels of the thorax may be divided
into a parietal and a visceral group. To the former group may be assigned the
lymphatics of the intercostal spaces and those of the diaphragm.
The intercostal lymphatics form plexuses in each intercostal space, which
receive lymph from the periosteum of the ribs and from the parietal pleura, and
from which the drainage is either ventral or dorsal. From the dorsal half of
each space the drainage is to the intercostal nodes, while from the ventral half it is
toward the internal mammary nodes.
The lymphatics of the diaphragm. — There is an exceedingly rich plexus of
capillaries both on the pleural and on the abdominal surface of the diaphragm,
especially in the region of the central tendon, these plexuses lying in the subserous
layers and being freely connected by vessels which perforate the muscle. There
is, however, only slight communication between the plexuses of the right and left
sides of the diaphragm. The vessels lie between the coarse muscle bundles,
forming a very characteristic picture, in which the lymphatics stream outward
radially, like the spokes of a wheel. The collecting vessels empty into three
groups of small nodes on the convex surface. The ventral group lies ventral to
the central tendon. Two or three nodes in the centre of this group receive
LYMPHATICS OF THE LUNGS
729
afferents from the liver and none from the diaphragm, but the rest receive
vessels from the ventral sm'face of the diaphragm and the efferents of all pass to
the lower set of anterior mediastinal nodes.
The middle group consists of from three to six nodes, which lie, on the left side,
near the point where the phrenic nerve enters the diaphragm; on the right side,
near the vena cava.
The dorsal group of four or five nodes is placed between the pillars of the
diaphragm. The vessels from the lateral and dorsal groups pass to the posterior
mediastinal nodes, and also to the upper coeliac nodes, which likewise receive the
drainage from the dorsal part of the abdominal surface of the diaphragm.
i
Fig. 573. — The Lymphatics op the (Esophagus. (After Sakata.)
Inferior deep cervicl nodes
Deep cervical node
^Ilecurrent nerve
'Bronchial node
To the visceral group of thoracic lymphatics belong the vessels of the thymus,
the lungs, the heart, and the oesophagus.
The lymphatics of the thymus drain, according to Severeanu, into three sets
of glands, an anterior, a ventral and a dorsal group. The anterior set, one gland
on each side, lies lateral to the cephalic end of the thymus, and drains into the
jugular or subclavian trunlc. The ventral set includes 4-6 of the anterior medi-
astinal lymph-glands. The dorsal set, 2 on each side, is made up of anterior
mediastinal glands lying between the thymus and the pericardium.
The lymphatics of the lungs are arranged in two sets. A deep set takes its
origin in plexuses which surround the terminal bronchi and follows the course of
the bronchi, the pulmonar.y artery, and the pulmonary vein to the pulmonary
nodes at the hilus, whence the stream passes to the main bronchial nodes (fig. 569),
especially to those situated in the angle formed by the bifurcation of the trachea,
I
730 THE LYMPHATIC SYSTEM
and thence to the broncho-mediastinal trunk. A superficial set arises in a network
situated upon the surface of the lung beneath the visceral layer of the pleura.
According to Miller, who has studied the lymphatics of lung and pleura most carefully in
dog and man, the only communications between the lymphatics of the pleura and the deep lym-
phatics oociu- around the veins which reach the pleural surface. These vessels are provided
with valves so that the lymph stream passes, in them, toward the pleural surface. The collect-
ing stems of the subpleural lymphatics pass independently to the pulmonary nodes.
Lymphatics of the heart. — The superficial (subepicardial) tymphatics of the
heart collect to two main stems which accompany the main coronary vessels.
The right stem accompanies the right coronary artery to its origin, passes on
over the arch of the aorta and empties into one of the anterior mediastinal lymph-
nodes. The left stem, formed by two stems accompanying the circumflex and
anterior descending branches of the coronary vein, passes behind the arch of the
aorta to an anterior mediastinal lymph-gland. Two small subepicardial inter-
calated nodes have been described along these trunks.
Subendocardial lymphatics have been described in animals, which connect
by vessels passing through the musculature with the superficial lymphatics.
Parenchymatous lymphatics have recently been demonstrated by Bock.
The course of their efferent vessels has not yet been described.
The lymphatic vessels of the oesophagus, which will here be considered
throughout its entire extent, cervical as well as thoracic, are arranged in two
plexuses, one of which occurs in the mucosa and the other in the submucosa. The
collecting vessels arising from the plexuses may be divided into three sets, of
which the uppermost pass to outlying nodes belonging to the deep cervical chain,
those from the thoracic portion of the tube pass to the bronchial and posterior
mediastinal nodes, while those from its lowermost part pass to the superior gastric
nodes (fig. 573).
D. THE LYMPHATICS OF THE ABDOMEN AND PELVIS
In the following section there will be described successively the lymphatic
nodes of the abdomen and pelvis, the lymphatic vessels of the abdominal walls,
and the visceral lymphatic vessels.
1. The Lymphatic Nodes of the Abdomen and Pelvis
The lymphatics which connect directly with the thoracic duct, though
complicated, may be described briefly by saying that they follow the aorta and its
branches. In the abdomen there are four main chains along the aorta — (1) the
left lumbar chain; (2) the right lumbar chain; (3) the pre-aortic chain; and (4)
the post-aortic chain.
The right and left lumbar nodes [Igl. lumbales], form an almost continuous
chain along the abdominal aorta, resting upon the psoas muscles, some of those
on the right side being ventral and some dorsal to the inferior vena cava. They
receive: — (1) the efferent lymphatics of the common ihac nodes, and hence drain
the leg and external genitaha; (2) the efferent lymphatics that follow the lumbar
arteries and hence drain the abdominal AvaU; (3) the efferents that follow the
paired visceral aortic branches, namely, those from the kidneys, supra-renal, and
internal reproductive organs. On the right side, the lymphatics from the re-
productive organs pass to the nodes ventral to the vena cava — those of the
abdominal walls pass to the dorsal set, while those from the kidney pass to both
sets.
The efferent vessels of the lower lumbar nodes pass to higher ones and so on up
the chain, the vessels from the uppermost nodes uniting to form a single lumbar
trunk on each side. These trunks pass to the thoracic duct, forming two of the
so-called trunks of origin of that vessel (fig. 571).
The pre-aortic nodes [lymphoglandulte coeliacEe] are arranged in three groups
at the root of each of the three unpaired visceral branches of the aorta — the
cceliac, the superior mesenteric, and the inferior mesenteric arteries. The
cceliac nodes are from one to three in number, and are in reality parts of chains of
nodes extending along the branches of the artery and constituting the hepatic,
gastric, and splenic nodes. They drain the stomach, duodenum, liver, pancreas,
and spleen.
LYMPHATICS OF ABDOMEN
731
The superior mesenteric group is larger, and is continuous with the mesenteric
nodes lying in the root of the mesentery. This group drains the remainder of the
small intestine, the CEecum and appendix, the ascending and transverse colons, and
the pancreas.
The inferior mesenteric group usually has two nodes, one on either side of the
artery. It drains the rectum and descending and sigmoid colons. All the nodes
in the mesentery and intestinal walls may be considered as outlying nodes of the
pre-aortic group. They will be studied in connection with the visceral lymphatics.
The inferior mesenteric nodes drain into the neighbouring lumbar nodes, and
also directly upward to the superior mesenteric nodes, and then again to the
cceliac nodes. From the last a single stem, the intestinal trunk, arises and passes
either to the right lumbar trunk or directly to the thoracic duct, forming the
third of the so-called trunks of origin of the duct.
Fig. 574. — Abdominal Acetic Nodes in the New-bokn. (Poirier and Charpy.)
■Suprarenal gland
Inferior phrenic
artery
esen- / \ \0 \f \i\^\^ / I V
;ry ■■■■/— s— u^ \^^^^)_^it^ HI \
Left spermatic
Right aortic node
I,eft aortic nodes
Hypogastric artery
The post -aortic nodes are not true regional nodes, but receive vessels from the
lumbar and pre-aortic chains.
Below the bifurcation of the aorta there are three large chains, the common
iliac, the external iliac, and the hypogastric.
The common iliac nodes [Igl. iliacse], are in three groups (fig. 575). The
external set consists of about two nodes, which are in reality a part of a continuous
chain extending along the side of the aorta, common iliac, and external iliac
arteries. A second set of two to four posterior nodes lies behind the artery.
These two groups receive the efferent vessels of the external iliac and hypogastric
chains. The internal set usually consists of two nodes which rest upon the
promontory of the sacrum. They receive vessels from the sacral nodes, together
with most of those from the pelvic viscera, namely, from the prostate, neck of
the bladder, neck of the uterus, the vagina, and part of the rectum. The efferent
lymphatic vessels of the common iliac nodes pass to the lumbar chain.
732
THE LYMPHATIC SYSTEM
External iliac nodes. — These are likewise in three sets — -external, middle, and
internal. The external chain consists of three or four nodes, the lowest one being
behind the crural arch. They receive: — (1) some of the vessels of the superficial
and deep inguinal nodes; (2) vessels from the glans or chtoris, which come tlirough
the inguinal canal; (3) vessels from the part of the abdominal wall supplied by the
deep epigastric and deep circumflex arteries, along which there may be a few
outlying nodes — the epigastric nodes.
The middle chain consists of two or three nodes behind the artery. When
there are three, the lowest is likewise near the crural arch. It receives vessels
from the bladder, prostate, neck of the uterus, and upper portion of the vagina.
The internal chain consists of three or four nodes, and is the continuation of the
deep inguinal nodes. Its lowest nodes are likewise near the femoral ring, while the
next node is large and constant, and usually lies within the pelvis. This chain
Fig. 575. — Ilio-pelvic Nodes. (Cunto and Marcille.)
Left aortic node
Right aortic node
Node of the pro- i ^ i i, .^ ,, ,.
Obturator nerve
Obturator artery
External iliac node
Retrocrural node
Obturator node
Hypogastric artery
receives many vessels: — (1) from the superficial and deep inguinal nodes; (2)
from the glans and clitoris through the femoral canal; (3) from the abdominal
wall; (4) from the neighbourhood of the obturator vessels; (5) from the neck of
the bladder, the prostate, and membranous part of the urethra; (6) from the
hypogastric chain.
Thus, to sum up the nodes of the external iliac chains: — they are a part of a
chain which includes the lumbar, common iliac, external iliac, and inguinal nodes.
It will be noted that this extensive chain stops, for the most part, with the deep
inguinal group. The external iliac nodes receive the efferents of the superficial
and deep inguinal nodes; the middle and internal groups receive vessels from the
pelvis. The efferent vessels of all the nodes in the chain pass to the higher nodes.
The hypogastric nodes [Igl. hypogastricse]. — ^These nodes are in groups near
the origin of the branches of the hypogastric (internal iliac) artery. Thus they
occur near the origin of the obturator, the uterine, or prostatic, the trunk of the
LYMPHATICS OF ALIMENTARY TRACT 733
inferior gluteal (sciatic) and pudic, the middle hjemorrhoidal, and the lateral
sacral arteries. All the nodes are beneath the pelvic fascia, and are connected by-
numerous anastomoses. They receive lymphatics from the structures supplied
by the corresponding arteries, namely, from the pelvic viscera, the perineum, and
the posterior surface of the thigh and gluteal region. Their efferent vessels pass
partly to the middle group of the common iliac nodes, and partly to the posterior
nodes of the same chain.
The sacral nodes [Igl. sacrales]. — These nodes, 5 or 6 in number, lie in the
hollow of the sacrum, in or near the mid-line. They receive afferent vessels
from rectum and prostate, and their efferents pass to the hypogastric and lumbar
nodes.
2. THE LYMPHATIC VESSELS OF THE ABDOMINAL WALLS
The lymphatic vessels of the abdominal walls are arranged in two sets, one of
which is subcutaneous and the other deep or aponeurotic. The subcutaneous
vessels form a rich network through all the subcutaneous tissue of the abdomen,
anastomosing above with the subcutaneous plexus of the thorax. The collecting
vessels converge toward the inguinal region, those from the posterior wall
curving forward along the crest of the ilium, and they all terminate in the super-
ficial inguinal nodes.
The deep vessels drain along three principal lines. (1) A set of collecting
vessels follows the line of the deep epigastric artery to terminate in the lower
external iliac nodes; (2) a second set follows the deep circumflex iliac vessels to
the same nodes; and (3) a third set follows the lumbar vessels to terminate in the
nodes of the lumbar chain. A group of small epigastric nodes, which may be
regarded as offsets from the iliac chain, occur on the lymph-vessels which ac-
company the deep epigastric vessels, not far from their termination, and a
second less constant group of usually three small umbilical nodes occurs in the
vicinity of the umbilicus in the network covering the posterior layer of the
sheath of the rectus abdominis muscle.
3. THE VISCERAL LYMPHATIC VESSELS OF THE ABDOMEN AND
PELVIS
The lymphatics to the viscera follow along the course of the arteries. At the
point where the artery of an organ branches from the aorta there is a group of
nodes which represents the main regional group, and a second chain of nodes
extends along the artery. The final arrangement of nodes and ducts varies with
each organ.
Though the lymphatics follow the blood-vessels, the lymphatic capillaries in the regions where
their relations are known are separated from the vascular capillaries; in the intestinal villi,
for example, the lymphatic capillaries are central, while the vascular capillary plexuses are
peripheral. The relation of the lymphatic capillaries to the essential structures of each organ,
that is to say, the arrangement of the lymphatics in the absorbing area, is not yet clear in many
organs, and this is a point which can be worked out by tracing the development and gradual
invasion of each organ by the lymphatics. The old theory of the origin of the lymphatics
from the tissue-spaces made this problem most difficult of attack.
In almost all organs there is a peripheral or capsular lymphatic plexus, which
anastomoses with the parietal lymphatics, these anastomoses being particularly
well developed in the case of the liver. In addition there are one or two deep
plexuses in the great majority of the organs which drain partly directly to their
regional nodes and partly by way of the peripheral plexus.
The Lymphatics of the Alimentary Tract
The lymphatics of the mouth, pharynx, and oesophagus have already been
described (pp. 715, 730). In general, throughout the abdominal part of the ali-
mentary canal, the distribution of nodes is as follows: — (1) There are primary
regional nodes situated at the roots of the arteries as they leave the aorta, that is
to say, aroundthe coeliac and the superior and inferior mesenteric arteries; these
(
734 THE LYMPHATIC SYSTEM
drain large segments of the intestine; (2) groups of definite and constant nodes
placed along the branches of the arteries in the root of the mesentery; these drain a
definite smaller segment of the intestine; (3) chains of nodes along the anasto-
motic loops of the arteries, close to the intestinal wall ; these are of the type called
'intercalated nodes'; (4) solitary or compound follicles, situated within the
submucosa or capillary zone of the lymphatics.
What may be taken as the typical arrangement of the lymphatic vessels in the
intestine may be seen in fig. 576. There are three zones in which the capillary
plexuses are spread out, namely, in the subserosa, the submucosa, and the
mucosa. There is an abundant plexus of large capillaries just beneath the serosa;
inthe submucosa the plexus is also formed by large capillaries, while the mucosal
plexus is finer. The lymph-foUicles lie in the zone of the mucosal plexus, and it is
from this that the central chyle vessels of the villi arise. The collecting vessels
are formed by the union of vessels from the submucous and subserous plexuses.
They traverse the three sets of nodes just described.
The lymphatics of the stomach (fig. 577) . — The stomach differs from the rest of
the alimentary canal in its blood-supply in having a ventral anastomotic loop,
namely, that along the lesser curvature. Along this loop is the superior gastric
chain [Igl. gastricse superiores] of nodes, lying between the folds of the lesser
omentum, some of them being on the posterior surface of the stomach. This is
the most important group of nodes draining the stomach, and it has been shown
that the lymph-vessels from the pylorus run obliquely across the stomach to the
main mass of nodes near the cardia, an important point in the surgery of the
pylorus. The efferent vessels of the chain pass to the coeliac nodes. The vessels
of the greater curvature pass to a group of inferior gastric nodes [Igl. gastricae
inferiores], situated along the right gastro-epiploic artery, while those of the fundus
follow the short gastric and left gastro-epiploic vessels to the nodes which lie
along the splenic artery, both these sets of nodes also draining to the coeliac group.
There is a zone half-way between the lesser and greater curvatures, in which the
lymphatics are scanty. The lymphatics of the cardia connect with those of the
oesophagus, and the mucosal plexus of the pylorus is continuous with that of the
duodenum.
The lymphatics of the duodenum. — The lymphatics of the duodenum depart
somewhat from the type, owing to its relations with the pancreas and the bile-
ducts. The collecting vessels end: — (1) in nodes ventral to the pancreas, which
follow the pancreatico-duodenal artery to the hepatic chain; (2) in nodes dorsal to
the pancreas, which follow the superior mesenteric artery to the superior mesen-
teric nodes. There are anastomoses between the lymphatics of the duodenum
and those of the pylorus, of the pancreas, and of the chain along the common
bile-duct.
The lymphatics of the jejuno-ileum (fig. 578) have already served as the type
of the arrangement of the intestinal lymphatics (see above). The mass of
mesenteric nodes [Igl. mesentericse] to which the lymphatics of the small intestine
pass is the largest and one of the most important in the body, its individual nodes
numbering anywhere from 130 to 150.
The lymphatics of the ileo-caecal region. — The surgical importance of the
lymph-nodes in connection with the appendix warrants a detailed description of
them in which the observations of Broclel will be followed. The drainage of the
caecum and appendix is along the ileo-colic artery, and is carried on by three sets
of collecting vessels — (1) an anterior cajcal set, which generally pass through
one or more outlying nodes before reaching the ileo-csecal mesenteric nodes; (2) a
similar posterior set; and (3) an appendicular set, three to sLx in number, which
usually pass directly to the ileo-csecal nodes. The appendix thus has an inde-
pendent drainage into one or two ileo-c£ecal nodes, about 3 cm. above the ileum.
The ileo-csecal chain drains through the mesenteric nodes to the superior mesen-
teric group (figs. 579, 580).
The lymphatics of the large intestine. — Along the ascending colon there are
but few nodes on the terminal vascular arches, but the number increases along
the transverse colon, especially at its two angles. These nodes, together with
those along the descending and sigmoid colons, are termed the meso-colic nodes
[Igl. mesocolicse], and they drain partly to the superior mesenteric and partly to
the inferior mesenteric nodes, their efferents following the corresponding arteries.
LYMPHATICS OF RECTUM AND ANUS
735
The lymphatics of the transverse colon connect with those of the omentum; those
of the descending colon are more scanty.
The lymphatics of the rectum and anus. — There are three lymphatic zones
of the rectum and anus. (1) An inferior zone, corresponding to the anal integu-
ment, in which the capillary networks, both superficial and deep, are extremely
abundant, and from which from three to five collecting vessels on either side pass
to the inguinal region and end in the medial superficial inguinal nodes. (2) A
Pig. 576. — -The Lymphatic Vessels of the Intestine. (After Mall.)
(
middle zone, corresponding with the transition zone of epithelium — that is, with
the mucous membrane below the columns of Morgagni. Here the network is
coarse, and has its meshes arranged vertically; its ducts drain partly into nodes
situated along the inferior and middle hsemorrhoidal arteries, and partly pass to
nodes in the meso-rectum, situated along the superior hsemorrhoidal artery and
known as the ano-rectal nodes. (3) The superior zone corresponds to the re-
mainder of the rectal mucous membrane, and contains a rich network whose
collecting vessels pass to the ano-rectal glands, and thence along the superior
hsemorrhoidal arteries to the inferior mesenteric nodes.
736 THE LYMPHATIC SYSTEM
Lymphatics of the liver. — The lymphatic drainage of the liver is complicated
and has great need of being entirely restudied from the standpoint of development.
Its course is mainly to the coeliac nodes, but on the way it passes through a sec-
ondary group of three to six hepatic nodes [Igl. hepaticse], situated along the
hepatic artery. Some of these nodes are along the horizontal part of the artery,
parallel to the superior border of the pancreas, while the rest follow the artery
in its vertical course along with the portal vein, and become continuous at the
portal fissure with two distinct chains of nodes, one of which follows the hepatic
artery and portal vein, and the other the cystic and common bile-ducts. These
nodes are variable, but one constant node is at the junction of the cystic and
hepatic ducts. A part of the drainage of the liver is also through the diaphrag-
matic nodes.
The superficial collecting lymph-vessels of the liver have been studied by
Sappey. Those from the superior surface include three sets. From the dorsal
part vessels pass through the diaphragm with the vena cava, and end in the adja-
cent posterior mediastinal nodes. Some of these vessels from the right lobe pass
in the coronary ligament to the coeliac nodes, and some from the left lobe to the
superior gastric nodes. The second set of vessels from the superior surface runs
over the ventral border to the hepatic nodes situated in the portal fissure. The
third and most important set arises near the falciform ligament, and passes
Fig. 577. — The Lymphatic Zones of the Stomach. (Cunto.)
jgi^^^'^ ^r^^'^° splenic nodes
To superior gastric nodes >*^ iSi^^ y/i
To inferior gastric node
partly dorsalward to the anterior mediastinal group of nodes on the upper surface
of the diaphragm, and to the nodes around the vena cava, and partly ventral-
ward to the hepatic nodes of the portal fissure.
The collecting vessels of the inferior surface pass to the nodes situated in the
portal fissure, either along the artery or the bile-ducts.
The lymphatics of the gall-bladder join the hepatic nodes along the cystic and
common bile-ducts, and also the superior pancreatic nodes.
Lymphatics of the pancreas. — The lymph-vessels which drain the pancreas
fall, according to Bartels, into four groups: left, anterior (upper), right and
posterior (lower). (1) The left group drain the tail of the pancreas and pass to
the splenic lymph-nodes, at the hilus of the spleen. (2) Anteriorly lymphatics
pass to "superior pancreatic lymph-nodes," superior gastric and hepatic nodes.
(3) To the right, lymphatics pass to " pancreatico-duodenal lymph-nodes."
(4) Posteriorly lymphatics pass to the aortic, mesenteric, meso-colic, and inferior
pancreatic nodes. The siDlenic, superior pancreatic, inferior pancreatic, and
pancreatico-duodenal nodes are usually grouped together as " lymphoglandulse
pancreatico-l'enales." Anastomoses exist between the lymphatics of the pancreas
and those of the duodenum.
The lymphatics of the spleen (fig. 582) are found only in the form of a sub-
capsular plexus, there being no deep network (Mall). They pass to the splenic
nodes [Igl. pancreatico-lienales], which are variable in number and are situated
LYMPHATICS OF THE KIDNEY
737
along the course of the splenic vessels. In addition to the spleen they drain the
fundus of the stomach and a part of the pancreas.
Fig. 578.— Lymphatics op the Small Intestine. (After Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
{
The Lymphatics of the Excretory Organs and of the Suprarenal
The lymphatics of the kidney.— The lymphatic vessels from the deep capsular
and parenchymatous lymphatics of the kidney run to the nodes of the lumbar
cham (fig. 583). On the right side, part of the nodes concerned lie ventral and
I
738
THE LYMPHATIC SYSTEM
part dorsal to the renal vein; one of the nodes lies as far caudalward as the bifurca-
tion of the aorta; and one or two vessels may pass to pre-aortic nodes. On the
left side the vessels end in four or five nodes of the lumbar group. The efferents
of these nodes pass through the diaphragm and end in the thoracic duct.
The lymphatics of the Suprarenal. — The lymphatic vessels coming from the
capsular and parenchymatous plexuses pass, on the right side, into two or three
anterior para-aortic nodes, and a small retro-venous gland, near the pillar of the
diaphragm; on the left side, into para-aortic nodes, and, in part, through the
diaphragm, in company with the splanchnic nerve, to a posterior mediastinal
Fig. 579. — The Lymphatic Circulation of the Ileo-c^cal Region, Anterior View.
(After Kelly.)
gland, lying between the ninth thoracic vertebra and the aorta. Anasto-
moses occur with the lymphatics of the kidney.
In addition to the capsular lymphatics proper, Kumita describes a subserous
plexus, which is present over both kidney and adrenal, which anastomoses with
the lymphatics of the liver and diaphragm. The efferents of this plexus collect,
on the right side, to a gland placed to the right of the inferior vena cava, anterior
to the right renal vein, and on the left side to a gland anterior to the left renal
vein.
The lymphatics of the ureter. — Sakata has recently studied the lymphatics of
the ureter. They fall into three groups: (1) An anterior (upper) group, which
run to the anterior lumbar nodes, or join the renal lymphatics; (2) a middle
group which pass to the posterior lumbar and interiliac nodes; (3) a posterior
(lower) group which pass to hypogastric nodes and which anastomose with lym-
phatics of the bladder.
LYMPHATICS OF PROSTATE
739
The lymphatics of the bladder. — The collecting vessels from the lower part of
the ventral surface pass to a node of the external iliac group, situated near the
femoral ring and the obturator nerve; those from the upper part of the ventral and
dorsal surfaces pass to the middle node of the middle group of the external ihac
chain, and from the rest of the dorsal surface they pass either to the hypogastric
i
Fig. 580.-
-The Lymphatic Circulation op the Ileo-c^cal Region Posterior View.
(After KeUy.)
nodes or beyond these to the nodes at the bifurcation of the aorta (fig. 584).
In this latter group end also the vessels from the neck of the bladder. Along some
of the lymphatics of the bladder are intercalated lymph-nodes, which have been
termed anterior and lateral vesical nodes.
The lymphatics of the prostate. — The lymphatics of the prostate have been
studied in the dog by Walker and in man by Bruhns. The collecting vessels, sbc
to eight on each side, pass along the prostatic artery to the nodes along the ex-
ternal border of the hypogastric artery. These nodes are connected with those
along the external and common iliac arteries, and it is possible, from an injection
of the prostate, to fill the entire chain of nodes as far as the renal artery. A
trunk from the posterior surface runs up over the bladder and curves outward to
740 THE LYMPHATIC SYSTEM
the middle node of the middle group of the external iliac chain, and still other vessels
from the posterior surface run first downward, pass around the rectum, and then
ascend to the lateral sacral nodes. From the anterior surface a descending duct
may follow the deep artery of the penis, and the internal pudic to the hypogastric
Fig. 581. — The Superficial Lymphatic Netwoek of the Liver. (After Teichmann).
Fig. 682. — Lymphatics of the Periphery of a Pig's Spleen. (After Teichmann.)
nodes (fig. 585) . The lymphatics of the prostate anastomose with those of the
bladder, ductus deferens and rectum.
The lymphatics of the urethra. — 1. In the Male. — The capillary plexus of the
urethra is in the mucous membrane. The collecting vessels from the mucous
LYMPHATICS OF URINARY TRACT
Fig. 583. — Lymphatics of the Kidney. (After Poirier and Cunfio.)
741
Suprarenal artery-
Pre-aorticnode
i
Fig. 584. — Lymphatics of the Bladder. (After Cunco and Marcille.)
External iliac node-
Collecting trunks
of upper dorsal
surface
Collecting trunk of
upper dorsal
surface
Collecting trunk of ,
inferior ventral
surface
Hypogastric node
Hypogastric node
Ureter
Collecting trunks
along inferior
vesical artery
Collecting trunks
to end in the
node of the
promontory
742
THE LYMPHATIC SYSTEM
membrane of the glans follow the dorsal vein. Those from the penile and^mem-
branous portions of the urethra start from the inferior surface and curve around
the corpora cavernosa, as seen in fig. 586, to join the others along the dorsal vein.
These vessels run with the vein to the symphj^sis, where the}' form a plexus in
which there may be some small intercalated nodes. From this plexus vessels
pass in two directions: — (1) Three or four vessels, the crural trunks, pass to the
deep inguinal and external iliac nodes, and (2) one vessel enters the inguinal
canal and ends in one of the external iliac nodes.
The vessels from the bulbar and membranous portions either follow the internal
pudic arterj', or pass to the symphj-sis and end in the external iliac nodes, or pass
onto the surface of the bladder and thence to the external iliac chain. The
Fig. 585. — The Lymphatics of the Prostate. (After Ciin^o and Marcille.)
External iliac / —
nodes |
Retro prostatic
lymphatics
Collecting vessels
from prostate to
Node of the pro-
montory
Lateral sacral
Collecting vessels
from prostate
to node of pro-
montory
Middle hamor-
rhoidal node
and trunks
Ijinphatics of the prostatic portion run with the prostatic ducts. The lymphatics
of the urethra anastomose with those of the bladder and those of the glans.
2. Inthe female the Ij-mphatic vessels of the urethra end in the external iliac
and hypogastric nodes.
Lymphatics of the Rephoductive Org.vns
In the Male (figs. 585, 586, 587)
The IjTQphatics of the external genitaha will be first described and then those
of the internal organs (fig. 589).
The lymphatics of the scrotum form a rich plexus which has been pictured by
Teichmann (fig. 547). The collecting vessels, ten to fifteen on either side, arise
near the raphe and pass to the root of the penis, where some curve lateralward to
the superior medial superficial inguinal nodes; while others, coming from the
lateral surface of the scrotum, pass to the corresponding inferior nodes.
LYMPHATICS OF REPRODUCTIVE ORGAXS
743
Fig. 586. — ^Lymphatics of the Penile axb Membraxous Portioxs of the Urethra. (After
Cuneo and Marcille.)
Collecting trunk
in front of —
symphysis
{
Vessel along inter-
nal mdic artery
Vessel from anterior
— surface of the
prostate
Collecting trunk
behind the
symphysis
Vessel along inter-
nal pudic artery
Fig. 5S7. — ^Ltmphatics of the Glaxs Pexis ix a Xew-borx Child. (Cuneo and Marcille.)
External iliac
node
Node in
abdominal
inguinal ring
Presymphysial'
node
Network ofr^fg^"'--
glans penis '"'
{
744
THE LYMPHATIC SYSTEM
The lymphatics of the penis.— (1) The cutaneous lymphatics form a plexus
from which collecting vessels follow the dorsal vein and end in the superficial
mguinal nodes. (2) The lymphatics of the glans form an exceedingly rich
plexus from which vessels follow the dorsal vein of the penis, as described under
the urethra, and end in the deep inguinal and external iliac nodes. (3) The
lymphatics of the erectile structures are little known.
The lymphatics of the testis are both superficial and deep, the latter being
exceedmgly hard to inject. The collecting vessels follow the spermatic cord and
artery and end in the lumbar nodes.
.—Lymphatics of the Pemnedm. (After Toldt, "Atlas of Human Anatomy," Reb-
man, London and New York.)
Dorsal lymph-vessels of the clitoris
Glans clitoridis
Fig. 688,
Superficial epigastric vein \
Superficial inguinal lymph-nodes
Labium majus
Region of the tuberosity of the ischium /
Fat of ischio -rectal fossa Anus
The lymphatics of the ductus deferens and vesiculse seminales. — In the
ductus deferens only a superficial set has been injected, and its vessels passlto
the external ihac nodes. The plexus of the vesiculaj seminales is double, super-
ficial and deep, and its vessels pass to the external iliac and hypogastric nodes.
In the Fernale
(Figs. 588, 589, 590)
The lymphatics of the vulva.— Throughout the vulva there is an exceedingly
rich, superficial lymphatic plexus, from which collecting vessels pass to the
symphysis and there turn lateralward to the medial superficial inguinal' nodes.
The fact that the capillary plexus is continuous from side to side and that there
is a plexus of the vessels in front of the symphysis, makes the nodes of both sides
liable to infection from a unilateral lesion.
LYMPHATICS OF VAGINA
745
The lymphatics of the clitoris. — The lymphatics of the glans of the clitoris
form an abundant network from which collecting vessels pass toward the symphy-
sis pubis, and thence principally to the deeper inguinal nodes, one or two, however,
passing through the inguinal canal to terminate in the lower external iliac nodes.
The lymphatics of the ovary. — The ovary has a remarkably rich lymphatic
plexus, from which from four to six vessels leave the hilus and follow the ovarian
artery to the lumbar nodes. One vessel may run in the broad ligament to the
internal iliac group.
The lymphatics of the Fallopian tube form three capillary networks from
which collecting vessels run in part with those of the ovary, and in part with the
uterine lymph-vessels.
The lymphatics of the uterus. — According to Poirier, the lymphatics of the
uterus arise from three capillary plexuses, a mucous, a muscular, and a peritoneal.
The collecting vessels from the body of the uterus are in three sets: — (1) Those
from the fundus, consisting of four or five vessels, run lateralward in the suspen-
FiG. 589. — Lymphatics op the Internal Genital Organs in the Female. (After Poirier.
Vena cava-
Kidney
Right renal vein'
(
Right spermatic artery
Lumbar node
Lumbar node —
Anterior crural nerve-
Peritoneum-
Lymphatics in utero-sacral
ligament
Cervical lymphatics—-
Ovary —
Parovarium —
Lymphatics of round ^
ligament
/ — ^Lumbar vein
Spermatic artery
Ureter
Inferior mesenteric artery
Middle lumbar node
Middle sacral artery
Ovarian lymphatics
Pelvic colon
— Lymphatics of the tube
„nterine tube (Falloppii)
sory ligament of the ovary and follow the ovarian vessels to the lumbar and pre-
aortic nodes. They anastomose with the lymphatics from the ovary opposite the
fifth lumbar vertebra; (2) some small vessels from the fundus follow the round
ligament of the uterus and terminate in the inguinal nodes; and (3) others from the
body of the uterus pass laterally with the uterine vessels and terminate in the iliac
nodes.
The collecting vessels from the cervix, five to eight in number, form a large
lymphatic plexus just after leaving the cervix. From this plexus run three sets of
vessels. Two or three vessels pass lateralward with the uterine artery in front of
the ureter, and end in the external iliac nodes; a second set passes behind the
ureter and ends in a node of the hypogastric group, and a third set from the
posterior surface runs downward over the vagina and then backward and upward
to end in the lateral sacral nodes and node of the promontory of the sacrum.
The lymphatics of the vagina (fig. 590) . — -There are two lymphatic plexuses in
the vagina, a superficial and deep — the latter, the mucosal plexus, being ex-
ceedingly rich. The collecting vessels are in three groups. The superior set
drains the upper third of the vagina and takes the same course as those from the
lower cervical portion of the uterus; the middle set follows the vaginal artery to
746 THE LYMPHATIC SYSTEM
the hypogastric nodes; and the inferior set runs to the lateral sacral nodes and to
those of the promontory. The capillary network of the lower part of the vagina
is continuous with the plexus of the vulva, which drains to the inguinal nodes.
Fig. 590. — ^Lymphatics of the Vagina. (After Poirier.)
Utero-vaginal lymphatics
Vaginal lymphatics
(middle)
E. THE LYMPHATICS OF THE LOWER EXTREMITY
1. THE LYMPHATIC NODES OF THE LOWER EXTREMITY
The principal group of nodes of the lower extremity is situated in the in-
guinal region, and hence is known as the inguinal group. It is in many respects
similar to the axillary group, although it is not quite equivalent to it develop-
mentally. The nodes composing it are divisible into a superficial and a deep
group, the former containing many more and larger nodes than the latter.
Furthermore, it is convenient to divide each of these groups into an upper and a
lower set, the dividing line being an arbitrary line drawn horizontally through the
point where the saphenous vein pierces the fascia of the fossa ovalis. The nodes
above this line are termed collectively the inguinal nodes, while those below it
are known as the subinguinal nodes.
The superficial inguinal nodes [Igl. inguinales superficiales] (fig. 591), lie
along the base of the femoral trigone immediately below Poupart's ligament,
superficial to the fascia lata. Then number varies from ten to twenty. They
receive the subcutaneous drainage of the abdominal walls, the gluteal region,
and the perineal region, and their efferents descend to the fossa ovalis, which they
perforate along with the saphenous vein and terminate in the lower external
iliac nodes.
The superficial subinguinal nodes [Igl. subinguinales superficiales], occupy
the lower part of the femoral trigone and receive the entire superficial drainage
of the leg, as well as a few vessels from the gluteal region and from the perineum.
Thek efferents pierce the fossa ovalis and pass partly to the deep subinguinal
nodes and partly directly to the lower external ihac nodes.
LYMPH-NODES OF LOWER LIMB
747
The deep nodes. — The deep nodes are small, and vary from one to three.
They lie medial to the femoral vein, the highest one (node of Cloquet or of
Rosenmiiller) being placed in the femoral ring and being of especial surgical
{
Fig. 591.-
-The Sttpebficial Inguinal Nodes. (After Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Inguinal 1 \
ligament ft vs
(Poupart s)
Inguinal fc\
lymph-nodes^^ ) /^""^
Femoral
artery
Femoral vein
Falciform
margin
Superficial ^ ' \
subinguinal
nod
Great saphen- Tjj^^
ous vein lH IH \i
interest in that, when enlarged, it may simulate a strangulated hernia. The
lowest node is below the point where the lesser saphenous joins the femoral vein.
These deep nodes receive the deep lymphatics of the leg, the vessels from the
glans penis in the male, and the clitoris in the female, and some of the vessels
from the superficial subinguinal nodes. Their efferent vessels enter the external
iliac nodes.
In addition to the inguinal group of nodes there are some other nodes in the
lower limb situated along the course of the deep vessels. Thus there is a node in
the course of the anterior tibial vessels below the knee, and there is a small
(
748
THE LYMPHATIC SYSTEM
group of popliteal nodes [Igl. popliteae], in the popliteal space, which are in the
course of the lesser saphenous vessels, and receive the vessels which accompany
the posterior tibial and peroneal vessels and those which drain the knee-joint.
Fig. 592. — The Superficial Lymphatics op the Lowee Extremity. (After Toldt, "Atlas of
Human Anatomy," Rebman, London and New York.)
Superficial epigastric vein
Inguinal node:
Superficial subinguinal nodes
Great saphenous vein
Accessory saphenous '
2. THE LYMPHATIC VESSELS OF THE LOWER EXTREMITY
As in the upper extremity, the subcutaneous capillary plexus of the lower
varies greatly in complexity, being most abundant in the soles of the feet. The
collecting vessels form two main groups. The medial, larger group follows the
saphenous vein, and ends in the superficial subinguinal nodes, while the lateral
LYMPH-VESSELS OF LOWER LIMB
749
group curves around to join the medial, partly in the leg and partly in the thigh.
Two or three vessels from the heel follow the lesser saphenous vein to the popliteal
space. The vessels from the upper and dorsal part of the thigh curve around on
both sides to reach the superficial inguinal nodes. The vessels of the anus and
Fig. 593. — The Lymphatics of the Back of the Lower Extremity. (After Toldt, "Atlas of
Human Anatomy," Rebman, London and New York.)
Popliteal lymph-nodes—
Small saphenous
Deep lymphatic vessels
perineum, as well as those from the external genitalia, except from the glans penis
or the clitoris, pass to the medial nodes of the superficial inguinal group.
The deep vessels follow the course of the arteries of the leg, those accompany-
ing the dorsalis pedis and anterior tibial arteries coming into relation with the
(
750 THE LYMPHATIC SYSTEM
anterior tibial node, when it is present, and then passing backward to join the
vessels which accompany the posterior tibial and peroneal arteries. These
terminate in the popliteal nodes, from which efferents follow the com-se of the
femoral artery and terminate in the deep inguinal nodes. The deep lymphatic
vessels accompanying the gluteal and obturator arteries pass to the hypogastric
nodes.
Lymphatics of the hip-joint. — According to Clermont, they accompany, in the main, the
arteries about the joint. (1) Satellites of the anterior circumfle.x artery, draining almost the
entire ventral surface, pass to the lateral inferior external iliac node. (2) Satellites of the pos-
terior circumflex artery, draining the dorsal and medial surfaces, empty into the medial inferior
external iliac node, occasionally into one of the deep inguinal nodes. (3) Satellites of the
obturator vessel, draining the round ligament, empty into the obturator or hypogastric nodes.
(4) Satellites of the inferior gluteal vessels, draining the dorsal surface, empty into three small
nodes along the internal pudic and inferior gluteal arteries. Less important ("accessory")
vessels are: satellites of the superior gluteal artery leading to a gluteal node; vessels from the
dorsal surface which cross the lateral border of the pectineus to reach the medial inferior
external iliac node; and vessels from the ventral surface, crossing parallel to the cotyloid notch,
passing under the psoas to the lateral inferior external Uiae or one of the deep inguinal nodes.
Lymphatics of the knee-joint. — According to Tanasesco the lymphatics draining the struc-
tures around the knee-joint in the main follow the arteries about the joint and pass largely to
the more deeply placed of the popliteal nodes. Some (superficial) follow the great saphenous
vein to the subinguinal nodes, and sometimes deep vessels pass the pophteal nodes and, ac-
companying the femoral artery, run to the deep inguinal or inferior external iliac.
References for lymphatic system. — (Development) : Sabin, Amer. Jour.
Anat., vols. 1, 3, 4, 9, also in Keibel and Mall's Human Embryology; Lewis,
Amer. Join-. Anat., vols. 5, 9; Huntington and McClure, Amer. Jour. Anat.,
vol. 10; Clark, E. L., Anat. Record, vol. 6; Clark, E. R., Amer. Jour. Anat.,
vol.13. (Regeneration): Meyer, Johns Hopkins Hosp. Bui., vol. 17. (General):
Bartels, in von Bardeleben's Handbuch d. Anatomic; Sappey, "Description
et Iconographie des Vaisseaux Lymphatiques," Paris, 1885; Teichmann, "Das
Saugadersystem," Leipzig, 1861. (Muscle, etc.): Aagaard, Anat. Hefte, Bd. 47.
(Connective tissue): von Recklinghausen, "Die Lymphgefasse u. ihre Beziehung
zum Bindegewebe," Berhn, 1862. (Stomata): Walter, Anat. Hefte, Bd. 46.
(Lung): Miller, Anat. Rec, vol. 5. (Teeth): Schweitzer, Arch. f. mikr. Anat.,
Bd. 74. (Hoemolyinph glands): von Schumacher, Arch. f. mikr. Anat., Bd. 81.
Tumors): Evans, Beitr.z. klin. Chir., Bd. 78.
i
SECTION VII
THE NERVOUS SYSTEM
Revised for the Fifth Edition
Bt IRVING HARDESTY, A.B., Ph.D.
PBOPESSOR OP ANATOMY, THE TDLANE UNIVERBITT OP LOUISIANA
THE nervous system of man, both anatomically and functionally, is the most
highly developed and definitely distributed of all the systems of the body.
It consists of an aggregation of peculiarly differentiated tissue-elements,
so arranged that through them stimuli may be transmitted from and to all the
other tissue systems or functional apparatuses. It is a mechanism with parts so
adjusted that stimuli affecting one tissue may be conveyed, controlled, modified,
and distributed to other tissues so that the appropriate reactions result. While
protoplasm will react without nerves, while muscle will contract without the
mediation of nerves, yet the nervous system is of the most vital importance to
the higher organisms in that the stimuli required for the functioning of the organs
are so distributed throughout their component elements that the necessary
harmonious and coordinate activities are produced. For this purpose the
nervous sj^stem permeates every organ of the body; nerve cell-bodies, accu-
mulated into groups, receive impulses and give rise to the nerves which ramify
and divide into smaller and smaller branches till the division attains the individual
nerve-fibres of which the nerves are composed, and even the fibres bifurcate
repeatedly before their final termination upon their allotted elements. So
intimate and extensive is the distribution throughout that could all the other
tissues of the body be dissolved away, still there would be left in gossamer its
form and proportions — a phantom of the body composed entirely of nerves.
The parent portion or axis of the system extends along the dorsal mid-line of
the body, surrounded by bone and, in addition, protected and supported by a
series of especially constructed membranes or meninges, the outermost of which
is the strongest. The cephalic end of the axis, the encephalon, is remarkably
enlarged in man, and is enclosed within the largest portion of the bony cavity,
the cranium, while the remainder of the central axis, the spinal cord, continues
through the foramen magnum and lies in the vertebral canal.
The intimate connection of the axis with all the parts of the body is attained
by means of forty-six pairs of nerves, which are attached to the axis at somewhat
regular intervals along its extent. They course from their segments of attach-
ment through the meninges and through their respective foramina in the bony
cavity to the periphery. Of these craniospinal nerves, fifteen pairs pass
through the cranium and are attached to the encephalon, and thirty-one pairs
to the spinal cord. Some of the cranial nerves and all of the thirty-one pairs of
spinal nerves contain both afferent fibres, which convey impulses from the per-
ipheral tissues to the central axis, and efferent fibres, which convey impulses from
the axis to the peripheral tissues. The different pans of nerves possess the two
types of fibres in varying proportions.
Upon approaching the spinal cord, each spinal nerve is separated into two roots
■ — its posterior or dorsal root and its anterior or ventral root. The afferent fibres
enter the axis by way of the dorsal roots, which are, therefore, the sensory roots,
and the efl^erent fibres leave the axis by way of the ventral or motor roots.
As usually studied, the nervous sj'stem is referred to in two main divisions : —
(1) The central nervous system, composed of — (a) The spinal cord, or medulla
spinalis, and (6) the brain or encephalon.
751
752
THE NERVOUS SYSTEM
Fig. 594. — Showing the Ventral Aspect of the Central Nervous System, with the Proxi-
mal Portions of the Cranio-spinal Nerves attached and the Relation op the
Proximal Portion (Gancliated Cord) of the Sympathetic Nervous System. The
Encephalon or Brain is Straightened Dorsalward prom its more Horizontal
Position with Reference to the Spinal Cord. The Spinal Ganglia and the Dorsal
and Ventral roots of the Spinal Nerves may be noted.
(Composite drawing in part after Allen Thompson from Rauber — modified.')
Superior cervical sympathetic
ganglion
Middle cervical sympathetic
ganglion
Inferior cervical sympathetic
ganglion
n I Thoracic nerve
Gangliated cord
~/-~t Cervical nerve
I Lumbar nerve
-] Sacral nerve
VJ Coccygeal nerve
Filum terminale
DEVELOPMENT OF NERVOUS SYSTEM
753
Neurenteric canal
Primitive groove
Body-stalk
754 THE NERVOUS SYSTEM
(2) The peripheral nervous system, composed of — (a) The cranio-spinal
nerves, and (6) the sympathetic nervous system.
All these parts are so intimately connected with each other that the division is
purely arbitrary. The cranio-spinal nerves are anatomically continuous with the
central system; their component fibres either arise within or terminate within
the confines of the central system, and thus actually contribute to its bulk. The
sympathetic system, however, may be more nearly considered as having a
domain of its own. By communicating rami, it is intimately associated with the
cranio-spinal nerves and thus with the central system, both receiving impulses
from the central system and transmitting impulses which enter it. But, while its
activities are largely under the control of the central system, it is possible that
impulses may arise in the domain of the sympathetic system and, mediated by
its nerves, produce reactions in the tissues it supplies without involving the
central system at all. For this reason, as well as because of the structural
peculiarities of the sympathetic system, the nervous system is sometimes divided
into — (1) the cranio-spinal system, consisting of (a) the central system and (b)
the cranio-spinal nerves; (2) the sympathetic nervous system, consisting of its
various peripheral ganglia and their outgrowths forming its plexuses.
Within and closely pro.ximal to the central system or axis are grouped the parent cell-bodies
whose processes comprise the nerve fibres of the cranio-spinal nerves. Other groups of nerve
cell-bodies, distributed in the periphery without the bounds of the central system,, give rise
to the fibres of the sympathetic nerves and plexuses. Any group of such cell-bodies situated
in the periphery, whether belonging to the cranio-spinal or sympathetic system, is known as a
ganglion.
THE DEVELOPMENT OF THE NERVOUS SYSTEM
The essential elements of the nervous system, the nerve cell-bodies and the
essential portion of all nerve fibres, central, cranio-spinal and sympathetic, de-
velop from one of the embryonic germ layers, the ectoderm, and all arise from a
given region of that germ layer. Further a small portion of the supporting tissue
of the nervous system, the neuroglia, is of the same origin.
In its development the nervous system is precocious. It is the first of the functional
apparatuses to begin differentiation and is the first to acquire its form. The first trace of
the embryo appears on the developing ovum as the embryonic area, and the rapidly proliferating
cells of this area shortly become arranged into the three germinal layers: — the outer layer or
ectoderm, the middle layer or mesoderm, and the inner layer or entoderm. Early in the process
of this arrangement there is formed along the axial fine of the embryonic area a thickened plate
of ectodermal cells, the neural plate. In the further proliferation of these cells, the margins
of the neural plate, which he parallel with the long axis of the embryonic area, rise shghtly above
the general surface, forming the neural folds, and the floor of the plate between the folds under-
goes a slight invagination, the process resulting in the neural groove (fig. 595, A, A', B and B^).
As development proceeds and the embryonic area assumes the form of a distinct embryo, the
neural folds or lips of the groove graduaUy converge, and beginning at the oral end, finally unite.
Thus the groove is converted into the neural tube, extending along the dorsal mid-hne and en-
closed within the body of the embryo by the now continuous ectoderm above (fig 595, C^,
D and D').
For a time the neural tube remains connected with the inner surface of the general ectoderm
along the line of fusion by a residual lamina of ectodermal cells. This lamina is known as the
ganglion crest (neural crest). It is a product of the proliferation of the ectoderm during the
process of fusion, consists of the cells which composed the transition between the closing lips
of the original groove and the general ectoderm or skin, and whose fusion aided in the closure
of the tube. The ectoderm soon becomes separated from the ganghon crest and the cells of the
crest become distinctly differentiated from the cells of the neural tube. The essential elements
of the entire nervous system together with the neuroglia are derived from the cells of the neural
tube and the cells of the ganglion crest.
Fig. 595. — Dorsal Surface Views of Human Embryos and Diagrams of Transverse
Sections Illustrating the Development or the Neural Tube.
A, dorsal view of human embryo at beginning of infolding of neural plate to form neural
groove. Amnion partly removed. (Graf Spee, from Keibel and Mall.) A', diagram of
portion of a transverse section of an embryo as though taken through A at the fine a'.
B, dorsal view of human embryo of 7 somites, neural tube not yet closed, Mall Collection.
(Dandy, from Keibel and Mall.) B', diagram of portion of a transverse section of an embryo
as though taken through B at the line b'. C'-, diagram of portion of a transverse section of
an embryo as though taken through D at fine c'. D, dorsal view of human embryo of 8
somites, 2.11 m.m. long, neural tube closed except at caudal end. (KoUmann, from
Keibel and Mall.) D', diagram of a portion of a transverse section of an embryo as though
taken through D at^line d^
DEVELOPMENT OF NERVOUS SYSTEM
755
Before the caudal extremity of the tube is entirely closed, its oral end undergoes marked
enlargement and becomes distended into three vesicular dilations, the anterior, middle, and
posterior primary brain vesicles. The anterior of these primary vesicles give off a series of
secondary vesicles and by these, followed by further dilations, flexures of its axis, and by
means of locahzed thickenings of its walls, the portion of the tube included in the three primary
vesicles develops into the encephalon or brain of the adult. The remainder of the tube becomes
the spinal cord. This latter portion retains the simpler form. By the proliferation and migra-
tion laterally of the cells lining this portion of the tube, there results a comparatively even
bilateral thickening of its walls so that the mature spinal cord retains a cylindrical form through-
out its length.
The proliferating and migrating cells of the wall of the neural tube are known as germinal
cells. The products of their division are apparently indifferent at first, but later they become
differentiated into two varieties: (1) spongioblasts, or those cells which will develop into neu-
roglia, and (2) neiiroblasts, or those which will increase in size, develop processes and become
nerve cell-bodies.' As described below, the processes given off by a neuroblast are of two general
characters: (1) a long process or axone which goes to form nerves, nerve roots, and nerve fasciculi,
and (2) dendritic processes which are numerous, branch much more frequently and extend but
a short distance from the cell-body. An adult cell-body with all its processes is known as a
neurone and the neuroblasts of the developing system become transformed into the neurones
Fig. 596. — Diagrams of Tkansvebse Sections or Embryonic Spinal Cords showing the
Migration of the Cells op the Ganglion Crest to form the Spinal and Sympathetic
Ganglia and the Origin of the Dorsal and Ventral Roots of the Spinal Nerves.
A, a- stage following D' of fig. 595. B, a later stage in which the ganglia and the components of
the nerve are assuming their form resulting from the further migration and from processes
being given off by the neuroblasts.
— Spinal ganglion
Sympatheti
of the varying sizes, shapes, and arrangements of processes characteristic of different divisions
and localities of the nervous system. Usually the fii-st process to be noted is that which will
become the axone or nerve fibre.
Neurones whose cell-bodies belong to the peripheral nervous system are not developed
within the walls of the neural tube or central nervous system at all. These, comprising the
spinal ganglion neurones and those of the sympathetic system, are derived from the cells of the
ganglion crest. The wedge-shaped lamina of cells, comprising the ganghon crest, through
rapid cell division, gradually extends outward and ventralward over the surface of the neural
tube along either side. Soon the prohferation becomes most active in regions corresponding to
the mesodermic somites or primitive body segments and this, together with the stress of the
growing length of the body, results in the ganghon crest (originally a lamina) becoming seg-
mented also. The segments or locahsed cell masses thus formed are the beginning not only of
the spinal ganglia, but also of the ganglia of the entu-e sympathetic system. The cells of the
crest migrate to assume a more lateral position, and then occurs a separation of their ranks.
A portion of them remain in a dorsolateral position near the wall of the neural tube and develop
into the neurones of the spinal ganglia (the sensory neurones of the spinal nerves), but others
wander further out into the periphery and become the neurones of the sympathetic. Certain
of those of this more nomadic group of cells settle within the vicinity of the vertebral column and
by sending out their processes, form the gangliated cord or the proximal chain of sj^mpathetic
ganglia; others migrate further, but in more broken rank, and become the gangha of the pre-
vertebral plexuses (as the cardiac, coeliac and hypogastric plexuses), or the scattered intermediate
chain of ganglia; while still others wander into the very walls of the peripheral organs and
756
THE NERVOUS SYSTEM
Fig. 597. — ^Diagram Showing the Chief Paths of Migration of the Cells from
THE Ganglia of the Spinal and Cranial Nerves to form the Adult Sympathetic
System (After Schwalbe, modified.)
Carotid plexus
Vagus
I. cervical spinal
Middle cervica'
Inferior cervical
ganglion
Sympathetic trunl
I. lumbar spinal
ganglion
I. sacral spinal
ganglion
Ciliary ganglion
Otic ganglion
Spheno-palatine
Submaxillary
Pharyngeal plexus
Pulmonary plexus
Cardiac plexus
(Esophageal
plexus
Coronary plexus
Gastric plexus
Cceliac (solar)
plexus
Submucous and
myenteric plex-
uses (Meissner
and Auerbach)
Aortic plexus
Inferior mesenteric
plexus
Pelvic plexuses
Coccygeal ganglion
DEVELOPMENT OF NERVOUS SYSTEM
757
occur singly or in groups in such plexuses as those of Auerbach and Meissner, within the tunics
of the walls of the alimentary canal. Scattered along between these proximal, intermediate,
and distal groups there are to be found small straggling gangha, many of which contain so few
cell-bodies that they are indistinguishable with the unaided eye. All these sympathetic neu-
rones, however, are always either directly or indirectly anatomically associated with and
Fig, 598. — Diagrams of Oral Portion of Human Neural Tube Showing the Three
Primary Brain Vesicles and Some of the Secondary Vesicles Derived from Them.
A, diagram of dorsal view of early stage. B, lateral view at about the third week. C, lateral
view at about the eighth week. After His, modified, m, mamillary vesicle; i, infundibular
recess; o, oKactory vesicle.
Anterior primary veeicle
^ optic veeic]
"middle primary vesicle
-'Posterior primary vesicle
Auditory vesicl
Middle primary vesicle ^
epiphysis
Anterior primary
Telencephalon^
spinal cord
-cerebellum
^ ;*Posteriorprimary
vesicle
medulla
olfactory vesicle- -^'•''
optic vesicle"' /
Pontine fltaure
cervical flexure
Fig. 599. — Diagrammatic Sagittal Section of a Vertebrate Brain. (After Huxley.)
4, fourth ventricle; s, cerebral aqueduct; 3, third ventricle.
Corpora quadrigemina Mid -brain Epiphysis
Lateral ventricle
Cerebral hemisphere
Corpus striatum
Pons Varoli
(.hind -brain J
Cerebral peduncle
Thalamus [ Hypophysis Foramen of Monro
Hypothalamus
Fig. 600.— Diagrammatic Horizontal Section of a Vertebrate Brain. (Afte Huxley.)
4, fourth ventricle; 3, third ventricle.
Metencephalon Thalamus
Medulla oblongata ^^
Cerebellum
—Lateral ventricle
Lamina terminalis
Corpus striatum
Mid-brain Epiphysis Foramen of Monro
largely under the control of the neurones of the central system through central visceral eferent
fibres passing to them by way of the rami communicantes or by way of the peripheral distri-
bution of the spinal nerves.
The ganglia of the sensory portions of all those cranial nerves attached to the inferior of
the main divisions of the brain and all the sympathetic ganglia of the head have an origin
similar to that of the spinal and sympathetic gangha in the remainder of the body.
The behavior of the walls of the three primary vesicles, into which the oral end of the neural
tube is converted, is much more complex than in case of the spinal cord. Their walls do not
758
THE NERVOUS SYSTEM
thicken uniformly and, to give rise to the form of the adult brain, the anterior and the posterior
of the three vesicles give off secondary vesicles.
The walls of the posterior primary vesicle give rise to the posterior of the main divisions
of the brain, the hind brain or rhombencephalon, the cerebellum developing from the anterior
portion only of its dorsal wall, and the medulla oblongata and pons from its ventral wall. Its
cavity persists and enlarges into the fourth ventricle of the adult, while the posterior portion
of its dorsal wall does not develop functional nervous tissue at all but persists as a thin membrane
known as the chorioid tela of the fourth ventricle. The cells which form the ganglia of the audi-
tory and vestibular nerves arise from the dorsolateral regions of this vesicle.
From the middle primary vesicle comes the mid-brain or mesencephalon, the corprora quad-
rigemina [colliculi] developing from its entire dorsal wall and the cerebral peduncles occupying
its ventral wall. The constriction between the middle and posterior vesicles becomes the
isthmus of the rhombencephalon.
The anterior or first primary vesicle undergoes greater elaboration than either of the other
two. At an early period it gives off a series of secondary vesicles or diverticula. First, two
ventrolateral outpouchings occur, the optic vesicles, which later become the optic stalks and
optic cups of the embryo. A medial protuberance becomes evident in its antero-dorsal wall
and from each side of this quickly starts a lateral diverticulum. The two lateral diverticula
thus arising from the protuberance are the beginning of the two cerebral hemispheres or the
telencephalon, and the vesicular cavities contained persist as the two lateral ventricles of the
brain. Soon, each of these vesicular rudiments of the hemispheres gives off ventrally from its
anterior part a narrow tube-like diverticulum, each continuous into the parent primary vesicle.
These are the olfactory vesicles which are transformed into the olfactory bulbs and olfactory
tracts^ of the adult encephalon. (See fig. 598, B. and C.) As development proceeds, the
cavities of the olfactory vesicles become occluded in man. However, in many of those animals
Fig. 601. — Diagram op Mesial Section op the Human Beain showing the Segments and
THE Flexures and the Expansion of the Cebebral Hemispheres over the Other
Portions op the Beain. The Thalamus is not shown.
Cerebral hemisphere
Corpus callosum
i- Septum pellucidum
Third ventricle
Fourth ventricli
Hypophysis
Cerebral peduncle
Pons 1
(
Medulla oblongata !
Spinal cord
in which the olfactory apparatus attains greater relative development than in man, these cavi-
ties persist as the olfactory ventricles. The cavities of the optic vesicles never persist as ven-
tricles in the adult. They form stalks which represent the future courses of the optic nerves,
while from their extremities are developed the retina;, portions of the ciliary bodies and portions
of the iris of the ocular bulbs.
In addition to that which forms the cerebral hemispheres, the remaining portion of the
anterior primary vesicle becomes the diencephalon or inter-brain. The lateral walls of this part
thicken to form the tiialami, the posterior end of its dorsal wall gives off a secondary vesicle
which becomes the pineal body or epiphysis, and from its ventral waU projects the infundibular
recess which becomes the posterior lobe of the hypophysis with its infundibulum and tuber
cinereum.
The adult human brain is characterised by the preponderant development of the cerebral
hemispheres. The secondary vesicles forming these expand till, held within the cranial cavity,
the hemispheres come to extend posteriorly completely over the thalamencephalon and the
mesencephalon and even overlap the cerebellum to its posterior border. Their cavities, which
persist from their origin from the anterior primary vesicle, are correspondingly large (the lateral
ventricles) and comprise two of the four ventricles of the adult brain. The third ventricle be-
comes a narrow cavity situated between the two thalami. It represents the original cavity
of the anterior primary vesicle from which the structures above mentioned arose as secondary
vesicles. It remains continuous with the lateral ventricles by the two inter-ventricular foramina,
known also as the /ora?«ma of mom'o, one into each cerebral hemisphere. The fourth ventricle
of the adult represents the cavity of the posterior primary vesicle and comes to he between
the cerebellum and medulla oblongata, since the cerebellum likewise extends posteriorly from
its region of origin. The cavity of the middle primary vesicle becomes the cerebral aqueduct,
or aqueduct of Sylvius, passing under the corpora quadrigemina and connecting the fourth or
posterior ventricle with the third.
Development of the nerve fibres. — All axones begin as outgrowths or processes of the cyto-
plasm of neuroblasts. Most of such processes are sent out at a very early stage in the develop-
ment of the nervous system and extend to the tissues they are to innervate when these tissues
are as yet quite near the neural tube. Then, as the structures of the body elaborate and assume
DEVELOPMENT OF NERVOUS SYSTEM
759
their final forms and positions more remote from the central nervous system, the axones ter-
minating in them must necessarily grow and be drawn out with the structures. At need,
later axones are sent out by neurones developing later to supply the growth demands. Such
axones follow the general paths made by those aheady extending to the tissues requiring them.
Being processes of the cytoplasm of the cell-body, the growth and Ufe of all axones (and dendrites)
is under the control of the nucleus in the cell-body. They grow by absorbing nourishment,
or having added to them substances, from the tissue stroma through which they pass, which
stroma may be either ectodermal or mesodermal in origin.
The great majority of axones in the central nervous sytem and all in the peripheral system
have sheaths about them. The sheath is an acquired structure and is not added till a rela-
tively late period of development. These sheaths are of two general varieties, sheaths con-
FiG. 602. — Diagram illusteating the Gross Divisions of the Central Nervous System.
Olivary body—
--,___ Mesencephalon j
(mid-brain) J
^« Pons (Varoli)
Myelencephalon
(medulla oblongata)
//-"•Pars cervicalis
-Pars thoracalis
-""Pars lumbalis
Spinal cord
(medulla spinalis)
sisting merely of a fibrous coat with the nuclei belonging to it, and sheaths in which there has
been added a coating of fat or myeUn, medullary sheaths. A nerve fibre consists of an axone and
its sheath whether meduUated or non-medullated.
In the embryo, axones are given off from the developing neurones at a time when the
entire ectodermic neural tube and embryonic ganglia and the mesodermic tissue surrounding
them are each void of definite cell boundaries, each being a continuous mass of nucleated
protoplasm, a syncyiium. From these syncytia are developed the fibrous connective tissues
of the later framework supporting the nervous system. Of this, the fibrous tissue, neuroglia,
is derived from the ectodermal syncytium, while the white and elastic fibrous tissues are derived
from the mesodermal or mesenchymal syncytium. Before any connective tissue fibrils are
developed in either syncytium, before and at the time of the ingrowth of blood-vessels into the
developing gangha and the neural tube from the mesenchyme about them, there occurs an
invasion of the mesenchymal syncytium into the ectodermal sjmcytium. This invasion
occurs both as independent ingrowths and fusions at the periphery of the neural tube and by
760
THE NERVOUS SYSTEM
the mesenchymal tissue being carried in by the ingrowing blood-vessels. After the mixture of
the nuclei resulting from this fusion of the syncytia from the two sources, nuclei of mesodermal
origin cannot be distinguished from those of ectodermal origin. Further, axones outgrowing
from the embryonic ganglia and neural tube carry with them adhering portions of the ectodermal
syncytium into the surrounding mesenchymal (fig. 603).
As development proceeds further, each syncytium becomes resolved into a reticulum of
granular endoplasmic processes, containing the nuclei, with transparent exoplasm occupying
its meshes. Fibrils soon form in the exoplasm and from these develop the connective-tissue
fibres, whether neurogha in the central nervous system or mesenchymal fibrous tissue both without
and within it. Certain of these fibrils of course surround the axones imbedded among them
and from condensations of such fibrils are derived the fibrous sheaths of the axones, the sheath
nuclei being acquhed from the adjacent nuclei of the original syncytium. These sheaths
become more dense or pronounced as the axones extend and the fibrous tissue increases with
growth, but there are always present fine marginal fibrils by which the sheaths grade into the
looser fibrous tissue about them. It is generally beUeved that the tissue giving rise to these
Fig. 603. — Drawings Illustrating the Origin of the Axone and the Development of
THE Medullary Sheaths.
A, ventral portion of transverse section of an embryonic spinal cord involving portion of
periphery of future ventral horn and part of the mesenchymal (mesodermal) syncytium out-
side the external limiting membrane of the cord. B, later stage of ventral root (peripheral)
axone with myehn droplets adhering to it and fibrillated stroma surrounding it. C, stage
in which myehn droplets, supported by fibrils of stroma, have increased and accumulated
to form a practically continuous myehn or meduUary sheath. D, final stage with medullary
sheath of even thickness, showing a node, and showing a neurilemma, sheath nucleus and
fibrous framework of the myehn ("neurokeratin") derived from the fibrils of the original
stroma.
Myel'n
- Neurilemma
Mesenchymal
syncytium
axone sheaths is of mesodermal origin. However, in amphibian larvae, Harrison has shown that
some sheath nuclei at least are derived from the nuclei of the ectodermal syncytium of the
ganghon crest, and Neal has noted in elasmobranchs the fact that nuclei migrate from the ven-
tral waU of the neural tube along with the axones growing out to form the ventral roots of the
spinal nerves. Whether aU or any of these nuclei are originally ectoderrnal, and, if so, whether
such ectodermal tissue gives rise to all axone sheaths, especiaUy in the higher animals, are
questionable contentions.
Axones possessing only fibrous sheaths comprise the non-meduUated nerve fibres. The
majority of the sympathetic fibres are of this variety, and Ranson has found numerous non-
meduUated fibres present in the spinal nerves. The generally accepted form of non-medullated
sympathetic fibres may be seen in fig. 609, C.
MeduUated fibres are those which possess an investing coat of fat or myehn in addition to
the fibrous sheath. Most of the fibres in the central nervous system and most of those belong-
ing to the cranio-spinal nerves proper acquire myehn sheaths. Myehn begins to appear upon
axones shortly after the beginning development in the syncytium of the fibrils of the fibrous
connective tissue, and thus after the beginnings of what will become the fibrous sheaths. The
fibrous portions of the sheaths in the central nervous system develop less rapidly and are far
more scant than those of the medullated fibres of the peripheral nerves. Probably because
of this, it has been claimed that myehn begins to appear on the axones of the central system
before the appearance of the fibrous sheath. In man, the first appearance of myelin occurs at
about the fourth month, but myelinisation is not completed tiU after birth. The cranio-spinal
nerves contain completely meduUated fibres before the central system does.
Myehn first appears as small droplets adhering to the axone at irregular intervals. These
droplets increase in size and number and gradually accumulate to form a practicaUy continuous
sheath of fat immediately investing the axone. They probably result from the coalescence of
finer droplets floating in the surrounding fibrillated stroma. However, coUecting upon the axone,
DEVELOPMENT OF NERVOUS SYSTEM
761
the myelin retains the form of an emulsion, and as it increases in amount it incloses the adjacent
fibrils which serve as a framework supporting the droplets of the emulsion in its meshes. Thus
supported, the increasing myelin does not inclose the adjacent nuclei and endoplasm of the
original syncytium. Probably because of the fibrous support of the myehn thus obtained,
medullating fibres may be often seen presenting the beaded appearance shown in fig. 603, C,
instead of an even distribution of the emulsion after it has become continuous along the axone.
The "beads" probably represent the uneven beginning of the accumulation indicated in B
of this figure. Increasing further, the myelin becomes a cyhnder of even thickness, the adjacent
nuclei being pressed away against its surface and the adjacent fibrils also condensed upon it.
There is good reason to believe that the fibrous portion of the sheath, the primilive sheath
or neurilemma, of the meduUated axone arises as a condensation of the fibrils of the surrounding
stroma during development, that the sheath cells represent certain of the nearest nuclei in-
corporated from the original syncytium, and that the so-called neuro-keralin of the myehn
represents the fibrous framework of the myehn inclosed by it during its accumulation upon the
Fig. 604. — Showing Some of the Varieties op the Cell-bodies op the Neurones
OP the Human Nervous System, including the Dendrites and Small Portions op
THE Axones. Axone Sheaths not included.
A. From spinal ganghon. B. From ventral horn of spinal cord. C. Pyramidal cell from cere-
bral cortex. D. Purkinje cell from cerebellar cortex. E. Golgi cell of type II from spinal
cord. E. Fusiform cell from cerebral cortex. G. Sympathetic, a, axone; d, dendrites; c,
collateral branches; ad, apical dendrites; hd, basal dendrites; c, central process; p, peripheral
process.
axone. The theory that the myehn arises as a differentiated portion of the axone and the theory
that it is formed by the neurilemma have been advanced. That it is accumulated from the
immediately surrounding fluid of the stroma and adheres to the axone, added droplets coalescing
there, in preference to other tissue elements because of some physical or chemical peculiarity
of the axone, is more probably correct.
As the medullary sheath approaches completeness, constrictions may be observed at more
or less regular intervals at which the myelin emulsion is absent. There are the nodes of
Ranvier. The process by which they arise is not clearly understood. While the fibre is growing
in length, new myehn is added at the nodes. The internodal segments of the sheath increase
in length with age, and each segment may possess from one to several sheath nuclei.
In adolescence, fibres whose medullary sheaths are in various stages of completeness may
be found both in nerve bundles in the central system and in the cranio-spinal nerves, and in
both, the sheaths of some axones certainly never acquire mj'ehn. Also, in the adult, fibres
whose medullary sheaths present the beaded appearance may be observed, probably repre-
senting cases of arrested accumulation of myelin. According to Westphal there is a slight in-
crease in the thickness of the sheath with age. Larger axones acquire thicker sheaths of myeUn
than smaller ones. Some fibres of the sympathetic system are meduhated but in such the
myelin sheath is relatively thinner than in the cranio-spinal system. Beaded sheaths are
frequent in sympathetic rami, though non-meduUated fibres are most abundant.
762 THE NERVOUS SYSTEM
FUNDAMENTALS OF CONSTRUCTION
The functionally mature nervous system consists of peculiarly differentiated
essential cell elements held in place by two forms of supporting tissue and supplied
with abundant blood-vessels.
The nervous element is distinguished from all other units of the structure of
organs in that its cell-body gives off outgrowths or processes of peculiarly great
length and characteristic form. Knowledge of the possible lengths and com-
plexity of these processes is comparatively recent and, to include them together
with their parent cell-body, which has long been known as the 7ierue cell, the
term neurone is used. The neurone, therefore, may be defined as the nerve cell-
bodj' with all its processes, however numerous and far reaching they may be. As
a class of tissue elements, all neurones possess characteristics distinguishing
them from other tissue elements, but the varieties within this class vary greatly.
They vary in form both according to function and according to their locality in
the nervous sj^stem. They vary in different animals, those in the higher animals
being more complex in form. Fig. 604 gives illustrations of the external form of
the cell-body of a few of the types found in the human nervous system.
The cell-body of the neurone gives off two general types of processes,
■dendrites and axones:
(1) The dendritic processes or dendrites. These are the more numerous, the shorter, and
the more frequently branching processes. They branch dichotomously and with rapid decrease
in diameter as tliey branch. They serve to increase the absorbing surface of the cell-body
for purposes of nutrition. Nerve impulses transmitted to the neurone are received by them and,
therefore, they also serve to increase the recipient surface of the neurone. They never acquire
meduUary sheaths. Since they convey impulses toward the cell-body, they are known as
cellipital processes. Their absorbing and receptive surfaces are further increased by the presence
of thickly placed, very minute projections known as "pin-head processes" or gemmules.
(2) The axone (neuraxis). Each neurone possesses properly but one of these processes.
It arises from the cell-body more abruptly and quickly becomes smaller in diameter than are
most dendrites before the latter decrease by branching. It is the longest process, in most cases
very much longer than dendrites. Computation shows that some axones may contain nearly
200 times the volume of the parent cell-body of the neurone. Occasionally the axone gives off
a few small branches near the cell-body. These are known as collaterals and are given off at
practically right angles instead of dichotomously. Regardless of its branching, the axone
maintains a practically uniform diameter throughout its long course. Its usual nervous func-
tion is to convey the impulses away from the cell-body, either to transmit them to other neu-
rones by contact upon their dendrites, etc., or to appropriate elements of the other tissue
systems of the body. Thus the axones are the cellifugal processes. There is one weU-known
partial exception to this, namely, a part of the axone of the spinal ganglion type of neurone,
the peripheral sensory neurone. The axone of this bifurcates a short distance from the cell-
body into a peripheral and a central branch. See fig. 604, A, and fig. 610. The peripheral
branch collects sensory impulses from the tissues of the body, the skin, etc., and, in conveying
them to the central system, must necessarily convey them toward the cell-body as far as the
point of bifurcation. Thence the impulse goes on in the central branch, stiU toward the central
system but now, in conformity, away from the cell-body of the neurone. While the continued
vitality of the axone is dependent upon the cell-body, in the peculiar case of the spinal ganglion
neurone the impulse does not necessarily pass through the ceU-body. Experiments with the
lower animals have shown that the impulses pass in the fibre from the peripheral tissues to the
central system when the cell-bod^' has been cut away.
Terminations of axones. — At its final termination, well beyond its collateral branches and
usually a considerable length from its ceU-body, the axone practically always divides into two
or more terminal branches, and each of these breaks up, now dichotomously, into numerous
terminal twigs. These terminal twigs are known as telodendria. Telodendria vary in number
and characterof form according to the tissues in and upon which they terminate. Functionally,
they are of three classes: Those terminating upon and in the other (peripheral) tissues of the
body are either (1) sensory or (2) motor. In order to transmit impulses from one neurone to
another, telodendria of the axone of one neurone are placed in contact with the dendrites or
cell-body of another neurone forming (3) synapses. Upon approaching its termination, every
axone loses its sheath, its telodendria being necessarily bare.
Sensory or afferent axones, receiving impulses from the skin or other epithelial surfaces,
break up into very numerous telodendria each of which terminates directly upon the surface
of the epitheUal cell, such as the cells of the germinative (Malpigin) layer of the skin or
those of its basal or columnar layer. Such telodendria are known as free terminations. Free
terminations are also to be found in the connective tissues of the body. A second varietj' of
peripheral termination of afferent axones is the encapsulated for jn. These are known as 'end
organs' and 'corpuscles' and are named according to their complexity and position. Three
of the different forms of them are shown in fig. 605, B, C, and D. These are always situated
in fibrous connective tissue from which their capsules are derived. Their most elaborate form
is the lamellated or Pacinian corpuscle. Besides the motor axones terminating upon the
fibres of voluntary or skeletal muscle, sensory impulses are carried from this tissue and one of
the forms of telodendria for this purpose terminates upon the muscle fibre. This is known as
PERIPHERAL TERMINATIONS OF AXONES
763
Fig. 605.— Showing Some Varieties op Pekipheeal Terminations of Axones.
'Free termination' in epithelium (after Retzius). B. Krause's corpuscle from conjunctiva
(after Dogiel). C. Meissner's corpuscle from skin (after Dogiel). D. Pacinian corpuscle
(after Dogiel). E. Termination upon tendon sheath (Huber and DeWitt). F. Neuro- mus-
cular spindle (after Ruffini). G. Motor termination upon smooth muscle-cell. H. Motor
'end-plate' on skeletal muscle fibre (after Bohmandvon Davidoff). a, axone; t, telodendria.
a yf:._
764
THE NERVOUS SYSTEM
the 'neuromuscular spindle.' In it, the axone penetrates the sarcolemma and breaks into
telodendria which coil spirally about the muscle fibre. The most extensive and elaborate form
of sensory telodendria are those which spread out in plate-form upon tendons sheaths.
Fig. 606. — Schemes showing Two Forms of Synapses or the Termination of Axones upon
Cell-bodies of other Neurones.
A. In ventral horn of spinal cord. B. In spinal ganglia.
Fig. 607. — Drawings Illustrating two General Types of Arrangement op Neuro-
FIBRILL^ IN the CeLL-BODIES OF NeURONES.
A, cell-body of spinal-ganglion neurone. B, selected "giant pyramidal cell" from cerebral
cortex, human, a, axone.
Motor peripheral axones terminate upon muscle and upon the secretory cell of glands
(secretory axones). The motor cranio-spinal axones terminate upon skeletal (voluntary) muscle
fibres and upon the cell-bodies of sympathetic neurones, the axones of which latter termmate
upon cardiac muscle, smooth muscle fibres, and (secretory) in glands. Upon skeletal muscle,
the terminal branch of the axone loses its sheath and breaks up into numerous telodendria which
themselves branch and show very evident, irregular varicosities, the whole of which spread out
STRUCTURE OF THE NEURONE
765
in plate-form, and lie in contact with the substance of the muscle fibre. In man and all mammals,
the area covered is usually somewhat oval and is marked by a granular differentiation of the
muscle substance. This with the telodendria is known as a motor end-plate. The telodendria
of sympathetic axones ending upon cardiac and smooth muscle fibres are fewer and simpler than
those of cranio-spinal axones upon skeletal muscle. They consist of a few fine fibrils, with very
small varicosities along them and at their ultimate terminations, which run longitudinally along
the muscle fibre in close relation with its substance. Those upon gland cells are similar in
character except that they often form a loose pericellular plexus about and upon the cell. The
varicosities of telodendria are sometimes called end-feet and closer study of them has shown that
they themselves consist of fine plexuses of the neuro-fibrils described below as contained in the
cell-body of the neurone and extending throughout all its processes. Quite recently Boek has
found that a sympathetic axone may sometimes accompany a cranio-spinal axone to an end
plate on a skeletal muscle fibre.
^Synapses. — Every functionally complete nerve pathway consists of two or more neurones
arranged in series. Very often, the series consists of many more than two, the impulses being
transmitted from neurone to neurone. The axone, bearing the impulse away from the cell-body
of one neurone, gives off terminal branches, each of which loses its sheath and breaks up into
telodendria which twine themselves upon the dendrites or cell-body of another neurone. The
mpulse is transferred from one neurone to another by means of contact rather than by direct
anatomical continuity of the parts of the two neurones. Such terminations of axones are known
as synapses.
Fig. 608. — Drawings Illustrating the Abundance and General Arrangement op the
Tigroid Masses in Cell-bodies of Neurones in Resting Condition.
A, cell-body from spinal ganglion. B, large cell-body from ventral horn of spinal cord, a,
axone. d, dendrites.
Capsule
'd
a-
B
In the terminal arrangement of the telodendria, synapses assume forms varying from com-
pact "pericellular basketa" and "climbing fibres" to the more open arborisations composed of
fewer twigs in simpler arrangements, "end-brushes." In case of the spinal ganghon type of
neurone, the cell-body of the majority of which has no dendritic processes, the telodendria of the
visiting axone form an anastomosing pericellular plexus inclosing the entire cell-body. This and
the simple end-brush form of synapses are illustrated in fig. 606. It should be mentioned that,
contrary to the general belief that impulses are transmitted by simple contact of the neurones in
the series, it has been claimed that the ultimate twigs of the telodendria frequently penetrate the
substance of the receiving cell-body and are fused in continuity. If during the processes of
growth this becomes true, instead of being an appearance produced by the technique employed,
it is better considered as merely an exception to the general rule.
Internal structure of the neurone. — The ceU-body of the neurone consists of a large, spherical,
vesicular nucleus and a cytoplasm continuous into its axone and dendritic outgrowths. Its
nucleus is further characterized by having most usually but one nucleolus, large, spherical and
densely staining, situated in a karyoplasm containing otherwise a remarkably small amount of
chromatin. Of the cytoplasm, the two most interesting structures are its fibrillar and its gran-
ular components.
The fibrillar structure, known as the neuro-fibrillce, represents a growth and elaboration of
the spongioplasniic reticulum of the original, embryonal cell. The filaments increase in thick-
ness during the development of the neurone, and, in the sending out of its processes, the meshes
of the original reticulum become so drawn out in the processes as to give the appearance of a more
or less parallel arrangement of threads. The reticular or net-like arrangement is usuallj- more
nearly retained in the cytoplasm immediately about the nucleus, since here the stress of the out-
growing processes is less directly applied. In the cell-body of the spinal ganglion type of neu-
rone, when no dendrites are given off, the net-like arrangement is apparent tlu-oughout the cyto-
plasm except in that region giving rise to the axone. On the other hand, in the typical so-called
"pyramidal cell" of the cerebral cortex, from which two chief processes, the axone and the apical
766
THE NERVOUS SYSTEM
dendrite, are given off from opposite poles, the more reticular arrangement about the nucleus is
often practically obliterated by the opposing growth stress.
So manifest does the parallel appearance of the neuro-fibrillfe in the processes often become
that it has been interpreted as a series of individual and independent fibrils. In the application
of gold chloride and similar methods to the neurones of lower forms, the reduced reagent is often
precipitated upon the fibrils in parallel, seemingly independent lines. And, assuming the ex-
istence of independent fibrils, it has been contended that the neurone is not the functional unit
of the nervous system but is itself composed of numerous functional units, individual fibrils,
each for the conduction of nerve impulses. More recent and trustworthy methods, however,
show that the neuro-fibrillaj retain their original reticular form, the threads anastomosing in
all planes, and that the meshes of the net may, in the processes, be so drawn in one direction
that a parallel appearance predominates. Further, it is now held that the neuroplasm, or the
more fluid substance in which the fibrils lie throughout, is capable, and probably fully as cap-
able, of conducting impulses as the fibrils.
Of the granules in the cytoplasm, the most interesting are those first described in detail by
Nissl. These are the most abundant of those in the cell-body and are known as tigroid masses
or Nissl bodies. They consist of numerous basophilic granules collected into clumps or masses of
varying size. They are known to disappear during fatigue of the nervous system and they are
more abundant in animals after a period of rest. They are distributed throughout the cyto-
plasm of the cell-body with the interesting exception that they are not found in the axone nor in
the immediate vicinity of its place of origin from the cytoplasm, leaving a free region known as
the axone hillock. As accumulated masses, they show characteristic shapes and arrangement
Fig. 609. — Showing Pieces of Axones.
A. From a cranio-spinal nerve. B. From the spinal cord. C. From the sympathetic, a,
axones; m, medullary sheath; w, nodeof Ranvier;s, neurilemma or sheath of Schwann with
occasional sheath-nuclei.
which are interpreted as signifying the shapes and arrangement of the spaces or meshes they
occupy in the reticulum of the neuro-fibriUai. In cell-bodies of the varieties found in the ventral
horns of the spinal cord or in the cerebral and cerebellar cortex, for example, the masses situated
immediately about the nucleus are smaller, more numerous and of irregular shape. Nearer and
in the beginnings of the dendrites, they are larger and mostly of fusiform or diamond shape.
Farther out in the dendrites, they become more and more thin and attenuated; and in the dis-
tant reaches of the dendrites they are invisible or absent. In the cell-body of the spinal ganglion
they are of irregular shape, smaller and more numerous throughout the cytoplasm, being slightly
smaller and more thickly placed in the immediate vicinity of the nucleus. In all neurones
several hours post-mortem, they appear in fewer and larger masses and it was in this condition
that Nissl originally described them in man. Closely examined, the masses of all sizes are found
to be accumulations of finer granules. Functionally they are supposed to be of nutritive signi-
ficance, substances in unstable chemical equiblibrium, energy stored in the cytoplasm, capable
at need of being split into simpler forms usable in the activities of the neurone. The fact that
tigroid masses are absent from the axone hillock, the axone, and the distant reaches of the den-
drites may signify that the substance is chiefly present here only in the spUt and usable form.
Also, in the axone especially, the neurofibrilla? are so closely arranged that the meshes of their
net here are too small to contain masses of appreciable size. Close examination of the axone
hillock and longitudinal sections of the axone in deeply stained preparations usually show a few
very minute basophilic granules.
Sheaths of the axone. — The great majority of axones acquire sheaths about them which
isolate and protect them in their course through other tissues or in company with other axones.
A nerve fibre is an axone together with its sheath. In transverse sections, the axone comprises
CONNECTIVE TISSUE OF NERVOUS SYSTEM
767
the central portion of the nerve fibre or its so-called "axis-cylinder." It is of course the essen-
tial portion of the fibre. As noted above in describing their development, nerve fibres are classified
according to the character of the sheaths. Those which possess sheaths of myehn, a peculiar
form of fat, are known as medullaled fibres, and those in which the sheaths are merely mem-
branes of condensed fibrous tissue, void of myelin, are non-medullated fibres. A medullated
fibre also possesses a fibrous membrane outside its myeUn sheath, known as the neurilemma or
sheath of Schwann. The neurilemma is of the same origin and general structure as the sheath
of the non-medullated fibre, and both possess nuclei scattered along thern. Medullated fibres,
at more or less regular intervals, show constrictions at which the myelin sheath ceases, but
over which the neurilemma continues. These constrictions are the 7iodes of Ranvier. The mye-
lin is in the form of an emulsion, whose fat droplets are supported in a fine fibrous reticulum
(neurokeratin), while the neurilemma without serves to hold it in place. The neurilemma pos-
sesses from one to three or four sheath nuclei between adjacent nodes of Ranvier.
There is no sharp line of separation between medullated and non-medullated fibres, for in
any locality there may be found axones in all degrees of medullation. Most of the fibres
Fig. 610. — Diagram op Transverse Section op Spinal Cord with Roots of Spinal Nerve
AND Neighbouring Ganglia Attached, Illustrating Simplest Forms op Neurone
Chains.
Fasciculus cuneatus
Cephalic branch of spinal ganglion neurone
belonging to the sympathetic system (processes of sympathetic neurones) are non-medullated,
but both partially medullated and completely medullated sympathetic fibres may be found.
(See fig. 609.) The myehn sheaths of completely medullated sympathetic fibres are always
thinner and less well developed than those of meduUated cranio-spinal fibres. Most of the
fibres belonging to the cranio-spinal nerves and to the central nervous system are medullated,
but among the fibres belonging to either there are to be found numerous non-medullated fibres.
As indicated in fig. 609, nodes of Ranvier are absent in the medullated fibres of the central
system.
In all the higher vertebrates, the myehn sheath always begins on the axone a short distance
from its parent cell-body. The neurilemma of the medullated and the fibrous membrane of
the non-medullated fibre are each faintly continuous with the fibrous connective tissue sur-
rounding it, and, in the cranio-spinal and sympathetic ganglia, in which each cell-body of the
neurone has a fibrous capsule about it, the fibrous membrane or the neurilemma, as the case
may be, is directly continuous into the capsule of the ceU-body. Upon approaching its final
termination, in other tissues or upon the dendrites or cell-body of other neurones, the nerve
fibre always loses its sheath, the telodendria of the axone always being bare when placed in
contact with the other element. In losing the sheath, the myelin sheath, if present, always
ceases and the fibrous membrane becomes continuous with the tissue investing the receiving
element, whether the capsule of the ganglion cell, the sarcolemma of the skeletal muscle fibre,
the corium of the skin, or the connective-tissue capsule of the encapsulated terminal corpuscle,
The connective tissue of the nervous system is of two main varieties — while fibrous connec-
tive tissue and neuroglia. White fibrous tissue alone supports and binds together the peripheral
system, and it is the chief supporting tissue of the central system. As connective tissues, these
two varieties are quite similar in structure, each consisting of fine fibriUiE, either dispersed or in
bundles, among which are distributed the nuclei of the parent syncytium. In both tissues
nuclei are frequently found possessing varying amounts of cytoplasm which has not yet been
transformed into the essential fibrils.
In addition to its enveloping membranes, the three meninges, which are of white fibrous
tissue, the white fibrous tissue supporting the central system within is quite abundant. It is aU
768 THE NERVOUS SYSTEM
sent in from without, either as ingrowths of the developing pia mater, the most proximal of the
membranes, or is carried in with the blood-vessels, of the walls of which it is an abundant
component. Practically, the neuroglia as a connective tissue proper differs from white fibrous
tissue only in origin and in its chemical or staining properties. Based upon the latter, there are
methods of technique by which the two may be distinguished. White fibrous tissue is derived
from the middle germ layer or the mesoderm, while neurogha comes from the ectoderm. The
epithelium lining the central canal of the spinal cord and the ventricles of the encephalon, with
which the canal is continuous, is the remains of the mother tissue of the neuroglia, and in the
adult is the only vestige representing its origin. The cells of this epithelium are known as
ependymal cells, and they are usually classed as a variety of neuroglia.
Axones, with their meduUated or non-meduUated sheaths (nerve fibres)
comprise all nerves in the periphery and all nerve tracts in the central system.
White substance [substantia alba] ("white matter") consists of a portion of
nervous tissue in which medullated fibres predominate. The myelin sheaths,
being in the form of a fat emulsion, reflect the entire spectrum and thus appear
white.
Grey substance [substantia grisea] ("grey matter") is a portion of nervous
tissue in which medullated axones do not predominate. Thus sympathetic
ganglia and sympathetic nerves may be grey, though the term is usually applied
to grey portions of the central system, such as the cerebral cortex, the central
grey column of the spinal cord, etc. Such grey regions contain more cell-bodies
of neurones than other regions, though at least half of their volume may consist
of neuroglia, white fibrous connective tissue, blood-vessels, and axones of both
varieties.
Neurone chains. — As noted above, the numerous neurones comprising the nervous system
are functionally and anatomically related to aU the other tissues of the body and to each other.
A functionally complete nerve pathway extends from the tissue in which the nerve impulse is
aroused to the tissue in which a resultant reaction occurs. It is known that the simplest
possible of such paths necessarily comprises at least two neurones. The great majority involve
a greater number. The axone of one neurone bearing impulses from the peripheral tissue
transfers the impulses to the dendrites or cell-body of another by synapsis, and the axone of this,
in the same way, transfers them to another and so on till the final neurone receives the impulses
and the telodendria of its axone transfer the impulse to the tissue element which reacts in re-
sponse to the stimulus brought. Neurones are thus linked together in chains. A neurone
chain may be defined, therefore, as a number of neurones associated with each other in series
to form a functionally complete nerve pathway. Examples of the simplest forms of neurone
chains as contained in the spinal cord are illustrated in fig. 610. An impulse aroused in the skin
is borne by the spinal ganglion neurone to the spinal cord where, in the left half of the figure,
telodendria of one of the terminal branches of its axone form synapses with a neurone in the
ventral horn, and the axone of this bears the impulse out of the spinal cord to transmit it proba-
bly direct to skeletal muscle. This arrangement involves but two neurones and is supposed
to be relatively rare. In the right half of the figure, a third neurone is seen interposed. This is
a neurone, numerous in grey substance everywhere, whose axone is relatively short and branches
frequently, making possible several synapses in the near neighbourhood of its parent cell-body.
Its type is referred to as the Golgi neurone of type II. This interposed, gives a chain of three
neurones between the origin of the impulse in the periphery and the contraction of muscle in
response. Simple chains like these can result only in reflex activities and such chains are often
called reflex arcs. Another chain is indicated in the figure in which the reflex action involves
involuntary or smooth muscle. This must involve at least one sympathetic neurone, and, should
the Golgi neurone of type II form synapses with the ventral horn neurone involved, a chain
composed of four neurones results. In the more extensive and complex neurone chains, such
as those in which the impulse from the skin, as above, ascends to the cerebral cortex and the
resultant muscular contraction is thrown under cerebral control, each of the several neurones or
links in the series is not only referred to by name according to the position of its cell-body, but
each is often called according to its order in the series, as "neurone of first order," "second
order," "third order," etc.
A given axone may break into a considerable number of branches each of which forms
synapses with a different second neurone, or, if peripheral, the telodendria of each branch may
terminate upon a separate peripheral tissue element. Thus, a given impulse aroused in a
peripheral tissue element may be transmitted to an ever increasing number of neurones,
and the initial neurone may comprise the first link in a number of neurone chains. Such is
quite general in the structural plan of the nervous system throughout. It is thought possible
to consider each neurone interposed in a chain as a separate source of energy, a sort of relay
in the nerve path; that the impulse passing through the axone is gradually weakened in over-
coming resistance, but, when transferred to another neurone, it incites a splitting into usable
form of the substance represented by the tigroid masses and thus a liberation of energy or a
reinforcement of the impulse. Further, thus is made possible the economy of one neurone
serving as a hnk in a number of nem-one chains.
The axones (nerve fibres) taking part in the various neurone chains course in bundles of
varying size, the larger of which have names. And there is a general tendency with axones of
the same function and the same origin to course in company with each other. A fibre bearing
impulses from the peripheral tissues to the central system is an afferent fibre or sensory fibre. A
fibre bearing impulses out of the central system to peripheral tissues is an efferent fibre or motor
RELATIONS OF NEURONES
769
fibre. Efferent fibres which bear impulses to skeletal muscle are known as somatic ejferent
fibres, while those which terminate upon the cell-bodies of sympathetic neurones and thus bear
impulses destined for smooth muscle, cardiac muscle and glands (secretory) are visceral or
splanchnic efferent fibres.
A nerve is a closely associated aggregation of parallel nerve fibres coursing in the periphery.
It may be spinal, cranial or sympathetic according to its attachment or according to the origin
of the majority of its fibres. It may contain several functional and structural varieties of fibres.
The spinal nerves contain all structural varieties. Nerve roots are those bundles of fibres which
join to form a nerve. Most of the cranial nerves have but one root of origin. Nerve roots, in
their turn, are formed by the junction of smaller root-filaments. Nerve branches result from
the division of the nerve, the separation of its component fibres into separate bundles. Some
branches are of sufficient size and significance to be called nerves and given separate names.
The smaller branches are called rami, twigs, etc.
In the central system, a given bundle of fibres is called a fasciculus, while two or more adja-
FiG. 611. — Diagram of.Transveese Section op Medulla Oblongata, Illustrating Nuclei
OF Termination and Nuclei or Origin.
cent fasciculi com'sing parallel to each other comprise a funiculus, a bundle of bundles. The.
central nervous system is bilaterally symmetrical throughout its length. A bundle of fibres
arising from cell-bodies situated on one side and crossing the mid-line transversely to terminate
in the opposite side is a commissure. The commissures vary greatly in size and contain fibres
crossing in both directions. Scattered fibres which cross the mid-line are commissural fibres.
Fibres of varying lengtli, arising from cell-bodies situated in one locality of the central sj-stem,
which do not cross the mid-Une, but terminate in other localities of the same side, above and
below the level of their origin or in a different region of the same level, form association fasciculi.
The shortest association fasciculi, not extending bejj^ond the bounds of a given division of the
central sj-stem, are known as fasciculi proprii. When bundles of the same origin, functional
direction and significance, running one on either side of the mid-line, cross the mid-line they
are said to decussate and the crossing is known as a decussation. In the decussations, the direc-
tion of the crossing is oblique rather than transverse.
The cell-bodies of neurones whose axones go to form certain nerve roots, fasciculi and certain
commissures show a tendency to accumulation in localized masses. In the peripheral system,
such an accumulation of cell-bodies is known as a ganglion; in the central system such is distin-
guished as a nucleus. Thus, there are the sympathetic ganglia which give rise to sympathetic
nerves and sympathetic roots of nerves; and on the beginning of each spinal nerve there is a
spinal ganglion which gives rise to the afferent fibres of its dorsal root and in its nerve trunk.
There are ganglia on the cranial nerves which give rise to the afferent or sensory axones in them
and which are of the same significance as the spinal ganglia. Every ganglion, therefore, has
770 THE NERVOUS SYSTEM
connected with it bundles of nerve fibres. Some of these fibres bear impulses from neighboring
ganglia or from the tissues of the neighboring organs and transmit them to the cell-bodies of the
ganglion ; others arise from the cell-bodies in the ganglion and bear impulses to the central system
or, in case of the sympathetic, to other ganglia or to the tissues of the peripheral organs. Nec-
essarily, the larger the ganglion, the larger will be the bundles of fibres connected with it.
Nuclei may be considered in two general classes: (1) Recipient nuclei or nuclei of termina-
tion, and (2) Nuclei of origin.
A nucleus of termination is an accumulation of cell-bodies in which the axones of a given
fasciculus or of a nerve root terminate, that is, ceU-bodies which, by synapses, receive the im-
pulses borne by the terminating axones. In most cases the impulses transferred to a nucleus so
named are sensory in character. The nucleus may be considered as a defined region in which
neurones of the next order are interpolated in a given nerve pathway or system of neurone
chains. Fasciculi in the spinal cord which bear impulses to the cerebrum have their nuclei
of termination in the meduUa oblongata, and the sensory or afferent axones of the cranial
nerves find their nuclei of termination upon entering the central system.
A nucleus of origin is an accumulation of ceU-bodies of neurones which give origin to the
axones going to form a given nerve root or a fasciculus. Strictly speaking, a nucleus of ter-
mination for one nerve tract is the nucleus of origin for another, the next link in the neurone
chain. However, the term is commonly used to distinguish a group of cell-bodies giving rise to a
motor nerve tract. Thus each motor cranial nerve has its nucleus of origin within the central
system. The central grey substance of the spinal cord is in the form of a column continuous
throughout the length of the cord and so the cell-bodies in the ventral horns of this column which
give rise to the motor or afferent roots of the spinal nerves are not considered as grouped into
nuclei of origin, one for each of the motor roots.
The dorsal root of each spinal nerve is afferent or sensory in function and its axones arise as
processes of cell-bodies comprising the spinal ganglion of the nerve. The afferent or sensory
fibres of the cranial nerves arise as processes of ceU-bodies comprising the gangha of the cranial
nerves, which ganglia are, in development and character, exactly homologous to the spinal
ganglia.
The ventral root of each spinal nerve is efferent or motor in function and its fibres arise as
processes of cell-bodies situated in the ventral horn of the grey substance of the spinal cord.
The efferent or motor fibres of the'cranial nerves arise as processes of ceU-bodies accumulated as
nuclei of origin in the grey substance of the encephalon, and homologous with those cell-bodies
of the ventral horns of the spinal cord which give origin to the ventral-root fibres.
The general relation of the cerebrum (which includes the mesencephalon) to the remainder
of the nevous system is a crossed relation. Neurone chains from the general body to the cere-
brum, via the spinal nerves and cord and via the cranial nerves and medulla oblongata and pons
of one side, cross the mid-line to terminate in the opposite side of the cerebrum. Axones, and
neurone chains, arising in response in one side of the cerebrum, likewise usually decussate in
descending to terminate in the respective regions of the opposite side.
Many of the names given nervous structures, prior to 1850 especially, instead of suggesting
something of their functional or anatomical significance, indicate nothing more than active
imaginations for accidental resemblances between the various structures of the nervous system
and objects in ordinary domestic environment. Also, quite often the name given a structure is
merely the name of some anatomist associated with it. The much needed elimination of these
old non-descriptive names is proving a very slow process. Attempts have often increased the
difficulty by making necessary the use of several names for a given structure instead of one. The
most recent and concerted attempt, the nomenclature known as the BNA (anatomical names
chosen by a commission appointed for the purpose which convened in Basle in 189.5), has been
adopted by modern text-books. It is here used in the form of the English equivalents of the
Latin terms, except in cases of those Latin terms which have become so commonly used as to be
considered words incorporated into the English language. The BNA has retained manj' of the
old names and, since a name should indicate something of the locality and significance of the
structure to which it is applied, it is not yet wholly satisfactory throughout. In applying the
names of a few fasciculi, the BNA in the following pages is slightly modified by so compounding
the name that the first word in the compound indicates the locality of origin of the fasciculus and
the second, the locahty of its termination. Thus, "Dorsal spino-cerebellar fasciculus" indicates
the more dorsally coursing of the fasciculi which arise from cell-bodies in the spinal cord and
terminate in the cerebellum. This principle appUes to many of the BNA names without change,
as "lateral cerebrospinal fasciculus."
THE CENTRAL NERVOUS SYSTEM
The central nervous system [systema nervorum centrale] or organ is an
aggregation of nuclei, fasciculi and commissures — a large axis of grey and white
substance situated in the dorsal mid-line of the body — and the bundles of fibres
connecting it with the tissues of other systems and with the peripheral ganglia are
of necessity correspondingly large. So numerous are the axones connecting it
and so intimately are its neurones associated that a disturbance affecting any one
part of the system may extend to influence all other parts. The enlarged
cephalic extremity of this central axis, the brain or encephalon, is a special ag-
gregation of nuclei and masses of grey substance, many of which are much larger
than any found in the periphery.
MORPHOLOGY OF SPINAL CORD 771
In the study of the central nervous system its enveloping membranes or
meninges are met with first, and logically should be considered first, but since a
comprehensive description of these membranes involves a foreknowledge of the
various structures with which they are related, it is more expedient to consider
them after making a closer study of the entire system they envelop.
For convenience of study, the central nervous system is separated into the
gross divisions, spinal cord and brain (encephalon) as illustrated in fig. 602.
Each of these divisions will be subdivided and considered with especial reference
to its anatomical and functional relations to the other divisions and the inter-
relations of its component parts.
I. THE SPINAL CORD
The spinal cord [medulla spinalis] is the lower (caudal) and most attenuated
portion of the central nervous system. It is approximately cylindrical in form
and terminates conically. Its average length in the adult is 45 cm. (18 in.) in the
male and 42 cm. in the female. It weighs from 26 to 28 grams or about 2 per
cent, of the entire cerebro-spinal axis.
After birth it grows more rapidly and for a longer period than the encephalon, increasing
in weight more than sevenfold, while the brain increases less than half that amount. Its specific
gravity is given as 1.038.
The Line of division between the spinal cord and the medulla oblongata is arbitrary. The
outer border of the foramen magnum is commonly given, or, better, a transverse line just below
the decussation of the pyramids. Lying in the vertebral canal, the adult cord usually extends
to the upper border of the body of the second lumbar vertebra. However, cases may be found
among taller individuals in which it extends^'no farther than the last thoracic vertebra. With
increase in stature, its actual length increases, but the extent to which it may descend the verte-
bral canal decreases. Up to the third month of intra-uterine life it occupies the entire length
of the vertebral canal, but owing to the fact that the vertebral column lengthens more rapidly
and for a longer period than does the spinal cord, the latter, being attached to the brain above,
soon ceases to occupy the entire canal. At birth its average extent is to the body of the third
lumbar vertebra.
External Morphology of the Spinal Cord
In position in the body, the spinal cord conforms to the curvatures of the
canal in which it lies. In addition to the bony wall of the vertebral canal, it is
enveloped and protected by its three membranes or meninges, which are con-
tinuous with the like membranes of the encephalon: first, the pia mater, which
closely invests the cord and sends ingrowths into its substance, contributing to its
support; second, the arachnoid, a, loosely constructed, thin membrane, separated
from the pia mater by a considerable subarachnoid space ; thnd, the dura niater,
the outermost and thickest of the membranes, separated from the arachnoid by
merely a sHt-hke space, the subdural space.
The intimate association of the central system with all the peripheral organs is
attained chiefly through the spinal cord, and this is accomplished by means of
thirty-one pairs of spinal nerves, which are attached along its lateral aspects. The
nerves of each pair are attached opposite each other at more or less equal intervals
along its entire length, and in passing to the periphery they penetrate the men-
inges, which contribute to and are continuous with the connective-tissue sheaths
investing them. Each nerve is attached by two roots, an afferent or dorsal root,
which enters the cord along its postero-lateral sulcus, and an efferent or ventral
root, which makes its exit along the ventro-lateral aspect.
With its inequahties in thickness and its conical termination the spinal cord is
subdivided into four parts or regions: — (1) The cervical portion, with eight pairs
of cervical nerves; (2) the thoracic portion, with twelve pairs of thoracic nerves;
(3) the lumbar portion, with five pairs of lumbar nerves; and (4) the conus
meduUaris, or sacral portion, with five pairs of sacral and one pair of coccygeal
nerves. From the termination of the conus meduUaris, the pia mater continues
below in the subarachnoid space into the portion of the vertebral canal not
occupied by the spinal cord, and forms the non-nervous, slender, thread-like
terminus, the filu7n terminale. This becomes continuous with the dura mater at
its lower extremity.
772
THE NERVOUS SYSTEM
In the early fetus the spinal nerves pass from their attachment to the spinal
cord outward through the intervertebral foramina at right angles to the long axis
of the cord, but, owing to the fact that the vertebral column increases consider-
ably in length after the spinal cord has practically ceased growing, the nerve-roots
become drawn caudad from their points of attachment, and, as is necessarily
the case, their respective foramina are displaced progressively downward as the
termination of the cord is approached, until finally the roots of the lumbar and
sacral nerves extend downward as a brush of parallel bundles considerably
below the levels at which they are attached. This brush of nerve-roots is the
Cauda equina. The dura mater, being more closely related to the bony wall of the
canal than to the spinal cord, extends with the vertebral column and thus en-
velops the Cauda equina, undergoing a slightly bulbous, conical dilation which
decreases rapidly and terminates in the attenuated canal of the coccyx as the
coccygeal ligament.
The enlargements. — Wherever there is a greater mass of tissue to be in-
nervated, the region of the nervous system supplying such must of necessity
possess a greater number of neurones. Therefore, the regions of the spinal cord
associated with the skin and musculature of the regions of the superior and
Fig. 612.— Dorsal View of Portion of Spinal Cord in Position in Vertebral Canal
Dura mater spinalis — -^fe^V{?/ "^T^felf^'" ■^^"^chnoidea spinalis
■ --■* Lower cervical region
^ Spinal nerve
Thoracic region
inferior limbs are thicker than the regions from which the neck or trunk alone are
innervated. Thus in the lower cervical region the spinal cord becomes broadened
into the cervical enlargement, and likewise in the lumbar region occurs the Imnbar
enlargement. The spinal nerves attached to these regions are of greater size
than in other regions.
The cervical enlargement [intumescentia cervicalis] begins with the third
cervical vertebra, acquires its greatest breadth (12 to 14 mm.) opposite the lower
part of the fifth cervical vertebra (origin of the sixth cervical nerves), and extends
to opposite the second thoracic vertebra. Unlike the lumbar enlargement, its
lateral is noticeably greater than its dorso-ventral diameter.
The lumbar enlargement [intumescentia lumbalis] begins gradually with the
ninth or tenth thoracic vertebra, is most marked at the twelfth thoracic vertebra
(origin of the fourth lumbar nerves), and rapidly diminishes into the conus
medullaris.
Both the lumbar and thoracic regions are practically circular in transverse section. Neither
diameter of the lumbar is ever so great as the lateral diameter of the cervical enlargement.
The thoracic part attains its smallest diameter opposite the fifth and si.xth thoracic vertebrae
(attachment of the seventh and eighth thoracic nerves.)
The enlargements occur with the development of the upper and lower limbs. In the embyro
they are not evident until the limbs are formed. In the orang-utan and gorilla the cervical
enlargement is greatly developed; the ostrich and emu have practically none at all.
Surface of the spinal cord. — The cord is separated into nearly symmetrical
right and left halves by the broad anterior median fissure into which the pia mater
is duplicated, and opposite this, on the dorsal surface, by the posterior median
sulcus. Along the lower two-thirds of the cord this sulcus is shallowed to little
SURFACE OF SPINAL CORD
773
more than a line which marks the position of the posterior median septum; in
the medulla oblongata it opens up and attains the character of a fissure. Each
of the two lateral halves of the cord is marked off into a posterior, lateral, and
anterior division by two other longitudinal sulci. Of these, the postero-lateral
sulcus occurs as a shght groove 2 to 3| mm. lateral from the posterior median
sulcus, and is the groove in which the root filaments of the dorsal roots enter the
cord in regular linear series. The ventral division is separated from the lateral
Fig. 613. — Drawing prom Specimen showing Cauda Equina, the Roots op Certain of
THE Spinal Nerves which form it, and its Accompanying Dura Mater. (Dorsal aspect.)
V / -Dura mater spinalis
I Lumbar enlargement
Conus meduUaris
Filum terminale
Coccygeal ligament (filum
matris spinalis)
by the antero -lateral sulcus. This is rather an irregular, linear area than a
sulcus. It is from 1 to 2 mm. broad, and represents the area along which the
efferent fibres make their exit from the cord to be assembled into the respective
ventral roots. This area varies in width according to the size of the nerve-roots,
and, like the postero-lateral sulcus, its distance from the mid-line varies according
to locality, being greatest on the enlargements of the cord. In the cervical region,
and along a part of the thoracic, the posterior division is subdivided by a delicate
longitudinal groove, the postero-intermediate sulcus, which becomes more evident
774
THE NERVOUS SYSTEM
towardjthe medulla oblongata and represents the line of demarcation between the
fasciculus gracihs and the fasciculus cuneatus. Occasionally in the upper cervical
region a similar line may be seen along the ventral aspect close to the anterior
Fig. 614. — Posterior and Anterior Views of the Spinal Cord. (Modified from Quain.)
Clava ^,
Funiculus cuneatus'
Postero -median sulcus f
Postero-Iateral sulcus
Postero-lateral sulcus- -
Postero-median sulcus ^l}-i
Cervical
enlargement
I/Umbar
enlargement
Olivary body
Lateral funiculus
Decussation of pyramids
I- ^U Anterior median fissure
Antero-Iateral sulcus
(Line of ventral nerve-
roots)
Anterior median fissure
median fissure. This is the antero-intermediate sulcus, forming the lateral
boundary of the ventral cerebro-spinal fasciculus.
Collectively, the entire space between the posterior median sulcus and the line
of attachment of the dorsal roots is occupied by the posterior funiculus; the
lateral space between the line of attachment of the dorsal and that of the ventral
GREY SUBSTANCE OF SPINAL CORD
775
roots, by the lateral funiculus; and the space between the ventral roots and the
anterior median fissure, by the anterior funiculus. Each of these funiculi is
subdivided within into its component fasciculi.
The dorsal and ventral nerve-roots are not attached to the cord as such, but are
first frayed out into numerous thread-like bundles of axones which are distributed
along their lines of entrance and exit. These bundles are the root filaments
[fila radicularia] of the respective roots. The fila of the larger spinal nerves are
fanned out to the extent of forming almost continuous lines of attachment, while
in the thoracic nerves there are appreciable intervals between those of adjacent
roots. Throughout, the intervals are less between the fila of the ventral than
between those of the dorsal roots.
Internal Structure of the Spinal Cord
By reflected light masses of medullated axones appear white in the fresh, and
such masses are known as white substance. The spinaal cord consists of a
continuous, centrally placed column of grey substance surrounded by a variously
thickened tunic of white substance. The closely investing pia mater sends
Fig. 615.-
-A, Ventral, and B, Dorsal, Views op Portion op Spinal Cord showing
Modes op Attachment op Dorsal and Ventral Roots.
Antero-Iateral sulcus (line of ventral roots)
/'^Anterior median fissure
Posteriormedian sulcus
/ Posterior in-
numerous ingrowths into the cord, bearing blood-vessels and contributing to its
internal supporting tissue. The volume of white and of grey substance varies
both absolutely and relatively at different levels of the cord. The absolute
amount of grey substance increases with the enlargements. The absolute
amount of white substance also increases with the enlargements coincident with
the greater amount of grey substance in those regions. The relative amount of
white substance increases in passing from the conus medullaris to the medulla
oblongata, due to the fact that the ascending and descending axones associating
the cord with the encephalon are the one contributed to the cord and the other
gradually terminating in it at different levels along its entire descent.
The grey substance. — In the embryo all the nerve-cells of the grey substance
are derived from the cells lining the neural tube, and in the adult the column of
grey substance, though greatly modified in shape, still retains its position about
the central canal. In transverse section the column appears as a grey figure of
two laterally developed halves, connected across the mid-line by a more attenu-
ated portion, the whole roughly resembling the letter H. The cross-bar of the H
is known as the grey commissure. Naturally, it contains the central canal, which is
quite small and is either rounded or laterally or ventrally oval in section, according
to the level of the cord in which it is examined. The canal continues upward, and
in the medulla oblongata opens out into the fourth ventricle. Downward, in the
extremity of the conus medullaris, it widens slightly and forms the rhomboidal
sinus or terminal ventricle, then is suddenly constricted into an extremely small
776 THE NERVOUS SYSTEM
canal extending a short distance into the filum terminale, and there ends blindly.
The grey commissure always lies somewhat nearer the ventral than the dorsal
surface of the cord, and itself contains a few medullated axones which vary in
amount in the different regions of the cord. The medullated axones crossing the
mid-line on the ventral side of the central canal form the ventral or anterior white
commissure ; those, usually much fewer in number, crossing on the dorsal side of
the central canal, form the dorsal or posterior white commissure. These two
commissures comprise fibres crossing in the grey substance as distinguished from
others which cross in the white substance dorsal and ventral to them. The axones
of these commissures serve in functionally associating the two lateral halves of the
grey, column.
Each lateral half of the grey column presents a somewhat crescentic or comma-
shaped appearance in transverse section, which also varies at the different levels
of the cord. At all levels each half presents two vertical, well-defined horns,
themselves spoken of as columns of grey substance. The dorsal horn [columna
posterior] extends posteriorly and somewhat laterally toward the surface of the
cord along the line of the postero-lateral sulcus. It is composed of an apex and a
neck [cervix columnse posterioris].
In structure the apex is peculiar. The greater portion of it consists of a mass of small
nerve-cells and neurogha tissue, among which a gelatinous substance of questionable origin
predominates, giving the horn a semi-translucent appearance. This is termed the gelatinous
substance of Rolando, to distinguish it from a similar appearance immediate^ about the central
canal, the central gelatinous substance. The apex of the dorsal horn is widest in the regions
of the enlargements, especially the lumbar, and the gelatinous substance of Rolando is most
marked in the cervical region. In these regions the cervix consists of a slight constriction of
the dorsal horn between the apex and the line of the grey commissure. In the thoracic region,
however, the base of the cervix is the thiclcest part of the dorsal horn. This thickness is due to
the presence there of the nucleus dorsalis, or Clarke's column — a column of grey substance
containing numerous nerve-cells of larger size than elsewhere in the dorsal horn, and extending
between the seventh cervical and third lumbar segments of the cord. Tapering finelj' at its
ends, this nucleus attains its height in the lower thoracic or first lumbar segment. About the
ventro-lateral periphery of the nucleus dorsalis are scattered nerve-cells of the same type as
contained in it. These cells ai'e sometimes distinguished as Stilling's nucleus, though Clarke's
column was also described by Stilling. They are more numerous about the lower extremity
of the nucleus dorsalis, and they continue to appear below its termination in the lumbar region.
The ventral horn [columna anterior] of each lateral half of the grey figure is
directed ventrally toward the surface of the spinal cord, pointing toward the
antero-lateral sulcus. It contains the cell-bodies which give origin to the efferent
or ventral root axones, and these axones make their emergence from the spinal
cord along the antero-lateral sulcus. The ventral horns vary markedly in shape
in the different regions. In certain segments each ventral horn is thickened later-
ally and thus presents its two component columns of grey substance : the lateral
horn [columna laterahs], a triangular projection of grey substance into the
surrounding white substance, in line with or a little ventral to the line of the grey
commissure; and the ventral horn proper [columna anterior], projecting ventrally.
In the mid-thoracic region the lateral horn is relatively insignificant, and the
anterior horn is quite slender; in the cervical and lumbar enlargements both horns
are considerably enlarged.
The grey substance is not sharply demarcated from the white. In the
blending of the two there are often small fasciculi of white substance embedded
in the grey, and likewise the grey substance sends fine processes among the axones
composing the white substance. Such processes or grey trabeculse are most
marked along the lateral aspects of the grey figure and present there the appear-
ance known as the reticular formation. The reticular formation of the spinal
cord is most evident in the cervical region (fig. 616).
Minute structure. — The large cell-bodies of the ventral horn as a whole are divisible into
four groups, only three of which are to be distinguished in the mid-thoracic region of the spinal
cord: — (1) A ventral group of cells, sometimes separated into a ventro-lateral and a ventro-
medial portion (see figs. 616, 619), occupies the ventral horn proper, is constant throughout
the entire length of the cord, and contributes axones to the ventral root, most of which probably
supply the muscles adjacent to the vertebral column; (2) a dorso-medial group of cells, situated
in the medial part of the ventral horn, just below the level of the central canal, gives origin to
axones some of which go to the ventral root of the same side, but most of which cross the mid-
line vi& the anterior white commissure, either to pass out in the ventral root of the opposite
side or to enter the white substance of that side and course upward or downward, associating
with other levels of the cord. Some of its axones terminate among the cells of the ventral horn
WHITE SUBSTANCE OF SPINAL CORD 111
in the same level of the opposite side; (3) a lalEral group of cells, sometimes separated into a dorso-
lateral and a ventro-lateral portion, occupies the lateral column or horn, and is best differentiated
in the cervical and lumbar enlargements. Most of the axones arising from its larger cells are
contributed to the ventral root of the same side, and such axones probably supply the muscles
of the extremities. Some of those from its ventral portion are distributed to the muscles of
the body-wall; the dorso-lateral portion is that part of the lateral column \vhich persists
throughout the cord, and is considered as supplying the visceral efferent fibres in the ventral
roots. (4) an intermediate group, occupying the mid-dorsal portion of the ventral horn.
Axones arising from its cells are probably seldom contributed to the ventral root, but instead
course wholly within the central nervous system. Some pass to the opposite side of the cord,
chiefly via the anterior and possibly the posterior white commissure, to terminate either in the
same or different levels of the grey column. Others of longer course pass to the periphery of
the cord, join one of the spino-cerebellar fasoicuh, and pass upward to the cerebellum.
Furthermore, there are scattered throughout the grey substance many smaller cell-bodies
of neurones. These give rise to axones of shorter course, either commissural or associational
proper. Of such axones many are quite short, coursing practically in the same level as that in
which their cells of origin are located, and serve to associate the different parts of the grey sub-
stance of that level. Others course varying distances upward and downward for the association
of different levels of the grey column.
It is evident from the above that in addition to the various nerve-ceUs it contains, there is
also to be found a felt-work of axones in the grey substance. Many of these axones are
meduUated, though not in sufficient abundance to destroy the grey character of the substance.
The felt-work is composed of three general varieties of fibres: — (1) The terminal branches of
axones entering from the fasciculi of the white substance and forming end-brushes about the
various cell-bodies in the grey substance (partly meduUated) ; (2) axones given off from the cells
of the grey substance and which pass into the surrounding white substance either to enter the
ventral-roots or to join the ascending and descending fasciculi within the spinal cord (partly
meduUated); (3) axones of Golgi neurones of type 11, which do not pass outside the confines
of the grey substance (non-meduUated). Some axones of any of these varieties may
cross the mid-line and thus become commissural. In general all fibres of long course acquire
medullary sheaths a short distance from then- cells of origin, and lose them again just before
termination.
The white substance of the spinal cord. — The great mass of the axones of the
spinal cord course longitudinally and form the thick mantle surrounding the
column of grey substance. This mantle is divided into right and left homo-
lateral halves by the anterior median fissure along its ventral aspect, and along
its dorsal aspect by the posterior median septum, which is for the most part a
connective-tissue partition derived from the pia mater along the line of the
posterior median sulcus. The mantle is supported internally by interwoven
neuroglia and white fibrous connective tissue, the latter, derived chiefly from the
pia mater, closely investing it without.
The axones of the white substance belong to three general neurone systems: —
(1) The spino-cerebral and cerebrospinal system, which consists of axones of long
course, one set ascending and another descending, forming links in the neurone
chains between the cerebrum and the peripheral organs. The ascending axones
of this system collect the general bodily sensations which are conve.yed
to the cerebrum, the cells of which in response contribute axones which descend
the cord, conveying efferent or motor impulses. (2) The spino-cerebellar and
cerebellospinal system consists of conduction paths, one set ascending and another
descending, which are connections between cerebellar structures and the grey
substance of the spinal cord. (3) The spinal association and commissural system
of axones which serve to associate the different levels and the two sides of the spinal
cord and which are proper to the spinal cord, i. e., they do not pass outside its
confines.
Both the first and second systems increase in bulk as the cord is ascended.
The ascending axones of each system are contributed to the white substance of the
cord along its length, and therefore accumulate upward; the axones descending
from the encephalon are distributed to the different levels of the cord along its
length, and therefore diminish downward.
The mass of the third system of axones varies according to locality. Wherever
there is a greater mass of neurones to be associated, as there is in the enlargements
of the cord, a greater number of these axones is required. Their cells of origin,
being in the grey substance of the cord, contribute to its bulk and thus both the
cells and the axones of this S3^stem serve to make the enlargements more marked.
In the lumbar and sacral regions the greater mass of the entire white substance
consists of axones belonging to this system. It forms a dense felt-work about
the grey column throughout the cord. Necessarily this system contains axones
of various lengths. Some merely associate different levels within a single segment
778
THE NERVOUS SYSTEM
Fig. 616. — Transverse Sections prom Different Segments of the Spinal Cord, show-
ing Shape and Relative Proportions of Grey and White Substance in the Various
Regions.
Posterior funiculus
Fasciculus cuneatus
Anterior funiculus
Cervical I
Fasciculus
gracilis Posterior septum
^ Dorsal (posterior) root
D erior) horn
Thoracic \ III
CONDUCTION PATHS
779
of the cord; others associate the different segments with each other. Axones
which associate the structures of the spinal cord with those of the medulla
■ oblongata may be included in this system. Many of these axones cross the mid-
line both in the grey and in the white substance to associate the neurones of the
two sides of the grey column. For purposes of distinction, such as cross the mid-
line are called commissural fibres, while those which course upward and down-
FiG. QilG— Continued.
Sacral IV
Coccygeal
ward on the same side are association fibres. Coursing in longitudinal bundles
about the grey figure, the latter compose the fasciculi proprii or ' ground bundles '
of the spinal cord.
METHODS BY WHICH THE CONDUCTION PATHS HAVE BEEN
DETERMINED
A purely anatomical examination of a normal adult cord, prepared by whatever means,
gives no indication of the fact that the mass of longitudinally coursing fibres of the white sub-
780 THE NERVOUS SYSTEM
stance is composed of more or less definite bundles or fasciculi, each having a definite course,
and whose axones form links (conduction paths) in a definite system of neurone chains.
Present information as to the size, position, and connections of the various fascicuH is based ,
upon evidence obtained by three different lines of investigation: —
(1) Physiological investigation. — (a) Direct stimulation of definite bundles or areas in
section and carefully noting the resulting reactions which indicate the function and course of
the axones stimulated, (b) 'WaUerian degeneration' and the application of such methods as
that of Marchi. When an axone is severed, that portion of it which is separated from its parent
cell-body degenerates. Likewise a bundle of axones severed from their cells of origin, whether
by accident or design, will degenerate from the point of the lesion on to the locality of their
termination in whichever direction thisimay be. This phenomenon was noted by Waller in
1852 and is known as WaUerian degeneration. By the application of a staining technique
which is differential for degenerated or degenerating axones and a study of serial sections con-
taining the axones in question, their course and distribution may be determined. The locality
of their cells of origin, if unknown, may be determined by repeated experiment till a point of
lesion is found not followed by degeneration of the axones under investigation, (c) The axonic
reaction or 'reaction from a distance.' Cell-bodies whose axones have been severed undergo
chemical change and stain differently from those whose axones are intact. Thus cell-bodies
giving origin to a bundle of severed axones may be located in correctly stained sections of the
region containing them.
(2) Embryological evidence. — In the first stages of their development axones of the cere-
bro-spinal nervous system are non-medullated. They acquire their sheaths of myelin later.
Axone pathways forming different chains become medullated at different periods. Based
upon this fact a method of investigation originated by Flechsig is employed, by which the posi-
tion and course of various pathways may be determined. A staining method differential for
medullated axones alone is apphed to the nervous systems of foetuses of different ages, and path-
ways meduUated at given stages may be followed from the locality of their origin to their
termination. In the later stages, when most of the pathways are medullated and therefore
stain alike, the less precocious pathways may be followed by their absence of meduUation.
(3) Direct anatomical evidence. — (a) Stains differential for axones alone are applied to a
given locality to determine the fact that the axones of a given bundle actually arise from the
cell-bodies there, or that axones traced to a given locality actually terminate about the cell-
bodies of that looahty. For example, it may be proved anatomically that the axones of a dorsal
root arise from the cells of the corresponding spinal ganglion, and then these axones may be
traced into the spinal cord and their terminations noted either by collateral or terminal twigs,
or the fasciculus they join in their cephalic course may be determined. (6) The staining prop-
erties and the size and distribution of the tigroid masses in the cell-bodies of sensory neurones
differ from those in the motor neurones, and recently Malone has claimed that, in the central
system, the cell-bodies in the nuclei of sensory neurone chains, those ascending toward the cere-
bral cortex, may be distinguished from the cell-bodies of the motor or descending chains by the
arrangement and size of their tigroid masses. He claims further that in the same way, the cell-
bodies of the somatic efferent neurones may be distinguished from those of the visceral
efferent neurones. In this way the locaUty of origin of certain physiologically known paths
may be determined.
(4) The so-called paihologico-anatomical method is based upon the same general principles
as is the physiological (or experimental) method. A pathological lesion, a local infection or a
tumor for example, may destroy a nucleus of cell-bodies or sever a bundle of axones, and the
resulting degeneration of the axones may be followed through serial sections suitably prepared.
The locahty of the lesion known, the path may be followed to determine the locality of its ter-
mination; its locality of termination known from the symptoms resulting, the path may be fol-
lowed to its cells of origin, or to determine whatever be the locality of the lesion.
Funiculi. — In order that the various fasciculi may be referred to with
greater ease, the white substance of the spinal cord in section is divided into three
areas known as funiculi or columns and which correspond to the funiculi already
mentioned as evident upon the surface of the cord when intact. The funiculi are
outlined wholly upon the basis of their position in the cord and with reference to
the median line and the contour of the column of grey substance; their component
fascicuh are defined upon the basis of function. (1) The 'posterior funiculus or
column is bounded by the posterior median septum and the line of the dorsal horn;
(2) the lateral funiculus or column is bounded by the lateral concavity of the grey
column and the lines of entrance and exit of the dorsal and ventral roots; (3) the
ventral funiculus or column is bounded by the Hne of exit of the ventral roots,
and by the anterior median fissure.
The posterior funiculus or column [funiculus posterior]. — This funiculus is
composed of two general varieties of axones arranged in five fasciculi. First, and
constituting the predominant type in all the higher segments of the cord, are the
afi'erent or general sensory axones, which arise in the spinal ganglia, enter the cord
by the dorsal roots, assume their clistribution to the neurones of the cord, and then
take their ascending course toward the encephalon. The axone of the spinal
ganglion neurone undergoes a T-shaped division a short distance from the cell-
body, one limb of this division terminating in the peripheral organs and the other
going to form the dorsal root. Upon entering the cord the dorsal root axones
POSTERIOR FUNICULUS
781
undergo a Y-shaped bifurcation in the neighbourhood of the dorsal horn, one
branch ascending and the other descending. Their ascending branches form the
fasciculus gracilis (Goll's column) and the fasciculus cuneatus(Burdach's column).
These fasciculi are the chief ascending or sensory spino-cerebral connections, the
direct sensory path to the brain. The neurones represented in them con-
stitute the first link in the nem-one chain between the periphery of the bodj'- and
the cerebral cortex.
Fig. 617. — Showing Disposition or the Dorsal Root Fibres Upon Entering the Spinal
Coed. (From Edinger, after Cajal.)
A, shows dorsal root axones DR, entering the spinal cord, bifurcating at B, and giving off collat-
erals C to the neurones of the cord. B shows the telodendria of these axones or of their
collaterals displayed upon cell-bodies of the grey substance of the cord.
In threading their way toward the brain, these sensory axones tend to work toward the mid-
line. Therefore tliose of longer course are to be found nearer the posterior septum, in the upper
segments of tlie cord, than those axones which enter the cord by the dorsal roots of the upper
segments. Thus it is that the fasciculus gracilis, the medial of the two fasciculi, contains the
axones which arise in the spinal ganglia of the sacral and lumbar segments. In other words, it ia
the fasciculus bearing sensory impulses from the lower limbs to the brain, while the fasciculus
cuneatus, the lateral of the two, is the corresponding pathway for the higher levels. Naturally,
there is no fasciculus cuneatus as such in the lower segments of the spinal cord. The axones
being mucli blended at first, it is only in the upper thoracic and cervical region that there is
any anatomical demarcation between the two fasciculi. In this region the two become so dis-
tinct that there is in some cases an apparent connective-tissue septum between them, continuing
inward from the postero-intermediate sulcus — the surface indication of the hne of their junction
(fig. 616).
Upon reaching the medulla oblongata the fibres of the fasciculus gracilis and the fasciculus
cuneatus terminate about cells grouped to form the nuclei of these fasciculi. The nucleus of the
fasciculus gracilis is situated medially and begins just below the point at which the central canal
opens into the fourth ventricle; the nucleus of the fasciculus cuneatus is placed laterally and ex-
tends somewhat higher than the other nucleus. The neurones whose cell-bodies compose these
782 THE NERVOUS SYSTEM
nuclei constitute the second links in the neurone chains conveying sensory impulses from the
periphery to the cerebral cortex.
The descending or caudal branches of the dorsal root axones are concerned
wholly with the neurones of the spinal cord. They descend varying distances,
some of them as much as four segments of the cord, and give off numerous col-
laterals on their way to the cells of the grey column. Those terminating about
cell-bodies of the ventral horn which give rise to the ventral or motor root-fibres,
are responsible for certain of the so-called 'reflex activities' and thus contribute
to the simplest of the reflex arcs. In descending they serve to associate different
levels of the grey substance of the cord with impulses entering by way of a single
dorsal root. Some of their collaterals cross the mid-line in the posterior white
commissure, and thus become connected with neurones of the opposite side. The
caudal branches of longer course are scattered throughout the ventral portion of
the fasciculus cuneatus {middle root zone) , and the longest show a tendency to
collect along the border-line between the fasciculus cuneatus and the fasciculus
gracilis, and thus contribute largely to the comma-shaped fasciculus. Also some
of the longest of them in the lower levels course in the oval bundle or septo-
marginal root zone.
The ascending branches of the dorsal root axones also give off collaterals to the grey sub-
stance of the cord, thus extending the area of distribution of a given dorsal nerve-root to levels of
the cord above the region at which the root enters.
The greater number of the terminations of dorsal root axones within the spinal
cord are concerned first with neurones other than those contributing ventral root-
fibres. The greater mass of the neurones concerned are those of the Golgi type II
and those contributing the fasciculi proprii or ground bundles of the spinal cord,
or the second variety of axones composing the posterior funiculus. The latter
fasciculi arise from the smaller cells of the grey column.
These axones pass from the grey substance to enter the surrounding white substance, bifurcate
into ascending and descending branches, which in their turn give off numerous collaterals to the
cells of the grey substance of the levels through which they pass. The cell-bodies giving origin
to such axones are so numerous that the entire column of grey substance is surrounded by a
continuous felt-work of axones of this variety.
The dorsal fasciculus proprius (anterior root zone of posterior column) arises chiefly from
cells situated in the dorsal horn (slraium zonale). Coincident with the ingrowth and arrange-
ment of the fasciculi gracilis and cuneatus many fibres of the dorsal fasciculus proprius go to form
both the oval bundle and the comma-shaped fasciculus. Thus these two bundles are mixed,
being fasciculi proprii which contain caudal branches of dorsal root axones. The association
fibres in the oval bundle are the longest of any belonging to the dorsal fasciculus proprius. The
cephalic and caudal branches combined of some are said to extend more than half the length of
the cord and it has been claimed that some even associate the cervical region with the conus
meduUaris. Based upon this claim, Obersteiner has called the oval bundle, the "dorso-medial
sacral field" and Edinger has referred to the most dorsal part of it as the "tractus cervico-lum-
balis dorsalis." The 'median triangle' is formed by the continuation of the dorsal fasciculi proprii
with the oval or septo-marginal fasciculus. Some of the axones of the dorsal fasciculus proprius
cross the midline to distribute impulses to the neurones of the opposite side. These commissural
axones, together with certain collaterals of the dorsal root axones, which cross the mid-line out-
side the dorsal white commissure, compose the so-called cornu-commissural tract at the base of
the posterior septum.
The lateral funiculus or column [funiculus lateralis]. — Not all the axones of
the posterior or dorsal nerve-roots extend to the encephalon. Estimation shows
that the sum of all the dorsal roots is greatly in excess of the sum contained in the
fasciculi cuneatus and gracilis just before these enter their nuclei of termination.
Therefore many of the ascending dorsal root axones are concerned with spinal-
cord relations wholly.
The marginal zone of Lissauer, situated along the lateral margin of the postero-lateral sulcus.
is composed largely of dorsal root axones. Many of these finally work across the line of the
sulcus into the posterior funiculus. Many of the dorsal root-fibres which do not reach the brain
occur in Lissauer's zone. Many others of course occur throughout the posterior column.
Lissauer's zone also contains some fibres arising from the small cells of the dorsal horn, and to
this extent corresponds to a fasciculus proprius. Ranson has found that large numbers of the
non-meduUated dorsal root axones which enter the cord are contributed to Lissauer's zone.
The lateral fasciculus proprius (lateral ground bundle, lateral limiting layer)
is situated in the lateral concavity of the grey column and is continuous with the
other fasciculi proprii both dorsal and ventral. Beyond that it probably contains
LATERAL CEREBROSPINAL FASCICULUS
783
fewer commissural axones, it is of the same general significance as the others.
It is frequently divided into small bundles by the reticular formation (see fig. 616).
The lateral cerebro-spinal fasciculus (crossed p.yramidal tract). In contrast
to the sensory fibres passing through the spinal cord conveying impulses destined
to reach the cerebral cortex, axones are given off from the pyramidal cells of the
Fig. 618. — Diageam Illustrating the Formation of the Fasciculi Proprii (association
fasciculi) and the Commissural Fibres of the Spinal Cord, and the General Archi-
tecture OF THE Cord as a Mechanism for Reflex Activities.
The ventral fasciculus proprius is omitted and the lateral is shown on one side only. The lower
spinal ganglion neurone shown illustrates the type whose ascending branch is of much longer
extent than that of the upper one.
-* Dorsal fasciculus proprius
Commissural
neurone in
ventral fas- *— -
ciculus
proprius
Lateral
fasciculus 'i^
proprius
cortex, which descend to terminate about the cells of the grey substance of the
spinal cord, chiefly the cells which give origin to the ventral root-fibers.
Upon reaching the medulla oblongata in their descent, these axones are accumulated into
two well-defined, ventrally placed bundles, the pyramids, one from each cerebral hemisphere.
In passing through the brain stem the pyramids contribute many fibres which cross the mid-line
to terminate in the motor nuclei of the cranial nerves of the opposite side, and thus decrease
appreciably in bulk. According to the estimate of Thompson, only about 160,000 of the
pyramidal fibres are destined to enter the spinal cord.
Upon reaching the lower part of the medulla, the greater mass of the fibres of each pyramid,
which are destined to enter the cord, suddenly cross the mid-line in the 'decussation of the
784 THE NERVOUS SYSTEM
pyramids.' The remainder retain their ventral position in their descent decussating gradually
in the cord itself. The pyramidal fibres which cross in the medulla course in the lateral column
ventral to Lissauer'sjzone, and lateral to the lateral fasciculus proprius, and form the lateral
cerebrospinal fasciculus (crossed pyramidal tract). It is a large fasciculus, oval shaped in
transection, and since its axones terminate in the grey column of the cord all along its length, it
decreases in bulk as the cord is descended.
In addition to the three dispositions of the dorsal root axones given above,
certain of them, either by collaterals or terminal twigs, form telodendria about the
cells of the dorsal nucleus (Clarke's column), which nucleus extends from about
the seventh cervical to the third lumbar segment of the cord. The axones given
off by these cells pass to the dorso-lateral periphery of the lateral funiculus, and
there collect to form the dorsal spino-cerebellar fasciculus (direct cerebellar
tract of Flechsig). As such they ascend without interruption, and in the
upper level of the medulla oblongata pass into the cerebellum by way of the
inferior cerebellar peduncle or restiform body. Necessarily, this fasciculus is not
evident in levels below the extent of the nucleus dorsalis.
Also situated superficially in the lateral funiculus is another ascending con-
duction path, and, like the dorsal spino-cerebellar fasciculus, to which it is ad-
jacent, it is also in part at least a cerebellar connection. Its position suggests its
name, superficial ventro-lateral spino-cerebellar fasciculus (Gowers' tract).
This tract at'present'does not include as great an area in transverse section as when originally
described. The more internal portion of the original Gowers' tract is now given a separate sig-
nificance, and will be considered separately. While the exact location in the grey column of all
the cell-bodies giving origin to the superficial ventro-lateral spino-cerebellar fasciculus is un-
certain, it is known that certain ventral horn cells contribute their axones to it. Many of its
cells of origin are scattered in the area immediately ventral to the nucleus dorsalis, others in the
intermediate and mesial portion of the lateral group of ventral horn cells. In the lumbar region
these cells are quite numerous, and, therefore, the fasciculus begins at a lower level in the spinal
cord than does the direct cerebellar tract. In degenerations it becomes visible in the upper seg-
ments of the lumbar region, and has been proved to increase notably in volume as the cord is
ascended. Its axones arise for the most part directly from cell-bodies of the same side of the
cord, though it has been shown by several investigators that many of its axones come from the
grey substance of the opposite side by way of the ventral white commissure. Terminal twigs and
collaterals of the dorsal root-fibres, mostly of the same side, but occasionally from the opposite
side, terminate about its cells of origin. At one time Gowers' tract was considered an entity, but
now, even in the more Umited area it occupies, it must be considered a mixture of axones of several
terminal destinations or distinct neurone systems. The destination of some of its axones has
not been determined with certainty. A portion, the spino-cerebellar fasciculus proper, go to
the cerebellum, and there have been traced to the cortex of the superior vermis. Most of these
reach the cerebellum not by way of the restiform body, as does the dorsal spino-cerebellar tract,
but pass on in the brain-stem to the level of the inferior corpora quadrigemina, and there turn
back£to join the brachiumjconjunctivum or superior cerebellar peduncle. (Auerbach, Mott,
Hoche.) Only a few of its_ axones leave the fasciculus lower down in the medulla, to enter the
cerebellum by way of the restiform body, in company with the dorsal spino-cerebellar tract.
(Rossolimo, Tschermak.) Another portion of its axones are thought to reach the cerebrum,
probably the nucleus lentiformis, though it has not been positively traced further than the
superior corpora quadrigemina. Many axones in Gowers' tract of the cord correspond to
those of the fasciculi proprii, and merely run varying distances in the cord, to turn again into
its grey substance. Schaeffer followed some of these from the lumbar region up to the level
of the second cervical nerve.
In the ventro-mesial border of Gowers' tract and immediately upon the
periphery, near the antero-lateral sulcus (exit of ventral nerve-roots), there is
found in the higher segments of the cord a small oval bundle, the spino-olivary
fasciculus or Helweg's (Bechterew's) bundle. The functional direction of its
fibres has not been settled.
It is asserted to arise from cell-bodies of the ohve in the medulla oblongata, and in the cord
is beheved to be associated with the cells of the ventral column of grey substance, probably
those of the lateral; horn. More recent claims assert that it arises fron cell bodies inithe cord
and thus is spino-olivary. By some observers it has been traced as far down as the mid-thoracic
region; by others, however, only as far as the third cervicalfsegment. The olives being nuclei
largely concerned with cerebellar connections, Helweg's fasciculus is probably an indirect
cerebellar association with the spinal cord neurones. It is composed of axones of relatively very
small diameter, andjt is one of the last fasciculi of the spinal cord to become meduUated.
Situated between the superficial ventro-lateral spino-cerebellar fasciculus and
the lateral fasciculus proprius is an area which, in transverse sections, may be, by
position, referred to collectively as the intermediate fasciculus. So intermingled
are the axones comprising it that it has been called the mixed lateral zone. It
contains fibres of at least five functional varieties:
FASCICULI OF SPINAL CORD
785
786 THE NERVOUS SYSTEM
(1) Fibres belonging to the lateral fasciculus proprius which are of longer extent gradually
course farther away from the grey substance of the cord and such mix into the intermediate
fasciculus.
(2) It is said to contain fibres descending from the cerebellum to associate with the neurones
of spinal cord, probably directly with the ventral root or motor neurones.
(3) The rubro-spinal fasciculus. — This arises from cell-bodies in the red nucleus of the
tegmentum (in the mesencephalon) and is a crossed fasciculus. Axones arising from the red
nucleus of one side cross the mid-Une while yet in the mesencephalon and descend in the lateral
funiculus of the cord to terminate gradually about ceU-bodies of the ventral horn, both those
which give rise of ventral root fibres and those which contribute to the fascicuU proprii. Its
fibres are more thickly bundled in a crescentic area fitting onto the ventral side of the lateral
cerebro-spinal fasciculus, and some are said to mix into the area of this latter.
(4) The vestibulo-spinal fasciculus. — This is sometimes called the lateral vestibulo-spinal
fasciculus from the fact that there is a tract of similar significance in the ventral funiculus of
the cord. It arises from some of the ceU-bodies comprising Deiter's nucleus, the lateral nucleus
of termination of the vestibular nerve, and from some of those of the spinal nucleus (nucleus
of the descending root) of this nerve, all of which is in the medulla. _ It descends the cord, un-
crossed, to terminate gradually about ventral horn cells, thus comprising a part of the apparatus
for the equilibration of the body. . Its fibres are thought to be more closely collected in the area
immediately ventral to the rubro-spinal fasciculus, but of course commingle with the latter.
(5) The corpora-quadrigemina-thalamus path. The most lateral portion of the intermediate
fasciculus, a small area once included in Gower's tract, contains fibres both ascending and de-
scending, connecting the spinal cord with the thalamus (diencephalon) and the quadrigeminate
bodies of the mesencephalon. These are crossed paths. The ascending fibres arise from ceU-
bodies in the ventral horn of one side, cross in the ventral white commissure (commissural
neurones) and course upward in the intermediate fasciculus to their termination in the opposite
side. Those terminating about cell-bodies in the thalamus form what is known as the spino-
thalamic tract, while those terminating in the nuclei of the quadrigeminate bodies are called
the spino-mesencephalic or spino-tectal tract (Iradus spino-tectalis) . It is not known in which
region of the cord most of these fibres arise but it is quite probably the cervical region. The
fibres which arise from cell-bodies of the thalamus and nuclei of the quadrigeminate bodies cross
the mid-line in the mesencephalon and descend the cord to terminate graduaDy about cell-
iDodies in the ventral horn ol the opposite side. Those from the thalamus are known as the
thalamo-spinal tract and those from the quadrigemina, as the mesencephalo- or tecto-spinal
tract. The latter is thought to be the larger.
By the fibres of the above tracts general sensory impulses from the body (skin, etc.) are
carried to the central portion of the optic apparatus, and the descending fibres give a simple
anatomical possibility for the movements of the body in response to visual and auditory im-
pulses. The descending fibres are thought to terminate chiefly in contact with association
neurones of the fasciculi proprii, these transferring the impulses to the neurones giving origin
to the ventral or motor root fibres, but some are thought to terminate directly about the cell-
bodies of ventral-root neurones. A portion of the intermediate fasciculus, most adjacent to
Gower's tract, has been designated as Loewenthal's tract.
The anterior funiculus or column [funiculus anterior]. — The intermediate
fasciculus is continued ventrally and mesially across the line of exit of the ventral
root axones, and thus into the anterior funiculus. This portion is also mixed, but
its axones of long course associate somewhat different portions of the nerve axis
from those connected by the more lateral portion.
According to the studies of Flechsig, von Bechterew, and Held, this mesial portion contains
fibres, both ascending and descending, which associate the various levels of the grey substance
of the spinal cord with the neurones in the reticular formation of the medulla oblongata.
The levels to which they have been traced comprise the olivary nuclei, which are largely
concerned in cerebellar connections, and the nuclei of the vagus, glosso-pharyngeal, auditory,
facial and the spinal tract of the trigeminus. Also some of the ascending fibres are probably
associated with the nuclei of the eye-moving nerves. This portion of the intermediate
fasciculus also grades into and is mixed with the axones of the ventral fasciculus proprius, as is
its lateral portion with the lateral fasciculus proprius. In other words, the fasciculi proprii
proper, the axones nearest the grey substance, serve for the intersegmental association of the
different levels ol the grey substance of the cord, while the intermediate fasciculus contains
axones of longer course which serve to associate more distant levels of the grey substance
of the nerve axis — that of the spinal cord with its upward continuation into the medulla
oblongata, pons and mesencephalon.
The anterior marginal fasciculus, ventral vestibulo-spinal tract (Loewenthal's
tract) forms the superficial boundary of the mesial portion of the intermediate
fasciculus. It is a narrow band, parallel with the surface of the cord, and extends
mesially from the mesial extremity of Gowers' tract (from Helweg's bundle) to
the beginning of the anterior median fissure.
The axones belonging to it proper are descending from the recipient nuclei of the vestibular
nerve. Of these nuclei it has been held by some investigators that only Deiters' nucleus (the
lateral nucleus of termination in the upper extremity of the medulla oblongata) gives origin
to the axones of the anterior marginal fasciculus. Others agree with Tschermak that the superior
and more laterally situated Bechterew's nucleus of the vestibular nerve also contributes axones
ANTERIOR MARGINAL FASCICULUS
787
to it, and quite probably the nucleus of the spinal root of the vestibular adds further axones.
Still other investigations have shown that a part at least of the fasciculus comes from the
nucleus fastigius (roof nucleus) of the cerebellum. Since many axones from both Deiters'
and Beehterew's nucleus terminate in the nucleus fastigius, the ventral vestibulo-spinal fasciculus
Fig. 620.— Diagram of Spinal Cord Illustrating the Two Chief Varieties of Spino-
CEREBRAL AND Cerebro-spinal Neurone Chains. The Ventral tecto-spinal (sulco-
marginal) fasciculus, fibres descending from the superior quadrigeminate bodies, is not
filled in.
Soni£esthetic i
Optic thalamus
. of cerebral cortex
Tecto-spinal tract
Decussation of
1 emnisci
Decussation of
pyramids
Cervical region of
spinal cord
Superior quadrigeminate body
1 1 ,-. Inferior quadrigeminate body
'i. Nucleus of fasciculus cuneatus
TT- Nucleus of fasciculus gracilis
! j ^> Spino -thalamic and spino-mesencephalic paths
~__ Fasciculus cuneatus
Posterior (dorsal) root
Spinal ganglion
Lumbar region of
spinal cord
IS, in any case, a conduction path from the nerve connections for equilibration to the grey sub-
stance of the spinal cord. The fasciculus is said to extend as far as the sacral region of the
cord, its axones terminating about the cells of the ventral horns. The term "ventral" is
added to its name to distinguish it from the vestibulo-spinal tract described above as coursing
in the lateral funiculus. It is considered an uncrossed pathway.
788 THE NERVOUS SYSTEM
The ventral cerebro-spinal fasciculus (anterior or direct pyramidal tract),
as stated above, is the uucrossed portion of the descending cerebro-spinal system of
nem-ones. It is a small, oblong bundle, situated mesially in the anterior funiculus,
parallel with the anterior median fissure. Like the lateral cerebro-spinal fasci-
culus (crossed pyramidal tract), its axones arise from the large pyramidal cells
of the motor area of the cerebral cortex, and transmit their impulses to the neu-
rones of the ventral horns of the grey substance of the spinal cord, and almost
entirely to those ne.urones which give origin to the ventral or motor root fibres.
It represents merely a delayed decussation of the pyramidal fibres, for instead of crossing
to the opposite side in the lower portion of the medulla oblongata, as do the fibres of the lateral
fasciculus, its fibres decussate all along its course, crossing in the ventral white commissure and
in the commissural bundle of the cord to terminate about the ventral horn cells of the opposite
side. Hoohe, employing Marchi's method, found that a few of its fibres terminate in the ven-
tral horn of the same side. This conforms to the pathological and experimental evidence that
there are homolateral or uncrossed fibres in the crossed pyramidal tracts also. Like the crossed
tract, the ventral pyramidal tract diminishes rapidly in volume as it descends the cord. Its
loss is greatest in the cervical enlargement, and it is entirely exhausted in the thoracic cord.
With the exception of the anthropoid apes and certain monkeys, none of the mammalia below
man, which have been investigated, possess this ventral pyramidal tract
Lying between the ventral cerebro-spinal fasciculus and the pia mater of the
anterior median fissure is a thin tract of descending axones continuous ventrally
with the anterior marginal fasciculus. From its position it is known as the sulco-
marginal fasciculus; functionally it is the ventral mesencephalo-spinal (tecto-
spinal) tract.
The extent of its course in the spinal cord is uncertain. It arises from the cells of the grey
substance of the superior pair of the quadrigeminate bodies, and there, in largest part at
least, it crosses the mid-line, and in the so-called 'optic acoustic reflex path' descends through
the medulla oblongata into the spinal cord of the opposite side. The superior quadrigeminate
bodies having to do with sight, this tract forms a second path conveying visual impulses to the
neurones of the spinal cord.
The commissural bundle is situated about the floor of the anterior median
fissm-e, and is the most dorsal tract of the anterior funiculus. It contains decus-
sating or commissural axones of three varieties.
(1) It contains the decussating axones of the ventral cerebro-spinal fasciculus throughout
the extent of that fasciculus; (2) it is chiefly composed of the axones of the ventral fasciculus
proprius which arise in the grey substance (ventral horn) of one side, cross the mid-line as com-
missural fibres, and course both upward and downward to be distributed to the neurones of
different levels of the grey substance of the opposite side; (3) it contains decussating axones which
arise from cell-bodies in the grey substance of one side and cross the mid-line to terminate
about cell-bodies in practically the same level of the opposite side. The latter are merely
axones belonging to the ventral white commissiu-e which course without the confines of the grey
figure. The commissural bundle is present throughout the length of the spinal cord, and is
largest in the enlargements, i. e., where the association and commissural neurones occur in
greater number generally. In its two last-mentioned varieties of axones it corresponds to the
commissural portion of the dorsal fasciculus proprius (the cornu-commissural bundle).
The ventral fasciculus proprius is but a continuation of the lateral fasciculus proprius, and
is composed of ascending and descending association fibres of the same general significance.
SUMMARY OF THE SPINAL CORD
The spinal cord contains two general classes of axones arranged into three
general systems. It contains axones which — (a) enter it from cell-bodies situated
outside its boundaries, i. e., in the spinal ganglia and in the encephalon, and (b)
axones which arise from cell-bodies situated within its own grey substance, some
of which axones pass outside its boundaries both to the periphery and into the
encephalon; some of which remain wholly within it. Its axones comprise — (1)
a system for the intersegmental association of its grey substance, both ascending
and descending, association proper and commissural; (2) a spino-cerebral and
cerebro-spinal system, ascending and descending; and (3) a spino-cerebellar and
cerebello-spinal system, ascending and descending.
For these relations the grey substance of the cord contains three general classes
of nerve-cells: — those which give rise to the peripheral efferent or motor axones
of the ventral roots; those which give rise to central axones of long course, going
to the encephalon; and those which supply its central axones of shorter course,
the association and commissural systems.
SUMMARY OF SPINAL CORD 789
The three systems : (1) Association and commissural. — Axones of spinal ganglion (afferent)
neurones bifurcate within the cord into cephalic and caudal branches which extend varying
distances upward and downward and terminate, (a) about cell-bodies whose axones are short
and terminate within the grey substance of the same side and in the same level as their cell-
bodies {Golgi neurones of type II); (b) about ceO-bodies whose axones pass without the grey sub-
stance, bifurcate into cephalic and caudal branches to terminate in the grey substance of the
same side but in various levels above and below (association fibres in the dorsal, lateral and ven-
tral fasciculi proprii); (c) about cell-bodies whose axones cross the mid-line to terminate either
in the same level of the grey substance of the opposite side, or bifurcate and the cephalic and
caudal branches pass in the fasciculi proprii to terminate in various levels of the grey substance
of the opposite side. The longer cephalic branches of (b) and (c) may terminate in the meduUa
oblongata. All, associated with ventral root (efferent) neurones, belong to the neurone chains
for the so-oaOed reflex activities.
(2) The cerebral system. — (a) The cephalic branches of certain spinal ganglion neurones
ascend beyond the bounds of the spinal cord to terminate within the medulla. Those ascend-
ing from the spinal ganglia of lower thoracic and lumbo-sacral segments accumulate mesiaUy
to form the fasciculus gracilis which terminates in the nucleus of this fasciculus; those arising
from the upper thoracic and cervical segments accumulate more laterally in the posterior funi-
culus to form the fasciculus cuneatus which terminates in the nucleus of the fasciculus cuneatus.
(6) The impulses transferred to the neurones of these nuclei are borne across the mid-line and
finall}' reach the sensory-motor area of the cerebral cortex, and cell-bodies here give rise to axones
which descend, some decussating in the medulla to form the lateral cerebrospinal fasciculus,
others form the uncrossed ventral cerebrospinal fasciculus which crosses the mid-line as it de-
scends the cord. Both of these fasciculi transfer their impulses either directly to efferent ven-
tral horn neurones, or to association neurones and these to the efferent neurones, (c) The
cephalic and caudal branches of spinal ganglion neurones terminate about cell-bodies in the grey
substance of the cord whose axones cross the mid-line and ascend laterally to terminate either
in the quadrigeminate bodies {spino-mesencephalic tract), or in the thalamus (spino-thalamic
trad), (d) Cell-bodies in thalamus and superior quadrigeminate bodies (receiving optic im-
pulses) and in the inferior quadrigeminate bodies (probably mediating auditory impulses),
give axones which cross the mid-line in the mesencephalon and descend, forming the thalamo-
spinal and mesencephalospinal tracts, to terminate in contact with the efferent neurones of the
cord. Axones from both sources descend in the lateral funiculus, while from the superior
quadrigeminate body, a separate bundle descends in the ventral funiculus as the sulco-marginal
{ventral mesencephalospinal) fasciculus, (e) The rubrospinal tract arises from cell-bodies in
the red nucleus (in the mesencephalon), crosses the mid-line and descends in the lateral funiculus
to transfer (probably cerebellar) impulses to the efferent neurones of the spinal cord.
(.3) The cerebellar system. — (a) The cephalic and caudal branches of spinal ganglion
neurones give telodendria about the cell-bodies forming the dorsal nucleus of the cord (Clarke's
column) and about cell-bodies situated in grey substances ventral to the dorsal nucleus ("Still-
ing's nucleus") and in the lateral horn. Axones arising from the cells of the dorsal nucleus
pass laterally to form the dorsal spino-cerebellar fasciculus which ascends into the cerebellum by
way of its inferior peduncle of the same side and terminates about cell-bodies of its cortex.
Axones arising from Stilling's nucleus and the lateral horn cells, of both the same and opposite
sides of the cord, accumulate to form the superficial venlro-lateral spino-cerebellar fasciculus,
which ascends to enter the cerebellum by way of its superior peduncle and terminate about the
cells of the cerebellar cortex, (b) A few axones arising in the roof nucleus of the cerebellum
probably descent? in the animor marginal fasciculus in company with the ventral vestibulospinal
tract to terminate upon the efferent neurones of the cord, (c) The inferior olivary nucleus, in the
medulla, is a cerebellar relay and its cell-bodies are associated with the neurones of the upper por-
tion of the same side of the spinal cord. Whether the axones arise in the olivary nucleus or
in the grey substance of the cord is uncertain, but the more usual supposition favours the cord
and thus the name, spino-olivary fasciculus is given them, (rf) Among its other functions,
the cerebellum is concerned with equilibration. The vestibular nerve is the afferent nerve of
equilibration and a large mass of the axones arising from its nuclei of termination terminate
in the cerebellum, in the roof nuclei especially. Axones arising from cell-bodies in Deiters'
nucleus (its lateral nucleus of termination) and in the nucleus of its descending root descend
the cord in the lateral funiculus to form the (lateral) vestibulospinal tract, and also in the anterior
marginal fasciculus to form ventral vestibulospinal tract. Impulses borne by these axones reach
the efferent or motor root neurones. The rubro-spinal fasciculus, mentioned above also may
be possibly considered as belonging to the cerebellar system.
Sympathetic relations. — The cell-bodies of the efferent neurones in the ventral horns are
of two general varieties: (a) those whose axones terminate upon skeletal muscle (somatic
efferent), and (6) those whose axones terminate in contact with cell-bodies of sympathetic
neurones, the splanchnic or visceral efferent neurones. The axones of the sympathetic neurones,
in their turn, terminate upon cardiac and smooth muscle (motor) and in glands (secretory).
Like the somatic, the visceral efferent neurones receive impulses within the ventral horns
(a) from the cephalic and caudal branches of spinal ganglion neurones, (b) the descending cere-
bro-spinal fasciculi, and (c) from either, by way of the fasciculi proprii and Golgi neurones of
type II. Their cell-bodies are situated for the most part in the dorsal portion of the lateral
horn (dorso-lateral group of cells), which is the only portion of the lateral horn present in the
thoracic region of the cord. Many of the visceral efferent fibres leave the spinal nerves distal
to the spinal ganglia and make the white communicating rami, thus going to the nearest sym-
pathetic ganglia; others pass on in the spinal nerve and its branches to terminate in more distal
sympathetic ganglia. Dogiel has described axones which arise in sympathetic ganglia and termi-
nate upon the ceU-bodies of the spinal ganglia. Such convey sensory impulses which, however,
enter the spinal cord by way of the dorsal root branch of the spinal ganglion neurone. Such
afferent sympathetic neurones are relatively rare, the peripheral distribution of the ordinary
790
THE NERVOUS SYSTEM
Fig. 621. — Schematic Representation op the More Important Architectural Relations
OF Neurones in the Spinal Cord, Omitting those Involving the Mesencephalon
AND Thalamus.
a, afferent (spinal ganglion) axone of spino-oerebral chain with bifui'cation and caudal branch;
b, afferent axone coursing in Lissauer's zone and distributed wholly within the cord;
c, collaterals of a and b disposed in three ways; p, pyramidal axone in lateral (crossed)
cerebro-spinal fasciculus distributed to levels of grey substance; pa, axone in ventral cerebro-
spinal fasciculus decussating before termination; v, ventral root or motor neurones; n,
nucleus dorsalis giving axone to dorsal spino-oerebellar fasciculus; g, ascending neurones
of Gowers' tract; d, descending axone from cerebellum (probable); fp, neurones of fasciculi
proprii, association proper; h, commissural neurones; e, Golgi cell of type II.
ORDER OF MEDULLATION
791
spinal ganglion neurone in the domain of the sympathetic supplying the needs for sensory
axones.
In transverse sections of the spinal cord, the relative area of white substance
as compared with that of grey increases as the cord is ascended. The absolute
area of each varies with the localitj^, both being greatest in the enlargements. The
grey substance predominates in the conus medullaris and lower lumbar segments.
The white substance begins to predominate in the upper lumbar segments, not
because of the increased presence of ascending and descending cerebral and cere-
bellar axones, but because of the increased volume of the fasciculi proprii coinci-
dent with the greater mass of grey substance to be intersegmentally associated in
this region. In the thoracic region the greatly predominating white substance
Fig. 622. — Graphic Representation of the Varying Amounts of Grey and White Sub-
stance AND OF THE VARIATIONS IN AbEA OF ENTIRE SECTIONS OP THE DIFFERENT SEGMENTS
OF THE Spinal Cord. (From Donaldson and Davis.)
(Based upon measurements from several adult human spinal cords.)
Curves showinO area of cross seel ion of human spinnl cord.
-Whife ma\ter
Grey matter.
-Entire section.
In ra IF ¥ w Mnn I n m w v yj yh yjii ix x xi xii i ii m ivyi iiiiiivn
CERVICAL THORACIC LUMBAR SACRAL
is composed mostly of the axones of long course. The greatly increased absolute
amount of white substance in the cervical region is due both to the greater ac-
cumulation of cerebral and cerebellar axones in this region and to the increased
volume of the fasciculi proprii of the cervical enlargement.
ORDER OF MEDULLATION OF THE FASCICULI OF THE CORD
The axones of the spinal cord begin to acquire their myehn sheaths during the fifth month of
intra-uterine hfe and myehnization is not fuUy completed till between the fifteenth and twentieth
years. In general, axones which have the same origin and the same locality of termination — ■
the same function — acquire their sheaths at the same time. While it has been proved that the
medullary sheath does not necessarily precede the functioning of an axone, it may be said that
those fasciculi which first attain complete and definite functional ability are the first to become
medullated. At birth all the fascicuh of the spinal cord are meduUated except Helweg's fasci-
culus, and occasionally the lateral and ventral cerebro-spinal tracts. The latter tracts vary
considerably and in general may be said to become medullated between the ninth month (before
birth) and the second year. As indicated by their meduUation, those axones by which the cord
is enabled to function as an organ per se, that is, the axones making possible the simpler reflex
activities, complete their development before those axones which involve the brain with the
activities of the cord.
According to Flechsig and van Gehuohten, and investigators succeeding them, the following
is the order in which the axones of the cord become medullated: —
(1) The afferent and efferent nerve-roots and commissural fibres of the grey substance.
(2) The fasciculi proprii, first the ventral, then the lateral, and last the dorsal, fasciculus
proprius.
(3) The fasciculus cuneatus (Burdach's column) and Lissauer's zone — the area of tho.se
ascending spino-cerebral fibres which run the shorter course and which convey impulses from
the upper limbs, thorax and neck.
(4) Fasciculus gracilis (GoU's column).
(5) The dorsal spino-cerebeUar fasciculus (direct cerebellar tract).
(6) The superficial antero-lateral spino-cerebeUar fasciculus (Gowers' tract).
1(7) The lateral cerebro-spinal fasciculus (crossed pyramidal) and the ventral cerebro-
spinal fasciculus (direct pyramidal tract).
(8) The spino-olivary or Helweg's (Beohterew's) fasciculus.
792
THE NERVOUS SYSTEM
The axones descending from the cerebellum and the brain-stem are so mixed with other
axones that it is difficult to determine the sequence of their medullation. The fasciculi contaia-
ing them also contain axones of the variety in the fasciculi proprii and so show medullation early.
It is probable that the ascending, spino-cerebellar, fibres acquire their myeUn earlier than the
descending, if descending exist.
Blood Supply of the Spinal Cord
The spinal rami of the sacral, lumbar, intercostal, or vertebral arteries, as the case may be,
accompany the spinal nerves through the intervertebral foramina, traverse the dura mater
and arachnoid, and each divides into a dorsal and a ventral radicular artery. These accompany
the nerve-roots to the surface of the cord, and there break up into an anastomosing plexus in
the pia mater. From this plexus are derived three tortuously coursing longitudinal arteries
and! numerous independent central branches, which latter penetrate the cord direct. Of the
longitudinal arteries, the anterior spinal artery zigzags along the anterior median fissure and
gives off the anterior central branches, which pass into the fissure and penetrate the cord. These
branches give ofT a few twigs to the white substance in passing, but their most partial distribu-
tion is to the ventral portion of the grey substance. The two posterior spinal arteries, one on
each side, course near the hnes of entrance of the dorsal root-fibres. They each branch and
anastomose, so that often two or more posterior arteries may appear in section upon either side
Fig. 623. — Semi-diagrammatic Representation of the Blood Supply op the Spinal Cobd,
Posterior external spinal veins
Posterior radicular vein ,'~ ' " . ..^^^ Posterior central artery and vein
Posterior spinal artery
/PeripKeral arterial plexus
Posterior radicular artery
Intercostal artery
Anterior radicu- Spinal ramus
\ "x lar artery
V Internal spinal vein
i Anterior central artery
Anterior spinal artery
Anterior central vein
of the dorsal root. These give off transverse or central twigs to the white substance, but espe-
cially to the grey substance of the dorsal horns. Of the remaining central branches many enter
the cord along the efferent fibres of the ventral roots, and are distributed chiefly to the grey
substance; others from the peripheral plexus throughout penetrate the cord and break up into
capillaries within the white substance. Some of the terminal twigs of these also enter the grey
substance. The blood supply of the grey substance is so much more abundant than that of
the white substance that in. injected preparations the outline of the grey figure may be easily
distinguished by its abundance of capillaries alone. The central branches are of the terminal
variety. In the white substance the capillaries run for the most part longitudinally, or
parallel with the axones.
The venous system is quite similar to the arterial. The blood of the central arteries is col-
lected into corresponding central venous branches which converge into a superficial venous
plexus in which are six main longitudinal channels, one along the posterior median sulcus, one
along the anterior median fissure, and one along each of the four lines of the nerve-roots.
These comprise the posterior and anterior external spinal veins (fig. 623).
The internal spinal veins course along the ventral surface of the grey commissure, and arise
from the convergence of certain of the twigs of the anterior central vein. The posterior central
vein courses along the posterior median septum in company with the posterior central artery,
and empties into the median dorsal vein. The venous system communicates with the coarser
extra-dural or internal vertebral plexus chiefly by way of the radicular veins.
II. THE BRAIN OR ENCEPHALON
The brain is that greatly modified and enlarged portion of the central nervous
system which is enclosed within the cranial cavity. It is surrounded and sup-
ported by the same three membranes (meninges) that envelop the spinal cord.
GENERAL TOPOGRAPHY
793
While there is a considerable subarachnoid space, the brain more nearly fills its
cavity than does the spinal cord.
The average length of the brain is about 165 mm. and its greatest transverEe diameter
about 140 mm. It averages longer in the male than in the female. Exclusive of its dura mater,
the normal brain weighs from 1100 to 1700 gm. (40-60 oz.), varying in weight with the stature
of the individual or with the bulk of the tissues to be innervated. Its average weight is 1360
gm. (48 oz.) in males and 1260 gm. (44 oz.) in females. It averages about fifty times heavier
than the spinal cord, or about 98 per cent, of the entire cerebro-spinal axis. In its precocious
growth it is at birth relatively much larger than at maturity. At birth it comprises about 13
per cent, of the total body-weight, while at maturity it averages only about 2 per cent of
the weight of the body. Its specific gravity averages 1.036. In proportion to the body-
weight the brain-weight averages somewhat higher in smaller men and women. Some very
small dogs and monkeys and some mice have brains heavier in proportion to body-weight
than man.
The minimal weight of the adult brain compatible with human intelligence may be placed
at from 950 to 1000 grams. Above the minimal, there is only a general relation between the
degree of intelligence and the weight of the brain, owing to the fact that several factors may be
coincident with large brains. It may be said in general, however, that the average brain weight
of eminent men is above the general average. Some men judged eminent have had brains weigh-
ing less than the general average. Of the records generally accepted, the greatest brain weight
Fig. 624. — Mesial Section of the Head of a Female Thirty-five Yeaks Old .
Corpus callosuiu
Septum
pellucidum
Thalamus
Vein of Galen - -
Epiphysis
Posterior cere-
bral artery
Corpora ^
quadrigemina
Third nerve " ^V
Straight sinus
Cerebellum
Occipital sinus
Fourth ventricle
Sulcus cinguli
Fornix
Crista galli
Anterior cere-
bral artery
Optic chiasma
Sphenoidal
Pons
Medulla ob-
for eminent men is 2012 grams, recorded for the poet and noveUst, Ivan Tourgenieff. The trust-
worthiness of this weighing is doubted by some authorities. From the undisputed records the
following may be taken: Cuvier, 1830 grams; John Abercrombie, 1786 grams; Thackery, 1658
grams; Kant, 1600 grams; Spurzheim, 1559 grams; Daniel Webster, 1518 grams; Louis Agassiz,
1495 grams; Dante, 1420 grams; Helmholtz, 1440 grams; Goltz, 1395 grams; Liebig, 1352 grams;
Walt Whitman, 1282 grams; Gall, 1198 grams. In the average brain weights for the races that
for the Caucasian stands highest, the Chinese standing next, then the Malay, followed by the
Negro, with the AustraUan lowest.
The differences between the meninges of the brain and those of the spinal cord occur chiefly
in the dura mater. (1) The dura maler is about double the thickness of that of the spinal cord,
and consists of two closely adhering layers, the outermost of which serves as the internal peri-
osteum of the cranial bones, while that of the cord is entirely separate from the periosteum
lining the vertebral canal. (2) The inner layer is duplicated in places into strong partitions
which extend between the great natural divisions of the encephalon. Of these, the sickle-
shaped ialx cerebri extends between the hemispheres of the cerebrum, the crescentic tentorium
cerebelli extends between the cerebellum and the overlapping posterior portion of the cerebrum,
and the smaller falx cerebelli occupies the notch between the hemispheres of the cerebellum.
Contained within these partitions of the dura mater are the great collecting venous sinuses of
the brain. These will be considered in the more detailed description of the cranial meninges.
General topography. — In its superior aspect or convex surface the encephalon
is oval in contour, with its frontal pole usually narrower than its occipital pole.
794 THE NERVOUS SYSTEM
Viewed from above, the cerebrum comprises almost the entire dorsal aspect, the
occipital lobes overlapping the cerebellum to such an extent that only the lateral
and lower margins of the cerebellar hemispheres are visible. The great longitu-
dinal fissure of the cerebrum separates the cerebral hemispheres.
Laterally the temporal lobes, with their rounded anterior extremities, the tem-
poral poles, are each separated from the frontal and parietal lobes above by the
lateral cerebral fissure (fissme of Sylvius) . In the depths of this fissure and over-
lapped by the temporal lobe is situated the insula, or island of Reil (central lobe).
The surface of each cerebral hemisphere is thrown into numerous folds or
curved elevations, the gyri cerebri or convolutions, which are separated from each
other by slit-like fissures, the sulci cerebri. The gyri (and sulci) vary greatly in
length, in depth, and in their degrees of curvature. The larger and deeper of them
are similar in the two hemispheres; most of them are individually variable, but
each gyrus of one hemisphere is homologous with that of the like region of the
other hemisphere. By gently pressing open the great longitudinal fissure, the
corpus callosum, the chief commissural pathway between the cerebral hemi-
spheres, may be seen. The occipital margin of this large transverse band of white
substance is rounded and thickened into the splenium of the corpus callosum,
while its frontal margin is curved ventrally into its genu and rostrum.
The base of the encephalon (fig. 625) is more irregular than the convex surface,
and consists of a greater variety of structures. In the mid-line between the frontal
lobes appears the anterior and inferior extension of the great longitudinal fissure.
When the margins of this are separated, the outer aspect of the rostrum of the
corpus callosum, the downward continuation of the curve of the genu, is exposed.
The inferior surface of each frontal lobe is concave, due to its compression upon
the superior wall of the orbit. The orbital gyri with their respective orbital sulci
occupy this concave area.
The cranial nerves [nervi cerebrales]. — Along the mesial border of each orbital
area, and parallel with the great longitudinal fissure, lie the olfactory bulbs con-
tinued into the olfactory tracts. Each olfactory bulb is the first central connection
or the ' nucleus of reception' of the olfactory nerve, the first of the cranial nerves.
A few fine filaments of this nerve may often be discerned penetrating the ventral
surface of the bulb. The olfactory bulb and tract lies in the olfactory sulcus,
which forms the lateral boundary of the gyrus rectus, the most mesial gyrus of the
inferior surface of the frontal lobe. Upon reaching the area of Broca (area parol-
factoria), or the region about the medial extremity of the gyrus rectus, each
olfactory tract undergoes a slight expansion, the olfactory tubercle, and then
divides into tliree roots or olfactory striae — a medial, an intermediate, and a lateral,
which comprise the olfactory trigone. The striae begin their respective courses
upon the anterior perforated substance, an area which contains numerous small
foramina through which the antero-lateral group of central cerebral arteries enters
the brain. This region forms the anterior boundary of that area of the base of
the encephalon in which the substance of the brain becomes continuous across the
mid-line.
At the medial boundary of the anterior perforated substance the optic nerves
come together and fuse to form the optic chiasma. Thence the optic tracts dis-
appear under the poles of the temporal lobes in their backward course to the thai-
ami and the geniculate bodies or metathalami.
Immediately behind the optic chiasma occurs that diverticulum from the floor
of the third ventricle known as the tuber cinereum. It is connected by its tubular
stalk, the infundibulum, with the hypophysis or pituitary body, which occupies
its special depression (sella turcica) in the floor of the cranium and is usually torn
from the encephalon in the process of its removal. Behind the tuber cinereum
are the two mammillary bodies (corpora albicantia), each of which is connected
with the fornix, one of the larger association fasciculi of the cerebrum. The
peduncles of the cerebrum (crura cerebri) are the two great funiculi which asso-
ciate the cerebral hemispheres with all the structm-es below them. They diverge
from the anterior border of the pons (Varoli) and, one for each hemisphere, dis-
appear under the poles of the temporal lobes. The pons (brachium pontis or
middle cerebellar peduncle) is chiefly a bridge of white substance or a commissure
between the cerebellar hemispheres.
CRANIAL NERVES
795
The oculomotor or third pair of cranial nerves make their exit from the poste-
rior perforated substance in the interpeduncular fossa just behind the corpora
mammillaria.
Tlie trochlear nerves emerge around the lateral aspects of the pedunculi
cerebri along the anterior border of the pons. The trochlear is the smallest of the
cranial nerves, and the only pair arising from the dorsal aspect of the brain.
The trigeminus, or fifth cranial nerve, is the largest. It penetrates the pons to
find its recipient nuclei in the depths of the brain-stem. It is a purely sensory
nerve, but it is accompanied by the much smaller masticator nerve which is motor
and is usually referred to as the motor root of the trigeminus.
Fig. 625. — View of the Base op the Beain. (After Beaunis.)
Gyri orbitales
Anterior perfor-
ated substance
Hypophysis
tuber
Inferior vermis
Five pairs of cranial nerves are attached to the brain-stem along the inferior
border of the pons: — the abducens nerve, which is motor, emerges near the
mid-line; the facial, motor, emerges from the more lateral aspect of the brain-
stem ; the glosso-palatine or the intermediate nerve of Wrisberg, largely sensory,
is attached in company with the facial; and, entering the extreme lateral aspect
of the stem are the cochlear and vestibular nerves. These latter two, when taken
together as one, are known as the acoustic (auditory) or eighth cranial nerve.
They are both purely sensory. The cochlear courses for the most part laterally
and dorsally around the inferior cerebellar -peduncle, giving it the appearance
from which it derives its name, 'restiform body.'
The remaining four pairs of the cranial nerves are attached directly to the
medulla oblongata. This comprises that portion of the brain-stem beginning at
the inferior border of the pons above, and continuous with the first segment of
the spinal cord below. On its ventral surface the pyramids and the olives (olivary
bodies) are the two most prominent structures. The pyramids, which are con-
tinuous below into the pyramidal (cerebro-spinal) tracts of the spinal cord, form
the two tapering prominences along either side of the anterior median fissure; the
olives are the oblong oval elevations situated between the pyramids and the resti-
796 THE NERVOUS SYSTEM
form bodies, and each is the superficial indication of the inferior 'olivary nucleus.
The glosso-pharyngeal, the vagus (pneumogastric), and the spinal accessory
cranial nerves are attached along the lateral aspect of the medulla oblongata in
line with the facial nerve and between the olive and the restiform body. The
spinal accessory, purely motor, is assembled from a series of rootlets which
emerge from the lateral aspect of the first three or four cervical segments of the
spinal cord, as well as from the medulla. It becomes fully formed before reaching
the level of the olive, and passes lateralward in company with the vagus and fur-
ther on joins the latter in part. The root filaments of the vagus and glosso-
pharyngeal are arranged in a continuous series, and, if severed near the surface of
the medulla, those belonging to the one nerve are difficult to distinguish from
those belonging to the other. Both of these are mixed motor and sensory.
The hypoglossal, purely motor, emerges as a series of rootlets between the
pyramid and the olive. Thus it arises nearer the mid-line, and in line with the
abducens, trochlear, and oculomotor.
If the occipital lobes be lifted from the superior surface of the cerebellum and
the tentorium cerebelli removed, the quadrigeminate bodies of the mid-brain or
mesencephalon may be observed. These are situated above the cerebral pedun-
cles, in the region of the ventral appearance of the oculomotor and trochlear
nerves. Resting upon the superior pair of the quadrigeminate bodies [colliculi
superiores] is the epiphysis or pineal body, and just anterior to this is the cavity of
the third ventricle, bounded laterally by the thalami and roofed over by the tela
chorioidea of the third ventricle (velum interpositum) .
By separating the inferior margin of the cerebellum from the dorsal surface of
the medulla oblongata the lower portion of the fourth ventricle (rhomboid fossa)
may be seen. The cisterna cerebello-meduUaris, the subarachnoid space in this
region, is occupied in part by a thickening of the arachnoid. This is continuous
with the tela chorioidea (ligula) and chorioid plexus of the fourth ventricle. The
former roofs over the lower portion of the fourth ventricle, and, passing through it
in the medial fine, is the lymph passage, the foramen of Magendie, by which the
cavity of the fourth ventricle communicates with the subarachnoid space. The
fourth ventricle, as it becomes continuous with the central canal of the spinal cord,
terminates in a point, the calamus scriptorius. From the inferior surface, the
cerebellar hemispheres are more definitely demarcated, and between them is the
vermis or central lobe of the cerebellum.
Divisions of the encephalon. — The encephalon as a whole is developed from a
series of expansions, flexures, and thickenings of the wall of the cephalic portion of
the primitive neural tube, the three primary brain vesicles. Being continuous
with the spinal cord, it is arbitrarily considered as beginning just below the
level of the decussation of the pyramids, or at a line drawn transversely between
the decussation of the pyramids and the level of the first pair of cervical nerves.
In its general conformation four natural divisions of the brain are apparent:
the two most enlarged portions — (1) the cerebral hemispheres and (2) the cere-
bellum; (3) the mid-brain (mesencephalon) between the cerebral hemispheres and
the cerebellum, and (4) the medulla oblongata, the portion below the pons and
above the spinal cord (fig. 602). However, the most logical and advantageous
arrangement of the divisions and subdivisions of the encephalon is on the basis of
their development from the walls of the embryonic brain vesicles. (See fig. 598.)
On this basis, for example, both the medulla oblongata and the cerebellum
with its pons are derived from the posterior of the primary vesicles, and are,
therefore, included in a single gross division of the encephalon, viz., the rhomben-
cephalon. In the following outline the anatomical components of the enceph-
alon are arranged with reference to the three primary vesicles from the walls
of which they are derived, and the primary flexures and thickenings of the walls
of which they are elaborations.
During the early growth of the neural tube its basal or ventral portion and the lateral por-
tions acquire a greater thickness than the roof of the tube, and thus the tutpe is longitudinally
divided into a basal or ventral zone and an alar or dorsal zone. This is especially marked in the
brain vesicles. Structures arising from the dorsal zone begin as localised thickenings of the
roof. For example, in the rhombencephalon the greater part of the medulla oblongata and of
the pons region is derived from the ventral zone, while the cerebellum is derived from the dorsal
zone. The first of the flexures occurs in the region of the future mesencephalon, and is known
as the cephalic flexure; next occurs the cervical flexure, at the junction with the spinal cord;
DIVISIONS OF THE ENCEPHALON
797
O
O
W
H
O
CO
O
h-l
02
I— I
>
i=< d
gs
798
THE NERVOUS SYSTEM
Fig. 626.— Median Sagittal Section theough Embryonic Human Bbain at End of Fiest
Month. (After His.)
(Showing the locahties of origin of the derivatives of the three primary vesicles named in outline
on p. 797.)
Hypophysis (anterior sii
Ventral zone
Dorsal zone
Fig. 627. — Sagittal Section op Brain of Human Embryo of the Third Month. (After His)
(Reference numerals correspond with those of fig. 626 and those after names of parts in outline
on p. 797.)
MEDULLA OBLONGATA
799
third, the pontine flexure, in the region of the future fourth ventricle. Both the cervical and
pontine flexures, while having a significance in the growth processes, are almost entirely ob-
literated in the later growth of the encephalon.
The location of the development of the various parts of the encephalon may be
determined, and their elaboration and changes in shape and positionmay be traced
by comparing the accompanying figs. 626, 627, 628. The reference numbers in
Fig. 628. — Median Sagittal Section op Adult Human Brain. (Drawing of model by His.)
(Reference numerals same as in figs. 626 and 627.)
Olfactory bulb
Optic chiasma
Infundibulum
the last three figures correspond with the like numerals after the names of the
parts on p. 797 in the outline of the divisions of the encephalon. The more
detailed subdivisions of the parts will be met with in their individual descriptions.
THE RHOMBENCEPHALON
1. THE MEDULLA OBLONGATA
The medulla oblongata [myelencephalon] is the upward continuation of the
spinal cord. It is only about 25 mm. long, extending from just above the first
cervical nerve (beginning of the first cervical segment of the spinal cord) to the
inferior border of the pons. It lies almost wholly within the cranial cavity, resting
upon the superior surface of the basal portion of the occipital bone, with its lower
extremity in the foramen magnum. Its weight is from 6 to 7 gm. or about one-
half of one per cent of the whole cerebro-spinal axis. It is a continuation of the
spinal cord, and more. It contains structures continuous with and homologous
to the structures of the spinal cord, and in addition it contains structures which
have no homologues in the spinal cord. Due in part to these additional struc-
tures, the medulla, as it approaches the pons, rapidly expands in both its dorso-
ventral and especially in its lateral diameters. With it are associated nine of the
pairs of cranial nerves.
On its anterior or ventral aspect the anterior median fissure of the spinal cord
becomes broader and deeper because of the great height attained by the pyramids.
At the level at which the pyramids emerge from the pons, the region in which they
are largest, the fissure terminates in a triangular recess so deep as to merit the
name foramen caecum. The pyramids are the great descending cerebral or motor
funiculi. In the medulla oblongata they decrease in bulk in passing toward the
spinal cord, for the reason that many of the pyramidal axones are contributed to
structm-es of the medulla, chieflj^ after crossing the mid-line. At the lower end of
the medulla occurs the decussation of the pyramids, by which the anterior median
fissure is almost obliterated for about 6 mm., and which, upon removal of the pia
mater, may be easily observed as bundles of fibres interdigitating obliquely across
the mid-line.
Not aU the p)Tamidal fibres cross to the opposite side at this level in man, but a portion
of those coursing in the lateral portion of the pyramid maintain their ventro-mesial position
800
THE NERVOUS SYSTEM
and continue directly into the spinal cord, to form there the ventral cerebro-spinal fasciculus or
direct pyramidal tract. However, most of such fibres finally cross the mid-line during their
course in the spinal cord. The exact proportion of the direct fibres is variable, but always the
greater mass of each pjrramid crosses to the opposite side at the level of the decussation of the
pyramids, and descends the cord as the lateral cerebro-spinal fasciculus or crossed pyramidal
tract. Both of these pjnramidal tracts are described in the discussion of the fascicuU of the
cord.
Fig. 629. — Semi-diagbammatic Representation of the Ventral Aspect of the Rhomben-
cephalon AND Adjacent Portions of the Cerebrum. _ (Modified from Quain.)
Insula
Olfactory tract
Hypophysis
— Optic nerve
Optic tract
Mammillary bodies
Cerebral peduncle
Semilunar (Gasser
ian) ganglion
Oblique fasciculus
of pons
Tuber cinereum
Oculomotor nerve
,-- (in)
Lateral geniculate
body
- Trochlear nerve (IV)
/ ~~- Trigeminus (V)
. Abducens (VI)
— Brachlum of pons
Facial nerve (Vn)
~ Glosso-palatine nerve
(intermediate part of
X facial)
Cochlear and vestibular
\ nerves (Acoustic or VIII)
\ Glosso-pharyngeal nerve (IX)
Vagus nerve (XJ
\ Accessory nerve (XI)
(spmal accessory)
Decussation of pyramids
Each pyramid is bounded laterally by the antero-lateral sulcus, also continu-
ous with that of the same name in the spinal cord. Toward the pons this sulcus
separates the pyramid from the olive [oliva] (inferior olivary nucleus), and in the
region of the olive there emerge along this sulcus the root filaments of the hypo-
glossal nerve. These are in line with the filaments of the ventral roots of the spinal
nerves. The olives, as their name implies, are oblong oval eminences about 1.2
cm. in length. They extend to the border of the pons, and are somewhat thicker
at their upper ends. Their surfaces are usually smooth, except at their lower ends,
where they frequently appear ribbed, owing to bundles of the external arcuate
fibres passing across them to and from the restiform body, which occupies the
extreme lateral portion of the medulla. Along the line between the restiform body
and the olive are attached .the root filaments of the vagus, glosso-'pharyngeal,
and spinal accessory nerves. Both the abducens and the facial nerve emerge along
the inferior border of the pons, the facial in line with the glosso-pharyngeal, but
the abducens in line with the hypoglossus.
Dorsal aspect. — The increased lateral diameter of the medulla oblongata is
contributed to a great extent by the restiform bodies. These are the inferior cere-
MEDULLA OBLONGATA
801
bellar peduncles (crura cerebelli ad medullam oblongatam) and contain the major-
ity of the ascending fibres, which associate the cerebellum with the structures
below it.
In toto, the restiform bodies are much larger than could be formed by the combined cere-
bellar fasciculi of the spinal cord, their great size being due to their receiving numerous axones
coursing in both directions, which connect the cerebellum with structures contained in the
medulla oblongata alone, so that in the medulla they increase as they approach the cerebellum.
Their mesial borders form the lateral boundaries of the fourth ventricle. Their name (resliform,
meaning rope-hlie) was suggested from the appearance frequently given them by the fibres
of the cochlear (acoustic division of the eighth) nerve, which course around their lateral per-
iphery to become the strice medullares in the floor of the fourth ventricle.
Fia. 630. — Diagram Showing the DBctrssATioN op the Pyramids.
The uppermost level represented is near the inferior border of the pons.
Chorioid tela of fourth ventricle
Solitary tract
--Nucleus of vestibular nerve
y--' Restiform body
. Spinal tract of trigeminus
•Nucleus of cochlear nerve
-Vagus nerve
Hypoglossal nerve
Pyramid
Spinal tract of trigeminus
Decussation of pyramids
Lateral cerebro-spinal fasciculus
^crossed pyramidal tract)
Ventral cerebro-spinal fasciculus
(direct pyramidal tract)
Upon removal of the cerebellum it may be seen that below the calamus scrip-
torius (inferior terminus of the fourth ventricle) the structures manifest in the dor-
sal surface of the medulla are directly continuous with those of the spinal cord.
The fasciculus gracilis (Goll's column) of the spinal cord acquires a greater height
and volume and becomes the funiculus gracilis of the medulla, and because of this
increased height the posterior median sulcus of the cord becomes deepened into the
posterior median fissure. The posterior intermediate sulcus is also accentuated
by the fasciculus cuneatus (Burdach's column) likewise now enlarged into the
funiculus cuneatus of the medulla. The lateral funiculus of the medulla, of
course, does not contain the lateral or crossed pyramidal tract present in the spi-
nal cord.
At the border of the calamus scriptorius the funiculus gracilis terminates in a
slight elevation, the clava, which is the superficial indication of the nucleus of the
fasciculus gracilis. Beginning somewhat more anteriorly, and having a somewhat
greater length, is a similar enlargement of the funiculus cuneatus, the tuberculum
cuneatum or nucleus of the fasciculus cuneatus.
802
THE NERVOUS SYSTEM
These nuclei are the groups of nerve cell-bodies about which the ascending or sensory
axones of the respective fasciculi terminate or where the sensory impulses are transferred to a
second neurone in their course to the structui-es of the encephalon. These cell-bodies in their
turn give off axones which immediately cross the mid-line and assume a more ventral position,
contributing largely to the lemniscus or fillet of the opposite side, and thus such axones are the
encephalic continuation of the central sensory pathway conveying impulses from the periphery
of one side of the body to the opposite side of the cerebrum. The crossing of these axonesjis
known as the decussation of the lemnisci.
Fig. 631. — Dohsal Aspect op Medulla Oblongata and Mesencephalon, Showing the
Floor of the Fourth Ventricle (Rhomboid Fossa). (Modified from Spalteholz.)
aedullaiis of thalamus \ r ^ . ,
Internal capsule
Habenular commisbur
\
Trigonum habenuls v / \
Epiphysis
Brachium of infErior
quadrigeminate todv
Cerebral pi dund
Anterior medullary velu
Brachium conjunctiva m
Brachium of pons "
Restiformbodj
""-y
Calamus scriptorms
Funiculus gracilis
Funiculus cuneatus
Lateral funiculus
~ Caudate nucleus
.^j^— Taenia chorioidea
Stria terminalis
~ ~ of thalamus
^1£4.S.l i^' tnaiamus
Quadrigeminate bodies
Trochlear nerve
^~ Lingula cerebelli
Trigonum of vagus (ala cinerea)
"-- Nucleus of fasciculus cuneatus
- Obex
Nucleus of fasciculus gracilis (clava)
■Posterior median fis
•Posterior intermediate sulcus^
With the termination of the dorsal funiculi and the ventral course of the fibres
of the lemnisci in their decussation, the central canal of the spinal cord loses its
roof of nervous tissue in the medulla and comes to the surface as the fourth ven-
tricle. The floor of the fourth ventricle, which corresponds to the floor of the
central canal, is considerably widened into two lateral recesses opposite the junc-
tion of the inferior and middle cerebellar peduncles of either side, and, being
pointed at both its superior and inferior extremities, it is rhomboidal in shape and
thus is the rhomboid fossa. The pia mater of the spinal cord is maintained across
the tip of the calamus scriptorius to form the obex, a small, semilunar lamina
roofing over the immediate opening of the central canal. The obex carries a few
medullated commissural fibres. . '
MEDULLA OBLONGATA
803
Fia. 632. — Diagram of the Spino-cerebellar FAscicuiii and the Origin and Decussa-
tion OF the Lemnisci.
Nucleus of spinal
tract of trigeminus^
Spinal tract o£ \
trigeminus \
Root filaments of glosso-
pharyngeal ]
Nucleus of ala cinerea
804 THE NERVOUS SYSTEM.
2. THE PONS
The pons (Varoli) is, for the most part,- a great commissure or 'bridge' of
white substance coursing about the ventral aspect of the brain-stem, and connect-
ing the cerebellar hemisphere of one side with that of the other. In addition it
contains fibres passing both to and from the structures of the brain-stem and the
grey substance of the cerebellum, and fibres descending from the cerebral cortex.
Each of its lateral halves forms the middle of the three cerebellar peduncles, the
hrachium pontis of either side.
In size it naturally varies directly with the development of the cerebellum, both
in a given animal and relatively throughout the animal series. In man it attains
its greatest relative size, and possesses a median or basilar sulcus in which lies
the basilar artery. Its sagittal dimension varies from 25 to 30 mm., while its
transverse dimension (longitudinal with the course of its fibres) is somewhat
greater. It is a rounded white prominence interposed between the visible portion
of the cerebral peduncles (crura) above and the medulla oblongata below. Its
inferior margin is rounded to form the inferior pontine sulcus, which, between the
points of the emergence of the pyramids, is continuous with and transverse to
the foramen cjecum. Its superior margin is thicker and is rounded to form the
superior pontine sulcus, which, between the cerebral peduncles, is continuous with
and transverse to the interpeduncular fossa. (See fig. 629.) It is bilaterally sym-
metrical. The ventro-lateral bulgings of its sides (and, therefore, the basilar
sulcus) are produced by the passage through it of the fibres of the cerebral pedun-
cles from above, to reappear as the pyramids below. Its ventral surface rests
upon the basilar process of the occipital bone and the dorsum sellse of the sphenoid,
while its lateral surfaces are adjacent to the posterior parts of the petrous portions
of the temporal bones.
The fibres of the thicker superior portion of the pons (Jasciculus superior pontis) course
obliquely downward to their entrance into the brachium of the pons and the cerebellar hemis-
phere; those of the lower and mid-portions (Jasciculus medius pontis) course more transversely,
naturally converging upon approaching the cerebellum. Certain fibres of the upper mid-
portion course at first transversely and then turn abruptly downward across the fibres above
them, to join the inferior portion of the brachium pontis. This bundle is termed the oblique
fasciculus (fig. 629). The trigeminus or fifth cranial nerve penetrates the superior lateral por-
tion of each brachium pontis near the point of the downward turn of the obhque fasciculus; its
large afferent root and the masticator nerve (its small efferent root) accompany each other quite
closely. On either side of the basal surface of the pons usually may be seen a small bundle
of fibres which begins in the interpeduncular fossa, near or in the sulcus of the oculomotor
nerve. It passes laterally along or under the superior border of the pons, loses some of its fibres
in the lateral sulcus of the mesencephalon, then runs inferiorly between the superior cerebellar
peduncle and the brachium of the pons to disappear in the junction of these. Being sometimes
double, it is known as the lateral filaments of the pons {fila lateralia pontis or Icenia pontis).
The location of the cell-bodies giving origin to it is uncertain.
That portion of the rhombencephalon overlying the pons and forming the floor of the
fourth ventricle is not really a part of the pons at aU. It is merely a continuation of the brain-
stem from the meduOa below to the structures above. Therefore on the dorsal surface there is
no line of demarcation between the pons and medulla below or between the pons and isthmus
above. The fibres of the trigeminus and masticator nerve pass through the pontine fibres to
and from their nuclei in the brain-stem.
3. THE CEREBELLUM
The cerebellum or hind brain is the largest portion of the rhombencephalon.
It lies in the posterior or cerebellar fossa of the cranium, and dorsal to the pons and
medulla oblongata, overhanging the latter. It fits under the occipital lobes of the
cerebral hemispheres, from which it is separated by a strong dupUcation of the
inner layer of the dura mater, the tentorium cerebelli.
Its greatest diameter Ues transversely, and its average weight, exclusive of the dura mater,
is about 140 gm., or about 10 per cent, of the entire encephalon. It varies in development
with the cerebrum, and, like it, averages larger in the male. It is relatively larger in adults
than in children. Its development begins as a thickening of the anterior portion of the roof
(dorsal zone) of the posterior of the three primary brain vesicles. Resting upon the brain-
stem, it roofs over the fourth ventricle and is connected with the structures anterior, below,
and posterior to it by its three pairs of peduncles.
The surface of the cerebellum is thrown into numerous narrow folia or gyri,
which in the given locaHties run more or less parallel with each other. They are
THE CEREBELLUM
805
separated by narrow but relatively deep sulci. Unlike the spinal cord and
medulla, in which the grey substance is centrally placed and surrounded by a
mantle of white substance, the surface of the cerebellum is itself a cortex of grey
substance, the cortical substance [substantia corticalis], enclosing a core of white
substance, the medullary body [corpus medullare]. However, within this central
core of white substance are situated definite grey masses, the nuclei of the
ere bellum.
The gross divisions of the cerebellum are three: the two larger lateral portions,
the hemispheres, and between these the smaller central portion, the vermis.
The demarcation between these gross divisions is not very evident from the dorsal
surface, because the hemispheres in their extraordinary development in man
encroach upon the vermis, and, being pressed under the overlapping occipital
ends of the cerebral hemispheres, they become partially fused upon the vermis
Fig. 633. — Section of Head Passing Through the Mastoid Processhs op the Temporal
Bones and Behind the Medulla Oblongata. Showing the Position op the Cere-
bellum.
(From a mounted specimen in the Anatomical Department of Trinity College, Dublin.)
Corpus callosum
Chorioid pli
Veins of Galen
Tentoriun
cerebel]
Transverse sinus
Dentate nucleus
Caudate nucleus
Lateral ventricle
Superior petrosal
Mastoid antrum
Transverse sinus
Mastoid process
along the dorsal mid-line. Though differentiated simultaneously with the cere-
bellar hemispheres in the human fcetus, in most of the mammalia the vermis is
the largest and most evident of the parts, and it is practically the only part which
exists in the fishes, reptiles, and birds. In man, owing to the fact that the vermis
does not keep pace in development with the hemispheres, there results a very
decided notch between the two hemispheres along the line of the entire ventral and
inferior aspect of the cerebellum, the floor of this notch being the surface of the
vermis. The inferior portion of the notch is the posterior cerebellar notch
(incisura marsupialis) ; its prolongation above is wider than below, and is termed
the superior cerebellar notch. It is occupied by a fold of the diu'a mater, the
falx cerebelli. With the variations in contour of the cerebellum, certain of its
sulci are broader and deeper, and merit the name fissures. These are more or less
definitely placed, and subdivide the hemispheres into lobes'and the vermis (the
median lobe) into lobules.
Superior surface. — The superior surface is bounded from the inferior sm-face
by the horizontal fissure (fig. 635) which extends ventrolaterally, to the entrance of
the brachium of the pons. Between this and the extreme anterior border of the
dorsal surface are two other fissures, the posterior and anterior semilunar fissures.
These, Hke the horizontal fissure, may be traced, with slight interruptions, across
the mid-line, and consequently mark off not onl}^ the two hemispheres but also the
vermis into corresponding divisions.
806
THE NERVOUS SYSTEM
The superior semilunar lobe [lobulus semilunaris superior] (postero-superior
lobe) of each hemisphere lies between the horizontal and the posterior semilunar
fissm-es. It largely composes the outer border of the cerebellum, and, therefore,
is the longest of the lobes.
The adjacent surface of the hemispheres, because of the frequently less com-
plete development of the anterior semilunar fissure, is sometimes referred to as the
quadrangular lobe, with its posterior and its anterior portions. On the other
hand, especially when the anterior semilunar fissure is well marked, this area may
be divided into — (1) the posterior semilunar lobe, between the posterior and
anterior semilunar fissures, and (2) the anterior seynilunar lobe, anterior to the
anterior semilunar fissure (fig. 635).
Anterior to the quadrangular lobe on each hemisphere is the ala of the
central lobule, bounded by the postcentral and the precentral sulcus. Anterior
to this, on the anterior margin of the hemisphere, is the vinculum lingulae,
a slender process continuous with the lingula of the vermis (fig. 658).
Fig. 634. — Median Section Through Cerebellum and Brain-stem. (Allen Thompson,
after Reiohert.)
1. culmen monticuli; 2, superior semilunar lobe; 3, inferior semilunar lobe; 4, slender lobe;
5, biventral lobe; 6, tonsil.
Cerebral peduncle
Massa intermedia
Thalamus
Epiphysis (pineal body)
Corpora quadrigemina
Derive r-<ry^r^l
Uvula of.
vermis
Pyramid-
stria medullaris thalami
Third ventricle
Column of fornix
Anterior commissure
Lamina terminalis
Z7 Tuber cinereum
Recessus infun-
dibuli
Hypophysis (pit-
uitary body)
AquiEductus cerebri (Sylvii)
Pons
■Fourth ventricle
-Tela chorioidea of fourth ventricle
Medulla oblongata
The superior aspect of the vermis, the superior vermis, because of the fusion of
the hemispheres, is, for the most part, a slight ridge, the monticulus (fig. 635),
instead of a depression. However, in the posterior portion of the dorsal surfacethe
depression of the posterior notch begins, and here the horizontal and the posterior
semilunar fissures approach each other so closely that the corresponding sub-
division of the vermis is seldom more than a single folium, the folium vermis
(cacuminis) . >
The monticulus proper is divided into an inferior lobule, the declive, and a
superior lobule, the culmen. These appear as continuations across the mid-
line of the posterior and anterior semilunar lobes of the hemispheres, and are
separated by the corresponding fissures (fig. 635).
At the extreme anterior part of the superior surface and in the bottom of the
anterior cerebellar notch lies a more definitely defined portion of the vermis.
This is the central lobule (fig. 635). It is broadened laterally into two pointed
wings, the alee of the central lobule, the folia of which, if present, are parallel with
those of the anterior semilunar lobes and separated from them by the post-
central sulcus.
If the anterior margin of the central lobule be lifted, the lingula cerebelli
THE CEREBELLUM
807
{lingula vermis) will appear separated from the central lobule by the pre-central
sulcus. It is a thin, tongue-like anterior projection of the cortical substance
comprising four to eight folia adhering upon the anterior medullary velwm, the roof
of the superior portion of the fourth ventricle.
Inferior surface. — ^The three cerebellar peduncles of each side join to form a
single mass of white substance, and enter the ventral aspect of each hemisphere at
the medial and ventral extremity of the horizontal fissure. The inferior surface
of the cerebellum is less convex than the superior surface. The hemispheres are
decidedly separated by a continuation of the posterior cerebellar notch, which
becomes broader, the vallecula of the cerebellum, which contains the inferior
portion of the vermis, vermis inferior, and whose margins embrace the medulla
oblongata. The inferior surfaces of the hemispheres are each divided by the
intervening fissures into four lobes (fig. 636).
Fig. 635.— Diagram op the Superior Surface of the Cerebellum.
Tegmentum
Frenulum veil
Ala of central lobuli
Cerebral peduncle
Substantia nigra
Inferior quadrigemmate body
Central lobule
/f"X^, Culmen of
Posterior cerebellar notcb
Declive of monticulus
Folium of vermis
Below, the inferior semilunar lobe (postero-inferior lobe) is separated from the
superior semilunar lobe of the superior surface by the horizontal fissure. It is the
largest of the inferior lobes, and is broader at its medial extremity. Frequently
two and sometimes three of its curved sulci appear deeper than others, and sep-
arate it into two or three slender lobules [lobuli graciles]. More commonly there
are two of these, the lobulus gracilis posterior and lobulus gracilis anterior, separated
by the postero-inferior sulcus.
The biventral lobe is smaller and more curved than the inferior semilunar lobe,
from the anterior margin of which it is separated by the curved antero -inferior
sulcus. Its medial extremity is pointed and does not extend to the vermis; its
lateral extremity is broader and curves anteriorly to the ventral extremity of the
horizontal fissure — the line of outer termination of the inferior semilunar lobe.
The tonsil [tonsilla cerebelli] (amygdala) is a rounded, triangular mass, placed
mesially within the inner curvature of the biventral lobe, and separated from it
by the retrotonsillar fissure. Its inferior mesial border slightly overlaps the
vermis.
The smallest of the lobes is the flocculus. It lies adjacent to the inferior and
lateral surface of the mass of white substance produced by the confluence of the
three cerebellar peduncles, and extends into the mesial extremity of the horizon-
tal fissure. It is so flattened that its short folia give it the appearance suggesting
its name. Occasionally there is added a second, less perfectly formed portion,
the secondary flocculus. From each floccular lobe there passes toward the mid-
line a thin band of white substance, the peduncle of the flocculus ; these extend
808 THE NERVOUS SYSTEM
to meet each other at the most anterior portion of the inferior vermis, and thus
form the narrow posterior medullary velum.
The inferior vermis (figs. 634, 636) is more definitely demarcated than the
superior. Lying in the floor of the vallecula cerebelli, it is separated on each side
from the adjacent lobes of the hemispheres by a well-marked sulcus about it,
the nidus avis. By contour and by deeper transverse fissures (sulci) occurring
at intervals across it, four divisions or lobules of the inferior vermis are recognised.
These lobules, like those of the superior vermis, are each in intimate relation with
the pair of lobes of the hemispheres adjacent to it on either side.
1. The tuber vermis is adjacent to the folium vermis of the superior aspect, and
thus is the most inferior lobule of the inferior vermis. It is a short, somewhat
pyramidal-shaped division, whose four or five transversely arranged folia are con-
tinuous with the folia of the inferior semilunar lobes on either side.
2. The pyramid is separated from the tuber vermis by the post-pyramidal
sulcus. Its several folia cross the vallecula cerebelli and curve to connect with
the biventral lobes on either side.
3. The uvulva is separated from the pyramid by the prepyramidal sulcus.
It is triangular in shape. Its base or broader inferior portion appears as two
laterally projecting ridges of grey substance, the furrowed bands or alee uvulce,
which extend across the floor of the nidus avis and under the mesial margins of the
tonsils on either side. In these bands its folia curve and become continuous with
the tonsils. The uvula and the two tonsils are sometimes referred to collectively
as the uvular lobe.
4. The nodule is the smallest and most anterior division of the inferior vermis.
It is separated from the uvula by the post-nodular sulcus, and is closely associated
anteriorly with the posterior medullary velum, the transverse continuation of the
peduncles of the floccular lobes.
StTMMAET OF EXTERNAL FEATURES OP CEREBELLUM
Superior Surface.
Hemisphere Vermis
Anterior border — Anterior medullary velum — Anterior border
Vinculum of Lingula Lingula
Precentral sulcus
Ala of central lobule Central lobule
Post-central sulcus
C Anterior semilunar lobule Culmen
Quadran- I Anterior semilunar fissure [ Monticulus
gular lobe ] Posterior semilunar lobule Declive
[ Posterior semilunar fissiire
Superior semilunar lobe Folium.
Horizontal Fissure
Inferior Surface
Horizontal Fissure
Inferior f Posterior slender lobule 1
semilunar -j Posterior-inferior sulcus [ Tuber
lobe [ Anterior slender lobule J
Anterior-inferior sulcus Post-pyramidal sulcus
Biventral lobe Pyramid
Retro-tonsillar fissure Prepyramidal sulcus
Tonsil Uvula
Horizontal Fissure Post^nodular sulcus
Flocculus Nodule
Posterior medullary velum
Internal structure of the cerebellum (fig. 637). — The white substance of the
cerebellum is continuous with its peduncles and forms a compact central mass.
Over the surface of this the grey substance or cortex is spread in a thin but uniform
and much folded layer. Upon section of the cerebellum certain of the sulci as
well as the fissures are shown to be much deeper than is apparent from the surface.
The deeper sulci separate the lobes into divisions, the medullary laminae, each of
which is composed of a number of folia and each of which has its own core of white
substance. The folia of the laminae line the sulci (and fissures), and also comprise
their surface aspect, and are separated by the shallow, secondary sulci. The larger
NUCLEI OF THE CEREBELLUM
809
laminae are subdivided into from two to four secondary laminae of varying size.
Such subdivision is especially marked in the vermis. Here each lamina comprises
a lobule and is, therefore, separated by a fissure, and each lobule is usually sub-
divided with the exception of the nodule, the folium, and the lingula. In sagittal
sections, or sections transverse to the general direction of the sulci, this arrange-
ment of the laminae gives a foliate appearance, which, especially in sagittal sec-
tions of the vermis, is termed the arbor vitae (see fig. 634).
IThe cerebellar cortex consists of three layers and contains four general types of cell-bodies
of_neurones, aD of which possess features pecuHar to the cerebellum.
The outermost or molecular layer contains small stellate cells, "basket cells," with rel-
atively long dendrites. These serve to associate the different portions of a given fohum.
The axones of the largest of them give off branches which form pericellular baskets about the
bodies of the cells of Purkinje, each axone contributing to several baskets. The layer of Pur-
kinje cells, or the middle layer, is quite thin. The bodies of the cells of Purkinje are arranged
in a single layer, and their elaborate systems of dendrites extend throughout and largely compose
the molecular layer. The dendrites of these, the most essential cells of the cortex, are displayed
in the form of arborescent fans (see fig. 604), arranged parallel with each other and transverse
Fig. 636. — Diagram of the Inperioe Surface op the Cerebellum after the Removal
OF the Medulla Oblongata, Pons, and Mesencephalon.
The tonsil of the right side is omitted in order to display the connection of the pyramid
with the biventral lobe, the furrowed band of the uvula, and more fuUy the posterior meduUary
velum. The anterior notch is less evident than in the actual specimen.
Superior cerebellar peduncle
Posterior medullary velum
Middle cerebellar peduncle
(brachium of pons)
Flocculus
Biventral lobe
Anterior slender
lobule
Posterior _J
slender \ , ,
lobule \\\
Inferior semilu- . — ^
nar lobe
Anterior
Fourth medullary
ventricle velum Lingula
Tuber vermis 1 Pyramid
Posterior cerebellar notch
to the long axis of the folium containing them. Their axones are given off from the base of the
ceU-body and acquire their medullary sheaths quite close to the ceU-body, and, after giving off
several collaterals in the inner layer, pass into the general white substance and thence to other
laminae or lobes. Certain of them go to structures outside the cerebellum. The inner layer
is the granular layer. It contains numerous small nerve-cells or " granule-ceUs " which pos-
sess from two to five radiating dendrites, unbranched except at their termination, which occurs
suddenly in the form of three to six claw-hke twigs. Thek axones are given off either from the
ceU-body direct or more often from the base of one of the dendrites, and pass outward into
the molecular layer, where they bifurcate and course in both directions parallel to the long axis
of the folium, to become associated with the dendrites of the cells of Purkinje. In the layer
of the cells of Purkinje there is situated at intervals a neurone of the Golgi type II (see fig.
604). The short, elaborately branched a.xone of this neurone is distributed among the cells
of the granular layer. Axones conveying impulses to the cerebellar cortex terminate in the
granular layer as 'moss fibres,' or directly upon the cells of Purkinje as 'climbing fibres,' and
probably upon the cells of the Golgi type II.
Thus the neurones which receive impulses coming to the cortex are the cells of Purkinje,
probably the Golgi cells of type II, and the granule-cells; those which distribute these impulses
to other neurones of the folium are the Golgi cells of type II, the granule-ceUs, and the basket-
cells (association neurones), and the collaterals of the cells of Purkinje. Impulses are conveyed
from the cortex of a folium to that of other folia, lamina, lobules or lobes, or to the nuclei of
the cerebellum, or to structures outside the cerebellum by the axones of the cells of Purkinje.
The nuclei of the cerebellum (fig. 637) are in its central core of white substance.
They are four in number, and all are paired, those of each pair being situated
opposite each other on either side of the mid-line.
810
THE NERVOUS SYSTEM
1. The largest of them is the dentate nucleus. This is an isolated mass of
grey substance situated in the core of white substance of each hemisphere. It is
in the form of a folded or corrugated cup-shaped lamina, with the opening of the
cup (hilus) directed anteriorly and obliquely toward the mid-line. It contains a
mass of white substance and possesses a capsule. Its cell-bodies give rise to most
of the fibres forming the superior cerebellar peduncles.
2. The nucleus emboliformis is an oblong and much smaller mass of grey
substance, which lies immediately medial to the hilus of the dentate nucleus. It
is probably of the same significance as the dentate nucleus, being merely a portion
separated from it.
3. The nucleus globosus, the smallest of the cerebellar nuclei, is an irregular
horizontal mass of grey substance with its larger end placed in front. It lies
close to the medial side of the nucleus emboliformis, and often appears separated
into two or more rounded or globular masses.
4. The roof nucleus [nucleus fastigii] is the second largest of the cerebellar
nuclei, and is the most mesially placed. The pair is situated in the roof of the
Fig. 637. — Section op Cerebellum and Brain-stem Passing Obliquely Through Inferior
Portion of Cerebellum to Superior Margin op Pons. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Posterior cerebellar notch
Medullary lami
Cortical substance
Corpus medullare
Vermis (superior)
Nucleus
globosus
Capsule of dei
tate nucleus
Dentate nucleus
Core of the dentate nucleus
Hilus of dentate nucleus
Brachium conjunctivum
Fourth ventricl
Fossa rhomboidea (pars superior)
Stratum nucleare
Decussation of brachium
conjunctivum
Roof nucleus
Nucleus emboliformis
Lingula cerebelli
Anterior medullary velum
Substantia ferruginea
Lateral lemniscus
Medial longitudinal fasciculus
Raphe of medulla oblongata
Cerebral peduncle
Interpeduncular fossa
fourth ventricle, and so near the mid-line that both nuclei are in the white sub-
stance of the vermis. They are ovoid in shape, and the nucleus of one side receives
axones from the nucleus of the vestibular nerve chiefly of the opposite side, the
decussation of these axones taking place in the vermis. Its cells are larger than
those of the two first-mentioned nuclei.
The peduncles of the cerebellum. — The peduncles consist of three pairs — the
inferior, middle, and superior. The three peduncles of each side come together at
the level of the lower border of the pons, and the entering and emerging fibres of
which they are composed become continuous with the central core of white sub-
stance of the cerebellar hemispheres. (Fig. 631, 638, 639.)
The restiform body of the medulla oblongata is the inferior peduncle. It
forms the lateral boundary of the inferior portion of the fourth ventricle, and upon
reaching the level of the pons turns sharply backward into the cerebellum. In
the region of the turn it is encircled externally by fibres of the cochlear nerve. It
contains fibres, both ascending and descending, between the cerebellar cortex and
the structures below the cerebellum.
Its fibres include: (1) fibres from the spinal cord including the dorsal spino-cerebellar
fasciculus (direct cerebellar tract) and probably a small proportion of the ascending fibres of
the superficial ventro-lateral spino-cerebeUar fasciculus (Cowers' tract); (2) fibres from the
PEDUNCLES OF THE CEREBELLUM
811
olive of the same and opposite side of the medulla oblongata; (3) fibres from the nuclei of the
funiculus gracilis and cuneatus of the same and opposite sides; (4) fibres to and from the
olive of the opposite side; (5) fibres to the nuclei of the motor cranial nerves; (6) fibres
descending to the ventral horn cells of the spinal cord. The ascending or afferent fibres of the
spino-cerebellar and cerebeUo-olivary fasciculi are the principal components of the inferior ped-
uncle; the existence of fibres (5) and (6) is not weU estabhshed. Of these, the fibres of the direct
cerebellar tract terminate in the cortex of the superior vermis of both sides of the mid-hne, but,
for the most part, in that of the same side. The olivary fibres end in the cortex of both the su-
perior vermis and the adjacent cortex of the hemispheres, and some of them terminate in the
nucleus dentatus.
The brachium pontis'or the middle peduncle is the largest of the three cere-
bellar peduncles. In it the pons fibres pass slightly downward and into the cere-
bellar hemisphere, between the lips of the anterior part of the horizontal fissure,
entering lateral to the inferior peduncle.
Fig. 638. — Transparency Drawing Showing the Origin, Course, and Connections op the
Sttperior Cerebellar Peduncles (Brachia Conjunctiva) in the Formation op
'Stilling's Scissors.'
Thalamus
-\- - Internal capsule
* Bundle from red nucleus to
internal capsule
"* Red nucleus
Decussation of brachia conjunctiva
Brachium conjunctivum
(supenor peduncle)
Inferior peduncle
(restiform body)
Bundle to cerebellar
cortex
Dentate nucleus
Medulla oblongata
It consists of the transverse fibres of the pons, and within the cerebellum its fibres are dis-
tributed in two main groups — the upper transverse fibres of the pons apparently pass downward
to radiate in the lower portion of the hemisphere, whUe the lower transverse fibres pass upward
and medialward to radiate in the superior part of the hemisphere and vermis. For the most
part the fibres of the middle peduncle may be considered as commissural fibres, passing from
one side of the cerebellum to the other. Each peduncle contains fibres coursing in opposite
directions. Many of these fibres are interrupted in their course to the opposite side by cells
scattered throughout the pons, nuclei of the pons, and, therefore, in each brachium pontis some
of the fibres are processes of the cells of the cerebellum and course toward the opposite side,
while others are processes of the cells of the pontine nuclei and course to the cerebellar hemis-
phere of the same side. Many cell-bodies of the nuclei of the pons whose axones terminate
in the cerebellum receive impulses from fibres descending from the cerebral cortex of the opposite
side — coriico-pontine fibres. Furthermore, there are evidences after degeneration that the
brachium pontis also contains a few fibres from the cerebellum to the structures of the brain-
stem and spinal cord.
812 THE NERVOUS SYSTEM
The brachium conjunctivum or superior cerebellar peduncle emerges from the
cerebellum on the medial side of the brachium pontis and also on the superior and
medial side of the course of the restiform body. It forms the lateral boundary of
the superior portion of the fourth ventricle and is the cerebello-cerebral peduncle.
Its transverse sectioii appears semilunar in shape, with the concave side next to the
cavity of the ventricle. The medial border, which inclines toward the mid-line,
is connected with that of the corresponding peduncle of the opposite side by the
anterior medullary velum, which thus roofs over the superior part of the fourth
ventricle. The lateral border is distinguished from the pons by an open furrow
or lateral sulcus.
The superior cerebellar peduncles are almost entirely efferent pathways as to the cerebellum
and form the chief connections between the cerebellum and the cerebrum. They arise almost
wholly from the dentate nuclei. As they course forward they slightly converge and disappear
under the inferior quadrigeminate bodies. Here, in the tegmentum of the mesencephalon,
they undergo an almost total decussation, and then the majority of the fibres of each peduncle,
having thus crossed the mid-line, terminate in the red nucleus of the opposite side. The red,
nucleus lies in the tegmentum of the mesencephalon, below the superior quadrigeminate bodies,
and therefore quite close to the decussation. The cells of the red nucleus, about which the
fibres of the peduncle terminate^ in their turn send processes (axones) into (1) the rubro-spinal
tract of the spinal cord and (2) mto the prosencephalon, most of which latter terminate in the
thalamus whose ceU-bodies give fibres to the cerebral cortex by way of the internal capsule;
but some pass from the red nucleus under the thalamus to join the internal capsule.
In addition to the fibres having the origin and course described above, and which constitute
the greater mass of the superior cerebellar peduncle, each peduncle is said to contain fibres
which — (1) arise in the cerebellar cortex of the same and opposite sides of the mid-line, instead
of from the dentate nucleus, and which join the peduncle at the side of the dentate nucleus,
between it and the restiform body; (2) fibres which do not cross the mid-line in the decussation,
but terminate in the red nucleus of the same side; (3) some fibres are not interrupted in the red
nucleus, but pass directly into the thalamus; (4) a small proportion of fibres afferent as to the
cerebellum, which arise in the structures of the cerebrum and pass in to the cerebellum; and
(5) the greater part, if not all, of the ascending fibres of the superficial ventro-lateral spino-
cerebellar fasciculus (Gowers' tract) of the spinal cord. The latter, instead of entering
the cerebellum by way of the restiform body, are deflected in the upper medulla and pass
in the lateral tegmentum of the pons to the anterior medullary velum, where they turn back-
ward to enter the cerebellum in its superior peduncle and pass to its cortex, probably from the
lateral side of the dentate nucleus (see fig. 656).
The anatomy of the fourth ventricle. — The fourth ventricle is rhomboidal in
shape, being considerably widened at the level of the brachia pontis and pointed at
each end. Its floor consists of a slight depression in the brain-stem, the fossa
rhomboidea, and corresponds to the floor of the central canal. Its pointed inferior
end, the calamus scriptorius, is directly continuous with the central canal, and its
narrowed superior end is continued into the aquseductus cerebri (Sylvii) of the
mesencephalon, which is nothing more than a resumption of the tubular form of
the canal.
The entire cavity of the ventricle is lined with an epithelium which is continuous with the
epithehum, or ependyma, of the central canal below and the aqueduct above. The entire
ventricle involves the isthmus of the rhombencephalon, the metencephalon and a portion of the
medulla oblongata. It is divided for study into an inferior, an intermediate and a superior
part.
The roof of the superior portion of the fourth ventricle is nervous, consisting of a
thin lamina of white substance, the anterior (superior) inedullary velum, thickened
at the sides by the brachia conjunctiva. At its extreme mesencephalic end (in the
isthmus of the rhombencephalon) the anterior medullary velum is slightly thick-
ened by a continuation of the white substance of the inferior quadrigeminate
bodies, forming the frenulum veil. The inferior portion of the velum is contin-
uous with the white substance of the cerebellum, and is covered by the lingula
cerebelli, an extension of the cortical substance of the superior vermis (fig. 631).
The roof of the intermediate portion of the fourth ventricle is formed by the
cerebellum proper, the vermis and the mesial portions of the hemispheres. The
nervous portion of the roof terminates with the posterior (inferior) medullary
velum, a thin, narrow band of white substance which is the continuation of the
peduncles of the fioccular lobes, and which connects them at the mid-line with the
nodule of the inferior vermis.
The roof of the inferior portion of the fourth ventricle is non-nervous. It is
the chorioid tela of the fourth ventricle, a semilunar lamina consisting of the epi-
thelial lining of the ventricle, reinforced by a continuation of the connective tissue
of the pia mater and the adjacent portion of the arachnoid. Along the line of its
THE FOURTH VENTRICLE
813
attachment to the surface of the medulla it is thickened, and in sections this por-
tion bears the name ligula {toRiiia ventriculi quarti). The thickest portion spans
the tip of the calamus scriptorius and is termed the obex. The width of the ven-
tricular cavity is extended laterally from its widest part into the lateral recesses.
narrow pockets on each side and around the upper parts of the restiform bodies.
In the mid-Hne of the lower part of the chorioid tela there is a more or less well-
marked opening, the foramen of Magendie (medial aperture of the fourth ventricle),
which is a lymph-channel connecting the cavity of the ventricle with the subarach-
noid space. There is a similar opening from each lateral recess {lateral apertures
of Key and Retzius).
The chorioid plexuses of the fourth ventricle consist of highly vascular, lobular,
villus-like processes of the ventricular lining (and pia-mater) of the chorioid tela.
They are reddish in the fresh specimen, and the epithelial lining of the ventricle is
closely adapted to the unevennesses of their surfaces. From below they run as
Fig. 639. — Diagram of the Roop and Lateral Boundaries of the Fourth Ventricle.
The trochlear nerve should be shown emerging from the lateral boundary of the frenulum veli.
Ii.ferior quadrigeminate body
Trochlear nerve
Axilerior medullary velum
Biachium coniunctivum
Brachlum of pOQS
Restiform body
Ligula teenia
Chorioid tela of
fourth ventricle
Cuneate tubercle
Clava
Tubercle of Rolando
Frenulum veli
Lateral lemniscus
Lingula of vernis
Fourth ventricle
Posterior medullary velum
Chorioid plexus
Foramen of Magendie
two parallel masses on either side of the mid-line, which become united above,
and then are separated again into two lateral processes which bend at right angles
and project into the lateral recesses. Portions frequently protrude through the
three openings of the ventricle into the subarachnoid space.
The floor of the fourth ventricle [fossa rhomboidea] (fig. 640). — This is thrown
into eminences and depressions indicative of the internal structures of the
brain-stem subjacent to it. Its inferior portion is the dorsal surface of the upper
portion of the medulla oblongata; its intermediate portion is the dorsal surface
of the pons region, while its superior portion belongs to the isthmus of the
rhombencephalon. Its triangular lower e.xtremity terminates as the opening of
the central canal of the spinal cord. This portion is deepened at the obex and
shows furrows which point downward and converge medialward, giving the
appearance known as the calamus scriptorius. The mid-line of the floor is sharply
distinguished by the well-marked median sulcus, which becomes shallower above
than below. In the tip of the calamus scriptorius, immediately anterior to the
obex, the median sulcus deepens to become continuous into the central canal.
This terminal depression is known as the ventricle of Arantius. Throughout the
length of the floor on either side of the median sulcus is a continuous ridge, the
medial eminence, which is bounded laterally by the limiting sulcus. Underlying
the floor of the ventricle is a layer of grey substance of varying thickness, which is
continuous with that surrounding the central canal of the cord. The medial
eminence is subdivided into portions of unequal width and elevation, and the
limiting sulcus accordingly shows fovesE of different depths.
814
THE NERVOUS SYSTEM
Beginning at the calamus soriptorius, the following areas of the floor of the fourth ventricle
are usually distinguished (fig. 640) : —
The area postrema of Retzius is a superficial vascular structure bounded inferiorly by the
tEenia and overlying the terminal portion of the nucleus of the fasciculus gracilis (clava) and a
portion of the nucleus of termination of the vagus nerve. The funiculus separans, a short
oblique fold of the floor, composed chiefly of neurogUa, separates the area postrema from the
ala cinerea (irigonum vagi), which is an oblique, grey-coloured, wing-shaped eminence indicating
the middle third of the nucleus of termination (recipient nucleus) of the vagus and glosso-
pharyngeal nerves. At the superior extremity of the ala cinerea is a well-marked triangular
depression of the limiting sulcus known as the inferior fovea. Mesial to and extending above
the ala cinerea is a narrow triangular eminence lying close to the median sulcus, which represents
the nucleus of origin of the hypoglossal nerve, the hypoglossal eminence [trigonum n. hypoglossi].
The lateral field of this eminence shows small oblique rugse, giving it a "feathery" appearance,
the area plumiformis of Retzius. The nucleus intercalatus of Van Gehuchten is a wedge-
shaped portion very slightly demarcated from the hypoglossal eminence, and intercalated
between it and the inferior fovea. This nucleus is considered by some observers as an inferior
Fig. 640. — Dohsal Surface of the Brain-stem Showing the Anatomy of the Flock op the
Fourth Ventricle. (Modified from Spalteholz.)
Median sulcus
Limiting sulcus ^
Aqueduct of cerebrum
Nucleus incertus
^^ Locus cffiruleus
Medial eminence ^■'^^
Acoustic medullary striae ■
Inferior fovea - '
Nucleus of fasciculus cuneatus — '
Taenia of fourth ventricle ^'
Area postrema^'
Nucleus of fasciculus gracilis (clava)
Posterior median fissure.
Nucleus of coch-
*'^^^ ^ learis (tuberculum
'' ^ ' acusticum)
Acustic area (nucleus
vestibularis)
^ Nucleus intercalatus
"~ Hypoglossal eminence (trigone)
^^ Irigonum vagi (ala cinerea)
^ Funiculus separans
Obex
medial extension of the nucleus of termination of the vestibular nerve (area acustica), but
Streeter, who has made a detailed study of the floor of the fourth ventricle by means of serial
sections, doubts that it is a part of this nucleus. It is much more probable that it supplies
visceral efferent flbres to the vagus and is thus a continuation of the dorsal efferent nucleus of
the vagus.
Superior to the inferior fovea, and crossing each half of the floor of the fourth ventricle,
are the acoustic striae. These are bundles of axones arising in the dorsal nuclei of termination
of the cochlear or auditory nerve, which are situated in the lateral periphery of each restiform
body. The bundles course around the dorsal periphery of the upper portion of the restiform
body, then across each half of the floor of the ventricle to the median sulcus, in which they
suddenly turn ventrally into the substance of the medulla oblongata, and in doing so they cross
the mid-line to enter the substance of the opposite side. The striie vary greatly in different
individuals, both in the degree of their prominence and their direction. Sometimes no striae
are visible from the surface. Frequently a bundle may be discerned which courses obliquely
upward and lateralward from the median sulcus to disappear in the floor further away from
the mid-Une and again, a bundle may depart from the transverse course before reaching the
median sulcus. Such a bundle ascending is sometimes called conductor sonorus. The acoustic
striae cross the acoustic area. This is the flattened elevation which occupies the whole lateral
portion of the intermediate portion of the floor of the ventricle, lateral to the limiting sulcus,
and extends into the inferior portion lateral to the inferior fovea. It represents the subjacent
STRUCTURE OF MEDULLA OBLONGATA 815
nucleus of termination of the vestibular nerve. The dorsal and ventral nuclei of the cochlear
nerve {iuberculum acusticum) are indicated by the ventro-lateral fullness in the contour of
the restiform body. In many of the mammals they produce a well-marked protuberance.
In its superior portion the medial eminence occupies the greater part of the floor of the
fourth ventricle, and in the upper part of the intermediate portion of the floor it presents a
broader, well-marked, elongated elevation, the eminence of the facial and abducens or the
colliculus facialis. This represents the mesiaOy placed nucleus of origin of the abducens and
the genu of the root of the facial nerve, which root courses around and above the nucleus of the
abducens. The nucleus of the facial is too deeply situated to produce an eminence. Lateral
to this eminence is a depression of the limiting sulcus, which overUes the mesial part of the region
of the larger portion of the nucleus of termination of the trigeminus, and is the fovea trigemini
or superior fovea. The strip of the floor above the superior fovea and lateral to the medial
eminence often appears greyish blue or dark brown, owing to pigmented cells subjacent to it,
and is known as the locus caeruleus. It also represents a portion of the nucleus of the trigem-
inus. The most superior portion of the medial eminence becomes narrow and lies close to
the mid-line. The function of the underlying grey substance producing it is uncertain, and
for this reason Streeter has named the elevation nucleus incertus, noting that by position it is
closely related to the upper portion of the nucleus of the trigeminus.
Internal Structure of the Medulla Oblongata and Pons
The finer detail of the internal structure lies within the scope of microscopic rather than
of gross anatomy. However, the significance and relations of certain of the more important
and larger of the internal structures of the meduUa and pons as observed in sections may be
considered.
The entire brain-stem may be regarded as an upward continuation of the spinal cord, to
which structures are added giving each part its peculiar character and conformation, and in
which the structures characteristic of the spinal cord are modified in varying degrees.
The pyramids, the great descending or motor cerebro-spinal fasciculi, are directly con-
tinuous into the pyramidal fasciculi of the spinal cord. They form the extreme ventro-medial
portion of the medulla, and from the fact that they contribute numerous fibres to the efferent
nuclei (nuclei of origin) of the cranial nerves and to other portions of the grey substance of
the brain-stem, they decrease appreciably in bulk in descending toward the spinal cord.
Most of the fibres contributed to the medulla, as well as to other divisions of the brain-stem,
decussate as they leave the pyramids, and terminate in the grey substance of the opposite
side. However, the chief decussation of the pyramids occurs in the lower end of the medulla.
Here usually about three-fourths of the fibres then comprising the pyramids cross the mid-
line to form the lateral cerebro-spinal fasciculus (crossed pyramidal tract) of the spinal cord
immediately below. The remaining fourth, comprising the more lateral fibres or those furthest
away from the mid-line, continues uncrossed into the spinal cord as the ventral cerebro-spinal
fasciculus or direct pyramidal tract. The majority of the latter fibres decussate gradually
in the commissural bundle and in the ventral white commissure of the cord as they approach
the levels of their termination. In practically all vertebrates except man and the apes there
are no ventral pyramidal fasciculi, the decussation in the medulla being a total one. In man,
the proportion of fibres crossing in the chief decussation varies. Cases have been noted in
which apparently the entire pjTamids decussate at this level. In other cases the direct or
ventral pyramidal tract may be much larger than usual, at the expense of the lateral. The
decussation usuaUy appears to be symmetrical and it occurs so suddenly that the fibres, in
coursing from the ventral to the lateral positions, detach the tips of the ventral horns of the
spinal cord from the remainder of the grey figure, and these appear as isolated, irregularly
shaped masses of grey substance in transverse sections of the medulla. From this level upward
the outline of the grey figure of the cord is lost, and the cell-columns of the ventral horns occur
in more or less detached groups as the motor nuclei of the cranial nerves.
The origin and decussation of the lemnisci (fillet) begins immediately above the decussa-
tion of the pyramids, and here the arrangements characteristic of the spinal cord are further
modified. The dorsal portion of the grey figure of the cord is manifest up to this level, but
here, after a considerable increase in its thickness, the grey commissure gives rise to two thick
dorsal outgrowths on each side of the mid-hne. These dorsal projections of grey substance
comprise the nuclei of termination (relays) of the chief ascending or sensory spino-cerebral
fasciculi of the spinal cord. The nucleus of the fasciculus gracilis (nucleus of GoU's column)
arises a little before the nucleus of the fasciculus cuneatus (nucleus of Burdach's column).
The former extends slightly downward from its point of origin, so that its inferior extremity is
included in sections through the decussation of the pyramids (fig. 6il). It produces a slight
bulbous enlargement (the clava) of the end of the funiculus gracihs, while the nucleus of the
fasciculus cuneatus corresponds to the cuneate tubercle of the external contour of the meduUa
(figs. 632, 640). From the cells of these nuclei arise the lemniscus — the cephalic continuation
of the spino-cerebral pathway which conveys the general bodily sensations to the cerebrum.
In passing out of the nuclei the fibres of the lemniscus course in a ventro-medial direction.
Curving around the region of the central canal, they contribute largely to the internal arcuate
fibres, then, sweeping across the mid-line, they convert it into the raphe, and immediately after
crossing (decussating) they turn cephalad and collect to form the bundle known as the lemniscus.
In the medulla, the lemnisci are two thin bands of fibres spread vertically on each side of
the raphe, with their lower or ventral edges thicker than their dorsal edges. In their course
toward the cerebrum they increase in bulk, owing chiefly to fibres being added to them from
the nuclei of termination of the aiferent roots of the cranial nerves, which fibres likewise cross
the mid-line as internal arcuate fibres to join the lemniscus of the opposite side. In passing
816
THE NERVOUS SYSTEM
through the pons, the lemnisci gradually become spread horizontally, and beyond the pons
their then more lateral portions are further displaced and come to course in the lateral borders
of the isthmus rhombencephali and mesencephalon, while the medial portions remain nearer
the mid-line. This lateral spreading of each lemniscus produces the lateral lemniscus and the
medial lemniscus, distinguished in transverse sections of the superior pons and mesencephahc
Fia. 641. — Transverse Section of Medulla Oblongata at the Level of the Decussation
OF THE Pyramids.
Central grey substance
Nucleus of fasciculus gracilis
Funiculus cuneatus
j^^^-Substantia gelatinosa (Rolandi)
Spinal tract of trigeminus
if' ' Gowers' tract
» Lateral cerebro-spinal fasciculus
V '^ Ventral horn
\ Decussation of pyramids
Pyramid
regions of the brain stem (fig. 660). The lateral lemniscus is contributed very largely by the
cell-bodies of the nuclei of termination of the cochlear nerve of the opposite side.
The reticular formation of the medulla and pons region is considerably more abundant
than in the spinal cord. As in the spinal cord, it consists of grey substance through which
nerve-fibres, singly and in small bundles, course in all directions, and more sparsely than in
other regions. In the medulla it is traversed by the internal arcuate fibres. It may be con-
FiQ. 642. — Transverse Section of Medulla Oblongata at Level of the Decussation of
THE Lemnisci,
Posterior median fissure
Central grey substance
Nucleus of hypogl
Internal arcuate fibers
Root filum of hypoglossus
Nucleus of inferior olivi
Medial accessory olivary nucleu
Nucleus of fasciculus gracilis
* Commissural nucleus of ala i
' / Nucleus of fasciculus cuneatus
Dorsal external arcuate fibres
is of spinal tract of
trigemi-nus
-- Spinal tract of trigi
Raphe'
'-- -' Restiform body
■Nucleus lateralis
V Substantia reticularis
Ventra.1 external arcuate fibres
Decussation of lemnisci
sidered an enlarged continuation of the middle portion of the grey column of the cord, dispersed
by numerous fibres, giving it the reticulated appearance which suggests its name. Its numer-
ous nerve-cells belong, for the most part, to the association and commissural systems of the brain
stem, and, therefore, the fibres arising in it correspond largely to the fasciculi proprii of the
spinal cord. As in the cord, most of the fibres are of short course, serving to associate different
portions of the same level and adjacent levels with each other. Those of long course show a
tendency to collect into a small, well-marked bundle which courses one on each side close_ to
the mid-line, ventral to the central canal in the closed part of the medulla, and near the median
sulcus of the floor of the fourth ventricle, in the open part. In the mesencephalon this bundle is
again situated closely ventral to the aquaeductus cerebri.
STRUCTURE OF MEDULLA OBLONGATA
817
This bundle is known as the medial longitudinal fasciculus (posterior longitudinal bundle).
It corresponds more nearly to the ventral fasciculus proprius of the spinal cord than to others
of the fasciculi proprii. In the medulla it appears as the dorsal edge of the lemniscus, but in
the shifting of the position of the lemniscus in the pons region, it retains its medial position and
thus becomes isolated. By position it is especially adapted for the association of the nuclei
of the cranial nerves. Evidence has been found that those fibres which arise in the corpora
quadrigemina and descend the spinal cord in its sulco-marginal or ventral mesencephalo-spinal
fasciculus, pass through the medulla in the medial longitudinal fasciculus. The nuclei of
termination of the vestibular nerve are said also to contribute many fibres to it.
The inferior olivary nucleus is an added structui-e in the medulla oblongata, i. e., it has
no homologue in the spinal cord. The two of them occupy the olivary prominences, the olives
of the exterior, and constitute the most conspicuous and striking isolated masses of grey sub-
stance in sections of the medulla. They appear as crenated laminae of grey substance folded
so as to encup a dense mass of white substance, and in actual shape the entire nucleus has
the form of an irregular corrugated cup with the opening or hilus on the side toward the mid-
line. The mass is so crumpled that the diameter of the hilus is appreciably less than the length
of the nucleus, and thus transverse sections of either extremity of it appear as closed capsules.
Fig. 643. — Transverse Section op Medulla Oblongata Through Nuclei of Vagus and
HyPOGLOSSUS AND THROUGH THE MlDDLE OP THE OlIVES.
Medial longitudinal fasciculus
Chorioid tela of fourth ventricle
Nucleus of hypoglossus
Medial nucleus of vestibular nerve "**
Descending (spinal) nucleus
of vestibular nerve
Nucleus ambiguus
Dorsal accessory
olivary nucleus
Root filum of hypo
glossus
Nucleus of ala cinerea (trigonum vagi)
/ Dorsal efferent nucleus of vagus
' ' Solitary tract
Nucleus of solitary tract
__ /
'^j^J/' /^"s^ ' — Nucleus of fasciculus
^"^'^ ''< -^ ^^' cunatus
■^ ^ ^^^*^ ^ Nucleus of spinal tract
^ ""^ \ ./Jal^^r °^ trigeminus
Restiform body
Spinal tract of
trigeminus
Cerebello-olivary
fibres
Root filum of vagus
— Nucleus lateralis
Thalamo-olivary tract
' '' Pyramid
Lemniscus Raphe
There are several small detached portions of the olivary nucleus known as the accessory
olivary nuclei. These are named according to their position with reference to the chief portion
or olive proper. They are plates less corrugated than the chief nucleus, and appear rod-like
in sections. The largest is the dorsal accessory olivary nucleus. The medial accessory olivary
nucleus is widest at its inferior end, which extends a little below the inferior extremity of the
chief nucleus. The lateral accessory olivary nucleus is the smallest. In serial sections the
accessory nuclei are found to be plates of grey substance usually continuous with one another.
The oUvary nuclei are mainly cerebellar connections. By both ascending and descending
fibres each cerebellar hemisphere is connected with the olivary nucleus of the same and opposite
sides. Serial sections of a human brain with congenital absence of one cerebellar hemisphere,
described by Strong, show that the chief connection of a hemisphere is with the olive of the oppo-
site side. These fibres necessarily pass between the cerebellum and the olives by way of the
restiform body, and, in so doing, form an obliquely coursing bundle in the lateral border of
the medulla known as the cerebello-olivary fibres (fig. 643). The olivary nuclei also comprise a
secondary relay between the spinal cord and the cerebellum by way of the spino-olivary fas-
ciculus of the cervical cord, and it will be noted that they receive fibres from the thalami. The
latter fibres, the thalamo-olivary tract, approach the olive at its lateral periphery, while upward
through the brain-stem the tract courses in a more medial position. This tract comprises one of
the cerebro-cerebellar paths. Arising in the thalamus and terminating in the olive, its impulses
reach the opposite cerebellar hemisphere by way of the cerebeUo-ohvary fibres.
The arcuate fibres are referred to as internal and external, according as they course dorsal
or ventral to the inferior ohvary nucleus.
The internal arcuate fibres comprise fibres destined for both the cerebellum and cerebrum,
and also for the association of the tegmental grey substance of the two sides in which they course.
Certain of the fibres passing between one restiform body (cerebellar hemisphere) and the
olive of the opposite side course internal to the olive of the same side, and thus form the ventral
portion of the internal arcuate fibres. As noted above, the internal arcuate fibres consist in
818 THE NERVOUS SYSTEM
greatest part of fibres being contributed to the lemnisci, arising from the cells of the nucleus of
the fasciculus gracOis and fasciculus cuneatus and sweeping downward and decussating to form
the lemniscus of the opposite side. However, all the fibres arising in these nuclei do not enter
the lemniscus. A few of them cross the mid-line with the internal arcuates, but pass on to
enter the restiform body (cerebellar hemisphere) of the opposite side. Some of these course
ventraUy and, upon approaching the olive of the opposite side, are deflected around the ventral
side of both the olive and the pyramid, and thus pass to the restiform body as external arcuate
fibres also. Certain of the internal arcuate fibres arise from the cells of the nuclei of termina-
tion of the cranial nerves and from small cells situated in the grey substance of the reticular
formation. These, in crossing the mid-line, correspond to the white commissures of the spinal
cord. Some of them terminate in the meduUa; others, especially those from the nuclei of
termination of the cranial nerves, join the lemniscus and pass toward the cerebrum; others
reach the cerebellar hemisphere of the opposite side.
The external arcuate fibres, in addition to those mentioned above, comprise certain fibres
which arise in the nuclei of the fasciculus gracilis and cuneatus and pursue a dorso-lateral course
to enter the restiform body (cerebellar hemisphere) ol the same side. These form the dorsal
segment of the external arcuates. The greater mass of the external arcuates are cerebello-
oHvary fibres. Certain of those passing from one olive to the restiform body of the opposite
side are deflected at the raphe, and course on the ventral side of both the other olive and the
pyramid in order to reach the opposite cerebeUo-ohvary bundle. Likewise, those passing
from the restiform body to the opposite olive are deflected by the olive of the same side
and pursue a similar course to the raphe. While out of the hilus of each olive streams a
dense mass of white substance, yet many of the fibres concerned with the olive pierce its walls
from all sides.
Many of the external arcuate fibres are said to be interrupted in the nucleus arcuatus.
This is a thin sheet of grey substance, variable in amount, which lies on the ventral aspect of
Fig. 644. — Reconstruction of the Inferior Olivary Nucleus, Dorso-lateral Surface.
(After Sabin.)
each pyramid, and, though it decreases inferiorly, it may be evident down to the decussation
of the pjTamids. The nucleus receives its name from the fact that its larger portion is inter-
polated in the course of the external arcuates. It is continuous anteriorly with the grey
substance or nuclei of the pons.
The external arcuate fibres of longer course, like the olives with which they are largely
concerned, have no homologues in the spinal cord.
The central canal of the closed portion of the meduUa is surrounded by a greater amount
of central grey substance, substantia grisea centralis, than is the canal in the spinal cord.
This is largely gelatinous substance, the central gelatinous substance, and the nerve-fibres in
coursing through the grey substance are partially deflected by it, leaving it as a cyhndrical,
more evident area of grey substance than in other regions. In the open portion of the meduUa
the central grey substance naturally forms a more transparent lamina just under the floor
of the fourth ventricle. In the mesencephalon it again surrounds the reformed canal or aque-
duct of the cerebrum.
The central connections of the cranial nerves are most easily homologised
with spinal-cord structures. Functionally the cranial nerves are of three varie-
ties:— (1) the motor or efferent nerves, comprising the oculomotor, the trochlear,
masticator, the abducens, the facial, the spinal accessory, and the hypoglossus;
(2) the sensory or afferent, comprising the olfactory, the optic, the trigeminus, the
vestibular, and the cochlear and (3) the mixed, motor and sensory nerves,
comprising the glosso-palatine, the glosso-pharyngeal, and the vagus. The
nuclei of origin of the motor or efferent cranial nerves and the efferent portions of
the mixed nerves are directly continuous with the cell columns of the ventral
horns of the spinal cord, while the emerging root filaments and roots of these
nerves correspond to the ventral roots of the spinal nerves. The nuclei of ter-
STRUCTURE OF MEDULLA OBLONGATA
819
mination of the afferent or sensory cranial nerves and of the sensory portions of the
mixed nerves correspond directly to the nuclei of the fasciculus gracilis and
fasciculus cuneatus, and to the cell-bodies of association and commissural neu-
rones of the medulla and cord and, functionally, are merely anterior continua-
tions of these.
The nuclei of the efferent or motor cranial nerves lie in two parallel lines, one
near the mid-line arid the other more laterally placed. The nuclei giving origin
to the oculomotor, the trochlear, the abducens, and the hypoglossus are near the
mid-line, and correspond to the ventro-medial and dorso-medial cell groups of the
ventral horns of the spinal cord; the nuclei of origin of the masticator (motor
Figs. 645 and 646. — Diagrams showing the Composition op the Cerebellar Portions
OF the Internal and External Arcuate Fibres.
Nucleus of Commissural nucleus
fasciculus of ala cinerea
gracilis
Spinal tract of trigemi]
Dorsal external arcuate fibres
-Restiform body
Ventral external arcuate fibers
Nucleus of tractus solitarius
Nucleus of ala cinerea ; Medial nucleus and descending root ot
vestibular nerve
Nucleus of fasciculus
cuneatus
^Nucleus ambiguus
-\ — Restiform body
Root filum of vagus
Cerebello-olivary fibres
Ventral external arcuate fibres
root of the trigeminus) of the facial, and the nucleus ambiguus: giving origin to
the motor portions of the glosso-pharyngeal and vagus nerves, together with the
nucleus of the spinal accessory, correspond to the ventro-lateral and dorso-lateral
cell-groups of the ventral horns of the spinal cord. The nerve-roots having medial
nuclei of origin are those which make their exit from the brain-stem along tlie more
media,l superficial line, while those having the more lateral nuclei comprise the
more lateral hne of roots apparent on the surface of the stem. Some of the effer-
ent fibres of the vagus, supposedly visceral efferent, arise from a small nucleus
dorso-medial to the nucleus ambiguus, the dorsal efferent nucleus of the vagus.
i he first two pau-s of cranial nerves, the olfactory and optic, are attached to the
820 THE NERVOUS SYSTEM
prosencephalon. These are purely sensory, and make their entrance near the
mid-line of the brain, both having superficially placed nuclei of termination. Of
the other nerves, all having sensory or afferent functions enter the brain along the
lateral or more dorsal line, and the ganglia giving origin to their afferent axones
correspond directly to the spinal ganglia of the dorsal or afferent roots of the
spinal nerves.
Commissural and associational neurones are much more numerous in the
brain-stem than in the spinal cord. Their axones serve to connect the struc-
tures on the two sides of the mid-line and to associate the different levels of the
same side. Just as in the spinal cord, those of longer com-se correspond to the
fasciculi proprii. Many of their axones descend into the spinal cord.
Of the fifteen pairs of cranial nerves, eleven pairs are attached to the medulla
oblongata and pons, viz., the trigeminus, the masticator, abducens, facial,
glosso-palatine, vestibular, cochlear, glosso-pharyngeal, vagus, spinal accessory,
and hypoglossus.
The hypoglossus, the motor nerve of the tongue, has its nucleus of origin beginning
in the lower portion of the floor of the fourth ventricle at the level of the acustic striae. It '
is a long nucleus, lying close to the mid-line and just under the floor of the ventricle (hypoglossal
eminence) and extending down to the region of the funiculus separans. Here it curves ventrally
to a slight degree, and below the obex assumes a position ventro-lateral to the central canal,
and thus extends a short distance below the level of the inferior tip of the olive. The nerve
arises as a series of rootlets which traverse the entii-e thickness of the medulla (fig. 643), to
emerge in line in the furrow between the olive and the pyramid and fuse to form the trunk of
the nerve. The lowermost of the rootlets usually emerge below the ohve. The nucleus
receives impulses — (1) from the cerebrum by way of divergent fibres from the pyramid of the
opposite side (voluntary); (2) impulses brought in by the sensory fibres of the cranial nerves
(reflex); and (3) by axones from other levels of the medulla (associational). None of its axones
are supposed to decussate, though numerous commissural fibres are known to pass between
the nuclei of the two sides.
The spinal accessory is likewise a purely motor nerve, and has a laterally placed, long, and
much attenuated nucleus of origin. Above, its nucleus is in line with and practically continu-
ous with the nucleus giving motor fibres to the vagus and glosso-pharyngeus (nucleus ambiguus).
Below, it consists of the lateral and dorso-lateral groups of cells of the ventral horn of the first
five or six segments of the spinal cord. The nerve arises as a series of rootlets which emerge
laterally and join a common trunk, which passes upward between the dorsal and ventral roots
of the upper cervical nerves and parallel with the meduOa to turn lateralward in company
with the vagus. (See fig. 629). The upper rootlets arise from that part of the nucleus con-
tiguous to the inferior end of the nucleus ambiguus, and are described as comprising the medullary
or accessory part of the nerve; those which arise from the ventral horn cells below are described
as the spinal part. The trunk of the spinal accessory fuses with the vagus in the region be-
tween its two ganglia, and, before separation, contributes fibres (the accessory part) to the
trunk of the vagus. Some of the accessory fibres are distributed as motor fibres to the muscles
of the larynx and some of them are visceral efferent fibres. The latter probably terminate
chiefly in sympathetic ganglia which send axones to the heart. The spinal part is distributed to
the sterno-mastoid and trapezius muscles. The nucleus of the spinal accessory receives termi-
nal twigs of pyramidal fibres from the opposite side and is otherwise subjected to influences
similar to those afi'ecting the cells giving origin to the motor roots of the spinal nerves.
The vagus or pneumogastric and the glosso-pharyngeus, though they have widely different
peripheral distributions, are so similar in origin and central connections that they may be
described together. Both contain efferent fibres, though both are in greater part sensory.
They are similar as to the origin of both their efferent and afferent components. The afferent
fibres of the vagus arise in its jugular gangUon and its nodosal ganghon (ganglion of the trunk);
the afferent fibres of the glosso-pharyngeus arise in its superior ganghon and its petrosal ganghon.
In both nerves these fibres enter the lateral aspect of the medulla and bifurcate into ascending
and descending branches, similar to those of the dorsal root-fibres in the spinal cord. Some
of these branches terminate in practically the same level of the medulla about cell-bodies
situated on the same and the opposite sides. Such branches end chiefly in the nuclei of the
hypoglossal and spinal accessorj^, and about the cells giving origin to the efferent components
of the vagus and glosso-pharyngeus themselves — short reflex arcs. However, most of the
afferent fibres terminate in the nucleus of termination of the vagus and glosso-pharyngeus: — (1)
the nucleus of the ala cinerea, the middle portion of which is indicated in the floor of the fourth
ventricle by the ala cinerea; (2) in the closed portion of the medulla, the lower end of the
nucleus of the ala cinerea comes to lie in the dorso-lateral proximity of the central canal, and
this portion is known as the commissural nucleus of the ala cinera (figs. 642 and 645) from the
fact that fibres may be seen which pass directly from it across the mid-line; (3) the longer of
the descending branches of the bifurcated fibres collect to form the solitary tract, a compact
bundle situated dorsaUy just ventro-lateral to the nucleus of the ala cinerea and quite con-
spicuous in sections of the medulla. The fibres of this bundle terminate in the nucleus of the
solitary trad, which is but a ventro-lateral and downward continuation of the nucleus of the
ala cinerea enclosing the bundles forming the tract. It is most probable that the fibres of the
solitary tract are chiefly from the vagus (pneumogastric), though Bruce has found evidence
that the glosso-pharyngeal contributes to it appreciably. It decreases rapidly in descending
the medulla, owing to the rapid termination of its fibres about the cells of its nucleus. It,
NUCLEI OF CRANIAL NERVES
821
with the axones given by the cells of its nucleus, is believed to extend as far downward as the
level of the fourth cervical segment of the spinal cord. This being in the level of origin of
the phrenic nerve, the tract forms a link in the respiratory apparatus which aids in the co-
ordinated respiratory movements. The axones given off by the cells of the nucleus of the
ala cinerea (terminal nuclei of the vagus and glosso-pharyngeus) course on both sides of the
Fig. 647. — Scheme showing the Relative Size and Position op the Nttclei of Origin
(Red) of the Motor and the Nuclei op Termination (Blue) op the Sensory
Cranial Nerves.
Nucleus of olfactory nerve
Nucleus of oculomotor nerve "
Nucleus of trochlear nerve
Nucleus of mesencephalic root of
masticator
Chief motor nucleus of
masticator
Nucleus of facial'
Nucleus of abducens*'
Nucleus ambiguus (vagus and
glosso-pharyngeus)
Nuclei of optic
Nucleus of hypoglossus "
Nucleus of spinal accessory nerve
^ Pulvinar o
\ thalamus
Lateral genic-
ulate body I nerve
Nucleus of supe-
rior colliculus I
- Sensory nucleus of trigeminus
, Nucleus of vestibular nerve
~ Dorsal nucleus of cochlear nerve
Nucleus alSE cinerege (vagus and
glosso-pharyngeus)
Solitary tract (vagus and glo
pharyngeus)
--Nucleus of spinal tract of trigeminus
mid-line, associating nuclei of other cranial nerves with vagus and glosso-pharyngeal impulses,
many decussating to be distributed to the structures of the opposite side. Many join the lemnis-
cus of the opposite side and pass into the cerebrum; others are distributed to the motor neu-
rones of the cervical cord of the same and opposite sides (reflex axones), and no doubt
others form central connections with the cells of the reticular formation of the medulla,
though their precise relations have not been determined. ' '
822
THE NERVOUS SYSTEM
Cell-bodies in the nucleus of the ala cinerea, the nucleus of the solitary tract and in the
commissural nucleus of the ala cinerea comprise the so-called respiratory and vaso-motor
nuclei ("centres") of the medulla. Some of the caudal branches of the axones given off by
the cells of these nuclei descend the spinal cord, not only to the segments giving origin to
the phrenic nerve, but also to those supplying the intercostal and levatores costarum muscles.
Some of these augment the solitary tract; most of them descend in the reticular formation of
the meduUa and cord. Further, axones given off by these cells convey vaso-motor impulses
which are distributed to visceral efferent neurones throughout the cord.
Fig. 648. — Diagbam illustrating Principal Central Relations op the Vagus Nerve,
EXCLUSIVE OF RELATIONS TO DESCENDING CeREBBAL OR PYRAMIDAL FIBRES.
Medial lemniscus
Dorsal efferent nucli
of vagus
Nucleus of hypogli
, Nucleus of ala cinerea
Nucleus anbiguus
— p# Ganglia of vagus
Solitary tract and nucleus
of solitary tract
The nuclei of origin of the motor fibres of the vagus and glosso-pharyngeus are the dorsal
efferent nucleus of the vagus and the nucleus ambiguus. The cells of the dorsal nucleus
of the vagus lie somewhat clustered in the ventro-mesial side of the nucleus of the ala cinerea
and lateral to the nucleus of the hypoglossus. Their axones pass outward among the entering or
afferent vagus fibres, and it is suggested that most of them are visceral efferent fibres of the
vagus, i. e., they terminate about sympathetic neurones. The nucleus ambiguus or ventral
efferent nucleus of both nerves hes in the lateral half of the reticular formation, about mid-way
between the olive and the line traversed by the rootlets of the two nerves. Its upper end is
larger. Its cells are considerably dispersed by the fibres of the reticular formation. The
axones arising from its cells course at first dorsalward and then turn abruptly outward to join
NUCLEI OF VESTIBULAR NERVE
823
the rootlets of the vagus or glosso-pharyngeus, as the case may be. The vagus is thought to
receive more efferent fibres from the nucleus ambiguus than does the glosso-pharyngeus, and
Cunningham notes that it may be questioned whether the latter nerve contains any motor
fibres at all, there being paths by which the fibres of its motor branch (to the stylo-pharyngeus
muscle) might enter it other than direct from motor nuclei.
The oesiibtdar and cochlear nerves are usually considered as one nerve and together are
designated as the acoustic or eighth cranial nerve. While both are purely sensory, are similar
in development and course together, they are distinct as to function and their nuclei of termina-
tion differ. They are here described as separate cranial nerves. The two nerves approach the
brain stem together and enter it at the lateral aspect of the junction of medulla oblongata and
pons.
The vestibular nerve arises as the central processes of the bipolar cells of the vestibular
ganglion, and passes into the brain-stem on the ventro-mesial side of the restiform body to find
its nucleus of termination (nucleus vestibularis) in the floor of the fourth ventricle. This
nucleus occupies a triangular area of considerable extent (area acustica, fig. 640), and is usually
subdivided into a lateral nucleus (Deiters'), a medial 7iucleus (Schwalbe's), a superior nucleus
(Bechterew's), and an inferior nucleus (nucleus spinaUs). The latter is a downward pro-
longation of the general nucleus vestibularis which accompanies the descending or spinal root
of the nerve.
Fig. 649. — Transverse Section of Medulla at Inferior Border of Pons.
Medial longitudinal fasciculus
Nucleus of medial
^ eminence
Acoustic medullary
^ \ stria
Descending root of i
fibular I
^Dorsal root of coch-
■^ Restiform body
Dorsal nucleus
of cochlear
nerve
^ Cochlear nerve
'Vestibular nerve
Root filum of glosso pharyngeus
Cerebello-olivary fibres
Thalamo-oUvary tract
Nucleus of inferior olive
'^ External arcuate fibres
Nucleus arcuatas
From the cells of the lateral and inferior nuclei axones are given off which form paths to
the lateral funiculus of the spinal cord (vestibulo-spinal fasciculus, fig. 619) and to its anterior
marginal fasciculus (ventral vestibulo-spinal tract). From both the lateral nucleus and the
superior nucleus a special path is given off which passes upward and terminates in the roof
nucleus of the cerebellum (nucleus fastigii) of the opposite side and in the nucleus dentatus and
the cortex of the vermis. Also, fibres arising in the nuclei fastigii are said to terminate in the
lateral (Deiters') nucleus in addition to those which probably descend into the anterior
marginal fasciculus of the spinal cord. From the medial and also from the superior nucleus
fibres pass to the medial longitudinal fasciculus of both sides, and are distributed to the
nucleus of the abducens of the same side and to the nuclei of the trochlear and oculo-
motor nerves of the opposite side and of the masticator nerve of the same and opposite sides.
From the lateral and medial nuclei, and probably from aU, fibres arise which cross the mid-
line to enter the lemniscus and ascend to the cerebrum (lateral portion of the thalamus) on
the opposite side. The lateral (Deiters') nucleus is said to contribute more fibres to the
medial longitudinal fasciculus than does a nucleus of any other cranial nerve. If any of these
fibres descend the cord, they must do so in its anterior marginal fasciculus.
The inferior nucleus is accompanied by the descending or spinal root of the vestibular nerve,
which begins to assemble in the nuclei above. This root is composed of both caudal branches
of' the entering fibres of the nerve and chiefly of fibres arising from the cells of its nuclei.
Thus for the vestibular nerve it corresponds in every way to the solitary tract for the vagus,
and to the spinal tract of the trigeminus. Such of its fibres as descend into the spinal cord
most probably do so in the lateral vestibulo-spinal fasciculus.
Many of the anatomical details of the central connections of the vestibular nerve have not
yet been determined with exactness. In addition to whatever other functions it may have,
824
THE NERVOUS SYSTEM
it is considered to be the nerve of equilibration, and the connections noted above may be
considered the pathways by which it exercises this function. The fibres of the apparatus which
are represented in the spinal cord are supposed to convey impulses to the ventral horn (motor)
cells of the cord as far down as the lumbar region.
The cochlear nerve, the auditory nerve proper, arises as the central processes of the bipolar
cells of the spiral ganglion of the cochlea. In the lateral periphery of the restiform body, just
before the latter enters the cerebellum, the nerve finds its two nuclei of termination, the ventral
nucleus and the dorsal nucleus (tuberculum acusticum, fig. 640).
From the dorsal nucleus arise the acoustic medullary strice. These bundles pass around the
dorsal aspect of the restiform body and course just under the ependyma of the floor of the fourth
ventricle to the mid-line, where they suddenly turn downward into the substance of the medullsa
and in doing so, cross to the opposite side and join the lemniscus. As the lemniscus becomes
separated higher up into a medial and lateral portion, these fibres course in the lateral lemniscul
and are distributed chiefly to the grey substance of the inferior quadrigeminate and media,
Fig. 650. — Scheme showing Some of the Central Connections op the Acoustic Nerve.
(In part after Edinger.)
Medial geniculate body
Inferior quadrigeminate body
Nucleus of trochlear nerve
Nucleus fastigii
Nucleus emboUforniis
,' Dentate nucleus
Lateral nucleus of
vestibular nerve
Restiform body
Dorsal nucleus of
cochlear nerve
Ventral nucleus of
cochlear nerve
Cochlear nerve
Peduncle of superior olivei
^ Vestibular nerve
Superior olivary nucleus
Trapezoid body
geniculate body of that side. At the mid-line some of their fibres join the median longitudinal
fasciculus and by way of it are distributed to the nuclei of origin of other cranial nerves. In
frequent cases, the acoustic striae course so deeply beneath the ependyma as not to be super-
ficially visible in the floor of the fourth ventricle.
From the ventral nucleus of termination fibres arise which terminate about the cells of the
superior olivary nucleus of the same and opposite sides. The superior olive is a small accumu-
lation of grey substance which lies in the level of the inferior portion of the pons, and in line
with the much larger inferior ohvary nucleus of the medulla. However, it is not analogous
to the latter in any sense. The two superior olives form links in the central acoustic chain.
From cells of the superior ohvary nucleus of the same and opposite sides, fibres arise which pass
by way of the lateral lemniscus and terminate in the grey substance of the inferior quadri-
geminate body and in the medial geniculate body, thus associating these bodies with the ventral
nucleus of cochlear termination of the opposite side. From the medial geniculate body fibres
arise which pass to the cortex of the superior temporal gyrus. This path is supplemented by
fibres arising in the inferior quadrigeminate body, which likewise go to the temporal lobe. In
the lateral lemniscus some of the acoustic fibres are interrupted by cells of the nucleus of the
lateral lemniscus. In crossing the mid-line, between the superior olives, the fibres from the two
sources form a more or less compact bundle, the corpus trapezoideum (trapezium). To this
are added fibres crossing between the nuclei trapeozidei, smaller masses of grey substance
just ventral to the superior olives and probably of the same significance.
Also, some fibres arising in the nuclei of termination of the cochlear nerve pass to the in-
ferior quadrigeminate body of the same side. On the other hand, the connection with the medial
NUCLEI OF CRANIAL NERVES
825
geniculate body is thought to be wholly a crossed one. Further, some fibres are described aa
terminating in the superior quadrigeminale body of both the same and the opposite side. These,
forming the stratum lemnisci of this body, are especially suggestive of associating auditory
impulses with eye movements.
All the fibres arising in the superior ohvary nucleus do not enter the corpus trapezoideum
and the lateral lemniscus. A small bundle, the peduncle of the superior olive, arises in each
nucleus and courses dorsally to the region of the nucleus of the abducens. Here certain of its
fibres terminate about the cells of the nucleus of the abducens, while others enter the medial
longitudinal fasciculus and pass to the nuclei of the trochlear and oculomotor nerves, thus
further establishing connections between auditory impulses and eye movements.
The facial nerve is commonly described as consisting of the "facial proper" and its so-called
sensory root or pars intermedia, the two together being designated as the seventh cranial nerve.
However, the pars intermedia neither serves as a sensory root for the facial nor is it purely
sensory. Many years ago Sapolini considered it a separate nerve and later it was called the
intermediate nerve of Wrisberg. More recent investigations of its development and distribution,
especially those of Streeter and Sheldon, further indicate that it merits a separate description
Fig. 651. — Transverse Section through Inferior Border op Pons and Portion of
Overlying Cerebellum (From ViUiger.)
Nucleus of roof
Nucleus globosus
Nucleus emboliformis-
Dentate nucleus
Superior nucleus
of vestibular
(Becht
Lateral nucleus of
vestibular
(Deiters')
Spinal tract of
trigeminus ' \\
Nucleus of facial
M|fw^»~~ K estif orm body
Superior olive
Thalamo-ohvans tract
and a separate name, and, indicative of its distribution, it is here described as the glosso-palatine
nerve. The facial, the glosso-palatine and the abducens all have their nuclei within the level
of the pons though the roots of all appear from under its inferior border.
The facial [nervus faciahs] has its nucleus (of origin) in the ventro-lateral region of the
reticular formation, superior to and in line with the nucleus ambiguus. The axones given off
by the cell-bodies of the nucleus collect into a bundle which, instead of passing ventrally and
directly to the exterior of the pons, courses at first dorso-mesially to the mesial side of the nucleus
of the abducens (ascending root of the facial) ; then it turns and courses superiorly for a few milli-
metres, parallel with the nucleus of the abducens and immediately beneath the floor of the fourth
ventricle {genu internum); then it turns abruptly and pursues a ventro-lateral and inferior
direction to its point of exit at the inferior border of the pons, just lateral to the olive and
mesial to the entrance of the vestibular nerve. Its exit usually involves a few pons fibres.
In transverse sections through the middle of the nucleus of the abducens the genu of the facial
appears as a compact transversely cut bundle at the dorso-medial side of this nucleus.
The nucleus of the facial is described as consisting of two chief groups of cells, an anterior
and a posterior group which give rise respectively to the axones of the superior and inferior
branches of the facial nerve. It receives cortical impulses from the lower portion of the anteiior
central gjTus of the cerebral cortex, from the root fibres of the trigeminus of the same side, which
serves as its sensory root, and (chiefly) fibres arising from the nuclei of termination of the
trigeminus. The nuclei of termination of the optic and the auditory nerves of the same and
opposite sides give rise to fibres which terminate about its cells. The fibres from the cerebral
cortex descend in the pyramidal fasciculi and cross by way of the raphe and arcuate fibres to
terminate in the nucleus of the opposite side. The anterior group of the cells of the facial
nucleus must receive cortical fibres not only from the cerebral hemisphere of the opposite but
also from that of the same side, evidenced by the fact that the superior branch of the nerve is
but little affected in facial paralysis resulting from a lesion in the cerebral cortex of one side.
A lesion destroying the root of the nerve or its nucleus of origin will of course give total facial
paralysis in the side of the lesion.
826
THE NERVOUS SYSTEM
The glosso-palatine nerve {nervus intermedius, sensory root of facial, etc.) is a mixed nerve
but largely sensory. It accompanies the facial from a short distance beyond the geniculum (genu
externum) of the facial to its attachment to the brain stem. Its sensory fibres arise as T-fibres of
the cells of the geniculate ganglion (at the geniculum of the facial) . The peripheral processes go aa
the chorda tympani to supply the epitheUum of the anterior part of the tongue and that of the
palate, especially of the palatine arches. The central processes enter the brain stem, bifurcate
into caudal and cephahc branches, and find their nucleus of termination in a superior extension
of the nucleus of the solitary tract (the ventral portion of the nucleus of the ala cinerea). The
geniculate ganghon contains some ceU-bodies of sympathetic neurones, left over in it during
the period of migration form its homologue of the ganglion crest.
The efferent fibres of the glosso-palatine arise from ceU-bodies lying dorso-medial to the
nucleus of the facial and in the level between this and the nucleus of the masticator nerve
superior to it. Its cells are usually scattered in the reticular formation in Mne with the dorsal
efferent nucleus of the vagus. Since most of its fibres, at least, are concerned with sympathetic
neurones (terminate in sympathetic gangha) and convey secretory impulses destined for the
salivary glands, it has been called the nucleus salivatorius.
Fig. 652. — Transverse Section through Pons and Portion of CEREBELLtrM at Level
OP Nuclei and Root Filaments of Abducens and Facial Nerves. (From Villiger.)
Nucleus globosus
Nucleus emboliformis
Brachium conjunctivum
Restiform body
Tractus thalamo-olivaris
Corpus trapezoideum and medial
Fourth ventricle
Brachium conjunctivum
Genu of facial nerve (pars
ascendens n. facialis)
Tractus nucleo-cerebellaris
Nucleus of abducens
Nuclei and root of
~ trigeminus
Brachium pontis
Nucleus reticularis
tegmenti
Beep stratum of pons
Superficial stratum of pons
Pyramid
Medial stratum of pons
The abducens is a smaU, purely motor nerve, which suppUes the lateral rectus muscle
of the eye. Its nucleus of origin Hes close to the mid-line in the medial eminence of the floor
of the fourth ventricle, and in line with that of the hypoglossus. Its root-fibres, uncrossed, pursue
a ventral course, inclining a Httle laterally and curving inferiorly to emerge from under the
inferior border of the pons. They pass lateral to the pyramid, and often between some of its
fascicuh. The nucleus receives cortical or voluntary impulses by way of the pyramidal
fascicuU chiefly of the opposite side. Its connection with the auditory apparatus and the
medial longitudinal fasciculus has already been noted. It probably receives afferent impulses
through the fibres of the trigeminus as well as by fibres descending from the nuclei of termi-
nation of the optic nerve. It is also associated, by way of the medial longitudinal fasciculus,
with the nucleus of the oculomotor nerve of the same and opposite sides.
The trigeminus is considerably larger than any of the nerves inferior to it, and has the most
extensive central connections of any of the cranial nerves. It is a purely sensory nerve which
enters through the brachium pontis in line with the facial nerve. It serves as the nerve of
general sensibility for the face from the vertex of the scalp downward, and thus it corresponds
to the afferent fibres (dorsal root) for all the nerves giving motor supply to structures underlying
its domain. Its fibres arise from its large, trilobed, semilunar (Gasserian) ganglion, situated
outside the brain. This corresponds to the dorsal root ganglion of a spinal nerve, and its cells
give off the characteristic T-fibres with peripheral and central branches. The central or
afferent branches upon entering the brain-stem bifurcate into ascending and descending divi-
sions, just as the entering dorsal root-fibres of the spinal nerves, and find their nucleus of ter-
mination in a dorso-lateral column of grey substance, lying deeply and extending longitudinally
through the brain stem, and consisting of the upward continuation of the gelatinous substance
of Rolando of the spinal cord. Opposite the entrance of the nerve is a considerably thickened
portion of this column of grey substance, known as the sensory nucleus of the trigeminus, and
the remainder below is called the nucleus of the spinal tract (fig. 647). Both parts are equally
"sensory." After bifurcation the branches of the entering fibres of the trigeminus terminate
about the cells of these nuclei. The descending branches are much longer than the ascending,
NUCLEI OF CRANIAL NERVES
827
Fig. 653. — Dkawing of Model of Bbain-stem showing the Nuclei of Origin of the
Motor Cranial Nerves. (After Sabin.)
828
THE NERVOUS SYSTEM
and in passing downward form the spinal tract of the trigeminus, weU marked in aU transverse
sections of the meduDa oblongata figs. 641, 642, 643, 649). The spinal tract decreases Snfdfv
m descendmg the medulla, owing to the rapid termination of its fibr1L"n the nucleus ofthetmct^^
^'^■fi^'^^''*'^'''^'^ Illustrating the Principal Central Connections of the Trigeminus
orP™lMIDAL°FlBRET'''' ^""^^^'^^ °^ ^HEIR RELATIONS TO DESCENDING CeR^rIl
Mesencephalic
nucleus and
root of masti-
cator nerve
Medial lem-
niscus
Medial longi-
tudinal
fasciculus
\ Masticator nerve
\
Semilunar ganglion
■Fasciculus proprius
It has been traced as far down as the second cervical segment of the spinal cord. The ascending
Pvt.n«i^n ^^^ f^'^l' T'* °^ *^^'^, terminate in the 'sensory nucleus,' and, therefore, the
extension upward into the mesencephalon of the nucleus of termination of the trigeminus is
both shorter and more scant than the spinal extension.
Axones from the nucleus of termination of the trigeminus are distributed— (1) to the nuclei
01 masticator nerve of the same and opposite sides (short or simple reflex fibres); (2) to the
INTERNAL STRUCTURE OF THE PONS
829
nuclei of the other motor cranial nerves, especially of the facial; (3) to the thalamus of the same
and chiefly the opposite side, and thus, through interpolation of thalamic neurones, their
impulses reach the somaisthetio area of the cerebral cortex. These fibres ascend in the recticular
formation of the opposite side, most of them finally coursing strictly withia the medial lemniscus.
In crossing the mid-line they contribute to the internal arcuates. (4) Some fibres of both
the trigeminus direct and from its nucleus pass laterally into the cerebellum. The longer of
the reflex or association axones arising in the nucleus of termination may contribute to the
medial longitudinal fasciculus; many of them descend to terminate in the grey substance of the
spinal cord below the levels in which the fibres of the spinal tract proper terminate. The
nucleus of termination is directly homologous to the nuclei of the fasciculus graciUs and fasci-
culus cuneatus, and, like the nuclei of termination of all sensory cranial nerves, it contains
cell-bodies homologous to those which give rise to the fasciculi proprii and commissural fibres
of the spinal cord.
The masticator nerve [porlio minor n. irigemini] is a purely motor nerve, usually called the
motor root of the trigeminus from the fact only that it makes its exit from the pons by the side
of the entering fibres of the trigeminus, passes outward over the ventro-mesial side of the
semilunar ganglion and accompanies the inferior maxiUary division (mandibular nerve) of the
trigeminus till it divides totally into its branches for the motor supply of the muscles of mastica-
tion. It serves, therefore, as but a relatively small part of the "motor root" of the trigeminus.
The nucleus of origin of the masticator nerve is attenuated into two parts: (1) The chief
nucleus (nucleus princeps) lies on the dorso-medial side of the larger portion (sensory nucleus)
of the nucleus of termination of the trigeminus. It is the larger of the two parts and gives
origin to much the greater part of the masticator. (2) Scattered anteriorly and continuous
Fig. 655. — Transverse Section Through i Upper Part of Pons at the Level of the
Entrance op the Trigeminus. (From Villiger.)
Anterior medullary velum
Gowers' tract-
Fourth ventricle
Fasc. long, dorsalis
(Schiitz)
Medial longitudinal
fasciculus
Corpus trapez.
and medial
lemniscus
Deep stratum of
pons
Brachium conjunctivum
Sensory nucleus of
trigeminus
Chief nucleus of ma
ticator nerve
Thalamo-
olivary tract
Lateral
aJ lemniscus
JS^ Brachium
pontis
Superficial stratum of pons
with the chief nucleus, in line with the locus coci'uleus, are the cell-bodies usually described as
the nucleus of the mesencephalic (descending) root. These cells lie in decreasing linear distribu-
tion, through the mesencephalon, as far anterior as the posterior commissure of the cerebrum,
and the mesencephalic root of the nerve accumulates as it descends to join the exit of the
fibres arising from the chief nucleus. The average diameter of its cells is somewhat less than
for the chief nucleus.
It is not clearly settled that the fibres arising from the mesencephahc nucleus of the masti-
cator nerve go to the muscles of mastication. As suggested by KoUiker, some of these may
supply the tensor veli palatini and tensor tympani muscles. Recent investigations of lower ani-
mals by Johnston and Willems indicate that the mesencephalic root may contain no motor
fibres at all, representing instead a portion of the sensory trigeminus fibres. It is claimed that
some fibres in descendtug give off collaterals which terminate about cells in the chief nucleus,
and thus an impulse descending by them is given a wider distribution and also reinforced by
the interpolation of another neurone. Such fibres, however, maj' be the sensory fibres just
mentioned terminating upon the cells of the nucleus to form simple reflex arcs.
It is claimed that each masticator nerve receives a few fibres arising from the cells of the
nucleus of that of the opposite side.
Both parts of the nucleus of the masticator receive afferent impulses brought in by the
trigeminus of the same (chiefly) and of the opposite side, and both receive cortical impulses
by fibres from the inferior portion of the precentral gyrus which descend in the cerebral ped-
uncles and cross to terminate in the nucleus of the opposite side.
The internal structure of the pons. — The nuclei and roots of the trigeminus, masticator,
abducens, facial, glosso-palatine, cochlear and vestibular nerves are extended within the level
830
THE NERVOUS SYSTEM
of the pons, and their position and course have been described above. The pons proper
(the bridge) consists of a mass of transversely running fibres continuous on either side into
the brachia pontis or middle cerebellar peduncles. In the animal series the relative amount
of these fibres varies with the size of the cerebellum upon which they are dependent. They
are relatively more abundant in man than in other animals.
In transverse sections the pons fibres are seen to course ventrally about the main axis of
the brain-stem, making it possible to divide the section into a basilar or ventral part and a dorsal
part {tegmentum). The fibres in their transverse and ventral course around the medulla oblon-
gata involve the pyramids. At the inferior border of the pons the fibres little more than separate
the pyramids as such from the main axis of the brain-stem, but more superiorly the pons fibres
pass through the pyramids, splitting them into the pyramidal fasciculi. These pyramidal or
chief longitudinal fibres of the pons are the continuation of the basal portion of the cerebral
peduncles through the pons, to emerge as the pyramids proper at its inferior border. They
occupy an intermediate or central area among the pons fibres of either side, leaving the periphery
of the pons uninvaded. The superficial pons fibres form the solid bundle of its ventral and lateral
periphery and the deep pons fibres form similar bundles dorsaUy enclosing the area of pyramidal
fasciculi (fig. 655).
In transverse sections through the inferior portion of the pons, the dorsal or tegmental part
consists of structures continuous with and analogous to the structures of the meduUa oblongata
immediately below, exclusive of the pyramids. In addition, this region contains the superior
ohvary nucleus and the corpus trapezoideum. The significance of these structures and their
relation to the nucleus of termination of the cochlear nerve is shown in figs. 650, 651 and 652. In
this region the lemniscus (fillet) changes from the sagittal to the coronal plane, and its
Fig. 656.-
-DiAGBAM SHOWING THE RhOMBENCEPHALIC CoUBSE OP GOWEBS' TrACT AND THE
Direct Cerebellar Tract.
Brachium conjunctivum
Dorsal spino-cerebellar fasciculus
(direct cerebellar tract)
Superficial antero-lateral spino-cerebellar
fasciculus (Gowers' tract)
lateral edges are becoming drawn outward and carry the lateral lemniscus of the regions
superior to this. The medial longitudinal fasciculus, left alone by the change in the arrangement
of the leminscus, maintains its dorsal position throughout the pons and into the mesencephalon
above. The thalamo-olivary tract appears loosely collected in the dorsal part of the pons,
dorso-medial to the nucleus of the superior olive.
The restiform body acquires in this inferior region a more dorso-lateral position than in the
medulla below. Its fibres are beginning to turn upward in their course to the cerebellum mesial
to the brachium pontis. Here the restiform body is nearing completion, and the fibres now
contained in it may be summarised as foUows: —
(1) The fibres of the dorsal spino-cerebellar fasciculus (direct cerebellar tract) of the same
side.
(2) Fibres from the nuclei of the fasciculus gracilis and fasciculus cuneatus of the same and
opposite side (external arcuate fibres).
(3) Fibres to and from the inferior olives of the same and (chiefly) the opposite side (cere-
bello-olivary fibres).
(4) Sensory cerebellar fibres from the nuclei of termination of the vagus, glosso-pharyngeus,
vestibular and trigeminus, vestibular especially, and from the cells of the reticular formation.
(5) Descending fibres to the motor nuclei of the vagus and glosso-pharyngeal, and fibres
descending into the anterior marginal fasciculus of the spinal cord, the latter, however, being
in large part interrupted by cells in the nuclei of the vestibular nerve.
(6) A few fibres arising from the arcuate nuclei. These nuclei are continuous superiorly
with the nuclei of the pons and some of their fibres are described as entering the cerebellum by
way of the restiform body instead of by way of the brachium of the pons as in the levels above.
The ascending fibres of the restiform body are distributed to the cortex of the vermis, the
nucleus of the roof (fastigii), the nucleus dentatus, nucleus emboliformis, and nucleus globosus.
Very few if any of the fibres ascending the cord in Gowers' tract enter the cerebellum by way
of the restiform body. This tract (the superficial antero-lateral spino-cerebellar fasciculus)
GREY SUBSTANCE OF THE PONS
831
ascends the medulla, dispersed in the reticular formation, and therefore in a more ventral posi-
tion than that of the direct cerebellar tract. In this position it becomes enclosed by the
fibres of the pons, and so it passes upward, beyond the pons, around the lateral lemniscus to
the brachium conjunctivum, and there turns back to enter the cerebellum by way of its supe-
rior peduncle. Certain clinical phenomena, probably purely psychological, have been alleged to
indicate that some of the fibres of Gowers' tract pass on to the cerebrum instead of turning in
the medullary velum to enter the cerebellum.
The dorsal part of a transverse section through the upper part of the pons contains the
superior cerebellar peduncles [brachia conjunctiva] instead of the restiform bodies or inferior
peduncles. Instead of the cerebellum forming the roof of the fourth ventricle, in this region
the roof is formed by the anterior medullary velum bridging the space between the two brachia
conjunctiva. Adhering upon the meduUary velum is the lingula cerebelli — the superior and
ventral extremity of the superior vermis. This is the only portion of the cerebellum attached
to this region.
The lemniscus (fUlet) is found more lateral than at the inferior border of the pons, and is
divided into the medial lemniscus and lateral lemniscus proper. The lateral lemniscus has shifted
dorsally until in this region it courses in the dorso-lateral margin of the section external to the
brachium conjunctivum. The mesencephalic root of the masticatornerve occurs in the dorso-
FiG. 657. — Diagram showing Connections op the Fibres of the Pons.
The plane of the section is obliquely transverse or parallel with the direction of the brachia pontis
J]^ —— Restiform body
Medial descending
cerebro-pontile path
•^Medial lemniscus
Longitudinal (pyramidal) fasciculi
lateral margin of transverse sections through this region, and this and the trigeminus are the
only cranial nerves represented here.
The transverse fibres of the ventral part of the section (pons proper), and therefore the
brachia pontis, consist of fibres coursing in opposite directions. Many are fibres which are out-
growths of the Purkinje cells of the cortex of the cerebellar hemispheres, and pass either directly
to the cerebellar hemisphere of the opposite side or turn dorsalward in the raphe to course
longitudinally in the brain-stem both toward the spinal cord and toward the mesencephalon.
Others terminate in the grey substance (nuclei) of the pons. Others are fibres which arise in
the grey substance of the pons and pass to the cerebellar hemispheres, and still others are
the cerebro-pontile fibres, from the temporal, occipital and frontal lobes.
The grey substance of the pons [nuclei pontis 1 occurs quite abundantly. At the inferior
border of the pons it is found concentrated about the then more accumulated bundles of the
emerging pyramids, and serial sections show it to be a direct upward continuation of the arcuate
nuclei of the medulla oblongata below. Higher up it is dispersed throughout the central area
in the interspaces between the transverse pontile and longitudinal pyramidal fasciculi. A
large portion of the nerve-fibres passing through it are thought to iDe interrupted by its cells,
which thus serve as links in some of the neurone chains represented by the fibres of the pons.
Of the more important of such relations, the following are said to exist: —
(1) Fibres which arise in the cortex of one cerebellar hemisphere and terminate about cells
of the nucleus pontis of the same and opposite side of the mid-line. These cells give off axones
which pass to the other cerebellar hemisphere. In this relation the nuclei of the pons are
analogous to the arcuate nuclei, save that the cerebellar fibres interrupted in the former are
connected with the cerebellum by way of the brachia pontis instead of the restiform bodies.
832 THE NERVOUS SYSTEM
(2) Certain of the descending oerebro-pontile fibres terminate about cells of the nuclei of
the pons. Such cells give off fibres which probably, for the most part, pass to the cerebellar
hemispheres, the impulses from the cerebral hemisphere of one side being conveyed to the
opposite cerebellar hemisphere. Most of the descending cerebro-pontile fibres are thought to
cross the mid-line to terminate about cells of the nuclei of the pons of the opposite side, a rela-
tion not sufficiently emphasised in the accompanying diagram (fig. 657).
Of the cerebro-pontile paths, the frontal pontile path (Ai-nold's bundle) is described as
arising in the cortex of the frontal lobe (frontal operculum) passing in the anterior portion of
the internal capsule down into the medial part of the base of the cerebral peduncle, and terminat-
ing in the grey substance of the pons. The descending temporal pontile path, sometimes
caOed Turk's bundle, arises in the cortex of the temporal lobe, traverses the posterior portion
of the internal capsule, lies lateral in the pyramidal portion of the cerebral peduncle, and termi-
nates in the grey substance of the pons. In the posterior part of the internal capsule, the tem-
poral pontile path is joined by a small bundle arising in the occipital lobe and going to the
pons nuclei. This, supposedly smaller than the other two, adds an occipito-pontile path.
The total area in cross section of the pyramidal fasciculi as they enter the pons above is
considerably greater than that which they possess as they emerge as the pyramids of the medulla
below. The difference is considered very appreciably greater than can be explained as due
to the loss of pyramidal fibres supplied to the nuclei of origin of the cranial nerves lying within
the level of the pons, and the additional difference is explained as due to the termination
within the pons of the oerebro-pontile paths.
THE ISTHMUS OF THE RHOMBENCEPHALON
The isthmus of the rhombencephalon is nothing more than the transition of
the metencephalon into the mesencephalon above. It is quite short and com-
prised of only the structures which run through it, namely, the brachia conjunc-
tiva (superior peduncles of the cerebellum), the anterior medullary velum, the
lateral sulcus of the mesencephalon, the cerebral peduncles, and the inferior end of
the interpeduncular fossa. It surrounds the superior extremity of the fourth
ventricle. The lateral and medial lemnisci, the superior extension of the nucleus
of the trigeminus, the mesencephalic nucleus and root of the masticator nerve and
Gowers' tract extend through it. At the mid-line, just inferior to the inferior
quadrigeminate bodies is the frenulum of the anterior medullary velum and the
trochlear nerves, emerging at the sides of this, course ventrally around the sides
of the isthmus. In the lateral sulcus, the isthmus shows usually a small triangular
elevation known as the trigonum lemnisci from the fact that the lateral lemniscus
tends toward the surface in this region.
Functions of the cerebellum. — From the above descriptions involving the structures of the
metencephalon, it may be noted (1) that a given side of the cerebellum is associated chiefly
with the same side of the general body and with the opposite side of the cerebrum. (2) That
it receives afferent impulses from the spinal cord (brought into the cord by the dorsal roots of
the spinal nerves) by way of the direct cerebellar fasciculus of the same side, and by Gowers'
tract and from the nuclei of the fasciculus gracilis and cimeatus of the same and opposite sides.
It further receives afferent impulses from the nuclei of termination of the trigeminus, glosso-
pharyngeal and vagus of the same side chiefly, and especially does it receive afferent impulses
from the nuclei of the vestibular nerve of the opposite and same side. (3) That the cerebellum
sends impulses to the red nucleus, the thalamus and the cerebral cortex of the opposite side,
and some of its fibres terminate in the nuclei of termination of the vestibular nerve and probably
some fibres arising in its roof nuclei descend into the spinal cord direct. (4) That the cerebel-
lum receives impulses from the thalamus of the opposite side by way of the thalamo-olivary
tract and the inferior olive, and especially from the cerebral cortex of the opposite side by way
of the frontal, temporal and occipital pontile paths and the nuclei of the pons. Further,
fibres from the general pyramidal fascicuh are described as terminating about ceUs of the nuclei
of the pons.
Taking into consideration these known associations of the cerebellum, the anatomically
possible paths which in part may distribute cerebellar impulses to the grey substance sending
efferent fibres to the peripheral tissues are (1) the general pyramidal fasciculi whose cortex
of origin may receive impulses by fibroi proprioe from the cortical areas receiving impulses from
the cerebellum. The pyramidal fasciculi, decussating, distribute impulses to the grey substance
of i the medulla and cord of the same side as that from which the cerebeUo-cerebral impulses
passed to the cortex. (2) The lateral vestibulo-spinal and the anterior marginal fasciculi to
the ventral horn of the spinal cord of the same side, probably carrying impulses descending
from the cerebellum as well as impulses brought in by the vestibular nerve and descending
direct from its nuclei of termination into the spinal cord. (3) The rubro-spinal tract of the
cord and probably some of the thalamo-spinal fibres (corpora-quadrigemina-thalamus path),
the red nuclei and thalami being associated abundantly with the cerebellum. These tracts
Hkewise decussate in descending but likewise do the cerebellar impulses ascending to their cells
of origin.
Whatever other functions it may possess, developmental defects and pathologic lesions
show that the cerebellum has to do with the equilibration of the body and the finer coordinations,
adjustive control of the contractions of functionally correlated groups of muscles. Making this
THE MESENCEPHALON 833
possible, in part at least, it is seen above that is it associated (1) directly with the special nerve
of equihbration, the vestibular; (2) with the optic apparatus by way of the thalamus, and (3)
with the afferent impulses from the general body, by way of the direct cerebellar and Gowers'
tracts, by way of the nuclei of the fasciculus gracilis and cuneatus, and the nuclei of termination
of the trigeminus, glosso-pharyngeal and vagus. It has been suggested that by way of these
latter paths the cerebellum deals especially with those general afferent impulses which arise
within the muscles of the body (neuro-musoular spindles, etc.) and which are grouped under the
name "muscular sense." The cerebellum can be considered as an enlarged and modified por-
tion of the grey substance of the spinal cord, receiving a greater number and variety of afferent
impulses and with them mediating more comprehensive and complicated reflex activities than
is possible with the less abundant grey substance of a given portion of the cord proper.
SUMMARY OF PRINCIPAL STRUCTURES IN RHOMBENCEPHALON
A. Gross Exterior.
1. Medulla Oblongata (Myelencephalon).
f Cerebellum I Hemispheres — lobes and lobules.
I I Vermis — lobules and lingula.
2. Metencephalon \ Pons { Dorsal part (preoblongata).
^ y Ventral part (pons proper).
I superior — brachium conjunctivum.
[ Cerebellar peduncles \ middle — brachium of pons.
[ inferior — restiform body.
3. Isthmus of Rhombencephalon.
4. Fourth Ventricle and its Chorioid tela.
5. Anterior and Posterior Medullary Vela.
B. Grey and White Substance.
1. Funiculus gracilis, nucleus of fasciculus gracihs, funiculus cuneatus, nucleus of fasciculus
cuneatus.
2. Internal and external arcuate fibres, decussation of lemnisci, lemniscus, medial lemniscus,
lateral lemniscus.
3. Cerebral peduncles, pyramidal fasciculi, pyramids, decussation of pyramids, arcuate
nuclei.
4. Superficial and deep strata of pons, nuclei of pons, branchia of pons.
5. Inferior olivary nuclei, cerebello-olivary fibres, thalamo-olivary tract, spino-olivary tract.
6. Nuclei emboliformis, globosus and fastigii (of the roof), and nucleus dentatus with bra-
chium conjunctivum of cerebellum.
7. Central gelatinous substance and gelatinous substance of Rolando.
8. Reticular formation.
9. Hypoglossal nerve and nucleus of hypoglossal.
10. Spinal accessory nerve and lateral nucleus.
11. Vagus and glossopharyngeal nerves, nucleus of ala cinerea, solitary tract and nucleus
of solitary tract, commissural nucleus of ala cinerea, nucleus ambiguus, dorsal efferent nucleus
of vagus.
12. Vestibular nerve — its superior nucleus (Bechterew), its medial nucleus (Schwalbe),
its lateral nucleus (Deiters), and the nucleus of its descending (spinal) root.
13. Cochlear nerve, dorsal nucleus and ventral nucleus of cochlear, acoustic medullary striae,
nucleus of superior olive, trapezoid body, nucleus trapezoidei, lateral lemniscus, nucleus of
lateral lemniscus.
14. Facial nerve and nucleus of facial nerve.
15. Glosso-palatine nerve, nucleus of glosso-palatine and nucleus salivatorius.
16. Abducens and nucleus of abducens.
17. Trigeminus, "sensory nucleus" of trigeminus, spinal tract and nucleus of spinal tract
of trigeminus.
18. Masticator nerve, chief nucleus and (so-called) mesencephaUc nucleus and root of
masticator.
19. Medial longitudinal fasciculus.
20. Nucleus intercalatus, nucleus of median eminence, nucleus incertus.
THE CEREBRUM
1. THE MESENCEPHALON
The mesencephalon or mid-brain is that small portion of the encephalon which
is situated between and connects the rhombencephalon below with the prosen-
cephalon above. It is continuous with the isthmus rhombencephali, and occupies
the tentorial notch, the aperture of the dm-a mater which connects the meningeal
cavity containing the cerebellum with that occupied by the prosencephalon.
Its greatest length is about 18 mm., and it is broader ventrally than dorsally.
Its dorsal surface is hidden by the overlapping occipital lobes of the cerebral hemis-
pheres. It consists of — (1) the lamina quadrigemina, a plate of mixed grey
and white substance which goes over lateralward and below into (2), the cerebral
834
THE NERVOUS SYSTEM
peduncles (crura) and their tegmental structures, and it contains (3), the nuclei
of origin of the trochlear and oculomotor nerves. It arises from thickenings of the
walls of the middle cerebral vesicle of the embryo, the lamina quadrigemina
arising from the dorsal or alar lamina of this portion of the neural tube, while the
basal lamina thickens to form the nuclei of the nerves, the substantia nigra, etc.,
and by the ingrowing of the cerebral peduncles. By means of the lamina quad-
rigemina roofing it over, the neural canal throughout the mesencephalon retains
its tubular form and is known as the aquaeductus cerebri (Sylvii) , connecting the
cavity of tlie fourth ventricle below with that of the third ventricle above.
External features. — Dorsal surface. — The lamina quadrigemina shows four
well-rounded elevations, the quadrigeminate bodies [corpora quadrigemina],
divided by a flat median groove crossed at right angles by a transverse groove.
The anterior pair of these, the superior quadrigeminate bodies [colliculi], are
Fig. 668. — Dorsal Surface op Mesencephalon and Adjacent Parts. (After Spalteholz.)
Epiphysis (lifted)
Taenia cliorioidea
■Camina affiza
Supi
Brachium quadn
geminum superiu
Bracliium quadn
geminum Infenus ^
Medial genicu
late body
lateral genicu-
late body
Cerebral peduncle
Inferior colhculus
Frenulum of anterior med
ullary velum
Trigone of lemniscus
Trochlear nerve
Brachium conjunctivum
Lateral filaments of pons-
" Trigeminus
— Lingula of vermis
Vinculum of lingula
Brachium of pons
Cerebellum (cut)
larger though less prominent than the inferior pair or inferior colliculi. Each
colliculus is continued laterally and upward into its arm or brachium. The
inferior brachium proceeds from the inferior colliculus, disappears beneath and is
continuous into the medial geniculate body, and enters the thalamus. The supe-
rior brachium proceeds from the superior colliculus, disappears between the medial
geniculate body and the overlapping pulvinar of the thalamus, and becomes con-
tinuous with the lateral geniculate body and thus with the lateral root of the optic
tract.
The geniculate bodies are rounded elevations of grey substance which arise as detached
portions of the thalami, and therefore belong to the thalamencephalon rather than to the
mesencephalon. The superior quadrigeminate body or superior colliculus and the lateral gen-
iculate body are a part of the optic apparatus, while the inferior colliculus and the medial genicu-
late body belong chiefly to the auditory apparatus (see Central Connections of Cochlear
Nerve). Just as the terminal cochlear nuclei are connected by a few fibres with the superior
colliculus, so do some fibres from the optic tract pass mto the inferior colliculus. Also some
fibres form the optic tract (mesial root) are said to terminate in the medial geniculate body.
Resting in the broadened medial groove between the superior quadrigeminate bodies lies
the non-nervous epiphysis or pineal body. This also belongs to the thalamencephalon.
Under the stem of the epiphysis is a strong transverse band of white substance crossing the
THE MESENCEPHALON
835
mid-line as a bridge over the opening of the cerebral aqueduct into the third ventricle. This is
the posterior commissure of the cerebrum, and contains commissural fibres arising in both the
thalamencephalon and mesencephalon. The triangular area bounded by the stem of the epi-
physis, the thalamus, and the superior coUiculus with its brachium, is known as the habenular
trigone.
Inferiorly, the lamina quadrigemina is continuous with the isthmus of the
rhombencephalon by way of the brachia conjunctiva or superior cerebellar pedun-
cles, and the anterior medullary velum which bridges between the mesial margins
of these peduncles. The narrowed upper end of the velum, the part directly below
the inferior quadrigeminate bodies, is thickened into a well-defined white band
known as the frenulum veil. From the lateral margins of this band on each side
and just below the inferior quadrigeminate bodies emerge the trochlear nerves
(the fourth pair of cranial nerves), and the increased thickness of the band is
largely due to the decussation of this pair of nerves taking place within it.
The brachium conjunctivum, together with the inferior and superior colliculi
of each side, form a marked ridge which results in the lateral sulcus of the mesen-
cephalon, a lateral depression between the base of this ridge and the cerebral
peduncle below and continuous into the transverse sulcus at the superior border
Fig. 659. — Diagram op Lateral View of Mesencephalon and Adjacent STRtrcTURES.
(After Gegenbaur, modified.)
Pulvinar of thalamus
Lateral geniculate body
Cerebral peduncle
Epiphysis
Medial geniculate body
Quadrigeminate bodies
iuJ ^ Lateral lemniscus
Superior cerebellar peduncle
Middle cerebellar peduncle
Inferior cerebellar peduncle
of the pons. The ridge is thickened laterally by the lateral lemniscus, which is
disposed as a band of white substance passing obhquely upward from under the
brachium pontis, applied to the lateral surface of the brachium conjunctivum and
which enters the lateral margin of the mesencephalon. The region at which the
lateral lemniscus approaches nearest the surface and in which the largest portion
of its nucleus lies is the slightly elevated trigone of the lemniscus.
The ventral surface of the mesencephalon is formed by the cerebral peduncles
(crura), two large bundles of white substance which are close to one another at the
superior margin of the pons, but immediately diverge somewhat, producing
the interpeduncular fossa, and in so doing pass upward and lateralward to disap-
pear beneath the optic tracts (fig. 629) . The posterior recess of the interpeduncu-
lar fossa extends slightly under the superior margin of the pons, while its anterior
recess is occupied by the corpora mammillaria of the prosencephalon. The tri-
angular floor of the fossa is the posterior perforated substance, a greyish area
presenting numerous openings for the passage of blood-vessels. It is divided by
a shallow median groove and is marked off from the medial surface of each peduncle
by the oculomotor sulcus, out of which emerge the roots of the oculomotor nerves.
The ventral surface of each peduncle is rounded and has a somewhat twisted
appearance, indicating that its fibres curve from above medialward and downward.
Sometimes two small, more or less transverse bands of fibres may be noted crossing
the peduncle — an inferior, the tcenia pontis, and a superior, the transverse pedun-
836
THE NERVOUS SYSTEM
cular tract. The inferior represents detached fibres of the pons; the superior,
running from the brachium of the inferior quadrigeminate body and disappearing
in the oculomotor sulcus, appears to be derived from the quadrigeminate bodies.
Since it is well developed in the cat, dog, sheep, and rabbit, but is absent or little
marked in the mole, it is supposed to be concerned with the optic apparatus.
Internal structure. — Transverse sections of the mesencephalon throughout
are composed of — (1) a dorsal -part, consisting of the lamina quadrigemina or the
grey sulDstance of the corpora quadrigemina, with the strata and bundles of
nerve-fibres connected with them, and the abundant central grey .substance
sm-rounding the aqueduct; (2) a tegmental part, consisting of the upward con-
tinuation of the reticular formation of the medulla oblongata and that of the
Fig. 660. — Transverse Section Through the Inpekior Quadrigeminate Bodies.
Central grey substance
Stratum zonaIe-~,
Aqueduct of-^ &
cerebrum / ~ -
Nucleus of mesen-
cephalic (descend- ,
ing) root of masti- y't^ ^
cater ■'^ »■
Nucleus of trochlear -
nerve
of lateral lemniscus
Lateral lemniscus (acoustic)
Thalamo-olivary tract
Medial lemniscus
Decussation of
brachia conjunctiva
Posterior recess of in^
terpeduncular fossa
Substantia nigra
Basis of cerebral peduncle
Superficial stratum of pons
dorsal (tegmental) portion of the pons region, to which are added the superior
cerebellar peduncles and the red nuclei of the tegmentum in which these peduncles
terminate; (3) a paired ventral part, the cerebral peduncles, each of which consists
of a thick, pigmented stratum of grey substance, the substantia nigra, spread
upon the large, superficial, and somewhat crescentic tract of white substance
known as the basis of the peduncle. The cerebral peduncles correspond to the
longitudinal or pyramidal fasciculi of the pons and medulla. Likewise the
lemniscus and the medial longitudinal fasciculus of the medulla and pons continue
through all sections of the mesencephalon.
The central grey substance is a continuation of the central gelatinous
substance of the spinal cord and the similar stratum of the medulla and that
which immediately underlies the ependyma of the fourth ventricle. As in the
spinal cord and medulla, it is largely composed of gelatinous substance. It is
much more abundant in the mesencephalon, and in sections appears as a cir-
cumscribed area comparatively void of nerve-fibres.
The nucleus of the mesencephalic root of the masticator nerve may likewise be traced through-
out the mesencephalon. It consists of a few small bundles of fibres surrounding a thin strand
THE MESENCEPHALON 837
of nerve-cells which give origin to its fibres. It courses caudalward close to the lateral margin
of the central grey substance, and is quite small at its beginning in the extreme superior part of
the mesencephalon, but as it descends toward the exit of its fibres from the pons, it increases
slightly in size, due to the progressive addition of fibres. Its nucleus also increases sUghtly
in bulk in approaching the region of the chief motor nucleus of the nerve. As mentioned
above, the investigations of Johnston and Willems in lower animals suggest that the cells of
the mesencephalic nucleus may be sensory instead of motor in character. The sensory
nucleus (nucleus of termination) of the trigeminus tapers rapidly and probably does not
extend throughout the mesencephalon.
The nuclei of the trochlear and oculomotor nerves form a practically continuous
column of nerve-cells extending close to the mid-line and ventral to the aqueduct
of the cerebrum. They are in hne with the nuclei of origin of the abducens and
hypoglossus, and, like them, may be regarded as an upward continuation of the
ventral group of the cells of the ventral horn of the spinal cord. The portion of
the column giving origin to the oculomotor nerve is considerably larger than that
for the trochlear.
Fig. 661 . — Diagrams showing the Course op Origin of the Trochlear Nerves. (Stilling.
The upper figure shows roughly the entire central course of the trochlear nerves; the lower rep-
resents their region of exit in transverse section.
Aquasductus cerebri
of trochlear, nerve TT'^A
(^■'
Decussation of trochlear nerves
\
, Trochlear nerve
^- — - — '
i-i — —
-V Aquaeductus cerebri
r w. 'X — Mesencephalic root
\ \\ \ of masticator
"' ^'- ■■ Brachium conjunctivum
Lateral lemniscus
A transverse section through the inferior quadrigeminate bodies involves a
portion of the decussation of the brachia conjunctiva and the nuclei of origin of
the trochlear nerves, while a transverse section through the superior quadri-
geminate bodies passes through the red nuclei of the tegmentum and the nuclei
of origin of the oculomotor nerves. The latter section will also involve the
brachia of the inferior quadrigeminate bodies and the medial geniculate bodies
connected with them, and, if slanting slightly forward it will involve the pul-
vinars of the thalami and the lateral geniculate bodies.
The trochlear or fourth nerve is the smallest of the cranial nerves, and is the
only one which makes its exit from the dorsal surface of the brain, as well as the
only one whose fibres undergo a total decussation.
Its nucleus of origin is situated beneath the inferior quadrigeminate bodies in the ventral
margin of the central grey substance, quite close to the mid-line and to its fellow nucleus of
the opposite side, and it is closely associated with the dorso-mesial margin of the medial longi-
tudinal fasciculus. Its root-fibres pass lateralward and dorsalward, curving around the margin
of the central grey substance, mesial to the mesencephalic root of the masticator nerve. As
the root curves toward the mid-line in the dorsal region just beneath the inferior quadrigeminate
bodies, it turns sharply and courses inferiorly to approach the surface in the superior portion
of the anterior medullary velum, the frenulum veli. In this it meets and undergoes a total
decussation with the root of its fellow nerve, and then emerges at the medial margin of the supe-
rior cerebellar peduncle of the opposite side. Having emerged, it then passes ventraUy
around the cerebral peduncle, and thence pursues its course to the superior obhque muscle of
the eye. It receives optic impulses from the superior quadrigeminate bodies and impulses
from the cerebral cortex of chiefly the same side, and it is associated with the nuclei of other
cranial nerves by way of the medial longitudinal fasciculus.
838
THE NERVOUS SYSTEM
The oculomotor or third nerve, like the trochlear, is purely motor. It is the
largest of the eye-muscle nerves. It supplies in all seven muscles of the optic
apparatus: — two intrinsic, the sphincter iridis and the ciliary muscle, and five
extrinsic. Of the latter, the levator palpebrse superioris is of the upper eyelid,
while the remaining four, the superior, medial, and inferior recti and the obliquus
inferior, are attached to the bulb of the eye. As is to be expected, its nucleus of
origin is larger and much more complicated than that of the trochlear nerve.
Practically continuous with that of the trochlear below, the nucleus is 5 or 6 mm. in length
and extends anteriorly a short distance beyond the bounds of the mesencephalon into the grey
substance by the side of the third ventricle. It hes in the ventral part of the central grey
substance, and is very intimately associated with the medial longitudinal fasciculus. Its thickest
Fig. 662. — Transverse Section Through Level op Superior Quadrigbminate Bodies.
Stratum zonale of thalamus
N Stratum zonale
/ Nucleus of superior colliculus
Epiphysis (pineal
^'—'^—•" bodyj
^^ Central grey
^^^Va - "^ ~ " substance
Optic-acoustic
reflex path
f — ^ Aquasductus
cerebri
Nucleus of mes-
— encephalic (de-
scending) root of
masticator
nerve
Nucleus of
^ oculo-motor
Fila of oculomotor nerve
Substantia nigra
portion is beneath the summit of the superior quadrigeminate body. The root-fibres leave the
nucleus from its ventral side and collect into bundles which pass through the medial longitudinal
fasciculus and course ventrally to the mesial portion of the substantia nigra, where they emerge
in from six to fifteen rootlets which blend to form the trunk of the nerve in the oculomotor
sulcus of the cerebral peduncles. Those bundles which arise from the more lateral portion of
the nucleus course in a series of curves through and around the substance of the red nucleus
below and, in the substantia nigra, join those which pursue the more direct course. The trunk
thus assembled passes lateralward around the mesial border of the cerebral peduncle.
A portion of the fibres of the oculomotor nerve upon leaving the nucleus decussate in the
tegmentum immediately below and pass into the nerve of the opposite side, in which they are
beUeved to be distributed to the opposite medial rectus muscle. The ceUs of the nucleus have
been variously grouped and subdivided with reference to the difTerent muscles supphed by the
nerve. Perlia has divided them into eight cell-groups. The nucleus may be more easily con-
sidered as composed of an inferior and a superior medial group. The inferior group consists of
a long lateral portion continuous with the nucleus of the trochlear nerve below, and a smaller
medial portion, situated in the medial plane and continuous across the mid-line with its fellow
of the opposite side. The superior medial group consists of cells of smaller size than the
inferior, and is known as the nucleus of Edinger and Weslphal. It is believed to give origin to
THE LEMNISCUS
839
the fibres (visceral efferent fibres) which terminate in the ciliary ganglion, axones from which
supply the two intrinsic muscles concerned, viz., the ciliary muscle and the sphincter iridis.
The nucleus of the oculomotor is associated with the remainder of the optic apparatus — (1)
by way of the neurones of the superior quadrigemtnate body with the optic tract (retina) and
it receives impulses from the occipital part of the cerebral cortex of the same and the opposite
sides, and probably from the motor cortex of the frontal lobe; (2) by way of the medial longitudi-
nal fasciculus with the nuclei of the trochlear and abducens (the latter making possible the co-
ordinate action of the lateral and medial recti for the conjugate eye movements produced by
these muscles), and with the nucleus of the facial (associating the innervation of the levator
palpebrifi with that of the orbicularis oculi); (3) with the nuclei of termination of the sensory
nerves, especially the auditory, by way of the lateral lemniscus and medial longitudinal
fasciculus. It is probably connected with the cerebellum by way of the brachia conjunctiva
and red nuclei.
Fig. 663. — Diagram of Longitudinal Section of NtrcLEus of Oculomotoe Neeve.
(After Edinger.)
Nucleus of posterior com-
missure and med. longit.
fasc.
Medial longitudinal
fasciculus
Ciliary muscles (a) and
sphincter of iris (b)
Levator palpebrse
Superior rectus
Medial rectus
Inferior oblique
Inferior rectus
Superior group(nucleus
of Edinger and West-
phal)
.--Inferior group
The eminence representing the inferior quadrigeminate body proper consists
of an oval mass of grey substance, the nucleus of the inferior coUiculus, containing
numerous nerve-cells, most of which are of small size. A thin superficial lamina
of white substance, the stratum zonale, forms its outermost boundary, and
fibres from the lateral lemniscus enter it laterally and from below {stratum
lemnisci). Near the lateral margin of the central grey substance occurs the
beginning of the inferior brachium, a bundle containing fibres to and from the
medial geniculate body and the inferior quadrigeminate body.
The lemniscus in the mesencephalon is considered in two parts. The more
lateral portion of the lemniscal plate occuring in the pons has here spread
dorso-latorally, and occupies a position in the lateral margin of the section, and is
known as the lateral lemniscus, while the medial portion which remains practically
unchanged in the tegmentum is distinguished as the medial lemniscus. (See
fig. 660). In the upper portion of the lateral lemniscus occurs a small, scattered
mass of grey substance, the nucleus of the lateral lemniscus, in which manj' of its
fibres are interrupted.
The upper and greater portion of the lateral lemniscus with its nucleus belongs to the
auditory apparatus, being connected with the nucleus of termination of the cochlear nerve,
chiefly of the opposite side. (See fig. 650.) A large part of the fibres of this portion terminate
in the inferior quadrigeminate bodies. Many of the latter enter at once the nucleus of the body
840 THE NERVOUS SYSTEM
(nucleus of inferior colliculus) of the same side, and disappear among its cells; others cross the
mid-line to the quadrigeminate body of the opposite side. In crossing, some pass superficially
and thus contribute to the stratum zonale, while others pass either through the nucleus or below
it and cross beneath the floor of the mecUan groove between the stratum zonale and the dorsal
surface of the central grey substance, forming there an evident decussation with similar fibres
crossing from the opposite side. Most of the fibres arising from the cells of the nucleus of the
inferior quadrigeminate body pass by way of the inferior brachium to the medial geniculate
body and the thalamus; some pass ventrally to terminate in the nucleus of origin of the trochlear
nerve and some pass forward and laterally to terminate in the cortex of the superior gyrus of
the temporal lobe, the cortical area of hearing. Another portion of the lateral lemniscus passes
obliquely forward in company with the inferior brachium, and terminates in the medial gen-
iculate body. Thus a large portion of the lateral lemniscus, the inferior quadrigeminate bodies
with their brachia and the medial geniculate bodies are concerned with the sense of hearing.
The nucleus of the inferior quadrigeminate body receives fibres which arise in the cortex of the
superior temporal gyrus of chiefly the same side.
Practically all the remainder of the lateral lemniscus terminates in the nucleus, or stratum
cinereum, of the superior quadrigeminate body of the same and opposite sides. They approach
the nucleus from below, and contribute to the well-marked band of fibres coursing on the dorso-
lateral margin of the central grey substance, and known as the 'optic-acoustic reflex path' or
stratum lemnisci (fig. 662).
The medial lemniscus arises in the medulla oblongata from the nuclei (of termination) of
the funiculus gracilis and funiculus cimeatus of the opposite side, and likewise from the nuclei
of termination of the sensory roots of the cranial nerves of the opposite side. It is, therefore,
a continuation of the central sensory pathway conveying the general bodily (including the
head) sensations into the prosencephalon. CoursLag still more laterally than in the pons below,
it passes into the hypothalamic grey substance, in the lateral portion of which most of its fibres
terminate. By axones given off from the cells of the hypothalamic nucleus the impulses borne
thither by the lemniscus are conveyed by way of the internal capsule and corona radiata to the
gyri of the somsesthetic area of the cerebral cortex.
The basis (pes) pedunculi comprises the great descending pathway from the
cerebral cortex, and thus is continuous with the internal capsule of the telen-
cephalon.
The principal components of each basis pedunculi are as follows: — (1) The pyramidal fibres,
which occupy the middle portion of the peduncle and comprise three-fifths of its bulk, and which
are outgrowths of the giant pyramidal cells of the somaesthetic area of the cerebral cortex,
chiefly the anterior central gyi'us. These supply ' voluntary ' impulses to the motor nuclei of
the cranial nerves on the opposite side, form the pyramids of the medulla, and are distributed
to the ventral horn cells of the spinal cord of the opposite side. (2) The frontal pontile fibres,
which course in the mesial part of the peduncle from the cortex of the frontal lobe to their
termination in the grey substance of the pons. (3) The occipital and temporal pontile fibres.
which run in the ventral and lateral portion of the peduncle from their origin in the occipital
and temporal lobes to their termination in the grey substance of the pons.
The substantia nigra is continuous with the grey substance of the pons and
that of the reticular formation below, and with that of the hypothalamic region
above. Its remarkable abundance begins at the superior border of the pons, and
it conforms to the crescentic inner contour of the cerebral peduncle, sending
numerous processes which occupy the inter-fascicular spaces of the latter. It
contains numerous deeply pigmented nerve-cells, which in the fresh specimen
give the appearance suggesting its name.
Its anatomical significance is not well understood. It is known that some fibres of the
medial lemniscus terminate about its ceUs instead of in the hypothalamus higher up, and Melius
has found in the monkey that a large portion of the pyramidal fibres arising in the thumb area
of the cerebral cortex are interrupted in the substantia nigra. It is probable that other fibres
of the peduncle also terminate here.
The brachia conjunctiva or superior cerebellar peduncles, in passing from their
origin in the dentate nuclei, lose their flattened form and enter the mesencephalon
as rounded bundles. In the tegmentum, under the inferior colliculi, the two
brachia come together and undergo a sudden and complete decussation. Through
this decussation the fibres of the brachium of one side pass forward to terminate,
most of them, in the red nucleus [nucleus ruber] of the tegmentum of the opposite
side (fig. 589). Some fibres are said to pass the red nucleus and terminate in the
ventrolateral part of the thalamus.
The red nuclei are two large, globular masses of nerve-cells situated in the
tegmentum under the superior quadrigeminate bodies. At all levels they are
considerably mixed with the entering bundles of the brachia conjunctiva, and
they contain a pigment which in the fresh condition gives them a reddish colour,
suggesting their name.
They receive in addition descending fibres from the cerebral cortex (frontal operculum)
and from the nuclei of the corpus striatum. From the cells of each red nucleus arise fibres
THE MESENCEPHALON
841
which pass — (1) into the thalamus and to the telencephalon (prosencephalic continuation of the
cerebellar path), and (2) fibres which descend into the spinal cord, the 'rubro-spinal tract,'
in the lateral funiculus (fig. 619). The latter cross from the red nucleus of the opposite
side and descend in the tegmentum. The red nuclei are also in relation with the fasciculus
relroflexus of Meynert, which belongs to the inter-brain.
Fig. 664. — Scheme to Illustrate the Principal or Crossed Relations op the Descend-
ing Cortical (Pyramidal) Fibrbs to the Nuclei op Origin op the Cranial Nerves.
'^ Motor gyri of cerebral cortex
Corona radiata
^Internal capsule
^ -Cerebral peduncle
^ -Nucleus of oculomotor nerve
.-■Nucleus of trochlear nerve
Nucleus of mesencephalic
' " root of masticator nerve
Nucleus of facial nerve
Nucleus of glosso-palatine
: of abducens
^ _. Nucleus ambiguus
.Dorsal efferent nucleus
of vagus
^Nucleus of hypoglossal nerve
-Nucleus of accessory nerve
_ --Decussation of the pyramids
The thalamo -olivary tract courses in the mesencephalon more dorsally than in the pons
region. It runs in the ventro-lateral boundary of central grey substance just lateral to the
nuclei of the trochlear and oculomotor nerves.
A small guadrigemino-pontile strand of fibres has been described as arising in the quadri-
gemina, especially the inferior pair, and terminating in the nuclei of the pons. Impulses carried
by these fibres are probably destined for the cerebellar hemisphere of the opposite side.
The superior quadrigeminate bodies (superior colliculi) are phylogenetically
more important than the inferior. In certain of the lower vertebrates they are
842 THE NERVOUS SYSTEM
enormously developed and in most of the mammals they are relatively larger and
appear more complicated in structure than in man. They are concerned almost
wholly with the visual apparatus, mediating most of the reflexes with which it
is concerned.
The nucleus of the superior colliculus is of somewhat greater bulk than that of the inferior.
It is capped by a strong stratum zonale (fig. 662), which has been described as composed chiefly
of retinal fibres, passing to it from the optic tract by way of the superior brachium, but, since
Cajal found in the rabbit that extirpation of the eye is followed by very slight degeneration of
the stratum zonale, it is probable that it is composed of other than retinal fibres — possibly
fibres from the occipital cortex and fibres arising within the nucleus itself. The nucleus is
separated from the central grey substance by a weU-marked band of fibres, the stratum album
profundum. This contains fibres from two sources: — (1) fibres from the lateral lemniscus
which approach the nucleus from the under side, some to terminate within it, others to cross
to the nucleus of the opposite side; (2) fibres which arise within the nucleus and course ventrally
around the central grey substance, both to terminate in the nucleus of the oculomotor nerve and
to join the medial longitudinal fasciculus and pass probably to the nuclei of the trochlear and
abducens. The lemniscus fibres often course less deeply than (2) and give the stratum lemnisci.
The optic fibres proper approach the nucleus by way of the superior brachium, and are dispersed
directly among its cells; only a small proportion of them cross over to terminate in the nucleus
of the opposite side. They consist of two varieties: — (1) retinal fibres which arise in the gang-
lion-cell layer of the retina and enter the superior brachium at its junction with the lateral root
of the optic tract, and (2) fibres from the visual area of the occipital lobe of the cerebral hemi-
sphere. Sometimes the optic fibres in their course within the nucleus of the superior coUiculus
form a more or less evident stratum near the stratum album profundum. This is known as the
stratum oplicum (stratum album medium). The portion of the nucleus between this stratum
and the stratum zonale is called the stratum cinereum.
The fibres entering the nucleus from the lateral lemniscus probably all represent auditory
connections. The stratum album profundum, composed of the lemniscus fibres and fibres
from cells of the nucleus, and the stratum opticum together, form the so-caOed 'optic-acoustic
reflex path' (fig. 662).
The mesencephalo-spinal amd the spine -mesencephalic (spino-tectal) paths course together
ventro-lateral to the nuclei of the coUiculi. In the superior quadrigeminate bodies they course
in the dorsal edge of the median lemniscus, between the stratum opticum and stratum album
profundum.
From the various studies that have been made it appears that the superior coUiculus of the
corpora quadrigemina is merely the central reflex organ concerned in the control of the eye
muscles — eye muscle refle.xes which result from retinal and cochlear stimulation, and from some
general body sensations by way of the spinal cord. Fibres from its nucleus to the visual area
of the occipital cortex have been claimed for certain mammals, but in man the superior colliculus
may be entirely destroyed without disturbance of the perception of light or color and flbres
arising from its nucleus to terminate in the cerebral cortex are denied.
In the level of the anterior part of the superior colliculus the fibres which arise from the cells
of its nucleus and course ventrally in the stratum album profundum ooUect into a strong bundle.
This bundle passes ventral to the medial longitudinal fasciculus and, in the space between the
two red nuclei, it forms a dense decussation with the similar bundle from the opposite side. In
decussating the fibres turn in spray-like curves downward and soon join the medial longitudinal
fasciculus. This is the 'fountain decussation' of Forel. It is said to be augmented by decus-
sating fibres from the two red nuclei.
There is abundant evidence that fibres arising in the corpora quadrigemina descend into
the spinal cord. Various studies make it appear that at least part of these are fibres from the
fountain decussation, and that these course through the medulla oblongata in the ventral part
of the medial longitudinal fasciculus, and thence descend into the cord in the 'quadrigemino-
thalamus path' (lateral mesencephalo-spinal tract) (fig. 619). The medial longitudinal fasci-
culus is continuous with the ventral fasciculus proprius of the spinal cord and most of these
fibres arising in the superior quadrigeminate bodies retain their ventral position in the cord
as the sulco-marginal fasciculus of the opposite side. Their termination about those ventral
horn cells of the cervical cord which send fibres through the rami communicantes probably
establishes the pathway by which the superior quadrigeminate bodies are connected with the
cervical sympathetic ganglia, and by which may be explained the disturbances in pupillary
contraction induced by lesions of the lower cervical cord.
The medial geniculate body and the medial root of the optic tract, which runs into the
former, probably have nothing to do with the functions of the optic apparatus. Both remain
intact after extirpation of the eyes. The medial root of the optic tract is apparently nothing
more than the beginning of the inferior cerebral (Gudden's) commissure, a bundle passing by
way of the optic tract, connecting the medial geniculate body of one side with that of the other
side, and probably with the inferior colliculus.
The medial longitudinal fasciculus (posterior longitudinal fasciculus), con-
tinuous into the ventral fasciculus proprius and the sulco-marginal fasciculus of
the spinal cord, extends throughout tlae rhombencephalon and mesencephalon,
and is represented in the hypothalamic region of the prosencephalon. Deserted
by the lemniscus at the inferior border of the pons, it maintains its closely medial
position and courses throughout in the immediate ventral margin of the central
grey substance of the medulla and floor of the fourth ventricle, and likewise
in the ventral margin of the central grey substance of the mesencephalon.
THE PROSENCEPHALON 843
The two fasciculi constitute the principal association pathways of the brain-stem, and, true
to their nature as such, they are among the first of its pathways to acquire medullation. In the
mesencephalon they become two of its most conspicuous tracts, and their course, in most inti-
mate association with the nuclei of origin of the nerves supplying the eye muscles, suggests
what is probably one of their most important functions, viz., that of associating these nuclei
with each other and of bearing to them fibres from the nuclei of the other cranial nerves neces-
sary for the co-ordinate action of the muscles of the optic apparatus associated with the functions
of these other nerves.
Fibres from each medial longitudinal fasciculus terminate either by collaterals or terminal
arborisations about the cells of the motor nuclei of aU the cranial nerves, and each nucleus prob-
ably contributes fibres to it. It also receives fibres from the nuclei of termination of the sensory
nerves especially the vestibular. Thus it contains fibres coursing in both directions, and,
while it is continually losing fibres by termination, it is being continually recruited and so
maintains a practically uniform bulk. Thus, a given lesion never results iu its total degenera-
tion. Many of the fibres coursing in it arise from the opposite side of the mid-line. A special
contribution of fibres of this kind is received by way of the fovmtain decussation from the
nucleus of the superior coUiculus of the opposite side. As noted above, it is in part continu-
ous into the spinal cord as the ventral fasciculus proprius. It receives some fibres by way of
the posterior commissure of the prosencephalon from a small nucleus common to it and the
posterior commissure situated in the superior extension of the central grey substance of the
mesencephalon. Van Gehuchten and Edinger describe for it a special nucleus of the medial
longitudinal fasciculus situated beyond this commissure in the hypothalamic rsgion. This
nucleus may be explained as an accumulation of the gray substance of the reticular forma-
tion below and as receiving impulses from the structures of the prosencephalon which are dis-
tributed by its axones to the structures below by way of the medial longitudinal fasciculus.
Scattered in the posterior part of the posterior perforated substance, near the superior
border of the pons, is a small group of ceU-bodies forming the inter -peduncular nucleus (inter-
peduncular gangUon of von Gudden). Fibres arising in the habenular nucleus of the diencepha-
lon curve posteriorly, forming the fasciculus retroflexus of Meynert, and terminate about its
cells. Fibres arising from its cells course dorsalward and terminate about association neurones
in the ventral periphery of the central grey substance. It is concerned with olfactory impulses.
SUMMARY OF THE MESENCEPHALON
1. Quadrigeminate bodies:
(a) Inferior coUicuU, their nuclei and brachia.
(6) Superior colhculi, their nuclei and brachia.
2. Pedimcles of the cerebrum
3. Aqueduct of the cerebrum.
4. Central grey substance.
5. Substantia nigra.
6. Decussation of superior cerebellar peduncles and the red nuclei.
7. Medial lemniscus, lateral lemniscus and nucleus of lateral lemniscus.
8. Mesencephalic nucleus and root of masticator nerve.
9. Trochlear nerve and its nucleus.
10. Oculomotor nerve and its nucleus.
11. Mesencephalo-spinal and rubro-spinal tracts.
12. Medial longitudinal fasciculus, its nucleus, the nucleus of the posterior commissure.
13. The fountain decussation.
14. Interpeduncular nucleus.
As frequently reaUzed in the above, the structures of the mesencephalon are both overlapped
by, and are of necessity functionally continuous with, the structures of the next and most ante-
rior division of the encephalon, the prosencephalon.
2. THE PROSENCEPHALON
The prosencephalon or fore-brain includes those portions of the encephalon
derived from the walls of the anterior of the three embryonic brain-vesicles. In
its adult architecture it consists of — (1) the diencephalon (interbrain), comprising
the thalamencephalon or the thalami and the structm-es derived from and
immediately adjacent to them, and, in addition, the mammillary portion of the
hypothalamic region; (2) the telencephalon (end -brain), comprising the optic
portion of the hypothalamic region and the cerebral hemispheres proper. The
last mentioned consist of the entire cerebral cortex or superficial mantle of grey
substance, including the rhinencephalon, and also the basal ganglia or buried
nuclei (corpus striatum), together with the tracts of white substance connecting
and associating the different regions of the hemispheres with each other and with
the structures of the other divisions of the central nervous system.
EXTERNAL FEATURES OF THE PROSENCEPHALON
A. THE DIENCEPHALON. — The basal surface of this division of the brain
consists of only the mammillary portion of the hypothalamic region (fig. 668).
844
THE NERVOUS SYSTEM
This comprises — (1) the mammillary bodies [corpora mammillaria] (albicantia) ,
the two rounded projections situated in the anterior part of the interpeduncular
fossa, and (2) the anterior portion of the posterior perforated substance or the
small triangle of grey substance forming the floor of the posterior part of the
third ventricle, and which represents numerous openings for the passage of
branches of the posterior cerebral arteries (fig. 668) . The hypothalamic portions
of the cerebral peduncles might be included. The structures of the optic or re-
maining portion of the hypothalamus belong to the telencephalon.
The upper or dorsal surface of the diencephalon is completely overlapped and
hidden by the telencephalon, and covered by the intervening ingrowth of the
Fig. 665. — Doesal Surface of Diencephalon with Adjacent Structukes.
(After Obersteiner.)
Coipus callosum
Fifth ventricle
Septum pellucidum
Caudate nucleus
Lateral sul
encephalon
Eminence of hypoglossal
Restifcrm body
Clava
Posterior fissure
Postero-intermediate sulcus
Postero-lateral sulcus
Habenular commissure
Epiphysis
Sulcus cor]
media
Inferior coUiculus
Frenulum veli
Lingula cerebelli
Acoustic area
vagi
Tuberculum cuneatum
Funiculus gracilis
Funiculus cuneatus
Lateral funiculus
cerebral meninges, the tela chorioidea of the third ventricle (velum interpositum).
These removed (fig. 665), it is seen that the thalami on either side are by far the
most conspicuous objects of the diencephalon. They, together with the parts
developed in connection with them, are distinguished as the thalamencpehalon.
The thalamencephalon consists of — (1) the thalami; (2) the metathalamus or
geniculate bodies; and (3) the epithalanius, comprising the epiphysis with the
posterior commissure below it and the habenular trigone on either side.
The thalami are two ovoid, couch-like masses of grey substance which form
the lateral walls of the third ventricle. The cavity of the ventricle is narrow, and
quite frequently the thalami are continuous through it across the mid-hne by a
small but variable neck of grey substance, the massa intermedia ("middle com-
missure"). The upper surfaces of the thalami are free. The edges of the tela
chorioidea of the third ventricle are attached to the lateral part of the surface of
each thalamus, and, when removed, leave the taenia chorioidea lying in the chori-
THE DIENCEPHALON
845
oidal sulcus. Each thalamus is separated laterally from the caudate nucleus of
the telencephalon, by a linear continuation of the white substance below, known
as the stria terminalis thalami (taenia semicircularis). Like the quadrigemina,
each thalamus is covered by a thin capsule of white substance, the stratum
zonale. The average length of the thalamus is about 38 mm., and its width about
14 mm.; its inferior extremity is directed obliquely lateralward. The dorsal
surface usually shows four eminences, indicating the position of the so-called
nuclei of the thalamus within. These are the anterior nucleus or anterior tubercle,
the medial nucleus or tubercle, the lateral nucleus, and the pulvinar, the tubercle of
the posterior extremity. The pulvinar of the human brain is peculiar in the fact
that it is so developed as to project inferiorly and slightly overhang the level of
the quadrigeminate bodies. The projecting portion assumes relations with the
optic tract and the metathalamus.
Fig. 666.-
-DissECTioN OF Brain showing Metathalamus and Pulvinar with Adjacent
Structures.
Caudate nucleus
Stria terminalis of thalamus
Pulvinar
Optic tract
Inferior quadrigemi
nate body
Medial geniculate body
Lateral geniculate body
Mammillary body
Optic tract
Olfactory buib
Insula (central lobe)
Tail of caudate nuclei
Both the structures of the metathalamus, the lateral and medial geniculate
bodies, are connected with the optic tract, but it is thought that actual visual
axones terminate only in the lateral genticulate body. As the optic tract curves
around the cerebral peduncle it divides into two main roots. The lateral gen-
iculate body receives a small portion of the fibres of the lateral root of the optic
tract; the remainder pass under this body and enter the pulvinar of the thalamus.
The medial geniculate body is connected with the medial root of the optic tract,
which root consists largely, not of retinal fibres, as does the lateral root, but of the
fibres forming Gudden's commissure (the inferior cerebral commissure). The
retinal fibres contained in the medial root pass to terminate in the superior
quadrigeminate bodies.
Of the epithalamus, the epiphysis (pineal body, conarium) is the most con-
spicuous external feature. This is an unpaired, cone-shaped structure, about 7
mm. long and 4 mm. broad, which also projects upon the mesencephalon so that
its body rests in the groove between the superior quadrigeminate bodies. Its
stem is attached in the mid-line at the posterior extremity of the third ventricle,
and therefore just above the posterior commissure of the cerebrum (fig. 658).
It is covered by pia mater, and is involved in a continuation of the tela chorioidea
846
THE NERVOUS SYSTEM
of the third ventricle. Though it develops as a diverticulum of that portion of
the anterior primary vesicle which gives origin to the thalamencephalon, it is
wholly a non-nervous structure, other than the sympathetic fibres which enter it
for the supply of its blood-vessels.
It consists of a dense capsule of fibrous tissue (pia mater) from which numerous septa pass
inward, dividing tlie interior into a number of intercommunicating compartments filled with
epithelial (ependymal) cells of the same origin as the ependyma lining the ventricles and aque-
duct below. Among these cells are frequently found small accretions (brain-sand, acervulus
cerebri), consisting of mixed phosphates of lime, magnesia, and ammonia and carbonates of
lime. The compartments form a closed system. In function the epiphysis ranks as one of the
glands of internal secretion of the body, and it is often referred to as the 'pineal gland.' How-
ever, it is perhaps funotionless in man.
Fig. 667. — Mesial Section of Entire Brain, showing Mesial Surface of Diencephalon
_^'7' ; AND Telencephalon. (After Henle.)
Massa
Hypothalamic sulcus intermedia Interventricular foramen (Monroi)
Posterior commissure \ i .
/ Sulcus of corpus callosum
Epiphys
Splemum of corpus
callos
Lamina
quadrigemina
Anterior commissure
Sub-callosal
gyrus
Aqueduct of
cerebrum (Sylvii)
Anterior medullary
velum
Genu of corpus
V callosum
Rostrum of corpus
callosum
Lamina terminalis
Cerebellum
Fourth ventricle
Hypo- \ Optic 1
Medulla / / I Physis Qptic chiasma
Pons Mammil- Tuber
lary body cinereum
Apparently arising from the base of the epiphysis, but having practically
nothing to do with it, are the striae meduUares of the thalamus (striae pineales,
pedunculi conarii, taenia thalami, habenulse) . These are two thin bands of white
substance which extend from under the epiphysis anteriorly upon the thalamus,
along the superior border of each lateral wall of the third ventricle, and thus form
the boundaries between the superior and mesial surfaces of each thalamus.
They have been called the habenulce, from their relation to the habenular nucleus, situated
in the mesial grey substance at their inferior ends. They are continuous across the mid-line
in the habenular commissure, just below the neck of the epiphysis, and between it and the pos-
terior cerebral commissure, or, rather the superior part of the latter (figs. 631, 665). It will be
seen below that each habenula contains olfactory fibers from the fornix, the anterior perfor-
ated substance and the septum pellucidum, as well as fibres out of the thalamus, and that most
of its fibres terminate in the habenular nucleus.
The ventro-lateral surface of the thalamencephalon is continuous into the
hypothalamic tegmental region, the upward continuation of the tegmental grey
substance of the mesencephalon. It is also adjacent to a portion of the internal
capsule. Both these relationships, as well as the fibre connections of the dien-
cephalon with the structures above and below it, are deferred until the discussion
of the internal structure of the prosencephalon.
The mesial surface of the diencephalon (fig. 667), allows a better view of the
shape and relations of the third ventricle. Below the line of the massa inter-
media the ventricle is usually somewhat wider than it is along the upper margins of
THE TELENCEPHALON
847
the thalami. This greater width is occasioned by a groove in the ventromesial
surface of each thalamus, known as the hjrpothalamic sulcus (sulcus of Monro).
It is along the line of this sulcus that the third ventricle is continuous with the
aqueduct of the cerebrum, and thus with the fourth ventricle below, and, likewise,
with the two lateral ventricles of the cerebral hemispheres at its anterior end.
The latter junction occurs through a small oblique aperture, the interventricular
foramen (foramen of Monro), one into each lateral ventricle. The dorsal or
upper portion of the third ventricle extends posteriorly beneath its chorioid tela
Fig. 668. — Ventral Aspect of Brain-stem Including Mammillaht and Optic Portions
OF THE Hypothalamus.
Insula
Anterior perforated
substance ^^|
nillary bodies,
Cerebral peduncle
Semilunar (Gasser
ian) ganglion
Oblique fascicul
of pons
Hypophysis
1 TN
Optic nerve
Optic tract
Oculomotor nerve
Hypoglossal nerve
Decussation of pyramids
_-- Cervical II
(velum interpositum) to form a small postfiiur n^ccss about the epiphysis. This is
known as the supra-pineal recess. The anterior and ventral extremity of the
third ventricle involves the pars optica hypothalami, which belongs to the
telencephalon.
B. THE TELENCEPHALON. — External features. — The optic portion of the
hypothalamus consists of that small central area of the basal surface of the telen-
cephalon which includes and surrounds the optic chiasma, and comprises the
structures of the floor of the anterior and ventral portion of the third ventricle.
The area extends anteriorly from the mammillary bodies in the interpeduncular
fossa, and includes the tuber cinereum and hypophysis behind the optic chiasma,
and some of the anterior perforated substance in front of it.
The most anterior portion of the third ventricle is in the form of a ventral ex-
tension. The wall of this portion is almost wholly non-nervous and quite thin,
and thus the cavity of the ventricle is but thinly separated from the exterior of
848 THE NERVOUS SYSTEM
the brain. The front portion of this wall is the lamina terminalis and in the ven-
tricular side of the upper part of this lamina the anterior commissure of the
cerebrum is apparent.
The optic chiasma lies across and presses into the lower portion of the lamina
terminalis, and in so doing produces an anterior recess in the cavity of the ventri-
cle known as the optic recess. Behind the optic chiasma the floor of the third
ventricle bulges slightly, giving the outward appearance known as the tuber
cinereum, and the cavity bounded by this terminates in the infundibular recess.
The tuber cinereum then is a hollow, conical projection of the floor of the
third ventricle, between the corpora mammillaria and the optic chiasma. Its wall
is continuous anteriorly with the lamina terminalis and laterally with the anterior
perforated substance.
The infundibulum is but the attenuated apex of the conical tuber cinereum,
and forms the neck connecting it with the hypophysis. It is so drawn out that it
is referred to as the stalk of the hypophysis. The cavity of the tuber cinereum
(infundibular recess) is sometimes maintained throughout the greater part of the
length of the infundibulum, giving it the form of a long-necked funnel. Near the
hypophysis the cavity is always occluded.
Fig. 669. — Diagrams op the Hypophysis Cerebri. (After Testut.)
A, posterior surface; B. transverse section; C, sagittal section; 1, anterior lobe; 2, posterior
lobe; 3, infundibulum; 4, optic chiasma; 5, infundibular recess; 6, optic recess. In C the
infundibulum is relatively much shorter than in the actual specimen.
The hypophysis cerebri (pituitary body or gland) is an ovoid mass terminating
the infundibulum. It lies in the sella turcica of the sphenoid bone, where it is held
down and roofed in by the diaphragma selloe, a spheroid pocket of the dura mater.
It consists of two lobes, a large anterior lobe, the glandular or buccal lobe, and a
smaller posterior or cerebral lobe. The posterior lobe is usually enclasped in a
concavity of the anterior lobe.
Development. — The posterior or cerebral lobe alone is originally continuous with and a part
of the infundibulum. It alone represents the termination of the hollow diverticulum which,
in the embryo, grows downward from that part of the anterior cerebral vesicle which later
becomes the third ventricle. The driginal cavity afterward becomes obliterated except in the
upper part of the infundibulum. It is, therefore, of cerebral origin. The anterior or buccal
lobe arises quite differently. It is developed from an upward tubular diverticulum (Rathke's
pouch) of the primitive buccal cavity. In the higher vertebrates, including man, its connection
with the buccal cavity becomes obliterated as the cartilaginous base of the cranium is consoli-
dated, but in the myxinoid fishes the connection remains patent in the adult. Cut off within
the cranial cavity, the embryonic buccal lobe assumes its intimate association with the cerebral
lobe. In about the second month of fetal life it begins to develop numerous secondary diverti-
cula which become the epithelial structures evident in the adult human subject.
Structure. — The posterior or cerebral lobe retains no organized structure. It may be said
to consist of a mass of neuroglia and other fibrous connective tissue with the cells belonging to
these and a moderate suppl}' of blood-vessels, with some sympathetic cell-bodies and fibres for
the blood-vessels. The anterior or glandular lobe is probably the functional part of the organ.
In addition to its abundant supporting tissue, it consists of compartments lined with two kinds of
ouboidal cells — cells of different size and different staining properties. The principal or more
numerous cells are smaller, with thicldy granular cytoplasm. In mi.xtures containing orange G
and fuchsin these cells stain orange, while the chromophile cells, the larger and less numerous
variety, take the fuchsin deeply. The compartments have an abundant blood supply. Near
the interlobar septum, the cells frequently are arranged to form small vesicles which contain
colloid substance, resembling the typical structure of the thyreoid body.
Like the epiphysis, the hypophysis must be regarded as glandular — a gland with internal
secretion. In the case of giants and in acromegaly it is usually greatly enlarged. The principal
cells increase greatly in number after removal of the thyreoid body.
The fundaments of the optic nerve are derived from this portion of the telen-
cephalon, though the nuclei of termination of its fibres are located in the thalam-
THE OPTIC TRACTS
849
encephalon and mesencephalon. The optic apparatus consists of the retinae
and optic nerves, the optic chiasma, the optic tracts, the superior quadrigeminate
bodies with their relations with the nuclei of the eye-moving nerves, the meta-
thalamus, the pulvinar of the thalamus, and the visual area of the cerebral cortex
of the occipital lobe. The fibres of the optic nerves arise from the cells of the
ganglion-cell layer of the retinae. The fibres which arise in the mesial or nasal
halves of each retina cross the mid-line to find their nuclei of termination in the
central grey substance of the opposite side, while those from the outer or lateral
halves terminate on the same side (fig. 670.)
The optic chiasma (optic commissure) is functionally independent of the struc-
tures of the optic portion of the hypothalamus adjacent to it. It is formed by the
Fig. 670. — Diagram of the Principal Components op the Optic Apparatus. (After
Cunningham.)
approach and fusion of the two optic nerves, and is knit together by the decussat-
ing fibres from the nasal halves of each retina, and, in addition, by the fibres of
Gudden's commissure which is contained in it.
Beyond the chiasma the optic fibres continue as the optic tracts which course
posteriorly around the cerebral peduncles to attain their entrance into the thalam-
enchephalon and mesencephalon. Upon reaching the pulvinar of the thalamus
each optic tract divides into two roots, a lateral and mesial.
The lateral root contains practically all of the true visual fibres — fibres arising from the latera
half of the retina of the same side and the nasal half of the retina of the opposite side. These
fibres are distributed to three localities: — (1) part of them terminate in the lateral geniculate
body; (2) the greater portion pass over and around the lateral geniculate body and enter the
pulvinar; (3) a considerable portion enter the superior quadrigeminal brachium and course in
it to terminate in the nucleus of the superior quadrigeminate body. The most evident function
of this latter portion is to bear impulses which, by way of the neurones of the quadrigeminate
body, are distributed to the nuclei of the oculomotor, trochlear, and abducent nerves, and thus
mediate eye-moving refiexes. The cells of the lateral geniculate body and the pulvinar, about
which the retinal fibres terminate, give off a.xones which terminate in the cortex of the visual
area, chiefly the gyri about the calcarine fissure of the occipital lobe. In reaching this area they
curve upward and backward, coursing in a compact band of white substance known as the optic
850 THE NERVOUS SYSTEM
radiation (radiatio oocipito-thalamica, fig. 699). Whetlier any fibres of the optic radiation arise
in tlie superor quadrigeminate body is doubtful. It also is in large part composed of fibres
arising from the cells of the visual area, which pass from the cortex to the pulvinar, superior
quadrigeminate bodies, and possibly some to the medulla oblongata and spinal cord.
The mesial root of the optic tract contains few true visual fibres. It runs into the medial
geniculate body, and neither it nor this body are appreciably affected after extirpation of both
eyes. It may be considered as largely representing the fibres of Gudden's commissure (infe-
rior cerebral commissure). This commissure consists of fibres which connect the medial genicu-
late bodies of the two sides with each other, and which, instead of crossing the mid-line through
the mesencephalon, course in the optic tracts and cross by way of the posterior portion of the
optic chiasma. It consists of fibres which both arise and terminate in each of the bodies, and,
therefore, of fibres coursing in both directions. It is also claimed that the fibres of Gudden's
commissure connect the medial geniculate body of each side with the inferior colliculus of the
opposite side.
THE CEREBEAL HEMISPHERES
The cerebral hemispheres in man form by far the largest part of the central
nervous system. Together, when viewed from above, they present an ovoid
surface, markedly convex upward, which corresponds to the inner surface of the
vault of the cranium. The greater transverse diameter of this surface' lies
posteriorly in the vicinity of the parietal eminences of the cranium. The outline
of the superior aspect varies according to the form of the cranium, being more
spheroidal in the brachycephalic and more ellipsoidal in the dolichocephalic
forms. The hemispheres are separated from each other superiorly by a deep
median slit, the longitudinal fissure, into which fits a duplication of the inner layer
of the dura mater known as the falx cerebri. The posterior or occipital extrem-
ities of the hemispheres overlap the cerebellum, and thus entirely conceal the
mesencephalon and thalamencephalon. They are separated from the superior
surface of the cerebellum and the corpora quadrigemina by the deep transverse
fissure. This is occupied by the tentorium cerebelli, which is similar to and con-
tinuous with the falx cerebri and is connected with the tela chorioidea of the third
ventricle below.
Each of the hemispheres is usually described as having three poles or projecting
extremities, and three surfaces bounded by intervening borders. The most
anterior projection is the frontal pole. This is near the mid-line, and with its
fellow of the other hemisphere, forms the frontal end of the ovoid contour of the
cerebrum. The occipital pole is the most projecting portion of the posterior and
inferior end, and is more pointed than the frontal pole. The infero-lateral por-
tion of the hemisphere is separated anteriorly by the deep lateral fissure (fissure
of Sylvius) into a distinct division, the temporal lobe, and the anterior portion
of this lobe projects prominently forward and is known as the temporal pole.
The surfaces of the hemisphere are — (1) the lateral or convex surface; (2) the
medial surface; and (3) the hasal surface. The convex surface comprises the
entire rounded aspect of the hemisphere visible previous to manipulation or
dissection, and is the surface subjacent to the vault of the cranium. The mesial
surface is perpendicular, flat, and parallel with that of the other hemisphere, the
two bounding the longitudinal fissure and for the most part in contact with the
falx cerebri. The superomesial border intervenes between the convex and medial
surfaces, and is thus convex and extends from the frontal to the occipital pole.
The more complex hasal surface fits into the anterior and middle cranial
fossae, and posteriorly rests upon the tentorium cerebelh. Thus it is subdivided
into — (a) an orbital area, which is slightly concave, since it is adapted to the
orbital plate of the frontal bone, and is separated from the convex surface by the
necessarily arched superciliary border and from the mesial surface by the medial
orbital border, the latter being straight and extending from the frontal pole
mesial to the olfactory bulb and tract; (fo) a tentorial area or surface, which is arched
in conformity with the dorsal surface of the cerebellum. This is separated from
the convex surface by the infero-lateral border, which runs from the occipital to
the temporal pole; and from the mesial surface by the medial occipital border,
which is a more or less rounded ridge extending from the occipital pole obliquely
upward in the angle formed by the junction of the perpendicular falx cerebri and
the horizontal tentorium cerebeUi. This border is best seen in brains which have
been hardened with the membranes in situ. The remainder of the basal surface
includes the ojDtic portion of the hypothalamus already considered, and the small
THE CORPUS CALLOSUM
851
depressed and punctate area, the anterior perforated substance, which is pene-
trated by the antero-lateral group of the central branches of the anterior and
middle cerebral arteries and into which the striae of the olfactory trigone disappear.
In addition to the orbital area the basal surface of the hemisphere shows signs of
the impress of the petrous portion of the temporal bone and of the great wing of
the sphenoid.
The corpus callosum. — In their early development as lateral dilations of the
anterior primary brain-vesicles, the hemispheres are connected with each other
only at the anterior end of the thalamencephalon, where they are both continuous
with the lamina terminalis. As development proceeds and the hemispheres
extend upward, backward, forward, and laterally to completely conceal the base,,
and as the palhum, or cortex, thickens and its folds begin to appear, the two hemi-
spheres become united across the mid-hne above the thalamencephalon and the
third ventricle by the inter-growth of the great cerebral commissure, the corpus
callosum. After removal of the falx cerebri from the longitudinal fissure, the
Fig. 671. — Mesial and Tentorial Surfaces op Right Cerebral Hemisphere, Viewed from
THE Left. (After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Sulcus oi corpus callosum
Body of fornix J
Body of corpus callosum ' ' Thalamus
Interventricular foramen \^,.-»— -«-s..^--''^-w/ Crus of fonux
Cut surface of cerebral peduncle
Genu of corpus callosum
of corpus callo
Columns of formx
Anterior comnussure/
Optic chiasma
Columns of formx'
Corpus mammillare
'^' Isthmus of gyrus fornicatus
^ * Chorioid fissure
, \ Fimbria
I * Hippocampal fissure
1 I Impressure for petrous bone
Mammillo-thalamic fasciculus Dentate fascia
dorsal surface of the corpus callosum 'may be exposed by drawing apart the
contiguous mesial surfaces of the hemispheres. It consists of a dense mass of
pure white substance coursing transversely, and arises as out-growths from the
cortical cells of both hemispheres. Thus it is the great pathway which associates
the cortex of the two sides of the telencephalon. Only the smaller medial
portion of the body lies free in the floor of the longitudinal fissure, by far the greater
part being concealed in the substance of the hemispheres, where its fibres radiate
to and from different localities of the pallium, forming the radiation of the corpus
callosum. Its surface shows numerous transverse markings, the transverse strice,
which indicate the course of its component bundles of fibres. In addition there
may be seen two delicate, variable longitudinal bands running over its surface
on each side of the mid-line. The medial longitudinal stria {stria Lancisii)
runs close to the median plane, around the anterior end from the gyrus subcallosus
(fig. 672), and over the posterior end downward and lateralward to disaiipcai' in
the hippocampal gyrus of the base of the telencephalon. The lateral longitudinal
stria is more delicate than the mesial stria, courses lateral to the medial stria, and
can be seen only within the sulcus of the corpus callosum (fig. 672). Both
striae are composed largely of axones having to do with the olfactory apparatus.
When severed along the median plane, it may be seen that the anterior margin
of the corpus callosum is turned abruptly downward, forming the genu, and that
this turn continues, so that the tapering edge of the body points posteriorly and
852
THE NERVOUS SYSTEM
constitutes the rostrum (figs. 667, 671). The rostrum is in contact with the
lamina terminalis of the third ventricle below by a short, thin, dorso-frontal
continuation of this lamina, linown as the rostral lamina. The rostral lamina may
be considered as beginning at the anterior cerebral commissure with the anterior
aspect of which it is in contact, and extending to the rostrum. Beginning with the
rostrum and genu, the corpus callosum arches backward as the body of the corpus
callosum, and ends over the quadrigeminate region in its rounded, thickened
posterior margin, the splenium. It is bounded above by the sulcus of the corpus
callosum, and, attached to its concave inferior surface, are the chorioid tela of the
third ventricle, the fornix, the septum pellucidum, and the medial walls of the
lateral ventricles.
Each cerebral hemisphere includes — -(1) a superficial and much folded mantle
or pallium, divided into lobes and gyri, and consisting of grey substance, the
cortex, covering an abundant mass of white substance; (2) a modified portion, the
Fig. 672. — Diagram of Convex Surface of Right Ceeebral Hemisphere and Part of
Upper Surface of Corpus Callosum.
Paramesial sulcus
Superior frontal sulcus
M iddle frontal sulcus
Inferior frontal sulcus
Precentral sulcus
Lateral longitudinal stria
Medial longitudinal stria
Corpus callosum
Central sulcus (Rolandi)
Postcentral sulcus
Lateral fissure (Sylvii)
Intraparietal sulcus
.Lateraroccipital sulcus
Transverse occipital sulcus
rhinencephalon, having especially to do with the impulses brought in by the olfac-
tory nerve; (3) a cavity , the lateral ventricle; and (4) a buried mass of grey sub-
stance, the caudate and lenticular nuclei, which together with the internal capsule
of white substance, are known as the corpus striatum.
Gyri, fissures, and sulci. — The cerebral pallium is thrown into numerous and
variable folds or gyri (convolutions). These are separated from each other by
corresponding furrows, tlie deeper and most constant of which are called fissures;
the remainder, sulci. All the fissures and the main sulci are named. There are,
however, numerous small and shallow sulci to which names are seldom given.
These occur as short branches of main sulci or as short, isolated furrows bounding
small gyri which connect adjacent gyri. These small gyri are likewise seldom
given individual names. They are very variable both in different specimens and
in the two hemispheres of the same specimen. Collectively, they are the so-called
transitory gyri (gyri transitivi). Certain groups of them are named according to
their locahty, such as orbital gyri and lateral occipital gyri. Even the main gyri
[gyri profundi] (and sulci) are very irregular in detail. Some of the main and
deeper fissures are considerably deeper than others. Some are infoldings of the
grey cortex so deep that a portion of their course may be indicated as slight bulgings
in the walls of the lateral ventricles, e. g., the hippocampal and collateral fissures.
While the general surface pattern is similar for all normal human brains, yet when
a detailed comparison is made, the given gyri of different specimens are found to
LOBES OF THE TELENCEPHALON 853
vary greatly. The main gyii of the two hemispheres of the same brain, how-
ever, are nearly alike.
Origin of the gyri. — The gjrri (and sulci) are the result of processes of unequal growth —
folds necessarily resulting from the surface portion of the hemispheres increasing mucli more
rapidly than the central core. In the early periods of fetal life the surfaces of the hemispheres
are quite smooth. In many of the smaller mammals this condition is retained throughout life,
but in the larger mammals, including man, as development proceeds the cerebral cortex becomes
thrown into folds. The absolute amount of the grey substance of the hemispheres varies with
the bulk of the animal, and apparently with its mental capabihties. This is especially true of
the cortex, for in the larger brains, and that of man especially, by far the greater amount of the
cerebral grey substance lies on the surface. Therefore, in either the growth or evolution of a
smaU animal into a large one the amount of cerebral grey substance is increased, and in this
increase the surface area of the brain is necessarily enlarged. It is a geometrical law that in the
growth of a body the surface increases with the square, while the volume increases with the
cube of the diameter. The cerebral hemisphere is a mass the increase of whose volume does not
keep the required pace with the increase of its surface area or cortical layer. The white sub-
stance which forms the palUum arises in large measure as outgrowths from the cells of the
cortical layer, and thus it can only increase in a certain proportion to the grey substance.
Therefore, the surface mantle of grey substance of a hemisphere, enlarged in accordance with an
increased bulk of body, is greater than is necessary to cover the surface of the geometrical figure
formed by the combined white and grey substance. Consequently, in order to possess the
preponderant amount of grey substance, the surface of the hemisphere is of necessity thrown
into folds. It follows also that the thinner the cortical layer in proportion to the volume of
the hemisphere, the greater and more folded will be the surface area. In accordance with this
theory small animals have smooth or relatively smooth hemispheres, and that independently of
their position in the animal scale or the amount of their inteUigence, while large animals have
convoluted brains.
The sulci in general begin to appear with the fifth month of fetal life, the larger of them,
the fissures, appearing first and in a more or less regular order. Up to the fifth month the en-
cephalon, due to its rapid growth, closely occupies the cranial capsule. During the fifth month
the cranium begins to grow more rapidly than the encephalon, and a space is formed between
the cerebrum and the inner surface of the cranium. This space allows further expansion of the
palUura, and at the time the space is relatively greatest (during the sixth month) the form and
direction of the principal gyri and sulci begin to be indicated. As growth proceeds the unre-
stricted expansion of the pallium results in the gyri again approaching the wall of the cranium,
and during the eighth month of fetal life they again come in contact with it. Finally, the later
relative growth of the cranium results in the space found between it and the cortex in the adult.
It is obvious that the relation of the cranium may be a factor in the causation of the gyri, for
the increase of surface area necessitated by the increased amount of cortical grey substance
might be limited by a cranial cavity of small size. It is probable that the second contact of the
cortex with the cranium (during the eighth month) may at least cause a deepening and accentua-
tion of the gyri already begun. Evidently the form of the cranium modifies the gyri, and to a
certain extent probably determines their direction, for in long, dolichocephahe crania the an-
tero-posterior gyri are most accentuated, and in the wide, brachycephalic crania the transverse
gyri are most marked. At birth all the main fissures and sulci are present, but some of the
smaller sulci appear later. In the growing pallium both the bottoms of the sulci as well as the
summits of the gyri move away from the geometrical center of the hemisphere, the summits more
rapidly, and hence the sulci or fissures first formed grow gradually deeper as long as growth
continues.
The mechanical factors in the growth processes which result in the more or less regular
arrangement of the gyri of the hemispheres of a given group of animals have not been satis-
factorily determined. It has been suggested that the differences in arrangement of the gyri in
different groups of animals may be in part dependent upon the functional importance of the
various regions — the amount of grey substance of a region varying with the functional impor-
tance, and the consequent local increases being accompanied by resultant local foldings. This
idea is supported by the fact that while the soma^sthetic (sensory-motor) area of the cortex
varies with the bullc of the body, the frontal gyri, so much developed in man and which are
one of the chief regions of the assooiational phenomena, are relatively independent of and do
not vary with the weight of either the body or the brain.
Surface area. — The total surface area of the adult human telencephalon is about 2300 sq.
cm. Of this area almost exactly one-third is contained on the outer or exposed surfaces of the
gyri, while the other two-thirds is found in the walls of the sulci and fissures.
Lobes of the Telencephalon and the Gyri and Sulci
The folded pallium of each hemisphere is arbitrarily divided into lobes, partly
by the use of certain of the main fissures and sulci as boundaries and partly by the
use of imaginary Hues (figs. 672, 673). These divisions are sbc in number, them-
selves subdivided into their component gyri: —
(1) Temporal lobe.
(2) Insula (Central lobe or Island of Reil).
(3) Frontal lobe.
(4) Parietal lobe.
(5) Occipital lobe.
854
THE NERVOUS SYSTEM
(6) Olfactory brain or rhinencephalon (including structures comprised in the
other lobes and often grouped under the two names olfactory lobe and limbic
lobe) .
This division of the cortex of the hemisphere is largely a merely topographical
one. With the exception of the temporal lobe and the rhinencephalon, it has
little of either morphological or functional value. The occipital lobe contains the
recognised visual area of the cortex, but this area, as such, does not involve all of
the lobe. In their functional significance, the frontal and parietal lobes, especi-
ally, overlap each other.
The temporal lobe. — This is the first lobe whose demarciition is indicated.
During the second month of intra-uterine life there appears a slight depression on
the lateral aspect of the then smooth hemisphere. As the pallium further grows,
this depression deepens into a well-marked fossa with a relatively broad floor.
This fossa marks the beginning of the lateral cerebral fissure or fissure of Sylvius,
and is, therefore, known as the Sylvian fossa. As the pallium continues to project
outward, the folds which form the margins of the Sylvian fossa increase in size
and height and begin to overlap and conceal its broad floor, which is the beginning
Fig. 673. — Diagram of the Convex Surface of the Left Cerebral Hemisphere showing
THE Five Principal Lobes op the Pallium.
The opercular regions of the frontal, parietal, and temporal lobes are removed to show the cen-
tral lobe or island of Reil.
Central sulcus (Roland!)
Parietal lobe
Central lobe (insula)
Central sulcus of insula
of the insula. The overlapping folds thus become the opercula, and as their lips
approach each other, there results the deep fissure of Sylvius, which marks off
anteriorly an infero-lateral limb of the pallium, termed by position the temporal
lobe. As growth proceeds further, the temporal lobe thickens, the temporal pole
extends further forward and becomes a free projection, thus lengthening the
fissure of Sylvius and resulting in the inferior extension or stem of this fissure,
which runs between the temporal pole and the frontal lobe and curves under so as
to appear on the basal surface of the hemisphere. Finally the cortex of the lobe
itself is thrown into folds or gyri. Its posterior end is never marked off from the
lobes above and behind, except by arbitrary fines which will be mentioned in con-
nection with those lobes.
The temporal lobe forms part of the lateral convex and tentorial surfaces of the
hemisphere, and its anterior portion is adapted to the surface of the middle
cranial fossa. It thus has a superior and lateral surface and a basal and tentorial
surface. In these surfaces are the following gyri with their intervening and
bounding sulci (fig. 674) : —
The superior temporal gyrus is bounded by the posterior ramus of the lateral
fissure, and extends from the temporal pole backward into the supra-marginal
region of the parietal lobe above. The upper margin of this gyrus constitutes the
temporal operculum, in that it aids in overlapping and enclosing the insula in the
floor of the lateral fissure. This margin is for the most part smooth, being
THE TEMPORAL LOBE
855
occasionally interrupted by a few weak twigs of the lateral fissure. It is separated
from the gyrus below by the superior temporal sulcus, which is parallel with the
posterior ramus of the lateral fissure and is frequently called the parallel sulcus.
The posterior extremity of this sulcus divides the angular gyrus of the parietal
lobe, and its anterior end disappears in the temporal pole, sometimes as a continu-
ous groove, sometimes in isolated pieces.
The middle temporal gyrus likewise begins in the temporal pole and is con-
tinuous backward into the angular gyrus of the parietal lobe.
The inferior temporal gyrus forms the infero-lateral border of the temporal
lobe, and is usually more broken up than the two gyri above it. It begins
continuous with them in the frontal pole, and extends horizontally backward into
the lateral gyri of the occipital lobe. It is separated from the middle gyrus by the
middle temporal sulcus, which likewise is never so continuous a furrow as the
superior temporal sulcus. Frequently this sulcus occurs in detached portions
and often terminates within the temporal lobe.
Fig. 674. — Outline Dkawing of Convex Surface of Left Cerebral Hemisphere.
(After Toldt, "Atlas of Human .^atomy," Rebman, London and New York.)
Precentral sulcus Central sulcus (RolandiJ
Inferior
frontal sulcus\
y^ ^ \/^ ^ f vj? . ^ > ,^,^
Horizontal ramus "
of interparietal
sulcus
Superior ex-
tremity of
parieto-occi-
pital tissure
Gyri,
LpitalesI Transverse
Inferior
frontal
gyrus
The fusiform gyrus is in the basal and tentorial surface of the temporal lobe
(fig. 676). Its usual somewhat spindle shape suggests its name, and it is con-
tinuous backward into the occipital gyri, or its posterior end may be completely
isolated by a union of the inferior temporal sulcus and the collateral fissure,
which two furrows separate it from its neighbours on either side. Anteriorly the
fusiform gyrus runs into the common substance of the other three gyri at the
temporal pole.
The lingual gyrus is usually included in the tentorial surface of the temporal
lobe, though in some texts it is regarded as a part of the occipital lobe. Its larger,
posterior portion lies within the boundaries of the occipital lobe. Bounded
laterally by the collateral fissure, it is continuous anteriorly into the hippocampai
gyrus of the rhinencephalon (fig. 676).
All of the sulci give off occasional lateral twigs {transverse temporal sulci) which
themselves may or may not branch, and which tend to divide the main gyri into
transverse temporal gyri.
The lateral fissure (fissure of Sylvius). — -As promised in its origin by the over-
lapping and enclosing of the broad floor of the Sylvian fossa by the adjacent folds
of the pallium, the lateral fissure is the deepest and most conspicuous fissure of
the cerebral hemisphere. Its main divisions are a short stem and three main
branches. The stem lies in the basal surface of the hemisphere, where it begins
856
THE NERVOUS SYSTEM
in a depression in the anterior perforated substance, the vallecula Sylvii, and passes
forward and upward between and separating the temporal pole and the super-
ciliary border of the frontal lobe. It corresponds in direction with the posterior
border of the lesser wing of the sphenoid bone, which projects backward into it,
and it contains the middle cerebral artery, the Sylvian vein, and the sinus alse
parvse. It appears on the upper surface at a point known in cranial topography
as the Sylvian point, where it divides into its three main branches : —
(1) The posterior ramus is the linear continuation of the fissure, and runs
horizontally backward and upward to terminate in the supra-marginal gyrus of
the parietal lobe.
(2) The anterior ascending ramus passes upward for about 10 mm., sub-
dividing the inferior gyrus of the frontal lobe.
(3) The anterior horizontal ramus passes forward from the stem of the fissure
about 10 mm., and likewise into the' inferior frontal gyrus, but parallel with the
superciliary border.
Fig. 675. — The Insula with its Gtki and StrLCi. (Shown by widely separating the opercula.)
Gyri breves )
Operculum ' I „ t of insula
C^yrus longus J
Circular sulcus
Transverse
-W — J> temporal
" gyri
Central sulcus of
Superior temporal gyrus
These branches, together with certain smaller collateral twigs, divide the over-
lapping or opercular portions of the adjacent pallium into (a) the tem-poral opercu-
lum, which lies below the posterior ramus; {h) the fronto-parietal operculum, or
operculum proper, which lies above and behind the anterior ascending ramus; (c)
the frontal operculum,, between the latter and the anterior horizontal ramus; {d)
and the orbital operculum, below the anterior horizontal ramus. Collectively the
opercula are known as the opercula of the insula.
The insula (central lobe). — The insula or island of Reil is a triangular area of
the cerebral cortex lying in the floor of the lateral fissure, and concealed by the
opercula. Of these, the temporal operculum overlaps the insula to a greater
extent than either the frontal or parietal. More than half of it may, therefore,
be exposed, by gently pressing away the temporal lobe. The insula corresponds
to the broad floor of the Sylvian fossa of the embryonic brain. In the developed
condition its surface is convex lateralward and is itself folded into gyri. The apex
of the triangle appears upon the basal surface of the hemisphere, and is the only
portion which may be seen without disturbing the specimen. The apex appears
as the end of a small gyrus under the temporal pole, and in close relation with the
THE FRONTAL LOBE
857
anterior perforated substance and the vallecula Sylvii, and is known as the
limen of the insula. In the folding process by which the opercula accomplish
the overlapping and enclosing of the island, there results a deep sulcus which sur-
rounds its entire area except at the limen insulse. This is known as the circular
sulcus, or limiting sulcus of Reil. The gyri (and sulci) of the insula radiate from
the apex of the triangle. The central sulcus of the insula is the deepest. It runs
from below backward and upward, parallel with the central sulcus of Rolando
above and divides the insula into a larger anterior and a smaller posterior portion.
The anterior portion consists of from three to five short irregular gyri breves or
precentral gyri, separated by sulci brevis ; the posterior portion consists of a single,
slightly furrowed gyrus, which is long and arched and extends from the apex to
the base of tlTe triangle, the gyrus longus.
In a recent study of the insula of more than 200 human brains, including a few of idiots
and paralytics and a series of young fcetuses, Nelidoff finds that the left island is more deeply
marked by sulci and averages 11 mm. longer than the right; that, of the sulci in the island, the
central sulcus is the first to appear, is the most persistent sulcus in defective brains, though
occasionally absent in microcephalic idiots, and that in the average it is more pronounced
in males than in females.
The frontal lobe. — This is the most anterior of the lobes of the hemisphere,
and hke the two lobes behind, it has a convex or lateral, a basal, and a mesial
surface. The convex surface begins with the frontal pole, and is bounded
posteriorly by the central sulcus {Rolandi). The basal surface extends backward
to the stem of the lateral fissure, covered by the frontal pole. The mesial surface
is separated from the gyrus cinguli of the rhinencephalon (limbic lobe) by the sub-
frontal part of the sulcus cinguli (calloso-marginal fissure), and from the parietal
lobe by a line drawn perpendicularly from the upper extremity of the central
sulcus (Rolandi) to the sulcus cinguli. These surfaces include the following gyri
and sulci: — •
Convex
surface
Basal
surface
Mesial
surface
Gyri.
Anterior central gyrus.
Superior frontal gyrus.
Middle frontal gyrus <
Inferior frontal gyrus \
Sulci.
Precentral sulcus
Superior portion.
Inferior portion.
Opercular portion.
Triangular portion.
Orbital portion.
Orbital gyri
Lateral.
Anterior.
Posterior.
Medial.
Gyrus rectus.
Superior frontal gyrus.
Marginal gyrus.
Paracentral lobule (anterior part).
Superior.
Inferior.
Superior frontal sulcus.
Middle frontal sulcus.
Inferior frontal sulcus.
Anterior ascending ramus of lateral
fissure.
Anterior horizontal ramus of lat-
eral fissure.
Lateral.
Orbital sulci \ Medial.
Transverse.
Olfactory sulcus.
Rostral sulci.
Many of the sulci, especially the superior frontal and the rostral sulci, often
give off twigs or are broken up into short furrows which give rise to small folds
[gyri transitivi], too inconstant to be given special names.
The anterior central gyrus (ascending frontal convolution) is the only gyrus
of the frontal lobe having a vertical direction. It lies parallel to the central sulcus
(Rolandi), and thus extends obliquely across the convex surface from the posterior
ramus of the lateral fissure (frontal operculum) to the supero-mesial border, and is
continuous on the mesial surface with the anterior portion of the para-central
lobule. It comprises the larger part of the motor portion of the somsesthetic
(sensory-motor) area of the cerebral cortex. It is separated from the horizontal
frontal gyri in front of it by the precentral sulcus.
This sulcus is developed in three parts, but the upper and middle parts in the foetal brain
usually fuse together, so that in the later condition it consists of a superior and an inferior
segment. The superior cuts the supero-mesial border of the hemisphere and appears on the
mesial surface in the paracentral lobule. On the convex surface it is usually cormected with the
posterior end of the superior frontal sulcus (fig. 674).
The superior frontal gyrus is a relatively broad, uneven convolution, com-
prising the anterior portion of the supero-mesial border of the hemisphere, and
therefore extends horizontally from the precentral sulcus to the frontal pole. It
is sometimes inperfectly divided into a superior and an inferior part by a series of
858 THE NERVOUS SYSTEM
detached, irregular furrows, spoken of collectively as the para-medial sulcus.
The resulting transitory gyri are of considerable interest in that they are peculiar
to the human brain, and are said to be more marked in the higher than in the
lower types.
The middle frontal gyrus is likewise a broad strip of pallium extending from
the precentral sulcus to the temporal pole. It is separated from the superior
frontal gyrus by the superior frontal sulcus, which is usually continuous into the
superior section of the precentral sulcus and thence extends horizontally to the
frontal pole. The middle frontal gyrus is in most cases subdivided anteriorly
into a superior and an inferior portioii by a middle frontal sulcus. This sulcus begins
above and runs into the frontal pole, where, upon reaching the superciliary border,
it frequently bifurcates into a transverse furrow, known as the Jronto-marginal
sulcus.
The inferior frontal gyrus forms the superior wall of the lateral fissure, and is
separated from the middle frontal gyrus by the inferior frontal sulcus. This
sulcus usually begins continuous with the inferior section of the precentral sulcus,
and extends, very irregularly and frequently interrupted, toward the frontal pole.
The gyrus abuts upon the anterior central gyrus, and its posterior portion is
divided into three parts (the frontal opercula) by the anterior ascending and
horizontal rami of the lateral fissure. The part behind the anterior ascending
ramus is the opercular portion (a part of the fronto-parietal operculum or opercu-
lum proper), sometimes referred to as the basilar portion. In most brains this
part is traversed by a short oblique furrow, the diagonal sulcus. The part be-
tween the two anterior rami of the lateral fissure is the cap-shaped triangular
portion. This portion frequently involves one and sometimes two descending
twigs of the inferior frontal sulcus. The part below the anterior horizontal ramus
is by position the orbital portion.
It is seen that the inferior frontal gyrus gives rise to the whole of the frontal operculum and
the antei'ior half of the fronto-parietal operculum. The opercular portion is of special interest
in that in the left hemisphere it constitutes the celebrated convolution of Broca, the motor area
for the function of speech. The area controlling speech, however, involves that part of the
triangular portion bounding the anterior ascending ramus of the lateral fissure as well, and
both these parts often appear more developed on the left hemisphere. The development of
the opercula of the inferior frontal gyrus is a distinctive characteristic of the human brain.
This gyrus does not develop opercula even in the highest varieties of apes. The development of
the function of speech in man no doubt influences the development of the frontal opercula.
On the basal surface (fig. 676) of the frontal lobe is the orbital area and the
gyrus rectus. The more pronounced of the orbital sulci are often so joined with
each other as to form an H-shaped figure standing parallel to the mesial plane,
and thus they comprise a medial, a lateral and a transverse orbtial sulcus.
This figure naturally divides the orbital area into four gyri: — (1) The lateral
orbital gyrus is tlie basal continuation of the inferior frontal gyrus, and is thus
related to the orbital portion of the frontal operculum; (2) the anterior orbital
gyrus is continuous at the pole with the middle frontal gyrus; (3) the posterior
orbital gyrus is closely related to the limen insulse and the stem of the lateral
fissure, and its outer part is in relation with the orbital portion of the operculum ;
(4) the medial orbital gyrus is continuous over the superciliarj^ border with the
superior frontal gyrus. It frequently contains one or two short, isolated sulci.
Its mesial boundary is the straight olfactory sulcus, in which lies the olfactory
bulb and tract of the rhinencephalon. This sulcus marks off a narrow straight
strip of cortex between it and the mesial border of the lobe known as the gyrus
rectus. The posterior portion of the gyrus rectus comprises a part of the parol-
factory area or Broca's area, which functionally belongs to the rhinencephalon.
As an area or field, this appears mesially lying between the anterior and posterior
parolfactory sulci.
On the mesial surface (fig. 679), of the frontal lobe the superior frontal gyrus is
separated from the gyrus cinguli of the rhinencephalon (limbic lobe) by the well-
marked sulcus cinguli. Anteriorly the superior frontal gyrus is subdivided by the
main stem of the rostral sulci into a marginal gyrus, and what may be termed a
sub'marginal gyrus. The marginal gyrus is usually broken into smaller parts by
twifi's of the rostral sulci, most of which are perpendicular to the main stem, while
the submargJnal gyrus is less frequently interrupted. Posteriorly the superior
frontal gyrus constitutes the anterior portion of the paracentral lobide, a part of
THE CENTRAL SULCUS
859
the somsesthetic area of the mesial surface of the hemisphere. This lobule is
usually marked off anteriorly by a vertical twig from the sulcus cinguli.
The sulcus cinguli (calloso-marginal fissure) is the longest and one of the most
prominent sulci on the mesial surface of the hemisphere. It divides the anterior
portion of the mesial surface into a marginal part above and a callosal part below
— in other words, it separates the superior frontal gyrus from the gyrus cinguli.
Its subfrontal portion begins below the rostrum of the corpus callosum and curves
forward and upward around the genu, and then turns backward above the body
of the corpus callosum. Before it reaches the level of the splenium, it turns up-
ward and cuts and terminates in the supero-mesial border of the hemisphere, as
the next sulcus behind the upper termination of the central sulcus. This upward
Fig. 676. — Basal Surface of the Cehebbal Hemisphebes. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Longitudinal fissure
Frontal pol
Olfactory sulcus
Orbital sulci
Olfactory bulb
Olfactory tract
Medial, intermediate, and
lateral olfactory strige
Temporal pole
Olfactory trigone^ I ^
Optic chiasma ~4-A^
Chorioid fissure -^[
Collateral fissure
Isthmus of gyrus fornicatus
Substantia nigra
Tegmentum of
mesencephalon
Gyrus fornicatus
Occipital pole
Aquseductus cerebri
(Sylvu)
Lamina quadrigemina
of corpus callosum
Longitudinal fissure
turn is the marginal portion of the sulcus cinguli. It is sometimes an abrupt
curve and sometimes curves gradually, but its marginal relation to the upper end
of the central sulcus is so constant that it serves as a means by which either of the
sulci may be identified. The marginal portion separates the paracentral lobule
from the precuneus (quadrate lobule), and is wholly within the parietal lobe.
One of the most constant twigs of the sulcus cinguli is that which marks off the
paracentral lobule from the superior frontal gyrus. Another sometimes divides
the paracentral lobule into its frontal and parietal portions.
The sulcus cinguli is developed from two and sometimes three (anterior, middle, and pos-
terior) separate furrows, which later extend and fuse into continuity. This metliod of its
development may explain the irregularities frequently met with and the fact that sometimes
in the adult the sulcus occurs in separate pieces.
The central sulcus (fissure of Rolando) (figs. 674, 678) is one of the principal land-
marks of the convex surface of the hemisphere. It separates the frontal from the
parietal lobe, and likewise divides the somsesthetic area of the palUum. Its
860 THE NERVOUS SYSTEM
upper end terminates in and usually cuts the supero-mesial border of the hemis-
phere immediately in front of the termination of the marginal portion of the sulcus
cinguli. Thence it pursues an oblique though sinuous course forward across the
convex surface of the hemisphere, forming on the average an angle of about 72°
with the supero-mesial border (Rolandic angle), and terminates in the fronto-
parietal operculum immediately above the posterior ramus, and about 2.5 cm. be-
hind the point of origin of the anterior rami of the lateral fissure. It rarely cuts
through the fronto-parietal operculum. In its sinuous course, varying from the
line of its supero-mesial end, two bends are marked (fig. 677) : — (1) The superior
genu occurs at about the junction of the upper and middle thirds of the sulcus and
is concave forward. It accommodates the greater part of that portion of the cor-
tex which is the motor area for the muscles of the leg and trunk, and the develop-
ment of this area in man probably aids in producing it. (2) The inferior genu
occurs below, is concave forward and is commonly a little more marked than the
superior genu. It is probably in part a result of the superior genu — the turn of the
sulcus in resuming its general course, but it may further result from the develop-
ment of the shoulder and arm area of the cortex which occupies its concavity.
Fig. 677. — Diagram Representing the Most Common Form of the Central Sulcus and
Indicating the Regions of Junction upon it of the Areas of the Peecenteal Gyrus
Devoted to the Dipfeeent Regions of the Body, as Estimated by Symington and
Crymble.
Superior-mesial border of hemisphere ' ^'''' ^^
Regionof junctionof legand trunk areas
Region of junction of trunli and
Lateral end of sulcus ,
Operculum
The central sulcus (Rolandi) appears in the pallium of the fcetus during the latter part of
the fifth month. It then consists of a lower longer and an upper shorter part. Usually these
two parts become continuous before birth; very rarely do they remain separate in the adult.
The point of their fusion is sometimes manifest within the depth of the sulcus. If the lips of
the sulcus be pressed widely apart at about the region of the junction of its middle and upper
thirds, it will be found that the opposing walls give off a number of protuberances or lateral gyri,
which dovetail into each other when the sulcus is closed. Sometimes two of these lateral gyri
appear fused across the floor of the sulcus, so as to form a bridge of grey substance known as the
deep annectant gyrus. This interruption of the continuity of the sulcus, when present, repre-
sents the point at which the two parts of the sulcus in the fcctal brain joined each other without
the continuity becoming wholly completed in the adult. The genua of the adult sulcus may
often be due to the precedent parts not being ia hne at the time of their fusion.
From a special study of the central sulcus of 237 normal adult hemispheres, Symington
and Crymble (1913) give the following details: (1) that the most common course of the sulcus
is that illustrated in fig. 677, above; (2) that it varies in depth both in a given specimen and in
different specimens — the greatest variations in depth reported for a given sulcus being from
22 to 12 millimeters, the shallowest part being in the region of the deep annectant gyrus; (3)
that the average length from the supero-mesial border of the hemisphere to the opercular
end of the sulcus is about 9 cm. in direct line and 10.4 cm. following the curves of the sulcus.
The average length of the curved floor is 7.9 cm. (4) From the supro-meisal end of the sulcus
to the points of junction of the general areas of the precentral gyrus, direct line measurements
give averages, (a) to the junction of leg and trunk areas, 3.5 cm.; (b) to junction of trunk and
arm areas, 4.5 cm.; (c) to junction of arm and face areas, 7.5 cm.
The parietal lobe. — The parietal lobe occupies a somewhat smaller area of
the human telencephalon than either the frontal or the temporal lobe. It has a
convex and a mesial surface, but no basal surface. It is separated from the
frontal lobe in front by the central sulcus; from the occipital lobe behind, on the
mesial surface by the parieto-occi-pital fissure (fig. 650), and, on the convex surface,
THE PARIETAL LOBE
861
by an arbitrary line drawn transversely around the convex surface of the hemi-
sphere from the superior extremity of this fissure to the infero-lateral border;
and it is separated from the temporal lobe below by the horizontal part of the
posterior ramus of the lateral fissure, and by a line drawn in continuity with this
horizontal part to intersect the transverse line drawn to limit it from the occipital
lobe.
. The preoccipital notch. — In situ, the infero-lateral border of the posterior portion of the
hemisphere rests over a small portion of the parieto-mastoid suture of the cranium, and upon
this structure occurs a fold or vertical thickening of the dura mater, which slightly indents the
infero-lateral border. This indentation occurs about 4 cm. from the occipital pole, and is con-
sidered one of the points of hmitation of the parietal from the occipital lobe, and is therefore
called the preoccipital notch. While during late foetal Ufe and early childhood it is well marked,
it is usually very shght in the adult bram, and is, as a rule, evident only in brains hardened
Fig. 678. — Convex Surface of the Cerebral Hemispheres as Viewed prom Above.
(After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Frontal pole
Supero-mesial border
^5^- Longitudinal fissure
Precentral sulcus
Central sulcus
Interparietal sulc
Superior occipital sulci
,^ Occipital pole
in situ. When it is visible, the arbitrary transverse line from the superior extremity of the
parieto-occipital fissure, used as a boundary, between the convex surfaces of the parietal and
occipital lobes, should be so drawn as to bisect the preoccipital notch.
The convex surface of the parietal lobe comprises the following gyri and sulci : —
The posterior central gyrus (ascending parietal) extends obliquely across the
hemisphere parallel with the anterior central gyrus of the frontal lobe, from which
it is separated by the central sulcus. Its inferior end is bounded by the posterior
ramus of the lateral fissure, and constitutes the posterior or parietal portion of the
fronto-parietal operculum. Its upper end takes part in the supero-mesial
border of the hemisphere, and is bounded posteriorly by the tip end of the
marginal portion of the sulcus cinguli. Its postero-lateral boundary consists
of the two more or less vertical rami or factors of the interparietal sulcus, viz., the
inferior and superior portions of the postcentral sulcus, either continuous -nith each
other or detached.
The interparietal sulcus (intraparietal) is often the most complicated sulcus
of the pallium. Its development usually begins as four different furrows in the
foetal brain, and the difficulty with which it is traced in the adult brain depends
862
THE NERVOUS SYSTEM
upon the extent to which these four factors become continuous in the later de-
velopment. When continuity of the furrows is well established, the entire sulcus
may be described as consisting of a convex horizontal ramus, which gives off a few
short collateral twigs and wliose either end is in the form of an irregular, reclining
-\ . The transverse bar of the anterior end arises fron two of the four factors of
the entire sulcus: — (1) an inferior furrow, the inferior postcentral sulcus, commenc-
ing above the posterior ramus of the lateral fissure and ascending as the boundary
of the lower half of the posterior central gyrus, and (2) a superior furrow, the
superior postcentral sulcus, lying behind the upper portion of the posterior central
gyrus, and which, upon approaching the supero-mesial border, may turn back-
ward a short distance parallel with the horizontal ramus, as in fig. 674. When
confluent, these two factors form together a continuous postcentral sulcus.
In the adult the inferior of the two is always continuous with the horizontal
ramus; when confluent, the two figures join so as to form the transverse bar of
the anterior end of this ramus. The horizontal ramus, which represents the
Fig. 679. — Outline Drawing op Mesial Surface of Left Cerebral Hemisphere.
(After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Sulcus cinguli (marginal portion)
Parieto-occipital fissun
Calcarine fissure
Sulcus cinguli (subfrontal portion)
Sulcus corporis callosi
'. Genu of corpus callosum
\ \ \ Rostum of corpus callosum
, v^ \ Anterior parolfactory sulcus
\ \ Parolfactory area (Broca's area)
\ Posterior parolfactory sulcus
Sub-callosal gyrus (peduncle of
/ corpus callosum)
Tuber cinereum Infundibulum
third of the primary furrows, is continued backward past the superior extremity
of the parieto-occipital fissure into the occipital lobe, where it usually joins the
occipital ramus, the fourth of the primary furrows. This ramus divides shortly
into two branches which run at right angles to the stem, forming the transverse
occipital sulcus, and thus arises the transverse bar of the posterior end of the inter-
parietal sulcus. The occipital ramus may, however, consist of little more than
the transverse bar, which may or may not be joined by the horizontal ramus.
The occipital ram.us is more frequently separate from the horizontal than is the
postcentral sulcus. In their development the inferior postcentral sulcus appears
first (during the latter part of the sixth month), the occipital ramus second, the
horizontal ramus third, and last, the superior postcentral sulcus.
The superior parietal lobule (gyrus) is the area of the supero-mesial border
of the parietal lobe. It is limited in front by the superior postcentral sulcus,
below by the horizontal ramus of the interparietal sulcus, and posteriorly it is
continuous around the superior end of the parieto-occipital fissure into the cortex
of the occipital lobe. It is a relatively wide area (lobule),' always invaded by
collateral twigs of its limiting sulci, and usually contains a few short, isolated
furrows. When the parieto-occipital fissure is considerably prolonged over the
supero-mesial border (external parieto-occipital fissure), the continuation of the
THE OCCIPITAL LOBE 863
lobule about the end of this fissure presents the appearance described as the
parieto-occipital arch.
The inferior parietal lobule is limited in front by the inferior postcentral
sulcus, and above by the horizontal ramus of the interparietal sulcus. It is con-
tinuous with the cortex of the temporal lobe below, and with that of the occipital
lobe behind, and is therefore invaded by the ends of the sulci belonging to these
lobes. Its anterior portion is separated from the temporal lobe by the horizontal
portion of the posterior ramus of the lateral fissure. The upturned end of this
ramus invades the anterior portion of the lobule and the broad fold, arched around
this end and continuous behind it into the superior temporal gyrus, is known as
the supramarginal gryus — the area to which auditory word- and tone-images are
attributed. The angular gyrus is the portion which embraces the posterior end
of the superior temporal sulcus, and is continuous behind this into the middle
temporal gyrus and in front with the superior temporal gyrus. It is the area for
visual word images. Its shape is usually such as to suggest its name. The most
posterior part of the inferior parietal lobule, when arching in a similar way about
the end of the middle temporal sulcus and continuous with the temporal gyri
on its either side, is known as the post -parietal gyrus. This is a smaller area than
either of the other two, and, owing to the variability of the end of the middle tem-
poral sulcus, is not always evident.
The mesial surface of the parietal lobe is divided into two parts by the marginal
portion of the sulcus cinguli. The anterior and smaller part is the mesial con-
tinuation of the posterior central gyrus, and comprises the posterior portion of
the paracentral lobule. It is limited from the part of this lobule belonging to the
frontal lobe by a vertical line drawn from the marginal extremity of the central
sulcus. The praecuneus {quadrate lobule) is the posterior and larger part of the
mesial surface of the parietal lobe. It is separatd from the cuneus of the occipital
lobe by the parieto-occipital fissure, and is imperfectly separated from the gyrus
cinguli (limbic lobe) below by the sub-parietal sulcus (postlimbic fissure), branches
of which invade it extensively.
The occipital lobe. — This is a relatively small, trifacial, pyramidal segment,
comprising the posterior extremity of the hemisphere, its apex being the occipital
pole. Though one of the natural divisions of the cerebral hemisphere, it is very
indefinitely marked off from the lobes anterior to it. Though it contains the
cortical area of the visual apparatus, only in the brains of man and the apes does
it occur as a well-defined posterior projection. In most of the mammalia it is
not differentiated at all. Its three surfaces comprise a convex, a mesial, and a
tentorial surface.
Its convex surface is separated from that of the parietal and temporal lobes by
the superior and external extremity of the parieto-occipital fissure, and by an
arbitrary line drawn transversely from this extremity to the infero-lateral border
of the hemisphere, or so drawn as to bisect the pre-occipital notch when this is
evident. The sulci which occur on the convex surface may be described as two,
though both of these are very variable in their e.xtent and shape, and their
branches are inconstant both as to number and length. (1) the transverse oc-
cipital sulcus is the most constant in shape. It extends a variable distance
transversely across the superior portion of the lobe, and, as noted above, it is
frequently continuous with the interparietal sulcus through its occipital ramus,
and when so, it appears as the posterior terminal bifurcation of this sulcus
(fig. 674). When detached, it often occurs merely as a definite furrow with few
rami, and sometimes the ramus by which it otherwise would join the inter-
parietal sulcus is entirely absent. (2) The lateral occipital sulcus is always
short, and has its deepest portion below the transverse sulcus. It usually has a
somewhat oblique course toward the supero-mesial border. Sometimes it occurs
in several detached pieces, then known collectively as the lateral occipital sulci.
Therefore, the gyri of the convex surface of the lobe are also variable. They are not
sufficiently constant to merit individual names. The lateral occipital sulcus or sulci roughly
divide them into an inferior and lateral area, known as the lateral occipital gyri, and into a
uperior larea, the superior occipital gyri. The lateral area is continuous into the gyri of the
temporal lobe, while the superior area is continuous into the gyri of the parietal lobe.
The mesial surface of the occipital lobe is separated from that of the parietal
lobe (precuneus) and from the gyrus cinguh of the limbic lobe by the well-
864 THE NERVOUS SYSTEM
marked parieto-occipital fissure. It comprises the constantly defined, wedge-
shaped lobule known as the cuneus, and the posterior and mesial extremitj'- of the
lingual gyrus. Since the greater portion of the length of the lingual gyrus is
involved in the basal surface of the temporal lobe, this gyrus as a whole has been
considered as belonging to the temporal lobe (see figs. 671, 676). The cuneus
is separated from the hngual gyrus by the posterior portion of the calcarine
fissure, which always terminates in a bifurcation, one limb of which invades the
cuneus near the superomesial border. In addition the cuneus may contain
other twigs from both the fissures bounding it, and also, when wide, may contain
one or more short, detached sulci cunei.
The calcarine fissure and the parieto-occipital fissure are almost invariably joined in the
human brain, forming a Y-shaped figure, the prongs of which give the cuneus its shape. The
calcarine fissure begins on the tentorial surface in the posterior portion of the hippocampal
gyrus of the Umbic lobe, below the splenium of the corpus callosum, and extends backward
across the internal occipital border of the hemisphere. It then bends downward and proceeds
to its terminal bifurcation in the polar portion of the occipital lobe. The stem or hippocampal
portion of the fissure is deeper than the posterior or occipital portion. It produces a well-
marked eminence in the medial wall of the posterior cornu of the lateral ventricle, known a^ the
calcar avis or hippocampus minor. It is developed separately from the posterior portion, which
itself first appears as two grooves. All three parts are usually continuous with each other before
birth.
The parieto-occipital fissure usually appears from the first as a continuous groove. It
begins in the supero-mesial border of the hemisphere, rarely extending into the convex surface
more than 10 mm. (external parieto-occipital fissure), thence it extends vertically downward
across the mesial surface (internal parieto-occipital fissure), and terminates by joining the cal-
carine fissure at the region of the downward bend of the latter, or at about the junction of its
anterior and middle thirds. In certain of the lower apes and in the brain of the chimpanzee
there is no junction between the two fissures, they being kept apart by a narrow neck of cortex,
the gyrus cunei. Neither are they joined in the human foetus. If in the adult human brain
the region of their'junction be opened widely, there will be found a submerged transitory gyrus
(deep annectant gyrus), which is the gyrus cunei, superficial in the fcetus. In the higher apes
and in micro-cephalic idiots this gyrus may be on the surface or partially submerged. Two
other transitory gyri (annectant gyxi) are to be found by pressing open the calcarine fissure,
and they mark the points at which its three original grooves became continuous during its
development into a boundary between the cuneus and the lingual gyi'us. Of these, the anterior
cuneo-lingual gyrus crosses the floor of the calcarine fissure on the posterior side of its junction
with the parieto-occipital fissure, and therefore near the gyrus cunei. The posterior cuneo-
lingual gyrus occurs near the region of the terminal bifurcation of the fissure.
The tentorial surface of the occipital lobe is blended intimately with that of
the temporal lobe, from which it is separated only by an arbitrary line drawn to
join the line of demarcation for the convex surface, at the region of the pre-
occipital notch, and thence to the isthmus of the gyrus fornicatus — the narrow
neck of cortex connecting the gyrus cinguh with the hippocampal gyrus, just below
the splenium of the corpus callosum (see fig. 671). The gyri blending the occip-
ital and temporal lobes across this fine are the lingual gyrus, already mentioned,
and the fusiform gyrus (occipito-temporal convolution). In fact, the tentorial
surface of the lobe may be considered as nothing more than the posterior ex-
tremity of the fusiform gyrus, and the inferior portion of the same extremity of the
lingual gyrus. The former is often somewhat broken up and is then continuous
into the lateral occipital gyri. The two gyri are separated by the collateral fissure
the posterior end of which extends into the occipital lobe. The fusiform gyrus is
bounded laterally by the inferior temporal sulcus, which sometimes is continuous
by a lateral twig, across the posterior end of this gyrus, with the collateral fissure.
The Rhinencephalon
The rhinencephalon or olfactory brain includes those portions of the cerebral
hemisphere which are chiefly concerned as the central components of thie olfactory
apparatus. Owing to the preponderant development of the other divisions of the
hemisphere, the parts comprising this division appear relatively but feebly de-
veloped in the human brain. In most of the mammals the sense of smell is
relatively much more highly developed, and in many of the larger mammals
the parts comprising the rhinencephalon are of greater absolute size than in man,
though their cerebral hemispheres may be considerably smaller. In the human
foetus the parts of the rhinencephalon are relatively much more prominent than
after the completed differentiations into the adult condition. In the broader
THE RHINENCEPHALON
865
sense of the term the rhinencephalon includes those parts of the hemisphere
usually classed as comprising two lobes, viz., the olfactory lobe and the limbic
lobe. Neither of these is a 'lobe' in the sense of comprising a definite segment
of the hemisphere, as do the other lobes, and therefore the rhinencephalon
cannot be called a distinct lobe. It is so strung out that by one or the other of
its parts it is either in contact or continuity with each of the other lobes of
the hemisphere.
Morphologically, the rhinencephalon may be divided into an anterior and a
posterior division.
The anterior division. — the olfactory lobe proper, belongs almost wholly to
the base of the encephalon, and consists of the following parts: —
(1) The olfactory bulb is an elongated, oval enlargement of grey substance
which lies upon the lamina cribrosa of the ethmoid bone, and, practically free, it
presses under the anterior end of the olfactory sulcus in the basal surface of the
frontal lobe. The numerous thin filaments of nonmeduUated axones of the
olfactory nerve enter the cranium through the foramina of the lamina cribrosa and
pass into the ventral surface of the bulb.
Fig. 680. — Brain of Human Fcbtus of 22.5 Cm. (Beginning of Fifth Month), showing
THE Parts of the Developing Rhinencephalon Apparent on the Basal Surface.
(After Retzius.)
dial olfactory gyrus (stria)
Lateral olfactory gyrus (stria)
Posterior parolfactory sulcus
Uncus (hippocampal gyrus)
Limen insulae
■Anterior perforated substance
Hippocampal gyrus
(2) The olfactory tract is a triangular band of white substance which arises in
the olfactory bulb, and continues backward about 20 mm. to the region of the
anterior perforated substance. It appears triangular in transverse section from
the fact that its upper side fits into the olfactory sulcus. It becomes somewhat
broader at its posterior end.
(3) The olfactory trigone {olfactory tubercle) is the small triangular ridge, the
posterior continuation of the olfactory tract joining the anterior perforated sub-
stance. In it the olfactory tract breaks up into three roots, the lateral, in-
termediate, and medial olfactory strice {gyri). The lateral olfactory stria em-
phasizes the lateral portion of the trigone into the lateral olfactory gyrus, a portion
of which is directly continuous into the lijnen insulce (figs. 676, 680).
While a few of the fibres of the lateral stria penetrate this region, the greater mass of them
pass obhquely lateralward over it and gradually disappear in the antero-lateral portion of the
anterior perforated substance, in which some of them terminate, but through which most of
them pass to curve into the anterior end of the hippocampal gyrus and terminate there, chiefly
in the uncus. In most of the mammals the lateral stria is so strong that it appears as a super-
ficial white band passing directly into the uncus. In the early foetus it is seen to enter the
uncus in two branches, forming the medial semilunar gyms and the lateral gyrus ambiens upon
the uncus. A portion of the limen insulce belongs to the rhinencephalon.
(4) The parolfactory area (Broca's area) involves the mesial extension of the
olfactory trigone, and is concerned with the medial olfactory stria. On the basal
surface of the hemisphere this area involves the posterior extremity of the gyrus
rectus — a portion of which is sometimes separated from the remainder of the gyrus
by a ventral prolongation of the anterior parolfactory sulcus of the medial surface
(see figs. 679, 706). This prolongation when present has been called the
fissura serotina. On the medial surface the parolfactory area appears as a
866 THE NERVOUS SYSTEM
definite gyrus. In front this is separated from the superior frontal gyrus by the
anterior -parolfactory sulcus, and from the subcallosal gyrus behind by the deeper
posterior parolfactory sulcus (fig. 679) . It is continuous above into the gyrus cin-
guli of the limbic lobe, a portion of the posterior part of the rhinencephalon.
A large portion of the fibres of the medial stria are lost in the parolfactory area, and are
known to terminate about the cells there. This stria or root of the olfactory tract forms a
slight ridge on the ventral surface of the area, which is frequently pi-ominent enough to retain
the name medial olfactory gyrus appUed to it in the foetal brain (fig. 680).
(5) The subcallosal gyrus (peduncle of the corpus callosum) is the narrow fold
of the pallium which lies between the posterior parolfactory sulcus and the rostral
lamina and the ventral continuation of the latter into the lamina terminalis. It
begins above, in part fused to the rostrum of the corpus callosum, and in part
continuous with the gyrus cinguli, and ventrally it goes over lateral ward and
posteriorly into that portion of the anterior perforated substance known as the
diagonal band of Broca, and in this way it extends into the uncus. Mesially, it
approaches its fellow of the opposite side so closely that the groove separating
the two is known as the median subcallosal sulcus of Retzius. Some fibres of the
medial olfactory stria disappear in the substance of the subcallosal gyrus.
(6) The anterior perforated substance must be considered with the rhinen-
cephalon, but, like the limen insulae, it can only be considered as belonging in part
to this division of the brain. It comprises the basal region between the optic
chiasma and tract and the olfactory trigone. Usually the posterior parolfactory
sulcus (fissura jmnia of the embryo) is sufficiently evident to more or less
distinctly separate it from the latter. Its postero-lateral area is occupied by the
diagonal band of Broca. A few fibres from the medial stria are known to dis-
appear within its depths, and, as mentioned above, many fibres from the lateral
stria also pass into it. The intermediate olfactory stria is always much the weakest
of the three striae, and in many specimens is apparently absent. The fibres of this
stria run almost straight backward and plunge directly into the anterior area of
the anterior perforated substance, where some of them are known to terminate,
while others continue into the uncus.
On embryological grounds, the subcallosal gyrus and the anterior perforated substance are
classed with the posterior division of the 'olfactory' lobe or anterior division of the rhinen-
cephalon.
The olfactory bulb and tract arise as a hollow outgrowth from the lower and anterior part
of the anterior of the three primary vesicles. It is a tubular structure at first, and in many of
the mammals the cavity maintains throughout hfe as the olfactory ventricle. In man the cavity
becomes occluded and the ependyma and gelatinous substance which surround it become
the grey core of the bulb and tract of the adult.
The grey substance persists and develops chiefly in the bulb, and in fact produces it as such.
It is much thicker on the inferior surface of the bulb than on the superior surface, and in section
shows definite layers. From within outward, the principal of these layers are — (1) the layer of
large cells whose shape suggests their name, mitral cells; (2) large dendrites of the mitral cells
project toward the inferior surface of the bulb and there break up into numerous telodendria
which copiously form synapses with like telodendria of the entering fibres of the olfactory nerve,
thus forming rounded, much tangled glomeruli and the layer containing these, the glomerular
layer; (3) the superficial layer, or olfactory layer, consists of the fibres of the olfactory nerve
which form a dense interlacement with each other on the inferior surface of the bulb before they
pass into its interior. The superior surface of the bulb becomes formed almost wholly of the
fibres which arise as axones of the mitral cells and pass backward to form the olfactory tract, and
thence to their localities of termination, chiefly by way of the three striiE. Along the dorsal,
covered, aspect of the olfactory tract the gelatinous substance of the core may show through as
a grey ridge.
The posterior division of the rhinencephalon or the so-called limbic lobe (a
name introduced by Broca in 1878) takes part in both the medial and tentorial
surfaces of the hemisphere (fig. 681). Seen from the medial surface, it forms an
irregular eUiptical figure which encloses the corpus callosum and the extremities
of which approach each other at the anterior perforated substance, where they
are continuous with the structures of the anterior division of the rhinencephalon.
The figure is bounded externally by the sulcus cinguU above, by the subparietal
sulcus (postlimbic sulcus) and the anterior limb of the calcarine fissure behind,
and by the collateral fissure below. These respectively separate it from the
frontal, parietal, occipital, and temporal lobes. It comprises the following
THE RHINENCEPHALON
867
structures which are either wholly or in part devoted to the functions of the
olfactory apparatus: —
Part of gyrus cinguli and cingulum.
Isthmus of the gj^rus fornicatus.
1. Gyrus fornicatus i f hippocampal gyrus.
TT- uncus.
Hippocampus ^^^^^^^ ^^^^^ ^^^^^.^^
[ fimbria.
2. The medial and lateral longitudinal strise upon the corpus callosum.
3. The fornix.
4. The mammillary body, the mammillo-thalamic fasciculus to the anterior
nucleus of the thalamus and the mammillo-peduncular fasciculus.
5. Part of anterior cerebral commissure.
6. Part of septum pellucidum.
7. Most of medullary stria of thalamus.
8. Most of habenular nucleus.
The gyrus fornicatus comprises the greater mass of the limbic lobe. As seen
above, it is a term used to collectively represent a number of conjoined structures.
Fig. 681. — Diagram showing Position of Structures Comprising the Limbic Lobe as
Seen from the Mesial Aspect of the Cerebral Hemisphere.
Fasciola cinerea
Mammillo-thalamic fasciculus
(Vicq d'azyri)
^V ^ Gyrus cinguli
X \ Medial and lateral
.' \ V — longitudinal striae of
\ \ corpus callosum
Septum pellucidum
Subcallosal gyrus
Olfactory bulb
Medial olfactory stria
Mammillary body
Lateral olfactory stria
Dentate fascia or gyrus
Being an incomplete ellipse in form, its two ends are united to form a closed ring
by means of the connection of the parolfactory area with the gyrus cinguli and
the connection of the anterior perforated substance with the uncus of the hippo-
campal gyrus. It is best described in terms of its three component parts indi-
cated above:
The gyrus cinguli begins in junction with the area parolfactoria below the
anterior end of the corpus callosum, and curves above so as to entirely embrace
the upper surface of the latter. It is separated from the frontal lobe by the sulcus
cinguli (calloso-marginal fissure), from the parietal lobe by the subparietal sulcus,
and from the corpus callosum below by the sulcus of the corpus callosum. By the
latter it is separated from the longitudinal strite of the upper surface of the corpus
callosum.
The gyrus cinguli covers over, and its cells are closely associated with, the cingulum, a well-
marked arcuate band of white substance, which follows the gyrus in its bend around the rostrum
and backward to turn around the splenium of the corpus callosum in the isthmus of the gjTus
fornicatus, and then to course forward into the hippocampal gyrus and the uncus. The cingulum
is largely an association fasciculus between the gjTi of the temporal lobe and those gyri on the
mesial surface of the cerebral hemisphere, its fibres for the most part running short courses, being
continually added to it and continually leaving it. However, it contains olfactory axones
running in two directions: (1) fibres from the medial olfactory stria and fibres arising in the
parolfactory area, the gyrus subcaDosus and the anterior perforated substance which course
posteriorly for distribution in the cortex of the gjTUs cinguli and hippocampal gyrus; (2) fibres
arising in the hippocampal gyrus, especially the uncus, to course dorsalward through the isthmus
and then forward as association fibres. Some fibres arising from the cortical cells of the g3TUS
cinguli pass inferiorly through the cingulum, through the corpus callosum and, anteriorly,
through the septum pellucidum to join the fornix below {perforating fibres of Ike fornix).
The isthmus of the gyrus fornicatus is the constricted portion connecting the
posterior end of the gja-us cinguli with that of the hippocampal gyrus (fig. 619
868 THE NERVOUS SYSTEM
and 671). It is bounded externally by the anterior end of the calcarine fissure,
and incloses the posterior turn of the cingulum.
The hippocampus is the name applied to the curved appearances produced in
the floor of the lateral ventricle by the peculiar foldings of this part of the cerebral
cortex. The hippocanipal gyi'us (gyrus of the hippocampus) is the main gyrus of
the tentorial surface of the hmbic lobe. Externally it is separated from the fusi-
form gyrus by the collateral fissure, and it is bounded internally by the hippo-
campal or, more inclusive, the chorioid fissure. Posteriorly it is partially divided
by the calcarine fissme into the lingual gyrus (of the temporal lobe) and the
isthmus of the gyrus fornicatus. Its anterior extremity is hooked backward and
is known as the uncus {gyrus uncinatus) . This is almost entirely separated from
the temporal lobe by a groove, the temporal notch. If the hippocampal fissure
be opened up, the dentate gyrus or fascia and the fimbria will be seen. These lie
side by side, separated by the shallow fimbrio -dentate sulcus (fig. 690.)
The free edge of the dentate gyrus presents a peculiarly notched appearance, produced by
numerous parallel grooves cutting it transversely. Its posterior end, sometimes called the
fasciola cinerea, continues backward over the splenium of the corpus callosum, and upon the
upper surface of the corpus callosum appears as a thin strip of grey substance which contains
embedded in it the medial and lateral longitudinal strice. This thin strip is sometimes called the
supracallosal gyrus (gyrus epicallosus, induseum griseum), and is thought to represent a ves-
tigial part of the hippocampal gyrus. Closely beneath the splenium of the corpus caUosum, on
the supero-mesial side of the hippocampal gyrus and mesial to the dentate gyrus, there sometimes
occur suggestions of round or oval elevations of the grey substance which have been called
the "callosal convolutions" or gyri Andrece Retzii. Rarely are they strongly developed, but when
so they often produce a spiral appearance.
The fimbria is but the fimbriated, free border of the posterior end or origin
of the fornix, so folded as to project into the hippocampal fissure, parallel with the
dentate gyrus (fig. 690). It is a conspicuous iDand composed almost entirely of
white substance, continuous laterally with the thick stratum covering the ven-
tricular surface of the hippocampus. It begins anteriorly in the hook or recurved
extremity of the uncus. Traced backward, it is seen so curve upward, and within
the ventricle it becomes part of the general accumulation of the white substance
(alveus) of the surface of the hippocampus, which accumulation is the beginning
of the fornix. The free border of the fimbria (seen in section) is known as the
tcenia fimhrim. The fimbria is separated from the cerebral peduncles by the
chorioid fissure, the thin, non-nervous floor of which alone intervenes between the
exterior of the brain and the cavity of the lateral ventricle within.
The hippocampal fissure attains its greatest depth between the dentate gyrus
and the hippocampal gyrus, and the resulting eminence produced in the floor of
the lateral ventricle is known as the hippocampus major, as distinguished from
the lesser eminence produced posteriorly by the end of the calcarine fissme and
known as the hippocampus minor [calcar avis]. The collateral fissure may like-
wise produce a bulging in the wall of the ventricle, the collateral eminence. In
transverse sections of the hippocampus major, the layers of grey and white sub-
stance present a coiled appearance known as the cornu ammonis. Externally
the medial surface of the hippocampal gyrus adjoining the dentate gyrus has
reflected over it a delicate reticular layer of white substance known as the sub-
stantia reticularis alba (Arnoldi).
The fornix is the great association pathway of the limbic lobe, and appears to
be wholly concerned in the apparatus of the rhinencephalon. It is a bilateral
structure arched beneath the corpus callosum, with which it is connected ante-
riorly by the septum pellucidum. Posteriorly it passes in contact with the
splenium. It consists of two prominent strips of white substance, one for each
hemisphere, the ends of which are separate from each other, while their inter-
mediate parts are fused across the mid-line. These run above the chorioid tela of
the third ventricle, and their lateral edges (tcenice fornicis) rest, on each side, along
the line of the taenia chorioidea. The posterior, separate ends are known as the
posterior pillars or crura of the fornix; the fused, intermediate portion is the body,
and the separate, anterior ends are the anterior pillars or columns of the fornix.
The posterior pillars [crura] of the fornix. — When seen from the medial
aspect of the hemisphere, the fused portion of the fornix, in the separation of the
hemispheres, is split along the mid-line (fig. 671). The half under examination
THE FORNIX
869
may be seen to course obliquely lateralward under the splenium of the corpus cal-
losum, and then, continuous into the fimbria, to curve forward and ventralward
toward the uncus. The greater mass of the fibres coursing in the fornix arise as
outgrowths of the cells of the uncus, hippocampal gyrus, and dentate gyrus. They
accumulate as a dense stratum on the ventricular surface of these gyri, termed the
alveus, which crops outward as the fimbria and which passes backward and up-
ward; upon reaching the region of the splenium it turns obliquely forward under
Fig. 682. — Diagram Showing Fornix and its Connections as seen from Above.
olfactory bulb -
Medial olfactory stria
Subcallosal gyrus
Column (anterior pillar)
Fimbria
Mammillo-thalamic fasciculus
Stria terminalis of thalamus
Stria meduUaris of thalamus
Crus (posterior pillai)
Epiphysis (below)
Amygdaloid nucleus
Hippocampus major
Hippocampal commissure (lyra)
it and approa(3hes the mid-line, to fuse with the hke bundle from the gyri of the
hippocampus of the opposite side. The bundles thus arising from the two sides
are the pillars or crura of the fornix. They appear as two flattened bands of white
substance which come in close contact with and even adhere to the splenium.
The angle formed by the mutual approach of the posterior pillars of the fornix is crossed
by a lamina of commissural fibres connecting the hippocampal gyri of the two hemispheres
(fig. 684). This lamina is the hippocampal commissure or transverse fornix. Like those of the
fornix, its fibres arise from the cortex of the hippocampal gyri, but they serve as commissural
fibres between the hippocampal gyri of the two hemispheres. Being of a different functional
direction, it should not be considered a part of the fornix. The angle formed by the two pos-
FiG. 683. — Diagram Illttsteating the Origin and Course of Forndc as viewed from the
Side.
Gyrus cinguli -
Cinguli
Longitudinal stris--
Fornix
Perforating fibres
Thalamic medullary stria
Habenular nucleus
Olfactory bulb and tract
Anterior perforated substanci
Uncus -
---Longitudinal strise
Calcarine fissure
^Fimbria
Hippocampal gyrus
Mammillary body
terior pillars of the fornix as traversed by the hippocampal commissure gives a picture named the
psalterium or lyra. Usually the hippocampal commissure and the posterior pillars (crura) are
in close contact with the under surface of the splenium. When occasionally they do not adhere,
the space between is known as Verga's ventricle. According to recent studies of brains with
degenerated corpus callosum, further commissural fibres between the limbic lobes course in the
posterior angle of the septum pellucidum, and all along, transverse to the body of the fornix.
The body of the fornix appears as a triangular plate of white substance
produced by the fusion of the pillars. Its base or widest portion is behind. It
is not always bilaterally symmetrical. Its upper surface is attached by the septum
870
THE NERVOUS SYSTEM
pellucidum to the lower surface of the corpus callosum. Below, it lies over the
chorioid tela of the third ventricle, which separates it mesially from the cavity
of the third ventricle and laterally from the upper surfaces of the thalami. Its
sharp lateral edge or margin (taenia fornicis) projects into the lateral ventricle
of either side in relation with the chorioid plexus of that ventricle, and thus the
lateral portion of its upper surface forms part of the floor of the lateral ventricle —
an arrangement to be expected, since the posterior pillars arise from the floor of
Fig. 684. — Horizontal Section of Telencephalon showing Bodt of Fornix and Hippo-
CAMPAL Commissure as seen from Below and the Anterior Commissure in Section.
(After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Genu of corpus callosum
Parolfactory area (Broc^) ^ ^^^ ^„:,.-^ ^/ ^^^^^^^ „f ^^^^^^ ^^^^^^^
Triangular recess /f^ if \\\ TVX. ^^^^ ^^ caudate nucleus
Putamen of lenticular nucleus
Temporal lobe ^
Lateral cerebral fissure
(Sylvii)
Claustrum
External capsule
Internal capsule —
Interventricular fora-
men (MonroiJ
Crus of fornix
Gyrus cinguU '
Parieto-occipital fissure
Globus pallidus
Habenular nucleus
fTail of caudate
nucleus
^ — Inferior cornu of lat-
eral ventricle
Longitudinal fissure
Medial surface of hemisphere
Cuneus
Calcarine fissure
the ventricle, viz., the hippocampus. The ventricular portion is covered by a
layer of ependyma in common with that lining the rest of the ventricle.
Along its body the fornix receives fibres arising from the cells of the cortex of the gjTus
cinguli and fibres from the longitudinal striaj upon the dorsal surface of the corpus callosum.
These are known as the perforating fibres of the fornix. In their ventral course, they pass ob-
liquely forward through the corpus callosum and, anteriorly, through the posterior angle of the
septum pellucidum to join the fornix and course in its functional direction. Tlie fibres arising
in the cortex of the gyrus cinguli may course short distances in the cingulum before perforating
the corpus callosum.
The columns or anterior pillars of the fornix [coluranse fornicis], are two separ-
ate, cyhndrical bundles which pass forward from the apex of the body of the fornix
and then turn sharply downward along the anterior boundary of the third ven-
tricle, just behind the anterior cerebral commissure. A part of each column, the
/ree portion [pars libera], forms the anterior boundary of the interventricular
foramen (Monroi). Thence the covered portion [pars tecta] sinks into the grey
ANTERIOR CEREBRAL COMMISSURE 871
substance of the lateral wall of the third ventricle, and passes downward to the
base of the brain, where it appears on the exterior as the mammillary body
[corpus mammillare] (fig. 671).
Some of its fibres are interrupted in the nuclei of the mammillary body, chiefly in its lateral
nucleus; probably most of them merely double back, forming a genu. From the mammUlary
body the fibres are disposed in at least three ways: — (1) The greater part perhaps pass directly
upward and are lost in the anterior nucleus of the thalamus, where they ramify freely and term-
inate about its cells. These fibres form the bundle known as the mammillo-thalamic fasciculus,
or bundle of Vicq d'Azyr; (2) A portion of the fibres go to form a mammillo-mesencephalic fas-
ciculus (tegmento-mammiilary fasciculus, mammillo-peduncular fasciculus. This begins in the
mammillary body and passes caudalward into the mesencephalon to terminate about cell-bodies in
or in the region of, the so-called nucleus of the medial longitudinal fasciculus and posterior com-
missure. Fibres given by these cell-bodies may convey impulses by way of the medial longi-
tudinal fasciculus or the general reticular formation to the nuclei in the mesencephalon, rhomb-
encephalon and perhaps into the spinal cord. Some of this portion of the fibres from the mam-
millary body are said to pass caudalward through the mesencephalon without interruption
there. (3) A portion of the fibres decussate in the superior parts of the mamillary bodies
and are distributed to both the thalamus and the mesencephalon of the opposite side. This
decussation is the supraraamillary commissure.
As seen above, the fornix as a whole is composed of longitudinally directed fibres, some of
which, however, cross the mid-line in the region of its body and course in the columns of the
opposite side. For the greater part, its fibres rise from the cells of the hippocampal gyri, but
it is known to contain some fibres which arise in the anterior perforated substance and sub-
callosal gyrus and course through the fornix to the hippocampal gyri.
The medial and lateral longitudinal striae upon the corpus callosum consist of olfactory
fibres coursing in both directions: (1) fibres arising in the parolfactory area, the subcallosal
gyrus and the anterior perforated substance (diagonal band of Broca) course posteriorly and
then inferiorly in them to the grey substance of the gryi of the hippocampus; (2) and chiefly,
fibres from the hippocampal gyri course in them anteriorly and inferiorly around the rostrum
of the corpus callosum, through the ventral part of the septum pelluoidum, to join the fornix.
It is suggested that the strise, especially the medial, may be considered as a part of the fornix
detached upon the dorsal surface of the corpus callosum during the projection of the latter
between the cerebral hemispheres. The medial stria is often called the stria Lancisii.
The anterior cerebral commissure is only in part concerned in the rhinenceph-
alon; it consists in greater part of commissural fibres connecting the two temporal
lobes. It forms one of the four commissures of the telencephalon, the other three
being the corpus callosum, the hippocampal commissure and the inferior cerebral
commissure. It is a bundle of white substance with a slightly twisted appearance,
which crosses the mid-line in the anterior boundary of the third ventricle be-
tween the lamina terminalis and the columns of the fornix (figs. 671 and 684),
just below the interventricular foramen (foramen of Monro). In each hemis-
phere its main or temporal portion passes lateralward and slightly backward
beneath the head of the caudate nucleus and through the anterior end of the
lenticular nucleus, and thence is dispersed to the grey substance of the temporal
lobe.
It contains fibres both to and from the temporal lobe of each side. In addition to these
fibres the anterior commissure carries in its frontal side two sets of fibres belonging to the ol-
factory apparatus: — (1) fibres arising in the olfactory bulb of one side, which pass by way of the
medial olfactory striae through it to the olfactory bulb of the opposite side; (2) fibres which pass
through it from the medial stria (olfactory bulb) of one side to the uncus of the opposite side.
The anterior commissure is a more primitive commissure than the corpus callosum, in that
it is present in the lower forms when the latter is absent, and diminishes in relative size and
importance as the corpus callosum appears and increases in size. In man the appearance of the
anterior commissure precedes but little that of the corpus callosum. During the fifth month
the lamina terminalis, which then alone unites the anterior ends of the two hemispheres, develops
a thickening of its dorsal portion. In a part of this thickening, transverse fibres begin to appear
and their increase in number results in the partial separation posteriorly of the part containing
them from the rest of the lamina, and then follows the differentiation of this part into the anterior
commissure. The remainder of the thickening of the lamina continues to increase in size with
the increase of the hemispheres; its upper edge is directed posteriorly, and fibres begin to appear
in it which arise in the cortex of one side and cross over to that of the other side. These fibres
form the corpus callosum.
The corpus callosum, a development of fibres in the upper, expanded portion of the lamina
terminalis, thus bridges over a portion of the longitudinal fissure between the hemispheres. In
the mean time, the /ornts arises as two bundles of fibres, one from the hippocampus of each side.
In the complex mechanics of the development of the cerebrum these two bundles approach each
other under the corpus callosum, fuse for a certain distance, and together arch the cavity of
the third ventricle and come to acquire their adult position. There results from these processes
of growth a completely enclosed space, a portion of the longitudinal fissure, the roof of which
is the corpus callosum, its floor, the body of the fornix, and its lateral walls, portions of the
mesial surfaces of the two cerebral hemispheres. The lateral walls of this space do not thicken
872
THE NERVOUS SYSTEM
as do the other regions of the pallium, but remain thin and constitute the septum pellucidum of
the adult, the space itself being the so-called fifth ventricle or cavity of the septum pellucidum.
The septum pellucidum is a thin, approximately triangular, vertically placed
partition which separates the anterior portions of the two lateral ventricles from
each other. Its widest portion lies in front, bounded by the genu and rostrum
of the corpus callosum, the rostral lamina, and the anterior pillars of the
fornix, to all of which it is attached. Prolonged backward under the body of the
corpus callosum, it narrows rapidly and terminates at the line of adherence be-
tween the posterior portion of the fornix and the splenium of the corpus callosum.
It consists of two thin layers, the laminae of the septum pellucidum, arrested
developments of portions of the pallium of the hemispheres. The laminae
enclose a narrow median cavity known as the fifth ventricle [cavum septi pellucidi].
This cavity is of very variable size, is completely closed, and does not merit the
term ' ventricle, ' as apphed to the other cavities of the brain, in that it has no
communication with the ventricular system and has a different lining from the
other ventricles.
Fig. 685. — Diagram showing Some of the Pkincipal Tracts and Synapses of the Ol-
factory Apparatus.
Perforating fibre
Fornix
Anterior commissure '.
Medullary stria of thalamus
Subcallosal gyrus
Parolfactory are
^ Longitudinal strise
on corpus callosum
Hippocampal com-
(Lyre)
*" Habenular nucleus
, Habenulo-pedun-
cular tract (fasci-
culus retroflexus)
^* Mammillo-mesen-
^"^0^^ cephalic fasciculus
^ ,---"^^ Penduculo-tegmental
'"^^ tract
Interpeduncular nucleus
Uncinat'
fasciculus '
Uncus
\ Fimbria hippocampi
Mammillary body
Anterior perforated substance
Olfactory epithelium
Each lamina of the septum pellucidum consists of a layer of degenerated grey substance next
to the fifth ventricle and a layer of white substance next to the lateral ventricle, the latter covered
by a layer of ependyma common to that ventricle. The white substance consists in part of
fibres belonging to the general association systems of the hemispheres, and in part of four varie-
ties of fibres concerned with the rhinencephalon: — (1) fibres from each medial olfactory stria
are known to reach the septum pellucidum and thence go by way of the fornix to the hippo-
campus major; (2) fibres are thought to be contributed by the fornix to the septum pellucidum,
and through it reach the subcallosal gyrus and perhaps the parolfactory area and even the ol-
factory bulb ; (3) the posterior angle of the septum pellucidum is preforated by some commissural
fibres passing from the body of the fornix and by some perforating fibres of the fornix, passing
from above through it to the fornix below; (4) anteriorly, some fibres from the longitudinal
strife upon the corpus callosum pass tlirough its inferior portion to join the fornix.
The medullary stria of the thalamus [stria meduUaris thalami] {striai pinealis, lamia thalami),
already described as to position, receives fibres from three sources, the majority at least of
which belong to the rhinencephalon: (1) fibres from the fornix near-by and thus from the cor-
tex of hippocampal gyrus and gryus cinguli (a cortico-habenular tract) ; (2) fibres from the parol-
factory area and the anterior perforated substance, through the septum pellucidum and lamina
terminahs (a more direct olfaoto-habenular tract) ; (3) fibres arising from the cell-bodies in the
thalamus, supposedly chiefly from its anterior (olfactory) nucleus. These latter fibres make a
thalamo-habenular tract.
The majority of the fibres of the medullary striae terminate in the habenular nuclei, situated
at the two sides of the stalk of the epiphysis. Most terminate in the habenular nucleus of the
same side. Some cross in the habenular commissure (dorsal part of the posterior cerebral com-
missure) and terminate in the nucleus of the opposite side. A few are claimed to pass to the
nuclei of the quadrigeminate bodies and a few others to join the association tracts of the mesen-
cephalon. Axones given off by the cells of the habenular nucleus curve anteriorly, inferiorly,
and then course posteriorly (fasciculus retroflexus) to terminate in the interpeduncular nucleus
THE LATERAh VENTRICLES 873
(a hahenulo-peduncular tract), and fibres arising in this latter nucleus pass to the cells about the
central grey substance of the mesenecphalon (an inter-pedunculo-tegmental tract). The two
mesencephalic paths here noted and the mammillo-mesencephalic fasciculus noted above give
three anatomical possibilities for olfactory reflex activities, visceral (or sympathetic) and
somatic, involving the motor cranial nerves and possibly the spinal nerves. Fibres arising in the
cortex of the hippocampal gyrus, uncus especiaDy, may pass by way of the cingulum and thence
by any suitable association fasciculus of the cerebral hemisphere to the motor area of the cere-
bral cortex; also fibres may arise from the anterior nucleus of the thalamus and pass to the motor
cortex by way of the internal capsule. From the motor cortex, the descending pyramidal
fibres give the possibihties for any higher cortical activities induced by smell.
A more direct mesencephahc path has been suggested by Wallenberg, namely, that cells
in the olfactory trigone and anterior perforated substance, about which terminates fibres of
the olfactory tract, send axones directly postei-iorly, ai'ound the tuber cinereum, to terminate
in the mammiUary body and thence the impulses may go to the mesencephalon. Such fibres,
if they exist, would form an olfacto-mammillary tract. A path is described in the hedge-hog
which arises from cells in the olfactory trigone and passes directly posteriorly to terminate in
the grey substance of the mesencephalon — an olfacto-mesencephalic tract.
To the complicated central connections of the sense of smell, Dejerine adds yet another path,
namely, a portion at least of the terminal stria [stria terminalis] of the thalamus (taenia semi-
circularis). This contains fibres arising from cells in the anterior perforated substance and in
the septum pellucidum and fibres from the opposite side by way of the anterior commissure. It
runs a crescentic course posteriorly, bounding the thalamus from the caudate nucleus, turning
downward and then anteriorly in the wall of the inferior cornu of the lateral ventricle to termi-
nate in the amygdaloid nucleus, which latter is a more or less detached bit of the cortex of the
extreme anterior portion of the hippocampal gyrus (uncus). The stria is said also to contain
fibres which arise in the amygdaloid nucleus and course in it forward to be given off to the thala-
mus and probably to the internal capsule and thence to the cerebral cortex above.
SUMMARY OF THE OLFACTORY APPARATUS
I. Peripheral part.
(1) Olfactory area of nasal epithelium containing the cell-bodies and peripheral processes
of olfactory neurones (olfactory ganglion).
(2) Non-meduIIated central processes of olfactory neurones, the olfactory nerve, passing as
numerous filaments through the cribriform plate of the ethmoid, to terminate in contact with
the dendrites of the "mitral cells" (stratum glomerulosum) in the olfactory bulb.
II. The Rhinencephalon.
A. The anterior division.
(1) Olfactory bulb, olfactory tract, olfactory trigone (tubercle), lateral olfactory stria
(gyrus), medial and intermediate olfactory stria;.
(2) The parolfactory area, subcallosal gyi'us, anterior perforated substance including the
diagonal band of Broca.
B. The posterior division.
(1) Part of anterior commissure, septum pellucidum, uncinate fasciculus, hippocampal
gyrus (uncus especially), dentate g3Tus, gyrus cinguU and cingulum.
(2) Fimbria, hippocampal commissure, fornix, longitudinal strise upon corpus callosum,
mammiUary body, mammillo-thalamic fasciculus, mammiUo-mesencephahc fasciculus.
(3) The anterior nucleus of the thalamus.
(4) The medullary stria of the thalamus, habenular nucleus, fasciculus retroflexus, inter-
peduncular nucleus, and Lnterpedunculo-tegmental tract.
(5) Probably an olfacto-mammillary and an olfacto-mesencephalic tract, and a part of the
terminal stria of the thalamus with the amygdaloid nucleus.
THE LATERAL VENTRICLES
Two of the four cavities of the ventricular system of the brain are in the telen-
cephalon. From their position, one in each cerebral hemisphere, they are known
as the lateral ventricles. They arise as lateral dilations of the cavity of the anter-
ior of the prhnary vesicles, and, just as the fourth ventricle remains in communi-
cation with the third by way of the aqueduct of the cerebrum, so the lateral are
connected with the third by the two interventricular foramina (Monroi). The
whole ventricular system, including the central canal of the spinal cord, is Hned
by a continuous layer of ependyma and contains a small quantity of liquid known
as the cerebro-spinal fluid.
Each lateral ventricle is of an irregular, horseshoe shape. It consists of a
central portion or body and three cornua, which correspond to the three poles of
the hemisphere. The portion projecting into the frontal lobe is known as the
anterior cornu, that projecting into the occipital lobe is the posterior cornu, and
the portion which sweeps anteriorly downward into the temporal lobe is the
inferior cornu. The ventricles of different individuals vary considerably in capac-
ity, and the cavity of a given ventricle is not uniform throughout. In some
874
THE NERVOUS SYSTEM
localities the space may be quite appreciable, while in other places the walls may
be approximate or even in apposition. Each lateral ventricle is a completely
closed cavity except at the interventricular foramen. However, a strip of the
floor of the inferior cornu is separated from the exterior of the brain by only the
thin, non-nervous lamina forming the floor of the chorioid fissure.
The interventricular foramen (foramen of Monro), by which the lateral ven-
tricle is continuous with the cavity of the third ventricle, is a small, roundish chan-
FiG. 686. — A Cast of the Four Ventricles of the Encephalon. (After Weloker.)
Anterior cornu of lateral ventricle "
Interventricular foramen (Monro!)
Third ventricle
Inferior cornu of lateral ventricle
Aqueduct of cerebrum
Fourth ventricle
Posterior cornu of lateral ventricle'
nel, 2 to 4 mm. wide, which opens into the mesial side of the posterior end of the
anterior cornu. It is bounded in front by the free portion of the anterior pillars
of the fornix, and behind by the anterior tubercle of the thalamus. That the greater
part of the lateral ventricle is posterior to it is due to the backward extension of
Fig. 687. — Di.4.gram of Sagittal Section through Lateral Part of Right Hemisphbke
SHOWING Lateral Ventricle from the Mesial Side of the Section.
Chorioid plexus
Septum pellucidum
Fornix
Caudate nucleus
Interventricular foramen
Caudate nucleus
Hippocampus major
Chorioid plexus of inferior cornu
Internal capsule
Lenticular nucleus
Anterior commissure
the hemispheres during their growth and elaboration. Through the two foramina
indirectly, the cavities of the two lateral ventricles are in communication with
each other.
The walls of the lateral ventricle. — The anterior cornu is a bowl-like cavity,
convex forward and extending downward and medial ward into the frontal lobe.
Above and anteriorly it is bounded by the under surface of the corpus callosum and
the radiations of its genu into the substance of the frontal lobe. Its median bound-
ary is the septum pellucidum; the head of the caudate nucleus (part of the corpus
striatum) gives it a bulging, infero-lateral wall, and the balance of its floor is
formed by the white substance of the orbital part of the frontal lobe.
THE LATERAL VENTRICLES
875
The central portion or body is more nearly horizontal. It lies within the
parietal lobe and extends from the interventricular foramen to the level of the
splenium of the corpus callosum. Its roof is formed by the inferior surface of the
body of the corpus callosum, and its mesial wall consists of the posterior part of
the septum pellucidum, attaching the fornix to the under surface of the corpus
callosum. Like the anterior horn, it is given an oblique, infero-lateral wall by
the narrower, middle part of the caudate nucleus. Several structures contribute
to its floor: — (1) the stria terminalis of the thalamus, a hne of white substance
conforming to the genu of the internal capsule without, and constituting the
Fig. 688. — Horizontal Dissection of the Cerebral Hemispheres.
The fornix has been removed to show the relation of the tela chorioidea of the third ventricle to
the chorioid plexus of the lateral ventricles. (From a mounted specimen in the Anatomical
Department of Trmity College Dulilin )
Corpus
callosum
(dissected)
Veins of Galen
Crus of fornix
Straight sinus.
boundary between the caudate nucleus and the thalamus, and containing (2) the
vena terminalis (vein of the corpus striatum); (3) the lamina affixa, a mesial
continuation of the stria terminalis upon the surface of (4) the lateral part of the
thalamus; (5) the medial edge of the lamina affixa, the tsenia chorioidea, and the
chorioid plexus continuing under (6) the edge (taenia) of the body and the begin-
ning crura (posterior pillars) of the fornix (fig. 688).
The chorioid plexus of the lateral ventricle is continuous with that of the third
ventricle. The chorioid tela of the third ventricle (velum interpositum) con-
tinues under the taenia of the fornix into the lateral ventricle, and there, along the
line of the taenia chorioidea, becomes elaborated into a varicose, convoluted,
villus-like fringe, rich in venous capillaries and lymphatics. This fringe is the
chorioid plexus. It is continuous anteriorly, at the interventricular foramen, with
the corresponding plexus of the opposite lateral ventricle and with the chorioid
plexus of the third ventricle. The latter consists of two similar but smaller
fringes, which project close together into the cavity of the third ventricle from the
median portion of the ventral surface of the chorioid tela. Behind, the chorioid
876
THE NERVOUS SYSTEM
plexus of the lateral ventricle curves posteriorly and inferiorly into the inferior
cornu, being especially well developed at the region of its entrance into the latter,
into what is called the chorioid glomus.
Though apparently lying free in the ventricle, the chorioid plexus is invested throughout
by a layer of epithelium, the epithelial chorioid lamina, which is adapted to all its unevennesses
of surface and which is a continuation of the ependymal lining of the remainder of the ventricle
— continuous, on the one hand, with that of the lamina affixa and thalamus, and, on the other,
with the epithehal covering upon the upper surface of the tania of the fornix and fimbria.
The posterior cornu of the lateral ventricle is a crescentic cleft of variable length,
convex lateralward, which is carried backward from the posterior end of the body
of the ventricle and, curving medialward, comes to a point in the occipital lobe.
Its roof and lateral wall are formed by a portion of the posterior radiation of the
corpus callosum, which forms a layer, from its appearance known as the tapetum.
In transverse sections of the occipital lobe (fig. 699) the tapetum appears as a
Fig. 689. — Diagrammatic Transverse Section op Prosencephalon through Bodies of
Lateral Ventricles and Middle op Thalamencephalon.
Fifth ventricle . Fornix
Caudate
nucleus
Lamina affixa
Vena ter-
minalis
Stria ter-
minalisof / /«i\ \ "^ T "^1^ < ! // \ -Chorioid tela
thalamus «v.smwa \ \ \ # ^ i-ii»i«t-^
f Puta- /^#%*^\ \ \ / VlliH ^ I / I i _\ 'Thalamus
§» men /*' ^ \\ W / ili Oii \m \ // // \ Third
Globus
pallidus
Caudate
nucleus
Chorioid
plexus
Inferior cornu
of lateral
ventricle
Fimbria
Mammillo-
thalamic
fasciculus
Internal
capsule
thin lamina of obliquely cut white substance immediately bounding the cavity,
while outside the tapetum occurs a thicker layer of more transversely cut fibres,
the occipito-thalamic radiation. In the medial or inner wall of the posterior horn
run two variable longitudinal eminences: — (1) The superior of these is the bulb of
the posterior cornu, and is formed by the occipital portion of the radiation of the
corpus callosum (splenium), which bends around the impression of the deep pa-
rieto-occipital fissure, and, hook-like, sweeps into the occipital lobe. In horizontal
sections these fibres, together with the splenium and the similar fibres into the
opposite occipital lobe, form the figure known as the forceps major. (2) The
inferior and thicker of the eminences is the hippocampus minor [calcar avis]
(cock's spur), and is due to the anterior part of the calcarine fissure, by which the
wall of the hemisphere is projected into the ventricle. The posterior horn, like
the anterior, is not entered by the chorioid plexu i.
The inferior cornu. — In its inferior and slightly lateral origin from the region
of junction between the body of the ventricle and the posterior cornu, the inferior
horn aids in producing a somewhat triangular dilation of the cavity known as the
collateral trigone. Beginning as a part of the trigone, the cavity of this horn at
first passes posteriorly and lateralward, but then suddenly curves anteriorly and
THE CAUDATE NUCLEUS
877
inferiorly into the medial part of the temporal lobe nearly parallel wdth the supe-
rior temporal sulcus. Above, it follows the curved crura (posterior pillars) of the
fornix and fimbria; below, it does not extend to the temporal pole by from 2 to 3
cm. The roof and lateral wall are, for the most part, like those of the posterior
horn, being formed by the tapetum, but medialward a strip of the roof is formed by
the attenuated, inferior prolongation, or tail, of the caudate nucleus, together
with the inferior extension of the stria terminalis of the thalamus. At the end of
the inferior horn the roof shows a bulging, the amygdaloid tubercle, situated at
the termination of the tail of the caudate nucleus. This bulging is produced by
the amygdaloid nucleus, an accumulation of grey substance continuous with
that of the cortex of the hippocampal gyrus, and which gives origin to part of the
longitudinal fibres coursing in the stria terminalis of the thalamus.
In the medial wall and floor of the inferior horn the follo'ning structures are
shown: — (1) In the posterior or trigonal part of the floor is the longitudinal
collateral eminence, a bulging, very variable in development in different speci-
mens, produced by the collateral fissure. This is often pronouncedly in two parts,
a posterior prominence corresponding to the middle portion of the collateral fissure
and an anterior prominence (less frequent) produced by the anterior part of the
Fig. 690. — Dissection of Right Temporal Lobe showing the Medial Wall op the End
OP the Inperior Horn op the Lateral Ventricle. (From Spalteholz.)
Digitations of
hippocampus
Fimbria of
hippocampus
Hippocampal fissure
Dentate gyrus or fascia ^ ^
Substantia reticularis i
alba (Arnoldi) I
Hippocampal gyrus
■■ Hippocampus
Collateral eminence
Tffinia fimbriae j
Collateral fissure
fissure. (2) Medial to this eminence lies the inferior extension of the chorioid
plexus, usually more voluminous than the part in the bodj^ of the ventricle. (3)
Partly covered by the chorioid plexus is the hippocampus major, a prominent,
sickle-like ridge corresponding to the indentation of the hippocampal fissure. It
begins as a narrow ridge posteriorly, at the end of the body of the ventricle, as the
extension of the posterior pillar of the fornbc, and expands anteriorly as the ven-
tricular surface of the uncus. Its surface is not regular, but shows a concave
medial margin as distinguished from a wider, convex, lateral sm'face. Its ter-
mination in front (pes hippocampi) is divided by two or three flat, radial grooves
into a corresponding number of short elevations known as the hippocampal dig-
itations. It is covered by a thick stratum of white substance, the alveus, arising
from its depths and continued mesially into the fimbria. (4) The fimbria is so
folded that its margin, ta:nia fimhrice, lies in the cavity of the inferior horn attached
to the chorioid plexus and the thin, non-nervous floor of the chorioid fissure.
The caudate nucleus (fig. 691). — As realised in the study of the lateral ven-
tricle, the caudate nucleus is a comma-shaped mass of grey substance with a
long, much-curved, and attenuated tail. Its head forms the bulging lateral wall
of the anterior horn; thence it proceeds posteriorly in the lateral wall of the body
of the ventricle and, at the collateral trigone, curves downward and its tail becomes
878
THE NERVOUS SYSTEM
a medial portion of the roof of the inferior horn. It is separated from the thala-
mus adjacent to it by the stria terminalis of the thalamus (taenia semicircularis).
The end of its tail extends anteriorly below to the level of the anterior horn of the
ventricle above. Owing to its much curved shape, both horizontal and vertical
sections of the hemisphere passing through the inferior horn may contain the
nucleus cut at two places (see figs. 694 and 698.)
The caudate nucleus is the intraventricular of the two masses of grey substance
which together are sometimes referred to as the basal ganglia. The extraventri-
cular of these masses is the lenticular nucleus, which is bmied in the substance of
the hemisphere, laterally and inferior to the caudate nucleus. The two masses
Fig. 691. — Diageams of Lateral View and Sections op the NtrcLEi of the Corpus Stria-
tum WITH THE Internal Capsule Omitted.
A and B below represent horizontal sections along the lines A and B in the figure above. The
figure also shows the relative position of the thalamus and the amygdaloid nucleus.
date nucleus
Lenticular nucleus
Amygdaloid nucleus
Caudate nucleus
^^^7 Thalamus
Tail of caudate
Internal capsule
Lenticular nucleus
Caudate nucleus
Tail of caudate nucleus
Internal capsule
are separated by the internal capsule, a thick band of nerve-fibres continuous into
the cerebral peduncles, and connecting the grey cortex of the hemisphere with the
structures inferior to it. Anteriorly and below, the two nuclei become continuous
and the white substance of the internal capsule, in separating them posteriorly,
contributes to the striated appearance in sections, known collectively as the corpus
striatum (figs. 692, 695) . The corpus striatum as such is described below.
INTERNAL STRUCTURE OF THE PROSENCEPHALON
From the above examinations of their external and ventricular sinfaces, it is
apparent that the cerebral hemispheres consist of a folded, external mantle of
grey substance, the cortex cerebri, spread more or less evenly over an internal mass
THE LENTICULAR NUCLEUS 879
of white substance which contains embedded within it certain masses of grey sub-
stance, the chief of which are known as the caudate and lenticular nuclei of the
corpus striatum. In addition, the hemispheres of the telencephalon overlie and
are in functional connection with the structures of the diencephalon below, the
chief of which are the thalamencephalon and the bases of the cerebral peduncles.
The grey substance of the telencephalon. — The grey substance is in intimate
relation with the white substance, and in fact its cells give origin to the greater
part of the fibres composing the white substance. The accumulations of grey
substance to be considered are the cerebral cortex, with its variations in thickness
and arrangement, the corpus striatum, the claustrum, and the amygdaloid nucleus.
The cerebral cortex [substantia corticalis] is distributed over the entire surface
of each hemisphere except the peduncular region of the base and the region of the
corpus callosum and fornix of the medial surface. Numerous measmrements
have been made to determine its average thickness. These have shown that the
mantle is not uniformly distributed: — (1) that it is thicker on the convex surface
than on the basal and medial surfaces; (2) that on the convex smrface it is thicker
on the central region of the hemisphere, somsesthetic area, than at the poles; (3)
that in the average normal specimen it averages somewhat thicker on the left than
on the right hemisphere; (4) that its average thickness varies greatly in different
individuals, and that the thickness decreases with old age; (5) that it is probably
somewhat thicker in males than in females, and (6) that in a given specimen it
averages thicker on the summits of the gyri than in the floor of the corresponding
sulci. In the normal adult conditions it averages about 4 mm. thick on the ante-
rior and posterior central gyri, in the somsesthetic area, while it attains its mimi-
mum thickness of about 2.5 mm. on the basal surface of the occipital and frontal
lobes. Its total average thickness is about 2.9 mm. The practically non-
nervous floor of the third ventricle and that of the chorioid fissure are very much
thinner but are not considered in these measurements.
The cerebral cortex consists of layers of the cell-bodies of neurones, chiefly of the pyramidal
type (fig. 604), which receive impulses from the structures below and from other regions of the
cortex by way of fibres reaching them through the internal mass of white substance, and which
in turn contribute fibres to the white substance. Certain fibres of shorter course and numerous
collateral branches of fibres passing out of the cortex are devoted to the association of the region
of their origin with the cortex of the immediate vicinity of their origin, and most of these course
within the grey cortex itself. In certain gyri, such as the anterior central gyri and those of the
medial surface of the occipital lobe, these short association fibres accumulate into strata, and
in vertical sections give the cortex a stratified appearance. Two such strata of white substance
may be noted in the above localities, one lying about midway in the thickness of the cortex and
one slightly internal to this. They are known as the inner and outer stripes of Baillarger. In
addition, a thin, superficial or tangential layer of fibres may often be distinguished lying in the
surface of the cortex. Transverse sections through the anterior end of the hippocampus show
a coiled arrangement of the layers of white substance, to which has been given the name cornu
ammonis. The peculiar structure and appearance of the olfactory bulb and tract, parts of
the cortex, have already been mentioned.
The corpus striatum is so called on account of the appearance in section of
its component parts, the caudate and lenticular nuclei (basal ganglia) and the
internal capsule between them. The two nuclei are directly continuous with
each other at their anterior ends (fig. 691), and in addition they are connected by
numerous small bands of grey substance which pass from one to the other through
the internal capsule, especially its anterior part. Also each nucleus contributes
numerous fibres to, and receives fibres from, the internal capsule. These bundles
of fibres both arising and terminating within the nuclei, together with the grey
substance among the fibres of the capsule, produce the ribbed and striped appear-
ance suggesting the name, corpus striatum. The caudate nucleus — the intra-
ventricular part of the corpus striatum — hes with its thicker anterior part (head)
closely related to the internal capsule, but its tail passes posteriorly around the
posterior border of the capsule and curves downward and anteriorly into the roof
of the inferior cornu of the lateral ventricle.
The lenticular nucleus [nucleus lentiformis] — the extraventricular part of
the corpus striatum — is embedded in the white substance of the cerebral hemi-
sphere. It is somewhat pyriform in shape, not being so long as the caudate
nucleus, and neither having a tail nor extending so far anteriorly. Its lower sur-
face is separated from the inferior cornu of the lateral ventricle by the white sub-
stance of the roof of that cornu, and by the tail of the caudate nucleus, and, fur-
880 THE NERVOUS SYSTEM
ther forward, the anterior commissure passes through its base. Its lateral sur-
face is rounded and conforms both in extent and curvature with the surface of the
insula, from which it is separated by the fibres of the external capsule and the
intervening claustrum. Its oblique superior and mesial surface is adapted to the
lateral surface of the internal capsule, and it comes to a rounded apex in the angle
formed by the internal capsule and a plane parallel with the base of the hemi-
sphere. In both horizontal and coronal (transverse) sections through its middle
it resembles a compound biconvex lens. Internally this appearance is produced
by two vertically curving laminae of white substance, an external and an internal
medullary lamina, which divide its substance into three zones: — the two medial
zones together form an area, triangular in section, known as the globus pallidus ;
the lateral, larger and more grey, concavo-convex zone is the putamen. Radiat-
ing fibres from the medullary laminae extend into the zones, especially those of the
globus pallidus. These zones disappear in transverse sections of the anterior
Fig. 692. — Coronal Section of Telencephalon Passing Through Fbontal Lobes and
Anterior Portion of Corpus Striatum.
(From mounted specimen in the Anatnmiral Department of Trinity College, Dublin.)
Longi-
tudin
fissure
Olfactory tract'
portion of the lenticular nucleus (fig. 692), due to the fact that the larger putamen
alone comprises this portion and alone becomes continuous with the caudate
nucleus. (See figs. 691, 696.)
Connections. — Both nuclei of the corpus striatum become continuous with the cortex in
the region of the anterior perforated substance, and the putamen of the lenticular nucleus may
blend with the anterior part of the base of the claustrum. The following are the principal fibre
connections: — (1) Fibres arising in the nuclei which join the internal capsule to reach the
cerebral cortex, and fibres arising in the cortex which descend by the same course to the cells
of the nuclei. (2) Fibres which pass in both directions between the thalamus and the corpus
striatum (caudate nucleus especially). These are more abundant anteriorly, and necessarily
pass through the internal capsule. (3) The ansa lenticularis, or strio-subthalamio radiation,
a usually distinct lamina, composed largely of fibres passing inferiorly between the thalamus
and lenticular nucleus. It passes from the basal aspect of the anterior tubercle of the thalamus
and curves below through the internal capsule to the basal surface of the lenticular nucleus,
and there its fibres are distributed upward through its medullary lamina to the globus pallidus
and putamen. Some enter the internal capsule and reach the cortex, chiefly that of the tem-
poral lobe. The ansa lenticularis also contains fibres from the cortex of the temporal lobe to
terminate in the inferior and mesial parts of the thalamus. The fibres associating the thalamus
with the temporal lobe belong to the so-called inferior peduncle of the thalamus. (4) Fibres
connecting both nuclei (chiefly the caudate) with the red nucleus and substantia nigra of the
mesencephalon. These pass through the hypothalamic region and along the cerebral peduncle.
No definitely localised functions have been with certainty ascribed to either nucleus. They
serve as 1-elays in the pathways associating the cortical grey substance with the structures below
and in them the neurones concerned in these pathways are greatly increased.
The claustrum is a triangular plate of grey substance which is embedded in
the white substance between the lenticular nucleus and the insula. Its medial
THE THALAMUS
881
surface is concave, conforming to the convexity of the putamen. The sheet of
white substance intervening between it and the putamen is known as the external
capsule. Its lateral surface shows ridges or projections in section which conform
to the neighbouring gyri of the insula, and it is spread through an area which quite
closely coincides with that of the inusla. Below and anteriorly it becomes con-
tinuous with the cortex of the anterior perforated substance and with the lenticu-
lar nucleus at the region of the junction of these. Above and posteriorly it gradu-
ally becomes thinner, and finally disappears in the white substance about it.
In origin it is thought to be a detached portion of the cortical grey substance of
the insula.
The amygdaloid nucleus [nucleus amygdalae] is represented by the amygda-
loid tubercle, which has already been described in the extremity of the inferior
cornu of the lateral ventricle (figs. 666 and 691). It is an almond-shaped mass of
cells joined to the tail of the caudate nucleus, continuous above with the putamen
and anteriorly continuous with the cortex of the hippocampal gyrus.
Fig. 693. — Coronal Section op Telencephalon through the Anterior Commissure,
Optic Chiasma, and Trunk op Corpus Callosum. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Caudate nucleus
(head)
Internal capsule
(frontal portion
^,' Longitudinal fissure
Corpus callosum
Anterior cornu
of lateral ven-
tricle
Chorioid plexus
of lateral i
The chief connections of the amygdaloid nucleus by way of the stria tertjiinalis of the
thalamus are noted above under the description of the posterior division of the rhinencephalon.
The amygdaloid nucleus, like the claustrum, is thought to represent a detached portion of the
cortex, it being detached from the uncus. Considering this and its chief connections, it, with
the stria terminahs of the thalamus, are concerned in the central portion of the olfactory
apparatus.
The thalamus and hypothalamus. — The external features of these portions of
the prosencephalon have been described in their natural place, but inasmuch as
they contain the chief relays between the telencephalon and the divisions of the
nervous system caudal to the prosencephalon, the consideration of their internal
structure has been deferred till now. The principal grey masses to be considered
are the thalamus and the hypothalamic nucleus. The structures comprising the
metathalamus and epithalamus have already been mentioned in their relations
with the mesencephalon and the optic and auditory apparatus.
The thalamus has upon its upper surface, under its ependyma, a thin stratum
zonale of white substance, derived in part from the incoming fibres and in part
from its own cells. Its oblique lateral surface conforms to the medial surface of the
internal capsule; its vertical medial surface forms the lateral wall of the third
ventricle, and below it is continuous into the hypothalamic (tegmental) region.
882
THE NERVOUS SYSTEM
Its upper surface shows a middle, an anterior, and a posterior prominence or tuber-
cle. The anterior tubercle (nucleus) forms the posterior boundary of the inter-
ventricular foramen; the posterior tubercle is the cushion-like pulvinar which
projects backward over the lateral geniculate body and the brachium of the
superior quadrigeminate body.
A horizontal section through the supero-medial edge, spHtting the stria medul-
laris of the thalamus and thus passing above the massa intermedia, shows the grey
mass of the thalamus divided into segments or nuclei by a more or less distinct
internal medullary lamina. This extends the whole length of the thalamus,
dividing its middle and posterior portion into the medial and the lateral nucleus.
Fia. 694. — HoKizoNTAii Dissection showing the Grey and White Substance op the
Telencephalon Below the Corpus Callosum and the Relative Position of the
Thalamencephalon. (After Landois and Stirling.)
Gyrus cinguU
Genu of corpus callosum
Anterior cornu
Caudate nucleus
Internal capsule
(Frontal portion)
External capsule
_ ^ . f Putamen
Lenticular Globus.
nucleus | palUdus
Claustrum
Internal capsule (occr
pital portion)
Medial geniculate
body
Tail of caudate
nucleus
Hippocampus major'
Hippocampus minor'
Septum pellucidum
Corpus striatum
Column of fornix
Clava
Funiculus cuneatus
Funiculus gracilis
Anteriorly the lamina bifurcates into a medial limb, extending to the medial sur-
face of the thalamus, and a lateral limb, extending forward to join the genu of the
internal capsule (figs. 695, 700). This bifurcation results in a cup-like sheet of
white substance which encloses the anterior nucleus. On the lateral surface of
the section, next to the internal capsule, there may usually be distinguished an
external medullary lamina, separated from the white substance of the capsule
by a reticular layer of mixed white and grey substance.
The anterior nucleus, lying partially encapsulated in the bifurcation of the
internal medullary lamina, is somewhat wedge-shaped and points backward be-
tween the anterior portions of the lateral and medial nuclei.
It is composed chiefly of large cells, and constitutes the anterior tubercle of the superior
aspect. Its principal connection from below is with the nuclei of the mammillary body of the
same and opposite sides, and with uninterrupted fibres derived from the columns of the forni.x.
THE THALAMUS
883
The fibres from both sources enter it by way of the mammillo-thalamic fasciculus (figs. 671 and
695). The significance of this connection is mentioned in the description of the limbic lobe.
The lateral nucleus, lying between the external and internal medullary lam-
inae, extends posteriorly to include the entire pulvinar.
The pulvinar, as already noted, together with the lateral geniculate body, constitutes the
prosencephalic nucleus of termination of the optic tract, and the stratum zonale upon the surface
of this nucleus might be called the stratum opticum. The anterior portion of the lateral
nucleus receives fibres inferiorly from the red nucleus, from the brachium conjunctivum
(cerebellum direct), and some fibres of the medial lemniscus terminate about its cells.
The medial nucleus lies medial to the internal medullary lamina and forms the
posterior portion of the lateral wall of the third ventricle. It is shorter than the
lateral nucleus, and is less extensively pervaded by fibres.
Fig. 695. — Coronal Section of Prosencephalon through Thalamencephalon at Region
OP Corpora Mammillaria. (Seen from in front.) (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Lateral ventricle ^ __.._-^ , ^ , . , , , Corpus callosum
(central portion)
Chorioid plexus
of lateral ven-
tricle
Caudate nucleus ^
Massa inter- ~,-
media
Internal capsule
Lenti- [ (Puta
cular ! men
nu- I Globus
cleus I pallidus
External capsule
Claustrum
Ansa peduncu-
laris
Optic tract
Inferior peduncle ^
of thalamus
Inferior cornu of
lateral ventricle
Hippocampal ^
digitations
Oculomotor nerve
Fornix
It is thought to receive fibres from the red nucleus, and perhaps some from the lemniscus,
and is usually continuous across the third ventricle with the opposite medial nucleus by the
massa intermedia.
In comparative anatomy, the nuclei of the thalamus have been variously subdivided by
the different investigators. All the nuclei are connected with the lenticular nucleus by fibres
passing between the two through the internal capsule directly, and by fibres curving from below,
chiefly from the anterior, lateral and medial nuclei, and passing in the ansa lenticularis.
The cortical connections of the thalamus are abundant. They consist of fibres
both to and from the cortex of the different lobes of the hemisphere, the greater
part arising in the thalamus and terminating in the cortex. These fibres collect
in the internal and external medullary laminae and the stratum zonale; most of
them enter the internal capsule and thence radiate to the different parts of the
cortex.
They form the so-called peduncles of the thalamus, which have been distinguished both by
the Flechsig method of investigation and by the degeneration method. The anterior or frontal
peduncle passes from the lateral and anterior part of the thalamus through the frontal portion
of the internal capsule, and radiates to the cortex of the frontal lobe. (See fig. 700.) The
middle or parietal peduncle passes from the lateral surface of the thalamus through the inter-
mediate part of the internal capsule, and upward to the cortex of the parietal lobe. The pos-
terior or occipital peduncle passes chiefly from the pulvinar, through the occipital portion of the
internal capsule, and radiates backward to the occipital lobe by way of the occipito-thalamic
(optic) radiation (fig. 699). The inferior peduncle passes from the medial and basal surface
of the thalamus (from the anterior and medial nuclei chiefly), turns outward to course beneath
the lenticular nucleus, and radiates to the cortex of the temporal lobe and insula. The fibres
of this peduncle course chiefly in the ansa lenticularis (fig. 695). Some turn upward in the
external capsule to reach the cortex above the insula; others pass upward through the medullary
laminae of the lenticular nucleus.
884 THE NERVOUS SYSTEM
The h3rpothalamic nuclues (fig. 698) , or body of Luys, is the principal nucleus of
termination of the medial lemniscus, the great sensory spino-cerebral pathwayl
It is a biconvex plate of grey substance situated on the basal aspect of the latera.
and anterior nuclei of the thalamus, and between these and the basis of the cerebral
Fig. 696. — Horizontal Sections of the Peosencephalon through the Thalamus and
Corpus Striatum.
The plane of the section of the left hemisphere splits the medullary stria of the thalamus and
is about 15 millimeters superior to the plane through which the right hemisphere is cut.
(After Toldt.)
Trunk of corpus caliosum
Septum pellucidum
Genu of corpus caliosum
Anterior cornu of lateral ventricle
Head of caudate nucleus
Column of fornix
Internal capsule
Island of Reil
(insula)
Chorioid glomu:
Occipito-
thalamic
radiation
Splenium of corpus caliosum
Calcarine fissure
peduncle, or rather the substantia nigra, which is spread upon the dorsal surface
of the peduncle, and which, though greatly diminished, extends into the hypo-
thalamic region. The hypothalamic nucleus presents a brownish-pink colour
in fresh material, due to pigment in its cells and to its abundant blood capillaries.
It contains the cell-bodies of the neurones of the third order in this pathway, those of the
first order being situated in the spinal ganglia, and those of the second order in the nuclei of the
fasciculus gracilis and fasciculus cimeatus. It is enclosed by a thin capsule of white substance,
some of the fibres of which seem to decussate with those of the opposite side in the floor of the
third ventricle, above and just behind the region of the corpora mammiUaria. By far the greater
part of the fibres arising from the nucleus join the internal capsule, and through it ascend to
WHITE SUBSTANCE OF TELENCEPHALON 885
radiate to the cortex of the pre- and post-central gyri, the sensory-motor or somsesthetic area
of the hemisphere. The majority terminate in the post-central gyrus.
All the fibres connecting the cerebral cortex with both the thalamus and the hypothalamic
nucleus belong to the so-called projection fibres of the cerebral hemisphere.
The habenular nucleus and the fasciculus relroflexus of Meynert have been noted in the de-
scription of the rhinencephalon. The habenular nucleus, a part of the epithalainus, is a small
group of nerve cells situated in the habenular trigone just infero-lateral to the epiphysis. The
fibres of the medullary stria of the thalamus (habenula) terminate about its cells. A small
bundle of fibres crossing the mid-hne under the epiphysis in the superior aspect of the posterior
cerebral commissure is called the commissure of the habenuloe, from the fact that it connects the
habenular nuclei of the two sides.
Fig. BOy.' — Oblique Feontal Section through the Brain in the Direction of the
Cerebral Peduncles and the Pyramids. (Seen from in front.) (After Toldt, "Atlas
of Human Anatomy," Rebman, London and New York.)
Longitudinal fissure
Radiation of corpus callosum
Septum pE llucidum
Superior frontal gyrus
Body of corpus callosum
Anterior horn of lateral ventricle
Head of caudate nucleus
Corona radiata
Column of formz
Internal capsule
Thalamus ~
Third ventricle -
Cerebral peduncle
Brachium pontis
Longitudinal pyramidal
fasciculi of pons
Superficial fibres of pons /'
Pyramid
External capsule
Globus pallldus
Optic tract
Mammillary body
Oculo-motor nerve
Trigeminal nerve
Facial and cochlear
Glosso-pharyngeal nerve
Vagus nerve
Inferior ohvary nucle
Decussation of pyramids
The fasciculus retroflexus (Meynerti) is a relatively strong bundle of medullated fibres
which runs downward and then turns caudalward from the habenular nucleus toward the inferior
portion of the interpeduncular fossa. It has been shown that many, at least, of the fibres of
this bundle arise from the cells of the habenular nucleus. In its slightly caudad course, the
bundle passes obliquely through the red nucleus, entering the medial superior aspect and making
its exit from the ventro-mesial side of the inferior extremity of this nucleus. In the animals in
which it has been studied, the bundle ends in the interpeduncular nucleus (ganglion), a group of
nerve cells lying in the floor of the interpeduncular fossa at the level of the inferior quadrigemina.
In man, the interpeduncular nucleus is not definitely assembled and the bundle seems to dis-
appear in the posterior perforated substance. However, the microscope shows cells dispersed
among the fibres of the bundle and these cells probably represent the nucleus.
The white substance of the telencephalon. — A horizontal section through the
upper part of the trunk of the corpus callosum will pass above the basal grey
substance of the corpus striatum, and, aided by the corpus callosum, each hemi-
sphere in such a section will appear as if consisting of a solid, half-oval mass of
white substance, bounded without by the grey layer of the cortex (fig. 672). As
886
THE NERVOUS SYSTEM
seen at this level, the white substance of each hemisphere is known as the centrum
semiovale. Horizontal sections passing below the body of the corpus callosum
involve the corpus striatum and thalamus, and the appearance of the white sub-
stance is modified accordingly (fig. 694).
In the white substance of the cerebral hemispheres as a whole three main sys-
tems of fibres are recognised: — projection fibres, commissural fibres, and associa-
tion fibres. The projection fibres are those of a more or less vertical course, which
pass to and from the cortex of the hemisphere, associating it with the structures
below the confines of the hemisphere. The commissural fibres are those of a
transverse or horizontal course, which cross the mid-line and functionally connect
the two hemispheres with each other. The association fibres are those which
neither cross the mid-line nor pass beyond the bounds of the hemisphere in which
they arise, but instead associate the different parts of the same hemisphere — lobes
with lobes and gyri with gyri. The fibres which associate the cortex with the
Fig. 698. — Coronal Section op Brain Passing Through the Pulvinah of the Thalamus
AND the Uncus of the Hippocampal Gyrus. (After Toldt.)
Chorioid tela of ■
third ventricle
\ \ I r'n/n "'/'/" ~'»*ip''/^>' '^
Chorioid plexus
of third ven-
tricle
Internal capsult
Habenular
nucleus
Tail of caudate
nucleus
Optic tract
Fimbria of
hippocampus
Peduncle of
cerebrum
Post, recess of
interpeduncular
Red nucleus
nuclei of the corpus striatum must also be classed as association fibres, since these
masses of grey substance are a part of the telencephalon, while by definition those
which associate the thalamus and hypothalamus with the cortex belong to the
projection system. Some of the fibre bundles of the above systems have already
been described in connection with the parts with which they are concerned.
The projection fibres of the hemisphere comprise both ascending and descend-
ing fibres between the cerebral cortex and structures below the bounds of the hemi-
sphere, i.e., some arise in the structures below and terminate in the cortex; others
arise from the cortical cells and terminate in the structures below, including the
grey substance of the thalamencephalon, mesencephalon, rhombencephalon, and
spinal cord. The projection fibres are given different names in the hemisphere
according to their arrangement and the appearances to which they contribute
in the dissections. Beginning with the pyramidal fasciculi and the basis of the
peduncle, they contribute — (1) to the internal capsule and some to the external
capsule and (2) to the corona radiata.
The internal capsule [capsula interna] is a band of white substance, consisting
of the ascending fibres from the nuclei of the thalamus, hypothalamus, and corpus
striatum, reinforced by the descending fibres from the cortex to these nuclei and
by those descending in the cerebral peduncle to terminate in the mesencephalon,
rhombencephalon and spinal cord. It is a broad, fan-like mass of fibres, which
increases in width from the base of the hemisphere upward, and which is spread
between the lenticular nucleus on its lateral aspect and the caudate nucleus and
THE CORONA RADIATA
887
thalamus on its medial side. To reach the cortex above, the course of its fibres
necessarily intersects that of the radiations of the corpus callosum, and thus,
together with the corpus callosum, the fan-like bands of the two hemispheres form
a capsule containing the thalami, the third ventricle, the caudate nuclei, and the
anterior and central portions of the lateral ventricles. In horizontal sections,
each internal capsule appears bent at an angle, the genu, which approaches the
cavity of the lateral ventricle along the line of the boundary between the thalamus
and the caudate nucleus. Along the genu runs the stria terminalis of the thala-
mus, and through the genu the capsule receives fibres from the internal medullary
lamina of the thalamus, from the stratum zonale of the thalamus and from that
of the caudate nucleus. At the genu each capsule is separable into two parts: —
(1) the anterior (frontal) portion, spreading between the caudate and lenticular
nuclei; (2) the posterior (occipital) portion, between the lenticular nucleus and the
thalamus (fig. 700.)
Fig. 699. — Coeonal Section THROtroH the Splenium op the Corpus Callosum and the
Posterior Cornua op the Lateral Ventricles. (Viewed from behind.) (After Toldt,
"Atlas of Human Anatomy," Rebman, London and New York.)
Radiation of, corpus callosum
Bulb of posterioi
Splen
Corpora quadri-
gemina
L of corpus callosum
Tela chorioidea
of third ven-
tricle
Medial longitu. L
dinal fasciculus
Cerebellum
Brachium pontis
Flocculus
Epiphysis
Posterior cornu
^ ^ ^ of lateral ven-
tiicle
^ Glomus chori-
^ ^ oideum
Tapetum
_ Occipito-thalamic
radiation
Collateral emin-
en:e
Collateral fissure
Lateral Lemniscus
Brachium con-
junctivum
Central grey
substance
Medial lemniscus
Pyramid
FunctionaOy, the internal capsule may be divided into a frontal, a fronto-parietal and an
occipital part. The frontal part consists of (1) an anterior segment, carrying chiefly fibres
coursing in both directions between the thalamus and the cortex of the frontal lobe, and (2)
a posterior segment carrying the frontol-pontUe tract.
The fronto-parietal part may be considered in four segments; — (1) An anterior segment,
the genu, carrying fibres from the cortex to the nuclei of the motor cranial nerves; (2) posterior
to this is the corticospinal segment for the arm and thorax, descending cortical fibres to the regions
of the spinal cord supplying these; (3) next is the corticospinal segment }or the lower extremity;
(4) a posterior segment carrying the general sensory path ascending from the hypothalamic
nucleus, the infero-lateral part of the thalamus and the red nucleus to the cortex. All the
segments of the fronto-parietal part carry in addition, fibres in both directions between the
cortex above and the thalamus and the nuclei of the striate body.
The occipital part consists (1) of an anterior segment which carries the temporal and occipital
pontile paths, and (2) a posterior segment carrying the visual fibres between the occipital cortex
and the nuclei of termination of the optic nerve. This segment also carries the auditory fibres
passing between the cortex of the superior temporal gyrus and the regions of termination of the
lateral lemniscus. Thus it carries a visual and an auditory path.
The corona radiata. — Above the corpus callosum and laterally joining its
radiations, the fibres of the internal capsule are dispersed in all directions. The
appearance known in coronal sections of the hemispheres as the corona radiata is
produced by the ascending and descending fibres of the internal capsule combined
with the radiations of the corpus callosum. The radiations related to the internal
THE NERVOUS SYSTEM
capsule may be divided into a frontal, a parietal and an occipital part, corres-
ponding to the frontal, parietal and occipital peduncles of the thalamus, or to the
parts of the internal capsule.
The radiation derived from the posterior segment of the occipital part of the
internal capsule, the visual path, accumulates into a well-defined band of fibres
which passes posteriorly into the occipital lobe, spreading in the lateral wall of the
posterior cornu of the lateral ventricle immediately lateral to the tapetum. This
band consists for the most part of fibres arising in the pulvinar of the thalamus and
Fig. 700.-
-DiAGBAM TO Indicate the Relative positions of the Projection Fibees in
THE Intehnal Capsule. (In part after VilEger.)
yy4 y Stria terminalis of
'/^j / thalamus
«?■,////'/ •• Fronto-pon-
-™ Cortico-spinal
path (arm)
~~ ^ Cortico-spinal
path (leg)
"^ General sen-
sory path
■ ^ Temporal 1
and occipital
pontile path I
■^ visual and
auditory path J
Fronto-
parietal
part
in the lateral geniculate body and going to the visual area of the occipital cortex,
and of fibres arising in this cortex to terminate in the thalamus and mesenceph-
alon. Being thus concerned with the optic apparatus, it is known as the occipito-
thalamic radiation or optic radiation (fig. 699).
The external capsule is, as already noted, a thin sheet of white substance
spread between the claustrum and the lenticular nucleus.
It owes its appearance as such to the presence of the claustrum. It joins the internal cap-
sule at the upper, posterior, and anterior borders of the putamen, and below the claustrum it
is continuous with the general white substance of the temporal lobe. Thus it contributes to
an encapsulation of the lenticular nucleus by white substance. Most of the fibres contained
in it belong to the association system. Its projection fibres consist of those of the inferior
peduncle of the thalamus, which pass from the basal surface of the thalamus and, instead of
continuing below to the cortex of the temporal lobe and insula, turn upward, around the lenticu-
lar nucleus to the cortex above the insula. Some of these thalamus fibres are known to pass
upward through the lamina; of the lenticular nucleus instead of through the external capsule.
DESCENDING PROJECTION FIBERS 889
The ascending projection fibres arise mostly from the cells of the nuclei of the
thalamus and hypothalamic nucleus; some arise from nuclei in the mesencephalon
and from the red nucleus.
They may be summarised as follows: —
(1) The terminal part of the general sensory pathway of the body. The portion of the medial
lemniscus which arises in the nuclei of the fasciculus gracilis and cuneatus, of the opposite side,
terminates in the hypothalamic nucleus and the inferior portion of the lateral nucleus of the
thalamus. The projection fibres given off by the latter nuclei pass chiefly through the posterior
segment of the fronto-parietal part of the internal capsule and radiate to and terminate in the
somaesthetic area of the cortex, chiefly in the posterior central gyrus. Some few pass outside
around the lenticular nucleus, and ascend by way of the external capsule.
(2) The terminal part of the general sensory pathway of the head and neck. The nuclei of
termination of the sensory portions of the cranial nerves of the rhombencephalon (except the
nuclei of the cochlear nerve) give fibres which course upward in the medial lemniscus (fillet)
and reticular substance of the opposite side and terminate in the infero-lateral portions of the
thalamus and in the h3rpothalamic nucleus. Thence arise projection fibres which ascend to
the somaesthetic area by practically the same route as those of the general sensory system for
the body.
' (3) The terminal part of the auditory pathway. The ventral and dorsal nuclei of termina-
tion of the cochlear nerve send impulses which, by way of the lateral lemniscus, are distributed
to the inferior quadrigeminate body, the medial geniculate body, and the nucleus of the lateral
lemniscus of the opposite side. These nuclei send projection fibres through the posterior
segment of the fronto-parietal part of the internal capsule, and thence by the temporal portion
of the corona radiata to the cortex of the superior temporal gjrrus (auditory area). Probably
some of these fibres pass by way of the inferior peduncle of the thalamus. Some of the fibres
arising in the nuclei of termination of the vestibular nerve convey impulses which reach the
somaesthetic area, but the origin of the terminal portion of this system is uncertain.
(4) The terminal part of the visual pathway. The cells of the pulvinar and the lateral
geniculate body, serving as nuclei of termination of the optic tract, give off projection fibres
which pass by way of the posterior segment of the occipital portion of the internal capsule
and the occipito-thalamic radiation to the cortex of the occipital lobe, chiefly the region about
the posterior end of the calcarine fissure — the visual area.
(5) The terminal ascending cerebellar pathway. The fibres of the brachium conjunctivum,
after decussating, terminate both in the red nucleus and in the lateral nucleus of the thalamus.
Some fibres from the red nucleus become projection fibres direct, others terminate in the
medial and anterior portion of the lateral nucleus of the thalamus. From the thalamus the
projection fibres of this system pass in the parietal peduncle of the thalamus to the somaesthetic
area.
The descending projection fibres arise as outgrowths of the pyramidal cells
of the cerebral cortex. Practically all of them cross to the opposite side in their
descent to the structures of the brain stem and spinal cord. The majority of them
arise near and within the gyri in which the respective ascending fibres terminate.
Those transmitting cortical impulses to the cells giving origin to the motor fibres
of the cranial and spinal nerves arise chiefly from the giant pyramidal cells of the
precentral (anterior central) gyrus, the paracentral lobule and the posterior ends
of the superior, middle, and inferior frontal gyri. These latter occupy nearly
three-fourths (the anterior three segments) of the fronto-parietal part of the inter-
nal capsule and the middle three-fifths of the basis of the cerebral peduncle, and
are usually called 'pyramidal fibres (fig. 700).
The principal descending projection fibres may be grouped as follows:
(1) The pyramidal fibres to the spinal cord (cortico-spinal or pyramidal fascicuh proper).
These arise from the giant pyramidal cells of the upper two-thirds of the precentral gyrus,
the anterior portion of the paracentral lobule and the posterior third of the superior frontal
gyrus. Those for the lumbo-sacral region of the spinal cord arise nearest the supero-mesial
border of the cerebral hemisphere. The tract descends through the two middle segments of
the fronto-parietal part of the internal capsule. Those carrying cortical impulses for the
muscles of the arm and shoulder course in the segment anterior to the course of those for the
muscles of the leg. Both continue through the cerebral peduncles and the pons and through
the pyramids of the medulla, and then decussate, passing down the spinal cord to terminate
about the ventral horn ccUs (the origin of the motor nerve roots) of the opposite side.
(2) The pyramidal fibres to the nuclei of origin of the motor cranial nerves arise from
the pyramidal cells in the inferior third of the precentral gyrus, the posterior end of the inferior
frontal gyrus, the opercular margin of the posterior central gyrus, and probably some (for eye
movements) in the posterior end of the middle frontal gyrus. The locality of the origin of
the pyramidal fibres terminating in the nuclei of the facial and hypoglossal nerves only has been
determined with certainty. The general tract passes in the genu of the internal capsule,
through the cerebral peduncle, and, gradually decussating along the brain stem, terminates in
the nuclei of the motor cranial nerves of the opposite side.
(3) The frontal pontile path (Arnold's bundle) arises in the cortex of the frontal lobe,
anterior to the precentral gyrus, descends through the frontal part of the corona radiata and
posterior segment of the frontal portion of the internal capsule into the fronto-mesial portion of
the cerebral peduncle, and terminates in the nuclei of the pons.
890 THE NERVOUS SYSTEM
(4) The temporal pontile path (Turk's bundle) arises in the cortex of the superior and middle
temporal gyri, passes through the posterior segment of the occipital part of the internal capsule,
enters the cerebral peduncle postero-lateral to its pyramidal portion, and terminates in the
nuclei of the pons. An occipito-pontile path is described as arising in the occipital cortex and
joining the temporal pontile path in the internal capsule to pass to the nuclei of the pons.
(5) The occipito-mesencephalic path (Flechsig's secondary optic radiation) arises in the
cortex of the visual area of the occipital lobe (cuneus and about the calcarine fissure), passes
forward through the occipito-thalamic radiation, downward in the posterior segment of the
occipital portion of the internal capsule, and terminates in the nucleus of the superior quadri-
geminate body and the lateral geniculate body. It is probable that some of its fibres terminate
directly in the nuclei of the eye-moving nerves.
(6) Those fibres of the fornix which arise in the hippocampus and terminate in the corpus
mammiUare or pass through it to the anterior nucleus of the thalamus of the same and opposite
side (mammiUo-thalamic fasciculus) or pass into the mescencephalon and probably to structures
lower down.
The commissural system of fibres. — ^The commisstiral fibres of the telenceph-
alon serve to connect or associate the functional activities of one hemisphere
with those of the other. They consist of three groups: — The corpus callosum,
the anterior commissure and the hippocampal commissure.
(1) The corpus callosum, the great commissure of the brain. A general description of
this with the medial and lateral striae running over it has aheady been given. It is a thick band
of white substance, about 10 cm. wide, which crosses between the two hemispheres at the bottom
of the longitudinal fissure. Its shape is such that in its medial transverse section its parts are
given the names splenium, body, genu, and rostrum (figs. 667 and 679). Its lower surface is
medially joined to the fornix, in part by the septum peUucidum and in part directly. Laterally
it is the tapetum of the roof of the lateral ventricle of either side. The majority of its fibres
arise from the cortical cells of the two hemispheres, and terminate in the cortex of the side
opposite that of their origin. In dissections, its fibres are seen to radiate toward all parts of
the cortex — the radiation of the corpus callosum. These radiations may be divided into
frontal, parietal, temporal and occipital parts. The occipital parts curve posteriorly in two
strong bands from the splenium into the occipital lobes, producing the figure known as the
forceps major. Anteriorly, the frontal parts are two similar but lesser bands which curve
from the genu forward into the frontal lobe, producing the forceps minor.
(2) The anterior commissure has been described in connection with the rhinencephalon.
In addition to the ohactory fibres coursing through it from the olfactory bulb and parolfactory
area of one hemisphere to the uncus of the opposite hemisphere, its greater part consists of
fibres which arise in the cortex of the temporal lobe, the uncus chiefly, of one side and terminate
in that of the opposite side. It crosses in the substance of the anterior boundary of the third
ventricle, and through the inferior portions of the lenticular nuclei, and can be seen only in
dissections (figs. 684, 693). It is a relatively small, round bundle, and its mid-portion
between its terminal radiations presents a somewhat twisted appearance.
(3) The hippocampal commissure (transverse fornix) belongs wholly to the limbic lobe
(rhinencephalon), and has been described there. It connects the hippocampal gyri of the
two sides, and crosses the mid-Mne under and usually adhering to the under surface of the
splenium of the corpus callosum. Crossing the body of the fornix, it thins anteriorly and ceases
in the posterior angle of the septum peUucidum.
With these three commissures of the telencephalon, the three other commissures of the
prosencephalon should be called to mind. The inferior cerebral commissure (Gudden's
commissure), while occurring in the optic chiasma and allotted by position to the telencephalon,
really belongs to the diencephalon since it connects with each other the medial geniculate
bodies of the two sides. The supra-mammillary commissure, connecting the nuclei of the mam-
miUary bodies of the two sides, is allotted to the diencephalon. The posterior cerebral com-
missure, situated just below the stalk of the epiphysis, belongs to both the diencephalon and
mesencephalon. Its superior part, the habenular commissure, connecting the two nuclei of the
habenulae, belongs wholly to the diencephalon. In its inferior part, the fibres arising in the
thalamus of one side and terminating in that of the other side belong likewise to the diencephalon,
but those passing between the superior quadrigeminate bodies of the two sides and between
the so-called nuclei of the medial longitudinal fasciculi belong to the mesencephalon.
The association system of the hemisphere. — The possibilities for association
bundles connecting the different parts of the same hemisphere with each other are
innumerable, and a large number are recognised. They serve for the distribution
or diffusion of impulses brought in from the exterior by the ascending projection
system, and it is by means of them that the different areas of the cortex may
function in harmony and coordination. Most of the association bundles are
supposed to contain fibres coursing in both directions. Several of them have
already been described in company with the grey masses with which they are
concerned. They may be summarised as follows (see figs. 683, 701 and 702) : — ■
(1) Those of short course, the fibrse propriae, which associate contiguous gyri with each
other. These arise from the ceUs of a gyrus and loop around the bottoms of the sulci, continu-
ally receiving and losing fibres in the cortex they associate. The stripes of BaiUarger within
the cortical layer might be included among the short association bundles.
(2) The cingulum (girdle) lies in the gyrus cinguli and is shaped correspondingly. It
ASSOCIATION FIBRES
891
extends from the anterior perforated substance and the subcallosal gyrus around the genu of the
corpus callosum, then, under cover of the gyrus cinguU and around the splenium, and thence
downward and forward in the hippocampal gyrus to the uncus. It is chiefly an aggregation of
fibres of short course — fibres which associate neighbouring portions of the cortical substance
Fig. 701. — Photogeaph of "Torn Preparation " op Cerebral Hemisphere showing
SOME OP THE Association Fasciculi. (After R. B. Bean.)
Central sulcus
External capsule
Superior and inferior longitudinal fasciculi
and temporal pontile path
External capsule, posterior part
Fig. 702. — Schematic Representation op Certain op the Association Pathways of the
Cerebral Hemisphere.
Fibrse proprise
Superior longitudinal ,'j
fasciculus ^ ' ■,
Stria terminalis \ ^' ';
of thalamus \ ^— *w^ "y-^ "^ ,'' '; Cingulum
Uncinate fasciculus
Inferior longitudinal fasciculus
beneath which they course, and which, by continually overlapping each other, form the bundle.
(3) The uncinate fasciculus is a hook-shaped bundle which associates the uncus and anterior
portion of the temporal lobe with the olfactory bulb, parolfactory area and anterior perforated
substance and perhaps the frontal pole with the orbital gyri. Its shape is due to its having to
curve medialward around the stem of the lateral cerebral fissure.
892
THE NERVOUS SYSTEM
(4) The superior longitudinal fasciculus is the longest of the association paths, and asso-
ciates the frontal, occipital, and temporal lobes. From the frontal lobe it passes laterally in
the frontal and parietal operculum, transverse to the radiations of the corpus callosum and the
lower part of the corona radiata, and above the insula to the region of the posterior end of the
lateral fissure, and thence it curves downward and forward to the cortex of the temporal lobe.
Some of its fibres extend to the cortex of the temporal pole. The occipital portion consists
of a loose bundle given off from the region of the downward curve, which radiates thence to
the occipital cortex.
(5) The inferior longitudinal fasciculus associates the temporal and occipital lobes and
extends along the whole length of these lobes parallel with their tentorial surfaces. Posteriorly
it courses lateral to the lower part of the oceipito-thalamic radiation, from which it differs by
Fig. 703. — Diagrams Suggesting the General Motor, General and Special Sensory
AND THE Association Areas of the Convex and Mesial Surfaces of the Cerebral
Hemisphere.
Parietal
*' association
area
Temporo-occlpifal
association area
Frontal
-association
area
Temporo- occipital
association area
the fact that its fibres are less compactly arranged. It associates the lingual and fusiform gyri
and the cuneus with the temporal pole.
(6) The medial and lateral longitudinal striae of the upper surface of the corpus caUosum
may be considered among the association pathways, since most of their fibres associate the grey
substance of the hippocampal gyrus with the subcallosal gyrus and the anterior perforated
substance of the same hemisphere. Their significance as parts of the rhinencephalon has already
been given.
(7) Likewise the longitudinal fibres in the stria terminalis of the thalamus (taenia semi-
circularis) may be considered among the association pathways, since these connect the amyg-
daloid nucleus with the anterior perforated substance.
(8) The numerous fibres passing in both directions between the cerebral cortex and the
nuclei of the corpus striatum belong to the association system. These do not form a definite
bundle, but, instead, contribute appreciably to the corona radiata. However, a pathway
described as the occipito-frontal fasciculus probably consists largely of the more sagittally
running fibres of this nature. The existence of this fasciculus has been noted in degenerations
and in cases of arrested development of the corpus callosum. Its fibres are described as con-
tributing greatly to the tapetum, and as coursing beneath the corpus callosum immediately
FUNCTIONAL AREAS OF CORTEX 893
next to the ependyma of the lateral ventricle. As a mass, they appear in intimate connection
with the caudate nucleus, and are spread toward both the frontal and the occipital lobes (chiefly
the latter), in the mesial part of the corona radiata of those lobes. It is described as also con-
taining fibres in both directions associating the occipital with the temporal lobe. Vertical
association fibres pass through the caudate and lenticular nuclei between the cortex above and
that of the temporal lobe below.
(9) Since the olfactory bulb is a part of the hemisphere proper, the olfactory tract may be
considered an association pathway connecting the olfactory bulb with the parolfactory area,
the subcallosal gyrus, the anterior perforated substance, and the uncus. As already shown,
a portion of the fibres of the tract belongs to the commissural system.
THE FUNCTIONAL AREAS OF THE CEREBRAL CORTEX
The definitely known areas of specific function of the human cerebral cortex are relatively
small. They comprise but little more than a third of the area of the entire hemisphere. They
are — (1) the general sensory-motor or somaisthetic area, and (2) the areas for the organs of
special sense. They represent portions of the cortex in which terminate sensory or ascending
projection fibres bearing impulses from the given peripheral structures, and in which arise motor
or descending projection fibres bearing impulses in response.
Knowledge of the location of the areas has been obtained — (1) by the Flechsig method of
investigation, and to a considerable extent by Flechsig himself; (2) from clinico-pathological
observations, largely studies of the phenomena resulting from brain tumors and traumatic
lesions; (3) by experimental excitation of the cortex of monkeys and apes, the resulting phe-
nomena being correlated with the anatomical findings and compared with the observations upon
the human brain. The remaining larger and less known areas of the cortex are referred to as
'association centres' or areas of the 'higher psychic activities.'
In development, the sensory fibres to the specific areas acquire their medullary sheaths
first, before birth, and then the respective motor fibres from each become medullated. It ia
not till a month after birth that the association centres show medullation and therefore acquire
active functional connection with the specific areas.
In defining an area it is not claimed that all the fibres bearing a given type of impulse
terminate in that area, nor that all the motor fibres leading to the given reaction originate in
the area. It can only be said that of the fibres concerned in a given group of reactions, more
terminate and arise in the areas cited than in any other areas of the cortex. The corresponding
motor fibres arise both in the region of the termination of the sensory fibres (sensory area)
and also in a zone (motor area) either partially surrounding or bordering upon a part of the
region of termination.
The different areas are as follows: —
(1) The somaesthetic (sensory-motor) area, the area of general sensibility, and the area in
which arise the larger part of the cerebral motor or pyramidal fibres for the cortical control
of the general muscular system. As is to be expected, it is the largest of the specific areas. It
includes the anterior central gyrus, posterior central gyrus, the posterior ends of the superior,
middle, and inferior frontal gyri, the paracentral lobules, and the immediately adjacent part of
the gyrus cinguli. The ascending or sensory fibres are found to terminate most abundantly
in the part posterior to the central sulcus (Rolandi), the posterior central gyrus being the special
area of cutaneous sensibility, and the adjacent anterior ends of the horizontal parietal gyri have
been designated as the area of 'muscular sense.' Both these areas are carried over upon the
medial surface to involve the lower part of the paracentral lobule and a part of the gyrus cinguli.
The anterior central gyrus gives origin to relatively more motor fibres than the other portions of
the somffisthetic area. In distribution, the muscles furthest away from the cortex are innervated
from the most superior part of the area, the leg area being in the supero-mesial border of the
hemisphere, while that from the head is in the anterior and inferior part of the area (fig. 703).
The muscles of mastication and the laryngeal muscles are controlled from the fronto-parietal
operculum. Broca's convolution, the opercular portion and part of the triangular portion
of the inferior frontal gyrus, of the left hemisphere, constitutes the especial motor area of speech,
and Mills has extended this area to include the supero-anterior portion of the insula below.
The various authorities differ considerably as to the exact locations of many of the areas for
the cortical control of given sets of muscles. Further observations must be skillfully made
tor localisation of areas of the human cortex in detail and further correlations must be deter-
mined between the experiments upon the cortex of anthropoid apes and the functions of that
of man. The accompanying diagrams are compiled from several of the diagrams more usually
given and must be considered as only approximately correct.
(2) The visual area. — The especial sensory portion of this area is that immediately border-
ing upon either side of the posterior part of the calcarine fissure. The entire area, motor and
sensory overlapping each other, includes the whole of the cuneus. The motor visual area proper
is described as the more peripheral portion of the entire area. In addition, an area producing
eye movements is described as situated in the posterior end of the middle frontal gyrus.
(3) The auditory (cochlear) area comprises the middle third of the superior temporal gyrus
and the transverse temporal gyri of the temporal operculum. The motor portion of this area
hes in its inferior border. The fibres arising in the area course downward ia the temporal
pontile path to the motor nuclei of the medulla.
(4) The olfactory area consists of the olfactory trigone, the parolfactory area, the sub-
callosal gyrus, part of the anterior perforated substance, the hippocampal gyrus (especiaUj' the
uncus), and the callosal half of the gyrus cinguli. Its motor or efferent area lies chiefly in the
hippocampal g3T.'us, the fibres from which pass out from the telencephalon by way of the fornix
and cingulum.
894
THE NERVOUS SYSTEM
(5) The gustatory area is supposed to comprise the anterior portion of the fusiform gyrus
and the zone (motor portion) about the anterior extremity of the inferior temporal sulcus.
(6) The assocaition areas. — The relatively large areas allotted at present to the so-called
higher psychic activities are indicated in fig. 703. The great relative extent of these is one of
the characteristics of the human brain. They probably merely represent the portions of the
cortex of which httle is known, and may eventually be subdivided into more specific areas.
They are considered to be connected with the structures below by fewer projection fibres than
are the recognised areas named above, while, on the other hand, they are rich in association
fibres. By means of the latter they are in intimate connection with the specific areas and have
abundant means of correlating and exercising a controlhng influence upon the functions of these
areas. According to Flechsig, they consist of — (1) a parietal association area, comprising that
part of the parietal cortex between the somaesthetic area and the visual area; (2) an occipito-
temporal association area, including the unspecified portions of the temporal lobe and the ad-
joining portion of the occipital lobe not included in the visual area; (3) a frontal association
area, including all the frontal lobe anterior to the somesthetic and olfactory area. In the
folds of the inferior parietal lobule of the parietal association area such intellectual activities
as the optic discrimination of words, letters, numbers, and objects generally are supposed to
Fig. 704. — Convex Surface op left Cebebral Hemisphere with Diagrammatic Presenta-
tion OF the Areas Suggested as Concerned with Speech.
Area for coordination of muscles producing speech
f (Broca's convolution)
I Motor area for hand (graphic)
Motor area for mouth and larynx
^ Auditory word
images
Visual word
' images
Auditory area
Word understanding
take place, while the superior parietal lobule continued into the posterior part of the praecxmeus
is the general region for the perception of form and solidity of objects — the stereognostic centre.
The insula is suggested as the area in which auditory, olfactory and gustatory impulses
are associated with the motor areas beginning in the operculum dorso-laterally adjacent to it.
Observations of symptoms and the position of lesions accompanying them have made it
possible to arrive at some trustworthy conclusions regarding the cortical areas controlling
speech. Broca announced in 1861 that the inferior frontal gjTus of the left hemisphere was
peculiarly concerned with speech. This area was later confined to the posterior end or opercular
portion of this gyrus and the name "Broca's Convolution" was given it. It is now known that
Broca's convolution and the adjacent portion of the triangular part of the inferior frontal gyrus
as well comprise the motor area or emissive speech area — the area especially devoted to the
control of that coordinated action of the muscles concerned which makes possible articulate
speech. Patients in whom this area is impaired are unable to give utterance to words though
they may understand them both written and spoken, and though they may give utterance to
sound. This inability is known as motor aphasia. Results of observed lesions have further
shown that the area in which the auditory images of words are retained (word memories) com-
prises the posterior end of the superior temporal gyrus and the adjoining portion of the supra-
marginal gyrus. Injury to this area is accompanied by inability to recognise spoken words
although the patient hears them and may recognise and understand written words, a phe-
nomenon known as "word-deafness" or sensory aphasia. This area may be considered as
continuous with the superior portion of the posterior end of the middle temporal gyrus which
has been suggested as the area of "word-understanding," or "lalognosis." On the other
hand, the area in which visual images of words are retained is located as the angular gyrus.
Injury to this results in an inability to recognise printed or written words although the patient
CONDUCTION PATHS 895
may hear, understand and speak them. This is called "word-Uindness." This area is nearest
the special area of vision on the one hand and on the other hand, is continuous into the area to
which word-understanding is attributed. For purposes of writing, it must be associated with
the motor area for the muscles of the hand in the precentral gyrus.
While the motor area for speech is most functional in the left hemisphere, the remaining
areas concerned are probably equally developed in the two hemispheres.
III. GENERAL SUMMARY OF SOME OF THE PRINCIPAL
CONDUCTION PATHS OF THE NERVOUS SYSTEM
In the following summary the arabic numerals indicate paragraphs in which are mentioned
the nuclei or ganglia containing the cell-bodies of the neurones interposed in the chains; the
small letters indicate the different names given to the different levels of the pathways through
which their fibres run. For detailed descriptions of either nuclei or pathways see pages de-
scribing them. Only the more common neurone chains are followed here.
I. The Spino-cbrebhal and Cerebro-spinal Path
A. The ascending system of neurones, (fig. 706)
1. Spinal ganglion — neurone of first order.
(a) Terminal corpuscles and peripheral process of T-fibre.
(6) Dorsal or afferent root of spinal nerve.
(c) Ascending branch of bifurcation of dorsal root fibre in fasciculus gracihs, or
fasciculus cuneatus of spinal cord.
2. Nucleus of fasciculus gracilis or nucleus of fasciculus cuneatus in meduUa oblongata —
neurone of second order,
(a) Internal arcuate fibres.
(6) Decussation of lemniscus.
(c) Interolivary stratum of lemniscus of opposite side.
(d) Medial lemniscus.
3. Hypothalamic nucleus and lateral nucleus of thalamus — neurone of third order.
(a) Internal capsule, posterior segment of fronto-parietal portion.
(6) Corona radiata, fronto-parietal part.
(c) Posterior central gyrus of somsesthetic area of cerebral cortex.
B. Descending system of neurones (fig. 706).
1. Giant pyramidal cells of precentral g}TUS of somaesthetic area.
(o) Corona radiata, fronto-parietal part.
(6) Internal capsule, middle segments of fronto-parietal portion.
(c) Basis of the cerebral peduncle and the peduncle.
(d) Pyramid of medulla oblongata.
(el) Decussation of pyramids.
(/') Lateral cerebro-spinal fasciculus (crossed pyramidal tract),
(e^) Ventral cerebro-spinal fasciculus (direct or uncrossed pyramidal tract).
(P) Gradual decussation of latter in cervical and upper thoracic regions of spinal
cord.
2. Cells of ventral horn of spinal cord of opposite side,
(o) Ventral or efferent roots of spinal nerves.
(6) Peripheral nerve-trunks directly to skeletal muscles or indirectly to smooth
muscle or glands by way of sympathetic neurones.
II. Short 'Reflex' Paths of Spinal Cord
1. Spinal gangha.
(o) Terminal corpuscles and peripheral process of T-fibres.
(6) Dorsal root of spinal nerve.
(c) Collaterals and descending branches of bifurcation of dorsal root fibres in spinal cord
(d) Directly to ventral horn cells of same level of spinal cord.
(e) Or, more commonly, to same through intermediation of Golgi cell of type II.
(/) Or to neurones of fasciculi proprii to ventral horn cells of other levels of spinal cord.
2. Ventral horn cells of same (chiefly) and opposite side and thence by way of ventral roots
and peripheral nerve trunks directly to muscles.
3. Dorso-lateral group of ventral horn cells of same (chiefly) and opposite sides and
thence by ventral root fibres to cell-bodies in sympathetic gangha.
4. Sympathetic axones to smooth muscle or glands.
III. Cerebral Path for the Cranial Nerves, ExcLusrvE of Those of Special Sense
A. Ascending system of neurones.
1, Ganglia of origin of sensory components of vagus, glossopharyngeus, glosso-palatine
and trigeminus.
(a) Peripheral arborisations and afferent peripheral branches of T-fibres of same.
(6) Central branches of T-fibres of same (sensory nerve roots).
2. Nuclei of termination of central branches (bifurcated and imbifurcated) in meduUa
oblongata,
(a) Reticular formation, internal arcuate fibres and medial lemniscus of the opposite
side.
896
THE NERVOUS SYSTEM
3. Hypothalamic nucleus and lateral nucleus of thalamus.
(a) Internal capsule, posterior segment of fronto-parietal portion.
(6) Corona radiata, fronto-parietal part.
(c) Cerebral cortex — chiefly lower third of posterior central gyrus.
Fig. 705. — Scheme of Ascending or Spino-cerebeal Conduction Pathways.
-Fibrse propriEe
P3Tamidal fibre
Corona radiata
■Internal capsule
-Hypothalamic nucleus
.Nuclei of termination of
sensory cranial ]
Ganglia of sensory cranial nerves
Nucleus of spinal tract of trigeminus
.Nucleus of fasciculus
cuneatus
■Nucleus of fasciculus
gracilis
^N. Posterior root
' Spinal
ganglion
'Fasciculus cuneatus
•Fasciculus gracilis
B. Descending system of neurones.
1. Pyramidal cells of opercular region of soma^sthetic area.
(a) Corona radiata, fronto-parietal.
(b) Internal capsule, genu chiefly.
(c) Basis of cerebral peduncle and peduncle.
(d) Decussation in brain stem.
CONDUCTION PATHS
897
2. Nuclei of origin of motor cranial nerves and motor components of mixed cranial
nerves, of opposite side chiefly and thence by way of these nerves to the respective
muscles supplied.
Notes: (1) Most of the descending cortical fibres to the nucleus of origin of the trochlear
Fig. 706. — Scheme of Descending Ceeebeo-spinal Conduction Pathways.
Caoidate nucleus'
Internal capsule
Cerebral
peduncle
Trochlear nerv
Medulla oblongati
Ventral roots of
spinal nerves
Ventral white
commissure
nerve and that portion of the nucleus of the oculomotor which supplies the internal rectus
muscle apparently do not decussate but terminate in the nuclei of the same side.
(2) The efferent nucleus of the glosso-palatine (salivatory nucleus) and the dorsal efferent
nucleus of the vagus give rise to visceral efferent fibres, i.e., carry impulses destined for smooth
muscle and glands by way of sympathetic neurones. The same is true for the supero-median
part of the nucleus of the oculomotor.
898 THE NERVOUS SYSTEM
(3) The nuclei of termination of the cranial nerves, especially those of the vestibular and
trigeminus, send fibres also into the cerebellum.
IV. The Short 'Reflex' Paths of the Cranial Nehves
These consist of the central branches of their afferent or sensory fibres, bearing impulses to
the nuclei of origin of both their own motor components and to the nuclei of origin of other
Fig. 707. — Scheme of Principal Ascending Cerebellar Conduction Paths.
-*• Corona radiata
Thalamus
Lateral nucleus of
thalamus
- Internal capsule
Red nucleus
Decussation of brachia conjunctiva
Nucleus fastigii
Dentate nucleus
3 v^eicuciiuut
(displaced)
--._ Ganglia of afferent cranial nerves
--'' (vestibular chiefly)
— • Nucleus of funiculus cuneatus
' Nucleus of funiculus gracilis
> Spinal ganglia
motor nerves. Fibres to the more distant nuclei pass to them by way of the medial longi-
tudinal fasciculus. Instead of terminating in the motor nuclei directly, the sensory fibres are
usually interrupted by a third or intermediate neurone interposed in the chain. The vagus and
glosso-pharyngcus are connected by way of the solitary fasciculus and its nucleus with the
structures below their level of entrance, even with the ventral horn cells of the upper segments
of the cervical cord, and through these with the muscles of respiration.
CONDUCTION PATHS 899
V. Conduction Paths Involving the Cerebellum
A. Ascending cerebellar pathways.
1. Spinal ganglia.
(a) Dorsal roots of spinal nerves.
(6) Collaterals and descendiag branches of bifurcation of dorsal root fibres in spinal
cord, chiefly those conveying impulses of muscle-sense.
2x. Dorsal nucleus (Clarke's column).
(o) Dorsal spino-cerebellar fasciculus (direct cerebellar tract).
(6) Restiform body (inferior cerebellar peduncle) —
(c) Joined in meduUa by external arcuate fibres (crossed and uncrossed fibres arising
in nuclei of funiculus gracilis and cuneatus) ;
(d) Joined in medulla by fibres arising in nuclei of termination of afferent vagus,
glosso-pharyngeal, vestibular, and trigeminal nerves;
(e) Joined by fibres both to and from (ascending and descending) the inferior olivary
nucleus of the same and opposite sides (cerebello-olivary fibres).
2y. Nerve-cells in base of ventral horn of same and opposite side.
(a) Superficial antero-lateral spino-cerebellar fasciculus (Gowers' tract), ascending
through spinal cord and reticular formation' of medulla and pons.
(6) Anterior meduUary velum and brachium conjunctivum to cerebellar cortex
(vermis).
3. Cerebellar cortex (vermis), dentate nucleus, nucleus fastigii, nucleus emboliformis,
and nucleus globosus.
(a) White substance (corpus medullars) of cerebellum, associating various regions
of its cortex and its nuclei with each other.
(6) Brachium conjunctivum (superior cerebellar peduncle) arising chiefly from
dentate nucleus,
(c) Decussation of brachium conjunctivum.
4. Red nucleus and ventral portion of lateral nucleus of thalamus. Most fibres of the
brachium conjunctivum terminate in the red nucleus; many merely give off
collaterals to it in passing to their termination in the thalamus. Most of the
ascending fibres arising in the red nucleus also terminate in the ventral part
of the thalamus; some ascend to the cerebral cortex direct.
(a) Internal capsule, middle third, and fronto-parietal part of corona radiata.
(6) Somsesthetic area of cerebral cortex and cortex of frontal lobe anterior to it.
(c) Inferior peduncle of thalamus to cortex of temporal lobe.
B. Descending cerebrocerebellar paths.
1. Pyramdial cells of somsesthetic area send fibres through corona radiata, internal
capsule, and cerebral peduncle to nuclei of pons and arcuate nucleus of same and
opposite side.
2. Gelt of cortex of posterior part of frontal lobe give fibres to form frontal pontile
path through frontal parts of corona radiata and internal capsule and through medial
part of cerebral peduncle to nuclei of pons of opposite side.
3. Cells of cortex of temporal lobe (superior and middle gyri) give fibres to form temporal
pontile path which passes under the lenticular nucleus into anterior segment of
occipital portion of internal capsule and lateral part of cerebral peduncle to nuclei of
pons of opposite side. This path is joined in the internal capsule by a small occipito-
pontile path.
4. Cells of nuclei of pons send fibres by way of brachium pontis (middle cerebeOar
peduncle) to cortex of cerebellar hemisphere, of side opposite to that of the origin
of the cei-ebral fibres making synapses with the cells of the pons.
C. Descending cerebellospinal paths.
1. From cells of nucleus fastigii of same and opposite sides and probably from other nuclei
of cerebellum arise fibres which terminate in the nuclei of termination of the vestib-
ular nerve and these send fibres into the intermediate and anterior marginal fasciculi
of spinal cord (fig. 619), and thence to the cells of the anterior horn.
2. Probably connected with the cerebellum is the pathway arising in the red nucleus
of the opposite side and descending in the rubro-spinal tract of the lateral funiculus
of the spinal cord (fig. 619). The rubro-spinal tract decussates in the ventral portion
of the tegmentum of the mesencephalon and is said to pass through the medulla oblon-
gata in the medial longitudinal fasciculus. It must be noted here that some fibres
arising in the cortex of the frontal lobe terminate in the red nucleus.
VI. The Vestibular Conduction Paths (Equilibration)
1. Vestibular ganglion gives origin to the peripheral utricular and three ampullar
branches and to the combined and centrally directed vestibular nerve.
2. Lateral vestibular nucleus (Deiters'), medial nucleus, superior nucleus, and nucleus
of descending or spinal root (nuclei of termination) give origin to fibres as follows: —
(a) From lateral and superior nuclei to nucleus fastigii of opposite side and to
cortex of vermis and to dentate nucleus (cerebellar connection).
(6) From medial and superior nuclei to nuclei of origin of eye-muscle nerves of
same and opposite sides, by way of medial longitudinal fascicuh.
(c) From lateral nucleus and nucleus of descending root through reticular formation
into_lateral and ventral vestibulo-spinal tracts of spinal cord.
900
THE NERVOUS SYSTEM
(d) The nuclei receive fibres from the grey substance of the vermis. It is probable
that all the nuclei of termination give off fibres bearing ascending impulses which
ultimately reach the somresthetic area, but the course pursued and neurones
involved in such a chain are uncertain.
VII. The Auditory Conduction Path (Cochlear Nerve)
1. Spiral ganglion of the cochlea gives origin to short peripheral fibres to organ of
Corti, and to the centrally directed cochlear nerve.
2. Dorsal and ventral nuclei of the cochlear nerve (nuclei of termination).
(o) Striae medullares arise from dorsal nucleus and pass around outer side of resti-
form body (acoustic tubercle), then medianward under ependyma of floor
of fourth ventricle to mid-line, then ventralward into tegmentum, where
they decussate and join trapezoid body and lateral lemniscus of opposite side.
Fig. 708. — -Diagram Showing Some op the Connections op the Vbstibxjlar and Cochlear
Nerves.
Medial geniculate body
Nucleus of lateral lemmscus
Medial longitudinal fasciculus
Lateral lemniscus.
Peduncle of superior olive.
^Inferior quadngeminate body
Nucleus of trochlear nerve
Nucleus fastigii
Nucleus emboliformis
Dentate nucleus
^ Lateral nucleus of
"■' vestibular nerve
_^Restiform body
Dorsal nucleus of
^'^ cochlear nerve
^^Ventral nucleus of
'' cochlear nerve
.Cochlear nerve
Superior olivary nucleus
Trapezoid body
(6) Fibres arising in ventral nucleus pass ventraDy medianward and some termi-
nate in the superior ohvary nucleus of same side; others pass by way of trapezoid
body and lateral lemniscus to terminate in superior olivary nucleus, nucleus
of lateral lemniscus, medial geniculate body and nucleus of inferior quadri-
geminate body of the opposite side.
3. Nuclei of superior olives of both sides and nucleus of lateral lemniscus send fibres
by way of lateral lemniscus to inferior quadrigeminate body and through inferior
brachium to medial geniculate body, and some may pass uninterrupted to the
cortex of the temporal lobe.
4. Fibres from medial geniculate body and probably from nucleus of inferior quadri-
geminate body pass into internal capsule and through temporal part of corona radiata
to middle third of superior temporal gyrus and adjacent portions (auditory area).
6. From strife medullares and from superior ohvary nucleus (peduncle of superior olive)
arise fibres which terminate in nucleus of abducens or pass by way of the medial
longitudinal fasciculus to other motor nuclei of cranial nerves. It is probable that
fibres from the auditory area of the cerebral cortex are also distributed to nuclei of
the cranial nerves.
VIII. Conduction Paths op the Optic Apparatus
. Oplic impulses.
1. 'Bipolar' cells of retina with short (peripheral) processes to layer of rods and cones
(neuro-epithehum) and short centrally directed processes to ganglion-cell layer
of retina (nucleus of termination).
CONDUCTION PATHS
901
2. Ganglion-cells of retina give origin to —
(o) Optic stratum of retina.
(6) Optic nerve.
(c) Optic chiasma; fibres from nasal side of retina cross in chiasma to opposite side;
fibres from lateral side of retina continue on same side in—
(d) Optic tract to —
3. Pulvinar of thalamus, lateral geniculate body, and nucleus of superior quadrigeminate
body.
(o) Fibres from nucleus of superior quadrigeminate body pass ventrally, to nuclei of
origin of oculomotor and trochlear nerves and to medial longitudinal fasciculus
of same and opposite sides, and from it are distributed to nucleus of origin, of
abducens.
(6) Fibres from lateral geniculate body and pulvinar pass through occipitafportion
of internal capsule and oocipito- thalamic radiation (optic radiation) to cortex of
occipital lobe (visual area).
Fig. 709. — Diagram of Principal Pathways of Optic Apparatus. (After Cunningham,)
CORP. GEN. M
4. Cells of visual area of cortex send fibres through occipito-thalamic radiation and
occipital portion of internal capsule to nucleus of superior quadrigeminate body
(oocipito-mesencephalic fasciculus), and thence, probably interrupted by cells of
this nucleus, to nuclei of eye-muscle nerves.
5. Cells of nucleus of superior quadrigeminate body and pulvinar send fibres by way of
medial longitudinal iasciculus into lateral and ventral funicuU of spinal cord (see
fig. 619), chiefly of the opposite side. Fibres from the quadrigeminate body cross
mid-line chiefly in decussation of 'optic-acoustic reflex path' (fig. 662).
6. The smaller cells of the supero-mesial group of the nucleus of the oculomotor nerve
(nucleus of Edinger and Westphal) send axones, by way of the trunk of the nerve
and the short root of the ciliary ganglion, which terminate about cells in —
7. The ciliary gangUon, whose cells send axones to enter the ocular bulb and termi-
nate upon the smooth muscle fibres of the cihary body and iris.
B. Skin-pupillary reflexes.
1. Peripheral processes of spinal gangUon cells terminating in the skin and central
processes of same entering by way of dorsal roots of cervical nerves to bifurcate in
spinal cord and give terminal twigs about — •
2. Cells of the dorso-lateral group of the ventral horn of the same and opposite sides.
These cells send (visceral efferent) axones to terminate about cells in —
902
THE NERVOUS SYSTEM
3. The superior cervical sympathetic ganglion, which cells send axones chiefly by way
of the carotid plexus and the sympathetic roots of the ciUary ganglion to terminat
about cells in —
4. The ciliary ganglion. Such cells send axones into the ocular bulb to terminate in
the ciliary body and radial muscle fibres of the iris, producing dilation of the pupil.
C. Auditory-eye reflexes.
1. Cells of the nuclei of termination of the cochlear nerve and superior olive send fibres
by way of the medial longitudinal fasciculus (some to this by way of the peduncle
of the superior olive) to the nuclei of origin of the eye-moving nerves.
2. The same nuclei of the cochlear nerve send axones by way of the lateral lemniscus
to terminate in the superior quadrigeminate body and thence may be sent impulses
which are distributed to the nuclei of the eye-moving nerves.
IX. Principal Conduction Paths op Olfactoky Apparatus
1. Bipolar cells of olfactory region of nasal epithelium send short (peripheral) processes
toward surface of nasal cavity and centrally directed processes, the olfactory nerve,
through lamina cribrosa of ethmoid bone into olfactory bulb (glomerular layer).
2. 'Mitral cells' of olfactory bulb give fibres which form —
(a) The olfactory tract which divides into — ■
Fig. 710.-
-Diagram SHcmNG Some of the Principal Tracts and Synapses op the Olpac-
TORY Apparatus.
Anterior
Subcallosal gyrus
Parolfactory area
Gyrus rectus ^
Olfactory tract
Olfactory bulb
Perforating fibres
\ Medullary stria of thalamus
^ Longitudinal striae
on corpus callosum
Hippocampal com-
(Lyre)
~* Habenular nucleus
_ . Habenulo-pedun-
cular tract (fasci-
culus retroflexus)
Mammillo-mesen-
o cephalic fasciculus
■ ^x Penduculo-tegmental
tract
Interpeduncular nucleus
Fimbria hippocampi
Uary body
Anterior perforated substance
Olfactory epithelium
(6) Medial olfactory stria through which fibres pass — (1) into parolfactory area (Broca's
area); (2) into subcallosal gyrus; and (3) by way of anterior cerebral commissure
to olfactory bulb and uncus of hippocampal gyrus of opposite side.
(c) Intermediate olfactory stria to anterior perforated substance.
(d) Lateral olfactory stria, which terminates to some extent in anterior perforated
substance, but chiefly in uncus, hippocampal gyrus, and gyrus cinguU (olfactory
area) of same side.
3. Cells of uncus and hippocampal gyrus give fibres which form —
(a) The cingulum (in part), by which they are associated with the cortex of the gyrus
cinguli and other areas of the cerebral cortex.
(b) The hippocampal commissure (in part), by which they are connected with the grey
substance of the opposite side.
(c) The fornix, which, interrupted in part in the nuclei of the corpus mammUlare,
conveys impulses — (1) to the anterior nucleus of thalamus of the same (chiefly)
and opposite sides (mammillo-thalamic fasciculus), and (2) into the mesencephalon
and substantia nigra (mammillo-mesencephalic fasciculus), and by way of this
tract probably to the nuclei of the mesencephalon and medulla oblongata.
4. The parolfactory area, anterior perforated substance, anterior portion of thalamus and
fornix give fibres which form the medullary stria of the thalamus and which terminate
in the habenular nucleus.
5. Habenular nucleus sends fibres in fasciculus retroflexus to terminate in interpeduncular
nucleus.
6. Interpeduncular nucleus sends fibres to nuclei of mesencephalon and probably to
structures below it.
RELATIONS OF BRAIN AND CRANIUM
903
The Relations of the Brain to the Walls of the Ceanial Cavity
The precise methods by which the exact positions of the most important fissures, sulci,
gyri, and areas can be ascertained and mapped out on the surface of the head in the living subject
are fully described in Section XIII. Here, only a very general survey of the relations of the
brain to the cranial bones is given and from a purely anatomical standpoint.
The parts of the brain which lie in closest relation with the walls of the cranial cavity are
the olfactory bulb and tract, the basal and lateral surfaces of the cerebral hemispheres, the
inferior surfaces of the lateral lobes of the cerebellum, the ventral surfaces of the medulla and
pons, and the hypophysis.
Certain of these portions of the brain lie in relation with the basi-cranial axis, that is, with
the basi-oGcipital, the basi-sphenoid, and the ethmoid bones, while others are associated with the
sides and vault of the cranial cavity. Considering the former portions first, the ventral surface
of the medulla oblongata, which is formed by the pyramids, lies upon the upper surface of
the basi-occipital bone. More superiorly the ventral surface of the pons rests upon the basi-
Fig. 711. — Drawing of a Cast of the Head op an Adttlt Male.
(Prepared by Professor CuiininKliam to illustrate cranio-cerebral topography.)
Position of
frontal
eminence
Transverse
(lateral)
sinus
sphenoid, from which it is partly separated by the basilar artery and the pair of abducens
nerves. In front of the dorsum sella3 the hypophysis (pituitary body) is lodged in the hypophyseal
fossa. Still further forward the olfactory tracts he in grooves on the upper surface of the pre-
sphenoid section of the sphenoid bone; and in front of the sphenoid the olfactory bulbs rest upon
the cribriform plates of the ethmoid.
Posterior and lateral to the posterior part of the foramen magnum the lateral lobes of the
cerebellum are in relation with the cranial wall, resting upon the lower parts of the supra-
occipital and the posterior parts of the ex-occipital portions of the occipital bone, while anteriorly
each lobe is in relation with the inner surface of the mastoid process and the posterior surface
of the petrous portion of the temporal bone. The area of the skull wall which is in close re-
lationship with the cerebellar hemispheres may be indicated, on the external surface of the skull,
by a line which commences at the inferior part of the external occipital protuberance and thence
runs upward and lateralward. It crosses the superior nuchal line a httle beyond its centre, and,
continuing in the same direction, crosses the inferior part of the lambdoid suture and reaches a
Eoint directly above the asterion (the meeting-point of the occipital, temporal, and parietal
ones) ; thence it descends, just in front of the occipito-mastoid suture, to the tip of the mastoid
process, and there turns medialward to its termination at the margin of the foramen magnum,
immediately behind the posterior end of the oociptal condyle.
The basal surface of each cerebral hemisphere may be said to consist of two parts, an anterior
and a posterior, separated by the stem of the lateral cerebral fissure. The anterior part, formed
904
THE NERVOUS SYSTEM
by the orbital surface of the frontal lobe, rests upon the upper surfaces of the orbital plate of
the frontal bone and the lesser wing of the sphenoid. It is, therefore, in close relation with the
upper wall of the orbital cavity. The posterior part, behind the stem of the lateral fissure,
begins with the anterior portion of the temporal lobe, including its pole. The pole itself
projects against the orbital plate of the great wing of the sphenoid bone, and it is in relationship
with the posterior part of the lateral wall of the orbit. The basal surface of the hemisphere,
behind the pole of the temporal lobe is in contact with the upper surfaces of the great wing of
the sphenoid and the petrous part of the temporal bone.
The convex surfaces of the cerebral hemispheres have the most extensive relationships with
the cranial wall, and it is more especially to these surfaces that the surgeon turns his attention.
The general area in which the convex surface of each cerebral hemisphere is in relation with the
skuU bones is readily indicated by a series of lines which correspond with the positions of its
superciliary, infero-lateral, and supero-mesial borders.
The line marking the superciliary margin of the hemisphere commences at the nasion (the
mid-point of the fronto-nasal suture) ; it passes lateralward above the superciliary ridge, crosses
the temporal ridge, then, turning posteriorly in the temporal fossa, it reaches the parieto-
sphenoidal suture, and continues backward along it to its posterior extremity.
Fig. 712. — Drawing op a Cast of the Head of a Newly Born Male Infant.
(Prepared by Professor Cunningham to illustrate cranio-cerebral topography.)
Interparietal
sulcus
External part of
parieto-occip-
ital fissure
Position of
frontal eminence
Lateral fissure
The line marking out the infero-lateral border commences at the posterior end of the parieto-
sphenoidal suture, whence it passes downward, in front of the spheno-squamous suture, to the
infra-temporal ci-est (pterygoid ridge) ; there it turns posteriorly and, running parallel with and
mesial to the zygomatic arch, it crosses the root of the zygoma, and, ascending slightly, it passes
above the external auditory meatus. Continuing backward with an incliriation upward it
reaches a point immediately above the asterion; thence it descends, and, crossing the inferior
part of the lambdoid suture and the superior nuchal line, it passes medialward to the inferior
part of the external occipital protuberance.
The supero-mesial border of the hemisphere is defined by a line which runs from the nasion
to the inion. This line should be drawn about 5 mm. lateral to the sagittal suture, because
the mesial area is occupied by the superior sagittal sinus, and it should be further away from
the middle line on the right than on the left side, because the sinus tends to he more to the
right side.
The area of the skull wall enclosed by the three lines which mark the positions of the super-
ciliary, infero-lateral, and the supero-mesial borders of the cerebral hemisphere is formed by the
vertical plate of the frontal bone, the parietal bone, the great wing of the sphenoid, the squamous
part of the temporal, and the upper section of the supra-occipital segment of the occipital bone.
It covers the outer surfaces of the frontal, parietal, temporal, and occipital lobes of the cerebrum
and the fissures and sulci which bound and mark them.
In every consideration of the topographical relations of the cerebral g3Ti to the walls of the
cranial cavity it must be borne in mind that the conditions are not constant, and that, therefore,
the relations are variable. The three main factors upon which this variability depends are age,
sex, and the shape of the skull. As examples of the variations which occur it may be mentioned
that the lateral cerebral fissure is relatively higher in the child than in the adult (compare
figs. 711 and 712). The supero-mesial end of the central sulcus is further away from the coronal
suture in the female and in the child than in the adult male, and in dolichocephalic than in
BLOOD-SUPPLY OF BRAIN 905
braohycephalic heads. The angle formed between the Hne of the central fissure and the mid-
sagittal plane, which averages about 68° in the adult, is more acute in dolichocephalic heads,
and the external part of the parieto-occipital fissure is further forward in the child, and possibly
in the female, than it is in the adult male.
The position of the posterior horizontal limb of the lateral fissure varies even in the adult.
Its posterior part is always under cover of the parietal bone, and it terminates either in front of
or inferior to the parietal eminence, but the anterior part may be above, parallel with, or inferior
to the squamo-parietal suture. In the adult the anterior part of the fissure runs upward and
backward from the posterior end of the spheno-parietal suture along the anterior part of the
squamo-parietal suture to its highest point; thence it continues in the same direction beneath the
parietal bone toward the lambda, terminating either in front of or below the parietal eminence.
In the child, however, the fissure is considerably above the hne of the squamo-parietal suture
(fig. 712), which it gradually approaches, attaining its adult position about the ninth year.
This change of position, which occurs during the first nine years, is due partly to the ascent of
the sutural hne and partly to the descent of the fissure on the surface of the brain.
The frontal bone always covers the superior, middle, and inferior frontal gyri, except their
posterior extremities, which are beneath the parietal bone (fig. 711). The ascending limb (ramus
anterior ascendens) of the lateral fissure, which cuts into the posterior part of the inferior frontal
gyrus, runs parallel with and under cover of the lower part of the coronal suture, or immediately
in front of it, and the anterior horizontal hmb is parallel with and beneath the upper margin of
the great wing of the sphenoid.
The parietal bone is in relation with the convex surfaces of four lobes of the brain. Speaking
very generally, it may be said that the anterior third covers the posterior part of the frontal
lobe, including the anterior central gyrus, and the posterior ends of the superior, middle, and in-
ferior frontal gyri and the precentral sulcus. The posterior two-thirds of the bone are superficial
to the perietal lobe, the posterior part of the temporal lobe, the anterior part of the occipital lobe,
the posterior part of the horizontal limb of the lateral fissure, the superior and inferior parts of
the post-central sulcus, the interparietal sulcus, the posterior sections of the superior and middle
temporal sulci, and the external part of the parieto-occipital fissure. The central sulcus is
beneath the parietal bone at the junction of its middle and anterior thirds (fig. 711).
In the adult, the upper end of the central sulcus is situated at about 55 per cent, of the whole
length of the naso-inionic hne posterior to the nasion. It is about 4 or 5 cm. from the coronal
suture. The inferior end of the sulcus, which extends to near the posterior horizontal limb
of the lateral fissure, lies beneath the point of intersection of the auriculo-bregmatic line with
a hne drawn from the stephanion (the point where the temporal ridge cuts the coronal suture)
to the asterion. This point is about 46 per cent, of the horizontal arc measured from the
glabella to the inion.
The superior end of the parieto-occipital fissure usually lies about 6 mm. in front of the
lambda, and the course of the fissure may be indicated by a line drawn from 5 mm. in front of
the lambda to a point immediately above the asterion, and, as the latter point corresponds with
the pre-occipital notch on the infero-lateral border of the hemisphere, the line in question will
indicate the adjacent margins of the parietal, temporal, and occipital lobes.
The occipital bone is in close relation with the cerebellum, as already pointed out, but it
also covers the posterior part of the lateral surface of the occipital lobe of the cerebral hemisphere.
The great wing of the sphenoid covers the outer surface of the pole of the temporal lobe, and
the squamous part of the temporal bone covers the anterior parts of the superior, middle, and
inferior temporal gyri and the sulci which separate them.
The Blood Supply of the Encephalon
The double origin of the continuous arterial system of the brain given by the confluence of
the two vertebral arteries and the two internal carotid arteries, together with the description
of the general distribution of the different cerebral, mesencephalic, and cerebellar arteries into
which the system is divided, and the origin and course of the corresponding veins, are fuUy dealt
with in Section V. Here attention may be called briefly to the abundant and systematic
internal distribution of the terminal branches of the system and their intimate arrangement for
the actual nourishment of the nervous tissues within.
The general plan of the blood supply for the entire encephalon may be summarised as fol-
lows:— (1) At their origin the different arteries are so connected, directly or indirectly, on the
base of the encephalon, that the blood approaching the brain by way of the vertebral and
internal carotid arteries is practically a common supply for all the arteries of the encephalon,
and a given part of it may possibly pass mto any one of them. (2) In the pia mater of each
gross division of the encephalon the different arteries again become coimected with each
other in a superficial, freely anastomosing plexus, contmuous thi'oughout. (3) From this
plexus of the surface, naturally composed in part of the trunks of the different arteries
themselves, arise branches which enter directly into the nervous substance and which break
up into twigs that are terminal; i. e., twigs that do not anastomose with each other. (4) The
arterial capillary system arising from the terminal twigs passes over into venous capillaries
which converge to form corresponding venous twigs which in their turn pass to the sm-face
and join in forming a peripheral, anastomosing venous plexus superimposed upon the similar
arterial plexus. (5) From this venous plexus arise the different veins of the encephalon which
may or may not accompany the arteries for a short distance, and which finaUy empty into the
sinuses in the cranial dura mater. These, likewise confluent, empty into the internal jugular
veins. The chorioid plexuses of the ventricles of the brain are modifications of the general
anastomosing peripheral plexuses. The chorioid plexuses of the lateral and third ventricles
are derived largely from branches of the chorioid arteries, which arises separately from the
internal carotid artery.
906
THE NERVOUS SYSTEM
The blood supply of the cerebrum may best be taken as an illustration of the general plan
of the blood-vascular system of the encephalon. The terminal or internal branches of the
surface plexus, derived from the posterior, middle, and anterior cerebral arteries, are arranged
into two groups, a central or ganglionic and a cortical group. The central branches themselves
form four groups in each hemisphere: —
(1) The antero-mesial group consists of terminal branches from the plexus of the domain
of the anterior cerebral artery, which pass through the medial part of the anterior perforated
substance and supply the head of the caudate nucleus, the septum peUucidum, the columns
of the fornix, and the lamina terminaUs.
(2) The antero-lateral group consists of terminal branches from the domain of the middle
cerebral artery. These pierce the anterior perforated substance in two sub-groups — (a) the
internal and (6) the external striate arteries (fig. 713). The internal striate arteries pass
thi'ough the segments of the globus paUidus of the lenticular nucleus and through the internal
capsule, to both of which they give branches, and they terminate in the caudate nucleus and
thalamus. The external striate arteries are larger and more numerous. They pass upward
between the external capsule and the putameu, and then through or around the upper part
of the putamen into the internal capsule, where they form two groups, the lenticulo-lhalamic
and the lenticulo-caudate groups. The former terminate in the thalamus and the latter in the
caudate nucleus. On account of its larger size at its origin and its direct linear continuation
with the internal carotid, emboU {thrombi) pass more frequently into the middle cerebral artery
Fig. 713. — Diagram Showing the Manner of Distribution of the Cortical and Central
Branches of the Cerebral Arteries.
Cortical arteries.
External striate arteries-
Middle cerebral artery
Caudate nucleus
Thalamus
Tuber cinereum
Internal striate arteries
than into the anterior cerebral artery. One of the lenticulo-caudate arteries which is larger
and longer than the others and which is a direct branch from the middle cerebral artery has been
called the 'artery of cerebral hemorrhage' (Charcot), on account of the greater frequency
with which it is ruptured.
(3) The postero-medial central arteries are terminal branches of the posterior cerebral
artery. They also enter the anterior perforated substance, but supply the floor of the third
ventricle, the posterior part of the thalamus, and the hypothalamic region.
(4) The postero-lateral group are also terminal branches of the posterior cerebral artery.
They supply the posterior part of the internal capsule, the pulvinar of the thalamus, the gen-
iculate bodies, the corpora quadrigemina and their brachia, the epiphysis, and the cerebral
pedunces.
The cortical group of the cerebral arteries arise from the anastomosing plexus in the pia
mater of the cortical surfaces of the hemisphere. They pass into the cortical substance both
from the summits of the gyri and from the walls of the sulci. They consist of short, medium,
and long branches, and pass at right angles into the gyri. The short branches terminate in the
cortical substance; the medium branches supply the more adjacent white substance, and the
longer branches pass more deeply into the general medullary centre of the hemisphere.
All of both the central or ganglionic and the cortical arteries are terminal in the sense that
they do not anastomose in the substance of the cerebrum.
The blood-vascular system of the other divisions of the encephalon is in accordance with
the same general plan of that of the cerebrum. Slight individual modifications of the general
plan are to be expected.
BLOOD-VESSELS OF CEREBELLUM
907
The blood-vessels of the mesencephalon, in addition to the supply derived from the postero-
lateral group of central arteries, include the vessels of the quadrigeminate bodies and those of the
cerebral peduncles. The arteries of the quadrigeminate bodies are usually six in number,
three for each side — the superior, middle, and inferior quadrigeminate arteries. The superior
and middle are branches of the posterior cerebral arteries, and the inferior are branches of the
superior cerebellar arteries. The superior supply the superior quadrigeminate bodies and the
epiphysis; the middle supply both the superior and inferior quadrigeminate bodies, and the
inferior the inferior quadrigeminate bodies. They all anastomose in the pia on the surface of the
stratum zouale, forming a fine-meshed plexus, and from this superficial plexus the terminal
branches pass into the substance of the bodies. The veins terminate in the vein of Galen (v.
cerebri magna.)
The arteries of the cerebral peduncles form two groups, mesial and lateral. The mesial
peduncular arteries are branches of the basilar and the posterior cerebral arteries. They pass
to the medial sides of the pendunoles and supply the superior and medial part of the tegmentum.
The vessels of this group which accompany the fibres of the oculomotor nerves are known as the
radicular arteries; they supply the root-fibres and the nuclei of the nerves, which receive no
other branches. The lateral peduncular arteries are branches of the posterior cerebral and
Fig. 714.-
-Showing the Capillary Supplt op the Cerebellar Cortex.
"Journal of Comparative Neurology," Vol. IX.)
(After Aby,
Capillaries
of molecu-
lar layer
Line of the
Purkinje
cells
Recurrent
capillaries
to granular
layer
Arteriole
through
cortex to
medulla
Recurrent
capillaries
to granular
layer
Line of the
Purkinje
cells
Arteriole
passing
through
cortex to
medulla
Recurrent
capillary to
granular
layer
Recurrent
capillaries
to molecu-
lar layer
Junction of
cortex and
meduUa
Capillaries
of molecu-
lar layer
Junction of
cortex and
medulla
Arteriole
passing
through
cortex to
medulla
superior cerebellar arteries. They supply the lateral portions of the peduncles and the lateral
part of the tegmentum. The veins of the mid-brain terminate in the basilar veins and the vein
of Galen.
The blood-vessels of the cerebellum. — Six arteries supply the cerebellum; two, the
posterior inferior cerebellar, are derived from the vertebral arteries, and the remaining four,
two anterior inferior and two superior cerebellar, from the basilar artery. The course and
general distribution of the arteries are described m Section V, but here it must be noted that the
branches of these six vessels form a rich network in the pia mater on the surfaces of the cerebellar
lobes, and that extensions of the plexus pass with the folds of the pia mater into the sulci and
fissures. From the superficial plexus terminal branches pass mto the interior of the cerebellum
and their collaterals form capillary plexuses in the white and grey substance. The extensions
of the surface plexus are of three lengths: — (1) a longer set, which pass through the cortex of the
cerebellum and supply the white substance of the corpus meduUare; (2) a set of shorter arterioles
which pass through the molecular layer of the cortex and break up in its granular layer; (3) the
shortest set pass into the cortex and immediately break up in its molecular layer. The meshes
of the capillary plexuses in the grey susbtance are ovoidal and their axes run radially. The
meshes of the plexuses in the white substance are parallel with the nerve-fibres. In addition to
the vessels mentioned, a distinct branch is distributed to each dentate nucleus. This springs
either from the superior cerebellar or from the anterior inferior cerebellar artery of the corre-
sponding side.
908 THE NERVOUS SYSTEM
The efferent veins of the cerebellum do not accompany the arteries; they spring from a
plexus in the pia mater which receives tributaries from the interior, and they form three groups
on each cerebellar surface, the vermian veins and the lateral veins. The superior vermian vein
runs forward on the superior surface of the vermis and terminates in the vein of Galen. The
inferior vermian vein runs posteriorly and ends in one of the transverse sinuses. The superior
lateral veins open into the superior petrosal or transverse sinuses, and the inferior lateral veins
into the inferior petrosal and transverse sinuses. The vein from the dentate nucleus usuaDy
joins the inferior lateral veins.
The blood-vessels of the pons. — The arteries to the pons are branches of the basilar artery,
and of its anterior inferior and superior cerebellar branches. The plexus in the pia mater
is comparatively unimportant, and the branches which enter the substance of the pons form
two main groups, the central and the peripheral. The central arteries spring directly from the
basilar. They pass backward along the raphe, giving branches to the adjacent parts, and they
terminate in the nuclei of the pons and those in the floor of the fourth ventricle. The peripheral
arteries are radicular and intermediate. The radicular branches spring from the peripheral
plexus and from the anterior inferior cerebellar arteries; they accompany the roots of the
trigeminus, abducens, facial, vestibular, and cochlear nerves, supply their fibres and the adjacent
parts, and they end in the grey nuclei with which the nerve-fibres are connected. The inter-
mediate arteries enter the surfaces of the pons irregularly and break up into capillaries in its
substance. The veins form a plexus on the surface. The dorsal and lateral part of this plexu-
is drained into the basilar vein on each side, and the inferior part is connected by efferent
channels with the inferior petrosal sinus and the cerebellar veins.
The blood-vessels of the medulla oblongata. — The arteries of the medulla are derived
directly from the vertebral arteries, from their anterior and posterior spinal and posterior inferior
cerebellar branches, and from the basilar artery. The branches of these vessels form a plexus in
the pia mater from which, and from the arteries themselves, three main groups of vessels pass
into the medulla — the chorioidal, the central, and the peripheral. The chorioidal arteries are
derived chiefly from the posterior inferior cerebellar arteries. They supply the chorioid plexus
of the fourth ventricle. The anterior central arteries rise from the anterior spinal artery, from
the basilar artery, and from the peripheral plexus; they pass caudalward along the raphe,
supplying the adjacent parts of the ventral funicuh and the olivary bodies, and they break up
into fine terminals in the grey substance of the floor of the fourth ventricle around the nuclei
of the cranial nerves. The posterior central arteries spring from the posterior spinal arteries;
they pass down the median septum of the inferior part of the medulla and supply the adjacent
nervous substance. The peripheral arteries, like those of the spinal cord, are separable into
radicular and intermediate groups. The radicular arteries pass from the anterior and posterior
spinal branches and from the trunks of the vertebral arteries and accompany the fibres of the
last six cranial nerves into the substance of the medulla. They supply the nerve-roots and
adjacent white substance and they terminate in capillaries in the grey substance of the lateral
part of the floor of the ventricle. The intermediate peripheral arteries spring from the arteries
previously named and from the peripheral plexus, and they pass directly into the funiculi of
the meduUa, where they terminate in a capillary plexus which supplies the white substance and
the grey nuclei; some of these arteries, more especially those derived from the posterior inferior
cerebellar and the posterior spinal arteries, extend inward to the lateral part of the floor of the
fourth ventricle.
The veins which issue from the medulla form a peripheral plexus in the pia mater in which
there are two main longitudinal channels, an anterior median and a posterior median vein.
The former communicates posteriorly with the anterior median vein of the cord, and anteriorly
with the veins of the pons and with the veins which accompany the hypoglossal nerves. The
latter veins empty into the internal jugular veins. The posterior median vein is continuous
caudally with the corresponding vein of the cord, and anteriorly, in the region of the calamus
scriptorius, it divides into branches which join the radicular veins. The blood is carried
away from the peripheral plexus mainly by the radicular veins, which pass along the roots of
the last six cranial nerves. Those which accompany the hypoglossal nerves have already
been referred to. The others end in the terminal parts of the transverse sinuses, the inferior
petrosal sinuses, or the inferior part of the occipital sinuses.
The nerve supply of the blood-vessels of the brain consists of a perivascular plexus of sympa-
thetic nerve-fibres upon the walls of the vessels and meduUated fibres which accompany the
vessels and apparently terminate, for the most part, in the connective tissue about them. The
former are thought to be vaso-motor in function; the latter probably sensory fibres of the
cranio-spinal type. Nerves have been described only for the larger vessels.
IV. THE MENINGES
Three membranes, collectively called the meninges, envelope the entire cen-
tral nervous system, separate it from the walls of the bony cavities in which it lies,
and aid in its protection and support. They consist of feltworks in which white
fibrous connective tissue predominates, and through them pass the blood-vessels
which supply the central nerve-axis and the nerves by which the axis is connected
with the periphery. Though there are definite spaces or cavities between them,
the membranes are not wholly separated from each other, and they are both
continuous with and contribute to the walls of the blood-vessels and the sheaths
(epineurium) of the nerves passing through them. Beginning with the outermost,
they are — (1) the dura mater, the thickest, most dense and resistant of the mem-
THE DURA MATER
909
Fia. 715. — Showing the Spinal Dura Mater Exposed in situ. (Dorsal aspect.) (After
Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Foramen magnum
Vertebral artery ,
Transverse process of atlas"
■ Cervical nerve I
Spinal dura mater^^
Epidural cavity,^ f-j
^^?]^ii-) Thoracic nerve I
^Spinal ganglion
^Anterior ramus
^Posterior ramus
Posterior costotransverse ligament**'
Costal process of lumbar vertebrae*.
. Lumbar nerve I
Sacrum (dorsal surface)
Anterior sacral foramina^:
- Sacral nerve I
Posterior ramus of sacral nerve I
Filum of dura mater
(coccygeal ligament)
Sacral canal-
, Continuation of spinal dura mater
upon the roots of the sacral nerves.
' Coccygeal nerve
910
THE NERVOUS SYSTEM
branes; (2) the arachnoid, the much less dense, web-hke middle membrane;
and (3) the pia mater, a thin, compact membrane, closely adapted to the sm-face
of the central system, into which it sends numerous connective-tissue processes.
It is highly vascular in that it contains the rich superficial plexuses of blood-
vessels from which the intrinsic blood supply of the central system is derived.
The space between the dura mater and the arachnoid is known as the sub-dural
Fig. 716. — Dorsal Aspect of the Medulla Oblongata and Spinal Cord with the Dura
Mater Partially Removed. (Hirschfeld and Leveill6.)
A B
Superior peduncle
of the cerebellum
Median sulcus ot
4tli ventricle
Glosso-pharyngeus
Vagus
Spinal accessory
A ventral root
A dorsal root
lllfnrrfc^^-^-^^ Fiium
terminale
surround-
ed by
Cauda
equina
ni.— (.^1
IV.-.r^ 1
-Spinal
ganglion
cavity, and that between the arachnoid and the pia mater is the sub-arachnoid
cavity.
The Duea Mater
In the fresh condition the dura mater appears as a bluish-white, exceedingly
resistant membrane, forming the outermost envelope of the entire central nervous
system. Its external surface or that next to the bony wall is rough, while its
internal surface appears smooth, due to the fact that the subdural cavity partakes
of the nature and has the hning of a lymph-space. The cranial dura mater
consists of two distinct, closely associated layers, the outermost of which serves
as the internal periosteum of the cranial bones. The spinal dura mater is
described as consisting of but one layer. The internal periosteum of the spinal
SPINAL DURA MATER
911
canal, though continuous at the foramen magnum with the outer layer of the
cranial dura mater, is not considered a part of the spinal dura mater, from the
fact that it is so widely separated from the layer actually investing the spinal
cord. Thus, since the cranial and spinal portions of the dura mater differ, they
are described separately.
The spinal dura mater is a fibrous tube with funnel-shaped caudal end which
encloses and forms the outermost support of the spinal cord. It consists of but
one layer and this corresponds to the inner layer of the cranial dura mater. It
begins at the foramen magnum and terminates in the spinal canal at about the
level of the second piece of the os sacrum. It is firmly attached to the periosteum of
the surrounding bones only in certain localities: —
(1) The upper end of the tube blends intimately with the periosteum of the margin of the
foramen magnum, and thus in this locality it becomes continuous with the outer layer of the
cranial dura mater. Also in this locahty it is attached firmly, though less intimately, to the
periosteum of the posterior surfaces of the second and third cervical vertebrae. This locahty
may be considered the upper fixation-point of the spinal dura mater. (2) It extends laterally
and contributes to the connective tissue investments of each pair of spinal nerves, and as such
it passes into the intervertebral foramina and becomes continuous with the periosteum
lining each. (3) Along its ventral aspect the spinal dura mater is attached by numerous proc-
FiG. 717. — View of Membranes op Spinal Cord from Ventral Aspect. (EUis.)
Spinal dura mater'
Spinal arachnoid
Dorsal root
Ventral root
Ligamentum denticulatum
esses to the posterior longitudinal ligament of the vertebral canal. These attachments are
more or less delicate, loose, and irregular, and are easily torn or cut in removing the speci-
men. They are stronger and more numerous in the cervical and lumbar regions than in the
thoracic. (4) In the space between the dura and the walls of the vertebral canal (epidural
cavity) lies the rich internal vertebral venous plexus, and along the lateral aspect the dura is
occasionally connected with the periosteum through the tissue of the walls of the vessels of this
plexus, especially in case of the vessels which penetrate the dura. Along its dorsal aspect the
spinal dura mater is practically free from the wall of the vertebral canal. (5) At its lower
and funnel-shaped extremity, opposite the second sacral vertebra, the tube suddenly contracts
into a filament extending into the coccyx and breaking up into a number of processes which
become continuous with the periosteum of the dorsal surface of the coccyx. This filament
is the coccygeal ligament or filum of the dura mater, and its attachment may be considered
the lower fixation-point of the spinal dura mater. (See figs. 613 and 715). The extent of the
tube is maintained chiefly by means of the two fixation-points, for all the other_ attachments
are sufficiently loose to permit of the movements of the vertebral column.
The inner surface of the spinal dura mater appears smooth, but upon closer
examination it is found to be connected with the arachnoid by a few delicate sub-
dural trabeculse — occasional fine strands of connective tissue bridging the sub-
dural space (fig. 725). Along its lateral aspects the inner sm-face is at intervals
quite firmly attached to the pia mater by the dentations of the ligamenta dentic-
ulata, which are prolonged through the arachnoid.
912
THE NERVOUS SYSTEM
Further, it is continuous at intervals with both the pia mater and arachnoid by way of the
connective-tissue sheaths of the nerve-roots which are prolonged from the pia and blend with
the dura mater in the passage of the nerve-roots through it. The dura is also pierced by the
spinal rami of the vertebral arteries, and the connective tissue of the outer walls of these vessels
blends with aU three of the meninges. The filum terminate of the pia mater extends below the
termination of the spinal cord into the point of the funnel-shaped end of the dura mater, and
there blends with it in line with the coccygeal ligament of the outer surface.
The tube of the spinal dura mater varies in calibre with the variations in the
diameter of the spinal cord. However, the termination of its cavity occurs about
seven segments below the termination of the spinal cord. This extension con-
tains the long intra-dural nerve-roots forming the cauda equina, and the calibre
of this part, before its sudden contraction, is about as great as that found in any
Fig. 718. — The Dura Mater Encephali of the Base op the CRANitrM.
(After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Position of crista galli Process of dura in foramen csecum
Circular sinus
Circular sinus
\
Olfactory bulb
Eyeball
Ophthalmic vein
Cavernous sinus
Connection with
the rete f oraminis
ovalis
Internal carotid
artery
Bulb of the internal
jugular vein
Transverse sinuS'
Vertebral artery ""
Fold of dura mater^
Vrt«^ Maxillary nerve
\
i « Mandibular
i Jl-»" nerve
Abducens nerve
Acoustic nerve
jlossophar;
nerve
Vagus nerve
Accessory nerve
Hypoglossal nerve
First spinal nerve
/
Dura mater
other region. As each pair of nerve-roots of the cauda equina passes outward,
they lie free for a variable distance in a tubular extension of the dura before the
latter blends with and contributes to the thickness of their sheath.
The subdural cavity, the space between the dura mater and the arachnoid, is
the thinnest of the meningeal spaces. Along the ventral aspect especially, the
spinal arachnoid is quite closely applied to the inner surface of the dura mater. It
contains a small amount of cerebro-spinal fluid (lymph) which prevents friction
between the opposing surfaces, and is continuous with the fluid in the like space
of the cranial meninges.
The space communicates with the venous sinuses of the cranium in the region of the
Pacchionian bodies, and its fluid is likewise in contact with the blood-vessels passing through it.
It is probably continuous with the lymph-spaces of the nerve-roots passing through it, for
colored fluids injected into it pass into the nerve-roots. The arachnoid is so thin and gauze-
Uke that a ready interchange of fiuids between this space and the subarachnoid space is possible
by simple filtration.
CRANIAL DURA MATER
913
The cranial dura mater [dura mater encephali]. — The dura mater investing the
brain performs a double function — it serves as an internal periosteum for the
cranial bones and gives support and protection to the brain. In conformity with
its double function it consists of two layers, easily separable in the child, but
closely adhering to each other in the adult, except in occasional localities, where
there exist small clefts lined with endothelium. The large blood sinuses and ven-
ous lacunse, corresponding to the internal vertebral venous plexus of the vertebral
canal, are placed between the two layers and the semilunar ganglia of the trigem-
ini also lie between them. The cranial dura begins with the adhesion of the
spinal dura mater to the periosteum at the foramen magnum, and it forms a sac-
like envelope about the entire encephalon. Consisting of two layers, it is a much
thicker membrane than that of the spinal cord.
The outer surface of the cranial dura mater when torn away from the cranial
bones appears very uneven, and when placed in water presents a flocculent
appearance.
G. 719. — CoBONAL Section of the Head, Passing through the Posterior Horns of
THE Lateral VENTRicLEb
From a mounted specimen m the Anatomical Department of Trinity College, Dublin.
Inferior long
itudinal fas
ciculus
Transverse sinus
Dentate nucleus Tentorium cerebelli
This is due to the many fine bundles of connective tissue and the blood-vessels which pass
between the dura and the cranial bones and which are partially pulled out of their openings in
the latter in the process of separation. The abundance of these connections, and, therefore,
the degree of adhesion to the bones, varies in different localities. The separation is much less
difficult from the inner table of the bones of the vault of the cranium than from the bones of
the base of the cavity. The adhesions to the vault of the cranium are most firm along the lines
of the sutures. This is due to the fact that during the period before the sutures are closed the
outer layer of the dura mater is directly continuous with the external periosteum, and, in
consequence of this condition during development, the connective-tissue connection is more
abundant along these lines and some is even caught in the closure of the sutures. Along the
vault there are occasionally noticed small lymph-spaces between the bone and the dura mater.
The stronger adherence to the base of the cranial cavity is due to the numerous foramina in the
floor, through which all the larger cranial blood-vessels and the cranial nerves pass, and the
dura mater is continuous with the connective-tissue investments of these as well as with the
periosteum lining the foramina. Also the floor of the cavitj' is more uneven than the vault, and
the projections of the bones here tend to increase the firmness of attachment. The weight of
the brain upon the floor probably contributes to the result.
The inner surface of the inner layer of the cranial dura mater forms the outer
boundary of the subdural cavity. Except for the occasional delicate subdural
trabeculse and the passage of blood-vessels and nerve-roots, this surface appears
914
THE NERVOUS SYSTEM
smooth and glistening, being lined by a layer of endothelium and containing a
small amount of the cerebro-spinal lymph.
The subdural cavity of the base of the brain is prolonged a short distance outward along
the roots of the various cranial nerves before it is obUterated by the blending of the dura
mater with the sheaths of the nerves. This outward extension of the space is most marked
about tlie optic and auditory nerves. In the optic especially, the dura mater remains separate
from the nerve throughout its length, only fusing with its sheath upon the posterior surface of
the ocular bulb (fig. 718).
One of the most striking differences between the cranial dura mater and that of
the spinal cord is that the inner layer of the former undergoes striking septa-like
duplications or folds, forming exceedingly strong partitions which project between
the larger subdivisions of the encephalon. These are four in number, two large
and two small — the falx cerebri and the tentorium cerebelli; the falx cerebelli
and the diaphragma sellse. The larger enclose within their folds the great venous
sinuses, into which most of the spent blood of the encephalon collects to pass out-
ward by way of the internal jugular veins (figs. 720, 721).
Fig. 720. — The Cranium with Encephalon Removed to show the Falx Cerebri, the
Tentorium Cerebelli, and the Places where the Cranial Nerves pierce the Dura
Mater. (Sappey.)
Trochlear nerve Oculomotor nerve
Falx cerebri
Superior sagit-
tal sinus
Inferior sagit-
tal sinus
Vein of Galen
artery
Internal
carotid artery
Falx cerebelli
Facial and
auditory nerves
Glassopharyngeal, vag:us
and accessory nerves
Hypoglossal nerve
Second cervical nerve
First Inferior Abducens Trigeminus
cervical petrosal nerve nerve
Ligamentum denticulatum nerve sinus
The falx cerebri is the most striking of these partitions. It is a sickle-shaped
fold which projects vertically from the vault into the longitudinal fissure between
the cerebral hemispheres. It begins attached to the crista galli in front, and
arches to terminate by blending with the superior surface of the hirozontally
placed tentorium cerebelli. Its convex, superior border joins the outer layer of the
dura along the medial plane of the vault, and encloses the superior sagittal sinus.
Its concave border is free and contains in its posterior two-thirds the smaller
inferior sagittal sinus. The anterior and narrower end is often perforated and
occasionally so much so as to appear as a coarse, fibrous reticulum. The pos-
terior part of the concave border touches the upper surface of the corpus callosum,
but the anterior part, which does not descend so low, is separated from the corpus
callosum by a part of the subarachnoid space. The base of the fold which slopes
downward and blends with the upper surface of the tentorium cerebelli, contains
the straight sinus running along the line of junction.
The tentorium cerebelli is a large transverse, semilunar fold, concave forward.
It descends from its central part which is elevated, and consequently it forms a
i
THE DURA MATER
915
tent-shaped covering. Its superior surface is in relation with the tentorial surfaces
of the hemispheres, and its inferior surface conforms accurately to the superior
surface of the cerebellum. The outer or convex border of the fold is attached
on each side to the posterior clinoid process, the superior border of the petrous
portion of the temporal bone, the mastoid portion of the temporal bone, the pos-
terior inferior angle of the parietal bone, and the horizontal ridge of the occipital
bone. The transverse sinus lies in this border. From the internal occipital pro-
tuberance to the mastoid portion of the temporal bone and along the petrous part
of the temporal bone it encloses the superior petrosal sinus.
The greater part of the inner or anterior border of the tentorium is free, and it
forms the superior and lateral boundaries of an arched cavity, the tentorial notch
or foramen ovale of Pacchioni, which encloses the mesencephalon, and through
which ascend the cerebral peduncles and the posterior cerebral arteries. The
anterior extremities of the inner border cross the outer border, and they are
attached to the anterior clinoid processes. A depressed angle is formed between
Fig. 721.— Showing the Upper Surface op the Tentorium Cbrebelli and the Tentorial
Notch through which the Mid-bkain and Posterior Cerebral Arteries enter the
Middle Fossa of the Cranium.
Infundibulum _
Crista galli
Optic nerve
Middle cerebral
artery
Arterior cerebral
artery
Posterior commu-
nicating artery
Cavernous sinus
Superior cerebel-
lar artery
Posterior cerebral
artery
Superior petrosal
sinus
Free border of
tentorium bound-
ing tentorial notcb
Optic tract
Oculomotor nerve
Cerebral
peduncle
Aqueduct of
cerebrum
Mesencepbalon
Falx cerebri
Transverse sinus
Superior sagittal sinus
the inner and outer borders of the tentorium in the middle fossa of the skull at
the lateral portion of the posterior clinoid process, and in this angle the root of the
oculo-motor nerve pierces the inner layer of the dura mater.
The falx cerebelli is a small, sickle-shaped, triangular fold which projects
forward into the small groove {-posterior cerebellar notch), between the hemispheres
of the cerebellum. Its base is attached to the tentorium; its postero-inferior
border, along which runs the occipital sinus, is attached to the internal occipital
crest. Its anterior border is free, and its apex, which lies immediately above the
foramen magnum, usually bifurcates as it disappears anteriorly, grasping the
foramen magnum from behind. Bifurcation is always the case when the internal
occipital crest splits below to enclose a vermiform fossa.
The diaphragma sellae is a small circular fold, deficient in the centre, which
projects horizontally from the margins of the hypophyseal fossa or sella turcica.
Its lateral border is attached to the clinoid processes and the limbus of the sphe-
916
THE NERVOUS SYSTEM
noid, and its medial border forms the boundary of the foramen of the diaphragma
sellce and surrounds the infundibulum. Its superior surface is in relation with the
base of the brain, and its inferior surface is in relation with the hypophysis, which
it binds down in the hypophyseal fossa.
The spaces which lie between the layers of the cranial dura mater are Meckel's
caves, the spaces which lodge the endolymphatic sacs, and the blood sinuses and
lacunae.
Meckel's caves are two cleft-like spaces or niches which lie, one on each side,
in the trigeminal impression on the apex of the petrous portion of the temporal
bone. Each space lodges the semilunar (Gasserian) ganglion and the trigeminus
and masticator nerves of the corresponding side, and it communicates with the
subdm-al space in the posterior fossa of the cranium by an oval opening, which lies
above the superior border of the petrous portion of the temporal bone and inferior
to the superior petrosal sinus.
Fig. 722. — Showing Blood-vessels of Cranial Dura Mater and Cranial Nerves in the
Base op the Skull.
(On the left side the dura mater has been removed from the middle fossa.)
Meningeal branch of an-
terior etlunoidal artery
Meningeal branch of pos
terior ethmoidal artery
Middle meningeal
artery
Ophthalmic division of
trigeminus
Oculomotor nerve
Cavernous sinus.
Trochlear nerve
Auditory and facial
nerves
Superior petrosal sinus
Inferior petrosal sinus
Petro-squamous sinus
Spinal accessory nerve
Sigmoid sinus
Posterior meningeal
branch of vertebral
artery
Left marginal sinus
Left transverse sinus
Superior sagittal sinus
Circular sinus
Carotid artery
Abducens
^....ilar artery
Basilar plexus of
veins
-^ —j- Auditory artery
—L Vertebral artery
— j-Glosso -pharyngeal
, and vagus nerves
^Anterior spinal
py artery
' ^Hypoglossal nerve
Spinal accessory
Right marginal sinus
Right transverse sinus
The space which contains the endolymphatic sac on each side hes behind the
petrous portion of the temporal bone and communicates with the aquseductus
vestibuli.
The venous sinuses and lacunae. — The cranial blood sinuses have already been fully
described in the account of the vascular system, and it is sufficient to note here that they are
continuous, on the one hand, with the meningeal veins, and, on'the other, with the veins outside
the cranial waDs. The vessels which establish communication between the blood sinuses and
the extracranial veins are referred to collectively as emissary veins. They possibly help to
maintain the regularity of the cranial circulation, and they have therefore a certain amount of
practical importance.
The sinuses which are connected with the extracranial^veins by emissary veins are the
superior sagittal, the transverse (lateral), and the cavernous. Three or four emissary veins
pass from the superior sagittal sinus; — one passes through the foramen caecum and communicates
with the veins of the roof of the nose, or, through the nasal bones, with the angular veins.
Two pass through the parietal foramina and establish communications with the occipital
veins, and a fourth, which is very inconstant, pierces the occipital protuberance and joins the
tributaries of the occipital veins. Connecting each lateral sinus with the extracranial veins
THE ARACHNOID 917
there are, as a rule, two emissary veins: — one, the mastoid emissary vein, which passes through
the mastoid foramen to the occipital or posterior auricular vein; and the other, the post-condy-
loid vein, which traverses the condyloid (posterior condyloid) foramen and joins the suboccipital
plexus. The cavernous sinus is in communication anteriorly with the superior ophthalmic
vein, and through the latter with the angular vein; it is connected with the pterygoid plexus
by emissary veins which pass either through the foramen ovale or the foramen Vesalii, and
with the pharyngeal plexus by small venous channels which accompany the internal carotid
artery through the carotid canal.
The venous lacunae or spaces are small clefts lined by endotheUum which communicate
with the meningeal veins and with the blood sinuses. They also have communications with
the emissary veins and the diploic veins. They lie between the outer and inner layers of the
dura mater, the majority of them at the sides of the superior sagittal sinus, but others are found
in the tentorium associated with the transverse sinuses and the straight sinus.
Blood-vessels. — The blood supply of the cranial dura mater is derived from the meningeal
arteries, which ramify in its outer layer. The more important of these arteries have already
been described in the account of the vascular system, and it is only necessary here to recall
the fact that the greater part of the dura mater above the tentorium cerebelli is supplied by
branches of the middle meningeal arteries. These are reinforced — (1) at the vertex by branches
of the occipital arteries which enter through the parietal foramina; (2) in the middle fossa by
the small meningeal arteries' and by meningeal branches of the internal carotid, lacrimal,
and ascending pharyngeal arteries; and (3) in the anterior fossa by meningeal branches of the
anterior and posterior ethmoidal arteries.
The dura mater in the posterior fossa of the skull, below the tentorium cerebelU, also re-
ceives branches from the middle meningeal arteries, but its blood supply is derived mainly — (1)
from the meningeal branches of the vertebral arteries which enter- the fossa through the foramen
magnum, (2) from meningeal branches of the occipital arteries which enter through the mastoid
and hypoglossal foramina, and (3) from meningeal branches of the occipital and ascending
pharyngeal arteries which enter through the jugular and hypoglossal (anterior condyloid)
foramina.
The meningeal veins accompany the arteries as vena comitantes, usually one vein with each
artery. The middle meningeal artery usually has two venae comitantes. The meningeal veins
communicate with the venous sinuses and with the diploic veins, and, unlike ordinary veins,
they do not increase much in calibre as they approach their terminations.
The nerves of the dura mater are partly derived from the sympathetic filaments which
accompany the arteries and partly from the cranial nerves. The nerves, other than sympathetic
filaments, which supply the cranial dura mater are sensory fibres derived from the trigeminus
and vagus nerves, and possibly from the first cervical nerves. The branches from the trigeminus
are derived from the three divisions of that nerve on each side, and it has been stated that
branches are given from the nasal branch of the ophthalmic division to the dura mater in the
anterior fossa.
The meningeal branch of the ophthalmic division of the trigeminus supplies the tentorium ;
that from the maxillary division accompanies the branches of the middle meningeal artery.
The meningeal branch of the mandibular division (nervus spinosus) passes into the skull through
the foramen spinosum and is distributed to the dura mater over the great wing of the sphenoid
and to the mastoid ceOs. The "recurrent branch of the hypoglossal nerve" passes to the dura
mater of the posterior fossa of the cranium. This recurrent or meningeal branch of the hypo-
glossal nerve really consists of fibres derived from the superior cervical ganglion of the sympa-
thetic, and contains sensorj' fibres from the first and second cervical nerves. The meningeal
branch of the vagus springs from the ganglion of the root of that nerve, and is distributed in the
posterior cranial fossa. The sympathetic filaments are distributed to the smooth muscle of the
walls of the blood-vessels.
The cranial subdiiral cavity is not of uniform thickness throughout, being
thinner along the basal aspect of the encephalon. The lymph contained in it is
usually but little more than is sufficient to keep moist its bounding surfaces. It
is continuous with the lymph capillaries of the nerves and those of all the tissues
it bathes, and it is continuous with the similar cavity of the spinal canal. Its
lymph is in free contact with the blood-vessels passing through it and with
those in the tissues it bathes, and it is replenished by filtration through their
walls. Though extensive, the subdural space is thin at best, for the dura mater is
quite closely applied to the second of the three meninges.
The Arachnoid
The arachnoid or ' serous ' membrane is the middle of the three meninges of the
central nervous system. As in the case of the other two, an attempt is made to
give this membrane a name descriptive of its texture. It is a gauzy reticulum of
almost web-like delicacy, which in reality pervades the space it occupies.
Its outer surface, or that closely related to the dura mater and bounding the subdural cavity
alone shows a sufficiently organized structure to merit the name of membrane. This surface
is covered by a layer of endothehum which is identical with that lining the inner surface of the
dura mater and is continuous with it by way of the endothehal cells covering the blood-vessels,
918
THE NERVOUS SYSTEM
the nerve-roots, the ligamenta dentioulata of the spinal cord, and the occasional delicate tra-
beculae passing between the dura mater and the arachnoid. Immediately under the endothehum,
the connective-tissue fibres of the arachnoid are woven into a very thin, more or less compact
web. This, however, quickly grades into a loose, spongy reticulum which pervades the thick
subarachnoid cavity throughout, and the strands of which are directly continuous into the
more compact tissue of the pia mater. Thus an inner surface can hardly be claimed. This
loose, sponge-like arachnoid tissue holds the cerebro-spinal fluid of the subarachnoid cavity,
the meshes of the sponge constituting a reticular web of intercommunicating spaces hned by
endothehoidal cells covering the strands of the web. The cranial subarachnoid cavity is larger,
and the strands of the web are relatively more abundant than in that of the spinal canal. In
addition, the cavity is traversed by the spinal and cranial nerves, by the blood-vessels passing
to] and from the pia, and, in the spinal canal distinctively, it is traversed by the ligamenta
denticulata and the filum terminale. Through these the arachnoid is further continuous with
the pia mater.
The cranial arachnoid is directly continuous into that of the spinal cord, and
in the two localities does not differ as much as does the dura mater. Within the
cranium, the arachnoid does not closely follow the surface of the encephalon. It
is folded in between the cerebellum and cerebral hemispheres, following the con-
tour of the tentorium cerebelli, but it does not dip into the fissures and sulci except
the anterior part of the longitudinal fissure and slightly into the lateral (Sylvian)
fissure. Otherwise it fills in the inequalities of surface of the encephalon, its outer
surface forming a sheet enveloping the whole and bridging over the sulci and the
deeper grooves between the gross divisions. Upon the summits of the gyri it is
more closely applied to the pia mater, and there its reticulum becomes so dense
Fig. 723. — Diagram showing the Relations op the Pia Mater, the Arachnoid, and the
Stibarachnoid Cavity to the Brain.
Pia mater Subarachnoid cavity
Third ventricle
Infundibulum
Clsterna basalis
Cisterna pontis
Fourth ventricle
Cisterna cerebello-
medullaris
Foramen of
Magendie
that the two membranes almost appear as one. The sulci, occupied by looser
reticulum, form a continuous system of channels filled more abundantly by the
cerebro-spinal fluid.
The arachnoid folds in between the cerebellum and medulla oblongata, and
at the base of the brain it ensheathes the olfactory bulbs and tracts, and its outer
surface forms a continuous sheet stretching from one temporal lobe to the other
and bridging over the interpeduncular fossa and the inequahties of surface in the
region of the optic chiasma and the stems of the lateral fissures. Obviously,
therefore, the subarachnoid cavity between its outer surface and the pia mater is of
considerable depth in certain localities. These localities comprise the subarach-
noid cisternoe. These occur where the cavity at the base of the brain is especially
large, and make possible a 'water-bed' which serves to protect the brain from
injurious contact with the bones.
The foUowing cisternae are distinguished (fig. 723) : —
(1) The cisterna basalis lies at the base of the cerebrum and is divided by the optic chiasma
into two parts — (a) the cisterna chiasmatis and (b) the cisterna interpeduncularis.
(2) The cisterna pontis is situated about the pons, especially in its basilar sulcus and the
THE SPINAL ARACHNOID
919
transverse fissures of either border, and is continuous anteriorly with the cisterna basalis and
posteriorly with the subarachnoid cavity about the medulla.
(3) The cisterna superior Ues in the angle between the splenium of the corpus callosum
and the superior surfaces of the cerebellum and the mesencephalon, and is connected ventrally,
around the cerebral peduncles, with the cisterna basalis.
(4) The cisterna cerebello-medullaris (cisterna magna) is the cavity between the inferior
surface of the cerebellum and the dorsal surface of the medulla oblongata. It is continuous
below into the spinal subarachnoid space. The fluid in this cavity is directly continuous with
that in the fourth ventricle by way of the foramen of Magendie (median aperture of the fourth
ventricle).
Pacchionian bodies [granulationes arachnoideales] (fig. 724.) — In certain situ-
ations, more particularly along the margins of the longitudinal fissure, particu-
larly in the frontal region, and to a much less extent upon the superior surface of
the vermis of the cerebellum, the subarachnoid tissue elaborates numerous small,
ovoid or spherical nodules, the Pacchionian bodies. Each body or arachnoid
villus consists of a retiform network of subarachnoid substance and its meshes are
filled with cerebro-spinal fluid. The Pacchionian bodies on the vertex of the brain
project through the inner layer of the dura mater, both into the superior sagittal
sinus and into the venous spaces or parasinoidal sinuses which lie at the sides of
that sinus, and, as they become larger, they press against the outer layer of the
dura mater and produce ovoid depressions in the inner plate of the cranium.
Fig. 724. — Coronal Section transverse to the Great Longitudinal Fissure, Showing
THE Meninges. (Key and Retzius.)
Subarachnoid space Superior sagittal sinus Pacchionian body
-Corpus callosum
They probably facihtate the passage of lymph from the subarachnoid cavity into the
blood sinuses, and thus may aid in relieving pressure within. On the other hand, through them
the cerebro-spinal fluid is replenished at need from the blood plasma. They are not present
at birth, but they appear at the tenth year and increase in number and size with advancing age.
They are less marked in the female than in the male.
The spinal arachnoid (figs. 725, 726) is a loose, reticular sac which is most
capacious about the lumbar enlargement of the spinal cord and about the Cauda
equina. Like that of the encephalon, the portion next to the dura mater alone
resembles a membrane, being a loosely organized feltwork, covered on the side of
the subdural cavity by a layer of endothelium common to that cavity. Through-
out its length the spinal subarachnoid cavity is relatively wide, and, as in the
cranium, contains a fine, spongy, web-like reticulum, numerous threads of which
are continuous with the pia mater. This spongy tissue is the inner modification
of the arachnoid, and its meshes are occupied by the cerebro-spinal fluid. It is
not so abundant as in the cranial subarachnoid cavity.
In addition to the delicate threads, the arachnoid is more firmly attached to the pia mater
by three incomplete partitions. The most continuous of these is arranged along the dorsal
mid-line and is known as the septum posticum of Schwalbe (subarachnoid septum). This may
be described as a linear accumulation of the spongy tissue which pervades the subarachnoid
space. It is most incomplete in the upper cervical region, where it becomes merely a line of
threads connecting with the pia. It is most complete as a septum in the lower cervical and in
the thoracic region, but at best it maintains a spongy character. The other two partitions are
920
THE NERVOUS SYSTEM
formed by the denticulate ligaments, which extend laterally from either side of the spinal cord,
connecting the pia and dura mater and involving the arachnoid in passing through it. Within
the subarachnoid cavity these form more or less complete septa, though outside the arachnoid
they are attached to the dura only at the intervals of their pointed dentations. They belong
to the pia mater and will be described with it. The arachnoid is further continuous with
the pia by way of the connective-tissue sheaths of the roots of the spinal nerves and the blood-
vessels passing through the subarachnoid cavity.
Vessels and nerves. — The arachnoid has no special blood supply and probably no special
nerves other than those supplying the walls of the blood-vessels passing through it.
The cerebro-spinal fluid. — The subarachnoid cavity is the great lymph-space of the central
nervous system. That of the spinal region is directly continuous into that of the cranium, and
the fluid contained communicates freely with that in the ventricles of the brain and the central
canal of the meduUa and spinal cord by way of the foramen of Magendie or medial aperture
into the fourth ventricle. In addition, there are the lateral apertures into the fourth ventricle
and there is possible an interchange of fluid between the lateral ventricle and the subarachnoid
cavity of the base of the brain by diffusion through the thin floor of the chorioid fissure. The
arachnoid throughout is not a membrane sufficiently compact to seriously oppose diffusion
between the fluid contained in its cavity and that contained in the subdural cavity, and the
endotheUum covering it probably even facilitates such activities. The cerebro-spinal fluid
occupying the cavities is a transparent fluid of a slight yellow tinge, characteristic of the
Fig. 725. — Diagram op Transverse Section op Upper Thoracic Region of the Spinal
Cord showing the Relations op the Spinal Meninges and their Cavities.
Dura mater
Arachnoidea
( Pia mater
Septum posticum
Subdural trabeculee
Subdural space
Fila of dorsal root
^^Subarachnoid cavity
Denticulate ligament
§*1 =* Fila of ventral root
^ * ^ * Linea splendens with anterior
^ "- ^ \ spinal artery
Epidural trabecule to periosteum
lymph in other lymph-spaces of the body. It is not very great in amount, probably never
exceeding 200 c.c. in normal conditions. It is greatest in amount in old age, when the cavities
are larger, due to atrophy and shrinkage of the nervous tissues. It collects from the lymph
spaces in the meninges, and from exudation through the walls of the vascular chorioid plexuses
and sinuses of the system it bathes. Its amount may be temporarily increased by a period
of increased blood-pressure in the cranial vessels. Pressure due to its abundance may be
relieved by diffusion through the membranes containing it, and especially through the viUi
of the Pacchionian bodies into the venous sinuses and lacunae and thence into the venous system
through the internal jugular veins.
The Pia Mater
The pia mater, the third of the meninges, is a thin membrane which envelopes
and closely adheres to the entire central nervous system and sends numerous proc-
esses into its substance. It likewise contributes the most proximal and compact
portion of the sheaths worn by the nerve-roots in their passage through the menin-
geal spaces. It is very vascular in that the superficial plexuses of blood-vessels of
THE PI A MATER
921
both the brain and spinal cord ramify in it as they give off the central branches
into the nervous substance. The structure and arrangement of the membrane
vary somewhat in the cranial and spinal regions.
The spinal pia mater consists of two layers, an inner and an outer. It is
thicker and more compact than that of the encephalon, due to the extra develop-
ment of its outer layer, which is in the form of a strong, fibrous layer with the
fibres arranged for the most part longitudinally.
The spinal pia mater also appears less vascular than the cranial from the fact that the
blood-vessels composing the plexus lying in it are obviously much smaller than those of the
encephalon. Its inner layer is a thin feltworlt of fibres which is closely adherent to the surface
of the spinal cord throughout, sending numerous connective-tissue processes into it which
contributes to the support of the nervous tissues. The larger of these processes carry with them
the numerous intrinsic blood-vessels from the superficial plexus. The two layers are closely
connected with each other, and are distinguished by the difference in the arrangement of their
fibres.
The membrane dips into the anterior median fissure and bridges it over by forming an
extra thickening along it. This thickening appears as a band along the mid-line of the ventral
surface of the cord, the linea splendens (fig. 717). It carries, or ensheathes, the anterior spinal
artery, the largest of the arterial trunks of the superficial ple.xus (fig. 725).
Fig. 726. — Diagram showing Rel.ations op Meninges to Spinal Nekve-hoots.
Denticulate ligament
Body of vertebra
Periosteum
Bura mater
Subdural cavity
Arachnoid
Subarachnoid cavity
Pia mater
Intervertebral foramen-
The pia mater contributes the innermost and most compact portion of the epineurium of
each of the nerve-roots, and thus, upon the roots, it is prolonged laterally into the intervertebral
foramina, where the dura mater blends with it in producing the increased thickness of the
epineurium.
From each side of the cord the pia mater gives off a leaf-like fold, the den-
ticulate ligament, which spreads laterally toward the dura mater midway between
the lines of attachment of the dorsal and ventral nerve-roots. The outer border of
this fold is dentate or scalloped into about twenty-one pointed processes, which
extend through the arachnoid and are attached to the inner surface of the dura
mater. The dentations are usually inserted between the levels of exit of the roots
of the spinal nerves, the uppermost one a little cephalad to the first cervical nerve
and the region where the vertebral artery perforates the dura mater; the most
caudal one between the last thoracic and first lumbar nerves, or, between the last
two thoracic nerves. The ligaments, aided slightly by the septum posticum,
serve to hold the spinal cord more or less suspended in the subarachnoid cavity.
Below, at the sudden, conical termination of the spinal cord in the lumbar
portion of the spinal canal, the pia mater is spun out into a thin, tubular filament,
the filum terminale, which continues caudalward into the sac formed by the dura
mater about the cauda equina, and at the end fuses with the dura mater in line
with the filum of the spinal dura mater (coccygeal ligament) of the outside (figs.
613, 715).
922
THE NERVOUS SYSTEM
The cranial pia mater is closely applied to the external surface of the brain,
dipping into all the fissures, furrows, and sulci. It is connected with the arach-
noid by numerous filaments of the spongy subarachnoid tissue and by the blood-
vessels traversing the subarachnoid cavity. It is also pierced by the cranial
nerves, and furnishes them their sheaths, which become continuous with the
arachnoid and dura mater.
Its outer surface bounds the subarachnoid cavity. It is with difficulty separable into two
layers of mixed white fibrous and elastic connective tissue, with slightly pigmented con-
nective-tissue cells enmeshed between them. Its inner surface sends a large number of fibrous
processes into the nervous substance, which blend with the neuroglia and aid in the support
of the nervous elements. The larger of these processes accompany the central arterial and
venous branches of the rich superficial plexuses of blood-vessels contained in the pia on the
surface of the brain. Pieces of the pia when pulled off and placed in water present a flocculent
appearance as to their inner surfaces, due to these processes having been pulled out.
The cranial pia mater sends strong, vascular duplications into two of the great
fissures of the encephalon; viz., the transverse cerebellar fissure, between the cere-
bellum and the medulla oblongata, and the transverse cerebral fissure, between the
cerebellum, mesencephalon, and thalamencephalon, and the overhanging cerebral
hemispheres. These duplications are spread over the cavities of the fourth and
third ventricles, and are known as the chorioid telce of these ventricles respectively.
Fig. 727. — Diagram showing Chorioid Tela of Fourth Ventricle after Removal of
Cerebellum.
(The trochlear nerve should be shown emerging from the frenulum veli.)
Inferior quadrigeminate body
Trochlear nerve
Superior medullary velum
Brachium conjunctivuMl
Brachium of pons
Restiform body
Ligula (taenia)
Chorioid tela of
fourth ventricle
Cuneate tubercle
Clava
Tubercle of Rolando
Frenulum veil
Lateral lemniscus
Lingula of cerebellum
Fourth ventricle
VeBsels to chorioid plexus
Inferior medullary velum
Chorioid plexus
The tela chorioidea of the fourth ventricle lies in the transverse cerebellar
fissure, between the inferior surface of the cerebellum (vermis chiefly) and the
dorsal surface of the medulla (fourth ventricle). The two layers of this fold of
the pia remain separate and a portion of the cisterna posterior of the subarachnoid
cavity lies between them. The inferior of the layers is the tela chorioidea
(fig. 727.) It is triangular in shape, with its base cephalad at the nodule of the
vermis and its apex below at the level of the tuber vermis. The superior layer of
the fold is the pia mater of the vermis. The tela chorioidea is strengthened by the
epithelial roof (ependyma) of the fourth ventricle and is continuous with the pia
mater of the medulla oblongata and spinal cord. In roofing over the fourth
ventricle the tela chorioidea of the fourth ventricle constitutes the ligula and
the obex. A little above the calamus scriptorius it is pierced by the foramen of
Magendie and the two lateral apertures into the fourth ventricle.
In front of the foramen of Magendie the vessels of the chorioid tela, which are
derived from the posterior inferior cerebellar arteries, form two longitudinal,
lobulated strands which invaginate the epithelial roof of the ventricle, one on
either side of the mid-hne, and project into its cavity. These form the chorioid
THE CHORIOID TELA
923
plexus of the fourth ventricle. At the base of the tela the two chorioid plex-
uses join each other and then turn transversely lateral ward into the lateral re-
cesses of the ventricle, where they pass behind the restiform bodies and form the
' cornucopicB.'
The chorioid tela of the third ventricle, or velum interpositum, is a triangular
duplication of the pia mater which extends between the fornix above and the thai-
ami and third ventricle below, and in front fuses with the brain substance at the
interventricular foramina.
In the transverse cerebral fissure the layers of pia forming this tela are separate, the upper
being the pia of the under surface of the corpus caUosum and continuous with that of the ten-
torial surfaces of the occipital lobes; the lower being continuous into the pia enfolding the
epiphysis, and covering the mesencephalon, anterior medullary velum, and cerebellum. The
Fig. 728. — Hokizontal Dissection op the Cerebrum showing the Tela Chorioidea of
THE Third Ventricle.
(From a mounted specimen in the Anatomical Department of Trinity College, DubUn.)
The fornix has been removed to show the chorioid tela of the third ventricle.
Corpus
caUosum
(dissected)
Veins ofGalei
Crura of fornix.
Septum
pellucidum
Thalamus
Chorioid tela
(velum inter-
positum)
Chorioid
plexus
Fimbria
Hippocampus
major
Collateral
eminence
layers forming the portion of the dupUcation which roofs over the third ventricle are loosely
adherent to each other and form the tela chorioidea proper of that ventricle. The upper surface
of this portion is in relation with the fornix and its lower surface, covered by the epithelial
chorioid lamina, lies laterally over the superior surfaces of both thalami, and mesiaUy forms the
roof of the third ventricle between them. The epitheUum or ependyma is continuous with that
covering the thalami and lining the ventricles. Between the two layers of this portion, and
embedded in a small amount of the spongy subarachnoid tissue retained between them, are
the two veins of Galen, the internal cerebral veins. Posteriorly these veins unite in the region
of the epiphysis to form the single great cerebral vein (vena cerebri magna) which empties into
the straight sinus. Anteriorly the veins of Galen receive the veins of the septum pellucidum
from each lamina of the septum pellucidum above, and also the terminal vein (vein of corpus
striatum), lying in the stria terminahs of the thalamus, empties into them from each side.
The chorioid tela of the third ventricle or velum interpositum extends laterally
between the fornix and fimbria above and the stria terminalis of the thalamus be-
924
THE NERVOUS SYSTEM
low into each lateral ventricle. The blood-vessels of the border proj ecting into the
lateral ventricle are amplified into a plexus which appears as a strip of reddish,
lobulated, villus-like processes known as the chorioid plexus of the lateral ven-
tricle. The plexus, being in the border of the tela, begins at the interventricular
foramen, extends through the body or central portion of the ventricle, and down-
ward into its inferior cornu. It is most developed at the junction of the body with
the inferior cornu, and is there known as the glomus chorioideum.
From the under surface of the chorioid tela of the third ventricle, hanging
down on either side of the mid-line into the cavity of the ventricle, are two other
longitudinal, lobulated strands of blood-vessels which are the chorioid plexuses of
the third ventricle. At the anterior end of the third ventricle these two plexuses
join with each other and also with the plexus of the lateral ventricle of each side
through the interventricular foramina.
The chorioid plexuses of both the ventricles are covered by a layer of ependyma, epithelial
chorioid lamina, which is but a reflexion of the ependyma lining the cavities throughout and
represents the remains of the germinal layer of the embryonic brain vesicles. The blood-vessels
Fig. 729. — Diagram op Coronal Section of Cerebrum through Middle of Thalamen-
CEPHALON SHOWING RELATIONS OF PlA MaTER EnCEPHALI AND ChORIOID PlEXUSES OP
Third and Lateral Ventricles.
Fifth ventricle Fornix
of the chorioid plexus of the lateral ventricle receive blood by the chorioid artery (a direct branch
of the internal carotid), which enters the plex-us through the chorioid fissure immediately mesial
to the uncus, and also by the chorioidal branches of the posterior cerebral artery, which supply
the plexus of the body of the ventricle. The chorioid plexuses of the third ventricle receive blood
chiefly by branches from the superior cerebellar arteries. The greater part of the blood of both
plexuses passes out by way of the tortuous chorioid veins, which, at the interventricular foramen,
empty into the vense terminates (veins of the corpus striatum), which, in their turn, go to form
the greater part of the veins of Galen. Thence the blood passes by way of the vena cerebri
magna into the straight sinus. It is probable that a large part of the oerebro-spinal fluid of the
third and lateral ventricles is derived by diffusion through the walls of the vessels of the chorioid
plexuses.
THE PERIPHERAL NERVOUS SYSTEM
The intimate connection and consequent control exercised by the central
nervous system over all the tissues and organs of the body is attained through the
THE PERIPHERAL NERVOUS SYSTEM
925
Fig. 730. — Showing the Relation between the Central and the Peripheral Nervous
Systems.
(Combination drawing, spinal part after Allen Thompson, from Rauber.)
-/" - I Cervical nerve
Gangliated cord
vi Coccygeal nerve
Filum terminale
926 THE NERVOUS SYSTEM
peripheral nervous system. This system, abundantly attached to the central
system, consists of numerous bundles of nerve-fibres which divide and ramify
throughout the body, anastomosing with each other and forming various plexuses,
large and small. The terminal rami divide and subdivide until the divisions attain
the individual nerve-fibres of which they are composed, and finally the nerve-
fibres themselves divide and terminate in relations with their allotted peripheral
elements. It is by means of this system that stimuli arising in the peripheral
tissues are conveyed to the central system, and that impulses in response are borne
from the central system to the peripheral organs. For pm-poses of description, as
well as upon the basis of certain differences in structm-e, arrangement, and dis-
tribution, the peripheral nervous system is separated into two main divisions: —
(1) the cranio-spinal and (2) the sympathetic system.
Both of these divisions include numerous ganglia or peripheral groups of nerve-
cells from which arise a considerable proportion of the fibres forming their nerve-
trunks, but neither of the divisions may be considered wholly apart from the
central system nor are they independent or separate from each other. The sen-
sory or afferent fibres of the cranio-spinal nerves pass by way of the afferent nerve-
roots into the central system and contribute appreciably to its bulk, and the motor
or efferent fibres of these nerves have their cells of origin (nuclei) situated within
the confines of the central system. The sympathetic system is intimately asso-
ciated with the cranio-spinal, and consequently with the central system — (1)
by means of fibres which enter and terminate in the cranio-spinal gangha and
transfer impulses which enter the central system; (2) by efferent fibres of central
origin which com'se in the nerve-trunks and terminate in the ganglia of the sym-
pathetic system; (3) also, the sympathetic trunks usually contain numerous
afferent cranio-spinal fibres which thus course to their peripheral termination,
usually in the so-called 'splanchnic area,' or domain of the sympathetic, in
company with the sympathetic fibres. Likewise the peripheral branches of
the cranio-spinal nerves often carry for varying distances numerous sympathetic
fibres which are on their way to terminate either in other sympathetic ganglia or
upon their allotted peripheral tissue-elements.
The following differences between the cranio-spinal and sympathetic systems of nerves may
be cited: — (1) The cranio-spinal nerves are anatomically continuous with the brain and spinal-
cord; probably no fibres arising in the sympathetic gangha actually enter the central system
other than for the innervation of its blood-vessels, (2) The gangha of the cranio-spinal
nerves all lie quite near the central axis, in hne on either side of it, and at more or less regular
intervals; the sympathetic gangha are scattered throughout the body tissues, are far more
numerous and more variable in size, and probably only the larger of them are symmetrical
for the two sides of the body. (3) The cranio-spinal nerves are paired throughout, and the
nerves of each pair are symmetrical as to their origin and also, with certain exceptions (notably
the vagus), in their course and distribution; most of the larger and more proximal of the sym-
pathetic nerve-trunks are symmetrical for the two sides of the body; many of them are not,
and many of the smaller and most of the more peripheral nerves and gangha, large and srnall,
are not paired at all. (4) Even in their finer twigs, the cranio-spinal nerves of the two sides
probably do not anastomose with each other across the mid-hne of the body; the sympathetic
nerves do so abundantly, especially within the body cavity. (5) The cranio-spinal nerve; are
distributed to the ordinary sensory surfaces of the body and the organs of special sense and to
the somatic, striated or 'voluntary' muscles of the body; the sympathetic fibres are devoted
chiefly to the supply of the so-caUed involuntary muscles of the body, including the smooth
muscle in the walls of the viscera and in the walls of the blood and lymph vascular-systems,
while others serve as secretory fibres to the glands. (6) Cranio-spinal nerve-fibres are char-
acterized in general by well-developed medullary sheaths, making the nerves appear as white
strands; most of the sympathetic fibres are non-medullated, some are completely and some
partially medullated, but none possess as thick medullary sheaths as those of the cranio-spinal
nerves. Thus sympathetic nerves appear as grey strands.
The cranio-spinal nerves.^ — There are forty-six pairs of cranio-spinal nerves,
of which thirty-one pairs are attached to the spinal cord (spinal nerves) and fifteen
pairs to the encephalon (cranial nerves) . The spinal nerves are the more primi-
tive and retain the typical character, i. e., each is attached to the spinal cord by two
roots, a dorsal or sensory ganglionated root, and a ventral, which is motor, and
thus not ganglionated. Most of the cranial nerves have only one root, which in
come cases corresponds to a dorsal root and therefore has a ganglion, and in other
cases corresponds, physiologically at least, to a ventral root of a spinal nerve.
Among other differences, the fibres of the first cranial nerve, for example, do not
collect to form a distinct nerve-trunk.
THE CRANIAL NERVES 927
I. THE CRANIAL NERVES
Customarily, the cranial nerves are described as comprising twelve pairs and
each is referred to by number. However, present knowledge of their origin,
central connections and peripheral distribution suggests that those enumerated as
the fifth, seventh, and eighth pairs under the old nomenclature are better each
separated into its two component nerves, each of which merits a separate descrip-
tion and a separate name. None of the cranial nerves corresponds closely to
a typical spinal nerve with its motor and sensory root. The so-called motor por-
tion of the fifth is no more its motor root than is the seventh nerve. The sensory
portion of the seventh is not wholly sensory and rather resembles the ninth pair in
distribution, and it has long been commonly referred to as a separate nerve. The
two parts of the eighth nerve, both sensory, are known to be wholly different in
functional character and are so named. Further, the names of the nerves, descrip-
tive of their function, are pedagogically much more eflacient than the use of num-
bers in referring to them.
Separating the three pairs mentioned, each into its two nerves, gives fifteen
pairs instead of twelve. Their names and functional nature are given in the fol-
lowing table. The Roman numerals given in parentheses correspond to the serial
numbers given when twelve pairs only are considered. It is also customary to
enumerate the cranial nerves from in front backward and caudalward, and this
custom is followed here, but again it would be pedagogically better to take them
in the reverse order. Then each in its turn could be directly considered as in
continuous series with the spinal nerves below and the similarities to and progres-
sive modifications from the spinal type could be better realized. It will be remem-
bered that somatic motor or efferent fibres are those which terminate directly upon
the fibres of skeletal muscle while visceral motor fibres transfer their impulses to
sympathetic neurones, and the axones of the latter terminate upon gland cells and
upon the fibres of cardiac and smooth muscle.
Name Nature General Distribution
Olfactory (I) Sensory Olfactory region, nasal epithelium.
Optic (II) Sensory Retina.
Oculomotor (III) Motor { |-^- ; ; ■ ; ; ; ; if.tr/bt/y.Tif "'
Trochlear (IV) Motor-somatic Eye-moving muscles.
Abducens (VI) Motor-somatic Eye-moving muscles.
Trigeminus (V) Sensory Face, mouth, and scalp.
Masticator (minor part or Motor-somatic Muscles of mastication.
motor root of trigeminus).
T?„„;„i /^7TT^ A/r„i„> / Somatic Facial muscles.
Facial (VII) Motor '^ visceral (?) Sahvary glands, vessels(?).
Glossopalatine. (Intermedi- ( Sensory Tongue, palate.
ate pari of facial). \ Motor- visceral Sahvary glands.
Cochlear (auditory) (VIII).. Sensory Internal ear.
Vestibular (equilibrator) Sensory Semicircular canals, utriculus, sac-
(VIII). cuius.
i Sensory Tongue, palate, pharynx.
,;,„.„,/ Somatic Pharynx.
Motor| yjgj.gj.^j Glands and vessels.
Sensory Alimentary canal, lung, heart.
Motor I Somatic Larynx, pharynx.
\ Visceral Alimentary canal, heart, larjmx, tra-
chea, lung.
Hypoglossal (XII) Motor-somatic Tongue-moving muscles.
Q„;„„i „„„„„ cvTN A/i«t„. /Somatic Neck and shoulder muscles.
Spmal acessory (XI) Motor | visceral Pharynx, larynx, heart.
The cranial nerves, like the spinal nerves, are developed from cells of the primi-
tive neural tube and, beginning with the fifth pair downward, all the sensory
nerves are developed from the cells corresponding to those of the ganglion crest
which give origin to the spinal ganglia with the sensory components or dorsal roots
of the spinal nerves. Otherwise between the cranial nerves and the spinal nerves
there are many important differences. Each spinal nerve has a dorsal or sensory
root, which springs from the cells of a spinal ganglion; a ventral or motor root,
whose fibres are processes of the nerve-cells which are situated in the walls of the
central system, and at their attachment to the surface of the cord the two roots are
some distance apart. Only one of the (usually considered) twelve pairs of cranial
928
THE NERVOUS SYSTEM
nerves corresponds at all closely with typical spinal nerves. This one is the
trigeminus which possesses a sensory ganglionated root and near its attachment
is accompanied by a small motor nerve, the masticator, which serves in very
small part as a corresponding motor root of the trigeminus. But even in this case
where the similarity between the cranial and spinal nerves is greatest, there are
still points of anatomical difference, which if not essential are very obvious, for
the so-called motor root joins not the whole but only with one branch of the sen-
sory portion. The two are only slightly separated from each other at their attach-
ment to the surface of the brain. All the other cranial nerves differ in a still more
marked manner from typical spinal nerves. The first nerve is an afferent nerve
whose cells of origin (olfactory ganglion) are scattered in the mucous membrane
Fig. 731. — -Subface Attachment op the Cranial Nerves.
(After Allen Thomson, modified.)
Insula
/ Olfactory tract
Hypophysis
Anterior perforated
substance"^^^^J
Corpora mammillai
N. opticus (II)
Optic tract
Cerebral peduncl
Oblique fasciculus
— Tuber cinereum
N. oculomotorius
(m)
-- N. trochlearis (IV)
\ "N. masticatorius
"^ N. trigeminus (V)
,___.. N abducens (VI)
,' Brachium pontis
N. facialis (VH)
N. glossopalatinus
^ N. cochlearis and N,
vestibularis (VM)
N- glosso-pbaryngeus (IX)
N. vagus (X)
N. accesfeorius (XI)
(spinal accessory)
N. Hypoglossus (XU)
Pyramid
Decussation of pyramids'
_ Cervical II
of the nose, an organ of special sense, and its fibres are not collected together into a
nerve-trunk, but pass, as a number of small bundles, through the lamina cribrosa
of the ethmoid bone directly into the olfactory bulb. The optic nerve is also a
nerve of special sense. Its fibres form a very distinct bundle, similar in appear-
ance to an ordinary nerve, from which, however, it differs essentially, both with
regard to structure and development; for, unlike an ordinary nerve, its connective
tissue consists to a large extent of neurogha instead of ordinary connective tissue,
and its component nerve-fibres are of much smaller calibre than those of an ordi-
nary nerve. It represents the location of the original optic stalk, a diverticulum
from the neural tube and it associates the retina (optic cup) , a bit of modified cor-
THE TERMINAL NERVE 929
tex, with the encephalon. The optic nerve, therefore, corresponds more closely
with an association tract of the central system than with an ordinary nerve.
The oculomotor, trochlear, abducens and hypoglossal nerves are purely motor
nerves, and thus correspond only with the ventral roots of spinal nerves. The
spinal accessory is also purely motor. Its fibres arise from the cells of the anterior
horn of the spinal cord and from a nucleus of the medulla which represents a dis-
placed portion of that horn, but they do not leave the surface of the spinal cord and
brain in the usual situation of ventral roots. On the contrary, they emerge in a
series of rootlets from the lateral funiculus of the cord on the dorsal side of the
ligamentum denticulatum, and from the upward prolongation of this funiculus.
The cochlear and vestibular are nerves of special sense, and in some respects
both correspond closely with the dorsal root of a typical spinal nerve, and the gan-
glia of both represent spinal ganglia, but their distribution is limited to the mem-
branous labyrinth.
The vagus and glosso-pharyngeal nerves contain both motor and sensory fibres,
but they differ from typical spinal nerves in that the motor fibres, in company
with the sensory, issue from the postero-lateral sulcus of the medulla, and they are
intimately intermingled, from their origin, with the sensory fibres, which latter
arise from ganglia interposed in the trunks of the nerves and otherwise correspond
with the fibres of the dorsal root of a typical spinal nerve.
Superficial attachments and origins. — It is customary to speak of the area
where the nerve-fibres leave or enter the brain substance as the superficial
attachments of the cranial nerves, and the groups of cells from which the fibres
spring, and about which they terminate, as their nuclei of origin or termination,
respectively.
THE OLFACTORY NERVES
The olfactory nerve-fibres are the central processes of the bipolar olfactory
nerve cell-bodies situated in the olfactory region of the nasal mucous membrane.
In man, the olfactory region comprises the epithelium upon the superior third of
the nasal septum and that upon practically the whole of the superior nasal concha.
The area is relatively small as compared with that of other mammals and, as in
other mammals, is characterized by an increased thickness of the epithelium and a
yellowish brown colour in the fresh. The peripheral processes of the olfactory
cell-bodies (the olfactory gangUon) are short and extend only to the surface of the
olfactory epithehum. As the central processes pass upward from their cells of
origin they form plexuses in the mucous membrane, and from the upper parts of
these plexuses, immediately below the lamiiia cribrosa of the ethmoid, about
twenty filaments issue on each side. These filaments comprise the olfactory
nerve. They are non-medullated. They pass upward, through the foramina in
the lamina cribrosa, into the anterior fossa of the cranium in two rows, and after
piercing the dura mater, the arachnoid, and the pia mater, they enter the inferior
surface of the olfactory bulb. They contribute to the superficial stratum of nerve-
fibres on the inferior surface of the olfactory bulb and end in the glomeruli, which
are formed by the terminal ramifications of the olfactory nerve-fibres intermingled
with the similar ramifications of the main dendrites of the large mitral cells which
lie in the deeper part of the grey substance of the olfactory bulb.
The olfactory nerve-fibres are grey fibres, since they do not possess medullary sheaths,
and they are bound together into nerves by connective-tissue sheaths derived from the pia
mater, from the subarachnoid tissue, and from the dura mater. Prolongations of the subarach-
noid space pass outward along the nerves for a short distance.
Central connections. — The olfactory impulses are transmitted by way of the peripheral proc-
esses of the olfactory neurones through the cell-bodies and the olfactory nerve-fibres and
through the glomeruli to the mitral cells. Thence they are carried by the central processes
(axones) of the mitral cells, which pass backward along each olfactorj' tract and its three olfac-
tory strise (see Rhinencephalon, p. 864).
THE TERMINAL NERVE (Nervus Terminalis)
In lower vertebrates and recently in those mammals whose sense of smell is relatively much
more developed than in man, three nerves have been found concerned with the olfactorj' appara-
tus:— ■(!) The olfactory nerve proper whose fibres, as noted above, are the central processes of
930 THE NERVOUS SYSTEM
the nerve cell-bodies situated in the epithelium of the olfactory region of the nasal mucosa, and
which terminate in the olfactory bulb; (2) The vomero-nasal nerve, whose fibres are the central
processes of nerve cell-bodies situated in the epithelium of the vomero-nasal (Jacobson's) organ
and which pass caudalward in the submucosa and upward to join the filaments of the olfactory
nerve proper and which, in the dog, cat, rabbit, rat, etc., terminate in the accessory olfactory
bulb — a small protuberance possessed by these animals on the postero-median aspect of the
olfactory bulb proper; (3) The terminal nerve, a small plexiform nerve, which unlike the other
two, is ganglionated.
In man, the vomero-nasal (Jacobson's) organ is rudimentary after birth and, therefore, the
vomero-nasal nerve is not present, the only fibres for the vomero-nasal region being those of gen-
eral sensibility from the trigeminus and sympathetic fibres common to the epithelium of the
entire nasal fossa.
The terminal nerve has been recently described as present in the human foetus and it is men-
tioned here because of the expressed belief that it is present in the adult. From the observations
recorded for human and rabbit foetuses and the adult dog and cat, the following description may
be given: It is variably plexiform throughout its course. Its peripheral twigs are distributed
to the mucosa of the nasal septum, some to the mucosa joining the olfactory region while other
and larger twigs extend further forward and are distributed to mucosa of the vomero-nasal organ,
accompanying and sharing in the distribution of the vomero-nasal nerve when this is present.
Its central connections are in the form of two or three small roots which pass through the cribri-
form plate of the ethmoid bone in company with and mesial to the vomero-nasal nerve and then,
still plexiform, extend caudalward over the infero-mesial aspect of the olfactory bulb and upon
the olfactory peduncle or stalk (olfactory tract) beyond, a root often extending to near_the
lamina terminalis and optic chiasma. The roots disappear in the mesial and infero-mesial
aspect of the frontal portion of the brain at different localities caudal to the olfactory bulb and
usually near the olfactory peduncle, but often one may disappear in the region corresponding to
the anterior perforated substance of the adult human brain.
Numerous small groups of ganglion cells are found interposed along both the peripheral and
intracranial course of the terminal nerve. A group, larger in size than the others and situated in
the intracranial course of the nerve, is called the ganglion ierminale. The fibres of the nerve are
non-medullated. Both the ganglion cells and the fibres of the nerve are described as having
more the appearances characteristic of sympathetic neurones than of cranio-spinal. On the
other hand, our conceptions of sympathetic neurones do not permit of their terminating within
the central system except for the innervation of its bloodvessels. It may result that, instead of
being an independent nerve as now claimed, the nervus terminalis is a part of the forward exten-
sion of the cephalic sympathetic, the larger ganglia and plexuses of which latter are well known,
and that its neurones receive and convey impulses to the gland cells of the nasal mucosa and to
the muscle of the blood-vessels of the mucosa and those supplying the infero-mesial part of the
frontal end of the cerebrum.
THE OPTIC NERVES
The fibres of the optic nerve are the central processes of the ganglion cells of the
retina. Within the ocular bulb they converge to the optic papilla, where they
are accumulated into a rounded bundle, the optic nerve. The nerve thus formed
pierces the chorioid and the sclerotic coats, and, at the back of the bulb, enters the
orbital fat, in which it passes backward and medialward to the optic foramen.
After traversing the foramen it enters the middle fossa of the cranium, and anas-
tomoses with its fellow from the opposite side, forming the optic chiasma. It
may, therefore, for descriptive purposes, be divided into four portions — the
intra-ocular, the intra-orbital, the intra-osseous, and the intra-cranial. The
total length of the nerve varies from forty-five to fifty millimetres.
The intra-ocular part is rather less than one millimetre in length. It passes
backward from the optic papilla through the chorioid and through the sclerotic
coats of the bulb. As it passes through the latter coat of the bulb in many sep-
arate bundles, the area it traverses has a cribriform appearance when the nerve
is removed, and consequently is known as the lamina cribrosa sclerce.
The intra-orbital part of the nerve emerges from the sclerotic about three milli-
metres below and to the median side of the posterior pole of the bulbus, and it is
about thirty millimetres long. It passes backward and medialward, surrounded
by the posterior part of the fascia bulbi (Tenon's capsule) and by the orbital fat,
to the optic foramen.
As it runs backward in the orbit it is in relation above with the naso-ciliary (nasal) nerve and
the ophthalmic artery which pass obliquely from behind and laterally, forward and medialward
across the junction of its posterior and middle thirds, and also in relation with the superior oph-
thalmic vein, the superior rectus muscle, and the upper branch of the oculo-motor nerve. Below
it are the inferior rectus muscle, and the inferior division of the oculo-motor nerve. To its lateral
side, near the posterior part of the orbit, are the ophthalmic artery, the ciliary ganglion, the
abducens nerve,, and the external rectus muscle. The anterior two-thirds of this portion of the
optic nerve are surrounded by the ciliary arteries and the ciliary nerves and it is penetrated on its
THE OCULO-MOTOR NERVES
931
medial and lower aspect by the central artery of the retina. As it enters the optic foramen to
become continuous with the intra-osseous part, it is in close relation with the ligaments of Lock-
wood and Zinn (annulus tendineus communis) and with the four recti muscles which arise from
them.
The intra-osseous portion is from six to seven millimetres long. It lies be-
tween the roots of the small wing of the sphenoid and the body of that bone, and it
is in relation below and laterally with the ophthalmic artery.
The intra-cranial portion, which is from ten to twelve millimetres long, runs
backward and medialward, beneath the posterior end of the olfactory tract, and
above the ophthalmic artery, the medial border of the internal carotid artery
and the diaphragma sellse to the chiasma. From the chiasma to the central
connections of the nerve, the path is known as the optic tract.
Central connections. — The central connections of the fibres of the optic nerve have been
considered with the optic chiasma and the optic tract (see p. 849).
Fig. 732. — Nerves op the Nasal Cavitt.
Nasal branch
^ ^ , . "' ethmoidal Olfactory
^"' * " nerve plexus
Superior nasal co:
Sphenoidal sinus
Spheno-palatine
ganglion
Palatine nerves
— Nasal branches
Posterior palatine
Anterior palatine
Middle palatine
The sheaths of the optic nerve. — The optic nerve receives a sheath from
each of the membranes of the brain, and prolongations of the subdural and sub-
arachnoid cavities also pass outward along it to the posterior part of the sclera.
THE OCULO-MOTOR NERVES
The oculo-motor or third cranial nerve is a purely motor nerve. Each sup-
plies seven muscles connected with the eye, two of which, the sphincter of the iris
and cihary muscle, are within the ocular bulb. The remaining five are in the orbi-
tal cavity, and four of them — the superior, inferior, and medial recti and the
inferior oblique — are attached to the bulb, while the fifth, the levator palpebrje
superioris, is inserted into the upper eyelid.
The fibres of the oculo-motor nerve spring from their nucleus of origin situated in the grey
substance of the floor of the cerebral aquteduct in the region of the superior quadrigeminate
body (fig. 662). The cells of tliis nucleus are divided into two main groups, a superior and an
inferior (fig. 663). The superior group includes two nuclei, a medial and a lateral. The latter,
besides being lateral, is also somewhat dorsal to the former. The inferior group has been
divided into five secondary nuclei, according to the eye-muscles the cells of each group innervate.
Three of the five lie lateral to the others and somewhat dorsally, and of the remaining two,
which are placed more medially, one encroaches upon the mid-line (nucleits mediaiis) and is con-
932
THE NERVOUS SYSTEM
tinuous with the corresponding group of the opposite side and is common to the oculo-motor
nerves of both sides.
It has been foimd, by the study of diseased conditions and by experiments with animals,
that the centres of innervation of the eye-muscles suppUed by the nerve correspond to the above
divisions of both the superior and inferior group of cells into a medial and lateral series. The
relative position of the divisions of each group and the muscles they are thought to innervate
are shown in the following diagram devised by Starr: —
Mesial Plane.
StrPBRIOR
Grotip.
Inferior
Group.
Sphincter
of Iris.
Ciliary
Muscle.
Ciliary
Muscle.
Sphincter
of Iris.
Levator
Palpcbrae
Superioris.
Medial
Rectus.
Medial
Rectus.
Levator
Palpebrse
Superioris.
1
Superior
Rectus.
Inferior
Rectus.
Inferior
Rectus.
Superior
Rectus.
Inferior
Oblique.
Inferior
Oblique.
As they leave their nucleus of origin in the mid-brain, the fibres of the oculo-
motor nerve form a series of fasciculi, which curve ventrally around and through
the red nucleus and the medial part of the substantia nigra, to the oculo-motor
sulcus on the medial surface of the cerebral peduncle, where they emerge in from
six to fifteen small bundles which pierce the pia mater and collect into the trunk
of the nerve. Immediately after its formation along the oculo-motor sulcus, the
trunk of the nerve passes between the posterior cerebral and the superior cere-
bellar arteries, and, running downward, forward, and laterally in the posterior
part of the cisterna basalis, it crosses the anterior part of the attached border of the
tentorium cerebelli at the side of the dorsum sellse, and, piercing the arachnoid
and the inner layer of the dura mater, it enters the wall of the cavernous sinus
about midway between the anterior and posterior clinoid processes. Immediately
after its entry into the wall of the sinus it lies at a higher level than the trochlear
nerve, but the latter soon crosses on its lateral side and gets above it, and directly
afterward the oculo-motor nerve divides into a smaller superior and a larger
inferior branch (fig. 734). Before its division communications join it from the
cavernous plexus of the sympathetic about the internal carotid artery, and from
the ophthalmic division of the trigeminus. Both branches proceed forward, and
the nasal branch of the trigeminus, which has passed upward, on the lateral side of
the inferior branch of the oculomotor lies between them. At the anterior end of
the cavernous sinus the two branches pass through the superior orbital (sphe-
noidal) fissure, between the heads of the lateral rectus muscle, and enter the or-
bital cavity. In the orbit, the superior branch hes between the superior rectus and
the optic nerve; it supplies the superior rectus and then turns round the medial
border of that muscle and terminates in the levator palpebrse superioris. The
inferior branch runs forward, beneath the optic nerve, and divides into three
branches which supply the inferior and medial recti and the inferior oblique.
The branch to the inferior oblique muscle is connected with the ciliary ganglion
by a short thick offset, the short root of the ciliary ganglion, by mediation of the
sympathetic neurones of which the oculo-motor nerve sends impulses to the ciliary
muscle and the sphincter muscle of the iris. The inferior branch also gives some
small twigs to the inferior rectus. The branches of the oculo-motor nerve, which
supply the recti muscles, enter the muscles on their ocular surfaces, but the branch
to the inferior oblique muscle enters the posterior border of that muscle.
THE TROCHLEAR NERVES
933
Some of the fibres which spring from the medial portion of the oculo-motor nucleus do not
pass into the nerve of the same side, but into that of the opposite side, and it is beheved that
they are distributed to the opposite medial rectus muscle. Other fibres which arise from the
nucleus descend in the medial longitudinal fasciculus and either terminate about the cells of
the nucleus of the facial or join the facial nerve, in which they pass to the upper part of the
orbicularis palpebrarum. The eye is opened by the oculo-motor and closed by the facial nerve.
Central connections. — The nucleus of the oculo-motor is associated with the middle portion of
the anterior central gyrus, the posterior end of the middle frontal gyrus and with the cortex about
the visual area of the occipital lobe of the opposite side of the brain by the pyramidal fibres. It is
probably associated with the cerebellum by the fibres in the superior cerebellar peduncles, with
the superior calliculus, and with the sensory nuclei of the other cranial nerves by the medial
longitudinal fasciculus. To produce the coordinated activities of the eye-moving muscles, it
must be associated with the nuclei of the trochlear and abducens.
THE TROCHLEAR NERVES
The fibres of each trochlear or fourth nerve (or patheticus) spring from the
cells of a nucleus which lies in the grey substance of the floor of the cerebral aquse-
duct in hne with the oculo-motor nucleus, but in the region of the inferior quadri-
geminate bodies. As the fibres pass from their origins they rim ventrally and lat-
erally in the substance of the tegmentum for a short distance, then they curve
medianward and dorsalward, and, in passing through the anterior end of the supe-
rior medullary velum they decussate totally with the fibres of the trochlear nerve
Fig. 733. — Diagrams op Sections through the Origin op the Trochlear Nerve. (Still-
ing.) (The upper figure is an obUque section, the lower is a coronal section.)
Cerebral aqueduct-
Nucleus of trochlear nerve
Trochlear nerve
Trochleai nerve
■Cerebral aqueduct
Nucleus of masticator
Brachium conjunctivum
•Lateral lemniscus
of the opposite side. After the decussation the fibres emerge from the surface of
the superior medullary velum, at the side of the frenulum veli, usually in two small
bundles, which pierce the pia mater and join together to form the slender trunk of
the nerve. This trunk curves forward and ventralward to the base of the brain
around the sides of the superior peduncle of the cerebellum and cerebral peduncle
of the side opposite to that in which the nerve originates, running parallel with and
between the superior cerebellar and posterior cerebral arteries. As it reaches the
base of the brain behind the optic tract the nerve enters the cisterna basalis, in
which it runs forward, immediately beneath or piercing the free border of the ten-
torium cerebelli, to the superior border of the petrous portion of the temporal
bone, where it pierces the arachnoid and the dura mater and enters the posterior
end of the lateral wall of the cavernous sinus. In the wall of the cavernous sinus
it receives communications from the cavernous plexus of the sympathetic and bj'
a small filament from the ophthalmic division of the trigeminus. It gradually
ascends, as it passes forward in the lateral wall of the sinus, and, beyond the
middle of the sinus, it crosses the lateral side of the trunk of the oculo-motor
nerve and gains a higher position. At the anterior end of the sinus the nerve
934 THE NERVOUS SYSTEM
enters the orbit above the lateral rectus and immediately turns medialward
between the periosteum of the roof of the orbit and the levator palpebrae superioris.
At the medial border of the roof it turns forward to its termination, and enters
the orbital or superior surface of the superior oblique muscle to which its fibres
are distributed.
The central connections of the nucleus of the trochlear nerve are similar to those of the
oculo-motor save that its cells probably do not send fibres which connect with the facial nerve.
The trochlear is peculiar in that — (1) it is the smallest of the cranial nerves; (2) it is the
only nerve having its superficial attachment upon the dorsal aspect of the euoephalon; (3) it
is the only cranial nerve whose fibres undergo a total decussation, and (4) in that it terminates
in a muscle of the side of the body opposite that in which it has its origin. GaskeU has suggested
that this latter condition has probably been brought about, phylogenetically, by the trans-
ference of the muscles which have carried their nerves with them. It should be remembered
that most of the fibres arising from the medial group of the cells of the nucleus of the oculo-motor,
cross the opposite side. This is thought to be especially true for those supplying the medial
rectus muscle.
THE ABDUCENS
The abducens (or sixth nerve) on each side arises from the cells of a nucleus
which lies in the grey substance of the floor of the fourth ventricle in the region of
the inferior part of the pons. The nucleus is situated close to the middle line,
ventral to the acoustic medullary strise and beneath the colliculus facialis and
it is in direct linear series with the nuclei of the oculo-motor, trochlear and hypo-
glossal nerves. It is the third of the eye-moving nerves. The fibres which pass
from the nucleus into the nerve run inferiorly and ventralward through the ret-
icular formation, the trapezium, and the pyramidal fasciculi, and they emerge
from the ventral surface of the medulla in the sulcus at the inferior border of the
pons and the upper end of the pyramid of the medulla. From this superficial
attachment the nerve runs upward and forward in the subarachnoid space between
the pons and the basisphenoid and at the side of the basilar artery. A little below
the level of the upper border of the petrous portion of the temporal bone it pierces
the dura mater, passes beneath the petro-sphenoidal hgament, at the side of the
dorsum sellte, and enters the cavernous sinus, in which it runs forward along the
lateral side of the internal carotid artery. At the anterior end of the sinus it
passes through the superior orbital (sphenoidal) fissure between the heads of
the rectus lateralis, below the inferior branch of the oculo-motor nerve, and above
the ophthalmic vein. In the orbit it runs forward on the inner or ocular surface
of the rectus lateralis, and finally it pierces this muscle and terminates upon its
fibres.
While it is in the cavernous sinus it receives communications from the carotid
plexus of the sympathetic and from the ophthalmic nerve.
All the fibres arising in the nucleus of the sixth nerve do not pass into the sixth nerve. Some
of them ascend in the medial longitudinal fasciculus of the same and opposite sides, and ter-
minate about cells of the medial group of the nucleus of the oculo-motor nerve, by which the
impulses are conveyed to the opposite medial rectus muscle. Thus impulses reaching the abdu-
cens nucleus can throw into simultaneous action the lateral rectus of the same side and the
medial rectus of the opposite side, and thus turn both ej'es in the same direction.
Central connections. — The nucleus of the abducens receives impulses from the anterior
central gyrus of the opposite side by the pj'ramidal fibres, and it is associated with the sensory
nuclei of other nerves by way of the medial longitudinal fasciculus, and that of the trigemiuus
especially through the reticular formation.
THE TRIGEMINUS
The trigeminus is the largest of the cranial nerves with the exception of the
optic. It is usually described as the fifth cranial nerve and as possessing both a
sensory and a motor root. For reasons already given, the "motor root" is here
described separately and given the separate name, masticator nerve. The
fibres of the trigeminus, which are all sensory, spring from the cells of the semi-
lunar (Gasserian) ganglion, which corresponds with the ganglion of the dorsal
root of a spinal nerve, and they enter the brain stem through the side of the
anterior third of the pons.
BRANCHES OF THE TRIGEMINUS 935
The semilunar (Gasserian) ganglion is a semilunar mass which lies in
Meckel's cave, a cleft in the dura mater above a depression in the medial part of
the upper surface of the petrous portion of the temporal bone. The convexity of
the ganglion is turned forward, and from it three large nerves, the ophthalmic,
the maxillary, and the mandibular, are given off. From the concavity, which is
directed backward, springs the root of the nerve. The medial end of the ganglion
is in close relation with the cavernous sinus and the internal carotid artery at the
foramen lacerum, and the lateral end lies to the medial side of the foramen ovale.
The surfaces of the ganglion are striated, due to bundles of fibres traversing them.
The upper surface is separated by the dura mater from the temporal lobe of the
brain, and the lower rests upon the masticator nerve and the outer layer of dura
mater upon the petrous portion of the temporal bone.
The fibres of the trigeminus root as they leave the semilunar (Gasserian) ganglion, form from
thirty to forty fasciculi which are bound together into a flat band, from six to seven millimetres
broad, which passes backward over the upper border of the petrous portion of the temporal
bone and below the superior petrosal sinus into the posterior fossa of the cranium. In the
posterior fossa it runs backward, medialward, and downward, and passes into the pons through
its continuation into the middle peduncle of the cerebellum. In the tegmentum of the pons
region, the fibres bifurcate into ascending and descending branches which terminate about
the cells of the nucleus of termination of the trigeminus. This nucleus, large at the level of
the entrance of the root, has tapering superior and inferior e.xtremities. The inferior ex-
tremity of the nucleus, which is much the longer, descends as low as the upper portion of the
spinal cord and the fibres of the root terminating about the cells of this extremity are known
as the spinal tract of the trigeminus.
Central connections. — The nuclei of termination of the trigeminus send impulses to the
somaesthetic area of the cortex of the opposite side by the fibres of the medial lemniscus (fillet)
and, for reflex actions, to the motor nuclei of other cranial nerves by the medial longitudinal
fasciculus and by fascicuU propri in the reticular formation of the same, and opposite sides.
THE BRANCHES OF THE TRIGEMINUS
The main branches of the trigeminus, given off by the front side of the semi-
lunar ganglion, are three in number (ophthalmic, maxillary, and mandibular) ,
each of which is referred to as a nerve and each of which is purely sensory, though
the third branch, or mandibular nerve, is joined by the fibres of the masticator
nerve which is motor.
(1) The Ophthalmic Nerve or First Division
The ophthalmic nerve, the first division of the trigeminus, is the smallest of the
three branches which arise from the semilunar (Gasserian) ganglion. It springs
from the medial part of the front of the ganglion and passes forward, in the lateral
wall of the cavernous sinus, where it lies below the trochlear nerve and lateral to
the abducens nerve and the internal carotid artery (fig. 734). A short distance
behind the superior orbital (sphenoidal) fissure the nerve divides into three ter-
minal branches — the frontal, lacrimal, and naso-ciliary (nasal) nerves. They
pierce the dura mater, which closes the fissure, and pass forward into the orbit.
Before its division the ophthalmic nerve receives filaments from the cavernous
plexus of the sympathetic and it gives off, soon after its origin, a tentorial (recur-
rent meningeal) branch which runs backward, in close association with the troch-
lear nerve, and ramifies between the layers of the tentorium cerebelli. Further
forward three branches spring from the ophthalmic nerve which contribute sen-
sory fibres to the oculo-motor, trochlear, and abducens nerves.
The terminal branches. — (a) The frontal nerve is the largest terminal
branch. It pierces the dura mater and passes into the orbit through the superior
orbital (sphenoidal) fissure, above the rectus lateralis and a little below and to
the lateral side of the trochlear nerve. In the orbit it runs forward, between the
levator palpebrse superioris and the periosteum, and breaks up into three branches,
the supra-orbital, frontal proper, and supratrochlear.
The supra-orbital nerve, the largest of the three branches, leaves the orbit at the supra-
orbital notch (fig. 734). As it passes thi-ough the notch it gives off a small branch which enters
the bone and supphes the diploe and the mucous membrane of the frontal sinus. Its terminal
branches give twigs to the pericranium and to the skin of the scalp, the upper ej-eUd, the frontal
936
THE NERVOUS SYSTEM
region, and the parietal region almost as far as the lambdoid suture (fig. 740). One branch
running at the upper margin of the orbital cavity unites with a branch of the facial nerve.
The frontal branch, given off at a variable point, lies medial to the supra-orbital, passes
through the frontal foramen, and is distributed to the skin of the forehead and upper eyehd
(fig. 734).
The supratrochlear branch runs forward and medialward toward the upper and medial
angle of the orbit, where it passes above the pulley of the superior obhque muscle, pierces the
palpebral fascia, and ascends to the lower and middle part of the forehead, accompanied by
the frontal artery (fig. 734). Before it leaves the orbit it sends a branch downward behind or
in front of the pulley of the obliquus superior which joins with the infratrochlear nerve, and as
it leaves the orbit it gives off filaments to supply the skin and conjunctiva of the medial third
of the upper eyelid. Its terminal branches pierce the orbicularis and frontalis, and, as they pass
to the skin of the forehead, they communicate with branches of the facial nerve.
(b) The lacrimal nerve [n. lacrimalis] is the smallest of the three branches of the
ophthalmic division. It passes through the superior orbital (sphenoidal) fissure
lateral to and slightly below the frontal nerve, and is directed forward and lateral-
FiG. 734. — Nerves op the Orbit from Above and Behind. (Schematic.)
Infratrochlear
1 Supratrochlear
I 1 Frontal branch of frontal
, Supraorbital
Superior ob-^
lique muscle""
Trochlear
Naso-ciliary
(nasal) "
Annular com-
mon tendon
of Zinn
Optic nerve -
Internal car-
otid artery
Abducens ^-r
Semilunar ^
(Gasserian) "^ j ^
Levator palpebrse
superioris
Superior rectus
Lacrimal gland
Frontal
Short ciliary nerves
Anastomosing branch
with zygomatic
Lacrimal
Long ciliary nerves
Inferior rectus
Branch to internal
oblique
Lateral rectus
Ciliary ganghon
Sympathetic ] Roots of
Short } ciliary
Long J ganghon
Abducens
Inferior branch of
oculo-motor
Superior branch of
oculo-motor
Lateral rectus (lat.
head)
Ophthalmic
Maxillary
Mandibular
A' — Foramen spinosum
ward, along the upper border of the rectus lateralis to the lacrimal gland (fig. 734) .
On the lateral wall of the orbit it receives a small branch from the zygomatic
nerve (the orbital branch of the maxillary nerve). This branch brings to the
lacrimal nerve secretory fibres for the lacrimal gland. A small twig passes beyond
the gland, pierces the palpebral fascia, supplies filaments to the conjunctiva, and
is then distributed to the integument at the lateral angle of the eye and to the skin
over the zygomatic process of the frontal bone.
(c) The naso-ciliary (nasal) nerve enters the orbit between the two heads of the
rectus lateralis and between the superior and inferior branches of the oculo-motor
nerve. In the orbit it lies at first lateral to the optic nerve, but, as it runs obliquely
forward and medialward to the medial wall of the orbital cavity, it crosses above
the optic nerve and between it and the rectus superior, and near the border of the
rectus medialis it divides into its terminal branches, the chief of which are the
infratrochlear and anterior ethmoidal nerves (fig. 734). In addition to those
received from the cavernous plexus before the division of the ophthalmic nerve ,
THE MAXILLARY NERVE 937
the naso-ciliary nei've itself receives numerous sympathetic (secretory and vaso-
motor) fibres.
Its several branches are: (i) The long root of the ciliary ganglion which is given off at the
superior orbital (sphenoidal) fissure. It is a slender filament which runs forward on the lateral
side of the optic nerve to the superior and posterior part of the ciliary ganglion (fig. 734).
(ii) The long ciliary nerves, usually two in number, which arise from the naso-cihary nerve
as the latter is crossing above the optic nerve. They run forward, on the medial side of the optic
nerve, pierce the sclerotic, and are distributed with the lower set of short ciliary nerves (fig. 734).
The long root of the cihary ganglion and the long ciUary nerves carry sensory fibres which
belong to the naso-ciliary nerve proper, most of which merely pass through the ganglion, and
it carries sympathetic fibres, added to it, most of which may terminate about the cell-bodies of
the ganglion.
(iii) The posterior ethmoidal (spheno-ethmoidal) branch springs from the posterior border
of the naso-ciUary nerve near the upper border of the rectus medialis. It passes through the
posterior ethmoidal canal and is distributed to the mucous membrane of the posterior ethmoidal
cells and the sphenoidal sinus.
(iv) The infratrochlear nerve passes forward between the obhquus superior and the rectus
medialis, and under the pulley of the former muscle divides into two branches: — The superior
palpebral branch helps to supply the eyehds with sensory fibres and usually anastomoses with
the supratrochlear nerve. The inferior palpebral branch is distributed to the lacrimal sac,
the conjunctiva and skin of the medial part of the upper eyehd, the caruncle, and the skin of
the upper part of the side of the nose.
(v) The anterior ethmoidal (distal part of the nasal) nerve, passing forward and medial-
ward between the obhquus superior and the rectus medialis, leaves the orbit through the anterior
ethmoidal foramen, accompanied by the anterior ethmoidal vessels, and enters into the anterior
fossa of the cranium (fig. 734). It then crosses the lamina cribrosa of the ethmoid, lying outside
the dura mater, which separates it from the olfactory bulb, and descends into the nasal fossa
through the ethmoidal fissure, a slit-like aperture at the side of the crista galli. In the sub-
mucosa of the nasal fossa it terminates by dividing into two sets of anterior nasal branches:
the internal nasal branches and the external nasal branch (fig. 732).
The internal nasal branches divide into the medial nasal branches (the septal branches of
the nasal nerve), which run downward and forward on the upper and front part of the septum,
and the lateral nasal branches (the external terminal branch of the nasal nerve), which give
twigs to the anterior extremities of the superior and middle nasal conchae (turbinated bones),
and to the mucous membrane of the lateral wall of the nose (fig. 732).
The external nasal branch (the anterior terminal branch of the nasal nerve) runs downward
in a groove on the inner surface of the nasal bone. It pierces the wall of the nose between the
nasal bone and the upper lateral cartilage, and supphes the integument of the lower part of
the dorsum of the nose as far as the tip.
(2) The Maxillary Nerve or Second Division of the Trigeminus
The maxillary nerve is entirely sensory in function and it is intermediate in
size between the ophthalmic and mandibular nerves.
It springs from the middle of the anterior border of the semilunar (Gasserian)
ganglion and runs forward in the lower and outer part of the lateral wall of the
cavernous sinus (fig. 735). Leaving the middle fossa of the cranium, by passing
through the foramen rotundum, it enters the pterygo-palatine (spheno-maxillary)
fossa (fig. 734), where it is joined by twigs with the spheno-palatine ganglion;
then, changing its name, it passes forward, as the infra-orbital nerve, through the
inferior orbital (spheno-maxillary) fissure into the infra-orbital sulcus in the floor
of the orbit; continuing forward it traverses the infra-orbital canal accompanied
by the infra-orbital artery, and appears in the face, beneath the levator labii
superioris (quadratus) and above the levator anguli oris (caninus) where it divides
into four sets of terminal branches which anastomose more or less freely with
branches of the facial nerve to form the infra-orbital plexus.
Branches. — The branches of the maxillary nerve are — (a) branches given off
in the middle fossa of the cranium; (6) branches given off in the pterygo-palatine
(spheno-maxillary) fossa; (c) branches given off in the infra-orbital sulcus and
canal; and (d) terminal branches.
(a) The middle (recurrent) meningeal branch, given off in the middle fossa
of the cranium, breaks up into numerous branches which supply the dura mater
with sensory fibres, reinforce the sympathetic plexus on the middle meningeal
artery, and anastomose with the spinous nerve (the recurrent branch of the man-
dibular nerve).
(b) The branches given off in the pterygo-palatine (spheno-maxillar}^ fossa
are the spheno-palatine nerves, the zygomatic branch of the maxillary nerve, and
the posterior superior alveolar nerves.
938
THE NERVOUS SYSTEM
The spheno -palatine nerve has two or three branches which descend in the pterygo-
palatine fossa and give a small part of their fibres to the spheno-palatine (Meckel's) ganghon
(fig. 735), the larger part of their fibres passing tlirough the ganghon into its orbital, nasal,
and palatine branches. (See Spheno-p.\l.\tine Ganglion, p. 962.)
The zygomatic (orbital or temporo-malar) branch, given off from the upper surface of the
maxiUary nerve, passes forward and lateralward, and, at the end of the inferior orbital (spheno-
maxillary) fissure, passes through it into the orbit and divides into two branches, facial and
temporal.
The zygomatico -facial (malar) branch runs forward, passes through a zygomatico-orbital
foramen, then thi-ough the zygomatico-facial (malar) foramen, pierces the orbicularis palpe-
brarum, communicates with the zygomatic (malar) branch of the facial nerve, and supplies
the skin of the prominence of the cheek. The zygomatico -temporal (temporal) branch runs
upward in a groove in the lateral wall of the orbit, passes through a zygomatico-orbital foramen,
then through the zygomatico-temporal (spheno-malar) foramen, and enters the temporal fossa.
It turns around the anterior border of the temporal muscle, pierces the deep layer of the temporal
fascia, and runs backward for a short distance in the fat between the superficial and deep lam-
ellae, then, turning lateralward, it pierces the superficial lamellae about an inch above the zygoma,
anastomoses with the temporal branch of the facial nerve, and supphes the skin of the anterior
part of the temporal region.
The infra-orbital nerve, that part of the maxiUary nerve lying distal to the spheno-
palatine ganghon, enters the orbit through the inferior orbital (spheno-maxiUary) fissure,
accompanied by the infra-orbital artery, and with it passes through the infra-orbital canal
(fig. 735) to the face, where it divides into four sets of terminal branches, some of which, by
anastomoses with the branches of the facial nerve, form the infra-orbital plexus.
Three sets of superior alveolar nerves arise from the maxillary and the infra-orbital nerves,
namely, the posterior superior alveolar branches, the middle superior alveolar branch, and the
anterior superior alveolar branches.
Fig. 735. — Lateral View of the Maxillary Nerve.
Mandibular Ophthalmic MaxiUary Zygomatic
lunar- \ <•
(Gasser- V,,
ian) r ^
ganglion ^ •
y Anterior
\^,' superior
v*s^ alveolar
branches
Vidian
Spheno-palatine ganglion
Spheno-palatine nerves/
Posterior inferior nasal
Posterior superior alveolar branches
Middle superior alveolar branch
The posterior superior alveolar (dental) nerves are usually two in number, but sometimes
arise by a single trunk. They pass downward and lateralward through the pterygo-maxillary
fissure into the zygomatic fossa, where they give branches to the mucous membrane of the gums
and the posterior part of the mouth; then they enter the posterior alveolar (dental) canals and
unite with the other alveolar branches to form the superior dental plexus, through which they
give branches to the roots and pulp cavities of the molar teeth and to the mucous membrane
of the maxillary sinus (fig. 735).
(c) The branches given off in the infra-orbital sulcus and canal are the middle
and anterior superior alveolar (dental) nerves.
(i) The middle superior alveolar (dental) nerve leaves the infra-orbital nerve in the pos-
terior part of the inlVa-orliital sulcus, and, pa.ssing downward and forward in a canal in the max-
illa, it divides into terminal branches that anastomose with the other alveolar branches to form
the superior dental plexus. Through the plexus it supplies the bicuspid teeth and gives branches
to the mucous membrane of the maxillary sinus and also to the gums (fig. 735).
THE MANDIBULAR NERVE 939
(ii) The anterior superior alveolar (dental) nerve is the largest of the superior alveolar
nerves. It is given off by the infra-orbital nerve in the anterior part of the infra-orbital canal,
and passes downward in a bony canal in the anterior wall of the maxilla. After uniting with
the other alveolar nerves to form the superior dental ple.xus, it supplies the canines and the
incisors and gives branches to the mucous membrane of the maxillary sinus and the gums (fig.
735). It also gives off a nasal branch which enters the nasal fossa through a small foramen, and
supphes the mucous membrane of the anterior part of the inferior meatus and the adjacent
part of the floor of the nasal cavity.
(iii) The superior dental plexus is formed in the bony alveolar canals by the three superior
alveolar nerves. It is convex downward and anastomoses across the mid-line with the corre-
sponding plexus of the other side (fig. 735). From it arise the superior dental branches supply-
ing the superior canines and incisors, superior gingival branches supplying the gums, and also
branches to the mucous membrane of the maxiUary sinus and to the bone. On the plexus are
two gangliform enlargements, one, called the ganglion of Valentine, situated at the junction of
the middle and the posterior branches, and the other, called the ganglion of Bochdalek, at the
junction of the middle and anterior branches.
(d) The terminal branches of the maxillary nerve are the inferior palpebral,
the external and internal nasal (nasal), and the superior labial.
The inferior palpebral branches, usually two, pass upward and supply sensory fibres to all
the skin and conjunctiva of the lower eyelid (fig. 740).
The external nasal branches pass medialward under cover of the levator labii superioris
(quadratus), and supply the skin of the posterior part of the lateral aspect of the nose.
The internal nasal branches pass downward and medialward under the lateral wall of the
aose, and then turn ujnvard to supply the skin of the vestibule of the nose.
The superior labial branches, three or four in number, as a rule are larger than the palpebral
and nasal branches. They pass downward to supply the skin and mucous membrane of the
upper Up and the neighbouring part of the cheek.
(3) The Mandtbular Nerve or Third Division of the Trigeminus
The mandibular division is the largest of the three divisions of the trigeminus
(figs. 736 and 740). As a nerve, it is usually described as formed by the union of
two distinct nerves, namely, the entire masticator nerve and the large bundle
of sensory fibres derived from the semilunar (Gasserian) ganglion which pass
peripherally as the third division of the trigeminus. These two nerves remain
separate until they pass through the foramen ovale and then unite immediately
outside the skull to form a large trunk which almost directly after its formation
divides into a small anterior and a larger posterior portion. The trunk is situated
between the pterygoideus externus, laterally, and the otic ganglion and the
tensor palati medially. In front of it is the posterior border of the pterygoideus
internus, and behind it, the middle meningeal artery. Two branches arise from
the trunk of the nerve before its division, namely, the spinous (recurrent) nerve
and the nerve to the pterygoideus internus.
The spinous (recurrent) nerve, after receiving a vasomotor filament from the otic ganglion,
enters the cranium through the foramen spinosum, accompanying the middle meningeal artery,
and divides into an anterior and a posterior branch. The anterior branch communicates with
the meningeal branch of the maxillary division of the trigeminus, furnishes filaments to the
dura mater, and ends in the osseous substance of the great wing of the sphenoid. The posterior
branch traverses the petrosquamous suture and ends in the Uning membrane of the mastoid
ceUs.
The fibres going to form the neriie to the internal pterygoid muscle are almost wholly motor
fibres and therefore comprise a branch of the masticator nerve and are described as such under
the description of the masticator (fig. 737).
The anterior portion of the mendibular nerve is smaller than the posterior and
is chiefly composed of motor fibres which form branches of the masticator nerve
and supply the muscles of mastication, the temporalis, masseter, and pteryg-
oideus externus. Practically all of the sensory fibres of the anterior portion (fibres
of the mandibular nerve proper) form the buccinator (long buccal) nerve. The
latter is accompanied, in the first part of its course, by a small strand of motor or
masticator fibres which leaves it to end in the anterior part of the temporal
muscle.
The buccinator (long buccal) nerve, entirely sensory, passes between the two heads of the
external pterygoid muscle and runs do\\Tiward and forward under cover of or through the ante-
rior fibres of the temporahs to the cheek (fig. 736). As it passes forward it emerges from under
cover of the anterior border of the masseter and lies on the superficial surface of the buccinator,
where it interlaces with the buccal branches of the facial nerve and gives off filaments to supply
the superjacent skin; finally it pierces the buccinator and supphes the mucous membrane on its
940
THE NERVOUS SYSTEM
inner surface as far forward as the angle of the mouth. The fibres of the anterior deep temporal
nerve, a branch of the masticator, are frequently associated with the buccinator until the latter
has passed between the heads of the external pterygoid; then the anterior deep temporal nerve
separates from the buccinator and passes upward on the lateral surface of the upper head of the
external pterygoid.
The posterior portion of the mandibular nerve divides into three large branches.
Two of these, the lingual and the auriculo-temporal nerves, are exclusively-
sensory; the third, the inferior alveolar (dental) nerve, contains a strand of motor
fibres, the mylo-hj^oid nerve, which comprise a branch of the masticator nerve.
The lingual nerve is the most anterior branch of the mandibular nerve (figs.
736, 743) . It lies in front and to the medial side of the inferior alveolar (dental)
nerve and descends at first on the medial side of the pterygoideus externus, then
between the pterygoideus internus and the ramus of the mandible to the posterior
part of the mylohyoid ridge, where it passes off the anterior border of the ptery-
goideus internus; at this point it is situated a short distance behind the last
Fig. 736. — DisTRiBTrTioN of the Mandibular Division op the Trigeminus combined with
Branches op the Masticator Nerve. (Henle.)
Auriculo-temporal
nerve
Posterior deep
temporal nerve
Nerve to masseter
Mylo-hyoid ne
Lingual nerve
molar tooth and is covered in front by the mucous membrane of the posterior
part of the mouth cavity. After leaving the pterygoideus internus it crosses the
fibres of the superior constrictor, which are attached to the mandible, and turns
forward toward the tip of the tongue, crossing the lateral surfaces of the stylo-
glossus, hyoglossus, and genioglossus. In its com-se across the hyoglossus it
lies first above, then to the lateral side of, and finally below Wharton's duct, and
as it ascends on the genioglossus it lies on the medial side of the duct.
Communications and branches. — While it is on the medial side of the pterygoideus externus
the lingual nerve is joined, at an acute angle, by the chorda tympani (figs. 736, 743), a branch
of the glosso-palatine nerve, and as it hes between the ramus of the mandible and the pterygoid-
eus internus it is connected by a branch with the inferior alveolar (dental) nerve, and gives off
one or two small branches, the rami isthmi faucium, which are ditributed as sensory fibres to
the tonsil and the mucous membrane of the posterior part of the mouth (fig. 743).
While it is above the duct it gives a branch, which contains many sensory and visceral
motor chorda tympani fibres, to the submaxillary ganghon (.seep. 963), and it receives branches,
chiefly sympathetic, from that ganglion. A little further forward it is connected by one or two
branches, which run along the anterior border of the hyoglossus, with the hypoglossal nerve
THE MANDIBULAR NERVE 941
(fig. 743). It then gives off the sublingual nerve, which runs forward to supply the subHngual
gland and the neighbouring mucous membrane (fig. 74.3). Its terminal (lingual) branches are
derived chiefly from the glosso-palatine nerve. They pierce the muscular substance of the
tongue and are distributed to the mucous membrane of its anterior two-thu-ds. They interlace
with similar branches of the other side and with branches of the glosso-pharyngeal nerve.
The inferior alveolar (dental) nerve is the largest branch of the posterior
portion of the mandibular nerve. It commences on the medial side of the ex-
ternal pterygoid muscle and descends to the interval between the spheno-man-
dibular ligament and the ramus of the mandible, where it receives one or two
communicating branches from the lingual nerve. Opposite the middle of the
medial surface of the ramus it enters the mandibular (inferior dental) canal, ac-
companied by the inferior alveolar (dental) artery, which lies in front of the nerve,
and it runs downward and forward through the ramus and the body of the
mandible (fig. 736). At the mental foramen it divides into two parts, one of
which, the mental nerve, passes out through the mental foramen, the other, com-
monly called the incisive branch, continues forward in the canal, and supplies,
through the inferior dental plexus, the inferior canine and incisor teeth and the
corresponding regions of the gums.
Branches. — ^The branches of the inferior alveolar (dental) nerve are branches
forming the inferior dental plexus, and the mental branch. A bundle of motor
fibres, the mylohyoid nerve, a branch of the masticator nerve, is given off just
before the inferior alevolar nerve enters the mandibular canal.
The inferior dental plexus is formed by a series of branches which communicate with one
another within the bone, giving rise to a fine network. From this plexus two sets of branches
are given off: — the inferior dental branches, corresponding in number to the roots of the teeth,
enter the minute foramina of the apices of the roots and end in the pulp; the second set, the
inferior gingival branches, supply the gums.
The mental nerve is a nerve of considerable size which emerges through the mental foramen
(fig. 736). It communicates, near its exit from the bone, with branches of the facial nerve, and
then divides into three branches. The smallest branch, turning downward, divides into several
twigs, the menial branches, which supply the integument of the chin. _ The other two, inferior
labial branches, pass upward, diverging as they ascend, and divide into a number of twigs.
The stoutest twigs ramify to the mucous membrane which lines the lower hp. Other twigs
are distributed to the integument and fascia of the hp and chin.
The auriculo -temporal nerve usually arises from the posterior portion of the
mandibular nerve by two roots which embrace the middle meningeal artery and
unite behind it to form the trunk of the nerve. The trunk passes backward on
the medial aspect of the pterygoideus externus, and between the spheno-man-
dibular ligament and the temporo-mandibular articulation, lying in close relation
with the capsule of the joint. Behind the joint it enters the upper part of the
parotid gland, through which it turns upward and lateralward. It emerges from
the upper end of the gland, crosses the root of the zygoma close to the posterior
border of the superficial temporal artery, and divides into auricular and temporal
terminal branches at the level of the tragus of the pinna (fig. 736) .
Communications. — (a) Each of the two roots of the nerve receives a communication from
the otic ganglion containing fibres derived from the glosso-pharyngeal nerve. These fibres
have passed from the glosso-pharyngeal through the tympanic plex-us and the smaU superficial
petrosal nerve and through the otic ganglion.
(b) Sensory filaments pass from the auriculo-temporal nerve to the temporo-facial branch
of the facial nerve.
(c) Filaments of connection with the sympathetic plexus on the internal maxiUary artery.
(d) A communication to the inferior alveolar (dental) nerve.
Branches of the auriculo-temporal nerve. — (a) An articular branch to the temporo-man-
dibular joint, given off as the nerve lies on the medial side of the capsule.
(6) Branches to the external auditory meatus. Two branches, as a rule, are given off in
the parotid gland. They enter the meatus by passing between the cartilage and the bone and
supply the upper part of the meatus, the membrana tympani by a fine branch, and occasionally
the lower branch gives twigs to the skin of the lobule of the pinna.
(c) Parotid branches are distributed to the substance of the parotid gland. Sensory or
trigeminal fibres for the gland spring either directly from the nerve or from the communicating
branches previously given by it to the glosso-palatine nerve. The parotid branches also con-
tain filDres derived from the glosso-pharyngeal nerve which pass successively through its tym-
panic branch, the tympanic plexus, the small superficial petrosal nerve, the otic ganglion, and
the communicating twigs from the otic ganglion to the roots of the auriculo-temporal nerve.
The parotid branches are later again mentioned as concerned chiefiy with the ganglialed
cephalic plexus.
(d) The anterior auricular branches, usually two in number, are distributed to the skin
of the tragus and the upper and outer part of the pinna.
942
THE NERVOUS SYSTEM
(e) The superficial temporal branches supply the integument of the greater part of the tem-
poral region, and anastomose with the temporal branch of the facial nerve.
THE MASTICATOR NERVE (Fig. 737)
The masticator nerve (motor root or portio minor of trigeminus) . The fibres
of the masticator nerve spring from two nuclei, a slender upper or mesencephalic
nucleus and a clustered lower or chief nucleus. The fibres arising in the mesen-
cephalic nucleus descend along the lateral aspect of the nucleus to the pons as
the descending or mesencephalic root;* here they join the fibres from the chief motor
nucleus and issue with them from the side of the pons in from six to ten root
filaments. These blend to form the nerve, which is from one and a half to two
millimetres broad. At the point where it emerges from the pons the nerve is in
front of and ventral to the root of the trigeminus and it is separated from the
latter by a few of the transverse fibres of the pons which constitute the lingula oj
Wrisberg. From its superficial exit from the pons, the masticator nerve passes
upward, lateralward, and forward in the posterior fossa of the cranum, and along
the medial and anterior aspect of the trigeminus, to the mouth of Meckel's cave.
In this cavity it runs lateralward below the semilunar (Gasserian) ganglion to the
foramen ovale, through which it passes to join the mandibular division of the
Fig. 737. — Schematic Representation of the Masticator Nerve and its Branches
(in Black). Lateral view. Modified from Spalteholz.
Gasserian ganglion
Masticator nerve / External pterygoid nerve
Auriculo-temporal i
1
\
1
Internal maxillary artery\
Posterior deep
temporal nerve
Anterior deep
temporal nerve
Internal pterygoid
nerve
Masseter nerve
Buccinator nerve
External carotid artery -■'
Mylo-hyoid nerve ^ "
trigeminus immediately outside and below the base of the skull. The nerve is
purely motor and its fibres are devoted almost wholly to the muscles having to do
with mastication.
Central connections. — The nuclei of origin of the masticator nerve are connected with the
lower part of the somaesthetic area of the cerebral cortex of the opposite side by the p}Tamidal
fibres descending in the genu of the internal capsule, and they are associated with the sensory
nuclei of other cranial nerves through the reticular formation and by the medial longitudinal
fasciculus.
Branches. — Almost immediately after joining the trunk of the mandibular
nerve, most of the fibres of the masticator leave it to form the greater part of the
so-called anterior portion of the mandibular. However, one branch of masticator
fibres, the nerve to the internal pterygoid muscle, is given off from the mandibular
just before its division into anterior and posterior portions. The masticator
* Recent investigations indicate that the mesenephalic root is not wholly motor but at
least in part sensory in character, and thus belongs partly to the trigeminal nerve. (See
page 829.)
THE FACIAL NERVE 943
branches derived from the anterior portion are the deep tem-poral nerves, the
masseteric nerve, and the nerve to the external -pterygoid. One branch, the
mylo-hyoid nerve, is carried in the posterior portion of the mandibular and is given
off from its inferior alveolar branch.
The nerve to the internal pterygoid passes under cover of a dense layer of fascia derived
from an expansion of the ligamentum pterygo-spinosum, and enters the deep surface of the
muscle. Near its commencement this nerve furnishes a visceral motor root to the otic ganglion,
and small twigs to the tensor tympani and tensor palati.
The deep temporal nerves, usually two in number, posterior and anterior, pass between the
bone and the upper border of the external pterygoid muscle, and turn upward around the infra-
temporal crest of the sphenoid bone to end in the deep surface of the temporalis (fig. 736).
The posterior of the two often arises in common with the masseteric nerve. The anterior is
frequently associated with the buccinator (long buccal) nerve till the latter has passed between
the two heads of the pterygoideus externus. There is frequently a third branch, the medius,
which passes lateralward above the pterygoideus externus, and turns upward close to the bone
to enter the deep surface of that muscle. A small strand of masticator fibres accompanies the
buccinator nerve to enter and end in the anterior part of the temporal muscle.
The masseteric nerve, which frequently arises in common with the posterior deep temporal
nerve, passes between the bone and the pterygoideus externus, and accompanies the masseteric
artery through the notch of the mandible to be distributed to the masseter (fig. 736). It is
easily traced through the deeper fibres nearly to the anterior border of the masseter. As
it emerges above the pterygoideus externus it gives off a twig to the temporo-mandibular
articulation.
The nerve to the external pterygoid, after a course of about 3 mm. (an eighth of an inch),
divides into twigs which enter the deep surface of the two heads of the muscle. It is usually
adherent at its origin to the buccinator nerve.
The mylo-hyoid branch, carried in the posterior portion of the mandibular nerve, is given
off immediately before the inferior alveolar (dental) nerve enters the mandibular (inferior dental)
canal. It pierces the lower and back part of the spheno-mandibular ligament and runs down-
ward and forward in the mylo-hyoid groove between the mandible on the lateral side, and the
internal pterygoid muscle and the lateral surface of the submaxillary gland on the medial side.
In the anterior part of the digastric triangle it is continued forward between the anterior part
of the submaxillary gland and the mylo-hyoideus, and it breaks up into branches which supply
the mylo-hyoideus and the anterior belly of the digastric (fig. 736).
THE FACIAL NERVE
The facial or seventh nerve is purely motor. It is accompanied a short
distance by a bundle usually called its sensory root or the intermediate nerve.
This latter, however, on the Ijasis of its origin, distribution, and mixed instead of
sensory character, is described separately below as the glosso-palatine nerve.
It is smaller than the facial, is fused to the trunk of the facial and the ganglion
giving rise to its sensory fibres is situated upon the external genu of the facial
(figs. 738 and 741).
The fibres of the facial nerve (fig. 738) spring from a nucleus of cells situated
laterally in the reticular formation at the level of the lower pons, dorsal to the supe-
rior olive, and between the root fibres of the abducens nerve and the laterally placed
spinal tract of the trigeminus. From this nucleus the fibres of the nerve pass
medially and dorsalward to the floor of the fourth ventricle and, just under the
floor, they turn anteriorly, passing dorsal to the nucleus of the abducens (fig. 653,
p. 827). At the anterior end of this nucleus they turn sharply ventralward and
lateralward, and at this point it is claimed that fibres descending in the near-by
medial longitudinal fasciculus from the nucleus of the oculo-motor nerve of the
same side become intermingled with the fibres of the facial nerve and pass
outward with them. This, however, is uncertain. Continuing ventralwai'd
through the reticular formation the fibres of the facial emerge from the brain-stem
at the inferior border of the pons, lateral to the superficial attachment of the
abducens. At the point of its emergence, the facial nerve pierces the pia mater,
from which it receives a sheath, and then proceeds forward and lateralward
in the posterior fossa of the cranium to the internal auditory meatus, which it
enters in company with the glosso-palatine nerve and with the cochlear and
vestibular nerves. As it lies in the meatus it is situated above and in front of
the latter nerves, from which it is separated by the glosso-palatine, and it is
surrounded, together with these three nerves, by sheaths of both the arachnoid
and the dura mater and by prolongations of the subarachnoid and sub-dural
spaces. While it is still in the meatus it blends with the glosso-palatine and thus
the combined trunk is formed. At the outer end of the meatus the trunk pierces
944
THE NERVOUS SYSTEM
the arachnoid and the dura mater and enters the facial canal (aqueduct of Fallo-
pius), in which it runs forward and slightly lateralward to the hiatus Fallopii,
where it makes an angular bend, the external genu [geniculum], around the
anterior boundary of the vestibule of the inner ear; this bend is enlarged by the
adhesion of the geniculate ganglion (of the glosso-palatine) upon its anterior
border. From the geniculum the facial nerve runs backward in the facial canal
along the lateral wall of the vestibule and the medial wall of the tympanum, above
the fenestra vestibuli (ovalis), to the junction of the medial and posterior walls of
the tympanic cavity; then, bending downward, it descends in the posterior wall
to the stylo-mastoid foramen. As soon as it emerges from the stylo-mastoid
foramen it turns forward around the lateral side of the base of the styloid process.
Fig. 738.-
Fibres from oc-
ulomotor nerve
Nucleus of
abducens
Diagram of the Facial (Yellow) and Glosso-palatine Nerve (Blue).
Facial i
Glosso-
palatine
Internal
auditory
meatus
Small superficial
petrosal nerve
Fenestra vestibuli
Tympanic plexus
Chorda tympani
Communication to
auricular branch
of vagus
Fenestra cochlese
Posterior auricular
Communication to
glosso-pharyngeal
Nerve to post, belly
of diagastric
Nerve to stylo-
hyoideus
Styloid process
Tympanic branch of facial nerve
Hilary
Spheno-
palatine
ganglion
Vidian nerve
Great deep
petrosal nerve
Middle memng(
Foramen ovale artery
Otic ganglion
Spine of sphenoid
Communication fron
temporal
Chorda tympani
Communication from auricular
branch of glosso-pharyngeal
Lingual nerve
Small deep petrosal nerve
and plunges into the substance of the parotid gland, where it divides into its
cervico-facial and temporo-facial terminal divisions. Before its terminal divisions,
the nerve gives off three, and sometimes four, small branches: one, the nerve to
the stapedius muscle, before it leaves the skull, the others after it leaves the skull.
The nerve to the stapedius is given off from the facial nerve as it descends in the posterior
wall of the tympanum behind the pyramidal eminence. It is stated that filaments are also
given off from the facial to the auditory artery (probably visceral motor from the glosso-palatine)
while the nerve is passing through the internal auditory meatus.
After it leaves the skull the facial nerve gives off two or three coll terai
branches and its two terminal divisions, the temporo-facial and cervico-facial.
The collateral branches are the posterior auricular nerve, a branch to the posterior
belly of the digastric, and sometimes a lingual branch.
(1) The posterior auricular nerve is the first branch of the extracranial portion of the facial
nerve. It passes between the parotid gland and the anterior border of the sterno-mastoid
muscle and runs upward in the deep interval between the external auditory meatus and the
mastoid process. In this situation it communicates with the auricular branch of the vagus.
It supplies the auricularis posterior, sends a slender twig upward to the am-ioularis superior,
and ends in a long slender branch, the occipital branch, which passes backward to supply the
occipitalis muscle. It also receives filaments from the small occipital and great auricular nerves,
and supplies the intrinsic muscles of the auricle (pinna).
(2) The nerve to the posterior belly of the digastric arises from the facial nerve close to
the stylo-mastoid foramen and enters the muscle near its centre, or sometimes near its origin.
It usually gives off two branches: the nerve to the stylo-hyoid, which sometimes arises directly
from the facial nerve and passes to the upper part of the muscle that it supplies, and the anas-
tomotic branch, which joins the glosso-pharyngeal nerve below its petrous ganglion.
(3) The lingual branch, first described by CruveiUiier, is not commonly present. It arises
a little below the nerve to the stylo-hyoideus and runs downward and medialward to the base
of the tongue. In its course it passes to the medial sides of the stylo-glossus and stylo-pharyn-
THE FACIAL NERVE
945
geus, and runs downward along the anterior border of the latter muscle to the wall of the
pharynx. It pierces the superior constrictor, insinuates itself between the tonsil and the anterior
piUar of the fauces, and it is stated that it gives filaments to the base of the tongue and to the
stylo-glossus and glosso-palatinus (palato-glossus) muscles.
The terminal divisions. — In the substance of the parotid gland the two
terminal divisions of the facial nerve he superficial to the external carotid artery
and to the posterior facial (temporo-maxillary) vein. The way in which these
terminal divisions give off their branches varies much in different subjects and
often on the opposite sides of the same subject. One of the more common forms
is here described.
The temporo-facial or upper division runs upward and forward, and, after
receiving communicating twigs from the auriculo-temporal nerve, gives off tem-
poral and zygomatic (malar) branches. The cervico -facial or lower division runs
downward and forward, receives branches from the great auricular nerve, and
Fig. 739. — The Right Facial Nekvb, within the Skull, and the Relations op the
Glosso-palatine and Glosso-pharyngeal Nerves with the Tympanic and
Internal Carotid Plexuses. (From Sobotta's Atlas, modified.)
Tensor tympani muscle Deep petrosal nerve
Auditory (Eustachian) tubi
Superior carotico-tympanic n.
Great superficial petrosal n
Ramus anastomotic with tympanic plexus
Geniculate gangli'
Glosso-palatine n
Stapes Facial n
Tympanic sinus
Stapedius muscl
stapedius,
nerve
Maxillary nerve (lifted)
' Nerve of pterygoid canal
(Vidian)
Spheno-palatine ganglion
Mastoid cells
Chorda tympani
Stylo-mastoid foramen
Tympanic
Petrosal ganglion of glosso
pharyngeal ^
Nodosal ganghon of vagus .
Superior cervical sympathetic ganghon
gives off — (1) buccal branches, comprising what have been called infraorbital
and buccal branches; (2) the marginal mandibular (supra-mandibular) branch;
and (3) the ramus colli (infra-mandibular branch). These branches from the
two terminal divisions anastomose freely to form the parotid plexus (pes anserinus).
The temporal branches passing upward communicate freely with each other and with the
zygomatic branches. They also communicate with the zygomatico-temporal branch of the
zygomatic nerve (the orbital branch of the maxillary nerve) and with the supra-orbital nerve.
They supply the frontalis, orbicularis oouli, corrugator supercilii, and auricularis anterior and
superior (fig. 740).
The zygomatic (malar) branches passing upward and forward, communicate with the buccal
branches of the facial nerve; with the zygomatico-facial branch of the zygomatic nerve (the
orbital branch of the maxillary nerve) ; with the supraorbital and lacrimal branches of the oph-
thalmic nerve, and with the palpebral twigs of the maxillary. They supply both ej'ehds, the
orbicularis oculi, and tlie zygomaticus (fig. 740).
The buccal (infra-orbital and buccal) branches arise sometimes from the lower terminal
division and sometimes from both the upper and the lower terminal divisions. The buccal
branches, passing forward upon the masseter and underneath the zygomaticus and quadratus
labii superioris, interlace with the zygomatic and marginal mandibular (supra-mandibular)
branches of the facial nerve, with the buccinator (long buccal) branch of the trigeminus, and with
the terminal branches of the maxillary nerve, forming with the last-named nerve the infra-
orbital plexus. They supply the zygomaticus, risorius, quadratus labii superioris, caninus.
946
THE NERVOUS SYSTEM
buccinator, inoisivi, orbicularis oris, triangularis, quadratus labii inferioris, and the muscles
of the nose (fig. 740).
The marginal mandibular (supra-mandibular) branch, passing downward and forward under
cover of the risorius and the depressors of the lower hp, commimicates with the buccal branches
and with the ramus colli of the facial nerve, and with the mental branch of the mandibular nerve.
It supplies the quadratus labii inferioris and mentalis.
The ramus colli (infra-mandibular branch) runs downward and forward under cover of
the platysma, which muscle it innervates (fig. 740). Beneath the platysma it forms one or
more communicating loops, near its commencement, with the great auricular nerve, and longer
loops, lower down, with the superficial cervical nerve.
Central connections. — The nucleus of origin of the facial in the rhombencephalon includes
an anterior and a posterior group of cells which give rise respectively to its upper and lower ter-
minal divisions. They are associated with the somaesthetic area (lower third of the anterior
central gyrus) by way of the pyramidal fasciculi of the opposite and same sides, and with the
nuclei of the other cranial nerves, including the nucleus of termination of the glosso-palatine, by
way of the reticular formation and the medial longitudinal fasciculus.
Fig. 740. — S"0pekpicial_ Distribution of the Facial and other Nerves of the Head.
(After Hirschfield and Leveill(5.)
Supra-orbital
Palpebral twig of
lacrimal
Infratrochlear
Temporal braacli
of facial
Zygomatic br.
of facial
Maxillary div.
of trigeminus
Posterior auricular
Auriculo-temporal
Lesser occipital
Great auricular
Cervical cutaneous
GLOSSO-PALATINE NERVE
The glosso-palatine nerve (sensory root or pars intermedia of facial, nerve of
Wrisberg) contains both sen.sory and motor fibres. While it has a separate
attachment to the medulla, it courses in close company with the facial and, in
the internal auditory meatus, it is involved in the same sheath with the facial,
which relation is maintained by its larger part thence through the facial canal till
a short distance above the stylo-mastoid foramen. Here this larger part leaves
the trunk of the facial as the chorda tympani nerve. The origin, central connec-
tions and peripheral distribution of the glosso-palatine are similar to those of the
THE GLOSSO-PALATINE NERVE 947
glosso-pharyngeal nerve and suggest that it may be considered an aberrant portion
of that nerve.
The sensory portion is much greater than the motor. Its fibres arise from cells
situated in the geniculate ganglion which thus corresponds to a spinal ganglion.
The central processes from these cells pass medialward in the facial canal (aqueduct
of Fallopius) enclosed in the sheath of the facial nerve, which they leave in passing
through the internal auditory meatus, to turn slightly downward in the posterior
fossa of the cranium and enter the medulla at the inferior border of the pons, be-
tween the attachments of the facial and vestibular nerves. They com-se through
the reticular formation of the medulla, medianward and dorsalward to terminate
about cells which comprise a superior extension of the nucleus of termination
of the glosso-pharyngeal nerve (nucleus of ala cmerea). The peripheral processes
from the geniculate ganglion are distributed chiefly to the epithelium covering the
soft palate, portions of the glosso-palatine arches, and the anterior two thirds of
the tongue.
The geniculate ganglion is so named from the fact that it is embedded upon the
anterior border of the external genu {geniculum, great bend) of the facial nerve,
behind the hiatus Fallopii. It is somewhat triangular in form. From its supero-
medial angle leave the central processes of its cells, the root of the nerve; from its
infero-lateral angle leave the fibres which later leave the sheath of the facial as the
chorda tympani, and its anterior angle is connected with the great superficial
petrosal nerve (figs. 738 and 741). The geniculate ganglion contains a rel-
atively large number of cell-bodies of sympathetic neurones many of whose
processes run in this latter nerve, a relation mentioned below with the gangliated
cephalic plexus.
The motor portion of the glosso-palatine consists for the most part of visceral
efferent fibres, chiefly secretory. These arise in the medulla oblongata from a
small group of cells scattered in the reticular formation dorso-medial to the
nucleus of the facial and in line with the dorsal efferent nucleus of the vagus
below. It is called the salivaiory nucleus. The fibres course ventralward and
lateralward to their exit, mingle with the entering sensory fibres of the glosso-
palatine in the sheath of the facial and, through the branches of the glosso-
palatine, pass to terminate in sympathetic ganglia of the head, large and small.
These gangfia send axones which terminate in the smooth muscle of vessels and
about the cells of the glands of the lingual and palatine mucous membrane and of
the salivary glands proper. Some of the motor fibres of the nerve terminate in
contact with the sympathetic cells remaining in the geniculate ganglion and which
give rise to sympathetic fibres issuing from it. Most of the motor fibres pass
into the great superficial petrosal nerve and the chorda tympani to terminate in
(chiefly) or pass through the spheno-palatine and submaxillary ganglia re-
spectivelJ^ Some may pass by the geniculo-tympanic branch and tympanic
plexus to end in the otic ganghon. Many no doubt end in the smafler ganglia
involved in the various sympathetic plexuses. It is suggested that the motor
part carries secretory impulses destined chiefly for the sub-maxillary and sublin-
gual glands. A small gangliated plexus on the capsule of the medial side of the
parotid gland has been frequently dissected and found to communicate freely with
twigs from the facial nerve and twigs concerned with the trigeminus. It is
possible that some glosso-palatine visceral motor fibres terminate in these ganglia
for secretory impulses to the parotid gland as well.
Central connections. — The nucleus of termination of tlie glosso-palatine nerve (superior
extension of the nucleus of termination of the sensory portion of the glosso-pharyngeal) is
associated with the somffisthetic area of the cerebral cortex of the opposite and same sides by
way of the medial lemniscus, and with the saUvatory nucleus and motor nuclei of other cranial
nerves by way of the reticular formation and medial longitudinal fasciculus. The nucleus of
origin of the motor portion (sahvatory nucleus) may be associated not only with the nucleus
of termination of the sensory part, but with the nuclei of termination of other cranial nerves,
and perhaps with the motor area of the cortex of the opposite side by way of the pjTamidal
fascicuh.
Branches and communications. — Aside from its two or three small collateral
twigs of communication, the fibres of the glosso-palatine course in two main
branches or nerves: (1) the great superficial petrosal nerve, continued through
the Vidian nerve, and extended through and beyond the spheno-palatine ganglion
as the palatine portion of the glosso-palatine (palatine nerve) ; (2) the chorda tym-
948
THE NERVOUS SYSTEM
pani, the larger branch, which extends to join and contribute its quota of fibres
to the lingual nerve, a branch of the trigeminus.
In the internal auditory meatus, the glosso-palatine gives two delicate
collaterals to the vestibular nerve, and some filaments (visceral motor probably)
are described as given to the auditory artery and to the temporal bone.
A small geniculo-tympanic branch is given, in the facial canal, from the geniculate ganglion
to the small superficial petrosal nerve. This is probably aU visceral motor and sympathetic
fibres (fig. 741).
There may occur a twig arising from or near the beginning of the chorda tympani and form-
ing a cormnunicatio?i vnih the auricular branch of the vagus.
A large part of the great superficial petrosal nerve is formed of glosso-palatine fibres.
This nerve is further described below in its relation to the spheno-palatine ganglion. It arises
from the anterior angle of the geniculate ganglion, enters the middle fossa of the cranium through
Fig. 741. — Diagram of the Glosso-palatine Nekve (Black) and the Relations op the
Gangliated Cephalic Plexus to otheb Cbanial Nebves. (After Bean.) Broken Mnes,
motor; continuous hues, S3'mpathetic; glosso-palatine in solid black. Medial view. Left
side.
Superior cervical
sympathetic gangli
Ciliary
ganglion
-- Ophthalmic nerve
kw "\ X Maxillary nerve
i\i) - - -V^N.^-- Mandibular nerve
-\V -^V^V^^^-^-v^ Great deep
jV ' \ ^^M~^ petrosal nerve
'^\.\N^^^^~- Sphenopalatine
'A\'\\\rl^ ganglion
Palatine portion of
glosso-palatine nerve
Nerve of pterygoid
canal (Vidian nerve)
Otic ganglion
Middle meningeal
. , artery
( Submaxillary ganglion
External maxillary
artery
the hiatus FaUopii, and passes beneath the semilunar ganglion into the foramen lacerum, where
it joins with the great deep petrosal nerve to form the Vidian nerve. Thence the glosso-
palatine portion passes over or through the spheno-palatine ganglion to form the greater part
of the small and middle palatine nerves which are distributed to the epithelium and glands of
the soft palate, some of the sensory fibres probably terminating in the taste organs found there;
the remainder serving as fibres of general sensibility. It is probable that most of the motor
glosso-palatine fibres in the great superficial petrosal nerve terminate in the spheno-palatine
ganglion; some may pass to the carotid plexus and to smaU gangUa elsewhere.
The chorda tympani consists to a very large extent of sensory fibres (peripheral processes
of the cells of the geniculate ganglion), but it also contains motor fibres and is thus also a mixed
nerve. It leaves the trunk of the facial nerve a short distance above the stylo-mastoid foramen,
and pursues a slightly recurrent course upward and forward in the canaliculus chorda tympani
(iter chordae posterius), a minute canal in the posterior wall of the tympanic cavity, and it
THE VESTIBULAR NERVE
949
enters that cavity close to the posterior border of the membrana tympani. It crosses the cavity,
running on the medial surface of the tympanic membrane at the junction of its upper and middle
thirds, covered by the mucous membrane lining the tympanic cavity, and passes to the medial
Bide of the manubi-ium of the malleus above the tendon of the tensor tympani. It leaves the
tympanic cavity and passes to the base of the skull through a smaU foramen (the iter chordae
anterius) at the medial end of the petro-tympanic (Glaserian) fissure. At the base of the skull
it inclines downward and forward on the medial side of the spine of the sphenoid, which it
frequently grooves, and, on the medial side of the pterygoideus externus, it joins the posterior
border of the hngual nerve at an acute angle. Some of its fibres (motor chiefly) leave the lingual
nerve and pass to the sub-maxillary ganglion, and others (sensory) continue forward to the
tongue, where, in company with fibres of the lingual nerve, they terminate in the epithehum
covering the anterior two-thirds of the tongue. Some probably serve to convey sensations of
taste, most of them are fibres of general sensibility. Before it joins the lingual nerve the chorda
tympani receives a communicating twig from the otic ganglion (figs. 738, 741).
THE VESTIBULAR NERVE
The vestibular nerve is purely sensory. With the peripheral processes of its
cells of origin terminating in the neuro-epithelium of the semicircular canals and
Fig. 742. — The Left Membeanoits Labyrinth of a Human Fcetus-of lO Weeks (30 mm.),
Lateral Aspect. Vestibular ganglion and nerve, red; cochlear nerve, yellow. (Streeter,
American Journal of Anatomy.)
a. 3omm. lateral.
the vestibule, and their central processes conveying impulses which are dis-
tributed to the gray substance of the cerebellum and spinal cord, the nerve com-
prises a most important part of the apparatus for the equilibration of the body.
It has been customary to describe the vestibular [radix vestibularis] and the coch-
lear [radix cochlearis] nerves combined as the acoustic (auditory) or eighth cranial
nerve. While the two are blended in a common sheath from near the medulla to
the bottom of the internal auditory meatus, they are likewise partty enclosed in
the same sheath with the facial and glosso-palatine nerves and the internal audi-
tory artery which accompany them in this meatus. At the bottom of the meatus
950 THE NERVOUS SYSTEM
the vestibular and the cochlear are separate; they are separate at their entrance
into the lateral aspect of the medulla oblongata; and their central connections,
peripheral distributions and functions are different.
The vestibular nerve arises as processes of the cells of the vestibular ganglion
(ganglion of Scarpa), situated upon and blended within the nerve at the bottom
of the internal auditory meatus. Unlike the ordinary spinal ganglion, to which
it corresponds, the cells of the vestibular ganglion retain an embryonal, "bipolar,"
form. The central processes course v/ith the cochlear nerve in the internal
auditory meatus medialward, caudad and slightly downward, inferior to the
accompanying' if acial and glosso-palatine nerves, and, arching ventrally around
the restiform body, they enter the medulla at the inferior border of the pons, lat-
eral to the glosso-palatine and facial and medial to the entrance of the cochlear
nerve. They find their nucleus of termination spread in the floor of the fourth
ventricle and grouped as the median, the lateral (Deiters'), the superior, and the
nucleus of the spinal root of the vestibular nei've. In the internal auditory mea-
tus, the vestibular nerve is connected by two small filaments of fibres with the
glosso-palatine nerve. These are either visceral motor fibres for the vessels of the
domain of the vestibular or are aberrant fibres which course only temporarily
with the vestibular and return to the glosso-palatine.
The peripheral processes of the cells of the vestibular ganglion terminate in the
specialised or neuro-epithelium comprising the maculm in the sacculus and the
utriculus and the cristce in the ampullte of the three semicircular canals. Thus
there are five terminal branches of the nerve. None of its fibres terminates in the
cochlea. The vestibular ganglion has a lobar form, one lobe giving rise to a
superior utriculo-ampuUar division which divides into three terminal branches; the
other giving a sacculo-ampuUar division which gives two terminals.
The superior or utriculo -ampullar branch divides into the following terminal
branches: —
(1) The utricular branch passes through the superior macula cribrosa of the vestibule
and terminates in the macula acustica of the utriculus.
(2) Accompanying the utricular branch through the superior macula cribrosa is a branch,
the superior ampuUar, to the crista acustica of the ampulla of the superior semicircular canal,
and —
(3) A similar branch, the lateral ampullar, to the ampulla of the lateral semicircular canal.
The inferior or saccule -ampullar branch accompanies the cochlear nerve a
short distance further than the superior, and divides into —
(4) A branch, the posterior ampullar, which passes through the foramen singulare and the
inferior macula cribrosa and tormiiiatcs in the ampulla of the posterior semicircular canal, and —
(5) A branch, the saccular, which passes through the middle macula cribrosa and terminates
in the macula acustica of the sacculus.
The central connections of the vestibular nerve are described in detail on pages 823, 824.
Its large nucleus of termination, spread through the area acustica in the floor of the fourth
ventricle, and divided into four sub-nuclei, is associated with the nuclei fastigii, globosus, and
emboliformis of the cerebellum, with the nuclei of the eye-moving nerves, with the spinal cord,
and probably with the cerebral corte.x.
THE COCHLEAR OR AUDITORY NERVE
The fibres of the cochlear nerve are distributed to the organ of Corti in the
cochlea, and so are considered as comprising the auditory nerve proper. They
arise from the long, coiled spiral ganglion of the cochlea, the cells of which, like
those of the vestibular ganglion, are bipolar. The peripheral processes of these
cehs are shorter than those of the vestibular ganglion. They terminate about the
auditory or hair-ceUs of the organ of Corti and thus collect impulses aroused by
stimuli affecting these cells. The central processes of the ganglion cells continue
through the modiolar canal and the tractus spiralis foraminosus of the cochlea,
and thence, joining the vestibular nerve through the internal auditory meatus,
accompanying the facial nerve and internal auditory artery, they course medial-
ward and downward, approach and enclasp the restiform body (fig. 665) and
enter the lateral aspect of brain-stem to terminate in their dorsal and ventral
nuclei. A description of these nuclei and the further central connections of the
cochlea with the superior olive, the nuclei of the eye-moving nerves, the inferior
quadrigeminate bodies, the medial geniculate bodies, and with the cerebellum
and temporal lobes of the cerebral hemispheres is given on pages 824, 839.
THE GLOSSO-PHARYNGEAL NERVE 951
The cochlear nerve is separate from the vestibular at the bottom of the internal
auditory meatus and at its entrance into the medulla.
THE GLOSSO-PHARYNGEAL NERVE
The glosso-pharyngeal or ninth cranial nerves are mixed nerves and each is
attached to the medulla by several roots which enter the posterolateral sulcus,
dorsal to the anterior end of the olivary body and in direct line with the facial
nerve.
The filaments, when traced lateralward, are seen to blend, in front of the
flocculus, into a trunlc which hes in front of the vagus nerve, but which passes
through a separate opening through the arachnoid and the dura mater and through
the jugular foramen. In the foramen this trunk hes in front, and lateral to the
vagus nerve in a groove on the petrous portion of the temporal bone; and in this
situation two ganglia are interposed in it, a superior or jugular, and an inferior
or petrosal. After it emerges from the jugular foramen the glosso-pharyngeal
nerve descends at first between the internal carotid artery and the internal jugular
vein and to the lateral side of the vagus; then, bending forward and medialward,
it descends medial to the styloid process and the muscles arising from it, and
turning around the lower border of the stylo-pharyngeus it passes between the
internal and the external carotid arteries, crosses the superficial surface of the
stylo-pharyngeus, and runs forward and upward medial to the hyoglossus muscle
and across the middle constrictor and the stylo-hyoid ligament, to the base of the
tongue (fig. 743).
Ganglia. — The superior or jugular ganglion (ganglion of Ehrenritter), is a small,
ovoid, reddish-grey body which lies on the back part of the nerve-trunk in the
upper part of the jugular foramen. No branches arise from it. It is sometimes
continuous with the petrosal ganglion or it may be absent.
The inferior or petrosal ganglion, (ganglion of Andersch), is an ovoid grey
body which lies in the lower part of the jugular foramen, and appears to include
all the fibres of the nerve.
Branches and communications. — (1) The petrosal ganglion is connected with the superior
cervical ganglion of the sympathetic by a fine filament.
(2) It also has a filament of communication with the auricular branch of the vagus which
varies inversely in size with the latter branch and sometimes entirely replaces it. This filament
may be absent.
(3) An inconstant communication with the ganglion of the root of the vagus.
(4) A short distance below the petrous gangUon the trunk of the nerve is connected by a
twig with that branch of the facial nerve which supplies the posterior belly of the digastric
muscle. There is also a small twig (probalily sensdryl to the stylo-hyoid.
(5) From the petrosal ganglion : The tympanic branch (nerve of Jacobson) arises from the
petrosal ganglion and passes through a foramen, which lies in the ridge of bone between the car-
otid canal and the jugular fossa, into the tympanic canahculus (Jacobson's canal), where it is
surrounded by a small, fusiform mass of vascular tissue, the iniumesceniia tympanica. After
traversing the tympanic canaliculus it enters the tympanum at the junction of its lower and
medial walls, and, ascending on the medial wall, breaks up into a number of branches which take
part in the formation of the tympanic plexus on the surface of the promontory (fig. 739). The
continuation of the nerve emerges from this plexus as the small superficial petrosal nerve, which
runs through a small canal in the petrous portion of the temporal bone, beneath the canal for the
tensor tympani, and appears in the middle fossa of the cranium through a foramen which lies
in front of the hiatus Fallopii. From this foramen it runs forward and passes through the fora-
men ovale, the canaliculus innominatus, or the spheno-petrosal suture, and enters the zygomatic
fossa, where it joins the otic ganghon. While it is in tlie canal in the temporal bone the small
superficial petrosal nerve is joined by a geniculo-tympanic branch from the geniculate gangUon
of the glosso-palatine nerve.
(6) Branches from the tympanic plexus : — (a) The tubal branch (ramus tubae), a dehcate
branch, which runs forward to the mucous membrane of the tuba auditiva (Eustachian tube)
and sends filaments backward to the region of the fenestra vestibuli (ovahs) and the fenestra
cochleaj (rotunda).
(6) The superior and inferior carotico-tympanic (carotid) branches pass medianward to
the internal carotid plexus (fig. 741).
The above communications carry fibres almost entirely concerned with the sympathetic
plexuses of the head and they will be again mentioned below with the gangUated cephalic plexus.
Branches from the trunk of the nerve : — (1) Pharyngeal branches, which may be two or
three in number, arise from the nerve a short distance below the petrosal ganglion. The prin-
cipal and most constant of these passes on the lateral side of the internal carotid artery, and
after a very short independent course joins with the pharyngeal branch of the vagus and with
branches of the superior cervical ganglion to form the pharyngeal plexus (fig. 743).
952 . THE NERVOUS SYSTEM
(2) A muscular brancli is distributed to the stylo-pharyngeus muscle. This branch re-
ceives a communication from the facial nerve (fig. 743).
(3) The tonsillar branches are a number of small twigs which arise under cover of the hyo-
glossus muscle; they proceed to the tonsil, around which they form a plexus, the circulus
tonsillaris. From this plexus fine twigs proceed to the glosso-palatine arches (pillars of the
fauces) and to the soft palate.
(4) The lingual branches are the terminal branches of the nerve and supply the mucous
membrane of the posterior half of the dorsum of the tongue, where, chiefly as taste-fibres, they
are distributed to the vallate papillae. Some small twigs pass backward to the follicular glands of
the tongue, and to the anterior surface of the epiglottis. Other twigs are distributed around the
foramen officum, where they communicate with the corresponding twigs of the opposite side.
The sensory fibres. — The sensory fibres of the glosso-pharyngeal nerve spring from the supe-
rior and petrosal ganglia and pass peripherally and centrally. The peripheral processes of the
ganglion cells are those which are distributed to the mucous membrane (taste-buds) of the tongue
and pharynx, and the central processes pass medialward to the medulla. In the medulla they
pass dorsalward and medianward through the reticular formation and, bifurcating into ascend-
ing and descending branches, they end in the nucleus of termination of the glosso-pharyngeal
nerve, that is, in the superior part of the nucleus alae cinereae and in the nucleus of the tractus
solitarius.
The motor fibres arise from the nucleus ambiguus in the lateral funiculus of the medulla,
in fine with the nucleus of origin of the facial nerve. From this nucleus they pass at first
dorsalward and then, turning lateralward, they emerge and join the sensory fibres and run with
them in the trunk of the nerve (fig. 646).
Van Gehuchten's observations point to the conclusion that one motor nucleus of the glosso-
pharyngeal nerve is separate from and Kes above and to the medial side of the nucleus ambiguus,
and that a portion of the nucleus of the ala cinerea is also a motor nucleus common to the
glosso-pharyngeal and vagus nerves. It is quite probable that the former motor nucleus is
that now considered as the dorsal motor nucleus of the vagus. An unknown proportion of
the motor fibres are visceral motor and course in the various communications of the glosso-
phar3mgeal nerve with cephalic plexus.
Central connections. — The nuclei of termination of the glosso-pharyngeal nerve are asso-
ciated with the motor nuclei of other cranial nerves by the medial longitudinal fasciculus, and
with the somaesthetic area of the cortex cerebri of the opposite side by the medial lemniscus
(fillet). The motor nucleus of the nerve is associated with the somaesthetic area by the pyra-
midal fibres.
THE HYPOGLOSSAL NERVE
The hypoglossal nerves are exclusively motor; they supply the genio-hyoidei
and the extrinsic and intrinsic muscles of the tongue except the glosso-palatini.
They are usually designated as the twelfth pair of cranial nerves. The fibres of
each nerve issue from the cells of an elongated nucleus which lies in the floor
of the central canal in the lower half of the medulla and in the floor of the fourth
ventricle in the upper half beneath the trigonum hypoglossi. This nucleus is the
upward continuation of the ventro-medial group of cells of the ventral horn of the
spinal cord. From their origin the fibres run ventralward and somewhat lateral-
ward, probably joined in the medulla by a few fibres from the nucleus ambiguus
which is a segment of the upward prolongation of the lateral group of cells of the
ventral horn. The conjoined fibres issue from the medulla in the sulcus between
the pyramid and the olivary body, in a series of from ten to sixteen root filaments,
which pierce the pia mater and unite with each other to form two bundles (fig.
731). These bundles pass forward and lateralward to the hypoglossal (anterior
condyloid) foramen, where they pierce the arachnoid and dura mater. In the
outer part of the foramen the two bundles unite to form the trunk of the nerve.
At its commencement, at the base of the skull, the trunk of the hypoglossus lies on
the medial side of the vagus, but as it descends in the neck it turns gradually
around the dorsal and the lateral side of the latter nerve, lying between it and the
internal jugular vein, and a little above the level of the hyoid bone it bends for-
ward, and crosses lateral to the internal carotid artery, the root of origin of the
occipital artery, the external carotid, and the loop formed by the first part of the
lingual artery (fig. 743). After crossing the lingual artery it proceeds forward
on the lateral svnface of the hyo-glossus, crossing to the medial side of the posterior
belly of the digastric, and the stylo-hyoid muscles. It disappears in the anterior
part of the submaxillary region between the mylo-hyoid and the hyo-glossus, and
divides into its terminal branches between the latter muscle and the genio-glossus.
As it descends in the neck the trunk lies deeply between the internal jugular vein and
the internal carotid artery under cover of the parotid gland, the styloid muscles, and the pos-
terior beUy of the digastric, and it is crossed superficially by the posterior auricular and the occip-
ital arteries. As it turns forward around the root of the occipital artery the sterno-mastoid
branch of that vessel hooks downward across the nerve, and as it turns forward on the hyo-
THE HYPOGLOSSAL NERVE
953
glossus muscle it lies immediately above the ranine vein. It is crossed by the posterior belly
of the digastric and the stylo-hyoid muscle, and it is covered superficially, behind the mylo-
hyoid, by the lower part of the submaxillary gland.
Communications. — The hypoglossus is connected with the first cervical gan-
glion of the sympathetic, with the ganglion nodosum of the vagus, with the loop
between the first and second cervical nerves, and with the lingual nerve; the
latter communication is established along the anterior border of the hyo-glossus
muscle (figs. 743 and 744).
Terminal branches. — These include (1) a meningeal branch; (2) branches from
the cervical plexus; and (3) branches from the hypoglossus proper.
(1) A meningeal branch, frequently represented by two filaments, is given off in the hypo-
glossal (anterior condyloid) canal. It passes backward into the posterior fossa of the cranium
and is distributed to the dura mater. It was believed at one time that the fibres of the meningeal
branch were derived from the lingual nerve, but it is now deemed more probable that they are
either sensory or visceral motor fibres from the cervical nerves, or from the vagus.
Fig. 743. — The Hypoglossal, Glosso-phartngeal, and Lingual Nerves. (Spalteholz.)
Ganglion nodosum
Cut surface of the styloid
process ._-
Internal jugular
vein
Facial nerve
(cut off)
Spinal accessory
(external branch )
Transverse proc-
ess of atlas
Anterior branch
of first cervical
Glosso- Internal
pharyngeal carotid Semilunar
nerve artery ganglion
^
Pharyn-
r Of vagus
Of glos-
branches | fy^l^l{
Anterior branch of
second cervical nerve
'Stylo -pharyngeal
branch
Stylo-pharyngeus
Hypoglossal nerve
External carotid artery
Anterior branch of
third cervical nerve
Descendeus cervicalis
(hypoglossi)
Anterior branch of fourth
cervical nerve
Steruo-mastoideus i
Ansa cervicalis
(hypoglossi)
Ophthalmic
_ Maxillary
nerve
' Mandibular
— nerve
Lateral plate
— of pterygoid
process
,, Chorda
tympani
^ensor veli
palatini
Lingual nerve
Buccinator
Branches to
isthmus of
fauces
ff- Stylo-
glossus
Vagus i
Lingual
branches of
lingual nerve
Sublingual
nerve
Anastomotic
"^N-.branch to
., hypoglossal
Genio-glossus
Lingual branches
\ \ of hypoglossal
N Genio-liyoideus
Hyoglossus
Thyreo-hyoid branch
Lingual artery
Phrenic nerve ~
Superior thyreoid artery
Thyreo-hyoideus
Branch to the sterno-hyoideus
Common carotid artery
(2) Branches which consist of fibres derived from the cervical plexus. — The descendens
cervicalis (hypoglossi) and the muscular twig to the thyi'eo-hyoid muscle, though apparently
arising from the hypoglossal nerve, consists entirely of fibres which have passed into the hypo-
glossal nerve from the loop between the first two cervical nerves. Therefore, neither of them
are branches of the hypoglossus proper. (See fig. 752.)
(a) The descendens cervicalis (hypoglossi) parts company with the hypoglossus at the point
where the latter hooks around the occipital artery (fig. 743). It runs downward and slightly
medialward on the sheath of the great vessels (occasionally within the sheath), and is joined
at a variable level by branches from the second and third cervical nerves, forming with them a
loop, the cervical loop [ansa hypoglossi] (fig. 743). The cervical loop rnay be placed at any level
from a point immediately below the occipital artery to about four centinietres above the sternum.
From this loop aU the muscles attached to the hyoid bone are supphed. A twig to the anterior
belly of the omo-hyoid arises from the descendens cervicalis in the upper part of its course.
The nerves which supply the sterno-hyoid, sterno-thyreoid, and posterior belly of the omo-
hyoid are given off by the cervical loop. Twigs from the first two nerves pass downward in
the muscles behind the manubrium sterni and •in rare cases communicate with the phrenic
954 THE NERVOUS SYSTEM
nerve within the thorax. The nerve to the posterior belly of the omo-hyoid runs in a loop of
the cervical fascia below the central tendon of the muscle.
(b) The nerve to the thyreo-hyoid leaves the hypoglossus near the tip of the great cornu of
the hyoid bone, and runs obhquely downward and medialward to reach the muscle. AU the
fibres in (a) and (b) are derived from the first, second and third cervical nerves.
(c) The nerve to the genio-hyoid arises under cover of the mylo-hyoid, where loops are
formed with the lingual nerve from which loops branches pass into the muscle. It probably
contains some true h}fpoglossal fibres.
(3) The branches of the hypoglossus proper, the rami linguales, supply the stylo-glossus,
hj'O-glossus, genio-glossus, and the intrinsic muscular fibres of the tongue.
The nerve to the stylo-glossus is given off near the posterior border of the hyo-glossus.
It pierces the st3'lo-glossus, and its fibres pursue a more or less recurrent course within the muscle.
The nerves to the hyo-glossus are several twigs which are supphed to the muscle as the
hypoglossal nerve crosses it.
The nerve to the genio-glossus arises under cover of the mylo-hyoid in common with the ter-
minal branches to the intrinsic muscles of the tongue. It communicates freely with branches of
the lingual, forming long loops which lie on the genio-glossus. From these loops twigs pass into
the genio-glossus and into the muscular substance of the tongue.
Central connections. — The nucleus of origin of the hypoglossus is associated with the som-
Eesthetic area (operculum) of the cortex cerebri of the opposite side by the pyramidal fibres,
and it is connected with the sensory nuclei (nuclei of termination) of other cranial nerves by
way of the reticular formation and the medial longitudinal fasciculus.
THE VAGUS OR PNEUMOGASTRIC NERVE
The vagus or pneumogastric nerves are the longest of the cranial nerves, and
they are remarkable for their almost vertical course, their asymmetry, and their
extensive distribution, for, in addition to supplying the lung and stomach, as the
name ' pneumo-gastric ' indicates, each nerve gives branches to the external ear,
the pharynx, the larynx, the trachea, the oesophagus, the heart, and the abdominal
viscera. They are commonly referred to as the tenth pair of cranial nerves.
Each nerve is attached to the side of the medulla, in the postero-lateral sulcus,
dorsal to the olivary body, by from twelve to fifteen root filaments which are in
linear series with the filaments of the glosso-pharyngeal nerve. The filaments
contain both sensory and motor fibres. They pierce the pia mater, from which
they receive sheaths, and, traced outward, they pass into the posterior fossa of the
cranium toward the jugular foramen and unite to form the trunk of the nerve,
which passes through openings in the arachnoid and the dtira mater which are
common to it and to the spinal accessory nerve. In the jugular foramen a small
spherical ganglion, the jugular ganglion (ganglion of the root) , is interposed in the
trunk which here turns at right angles to its former course and descends through
the neck. As it leaves the jugular foramen it is joined by the internal or accessory
portion of the spinal accessory nerve, and immediately below this junction it
enters a large ovoid ganglion, the ganglio7i nodosum or ganglion of the trimk (fig.
743). As it descends through the neck the nerve passes ventral and somewhat
lateral to the superior cervical sympathetic ganglion, and in front of the longus
capitis and longus colh, from which it is separated by the prevertebral fascia. In
the upper part of the neck it is placed between the internal carotid artery and the
internal jugular vein, and on a plane dorsal to them, the artery being ventral and
mesial, and the vein ventral and lateral. In the lower part of the neck it occupies
a similar position in regard to the common carotid artery and the internal jugular
vein, and the three structures are enclosed in a common sheath derived from the
deep cervical fascia, but within the sheath each structure occupies a separate
compartment (fig. 743) . In the root of the neck and in the thorax the relations of
the nerves of the two sides of the body differ somewhat, and they must, therefore,
be considered separately.
The right vagus passes in front of the first part of the right subclavian artery in the root of
the neck and then descends in the thorax, passing obliquely downward and backward on the right
of the trachea, and behind the right innominate vein and the superior vena cava, to the back of
the root of the right lung. Just before it reaches the right bronchus it lies close to the medial
side of the vena azygos as the latter hooks forward over the root of the lung. At the back of the
right bronchus the right vagus breaks up into a number of branches which join with the branches
of tlie sympathetic to form the right posterior pulmonary plexus, and from this plexus it issues
in'the form of one or more cords, combined .sensory, visceral motor and sympathetic, which de-
scend on the cesophagus and break up into branches which join with branches of the left vagus,
forming the posterior oesophageal plexus. At the lower part of the thorax fibres of this plexus
become again associated in one trunk which passes througli the diaphragm on the posterior
THE VAGUS NERVE
955
surface of the oesophagus, and is distributed to the posterior surface of the stomach and to the
coeliac (solar) plexus and its offsets.
The left vagus descends through the root of the neck between the carotid and subclavian
arteries and in front of the thoracic duct. In the upper part of the superior mediastinum it ia
crossed in front by the left phrenic nerve, and in the lower part of the same region it crosses in
Fig. 744. — Diagram of the Branches of the Vagus Nerves.
Auricular branch
Meningeal branch
Ganglion of root
Spinal accessory nerve
' Hypoglossal nerve
Loop between first two cervical
External carotid artery
Cardiac branch from recurrent
nerve
Thoracic cardiac branch
(right vagus)
Hepatic plexus
Coeliac plexus
front of the root of the subclavian artery and the arch of the aorta and behind the left superior
intercostal vein. Below the aortic arch it passes behind the left bronchus and divides into
branches which unite with twigs of the sj'mpathetic to form the left posterior pulmonary plexus.
Prom this plexus the fibres of the left vagus issue as one or more cords that break up into anas-
tomosing branches to form the anterior oesophageal plexus. At the lower part of the thorax
this plexus becomes a single trunk, which passes through the diaphragm on the anterior surface
of the oesophagus, and it is distributed to_the anterior surface of the stomach and tothe liver.
956 THE NERVOUS SYSTEM
The jugular ganglion (ganglion of the root) is a spherical grey mass about
five miUimetres in diameter which lies in the jugular foramen (fig. 744). It is
connected with the spinal accessory nerve and with the superior cervical sympa-
thetic ganglion, and it gives off an auricular branch, by means of which it becomes
associated with the facial and glosso-pharyngeal nerves, and a recurrent meningeal
branch.
The ganglion nodosum (ganglion of the trunk) lies below the base of the
skull and in front of the upper part of the internal jugular vein. It is of flattened
ovoid form and about seventeen miUimetres long and four millimetres broad
(figs. 744 and 743). It is joined by the accessory part of the spinal accessory
nerve, and is associated with the hypoglossal nerve, with the superior cervical
ganglion of the sympathetic, and with the loop between the first two cervical
nerves, and it gives off a pharyngeal, a superior laryngeal, and a superior cardiac
branch. Both ganglia and especially the nodosal retain numerous cell-bodies of
sympathetic neurones and the twigs issuing from the ganglia thus contain sympa-
thetic fibres. The greater part of the cell-bodies are of sensory neurones.
Communications. — The vagus nerve is connected with the glosso-pharyngeal,
spinal accessory and hypoglossal nerves, with the sympathetic, and with the loop
between the first and second cervical nerves.
(1) Two communications exist between the vagus and glosso-pharyngeal nerves: one
between their trunlis, just below the base of the skull, and one, in the region of their gangha,
consisting of one or two filaments. When two filaments are present one passes from the jugular
gangUon and the other from the auricular nerve to the petrosal ganghon of the glosso-pharyngeal
nerve. Either or both of these filaments may be absent.
(2) Two twigs pass from the spinal accessory nerve to the ganglion nodosum, and at a
lower level the accessory part of the spinal accessory nerve also joins the same gangUon (fig.
744). The majority of the fibres of the accessory part of the spinal accessory nerve merely
pass across the surface of the ganglion and are continued into the pharyngeal and superior
laryngeal branches of the vagus, but a certain number blend with the trunk of the vagus and
are continued into its recurrent laryngeal and cardiac branches.
(3) Two or three fine filaments connect the ganghon nodosum with the hypoglossal nerve
as the latter turns around the lower part of the gangUon (fig. 744).
(4) Fibres pass from the superior cervical ganghon of the sympathetic to both ganglia
of the vagus (fig. 744).
(5) A twig sometimes passes from the loop between the first two cervical nerves to the
gangUon nodosum (fig. 744).
Terminal branches. — These are the meningeal, auricular, pharyngeal, superior
laryngeal, recurrent (inferior laryngeal), cardiac, bronchial, pericardial, oesopha-
geal, and the abdominal branches.
(1) The meningeal or recurrent branch is a slender filament which is given off from the
jugular ganglion. It takes a recurrent course through the jugular foramen, and is distributed
to the dura mater around the transverse (lateral) sinus.
(2) The auricular branch, or nerve of Arnold, arises from the jugular gangUon in the jugular
foramen. It receives a branch from the petrosal gangUon of the glosso-pharyngeal, enters the
petrous part of the temporal bone through a foramen in the lateral wall of the jugular fossa,
and communicates with the facial nerve or merely Ues in contact with it as far as the stylo-
mastoid foramen. It usually leaves the temporal bone by the stylo-mastoid foramen, but it
may pass through the tympano-mastoid fissure, and it divides, behind the pinna, into two
branches, one of which joins the posterior auricular branch of the facial while the other suppUes
sensory fibres to the posterior and inferior part of the external auditory meatus and the back
of the pinna. It also suppUes twigs to the osseous part of the external auditory meatus and
to the lower part of the outer surface of the tympanic membrane.
(3) The pharyngeal branches may be two or three in number. The principal of these
joins the pharyngeal branch of the glosso-pharyngeal on the lateral surface of the internal car-
otid artery, and after passing with the latter medial to the external carotid artery it turns
downward and medialward to reach the posterior aspect of the pharynx. Here the two nerves
are joined by branches from the superior cervical ganglion of the sympathetic, with which they
form the pharyngeal plexus (figs. 743, 744). Branches from this plexus supply sensory fibres
to the mucous membrane of the pharynx and motor fibres to the constrictores pharyngis, levator
palatini, uvulae, glosso-palatinus, and pharyngo-palatinus.
(4) The superior laryngeal nerve arises from the lower part of the ganghon
nodosum, and passes obliquely downward and medialward behind and medial to
both internal and external carotid arteries toward the larynx. In this course it
describes a curve with the convexity downward and lateralward and divides into
(i) a larger internal and (ii) a smaller external branch (fig. 744). Before its
division it is joined by twigs with the sympathetic and with the pharyngeal plexus,
and it gives a small branch to the internal carotid artery.
THE VAGUS NERVE 957
(a) The internal branch accompanies the superior laryngeal artery to the interval between
the upper border of the thyreoid cartilage and the great cornu of the hyoid bone. It passes
under cover of the thyreo-hyoid muscle and pierces the hyo-thyreoid membrane to gain the
interior of the pharynx, where it hes in the lateral wall of the sinus piriformis and divides into
a number of diverging branches. The ascending branches supply the mucous membrane on
both surfaces of the epiglottis, and probably that of a small part of the root of the tongue. The
descending branches ramify in the mucous membrane lining the larjmx, and supply the mucous
membrane which covers the back of the cricoid cartilage. One of the descending branches
passes downward on the internal muscles of the larynx to anastomose with the terminal part of
the inferior (recurrent) laryngeal nerve.
(b) The external branch runs downward on the inferior constrictor to the lower border of
the th}Teoid cartilage, where it ends, for the most part, in the crico-thyreoid muscle. A few
filaments pierce the crico-thyreoid membrane and are distributed to the membrane lining the
larynx. It occasionally gives off a cardiac branch which joins one of the cardiac branches of
the sympathetic; it also furnishes twigs to the inferior constrictor, and communicating twigs
to the pharyngeal plexus, and it receives a communication from the superior cervical gangUon
of the sympathetic.
(5) The recurrent (inferior or recurrent laryngeal) nerve of the right side
arises from the vagus at the root of the neck in front of the right subclavian
artery. It hooks around the artery, passing below and then behind that vessel,
and runs upward and slightly medialward, crossing obliquely behind the common
carotid artery (fig. 744). Having gained the side of the trachea, it runs upward in
the groove between the trachea and the CBsophagus, accompanying branches of the
inferior thja-eoid artery, and, near the level of the lower border of the cricoid car-
tilage, becomes the inferior laryngeal nerve.
In its course the right recurrent nerve gives off branches to the trachea, cesophageal branches
to the ojsophagus and pharynx, and, near its commencement, one or more inferior cardiac
branches. It communicates with the inferior cervical sympathetic ganghon and with the superior
laryngeal nerve.
The inferior laryngeal nerve, the continuation of the recurrent, ascends between the trachea
and oesophagus, enters the larynx under cover of the inferior constrictor of the pharynx, and
divides into two branches, anterior and posterior. The anterior branch passes upward and for-
ward on the crico-arytajnoideus lateralis and thyreo-arytajnoideus, and supplies these muscles
and also the vocalis, arytsenoideus obliquus, ary-epiglotticus, and thyreo-epiglotticus. The
posterior branch, passing upward, supplies the crico-arytaenoideus posterior and arytsenoideus
obliquus, and anastomoses with the medial branch of the superior laryngeal nerve.
On the left side the recurrent nerve arises in front of the aortic arch and winds
around the concavity of the arch lateral to the ligamentum arteriosum. It crosses
obliquely behind the root of the left common carotid artery, gains the angular
interval between the oesophagus and trachea, and corresponds with the nerve of
the right side in the remainder of its course and distribution (fig. 744).
(6) Cardiac branches. — Of these branches of the vagus, there are two sets, the
superior and inferior. All the branches of both sets pass to the deep part of the
cardiac plexus except a superior branch on the left side that passes to the super-
ficial part of the cardiac plexus. All contain visceral motor, sympathetic and
sensory fibres.
(a) The superior (superior and inferior cervical) cardiac nerves arise from the vagus and
its branches in the neck (figs. 744, 786). Some of these branches on both sides join with the
cardiac branches of the sympathetic in the neck and pass with them to the cardiac plexus. Some
on the right side pass independently through the thorax to the deep part of the cardiac plexus,
and a branch on the left side passes through the thorax to the superficial part of the cardiac
plexus.
(b) The inferior (thoracic) cardiac branches. — These branches on the right side arise in
part from the recurrent nerve and in part from the main trunk of the vagus, while on the left
side they usually arise entirely from the recurrent. AU these branches pass to the deep part
of the cardiac plexus (figs. 744, 786).
(7) The bronchial (pulmonary) branches are anterior and posterior (fig. 744) .
(a) The anterior bronchial (pulmonary) branches consist of a few small branches which arise
at the upper border of the root of the lung. They pass forward to gain the anterior aspect of
the bronchus, where they communicate with the sympathetic and form the anterior pulmonary
plexus, from which fine twigs pass along the bronchus.
(b) The posterior bronchial (pulmonary) branches. — Almost the entire remaining trunk
of the vagus usuallj' divides into these branches, which join with branches from the second,
third, and fourth thoracic ganglia of the sympathetic to form the posterior pulmonary plexus
(fig. 744). The plexuses of the two sides join freely behind the bifurcation of the trachea,
and branches from the plexus pass along each bronchus into the lung.
(8) The pericardial branches pass from the trunk of the vagus or from the bronchial or
oesophageal plexuses to the anterior and posterior surfaces of the pericardium. They are
chiefly sensory.
958 THE NERVOUS SYSTEM
(9) CEsophageal branches, given off by the trunk of the nerve above the bronchial plexuses
and from the oesophageal plexuses lower down, pass to the wall of the oesophagus.
(10) Abdominal branches. — The terminal part of the left vagus divides into many branches,
some of which communicate freely along the lesser curvature of the stomach with filaments
from the gastric plexus of the sympathetic, and to some extent with branches of the right vagus,
to form the elongated anterior gastric plexus (fig. 744). From this plexus as well as from the
nerve-trunk, gastric branches are given to the anterior surface of the stomach. Hepatic
branches from the trunk or from this plexus pass in the lesser omentum to the hepatic plexus
(fig. 744). The terminal part of the right vagus divides into many branches, and forms along
the lesser curvature of the stomach an elongated posterior gastric plexus by communications
with branches from the gastric plexus of the sympathetic and with branches from the right vagus.
Gastric branches are given off by the trunk of the nerve and from this plexus. Coeliac branches
are given by the trunk to the cceliac (solar) plexus, and splenic and renal branches, either
directly or through the coeliac (solar) plexus, are given to the splenic and renal plexuses (fig. 744) .
Central connections. — The sensory fibres of the vagus are processes of the cells of the jugular
ganglion and the ganglion nodosum. The peripheral fibres from these cells bring in sensory
impulses from the periphery, and their central fibres convey the impulses to the brain. The
latter fibres enter the medulla in the filaments of attachment in the postero-lateral sulcus, and,
in the reticular formation, they bifurcate into ascending and descending branches which end in
the nuclei of termination of the vagus, namely, in the nucleus alae cinerese in the floor of the
fourth ventricle and in the nucleus tractus solitarii. The tractus solitarius consists largely of the
descending branches. These and the axones arising from the nuclei of termination of the vagus
descend the spinal cord to terminate about ventral horn cells which give origin to the phrenic
nerve and to motor fibres supplying other muscles of respiration, and they also convey impulses
which are distributed to visceral motor neurones along the spinal cord.
The motor fibres spring from the nucleus ambiguus and from the dorsal efferent (motor)
nucleus of the vagus, described on page 820. They join the sensory fibres in the reticular
formation. Some of the motor fibres, especially those from the dorsal efferent nucleus, are
visceral motor fibres.
The central connections of the vagus are similar to those of the glosso-pharyngeal nerve
(fig. 647). Van Gehuchten's observations point to the conclusion that the chief nucleus of
termination of the vagus nerve is that of the tractus solitarius.
THE SPINAL ACCESSORY NERVE
The spinal accessory nerve [n. accessorius] is exclusively motor. It consists of
two parts, the accessory or superior, and the spinal or inferior part.
The fibres of the accessory or superior portion [ramus internus] ("accessory
vagus") spring chiefly from the inferior continuation of the nucleus ambiguus, in
common with the motor fibres of the vagus above, and they pass through the
reticular formation to the postero-lateral sulcus of the medulla, where they emerge
as a series of filaments, below those of the vagus. The filaments pierce the pia
mater and unite, as they pass outward in the posterior fossa of the cranium, to
form a part of the nerve which enters the apertm-e in the dura mater common to
the vagus and spinal accessory nerves. In the aperture this trunk is joined by the
spinal portion of the nerve.
The spinal or inferior portion [ramus externus] arises from the ventro-lateral
cells of the ventral horn of the cord as low as the fifth, and rarely the seventh,
cervical nerve. The fibres pass dorsalward and lateralward from their origins
through the lateral part of the ventral horn and through the lateral funiculus of
white substance, and they emerge from the lateral aspect of the cord behind the
ligamentum denticulatum, along an oblique line, the lower fibres passing out
immediately dorsal to the ligament, and the upper close to and sometimes in
association with the dorsal roots of the upper two spinal nerves. As the spinal
fibres pass out of the surface of the cord they unite to form an ascending strand
which enters the posterior fossa of the cranium, through the foramen magnum,
and, turning lateralward, blends more or less intimately with the accessory por-
tion. Thus combined, the nerve enters the jugular foramen in company with the
vagus, but here it is again separated into its two branches, which contain chiefly
the same fibres as the original superior and inferior parts.
The superior branch, or accessory portion of the nerve, gives one or more filaments to the
jugular ganghon (ganglion of the root of the vagus), and then joins either the trunk of the vagus
directly or its ganglion nodosum, the fibres of the branch being contributed to the pharyngeal,
laryngeal, and cardiac branches of the vagus. Fibres corresponding to the white rami communi-
cantes, absent in the cervical nerves, probably enter the cervical sympathetic ganglion through
this ramus of the spinal accessory nerve. The fibres from the accessory to the vagus therefore
probably include visceral motor and cardio-inhibitory fibres.
The inferior branch or the spinal portion runs backward and downward under cover of the
posterior belly of the digastric and the sterno-mastoid. It usually crosses in front of and to
the lateral side of the internal jugular vein and between it and the occipital artery; then it
GANGLIATED CEPHALIC PLEXUS 959
pierces the slerno-mastoid, supplies filaments to it, and interlaces in its substance with branches
of the Second cervical nerve. It emerges from the posterior border of the sterno-mastoid
slightly above the level of the upper border of the thyreoid cartilage, passes obliquely downward
and backward across the occipital portion of the posterior triangle, and disappears beneath the
trapezius about the junction of the middle and lower thirds of the anterior border of that muscle
(fig. 743). In the posterior triangle it receives communications from the third and fourth
cervical nerves, and beneath the trapezius its fibres form a plexus with other branches of the
same nerves. Its terminal filaments are distributed to the trapezius and they can be traced
almost to the lower extremity of that muscle.
Central connections. — The nuclei of origin, like other motor nuclei, are connected with the
somsesthetic area of the cerebral cortex of the opposite side by the pyramidal fibres, and they are
associated with the sensory nuclei of other cranial nerves by the medial longitudinal fasciculus,
and with sensations brought in by the spinal nerves by the fibres of the fasciculi proprii.
THE GANGLIATED CEPHALIC PLEXUS
The Sympathetic Ganglia of the Head and Their Associations with
THE Cranial Nerves
The sympathetic system of the head, like that of the remainder of the body
described below, is arranged in the form of a continuous gangHated plexus subdi-
vided into sub-plexuses. Unlike the great unpaired prevertebral plexuses in the
thoracic and abdominal cavities, all the larger sympathetic ganglia of the head are
paired, gangha corresponding to each other being found on either side. Thus
they may be considered as an upward extension of the series of paired lumbar,
thoracic and cervical ganglia belonging to the sympathetic trunks lying along
either side of the vertebral column. Numerous small ganglia, many of them
microscopic, occur in the sub-plexuses throughout the head. These are irregular
in size and position and those in the region of the median line are no doubt
unpaired.
In origin, the ganglia of the cephalic plexus consist of cell-bodies which, in the early stages
of development, migrated from the fundaments of the ganglia of the vagus, glosso-phar3mgeal
and glosso-palatine nerves, and most especially from that of the semilunar (Gasserian) ganglion
of the trigeminus — a developmental relation identical with that of the remainder of the sym-
pathetic system to the ganglia of the spinal nerves. Just as is known for the spina! ganglia,
some cell-bodies destined to develop into sympathetic neurones, instead of migrating, remained
within the confines of the ganglia of the above nerves, in company with the cell-bodies of their
sensory neurones. This is thought to be especially true for the geniculate, the petrosal and the
jugular ganglion. Therefore these ganglia must be considered as in small part sympathetic
ganglia.
The gangliated cephalic plexus could properly be included as a division of the general sym-
pathetic system described later. However, because its larger ganglia are so intimately asso-
ciated with branches of the oculomotor, trigeminal, masticator, glosso-palatine, glosso-pharyngeal
and vagus nerves, it is customary to describe it in connexion with the cranial nerves.
The larger ganglia, one on either side of the head, comprise the ciliary ganglion,
the spheno-palatine (Meckel's) ganghon, the otic and the submaxillary ganglion.
To these must be added portions of the geniculate, petrosal, jugular and the gan-
ghon nodosum, and a part of the superior cervical sympathetic ganglion. The
chief relations of the gangliated cephalic plexus to the cranial nerves are shown in
fig. 741.
The so-called roots and branches of the ganglia carry three varieties of fibres:
(1) Sensory, (2) Motor (visceral motor or preganglionic), and (3) Sympathetic.
Most roots and branches are mixed, the name of a root being determined only by
the variety of fibres predominating in it.
A bundle of sensory fibres going to a ganghon is called its sensory root. Such, however,
cannot comprise a true root since none of its fibres arises in the ganghon and very few or none may
terminate in it. The only sensory fibres terminating in a ganghon are the few which may ap-
proach it in any of the roots to terminate in its capsule or the capsules of its cells and convey
impulses of general sensibility from the ganghon to the central nervous system. Almost all of
the fibres of a "sensory root" merely pass around or through a ganglion and into its branches
beyond, which they borrow as paths for reaching their allotted fields of distribution. In this
relation it should be realized that while the cihary, spheno-palatine, otic and submaxillary
ganglia are customarily described under the discussion of the trigeminus, this nerve has func-
tionally less to do with them than any of the other cranial nerves with which they are associated.
Bundles of trigeminal (sensory) fibres, traceable in gross anatomy because meduUated and of
appreciable size, pass to the gangha, but only to pass through them as continuations of the ter-
minal branches of the trigeminus.
The so-called motor root of a ganglion may carry two kinds of fibres: (a) visceral motor
(preganglionic) fibres, arising in the nuclei of origin in the central system and passing in the trunk
960
THE NERVOUS SYSTEM
and branches of a cranial nerve (oculomotor, masticator, etc.) to enter and terminate in contact
with the ceU-bodies of the ganglion, which, in their turn, give fibres to the branches of the gang-
lion; (b) fibres of the same origin, name and course but which may pass thi-ough the ganglion to
terminate in contact with the cells of a more distant ganglion. Any root, the motor especially,
may contain somatic motor fibres, that is, fibres of central origin which pass through the gang-
lion uninterrupted and into its branches to terminate upon the fibres of skeletal (voluntary)
muscle.
A sympathetic root likewise may carry two and perhaps three varieties of fibres conforming
to the name: (a) fibres arising from the cells of other sympathetic gangha and terminating in the
ganghon in question; (b) fibres arising in other ganglia which pass through the gangfion in
question to enter its branches and terminate either in other ganglia or upon their allotted mus-
cular or glandular elements. A third is the fibre of the sensory sympathetic neurone, probably
quite rare, which may arise from a cell-body in the ganglion and pass centralward in its root and
in the appropi'iate cranial nerve to terminate about a cell-body of the dorsal-root or spinal gang-
hon type, the central process of which latter conveys this sensory impulse of sympathetic origin
into the central system just as sensory oranio-spinal impulses are conveyed.
Fig. 745. — Diagram to Illtjsteate the Sthtjctural Relations op the Roots and
BsANCHES OF A CEPHALIC SYMPATHETIC GANGLION. Sensory fibres, blue; motor, red;
sympathetic, black.
Sensory fibre terminating in capsule
of ganglion and capsule of its cells
Sensory root
Sympathetic root
Branches of distribution
The branches of distribution of the gangha, the larger of them often called nerves, are those
bundles in which the fibres, both arising in or passing through the gangha, course toward their
terminations upon their allotted tissue elements of the head. The larger gangha of the head are
described as each possessing the three roots above mentioned. In the branches pass fibres
motor to the vessels of the head, to the intrinsic muscles of the eye bulb, to the [lacrimal glands,
the mucous membranes (gland cells) of the nasal and oral cavities and the salivary glands, and
sensory fibres conveying impulses from these structures.
The plexuses into which the gangliated cephalic plexus is divided and which connect the
ganglia to form it, are numerous and vary greatly in size. They underlie the mucous membranes
and they surround all the vessels and glands. They are named according to their locahty.
The largest of them are the tympanic plexus and the carotid and cavernous plexuses. They
have been repeatedly referred to in their relations to the branches of the cranial nerves.
Of the numerous branches described from the superior cervical sympathetic ganglion, the
two large ones which pass upward associate it especially with the gangliated cephalic plexus.
That branch known as the internal carotid nerve may be considered as the direct continuation
upward of the gangUated sympathetic trunk of the body. Through the branches of this, the
carotico-tympanic and the deep petrosal nerves, and through the plexuses derived from it, the
superior cervical ganghon may be associated with practically all the other sympathetic gangha
of the head (figs. 7.39 and 741). The other branch from the superior cervical ganghon, the
jugular nerve, associates it with the ganglia of the glosso-pharyngeal and vagus nerves, with the
petrosa ganghon by a direct branch and with the gangha of the vagus through the nodosal
plexus. These latter gangha (and the nerves to which they belong) are connected, chiefly by
THE CILIARY GANGLION 961
way of the tympanic nerve, which is from the petrosal ganghon, with the tympanic plexus (fig.
741).
The tympanic plexus serves as a common point of distribution of fibres from the superior
cervical sympathetic ganglion, the gangha of the vagus, the petrosal ganghon, and the geniculate
ganglion, to the cavernous and carotid plexuses and to the spheno-palatine and otic gangha.
The superior cervical ganglion is associated with the cavernous and carotid plexuses direct by
the internal carotid nerve and with the tympanic plexus by the Inferior and superior carotico-
tympanic nerves. The tympanic plexus receives fibres from the geniculate ganghon by a small
geniculo-tympanic branch and it is connected with the spheno-palatine ganghon by a small
anastomotic or tympano-petrosal branch to the great superficial petrosal nerve, and with the otic
ganglion by the small superficial petrosal nerve. It is not directly connected with either the
cihary or the submaxillary ganglion. However, these ganglia, as well as the sphenopalatine
and otic, are connected with the carotid plexus either directly by named branches or indirectly
by way of plexuses derived from the carotid. The geniculo-tympanic branch, the tympanic
nerve and twigs of the nodosal plexus may be considered as analogous to the rami oommunicantes
of^the spinal nerves.
The parotid branches, described above as branches of the auriculo-temporal nerve (from the
trigeminus) and as containing fibres from the glossopharyngeal, should be mentioned here as
belonging to the gangliated cephalic plexus. These branches are sympathetic fibres arising
in the otic ganglion and passing as branches of the ganglion to the auriculo-temporal in which
they remain till this nerve enters the parotid gland and then they are distributed to the gland.
The visceral motor or preganglionic fibres which terminate about their cells of origin in the otic
ganglion are derived from the glosso-pharyngeal nerve and pass successively through the tym-
panic nerve, the tympanic plexus, and the small superficial petrosal nerve to the otic ganglion.
The tympanic nerve (tympanic branch of the glosso-pharyngeal, or nerve of Jacobson), the
branch to the Eustachian tube (ramus tubes), and the superior and inferior carotico-lympanic
branches are also described as branches of the glosso-pharyngeal nerve. These must hkewise
be considered as belonging to the gangliated cephahc plexus.
For purposes of dissection, it may be more expedient to consider separately,
with its roots and branches, each of the larger ganglia of the gangliated cephalic
plexus. Under this heading belong in part the geniculate ganglion of the glosso-
palatine nerve, and the ganglia of the glosso-pharyngeal and vagus, especially the
petrosal ganglion of the former and the jugular ganglion of the latter, from the
fact that these ganglia contain numerous cell-bodies of sympathetic neurones as
well as those of the sensory neurones of their nerves.
These ganglia, however, have been described with their corresponding cranial nerves. The
sensory and motor roots of their sympathetic portions are contained in the roots of their nerves.
The geniculate probably has no sympathetic root. The sympathetic roots of the petrosal and
jugular ganglia are contained in the branches of the jugular nerve. The chief branches of
distribution of the geniculate are the geniculo-tympanic branch, the great superficial petrosal
nerve, and the external superficial petrosal nerve. The branches of the petrosal ganghon are
the tympanic nerve and its branches of the tympanic plexus. The chief branch of distribution
from the jugular ganglion is contained in the auricular branch of the vagus, or nerve of Arnold,
supplemented by sympathetic fibres in the trunk of the vagus itself.
The principal cephalic sympathetic ganglia are the ciliary, the spheno-palatine
(Meckel's), the otic and the submaxillary.
The Ciliary Ganglion
The ciliary, lenticular, or ophthalmic ganglion lies in the posterior part of the
orbital cavity, about 6 mm. in front of the superior orbital (sphenoidal) fissure,
to the lateral side of the optic nerve, and between the optic nerve and the external
rectus muscle. It is a small, reddish, quadrangular body, compressed laterally,
and it measures about two millimetres from before backward (fig. 734).
Roots. — (o) Its motor or short root enters its lower and posterior angle and is a visceral
motor branch derived from the branch of the inferior division of the oculomotor nerve which
supplies the inferior oblique muscle. The fibres of the motor root probably all terminate in the
ciliary ganglion in connection with motor sympathetic neurones.
(6) The sensory or long root passes through the upper and back part of the ganglion. It
is a branch of the naso-oiliary (nasal) nerve and is, therefore, composed of fibres from the
trigeminus passing through the ganglion.
(c) The sympathetic root consists of fibres derived from the cavernous plexus of the
sympathetic; it passes to the ganglion with the long root.
Branches. — From three to six short ciliary nerves emerge from the anterior border of the
ganglion ; they divide as they pass forward and eventually form about twenty nerves which are
arranged in aii upper and a lower group, and the latter group is joined by the long ciliary
branches of the naso-ciliary (nasal) nerve, now sensory and sympathetic (fig. 73-1). When
they reach the eyeball, the ciliary nerves pierce the sclerotic around the optic nerve, and pass
forward in grooves on the inner surface of the sclera. The sympathetic fibres contained are dis-
tributed as motor fibres to the ciliary muscle, the sphincter of the iris, and to the vessels of these
and of the cornea.
962 THE NERVOUS SYSTEM
The Spheno-palatine or Meckel's Ganglion
This ganglion is associated with the maxillary nerve (fig. 743). It is a small
reddish-grey body of triangular form, which is flattened at the sides, and measiu-es
about five millimetres from before backward. It lies deeply in the pterygo-
palatine (spheno-maxillary) fossa at the lateral side of the spheno-palatine fora-
men and in front of the anterior end of the pterygoid (Vidian) canal. It is
attached to the maxillary nerve, from which it receives its sensory root, and it is
connected with the Vidian nerve, which furnishes it with motor and sympathetic
filaments (fig. 739).
The exact position of the ganghon depends upon the size and shape of the sphenoidal air
cells. When these are small, or high and narrow, the ganglion lies lateral to them; when they
are large, or broad and fiat, the ganglion lies inferior to them. Sometimes it may lie anterior
to them if the cells are short from in front backward. The ganglion may be reached with ease
by chipping away the bone around the sphenoidal air cells after the skull is divided sagitally.
Roots. — (a) Its motor root, consisting of visceral motor fibres of the glosso-palatine nerve,
is contained in the great superficial petrosal nerve which is incorporated in the Vidian nerve.
It springs from the anterior angle of the geniculate ganglion and passes through the hiatus
of the facial canal (hiatus Fallopii) into the middle fossa of the cranium, where it runs forward
and medialward, in a groove on the upper surface of the petrous part of the temporal bone, to
the foramen laoerum, and in this part of its course it passes beneath the semilunar (Gasserian)
ganghon and the masticator nerve. In the foramen lacerum it joins with the great deep petrosal
nerve to form the Vidian nerve (nerve of the pterygoid canal), which passes forward through the
pterygoid (Vidian) canal and its motor and sympathetic fibres terminate in the spheno-palatine
ganglion in the pterygo-palatine (spheno-maxillary) fossa. The great superficial petrosal nerve
contains sensory as well as sympathetic and motor fibres. The sensory fibres pass through the
ganghon and, in the small palatine nerve, descend to the soft palate, where they terminate in
the epithelium covering it and some are probably concerned with peripheral taste organs
found there. They arise from the cells of the geniculate ganglion and therefore belong to the
glosso-palatine nerve.
(6) The sympathetic root is the great deep petrosal portion of the Vidian nerve. This
root, which is of reddish colour and of soft texture, springs from the carotid plexus which lies
on the outer side of the internal carotid artery in the carotid canal. It enters the foramen
lacerum through the apex of the petrous portion of the temporal bone, and unites with the great
superficial petrosal branch of the facial nerve to form the Vidian nerve. The great superficial
petrosal nerve also carries sympathetic fibres to the spheno-palatine ganglion, derived from the
geniculate ganglion and from the tj'mpanic plexus.
The Vidian nerve [n. canalis pterygoidei] commences by the union of the great superficial
and deep petrosal nerves in the foramen lacerum, and runs forward through the pterygoid
(Vidian) canal to the pterygo-palatine (spheno-maxillary) fossa to the spheno-palatine ganglion.
The Vidian nerve often may be seen in a ridge of bone along the floor of the sphenoidal cells
and its direction there depends upon the position of the spheno-palatine ganglion. While it is
in the pterygoid canal the Vidian nerve is joined by a sphenoidal filament from the otic ganghon,
and it gives branches to the upper and back part of the roof and septum of the nose, and to the
lower end of the Eustachian tube.
(c) The sensory roots consist of the sensory fibres mentioned above in the great superficial
petrosal nerve and of usually two spheno-palatine branches from the maxillary nerve. The
majority of the fibres of these roots do not join the ganghon, but pass by its medial side and
enter the palatine branches.
Branches. — The branches of the ganghon, containing sensory, vaso-motor and secretory
fibres, are orbital or ascending, internal or nasal, descending or palatine, and posterior or pharyn-
geal.
Ascending branches. — The orbital or ascending branches are two or three small twigs
which enter the orbit through the inferior orbital (spheno-maxillary) fissure and proceed, within
the periosteum, to the inner wall of the orbit, where they pass through the posterior ethmoidal
foramen and through the foramina in the suture behind that foramen to be distributed to the
mucous membrane which lines the posterior ethmoidal cells and the sphenoidal sinus.
Internal branches. — The internal or nasal branches are derived in part from the medial
side of the ganglion, but are also largely made up of fibres which pass from the spheno-palatine
branches of the maxillary nerve without traversing the ganglionic substance. They are dis-
posed in two sets, the lateral and the medial (septal) posterior superior nasal branches.
The lateral posterior superior nasal branches are six or seven small twigs which pass through
the spheno-palatine foramen, and are distributed to the mucous membrane covering the poster-
ior parts of the superior and middle nasal conchae (turbinated bones) (fig. 732). They also
furnish twigs to the lining membrane of the posterior etlimoidal cells.
The medial posterior superior nasal (septal) branches, two or three in number, pass medial-
ward through the spheno-palatine foramen. They cross the roof of the nasal fossa to reach the
back part of the nasal septum, where the smaller twigs terminate. The largest nerve of the set,
the naso-palatine nerve, or nerve of Cotunnius, runs downward and forward in a groove in the
vomer between the periosteum and the mucous membrane to the incisive (anterior palatine)
canal, where it communicates with the nasal branch of the anterior superior alveolar nerve.
The two naso-palatine nerves then pass through the foramina of Scarpa in the intermaxillary
suture, the left nerve passing through the anterior of the two foramina. In the lower part
of the incisive (anterior palatine) canal the two nerves form a plexiform communication (for-
THE SUBMAXILLARY GANGLION 963
merly described as Cloquet's ganglion) and they furnisli twigs to the anterior or premaxillary
part of the hard palate behind the incisor teeth. In this situation they communicate with the
anterior palatine nerves.
Descending branches. — The descending branches are the great or anterior, the posterior,
and the middle (external) palatine nerves. Like the internal set of branches, they are in part
derived from the ganglion and in part are directly continuous with the spheno-palatine nerves
(fig. 732).
The great or anterior palatine nerve, its sensory fibres derived from the maxillary nerve,
arises from the inferior angle of Meckel's ganglion, and passes downward through the pterygo-
palatine canal, accompanied by the descending palatine artery. Emerging from the canal at
the greater (posterior) palatine foramen it divides into two or three branches, which pass for-
ward in gi-ooves in the hard palate and supply the glands and mucous membrane of the hard
palate and the gums on the inner aspect of the alveolar border of the upper jaw. During its
cour.se through the pterygo-palatine canal the anterior palatine nerve gives off the posterior
inferior nasal nerves. These nerves pass through small openings in the perpendicular plate
of the palate bone to supply the mucous membrane covering the posterior part of the inferior
nasal concha (turbinated bone) and the adjacent portions of the middle and inferior meatuses
of the nose.
The posterior or small palatine nerve passes downward through a lesser palatine foramen
(accessory palatine canal), and enters the soft palate, distributing branches to that organ, to
the uvula, and to the tonsil. Its sensory fibres are derived from the glosso-palatine nerve,
through the great superficial petrosal nerve and through the spheno-palatine ganglion. It
was formerly believed to convey motor fibres from the facial nerve to the levator palati and
azygos uvulae, but it is now beheved that these muscles are supplied by the spinal accessory
nerve through the pharyngeal plexus (fig. 732).
The middle (external) palatine nerve, the smallest of the three, in part, likewise from the
glosso-palatine nerve, traverses a lesser palatine foramen and supplies twigs to the tonsil and
to the adjacent part of the soft palate (fig. 732).
Posterior branch. — The pharyngeal branch, which is of small size, passes backward and
somewhat medialward through the pharyngeal canal accompanied by a pharj'ngeal branch
of the spheno-palatine artery. It is distributed to the mucous membrane of the uppermost
part of the pharynx, to the upper part of the posterior nares, to the opening of the Eustachian
tube, and to the lining of the sphenoidal sinus. Its sensory fibres are derived from the maxillary
nerve.
The Otic Ganglion
The otic or Arnold's ganglion is a small reddish-grey body which is associated
with the mandibular nerve. It lies deeply in the zygomatic fossa, immediately
below the foramen ovale, on the inner side of the trunk of the mandibular nerve.
It is in relation internally with the tensor palati, which separates it from the Eusta-
chian tube. In front of it is the posterior border of the pterygoideus internus, and
behind it lie the middle and small meningeal arteries. It is compressed laterally,
and its greatest diameter, which lies antero-posteriorly, is about three millimetres.
Roots. — The ganglion is closely connected with the nerve to the pterygoideus internus,
through which it may receive a motor root from the masticator nerve. Through the small
superficial petrosal nerve, which joins the upper and back part of the ganglion, it receives a
motor root from the glosso-palatine nerve and sensory and motor fibres from the glosso-
pharyngeal nerve. It receives also a slender sphenoidal filament from the Vidian nerve.
The sympathetic roots are derived from the small superficial petrosal nerve and from the
sympathetic plexus on the middle meningeal artery.
Branches. — The communicating branches which pass from the ganglion are: — (1) The
filaments to the chorda tympani; some of whose fibres probably terminate in the submaxillary
ganglion; (2) filaments to the auriculo-temporal nerve; (3) filaments to the spinous nerve
(the recurrent branch of the mandibular nerve). The branches of distribution are sympathetic
to the vessels and somatic motor branches to the tensor tympani, and tensor veli palatini.
The Submaxillary Ganglion
The submaxillary ganglion is suspended from the lingual division of the man-
dibular nerve by anterior and posterior branches. It is a small reddish body, of
triangular or fusiform shape, which lies between the mylo-hyoideus and hyo-
glossus and above the duct of the submaxillary gland.
Roots. — The sensory root is received from the lingual nerve. The motor root is from both
the masticator nerve by way of the lingual nerve, and from the glosso-palatine nerve by way of
the chorda tympani. The motor fibres pass from the chorda tympani after it has joined the
lingual, and the sensory fibres come directly from the lingual nerve. The sympathetic root is
formed by filaments from the sympathetic plexus on the facial artery.
Branches. — (a) Five or six glandular branches are given to the submaxillary gland and to
Wharton's duct.
(6) Branches to the lingual nerve and the sublingual gland.
(c) To the mucous membrane of the floor of the mouth.
964
THE NERVOUS SYSTEM
II. THE SPINAL NERVES
The spinal nerves are arranged in pairs, the nerves of each pair being symmet-
rical in their attachment to either side of their respective segment of the spinal
cord, and, in general, symmetrical in their course and distribution. There are
usually thirty-one pairs of functional spinal nerves. For purposes of description
these are topographically separated into eight pairs of cervical nerves, twelve pairs
of thoracic nerves, five pairs of lumbar, five pairs of sacral, and one pair of coccygeal
nerves. Occasionally the coccygeal or thirty-first pair is practically wanting,
while, on the other hand, there may be frequently found small filaments represent-
ing one or even two additional pairs of coccygeal nerves below the thirty-first
pair. These rudimentary coccygeal nerves are probably not functional. They
never pass outside the vertebral canal, and often even remain within the tubular
portion of the filum terminale. There sometimes occurs an increase in the number
of vertebrae in the vertebral column and in such cases there is always a correspond-
ing increase in the number of the spinal nerves.
Origin and attachment. — Each spinal nerve (unlike the cranial nerves) is
attached to the spinal cord by two roots: — a sensory or afferent dorsal root [radix
posterior] and a motor or efferent ventral root [radix anterior]. Each dorsal root
has interposed in its course an ovoid mass of nerve-cells, the spinal ganglion, and
the nerve-fibres forming the root arise from the cells of this ganglion and are thus
of peripheral origin. The fibres composing the ventral root, on the other hand, are
of central origin; they arise from the large motor cells of the ventral horn of the
grey column within the spinal cord.
Each dorsal root-fibre upon leaving its cell of origin pursues a short tortuous course within
the spinal ganglion and ^hen undergoes a T-shaped bifurcation, one product of which passes
toward the periphery, where it terminates for the collection of sensations and is known as the
peripheral branch, or, since it conveys impulses toward the cell-body, the dendrite of the spinal
Fig. 746. — Ventral and Dohsal Views op Spinal Cord showing Manner of Attachment
OF Dorsal and Ventral Roots.
Antero-lateral sulcus (line of ventral i
/"Anterior median fissure
Posterior median sulcus
/Posterior in-
ganglion neurone. It is more correct, however, to consider the T-fibre as a bifurcated axone.
The other product of the bifurcation, the central branch, passes into the spinal cord and in its
course toward the cord contributes to form the dorsal root proper.
The central branches, upon emerging from the spinal ganglia, form a single compact bundle
at first, which passes through the dura mater of the spinal cord and then breaks up into a series,
of root-filaments [fila radicularia]. These thread-like bundles of fibres spread out vertically
in a fan-like manner and enter the cord in a direct linear series along its postero-lateral sulcus.
The fibres of the ventral root emerge from the cord in a series of more finely divided root fila-
ments, which, unlike the entering filaments of the dorsal root, are not arranged in direct linear
series, but make their exit over a strip of the ventro-lateral aspect of the cord in some places as
much as two millimetres wide.
As they enter the spinal cord the fibres of the dorsal roots undergo a Y-shaped division,
both products of which course in the cord longitudinally, an ascending and a descending branch.
The descending or caudal branches are shorter than the ascending, and soon enter and terminate
THE SPINAL NERVES 965
about the cells within the grey column of the cord, forming either associational, commissural,
or reflex connections, or about cells whose fibres form cerebellar connections. The ascending
or cephalic branches are either short, intermediate, or long. The short and intermediate
branches are similar in function to the descending branches, save that they become associated
with the grey substance of segments of the cord above rather than below the level of their en-
trance. The long branches convey impulses destined for the structures of the brain, and pass
upward in the fasciculus gracilis or fasciculus cuneatus of the cord, and terminate in the nuclei
of these fasciculi in the meduUa oblongata (figs. 618 and 620).
Aberrant spinal ganglia. — In serial sections on either side of the spinal ganglion of a nerve
there may often be found outlying cells either scattered or in groups of sufficient size to be called
small gangUa. Such are more often found in the dorsal roots of the lumbar and sacral nerves.
These cells are nothing more than spinal ganghon-cells displaced in the growth processes,
and have the same nature and function as those in the ganghon. In some animals occasional
cells very rarely have been found in the outer portion of the ventral root. These probably
represent afferent fibres which enter the cord by way of the ventral root. Likewise, especially
in the birds and amphibia, it has been shown that occasional efferent fibres may pass from the
grey substance of the cord to the periphery by way of the dorsal instead of the ventral root.
Relative size of the roots. — The sensory or dorsal root is larger than the ventral
root, indicating that the sensory area to be supplied is greater and perhaps more
abundantly innervated than the area requiring motor fibres.
It has been shown that in the entire thirty-one spinal nerves of one side of the body of man
the dorsal root-fibres number 653,627, while all the corresponding ventral roots contain but
233,700 fibres, a ratio of 3.2 : 1. (Ingbert.) In the increase in the size of the nerves for the
supply of the limbs the gain of dorsal root or sensory fibres is far greater than the gain of ventral
root-fibres. The first cervical or the sub-occipital nerve is always an exception to the rule;
its dorsal root is always smaller than its ventral, and in rare cases may be rudimentary or entirely
absent. The spinal ganghon and, therefore, the sensory root of the coccygeal nerve, is also
quite frequently absent.
The dorsal and ventral root-fibres of each spinal nerve proceed outward from
their segment of attachment to the spinal cord, pierce the pia mater and arachnoid,
collect to form their respective roots, and pass into their respective intervertebral
foramina. On the immediate peripheral side of the spinal ganglion the two roots
blend, giving origin to the thus mixed nerve-trunk. As the trunk, the sensory
and motor fibres make their exit from the vertebral canal through the interverte-
bral foramen.
Relation to the meninges. — The root filaments of each nerve receive connec-
tive-tissue support from the pia mater and arachnoid in passing through them. In
the sub-arachnoid cavity they become assembled into their respective nerve-roots;
and the roots, closely approaching each other, pass into the dura mater, from which
they receive separate sheaths at first, but at the peripheral side of the ganglion
these sheaths blend into one, which, with the subsequent blending of the roots,
becomes the sheath or epineurium of the nerve trunk. By means of the sheaths
derived from the meninges, especially the dura, the nerve-roots and the trunk are
attached to the periosteum of the margins of the intervertebral foramina and
thus are enabled to give some lateral support to the spinal cord in the upper por-
tion of the canal.
The majority of the spinal ganglia lie in the intervertebral foramina, closely ensheathed,
and thus outside the actual sac or cavity of the dura mater. The gangha of the last lumbar
and first four sacral nerves he inside the vertebral canal, but since the sheath derived from the
dura mater closely adheres to them, they are still outside the sac of the dura mater. The gan-
gha of the last sacral and of the coccygeal nerves (when present) lie in tubular extensions of the
sub-dural cavity, and thus not only within the vertebral canal, but actually within the sac of
the dura mater. The trunk of the first cervical nerve is assembled within the sac of the dura
mater, and, therefore, the spinal ganghon of this nerve, when present, may he within the sac.
Course and direction of emergence. — Invested with the connective-tissue
sheath derived from the meninges, each thoracic, lumbar and sacral nerve emerges
from the vertebral canal through the intervertebral foramen below the correspond-
ing vertebra, and all the nerves are in relation with the spinal rami of the arteries
and veins associated with the blood supply of the given localities of the spinal cord.
The first cervical nerve does not pass outward in an intervertebral foramen proper, but
between the occipital bone and the posterior arch of the atlas and beneath the vertebral artery.
Thus the eighth or last cervical nerve emerges between the seventh cervical and the first thor-
acic vertebra.
The first and second pairs of cervical nerves pass out of the vertebral canal almost at right
angles to the levels of their attachment to the spinal cord. During the early periods of develop-
ment the level of exit of each pair of spinal nerves is opposite the level of its attachment to the
966
THE NERVOUS SYSTEM
cord, but, owing to the fact that in the later periods the vertebral column grows more rapidly
than the cord and increases considerably in length after the cord has practically ceased growing,
all the spinal nerves, with the exception of the first two, pass downward as well as outward.
The obhquity of their course from the level of attachment to the level of exit increases progres-
sively from above downward, and, as the cord ends at the level of the first or second lumbar
vertebra, the roots of the lower lumbar and of the sacral nerves pass at first vertically downward
within the dura mater, and form aroimd the filum terminale a tapering sheaf of nerve-roots,
the Cauda equina (horse's tail) (fig. 613, p. 773).
Topography of attachment. — The relations between the levels of attachment of
the spinal nerves to the cord and the spinous processes of the vertebrae situated
opposite these levels have been investigated by Nuhn and by Reid. The follow-
ing table compiled by Reid gives the extreme limits of attachment as observed in
six subjects.
Table of Topogkaphy of Attachment of Spinal Nerves to the Spinal Cord. (Reid.)
(A) signifies the highest level at which the root filaments of a given nerve are attached
to the cord, and (B) the lowest level observed. For example, the root filaments of the sixth
thoracic nerve may be attached as high as the lower border of the spinous process of the second
thoracic vertebra, or some may be attached as low as the upper border of the spinous process of
the fifth thoracic vertebra, but in a given subject they do not necessarily extend either as high
or as low as either of the levels indicated.
Nerves
Second cervical (A) A httle above the posterior arch of atlas.
(B) Midway between posterior arch of atlas and spine of epistropheus.
Third " (A) A Uttle below posterior arch of atlas.
(B) Junction of upper two-thirds and lower third of spine of epistropheus.
Fourth " (A) Just below upper border of spine of epistropheus.
(B) Middle of spine of third cervical vertebra.
Fifth " (A) Just below lower border of spine of epistropheus.
(B) Just below lower border of spine of fourth cervical vertebra.
Sixth " (A) Lower border of spine of third cervical vertebra.
(B) Lower border of spine of fifth cervical vertebra.
Seventh " (A) Just below upper border of spine of fourth cervical vertebra.
(B) Just above lower border of spine of sixth cervical vertebra.
Eighth " (A) Upper border of spine of fifth cervical vertebra.
(B) Upper border of spine of seventh cervical vertebra.
First thoracic (A) Midway between spines of fifth cervical and sixth cervical vertebra.
(B) Junction of upper two-thirds and lower third of interval between seventh
cervical and first thoracic vertebra.
Second " (A) Lower border of spine of sixth cervical vertebra.
(B) Just above lower border of spine of first thoracic vertebra.
Third thoracic (A) Just above middle of spine of seventh cervical vertebra.
(B) Lower border of spine of second thoracic vertebra.
Fourth " (A) Just below upper border of spine of first thoracic vertebra.
(B) Junction of upper third and lower two-thirds of spine of third thoracic
vertebra.
Fifth " (A) Upper border of spine of second thoracic vertebra.
(B) Junction of upper quarter and lower three-quarters of spine of fourth
thoracic vertebra.
Sixth " (A) Lower border of spine of second thoracic vertebra.
(B) Just below upper border of spine of fifth thoracic vertebra.
Seventh " (A) Junction of upper third and lower two-thirds of spine of fourth thoracic
vertebra.
(B) Just above lower border of spine of fifth thoracic vertebra.
Eighth " (A) Junction of upper two-thirds and lower third of interval between spines
of fourth thoracic and fifth thoracic vertebra.
(B) Junction of upper quarter and lower three-quarters of spine of sixth
thoracic vertebra.
Ninth " (A) Midway between spines of fifth thoracic and sixth thoracic vertebra.
(B) Upper border of spine of seventh thoracic vertebra.
Tenth " (A) Midway between "spines of sixth thoracic and seventh thoracic vertebra.
(B) Middle of the spine of eighth thoracic vertebra.
Eleventh " (A) Junction of upper quarter and lower three-quarters of spine of seventh
thoracic vertebra.
(B) Just above spine of ninth thoracic vertebra.
Twelfth " (A) Junction of upper quarter and lower three-quarters of spine of eighth
thoracic vertebra.
(B) Just below spine of ninth thoracic vertebra.
First lumbar (A) Midway between spines of eighth thoracic and ninth thoracic vertebrae.
(B) Lower border of spine of tenth thoracic vertebra.
Second " (A) Middle of spine of ninth thoracic vertebra.
(B) Junction of upper third and lower two-thirds of spine of eleventh thoracic
vertebra.
PRIMARY DIVISIONS OF SPINAL NERVES
967
Nerves
Third
Fourth
Fifth
First sacral
Fifth
Coccygeal
(A) Middle of spine of tenth thoracic vertebra.
(B) Just below spine of eleventh thoracic vertebra.
(A) Just below spine of tenth thoracic vertebra.
(B) Junction of upper quarter and lower three-quarters of spine of twelfth
thoracic vertebra.
(A) Junction of upper third and lower two-thirds of spine of eleventh thoracic
vertebra.
(B) Middle of spine of twelfth thoracic vertebra.
(A) Just above lower border of spine of eleventh thoracic vertebra.
(B) Lower border of spine of first lumbar vertebra.
(A) Lower border of spine of first lumbar vertebra.
(B) Just below upper border of spine of second lumbar vertebra.
Relative size of the nerves. — The size of the different spinal nerves varies
greatly. Just as the spinal cord shows marked enlargements in the cervical and
lumbar regions necessitated by the greater amount of innervation required of these
regions for the structures of the upper and lower limbs, so the nerves attached to
these regions are considerably larger than elsewhere.
The smaller nerves are found at the two extremities of the cord and in the mid-thoracic
region. The smallest nerve is the coccygeal, and the next in order of size are the lower sacral
and the first two or three cervical nerves. The largest nerves are those which contribute
most to the great nerve trunks for the innervation of the skin and muscles of the limbs: — the
lower cervical and first thoracic for the upper limbs and the lower lumbar and first sacral for
the lower Umbs. The nerves gradually increase in the series in passing from the smaller toward
the larger.
Fig. 747. — Diagrams Illustrating the Origin and DisTRiBtrTioN op a Typical Spinal
Nerve.
A, in thoracic region; B, in region of a limb (highly schematic).
Medial
branch
' Lateral
branch
Posterior
primary
division
Anterior
primary
division
Lateral
branch
Anterior
or ventral
branch
Medial
branch
Lateral
branch
Posterior
primary
\ division
Anterior
primary
division
Lateral
or dorsal
\ branch
Alimentary canal
The primary divisions of the nerve-trunk. — A typical spinal nerve (middle
thoracic, for example), just as it emerges from the intervertebral foramen, divides
into four branches: — the two large primary divisions; viz., the posterior primary
division [ramus posterior] and the anterior primary division [ramus anterior];
third, the small ramus communicans, by which it is connected with the sympa-
thetic; and fourth, the smaller, ramus meningeus {recurrent branch), which im-
mediately turns centralward for the innervation of the membranes and vessels of
the spinal cord.
In general, the posterior primary division passes dorsalward between the arches
or transverse processes of the two adjacent vertebrae in relation with the anterior
costo-transverse ligament, and then divides (with the exception of the first cer-
vical, the fourth and fifth thoracic, and the coccygeal nerves) into a medial (inter-
nal) branch and a lateral (external) branch. The medial branch turns toward the
spinous processes of the vertebrse, and supplies the bones and joints and the mus-
cles about them, and may or may not supply the skin overlying them. The
lateral branch turns dorsalward and also supplies the adjacent muscles and bones,
and, if the medial branch has not supplied the overlying skin, it also terminates
in cutaneous twigs.
968
THE NERVOUS SYSTEM
In the upper half of the spinal nerves the medial branches supply the skin; in the lower half,
it is the lateral branches which do so. Both branches of almost aU the posterior divisions, espe-
cially those of the lower nerves, show a tendency to run caudalward and thus are distributed
to muscles and skin below the levels of their respective intervertebral foramina. They never
supply the muscles of the limbs, though their cutaneous distribution extends upon the buttock,
the shoulder, and the skin of the back of the head as far upward as the vertex. The posterior
primary divisions, with the exception of those of the first three cervical nerves, are much smaller
than the anterior primary divisions.
As their mixed function suggests, the posterior primary divisions contain both nerve-fibres
from the ventral roots and peripheral processes of the spinal ganghon-cells. If the nerve-trunk
on the immediate peripheral side of the spinal ganghon be teased, bimdles of ventral root-fibres
may be seen crossing the trunk obliquely to enter the posterior division, and fibres from the
spinal ganghon may be also traced into it. Also a few sympathetic fibres, derived chiefly by
way of the ramus communicans, are known to course in it for distribution in the walls of the
blood-vessels, etc., of the area it suppUes.
The anterior primary divisions run lateralward and ventralward. With the
exception of the first two cervical nerves, which contribute the hypoglossal loop,
they are larger than the posterior primary divisions, and appear as direct continu-
ations of the nerve-trunks. Only in case of most of the thoracic nerves do thej^
remain independent in their course. In these they run lateralward and ventral-
ward in the body-wall. In general, these divisions supply the lateral and ventral
Fig. 748.-
-DlAGBAM IlLTJSTRATING THE OrIGIN OF THE COMPONENT NEEVE-FrBKES OF THE
Pbimaey Divisions of a Typical Spinal Nerve.
Spinal ganglion neurone
to capsule of ganglion
^ Gray ramus communicans
— White ramus com
Sympathetic ganglion \ Gangliated
Sympathetic trunk j trunk
Sympathetic cell body in spinal
ganglion
Posterior primary division \ Spinal
Anterior primary division J nerve
^>^ ^Gray ramus communicans
\ ^White ramus communicans
Sensory sympathetic neurone
Branch to prevertebral ganglion
parts of the body, the limbs, and the perineum. In the cervical, lumbar, and
sacral regions they lose their anatomical identity by dividing, subdividing, and
anastomosing with each other so as to give rise to the three great spinal plexuses of
the body — the cervical, the brachial, and the lumbo-sacral plexuses. The major-
ity of the thoracic nerves retain the typical or primitive character in both their
anterior and posterior primary divisions. In them the anterior division (inter-
costal nerve) divides into a lateral or dorsal and an anterior or ventral branch,
both of which subdivide. The lateral branch is chiefly cutaneous; it pierces the
superficial muscles and, in the subcutaneous connective tissue, divides into a
smaller posterior and a larger anterior ramus, which respectively supply the skin
of the sides and the lateral part of the ventral surface of the body. The anterior
branch continues ventralward iii the body-wall, giving off twigs along its course to
the adjacent muscles and bones, and, as it approaches the ventral mid-fine of the
body, it turns sharply lateralward and sends rami medialward and lateralward to
supply the skin of the ventral aspect of the bodjr. In the region of the limbs the
typical arrangement is interfered with in that what corresponds to the lateral and
anterior branches of the division are carried out into the limbs for the skin and
muscles there, instead of supplying the lateral and ventral parts of the body-wall.
RAMI COMMUNICANTES
969
Nerve-fibres arising in the spinal ganglion and fibres from the ventral root pass
directly from the nerve-trunk into the anterior primary division of the spinal
nerve. This division also receives sympathetic nerve-fibres by way of the ramus
communicans. These latter accompany the division and are distributed to their
allotted elements in the territory it supplies.
Fig. 749. — Table Giving the Approximate Areas of Distribution of the Different
Spinal Nerves with a Diagram showing Their Respective Levels of Exit from the
Vertebral Column. (Arranged by Dr. Gowers.)
MOTOR SENSORY REFLEX
Sterno -mastoid
Trapezius
\ Serratus
j Shoulder
Arm } muse.
Flexors, hip
Extensors, knee
Extensors (?■)
Flexors, knee (?)
Muscles of leg m(
ing foot
J Perineal and anal
muscles
Neck and scalp
1 Neck and shoulder
I Shoulder
Arm
[ Front of thorax
Abdomen
(.Umbilicus 10th)
I- Groin and scrotum
I (front) ■ Cremasteric
I [ Lateral side ! | |
I Knee-joint
j ( Medial side
' Leg, medial side
Buttock, lower
Back of thigh
Leg 1
and } except medial
I [ foot j part
I Perineum and anus
Foot-clonus
Plantar
The rami communicantes are small, short, thread-like branches by which the
nerve-trunks are connected with the nearest ganglion of the vertically running
gangliated cord of the sympathetic (sympathetic trunk). The trunk or anterior
primary division of every spinal nerve has at least one of these; most of the nerves
have two, and sometimes there are three. The nerves of the cervical region usu-
ally have but one, and this is composed largely of sympathetic fibres (grey
970 THE NERVOUS SYSTEM
ramus). Where there are two, one usually contains medullated fibres, chiefly
from the ventral root, sufficient to give it a whiter appearance (white ramus).
In the upper cervical and in the sacral regions one sympathetic ganglion may be connected
with two or more spinal nerves, and sometimes one nerve is connected with two ganglia. The
rami communicantes of the spinal nerves are equivalent to the communicating rami connecting
certain of the cranial nerves with the sympathetic system (trigeminus, glosso-pharyngeus, vagus) .
The medullated fibres of the rami and, therefore, the white rami consist chiefly of fibres from the
spinal nerves, viz., fibres from the spinal ganglion-cells which enter and course to their distri-
bution through branches of the sympathetic nerves, visceral afferent fibres, and fibres from
the ventral roots of the spinal nerves which terminate in the sympathetic ganglia, visceral
efferent (preganghonic) fibres. Thus the white rami have been termed the visceral divisions
of the spinal nerves. The grey rami consist chiefly of sympathetic fibres, most of which are
non-meduUated or partially medullated, and which course to their distribution by way of
the spinal nerves. Some of the sympathetic fibres terminate in the spinal ganghon, afferent
sympathetic fibres (fig. 748). The usual absence of white rami communicantes from the cervical
nerves is explained on the grounds — (1) that probably relatively few efferent visceral fibres
are given to the sympathetic from this region of the cord; (2) that many of the visceral efferent
fibres which do arise from this region of the cord probably join the rootlets of the spinal accessory
nerve and pass to the sympathetic system through the trunk of this nerve, and through the vagus
with which it anastomoses; and (3) that such of these fibres as are given off from the lower
segments of the cervical region, descend the cord and pass out by way of the upper thoracic
nerves which give very evident white rami to the sympathetic.
The meningeal or recurrent branch (figs. 747, 748, and 762) is very small and variable,
and is often difficult to find in ordinary dissections. It is given off from the nerve-trunk just
before its anterior and posterior primary divisions are formed. It consists of a few peripheral
branches of spinal ganglion-cells (sensory fibres) which leave the nerve-trunk and re-enter the
vertebral canal for the sensory innervation of the meninges, and which are joined by a twig
from the grey ramus or directly from the nearest sympathetic ganglion (vaso-motor fibres).
There is considerable evidence, both physiological and anatomical, obtained chiefly from the
animals, which shows that at times certain of the peripheral spinal ganghon or sensory fibres
may turn backward in the nerve-trunk and pass to the meninges within the ventral root instead
of contributing to a recurrent branch. The occurrence of such fibres in the ventral root explains
the physiological phenomenon known as 'recurrent sensibility.' Likewise, sympathetic fibres
entering the trunk through the grey ramus may pass to the meninges by way of the ventral
root, and at times the recurrent branch is probably absent altogether, its place being taken
entirely by the meningeal fibres passing in the ventral root.
Areas of distribution of the spinal nerves. — Both the posterior and anterior
primary divisions divide and subdivide repeatedly, and their component fibres are
distributed to areas of the body more or less constant for the nerves of each pair,
but the distribution of the different nerves is very variable. Corresponding to
their attachment, each to a given segment of the spinal cord, the nerves have pri-
marily a segmental distribution, but, owing to the developmental changes and
displacement of parts during the growth of the body, the segmental distribution
becomes greatly obscured and in some nerves practically obliterated. Naturally
it is more retained by the nerves supplying the trunk than by those contributing to
the innervation of the limbs and head, and the areas supplied by the posterior
primary divisions are less disturbed than those supplied by the anterior. The
segmental areas of cutaneous distribution of the posterior divisions are more evi-
dent than the areas of muscle supplied by these divisions, from the fact that the
segmental myotomes from which the dorsal muscles arise fuse together and over-
lap each other considerably during development. No nerve has a definitely pre-
scribed area of distribution, cutaneous or muscular, for its area is always consider-
ably overlapped by the areas of the nerves adjacent to it. The mid-thoracic
nerves more nearly supply a definitely prescribed belt of the body.
A. POSTERIOR PRIMARY DIVISIONS
The posterior primary divisions of the spinal nerves spring from the trunks
immediately outside the intervertebral foramina, and they pass dorsalward
between the adjacent transverse processes. With the exceptions of the first and
second cervical nerves they are smaller than the corresponding anterior primary
divisions, which in these nerves is smaller from the fact that a large portion of
them go over into the hypoglossal or cervical loop. The posterior primary divi-
sions, after passing between the transverse processes into the region of the back,
divide into medial and lateral branches. This division, however, does not occur
in the cases of the first cervical, the last two sacral, and the coccygeal nerves.
THORACIC NERVES 971
1. Cervical Nerves
The posterior primary division of the first cervical or sub -occipital nerve
springs from the trunk, between the vertebral artery and the posterior arch of
the atlas, passes dorsalward into the sub-occipital triangle, and breaks up into
branches which supply the superior oblique, the inferior oblique, and the major
rectus capitis posterior muscles, which form the lateral boundaries of the triangle.
It also gives a branch across the posterior surface of the major rectus capitis pos-
terior to the minor rectus capitis posterior, and a branch to the semispinalis
capitis (complexus) in the roof of the triangle.
It communicates with the medial branch of the posterior primary division of the second
cervical nerve, either through or over the inferior obUque muscle, and it occasionally gives a
cutaneous branch to the skin of the upper part of the back of the neck and the lower part of
the scalp.
The posterior primary division of the second cervical nerve is the largest pos-
terior division of all the cervical nerves. It divides into a small lateral branch and
a very large medial branch. The lateral branch gives a twig to the inferior oblique
and terminates in branches which supply the splenius and longissimus capitis
(trachelo-mastoid) muscles. The medial branch is the greater occipital nerve.
It turns around the lower border of the inferior oblique, crosses the sub-occipital
triangle obliquely, pierces the semispinalis capitis (complexus), the tendon of the
trapezius, and the deep cervical fascia, passing through the latter immediately
below the superior nuchal line of the occipital bone, and it divides into several
terminal sensory branches which ramify in the superficial fascia of the scalp.
It gives one or two motor twigs to the semispinalis capitis (complexus), and its terminal
branches which are accompanied by branches of the occipital artery supply the skin of the scalp,
above the superior nuchal Une, as far forward as the vertex. Occasionally one branch reaches
the pinna and supplies the skin on the upper part of its medial aspect. As it turns around the
inferior oblique it gives branches which join with the medial branches of the posterior primary
divisions of the first and third cervical nerves, and in this manner a small looped plexus is formed
beneath the semispinalis capitis (complexus) muscle, the posterior cervical plexus of Cruveilhier.
The posterior primary branches of the third, fourth, and fifth cervical nerves
divide at the lateral border of the semispinalis colli into medial and lateral branches.
The medial branches of the third, fourth, and fifth nerves run backward between
the semispinalis colli and capitis (complexus), supplying both muscles. Then,
after passing backward between the semispinalis capitis and the ligamentum
nuchse, they pierce the origin of the trapezius and supply the skin of the back of
the neck. The greater part of the medial branch of the third nerve, which runs
upward in the superficial fascia to the scalp, is called the third or smallest occipital
nerve ; it interlaces with the greater occipital nerve, and it supplies the skin of the
upper part of the back of the neck, near the middle line, and the skin of the
scalp in the region of the external occipital protuberance.
The medial branches of the posterior primary divisions of the sixth, seventh,
and eighth cervical nerves pass to the median side of the semispinalis colli, between
it and the subjacent multifidus spinse, and they end in the neighbouring muscles.
The lateral branches of the posterior primary divisions of the last five cervical
nerves are small and they are distributed to the longissimus capitis (trachelo-
mastoid), the ilio-costalis cervicis (cervicalis ascendens), the longissimus cervicis
(transversalis cervicis), the semispinalis capitis (complexus), and the splenius
muscles.
2. Thohacic Nerves
The posterior primary divisions of all the thoracic nerves divide into medial
and lateral branches while in the vertebral groove. The medial branches of the
upper six thoracic nerves pass dorsalward between the semispinalis dorsi and the
multifidus spinje; they supply the spinalis dorsi, the semispinahs dorsi, the multi-
fidus spinse, the rotatores spinse, the intertransversales, and the interspinales
muscles; and they end in cutaneous branches which, after piercing the trapezius,
turn lateralward in the superficial fascia of the back, and supply the skin as far as
the middle of the scapula. The cutaneous branch of the second nerve is the larg-
est; it can be traced lateralward as far as the acromion process. The medial
branches of the lower six thoracic nerves run dorsalward, between the longissi-
972
THE NERVOUS SYSTEM
mus dorsi and the multifidus spinae; they chiefly end in twigs to the adjacent
muscles, but not uncommonly they give small cutaneous twigs which pierce the
latissimus dorsi and the trapezius and end in the skin near the mid-line of the back.
The lateral branches of the upper six thoracic nerves pass between the longis-
FlG. 750. DlSTRLBCTION OF THE POSTERIOR PRIMARY DIVISIONS OP THE^SPINAL NeRVES.
(Henle.)
Semispinalis colli-
Multifidus spinx
Gluteus mazimus
simus dorsi and the ilio-costalis dorsi (accessorius) and end in those muscles, but
the lateral branches of the six lower nerves are longer; they pass into the interval
between the longissimus dorsi and the ilio-costalis dorsi and give branches to them,
and then they pierce the latissimus dorsi and are distributed to the skin of the
lower and lateral part of the back.
ANTERIOR PRIMARY DIVISIONS - 973
3. Lumbar Nerves
The medial branches of the posterior primary divisions of all the lumbar
nerves end in the multifidus spinse and those of the three lower nerves send very
small branches to the skin of the sacral region.
The lateral branches of the upper three nerves pass obliquely lateralward,
supplying twigs to the adjacent muscles, pierce the posterior layer of the lumbar
aponeurosis at the lateral bord^' of the sacro-spinalis (erector spinse) and enter
the subcutaneous tissue. They are, for the most part, cutaneous, forming the
superior clunial nerves, which cross the crest of the iUum and pass downward to
occupy different planes in the thick superficial fascia which covers the upper part
of the gluteus medius.
The branch from the first lumbar nerve is comparatively small, and occupies the most super-
ficial plane. The second occupies an intermediate position. The lateral branch from the third
nerve is the largest of the three, and occupies the lowest position; it distributes branches over
the gluteus maximus as far as the great trochanter. The three nerves anastomose with one
another and also with the cutaneous branches from the posterior primary divisions of the two
upper sacral nerves.
The lateral branch of the fourth lumbar nerve is of small size and ends in the
lower part of the sacro-spinalis (erector spinas). That of the fifth lumbar is
distributed to the sacro-spinalis and communicates with the first sacral nerve.
4. Saceal Nerves
The posterior primary divisions of the upper four sacral nerves escape from the
vertebral canal by passing through the posterior sacral foramina; those of the
fifth sacral nerve pass out through the hiatus sacralis between the posterior sacro-
coccygeal ligaments. Those of the upper three sacral nerves divide in the ordi-
nary manner into medial and lateral branches. Those of the lower two sacral
nerves remain undivided.
The medial branches of the upper three sacral nerves are of small size, and are
distributed to the multifidus spinse. The lateral branches anastomose with one
another and with the lateral branch of the last lumbar nerve, forming loops on
the posterior surface of the sacrum from which branches proceed to the posterior
surface of the sacro-tuberous (great sacro-sciatic) ligament, where they anasto-
mose and form a second series of loops, from which loops two or three branches are
given off. These branches pierce the gluteus maximus and come to the surface
of that muscle in a line between the posterior superior spine of the ilium and
the tip of the coccyx. Then, as the middle clunial nerves, they are distributed
to the integument over the medial part of the gluteus maximus, and communi-
cate, in their course through the superficial fascia, with the posterior branches
of the lumbar nerves.
The posterior divisions of the lower two sacral nerves unite with one another,
with the posterior branch of the third sacral, and with the coccygeal nerve, form-
ing loops from which twigs pass to the integument over the lower end of the
coccyx.
The posterior primary division of the coccygeal nerve is also undivided. It
separates from the anterior division in the sacral canal and emerges through the
hiatus sacralis, pierces the hgaments which close the lower part of that canal,
receives a communication from the posterior division of the last sacral nerve, and
ends in the skin over the dorsal aspect of the coccyx.
B. ANTERIOR PRIMARY DIVISIONS
The anterior primary divisions of the spinal nerves are larger than the pos-
terior primary divisions, and each is joined near its origin bj^ a grey ramus commu-
nicans from the sympathetic gangUated cord (figs. 751, 752, 762). Beginning with
the first or second thoracic nerve and ending with the second or third lumber
nerve, each anterior division sends to the gangliated cord a white ramus communi-
cans. The same is true of the second and third or of the third and fourth sacral
nerves. These white rami are appropriately designated the visceral branches of
974 THE NERVOUS SYSTEM
the spinal nerves. The anterior primary divisions of the cervical, lumbar, sacral,
and coccygeal nerves unite with one another to form plexuses, but the anterior
primary divisions of the thoracic nerves, except the first and last, remain separate,
pursue independent courses, and each divides, in a typical manner, into a lateral
and an anterior or ventral branch. The separation of the anterior primary divi-
sion into lateral and anterior branches is not confined to the thoracic nerves; it
occurs also in the lower cervical, the lumbar, and the sacral nerves, but such a divi-
sion cannot be clearly distinguished either in the upper cervical nerves, or in the
coccygeal nerve.
1. CERVICAL NERVES
The anterior primary divisions of the upper four cervical nerves unite to form
the cervical plexus, and each receives a communicating branch from the superior
cervical sympathetic ganglion. The anterior divisions of the lower four cervical
nerves are joined by the greater part of the first thoracic nerve and they unite to
form the brachial plexus (figs. 751, 754, 755). The fifth and sixth cervical nerves
receive communicating branches from the middle cervical sympathetic ganglion,
and the seventh and eighth from the inferior cervical ganglion, while the first
thoracic nerve is always connected with the first thoracic sympathetic gang-
lion by a grey ramus (figs. 751, 786) and in most cases also by a white ramus
communicans.
THE CERVICAL PLEXUS
The cervical plexus (figs. 751, 752) is formed by the anterior primary divisions
of the upper fom- cervical nerves which constitute the roots of the plexus. It
lies in the upper part of the side of the neck, under cover of the sterno-mastoid,
and upon the levator scapulse and the scalenus medius. It is a looped plexus,
consisting of three loops.
A large part of the anterior primary division of the first cervical nerve is given
to the hypoglossal or cervical loop; the remainder passes to the cervical plexus and
in doing so it runs lateralward on the posterior arch of the atlas beneath the verte-
bral artery, then it turns forward, between the vertebral artery and the outer side
of the upper articular process of the atlas, and finally it descends, in front of the
transverse process of the atlas, and unites with the upper branch of the second
nerve, forming with it the first loop of the plexus. It gives branches to the rectus
capitis lateralis, longus capitis (major rectus capitis anterior), and to the rectus
capitis anterior (minor). The division communicates with the ganglion of the
trunk of the vagus and with the superior cervical ganglion of the sympathetic
system (fig. 752) . From the first loop of the plexus, two branches of the division
pass over into the sheath of the hypoglossal nerve and descend with it to contrib-
ute to the hypoglossal loop [ansa hypoglossi] or better, the cervical loop. The
fibres entering the sheath of the hypoglossus, after giving a few twigs to the
gpnio-hyoid and thyreo-hyoid muscles, leave the sheath as the descendens cer-
vicalis (hypoglossi) and this latter joins the communicans cervicalis, (the portion
of the loop from the second and third cervical nerves) and thus completes the
cervical or hypoglossal loop.
This loop usually may be found between the sheaths of the sterno-mastoid muscle and the
carotid artery, superficial to the internal jugular vein; sometimes it may lie in the carotid
sheath between the carotid artery and the internal jugular vein; rarely it may lie dorsal to both
the artery and vein. Sometimes it is relatively long, descending toward the sternum below the
level of the thyreoid cartilage; again it is quite short and occurs near the level of the hyoid
bone. The descendens cervicahs (hypoglossi) parts company with the hypoglossal nerve at
the level at which the nerve curves around the occipital artery. It runs downward and shghtly
medialward on the sheaths of the great vessels and occasionally within the sheath of one of
them.
The second cervical nerve (anterior primary division) passes behind the upper
articular process of the axis and the vertebral artery, and between the inter-
transverse muscles extending from the first to the second cervical vertebrse, to
the interval between the scalenus medius and the longus capitis (rectus capitis
anterior major), where it divides into two parts. The upper part ascends and
unites with the first nerve to form the first loop of the plexus, and the lower branch
passes downward and dorsalward and joins the upper branch of the third nerve in
CERVICAL PLEXUS
975
the second loop of the plexus (figs. 751, 752). This branch gives off the small
occipital nerve and a filament to the sterno-mastoid, which communicates with
the spinal accessory nerve in the substance of the muscle, and it gives branches
which assist in forming the hypoglossal or cervical loop (ansa hypoglossi) the cer-
vical cutaneous and the great auricular nerves (fig. 752).
Fig. 751. — Origin of the Cervical and Brachial Plexus. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Anatomy," Rebman
Muscular branch to rectus capitis anterior and
lateralis and longus capitis m^ \
Rectus capitis lateralis s^^W,
Muscular branch to longus capitis and longus colli
eating branch to descendens
2rvicalis (hypoglossi)
Small occipital
Communicating branch to spinal accessory
Great auricular -,^
Cervical cutaneous
Muscular branch
Supra -da viculaiis -v;-
Phrenic .-i^
Dorsal scapul
Supra-scapular
Axillary
Internal carotid artery
Rectus capitis anterior
Radial
Musculo-cutaneous .
Medial ulnar
Anti -brachial
cutaneous
Internal car-
otid nerve
First cervical
nerve
Ramus communi-
cans
Second cervical
nerve
Superior cervical
ganglion
Third and fourth
cervical nerves
Ramus communi-
cans
Vertebral artery
Ganglia ted trunk
^ Fifth, sixth and
seventh cer-
vical nerves
Middle cervical
ganglion
Eighth cervical
nerve
Inferior cervical
ganghon
First thoracic
nerve
Vertebral
exus
Subscapular ^''''''
Long thoracic
Serratus anterior
Anterior thoracic
Scalenus medius
Subclavian
artery
The third and fourth cervical nerves pass behind the vertebral artery (fig. 751)
and between the intertransverse muscles to the interval between the scalenus
medius and the longus capitis (rectus capitis anterior major), where the third
unites with the second and fourth nerves and completes the lower two loops of the
plexus. The anterior primary divisions of these nerves are about double the size
of the preceding. The third gives off branches to the hypoglossal loop, to the
976
THE NERVOUS SYSTEM
larger part of the great auricular and cervical cutaneous nerves, a branch to the
phrenic, a branch to the supra-clavicular nerves, and muscular branches to the
scalenus medius, levator scapulse, longus capitis, and trapezius (fig. 752). The
trapezius branch joins the spinal accessory nerve beneath the muscle. The
fourth nerve gives a branch to the phrenic, a branch to the supra-clavicular nerves,
and muscular branches to the scalenus medius, levator scapulae, longus colli, and
trapezius (fig. 752). The branch to the trapezius unites with the one from the
third nerve and joins the spinal accessory nerve beneath the muscle.
The fibres forming the cervical (hypoglossal) loop innervate all the muscles
of the infra-hyoid group, though twigs to the genio-hyoid and thyreohyoid
seemingly enter these muscles from the trunk of the hypoglossus (fig. 752).
Fig. 752. — Diagram op the Cervical Plexus.
Ganglion of trunk
of vagus
Sterno-mastoid
Small occipital
Great auricular
Scalenus medius
Spinal accessory
Cervical cutaneous
Scalenus
medius
Levator scapulae -
Sympathetic -
Longus capitis
Rectus capitis anterior
Rectus capitis lateralis
Hypoglossal nerve
Superior cervical
sympathetic ganglion
Scalenus anterior
S t e r n o -thyreoid
Trapezius Posterior Middle _ Anterior supraclavicular
supraclavicular supraclavicular
The nerve to genio-hyoid is given off from the trunk under cover of the mylo-hyoid in com-
mon with the terminal branches of the hypoglossal proper going to the intrinsic muscles of the
tongue. The nerve to the thyreo-hyoid muscles leaves the trunk of the hypoglossal near the
tip of the great cornu of the hyoid bone, running obUquely downward and medianward to reach
its muscle. A twig to the anterior belly of the omo-hyoid is given from the upper part of the
descendens cervicalis and the nerves for the sterno-hyoid, the sterno-thyreoid and the pos-
terior belly of the omo-hyoid are supplied from the turn of the loop (fig. 7.52). The nerves to
the sterno-hyoid and sterno-thyreoid send twigs downward in the muscles behind the manubrium
sterni and fibres from these in rare cases join the phrenic nerve in the thorax. The nerve to
the posterior belly of the omo-hyoid courses as a loop in the cervical fascia below the central
tendon of its muscle.
Each root of the cervical plexus receives a communicating grey ramus from
the superior cervical ganglion of the sympathetic, and from the roots and loops of
BRANCHES OF CERVICAL PLEXUS
977
the plexus a number of branches arise which form two main groups, the superficial
and the deep.
Superficial Branches of the Cervical Plexus
The superficial branches are described, according to the direction in which
they run, as ascending, transverse, and descending branches. The ascending
branches are the small occipital and the great auricular nerves. There is only one
transverse branch, the cervical cutaneous (transverse cervical), and the descending
branches are distinguished as the supraclavicular nerves and the cervical (hypo-
glossal) loop.
The ascending branches. — (1) The small occipital nerve (fig. 751) arises from
the second and third cervical nerves, or from the loop between them, and runs
Fig. 753.-
-SuPEHFiciAL Branches op the Cervical Plexus.
(After Hirschfeld and Leveill6.)
Posterior
auricular
nerve
Auricular br of
great auricular V*
Cervical brauch
of facial
Cervical cutaneous- ^
Branches of cervical f
cutaneous nerve \
Great occipital
Great auricular
Mastoid br. or 2nd
small occipital
Spinal accessory
Twigs from the
mastoid branch
Br. to levator
scapulse
Posterior supra-
clavicular
Middle supra-
clavicular
upward and^dorsalward to the posterior border of the sterno-mastoid, where it
hooks around the lower border of the spinal accessory nerve and then ascends
along the posterior border of the muscle to the mastoid process. It pierces the
deep cervical fascia and passes across the posterior part of the insertion of the
sterno-mastoid into the superficial fascia of the scalp, in which it breaks up into
auricular, mastoid, and occipital terminal branches.
(a) The auriculax branch runs upward and slighly forward to reach the integument on the
upper median part of the auricle (pinna), wliioh it supphes. (6) The mastoid branch is distrib-
uted to the slvin covering the base of the mastoid process, (c) The occipital branches ramify
over the occipitaUs muscle and are distributed to the skin of the scalp ' they communicate with
one another and with the great occipital nerve. The branches of the small occipital nerve
978 THE NERVOUS SYSTEM
anastomose with twigs of the posterior auricular, great auricular, and great occipital nerves
(fig. 753).
(2) The great atiricular nerve arises from the second and third cervical nerves
(figs. 751, 752). It accompanies the small occipital to the posterior border of
the sterno-mastoid, but at that point it diverges from the small occipital (fig. 753)
and runs upward and forward across the sterno-mastoid toward the angle of the
mandible. When it is about half-way across the muscle it begins to break up into
its terminal branches, which are named, according to the area of their distribution,
mastoid, auricular, and facial.
As the nerve ascends obliquely across the sterno-mastoid it is embedded in the deep cervical
fascia, is covered by superficial fascia and the platysma, and it lies parallel with and slightly
dorsal to the external jugular vein, (a) The mastoid branch is small, and is distributed to the
integument covering the mastoid process. It anastomoses with the posterior auricular and small
occipital nerves. (6) The auricular branches are three or four stout twigs which interlace with
the branches of the posterior auricular nerve; they cross the superficial surface of the posterior
auricular branch of the facial, and are distributed to the skin on the back of the auricle with the
exception of its uppermost part. One or two twigs pass through fissures in the cartilage of the
auricle, and are distributed to the integument on the lateral surface of the lobule and the lateral
surface of the lower part of the helix and anthelix. (c) The facial branches pass upward and
forward among the superficial lobules of the parotid gland, and supply the skin over that gland
and immediately in front of it, and they anastomose in the substance of the gland with the cer-
vico-facial division of the facial nerve. In some cases fine twigs may be traced forward nearly
to the angle of the mouth.
Transverse branch of the plexus. — The superficial cervical cutaneous nerve
(transverse cervical) arises from the second and third cervical nerves (figs. 751,
752), and appears at the posterior border of the sterno-mastoid, a little below the
great auricular nerve. It passes transversely across the sterno-mastoid under
cover of the integument, platysma, and external jugular vein, and divides into a
number of twigs which spread out after the manner of a fan, and, as they approach
the middle line, extend from the chin to the sternum (fig. 753).
The upper two or three of these twigs unite, beneath the platysma, with the cervical (infra-
mandibular) branch of the facial and thus form loops. From the terminal branches of the nerve
numerous twigs arise which pierce the platysma and end in the skin of the front part of the neck.
The descending or supra-clavicular branches. — These are derived from the
third and fourth cervical nerves (figs. 751, 752), and arise under cover of the
sterno-mastoid. At their commencements they are usually united with the mus-
cular branches destined for the trapezius. They become superficial at the middle
of the posterior border of the sterno-mastoid, and as they pass downward they
pierce the deep cervical fascia. They include the following:
(1) The anterior supra-clavicular (suprasternal) branches (fig. 753) are small, and cross
over the clavicular attachment of the sterno-mastoid to reach the integument over the upper part
of the manulDrium sterni. They also supply the sterno-clavicular joint. (2) The middle
supra-clavicular (supra-clavicular) nerves are of considerable size. They cross in front of the
middle third of the clavicle under cover of the platysma, and are distributed to the skin cover-
ing the upper part of the pectoralis major as low as the third rib. (3) The posterior supra-
clavicular (supra-acromial) branches (fig. 753) cross the clavicular insertion of the trapezius
and the acromion process. They are distributed to the skin which covers the upper two-thirds of
the deltoid muscle and they supply the acromio-clavicular joint.
Deep Branches of the Cervical Plexus
The deep branches of the plexus pass lateralward and dorsalward, or ventral-
ward and medialward; therefore they form two series, the lateral and the medial.
The lateral branches of the deep series include communicating branches from
the second, third, and fourth cervical nerves to the spinal accessory nerve, and
muscular branches to the sterno-mastoid and the scalenus medius, levator scap-
ulse, and trapezius.
The communicating branches. — The communicating branch from the second cervical
nerve is ultimately distributed to the sterno-mastoid, and those from the third and fourth nerves
end in the trapezius.
1. The nerve to the sterno-mastoid arises from the second cervical nerve (fig. 753). It
pierces the deep surface of the sterno-mastoid, and coinmunicates within the muscle with the
spinal accessory nerve.
2. The nerves to the scalenus medius (fig. 752) are derived from the third or fourth
to the eighth cervical nerves close to their exit from the intervertebral foramina.
BRANCHES OF CERVICAL PLEXUS 979
3. The nerves to the levator scapulae (fig. 752) are derived from the third and fourth cervical
nerves, and occasionally from the second or fifth. They pierce the superficial surface of the
levator scapute, and supply the upper three divisions of that muscle.
4. The branches to the trapezius (fig. 752) are usually in the form of two stout twigs which
are given off by the third and fourth cervical nerves. They emerge from under cover of the
sterno-mastoid at its posterior border and cross the posterior superior triangle of the neck at a
lower level than the spinal accessory nerve (fig. 753). They pass under cover of the trapezius
in company with the last-named nerve, and communicate with it to form the subtrapezial
plexus, from which the trapezius is supplied.
The medial branches of the deep series also comprise communicating and mus-
cular branches.
The communicating branches (figs. 751, 752) include (1) branches which connect each
of the first four cervical nerves with the superior cervical ganghon of the sympathetic; (2) a
branch to the vagus; (3) a branch to the hypoglossal; and (4) branches which pass from the
second and third cervical nerves to the descendens cervicalis (hypoglossi) . The ultimate dis-
tribution of the twigs connected with the sympathetic and the vagus nerves is not known, but
the fibres which pass to the hypoglossal nerve pass from it to the thyreo-hyoideus muscle, and
to the descendens cervicalis and the latter joins with the branches from the second and third
cervical nerves, forming with them the cervical or hypoglossal loop [ansa hypoglossi] which
lies on the carotid sheath. From this loop the two beUies of the omo-hyoid muscle and the
sterno-hyoid and sterno-thyreoid muscles are supphed as described above.
The muscular branches supply the rectus capitis lateralis, the longus cap'tis
(rectus capitis anterior major), the rectus capitis anterior (minor), the scalenus
anterior, and the diaphragm. The nerve to the latter muscle is the phrenic.
1. The branch to the rectus capitis lateralis is furnished to that muscle by the first cervical
nerve as it crosses the deep surface of the muscle.
2. The nerve to the rectus capitis anterior (minor) is given off by the first nerve at the
upper part of the loop in front of the transverse process of the atlas.
3. The longus capitis (rectus capitis anterior major) receives twigs from the upper four
cervical nerves.
4. The longus colli receives branches from the second, third, and fourth cervical nerves,
and additional branches also from the fifth and sixth nerves.
5. The phrenic nerve (fig. 752) springs chiefly from the fourth cervical nerve,
but it usually receives a twig from the third and another from the fifth cervical
nerve, a small communicating branch from the sympathetic, and, rarely, a branch
from the vagus. The twig from the fifth cervical nerve is frequently connected
with the nerve to the subclavius. After the union of its roots the phrenic nerve
passes downward and medialward on the scalenus anterior (fig. 755). In this
part of its course it is crossed by the tendon of the omo-hyoid and by the trans-
verse cervical and transverse scapular (suprascapular) arteries. It is overlapped
by the internal jugular vein, and it is covered by the sterno-mastoid muscle. At
the root of the neck the left phrenic nerve lies behind the terminal portion of the
thoracic duct, and each nerve passes off the anterior border of the scalenus anterior
and descends in front of the first part of the subclavian artery and the pleura imme-
diately below that artery; each nerve passes dorsal to the terminus of the sub-
clavian vein, crosses either in front of or dorsal to the internal mammary artery and
gains the medial surface of the pleural sac. From the root of the neck the rela-
tions of the phrenic nerves differ. The right phrenic nerve descends along the medial
surface of the right pleural sac and crosses in front of the root of the lung. It is
accompanied by the pericardiaco-phrenic artery (comes nervi phrenici), and it is
in relation medially, and from above downward, with the right innominate vein,
the superior vena cava, and the pericardium, the latter membrane separating it
from the wall of the right atrium (auricle) . The left phrenic nerve descends along
the medial surface of the left pleural sac accompanied by the pericardiaco-phrenic
(comes nervi phrenici) artery. In the superior mediastinum it lies between the
left common carotid and the left subclavian arteries, and it crosses in front of the
left vagus, the left superior intercostal vein, and the arch of the aorta. Below
the arch of the aorta it crosses in front of the root of the left lung, and then hes
along the left lateral surface of the pericardium, which separates it from the wall of
the left ventricle.
Branches. — Both phrenic nerves distribute branches to the pericardium and to the pleura.
The right nerve gives off a branch, pericardiac, which accompanies the superior vena cava and
supplies the pericardium. Each phrenic nerve divides into numerous terminal phrenico-
abdominal branches. As a rule, the right phrenic nerve divides into two main terminal branches,
an anterior and a posterior. The anterior branch runs forward and one of its terminal filaments
980
THE NERVOUS SYSTEM
anastomoses with the phrenic of the opposite side in front of the pericardium; others descend
between the sternal and costal attachments of the diaphragm into the abdomen, where some of
them supply the diaphragm and others descend in the falciform Ugament to the peritoneum on
the upper surface of the liver. The posterior branch passes through the vena caval opening and
ramifies upon the lower surface of the diaphragm, anastomosing with the diaphragmatic plexus
of the sympathetic, and its terminal branches supply the muscular fibi-es of the right half of
the diaphragm, the inferior vena cava, and the right suprarenal gland.
The left phrenic nerve divides into several branches. One of the most anterior branches
anastomoses with the right phrenic nerve; the others pierce the diaphragm and ramify on its
under surface, where they anastomose with filaments of the left diaphragmatic plexus of the
sympathetic and supply the left half of the diaphragm and the left suprarenal gland. The left
phrenic nerve is considerably longer than the right nerve, partly on account of the lower level
of the diaphragm on the left side, and partly on account of the greater convexity of the left
side of the pericardium.
THE BRACHIAL PLEXUS
The brachial plexus (figs. 751, 754, 755) is formed by the anterior primary
divisions of the four lower cervical nerves and the greater part of that of the
Fig. 754. — Diagbam op a Common Form op Bbachial Plexus.
The posterior cord of the plexus is darkly shaded.
Fifth cervical — ^j\ \( From fourth cervical
Sixth cervical
Seventh cervic;
Eighth cervical
Long thoracic.
First thoracic.
First intercostal
Second thoracic
Second intercostal
Third thoracic
Third intercostal
ical^^
-Nerve to subclavius
- Suprascapular
Anterior thoracic nerves
Lateral cord of plexus
N.^ = — Radial (musculo-spiral)
— ;_: <rX;^ — Medial cord of plexus
Thoraco-dorsal
Median
trinar
Medial antibrachial
cutaneous
Medial brachial cuta-
neous (nerve of
Wrisberg)
Intercosto-brachial Lateral cutaneous
first thoracic nerve. It is usually joined by small twigs from the foxirth cervical
and second thoracic nerves.
The anterior primary divisions of the lower four cervical nerves, after passing
dorsal to the vertebral artery and between the anterior and posterior parts of the
intertransverse muscles, pass into the posterior triangle in the interval between
the adjacent borders of the anterior and middle scalene muscles, where the fifth
and sixth nerves receive a grey ramus communicans each from the middle cervical
sympathetic ganglion, and the seventh and eighth nerves each receive a grey
ramus from the inferior cervical sympathetic ganglion. The first thoracic is
connected by two rami communicantes with the first thoracic sympathetic gang-
lion, and it divides into a smaller and a larger branch. The smaller branch passes
along the intercostal space as the first intercostal nerve, and the larger branch,
after being joined by a twig from the second thoracic nerve, passes upward and
lateralward, in front of the neck of the first rib and behind the apex of the pleural
sac, into the lower part of the posterior triangle of the neck, where it takes part in
the formation of the plexus.
The anterior primary divisions of those cervical nerves that form the brachial
plexus may be considered as typically giving off anterior and posterior branches,
THE BRACHIAL PLEXUS
981
except that the fifth and sixth nerves often unite before branching and give off
their posterior branches as a common trunk, and the eighth nerve often receives
its branch from the first thoracic nerve before giving off its posterior branch.
It is on account of this variation in the point of union of the fifth and sixth
cervical nerves and of the eighth cervical and first thoracic nerves that so many
different forms of the plexus have been pictured and described. But if the differ-
ences in primary branching be borne in mind, the formation of the plexus is always
uniform and simple, notwithstanding its different appearances.
Fig. 755. — The Brachial Plexus and its Branches op the Region of the Neck and
Shoulder. (After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Internal jugular vein
Phrenic / "'T^
Branch to levator scapulae ( '
■ branch of cervical V
f Dorsal scapular
Long thoracic
Supra-clavicular
portion of plexus
Subscapular
Auxiliary and radial
Twig to coraco-brachiahs
Musculo-cutaneous
__ Descendens cer-
vicalis (hypoglossi)
Sterno-tiyoideus
^ and sterno-
thyreoideus
Subclavian
muscle and
nerve
^^ Anterior
^ .thoracic
Muscular
branches of
axillary
Branches
to bicep
brachii
Lateral
antibrachial '
cutaneous
/ L-one: thoracic to
■' serratus anterior
/ \^ Thoraco-dorsal to
''^ latissimus dorsi
\
Median
Bracliial artery
~^ Ulnar
Medial antibrachi:
cutaneous
Three cords are formed from these branches in the following manner: — (1)
The lateral (outer) cord [fasciculus lateralis] is formed by the anterior branches of
the fifth, sbcth, and seventh nerves; (2) the medial (inner) cord [fasciculus medi-
alis], by the anterior branches of the eighth cervical and first thoracic nerves; and
(3) the 'posterior cord [fasciculus posterior], by the posterior branches of all of these
cervical nerves.
Relations. — The plexus extends from the lateral border of the scalenus anterior, where the
roots of its constituent nerves appear, to the lower border of the peotoralis minor, where each
982 THE NERVOUS SYSTEM
of its three cords divides into two terminal branches, and it lies in the posterior triangle, in the
root of the neck, and in the axillary fossa. In the posterior triangle and in the root of the neck
it is in relation liehind with the scalenus medius (figs. 751, 755). In the posterior triangle it is
covered superficially by the skin and superficial fascia, the pJatysma, the supra-clavicular
branches of the cervical plexus, and the deep fascia, and it is crossed by the lower part of the
external jugular vein, by the nerve to the subclavius, the transverse cervical vein and the
transverse scapular (supra-scapular) vein, the posterior belly of the omo-hyoid muscle, and by
the transverse cervical artery. At the root of the neck it lies behind the clavicle and the sub-
clavius muscle, and the transverse scapular (suprascapular) artery crosses in front of it. In the
axillary fossa the cords are arranged around the axillary artery, the lateral (outer) cord lying
lateral to the artery, the medial (inner) cord medial to it, and the posterior cord dorsal to the
artery. In this region the posterior relations of the plexus are the fat in the upper part of the
fossa and the subscapularis muscle, and it is covered in front by the pectoral muscles and the
coraco-clavicular fascia. The lower border of the plexus is in relation in the posterior triangle
and at the root of the neck with the pleura and the first rib, and it is overlapped in front by the
third part of the subclavian artery. In the axillary fossa the medial cord which forms the lower
border of the plexus is overlapped anteriorly by the axillary vein. The upper and lateral border
of the plexus has no very important relations.
In gross, the brachial plexus may be formulated as beginning with five nerves
and terminating in five nerves, with its intermediate portions displayed in sets of
threes. It begins with the fifth, sixth, seventh and eighth cervical and first
thoracic nerves; it terminates as a plexus with the formation of the musculo-
cutaneous, radial, axillary, median, and ulnar nerves; in its intermediate portions,
first main trunlcs are formed and these divide into two sets of threes which, by
union, give rise to three cords. The branches from the cords are three main
lateral branches from each and the terminal branches of the plexus. The lateral
branches, according as they are given off above, below, and dorsal to the clavicle,
are grouped as the supra-clavicular, the infra-clavicular and the subscapular por-
tions of the plexus.
The branches of the supra-clavicular portion. — After the roots of the plexus
have received communications from the sympathetic, which have already been
referred to, they give off a series of muscular branches, viz. — the posterior thoracic
nerves (the dorsal scapular and the long thoracic nerve), the suprascapular nerve,
a twig to the phrenic, the nerve to the subclavius, and small twigs to the scalene
muscles and the longus colli muscle.
The posterior thoracic nerves are two in number: — (a) the dorsal scapular
(nerve to the rhomboids) arises principally from the fifth cervical nerve, but it
frequently receives a twig from tihe fourth nerve (fig. 751).
It passes downward and dorsalward, across the middle scalene, parallel with and below the
spinal accessory nerve to the anterior border of the levator scapulae, under which it disappears.
It continues its descent under cover of the levator scapulae and the rhomboids almost to the
lower angle of the scapula, lying a little medial to the posterior border of the bone, and it supplies
the lower fibres of the levator and the smaller and larger rhomboid muscles.
(&) The long thoracic nerve (external respiratory nerve of Bell) supplies the
serratus anterior.
It usually arises, by three roots, from the fifth, sixth, and seventh cervical nerves. The
last is sometimes absent (figs. 751 and 754). The upper two roots traverse the substance of
the scalenus medius; the root from the seventh passes in front of that muscle. Twigs are fur-
nished to the superior portion of the serratus anterior by the upper two roots; lower down they
unite and are subsequently joined by the root from the seventh when present. The trunk of the
nerve passes downward behind the brachial plexus and the first stage of the axillary artery,
and runs along the axihary surface of the serratus anterior (magnus), supplying twigs to each of
the digitations of that muscle (fig. 755).
The suprascapular nerve (fig. 751) supplies the supraspinatus and infraspi-
natus muscles.
It receives fibres from the fifth and sixth cervical nerves, and occasionally also a twig from
the fourth nerve. It is a nerve of considerable size, and it passes downward and dorsalward
parallel with the dorsal scapular nerve, at first along the upper border of the posterior belly
of the omo-hyoid muscle, then internal to the latter muscle and under cover of the anterior
border of the trapezius to the suprascapular notch (fig. 755), where it comes into relation with
the transverse scapular (suprascapular) artery. It is separated from the artery at the notch
by the superior transverse ligament, the nerve passing through the notch and the artery above
the ligament. After entering the supraspinous fossa the nerve supplies branches to the supra-
spinatus and a branch to the shoulder-joint; then it descends through the great scapular notch
between the bone and the inferior transverse ligament to the infraspinous fossa, where it ter-
minates in the infraspinatus muscle.
The twig to the phrenic (fig. 751) arises from the fifth cervical nerve close to the point where
the latter nerve receives its twig from the cervical plexus.
MEDIAL BRACHIAL CUTANEOUS NERVE
983
The nerve to the subclavius (fig. 755) is a small twig which arises from the fifth nerve or
from the upper trunk of the plexus, but occasionally it receives additional fibres from the
fourth and sixth nerves. It runs downward in front of the lower part of the plexus and the third
stage of the subclavian artery and, after giving off sometimes a branch to the phrenic, pierces the
posterior layer of the coraco-clavicular fascia, and enters the subclavius at its lower border._
Variety. — In rare cases the entire phrenic nerve may pass vid the nerve to the subclavius
in front of the third stage of the subclavian artery.
The scaleni and longus colli (figs. 751, 754) are supplied by twigs which arise from the lower
three or four cervical nerves immediately after their exit from the intervertebral foramina.
The lateral branches of the infra-clavicular portion of the brachial plexus
are the anterior thoracic nerves, from the lateral and medial cords respectively,
the medial antibrachial (internal) cutaneous and the medial brachial (lesser
internal) cutaneous nerves, from the medial cord, and the subscapular nerves
and thoraco-dorsal from the posterior cord.
The lateral anterior thoracic nerve joins with the medial to form a loop which
supplies the pectoralis major and minor.
Fig. 756.-
-DlSTBIBUTION OF CuTANEOrrS NeRVES ON THE ANTERIOR AND PoSTEHIOR ASPECTS
OF THE Superior Extremity.
Medial anti-
brachial
cutaneous
Supra-acromial
Lateral brachial
cutaneous
Intercosto-
brachial
Twig of medial
antibrachial
cutaneous
Dorsal
antibrachial
cutaneous
Lateral anti-
brachial
cutaneous
(musculo-
cutaneous I
Supraacromial
It arises from the lateral cord of the plexus and contains fibres from the fifth, sixth, and
seventh cervical nerves (figs. 751, 754, 755). After joining the medial anterior thoracic it pierces
the coraco-clavicular fascia and ends in branches that supply the pectoraUs major muscle.
The medial anterior thoracic nerve arises from the medial cord (figs. 751, 754, 755), contains
fibres from the eighth cervical and first thoracic nerves, and passes forward between the first
stage of the axillary artery and the axillary vein. It unites with a branch from the lateral
anterior thoracic, to form a loop which is placed in front of the first stage of the axillary artery;
it gives branches to the pectoralis minor, and branches which pass through the latter muscle and
end in the pectorahs major. From the loop additional branches are furnished to the pectoralis
major.
The medial brachial (lesser internal) cutaneous nerve, or nerve of Wrisberg
(fig. 754), arises from the medial cord of the brachial plexus and sometimes con-
tains fibres from the eighth cervical and first thoracic nerves, but usually fibres
984 THE NERVOUS SYSTEM
from the first thoracic nerve alone. It runs downward on the medial side of the
axillary vein, being separated by that vessel from the ulnar nerve, and it continues
downward with a slight inclination dorsalward under cover of the deep fascia on
the inner side of the arm. At the middle of the arm it pierces the deep fascia,
and near the bend of the elbow it turns somewhat sharply dorsalward to supply
the integument which covers the olecranon process (fig. 756).
As it traverses the axilla the nerve of Wrisberg communicates with the intercosto-braohial
nerve, forming one, or sometimes two loops (fig. 754). In its course clown the arm it gives a
few fine twigs to the integument. This nerve may be absent, its place being taken by the inter-
costo-braohial or by part of the posterior brachial (.internal) cutaneous branch of the radial
(musculo-spu-al) or, rarely, by a branch from the fu'st intercostal nerve.
The medial antibrachial (internal) cutaneous nerve (figs. 751 and 754) arises
from the medial cord in close relation with the ulnar nerve. It contains fibres
from the eighth cervical and first thoracic nerves. At its origin it lies directly on
the medial side of the axillary artery (fig. 755), but it soon becomes more super-
ficial and then lies in the groove between the arterj^ and the vein. In the upper
two-thirds of the arm it lies in front and to the medial side of the brachial artery.
It divides into two branches (volar and ulnar) which supply the medial aspect
of the forearm.
At the junction of the middle and lower thirds of the arm this nerve pierces the deep fascia,
in company with the basilic vein, and divides into an anterior and a posterior branch. Previous
to its division it gives off twigs which pierce the deep fascia and supply the integument of the
upper and medial part of the arm. The volar (anterior) branch is larger than the ulnar (pos-
terior) ; it passes in front of or dorsal to the median basilic vein, and divides into several twigs
which run down the forearm, supplying the integument covering its anterior and medial aspect
as far as the wrist, and anastomosing with the branches of the ulnar nerve. The ulnar (posterior)
branch passes downward and dorsalward in front of the medial condyle of the humerus, and di-
vides into branches which supply the skin on the postero-medial aspect of the forearm. It
anastomoses with the dorsal antibrachial (inferior external) cutaneous branch of the radial
(musculo-spiral) nerve and the dorsal branch of the ulnar nerve).
The subscapular nerves are branches of the posterior cord (fig. 754). They
are three in number, are distinguished as upper, thoraco-dorsal or middle, and
lower, and are distributed to the subscapularis, latissimus dorsi, and teres major
muscles.
The upper or short subscapular nerve is derived from the fifth and sixth cervical nerves.
It hes in the upper and posterior part of the a.xillary fossa, and it is distributed exclusively to
the subscapularis muscle. It is occasionally double.
The thoraco-dorsal, middle, or long subscapular nerve consists mainly of fibres from the
seventh and eighth cervical nerves, but it may contain fibres from the fifth or the sixth nerve.
It passes behind the axillary artery, accompanies the subscapular artery along the axillary margin
of the subscapularis muscle, and ends in the latissimus dorsi (fig. 755).
The lower subscapular nerve, carrying fibres from the fifth and sixth cervical nerves,
passes behind the subscapular artery, below the circumflex branch (dorsahs scapulae), and is
distributed to the teres major, and furnishes to the subscapularis one or two twigs which enter
that muscle near its axillary margin.
The terminal branches of the plexus are two from each cord. The posterior
cord divides into the axillary (circumflex) and the radial (musculo-spiral) nerves.
The lateral cord divides into the musculo-cutaneous nerve, and the lateral root of
the median nerve; the medial cord divides into the ulnar nerve, and the medial
root of the median nerve, the median nerve as a whole being one of the five ter-
minal branches of the plexus.
The axillary (circumflex) nerve is the smaller of the two terminal branches of
the posterior cord, and contains fibres from the fifth and sixth cervical nerves
(figs. 751 and 754). At the lower border of the subscapularis it passes dorsalward
and accompanies the posterior circumflex artery through the quadrilateral space,
which is bounded by the teres major, long head of triceps, and subscapularis mus-
cles, and the surgical neck of the humerus, and it divides into a smaller superior
and. a larger inferior division. Previous to its division it furnishes an articular
twig to the shoulder-joint. This twig pierces the inferior part of the articular
capsule.
The superior division accompanies the posterior circumflex artery around the
neck of the humerus, and gives off a number of stout twigs which enter the del-
toid muscle (fig. 755) . A few fine filaments pierce the deltoid and end in the integ-
ument which covers the middle third of that muscle.
THE RADIAL NERVE 985
The inferior division divides into cutaneous and muscular branches. The
cutaneous branch (the lateral brachial cutaneous nerve) turns around the pos-
terior border of the deltoid, pierces the deep fascia, and supplies the skin covering
the lower third of the deltoid and a small area of integument below the insertion of
the muscle (fig. 756). One muscular branch is distributed to the teres minor; it '
swells out into an ovoid or fusiform, reddish, gangliform enlargement before
entering the muscle. Other branches supply the lower and posterior part of the
deltoid.
The radial (musculo-spiral) nerve is the largest branch of the brachial plexus.
It contains fibres from the sixth, seventh, and eighth cervical and sometimes
from the fifth cervical and first thoracic nerves (figs. 751, 754). It commences
at the lower border of the pectoralis minor, as the direct continuation of the
posterior cord of the brachial plexus, and passes downward and lateralward in the
axillary fossa behind the third part of the axillary artery (fig. 755) and in front of
the subscapulars, latissimus dorsi, and teres major muscles. From the lower
border of the axillary fossa it descends into the arm, where it lies, at' first, on the
medial side of the upper third of the humerus, behind the brachial artery and in
front of the long head of the triceps ; then it runs obliquely downward and lateral-
ward behind the middle third of the humerus, in the groove for the radial nerve
(musculo-spiral groove), and between the lateral and medial heads of the triceps.
It is accompanied, in this part of its course, by the profunda artery. At the junc-
tion of the middle and lower thirds of the humerus it reaches the lateral side of the
arm, pierces the external intermuscular septum, and runs downward and forward
between the brachio-radialis and extensor carpi radialis longus externally, and
the brachialis internally (fig. 758), and it terminates, a short distance above the
capitulum, by dividing into deep and superficial terminal branches. In the last
part of its course it is accompanied by the anterior terminal branch of the pro-
funda artery.
Branches. — The branches of the radial or musculo-spiral nerve are cutaneous,
muscular, articular^ and terminal, but for practical purposes it is best to consider
them in association with the situations of their origins. While it is in the axillary
fossa the radial (musculo-spiral) nerve gives branches to the medial and long
heads of the triceps (fig. 758), and a medial cutaneous branch. The branch to the
long head of the triceps at once enters the substance of the muscle, that to the
medial head breaks into branches which terminate in the muscle at different levels,
and one of them, the ulnar collateral nerve, accompanies the ulnar nerve to the
lower part of the arm. The posterior brachial (internal) cutaneous branch
crosses the tendon of the latissimus dorsi, passes dorsal to the intercosto-brachial
(intercosto-humeral) nerve, pierces the deep fascia, and is distributed to the skin
of the middle of the back of the arm below the deltoid.
While it lies behind the middle third of the humerus, the radial nerve gives
branches to the lateral and medial heads of the triceps and to the anconeus. The
latter branch descends in the substance of the median head of the triceps, close to
the bone, and it is accompanied by a small branch of the profunda artery. The
dorsal antibrachial (external) cutaneous branch, passing down between the
lateral and median heads of the triceps, divides near the elbow into its upper and
lower branches (fig. 756), each of which perforates either the lateral head of the
triceps muscle near its attachment to the humerus or the external intermuscular
septum.
The upper branch, much the smaller, pierces the deep fascia in the line of the external inter-
muscular septum; it accompanies the lower part of the cephaUc vein, and supphes the skin over
the lower half of the lateral and anterior aspect of the arm. The lower branch is of considerable
size. It pierces the deep fascia a httle below the upper branch, runs behind the external con-
dyle, and supplies the skin of the middle of the back of the forearm as far as the wrist, an-
astomosing with the medial antibrachial (internal) cutaneous and musculo-cutaneous nerves
(fig. 759).
After the radial nerve has pierced the external intermuscular septum it gives
branches to the brachio-radialis, extensor carpi radialis longus, and to the lateral
portion of the brachialis (fig. 759). From one of these branches an articular
filament is distributed to the elbow-joint.
The terminal branches of the radial nei"ve are: — a motor branch, the deep
radial, to the supinator and extensor muscles of the forearm, and a sensory
THE NERVOUS SYSTEM
branch, the superficial radial, which supplies the dorsal aspect of the radial half
of the hand.
The deep radial [ramus profundus] (posterior interosseous) nerve runs down-
ward in the interval between the brachialis and extensor carpi radialis longus.
It passes in front of the lateral part of the elbow-joint, and after giving off branches
to supply the extensor carpi radialis brevis and supinator, it is crossed in front
by the radial recurrent artery (fig. 759) . It then runs downward and dorsalward
through the substance of the supinator, and enters the interval between the
superficial and deep layers of muscles at the back of the forearm, where it comes
into relation with the posterior interosseous artery, and accompanies it across
Fig. 767. — A Dissection or the Cutaneous Nbeves on the Dohsal Aspect of the Hand
AND Fingers. (H. St. J. B.)
The branches of the median nerve are shown in black.
Dorsal branch of
ulnar nerve
Branch of radial (musculo-spiral)
— Superficial radial (radial) nerve
the abductor pollicis longus. At the lower border of the latter muscle it gives off
a branch to the extensor pollicis longus, and another which crosses this muscle to
the extensor indicis proprius.
Continuing distalward as the dorsal antibrachial interosseous nerve the deep radial leaves the
posterior interosseous artery, dips beneath the e.xtensor pollicis longus, and joins the volar inter-
osseous artery. It accompanies this artery upon the interosseous membrane and upon the back
of the radius, passes through the groove for the extensor digitorum communis and extensor
indicis proprius to the dorsum of the wrist, and terminates in a gangliform enlargement which
gives branches to the carpal articulations. The muscles supplied by the deep radial nerve
are the extensor carpi radialis brevis, brachio-radialis (supinator longus), extensor digitorum
communis, extensor digiti quinti proprius, extensor carpi ulnaris, extensor indicis proprius,
and the extensor muscles of the thumb. The supinator (brevis) receives two twigs, one of which
is given off before the nerve pierces the muscle and the other while it is passmg through it.
THE ULNAR NERVE 987
The superficial radial (radial) nerve [ramus superficialis n. radialis] is some-
what smaller than the deep radial (posterior interosseous), and is a purely cuta-
neous nerve. It runs downward under cover of the brachio-radialis, passing in
front of the elbow-joint, the radial recurrent artery, and the supinator (brevis).
At the lower border of the supinator it approaches the radial artery at an acute
angle, and runs parallel to the lateral side of that vessel in the middle third of the
forearm, across the pronator teres. At the lower border of the pronator teres it
bends dorsalward on the deep surface of the tendon of the brachio-radialis, and
appears on the back of the forearm. It pierces the deep fascia and is directed
across the dorsal carpal (posterior annular) ligament toward the dorsum of the
wrist, where it divides into its terminal branches (fig. 759).
The most lateral of these branches suppUes the skin on the radial part of the thenar eminence;
the most medial, designated the ulnar anastomotic branch, communicates with the'dorsal branch
of the ulnar nerve. The other terminal branches, the dorsal digital nerves, supply to a variable
extent the skin on the dorsum of the first digit, both sides of the second and the radial side
of the third digit. These branches usually extend to the base of the nail of the first digit, to the
distal interphalangeal joint of the second, not quite to the proximal interphalangeal joint of
the third, and to the metacarpo-phalangeal joint of the fourth digit.
The terminal branches of the lateral cord of the brachial plexus are the mus-
culo-cutaneous and the lateral component of the median nei-ve. The latter nerve
will be described with the medial cord.
The musculo-cutaneous nerve is composed of fibres derived chiefly from the
anterior divisions of the fifth and sixth cervical nerves, together usually with
some fibres from that of the seventh (figs. 751 and 754). The nerve to the coraco-
brachialis usually consists of two or three twigs given off from the nerve close to
its origin before it enters the muscle (fig. 755). Sometimes, however, the fibres
from the seventh cervical nerve pass directly to this muscle without joining the
main trunk. The musculo-cutaneous nerve is placed at first close to the lateral
sideof the axillary artery (fig. 755), but soon it leaves that vessel and, piercing the
coraco-brachialis muscle, it passes obliquely downward and lateralward between
the biceps and brachialis muscles. Soon after piercing the coraco-brachialis it
gives off muscular branches to each head of the biceps and to the brachialis (fig.
758). It also gives twigs to the humerus, to the nutrient artery, and gives the chief
supply to the elbow-joint. Below the branch to the brachialis the cutaneous por-
tion of the nerve forms the lateral antibrachial cutaneous nerve (figs. 756, 758) .
This portion continues downward between the biceps and brachialis, pierces the
deep fascia at the lateral border of the former muscle a little above the bend of the
elbow, receives a communication from the upper branch of the dorsal antibrachial
(upper external) cutaneous branch of the radial (musculo-spiral) nerve, passes
dorsal to the median cephalic vein, and divides into an anterior and a posterior
branch.
The anterior branch runs downward on the lateral and anterior part of the forearm, sup-
plying the integument of that region, and it terminates in the skin covering the middle part of
the thenar eminence (fig. 759). A short distance above the wrist, after it has received a com-
municating twig from the superficial radial nerve, it gives off an articular branch to the carpal
joints. This branch pierces the deep fascia and accompanies the radial artery to the dorsum
of the wrist. The posterior terminal branch is small, and is directed downward and backward
in front of the external condyle of the humerus, to be distributed to the skin on the lateral and
posterior aspect of the forearm as low as the wrist (fig. 756). It anastomoses with the superficial
radial and with the lower branch of the dorsal antibrachial (lower external) cutaneous branch
of the radial nerve.
The terminal branches of the medial cord of the brachial plexus are the ulnar
nerve and the medial component of the median nerve. Neither of these gives any
branches in the upper arm, and thus they differ from the other terminal branches
of the plexus. They both supply the muscles and joints of the forearm, and the
muscles, joints, and integument of the hand.
The ulnar nerve, which is the largest branch of the medial cord of the brachial
plexus, contains fibres from the anterior divisions of the eighth cervical and first
thoracic nerves (figs. 752 and 762). It commences at the lower border of the
pectoralis minor and runs downward in the axillary fossa in the posterior angle
between the axillary artery and vein. In the upper half of the arm it lies on the
medial side of the brachial artery (fig. 755), but at the level of the insertion of the
THE NERVOUS SYSTEM
coraco-brachialis it passes backward at an acute angle, and, accompanied by the
superior ulnar collateral (inferior profunda) artery, it pierces the internal inter-
muscular septum. After passing through the septum it runs downward, in a
groove in the medial head of the triceps (fig. 758), to the interval between the olec-
FiG. 758. — Nerves op the Right Upper Arm viewed from in Front. (Spalteholz.)
Latissimus dorsi
Teres major
Radial (musculo -spiral) nerve
Musculo-cutaneous nerve -
Muscular branch r
Deltoid -
Coraco-brachialis -
Median nerve
Biceps brachii
Musculo-cutaneous nerve
Anastomosis with median
(variable)
Muscular branch to biceps .
Muscular branches to long
head of triceps
Ulnar nerve
Brachial artery
Triceps (long head)
.. Muscular branch to medial
head of triceps
Triceps (medial head)
Medial inter-muscular septum
— Median nerve
Radial (musculo-spiral) nerve
Supinator -
Deep radial
Brachio-radialis
Superficial radial
Radial artery —
Pronator teres
Muscular branches to flexor
carpi radialis, palmaris
longus, and flexor digitorum
sublimis
Flexor carpi radialis
ranon process and the medial condyle of the humerus, and in this part of its
course it is closely bound to the muscle by the deep fascia. Immediately below
the medial condyle it passes between the two heads of the flexor carpi ulnaris,
along the medial side of the medial collateral ligament of the elbow, and it comes
into relation with the dorsal ulnar recurrent artery.
THE ULNAR NERVE 989
In the upper forearm the ulnar nerve has on the flexor digitorum profundus, covered by the
flexor carpi uhiaris. Near the junction of the upper and middle thirds of the forearm it is joined
by the ulnar artery, which accompanies it to its termination, lying throughout on its radial side
(fig. 759). In the lower part of the forearm it still rests on the flexor digitorum profundus, but
Fig. 759. — Deep Nerves op the Volar Surface op the Forearm. (After Toldt, "Atlas
of Human Anatomy," Rebman, London and New York.)
Biceps brachu
I
Bracliialis* m.
Radial (musculo-spiral) nerve
Muscular branches
Medial intermuscular septum
Brachial artery
Deep radial"
Superficial radial.
Muscular branches '
Median nerve (drawn
^ medialward)
-Muscular branches
Common head for the super-
AV ' ficial palmar muscles
brevis
Ulnar artery
[ longus ..■
Brachio-radialis --
Muscular branch
-- Flexor carpi ulnaris
Pronator teres --
Radial artery.
Lateral antibrachial cutaneous nerve
Flexor pollicis longus
Superficial radial
Palmar branch of median -
Twig to wrist-joiut -
Tendon of flexor carpi radial;
Twig to wrist-joint >■•
Transverse carpal ligament ^
Volar antibrachial interosseous
- Palmar cutaneous branch (cut short)
Median nerve
Pisiform bone
_ Deep branch of ulnar
Abductor digiti quinti
, Flexor digiti quinti brevis
'*-* Palmaris brevis
between the flexor carpi ulnaris and flexor digitorum sublimis, and is covered only by skin and
fascia. At a variable point in this part of the forearm, usually about 5 to S cm. (2 to 3 in.)
from the carpus, the nerve divides into its two terminal branches, a dorsal branch to the dorsal
aspect of the hand, and a volar branch to the volar aspect.
990
THE NERVOUS SYSTEM
Branches. — ^The ulnar resembles the median nerve in not furnishing any
branches to the upper arm. As it passes between the olecranon process and the
medial condyle it gives off two or three fine filaments to the elbow-joint. In
the upper part of the forearm it supplies the flexor carpi ulnaris and the medial
portion of the flexor digitorum profundus, and in the lower half it gives off the
three cutaneous branches. In the palm of the hand it supplies the integument
of the hypothenar eminence, the fifth digit, and half of the fourth digit, and part
of the skin of the dorsum. It also supplies the short intrinsic muscles of the
hand with the exception of the abductor poUicis, the opponens, the lateral head
of the flexor poUicis brevis, and the two lateral lumbricales.
The nerves to the flexor carpi ulnaris and to the medial two divisions of the flexor digitorum
profundus arise from the ulnar nerve in the upper third of the forearm.
Cutaneous branches. — About the middle of the forearm the ulnar nerve gives off two
cutaneous branches: — one pierces the fascia and anastomoses with the volar branch of the
medial antibrachial (internal) cutaneous nerve, and the other, the palmar cutaneous branch,
runs downward in front of the ulnar artery (fig. 759) and is conducted by this vessel into the palm
Fig. 760. — Diagrams Illustrating a Common Distribution op Cutaneous Nerves op
Ulnar branch
of medial anti- '
brachial
cutaneous
Dorsal cutane-
ous branch'
of ulnar
Dorsal digital
nerves (ulnar)
Forearm. A, dorsum; B, volar aspect
Dorsal antibrachial...// \
cutaneous (radial) l/j \
Dorsal antibrachial ' ' ^
cutaneous (radial)
\ Lateral antibrachial
'* cutaneous (musculo..
cutaneous)
Lateral antibrachial
cutaneous (musculo-
cutaneous
Median nerve
.-Superficial radial
Superficial radial
From
lateral anti-
brachial Dorsal
cutaneous digital
branches
of radial
Dorsal branches
of radial
Dorsal branches of
proper volar dii^tal
Dorsal nerves (median)'
-^*» branches of proper
volar digital
nerves (median)
Ulnar branches
dial anti-
brachial cuta-
neous
Volar branches of
medial anti-
brachial cutaneus
-.-Volar branch of ulnar
.^Cutaneous branches
of common volar
digital nerves
Proper volar
digital nerves
(ulnar)
(fig. 756). It furnishes some filaments to the vessel, supplies a few twigs to the skin of the hypo-
thenar eminence, and ends in the integument covering the central depressed surface of the palm.
The dorsal or posterior cutaneous branch, usually the smaller of the terminal branches,
arises about 5 cm. (2 in.) above the wrist-joint, and passes backward under cover of the flexor
carpi ulnaris to reach the dorsal aspect of the wrist (fig. 761), where it gives off dehoate branches
to anastomose with branches of the medial antibrachial (internal) cutaneous, the dorsal anti-
brachial (external) cutaneous branch of the radial (musculo-spiral), the lateral antibrachial
cutaneous of the musculo-cutaneous nerve, and with branches of the superficial radial, and then
divides into five branches, the dorsal digitals (fig. 757), which are distributed to the ulnar
sides of the third, fourth, and fifth digits and the radial sides of the fourth and fifth digits.
These branches usually extend on the fifth digit only as far as the base of the terminal phalanx,
and on the fourth digit as far as the base of the second phalanx. The more distal parts of
these digits are supplied by palmar digital branches of the ulnar nerve.
The volar branch, the other terminal branch of the ulnar nerve, continues its course between
the flexor carpi ulnaris and flexor digitorum sublimis, on the medial side of the ulnar artery, to
the wrist, where, on the lateral side of the pisiform bone, it divides into a superficial and a
d£ep branch (figs. 759 and 761). The latter accompanies the deep branch of the ulnar artery
into the interval between the abductor digiti quinti and flexor digiti quinti brevis, and then
THE MEDIAN NERVE
991
passes through the fibres of the opponens digiti quinti to reach the deep surface of the flexor
tendons and theu- synovial sheaths. It supphes the abductor and opponens digiti quinti, the
flexor digiti quinti brevis, the third and fourth lumbricales, all the interossei, the adductors of
the thumb, and the medial head, and occasionally the lateral head, of the flexor poUicis brevis.
The superficial branch gives off a branch to supply the palmaris brevis muscle, an anastomosing
branch to the median nerve, and then divides into two branches, the proper volar digital branch,
which is distributed to the medial side of the fifth digit on its volar aspect, and the common
volar digital branch, which passes underneath the palmar aponeurosis and divides into two
branches, which supply the contiguous margins of the fourth and fifth digits. These branches
usually supply also the dorsal surface of the second and third phalanges of the same digits.
The median nerve contains fibres of the sixth, seventh, and eighth cervical
nerves and of the first thoracic, and sometimes of the fifth cervical nerve. The
trunk is formed a little below the lower margin of the pectorahs minor, by the
Fig. 761. — Nerves op the Palmar Surface op the Hand. (Testut.)
The transverse carpal (anterior annular) ligament, superficial palmar arch, the flexor tendons
of the digits, and the proximal portions of the lumbrical muscles have been removed.
Superficial radial
Palmar branch of median
Branches of superficial radial
Branch to adductor polhi
Proper volar digital -y^
Deep branch of ulnar
Dorsal branch of ulnar
— Superficial branch
-Muscular branch
'almar cutaneous brancb
— Branch to lumbrical IV
■Common volar digital
•Proper volar digital
union of two components, one from the medial and one from the lateral cord "of
the brachial plexus (fig. 755). The medial component passes obliquely across the
third part of the axillary artery, and in the upper part of the trunk the fibres of the
two components are felted together. From its commencement the median nerve
runs almost vertically through the lower part of the axillary fossa and through the
arm and forearm to the hand.
In the fossa it hes lateral to the axillary artery and it is overlapped, on its lateral side, by
the cqraco-brachiahs muscle. In the upper half of the arm it lies along the lateral side of the
brachial artery, and it is overlapped by the medial border of the biceps. At the middle of the
arm it passes in front of the brachial artery, and then it descends, on the medial side of the artery,
to the elbow. In the upper part of the antecubital fossa it is still at the medial side of the bra-
chial artery, but separated from it by a small interval, and in the lower part of the fossa it Lies
992 THE NERVOUS SYSTEM
along the medial side of the ulnar artery. In case of the high division of the brachial artery,
when the radial and the ulnar arteries lie together in the upper arm, the median nerve may pass
between them and then one or the other of the arteries will be superficial to the nerve. As
it leaves the antecubital fossa it passes between the two heads of the pronator teres, and it
crosses in front of the ulnar artery (fig. 759), from which it is separated by the deep head of the
pronator. In the forearm it passes vertically downward, accompanied by the median (comes
nervi mediani) artery. In the upper two-thirds of this region it lies deeply, between the flexor
digitorum sublimis and the flexor digitorum profundus, but in the lower third it becomes more
superficial, and is placed beneath the deep fascia, between the flexor carpi radialis on the radial
side and the palmaris longus and flexor digitorum sublimis tendons on the ulnar side. It crosses
beneath the transverse carpal (anterior annular) ligament, in front of the flexor tendons, and
in the palm at the lower border of the ligament it enlarges and divides into three branches, the
common volar digital nerves (fig. 760).
Branches. — The median nerve does not supply any part of the upper arm.
In front of the elbow-joint it furnishes one or two filaments to that articulation.
In the forearm it supplies all the superficial anterior muscles (with the exception
of the flexor carpi ulnaris) directly from its trunk, and it supplies the deep
muscles (with the exception of the ulnar half of the flexor digitorum profundus)
by its volar (anterior) interosseous branch. Thus in general it supplies the
pronator and flexor muscles of the forearm (radial side). In the hand it supplies
the group of short muscles of the thumb, which are placed on the radial side of
the tendon of the flexor pollicis longus, the two lateral lumbricales, the integument
covering the central, part of the palm and ulnar aspect of the thenar eminence, and
the palmar aspect of the first, second, third, and radial half of the fourth digits.
It also sends twigs to the dorsal aspect of these digits.
The nerve to the pronator teres usually arises a little above the bend of the elbow, and
pierces the lateral border of the muscle (figs. 759 and 761). It may arise in a common trunk
with the following nerves: —
The nerves to the flexor carpi radialis, palmaris longus, and flexor digitorum sublimis
arise a Uttle lower down, and pierce the pronator-flexor mass of muscles to end in the respective
members of the group for which they are destined (fig. 758).
The volar (anterior) interosseous nerve arises from the median at the level of the bicipital
tubercle of the radius (fig. 759), and runs downward, on the interosseous membrane, accom-
panied by the volar (anterior) interosseous artery. It passes under cover of the pronator quad-
ratus, and pierces the deep surface of that muscle, which it supplies. The volar interosseous
nerve also furnishes a twig to the front of the wrist-joint, and supphes the flexor digitorum
profundus and the flexor poUicis longus. The nerve to the former muscle arises from the volar
interosseous near its commencement; it supplies the outer two divisions of the muscle, and it
communicates within the substance of the muscle with twigs derived from the ulnar nerve.
It also supphes a branch to the interosseous membrane which runs downward upon, or in,
the membrane, supplying it and giving branches to the volar (anterior) interosseous and nutrient
arteries and to the periosteum of the radius, the ulna, and the carpus.
The palmar cutaneous branch arises immediately above the transverse carpal (anterior
annular) ligament and passes between the tendons of the flexor carpi radialis and the palmaris
longus (fig. 759). It then crosses the superficial surface of the transverse carpal ligament,
and is distributed to the integument and fascia on the central, depressed surface of the palm.
It also supplies a few twigs to the medial border of the thenar eminence; these twigs commu-
nicate with the musculo-cutaneous and superficial radial nerves.
The three common volar digital nerves pass in the palm of the hand dorsal to the superficial
palmar arch and its digital branches, while the proper volar digitals, branches of these nerves,
lie on the volar side of the digital arteries.
The first of the common volar digital nerves gives off a branch to supply the abductor
pollicis, the opponens, and the superficial head of the flexor pollicis brevis, and joins by a delicate
branch with the deep branch of the ulnar nerve. It then divides into three proper volar digitals
(fig. 761). The lateral of these passes obhquely across the long flexor tendon of the thumb and
runs along the radial border of the thumb to its extremity. It gives numerous branches to the
pulp of the thumb, and a strong twig which passes to the dorsum to supply the matrix of the
nail. The second of these proper volar digitals supplies the medial side of the volar aspect of
the thumb and gives off a twig to the matrix of the thumb nail. The third supplies the radial
side of the second digit and gives a twig to the flrst lumbrical muscle.
The second common volar digital sends a twig to the second lumbrical muscle, and divides
a httle above the metacarpo-phalangeal articulation into two proper volar digitals, which
respectively supply the adjacent sides of the second and third digits.
The third common volar digital communicates with the ulnar nerve, often gives a branch
to the third lumbrical muscle, and divides into two proper volar digitals which supply the adja-
cent sides of the third and fourth digits.
As the proper volar digitals pass along the margins of the fingers they give off twigs for
the innervation of the skin on the dorsum of the second and third phalanges and the matrix
of their nails. Each of the nerves terminates in filaments to the pulp of the finger.
RELATIONS OF NERVES
993
Table Showing Relation op Cervical and Thoracic Nerves to
Branches op Brachial Plexus
Nerves Contributing. Nerves, Branches op Plexus.
5C f Dorsal scapular (nerve to rhomboids)
\ Nerve to subclavius
( Suprascapular
5 and 6 C J ^erve to subclavius
1 Upper subscapular
Lower subscapular
*■ Axillary (circumflex)
5 6 and 7 C I ^°"S (posterior) thoracic
' ' I Lateral anterior thoracic
5, 6, and (7) C Musculo-cutaneous
(5), 6, 7, 8 C Radial (musculo-spiral)
(5), 6, 7, 8 C, and 1 T Median
7 and 8 C Thoraco-dorsal (middle or long subscapular)
f Medial anterior thoracic
8 C. andl T \ Uhiar
[ Medial antibrachial (internal) cutaneous
IT Medial brachial (lesser internal) cutaneous
Table Showing the Relations op the Cervical Nerves to the Muscles
OF the Upper Extremity
Nerves Contributing.
Accessory, 2 C
3, 4C...
3 and 4 C
Muscles.
5 and 6 C.
6C.
6 and 7 C.
5, 6, and;i;7 C.
7C.
7 and 8 C
5, 6, 7, andSC.
8 C
7, 8 Cand'l T.
8C.and IT.
Sterno-mastoid
Trapezius
Levator scapulae
Subclavius
Supraspinatus
Infraspinatus
Subscapularis
Teres major
Teres minor
Deltoid
Brachiahs
^ Biceps
Braohioradialis
Supinator
■I Pronator teres
Fle.xor carpi radialis
I Palmaris longus
I Ext. carpi radialis longus
I " " brevis
\ Abductor pollicis brevis
Opponens "
I Flexor poUicis brevis (superf.
head)
Serratus anterior
Coraoo-brachialis
Ext. digitorum coram.
" digiti quinti proprius
" carpi ulnaris
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Ext. indicus proprius
Latissimus dorsi
Triceps
Anconeus
Pectoralis major
Dorsal inteross.
Palmar "
Add. pollicis
" pollicis trans.
Flex, polhois brev. (deep)
Pectoralis minor
Flex, digit, subl.
Lumbricalis
Flex, carpi ulnaris
" digit, prof.
" pollicis long.
Pronator quadratus
Nerves to Muscles.
Spinal accessory
" , 3 and 4 C.
3 and 4 C.
Nerve to subclavius
!• Suprascapular
Upper and lower subscapular
Lower subscapular
Axillary (circumfle.x)
Musculo-cutaneous
Radial (musculo-spiral)
Deep radial (posterior interosseous)
Median
Radial (musculo-spiral)
Deep radial (posterior interosseous)
Median
Long (posterior) thoracic
Musculo-cutaneous
Deep radial (posterior interosseous)
Thoraco-dorsal (long"subscapular)
Radial (musculo-spiral)
Lat. and med. ant. thoracic
Ulnar ■
Med. ant. thoracic
Median
" and ulnar
Ulnar
" and median
Median
994
THE NERVOUS SYSTEM
2. THE THORACIC NERVES
The anterior primary divisions of the thoracic nerves, with the exception of
the first, retain, in the simplest form, the characters of anterior primary divisions
of the typical spinal nerve. They do not form plexuses, but remain distinct from
each other. Each divides into an easily recognisable lateral or dorsal and anterior
or ventral branch (figs. 762 and 763), and they are not distributed to the limbs.
The first, second, and last thoracic nerves, on account of their pecuUarities, require
separate description. The remainder are separable into two groups, an upper and
a lower. The upper group consists of four nerves, the third to the sixth inclusive,
which are distributed entirely to the thoracic wall. The lower group contains
five nerves, the seventh to the eleventh inclusive, which are distributed partly
Fig. 762. — Diagram of the Distribution of a Typical Thoracic Nerve.
Longissimus dorsi
Semispinalis dorsi
Medial branch' i y
Superior costo-transversf~ '
ligament
Dorsal root
Ventral root
Recurrent branch'
Sympathetic ganglion-
Viceral branch
Branch to aorta'
(Esophagu
Internal mammary artery
Transverse thoracic muscle
Ilio-costalisldorsi
Lateral branch
Posterior primary division
Anterior primary division
Internal intercostal muscle
External intercostal muscle
■Lateral cutaneous bianch
Anterior branch
Anterior intercostal membrane
to the thoracic and partly to the abdominal wall. The upper group is therefore
purely thoracic in distribution, and the lower thoraco-abdominal.
The first thoracic nerve is connected with the first thoracic sympathetic gang-
lion, and it frequently is joined by a small branch with the second nerve. It is
distributed chiefly to the upper limb. Opposite the superior costo-transverse
ligament of the second rib it divides into a larger and a smaller branch; the
larger passes upward and lateralward, between the apex of the pleura and the
neck of the first rib, and on the lateral side of the superior intercostal artery, to
the root of the neck, where it joins the brachial plexus. The smaller branch con-
tinues along the intercostal space, below the first rib and between the intercostal
muscles in which, as a rule, all its fibres terminate.
However, the smaller branch may give off a lateral cutaneous branch which connects with the
medial brachial (lesser internal) cutaneous nerve and with the intercosto-brachial nerve in the
axillary fossa; and occasionally it terminates in an anterior cutaneous branch at the anterior
extremity of the first intercostal space.
The second thoracic nerve, as it lies between the pleura and the superior
costo-transverse ligament of the third rib, gives a branch to the first nerve, then
it pierces the posterior intercostal membrane and passes between the external and
internal intercostal muscles in the second intercostal space. In the dorsal part
of the space it sends branches backward, through the external intercostal muscle,
THE THORACIC NERVES 995
to supply the second levator costse and the serratus posterior superior, and then
it divides into a lateral and an anterior branch. The two branches run forward
together to the mid-axillary line, where the lateral branch pierces the external
intercostal muscle and passes between two digitations of the serratus anterior
(magnus) into the axillary fossa; the anterior branch enters the substance of the
internal intercostal muscle.
The lateral branch, the intercosto-brachial (intercosto-humeral) , may divide into a small
anterior and a large posterior division, or the anterior division may be absent. In either case
the lateral branch anastomoses with the medial brachial (lesser internal) cutaneous nerve, and
usually with the lateral branch of the third intercostal nerve; it also anastomoses with the lateral
branch of the first nerve, if the latter is present. After forming these junctions it passes out
of the axillary fossa, pierces the deep fascia, and supplies the integument in the upper and pos-
terior half of the arm. It also gives off a few filaments which terminate in the skin over the
ajdllary border of the scapula. The size of the intercosto-brachial nerve and the extent of its
distribution are usually in inverse proportion to the size of the other cutaneous nerves of the
upper arm, especially the middle brachial (lesser internal) cutaneous. When the latter nerve
is absent, the intercosto-brachial usually takes its place.
The course and distribution of the anterior branch, when it is present, being similar to the
course and distribution of the anterior branches of the next four nerves, do not require a separate
description.
The thoracic intercostal nerves (upper group). — The third, fourth, fifth, and
sixth thoracic nerves, in the posterior parts of the intercostal spaces, give muscu-
lar branches to the levatores costarum, the first to the fourth also giving branches
to the serratus posterior superior. They pass forward a short distance between
the external and internal intercostals, giving twigs to these muscles, and divide
into two branches, lateral and anterior.
The lateral cutaneous branches continue forward between the intercostal
muscles, and, near the mid-axillary line, pierce the external intercostals and
serratus anterior (magnus) and divide into two branches, posterior and anterior.
The posterior branches pass backward over the latissimus dorsi to supply the skin
in the lower part of the scapular region. The anterior branches, in the four nerves,
increase in size from above downward. They pass around the lateral border of
the great pectoral muscle and are distributed to the integument over the front
of the thorax and m'anima, sending filaments, the lateral mammary branches, into
the latter organ. The lowest two nerves also supply twigs to the upper digita-
tions of the external oblique muscle.
The anterior branches run obliquely forward and medialward through the
substance of the internal intercostal muscles, reaching the deep surface of these
muscles at the extremity of the costal cartilages (fig. 762). They continue
forward between these muscles and the pleura, pass in front of the internal
■ mammary artery, turn abruptly ventralward a short distance from the sternum,
pierce the internal intercostals, the anterior intercostal membrane, and the pec-
toralis major, and give off three sets of terminal branches. One set supplies the
transverse thoracic muscle and the back of the sternum. A second set, cutaneous,
runs mesially. The third set passes laterally over the pectoralis major, supplying
the skin in that region, and, in the female, the mammary gland through the
medial mammary branches. The anterior branches in their course supply the
intercostal and subcostal muscles and give filaments that supply the ribs, the
periosteum, and the pleura.
The thoraco-abdominal nerves (lower group). — The relations of the posterior
portions of the seventh, eighth, ninth, tenth, and eleventh thoracic nei'ves to the
thoracic wall are similar to those of the upper thoracic intercostal nerves. Each
divides in a similar manner into a lateral and an anterior branch, but these branches
are distributed partly to the abdominal and partly to the thoracic wall, and the
smaller muscular branches have also different distributions.
The lateral branches, lateral cutaneous nerves of the abdomen, pierce the
external intercostal muscles and pass through or between the digitations of the
external oblique into the subcutaneous tissue, where they divide in the typical
way into anterior and posterior branches. The posterior branches pass backward
over the latissimus dorsi. The anterior branches give filaments to the digitations
of the external oblique and extend forward, medialward and downward to the
outer border of the sheath of the rectus.
The anterior branches pass forward between the external and internal
intercostal muscles, to the ends of the intercostal spaces; there they insinuate
996 THE NERVOUS SYSTEM
themselves between the interdigitating slips of the diaphragm and the transversus
abdominis and enter the abdominal wall. The seventh, eighth, and ninth nerves,
in their transit from the thoracic to the abdominal wall, pass behind the upturned
ends of the eighth, ninth, and tenth rib-cartilages respectively. Having entered
the abdominal wall the nerves run forward between the transversus abdominis
and the internal oblique, muscles to the outer border of the rectus abdominis,
where they pierce the posterior lamella of the internal oblique aponeurosis and
enter the sheath of the rectus. In the sheath they pass through the substance of
the rectus. Finally they turn directly forward, pierce the anterior part of the
sheath, and become anterior cutaneous nerves of the abdomen.
The muscular branches. — Muscular branches from all the thoraco-abdominal
nerves are distributed to the levatores costarum, the intercostal muscles, the
transversus abdominis, the internal oblique, and to the rectus abdominis, and the
ninth, tenth, and eleventh nerves gives branches also to the serratus posterior
inferior. Branches are also distributed from a variable number of the lower nerves
to the costal portions of the diaphragm.
The last thoracic nerve. — The anterior primary division of the last thoracic
nerve is distributed to the wall of the abdomen and to the skin of the upper and
front part of the buttock. It appears in the thoracic wall immediately below the
last rib, where it communicates with the sympathetic cord and gives off a com-
municating branch to the first lumbar nerve. It passes from the thorax into the
abdomen beneath the lateral lumbo-costal arch (external arcuate ligament),
accompanied by the subcostal artery, and it runs across the upper part of the
quadratus lumborum dorsal to the kidney and to the ascending or the descending
colon according to the side considered. At the lateral border of the quadratus
lumborum it pierces the aponeurosis of attachment of the transversus abdominis
muscle and divides, between the transversus and the internal oblique muscle, into
a lateral and an anterior branch. It gives branches to the transversus abdominis,
the quadratus lumborum, and the internal oblique muscles.
The anterior branch passes forward, between the internal oblique and the transversus
abdominis, to which it suppUes twigs. It enters the sheath of the rectus, turns forward through
that muscle, and terminates in branches which become cutaneous midway between the umbilicus
and the symphysis. Before it becomes cutaneous it supplies twigs to the transversus abdominis,
the internal oblique, the rectus abdominis, and the pyramidalis muscles.
The lateral branch pierces the internal obhque; it supplies the lowest digitation of the
external obhque, and then pierces the latter muscle from 2.5 to S cm. (1 to 3 in.) above the iliac
crest, and descends in the superficial fascia of the anterior part of the gluteal region, crossing the
ihac crest about 2.5 cm. (1 in.) behind its anterior extremity and reaching as far down as the
level of the great trochanter. Occasionally this branch is absent and its place is taken by the
iliac branch of the ilio-hypogastric. In such oases, however, the branch from the last thoracic
to the first lumbar nerve is larger than usual.
THE LUMBO-SACRAL PLEXUS
The lumbo-sacral plexus is formed by the union of the anterior primary
divisions of the lumbar, sacral, and coccygeal nerves. In about 50 per cent, of
cases it receives a branch from the twelfth thoracic nerve. Its components are
distributed to the lower extremity in a manner homologous and similar to the
distribution of the parts of the brachial plexus to the upper extremity; the
lumbar nerves are distributed similarly to the nerves formed from the anterior
(medial and lateral) cords of the brachial plexus, and the sacral nerves are
distributed in a manner similar to the distribution of the nerves from the posterior
cord of the brachial plexus.
Partly for convenience of description and partly on account of the differences
in position and course of some of the nerves arising from it, this plexus is sub-
divided into four parts — the lumbar, sacral, pudendal, and coccygeal plexuses.
These plexuses overlap so that there is no definite line of demarcation between
them. However, they will be considered separately.
3. THE LUMBAR NERVES
The anterior primary divisions of the five lumbar nerves increase in size from
the first to the last. Each lumbar nerve is connected by one or two long, slender
THE LUMBAR NERVES
997
rami with a lumbar sympathetic ganglion. The first three nerves and the greater
part of the fom-th enter into the formation of the lumbar plexus, and the smaller
Fig. 763. — Cutaneous Nerves of the Thorax and Abdomen, viewed prom the Side.
(After Henle.)
PectoraliB major
Supraclavicular branch of
cervical plexus
Pectoralis minor
Sheath of rectus _-
Ilio-hypogastric
Brachial plexus
Intercosto-brachial
part of the fourth and the fifth nerve commonly unite to form the lumbo-sacral
cord which takes part in the formation of the sacral plexus (figs. 764, 765) . When
the fourth nerve enters into the formation of both lumbar and sacral plexuses,
998 THE NERVOUS SYSTEM
it may be called the furcal nerve, but this name is also applied to any of the
nerves that enter into the formation of both plexuses, so there may be one or more
furcal nerves.
THE LUMBAR PLEXUS
Although the lumbar plexus is ordinarily formed by the first three lumbar
nerves and a part of the fourth, yet it is subject to considerable variation in the
manner of its formation.
Owing to this variation three general classes of plexuses may be found, proximal or pre-
fixed, ordinary, and distal or post-fixed. The basis of classification is the relation of the nerves
of the limb to the spinal nerves which enter into their formation. The intermediate or slighter
degrees of variation may consist only of changes in the size of the portions contributed by the
diHerent spinal nerves to a given peripheral nerve, for a given nerve may receive a larger share
of its fibres from a more proximal spinal nerve, and a smaller share from a more distal nerve, or
vice versd. However, in the more marked degrees of variation the origin of a given peripheral
nerve may vary in either direction to the extent of one spinal nerve. The more extreme types
of the plexuses are sometimes associated with abnormal conditions of the vertebral column.
It has been suggested that when the prefixed or proximal condition occurs, it indicates that the
lower limb is placed a segment more proximal than in the ordinary cases, and when the distal
condition is present, that the limb is arranged a segment more distal. Three types each of the
proximal and the distal classes and one type of the ordinary class have been described by Bar-
deen. His statistics are made use of in the compilation of the following tables, in which are
shown the range of variation and the common composition of each class of plexus: —
Composition of the Nerves of the Lumbar Plexus
Range of Variation
Nerve. Proximal. Ordinary. Distal.
Lateral (external) cutaneous 12 T, 1, 2, 3 L. 1, 2, 3, 4 L. 1, 2, 3, 4 L.
Femoral (anterior crural) ... 12 T, 1, 2, 3, 4 L. 1, 2, 3, 4 L. 1, 2, 3, 4, 5 L.
Obturator 1, 2, 3, 4 L. 1, 2, 3, 4 L. 2, 3, 4, 5 L.
Furcal 3 or 3, 4 L. 4 L. 4, 5 or 5 L.
Common Composition
Nerve. Proximal. Ordinary. Distal.
Lateral (external) cutaneous 1, 2 L. 1, 2, 3 L. 2, 3 L.
Femoral (anterior crural) . . 1, 2, 3, 4 L. 2, 3, 4 L. 2, 3, 4, 5, L.
Obturator 1, 2, 3, 4 L. 2, 3, 4 L. 2, 3, 4 L.
Furcal 4 L. 4 L. 4 L.
The lumbar plexus lies in the posterior part of the psoas muscle (fig. 765), in
front of the transverse processes of the lumbar vertebrae and the medial border
of the quadratus lumborum, and its terminal branches are distributed to the
lower part of the abdominal wall, the front and medial part of the thigh, the
external genital organs, the front of the knee, the medial side of the leg, and the
medial side of the foot.
The first and second of the lumbar nerves give collateral muscular branches to
the quadratus lumborum muscle, and the second and third nerves give similar
branches to the psoas. The remaining branches of the plexus are terminal
branches. The first lumbar nerve, after it has been joined by the branch from the
last thoracic nerve, divides into three terminal branches, the ilio-hypogastric
nerve, the ilio-inguinal nerve, and a branch which joins the second nerve. The
fibres of this latter branch pass mainly into the genito-femoral (genito-crural)
nerve, but occasionally some of them enter the femoral (anterior crural) and
obturator nerves. The remaining nerves divide into anterior or ventral and
posterior or dorsal divisions. The anterior divisions form a portion of the genito-
femoral (genito-crural) nerve and the obturator nerve, and the posterior divisions
enter the lateral (external) cutaneous and femoral (anterior crural) nerves.
All the terminal branches of the plexus are formed in the substance of the
psoas muscle; four of them, the ilio-hypogastric, the ilio-inguinal, the lateral
(external) cutaneous, and the femoral (anterior crural), leave the muscle at its
lateral border. The genito-femoral (genito-crural) passes through its anterior
surface, and the obturator through its medial border.
Terminal branches. — The ilio-hypogastric nerve springs from the first
lumbar nerve, after the latter has been joined by the communicating branch
THE LUMBAR PLEXUS
999
from the last thoracic nerve, as it is in about 50 per cent, of the cases, and it thus
contains fibres of both the last thoracic and the iirst lumbar nerves. It pierces
the lateral border of the psoas and crosses in front of the quadratus lumborum
(fig. 765), and behind the kidney and the colon. At the lateral border of the
quadratus it pierces the aponeurosis of origin of the transversus abdominis and
enters the areolar tissue between the transversus and the internal oblique, where
it frequently communicates with the last thoracic and with the ilio-inguinal
Fig. 764. — Diagram of a Common Form of Lumbo-saceal Plexus. (Modified from
Paterson.)
From last thoracic nerve •<
- r — First lumbar
Genito-femoral
lUo-hypogastrici
Ilio-inguinal>
Lateral cutaneo
Obturator
Accessory obturator.
To superior gluteal
To inferior gluteal ---
To piriformis -
Sciatic _ ^^
J/
To quadratus femons
Common
peroneal
section
- — •Second lumbar
— —Third lumbar
Fourth lumbar
Fifth lumbar
- Second sacral
- Third sacral J
• Visceral branches
- Fourth sacral
. Visceral branches
■• Perineal
* Fifth sacral
- To coccygeus
- To levator ani
To hamstrings
' Fosterior femora] Perforating
t cutaneous cutaneous
To obturator internus
nerve, and it divides into an iliac and a hypogastric branch, which correspond,
respectively, with the lateral and anterior branches of a typical spinal nerve.
The anterior cutaneous (hypogastric) branch passes forward and downward, between the
transversus abdominis and the internal oblique muscles, giving branches to both; it communi-
cates with the ilio-inguinal nerve, and, near the anterior superior spine of the ilium, it pierces
the internal oblique muscle and continues forward beneath the external obhque aponeurosis
toward the middle line. About 2. .5 cm. (1 in.) above the subcutaneous inguinal ring it pierces
the aponeurosis of the external oblique, becomes subcutaneous, and supplies the skin above the
symphysis.
The lateral cutaneous (iliac) branch pierces the internal and external obhque muscles,
emerging through the latter above the iUac crest at the junction of its anterior and middle
thirds (fig. 769). It is distributed to the integument of the upper and lateral part of the thigh,
in the neighborhood of the gluteus medius and tensor fasciae latae muscles (fig. 768).
1000 THE NERVOUS SYSTEM
The ilio-inguinal nerve arises principally from the first lumbar nerve, but it
frequently contains fibres of the last thoracic nerve. It emerges from the lateral
border of the psoas, at a lower level than the ilio-hypogastric nerve, and passes
across the quadratus lumborum (figs. 765, 766). As a rule, it is below the level
of the inferior end of the kidney, but it passes dorsal to the ascending or the
descending colon according to the side considered, and crosses the posterior part
of the inner lip of the iliac crest; it then runs forward on the upper part of the
iliacus, pierces the transverus abdominis near the anterior part of the crest, and
communicates with the anterior cutaneous (hypogastric) branch of the ilio-
hypogastric nerve. A short distance below the anterior superior spine it passes
through the internal oblique muscle, and then descends in the inguinal canal to
the subcutaneous inguinal (external abdominal) ring, through which it emerges
into the thigh on the lateral side of the spermatic cord (fig. 763). It is distributed
to the skin of the upper and medial part of the thigh, in the male to the root of the
penis and to the skin of the root of the scrotum through the anterior scrotal
nerves (fig. 768), and in the female to the mons veneris and labium majus through
the anterior labial nerves.
Not uncommonly the iho-inguinal nerve is blended with the iho-hypogastric nerve and
separates from the latter between the transversus abdominis and the internal obUque muscles.
It may be replaced by branches of the genito-femoral (genito-orural) nerve, or it may replace
that nerve or the lateral cutaneous nerve.
cs
The genito-femoral (genito-crural) nerve is connected with the first and
second lumbar nerves, but the majority of its fibres are derived from the second
nerve. It passes obliquely forwarcl and downward through the psoas and emerges
from the anterior surface of that muscle, close to its medial border, at the level
of the lower border of the third lumbar vertebra. After emerging from the sub-
stance of the psoas it runs downward on the anterior surface of the muscle
(fig. 765), to the lateral side of the aorta and the common iliac artery, passes
behind the ureter and divides into two branches, an external spermatic or genital,
and a lumbo-inguinal or crural (fig. 766). Occasionally it divides in the substance
of the psoas, and then the two branches issue separately through the anterior
surface of the muscle.
The external spermatic (genital) branch runs downward on the psoas muscle, external to
the external iliac artery; it gives a branch to the psoas, and at Poupart's hgament it turns
around the inferior epigastric artery and enters the inguinal canal, accompanjdng the spermatic
cord in the male or the round hgament in the female. It suppUes the cremaster muscle, and
gives twigs to the integument of the scrotum (fig. 766) or the labium majus.
The lumbo-inguinal (crural) branch passes downward along the external ihac artery and
beneath Poupart's hgament into the thigh, which it enters to the lateral side of the femoral
artery. A short distance below Poupart's ligament it pierces the fascia lata or passes through
the fossa ovalis (saphenous opening) and supplies the skin in the middle of the upper part of the
thigh. A short distance below Poupart's hgament it sometimes sends branches to the anterior
branch bf the lateral cutaneous nerve, and about the middle of the thigh it often joins with the
cutaneous branches of the femoral (anterior crural) nerve.
The lateral cutaneous nerve receives fibres from the dorsal branches of the
anterior primary divisions of the second and third lumbar nerves, and frequently
some fibres from the first lumbar (fig. 769). It emerges from the lateral border
of the psoas and passes obliquely across the iliacus dorsal to the iliac fascia, and
dorsal to the caecum on the right side and the sigmoid colon on the left side, to a
point immediately below the anterior superior spine of the ilium, where it passes
below Poupart's ligament into the lateral angle of the femoral trigone (Scarpa's
triangle). Leaving the trigone at once it passes through, behind, or in front of
the sartorius and divides into two branches, anterior and posterior, which enter
the deep fascia (fig. 766).
The posterior branch of the lateral cutaneous nerve breaks up into several secondary
branches which become subcutaneous, and they supply the integument of the lateral part of the
thigh, from the great trochanter to the level of the middle of the femur. The anterior branch
runs downward in a canal in the deep fascia, for three or four inches, before it becomes sub-
cutaneous. It usually divides into two branches, a lateral and a medial. The lateral branch
supplies the skin of the lower half of the lateral side of the thigh, and the medial branch is dis-
tributed to the skin of the lateral side of the front of the thigh as far as the knee (fig. 766).
Its lower filaments frequently unite with the cutaneous branches of the femoral (anterior
THE FEMORAL NERVE
1001
crural), and with the patellar branch of the saphenous nerve in front of the patella, forming
with them the patellar plexus.
The femoral (anterior crural) nerve is the largest terminal branch of the lum-
bar plexus. It is formed chiefly by fibres of the dorsal branches of the anterior
primary divisions of the second, third, and fourth lunibar nerves, but it sometimes
receives fibres from the first nerve also (figs. 765 and 769). It emerges from the
lateral border of the psoas a short distance above Poupart's ligament, and descends
in the groove between the psoas and the iliacus, behindPoupart's ligment, into
Fig. 765. — Lumbo-sacral Plexus. (After Toldt, 'Atlas of Human Anatomy,' Rebman,
London and New York.)
Lumbar vertebrae
Medial crus of diaphrag:
Rib XU
Psoas minor
Intercostal XII
/I
Q jadratus lumborum -^ /? I
lUo-hypogastnCs^/^/' '-J, ''j
Ilio-mgumal v.^ MMtjK')
Psoas major
Transversus v// '^ /A
abdominis " ^
Genito-femoral-'
' Lumbar I (anterior bran::h)
/Muscular branch
-■ Ilio -hypogastric
'Psoas minor
*^ //Ifa^W ^<*|^^-=' R^mi communicantes
^\^j^^p^.^ Sympathetic trunk
Lumbar II
Muscular branche
V^ Gemto-femoral
Obturator fascia
Piriformis with its muscular branch
j^y s. Muscular
branches for
J iliacus
'J> Fe
J ^Obturator
^Lumbo-sacral trunk
g!^^ \ \ '^^^^^ ^ Piriformis
|_^A^/l " ' ^P// \ Y*^ \Sciatic
V7 J; ^/Mt \ \ \ Sacral pie
~^ N ^v Posterior cutaneo
Ganghon coccygeum impar / / jj
Coccygeal ' /
Ano-coccygeal
Middle h£emorrhoidal and
\ inferior ve;
Pudendal plexus
the femoral trigone (Scarpa's triangle), where it lies to the lateral side of the
femoral artery (fig. 767) , from which it is separated by some of the fibres of the
psoas. In this situation it is flattened out and it divides into two series of ter-
minal branches, the superficial and the deep. In general, they supply the muscles
and skin on the anterior aspect of the thigh.
Branches. — The branches of the femoral nerve are collateral and terminal.
The collateral branches are twigs of supply to the ihacus, and a branch to the
femoral artery; they are given off before the nerve enters the femoral trigone.
1002
THE NERVOUS SYSTEM
The terminal branches form two groups, the superficial and the deep.
The superficial terminal branches are two muscular branches, the nerve to
the pectineus, and the nerve to the sartorius, and two anterior cutaneous branches.
Fig. 766. — Cutaneous Nerves of the Right Thigh, (Spalteholz.)
(The iliac fascia has been removed, the fascia lata retained.)
Ilio-hypogast:
Ilio -inguinal
Transversus abdominis.
Obliquus internus abdom-
inis
Obliquus externus ab- •
dominis
Lateral cutaneous branch •■
of inter- costal XU
Intercostal XII
Lateral cutaneous
Lumbo-inguinal nerve -
Psoas minor
Genito-femoral nerve
_N Psoas major
^j Lateral cutaneous nerve
' Iliacus
... External iliac artery
., External spermatic nerve
-^„^ ,. Lumbo-inguinal nerve
.•^1^. _ Femoral nerve
( Internal spermatic artery and
— Ductus deferens
--y,-- Rectus abdominis
Anterior cutaneous branch
of ilio-hypogastric nerve
Fossa ovalis
External spermatic nerve
Anterior scrotal nerves
Ixii.... Spermatic cord
Great saphenous vein
Anterior cutaneous branches
'' of femoral nerve
(Anterior cutaneous branches
of femoral nerve
'The nerve to the pectineus passes medially and downward behind the femoral sheath and in
front of the psoas to the anterior surface of the pectineus, in which it terminates.
The nerve to the sartorius accompanies the middle cutaneous nerve; it leaves the latter
nerve above the sartorius and ends in the upper part of the muscle.
THE OBTURATOR NERVE 1003
The anterior (middle and internal) cutaneous nerves are best described separately. The
middle cutaneous nerve soon divides into two branches, medial and lateral. The lateral branch
pierces the sartorius and both branches become cutaneous about the junction of the upper and
middle thirds of the tliigh (figs. 766, 768). They descend along the medial part of the front of
the thigh to the knee, supplying the skin in the lower two-thirds of the medial part of the front
of the thigh, and their terminal filaments take part in the formation of the patellar plexus.
About the middle of the thigh the middle cutaneous is often joined by a twig with the lumbo-
inguinal nerve (crural branch of the genito-crural nerve). The medial or internal cutaneous
nerve runs downward and medialward along the lateral side of the femoral artery, to the apex of
the femoral trigone (Scarpa's triangle), where it crosses in front of the artery and divides into an
anterior and a posterior terminal branch. Before this division takes place, however, two or
three collateral branches are given off from the trunk. The highest of these passes through the
fossa ovalis (saphenous opening), or it pierces the deep fascia immediately below the opening, and
supplies the skin as low as the middle of the thigh. The lowest pierces the deep fascia at the
middle of the thigh and it descends in the subcutaneous tissue, supplying the skin on the medial
side of the thigh from the middle of the thigh to the knee (figs. 768, 769). This nerve frequently
varies in size inversely with the cutaneous branches of the obturator and saphenous nerves.
The anterior branch of the internal cutaneous nerve passes vertically downward to the
junction of the middle and lower thirds of the thigh, where it pierces the deep fascia. It
still continues downward for a short distance, then it turns lateralward and passes to the
front of the knee, where it enters into the patellar plexus.
The posterior branch descends along the dorsal border of the sartorius, and it gives off a
branch which passes beneath that muscle to unite with twigs from the saphenous and from the
superficial division of the obturator nerve, forming with them the subsartorial plexus which
lies on the roof of the adductor (Hunter's) canal. At the medial side of the knee the nerve
pierces the deep fascia and it descends to the middle of the calf (figs. 766, 768).
The deep terminal branches of the femoral nerve are six in number, one
cutaneous branch, the saphenous, and five muscular branches. The branches
radiate from the termination of the trunk of the femoral nerve, and thej^ are
arranged in the following order from medial to lateral: — the saphenous nerve,
the nerve to the vastus medialis, the nerve to the articularis genu (subcrureus) ,
the nerve to the vastus intermedins (crureus), the nerve to the vastus lateralis,
and the nerve to the rectus femoris.
The saphenous nerve passes down through Scarpa's triangle along the lateral side of the
femoral artery. At the apex of the triangle it enters the adductor (Hunter's) canal and descends
through it, lying first to the lateral side, then in front, and finally to the medial side of the artery
(fig. 767). After emerging from the lower end of the canal, accompanied by the superficial
branch of the genu suprema (anastomotic) artery, it passes between the dorsal border of the
sartorius and the anterior border of the tendon of the gracihs, and, becoming superficial, it
enters into relationship with the great saphenous vein and descends with it along the inner border
of the upper two-thirds of the tibia (fig. 768). It crosses the medial surface of the lower third
of the tibia, passes in front of the internal malleolus, and runs forward along the medial border
of the foot to the ball of the great toe.
While it is in the adductor (Hunter's) canal it gives off a twig to the subsartorial plexus.
Before it passes from under cover of the sartorius it gives off an infra-patellar branch, which
Eierces the sartorius just above the knee and passes outward to the patellar plexus. After it
ecomes superficial it supphes the integument on the medial side of the leg and foot, and it
anastomoses, in the foot, with the medial dorsal cutaneous branch of the superficial peroneal
(musculo-outaneous) nerve.
The nerve to the vastus medialis accompanies the saphenous nerve in the femoral trigone
(Scarpa's triangle), lying to its outer side. At the upper end of the adductor canal it passes
beneath the sartorius, external to the roof of the canal, and enters the medial surface of the vas-
tus medialis. It sends a twig down to the knee-joint.
The nerve to the articularis genu (subcrureus), usually a terminal branch of the femoral,
frequently arises from the nerve to the vastus intermedins. It passes between the vastus
medialis and the vastus intermedins to the lower third of the thigh, where it supplies the artic-
ularis genu and sends a branch to the knee-joint.
The nerve to the vastus intermedins (crureus) is represented by two or three branches which
enter the upper part of the muscle. One of them frequently sends a twig to the knee-joint.
The nerve to the vastus lateralis pas.ses downward behind the rectus and along the anterior
border of the vastus lateralis accompanied by the descending branch of the lateral circumfiex
artery. It also sends a branch to the knee-joint.
'The nerve to the rectus femoris (fig. 767) enters the deep surface of that muscle, having
previously given off a twig to the hip-joint which accompanies the ascending branch of the
external circumflex artery.
The obturator nerve contains fibres from the anterior primary divisions of the
second, third, and fourth lumbar nerves, but its largest root is derived from the
third nerve (figs. 765, 769). It sometimes receives fibres from the first and third
lumbar nerves. It emerges from the medial border of the psoas at the dorsal
part of the brim of the pelvis, where it lies in close relation with the lumbo-sacrai
trunk of the plexus, from which it is separated by the iho-lumbar artery. Im-
mediately after its exit from the psoas it pierces the pelvic fascia, crosses the
1004
THE NERVOUS SYSTEM
lateral side of the internal iliac vessels and the ureter, and runs forward in the
extraperitoneal fat, below the obliterated hypogastric artery and along the
upper part of the medial surface of the obturator internus to the upper part of the
obturator foramen, where it passes through the obturator canal below the so-
called horizontal ramus of the pubis and above the obturator membrane, into the
upper part of the thigh. It is accompanied in the pelvis and the obturator canal
by the obtm-ator arterj^, which lies at a lower level than the nerve, and it divides
Fig. 767. — Femoral and Obtubator Nerves. (Ellis.)
Femoral vein Femoral artery
Pectineus
Obturator (anterior div.)
Adductor longus
Adductor brevis
Adductor magnus
Geniculate branch of obturator
Semi-membranosus
Tensor fasciae latffi
Profunda artery
Pectineus
Rectus femoris
Saphenous
Nerve to vastus medialis
Adductor longus
Femoral artery
Genu suprema artery
Patellar branch of saphenous
in the obturator canal into two branches, an anterior and a posterior, which
supply the adductor group of muscles, the hip and knee-joints, and the skin on the
medial aspect of the leg.
The anterior branch of the obturator has a twig joining it with the accessory
obturator nerve, if that nerve is present, and then descends behind the pectineus
and adductor longus and in front of the obturator externus and adductor magnus
muscles (fig. 767). Its branches are: —
1. A twig to the accessory obturator nerve if the latter is present.
2. An articular branch to the hip-joint.
3. Muscular branches to the gracihs, adductor longus, and, usuaOy, to the adductor
brevis.
4. Two terminal branches, of which one is distributed to the femoral artery and the other
communicates with the subsartorial plexus. The subsartorial branch is occasionally longer
THE LUMBOSACRAL TRUNK
1005
than usual, and it then descends, along the dorsal border of the sartorius, to the medial side of the
knee, where it enters the subcutaneous tissue, and, proceeding downward, supplies the skin
on the medial side of the leg as far as the middle of the calf. Twigs join it with the saphenous.
The posterior branch of the obturator (fig. 767) pierces the upper part of the
obturator externus and passes downward between the adductor brevis and adduc-
tor magnus. Its branches are: —
1. Muscular branches to the obturator externus, to the oblique fibres of the adductor magnua
and to the adductor brevis when the latter is not entirely suppUed by the anterior branch.
The branch to the obturator externus is given off in the obturator canal.
2. An articular branch to the knee-joint which appears in some cases to be the continuation
of the trunk of the posterior branch (fig. 767). It either pierces the lower part of the adductor
Fig. 768. — Distribution op Cutaneous Nerves on the Postebior and Anterior Aspects
OF the Inferior Extremity.
Middle clunial
Infra-patellar
branch of
saphenous
Superficial
peroneal
Deep peroneal
magnus, or it passes through the opening for the femoral artery. In the popliteal space it
descends on the popUteal artery to the back of the joint, where it pierces the posterior hgament,
and its terminal filaments are distributed to the crucial ligaments and the structures in their
immediate neighbourhood. This branch is not uncomraoulj' absent. Occasionally the posterior
branch of the obturator nerve also supples a twig to the hip-joint.
The accessory obturator nerve arises from the third or fourth or from the third and fourth
lumbar nerves, in the angles between the roots of the femoral (anterior crural) and obturator
nerves. It is present in about twenty-nine per cent, of all cases (Eisler). It is often closely
associated with the obturator nerve to the level of the brim of the pelvis, but instead of passing
through the obturator foramen, it descends along the medial border of the psoas, crosses the
anterior part of the brim of the pelvis, passes beneath the pectineus, and terminates in three
main branches. One of these branches joins the anterior division of the obturator nerve,
another supplies the pectineus, and the third is distributed to the hip-joint.
The Lumbo-sacral Trunk
The trunk of the plexus usually formed by the union of the smaller part of
the fourth and the entire fifth lumbar nerves is called the lumbo-sacral trunk
1006 THE NERVOUS SYSTEM
(figs. 765, 769). Sometimes the larger part of the fourth nerve may help to
form the trunk. It may receive fibres from the third lumbar nerve or be formed
entirely from the fifth. At its formation it is situated on the ala of the sacrum
under cover of the psoas. It descends into the pelvis, and, as it crosses the
anterior border of the ala of the sacrum, it emerges from beneath the psoas at the
medial side of the obturator nerve, from which it is separated by the ilio-lumbar
artery. It passes behind the common iliac vessels and unites with the first and
second sacral nerves, forming with them the upper trunk of the sacral plexus.
4. SACRAL NERVES
The anterior primary divisions of the upper four sacral nerves enter the pelvis
through the anterior sacral foramina and they diminish in size progressively from
above downward. The first sacral is the largest of the spinal nerves, the second
is slightly smaller than the first, while the third and fourth are relatively small.
The fifth sacral nerve is still smaller than the fourth; it enters the pelvis between
the sacrum and the coccyx. The anterior divisions of these nerves enter into the
formation of three parts of the lumbo-sacral plexus, the sacral, pudendal, and
coccygeal.
Sacral Plexus
The sacral plexus shows in its formation variations similar to those of the
lumbar plexus; hence there are also seven types of this plexus, three of them
belonging to the prefixed or proximal class, three to the postfixed or distal class,
and one to the ordinary class. The following tables show the range of variation
and the common arrangement in these classes: — •
Composition of the Nerves of the Sacral Plexus
Range of Variation
Nerve. Proximal.
Furcal 3 or 3, 4 L.
Common peroneal (exter-
nal popliteal) 3, 4, 5 L. 1, 2 S.
Tibial (internal popliteal) 3, 4, 5 L. 1, 2, S.
Posterior femoral cutane-
ous (smaU sciatic) 5 L. 1, 2, 3 S. 5 L.l, 2, 3, 4 S. 5 L. 1, 2, 3, 4 S.
Common Composition
Nerve. Proximal. Ordinary. Distal.
Furcal 4 L. 4L. 4L.
Common peroneal (exter-
nal popliteal 4, 5 L. 1, 2 S. 4, 5 L. 1, 2 S. 4, 5 L. 1, 2 S.
Tibial (internal popliteal) . 4, 5 L. 1,2 S. 4, 5 L. 1, 2, 3 S. 4, , 1^. 1, 2, 3, 4 S.
Posterior femoral cutane-
ous (small sciatic) 1, 2, 3 S. 1, 2, 3 S. 2, 3 S.
The ordinary type of sacral plexus is commonly formed by the smaller part of
the anterior division of the fourth lumbar nerve and the entire anterior division of
the fifth lumbar nerve, together with the first and parts of the second and third
sacral nerves.
The plexus lies in the pelvis on the anterior surface of the piriformis (fig. 765)
and behind the pelvic fascia and the branches of the hypogastric (internal iliac)
artery. It is also dorsal to the coils of intestine, the lower part of the ilio-pelvic
colon lying in front of the left plexus, and the lower part of the ileum in front of the
right plexus.
The branches given off by this plexus are : — visceral, cutaneous, and muscular.
Visceral branches are given off from the second, third, and fourth sacral
nerves to the pelvic viscera.
The visceral branches correspond to white rami communicantes, through not joining the
sympathetic trunk. The branches from the second and fourth sacral nerves are inconstant.
Ordinary.
Distal.
4L.
4, 5 or 5 L.
4, 5 L. I, 2 S.
4, 5, L. 1, 2, 3 S.
4, 5 L. 1, 2, 3 S.
4, 5 L. 1, 2, 3, 4, S.
THE SACRAL PLEXUS 1007
Cutaneous branches. — (a) The posterior femoral cutaneous (small sciatic)
nerve arises partly from the anterior and partly from the posterior branches of
the anterior primary divisions of the first, second, and third sacral nerves. It
lies on the back of the plexus (figs. 765, 769), leaves the pelvis at the lower
border of the piriformis, and descends in the buttock between the gluteus maxi-
mus and the posterior surface of the sciatic nerve (fig. 770). At the lower
border of the gluteus maximus it passes behind the long head of the biceps femoris,
and descends, immediately beneath the deep fascia, through the thigh and the
upper part of the popliteal space (fig. 740). At the lower part of the popliteal
region it perforates the deep fascia, and it terminates in branches which are dis-
tributed to the skin of the calf.
Branches of the small sciatic. — 1. Perineal branches are distributed in part to the skin of
the upper and medial sides of the thigh on its dorsal aspect. One of the branches, kno\\Ti as the
long pudendal nerve, runs forward and medialward in front of the tuberosity of the ischium to
the lateral margin of the anterior part of the perineum, where it perforates the fascia lata and
CoUes' fascia and enters the anterior compartment of the perineum. In the perineum twigs
join it with the superficial perineal nerves, and its terminal filaments are distributed to the skin
of the scrotum in the male, and to the labium majus in the female.
2. Inferior clunial (gluteal) branches, two or three in number, are given off beneath the
gluteus maximus; they turn around the lower border of this muscle and are distributed to the
skin of the lower and lateral part of the gluteal region.
3. Femoral cutaneous branches are given off as the nerve descends through the thigh.
They perforate the deep fascia and are distributed to the skin of the back of the thigh, especially
on the medial side.
In case of the separate origin of the tibial (internal popliteal) and common peroneal (external
popliteal) nerves, the posterior femoral cutaneous (small sciatic) also arises from the sacral
plexus in two parts. The ventral portion descends with the tibial nerve below the piriformis and
gives off the perineal branches and medial femoral branches, while the dorsal portion passes
through that muscle with the common peroneal nerve, and furnishes the gluteal and lateral
femoral branches.
(6) The inferior medial clunial (perforating cutaneous) nerve arises from the posterior
portion of the second and third sacral nerves (figs. 765, 769). It perforates the lower part of the
sacro-tuberous (great sciatic) ligament, turns around the inferior border of the gluteus maximus,
and is distribtued to the skin over the lower and medial part of that muscle. It is sometimes
associated at its origin with the pudic nerve. It is not always present. Its place is sometirnes
taken by a small nerve (the greater coccygeal perforating nerve of Eisler), arising from the third
and fourth or fourth and fifth sacral nerves, and sometimes it is represented by a branch of the
posterior femoral cutaneous.
Muscular branches of the sacral plexus. — (a) One or two small nerves to the
piriformis pass from the posterior divisions of the first and second sacral nerves.
(b) The superior gluteal nerve receives fibres from the posterior branches of
the fourth and fifth lumbar, and the first sacral nerves. It passes out of the
pelvis through the great sciatic foramen, above the upper border of the piriformis,
and it is accompanied by the superior gluteal artery. As soon as it enters the
buttock it divides into two branches, an upper and a lower.
1. The upper branch is the smaller. It accompanies the upper branch of the deep division
of the superior gluteal artery below the middle curved line of the ihum, and it ends entirely
in the gluteus medius (fig. 770).
2. The lower branch, larger than the upper, passes forward across the middle of the gluteus
minimus, with the lower branch of the gluteal artery; it supphes the gluteus medius and the
gluteus minimus, and it ends in the medial and posterior part of the tensor fasoias latse.
(c) The inferior gluteal nerve is formed by fibres from the posterior branches
of the fifth lumbar, and the first and second sacral nerves. It passes through the
great sciatic foramen, below the piriformis, and divides into a number of branches
which end in the gluteus maximus (figs. 765, 769).
(d) The nerve of the quadratus femoris is formed by the anterior branches of
the fom'th and fifth lumbar and the first and second sacral nerves. It lies on the
front of the plexus and issues from the pelvis below the piriformis. In the
buttock it lies at first between the sciatic nerve and the back of the ischium, and,
at a lower level , between the obtxu-ator internus with the gemelli and the ischium .
It terminates in the anterior surface of the quadratus femoris, having previouslj^
given off a branch to the hip-joint and another to the inferior gemellus.
(e) The nerve of the obturator internus is formed by the anterior branches
of the fifth lumbar, and the first and second sacral nerves (figs. 765, 769). It
leaves the pelvis below the pii-iformis, and crosses the spine of the ischium on the
1008
THE NERVOUS SYSTEM
lateral side of the internal pudic artery and on the medial side of the sciatic nerve.
It gives a branch to the gemellus superior, and turns forward through the small
sciatic foramen into the perineum, where it terminates in the inner surface of the
obturator internus.
The sciatic nerve [n. ischiadicus]. — -The sciatic is not only the largest nerve
of the sacral plexus, but it is also the largest nerve in the body. Its terminal
branches are chiefly muscular, though some of its fibres are cutaneous. Although
it is referred to as one trunk, it consists in reality of peroneal (lateral) and tibial
(medial popliteal) portions, which are bound together by a sheath of fibrous tissue
as far as the upper end of the popliteal space. In about 10 per cent, of the cases
the two parts remain separate, and in such cases the peroneal (lateral popliteal)
Fig. 769. — A Dissection op the Lumbar and Saceal Plexuses, from Behind.
(The anterior crural nerve is placed between the external cutaneous and obturator nerves.)
Dura mater of cord
Last thoracic nerve
Ilio -hypogastric
Iliac branch of ilio
hypogastric
Gluteus medius
Superior gluteal artery
Superior gluteal
Sciatic nerve
Inferior gluteal nerve
G eni to -femoral
Cauda equina
Filum terminale
Lateral cutaneous
Obturator
\^ ' — Lumbo-sacral trunk
-^i First sacral nerve
Fifth sacral nerve
Visceral branches
Inferior gluteal artery
Sacro-spinous
ligament
Pudic nerve
Inferior medial clunial
of second and third
sacral i
part usually pierces the piriformis. The peroneal portion of the nerve consists of
fibres derived from the dorsal branches of the anterior primary divisions of the
fourth and fifth lumbar and the first and second sacral nerves, while the tibial
part is formed by the fibres from the anterior branches of the fourth and fifth
lumbar, and the first, second, and third sacral nerves (figs. 765, 769). ^ The com-
mon trunk leaves the pelvis by passing through the great sacro-sciatic foramen,
usually below the piriformis, and descends through the buttock, running midway
between the tuber ischii and the great trochanter (fig. 770). Passing down the
thigh, the trunk terminates at the upper angle of the popliteal space by dividing
THE SCIATIC NERVE
1009
into the common peroneal (external politeal) and the tibial (internal popliteal)
nerves (fig. 771).
The relation of the trunk to the piriformis muscle is more or less unique. It may pass either
above or below the muscle, it may spht and pass around the muscle, or the muscle may be spUt
and surround the nerve. Again, there may be a sphtting of both the muscle and the nerve, in
which case any possible combination of the four parts may occur; a portion of the nerve may be
above and a portion between the parts of the muscle, or a portion may be below and a portion
between. The trunk of the nerve hes deeply in the thigh, and it is covered posteriorly by the
skin and fascia, the gluteus maximus and the long head of the biceps femoris. Anteriorly it
is in relation, from above downward, with the following structures: — the posterior surface of
the ischium and the nerve to the quadratus femoris, the gemellus superior, obturator internus,
gemellus inferior, quadratus femoris, and adductor magnus muscles.
Muscular branches of the sciatic are given off at the upper part of the thigh to
the semitendinosus, to the long head of the biceps femoris, to the semi membranosus,
Fig. 770. — A Dissection op the Nerves in the Gluteal Region.
(The gluteus maximus and gluteus medius have been divided near their insertions, and thrown
upward.)
Inferior gluteral artery
-Gluteus maximus
Inferior gluteal nerve
Gluteal artery
Sacro-tuberous
ligament
Comes nervi
ischiadici
Gemellus
inferior
Tuberosity of
ischium
Long pudendal
\ Adductor
^ magnus
Sciatic nerve
Posterior
cutaneous
nerve
Tendon of obturator externus
Vastus externus
Gluteus maximus
and to the adductor magnus, and, about the middle of the thigh, a branch is fur-
nished to the short head of the biceps.
The branch to the short head of the biceps femoris is derived from the peroneal (lateral
popliteal) portion of the nerve, while all the other muscular branches are given off by the tibial
(medial pophteal) part. The semitendinosus receives two branches, one which enters it above
and another which passes into it below its tendinous intersection. The nerve to the long head
of the biceps descends along the sciatic trunk and enters the middle of the deep surface of the
muscle. The nerves to the semimembranosus and adductor magnus arise by a common trunk
' which divides into three or four branches. One branch ends in the adductor, and the others
are distributed to the semimembranosus. The branch to the adductor magnus supplies only
those fibres of the muscle which begin from the tuberosity of the ischium and descend vertically
to the medial condyle of the femur.
At the apex of the popliteal space the two component parts of the common
trunk of the sciatic become distinct. The tibial nerve (internal popliteal) , formed
by fibres from the anterior branches of the fourth and fifth lumbar and first,
second, and third sacral nerves, passes vertically through the popliteal space,
descends through the leg to a point midway between the medial malleolus and
the most prominent part of the medial tubercle of the os calcis, where it divides
into its terminal branches, the lateral plantar and the medial plantar nerves.
The part of the nerve from the point of bifurcation to the lower border of the
popliteus muscle is sometimes called the internal popliteal; the part of the nerve
in the dorsum of the leg being then designated the posterior tibial nerve.
1010 THE NERVOUS SYSTEM
In the upper part of the pophteal space the tibial nerve lies relatively superficially, being
covered dorsally by the skin and fascia, while in the lower part of the space it is overlapped by
the heads of the gastrocnemius and is crossed by the plantaris. In the upper part of the space
it lies in front of the posterior femoral cutaneous (small sciatic) nerve and to the lateral side of
the vein and artery; at the middle of the space it is dorsal and in the lower part of the space
it is medial to both of them.
The branches given off by the tibial nerve in the popliteal space are articular,
cutaneous, and muscular.
The articular branches are usually three in number, a superior and an inferior
internal articular and an azygos articular. They accompany the corresponding
arteries, and, after piercing the ligaments, are distributed in the interior of the
joint. The superior branch is often wanting.
The cutaneous branch, the medial sural cutaneous (tibial communicating)
nerve, descends between the heads of the gastrocnemius, beneath the deep
fascia, to the middle of the calf, where it pierces the fascia and unites with the
peroneal anastomotic branch of the lateral sural cutaneous to form the sural
(external saphenous) nerve, through which its fibres are distributed to the skin
of the lower and dorsal part of the leg and the lateral side of the foot.
The muscular branches are distributed to both heads of the gastrocnemius, to
the plantaris, soleus, and popliteus.
The nerve io the soleus is relatively large, and passes between the lateral head of the gastroc-
nemius and the plantaris before it reaches its termination (fig. 771). The nerve to the popliteus
descends on the posterior surface of the muscle, turns around its lower border, and is distributed
on its anterior aspect. In addition to supplying the popliteus, it gives articular branches to
the knee and superior tibio-fibular joints, a branch to the tibia which accompanies the medullary
artery, and a long, slender twig which gives filaments to the anterior and posterior tibial arteries,
and it descends as the interosseous crural nerve on the interosseous membrane to the inferior
tibio-fibular joint. It also gives branches to the interosseous membrane and to the periosteum
of the lower part of the tibia.
Relations. — In the upper part of the leg the tibial nerve is placed deeply, under the gas-
trocnemius and soleus, but in the lower half it is merely covered by the deep fascia, which is
thickened between the medial maleolus and the calcaneus to form the lacinate (internal annular)
ligament, and the termination of the nerve lies either under cover of this hgament, or under the
attachment of the abductor hallucis. The anterior relations of the nerve are, from above down-
ward, the tibialis posterior, the flexor digitorum longus, the lower part of the tibia, and the pos-
terior ligament of the ankle-joint. For a short distance after its commencement the nerve lies
to the medial side of the posterior tibial artery; then it crosses behind the artery and runs down-
ward along its lateral aspect.
The branches of the lower part of the tibial nerve (below the popliteal space)
are likewise muscular, cutaneous, and articular. They are supplied to the deep
muscles of the dorsum of the leg, to the fibula, to the skin of the heel and foot, and
to the ankle-joint. Several of the terminal branches are important enough to
receive special names and special treatment.
The muscular branches pass from the upper part of the nerve to the tibiahs posterior,
flexor digitorum longus, soleus, and flexor haUuois longus. The fibular branch arises with the
nerve to the flexor hallucis longus, and accompanies the peroneal artery. It supplies the peri-
osteum and gives filaments which accompany the medullary artery.
The articular branches arise from the lower part of the nerve, immediately above its
terminal branches, and they pass into the ankle-joint through the deltoid ligament.
The medial calcaneal (calcaneo-plantar cutaneous) nerves ai-ise from the trunk of the
tibial nerve in the lower part of the leg. They pierce the laciniate (internal annular) ligament,
and are distributed to the integument of the medial side and plantar surface of the heel and
the adjoining part of the sole of the foot (fig. 771).
Terminal branches of tibial nerve. — The medial plantar nerve is the larger of
the two terminal branches of the tibial nerve. It commences under cover of the
lower border of the laciniate (internal annular) ligament, or under the posterior
border of the abductor hallucis, and passes forward, accompanied by the small
internal plantar artery, in the inter-muscular septum between the abductor
hallucis and the flexor digitorum brevis. At the middle of the length of the foot
it becomes superficial, in the interval between the two muscles, and divides into
four sets of terminal branches (fig. 772) : —
(a) Muscular branches pass from the trunk of the nerve to the abductor
hallucis and the flexor digitorum brevis.
(6) Articular branches are distributed to the talo-navicular (astragalo-
sacphoid) and the naviculari-cuneiform'joint.
(c) Plantar cutaneous branches are supplied to the skin of the medial part of
the sole.
THE TIBIAL NERVE
1011
{d) The digital branches are four in number, the first, a proper plantar digital,
the secondj third, and fourth, the common plantar digitals. Near the bases of the
Fig. 771. — Muscle Nerves of the Right Leg, viewed from Behind. (Spalteholz.)
The semitendinosus, semimembranosus, biceps femoris, gastrocnemius, plantaris, soleus, and
flexor hallucis longus have been wholly or in part removed.
Sciatic nerve ■
Popliteal vein —
Popliteal artery --
Adductor magnus -- J
Vastus medialis ^'-'^■r ., ■ -- > ; ■ ' i
Articular branch - - -j.-^r ;- ^r ^j^ , "1
Tibial nerve
1
Semimembranosus — r-?
Medial head of gastrocnemius — Jf-
Lateral head of gastrocnemius ■'
Popliteus
■"Biceps f'
—Medial sural cutaneous nerve
— Common peroneal nerve
~ Articular branch
■- Lateral sural cutaneous nerve
/^M^--^-"***" Muscular branches
Plantar muscle
Head of fibula
— Interosseus cruris nerve
— Popliteal artery
Soleus (cut) — -
-Muscular branch
Posterior tibial artery ■
Tibial nerve
Muscular branch *
Flexor digitorum longus
Posterior tibisil artery — g
Tibialis posterior
\Jd
|--PeroneaI artery
— Muscular branch
Flexor hallucis longus
— Peroneus longus
5--Peroneal artery
Tendo calcaneus (Achillis)
Articular branch •
Medial calcaneal nerves
Posterior tibial artery '
Laciniate ligament
|--- Articular branch
— Flexor hallucis longus (cut)
^---Sural nerve
-Lateral calcaneal branches
metatarsal bones, the second, third and fourth common plantar digital divide
into proper plantar digital nerves.
The first proper plantar digital nerve becomes subcutaneous farther back than the others,
and, after sending a branch to the flexor hallucis brevis, passes to the medial side of the great
1012
THE NERVOUS SYSTEM
toe. The second (common digital) nerve gives a twig to the first lumbrical and bifurcates
to supply the adjacent sides of the first and second toes. The third supplies the adjacent sides
of the second and third toes, and the fourth, after connecting with the superficial branch of the
lateral plantar nerve, divides to supply the adjacent sides of the third and fourth toes. All the
proper digital nerves run along the sides of the toes and he below the corresponding arteries;
they supply the joints of the toes, and each gives off a dorsal branch to the skin over the second
and terminal phalanges and to the bed of the nail. All of them give fibres terminating in
numerous Pacinian corpuscles.
The lateral plantar nerve is the smaller of the two terminal branches of the
tibial nerve. It commences at the lower border of the laciniate (internal annular)
Fig. 772. — Superficial Nerves in the Sole op the Foot. (Ellis.)
Abductor hallucis-
Flexor digitorum brevis"
Medial plantar
Medial plantar artery.
Proper plantar digital
nerve to medial side
of hallux
Abductor minimi digit!
Lateral plantar artery
Lateral plantar nerve
Proper plantar digital
branches of the
lateral plantar
.ti^-
Proper plantar digital
branches of the
11 J medial plantar
ligament, or under cover of the origin of the abductor hallucis, and passes forward
and lateralward to the base of the fifth metatarsal bone, where it divides into a
superficial and a deep branch (fig. 772). As it runs forward and lateralward it
it is superficial to the tendon of the flexor hallucis longus and to the quadratus
plantse (flexor accessorius), and deep to the flexor digitorum brevis. At its ter-
mination it lies in the interval between the flexor digitorum brevis and abductor
digiti quinti.
Branches. — -From the trunk of the lateral plantar nerve muscular, superficial
and deep, and articular branches are given off.
THE COMMON PERONEAL NERVE 1013
The muscular branches arise from the commencement of the nerve and are dis-
tributed to the abductor digiti quinti and quadratus plantse.
The articular branches supply the calcaneo-cuboid joint.
The superficial branch supplies muscular filaments to the flexor digiti quinti
brevis, the opponens, the third plantar and fourth dorsal interosseous muscles,
and divides into two common plantar digital nerves, each of which subdivides to
form proper plantar digital nerves.
The lateral of the two common branches supplies the lateral side of the fifth digit; the medial
connects with the lateral digital branch of the medial plantar nerve (fig. 772) and divides into
proper plantar digital nerves for the adjacent sides of the fourth and fifth digits. The digital
branches of the superficial division of the lateral plantar, like those of the medial plantar, supply
the skin of the toes and the beds of the nails, and their fibres terminate in numerouos Pacinian
corpuscles.
The deep branch passes forward and medialward into the deep part of the
sole with the plantar arterial arch. It runs deep to the quadratus plantse, the long
flexor tendons and the lumbricals, and the oblique adductor of the great toe. It
lies, therefore, immediately beneath the bases of the metatarsal bones and it
supplies the following muscular and articular branches: — •
Muscular branches to the lateral three lumbricals, the interossei of the medial three inter-
metatarsal spaces, and the transverse and oblique adductor muscles of the great toe.
Articular branches to the intertarsal and to the tarso-metatarsal joints and not uncommonly
to the metatarso-phalangeal joints also. Filaments from the deep branch frequently pass
through the interosseous spaces and join with the interosseous branches of the deep peroneal
(anterior tibial) nerve.
The common peroneal (external popliteal) nerve. — ^At the apex of the pop-
liteal space, where the two component parts of the sciatic trunk usually become
distinct, the lateral portion receives the name common peroneal nerve. It de-
scends along the posterior border of the biceps femoris, which forms the upper part
of the lateral boundary of the space (fig. 771). It leaves the space at the lateral
angle, crosses the plantaris, the lateral head of the gastrocnemius, the pop-
liteus, and the inferior external artery, and descends behind the upper part of the
soleus, to the neck of the fibula, where it turns forward between the peroneus
longus and the bone, and breaks up into its three terminal branches, the recurrent
articular, the superficial peroneal (musculo-cutaneous), and the deep peroneal
(anterior tibial) nerves (fig. 773).
Upper branches. — While it is in the popliteal space the common peroneal
(external popliteal) nerve gives off two articular branches and a cutaneous branch.
The superior articular branch accompanies the superior external articular artery. The
lateral head of the gastrocnemius, and it joins the inferior external articular artery behind the
tendon of the biceps femoris. Both the upper and lower articular branches pierce the ligaments
and are distributed in the interior of the knee joint.
The cutaneous branch {communicans fibularis) , lateral sural cutaneous, is extremely variable
both as to the number of its branches and as to the place of its anastomosis with the medial
sural cutaneous. Leaving the common peroneal (external popliteal) in the popliteal space, it
descends between the deep fascia and the lateral head of the gastrocnemius to the middle of
the calf, where it pierces the fascia and unites with the medial sural cutaneous to form the
sural (external saphenous) nerve. In its course it may give off no branches; or it may give off
several, some of which supply the skin of the dorsum of the leg, while one of them, the peroneal
anastomotic branch, unites with the medial sural cutaneous to form the sural (short saphenous)
nerve. The junction of the peroneal anastomotic branch with the medial sural cutaneous may
take place at any point between the popliteal space and the lower third of the leg.
The sural (external or short saphenous) nerve is formed by the union of the
lateral sural cutaneous nerve either directly, or tlu-ough a connecting branch,
the peroneal anastomotic, with the medial sural cutaneous (fig. 771). It descends
along the lateral border of the tendo Achillis, giving branches to the lower and
lateral part of the leg, and lateral calcaneal branches to the lateral side of the heel.
It passes dorsal to the lateral malleolus, turns forward across the lateral surface of
the cruciate (external annular) ligament, and becomes the lateral dorsal cutaneous
nerve. Continuing along the lateral side of the foot it divides into two branches,
the dorsal digitals, one of which supplies the lateral side of the fifth digit, while the
other anastomoses with or takes the place of a branch of the superficial peroneal
(musculo-cutaneous) nerve, which is distributed to the adjacent sides of the fourth
and fifth digits (fig. 773).
The terminal branches of the common peroneal. — (1) The recurrent articular
nerve passes medialward, around the neck of the fibula, and through the upper
1014
THE NERVOUS SYSTEM
part of the attachment of the extensor digitorum longus. At the medial border
of the fibula it becomes associated with the anterior tibial recmrent artery, with
which it ascends through the upper part of the tibialis anterior to the head of the
Fig. 773. — Distrebtjtion of the Superficial and Deep Peroneal Nerves on the Ante-
rior Aspect of the Leg and on the Dorsum of the Foot. (Hirschfeld and Leveill^.)
Common peroneal nerve-
Recurrent articular'
Superficial peroneal
Branch to peroneus longus'
Branch to external
digitorum longus
Branch to peroneus brevis'
Superficial peroneal'
Intermediate dorsal cutaneous-
Lateral dorsal cutaneous'
Deep peroneal nerve
■Anterior tibial artery
Tibialis anterior
'Deep peroneal nerve
Medial dorsal cutaneous
Deep peroneal (lateral division)
Deep peroneal (medial division)
tibia and the knee-joint. It supplies the tibialis anterior, the superior tibio-
fibular joint, and the knee-joint.
(2) The superficial peroneal (musculo-cutaneous) nerve arises from the com-
mon peroneal between the peroneus longus and the neck of the fibula and de-
scends in the intermuscular septum between the long and short peronei on the
I
THE DEEP PERONEAL NERVE 1015
lateral side, and the extensor digitorum longus on the medial side. It gives off
muscular and cutaneous branches in its descent, and at the junction of the middle
and lower thii-ds of the leg it pierces the deep fascia and divides into a medial
and a lateral branch (fig. 773).
Muscular branches are given off from the superficial peroneal to the peroneus
longus and peroneus brevis before the nerve pierces the deep fascia.
Cutaneous branches pass from the trunk of the superficial peroneal to the
skin of the lower part of the front of the leg.
The medial dorsal cutaneous (internal cruciate branch of the superficial
peroneal), passes downward and medialward across the transverse and the cru-
ciate (anterior annular) ligament of the ankle and subdivides into two branches.
The medial branch passes to the medial side of the great toe; it also supplies twigs
to the skin of the medial side of the foot, and it anastomoses with the deep saphen-
ous nerve and with the medial terminal branch of the deep peroneal (anterior
tibial) nerve. The lateral branch passes to the base of the cleft between the second
and third toes and divides into two dorsal digital branches which supply the
adjacent sides of the cleft.
The lateral branch (intermediate dorsal cutaneous) of the superficial peroneal,
in separating from the medial, crosses in front of the cruciate ligament and divides
into two dorsal digital branches, which pass beneath the dorsal venous arch.
The medial of these branches supplies the adjacent sides of the third and fourth
toes (fig. 773). The lateral branch communicates with the sural (external saphen-
ous) nerve and is distributed to the adjacent sides of the fourth and fifth toes.
This latter branch is frequently replaced by the sural nei-ve.
(3) The deep peroneal (anterior tibial) nerve springs from the end of the
common peroneal (external popliteal) nerve between the peroneus longus muscle
and the neck of the fibula. It passes forward and medialward through the upper
part of the origin of the extensor digitorum longus, to the interval between that
muscle and the tibialis anterior; then it descends, in the anterior compartment of
the leg, to the ankle, where it divides into a medial and a lateral terminal
branch (fig. 773).
In the upper part of the leg the deep peroneal nerve lies between the extensor digitorum lon-
gus and tibialis anterior and lateral to the anterior tibial artery. In the middle of the leg it is in
front of the artery and between the extensor hallucis longus and tibiaMs anterior; then it crosses
beneath the extensor hallucis, and in the lower third of the leg it is again to the lateral side of
the artery, but between the extensor hallucis longus and the extensor digitorum longus.
Branches furnished from the trunk of the deep peroneal are muscular, articu-
lar, and terminal.
The muscular branches supply the tibialis anterior, extensor digitorum
longus, extensor hallucis longus, and peroneus tertius.
Articular filaments are given to the ankle-joint and the inferior tibio-fibular
articulation.
Terminal branches. — The medial terminal branch passes downward along
the side of the dorsalis pedis artery and divides into two dorsal digital branches
which supply the adjacent sides of the first and second toes. It also gives fila-
ments to the periosteum of the adjacent bones, to the metatarso-phalangeal and
interphalangeal articulations, a twig to the dorsal interosseous muscle of the
first space, and a perforating twig which connects with the lateral plantar nerve.
The lateral terminal branch passes lateralward, beneath the extensor digitorum
brevis, and it ends in a gangliform enlargement from which branches are dis-
tributed to the extensor digitorum brevis, the tarsal joints, and to the three lateral
intermetatarsal spaces. The latter branches supply the neighbouring bones,
periosteum, and joints. They give off perforating twigs, which pass through the
spaces and anastomose with branches of the lateral plantar nerve, and the
most medial also gives a twig to the second dorsal interosseous muscle.
1016
THE NERVOUS SYSTEM
Table Showing Ordinary Relations op Lumbar and Sackal Nerves to
Branches op the Lumbar and Sacral Plexuses and to the Pudic Nerve
Neeves Contributing.
Nerves.
Nerves.
Femoral
Obturator
1 L, / Ilio-hypogastric
\ Ilio-inguinal
1 and 2 L Genito-femoral
1, 2, and 3 L Lateral cutaneous
2, 3, and 4 L ( Femoral
1 Ubturator
4, 5 L., and 1 S / Superior gluteal
( JNerve to quadratus lemons
4, 5 L., 1 and 2 S Sciatic (peroneal part)
4, 5 L., 1, 2, and 3 S Sciatic (tibial part)
5 L., 1 and 2 S . . I Inferior gluteal
1 Nerve to obturator internus
1 and 2 S Nerve to piriformis
2 and 3 S Medial inferior clunial
1, 2, and 3 S Posterior femoral cutaneous
2, 3, and 4 S Pudic
Table Showing Relations op Muscles op Lower Extremity to Nerves op
Lumbar and Sacral Plexuses
Nerves Contributing. Muscles.
Illio-psoas
Sartorius
rectineus
Adductor longus
2, 3, and 4 L 19^"'^'! u ■
I Adductor brevis
3 and 4 L < Quadriceps femoris
\ Obturator externus
3, 4, and 5 L _ Adductor magnus
' Gluteus medius
" minimus
Tensor fasc. latae
Semimembranosus
Plantaris
Popliteus
Quadratus femoris
Inferior gemellus
' Flex, digit, long.
Tibialis posterior
Flexor digit, brev.
" haUucis brev.
Abductor hallucis
First lumbrical
Superior gemellus
Obturator internus
Gluteus maximus
Semitendinosus
Soleus
I Flex, hallucis long.
I Piriformis
I Gastrocnemius
I Flexor quadratus plantse
1 and 2 S ] ^*"^- 1^?^*^ '^^^iti
I Plantar interossei
I Dorsal "
I Add. haUucis trans.
l " " obliq.
1, 2, and 3 S Long head of biceps femoris
f Ext. haU. long.
" digit. "
" digit, brev.
4, 5 L., and IS \ Tibialis anterior
4, 5L., and 1 S.
5L., and 1 S.
5L., 1 and2S.
Peroneus tertius
longus
brevis
THE PUDENDAL PLEXUS
Femoral
Obturator
Obturator and sciatic
Superior gluteal
Sciatic
Tibial
Nerve to quad. fern.
Tibial
Posterior medial
Plantar
Nerve to obt. int.
Inferior gluteal
Sciatic
Tibial
Tibial
Lateral plantar
Sciatic
Deep peroneal
Superficial peroneal
" peroneal
The pudendal plexus, like the parts of the lumbo-sacral plexus ah-eady
described, varies in its formation. The accompanying tables show the extreme
THE PUDENDAL PLEXUS 1017
range of variation and the common method of formation of the large nerve of this
plexus in each of the three classes.
COMPOSITION OF THE NERVES OF THE PUDENDAL PLEXUS
Range of Variation
Nerve. Proximal. Ordinary. Distal.
Pudic nerve 1,2,3,4,5 8. 1,2,3,4 8. 2,3,4,5 8.
Common Composition
Nerve. Proximal. Ordinary. Distal.
Pudic nerve 2,3 8. 2,3,4 8. 3, 4 S.
The pudendal plexus is commonly formed by parts of the anterior divisions of
the second, third, and fourth sacral nerves. It lies in the lower part of the back
of the pelvis, and gives off visceral, muscular, and terminal branches.
Visceral branches (pelvic splanchnics) arise from the third and fourth sacral
nerves especially, and enter branches of the sympathetic plexus. They are
distributed both directly (their afferent or sensory fibres terminating in the pelvic
viscera) and by their visceral efferent fibres terminating in the ganglia of the
sympathetic plexus to the pelvic viscera (figs. 765, 791). The middle hsemor-
rhoidal nerves pass to the rectum, the inferior vesical nerves to the bladder, and,
in the female, the vaginal nerves to the vagina fsee Sympathetic System).
Muscular branches are given by the fourth sacral nerve to the coccygeus,
levator ani, and sphincter ani externus (fig. 765).
The nerves to the two former muscles pass into the pelvic surfaces of the muscles, but that
to the last-named muscle, called the perineal branch, passes backward between the levator
ani and the coccygeus, or through the posterior fibres of the latter muscle, into the posterior
part of the ischio-rectal fossa, and, in addition to supplying the sphincter ani, it gives cutaneous
filaments to the skin between the anus and the coccyx.
Terminal branches. — The pudic nerve [n. pudendus] rises usually from the
anterior primary divisions of the second, third, and fourth sacral nerves (fig. 765).
It emerges from the pelvis below the piriformis, crosses the spine of the ischium,
lying to the medial side of the internal pudic artery (fig. 769), and accompanies
the artery, through the small sciatic foramen, into Alcock's canal in the ob-
turator fascia on the lateral wall of the ischio-rectal fossa, where it terminates by
dividing into three branches, the inferior hsemorrhoidal, the perineal, and the
dorsal nerve of the penis.
The inferior haemorrhoidal nerves frequently arise independently from the
third and fourth sacral nerves, pierce the medial wall of Alcock's canal, and pass
forward and medialward through the ischio-rectal fat to supply the sphincter ani
externus and adjacent skin. They anastomose with branches of the perineal
nerve.
The perineal nerve runs forward for a short distance in Alcock's canal and
divides into a deep and a superficial branch. The deep branch breaks up into
filaments, one or two of which pierce the medial wall of the canal and pass
medialward to the anterior fibres of the sphincter and levator ani. The re-
maining part of the nerve pierces the base of the m-o-genital trigone (triangular
ligament), and enters the superficial pouch of the urethral triangle, where it is
distributed to the bulb of the urethra, and to the transversus perinei, bulbocaver-
nosus, and ischiocavernosus. It also sends some sensory filaments to the mucous
membrane of the urethra. The superficial branch almost at once divides into
medial and lateral branches, the posterior scrotal (labial) nerves.
Both branches pass through the wall of Alcock's canal into the anterior part of the ischio-
rectal fossa, then they pierce the base of the uro-genital trigone, and enter the superficial pouch
of the urethral triangle. The lateral branch usually passes below the transversus perinei,
and the medial branch above the muscle or through its fibres. The lateral branch connects
with the long pudendal nerve, and with the inferior hsemorrhoidal nerve, and both branches
end in terminal filaments which anastomose and which are distributed to the skin of the scrotum
and the anterior part of the perineum in the male, and to the labium majus in the female.
1018 THE NERVOUS SYSTEM
The dorsal nerve of the penis runs forward in Alcock's canal above the
internal pudic artery. It pierces the base of the uro-genital trigone, continues
forward between the layers of the trigone, embedded in the fibres of the con-
strictor urethrse, and it gradually passes to the lateral side of the internal pudic
artery. A short distance below the pudic arch it pierces the anterior layer of the
uro-genital trigone, gives a branch to the corpus cavernosum penis, passes
forward between that structure and the bone, and turns downward on the dorsum
of the penis, passing between the layers of the fundiform (suspensory) ligament
and along the outer side of the dorsal artery of the penis. It supplies the skin
of the dorsum of the penis, and, having given branches to the prepuce, it breaks
up into terminal filaments which are distributed to the glans penis.
The dorsal nerve of the clitoris is much smaller than the dorsal nerve of the
penis to which it corresponds. Is is distributed to the clitories.
THE COCCYGEAL PLEXUS
This plexus is frequently, and with some reason, considered as a subdivision of
the pudendal plexus, and sometimes it is described with the coccygeal nerves.
It is formed chiefly by the anterior division of the fifth sacral nerve and the
coccygeal nerve, but it receives a small filament from the anterior division of the
fourth sacral nerve (figs. 765, 769). These constituents unite to form plexiform
cords lying on either side of the coccyx. From these cords arise the ano-coccygeal
nerves, which pierce the sacro-tuberous (great sacro-sciatic) ligament and supply
the skin in the neighbourhood of the coccyx.
III. THE DISTRIBUTION OF THE CUTANEOUS BRANCHES
OF THE SENSORY AND MIXED CRANIAL
AND SPINAL NERVES
The cutaneous filaments of the sensory and mixed nerves are distributed to
definite regions of the surface of the body which are known as 'cutaneous areas.'
Each cutaneous area has one special nerve of supply and the central part of the
area receives that nerve alone, but wherever the borders of two areas meet they
reciprocally overlap, therefore each margin of every cutaneous area has two
nerves of supply, its own nerve and that of an adjacent area, and of these, some-
times one and sometimes the other preponderates.
The Cutaneous Areas of the Scalp
The limits of the cutaneous areas in the scalp region are indicated in figs. 774, 776, but
in general terms it may be said that the skin of the scalp in front of the pinna is supphed by
four cutaneous nerves, viz. , the mesial part by the supratrochlear and the supra-orbital branches
of the ophthalmic division of the trigeminus, and the lateral part by the temporal branch of the
maxillary division, and the auriculo-temporal branch of the mandibular division of the same
nerve.
The portion of the scalp behind the pinna also receives four cutaneous nerves; laterally it
is supplied by the great auricular and small occipital branches of the cervical plexus which
contain filaments from the second and third cervical nerves, and medially it receives the great
and smallest occipital nerves which are derived from the internal branches of the posterior
primary divisions of the second and third cervical nerves respectively.
The Cutaneous Areas of the Face
With the exception of the skin over the posterior part of the masseter muscle, the whole
of the skin of the face is supplied by the branches of the trigeminus. The nose is supplied
medially by the supratrochlear, the infratrochlear, and the nasal branches of the ophthalmic
division, and laterally by the infra-orbital branch of the maxillary division. The upper eyelid
is supplied by the supratrochlear, the supra-orbital, and the lacrimal branches of the ophthal-
mic division; the lower eyelid by the infratrochlear branch of the ophthalmic division and
by the infra-orbital and the zygomatico-facial (malar) branches of the maxillary division.
The skin over the upper jaw and the zygomatic (malar) bone is supplied by the infra-orbital
and zygomatico-facial branches of the maxillary division, that over the buccinator by the buccal
branch of the mandibular division, and that over the lower jaw, fiom in front backward, by
the mental, buccal, and auriculo-temporal branches of the mandibular division, except a small
part near the posterior border which receives its supply from the great auricular nerve.
CUTANEOUS AREAS OF THE NECK
The Cutaneous Areas of the Auricle (Pinna)
1019
The upper two-thirds of the outer surface of the pinna are suppUed by the auriculo-temporal
branch of the mandibular division of the trigeminus, and the lower third by twigs of the great
Fig 774— Diageam of the Cutaneous Nerve Areas of the Head and Neck.
Red— ophthalmic division of trigeminus. White-maxillary division of trigemmus.
Blue— mandibular division of trigemmus.
Dotted shading— Posterior primary divisions of cervical nerves. .
Obhque shading— Ascending and transverse superficial branches of cervical plexus.
Transverse shadmg— Descending superficial branches of cervical plexus.
It i^ult be remembered that the boundaries of each area are not distmct; wherever two
areas meet they overlap.
Supra-trochlear
Lacrimal
Infra -trochlear
Smallest occipital ^\-*V/.'
auricular nerve. The lower three-fourths of the cranial surface of the pinna are supphed by
the great auricular nerve, and the upper fourth by the small occipital nerve. The posterior
surffce of the external auditory meatus receives filaments from the auricular branch of the
vagus.
The Cutaneous Areas of the Neck
The skin over the anterior part of the neck is supplied by the superficial cervical branch
of the cervical plexus, which contains fibres from the second and third cervical nerves and
in the lower part of its extent, by the anterior supra-clavicular nerves (suprasternal branches).
1020
THE NERVOUS SYSTEM
which convey twigs of the third and fourth cervical nerves (fig. 774). The lateral part of the
neck receives filaments from the second, third, and fourth cervical nerves by way of the great
auricular, small occipital, and middle supraclavicular (supra-clavicular) branches of the cervical
plexus, and posteriorly the skin of the neck is suppUed by the small occipital nerve and by the
medial branches of the posterior primary divisions of the cervical nerves from the second to
the sixth inclusive (fig. 776).
The Cutaneous Areas of the Trunk
The skin over the ventral aspect of the trunk as far down as the third rib is supphed by
the anterior supra-clavicular (suprasternal) and middle supra-olavicular (supra-clavicular)
branches of the cervical plexus, which contain filaments from the third and fourth cervical
nerves (fig: 776). From the third rib to tlie lower part of the abdominal wall the skin receives
the anterior cutaneous branches, and the anterior divisions of the lateral cutaneous branches of
Fig. 775. — Diagram of the Cutanbotts Areas of the Side of the Body and Part of the
Limb. (After Head.)
the thoracic nerves except the first, second, and twelfth (fig. 776). The skin over the lower
and anterior part of the abdominal wall is supplied by the iho-hypogastric branch of the first
lumbar nerve.
The cutaneous supply of the lateral aspects of the body is derived from the lateral branches
of the anterior primary divisions of the thoracic nerves from the second to the eleventh, and
the skin over the dorsal aspect of the body is supplied laterally by the posterior divisions of
the lateral branches of the thoracic nerves from the third to the eleventh, and medially by the
posterior primary divisions of the thoracic nerves, in the upper half by their medial branches
and in the lower half principally by their lateral branches.
THE CUTANEOUS AREAS OF THE LIMBS
The areas of skin of the upper and lower limbs which are supplied by the branches of the
brachial, lumbar, and sacral plexuses are indicated in fig. 776, and the spinal nerves which con-
tribute to each nerve area are noted. The question of the skin areas supplied by any given spinal
nerve is one of great chnical importance, in connection with the diagnosis of injuries of nerves
and of pathological conditions affecting them. Therefore, considerable attention has been
directed to the matter and it has been found that the areas which become hypersensitive
when certain spinal nerve-roots are irritated, or anaesthetic when the roots are destroyed, do
CUTANEOUS AREAS OF THE BODY
1021
Fig. 776. — Diagram showing Areas op Distriution of Cutaneous Nerves.
Head : —
Red — Ophthalmic division of trigeminus. White — maxillary division of trigeminus.
Blue — mandibular division of trigeminus. Dotted area — Posterior primary divisions
of cervical nerves. Oblique and transverse shading — Branches of cervical plexus.
Body and Limbs : —
Red — Anterior branches of anterior primary divisions.. Blue — Posterior branches of
anterior primary divisions. Two colours in one area indicate that the area is supplied
by two sets of nerves, and it should be remembered that wherever two nerve areas
approach each other they overlap. The dotted blue area of the posterior femoral
cutaneous (small sciatic) indicates that the nerve comes from the posterior as well as
from the anterior parts of the anterior primary divisions of the sacral nerves, but it
supplies a flexor area. The area of the inferior medial cluneal nerve is left uncoloured,
because its true nature is uncertain. Dotted shading — posterior primary divisions.
The numbers and initial letters refer to the respective spinal nerves from which the
nerves are derived.
Ophthalmic division of trigeminus - -
Mandibular division of trigeminus
Maxillary division of trigeminus
Supraorbital
Great auricular -
Cutaneous colli, 3, 3 C -.
Supra -clavi cular
Axillary
Lateral cutaneous nerves
Anterior cutaneous nerves
Medial brachial cutaneous
and intercosto-
brachial, 1,2 T
Posterior brachial,
cutaneous
Medial antibrachial
cutaneous
Musculo-cutaneous
(Lateral antibrachialj
Lateral femoral cutaneous
Geni to -femoral
Superficial
radial, 6 C
Ilio-inguinial, i L
Median, 6,7, C. i T
Ulnar, i T
Supra-clavicular, 3, 4 C
Axillary, 5, 6 C
Lateral branches of
thoracic nerves
Posterior brachial
cutaneous
Medial and intercosto-
brachial cutaneous
Medial antibrachial
cutaneous
Dorsal antibrachial
cutaneous, 6, 7, 8 C
Medial antibrachial
cutaneous
Superior clunial
Lateral cutaneous of
ilio-hypogastric
Musculo-cutaneous, 5, 6 C
Middle clunial
Inferior medial
clunial 2, 3 S
Ulnar, 8 C
Superficial
radial, 6, 7 C
Area supplied by
superficial radial
and ulnar
Median, 6,7, 8 C, i T
Common peroneal —
Saphenous —
Superficial peroneal
Deep peroneal
Medial plantar
Lateral femoral cutaneous
Posterior femoral cutaneous
Common peroneal, 5 L, i, 2 S
Saphenous, 3, 4 L
Medial calcaneal of tibial, i, 2 S
■ J'-ii Lateral plantar, i, 2 S
V...
Medial plantar, 4, 5 L,
1022
THE NERVOUS SYSTEM
not correspond exactly with the regions to which the fibres of the roots can apparently be
traced by dissection. Moreover, it has been discovered, partly by clinical observations on the
human subject and partly by experiment on monkeys, that the nerves of the hmbs have a
more or less definite segmental distribution. To understand clearly this segmental arrange-
ment the reader must remember that in the embryonic stage when no limbs are present the
body is formed of a series of similar segments, each of which is provided with its own nerve.
At a later stage when the limbs grow outward, each limb is formed by portions of a definite
number of segments which fuse together into a common mass of somewhat wedge-hke outline.
Each rudimentary limb possesses a dorsal and a ventral surface. The dorsal surfaces of both
the upper and the lower limbs are originally the extensor surfaces, and the ventral surfaces the
flexor surfaces, but, as the upper limb rotates lateralward and the lower limb rotates median-
ward as development proceeds, in the adult, the extensor surface of the upper Umb becomes the
posterior surface, and the extensor surface of the lower limb, the anterior surface. The preaxial
border of the upper limb is the radial or thumb border, and the postaxial border, the ulnar or
little finger border. The preaxial border of the lower hmb is the tibial or great toe border,
and the postaxial border, the fibular or little toe border. As projections of the segments of the
body grow out to form the limb-buds and limbs each projection carries with it the whole or
part of the nerve of the segment to which it belongs, and therefore the number of body segments
which take part in a hmb is indicated by the number of spinal nerves which pass into it. If
these facts are remembered it will naturally be expected (1) that the highest spinal nerves
passing into a hmb will be associated with its preaxial portion and the lowest with its post-
FiG. 777. — Diagrams A, B, and C, Illustrating Stages in the Projection op the Limb-
BDDS FOR THE IJPPER EXTREMITY, AND THE DRAWING OUT OF THE NeRVBS OF THE CORKESPOND-
ing Body SegmentsfoetheCutanbous Areas of the Preaxial and Postaxial Border of
THE Limb.
Postaxial border shaded.
axial portion; (2) that only the nerves of those segments forming middle or central portions of
the limbs will extend to the tips of the hmbs; (3) that the highest and lowest segments in each
hmb area wiU take a smaller part in the formation of the limb that the -middle segments; and
(4) that, consequently, the highest and lowest nerves wiU pass outward into the limb for a
shorter distance than the middle nerves. Observers are not yet in perfect agreement as to the
exact distribution of each nerve, but the diagrams in figs. 775 to 781 show the embryonic
derivation of the cutaneous areas and the adult dorso-ventral segmental arrangement in the
projected portions of both the upper and lower limbs as assumed from clinical observations.
In the upper parts of the lower limbs, the original segmental distributuion appears to be masked.
This may be due (1) partly to the fact that the areas recognisable by clinical phenomena do
not correspond exactly with the areas to which definite dorsal root-fibres are distributed, but
rather to definite segments of the grey substance of the spinal cord with which the root-fibres
are connected; (2) partly to the overlapping of segments and the acquired preponderance of one
nerve over another in the overlapping areas, and (3) partly to the fact that in the lower hmb
there has been a greater amount of shifting of parts to result in the fixed fiat position of the
sole of the foot; (4) and partly to the incompleteness of the data which are at our disposal in
the case of the human subject. Sherrington has proved that in the monkey the sensory areas
of the limbs are arranged in serial correspondence with the spinal nerves, the middle nerves
of each limb series passing to the distal extremity while the higher and lower nerves are
limited to the proximal regions. Thorburn's observations, which differ from Head's, are,
especially as regards the upper limb, in close conformity with the results obtained by Sherring-
ton's experiments on monkeys.
Each limb may be divided into its preaxial and postaxial borders by a line drawn longi-
tudinally along the middle of both its anterior and posterior surfaces (compare figs. 777 and 779)
The cutaneous nerves to the preaxial border are from the cephalic portion of the hmb plexus,
and those to the postaxial are from the caudal components of the plexus. Thus the thumb
and index finger are cephalad.
The Cutaneous Areas of the Upper Limb
A line passing along the middle of both the anterior and posterior surfaces of the upper ex-
tremity to the tip of the middle finger (fig. 779) separates the preaxial from the postaxial
border and passes longitudinally along the area of the cutaneous fibres derived from the seventh
cervical nerve.
CUTANEOUS AREAS OF THE LIMBS
1023
The skin over the upper third of the deltoid muscle is supplied by the posterior supra-
clavicular (supra-acromial) and middle supra-clavicular (supra-clavicular) nerves, which are
branches of the cervical plexus containing fibres of the third and fourth cervical nerves, and
that over the lower two-thirds by the axillary (circumflex) nerve which conveys fibres of the
fifth and sixth cervical nerves (fig. 776).
The skin over the lateral surface of the upper arm is supphed externally by the axillary
(circumflex) nerve above, and below by the superior branch of the dorsal antibrachial cutaneous,
Fig. 778. — Diagram of the Cutaneous Areas op the Upper Extremity.
(Modified from Head.)
the external cutaneous branch of the radial (musculo-spiral) nerve. The former contains
filaments of both the fifth and sixth cervical nerves, and the latter filaments of the sixth alone.
The skin of the medial side of the upper arm is supplied by the medial antibrachial cutaneous
(internal cutaneous) nerve with fibres of the eighth cervical and first thoracic nerves, and by
the medial brachial cutaneous (lesser internal cutaneous) and intercosto-brachial (intercosto-
humeral) nerves which are derived from the first and second thoracic nerves. The dorsal side
of the upper arm is supphed, laterally, by the fifth and sixth cervical nerves through the axillary
Fig. 779. — Diagram of the Cutaneous Areas op the Upper EIxtremitt.
The solid middle lines are drawn to separate preaxial (radial) borders from postaxial borders.
(After Thorburn, modified.)
(circumflex) nerve and by the dorsal antibrachial cutaneous; the middle portion, by the seventh
cervical nerve through the posterior brachial cutaneous, the internal cutaneous branch of the
radial (musculo-spiral) nerve; and the medial portion by the first and second thoracic nerves
through the medial brachial cutaneous (lesser internal cutaneous) nerve, and the intercosto-
brachial (intercosto-humeral) nerve (fig. 776).
The front of the forearm is divided into three areas, a lateral which is supphed by the fifth,
sixth, and possibly the seventh cervical nerves, through the musculo-cutaneous branch of the
1024
THE NERVOUS SYSTEM
brachial plexus; a middle which is supplied by the seventh cervical nerve as above, and a medial
area supplied by the eighth cervical and first thoracic nerve through the medial antibrachial
cutaneous (internal cutaneous) nerve. On the dorsal side of the forearm there are three areas:
— (1) a lateral suppUed by fibres of the fifth and sixth cervical nerves through the musculo-
cutaneous nerve; (2) a middle, which receives fibres of the seventh, and probably some from the
sixth and eighth cervical nerves through the lower branch of the dorsal antibrachial cutaneous
of the radial (inferior external cutaneous branch of the musculo-spiral nerve), and (3) a medial
which receives the eighth cervical and first thoracic nerves through the medial antibrachial
cutaneous (figs. 776, 779).
The palm of the hand is supplied by the sixth, seventh, and eighth cervical nerves through
the superficial radial (radial) nerve, and through the median and ulnar nerves. The super-
ficial radial supplies the radial side of the thumb by its palmar cutaneous branch. The re-
mainder of the palm and the palmar aspects of the fingers are supplied by the median and
ulnar nerves through their palmar cutaneous and digital branches, the median supplying
three and a half digits and the ulnar the remaining one and a half (figs. 776 and 779).
The dorsal aspect of the hand is suppUed by the sixth, seventh, and eighth cervical nerves,
which reach it through the superficial radial( radial) and through the median and ulnar nerves.
The superficial radial supplies the lateral part of the dorsum and the lateral three and a half
digits, except the lower portions of the second, third, and half of the fourth digits, which
■receive twigs from the median nerve; the ulnar nerve supplies the ulnar half of the dorsum of
Fia. 780.— Diagram op the Cutaneotts Areas op the Lower Extremity. (After Head.)
the hand, including the medial one and a half digits. The areas supplied by definite spinal
nerves, according to the observations of Head and Thorburn, are shown in figures 778 and 779
respectively.
The Cutaneous Areas of the Lower Extremity
The segmental arrangement of the cutaneous areas of the lower extremity is not so well
retained as in the upper, due largely to a greater amount of developmental shifting of the parts.
Both of the lines separating the areas of the lumbar (cephalic) and the sacral (caudal) parts
of the lumbo-sacral plexus he on the dorsal aspect of the limb. The nerves from the lumbar
part of the plexus are distributed to the entire anterior and the medial and lateral surfaces of
the hmb and to the muscles of the anterior and medial portions of the thigh and the anterior
portion of the leg, whereas the cutaneous nerves from the sacral part of the plexus are con-
fined to a narrow strip along the dorsal aspect of the limb (fig. 781). However, the muscular
distribution of the sacral part is as much expanded as its cutaneous area is contracted; it supplies
the muscles in the dorsal portions of the hip, thigh and knee, the whole of the dorsal part of
the leg and ankle and the plantar muscles of the foot.
There are six cutaneous areas in the region of the buttock, three upper and three lower.
Of the upper areas the lateral is supplied by the anterior primary divisions of the last thoracic
and first lumbar nerves through the iliac branches of the last thoracic and the iho-hypogastric
nerves; the middle upper area receives the lateral divisions of the posterior primary branches
of the upper three lumbar nerves, and the medial upper area is supplied by twigs from the lateral
branches of the posterior primary divisions of the upper two or three sacral nerves (figs. 776,
780).
CUTANEOUS AREAS OF THE LIMBS
1025
Of the lower three areas, the lateral receives filaments from the second and third lumbar
nerves through the lateral femoral cutaneous (external cutaneous) branch of the lumbar plexus;
the middle area is supplied by the first, second, and third sacral nerves through the posterior
femoral cutaneous (small sciatic) nerve; and the medial area by the second and third sacral
nerves through the medial inferior clunial (perforating cutaneous) branch of the sacral plexus
(fig. 776).
On the back of the thigh there are three areas. According to Head, the medial and lateral
areas are supphed by the second and third lumbar nerves, the former through the lateral
femoral cutaneous (external cutaneous) branch of the lumbar plexus, and the latter through
the anterior cutaneous branches of the femoral (internal cutaneous branch of the anterior crural)
nerve. The middle area receives twigs from the first, second, and third sacral nerves through
the posterior femoral cutaneous (small sciatic), a branch of the sacral plexus.
The front of the thigh is supplied by the first, second, and third lumbar nerves, and,
according to Head, there are five cutaneous areas. The lateral area receives twigs of the
second and third lumbar nerves through the lateral (external) cutaneous nerves. There are
two medial areas, an upper and a lower. The former is supplied by the lumbo-tnguinal (crural)
branch of the genito-femoral (genito- crural), which conveys twigs of the first and second lumbar
nerves; the latter receives fibres of the second and third lumbar nerves through one of the an-
FiG. 781.
-Diagram op the Cutaneous Areas of the Lower Extremity
(After Thorburn, modified.)
t'W
terior (middle) cutaneous branches of the femoral (anterior crural) nerve. The small upper
and medial area is supplied by the first lumbar nerve through the iUo-inguinal, and the lower
medial area receives twigs of the second and third lumbar nerves through one of the anterior
cutaneous branches (internal cutaneous) of the femoral (anterior crural) nerve (fig. 776).
The front of the knee is supplied by the second, third, and fourth lumbar nerves through
the anterior (middle and internal) cutaneous and saphenous (long saphenous) branches of the
femoral (fig. 776).
Of the skin over the region of the popliteal space, the medial portion receives fibres from the
second, third, and fourth lumbar nerves through the anterior (internal) cutaneous branch of
the femoral (anterior crural) nerve and through the superficial division of the obturator nerve;
the middle and lateral portion receives twigs of the first three sacral nerves through the pos-
terior cutaneous (small sciatic) nerve (fig. 776).
The skin over the front and medial side of the leg is supplied by the fourth lumbar nerve
through the saphenous nerve, and the skin of the front and lateral side receives nerve-fibres from
the fifth lumbar nerves through the sural cutaneous (fibular communicating) branch of the
common peroneal (external popliteal) nerve.
In the skin of the back of the leg four areas can be distinguished, a medial, two middle,
upper and lower, and a lateral area. The medial area is supphed by the fourth lumbar nerves
through an anterior cutaneous branch (internal cutaneous) of the femoral (anterior crural)
1026
THE NERVOUS SYSTEM
nerve and the superficial branch of the obturator nerve. The upper middle area is supplied
by the second, and third sacral nerves through the posterior femoral cutaneous (small sciatic)
nerve, and the lower middle area by the first sacral nerve through the sural (external saphenous)
nerve. The lateral area is supphed by the fifth lumbar nerve through the lateral sural cutaneous
(fibular communicating) branch of the common peroneal (external popliteal) nerve (fig. 776, 780,
781).
The skin of the dorsum of the foot is supplied principally by the fifth lumbar and by the
first sacral nerves," the majority of the nerve-fibres travel by the superficial peroneal (musculo-
cutaneous) nerve, but the adjacent sides of the first and second toes are supplied by the femoral
(anterior crural) nerve and the side of the dorsum of the httle toe is supplied through the
sural (external saphenous).
The skin of the region of the heel is supplied by the first sacral nerve, the medial surface
and medial part of the under surface by the medial calcaneal branches of the tibial (calcaneo-
plantar) nerve and the posterior, external, and lower aspects by the sural (external saphenous)
nerve (fig. 776).
The sole of the foot in front of the heel receives cutaneous fibres from the fifth lumbar
and the first sacral nerves; the medial area, which includes the medial three and a half digits,
being supplied by the medial plantar nerve which conveys fibres of the fifth lumbar and the first
sacral nerves; and the lateral area by the fifth lumbar nerve through the lateral plantar nerve.
The medial side of the foot is supphed by the first sacral and fourth lumbar nerves through
the saphenous nerve and the lateral side by the fifth lumbar nerve through the sural (external
saphenous) nerve.
The skin of the scrotum and penis is supphed by the first lumbar nerve through the iho-
inguinal nerves, and by the second and third sacral nerves through the perineal and dorsal penile
branches of the pudendal (pudic) nerve.
The cutaneous areas of the lower extremity which have been demarcated by Head and
Thorburn are shown in fig. 780. These do not conform wholly with each other nor with the
areas given in more detail in fig. 776, due probably to individual differences in subject and
observer and to the difficulties coincident with the overlapping of the areas. Fig. 781 is more
general in character and is considered more approximately correct.
The homology of the parts of the plexuses of the upper and lower extremities is not well
carried out in the distribution of the nerves. The radial and great sciatic nerves are similar
to the extent that the one arises from the posterior cord of the brachial plexus and the other
from the sacral ple.xus, and that the one is distributed to the dorsal aspect of the arm and the
other to the dorsal surface of the lower extremity, but the great sciatic supplies the sole of the
foot, and the plantar muscles, whereas the radial does not supply the palm of the hand and the
palmar muscles.
THE SYMPATHETIC SYSTEM
The so-called sympathetic system is that portion of the peripheral nervous
system which is especially concerned in the distribution of impulses to the
Fig. 782. — Diagram showing two stages of the Migration op the Primitive Ganglia
PROM THE Ganglion Crest; A. the Division of the Primitive Ganglia into Spinal
AND Sympathetic Portions, and B. the Formation op the Nerves.
~-^ Ectoderm
ganglion
glandular tissues, to the muscle of the heart and blood-vessels, and to the non-
striated muscular tissue of the body wherever found. Since these tissues are most
THE SYMPATHETIC SYSTEM
1027
Fig. 783. — Diagram Showing the Chief Paths of Migration op the Cells from
THE Ganglia of the Spinal and Cranial Nerves to form the Adult Sympathetic
System (After Schwalbe, modified.)
Carotid plexus
Closso-pharyngeal
Vagus nerve
I. cervical spinal
ganglion
Superior cervical
ganglion
Inf.
Middle cervical
ganglion
Tior cervical
ganglion
I. thoracic spinal
ganglion
Sympathetic trunk
I, lumbar spinal
ganglion
I. sacral spinal
ganglion
Pharyngeal plexus
Coccygeal spinal
ganglion
Aortic plexus
Inferior mesenteric
plexus
Pelvic plexuses
Coccygeal ganglion
1028
THE NERVOUS SYSTEM
abundant in and largely comprise the viscera or splanchnic organs of the body,
the largest and most evident of the structures comprising the sympathetic system
are found either in or near the cavities containing the viscera. However, the
Fig. 784. — Scheme showing General Plan of the Coarser Portions op the Sympa-
thetic Nervous System and its Principal Communications with the Cbrebro-spinal
System. (After Flower, modified.)
Intgrfta! CttToUd pU
J^ami communicantes
Jittuieen ^anffUated cord and
Jniular G(imlion of vafju-f *'
To Petrosal ganglion o/^_
glossopharyngeal
Cervical nerve J
JI-
m
" Ciliary ganafien
^ . &7jjy/imM)doium^.Vayi^ ' Spfieno-palatine^eckl'syanaiion .
mpocAsmic piekus
Ga/iff//on Cocci/ffeum impar
finer divisions of the system ramify throughout the whole body, supplying vaso-
motor fibres to the blood-vessels throughout their course, controlling the glands
of the skin, and supplying pilo-motor fibres for the hairs, forming intrinsic
plexuses within the walls of the viscera, and it is claimed that a few of its neurones
THE SYMPATHETIC SYSTEM
1029
convey inpulses toward the central system (sensory sympathetic neurones).
While it is very probable that certain of the simpler reflexes of the splanchnic
organs may be mediated by the sympathetic system alone, yet the sympathetic
is by no means independent of the cranio-spinal system, but is rather, both ana-
tomically and functionally merely a part of one continuous whole. Throughout,
it shares its domain of termination with cranio-spinal fibres, chiefly of the sensory
variety, and most of its rami and terminal branches carry a few cranio-spinal
fibres toward their areas of distribution. Likewise the cranio-spina,l nerves carry
numerous sympathetic fibres gained by way of rami connecting the two systems.
Like the cranio-spinal system, the sympathetic consists of cell-bodies, each of which gives
off one axone. In addition, the cell-bodies give off numerous dichotomously branched den-
drites by which their receptive surfaces are increased, and they are accumulated into ganglia,
large and small. The larger ganglia have more or less constant positions, shapes, and arrange-
ments, while the smaller, some of which are microscopic, are scattered throughout the body in
a seemingly more indefinite manner. The axones or fibres arising in these gangha are given off
in trunks and rami which associate the ganglia with each other or with the cranio-spinal system,
or which pass from the ganglia to be distributed directly upon their allotted elements.
The sympathetic fibres arising from the ganglia are, for the most part, either totally non-
medullated or partially medullated. Some fibres are completely medullated near their cells
of origin, but lose their meduUary sheaths before reaching their terminations. Some of them
possess complete medullary sheaths throughout, but in no cases are the sheaths as thick or
well developed as is the rule with the cranio-spinal fibres. Thus, nerve-trunks and rami in
which sympathetic fibres predominate appear greyish in colour and more indefinite, as dis-
tinguished from those of the cranio-spinal nerves, which always appear a glistening white, due
to hght being reflected from the emulsified myelin of the sheaths of their fibres.
Origin of the S3rmpathetic system. — Not only must the cranio-spinal and sympathetic
systems be considered anatomically continuous and dependent, but ako the neurones of the
two systems have a common origin, namely, the ectoderm of the dorsal mid-line of the embryo.
The cells of the ganglion crest (see p. 754) become arranged in segmental groups and soon
separate into two varieties: — those which will remain near the spinal cord and develop into
the spinal ganglia, and those which, during the growth processes, migrate and become displaced
further into the periphery and form the sympathetic gangha.
Fig. 785. — Scheme showing the Connection between the Sympathetic and the Cranio-
spinal AND Central Nbrvous Systems.
Spinal ganglion neurone
to capsule of ganglion
Meningeal ramus
Dorso-Iateral group of '
ventral horn ceUs Ventral
root
/ J Gray ramus communicans
~yt^y White ramus co mmunicans
Sympathetic ganglion 1 Gangliated
^ Sympathetic trunk / trunk
' Sympathetic cell body in spinal
ganglion
Posterior primary division 1 Spinal
Anterior primary division J nerve
^^^ ^Gray ramus communicans
\ ^White ramus communicans
Sensory sympathetic neurone
Branch to prevertebral ganglion
In the development of the sympathetic system the migration from the
vicinity of the central system occurs to varying extents, so that in the adult the
cells comprise three general groups of ganglia situated different distances away
from the central nerve axis. — (1) A large portion of the cells remain near the
central system and form a linear series of ganglia which, with the trunks con-
necting them, become two gangliated nerve trunks extending along each side,
proximal to and parallel with the vertebral column; (2) a still larger portion of the
cells migrate further toward the periphery and are accumulated into ganglia
which assume an intermediate position and which, with the rami associating them
with each other and with other structures, form a series of great prevertebral
1030 THE NERVOUS SYSTEM
plexuses; (3) still other cells wander even further away from the locality of their
origin and invade the very walls of the organs innervated by the sympathetic
system. The latter cells occur as numerous small terminal ganglia, most of which
are microscopic and which, with the twigs connecting them, form the most
peripheral of the sympathetic plexuses. Examples of these are the intrinsic
ganglia of the heart and pancreas and the plexuses of Auerbach and Meissner
in the walls of the digestive canal. Small, straggling ganglia may be found
scattered between these three general groups. In the head, the gangliated trunks
and great prevertebral plexuses are represented by the ciliary, sphenopalatine, otic
and submaxillary ganglia and the plexuses associated with these. The supporting
tissue of the sympathetic system accumulates early and is probably all of meso-
dermic origin.
Construction of the sympathetic system. — The sympathetic ganglia may be
considered as relays in the pathways for the transmission of impulses from the
region in which they arise to the tissues in which they are distributed; the cells
composing the ganglia are the cell-bodies of the neurones interposed in the
various neurone chains performing this function. A fibre arising from a cell-body
in a given ganglion may pass out of the ganglion and proceed directly to its
termination upon a smooth muscle-fibre or gland-cell, or it may pass through a
connecting trunk to another ganglion and there terminate about and thus trans-
mit the impulse to another cell, which, in its turn, may give off the fibre which
bears the impulse to the appropriate tissue-element. Fibres arising in given
ganglia may pass uninterrupted through other ganglia and proceed to their re-
spective destinations. On the other hand, several neurones may be involved in
the transmission of a given impulse when sent from a region distant from the tissue
to which it is distributed.
Communication between the central nervous system and the sympathetic is
established through both efferent and afferent fibres. In the region of the
spinal cord both varieties of fibres pass from one system to the other by way of the
rami communicantes, delicate bundles of fibres connecting the nearby sympa-
thetic trunk with the respective spinal nerves (fig. 785).
The efferent fibres of the rami arise in the ventral horn (dorso-lateral cell-group chiefly) of
the spinal cord, emerge through the ventral roots, enter the rami, and terminate chiefly about
the cells of the nearest sympathetic ganglion; some, however, may pass through or over the
ganglion of the sympathetic cord and terminate about cells in more distant ganglia. Since
these fibres transmit impulses from the central to the sympathetic system, they are known as
visceral efferent fibres. They are of smaller size than is the average for the cranio-spinal effer-
ent or motor fibres of the ventral root. The visceral afferent fibres are of two varieties: — (1)
Peripheral processes of the spinal ganglion-cells which run outward in the nerve-trunk, enter
the rami communicantes, pass through the various connecting trunks and terminal rami of the
sympathetic and terminate in the tissues supplied by these rami. . Such are merely sensory fibres
of the cranio-spinal type which collect impulses in the domain of the sympathetic and convey
them to the central system by way of the sympathetic nerves and the dorsal roots of the spinal
nerves. (2) Afferent sympathetic fibres proper. The actual existence of these has not been
long established, and their relative abundance is as yet uncertain. They consist of fibres arising
in the sympathetic ganglia which enter the spinal ganglia by way of the rami commnicantes
and the cranio-spinal nerve-trunk and terminate in arborisations about the spinal ganglion-cells
(fig. 785). The afferent impulses transmitted by these sympathetic fibres are borne into the
spinal cord or brain by way of the cranio-spinal fibres of the dorsal roots. These sensory
sympathetic fibres must necessarily either receive the impulses they bear from sympathetic
neurones having both peripheral and central processes or they themselves must be axones or
central processes of neurones having also processes terminating in the peripheral tissues.
Doubtless the variety of visceral afferent fibres first mentioned greatly predominates.
The thoracic and the lumbar spinal nerves are connected with the sympathetic
trunk (gangliated cord) by two rami communicantes. Most of both the visceral
efferent and also the visceral afferent fibres (which arise in the spinal ganglia)
pass by way of a separate ramus. Both these varieties being of the cranio-spinal
type, and, therefore, medullated, they give the ramus a white appearance meriting
the name white ramus communicans. Fibres of the sympathetic type predomi-
nate in the second ramus and thus it is the grey ramus communicans. The latter
consists of: — (1) afferent sympathetic fibres and (2) of sympathetic fibres which
join the primary divisions of the spinal nerves and course in them to their allotted
tissues (fig. 785).
In the sacral region, most of the visceral efferent fibres pass over the ganglia of the sympa-
thetic trunk and terminate in the more peripheral ganglia of the plexuses of this region. This is
THE SYMPATHETIC SYSTEM
1031
especially true for the fibres passing from the second, third, and fourth sacral nerves. In the cer-
vical region white rami are not in evidence, a fact probably exphcable as due to an arrangement
by which at least most of the visceral efferent fibres arising in the cervical segments of the spinal
cord pass downward in these segments and join the sympathetic tlirough the white rami of the
upper thoracic nerves; others may enter the cervical portion of the gangliated cord through the
spinal accessory or eleventh cranial nerve, rather than through individual white rami, while
others pass into the nerves of the brachial plexus to terminate in the minute ganglia of the plex-
uses upon the blood-vessels of the limb. All the spinal nerves are joined by grey rami communi-
cantes from the sympathetic trunk.
Vaso-motor fibres to the meninges and intrinsic blood-vessels of the spinal
cord pass to the spinal nerves by way of the grey rami. Thence they may reach
the meninges by one of three ways: — (1) through the delicate recurrent or
meningeal branch of the spinal nerve (fig. 785) ; (2) through the trunk and ventral
Fig. 786. — Diagram suggesting the Origin, Course and Connections of
Sympathetic Nerve-fibres.
Spinal ganglion •-
Sympathetic trunk
SympatliQtic ganglion
Grey ramus communicans
White ramus communicans
White ramus communicans
Grey
Sympathetic trunk
communicans ^
root of the spinal nerve; (3) probably more rarely, through the trunk and dorsal
root of the spinal nerve (fig. 786).
Corresponding communications exist between the cranial nerves and the sympathetic,
but the corresponding rami usually extend further toward the periphery and in not so regular a
manner as the communications between the spinal nerves and the sympathetic system. The
mesencephalon, for example, is chiefly connected with the ciUary ganglion of the sympathetic
by_ fibres which are sent through the oculo-motor nerve and which enter this ganghon by way
of its short root and terminate about its cells. Visceral efferent fibres from the rhombencephalon
pass outward to the sympathetic in the roots of the facial, glosso-palatine, glosso-pharyngeal.
1032 THE NERVOUS SYSTEM
vagus, and spinal accessory nerves, all of which have more or less irregularly disposed com-
municating rami. The ganglia of origin of the vagus, more than perhaps any other nerve, both
receive impulses from visceral efferent fibres and give origin to sympathetic fibres. Likewise
twigs of other cranial nerves, especially of the trigeminus, connect with (pass through) the small
sympathetic ganglia of the head. The meningeal branches given by certain of the cranial nerves
contain vaso-motor fibres, and these correspond to the sympathetic fibres in the recurrent
branches and in the roots of the spinal nerves.
It is known that spinal ganglia and certain of the ganglia of the cranial nerves
contain cell-bodies of sympathetic neurones — cell-bodies which, during the period
of the migration peripheralward, remained within the confines of these ganglia
(fig. 785). These cell bodies receive efferent impulses from ventral root fibres
and send their axones further into the periphery just as if in the sympathetic
ganglion. Their relative abundance is not known. It is supposed that the ganglia
of the vagus, glosso-pharyngeus, trigeminus and the geniculate ganglion contain
a considerable proportion of such sympathetic cell-bodies.
From the above it may be seen that the ganglia and connecting trunks and rami
of the sympathetic system may be divided as follows: — (1) The two sympathetic
gangliated trunks lying proximal to and parallel with the vertebral column; (2) the
great prevertebral plexuses, of which there are roughly four, one in the head, one
in the thorax, one in the abdomen, and one in the pelvic cavity (fig. 784), each of
which is subdivided; (3) the numerous terminal ganglia and plexuses situated
either within or close to the walls of the various organs; (4) the trunks and rami
associating the ganglia with each other and thus contributing to the plexuses, or
connecting the ganglia with other nerves or with the organs with whose innerva-
tion they are concerned. The trunks and rami may be divided into — (a) the
rami communicantes, or central branches, connecting the sympathetic with the
cranio-spinal and central systems; (Ja) associative trunks, best considered as those
which associate sympathetic ganglia situated on the same side of the body; (c)
commissural branches, or those which associate ganglia situated on opposite sides
of the mid-line of the body, such as the transverse connecting branches between
the sympathetic trunk in the lumbo-sacral region (fig. 787) , or all the associating
trunks between the ganglia of plexuses occupying the mid-region of the body;
{d) terminal or peripheral branches, or those which pass from the ganglia to their
final distribution apparently uninterrupted by other ganglia.
THE SYMPATHETIC TRUNKS
The sympathetic gangliated trunks, or gangliated cords, of the sympathetic
system are two symmetrical trunks with ganglia interposed in them at intervals
of varying regularity, and extending vertically, one on each side of the ventral
aspect of the vertebral column, from the second cervical vertebra to the first
piece of the coccyx. Upon the coccyx the two trunks unite and terminate in a
single medial ganglion, the ganglion coccygeum impar. The various ganglia are
connected with the cranio-spinal nerves by the rami communicantes. Mor-
phologically, each trunk might be expected to possess thirty-one ganglia, one for
each spinal nerve, but, owing to the fusion of adjacent ganglia in certain regions,
especially in the cervical, there are in the adult only twenty-one or twenty-two
ganglia in each trunk. These occur as three cervical ganglia, ten or eleven thoracic
ganglia, four lumbar and four sacral ganglia, and the ganglia n coccygeum impar,
which is common to both trunks.
In the cervical region the sympathetic trunks lie in front of the transverse processes of the
vertebra3, from which they are separated by the longus capitis (rectus capitis anticus major)
and longus colli; in the thoracic region they he at the sides of the bodies of the vertebrae and on
the heads of the ribs; in the lumbar region they are placed more ventraUy with reference to
the spinal nerves and more in front of the bodies of the vertebrte and along the anterior borders
of the psoas muscles; in the pelvis the ganglia lie between and ventral to the openings of the
sacral foramina. In the lower lumbar and sacral region one gangUon may send rami commu-
nicantes to two spinal nerves and one spinal nerve may be connected with two gangha. The
ganglia of the trunks throughout give off associative branches to the gangha of the prevertebral
plexuses and branches to the nearby viscera and blood-vessels. These branches may appear
either white or grey according to the predominance of meduUated or non-medullated fibres in
them. In the lumbo-sacral region commissural or transverse branches between the gangha
of the two trunks are especially abundant. In trunks having a whiter appearance, the greater
part of the meduUated fibres producing it are sensory and visceral motor fibres from the spinal
nerves which have passed through the sympathetic ganglia without termination. The nerve
trunks connecting the ganglia of the sympathetic trunks all contain three varieties of fibres: — (1)
THE SYMPATHETIC TRUNK 1033
visceral motor fibres which have entered them in the white rami communicantes from the spinal
nerves of higher or lower levels, and which are coursing in them to terminate in other gangUa,
either in the trunks above or below or in ganglia not belonging to the trunks; (2) fibres arising in
sympathetic ganglia of a higher or lower level and passing upward or downward to terminate
in other ganglia of the trunk or to issue from the trunk and proceed to more peripheral ganglia or
to ganglia of the opposite trunk (both associative and commissural fibres); (3) afferent fibres
or sensory fibres arising either in the spinal ganglia, or sensory sympathetic fibres arising in
sympathetic ganglia and coursing in the trunk to pass into spinal ganglia above or below by way
of the grey rami communicantes.
THE CEPHALIC AND CERVICAL PORTIONS OF THE SYMPATHETIC
TRUNK
The cephalic portion of the sympathetic system consists of numerous small
ganglia and of numerous plexuses connected with the internal carotid nerve, the
ascending branch given off by the superior cervical sympathetic ganglion. The
cephalic ganglia are all relatively small. There are four considered in the
ordinary macroscopic dissections, namely, the ciliary or ophthalmic, the spheno-
palatine or Meckel's ganglion, the otic, and the submaxillary. To these may be
added a portion of the superior cervical sympathetic ganglion, the sympathetic
portions of the nodosal, petrous, geniculate and semilunar ganglia, and the var-
ious small ganglia dispersed in the plexuses. These ganglia with their roots or
communicating branches have been described in their relations with the divisions
of the trigeminus and with the oculo-motor, glosso-palatine, vagus and facial
nerves.
The internal carotid nerve, the ascending branch from the superior cervical
sympathetic ganglion, may be regarded as an upward prolongation of the primi-
tive sympathetic trunk.
It arises from the upper end of the superior cervical ganglion and passes through the carotid
canal into the cranial cavity. It divides into two branches which subdivide to form a coarse
plexus, the internal carotid plexus, which partly surrounds the internal carotid artery before
the latter enters the cavernous sinus (fig. 787 and 788). It passes with the artery to the caver-
nous sinus, where it forms the finer meshed cavernous plexus.
The internal carotid plexus supplies offsets to the artery and receives branches
from the tympanic plexus through the inferior carotico-tympanic nerve and
from the spheno-palatine ganglion through the great deep petrosal nerve. It also
communicates by fine branches with the semilunar (Gasserian) ganglion and
with the abducens nerve.
The cavernous plexus gives branches of communication to the oculo-motor
and trochlear nerves and to the opthalmic division of the trigeminus. According
to Toldt and Spalteholz, it communicates with the tympanic plexus through the
superior carotico-tympanic (small deep petrosal) nerve. It also communicates
with the ciliary ganglion through the long root of the ciliary ganglion and usually
through a separate sympathetic root of this ganglion. These branches may pass
through the superior orbital (sphenoidal) fissure either separately or with the naso-
ciliary (nasal) nerve.
The cavernous plexus also gives branches to the carotid artery and filaments of the plexus
accompany small branches of the artery to the hypophysis (pituitary body) and to the dura
mater on the sphenoid bone.
The terminal branches of the cavernous plexus consist of delicate filaments that anastomose
freely, forming fine plexuses, and pass from the cavernous plexus along the terminal divisions
of the internal carotid artery and their branches. These fine plexuses take the name of the
artery on which they lie. The four larger of them are the plexuses of the anterior and middle
cerebral arteries, the plexus of the chorioid artery, and the ophthalmic plexus.
The cervical portion of the sympathetic cord extends upward along the great
vessels of the neck. No white rami communicantes connect it directly with the
spinal cord, but instead it receives visceral efferent fibres from the upper thoracic
spinal nerves through the sympathetic trunk, and probably also from the cervical
spinal cord through the spinal acessory nerve and the connections with the vagus.
It sends grey rami communicantes to each of the cervical nerves. It extends
from the subclavian artery to the base of the skull, lying dorsal to the sheath of
the great vessels and in front of the longus capitis and longus colli, which separate
is from the transverse processes of the cervical vertebrae (fig. 787). It usually
1034
THE NERVOUS SYSTEM
Fig. 787. — Showing the Sympathetic Trunks in their Relation to the Vertebral
Column, to the Spinal Nerves, and to each Other. (Modified from^Toldt, "Atlas of
Human Anatomy," Rebman, London and New York.)
Cavernous plexus
Internal carotid plexi
Internal carotid nerve
Jugular nerve
Vagus
Superior cervical ganglion -
rical plexus
Cervical portion of sympathetic trunk
Superior cardiac nerve'
Rami communicantes
Middle cervical ganglion
Brachial plexus
Inferior cervical ganghon
.First thora.,ic ganghon'
Ansa subclavia (Vieussenii)
Inferior cardiac
or and middle c
nerves
Pulmonary branches
Twigs to aortic plexus
Splanchnic gangUons.
Last thoracic ganghon^
Splanchnic minor nerve
Medial part of lumbo
costal arch
Lateral part of lumbo-costal arch
Psoas major-
Second lumbar nerve
Twelfth intercostal nerve
Lumbar plexus
Li Glossopharyngeus
..- Jugular nerve
--—Pharyngeal plexus
■"-» Pharyngeal branches
**Vagus
External carotid nerves
ylnfenor thyreoid plexus
Vertebral plexus
Subclavian plexus
Rami communicantes
Thoracic portion of
sympathetic trunk
Thoracic ganglia
.-.Intercostal nerves
— Greater splanchnic nerve
/^„- Lesser splanchnic nerve
>-^ /^ I -Thoracic aortic plexus
splanchnic nerve
Greater splanchnic nerve
Branches to phrenic plexus
..•Branches to coeliac ganglia
**Rami communicantes
Rami communicantes
Lumbo-sacral trunk
Rami communicantes
Branches to abdominal
aortic plexus
Branches to hypogastric
plexus
^. Fifth lumbar ganglion
._ Commissural branches
■First sacral ganglion
U V '"-^^Rami communicantes
Ganghon coccygeum impar
SUPERIOR CERVICAL GANGLION
1035
has but three ganglia, one at each end, the superior and inferior, and one between
these two, called the middle ganglion. The latter varies somewhat in position and
is sometimes absent.
1. Superior Cervical Ganglion
The superior cervical ganglion is usually fusiform in shape and is sometimes
marked by one or more constrictions. There is ground for the belief that it is
formed by the coalescence of four ganglia corresponding to the first four cervical
nerves. It varies from an inch to one and one-half inches (2.5 to 3.7 cm.) in
length, lying dorsal to the upper part of the sheath of the great vessels of the neck
and in front of the transverse processes of the second and third cervical vertebrae.
Fig. 788. — Diagram op the Glosso-palatine Nerve and the Relations op the Gangli-
ATED Cephalic Plexus to other Cranial Nerves. (After Bean.)
Broken lines, motor; continuous lines, sympathetic; glosso-palatine .in solid black. Medial
view. Left side.
£ > en d
S a « 3
Glosso-palatine ." g « S " a ° 3 -g p, ' ' '
Carotid
_ ^ artery Oculomotor nerve
Chorda tympani
Ciliary
ganglion
— Ophthalniic nerve
.1 i V ^ Maxillary nerve
4^i)--\-TX— Mandibular nerve
jV/^wSj^^^::^;^^ Great deep
\\ » \ » "'^"^yi^ petrosal nerve
W'W^^^^""' Sphenopalatine
'A ^ ^ \r\^ ganglion
Palatine portion of
glosso-palatine nerve
Nerve of pterygoid
canal (Vidian nerve)
Otic ganglion
• Middle meningeal
([l\ artery
\
i^ r Submaxillary ganglion
)nr\rr
External ma^llaiy
artery
It occasionally extends upward as high as the transverse process of the first
vertebra (fig. 787). It is connected with the middle cervical ganglion by the
intervening trunk, and it gives off a large number of communicating branches.
Rarely, the ganglion may be double or split with a ventral portion lying superfi-
cial to the carotid sheath and a dorsal portion dorsal to the sheath, connected by
sympathetic filaments near the superior and inferior extremities of the ganglion.
Communications: — (1) Four grey rami communicantes associate the ganglion with the
anterior primary divisions of the first four cervical nerves.
(2) Communicating branches to the cranial nerves. — An iiTegular number of small twigs
pass between the superior cervical gangUon and the hypoglossal nerve and to the ganghon nodo-
sum of the vagus. A named branch, the jugular nerve, runs upward to the base of the skull
and divides into two branches, one of which enters the jugular foramen and terminates in the
jugular ganghon of the vagus, and the other ends in the petrous ganghon of the glosso-
pharyngeus. (See fig. 788).
1036 THE NERVOUS SYSTEM
(3) Four or five laryngo -pharyngeal branches come from the superior ganglion and the
plexus extending downward from it, and pass forward and medialward, lateral to the carotid
vessels, to the wall of the pharynx, where they unite on the middle constrictor with the pharyn-
geal branches of the glosso-pharyngeus and vagus, forming with them the pharyngeal plexus,
from which branches are distributed to the walls of the pharynx and to the superior and
external laryngeal nerves (fig. 787).
(4) The superior cervical cardiac nerve springs from the lower part of the ganglion or from
the trunk immediately below it. It passes downward behind the carotid sheath, either in front
of or dorsal to the inferior thyreoid artery, and in front of the longus colli, and establishes
communications with the upper cervical cardiac branch of the vagus, the middle cervical cardiac
branch of the sympathetic, and with the inferior and external laryngeal nerves. At the root
of the neck the nerve of the right side passes in front of or behind the first part of the right sub-
clavian artery, and is continued along the innominate artery to the front of the bifurcation of
the trachea, where it ends in the deep part of the cardiac plexus. The left nerve passes into the
thorax along the front of the left common carotid artery, crosses the front of the arch of the aorta
immediately anterior to the vagus, and terminates in the superficial part of the cardiac plexus
(fig. 789). Filaments from both the right and left nerves pass to the inferior thyreoid plexus.
(5) The external carotid nerves (fig. 787) pass forward from the .superior cervical ganglion
to the external carotid arlcry, where they divide into branches which anastomose freely to form
around the artery the external carotid plexus. This plexus extends to the beginning of the
artery, and is continued upon the common carotid artery as the common carotid plexus. From
the external carotid plexus, filaments pass to form secondary plexuses around each of the
branches of the external carotid artery. These plexuses take the names of the arteries which
they follow, namely, the superior thyreoid plexus, lingual plexus, etc. Filaments pass from
the external carotid plexus to the glomus caroticum (the carotid gland), and from the superior
thyreoid plexus to the thyreoid gland.
From the external maxillary (facial) plexus passes the sympathetic root of the submaxillary
glion.
A part of the internal maxillary plexus is continued upon the middle meningeal artery as
the meningeal plexus. From this plexus filaments pass to the otic ganglion, and sometimes
a branch, called by English anatomists the external superficial petrossal nerve, passes to the
geniculate ganglion.
(6) Small branches to the ligaments and bones of the upper part of the vertebral column.
(7) The internal carotid nerve (ascending branch) and plexus have been described with
the cephalic portion of the sympathetic system.
2. The Middle Cervical Ganglion
The middle cervical ganglion is small and somewhat triangular in outline. It
is sometimes absent. Its position is variable, but it commonly lies about the
level of the cricoid cartilage, in front of the bend of the inferior thyreoid artery
(fig. 787), and it is associated with the superior cervical ganglion and with the
inferior cervical ganglion by the trunk of the gangliated cord. From the lower
part of the middle ganglion some filaments pass dorsal to the subclavian artery,
while others pass in front of and beneath that artery and anastomose with the
first-mentioned filaments to form a loop, the ansa subclavia {ansa Vieussenii)
(figs. 751, 787). Filaments from this loop to the inferior cervical ganglion thus
form another communication between the middle and inferior cervical ganglia.
Connections. — The middle cervical ganghon gives off four or more rami.
Two (a and h) are grey rami communicantes which connect the middle ganglion with the
anterior primary iDranches of the fifth and sixth cervical nerves.
(c) One or more peripheral branches pass along the inferior thyreoid artery and anastomose
with branches from the superior and middle cardiac nerves and from the inferior cervical
ganghon, thus taking part in the formation of the inferior thyreoid plexus, from which branches
pass to the thyreoid gland.
{d) The middle cardiac nerve arises by one or more branches from the ganghon, or from
the trunk of the cord, and passes downward dorsal to the common carotid artery and, on the
right side, either in front of or dorsal to the subclavian artery, and then along the innominate
artery to the deep part of the cardiac plexus (figs. 787 and 789). It is frequently larger than
the superior cardiac nerve. On the left side the nerve runs between the subclavian and common
carotid arteries. On both sides the nerve communicates with the inferior laryngeal nerve and
external laryngeal nerve.
The middle cervical ganglion also gives branches to the common carotid plexus.
3. The Inferior Cervical Ganglion
The inferior cervical ganglion is irregular in form. It is larger than the
middle cervical ganglion, and it lies deeply in the root of the neck dorsal to the
vertebral artery or the first part of the subclavian artery, and ventral to the
interval between the transverse processes of the last cervical and the first thoracic
vertebrse (figs. 759, 761). It is connected with the middle cervical ganglion by
THE SYMPATHETIC TRUNK 1037
the sympathetic trunk, and by filaments passing to the ansa subclavia (Vieussenii),
and it is either blended directly with the first thoracic ganglion or connected with
it by a short stout portion of the trunk. It gives rami to the last two cervical
nerves and peripheral branches to the vertebral and internal mammary arteries,
to the heart, and to the inferior thyreoid plexus.
Connections. — (1) The rami to the seventh and eighth cervical nerves are grey rami
communicantes.
(2) The branches to the vertebral artery are large and they unite with similar branches
from the first thoracic ganglion to form a plexus, the vertebral plexus (fig. 787), which accom-
panies the artery into the posterior fossa of the cranium, where it is continued on the basilar
artery. The plexus communicates in the neck by delicate threads with the cervical spinal
nerves. These are probably meningeal rami.
(3) The branches to the internal mammary artery form the internal mammary plexus.
(4) The inferior cardiac nerve may arise from the inferior cervical ganglion, from the first
thoracic ganglion, or by filaments from both these ganglia (figs. 787 and 789). It communicates
with the recurrent laryngeal nerve and with the middle cardiac nerve, and passes to the deep
part of the cardiac plexus. On the left side it frequently joins the middle cardiac nerve to
form a common trunk.
Construction of the cervical portion of the sympathetic trunk. — This portion of the trunk
contains both meduUated and non-medullated fibres, and a large part of the former are of
cranio-spinal origin. In the absence of white rami communicantes to this portion of the sym-
pathetic trunk, it is evident that few if any of the cranio-spinal or efferent visceral fibres are
contributed to it below the superior ganglion by the cervical region of the spinal cord. Instead,
such fibres are known to enter by way of the white rami from the upper thoracic nerves, and
to ascend to this portion of the sympathetic trunk. Most of these fibres terminate about the
cells of the superior, middle, and inferior cervical ganglia, and these cells in their turn give off
sympathetic fibres which pass by way of the branches mentioned above for the cephalic and
cervical portions, to their distribution in the structures of the head, neck, and thorax. The
efferent visceral fibres which terminate in the superior ganghon especially are among those
which mediate — (1) vaso-motor impulses for the head; (2) secretory impulses for the submaxil-
lary gland; (3) pilo-motor impulses for the hairs of the face and neck; (4) motor impulses for the
smooth muscle of the eyelids and orbit, and (5) dilator impulses for the pupil. The sympathetic
or grey fibres in the cervical portion of the sympathetic trunk arise from the cells of the upper
thoracic and the cervical ganglia, and are passing either to connect the ganglia with each other
or to enter the peripheral branches and proceed to their terminal distribution.
THE THORACIC PORTION OF THE SYMPATHETIC TRUNK
The thoracic part of the gangliated trunk runs downward on the heads of the
ribs from the first to the tenth, and then passes a little ventralward on the sides
of the bodies of the lower two thoracic vertebrse. Above it is continuous with the
cervical portion at the root of the neck, dorsal to the vertebral artery. Below it
leaves the thorax dorsal to the medial lumbo-costal arch (arcuate ligament), or
sometimes dorsal to the lateral lumbo-costal arch, and continues into the lumbar
portion of the trunk. It lies behind the costal pleura and crosses over the aortic
intercostal arteries.
The number of ganglia in this part of the trunk is variable. There are
usually ten or eleven, but the first is sometimes fused with the inferior cervical
ganglion and occasionally other ganglia fuse. The ganglia are irregularly
angular or fusiform in shape, and lie on the head of the ribs, on the costo-vertebral
articulations, or on the bodies of the vertebrae. The portions of the trunk
connecting the ganglia usually are single, but sometimes they are composed of
two or three small cords in juxtaposition. Each ganglion, with the possible
exception of the first, receives a white ramus comnmnicans from a thoracic nerve
and all give off grey rami communicantes to these nerves.
The white rami communicantes, as they approach the sympathetic trunk,
quite often appear double, due to the separation of a large portion of their fibres
into two main streams, one passing upward in the sympathetic trunk, and one
passing downward. Of the white rami from the upper five thoracic nerves, the
upward stream of fibres is much larger than the downward, due to the fact that a
greater part of the efferent visceral fibers from these nerves are distributed through
the cervical portion of the sympathetic trunk, as noted above in the construction
of that portion. Usually the white rami from the spinal nerves pass directly to
the corresponding ganglia of the trunk, and thus lie in company with the corre-
sponding grey rami. Sometimes, however, they may join the intermediate por-
tions of the trunk, and in the lower thoracic region especially, a ramus may pass
from a nerve to the ganglion corresponding to the nerve above or below. The
1038 THE NERVOUS SYSTEM
fibres of the white rami from the lower thoracic nerves are in greater part directed
downward in the sympathetic trunk, and also downward in its peripheral
branches, to be distributed to the abdominal viscera. In all cases, however, some
of the fibres of the thoracic white rami terminate in the ganglia nearest their
junction with the trunk, while others pass into the nearest peripheral branches.
In this way the white rami from all the thoracic spinal nerves, especially those
of the mid-region, are directly concerned in the innervation of the thoracic
viscera, lungs, oesophagus, aorta, etc.
The first thoracic ganglion is larger than the other ganglia of this region and is
irregular in form. It may be narrowly ovoid or semilunar. It lies in front of the
neck of the first rib, behind the pleura, and on the medial side of the costo-
cervical trunk (superior intercostal artery), which vessel separates it from the
prolongation of the portion of the first thoracic nerve which passes to the brachial
plexus. It sometimes fuses with the inferior cervical ganglion, and, on the other
hand, sometimes extends to the upper part of the second rib to fuse with the
second thoracic ganglion. The result of the latter fusion resembles the stellate
ganglion of the carnivora, and when it occurs, is sometimes referred to as the
ganglion stellatimn. When well developed, the first ganglion sends a branch to the
cardiac plexus, forming the fourth cardiac nerve of Valentin. ^
The second thoracic ganglion, triangular in shape and almost as large as the
preceding, is sometimes placed on the costo-vertebral articulation, and is some-
times partly concealed by the first rib.
The third to the ninth thoracic ganglia are usually placed opposite the heads of
the corresponding ribs, but the tenth and eleventh may lie on the bodies of the
vertebrae.
The fibres passing from the ganglia form two groups of branches, the central
and the peripheral.
The central branches are the grey rami communicantes, which pass from the
ganglia to the corresponding spinal nerves. After they have joined with the
anterior primary divisions of the nerves, the fibres of these rami divide into four
groups: — (1) Fibres which pass medialward along the roots of the nerves to supply
vessels of the membranes of the spinal cord, or enter a meningeal or recurrent
branch for the same purpose; (2) fibres which enter the spinal ganglion and
terminate there (sensory sympathetic fibres) ; (3) fibres which pass dorsalward
into the posterior primary divisions of the nerves; (4) fibres which pass lateral-
ward in the anterior primary divisions of the nerves. The last two groups of
fibres are distributed to the muscle of the blood-vessels of the body-walls, to the
skin-glands, and to the muscles of the hairs of the body.
The peripheral branches of the ganglia form two series, an upper and a
lower.
Those of the upper' series pass from the upper four or five ganglia ventralward
to be distributed as follows: —
(1) Pulmonary branches which accompany the intercostal arteries toward their aortic
origin without forming plexuses around them, and pass to the posterior pulmonary plexus
(fig. 789).
(2) Aortic branches, some of which arise directly from the gangha and some from the
pulmonary branches, and unite with branches from the cardiac plexus and from the splanchnic
nerves to surround the aorta as the thoracic aortic plexus (fig. 789). This plexus accompanies
the aorta into the abdomen and there joins with the coehac (solar) plexus.
(3) (Esophageal branches join with the oesophageal plexus of the vagus.
(4) Vertebral branches, some of which pass with the nutrient arteries into the bodies of
the vertebra; and some of which pass to the median line and there anastomose with similar
branches from the opposite side (commissural branches).
The peripheral ganglionic branches forming the lower series consist largely of
efferent and afferent fibres from the spinal nerves, which pass through the gangha
and reinforce the sympathetic filaments proper. Thus composed, these branches
run ventralward and medialward on the sides of the bodies of the vertebrae and
unite to form the splanchnic nerves which supply the abdominal organs, the
afferent fibres serving to collect sensory impulses in this domain of the sym-
pathetic.
(1) The great splanchnic nerve may be formed by branches from all the thoracic ganglia
from the fifth to the tenth inclusive, or it may receive fibres from only two or three of these
THE SYMPATHETIC TRUNK 1039
ganglia (fig. 787). It is usually formed by branches from the fifth to the tenth. The superior
branch, usually the largest, receives smaller inferior branches from the lower ganglia as it passes
downward on the sides of the bodies of the vertebrae in the posterior mediastinum. The nerve
enters the abdominal cavity bypassing through the crus of the diaphragm, and joins the upper
end of the coeliac (semilunar) ganglion of the coeliac (solar) plexus. Near the disk between the
eleventh and the twelfth thoracic vertebra there is formed on the nerve the splanchnic ganglion.
Filaments from the nerve and from this ganglion pass along the intercostal arteries to the aorta,
oesophagus, and the thoracic duct, and some fibres from the right side pass to the vena azygos
(major). Sometimes this nerve divides into two cords, giving off numerous branches which
anastomose with each other and with the lesser splanchnic nerve to form a plexus, in the meshes
of which are found some small ganglia.
(2) The lesser splanchnic nerve receives fibres from the ninth and tenth gangha. Its
course is similar to that of the great splanchnic nerve (fig. 787), but on a more dorsal plane, and
it terminates in the cceliac (solar) and renal plexuses.
(3) The least splanchnic nerve, not always present, arises from the last thoracic ganghon
or sometimes from the small splanchnic nerve. It passes through the crus of the diaphragm
and ends in the renal plexus.
Construction of the thoracic portion of the cord. — The majority of the visceral efferent
fibres which pass from the central nervous system enter the thoracic portion of the sympathetic
trunk; some end there in ramifications around the cells of its ganglia, while others merely pass
through on their way to more distant terminations. With regard to those which terminate
in the gangha, it has been shown that in the dog and cat many end in the ganglion stellatum
which corresponds with the last cervical and the upper three or four thoracic ganglia in man.
Among these are the fibres conveying secretory impulses to the sweat-glands of the upper hmb,
which emerge from the spinal cord in the thoracic nerves from the sixth to the ninth, and, in
the dog, those which convey and transfer vaso-constrictor impulses to the sympathetic neurones
supplying the pulmonary blood-vessels. These visceral efferent fibres leave the spinal cord
in the second to the seventh thoracic nerves. Other fibres which terminate around the thoracic
sympathetic ganglion-cells in the dog and cat are the vaso-constrictor fibres for the upper limbs
and some of the vaso-constrictor fibres for the lower limbs.
Of the fibres which traverse the thoracic portion of the sympathetic trunk to gain more
distant terminations, some ascend to the cervical region (p. 1033), others descend to the lumbar
region, and many pass by the immediate peripheral branches to the splanchnic nerves.
Among those which descend to the lumbar region are pilo-motor fibres, vaso-motor fibres,
and secretory fibres to the lower limb, some vaso-constrictor fibres to the abdominal blood-
vessels, motor fibres to the circular, and inhibitory fibres to the longitudinal muscle of the
rectum. The latter enter the sympathetic trunk by the lower thoracic nerves and pass in the
lumbar peripheral branches to the aortic plexus, and terminate around the cells of the inferior
mesenteric ganglion.
The visceral efferent fibres which pass through the thoracic ganglia to the splanchnic nerves
are mainly vaso-motor fibres to the abdominal blood-vessels; the majority of them probably
terminate around the cells of the ganglia in the coelio (solar) plexus, but those for the renal blood-
vessels no doubt end in the renal ganglia. In addition to all the above-mentioned fibres there
are in the thoracic part of the sympathetic trunk afferent fibres of both sympathetic and cere-
bro-spinal type, passing toward the spinal ganglia and the latter, greatly predominating, pass
into the dorsal roots of the thoracic spinal nerves.
THE LUMBAR PORTION OF THE SYMPATHETIC TRUNK
The lumbar portion of each trunk lies on the fronts of the bodies of the verte-
brae along the anterior border of the psoas muscle, and nearer to the median line
than the thoracic portion. It is connected with the thoracic portion of the
sympathetic trunk by a slender intermediate portion of the trunk that may pass
through the diaphragm or dorsal to it (fig. 787). The continuation of the
lumbar into the sacral portion is also slender, and descends dorsal to the common
iliac artery. The right trunk is partly covered by the vena cava inferior and the
left by the aorta.
The ganglia, which are small and oval, vary in number from three to eight, but
are usually four. Rarely they are so fused as to form one continuous ganglion.
White rami communicantes pass to the ganglia from the first two or three
lumbar nerves only. This portion of the sympathetic trunk also receives visceral
efferent and afferent fibres which are derived from the white rami communicantes
of the lower thoracic nerves and continue downward in the trunk.
Branches. — As in the thoracic region, the branches from the gangha are central and per-
ipheral. The central are grey rami communicantes. There may be two branches to a nerve
or one ramus may divide so as to join two adjacent spinal nerves. Sometimes a spinal nerve
may receive as many as five grey rami from the sympathetic trunk.
The peripheral branches include; — (a) Branches passing to the aorta and taking part in
the formation of the aortic plexus; (6) branches which descend in front of the common ihac
artery to the hypogastric plexus; and (c) branches to the vertebrse and ligaments.
1040 THE NERVOUS SYSTEM
THE SACRAL PORTION OF THE SYMPATHETIC TRUNK
The sacral part of each truak passes downward in front of the sacrum, imme-
diately lateral to the medial borders of the anterior sacral foramina. It is
continuous above with the lumbar portion of the trunk, and below it anastomoses
freely in front of the coccyx with the trunk of the other side to form a plexus
in the terminus of which is the coccygeal ganglion {ganglion coccygeum impar)
(fig. 787). Like the cervical and lower lumbar portions of the sympathetic
trunk, the sacral part receives no white rami communicantes from the spinal
nerves.
The sacral ganglia are small in size, and usually four in number. The varia-
tion both in size and number is more marked in this portion of the trunk than in
the two parts above.
Branches. — The branches of the sacral gangha include: —
(1) Grey rami communicantes to the sacral nerves.
(2) Branches to the front of the sacrum which anastomose with their fellows of the opposite
side (commissural branches).
(3) Branches which enter into the formation of the plexus on the middle sacral artery.
(4) Branches which join the pelvic plexuses.
(5) Branches given off by the ganglion coccygeum impar to the coccyx and its ligaments
and to the glomus coccygeum (coccygeal gland).
Construction of the lumbar and sacral portions of the gangliated trunk. — The ganglia
of both these portions of the trunk are very variable in shape, size, position, and number. There
are usually four gangha belonging to each portion, but sometimes as many as eight may be
distinguished in the lumbar and at other times there may be as many as six in the sacral portion.
In the majority of cases, especially in the sacral region, these masses of cells are so fused that
their number is less than the number of the spinal nerves with which they are associated. As
noted above, only the first two or three lumbar spinal nerves send white rami which enter these
ganglia directly as such. However, visceral efferent fibres descend this entire stretch of the
trunk, through both the lumbar and sacral portions, from the white rami of the lower thoracic
and the upper lumbar nerves above. These fibres either terminate in the various gangha or
pass uninterrupted to the more distant sympathetic cell-bodies which are concerned in impulses
that are vaso-motor to the genital organs, motor for the uterus, the vas deferens, and the mus-
cular coats (circular coat especially) of the bladder. Also, some of them convey secretory, pilo-
motor, and vaso-motor impulses for the glands, skin, and vessels of the lower extremity in
addition to the similar impulses conveyed in the peripheral branches from the lower part of
the thoracic portion of the sympathetic trunk. The motor impulses for the uterus or vas
deferens and for the bladder pass, in most part probably, by way of the peripheral branches
from the lumbar portion of the cord, through the aortic plexus to the inferior mesenteric gang-
lion; others, the vaso-motor impulses to the genital organs especially, pass by way of the sacral
ganglia and the peripheral branches from them to the hypogastric or pelvic plexus and the appro-
priate subplexuses of this region. Of the vaso-motor fibres for the penis, some of the constrictor
fibres pass down the sacral portion of the sympathetic trunk and terminate about the cells of
the sacral ganglia, and these cells send out sympathetic fibres which join and course in the pudic
nerve (n. pudendus).
All of both the lumbar and sacral spinal nerves receive grey rami from the gangliated trunk.
These, just as those from the other portions of the trunk, consist of — (1) vaso-motor fibres to
vessels of the meninges and the vertebral canal; (2) sympathetic fibres which join the divisions
of the spinal nerves and course in them to their distribution, and (3) afferent sympathetic
fibres terminating in the spinal ganglia.
In addition to the visceral efferent fibres, the branches of the lumbo-sacral portion of the
sympathetic trunk carry cerebro-spinal fibres of general sensibility — sensory fibres arising in
the spinal gangha of this and the lower thoracic region.
There are no white rami proper passing from the sacral spinal nerves to course or terminate
in the sympathetic trunk. Visceral efferent fibres are given off by these nerves in abundance,
but, instead of entering the trunk and its ganglia, they form bundles which pass over the trunk
and directly into its peripheral branches and to the more distant ganglia. The bundles passing
from the second, third, and fourth sacral nerves are large and especially definite. While
homologous to white rami, such bundles are better known as the visceral branches of the sacral
nerves or the plevic splanchnics. They contain some spinal sensory fibres, but consist for the
most part of visceral efferent, conveying impulses, vaso-motor (vaso-dilator, chiefly) to the gen-
ital organs, both motor and inhibitory for the rectum, uterus, and bladder (longitudinal coat
especially), and secretory for the prostate gland. These fibres contribute to the hypogastric
plexus and are interrupted in the small gangUa of its sub-plexuses, named according to the
various urino-genital organs concerned.
THE GREAT PREVERTEBRAL PLEXUSES
The great prevertebral plexuses, in the body cavities, are three in number —
the cardiac, the coeliac (solar or epigastric), and the hypogastric or pelvic. The
cardiac plexus lies behind and below the arch of the aorta, and the coeliac and
THE CARDIAC PLEXUS 1041
hypogastric plexuses are situated in front of the lumbar vertebrae. Each plexus
receives not only sympathetic fibres which have passed from or through the
ganglia of the sympathetic trunks of either side, but also both afferent and efferent
cranio-spinal nerve-fibres derived directly from the cranio-spinal nerves. In
addition the cardiac and coeliac plexuses receive both efferent visceral and cranio-
spinal sensory or afferent visceral fibres from both vagus nerves. It should be
clearly understood that the branches which run from the sympathetic gangliated
trunks to the prevertebral plexuses contain meduUated fibres which are passing,
like the fibres from the sacral nei'ves, directly from the spinal cord to terminate
about the cells of the plexuses.
1. The Cardiac Plexus
The cardiac plexus is formed by the cardiac branches from both vagus nerves
and from both sympathetic trunks. It lies beneath and dorsal to the arch of the
aorta, in front of the bifurcation of the trachea, and extends a short distance
upward on the sides of the trachea. It is composed of a superficial and a deep
part (fig. 789).
The superficial part of the cardiac plexus is much smaller than the deep part,
and lies beneath the arch of the aorta in front of the right pulmonary artery. It
is formed chiefiy by the cardiac branches of the left vagus and by the left superior
cardiac nerve, but sometimes receives filaments from the deep cardiac plexus.
The cardiac ganglion (ganglion of Wrisberg,) usually found connected with this
plexus, lies on the right side of the ligamentum arteriosum.
Branches. — From this plexus some branches pass to the left half of the deep cardiac plexus,
and others accompany the left pulmonary artery to the left anterior pulmonary plexus. It also
sends branches to the right anterior coronary plexus. ,
The deep portion of the cardiac plexus lies dorsal to the arch of the aorta at the
sides of the lower part of the trachea and in front of its bifurcation. It consists of
two lateral parts, more or less distinct, connected by numerous branches, which
pass around the lower part of the trachea. It is formed by the superior, middle,
and inferior cervical cardiac branches from the right sympathetic trunk, the mid-
dle and inferior cervical cardiac branches from the left trunk, and all the cervical
and thoracic cardiac branches of the vagus except the superior cervical cardiac
branch of the left vagus. It also receives branches from the superficial cardiac
plexus.
The left part of the deep cardiac plexus gives branches to the left atrium (auricle) of the heart,
to the left anterior pulmonary plexus, to the left coronary plexus, and sometimes to the super-
ficial part of the cardiac plexus.
The right part of the deep cardiac plexus gives branches to the right atrium, to the right an-
terior pulmonary plexus, and to the right and the left coronary plexuses (fig. 789). The branches
to the left coronary plexus pass behind the pulmonary artery. Some of those to the right coro-
nary plexus pass anterior and some posterior to the right pulmonary artery.
The coronary plexuses are formed by branches given off by the cardiac plexus.
They accompany the coronary arteries and are right and left.
The right {anterior) coronary -plexus receives filaments from the superficial part
of the cardiac plexus, but is formed chiefiy by filaments from the right portion of
the deep cardiac plexus (fig. 789). Its distribution to the heart follows that of
the right coronary artery.
The left {posterior) coronary plexus is larger than the right plexus, and is formed
for the most part by filaments from the left portion of the deep cardiac plexus, but
it receives some filaments from the right portion of the deep cardiac plexus
(fig. 789). Its distribution to the heart follows that of the left coronary artery.
The cardiac plexus and the network of nervous structures in the walls of the atria are the
remains of the primitive plexuses found in the embryo, which are called the bulbarj the inter-
mediate, and the atrial plexuses, terms which sufficiently indicate their relative positions. The
bulbar plexus gives off the coronary nerves and is transformed into the superficial part of the
deep cardiac plexus; the remainder of the deep cardiac plexus is formed by the intermediate
plexus, and the atrial plexus becomes the network of the atrium.
The fibres which pass to the cardiac plexus are meduUated and non-meduUated; the former
1042
THE NERVOUS SYSTEM
Fig. 789. Caediac, Pulmonary, and Coronary Plexuses. (Schematic.)
(Modified from Cunningham.)
Superior cardiac nerve-
Middle cardiac nerve'
Cervical cardiac branches
of vagus
Inferior cardiac nerve-
Recurrent nerve^
Thoracic cardiac branches,
of vagus
Right coronary plexus— —
Middle cervical
ganglion
_ Inferior cervical
ganglion
Deep cardiac plexus
Superficial cardiac plexus
NLeft posterior pulmonary
plexus
- Left coronary pie:
THE C (ELI AC PLEXUS 1043
are the so-called inhibitory, the latter motor. The inhibitory impulses leave the central
nervous system by the spinal accessory and vagus nerves. The motor iibres leave the spinal
cord by the ventral roots and white rami communicantes of the thoracic nerves and terminate
about the cells of the intervening sympathetic ganglia. From the cells of these gangha arise
the non-meduUated (grey) fibres of the plexus. These fibres terminate directly upon the fibres
of cardiac muscle or about the cells of the minute intrinsic cardiac ganglia which in their turn
give axones to the muscle.
2. The Pulmonary Plexuses
The pulmonary plexuses are a continuation of the cardiac plexuses. The
two are so intimately joined that it is difficult to distinguish them as separate
plexuses. The pulmonary are formed by fibres from both the vagus and sympa-
thetic nerves. The anterior and posterior pulmonary branches of the vagus
unite, dorsal to the bifurcation of the trachea, with fibres from the second, third
and fourth ganglia of the thoracic portion of the sympathetic trunk to form the
anterior and posterior pulmonary plexuses that lie ventral and dorsal to the
bifurcation of the trachea. Here the pulmonary plexuses of both sides connect
with each other freely. Leaving the trachea, the plexuses pass into the lungs
along the pulmonary arteries (figs. 744, 789) . The parts of the plexus of each side
are named according to their position anterior or posterior to the right and left
pulmonary arteries; thus, there is a right anterior and a right posterior, a left
anterior and a left posterior pulmonary plexus.
3. The C celiac Plexus
The coeliac (solar or epigastric) plexus is the largest of the prevertebral
plexuses. It is unpaired, and is continuous above with the aortic plexus of the
thorax and below with the abdominal aortic and superior mesenteric plexuses.
It lies in the epigastric region of the abdomen behind the bursa omentalis (lesser
sac of the peritoneum) and the pancreas, upon the crura of the diaphragm and over
the abdominal aorta, and around the origin of the coeliac and the superior mesen-
teric arteries. It occupies the interval between the suprarenal bodies and extends
downward as far as the renal arteries. It is formed by the great and the lesser
splanchnic nerves of both sides, by coeliac branches of the right vagus, and by
filaments from the upper lumbar ganglia of the sympathetic trunlc. It sometimes
receives coeliac branches from the left vagus. It contains two large ganglia, the
right and left coeliac (semilunar) ganglia (fig. 790).
The coeliac (semilunar) ganglia are two large, flat, irregularly shaped masses,
separable into a varying number of ganglia. These two masses, or rather the
smaller ganglia which compose them, are associated by a varying number of com-
municating branches. Each mass, right and left, lies upon the corresponding crus
of the diaphragm, at the medial border of the corresponding suprarenal body,
being sometimes overlapped by this body. The right mass lies behind the inferior
vena cava. Each coeliac ganglion receives at its upper border the greater
splanchnic nerve, and, near its lower border, lying over the origin of the renal
artery, is a more or less detached part, known as the aortico-renal ganglion.
This ganglion receives the lesser splanchnic nerve and may seemingly give origin
to the greater part of the renal plexus. Another part of the cceliac ganglion, often
found dorsal to the origin of the superior mesenteric artery, is known as the
superior mesenteric ganglion (fig. 790) .
From the coeliac plexus and its ganglia subordinate plexuses are continued
upon the aorta and its branches. These comprise both paired and unpaired
plexuses. The paired plexuses are the phrenic, suprarenal and renal, the sper-
matic in the male, and, in the female, the ovarian plexuses. The unpaired plex-
uses are the aortic, hepatic, splenic, superior gastric, inferior gastric, superior mesen-
teric, and inferior mesenteric.
That part of the coeliac plexus surrounding the coeliac artery was formerly
described as the coeliac plexus. It is better considered as an unnamed part of the
larger coeliac (solar) plexus. This part of the plexus receives fibres from both
vagus nerves, and gives filaments that form plexuses around the branches of the
cceliac artery and their ramifications.
1044
THE NERVOUS SYSTEM
The paired subordinate plexuses of the coeliac. — (1) The phrenic (diaphragmatic) plexuses
consist of fibres from the upper part of the cceliac ganglia, which follow the inferior phrenic
arteries and their branches on the under surface of the diaphragm (fig. 790). Filaments are
given off by the roots of the plexuses to the suprarenal bodies, and others unite with the ter-
minal branches of the phrenic nerves. The point of junction with the right phrenic nerve is
marked by the phrenic ganglion, from which branches are distributed to the inferior vena cava,
to the right suprarenal body, and to the hepatic plexus.
(2) The suprarenal plexuses are comparatively large plexuses, formed mainly by branches
from the cceliac (semilunar) ganglia. However, fibres come to them from the coeliac plexus
Fig, 790. — Abdominal Plexuses of the Sympathetic. (After Toldt, "Atlas of Human
Anatomy," Rebman, London and New York.)
Coeliac plexus Left vagus nerve
Phrenic pie
..-,<i^r^*
Right vagus nerve
Superior gastric plexus
X Phrenic plexus
' Suprarenal plexus
\
_3~Splenic plexus
along the suprarenal arteries, from the phrenic plexus along the inferior phrenic arteries, and
from the renal plexus along the inferior suprarenal arteries. They are distributed to the-
substance of the suprarenal bodies. Cell-bodies of sympathetic neurones are enclosed within
the suprarenal bodies forming intrinsic ganglia. The medulla of the suprarenal is of ecto-
dermal origin and considered as derived from undeveloped components of the sympathetic
nervous system.
(3) The renal plexuses receive fibres from the lower part of the coeliac ganglia and from
the coeliac and aortic plexuses. They also receive filaments from the least splanchnic nerves,
when these nerves are present, and sometimes filaments from the small splanchnic nerves and
from the first lumbar ganghon of the sympathetic trunk. These plexuses pass along the renal
arteries into the substance of the kidneys. Most of the fibres of each renal plexus are grey fibres,
and as they pass to the kidneys small renal ganglia are present upon them. Both renal
plexuses give branches to the corresponding spermatic plexuses and to the ureter, and the
right renal plexus gives filaments also to the inferior vena cava.
THE HYPOGASTRIC PLEXUS 1045
(4a) The spermatic plexuses (fig. 790) are formed by fibres from the renal and aortic
plexuses. They accompany the spermatic arteries and are joined at the abdominal inguinal
(internal abdominal) ring by fibres that have passed along the vas deferens from the pelvic
plexuses. Their terminal filaments are distributed to the testis and the epididymis.
(4b) The ovarian plexuses are formed in the female like the spermatic plexuses in the
male. They accompany the ovarian arteries and, in the broad ligament, receive fibres from
the utero-vaginal plexus. They supply the ovaries, the broad ligaments, and the Fallopian
tubes, and send some fibres to the fundus of the uterus, where they become continuous with
the utero-vaginal plexus.
The unpaired subordinate plexuses: — (I) The abdominal aortic plexus is formed by
two strands of fibres which descend along the sides of the aorta and communicate with each
other across its ventral aspect. It is connected above with the renal plexuses, and it receives
peripheral branches from some of the lumbar ganglia of the sympathetic trunk on each side. It
often contains a number of ganglia, which are situated at the points where the peripheral
branches join the plexus, and it terminates below, chiefly by anastomoses with the hypogastric
plexus (figs. 790 and 791). Besides giving filaments to the inferior vena cava, it also gives
fibres that form plexuses along each of the branches of the aorta. The fibres tnat pass from
the lower end of the aortic plexus upon the common ihac artery form the iliac plexus, which
is continued along the femoral artery as the femoral plexus, and still further along the popliteal
artery as the popliteal plexus.
(2) The superior gastric (coronary) plexus, receiving filaments from the coeliac plexus,
accompanies the left gastric (coronary) artery along the lesser curvature of the stomach.
Its filaments anastomose with filaments of the vagus nerves and with the plexus that accom-
panies the right gastric (pyloric) artery (fig. 790), and it gives fibres to the walls of the stomach
which terminate within the walls, about the cell bodies of the delicate gangliated plexus myen-
tericus and plexus submucosus (plexuses of Auerbach and Meissner). The axones of these
supply' the smooth muscle of the stomach walls and its vessels.
(.3) The inferior gastric plexus receives from the splenic plexus filaments that accompany
the left gastro-epiploic artery. It gives filaments to the walls of the stomach, which terminate
as in the superior gastric plexus, and it receives filaments from the vagus nerves and from
the plexus that accompanies the right gastro-epiploic artery.
(4) The hepatic plexus receives filaments from the cceUac plexus and from the left vagus.
It accompanies the hepatic artery and gives fibres that form plexuses on the branches of the
artery and on their ramifications within the liver and gives secretory fibres to the liver cells.
It also gives filaments to the portal vein (fig. 790).
The splenic or lienal plexus is formed by filaments from the coeliac plexus, the left cceliac
(semilunar) ganglion, and from the right vagus. It accompanies the splenic artery and gives
filaments which form plexuses on the branches of this artery, and which pass with the branches
to supply fibres to the stomach and the pancreas (fig. 790).
(5) The superior mesenteric plexus is formed chiefly by filaments from the lower part
of the coeliac plexus, but it also receives fibres from the right vagus and fibres direct from the
coeliac (semilunar) gangUa. At the origin of this plexus, dorsal to the superior mesenteric
artery, lies the superior mesenteric ganglion (fig. 790). The filaments of the plexus, which are
white and firm, accompany the superior mesenteric artery and, following its branches and their
ramifications, are distributed to the walls of the small intestine, the caecum, and the ascending
and transverse colon. From the secondary plexuses that accompany the branches of the artery
fibres pass to form still other plexuses that lie near the wall of the intestine, between the branches
of the artery and between the layers of the mesentery. Filaments pass with the branches of
the arteries and from plexuses between them into the intestinal wall, and there form between
the longitudinal and circular muscle layers of the intestine the fine ganghated plexus myen-
tericus (plexus of Auerbach), and filaments from this plexus form in the submucosa the deUcate
plexus submucosus or plexus of Meissner. From these latter plexuses fibres arise which ter-
minate upon the gland cells and smooth muscle fibres of the intestinal wall and its vessels.
The white appearance of the filaments of the superior mesenteric plexus is due to the large
number of cranio-spinal sensory and visceral motor fibres (vagus especially) in it.
(6) The inferior mesenteric plexus is derived chiefly from the left side of the aortic plexus.
It descends upon the inferior mesenteric artery and gives off filaments which accompany the
branches of the artery and are distributed to the descendiog colon and to the iho-pelvic colon
(figs. 790 and 791). The filaments which accompany the left colic brunch of the inferior mesen-
teric artery anastomose with the filaments of the superior mesenteric plexus which accompany
the middle coHc artery. The filaments which accompany the superior hasmorrhoidal artery
form the superior hsemorrhoidal plexus. This plexus gives off the superior hcemorrhoidal
nerves (fig. 791) which supply the upper part of the rectum and anastomose with the middle
hcemorrhoidal plexus.
4. The Hypogastric Plexus
The hypogastric plexus Ues partly in the abdominal cavity and partly in the
pelvic cavity. It is formed chiefly by filaments continued downward from the
aortic plexus, and by the pelvic splanchnics and peripheral branches from the
lumbo-sacral nerves and sympathetic trunk (fig. 784). The abdominal part of
this plexus consists of plexiform bundles of fibres descending between the common
iliac arteries and interlacing in front of the fifth lumbar vertebra to form a broad,
flattened, plexiform mass. In its extent it receives branches from the lumbar
ganglia of the sympathetic trunk. This plexiform mass then divides into two
1046
THE NERVOUS SYSTEM
parts, right and left, which descend into the pelvic cavity and which, by English
authors, are frequently designated as the pelvic plexuses.
The pelvic parts of the hypogastric plexus (pelvic plexuses) lie at the sides of the
rectum in the male, and at the sides of the rectum and the vagina in the female.
They receive peripheral branches from the sacral ganglia of the sympathetic trunk
and visceral efferent fibres by way of the pelvic splanchnics from the second and
Fig. 791. — The Hypogastric and Sub-plexuses of the Pelvic Cavity. (After Spalteholz.)
Abdominal aortic plexus -^'^'^^"^ ^ ^ Sympathetic ganghated trunk
b-\y J,-' ^"^~x.-' Lumbar ganglion
— Iliac plexus
*-J- Transverse process of fourth
lumbar vertebra
Hypogastric plexus
Anterior prii
" fifth lumbi
Inferior mesenteric plexus
1^\ \ ^^__Lef t branch of the
\ ^ K»» ""*"> X"* hypogastric plexus
*^ *»t,^ V — Sympathetic trunk
'^"■f^-^^X Superior
~ *'^^^ -^K--^ — h£emorrhoidal
Sacral
plexus
Visceral branches of
pudendal plexus
- Middle hsEmorrhoidal plexus
"- Pudic nerve
"Ureter
Vesicula seminalis
Prostatic plexus
Rectum
Levator am
Cavernous plexus of penis
Great cavernous nerve
third or third and fourth sacral spinal nerves. Each pelvic part of the plexus
accompanies the corresponding hypogastric (internal ihac) artery, and gives off
secondary plexuses that continue on the branches of the artery to the pelvic
viscera. Of these secondary plexuses, the middle hsemorrhoidal and the vesical
plexus are common to both sexes and are paired.
The middle hsemorrhoidal plexus passes on each side along the middle hsemorrhoidal artery
to the rectum, where it receives the superior hsemorrhoidal nerves and sends filaments into the
wall of the rectum (fig. 791).
REFERENCES FOR NERVOUS SYSTEM 1047
The vesical plexus receives some branches from the pelvic parts of the hypogastric plexus,
but is largely reinforced by way of the pelvic splanchnios, from the third and fourth sacral
nerves. Each part passes along the corresponding vesical arteries to the bladder, and gives
off two sets of branches, namely, the superior vesical nerves (fig. 791), which supply the upper
part of the bladder-waU and send some branches to the ureter, and the inferior vesical nerves,
which supply the lower part of the bladder and, in the male, give secondary deferential plexuses
to the vas deferens. These plexuses surround the vasa deferentia and the vesiculse seminales
and anastomose with the spermatic plexuses.
The prostatic plexus, found only in the male, is formed in two parts by nerves of con-
siderable size, and lies chiefly on the sides of the prostate gland between it and the levator ani
(fig. 791). Each of the.se parts supplies the gland and the prostatic part of the urethra^ and
sends offsets to the neck of the bladder and the vesioute seminales. This plexus is contmued
forward on either side to form the cavernous plexus of the penis (fig. 791), which anastomoses
with branches of the dorsal nerve of the penis, gives off branches to the membranous part of
the urethra, and also gives origin to two sets of nerves, namely, the large and the small cavernous
nerves of the penis.
The large cavernous nerve, one on each side, runs forward to the middle of the dorsum of
the penis, where it anastomoses with the dorsal nerve of the penis on the corresponding side,
and ends in twigs which are distributed chiefly to the walls of the sinuses of the corpus caver-
nosum penis, but some of the terminal filaments supply the corpus cavernosum urethrte (corpus
spongiosum) (fig. 791).
The small cavernous nerves are small filaments which pierce the uro-genital trigone (tri-
angular ligament) and the compressor urethra;, and enter the posterior part of the corpus
cavernosum.
The utero-vaginal plexus, found in the female, is formed in its upper part on each side
largely by fibres clerived from the pelvic part of the hypogastric plexus, but it receives some
fibres from the pelvic splanchnics of the third and fourth sacral nerves. The nerves from this
part of the plexus accompany the uterine arteries as they pass between the layers of the broad
ligament. Some accompany each uterine artery and its branches to their termination, but a
considerable number of fibres leave the artery and pass into the body of the uterus to supply
its lower part and cervix. Between the layers of the broad ligament this plexus anastomoses
with the ovarian plexus and sends some filaments to the uterine tube (Fallopian tube). The
lower part of the plexus ulero-vaginalis receives some fibres on each side from the pelvic part of
the hypogastric plexus, but it is formed chiefly by efferent visceral fibres from the second, third,
and fourth sacral nerves. These fibres terminate in contact with intrinsic cell-bodies whose
axones supply the wall and mucous membrane of the vagina and urethra. From the plexus on
the anterior surface of the vagina fibres pass to form the cavernous plexus of the clitoris, which
gives off the great and lesser cavernous nerves of the clitoris for the supply of the clitoris. The
utero-vaginal plexus of the female corresponds to the prostatic plexus of the male.
References for the Nervous System. A. General. Barker, Nervous
System, 1899; Edinger, Vorlesungen, 1908; Johnston, Nervous System, 1906;
(phylogeny) Parker, Anat. Eec, vol. 4; {develo-pment) Streeter, in Keibel and
Mall's Human Embryology. B. Brain and Spinal Cord. Bechterew, Funktio-
nen der Nervencentra, 3 vols., 1908; {cell-structure) Malone, Anat. Rec, vol. 7;
{axone-sheaths) Hardesty, Amer. Jom*. Anat., vol. 4; (cortical localization)
Donaldson, Jour. Nerv. and Mental Dis., vol. 13; Smith, Jour. Anat. and
Physiol., vol. 41; Israelsohn Ai'b. Wien. neurol. Inst., vol. 20; (central fissure)
Symington and Crymble, Jour. Anat. and Physiol., vol. 47; (brain-weight) Pearl,
Jour. Comp. Neurol., vol. 25; Spitzka, Phila. Med. Jour., 1903; (ventricles
Harvey, Anat. Rec, vol. 4; (mid-brain and medulla) Sabin, Atlas, 1901; (tri-
geminal nuclei) Willems, Nevraxe, T. 12; (spinal cord, cornparative) BuUard,
Amer. Jour. Anat., vol. 14. C. Peripheral. (Histogenesis) Bardeen, Amer.
Jour. Anat., vol. 2; (experimental) Harrison, Amer. Jour. Anat., vol. 5; Jour.
Exper. ZooL, vol. 9; (phylogeny of facial) Sheldon, Anat. Rec, vol. 3; (trigeminus)
Symington, Jour. Anat. and Physiol., vol. 45; (nervus termnialis) Johnston, Anat.
Rec, vol. 8. (afferent spinal neurones) Ranson, Jour. Comp. Neurol., vol. 18;
(structure) Ranson, Anat. Rec, vol. 3; (brachial plexus) Todd, Anat. Anz., Bd. 42;
(abdominal, statistical) Bardeen, Amer. Jour. Anat., vol. 1 (sympathetic termina-
tions) Boeke, Anat. Anz., vol. 44.
SECTION YIII
SPECIAL SENSE OEGANS
Revised for the Fifth Edition
By DAVID WATERSTON, M.A.,M.D., F.R.C.S.E., King's College, London
PROFESSOR OF ANATOMY IN THE UNrVERSITT OF LONDON
GENERAL CONSIDERATIONS
THE term "special sense organs" indicates those structures situated on or
near the surface of the body which receive the impressions of sound, light
taste and smell, and transmit them to the brain in the form of nerve
impulses.
The essential difference between what is termed general sensibility and the
special senses lies in the fact that the organs of special sense are each sensitive to
a specific stimulus which does not affect the general sensory apparatus of the
body surface to an appreciable degree.
Thus, the waves of light or of sound, flavoured substances which have a taste, and the
minute particles which stimulate the sensory organ for smell — all these varied stimuli create
no impression when they come into contact with the sensitive general surface of the body.
The vibration of sound waves present in an organ pipe may indeed be felt by the hand, but
the sensation is that of vibration and not of sound.
This difference in function between the ordinary and the special senses
as well as the difference between the individual organs of special sense, is as-
sociated with a difference in structure; for each special sense organ has a charac-
teristic receptive mechanism of cells highly specialised in form and structure,
which receive the stimuli coming from without, and transmit them to the brain in
the form of a nerve-current. These cells may be derived by the specialisation of
certain cells coming directly from the surface of the body, or they may be cells
derived from the central nervous system — as in the case of the eye. In this case,
the cells are placed in close relation to the terminals of a special cranial nerve.
Many of the sense organs, and especially the eye and ear, are highly com-
plex in structure. The complexity is due largely to the elaborate mechanical
arrangement for receiving the external stimulus, and for conveying it to, or
focussing it upon, the sensory cells proper.
It must always be borne in mind that sensation itself is a function of the brain — it is the
response in consciousness to the afferent impressions transmitted to the brain by the sensory
nerves. Further, the quality of the sensation does not arise in the sense organ, but in the brain
itself. Thus, stimulation of the trunk of the optic nerve by mechanical means produces
sensations of light, apart from stimulation of the retina.
In the following account, the organs of smell, taste, vision and hearing will be
successively considered.
I. THE OLFACTORY ORGAN
The olfactory apparatus [organon olfactus] in man does not reach the high
development which is found in many of the lower animals. In them, not only is
the sensory apparatus found distributed over a large area of the nasal mucous
membrane, but the central connections of the olfactory nerves make up a
considerable portion of the brain, including all those structures known under the
name of rhinencephalon. In man, sensibility to smell is localised to a compara-
tively limited area in the upper part of the nasal cavity, known as the olfactory
area.
The structure of the nose in all its parts has been fully dealt with in the
1049
1050
SPECIAL SENSE ORGANS
section on the Respiratory System — and hence it is not necessary to describe
the whole nasal cavity.
The olfactory area of the nose includes the uppermost part of the nasal fossae
on the lateral wall above the superior concha, and a slightly larger area of the
septum.
Fig. 792 shows the size of this area, and it will be noticed that the area on the
lateral wall of the nose does not coincide with the area of the superior concha, but
is rather smaller. It should be added that the olfactory nerves can be traced
to a somewhat larger area of the mucous membrane, to the middle concha;
it is, therefore, possible that the area indicated is too small.
The mucous membrane in the olfactory area has special characters, both naked
eye and microscopic, which distinguish it from the rest of the nasal mucous
Fig. 792. — Diagram op the Distribution op the Nerves in the Nasal Cavity. (Poirier
and Charpy.) The olfactory area is represented by dots. A, septum. B, lateral wall.
Posterior su-
, , , t . A Afiterior perior nasal
Posterior superior nasal / [ r \ • \ ethmoid
- , ^ — "^'W
membrane. It is usually of a yellowish colour, and is soft and pulpy in consistence
It is covered by a columnar ciliated epithelium and contains numerous glands
(glands of Bowman) .
The olfactory apparatus within it consists of the olfactory cells. These cells are elongated
spindle-shaped structures, lying between the deeper parts of the investing columnar cells.
From each a slender process passes to the surface of the mucosa, and terminates in a group of
short hair-like processes, the olfactory hairs (v. Bumm), while from the deep portion of the cell
a long slender process passes deeply into the mucosa. These processes resemble nerve filaments,
with no medullary sheath, and they pass in the olfactory nerves to the olfactory bulb, in which
they terminate in arborisation around the dendritic enlargements of the mitral cells of the
olfactory bulb (see fig. 795; also Olfactory Nerve, p. 929).
Fig. 793. — Section Showing the Development op the Olpactort Pit.
The connections of the olfactory bundle and tract with the brain are fully
dealt with in the section on the Nervous System.
The development of the olfactory organ is connected with the development of the nose,
which represents at first only the olfactory portion. About the third week, a localised thicken-
ing of the surface epithelium occurs on the antero-ventral aspect of the head in the region of the
fore-brain, forming on each side an olfactory plate. These plates become depressed from the sur-
face by the growth of the margins, giving rise to the olfactory pits. The further changes are
THE EYE
1051
associated with the formation of the face and nose (see Morphogenesis). The cells of the sur-
face epithelium on the olfactory pits in part form olfactory cells, and send processes inward which
pass to the olfactory lobe of the brain, and form the olfactory nerve.
The organ of Jacobson is a small rudimentary structure in man. It is represented by a
minute canal, 2 to 9 mm. long, placed on each side in the lower portion of the nasal septum,
opening on the surface slightly above the orifice of the naso-palatine canal. Below it lies a
small piece of cartilage, lying below the cartilage of the septum, and known as Jacobson's carti-
lage. The canal is lined by epithelium, but contains no olfactory cells. It is developed from
a small portion of the olfactory plate which becomes separated from the area which gives rise
to epithelium of the olf actor j' region.
II. ORGAN OF TASTE
The taste organs [organon gustus] consist of minute epithelial structures, the
taste buds [calyculi gustatorii], situated mainly in the epithelial covering of the
tongue and also in the epiglottis.
In the tongue, the taste buds are found mainly on the walls of the vallate
papillse (see p. 1106), but they are found to a slight extent scattered over the
whole area of distribution of the glosso-pharyngeal nerve, on the surface of the
foliate and fungiform papillse, and on the plicse fimbriatse on the lower surface of the
tongue.
Tigs. 794 and 795. — Diagrams Illustrating the Structure of the Taste Buds
AND the Olfactory Mucosa.
In the foetus, the distribution is even wider, and they have been described as occurring on
the soft palate, palatine arches, uvula, and in the mucous membrane covering the medial surfaces
of the arytenoid cartilages. It is possible that such structures, though found in these regions
in the foetus, usually disappear in the adult.
Each taste bud is a hollow conical or oval structure, measuring .07-.08 mm.
in length. At one end it opens by a small channel, termed the pore canal, which
passes to the surface between adjacent epithelial cells. The surface opening is
termed the outer -pore and the opening at the taste bud the inner taste pore.
The taste bud consists of epitheUal supporting, of gustatory and of basal cells, arranged as
seen in figure 794. The gustatory cells are long slender fusiform cells. The free end of
each passes to the inner taste pore, and terminates in stiff hair-like processes, which project
toward the pore canal. The deep end of each is connected with a basal cell. Terminal branches
of the glosso-pharyngeal nerve ramify around the gustatory cells, and convey to the brain the
impulses generated by contact of the ends of these cells with sapid particles. The epithelial
supporting cells line the taste buds, and also project into the interior between the olfactory cells.
Development. — The taste buds appear comparatively late in embryonic life — about the
third month. They arise mainly from the entodermal portion of the tongue, b}' differentiation
of the deeper cells of the epithelial covering over localised areas. Around these cells terminations
of the glosso-pharyngeal nerve are found. These cells assume the characteristic shape and
arrangement of the adult to form a taste bud. At first the opening of the bud lies upon the
surface, but as the surrounding epithelial cells increase in size and thickness, the pore-canal is
formed as a space between adjacent epithelial cells on the summit of the bud.
III. THE EYE
The sensory portion of the eye is the retina, a cup-shaped membrane, which
lines the posterior half of the eyeball. It is formed of layers of nerve cells, from
1052
SPECIAL SENSE ORGANS
which processes pass to the brain in the optic nerve. The eyeball is a hollow spher-
ical structure, whose wall is formed externally by a fibrous tunic including the
sclera (the white of the eye), and the cornea (the transparent area in the anterior
aspect of the eyeball). Internal to the tunic formed by these membranes is a
pigmented vascular membrane, the chorioidal membrane, of which the anterior
part forms the iris, or the coloured part of the eye.
Within these tunics is formed a cavity, in which lies the crystalline lens of the
eye. In front and behind the lens are two chambers; that in front of the lens
contains the aqueous humour and that behind it the vitreous.
The study of the eye is best undertaken by examining the eye in the living, and
subsequently by the dissection of specimens, and that order is followed in this
account.
General Surface View
The two eyes are situated nearly in the line where the upper and middle thirds of the face
meet; they lie right and left of the root of the nose, the most prominent part of the front of each
globe being about 3 cm. (1 J in.) from the mid-line of the face. Each eye is overshadowed by
the corresponding eyebrow, and is capable of being concealed by its eyehds, upper and lower.
The orbital margin may be traced all round with the finger. At the junction of the medial
and intermediate thirds of the upper margin the supraorbital notch (incisura supraorbitalis)
can usually be felt, and the supraorbital nerve passing through it can sometimes be made to
roll from side to side under the finger. The medial margin is the most difficult to trace in this
way, partly because it is more rounded ofi' than the others, partly because it is bridged over by
a firm band (medial palpebral ligament), passing medially from the medial angle of the eyelids;
below this band, however, a sharp bony crest is felt, which lies anterior to the lacrimal sac.
Note how the eye is protectedby the rim of the orbit, above and below; if we lay a hard flat
Fig. 796. — View of the Eye with Eyelids Open.
Palpebra superior (pars tarsalis)
Cilia I Sulcus orbitopalpebralis superior
Sclera r ' I Angulus oculi medialis
' Medial palpebral commissure
Ins I
^ Pupil Caruncula lacrimalis
Palpebra inferior
body over the orbital opening, it will rest upon the upper and lower bony prominences, and will
not touch the surface of the globe. Medially, the eye is protected from injury mainly by the
bridge of the nose; laterally it is most readily vulnerable, as here the orbital rim is comparatively
low. With one finger placed over the closed upper lid, press the eyeball gently backward into
the orbit, and observe the elastic resistance met with, due to the fact that the globe rests pos-
teriorly on a pad of fat.
The space between the free edges of the upper and lower lids is known as the palpebral
aperture [rima palpebrarum]: it is a mere slit when the lids are closed; but when they are open
its shape is, roughly, that of an almond lying with its long axis horizontal, and about thirty
millimetres in length.
When the eyes are directed to an object straight in front of them, this aperture is about
twelve millimetres wide, but its width varies with upward and downward movements of the
eyeball, being greatest on looking strongly upward, diminishing gradually as the eye looks
progi'essively lower. The angles formed by the meeting of the lids at each end of the palpebral
aperture are named respectively the lateral and medial angles (or canthi) [angulus oculi later-
alis, medialis], of which the lateral is sharp, while the medial is rounded off. On a closer in-
spection, it will be found that, for the last five millimetres or so before reaching the medial angle
the edges of the lids run an almost parallel course, and are here devoid of lashes. Through the
open palpebral aperture the front of the eyeball comes into view, extending quHe to the lateral,
but not reaching as far as the medial, angle; just within the latter we find a small reddish promi-
nence, the lacrimal caruncle [caruncula lacrimalis] ; and between this and the eyeball a fold of
SURFACE VIEW OF THE EYE
1053
conjunctiva known as the plica semilunaris. While the eye is open, press one finger on the skin,
a little beyond the lateral angle, and draw it firmly away from the middle line; observe that the
upper lid then falls over the eyeball, and that the outline of a firm band already referred to
(the medial palpebral ligament) becomes evident, passing between the medial angle and the
nose. The falling of the lid is caused by our dragging upon a ligament (the lateral palpebral
raph6) to which the lateral end of its tarsus is attached, and so putting the lid itself upon the
stretch. If, while the eyeball is directed downward, we place one finger on the lateral end of the
upper eyelid and draw it forcibly upward and laterally, we can usually cause the lower division
of the lacrimal gland to present just above the lateral angle.
Fig. 797. — View op the Eye with Eyelids Closed.
Sulcus orbitopalpebralis superior Angulus oculi medialis
Cilia Palpebra Medial palpebral commissure
inferior
The upper eyelid [palpebra superior] is much broader than the lower, extending upward
as far as the eyebrow. The skin covering it is loosely attached to the subjacent tissues above,
but more firmly below, nearer the free margin, where it overlies a firm fibrous tissue called the
tarsus superior. When the eye is open, a fold is present at the upper border of this lower more
tightly applied portion of skin, called the superior palpebral fold, and by it the lid is marked off
into an upper or orbital, and a lower or tarsal, division. The presence of the tarsus can be
readily appreciated on our pinching horizontally the entire thicloiess of the eyelid below the
palpebral fold. The lower eyelid [palpebra inferior] is similarly divided anatomically into a
tarsal and an orbital part, but the demarcation is sometimes unrecognisable on the surface,
Fig. 798. — View of Medial Region op the Eye, with the Eyelids Widely Separated
AND THE Eyeball Turned Laterally.
Edge of
palpebra superior
Tarsal (Meibomian) glands
though a fold or groove (the inferior palpebral) is usually visible when the eye is widely opened.
There is no precise limit of this lid below, but it maybe regarded ase.xtending to the level of the
lower margin of the orbit. Numerous very fine short hairs are seen on the anterior surface of
both eyelids. Each eyelid presents an anterior and a posterior surface, separated by a free
margin with two edges: — (a) An anterior, rounded edge [limbus palpebralis anterior] along
which the stiff cilia, or eyelashes, are closely placed in a triple row; and (b) a sharp posterior
edge [limbus palpetjralis posterior] which is applied to the surface of the globe (see fig. 813).
The cilia of both eyeUds have their points turned away from the palpebral aperture, so that
the upper ones curve upward, and the lower downward; the oiha of the upper lid are the stronger,
1054 SPECIAL SENSE ORGANS
and those in the middle of each row are longer than those at each end. Between the two edges
just described, the Ud-margin has a smooth surface, on which is a single row of minute apertures,
the openings of large modified sebaceous glands, the tarsal or Meibomian glands. It is by these
glistening, weU-lubricated surfaces that the opposite lids come into apposition when they are
closed. The secretion of these glands is known as the sebum palpebrale. The sharp posterior
edge of the lid-margin marks the situation of the transition of skin into mucous membrane.
Near the medial end of the margin of the lids we find a prominence, the lacrimal papilla, on the
summit of which is a small hole [punctum lacrimale], the opening of the lacrimal duct (ductus
lacrimaUs) for the passage of tears into the lacrimal sac. The lower punctum is rather larger
than the upper, and is placed further from the medial angle of the eye.
If we now examine the posterior surface of the eyelids — e. g., of the lower — we observe
that it is lined by a soft mucous membrane, the palpebral conjunctiva [tunica conjunctiva
palpebrarum]. Over the tarsal part of the lid the conjunctiva is closely adherent, but beyond
this it is freely movable along with the loose submucous tissue here present. On tracing it
backward, we find that it covers the whole posterior surface of the hds, and is then continued
forward over the front of the eyeball, forming the conjunctival tunic of the globe [tunica con-
junctiva bulbi]. The bend it makes as it changes its direction here is called the conjunctival
fornix [fornix oonjuuotivEe superior or inferior]. Numerous underlying blood-vessels are visible
through the palpebral conjunctiva, and under cover of its tarsal part we can see a series of nearly
straight, parallel, light yellow lines, arranged perpendicularly to the free margin of the hd —
the tarsal glands. The conjunctiva over the medial and lateral fourths of each lid is not quite
so smooth as elsewhere, and is normally of a deeper red colour; we shall find later that there are
glands well developed in these positions.
When the eyelids are opened naturally, we see through the palpebral aperture the following:
the greater part of the transparent cornea, and behind it the coloured iris with the pupil in its
centre; white sclera to the medial and lateral sides of the cornea; the semilunar fold and lacrimal
caruncle at the medial angle. The extent of the eyeball visible in this way varies according to
its position. Thus, with the eyes looking straight forward, the lower margin of the upper Ud
is nearly opposite to the top of the cornea, or, more strictly, to a line midway between the top
of the cornea and the upper border of the pupil, while the lower lid corresponds with the lower
margin of the cornea. When the eyes are directed strongly upward, the upper lid is relatively
on a slightly higher level, as it is simultaneously raised, but the lower lid now leaves a strip of
sclera exposed below the cornea. On looking downward the upper lid covers the upper part
of the cornea as low down as the level of the top of the pupil, while the lower hd is about mid-
way between the pupil and the lower margin of the cornea.
If we draw the eyelids forcibly apart, we expose the whole cornea, and a zone of sclera
about eight and a half milhmetres in breadth above and below, and ten milHmetres in breadth
to the lateral and medial sides — altogether about one-third of the globe; all the eyeball thus
exposed is covered by the ocular conjunctiva [tunica conjunctiva bulbi]. Over the sclera the
conjunctiva is freely movable, and through it we see superficial blood-vessels that can be made
to slip from side to side along with it (episcleral vessels). Occasionally other deeper vessels
may also be seen which do not move with the conjunctiva, but are attached to the sclera (an-
terior ciliary arteries and veins). Near the corneal border the conjunctiva ceases to be fieely
movable, and it is closely adherent to the whole anterior surface of the cornea, giving the latter
its characteristic bright, reflecting appearance; no blood-vessels are visible through it here in
health. When the lids are shut, the space enclosed between their posterior surfaces and the
front of the eyeball is thus everywhere lined by conjunctiva, and is known as the con-
junctival sac.
Not unfrequently the tendinous insertions of some or aU of the recti muscles into the sclera
may be seen through the conjunctiva, each insertion appearing as a series of whitish parallel
lines running toward, but terminating about seven mUhmetres from, the corresponding corneal
border.
The cornea appears as a transparent dome, having a curvature greater than that of the
sclera; the junction of the two unequally curved surfaces is marked by a shallow depression
running around the cornea, known as the scleral sulcus [sulcus sclerse]. In outline the cornea is
nearly circular, but its horizontal diameter is slightly greater than its vertical. Between it
and the iris a space exists, whose depth we can estimate roughly by looking at the eye from one
side; this space, or anterior chamber [camera ocuh anterior] is occupied by a clear fluid, the
aqueous humour. Almost the whole anterior surface of the iris is visible, its extreme periphery
only being concealed by sclera.
In colour the iris varies greatly in diiferent individuals. Near its centre (really a little up
and in) a round hole exists in the iris, the black pupil [pupUla], whose size varies considerably
in different eyes, and in the same eye according to temporary conditions, such as exposure to
light, etc.
On the surface of the iris we see a number of ridges [plicae iridis] running more or less radially ;
adjoining ones occasionaUy unite and interlace to some extent, so as to leave large depressed
meshes at intervals. These are the crypts of the iris. The radial ridges coming from the edge
of the pupil, and those coming from the more peripheral part of the iris, meet in a zigzag ele-
vated ridge concentric with the pupil, called the corona iridis, and by this ridge the iris is
roughly marked off into two unequal zones — an outer, the greater [annulus U'idis major] and
an inner, the lesser [annulus iridis minor]. The border next the pupil [margo pupillaris]
is edged with small, roundish, bead-like prominences of a dark brown colour, separated
from one another by depressions, so that it presents a finely notched contour. Not infrequently,
in a light-coloured iris, we may see the sphincter muscle through the anterior layers, in the form
of a ring about one millimetre in breadth around the pupil. The annulus iridis major may be
described as consisting of three parts: — (a) A comparatively smooth zone next the zigzag
ridge; (6) a middle area, showing concentric but incompletely circular furrows; (c) a small per-
ipheral darker part, presenting a sieve-like appearance. On the floor of the large depressed
THE EYEBALL
1055
meshes, or crypts, parallel radial vessels can be traced, belonging to the iris-stroma. The zig-
zag line mentioned above corresponds to the position of the circulus arteriosus minor. Occa-
sionally, especially in a hght iris, superficial pigment spots of a rusty brown colour occur.
(In examining the living eye, the ophthalmoscope may now be used, so as to gain a view
of the fundus, and to study the termination of the optic nerve, the distribution of the larger
retinal vessels, etc.)
The general red reflex obtained from the fundus is due to the blood in a capillary network
(chorio-capillaris) situated in the inner part of the chorioid. To the nasal side of the centre of
the fundus is a paler area of a disc shape corresponding to the intraocular end of the optic nerve,
and known as the papilla of the optic nerve [papilla n. optici]. This papilla (or 'optic disc')
is nearly circular, but usually slightly oval vertically; it is of a light orange-pink colour, with a
characteristic superficial translucency; its lateral third segment is paler than the rest as nerve-
fibres and capillaries here are fewer in number. About its centre we often observe a weU-
marked whitish depression [excavatio papillae n. optici], formed by the dispersion of the nerve-
fibres as they spread out over the fundus; at the bottom of this depression a sieve-like appearance
may be seen, due to the presence of the lamina cribrosa sclerae, which consists of a white fibrous
tissue framework, with small, roundish, light-grey meshes in it, through which the nerve-fibre
bundles pass. Also near the centre of the papiUa, the retinal blood-vessels first come into view,
the arteries narrower in size and lighter in colour than the veins; they divide dichotomously
as they are distributed over the fundus. The retina proper is so transparent as to be ophthal-
moscopically invisible, but its pigment-epithelium gives a very finely granular or darkly stippled
appearance to the general red reflex. In the centre of the fundus, and therefore to the lateral
side of the papilla, the ophthalmoscope often shows a shifting halo of light playing round a
Fig. 799. — The Normal Fundus op the Eyeball. (Parsons.)
horizontally oval, comparatively dark enclosed area; this latter corresponds to the yellow
spot [macula lutea] region, and about its centre a small pale spot usuafly marks the position of
the fovea centralis.
Two structures visible at the nasal end of the palpebral aperture have been previously
mentioned, and should now be examined more narrowly. The lacrimal caruncle is an island
of modified skin, and fine hairs can commonly be detected on its surface, and it contains sebaceous
and sweat glands. Lateral to it and separated from it by a narrow groove, is the semilunar
fold of conjunctiva; it rests on the eyeball, and is a rudiment of the third eyelid or nictitating
membrane, present in birds and well represented in many other vertebrates.
Examination of the Eyeball
(In the following account, the structure of the eyeball is described as it would
appear upon dissection.)
The eyeball [bulbus oculi] is almost spherical, but not perfectly so, mainly be-
cause its anterior, clear, or corneal segment has a greater curvature than the rest of
the eye. Considering it as a globe, it has an anterior pole [polus anterior] and
a posterior pole [polus posterior]; the former corresponding to the centre of the
front of the cornea, the latter to the center of the posterior curvature. An imag-
inary straight line joining the two poles is called the axis of the eyeball. The
equator of the eye is that part of its surface which lies midway between the two
poles. The various meridians are circles which intersect the poles. The sagittal
axis of the globe is the greatest (about 24 . 5 mm.), the vertical equatorial the least
1056
SPECIAL SENSE ORGANS
(about 23.5 mm.), and the transverse equatorial axis is intermediate in length
(about 23 . 9), so that the eyeball is in reality an ellipsoid, flattened slightly from
above downward. These figures refer to the adult male; in the female the eyeball
is . 5 mm. smaller in aU axes. Again, if the globe is divided in its mid-sagittal
plane, the nasal division will be found to be slightly smaller than the temporal.
The optic nerve joins the globe three or four millimetres to the nasal side of the
posterior pole.
The shape of the eye depends on, and is preserved by, the outermost tunic,
formed conjointly by the cornea and sclera, the entire outer surfaces of which are
now in view. The anterior or corneal part has already been examined. All around
the cornea there remains a little adherent conjunctiva; elsewhere, the sclerals
directly exposed, except for some loose connective tissue which adheres to it,
especially around the optic nerve entrance. In front of the equator we see the
tendinous insertions of the four recti muscles. Behind the equator are the inser-
tions of the two oblique muscles — that of the superior oblique tendinous, and
further forward; that of the inferior more fleshy, and placed between the optic
nerve and the lateral rectus.
Fig. 800. — Diagrammatic View of the Insertions of the Ocular Muscles.
Superior rectus
Lareral rectus
Inferior rectus
It is difficult to recognise the different recti muscles by their insertions if we do not know
whether the eye examined is a right or a left one. To determine this we should hold the globe
with the optic nerve toward us, and in the natural position with the superior oblique tendon
uppermost. The inferior oblique tendon will now point to the side to which the eye belongs,
and we can consequently determine the difTerent recti muscles.
The medial [m. rectus medialis] rectus is inserted nearest (5.5 to 7 mm. from) the corneal
border; the superior [m. rectus superior] rectus commonly, sometimes the lateral [m. rectus
laterahs], is inserted furthest from it (7.7 to 8 mm.). All the recti tendons are broad and thin,
but that of the medial is the broadest (8 to 10.3 mm.); those of the lateral and inferior the
narrowest (6 to 9.2, or 9.8 mm., respectively). The greatest interval between two neighbouring
tendons is that between the superior and medial recti (about 12 mm.); the least is between
the superior and lateral (7 mm.). The form of the lines of insertion of the different tendons
varies considerably, the inferior being almost straight, the superior and lateral convex forward,
the medial further removed from the corneal border below than above.
The insertions of the oblique muscles [mm. obliqui] are at more than double the average
distance of the insertions of the recti from the corneal border. That of the superior oblique is
found on the superior surface of the sclera, about sixteen millimetres from the corneal edge,
in the form of a line 10.7 mm. long sloping from before backward and medially. The inferior
oblique has a long fleshy insertion lying between the lateral rectus and the optic nerve entrance;
the posterior end of the insertion, which is also the higher, is only about five to six millipietres
from the optic nerve, and from this point it slopes forward, laterally, and slightly downward.
Several small nerves and two arteries may be seen running forward and ulti-
mately perforating the sclera not far from the entrance of the optic nerve. The
two arteries are the long posterior ciliary [aa. ciliares posteriores longi] ; they both
perforate the globe in the horizontal meridian, 3.5 mm. from the optic nerve, one
on the lateral, the other on the medial, side. The short ciliary arteries [aa. ciliares
THE EYEBALL 1057
posteriores breves] are too small to be seen in an ordinary examination. The
nerves are the long and short ciUary [nn. ciliareslongi, breves]. Nearer the equator
large venous trunks emerge; they can be traced for some distance in front of their
exit as dark lines, running antero-posteriorly internal to the sclera. The optic
nerve is seen in section, surrounded loosely by a thick outer sheath; in the centre of
the nerve-section a small red spot indicates the position of the central retinal
blood-vessels [a. et v. centralis retinae].
(The following structures appear in an eyeball divided into fore and hind halves by cutting
through it in the equatorial plane.)
1. Posterior hemisphere seen from in front. — This is much the same view that the ophthal-
moscope affords us. Unless the eye be very fresh, however, the retina will have lost its trans-
parency, and will now present the appearance of a thin whitish membrane, detached in folds
from the external coats, but still adherent at the optic papilla. The vitreous jelly lying within
the retinal cup may be torn away. In the human eye the retina next the posterior pole is stained
yellow [macula lutea]. On turning the retina over, a little pigment may be seen adhering to
its outer surface here and there. Cut through the retina close to the optic disc all around and
remove it: note how easily it is torn. We now see a dark brown surface, consisting of the
retinal pigment layer [stratum pigmenti retinas] adherent to the inner surface of the chorioid.
Brush off the retinal pigment under water. The chorioid thus exposed can for the most part
be fairly easily torn away from the thick sclera, as a lymph-space exists between them, but the
attachment is firm around the optic nerve entrance, and also where the arteries and nerves join
the chorioid after penetrating the sclera. The chorioid is darkly pigmented, of a brown colour,
with markings on its surfaces corresponding to the distribution of its large veins. The inner
Fig. 801. — Anteeiob Hemisphere of Eyeball, Viewed from Behind.
Pupil
Ciliary processes
surface of the sclera is of a light brownish colour, mainly from the presence of a delicate pig-
mented layer, the lamina suprachorioidea, which adheres partly to it, partly to the chorioid,
giving to their adjacent surfaces a flocculent appearance when examined under water.
2. Anterior hemisphere viewed from behind. — The round opening of the pupil is visible in
the middle, in front of the large clear crystalline lens. The retina proper extends forward a
little way from the line of section, and then ends abruptly in a wavy line called the era serrata,
beyond which it is only represented by a very thin membrane [pars ciliaris retinae]. Outside
the periphery of the lens are a number of ciliary processes arranged closely together in a circle
concentric with the pupil, and each radially elongated; posteriorly they are continuous with
n umerous fine folds, also radial, which soon get very indistinct as they pass backward, but
reach almost to the ora serrata [plicae ciliares]. Between the front of the ciliary processes and
the edge of the pupU lies the iris. On removal of the retina the inner surface of all this region
is seen to be darkly pigmented, but especially dark in front of the position of the ora serrata.
Vitreous probably still adheres to the back of the lens, and by pulhng upon it the lens can be
removed along with its capsule and suspensory ligament; some pigment will now be found
adhering to the front of the vitreous, torn from the ciliary processes, which are consequently
now lighter in colour than before. The lens-capsule is transparent, and has a smooth glistening
outer surface; through it a greyish, star-shaped figure may be observed on the anterior and
posterior surfaces of the lens. The suspensory ligament is a transparent membrane attached to
the capsule of the lens about its equator, and is best seen by floating the lens in water in a glass
vessel placed on a dark ground. On opening the capsule we expose the lens itself, which is
superficially soft and glutinous to the touch, but becomes firmer as we rub off its outer laj-ers and
approach its centre. Carefully tear the chorioid and iris from the sclerotic as far as possible;
a firm adhesion exists just behind the corneal periphery. The outer surface of the chorioid
thus exposed is found to be also rather darkly pigmented, taut it shows a white ring corresponding
to the adhesion just mentioned, and a pale area behind this ring indicates the position of
the ciliary muscle [m. ciharis]. On this surface numerous white nerve-cords are visible running
1058
SPECIAL SENSE ORGANS
forward. Observe that the iris, the ciliary processes, etc., and the chorioid are all different
parts of the same ocular tunic — mere local modifications of it. Similarly the sclera and cornea
are seen to blend together to form one outer coat.
An eyeball should now be placed for half an hour in a freezing mixture of crushed ice and
salt. It will thus become quite hard, and should at once be divided into two parts by cutting
it antero-posteriorly through the centre of the cornea and the optic nerve. We thus gain another
view of the relations of parts, the position of the lens between the aqueous and vitreous chambers,
etc. On removing the lens, vitreous, and retina, and brushing off its pigment, the light markings
corresponding to the chorioidal veins (venae vorticosse) should be noted, and their distribution
studied. Usually four vortices or fountain-like markings are found in the whole chorioid,
Fig. 802. — Horizontal Section of the Eyeball. X 4.
Anterior surface of lens
Optic axil
Corneal epithelium
Posterior surface of cornea '^^
Cornea
Crystalline lens
Zonula ciliaris
Posterior
surface of
lens
Sulcus sclerse
/ Lig. pectinatum iridis
I Posterior chamber
/ /Sinus venosus scle___
/ yScleral conjunctiva
^Anterior chambe
^^^^_- Angulus indis
Ciliary body
Ciliary processes
- Zonular fibres
Papilla of optic nerve
Lamina cribrosa scleras
A. Centralis retinse
Retina
dea
Macula latea and fovea centralis
Sclera
their points of junction situated at approximately equal distances from one another at about
the hne where the posterior and middle thii-ds of the globe meet. These sections should be kept
for reference while following the further description of the ocular tunics.
The coats of the eyeball. — 1. The outer, fibrous coat of the eye [tunica
fibrosa oculi] is formed by the sclera and cornea, which pass into one another
at the scleral sulcus. It consists throughout mainly of fine connective-tissue
fibres, arranged in interlacing bundles, with small lymph-spaces at intervals
between them. The naked-eye appearance of the two divisions of this fibrous
coat is, however, quite different, the cornea being transparent, while the sclera
is white and opaque.
The sclera encloses the posterior five-sixths or so of the eyeball. It is perfo-
THE CORNEA
1059
rated bj'' the entrance of the optic nerve, and the opening in the sclera, only
partially bridged across by fibres from the inner layers, forms the lamina
cribrosa.
The fibre-bundles composing the solera are arranged more irregularly than in the cornea,
and run mainly in two directions, viz., antero-posteriorly and circularly; the circular fibres
are particularly well developed just behind the sulcus. It is thickest (about 1 mm.) posteriorly,
where it is strengthened chiefly by the outer sheath of the optic nerve, and partly also by the
tissue surrounding the ciliary vessels and nerves. It becomes gradually thinner as it passes
forward, up to the line of insertion of the I'ecti muscles, where it is .3 mm. thick. In front of
that line it is again reinforced by their tendinous fibres becoming incorporated with it and its
thickness increases to .6 mm. In children the sclera is often so thin as to allow the underlying
chorioidal pigment to show through, its colour then appearing bluish white. In the aged, again,
it is sometimes yellowish. It always contains a few pigment cells, but these are in the deep
layer termed the lamina fusca, and only become visible externally where the sclera is pierced
by vessels and nerves going to the chorioid. It is almost non-vascidar, but quite at its anterior
end a large venous sinus [sinus venosus sclerse; canalis Schlemmi (Lauthi)], (canal of Schlemm)
runs in its deeper layers circularly around the cornea. Just in front of this sinus, at the corneal
limbus, the sclera merges into the cornea, its inner layers changing first, and finally the outer
ones.
Fig. 803.— Portion op Fig. 802, Enlarged.
Anterior surface of lens
Crystalline lens
Iris
/
Sulcus sclerEQ
t Lig, pectinatum iridis
I ^Posterior chamber
; venosus sclerae
/ Scleral conjunctiva
Anterior chamber
Angulus iridis
;.'*Circulus arteriosus majo
Ciliary muscle
Ciliary muscle, circular fibres
Ciliary processes
. Zonular fibres
Ora serrata
Insertion of
tendon of
rectus lateralis
The cornea forms the anterior sixth of the eyeball. It is thickest ,'at
its periphery (1.1 mm.) and becomes gradually thinner toward its centre
(0.8 mm.); the curvature of its posterior is consequently greater than that of its
anterior surface, but even the latter is more curved than the surface of the sclera.
In the cornea proper, fibre-bundles are arranged so as to form a series of superposed lameUse,
each of which is connected here and there to the adjacent ones by fibres passing from one to the
other, so that they can only be torn apart with difficulty. The corneal lymph-spaces communi-
cate with one another by very fine canals, and thus not only is a thorough lymph-circulation
provided for, but the protoplasm with which these spaces are partially occupied may be also
regarded as continuous throughout. It contains no blood-vessels, with the exception of a rich
plexus at its extreme periphery, on which its nutrition is ultimately dependent. The sinus
venosus o} Schlemm is an important channel for the return of blood and also of fluid which
transudes into it from the anterior chamber. It consists of a network of venous spaces, formed
of a principal vessel accompanied by several smaller ones, which unite with it and with one
another in a plexiform manner. -They commence indirectly with the spaces of the angle of the
iris and they are in direct communication with the anterior ciliary veins.
1060 SPECIAL SENSE ORGANS
The outer surface of the cornea is covered by an extension of the ocular conjunctiva, in
the form of an epitheUum several layers deep. The most external part of the true cornea appears
homogeneous, even when highly magnified and constitutes the anterior elastic lamina, Bow-
man's membrane, though there is reason to believe that its structure only differs from that
already described in the closeness of its fibrous texture; the two parts are certainly connected by
fine fibres. Posteriorly, the cornea is lined by a fu-m, thin, glass-hke layer (posterior elastic
lamina, membrane of Descemet), distinct from the corneal tissue both anatomically and chem-
ically. At the periphery this membrane breaks up into a number of fibres, which mainly arch
over to join the base of the iris and form part of the ligamentum pectinatum iridis. The pectin-
ate ligament is an open network of interlacing fibres, directly continuous with the circular
and longitudinal bundles of sclera surrounding the venous sinus of Schlemm (Henderson).
The interstices between these fibres constitute spaces (spaces of Fontana) [spatia anguli iridis
(Fontanse)] freely communicating with the aqueous chamber on the one hand, and indirectly
with the venous sinus of the sclera on the other. The posterior elastic lamina is in turn lined
by a single layer of flat cells, which are continuous peripherally with cells lining the spaces of the
angle and the anterior surface of the iris which form the endothelium of the anterior chamber.
The cornea is richly supplied with nerves, particularly in its most superficial layers.
2. The dark, middle, or vascular coat of the eye [tunica vasculosa oculi] i?
formed by the iris, ciliary body, and chorioid. It is closely applied to the sclera,
but actually joins it only at the anterior and posterior limits of their course to-
gether, viz., at the scleral sulcus, and around the optic nerve entrance. It is
separated from the sclera between these two points by a narrow slit-like lymp-
space [spatium perichorioideale]. In front of the sulcus, the middle coat is sepa-
rated from the outer (i. e., the iris from the cornea) by a considerable space filled
with fluid, caUed the anterior aqueous chamber. The vascular coat has two open-
ings in it; a larger one in front, the pupil, and a smaller one behind, for the passage
of the optic nerve. Its structure is that of a pigmented connective tissue, support-
ing numerous blood-vessels and containing many nerves and three deposits of
smooth muscle-fibres.
The chorioid [chorioidea] forms the posterior part of the vascular coat, and extends, with
slowly diminishing thickness, forward as far as the ora serrata. Its outer and inner surfaces
are botli formed by non-vascular layers; that covering the outer, the lamina suprachorioidea,
is pigmented, arranged in several fine loose lamelte; that covering the inner surface is a thin,
transparent, homogeneous membrane, called the basal lamina of the chorioid. The inter-
vening chorioidal stroma is very rich in blood-vessels, which are of largest size next its outer
surface constituting the lamina vasculosa. These become progressively smaller toward the
basal lamina, next to which is a layer of closely placed wide capillaries, called the lamina chorio-
capillaris. The pigment becomes less in amount as we pass inward, and finally ceases, being
absent entirely from the choriocapillary and basal laminae.
In front of the ora serrata the vascular coat becomes considerably modified'
and the part reaching from the ora serrata of the retina to the iris is termed the
ciliary region of the tract, or ciliary body [corpus ciliare]. Its superficial aspects
have been already briefly described. In front, the cihary processes, about seventy
in number, project toward the interior of the eye, forming the corona ciliaris. Be-
hind this part lies the orbiculus ciliaris, whose inner surface is almost smooth,
faint radial folds [plic£e ciliares] only being present, three or four of which join each
ciliary process.
The more minute structure of this ciliary region resembles closely that of the chorioid, except
that the chorio-capillaris is no longer present, that the stroma is thicker and richer in blood-
vessels, and that a muscular element (ciliary muscle) exists between the vascular layer and the
lamina suprachorioidea. On antero-posterior section the ciliary body is triangular; the shortest
side looks forward, and from about its middle the iris arises; the two long sides look respectively
inward and outward, the inner having the ciliary processes upon it, while the outer is formed by
the ciliary muscle. This muscle possesses smooth fibres and consists of an outer [fibrfe me-
ridionales (Brueckei)] and an inner division [fibra; circulares (Muelleri)]. The meridional fibres
take origin from the outer fibrous coat of the eye at the sclero-corneal junction in front, and pass-
ing backward to join the outer layers of the orbiculus ciliaris and chorioid; the circular fibres
are situated next to the ciliary processes. The entire muscle is destitute of pigment, and there-
fore is recognisable in the section by its light colour. The whole thickening of the vascular
tunic in this region, muscle and folds and processes together, is named the ciliary body. It
includes the corona ciliaris, formed of the ciliary processes and folds, and the orbicularis ciliaris
containing the ciliary muscle.
The iris projects into the interior of the front half of the eye in the form of a
circular disc perforated in the middle. The appearance of its anterior surface has
already been described. The anterior surface is covered with a layer of endothe-
lium except at the crypts near the cihary border. Thus the lymph spaces between
the stroma cells communicate directly with the anterior chamber. Its posterior
THE RETINA
1061
surface exhibits numerous radial folds running from the ciliary processes to near
the pupillary margin; a thick layer of black pigment covers it and curls around this
edge, so as to come into view all around the pupil as seen from in front. The
ciliary border of the iris is continuous with the front of the ciliary body, and there
it also receives fibres from the ligamentum pectinatum iridis; in other respects the
iris is quite free, merely resting on the front of the lens-capsule near the pupil.
Its stroma [stroma iridis] is spongy in character, being made up of vessels covered by a thick
adventitia, running from the periphery to the pupillary border, with interspaces filled by branch-
ing pigment cells, which are particularly abundant near the front surface. Deep in the stroma,
running around near the pupillary border, we find a broad flat band of smooth muscle-fibres,
constituting the m. sphincter pupillse. Immediately behind the vascular tissue hes a thin
membrane, consisting of fine, straight fibres running radially from the ciliary border to the
stroma behind the sphincter. The nature of these fibres was long in dispute, but they are now
accepted as being undoubtedly smooth muscular — and comprise the m. dilatator pupillae.
Fig. 804. — Diagrammatic Horizontal Section of Eyeball and Orbit.
(After Fuchs, much modified.)
Periorbita green; muscle-fascia red; Tenon's capsule yellow.
Lower lacrimal punctum
Cornea \ . Caruncle
Opening of Meibo:
Anterior chamber
Iris
Corona ciliaris
Orbiculus cili
Outer check ligament
Fovea centralis retina
Muscle-fascia
Orbital blood-vessel.
Central retinal vessels
optic nerve
External rectus muscle_
Inner palpebral ligament
Nasal process of
upper jaw
Anterior limb of
inner palpebral
ligament
Lacrimal sac
Posterior limb of inner
palpebral ligament
with Horner's muscle
springing from it
Lacrimal bone
Process of muscle-fas-
cia to under surface of
conjunctiva
Ora serrata
Tendon of insertion of
internal rectus
Inner check ligament
Periorbita
Orbital plate of ethmoid
bone
Posterior lamina of
muscle-fascia lined
by Tenon's capsule
Internal rectus muscle
The m. sphincter pupiUos and the ciliary muscle are supplied indirectly by the oculomotor
nerve through the ciliary ganglion. The dilatator pupillae is supplied by sympathetic fibres , which
have their origin from the cells of the superior cervical ganghon. Thence they ascend in the
carotid and cavernous plexuses, and join the ophthalmic division of the trigeminal nerve, passing
to the eyeball by way of the long ciliary nerves. The pre-ganglionic sympathetic fibres leave the
spinal cord by the motor roots of the first two or three thoracic nerves, and ascend the sympa-
thetic trunlv to the superior cervical ganglion without interruption.
The posterior surface of the iris is lined by pigment already mentioned, consisting of two
layers of pigmented cells, each layer representing the extension forward of one subdivision of
the retina. The anterior surface of the iris is covered by a delicate epithehal layer, continuous
with the ceils of the posterior elastic lamina of the cornea. The colour of the iris in
different individuals depends upon the amount of stromal pigment.
3. The retina. — The inner surface of the vascular coat is everywhere lined by a
layer of pigment of corresponding extent, which usually adheres to it closely on
dissection.
1062 SPECIAL SENSE ORGANS
Developmentally this general pigment lining is quite distinct from the vascular coat, and
represents the outer wall of the secondary optic vesicle or embryonic retina; it consists of a single
layer of pigmented epithelial cells. It is known as the slratum pigmenti. The amount of
pigment is greatest anteriorly, over the ciliary region and iris, and there is again a small local
increase posteriorly, corresponding to the macula lutea and to the edge of the optic nerve en-
trance. In the ciliary region these cells have recently been described as Uning numerous nar-
row tubular depressions in the inner part of the vascular tract, and they are said to have here a
special function, viz., that of secreting the intraocular fluid.
From the manner in which the secondary optic vesicle, or optic cup, is formed,
its two walls are necessarily continuous in front, at what may be termed the lip of
the cup; we have just observed that the outer wall lines the vascular coat every-
where and corresponds in extent; consequently, the lip must be looked for at the
edge of the pupil, i. e., at the termination of this coat anterorly. The inner wall of
the cup, consequently, reaches from the lip, or pupillary edge, in front to the optic
stalk or nerve behind, and is in close apposition to the pigment-epithelium; unlike
the outer, however, this wall is represented in the developed eye by tissues very
dissimilar in structure in different parts of its extent. Tracing it backward from
the pupillary edge, we find that over the whole posterior surface of the iris it exists
as a single layer of pigmented epithelium, the two layers of the cup having here
produced a double layer of pigment cells. At the root of the iris the single inner
layer of cells still exists; but now they become destitute of pigment, and this con-
dition obtains over the entire ciliary region, constituting what is known as the pars
ciliaris retinae. At the l^ne of the ora serrata the tissue derived from the inner
wall abruptly increases in thickness, and rapidly acquires that complexity of
structure characteristic of the retina proper, which extends from here to the optic
nerve and is termed the pars optica retinas. It consists of several layers — nerve-
fibres, nerve-cells, and nerve-epithelium — held together by a supporting frame-
work of delicate connective tissue.
The nerve-epithelium is on the outer surface, immediately applied to the pigment-epithe-
lium; at the posterior pole of the eye a small spot [fovea centralis] exists, where this is the only
retinal layer represented, and where consequently the retina is extremely thin. The nerve-
fibres run on the inner surface of the retina and are continuous with those of the optic nerve;
they constitute the only retinal layer that is continued into the intraocular end of the nerve.
The nerve-cells are found between these surface layers. The larger blood-vessels of the retina
run in the inner layers, and none encroach on the layer of nerve-epithelium.
Fig. 805. — The Lens. (Side view; enlarged.)
Within the coats mentioned, the interior of the eyeball is fully occupied by con-
cents, which are divided into three parts, which are named according to their
consistence and anatomical form. They are all transparent, as through them the
light has to pass so as to gain the retina. Of these, the only one that is sharply and
independently outlined is the lens, which is situated in the anterior half of the globe
at the level of the ciliary processes, where it is suspended between the other con-
tents, which fill respectively the space in front of it and the space behind it. The
space in front of the lens called the aqueous chamber; that behind the lens is the
vitreous chamber.
The lens [lens crystallina] is a biconvex disc, with its surfaces directed ante-
riorly and posteriorly; these surfaces meet at its rounded-off edge or equator
[sequator lentis] which is near (but does not touch) the adjacent ciliary processes.
The posterior is considerably more convex than the anterior surface; the central
part of each surface is called its pole [polus anterior; polus posterior]. The lens
is closely encased in a hyaline elastic capsule [capsula lentis] thicker over the an-
terior than over the posterior surface. Thus enclosed, it is held in position in the
globe by a suspensory ligament, attached to the lens capsule near the equator of
the eye, and swung from the ciliary region. Posteriorly, the lens rests in a cup
THE LENS
1063
formed by the front part of the vitreous, while its anterior capsule is in contact
with the aqueous fluid and lies close against the back of the pupillary margin of
the iris. When in position the lens measures nine millimetres across, and about
four millimetres between its poles.
On each surface a series of fine, sinuous, grey lines can be seen radiating from the pole to-
ward the equator, called respectively the anterior and posterior stellate figures. The liiies
observable on the posterior are always so placed as to be intermediate with those on the anterior
surface, so that on viewing them through the lens they occupy a position corresponding to the
Fig. 806. — Diagrammatic Representation op the Blood-vessels of the Eyeball.
(Parsons, after Leber.)
Arteries red; veins blue.
s.p., Short posterior ciliary arteries, l.p.c, Long posterior ciliary artery, a.c, Anterior
ciliary vessels. C of S., Canal of Schlemm. c.a.i.ma., Circulus arteriosus iridis rnajor. v.v,.
Venae vorticosEe. a. conj., Anterior conjunctival vessels, p. conj., Posterior conjunctival vessels.
intervals between the lines on the anterior surface. The lens-capsule is comparatively brittle,
and can be readily cut through when scraped with a sharp-pointed instrument; on doing so the
divided edges curl outward, away from the lenticular substance. When removed from its
capsule, the outer portion of the lens is found to be soft and glutinous, but its substance gets
progressively firmer as we approach the centre. This harder central part is known as the
nucleus [nucleus lentis], and the surrounding softer matter as cortex [substantia corticahsj.
The cortical part shows a tendency to peel off in successive layers. It consists of long fibres,
the ends of which meet in front and behind at the anterior and posterior stellate figures.
1064
SPECIAL SENSE ORGANS
Histologically the capsule is not in immediate contact with the cortex over the front surface
of the lens, a single layer of cells intervening, called the epithelium lentis.
The zonula ciliaris or suspensory ligament of the lens is formed by a number of
fine zonular fibres [fibrse zonulares] passing from the ciliary body. They are
attached to the lens-capsule a little in front of and behind the equator, and the
spaces included between the fibres of the ligament are termed the zonular
spaces [spatia zonularia]. A continuous space, which can.be injected after
death, round the margin of the lens is known as the canal of Petit. It is probably
an artefact. This space is bridged across by fine intermediate suspensory
fibres, and is occupied by fluid.
The vitreous body [corpus vitreum] is a transparent, colourless, jelly-like mass,
the vitreous humour, enclosed in a delicate, clear, structureless membrane, called
the hyaloid membrane. This latter is closely applied to the back of the posterior
lens-capsule and of the suppensorj^ ligament, and to the inner surface of the pars
ciliaris retinse, retina proper, and optic papilla. Although possessing some degree
of firmness, the vitreous humour contains quite 98 per cent, of water, and has no
definite structure.
Fig. 807. — Blood-vessels of the Eyeball, Lateral View.
Cornea
Anterior chamber
Sclero-corneal junction
g Anterior ciliary artery
Long posterior
"* ciliary artery
4 J'7~ """■■• V. Vorticosa
Optic nerve ----
Arteria centralis retinse
Membranes have been described in it, but these are really artificial products. In certain
situations spaces e.xist in the vitreous mass, the most determinate of which runs in the form of a
canal from the optic papilla to the posterior pole of the lens, corresponding to the position of
the foetal hyaloid artery (hyaloid canal or canalis hyaloidea). Other very fine spaces are de-
scribed running circularly in the peripheral part of the vitreous concentric with its outer sur-
face. Microscopically, wandering cells are found in the vitreous, which often here assume
pecuhar forms which the observer can, not infrequently, study subjectively.
The aqueous humour is a clear, watery fluid, occupying the space between the
cornea on the one hand, and the ciliary body, zonula ciliaris, and lens on the other.
The iris, projecting into this space, has both its surfaces liathed in the aqueous;
but, as its inner part rests on the lens, it is regarded as <liviiling the sjiace into two
parts, an anterior larger, and a posterior smaller, aqueous chamber [camera oculi
anterior; posterior], which communicate freely through the pupil.
Ciliary nerves of the eyeball. — The long and short ciliary nerves, after per-
forating the sclera run forward between it and the chorioid to the ciliary region.
LYMPHATIC SYSTEM OF EYEBALL 1065
where they form a plexus, from which proceed branches for the ciUary muscle, the
iris, and the cornea.
The nerves of the iris enter it at its ciliary border, and run toward its pupillary edge, losing
their medullary sheath sooner or later, and supplying especially the sphincter muscle. The
corneal nerves form an annular plexus near the limbus, from which a few twigs proceed to the
sclera and conjunctiva, while most of the offsets enter and run radially in the corneal stroma,
branching and anastomosing so as to form a plexus. The nerves entering the cornea are about
sixty in number, each containing from two to twelve non-medullated nerve-fibres.
Blood-vessels of the eyeball. — The eyeball receives blood from two sets of
vessels, viz., the retinal and the ciliary arteries, as described in the section on
the Blood-vascular System.
1. The arteria centralis retinae either comes direct from the ophthalmic artery, or from one
of its branches near the apex of the orbit. Entering the optic nerve twenty miUimetres or less
behind the globe, it runs forward in its axis to the end of the nerve-trunk, and then divides into
branches which run in the inner layers of the retina, and divide dichotomously as they radiate
toward the equator. The smaller branches lie more deeply in the retina, but none penetrate into
the nerve-epithelium, so that the fovea centralis is non-vascular. In the retina, the branches
of the central artery do not communicate with any other arteries, but while still in the optic
nerve fine communications take place between this artery and neighbouring vessels. Thus
(a) minute twigs from it, which help to nourish the axial pai-t of the nerve, communicate with
those running in the septa derived from the pial sheath. Again, as the nerve passes through
the sclera, it is surrounded by a vascular ring [circulus vasculosus n. optici (Halleri)], formed
of fine branches derived from the short posterior cihary arteries; fine twigs passing inward
from this ring to the optic nerve join the vessels of the pial sheath, and (b) an indirect communi-
cation is thus brought about between the retinal and ciliary vessels. Finally, as the nerve passes
through the chorioid, there is (c) a direct connection between these two sets of vessels, the cap-
illary network of the optic nerve being here continuous with the chorio-capillaris. Not infre-
quently, a branch from a short posterior ciliary artery pierces the optic papilla, and then courses
over the adjoining retina (a cilio-retinal artery), supplying the latter in part in place of the cen-
tral artery.
The branches of the a. centralis retina in the retina are: arteriola temporalis retinae supe-
rior, arteriola temporalis retinse inferior, arteriola nasalis retinae superior, arteriola nasalis
retinte inferior, arteriola macularis superior, arteriola macularis inferior, arteriola retinae
medialis.
The vena centralis retinae returns the blood of the corresponding artery and has branches
corresponding to those of the artery.
2. The ciliary system of blood-vessels (see Blood- Vascular Sj'stem). — There are three sets
of arteries belonging to this system, all derived directly or indirectly from the ophthalmic
artery.
(1) Short posterior ciliary arteries twelve to twenty in number, pierce the sclera round the
optic nerve entrance, and are distributed in the chorioid. Before entering the eyeball, small
twigs are given off to the adjoining sclera and to the dural sheath of the optic nerve.
(2) Two long posterior ciliary arteries, medial and lateral, piercing the sclera further from
the nerve than the short ciharies, run horizontally forward between the sclera and chorioid,
one on each side of the globe. On arriving at the ciliary body, they join with the anterior ciliary
arteries, forming the circulus arteriosus major, which sends off branches to the ciliary processes
and the iris. The long ciliaries also give twigs to the cihary muscle, and small recurrent branches
run backward to anastomose with the short ciliary arteries. The arteries of the iris run radially
toward the pupillary border, anastomosing with one another opposite the outer border of the
sphincter and forming there the circulus arteriosus minor.
(3) The anterior ciliary arteries come from the arteries of the four recti muscles, one or
two from each; they run forward, branching as they go, and finally pierce the sclera near the
corneal border. Externally to the globe they send twigs to the adjoining sclera, to the conjunc-
tiva, and to the border of the cornea. After passing through the sclera the arteries enter the
ciliary muscle, where they end in twigs to the muscle and to the circulus arteriosus major, and
in recurrent branches to the chorioid.
Veins. — The venous blood from almost the whole middle coat (chorioid, ciliary processes
and iris, and part of the ciliary muscle) ultimately leaves the eyeball by — (1) the venae vorticosae,
which have been already noticed in describing an antero-posterior section through the globe.
One large vein passes backward from each vortex, piercing the sclera obliquelj'; it is joined by
small episcleral veins when outside the globe.
(2) The anterior ciliary veins commence by the junction of a few small veins of the ciliary
muscle; they pass outward through the sclera near the corneal border, receiving blood from the
veins in connection with the sinus venosus of the sclera, and afterward from episcleral and con-
junctival veins, and from the marginal corneal plexus. Finally they join the veins running
in the recti muscles.
Lymphatic system of the eyeball. — Apart from those in the conjunctiva there
are no Ij^mphatic vessels in the eyeball, but the fluid is contained in spaces of vari-
ous sizes. These are usually divided into an anterior and a posterior set.
1. Anteriorly, we have the anterior and posterior aqueous chambers (together
composing the aqueous chamber of the ej^e), which communicate freelj' through the
pupil. The aqueous humour is formed in the posterior of these chambers by
1066
SPECIAL SENSE ORGANS
transudation from the vessels of the ciliary body and posterior surface of the iris
(see also page 1076). The stream passes mainly forward through the pupil into
the anterior aqueous chamber, whence it escapes slowly by passing through the
spaces of the angle of the iris into the venous sinus of the sclera, and thence into
the anterior ciliary veins. Part of the lymph-stream passes from the posterior
aqueous chamber backward into the zonular spaces, out of which fluid can pass
into the lens substance, or diffuse itself into the front of the vitreous body.
In the cornea the lymph travels in the spaces already mentioned as existing
between the fibre-bundles, and in the nerve-chaiinels and at the periphery of the
cornea it flows off into the lymphatic vessels of the conjunctiva.
In the iris there is a system of lymphatic spaces opening anteriorly into the
crypts of the surface, and communicating peripherally with the spaces of the angle
of the iris.
Fig. 808.-
-Lymphatic Spaces of the Eyeball (in green).
Anterior chamber
Filtration angl
Zonular space
V. Ciliaris anterior
Sinus venosus sclerse
Corpus ciliare
Spatium interfasciale (Tenoni)
Supravaginal space
Intervaginal space
2. Posteriorly, we have (a) the hyaloid canal, between the posterior pole of the
lens and the optic nerve entrance, and (6) the perivascular canals of the retina;
the lymph from both of these situations flows into the spaces of the optic nerve,
which communicate with the intervaginal spaces of the nerve, and thus with the
great intracranial spaces. Further, between chorioid and sclera we have (c) the
perichorioidal space, which gets the lymph from the chorioid, and communicates
with the interf ascial space (of Tenon) outside the sclera by perforations correspond-
ing to the vasa vorticosa and posterior cihary arteries, and with the intervaginal
spaces around the optic nerve entrance. The interfascial space of Tenon, again,
is continuous with the supravaginal space around the optic nerve, which conamuni-
cates both with the intervaginal spaces, with the lymph-spaces of the orbit, and
directly with the intracranial spaces at the apex of the orbit.
CAVITY OF THE ORBIT
General Arrangement of its Contents
The anterior wider half of the cavity is mainly occupied by the eyeball, which
lies almost axially, but is rather nearer to the upper and lateral than it is to the
other walls. The posterior two-thirds of the globe are in relation with soft parts,
MUSCLES OF THE ORBIT
1067
chiefly muscles and fat, and its posterior pole is situated midway between the base
(or opening) and the apex of the orbital cavity. The anterior third of the eye-
ball is naturally free, except for a thin covering of the conjunctiva, and projects
slightly beyond the opening of the orbit, the degree of prominence varying with
the amount of orbital fat, and also to some extent with the length of the globe. A
straight line joining the medial and lateral orbital margins usually cuts the eye
behind the cornea — laterally behind the ora serrata, medially further forward, at
the junction of the ciliary body and iris. The globe is held in position by numer-
ous bands of connective tissue. The lacrimal gland lies under the lateral part of
the roof of the orbit anteriorly. The orbital fat occupies the spaces between the
orbital muscles, and is in greatest amount immediately behind the eyeball; it also
exists between the muscles and the orbital walls in the anterior half of the cavity.
Six muscles, viz., the four recti, the superior oblique, and the levator palpebrae
superioris, arise at the apex of the orbit, and diverge as they pass forward. The
recti muscles — superior, inferior, lateral, and medial — rim each near the corre-
FiQ. 809.-
-Horizontal Section op the Oebital Region, Viewed From Above.
Nasal septum
Nasal fossa
/ Infundibulum
Ethmoidal cells
' Medial wall of orbit
Palpebra superior
Cornea
■^?*- Ciliary processes
1^'
Lateral v/all of orbit
spending orbital wall, but the superior is overlapped in part by the levator pal-
pebrae. The superior oblique lies about midway between the superior and medial
recti. A seventh muscle, the inferior oblique, has a short course entirely in the
anterior part of the orbit, coming from its medial wall and passing below the globe
between the termination of the inferior rectus and the orbital floor. The optic
nerve with its sheaths passes from the optic foramen to the back of the eyeball,
surrounded ^by the orbital fat, and more immediately by a loose connective tis-
sue. Among the contents of the cavity are also to be enumerated many vessels
and nerves and fibrous tissue septa, while its walls are clothed by periosteum
(periorbita) .
The muscles of the orbit are seven in number, of which six are ocular, i. e., are inserted into
the eyeball and rotate it in different directions. These ocular muscles are arranged in opponent
pairs, viz., superior and inferior recti, superior and inferior obliques, lateral and medial recti.
With the exception of the short inferior oblique, they all arise from the back of the orbit along
with the seventh orbital muscle, the levator palpebrse superioris. All these long muscles take
their origin from the periosteum in the vicinity of the optic foramen. The four recti muscles
arise from a fibrous ring, the annulus tendineus communis, which arches close over the upper
1068
SPECIAL SENSE ORGANS
and medial edge of the foramen, and extends down and out so as to embrace part of the opening
of the superior orbital fissure. Their origins may be said at first to form a short, common,
tendinous tube, from which the individual muscles soon separate, taking the positions indicated
by their respective names. The lateral rectus has two origins from bone, one on either side of
the superior orbital fissure. But in the fresh state the fissure is here bridged across by fibrous
tissue, from which this rectus also springs, so that its origin is in reality continuous. The part
of this fibrous ring nearest the foramen (corresponding to the origins of the superior and medial
recti) is closely connected with the outer sheath of the optic nerve. The remaining two long
muscles arise just outside the upper and medial part of the above-mentioned ring, and are often
partially united; the levator palpebrEB tendon is in close relation to the origin of the superior
rectus, while the superior oblique arises from the periosteum of the body of the sphenoid bone
one or two millimetres in front of the origin of the medial rectus.
The four recti muscles lie rather close to the coi-responding orbital walls for the first half of
their course, the superior rectus, however, being overlapped in part by the levator palpebrse;
they then tm-n toward the eyeball, running obliquely through the orbital fat, and are finally
inserted by broad, thin tendons into the sclera in front of the equator. From their respective
positions in the orbit, the axis of this cone of muscles is obHque to the antero-posterior axis of
the eyeball. The thickest of these muscles is the medial rectus, next the lateral, then the infe-
FiG. 810. — Dissection op the Left Orbit fkom in Front.
Levator palpebrse superioris
Sclera
Tendon of superior oblique
I Superior rectus
Lacrimal gland
•y -^' Lateral rectus
~ Inferior rectus
- Orbital adipose
Medial rectus
Inferior oblique
rior, and the superior rectus is the thinnest. As regards length, the muscular belly of the superior
rectus has the longest course, and the others diminish in the order — medial, lateral, and inferior
rectus. The lateral rectus is supplied by the abduoens nerve. The other three recti muscles
are aU supplied by the oculomotor nerve.
The levator palpebras superioris courses along the roof of the orbit close to the periosteum
for the greater part of its course, partially overlapping the superior rectus; it finally descends
through the orbital fat, and widens out to be inserted into the root of the upper hd. It may be
briefly described as being inserted in two distinct layers separated by a horizontal interval.
The upper or anterior layer of insertion is fibrous, and passes in front of the tarsus) where it comes
into relation with fibres of the orbicularis. The lower layer consists of smooth muscle (Miiller's
superior tarsal muscle), and is inserted along the upper border of the tarsus. The levator has
also, connections with the sheath of the superior rectus. These different insertions of the muscle
will be referred to later along with the description of the orbital fasciae and of the upper eyelid.
It gets its nerve supply from the oculomotor nerve, but the smooth muscle developed in its lower
layer of insertion is supplied by the sympathetic nervous system. As its name expresses, its
action is to raise the upper lid and to support it while the ej'e is open.
The superior oblique runs forward close to the medial part of the orbital roof until it reaches
the fovea trochlearis near the medial angular process, where it becomes tendinous and passes
through a fibro-cartilaginous pulley attached to the fovea just named. On passing through
this pulley, or trochlea, the tendon bends at an angle of 50°, running posteriorly and laterally
under the superior rectus to its insertion into the sclera. It is supplied by the trochlear nerve.
The inferior oblique arises from the front of the orbit, about the junction of its medial and
inferior walls, just lateral to the lower end of the lacrimal gi-oove. It runs, in a sloping direction,
laterally and posteriorly, lying at first between the inferior rectus and the orbital floor, then
between the lateral rectus and the globe; finally it ascends slightly, to be inserted by a short
MUSCLES OF THE ORBIT
1069
tendon into the sclera at the back of the eye. Its nervous supply is derived from the oculomotor
nerve. The precise manner of insertion of the different ocular muscles has been described
above (p. 1056). For muscles of the eyehds and eyebrows, see pp. 1077 and 1078.
Action of the ocular muscles. — While rotating the globe so that the cornea is turned in
different directions, the ocular muscles do not alter the position of the eyeball in the orbit either
Fig. 811. — Section through Contents of Right Orbit 8-11 mm. behind the Eyeball,
VIEWED FROM Behind. (After Lange.)
Supraorbital nerve
Supraorbital artery
Levator palpeb:
supenons muscle
Lacrimal nerve
Optic nerve
Ciliary artery
Central retinal v"'./
artery ^^-^
Ciliary artery
j — Ciliary artery
Oculomotor nerve
(branch to inferior
oblique muscle)
Fig. 812. — Diagram Representing the Origin of the Muscles at the Apex
OF the Right Orbit.
Lacrimal Frontal Trochlear Levator palpebree
nerve superioris
Superior oblique
-- — 1^ Optic nerve and
ophthalmic artery
Medial rectus
Lateral Naso- Abducens
rectus ciliary
nerve
Inferior rectus
Oculomotor nerve
laterally, vertically, or antero-post^riorly. In speaking, therefore, of the eye being moved
upward or laterally^ etc., it is the altered position of the cornea or front of the eye that we mean
to express; it is manifest that, if the cornea moves up, the back of the eyeball must simultane-
ously be depressed., and similarly with other movements. All the movements of the globe take
1070
SPECIAL SENSE ORGANS
place by rotation, on axes passing through the centre. Though the possible axes are numerous
in combined muscular action, there are three principal axes of rotation of the eyeball, and in
reference to these the action of individual muscles must be described. Two of these axes are
horizontal and one vertical; they all pass through the centre of rotation at right angles to one
another. By rotation of the eye on its vertical axis the cornea is moved laterally (toward the
temple) and medially (toward the nose) : movements called respectively abduction and adduc-
FiG. 813. — Dissection of the Muscles of the Right Orbit, Lateral View,
Frontal sinus
N. frontalis
Frontal sinus
Superior oblique \
Levator palpebrae superioris
Rectus superior ^
Rectus medialis \ ^
Optic nerve
Annulus tendineus com- >
mums (Zinni) ^
Lesser wing of sphenoid \
Sheath of optic nerve
Rectus inferior
Lateral rectus
Inferior oblique
tion. In upward and downward movements of the cornea the eye rotates on its horizontal
equatorial axis. The other principal axis of rotation is the sagittal, which we have previously
described as corresponding to the line joining the anterior and posterior poles of the globe
(page 1055). In rotation of the eye on its sagittal axis, therefore, the cornea may be said to
move as a wheel on its axle, for its centre now corresponds to one end of the axis; in other words,
this is a rotation of the cornea. Such movements may, consequently, be expressed with refer-
ence to their effect on an imaginary spoke of the corneal wheel — e. g., one- running vertically
Fig. 814. — Dissection of the Mttsclbs of the Left Okbit, From Above.
Lateral rectus
Inferior oblique J
Rectus medialis
Rectus superior
, Tendon of superior oblique '
! ; Trochlea of superior oblique
Levator palpebrae superioris
Levator palpebrae superioris
Periorbita
upward from the corneal centre. Thus we may say 'rotation of the cornea laterally' when this
part of the wheel moves toward the lateral angle, or 'medially' when toward the nose.
The only two muscles that rotate the eyeball merely on one axis are the lateral rectus and
the medial rectus ; the former abducting, and the latter adducting, the cornea. The action of
the superior and inferior recti is complicated by the obliquity of the axes of muscles and globe
previously mentioned.
ORBITAL FASCIM
1071
The chief action of the superior rectus is to draw the cornea upward, but at the same time
it adducts and rotates the cornea medially.
The inferior rectus mainly draws the cornea downward, also adducting it and rotating it
laterally.
The chief action of the superior oblique is to rotate the cornea medially, also drawing it
downward and slightly abducting it.
The inferior oblique mainly rotates the cornea laterally, also drawing it upward and slightly
abducting it.
The fasciae of the orbit [fascise orbitales]. — The orbital contents are bound to-
gether and supported by fibrous tissues, which are connected with each other, but
which may conveniently be regarded as belonging to tliree systems. These are : — •
(1) Those lining the bony walls; (2) those ensheathing the muscles; and (3) the
tissue which partially encapsules the eyeball.
1. The orbital periosteum [periorbita], is closely applied to the bones forming
the walls of the cavity, but may be stripped off with comparative ease. It pre-
sents openings for the passage of vessels and nerves entering and leaving the orbit.
Periorbita
Fig. 815. — Diagram Representing the Orbital Fasciss in Vertical Section.
black; muscular sheaths violet; Tenon's capsule green.
Tbicularis oculi
' Periorbita and septum orbitale
' Anterior insertion of levator palpebrae
Process from periorbita to slieatli of lacrimal gland
Sheath of levator palpebrse
Periorbita
. levator palpebrse superioris
. rectus superior
Space filled by orbital fat
Fascial sheath of optic
ic nerve
M. rectus inferior
M. obliquus inferior
Posteriorly this tissue is very firm, being joined by processes of the dura mater at the optic
foramen and superior orbital fissure; at the optic foramen it is also connected with the dm'a
sheath of the optic nerve. As it covers the inferior orbital (spheno-maxillary) fissure its fibres
are interwoven with smooth muscle, forming the orbital muscle of MtiUer. From its inner sur-
face processes run into the orbital cavity, separating the fat lobules. One important process
comes from the periorbita about midway along the roof of the orbit, runs forward to the back of
the upper division of the lacrimal gland, and there spUts, helping to form the gland-capsule:
this capsule is joined at its medial border by other periorbital bands coming off near the upper
orbital rim, and forming the suspensory ligament of the gland. On the side of the orbit the peri-
orbita sends fibrous processes to the trochlea of the superior obUque, which keep it in position.
On arriving at the lacrimal groove the periorbita divides into two layers, a thin posterior one
continuing to line the bone forming the floor of the groove, whilst the thicker anterior layer
bridges over the groove and the sac which lies in it, forming the limbs of the medial palpebral
ligament (p. 1052).
Quite anteriorly, at the rim of the orbit, the periorbita sends off a membranous process which
aids in forming the fibrous tissue of the eyelids (orbito -tarsal ligament, or palpebral fascia),
and is itself continuous with the periosteum of the bones outside the orbital margin.
2. The orbital muscles are connected by a common fascia, which splits at their
borders and furnishes a sheath to each. Processes of this fascia give membranous
investments for the vessels and nerves (including the optic nerve), splitting simi-
1072
SPECIAL SENSE ORGANS
larly to enclose them; these membranous processes also assist in separating the
fat lobules.
Posteriorly, this fascia is thin and loose, and blends with the periorbita at the origin of the
muscles. Anteriorly, it becomes thicker and firmer, accompanies the muscles to near the equa-
tor of the eyeball, and there divides into two laminte, an anterior and a posterior; the former
continues a forward course, forming a complete funnel-shaped investment all around, passing
ultimately to the eyelids and orbital margin — whilst the latter turns backward, covering the
hinder third of the globe.
The anterior lamina is a well-marked membrane everywhere, but in certain situations it
presents special bands of thickening, corresponding to the direct continuation forward of the
sheath of each rectus muscle. Above and below, this lamina spreads out in the form of two
large membranes, which are finally applied to the deep surface of the palpebral fascia; the lower
membrane constitutes what has been described as the suspensory hgament of the eyeball.'
The upper membrane requires a fuller description, as its distribution is modified by the presence
of the levator palpebrae muscle.
Fig. 816. — Hokizontal Section Through Left Orbit, viewed prom above.
(After von Gerlach. To show check ligaments, etc.)
Conjunctival fornix
Lacrimal gland
Palpebral raphe
Lateral check ligament-
Lateral orbital wall
Lateral rectus
Orbital fat
Space occupied by
subconjunctival tis-
^_^_^ sue, and by fascia
YhH bulbi further back
' Upper part of Horner's
muscle
Palpebral fascia
Medial check ligament
Medial wall of orbit
Medial rectus
Ethmoidal cells
The upper part of the sheath of the superior rectus (along with the adjoining membrane on
each side of it) passes to the deep surface of the levator, to which it closely adheres, and com-
pletely ensheaths this tendon by extending round its borders to its upper surface. The lower
part of this levator sheath is applied to the inferior surface of the deeper of the two divisions of
the levator muscle, superior tarsal muscle, and is attached to the upper border of the tarsus of
the upper lid, reaching on each side to the lateral and medial angles of the orbit. The upper
part of the sheath of the superior tarsal muscle reaches to the middle of the palpebral fascia, and
is mainly continued forward between the muscle and the fascia to the anterior surface of the
tarsus.
The lower membrane (suspensory ligament of the eyeball), joined by the sheath of the
inferior rectus, reaches forward to the attached (posterior) border of the tarsus of the lower lid,
where it is mainly attached, while a part of it extends to the lower palpebral fascia.
To understand the special bands of the anterior lamina mentioned above, we must follow
the sheath of each rectus muscle forward, when we find that, while it is rather loosely applied
to the muscular belly in its posterior two-thirds, it then suddenly becomes thicker, and is
firmly attached to the muscle for some distance before finally leaving it, and is thereafter often
accompanied by some muscle-fibres. The best developed of these bands, the lateral check
ligament, passes anteriorly and laterally to the lateral angle of the orbit, helping to support the
lacrimal gland on its way, and is inserted near the orbital edge immediately behind the
lateral palpebral raphe. The medial band, or medial check ligament, is larger than the lateral,
but not so thick; it passes forward and medially to be inserted into the upper part of the lacrimal
crest and just behind it. These two bands, lateral and medial, come from the sheaths of the
THE OPTIC NERVE 1073
corresponding recti muscles. From the sheath of the superior rectus come two thin bands, one
from each border. The medial joins the sheath of the tendon of the superior obhque; the
lateral goes to the lateral angle of the orbit, assisting in the support of part of the lacrimal
gland. The sheath of the inferior rectus is thickened in front, and, on leaving the muscle, goes
to the middle of the inferior oblique, splitting to enclose it; it then passes to be inserted into the
lower medial angle of the orbit close behind its margin, about midway between the medial check
ligament and the orbital attachment of the inferior obhque.
3. In addition to its partial investment by the muscle-fascia, the eyeball has a
special membrane enclosing its hinder two-thirds, the fascia bulbi ("Tenon's
capsule").
This is a thin, transparent tissue, situated immediately internal to the posterior lamina of
the muscle-fascia. It follows the curve of the solera from the insertion of the recti to about 3
mm. from the optic nerve entrance. There it leaves the eyeball and blends with the posterior
lamina of the muscle-fascia; the combined membrane may be traced backward, enveloping the
optic nerve-sheath loosely, approaching it as it nears the optic foramen, but never actually
joining it. The interval between it and the nerve-sheath is called the supravaginal lymph-space.
The fascia bulbi first comes into relation with the muscles at the point where they are left by
their proper sheaths; it there invests their tendons, forms a small serous bursa on the anterior
surface of each, and adheres to the sclera along a line running around the globe, just anterior
to the insertions of the four -recti muscles. Between this line and the corneal border, the con-
junctiva is separated from the sclei'a by the subconjunctival tissue, strengthened by a fine
expansion of the muscle-fascia.
The inner surface of the fascia is smooth, and is onlj^ connected with the sclera
by a loose, wide-meshed areolar tissue. This interval between the sclera and
fascia, known as the interfascial (Tenon's) space, is a Ij^mph cavitJ^ and permits
free movements of the eyeball within the capsule.
Relation of the Fascia Bulbi to the Oblique Muscles. — The fascia surrounds the posterior third
of the inferior oblique and its tendon, running along its ocular sm'face till it meets the fascial
band coming from the inferior rectus (see above), and forming a serous bursa on the superficial
surface of the oblique near its insertion. The tendon of the superior oblique for about its last
five milhmetres is invested solely by the fascia bulbi; in front of this, as far as the trochlea, the
tendon lies in a membranous tube derived from the muscle fascia, the inner lining of which is
smooth, and may be considered as a prolongation of the fascia bulbi.
The Optic Nerve
The part of this nerve with which we have here to do lies within the orbit, ex-
tending from the optic foramen to the eyeball (fig. 813). The length of this
portion of the nerve is from 20 to 30 mm. and its diameter about 5 mm. Its course
is somewhat S-shaped; thus, on entering the orbit, it describes a curve, with its
convexity down and laterally, and then a second slighter curve, convex medially.
Finally, it runs straight forward to the globe, which it enters 3 to 4 mm. to the
medial side of its posterior pole.
In its passage through the optic foramen the nerve is surrounded by a prolongation of the
meninges. The dura mater splits at the optic foramen, part of it joining the periorbita, while
the remainder continues to surround the nerve loosely as its outer or dural sheath. The nerve
is closely enveloped by a vascular covering derived from the pia mater, named accordingly the
pial sheath. The space between these two sheaths is subdivided by a fine prolongation of the
arachnoid (the arachnoidal sheath) into two parts, termed the intervaginal spaces [spatia inter-
vaginalia], viz., an outer, narrow, subdural, and an inner, wider, subarachnoid space, communi-
cating with the coiTesponding intracranial spaces. The arachnoidal sheath is connected with
the sheath on each side of it by numerous fine processes which bridge across the intervening
spaces. The pial sheath sends processes inward, which form a framework separating the bundles
of nerve-fibres; between the enclosed nerve-fibres and each mesh of this framework there is a
narrow interval occupied by lymph. The nerve-fibres are medullated, but have no primitive
sheath. About fifteen or twenty millimetres behind the globe the central vessels enter, piercing
obliquely the lower lateral quadrant of the nerve, and then run forward in its axis. They are
accompanied throughout by a special process of the pial sheath, which forms a fibrous cord in
the centre of the nerve.
On reaching the eyeball, the dural sheath is joined by the arachnoid, and turns away from
the nerve to be continued into the outer two-thirds of the sclera. Similarly the pial sheath also
here leaves the nerve, its greater part running into the inner third of the sclera, while a few of its
fibres join the chorioid; the intervaginal spaces consequently end abruptlj' in the sclera around
the nerve-entrance. In this locality the connective-tissue framework of the nerve becomes
thicker and closer in its meshwork, and has been already alluded to as the lamina cribrosa
sclerae. It is formed by processes passing out from the central fibrous cord at its termination
and by processes passing inward from the pial sheath, sclera, and chorioid. It does not pass
straight across the nerve, but follows the curve of the surrounding sclera, being therefore slightly
convex backward. The nerve-trunk here quickly becomes reduced to one-half its former diam-
1074
SPECIAL SENSE ORGANS
eter, the fibres losing their medullary sheath, and being continued henceforward as mere axis-
cylinders. Apart from the consequent loss of bulk, this histological change may be readUy
recognised macroscopicaUy in a longitudinal section of the nerve, its aspect here changing
from opaque white to semi-translucent grey. The part of the nerve within the lamina
cribrosa has aheady been noted in the ophthalinoscopic examination of the Uving eye (p. 1055).
The optic nerve is mainly nourished by fine vessels derived from those of the pial sheath,
which run into the substance of the nerve in the processes above mentioned. In front of the
entrance of the central retinal artery this vessel aids to some extent in the blood-supply of the
axial part of the nerve.
Fig. 817. — Tkansvehse Section through Optic Nerve, showing the Relations of its
Sheaths and Connective-tissue Framework.
Dural sheath
Arachnoidal sheath
Suharachnoid space
Subdural space -;
Central retinal artery
Central retinal vein
Connective-tissue frame-
work, with meshes in
which the nerve-fibre
bundles lie
Fig. 818. — ^Longitudinal Section through Termination of Optic Nerve.
"Pit in optic papilla
Chorioid ~;;^^5!i3?i,-__r""^^^^S?r^^S>k /a0^^-^ s.— ^m, ""^^i Retina
Short posterior^
ciUary artery
Central retinal
vessels
Dural sheath
Arachnoidal sheath
Optic nerve with
connective-tiss
framework
Pigment epithelium
Suprachorioidal
space
Lamina cribrosa
Sclera
The Blood-vessels and Nerves of the Orbit
As these structures will be more particularly described in other sections of this
work, a very short general account will suffice here.
Arteries. — The main blood-supply is afforded by the ophthalmic artery, a branch of the
internal carotid, which gains the orbit through the optic foramen, where it lies below and lateral
to the nerve. On entering the orbit it ascends, and passes obliquely over the optic nerve to
the medial wall of the orbit; in this early part of its course it gives off most of its branches, which
vary much in their manner of origin and also in their course. The arteries of the orbit are
remarkable for their tortuous course, for their delicate walls, and for their loose attachment to
the surrounding tissues. The ophthalmic artery gives off special branches in the orbit to the
lacrimal gland, the muscles, the retina (through the optic nerve), and the eyeball, as well as
to the meninges, the ethmoidal cells, and the nasal mucous membrane. Twigs from all the
different branches go to supply the fat, fasciae, and ordinary nerves of the orbit. Branches
which leave the orbit anteriorly ramify on the forehead and nose, and also go to the supply of
ORBITAL VESSELS AND NERVES
1075
the eyelids and the tear-passages. The ophthalmic artery has many anastomoses with branches
of the external carotid. The contents of the orbit are also supplied in part by the Infraorbital
artery, a branch of the internal maxillary; in particular this artery supplies part of the inferior
rectus and inferior oblique muscles in the cavity, and also gives a branch to the lower eyelid.
Veins. — Branches, corresponding generally to those of the artery, unite to form the superior
and inferior ophthalmic veins, which ultimately, either separately or united into one trunk,
pass through the superior orbital fissure and empty into the cavernous sinus. The inferior vein
is connected with the pterygoid plexus by a branch which leaves the orbit by the inferior orbital
fissure.
Nerves of the orbit. — These are (A) motor, (B) sensory, and (C) sympathetic, and aU
enter the orbit by the superior orbital fissure, with the exception of one small sensory branch
passing through the inferior orbital fissure. (The optic nerve has been already described, and
is not included in this account.)
A. The motor nerves are the oculomotor, trochlear, and abducens.
1. The oculomotor nerve enters the orbit in two parts, an upper smaller, and a lower
larger, division. The upper division [ramus superior] gives off two branches: one suppHes the
superior rectus, entering its lower surface far back; the other branch goes to the levator pal-
pebra?, entering its lower surface in its posterior third. The lower division [ramus inferior]
divides into three branches, of which one supplies the inferior rectus, entering its upper surface
Fig. 819. — The Blood-vessels of the Left Orbit, viewed from above.
Supraorbital artery-
Lacrimal gland'
Superior rectus, cut'
Eyeball
Lateral rectus
Lacrimal artery
Superior rectus, cut
Inferior ophthalmic vein
Superior ophthalmic vem
Opt]
Superior ophthalmic vein
Commencement of superior
ophthalmic vein
Reflected tendon of superior
oblique
Ophthalmic artery
7] Anterior ethmoidal artery
Posterior ethmoidal artery*
Ciliary arteries
Levator palpebr^e, cut
Common tendon ring
(of Zinn)
Ophthalmic artery
Optic chiasma
Internal carotid artery
far back, and another supplies the medial rectus, entering its medial surface a little behind
its middle. The third branch of the lower division gives (1) the short root to the cihary ganglion,
and (2) one or more twigs to the inferior rectus, and the remainder of this branch then enters
the lower surface of the inferior oblique muscle about its middle.
2. The trochlear nerve supplies the superior oblique muscle, entering its upper surface
about midway in its course.
3. The abducens nerve supplies the lateral rectus, entering its medial surface about the
junction of the posterior and middle thirds of the muscle.
As regards the manner of termination of these motor nerves, it is found that in aU the ocular
muscles the nerve on its entrance breaks up into numerous bundles of fibres, which form first
coarse and then fine plexuses, the latter ultimately sending off fine twigs supplying the muscle
throughout with nerve-endings. The posterior third of these muscles is, however, comparatively
poorly supplied with both kinds of plexuses and with nerve-endings.
B. The sensory nerves are supplied by the ophthalmic and maxillary divisions of the
trigeminal cranial nerve. The ophthalmic division is chiefly orbital; while the maxillary
sends only a small branch to the orbit.
1. The ophthalmic division of the trigeminal nerve enters the orbit in three divisions,
namely: —
(1) Frontal, spUtting subsequently into supratrochlear and supraorbital, both passing out
of the orbit. It is distributed to the corresponding upper eyehd, and the skin over the root of
the nose, the forehead, and the hairy scalp as far back as the coronal suture on the same side.
It also gives branches to the periosteum in this region, and to the frontal sinus.
(2) Lacrimal, supplying the lacrimal gland, anastomosing with a branch of the maxillary
1076
SPECIAL SENSE ORGANS
in the orbit, and finally piercing the upper eyelid. Outside the orbit it is distributed to the
lateral part of the upper lid, the conjunctiva at the lateral angle, and the skin between this and
the temporal region.
(3) Naso-ciliary [n. naso-ciUaris] giving off — (a) a branch to the ciliary gangUon, constituting
its long root ; (6) two or three long ciliary nerves; and (c) the injratrochlear, passing out of the orbit.
The nerve then leaves the orbit as the anterior ethmoidal nerve [n. ethnioidaUs anterior], re-
entering the cranial cavity before being finally distributed to the nose. The infratroohlear branch
[n. infratrochlearis], supplies the eyehds and skin of the side of the nose near the medial angle of
the eye, the lacrimal sac, caruncle, and plica semilunaris. The anterior ethmoidal nerve, after
its course in the cranial cavity, passes through an aperture in the front of the lamina cribrosa
of the ethmoid bone, and is ultimately distributed to the nasal mucous membrane, and to the
skin of the side and ridge of the nose near its tip.
2. The maxillary division of the fifth nerve gives a branch, called the zygomatic nerve,
which passes into the orbit through the inferior orbital fissure, anastomoses with the lacrimal,
and leaves the orbit in two divisions. These are distributed to the skin of the temple and of the
prominent part of the cheek.
A few minute twigs from the spheno-palatine ganghon, and sometimes from the maxillary
division of the fifth nerve, also pass through the inferior orbital fissure to supply the periorbita
in this neighbourhood.
C. The sympathetic nerves of the orbit are mainly derived from the plexus on the internal
carotid arterj'. With the exception of branches accompanying the ophthalmic artery, and of
the distinct sympathetic root of the ciUary ganghon, they enter the orbit in the substance of
Fig. 820. — Section through Contents op Right Orbit, 1-2 mm. in front of the Optic
Foramen, viewed from behind. (After Lange.)
Trochlear nerve
Superior rectus and levator palpe-.
bras superioris muscles
■ oblique musclC'
Ophthalmic vein
ve (frontal,
liary, and lacrimal
branches)
Medial rectus muscle— -^^ \
Inferior rectus muscle
'' \m — "'^'^ Ophthalmic vein
117.
Ophthalmic artery
Abducens nerve
Oculomotor nerve
Lateral rectus muscle
the other nerve-cords. The connections between the ocular nerves and the carotid plexus are
recognisable as fibres going to the oculomotor, abducens, and ophthalmic nerves; as a rule, the
comparatively large twigs going to the abducens join it furthest back, and those to the oculo-
motor furthest forward. Sympathetic connections with the trochlear nerve are very doubt-
ful. The special courses of the motor fibres to the dilatator pupillae muscle have already been
described.
The ciliary ganglion is situated between the optic nerve and lateral rectus far back in the
orbit. Its three roots — motor, sensory, and sympathetic — have been already mentioned.
Anteriorly, it gives off three to six smaU trunks, which subdivide to form the short ciliary nerves
[nn. cihares breves] about twenty in number, piercing the sclera around the optic nerve
entrance.
The lymphatic system of the orbit. — Although there are no lymphatic vessels
or glands in the orbit, the passage of lymph is nevertheless well provided for. We
have already observed the lymph channels within, between, and outside the
sheaths of the optic nerve, and have seen how these communicate anteriorly with
the lymph channels of the eyeball, and posteriorly with the intracranial meningeal
spaces. In addition, there are lymph-spaces around the blood-vessels, situated
between the outer coat and the loose investment furnished by the muscle fascia.
The nerves of the orbit (apart from the optic) are probably similarly surrounded
by lymph-spaces. In the absence of lymphatic vessels it is difficult to trace the
circulation thoroughly; much of the lymph from the orbital cavity is said to pass
into the parotid nodes.
The Eyelids
The cutaneous and conjunctival surfaces of the eyelids [palpebras] have al-
ready been examined (p. 1053), and the position of the tarsus has been indicated.
We have now to ascertain the nature and relations of the tarsus, and describe the
other tissues entering into the formation of the eyelids (fig. 821).
THE EYELIDS
1077
The skin here is thin, bearing fine hairs, and having small sebaceous and nu-
merous small sweat-glands. Immediately beneath it is a loose subcutaneous
tissue, destitute of fat, separating the skin from the palpebral part of the orbicu-
laris muscle. The lid-fibres of this muscle arise from the medial palpebral liga-
ment, and course over the whole upper and lower eyelids in a succession of arches,
so as to meet again beyond the lateral angle; there they in part join one another,
in part are inserted into the lateral palpebral raphe. The muscular fibres are
arranged in loose bundles, with spaces between them occupied by connective
tissue; in the upper lid these connective-tissue fibres may be traced upward and
backward into the fibrous expansion of the tendon of the levator palpebree supe-
FiG. 821. — Sagittal Section op the Upper Eyelid. (After Waldeyer and Fuohs.)
Orbicularis oculi -
Sweat gland ■
-!:•
Sebaceous gland —
Cross section of
orbicularis oculi
^^Sltt/
Ciliary gland (of Moll)
Ciha
^ :i
Anterior insertion of leva-
tor palpebree superioris
Superior tarsal muscle
of MuUer
- Fibres from levator to skin
7'
^ Mucous glands (Krause)
Conjunctival papillse over
attached border of tarsus
Mucous glands (of Krause)
^_ Tarsal (Meibomian) glands
M. ciliaris (Riolani)
Posterior edge of lid-margin
Opening of duct of tarsal gland
rioris. One strong bundle of orbicularis fibres, called the musculus ciliaris Riolani,
is found near the edge of the lid, in front of and behind the efferent ducts of the
tarsal glands (fig. 821).
A central connective tissue separates the orbicularis muscle from the tarsus in the tarsal
division of the lids. In the upper Ud this is to be regarded as mainly the anterior or fibrous
expansion of the tendon of the levator palpebrse, which sends connective-tissue septa between the
bundles of the overlying orbicularis (as just mentioned) going to the skin. In the orbital part
of this hd the central connective tissue includes also the palpebral fascia, lying here immediately
beneath the orbicularis muscle; but this soon thins off and fades into the more deeply placed
levator expansion. This latter is strengthened by an extension of the sheath of the superior
rectus, by which this muscle is enabled to influence the elevation of the Ud indirectl.y. In the
lower lid the central connective tissue similarly consists of palpebral fascia, blended with a thin
fibrous extension of the sheath of the inferior rectus. Immediately in front of each tarsus is
a little loose connective tissue, which contains the large blood-vessels and nerves of the hds.
The tarsus of each lid is a stiff plate of close connective tissue, with its sur-
faces directed anteriorly and posterior^; in its substance the tarsal glands are
1078 SPECIAL SENSE ORGANS
embedded. One tarsal border is free, viz., toward the edge of the lid, the other
is attached; the former is straight, while the latter is convex, especially in the
upper lid.
The length of each tarsus is about twenty millimetres. Its breadth is greatest in the middle
of the hd, and becomes gradually smaller toward 'each angle, where the tarsi are joined to the
lateral raphe and medial palpebral ligament. The breadth of the upper tarsus (10 mm.) is
about twice that of the lower. The thickness of each is greatest, and its texture closest, at the
middle of its length, thinning off toward the angles of the eye and toward both borders. Into
the superior anterior border of the upper tarsus the lower layer of the levator expansion is
attached, consisting of smooth muscle-fibres constituting the superior tarsal muscle of Mtiller.
In like manner, at the inferior border of the lower tarsus, bundles of smooth muscle-fibre are
inserted (the inferior tarsal muscle of Miiller), developed in what has been regarded as part
of the extension of the sheath of the inferior rectus.
The palpebral conjunctiva is firmly adherent to the posterior aspect of the
tarsus; but in the orbital part of the lid loose subconjunctival tissue intervenes
between it and Miiller's tarsal muscle. Lymphoid tissue occurs in the substance
of the conjunctiva, especially in its orbital division. Near the upper fornix, the
conjunctiva receives expansions of the tendon of the levator palpebrse and of the
sheath of the superior rectus, and, at the lower fornix, of the sheath of the inferior
rectus. The surface of the tarsal conjunctiva shows small elevations or papillae
everywhere; but these are particularly well marked over the attached border of
the tarsus.
Glands of the eyelids. — From its manner of formation the eyelid may be
regarded as consisting of two thicknesses of skin, the posterior having been
doubled back upon the anterior at the edge of the lid; thus the epidermis and
corium of the skin proper are represented respectively by the conjunctiva (epi-
thelium) and tarsus of the inner thickness. At the free border of the lid, accord-
ingly, we find glands corresponding to the sebaceous and sweat-glands of the skin,
viz., large sebaceous glands of the cilia (Zeiss's glands) and the ciliary glands of
Moll, which are modified sweat-glands. Again, in the inner skin-thickness of
the lid, the tarsal (Meibomian) glands are sebaceous.
Acino-tubular mucous glands occur at the attached border of the tarsus (Krause's or
Waldeyer's glands), and similar glands also occur at the fornix, and are especially abundant
near the outer angle of the upper lid, close to the efferent ducts of the lacrimal gland; from their
structure and the character of their secretion, these acinous or acino-tubular glands have been
termed by Henle 'accessory lacrimal glands.' Other simple tubular glands (Henle), formed
merely by the depressions between the papiUae, are best developed in the medial and lateral
fourths of the tarsal conjunctiva of both hds.
Blood-vessels. — The arteries run in the central connective tissue of the lids, mainly in
the form of arches near the borders of the tarsus, from which twigs go to the different pal-
pebral tissues. They are supplied by the lacrimal and palpebral branches of the ophthalmic,
and by small branches derived from the temporal artery. The veins are more numerous and
larger than the arteries, and form a close plexus beneath each fornix. They empty themselves
into the veins of the face at the medial, and into the orbital veins at the lateral angle of the eye.
The lymphatic vessels of the lids are numerous, and are principally situated in the con-
junctiva. Lymph-spaces also surround the follicles of the tarsal glands. The palpebral
lymphatic vessels from the lateral three-fourths of the lid pass through the anterior auricular
and parotid nodes; those from the medial fourth of the lower lid go to the facial and submaxil-
lary lymphatic nodes.
Nerves. — (a) Sensory. The upper lid is chiefly supplied by branches of the supraorbital
and supratrochlear nerves, the lower Ud by one or two branches of the infraoibital. At the
medial angle the infratrochlear nerve also aids in the supply, and, at the lateral angle, the
lacrimal, (b) Motor. The palpebral part of the orbicularis is suppKed by branches of the
facial nerve, which mainly enter it near the lateral angle. The tarsal muscles are suppUed
by the sympathetic nervous system.
The medial palpebral ligament has been referred to previously. Arising from
the frontal process of the maxilla, it extends laterally over the front wall of the
lacrimal sac, bends round the lateral wall of the sac, and then passes backward to
the posterior crest on the lacrimal bone. It is thus U-shaped, having its limbs
anterior and posterior, embracing the lacrimal sac; the anterior limb lies immedi-
ately beneath the skin, and is visible in the living. The palpebral fibres of the
orbicularis are inserted into the anterior surface of both limbs, those attached to
the posterior limb constituting the pars lacrimalis of the orbicularis palpebrarum
(Horner's muscle). The lateral palpebral raphe is merely a stronger development
of connective tissue in the orbicularis. Both ligaments are connected with the
tarsi as already mentioned.
LACRIMAL APPARATUS
1079
The Lacrimal Apparatus
The tears are secreted by an acinous gland, and flow through fine ducts to the
upper lateral part of the conjunctival sac, whence they pass over the cornea and
are drained off through the puncta, pass along the canaliculi into the lacrimal sac,
and ultimately down the naso-lacrimal duet to the inferior meatus of the nose.
The lacrimal gland is situated near the front of the lateral part of the roof of
the orbit, lying in a depression in the orbital plate of the frontal bone. It consists
of two very unequal parts, one placed above and the other beneath the tendinous
expansion of the levator palpebree superioris, but small gaps in the expansion per-
mit of connections between these two parts of the gland. The upper and larger
subdivision (superior lacrimal gland) is a firm elongated body, about the size of
a small almond; it has a greyish-red colour, and is made up of closely aggregated
lobules. The upper surface (next the orbital roof) is convex, and its lower surface
is slightly concave.
Anteriorly, the gland almost reaches the upper orbital margin, and it extends backward
for approximately one-fourth the depth of the orbit, measuring about twelve mUlimetres in
this direction. The lateral border of the gland descends to near the insertion of the fascial
expansion of the lateral rectus, while its medial border almost reaches the lateral edge of the
superior rectus; its transverse measurement is about twenty millimetres. It is enveloped in a
capsule, which is slung by strong fibrous bands passing to its medial border from the orbital
margin (suspensory hgament of the gland).
Fig. 822. — Dissection of the Eye to Show the Lacrimal Appakatus, Anterior View.
Inferior lacrimal gland
Excretory ducts/
Superior lacrimal gland i I
Palpebra superior
Tendon of superior oblique
} Superior lacrimal duct
^ Lacus lacrimalis
y Medial palpebral commissure
- Fornix of lacrimal sac
- Junction of lacrimal ducts
- Inferior lacrimal duct
- Nasolacrimal duct
^ I-- i' Lacrimal papilla and punctum
Inferior oblique
Palpebra inferior
The lower subdivision of the gland (^inferior lacrimal gland) is composed of
loosely applied lobules, and lies immediately over the lateral third of the upper
conjunctival fornix, reaching lateralward as far as the lateral angle.
Each subdivision of the gland possesses several excretory ducts, which all open
on the lateral part of the upper fornix conjunctivae, about four millimetres above
the upper border of the tarsus. Those of the superior gland, three or four in
number, pass betweefi the lobules of the lower gland; the most lateral duct is the
largest, and opens at the level of the lateral angle of the eye. The ducts of the
inferior gland in part discharge themselves into those of the upper, but there are
also several fine ducts from this subdivision that run an independent course.
Near the medial angle are the two puncta lacrimalia, upper and lower, each
situated at the summit of its papilla. The top of each papilla curves backward
toward the conjunctival sac, so that the puncta are well adapted for their function
of draining off any fluid collecting there.
The ductus (canaliculi) lacrimales extend from the puncta to the lacrimal sac.
The lumen at the pmrctum is horizontally oval, from its lips being slightly com-
pressed antero-posteriorly; the lumen of the lower punctum is somewhat larger
than that of the upper. As the lower papilla is a little further from the medial
angle of the eye than the upper, the corresponding canaliculus is longer.
On tracing either ductus from its origin, we flnd that at first it runs nearly
vertically for a short distance, then bends sharply toward the nose, and finally
1080 SPECIAL SENSE ORGANS
courses more or less horizontally, converging slightly toward its fellow, and not
infrequently joining it before opening into the sac. The calibre varies consider-
ably in this course, being narrowest a short distance from the punctum, and widest
at the bend, from which point it again narrows very gradually as it nears the sac.
The wall of the ductus consists mainly of elastic and white fibrous tissue, lined internally
by epitheUum, and covered externally by striated muscle (part of the orbicularis). The muscle-
fibres run parallel to the ductus in the horizontal part of its course; but they are placed, some
in front and some behind, around the vertical part, acting here as a kind of sphincter. Just
before their termination, the ducts pierce the periosteal thickening that constitutes the posterior
limb of the medial palpebral ligament.
The lacrimal sac [saccus lacrimalis] lies in a depression in the bone at the medial
angle of the orbit (the lacrimal fossa). It is vertically elongated, and narrows at
its upper and lower ends; the upper extremity or fundus is closed, while the lower
is continuous with the naso-lacrimal duct. Laterally, the sac is somewhat com-
pressed, so that its antero-posterior is greater than its transverse diameter. The
ducts, either separately or by a short common tube, open into a bulging on the
lateral surface of the sac near the fundus.
As has previously been mentioned, the sac is surrounded by periosteum, but between this
and the mucous membrane forming the true sac-wall there is a loose connective tissue, so that
the cavity is capable of considerable distention. The relations of the medial palpebral Ligament
have already been described; it is to be noted that the fundus of the sac extends above this
ligament.
The naso-lacrimal duct [ductus naso-lacrimalis] reaches from the lower end of
the sac to the top of the inferior meatus of the nose, opening into the latter just
beneath the adherent border of the inferior nasal concha. Traced from above,
its main direction is downward, but it has also a slight inclination backward and
laterally. It lies in a bony canal, whose periosteum forms its outer covering.
Between this and the mucous membrane of the duct there is a little intermediate
tissue, in which run veins of considerable size connected with the plexus of the
inferior concha. The duct does not usually open directly into the nasal cavity
at the lower end of the bony canal, but pierces the nasal mucous membrane very
obliquely, so that a flap [plica lacrimalis (Hasneri)] of mucous membrane covers
the lower border of the opening in the bone, upon which flap the tears first trickle
after escaping from the duct proper.
The sac and naso-lacrimal duct together constitute the lacrimal canal, lined throughout by
a continuous mucous membrane. This membrane presents folds in some situations, especially
near the opening of the canaliculi, at the junction of the sac and duct, and at the lower end of
the duct. That at the top of the duct is the most important, as it sometimes interferes with the
proper flow of tears out of the sac. The total length of the lacrimal canal is roughly twenty-four
millimetres, half of this being sac, and half naso-lacrimal duct. If, however, we reckon as duct
the obUque passage through the nasal mucous membrane, this measurement may occasionally
be increased by eight or ten millimetres. The lacrimal sac, when distended, measures about
six millimetres from before backward, by four millimetres transversely. The naso-lacrimal duct
is practically circular, and has a diameter of about three millimetres, rather less at its junction
with the sac, where we find the narrowest part of the whole lacrimal canal.
Development of the ■ Eye
The eye is developed from the three sources involving two fundamental embryonic layers —
the retina from a portion of the ectodermal wall of the forebrain on each side; the lens from the
ectodermal surface epithelium; and the sclera, cornea (except epithelium) and chorioidal
coat from the mesoderm which surrounds the former structures.
The process of development is, briefly, as follows: — The site of the eye is marked by a sUght
depression on the surface of the forebrain on either side. There later an outgrowth occurs
from the ventro-lateral aspect on each side of the forebrain, in the form of a hoUow vesicle,
whose cavity is continuous with that of the forebrain. This outgrowth is termed the •primary
optic vesicle [vesicula ophthalmicaj. The lateral surface of the vesicle comes into contact with
the surface epithelium of the head and this epithelium becomes thickened at the area of contact.
The superficial portion of the vesicle expands, while its connection with the brain remains
slender; becoming depressed on the surface, it forms a cup-shaped hollow, the secondary optic
vesicle or optic cup [caliculus ophthalmicus] whose wall is formed of two layers, an outer investing
layer and an inner inverted one.
The chorioidal fissure is present almost from the first stages, as a cleft on the ventral aspect
of both the distal portion of the vesicle, or cup, and of the stalk; and it is formed by an infolding
of the surface into the cavity of the vesicle along a narrow linear area.
In this cleft are found vessels which pass to the hollow of the optic cup. The margins of
the cleft meet and fuse, and enclose the vessels in the interior — hence the enclosure of the
a. centralis retina within the optic nerve, and of the hyaloid artery in the interior of the vitreous.
Should the margins of the cleft remain separate, the. condition of coloboma results.
DEVELOPMENT OF THE EYE
1081
From the optic cup is formed the whole of the retinal or nervous tunic. It will be noticed
that this tunic is composed of two layers, with a narrow sUt-like interval between them, but that
the layers are continuous with one another at the margin of the cup. This margin is afterward
found, in the fully developed eye, at the pupillary margin of the iris. The outer investing layer
forms the pigment layer, and the inner inverted layer gives rise to the other parts of the retina,
viz., the pars optica, over the bottom of the cup, the pars ciliaris, in the ciliary region, and the
pars iridica, near the margin of the original cup, including the dilatator and sphincter pupillae
muscles of the iris.
The lens is formed as a hollow invagination from the surface epitheKum, which sinks into
the hoUow of the optic cup. The margins meet and fuse, enclosing a cavity, and the lens mass
sinking more deeply in, loses its connection with the surface, and a layer of mesoderm passes
in between them.
The anlages of the lens and the primitive retina are at first in contact with one another.
They graduaUy draw apart, and the intervening space is filled by the vitreous humour. The
origin of the vitreous humour is not yet fully understood, but it appears to be developed from the
adjacent ectoderm of the optic cup, and in part from the surrounding mesoderm.
Figs. 823, 824, 825 and 826. — Sections Representing Four Successive Stages in the
Origin op the Optic^ Vesicle and the Development op the Eyeball.
■W
The optic cup and the lens are surrounded by mesoderm and from it are formed the struc-
tures of the tunica vasculosa (middle coat) in its different parts, viz., chorioid, ciliary body
and ins, and also the sclera and cornea (fibrous portion).
Bii I^^- f" n®''J5'" <'lia'»ber is formed by cleavage of the mesoderm, a space appearing in it,
hUed with fluid. The mesoderm surrounding this space forms the endothehum Hning the
anterior chamber. The mesoderm also forms a vascular covering for the front of the lens,
termed the capsula vasculosa leniis, or pupillary membrane, which disappears from the sur-
face of the lens in the later months of development.
The eyehds and conjunctiva are formed from the integumentary covering of the eye.
1 he former are mostly skin folds, which, at first separate, meet and fuse with one another along
their margin. Subsequently they become undermined by the ingrowth of epithelium from a
central horizontal sht, the rima palpebrarum ; the central part of the invading epithehum breaks
down, and the free folds are formed.
The lacrimal gland is developed from a series of tubular outgrowths from the conjunctival sac.
1082 SPECIAL SENSE ORGANS
The lacrimal canals and naso-lacrimal duct are formed by the growth of an epithelial
band which passes through the mesoderm to the nasal cavity along the naso-lacrimal groove.
This band loses its primitive connection with the groove, and is reunited to the lid margins
by secondary epithelial bands which grow from the naso-lacrimal duct to the lid margin. Simi-
larly a secondary connection is later made with the nasal cavity at the lower end of the duct.
The position of the naso-lacrimal duct corresponds to the line of union of the nasal and maxillary
processes; but the duct does not represent a portion of the cleft between these processes, and
is formed secondarily between them.
IV. THE EAR
Under the name of the ear [organon auditus] there is included a number of
structures of which some, the ear proper, constitute the auditory mechanism —
that is, an apparatus for the collection, transmission and reception of the waves of
sound; while others — the semicircular ducts and associated structures — are
concerned in receiving and transmitting impressions produced by movements of the
head. These impressions constitute the basis of what may be termed the static or
equilibratory sense, and afford data employed in estimating movements of the
body in relation to surrounding objects.
The former of these, the ear proper, consists of three main parts, each possess-
ing distinct structural and functional characters. The first portion, often known as
the external ear, consists of a receptive organ placed upon the surface of the head,
the auricle or pinna, and of a short tube, the external auditory meatus, which
leads into the interior, and is closed at its deep end by the tympanic membrane.
The second portion, known as the middle ear, consists of the tympanic cavity,
a small air-containing chamber in the petrous portion of the temporal bone, con-
nected with the nasal part of the pharynx by a tube, the auditory (or Eustachian)
tube. From the tympanic chamber a recess passes posteriorly and leads to a cavity
in the mastoid portion of the temporal bone, the mastoid or tympanic antrum.
A chain of three small bones transmits the sounds across the middle ear.
The third part, or internal ear which contains the essential sensory apparatus,
lies within the complex cavities in the interior of the petrous temporal bone known
as the osseous labyrinth. It consists of (1) the utricle and saccule, two small ves-
icular structures lying in the bony vestibule, and (2) the membranous semicir-
cular ducts and (3) the membranous cochlea, which lie within the corresponding
bony canals.
These structures are filled with fluid, the endolymph, and communicate with one
another. They are largelj' separated from the bony walls by fluid, perilymph, and
they are lined by sensory epithelium. Closely related to the epithelial sensory
cells are found the terminal branches of the cochlear and vestibular nerves.
The description of the three divisions of the ear is taken up in order from the
surface inward.
1. THE EXTERNAL EAR
The external ear consists of the auricle attached to the side of the head, and
the external auditory meatus leading from it to the middle ear (flg. 829).
THE AURICLE
The auricle, or pinna, is an irregular oval plate-like structure which lies upon
the lateral surface of the head. It presents a lateral and a medial surface. The
lateral surface is irregularly concave (fig. 827). The deepest part of its concavity
situated near the centre, is termed the concha, and it is partially divided by
a prominent oblique ridge, the crus of the helix, into a superior part, the cymba
conchae, and a large inferior part, the cavum conchae. The cavum conchse leads
into the external auditory meatus, and is bounded ventrally by a prominent proc-
ess, the tragus, which projects posteriorly over the entrance to the meatus. The
tragus, is separated from the crus of the helix by a well-marked depression, the
anterior incisure and has a small tubercle on it superiorly, the supratragic tuber-
cle. Bounding the cavum conchte posteriorly and inferiorly is a projection, the
antitragus, lying opposite, but inferior, to the tragus, and between the two is a
deep notch, the intertragic notch [incisura intertragica]. A prominent semicircular
THE AURICLE
1083
ridge, the anthelix, bounds the concha posteriorly and superiorly. Inferiorly it
is separated from the antitragus by a slight depression, the posterior auricular
sulcus. Superiorly the anthelix divides into two ridges, the crura of the anthelix,
and between these is a shallow depression, the triangular fossa. The superior and
dorsal margin of the auricle is inverted and forms a prominent rim, the helix, which
Fig. 827 — ^Lateral Surface or the Left Auriole.
Crura of anthelix
Crus of tne helix-
Anterior incisure-
Supratragic tubercle
Tragu;
Intertragic incisure-
HeUx
Auricular tubercle
Triangular fossa
Scapha
Cavum J
Anthelix
Posterior auricular sulcus
is continued anteriorly into the crus of the helix, and inferiorly into the lobule.
An elongated depression, partly overlapped by the helix, termed the scapha
(scaphoid fossa) separates the helix and the anthelix. Superiorly and dorsally
the free margin of the helix frequently presents a slight projection, the auricular,
tubercle (tubercle of Darwin).
Fig. 828. — Lateral and Medial Surface of the Cartilage of the Right Auricle and its
Muscles, etc.
Helicis major Obliquus Transversus
Helicis minor'
Ebrous band
pleting fore part of
meatus
l.yy Antitrago-helicin
Terminal fissure
Isthn
Antitragicus , Tragicus Spine of Fissure of Santorini
Lamina tragi helix Cartilage of meatus
Upon the medial surface of the auricle the depressions of the lateral surface are
represented by elevations, viz., the eminence of the concha, the eminence of the
scapha, and the eminence of the triangular fossa, respectively; and the elevations
by depressed areas, viz., the fossa of the anthelix, transverse sulcus of the anthelix.
1084 SPECIAL SENSE ORGANS
and the sulcus of the crus of the helix. The attachment of approximately one-
third of the medial surface covers up the two latter depressions. The cephalo-au-
ricular angle, between the dorsal free part of the auricle and the side of the
head, averages 20 to 30 degrees.
Structure of the Auricle
The features of the auricle just described are mainly produced by a plate of yellow elastic
cartilage, the auricular cartilage. In addition to the elevations and depressions already
noted, it presents the following additional features. Projecting anteriorly from the helix,
near the crus is a small tubercle, spine of the helix (fig 828) ; while the posterior margin of the
helix terminates in a pointed tail-like process, the cauda helicis which is separated inf eriorly
from the antitragus by the deep antitrago-helicine fissure. Another deep fissure, the terminal
notch [incisura terminalis auris], separates the cartilage of the auricle from that of the meatus,
leaving only a narrow strip, the isthmus, connecting the two. The cartilage of the tragus,
the lamina tragi, is separated from that of the auricle and is attached to the lateral margin of
the cartilage of the meatus.
The auricle is covered on both its medial and lateral aspects by skin which
closely follows the irregularities of the cartilage. Thus it is tightly bound to the
perichondrium of the lateral surface by the subcutaneous areolar tissue, but much
more loosely attached to the medial surface, and in the subcutaneous tissue there
is little fat except in the lobule, which is made up almost entirely of fat and tough
fibrous tissue. Hairs are abundant but rudimentary, except in the region of the
tragus and antitragus, where they may be large and long, particularly in males and
in the aged. Sebaceous glands are found on both surfaces, and are especially well
developed in the concha and triangular fossa, but sudoriferous glands are few and
scattered.
Ligaments and muscles. — The auricle is attached to the side of the head by the skin, by
the continuity of its cartilage with that of the acoustic meatus, and by certain extrinsic ligamente
and muscles. Three ligaments may be distinguished in the connective tissue: — The anterior
ligament, stretching from the zygoma to the helix and tragus; the superior ligament, from the
superior margin of the bony external acoustic meatus to the spine of the helix; and the posterior
ligament, from the mastoid process to the eminence of the concha. There are also three ex-
trinsic muscles, the anterior, superior, and posterior auricular (see p. 337, fig. 341). Six intrinsic
muscles are distinguished. These are poorly marked in man and vary much in development.
Upon the lateral surface (fig. 828) the helicis major stretches from the spine of the helix to
the ventral superior margin of the helix; the helicis minor overlies the crus helicis; the tragicus
runs vertically upon the tragus; and the antitragicus stretches from the antitragus to the cauda
helicis. Upon the medial surface (fig. 828) the transversus auriculae stretches between the
eminences of concha and scapha, and the obliquus between the eminences of the concha and the
triangular fossa. Two small muscles occasionally present are the m. pyramidalis auriculse
(Jungi) and the m. incisurse heUcis (Santorini).
Vessels and Nerves of the Auricle
The arteries are the auricular branch of the posterior auricular and the anterior auricular
branches of the superficial temporal arteries. The veins are the anterior auricular vein
of the posterior facial (temporal) and the auricular branches of the posterior auricular veins.
The latter vessels sometimes join the transverse (lateral) sinus through the mastoid emissary
vein. The lymphatics empty into the anterior, posterior and inferior auricular lymph-nodes.
The sensory nerves of the auricle are the branches of the great auricular, small occipital (p. 977,
fig. 753), and auriculo-temporal (p. 941, fig. 740). The muscles are suppUed by the posterior
auricular branch of the facial (p. 944, fig. 740).
Variations
There are many variations in the size, shape, and conformation of the auricle and in the
cephalo-auricular angle. These are associated not only with differences in sex, age, and race,
but are also found in individuals of the same family.
THE EXTERNAL AUDITORY MEATUS
The external auditory (acoustic) meatus [meatus acusticus externus] extends
medially and somewhat anteriorly and inf eriorly from the concha to the tympanic
membrane (fig. 829). It is about twenty-five mm. (1 in.) long, and, owing to the
obliquity of the tympanic membrane, its anterior and inferior wall is 5-6 mm.
EXTERNAL AUDITORY MEATUS
1085
longer than the posterior and superior. It consists of a lateral cartilaginous and
a medial osseous portion. The canal describes an S-shaped curve in both hori-
zontal and vertical directions. Near the auricular end it is convex anteriorly and
inferiorly, while at the tympanic end the curve is reversed, and is concave in the
same direction. The lumen is irregularly elliptical in outhne, the longer axis
being vertical at the auricular, but nearly horizontal at its tympanic end. The
meatus is constricted at about its centre, and also near the tympanum.
Fig. 829. — -Vertical Section of the Middle and External Ear.
Semi circular Glands in oq
canals (ducts) secus meatus
Tympanic membrane ^
Cochlea \ \
Cavity of tympanum \ f ''
Cartilaginous tuba auditiva
Cartilagp
— Osseous
meatus
Cartilage of
external
meatus
Parotid gland
Styloid process
Osseous tuba auditiva
Relations. — The anterior loall is in relation with the condyle of the mandible medially, and
with the parotid gland laterally; the inferior wall is closely bound to the parotid gland; and
the 'posterior tuall of the bony part is separated by only a thin plate of bone from the mastoid
cells. The superior loall is separated at its medial end by a thin plate of bone from the epi-
tympanic recess, and laterallj' a thicker layer of bone separates it from the cranial cavity.
Structure of the meatus. — The walls of the meatus are formed laterally of
fibro-cartilage and medially of bone, lined internally by skin. The cartilage is
folded upon itself to form a groove, deficient in its dorsal part, where the edges
of the cartilage are united by dense connective tissue. The cartilaginous groove
is thus converted into a canal. Medially, the cartilage forms about one-third of
the circumference; laterally, two-thirds. Two fissures (incisures of Santbrini)
usually occur in its anterior wall (fig. 828). Laterally the cartilage is directly
continuous with the cartilage of the auricle and medially it is firmly connected
with the lateral lip of the osseous portion. The osseous portion, which forms
slightly more than half the canal, is formed by the tympanic portion of the
temporal bone; it is described in connection with that bone.
The skin of the meatus forms a continuous covering for the canal and tympanic
membrane. It is thick in the cartilaginous, but very thin in the bony, part of the
meatus, especially near the tympanic end, where it is tightly bound to the perios-
teum . In the cartilaginous meatus it contains numerous fine hairs and sebaceous
glands, but neither hairs nor sebaceous glands are found in the bony meatus.
Tubular ceruminous glands, which secrete the cerumen (ear wax) , form a nearly
continuous layer throughout the cartilaginous, but occur on onlj- a small part of
the posterior and superior wall of the bonj', meatus. The openings of their ducts
appear as dark points to the naked eye (fig. 829).
1086
SPECIAL SENSE ORGANS
The arteries are branches from the posterior auricular, superficial temporal, and deep
auricular arteries (q.v.)- The veins and lymphatics connect with those of the auricle and
empty similarly. The nerves are branches from the auriculo-temporal and the auricular
ramus of the vagus.
2. THE MIDDLE EAR
Under the term middle ear there are included the tympanic cavity (tym-
panum), the tympanic antrum and the auditory (Eustachian) tube. These form
a continuous irregular passage, filled with air, and located within and upon the
surface of the temporal bone. The tympanum is shut off from the external ear
Fig. 830. — Frozen Coronal Section op the Right Ear. (Somewhat Enlarged.)
Chorda tympani
Manubrium mallei / Capitulum maUei
j Tympanic cavity
Stapes /
Facial nerve
Tympani membrane
Promontorium 1
Lamina spiralis
Modiolus '
\ I
Tempoial bone \
I Dura mater
/ Temporal bone
Temporal muscle
Cochlea
Internal carotid
Internal jugular vein
Internal carotid artery
Cartilage of meatus
' External auditory meatus (cartilaginous)
Parotid gland
by the tympanic membrane; and from the chamber which forms the internal ear
by the structures which fill in the cochlear and vestibular fenestra. It commu-
nicates with the pharynx by the auditory (Eustachian) tube. _ The structures of
the middle ear are of importance, and the study is somewhat difficult, on account
of the small size of the structures, the depth at which they lie, and the hard charac-
ter of the surrounding bone.
The illustrations (figs. 829, 830, 831, 833, 834) will help to explain the text and should
be constantly referred to. Figs. 830 and 831 are taken from frozen sections traversing the
right ear in the coronal planes; while figs. 833, 834 represent dissections.
The parts to be considered in order are the tympanic rnembrane, the tympanic
cavity, the tympanic antrum and the auditory (Eustachian) tube.
The Tympanic Membrane
The tympanic membrane [membrana tympani] (fig. 835) is elliptical in shape,
its long axis nearly vertical, measuring 9 to 10 mm., its short axis, 8 to 9 mm.
It slopes medially from the superior and posterior to the inferior and anterior
THE TYMPANIC MEMBRANE
1087
wall of the meatus, forming, as a rule, with the superior wall, an angle of 140
degrees. It varies, however, greatly in form, size, and obliquity. Viewed from
the meatus, it appears as a semitransparent membrane, which sometimes has a
reddish tinge. It is drawn medially and made funnel-shape by the manubrium of
the malleus, but the walls of the funnel bulge toward the meatus (fig. 834) . The
most depressed point at its centre, the umbo, is slightly inferior and posterior to
the centre of the membrane, and corresponds to the tip of the manubrium (fig.
832). From it a whitish streak, the malleolar stria, caused by the manubrium
shining through, passes superiorly toward the circumference. At the superior
end of the stria is a slight projection, the malleolar prominence, formed by the
lateral process of the malleus. From it two folds, the anterior and posterior
Fig. 831. — Frozen Coronal Section op the Right Ear. (Somewhat Enlarged.)
Prominence of facial canal
Medial tympanic wall
Tegmen tympani
Recessus epitympanicus \
Stapes
I
Facial nerve
^ Fenestra vestibuli
; Cochlea
, Facial, and cochlear
vestibular nerves
Cavum conchse
Internal carotid artery
Cartilage of meatus j
Parotid gland
plicffi, stretch to the extremities of the tympanic sulcus (fig. 832). The small
triangular area of the membrane bounded by the plicae, is termed the pars flaccida
(Shrapnell's membrane). It is thin and flaccid, and is attached directly to the
petrous bone in the tympanic notch (notch of Rivinus). The larger part of the
tympanic membrane, the pars tensa, is inferior to the plicae and is tightly stretched.
Its thickened margin, the limbus, is attached by a fibro -cartilaginous annulus
to the tympanic sulcus, and at the spines of the tympanic ring is continuous with
the plicae.
Structure of the tympanic membrane. — The tympanic membrane is about .1 mm. thick,
and consists of four layers. The lateral cutaneous layer, relatively thick, is a continuation
of the skin lining the external auditory meatus. Next to it is a radiate fibrous layer, composed
of connective tissue, the fibres of which are attached to the manubrium of the malleus and radiate
from it. Medial to it is the circular fibrous layer, which has its fibres arranged concentrically
and is esijecially thick at the cncumference. It is closely bound to the rachate layer. The
mucous layer, which is a continuation of the mucosa of the tympanic cavity, covers the medial
surface of the membrane smoothl}', except where the manubrium of the malleus causes a pro-
jection. The fibrous layers are attached to the fibro-cartilaginous ring and are not present
in the pars flaccida.
1088
SPECIAL SENSE ORGANS
The Tympanic Cavity
The tympanic cavity [cavum tympani], as has been stated, is an air-space,
lined with mucous membrane, situated between the external and the internal ear.
It is of irregular outline, but, roughty, it is a slit-like cavity, lying in an oblique
antero-posterior plane. Its transverse diameter measures only from 2-4 mm.,
while the vertical and antero-posterior diameters measure about 15 mm. (fig. 834).
It is narrowest at the centre, and wider superiorly than inferiorly. The bony
walls have already been partly described with the temporal bone, and hence the
description given here will refer to the appearance found in the fresh, or un-
macerated condition.
It will be noticed (see fig. 829) that the floor of the space is on very much
the same horizontal plane as the floor of the external meatus, and the lower
margin of the tympanic membrane. The roof, on the other hand, lies at a much
Fig. 832. — ^Lateral Surface op the Left Membhana Tympani. (Enlarged from life.)
Pars flaccida or Shrapnell's membrane Posterior plica
Malleolar prominence caused by'
lateral process of malleus
Long process of incus
Malleolar stria
7 Pars tensa of tympanic membrane
higher level than the upper margin of that membrane. Hence the cavity may
be divided into two regions, a loiver part, corresponding in extent to the tym-
panic membrane, and an upper, above the upper border of the membrane, known
as the epitympanic recess. This division forms a definite chamber, and con-
tains the head of the malleus and the body and short process of the incus.
It is on the posterior part of this chamber that the communication with the
tympanic antrum is found (fig. 835).
As the shape of the tympanum is irregular, its walls are not everywhere
clearly marked off from one another, but there may be recognized (figs. 829
and 835) a roof, or tegmental wall, a floor, or jugular wall, a medial or labyrin-
thine wall and a lateral or membranous wall, an anterior or carotid, and a pos-
terior or mastoid boundary or wall.
The roof, or tegmental wall, is formed by a portion of the tegmen tympani, a thin plate
of bone which is continued backward to form the roof of the tympanic antrum. This plate is
formed by the petrous part of the temporal bone, and at its lateral margin is the petro-squamous
suture, where a slight deficiency in the roof may occur.
The floor, or jugular wall is very narrow transversely, and is in intimate relation to the
internal jugular vein (fig. 831). As shown in fig. 833, the surface is frequently very irregular
from stalactite-lilve projections between which are the tympanic cellulas (air cells), while near
the back there is occasionally a marked projection corresponding externally to the root of the
styloid process.
The posterior or mastoid wall presents at its lower part, many additional tympanic ceUulse,
and higher up, an elevation, the pyramidal eminence, on whose apex is an aperture transmitting
the tendon of the stapedius muscle. The fleshy beUy of that muscle is contained in a cavity
in, the interior of the bony pyramid of the posterior wall. Lateral to this is an aperture, the
aperiura tympanica canaliculm chorda, through which the chorda tympani nerve enters the tym-
panum, covered by a reflexion of the mucous membrane. Between this opening and the pyra-
mid is a slight elevation; and above it is a fossa, termed the sinus posterior. Above this again
is a recess, where the posterior ligament of the incus is attached, known as the fossa incudis.
This portion of the posterior wall forms the boundary of the epitympanic recess. Here the
■cavity of the tympanum is continued with that of the antrum tympanicum, or mastoid antrum,
THE TYMPANIC CAVITY
1089
a large irregular space into which open the mastoid cells (see p. 1092). The boundaries of the
orifice are formed above by the tegmen tympani, medially by the prominences of the lateral
semicircular canal and facial nerve, and laterally by a plate of bone termed the scutum.
The carotid (anterior) wall presents superiorly the tensor tympani muscle in its canal,
and at a lower level the opening of the tuba audiliva (Eustachian tube) (fig. 835). Inferiorly,
a thin, bony wall, covered with tympanic cellulse and pierced by the carotico-tympanic nerves,
separates the tympanic cavity from the carotid canal.
The membranous (lateral) wall is formed mainly by the tympanic membrane, with the
small rim of bone to which it is attached, but superiorly the lateral wall of the epitympanic
recess is formed by a plate of bone termed the scutum.
The labyrinth (medial) wall (fig. 833) presents inferiorly the promontory, produced by the
first turn of the cochlea with the tympanic plexus (Jacobson's nerve) lodged in grooves upon its
surface. Inferior and posterior to the promontory is a depression or fossula at the bottom of
Fig. 833.-
-The Labyrinth (Medial) Wall op the Right Tympanum with the Tympanic
Ossicles in Position.
Short process of incu:
Long process of incus
Chorda tympani
Facial nerve
Pyramidal
eminence
Tendon of
stapedius
Stapes
Cochlear fossula —
Torn edge of mucosa
of superior liga-
ment of incus
Body of incus
Neck of malleus
Anterior malleolar
ligament
Lateral process of
malleus
Chorda tympani
j"" Tympanic pies
Promontory
Tympanic cellulae
which is the cochlear fenestra (fenestra rotunda), closed by the secondary tympanic membrane,
and posterior to the promontory is a smooth projection, the subiculum of the promontory, which
forms the inferior border of a rather deep depression known as the tympanic sinus. Anteriorly
and superiorly is the cochleariform process, and superiorly and posteriorly are a depression or
fossula leading to the vestibular fenestra (fenestra ovalis), which is closed by the base of the stapes,
the prominence of the facial (Fallopian) canal, and the prominence of the lateral semicii'oular
canal, the two latter being formed in the medial wall of the entrance to the mastoid antrum.
The tympanic mucous membrane forms a complete covering for the walls and
contents of the tympanic cavity. It is continuous anteriorly with the mucosa of
the tuba auditiva (Eustachian tube) and posteriorly with that of the tympanic
(mastoid) antrum and mastoid cells. It is a thin, transparent, vascular membrane
intimately united to the periosteum. As it passes from the walls to the contents of
the tympanic cavity, besides covering the ligaments of the malleus and the incus
and the tendons of the tensor tympani and stapedius muscles, it forms a number of
special folds and pouches.
The anterior malleolar fold is reflected from the tympanic membrane over the anterior
process and ligament of the malleus and the adjacent part of the chorda tympani, and the
posterior malleolar fold stretching between the manubrium and the posterior tympanic wall,
surrounds the lateral ligament of the malleus and the posterior part of the chorda tympani.
Each of these folds presents inferiorly a concave free border, and between them and the tym-
panic membrane are two blind pouches, the anterior and posterior malleolar recesses or pouches
1090
SPECIAL SENSE ORGANS
of Troltsch. Connected with the posterior recess is a third cul-de-sac, the superior recess of
the tympanic membrane, or pouch of Prussak, situated between the pars flaccida of the tym-
panic membrane and the neck of the malleus. The floor of this recess is formed by the lateral
process of the malleus, and is lower than its outlet; therefore, the recess may serve as a pocket
in which pus or other fluid may accumulate. A somewhat variable fold of mucosa, the plica
incudis, passes from the roof of the tympanic cavity to the body and short process of the incus.
The body and short process of the incus, the head of the malleus, and this fold incompletelj
separate off a lateral cupular portion of the epitympanic recess, and a stapedial fold stretches
from the posterior wall of the tympanic cavity and surrounds the stapes, including the oburator
membrane, which stretches between its crura. Other inconstant folds have been described.
The mucosa of the typanic cavity, except over the tympanic membrane, promontory, and
ossicles, is covered by a columnar ciliated epithelium.
Fig. 834. — The Tympanic Cavity, Antehiob Wall Removed,
Epitympanic recess
Lateral malleolar
ligament
Pars flaccida
Superior recess
Lateral process of
Anterior malleolar
ligament
Insertion of tensor
tampani
Manubrium of
malleus
External acoustic
meatus
Umbo and tip of
manubrium of
malleus
Tympanic cellula
Head of malleus
Neck of malleus
Facial nerve
Long process of
incus
Pyramidal
eminence
Tendon of
stapedius
Bones. — The tympanic cavity contains three small movable bones, joined to-
gether and to the walls of the cavity, and having attached to them special muscles
and ligaments. These auditory ossicles form a chain across the tympanic cavity
connecting the tympanic membrane and the vestibular (oval) fenestra. They are
the malleus, the incus, and the stapes, and are described in the section on Oste-
ology on p. 79.
Articulations of the ossicles. — The manubrium and lateral process of the maUeus are im-
oedded in the tympanic membrane. The margin of the irregularly elliptical articular surface
bn the posterior side of the head of the malleus is bound to the body of the incus by a thin
capsular ligament, forming a diarthrodial joint, the incudo-malleolar articulation. From the
inner surface of the capsular ligament, a wedge-shaped rim projects into the joint cavity and
incompletely divides it. The long crus of the incus lies parallel to the manubrium of the
malleus and on its superior and medial aspect (figs. 833 and 835). It ends in the lenticular
process. The convex extremity of this fits into the concavity on the head of the stapes, to
form a diarthrodial joint, the incudo-stapedial articulation. From its articulation with the
incus, the stapes passes almost horizontally across the tympanic cavity to its junction with
the medial wall. The cartilage-covered edge of the base is bound to the cartilage-covered rim
of the vestibular (oval) fenestra by the annular ligament of the base of the stapes, thus forming
the tympano-stapedial syndesmosis.
Ligaments of the ossicles. — In addition to the attachment of the manubrium
of the malleus and the base of the stapes to the walls of the tympanic cavity, the
bones have additional ligamentous attachments. The superior malleolar liga-
THE TYMPANIC CAVITY
1091
ment runs almost vertically from the superior wall of the epitympanic recess to the
head of the malleus (fig. 834) . The anterior malleolar ligament extends from the
angular spine of the sphenoid bone through the petro-tympanic (Glaserian) fissure
to the anterior or long process of the malleus, which it surrounds, and is inserted
with it into the neck of the malleus. The lateral malleolar ligament is short and
thick, and runs from the margins of the tympanic notch (notch of Rivinus) to the
neck of the malleus (fig. 834) . The posterior ligament of the incus passes from the
fossa on the posterior tympanic wall to the crus brevis of the incus (fig. 835) . The
superior ligament of the incus is little more than mucous membrane; it runs from
the tympanic roof to the body of the incus.
Muscles of the ossicles. — Each of the muscles of the ossicles is contained in a
bony canal. The tensor tympani is a pinniform muscle about 2 cm. long. It
arises from the cartilaginous part of the tuba auditiva (Eustachian tube), from the
Fig. 835. — Medial Surface op Right Membrana Tympani. (Enlarged.)
Superior malleolar ligament Incus
Head of malleus
Chorda tympani nerve
Tendon of tensor tympani
Manubrium of malleus
Tensor tympani muscle
Tuba auditiva
Posterior ligament of incus
Posterior portion of
epitympanic recess
■Base of stapes
'Lenticular process of incus
Posterior portion of
membrana tympani
adjacent part of the great wing of the sphenoid, and from the bony walls of the
semicanal which encloses it. It ends in a round tendon which turns almost at right
angles over the cochleariform process and passes laterally across the tympanic
cavity to be attached to the manubrium of the malleus near the neck. It draws
the manubrium medially and tightens the tympanic membrane, and is supplied by
the motor division of the trigeminal cranial nerve, through the tensor tympani
branch from the otic ganglion. The stapedius arises in the interior of the hollow
pyramidal eminence. The tendon escapes through the openings at the apex and
then turns inferiorly and is inserted on the posterior surface of the neck of
the stapes. It draws laterally the ventral border of the base of the stapes and is
supplied by the facial nerve.
Vessels and nerves. — The arteries of the tympanic cavity are the anterior tympanic from
the internal maxillary artery (fig. 451), the stylo-mastoid from the posterior auricular artery,
the superficial petrosal from the middle meningeal artery, the inferior-tympanic from the
ascending pharyngeal (fig. 446), and the carotio-tympanic branch from the internal carotid.
The veins empty into the superior petrosal sinus and into the posterior facial (temporo-
maxillary vein). The nerves are the tympanic plexus formed by the tympanic branch of the
glosso-pharyngeal (p. 951), and the inferior and superior carotico-tympanic nerves which join
the internal carotid plexus of the sympathetic (p. 960). The small superficial petrosal nerve
takes its origin from the tympanic plexus, and the chorda tympani crosses the t)"mpanic
cavity from the posterior to the anterior wall (p. 948, figs, 738 and 835).
1092 SPECIAL SENSE ORGANS
The Antrum Tympanicum
The aperture {aditus) in the upper part of the posterior wall of the tympanum
leads into the chamber termed the antrum tympanicum. This is a comparatively
large cavity, of irregular form, lying mainly behind but also somewhat above and
lateral to the tympanum, and extends to the medial end of the external auditory
meatus. It is lined by mucous membrane, continuous with that of the tympanic
cavity, and into it open the mastoid cells (cellulse mastoidese). These cells are
small, irregular cavities in the interior of the mastoid process and they com-
municate with one another freely. They vary exceedingly in their size and
asrangement.
The antrum tympanicum has a roof, formed by the tegmen tympani, a posterior wall,
separating it from the bend of the transverse sinus, a lateral wall, lying about 10 mm. from the
surface of the head, a inedial wall, and an anterior wall (see also p. 78).
The Auditory (Eustachian) Tube
The auditory tube [tuba auditiva] (Eustachian tube) (fig. 829) extends from
the carotid (anterior) wall of the tympanic cavity inferiorly, medially, and
anteriorly to the pharynx. It is about 37 mm. (1.5 in.) long. In the lateral
one-third of its length it has a bony wall, while in the medial two-thirds
this wall is cartilaginous. The osseous part (see p. 74) begins at the tympanic
ostium on the anterior wall of the tympanic cavity. It is in relation medially
and inferiorly with the carotid canal, and gradually contracts to its irregular
medial extremity, which is the narrowest point in the tube, and is termed the
isthmus. The cartilaginous part is firmly attached to the osseous and hes in a
sulcus at the base of the angular spine of the sphenoid bone. It gradually dilates
in its passage to the lateral wall of the pharynx, where its opening, pharyngeal
sotium, is just posterior to the inferior nasal concha (turbinated bone). The
walls of the cartilaginous part are formed by a cartilaginous plate which is folded
so as to form a trough-like structure, consisting of a medial and a lateral lamina,
completed inferiorly by a membranous lamina formed of connective tissue.
A small portion of the lumen in the superior part of the cartilaginous tube remains per-
manently open; elsewhere the walls are in contact, except during deglutition, when they are
opened by the tensor veli palatini muscles. The mucosa of the osseous part is thin, and firmly
attached to the bony wall, but in the cartilaginous part it becomes thicker, looser, and folded,
and contains mucous glands, especially near the pharynx, where there is also some adenoid
tissue.
3. THE INTERNAL EAR
The internal ear [auris interna] is the essential part of the organ of hearing.
It consists of a cavity, the osseous labyrinth, contained within the petrous portion
of the temporal bone, and enclosing a membranous labyrinth. The osseous
labyrinth is divided into cochlea, vestibule, and semicircular canals (seep. 80),
and the accompanying figures (338-838 )show their position and relations.
It will be noticed that the vestibule forms a central chamber, from which the semicircular
canals and the cochlea branch off; the former from the superior and dorsal portion, and the latter
from the ventral and inferior.
It will further be noticed that the bony wall of this vestibule shows depressions and ridges on
its interior, which are associated with parts of the membranous labyrinth, viz., an upper recess
for the utricle (fovea hemielliptica) and a lower recess for the saccule (foyea hemispherica).
There are openings in the bony wall for the entrance of nerves to the different parts of the
membranous labyrinth, and for the transmission of the ductus endolymphaticus, as well
as the small openings of the semicircular canals (ducts) and the opening of the cochlear canal
(or duct).
The membranous labyrinth, in which the auditory (acoustic) nerves (cochlear
and vestibular) end, lies within the osseous labyrinth, the form of which it more
or less closely resembles. Thus the membranous semicircular ducts lie within
the bony semicircular canals, the membranous cochlear duct within the bony
cochlea; while the vestibule contains two small membranous sacs, the utricle
and saccule, with their connections. The membranous structures are much
smaller in diameter than the osseous, and are partially separated from the bone
by an endothelial-Hned space which is filled with a fluid, the perilymph. The
THE MEMBRANOUS LABYRINTH
1093
membranes are in contact, however, with the bony wall along their convex margin,
and the utricle, saccule and cochlear canals are in contact with the bony walls
over the areas where the nerves enter them. The fluid which fills the mem-
branous labyrinth is termed the endolymph.
Fig. 836. — The Osseous Labyrinth of the Right Side.
(Modified from Soemmerring. Enlarged.)
Superior semicircular caiial<
Posterior semicircular canal
Lateral semicircular canal
Vestibule and fenestra ovahs'
Second turn of cochlea
Cupula of cocMea
Ampulla
Fenestra cochleari:
Commencement of first turn of the cochlea
The utricle is an oval tubular sac, whose rounded end lies in the superior and
dorsal portion of the vestibule. It is here tightly bound to the elliptic recess
(fovea hemielliptica) by connective tissue and by the entrance of the filaments
of the utricular division of the vestibular nerve as they pass from the superior
837. — Interior of the Osseous Labyrinth of the Left Side.
(Modified from Soemmerring. Enlarged.)
-Superior semicircular canal
Elliptic recess (fovea
hemielliptica)
Superficial recess (fo
hemispherica
Lamina spirali
Scaia tympani of cochlea.
•Posterior semicircular canal
Lateral semicircular canal
.Opening common to superior and
posterior semicircular canal
Internal aperture of vestibular
aquseduct
■Internal aperture of cochlear
canaliculus
macula cribrosa to the wall of the utricle. In the anterior part of the interior of
the utricle, an oval, whitish, thickened area, macula acustica utriculi, marks the
terminal distribution of the nerve, and posteriorly the utricle is joined by the
orifices of the semicircular ducts.
Fig. 838. — Interior of the Osseous Cochlea. (Enlarged.)
Lamina spiralis
Modiolus
The saccule is a flattened, oval sac, smaller than the utricle, and situated in
the anterior and inferior part of the vestibule. It is bound to the spherical recess
(fovea hemisphserica) by connective tissue and by the saccular division of the
1094
SPECIAL SENSE ORGANS
vestibular nerve, filaments of which extend from the middle macula cribrosa to
the anterior and medial wall of the saccule, to be distributed over a thickened
area, macula acustica sacculi. Anteriorly and inferiorly the saccule gradually
passes into a short canal, the ductus reuniens, which connects it with the cochlear
duct, and posteriorly the very small endolymphatic duct is attached (fig. 839).
Fig. 839. — Diagram of the Left Membranous Labyrinth. (Deaver.)
Superior and lateral membranous ampullje
Superior semicircular
duct
Cupular CEecum
Cochlear duct
Dtricle
Lateral semicircular duct
Posterior membranous ampulla
Ductus endolymphaticus
This extends through the aquseductus vestibuli to the posterior surface of the
petrous portion of the temporal bone, where it ends in a dilated blind pouch,
the endolymphatic sac, situated just beneath the dura. Just beyond the saccule,
the endolymphatic duct is joined at an acute angle by a short canal of minute
calibre, the utriculo-saccular duct, which opens into the utricle through its anterior
medial wall and, with the endolymphatic duct, connects it with the saccule.
Fig. 840. — Right Membranous Labyrinth of a Newborn Child. Exposed by Partial
Removal OF THE Bony Labyrinth. Dorsal view. (Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Facial nerve
Osseous lamina
spiralis
Lamina basilans
(membranous *•
lamina spiralis)
Scala tympani
Supenor semicircular duct
Common crus
Saccule i Posterior membranous ampulla
Posterior ampuUary nerve
The semicircular ducts (membranous semicircular canals) are situated within
the osseous semicircular canals and are, therefore, known as the lateral, superior,
and posterior semicircular ducts. They connect with the utricle by five openings,
the posterior and superior ducts uniting to form a common crus before their
THE MEMBRANOUS LABYRINTH
1095
termination. Each duct is less than a third of the diameter of the bony canal,
from which it is separated by a large perilymphatic space, except along the
greater cm*vature, where it is attached. The ducts are dilated in the bony
Fig. 841. — Schematic Representation of the Right Membranotjs Labyrinth and the
Divisions of the Acoustic Nerve. Dorsal view. (Toldt, "Atlas of Human Anatomy,"
Rebman, London and New York.)
Utriculo-saccular duct
Macula acustica of utricle
Macula acustica of saccule
Vestibular ganglion
Vestibular nerve
Saccular nerve \
Cochlear nerve.^^
Cochlear duct "
Saccule
Ductus reuniens (of Hensen)
Posterior ampullary nerve
--Superior semicircular duct
Ampullary cristae of the
superior and lateral
semi-circular ducts
— , Endolymphatic
duct
Posterior semicir-
cular duct
Ampullary crista of
the posterior semi-
circular duct
-" Endolymphatic ;
ampullse, producing the lateral, superior, and posterior membranous ampullae,
and on the attached surface of each of these there is a transverse groove, the
ampullary sulcus, for the ampullary division of the vestibular nerve, and corre-
sponding to the sulcus a ridge, the ampullary crista, projects into the interior.
Fig. 842. — Axial Section Through the Decalcified Cochlea of a Newborn Child
(Toldt, '* Atlas of Human Anatomy," Rebman, London and New York.)
Hamulus of lamina spirahs^
Apical spiral'^;;;
Helicotrema
Modiolus
Scala vestibuli
Cochlear duct
Lamina basilans
(membranous lamina'
spiralis)
Osseous lamina spirabs
Spiral ganglion of cochlea
Base of modiolus
Cochlear nerve
Internal acoustic meatus
Acoustic nerve (cochlear division)
rl^V^ Spiral ligament of cochlea
jj;^v^ScaIa tympan
f
Macula acustica sacculi
Wall of saccule
Saccular nerve
:tibular ganglion
Acoustic nerve (vestib-
ular division)
The cristse in the ampullee of the membranous semicircular ducts and the maculae
in the saccule and utricle are superficially covered with fine crystals of calcium
carbonate, otoconia (otohths).
1096
SPECIAL SENSE ORGANS
The cochlear duct (membranous cochlea or scala media) begins within the
cochlear recess of the vestibule in a blind pouch, the vestibular caecum, and
traversing the spiral canal of the cochlea, ends just beyond the hamulus of the
lamina spiralis in a second blind pouch, the cupular caecum. Close to the ves-
tibular caecum it is joined to the saccule by the ductus reuniens. It is lined
throughout by epithelium and is somewhat triangular in cross-section. Its
floor is formed by thickened periosteum over part of the osseous lamina spiralis
and by a fibrous membrane, the lamina basilaris, which stretches from the free
border of the lamina spiralis to a thickening of the periosteum, the spiral ligament
of the cochlea, on the peripheral wall.
The epithelium of this floor is greatly modified, forming the spiral organ (organ of Corti)
in which the fibres of the cochlear nerve terminate. The periplieral wall is formed by the
thickened periosteum upon the peripheral wall of the cochlear canal, while the third waU is
Figs. 843 and 844. — Sections Showing Early Stages in the Development op the Otic
Vesicle.
fomed by a thin vestibular membrane (membrane of Reissner) which passes from the periphera
wall to the osseous lamina spiralis near its free margin, forming with the lamina spiralis an angle
Ff 45 degrees. The cochlear duct and the osseous spiral lamina divide the cochlear spiral
canal into two parts, one next to the basilar membrane, the scala tympani, and one next to
the vestibular membrane, the scala vestibuli. The scala tympani unites with the scala vestibuli
at the helicotrema, and from the scala tympani a minute canal, the perilymphatic duct, passes
through the cochlear canaliculus and connects with the subarachnoid space. A thin fibrous
layer, the secondary tympanic membrane, closes the cochlear fenestra (fenestra rotunda)
and thus separates the scala tympani from the tympanic cavity, and the vestibular perilym-
phatic space (scala vestibuli) is separated from the tympanic cavity by the base of the stapes
in the vestibular fenestra (fenestra ovalis).
Vessels and nerves. — The internal auditory artery , fig. 514), a branch of the basilar artery,
accompanies the cochlear and vestibular nerve. It supplies the vestibule, semicircular canals,
and cochlea, and their membranous contents. The blood is returned by the internal auditory
vein into the inferior petrosal sinus, and by small veins which pass through the cochlear and
vestibular aqueducts to the inferior and superior petrosal sinuses. The acoustic nerve (p. 949,
figs. 841 and 842) consists of a vestibular and a cochlear division. The membranous ampuUse of
the semicircular ducts and the acoustic maculae of the utricle and saccule are supplied by
the vestibular nerve. The spiral organ (organ of Corti) in the cochlear duct is supphed by
the cochlear nerve.
Development of the Ear
The external and middle ears have a common origin quite distinct frorn that which gives
rise to the internal ears, and are to be regarded as portions of the branchial arch apparatus
secondarily adapted to auditory purposes.
The sensory epithelium lining the internal ear is derived from the otic vesicle, a structure
formed from the surface epithelium of the head, while the membrane and bones surrounding
it are formed from the mesoderm which surrounds the vesicle.
DEVELOPMENT OF THE EAR
1097
Internal ear. — The process of development is as follows (fig. 843-845) : —
By invagination from the surface, an epithelial-lined vesicle, termed the primitive otocyst
or otic vesicle, is formed dorsal to the extremity of the second branchial cleft. It is at first
merely a pit on the surface, but eventually it loses its connection with the surface epithe-
lium and sinks into the interior. It then undergoes the alterations in shape and form shown
in the accompanying fig. 845. The vesicle is at first somewhat oval, and a small hollow
stalk arises from it, the recess of the labyrinth, which forms the ductus endolymphaticus in
the adult. The ventral and dorsal portions of the cyst become enlarged. From the former two
hoUow plate-like projections arise, one placed vertically, the other horizontally, and along the
free margins of these plates are formed the semicircular ducts, the superior and posterior from
the vertical, and the lateral duct from the horizontal one. The central part of each plate be-
comes peforated, and the periphery is thus altered to the characteristic loop form of the adult
semicircular ducts. The portion of the vesicle lying between the dorsal and ventral enlarge-
ments forms the primitive atrium. It becomes divided into two chambers, an upper dorsal
connected with the semicircular ducts, forming the utricle, and an inferior ventral, the saccule,
which is connected with that portion of the ventral expansion from which the cochlea is formed.
The recess of the labyrinth retains its connection with the cavity of the vesicle at the narrow
stalk connecting utricle and saccule, (fig. 845). The cochlea is formed by an outgrowth from
the saccule, at first straight, and later coiled in the fashion formed in the adult.
Fig. 845. — Diageams Illustrating Successive Stages in the Development of the
Membranous Ear.
Semicircular canals Ductus endolym-
Semicircnlar Ductus endo- •i^^HSBmiiN. I
canal lymphaticus
Vestibular pouch
Recessus
Cochlear pouch
Ductus reuniens
Saccule
Utricle
Ductus reuniens
Cochlea
External and middle ear. — The external auditory meatus is formed from the dorsal part
of the first (external branchial) pouch, and the tympanic membrane from the membrane
which forms the floor of that pocket and separates it from the corresponding pharyngeal
(internal) pouch. Its outer surface is thus formed from ectoderm and the inner from endoderm.
The internal (pharyngeal) groove gives origin to the tympanic cavity and tuba auditiva,
the margins of the groove uniting.
The auricle is formed from nodular thickening of the tissue bounding the outer end of the
first branchial cleft. Three nodules are formed on the first (mandibular) and three on the second
(hyoid) arch. Behind the latter, the free margin of the auricle is formed by a folding off of the
integument. Later an additional tubercle is formed dorsally between the two sets of nodules.
From the mandibular nodules are formed mainly the tragus and the crus of the helix — from
the hyoid tubercles the scaphoid fossa, antitragus and the crus of the anthchx.
The auditory ossicles, and their muscles are formed from the neighbouring arches, the malleus
and incus, together with the tensor tympani, being derived from the first arch, while the stapes
and stapedius probably are derived from the second arch.
The tympanic cavity is at first quite small, but later increases greatly, partly by the con-
densation bf the loose areolar tissue which underlies its mucous membrane, the auditory ossicles
and their muscles being thus apparently brought within the cavity, and partty by the absorption
of the neighbouring bone. By this latter process the antrum and the tympanic and mastoid
cells are formed, all these depressions or cavities being lined by mucous membrane continuous
with that of the tj'mpanic cavit}'.
The Ear in the Child. — The ear in the newborn child shows several marked differences
from the adult ear.
Among the principal differences are the following: —
1. The external auditory meatus is very short, since the bony portion is undeveloped,
and is represented only by the tympanic ring. As a result of this, the tympanic membrane is
placed on a level with the surface of the head, and looks very much downward.
2. The mastoid or tympanic antrum is relatively very large, and lies above and behind the
tympanum. Its lateral wall is only about 1 mm. in thickness.
3. The mastoid process is not developed, and hence the stylomastoid foramen opens on
the surface behind the lower part of the tympanic ring. The exit of the facial nerve is therefore
much more upon the surface, and higher up than in the adult.
4. The auditory (Eustachian) tube is nearly horizontal in direction.
5. The ossicles are of nearly the] same size as in the adult.
1098 SPECIAL SENSE ORGANS
References for the Special Sense Organs. — For the development of the various
sense organs, see article by Keibel in Keibel and Mall's Human Embryology,
vol. 2. A. Visual. Graefe-Saemisch, Handbuch d. ges. Augenheilkunde;
Salzmann, Anat. u. Histol. d. Augapfels, 1912; various papers in Archiv f. Oph-
thalmologic; (Anterior chamber, etc.) Henderson, Ophthalmic Review, 1910-11;
{Optic disc) Johnson, Phil. Trans. Royal Soc. B. vol. 194; B. Auditory. Gray,
Labyrinth of Mammals, 1910; (Tectorial membrane, etc.) Hardesty, Amer. Jour.
Anat., vol. 8; (Auditory nerve, comparative) Holmes, Trans. Royal Irish Acad.,
vol. 32, ser. B; (Experimental embryology) Lewis, Amer. Jour. Anat., vols. 3, 7;
C. Olfactory. Read, Amer. Jour. Anat., vol. 8. D. Taste. Von Ebner, in Koel-
liker's Handbuch d. Gewebelehre; Graberg, Anat. Hefte, Bd. 12.
SECTION IX
DIGESTIVE SYSTEM
Revised for the Fifth Edition
By C. M. JACKSON, M.S., M.D.,
PROFESSOR OF ANATOMY IN THE UNIVERSITY OF MINNESOTA
IN order to furnish the living protoplasm with the materials necessary for
energy, growth and repair, a constant supply of food must be provided.
Most foods must be rendered soluble, and must undergo certain preliminary
chemical changes, in order to render them suitable for absorption and assimilation
by the cells of the body. For this preparation of the food-supply, the digestive
system [apparatus digestorius] is provided, which includes the alimentary canal
and certain accessory glands (salivary glands, liver and pancreas) . The alimen-
tary canal is divided into a number of successive segments, varying in size and
structure according to their function. These segments (fig. 846) include the
mouth, pharynx, oesophagus, stomach, small and large intestines.
Typical structure. — The most important layer of the tubular alimentary canal is the inner
mucous memhrane [tunica mucosa]. From its epithelial lining, the various digestive glands are
derived, and through it the process of absorption takes place. The epithelium is supported
by a fibrous tunic [lamina propria mucosa;] beneath which is a thin layer of smooth muscle
[lamina muscularis mucosae]. The layer next in importance is the muscular coat [tunica muscu-
laris] which propels the contents along the canal. It is typically composed of two layers of
smooth (involuntary) muscle, the inner circular and the outer longitudinal in arrangement.
Between the mucosa and the muscularis is a loose, fibrous submucous layer [tela submucosal,
which allows the folds in the mucosa to spread out when the canal is distended. Finally, there
is an outer fibrous coat [tunica fibrosa], which in the abdominal cavity becomes the smooth
serous coat [tunica serosa], or visceral layer of the peritoneum, which eliminates friction during
movements. The variations in the structure of the aUmentary canal in different regions are
due chiefly to differences in the mucosa.
Glands. — Since the glands form an important part of the digestive system, the classifica-
tion of glands in general will be discussed briefiy. A gland may be somewhat loosely defined
as an organ which elaborates a definite substance which is either a waste product to be eliminated
(excreted), or a secretion to be further utilized by the organism. Glands may be divided into
(a) ductless glands (e. g., spleen, thyreoid gland), which pour their secretions directly into the
blood or lymph; and (b) glands with ducts, which open upon an epithelial surface. Some organs,
however, belong in both classes (e. g., liver, pancreas).
The glands with ducts (the so-called true' glands) are always derived from an epithelial
surface and may be further subdivided upon the basis of either (1) form or (2) cell-structure.
According to form, glands are classified as either <?<iwtor or saccular (alveolar, acinous). Each
of these may be either simple or compound (branched). The compound saccular form is often
called racemose. Moreover, intermediate forms (tubulo-racemose) occur.
According to cell-structure and character of secretion, glands are divided into mucous
and serous types. In the mucous type, the ceUs appear larger and fighter (fig. 867) when swollen
with mucus which is secreted for purposes of lubrication. The goblet^ceUs of the intestine
represent imicellular glands of this type. In the serous (or albuminous) type of glands, the
cells usually appear somewhat smaller and more deeply stained, with numerous zymogen
granules (fig. 867). The secretion is a watery, albuminous fluid, which contains the digestive
enzymes. There occurs also a mixed type, with separate mucous and serous saccules, or both
types of cells may occur in the same saccule (the serous cells as 'demilunes' or 'crescents'
(fig. 867). In aU cases, the epithelial gland ceUs are supported by a fibrous connective-tissue
stroma, which provides a rich vascular and nerve-supply.
Morphology. — The alimentary canal in comparative anatomy is divided into the head-gut
(mouth and pharynx), fore-gut (cesophagus and stomach), mid-gut (smaU intestine), and hind-
gut (large intestine). Embryologically, the mid-gut corresponds roughly to the portion of the
archenteron attached to the yolk-sac, the portions of the archenteron anterior and posterior to
the yolk-sac being designated as fore-gut and hind-gut respectively. (See Section I, Morpho-
genesis.) The lining epithelium of the alimentarj' tract is endodermal, excepting the anal canal
and the mouth cavity, which are lined by invaginations of the ectoderm.
In the region of the mouth and pharynx, the digestive and respiratory systems are closely
related in position, structure, function and origin. Morphologically, the head-gut represents
a primitive aUmentary-respiratory apparatus.
1099
1100
DIGESTIVE SYSTEM
THE MOUTH
The oral cavity [cavum oris] represents the first segment of the alimentary
canal. Its walls are exceedingly specialised in structm-e, corresponding to its
manifold functions (mastication, insalivation, taste, speech, etc.).
Boundaries. — The oral cavity communicates anteriorly with the exterior
through the transverse oral fissure [rima oris], and posteriorly with the pharynx
through the isthmus of the fauces [isthmus faucium]. The anterolateral walls
are formed by the flexible lips and cheeks. The roof is chiefly immovable and is
Fig. 846. — Di.^gram op the Alimentary Canal.
NASAL CAVITY
PALATE
MOnTH CAVITY' /,'
TONGUE
NASAL PHARY1«C
formed by the upper jaw with the hard and soft palate. The movable floor is
formed by the lower jaw and the tongue.
Subdivisions. — The oral cavity is subdivided by the alveolar and dental
arches into an inner cavity, the oral cavity proper [cavum oris proprium], and an
outer vestibule [veigtibulum oris] adjacent to the lips and cheeks (fig. 848). When
the upper and the lower teeth are in apposition, the vestibule communicates
THE MOUTH
1101
with the oral cavity proper (aside from the small interdental spaces) only through
a space behind the last molar teeth on each side. Opening into the oral cavity are
certain accessory glands, the salivary glands.
Fig. 847. — Coronal Section thhotjgh Oral Region.
Maxillary sinus Nasal cavity
/ /
Lingual art
Platysma
Genio-glossus^'
Genio-hyoid
Sublingual
gland
— Exte
Uary art.
^Submaxillary gland
"^Sublingual art. and
Ungual n.
NMylohyoid
^^ Digastric
Structure. — Of the typical layers of the alimentary canal, only the mucous membrane can
be recognised as a continuous layer in the mouth cavity. Even this is greatly modified and in
structure somewhat resembles the skin, from which it is derived and with which it is continuous
Fig. 848. — Mid-sagittal Section of the Head, through Oral and Nasal Regions.
(Rauber-Kopsch.)
Cribriform plate
Spheno-ethmoidal
Hypophysis recess
\
Dorsum sellas
Choanal arch
Nasopharyngeal
meatus
Pharyngeal recess
Torus lubanus
Levator cushion
Anterior hp
Salpingopharyn
geal fold
Uvula
Foramen caecum
lingUEe
Palatopharyngeal fold
Hyoid bone
Mental spine
cisive canal
Upper lip
Vestibulum oris
Oral cavity proper
Lower Up
at the rima oris. The submucosa is a strong fibrous layer connecting the mucosa with adjacent
structures, and lodging numerous racemose mucous glands. The muscles in the walls of the
mouth cavity are not homologous with the typical muscularis of the alimentary canal. The
outer fibrous tunic is also wanting.
1102
DIGESTIVE SYSTEM
The development of the oral cavity. — As stated in the section on Morphogenesis, the oral
cavity has its origin in a depression, the oral fossa, situated between the ventrally bent, devel-
oping head and the region occupied by the developing heart. This fossa is bounded anteriorly
by the fronto-nasal process, and laterally by the maxillary and mandibular processes, portions
of the first branchial arches. The fossa is lined by ectoderm. Its floor is in apposition with
the cephalic end of the archenteron, lined by entoderm, the ectoderm of the oral fossa and the
entoderm of the archenteron being in immediate contact and forming the pharyngeal mem-
brane. The oral fossa deepens with further development, and becomes the oral sinus. The
pharjmgeal membrane becomes perforated in embryos about 2 mm. in length and disappears,
leaving a free communication between the oral sinus and archenteron. On each side of the
developing head and in a latero-ventral position there is early developed an area of thickened
ectoderm, known as the nasal area. These areas soon develop into depressions, the nasal fossae,
and assume a position, one on either side of the fronto-nasal process; on each side of the fronto-
nasal process there is developed a prominent protuberance, the globular process, each process
forming the median wall of a nasal fossa. The lateral wall of each nasal fossa also thickens
to form the lateral nasal process. With the further development, the ventral portion of each
lateral nasal process fuses with the corresponding globular process, the maxillary processes also
uniting with the globular processes, in this way separating the nasal fossae from the oral sinus.
With the further growth toward the median hne of the maxiUary processes the fronto-nasal
process becomes narrower, ultimately forming the nasal septum and a small median portion
of the upper jaw, the remainder of the upper jaw being formed by the maxillary processes, and
the lower jaw having its origin in the mandibular processes.
Fig. 849. — Sagittal Section of the Lower Lip. (Lewis and Stohr.)
Sebaceous gland
Tall papillffi— -/JJ'
Oblique sec- /
tion of palpillae
Labial gland
Hair shafts and
sebaceous glands
Sebaceous gland
Hair shaft
Artery
Bulb of a hair
Submucosa Orbicular Mimetic Conum Epidermis
muscle muscle
Variations. — The mouth is rarely absent, due to failure of the stomatodeal invagination,
or imperforate, due to atresia of the pharyngeal membrane. Other variations wiU be mentioned
in connection with the various mouth organs.
Comparative. — The phylogenetic origin of the mouth cavity from the integument is indi-
cated not only by the ectodermal origin of its lining epithelium, but by its general structure
and its appendages. Among the latter may be noted the teeth (representing modified dermal
papillae), sebaceous glands, and (in some rodents) even hairs in the mucosa lining pouches in
the cheeks.
THE LIPS AND CHEEKS
The lips [labia oris] form the anterior wall of the mouth cavity. The lower
Up [labium inferius] is marked off from the chin by the sulcus mentolabialis.
The upper lip [labium superius] extends upward to the nose medially and the sul-
cus nasolabialis laterally. The philtruni is a median groove on the upper lip
extending from the septum of the nose above to the labial tubercle [tuberculum
labii superioris] below, at the middle of the rima oris. On each side of the rima
oris the upper and the lower lips are continuous at the angle of the mouth [angulus
oris], which is usually opposite the first premolar teeth. Laterally, the lips are
THE LIPS AND CHEEKS
1103
continuous with the cheeks [buccse], which form the lateral walls of the mouth
cavity.
In structure, the lips (fig. 849) consist essentially in a middle layer of cross-striated muscle
(orbicularis oris) covered externally by skin which is continuous through the rima oris with the
mucosa forming the inner layer of the hps. The mucosa lines the vestibulum oris and is reflected
upon the gums above and below. In the median line above and below, there extends fi-om the
lip to the gum a small fold of the mucosa [frenulum labii superioris vel inferioris]. The structure
of the cheeks (figs. 847, 864) is similar to that of the lips but somewhat more complicated.
Fig. 850. — ^Labial and Buccal Glands Exposed by Dissection of the Skin feom in Front.
(From Toldt's Atlas.)
Labial glands ^PP^r Up
Tunica mucosa oris (tela submucosa)
Buccal glands
Labial glands
Lower Up
Buccinator
The muscular basis of the cheek is the buccinator muscle. External to this is a thick layer
of fat [corpus adiposum buccae] covered partly by the dermal muscles (platysma, zygomaticus,
etc.) and lastly the skin. Internally the cheek is lined by the mucosa, continuous with that
of the cheeks. The parotid duct opens into the vestibule opposite the second upper molar
tooth.
Glands. — The skin of the lips and cheeks is well supplied with the usual sudoriparous and
sebaceous glands. The mucosa likewise presents two kinds of glands, the sebaceous and the
mucous glands. The sebaceous glands are relatively few in number and variable, being present
in about 30 per cent, of cases in the adult (Stieda). They are similar in structure to those of
Fig. 851. — Section of Labial Mtcos-i Snr-mMj C lwd'; X 16 (From Toldt's Atlas.)
Epithelium — H^^^^^^^^S^IT^li ^S^W^^ilW- ~ Epithelium
Duct
- Accessory gland
Lan
Tela submucosa
M. orbicularis oris
Mucous gland
the skin (though not associated with hair foUicles), and when present are visible as small yellow-
ish bodies in the mucosa. They occur chiefly near the free margins of the lips and along the
cheek opposite the teeth.
The mucous glands are much more numerous and constantly present (figs. 850, 851). They
are all of the racemose type. They are variable but small in size, and closely packed together
in the submucosa of the lips [glandulte labiales], where they may easily be felt. Those of the
cheeks [gl. buccales] are less numerous. A few of them especially in the region of the molar
1104 DIGESTIVE SYSTEM
teeth [gl. molares], are placed outside the buccinator. The ducts of the molar glands pierce
this muscle near the parotid duct to open on the surface of the mucosa.
Vessels and nerves. — The mucosa of the lips and cheeks has a characteristic reddish hue, on
account of the numerous blood-vessels which are visible through the thick but transparent
stratified squamous epithelium (figs. 849, 851) The numerous papillae of the lamina propria
are highly vascular. The hlood-supply of the lips and cheeks is derived chiefly from the labial
(coronary) and buccal arteries. The rich nerve-supply (sensory) is from the infra-orbital,
mental and buccal branches of the fifth. The lips are especially sensitive near the rima oris.
Development. — During the second month in the human embryo, ledges of epithelium
grow into the substance of the mandibular and the fused fronto-nasal and maxillary processes.
These ledges develop into grooves which separate the upper and the lower lips from the upper
and the lower jaws, the grooves forming the oral vestibule.
The philtrum and labial tubercle are said to correspond to the lower part of the fronto-
nasal process. A failure of union between the globular and the maxillary processes presents an
arrest of development resulting in the malformation known as "hare-lip." ■
In the late fcetus and newborn, the red portion of the lips consists of an external smooth
pars glabra, and an inner zone, pars villosa, which is covered with numerous villus-like pro-
jections. The largest of these reach a length of 1 mm. They also extend backward in an irregu-
lar band along the mucosa of the cheek. They disappear during the first few weeks of post-
natal life.
In the infant, the corpus adiposum is especially well developed. On account of its supposed
aid as a support for the buccinator in sucking, it has been called the "sucking pad."
The sebaceous glands of the mucosa are said not to appear until about the age of puberty.
Variations. — As is well known, the lips and cheeks are exceedingly variable in shape, size
and structure in different individuals. There are also characteristic differences according to
race and sex in the form and structure of the lips, rima oris, beard, etc. The "harcrlip"
malformation was mentioned above.
Comparative. — Typical lips are found only in mammals, and are probably organs phylo-
genetically developed in connection with the process of suckling.
THE PALATE
The palate forms the roof of the mouth cavity proper, and consists of two por-
tions, the anterior or hard palate and the posterior or soft palate.
The hard palate [palatum durum] (figs. 848, 852) is continuous in front and
laterally with the alveolar processes of the upper jaw, and gives attachment
posteriorly to the soft palate. It separates the mouth from the nasal cavity. It
is supported by the palatine process of the maxilla and the horizontal part of the
palate bone. The oral surface is concave from side to side, and also from before
backward. It is covered by a thick, somewhat pale mucosa, which is firmly
adherent to the periosteum through the submucosa. The submucosa contains
numerous mucous glands [gl. palatinse] (fig. 852), similar to those of the lips.
In the median line of the hard palate is a line or ridge, the raphe (fig. 852)
terminating anteriorly in the small incisive papilla, which corresponds in position
to the bony incisive foramen. Anteriorly there occur four to six more or less
distinct transverse ridges [plicae palatinse transversse]. Near the posterior margin
of the hard palate there is on each side of the raphe a small pit (fig. 852), the
foveola palatina, which is variable and inconstant.
The soft palate [palatum moUe] (figs. 848, 892) separates the posterior portion
of the mouth cavity from the nasal part of the pharynx. It is attached to the
hard palate anteriorly and to the pharyngeal wall laterally. The posterior por-
tion or velum projects backward and downward into the pharynx. Its free mar-
gin presents a median conical projection, the uvula, and splits laterally on each
side to form two folds, the palatine arches, between which is located the palatine
tonsil (fig. 852). The palatine arches and tonsil will be described later in con-
nection with the pharynx.
Structure. — The soft palate is a fold of mucous membrane enclosing a fibrous aponeurosis,
muscles, vessels, and nerves. It is marked in the middle line by a raphe indicating the hue of
junction of the two halves from which it was formed.
The posterior layer of the mucous fold which is directed toward the cavity of the pharynx
is continuous with the na.sal mucous membrane; the anterior layer lies in the posterior boundary
of the mouth and is continuous with the mucous membrane of the hard palate. The structure
of the mucosa is very similar to that of the lips (fig. 849). Mucous glands are numerous in both
layers, but more especially in the anterior, and make up a large portion of the mucosa and sub-
mucosa (figs. 851, 852).
The aponeurosis is attached above to the posterior margin of the hard palate; laterally it
is continuous with the aponem-otic layer of the pharyngeal wall; below, toward the lower
margin of the velum, it gradually disappears. It gives attachment to fibres of the levator veli
palatini and the jjharyngo-palatinus (palato-pharyngeus) and to the tendon of the tensor veli
palatini.
THE PALATE
1105
Muscles. — The muscles of the soft palate are described later (p. 1134) with those of the
pharynx, with which they are closely associated.
Vessels and nerves. — The arterial supply of the hard palate is derived chiefly from the
major palatine branches of the internal maxillary. The arteries of the sojt palate include:
Fig. 852. — Roof op Mouth, Showing Haed and Soft Palate Dissected on One Side.
(Rauber-Kopsch.)
Papilla incisiva
Foveola
palatina
Arcus pharyngopalatinus
M. glosspalatiaus
Palatine tonsil
M. pharyngopalatinus
(1) Ascending palatine of external maxillary (facial); (2) pharyngeal branches of ascending
pharyngeal; (3) twigs from descending palatine of internal maxillary, which enter the smaller
palatine canals, are distributed to the soft palate and tonsils, and communicate with the
ascending palatine of the external maxillary (facial) artery; (4) lingual artery, by twigs from
the dorsal branch.
Fig. 853. — Developing Palatine Shelves, Viewed from Below. (McMurrich, from His.)
The sensory nerves to the'palate are derived chiefly from the fifth' through che sphenopalatine
ganglion. The hard palate is supplied by the nasopalatine and anterior palatine branches;
the soft palate chiefly by the median and posterior palatine branches. The motor nerves
will be mentioned later in connection witli the muscles.
1106 DIGESTIVE SYSTEM
The development of the palate. — The hard and soft palates arise (fig. 853) in two ridges
of tissue, designated the palate shelves, which develop on the inner surfaces of the maxillary
processes. These shelves grow toward the median line, and at the beginning of the third
month of fcetal life meet beneath the nasal septum, uniting with each other and with the nasal
septum, the union taking place from before backward. The incisive foramen indicates the
place of meeting of the premaxillary and palate shelves, which closes the primitive communi-
cation between the oral and the nasal cavity. A want of union of the palate shelves presents
an arrest of development known as cleft-palate. The uvula is similarly formed by the union of
the posterior ends of the lateral palate anlages, and a failure to unite may produce a bifid uvula.
The transverse palatine ridges are better developed in the infant than in the adult, and may
assist in holding the nipple in sucking.
Variations. — Cleft-palate and bifid uvula were mentioned above. The transverse palatine
ridges are quite variable in number and prominence. On each side of the incisive papilla
there is often found a small pit or shallow tube, a vestige of the embryonal incisive canal (Mer-
kel). Sometimes there is instead a single median pit, representing the lower end of the incisive
(Stenson's) canal. These pits are remnants of the primitive embryonic communication between
mouth and nasal cavities.
Comparative. — The palate is absent in fishes and amphibia, the ohoanse opening directly
into the primitive mouth cavity. In some birds, the palate shelves fail to unite, leaving a normal
cleft-palate. The incisive (Stenson's) canal remains open permanently in some mammals
(e. g., ruminants), bifurcating above and thus placing the mouth cavity in communication
with the nasal cavity on each side in the vicinity of Jacobson's organ. The transverse palatine
ridges are much better developed among many mammals, especially the carnivora.
THE TONGUE
The tongue [lingua] is a muscular organ covered with mucous membrane and
located in the floor of the mouth. It is an important organ of mastication, deglu-
tition, taste and speech. Upon its upper surface (figs. 854, 864) is a V-shaped
groove (sulcus terminalis) indicating the division of the tongue into two parts.
The larger anterior part, or body [corpus linguae] belongs to the floor of the mouth,
while the smaller posterior part, or root [radix linguae], forms the anterior wall of
the oral pharynx. The inferior surface (facies inferior) of the tongue is chiefly
attached to the muscles of the floor of the mouth, from the hyoid bone to the man-
dible (fig. 858). Anteriorly and laterally, however, the inferior surface of the
body is free and covered with mucosa. The superior surface of the body is called
the dorsum. It is separated from the inferior surface by the lateral margins,
which meet anteriorly at the tip [apex linguae].
The dorsum of the tongue usually presents a slight median groove [sulcus medi-
anus linguae]. Its posterior end corresponds to a small pit of variable depth, the
foramen ccecum, which is placed at the apex of the V-shaped terminal sulcus,
The dorsum of the body has a characteristic rough appearance due to numerous
small projections, the lingual papillce.
Lingual papillae. — Five or six varieties of papilte are distinguished, between which inter-
mediate forms occur. The conical [papillse conices] and thread-like [papillae filiformes] are
most numerous, and are arranged more or less distinctly in rows parallel with the terminal
sulcus (fig. 856). They are best developed toward the mid-line of the dorsum in its posterior
part. As shown in vertical section (fig. 856), each papilla consists of an axial core of vascular
fibrous tissue (from the lamina propria) often beset with smaller secondary papillse. The
stratified squamous epithelial covering often presents numerous thread-like prolongations from
the apex of the papilla. The papillse vary from 1 to 3 mm. in length.
The fungiform ("toad-stool shaped") papillae are somewhat similar to the conical in struc-
ture, but larger and more prominent, with an expanded free portion and a slightly constricted
stalk of attachment. They are relatively few in number and are scattered irregularly over
the dorsum, being most numerous near the margins (fig. 864). They are easily distinguished
in hfe by their larger size and reddish colour. A smaller, flattened variety of the fungiform is
sometimes called the lenticular ('lens-shaped') papillse. (This term, however, is apphed by
Toldt to certain small rounded- elevations with underlying lymphatic nodules in the mucosa of
the root of the tongue.)
The vallate (circumvallate) papillfe, usually seven to eleven in number, are conspicuous
and arranged in a V-shaped line parallel with and slightly anterior to the sulcus terminalis,
(figs. 854, 857). They are, as a rule, shaped hke short cyhnders, 1 to 2 mm. in width, and
somewhat less in height. As is shown in section (fig. 857), each is surrounded by a trench or
fossa, into the bottom of which open ducts of the serous glands of von Ebner. On the sides of
the fossaj are the taste-buds, as described in the section on Sense Organs.
The foliate papillie are represented by a few (five to eight) parallel transverse or vertical
folds of mucosa, along the margins of the tongue just anterior to the glosso-palatine arch on
each side (fig. 864). They are variable in size and sometimes rudimentary. In structure they
somewhat resemble the vallate papillse (though of different form), their walls being studded
with taste-buds.
THE TONGUE
1107
The free inferior surface of the tongue (fig. 858) is covered by a thin smooth
mucosa. In the median line is a prominent fold, the frenulum, which connects
the tongue with the mandible and the floor of the mouth. On each side of the
inferior surface, an irregular, variable, fringed fold, the plica fimbriata, extends
from near the apex backward approximately parallel with the lateral margin of
the tongue (fig. 858). Between the frenulum and the plicae fimbriatse, the lingual
(ranine) veins are visible on each side beneath the mucosa.
The root (or base) of the tongue [radix linguae] belongs to the pharynx, but is
here included with the mouth for convenience of description. Its free surface is
directed posteriorly, and represents the continuation of the dorsum linguae (fig.
854). Laterally it is continuous with the region of the palatine tonsils. Infe-
FiG. 854. — Dorsum and Root of the Tongue. (Papillae diagrammatic.)
Ventricular fold Lower part of pharynx
Extremity of __.
hyoid bone
Superior cornu of
thyreoid cartilage
Lateral glosso-
epiglottidean told
Anterior wall of the
pharynx
Cornicular tubercle
Cuneiform tubercle
Recessus piriformis
Vocal fold (true vocal
cord)
Median glosso-
epiglottidean fold
Pharyngopalatine arch
Glossopalatine arch
Vallate (circumvallate) papiU
Fungiform papillee
riorly it extends to the epiglottis, with which it is connected by a median and two
lateral folds, between which are the depressions known as the valleculce. The
mucosa over the root of the tongue is irregular and warty in appearance due to
the projections of the underlying nodular masses of lymphoid tissue, the lingual
follicles. A crypt or tubular pocket of surface epithelium usually dips down into
each of these follicles, as seen in surface view (fig. 854), and shown in section (fig.
859) . The follicles vary from 34 to 102 in number, the average being 66 (Ostman) j
and are somewhat irregular in size and form. They are often arranged in more or
less distinct longitudinal rows, with corresponding folds of the mucosa (Jurisch).
The lingual follicles are collectively designated as the lingual tonsil [tonsilla
linguae]. Between the lingual follicles and around the periphery of the lingual
tonsil there are found smaller ordinary nodules (without crypts) and indefinite
1108
DIGESTIVE SYSTEM
masses of lymphoid tissue. The sulcus terminalis forms a fairly sharp boundary
between the lymphoid mucosa of the root and the papillated mucosa of the body
of the tongue (fig. 854).
Fig. 865. — Left Side of the Tongue, with its Muscles, etc.
Stylo-glossus
Dorsum of tongue
Genio-hyoid
Genio-glossus
\
Styloid process
Stylo-hyoid
Root of tongue
Stylo-pharyngeus
Epiglottis (indicated by dotted lines)
Crxeater comu of hyoid bone
Cartilago triticea
Thyreoid cartilage
Median portion o£
crico-thyreoid
membrane
Cricoid cartilage
Glands. — The glands of the tongue are of three types — mucous, serous and mixed — and
are distributed as shown in fig. 860. The most numerous are those of the mucous type, which
Fig. 856. — Section of Lingual Papilla. X 20. (From Toldt's Atlas.)
Stratified epithelium
Secondary papilla
,Cl ' ^ ' ISWllfe \ PV\ Conical papilla
fM %mm mA
Filiform papillse
Capillary vessels
Artery
Vein
Lamina propria
Fascia linguae
Tongue muscle
are typical for the mouth cavity in general and resemble those already described in the lips,
cheeks and palate. They are spread over the entire surface of the root of the tongue, in the
THE TONGUE
1109
spaces between the lingual foUioles, usually opening upon the surface but in many cases into
the crypts. Anteriorly, they extend a short distance along the posterior portion of the lateral
Fig. 857. — Vertical Section of a Human Vallate Papilla With Lingual Glands.
X 25. (Lewis and Stbhr.)
Secondary papillee Taste bud
Orifice
of a
serous
Tuicapiopria \ XS?i jSH^" W^"'fS^ / e''*"*
Vallate papilla
Groove
Small
papilla
Inferior surface
Lateral margin
Plica fimbriata
Sublingual fold
Sublingual caruncle
margm of the tongue, and also occupy small areas in and near the mid-hne in front of the vallate
papillae.
In the immediate region of the vallate papiUse, and in the small lateral areas corresponding
1110
DIGESTIVE SYSTEM
to the foliate papiUse (i. e., in the regions of the taste-buds), the mucous glands are displaced by
the serous glands (of von Ebner), which have a watery secretion (fig. 860). Finally, on the
inferior surface of the tongue, on either side of the frenulum near the apex, are the anterior
lingual glands (glands of Nuhn or Blandin). Each is about 15 mm. in length, and is composed
of a group of racemose glands with three or four very small ducts opening on the surface of the
tongue near the plica fimbriata. The anterior lingual glands are deeply placed and are covered
not only by the mucosa, but also by some of the longitudinal muscle fibres (inferior longitudinal
and styloglossus). This gland is of the mixed type, though chiefly mucous.
Fig. 859. — From a Section of the Lingual Tonsil op an Adult Man. X 20. 1. Pit
containing leucocytes which have infiltrated its epithelium on the left side ; that on the right is
almost intact. (Lewis and Stohr.)
Median section of a nodule
BiSuse lumphoid tissue
Lymph nodules
Duct of a mucous gland'
J'J'3«^_/-rj:ji
Periphery of a nodule
Tunica propria
Fibrous capsule
Blood vessel
Muscles of the tongue. — A layer of fibrous connective tissue, the lingual septum, separates
the halves of the tongue, extending in the median plane from the apex to the root, where it is
attached below to the hyoid bone. The muscles of the tongue are classified as extrinsic and
intrinsic. The extrinsic muscles (fig. 855) extend into the tongue from without. They are
the hyoglossus, chondroglossus, genioglossus, styloglossus, and glossopalatinus (palatoglossus),
all of which are described elsewhere (see Section IV.)
Fig. 860. — Diagram op the Distribution of the Lingual Glands. Horizontal lines
indicate the mucous type; cross-hatched, the mixed type; and dotted areas, the serous type.
(After Oppel.)
The intrinsic muscles. — The longitudinalis superior (fig. 861) is a superficial longitudinal
stratum extending from the base to the apex of the tongue, immediately beneath the mucosa
of the dorsum, to which many of its fibres are attached. The longitudinalis inferior (fig. 861)
is composed of two muscle-bands extending from base to apex on the inferior surface of the
tongue, and ia situated between the hyoglossus and the genioglossus, some of its fibres near
the apex mixing with the styloglossus, while dorsaUy some are attached to the hyoid bone. The
transversus linguae (fig. 861) consists of fibres which pass transversely, and is situated between
THE TONGUE
nil
the superior and inferior longitudinal muscles. The fibres arise from, or pass through, the sep-
tum linguae, and are attached to the mucosa of the dorsum and lateral margins of the tongue.
The verticalis linguae (fig. 861) is composed of fibres which pass from the mucosa of the dorsum
to the mucosa of the inferior surface of the tongue, interlacing "with those of the other intrinsic
and extrinsic muscles.
Fig. 861. — Teansversb Section through the Left Half op the Tongue. (Magnified.)
(From a preparation by Mr. J. Pollard, Middlesex Hospital Museum.)
Transversus linguffi
Lateral margin of
tongue
Verticalis linguae
Vessels and nerves. — The lingual arteries furnish the principal blood-supply. The lingual
veins carry the blood from the tongue to the internal jugular. The lymphatics form a network
in the lamina propria, connected with a deeper network in the submucosa. The latter forms
plexuses around the lingual follicles. The efferent lymph-vessels from the tongue empty chiefly
into the superior deep cervical lymph-nodes. (For details concerning the blood- and lymph-
vessels, see Sections V and VI.) The nerves are motor and sensory. The hypoglossal nerve
Fig. 862. — Schematic Representation of the Distribution op tee Sensory Nerves
in'the Mucous Membrane op the Tongue. (Areas of distribution according to R. Zander.
White dotted area indicates vagus; oblique lines, glosso-pharyngeal; horizontal lines lingual
nerves.)
Right vagus nerve-
Right glosso-
pharyngeal
nerve
Left vagus nerve
eft glosso-phar-
yngeal nerve
Right lingual nerve
Left lingual nerve
supplies the intrinsic and all the extrinsic muscles of the tongue except the glossopalatinus
(palato-glossus), which is supplied from the pliar}'ngeal plexus. The sensory nerves (fig. 862)
are: — the lingual nerve, a branch of the mandibular division of the fifth, which, after joining with
the'chorc'.a tympani from the seventh, is distril^uted to the anterior two-thirds of the tongue and
represents the nerve of touch; the Ungual branches of the glossopharyngeal, which are distrib-
1112
DIGESTIVE SYSTEM
uted to the root of the tongue, including also the vallate and foliate papillae (nerve of taste) ;
and the superior laryngeal branch of the vagus, which supplies a small area near the epiglottis.
Development. — The development of the tongue is quite complicated. In general, the body
of the tongue is derived from the region corresponding to the ventral portion of the first arch,
just behind the mandible. It does not develop from the tuberculum impar, however, which is
a transitory structure (Hammar). The epithelium of the body of the tongue is probably of
ectodermal origin. The root of the tongue develops from the corresponding lower portion of the
second or hyoid arch, and its epithelium is endodermal in origin. The transverse groove be-
tween the two arches later becomes the sulcus tenninaUs. At the middle of this groove there
is an ingrowth of the epithelium to form the anlage of the thyreoid gland. The foramen ccecum
and the occasional ductus linguaHs represent persistent portions of the thyreoid duct. The third
arch does not appear to enter into the formation of the tongue, but forms the epiglottis
(Hammar).
The musculature of the tongue appears to develop from the mesenchyme in situ although
its innervation from the hypoglossal would indicate a derivation from the occipital myotomes.
A pair of premuscle masses appears in the 9 mm, embryo, the individual extrinsic muscles being
distinguishable at 14 mm., and the intrinsic at 20 mm. (W. H. Lewis). The glands appear
in the fourth fcetal month as solid epithelial downgrowths which later acquire a lumen. The
mucous glands appear first, the serous slightly later. Longitudinal folds in the mucosa of the
The Salivary Gi/ANDb
Accessory parotid
Duct of accessory
parotid
Duct of parotid
Frenulum linguas
Sublingual gland
Duct of submaxil
lary gland
Mylo-hyoid muscle
Anterior belly of
digastric muscle
Parotid gland
Masseter muscle
Posterior belly of
digastric muscle
Lingual nerve
Submaxillary
gland,
drawn backward
Deep portion of submaxillary gland
radix appear in the third or fourth fcetal month (Jurisch). The lymphoid tissue appears some-
what later as aggregations in the lamina propria, chiefly around the gland-ducts. From the
beginning, the lymphoid structures are subject to marked individual variations. Character-
istic, well-developed lingual follicles do not appear until some time after birth, however (Jurisch).
Of the lingual papilloe, the fungiform appear at the end of the third foetal month, followed
shortly by the fihform and vallate. The formation of the papillae is not completed at birth,
however, since they later undergo changes in number, form, size and arrangement. The
foliate papillae appear about the fifth foetal month. They are best developed in infants, under-
going retrogressive changes in the adult (Stahr). The same is true of the plicae fimbriatae.
Variations. — Of the manifold variations in the structure of the tongue, some have already
been mentioned. Additional mucous glands sometimes occur along the margin of the tongue
(completing Oppel's "glandular ring"). In "tongue-tied" individuals, the frenulum is ab-
normally short. A forked tongue (normal in some animals) is a rare congenital anomaly.
Another rare variation is the so-called "hairy" tongue, due to hypertrophy of the filiform
papillae. While the V-shaped arrangement of the vallate papillae is typical, the Y-form (two
to four papillae in the median line forming the stem of the Y) is nearly as frequent. Indeed,
in some of the coloured races the latter type seems to predominate. The sulcus terminalis
and foramen caecum are often indistinct and sometimes absent.
Comparative. — The tongue of fishes and lower amphibia contains neither glar.ds nor in-
trinsic musculature. Among higher vertebrates, the tongue varies exceedingly in form and
structure, but always contains intrinsic musculature and mucous glands. The latter primi-
tively form a ring around the margin and root of the tongue (Oppel). The serous glands occur
only in mammals, and are associated closely with the papillae bearing taste-buds. '
THE PAROTID GLAND
1113
The plica fimbriata in man is homologous with the 'sublingua' of lower mammals. Ac-
cording to Gegenbaur, the 'sublingua' represents the entire primitive vertebrate tongue,
but this view is opposed by Oppel. Among various mammals, the number of vallate papilte
varies from one to thirty, but the V- or Y-arrangement is typical. The region of the foliate
papillae ('marginal organ') is typical for mammals, and is much better developed in some
(e. g., rabbit) than in man. The mucosa of the root of the tongue is always different from that
of the body. The lingual papillae are especially developed in the tongue of carnivora.
THE SALIVARY GLANDS
Numerous glands — labial, buccal, palatine and lingual — have already been
mentioned, which pour their secretions into the mouth cavity. In addition to
these, there are three larger pairs, the salivary glands proper. They include the
parotid, the submaxillary, and the sublingual (the latter really a group of glands).
THE PAROTID GLAND
The parotid gland [gl. parotis] is the largest of the salivary glands, varying
from 15 to 30 gm. in weight. It is located below and in front of the ear in the
Fig. 864. — Horizontal Section throttgh Head at Level of Rima Oris. (After Henle,
modified.)
v. jugularis int.
Eigastric , n, hypoglossus
Sternomastoid
Stylo-hyoid V
v. jugularis est. ».^
A. carotis int.
I I N. vagus
I j I N. sympath. Dens,
\ \ I /A.pharyng. / Atlas
:- \ ', I j ^^'^' I I Longus colli
Longus capiti;
V. facialis post,
Stylo-glossus— i-v
Ramus of t I
mandible f t
Asc. palatine art.-
Int. pterygoi
Masseter
Lingual tonsil "
Sulcus terminalis -■
Foliate papillse -
Fungiform papilla
External maxillary art
Vestibule of mouth
nt
Retropharyngeal
lymph node
_-- — Superior constr.
Pharyngo-
palatine i
Fungiform papillEE "■ "" \ '^S,
Angle of mouth -->
retromandibular fossa (fig. 863), extending from the zygomatic arch above to the
angle of the mandible below.
Form and relations. — The parotid is somewhat prismatic or wedge-shaped
(figs. 863, 864), with three surfaces and three borders or angles. The lateral sur-
face is covered by skin and superficial fascia, and in its lower part by the platysma.
The anterior surface overlaps the masseter and extends medialward in contact
1114
DIGESTIVE SYSTEM
with the posterior border of the mandibular ramus and with the posterior aspect
of the internal pterygoid muscle. An irregular "pterygoid lobe" may extend
between the internal and the external pterygoid muscles. The posterior surface
is in contact with the sternomastoid muscle laterally, and with the styloid process
and associated muscles medially. Between the sternomastoid and styloid process
it touches the posterior belly of the digastric, and is in relation with the internal
carotid and jugular vessels. The various structures in contact with the parotid
gland often make more or less distinct grooves upon its posterior and anterior
surfaces.
Borders. — -The anterior border usually extends from below obliquely upward
and forward so as to give the whole superficial surface a triangular appearance.
Near the upper end of the anterior border, the parotid duct leaves the gland, and
just above this there is usually a small separate accessory lobe [gl. parotis acces-
soria], of variable form and size. The branches of the facial nerve also emerge
from the anterior border. The posterior border extends along the anterior aspect
of the sterno-mastoid muscle up to the mastoid process. The medial border
is deeply placed (at the junction of the anterior and posterior surfaces), and
approaches the wall of the pharynx.
The upper extremity of the parotid sends a process into the posterior part of
the manibular fossa, behind the condyle of the mandible, and is related with the
Fig. 865. — Diagram op Horizontal Section Showing the Parotid Compartment and
Relations. Arrow indicates opening in sheath. (Modified from Woolsey after Testut.)
EXTERNUi
CAROTI9
ARTERY
l»HAHYN-
FACIAL . -, , —»,,
NER\
PAROTID
APONEU-
ROSIS _
SUPERFIC t M ■ LAYER ^ ^^=>, \STYLOII
'LAYER 1 I ' \yif^ ^~S!K) ^PROCESS
AND ITS
MUSCLES
external auditory meatus. From the upper extremity emerge the superficial tem-
poral vessels and the auriculo-temporal nerve. The lower extremity is separated by
the stylo-mandibular ligament from the posterior end of the submaxillary gland.
Fascia. — As shown in fig. 865, the parotid gland is enclosed in a sheath (called the parotid
fascia or aponeurosis) derived from the deep fascia of the neighbourhood. The superficial
layer of the sheath covers the lateral surface of the gland, while the deep layers correspond to
the anterior and posterior surfaces of the gland. The sheath is very feeble or deficient at the
medial angle. The superficial and deep layers of the parotid sheath unite below to form a thick
fascial band extending from the angle of the mandible to the sterno-mastoid muscle.
Contents. — Within the sheath, the parotid gland is in intimate relation with numerous
important structures. Extending along the medial border, and partly embedded in the gland,
is the external carotid artery, dividing above into the superficial temporal and internal maxillary
(including the origins of the deep auricular and transverse facial); and the posterior facial
(temporo-maxillary) vein and branches. The auriculo-temporal nerve passes through the upper
part of the gland, while the facial nerve passes somewhat horizontally through it, dividing
into its temporo-facial and oervico-facial divisions. Finally, there are embedded m the gland
two or three deep lymphatic nodes, which receive lymphatic vessels from the external auditory
meatus, the soft palate and the posterior part of the nasal fossa; and several superficial_ nodes,
which receive lymphatic vessels from the temple, eyebrows and eyelids, cheek and auricle.
Structure. — The parotid is a racemose gland of the serous type.
THE SUBMAXILLARY GLAND
1115
Duct, vessels and nerves. — The duct of the parotid (Stenson's) issues from tlie anterior bor-
der of the gland, crosses the masseter a finger's breadth below the zygoma, and turns abruptly
medialward round its anterior border. It penetrates the fat of the cheek and the fibres of
the buccinator muscle, between which and the mucous membrane it runs for a short distance
before it terminates, sometimes on the summit of a little papilla, by a minute orifice. This
opening is placed opposite the crown of the second upper molar tooth. The duct commences
by numerous branches, which converge toward the anterior border of the gland, and receives
in its passage across the masseter the duct of the accessory parotid gland. The canal is about
the size of a crow-quill, length about 35 to 40 mm., diameter 3 mm. Its mucous membrane
is covered for a short distance, beginning with its oral termination, by stratified pavement
epitheUum, for the remainder of the distance by columnar epithelium. The coat of the duct
is thick and tough, and consists of fibrous tissue intermixed with nonstriated muscle-fibres.
The arteries are derived from those lying in the gland substance and from the posterior
auricular artery.
The veins terminate in the posterior facial (temporo-maxillary) trunk.
The nerves. — The parotid gland receives its secretory fibres from the otic ganglion, con-
veying impulses from the glosso-pharyngeal via the lesser petrosal and the auriculo-temporal;
its sensory supply through branches of the fifth nerve; and its sympathetic supply from the
carotid plexus. The lymphatics from the parotid gland terminate in the superficial and deep
cervical glands, especially in the deeper group of parotid nodes embedded in the substance of
the gland.
Variations. — The parotid is quite variable in size and in the form of its various processes,
especially of the accessory lobe, as already mentioned. The lobulations are less distinct in
infancy. Rarely the parotid is confined to the masseteric region, the retro-mandibular fossa
being filled with a fatty tissue enclosing the vessels and nerves normally found with the gland.
THE SUBMAXILLARY GLAND
The submaxillary gland [gl. submaxillaris] weighs 7 to 10 grams, and is of
about the form and size of a flattened walnut. It consists of a chief or superficial
part, and a smaller deep process. The chief portion is located in the digastric
triangle, and presents three surfaces — superficial, deep and lateral (figs. 847, 866).
Fig. 866. — Medial View of the Submaxillary and Sublingual Glands. (Sobotta —
McMurrich's Atlas.)
Sublingual caruncle Ductus sublingualis major
Orbicularis
Labial glands
Minor sublingual ducts
^Submaxillary ducts
---Lingual nerve
,Deep process of
^ submaxillary
/ 'A
Genio-glossus
Gemo-hyoideus
Mylo-byoideus
Submaxillar;
gland
Surfaces. — The superficial or latero-inferior surface is covered by skin, super-
ficial fascia, platysma and deep fascia (which forms an incomplete capsule around
the gland). It is crossed by the facial vein and by cervical branches of the facial
nerve. Several lymphatic glands, which receive vessels from the anterior facial
region, lie upon or embedded in this surface.
The lateral surface is the smallest of the three. It is in contact with the sub-
maxillary fossa of the medial surface of the mandible, and with the lower part of
the internal pterygoid muscle. The posterior aspect of the gland is deeply
grooved by the external maxillary (facial) artery and is separated from the parotid
gland by the stylo-mandibular ligament. The deep or medio-superior surface is
in contact with the lower surface of the mylohyoid, and behind this with thehyo-
1116
DIGESTIVE SYSTEM
glossus, stylohyoid and posterior belly of the digastric. Between this surface
and the mylohyoid muscle are the mylohyoid nerve and artery and the sub-
mental artery.
The deep portion is a tongue-like process which passes from the deep surface
of the submaxillary gland around the posterior border of the mylohyoid muscle,
and extends forward in company with the duct, under cover of (above) the mylo-
hyoid, and in relation with the hyoglossus and genioglossus muscles. At its
commencement, the deep process lies just below the submaxillary ganglion and
■ anteriorly it gives off the submaxillary duct as it approaches the sublingual gland.
Structure. — The submaxillary is a racemose gland belonging to the mixed type, some of
the acini being serous, others mucous (fig. 867).
The submaxillary (Wharton's) duct springs from the deep surface of the superficial part
of the gland; it passes forward and inward, along the medial surface of the deep lobe, and opens
by a small orifice on the summit of a papilla [caruncula sublinguahs] by the side of the frenulum
of the tongue. It is crossed superficially by the lingual nerve. It hes at first between the mylo-
FiQ. 867. — Section op the Submaxillary Gland op an Adult Man. X 252. (Lewis and
Stohr.)
Mucous gland cells
Connective tissue
Secretory duct
hyoid and hyoglossus; next, between the mylohyoid and genioglossus; and lastly, under cover
of the mucous membrane of the mouth, between the genioglossus and the sublingual gland.
The duct is about 5 cm. in length, and has comparatively thin walls. It is lined by columnar
epithelium.
Vessels and nerves. — The arteries to the gland are derived from the external maxillary
(facial) and lingual, and they are accompanied by corresponding veins.
The nerves. — The submaxillary gland receives its secretory fibres from numerous small
sympathetic ganglia situated on the submaxillary duct and in the hilus of the gland, these
conveying impulses from the chorda tympani; its sensory branches probably come from the
geniculate ganglion, and its sympathetic branches from the cervical sympathetic.
Variations. — Absence of the gland is a rare anomaly. A case is recorded (Turner) where
the submaxillary was placed entirely under cover of the mylohyoid, being closely associated
with the sublingual gland.
THE SUBLINGUAL GLAND
The sublingual gland [gl. sublingualis] — the smallest of the salivary glands
(2 to 3 gm.) is in reality a group of glands forming an elongated mass in the floor
of the mouth under the tongue (fig. 847) . Above, it forms a distinct ridge, covered
by a fold of mucosa (plica sublingualis) upon which its ducts open (fig. 866). It is
flattened from side to side, its loioer border resting upon the upper surface of the
mylohyoid, its lateral surface in contact with the sublingual fossa of the mandible,
and its medial surface with the geniohyoid, geniohyoglossus, lingual nerve, deep
lingual artery and submaxillary duct (fig. 863). Anteriorly it touches its fellow of
the opposite side, while 'posteriorly it is often related with the deep process of the
THE TEETH 1117
submaxillary gland. It has no distinct capsule, thus differing from the submaxil-
lary and parotid glands. In structure, it is a racemose mixed gland, but predomi-
inantly mucous.
Ducts. — The minor sublingual duels [ductus sublinguales minores], ducts of Rivinus, vary
from five to fifteen or more in number, and open on minute papillae along the crest of the plica
sublingualis (fig. 858). The anterior portion of the gland often forms a larger [Bartholin' s)
duel [ductus sublingualis major] which opens alongside the submaxillary duct on the caruncula
sublingualis (figs. 858, 866).
Vessels and nerves. — The arteries are derived from the sublingual and submental, with
corresponding vci^is. The lymphatics are tributaries of the superior deep cervical nodes.
Nerves. — The sublingual glands receive their secretory fibres from the subma.xillary and
associated sympathetic ganglia, conveying impulses from the chorda tympani; sympathetic,
branches come from the cervical sympathetic and sensory fibres probably from the geniculate
ganglion, although this question needs further investigation.
Development of the salivary glands. — The salivary glands appear early as buds from the
ectodermal epithelium extending into the adjacent mesenchyme of the mouth cavity. The
parotid appears first on the side of the mouth cavity in an embryo of 8 mm., as a groove which
becomes tubular and pushes back over the masseter to the ear region, developing branches (at
first solid). Around the gland and between the branches is mesenchyme which becomes
condensed to form the peripheral capsule. The submaxillary gland appears in the 13 mm.
embryo as a ridge in the epithelium of the alveolo-lingual groove. The solid cord (lumen
appearing later) grows forward to the region of its adult orifice. Its posterior end extends
backward and gives off solid branches which later form the acini and duct system of the mature
gland. The sublingual glands appear somewhat later (24 mm. embryo) as a series of separate
anlages of variable number, budding off in the positions where the adult ducts empty. The
major sublingual gland, if present, appears fii'st. The histogenetic development of the salivary
glands is not completed until some time after birth, probably about the time of weaning.
However, mucin cells appear in the sublingual glands in the foetus of four months and serous
cells in the parotid of five months.
Variations. — The duct of Bartholin is present in about half of the cases, and the corre-
sponding anterior part of the gland may be more or less separate [gl. sublingualis major]. The
number of ducts may reach thirty (TiUaux). Rarely processes from the gland may penetrate
the mylohyoid, appearing on its lower surface in one or more places (Moustin). Most of the
variations in this and the other salivary glands are due to developmental irregularities.
Comparative. — Oral glands are not found in the lower aquatic vertebrates. Mucous
glands occur in all terrestrial vertebrates, but true sahvary (digestive) glands appear only in
mammals. Although great variations occur in the different species of mammals, those in man
(excepting the anterior lingual) are typical for the order. The sublingual gland, however,
often occurs as two separate glands, corresponding to the sublinguaUs major and minor. The
parotid gland apparently has no representative in forms below mammals. In some mammals
(e. g., monkey) it has two main lobes — a larger superficial and a smaller deeper lobe between
which lies the facial nerve (Gregoire). Other oral glands (e. g., orbital, zygomatic) appear in
some mammals.
THE TEETH
The teeth [dentes] are highly specialized structures developed in the oral
mucosa as organs of mastication and also (in man) of speech. The adult indi-
vidual with perfect dentition has thirty-two teeth, arranged arch-like in the sock-
ets (alveoli) of the maxilla and the mandible. Sixteen belong to the upper or
maxillary arch; and sixteen to the lower or mandibular. The four central teeth
in each dental arch are the incisors; the tooth next to these on each side is the
canine; behind these are the two premolars (bicuspids) ; and lastly the three
molars. This relation of teeth is expressed by the following dental formula:
.21 2 3 „„
i2,Cj-,pm2,m3 = 32.
Form. — Each tooth [dens] has a crown [corona dentis], the portion exposed
beyond the gum, and covered with enamel (figs. 871, 872). The root [radix den-
tis] is the portion covered with cementura and embedded in the bony socket. At
the line of union of crown and root is the slightly constricted neck [coUum dentis].
The surface of the tooth directed toward the lip (or cheek) is termed the labial
(or buccal) surface [facies labialis; f. buccalis]; while that toward the tongue is
the lingual surface [f. lingualis]. The crowns of the opposite arches meet at the
masticating surface [f. masticatoria]. The surfaces in contact with the adjacent
teeth of the same arch [facies contactus] are, for the incisors and canines, termed
medial and lateral, while those for the premolars and molars are termed anterior
and posterior.
1118
DIGESTIVE SYSTEM
Structure. — As shown in longitudinal section (fig. 873), each tooth has a central cavity
[cavum dentis] or pulp cavity, which is filled with pulp [pulpa dentis]. The pulp is a soft fibrous
tissue richly supplied with vessels and sensory nerves which enter the root canal through the
apical /orame?i [foramen apicis dentis]. The body of the tooth, both crown and root, is composed
of a dense modified variety of bone called dentine [substantia eburnea]. It is yellowish in
colour. The striated appearance of the dentine is due to numerous fine canals, the dentinal
; ' ':■ Fig. 868. — Teeth of an Adult, Exteknal View.
Incisors Canine Premolar Molars Wisdom tooth
Fig. 869. — Teeth of Adult, Lingual Fig. 870. — Teeth of Adult, Labial and
Surfaces. (Broomell and Fischelis.) Buccal Surfaces. (Broomell and Fische-
lis.)
Fig. 871. — Canine Tooth, Lingual Surface. Fig. 872. — A Molar Tooth in Section.
n* Root
Cusp fP^^^^)
~ -Pulp cavity
Neck
Cingulum
tubules. These contain 'Tomes' fibrils,' which are long protoplasmic branches of the odonto-
blasts, a layer of cells on the surface of the pulp. At the outer surface of the dentine are numer-
ous small, irregular interglobular spaces, corresponduig in the root to Tomes' 'granular sheath'
(fig. 873). The dentine of the crown is covered with a layer of white enamel [substantia
adamantina], which is the hardest substance in the body. It is composed of numerous mmute
THE TEETH
1119
hexagonal -prisms [prismata adamantina] which are arranged perpendicular to the surface and
are of epithelial origin. In adult teeth, the enamel is often worn through in places, exposing
the yellowish dentine. The dentine of the root is covered by a thin layer of cementum [sub-
stantia ossea], a layer of bone which is very thin at the neck, but becomes thicker toward the
root apex (fig. 873). Surrounding the root is the aUeolar periosteum, a fibrous membrane
connecting the cementum firmly with the bony lining of the socket. For further details of
the minute structure of teeth, works on histology may be consulted.
Gums. — Covering the alveolar portions of the maxilla and mandible are the
gums [gingivae]. They are continuous with the mucosa of the vestibule exter-
FiG. 873. — Vertical Section op an Inferior Canine Tooth, in Situ.
Toldt's Atlas.)
X 4. (From
Transition from mandibular to
i^\ ^ alveolar periosteum
Pulp capillaries
Alveolar periosteum
Cementum
Compact bone of mandible
Marrow spaces of mandible
nally and of the palate or floor of the mouth internally. Like the mucosa of the
mouth elsewhere, they are covered with stratified squamous epithelium. The
lamina propria is especially thick and strong, and is firmly attached to the sub-
jacent bone. Around the neck of each tooth, the epithelium of the gum forms an
overlapping collar and the lamina propria is continuous with the alveolar perios-
teum (fig. 873).
The incisors.— (Figs. 868, 869, 870, 874.) The incisor teeth [dentes incisivi]
are so named on account of then: function in cutting the food. The crown has a
1120
DIGESTIVE SYSTEM
characteristic chisel shape. The masticating surface is narrow and chisel-edged.
In recently erupted teeth, the cutting edge is elevated into three small cusps,
which soon wear down, leaving a straight edge. These cusps correspond to three
indistinct ridges on the labial surfaces. The lateral angle of the crown is usually
more rounded than the medial. The labial surfaces are slightly convex, the lin-
FiG. 874. — Cross-Section of the Medi ^i. Upper Incisor, in Situ. X 4. (From Toldt's
\tl IS 1
Dentine of root of tooth
Root canal of tooth'
Alveolar periosteum
Wall of dental alveolus
gual slightly concave. The contact surfaces are somewhat triangular. The roots
of the incisors are single, though often longitudinally grooved, indicating traces of
a division. They are somewhat conical, but flattened from side to side, expecially
the lower set, and are slightly curved lateralward.
The upper or maxillary incisors are much larger than the lower. They are lodged in the
premaxilla, and are inclined downward and forward. They overlap the lower incisors in masti-
cation, hence the masticating surface is worn off and rounded at its posterior edge, while the
anterior edge becomes sharp and chisel-hke. The lingual surfaces of the crowns terminate
near the gum in a low, inverted V-shaped ridge, the basal ridge or cingulum. At the apex of
Fig. 875. — Variations in the Form of the Upper Third Molar. (BroomellandFischelis.)
the V, near the gum, there is often (especially on the lateral incisor) a smaU lingual cusp. The
medial upper incisor is distinguished from the lateral by its much larger size.
The lower or mandibular incisors are smaller than the upper, the cutting edges being only
about half as wide. Being overlapped by the upper set, the lower incisors have the masti-
cating surface worn ofT anteriorly, leaving a sharp cutting edge posteriorly. The lower mcisors
are vertically placed, and the crown becomes narrower toward the neck. A cingulum is rarely
visible. The medial lower incisor, unlike the upper, is slightly smaller than the lateral.
The canines.— (Figs. 868, 869, 870, 871.) The canine teeth [dentes canini]
so-called from their prominence in the dog-tribe, are the longest of all the teeth
(fig. 868). The crown is thicker and more conical than in the mcisors. The mas-
ticating surface forms a median angular poi nt, on either side of which the cutting
THE TEETH
1121
edge slopes to the lateral angle. The medial limb of the cutting edge is usually
somewhat shorter than the lateral, rendering the crown asymmetrical. The
labial surface is convex, the lingual somewhat concave. The root is single, long,
flattened from side to side and grooved on the sides as in the incisors. The canine
root is usually slightly curved lateralward. The bony alveolar protuberances
[juga alveolaria] are more prominent than those of any other teeth.
The upper canine slants forward and overlaps the lower, as in the incisors. The upper
canine also presents a well-marked cingulum, and usually a distinct lingual cusp (fig. 871)
below which a slight median ridge extends along the lingual surface. On the lower canine,
these structures are poorly marked or absent. The lower canine is somewhat smaller than the
upper, and its root is occasionally bifid.
The premolars.— (Figs. 868, 869, 870, 876, 877.) The premolars [dentes
premolares] are so named on account of their position in front of the molars. The
Fig.
876. — Dissection Showing the Roots op the Teeth. Teeth in Occlusion. X 1
(From Toldt's Atlas.)
Buccal surface
Wisdom tooth
Premolar teeth
Mental foramen
crown presents on the masticating surface two prominent cusps, on account of
which the premolars are often called 'bicuspids.' The buccal and lingual sur-
faces are convex especially from side to side, so that the crown is somewhat
cylindrical in form, with flattened, quadrilateral anterior and posterior contact
surfaces. The root is (usually) single and more or less flattened antero-posteriorly,
and usually somewhat curved backward.
The upper premolars are distinguished from the lower by a greater antero-posterior flatten-
ing of the crown and by a deep groove separating the cusps (excepting at their anterior and
posterior margins) on the masticating surface. In the first upper premolar the lingual cusp
and surface are decidedly smaller than the buccal; and the root is frequently bifid or double
(occasionally even triple). In the second upper premolar the lingual cusp and surface are as
large as the buccal; and the root, though deeply grooved, is rarely bifid.
In the lower premolars, the crowns are more cylindrical in form, and the cusps are united
by a median ridge so that the masticating surface presents two small pits. The roots are more
rounded and tapering, and rarely grooved. In the first lower premolar (like the corresponding
upper) the lingual cusp and surface are much smaller than the buccal, the lingual cusp some-
times being rudimentary; while in the second they are more nearly equal. The second lower
premolar is often slightly larger than the first, while in the upper premolars the converse is true.
It should be noted, however, that the premolars are quite variable in all respects, and it is
therefore often difficult to identify the individual isolated teeth.
The molars.— (Figs. 868, 869, 870, 872, 875, 876.) The molars [dentes mol-
ares] or 'grinders' are characterized by their large size, and by the presence of
1122
DIGESTIVE SYSTEM
three to five masticating cusps (hence sometimes called 'multicuspids')- The
crowns are massive, somewhat resembling rounded cubes, and the lingual and buc-
cal surfaces present vertical grooves continuous with the fissures separating the
cusps. The pulp cavity (fig. 872) has slight extensions corresponding to the cusps,
and also communicates with the canals of the roots, which are usually two or three
in number, and more or less curved.
Fig. 877. — Diagram Showing the Articulation of the Teeth. (Poirier-Charpy.)
labial-!/, WcalA
Vlmgual
^"8"^^ buoci
-lingual
The upper molars are most easily distinguished from the lower by the presence of a triple
root. The masticating surface is nearly square with rounded angles. They each have typically
four cusps, separated by grooves resembling a diagonally placed H (fig. 852). The crowns of
the upper molars are obliquely placed so as to slant downward and slightly lateralward.
Each upper molar has three roots, two buccal and one Ungual or palatal. They are aU
(especially the buccal) in more or less close relation with the floor of the maxillary antrum (of
Highmore) (fig. 876). The buccal roots are flattened antero-posteriorly, and longitudinally
grooved, and bent backward. The palatal root is more rounded, with a groove on the hngual
surface, and usually bent medialward. Either of the buccal roots may fuse with the palatal,
or there may be an extra fourth root.
As to the individual upper molars, the first has almost invariably four typical cusps (rarely
only three, or with an additional fifth rudimentary). The second upper molar has only three
cusps in about half of the cases (in Europeans), and four in the remainder. The third, or wisdom
tooth [dens serotinus] is exceedingly variable in size and form (fig. 875). It has three cusps
much more frequently than four, and its three roots are often more or less fused into a conical
mass. It is usually much smaller than the other molars, and is absent in nearly one-fifth of all
cases.
Fig. 878. — Diagrams Showing the Early Development or Three Teeth, One of which
IS Shown in Vertical Section. (Lewis and Stohr.)
Epithelium of the margin Enamel Dental
of the jaw organs groove
Dental ridge Z^-'''^
Papillae
A B
Enamel organs Necks of enamel organs
C D
The lower molars have usually four or five cusps (two lingual, and two or three buccal)
the fissures separating them being cross-shaped or stellate (fig. 864). The crowns incUne
upward and slightly medialward. They have each two roots, anterior and posterior, flattened
antero-posteriorly, and usually somewhat curved backward. The roots, especially the anterior,
may be longitudinally grooved. The anterior has two root-canals, the posterior usually only
one. The apices of the roots of the lower molars, especially of the third, approach the man-
dibular (inferior dental) canal (fig. 876).
Of the individual lower molars, the first is usually slightly the largest, and has five cusps
in the great majority of cases (variously estimated at from 60 to 95 per cent.), otherwise four.
The four main cusps (two buccal and two lingual) are separated by a cruciform fissure, which
bifurcates posteriorly to embrace the small fifth cusp (which is placed shghtly to the buccal
THE TEETH
1123
side) when present. The second lower molar has usually four cusps (75 to 85 per cent, of cases) ,
otherwise five, the fifth usually small or rudimentary. The roots are sometimes confluent.
The lower third or wisdom tooth, like the upper, is usually small and exceedingly variable
(fig. 875). It has usually four or five cusps; but the number may be increased to six or seven,
Fig. 879.^Modei, of Ectoderm op Jaw of Hitman Embryo 40 mm. Long, Showing
Dental Ridge with Enamel Organs for the First Teeth. (Kingsley, after Rose.) ,
or reduced to three, two, or one. The roots are often short and fused into a conical mass
in which sometimes only a single canal is present.
The dental arches. — On comparing the upper and the lower dental arches, it is seen that
the upper (fig. 852) forms an elliptical curve, while the lower (fig. 864) resembles a parabola.
Fig. 880. — Section Showing Later Stages op Tooth Development. (Szymonowicz.)
^^
^ .Epithelium of oral cavity
Enamel -
pulp
Inner _
enamel'"
cells
Neck of
enamel organ
Dental ridge
of permanent
tooth
, Bone trabecu-
l3s of lower jaw
The upper arch is slightly larger (due chiefly to the slant of the teeth, as previously explained)
so that it shghtly overlaps the lower when the teeth are in occlusion. Thus, as showli in fig.
876, the upper incisors (and canines) overlap the lower. The buccal cusps of the lower pre-
molars and molars fit into the groove between the upper buccal and lingual cusps; while the
upper lingual cusps correspond to the groove between lower buccal and lingual cusps. This
arrangement favors a more perfect mastication (see fig. 877).
Moreover, when viewed from the side (fig. 876), it is seen that in general, the corresponding
teeth of the upper and the lower arches are not opposite, but alternate with each other. This is
1124
DIGESTIVE SYSTEM
due chiefly to the great width of the upper central incisor. The lower molars, however, es-
pecially the third, are wider (antero-posteriorly) than the upper, so that the two arches are
nearly equal in length. The interdental line between the two arches is not straight, but shghtly
convex downward (fig. 876). In both arches, the crowns of the incisors and canines are taller
than those of the premolars and molars.
Vessels and nerves. — The vessels and nerves of the teeth are distributed partly to the
pulp and partly to the surrounding alveolar periosteum. The arteries are all derived from the
internal maxillary. Those for the upper teeth are the posterior superior alveolar and the
anterior superior alveolar (from the infraorbital). Similar branches to the lower jaw are given
off by the inferior alveolar. They give off twigs to the gums (rami gingivales), the alveolar
Fig. 881. — Hard Palate op a Child of Five Years, Showing Decidtjous Teeth.
Gubernacular canal
_ Palate process of maxilla
Greater palatine foramen
palatine foramea
periosteum (rr. alveolares), and the pulp cavities (rr. dentales). A dental branch enters each
root canal through the apical foramen, and breaks up into a rich peripheral capillary plexus
under the odontoblast layer. From this plex-us, the corresponding veins arise. There is a plex-us
of peridental lymphatics, which anastomose with those of the surrounding gums, and drain
chiefly into the submaxillary nodes. Lymphatics have also recently been demonstrated in the
pulp of the tooth (Schweitzer).
The nerves are sensory branches derived from the trigeminus. Those for the upper teeth
are from the anterior, middle, and posterior superior alveolar (fig. 735); while those for the
lower teeth are from the inferior alveolar (fig. 736). These nerves give numerous branches to
Fig. 882. — The Deciduous Teeth, External View.
Incisors Canine Deciduous molars
Maxillary or upper set
Mandibular or lower set
the gums, alveolar periosteum, and pulp cavities. The latter enter with the corresponding
vessels, and their distribution within the tooth is a subject of controversy. They may be
followed easily to a plexus under the odontoblasts; but whether they end freely, or in connection
with the odontoblasts (which by some are considered as peripheral sensory cells), or send fine
terminal branches out into the dentinal canals is still uncertain.
Development of the teeth. — The teeth represent calcified papillae of the oral mucosa, the
enamel being a derivative of the ectodermal epithehum, and the remainder of the tooth coming
from the underlying mesenchyme. The first trace of the teeth appears in the human embryo
of about 11 mm., in the form of an epithelial shelf, the dental ridge, extending into the mesen-
chyme corresponding to the future alveolar portions of the jaws (figs. 878, 879). From the
dental ridge there is later produced a series of cup-shaped enlargements, the enamel organs,
which become constricted off except for a slender neck attaching each to the common ridge.
By the end of the third foetal month, the twenty enamel organs of the temporary or deciduous
teeth are formed. The concavity of each enamel organ is filled by the dental papilla of mesen-
chyme.
THE TEETH
1125
A somewhat later stage in the organogenesis of a tooth is shown in fig. 880. The mesen-
chymal cells on the surface of the dental papilla, next to the enamel organ, form a single layer
of columnar cells, the odontoblasts. These cells form the dentine upon their outer surfaces,
gradually retreating toward the center of the tooth as the dentine increases in thickness. The
first dentine formed is irregular, enclosing the spatia interglobularia. The odontoblasts re-
main through life just beneath the dentine on the surface of the pulp, sending slender processes,
up into the dentinal tubules as previously noted in the structure of the adult tooth. The re-
mainder of the dental papilla becomes the pulp, receiving its vascular and nerve supply at the
point opposite the enamel organ, corresponding to the future root.
The enamel organ (fig. 880) is differentiated into three layers: a thin outer layer attached by
the neck to the dental ridge; a thick middle layer (forming the spongy "enamel pulp"); and a
single inner layer of cylindrical enamel cells, the adamantoblasts. The latter form the
prisms, which are deposited gradually upon the outer surface of the dentine.
Fig. 883. — Dissection Showing the Teeth at about Six Years.
Fischelis.)
(Broomell and
4^;,,>.^/,tijf|.
Surrounding the entire developing tooth there is formed a strong, fibrous connective-
tissue membrane, the tooth-sac. The deeper part of this sac later becomes the alveolar periosteum
around which the bony alveoli are formed. This bone may entirely surround the tooth-sac,
excepting at the summit, where a foramen persists through which a process of connective
tissue {gubernanilnm dentis) connects the tooth-sac with the overlying gum (see figs. 114, 881).
Upon the inner surface of the tooth-sac, next to the root, the bony cemenlum is deposited upon
the dentine. The root gradually elongates, and is usually not completed until long after the
eruption. The remaining superficial portion of the tooth-sac undergoes pressure atrophy and
absorption. The remnants of the enamel organ, however, persist and form a thin tough
cuticle [cuticula dentis], Nasmyth's membrane, which is soon worn off when the crown is exposed
at the surface.
From the remainder of the dental ridge, which lies on the lingual side of the deciduous
teeth (fig. 878), the permanent teeth are later derived in a very similar manner. (Rudimentary
indications of a prelacteal dental ridge have also been described.) The anlages of the per-
manent teeth therefore lie to the lingual side of the deciduous (fig. 883). From the posterior
end of the dental ridge a process extends into the jaw behind the deciduous teeth, and from
this process the permanent molars (which have no deciduous predecessors) are formed. At
birth, although no teeth have yet been cut, there are present in the gums the anlages of not
only all of the deciduous teeth, but also all of the permanent teeth, with two exceptions. Those
of the second molars do not appear until six weeks after birth, and of the third molars not until
the fifth year. The remnants of the dental ridges become broken up into small masses of
epithehal cells, which persist for a variable time.
1126
DIGESTIVE SYSTEM
The deciduous teeth. — The deciduous [dentes decidui], temporary or milk
teeth are twenty in number, corresponding to the following formula:
di|, dc[, dm| = 20.
The deciduous teeth (figs. 882, 883) are much smaller in size than the perma-
nent teeth, and their necks are more constricted. The enamel of the crown cap is
thicker. In general, their form and structure otherwise is very similar to that
Fia. 884. — Pulp-cavity op the Upper First Molar, From the Fifth to the Ninth Year
(Broomell and Fischelis.)
already described in the case of the permanent incisors and canines. The molars,
however, are different. Their cusps on the masticating surface are very sharp and
irregular. There are usually three 'cusps on the first upper molar and four on the
second; four cusps on the first lower molar and five on the second. The roots
Fig. 885. — Showing the Extent of Calcification op Deciduous Teeth. (Peirce.)
40weeks(newli.}
30weel(S(foe<ai>
18weeks(foetslX
17wee]i5(&etal>
correspond to those of the permanent molars (three above and two below), but
they are much more divergent, to allow room for the development of the corre-
sponding subjacent permanent premolar teeth. The first molar is always con-
siderably smaller than the second.
Fig." 886. — Showing the Extent op Calcification op the Permanent Teeth. (Peirce.)
Calcification in the dentine and enamel of the teeth does not begin until the anlages of
the crowns are well formed. The process of calcification follows that of the development of
the tooth in general, beginning in the superficial portion of the crown and gradually spreading
toward the root. Calcification in the deciduous teeth begins during the fifth foetal month, and
at birth the crowns are nearly completed (fig. 885). Of the permanent set of teeth, only the
first molar has begun to calcify at birth (fig. 886). Calcification of the other permanent teeth
begins during the second year; excepting the second molar, which begins during the fifth, and
the third molar, which begins about the eighth year. There are, however, great variations
THE TEETH 1127
in the time at which the caloificatioa of the various teeth begins. As a rule, the calcification
of the roots is not completed at the apices until some time after the crowns are exposed in
eruption.
Eruption of the teeth. — -Oa account of pressure due to growth and expansion at the root of
the tooth (and probably other obscure factors), the crowns are pushed toward the surface. The
overlying portion of the tooth-sac, together with corresponding portions of the temporary
alveolar bone, are absorbed, and the crown is "cut," i. e., breaks through the surface of the gum
in eruption. In the case of the permanent teeth, this is normally preceded by a shedding of
the deciduous teeth. The latter have been loosened by the absorption of their roots, which is
perhaps due largely to the activity of certain odontoclasts (like the osteoclasts of bone) which
are found in the region of absorption.
Time and order of eruption. — The time of the eruption of the various teeth is subject to
great variation, so that no two investigators agree upon it. Aside from the wisdom teeth, the
time of eruption is most variable in the canines and premolars, and least variable in the first
permanent molars (Rose). The eruption averages four and one-half months earliei in the
male, and is also earlier in well-to-do and city children (Rose). The order in which the teeth
appear is less variable. The average time at which the various deciduous and permanent
teeth appear is indicated approximately in the following table.
A. Deciduous Teeth
Months after Birth
(Average)
Lower central incisors 7 (6-8)
Upper central incisors 8-9
Upper lateral incisors 9-10
Lower lateral incisors 12-14
First molars 14
Canines 18
Second molars 22-24
B. Permanent Teeth
The average time at which the teeth in the lower jaw undergo eruption is shown in the table
below. The corresponding teeth in the upper jaw appear a little later : —
Years
First molars 6-7
Central incisors 7
Lateral incisors 8
First premolars 9-10
Second premolars 9-10
Canines 11
Second molars 12
Third molars (wisdom teeth) 17-25
Variations. — The great variabihty of the teeth has already been emphasized, and numerous
variations described in connection with the various individual teeth and their development.
In number, the teeth may be reduced, due to absence (oftenest of the third molar) or incom-
plete development with failure of eruption. An increase in the normal number is less common'
It may be only apparent, due to the retention of a deciduous tooth. There may rarely, however,
be a true extra third incisor or premolar, or a fourth molar. Aberrant teeth may occur either on
the labial or palatal side of the dental arch. A third dentition appears rarely in old age. In
form, there is much greater variation as before mentioned. All intermediate forms between
rudimentary and fully developed teeth may occur. Fusion between neighbouring teeth is
sometimes found, and deformities in the dental arches necessarily accompany palatal defects
involving the alveolar arches.
Comparative. — As the oral mucosa represents an invagination of the integument, so the
teeth are morphologically equivalent to dermal papilliE. The close relationship between the
teeth and the dermal appendages is clearly shown among many of the lower vertebrates, but
most clearly in the Selachians (which include sharks and allied forms). In fig. 887, which
illustrates a sagittal section through the lower jaw of a young dogfish, it is clearly evident that
the external placoid scales or 'dermal teeth' are continuous with the equivalent oral teeth
at the oral margin of the jaw. Both the dermal teeth and the oral teeth are composed of dentine
which presents an enlarged base and a somewhat conical apex. The base is embedded in the
fibrous lamina propria (often in bony plates) while the apex projects through the epithehum
and is covered with a thin cuticular layer the "enamel membrane." True enamel is usually
rudimentary or absent in the primitive teeth of lower vertebrates, and represents a secondary
acquisition. The dentine is in aU cases derived from the connective tissue, and the enamel
from the epithelium .
The process of development of the primitive oral teeth is also iDustrated in fig. 887. Just
within the oral margin there is a shelf-like downgrowth of the ectodermal epithelium, forming
a primitive germinal ridge. Along this ridge may be seen the anlages of several rows of teeth
in various stages of development. As fast as the mature teeth at the oral margin are worn off,
new teeth pass up from below to replace them. Thus the primitive form of dentition is polij-
■phyodont, with many sets of teeth developed successively thi'oughout hfe. As we pass up the
vertebrate scale there is a tendency to a reduction in the number of sets, although there is a
1128
DIGESTIVE SYSTEM
wide variation among the various forms. In most mammals, as in man, the number of sets of
teeth has been reduced to two, or diphyodojit dentition, with only traces of an earher (pre-
lacteal) and also a later (post-permanent) set. In some mammals (monotremes, oetacea)
the dentition has been reduced to a single set, jnonophyodont, while in birds all except rudi-
mentary traces of dentition have been lost.
pAs may be further observed in fig. 887, the primitive teeth are of a recurved conical form,
and serve primarily for grasping and holding the food. The speciahzation of the teeth for
purposes of mastication is in general a secondary acquisition amongst higher vertebrates.
It is also noteworthy that the primitive teeth, as found among nearly all forms below the
mammals, are practicaOy alike in form, i. e., homodont. Among mammals, however, there is
a marked speciahzation of the teeth, or helerodont dentition. The mammalian teeth are usually
differentiated into four distinct classes, incisors, canines, premolars and molars, similar to those
found in man.
The typical or complete mammalian dentition, however, contains a larger number of teeth
than found in man, and is represented by the formula
• 31 43
1—, c -, pm-, m-=44
3' 1' ^ 4' 3 **•
Thus it is evident that there has been a reduction in the incisors and premolars in the human
species, and there has been considerable discussion of the question as to which teeth of the
Fig. 887. — Section through Lower Jaw op Dog-fish, Showing the Development of the
Oral Teeth, and the Transition to Dermal Teeth. M, mandible. (After Gegenbaur.)
Intermediary forms — *- -
^,' Developing tooth
Skin of lower jaw
Dermal tooth ^
„ Dental epithelial ridge
... Epithelium of oral mucosa
«. Anlage of tooth
primitive series have been lost. This reduction in the number of teeth is probably correlated
with the general reduction in the jaws, which are relatively much larger and stronger in the
savage races and lower animals. The third molar, or wisdom tooth, is probably now on the
road to extinction, due to a continuation of the same evolutionary process.
Another interesting problem, concerning which there has been much speculation, is the
origin of the multicuspidate mammalian molar. It has clearly been derived from the primitive
conical type of the homodont dentition, but as to the method of evolution there is a difference
of opinion. According to one view (the 'concrescence' theory), the molar has been derived
by a process of fusion, each cusp representing a primitive conical tooth. Another view (the
'differentiation' theory) is that the molar represents a single primitive tooth, upon the crown
of which the various cusps have been differentiated. According to a third view, which is a
compromise, the tritubercular (tricuspid) form of tooth, which is that found in the earliest
fossil mammals, was derived by a process of concrescence of three primitive teeth, while from
this tricuspid form the multicuspidate molar has been derived by a process of differentiation.
THE PHARYNX
The pharynx is a vertical, tubular passage, flattened antero-posteriorly, and
extending from the base of the cranium above to the beginning of the oesophagus
below. Posteriorly, it is in contact with the bodies of the upper six cervical verte-
brae. Laterally, it is in relation with the internal and common carotid arteries,
THE PHARYNX
1129
the internal jugular vein, the sympathetic and the last four cranial nerves.
Anteriorly, it communicates above with the nasal cavity, beneath this with the
oral cavity, and below with the laryngeal cavity. The pharynx is correspondingly
divided into three parts: the nasal -pharynx [pars nasalis], which is exclusively
respiratory in function; the oral pharynx [pars oralis], which is both respiratory
and alimentary; and the laryngeal pharynx [pars laryngea], which is almost
entirely alimentary.
Size and form. — The average length of the pharynx is about 12 cm. (5
inches). It is widest at the nasal pharynx, with a constriction (isthmus) connect-
(Sobotta-McMurrioh.)
1. — The Interior op the Pharynx, Viewed prom Behind.
Pharyngeal tonsil geptum
Torus tubarius
L
Pharyngeal recess
Glossopalatine arch
Styloid process
Styloid muscles
Salpingopharyngeal
fold
Parotid gland
Pharyngopalatine arch
Pharyngo epiglottic fold
Aryepiglottic fold
Aditus laryngis
Cuneate tubercle "^S
Corniculate tubercle ^\
Fold of laryngeal l
Thyreoid gland
ing it with the widened oral pharynx, and is again somewhat narrowed at the junc-
tion of oral and laryngeal pharynx (fig. 888) . It is narrowest at the point where
it joins the oesophagus below. In sagittal section (fig.' 848), it is evident that the
anterior and posterior walls are closely approximated in the laryngeal pharynx,
and have only a small space between them in the oral pharynx. The nasal
pharynx, however, has a considerable antero-posterior depth, and by its bony
walls is always kept open for respiratory purposes.
Structure. — The pharynx approaches the typical structure of the alimentary canal, yet
differs from it in several important respects. The lining mucosa is continuous with that of the
various cavities which open into the pharynx. Above, it is closely adherent to the base of the
cranium, where it is thick and dark in colour. It becomes thinner where it approaches the open-
ings of the auditory tubes and choana;; and below it is paler and thrown into longitudinal folds.
The epithehum of the greater part of the nasal pharynx (from the orifice of the auditory tube
upward) is stratified cihated columnar, while that of the remainder of the pharynx is stratified
squamous.
1130 DIGESTIVE SYSTEM
External to the mucosa, there is a characteristic fibrous membrane, the pharyngeal apo-
neurosis [fascia pharyngobasilaris], which is well marked above, but below it loses its density
and gradually disappears as a definite structure. Above, it is attached to the basilar portion
of the occipital bone in front of the pharyngeal tubercle. Its attachment may be traced to
the apex of the petrous portion of the temporal bone, and thence to the auditory (Eustachian)
tube and medial lamina of the pterygoid process. It descends along the pterygo-mandibular
ligament to the posterior end of the mylohyoid ridge of the lower jaw, and passes thence along
the side of the tongue to the stylohyoid ligament, the hyoid bone, and thyreoid cartilage.
External to the pharyngeal aponeurosis is a thick muscular layer, made up of various cross-
striated muscles, as will be described later. Outside of the muscular layer is a thin fibrous
tunica adventitia, connected with the adjacent prevertebral fascia by a loose, areolar tissue.
This loose tissue allows movement of the pharynx, and also favours the spreading of post-
pharyngeal abscesses.
The nasal pharynx (figs. 848, 888) belongs, strictly speaking, with the nasal
fossa as a part of the respiratory rather than the digestive system. Its anterior
wall is occupied by the two choance (posterior nares), with the nasal septum
between them. The floor is formed by the upper surface of the soft palate and in
a direct posterior continuation of the floor of the nasal fossae. Posteriorly, how-
ever, the floor presents a more or less narrowed opening, the pharyngeal isthmus,
which communicates with the oral pharynx below. The isthmus is formed ante-
riorly by the uvula, laterally by the posterior (pharyngo-palatine) arches. These
slope backward and downward to the posterior wall of the pharynx, which forms
the posterior boundary of the isthmus. The floor and isthmus change their form
and position greatly during the action of the palatal muscles, as will be mentioned
later.
The lateral wall of the nasal pharynx presents above and behind, correspond-
ing to its widest point, a wide, slit-like lateral extension, the pharyngeal recess
[recessus pharyngeus] or fossa of Rosenmueller (fig. 888). Below and in front of
this recess, the greater part of the lateral wall is occupied by the aperture of the
auditory (Eustachian) tube [ostium pharyngeum tubse]. This is a somewhat
triangular, funnel-shaped opening, with an inconspicuous anterior lip [labium
anterius], a more distinct posterior lip [labium posterius], which presents poste-
riorly a rounded prominence (due to the projecting cartilage of the auditory tube),
called the torus tubarius. The prominence of the posterior lip facilitates the intro-
duction of the Eustachian catheter, in connection with which the location of the
aperture in the mid-lateral wall just above the level of the floor of the nasal fossa
should be carefully noted. On the lower aspect of the triangular apertm-e is a
slightly rounded fold, the levator cushion, which is a prominence caused by the
levator palati muscle. A fold of mucosa descending from the posterior lip of the
aperture to the lateral pharyngeal wall is the plica salpingo-pharyngea (due to
the m. salpingo-pharyngeus). An inconspicuous plica salpingo-palatina descends
from the anterior lip to the soft palate.
The posterior wall (fig. 848) of the nasal pharynx slopes from below upward
and forward, passing (at the level of the anterior arch of the atlas) into the roof
[fornix pharyngis]. The roof is attached chiefly to the basi-occipital and basi-
sphenoid bones, extending laterally to the carotid canal of the pyramid, and ante-
riorly to the base of the nasal septum. In the posterior wall of the nasal pharynx
there is found in the mucosa a variable and inconstant blind sac, the pharyngeal
bursa.
The mucosa of the roof, and to a certain extent also of the posterior wall,
especially in children, is thrown into numerous folds, which may be irregular or
radiate from the neighbourhood of the bursa. There is often a median longitu-
dinal groove (or sometimes ridge) at the posterior (inferior) end of which is the
bursa. These folds of the mucosa contain much lymphoid tissue, both diffuse
and in the form of numerous characteristic lymphoid nodules, with crypt-like
invaginations of the surface epithelium. This area constitutes the pharyngeal
tonsil [tonsilla pharyngea] (fig. 890), which is well-developed in children (often
abnormally enlarged, producing 'adenoids'), but usually, though not always,
atrophied in the adult. According to Symington, the involution of the pharyn-
geal tonsils begins at 6 or 7 years, and is usually completed at 10 years. In the
region of the pharyngeal tonsil and elsewhere, the mucosa presents numerous
small racemose mucous glands, especially thick in the palatal floor of the nasal
pharynx and similar to those of the oral cavity.
The oral pharynx (figs. 848, 864, 888) is continuous above through the pharyn-
THE PHARYNX
1131
geal isthmus with the nasal pharynx and below with the laryngeal pharynx. Its
posterior wall presents no special features. The anterior wall is deficient above,
where there is a communication with the mouth cavity through the isthmus
Fig. 889. — Vertical Section op a Human Palatine Tonsil, a, Stratified epithelium;
b, basement membrane; c, tunica propria; d, trabeculse; e, diffuse lymphoid tissue; /, nodules;
h, capsule; i, mucous glands; k, striated muscle; I, blood vessel; q, pits. (From Radasch.)
faucium. The faucial isthmus is bounded above by the uvula, laterally by the
anterior (glosso-palatine) arches, and below by the dorsum of the tongue in the
region of the sulcus terminalis. Below the faucial isthmus, the anterior wall of
Fig. 890. — Portion op a Cobonal Section through the Pharyngeal Region, Showing
Waldbyer's Tonsillar Ring. (Palatine tonsils hypertrophied. )
Temporal lobe
External pterygoid -
Tensor veli palatinJ
Levator veli palatini ^ ^.^ ^ yr -
Internal {[ V-i-Z^
maxillary art ,^ f "^^t^^^^
Neck.of mandible
Internal pterygoid
Superior constrictor
and capsule of tonsil
Styloglossus
Stylohyoid
Lymph node
Hypoglossal nerve
Lingual artery -^
Epiglottis
Cavity of larynx
V_^3 — J — ^
Palatine tonsil
(hypertrophied)
Angle of mandible
External maxillary
j~ artery
\ Lingual tonsil
"* M. hyoglossus
— Vallecula
-> . Platysma
the oral pharynx is formed by the root of the tongue, which has been described
previously. The lateral wall of the oral pharynx on each side presents the pala-
tine tonsil, enclosed in a somewhat triangular tonsillar fossa [sinus tonsillaris]
1132 DIGESTIVE SYSTEM
limited anteriorly and posteriorly by the anterior and posterior palatine arches,
and below by the root of the tongue.
The palatine arches are folds of the mucosa formed at the sides of the free
posterior border of the soft palate, as already mentioned in connection with that
organ. The anterior arch (or pillar) [arcus glossopalatinus] extends from the
soft palate downward and forward to the lateral margin of the tongue, just behind
the papillfe foliatse. It is a fold of mucosa due to the underlying glosso-palatine
muscle, and inconspicuous except when this muscle is in action, or when the
tongue is depressed. It forms the lateral boundary of the faucial isthmus. The
posterior arch [arcus pharyngopalatinus] is a more prominent fold which extends
from the soft palate in the region of the uvula downward and backward to join
the postero-lateral aspect of the pharyngeal wall. It forms the lateral boundary of
the pharyngeal isthmus, and encloses the pharyngo-palatine muscle, whose actior
will be explained later.
The palatine tonsil [tonsilla palatina] (figs. 864, 889, 890, 891) is a flattened
ovoidal body, usually visible through the mouth cavity and faucial isthmus, and
located on each side of the oral pharynx. The tonsil is extremely variable in
size, but in the young adult averages about 20 mm. in height, 15 mm. in width
(antero-posteriorly) and 12 mm. in thickness.
The lateral or attached surface of the tonsil is covered by a thin but firm
fibrous capsule, which is continuous with the pharyngeal aponeurosis, and in
contact with the middle constrictor muscle of the pharynx (fig. 864). Just out-
side the constrictor, the tonsil is in relation with the ascending pharyngeal and
ascending palatine arteries, but is separated by a considerable space from the
external and internal carotids. Rarely, however, the lingual or external maxil-
lary may extend up higher than usual, so as to be in close relation with the lower
aspect of the tonsil. Further lateralward, the palatine tonsil is in relation with
the internal pterygoid muscle, and on the surface corresponds to a point somewhat
above and in front of the angle of the mandible. The posterior border of the
tonsil is thicker than the anterior, and forms a somewhat flattened surface in con-
tact with the pharyngo-palatine muscle (fig. 891).
The medial or free surface of the tonsil is covered with mucosa and presents a
variable number (12 to 30) small pits which are the openings into the tubular or
slit-like crypts [fossulse tonsillares]. These crypts are somewhat more numerous
in the upper part of the tonsil, and are sometimes branched or irregular in form.
Usually they end blindly in the substance of the tonsil, surrounded by lymphoid
tissue in characteristic nodular masses (fig. 889). The lymphocytes normally
migrate through the stratified squamous epithelium lining the crypts (occasion-
ally eroding passages of considerable size), and escape into the pharyngeal and
mouth cavities, where they form the so-called salivary corpuscles. Around the
periphery of the palatine tonsil, within the capsule, are many mucous glands (fig.
889), similar to those described in connection with the lingual and pharyngeal
tonsils. The ducts of the mucous glands sometimes enter the crypts, but usually
pass to the surface chiefly around the margins of the palatine tonsil.
Tonsillar plicae and fossae. — Connected with the tonsil are certain important
folds and fossse. The plica triangularis (fig. 891) is a fold of variable extent and
appearance, placed just behind the anterior arch, wider below and narrower
above. According to Fetterolf, it is a prolongation of the tonsillar capsule, cov-
ered with mucosa. It may be adherent to the anterior part of the medial surface
of the tonsil, or it may be free, in which case it covers a recess called the anterior
tonsillar fossa. Occasionally there is a similar plica and fossa at the posterior
border of the tonsil. Above the tonsil there is similarly a supratonsillar fossa
[fossa supratonsillaris], which is also inconstant and exceedingly variable in size
and shape. Killian found a supratonsillar fossa or canal in 41 of 105 cadavers.
Tonsillar vessels. — The arteries to the tonsil include the anterior tonsillar (from the dorsalis
linguEe); the inferior tonsillar (from the external maxillary); the -posterior tonsillar (from the
ascending pharyngeal) and the superior tonsillar (from the descending palatine). These
pierce the capsule and supply the gland. The veins form a plexus around the capsule and empty
into the lingual vein and the pharyngeal plexus. The lymphatic relations of the palatine
tonsil are important. Afferent vessels are received from adjacent areas of the mucosa in the
pharynx, mouth and lower part of the nasal cavity (v. Lenart). These are connected with an
extensive lymphatic plexus around the lymph follicles within the tonsil. Efferent lymphatic
vessels pass chiefly to the upper deep cervical lymphatic nodes. One of these, located just
behind the angle of the mandible, is so closely connected with the tonsil, and so constantly
THE PALATINE TONSIL
1133
enlarged following tonsillar infection, that it has been called the tonsillar lymph gland (Wood).
There are also communications with the submaxillary and superficial cervical lymphatic nodes.
The tonsillar lymphatic vessels connect also with those of the lingual tonsil in the root of the
tongue.
The tonsillar ring. — The two palatine tonsils, together with the lingual tonsil below and the
pharyngeal tonsil above, form an almost complete ring of characteristic tonsillar tissue sur-
rounding the pharynx and known as Waldeyer's 'tonsillar ring' (fig. 890). It is a highly
specialized development of the diffuse lymphoid tissue which is found everywhere in the mucosa
of the alimentary and respiratory tracts. It may be noted that the 'tonsillar ring' corre-
sponds to the anterior limit of the embryonic foregut, hence the epithehum is of endodermic
origin. The arrangement of the tonsils, together with their lymphatic connections, has sug-
gested the widely accepted view that they are to be considered as protective mechanisms
whose function is to intercept infectious material which has entered the mouth or nasal cavities.
This theory is supported by the experiments of v. Lenart, who found that substances injected
into the nasal mucosa are intercepted partly in the tonsils, and partly in the cervical lymph
Fig. 891. — The Left Palatine Tonsil, Showing the Arterial Supply.
1, Mesial aspect. 2, Postero-lateral aspect. E, lateral surface. B, posterior surface.
T, medial surface. G, groove for pharyngo-palatine muscle. C, capsule. PT, plica triangu-
laris. Arteries: AA, anterior tonsillar (from dorsal lingual); PA, posterior tonsillar (from
ascending pharyngeal) ; SA, superior tonsillar (from descending palatine) ; lA, inferior tonsil-
lar (anterior from dorsal lingual; posterior from tonsillar branch of internal maxillary). (Fet-
terolf : Amer. J. Med. Sc, 1912.)
nodes. Oppel, however, opposes this view, holding that the function of the tonsils, as of lym-
phoid tissue elsewhere, is merely the production of lymphocytes.
Development of the tonsil. — According to Hammar, the palatine fossa (sinus tonsillaris)
is a derivative of the second inner branchial groove and is visible in the human embryo of 17
mm. There appears in the floor of the fossa a tubercle (tuberculum tonsillare) which later
becomes atrophied, excepting a portion which is converted into the plica triangularis. The
primitive tonsil becomes divided into two lobes, upper and lower, by a fold (plica intratonsillaris)
which later usually disappears. In the fojtus of about 100 mm. (crown-rump length) the
epithelium of the floor grows into the subjacent mesenchyme in the form of somewhat irregular
solid sprouts of epithelium. These later become hollow and form the crypts. Ai'ound them,
in about the sixth fa-tal month, the lymphoid tissue begins to accumulate, at first diffusely,
later forming characteristic follicles. The lymphocytes arise in situ from the connective-
tissue cells (Hammar) or by immigration from the blood-vessels (Stohr). Retterer's claim
that the tonsillar lymphoid cells are derived from the epithelial cells has not been confirmed.
The later fcetal development of the tonsil is subject to considerable individual variation.
The supratonsillar fossa is a remnant of the upper part of the primitive sinus tonsillaris, which
may be transformed into a canal by growth of adenoid tissue around it. It is inconstant and
quite variable in size and extent. A portion of the sinus may likewise persist anteriorly (an-
terior tonsillar fossa) between the tonsil and the plica triangularis, but this portion is usually
obliterated by fusion of the plica with the tonsil. The occasional retro-tonsillar fold and fossa
are said to arise secondarily (Hammar).
Variations in the tonsil. — The palatine tonsil, like the lingual and pharyngeal tonsils, is an
exceedingly variable organ. Many of the variations are developmental in origin, as above
indicated, and ai-e therefore congenital. Furthermore, the tonsils, hke all lymphoid structures,
are subject to marked age variations. Though fairly well formed at birth, they are yet some-
what undeveloped. They rapidly increase in relative size and complexity, however, being
1134
DIGESTIVE SYSTEM
best developed in childhood. After the age of puberty, they usually undergo certain retro-
gressive changes, become smaller in size, and in old age become almost entirely atrophied and
lost. They are also markedly subject to inflammatory hypertrophy, especially in children.
Variations in the relations of the blood-vessels were mentioned above.
The laryngeal pharynx (fig. 848) is the lower portion leading from the oral
pharynx above into the oesophagus below (at the level of the lower border of the
cricoid cartilage, usually opposite the sixth cervical centrum). It is wide above
Fig. 892. — The Muscles of the Soft Palate and the Palatal Arches as Seen fbom in
Front. (After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.)
Incisive papilla
Upper bp
Second molar
Maxillary tuberosity
Hamulus of internal
pterygoid plate
Transverse palatine ridges
^ Angle of mouth
- X^^^v. So^* parts of cheek (cut)
Oral vestibule
Palatine glands
Palatine foramen with
anterior palatine nerve
-Posterior nasal spine
'^^j^m/'^ Buccinator
X— . Pterygo-mandibular raphe
Levator veli palatini
Constrictor pharyngis
superior
Pharyngo-palatinus
Glosso-palatinus
Bucco-pharyngeal fascia
Palatine tonsil
''^W'W-^^ Stylo-glossus
fa ~^^^ Isthmus of the fauces
Dorsum of tongue
and narrow below (fig. 888) . Its posterior walls are continuous with those of the
oral pharynx and in relation with the vertebral centra. Its lateral walls are
attached to the hyoid bone and the posterior part of the medial surface of the
thyreoid cartilage. Anteriorly it is in relation with the larynx. In the median
line above is the epiglottis, below which is the superior aperture of the larynx.
Still lower is the posterior wall of the larynx, containing the arytenoid and lamina
of the cricoid cartilage. Laterally, are the pharyngo-epiglottic folds, and below
these on each side a deep, elongated fossa, the recessus piriformis, bounded
laterally by the medial surface of the thyreoid cartilage. The mucosa of the laryn-
geal pharynx is similar to that of the oral pharynx, and contains racemose mucous
glands, which are especially numerous in its anterior wall.
Muscles of the pharynx and soft palate. — These muscles (figs. 892, 893, 894),
which are here grouped together for convenience of description, are chiefly
sphincter-hke constrictors in function. They include the constrictors of the
faucial isthmus (mm. glossopalatini), the constrictors of the pharyngeal isthmus
MUSCLES OF PHARYNX AND PALATE
1135
(mm. pharyngopalatini) , the three pharyngeal constrictors, and also the levator
and the tensor veil palatini, the m. uvulae and the stylo-pharyngeus. The stylo-
pharyngeus and pharyngo-palatine muscles form an incomplete longitudinal layer
within the more circularly arranged constrictors of the pharynx.
Fig. 893. — View of Muscles of Soft Palate, as Seen feom Behind, Within the Pharynx.
(Modified from Bourgery.)
PharyngeaT "'' \ll
aponeurosis — ^
M. uvulae
Hamular process
Pharyngo-palatinus
Constrictor pharyngis
superior
Crico-arytaenoideus
posterior
Thyreoid cartilage
Cncoid cartilage
The muscles are arranged in layers either behind or in front of the aponeurosis,
and in a horizontal section of the soft palate the following layers are met with from
behind forward: (1) The mucous membrane on the pharyngeal surface; (2) the
posterior layer of the pharyngo-palatinus (palato-pharyngeus) ; (3) the m. uvulae;
(4) the levator veli palatini; (5) the anterior layer of the pharyngo-palatinus; (6)
the palatal aponeurosis with the tensor veli palatini; (7) the glosso-palatinus
palato-glossus) ; and (8) the mucous membrane on the oral aspect.
The glosso-palatinus (palato-glossus) is a cylindrical muscle extending between the soft
palate and the lateral border of the tongue. Origin. — From the oral surface of the palatal apo-
neurosis. Insertion. — (1) The superficial layer of muscles which covers the side and adjacent
part of the under surface of the tongue; (2) the transversus linguae. Structure. — At its origin
the muscle forms a thin sheet, but the fibres, passing lateralward, quiclcly concentrate to form
a cylindrical bundle, which passes downward beneath the mucous membrane of the pharynx
1136
DIGESTIVE SYSTEM
and in front of the tonsil, forming the glosso-palatine arch of the fauces. It reaches the side
of the tongue at the junction of its middle and posterior thirds, and some of its fibres continue
forward to join with those of the stylo-glossus and hyo-glossus, while the majority pass medially
to become continuous with the transversus linguse. Nerve-supply. — From the pharjmgeal
branches (plexus) of the vagus. Action. — (1) To draw the sides of the soft palate downward;
(2) to draw the sides of the tongue upward and backward. The combination of these actions
tends to constrict the faucial isthmus. (The origin and insertion of the glosso-palatinus as
given above are often described as reversed.)
The pharyngo-palatinus (palato-pharyngeus) — named from its attachments — is a thin
sheet. Origin. — (1) From the aponeurosis of the soft palate by two heads which are separated
by the insertion of the levator veli palatini; (2) by one or two narrow bundles from the lower
part of the cartilage of the auditory (Eustachian) tube (salpingo-pharyngeus) . Insertion. — (1)
By a narrow fasciculus into the posterior border of the thyreoid cartilage near the base of the
superior cornu ; (2) by a broad expansion into the fibrous layer of the pharynx at its lower part .
Fto. 894. — Thk Musrir=i op the Pharynx, Lateral View.
Medial lamina of
pterygoid process
Constrictor pharyngis
superior
Pterygo-mandibular raphe
Stylo-hyoid ligament
Stylo-pharyngeus
Crico-thyreoideus
Cricoid cartilage
Structure. — The upper head of the muscle consists of scattered fibres which blend with the oppo-
site muscle across the middle line; the lower head is thicker, and foUows the curve of the posterior
border of the palate. The two heads with the fasciculus from the auditory (Eustachian) tube
form a compact muscular band in the posterior palatine arch; the fibres mingle with those of
the stylo-pharyngeus, at the lower border of the superior constrictor, and then expand upon the
lower part of the pharynx. Nerve-supply. — From the pharyngeal branch (plexus) of the vagus.
Action. — (1) Approximates the posterior arches of the fauces; (2) depresses the soft palate;
(3) elevates the pharynx and larynx. (The origin and insertion above given are often described
as reversed.)
The inferior constrictor is thick and strong. It arises from the thyreoid cartilage im-
mediately behind the oblique hne and superior tubercle (thyreo-pharyngeus), and from a
tendinous arch extending between the inferior tubercle of the thyreoid and the cricoid cartilage
and also from the lateral surface of the cricoid cartilage (cricopharyngeus) (fig. 894). The
fibres spread backward and medialward, the lowest horizontally, whilst those above ascend
more and more obUquely, and are inserted into the fibrous raph6 of the pharynx. Some of
MUSCLES OF PHARYNX AND PALATE 1137
the lowest fibres are continuous with the muscular fibres of the oesophagus, and the upper over-
lap the middle constrictor (fig. 894). The nerve-supply of all three constrictors is from the
pharyngeal nerve.
Near the upper border the superior laryngeal nerve and artery pierce the thyreo-hyoid
membrane to reach the larynx. The inferior laryngeal nerve ascends beneath the lower border
immediately behind the crico-thyreoid articulation.
The middle constrictor is a fan-shaped muscle which arises from the lesser cornu of the
hyoid bone and from the stylo-hyoid Ugament (chondro-pharyngeus), and from the whole
length of the greater cornu (cerato-pharyngeus). The diverging fibres are inserted into the
median raphe, and blend with those of the opposite side. The lower fibres of the muscle descend,
beneath the inferior constrictor, to the lower part of the pharynx; the upper overlap the superior
constrictor, and reach the basilar process of the occipital bone, whilst the middle fibres run
transversely (fig. 894).
The glosso-pharyngeal nerve passes downward above its upper border, the stylo-pharyngeus
passes between it and the superior constrictor, and near its origin it is overlapped by the hyo-
glossus and crossed by the lingual artery.
The superior constrictor is quadrilateral in shape, pale, and thin (fig. 894). It arises
from the lower third of the hinder edge of the median lamina of the pterygoid process and its
hamular process (pterygo-pharyngeus), from the pterygo-mandibular ligament (buoco-pharyn-
geus), from the posterior fifth of the mylo-hyoid ridge of the mandible (mylo-pharyngeus),
and from the side of the root of the tongue (glosso-pharyngeus) . The fibres pass backward to
be inserted into the median raphd, the highest reaching the pharyngeal tubercle. The Eu-
stachian tube and the levator veli palatini are placed above the superior arched border, and the
space {sinus of Morgagni) between this and the basilar process, devoid of muscular fibres, is
strengthened by the pharjmgeal aponeurosis, this portion of it being semilunar in shape.
The stylo-pharyngeus arises from the base of the styloid process internally. It passes down-
ward and medialward to reach the pharynx between the superior and middle constrictors.
Its fibres spread out as it descends beneath the mucous membrane. At the lower border of
the superior constrictor some of its fibres join fibres of the pharyngo-palatinus (palato-pharyn-
geus), and are inserted mto the posterior border of the thyreoid cartilage (fig. 894); the rest
blend with the constrictors. The nerve-supply of the stylo-pharyngeus is from the glosso-phar-
yngeal nerve.
The levator veli palatini — named from its action on the velum of the soft palate — is some-
what rounded in its upper, but flattened in its lower, half. Origin. — (1) The inferior surface
of the petrous portion of the temporal, anterior to the orifice of the carotid canal; (2) the lower
margin of the cartilage of the auditory (Eustachian) tube. Insertion. — The aponeurosis of
the soft palate; the terminal fibres of the muscles of each side meet in the middle line in front
of the m. uvulae. Structure. — Its origin is by a short tendon; the muscle then becomes fleshy,
and continues so to its insertion. Nerve-supply. — From a pharyngeal branch (plexus) of the
vagus. Action. — (1) To raise up the velum of the soft palate, and bring it in contact with the
posterior wall of the pharynx; (2) to narrow the pharyngeal opening and to widen the isthmus of
the auditory (Eustachian) tube. (According to Cleland, it closes the pharyngeal opening of this
tube.)
The tensor veli palatini — named from its action on the velum of the soft palate — is a thin,
flat, and narrow sheet. Origin. — (1) The scaphoid fossa of the sphenoid; (2) the angular spine
of the sphenoid; (3) the lateral side of the membranous and cartilaginous wall of the auditory
(Eustachian) tube. Insertion. — (1) Into the transverse ridge on the under surface of the hori-
zontal plate of the palate bone; (2) the aponeurosis of the soft palate.
Structure. — Its belly as it descends between the pterygoideus internus and the internal
pterygoid plate is muscular. On approaching the hamular process it becomes tendinous, and
continues so to its insertion. A bursa is interposed between the hamular process and the tendon.
The belly of the muscle is at nearly a right angle with its tendon. Nerve-supply. — From the
mandibular division of the trigeminus through the tensor palati branch of the otic ganglion.
Actions. — (1) Tightens the soft palate; (2) opens the auditory (Eustachian) tube during deglu-
tition.
The m. uvulse. — so named by reason of its position in the uvula. Origin. — (1) From the
aponeurosis of the soft palate and tendinous expansions of the two tensores veli palatini. In-
sertion.— Into the uvula. Structure. — The muscle consists of two narrow parallel strips lying
on each side of the middle Une of the palate. Nerve-supply. — From the pharyngeal branch of
the vagus. Action. — To draw up the uvula.
Origin of the muscles. — According to W. H. Lewis, the tensor palati is a derivative of the
mandibular arch (probably split off from the pterygoid mass) ; the levator palati and m. uvulae
come with the facial musculature from the hyoid arch; the glosso-palatine, stylo-pharyngeus
and pharyngeal constrictors probably from the third visceral arch, in a pre-muscle mass visible
in a 9 mm. embryo. The adult innervation of the pharyngeal muscles does not agree entirely
with this, however. The pharyngeal muscles (as above stated) are innervated chiefly from the
vagus, whereas if derived from the third arch their innervation from the glosso-pharyngeus
would be expected.
Process of swallowing. — In the act of swallowing, practically aU of the muscles of the mouth,
tongue, palate and pharynx are involved. By compression of the hps and cheeks, together
with elevation of the tongue, the food is forced backward through the faucial isthmus into the
oral pharynx. Constriction of the faucial isthmus by the glosso-palatine muscles assists in
preventing a return to the mouth. By the action of the levator palati, tensor palati, and
pharyngo-palatine muscles, the soft palate is retracted and tightened, with constriction of the
pharyngeal isthmus, so as to prevent the passage of the food upward into the nasal pharynx.
The pharynx is dra-nm upward by the stylo-pharyngeus, and the pressure produced by the
pharyngeal constrictors (the contraction beginning above and extending downward) forces
the food dowTiward through the laryngeal pharynx and into the oesophagus. Passage of the
food into the larynx is prevented by constriction of the superior aperture of the larynx.
1138 DIGESTIVE SYSTEM
Vessels and nerves. — The vessels of the tonsil and the motor nerves of the various muscles
have aheady been mentioned. In general, the arteries to the pharynx are derived chiefly from
the ascending pharyngeal, the ascending palatine branch of the external maxillary, and the
descending palatine and pterygo-palatine branches of the internal maxillary. The veins
form a venous plexus between the pharyngeal constrictors and the pharyngeal aponeurosis,
and also an external plexus, communicating with the pterygoid plexus above and with the
posterior facial or internal jugular vein below. The lymphatic vessels pass chiefly to the
deep cervical nodes, those from the upper portion (including the pharyngeal tonsil) ending
partly in the retro-pharyngeal glands. The nerves of the pharynx, both motor and sensory, are
derived chiefly from the glosso-pharyngeal and vagus, by way of the pharyngeal plexus.
The development of the pharynx. — The pharynx is developed chiefly (if not entirely) from
the anterior end of the archenteron. In this portion of the archenteron, with the develop-
ment of the branchial arches, there are formed on each side four entodermal pouches or grooves
(with a rudimentary fifth), the branchial clefts (see p. 17). With further development the first
pair of branchial clefts form the tympanic cavities and the auditory or Eustachian tubes; the
lower portion of each second branchial cleft persists as a fossa in which a palatine tonsil is
developed ; the remains of the third and fourth pairs are found on each side in the vaUecula
and piriform sinus of the larynx. The origin of the pharyngeal tonsil may be observed in the
■third month of foetal life in the form of small folds of mucous membrane which, during the
sixth month, become infiltrated with diffuse adenoid tissue, lymph-nodules differentiating in this
toward the end of foetal life. The pharyngeal bursa, which is not a constant structure (Kilr
lian), may be observed as a small diverticulum of the pharyngeal waU, closely connected with
the anterior extremity of the notochord. The diverticulum develops independently of Rathke's
pouch (which gives rise to the anterior portion of the hypophysis), and is also apparently distinct
from Seesel's pocket.
The entire pharynx, like the associated facial region, is relatively small and undeveloped
in the foetus and newborn, but develops rapidly during infancy. The development of the
muscles and of the palatine tonsils has already been considered.
Variations. — Variations in the palatine and pharyngeal tonsils and in the pharyngeal bursa
have already been mentioned. Remnants of the visceral clefts may persist as aberrant diver-
-ticula or as 'branchial fistulae' connected with the pharynx. Many additional muscles have been
described, chiefly longitudinal muscles arising from the base of the cranium either by spUt-
•ting of those normally present, or as separate slips. A detailed description of these may be
found in Poirier-Charpy's work. Abnormally extensive fusion of the posterior arches of the
■palate with the walls of the pharynx may produce a congenital stenosis of the pharyngeal isthmusi
Comparative. — The pharynx is not distinctly separated from the mouth cavity in the
.lower vertebrates. It is the region containing the branchial or visceral clefts and is thus both
.respiratory and aUmentary in function. The nasal pharynx, including the apertures of the
•auditory tubes, becomes distinct along with the nasal cavity when the palate is formed (from
the reptiles upward). In the air-breathing vertebrates, the laryngeal aperture appears in
the ventral wall of the pharynx just anterior to the beginning of the cesophagus. Of the tonsils,
the pharyngeal are the most primitive, being present in the roof of the pharynx in amphibia,
weU-developed in reptiles, birds, and mammals (Killian). The palatine tonsils, on the other
hand, are characteristic of mammals, being rarely absent, however (e. g., rat, guinea pig).
From the embryological point of view, Hammar has classified the palatine ^tonsils in the
various mammals under (1) the primary type (including rabbit, cat, and dog), in which the
tonsil is formed from the embryonic tonsillar tubercle (described above under development
of tonsil); and (2) the secondary type (including pig, ox, sheep and man), in which the tonsilt
lar tubercle disappears and the tonsil is developed from the wall of the surrounding tonsillar
sinus. Typical epithelial crypts (highly branched in the ox) are found only in the secondary
•type. The tonsil may form a single (lymphoid) lobe (cat, pig, rabbit) or may develop typi-
cally two lobes (ox, sheep, man), separated by the intratonsillar fold. There are great varia-
tions among difl'erent species as to relative size, number and character of folds, crypts,
«tc. The intimate relation of the epithelium with the underlying lymphoid tissue is charac-
teristic and constant.
THE (ESOPHAGUS
The cesophagus (figs. 895, 896) is that portion of the alimentary tract which!
extends between the pharynx and the stomach. It is more constricted than the
rest of the canal, being narrowest at its commencement opposite the lower
border of the cricoid cartilage. It is again somewhat contracted behind the left
bronchus, and at its passage through the diaphragm, which is opposite the tenth
or eleventh thoracic vertebra. It has an average length of 25 cm. (varying from
20 to 35 cm.). The average distance from the rima oris to the beginning of the
cesophagus is about 15 cm. In its course downward the oesophagus follows the
curves of the vertebral column until it finally passes forward in front of, and
slightly to the left of, the aorta to gain the oesophageal opening in the diaphragm.
In addition to these curves it presents two lateral curvatures, one convex toward
the left side at the root of the neck and in the upper part of the thorax, and the
other concave toward the left in the lower part of the thorax where it leaves the
vertebral column. It lies in the middle line at its commencement (usually
opposite the sixth cervical vertebra), and again, at a lower level, opposite the fifth
thoracic vertebra.
THE (ESOPHAGUS
1139
After death the oesophagus is somewhat flattened from before backward, but
it is more rounded during life. It is closed except during the passage of food, etc.
The -peristaltic movements of the oesophagus can readily be observed by means of the Roent-
gen-rays. Solids often lodge a short time at the level of the arch of the aorta, but pass quickly
through the cardiac orifice. A swallow of liquid, on the other hand, is usually detained at the
lower end of the oesophagus (probably by sphincteric action of the cardia) for about seven
seconds before passing into the stomach (Pfahler).
Fig. 895. — The CEsophagus and Stomach. (Testut.)
Thyreoid cartilage'
Trachea
Left flexure of cesophagus
Aortic arch
Right flexure of oesophagus
Descending aorta
Hiatus (Esophagus
(Esophagus, pars abd
Lesser curvature
Pars pylorica
Descending duodenum
Inferior duodenu:
Fundus of stomach
— Greater curvature
Bifurcation of aorta
The oesophagus is divided into three parts: cervical, thoracic and abdominal.
Cervical portion. — The oesophagus has anteriorly the trachea, the posterior
portion of the left lateral lobe of the thyreoid gland, and the left recurrent nerve,
branches of the inferior thyreoid artery, and the carotid sheath. Posteriorly,
it rests upon the vertebral column, the longus colli muscles, and prevertebral
fascia. On its right side are placed the right carotid and right recurrent nerve;
and on the left side the left inferior thyreoid vessels, left carotid artery, left sub-
clavian, and the thoracic duct. The recurrent nerves pass upward on each side
to gain the interval between the trachea and oesophagus. The left nerve, as
already described, lies in front of the tube, and the right along its right border.
Thoracic portion. — The oesophagus descends in the thorax through the super-
ior and the posterior mediastina. In the superior mediastinum its anterior rela-
tions are the trachea, with the deep cardiac plexus in front of its bifurcation, the
left subclavian and carotid arteries crossing its left border obliquely, the left
recurrent nerve, and the arch of the aorta. To the left are the left carotid- and
subclavian arteries, the end of the arch of the aorta, and the left pleural sac. To
the right it is in relation with the right vagus nerve and the right pleural sac.
Posteriorly, it rests upon the vertebral column, the left longus colli muscle, and it
overlaps the thoracic duct. As it enters the posterior mediastinum, it passes behind
the left bronchus (or bifurcation of the trachea) and the right pulmonary artery,
resting posteriorly on the vertebral column and thoracic duct. In the posterior
1140
DIGESTIVE SYSTEM
mediastinum it has anteriorly the pericardium, which separates it from the left
atrium and a portion of the diaphragm; posteriorly it rests upon the vertebral
column, accessory hemiazygos and hemiazygos veins, the right aortic intercostal
arteries, the thoracic duct, and the descending aorta. To the right is the right
pleural sac, the vena azygos, which it partly overlaps, and below, the thoracic
duct. To the left in the upper part is the descending thoracic aorta, and,
below, the left pleural sac is separated from it by a little loose areolar tissue.
It is surrounded by the oesophageal ple.xus formed by the vagi nerves, and, as
they emerge from the lower part of the plexus, the left vagus lies in front of the
oesophagus and the right vagus behind.
Fig. 896. — Cross-sections Illustrating the Relations of the CEsoPHAGtrs at Various
Levels.
Abdominal portion. — The oesophagus lies in the epigastric region of the abdo-
men. Anteriorly is the left lobe of the liver. To the left the left lobe of the liver
and the fundus of the stomach. To the right the caudate (Spigelian) lobe of the
liver, and posteriorly the decussating fibres of the crura of the diaphragm and the
left inferior phrenic artery. The abdominal portion is very short, usuallj^ not
more than 2 cm. (4/5 inch) in length (see figs. 896 D, 907).
Structure. — The thick-walled oesophagus presents the four typical tunics of the alimentary
canal (fig. 897). The mucosa and the muscularis are the most important, the submucosa and
the external adventitia being accessory layers. The mucosa (fig. 897) is thick and strong, of
reddish colour in its upper portion and more greyish below. It presents deep longitudinal folds
to allow for distention, and when empty the lumen is therefore stellate in cross sections. The
hning epithelium is stratified squamous. The lamina propria presents numerous papiUse,
and is limited externally by a muscularis mucosm. This is a comparatively thick layer (except
at the upper end) and is composed of smooth muscle fibres, longitudinally arranged.
THE (ESOPHAGUS
1141
The submucosa (fig. 897) is a thick, very loose fibrous layer connecting the mucosa with the
muscularis. It contains numerous vessels and nerves, and mucous glands. The latter [gl.
oesophageae] are of the racemose type, Uke those of the mouth, and are variable in number.
There are also two sets of superficial glands, confined to the lamina propria, and resembling
the fundus glands of the stomach. The upper set (Rtidinger-Sohaffer glands) are found in 70
per cent, of oases, occurring above the level of the fifth tracheal ring. The lower set (ojsophageal
cardiac glands) form a ring around the ccsophagus just above the cardiac aperture. A few small
lymph nodes also occur in the submucosa, often around the ducts of the mucous glands.
The muscularis (fig. 897) is a thick reddish tunic with two distinct layers, approximately
equal in thickness. The fibres of the inner layer are arranged circularly and are continuous
with the inferior constrictor above and with the obhque fibres of the stomach below. The
fibres of the outer layer are longitudinal and commence above as three flattened bands: a strong
anterior band arising from the ridge on the back of the cricoid cartilage, and two lateral bands
blending with the fibres of the stylo-pharyngeus and the pharyngo-palatine. These all unite
into a continuous layer which below passes into the muscular coat of the stomach. The upper
third or fourth of the oesophagus contains e.xclusively cross-striated muscle fibres, like those
of the pharynx. Below this, there is a zone of intermingled smooth and cross-striated fibres.
The lower half of the cesophagus muscle is usually composed exclusively of smooth fibres.
Around the muscular coat is a thin loose fibrous layer [tunica adventitial connecting the
oesophagus with neighbouring structures.
Vessels and nerves. — The arterial supply of the oesophagus is derived from the inferior
thyreoid, the oesophageal branches of the aorta, the intercostals, the inferior phrenic and the
Fig. 897.-
-Transveesb Section of the Uppee Third of the Human CEsophagus.
(Lewis and Stohr.)
Stratified epithelium
X5.
Group of fat-cells'^^JI
*^^\ Circular muscles | Muscu-
■^''''^ Longitudinal muscles J laris
Lymph nodule
' "'^A Tunica adventitia
Mucous gland
left gastric arteries. Branches pierce the wall and supply the various coats. The veins
accompany the arteries. They form on the outer surface of the ccsophagus a venous plexus
opening into the gastric coronary vein below and the azygos and thyreoid veins above (thus
estabUshing a communication between portal and systemic veins). There are also numerous
lymphatics in the cesophagus arising chiefly in the mucosa and draining into the lower deep
cervical, posterior mediastinal and superior gastric nodes. The nerves form two sympathetic
plexuses, the submucous and the myenteric, from which the walls are supphed as will be de-
scribed later for the stomach and intestine. Branches are received from the sympathetics, and
from the vagus, including the recurrent nerve.
Development. — The embryonic oesophagus is at first relatively very short, but lengthens
rapidly in connection with the descent of the stomach. The upper end is still high in children,
corresponding to the higher vertebral level of the larynx. The lining epithehal cells are primi-
tively cylindrical in form, and irregular ciliated areas are found from the third foetal month up
to birth (F. T.Lewis). In the embryo of about 20 mm., there is a proHferation of the epithelium,
associated with the formation of vacuoles, but the lumen does not appear to be normally oc-
cluded. The primary longitudinal folds of the mucosa appear early (third month) and at the
lower end seem to participate in the rotation of the stomach (F. P. Johnson). The superficial
oesophageal glands appear about the fourth month (78 mm.), the deep glands at 240 mm.
(Johnson). Of the muscular layers, the circular appears first (at about 10 mm.) the longi-
tudinal shghtly later (17 mm.).
Variations. — Usually a bundle of smooth muscle connects the oesophagus with the left
bronchus [m. broncho-oesophageus], and another similarly with the left mediastinal pleura [m.
pleuro-oesophageus]. More rarely there are similar bands connecting with the trachea, peri-
1142
DIGESTIVE SYSTEM
cardium, etc. Pouch-like dilatations of the oesophagus may occur, especially in the upper
part of its posterior wall or at the lower end. According to C. R. Robinson, the latter include
(1) ampulla phrenica, just above the diaphragm, and (2) antrum cardiacum, in the abdominal
portion of the oesophagus. Diverticula also occur, some of which may be derived from the
embryonic vacuolization of the epithehum previously described, as may likewise the occasional
congenital atresia. Abnormal strictures of the ccsophagus may occur, oftenest at the upper
end, at the left bronchus, and near the lower end. Finally, the oesophagus may be in part
either double or absent, and may communicate by fistula with the trachea.
Comparative. — The length of the oesophagus varies with the length of the neck, being
shortest in fishes and amphibia where the cesophagus is not well marked off from the stomach.
The lining epithelium is stratified squamous in mammals and birds, but often ciliated in lower
forms. Mucous glands are absent in fishes, but occur typically m all higher forms. They
are found best developed toward the lower end of the cesophagus, except in mammals, where
they are usually more numerous at the upper end. Dilatations may occur normally, as in
the crop of birds, which is richly supphed with glands. The musculature of the oesophagus is
primitively entirely smooth (Oppel) as found in amphibia, reptiles and birds. A secondary
replacement by cross-striated muscle is found to a variable extent in the majority of mammals
and fishes.
THE ABDOMEN
The abdomen properly consists of that part of the body situated between the
thorax and the pelvis. It is bounded above by the diaphragm; below, by the brim
of the true pelvis; behind, by the vertebral column, diaphragm, quadratus lum-
borum and psoas muscles, and by the posterior portions of the ilia. At the sides
it is limited by the anterior parts of the ilia and the hinder segments of the muscles
which compose the anterior abdominal wall, viz., the transversus, internal oblique.
Fig. 898. — Diagram of the Abdominal Regions.
Joint between meso-sternum
and ensiform cartilage
Tip of ensiform cartilage
Costal border
■TJpper horizontal plane
Lower horizontal plane A, at
"level of tubercles of iliac crest
Lower horizontal plane B, at
' level of anterior iliac spines
Vertical plane A, from middle
of inguinal ligament
.Vertical plane B, at lateral bor-
der of rectus (semilunar line)
Summit of symphysis pubis
and external oblique. In front, besides these muscles, there are the two recti and
pyramidales muscles. External to the peritoneum the abdomen is hned by a
special layer of fascia.
It is customary for anatomists and physicians to divide, for purposes of descrip-
tion, the ventral surface of the abdomen, by means of two horizontal and two ver-
tical lines, into nine regions (fig. 898). A complete uniformity in the use of the
boundary hues marking these regional subdivisions has not as yet been attained,
although the variations in the schemes used are not marked as concerns the main
features. It should be borne in mind that it is necessary that the boundary lines
used should be converted into planes carried through the whole depth of the abdo-
men and defined on the dorsal as well as the ventral surface, and that the relations
defined can only be approximate, owing to the wide range of the physiological
variation in the position of the abdominal contents. The nine regions or subdivi-
sions may be outhned as follows: — The upper horizontal line or plane passes
through the lowest point of the tenth costal cartilages, about 5 cm. above the um-
bihcus, and dorsally through the second or third lumbar vertebra. The lower
THE ABDOMEN
1143
horizontal line and plane passes through the level of the anterior superior iliac
spines, and dorsally about 2.5 cm. below the promontory of the sacrum. Cun-
ningham has proposed that this hne be passed through the tuberculum cristse,
therefore in a plane slightly higher than the interspinous plane. For the longitu-
dinal hnes and planes it has been customary to run vertical hnes parallel with the
mid-body line or mid-sagittal plane, and from the middle of the inguinal Ugaments.
The outer border of each rectus would seem, however, preferable as a guide for
these longitudinal lines and planes, which may be easily locahsed above by the
lateral infra-costal furrow and below by the pubic spines, leaving thus on each side
an inguinal region which includes the whole of the inguinal canal. The boundary
lines here indicated may be made intelligible by a reference to fig. 898. The
regions thus outhned are known as the right and left hypochondriac and epigas-
tric regions, found above the upper horizontal line; the right and left lumbar and
the umbiUcal regions, found between the two horizontal lines; the right and left
Fig. 899. — The Adbominal Visceea in Situ, after Removal of the Anterior Abdom-
inal Wall (After Sarazm )
Transverse colon
Great omentum
Small intestine
Sigmoid coloDJ
inguinal or iliac and the hypogastric regions, found below the lower horizontal lines.
(According to the BNA, the lumbar regions are termed 'lateral abdominal'.)
On freely laying open an abdomen from the front, the general form of the space
is seen to be an irregular hexagon, the sides of which are formed as follows: — The
upper two by the margins of the costal cartilages with the ensiform cartilage
between; the two lateral sides by the edges of the lateral boundary; and the two
lower by the two inguinal ligaments which meet at the pubes.
In this irregular hexagon the following organs can be observed without dis-
arranging their normal position (fig. 899). Above, on the right side, under the
costal cartilages, can be seen the liver, which extends from the right across the
median line to a point below the left costal cartilages. Below the liver, and lying
to the left side, can be seen the anterior surface of the stomach; from the lower
border of the stomach the omentum extends downward, and shining through it
can be seen the middle part of the transverse colon. On each side and below the
1144
DIGESTIVE SYSTEM
irregularly folded omentum are exposed the coils of the small intestine; in the right
iliac fossa a part of the csecum appears;- and in the left iliac fossa the lower (iliac)
part of the descending colon and the beginning of the sigmoid colon.
To the left of the stomach and under cover of the lower ribs of the left side the
edge of the spleen may possibly be observed; and just below the edge of the liver,
and about the level of the tip of the ninth rib, the gall-bladder may be seen. The
dome of the urinary bladder may be noticed just behind the symphysis pubis and
in the median line. The disposition of the viscera in the foetus is shown in fig. 953.
General morphology — Before taking up the various individual organs included in the
abdominal and pelvic portions of the alimentary canal, a brief consideration of their general
morphology is desirable. The primitive canal, as already described in the embryo (in the
Fig. 900. — Digeammatic Representation of an Early Stage in the Development of
THE Alimentary Canal and the PERiTONEtrM. (After Sobotta-McMurrich.)
Lesser curvature CEsophagus
Ventral mesogastrium "v y^ Stomach
(lesser omentum) \ _^.?^=:S^r-_ / Greater curvature
Ventral mesogas-
trium (falciform
lig.)
Falciform lig.
Umbilical vein
Omphalo-mesenteric duct
Umbilical
Dorsal meso-
/ gastrium
Sup. mesenteric art.
Left colic flexure
Inf. mesenteric art.
Distal limb of intestinal loop
section on Morphogenesis), and as found in the lower vertebrates is a comparatively straight,
simple tube extending ventral to the body axis from mouth to anus. In the abdominal region
(and primitively throughout the whole trunk), the canal lies within the body cavity, which is
lined by parietal peritoneum. The visceral peritoneum is reflected from the mid-dorsal line
as a double layer, the ■primiiive dorsal mesentery, within which the vessels and nerves pass to
the walls of the canal. Within the dorsal mesentery are also the spleen and pancreas. In
the anterior (upper) region of the abdomen there is also a similar primitive ventral mesentery,
which contains the liver.
The relations above mentioned are indicated diagrammatically in fig. 900, which represents
a comparatively early stage in the development of the intestinal canal. The hver is already
almost completely separated from the diaphragm (with which it was intimately associated in
the earher septum transversum). The ventral mesentery persists in the form of (1) the gastro-
THE PERITONEUM 1145
hepatic or lesser omentum, connecting the stomach with the hver; and (2) the falciform ligament,
connecting the hver with the ventral body wall.
The stomach undergoes a rotation on its longitudinal axis so that its anterior border
(lesser curvature) is turned to the right, and its posterior border (greater curvature) to the left
(fig. 901). Thus the posterior mesentery of the stomach [mesogastrium], bulges to the left and
forward, carrying with it the spleen and pancreas. The portion of the mesentery corresponding
to the pancreas, and that from the spleen to the root of the mesentery, become fused with the
posterior body wall. The portion of the primitive mesogastrium between the stomach and
spleen persists as the gastro-splenic omentum (or ligament), while the lower portion arches
forward and downward as an extensive fold, the great omentum. The portion of the peritoneal
cavity left behind the stomach is termed the bursa omentalis, or lesser sac, the remainder of
the peritoneal cavity being the greater sac.
Along with the pancreas, the duodenum becomes adherent to the posterior wall. The
remainder of the intestine forms a loop (fig. 901), the upper portion of which forms the jejuno-
ileum, the lower portion the large intestine. The intestinal loop rotates counter-clockwise,
so that the csecum and ascending colon are carried over to the right side of the body cavity,
where (with the corresponding portion of the primitive mesentery) they become adherent to
the posterior body wall (fig. 901). The mesentery of the transverse colon persists (though
fused partly with the great omentum, as explained later under development). The descending
colon becomes displaced to the left side, and (together with its mesentery) becomes adherent
to the posterior wall of the abdomen. The mesentery of the sigmoid colon usually persists
(in part), whUe that of the rectum is obhterated. Through these modifications of the peri-
FiG. 901. — Diagrams Illustrating the Development of the Great Omentum, Mesentery,
ETC. A, Earlier Stage; B, Later Stage.
bid, caecum; dd, small intestine; dg, yolli-stallc; di, colon; du, duodenum; gc, greater
curvature of the stomach; gg, bile duct; gn, mesogastrium; k, point where the loops of the
intestine cross; mo, mesocolon; md, rectum; mes, mesentery; wf, vermiform appendix.
(McMurrich after Hertwig.)
mS
toneum, and through unequal growth in the different regions, the simple primitive intestinal
tube is transformed into the complicated adult canal. The details of the transformation will
be more fuUy discussed later.
Under certain rare conditions, the developmental process is modified so as to produce a
situs inversus, which may be partial or complete, involving both thoracic and abdominal
viscera. Under these circumstances, the viscera are transposed, the right and left sides being
reversed.
THE PERITONEUM
The peritoneum, as has been shown, is a serous membrane which lines the cav-
ity of the abdomen from the diaphragm to the pelvic floor, and invests or covers to
a varying extent the viscera which that cavity contains. Viewed in its very sim-
plest condition, it may be regarded as a closed sac, the inner surface of which is
smooth, while the outer surface is rough and is attached to the tissues which sur-
round it.
In the male subject the peritoneum forms actually a closed sac; but in the
female its wall exhibits two minute punctures, which correspond to the openings
of the Fallopian tubes. That part which lines the walls of the abdomen is termed
the parietal peritoneum; that which is reflected on to the viscera is the visceral
peritoneum. The disposition of the peritoneum may first be studied by noting
1146
DIGESTIVE SYSTEM
its arrangement as made evident in transverse sections of the abdomen at certain
levels.
The first section to be described shows the peritoneum in its simplest condition.
This is a transverse section through the body, at about the level of the upper sur-
face of the fourth lumbar vertebra, and therefore about the site of the umbilicus
(fig. 902).
Starting on the inner surface of the anterior abdominal wall, the peritoneum is seen to
cover the transversalis fascia, and indirectly the anterior abdominal muscles; then, passing
Fig. 902. — Diagram of Cross-section of the Abdomen, Showing the Peritoneal
Belations AT THE Level OF THE Umbilicus. A 0, Aorta. AS. COL., Ascending colon. DES.
COL., Descending colon. MES., Mesentery. M. COL., Descending mesocolon. »S/, Small
intestine. V.C., Vena cava inferior.
to the left, it lines the side of the abdomen, until it reaches the descending colon. This it covers,
as a rule, in front and on the sides, though occasionally it forms a mesocolon. Then it passes
over the bodies of the vertebrae with the large vessels upon them, and leaves the back of the abdo-
men to run forward and enclose the small intestine, returnuig again to the spine. The two
layers thus form the mesentery, having between them a middle layer [lamina mesenterii propria]
containing the terminal branches of the superior mesenteric vessels. It then passes over the
right half of the posterior abdominal wall, covering the ascending colon in front and at the
sides only (unless there be a mesocolon), and then passes on to the side and front of the abdomen
to the point from which it was first traced.
Fig. 903. — Diagram of Cross-section of the Abdomen, Showing the Peritoneal Rela-
tions AT THE Level of the Foramen op Winslow. (P. of W.)
Gastro-hepatic omeatum
In tracing the peritoneum in a section of the body opposite the stomach (fig.
903), on a level with the first lumbar vertebra, its course becomes more com-
plicated and difficult to follow.
In the section already given the peritoneum as a simple closed sac can be readily con-
ceived; but at the level now exposed the serous membrane has been so introverted that there
appear to be two sacs, one leading from the other, and known respectively as the greater and
the lesser sac of the peritoneum. They communicate through the epiploic foramen (of Winslow) .
The le.sser sac [bursa omentahs] is situated behind the stomach, so that on first opening the
abdomen no trace of it is to be seen. It extends downward [recessus inferior] between the layers
of the great omentum (though this part of the lesser sac is largely obliterated by adhesion
THE PERITONEUM
1147
in the adult). It extends upward [recessus superior] beiiind tlie caudate lobe of the liver.
The vestibule [vestibulum bur.sse omentalis] is the portion which lies just behind the lesser
omentum, and communicates with the greater sac through the epiploic foramen. In general,
the lesser sac is Umited anteriorly by the liver, stomach, and omenta; posteriorii/ by the posterior
abdominal wall, and below, behind the great omentum, by the transverse meso-colon. Its
disposition on vertical section is shown in fig. 904.
The epiploic foramen (foramen of Winslow) (figs. 903, 906) is situated just
below the liver; it looks toward the right, and will readily admit one or two fin-
gers. It is bounded superiorly by the caudate lobe of the liver; inferiorly,
by the duodenum (pars superior); posteriorly, by the vena cava; and anteriorly
by the right margin of the gastro-hepatic or lesser omentum, containing the struc-
tures passing to and from the hver. Starting at the epiploic foramen, the lesser
sac will be found to turn to the left.
Fig.
904. — DiAGEAM OP A Sagittal Section of the Trunk, Showing the Relations op the
Peritoneum. (Allen Thompson.)
Gastro-hepatic omentum
Stomach
Transverse colon
Mesentery
Smairintestine
Uterus
Epiploic foramen
Pancreas
Duodenum
■Transverse meso-colon
Aorta
If, now, the peritoneum be viewed in a transverse section of the body at the level named,
viz., through the first lumbar vertebra, it will be found that the section has probably passed
through the epiploic foramen (fig. 903). Starting at the front of the abdomen and- going to
theright, the peritoneum is seen to line the anterior abdominal wall, to pass over the side of
the abdomen, and to cover the front of the right kidney; it then extends on to the vena cava,
when it becomes a part of the lesser sac; then along the back of the lesser sac, over the aorta and
pancreas, which separate it from the vertebral column ; next it reaches the anterior of the two
internal surfaces of the spleen internal to the hilus. Here it meets with another layer of peri-
toneum, and helps to form the gastro-splenic ligament [lig. gastrolienale]. Leaving the spleen, it
changes its direction forward and to the right, and runs to the stomach, forming the posterior,
layer of the gastro-splenic hgament; it covers the posterior surface of the stomach, and leaves
its mesial border (lesser curvature) to form the posterior layer of the lesser omentum, and
then passes upward and to the right to the liver. In this transverse section it is only seen
passing on the right margin of the lesser omentum, where it forms the anterior boundary of the
epiploic foramen. Here it bends sharply around the omental margin enclosing the hepatic vessels
continuing to the left as the anterior layer of the lesser omentum; and then passing to the left
reaches the stomach, which it covers in front. It then forms the anterior layer of the gastro-
1148 DIGESTIVE SYSTEM
splenic ligament, and once more reaches the spleen. It passes right around the spleen to
the back of the hilus, where it is reflected on to the left kidney as the lieno-renal hgament
(fig. 903). Hence the peritoneum passes along the side and front of the abdomen to the point
from which it started. In this section the liver is so divided as to appear separated from all
connection with the other viscera and the abdominal wall, and to be surrounded by peritoneum.
The course of the peritoneum in a longitudinal section of the body will now
be considered (fig. 904). Starting at the umbilicus and passing downward, the
peritoneum is seen to line the anterior abdominal wall. Before reaching the pelvis
it covers also the urachus, the deep epigastric arteries, and obliterated hypogastric
arteries, which form ridges beneath it. For some little way above the os pubis
the peritoneum is loosely connected with the abdominal wall, a circumstance
which is made use of in supra-pubic cystotomy. Moreover, as the distended blad-
der rises from the pelvis it can detach the serous membrane to some extent from
the anterior abdominal wall. In extreme distension of the bladder the peritoneum
may be lifted up for some 5 cm. vertically above the symphysis. On reaching the
OS pubis it is reflected on to the upper part of the bladder, covering it as far back
as the base of the trigone; thence it is reflected on to the rectum, wihch it covers
in front and at the sides on its upper part, rarely forming a distinct mesorectum.
Between the bladder and rectum it forms in the male the recto-vesical pouch.
The mouth of this pouch is bounded on either side by a crescentic fold, the plica
semilunaris. In the female the peritoneum is reflected from the bladder on to the
uterus, which it covers; it then extends so far down in the pelvis as to pass over
the upper part of the vagina behind; thence it extends to the rectum. The peri-
toneum which invests the uterus is reflected laterally to form the broad ligaments.
The fold between the vagina and rectum forms the recto-vaginal pouch, or pouch
of Douglas. The membrane has now been traced back to the spine.
Following it upward, the sigmoid colon wifl be found to be completely covered
by peritoneum, a mesocolon attaching the gut to the abdominal wall (shown
in fig. 905). A little higher up in the median line the peritoneum passes forward,
to enclose the small intestine, and, returning to the spine, forms the mesentery
(fig. 904). It now passes over the third part of the duodenum to the pancreas,
from which point it again passes forward to form the lower layer of the transverse
mesocolon. It invests the transverse colon below and partly in front, and then
leaves it to pass downward to take part in the great omentum. Running down-
ward some distance, it returns and forms the anterior layer of the omentum. On
reaching the stomach it goes over the anterior surface, and at the upper border
forms the anterior layer of the lesser or gastro-hepatic omentum, which extends
between the stomach and the liver. It invests the inferior surface of the liver in
front of the transverse fissure, and, turning over its anterior border, covers the
upper surface. At the posterior limit of the upper surface it leaves the liver and
goes to the diaphragm, forming the superior layer of the coronary ligament. It
covers the anterior part of the dome of the diaphragm, and, once more reaching
the anterior abdominal wall, can be followed to the umbilicus, where it was first
described. This completes the boundary of the greater sac. On reference to the
diagram (fig. 904) the student might be led to suppose that the two sacs are quite
separate. This, of course, is not the case; but in a longitudinal section of the
body made anywhere to the left of the epiploic foramen (foramen of Winslow),
it is impossible to show the direct connection between the two sacs. (See fig. 905.)
The peritoneum has only been traced in this longitudinal section so far as it
concerns the greater sac. It now remains to follow upon the same section (fig.
904) such part of the membrane as forms the lesser sac. The peritoneum here
will be seen to cover the posterior surface of the stomach; thence from the lesser
curvature it runs upward to the liver, forming the posterior layer of the lesser or
gastro-hepatic omentum. It reaches the liver behind the transverse fissure. It
covers only a part of its posterior surface (caudate lobe), and is reflected on to the
diaphragm, forming the lower layer of the coronary ligament. It now goes down-
ward over the posterior part of the dome of the diaphragm to the spine, separated
from the latter by the great vessels. On reaching the anterior border of the pan-
creas it passes forward, and forms the upper layer of the transverse meso-colon.
It then covers the upper half of the transverse colon, and, descending, forms the
innermost layer of the great omentum. (The inner layers of the great omentum
are usually fused in the adult, however, thus obliterating this portion of the lesser
sac.) It now ascends, and, arriving at the greater curvature of the stomach,
THE PERITONEUM
1149
passes on to its posterior wall. At this point its description was commenced.
The general relations of the greater and the lesser sac are also evident in fig. 905
showing the hnes along which the parietal peritoneum is reflected from the pos-
terior abdominal wall as the visceral peritoneum, forming the various mesenteries
and covering the various abdominal organs.
Fig. 905. — Reflections of the Peritoneum on the Posterior Abdominal Wall.
(From Rauber-Kopsch, modified.)
T.. . „ Falciform lig.
Recessus superior omentalis
; Lig. triangulare sinistrum
Opening of hepatic
veins into V. cava
inferior
Lig. coronarium
Epiploic foramen
(of Winslowj
Hepato -duodenal
lig. and root struc-
tures of livei
Duodenum, parb
sup
Duodenum,
pars faoriz,
Radix mesenterii
Uncovered area
for ascending
colon
Plica gastro-
pancreatica
.,— Gastro-lienal
lig.
Bursa omen-
— talis, recessus
lienalis
Phreno-colic
lig.
Duodeno-
jejunal flexure
Uncovered area
for descending
colon
The precise manner in which certain organs — such as the hver, the caecum, the duodenum,
and the kidneys — are invested by peritoneum is described in the accounts of those viscera.
To such accounts the reader is referred for a description of the many 'ligaments' (such as
those of the bladder and liver) which are formed by the peritoneum.
The great omentum. — As is evident from its development, the great omentum
[omentum majus] is formed of four layers of peritoneum, though this is quite
impossible to demonstrate in an adult, the individual layers having become
adherent.
The great omentum acts as an apron, protecting the intestines and providing
1150
DIGESTIVE SYSTEM
them with a heat-economising covering of fat. It is nearly quadrilateral in shape,
and is variable in extent. In fig. 904 the great omentum is shown to be connected
with the greater curvature of the stomach, on the one hand, and the transverse
colon, on the other. Originally it extended backward above the transverse colon
and mesocolon to the posterior abdominal wall. The line along which it fuses with
the transverse colon and mesocolon during development is shown in fig. 904.
Mr. Lockwood has made some investigations on the lengths of the transverse meso-colon
and great omentum in thirty-three cases. In twenty, under the age of forty-five, only one sub-
ject had a great omentum long enough to be drawn beyond the pubic spine; in five, the omentum
reached as far as the pubes. In the cases beyond forty-five years it was the exception rather
than the rule to find an omentum which could not be puUed beyond the lower Umits of the
abdomen.
The lesser omentum [omentum minus] consists of a double layer of peritoneum
extending between the stomach and the liver. If the two anterior layers of the
great omentum are traced upward, they are seen to enclose the stomach, and then
Fig. 906. — Abdominal Visceka, Anterior View, after Removal of a Part of the Liver
AND Intestines. (Rauber-Kopsch.)
Right lung
lesser jOas|-:^epa
t"™ [ denallig.
Foramen epiploicum mm.! "t
Fundus of gall bladder SHSSu.
Right colic flexure
Duodenum
Right kidney
Radix mesenteni
Appendices epiploicee
Ileo-colic fold and fossa
Processus vermiformis
Phreno-
r^f~ ""'"^-
Duodeno-
/ jejunal flexure
Superior
II J mesenteric
\^ vessels
■ r~f1 Left kidney
\_M Abdominal
'M aorta
J^ Inf mesenteric
join together again at the lesser curvature to form the lesser omentum (fig. 904).
It is connected above with the portal (transverse) fissure and the fissure for the
ductus venosus; below, with the lesser curvature of the stomach; the left extrem-
ity encloses the oesophagus; the right border contains the hepatic vessels and is
free, forming the anterior boundary of the epiploic foramen (see fig. 906).
The lesser omentum is divided into two parts. The portion connecting the portal fissure
of the hver with the first part of the duodenum, and enclosing the root structures of the liver,
is called the hepalo-duodenal ligament [fig. hepatoduodenale]. The portion of the lesser omentum
connecting the lesser curvature of the stomach with the fissure of the ductus venosus is the
gastro-hepatic hgament [lig. hepatogastricum].
The gastro-splenic ligament [fig. gastrolienale] connects the left extremity of
the stomach with the spleen, continuing the layers of peritoneum which enclose
the stomach (fig. 903).
The gastro-phrenic and phreno-colic ligaments. — As the peritoneum passes
from the diaphragm to the stomach it forms a small fold just to the left of the
THE STOMACH 1151
oesophagus. This is the gastr o-phrenic ligament. A strong fold of the membrane
also extends from the diaphragm (opposite the tenth and eleventh ribs) to the
splenic flexure of the colon, and is knoM'n as the phreno-colic (costo-colic) hgament
[lig. phrenicolienale]. (See figs. 905, 906.)
Minute anatomy. — The peritoneum, like all serous membranes, consists of two layers; a
lining layer composed of simple squamous epithelium (mesothelium), and an underlying
layer of fibrous connective tissue. The latter is highly elastic, and denser in the parietal than
in the visceral layer. It often contains fat. In mesenteries and similar structures, the con-
nective tissue is usually very scanty, except surrounding the vessels and nerves. Ruptures
often occur in the omenta, which thus become fenestrated in structure. The visceral peritoneum
is usually closely attached to the organs for which it forms the outer serous tunic, but the pa-
rietal peritoneum is often loosely attached to the adjacent wall by a fatty subserous layer [tela
subserosa]. Smooth muscle occurs frequently in the various peritoneal folds.
The peritoneal cavity contains normally a very sUght amount of watery fluid, which
serves to lubricate the smooth peritoneal surface and thus to ehminate friction between
adjacent surfaces during the movements of the alimentary canal.
Vessels and nerves. — The peritoneum is in general somewhat sparsely supphed with blood-
vessels from various adjacent trunks. Lymph-vessels also occur, but they probably do not
connect directly with the peritoneal cavity by stomata (as is found in the frog and as claimed by
some to occur in man). They communicate with the lymphatics of neighbouring i-egions.
The nerves are also comparatively scarce. They are partly of sympathetic origin (vasomotor),
and partly sensory nerves from the intercostal (7th to 12th), and lumbar nerves. The sensory
nerves are more frequent in the parietal peritoneum and end in the connective tissue, either
freely or in special end-organs (varying from simple end-bulbs to Pacinian corpuscles).
Development. — The principal features in the development of the peritoneum have already
been mentioned in the section on Morphogenesis and in the remarks on the general morphology
of the intestinal canal (p. 19). Further details will be included later under the development of
the intestine, etc.
Variations. — Variations in the form and relations of the peritoneum are exceedingly
common, and are most commonly of developmental origin. Variations in the form and re-
lations of the various abdominal organs necessarily involve corresponding modifications in
the peritoneum. The diaphragm may be incomplete!}' formed, leaving the peritoneal cavity
in communication with the pleural, or more rarely the pericardial cavity. The primitive
dorsal mesentery of the intestine [mesenterium commune] may persist unmodified (in about
2 per cent, of adults), or the various secondary changes may be inhibited at any stage. Thus
the'stomach or the intestinal loop may fail, either wholly or partly, to undergo their character-
istic rotations. The adhesions of the various mesenteries may be incomplete, or they may be
more extensive than usual. For example, the sigmoid mesocolon may be more or less com-
pletely obliterated by adhesion, and numerous unusual peritoneal pockets or hgamentous bands
may be formed in this way in various localities. Variations thus due to extensions of the normal
developmental process are sometimes difficult to distinguish from pathological adhesions
caused by peritonitis.
Comparative. — As previously mentioned, the primitive body cavity in vertebrates extends
throughout the trunk region. In the oyclostomata, this primitive relation persists, the peri-
cardial cavity remaining in communication with the general body cavity. In all higher forms,
however, the pericardial cavity becomes entirely separated. In amphibia the lungs he in the
general (pleuroperitoneal) body cavity; in the reptiles and birds, they are partially separated;
but a complete separation of the pleural cavities occurs only with the formation of the definite
diaphragm in mammals.
The formation in the peritoneal cavity of a complete dorsal mesentery, and an incomplete
ventral mesentery (in the hepatic region) is typical for all classes of vertebrates. Slight
modifications in the form of the mesenteries depend chiefly upon the diiJerent degrees of com-
ple.xity in the development of the various parts of the intestinal tract. The marked changes
associated with extensive secondary adhesions of the primitive peritoneal structures are found
only among the higher mammaha, especially in man.
THE STOMACH
The stomach [ventriculus ; gaster] is a dilation of the alimentary canal suc-
ceeding the oesophagus. In the stomach the food is mixed with the gastric juice
and reduced to a viscid, pulpy liquid, the chyme [chymus], which undergoes a
certain amount of digestion and absorption before passing into the duodenum.
The stomach (figs. 906, 907) is a somewhat pear-shaped organ located in the
upper, left side of the abdominal cavity. It presents a body [corpus ventricuh],
with an enlarged upper end or fimdus, on the right side of which is the cardia,
the aperture communicating with the oesophagus. The body of the stomach is
extremely variable in form, as will be explained later, but is in general divisible
into a more expanded upper two-thirds, the cardiac portion [pars cardiaca],
which is nearly vertical, and a more constricted lower third, the pyloric portion
[pars pylorica], which tm-ns horizontally toward the right. The pyloric portion
often presents toward its lower end a slight, variable dilation, the antrum pylori,
1152
DIGESTIVE SYSTEM
succeeded by a short constricted pyloric canal (Jonnesco) . At the lower end of this
canal the pylorus forms the aperture leading into the duodenum, and contains a
thick sphincter derived from the circular fibres of the muscular layer. The stom-
ach has two borders and two surfaces. The medial (or upper) border forms the
lesser curvature [curvatura ventriculi minor], which is concave (except near the
pylorus) and gives attachment to the lesser omentum. The lateral (or lower)
border forms the greater curvature [curvatura ventriculi major], which is convex,
and gives attachment to the great omentum. The curvatures separate the
anterior surface [paries anterior], which faces forward and upward, from the
posterior surface [paries posterior], which is placed backward and downward.
Dimensions. — The dimensions of the stomach are subject to great variation
and therefore only a gross approximation can be given. The length of the lesser
curvature averages about 10 cm. (7.5 cm. to 15 cm.), and that of the greater
Fig. 907. — ^Longitudinal Section op Stomach, Showing the Interior of the Posterior
Half. (Rauber-Kopsoh.)
Fundus of stomach.
<Esophagus (pars abdominalis) — ^ ■* ^'^tc/
Pars cardiaca
L- Tunica mucosa
— Tela submucosa
Tunica serosa
PiiCEE mucosse
Sphincter pylori
Pyloric valve
Duodenum
(pars superior)
curvature is three or four times as great. The diameter varies exceedingly accord-
ing to the amount of contents. When nearly empty, it presents, especially in
the pyloric portion, a narrow tubular form, with a diameter of about 4 cm. or 5
cm. (fig. 1108, Section XIII). The diameter of the pylorus, which is the narrow-
est point in the alimentary canal when constricted is only about 1.5 cm. It is
distensible, however, as hard bodies with diameters of 2 cm. or more may readily
pass through.
The average capacity of the stomach is between one and two litres, being sub-
ject to extreme individual variations. In the newborn, it averages about 30 cc.
(25 to 35 cc), increasing very rapidly in the early postnatal months and reaching
an average of 270 cc. at one year (Lissenko). The average weight of the adult
stomach is about 135 gm.
Position and relations of the stomach. — The position and relations of the stom-
ach, like its form and structure, are subject to many variations in different indi-
THE STOMACH
1153
viduals, and in the same individual according to changes in physiological condition,
posture, etc. It is therefore difficult to give a concise and accurate description.
The normal position of the stomach has long been disputed. It is generally
recognised that the long axis is oblique, extending from above downward, forward
and to the right. Some, however, especially among the older anatomists, have
maintained that the gastric axis normally approaches more nearly to the horizon-
tal type, with the pylorus but little below the cardia (approximately the position
shown in figs. 915, 916). Others, especially among the more recent anatomists,
have maintained that the axis of the stomach is normally more nearly vertical in
position (see fig. 1125, Section XIII). The results of an extended and careful
study, both in formalin-hardened bodies and by means of the Roentgen-rays in the
living body, demonstrate that there is much variability in the position of the stom-
ach. Both the horizontal and the vertical types may occur as the extremes of
normal variation, but the more usual type is the intermediate oblique position.
The gastric axis, however, is not straight, but somewhat curved and bent in a
reverse L-shape. The larger cardiac portion is approximately vertical (especially
when the trunk is in the upright posture) the smaller pyloric portion more nearly
horizontal (figs. 895, 906, 918, 919). In the empty stomach, the pylorus opens
into the duodenum from left to right. In distention, however, the pylorus is
carried in front of the duodenum. In extreme distention, it is carried to the
right and downward so as to open upward and to the left.
Fig. 908. — Longitudinal Section op the Ptloeic Portion op the. Stomach. (Cunning-
ham, Trans. Royal Soc. Edinb., vol. 45.)
Sphinctenc cylinder
Duodeno-pyloric constriction \
Pyloric canal Sulcus intermedius
In surface relation (fig. 914), the stomach lies within the left hypochondriac
and the epigastric regions. Often, however, especially when distended, it extends
into the umbilical and even the right hypochondriac region. When empty, it
usually lies almost entirely in the left half of the body, with the pjdorus not more
than 1 cm. or 2 cm. to the right of the mid-sagittal plane. When distended, the
long axis of the stomach is lengthened and the pylorus is displaced 5 cm. or more
to the right and downward. In distention, the stomach expands in all directions
(except posteriorly) , and does not appear to rotate as is sometimes stated. The
position of the stomach, especially when distended, also varies appreciably accord-
ing to the posture of the body. It sags downward when the body is in the upright
position, and to the right or left when the body is placed on the corresponding
side. The cardia hes on the left side of the 10th or 11th thoracic vertebra, and
corresponds to a surface point behind the left 7th costal cartilage about 2.5 cm.
from its sternal end. The pylorus usually lies opposite the right side of the
1st lumbar vertebra, about midway between ensiform cartilage and umbilicus,
or in Addison's ' transpyloric line,' midwaj' between the suprasternal notch
and the symphysis pubis, when the body is recumbent; but descends to the 2d
or lower in upright posture. The Jwndus corresponds to the left dome of the
1154 DIGESTIVE SYSTEM
diaphragm (which separates it from the lung and heart) , opposite the sixth sterno-
costal junction. The fundus of course rises and falls with respiratory movements
of the diaphragm, the excursion being from 2 to 6 cm.
The relations of the stomach with surrounding organs are indicated diagram-
matically in figs. 915 and 916. The anterior surface is in contact on the right with
the left lobe of the liver, the pylorus reaching the quadrate lobe; on the left it
is in contact with the diaphragm (separating it from the heart and left lung) ;
and below with the anterior body wall by a triangular area of variable size.
The posterior surface is in relation (separated by the lesser sac) with the pancreas,
above which are areas of contact with the diaphragm, spleen, left kidney and
suprarenal body; below the pancreas, the stomach is in contact with the trans-
verse mesocolon, and through this with the transverse colon and coils of small
intestine. The relation with the duodeno-jejunal angle is indicated in fig. 895.
Further details concerning topography of the stomach are given in section XIII
on Clinical and Topographical Anatomy.
Peritoneal relations. — The stomach is covered by peritoneum in its whole
extent, except immediately along the curvatures and upon a small triangular
space at the back of the cardiac orifice, where the viscus lies in direct contact with
the diaphragm and possibly with the upper part of the left suprarenal gland.
It is enclosed between two layers. These two layers at its lesser curvature
come together to form the gastro-hepatic portion of the lesser omentum, and at
the greater curvature extend downward to form the great omentum (figs. 903,
904). At the left of the oesophagus the two layers pass to the diaphragm, form-
FiG. 909. — StTHFACE View of Gastric Mucosa. X 4. (Sobotta-McMurrich.)
Gastric areas and foveolge
ing the gastro-phrenic ligament; and at the fundus they pass on to the spleen,
forming the gastro-splenic ligament.
The posterior surface of the stomach is in relation with the lesser sac (bursa
omentalis), forming part of its anterior wall. The anterior surface of the stomach
is in relation with the greater sac of the peritoneal cavity.
Minute anatomy. — The stomach is composed of the four typical layers of the alimentary
canal — mucosa, submucosa, muscularis and serosa. The mucosa (figs. 907, 90S, and 909) is
thrown into a series of coarse folds (pUcse mucosoe), chiefly longitudinal, which disappear when
the stomach is distended. Along the lesser curvature, the ridges are more regular (corre-
sponding to Waldeyer's 'Magenstrasse') and form a longitudinal grooved channel from cardia
to pylorus. Upon closer examination (fig. 909) the inner surface of the mucosa presents a
somewhat warty ('mammilated') appearance, due to numerous small elevated areas [areae
gastricae], varying from 1 to 6 mm. in diameter. When examined with a lens, it is seen that
each area is beset with numerous small pits [foveolae gastricae], separated by partitions which
sometimes (especially in the pyloric region) bear villus-hke prolongations [plicae villosse].
The average number of foveolai is estimated at 87 per sq. mm., or more than 6 millions for
the entire stomach (Toldt). Into each pit or foveola open 3 to 5 gastric glands. The entire
surface is covered with a simple columnar mucigenous epithelium.
The relations of the mucosa in section are shown in fig. 910. The thickness of the mucosa
varies, being greatest (about 2 mm.) in the pyloric region, decreasing to less than .5 mm. in
the cardiac region (Kolliker). The lamina propria is crowded with glands, of which three
varieties are distinguished. The cardiac glands are tubulo-racemose (chiefly mucous) glands
occupying a narrow zone a few millimeters in width adjacent to the cardiac orifice. The
fundic glands [gl. gastricae propriae] occupy the greater part of the stomach, and are simple
(partly branched) tubular glands (fig. 910). They contain three varieties of cells— mucous
cells, peptic cells, and parietal cells. The parietal cells may secrete an organic chloride com-
pound, but the HCl of the gastric juice is formed not in the gland tubules but at the surface of
THE STOMACH
1155
the mucosa (Harvey and Bensley). The pyloric glands [gl. pyloricae] are branched tubular
glands occupying the pyloric region. Whether they are merely mucous or also secrete pepsin
is still in dispute.
The interstitial tissue of the lamina propria contains diffuse lymphoid tissue and a few
small lymph nodules, especially in the pyloric region. The muscularis mucosw is a thin sheet
of smooth muscle lying just below the fundus of the glands and is composed of an inner circular
and an outer longitudinal layer.
The tela submucosa (fig. 910) is a very loose areolar, vascular layer which permits the
wrinkling of the mucosa according to the degree of distention.
The tunica muscularis contains three layers of smooth muscle (figs. 911, 912, and 913).
The outer or longitudinal layer [stratum longitudinale] is thickest along the lesser curvature,
and is continuous with the longitudinal fibres of the oesophagus and the duodenum. On the
anterior and posterior walls of the antrum pylori, the longitudinal fibres form thickened bands.
Fig. 910. — Diagrammatic Section of the Stomach Wall Showing (A.) The Blood
vessels, (B) the Tunics, and (C) the Lymphatics. M, Mucosa. Mi, Muscularis mucoste. S,
Submucosa. I, Circular, and 0, longitudinal muscle layer. (Szymonowicz, after Mall.)
the ligamenla pylori. The middle or circular layer Istratum circulare] is continuous with the
circular fibres of oesophagus and duodenum and surrounds the entire stomach. It is especially
thickened in the region of the pyloric canal, at the lower end of which it forms a thickened
ring-like band, the pyloric sphincter [m. sphincter pylori]. The inner or oblique layer [fibrae
obliquse] is composed of fibres continuous with the deepest circular fibres of the oesophagus.
They form an incomplete layer which encircles the fundus and passes obliquels' downward
around the body of the stomach toward the greater curvature.
The external tunica serosa is formed by the peritoneum, and has the smooth shiny appear-
ance and the structure typical for a serous membrane.
Blood-vessels. — The stomach receives its blood-supply from many branches. From the
coeliac axis there is the left gastric artery, which runs along the lesser curve from left to right,
anastomosing with the right gastric branch of the hepatic. Along the greater curve run the
right and left gastro-epiploic arteries, anastomosing at the middle of the border, the left being
1156
DIGESTIVE SYSTEM
a branch of the splenic, the right a branch of the hepatic, through the gastro-duodenal artery.
The stomach also receives branches from the splenic (vasa brevia) at the fundus. The vascular
arches along the curvatures of the stomach are comparable to those in the intestinal mesentery
(MaU).
The blood of the stomach is returned into the portal vein. The coronary vein and pyloric
vein open separately into the portal vein ; the right gastro-epiploic vein opens into the superior
mesenteric, the left into the splenic.
The arrangement and distribution of the blood-vessels within the stomach wall are illus-
FiG. 911. — A Dissection of the MtrscuLATURE of the Stomach. (Lewis and Stohr,
after Spalteholz.) a and e, Longitudinal layer, b and d, Circular layer, c. Oblique layer.
Py, Pylorus. S.I., Sulcus intermedins.
&I.
trated in fig. 910. The rich capillary ple.xus in the mucosa supplies the glands and also serves
for absorption.
Lymphatics. — There is a set of nodes lying along the lesser and the pyloric portion of the
greater curvature, and others at the pyloric and cardiac ends. These are entered by lymphatic
vessels which, beginning in the mucous membrane (fig. 910), accompany all the gastric veins,
but chiefly those of the lesser curvature. Vessels also accompany the left gastro-epiploic veins
to terminate in the splenic nodes. On its wa}' to the receptaculum chyli, the gastric lymph
passes through groups of nodes [lymphoglandulae pancreaticoUenales] situated above and
behind the head and neck of the pancreas.
Figs. 912 and 913. — Dissections Showing the MtrsctrLAB Layers of the Stomach. X 1.
(From Toldt's Atlas.)
Circular layer
Longitudinal layer
Tela submucose
The arrangement of the lymphatic plexus within the stomach wall, beginning with blind
rootlets in the mucosa, is shown in fig. 910.
Nerves. — The nerves of the stomach are derived in part from the vagi (which form the motor
fibres of the stomach), the right vagus descending on the posterior wall, and the left on the
anterior wall. The stomach also receives sympathetic branches from the coeliac plexus, follow-
ing the arteries. Small ganglia occur along both vagus and sympathetic branches (Remak).
The nerves join the gangliated plexuses, myenteric and submucous, in the wall of the stomach,
J
THE STOMACH
1157
from which branches are distributed to the muscularis and the mucosa as for the intestine in
general.
Development. — The stomach at first lies in the mid-sagittal plane in the cervical region.
It participates in the general descent of the viscera (the cesophagus becoming correspondingly
lengthened) and reaches its permanent vertebral level in the 17 mm. embryo (Jackson). In
the meantime, beginning in the 7.5 mm. embryo (F. T. Lewis), a rotation of the stomach has
occurred. The rotation is around the long axis, so that the anterior border (lesser curvature)
is turned to the right, and the posterior border (greater curvature) to the left. The right
surface therefore becomes posterior and the left anterior. During the process of descent, the
pyloric end is the first to become fixed (at about 12 mm.). As the cardiac end continues to
descend, it is displaced to the left, so the oblique position of the stomach is estabUshed early.
The stomach is at first spindle-shaped, but the upper end begins to enlarge at about 10 mm.
The fundus develops somewhat later as a locahzed outgrowth (Keith and Jones).
The foetal stomach is somewhat crowded to the left by the relatively large liver (fig. 953).
Fig. 914. — Outline Showing the Average Position op the Abdominal. iVisceea in
40 Bodies, on a Centimetre Scale (Reduced to .36 Natural Size). ML, anterior mid-hne
EF, horizontal line half-way between pubes and suprasternal margin ("transpyloric" line),
CD, line half way between pubes and line EF. (Addison.)
13|1
Sim.
10
TT
8
t;
^
5
4
3^
2
1
1
2 1 3 1 4 1 5
6
7
8
9
10 1
1 12
13
■=3,
2
--
>i
^~-
/
f\
Notch |>
*
H
^
_8.
_7.
.6.
.5.
.4.
i^
"~.
/
7^
"
-s-
—
^
i
^=M::_
^^^1
I-
T
Ai ■ '
~^
~>
^
'
"^^Ms
V .
/
1
-^
.aC^
s
\
/
\
f
i --
-_
-"
J^
/. ,
^
A
r
-
/rip of 9th c c ^
1
.2.
J-
Eg
-xi
-2-
.3-
.4^
_5.
.6
_7
-8
_9
.IQ
)''
Cl
_1.
k'
4
-^-~.
■ —- '
-—
^' X
/
^
CI"
r^
"■",
T'e..°5
9tti C. C
r
^
y
\
w\
—
"
^
.>
^
-
'h.
n
,_
.F
V
di3c between!
ptebraQiVT^
fe
IP
~
"7~f
55
?\
1^
T
~
■
%i
Jr
k
i*
i
k
/
F'
^
'm
%
«j
'%
*f
/
[>an<.,.,=..
■^
c
/
(Ty'
V^
--/
r
/
y
ts-
f ii-'
\
y
'
''
Meso-Colon
/
/
-—
~^
-^
\u
p
i:
-X
J
^
ir
/
>^
MesoC
)lor
/
^
/
\
^ oe
'
iL
^
^
: I
<
'■
Irest of Iliun
»»-
— »
—
.1
^ ^
n
*
J
^
"-•
1 .i
"^
-~^
-^1
\
ly
-
^
t^
\
' *■
/
p^
N
S
<
^
}
1 M
,so-S
V
/
4.
n/
\
//
^\
—
begin.
\
y
.^^
— /
^
t)
K
//
\
V
/
'^
\
ill
-^
H-
^
\
'(
/
'
.5
-6
-7
_8
_9
10
11
12
13
y
s
r
'sa^
V
/
/
p'^
s.
S
'
Promontory
\
*
/
/
\
•^
1
n of-
/luscle
^
\
/
/
^ 1 Anterior
_ Superior-
llac Spine
\
'aoas"
\
\
^
^
/
\
*
^
\
/
\
\
/
^
/
■s
/
Poupart
\
Pubes
/
...
1..
en
1
1
and its relations to surrounding organs undergo considerable change. Even in the foetus it is
quite variable, but its general form and position do not differ essentially from the adult condition.
Glands. — According to Johnson, in an embryo of 16 mm., the lining epitheUum shows the
primitive foveols as pit-hke depressions which become elongated, forming irregular anasto-
mosing grooves, separated by vilJus-like projections. The pits multiply and deepen, and from
their bottoms the gastric glands bud off (at 120 mm.). The parietal cells appear very early
in the gland fundus, but the differentiation of gland cells is still incomplete at birth.
1158
DIGESTIVE SYSTEM
Figs. 915 and 916. — Diagrams of the Contact Areas of the Stomach, Anterior and
Posterior Views.
cardia
Mid- line
of body
Fig. 917. — ^The Abdominal Viscera, From Behind. (Riidinger,)
Larynx
Lung
Diaphragm
Pancreas
Spleen
Stomach
Descending colon
Inferior mesenteric vein
Superior mesenteric
vein
Ascending colon
THE STOMACH
1159
^The circular layer of muscle is indicated at 16 mm.; the longitudinal much later, about
90 mm., and not completed before 240 mm. (F. T. Lewis).
Variations. — The great variability of the stomach in form, position and relations has
already been repeatedly emphasized. These variations have been most carefully studied
recently by various observers in the living body by means of the Roentgen-rays. Some of the
results of study by this method are sho\vn in figs. 918, 919.
Peristalsis. — It would appear that most of the variations in the form of the stomach that
have been described are merely various phases in the series of changes undergone by the
stomach during the normal process of physiological digestion. The following account of these
changes is based largely upon the radiographic observations of Cole. Earlier observations by
various investigators upon the Uving stomach of man and lower animals (and especially the
radiographic study of the cat by Cannon) have shown that the cardiac portion of the stomach
is the first to become distended with food (and gas). Until a considerable degree of distention
is reached, the pyloric portion usually remains a somewhat narrow contracted canal, along
which distinct peristaltic contractions pass pylorusward.
Under favorable conditions, however, the peristaltic contractions may be observed to begin
in the cardiac portion, although they are usually most distinct in the pyloric portion. Each
individual contraction travels at the rate of about 2,5 cm. (1 inch) per second, so that it requires
several seconds for a contraction to travel from fundus to pylorus. The number of simultaneous
Fig. 918. — Different Forms of the Stomach as Shown by The Rcentgen Rats. Fundus
not represented. (Cole.)
C — "Drain-trap
D — "Fish-hook"
contractions present in the stomach varies from 1 to 6 or 7, 3 or 4 being the most common.
In fig. 919, a series of 10 successive radiographs show the progression in a stomach with four
simultaneous individual peristaltic contractions. The peristaltic movements are further com-
phcated by the appearance (simultaneously in all) of successive periods of 'systole,' during
which the peristaltic contractions become stronger and deeper, and ' diastole,' in which the
contractions relax and become less distinct (Cole). In fig. 919, phases 1 to 6 represent the
'systole,' and 7 to 10 the 'diastole.' A 'systole' and a 'diastole' together make up a
' gastric cycle.' During the entire progress of an individual peristaltic contraction from fundus
to pylorus, the number of 'cycles' appears to correspond to the number of peristaltic con-
tractions present. Thus the figure represents a stomach of the 4-cyole type. The time required
for a ' cycle ' varies widely, the average (in the 3- or 4-cycle type) being about 2 or 3 seconds.
In the earlier stages of gastric digestion the pylorus usually remains closed, but after a
variable time it relaxes slightly (lumen about 3 mm. in diameter) at intervals, allowing the
chyme to be spurted into the duodenum.
Thus the various constrictions often found in the formalin-hardened stomachs, and the
pyloric antrum, appear to be merely transient phases of the digestive process. The 'hour-
glass' stomach is in many cases to be explained in this way; in others, however, the constriction
is pathological and permanent. Various forms of abnormal lobulations and dilations also
rarely occur.
1160
DIGESTIVE SYSTEM
Gastroptosis is a very common abnormality in which the body of the stomach extends
vertically downward to the umbilicus, or lower, forming a sharp bend beyond which the pyloric
portion turns upward to reach its termination. This form is especially common in women,
due to tight lacing.
Fig. 919. — Serial Radiographs Taken at Short Intervals, Showing Diastole
(Phases 7-10) and Systole (Phases 1-6), and the Progression toward the Pylorus op a
Four-cyclBjType of Gastric Peristalsis. Fundus of the stomach not shown. (Cole.)
Comparative. — The primitive stomach is perhaps merely a receptacle for food, true'digestive
glands being absent in many of the fishes. The vertebrate stomach is a dilated sac of variable
form, but is typically somewhat looped, with cardiac and pyloric segments. In birds, there is
a peculiar arrangement, correlated with the absence of teeth. The stomach is divided into an
THE DUODENUM
1161
anterior glandular proventriculus, and a posterior muscular gizzard with a homy lining
serving to grind the food. The mammalian stomach is the most variable in form and
structure which are correlated with the method and character of alimentation. The cardiac
end of the stomach is often hned to a variable extent with a prolongation of the oesophageal
stratified squamous epithelium. The three kinds of glands, cardiac, fundic and pyloric, are
typically present. In general, the stomach is larger and more complicated in herbivora than
in carnivora. Instead of being a single sac, the stomach may be more or less divided into
chambers. An incomplete division into cardiac and pyloric portions is so common that it may
be considered typical. The most extreme specialization is found in the ruminants. In
these the stomach has four chambers, the first two of which, however, are expansions of the
oesophagus.
THE SMALL INTESTINE
The small intestine [intestinum tenue] extends from the pylorus to the ileo-
csecal orifice, and occupies most of the abdominal cavity below the liver and
stomach. It is a cylindrical tube whose diameter decreases from about 4 cm.
above to about 2.5 cm. at the lower end. Its length, when removed from the
body and measured fresh, averages about 7 metres (23 ft.) ; but when formalin-
hardened in situ, the length (which is probably nearer that during life) is only
about 4 metres. The length does not seem to vary according to sex, height or
weight in the adult, but it is said to be relatively longer in the child.
The small intestine includes two main divisions, the duodenum and the
mesenteric small intestine, the latter being further subdivided into jejunum and
ileum.
THE DUODENUM
The duodenum is the first part of the small intestine, and is very definite in
position and extent. It is firmly attached to the posterior abdominal wall, being
almost entirely retroperitoneal. It is the widest part of the small intestine, the
Fig. 920. — The Duodenum and Pancreas, Anterior View.
Superior layer of transverse meso-colon
Inferior layer of transverse meso-colon
Inferior part of duodenum
Superior mesenteric i
average width being 4 cm. or more, and is also the shortest segment, being only
about 25 cm. in length. In general, it is somewhat C-shaped, the concavity
enclosing the head of the pancreas (figs. 920, 921, 922).
Parts. — For convenience of description, the duodenum is divided into the
following parts: (1) the first or superior portion [pars superior] which is short
(5 cm. or less), leading from the pylorus and forming the superior flexure [flexura
duodenalis superior]; (2) the descending portion [pars descendens], about 7 or 8
cm. in length, which receives the bile and pancreatic ducts and joins the inferior
portion at the inferior flexure [flexm-a duodenalis inferior]; and (3) the inferior
portion [pars inferior], which is again subdivided into (a) transverse portion [pars
horizontaHs], about 10 cm. long, which usually ascends slightly and passes
gradually into (b) the ascending portion [pars ascendens], 2 or 3 cm. long, ter-
minating in the duodeno-jejunal flexure [flexura duodenojejunalis].
1162
DIGESTIVE SYSTEM
Position and relations. — As shown in fig. 914, the duodenum usually lies
chiefly in the lower part of the epigastric region, only the inferior (transverse)
portion extending into the umbilical region. All but the terminal (ascending)
portion of the duodenum lies to the right of the mid-line.
The superior portion usually lies at the level of the first lumbar vertebra (or
the disk below). It is covered anteriorly, and to a variable extent posteriorly,
by a prolongation of the peritoneum from the corresponding surfaces of the
stomach. It is somewhat freely movable. When the stomach is empty, it
extends from the pylorus almost horizontally to the right and backward. As
the stomach becomes distended, however, the pylorus is carried to the right and
downward for a variable distance, and the position of the superior part of the
duodenum is correspondingly altered.
Superiorly it is in contact with the hver (quadrate lobe) and the neck of the gall-bladder
and forms the lower boundary of the epiploic foramen; anteriorly, with the liver and (often)
the transverse colon; inferiorly and posteriorly, with the head of the pancreas below, and with
the common bile duct, hepatic vessels and portal vein above.
The second or descending portion of the duodenum extends along the right
side of the first to the third lumbar vertebra. It is covered antero-laterally by
peritoneum, excepting (usually) the area of contact with the transverse colon
(figs. 906, 920).
Posteriorly (fig. 956) it is in contact with the right kidney, ureter and renal vessels, and below
with the psoas muscle. Anteriorly (fig. 906) it is crossed by the transverse colon (the layers of
the transverse mesocolon usually separated by an area of direct contact); above the colon, it
may be in contact with the gall-bladder, and below the colon with coils of small intestine. The
Fig. 921. — The Duodenum and Pancbeas, Posterior View.
Portal vein
Terminal part of duodenum
Head of pancreas
left or medial aspect of the descending duodenum (figs. 920, 921, 922) is in contact with the
head of the pancreas, and some fibres from the muscular tunic are said to become intermingled
with the pancreatic lobules. Somewhat posteriorly the common bile duct descends between
pancreas and duodenum, and enters the descending duodenum, in common with the pancreatic
duct, about 10 cm. below the pylorus. The loop formed by the pancreatico-duodenal arteries
also runs along the descending duodenum.
The third or transverse portion of the duodenum usually crosses the body of
the third lumbar vertebra, ascending slightly from the right to the left side
(figs. 920, 921). It is covered anteriorly with peritoneum, excepting a small
space where the superior mesenteric vessels enter the root of the mesentery.
Anteriorly it is further in contact with coils of smaU intestine; superiorly, with the head of
the pancreas, and the inferior pancreatico-duodenal vessels; posteriorly, with the vena cava.
The terminal or ascending portion is covered anteriorly and laterally by
peritoneum, and is in contact with coils of the ileum. To the right it is in rela-
tion with the head of the pancreas (processus uncinatus) and the superior mesen-
teric vessels; and posteriorly with the psoas muscle, aorta and left renal vessels.
The duodeno-jejunal flexure usually lies opposite the second lumbar vertebra, and
is in contact above with the inferior surface of the body of the pancreas, and the
root of the transverse mesocolon.
THE DUODENUM
1163
Fig. 922. — ^Dissection op the Duodenum and Pancreas, Anterior View.
(Rauber-Kopsch.)
1164
DIGESTIVE SYSTEM
The end of the duodenum is firmly fixed in its place by the suspensorius duodeni. This
name has been given to a fibro-muscular band that contains, according to Treitz, non-striated
muscular fibres, and descends to the terminal part of the duodenum from the lumbar part
of the diaphragm, passing to the left of the cceliac artery and behind the pancreas. Lockwood
points out that this band is continued on, after being inserted into the duodenum, between
the layers of the mesentery. He suggests the name of the 'suspensory muscle of the duodenum
and mesentery,' and says, 'together with the other constituents of the root of the mesentery,
it forms a band of considerable strength, sufficient not only to support the weight of the intestines
and mesentery, but also to resist the pressure of the descent of the diaphragm.'
In connection with this fourth portion of the duodenum, mention may be made of certain
peritoneal folds and fosste which are of some surgical interest by reason of their being associated
with retro-peritoneal hernia. Four such fossEE may be mentioned, namely, the superior and in-
ferior duodenal fossa:, paraduodenal and the retroduodenal,; f osste. On drawing the terminal
portions of the duodenum to the right, two triangular folds of peritoneum, the superior and in-
ferior duodenal folds, which extend from the wall of the duodenum to the posterior abdominal wall
may be observed. Each fold has a free edge. Beneath each fold is found a pouch of peri-
toneum, constituting the superior and inferior duodenal fossae. The former, the smaller,
opens downward and is present in about 50 per cent., while the latter opens upward and is
present in about 75 per cent., of the subjects examined (Jonnesco). The paraduodenal fossa
(fossa of Landzert) is not often found in the adult; when present, it is situated to the left of the
last part of the duodenum, and is formed by a fold of peritoneum enclosing the inferior mesen-
teric vein. The retroduodenal fossa is a rare form extending from below upward behind the
transverse portion of the duodenum.
Interior of the duodenum. — -The interior of the first part of the duodenum
is smooth. The pylorus is often somewhat invaginated, much in the same way
that the uterus projects into the vagina (fig. 908). On account of this arrange-
FiG. 923. — Duodenal Foss^ and Folds. Paraduodenal fossa is not shown.
(After Cunningham.)
Transverse meso-colon
Transverse colon
Superior duodenal fossa
Inferior duodenal fossa
The mesentery
Inferior mesenteric vein
Inferior mesenteric artery
ment fwhich renders the complete emptying of the cavity somewhat difficult)
and also on account of the distensibility of this portion, it usually shows up very
distinctly in radiographic pictures as a ' cap ' to the pyloric end of the stomach
during digestion. In the lower portions of the duodenum, transverse ridges or
folds of the mucosa appear (fig. 922) which are also apparent in radiographs
occasionally. On the medial wall of the descending portion, posteriorly, about
half-way down, is a more or less distinct longitudinal fold [plica longitudinahs
duodeni], toward the lower end of which is a small elevation, the bile papillaj'or
papilla major [papilla duodeni], upon which open the common bile duct and the
pancreatic duct, either separately or by a common aperture (fig. 922). Above
the papilla there is usually a prominent hood-like fold (valvula connivens), and
below it a variable fold or frcenum which forms a continuation of the plica longi-
tudinahs. About 2 cm. (.9 to 3.5 cm., Baldwin) above and in front of the bile
papilla there is a second, smaller, rounded papilla minor, upon which the ac-
cessory pancreatic duct (of Santorini) ends.
The minute structure, vascular relations, development, variations, etc., of the duodenum
will be considered later, with those of the small intestine as a whole.
THE JEJUNUM AND ILEUM
1165
THE JEJUNUM AND ILEUM
The mesenteric portion of the small intestine is divided into an upper half
(or two-fifths) , the jejunum, and a lower half (or three-fifths) , the ileum. Although
the character of the gut changes considerably from the upper end of the jejunum
to the lower end of the ileum, the transition is gradual, and there is no definite
line of demarcation. In general, the jejunum is somewhat wider, has thicker walls,
is more vascular and has a more complicated mucosa. The lymphoid organs
(Peyer's patches) are, however, characteristic of the ileum.
The jejunum begins at the duodeno-jejunal flexure. The first coil is variable
in direction, being found (in order of frequency) as follows: (1) downward, for-
ward and to the left; (2) directly forward and downward; (.3) to the left, then
downward; (4) forward and to the right (Harman). Some further details as to
the position of the various succeeding coils are given later under the development
of the intestine (figs. 930, 931). While there is considerable individual variation,
it is true in general that the coils of jejunum occupy the upper and left portion of
the body cavity, while those of the ileuyn occupy the lower and right side, the lower
portion lying in the pelvic cavity. The ileum finally passes upward over the pel-
vic brim to the right iliac fossa where it terminates in the ileo-csecal orifice.
Fig. 924. — Pohtion of the Small. Intestine, Laid open to Show the Plic.e Circtj-
LARBS. (Brinton.)
The mesentery [mesenterium] is a fan-shaped fold extending from the duodeno-
jejunal flexure to the ileo-csecal junction. It is composed of a double layer of
peritoneum which encloses and supports the jejunum and ileum and their vessels,
connecting them with the abdominal wall. The root of the mesentery [radix
mesenterii] or parietal attachment, is only about 15 cm. long, corresponding to
a line extending from the duodeno-jejunal flexure obliquely downward and to the
right, across the transverse duodenum, the great vessels and the vertebral column
to the ileo-csecal junction (fig. 905).
The visceral attachment of the mesentery to the intestine, corresponding to the length of
the jejuno-ileum, is nearly 7 metres long, and is thinner than at the root. The loidth of the
mesentery, measured from parietal to visceral attachment, varies somewhat in different parts
of the canal, the average being 18 or 20 cm. (ranging from 15 to 22.5 cm.). It is narrow above
(also at the lower end), but reaches its full width about 30 cm. below its upper end. Between
the two peritoneal layers of the mesentery is a third layer [lamina mesenterii propria] con-
taining the superior mesenteric vessels (arteries, veins and lymphatics) with their branches and
accompanying nerves, the small mesenteric lymph-nodes (50 to 100 in number), and a variable
amount of fibro-adipose connective tissue.
Minute anatomy. — The small intestine has the four typical layers, — mucosa, submucosa,
muscularis and serosa (figs. 927, 928). They are, in general, somewhat similar in structure
to those of the stomach (fig. 910), excepting the mucosa.
The mucosa is lined with a simple cyhndrical epithehum, underneath which is a fibrous
lamina propria, limited externally by a muscularis mucosoe, as in the stomach. The muscularis
mucosae sends slender muscular bundles upward into the villi. The inner surface of the mucosa
(fig. 924) presents numerous coarse, closely set, transverse folds [plicaj circulares]. These are
permanent, crescentic folds, involving both mucosa and submucosa, and usually extending one-
half to two-thirds of the way around the lumen. They often branch and anastomose, sometimes
forming circles or spirals. The largest exceed 5 cm. in length and 3 mm. in width. The plicae
1166
DIGESTIVE SYSTEM
circulares are absent from the first part of the duodenum, but become well-marked in the descend-
ing portion (fig. 922). They are largest and best developed in the lower duodenum and upper
half of the jejunum, below which they graduaUy become smaller (fig. 924) and disappear at the
lower end of the ileum.
The digestive and absorptive surface of the small intestine is further greatly increased by
multitudes of small processes, the villi (figs. 925, 927), which give the mucosa a velvety appear-
ance. They are largest (.5 to .7 mm. in height) and most numerous in the duodenum and
jejunum, where they are typically leaf-shaped, and gradually become smaller, scattered and
conical in the ileum. The villi are much reduced in distention of the intestine, and may even
be temporarily obliterated. Between the bases of the vilh there open short, simple tubular
glands — the crypts of Lieberkuehn [gl. intestinales], whose fundus cells (of Paneth) probably
secrete digestive enzymes. In the duodenum there are found, in addition, the larger tubulo-
FiG. 925. — A, Surface View op the Hardened Mucosa op the Small Intestine. (After
Kolliker.) B, Side View of a Wax Reconstruction op the Epithelium in the Human
Duodenum. (Huber.) i g , Intestmal gland v , Villus
racemose glands of Brunner [gl. duodenales], which occupy the submucosa, and are especially
numerous in the upper portion of the duodenum. They are purely mucous in character ac-
cording to Bensley, although Oppel describes granular cells, similar to Paneth cells, which may
secrete digestive enzymes.
Scattered over the whole of the mucous membrane of the small intestine are numerous
small lymph-nodules, the larger of which extend into the submucosa; these are the so-caUed
solitary glands [noduli lymphatici solitarii]. Aggregations of lymph-nodules, known as Peyer's
patches [noduli lymphatici aggregati], situated in the mucosa and submucosa, are found in
the ileum especially toward the lower end (fig. 926). They are oval, from 1.2 to 7.5 cm. in
length and about 1 to 2.5 cm. in breadth, and are placed in the long axis of the bowel along a
line most remote from the mesentery. They are variable in number, the average being about
20 to 30.
Fig. 926.-
-SuRF.\CE View op the Mucosa op the Ileum, Showing Aggregated Lymph
Nodes (Peyer's Patch). (From Toldt's Atlas.)
Aggregated lymph nodes Solitary lymph nodes
(Peyer's patch)
The submucosa is in general a loose areolar layer containing vascular and sympathetic
plexuses (figs. 927, 928). The muscularis is composed of smooth muscle arranged in the two
typical layers, — a thinner, outer longitudinal and a thicker, inner circular, — both of which
become thinner toward the lower end of the ileum. The serosa is typical in structure, the
squamous epithelial covering being absent in the retroperitoneal areas of the duodenum.
Blood-supply of the small intestine. — The small intestine receives its blood from the superior
mesenteric artery and a branch coming indirectly from the hepatic, the superior pancreatico-
duodenal. The superior mesenteric artery runs between the layers of the mesentery and gives
off six or seven relatively large branches and a variable number of smaller branches. The
first two or three of the larger branches divide into an ascending and a descending branch,
which join above and below with the corresponding branches of the continguous arteries, form-
ing thus a single row of arches. From about the beginning of the second quarter of the small
THE JEJUNUM AND ILEUM
1167
Fig. 927. — Cross-section op Ileum (contracted), a, b, c, Villi, d,- Intestinal gland, e,
Tunica propria. /, /., Muscularis mucosa, g, Blood-vessel, h, Submucosa. i, Circular
muscle, k, Longitudinal muscle. I, Serosa, m, Subserosa. n, Aggregated lymph nodules
(Peyer's patch). (Radasch.)
'^^\
^ ^
x^.^;
)
/I I
41 J
'%— &
/
V
XJ^ t
Fig. 928. — Diagrams op the Vascular Supply and Nerves op the Small Intestine.
A, Blood vessels; arteries as coarse black lines, capillaries as fine Hnes, veins shaded (after.Mall).
B, Lymphatics (after Mall). C, Nerves, based on Golgi preparations (after Cajal). m, Mucosa.
mm., Muscularis mucosae, s.m., Submucosa. cm., Circular muscle, i.e.. Intermuscular
connective tissue. Z.m., Longitudinal muscle, s. Serosa, c.i., Central lymphatic. n.,"Nodule.
s.pl. Submucous plexus, m.pl.. Myenteric plexus. (Lewis and Stohr.)
m.m.
s.m.
^^^ '■''
m.pl,^=Af_ >.
1168 DIGESTIVE SYSTEM
intestine a second tier of arches, formed in a similar manner, is often noted, and below the middle
of the jejuno-ileum more than two tiers of arches may be present the complexity of the arches
increasing, while the size of the vessels diminishes. From the convex border of the most dis-
tally placed arches there pass to the intestine straight branches, so-called vasa recta. Near the
beginning of the jejunum these are numerous and large, and have a length of about 4 cm.,
and are quite regular. After the first third of the intestine is passed the vasa recta become
smaller and shorter, and toward the lower end of the ileum they become short and irregular
and are often less than 1 cm. in length. (Dwight.) The blood is returned by means of the
superior mesenteric vein, which, with the splenic vein, forms the portal. The vascular ar-
rangement in the intestinal wall is shown in fig. 928.
The lymphatic vessels form a continuous series, which is divided into two sets — viz., that
of the mucous membrane and that of the muscular coat. The lymph-vessels of both sets form
a copious plexus (fig. 928). The efferent lymphatic vessels form the so-called laoteals, which
pass through the mesenteric lymph-nodes, finally reaching the cisterna (receptaculum) chyli.
The nerves. — The small intestine is supplied by means of the superior mesenteric plexus
which is continuous with the lower part of the cceUac (solar) plexus. The branches follow the
blood-vessels, and finally form two plexuses: one (Auerbach's or myenteric) which lies between
the muscular coats; and another (Meissner's) in the submucous coat. The nerve fibres are
chiefly from the sympathetic, partly from the vagus.
Development of the small intestine. — As the intestine is being separated from the yolk-
vesicle it forms at first a relatively straight tube, and as the tube elongates there is formed a
single primary loop, situated in the sagittal plane of the embryo, which loop extends into the
coelom of the umbilical cord; to its summit is attached the constricted attachment of the yolk-
vesicle, the yolk-stalk (fig. 929). This primary loop of the intestine, as it elongates, turns on
an axis, so that its caudal portion turns toward the left and its cephalic portion toward the
right. We may then speak of a right and a left half of the loop. Near the top of the left half
of the loop, there is noted an enlargement which marks the caecum, the greater part of the left
Fig. 929. — Model of Stomach and Intestine of Human Embhyo 19 mm. Long. The
figures on the intestine indicate the primary coils (X 16). (Mall.)
half of the loop forming, therefore, the large intestine, while the right half of the loop forms the
small intestine. In the further growth of the loop the right half elongates more rapidly than
the left half, so that the caecum is no longer found in the middle of the loop. In an embryo
of the fifth week, as noted by Mall, whose account is here followed closely, 'the right half of
the loop has a number of small bends in it, which are of great importance in the further develop-
ment of the intestine.' These small bends or loops he has marked with the numbers 1, 2, 3, 4,
5, 6. (See figs. 929, 930, 931.) The first of these bends is primarily not clear, appearing as a
portion of the pyloric end of the stomach; however, it is recognised by the fact that the ducts
of the liver and pancreas terminate in it, marking it as the duodenum. The omphalo-mesenteric
veins and arteries, the future superior mesenteric vessels, pass through the middle of the
mesentery of the large primary loop and pass over the sixth bend or secondary loop, to which
is also attached the yolk-stalk. With the elongation of the intestine these six bends or loops
become accentuated and acquire secondary loops or coils, nearly all of which are still found in
the ccelorn of the umbihcal cord, but even with this more complicated coiling of the intestine
the six primary divisions may be clearly made out. (See fig. 929.)
The large mtestine, the left half of the large primary loop, lies in the sagittal plane of the
embryo and does not grow as rapidly as the small intestine, and while this is acquiring the
secondary coils, the whole mass rotates about the large intestine as an axis. 'By this process the
small intestine is gradually turned from the right to the left side of the body, and in so doing is
rolled under the superior mesenteric artery. This takes place while the large intestine has an
antero-posterior direction and before there is a transverse colon.' (Mall.) With the return
of the small intestine from the umbilical coelom to the peritoneal cavity, which occurs apparently
quite suddenly and during the middle of the fourth month, the caecum comes to lie in the right
half of the abdominal cavity, just below the liver; the greater portion of the remainder of the
large intestine then lies transversely across the abdominal cavity as the transverse colon. The
six groups of loops of the small intestine may still be recognised, the loops of the upper part
THE SMALL INTESTINE
1169
of the small intestine having roOed to the left of the superior mesenteric artery, while the loops
which were formerly in the cord are found in the right side of the abdominal cavity. It is
not difficult to trace these six groups of loops through the later stages of foetal life to the new-
born, and thence to the adult stage. In the adult, as also through the various stages of develop-
ment, loop 1 forms the duodenum. From the primary groups of coils marked 2 and 3 are
developed the greater part of the jejunum, arranged in two distinct groups of loops, situated
in the left hypochondriac region. The part of the intestine developed from group 4 of the
primary coils passes across the umbilical region to the right upper part of the abdomen. That
part developed from group 5 of the primary coils recrosses the median line to the left iliac fossa,
whUe that part derived from group 6 of the primary coils is found in the false pelvis and the
lower part of the abdominal cavity between the psoas muscles. (Mall.) Figs. 900, 901, 930
may serve to make clear these statements. They present what may be regarded as the normal
arrangement of the small intestine, having been found 21 times in 41 cadavers examined.
Variations from this arrangement occur; the great majority of such variations are, however,
not of sufficient importance to require special mention.
According to Johnson (upon whose descriptions the following account is based), there is
in embryos of 13 mm. to 23 mm. a formation of vacuoles in the duodenal epithelium, which
Fig. 930. — Model Showing Course
OF Intestine, Made phom Same Ca-
daver FROM WHICH Fig. 931 was Drawn.
(MaU.)
Fig. 931. — The Usttal Position of the
Intestine in the Abdominal Cavity. The
numbers in the figure mark the parts which are
homologous with the primary bends and groups
of coils numbered from 1 to 6. (Mall.)
leads to complete temporary occlusion of the lumen. A persistence of this condition may cause
permanent atresia. In the epithelium of the small intestine numerous pockets or cysts occur,
which usually disappear, but may persist and form permanent diverticula or accessory pancreas.
The villi begin to appear at 19 mm., first in the mucosa of the upper portion of the intestine, as
localized outgrowths which become arranged in longitudinal rows. The crypts of Lieberkuehn
bud off from the epithehum at 55 mm., and from those in the duodenum, the duodenal (Brun-
ner's) glands begin to bud off at 78 mm. The plicte circulares begin to appear at the mid-
region of the small intestine at 73 mm. The circular muscle layer begins to appear at about 12
mm., the longitudinal at 75 mm.
Variations in the small intestine. — Although relatively fixed in position, the duodenum
is quite variable in form. The C-shape previously described is the most common. When
the pylorus and the duodeno-jejunal flexure are approximated, the form is nearly circular.
When the two ends are more widely divergent, it approaches a U-form. Not infrequently,
the inferior portion ascends abruptly from the inferior angle, giving a V-form. Finally, the
terminal ascending portion may be very small or absent, in which case the duodenum ap-
proaches an L-form. Variations in the position of the various coils of the jejunum and ileum
have already been discussed. The lymph-nodules, including Feyer's patches, like all lym-
phoid structures, are prominent during youth, but become atrophied in old age.
Meckel's diverticulum, which represents a derivation from the embryonic yolk stalk and
sac, is found in about 2 per cent, of all adults. It is a blind tube or diverticulum of variable
1170 DIGESTIVE SYSTEM
size, usually approaching the intestine in width and averaging 5 cm. in length (ranging from
1 cm. to 13 cm.). Its attachment to the intestine varies from 15 cm. to 360 cm. (average
80 cm.) above the caecum. It is usually attached opposite the mesentery. It may end freely,
but is occasionally adherent to adjacent intestinal coils or connected with the anterior abdominal
wall by a cord or band-hke process.
Other diverticula of variable size and number may occur, usually along the mesenteric
border of the intestine. They may be either congenital (probably from the embryonic pockets
previously mentioned) or acquired. They occur most frequently in the duodenum (found by
Baldwin in 15 of 105 cases) where they are usually associated with the openings of the bile and
pancreatic ducts.
Comparative. — The comparative anatomy of the small intestine will be discussed later
together with that of the large intestine.
THE LARGE INTESTINE
The large intestine [intestinum crassum] is that part of the alimentary canal
which extends between the ileum and the anus. It is divided into the following
parts: Csecum, ascending, transverse, descending, and sigmoid colon, and rec-
tum. It is so arranged as to surround the small intestine, making a circuit around
the abdominal cavity from right to left (fig. 899). The caecum lies in the right
iliac fossa; thence the colon passes vertically upward on the right side (ascending
colon) until the liver is reached. Here it forms a more or less rectangular bend
(the right colic or hepatic flexure), and then passes transversely across the belly
(transverse colon) below the stomach. It then reaches the spleen, where it makes
a second sharp bend (the left colic or splenic flexure), and, passing vertically down-
ward on the left side (descending colon), reaches the left iliac fossa. At this point
it forms the loop of the sigmoid colon, and finally passes through the pelvis as the
rectum (fig. 906). The large intestine is much larger in diameter than the small
intestine, and is not so much convoluted. Excepting the dilated portion of the
rectum, it is wider at the beginning than at the end. It varies in width at different
parts from 3 to 8 cm. The length from the root of the appendix or tip of the cse-
cum to the point where the meso-colon ends is, in the male, about 140 cm., and
in the female about 130 cm. The average total length, including the rectum, is
about 150 cm. (5 ft.). The extremes found are 100 to 200 cm.
The large intestine, in all parts except the rectum, has a peculiar arrangement
of its walls, which gives it a very different appearance from the small intestine.
It is sacculated, and the sacculations [haustra] are produced by the gut having to
adapt its length to three shorter muscular bands which run the course of the intes-
tine. These bands, which are about 12 mm. wide and 1 mm. thick, aie really the
longitudinal fibres of the muscular wall, which are chiefly collected along three
lines (fig. 935). One band [taenia mesocolica], corresponding to the attachment of
the mesocolon, is posterior on the transverse colon, and postero-median on the
ascending and descending colons. A second band [taenia omentalis] is antero-
superior on the transverse colon, elsewhere postero-lateral. The third band
[taenia libera] is free; it is inferior on the transverse colon, anterior elsewhere. All
these bands start on the caecum at the vermiform process, and spread out to form
a uniform layer on the rectum. Between the sacculations are semilunar folds
[plicae semilunares coli], which involve the entire thickness of the intestinal wall,
forming crescentic ridges of the mucosa which project into the lumen (figs. 932,
935) . Along the free surface of the colon, especially near the taeniae, are numerous
small appendages [appendices epiploicae], which are pouches of peritoneum con-
taining fat (fig. 906).
The caecum. — The caecum [intestinum caecum] is a cul-de-sac forming the first
part of the large intestine. It is defined as that part of the colon which is situated
below the entrance of the ileum. Its breadth is about 7.5 cm., and its length
about 6 cm. (Fig. 932).
There is usually a more or less well-marked constriction opposite the ileo-
caecal orifice marking the boundary between caecum and colon. The caecum itself
also frequently presents a constriction dividing it into two sacculations.
It lies in the right iliac fossa, and is usually situated upon the iHo-psoas muscle,
and so placed that its apex or lowest point is just projecting beyond the medial
border of that muscle (figs. 899, 906). It is usually entirely enveloped in periton-
eum, and is free in the abdominal cavity, but more or less attached in about 10
per cent, of all cases. The apex of the caecum usually corresponds to a point a
THE LARGE INTESTINE
1171
little to the medial side of the middle of the inguinal ligament. Less frequently
the caecum will be found to be in relation with the iliacus muscle only; or the bulk
of it will lie upon that muscle, while the apex rests upon the psoas. In a number of
cases the caecum is entirely clear of both psoas and iliacus muscles, and hangs over
the pelvic brim, or is lodged entirely within the pelvic cavity. Sometimes the
caecum may pass even to the left of the median line of the body.
This part of the colon is liable to considerable variation.
Fig. 932. — Interior of the Caecum, Anterior View. (Rauber-Kopsch.)
-.-PUcEe semilunares coli
Frenulum (siaistrum) valvule coli
Frenulum
(dextrum) ,
valvulse
coli
Ostium et valvula processus vermiformis
Its variations in form may be described under four types:
1. The foetal type is conical in shape, the appendix arising from the apex, and forming a
continuation of the long axis of the colon. The three muscular bands which meet at the
appendix are nearly at equal distances apart (fig. 933, A). When the cascum is empty and
contracted it tends to approach this type.
2. The second form is more quadrilateral in shape than the last; the three bands retain
their relative positions; the appendix appears between two bulging saccuU, instead of at the
summit of a cone (fig. 933, B).
Fig. 933. — The Four Types op C^cum.
A B C
(Treves.)
3. In the third type, that part of the caecum lying to the right side of the anterior band
grows out of proportion to that part to the left of the band. The anterior wall becomes more
developed than the posterior, so that the apex is turned so much to the left and posteriorly
that it nearly meets the ileo-cajcal junction. A false apex is formed by the highly developed
part to the right of the anterior band. This is the usual caecum found (fig. 933, C).
1172
DIGESTIVE SYSTEM
4. In the fourth type, the development of the part to the right of the anterior band is
excessive, while the segment to the left of the band has atrophied. In this form the anterior
band runs to the inferior angle of junction of the ileum with the ciecum. The root of the
appendix is posterior to that angle. There is no trace of the original apex, and the appendix
appears to spring almost from the ileo-cscal junction (fig. 933, D.)
The ileo-csecal valve. — The ileo-caecal valve [valvula coli] is situated at the
entrance of the ileum into the large intestine at the upper border of the caecum,
on the posterior aspect and toward the medial side (fig. 932). The valve usually
lies nearly opposite the middle of a line from the anterior superior iliac spine (left)
to the umbilicus. The ileum passes from below upward and toward the right, and
terminates with a considerable degree of obliquity. The valve is formed by two
lip-like folds projecting into the large intestine, the upper [labium superius],
and the lower [labium inferius]. They are a little oblique. The opening between
them takes the form of a narrow transverse slit about 1.2 cm. in length. At the
ends of the slit the valves unite and are prolonged at either end as a ridge [frenu-
lum valvula; coli] partially surrounding the intestine.
Villi cover that surface of the folds looking toward the ileum; the surface toward the large
intestine is free from villi. In the formation of this valve the longitudinal muscular fibres
pass across from the ileum to the large intestine without dipping down between the two layers
of each fold. The circular muscular fibres, on the other hand, are contained between the
mucous and submucous layers which form these folds.
The efficiency of the valve in preventing the return of faeces is due largely to its oblique
position. (Symington.)
Fig. 934. — C^ctjm, Vermiform Process, and End of Ileum, with the Blood-supply and
THE Neighbouring Foss.e. (Woolsey, after Merkel.)
Sup. ileo-caec. fossa
Plic. ileocsec. ant.
T.V ,- imnmim'r^^ \ \ -^£r^ \ >.<///,- 'i e-^^'^biuiimijii • i Inf. ileo-CffiC. fossa
Plica csecabs HFPIIlii^^^ ^^i^^^r \'J^, 'lif^ ^^B?/
iMesenteriolum
Subcsecai fossa
Ileo-caecal fossae. — About the caecum, and especially in the vicinity of the ileo-
caecal junction, are certain fossae collectively known as the ileo-caecal fossae. Two
only appear to be fairly constant, although a third is now and then present.
The first, the superior ileo-cmcal or ileo-colic fossa, is formed by the passage across the
junction of the caecum and ileum of the anterior csecal artery, a branch of the ileo-cohc artery,
which produces a fold of peritoneum [plica ileocolica] limiting a pouch. It is on the anterior
aspect of the ileo-colic junction, and the pouch opens downward (figs. 906, 934). It is present
in about one-third of all cases.
The second fossa is not quite so simple. If the caecum be turned upward so as to expose
its posterior surface as it lies in situ, and if the appendix be drawn down so as to put its mesentery
on the stretch, a peculiar fold will be found to join that mesentery (fig. 934). This fold arises
from the border of the ileum opposite the insertion of its mesentery. It then passes over the
ileo-caecal jimction on its inferior aspect, is adherent to the caecum, and finaUy joins the surface
of the mesentery of the appendix. This fold is peculiar in the absence of any visible vessels,
and is often known as the 'bloodless fold of Treves.' Between it and the appendix there is an
almost constant fossa, the inferior ileo-eoeeal fossa. It is usually large, admitting two fingers,
and occurs in nearly 85 per cent, of all cases. It is bounded on one side by the smaU intestine,
and on the other by the ctecum. The appendix is occasionally found in the fossa.
The subciecal or retrocolic fossa is behind the caecum and is found in about ten per cent, of
aU cases. It may extend for some distance behind the ascending colon. The appendix may be
lodged in this fossa.
ParaccBcal fossse rarely occur, at the side of the caecum.
Variqtions. — In addition to variations already mentioned the caecum may vary in its general
i
THE LARGE INTESTINE
1173
development. It is sometimes small and insignificant; in other cases it reaches a large size.
It may be so rotated that the ileum passes behind the colon and opens on the right side. The
posterior part has been seen much more developed than the anterior, so that the ileum has
entered from the front, and the appendix has come off from the anterior wall. The c^cum
may remain undescended, and be found just under the liver or in the vicinity of the umbihcus.
In case the rotation of the embryonic intestinal loop fails to occur (which rarely happens)
the csecum may remain permanently upon the right side. If the normal process of adhesion
fails to occur, the caecum and colon, along with the small intestine, may remain suspended from
the mid-dorsal line by the primitive mesenleriuw. commune. Or any of the intermediate stages
of partial adhesion may persist.
The vermiform process. — Attached to what was originally the apex of the
caecum is a narrow, blind tube, the vermiform process [processus vermiformis] or
appendix. It comes off at a variable distance (usually about 2.5 cm.) below the
ileo-csecal valve on the postero-medial aspect of the csecum, though sometimes
from the lower end of the caecum, or elsewhere. On the interior, at the point
where it joins the caecum (fig. 932), there is a sUght inconstant valve [valvula pro-
cessus vermiformis]. The appendix joins the caecum at the point where the three
Fig. 9.35. — Cross-section of the Ascending Colon. (Allen Thomson.)
Crescentic ridge of mucous mem-
brane which divides the sacculi Longitudinal muscle
Tsenia libera
Mucous membrane'
Circular muscle
Appendix epiploica'
'Tsnia mesocolica
Mucous membrane
Tffinia omeatalis Circular
taeniae meet, and the anterior taenia forms the best guide to this point. In the
adult, the average length of the appendix is between 8 cm. and 10 cm., the extremes
being 2 cm. to 25 cm. It is usually much twisted and coiled upon itself. Its direc-
tion is most frequently downward toward the pelvic cavity, or upward and medial-
ward behind the ileum in the direction of the spleen. It occasionally turns lateral-
ward, or more rarely upward behind the caecum.
The vermiform process does not have a true mesentery, but usually (in about
90 per cent, of cases) is provided with a falciform fold [mesenteriolum] of periton-
eum, continuous with the left (lower) layer of the mesentery of the ileum (figs.
906, 934).
In general outline this fold of peritoneum is triangular. In the adult it does not extend
along the whole length of the tube. It is, in fact, too short for the appendix, and it is this
that accounts for the twisted condition of this process. Along the free margin of the fold runs
a branch of the ileo-coUc artery (fig. 934).
The ascending colon. — The ascending colon [colon ascendens] (figs. 906, 914)
extends in the right lumbar (lateral abdominal) region from the caecum to the infe-
rior surface of the liver, lateral to the gall-bladder, forming there the right colic
[flexura coli dextra] or hepatic flexure. Its average length is about 20 cm. (or
somewhat less when measured in site). It is covered by peritoneum in front and
on the side (fig. 902), but in a certain proportion of cases (26 per cent, according
to Treves) this part of the large intestine is connected with the posterior wall of
the abdomen by a meso-colon (usually very short) and is therefore surrounded by
peritoneum. Connected with the ascending colon is sometimes found a fold 'of
1174 DIGESTIVE SYSTEM
peritoneum, extending from the right side of the gut to the abdominal wall at a
little above the level of the highest part of the iUac crest. It forms a shelf upon
which rests the extreme right margin of the liver. It might be called the susten-
taculum hepatis.
The ascending colon is in relation behind with the right kidney, and the iliacus
and quadratus lumborum. In front are some of the coils of the ileum (fig. 899),
separating it from the anterior abdominal wall.
The transverse colon. — The transverse colon [colon transversum], smaller in
diameter than the ascending, extends from the lower surface of the liver to the
spleen. Its average length is from 40 to 50 cm. It describes an arch with its
convexity forward and downward. It crosses through the umbilical region from
the right hypochondrium to the left hypochondrium (figs. 899, 906, 914).
In the majority of cases the superficial part of the colic arch — as seen before
the viscera are disturbed — is either in whole or in greater part above a straight
line drawn transversely across the body between the highest points of the iliac
crest. In about one-fourth of all cases it lies, in whole or in greater part, below
this line.
Certain remarkable bends are sometimes formed by this part of the bowel.
The bending is always in the same direction, namely, downward, and is usually
abrupt and angular. The apex of the V or U-shaped bend thus formed may reach
the pubes. This bend appears to be due to two distinct causes: namely, long-
continued distention, on the one hand, and congenital malformation on the other.
The transverse colon is in relation above with the liver and gall-bladder, the
stomach, and at its left extremity with the spleen. The second portion of the
duodenum passes behind it. Below are the coils of the small intestine. It is
almost completely surrounded by peritoneum, being connected with the posterior
abdominal wall (chiefly the anterior border of the pancreas) by the transverse mes-
ocolon. This is usually lacking on the right of the mid-line, however, where the
colon crosses the descending duodenum and the head of the pancreas (fig. 905).
The descending colon [colon descendens] is 25 cm. to 30 cm. in length (less
when in situ) and extends from the spleen to the pelvic brim (figs. 906, 914). It
is more movable than the ascending colon and is also narrower. At its beginning
it is usually connected with the diaphragm, on a level with the tenth and eleventh
ribs, by a fold of peritoneum, the phreno-colic ligament [lig. phrenicocolicum]
(or sustentaculum lienis, from the fact that it supports the spleen). The bend
between the transverse colon and descending colon is called the left colic or splenic
flexure [flexura coli sinistra]. The descending colon is situated in the left hypo-
chondriac, lumbar and iliac regions (fig. 906). Its relations to the peritoneum
are the same as obtain with the ascending colon, that is, it is covered in front and
on the sides. A mesocolon is met with oftener on this side than on the light,
occurring in 36 per cent, of all cases (Treves) (see fig. 902). It is found especially
in the lower part of the descending colon, in the iliac fossa. This portion, extend-
ing from the iliac crest to the brim fsuperior aperture) of the pelvis, is sometimes
described as a separate segment, the iliac colon (Jonnesco).
The descending colon is covered anteriorly by coils of small intestine; pos-
teriorly it is in contact with the lower part of the left kidney, the quadi atus lum-
borum, iliacus and psoas muscles. It terminates by crossing medialward over the
psoas muscle and the external iliac vessels to join the sigmoid colon.
The sigmoid colon [colon sigmoideum] or pelvic colon, extends from the
descending colon to the rectum (figs. 906, 914). It includes what was formerly
described as the 'sigmoid flexure' and also the 'first portion' of the rectum.
These together form a single loop which cannot conveniently be divided into parts.
The loop, the sigmoid colon, begins at the margin of the psoas, and ends where
the sigmoid mesocolon ceases, opposite the second or third sacral vertebra.
The loop when unfolded describes a figure that may be compared to the capital
omega. The average length of this sigmoid colon is about 40 cm. The normal
position of the loop is not in the left iliac fossa, but wholly in the pelvis. The most
common disposition of it may now be described. The sigmoid (pelvic) colon
begins about midway between the lumbo-sacral eminence and the inguinal
(Poupart's) ligament. It descends at first along the left pelvic wall, and may at
once reach the pelvic floor. It then passes more or less horizontally and trans-
versely across the pelvis from left to right, and commonly comes into contact with
the right pelvic wall. At this point it is bent upon itself, and, passing once more
i
THE LARGE INTESTINE
1175
toward the left, reaches the middle line and joins the rectum. It will lie, there-
fore, in more or less direct contact with the bladder (and uterus in the female),
and may possibly touch the caecum. It is very closely related with the coils of
small intestine that occupy the pelvis, and by these coils the loop is usually hid-
den. In about 90 per cent, of cases, the sigmoid colon lies entirely within the
true pelvic cavity. In the remainder, it loops upward for a variable distance
toward the umbilicus, a position normally found in infancy.
Fig. 936. — Interior op the Rectum. (X §•) (From Toldt's Atlas.)
Jl ■— „,,^
Solitary lymph nodes
Tunica mucosa
Tunica f Longitudi-
laris Circular
'^"^ [ , layer
Pars analis recti
Rectal sinuses
Sphincter ani extemus
Sphincter ani internus
The sigmoid colon is attached to the abdominal and pelvic wall by the sigmoid mesocolon,
so that it is quite surrounded by peritoneum. The line of attachment of this mesocolon is
as follows : It usually crosses the psoas in a slight cm've upward so as to pass over the iliac vessels
at or about their bifurcation. The curve ends at a point either just to the medial side of the
psoas muscle, or between the psoas and the middle line, or, as is most frequently the case, just
over the bifurcation of the vessels. From this point the line of attachment proceeds vertically
Fig. 937.-
-MID-SAGITT.4.L Section of the Male Pelvis.
(Xi). (Braune.)
Bladder
Symphysis pubis.
Urethral bulb
Recto-vesicaJ pouch
Rectum
Transverse fold
Vesicula seminalis
■Ductus ejaculatorius
Prostate
External sphincter ani
^Internal sphincter ani
.External sphincter ani
down, taking at first a slight curve to the right. Its course is to the left of the middle line,
while its ending will be upon that line, about the second or third sacral vertebra. The sig-
moid mesocolon measures from 3 to 8.7 cm. in width — i. e., from the parietes to the bowel, —
at the widest point.
When a descending mesocolon exists, it joins that of the sigmoid colon. There is often
no mesocolon over the psoas, the gut being adherent to that muscle. In connection with the
sigmoid mesocolon is often found a fossa or pouch of peritoneum, known as the intersigtnoid
fossa [reeessus intersigmoideus]. This pouch is formed by the incomplete adhesion of the
1176
DIGESTIVE SYSTEM
primitive mesocolon to the posterior abdominal wall. It is generally found over the bifui-
cation of the iUao vessels. The pouch is funnel-shaped, and the opening looks downward and
to the left. It varies in depth from 2.5 to 3.7 cm., and is rarely the seat of the sigmoid hernia.
The rectum. — The rectum, according to the BNA nomenclature, is recognised
as a division separate from the large intestine. The term rectum is now limited
to that portion of the bowel below the mid-sacral region, where the mesocolon
ceases. It is divided into two portions: the first extends downward and forward,
in front of sacrum and coccyx, to the level of the pelvic floor ; the second portion
(the anal canal) extends from this point downward and backward to the anus
(figs. 937, 938).
Fig. 938. — Mid-sagittal Section of the Female Pelvis. (Spalteholz.)
Hypogastric artery
/ Hypogastric vein
' InJundibulum of tuba uterina
Suspensory ligament of ovary
External iliac vein
Ovary
Ampulla of tuba uterina
Ovarian ligament
Fundus uteri \
Ligamentum teres \
Transverse fold of *■ ^
bladder .>
Vertex of bladder ^ \ ^
Middle umbilical
ligament
Parietal peritoneum
uteri
Recto-uterine fold
, Recto-uter-
\ / ine (recto-
vaginal) pouch
TJrachus
Symphysis pubis
Labium majus
Body of uterus
Labium minus
External orifice of urethra
Urethra' ,
Internal orifie of urethra /
Orifice of vagina
Rectum
Posterior labium
External os uteri
Anterior labium
Anus
Vagina
' Vesico-uterine pouch
Vestibule
The upper or first portion of the rectum is about 10 cm. long, and is concave
forward [fiexura sacralis] except at the lower end where it curves backward and
downward [flexura perinealis] to join the second portion. The lower part of the
first portion often presents a dilation [ampulla recti], due to accumulation of
faeces. This part is sometimes described as the infra-peritoneal portion of the
rectum proper.
Anteriorly, the rectum is in contact with coils of ileum and, in the male, with the trigone of
the bladder, the vesiculse seminales, ductus deferentes, and posterior aspect of the prostate (fig.
937). In the female, it is in contact anteriorly with the vagina and the cervix uteri (fig. 938).
Posteriorly, it is in contact with the sacrum, coccyx and ano-coccygeal body.
In the male, a small band of muscle fibres, the recio-urethral muscle, extends from the per-
ineal flexure of the rectum to the membranous urethra.
THE RECTUM 1177
The peritoneum is reflected anteriorly from the rectum to the bladder in the
male (recto-vesical pouch) and to fornix of the vagina in the female (recto-vaginal
pouch). In the newborn, the peritoneum reaches to the base of the prostate
(Symington). On the posterior surface of the gut, there is no peritoneum below
a point about 12.5 cm. from the anus. Thus the peritoneum at the upper end of
the rectum entirely surrounds the gut. Lower down it covers only the sides and
anterior wall, and lower still the anterior wall only, where it is reflected upon the
bladder or vagina.
The second portion of the rectum, or anal canal [pars analis recti] is from 2.5
cm. to 3.5 cm. in length. From the lower end of the first portion, it turns at right
angles downward and backward, passing through the pelvic floor, and ending at
the anus. It is entirely below the peritoneum, and is surrounded by the two
sphincter muscles (figs. 936, 937).
Anteriorly is the bulb of the urethra and the posterior margin of the urogenital trigone in
the male (fig. 937), while in the female it is separated from the vestibule and the lower part of
the vagina by the 'perineal body' (fig. 938). Posteriorly it is connected with the tip of the
coccyx by the ano-coccygeal body. Laterally it is in contact with the margins of the levatores
ani, which act as an acoessory_ sphincter, and help to support the ampulla recti.
The anus. — The anus is the aperture by which the intestine opens externally.
During life it is contracted by the sphincters, so as to give the surrounding skin
a wrinkled appearance. Around the lower part of the rectum and anus certain
muscles that are connected with its proper function are situated. They are the
internal sphincter, the levator ani, and the external sphincter. The levator ani
and external sphincter will be found described in the section on Musculature.
The internal sphincter is a thickening of the circular fibres of the intestine, situated
around the second portion or anal canal. It forms a complete muscular ring, 2 to
3 mm. thick, and is composed of non-striated muscle.
The rectum differs from the rest of the colon in having smoother walls and no
appendices epiploicse. At the upper end of the rectum, the taenia libera and taenia
omentalis join to form a broad band which spreads out, covering the entire anter-
ior aspect of the rectum. Similarly the taenia mesocolica spreads out upon the
posterior aspect. Thus the rectum has a complete longitudinal muscle layer,
which, however, is thicker anteriorly and posteriorly than laterally. It sends a
bundle of fibres to the coccyx [m. recto-coccygeus]. Below, the longitudinal layer
passes between the two sphincters and breaks up into numerous bundles which are
interwoven with the external sphincter and levator ani, some of them terminating
in the circumanal skin.
Its mucous membrane is thicker than that of the rest of the large intestine. Certain
folds, chiefly longitudinal in direction, are seen in the lax state of the tube, which disappear
when distended, but Houston had described three permanent oblique transverse folds [plicae
transversales recti] (fig. 936), containing bundles of non-striated muscle-cells, which project
into the lumen of the tube: one is on the right at the level of the reflection of the peritoneum
from the rectum; and two are on the left, one above and one below the right fold. That upon
the right side is the largest and most constant, and its muscular bundle is sometimes called
the sphincter tertius. It is located about 7.5 cm. above the anus. These folds, like the corre-
sponding semilunar folds of the colon, when well marked involve the entire wall.
The mucous membrane of the upper portion of the anal canal presents a series of vertical
folds known as rectal columns [columnae rectales] (columns of Morgagni), containing bundles
of non-striated muscle longitudinally arranged. These columns become more prominent as
they extend downward. Just above the anus each two adjacent columns are united by an
arch-hke fold of mucous membrane, these folds forming what are known as the anal valves,
while the small fossse behind them are known as the rectal sinuses. The area below the valves
and extending to the anus is termed the annulus hcemorrhoidalis (fig. 936). This is lined by a
modified skin, while the area above the valves forms a transition to the typical mucosa of the
rectum.
Minute structure of the large intestine. — In general, the large intestine has the four coats
(fig. 939) — mucosa, submucosa, muscularis, and serosa — characteristic of the alimentary
canal. The mucosa lacks the villi and plicae circulares characteristic of the small intestine.
It contains many solitary lymphatic nodules, but no Peyer's patches. It differs from the
stomach in the absence of foveolse, and in the presence of large numbers of mucous 'goblet
cells' found both on the surface and along the numerous crypts of Lieberkuehn (which con-
tain no cells of Paneth). The subrnucosa is much as in the small intestine. The muscularis
has a continuous inner circular layer, the outer longitudinal fibres being chiefly gathered into
the three bands, the teniae coh, as above mentioned. The serosa is typical, excepting extra-
peritoneal areas where the epithehum is lacking. The appendices epiploicae were also mentioned
above.
The caecum and colon present no special features worthy of mention, beyond the typical
structure above outlined.
1178
DIGESTIVE SYSTEM
The vermiform process, however, differs in several important respects (fig. 940). The
walls are relatively thick and the lumen small. The solitary lymph nodules are closely packed
or confluent (especially in young people). They occupy the greater part of the sub mucosa,
and somewhat resemble the Payer's patches of the ileum. They, like all the lymphoid structures
Fig. 939. — Cross-section of the Large Intestine, a, Mucosa. 6, Submucosa. c, Mus-
cularis. d, Serosa. (Radasch.)
in general, tend to become atrophied in old age. Fat cells are usually abundant in the sub-
mucosa. The muscularis presents an inner circular layer and also a thin but complete outer
longitudinal layer. The serosa is typical. The lumen shows a progressive tendency to ob-
literation as age advances (Ribbert). This condition is never found in infancy but occurs
Fig. 940. — Transverse Section of the Human Vermiform Process. (X 20). (Stohr
and Lewis, from Sobotta.) Note absence of villi and abundance of lymph nodules. F, Clusters
of fat cells in submucosa. Only the inner part of the circular muscle is shown.
usually only partial) in over 25 per cent, of adults and in 50 per cent, of all cases over 50 years
of age. It is, however, somewhat uncertain whether this represents a normal process. In
obliteration, the glands and lymphoid nodules disappear, and the entire mucosa is transformed
into an axial mass of fibrous connective tissue.
The rectum also presents several peculiarities of structure. Attention has already been
/
THE LARGE INTESTINE 1179
called to the transverse folds (of Houston) and the rectal columns, sinuses and valves. Just
above the valves, the mucosa is transitional, the epithelium being partly stratified, and the
crypts of Lieberkuehn few and scattering. Below the valves, the annulus hEemorrhoidalis is
lined by a modified slcin. Hairs and sebaceous and sweat glands do not appear until just
outside the anal orifice. The thickening of the circular muscle to form the internal sphincter,
and the somewhat uniform disposition of the longitudinal muscle have already been mentioned,
as well as the absence of a serous coat in the lower portions.
Blood-vessels. — The large intestine is supplied with blood by the branches of the superior
mesenteric and inferior mesenteric arteries, while it also receives a blood-supply from the
internal iliac at the rectum. The vessels form a continuous series of arches from the caecum,
where the vasa intestini tenuis anastomose with the ileo-colic, the first branch of the superior
mesenteric given to the large intestine.
The blood-supply of the rectum is from the inferior mesenteric by the superior ha^morrhoidal,
from the hypogastric (internal ihac) by the middle haemorrhoidal, and from the internal pudic
by the inferior hEemorrhoidal. The vessels at the lower end of the rectum assume a longitudinal
direction, communicating freely near the anus, and less freely above.
The blood of the large intestine is returned into the portal vein by means of the superior
mesenteric and inferior mesenteric veins. At the rectum a communication is set up between
the systemic and portal system of veins, since some of the blood of that part of the intestine is
returned into the hypogastric (internal ihac) veins. In the lower end of the rectum the veins,
like the arteries, are arranged longitudinally. This arrangement is called the haemorrhoidal
plexus.
The vermiform process is supphed by a special branch of the ileo-colic artery (fig. 934).
This branch, the appendicular artery, crosses behind the terminal portion of the ileum (where
pressure may obstruct the circulation) to enter the mesenteriolum. An accessory artery of
small size also descends along the medial margin of the colon and caecum, entering the base of
the appendix.
The nerves and lymphatics of the large intestine differ in no important particular from those
of the small intestine, so far as their relations within the intestinal wall are concerned.
The efferent lymphatic vessels in general follow the blood-vessels and pass through cor-
responding lymph nodes in the various regions (see p. 734). Those of the caecum and vermi-
form process pass through the appendicular and ileo-caecal nodes; those of the colon through
mesocolic and mesenteric nodes. Those of the descending and sigmoid colons connect with
the inferior mesenteric and lumbar nodes. The superior zone of the rectum is drained by
lymphatics passing to the ano-rectal and inferior mesenteric nodes; the middle zone (region of
rectal columns) to nodes along the three haemorrhoidal arteries; the inferior zone (anal in-
tegument) chiefly to the superficial inguinal nodes.
Development of the large intestine. — At an early stage in the development of the intestinal .
canal, when this presents a single primary loop and soon after this loop has turned on its axis,
there is observed on the left half of the loop, near its top, an enlargement which marks the be-
ginning of the large intestine. With further growth this enlargement develops a lateral out-
growth on the side opposite to that to which the mesentery is attached, therefore free from the
mesentery. A conical projection of the large intestine or colon beyond the place where this is
joined to the small intestine is thus formed. This conical projection or pouch of the large in-
testine, which continues the colon somewhat beyond the insertion of the small intestine, develops
into the caecum and the vermiform process. It does not present, in its further growth, a uniform
enlargement. The portion nearest the colon grows in size more rapidly than the terminal por-
tion, this difference in size becoming more apparent as development proceeds, the smaller
terminal portion forming the vermiform process. On the return of the intestine to the peritoneal
cavity (in embryos of about 40 mm.) the csecum lies on the right side, immediately below the
liver. During the later fcetal months the caecum gradually descends into the right iliac fossa,
and there is thus established an ascending colon. The caecum may, however, even in the adult,
retain its embryonic position on the right side immediately beneath the liver, or may descend
farther than usual.
The ascending and descending colons, the sigmoid meso-colon (in part), and the rectum
with corresponding portions of the mesorectum, become adherent to the posterior body wall
during the fourth and fifth fcetal months. At the same time, the posterior layer of the great
omentum becomes fused with the upper (anterior) surface of the transverse meso-colon. The
layer of retroperitoneal fascia corresponding to the obliterated mesocolon is shown in fig. 1005.
Variations in the process of fusion give rise to numerous peritoneal variations in the adult.
The sigmoid colon is relatively long at birth. On account of the relatively small size of the
true pelvic cavity, both sigmoid colon and coils of ileum are usually excluded from it in the
foetus and infant.
In fcetuses of four to six months (length 100 mm. to 240 mm.) transitory viUi appear in
the mucosa throughout the large intestine, including the vermiform process. They appear
in rows, corresponding to longitudinal folds. Their early obliteration is possibly due to dis-
tention of the gut by the meconium.-' The glands bud off like those of the small intestine.
Lymphoid nodules are present abundantly in the vermiform process at birth (Johnson). The
circular muscular layer begins to appear in the lower part of the large intestine at 23 mm.;
the tenia at 75 to 99 mm. (F. T. Lewis).
Development of the rectum and anus. — The posterior end of the primitive intestine or arch-
enteron, designated the hind-gut, presents a terminal portion which is somewhat dilated and
known as the cloaca, into the lateral and ventral portions of which open the Wolffian ducts,
and from the ventral portion of which arises the allantois. The ventral portion of the cloaca,
which is an entodermal structure, comes in contact with the ectoderm to form the cloacal
membrane, and this forms the floor of a slight depression. For a time the cloaca or hind-gut
extends for some distance caudal to the cloacal membrane, forming what is known as the post
anal gut; this, however, soon disappears. Early in the development of the human embryo
1180 DIGESTIVE SYSTEM
when this has attained a length of about 6.5 mm., the fold which separates the cloaca and hind,
gut from the allantois deepens, and folds develop from the lateral walls of the cloaca which meet
and gradually separate the cloaca into a dorsal portion, which forms the rectum, and a ventral
portion which forms the uro-genital sinus. This uro-rectal septum extends in its further growth
until the cloacal membrane is reached, separating it into a ventral portion known as the uro-
genital membrane, and a dorsal portion known as the anal membrane. The anal membrane
ruptures comparatively late in development, establishing thus a communication between the
hind-gut (rectum) and the exterior. The mesoderm develops around the lower end of the
rectum, so that the ectoderm becomes slightly invaginated and hnes the portion of the anal
canal below the valves. A want of ruptui-e of the anal membrane constitutes an arrest of devel-
opment known as atresia of the anus.
Folds of the mucosa representing the rectal columns, valves and sinuses appear in embryos
during the third month, and are well developed during the latter half of the foetal period
(Johnson).
Variations. — The large intestine is exceedingly variable in its structure and relations,
especiaUy with reference to the peritoneum — so much so that it has been found more convenient
to include a consideration of the variations along with the preceding description of the individual
parts. The content of faeces (and gas) is as a rule relatively greatest in the csecum, decreasing
in ascending and transverse colons. The descending colon is usually empty, or nearly so, the
sigmoid colon and rectum somewhat variable. The rectal ampulla is usually more dilated in
women.
Comparative. — The morphology of both small and large intestines will be briefly considered
here. As previously mentioned, the primitive form of intestine is a comparatively straight
tube extending from stomach to anus, and connected by a primitive mesentery to the mid-
dorsal line of the body cavity. There is in many of the lower forms no clear division into small
and large intestine, though the rectal region is usually more dilated, and opens into a cloaca.
Diverticula often occur in the region between large and small intestine. In many fishes,
numerous "caeca" occur just below the pylorus, and in others an extensive spiral valve projects
into the lumen of the intestine. The absorptive and digestive surface of the mucosa is further
increased by the formation of various kinds of folds, and (beginning in amphibia) of villi.
Lymphoid tissue is typically present in the mucosa, often locaUzed in definite masses. Solitary
nodules appear in amphibia, and Peyer's patches in birds. Tubular mucous glands occur in
the lower forms, but Brunner's glands and crypts of Lieberkuehn with Paneth cells apparently
only in mammals. A cmcum is usually present from the reptiles upward (double in birds),
and often forms an important organ of digestion. The bile and pancreatic ducts open constantly
a short distance below the pylorus. The small intestine is always longer than the large, but
there is extreme variation in length among the various species. The four tunics — mucosa,
submucosa, muscularis and serosa — are tjqDical for vertebrates, the muscularis consisting of
inner circular and outer longitudinal smooth muscle fibres.
Among mammals, the divisions of the intestine correspond in general to those found in
the human species, but there is exceedingly great variation in the relative development of the
various parts. In general, the length, size and complexity of structure is relatively greatest
in the herbivora (whose food is more difficult of digestion), least in the carnivora, and intermediate
in the omnivora. Even in the same species, the structure of the intestine may be appreciably
modified according to habitual diet. The large intestine varies, but is always shorter and wider
than the small intestine. In mammals the rectum only is said to be homologous with the large
intestine of lower vertebrates. The cmcum is rarely absent and is enormously developed in
herbivora. It often contains large amounts of Ij'mphoid tissue, which, in pig and ox forms a
so-called 'intestinal tonsil. ' The vermiform process (found typically developed in man and
higher anthropoids) apparently represents a retrogressive evolutionary change in the cffical
apex, although this interpretation is denied by some (Berry), who interpret the appendix as a
progressive, functional lymphoid organ.
THE LIVER
The liver [hepar] is tiie largest gland in the body. Its secretion, the bile [bills ;
fel], is poured into the duodenum through the common bile duct. In addition it
has important functions as a 'ductless gland' in connection with the nitrogenous
and carbohydrate metabolism. In form it is a variable somewhat irregular mass,
roughly comparable to a modified hemisphere occupying the upper right portion of
the abdominal cavity (figs. 899, 914). It presents a convex, rounded upper or
parietal aspect, which is in contact with the diaphragm and adjacent body walls,
and a lower, flattened visceral surface, in contact with the abdominal viscera.
When viewed from the front, it is somewhat triangular in outline, occupying the
right hypochondriac, the epigastric and (slightly) the left hypochondriac regions.
Physical characters. — In weight, the liver averages about 1500 gm. (3| lbs.),
but it is exceedingly variable, commonly ranging from 1000 gm. to 2000 gm. Its
relative weight is also variable, averaging about 2.5 per cent, of the body in the
adult male (somewhat higher in the female). Its specific gravity averages 1.056,
so that the average weight of 1500 gm. would correspond to a volume of 1420 cc.
Its dimensions are also quite variable. Its greatest depth (antero-posterior)
averages about 15 cm., and its greatest height (vertical) is about the same. Its
THE LIVER
1181
width (horizontal) is about 20 cm., while its greatest length (measured obliquely
from side to side) averages about 25 cm. The colour of the liver is a reddish-
brown. It is firm in consistency, but friable, so that it is easily ruptured.
Surfaces and borders. — The most general division of the surface of the liver,
Fig. 941 — Superior Surface op the Liver.
Site of the caudate (Spigelian) lobe
as above stated, is into two — the parietal and the visceral. The parietal surface
is again subdivided, usually into two surfaces — posterior and superior.
The posterior surface [facies posterior] is triangular (fig. 943). It is wide on
the right, where the right lobe is in contact with the diaphragm (corresponding
Fig. 942. — Inferior Surface of the Liver.
Vena cava inferior
Common bile-duct
Portal
Hepatic artery
Caudate (Spigelian) lobe
Umbilical fissure
chiefly to the 'uncovered area' of the coronary ligament), and narrow on the
left side, where the posterior margin of the left lobe is likewise attached to the dia-
phragm. At the lower, left hand corner of the right lobe is a small triangular area
of contact with the suprarenal body [impressio suprarenalis]. Near the mid-line
1182
DIGESTIVE SYSTEM
is the caudate (Spigelian) lobe, opposite the tenth and eleventh thoracic vertebral
bodies, from which it is separated by the diaphragm (chiefly the right crus).
On the right of the caudate lobe is the fossa lodging the vena cava (sometimes
bridged over), while to the left is the fissure of the ductus venosus, giving attach-
ment to the upper portion of the lesser omentum (relations in cross-section shown
in fig. 945).
The superior surface [facies superior] is in general convex and moulded to the
inferior surface of the diaphragm (fig. 941). Tne relations in cross-section of the
Fig. 943.-
-PosTEEioE Surface of the Livdr.
Vena cava inferior
Tuber omentale
Papillary process of caudate (Spigelian) lobe
Impression for right kidney
body are shown in fig. 945. It extends downward upon the anterior abdominal
wall to a variable extent in the epigastric region, including the entire area of the
liver visible from the front (fig. 941). It also presents a broad area extending
downward on the right side. Symington accordingly distinguishes three surfaces
corresponding to the superior surface above described, viz., right surface, anterior
surface and superior surface. The superior surface is related above, through the
diaphragm, with the base of the right lung, the pericardium and heart, and (on
the extreme left) with the base of the left lung. Where it rests upon the liver,
the heart forms a shallow fossa [impressio cardiaca].
Fig. 944. — Diagram Showing Ligaments on the Dorso-inferior Aspect of the
LrvER. (Lewis and Stohr.) c.l., Coronary lig. f.l. Falciform lig. g.b., Gall bladder, l.o.,
Lesser omentum, l.t.l., Left triangular lig. o.b., Caudate lobe, p.v., Portal vein, r.l., Lig.
teres, r.t.l., Right triangular lig. v.c.i., Vena cava inf.
.Itl
The inferior or visceral stxrface [facies inferior] (fig. 942) faces downward and
backward. It is irregularly concave, with impressions due to contact with the
underlying viscera. It is divided into three lobes, right, left, and quadrate, whose
relations will be described later.
Of the borders, the anterior [margo anterior] is the best marked. It forms the
inferior boundary of the triangular anterior view of the liver (figs. 899, 914, 941),
and separates the superior from the inferior surface. Slightly to the left of the
mid-line, it often presents a slight umbilical notch [incisura umbilicalis], where it
THE LIVER
1183
is crossed by the falciform ligament. The posterior surface is separated from the
superior and inferior surfaces by ill-defined postero-superior and postero-inferior
borders.
Surface outline. — The average position of the hver may be outlined upon the anterior
surface of the body as follows (fig. 914): Locate one point on the right mid-clavicular (mid-
Poupart) line opposite the fifth rib; a second point on the left mid-clavicular line about 2 cm.
lower, in the fifth interspace; and a third point about 2 cm. below the costal arch (10th rib)
on the right lateral wall. A line slightly concave upward, joining the first and second points
defines the uppermost aspect of the lever. A line, strongly convex laterally, joining the first
and third points, defines the right side of the liver. Finally, a third line, joining the second and
third points, corresponds to the anterior border and defines the lowermost portion of the liver.
This line is subject to many individual variations. In general, it is usually slightly convex
downward as it crosses the epigastric region. It usually presents a slight umbilical notch, as
before mentioned, and frequently a notch for the fundus of the gall-bladder, which is placed near
the right mammarj' (mid-Poupart) line. The lower and right portion of the anterior border of
the liver runs somewhat parallel with the infracostal margin. In the upright position, and in
livers larger than usual, it extends about 2 cm. below the hypochondrium into the right lateral
abdominal (lumbar) region (fig. 914). In the supine position, however, the liver recedes about
2 cm. toward the head. The liver of course participates also in the respiratory movements of
the diaphragm.
Fig. 945.-
-Ceoss-section of Body at Level op the Eleventh Thoracic Vertebra.
(Poirier-Charpy.)
Caudate lobe of liver
Suprarenal gl.
Vena cava inf. 1 I Aorta
Spleen
Falciform lig.
Lobes and fissures. — The superior surface is divided by the falciform ligament
into two areas, corresponding to a larger right and a smaller left lobe (fig. 941).
On the posterior and inferior surfaces of the liver (figs. 942, 943), an H-shaped
arrangement of fossae and fissures completes the demarcation of lobes. The left
upright of the H [fossa sagittalis sinistra] corresponds to the prolongation of the
line of attachment of the falciform ligament. It is made up of the umbilical
fissure [fossa venae umbilicalis], containing the round ligament, on the inferior
surface; and of the fossa ductus venosi, containing the ligamentum venosum
(obliterated ductus venosus) and the upper part of the lesser omentum, on the
posterior surface of the liver. This left sagittal fossa separates the left lobe of the
liver from the right lobe (in the wider sense of the term). The right lobe is further
subdivided by the right upright and cross-bar of the H. The right upright [fossae
sagittales dextrae] is made up of the broad fossa for the gall-bladder [fossa vesicae
felleae] on the inferior surface, and the broad fossa vence cavce on the posterior sur-
face (fig. 943. These two fossae are not continuous, but are separated by a narrow
strip of liver, the caudate process of the caudate lobe (fig. 942). The cross-bar
of the H is formed by the transverse or portal fissure [porta hepatis], which encloses
the root structures of the liver, within the lower part of the lesser omentum (fig.
942). The area anterior to the cross-bar of the H corresponds to the quadrate
1184 DIGESTIVE SYSTEM
lobe of the inferior surface; that posterior to the cross-bar to the caudate lobe of
the posterior surface; while the remainder of the liver, to the right of the H, is
the right lobe (in the narrower sense).
The right lobe [lobus hepatis dexter] makes up the greater part of the hver. Its relations
on the superior and posterior surfaces have already been mentioned. On the inferior or visceral
surface (fig. 942), there appears posteriorly a large concavity [impressio renalis] for the right
kidney; medially a faint impression [impressio duodenalis] for the descending duodenum; and
antero-inferiorly a variable area [impressio coHca] of contact with the right (hepatic) flexure
of the colon. The caudate process joins the right with the caudate lobe.
The left lobe [lobus hepatis sinister] lies to the left of the left sagittal fissure and the falci-
form ligament. It is flattened but variable in form and size, and makes only about one-fifth
of the entire liver. In children and especially in early foetal life, it is relatively much larger.
At the left extremity, there is usually found in the adult liver a variable fibrous band [appendix
fibrosa hepatis] representing the atrophied remnant of the more extensive gland in earlier life.
In this fibrous appendix (and in other parts of the liver) the bile ducts of the atrophied liver
substance persist as vasa aberrantia hepatis.
The left lobe is related superiorly, through the diaphragm, with the heart and the base of
the left lung. Injeriorly (fig. 942) it presents a large concavity [impressio gastrioa] which is
in contact with the anterior surface of the stomach. Above and behind the gastric impression
is the rounded tuber omentale which is placed above the lesser curvature of the stomach and re-
lated, through the lesser omentum, with a corresponding tuberosity on the pancreas. To the
left of the tuber omentale, and near the posterior aspect of the liver, is a small inconspicuous
groove [impressio cesophagea] for the abdominal part of the oesophagus.
The quadrate lobe [lobus quadratus] lies, as before mentioned, on the inferior surface of
the liver (fig. 942) in the anterior or inferior area of the H. It is in contact with the pylorus
and the first part of the duodenum.
Pig. 946. — Relation op STBucTtrRBs at and Below the Teansvekse or Portal
PissuHE. Anteioe view. (Thane.)
Common bile-duct-
The caudate or Spigelian lobe [lobus caudatus; SpigeU] was described on the posterior sur-
face of the liver (fig. 943). Inferiorly, the caudate lobe, behind the portal fissure, is divided
by a notch into two processes. The left or papillary process [processus papillaris] is short and
rounded, and lies opposite the tuber omentale. In the fcetus it is relatively much larger and ia
in contact with the pancreas. The right or caudate process [processus caudatus] is of variable
size, and joins the caudate with the right lobe of the hver. It is usually small and inconspicuous.
In the foetus, however, it is relatively much larger, and extends downward to a variable extent
behind the duodenum and head of the pancreas. In the adult, it forms the upper boundary of
the epiploic foramen (of Winslow).
Peritoneal relations. — -The liver in the adult is almost entirely surrounded by
peritoneum. Although it develops together with the diaphragm in the common
septum transversum (as explained previously, see figs. 951,952), the peritoneum
soon extends in between liver and diaphragm, so that they remain in immediate
contact only in the so-called 'uncovered area.' This is an irregular area on the
posterior surface of the liver (chiefly on the right lobe), the margins of which cor-
respond to the coronary ligament (figs. 905, 944). The posterior surface of the
liver is therefore chiefly retroperitoneal, excepting the caudate (Spigelian) lobe,
which is in contact with the recessus superior of the bursa omentalis (fig. 905).
The superior and inferior surfaces of the liver are entirely covered with peritoneum,
excepting the lines of attachment of the various peritoneal ligaments, and the
fossa for the gall-bladder, which is usually directly in contact with the gall blad-
der with no intervening peritoneum.
Ligaments. — The liver is attached by five peritoneal ligaments — coronary,
right and left triangular (lateral) and falciform ligaments and lesser omentum—"
and two accessory ligaments — teres and venosum.
The coronary ligament [lig. coronarium hepatis], as before mentioned, corre-
THE LIVER 1185
sponds to the reflections of peritoneum from the liver to the diaphragm at the mar-
gins of the 'uncovered area' (fig. 944) on the posterior surface of the liver.
Within this uncovered area the hepatic veins join the inferior vena cava. The coronary
ligament, though somewhat irregular and variable in form, is elongated laterally and roughly
quadrangular. At the four angles, the peritoneal layers come together and are prolonged into
four ligaments — right and left triangular (lateral) and falciform hgaments and lesser omentum.
There is often also a special prolongation of the coronary ligament downward upon the right
kidney, forming the hepato-renal ligament [lig. hepatorenale]. This lies to the right of the fora-
men epiploicum.
The right triangular (or lateral) ligament [hg. triangulare dextrum] is a short but variable
prolongation of the coronary ligament to the right and downward (figs. 905, 944) . It connects
the posterior surface of the right lobe of the liver with the corresponding portion of the diaphragm.
The left triangular (lateral) ligament [lig. triangulare sinistrum] is a longer, narrower pro-
longation of the coronary ligament to the left (figs. 905, 944). It connects the posterior as-
pect of the left lobe of the hver with the corresponding portion of the diaphragm.
The falciform ligament [lig. falciforme hepatis] is a double layer of peritoneum
representing (as before mentioned) the ventral portion of the primitive ventral
mesogastrium.
Its upper end is continuous posteriorly with the coronary ligament. It passes forward
and downward over the superior surface of the liver. From its line of attachment to the liver
(between right and left lobes) it passes forward and slightly to the left to the attachment on the
anterior body wall. This attachment extends downward slightly to the right of the mid-line
to the umbilicus. The lower margin of the falciform ligament is free, and encloses the roimd
ligament.
The round ligament [lig. teres hepatis] is a fibrous cord representing the obliter-
ated foetal left umbilical vein. It extends upward from the umbilicus enclosed in
the lower margin of the falciform ligament.
At the anterior margin of the liver it passes backward on the inferior surface, enclosed in a
slight peritoneal fold at the bottom of the fossa vense umbilicalis (sometimes bridged over by
liver tissue). It ends by joining the left branch of the portal vein.
The ligamentum venosum [lig. venosum; Arantii] similarly represents the obliterated fcetal
ductus venosus. It is a fibrous cord lying in the fossa ductus venosi, and e.xtends from the left
branch of the portal vein upward to the left hepatic vein near its opening into the vena cava.
The ligamentum venosum lies within the hepatic attachment of the lesser omentum.
The lesser omentum [omentum minus] has already been discussed in connec-
tion with the peritoneum. It represents the dorsal part of the primitive ventral
mesogastrium, extending from the stomach to the liver. It includes two parts, as
shown in fig. 906.
The upper and larger part forms the gasiro-hepalic ligament [lig. hepato-gastricum], connect-
ing the liver (fossa ductus venosi) with the lesser curvature of the stomach. The upper part
of this ligament is somewhat thicker, the lower part thinner and more transparent. The rela-
tions of the lesser omentum in cross-section of the body are shown in fig. 903. The lower and
right portion of the lesser omentum extends beyond the pylorus and connects the portal fissure
with the duodenum, forming the hepalo-duodenal ligament [lig. hepatoduodenale] (fig. 905).
Its right margin forms the anterior boundary of the epiploic foramen (of Winslow). Between
its layers are located the root structures of the hver, as follows: hepatic artery to the left,
common bile duct to the right, portal vein behind and between. A special prolongation of the
hepato-duodenal ligament frequently extends downward to the transverse colon, forming the
hepato-colic ligament [lig. hepatocoHcum].
Fixation of the liver. — The liver is to a certain extent fixed in place by means of
its various ligaments, and especially through the attachment of the hepatic veins
to the inferior vena cava. On account of the close apposition of the liver to the
diaphragm, the atmospheric pressure also helps in its support. Finally, the sup-
port of the liver, as well as of the abdominal viscera in general, is dependent to a
considerable extent upon the tonic contraction of the abdominal muscles, which
exerts a constant pressure upon the abdominal contents.
Blood-vessels. — The liver receives its arterial supply of blood from the hepatic artery, a
branch of the coeliac, which passes up between the two layers of the lesser omentum, and
dividing into two branches, one for each lobe, enters the liver at the portal fissure. The right
branch gives off a branch to the gall-bladder. The liver receives a much larger supply of blood
from the portal vein, which conveys to the liver blood from the stomach, intestines, pancreas,
and spleen. It enters the portal fissure, and there divides into two branches. Below this
fissure the hepatic artery lies to the left, the bile-duct to the right, and the portal vein behind and
between the two (fig. 946). These three structures ascend to the liver between the layers of
the lesser omentum in front of the epiploic foramen. At the actual fissure the order of the three
structures from before backward is — duct, artery, vein.
1186 DIGESTIVE SYSTEM
The hepatic veins, by which the blood of the hver passes into the inferior vena cava, open
usually by two large and several small openings into that vessel on the posterior surface of the
gland at the bottom of the fossa venae cavoe.
Lymphatics. — The lymphatics are divided into a deep and a superficial set. The deep set
runs with the branches of the portal vein, artery, and duct through the liver, leaving at the portal
fissure, where they join the vessels of the superficial set. The efferent deep vessels after leaving
the portal fissure pass down in the lesser omentum in front of the portal vein, through the chain
of hepatic lymphatic nodes, and ultimately end in a group of nodes at the upper border of the
neck of the pancreas, in which the pyloric lymphatics also terminate.
The superficial set begins in the subperitoneal tissue. Those of the upper surface consist: —
(1) Of vessels which pass up, principally, in the falciform ligament and right and left triangular
ligaments, through the diaphragm, and so into the anterior mediastinal nodes, and finally
into the right lymphatic duct. Some lymphatics of the right triangular ligament pass to the
posterior mediastinal lymph-nodes and into the thoracic duct. (2) Of a set passing downward
over the anterior border of the liver to the hepatic nodes in the portal fissure, and over the pos-
terior surface to reach the superior gastric and coeliac nodes. On the lower surface, the lym-
phatics to the right of the gall-bladder enter the lumbar nodes. Those around the gall-bladder
enter the hepatic nodes of the lesser omentum. Those to the left of the gall-bladder enter the
superior gastric nodes.
Nerves. — The nerves of the liver are derived from the vagi (those from the left vagus
entering from the stomach through the lesser omentum), and from the coehac plexus of the
sympathetic (including right vagus branches) through a plexus accompanying the hepatic
artery. The terminations, so far as known, are chiefly to the walls of the vessels and of the bile
ducts.
Structure of the liver. — The liver is, for the greater part, covered by peritoneum, beneath
which is found the fibro-elastio layer known as Glisson's capsule. At the portal fissure, Ghsson's
capsule passes into the substance of the liver, accompanying the portal vessels, the branches of
the hepatic artery, and the bile-ducts. The hver substance is composed of vascular units
measuring from 1 to 2 mm., and Icnown as hver lobules. These are in part (man) separated by
Fig. 947. — Section of a Portal Canal. (Quain.)
Branch of porl'al vein
I I -^ Lymphatics in Glisson's capsule
Lymphatics in Glisson's capsule -r^^ I
-Branch of hepatic artery
a small amount of interlobular connective tissue, which is a continuation of Ghsson's capsule.
In this interlobular connective tissue are found the terminal branches of the portal vessels;
the hepatic artery, and the bile-ducts (figs. 947, 948). The branches of the portal vessels which
encircle the liver lobules are known as the interlobular veins. From these are given off hepatic
capillaries, which anastomose freely, but have in general a direction toward the centre of the
lobule, and unite to form the central or intralobular veins, which in turn unite to form the sub-
lobular veins, and these the hepatic veins. The intralobular branches of the hepatic arteries
form capillaries which unite with the capillaries of the intralobular portal veins.
The liver is a modified compound tubular gland. The liver-cells are arranged in anas-
tomosing cords and columns occupying the spaces formed by the hepatic capillaries. The
bile-ducts have their origin in so-called bile-capillaries [ductus biliferi], situated in the columns
of liver-cells; they anastomose freely and pass to the periphery of the lobules to form the pri-
mary divisions of the bile-ducts, and these unite to form the larger bile-ducts. The branches of
the portal vessel are accompanied in their course through the liver by the branches of the hepatic
artery and the bile-ducts, surrounded by extensions of Ghsson's capsule forming the so-called
'portal canals' (fig. 947). The branches of the hepatic vein are solitary, their walls are thin
and closely adherent to the liver substance, whence they remain wide open on sectioning the
liver.
While it is customary to describe thus the hver lobules, it would be more logical to con-
sider as the real lobules what Mall has described as the 'portal units.' Each portal unit
includes the territory supplied by one interlobular branch of the portal vein, and drained by
the accompanying bile-duct. The relations of the ordinary lobules and the portal units are
evident in fig. 948. The portal unit corresponds more nearly to the lobule of other glands,
where the duct is in the centre of the lobule.
THE LIVER
1187
Bile passages. — The bile passages, which transmit the bile from the liver to the
duodenum, include the gall-bladder, the cystic duct, the hepatic ducts, and the
common bile duct.
The gall-bladder [vesica fellea], which retains the bile, is situated between the
right and quadrate lobes on the lower surface of the liver. It is pear-shaped,
and when full, is usually seen projecting beyond the anterior border of the liver,
coming in contact with the abdominal wall opposite the ninth costal cartilage at
the lateral margin of the right rectus muscle (fig. 914). It extends back as far as
the portal fissure.
It measures in length, from before backward, 7 to 10 cm. It is 2.5 to 3.5 cm.
across at the widest part, and will hold about 35 cc. (Ij oz.). The broad end of the
sac is directed forward, downward, and to the right, and is called the fundus.
The narrow end, or neck [collum vesicae fellete], which is curved first to the right,
then to the left, lies within the gastro-duodenal Ugament at the portal fissure.
The intervening part is called the body [corpus vesicae felleae].
Fig. 948.-
-Diagram of the Portal Unit and Vascular Relations of the Hepatic Lobule.
(After Szymonowicz.)
PORTAL UNIT
PORTAL UNIT
Its upper surface is in contact with the liver, lying in the fossa of the gall-bladder. It is
attached to the liver by connective tissue. The lower surface is covered by peritoneum, which
passes over its sides and inferior surface, though occasionally it entirely surrounds the gall-
bladder, forming a sort of mesentery attaching to the liver. The lower surface comes into con-
tact with the first part of the duodenum and the transverse colon, and occasionally with the
pyloric end of the stomach or small intestine, which post mortem are often found stained with
bile.
The neck of the gall-bladder opens into the cystic duct [ductus cysticus].
This is a tube about 3.5 cm. long and 3 mm. wide, which unites with the hepatic
duct to form the ductus choledochus; it is directed backward and to the left as
it runs in the gastro-hepatic ligament, the common hepatic artery being to the left
and the right branch of the artery and portal vein behind. It joins the hepatic
duct at an acute angle, and is kept patent by a spiral valve [valvula spiralis;
Heisteri], formed by its mucous coat (fig. 949).
The hepatic duct [ductus hepaticus] Ijegins with a branch from each lobe, right
and left (that from the left receiving also the ducts from the caudate lobe), in
the portal fissure, and is directed downward and to the right within the portal
fissure and the hepato-duodenal ligament, the right branch of the hepatic artery
being behind and the left branch to the left. It is from 3 to 5 cm. long; its diame-
ter is about 4 mm. Uniting with the cystic duct, it forms the common bile-duct
[ductus choledochus].
1188
DIGESTIVE SYSTEM
The ductus choledochus or common bile-duct is about 7.5 cm. in length and
6 mm. in width. It passes down between the layers of the lesser omentum, in
front of the portal vein, and to the right of the hepatic artery (fig. 946) ; it then
passes behind the first part of the duodenum, then between the second part and the
head of the pancreas, being almost completely embedded in the substance of the
pancreas, and ends a little below the middle of the descending duodenum by open-
ing into that part of the intestine on its left side and somewhat behind (figs. 921,
Fig. 949.-
-Intekior of the Gall Bladder and Ducts. (From Toldt's Atlas.)
Tunica mucosa of gall bladder
Plicae tunicse mucosae
/ Spiral valve (of Heistet)
Common bile duct (ductus choledochus)
Biliary mucous glands
922, 957). It pierces the intestinal wall very obliquely, running between the
muscular layers for a distance of about 1 to 2 cm. There is a slight constriction
at its termination. The pancreatic duct is generally united with the ductus
choledochus just before its termination, and there is a slight papilla at their place
of opening on the mucous surface of the duodenum. This papilla is about 8 or
10 cm. from the pylorus. After the pancreatic duct has entered the bile-duct there
is (in about half the cases) a dilatation of the common tube called the ampulla of
Vater.
THE LIVER
1189
In its oblique course through the duodenal wall, the common bile duct is accompanied by
the pancreatic duct, the two together usually causing the pUca longitudinalis duodeni (fig. 922).
Circular muscle fibres join with bundles of longitudinal fibres at the lower part of the ducts
and form a sphincter around each (fig. 950). Contraction of the sphincter probably closes the
orifice of.'the common bile duct, so that (except during digestion) the bile is backed up into the
gall-bladder.
Structure of the gall-bladder. — The wall of the gall-bladder is made up of three coats —
mucosa, fibro-muscular and serosa.
Fig. 950. — Macerated Duodenal Portion op the Common Bile Duct, Showing
Musculature. B, Common bile duct. TT^, Pancreatic duct (of Wirsung). iS, Tij, Sphincter
fibres of Isile duct. H, Fibres of pancreatic duct. (Hendrickson.)
1. The mucosa is raised into folds bounding polygonal spaces, giving the interior a honey-*
comb appearance. It is lined with columnar epithelium, and contains a few tubular mucous
glands and lymph-nodules, and is hmited externally by a poorly developed muscularis mucosae.
At the neck the mucous membrane forms valve-like folds which project into the interior. This
layer contains an anastomosis of blood-vessels, the capillaries being most numerous in the folds
of the mucosa, and a fine plexus of lymphatics.
2. The fibro-muscular coat consists of interlacing bundles of non-striated muscle and fibrous
tissue not definitely arranged, the muscular bundles running longitudinally and obliquely
This layer contains the principal blood-vessels and lymphatics, and also a nerve plexus.
Fig. 951. — Diagrams op the Development op the Liver. (Lewis and Stbhr.)
A, The condition in a 4.0 mm.- human embryo. B, A 12 mm. pig. C, The arrangement of
ducts in the human adult, c. d., Cystic duct; c. p., cavity of the peritoneum; d., duodenum;
d.c, ductus choledochus; dia., diaphragm; div., diverticulum; /. I., falciform ligament; g. b.,
gall bladder; g. a., greater omentum; h. d., hepatic duct; ht., heart; int., intestine; li., liver;
I.O., lesser omentum; to., mediastinum; on., cesophagus; p. c, pericardial cavity; p. d. pan-
creatic duct; ph., pharynx; p. v., portal vein; st , stomach; Ir., trabecula; v. c. i., vena cava in-
ferior; v.v. vitelline vein; y. s., yolk sac.
v.v. ml. B
3. The serosa being formed by the peritoneum, is only found on the lower surface and part
of the sides.
The ducts consist of a fibro-muscular and a mucous layer. In the fibro-muscular layer are
non-striated muscle-cells which are chiefly circular, together with white fibrous tissue and elastic
fibres. The mucous layer is lined with columnar epithehum, and has manj' mucous glands. In
the cystic duct the mucous membrane is raised into folds, which are crescentic in form, and
directed so obUquely as to seem to surround the lumen of the tube in a spiral manner.
The development of the liver. — The relations which the liver bears to the diaphragm, to
its vessels and more especially the veins, and to its so-called hgaments, may be understood by
a reference to its development (figs. 951, 952). In discussing the development of the peritoneum
and the mesenteries it was shown that the liver has its origin in a bud of entoderm, which grows
1190
DIGESTIVE SYSTEM
into the transverse septum in the region where this is attached to the ventral mesoderm of the
developing intestine; and that, with further development, the transverse septum differentiates
into an upper thinner portion, inclosing the Cuvierian ducts, and destined to form the diaphragm,
and a lower thicker portion in which the liver develops. Shortly after the formation of the
entodermal bud which forms the liver this mass of epithelium taecomes penetrated by out-
growths from the omphalo-mesenteric veins, reducing the epithelial mass to anastomosing
trabeculae separated by blood-spaces forming a sinusoidal circulation. The definite hepatic
lobules are not differentiated until after birth. The process of the development of the lobules
is very complicated, the vascular arrangement being shifted repeatedly (Mall).
The liver rapidly enlarges, filling the upper portion of the abdominal cavity, and extending
along its ventral wall to the region of the umbilicus. During the enlargement it in a measure
outgrows the transverse septum, and there are developed grooves which result in an infolding
of the peritoneum covering the transverse septum, and which in part separate the developing
liver from that part of the septum destined to form the diaphragm_, and also from the ventral
abdominal wall. These grooves appear at the sides and also ventral to the hver, but do not
completely separate the liver from the diaphragm, nor do they meet in the median line. A
portion of the liver, therefore, remains uncovered by peritoneum, and remains attached to the
diaphragm; this area may be known as the uncovered or phrenic area of the hver. Around
this area the peritoneum of the hver is reflected on to the diaphragm, forming the coronary
ligament, with right and left extensions, designated as the right and left triangular hgaments.
Owing 'to the fact that the grooves which develop on the sides of the liver do not meet in the
median line, there persists a fold of peritoneum which attaches the Hver to the ventral abdominal
Fig. 952. — Diagram (A) : A Sagittal, Section of an Embryo showing the Liver en-
closed WITHIN THE Septum Transversum; (B) AFbontal Section of the same; (C) Fron-
tal Section of a Later Stage when the Liver has separated from the Diaphragm.
All, Allantois; CI, cloaca; D, diaphragm; Li, liver; Ls, falciform ligament of the liver, M,
mesentery; Mg, mesogastrium; Pc, pericardium; iS, stomach; ST, septum transversum; U,
umbilicus. (McMurrich.)
wall; this forms the falciform ligament, which divides the superior surface of the hver into a
right and a left lobe. The region of the attachment of the ventral mesentery (mesogastrium)
into which grows the entodermal liver bud, forms the lesser omentum. The developing liver
early comes into intimate relation with the omphalo-mesenteric veins, and a little later the um-
bilical veins. The developmental history of these veins and their relation to the developing
liver is discussed elsewhere (see Development of the Portal Vein and Inferior Vena
Cava, p. 694). After birth the left umbilical vein forms the hepatic ligamentum teres, situated
in the free edge of the falciform hgament. The ductus venosus likewise atrophies to form the
ligamentum venosum.
The gall-bladder has its origin in a groove lined by entoderm, which appears on the ventral
surface of the primitive intestine or archenteron, between the stomach and the yolk-vesicle.
From the cephalic end of this groove grows out the bud destined to form the liver; the caudal
end of the groove becomes gradually separated from the developing intestine to form a pouch,
lined by entoderm, which forms the beginning of the gall-bladder. With further growth the
attachment to the intestine of both the liver and the gall-bladder becomes narrowed to form the
ductus choledochus.
During development, the liver undergoes marked changes in form and relative size. It
grows with great rapidity in the embryo, its maximum relative size reaching 7 to 10 per cent, of
the entire body about the third prenatal month. At this time, the hver is globular in form, the
visceral surface very small, and the left lobe more nearly approaching the right in size. During
the later foetal months (fig. 953) and at birth, the liver forms about 5 per cent, of the whole
body. It stiU remains relatively large in infancy, but decreases to about 2.5 per cent, in the
adult. From the beginning, the relative weight of the liver averages slightly higher in the
female.
Variations of the liver and bile passages. — Many variations of the liver have already
been mentioned. In size, both relative and absolute, it is subject to marked individual varia-
tions, as well as according to age and sex (previously described). Inform, the liver is also quite
variable. There are two extreme types: (1) in which the liver is very wide, extending far over
into the left hypoohondrium, but relatively flattened from above downward; and (2) in which it
THE LIVER
1191
extends but slightly to the left, being somewhat flattened from side to side, and elongated
vertically. This type may occur as a result of tight lacing, in which the liver is frequently
deformed. The part projecting below the right costal margin may form the so-called 'Riedel's
lobe.' All intermediate forms between these two types occur. Its position and relations will
also vary necessarily according to differences in size and shape. For example, in the wide type
and also in enlarged livers, the left lobe may extend over upon the spleen, a relation which is
constant during prenatal life.
There may be supernumerary fissures, dividing the hver into additional lobes, as many as
16 having been described in an extreme case (Moser). These extra fissures often correspond
to fissures which are normal in other mammals. There may also be accessory lobes, usually
small, and connected with the main gland by stalks. Any one of the normal lobes may be
atrophied or absent. There may also be abnormal grooves on the parietal surface of the liver.
Of these, there are two varieties: (1) costal grooves, due to impressions of the overlying ribs
and costa! cartilages; and (2) diaphragmatic grooves, due to wrinkles in the diaphragm. These
Fig. 953. — The Viscera op the Fcettjs. (Rudinger.)
Thyreoid
Liver
Falciform ligament
Small intestine
Right ventricle
Stomach
Part of transverse colon
Hypogastric artery
grooves most frequently occur in females, as a result of tight lacing. The appendix fibrosa
has already been mentioned. There are numerous variation in the vascular arrangements, as
well as in the psritoneal relations (particularly in connection with the coronary ligament).
The bile passages are even more variable than the liver proper. The gall-bladder is variable
in size and capacity (25 cc. to 50 oc. or more), as well as in its position, and relations. The
fundus projects to a variable extent beyond the anterior margin of the liver so as to come into
contact with the abdominal wall in a little more than half the cases, but is often retracted. The
fossa of the gall-bladder is of variable depth, rarely so deep that it reaches the superior surface
of the liver. The peritoneum usually covers only the sides and inferior surface of the gall-
bladder, but occasionally surrounds it entirely, forming a short 'mesentery.' In rare cases
the gall-bladder is bilid or double, and is occasionally absent. There are numerous variations in
the bile-ducts. Rarely the hepatic ducts may communicate directly with the gall-bladder.
The point at which hepatic and cystic ducts unite is variable, which affects the relative lengths
of these and the ductus choledochus. The latter may open into the duodenum separately,
instead of with the pancreatic duct.
1192
DIGESTIVE SYSTEM
Comparative. — The liver arises in all vertebrates as an outgrowth of the entodermic epi-
thelium of the intestine just beyond the stomach. In amphioxus it remains a simple saccular
diverticulum, but in aU higher forms becomes a compound tubular gland. The tubular char-
acter becomes masked, however (in amniota, and especially in mammals), by the abundant
anastomosis between the tubules, forming what is called a 'solid' gland. The relations with
the portal venous system are constant. The liver frequently stores large quantities of fat, and
may even undergo a complete fatty metamorphosis (lamprey). The colour of the liver is usually
reddish-brown, but may be yellow, purple, green or even vermillion (due to bile pigments).
In size, the liver is variable, but is usually relatively larger in anamniota. Among mammals,
there is great variation according to diet, the liver being relatively larger in carnivora, smaller
in herbivora, and intermediate in omnivora (including man). It is also relatively larger in small
animals (including young and foetal stages), probably on account of their more intense metabo-
lism. There are typically two lobes, right and left, in the vertebrate hver. These are frequently
subdivided, however, especially in mammals, which often present numerous lobes.
The gall-bladder is typically present, as in man, but varies in form, size and position. It
may be completely buried in the fiver. In some species it is absent, in which case the hepatic
ducts open directly into the duodenum by one or more apertures. The hepatic and cystic
ducts typically unite to form a common bile-duct, as in man, but there are numerous variations
in the detailed arrangement of the ducts.
THE PANCREAS
The pancreas (figs. 922, 954, 955, 956) is an elongated gland extending trans-
versely across the posterior abdominal wall behind the stomach from the duode-
num to the spleen. Through the pancreatic duct, opening into the descending
duodenum, flows its secretion [succus pancreaticus], which is of importance in
digestion. The pancreas also has a very important internal secretion.
Fig. 954. — The Duodenum and Pancreas, Anterior View.
Superior layer of transverse meso-colon
Duodeno-jejunal Sesure
Inferior layer of transverse meso-colon
Inferior part of duodenum
Superior mesenteric vessels
The pancreas is greyish-pink in colour; average length {in situ), 12 cm. to 15
cm.; average weight about 80 gm. (extremes 60 gm. to 100 gm. or more); specific
gravity, 1.047, which is about the same as that of the salivary glands.
In position, the pancreas lies in the epigastric and left hypochondriac regions.
In form, it somewhat resembles a pistol, with the handle placed to the right and
the barrel to the left. The pancreas is accordingly divided into a head, lying
within the duodenal loop; a body, extending to the left; and a tail, or splenic
extremity.
The head [caput pancreatis] is a discoidal mass somewhat elongated vertically
and flattened dorso-ventrally. It forms the enlarged right extremity of the pan-
creas and lies within the concavity of the duodenum (flgs. 922, 954, 955). Its
relations are as follows (figs. 954, 955, 956) : Its posterior surface is placed opposite
the second and third lumbar vertebrae, and is in contact with the aorta, the vena
cava, the renal veins and right renal artery. The common bile-duct is also partly
embedded in this surface. Its anterior surface is crossed by the transverse colon,
above which is the pyloric extremity of the stomach, and below which are coils of
THE PANCREAS
1193
Fig. 955. — The Duodenum and Pancreas, Posterior View.
Portal vein
Terminal part of duodenum
Head of pancreas
Fig. 956. — Outline Showing the Average Position op the Deeper Abdominal
Viscera in 40 Bodies, on a Centimetre Scale (reduced to .36 natural size). AB, anterior
mid-line. EF, horizontal line half way between pubes and suprasternal margin. CD, line
half way between pubes and line EF. (Addison.)
13
12
11
10
9
a
7
6
FT
4
3
2
1
All 21 3 1 4 1 5 1 6 1 7
8
9
10
11
12
13
r
f "'*"""
Co
5ta
At
'\
\
-X
— .
V
\,
■'
/
\
.'
••.
■.
r-
■ri
:v.-'
\
'?•
^.
^■^
\
n^
^
/ •
""i
p^
if
,,
•
-3.
-'
f~
I
^
"T
^
•.
■■.:t:
1 1
^
/-
, \
1
^
"
■*
i
-^'V
\
!
/
\
^
>^
*
'
\
h
Bvv^?*
EO
/
\y
'/
|»
\
r
ir
^fe
w^
\\'r
■f?
!S»
^
W
^^
"?
The ri
/•
A
f
J the 1st dfeand 2nd
/
,f
^
^
J
r
■T
\
;
^3.
4-
.5.
Lumbarx
1 1
;
t
.,'-
f
i
N.
/
N
/
■«•
■■■^
/
/
1
j
y
\
/
^
y
V*
,.^
V
1
/
\
s
It
^,
fp
V
/
\
.7.
.8.
-■^
—
,/-
n
•^
/
— :
^
—
s
f
\
i
J
^
>-
_
—
"'
JO
'cr
II
0
^
nbilicua
Cl
.1.
-2
^
\
/
^
\
/
\
\
/
\
/
">
L_Ant
1 1 1
erior Superior i1
1
ac Sd
no
*. s'. s.
/
Sacral Promon
°7
y
;
-8.
-7-
_8
9f
10
.11
~^
\
^
\
/"
\
"^
^
/
%
Psoas M
iscle
/
ou
:a
-ig
y
tib
/
\
/
\
y
J13
\
Pubes
/
P 1
1194 DIGESTIVE SYSTEM
small intestine. Upon this surface are also the pancreatico-duodenal and (in
part) the superior mesenteric vessels. The margin of the head of the pancreas is
C-shaped, corresponding to the inner aspect of the duodenal loop, with which it
is closely related. Superiorly the margin is in contact with the pylorus and first
part of the duodenum; on the right, with the descending duodenum and the ter-
minal portion of the common bile duct ; inferiorly, with the horizontal, and on the
left, with the terminal ascending portion of the duodenum.
The lower and left portion of the head of the pancreas is hooked around behind
the superior mesenteric vessels, forming the processus uncinatus or pancreas of
Winslow (fig. 922). A groove, the pancreatic notch [incisura pancreatis], is thus
formed for the vessels. The morphology of this process is explained later under
development (fig. 958).
In the adult condition, the head of the pancreas is largely retroperitoneal.
The only portions covered by peritoneum are (1) a small area above the attach-
ment of the colon, and in relation with a pocket-like recess of the bursa omentalis,
and (2) a small area below the transverse colon, which is in relation with coils of
small intestine. The mesentery of the small intestine begins where the superior
mesenteric vessels pass downward from in front of the processus uncinatus.
The junction of the upper and left aspect of the head with the body of the
pancreas is called the neck. This is a somewhat constricted portion grooved
posteriorly by the superior mesenteric vessels, the vein here joining with the splenic
to form the portal vein (fig. 955). Anterior to the neck is the pyloric portion of
the stomach. The upper portion of the neck (together with a variable area on the
left end of the body) projects above the lesser curvature of the stomach. This
projection [tuber omentale] is related, through the lesser omentum, with a similar
tuberosity on the left lobe of the liver. The anterior aspect of the neck is covered
with peritoneum of the bursa omentalis (lesser sac), and is continuous with the
anterior surface of the body of the pancreas (fig. 922).
The body [corpus pancreatis] is the triangularly prismatic portion of the pan-
creas extending from the neck on the right to the tail on the left. Its direction is
transversely to the left and (usually) somewhat upward. It is therefore usually
placed at a somewhat higher level than the head, opposite the first lumbar verte-
bra. It presents three surfaces — anterior, posterior, and inferior — and three
borders — superior, anterior, and posterior.
Of the surfaces, the anterior [facies anterior] faces forward and somewhat
upward. It is covered with the peritoneum of the posterior wall of the bursa
omentalis (lesser sac), and forms a slightly concave area which is in contact with
the posterior surface of the stomach (figs. 904, 906). The posterior surface [f.
posterior] of the body of the pancreas is flattened and retroperitoneal. From right
to left it crosses the anterior aspect of aorta, left suprarenal body and left kidney.
The splenic vessels also run along the posterior surface, the artery, which is above,
corresponding more nearly with the superior border. The inferior surface [f.
inferior] is usually the narrowest of the three. It is covered by peritoneum (con-
tinuous with the lower layer of the transverse mesocolon) and is in contact with
the duodeno-jejunal angle medially and with coils of jejunum laterally.
Of the borders, the superior [margo superior] is related with the splenic artery
along its whole length from its origin in the coeliac, and the posterior [margo
posterior] separates posterior and inferior surfaces. The anterior border [margo
anterior] is sharp and prominent. It gives attachment to the transverse meso-
colon, whose upper layer (belonging to the lesser sac) is continuous with that on
the anterior surface of the pancreas, and whose lower layer (belonging to the
greater sac) is continuous with that on the inferior surface.
The tail of the pancreas [cauda pancreatis] is at the left extremity of the body.
It is variable in form, but usually somewhat blunted and upturned. It is almost
invariably in contact laterally with the medial aspect of the spleen, and inferiorly
with the splenic flexure of the colon. The splenic vessels often cross from above
in front of the tail of the pancreas on their way to join the spleen.
Ducts. — The pancreas has usually two ducts, the main pancreatic duct and the
accessory duct. The main pancreatic or duct of Wirsung [ductus pancreaticus;
Wirsungi] begins in the tail of the pancreas, and extends to the right within the
body of the pancreas, about midway between upper and posterior borders, but
nearer the posterior surface (figs. 922, 957). It runs a slightly sinuous course
THE PANCREAS
1195
receiving branches all along, which enter nearly at right angles. It is largest in
the head of the pancreas (diameter about 3 mm.) where it turns obliquely down-
ward. As it approaches the duodenum, it is joined by the common bile duct, the
two running side by side. They pass obliquely through the wall of the duodenum
for a distance of about 15 mm. (usually causing a fold of the mucosa, the plica
longitudinalis duodeni). They terminate finally, usually by a common aperture,
but sometimes separately, on the duodenal papilla major, as described in connec-
tion with the interior of the duodenum. The common aperture is somewhat nar-
row, but just preceding this the duct is frequently dilated, forming what is called
the ampulla of Vater.
The accessory pancreatic duct (duct of Santorini) is nearly always present
(figs. 922, 957), but variable. This duct is small, and lies within the head of the
pancreas. At its left end, it usually joins the main duct in the neck of the pan-
creas. From here it extends nearly horizontally across to the upper part of the
descending duodenum and, piercing its wall, usually ends upon the small papilla
minor, about 2 cm. above and slightly ventral to the papilla major. The relations
of the ducts are explained later under development.
Fig. 957. — The Pancreas and its Ducts, Dissected from Behind.
Duct of pancreas Accessory duct of Santorini Common bile-duct
Blood-vessels. — The pancreas receives blood chiefly from the splenic artery through its
pancreatic branches, and from the superior mesenteric and hepatic by the inferior and superior
pancreatico-duodenal arteries, which form a loop running around, below, and to the right of
its head.
The blood is returned into the portal vein by means of the splenic and superior mesenteric
veins.
Lymphatics. — ;The lymphatics terminate in numerous glands which lie near the root of the
superior mesenteric artery, above and below the neck of the pancreas. All the lymphatics
drain ultimately into the cceliac glands.
Nerves. — These are branches of the coeliac plexus which accompany the arteries entering
the gland. The main part of the coehac plexus lies behind the gland.
Minute anatomy. — In many respects, the pancreas resembles the salivary glands in struc-
ture, hence its German name 'Bauchspeicheldrtise' ('abdominal sahvary gland'). The
gland proper is racemose (or tubulo-racemose) in structure, the secreting cells characteristically
granular and 'serous' in type. The thin-walled 'intercalary ducts,' often invaginated to
form 'centroacinar' cells, are characteristic. The lobules are very loosely joined by areolar
tissue, and there is no distinct fibrous capsule around the gland. 'The most important of the
distinctive characters of the pancreas is the presence throughout the gland of numerous small
interlobular ceU-masses of varied form and size — the islets of Langerhans (fig. 959). These have
no ducts, but are richly supplied with blood-vessels. They are ductless glands of great import-
ance in sugar metabolism, and their removal or disease produces diabetes. While derived
embryologically from the same entodermal anlage which gives rise to the pancreas gland
proper, they apparently have no direct connections with it in the adult. The question as to
the possible metamorphosis of acini into islets, or vice versa, under certain conditions (e. g.,
hunger) in the adult has been much disputed. Bensley, however, has recently presented strong
evidence against this view.
Development of the pancreas. — The pancreas has its origin in three entodermal buds, one
of which (the dorsal anlage) grows from the dorsal portion of the duodenum, the other two
(ventral anlages) from either side of the bile-duct. Of the two latter, only that growing from
the right side of the bile-duct needs further consideration, as the other soon disappears. The
dorsal anlage grows at first more rapidly than the ventral, which arises from the bile-duct. In
their further growth both the dorsal and ventral anlages become lobed, these lobes dividing
further to form the ducts and the alveoh of the gland. By about the end of the second month
the distal end of the ventral portion comes in contact with the dorsal portion at a short distance
1196
DIGESTIVE SYSTEM
from the latter's connection with the duodenum. A fusion of the two portions thus takes
place in this region, and at the same time there is estabhshed by anastomosis a connection be-
tween the terminal branches of the main duct of the dorsal portion — duct of Santorini — and the
branches of the main duct of the ventral portion — the duct of Wirsung. With further devel-
opment the duct of Wirsung develops into the main pancreatic duct, the duct of the dorsal
Fig. 958.-
-DiAGEAM Showing the Relations of the Pancreas to the Primitive Mesen-
tery. (Poirier-Charpy.)
Aorta
Left gastric art.
Dorsal mesogastrium (pr.rtion
becoming adherent)
Tail of pancreas
Splenic art.
Right gastro-epiploic
art.
Superior pancre-
atico-duodenal
art.
Head of pancreas
Mesentery at duodeno-jejunal fle
''Processus uncinatus
Body of pancreas
Dorsal mesogastriu
(portion fusing w
transverse meso-
colon)
portion (duct of Santorini) either losing its connection with the duodenum or remaining as the
accessory pancreatic duct.
Thus of the adult gland, only the lower portion of the head is derived from the primitive
ventral anlage, although the duct of the latter drains nearly the entire adult gland. The upper
part of the head of the pancreas, and all of the body and tail are derived from the dorsal anlage;
although most of its duct joins with the duct of Wirsung to form the main pancreatic duct,
only a small part persisting as the accessory duct of Santorini.
Fig. 959. — Section op Human Pancreas, Magnified, Showing Several Islets of
Langerhans. (Radasch.) a, Interlobular connective tissue, containing an interlobular duct,
c, b. Capillary, d, Interlobular duct, e, Alveoli. /, Islet of Langerhans.
During the early stages in the development of the pancreas the entodermal buds from
which it forms grow into the mesoduodenum, and later the dorsal mesogastrium. With the
rotation of the stomach and the consequent change in the position of the mesogastrium and its
partial fusion with the abdominal wall, the pancreas assumes a retroperitoneal position. This
is illustrated by fig. 958. The head of the pancreas is involved in the rotation of the primitive
REFERENCES FOR DIGESTIVE SYSTEM 1197
intestinal loop counter-clockwise around the superior mesenteric artery. This accounts for
the position and the hook-like form of the processus uncinatus. Following this rotation, the
duodenum and the head of .the pancreas become pressed backward against the posterior ab-
dominal wall, where they become adherent, with fusion and obliteration of the primitive peri-
toneum. The body of the pancreas, extending mto the dorsal mesogastrium (fig. 900), is simi-
larly caught in the pouch-like downgrowth of the latter to form the bursa omentahs (lesser sac),
and is thereby carried over to the left side. When the posterior layer of the primitive bursa
fold becomes fused with the posterior abdominal wall, the enclosed pancreas is likewise fixed
and becomes retroperitoneal. Of these obUterated peritoneal layers of the embryo, only certain
layers of fascia remain as their representatives in the adult. From the lower aspect of the pan-
creas downward, the posterior layer of the bursa fold becomes fused with the transverse meso-
colon, so that in the adult the latter appears to arise from the anterior border of the pancreas
(fig. 904).
Variations. — Aside from minor fluctuations in size and form, the variations of the pancreas
are chiefly congenital and of embryonic origin. Cases of accessory or supernumerary pancreas are
not rare. They are usually of small size and have separate ducts. They may occur along the
wall of the duodenum, or even in the stomach or jejunum. They are perhaps m some way con-
nected with the numerous intestinal diverticula which occur in the embryo. Divided pancreas
differ from the accessory in that a mass of the pancreas becomes separated from the main gland,
connected only by a duct. This occurs oftenest in the region of the tail (sometimes extending
into the spleen) or of the processus uncinatus, forming what is termed a 'lesser pancreas.'
Sometimes a ring of glandular tissue from the head of the pancreas surrounds the descending
duodenum, forming an annular pancreas. Variations in the direction of the body are numerous;
it may be horizontal, ascending or bent in various ways. These are doubtless congenital vari-
ations, as similar types have been described in the foetus (Jackson). It has been experimentally
demonstrated that varying degrees of distention of the stomach and intestines affect profoundly
the form of the body of the pancreas. When the stomach alone is distended, the pancreas is
flattened antero-posteriorly, the inferior surface being practically obliterated. When both
stomach and intestines are distended, the pancreas is flattened from above downward, and
e.xtends forward hke a shelf, the posterior surface being much reduced (Jackson). Numerous
variations in the ducts are easily understood from their complicated development. The acces-
sory duct (of Satorini) is in the foetus as large as the main duct (of Wirsung), the preponderance
of the latter being established later. The accessory duct in the adult may be larger than usual,
and retain its primitive drainage, or even drain the entire gland in rare cases where the duct
of Wirsung is absent. Or the accessory duct may be rudimentary or (rarely) absent. Similar
variations occur in the main duct of Wirsung. Rarely the pancreas may open into the duo-
denum by three ducts, probably representing three embryonic anlages. Abnormalities of the
pancreas are often associated with duodenal diverticula.
Comparative. — The pancreas, like the liver, is constant throughout the vertebrates. It
always arises by budding off from the endodermal epithelium of the intestine, closely associated
with the Uver. There is typically a triple anlage (rarely multiple, which is perhaps the ancestral
type), with one dorsal and two ventral outgrowths. These fuse and form the adult pancreas
in a variety of ways. In many of the fishes, the pancreas is very small, diffuse and incon-
spicuous, sometimes embedded in the liver or intestinal wall. Of the three primitive ducts,
usually only two persist (as in man), but often only one, or all three (in birds). All three types
occur in mammals. The islets of Langerhans arise from the epithelial pancreas anlage, and ap-
pear to be constantly present, even in the lowest vertebrates. Laguesse even considers that
phylogeneticaUy they form the most primitive part of the pancreas, but this is doubtful.
References for digestive system. — General and Co7nparative: Quain's Anat-
omy, 11th ecL; Poirier-Charpy, Traits d'anatomie; Rauber-Kopsch, Lehrbuch
der Anatomie, 9te Aufl.; Oppel, Mikroskopische Anatomie, Bd. 1-3; also 'Ver-
dauungsapparat ' in Merkel and Bonnet's 'Ergebnisse'; Wiedersheim, Bau des
Menschen. Topography: (adult) Merkel, Topographische Anatomie; (develop-
mental) Jackson, Anat. Rec, vol. 3. Development: Keibel and Mall's Manual.
Teeth: Tomes, Dental Anatomy. Tonsils: (lingual) Jurisch, Anatomische,
Hefte, Bd. 47; (pharyngeal) Symington, Brit. Med. Jour. (Oct., 1910); (palatine)
Killian, Archiv f. LaryngoL, Bd. 7. (Esophagus: Goetsch, Amer. Jour. Anat.,
vol. 10. Stomach: (structure), Bensley, Buck's Ref. Handb. Med. Sc, vol.
7 (1904); (form) Cunningham, Trans Royal Soc. Edinb., vol. 45; (radiography)
Cole, Archives Roentgen Rays, 1911; also Journal Amer. Med. Assn., vol. 59.
Duodenum: (diverticula), Baldwin, Anat. Rec, vol. 5. Vermiform process: Berry
and Lack, Jour. Anat. and Phys., vol. 40. Rectum: Symington, Jour. Anat.
and Phys., vol. 46. Liver: Mall, Amer. Jour. Anat., vol. 5. Pancreas: (islets)
Bensley, Amer. Jour. Anat., vol. 12; (ducts) Baldwin, Anat. Rec, vol. 5.
SECTION X
THE RESPIRATOEY SYSTEM
Revised fob the Fifth Edition
By R. J. TERRY, A.B., M.D.,
PHOFESSOR OF ANATOMY IN WASHINGTON UNIVERSITr
R
ESPIRATION consists in the absorption by the organism of oxygen and
the discharge of a waste-product, carbon dioxide.
Among unicellular animals the oxygen is taken up directly from the medium — water or air —
in which they Hve, and the carbon dioxide given off into it. With the cells which make up the
body of higher animals the principle is the same, but the interchange of gases is indirect. The
blood stands as an intermediate element between the cells of the body and the medium inhabited
Fig. 960. — Dissection of a Male Negro, Age 43 Years, to Show the Organs of Res-
piration in Situ.
Frontal sinus'
Nasal cavityj
Thyreoid gland
Left bronchus
by the animals, and serves as a carrier of the gases between them. Moreover, special organs
are provided for the rapid interchange between air and blood, which constitute the so-caUed
respiratory system.
The respiratory system of air-breathing vertebrates consists of tubular and
cavernous organs constructed so as to permit of the atmospheric air reaching the
1199
1200
THE RESPIRATORY SYSTEM
blood circulating in the body. The essential organs in the system are the paired
lungs located in the thoracic cavity. Air is carried to and from the lungs by the
trachea and bronchi, and these simple transmitting tubes are in turn put into
communication with the exterior by the mediation of other organs. The latter
are, however, specially constructed in adaptation to other functions in addition
to those relating to respiration: the larynx for the production of the voice, the
pharynx and mouth in connection with alimentation, the nasal cavity and external
nose functioning in the sense of smell. (For the description of the mouth and
pharynx see Section IX; for the olfactory organ see Section VIII.)
The organs of circulation are always adapted to the form of the respiratory apparatus, and
among all higher animals a connection is established between heart and lungs by the pulmonary
artery, which carries venous blood to the latter, and by the pulmonary veins, which convey
arterial blood from the lungs to the heart, whence the aorta takes it into the general circulation.
In their origin and development the respiratory organs are closely associated with or
differentiated from the beginnings of the digestive apparatus. Thus the processes of the early
development of the nasal cavity and mouth are interdependent; the origin of the greater
part of the larynx, the trachea and lungs is by ventral outgrowth of the entodermal canal.
THE NOSE
The external nose [nasus externus] (fig. 961), shaped like a triangular pyramid,
is formed of a bony and cartilaginous framework covered by muscles and the in-
tegument of the face externally and lined within by periosteal and perichondral
layers overspread by mucous membrane. At the forehead, between the eyes, is
Fig. 961. — The Left Side of the External Nose, showing its Cartilages, etc.
Nasal bone
Nasal process of the maxilla
Lateral nasal cartilage
Nasal septal cartilage
Lateral cms of greater alar
cartilage
Medial crus of greater alar
cartilage
Sesamoid cartilages
Fibrous tissue
Lesser alar cartilages
Cellular tissue forming ala
the root of the nose [radix nasi], and from this, extending inferiorly and anteriorly,
is a rounded ventral border, the dorsum of the nose [dorsum nasi], which may be
either straight, convex, or concave, and which ends inferiorly at the apex of the
nose [apex nasi]. The superior part of the dorsum is known as the bridge. Inferi-
only, overhanging the upper lip, is the base of the nose [basis nasi] which presents
two orifices, the nares or nostrils, separated from one another by the inferior mov-
able part of the nasal septum [septum mobile nasi].
The nostril of man is remarkable on account of its position, facing as it does almost directly
downward. It is oval in form, with the long axis directed antero-posteriorly, or approximately
so, in Europeans. The size of the nostril is under the control of muscles (see p. 334) and may
be dilated or constricted by their action.
The sides of the nose slope from the dorsum laterally and posteriorly, and
THE NOSE
1201
below ferminate on each side in the margin of the nose [margo nasi]; posteriorly
and interiorly the sides are expanded and more convex, forming the alae nasi.
Each of these is separated from the rest of the lateral surface by a sulcus, and the
inferior free margin of each bounds a naris laterally.
Three types of nose, distinguished by differences in the proportion of breadth and length are
recognised by anthropologists: the leptorrhine or long, high nose; the platyrrhine or short, low
nose; the mesorrhine, a form intermediate between the other two. The leptorrhine type
prevails among white races, the platyrrhine in the blaeli peoples and the mesorrhine in the
red and yellow races.
Fig. 962. — Anterior View op the External Nose, showing its Cartilages, etc.
Lacrimal groove — 7 —
Groove on anterior border of
nasal septal cartilage
jid cartilages
Lesser alar cartilages
Cellular tissue of ala
Nasal process of the maxilla
Lateral nasal cartilage
Lateral crus of greater
alar cartilage
The framework of the external nose is formed partly of bone and partly of hyaline cartilage
The bones, which form only the smaller superior part, are the two nasal bones and the fronta
processes and anterior nasal spines of the two maxillae (pp. 87, 108).
The nasal cartilages [cartilagines nasi] are located about the piriform aperture
and constitute the larger part of the nasal framework. There are five principal
cartilages: superiorly, the two lateral nasal cartilages, interiorly the two greater
Fig. 963. — Inferior View op the External Nose, showing its Cartilages, etc.
ITasal septal cartilage -
Medial crus of greate:
alar cartilage
Nasal septal cartilage
Cellular tissue of ala
alar cartilages, and the single median nasal septal cartilage. Beides these there
are the lesser alar cartilages, the sesamoid cartilages, and the vomero-nasal carti-
lages of Jacobson. The lateral nasal cartilages [cartilagines nasi laterales] are
triangular and nearly flat lateral e.xpansions of the septal cartilage, placed one on
each side of the nose just inferior to the nasal bone. Each presents an inner and
an outer surface and three margins. The medial margin is continuous in its supe-
rior third with the anterior margin of the septal cartilage, and through this with its
1202
THE RESPIRATORY SYSTEM
fellow of the opposite side, but it is separated inferiorly from the septal cartilage
by a narrow cleft. The curved supero-lateral margin is firmly attached b}^ strong
fibrous tissue to the nasal bone and frontal process of the maxilla, and underlies
these bones for a considerable distance, especially near the septum. The inferior
margin is connected by fibrous tissue to the greater alar cartilage. The greater
alar cartilages [cartilagines alares majores], variable in form, are situated one on
each side of the apex of the nose (figs. 961, 963). Each is thin, pliant, curved,
and so folded that it forms a medial and a lateral crus, which bound and tend to
hold open each naris. The medial crus [crus mediale] is loosely attached to its
fellow of the opposite side, the two being situated inferior to the septal cartilage
and forming the tip of the nose and the inferior part of the mobile septum. The
lateral crus [crus laterale] joins the medial crus at the apex of the nose; it is
somewhat oval in shape, and curves dorsally in the superior and anterior portion
of the ala. It is connected posteriorly to the nasal margin of the maxilla by a
broad mass of dense fibrous and fatty tissue, and helps to maintain the contour
of this part of the nose.
Fig. 964. — Medial Wall of the Nasal Cavity, the Mucotts Membrane Being Removed.
The dotted line indicates the course of the incisive canal.
Nasal bone Frontal i
Lateral nasal
Groove between septal
and lateral nasal
cartilage
Thickened bord'
resting upon anterior
papilla Septal cartilage
Orifice of tuba auditiva
Soft palate
The angle formed by the crura (angulis pinnahs) varies with the shape of the nose; it aver-
ages 30°. The greater and lesser alar cartilages together form an incomplete ring arotmd the
naris.
A variable number of small cartilages, lesser alar cartilages [cartilagines alares minores]
are found in the fibrous tissue of the ala, and in the interval between each greater alar and
lateral cartilage occur one or more small plates, sesamoid cartilages [cartilagines sesamoidese]
(fig. 961).
The septal cartilage [cartilago septi nasi] (fig. 964) forms the anterior part of the
septum. It is quadrilateral in shape and fits into the triangular interval of the
bony septum. Its antero-superior margin in its upper part meets the inter-
nasal suture. Inferior to the nasal bone it presents a shallow groove which gradu-
ally narrows toward the tip of the nose, and whose borders are continuous supe-
riorly with the lateral nasal cartilages, but are separated from their inferior two-
thirds by a narrow slit. The most inferior part of this margin of the septal car-
tilage is placed between the greater alar cartilages. The antero-inferior margin
extends backward from the rounded anterior angle to the anterior nasal spine.
Inferiorly it is attached to the medial crus of the greater alar cartilage and to the
THE NASAL CAVITY
1203
mobile nasal septum. The postero-superior margin is attached to the perpen-
dicular plate of the ethmoid, and the postero-inferior margin joins the vomer and
the ventral part of the nasal crest of the maxilla, the cartilage broadening out to
obtain a wide though lax attachment to the nasal spine.
The shape of the septal cartilage varies with the extent of the ossification of the bony
septum. Even in the adult a strip of cartilage may extend for a varying distance postero-
superiorly between the vomer and perpendicular plate of the ethmoid, sometimes reaching the
body of the sphenoid; it is known as the sphenoidal process of the septal cartilage [proc-
essus sphenoidalis septi cartilaginei]. The vomero-nasal cartilage [cartilago vomero-nasalis
Jacobsoni*] is a narrow strip of cartilage firmly attached to each side of the septal cartilage,
where this joins the anterior portion of the vomer.
Muscles. — The muscles are grouped according to function as dilators and
contractors, the latter being comparatively feeble in their action. They are
described on p. 334.
The skin covering the external nose is thin and freely movable upon the sub-
jacent parts, except at the tip and over the cartilages, where it is much thicker,
Fig. 965. — Obliqite Section passing through the Nasal Cavity just in Front of the
CHOANiE. (Seen from behind.)
Crista galli
Front wall of left ' •>!/\
sphenoidal sinub
with orifice belov
Orifice of righl
sphenoidal sinus
Superior nasal concha
Middle nasal concha'
Upper surface of.
soft palate
more adherent, and furnished with numerous exceptionally large sebaceous glands.
At the nares it is reflected into the nasal cavity, where it passes into the mucous
membrane. The hairs on the skin of the nose are very fine, except in the nares,
where they may be strongly developed.
Vessels and nerves. — The arteries of the external nose are derived from the external maxil-
lary (facial) artery (pp. 540 and 541), the ophthalmic artery (p. 554), and the infra-orbital
artery (p. 549). The veins terminate in the anterior facial vein and the ophthalmic vein (p.
644). The lymphatics pass to the submaxillary lymphatic nodes (p. 712). The motor nerves
are branches of the facial (p. 946). The sensory nerves are derived from the trigeminal through
the frontal and naso-cihary branches of the ophthalmic (p. 936) and infra-orbital branch of the
maxiUary (p. 939).
The nasal cavity [cavum nasi] is the ample space situated between the floor of
the cranium and the roof of the mouth extending forward into the external nose
and backward to the nasal part of the pharynx. With the exception of the
inferior part of the nose its walls are of bone as already described (pp. 110, 112).
The cartilages and membranes of the nose complete the boundaries anteriorly.
Here the cavity opens to the exterior by the nares. At the back a free communi-
*Jaeobson: Danish anatomist. B. 17S3, D. 1843.
1204
THE RESPIRATORY SYSTEM
cation with the pharynx is established through the paired ehoana;. Furthermore
accessory nasal cavities, the paranasal sinuses, open into the cavum nasi. The
walls of the nasal cavity are covered with periosteum and mucosa, the latter pre-
senting important differences in the respiratory and olfactory regions. The
organ of smell, included in the nasal cavity, is described on p. 1049.
The cavum nasi is divided into right and left symmetrical parts, called the nasal
fossae, by the septum of the nose [septum nasi]. The latter is supported by a
framework composed of the osseous septum [septum nasi osseum] posteriorly, and
the cartilaginous septum [septum cartilagineum] anteriorly. Antero-inferiorly,
the small movable part of the septum is also called the membranous septum
[septum membranaceum].
The nasal septum is almost always straight in primitive races and Caucasian
children; but in a large proportion of Caucasian adults it is deflected to one side or
the other.
Fig. 966. — Sagittal Section through the Facial Part op the Head and the Bodies
OP THE UPPER THREE Cervical Vertebrae. The section lies to the right of the median
plane. The nasal septum has been removed. (Rauber-Kopsch.)
Cribriform plate
Spheno-ethmoidal ,
Hypophysis
Dorsum sellae
Choanal arch ..
Nasopharyngeal -
meatus
Pharyngeal tonsil
Torus tubarius
Levator cushion
Anterior lip
of tubal aperture
Salpingopharyn
goal fold
Uvula
Foramen cgecum
Palatopharyngeal fold
Incisive canal
Upper lip
Vestibulum oris
Mouth cavity proper
Lower lip
Sublingual mucosa
Hyoid bone
Mental spme
In the septum, upon each side, just superior to the nasal spines of the maxillas, there is
frequently a minute opening leading superiorly and posteriorly and ending blindly. This cavity
is closely related to the vomero-nasal cartilage and is a rudimentary representative of the vomero-
nasal organ (of Jacobson) [organon vomero-nasale], which in some animals is well developed
and receives a branch of the olfactory nerve. On the floor of the nasal cavity about 2 cm. from
the posterior margin of the naris and near the nasal septum a small depression, the nasopalatine
recess, is often seen. This is the mouth of the incisive duct [ductus incisivus] which leads into
the incisive canal for a greater or less distance and may even extend to the mouth, where its
termination is marked by the incisive papilla. The incisive duct indicates the position of a
foramen which in the embryo connected the mouth and nose.
The naris leads upward into the vestibule of the nose [vestibulum nasi], the
small cavity within the compass of the greater alar cartilage. Its walls are lined
with skin beset with the large hairs called vibrissas and containing many seba-
ceous glands. The vibrissae serve to protect the nasal cavity from the entrance of
foreign matter. On the lateral wall, the vestibule is marked off from the rest of
the nasal cavity by a cUstinct ridge, the limen nasi, corresponding to the superior
margin of the greater alar cartilage. On the lateral wall of the cavity within the
limen nasi are three antero-posterior ridges, the superior, middle, and inferior
I
THE NASAL MEATUSES
1205
conchae (fig. 966). These have a bony framework (described on pp. 83, 110)
and are covered by the mucous membrane of the nose. The conchje are not
parallel to one another but converge in a backward direction. The superior nasal
concha [concha nasaUs superior] is the smallest, projects only slightly medialward
and downward from the upper, posterior part of the lateral wall, overhanging the
groove called superior meatus of the nose. The middle nasal concha [concha
nasalis media] is extensive, reaching from the fore part to the posterior confines of
the lateral wall. Its free margin is nearly vertical in its anterior one-fourth, hori-
zontal and laterally rolled in the rest of its extent. Under cover of this concha
runs the middle meatus. The inferior nasal concha, [concha nasalis inferior] is the
longest, has a lateral attached and an inferior laterally rolled free margin running
near the floor of the nasal cavity. Beneath it lies the inferior meatus.
Meatuses of the nose [meatus nasi] (figs. 966, 968). The name common
meatus of the nose [meatus nasi communis] is given to that part of the nasal cav-
FiG. 967. — Frontal Section through the Facial Portion op the Head of a White
Man, Age 28 Years.
lofundibulum -
Ethmoidal cell —
Middle meatus
Maxillary sinus
Inferior meatus
ity which lies between the septum nasi and the nasal conchas and stretches from
floor to roof. The three meatuses under cover of the nasal conchae have been
mentioned. These passages all communicate freely with the common meatus,
extend antero- posteriorly and have a greater capacity in front than behind.
The superior meatus [meatus nasi superior] is the smallest of the three. Into
it open the posterior ethmoidal cells by one or two small foramina. The spheno-
palatine foramen, which communicates with the meatus in the dry skull, is entirely
covered up bj^ mucous membrane. The middle meatus [meatus nasi medius]
is a much larger passage. Upon its lateral wall is a rounded eminence, the
ethmoidal bulla, caused by the middle ethmoidal cells and perforated by the open-
ing into them. Inferior to this is a deep curved groove, the hiatus semilunaris,
which is continued superiorly by the ethmoidal infundibulum [infundibulum eth-
moidale] into the frontal sinus. It also receives the openings of the anterior eth-
moidal cells and the maxillary sinus. The inferior meatus [meatus nasi inferior]
is the longest of the three. Upon its lateral wall, just inferior to the attachment
of the inferior concha, is the slit-like opening of the naso-lacrimal duct [ductus
naso-lacrimalis], around the opening of which the mucous membrane forms a valve,
the plica lacrimalis (Hasneri).
Recent investigation of the nasal conchae indicates that two upper conchae (concha nasalis
superior and concha nasalis suprema [Santorini]) are more often present than one. Three upper
conchae are not rare.
1206 THE RESPIRATORY SYSTEM
The attached margins of the middle and inferior conchse are both arched, the convexities
being upward. The highest point of the convexity is near the middle of the attached margin
in the inferior concha and lies about 17 mm. above the floor of the nose; the anterior end of this
concha is approximately 25-35 mm. distant from the apex of the nose (KaUius).
From the anterior end of the middle concha a slight variable elevation of the mucous mem-
brane of the nose extends forward and downward. This, the agger nasi, which is regarded as
of constant occurrence in the new-born, appears to be a rudimentary representative of the naso-
turbinale of mammals (Schwalbe).
Below the agger nasi a broad depression of the lateral wall, the atrium meatus medii, leads
posteriorly beneath the anterior free margin of the middle concha to the middle meatus, while
above the agger, between it and the roof of the nasal cavity, the slight olfactory groove [sulcus
olfactorius] ascends upon the lateral wall to the olfactory region. In this region, above the
superior concha, is a corner of the nasal cavity of interest on account of the sphenoidal sinus
opening into it: this is the spheno-ethmoidal recess [recessus spheno-ethmoidalis].
Variation in the number and position of the openings into the meatuses is of practical inter-
est. An accessory mouth of the maxillary sinus is rather frequently met with, especially in old
people; it lies most commonly behind the hiatus semilunaris. The infundibulum ethmoidale
may open independently of the hiatus semilunaris at a spot beneath the anterior end of the at-
tached margin of the middle concha. In the inferior meatus the mouth of the naso-laorimal
duct, which is found 22-25 mm. behind the posterior margin of the nares, may have one or more
accessory openings associated with it; these are perforations of the plica lacrimalis.
Communication between the nasal cavity and the nasal part of the pharynx
is effected by means of the paired posterior apertures [choanse]. These are oval
in form, their height greater than their width. They are located at either side
of the posterior edge of the nasal septum and are limited above by the body of
the sphenoid, below by the line of junction of the hard and soft palate.
From the plane of the choana forward a rather constricted portion of the nasal cavity ex-
tends for a short distance to reach the level of the posterior ends of the middle and inferior con-
chse. Into this region, which is known as the meatus naso-pharyngeus, open posteriorly the
superior, middle and inferior meatuses. Posterior rhinoscopic examination reveals the choanse,
the naso-pharyngeal meatus, the posterior extremities of the three conchse and of the meatuses
beneath them.
Dimensions of the nasal cavity. — The length of the floor averages approximately 40 mm.,
the width 32 mm., the height from floor to lamina cribrosa 47 mm. The length of the lateral
wall is about 63 mm. The choana measures 29.8 mm. high and 15.5 mm. broad. The area of
the two nares is 2 sq. cm.
Paranasal sinuses [sinus paranasales] (figs. 964-968). — The location, form and
relations of the bony-walled spaces connected with the nasal cavity have been
fully described in the section on Osteology. The conditions observed in the
living subject differ in certain respects from those present in the macerated skull;
the spaces are lined by a mucous membrane which, though affecting but slightly
the form of these chambers, modifies considerably the openings by which they
communicate with the nasal cavity. These openings permit the entrance and
exit of air and to some extent the escape of fluids which may accumulate in the
sinuses. While the significance of these spaces is not at present clear it is, how-
ever, certain that they function in lightening the weight of the skull, and probable
that indirectly they serve in connection with the sense of smell.
Maxillary sinus (of Highmore*) [sinus maxillaris Highmori] (figs. 965, 966, 967).
Entrance into the maxillary sinus is offered through the middle part of the hiatus
semilunaris, that is, the deep, narrow notch between the ethmoidal bulla and un-
cinate process of the ethmoid. Viewed from within the sinus, the opening appears
as an oval window in the upper part of the medial wall — a position unfavourable
to the discharge of matter, when the body is in the upright posture. An accessory
opening, situated behind the normal ostium, is present in about 10 per cent, of
cases.
Measurements of 90 specimens of the adult sinus maxiUaris gave as the average the following
(Schaeffer) :
Dorsosuperior diagonal 38 mm.
Ventrosuperior diagonal 38.5 mm.
Superoinferior 33 mm.
Ventrodorsal ". 34 mm.
Mediolateral 23 mm.
Increase in capacity of the maxillary sinus is sometimes observed as the result of more or
less extensive excavation of the bony processes of the maxilla adjacent to it, viz. : the alveolar,
palatal, frontal and zygomatic. On the other hand narrowing of the cavity is encountered,
* Highmore, Nathaniel: English physician. B. 1613, D. 1685.
THE NASAL CAVITY
1207
caused by unusually thick walls of bone, bulging inward of the facial or nasal walls, and through
retention of teeth. Incomplete division into two parts through the presence of a septum has
several times been observed. Communication with ethmoidal cells and with the cavity of the
orbital process of the palate bone sometimes exists.
Frontal sinus [sinus frontalis] (figs. 78, 964, 968). — The paired frontal sinuses,
separated from each other by a bony septum, have in general the shape of a three-
sided pyramid with the base below and the apex formed above in the frontal
squama. In the base near the septum is located the superior aperture of the
infundibulum which, it will be recalled, opens inferiorly at the anterior extremity
of the hiatus semilunaris.
The form and size of the frontal sinuses are exceedingly variable. They may extend back-
ward in the orbital part of the frontal bone as far as the suture between it and the small wing of
the sphenoid; laterally into the zygomatic process; upward toward the coronal suture. The
capacity of the sinus, as determined in a small number of cases, varied from 3 to 7.8 ccm.
(Brvihl). Asymmetry of the septum is frequently observed. Absence of one of the sinuses is
not a rare condition; absence of both is occasionally encountered.
Fig. 968. — ^Left Nasal Cavity. (Rauber-Kopsch.)
Opening of
sphe-
Hypophysis noidal sinus
Choanal arch
Pharyngeal tonsil —
Torus tubanus"
Levator cushion
Anterior lip of
tubal aperture
Salpingo-
pharyngeal
fold
w Naso-pharyngeal
! meatus Sound
Uvula in naso-
lacrimal „
canal •- S
Ethmoidal cells [cellulse ethmoidales] (figs- 965, 968). — The openings of the
anterior cells into the semilunar hiatus and infundibulum, and of the posterior
cells at the superior meatus have already been described.
Communications between the ethmoidal cells and the sphenoidal and maxillary sinuses are
not rare; the cavity in the orbital process of the palate bone may open into the posterior cells.
In old age, foramina through the lamina papyracea may appear, leading to the introduction of
air into the orbit.
Sphenoidal sinus [sinus sphenoidalis] (figs. 964, 965, 966). — The apertures of
the paired sphenoidal sinuses are, on account of the mucous membrane covering,
much smaller than they are in the dried skull. They lie in the anterior wall near
the septum, nearer the roof than the floor, and open into the spheno-ethmoidal
recess.
Extension of the sphenoidal sinuses backward and also into neighbouring processes, and
communication with ethmoidal cells and with the small cavity of the orbital process of the palate
are not unusual. The capacity of the sinus varies between 1 and 4.2 ccm. (Briihl).
Functions of the paranasal sinuses. — Various functions have been attributed to the sinuses
near the nose, none of which is entirely satisfying. Medieval anatomists proposed that these
cavities contributed to the resonance of the voice, or that they supplied the mucus by which the
nasal cavity is kept moist. Lightening the skull, warming the inspired air and taking part,
indirectly, in the sense of smell are functions assigned by anatomists of later times.
The mucous membrane of the nose [membrana mucosa nasi]. — The nasal cav-
ity is completely lined with mucous membrane, which inferiorly, at the limen nasi
blends with the skin covering the walls of the vestibule (p. 1204). Posteriorly
it joins the mucous membrane of the pharynx and palate. It covers some of the
1208
THE RESPIRATORY SYSTEM
openings which are seen in the bony walls; those apertures, however, which
lead into the paranasal-sinuses and into the naso-lacrimal duct remain patent,
although as already stated the bony openings are much reduced in size.
In the nasal cavity the bright rose-red vascular mucous membrane is tightly bound to the
periosteum and perichondrium, and is covered with a cihated columnar epithelium. Numerous
large mucous nasal glands [glandules nasales] pour their more or less watery secretion over the
entire surface. A very considerable venous plexus is found in many parts of the nasal mucosa.
Over the inferior concha and to a less extent in the mucosa of the middle and superior conchEB,
it forms the cavernous plexuses of the conchse [plexus cavernosi concharum] contributing to
build up about these bodies a true erectile tissue. The thickness which these glands and venous
plexuses give to the mucous membrane of the conchoe causes the marked increase in size of
these bodies over that of their bony supports. The region covered by the mucous membrane
just described forms the greater part of the nasal cavity, and is loiowTi as the respiratory region
[regio respiratoria]. The mucous membrane of a small area over the superior concha and the
adjacent septal wall (fig. 969) has a somewhat different structure. In this area the olfactory
nerves are distributed, whence it is known as the olfactory region [regiojolfactoria] and its mucous
membrane, compared with that of the respiratory region, is less vascular, yellow or yellowish-
brown in colour, and covered by a non-ciliated epitheUum. Its cells, specially modified, some
of which are directly connected with the olfactory nerve, form the olfactory organ [organon
olfactus]. Small mucous olfactory glands [glanduloe olfactoria;] occur in the region. The
mucous membrane which lines the paranasal sinuses throughout is a continuation of the nasal
mucosa; it is, however, paler, less vascular, somewhat thinner, and more loosely attached to
the bones. Mucous glands are numerous.
The waving of the ciha in the nasal cavity is such as to sweep foreign matter toward the
choanje; in the paranasal sinuses, toward the nasal cavity.
Fig. 969. — Diagram of the Distribution of the Nerves in the Nasal Cavity. (Poirier
and Charpy.)
The olfactory area is represented by dots.
Posterior superior nasal
Posterior su-
Anterior perior nasal
ethmoid ant pal
Vessels and nerves. — The arteries of the nasal cavity are the spheno-palatine artery from
the internal maxillary which, through its posterior lateral nasal branches, supplies the middle
and inferior conchfe (p. 549), the anterior and posterior ethmoidal arteries from the ophthalmic
(p. 553), the descending palatine artery from the internal maxiUary (p. 549), and the superior
labial branch of the external ma.xiUary to the vestibule. The venous plexuses of the mucous
membrane are drained posteriorly by the spheno-palatine to join the pterygoid plexus, superiorlj
by the anterior and posterior ethmoidal veins to join the superior ophthalmic vein, and ante-
riorly by small branches to join the facial. The lymphatics form a weU-developed plexus which
is said to communicate indirectly, through the lymphatics surrounding the olfactory nerves,
with the subdural and subarachnoid spaces. Posteriorly two or more well-developed trunks
communicate with the pharyngeal lymphatics, and anteriorly the nasal lymphatics join with
the lymphatics of the face. The olfactory nerves pass through the cribriform plate of the
ethmoid bone and are distributed to the olfactory area (p. 929). The trigeminal nerve furnishes
the following branches to the nasal cavity: — branches from the naso-ciliary branch of the oph-
thalmic nerve ; the Vidian nerve ; the posterior superior and posterior inferior nasal and the ante-
rior palatine from the spheno-palatine ganglion (p. 962); the anterior superior alveolar from the
infra-orbital division of the maxillary nerve (p. 938).
The development of the nose. — The nasal cavity malves its appearance as a depression of
the ectoderm on either side of the median line, immediately in front of the oral fossa, with
which the depressions are at first continuous. Later, by the union of the maxillary and globular
processes (see p. 18), the depressions are separated from the anterior part of the oral fossa, and
this separation is continued by the formation of the palatal processes of the maxillas and palatine
bones, so that finally the nasal cavities communicate posteriorly only with the pharynx.
The cartilage which forms the lateral walls of the nasal fossas is at first quite smooth, but
later it becomes eroded by absorption, whereby the nasal concha; are formed. The erosion also
extends into the ethmoid bone, forming the ethmoidal cells, and into the neighbouring bones
to form the frontal, sphenoidal, and maxillarjf sinuses.
CARTILAGES OF THE LARYNX
THE LARYNX
1209
The larynx (figs. 960, 970, 971,), is a tubular organ, the framework of which is
made of cartilages joined together and of elastic membranes. Its inner surface
is covered by mucosa. From the membranes are formed a pair of vocal folds
which, by the passage of air through the larynx, are thrown into vibration and so
function in the generation of sound. These folds are affected in respect to their
Fig. 970. — View of Interior op Larynx as seen from above during Inspiration.
"Base of tongue
Median glo
Epiglottis
Tubercle of epiglotti
Ventricular fold
Ary-epiglottic fold
Cuneiform tubercle
Corniculate tubercle
Arytenoid commissure
Pharynx
tension and in their mutual relation by the actions of a system of laryngeal
muscles under the control of the vagus nerve and are made thereby, on the one
hand, to produce those modifications of the sound involved in the voice and on
the other hand to regulate the amount of air passing through the cavity of the
larynx. The latter communicates above with the pharynx by means of the
opening called the laryngeal aperture, and below with the cavity of the trachea.
Figure 970 shows the laiyngeal aperture with its boundaries, the epiglottis and
Fig. 971. — View of Interior of Larynx as seen from above during Vocalisation.
Base of tongue
Median glosso-epiglottic fold
Ventricular fold
Vocal fold
Piriform recess
Vocal process.
Epiglottis
Tubercle of epiglottis
Ventricle
Ary-epiglottic fold
the aryepiglottic folds ; also the cavity of the larynx where, on the walls right
and left, appear the ventricular and vocal folds with the chink called rima glot-
tidis separating them.
The position of the larynx and some of its important parts can be well seen in
a median section (fig. 972).
THE CARTILAGES OF THE LARYNX
The number of cartilages entering into the framework of the larj^nx is nine,
three of which are single and the rest in pairs. Their forms and positions are
shown in fig. 973.
1210
THE RESPIRATORY SYSTEM
The cricoid cartilage [cartilago cricoidea] (figs. 973, 974, 975, 978), single, has
been compared in its shape to a signet ring. Its position is at the lower end of
the larynx, where it is connected with the first ring of the trachea. Posteriorly
the cricoid cartilage expands into a broad lamina [lamina cartilaginis cricoidese]
which enters into the posterior boundary of the laryngeal cavity, while laterally
and in front it forms a narrow arch [arcus cartilaginis cricoideae]. On either side
of the upper margin of the lamina is the elliptical arytaenoid articular surface
[facies articularis arytsenoidea] its long axis parallel with the margin of the cricoid,
its steeply sloping surface convex for articulation with the arytsenoid cartilage.
The hinder surface of the lamina presents a median ridge and lateral impressions
for the attachment of the posterior crico-arytsenoid muscles. The arch, weakest
Fig. 972.-
-Median Section op a Man 21 Years of Age, showing the Position of Larynx
AND Trachea. (After W. Braune, from Poirier and Charpy.)
Epiglottis —
Hyoid bone^
Laryngeal
aperture
Fat mass'
Laryngeal
ventricle
Thyreoid
cartilage
Lamina of
cricoid
Arch of cricoid
Trachea
(Esophagus
Thyreoid body
Sterno-
thyreoid m.'
Sternum'
Left innominate.
vein
Innominate,
artery
Ascending aorta
Right lung —
Right auricle —
Pharynx
Arytaenoid
. cartilage
WW '„ ~"" Ventricular fold
^ \\\' ^ Vocal fold
\YI cervical
vertebra
in its middle part, presents concave upper and straight lower margins. A circular,
elevated thyreoid articular surface [facies articularis thyreoidea] for articulation
with the inferior cornu of the thyreoid cartilage is situated upon the side of the
cricoid where arch and lamina are continuous. The internal surface is covered by
the laryngeal mucosa.
The thyreoid cartilage [cartilago thyreoidea] (figs. 973, 974, 975, 977), single
and the largest in the laryngeal skeleton is composed of two broad laminae,
right and left, which meet and are fused anteriorly in the mid-line in a right angle,
partly covering the other cartilages laterally and in front. The laminae are stout,
but their connection at the angle is through a weak strip of cartilage. The upper
margin of each lamina is convex, and in front drops abruptly to form in the median
line the superior thyreoid notch [incisura thyreoidea superior] . The anterior edges
CARTILAGES OF THE LARYNX
1211
meeting in the angle produce the laryngeal prominence [prominentia laryngea]
("Adam's apple"), which is seen on the front of the neck. The horizontal in-
ferior margin presents near its middle the inferior thyreoid tubercle [tuberculum
thyreoideum inferius], and in the median line the inferior thyreoid notch [incisura
thyreoidea inferior]. The thick posterior margin of each lamina is continued above
the superior edge in the long superior cornu [cornu superius], and below the inferior
margin in the short inferior cornu [cornu inferius]. The former is directed slightly
backward and medial ward, and joins with the end of the greater cornu of the
hyoid by ligament. The inferior cornu, curving medialward as it descends, articu-
lates by a flat, circular facet upon the medial side of its extremity with the thy-
reoid articular surface of the cricoid cartilage. The external surface of the lamina
affords attachment for muscles and presents in its upper posterior part the
Fig. 973. — Caetilaqes op the Labynx seen prom behind in Their Natural Positions.
The CtTNEiFORM Cartilage is Somewhat Higher than Normal. (Merkel.)
Epiglottic cartilage
Corniculate cartilage
Arytaenoid cartilage
I — Superior cornu of thyreoid
Cuneiform cartilage
Thyreoid cartilage
Inferior cornu of thyreoid
Median crest
superior thyreoid tubercle [tuberculum thyreoideum superius] ; in its lower part
the inferior thyreoid tubercle. The internal surface of the thyreoid cartilage is
smooth.
A thyreoid foramen [foramen thyreoideum], sometimes seen in the upper part of the lamina,
giving passage to the superior laryngeal artery, results from the incomplete union of the fourth
and fifth branchial cartilages from which the lamina are derived. The oblique line [lines
obUqua], extending between the thyreoid tubercles, is commonly present and is regarded by
many anatomists as a normal feature of the external surface of the thyreoid cartilage. It
marks the attachment of the sternohyoid and thyreohyoid muscles. At the insertion of the
vocal ligaments in the angle of the laminae a small perichondral process is often observed.
The arytaenoid cartilages [cartilagines arytsenoidese] (figs. 973, 977, 978,
979), paired, surmount the lamina of the cricoid cartilage and give attachment to
the vocal ligaments, whose relations and state of tension are altered by the changes
in position which these cartilages are almost constantly undergoing.
Each cartilage is pyramidal in form, and moulded for the attachment of several
muscles. The apex, which is above, is bent backward and medialward and is
connected with a corniculate cartilage. The base, somewhat triangular in shape,
presents at the lateral and posterior part an oval or circular concave articular
surface [facies articularis], directed medialward and downward to meet the
aryteenoid articular surface of the cricoid cartilage. The lateral angle of the base
is prolonged into a stout muscular process [processus muscularis] for the attach-
1212
THE RESPIRATORY SYSTEM
ment of the crico-arytsenoid muscles, while the anterior angle is extended as a
sharp projection, the vocal process [processus vocalis], which serves for the
attachment of the vocal ligament. The surfaces of the arytsenoid are named
medial, posterior, and antero-lateral. The narrow medial surface, covered by the
mucosa of the larynx, is nearly vertical, and faces the corresponchng side of the
opposite arytsenoid, from which it is separated by a small space. The posterior
surface is concave for muscular attachment. The antero-lateral surface is the
largest, and presents an irregular contour.
On this surface a ridge, the arcuate crest [crista arcuata], extends horizontally between
two hollows — the triangular fovea [fovea triangularis] above, which lodges some mucous
glands, and a larger depression below, the oblong fovea [fovea oblonga] for the vocal muscle.
The colliculus is a small eminence found upon the anterior margin and antero-lateral surf ace.
Fig. 974. — Fkont View of the Laryngeal Skeleton. (Modified from Bourgery and Jacob.)
Greater corau of hyoid*
Body of hyoid
Lateral hyo-thyreoid ligament
Triticeous cartilage
Foramina for superior laryngeal
vessels and internal laryngeal n.
Median hyo-thyreoid ligament
Superior cornu of thyreoid
Superior thyreoid notch
Lamina of thyreoid
Oblique line
Median crico-thyreoid ligament.
Inferior cornu of thyr
Crico-thyreoid joint"
Crico-tracheal ligament
Tracheal cartilagt
The corniculate cartilages (of Santorini) [cartilagines corniculatse (Santorini*)]
(figs. 973, 977). — This pair of small conical cartilages is set upon the bent apices of
the arytsenoids, continuing their curves backward and mechalward.
The corniculate cartilage is not an independent structure in many lower animals, and its
continuity with the arytsenoid is sometimes met with in man where the two cartilages are
normally developed in a continuous mass of tissue.
The epiglottic cartilage [cartilago epiglottica] (figs. 973, 977, 981, 987),
unpaired, invested by mucosa behind and partly in front, thin and leaf-shaped,
stands behind the root of the tongue and the body of the hyoid. It lies above the
thyreoid cartilage, in front of the entrance of the larynx. The free upper margin
is convex, or notched; the lower end tapers to a short stalk, the petiole of the
epiglottis [petiolus epiglottidis], to which the thyreo-epiglottic ligament is
attached.
The anterior surface is free above and covered by mucosa; in its lower part
it is bound to the body of the hyoid, and is separated by a mass of fat from
* Santorini: Venetian anatomist. B. 1681, D. 1737.
JOINTS OF THE LARYNX
1213
the hyo-thyreoicl ligament. Its posterior surface above is saddle-shaped; below,
it is convex, presenting the epiglottic tubercle [tuberculum epiglotticum]. To
the margins are attached the ary-epiglottic folds. The epiglottic cartilage
presents numerous small holes and depressions for the accommodation of glands.
The cuneiform cartilages (of Wrisberg) [cartilagines cuneiformes (Wrisbergi*)]
(fig. 973) lie as small, rod-like bodies in the ary-epiglottic folds anterior to the
corniculate_ cartilages. They are variable in form and size and not rarely absent
altogether.
These cartilages are parts of the epiglottic cartilage in some mammals where, as in man,
they he in the ary-epiglottic folds. Their relations to the arytEcnoids are regarded as secondary.
Sutton has shown that in the ant-eater a continuous rim of yellow elastic cartilage extends
from the sides of the epiglottic cartilage to the summits of the aryttenoids. A minute unpaired
inlerarylmnoid or procricoid cartilage is rarely present imbedded in the cricopharyngeal ligament
and covered by the pharyngeal mucosa. It is a constant structure in certain mammals. A
pair of small sesamoid cariilages, also constantly present in some mammals, is occasionally
found in man at the lateral margins of the arytaenoids, connected with them and with the
corniculate cartilages by elastic ligaments.
Structure of the cartilages. — The thyreoid, cricoid, and greater part of the aryta;noid are
composed of hyaline cartilage; the epiglottic, corniculate, and cuneiform cartilages, as well as
the ape.x and vocal process of the arytsenoid, are of elastic cartilage. Certain parts of the laryn-
geal skeleton normally undergo calcification and subsequent ossification. Calcification begins
at about twenty years of age in the thyreoid and cricoid cartilages, and later in the arytenoid.
The process begins a little later in the female than in the male, and does not extend so rapidly.
The extent to which the cartilages are ossified and the time occupied in the process vary con-
siderably. The elastic elements are not involved in the process.
Fig. 975.-
FiG. 976.-
-Cricoid AND Arytenoid Cartilages seen prom Before.
-Cricoid and Arytenoid Cartilages seen erom the Left.
(Rauber-Kopsch.)
(Rauber-Kopsch.)
Corniculate cart.
Apex of arytjenoid
CoUiculus
" Arcuate crest
^ Muscular
process
■ Vocal process
Ary-corniculate synchondrosis
Corniculate
Colliculus..-
g, ^ Arcuate
Tnangular pit ** crest
Oblong pit "■■■■/"'^W^^ft- Muscular
Vocal process .— *''^^^ait^9*'^^SS|^H process
- . ^™-|..., Lamina of
.^'^ HIh cricoid
-Thyreoid
A 1. £ / w^mobUr't' nMMMjcffi^ artlcular
Arch of ...4i^mi!,,..: "mai surface
THE JOINTS AND FIBROUS MEMBRANES OF THE LARYNX
(1) Connections between the Laryngeal Cartilages
The crico-thyreoid articulation (figs. 973, 974, 975). — The articular surfaces
concerned are the thyreoid articular surface on the side of the cricoid and the
articular surface on the inferior cornu of the thyreoid cartilage. The crico-
thyreoid articular capsule [capsula articularis cricothyreoidea] attached around
the margins of these surfaces and certain accessory bands serve to bind the carti-
lages together.
The accessory bands, cerato-cricoid ligaments fall into three groups radiating from the
inferior cornu: the ligamenta ceratocricoidea posteriora upward and medialward to the superior
margin of the cricoid; tlie ligamenta ceratocricoidea lateralia downward at the side and back
of the capsule; the ligarnentum ceratocricoideum anterius downward and forward. The
capsule possesses a synovial layer.
A rotary movement about a transverse axis of the cricoid upon the thyreoid
or vice versa and a slight backward and forward gliding are permitted at this
joint.
* Wrisberg: German anatomist. B. 1737, D. 1808.
1214
THE RESPIRATORY SYSTEM
The crico-arytaenoid articulation [articulatio cricoarytsenoidea (figs. 973, 977,
978). — The articular surface of the cricoid cartilage and the articular surface
of the arytsenoid which enter into this articulation are so disposed that at no time
do they meet in complete apposition. A loose capsule [capsula articularis crico-
FiQ. 977. — The Laryngeal Skeleton seen from Behind. (Poirier and Charpy.)
— ____ Epiglottic cartilage
— . — ^Greater cornu of hyoid
-Triticeous cartilage
Hyo-thyreoid membrane——.
Posterior crico-arytae
ligament
Inferior comu of thyreoid
Lamina of cricoid
Membranous wall of trachea
Body of hyoid
Superior comu of thyreoid
"Thyreo-epigottic ligament
Corniculate cartilage
Corniculo- and crico-
geal ligaments
'ArytEenoid cartilage
Crico-aryt£enoid joint
Posterior cerato-cricoid
ligament
Crico-thyreoid joint
^Lateral cerato-cricoid ligament
Fig. 978. — The Larynx with its Ligaments, viewed from the Right. (The right lamina of
the thyreoid cartilage has been removed.) (Spalteholz.)
Eoiglottis
Ary-epiglo tti
fold (section
through the
mucous mem-
brane)
Arytenoid cartilage
Muscular process —
Crico-arytEenoid joint '^
Vocal process
Theyreoid articular surface'''
Tracheal cartilages <^
epiglottic ligament
—Median hyo-thyreoid ligament
'/'—Quadrangular membrane
— Thyreoid cartilage
Ventricular ligament
'Vocal ligament
"Elastic cone
Median crico-thyreoid ligament
- Arch of cricoid
— Cnco-tracheal ligament
— Annular ligament
arytaenoidea] of fibrous and synovial strata attached around the edges of the joint
surfaces unites the cartilages.
Posterior crico-arytsenoid ligament [Hg. cricoarytsenoideum posterius], attached above„ to
the medial surface of the base and muscular process of the arytainoid, and below to the lamina
MEMBRANES OF THE LARYNX 1215
of the cricoid, is important in helping to fix the former cartilage in place upon the sloping
arytaenoid articular surface of the cricoid and in limiting its movements. Motion at this
articulation is very free. The following simple movements of the arytaenoid are best under-
stood:— (1) gliding of the arytaenoid toward or away from its fellow; (2) inclining forward and
backward; (3) rotating on a vertical axis, so that the vocal process sweeps medialward or lateral-
ward and also a little downward or upward.
The union of the corniculate cartilage with the apex of the arytsenoid cartilage
[synchondrosis arycorniculata] is usually by connective tissue; rarely is there a
joint cavity.
The petiole of the epiglottic cartilage is connected with the thyreoid, below
and behind the superior notch, by a strong, elastic thyreo-epiglottic ligament
[lig. thyreoepiglotticum] (fig. 977).
(2) The Elastic Membrane of the Larynx
[Membrana elastica laryngis]
This name is given to a more or less continuous sheet of elastic fibres connected
with the deeper parts of the laryngeal mucosa. Its upper part is known as the
quadrangular membrane, the lower part as the elastic cone. A middle region of the
elastic membrane lies opposite the ventricle of the larynx.
The quadrangular membrane (figs. 978, 981, 988) extends from the ary-epi-
glottic folds above to the level of the ventricular folds (false vocal cords) below.
The lateral parts of this membrane are widely separated superiorly, but they con-
verge toward the middle line as they descend. Anteriorly, the membrane is
fixed in the angle of the thyreoid laminae and to the sides of the epiglottic car-
tilage; posteriorly, to the corniculate cartilages and to the arytaenoids. The
superior edge on either side lies within the ary-epiglottic fold, which it supports;
it slopes downward and backward and includes the cuneiform cartilage. The
inferior edge, horizontal and in a sagittal plane, is best developed in front, where
it is attached in the angle of the thyreoid a little way from the middle line ; behind,
it is fixed to the medial margin of the triangular fovea of the arytsenoid. This
inferior free margin, differentiated as the ventricular ligament [lig. ventriculare],
is enclosed within, and is the support for the ventricular fold.
Fia. 979. — The Elastic Cone seen from Above. (Modified from Luschka.)
Nodule of elastic tissue ^„..^I'erichondraI insertion of vocal ligaments
Nodule of elastic tissue
.Vocal ligament
Elastic I
tilage
Arytaenoid cartilage in transverse section
Posterior crico-arytaenoid ligament
The elastic cone [conus elasticus] (figs. 978, 979). — -This part of the elastic
membrane extends from the level of the vocal folds to the superior margin of the
cricoid cartilage. Its component fibres are attached in the re-entrant angle and
adjacent lower margin of the thyreoid cartilage, whence they spread downward
and backward to the upper edge of the cricoid arch and to the arytsenoid carti-
lages. The strong anterior portion, perforated by vessels, is the median crico-
thyreoid ligament [fig. cricothyreoideum (medium)] (figs. 974, 975). The lateral
parts (lateral portions of the crico-thyreoid membrane) present superior free
edges, somewhat thickened, which, running horizontally near the middle line from
the thyreoid angle to the vocal processes, constitute the vocal ligaments. These
are inserted anteriorly into a perichondral process in the thyreoid angle; poster-
iorly, they have a wide area of attachment to the upper and medial surfaces of the
vocal processes of the arytaenoids with the elastic fibres of which they are in part
continuous. A yellowish, cellular nodule (sometimes cartilage) occurs in the
1216
THE RESPIRATORY SYSTEM
anterior end of each ligament. The vocal ligaments enter into the formation of
the vocal folds (true vocal cords).
Fig. 980. — The Larynx seen from the Left Side. (Modified from Luschka.)
Epiglottis J
Hyoid bone
Thyreo-hyoid musclo— ^
Thyreoid cartilage-
Median crico-thyreoid ligament'
Crico-thyreoid muscle (straight part)
Tracheal cartilage
Internal laryngeal nerve
Hyo-thyreoid membrane
Superior laryngeal artery
Superior laryngeal vein
Cricothyreoid muscle (oblique part)
ry — Posterior crico-arytsenoid muscle
Cricoid cartilage
Fig. 981. — The Muscles and Ligaments of the Larynx seen from the Side. (The left
lamina of the thyreoid cartilage has been removed.)
Hyo-epiglottic ligament-
Body of hyoid.
Fat mas?.
Hyo-thyreoid membrane —
Thyreo-epiglottic muscle
Quadrangular membrane —
Thyreoid cartilage
External thyreo-arytaenoid muscle
Elastic cone
Lateral crico-arytaenoid muscle
Median crico-thyreoid ligament
Cricoid cartilage
■Ary-epiglottic fold
Ary-epiglottic and ary-
_| -'--• membranosus muscles
Posterior crico-arytaenoid muscle
-Thyreoid articular surface
Lamina of cricoid
Inferior laryngeal nerve
The median crico-thyreoid ligament is incised m the operation of laryngotomy. It is
crossed by the anastomotic arch of the crico-thyreoid arteries, which, however, can be avoided
in the operation by making a transverse cut through the ligament close to the superior margm
of the arch of the cricoid cartilage.
LIGAMENTS OF THE LARYNX 1217
(3) Connections between the Larynx and Neighbouring Structures
The hyo-thyreoid membrane [membrana hyothyreoidea] (figs. 977, 980, 981)
is a loose, fibrous, elastic sheet, binding together the thyreoid cartilage and hyoid
bone. It extends from the superior margin of the former to the greater cornua and
Fig. 982. — Scheme of Rima, showing Action of Posterior Crico-aryt^noid Muscle,
WHICH DRAWS THE ArttjEnoid Cartilage PROM I TO II. (Modified from Stirling.)
superior margin of the body of the latter. The superior laryngeal artery and vein
and the internal laryngeal nerve pass through it from the side. Its posterior and
lateral edge is cord-like, consisting of elastic fibres which stretch as the lateral
Fig. 983. — Scheme showing Action of the Transverse Arytenoid drawing Arytenoid
Cartilage from Neutral Position I to II. (Modified from Stirling.)
hyo-thyreoid ligament [lig. hyothyreoideum laterale] from the superior cornu of the
thyreoid to the greater cornu of the hyoid. A small cartilago triticea is sometimes
present in this band. The middle part, median hyo-thyreoid ligament [hg.
Fig. 984. — Scheme showing Action of Thyreo-arty^noid drawing the Vocal Processes
and the Vocal Ligaments from II to I. (Modified from Stirling.)
hyothyreoideum medium] thick and elastic, extends from the superior thyreoid
notch upward behind the body of the hyoid to be attached to its superior margin,
the hyoid bursa being interposed between the bone and the membrane.
1218 THE RESPIRATORY SYSTEM
The cartilage tritioea is the remains of a connection between the thyreoid and hyoid present
in the embryo. It persists in adult hfe in some lower animals.
The hyo-epiglottic ligament [lig. hyoepiglotticum] (figs. 978, 981) connects the
anterior surface of the epiglottic cartilage with the superior margin of the body and
the greater cornua of the hyoid. It is a broad sheet, lying above a mass of fat
which stands between the median hyo-thyreoid membrane and the epiglottis
and spreading laterally to join the pharyngeal aponeurosis in the region of the
piriform recess.
The name glosso-epiglottic ligament is given to the elastic fibres extending
between the root of the tongue and the epiglottis within the median glosso-epi-
glottic fold.
The corniculo -pharyngeal ligament (fig. 977) extends from the corniculate cartilage down-
ward and toward the median hne, attaching to the mucosa of the pharjoix and joining its
fellow behind the arytaenoid muscle. From this point a single band, the crico -pharyngeal liga-
ment [hg. oricopharyngeum], which may enclose a nodule of cartilage (the interarytsenoid
or procricoid cartilage), descends in the middle line, to be fixed to the cricoid lamina and into
the pharyngeal mucosa.
The larynx and trachea are united by fibrous membrane, the crico-tracheal
ligament [lig. cricotracheale] (figs. 974, 978), between the inferior margin of the
cricoid cartilage and the upper margin of the first tracheal ring. Posteriorly
the ligament is continued into the membranous wall of the trachea.
MUSCLES OF THE LARYNX
Of the many muscles connected with the larynx, two groups may be recog-
nised, the members of one coming from neighbouring parts, fixing themselves to
the larynx and acting upon the organ as a whole; the members of the other
group confining themselves exclusively to the larynx and acting so as to affect its
parts. The muscles composing the first group are described elsewhere. (See
Section IV.) The muscles of the second group are composed of striated fibres
and are supplied by the vagus nerve through its laryngeal branches. These
muscles are all more or less under cover of the thyreoid cartilage, with one ex-
ception, the crico-thyreoid.
The crico-thyreoid muscles [m. cricothyreoideus] (fig. 980) are placed one on
either side of the outer surface of the larynx in its lower part. Each muscle is
partially separated into an anterior straight [pars recta] and a posterior oblique
portion [pars obliqua], which together arise from the arch of the cricoid. The
fibres of the straight part ascend steeply and are inserted into the inferior margin
of the thyreoid cartilage. The oblique portion is inserted into the inferior cornu
and into the lower margin and inner surface of the thyreoid cartilage.
The straight part elevates the arch of the cricoid, causing the lamina, and with it the
arytsenoid cartilages, to sLuk, while the obhque part draws forward the thyreoid; thus the vocal
ligaments are made tense. The muscle is supplied by the external branch of the superior larjTi-
geal nerve. A connexion between the posterior part of this muscle and the inferior constrictor
of the pharynx and their common nerve-supply indicate their genetic relationship.
The posterior crico-arytffinoid muscle [m. cricoarytasnoideus posterior] (figs.
980, 981, 982), paired, is situated at the back of the larynx, covered by the submu-
cous coat of the pharynx. It is a thick, triangular mass which takes origin from
the posterior surface of the cricoid lamina, the two muscles being well separated
by the median crest of the cartilage. The lower fibres ascend and the upper
ones pass horizontally lateralward and are inserted into the muscular process
of the arytaenoid cartilage on its posterior surface and tip.
When these muscles contract, the muscular processes of the arytsenqids are puUed back-
ward and downward, while the vocal processes travel lateralward and a Uttle upward, so that
the rima glottidis is widened and the vocal hgaments made tense (fig. 982). The innervation
is by the posterior branch of the inferior laryngeal nerve.
In ether narcosis the dilator muscle is later paralyzed and afterward earlier restored than
the constrictors of the larynx.
At the lower margin of this muscle a small slip, the cerato-cricoid muscle [m. ceratocri-
coideus], is sometimes found, extending between the lamina of the cricoid and the inferior cornu
of the thyreoid cartilage.
The constrictor laryngis. — Whereas the crico-arytgenoideus posterior is a dila-
tor of the larynx, the several muscles now to be considered are in the main con-
MUSCLES OF THE LARYNX
1219
strictors. They form a ring, the constrictor laryrigis, around the laryngeal cavity,
interrupted, however, by the cartilages. In the larynx of amphibia and reptiles
a complete sphincter guards the entrance to the air-passages.
The following muscles are included in the constrictor group: —
The transverse arytaenoid muscle [m. arytaenoideus transversus] (figs. 981)
983, 985) is. a single muscle of quadrilateral form, extending across the middle
line from the posterior concave surface of one arytaenoid cartilage to that of the
other. Its anterior surface, between the cartilages, is covered by the laryngeal
mucosa; its posterior surface, crossed by the arytaenoideus obliquus, is clothed by
the submucous coat of the pharynx.
The arytaenoideus transversus approximates the arytenoid cartilages and their vocal proc-
esses, which are at the same time elevated, and the vocal Ugaments made tense. It is supplied
by the posterior branch of the inferior laryngeal nerve.
Fig. 985. — -The Nerves of the Larynx seen from Behind.
Greater cornu of hyoid
Triticeous cartilage
Ary-epiglottic fold
Superior cornu of
thyreoid
orniculate cartilage
Anterior branch of in-
ferior laryngeal nerve
Posterior branch of in-
ferior laryngeal nerve
Posterior crico-arytas-
noid muscle
Crico-thyreoid joint
Base of the tongue
Epiglottis
External branch of su-
perior laryngeal nerve
Internal branch of su-
perior laryngeal nerve
Cut edge of hyo-thy-
reoid membrane
Cuneiform tubercle
Oblique arytagnoid
Arytsenoid cartilage
Lamina of cricoid
Inferior laryngeal
The lateral crico -arytaenoid muscle [m. cricoarytaenoideus lateralis] (fig. 981)
arises from the upper margin and outer surface of the cricoid arch and from the
elastic cone, whence the fibres extend backward and upward to an insertion on
the anterior surface of the muscular process of the arytaenoid cartilage. This
muscle is inseparable from the thyreo-arytsenoideus in about half the cases.
The lateral oricoarytsnoids by their contraction cause the vocal processes to move toward
the median line and a little downward, so that the vocal Ugaments are approximated and shghtly
stretched. They antagonise the posterior crico-arytaenoids. The anterior branch of the in-
ferior laryngeal nerve supphes these muscles.
The external thyreo-arytaenoid muscle [m. thyreoarytsenoideus (externus)]
(figs. 981, 984, 988), variable in form and in the disposition of its fibres, is closely
connected with the preceding. It Hes under cover of the thyreoid lamina lateral
to the laryngeal saccule (ventricular appendix) and elastic cone. Arising within
the angle of the thyreoid laminae the muscle extends upward and backward to its
insertion on the lateral margin of the arytaenoid cartilage.
1220 THE RESPIRATORY SYSTEM
It draws forward the arytsenoid cartilage (and also tilts the cricoid), and rotates it so that
the vocal process passes medialward and downward, relaxing the vocal ligament. It is the
antagonist of the crioo-thyreoid (fig. 984). Its nerve-supply is the anterior branch of the in-
ferior laryngeal.
The vocal muscle [m. vocalis], (fig. 988), prismatic in form, is tiie inner con-
stant part of tlie thyreo-arytasnoideus. It lies in tiie vocal lip lateral to the vocal
ligament. Its fibres run from their origin in the angle of the thyreoid laminse to
their insertion in the vocal process and oblong fovea of the arytaenoid cartilage.
It draws forward the vocal process, relaxing the vocal ligament. Its nerve comes from the
anterior branch of the inferior laryngeal.
The insertion of certain fibres of this muscle into the elastic vocal ligament has been observed
(ary-vocalis muscle of Ludwig). D. Lewis has shown that some of the elastic fibres in the vocal
ligament are derived from the perimysium of the vocal muscle.
The ventricular muscle [m. ventricularis] consists of a few fibres derived from the thyreo-
arytffinoideus which reach the back of the laryngeal saccule and enter the ventricular fold.
The small thyreo-arytwnoideus superior extends from the angle of the thjrreoid to the muscular
process of the arytaenoid upon the lateral surface of the main muscle.
The oblique arytsenoid muscle [m. arytsenoideus obhquus] is a slender band
lying at the back of the larynx and under the pharyngeal submucosa. It arises
from the muscular process of the arytsenoid posteriorly, and, ascending obliquely,
crosses its fellow in the median line. Some fibres are inserted into the apex of
the opposite arytsenoid cartilage; other fibres sweep around the apex and accom-
pany the thyreo-arytsenoid to an insertion in the angle of the thyreoid cartilage,
constituting the thyreo-arytcenoideus obliquus.
This muscle contracts the laryngeal aperture and vestibule of the larynx. Its nerve is
derived from the anterior branch of the inferior laryngeal.
Closely connected with the thyreo-arytsenoideus is a bundle of fibres of fairly
regular occurrence, called the thyreo-epiglottic muscle [m. thyreoepiglotticus]
(fig. 981). It originates from the inner surface of the thyreoid lamina and pro-
ceeds upward and backward to end in the quadrangular membrane and to become
attached to the lateral border of the epiglottis.
The ary-membranosus and ary-epiglotlic muscles are inconstant fascicles of the constrictor
group which run in the ary-epiglottic fold and become fixed into the quadrangular membrane
and margin of the epiglottic cartilage.
Summary of the Actions of the Laryngeal Muscles
According to their actions, the laryngeal muscles may be divided into — (a) those which
effect the tension of the vocal folds; (b) those which control the rima glottidis; (c) those which
effect the closure of the laryngeal aperture and vestibule.
(a) The vocal ligaments are made tense by the action of the crico-thyreoid, the lateral and
posterior cricoarytsenoid and the transverse arytaenoid muscles. The vocal ligaments are re-
laxed as the result of the action of the external thyreo-arytaenoid and vocal muscles.
(6) The rima glottidis is widened by the crico-arytajnoideus posterior and made narrow
by the contraction of the arytaenoids. The crico-arytaenoideus lateralis also assists in closing
the rima glottidis by rotating the vocal processes medialward, and if the crico-arytsenoideus
posterior contracts simultaneously, it aids in the closure. The vocal hgaments are approxi-
mated also by the thyreo-arytaenoideus [externus].
(c) The laryngeal aperture and vestibule are closed mainly by the arytsenoideus transversus
and thyreo-arytsenoideus (externus), by which the arytaenoid cartilages are brought into apposi-
tion and drawn toward the epiglottis. Other muscles derived from the constrictor group,
arytaenoideus obliquus and ary-epiglotticus assist in closing the laryngeal aperture.
CAVITY OF THE LARYNX AND LARYNGEAL MUCOSA
The cavity of the larynx [cavum laryngis] is relatively narrow and does not
correspond in shape with the outer surface of the organ. Its form is shown in
fig. 986 taken from a cast of the laryngeal cavity and the spaces continuous with
it. Its walls are covered throughout by the mucous membrane of the larynx
(figs. 987, 988).
The mucosa of the larynx is continuous above with the mucous membrane
of the pharynx, below with that of the trachea (figs. 970, 971). At the root of
the tongue the pharyngeal mucosa is reflected backward to the anterior surface
of the epiglottis, presenting the median and lateral glosso-epiglottic folds [plica
CAVITY OF THE LARYNX
1221
glosso epiglottica medianaet lateralis]. From the sides of the pharynx it passes
medialward, first sinking between the thyreoid cartilage laterally and the aryt-
senoid and cricoid medially, entering into the walls of the piriform recess; then
passing over the superior margin of the quadrangular membrane to form the ary-
epiglottic fold.
At the medial side of the piriform recess a slight fold of the mucosa [phca nervi laryngei)
corresponds to the superior lar3Tigeal nerve. Between the root of the tongue and the epiglottis
is a depression subdivided in the middle line and limited laterally by the median and lateral
Fig. 986. — Cast of the Vestibulum and Cavum Oris, op the Phahtnx, Laeynx, op the
Upper Part op the Trachea and (Esophagus. Seen from in front And below. (Rauber-
Kopsch.)
Rima oris
Alveolar part of mandible
*■ --^'tf'-ymM Tongue
Glosso-epiglottic vallecula
S Vestibule of larynx
Piriform recess
Laryngeal ventricle
Cavum laryngis inferius
(Esophagus
glosso-epiglottic folds; this is the epiglottic vallecula [vallecula epiglottica]. The piriform
recess and the epiglottic vallecula are favorite sites for the lodgment of foreign bodies. The
ary-epiglottic fold [plica aryepiglottica] extends from the side of the epiglottis to the apex
of the aryt:rnoid cartilage; within it are fibres of the ary-epiglottic and thyreo-epiglottic
muscles and the cuneiform and corniculate cartilages. These cartilages correspond to two
rounded eminences on each side of the laryngeal entrance, the cuneiform and corniculate
tubercles [tuberculum cuneiforme (Wrisbergi); tubereulum corniculatum (Santorini)], respec-
tively. Of these, the former is often small and inconspicuous, the latter usually well developed
and prominent.
The cavity of the larynx above the level of the ventricular folds is known as the
vestibule [vestibulum laryngis]. This is wide in its upper part, but the sides
incline toward the median line in descending, and the cavity becomes narrow
1222
THE RESPIRATORY SYSTEM
transversely in approaching the region of the glottis. Here the cavity has received
the special name, superior entrance to the glottis [aditus glottidis superior]. The
parts of the framework of the larynx which enter into the walls of the vestibule are :
in front, the epiglottic and thyreoid cartilages with the thyreo-epiglottic hgament;
at the side, the quadrangular membrane, the cuneifoi-m and corniculate cartilages,
and the medial surface of the arytsenoid cartilage; behind, the anterior surface of
the transverse arytsenoid muscle. The vestibule communicates with the pharynx
by the laryngeal aperture [aditus laryngis] (figs. 970, 971, 972, 987), which
looks upward and backward. The form of the aperture is oval or triangular,
with the base in front; here it is bounded by the epiglottis; laterally by the ary-
epiglottic fold of the mucosa. Posteriorly the laryngeal aperture is prolonged as
a little notch between the corniculate cartilages and the apices of the arytsenoids
[incisura interarytsenoidea] limited behind by a commissure of the mucosa.
The high anterior waU of the vestibule presents a marked convexity, the tubercle of the
epiglottis [tuberculum epiglotticum], over the thyreo-epiglottic ligament. The lateral walls,
Fig. 987. — Median Section op the Larynx. (Merkel.)
Median glosso-epiglottic fold
Cuneiform tubercle'
Corniculate tubercle
Arytaenoid muscles'
Lamina of cricoid'
— Epiglotti:: cartilage
— ^Appendix of the ventricle
-/^ — Ventricular fold
Ventricle
Vocal fold
Thyreoid cartilage
Median crico-thyreoid ligament
Arch of cricoid
Crico-tracheal ligament
First tracheal cartilage
higher in front than behind, show two slight ridges, separated by a shallow groove, extending
downward from the cuneiform and corniculate tubercles. The posterior wall, very low, corre-
sponds to the commissure connecting the arytsenoid cartilages.
On either side of the vestibule, toward its inferior end, is the sagittally running
ventricular fold [plica ventricularis] (false vocal cord) (figs. 970, 971, 987, 988).
This appears as an elevation of the mucous coat of the lateral wall, prominent in
its middle and anteriorly, fading away posteriorly. The ventricular fold contains
the inferior free edge of the quadrangular membrane, that is, the ventricular liga-
ment, and numerous glands.
Wylie's experiments with the ventricular folds led him to conclude that the closure of the
glottis in defaecation and vomiting is mainly effected by the apposition of these folds. (Quain.)
The interval between the right and left ventricular folds, the vestibular slit
[rima vestibuli] leads downward to a space between the planes of the ventricular
and vocal folds, which extends on each side into the laryngeal ventricle [ventricu-
lus laryngis (Morgagni*)] (figs. 970, 971, 987, 988). The latter is a little antero-
posterior pocket of the mucosa reaching from the level of the arytsenoid nearly
to the angle of the thyreoid cartilage, and undermining the ventricular fold;
it opens into the cavity of the larynx by a narrow mouth limited above and below
by the ventricular and vocal folds. From its anterior part a small diverticulum,
* Morgagni. ItaUan anatomist. B. 1682, D. 1771.
THE VOCAL FOLDS
1223
the ventricular appendix [appendix ventriculi laryngis] extends upward between
the ventricular fold medially and the thyreo-arytsenoid muscle and thyreoid car-
tilage laterally. Many mucous glands open into it.
The appendix is occasionally so large as to reach the level of the upper margin of the thyreoid
cartilage or even the great cornu of the hyoid bone. The laryngeal pouches of some of the
apes are remarkably developed and appear to serve in affecting the resonance of the voice.
In man, their function, besides that of pouring out the secretion of the glands located within
their walls, is not known.
The vocal fold [plica vocalis] (or true vocal cord) (figs. 970, 971, 987, 988)
is the thin edge of a full, lip-like projection, the vocal lip. The vocal folds cor-
respond in antero-posterior extent to the vocal hgament, and stand nearer the
median line than the ventricular fold. In colour the vocal folds are pearly white,
excepting the anterior end of each, where there is a yellow spot [macula flava]
produced by a little mass of elastic tissue (sometimes cartilage) in the ligament.
The vocal lip [labium vocale] forms the floor of the ventricle and contains the upper
part of the elastic cone, whose thickened free edge, the vocal ligament, lies in the
Fig. 988. — Fbontal Section op a Larynx Hardened in Alcohol.
B. Anterior segment. (Poirier and Charpy.)
A. Posterior segment.
Cunei-
form
tubercle
Ventri-
cular
muscle
Appen-
dix
Thy-
. reo-
arytae-
noid
(ext.)
Cricoid
.Crico-
thyreoid
B.
vocal fold and along the vocal muscle. The two vocal lips with the vocal folds
and the intervening space, the rima glottidis, together constitute the sound-
producing apparatus, the glottis.
Below the vocal folds and the medial surfaces of the arytenoid cartilages
is a slit, the rima glottidis (figs. 970, 971, 988), the narrowest part of the laryngeal
cavity, extending from the arytsenoideus transversus muscle posteriorly to the
thyreoid cartilage in front. The portion of the rima between the vocal folds is
known as the pars intermembranacea ; that between the arytsenoids the pars
intercartilaginea. The rima glottidis in easy respiration is narrow and has the
form of a long triangle; in laboured breathing it is widely open and lozenge-shaped.
Below the level of the vocal folds is the space called the inferior entrance to
the glottis [aditus glottidis inferior] (fig. 988), which is narrow from side to side
above, wide and circular in section below — altogether somewhat funnel-shaped.
Its walls are formed by the elastic cone and by the arch and lamina of the cricoid
cartilage. The lining mucosa is separated from the elastic cone by numerous
glands and loose connective tissue, a condition favorable to the development of
oedema; below it is continuous with the mucosa of the trachea.
By means of the laryngoscope a more or less complete picture of the laryngeal aperture
and the cavity of the larynx can be obtained (figs. 970, 971). There appear, highest up, the
1224 THE RESPIRATORY SYSTEM
root of the tongue with the epiglottic valleculse and glosso-epiglottic folds leading backward
to the epiglottis; behind the latter, the triangular aperture of the larynx, bounded at the sides
by the ary-epiglottic folds. Further lateralward appear the piriform recesses, the laryngeal
portions of which lie as transverse fissures behind the laryngeal aperture. Within the ary-
epiglottic folds are seen the prominent corniculate tubercles on either side of the inter-
arytaenoid commissure and just anterior, the variable cuneiform tubercles. Within the vesti-
bule the epiglottic tubercle rises upon the anterior wall, while at the sides appear the ventricular
folds overhanging the slit-like openings of the laryngeal ventricles. Below this level the vocal
folds stand out on either side approaching nearer the median plane than do the ventricular
folds and conspicuous by their pearly whiteness. The form and extent of the rima glottidis
and of its divisions, the intermembranous and intercartilaginous parts, can be inspected. Far
down, the cricoid cartilage and anterior wall of the trachea may appear and under favourable
conditions a glimpse of the bifurcation of the latter can be obtained.
The mucous coat of the larynx [tunica mucosa laryngis] in general is covered by a ciliated
epithelium; the vocal lips, and, exceptionally, small areas of the mucosa of the laryngeal surface
of the epiglottis and the ventricular folds possess a covering of flat, non-ciliated cells. The
attachment of the mucosa to the underlying parts is very firm about the vocal folds and dorsal
side of the epiglottis, and loose in the ary-epiglottic folds, where much areolar tissue is present.
In general the mucosa is pink in colour, becoming bright red over the epiglottic tubercle and
edges of the epiglottis and fading over the vocal folds, which appear almost white.
Numerous mucous glands [glandulse laryngeal] occur about the larynx and are aggregated
into groups in certain places. One cluster of anterior glands [gl. laryiifjoa- nnteriores] is found
in front of and on the posterior side of the epiglottis; another, the middle glands [gl. laryngeae
media;], is in the ventricular fold, in the triangular fovea of the arytfonoid curtilage and clustered
about the cuneiform cartilage, while a third set, the posterior glands [gl. laryngea; posteriores],
is disposed about the transverse arytajnoid muscle. Many glands pour their secretion into the
appendix of the laryngeal ventricle, but there are none on or about the vocal folds. Lymph-
nodules of the larynx [noduli lymphatici laryngei] occur in the mucosa of the ventricle and on
the posterior surface of the epiglottis.
Position and relations. — The larynx opens above into the pharynx by the aditu and in thiss
region is connected with the hyoid bone. Below, its cavity leads into the trachea. Its position
in the neck is indicated on the surface by the laryngeal prominence (Adam's apple). It stands
in front of the fourth, fifth, sixth, and seventh cervical vertebrae; from these it is separated by
the prevertebral muscles and the pharynx, into the anterior wall of which it enters. The
integument and cervical fascia cover the larynx anteriorly in the middle line, while toward the
side are the sterno-hyoid, sterno-thryeoid, and thyreo-hyoid muscles. The lateral lobe of the
thyreoid gland and the inferior constrictor of the pharynx are in relation to it laterally, while
further removed are the great vessels and nerves of the neck.
Peculiarities of age and sex. Position. — The larynx is placed high in the neck in foetal
and infantile life and descends in later life. In a six-months foetus the organ is two vertebra
higher than in the adult. (Symington.) The descent of the larynx has-been attributed to
the vertical growth of the facial part of the skull, but this cause is questioned by Cunningham,
who points out the high position of the larynx in the anthropoid apes, where the facial growth
is more striking than in man; it appears also that the larynx follows the thoracic viscera in their
subsidence, which, according to Mehnert, continues until old age. At birth the interval between
the hyoid bone and thyreoid cartilage is relatively very small and increases but little during
early life.
Growth and form. — The larynx of the new-born is relatively large and in contour more
rounded than that of the adult. The organ continues to grow until the third year, when a
resting period begins, lasting until about twelve years of age, during which time there appears
to be no difference between the larynx of the male and that of the female. At puberty, while
no marked change is observable in the larynx of the female, rapid growth accompanied by
modification of form of the larynx is initiated in the male. The laryngeal cavity is enlarged,
the antero-posterior diameter markedly increased; the whole framework becomes stronger; the
thyreoid cartilage especially increases greatly in its dimensions, giving rise to the laryngeal
prominence; the vocal folds are lengthened and thickened, the voice changing in quality and
pitch. These changes are, for the most part, effected in about two years, but complete develop-
ment is not attained before twenty to twenty-five years of age. Castration is known to in-
fluence the development of the larynx, for in the eunuch it has been found to resemble that of a
young woman. The changes in the structure of the cartilages have already been described.
Dimensions. — In the male the distance from the upper edge of the epiglottis to the lower
margin of \\u: cricoid is 70 mm.; in the female, 48 mm. The transverse diameter is 40 mm.
in the nial(\ 'Ao mm. in the female. The greatest sagittal diameter is 40 mm. in the male, 37
mm. in the female. The vocal folds in the male measure relaxed about 15 mm., in the female,
but 11 mm.; when stretched, about 20 mm. and 15 mm. respectively. '
The length of the rima glottidis in the quiescent state is on the average 23 mm. in' the male;
17 mm. in the female. In the male the pars intermembranacea measures 15.5 mm., the pars
intercartilaginea, 7.5 mm. In the female these are 11,5 mm. and 5.5 mm. respectively. The
rima may be lengthened by stretching of the vocal folds to 27.5 mm. in the male and 20 mm. in
the female. (Moura.) In the male the width of the rima glottidis is 6-8 mm. in its widest
part, but may be increased nearly to 12 mm.
Vessels and nerves (figs. 980, 985), — The arteries supplying the larynx are the superior
and inferior laryngeal, which accompany the internal and inferior laryngeal nerves respectively,
and the crico-thyreoid arteries (see pp. 538, 564).
The superior and inferior laryngeal veins join the superior and inferior thyreoid veins re-
spectively.
The lymph vascular system is well developed throughout the larynx generally, but in the
THE TRACHEA AND BRONCHI
1225
vocal folds where the mucosa is thin and tightly bound down the vessels are scarce and small
in size (see p. 719).
The nerves of the larynx are the superior and inferior laryngeal branches of the vagus and
also certain branches of the sympathetic. Taste-buds occur and are abundant in the mucosa
of the posterior surface of the epiglottis. The innervation of the muscles has already been in-
dicated, and the description of the course and relations of these nerves will be found in the chapter
on the Peripheral Nervous System. It should be mentioned here, however, that the idea
of sharply limited territories of innervation, not only for the mucosa, but for the muscles as
well, has been brought into question by the researches of Semon and Horsley, E.xner, and others,
which show that the distribution and functions of the laryngeal nerves are e.xtremely complex.
The development of the larynx. — The larynx is developed partly from the lower portion
of the embryonic pharynx and partly from the upper portion of the trachea. The .cricoid carti-
lage represents the uppermost tracheal cartilage, while the thyreoid is formed by the fusion of
four cartilages representing the ventral portions of the cartilages of the fourth and fifth branchial
arches. The laryngeal muscles are derived from the musculature of these arches and conse-
quently their nerve-supply is from the vagus. Whether or not the arytenoid and epiglottic
cartilages are also derivatives of the branchial arches is uncertain, although it seems probable
that they are.
THE TRACHEA AND BRONCHI
The tubular trachea (figs. 972, 989), or windpipe, extends from the larynx
downward through the neck and into the thorax to end by dividing into two
branches, the right and left bronchi [bronchus (dexter et sinister)], which lead to
Fig. 989 — Trachea and Bronchi in Their Relations to the Great Vessels as seen from
Behind. (After Gegenbaur.)
Left subclavian artery
Superior vena cava
Right pulmonary veins
Inferior vena cava
the lungs. These tubes are simple transmitters of the respiratory air. Their walls
are, for the most part, stiff and elastic, consisting in large part of cartilage. While
the_ general form of these tubes is cyhndrical, a rounded contour is presented by
their walls only in front and at the sides, the posterior surface being flat. The
inner surface of the walls of the tubes presents a succession of slight annular pro-
jections caused by the cartilaginous rings which enter into their structure. The
calibre of the trachea varies at different levels, a cast of the lumen being in gen-
eral spindle-shaped. Its sectional area is less than the combined sectional areas
of the two bronchi. When the bifurcation of the trachea [bifurcatio tracheae] is
viewed by looking down into its cavity, a sagitally directed keel, the carina
tracheae (fig. 990), is seen standing between the openings which lead into the
bronchi. Its position is a httle to the left of the mid-plane of the trachea
in a slight majority of cases, or in the mid-plane in a large percentage.
1226 THE RESPIRATORY SYSTEM
Position and relations (figs. 972, 989, 1000). — The trachea lies in the median
plane, extending from the level of the sixth cervical vertebra downward and
backward, receding from the surface in following the curve of the vertebral col-
umn, and deviating a little to the right in approaching the level of the fourth
thoracic vertebra, where it divides. Its lower end is fixed so that with elevation
and descent of the larynx the tube is stretched and contracted, ■ changes in length
which also result from extension and flexion of the head and neck. The mobility
of the trachea is favored by its loose investment of connective tissue.
About half of the trachea lies in the neclj, but the extent varies with the length of the neck,
the position of the head and with age; the trachea holds a lower position in adult life than in
childhood and a still lower one in old age when the bifurcation may be as low as the sixth or
seventh thoracic vertebra. In front and closely connected with it is the isthmus of the thyreoid
gland, covering usually the second to fourth cartilages; anterior to this the cervical fascia and
integuments. The cervical aponeurosis is attached to the upper margin of the sternum in two
lamellae, with an interspace containing the venous jugular arch, a lymph gland, and some fat.
Between these aponeuroses and the trachea is another space containing the inferior thyreoid
veins and some tracheal lymph-glands, and sometimes a thyreoidea ima artery. The innominate
artery occasionally crosses the trachea obUquely in the root of the neck. Behind the trachea,
in its whole length, Ues the oesophagus, which in this part of its course inclines to the left.
On either side are the great vessels and nerves of the neck, and the lobes of the thyreoid gland.
The inferior laryngeal nerve lies in the angle between the (Esophagus and trachea.
Fig. 990. — Bifurcation op the Trachea showing the Tracheal Keel. R. L. Right and
left bronchi. (Heller and von Schrootter, from Poirier and Charpy.)
Within the thorax the trachea lies in the mediastinum, enveloped in loose areolar tissue
and fixed through strong fibrous connections with the central tendon of the diaphragm. The
innominate artery and the left common carotid are at first in front and then at its sides as they
ascend, while the left innominate vein and the remains of the thymus are further forward.
The aortic arch is in contact with the anterior surface of the trachea near the bifurcation.
On the right side are the vagus nerve, the arch of the vena azygos, the superior vena cava, and
the mediastinal pleura; on the left, the arch of the aorta, the left subclavian artery, and the
recurrent laryngeal nerve. A large group of bronchial lymph-glands [lymphoglandulae bron-
chiales] lies below the angle of bifurcation. The oesophagus is behind and to the left.
The bronchi take an obfique course to the hilus of the lung, where they branch.
The right bronchus is nearer to the vertical in its course than is the left; it is
also shorter and broader. These conditions, together with the position of the
tracheal keel, explain the more frequent entrance of foreign bodies into the right
than into the left bronchus. The asymmetrical course of the two bronchi is
probably genetically associated with the position of the heart and aorta.
The azygos vein arches over the right bronchus, the vagus passes behind, and the right
branch of the pulmonary artery crosses anteriorly below the level of the first (eparterial)
branch of the bronchus. The aorta arches over the left bronchus and gains its posterior surface
along with the cesophagus; the left branch of the pulmonary artery passes at first in front and
then above the bronchus.
Dimensions. — On account of their elasticity considerable difficulty is met with in obtaining
accurate measurements of the air-tubes. The length of the trachea is given at 95-122 mm.;
its transverse diameter 20-27 mm. ; the sagittal diameter 16-20 mm. The right bronchus has
a length of 25-34 mm.; the left, 41-47 mm. The transverse diameter of the right is 18 mm.; of
the left, 16 mm. The angle of bifurcation of the trachea varies from 56° to 90°, the mean
being 70.4° a wide angle corresponding to the breadth of the thorax of man. The right bronchus
makes an angle of 24.8° with the median plane; the left, 45.6°.
According to Tillaux the length of that portion of the trachea between the superior edge of
the sternum and the cricoid cartilage varies with age and sex as follows: —
Adult male, from 4.5 to 8.5 cm average, 6.5 cm.
Adult female, " 5 to 7.5 cm " 6.4 cm.
Boys 2| to 10 years, " 2.7 to 6.5 cm " 4.4 cm.
Girls 3i to 101 " " 4 to 6.5 cm " 5.1 cm.
THE TRACHEA AND BRONCHI
1227
The diameter of the lumen of the trachea when distended to a cylindrical form has been
measured by S&: —
New-born 4.12 to 5.6 mm.
Infant 2 years 7.5 to 8 mm.
Infant 4 to 7 8 to 10.5 mm.
Over 20 years, male 16 to 22.5 mm.
Over 20 years, female 13 to 16 mm.
Structure of the trachea and bronchi (figs. 978, 988, 989, 991).— The walls of
the trachea and bronchi are composed of a series of cartilages having the form of
incomplete rings, held together and enclosed by a strong and elastic fibrous mem-
brane. Posteriorly, where the rings are deficient, this membrane remains as the
membranous wall [paries membranacea] ; between the cartilages it constitutes
the annular ligaments [ligg. annularia (trachealia)].
Fig. 991. — Schematic Longitudinal Section of the Wall op the Trachea. (Gegenbaur.)
Fibrous membrane^
Annular ligament
Tracheal glandS'
Tracheal cartilage
A tracheal cartilage [cartilago trachealis] comprises a little more than two-
thirds of a circle. Its ends are rounded, its outer surface flat, while the inner sur-
face is convex from above downward; the upper and lower margins are nearly
parallel. The cartilages are from sixteen to twenty in number. The first is
usually broader than the type, and is connected by the crico-tracheal ligament
with the cricoid cartilage. Sometimes these two cartilages are in part continuous.
The last cartilage is adapted to the bifurcation of the trachea and presents at
the middle of its lower margin a hook-hke process. This turns backward between
the origins of the bronchi, and in the majority of cases gives a cartilaginous basis
to the tracheal carina. Some of the tracheal cartilages vary from the type by
bifurcating at one end. The cartilages keep the lumen of the trachea patent for
the free passage of the air. Calcification occurs as with the laryngeal cartilages,
but much later in life.
A mucous coat [tunica mucosa], soft and pinkish-white in colour, covers the
inner surface of the trachea; posteriorly it is thrown into longitudinal folds.
Mucous secreting tracheal glands [gl. tracheales] are present in the elastic sub-
mucous coat [tela submucosa] between the cartilages and at the back of the
trachea. A thin layer of transversely disposed smooth muscle-fibres, stretching
between the ends of the cartilages in the posterior wall, constitutes the muscular
1228 THE RESPIRATORY SYSTEM
coat [tunica muscularis]. Contraction of this trachealis muscle, as it is more prop-
erly named, causes the ends of the tracheal cartilages to be approximated and
the lumen of the wind-pipe to be diminished.
The structure of the walls of the bronchi is similar to that of the trachea. The
right bronchus possesses six to eight cartilages; the left, nine to twelve.
An inconstant broncho-asophageal muscle may connect the back of the left bronchus with
the gullet.
Vessels and nerves. — The arteries supplying these air-tubes come from the inferior thyreoid
and from the internal mammary by its anterior mediastinal or broncliial branches. Venous
radicles come together in the annular ligaments and join lateral veins on either side, which empty
the blood into the plexuses of the neighbouring thyreoid veins.
Lyinph-vessels are abundant, and are disposed in two sets, one in the mucosa, another in
the submucosa. They drain into the tracheal, bronchial and oesophageal lymph-glands.
Neri'es are provided by the vagus direct, by the inferior laryngeal, and by the sympathetic.
THE LUNGS
The lungs [pulmones], the essential organs of respiration, are constructed in
such a way as to permit the blood to come into close relation with the air (fig.
992). Their genetic connection with the entodermal canal has already been indi-
cated (see also p. 1099). In plan of structure the lung has been compared with
Fig. 992. — Schematic Section of a Lobule of the Lung showing the Relation of the
Blood-vessels to the Air-spaces. (After Miller, from the 'Reference Handbook of the
Medical Sciences.')
b.r. Respiratory bronchiole, d.al. Alveolar duct; a second alveolar duct is shown cut off.
a,a. Atria, s.al. Alveolar saccule, a.p. Alveolus, art. Pulmonary artery with its branches
to the atria and saccules, v. Pulmonary vein with its tributaries from the pleura (1), the
alveolar duct (2), and the place where the respiratory bronchiole divides into the two alveolar
ducts (3).
)sa/
a gland, since it is composed of a tree-like system of tubes terminating in expanded
spaces. Closely associated with the system of tubes are certain blood-vessels,
some of which take part in nourishing the organ, others participate in its special
mechanism.
The lungs are two in number, and lie one on either side of the thoracic cavity,
separated by a partition known as the mediastinum (figs. 993, 997, 1000). Serous
membranes covering the latter right and left are parts of two closed sacs, the
pleurse, each of which is reflected about a lung and the neighbouring chest-wall
after the manner of serous membranes in general. The space enclosed within the
sac-walls is the pleural cavity, genetically a subdivision of the ccelom.
Form (figs. 994, 998). — The lung is pyramidal or conical in form, with the base
[basis pulmonis] below and resting on the diaphragm, and with apex [apex pul-
moni.s] above, in the root of the neck. Two surfaces, costal and mediastinal, are
described. The broad convex costal surface [fades costalis] is directed against
THE LUNGS
1229
the thoracic wall in front, laterally and behind, and is marked by grooves corre-
sponding to the ribs. The mediastinal surface [f acies mediastinalis] is concave and
presents a contour adapted to structures of the mediastinum (fig. 994). A special
concavity on this surface, known as the cardiac fossa, corresponds to the promi-
nence of the heart and is deeper in the left lung than in the right. Above and
behind the cardiac fossa is a depression, the hilus of the lung [hilus pulmonis],
where the bronchus and pulmonary vessels and nerves together constituting the
root of the lung [radix pulmonis], enter and leave. Near the posterior edge of the
mediastinal surface is a groove, which ascends and turns forward over the hilus ;
the groove of the left lung is adapted to the cylindrical surface of the aorta;
that of the right, the vena azygos. A well-marked subclavian sulcus [sulcus sub-
FiG. 993. — Horizontal Section of the Thorax op a Man, aged Fifty-seven, at the Level
OP the Roots of the Lungs, seen prom Above. (J. S.) (Quain.) X 1.
A. A. Ascending aorta. A.M. Anterior mediastinum. A.V. Azygos vein. D.A. Descend-
ing aorta. E. Eparterial bronchus. I. Superior lobe of lung. L.B. Left bronchus. L.P.
Left phrenic. L.P.V. Left pulmonary vein. L.V. Left vagus. (Es. CEsophagus. P A.
Pulmonary artery. P.C. Pericardial cavity. R.B. Right bronchus. R.P.A. Right
branch of pulmonary artery. R.P.C. Right pleural cavity. R.P.N. Right phrenic.
R.P.V. Right pulmonary vein. R.V. Right vagus. S. Inferior lobe of lung. Sc.
Scapula. T.D. Thoracic duct. 3, 4, .5, 6, 7. Corresponding ribs.
clavius] extends upward on this surface to the apex, corresponding on the right
side to the lower part of the trachea and right subclavian artery, on the left tothe
left subclavian artery alone. Further forward is a groove adapted in the right
lung to the superior cava; in the left to the left innominate vein. The lung is not
in actual contact with these several structures, but is separated from them by the
mediastinal pleura. The mediastinal surface passes gradually into the costal
surface posteriorly, there being no proper posterior edge. Where the mediastinal
and costal surfaces meet in front, a sharp anterior margin [margo anterior] exists
(fig. 997). In the right lung this runs down in a gentle curve to turn lateralward
in the inferior margin. In the left lung the anterior margin is cut into by a wide
cardiac notch [incisura cardiaca], which is occupied bj' the heart in the pericardium
as it is pressed toward the anterior thoracic wall. The cardiac notch is separated
from the inferior margin by a little tongue of lung substance, the pulmonary
lingula [lingula pulmonis].
The base of the lung (fig. 994) presents the diaphragmatic surface [facies
diaphragmatica] concave and oblique in adaptation to the dome of the diaphragm.
It is limited by a sharp inferior margin [margo inferior], which follows the curves
of the mediastinal and costal surfaces, and fits into the angle between the dia-
phragm and thoracic wall.
1230
THE RESPIRATORY SYSTEM
The apex (figs. 994, 997, 998) is rounded and points upward with an inclination
forward and medially, accommodating itself to the structures within and about
the superior aperture of the thorax.
A deep interlobar fissure [incisura interlobaris] (figs. 994, 998), reaching
through the lung substance nearly to the hilus, divides each organ into a smaller
superior lobe [lobus superior] and a larger inferior lobe [lobus inferior]. The
interlobar fissure runs downward and forward beginning a short distance below the
apex, and reaching the base near the anterior margin in the left lung, somewhat
further back in the right lung. From the obliquity of the plane of the fissure it
will be noticed that the inferior lobe reaches posteriorly to within a short distance
of the apex, and includes the greater part of the back and base of the lung, while
the superior lobe takes in the anterior margin and apex. The presence of a mid-
dle lobe [lobus medius] disturbs the symmetry of the right lung. This results
from a deep, nearly horizontal incisure cutting through the lung somewhat below
its middle, and extending between the anterior margin and the main interlobar
fissure, which it reaches at about the level of the axillary line.
Fig. 994. — Left Lung, viewed pbom the Mediastinal Surface.
Apex Subclavian groove
I
(Spalteholz.)
Costal surface
Hilus, with line of section
of the pleura
Interlobar fissure — '
Left branch of puln
nary artery
Left bronchus-
Mediastinal surface
^^Left pulmonary veins
-Cardiac fossa
Pulmonary ligament —
-Anterior margin
Inferior lobc_.-
Inferior margin -
Interlobar fissure
Diaphragmatic surface
Besides possessing the individual peculiarities mentioned, the two lungs further differ from
each other in general form and weight, the right lung being considerably broader and heavier
than the left. The difference in length maintained by some anatomists, even if it prove constant,
must be slight and of httle practical importance. These difJerenoes seem to foUow the asym-
metry of the vault of the diaphragm and the position of the heart.
The hilus (fig. 994), already mentioned as situated on the mediastinal surface, presents in
the left lung a raquette-shaped outline. Its average height is about 8.8 cm. (Luschka);it
extends over both lobes. The hilu of the right lung, rather four-sided in outline and shorter
than that of the left, is related to the three lobes. The entering structures, constituting the
root of the lung (figs. 989, 993, 994), include the bronchus, pulmonary artery and veins, bron-
chial vessels, lymphatic vessels and glands, and pulmonary nerves. These are bound together
by connective tissue and invested by the pleura. The bronchus is in the posterior and upper
part of the root; the pulmonary vessels he anteriorly, the veins below the arteries.
The surface of the lung is marked off in polygonal areas of different sizes (secondary lobules)
by lines containing pigment. The pigmentation is especially deep on the lateral surface along
the furrows corresponding to the ribs.
THE BRONCHIAL TUBES
1231
Branching of the bronchial tubes (fig. 995) . — Each bronchus, from its origin at
the bifurcation of the trachea, takes an oblique course to the hilus, and then con-
tinues in the lung as a main tube, extending toward the posterior part of the base.
These stem-bronchi are curved, probably in adaptation to the heart, the right hke
the letter C and the left like an S. Throughout their course the stem-bronchi give
off in monopodic fashion collateral branches, the bronchial rami [rami bronchiales],
and these, branching in a similar way, reach all parts of the lung.
The first bronchial ramus of the right stem-bronchus arises above the place where the latter
is crossed by the pulmonary artery and is named the eparterial bronchial ramus [ramus
bronohialis eparterialis]; it supphes the superior lobe of the right lung, sending a special branch
to the apex. All other bronchial rami, whether in the right or left lung, take origin from the
Fig. 995. — Cast of the Air-tubes and Their Branches, viewed from in Front.
(Spalteholz.)
Ttachea (also the position of tlie median plane)
I
Bifurcation of trachea
/^ Left bronchus
Main bronchus
Hyparterial
branch to
middle lobe
Hyparterial branch
to superior lobe
Position of median plane
stem-bronchi below the level of the crossing of the pulmonary artery and are called hyparterial
bronchial rami [rami bronchiales hyparterialesj. The second bronchial branch of the right lung
goes to supply the middle lobe, while several bronchial branches enter the inferior lobe. On
the left side, the first bronchial branch arises below the crossing of the pulmonary artery, and
goes to supply the supei-ior lobe, providing it with an apical ramus. The other branches are
given to the inferior lobe.
Structure of the bronchial rami. — The larger bronchial rami contain in their walls both
C-shaped and irregular plates of cartilage, the latter gradually replacing the former as the
branches become smaller. The membranous wall is lost and plates of cartilage are disposed
on all sides. The mucosa, with ciUated epithehum, is thrown into longitudinal folds covering
bundles of elastic fibres of the membrana propria. Next to the latter is a continuous layer of
smooth muscle-fibres circularly arranged. Mucous secreting bronchial glands [gl. bronchiales]
are present as far as tubes of 1 mm. diameter; here the cartilages also disappear.
To W. S. IVIiller is due the credit of having greatly increased our knowledge of the finer
structure of the lung and for having presented the conception of the primary lung lobule now
generally accepted by anatomists. Some of the chief results of MiUer's work are embodied in
1232
THE RESPIRATORY SYSTEM
the following descriptions pertaining to the termination of the air-tubes and to the blood and
lymph vascular systems of the lungs and pleurse.
Through further branching of the bronchial rami a great number of very fine bronchioles
[bronchioli] are reached, whose walls possess a weak muscle layer and are lined by mucosa
having an epithelium of flattened non-ciliated cells. These, subdividing, give rise to the
respiratory bronchioles [bronchioh respiratorii], the walls of which are beset with alveoli
(fig. 992). From the respiratory bronchioles arise the alveolar ducts [ductuli alveolares], or
terminal bronchi, each of which leads to a group of air-spaces, called atria, each of which again
communicates with a second series of air-spaces, tlie air-sacs (alveolar sacs or infundibula),
whose walls are pouched out to form numerous pulmonary alveoli [alveoli pulmonum].
A terminal bronchus with its air-spaces and blood-vessels, lymphatics and nerves, together
form a pulmonary lobule [lobulus pulmonum], the unit of lung structure.
Aeby divided the bronchial branches into two sets, according to their relation to the pul-
monary artery. The branch arising above the place where the pulmonary artery crosses the
stem-bronchus he named the eparterial bronchus, and those arising below the crossing he called
hyparterial. An eparterial bronchus exists only on the right side ; all other branches are hy-
parterial. Since the eparterial supplies the superior lobe of the right lung and no eparterial
branch is present on the left side, Aeby concluded that the left lung had no lobe homologous
with the superior lobe of the right lung. He compared the middle lobe of the right with the
superior lobe of the left lung. The collateral branches of the stem-bronchi arise in a dorsal
and ventral series in the lower mammals, and the same arrangement, though less obvious,
obtains in man. According to the views of Aeby and Hasse, the first ventral branch of the right
side is distributed to the middle lobe, while the remaining three ventral and all the dorsal lateral
branches are given to the inferior lobe. On the left side, the first ventral branch is given to the
superior lobe; the other ventral branches and the dorsal branches are distributed to the inferior
lobe.
Fig. 996. — Scheme of the Bbonchial Tree According to Narath. A. Anterior view. B.
Right lateral view. (Poirier and Charpy.)
A. Apical bronchus, collateral of the first ventral and susceptible of becoming eparterial, Ap
in migrating to the bronchial trunk.
Narath considers the division of bronchial branches in accordance with their relation to
the pulmonary artery as of no great morphological significance. He attributes the apparent
differences on the two sides to a shifting in position of homologous branches. Thus, Narath
considers that the eparterial bronchus of Aebj' has become the first dorsal lateral branch by
displacement above the pulmonary artery and that it is homologous with an apical branch of
the left side, which retains its primitive origin from the first ventral branch (fig. 996) . Narath's
conception of the migration of the bronchial branches is supported by the results of Hunting-
ton's extensive stiulii's of the bronchial tree in mammals.
The physical properties of the lungs. — The average dimensions in the adult male are as
follows: Height of the lung is given at 2.5-27 cm., the greatest sagittal diameter at 16-17 cm.,
and the greatest transverse measurement as 10 cm. for the right and 7 cm. for the left. The
volume of the lungs when well expanded is 6500 c.c. (Merkel.) The loeight of the lungs can
be found only approximately on account of the presence of blood and mucus. In the adult
male the weight of both lungs is given as 1300 gm.; female, 1023 gm. The weight of the right
lung compared with the left is as 11 is to 10. Ried and Hutchinson found the weight of the
lungs compared with that of the body as 1 :37 (male), 1 :43 (female); in the foetus at term,
1 : 70. After respiration has been established, the lung, if placed in water, will float. Its
specific gravity is between 0.345 and 0.746, (Rauber.) The fcetal lung contains no air and is
heavier than water. Its specific gravity is 1.045 to 1.056. (Ivrause.) Lung tissue, free of
air, with vessels moderately filled, has likewise a specific gravity of 1.045 to 1.056. (Vierordt).
The colour of the lung result sfrom the presence of blood, pigment, and the air in the alveoli.
It varies therefore as these constituents are all or in part present and with differences in their
TOPOGRAPHY OF THE LUNGS
1233
proportions. Thus the general colour is red in the fcetus, pink, in the infant, and grey mottled
with black in the adult. The dark colour is traceable to the carbonaceous matter carried into
the lungs from the atmosphere.
In consistence the lung is soft and spongy, and when compressed between the fingers,
emits a crackling sound. Among the physical properties the elasticity of the lung is quite
remarkable: Under ordinary conditions the pressure of the air in the lung keeps the alveoli
and the organ as a whole distended, but when the pleura has been opened and the air pressure
equalised without and within, the lung collapses.
Topography. — The apices of the lungs extend upward as high as the first thoracic vertebra-
a level considerably higher than the superior margin of the sternum (figs. 997, 998). The sub,
clavian vein and artery and the brachial plexus, together with the anterior scalene muscle,
control to a certain degree the height reached. There seems to be no constant difference be-
tween the levels attained by the apices of the two lungs. The extent to which the apex rises
above the clavicle is rarely more than 3.5 cm. (Merkel), and will, of course, vary with individual
differences in the position and form of this bone. The average is not over 2.5 cm. (1 in.).
The base of the lung, resting on the diaphragm, is separated by that thin partition from the
underlying abdominal viscera: thus beneath the base of the right lung is the right lobe of the
liver, while under the left lung are the left lobe of the liver, the fundus of the stomach, and the
spleen. The position of the apex changes very little in respiration, and the same holds true for
Fig. 997. — Position of the Lungs from Before. (Merkel.)
, The parietal pleura is shaded and outlined in black.
the hinder bulky part of the lung. The latter rests against the side of the vertebral column in
the deep hollow of the angles of the ribs, and reaches below to the level of the eleventh costo-
vertebral joint (fig. 998). The anterior margins (fig. 997) descend in curves from behind the
sterno-clavicular joints, and run near together a little to the left of the median line. At the
level of the sixth costo-sternal junction the anterior margin of the right lung turns lateral-
ward to follow the sixth costal cartilage. The anterior margin of the left lung turns lateralward
a,long the fourth costal cartilage as far as the para-sternal line, descending in .a curve to the
lingula and thus forming the cardiac incisure. The positions of the inferior margins (figs.
997, 998) of the two lungs are practically alike in their positions. Each extends in a curve cov-
yex downward, behind the sixth costal cartilage in its entire length, crosses the costo-chondral
junction of the sixth rib to the superior margin of the eighth rib in the axillary hne, and so to
the ninth or tenth rib in the scapular line, whence they run horizontally medialward to the
eleventh costo-vertebral joint. *
* These relations are the mean between the conditions observed in the cadaver and as found
by physical examination of the hving. In old age the inferior margins of the lungs reach a
level one or two intercostal spaces lower than is the case in adult life (Mehnert).
1234
THE RESPIRATORY SYSTEM
The interlobar fissure (fig. 998) begins about 6 cm. below the apex of the lung at the level
of the head of the third rib. With the arm hanging at the side, a hne drawn across the back
from the third thoracic spine to the root of the scapular spine would indicate the course of
the upper part of this fissure. (Merkel.) Thence it passes downward and around the chest to
the end of the sixth bony rib in the mammillary line. Merkel points out the use of the root
of the scapular spine as a landmark for finding the limits of the lobes posteriorly: with the
arm hanging at the side all above this spot is superior lobe; aU below it the inferior. The short
fissure of the right lung begins at the main interlobar fissure in the axillary line, about the
level of the fourth rib or fourth interspace, and passes nearly horizontally to the anterior margin
of the lung at the level of the fourth costal arch.
The roots of the lungs are placed opposite the fifth, sixth, and seventh thoracic vertebrae.
The right root lies behind the inferior vena cava and under the arch of the azygos vein; the left
root is beneath the aortic arch and in front of the thoracic aorta. The phrenic nerve passes
in front of each root, the vagus behind. On the front and back are the pulmonary plexuses,
anterior and posterior. The ligament of the pleura goes from the lower edge of the root.
Vessels and nerves of the lungs. — The bronchial arteries (see p. 588), belonging to the
systemic system, carry blood for the novirishment of the lungs. They arise from the aorta or
from an intercostal artery, two for the left lung and one for the right, and, entering at the hilus,
Fig. 998. — Position of the Lungs from Behind. (Merkel.)
The pleura is represented as in Fig. 997.
reach the hinder wall of the main bronchus. The bronchial arteries accompany the bronchi,
whose walls they supply, as far as the distal ends of the alveolar ducts, beyond which they do
not go. These vessels also supply the lymph glands of the hilus, the walls of the large pulmonary
vessels, and the connective-tissue septa of the lung. Bronchial veins (see p. 664), anterior
and posterior, arise from the walls of the first two or three divisions of the bronchi and end in
the innominate and the azygos or in one of the intercostal veins; those arising from the walls
of the smaller tubes, including the alveolar ducts, join the pulmonary veins. The pulmonary
artery (see p. 528), entering the hilus in a plane anterior to the bronchus, tm-ns to the posterior
aspect of the main-stem, following its branches and their subdivisions to the lobules. Entering
the lobule, the last branch of the vessel gives off as many twigs as there are atria (fig. 992),
and these twigs end in dense capillary nets in the walls of the alveoli. Here the venous blood
brought by the pulmonary artery, separated from the air in the alveolus only by a thin septum,
is changed to arterial blood in the respiratory process. According to Miller, anastomosis
between the branches of the pulmonary artery are exceptional. Anastomosis between the
bronchial and pulmonary arteries has been claimed, but the connection apparently existing
between these vessels is through the radicles of the bronchial veins which join the pulmonary
veins. The pulmonary venous radicles begin at the capillary networks and drain the arterial
blood into the pulmonary veins, which run between adjacent lobules and which receive also
THE THORACIC CAVITY 1235
blood coming from the capillary network of the pulmonary pleura and from the capillary net-
work of the bronchi (fig. 992). Thus it wiU be seen that while the pulmonary vein carries
mainly arterial blood, it carries also some venous blood. The pulmonary veins (see p. 529)
follow the bronchial tree on the side opposite the arteries to the hilus, where, having converged
to two large trunks located in the root of the lung below the plane of the artery, they pass to the
left atrium. The pulmonary veins have no valves.
Lymphatics. — Miller has found the lymphatic vessels forming a closed tube system in the
walls of the bronchi, in the pleura, and along the branches of the pulmonary artery and veins.
Within the lung numerous pulmonary lymph-glands [lymphoglandulse pulmonales] are found
chiefly at the places of branching of the larger bronchi [lymphoglandulae bronchiales[. Scat-
tered along the latter, as well as associated with the branches of the pulmonary artery and
vein, are found masses of lymphoid tissue. Deposits of carbonaceous matter in the lymphoid
structures of the lung are present, except in early infancy ; the amount increases with age.
Nerves. — The vagus and sympathetic contribute to form the pulmonary plexuses in front
and behind the root of the lung, from which branches go to accompany bronchial arteries; a
smaller number accompany the air-tubes (see p. 957).
Variations. — Congenital absence of one or both lungs has been observed. Variations in the
lobes are not uncommon — four for the right and three for the left lung has been recorded. An
infracardiac lobe, as found in certain mammals, sometimes occurs; an infracardiac bronchus is,
however, constant in man. More or less complete fusion of the middle and upper lobes of the
right lung is not rare. The lungs may be symmetrical, with two lobes each, the apical bronchus
of the right springing from the first ventral bronchus, as is normal for the left lung (Waldeyer,
Narath) ; or the lungs may have three lobes each, the apical bronchus of the left arising from the
main bronchus. The apical bronchus of the right lung may arise from the trachea, an origin
that is normal in the hog and other artiodactyls.
Development of the lungs and trachea. — The first indication of the trachea and lungs
appears in embryos of about 32 mm. as a trough-like groove in the ventral wall of the upper
part of the oesophagus, communicating above with the pharynx. Later the groove becomes
constricted oi? from the oesophagus, the constriction extending from below upward, so that a
tube is formed which opens into the pharynx above. The lower end of this tube soon becomes
bilobed, and the lobes, elongating, give rise to additional lobes, of which there are primarily
three in the right side and two in the left. The upper unpaired portion of the tube becomes the
trachea, while the lobed lower portion gives rise to the bronchi and lungs, the complicated struc-
ture of the latter being produced by oft-repeated branchings of the bronchi.
THORACIC CAVITY
Thoracic cavity [cavum thoracis] is the term used to denote the space included
by the walls of the thorax and occupied by the thoracic viscera. These are, on
each side, the lung, surrounded by the pleural cavity, and in the middle the
pericardium and heart, great vessels, trachea and oesophagus, all closely associated
and forming a dividing wall, the mediastinal septum, standing between the right
and left sides of the thoracic space.
The limits of the thoracic space are given by the skeletal parts of the thorax
together with the ligaments involved in the articulations and the muscles and
membranes interposed between the bones. The arched diaphragm forms the
inferior limit; and the barrier presented by the scalene muscles and the cervical
fascia makes the superior boundary, which, it is to be observed, lies above the
plane of the superior aperture of the thorax and therefore in the base of the neck.
These boundaries are approached by the extension of the pleural cavities; yet
there intervenes the parietal layer of the pleural sac which is connected with
the thoracic walls by loose connective tissue, the endothoracic fascia [fascia
endothoracica].
The form of the thoracic space departs from the external contour of the thorax
chiefly through the projection into it of the ridge made by the succession of centra
of the thoracic spine, and by the presence on either side of the latter of the broad,
deep pulmonary sulcus. On account of these features a transverse section of the
thoracic space is somewhat heart-shaped, but, however, much compressed antero-
posteriorly (fig. 993).
The arch of the diaphragm on the right side rises to the level of the spinous process of the
seventh thoracic vertebra; on the left, to the level of the eighth thoracic spinous process. At
its circumference the diaphragm is in contact to a variable extent above its origin with the inner
surfaces of the costal arches. In the lower part of this zone a connection exists between the
muscle and the thoracic wall through a continuation of the endothoracic fascia; in the upper
part, the phrenico-costal sinus (see p. 1237) intervenes. The level reached by this deepest
part of the pleural cavity is lower than the summit of the peritoneal cavity, so they overlap to a
considerable extent.
1236
THE RESPIRATORY SYSTEM
THE PLEURA
The pleura (fig. 993) is a closed serous sac, which invests the lung (pulmonary
pleura), and lines the inner surface of the thoracic walls (parietal pleura). The
pleural cavity [cavum pleurae] is the capillary space enclosed by the walls of the sac
containing a little fluid which lubricates the apposed surfaces of the pulmonary
and parietal membranes. There are two pleurae, one in relation to each lung,
completely separated by a sagittal partition, the mediastinum.
FiQ. 999. — Plettral Cavity Opened From in Front.
1, first rib; 2, manubrium sterni; 3, acromial extremity of clavicle; 4, xiphoid process,
5, linea alba; 6, m. transversus abdominis; 7, seventh rib; 8, sternocleidomastoid m.; 9,
anterior scalene m.; 10, larynx; 11, thyreoid gland; 12, deep layer of cervical fascia in front
of the trachea; 13, corresponds to upper part of anterior mediastinal cave; 14, pleural cupola;
15, mediastinal pleura; 16, lower margin of costal pleura; 17, pericardium; 18, superior lobe
of lung; 19, middle lobe of right lung; 20, inferior lobe of lung; 21, diaphragm. (Rauber-
Kopsch.)
The pulmonary pleura [pleura pulmonalis] forms a smooth glistening coat over
the outer surface of the lung, with the tissue of which it is inseparably connected.
At the hilus the pulmonary pleura passes from the mediastinal surface of the lung
to cover the root above, in front, and behind, and becomes continuous medialward
with the parietal pleura of the mediastinum. Below the root of the lung the
pleura is reflected medialward in a double layer as the pulmonary ligament
[Hg. pulmonale] (fig. 994).
This presents anterior and posterior surfaces and three margins; the base is mostly free, and
directed toward the diaphragm, with which it is connected at its medial end; the apex is at the
lung root, one margin is next to the lung, and the other joins the mediastinal pleura.
THE PLEURA
1237
The parietal pleura [pleura parietalis] is divided, according to the regions of the chest with
which it is associated, into the costal, diaphragmatic, and mediastinal pleura. The costal
pleura [pleura costahs] hnes the thoracic wall, to which it is bound not very firmly by the
endothoracic fascia. It covers incompletely the back of the sternum and extends laterally upon
the ribs and "intercostal muscles. Posteriorly beyond the angles of the ribs it passes over the
anterior rami of the thoracic nerves and intercostal vessels, the heads of the ribs, and the
sympathetic trunk to the vertebral column; here it becomes continuous with the mediastinal
pleura. Above, the pleura reaches beyond the superior margin of the sternum into the root of
the neck, and in the form of a dome, the cupola of the pleura [cupola pleurae], is adapted to the
ape.x of the lung. It is supported by processes of the deep cervical fascia, and by a fibrous
aponeurosis known as Sibson's fascia, coming from the scalenus minimus muscle and connected
with the inner margin of the first rib. In relation to the pleural cupola are those structures
already described as grouped about the lung apex: the brachial plexus, subclavian artery, ante-
rior scalene muscle, and the subclavian vein, and, on the left side, in addition, the thoracic duct.
Below, the costal pleura is continuous with the diaphragmatic pleura [pleura diaphragmatica],
which adheres closely to the thoracic surface of the diaphragm and covers it, excepting the
pericardial area and where the diaphragm and thoracic wall are in contact.
The mediastinal pleura [pleura mediastinalis] is reflected from before backward at the
right and left sides of the mediastinum as the laminEB mediastinales, covering the pericardium
Fig. 1000. — Right Lateral Surface op the Mediastinum after Removal op the Pleura.
(Poii-ier and Charpy.)
Trachea . —
Phrenic nerve
[pleura pericardiaca], to which it is closely adherent, and also the other structures of
the mediastinum, with which the two layers are less firmly connected. Above the lung root
the mediastinal pleura stretches directly from the spine to the sternum; but at the level of the
root and below it, it is reflected laterally to the pulmonary pleura covering the root in front and
behind and forming the pulmonary ligament.
The right mediastinal lamina covers (fig. 1000) the right innominate vein, the superior vena
cava, the vena azygos, the trachea, the innominate artery, the right vagus and phrenic nerves,
and the oesophagus. The left lamina lies against the left innominate vein, the arch of the aorta
the left subclavian artery, the thoracic aorta, the left phrenic and vagus nerves, and the cesoph-
agus. About the base of the heart-sac are a number of adipose folds [plica? adiposis) projecting
from the pleura, the surfaces of which present some villous processes, the pleural villi [villi
pleurales] ; the latter also occur on the pulmonary pleura along the inferior margin of the lung.
The lines of pleural reflexion are of practical importance (figs. 997, 998, 1003). Posteriorly,
the costal pleura simply turns forward in a gentle curve to become the mediastinal pleura, but
anteriorly and inferiorly the membrane is folded upon itself, leaving intervening capiUary
spaces, the sinuses of the pleura [sinus pleurtT;]. Such a space is present where the costal pleura
is reflected upon the diaphragm, the sinus phrenicocostalis, the fold of the pleura occupying
the upper part of the angle between the thoracic wall and diaphragm, the endothoracic fascia
1238
THE RESPIRATORY SYSTEM
filling the lower part. The inferior margui of the lung enters this sinus a variable distance in
iuspiration. The line of the costo-diaphragmatio reflexion begins in front on the sixth costal
cartilage, which it follows, descending obliquely to cross the seventh interspace in the mam-
millary line. The greatest depth reached is at the tenth rib or interspace in the axillary line.
The line of reflexion then continues around the thorax ascending slightly to the twelfth costo-
vertebral joint.
The Ime of reflexion behind is sometimes found as low as the level of the transverse process
Figs. 1001 and 1002. — Boundaeibs op the Pleura and Lungs.
Lines of pleural reflection red, boundaries of the lungs and pulmonary lobes black.
1, sixth cervical vertebra; 2, first thoracic vetebra; 3, twelfth thoracic vertebra; 4, first
lumbar vertebra; 5, manubrium sterni; 6, body of sternum; 7, xiphoid process; 8, first rib;
9, cartilage of seventh rib; 10, 11, 12, tenth, eleventh and twelfth ribs. (Rauber-Kopsch.)
of the first lumbar vertebra. Such a possibility must be considered in operating upon the kidney.
The lines of reflexion of the costal pleura backward to the mediastinal pleura behind the
sternum begin opposite the sterno-clavicular joints, descend obhquely medialward to the level
of the second costal cartilage, whence they run near together or in contact, but to the left of the
medianHline, to the level of the fourth cartilage. The reflexion on the right side continues
from the sternum as far as the sixth rib cartilage, there turning laterally into the costo-dia-
phragmatic reflexion. The line on the left side, in the region of the cardiac notch (from the fourth
Fig.
J103. — Schematic Drawing to Represent the Maximum op Fluctuation in the
Position op the Anterior Lines op Pleural Reflexion. (Tanja.)
to the sixth cartilages), is a little to the left of the sternal margin. From this position of the
line of reflexion it happens that there is left uncovered by pleura a small area of the pericardium
which is in contact immediately with the chest-wall. A reduplication of the pleura takes
place along the anterior line of reflexion, and into the sinus costomediastinalis so formed the
thin anterior margin of the lung advances in inspiration. That part of the left costo-mediastinal
sinus which is in front of the pericardium is not completely filled by the margin of the lung.
Although the positions of the lines of reflexion of the mediastinal pleura here described are those
THE MEDIASTINAL SEPTUM 1239
usually encountered, it should be noted that they are subject to variation. The extremes of
variation of the anterior lines, as determined by Tanja, are indicated in fig. 1003.
Blood-vessels. — The vascular networks of the pulmonary pleura are derived from the
bronchial artery and probably to some extent from the pulmonary artery which in the dog, is
the only source of blood supply. The venous radicles arising from the network enter the lung.
(See radicles of the pulmonary vein on page 1235.) The parietal pleura is supplied by arteries
from several sources: internal mammary, intercostals, phrenics, mediastinal, and bronchial.
The veins correspond to the arteries. The lymphatics of the pulmonary pleura form rich
networks without definite relations to the lobules of the lung. They accompany the radicles
of the pulmonary veins and drain into the bronchial lymph-glands. In the parietal pleura
lymph-vessels are present most abundantly over the interspaces; they empty into the sternal
and intercostal glands. (See p. 728.) The nerves supplied to the pulmonary pleura are
branches from the pulmonary plexus; to the parietal pleura, from the intercostals, vagus,
phrenic, and sympathetic.
MEDIASTINAL SEPTUM
The two pleural cavities are separated from each other by the mediastinal sep-
tum [septum mediastinale] (fig. 1000). This is a sagittal partition extending
from the superior aperture of the thorax to the diaphragm between the thoracic
vertebrae and the sternum, its free surfaces, right and left, formed by the mediast-
inal layers of the pleurae. It is composed of the pericardium and heart and of
structures which, for the most part, extend in a longitudinal direction through the
thoracic cavity.
These include the oesophagus together with the vagus nerves, the thoracic duct, thoracic
aorta and azygos vein; the trachea, the pulmonary vessels and the arch of the aorta with its
great branches, the superior vena cava and its tributaries and the phrenic nerves; the thymus
gland, internal mammary vessels and many lymph glands throughout the septum. These
structures are packed together and supported by intervening connective tissue. Moreover,
the connection of the sheaths of the great vessels with processes of the cervical fascia and the
fixation of the pericardium to tlie diaphragm, give to the latter a strong support. Owing to
the position of the heart, the two sides of the septum are not symmetrical, and it follows from
the bulging of the left surface of the mediastinal septum that the left pleural cavity is encroached
upon.
The name mediastinal cavity has been applied to the two regions of the medi-
astinal partition which find themselves located, the one in front, the other behind
the plane of the heart. There is in reality no cavity, the term being used in this
connection merely to donate space. Between the two spaces are interposed the
pericardium and heart, the great vessels, trachea and bronchi. The anterior
mediastinal cavity [cavum mediastinale anterius] is small. Its lateral limits are
formed by the mediastinal layers of the pleurse, right and left, which are reflected
backward from the costal pleurae of the anterior thoracic wall. The space is
occupied by loose connective tissue, surrounding the thymus gland, the internal
mammary vessels and a number of lymph-glands.
Recalling the lines of reflexion of the mediastinal pleurfe as above described, the form,
position and extent of this space as observed from in front, will be understood; it is widest
behind the inferior end of the body of the sternum and fifth and sixth costal cartilages of the
left side {area inlerpleurica inferior) ; narrowest where the mediastinal layers are approximated
behind the body of the sternum, broader again where the laminae deviate posterior to the
manubrium sterni {area inlerpleurica superior). In the latter space lies the thymus gland and
the superior portions of the internal mammary vessels. In the area interpleurica inferior
the pericardium comes into immediate contact with the anterior thoracic wall, and here the
inferior portions of the left internal mammary vessels are found. The lymphatic vessels and
glands of the anterior mediastinal space belong to the anterior mediastinal and sternal groups.
The posterior mediastinal cavity [cavum mediastinale posterius] (fig. 1000),
hmited behind by the thoracic vertebrae and laterally by the mediastinal layers of
the pleurae where they are reflected forward from the costal plem-ae of the pos-
terior thoracic walls, is elongated and of more regular form than the anterior space.
It includes the thoracic aorta, the oesophagus and vagi, the thoracic duct, azygos
vein and lymph glands.
Within this space are also to be found the origins of the right intercostal arteries, the
hemiazygos and, when present, the accessory hemiazygos veins, terminations of some of the
left intercostal veins and the greater splanchnic nerves. The lymph glands belong to the
posterior mediastinal group.
(Pigs. 993, 994). — A subdivision of the mediastinal septum into anterior, middle, posterior,
and superior mediastinal spaces has long been customary, and is useful for descriptive purposes.
The superior mediastinum is that part of the mediastinum which Ues above the level of
1240 THE RESPIRATORY SYSTEM
the pericardium. It extends" between the first four thoracic vertebrse behind and the manu-
brium sterni in front, and contains the arch of the aorta and the great vessels arising from it,
the innominate veins, and the upper part of the superior vena cava, the thoracic duct, the lower
portion of the trachea, and a portion of the oesophagus, the phrenics, vagi, left recurrent and
cardiac nerves, and the thymus gland.
From the superior mediastinum the other three divisions of the space extend downward.
The anterior mediastinum is identical with that part of the anterior mediastinal cavity which
is below the level of manubrium sterni. The middle mediastinum lies between the layers of
the mediastinal pleura? in front of the root of the lungs; it contains the heart, enclosed in the
pericardium, and the phrenic nerves. The posterior mediastinum corresponds to that portion
of the posterior mediastinal cavity which extends below the plane of the fifth intervertebral
fibro-cartilage.
References for Respiratory System. A. External nose and nasal cavity.
Kallius, in von Bardeleben's Handbuch; Zuckerkandl, Normale u. path. Anatomie
d. Nasenhohle, Bd. 1, Wien, 1893; {Develo-pvient) His, Archiv f. Anat. u. Phys.,
1892; Killian, Arch. f. LaryngoL, Bd. 4, 1896; Schaeffer, Jour. MorphoL, vol.
21, 1910; {Concha) Peter, Arch. f. mikr. Anat., Bd. 60, 1902; {Paranasal sinuses)
Bartels, Zeitschr. f. Morph. u. Anthrop., Bd. 8; Turner, Accessory Sinuses of
the Nose, Edinburgh, 1901; {Anthropology) Hoyer, Morph. Arbeiten, vol. 4,
1894. B. Larynx. Gerlach, Anat. Hefte, H. 56; {Development) Lisser, Amer.
Jour. Anat., vol. 12; {Ossification) Scheier, Arch. f. mikr. Anat., Bd. 59.
C. Lungs. {Structure; vascular supply) Miller, Arch. f. Anat. u. Entw., 1900;
Amer. Jour. Anat., vol. 7; Schultze, Sitzb. AkadWiss., Berlin, 1906; {Develop-
ment) Flint, Amer. Jour. Anat., vol.6 {Topographical) Mehnert, Topogr. Alters-
veranderungen d. Atmungsapparatus, Jena, 1901. D. Pleura. Ruge Morph.
Jahrb. Be. 41.
SECTION XI
UEOGENITAL SYSTEM
Revised foe the Fifth Edition
By J. PLAYFAIR McMURRICH, A.M., Ph.D., LL.D.
PROFEasOR OF ANATOMY IN THE UNIVERSITY OP TORONTO
The urogenital system [apparatus urogenitalis] includes (A) the urinary
organs and (B) the reproductive organs.
A. THE URINARY ORGANS
THE organs forming the urinary apparatus [organa uropoetica] are the
kidneys, by which the secretion is produced; a duct, the ureter, proceeding
from each kidney and convejdng the secretion to the bladder, which
serves as a reservoir for the urine and from which, by a single duct, the urethra,
the secretion is carried to the exterior.
Fig. 1004. — Postero-medial Aspect of the Right Kidney.
THE KIDNEYS
The kidneys [renes] are paired organs situated in the abdominal region and
each is composed of a very great number of minute tubules, the renal tubules,
enclosed within a definite and firm fibrous capsule. Each kidney is somewhat
bean-shaped (fig. 1004) and is situated on the dorsal wall of the body, behind the
parietal peritoneum, in such a way that the ventral or visceral surface [facies ante-
rior] which is convex, looks obhquely ventrally and laterally, while the dorsal or
parietal surface [facies posterior], usually less convex, looks dorsally and somewhat
medially (fig. 1005). The upper extremity {extremitas superior] is usually larger
1241
1242
UROGENITAL SYSTEM
than the lower [extremitas inferior] and is about 1 cm. nearer the median sagittal
plane of the body, owing to the long axis of the organ being directed obliquely
downward and laterally. The lateral border [margo lateralis] is narrow and con-
vex, and the medial border [margo medialis], which looks medially and ventrally,
is concave, its middle third presenting a slit-hke aperture, the hilus. This opens
into a cavity, called the sinus (fig. 1006), which is about 2.5 cm. in depth and is
occupied mainly by the dilated upper extremity of the ureter, known as the renal
pelvis, the interval between this and the actual kidney substance containing adi-
pose tissue in which are imbedded the renal vessels and nerves.
Size. — The length of the kidney in the male averages 10-12 cm., its breadth about 5.5 cm.
and its thickness 3 cm.; it weighs 115-150 grams. The dimensions of the female kidney are
nearly as great, but its weight is from one-seventh to one-fifth less. In the child the organ is
relatively large, its weight compared with that of the entire body being about 1 : 133 at birth;
but its permanent relation, which is about 1:217, is usually attained at the end of the tenth
year.
Fig. 1005. — Diagram showing Relation of Kidnet to Capsule. (Gerota.)
Aorta
Pararenal adipose —
body
Aponeurosis of trans- Fascia of quadratus
versus abdominis lumborum
Renal fascia (posterior layer) Fascia of psoas
Investment and fixation. — The surface of the kidney is covered by a thin but
strong ^??roMs capsule [tunica fibrosa], which turns inward at the hilus to line the
walls of the sinus (fig. 1006). It may readily be peeled off from a healthy kidney,
except at the bottom of the sinus, where it is adherent to the blood-vessels entering
the kidney substance and to the terminal portions of the pelvis. External to
the capsule is a quantity of fat tissue, the adipose capsule [capsula adiposa],
which forms a complete investment for the organ and is prolonged through the
hilus into the sinus.
The peritoneum, which covers the ventral surface of the adipose capsule, has
usually been regarded as the principal means of fixation of the kidney, but in
reality this is accompHshed by means of a special renal fascia (fig. 1005), developed
from the subperitoneal areolar tissue (Gerota).
Renal fascia. — Lateral to the kidney there occurs between the transversalis fascia and the
peritoneum a subperitoneal fascia, which, as it approaches the convex border of the kidney,
divides into two layers, one of which passes in front of and the other behind the kidney, enclos-
ing the adipose capsule. Traced medially, the anterior layer of the renal fascia passes in front
THE KIDNEY
1243
of the renal vessels, and, over the aorta, becomes continuous with the corresponding layer of
the opposite side; upward, it passes over the suprarenal gland and at the upper border of that
organ becomes continuous with the posterior layer; and downward, it is lost in the adipose
tissue intervening between the iliac fascia and muscle. The posterior layer, which is the thicker
of the two, passes medially behind the renal vessels and is lost in the connective tissue in front
of the vertebral column, and below it is lost, like the anterior layer, in the ihac region. Behind
the posterior layer, between it and the quadratus lumborum, is a mass of adipose tissue, the
pararenal adipose body, and both layers are united to the fibrous capsule of the kidney by
trabeculae of connective tissue which transverse the adipose capsule.
Each kidney is, accordingly, supported by these trabecute in a space bounded laterally and
above by the layers of the renal fascia, and open medially and below. Should these trabeculse
become atrophied by wasting disease or ruptured by the pressure of the pregnant uterus, by
the improper use of corsets, or by any other cause, the phenomenon of movable or wandering
kidney may be set up by slight external violence, the organ tending to shift its place as far as
the attachment of its vessels to the main trunks and the arrangement of the renal fascia will
permit.
Position and relations. — The kidney is said to lie in the lumbar region. It is,
however, intersected by the horizontal and vertical planes which separate the
hypochondriac, lumbar, epigastric and umbilical regions from each other, and
hence belongs to all these segments of the abdominal space. Its vertical level
may be said to correspond to the last thoracic and upper two or three lumbar
Fig. 1006. — Section of Kidney showing the Sinus. (After Henle.)
Cortex-
Vessels
Bottom of
Attachment of calyx
Apex of papilla with orifices of — ( -=r^ ■
papillary ducts
Margin of hilus "
vertebrffi, the right lying in most cases from 8 to 12 mm. (| to \ in.) lower than
the left; but exceptions to this rule are not infrequent.
The posterior surface (figs. 1007, 1008), with the corresponding portion of the
fatty capsule and the pararenal adipose body, rests against the posterior ab-
dominal wall extending upward in front of the eleventh and twelfth ribs, and
medialward to overlap the tips of the transverse processes of the first and second
lumbar vertebrae; the left kidney usually reaches as high as the upper border of the
eleventh rib, the right only to its lower border. The only visceral relation pos-
teriorly is on the left side, where the spleen slightly overlaps the kidney opposite
the upper half of its lateral border, the adjacent surfaces of the two organs loeing,
however, covered by peritoneum. The parietal relations (fig. 1008) on both
sides are as follows: (1) the diaphragm, the left kidney, on account of its higher
position, entering more extensively into this relation than the right ; (2) the por-
tion of the transversalis fascia covering the ventral surface of the quadratus
lumborum; (3) the lateral border of the psoas; and (4) the last thoracic, ilio-
1244
UROGENITAL SYSTEM
hypogastric and ilio-inguinal nerves and the anterior divisions of the subcostal and
first lumbar vessels, all of which run obhquely downward and laterally in front
of the quadratus lumborum.
The upper extremity of each kidney is crowned by the suprarenal gland (figs.
1007, 1009), which encroaches also upon its ventral surface and medial border
and is fixed to it by fibres derived from the subperitoneal tissue.
The anterior surface of each kidney was primarily completely covered by
peritoneum that separated it from neighboring viscera, but, owing to secondary
changes whereby the ascending and descending colons, the duodenum and the
pancreas become retro-peritoneal organs, these come into direct relation with one
or the other of the kidneys and separate portions of them from actual contact
with the peritoneum. Thus, in the case of the right kidney (fig. 1009), the
Fig. 1007. — The Abdominal Viscera, seen from Behind.
(From the model of His.)
The kidneys are somewhat lower than usual in their relations to the ribs.
Caudate lobe of liv
Aorta
Outline of last nb
^
Spleen
Left kidney, with L
SUprarenal body j ^ ^A
Duodenum \—
Descending colon
Cut edge of i % .
peritoneum ^
Outline of iliac crest
- -^Lung
^eJ 1 ^^~^\^"*s^^~-. ~ "T Suprarenal body
"^ S^^ymmmmd- Outline of last rib
— r^i^irJi — Vena cava
Right kidney with
ureter medially
Small intestine
Outline of iliac crest
Colon ascendens
Termination of colon
Small intestine
•Bladder
mpulla of rectum
portion of the anterior surface immediately adjacent to the medial border has the
descending portion of the duodenum in direct contact with it, and throughout a
zone extending downward and laterally from the middle of the duodenal area to
the lateral border the ascending colon and right colic flexure. Almost the entire
upper half, however, and a small portion of the lower pole are covered directly
by peritoneum, the upper peritoneal area having an indirect relation with the
lower surface of the liver, upon which it produces the renal impression.
Similarly the anterior surface of the left kidney (fig. 1009) is in direct contact
with the pancreas throughout a broad transverse band situated a little above the
middle of the organ, and the splenic artery pursues its tortuous course along the
upper border of this pancreatic area, while the corresponding vein is interposed
between the pancreas and the surface of the kidney. The lateral portion of the
lower extremity is in direct contact with the descending colon and its splenic
THE KIDNEY
1245
flexure, but the remainder of the lower extremity and the whole of the upper one-
fourth of the organ is directly covered by peritoneum, the upper peritoneal area
having, as an indirect relation, the posterior surface of the stomach medially,
and the spleen laterally (figs. 956, 1009).
The medial border of the right kidney approaches the vena cava inferior very
closely, especially above; that of the left is separated from the aorta by an inter-
val of about 2.5 cm.
Fig. 1008. — Diagram of Relations of Posterior Suepace of Left Kidney.
1 Lower border of eleventh
j and twelfth ribs
Medial lumbo-costal arch
Lateral lumbo-costal arch
Variation in position. — The position of the kidneys in the abdominal cavity is subject
to considerable variation. Thus while the upper pole of the right kidney may be said to lie
typically opposite the lower half of the eleventh thoracic vertebra, it may be placed as high as
the lower part of the tenth thoracic or as low as the upper half of the fii'st lumbar. Similarly
while the upper pole of the left kidney is as a rule opposite the middle of the eleventh thoracic
vertebra it may lie half a vertebra higher or as low as the lower part of the second lumbar
vertebra. The lower poles are distant from the crests of the ilia anywhere from 1.0 cm.-3.0
Fig. 1009. — Diagram showing Anterior Relations of Kidneys and Suprarenal Bodies.
Duodenal area Hepatic area Gastric area
(non-peritoneal) (non-peritoneal) Caval area (peritoneal)
Duodenal area
(non-peritoneal) /ul'||i]||
Colic area [^
(non-peritoneal
Colic area
(non-peritoneal)
Peritoneal 'ixea wih right coUc vessels
Pentoneal area with left cohc vessels
cm., the distance being, as a rule, somewhat less in females than in males. Occasionally the
lower pole may even extend below the iliac crest, especially on the right side.
The lateral border of each kidney lies 8.5-10.0 cm. lateral to the spines of the lumbar
vertebrae, a distance that brings them lateral to the lateral edge of the sacro-spinahs muscle
and even to the lateral edge of the quadratus lumborum, so that this border may be readily
approached through the posterior wall of the body. It must be remembered, however, that
the upper part of the kidney rests upon the diaphragm, so that in the event of the twelfth rib
being very short there may be danger of the incision being carried too far upward, resulting in
injury to the diaphragm and pleura. It is also worthy of note that the diaphragmatic. area of
1246
UROGENITAL SYSTEM
the kidney corresponds with the region where a hiatus diaphragmaticus between the costal and
lumbar portions of the muscle may occur and if this be pronounced the upper part of the pos-
terior surface of the kidney may come into more or less direct relations to the pleura (fig. 1008).
Just as there may be variation in the position of the kidneys, so too there may be con-
siderable variation in the extent to which they are in relation to the various structures men-
tioned above. And this is especially true as regards their relations to the colons; for if the
kidneys were lower than usual they might lie entirely beneath the line of attachment of the
transverse mesocolon and thus have no direct relations with either colon, or on the other hand
either the ascending or descending colon, or both, may be provided with a mesentery, whereby
they would be removed from direct contact with the kidney.
Structure. — A section through the kidney shows its substance to be composed of an ex-
ternal or cortical [substantia corticalis] and an internal or medullary portion [substantia
medullaris] (fig. 1010). The medulla consists of a variable number (eight to eighteen) of
conical segments termed renal pyramids [pyramides renales (Malpighii)], the apices of which
project into the bottom of the sinus (fig. 1006) and are received into the primary segments
(calyces) of the pelvis, while their bases are turned toward the surface, but are separated from
it and from each other by the cortex. The pyramids are smooth and somewhat glistening in
section and are marked with delicate striae which converge from the base to the apex and in-
dicate the course of the renal tubules. The blunted apex, or papilla, of each pyramid, either
singly or blended with one or even two of its fellows, is embraced by a calyx (fig. 1006), and, if
examined with a hand-lens, will be seen to present a variable number (twelve to eighty) of
minute apertures, the foramina papillaria, which represent the terminations of as many
papillary ducts (of Bellini) through which the secretion escapes into the pelvis.
Fig. 1010. — Hohizontal Section of Kidney showing the Sinus.
Pyramid of
Malpighi
Column of Bertin
Interlobar
artery
Artery
Cortex with pyramids
Branch of artery Irregular branch of artery
Ureter Portion of
fatty capsule
The cortex may be regarded as composed of two portions, (1) a peripheral layer, the cor-
tex proper, which is about 12 mm. in thickness and extends from the fibrous capsule to
the bases of the pyramids, and (2) processes termed renal columns [columnse renales (Bertini)]
which dip inward between the pyramids to reach the bottom of the sinus (fig. 1010). In
section the cortex is somewhat granular in aspect, and when examined closely shows a differen-
tiation into a number of imperfectly separated portions termed cortical lobules [lobuli oorticales].
Each of these is composed of a convoluted portion [pars convoluta], surrounding an axial radiate
portion (pyramid of Ferrein) [pars radiata (processus Ferreini)]. The latter consists of a group
of tubules which extend from the cortex into the base of one of the medullary pyramids, whence
it is also termed a medullary ray; and each medullary pyramid is formed from the rays of a
number of cortical lobules, these structures, therefore, greatly exceeding the pyramids in
number.
Renal tubules (fig. 1011). — The structure described above is the result of the arrange-
ment of the renal tubules, which constitute the essential units of the kidney. Each of these com-
mences in a spherical glomerular capsule (fig. 1011), one wall of which is invaginated by a small
glomerulus of blood-vessels, the combination of glomerulus and capsule forming what is termed
a renal (Malpighian) corpuscle. These corpuscles are situated in the convoluted portions of
the cortical lobules, and from each of them there arises by a narrow neck a tubule, which quickly
becomes wide and convoluted, this fiortion being termed the first convoluted tubule. This
enters a medullary ray, where it narrows again and descends as a straight tubule, the de-
scending limb of Henle's loop, into the subjacent medullary pyramid, and, turning upon itself,
forming the loop of Henle, ascends to the cortex, where it again becomes wide and contorted,
forming the second convoluted tubule. This again lies in the convoluted portion of the cortical
lobule, and, becoming narrower, opens with other similar tubules into a straight or collecting
THE URETERS
1247
tubule, which occupies the axis of the medullary ray. Then, descending into the subjacent
medullary pyramid, it unites with other collecting tubules, and finally opens into the renal pelvis
at the summit of a papilla.
The tubules are hned with epithelium throughout, the cells being tesselated in the capsule,
irregularly cubical in the convoluted tubules and ascending limbs, flattened on the descending
limbs and loops of Henle, and columnar in the cortical collecting tubules and in the straight
tubules of the medulla.
Vessels (fig. 1011). — The kidney is very vascular. The larger arterial branches, arranged
in the sinus as has already been described, enter the substance of the kidney and pass up as the
interlobar arteries in the renal columns. On reaching the bases of the pyramids they bend so as
to run horizontaUy between these and the cortex, forming the arcuate arteries [arterife arciformes]
from which interlobular branches pass up into the cortex and supply afferent branches to the
Malpighian glomeruh. From the arcuate arteries numerous branches, the arterioloe rectces,
Fig. 1011. — Scheme of Tubules and Vessels op the Kidney.
Renal corpuscle
Cortical vein
Arcuate artery
Medullary artery
Efferent vessel
forming medullary
plexus
Papillary pli
surrounding th
foramina papill;
Renal corpuscle
Duct of Bellini open-
ing atthefora-
papillare
pass down into the pyramids, supplying the tubules of which these are composed. Efferent
stems which issue from the Malpighian glomeruli break up into capillaries which supply the
tubules contained in the cortex. Veins corresponding to the arteriolse rectce and to the inter-
lobular, arcuate and interlobar arteries occur, opening into the renal veins, and, at the surface
of the kidney, arranged in star-like groups, are the stellate veins [vense steUatae], which open
into the interlobular veins and also communicate with the veins of the adipose capsule. The
renal lymphatics may be divided into two sets, capsular and parenchymatous. They terminate
in the upper lumbar nodes.
Nerves. — The nerves form a plexus accompanying the vessels, and are derived from the
sympathetic and vagus through the renal plexuses.
Variations. — The kidney of a foetus differs from that of the adult in being divided into a
number of distinct renal lobes, each of which corresponds to the base of a renal pyramid and
1248 UROGENITAL SYSTEM
is capped by a thin layer of cortex. Such a condition is permanent in some of the lower animals;
but in man the superficial indications of morphological segmentation usually become obliterated
during the progress of growth of the cortical tissue, and are seldom visible after the age of ten.
Development. — In the development of the embryo, representatives of three different sets
of excretory organs occur, the permanent kidney (metanephros) being the last to form. The
two earlier sets (pronephros and mesonephros) have a common duct, the Wolffian duct, and
from the lower end of this an outgrowth develops, which extends upward on the posterior
abdominal wall and comes into connection with a mass of embryonic tissue known as the
metanephric blastema. The outgrowth gives rise to the ureter, pelvis and collecting tubules,
while the remaining portions of the tubules are formed from the blastema.
Various abnormalities may result from modifications of the development of the kidneys.
(1) Occasionally the ureteric outgrowth of one side fails to develop, the result being the occur-
rence of a single kidney. (2) The blastema may fail to attain its normal position, in which
case the kidney may be situated in the iliac region or even in the pelvis; or the blastema may be
drawn into an unusual position, the kidney resting on the vertebral column, or even on the
opposite side of the abdomen; (3) or the two blastemas may fuse to a greater or less extent,
forming a "horse-shoe kidney," extending across the vertebral column; or, if the fusion be more
extensive, an apparently single kidney, which may rest upon the vertebral column, or to one
side of it. Such fused kidneys may be distinguished from single kidneys by the fact that they
possess two ureters opening normally into the bladder. (4) In rare cases, a blastema may be-
come divided, an accessory kidney of varying size being thus produced. (5) Finally, in one or
more of the tubules there may be a failure of the union of the portion derived from the blas-
tema with the collecting tubule derived from the ureteric upgrowth, and the secretion having
no means of escape from such malformed tubules, they become greatly dilated, producing a
cystic kidney.
THE URETERS
The ureter (figs. 1004, 1007, 1012, 1015), which serves as the excretory duct
of the kidney, is a canal, expanded and irregularly branched above, but narrow
and of fairly uniform dimensions throughout the rest of its course. At its origin
in the renal sinus it consists of a number of short tubes, usually eight or nine, called
calyces minores (fig. 1012), each of which embraces a renal papilla, or occasionally
two papillae may be connected with a single calyx. These calyces minores open
directly or by means of short intermediate tubes (infundibula) into two short
passages, the superior and inferior calyces majores, which in turn unite after a
longer or shorter course to form the pelvis. Occasionally a third or middle calyx
major is present.
The pelvis [pelvis renalis] (fig. 1012) is usually more or less funnel-shaped,
being wider above, where it lies between the two lips of the hilus, and narrower
below, where it arches downward and medially to become continuous with the
ureter proper. It is, however, very variable in shape and in some cases is hardly
larger than the ureter. Usually it is flattened dorso-ventrally so that its anterior
and posterior walls are in contact and its cavity represented merely by a fissure.
The majority of the branches of the renal vein and artery lie in front of it, im-
bedded in fat tissue, and anterior to these are the descending portion of the duo-
denum on the right side and the pancreas on the left. The intra-renal portions of
the ducts, including the pelvis, are considered parts of the kidney.
The ureter proper (fig. 1007) extends from the termination of the pelvis to the
bladder, its course lying in the subperitoneal tissue. It is a tube about 5 mm. in
diameter when distended and it is fairly uniform in size, except that a slight con-
striction occurs where it enters the pelvis and a second one occurs at about the
middle of its abdominal portion. Its length is variously stated, but the average
in the male adult may be taken as about 30 cm., the right being usually a little
the shorter.
Course and relations. — The course of each ureter may be conveniently divided
into three portions, abdominal, pelvic, and vesical. The abdominal portion
[pars abdominalis] runs downward and shghtly medially and is in relation pos-
teriorly with the psoas muscle and its fascia; it crosses the genito-femoral nerve
obhquely and in the lower part of its course passes in front of the common iliac
artery near its bifurcation. Anteriorly it is covered by peritoneum and is crossed
by the spermatic or ovarian vessels. Medially it is in relation on the right side
with the inferior vena cava and on the left with the aorta, the vein being almost
in contact with the right ureter, while the artery is separated from the left one
by an interval that diminishes from 2.5 cm. above, to 1.5 cm. opposite the
bifurcation of the vessel.
The pelvic portion [pars pelvina] passes in front of the sacro-ihac articulation
THE URINARY BLADDER 1249
and then forward and downward upon the obturator internus and its fascia
behind and below the psoas, crossing the obturator vessels and nerve and having
anterior to it in the female the posterior border of the ovary. It thus reaches the
level of the floor of the peritoneal cavity, whereupon, at about the level of the
ischial spine, its course is directed forward and medially toward the bladder.
In this part of its course in the m.ale, it is crossed superiorly and medially by the
ductus deferens, and then passes under cover of the free extremity of the vesicula
seminalis, separated from its fellow by a distance of 37 mm. In the female it
runs parallel with, and 8 to 12 mm. distant from, the cervix uteri, passes behind
the uterine artery, through the uterine plexus of veins, and beneath the root of
the broad ligament, and finally crosses the upper third of the lateral wall of the
vagina to reach the vesico-vaginal interspace and enter the substance of the
bladder at about the junction of its posterior, superior and lateral surfaces.
The vesical portion, about 12 mm. in length, runs obliquely downward and
medialward through the coats of the bladder, and opens on its mucous surface
about 20 to 25 mm. from both its fellow and the internal urethral orifice.
Structure. — The wall of the ureter is about 1 mm. (jV in.) in thickness, and consists of a
mucous membrane, a muscular coat, and an external connective-tissue investment. The mucous
membrane is longitudinally plicated, and is lined by transitional epithelium, continuous with
that of the papillse above and with that of the bladder below. Mucous follicles of simple form
have been found in the upper part of the canal. The muscularis is about 0.5 mm. (1/50 in.) in
thickness, and consists of two layers, an external, composed of annular fibres, and an internal,
Fig. 1012. — Pelvis and Upper Portion op Ureter. (After Henle.)
Calyx minor
Infundibulum
Superior calyx nxajor
Inferior calyx major
of fibres longitudinally disposed. After the tube has entered the bladder the circular fibres form
a kind of sphincter around its vesical orifice; while the longitudinal fibres are continued onward
through the wall of the bladder and terminate beneath its mucous membrane.
Vessels and nerves. — The arteries supplying the pelvis and upper part of the ureter come
from the renal; the rest of the abdominal portion of the ureter is supplied by the spermatic
(or ovarian), and its pelvic portion receives branches from the middle haemorrhoidal and in-
ferior vesical; the veins terminate in the corresponding trunks; and the lymphatics pass to the
lumbar and hypogastric nodes. The nerves are supplied by the spermatic, renal, and hypo-
gastric plexuses.
Variations. — Occasionally the depression which separates the two calyces majores extends
through the pelvis, so that the calyces appear to open directly into the ureter. The fission may
also affect the ureter to a greater or less extent, in extreme cases producing a duplication of
the tube throughout its entire length.
THE URINARY BLADDER
The urinary bladder [vesica urinaria] is a receptacle, whose form, size, and
position vary with the amount of its contents. The adult organ in its empty or
moderately filled condition Hes entirely below the level of the obhque plane of
the pelvic inlet; but when considerably distended it rises into the abdomen and
shows itself beneath the parietes as a characteristic mesial projection above the
symphysis, a projection which in extreme distention of the bladder may extend
nearly to the level of the umbilicus.
1250
UROGENITAL SYSTEM
Form. — When distended it assumes in the male an ovoid shape with its
longest diameter directed from above downward and backward; but in the female
the transverse diameter is the greatest, in accordance with the greater breadth
of the pelvic cavity. In the child it is somewhat pear-shaped, the stalk being
represented by the urachus.
Parts. — ^For convenience in description five surfaces may be recognized, but
they are but indistinctly separated from each other. One, the anterior or pubic
surface, is directed forward and downward; second, the superior or intestinal
surface, looks upward; the third, the posterior surface, looks backward; and the
other two are the lateral surfaces. The anterior, superior, and lateral surfaces
meet at the vertex of the bladder, from which the middle umbilical ligament
(urachus) extends to the umbilicus; the posterior surface, sometimes flat and some-
times, especially in old age, convex, forms what is known as the base or fundus
[fundus vesicae] ; and the portion of the viscus intervening between the vertex and
Fig 1013 — Median Sagittal Section op the Male Pelvis
(From a prepaiation in the Museum of St Thomas's Hospital )
Small
intes-
tine
fundus is termed the body [corpus vesicae]. In the centre of the line between
the anterior and posterior surfaces is the internal urethral orifice [orificium urethrae
internum], by which the bladder communicates with the urethra, and the portion
of the organ immediately surrounding this is sometimes spoken of as the neck.
When the bladder is empty and relaxed, the superior surface sinks down upon
the anterior and posterior surfaces, thus becoming concave, and the cavity of the
organ is reduced to a T- or Y-shaped fissure. In the female, the cavity of the
empty bladder in mid-sagittal section often more nearly resembles a figure 7 (see
fig. 1014).
Relations. — The anterior surface looks downward and forward toward the
symphysis pubis (figs. 1013, 1014). It is uncovered by peritoneum, but is sepa-
rated from the pubic bones and anterior attachments of the obturatores interni
and the levatores ani by a space known as the prevesical space (cavum Retzii),
THE URINARY BLADDER
1251
which contains a variable quantity of loose fat continuous with the pelvic and
abdominal subperitoneal tissue. Each lateral surface is covered by peritoneum
down to the level at which it is crossed obliquely from behind forward and upward
by the obUterated hypogastric artery. Below this level it is separated from the
levator ani and obturator internus by subperitoneal tissue, which usually bears
much fat in its meshes and ensheaths the vesical vessels and nerves. It is also
crossed by the ductus deferens, which passes between the ureter and the wall
of the bladder, a little above the level at which the former enters the wall of the
bladder, at the junction of its lateral and posterior surfaces and about 3.5'^cm.
above the fundus. The posterior surface may be divided into two portions,
an upper covered by the peritoneum of the recto-vesical or vesico-uterine pouch
(fig. 1013), and a lower in direct contact in the male with the anterior wall of the
Fig. 1014. — Mid-sagittal Section of the Female Pelvis. (Spalteholz.)
Hypogastric artery
^t Hypogastric vein
Promontory / / Infundibulum of tuba uterina
Suspensory ligament of ovary
External ihac vein
Ovary
Ampulla of tuba utenua
Ovarian ligament
Fundus uteri
\
, Parietal peritoneum
Uterus
k. / Interna! orifice of
V / uterus
\/ y Recto uterine fold
X , Recto uterine
\ / muscle
Ligamentum teres
Transverse fold of
bladder
Vertex of bladder . ^\
Middle umbilical \
ligament
Urach
Symphysis pub
Labium majus
Body of uterus
Labium minus
External orifice of urethra
Urethra /' /
Internal orifice of urethra /
Orifice of vagina
Coccyx
Recto coccy-
\ geus muscle
Rectum
Posterior labium
External orifice of uterus
Anterior labium
Vagina
a.yuiKu. Vesico-uterine pouch
Vestibule
rectum and with the lower part of the ductus deferentes and the vesiculse semin-
ales. Between the diverging ductus deferentes there is a triangular space, whose
base is formed by the line of reflexion of the recto-vesical pouch of peritoneum
and the apex by the meeting of the ejaculatory ducts at the summit of the prostate.
It represents the area of direct contact of the posterior wall of the bladder withjthe
rectum. In the female the posterior surface is adherent in its lower part to the
cervix of the uterus and the upper part of the anterior wall of the vagina (fig. 1014),
but it is separated above from the body of the uterus by the shallow vesico-
uterine pouch of peritoneum.
The superior surface is entirely covered by peritoneum. It looks almost
1252
UROGENITAL SYSTEM
directly upward into the abdominal cavity and has resting upon it coils of the
small intestines and sometimes a portion of the sigmoid colon behind these.
Variation in position. — In the normal condition the bladder of the adult lies below the upper
border of the symphysis pubis, but if fully distended it may rise above this level, carrying
with it the reflexion of peritoneum from its upper surface to the anterior abdominal wall.
The anterior surface of the bladder is thus brought into relation with the anterior abdominal
wall, being separated from it only by the enlarged prevesical space, and it is thus possible to
enter the bladder above the symphysis pubis without penetrating the peritoneum.
In the infant, owing to the smaller extent of the pelvic cavity, the bladder hes at a some-
what higher level than in the adult and rises into the abdominal cavity. Indeed the entire
bladder is above the horizontal level of the pubic crests, the urethral orifice being behind the
upper margin of the symphysis pubis. As the child learns to walk, however, this position
gradually alters and usually by the age of six years the adult relations have been acquired.
The fixation of the bladder. — The reflections of the peritoneum from the
superior surface of the bladder to the anterior abdominal wall and from the sides
and back to the corresponding walls of the pelvis are sometimes described as the
superior, lateral and posterior false ligaments. Furthermore there extends from
the apex of the bladder to the umbilicus a fibrous cord, the urachus, the remains
of the embryonic allantois; this is described as the middle umbilical ligament of
the bladder (fig. 1014), and lateral umbilical ligaments are formed by the obliter-
ated hypogastric arteries which carried the foetal blood to the placenta and in the
Fig. 1015. — The Posterior Wall of the Bladder. (After Henle.)
Ductus deferens
Plica ureterica
Vesical aperture
Colliculus seminalis-
Opening of ejaculatory duct
Prostatic utriculu
Prostatic
adult are represented by fibrous cords passing over the sides of the bladder and
ascending to the umbilicus.
In addition to these structures certain thickenings of the endopelvic fascia,
where it comes into relation with the base of the bladder and prostate gland,
constitute what are termed the true ligaments. Two such thickenings extend
from the anterior surface of the capsule of the prostate gland, or from the lower
part of the anterior surface of the bladder in the female, to the pubic bones and
constitute what are known as the middle pubo-prostatic {pubo-vesical) ligaments,
with which muscle fibres [m. pubovesicahs] are usually associated. Similarly,
thickenings of the fascia extending from the sides of the prostate gland or from the
sides of the base of the bladder to the lateral walls of the pelvis form the lateral
true ligaments.
Muscle fibres [m. rectovesicahs] also occur in the subperitoneal tissue contained within
the peritoneal folds (posterior false ligaments) extending from the back of the bladder to the
posterior wall of the pelvis and bounding the recto-vesical pouch of peritoneum in the male.
They correspond to the mm. redouterini of the female.
The internal surface. — The mucous membrane lining the internal surface of
the bladder is soft and rose-coloured during life, and in the empty bladder is
thrown into irregular folds which become effaced by distention. It is modified
over a triangular area at the base of the bladder, termed the trigone [trigonum
vesicae (Lieutaudi)] (fig. 1015) whose three angles correspond with the orifices
of the urethra and of the two ureters, and are separated from one another by a
MALE REPRODUCTIVE ORGANS 1253
distance of 20 to 25 mm. This area is paler in colour and free from the plication
that characterizes the rest of the mucous membrane; it is bounded posteriorly
by a transv.erse ridge, the plica ureterica, extending between the orifices of the
ureters, and toward the urethral orifice presents a median longitudinal elevation,
the uvula vesicae, which is apt to be especially prominent in aged persons. The
internal urethral orifice is normally situated at the lowest point of the bladder, at
the junction of the anterior and posterior surfaces. It is surrounded by a more
or less distinct circular elevation, the urethral annulus, and is usually on a level
with about the center of the symphysis pubis and from 2.0 to 2.5 cm. behind it.
Structure. — The general characteristics of the mucous membrane of the bladder, which is
lined by epithelium of the transitional variety, have already been described. It rests upon a
loose submucous tissue, which contains numerous elastic fibres. The greater part of the thick-
ness of the waU is formed, however, of the muscular coal, consisting of non-striped muscle
tissue, the fibres of which are arranged in three more or less distinct layers. The outer layer
is composed mainly of longitudinal fibres, some of which are continued forward to the pubis
from the neck of the bladder to form the mm. pubovesioales and others backward to form the
mm. rectovesicales. To this outer layer the term m. detrusor uriruB has been applied, but it
should be noted that it does not contract independently of the circular layer. The middle
ayer is thicker than the outer and more uniformly developed. It consists of fibres having
for the most part a circular direction and is well developed over all the upper portion of the
bladder, but becomes thinner in the region corresponding to the trigone. It is here that the
inner layer is chiefly developed, consisting of fibres, which are situated partly in the submucous
tissue and have a general longitudinal direction throughout the region of the trigone. At
the neck of the bladder, however, they form a strong circular bundle, which is continued into
the prostatic portion of the urethra and forms what is termed the internal sphincter of the bladder.
Vessels. — The arteries of the bladder are usually two in number, the superior and inferior
vesical, branches of the hypogastric artery; the fundus also receives branches from the middle
hsemorrhoidal and in the female twigs are also sent to it from the uterine and vaginal arteries.
The veins form an extensive plexus at the sides of the bladder, from which stems pass to the
hypogastric trunk. The lymphatics accompany the veins and communicate with the hypo-
gastric nodes, some of those from the fundus passing to nodes situated at the promontory of
the sacrum.
Nerves. — -The nerves are derived partly from the hypogastric sympathetic plexus and partly
from the second and third sacral nerves. The fibres from the latter constitute the nervi
erigentes, stimulation of which produces contraction of the general musculature and rela.xation
of the internal sphincter. On each side of the bladder there is formed a sympathetic vesical
plexus, from which superior and inferior vesical nerves pass to the corresponding parts of the
bladder.
Development. — In the earlier stages of development the urogenital ducts and the digestive
tract open below into a common cavity, the cloaca, from the ventral portion of which a long
tubular outgrowth, the allantois, extends out to the placenta through the umbilical cord.
Later the cloaca becomes divided in the frontal plane into a ventral portion which receives the
urogenital ducts, and a dorsal portion, which becomes the lower end of the rectum. From
the upper part of the ventral portion the bladder is developed. Since the cloaca is fined by
endoderm the mucous membrane of the bladder is mainly derived from that embryonic layer,
but it is worthy of note that portions of the lower ends of the ureters are taken up into the wall
of the bladder, giving rise to the area of the trigone, whose mucous membrane is thus of meso-
dermal origin. The portion of the allantois within the body of the foetus is transformed after
birth into a fibrous cord, the urachus.
The urethra will be considered later in connection with the reproductive
organs.
B. THE REPRODUCTIVE ORGANS
The reproductive organs include those of the male [organa genitalia viriHa]
and those of the female [organa genitalia muliebria].
THE MALE REPRODUCTIVE ORGANS
The reproductive organs of the male consist of (1) two testes in which the
spermatozoa are formed, (2) their ducts, the ductus def erentes ; enclosed through-
out a portion of their course in the spermatic cord; and the seminal vesicles,
reservoirs for the semen, connected with the ductus def erentes; (3) the penis,
the organ of copulation, which is traversed by the urethra; (4) the urethra, a
canal into which the ductus deferentes open and which also gives exit to the
contents of the bladder; (5) the prostate gland, a musculoglandular structure
surrounding the beginning of the urethra; (6) the bulbo-urethral glands which
open into the urethra.
{
1254
UROGENITAL SYSTEM
1. The Testes and Their Appendages
The scrotum. — The two testes, together with the beginning of the ductus
deferentes, are contained within a pouch, the scrotum, which is divided into two
compartments by a median sagittal septum, the edge of which is indicated on the
surface by a ridge-hke thickening of the integument, termed the raphe.
This double condition of the scrotum is explained by its origin from the fusion of two out-
pouchings of the lower portion of the abdominal wall, the inguinal canals forming, as it were,
the necks of the outpouchings. The testes are primarily retroperitoneal abdominal organs,
but later they descend through the inguinal canals into the scrotal outpouchings, where they
lie between the peritoneal sac which each of these contains and the remaining layers of the wall,
thus retaining their retroperitoneal position. The peritoneal sacs are at first in communication
with the abdominal cavity, but after the descent of the testes each undergoes degeneration in
its upper part, the cavity disappearing and the peritoneal tissue becoming converted into a
portion of the connective tissue in which the ductus deferens and the vessels and nerves asso-
ciated with it are imbedded in their course through the spermatic cord. The portion of the sac
in relation with each testis persists, however, and wrapping itself around that structure forms
for it a serous investment, the tunica vaginalis propria (fig. 1016).
The integument oi the scrotum is more or less pigmented and presents numerous
transverse ridges extending laterally on either side from the raphe. It is furnished
in the adult with coarse, scattered hairs and its sebaceous and sudoriparous glands
are well developed. The deeper layers of the dermis, have a pinkish colour, and
form what is termed the dartos (fig. 1016), the colouration being due to the
Fig. 1016. — Horizontal Section op the Sceotum and Testis. (Diagrammatic.)
Skin
Dartos
Cremasteric fascia
Cremaster muscle
Septum scroti
Mediastinum testis
Ductus deferens
Parietal layer of tunica vaginalis
propria
Tunica vaginalis communis
Cavity of tunica vaginalis
Visceral layer of tunica vaginalis
propria
Tunica albuginea
Sinus epididymidis
Epididymis
presence in it of numerous non-striated muscle fibres, which are for the most
part arranged at right angles to the wrinkles of the surface and are the cause of
these. The more superficial fibres of the dartos, hke the rest of the integument,
form a common investment for both testes, but the deeper ones of either side bend
inward at the raphe and assist in the formation of the septum.
Internal to the dartos and closely related to it is a layer of laminated con-
nective tissue, the cremasteric fascia. It is destitute of fat and is continuous at
the subcutaneous inguinal ring with the intercrural fibres, being probably the
scrotal representative of the external oblique muscle. It is succeeded by a
strong sheet of fascia containing longitudinal bands of striated muscle tissue,
forming what is termed the cremaster muscle (figs. 389, 1016) and being con-
tinuous above with the fibres of the internal oblique muscle of the abdomen.
Internal to this is a thin layer of connective tissue, the tunica vaginalis communis,
which is continuous with the transversalis fascia at the inguinal ring, and, finally,
there is the tunica vaginalis propria, which forms the serous investment of the
testis and, as has been stated, is of peritoneal origin. Like other similar serous
investments it has the form of a double sac, the outer or parietal layer of which is
closely adherent to the tunica vaginahs communis and contains numerous non-
striped muscle fibres forming what has been termed the internal cremaster
muscle. The inner or visceral layer is thinner and closely invests the testis and a
THE TESTIS AND EPIDIDYMIS
1255
portion of the epididymis, being reflected from the inferior and posterior parts of
the latter to be continuous with the parietal layer. Toward the upper part of the
lateral surface of the testis it is folded in between that structure and the epididy-
mis, forming a well-marked pocket, the sinus eipididymidis (digital fossa) (fig.
1017), whose upper and lower lips form what are termed the ligamentaepididymidis.
Vessels and nerves. — The skin and dartos of the scrotum are supplied partly by the peri-
neal branch of the internal pudendal artery and partly by the external pudendal branches of
the femoral. The deeper layers are supplied by the spermatic branch of the inferior epigastric.
The veins accompany the arteries, the external pudendals opening into the internal saphenous
vein near its termination. The lymphatics terminate in the more medial inguinal nodes.
Several nerves take part in the supply of the scrotum. The external spermatic branch of the
genito-femoral gives sensory branches to the anterior and lateral surfaces and also supplies
the external cremaster muscle; the posterior surface is supplied by the periaeal branch of the
pudendal nerve; and the inferior surface by the perineal branches of the posterior femoral
Fig. 1017. — The Left Testis with Vessels and Duct. (After Sappey.)
Internal spermatic artery'
Internal spermatic veins-
Branch of spermatic artery
Head of epididy
Appendix testi
Lateral wall of body of testi
Ductus deferens with
deferential artery
Vein
Ductus deferens
Body of epididymis
Sinus epididymidis
Vessels of epididymis
Tail of epididymis
cutaneous. The anterior aspect of the scrotum is also supplied by anterior scrotal branches
of the ilio-inguinal. The non-striped musculature is probably supplied by the internal
spermatic nerve from the hypogastric plexus.
Hernia. — The communication of the tunica vaginaUs propria vrith the abdominal perito-
neum is usually obliterated within a few days after birth, but sometimes the process of oblitera-
tion is more or less incomplete. If the communication remains open there is a free passage
for a loop of the intestine to enter the cavity of the tunica vaginalis, such a condition consti-
tuting what is known as the congenital variety of inguinal hernia. If the communication be
interrupted only at the upper part of the original sac, so that the cavity of the tunica vagin-
alis propria extends a considerable distance up the spermatic cord a hernia, passing through
the inguinal canal, may invaginate the upper part of the tunica vaginalis into the lower, pro-
ducing what is termed the encysted variety of hernia. Or if, finally, the obliteration of the
communication begins in the neighbourhood of the testis, a funnel-shaped prolongation of the
peritoneal cavity may extend downward into the spermatic cord, and hernia into this con-
stitutes the variety known as hernia i^ito the funicular process.
The testis and epididymis. — The testes (fig. 1017) are the essential male organs
of reproduction and are contained within the scrotum. They are two in number,
1256
UROGENITAL SYSTEM
each being of a flattened oval form, with two surfaces, medial and lateral, two
borders, anterior and posterior, and two extremities, superior and inferior. To the
whole of the posterior border there is attached the epididymis, formed by the
efferent ducts. The testis is obliquely placed, so that the medial surface also looks
somewhat forward and downward.
The surface of the testis is covered by the visceral layer of the tunica vaginalis
propria except where it is in contact with the epididymis, and is formed by a
dense white inelastic capsule, the tunica albuginea, beneath which is a looser and
more vascular layer known as the tunica vascidosa. From the inner surface of the
albuginea, lamellae of connective tissue, known as septula, converge toward the
posterior border of the testis and toward its upper part unite together to form a
network (fig. 1018), the mediastinum testis (or corpus Highmori), through which
blood-vessels and lymphatics enter and leave the testis, while by the interspaces
of the network, known as the rete testis, the tubules of the testis are placed in com-
munication with the epididymis.
The septula divide the substance of the testis into a number of compartments or lohules,
each of which is occupied by a number of slender, greatly contorted canals, the seminiferous
tubules [tubuli seminiferi], from whose epithelial lining the spermatozoa are formed. The
tubules of each lobule converge to form a single, almost straight duct and these tubuli recti pass
Fig.
lOlS. — Diagram of the Testicular Tubules.
Ductus epididymidis
ua Lobulus epididymidis
Efferent ducts
Tunic albuginea receiving attacli-
ment of septula
Tubulus rectus
Rete testis in mediastinum testis
Ductus epididymidis
Ductulus aberrans
Ductus deferens
toward the mediastinum, where they open into the rete testis. In the lobules the seminif-
erous tubules are imbedded in a loose connective tissue that contains certain pecuhar cells,
the interstitial cells, to which has been attributed the formation of an internal secretion.
The epididymis (fig. 1017), which lies along the posterior border of the testis,
is an elongated structure with a body [corpus epididymidis], enlarged above to form
the head [caput] and to a less extent below to form the tail [cauda]. It is invested
by a tunica albuginea, continuous with, but much thinner than that of the testis,
and is formed mainly by the greatly contorted duct of the epididymis, which
represents the beginning of the ductus deferens.
The head is formed by 12-14 tubules, the efferent ducts (fig. 1018), which take their origin
from the rete testis as almost straight tubules, but gradually become greatly coiled, so that
each duct has the form of an elongated cone, its coiled portion forming what is termed a lobulus
epididymidis. At their coiled ends the various efferent ducts open into a single tube, the
ductus epididymidis. Its diameter is only about 0.4 mm., but it measures 6.0-7.0 metres (18-21
feet) in its entire length, being coiled so extensively as to be contained within the body and
tail of the epididymis. In this latter region it passes over into the ductus deferens.
Vessels. — The principal artery supplying the testis is the internal spermatic, from which
branches are also sent to the epididymis. The deferential artery, a branch of the superior
vesical, also sends branches to the epididymis and enters into extensive anastomoses with the
testicular branches of the internal spermatic, and anastomoses also occur with the vessels
supplying the scrotum. The veins correspond with the arteries. The lymphatics of the testis
and epididymis unite to form four to six large stems which pass upward in the spermatic cord
to terminate in the lower lumbar nodes.
Morphology. — The testis is primarily an abdominal organ and is developed in close relation-
ship with the provisional kidney [mesonephros] whose duct, indeed, becomes the ductus deferens
DUCTUS DEFERENS AND SEMINAL VESICLE 1257
and some of whose tubules, becoming the efferent ducts, place the seminiferous tubules in com-
naunioation with the ductus deferens. The epididymis may therefore be said to be developed
from the mesonephros. The portions of this structure that are not concerned in the formation
of the efferent ducts disappear for the most part; a few of the tubules persist, however, as
rudimentary organs associated with the epididymis. Among these may be mentioned one or
more blindly ending, coiled tubules, varying from 5-30 cm. in length, which are connected with
the ductus epididymidis usually in the tail of the epididymis. They are knowTi as the ducluli
aberrantes (fig. 1018) and may be regarded as persistent excretory mesonephric tubules. Another
of the rudimentary organs is the paradidymis {organ of Giraldes), which is a whitish body,
situated immediately above the head of the epididymis, and is composed of irregularly coiled
tubules, which terminate blindly at both extremities. They may be regarded as efferent
ducts that have failed to connect with the testis and are of interest in that they sometimes
develop into cysts connected with the epididymis.
In addition there is frequently attached to the upper pole of the testis a sohd oval body
composed of connective tissue, known as the appendix testis {hydatid of Morgagni) (fig. 1017).
It measures from 3 to 8 mm. in length and its significance is doubtful. A similar, though
smaller structure, the appendix epididymidis, is attached less frequently to the head of the
epididymis. It is usually provided with a distinct stalk and contains a cavity; it is believed to
represent the upper end of the Miillerian duct, present in the embryo and giving rise to the tuba
uterina in the female, but almost completely degenerating in the male.
The testis begins its descent from the abdominal cavity into the scrotum at the third month
of fetal life and reaches the abdominal inguinal ring at about the sixth month, but it is not
until shortly before birth that it arrives at its final location in the scrotum. The cause of the
descent is stiU uncertain, but it is supposed to be partly due to the failure of a band of connective
tissue, which extends from the lower pole of the embryonic testis to the bottom of the scrotal
pouch, to keep pace with the growth of the body walls. This hgament, which is known as the
gubernac.ulum testis, thus becomes relatively shorter and draws the testis downward toward the
point of its attachment to the scrotum. There are various features in the descent, however,
that cannot be explained by the simple traction of the gubernaculum and it must be regarded
as a complicated growth process whose meaning is yet uncertain. The gubernaculum testis
apparently undergoes degeneration after the testis has reached its definitive location and cannot
be recognized in connection with the adult testis.
Occasionally the descent of the testis is interrupted, the organ remaining either in the
abdomen or in the inguinal canal. This condition of cryptorchism is always associated with a
suppression of the function of the organ.
2. The Ductus Deferentes and Vesicul^ Seminales
Each ductus deferens is the continuation of a ductus epididymidis and ex-
tends from the tail of the epididymis to the prostatic portion of the urethra. At
its beginning it ascends along the posterior border of the epididymis (testicular
portion) and is at first slender and tortuous (fig. 1018), but before reaching the
level of the head of the epididymis it becomes straighter and thicker (fig. 1017),
owing to the development in its walls of strong layers of longitudinal and circular
non-striated muscle tissue. Thence it is continued almost vertically upward as
one of the constituents of the spermatic cord {funicular portion) to the subcu-
taneous inguinal ring, and, entering this, traverses the inguinal canal {inguinal
portion), still forming a portion of the cord. At the abdominal ring it separates
from the other constituents of the cord and, looping over the inferior epigastric
artery near its origin, passes downward and backward over the lateral surface of
the bladder {pelvic portion). At the junction of the posterior and lateral surfaces
of the bladder it passes medially to the ureter and is then continued downward,
forward and medially upon the base of the bladder until it reaches the prostate
gland (fig. 1019), whose substance it traverses, as the ductus ejaculatorius, to open
into the prostatic portion of the urethra (see p. 1263).
Just before it reaches the prostate gland each ductus deferens presents an
irregular spindle-shaped enlargement, the ampulla (figs. 1019, 1020), whose walls
are somewhat sacculated. Just beyond this it is joined upon its lateral surface
by a club-shaped lobulated structure, the vesicula seminalis (fig. 1019). Each
vesicle measures 4.5-5.5 cm. in length and has a greatest diameter of about 2 cm.
It rests upon the posterior surface of the bladder, lying parallel with and lateral
to the corresponding ductus deferens, and in its upper one-third is in relation
posteriorly with the peritoneum which forms the anterior wall of the recto-
vesical pouch, while below it is in contact with the anterior wall of the lower part
of the rectum, through which it may be palpated. Indeed, the two vesiculee,
together with the ductus deferentes, form the lateral boundaries of the triangular
area at the base of the bladder, throughout which that organ is in relation to the
rectum.
1258
UROGENITAL SYSTEM
Each vesicle is enclosed within a fine capsule of connective tissue, which contains numerous
non-striated muscle fibres and is continuous below with the capsule of the prostate gland.
On removing this capsule the vesicle will be found to consist of a greatly coiled tube, 10-12 cm.
Fig. 1019. — Ductus Depeeentes and Vesicul^ Seminales. (After Sappey.)
Ejaculatory duct
Prostatic utriculus —
CoUiculus seminali
Orifice of ejaculatory duct -J'- —
Ampulla of ductus deferens
Ejaculatory duct entering
prostatic fissure
Membranous urethra
Ductus deferens
Orifice of prostatic utriculus
Vesicula seminalis
Fig. 1020. — Ductus Deferens and Vesicula Seminalis dissected. (After Sappey.)
Diverticula! '"\^ ^ p^
Sacculi of ampulla of ductus deferens
Junction of ductus deferens and vesicula
seminalis
Ejaculatory duct
in length, which ends blindly and has attached to it on either side a number of short diverticula
(fig. 1020). The walls of the tube and diverticula are formed of smooth muscle tissue, arranged
in layers similar to those of the ductus deferentes, and are lined by a much folded mucous
THE SPERMATIC CORD
1259
membrane, whose cells contain considerable quantities of a yeUowish-brown pigment, and also
contribute a secretion to the seminal fluid. In addition to having this function the vesiculse
also serve as receptacles for the spermatozoa. They arise as diverticula from the embryonic
ductus deferens, and it is worthy of note that a number (4 or 5) of similar but quite small diver-
ticula arise from the upper part of each ductus ejaculatorius.
Vessels and nerves. — The artery supplying the ductus deferens is the a. deferentialis, a
branch of the superior vesical. It accompanies the ductus to the tail of the epididymis and also
gives a branch to the vesicula seminalis. The latter also receives branches from the middle
haemorrhoidal and inferior vesical arteries. The deferential vein accompanies the ductus
deferens to the base of the bladder where it breaks up into a plexus that communicates with
the seminal venous plexus formed by the veins from the seminal vesicles. This joins with the
vesical and pudendal ple.xus and so communicates with the hypogastric vein. The lymphatics
of the ductus deferentes and seminal vesicles pass to the external iliac and hypogastric
nodes. The nerves of both structures are derived from the hypogastric plexus.
The spermatic cord. — In its descent through the inguinal canal into the
scrotum the testis necessarily drags after it the ductus deferens and the testicular
vessels and nerves, these structures coming together at the abdominal inguinal
Fig. 1021. — Ceoss-section of the Spermatic Cord.
A. spermatica interna
N. spermaticus int.
Lympli vessel
Vv. spermaticae int.
Fascia cremasterica
Lymph vessel
Ductus deferens
Vv. spermaticse int
A. et V. deferentialis
V. spermatica ext.
ring to form what is termed the spermatic cord [funiculus spermaticus]. This
structure extends, therefore, from the abdominal inguinal ring, through the in-
guinal canal and the neck of the scrotal sack to the testis, and is enclosed within
the same investing layers as the testis.
Thus as it emerges from the subcutaneous inguinal ring it receives an investment of con-
nective tissue continuous with the intercrural fibres and the aponeurosis of the external oblique
muscle. This cremasteric fascia has beneath it bands of striated muscle tissue, the external
cremaster muscle (fig. 1021), especially developed on the posterior surface of the cord and con-
tinuous with the internal oblique muscle of the abdomen, and within these is an indistinct
layer of connective tissue, the tunica vaginalis communis, which is received at the abdominal
inguinal ring where it is continuous with the fascia transver.saUs.
Within the sheath thus formed there is a matrix of connective tissue, usually
containing considerable amounts of fat and strands of non-striated muscle tissue,
which form what is termed the internal cremaster muscle {funicular portion),
and imbedded in this connective tissue are the various essential constituents of
the cord. These are as follows (figs. 1017, 1021) : (1) the ductus deferens, occupy-
ing the posterior surface of the cord and having associated with it the deferential
artery and veins and the deferential plexus of nerve fibres; (2) the internal
spermatic artery, which occupies the axis of the cord and is surrounded by (3) the
internal spermatic veins, which form a complicated network, known as the pam-
1260
UROGENITAL SYSTEM
piniform plexus; (4) the testicular lymphatics; and (5) the internal spermatic
plexus of nerves from the hypogastric plexus; and (6) branches of the genito-
femoral nerve for the supply of the external cremaster muscles.
3. The Penis
The penis is composed of three rod-like bodies composed of erectile tissue
(fig. 1023), firmly united together and invested by fascia and integument (fig.
1022). When this erectile tissue becomes engorged with blood the organ assumes
an erect position, but otherwise it is pendulous, hanging downward in front of the
scrotum from its attachment to the symphysis pubis. The erectile bodies are,
however, prolonged backward beyond the symphysis pubis into the perineal re-
gion, and it is customary to speak of this perineal portion as the root of the penis
[radix penis] or pars fixa in contrast to the body of the penis [corpus penis] or pars
libera.
The body of the penis in its flaccid condition is almost cylindrical, but in
erection it becomes somewhat triangular in section, what was the anterior surface
or dorsum penis* becoming flattened, while the opposite one, the urethral surface
[facies urethralis], becomes more sharply rounded. At the free extremity of the
penis there is a blunt conical enlargement, the glans penis (fig. 1023), at the apex
of which is the external orifice of the methra. The glans is separated from the
body by a constriction, the ?ieck [coUum glandis], and from this region a fold of
integument arises, which more or less completely encloses the glans, forming the
prepuce [prseputium] (fig. 1024). The prepuce is quite free from the glans
dorsally but in the ventral mid-line it is attached to it, almost to the urethral
Fig. 1022. — Transverse Section through the Bodt op the Penis.
Superficial dorsal vein of penis
Dorsal artery ^ | /Deep dorsal vein
Tunica albuginea
Tunica albuginea-
Skin
Dartos
Septum
.Corpus cavernosum penis
Fascia penis
Artery
Urethra
Corpus cavernosum urethrs
orifice, by a narrow fine of adhesion, the frenulum [frenulum prseputii], which
contains blood-vessels of considerable size. The base of the glans has a well-
marked rounded border, the corona [corona glandis], and is deeply concave for the
reception of the distal ends of the corpora cavernosa penis.
The integument of the penis is continuous with that of the scrotum and like
it is pigmented and contains no fat. Immediately below it there is a layer of non-
striated muscular tissue, the dartos, and beneath this a layer of loose connective
tissue, containing the superficial vessels and nerves of the penis; beneath this
again is a denser, elastic sheet of connective tissue, the fascia penis (fig. 1022),
which encloses the erectile bodies as far as the base of the glans and is continuous
with the superficial fascia of the perineum and inguinal region. Where it passes
beneath the symphysis pubis it receives from the anterior surface of the latter a
strong band of fibrous tissue, which forms the suspensory ligament of the penis
[Hg. suspensorium penis].
Two of the erectile bodies of the penis, the corpora cavernosa penis, are paired
(fig. 1023). They are attached at their proximal ends to the base of the tuberosity
of the ischium, and in this part of their extent are termed the c7-ura penis, being
* It should be noted that the terms "dorsum" and "dorsal" are used for the penis in a
sense directly opposite their usual meaning.
THE PENIS 1261
composed of fibrotis connective tissue, whicli lias resting upon it the m. ischio-
cavernosus (see Section IV). The two crura are situated in the lateral portions
of the superficial perineal interspace and pass forward parallel with the rami of
the ischia and pubis, gradually becoming transformed into cavernous erectile
tissue. Shortly before they reach the level of the symphysis pubis the two
corpora come into contact in the median hne, their medial walls fusing to form a
septum, and thus united they extend throughout the entire length of the body of
the penis, occupying the dorsal portion of the space enclosed by the fascia penis
(fig. 1022) . They terminate at the posterior surface of the glans, where they taper
Fig. 1023. — Dissection of the Perineum Showing the STRtrcTTTBE and Relations op the
Penis.
Corona glandis —
Corpus cavernosum xirethr^
Corpus cavernosum penis ■
■ M, ischio-cavernosus
. Urogenital trigone
(diaphragm)
Prostate gland -
somewhat to be received into its basal concavity (fig. 1024). The septum in its
proximal part forms a complete partition between the two bodies, but distally it
is broken through by numerous clefts by which the blood lacunse of the two bodies
are placed in communication.
Each corpus cavernosum penis consists of a strong elastic fibrous sheath, the tunica albu-
ginea, from which trabeculiB extend into the substance of the organ, dividing it into a network
of communicating cavities, into which open terminal branches of the a. profunda penis, which
traverses the axis of the corpus. These cavities consequently are to be regarded as vascular
lacunae, which, becoming engorged with blood, produce the enlargement and erection of the
organ.
The third erectile organ is the corpus cavernosum urethra (formerly "corpus
spongiosum") (fig. 1023), so called because it is traversed throughout its entire
length by the urethra (fig. 1024). It is an unpaired, median structure, having no
1262
UROGENITAL SYSTEM
bony attachments and begins posteriorly in the superficial perineal interspace
with an enlargement, the bulb [bulbus urethrae] (fig. 1023), whose posterior surface
rests on the superficial fascia of the urogenital trigone and is enclosed by the m.
bulbo-cavernosus. Anteriorly the bulb gradually tapers to a rather slender
cylindrical portion, the body, very uniform in diameter, which extends throughout
the entire length of the body of the penis, lying in the median hne beneath the
fused corpora cavernosa penis (figs. 1022, 1023). At the neck of the penis it
undergoes a sudden enlargement to form the glans, the whole of that structure,
which has already been described, being formed by the corpus cavernosum
urethras. The structure of the corpus cavernosum urethrae is essentially the same
as that of the corpora cavernosa penis, the tunica albuginea, however, being much
thinner.
Vessels and nerves. — The principal arterial supply of the penis is derived from the internal
pudendal artery (see p. 610), although the proximal portion of its integument is also supplied
by the external pudendal branches of the femoral artery. The veins from the integument
Fig. 1024. — Mid-sagittal Section (diagrammatic) Showing Male Bladder, Ukethba, etc.
Symphysis pub:
Subpubic lig.
Suspensory lig.
Urogenital trigone
(diaphragm)
Bladder
Seminal vesicle
Ampulla
Prostate middle lobe
Ejaculatory duct
Prostatic utriculus
Prostate gland
Bulbo-iurethral
(Cowper's) gland
Ductus deferens
Prepuce.
Fossa navicularis
collect into one or more stems, the superficial dorsal veins, which run along the dorsal mid-line
and, diverging, open into the great saphenous vein. The deep veins from the corpora cavernosa
open into a median deep dorsal vein, which connects partly with the internal pudendal veins
and partly with the pudendal plexus. Both the superficial and deep lymphatics terminate in
the superficial inguinal nodes. The lymph-vessels from the glans are said to follow those of the
urethra and end in the deep inguinal and external iliac nodes.
The nerves supplying the penis are the anterior scrotal branches of the ilio-inguinal and the
perineal branches and dorsal nerve of the penis from the pudendal. Sympathetic fibres also
pass to the penis from the hypogastric plexus and with these fibres from the third and fourth
sacral nerves, which constitute what is termed the nervus erigens, since stiinulation of it pro-
duces erection of the organ. An anatomical provision for the production of this phenomenon has
been found in the occurrence of peculiar thickenings of the intima of the arteries of the penis,
by which the lamina of the vessels are greatly diminished or even occluded when in a state
of moderate contraction, as when the organ is flaccid. When the arteries are dilated the intimal
thickenings become reduced in height and the blood is afforded a free passage into the lacunar
spaces of the corpora cavernosa, which thus become engorged.
4. The Male Urethra
The urethra is the canal which extends from the bladder to the extremity of
the glans penis and serves for the passage of both the urine and the seminal fluid.
THE MALE URETHRA
1263
In its course (fig. 1024) it traverses first the prostate gland, then the urogenital
diaphgram and then the entire length of the corpus cavernosum urethrse, and may
thus be regarded as being composed of three portions.
The prostatic portion [pars prostatica] (fig. 1024) extends almost vertically
downward from the neck of the bladder, traversing the substance of the prostate
gland. In its proximal part there is on its posterior wall a median longitudinal
ridge, the crista urethralis, which below dilates into an oval enlargement, the
colliculus seminalis (figs. 1015, 1025), to accommodate which there is a marked
Fig. 1025. — The Male Urethra, cleft anteriorly to show the Mucous Coat.
Ureter , -^r * ^
Section of bladder
Internal urethral onfice
Openings of prostatic glands'
Prostatic utricnlus '^m ©j^
Follicular glands of dorsal wall — VmL ;. '
Bulbo-urethral gland
Septum of penis
Section of prostate
Colliculus seminalis
Ejaculatory duct
Openings of prostatic glands
"7 Membranous uerthra
Section of corpus cavernosum penis
Orifice of bulbo-urethral gland
Section of corpus cavernosum penis '^ ^ 1'
Bulbous portion of urethra
Mucous membrane
Fossa navicularis
External urethral orifice
widening of the lumen of the urethra in this part of its course. At the centre of
the colliculus there is an elongated opening of a pouch of varying depth, termed the
utricnlus prostaticus ("uterus masculinus"), which corresponds to the lower part
of the vagina in the female (see p. 1279). Situated one on either side of this are
the much smaller openings of the ejaculatory ducts. Owing to the prominence
formed by the coUiculus a section of the urethra in this region is somewhat
fl-shaped, and at the bottom of the furrows on either side of the median eleva-
1264 UROGENITAL SYSTEM
tion are the minute openings of the numerous ducts of the prostate gland
(fig. 1025). ^ ^
On its emergence from the prostate gland the urethra at once penetrates the
deep layer of fascia of the urogenital trigone and enters the deep perineal inter-
space, this portion of its course being known as the membranous portion [pars
membranacea]. Its direction is now downward and slightly forward, curving
beneath the subpubic ligament, from which it is separated by a plexus of veins and
by the fibres of the sphincter urethras membranaceae, which form an almost
complete investment for it. The lumen of this part of the urethra is much
narrower than that of the prostatic portion, and since it traverses the rather
unyielding fasciae of the urogenital trigone it is less dilatable than in other parts
of its extent, with the exception of the external orifice.
Passing through the superficial layer of fascia of the urogenital trigone the
urethra then enters the bulb of the corpus cavernosum urethrae (fig. 1024) and is
invested throughout the remainder of its extent by this structure, whence this
portion is known as the cavernous portion [pars cavernosa]. In its proximal part
this hes in the superficial interspace of the perineum and passes almost directly
forward; but more distally, where it enters the body of the penis, it accommodates
itself to the position of that organ, which it traverses lengthwise, lying in the mid-
line near its ventral surface (fig. 1022). Thus the proximal portion of the
cavernous and the whole of the membranous and prostatic portions have a
fixed position, whence they are sometimes associated as the pars fixa of the urethra,
while the penial portion forms the pars mobilis. On entering the bulb the lumen
of the urethra dilates somewhat and in this region has opening into it the ducts of
the bulbo-urethral glands (fig. 1025), but as it enters the body of the corpus caver-
nosum it diminishes again and maintains a uniform diameter throughout the
extent of that structure. When it reaches the glans penis it undergoes another
dilation, which is known as the fossa navicularis (fig. 1025), beyond which it
diminishes to the slit-hke external orifice, situated at the extremity of the glans
and forming the least dilatable portion of the entire urethral canal.
Throughout the greater part of its extent the cavernous portion of the urethra shows upon
its dorsal wall the openings of numerous tubular depressions of the mucous membrane, the
urethral lacunm [lacunas urethrales (Morgagnii)]. One of these, the lacuna magna, situated
m the mid-dorsal line of the proximal part of the fossa navicularis, has its orifice guarded by a
valve-hke fold [valvula fossEe navicularis] of the mucous membrane and is sufficiently large to
receive the point of a small catheter. Numerous minute glands [gl. urethrales] open upon
the surface of the urethral mucosa. They are most abundant in the anterior wall, but occur
also on the sides and floor.
,.„ Dimensions of the urethra.— The entire length of the urethra is somewhat variable in
ditterent individuals, the greatest variation being in the length of the pars mobihs. Of the pars
fi^a the prostatic portion is 2.5-3.0 cm. in length, the membranous portion about 1.0 cm., and
the fixed part of the cavernous portion 6.5 cm., the entire pars fixa having thus a length of some-
what over 10.0 cm. (4 in.). The average diameter of the urethra is 5.0-7.0 mm., but it will be
noted that the canal presents in its course three dilatations; namely, (1) at the fossa navic-
ularis, which begins about 0.5 cm. from the external orifice; (2) the bulb of the corpus caverno-
sum urethras; and (3) in the prostatic portion. Furthermore there are two regions in which it
is distinctly narrowed; namely, at the external orifice and in the memjjranous portion. While
the remaining portions are capable of considerable distention, these are relatively indistensible,
the maximum diameter to which they may be dilated being about 10 mm. Arranged in an
ascending order according to their capability for distention the parts would have the followmg
order: external orifice, membranous portion, penial portion, prostatic portion, bulbar portion.
5. The Prostate Gland
The prostate gland [prostata] (figs. 1013, 1019, 1024 and 1025) is a mass of
glandular and muscular tissue surrounding the proximal portion of the male
urethra, and may, indeed, be regarded as a special development of the wall of
this portion of the canal. It is a more or less flattened conical structure whose
base [basis prostatse] is in contact with the lower surface of the bladder and the
apex [apex prostatse] with the deep fascia of the urogenital trigone. Its anterior
surface [facies anterior] is in relation with the symphysis pubis, from which it is
separated by the pudendal plexus of veins, and posteriorly [facies posterior] it is
separated from the lower portion of the rectum only by some loose connective
tissue; laterally it is in relation with the levatores ani, receiving an investment from
the endopelvic fascia covering these.
i
THE FEMALE REPRODUCTIVE ORGANS 1265
The urethra enters the base of the gland near its anterior border and traverses
it almost vertically, so that the greater portion of the gland is posterior to the
canal. On the posterior surface of the gland is a more or less distinct median
vertical groove, which serves to separate the lateral portion as the lateral lobes
[lobus dexter et sinister], although the demarcation is merely a superficial one.
The groove terminates above in a well-marked notch on the posterior border of
the base, and immediately in front of this there is a deep funnel-shaped depression
of the surface, which receives the ejaculatory ducts. Beginning at this depression
two grooves pass forward and slightly lateralward across the surface of the base,
marking off a more or less pronounced median elevation, which constitutes what
is termed the middle lobe [lobus medius] (fig. 1024); since this lies beneath the
trigone of the bladder behind the internal orifice of the urethra its enlargement
may produce more or less occlusion of the latter.
Dimensions. — The longest axis of the prostate, which is almost vertical in the erect posture
measures 2.5-3.0 cm., the transverse diameter at the base is 4.0-4.5 cm. and the thickness 2.0-2.5
cm. Its iveight is normally 20-25 grms. but in old age it may be double that, its dimensions
having correspondingly increased.
Structure. — The prostate consists of some 15-30 branched tubular glands imbedded in
a matrix of connective tissue, containing a large amount of non-striped muscle tissue and form-
ing at the surface of the gland a strong fibro-muscular capsule from which prolongations are
contributed to the pubo-vesical ligaments and muscles. The glands, which vary greatly in
their development, are outgrowths from the mucous membrane of the urethra, into which their
ducts open at the bottom of the grooves that lie lateral to the colliculus seminahs; similarly,
the matrix with its muscle tissue is evidently the modified muscular coat of the urethra. Con-
sequently there is no distinct demarcation between the wall of the urethra and the substance
of the gland, and from the developmental standpoint the gland is to be regarded as the modified
wall of the urethra.
The facts that the prostate shows a special development at puberty and undergoes more or
less extensive degenerative changes with the cessation of the reproductive function, as seen in
old age and in castrates, indicate that it is associated physiologically with the reproductive
organs. Its secretion is a thin alkaline fluid, which may contain round or elongate, concen-
trically layered bodies, measuring 0.3-0.5 mm. in diameter and known as amyloid bodies,
although they are really albuminous in chemical composition. They are constantly found in
adults in the lumina of the glands and may become calcified. The secretion has been found to
have a stimulating effect upon the spermatozoa, and this may be its principal function.
Vessels and nerves. — The arterial supply of the prostate is derived from the inferior vesical
and middle hemorrhoidal branches of the hypogastric artery. The veins form a rich prostatic
plexus in the immediate vicinity of the gland, this being part of the general plexus at the base
of the bladder and communicating posteriorly with the seminal plexus and anteriorly with the
pudendal plexus. It drains finally into the hypogastric vein. The lymphatics are very abun-
dant and form a network on the posterior surface of the gland -from which four principal vessels
pass to the hypogastric nodes. The nerves are derived from the hypogastric plexus.
6. The Bulbo-urethral Gl.inds
The bulbo-urethral glands [gl. bulbo-urethralis (Cowperi)] or Cowper's glands
(figs. 1024, 1025) are two small tubulo-alveolar glands which fie one on either
side of the membranous portion of the urethra, imbedded among the fibres of the
sphincter urethrse membranacete, between the two layers of fascia of the uro-
genital trigone. Each is a rounded body with a diameter of 4.0-9.0 mm. and is
drained by a duct [ductus excretorius] which perforates the superficial fascia of the
trigone and, entering the substance of the bulb of the corpus cavernosum urethrse,
traverses it to open on the floor of the bulbar portion of the urethra after a total
course of 3.0-4.0 cm. Nothing is definitely known as to the nature of the secre-
tion or the functions of the glands.
THE FEMALE REPRODUCTIVE ORGANS
The organs of reproduction in the female consist of (1) the ovaries, the
essential organs of reproduction; (2) the tubce uterince (Fallopian tubes), which
serve as ducts for the conveyance of the ova to (3) the uterus, in which the embryo
normally undergoes its development; (4) the vagina, a canal by which the uterus
is placed in communication with the e.xterior; and (5) the external genitalia. In
addition it will be necessary to consider here the female urethra, although it differs
from that of the male in that it serves merely as a passage for the contents of the
bladder and does not transmit the reproductive elements.
i
{
1266
UROGENITAL SYSTEM
Fig; 1026. — The Female Organs of Generation. (Modified from Sappey.)
(Vagina divided and laid open behind.)
Posterior surface of body of uterus
Ovarian ligament
Ovary
Tuba uterina
Mesosalpinx
Fimbriated
extremity of tube
Fimbria ovarica
Mesometrium
Supravaginal zone of cervix
External orifice of uterus
Vaginal wall, divided
and reflected
Vagina, anterior wall
iG, 1027. — Diagrammatic Sagittal Section of the Broad Ligament.
Tuba uterina
Mesometriu:
Posterior surfac
Connective tissue and unstriped
muscle (utero-pelvic band)
Uterine veins
-Uterine artery
Ease of ligament
THE BROAD LIGAMENT
1267
Broad ligament. — ^The first three of these structures are entirelj^ contained
within the true pelvis and are associated with a transverse fold of peritoneum
which rises from the floor of the pelvic cavity between the bladder and the rectum,
incompletely dividing the cavity into an anterior and a posterior compartment.
It is known as the hroad ligament of the uterus [lig. latum uteri] (fig. 1026). The
broad ligament appears to extend laterally from the sides of the uterus to the
lateral walls and floor of the pelvis, although in reality it extends across the pelvic
cavity from side to side and encloses the uterus between the two layers of which
it is composed. It is attached to the floor of the pelvis below, where the two layers
are reflected, the one upon the anterior wall of the pelvis and the posterior and
superior surfaces of the bladder, and the other posteriorly over the floor of the
pelvis to the posterior pelvic wall and the rectum, forming the anterior wall of a
deep depression between the rectum and uterus, known as the recto-uterine pouch
(of Douglas) [excavatio rectouterina (cavum Douglasi)] (fig. 1035). Its lower
border also passes upward upon the sides of the pelvis, resting upon the pelvic
fascia, but its lateral borders are free, extending between the lateral wall of the
pelvis and the extremity of the tuba uterina on each side and forming what are
termed the infundibulo-pelvic ligaments. The upper border is also free and con-
tains the tuba uterina on either side, and the fundus of the uterus in the midline
(fig. 1027).
Fig. 1028. — Cross-sections of the Body Illustrating the Development of the Female
Urogenital system. A, at Higher Level. B, at Lower Level.
Epodpliorou
Attached to the posterior layer of the broad hgament a httle below its upper
border and therefore projecting into the posterior compartment of the pelvis,
there is a horizontal shelf, termed the mesovarium, since it has the ovary attached
to its free edge (fig. 1027). The portion of the broad hgament above this is known
as the mesosalpinx (salpinx = tuba), while that below istermed the mesometrium
(metra= uterus). The remaining structm-es that occur between the two layers
of the broad ligament will be described with the organs with which they are
associated, but it is to be noted that the ligament in its upper part is broader than
the transverse diameter of the pelvic cavity and its sides are accordingly folded
back upon the lateral walls of the cavity, following the course of the tuba uterina.
The broad ligament is the adult representative of the fold of peritoneum which encloses
the embryonic excretory organ, the mesonephros. This is for a time a voluminous organ,
projecting under cover of the peritoneum from the dorsal wall of the abdomen and bearing
upon its medial wall a thickening, the genital ridge (fig. 1028 A), from which the reproductive
gland develops. In the free edge of the peritoneum enclosing it two ducts occur, the Wolffian
duct, which is the duct of the excretory organ and becomes the ductus deferens of the male,
and the Miillerian duct. With the progress of development the two MuUerian ducts fuse in
the lower portions of their course to form the uterus and vagina (prostatic utriculus of the male),
while in their upper parts they remain separate and form the tubs uterinae. By this fusion
the two peritoneal folds are brought into continuity at their edges, and (the mesonephros de-
generating on the formation of the permanent kidney) constitute the broad ligament (fig.
1028 B). This structure therefore contains between its two layers the uterus and the remains
of the mesonephros, and has the ovary attached to its posterior surface. In the male what
corresponds to the broad hgament fuses with the peritoneum covering the posterior surface of
the bladder.
i
(
1268
UROGENITAL SYSTEM
1. The Ovaries
Form and position. — The ovarie,s [ovaria] are two whitish organs, situated
one on either side of the pelvic cavity. Each has somewhat the shape of an
almond (fig. 1026). It is attached by one of its edges [margo mesovaricus] to
the border of the mesovarium, and since it is along this line of attachment that
the vascular and nerve supply enters the substance of the organ, this border is
spoken of as the hilus [hilus ovarii]. The opposite border is free [margo liber].
The larger rounded end is directed toward the free extremity of the tuba uterina
and hence is known as the tubal extremity [extremitas tubaria], while the other,
the uterine extremity [extremitas uterina], is directed toward the uterus; the two
surfaces, owing to their topographic relations, are known as the lateral and medial
surfaces [facies mediahs et lateralis].
Fig. 1029. — The Female Pelvic Organs Viewed from Above. (Spalteholz.)
Sigmoid colon
' ~ Recto-uterine pouch
Rectum
Ureter \.
;-fflffs?r
Recto-uterine fold
/
Parietal peri-
/ . / toneum
/ Ureter
' •/
Suspensory
/ ligament of
/ ovary
! Ampulla
of tuba
/ uterina
^ ^i Isthmus
of tuba
uterina
^Ligamen-
tum teres
Transverse vesical fold
The exact position of the ovary in the pelvis is subject to some variation, but
typically it hes almost in a sagittal plane (fig. 1029) against the lateral wall of the
pelvis, resting in a distinct depression, the /ossa ovarica, lined by peritoneum and
bounded above by the external iliac vessels and behind by the ureter and uterine
artery, while beneath its floor are the obturator vessels and nerve. The long axis
of the ovary is almost vertical when the body is erect, the tubal pole being upward;
the mesovarial border is directed forward and laterally, its free border dorsally
and medially while its surfaces look almost laterally and medially.
Frequently, however, the uterus is displaced to one side, dragging the uterine extremity
of the opposite ovary (by the attachment of the ovarian ligament) toward the mid-plane. The
long axis of the ovary thus becomes oblique, approaching more or less the horizontal. The as-
cending portion of the tuba uterina rests upon its mesovarial border and the fimbriated mouth
THE UTERINE TUBES 1269
of the tube is in contact with its medial surface. When enlarged the ovary may be felt through
lateral wall of the vagina and, better, through that of the rectum; and its position with regard
to the surface may be indicated by a point midway between the anterior superior spine of the
ilium and the symphysis pubis or the opposite pubic tubercle.
The position assumed by the ovary is due to its attachment to the edge of
the mesovarium and to the upper portion of the broad hgament being broader
than the diameter of the pelvis, so that it is folded back upon the lateral walls of
the cavity. In addition to its attachment to the broad hgament through the
mesovarium, the ovary is also connected to the side of the uterus by the ovarian
ligament [hg. ovarii proprium] (fig. 1026), a' band of connective tissue with which
numerous non-striped muscle fibres are intermingled. It lies between the two
layers of the broad hgament, on the boundary line between the mesosalpinx and
the mesometrium, and extends from the uterine pole of the ovary to the side of the
uterus. Here it is attached just below the origin of the tuba uterina and above
the point of attachment of the round hgament of the uterus, with which it is
primarily continuous. Another Hgament, termed the suspensory ligament of the
ovary (figs. 1029, 1034), extends laterally between the two layers of the broad
hgament from the tubal extremity of the ovary to the pelvic walls, forming the
lateral portion of the lower boundary of the mesosalpinx. It is formed by the
vessels and nerves (internal spermatic) passing to and from the ovary, and from
the point where it meets the lateral pelvic wall it may be traced upward for some
distance upon the posterior wall of the abdomen, behind the peritoneum, which it
elevates into a more or less distinct fold, whose lateral wall on the right side
becomes continuous above with the peritoneum lining the subccecal fossa.
Size. — The size of the ovary varies considerably, that of the right side being as a rule
somewhat larger than that of the left. The length may be anywhere from 2.5 cm. to 5.0 cm., the
breadth about half the length and the thickness half the breadth. Its average weight in the
adult is from 6.0 to 8.0 grms., but in old age it may fall to 2.0 grms.
Structure. — The ovary is covered by a layer of columnar epithehum which is continuous
with the peritoneal epithelium along the line of the attachment of the mesovarium; the ovary
consequently is not covered by peritoneum, but is rather to be regarded as a local thickening
of the peritoneum. Its substance is a network of connective tissue, in which non-striped
muscle fibres also occur, and is known as the stroma. The more central portions of this are
largely occupied by blood-vessels but in the cortical portions are multitudes of immature ova,
surrounded by their follicle cells [follicuU oophori primarii]; and also numbers of cavities of
various sizes, lined with foUicle cells and filled with fluid, each containing an ovum [ovulumj
in a more or less advanced stage toward maturity. These are the Graafian follicles [follicuU
oophori vesiculosi (Graafi)], and as they ripen they increase in diameter and approach the
surface, upon which they may form marked prominences. When mature the follicles burst,
allowing the escape of the ovum, scars being thus formed upon the surface of the ovary that are
known as corpora albicantia. If, however, the ovum becomes fertilized and pregnancy results
the walls of the follicle undergo a remarkable development, forming what is known as a corpus
luteum.
Epoophoron and paroophoron. — Closely associated with the ovaries are two rudimentary
organs situated between the layers of the mesosalpinx and representing remains of the meso-
nephros of the embryo. The larger of these is the epoophoron (fig. 1030). It consists of a longi-
tudinal duct [ductus epoophori longitudinalis (Gartneri)], lying parallel with the tuba uterina
and closed at either extremity, and 10-15 transverse ducts [ductuli transversi], which open
into the longitudinal duct. It is the remains of the upper or reproductive portion of the meso-
nephros and therefore is the homologue of the epididymis of the male. In addition there is fre-
quently to be found in the neighbourhood of the epoophoron and close to the mouth of the tuba
uterina one or more stalked, oval cysts, the appendices vesiculosi {hydatids of Morgagni), which
may reach the size of a small pea.
The other organ is the parobphoron; it is much smaller than the epoophoron and usually
disappears before adult life, but when present consists of a small group of coiled tubules, more
or less distinct, representing a portion of the excretory portion of the mesonephros. Its equiva-
lent in the male is therefore the paradidymis.
Vessels and nerves. — The chief artery is the ovarian, which together with the ovarian veins
and lymphatics passes to the ovary in the suspensory ligament. An additional blood supply
is furnished by the ovarian branch of the uterme artery. The veins follow the course of the
arteries. As they emerge from the hilus they form a weU-developed plexus (pampiniform
plexus) between the laj'ers of the mesovarium. Unstriped muscle fibres occur in the meshes
of the plexus and the whole structure has much the appearance of erectile tissue. The lym-
phatics accompany the blood-vessels and terminate in the lumbar nodes. Nerves pass to the
ovary with the ovarian artery from the renal and aortic sympathetic plexus.
2. The Titb^ Uterine
The tubae uterinse or Fallopian tubes (figs. 1026, 1030) serve to convey the
ova to the uterus. They are two trumpet-shaped tubes, structurally continuous
1270
UROGENITAL SYSTEM
with the superior angles of the uterus and running in the superior border of the
broad hgament (mesosalpinx) to come into relation with the ovaries at their
distal extremities. Each tube opens proximally into the uterine cavity and dis-
tally communicates witli the pelvic portion of the peritoneal cavity by a funnel-
shaped mouth, the ostium abdominale, which under normal conditions is closely
applied to the surface of the ovary, so as to receive the ova as they are expelled
from the Graafian follicles. Each tube is from 7 to 14 cm. in length and con-
sists of a narrow straight portion, the isthmus, immediately adjoining the uterus,
followed by a broader, more or less flexuous portion, the mnpulla, which terminates
in a funnel-like dilatation, the infundibulum. The margins of the infundibulum
are fringed by numerous diverging processes, the fimbria, one of which, the
fimbria ovarica, is much longer than the rest and extends along the free border of
the mesosalpinx (the infundibulo-pelvic ligament) to reach the tubal pole of the
ovary.
The course of each tube is at first almost horizontally laterally and backward
from its attachment to the uterus, until it reaches the lateral wall of the pelvis
and there comes into relation with the uterine extremity of the ovary (figs.
1029, 1034). It then bends at right angles and passes almost vertically upward
1030. — The Broad Ligament and its Contents, seen prom the Front.
(After Sappey.)
EpoCphoron
Ampulla of Fallopian tube
Tuba uterina
External angle of uterus
Fimbriated extremity of tube
Fimbria ovarica
Round ligament
Ovarian ligament
Anterior peritoneal lamina
along the mesovarial border of the ovary until it reaches its tubal extremity,
where it curves downward and backward so that the mouth of the infundibulum
and the fimbriae rest upon the medial surface of the ovary.
Structure. — The tubas occupy the upper free edge of the mesosalpinx and are therefore
enclosed within a peritoneal covering [tunica serosa] except a small strip along their lower surface
(fig. 1027), and hence a rupture of one of them may lead to the escape of its contents either
into the peritoneal cavity or into the subserous areolar tissue between the two laj'ers of the broad
ligament. At the margins of the infundibulum and the borders of its fimbrite the peritoneal
epithelium becomes directly continuous with the mucous membrane lining the interior of
the tube. The subserous areolar tissue [tunica adventitial in the immediate vicinity of the tube
is lax and contains the blood-vessels and nerves by which the tube is supplied; it forms a loose
connection between the peritoneum and the muscular wall [timica muscularis] of the tube. This
consists of two layers of non-striped muscle fibres, an outer longitudinal and an inner circular
one, and reaches its greatest development toward the uterine end of the tube. The inner
layer [tunica mucosa] of the tube is hned by a columnar cihated epithelium which is raised into
numerous folds, simple in the region of the isthmus, but becoming higher and more complex
in the ampulla, where, in transverse sections, the lumen seems to have a lab3Tinthine form.
The beat of the cilia is toward the uterus.
Vessels and nerves. — The arteries of the tubaj are derived from the ovarian and uterine,
each of which gives off a tubal branch, which pass between the two layers of the mesosalpinx,
the one medially and the other laterally, and anastomose to form a single stem. The veins
accompany the arteries. The lymphatics accompany those from the ovary and fundus uteri and
terminate chiefly in the lumbar nodes. The nerves of the ampuUa are given off from the
branches passing to the ovary, while those of the isthmus come from the uterine branches.
THE UTERUS
1271
3. The Uterus
The uterus (fig. 1031) is an unpaired organ, situated between the two layers of
the broad ligament and communicating above with the tubse uterinse and below
with the vagina. It is pyriform in outhne, although flattened antero-posteriorly
(fig. 1032) and it is divided into two main portions, the body [corpus uteri] and the
cervix by a transverse constriction, the isthmus.
The body is the portion above the isthmus and in adults, especially in women
Fig. 1031. — The Posterior Surface of the Uterus. (After Sappey.)
---.__ — Tuba uterina
Supra-vaginal cervix
External orifice
Vaginal wall
\ \ ^Edge of peritoneum
Cervical attaciiment of vagina
who have borne children, is much larger than the cervix, although the reverse is
the case in children. In young girls the two parts are about equal in size. The
anterior or vesical surface [fades vesicalis] is almost flat (fig. 1032), while the pos-
terior or intestinal surface [facies intestinalis] is distinctly convex, the two
surfaces meeting in well-marked rounded borders, at the upper extremities of
which the tubas uterinse are attached. The superior border which extends be-
tween the points of attachment of the two tubse is thick and rounded and forms
Fig. 1032. — -Sagittal Section op the Virgin Uterus. (After Sappey.)
'A
Internal orifice
Canal of cervix
Posterior fornix
Posterior lip
Reflection of peritoneun
Anterior lip
Anterior forni:
External orifice
what is termed the fundus uteri. The cavity [cavum uteri] of the body is reduced
to a fissure by the antero-posterior flattening of the walls and has a triangular form
(fig. 1033), broad above where it communicates on either side with the cavity of a
tuba uterina and narrow below where it communicates with the cavity of the
cervix, this communication, which corresponds in position with the isthmus, form-
ing what is known as the internal orifice [orificium internum] (internal os uteri).
The cervix is more cj'lindrical in form, though slightly expanded in the middle
1272
UROGENITAL SYSTEM
of its length, and is divided into a suTpravaginal [portio supravaginalis] and a
vaginal -portion [portio vaginalis] by the attachment to it of the vagina (fig. 1031).
The line of this attachment is obhque, about one-third of the anterior surface of
the cervix and about one-half of the posterior surface belonging to the vaginal
portion. At the lower extremity of the cervix is the external orifice [orificium
externum] (external os uteri), which is round or oval before parturition has taken
place and is bounded by two prominent labia, anterior and posterior, the anterior
one [labium anterius] being shorter and thicker than the posterior [labium pos-
terius] and reaching a lower level (fig. 1032). In women who have borne children
the external orifice assumes a more slit-like form and the labia become notched
and irregular. The cavity of the cervix, known as the canal of the cervix [canaHs
cervicis], is fusiform in shape, and extends from the internal to the external
orifice. On its anterior and posterior walls are folds known as the plicce palmatce
(fig. 1033), consisting of a median longitudinal ridge from which shorter elevations
extend laterally and slightly upward; these are most distinct in young individuals
and are apt to become obliterated by parturition.
Fig. 1033. — Frontal Section of the Vihgin Uterus. (After Sappey.)
Uterine wall
Cavity of body
Internal orifice
Uterine wall
: with plicEe palmatse
External orifice
Vaginal wall
Position and relations. — The direction of the axis of the uterus is apparently
variable within considerable limits, not only in different individuals, but also in
any one individual in correspondence with the degree of distention of the bladder
anteriorly and the rectum posteriorly. In what may be regarded as the typical
condition (fig. 1034) the external orifice lies at about the level of the upper border
of the symphysis pubis and in the plane of the spines of the ischia. From this
point the axis of the cervix is directed upward and slightly forward, the lower
level of the anterior labium being thus brought about. The entire uterus is,
accordingly, anteverted, and, furthermore, the body is bent forward (anteflexed)
upon the cervix at the isthmus, the axis of the two portions making an angle,
open anteriorly, of from 70° to 100°. Frequently, also, the body is sHghtly in-
clined either to the right or to the left.
The anterior surface of the uterus rests upon the upper and posterior surfaces of the bladder
(fig. 1029), from which the body is separated by the utero-vesical pouch of peritoneum. The
anterior layer of the broad ligament as it passes over the anterior surface of the uterus forms
the posterior wall of this pouch and is reflected forward to the superior surface of the bladder
at about the level of the isthmus (fig. 1034), so that the whole of the anterior wall of the cervix
is below the floor of the pouch and is separated from the posterior surface of the bladder only
by connective tissue. Posteriorly, however, the peritoneal covering of the uterus, which here
forms the anterior wall of the recto-uterine pouch, e.xtends down as far as the uppermost
portion of the vagina and consequently invests the entire surface of the uterus, whose convex
posterior wall is thus separated from the rectum by the recto-uterine pouch (figs. 1029, 1035).
Coils of the small intestine rest upon the posterior surface of the body and may also be inter-
posed between the cervix and the rectum. An important relation is that of the ureters to the
cervix, these ducts, as they pass to the bladder, running parallel with the cervix at a distance
of from 8 to 12 mm. from it.
Ligaments. — The broad ligament between whose layers the uterus is situated
has already been described (p. 1267). In addition there is attached to each border
THE UTERUS
1273
Fig. 1034 — Mid-sagittal Section of the Female Pelvis (Spalteholz.)
Hypogastric artery
, Hypogastric vein
Promontory / / Infundibulum of tuba uterina
Ureter
Parietal pentoneum
Suspensory ligament of ovary
External iliac vein
Ovary
Ampulla of tuba utenna
Ovarian ligament
Fundus uteri \
Ligamentum teres \
Transverse fold of \ \
bladder >. \
Vertex of bladder v \ \
Middle umbilical \ \
ligament
Recto-uterine fold
Urach
Symphysis pubis
Labium maju
Body of uterus
Labium minus
External orifice of urethra /
Urethra
Internal orifice of urethra
Orifice of vagina
Rectum
Posterior labii
External orifice of uterus
Anterior labium
Hymen
Anus
Vagina
Vesico-uterine pouch
Vestibule
Fig. 1035. — Section of the Pelvis showing the Ligaments of the Uterus.
Symphysis
Prevesical fat
Bladder-waU
Obturator inter nus
Obturator fascia
Subperitoneal tissue
Broad ligament
Peritoneum
Sacro-tuberous
ligament
Utero-sacral ligament
running forward into
recto-uterine Ugament
Vesical cavity
Peritoneum of utero-
vesical pouch
Utero-vesical ligament
Broad ligament
Recto-uterine pouch
of Douglas
'^^5o ] ^^^^®^®
1274 UROGENITAL SYSTEM
of the uterus, immediately below the point of attachment of the ovarian ligament,
the ligamentum teres (round ligament) (fig. 1030), which is a fibrous cord con-
taioing non-striped muscle tissue. It extends downward, laterally and forward
between the two layers of the mesometrium toward the abdominal inguinal ring,
and, traversing this and the inguinal canal, it terminates in the labium majus by
becoming continuous with its connective tissue.
It is accompanied by a funicular branch of the ovarian artery and a branch from the ovarian
venous plexus, and in the lower part of its course by a branch from the inferior epigastric artery,
over which it passes as it enters the abdominal ring. In its course through the inguinal canal
it is accompanied by the iho-inguinal nerve and the external spermatic branch of the genito-
femoral.
The utero-sacral ligaments are flat fibro-muscular bands which extend, one on
each side, from the upper part of the cervix uteri to the sides of the sacrum op-
posite the lower border of the sacro-iliac articulation. They produce the recto-
uterine folds (fig. 1029) of peritoneum, which form the lateral boundaries of the
mouth of the recto-uterine pouch (of Douglas) and their muscle fibres [m. rec-
touterinus] are continuous at one extremity with the muscular tissue of the
uterus and at the other with that of the rectum.
Structure. — The portion of the broad ligament that invests the uterus forms the serous
covering [tunica serosa] of the organ and is sometimes termed the perimetrium. Over the fundus
and the greater portion of the body it is thin and firmly adherent to the subjacent muscular
substance of the uterus, so that it cannot readily be separated from it. Over the posterior
surface of the cervix and the lower part of the anterior surface of the body, however, it is thicker,
and is separated from the muscular substance by a layer of loose connective tissue, the para-
metrium, which also extends upward along the sides of the uterus between the two layers of the
broad hgament, with whose subserous areolar tissue it is continuous. Owing to this disposition
of the parametrium the whole of the cervix may be amputated without encroaching upon the
peritoneal cavity.
The main mass of the uterus is formed by the muscle tissue [tunica muscularis] or myome-
trium, whose fibres have a very complicated arrangement. Two principal layers may be
distinguished, an outer, wealv one, composed partly of longitudinal fibres continuous with those
of the tub® uterinje, and of the round and utero-sacral hgaments, and a much stronger inner
one, whose fibres run in various du-ections and have intermingled with them in the body of the
uterus large venous plexuses. The inner surface of the myometrium is hned by a mucous
membrane [tunica mucosa] or endometrium, which has a thickness of from 0.5 to 1.0 mm. and
is composed of tissue resembling embryonic connective tissue, bearing upon its free surface a
single layer of cihated columnar epithelium. On account of its structure the tissue is rather
delicate and friable, and numerous simple tubular glands, which open into the cavity of the
uterus, traverse its entire thickness. In the cervix the mouths of some of the glands may
become occluded, produci^g retention cysts, which appear as minute vesicles projecting from
the surface between the plicse palmatae; they are known as ovula Nabothi, after the anatomist
who first described them.
Vessels and nerves. — The principal artery of the uterus is the uterine, whose terminal
portion ascends along the lateral border of the uterus in a tortuous course through the para-
metrium, giving off as it goes lateral branches to both surfaces of the uterus. Above, it anasto-
moses with the ovarian artery, which thus forms an accessory source of blood supply during
pregnancy. The veins form a plexus that is drained by the ovarian and uterine veins, a com-
munication with the inferior epigastric being also made by way of the vein accompanying the
round ligament. The lymphatics from the greater portion of the body pass to the iliac
nodes: those of the fundus accompany the ovarian vessels to the lumbar nodes. A vessel also
accompanies the round hgament to terminate in one of the superficial inguinal nodes. The
lymph-vessels from the cervix terminate in the external iliac, hypogastric and lateral
sacral nodes.
The nerves of the uterus pass to it from two sympathetic gangha, situated one on either
side of the cervix, whence they are termed the cervical gangha, and forming part of the plexus
utero-vaginalis. Branches pass to the ganglia from the hypogastric plexus and also from the
second, third and fourth sacral nerves.
4. The Vagina
The vagina (fig. 1034) is a muscular, highly dilatable canal lined by mucous
membrane, and extends from the uterus to the external genitaUa, where it opens
to the exterior. Its long axis is practically parallel with that of the lower part
of the sacrum and it therefore meets the cervix uteri at a wide angle which is
open anteriorly. Its anterior wall is, accordingly, somewhat shorter than the
posterior, measuring 6.0-7.0 cm., while the posterior one is about 1.5 cm. longer.
It becomes continuous with the cervix uteri some distance above the lower
extremity of that structure, which thus projects into the lumen of the vagina, and
there is so formed a narrow circular space between the wall of the vagina and
THE VAGINA
1275
the vaginal portion of the cervix uteri. The roof of the space is formed by the
reflection of the vagina upon the cervix and is termed the fornix. Owing to the
greater length of the posterior wall of the vagina the portion of the circular space
below the posterior fornix is considerably deeper than that below the anterior.
In its ordinary condition the lumen of the vaginal canal is a fissure, which in
transverse section resembles the form of the letter H with a rather long trans-
verse bar (fig. 1036). On both the anterior and the posterior wall there is in the
median line a well-marked longitudinal ridge, the columna rugarum, which is
especially distinct in the lower part of the anterior wall, where it lies immediately
beneath the urethra and forms what is known as the urethral carina. From both
columnse other ridges pass laterally and upward on either side, forming the
rugw vaginales. Both these and the columnee diminish in distinctness with ad-
vance in age and with successive parturitions. Toward its lower end the vagina
traverses the urogenital trigone, being much less dilatable in this region than
elsewhere, and it opens below into the vestibule of the external genitalia. Its
orifice is partially closed by a fold of connective tissue, rich in blood-vessels, and
lined on both surfaces by mucous membrane. This membrane, known as the
Fig. 1036. — Horizontal Section of Vagina and adjacent Structures. (After Henle.)
hymen, has usually a somewhat semilunar form, surrounding the posterior border
of the orifice, but it may take the form of a circular curtain pierced by one or several
apertures.
It varies greatly in strength and development and although it is nearly always ruptured
by the first act of sexual congress, it may remain unbroken until parturition. Rarely it takes
the form of a complete imperforate curtain and may necessitate a surgical operation at the
commencement of the menstrual periods. After rupture the remains of the hymen persist as
small lobed or wart-like structures, the carunculoe hymenales, around the vaginal orifice.
Relations. — The uppermost part of the posterior wall of the vagina is in
relation with the peritoneum forming the floor of the recto-uterine pouch (of
Douglas), but elsewhere the canal is entirely below the floor of the peritoneal
cavity. Posteriorly it rests almost directly upon the rectum (flg. 1036), and the
contents of that viscus may be readily felt through its walls. Anteriorly it is in
intimate relation with the urethra and the posterior wall of the bladder (figs.
1034, 1036), while laterally it is crossed obliquely in its upper third by the ureters
as they pass to the base of the bladder, and in its lower two-thirds by the edges of
the anterior portion of the levatores ani. The duct of Gartner, the remains of the
lower portion of the Wolffian duct, may occasionally be found at the side of the
1276
UROGENITAL SYSTEM
upper half of the vagina as a minute tube or fibrous cord. The external orifice
is surrounded by the fibres of the bulbo-cavernosus muscle, which may be re-
garded as forming a sphincter {s-phinder vagince) .
Structure. — The wall of the vagina is formed mainly of non-striped muscle tissue, whose
fibres are indistinctly arranged in two layers, an outer longitudinal and a less distinct inner
circular one. Above, this tissue is continuous with that of the cervix uteri, as is also the mucous
membrane which lines the lumen. This differs from that of the cervix in having a stratified
squamous epithelium and in being destitute of glands.
Vessels and nerves. — The arteries of the upper part of the vagina are derived from the
vaginal branch of the uterine; its middle portion is supplied by a vaginal branch from the
inferior vesical and its lower part by the middle hssmorrhoidal and internal pudendal. The
veins form a rich plexus on the surface and drain into the hypogastric vein. The lymphalics
are very numerous and drain for the most part to the hypogastric and lateral sacral nodes; some
of those from the lower portion of the canal joining with those from the external genitalia to pass
to the inguinal nodes. The nerves passing to the vagina are derived from the utero-vaginal and
vesical plexuses.
5. The Female External Genitalia and Urethra
The female external genitalia [pudendum muliebre] (vulva) present an elon-
gated depression, occupying the entire perineal region and bounded laterally by
Fig. 1037. — The External Genitals op the Female.
Corpus clitoridis
Labium majus
Labium minus
Fossa navicularis
— ~ Frenulum labiorum pudendi
Posterior commissure
two folds of integument, the labia majora (fig. 1037). These anteriorly are
continued into the mojis pubis, an eminence of the integument over the symphysis
pubis due to a development of adipose tissue. The medial surfaces of the two
labia are normally iii contact, the fissure between them being termed the rinia
pudendi, and where they meet anteriorly and posteriorly they form the anterior
and posterior commissures [commissura labiorum anterior et posterior]. Just
anterior to the latter is an inconstant transverse fold, the frenuhim labiorum
pudendi ("fourchette") (fig. 1037). The mons and the outer sm-faces of the
labia are covered by short crisp hairs, but tlie medial surfaces of the labia are
smooth, possessing only rudimentary hairs, but beset with large sebaceous and
sudoriparous glands. The interior of the labia is occupied by a mass of fat tissue
in which the distal extremity of the round ligament of the uterus breaks up.
FEMALE EXTERNAL GENITALIA
1277
Within the depression bounded by the labia majora is a second pair of integu-
mental folds, the labia yninora (fig, 1037), which difTer from the labia majora in
being destitute of hairs and fat. They are usually concealed by the labia majora,
but are sometimes largely developed and may then project through tlie rima
pudendi, assuming a dried and pigmented appearance.
The labia minora divide and unite anteriorly over the distal extremity of the clitoris, form-
ing the prcepuiiuni cliioridis in front of the clitoris, and the frenulum diloridis behind it. Pos-
terior to this they diverge and reach their greatest height, gradually diminishing as they pass
backward to terminate in a slight, inconstant, transverse fold, the frenulum labiorum pudendi,
situated just anterior to the posterior commissure of the labia majora. Anterior to the frenu-
lum is the fossa navicularis of the vestibule.
The vestibule. — The space between the two labia minora is termed the
vestibule, and into its most anterior portion there projects the extremity of an
erectile organ, the clitoris (fig. 1037), which is comparable to the penis of the male.
It is, however, relatively small and is not perforated by the urethra, which lies
below it. It is composed of two masses of erectile tissue, the corpora cavernosa
clitoridis, which differ from the corresponding structures of the penis only in size.
They are attached posteriorl3^ to the rami of the pubis by the cr^ira clitoridis
(fig. 1038), and as they pass forward they converge and meet together to form the
body of the organ, which, beneath the symphysis pubis, bends sharply upon itself
Fig. 1038. — Diagrammatic Repkesentation of the Pehin^al Structures in the Female.
Glans clitoridis
Pars intermedialls
Mucous membrane of
vestibule
Urethral orifice
Ischio-pubic arch
Bulbo-cave
covering bulb'
vestibuU
Inferior layer of uro
genital trigone
Bulbus vestibuli
Greater vestibular
(Bartholin's) gland
External sphincter <
and passes posteriorly beneath the anterior commissure of the labia majora.
Distally the corpora cavernosa abut upon another mass of erectile tissue, which
fits hke a cap over their extremities; it is formed by an anterior prolongation of the
bulbi vestibuli and is termed the glans clitoridis, being comparable to the glans
penis, from which it differs only in not being perforated by the urethra.
A short distance posterior to the glans chtoridis is the opening of the urethra
[orificium urethrse externum], situated upon the summit of a slight papilla-like
elevation. Lateral to this orifice are sometimes found the openings, one on
either side, of two elongated slender ducts, the 'paraurethral ducts (ducts of Skene).
Still more posteriorly is the external orifice of the vagina [orificium vaginae],
partially closed in the virgin bj^ the hymen. Lateral to this, in the angles between
the hymen and the labium minus on either side, is the opening of the greater
vestibular gland, while the lesser glands open at various points on the floor of the
vestibule, sometimes at the bottom of more or less distinct depressions.
Beneath the floor of the vestibule and resting upon the superficial layer of the
urogenital trigone are two oval masses of erectile tissue, the hidbi vestibuli (fig.
1038), homologous with the corpus cavernosum urethriE of the male. They con-
sist principally of a dense network of anastomosing blood-vessels, enclosed within
1278 UROGENITAL SYSTEM
a thin investment of connective tissue. From the main mass of each bulbus a
slender prolongation, the pars intermedia, extends anteriorly past the side of the
urethra, to form the glans clitoridis.
The greater vestibular glands [gl. vestibularis major (Bartholini)] or glands of
Bartholin (fig. 1038) represent the bulbo-urethral glands of the male. They are
two small, compound tubular glands, situated one on either side immediately
posterior to the bulbi vestibuli.
The single duct of each gland opens on the floor of the vestibule in the angle between the
hymen and the orifice of the vagina and a httle posterior to the mid-transverse line of the latter.
Numerous small tubular glands occur in the integument forming the floor of the vestibule;
they are termed the lesser vestibular glands and are especially developed in the interval between
the urethral and vaginal orifices.
The muscles of the female external genitalia (fig. 1038) correspond to the
perineal muscles of the male (see Section IV). There are two transverse perineal
muscles, which have the same relations as in the male, and two ischio-cavernosi,
which are related to the crura clitoridis just as those of the male are to the crura
penis. The bulbo-cavernosi, however, present somewhat different relations, each
being band-like in form, arising from the central point of the perineum and ex-
tending forward past the orifice of the vagina, over the greater vestibular gland
and the bulbus, to form with its fellow of the other side a tendinous investment of
the body of the clitoris. The two muscles act as a sphincter to the vagina and
are sometimes termed the sphincter vagince.
The urethra. — The urethra of the female [urethra muKebris] (figs. 1034, 1036)
corresponds only to the prostatic and membranous portions of the male and is a
relatively short canal, measuring from 3.0 to 4.0 cm. in length. At its origin from
the bladder it lies about opposite the middle of the symphysis pubis and thence
extends downward and slightly forward to open into the vestibule between the
glans clitoridis and the orifice of the vagina. Its posterior wall is closely united
with the anterior wall of the vagina, especially in the lower part of its course where
it forms the urethral carina of the vaginal wall; laterally and anteriorly it is sur-
rounded by the pudendal plexus of veins.
Structure. — Its walls are very distensible, and are lined by a mucous membrane with
numerous longitudinal folds, one of which on the posterior side is more prominent and is
termed the crista urethralis. The mucosa contains numerous small glands [gl. urethrales],
a group of which on each side is drained by the inconstant ductus paraurethrahs. External
to the loose submucosa is a sheet of smooth muscle, whose fibres are arranged in an outer
circular and an inner longitudinal layer, a rich plexus of veins lying between the two and
giving the entire sheet a somewhat spongy appearance. The circular fibres are especially
developed at the vesical end of the canal, forming there a strong sphincter, and striped muscle
fibres, derived from the bulbo-cavernosus, form a sphincter around its vestibular orifice. The
female urethra differs from that of the male in not being enclosed within a prostate gland; but
what are probably rudiments of this structure are to be found in the groups of urethral glands
drained by the paraurethral ducts.
Vessels and nerves. — The arteries supplying the external female genitalia are the internal
and external pudendals, and the veins terminate in corresponding trunks. The lymphatics,
which are very richly developed, drain for the most part to the inguinal nodes; those from the
urethra pass to the iliac nodes. The nerves are partly sympathetic and partly spinal; the former
are derived from the hypogastric plexus, the latter principally from the pudendal, the anterior
portions of the labia majora being supplied by the iUo-inguinal and the external spermatic
branch of the genito-femoral.
DEVELOPMENT OF THE REPRODUCTIVE ORGANS
It has already been pointed out (p. 1267) that during development a transitory excretory
organ, the mesonephros or WolfEan body, reaches a high degree of development, and its duct,
the Wolffian duct, opens into a cloaca or common outlet for the intestinal and urinary passages.
The mesonephros forms a strong projection from the posterior wall of the abdomen into the
body cavity, and on the medial surface of the peritoneum which covers it a thickening appears
which is termed the genital ridge. The upper part of this ridge becomes the ovary or testis,
as the case may be, while the remainder of it becomes the ovarian and round ligaments in the
female and the gubernaculum testis in the male.
As the ovary or testis develops the tubules of the upper part of the Wolffian body enter
into relation with it, forming, indeed, in the case of the testis, a direct union with the semin-
ferous tubules. The Wolffian body then becomes divisible into a reproductive and an excretory
portion, and, when the metanephros or permanent kidney develops, the latter portion degene-
rates, leaving only a few rudiments, such as the paroophoron in the female (p. 1269) and the vas
aberrans and paradidymis (p. 1257) in the male. The reproductive portion also becomes much
reduced in the female, persisting as the tubules of the epoophoron (p. 1269), but in the male it
DEVELOPMENT OF THE REPRODUCTIVE ORGANS
1279
forms the lobules of the epididymis and serves to transmit the spermatozoa to the Wolffian
duct.
In addition to the Wolffian duct, a second duct, the Miillerian, occurs in connection with
the genito-urinary apparatus, and, like the Wolffian duct, it opens below into the cloaca. The
history of the two ducts is very different in the two sexes. In the male the Wolffian duct
persists to form the vas deferens, of which the seminal vesicle is an outgrowth and the ejaculatory
duct the continuation, while the MilUerian duct degenerates, its lower end persisting as the
prostatic utriculus and its upper end as the appendix of the epididymis. In the female, on
the contrary, it is the Miillerian duct which persists, its lower portion fusing with the duct of
the opposite side to form the vagina and uterus, while its upper portion forms the tuba
uterina. Inhibition of the fusion of the lower ends of the two Miillerian ducts gives rise to the
bihorned or divided uteri, or the bilocular uteri and vaginse which occasionally occur. The
Wolffian duct in the female almost completely disappears, persisting only as the longitudinal
tube of the epoophoron and as the rudimentary canal of Gartner (p. 1275) . With the degenera-
tion of the mesonephros the peritoneum which covered it becomes a thin fold, having in its
free edge the Miillerian duct and, on the fusion of the lower ends of the ducts, the two folds also
fuse and so give rise to the broad hgament.
Fig. 1039. — Development of the Reproductive Organs.
Epoophoron Wolffian body Epididymis
SinuB
pocu-
laris
INDIFFERENT
The developmental relations of the male and female organs may be seen from figure 1039
and also from the following table: —
Female
Ovary
f Ovarian ligament
, Round ligament
Epoophoron
Paroophoron
Longitudinal tubule of epoophoron
Canal of Gartner
Uterine (Fallopian) tube
Uterus
Vagina
Genital ridge
Wolffian body
Wolffian duct
Miillerian duct
Testis
Gubernaculum testis
Head of epididymis
-j Paradidymis 1
I Vas aberrans /
j Body and tail of epididymis
i Ductus deferens
! Ejaculatory duct
f Appendix of epididymis (?)
Prostatic utriculus
The development of the external organs of generation in the two sexes presents a similar
differentiation from a common condition. The division of the cloaca to form a urogenital
sinus and the terminal part of the rectum has already been noted (p. 1253). In the floor of the
sinus, to the sides of and above the urethral orifice, erectile tissue develops, forming a genital
tubercle. An outpouching of that portion of the anterior abdominal wall to which the round
ligament of the uterus or the gubernaculum was attached occurs to form the genital swellings.
1280 UROGENITAL SYSTEM
lying one on either side of the sinua, and medial to these a pair of folds develop at the borders
of the sinus, enclosing the genital tubercle above and forming the genital folds.
This condition practically represents the arrangement which persists to adult life in the
female. The genital tubercle becomes the clitoris, the genital swellings the labia raajora, the
genital folds the labia minora, and the urogenital sinus, into which the urethra and Miillerian
ducts (vagina) open, is the vestibule. In the male tlie development proceeds farther. The
genital tubercle elongates to form the penis, and the free edges of the genital folds meet together
and fuse, closing in the urogenital sinus and transforming it into the cavernous portion of the
urethra, thus bringing it about that the male urethra subserves both reproductive and urinary
functions. The genital swellings also meet and fuse together below the root of the penis, form-
ing the scrotum.
The homologies of the parts in the two sexes may be seen from the following table: —
Male Female
Urogenital sinus Cavernous portion of urethra Vestibule
Genital tubercle Penis Chtoris
Genital folds Integument and prepuce of penis Prepuce of clitoris and labia minora
Genital swellings Scrotum Labia majora
Inhibition of the development of the parts in the male or their over-development in the
female will produce a condition resembling superficially the normal condition of the opposite
sex, and constituting what is termed pseudo-hermaproditism; or a failure of the genital ridges
to fuse may result in what is known as hypospadias, the cavernous portion of the urethra being
merely a groove in the under surface of the otherwise normal penis.
References for the Urogenital System. A. Urinary tract. {General, incl.
literature to 1900) Disse, in von Bardeleben's Handbuch; {Renal blood-vessels)
Brodel, Proc. Ass'n Amer. Anatomists, 1901; {Renal tubules) Huber, Amer.
Jour. Anat., vol. 4; Peter, Die Nierenkanalchen, etc., Jena, 1909; {Topog-
raphy of female ureter) Tandler u. Halban, Monatschr. Geburtsh. u. Gynak.,
Bd. 15. B. Male reproductive tract. {General, incl. literature to 1903) Eberth,
in von Bardeleben's Handbuch; {Histology and development) von Lichtenberg,
Anat. Hefte, Bd. 31; Hill, Amer. Jour. Anat., vol. 9; {Prostate) Bruhns
{lymphatics) Arch. f. Anat. u. Entw., 1904; Ferguson {Stroma) Anat. Rec, vol.
5; Thompson (topography) Jour. Anat. and Physiol., vol. 47; {External
genitals) Forster, Zeitschr. f. Morph. u. Anthrop., Bd. 6. C. Female repro-
ductive tract. {General, incl. literature to 1896) Nagel, in von Bardeleben's
Handbuch; Waldeyer, Das Becken, Bonn, 1899; {Lymphatics) Bruhns, Arch,
f. Anat. u. Entw., 1898; Polano {ovary) Monatschr. Geburtsh. u. Gynak.,
Bd. 17; {Nerves) Roith, Arch. f. Gynak., Bd. 81; {Histology, ovary) von
Winiwarter, Anat. Anz., Bd. 33; {Develop?/ient, uterus) Hegar, Beitr. z. Geburtsh.
u. Gynak., Bd. 13; Stratz, Zeitschr. Geburtsh. u. Gynak., Bd. 72; {Lig.
eres) Sellheim, Beitr. z. Geburtsh. u. Gynak., Bd. 4, 1901.
SECTION XII
THE SKIN, MAMMAEY GLANDS
AND DUCTLESS GLANDS
Rewritten for the Fifth Edition
By ABRAM T. KERR, B.S., M.D.
PBOPESSOK OP ANATOMY IN THE
UNIVERSITT MEDICAL' COLLEGE
THE SKIN
THE covering which envelops the whole external surface of the body is
known as the common integument [integumentum commune]. This con-
sists of the cutis or skin proper and of appendages, the hair, nails, and skin
glands. The cutis is composed of a superficial epithelial layer, the epidermis,
derived from the ectoderm, and a deep connective tissue layer developed from the
mesoderm and divided into a superficial part, the corium, and a deeper part the
tela subcutanea (figs. 1040, 1041). The subcutaneous tela is not usually con-
sidered as a part of the skin in a restricted sense, but as a superficial fascia, which
name is often applied to it.
Fig. 1040. — Magnified Section of the Thickened Skin of the Palm op the Hand. X 6
Corpus papillare , l!^,_^
Retinaculum
Tela Subcutanea
The skin forms an encasement for the entire body broken only in the regions where it merges
with the mucous membranes. It serves not only as a direct physical protection to the under-
lying structures, but also, through its function as an organ of touch and of general sensibility,
it indirectly protects the body by the action of the special end organs and peripheral termina-
tions of the sensory nerves which thus bring the body into relations with its surroundings.
Through the radiation and conduction of heat to and from the blood circulating in it, through
the amount of secretion of its glands and the evaporation from its surface, the skin forms the
principal organ for the regulation of the bodily heat. By means of the action of its sweat and
sebaceous glands it possesses an important secretory function. It has also a minor role as an
organ of respiration and absorption.
The surface area of the skin corresponds approximately to the surface of the
body and naturally varies with the size of the individual. It has been variously
estimated at from 10,500 to 18,700 sq. cm. for a medium-sized adult male.
81 1281
1282 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
The aperturae cutis are holes through the skm where it joins with the mucous membrane,
usually without sharp line of demarcation, at the nares, the rima oris, the anus, and the external
urethra in the male, and at the vaginal vestibule in the female.
Owing to the fact that the skin extends beyond the surface at the aperaturse cutis, and
covers the major and minor pudendal labia, and the prepuce and extends into the external
acoustic canal, the surface area is slightly greater than the surface of the body.
The thickness of the skin varies in different regions of the body and also in
different individuals. The mean thickness is between 1 and 2 mm., the extremes
ranging from .3 to 4.0 mm. or more. This is exclusive of the subcutaneous tela.
The thickness appears to be in direct proportion to the amount of friction and
pressure to which the part is subjected. Thus it is thicker on the dorsal than on
the ventral surface of the trunk and neck, and on the flexor than on the extensor
surfaces of the hands and feet. Otherwise it is thicker upon the extensor than on
the flexor surface of the extremities.
1041. — ^Vertical Section prom the Sole of the Foot of an Adult.
Str.lir.)
X 25. (Lewis and
Duct of a sweat gland —
stratum corneum
,^ Stratum lucidum
Stratum granulosura
stratum germinativum
Coil of a sweat gland -
[ Corpus
I papillare
■ Tela subcutanea
Fat tissue ■ — fe^rj^ '^
^^^^fe.b:^i:.
The thickness of the skin is least upon the tympanum and it is also thin upon the eyehds
and penis. It obtains a thickness of 3 mm. on the volar surface of hands and plantar surface of
the feet and gains a thicliness of about 4 mm. on the cephalic part of the back and dorsal surface
of the neck. It is thinner in the aged than in the adult, thicker in men than in women, and
in the same sex is subject to much individual variation depending upon exercise, occupation,
etc. The vascularity of the skin also influences its thickness.
Over most of the surface of the body the skin is elastic and so loosely attached
that it may be stretched to a greater or less extent. The elasticity varies in
different individuals. Closely associated with the elasticity is the manner of
attachment of the skin to underlying structures. This varies somewhat according
to the tissues which are covered but the great motility is due in the main to the
very oblique arrangement of the connective tissue and elastic fibres of the deeper
layers of the skin; the fixity to the more vertical arrangement of these fibres. An
understanding of the looseness and elasticity of the skan is of much practical im-
portance to the surgeon in certain operations.
When the [traction is slow as over a slow-growing tumour, or over the abdomen and breasts in
pregnancy, the skin may be stretched to a very considerable degree. In these cases there are
often produced short parallel reddish streaks which when the stretching is reheved are re-
THE SKIN
1283
placed by whitish, silvery lines, striae or lineae albicantes, due to atrophy of the tissues. In
spite of this the skin usually retains enough elasticity to contract gradually to its former
extent as it does immediately after moderate stretching.
In most parts of the body the attachment is loose so that the skin is movable and may be
pinched up into folds. In some places the attachment of the skin is firm and there is no slip-
ping of the skin over underlying parts, as on the glans penis. In some other parts the motion
is very limited as in the scalp and the volar surface of the hands and the plantar surface of the
feet.
• Fig. 1042. — Finger Print (Natural Size) Showing Crist* and Sulci.
The colour of the skin varies greatly. It may be white, yellow, black, red, or
any of the shades of these colours, and, according to the colour, the races of man-
Idnd have been roughly divided. The colouration is due partly to pigment and
partly to the blood within the cutaneous vessels. The amount of pigment varies
with race, age, sex, and with exposure to the sun and air. In the white races the
skin of the child is a pinkish white, tending to become dead white in the adult
and yellowish in the aged, and it is normally more pigmented in certain regions,
such as the axillary region, the scrotum, the vulva, and the mammary areola.
Fig. 1043. — Diagram Showing the Arrangement of the Principal Crist.® of the Thumb
The colour of the white, yellow, red, and black races is not produced by the climate, as we
find different races existing under the same climatic conditions and the same coloured race under
different conditions of climate. Each race presents several variations of colour; for example,
in the white race we distinguish a blonde, a brimette, and an intermediate tj'pe. Anthropolo-
gists distinguish twenty to thirty different shades of colour in the skin. In blondes of the white
race under the action of strong sun light the skin passes from a rose white to a brick red or
becomes pigmented in spots, freckles. In the first case the pigment in the skin is not increased
to any great extent but the skin is affected by a superficial inflammation, erythema, associated
with exfoliation and often with the formation of blisters. In brunettes of the white race the sun
burns the skin a dark yellowish or reddish brown, the degree of pigmentation here being increased
and is spoken of as tan. The colouration is onlj' temporary and diminishes on withdrawal from
exposure. The sun darkens the skin in the yellow races also. In the newborn of the black
races the skin is of a reddish colour, since the pigment although developed to some extent is at
birth obscured by overlying opaque cells which later become transparent. The newborn of the
yellow races are also hghter than their parents. In white races the shade of the skin is clearer on
the ventral surface of the trimk and on the flexor surface of the extremities. In the black races
the volar surface of the hands and the plantar surface of the feet as well as the sides of the digits
are less deeply pigmented than the rest of the body. The colour of the skin is greatly influenced
by the blood in its deeper layers which during life gives it a more or less distinctly reddish tinge,
varying directly with the vascularity and inversely with the thickness of the epidermis. Absence
i
1284 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
of the normal pigment is a not uncommon congenital anomaly producing albinism or leuko-
derma. It may affect all the skin structures or it may be partial.
The skin presents certain elevations and depressions due to the fact that it
follows more or less closely the contour of the underlying structures, but in addi-
tion to this it possesses certain elevations and depressions peculiarly its own.
They are found on the skin in various parts of the body. Some are permanent,
others only temporary. Large permanent folds which include all the layers of
the skin are seen, as the prepuce of the penis and the pudendal labia. The most
marked depression is the umbilical fovea. Other conspicuous folds and furrows
are seen in the neighbourhood of the lips and eyelids. Certain other less permanent
folds and furrows are produced by the action of the joints, joint-furrows, and of
the muscles of expression of the skin,*'wrinkles."
Fig. 1044.-
-From a Photograph op the Superficial Fubhows on the Back of the Hand.
(X 1.)
Other minute folds and furrows which affect only the epidermis and the super-
ficial layer of the corium are seen in various places. These are represented by the
numerous fine superficial creases, unassociated with elevations, forming rhom-
boidal and triangular figures over almost the whole of the surface of the skin
(figs. 1042, 1043). They are especially numerous on the dorsal surface of the
hands (fig. 1044). The fine curvilinear ridges [cristse cutis] with intervening
furrows [sulci cutis] arranged in parallel lines in groups on the flexor surface of
the hands and feet are also of this type. They form patterns characteristic for
each individual and permanent throughout life.
Fig. 1045. — From a Photograph op the Skin Ridges and Papillae op the Palm op the
Hand. Epithelium Completely Removed Above; Partly Removed Below. (X 5.)
--^— Corpus papillare corii
";^ Sulci cutis
Among the projections are the large permanent folds of skin such as the labia pudendi, the
preputium penis, the frenula preputii, clitoridis, and labiorum pudendi, and less marked ridges
as the median raphe of the perineum, scrotum and penis, and the tuberculum labii superioris.
Of a somewhat different sort are the touch pads (toruli tactiles] of the hands and feet. Among
the larger depressions in addition to the umbilical fovea, is the coccygeal foveola, and a consider-
able num))er of well-marked permanent furrows found in various places, such as the nasolabial
and mentolabial sulci, the philtrum labii superioris, the infraorbital sulcus, and the infra- and
supraorbitial palpebral sulci. There are numerous articular furrows on both the flexor and
extensor surfaces produced by the action of the joints, and associated with intervening folds
of skin, particularly on the dorsal surface. They are especially noticeable on the hands. Varia-
tions of the palmar joint sulci are due to variations in opposition of the thumb and the use of
the fingers and the relative arrangement of the thumb and fingers and joints. They are of
THE EPIDERMIS 1285
especial medical and surgical importance as indicating topographically the position of the joints,
their relation to which has been recently made clearer by means of the X-ray.
The folds and furrows brought about through the action of the skin muscles run at right
angles to the muscle fibres and are more or less transitory at first but become more permanent
through repeated or long-continued action. They are represented by the wrinkles of the fore-
head, the lines of expression of the face, the transverse wrinkles of the scrotum and the radiating
folds around the anus. The more superficial cristae cutis and sulci cutis are arranged in groups
within and around the touch pads, on the volar surface of the hands and the plantar surface of
the feet (figs. 1042, 1043). The crista; of each group are parallel. They correspond to the rows
of papillfe of the corium.
Because the patterns of the crista; and sulci are characteristic for the individual, and per-
manent from youth to old age, they have been classified in a number of types and are important
medioolegally as a means of identification. The various systems of classification are based
upon the arrangement over the distal phalanges of the fingers and make use of (1) a transverse
ridge which is parallel with the articular plicae (2) a curved ridge with its convexity distally
and more or less closely meeting the first, medially and laterally, and (3) the curved and concen-
tric ridges between these two (fig. 1043).
There are also a great number of minute depressions which mark the points where the hairs
pierce the surface and where the glands open. These are popularly known as pores. Under
Fig. 1046. — PAPii.i,.ffi: of the Cohium after Maceration. From Retouched Photograph.
Epithelium Removed by Maceration. ( X 25.)
^>-Papinee corii
the influence of cold and emotion the hair muscles contract and cause a slight elevation of the
skin at the point where the hair emerges. This roughened appearance of the skin is popularly
known as "goose-flesh."
A complex wrinkling of the skin appears in old age, or in the course of exhausting diseases/as
a result of loss of elasticity and from absorption of the cutaneous and subcutaneous fat. Rounded
depressions called dimples are produced by the attachment of muscle-fibres to the deep surface
of the skin, as on the chin and cheek, and are made more evident by the contraction of these
fibres. Others are produced by the attachment of the skin by fibrous bands to bony eminences,
as the elbow, shoulder, vertebrse, and posterior iliac spines. They are best seen when the sub-
cutaneous adipose tissue is well developed.
The cutis is made up of two layers which are structurally and developmentally
markedly different. The superficial ectodermic portion, epidermis, is made up
almost entirely of closely packed epithelial cells, the deeper mesodermic part,
corium, is formed largely of connective-tissue fibres.
The epidermis (cuticle, scarf-skin) is a cellular non-vascular membrane which
forms the whole of the superficial layer of the skin and at the great openings
through the skin, as the mouth and anus, blends gradually with the mucous mem-
brane. It represents from one-tenth to over half the thickness of the skin, in
different parts of the body, the usual thickness being .05 to .2 mm., ranging from
.03 mm, to nearly 3 mm. The thickness varies also in different individuals.
Its deep surface is molded exactly to the underlying corium but its superficial
surface fails to reproduce all of the irregularities of the latter. In spite of this
close association, blood-vessels never enter the epidermis.
Structure of the epidermis. — The cells of the epidermis are packed together in many irregu-
lar layers. The deepest cells are soft protoplasmic, somewhat elongated, perpendicular to
i
1286 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
the surface of the corium and joined together by fine fibrils; more superficially they become
round or polyhedral. These cells together with several more superficial layers form a stratum
from which the other cells of the epidermis are developed and which therefore are laiown as the
stratum germinativum (Malpighii). The cells in the superficial part of this stratum, in some
situations, have a granular appearance forming a layer which is called the stratum granulosum.
Superficial to this there is, also only in some places, a layer in which the cells are somewhat
indistinct and transparent, and therefore known as the stratum lucidum. This is a transition
between the softer and more opaque stratum germinativum and the firmer and more transparent
superficial layer formed of large, flattened, dry, horny cells, known as stratum corneum.
In general the stratum germinativum is thicker than the stratum corneum. In certain
parts as the face, the back, the back of the hands and feet, the two layers are equal in thicloiess.
In other regions, as in the volar surface of the hands and plantar surface of the feet, the stratum
corneum is much thicker than the stratum germinativum varying from two to three or even five
times as thick. This increased thickness of the stratum corneum is not due to pressure alone
as it is well marked in the foetus, but it is not improbable that pressure may stimulate the
further growth of the cells.
Where the papilte of the corium are arranged in rows as on the volar surface of the hands
and the plantar surface of the feet, the epidermis is molded to these so as to appear as ridges
on the surface, already described as cristse. In most other places the irregularities of the papillae
of the corium do not show on the sm-face. At short and regular intervals on the cristse are
notches and transverse furrows which mark the openings of the sweat glands.
The separation of the epidermis from the corium by the accumulation of serous fluid between
the layers is known as a bUster. Sometimes it is only the separation of the superficial layers
from the deeper layers of the epidermis.
The skin is regenerated after a blister or a wound by growth of the cells of the stratum ger-
minativum. It is probable that cells of the superficial layers take no part in this. Therefore in
skin grafting the surgeon in order to transplant the cells of the stratum germinativum usually
includes all the layers of the epidermis and the extreme tips of the papillae of the corium as shown
by the minute bleeding points left on the surface from which the graft has been cut.
The pigment which gives the main colour to the skin is caused by the accumulation of pig-
ment granules, melanin, in the deepest cells of the stratum germinativum. It does not occur
until after the sixth month of foetal life and develops chiefly after birth. The blackness of the
skin of the negro depends almost entirely upon this pigment. Pigment granules are also found
to a less extent in more superficial cells and sometimes in the corium.
Development of the epidermis. — The epidermis is derived from the ectoderm, in early
embryos appearing as a double stratum of cells, the superficial layer of which is known as the
epitrichium or periderm, the deep layer becomes the stratum germinativum. By multiplica-
tion of the deep cells a number of layers are produced and the more superficial cells tend to
assume the adult characteristics. At about the sixth month of foetal hfe the epitrichial layer
finally disappears. The surface layers are cast off and mixing with the secretion of the cutaneous
glands form a yellowish layer over the surface of the skin of the foetus, the vernix caseosa.
Growth continues throughout life. New cells are formed in the deeper layers pushing the
older cells toward the surface. The character of the cells changes as they approach the surface,
the change being quite abrupt at the level of the stratum lucidum. As the form of the cells
changes, chemical and physical alterations of their contents occur. In most places the super-
ficial cells are represented by thin scales but in the palms and soles the cells are somewhat swol-
len. The superficial cells are being constantly thrown off and replaced by deeper ones.
The corium (cutis, cutis vera, derma) is a fibrous vascular sh.eath composed
of interwoven bundles of connective-tissue fibres intermixed with elastic fibres,
connective-tissue cells, fat, and scattered unstriped muscle-fibres. It is traversed
by rich plexuses of blood-vessels, lymph-vessels, and nerves, and encloses hair-
bulbs and sebaceous and sudoriferous glands. It varies in thickness from .3
mm. to 3.0 mm. or more, usually ranging from .5 to 1.5 mm. It is to this layer
that the strength and elasticity of the skin are due and it is also only this layer
which when properly cured we know as leather.
The superficial layer of the corium is of finer, closer texture, free from fat, and
forms a multitude of eminences called papillae corii (figs. 1040, 1045, 1046) which
project into corresponding depressions on the deep surface of the epidermis.
For this reason this part of the corium although but indistinctly separated from
the deeper layer is called the corpus papillare.
Some of the papillae contain vessels, others nerves, hence they are known as vascular or
tactile papillse. They are very closely set, varying considerably in number in different parts of
the body from .36 to 130 to a square millimetre, and it has been estimated that there are about
150 million papilloe on. the whole surface. They also vary greatly in size not only in different
regions but in the same region, being from .03 to .2 mm. or more in height.
The deeper layer of the corium, the tunica propria (stratum reticulare), is
composed of coarser and less compact bands of fibrous tissue intermingled with
small fat lobules. The fibrous and elastic tissue is arranged for the most part in
intercrossing bundles nearly parallel to the surface of the skin.
The bundles running in some directions are usually more strongly developed and more
numerous than those in others but the direction of the strongly developed bundles varies in
THE TELA SUBCUTANEA
1287
different parts of the body. In general those are best developed which have a direction parallel
with the usual lines of tension of the slcin, hence it results that wounds of the skin tend to gape
most at right angles to these lines. The bundles take a direction nearly at right angles to the
long axis of the hmbs, and on the trunk run obhquely, caudally, and laterally from the spine
(figs. 1047, 1048). On the scalp, forehead, chin, and epigastrium, equally strong bundles cross
in all directions, and a round wound, instead of being linear as elsewhere, appears as a ragged or
triangular hole. The arrangement of the connective-tissue bundles influences the arrangement
of the blood-vessels of the skin.
The tela subcutanea or superficial fascia is also a fibrous vascular layer which
passes as a gradual transition without definite line of demarcation from the deep
surface of the tunica propria of the corium to connect it with the underlying
structures.
Like the tunica propria it is composed of bundles of connective tissue containing elastic
fibres and fat, but the bundles are larger and more loosely arranged, and form more distinct
cormeotive-tissue septa, which divide the fat, when present, into smaller and larger lobules.
Where these connecting strands are especially large and well defined, they are known as re-
tinacula. Over almost the whole surface of the body the connective-tissue strands of the tela
Figs. 1047 and 1048. — Diagrams Showing the Arbangembnt op the Connective
Tissue Bundles of the Skin on the Anterior and Posterior Surfaces of the Body.
(After Langer.)
are arranged nearly parallel with the surface, and bind the skin so loosely to the parts beneath
that it may stretch and move freely over the deeper parts. In some situations the connective-
tissue bundles of the tela subcutanea run almost at right angles to the surface and bind the skin
firmly to the deep fascia, as in the flexor surface of the hands and feet and in the scalp and face.
The quantity of subcutaneous fat varies considerably in different parts of the
body. It is, for instance, entirely absent in the penis, scrotum, and eyeUds. When
it is abundant, the subcutaneous layer is known as the panniculus adiposus.
In some situations, as in the caudal portion of the abdomen and in the perineum, the
connective tissue is so arranged that the panniculus may be divided into layers, so that a
superficial and a deep layer of the superficial fascia may be recognised. The fat is well de-
veloped over the nates, volar surface of the hands and plantar surface of the feet, where it
serves as pads or cushions; in the scalp it appears as a single uniform lobulated layer between the
corium and the aponeurosis of the epicranial muscle; and on other parts of the surface it is some-
what unequally distributed and shows a tendency to accumulate in apparent disproportion in
some localities, as on the abdomen, over the symphysis pubis, about the mammse in females,
etc. Everywhere except on the scalp it may undergo rapid and visible increase or decrease
under the influence of change of nutrition.
1288 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
The amount of elastic tissue mixed with the white fibrous connective tissue of which the
corium and subcutaneous tela mainly consist varies in the different parts of the body. It is
especially abundant in the deeper layer of the tela over the caudal part of the ventral ab-
dominal wall where it forms almost a continuous sheet. Many elastic fibres also accompany the
blood-vessels and are mingled with the connective-tissue sheaths around the hairs, the sweat
glands, and their ducts.
The papillce corii are usually simple cones but some are bulbous at their ends and others
have duplicated apices. They may be perpendicular to the surface or oblique, in some places
overlapping. Those on the flexor surfaces of the hands and feet are best developed and are
arranged in rows so as to form long parallel curvilinear ridges, two of which are grouped together
and correspond to one crista on the surface of the epidermis (figs. 1045, 1046). When there are
no papillary ridges the papilte are irregularly scattered, shorter, and may disappear in places
or be replaced by ridges. The papilliE serve to give a greater surface area to the corium so as
to bring a greater number of blood-vessels and nerves into closer relation with the epidermis and
thus with the surface of the body. They are best developed where the epidermis is thickest.
Thus they are the largest on the flexor surface of the hands and feet and beneath the nails and
are smallest on the face, scrotum, and mammEe.
The skin, as removed in the dissecting room, usually includes the epidermis and more or
less of the corium and subcutaneous tela. The cut surface is formed of connective tissue which
has a shining bluish-white appearance with minute pits closely scattered over the surface.
These pits are usually more or less completely filled with small yellow fat lobules.
Skin muscles. — In the subcutaneous tela and the corium muscle fibres are
found in large and small groups. These are of two kinds, striated muscle and
unstriated muscle.
Subcutaneous planes of striated muscle are relatively scanty in man when compared with the
great panniculus carnosus of the lower mammalia. This is mainly represented by the platysma
in the neck which has both its origin and part of its insertion in the skin. Closely associated
with this are the muscles of expression of the face and the palmaris brevis muscle which have
one end terminating in the deep surface of the skin. The epicranial muscle is also considered by
some to belong to this group.
Unstriated muscle fibres are scattered through the corium collected into bundles in the
neighbourhood of the sebaceous glands and the hairs. They are described in connection with
these latter (p. 1293). In addition to these unstriated muscles are found in the scrotum as the
dartos, in the perineum, around the anus, and beneath the papilla and areola of the mammary
gland.
Burssa mucosae subcutanea. — In some situations where the integument is
exposed to repeated friction over subjacent bones or other hard structures its
movements are facilitated by the development of sac-like interspaces in the sub-
cutaneous tissue, the subcutaneous mucous bursse. They are similar to the more
deeply placed bursse which are found in relation with muscle tendons. Their
occurrence is quite variable. In some individuals they are numerous, in others
very few. They have a considerable practical importance from the fact that they
may become greatly swollen.
The most constant subcutaneous mucous bursae are the following:
Bursa anguli mandibulae; B. subcutanea prementalis, between the periosteum and soft parts
over the tip of the chin; B. subcutanea prominentise laryngese over the ventral prominence of
the thyreoid cartilage of the larynx (often found in the male; B. subcutanea acromialis, between
the acromion and the skin; B. subcutanea olecrani, beneath the skin on the dorsal surface of
the olecranon; B. subcutanea epicondyli humeri lateralis, found beneath the skin over the
lateral epioondyle of the humerus (occasional); B. subcutanea epicondyli humeri medialis,
between the skin and the medial epicondyle of the humerus (more frequent); B. subcutanea
metacarpophalangea dorsalis, between the sldn and the dorsal side of the metacarpophalangeal
joints (occasional, especially the fifth); B. subcutanea digitorum dorsalis, beneath the skin over
the proximal finger-joints; and rarely over the distal finger-joints; B. subcutanea trochanterica,
between the skin and the great trochanter of the femur; B. subcutanea praepatellaris, beneath
the skin covering the caudal half of the patella; B. subcutanea infrapatellaris, between the skin
and the cephahc end of the ligamentum patella;; B. subcutanea tuberositatis tibiae ventral to
the tibial tuberosity, covered by skin or by skin and crural fascia; B. subcutanea malleoli
lateralis, between the skin and the point of the lateral malleolus; B. subcutanea malleoli me-
dialis, between the skin and medial malleolus; B. subcutanea calcanea, in the sole of the foot
between the skin and the plantar surface of the calcaneum; B. subcutanea sacralis, beneath
the skin which covers the lumbodorsal fascia and the region between the sacrum and coccyx.
Blood-vessels of the skin. — Both the corium and the subcutaneous tela are very vascular,
but the size and number of vessels varies in different situations. Although the origin of the
cutaneous arteries from the deep arteries and the positions where the subcutaneous arteries
pierce the muscles vary greatly, the areas supplied by certain groups of arteries and the direc-
tion in which the arteries of the skin run show much regularity. Moreover the metameric
arrangement of the arteries in the skin is clearly seen, especially upon the trunk. We can recog-
nise two groups of skin arteries. One group is represented by a small number of rather large
branches which are distributed throughout or principally in the subcutaneous tela and corium,
as the inferior superficial epigastric artery, the arteries of the scalp, etc. These arteries tend to
NERVES OF THE SKIN
1289
disturb the metameric arrangement. In the other group the arteries are intrinsically for the
supply of other organs but give off small end twigs to the skin, e. g., the arteries to the superficial
muscles.
The arteries enter the corium from the subcutaneous tela, break up into smaller branches
anastomose freely and in the deepest layer of the corium form a network, the cutaneous rate
(subcutaneous plexus), rete arteriosum cutaneum, from which small branches are given off to
supply the fat and sweat glands and also to the papillary layer of the corium. Here another
network of arteries is formed, the subpapillary rete, rete arteriosum subpapillare. From the
subpapillary plexus, minute twigs pass to the papilla;, to the hair follicles, and to the sebaceous
and sudoriferous glands.
The cutaneous veins like the arteries may be divided into three groups: (1) small radicals
which accompany the corresponding arteries and go to make up veins whose main function is to
collect the blood from the muscles; (2) larger branches accompanying the arteries whose main
course is in the subcutaneous tela as the inferior superficial epigastric vein; (3) large veins which
run in the subcutaneous tela but have a course independent of the arteries such as those seen
through the slcin on the hands and arms. These large vessels will be found described in con-
nection with the general description of the veins (Section V).
Minute venules arise from the capillaries of the papilla, accompany the arteries and form
parallel with the surface of the skin a series of closely connected plexuses. Four such plexuses,
Fig. 1049. — Cutaneous Nerves of the Middle Finger and Lamellotts (Pacinian) Cor-
n s, MS ,ri(.iii T,.!,irs \ths)
Twig from n. digitalis
Volaris proprius
LamellousCPacinian'^
puscles with nerves
■ Interdigital fold
Cut edge of skin along
mid-line of dorsal sur-
face of finger
Mid-line of volar surface of finger
more distinct than the arterial, may be recognised in some situations. Of these retia venosa
one is situated just beneath the papilla;, and another at the junction of the corium and subcu-
taneous tela. They receive branches from the fat, hair folhcles, and glands, and empty into the
large veins of the sldn situated in the subcutaneous tissue.
Lymphatics of the skin. — The cutaneous lymphatic vessels are found in the skin of all parts
of the body but are more abundant in certain places. The lymph-vessels of the skin are
developmentally among the first lymph-vessels to appear. The larger vessels and glands of the
subcutaneous tela will be found described in connection with the general lymphatic system
Section VI). In the corium the lymphatics from the papillae form a subpapillary network
which opens into a subcutaneous plexus connected with the larger lymph-vessels of the subcu-
taneous tela. There are no lymph-vessels in the epidermis, but this is supposed to be nourished
by the lymph in the tissue spaces between the cells and these spaces connect indirectly with the
lymph-vessels.
The nerves. — The skin has one of the richest nerve supplies of the body. The nerves are in
greater proportion in those parts which are most sensitive. The various skin areas are supplied
by specific (segmental) nerves with much greater regularity than in the case of the arteries. The
nerves supplying adjoining areas overlap so that there is an intermediate space supphed by both.
The variations consist in an extension of one area and a corresponding contraction of an adjoin-
ing area. The distribution of the nerves in the skin shows, especially on the trunk and neck, a
marked metameric arrangement. The arrangement of these nerves in the subcutaneous tela
1290 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
and their areas of distribution will be found described in detail in the section on the Nervous
System.
With the exception of the nerves to the sudoriferous and sebaceous glands, the skin-muscles
and blood-vessels, all the cutaneous nerves are sensory. They have diverse modes of termina-
tion. Some end in the subcutaneous tela; others, the greater number, terminate in the corium;
still others extend to the epidermis.
Toward their termination the nerves branch and rebranch, and just beneath the surface they
form a great number of small twigs from which the terminal fibres arise. These may be divided
into two groups, those that end freely and those whose termination is surrounded by a capsule.
The free ends are slightly enlarged and terminate in the epidermis and in certain regions in the
corium. The encapsulated terminations form special end organs and are found in the corium as
the bulbous corpuscles (end-bulbs of Krause) [corpuscula bulboidea, Krauserii]; the tactile
corpuscles (corpuscles of Meissner or Wagner) [corpuscula tactus, MeissneriJ; and the genital
corpuscles [corpuscula nervorum genitalia[. In the subcutaneous tela the end-bulbs are seen as
the lamellous corpuscles (corpuscles of Vater: Pacinian corpuscles), [corpuscula lamellosa;
Vateri, Pacini[ shown in fig. 1049; the Golgi-Mazzoni corpuscles and the Rufflni corpuscles.
All the terminations except the lamellous corpuscles are microscopic, not exceeding 0.2 mm. in
length. The lamellous corpuscles, which are readily seen in reflecting the skin from the fingers
and toes, may be as much as 2 mm. long and half as thick (fig. 1049). The exact function of
each of the various endings is not known. They are undoubtedly sensory fibres except those to
the glands, muscles, and blood-vessels.
Development of the corium and subcutaneous tela. — The corium is developed from the
superficial part of the myotome or dermo-muscular plate of mesoderm. At first it is very largely
cellular but later fibres are produced. In the earlier stages the corium and tela subcutanea are not
distinguishable and only in the later embryonic period may the corium be separated into the
papillary stratum and the tunica propria.
THE APPENDAGES OF THE SKIN
The appendages of the skin include: (A) the hairs; (B) the nails; (C) the
cutaneous glands; and (D) the mammary glands.
A. THE HAIRS
The hairs [pili] are less developed in man than in any other primate. Where
well developed they in themselves serve as a protective organ and moreover
through their connection with the nervous system they become in a measure
organs of special sense. They are strong, flexible, somewhat elastic, and poor
conductors of heat. They cover the entire surface of the body with the following
exceptions: The flexor surfaces of the hands and feet; the dorsal bends and sides
of the fingers and toes; the dorsal surfaces of the distal phalanges of the fingers
and toes; the red borders of the lips; the glands and inner surface of the prepuce
of the penis and clitoris; the inner surface of the labia majora; the labia minora
and the papilla mammae.
The size and length of hairs varies greatly not only in different parts of the
body but also in different individuals and races. In certain situations the hairs
are especially long and large and are designated by special names.
Thus upon the scalp, capilli, in the axillary region, hirci, and after puberty upon the face in
the male, the beard, barba, and in the pubic region in both sexes, pubes. The pubic hairs extend
upon the external genital organs and upon the ventral abdominal wall toward the umbilicus.
All of the hairs of these regions are not long and large but short and finer hairs are mixed
with them in varying numbers. Strong, well-developed short hairs are found in connection with
the organs of sense forming the eyebrows, supercilia, the eyelashes, cilia, at the entrance to the
external acoustic meatus, tragi, and at the nares, vibrissse. Upon the extensor surfaces of the
extremities, upon the chest, and in other situations in some individuals, especially in adult
males, the hairs are also longer and stronger than upon the rest of the body, where they are, as a
rule, short, fine and downy. The first hairs appearing in the foetus are very fine, and are called
lanugo. The long hairs of the adult scalp may attain a length of ISO cm. or more; the short
hairs average from .5 to 1.3 cm. in length, while the lanugo does not exceed 1.4 cm.
Excess of long hairs, hypertrichosis, may involve the whole hairy surface of the body. It is
usually inherited and affects several individuals in the same family. Local areas of long hairs
also occur as over naevi and upon the sacrum. Local congestion due to inflammation, irritation,
or pressure may cause hypertrichosis. In women, hair upon the upper lip or other parts of the
face may be an inherited peculiarity or due to some abnormahty of the sexual organs. It is also
not uncommon after the menopause.
In diameter the hairs vary from .005 mm. for the finest lanugo to .203 mm.
for the coarsest hair of the beard ; but they usually taper toward the tip and also
are narrower toward the base. As a general rule, blonde hairs are the finest and
black hairs the coarsest.
THE HAIRS
1291
In colour the hairs may be either blonde, brown, black, red, or some gradation
of these colours. The colour varies with the race, and also with the individual,
and according to age. It is due to pigment in the cells of the hair but is also
influenced by the amount of air between the cells.
Greying and whitening of the hair is due not only to a decrease of pigment but also to an
increase in the amount of air between the cells. Sudden blanching of the hair is thought to be
due almost entirely to an increase in the quantity of this contained air. Whitening of the hair is
physiological in old age and not infrequent in younger persons. This may be an inherited pecul-
iarity or may follow mental overwork, nervous shock, or prolonged disease. Local blanching is
also seen as the result of disease.
The hair may be straight, waved, curled, or frizzled in varying degree. Here also there is
not only an individual but also a racial variation, as instanced in the curled or crinkled hair of
the African negro and the straight hair of the American Indian. The curliness is caused by the
form and the manner of implantation in the skin. Straight hairs are round or oval in transection
Fig.
1050. — Longitudinal Section of a Growing Hair of the Head.
Toldt's Atlas.)
(X30.) (From
Epidermal
coat of
follicle
Scapus pili (shaft)
Collum foUiculi pili-
Inner root sheath
Outer root sheath '
Radix pili (root i
■ Substantia corticalis
— " Substantia medullaris
Sebaceous gland
f
\ Arrector pili muscle
Outer fibrous layer —
Dermal I , ^. ,
coat of 1 I°°<=' fi''""^ '^y" ~~ •
follicle
I Hyaline layer ;
Bulbus pil
Fundus folliculi pil
and curled hairs are more flattened. The root of curled hair has been observed in certain
instances, as in the negro, to have a curved course in the skin which may account in a measure
for its curliuess.
The hairs are arranged singly or in groups of from two to five and, except those of the eye-
lashes, are implanted at oblique angles to the surface of the skin. The directions in which the
hairs point are constant throughout life for the same individual. They are arranged in tracts
in which the hairs diverge from a centre in whorls, the vortices pilorum.
These vortices are found oonstantty in certain definite regions and apportion the whole hairy
surface. The centres of vortices are found at the vertex (sometimes double) upon the face,
around the external auditory meatus, in the axilla, in the inguinal region, and sometimes on the
lateral surface of the body. These are all paired except as a rule the first. Where adjoining
vortices come together the hairs are arranged in lines along which they all point in nearly the
same direction, only slightly diverging, forming the hair streams, fiumina pilorum. In other
lines and places the hairs point in converging directions such as at the umbihcus and over the
tip of the coccyx.
1292 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
The number of hairs to the square centimetre varies in different parts of the body and also in
the same situation with the individual and with differences in race, colour and diameters.
The hairs are most numerous on the head, ranging from 170 to 300 to the square centimetre
at the vertex. They are less numerous on other parts of the body, varying from 23 to 44 (per
square centimetre) on the chin, and from 24 to 80 on the forearm. The greatest number is
found with blonde hair, the next with brown, then black, and the least with red hair.
The structure of the hair. — Each hair consists of a shaft [scapus pili] (fig. 1050)
projecting from the free surface of the skin to end (unless broken or cut) in a
conical end [apex pih], and of a root [radix pili], imbedded in the case of the lanugo
hair in the corium and of the larger hairs at various depths in the subcutaneous
tela. Surrounding the root is a downgrowth of the skin known as the follicle
[folliculus pili].
Fig. 1051. — ^Longitudinal Section of a Hair Ready to Fall out, with Follicle roR New
Haik. (X30) (From Toldt's Atlas.)
, Shaft
Orifice of sebace
ous gland
Dermal coat of hair -follicle
iA Epidermal coat of hair-follicle
Hair-knot (modified hair -bulb)
The root of the hair at its deepest parts swells to from one and one-half to three
times the diameter of the shaft forming thus the bulb [bulbus pili] (fig. 1050).
The bulb is hollow and a vascular connective-tissue process, the hair papilla [papilla
pili] (figs. 1050, 1051) extends from the deepest part of the follicle into the cavity
in its base. The follicle consists of an external connective-tissue portion formed
by the corium, the theca folliculi and an internal epithelial portion belonging to
the epidermis and divided into two portions, the inner and outer root sheaths
(fig. 1050).
The theca of the follicle is composed of an outer loose longitudinal and a middle circular
layer of connective tissue and an inner basement membrane. The outer root sheath is directly
connected with the stratum germinativum of the epidermis. In its deeper part it consists of
several layers of cells but of only one near the surface. The inner root sheath has been divided
into three layers. At the junction of the outer and middle thirds of the follicle of most of the
hairs, the ducts of usually two or more sebaceous glands connect with the space between the hair
THE NAILS
1293
and its follicle (figs. 1050, 1051). Immediately beneath this is the narrowest part of the follicle
the neck [collum folhcuU piU], especially important as the position of the nerve ending of the
hair.
The hair is formed of epithelial cells arranged in two and sometimes three layers; an outer
single-celled layer of transparent over-lapping cells, the cuticle, an intermediate layer several
cells thick formed of irregular fusiform horny cells containing pigment and arranged in fibrous
strands, the substantia corticalis, and in some of the larger hairs an internal two or three celled
layer of angular cells occupying the center of the hair shaft for only part of its length, the
substantia meduUaris. Between both the cortical and medullary cells are spaces containing air.
In the hair bulb, where the cells are larger and softer the layers are not distinguishable. The
cells here being in process of division and being gradually transformed into the horny cells of
the shaft.
Many of the hairs have in connection with their follicle round or flat bundles
of unstriped muscle fibres, the arrectores pilorum (figs. 1050, 1052). These are
situated on the side toward which the hairs point, their deep ends being attached
to the hair follicle beneath the sebaceous glands which they more or less embrace
and their superficial ends connected with the papillary layer of the skin. Con-
traction of the arrectores not only causes the hairs to become more erect and the
skin around them to project somewhat causing "goose flesh, " but also compresses
the sebaceous glands which are situated between the follicle and muscle and helps
to empty the glands of their secretion.
Vertical Section of the Skin fbom Scalp.
— Sebaceous gland
Fat and connec
tive tissue
The blood supply of the hairs. — The hair follicles arc surrounded by a capillary network
of arteries connected with those of the corium and the papill-ae are also supplied with loops of
arteries.
The nerves of the corium supply branches to the hairs. Some of these branches enter the
papillEE, others surround the follicle at its neck and are distributed among the cells of the outer
root sheath.
Development. — The hairs are developed from the epidermis by thickenings and down-
growths into the corium of plugs of epithelium. The deepest parts of these plugs become swol-
len to form bulbs and from these the hairs are produced. The central cells of the epithehal
downgrowths disintegrate producing the lumen of the follicle. The hairs continue to grow from
the deeper cells and protrude from their follicles between the fifth and seventh foetal months.
Abnormally they may be scanty at birth and rarely entirely absent, alopecia. The lanugo hairs
which cover all the hairy parts of the body at birth are soon shed and replaced by new hairs in-
the old follicles. Throughout lite also the hairs are being constantly shed and replaced by new
ones. This is accompanied by cornification of the bulb and fibrillation of the deep end of the
hair (fig. 1051). Thinning of the hair and baldness occur when the shed hairs cease to be
replaced. This is common in old age and a premature baldness appears to run in certain fam-
ilies. The rate of growth is normally from 1 to 1.5 cm. per month, but is subject to variation.
B. THE NAILS
The nails [ungues] are thin, semi-transparent, horny epidermic plates upon the
dorsal surfaces of the distal phalanges of the fingers and toes. Through their
hardness they serve as protective organs not only by covering the nerve endings
and other delicate structures of the skin; but also by acting as natural weapons.
On the fingers they form useful tools. They are four-sided plates presenting a dis-
1294 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
tal free border [margo liber], which overhangs the tips of the fingers, an irregular,
sharp proximal edge [margo occultus], and on each side a somewhat thinned
border [margo lateralis] (fig. 1053).
Fig. 1053.-
-DoHSAL Surface of Isolated Finger Nail.
Margo liber
Corpus unguis
(XI.) (From Toldt's Atlas.)
^ A ■ |l''hl,':??W- Lunula
Radix unguis ---fj-'f'&Wjmil
Margo occultus
Each nail is composed of an exposed distal part, the body [corpus unguis],
and a proximal covered part, the root [radix unguis], (fig. 1053), which ends in
the margo occultus. The nail is at a slightly deeper level than the surrounding
skin which overhangs the root and the lateral margins in a fold, the nail wall
Fig. 1054. — Finger Nail and Nail Bed.
Corpus unguis
Margo lateralis
Lunula
Vallum unguis
Radix unguis- —
Matrix unguis
Cristse matricis unguis
Sulci matricis unguis
Margo occultus
[vallum unguis] (figs. 1054, 1055, 1056). The epidermis of the free edge of the
nail wall, especially proximally, is thickened and often appears as a ragged edge.
At a deeper level than the above and extending somewhat more distally is a vari-
ably developed thin parchment-like membrane, the eponychium, closely attached to
Fig. 1055. — ^Longitudinal Section Through the Tip op the Middle Finger. ( X 2)
(From Toldt's Atlas.)
Stratum corneum
Stratum germinativum
Corpus papiUare
Margo liber
Stratum corneum
Stratum germinativum
1/ Matrix unguis
. Radix unguis
the superficial surface of the nail. It is the representative of the superficial layers
of the embryonic epidermis which do not take part in the formation of the nail.
The groove which is formed between the vallum and the underlying nail bed is
known as the sulcus matricis unguis. This lodges the root and lateral margins
THE NAILS
1395
of the nail and is deepest in the centre of the root, becomes shallower toward the
lateral margins, and finally disappears entirely toward the free border of the
nail (figs. 1055, 1056).
The dorsal free exposed surface of the nail is formed by a hardened, thickened, horny layer of
epithelium corresponding to the deeper parts of the stratum corneum (or the stratum lucidum)
of the skin, the stratum corneum unguis (fig. 1056). It is convex from side to side (especially
on the fifth finger), and also in some cases longitudinally. It presents a number of more or less
well-marked fine longitudinal ridges. The stratum corneum forms the principal thickness of
the nail. It is thicker and more solid on the toes than on the fingers. The portion of the
nail which projects beyond the skin of the fingers and toes is greyish-white in colour. Unless
broken or cut, it curves ventrally upon the ball of the finger or toe and tends to become long and
claw-like. It may attain a length of 3 or more centimetres.
The concave volar or plantar surface of the nail is softer and is formed of a layer of epithehal
cells which corresponds to the stratum germuiativum (Malpgihii) of the skin and is known as
the stratum germinativum unguis (fig. 1056). Because of the transparency of both layers of
the nail the blood in the underlying matrix is seen through the body of the nail and gives to it a
Fig. 1056. — Cross-section Through the Nail and Tip of the Ring Finger. (X4).
(From Toldt's Atlas.)
Corpus unguis
Cristffi matricis unguis
Vallum unguis ^
Sulcus matricis
unguis
Periosteum ^^^ "^
Retinacula cutis '^ ^^
CristEe cutis
Volar surface of finger
Stratum corneum unguis
Stratum germinativum
Matrix unguis
pinkish colour; but toward the root of the nail there is a semilunar area convex distally, the
lunula, which is less transparent and opaque whitish in color (fig. 1053). The lunula is vari-
ously developed in different individuals. It is largest on the thumb and is often abssnt on the
little finger. It is also smaller on the toes than on the fingers.
The stratum corneum unguis consist of thin, flattened, transparent, horny scales with shrunken
nuclei. These cells are intimately joined together in thin layers. The stratum germina-
tivum unguis is formed of cells continuous with and resembling those of the corresponding
layer of the epidermis. Air may occur between the cells as with the hair. The cells of the root
are not yet cornified or dried out.
The stratum germinativum unguis rests upon the corium, which here forms the so-called
nail bed [matrix unguis].' This is made up of a dense feltwork of connective tissue fibres
without fat. It is highly vascular and sensitive and the vertically arranged bundles bind the
nails tightly to the periosteum of the termmal phalanges. The papillte of the matrix beneath the
body of the nail are arranged in stronglj' marked longitudinal ridges, the cristee matricis unguis.
The cristffi and papilla; of the matrix fit into corresponding depressions on the deep surface of
the stratum germinativum unguis.
The cristse of the matrix are small and low proximally and become larger and fewer distally.
Those toward the lateral borders are somewhat oblique. The papillae of the root are not in rows
but are irregularly arranged and disappear entirely near the distal border of the lunula. Toward
the free border of the nail the papilte become large and change in character to that of the adja-
cent skin.
The best developed nails are those of the thumbs and great toes, the least developed, those
of the fifth digits which on the toes are often represented only by a horny tubercle.
Blood-supply of the nails. — The arteries are numerous in the matrix beneath the body of the
nail but fewer beneath the root. They pass from the deep parts of the nail bed toward the sur-
face, running in the main longitudinally and sending anastomosing branches to tlie papillte.
The nerves beneath the nail are abundant and terminate in free sensorjf endings and in special
end organs of several sorts.
1 The term nail bed is applied by some anatomists to that part of the corium beneath the
body of the nail, the term matrix being reserved for the corium beneath the lunula and root.
i
1296 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
Development of the nails. — The nails are developed from the epidermis. In early embryos
over the dorsal surface of each distal phalanx there is seen a smoother and more adherent area
of skin which becomes Umited by folds distally as well as proximally and laterally. It is also
distinguished by a greater number of cell layers which later become flatter than the surrounding
cells. The number of cell layers still further increases and at about the fifth foetal month the
nail proper is formed by the deeper lying cells over an area extending from the proximal fold
to the distal end of the lunula. The nail is pushed distally by constant formation of new cells
in the same way as it continues to grow throughout life. The surface epithelial cells of the nail
field cover the nail for some time as a thin layer, the eponychium, which later disappears except
a small fringe near the root.
Growth of the Nails. — The nail grows in length and thickness by multiplication of those
cells of the stratum germinativum which are situated between the margo occultus of the root
and the distal border of the lunula. The older cells are pushed distally and toward the sur-
face by the deeper cells. As a result the nail becomes gradually thicker from the occult bor-
der as far as the distal margin of the lunula. Over the rest of the nail bed no thickening appears
to take place. The rate of growth is faster on the fingers than on the toes and varies with age,
season, and the individual. When the nail is torn off, or detached through inflammation, it
may be regenerated if the cells of the stratum germinativum have not been destroyed.
Congenital hypertrophy of the nails sometimes occurs, but absence or imperfect development is
rarely seen. The white spots so frequently seen in the nail are caused by air between the cell
layers due usually to injury or impaired development.
C. THE CUTANEOUS GLANDS
The glands of the skin [glandulae cutis] are of two kinds: glomiform glands,
and sebaceous glands. The glomiform ("skein-like") glands [glandulae glomi-
formes] are of four types: sudoriferous glands, ciliary glands, ceruminous glands
and circumanal glands.
Fig. 1057. — Vertical Section of the Palmar Skin Showing an Isolated
Sudoriferous Gland. (Testut.)
1, Stratum corneum; 2, Malpighian layer; 3. corium; 4, papilla; 5, body of sudoriferous gland;
and 6, 7, its excretory duct; 8, orifice of duct on surface; 9, subcutaneous fat.
The sudoriferous glands [glandulae sudoriferae] or sweat glands are modified
simple tubular glands which secrete the siveat [sudor]. They are found in the
skin of all parts of the body except that part of the terminal phalanges covered
by the nails, the concave surface of the concha of the ear, the labia minora, and the
inferior part of the labia majora in the female and the surface of the prepuce
and the glans penis in the male. The number found in different parts of the body
varies greatly. They are very few on the convex surface of the concha and on
THE CERUMINOUS GLANDS 1297
the eyelid. They are also rather scanty on the dorsal surface of the trunk
and neck, more numerous on the ventral surface of these parts and on the
extensor surfaces of the extremities, still more numerous on the flexor surfaces,
and most numerous on the volar surface of the hands and plantar surface of the
feet. They vary from less than 57 to more than 370 to the square centimetre.
The total number has been variously estimated at from two to fifteen millions.
Each gland (fig. 1057) consists of a secretory portion or body [corpus gl.
sudoriferae], and an excretory duct [ductus sudoriferus], which opens on the sur-
face of the skin by a mouth visible to the unaided eye, the so-called 'pore' [porus
sudoriferus]. Occasionally the duct opens into a hair follicle.
The bodies of the glands are irregular or flattened spherical masses, yellowish or yellowish
red in colour and somewhat transparent. They vary in size from .06 to 4 mm. or more with a
mean diameter of .2 to .4 mm., the largest being found in the axilla. They are formed of the
irregularly, many times coiled, terminal part of the gland tube. The bodies of the glands are
situated in the deeper part of the corium or in the subcutaneous tela.
The wall of the rather wide-lumened gland tube is formed of a single layer of cubical or col-
umnar epithelium containing fat and pigment granules and surrounded externally by a basement
membrane. Enclosing these is a more or less dense connective-tissue sheath. In many of the
glands, especially the larger ones, there is a layer of obliquely running unstriped muscle fibres,
the so-called myoepithelium, between the basement membrane and the cells. In some cases
the bodies of the glands are imbedded in a more or less dense mass of lymphoid tissue.
The ducts, beginning as several coils bound up with those of the bodies, extend often in a
straight or sUghtly wavy course nearly at right angles to the surface as far as the epidermis.
This they pierce as spiral canals of from two to sixteen turns, more marked where the epidermis
is thickest (fig. 1041), and opened on the surface by somewhat widened funnel-shaped mouths.
The ducts pass between the papilla? of the corium and open on the summits of the cutaneous
cristae where these are present. The diameter of the ducts is distinctly smaller than that of
the secreting part of the glands, and this is true of the lumen also.
The ducts are lined by a stratified epithelium composed of two, three, or more layers of cella
resting on a basement membrane without any intervening layers of muscle-cells, and surrounded
by a connective-tissue sheath. This latter as well as the basement membrane ceases at the
epidermis and the epithelial cells of the duct walls join those of the stratum germinativum. The
duct for the rest of its course to the surface is merely a canal through the cells of the epidermis.
The degree of development of the sweat glands varies with the situation, the individual, and
also racially, as instanced by their great development in the negro. In some individuals the
perspiration is much more profuse than in others. The glands are smaller in the aged than in
the young. The odour of the sweat is peculiar and more or less characteristic, varying with the
individual.
The sudoriferous glands in the axillary region seem to be in some way connected with the sex-
ual function for although a large number persist as small glands, others undergo further develop-
ment beginning about the ninth year in the female and at puberty in the male. These glands in
places form almost a continuous layer and are formed of large partly branched tubules with high
secreting cells. The reddish colour of the sweat in the axillary and some other regions, especially
in certain individuals, is probably derived from the pigment granules which are found in the
glands here. The oil in the secretion lubricates the skin and keeps it soft and supple.
Blood-supply of the sudoriferous glands. — The sudoriferous glands are supplied from the
deep cutaneous plexus by an abundant network of arteries which surround and penetrate
between the coils of the gland tubules.
Nerves. — There is an enclosing network of nerve fibres some of which have been traced to
the gland cells.
Development. — The sudoriferous glands are seen first in the fourth or fifth foetal month.
The anlages resemble closely those of the hair, but the cells are not so loosely packed. They
project down as solid plugs which become long, slender, and tortuous rods. In the seventh
foetal month the rods begin to develop a lumen in the deeper parts, which also now begin to coil.
A lumen soon develops also in the superficial parts and joins that in the deeper part of the
gland. The outer of the two layers of epitheUum in the ducts becomes transformed at its transi-
tion into the gland proper into the myoepithelial layer.
The ciliary glands [gl. ciliares; Molli] are modified sudoriferous glands of the
branched tubo-alveolar type. They have simpler coils but are larger than ordi-
nary sweat glands. They are situated in the eyelids near their free borders
and open into the follicles of the cilia or close to them (see Section VIII).
The circumanal glands [gl. circumanales] are found in a circular area about
1.5 cm. wide which surrounds the anus, a short distance from it.
These glands are several times the size of the ordinary sweat glands and resemble the glands
found in the axilla, their secretion likewise having a strong odour. They are branching tubular
glands. The other kinds of glands which are found in this same area are ordinary sweat glands,
glands with straight duets, with saccules and secondary alveoli, and tubo-alveolar glands.
Cerumimous glands [gl. ceruminosse] are glomiform glands somewhat modi-
fied from the sudoriferous type. They are branched tubo-alveolar glands
(
1298 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
with relatively large lumina in the coils and narrow short ducts, and occur only
in the external acoustic (auditory) meatus.
They are very abundant on the dorsal and superior part of the acoustic meatus in the region of
the cartilaginous part, where in the adult most of them open on the surface of the skin close to
hairs. Others open into the hair follicles as they all do in the foetus and child. Their secretion,
the cerumen, is, when freshly secreted, a fluid or semifluid oily material of a yellowish-brown
colour, which on exposure to the air becomes solid like wax.
The sebaceous glands [gl. sebaceae] are simple branched or unbranched
alveolar glands distributed over nearly the whole surface of the body. Nine-
tenths of them are closely associated with the hairs, into the follicles of which
they empty (figs. 1050, 1051), and are therefore absent from certain of the non-
hairy parts of the body, as the flexor surfaces of the hands and feet, the dorsal
surfaces of the distal phalanges of the fingers and toes. On the other hand, a few
are found, usually much modified, opening independent of the hair follicles, as
at the angles of the red margins of the lips, around the nares, around the anus,
and the tarsal (Meibomian) glands in the eyelids. Modified sebaceous glands
are also found upon the mammary papilla and areola in the female, and in some
cases upon the superficial surface of the glans and the surface of the prepuce of
the penis, here known as preputial glands ; also a few very small ones may be found
upon the labia minora, the glans and prepuce of the clitoris.
The glands vary in size in different situations and also in individuals and races. They
range from .2 to 2.2 mm. long and nearly as broad. Among the smallest are those of the scalp.
The largest are found on the alse of the nose and on the cheeks where their ducts are visible to
the unaided eye. They are also large on the mons pubis, labia majora, scrotum, about the anus
and on the mammary areola. Smaller glands are also found associated with these large ones.
The size of the glands is independent of the size of the hairs with which they are associated but
the number of glands depends upon the size of the hair. On small hairs one or more glands are
always found and on large hairs there may be a whole wreath of from four to six separate glands
opening into the hair follicle.
The number of sebaceous glands has never been exactly estimated, although, it is known
that they are less numerous than the sudoriferous glands. This is very evident on the extrem-
ities, trunk, and neck, where they bear a relation of 1 to 6 or 8. On the scalp, concha of the ear,
and skin of the face they are about equal in number while on the forehead, alae of the nose, free
borders of the eyehds and external genital organs in the female the number of sebaceous glands
is greater than the number of sudoriferous glands.
Each sebaceous gland consists of a secretory portion, the body, connected with
the hair follicle or the surface of the skin by a wide short duct. In the small
glands, the body of the gland may consist of a single alveolus but in the larger
glands there are from four to twenty of these connected by irregular ducts to a
single excretory duct.
The ducts open into the hair follicles near their necks between the inner root sheath and the
hair or upon the surface of the skin. They are always very short, cylindrical, or infimdibuli-
form, and their epithelium is directly connected with that of the outer root sheath of the hau'
folhcle or with the epidermis where the hair is wanting.
The glands lie in the superficial layers of the corium and where one or a few are connected to
a single hair, they usually open into the hair follicles on the side toward which the hairs point.
Where there are several glands for one hair they may completely surround the hairs like a rosette.
The cells of the body of the gland and of the duct are surrounded by a basement membrane
outside of which is a connective-tissue sheath, both of which are continuous with corresponding
coverings of the hair folhcle.
The periphery of the alveolus is formed of small cubical epithehal cells, the central part of
larger and more rounded cells. The cells of the alveolus show all stages of fatty degeneration,
the peripheral cells contain small fatty particles, those nearest the centre larger and more nu-
merous fat droplets, some of them being completely broken down. There is no distinct lumen to
the alveolus but this is filled with degenerated cells, fatty particles and ddbris of broken-down and
cast-off cells. The deeper cells continue to multiply and push the more superficial cells toward
the lumen where they in turn are cast off. The secretion thus formed is known as the sebum
cutaneum. It is a whitish or whitish-yellow mass composed of fat and broken-down cells of the
consistency of thick oil which spreads over the surface of the skin and hair as a lubricant.
Through the decomposition of its fat more or less odour is produced. When the gland duct is
blocked the secretion is retained and becomes more solid and is known as a comedo. The active
secretion of the sebaceous glands does not begin before the fifth or sixth year of life. It attains
its maximum in the adult and decreases in the aged.
The relation of the arreotores pilorum to the sebaceous glands has been described in con-
nection with the relation of these muscles to the hairs.
Vessels and nerves. — The sebaceous glands are surrounded by a fine capillary plexus of
blood-vessels closely associated with those of the hairs and skin. Concerning their lymph-
vessels little is known. The nerves of the sebaceous glands are connected with those of the
skin and hair but the exact manner of distribution is not clearly understood.]
THE MAMMARY GLANDS
1299
Development. — The sebaceous glands appear lirst in the fifth foetal month as single, rarely
double, buds on the anlages of the hair follicles. The distal ends of these enlarge and become
lobulated. In these solid masses of cells lumina for the alveoli and the ducts later are formed,
through the fatty degeneration of the central cells. The oily contents of these cells together
with the debris and the cast-off surface cells of the epidermis form the vernix caseosa on the sur-
face of.the foetus.
D. THE MAMMARY GLANDS
The mammary glands [mammae] or breasts are modified cutaneous glands.
In tlie male they remain rudimentary and functionless throughout life, but in
the female they are functionally closely associated with the reproductive organs
since they secrete the milk for the nourishment of the newborn and are subjected
to marked changes at puberty, throughout pregnancy, during and after lacta-
tion, and after the menopause.
Fig. 1058. — The Right Mamma op a Girl 18 Years Old. (Modified from Spalteholz.)
Areolar
gland'
Papilla
Areola
The two mammffi (fig. 1058) are situated on the ventral surface of the thorax
one on each side of the sternum. As examined from the surface in a well-developed
nulliparous female they appear to extend from the second or third rib to the si.xth
or seventh costal cartilage and from the lateral border of the sternum to beyond
the ventral folds of the axillse. Separating the two mammae there is a median
unraised area of variable size, the sinus mammarum.
In shape they are conical or hemispherical, and in consistency somewhat
firm and elastic: The size of the two breasts is seldom equal, the left, as a rule
being slightly the larger. Each measures from 10 to 13 cm. in diameter being
slightly longer in the direction parallel to the lateral border of the pectoralis major
muscle. The weight of each gland varies from 140 to 200 grams, or more.
Each mamma presents for examination a ventral surface and a dorsal surface.
The ventral surface is free, covered by skin, smooth and convex. It is continuous
i
1300 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
cephalically, without sharp demarcation, with the ventral surface of the thorax
but laterally and caudally it is usually sharply defined (figs. 1058, 1060). It is
Fig. 1059. — The Female Mamma Dt-hing Lactation. (After Luschka.)
Adipose loculus
Gland loculus
Fig. 1060. — Sagittal Section of the Right Mamma of a Woman Twenty-two Years
Old (Testut )
Pectoralis major
Skin
Retinaculum cutis /"^
Pyramidal process
„, Pectoralis minor
■jfS^ -Intercostal muscle
Pectoral fascia
Connective tissue
Superficial fascia
--^(^ horizontal plane
Fifth nb
Pyramidal process
Rectinaculum Fat
cutis
External oblique
most prominent slightly meso-caudal to the centre and at this point there is a
marked pigmented projection, the nipple [papilla mammse] surrounded by a
THE MAMMARY GLANDS
1301
slightly raised area, also pigmented, the areola mammae. These two structures
will be described separately later.
The dorsal surface of the mammary gland (figs. 1060, 1061) is attached and
concave. It is in relation in its cephalo-medial two-thirds with the fsacia over the
pectoralis major muscle. In its caudo-lateral third it extends over the base of
the axillary fossa, where it is in relation with lymphatic glands and with the ser-
ratus anterior muscle, and at its most caudal part, sometimes with the external
abdominal oblique muscle.
The usual number of breasts in the human species is two; rarely is the number reduced,
much more often do we find an increase in this number. Each of these conditions is found in
both sexes and may be complete or partial. Complete suppression of both breasts, amastia, is
one of the rarest anomaUes and is usually associated with other defects. Complete absence of
one is less rare. A more frequent condition is arrest of development, micromastia, leading to
rudimentary but functionless organs. Absence of the nipple, athelia, is much commoner and
generally affects both breasts. All grades of the imperfection from complete absence to
shghtly imperfect nipple may be found. When there is an increase this may include the whole
breast, polymastia, or just the nipple, polythelia. The supernumerary structures [mammae
Fig. 1061. — Horizontal Section of the Right Mamma or a Woman 22 Years Old.
(Testut.)
Pyramidal process
Skin
Retinaculum cutis
Areola
Duct
-^ Retinaculum cutis
■^ Pyramidal proces
ir1?X -Skin
Superficial fascia
Connective tissue
' Sixth rib
-IntercQstals
accessori8e] may be represented only bj' a pigmented area representing an areola; or by a nipple
with or without an areola; by a gland with a more or less perfect nipple and areola; or with
ducts opening without a nipple; or there may be no opening on the surface. The extra mamma
is very rarely perfectly developed and functional. Various observers have found the super-
numerary breasts or nipples occurring in from 1 to 7 per cent, of the cases examined and some-
what oftener in males than in females. The extra organs are found more frequently on the left
side, usually along a line extending from the axilla toward the genitalia. Tliis corresponds to
the position in which the mammae occur m some other mammals and also to the milk line of the
embryo. Although they are occasionally found in other situations, over 90 per cent, of them
are encountered upon the ventral surface of the thorax along the above-mentioned line caudal
and medial to the normal pair of breasts. They are frequently hereditary. It is doubtful
whether their possessors are either more fertile or more Uable to bear twins.
The shape of the breasts varies with the development and functional activity'and the amount
of fat. The smooth, somewhat conical breast of the nullipara becomes hemispherical with
increase in the amount of fat, while in emaciation it may be reduced to a flattened disc with an
irregular surface. After lactation the breasts tend to become more pendulous with marked
sulci between them and the thoracic walls, and after repeated pregnancies they may become elon-
gated so as to be almost conical or even have pedunculated bases.
The size of the mammary gland in girls remains relatively the same as in the
infant up to puberty when it suddenly increases considerably and continues for a
time to enlarge slightly at each menstrual period. There is also a temporary
enlargement and soreness at each menstrual period, due perhaps to the increased
vascular supply. Until the age of puberty the glands measure 8 to 10 mm. in
diameter but when they have attained their complete adult development they
have increased to 100 to 110 mm. in the cephalo-medial, 120 to 130 mm. in the
cephalo-lateral (obliquely from above downward) direction, and 50 to 60 mm. in
thickness. During pregnancy the breasts again increase in size, more especially
i
1302 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
after the birth of the child. When their full functional activity is established,
their volume may be two or three times as great as before pregnancy. After lacta-
tion they return again nearly to their former size, which they retain until another
pregnancy. After the menopause the useless glands in some cases atrophy and
are reduced to small discoidal masses. In others, especially in fat individuals,
although the secreting tissue disappears, it is replaced by fat so that there is little
or no reduction in size. In addition to the above-mentioned variations in size,
the breasts are subject to great individual differences, the cause of which is little
understood. Large robust women are sometimes seen with small mammary
glands, and small women with large glands. In some individuals they are espe-
cially large.
The weight of each mamma varies, naturally, with the volume, increasing from 30 to 60
centigrams in the small gland of a young child to 140 to 200 grams after puberty and in nursing
women reaching 400 to 500 and occasionally 800 to 900 grams.
The firm and elastic, well-developed breasts of young nullipara become during lactation
even more firm and tense, but after lactation especially if there has been a long period of nursing
they lose their consistency and after several pregnancies become soft and flabby.
The sulcus which defines the caudal border of the breast is but little marked in thin nulli-
para, more marked in fat women, and especially evident in some multipara. The relations of
the dorsal surface of the gland vary somewhat with the position. The level varies with the
stature; as a rule, in tall women it is more caudal and in short and broad-chested women it is
more cephalic. The tightness of the attachment to the sheath of the pectoralis major muscle is
quite variable, but even when quite loose there is some movement of the breast when the arm is
raised. The glandular tissue of that part of the breast which overhangs the axilla may be in
direct contact with the lymphatic glands.
Structure. — The mammary glands are composed of the essential epithelial
glandular tissue, the parenchyma, the supporting and enclosing connective
tissue of the subcutaneous tela, the stroma, and the covering cutaneous layer.
Parenchyma. — The essential part of each mamma is a flattened, circular mass
of glandular tissue of a whitish or reddish-white colour, the corpus mammae. This
is thickest opposite the nipple and thinner toward the periphery. The ventral
surface of this mass is convex and made uneven by numerous irregular pyramidal
processes which project toward the skin. The dorsal surface, or base, is flat or
slightly concave and much less irregular than the ventral surface. Minute proc-
esses of glandular tissue extend from the corpus mammse into the retromammary
tissue, some of them accompanying the septa of the pectoral fascia between the
bundles of muscle fibres of the pectoralis major muscle. The circumference of the
mamma is thick and well defined, more marked caudally than cephalically, but
it presents numerous irregular processes which extend beyond the limits apparent
from the surface. One of these especially large and well marked extends cephalo-
laterally into the axillary fossa, and there are frequently other large but less-
marked projections.
The corpus mammae is not a single structure but is composed of from fifteen to
twenty separate lobes [lobi mammse] (fig. 1059). These are larger and smaller
irregular flattened pyramidal groups of glandular tissue, with their apices toward
the nipple and their bases radiating toward the periphery of the gland.
Each lobe has a single excretory duct [ductus lactiferus] (figs. 1059, 1060,
1061), which opens by a contracted orifice [porus lactiferus] in a depression upon
the tip of the nipple. When traced from the pore toward the circumference of
the gland, the ducts are seen to run first directly dorsally through the nipple,
parallel and close to one another. From the base of the nipple they diverge.
Each duct is here visible to the unaided eye and measures from 1.5 to 2.5 mm. in
diameter. Beneath the areola its diameter increases for a short distance to from
4 to 9 mm., forming thus a reservoir, the ampulla or sinus lactiferus, in which the
secretion may accumulate for a time. Beyond this dilation the duct continues,
gradually decreasing in size as it breaks up into smaller and smaller branches,
There is no anastomosis between the ducts during their course, although at or
beneath the pore two or more ducts may join to have a common opening. They
possess no valves but when empty their inner surface is thrown into longitudinal
plicse.
The ducts have an external coat of white fibrous connective tissue mixed with circular and
longitudinal elastic fibres. They are lined with a simple cuboidal or columnar epithelium,
except near the orifice, where it is stratified squamous. External to the lining epithelium there
THE MAMMARY GLANDS 1303
occurs in the smaller ducts a second layer of elongated cells resembling the myoepithelium of the
sudoriparous glands.
Each of the terminal branches of a duct ends in a tubulosaccular, spherical or pyriform alveo-
lus. A number of these alveoli which open into a common branch of the duct, when grouped
together and bound up with connective tissue, constitute a lobule of the gland (lobulus mammae).
A lobe is made up of all the lobules whose ducts join one common excretory duct.
The alveoli are composed typically of a single layer of epithehal cells enclosed by a basement
membrane. This layer is the true secretory epithelium. It consists in the more active gland
of granular polyhedral or cuboidal cells which may be so closely placed as to leave almost no
lumen to the alveoh. During lactation these cells may be found in different stages of secretory
activity, their central ends being filled with minute oil globules and more or less flattened accord-
ing to the degree of distention of the alveoli. The alveoli and ductules now possess considerable
lumina which are filled with the above-mentioned millc globules Uberated from the cells and sus-
pended in a serous fluid also secreted by the cells. TMs constitutes the milk (lac femininum).
Stroma. — The lobes, lobules, and alveoli are completely covered by a connective-tissue
sheath too delicate to constitute a distinct capsule. Outside of this the whole gland is embedded
in the subcutaneous tela which forms for it a sheath, capsula adiposa mammae. This is particu-
larly well developed on the ventral surface where the fat fills in between the irregularities caused
by the lobes and lobules and gives to the surface of the gland its smooth appearance. Within
the corpus mammte there is little fat between the lobules in nulhpariB but much more fat is found
here in the stroma in multipara;. When the fat is absorbed, as it is during lactation and in
emaciation, the lobules stand out much more distinctly. There is however, no fat immediately
beneath the areola and nipple. The connective tissue is here loosely arranged and allows free
motility of the nipple and also permits the more easy distention of the ducts and sinuses during
lactation. The connective-tissue strands, retinacula mammae, which extend from the apices
of the glandular processes on the ventral surface of the mamma are connected to the cerium and
correspond to the retinacula cutis found in other situations. These are sometimes particularly
well developed over the cephaUc part of the mamma and have been called the suspensory liga-
ment of Cooper.
The dorsal surface of the mamma is bound to the pectoral fascia by loose connective tissue
containing, as a rule, only a small amount of retromammary fat (figs. 1060, 1061). The attach-
ment to the sheath of the pectorahs major muscle is at times so loose that the spaces between
the connective tissue appear to form serous sinuses, the sub- or retromammary bursas.
In addition to the axillary process or 'tail' of the gland, a projection is sometimes seen extend-
ing toward the sternum and another caudolaterally; also processes extending toward the clavicle
and caudomedially have been described. Besides these large projections there are numerous
branched interlacing processes which combine into larger and smaller masses on the ventral
surface and exist as minute extensions on the dorsal sm'face. In thin women, the parenchyma
at the apex of these triangular processes reaches nearly to the surface.
A mammary gland may be made up of a larger amount of stroma and a smaller amount of
glandular tissue, or the reverse, and therefore a small breast may fiu-nish more milk than a large
one. There is also a variation in different parts of the same breast, one lobe or section may have
well-developed lobules while in another they remain almost as at puberty, merely branching
ducts.
The glandular tissue when sectioned is whitish with a greyish or pinkish cast and is firm and
resistant, almost cartilaginous in consistency. It is thus easily distinguished from the adipose
capsule.
Changes due to age and functional activity. — At birth the mamma consists mainly of
fifteen to twenty slightly branched ducts lined with stratified squamous or columnar epithelium.
In spite of the lack of true glandular tissue, within the first few days there may be such rapid
cell proliferation that the ducts become distended with cells and detritus. By pressure upon the
gland a few drops of this material may be expressed which constitutes the so-called 'witches
milk.' From birth until puberty the mamma remains rudimentary, simply keeping pace with
the general body growth, but in the female, at puberty, an abrupt change occurs. The tubules
grow rapidly into the smTOunding tissue and some acini (alveoli) appear; the stroma and fat are
also greatly increased; and the breast becomes rounded and well formed but consists mainly of
fatty stroma and ducts, with but a very small number (if any) of true secreting acini. At this
time in both boys and girls the breast may become swollen and tender and a milk-hke secretion
may be produced similar to that at birth. The great increase in volume during pregnancy and
lactation is due to the increase in the size and number of the lobules and acini, and is accom-
panied by a decrease in the interlobular and intralobular stroma and in the fat, so that the gland
feels hard and imeven. The acini appear first in the periphery, thence along the larger ducts
toward the centre of the corpus mammte.
The secretion of the gland for the first two or three days after parturition until the free secre-
tion of milk is established is termed the colostrum. It differs from normal milk not only in
chemical composition but also in containing larger fat globules and special cells known as
colostrum corpuscles.
The decrease of the gland nearly to its original size after lactation is due to an involution
of the parenchyma, the acini being reduced to narrow tubules, most of them completely atrophy-
ing. With this is associated a development of fat and fibrous stroma. The gland does not,
however, regain its virgin appearance but its main mass is looser and more irregular, less dis-
tinct, and the peripheral processes larger, while the stroma contains numerous fat-lobules. This
causes the breast to be less smooth, fii-m, and elastic, and it tends to become pendulous and form
a sulcus where it overhangs its base. With the end of sexual activity the secreting portions of
the glands gradually atrophy, finally leaving Uttle more than the ducts. Even these undergo
senile atrophj', and the main mass of the gland is represented only by a flattened disc, in which
the peripheral processes can scarcely be made out. In fat women there may be little reduction
in size, but the breast is here transformed almost entirely into fat.
i
1304 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
The skin covering the ventral surface of the breast is very white, covered with
lanugo hairs associated with sebaceous glands, and contains many sweat glands of
the ordinary type. It is so thin that the subjacent veins are readily seen through
it. It is closely adherent to the subjacent fatty layer but its flexibility, elasticity,
and motility over the deeper glandular tissue permit much stretching during the
enlargement which occurs at the time of lactation. In spite of this, linea albi-
cantes are often produced especially when the breasts have been unusually large.
Aside from the above-mentioned particulars, it does not differ from the skin of
the adjacent part of the thorax, except over the centre of the breast where it
forms the areola and nipple.
The areola mammae (figs. 1058, 1059, 1060, 1061) is covered by a thin, deli-
cate, pigmented skin. The colour in young nulliparae is reddish, the shade varjang
with the complexion. During pregnancy the colour darkens, slightly in blondes,
but so as to become almost black in marked brunettes.
This pigmentation serves as one of the signs of gestation. After lactation the colour fades,
but little pigmentation remaining in blondes, considerable in brunettes. During pregnancy-
there is sometimes seen extending more or less beyond the areola a less deeply and less uniformly
pigmented ring, the secondary areola. In size, the areola is subject to considerable individual
variation and is increased in pregnancy.
The surface of the areola is roughened by a number of slight elevations irregu-
larly arranged. These are due to underlying large sebaceous and rudimentary
milk glands [gl. areolares; Montgomerii], tubercles of Montgomery. Projections
caused by sebaceous glands are also found in the secondary areola. All of these
tubercles enlarge greatly during pregnancy and the glands produce a slight secre-
tion which is discharged through ducts that open on their summits. The sweat
glands are few but large, and in addition to the lanugo hairs there are usually
several well-developed hairs.
The corium of the areola is devoid of fat but contains a well-developed layer of smooth muscle
fibres, the fascicles of which intercross in various directions but may be seen to be mainly of two
orders, circular and radial. They are continuous with those of the nipple. The circular
fibres are most numerous adjacent to the nipple, where they may form a layer nearly 2 mm. in
thickness.
The areola varies greatly in size, measuring from 15 to 60 mm. in diameter. There is some
confusion in regard to the areolar glands and the tubercles of Montgomery. Some consider
the tubercles to be caused by the areolar glands, others consider them caused by the sebaceous
glands. Sebaceous glands undoubtedly cause the projections in the secondary areola. The
sudoriferous glands of the areola are large and compound tubular glands with a comphcated
glomerulus and are considered as transitions between sweat and mammary glands. The seba-
ceous glands are even more numerous than the sudoriferous and are composed of several lobes.
They also have been considered by some as intermediate stages in the formation of mammary
glands, but this is improbable. There are ten to fifteen very small areolar glands (though Pinard
found an average of but four to each breast), whose structure is essentially identical with that
of the principal mammary glands. They have dilations on their ducts and they open on the
areola at times in common with a sebaceous gland.
The nipple [papilla mamma] (figs. 1058, 1059, 1060, 1061) in well-developed
nulliparae is situated slightly meso-caudal to the centre of the breast and on a
level with the fourth rib or fourth intercostal space about 12 cm. from the median
line. But its position in reference to the thoracic wall varies greatly with age,
individual, and the present and past activity of the gland. The nipple is usually
somewhat conical or cylindrical with a rounded fissured tip marked by fifteen to
twenty minute depressions into which the lactiferous ducts empty. The average
length of the nipple is 10 mm. to 12 mm. The skin is thin, wrinkled, and pig-
mented like the areola, except over the tip of the nipple where there is no pigment.
The corium of the nipple has many large vascular and nervous papilla; and there is no fat in
it. Hairs and sudoriferous glands are absent but sebaceous glands are present in great numbers.
Their secretion here and over the areola serves to keep the skin soft and to protect it from the
saliva of the nursing infant. In the deeper layers of the corium smooth muscle fibres form a
loose stratum continuous with that of the areola. This is made up principally of an external
circular layer and to a slight extent by an internal layer whose bundles of fibres are parallel with
the milk ducts. Numerous interlacing muscle fibres connected with these layers and mixed
with loose connective tissue, and elastic fibres, but no fat, surround the lactiferous ducts as they
pass through the axis of the nipple.
The nipple usually does not project from the surface until the third year. It soon becomes
conical but does not attain its full size until shortly after puberty. The size of the nipple is
variable, ordinarily in proportion to the size of the gland, but large nipples are sometimes found
on small breasts and small nipples on large breasts. During pregnancy the nipple increases in
THE MAMMARY GLANDS 1305
size and becomes more sensitive and more easily erectile. The shape of the nipple in addition to
conical or cylindrical may be hemispherical, flattened, discoidal, or slightly pedunculated. Its
end may be invagtnated or the entire nipple retracted beneath the surface of the gland and pro-
jecting only in response to stimuli.
The circular muscle fibres of the nipple act like those at its base in the areola. By inter-
mittent, rhythmic contractions they tend to empty the lactiferous ducts; by continuous and tight
contraction they act as a sphincter. When contracted they also narrow the nipple, make it
harder, erect, and more projecting. When the vertical fibres contract they depress the tip of
the nipple or they may retract the whole nipple beneath the surface. The muscle of the areola
when stimulated puckers the skin toward the nipple causing circular concentric folds in the
skin of the areola.
The male mammary gland [mamma virilis]. This develops exactly as with
the female. From birth to puberty the glands in the two sexes have a parallel
growth and development, but from this time on the glands in the male grow but
slightly and reach their full development about the twentieth year.
The corpus mammae in the adult male measures from 1.5 to 2.5 cm. in diametei and .3 to
.5 cm. in thickness. It is whitish in colour, tough, and stringy. It is composed of the same
number of lobes as in the female but these consist of little more than short ducts with no true
acini and may be reduced to mere epitheUal or connective-tissue strands. The areola and nipple
are present and pigmented, but the nipple averages only 2 to 5 mm. in height. The areola has
a diameter of 2 to 3 cm. and is covered with hairs. The areolar tubercles may be recognised
and the areolar muscle is present. The position of the nipple in relation to the chest-wall is
more constant than in the female as the breast is less movable. It is seldom beyond the limits
of the fourth intercostal space or the two adjacent ribs, and averages 12 cm. from the median
line. Occasionally the male breast may hypertrophy on one or both sides, gynecomastia.
Blood-supply. — The main arterial supply to the mammary gland is from mam-
mary rami of perforating branches of the internal mammary artery (p. 567).
Usually that from the second or third intercostal space is especially large. Small
branches, external mammary rami, are also supplied to the caudal and lateral
segments of the breast by the lateral thoracic artery (p. 571 ). Some rami from
the thoracoacromial or supreme thoracic arteries (p. 571) may reach the cephalo-
lateral segment of the breast and small twigs, lateral mammary rami, from the
anterior branches of the lateral cutaneous rami of the aortic intercostal arteries (p.
589) supply its deep surface.
These vessels anastomose freely and form a wide-meshed network in the stroma of the ventral
and dorsal surfaces from which branches proceed around the lobes and lobules and finally form a
close network of capillaries around the alveoli. From these, venous capillaries arise and pass in
two groups, one deep, accompanying the arteries, the others superficial. These latter extend to
the ventral surface of the gland to form a loose network beneath the skin. During lactation
these subcutaneous veins show through the sldn as bluish lines, and frequently form a more or
less complete circle around the nipple. They connect with the superficial veins of the neck
superiorly, with those of the abdomen inferiorly, and with the thoracoepigastric vein laterally.
The deep veins carry the blood to larger vessels, which empty into the subclavian, the inter-
costal, the internal mammary, and the axillary; and the superficial group may connect with the
external jugular and femoral veins.
The lymphatics. — The lymphatics of the mammae are extremely numerous,
forming rich plexuses and free anastomoses. Their exact origin and distribution
are not yet fully understood, but it is clear that there is a rich plexus in the skin of
the areola and nipple which empties mainly into a subareolar plexus. Deep lym-
phatics arise in the spaces around the alveoli in all parts of the gland, and most of
these converge toward the nipple where they join the subareolar plexuses. They
anastomose freely with the cutaneous lymphatics and many of them empty into
the subareolar plexus through large lymph-vessels which run parallel with the
lacteal ducts. From the subareolar plexus usually two large lymph-vessels arise
and pass toward the axilla to empty into the axillary lymph-glands (p. 719).
Other lymphatic vessels of the mammary gland follow the course of the various
blood-vessels.
There is usually a third trunk from the cephahc part of the breast and often a fourth from
the caudal segment which join with the others to the axillary glands. The lymphatics of the
mammary gland also commimicate with the lymphatics of the skin, the ventral chest-wall
and those of the deep fascia over the pectoral muscles, as well as the lymphatics of the opposite
side. They also empty into the lymphatics which accompany the blood-vessels of this region,
and thus communicate with the axillarj', subclavicular, and supraclavicular lymphatic nodes
(p. 722). Moreover, those from the medial portion of the gland accompany the branches of
the internal mammary artery and empty into the sternal glands along the artery within the
thorax. Since cancer of the breast extends and is disseminated through Ij'mphatic channels,
their distribution and connections are of great practical importance.
i
1306 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
The nerves. — The gland proper receives its nerves laterally from the lateral mammary rami
of the anterior rami of the lateral cutaneous branches of the fourth to sixth intercostal nerves
and medially from the medial mammary rami of the anterior cutaneous branches of the second
to the fourth intercostal nerves. The skin over the breast receives in addition to branches from
the above nerves, branches from the supraclavicular nerves of the cervical plexus. It is alto-
gether probable that sympathetic fibres reach the gland but by what course is not yet clear.
The nerves are distributed in part to the sliin, in part to the plain muscle of the areola and nip-
ple, some to the blood-vessels, and others to the glandular tissue. The secretion is, however,
not entirely controlled by nerves as it is influenced also by hormones from other organs brought
to it by the blood.
Development. — In very early embryos the epithelium over an area on the side of the body
extending from the fore to the hind limb (or beyond these limits) is seen to be deeper and more
cubical, the mammary streak. In this area there is produced by multiplication of cells a ridge,
the mammry line or ridge. In spots along this line, corresponding to the relative position of
the mammary glands in some mammals and the supernumerary mammse in man, the epithelium
thickens. The intervening parts of the line disappear as the spots enlarge to form transient
mammary hillocks. In man ordinarily development proceeds in but one of these hillocks on
each side. The deep surface of the hillock projects into the corium as the superficial surface
flattens out and the mesodermic cells of the corium condense around the ingrowth producing
the nipple zone. Rapid proliferation of the deeper cells produces a club-shaped stage from the
deeper surface of which small bud-like masses of epithelial cells sprout and extend as solid plugs
into the corium. These are the anlages of the true secreting part of tlie gland and the number of
buds corresponds to the number of lobes of the future gland. The sprouts extend beyond and
beneath the nipple zone and are supported by closely packed connective-tissue cells forming the
stroma zone. The epithelial buds continue to grow and branch and a lumen is finally produced
in the originally solid plugs. The primary epithelial ingrowth degenerates and ultimately dis-
appears. A cavity is produced in it which later connects with the lumina of the gland ducts.
The depressed nipple zone becomes elevated above the surface soon after birth. Further
development of the mammary gland has been discussed previously under changes due to age
and functional activity (p. 1303).
THE DUCTLESS GLANDS
Under the term ductless glands are included not only certain glandular struc-
tures of epithelial origin with a more or less definitely known function and an
internal secretion but also certain organs whose function is not definitely known or
understood. Of the organs here considered, the function of the thyreoid gland,
the parathyreoid glands, the chromaffin system, the medullary portion of the
suprarenal glands, and the aortic paraganglia is somewhat definitely known.
But the function of the thymus, the spleen, the cortical portion of the superenal
glands, the glomus caroticum, and the glomus coccygeum is still in doubt;
although probably some, if not all of them, have an internal secretion or at any
rate are closely associated with the other glands of internal secretion. The hypo-
physis and the pineal body are not considered in this connection but will be found
described with the brain (pp. 845,848). The lymph-nodes, which may also
be considered as ductless glands, are described in Section VI. Many of the
true glands, such as the liver, pancreas and sexual glands, have also internal secre-
tions which pass directly into the vascular system as in the ductless glands.
THE SPLEEN
The spleen [lien] is a large blood-vascular organ closely associated with the
lymphatic system. Its exact function is still in doubt.
Position. — The spleen is situated in the dorsal part of the left cephalic segment
of the abdominal cavity so deeply placed against the diaphragm and dorsal to the
stomach and colon as to be invisible from the ventral surface of the body when the
abdominal cavity is opened. It is mainly in the left hypochondriac region but its
deepest and most cephalic part extends also into the epigastric region. It is
obliquely placed with its long axis corresponding approximately to the line of the
caudal ribs. It tends to become more vertical when the stomach is fully distended
but when the stomach is empty and the colon distended it assumes a more hori-
zontal position. Changes in the attitude of the body also cause slight altera-
tions in the situation of the spleen. It moves with the excursions of the dia-
phragm in expiration and inspiration.
The colour of the spleen is, in life, a dark bluish-red or brownish-red, but after
death it becomes darker with a more bluish or violet tint.
The size of the spleen is perhaps more variable than that of any other large
THE SPLEEN
1307
organ in the body. Not only does the size differ in different individuals but it
changes greatly with the blood content in the same individual. There is a dis-
tinct expansion for a time after each meal and the spleen contracts and expands
rythmically.
Fig. 1062. — Wedge-shaped Spleen, Viscebal Surface.
Diaphragmatic surface Margo anterior
Extremitas superior
Margo posterior
Margo posteno.
Lower end of renal surface
Gastric surface
Extremitas inferior
In the adult it usually measures 10 to 15 cm. in length, 7.5 to 10 cm. in breadth, and 2.5 to
4 cm. in thickness. The weight usually ranges from 150 to 225 gm. At birth it represents
from jitg to jjo of the total body weight and this porportion is maintained wuthout much varia-
tion until the age of fifty years, when (like the lymphoid organs in general) it begins to diminish
Fig. 1063. — Tetkahedral-shaped Spleen, Visceral Surface.
Extremitas superior
Renal surface-
Margo posterior
Intermediate angle
Posterior extremity
Gastric surface
Hilus lienis
Margo anterior
Anterior extremity
in size. This diminution continues until in the very old it represents but y J „ of the body weight-
There is no great difference in relative size in the two sexes.
The spleen is somewhat soft and very friable. It is elastic, extensible, contractile, and
extremely vascular.
Shape. — Iia form the spleen varies greatly. This is due largely to its softness
which permits considerable modifications by the pressure of the distended or con-
1308 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
tracted surrounding hollow viscera. When in situ with the stomach distended, its
shape may be compared to a blunt spherical wedge with a concave apex and
rounded extremities, and possessing therefore three surfaces (fig. 1062); but
when the stomach is contracted and the left flexure of the colon distended an addi-
tional surface is produced and its shape becomes tetrahedral (fig. 1063). Inter-
FiG. 1064. — Spleen Showing Tttbebcle on the Intermediate Border.
-Extremitas superior
Gastric surface
Margo anterior
Extremitas inferior
mediate forms between these extremes are produced by variations in the degree
of distention of stomach and colon. The spleen presents two aspects: lateral or
parietal, against the diaphragm; and medial or visceral, toward the abdominal
cavity. In its usual wedge form the three surfaces of the spleen are diaphrag-
matic, gastric, and renal. There are three borders, anterior, posterior, and inter-
mediate; and two extremities, superior and inferior.
Fig. 1065.-
-Cross-section op the Body at the Lower Part of the Epigastric Region.
(Rtidinger.)
Transverse colon Aorta
Stomacli
Liver
Gall-bladder
Kidney
The diaphragmatic surface [facies diaphragmatica] is a smooth convex surface
with an irregularly oval outline, in the wedge-shaped spleens wider cephalically,
but in the tetrahedral-shaped spleens wider caudally. It looks dorsally toward
the left and somewhat cephahcally.
It lies against the diaphragm over an area opposite the ninth, tenth, and eleventh ribs and
the intervening intercostal spaces, with its long axis corresponding in a general way to the course
THE SPLEEN
1309
of the ribs. Although it is separated from the ribs by the peritoneum, the diaphragm, and the
left pleural cavity (cephalically also by the left lung) (figs. 1065, 1066), the ribs sometimes make
impressions upon it.
The gastric surface [facies gastrica] is a semilunar-shaped surface, concave
cephalo-caudally and from side to side, wiiich looks ventrally to the right and
somewhat caudally (figs. 1062, 1065, 1066). Nearly parallel with the dorsal
boundary of this surface is a narrow depression usually formed by a series of pits,
as a rule six or eight, which together form the hilus of the spleen [hilus lienis].
In this situation the vessels and nerves enter and leave the spleen, the vein being
dorsal.
When the stomach is distended it is in contact with the major part of the gastric surface;
the left flexure of the colon forming an impression upon a small area near the caudal extremity
and the taU of the pancreas, as a rule, resting against a narrow area dorsal to the hilus or just
Fig. 1066. — Sagittal Section through the Left Side op the Body, Showing the
Relations of the Spleen. IX, X, XI, XII, corresponding ribs. 1, Left kidney; 2, spleen; 3,
pancreas; 4, splenic vessels; 5, transverse colon; 6, stomach; 7, left lobe of liver; 12, lung; 14, heart;
16, diaphragm. (Testut and Jacob.)
L' ' vnr
cephalic to the colon. When the stomach is empty and contracted and the colon distended the
size of the gastric area is considerably decreased and the relative size of the coUc impression
greatly increased so as to form upon the spleen in this situation a colic or basal surface (fig.
1063). The stomach is, however, at all times in contact with some part of the spleen.
The renal surface [facies renalis] the smallest of the three surfaces, shorter as
well as narrower than the gastric surface, is an oblong, flat or slightly concave
area, which faces dorsally, to the right and slightly caudally. It is in relation
with the anterior surface of the left kidney (fig. 1066).
In some cases the cephalic third of the renal surface is also in relation with the anterior sur-
face of the suprarenal gland. It is separated from these latter structures, however, by the renal
adipose capsule as well as by the peritoneum. The tail of the pancreas in some cases is in con-
tact with a small area on the ventral part of this surface. In fat individuals these relations are
not as intimate as the relations with other organs because of the large amount of suprarenal
fat.
The anterior border [margo anterior] is clearly defined, thin, sharp, and more or
less convex. It is marked in over 90 per cent, of the cases by one or more trans-
verse or oblique notches, especially in its cephalic part. It is placed between the
1310 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
diaphragm and the stomach and separates the diaphragmatic from the gastric
surface (figs. 1062-1065).
The posterior border [margo posterior] is rounded, shorter, and straighter than
the anterior border and is notched in less than a third of the cases. It separates
the diaphragmatic from the renal surface and is lodged in the angle between the
left kidney and the diaphragm (figs. 1062-1065).
The intermediate border is a blunt ridge dorsal to the hilus, separating the
gastric from the renal surface.
It may be clearly defined or more or less obscure and often shows a marked tubercle (fig.
1064). When the stomach is contracted and the colon distended this border divides caudally
into ventral and dorsal limbs both of which may be well marked or either may be deficient
depending on the direction and degree of pressure of surrounding organs. When well marked
there is produced at the point where the two limbs diverge a more or less marked projection, the
intermediate extremity or angle (fig. 1063).
The superior extremity [extremitas superior], usually larger than the inferior
extremity in the wedge-shaped spleens but smaller in the tetrahedral form, is
rounded and bent medially. It extends as high as the tenth thoracic vertebra and
lies 1 to 2 cm. from the vertebral column.
The inferior extremity [extremitas inferior], also somewhat rounded, is directed
toward the left and caudally. It is in relation with the phrenicocolic ligament.
When the stomach is contracted and the colon distended the inferior extremity becomes much
broader, in extreme cases forming a distinct inferior border ending ventrally in the anterior
margin as an anterior extremity and dorsally in the posterior margin as the posterior extremity
(fig. 1063).
In the tetrahedral-shaped spleen the additional surface produced by the pres-
sure of the colon is known as the basal or colic surface (fig. 1063). This varies in
size reciprocally with the degree of pressure of colon and stomach.
When well developed the cohc surface is concave and is separated from the renal and gastric
surfaces by the more or less sliarply defined dorsal and ventral limbs of the intermediate border
and separated from the diaphragmatic surface by an inferior margin produced from the broadened
inferior extremity. The left flexure of the colon is in contact with the greater part of this sur-
face, but the pancreas also usually hes against it in its cephahc part (fig. 1063).
Peritoneal relations. — The surface of the spleen is completely covered, except
for a small area at the hilus, by a peritoneal coat, the tunica serosa. Ventral to
the hilus a double layer of peritoneum is prolonged from the spleen to the left
side of the greater curvature of the stomach and the left edge of the ventral layer
of the great omentum, forming the gastrolienal ligament which contains the short
gastric arteries and veins. Dorsally a second double layer of peritoneum extends
from the hilus to the ventral surface of the kidney and the caudal surface of the
diaphragm forming the phrenicolienal (lienorenal) ligament. This ligament
encloses the splenic artery and veins as they pass to and from the spleen. It is
also between the two layers of peritoneum of this ligament that the tail of the pan-
creas reaches the spleen (fig. 1065). Except by these two Hgaments the spleen
has normally no attachment to the abdominal wall or to any of the surrounding
viscera. The gastroHenal, and more especially the phrenicohenal ligament, serve
in a measure to anchor the spleen in its place in the abdominal cavity but in addi-
tion to these the spleen is supported by a fold of peritoneum which e.xtends from
the left cohc flexure to the parietal peritoneum over the diaphragm, the phrenico-
colic ligament. This serves as a shng in which the inferior extremity of the spleen
rests. The spleen, however, is held in position in the abdominal cavity mainly by
the intraabdominal pressure.
Topography. — The superior extremity of an average-sized spleen is located between the angle
and tubercle of the tenth rib on the left side and about 3 to 4 cm. from the median line on a level
with the spinous process of the ninth thoracic vertebra. In the majority of cases, it does not
extend more than 2 cm. either cephalic or caudal to a transverse plane at the level of the infra-
sternal notch. The inferior extremity reaches nearly to the midaxillary lioe in the tenth inter-
costal space and 10 to 15 cm. from the superior extremity. The long axis therefore corresponds
nearly to the shaft of the tenth rib. The posterior border lies beneath the cephalic border of
the eleventh rib. The whole spleen (unless enlarged) lies dorsal to a plane passed through the
midaxillary lines and is lateral to a line from the left sternoclavicular joint to the tip of the
left eleventh rib. In deep inspiration the spleen is greatly depressed and if enlarged may be
felt beneath the ribs.
Variations. — From the mean weight between 150 and 200 gm. there are wide variations. It
is not rare to find spleens weighing 80 to 100 gin. and they are recorded as light as 10 and
THE SPLEEN
1311
20 gm. On the other hand, spleens weighing 3000 to 4000 gm. are sometimes foimd. These are
usually, however, associated with an acute infectious disease, such as malaria or typhoid fever,
or a progressive metamorphosis, such as leukemia.
Congenital absence of the spleen is one of the rarest anomaUes. The presence of more than
one spleen is the commonest anomaly of the spleen. Adami has found accessory spleens to
occur in 11 per cent, of all autopsies. They are round or oblong and vary in size from a pea, or
smaller, to a walnut. There are most often one or two but there may be twenty or more.
They are found near the hilus on the dorsal side of the gastroUenal ligament, less often, in the
great omentum, in the mesentery, on the wall of the intestine, or in the tail of the pancreas.
In certain cases the left lobe of the liver is very long and prolonged far to the left and sepa-
rates the spleen from the diaphragm. This is the rule in the foetus and is often found in the
infant but is exceptional in the adult.
Exceptionally the spleen may be placed far caudal to the normal situation extending into
the iliac region and even into the pelvis. This is due in part to congenital laxness of the supports,
also to increase in weight. The spleen has been found in almost every part of the abdominal
cavity and in transposition of the viscera it is upon the right side.
One or more notches on the anterior border are present according to Parsons in 93 per cent,
of the oases, two or more in 66 per cent., but five, six, or seven much more rarely. On the pos-
terior border notches are found in 32 per cent, of the cases, and on the inferior border in 8 per
cent. In 20 per cent, of the cases a marked fissure, occasionally more than one, is found on the
diaphragmatic surface. Most frequently it begins at one of the notches in the posterior border
and passes for a distance across the surface, rarely reaching the anterior border. Occasionally
such a fissure starts from the anterior border and rarely there is such a fissure connecting with
neither border.
Fig. 1067. — Portion op Section op the Spleen of an Adult Man.
(Lewis and Stohr.)
X15.
'( 1 f
Splenic pulp
Spindle-shaped nodule
Trabeculse lienis
Central arteries in
splenic nodules
Structure. — The peritoneal covering of tlie spleen, tunica serosa, is intimately
bound to the underlying, whitish, highly elastic fibrous capsule, the tunica albu-
ginea (fig. 1067). This is composed mainly of white fibrous connective tissue but
contains numerous fine elastic fibers, and a few smooth muscle fibres. It is much
thicker than the serous covering and completely invests the spleen. From its
dee]) s\irt':ice the tunica albuginea gives off into the interior numerous trabecule,
trabeculae lienis, which join with one another and form a framework in which
course the blood-vessels, more especially the veins. It is through the contraction
of the smooth muscle fibres in the tunica albuginea and trabeculae, that the regular
periodic contraction and expansion of the spleen is produced.
In the meshes of the trabecular network, lymphoid tissue which forms the
proper splenic tissue, the pulpa lienis, is located. This is soft, friable, and dark
brownish or bluish-red in colour. In this, in a fresh spleen, are seen small round
whitish or greyish masses from .25 to 1.5 mm. in diameter, the Malpighian cor-
puscles [noduli lymphatici lienales; Malpighii].
The trabecula3 are in connection with a reticular network which permeates the spleen sub-
stance or spleen-pulp. Mall has shown that the trabeculse and vascular system together out-
1312 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
line masses of spleen-pulp about 1 mm. in diameter, known as splenic lobules. Each lobule is
bounded by three main trabeculae, from each of which secondary trabeculoB pass into the sub-
stance of the lobule incompletely subdividing it into compartments, filled with splenic pulp,
arranged in the form of anastomosing columns or cords and designated as pulp-cords. The
branches of the splenic artery, after coursing for a short distance in the main trabeculae, leave
these, and, after further division, become surrounded with a layer of adenoid tissue, which layer
presents here and there irregular thickenings forming the Malpighian corpuscles. An arterial
branch, surrounded with adenoid tissue, enters the apex of a splenic lobule, constituting its
intralobular vessel, which, soon after entering the lobule, loses its adenoid sheath and then
sends a branch to each of the above-mentioned compartments. These branches do not anas-
tomose. They give off terminal branches which course in the pulp-cords, form dilations,
ampuUse, and terminate directly or indirectly in the large venous spaces found between the pulp-
cords. From the latter the blood passes, by means of small intralobular veins, to interlobular
veins situated in the trabeculae bounding the lobules. Some of the ampullae are connected with
one another by capillary branches.
Blood-supply. — The spleen receives its blood from the splenic artery, which is very large in
proportion to the size of the organ it supplies. It divides in the phrenicolienal ligament into
from three to six or eight branches, rami lienales (fig. 1062), which enter the spleen at the hilus.
After entering the spleen the arteries divide and subdivide and run to their termination in the
ampullae without anastomosing. They form what are known as terminal arteries. The main
splenic artery is very tortuous. The vein, vena lienalis, leaves the spleen usually by the same
number of branches as the entering artery. These imite in the phrenicohenal ligament to form
a large trunk which is straighter than the splenic artery and hes caudal to it.
The lymphatics. — A superficial and a deep set of lymphatics have been described in the
spleen. The former is said to form a plexus beneath the peritoneum and the latter to be derived
from the fine perivascular spaces in the adenoid tissue around the vessels. From these several
trunks arise and joining at the hilus pass between the layers of the phrenicolienal hgament to
empty into the lymph-glands dorsal to and around the cephalic border of the tail of the pancreas.
The presence of both superficial and deep sets of lymphatics in the human spleen has been denied
by some investigators. According to Mall, there is no deep set.
The nerves. — The nerves are derived from the right vagus and from the coeliac plexus.
They enter the spleen at the hilus, accompanying the branches of the lienal artery. They are
composed mostly of non-medullated fibres which form a rich plexus around the arteries supply-
ing the muscular fibres in the media while a second group has been traced to the muscular fibres
of the trabecule.
Development of the spleen. — The first anlage of the spleen is seen in the fifth week of foetal
life as a swelling on the dorsal (left) surface of the mesogastrium. This is due to an increase in
the mesenchymal cells as well as to a thickening of the coelomic epithelium. This latter becomes
stratified, and indistinctly differentiated from the underlying embryonic connective tissue
through the transformation of the deepest of the epithelial cells into mesenchymal cells. As
development proceeds the thickened mass becomes entirely isolated and the ccelomic epithelium
covers it as a single layer.
The arteries are seen first as a capillary network throughout the organ which considerably
later become arranged as tufts of widened capillaries, the anlage, of the vascular structural unit.
These spherical groups of arterial capillaries leading by wide openings into a wide meshed venous
plexus are boimded by trabecule from the capsule. The number of structural units in the
spleen seems to be fixed fairly early but the size and complexity changes greatly. The spherical
mass with a single central artery changes to the adult condition where the central artery gives
off side branches, each of which has a spherical mass of capillaries, and the pulp intervenes
between the artery and the vein so that the capillary circulation of the early embryo becomes
the cavernous circulation of the adult. The lienal lymphatic nodules of Malpighi and the splenic
pulp appear only in the latter half of embryonic life.
THYREOID GLAND
The thyreoid gland [glandula thyreoiclea] is an extremely vascular, ductless
gland, whose internal secretion, acting as a stimulus to the tissues, has a profound
influence on the nutrition of the body and on the nervous system. It is a single
organ composed of two lateral, frequently unsymmetrical, masses, joined to-
gether by a transverse median band. The median transverse band or isthmus
[isthmus gl. thyreoidese] is thin and narrow, and often has a long slender process,
' the pyramidal lobe [lobus pyramidalis], extending from it cephalically. The lat-
eral parts or lobes [lobi, dexter et sinister] form the principal mass of the gland.
It is situated in the ventral portion of the middle third of the neck on both
sides of the larynx and the cephalic end of the trachea, dorsal to the infrahyoid
group of muscles.
The consistency of the thyreoid gland is uniformly soft and compressible. The
colour is reddish, with a brownish or yellowish cast, but becoming more bluish or
reddish with changes in its blood content.
The size is subject to considerable individual variation and is slightly greater
in women than in men. The normal thyreoid gland measures from 4 to 6 cm.
in width at its widest part. The lateral lobes measure from 5 to 8 cm. in length.
THE THYREOID GLAND
1313
about 2 cm. in width, and from 1.5 to 2.5 cm. in thickness. The right is usually a
little longer than the left. The isthmus averages from .6 to .8 cm. in thickness
and from .5 to 1.5 cm. in height.
The weight of the normal gland averages about 30 grams; but many specimens are found as
light as 20 grams, and others weigh as much as 60 grams.
When hyperemio or congested the size of the gland may be markedly augumented. This
occurs normally in most women at puberty and dm-ing menstruation and pregnancy. In
various abnormal conditions of the gland there is an increase in size, sometimes to a marked
degree. These enlargements are ordinarily grouped under the term struma or goitre, and may
be associated with either a hyper- or hyposecretion of the gland. Decrease in size is common in
old age and may appear prematurely in certain diseases.
The shape of the gland as viewed from the ventral surface is that of a capital
U with the concavity directed cephahcally (fig. 1068). The sides of the U are
formed of the more or less elongated lobes connected slightly cephahc to their
Fig. 1068. — Ventral View op the Thyreoid Gland.
t of hyoid bo
-Body of hyoid bone
Hyo-tbyreoid ligament —
Thyreoid cartilage
Thyreoid isthmus
Hyo-thyreoid membrane
Thyreo-hyoid muscle
Inferior constrictor
Sterno-thyreoid muscle
Median portion of crico-
thyreoid membrane
Crico-thyreoid muscle
Lateral lobe of thyreoid gland
thickened caudal ends by the thin transverse isthmus. In transverse sections
through the isthmus the gland is also U-shaped with the concavity directed dor-
sally, the lobes being on each side and the isthmus ventral to the trachea (fig.
1068). The surface of the gland is somewhat unevenly roughened.
The isthmus glandulae thyreoidae usually becomes wider laterally where it is
attached by its two extremities to the lateral lobes (figs. 1068, 1069). Its ventral
surface which is flat or somewhat convex is covered superficially by the sub-
cutaneous tela and skin and beneath these by the superficial and middle layers of
the cervical fascia. Between the layers of cervical fascia and close to the median
line is the sterno-hyoid muscle and more laterally and deeper the sterno-thyreoid
muscle. The dorsal surface is concave and is in relation with the first two to four
rings of the trachea and sometimes with the cricoid cartilage.
The size and form of the isthmus is subject to considerable variation. It may be very short.
Rarely it is wanting entirely or connects with but one lateral lobe. Its superior border is, as a
rule, concave and is connected in many cases with the pyramidal lobe. The caudal border,
although usually on the third ring of the trachea and 2.5 to 3 cm. from the jugular notch of the
sternum, may be especially developed so that it extends caudally beyond the lateral lobes and
produces a process which is known as the medial lobe.
i
1314 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
The pyramidal lobe is usually a narrow elongated flattened somewhat conical
process of thyreoid tissue representing the persistent portion of the median embry-
onic thyreoid (fig. 1069). Its base is attached ordinarily to the left side of the
Fig. 1069. — Thyreoid Gland, with Pthamidal Lobe and Levator Muscle.
Sterno-hyoid ligament
Sterno-hyoid muscle
Omo-hyoid
Thyreo-hyoid
Body of hyoid bone
F/— Hyo-thyreoid ligament
•llljl
Hyo-thyreoid membrane
Levator glandules thyreoidese
Thyreoid cartilage
Pyramidal lobe of thyreoid gland
Left lateral lobe
superior border of the isthmus and its apex which extends cephalically a variable
distance, often to the superior border of the thyreoid cartilage, is attached by a
fibrous cord, the thyreoid ligament.
The pyramidal lobe is not always present. Some investigators have fomid it present in
only 40 per cent of all cases ; others in as high as 90 per cent. The average is somewhere between
Fig. 1070. — Cross-section op Neck Showing Relations op the Thyreoid Gland.
(After Braune, from Porier and Charpy.)
Sterno-hyoid
--Sterno-thyroid
• Trachea
Omohyoid
'ni//|/ffl^ffll^^^^'^>^^.^^^ Platysma
laV>Cl'^'^ ^ Sterno-mastoid
■/ \ \ ■ t /'/ij'i.MlJL -- ^-J LateraMobe of
4i' \ ^ -^ ^^1 r.^f?^Kl^X il '^y'-idsland
^^>#i"'^'-A ^*>tenD«rf!>"' )|\v. "> ;;*^ 'SfflH»^^^l&.>^ A carotiscom.
^ ^^ p^=^_=^r^#;— .t-;^__— ^ l^r ^ - N. vagus
K%'''Vp'^eh"8fCSf^PfW^W^ T^ ^^'' *• ttyreoidea sup.
t^^->^,'ii'^'^*i.^M^W ^ ^^- Sympathetic trunk
^t^J^^i^MmVTi^'l ^ A. thyreoideainf.
A. vertebralis
these extremes. It is closely adherent to the subjacent structures, usually at one side of
the median line, more often the left. The superficial relations of the pyramidal lobe are
similar to those of the isthmus. Its deep surface is in relation also with the cricoid and thyreoid
cartilages, the crico-thyreoid muscle and the hyo-thyreoid ligament.
THE THYREOID GLAND 1315
The pyramidal lobe, though usually single, may be double or bifid at its caudal end, one
process joining each lateral lobe. It may be attached in the angle between the isthmus and
one of the lateral lobes, or to the lateral lobe itself. It may be cylindrical, band-hke, or swollen
at its centre or cephaho end and is occasionally entirely separate from the rest of the th}Teoid
or divided into separate detached parts, thus forming accessory th}Teoids. The apex in some
cases extends to the middle of the thyreohyoid membrane or rarely to or beyond the hyoid
bone or the process may be quite short. In the thyreoid ligament, attached to the apex,
muscle fibres are sometimes found, aberrant parts of the infrahyoid muscles, the levator of the
thyreoid gland.
The thyreoid lobes, right and left, are placed on each side of the trachea and
larynx (figs. 1068, 1069, 1070). Each lobe is somewhat pyramidal in shape and
presents for examination a base, an apex, a medial, a ventro-lateral, and a dorsal
surface.
The base is roughly convex or pointed, rarely flattened, usually at the level of
the fifth or sixth ring of the trachea (figs. 1068, 1069).
It is separated from the jugular notch of the sternum by a distance of 1.5 to 2 cm. but when
the head is extended the distance is greatly increased. It is in relation with the inferior thy-
reoid artery and numerous veins, mostly tributaries of the inferior thyreoid vein.
The apex is pointed or rounded (figs. 1068, 1069). It is directed cephalo-
dorsally and is situated at the dorsal border of the lateral lamina of the thyreoid
cartilage at the level of its caudal, or rarely its middle, third. '
It is covered by the sterno-thyreoid muscle beneath which the superior thyreoid artery
accompanied by the corresponding vein crosses the apex to reach the gland. It is also crossed
in this situation by the external ramus of the superior laryngeal nerve as it passes to the crico-
thyreoid muscle.
The medial surface of the lateral lobe is concave and intimately bound to the
trachea and cricoid cartilage (fig. 1070). Toward the apex it becomes more
flattened where it comes into contact with the lateral lamina of the thyreoid
cartilage.
At the border where this surface joins with the dorsal surface it is in relation with the
oesophagus and pharynx, and in the angle between these structures and the trachea and larynx
it is close to the recurrent laryngeal nerve.
The dorsal surface (fig. 1070) is broad and rounded caudally, but toward the
apex is reduced to a mere border. It lies upon the fascial sheath containing the
common carotid artery, the jugular vein, and vagus nerve, most intimately
related to the common carotid artery which usually produces a groove in it.
The inferior thyreoid artery sends large branches over this surface. The inferior thyreoid
veins also have large branches here. Imbedded in the connective tissue in relation with this
surface the parathyreoid bodies are found, and in some cases the recurrent nerves are placed so
far laterally that they also touch this siu-face. In many cases the sympathetic trunk and the
middle cervical ganglia of the sympathetic with the cardiac branches are closely related to the
dorsal surface of the gland.
The ventro-lateral surface is convex and is separated by loose connective tis-
sue from the overlapping sterno-thyreoid, sterno-hyoid, and omo-hyoid muscles.
More superficial on its lateral aspect is the sterno-cleido-mastoid muscle. The above
muscles are enclosed by the superficial and middle sheets of the cervical fascia. In the subcu-
taneous tela the platysma muscle spreads over the gland. This surface of the gland is
covered by a plexus of veins and by branches of the superior thyreoid artery.
Accessory thyreoid glands are small masses of glandular tissue one or more of which may
be found situated in the median line or at one side of it anywhere between the isthmus and the
root of the tongue. They vary considerably in size and represent parts of the pyramidal lobe
or isthmus which have become completely separated from the rest of the gland. In structure
they are composed of the same tissue as the rest of the gland.
Fixation. — In addition to the connective tissue which binds the thyreoid gland
to the trachea, it is attached by the connection of its capsule with the cervical
fascia and by the fibrous prolongations from the capsule.
These prolongations are found medially attaching the isthmus and adjoining portions of
the lateral lobes to the ventral surface of the cricoid cartilage, the caudal border of the thyreoid
cartilage, and the sheath of the crico-thyreoid muscles, and laterally attaching the lateral lobes
to the trachea and lateral surface of the cricoid cartilage. In addition to these the connection
of the vessels and nerves to the gland helps to fix it in position.
Structure. — The thyreoid gland like other glands is composed of a connective-
tissue stroma supporting an epithelial secreting parenchyma.
1316 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
The connective tissue which covers the surface of the gland forming for it a
capsule, may be divided into two layers, superficial and deep.
The superficial layer intimately connected with and derived from the fascia colli as pointed
out above has an important fimotion in supporting and fixing the gland. This layer is in some
cases thin and transparent; in other cases it is very tough and thick. It is connected by loose
areolar tissue with the thin deep layer of the capsule. Between these two layers the larger
vessels run for a space before entering the gland and the veins, particularly, form here con-
siderable plexuses.
From the deeper layer of the capsule numerous trabeculse and septa carrying
blood-vessels, lymphatics, and nerves pass into the gland and imperfectly separate
its parenchyma into irregular masses of variable size, the lobules [lobuli]. Each
lobule is composed of a number of closed, non-communicating, irregular, spherical,
ovoid, or sometimes branched alveoli, acini or vesicles, varying in size from .045
to .22 mm. in diameter and separated and bound together by a vascular connect-
ive tissue continuous with that surrounding the lobules and with that of the cap-
FiQ. 1071. — Arteries of the Thyreoid Gland, Anterior View. 1. Lateral lobe; 1'
pyramidal lobe; 2, trachea; 3, thjrreoid cartilage; 4, crico-thyreoid membrane; 5, hyo-thyreoid
membrane; 6, 7, 8, 9, inferior thyreoid artery and branches; 10, 11, 12, 13, 14, 15, superior;
thyreoid artery and branches; 16, thyreoidea ima. (Testut and Jacob.)
— I'l 4i
sale. The vesicles are filled with a yellowish viscous fluid, known as coUoid,
the secretion of the epithelial cells.
The vesicles are lined with a single layer of epithelial cells of a fairly uniform cuboidal or
columnar shape, becoming flattened in distended vesicles and ia old age. The cells are not
supported by a basement membrane but are in close relation with connective tissue and
capillary blood-vessels. An extremely rich lymphatic network surrounds the vesicles and the
lymph-vessels come into intimate relation with the cells. Through these vessels the secretion
is conveyed from the gland to the general circulation.
Blood-vessels. — The thyreoid gland has an extremely abundant blood-
supply. The arteries are usually four in number but occasionally five (figs.
1071-1073).
The superior thyreoid arteries divide into two, three, or more main branches which reach the
gland near the apex of the lateral lobes and supply mainly the ventral and medial surfaces of the
cephahc portion of the lobes (fig. 1071). There is usually also a dorsal branch, which anasto-
moses with a branch from the inferior thyreoid. One of the ventral branches frequently con-
nects along the cephalic border of the isthmus with its fellow of the opposite side. The inferior
thyreoid arteries break up into two or three main branches, occasionally into many fine twigs,
which reach the dorsal surface of the lateral lobes near the eaudolateral borders and supply
THE THYREOID GLAND
1317
mainly the dorsal and lateral surfaces of the caudal part of the gland (fig. 1071). There is
usually a well-marked branch which passes cephalioally to anastomose with a good-sized
branch from the superior thyreoid. Small branches are distributed to the ventral surface of the
caudal portion of the lobes and isthmus. The small fifth artery, the thyreoid ima artery,
occasionally present, ascends on the ventral surface of the trachea and reaches the gland at the
caudal border of the isthmus or of either lobe. It anastomoses with the other arteries which
may be correspondingly reduced in size. The above-mentioned arteries branch freely and are
distributed over the surface of the gland between the two layers of the capsule where they
anastomose extensively with one another and with the arteries of the opposite side. From the
surface plexus branches pass with the septa and trabeculse through the gland to break up into
the capillary plexuses around the vesicles.
The relation of the inferior thyreoid artery to the recurrent nerve is important from a
surgical point of view but unfortunately is not constant. In some cases the nerve is ventral
to the artery, more often on the right, in other cases it is dorsal and often the nerve passes be-
tween the branches of the artery. Their relation is most intimate close to the trachea Fig. 1073.
Fig. 1072. — Vessels of the Thyreoid Gland, Anterior View. 1, 2, 3, Lateral lobes and
isthmus; 4, pyramidal lobe; 5, hyoid bone; 6, thyreoid cartilage; 7, trachea; 8, common carotid;.
9, internal jugular; 10, thyreo-linguo-facial vein; 11, superior thyreoid artery; 12, inferior laryn-
geal vessels; 13, middle thyreoid vein; 14, subclavian artery; 15, inferior thyreoid artery; 16^
inferior lateral thyreoid veins; 17, inferior medial thyreoid veins; 18, left innominate vein; Ift
aortic arch; 20, vagus nerve. (Testut.)
The veins (fig. 1072) issue from the substance of the gland along the septa
which penetrate from its capsule. Between the two layers of the capsule they
form a rich plexus of large vessels from which three large branches issue on each
side.
The superior thyreoid veins leave the capsule of the ventral surfaces of the lateral lobes
near their apices and pass cephalo-laterally to empty into the internal jugular veins, sometimes
with the facial veins. The middle thyreoid veins are sometimes absent, when present they^are
often very small and pass from the lateral border of the lateral lobes laterally to empty in to' the
internal jugular vein. The inferior thyreoid veins arise from the caudal and lateral part of
the dorsal surfaces of the lateral lobes and pass caudolaterally to open into the innominate
veins. Ventral to tlie trachea, caudal to the isthmus, the two inferior thyreoid veins are
connected by numerous cross anastomoses and occasionally they open by a single trunk which
joins the left innominate vein. A thyreoidea ima vein is sometimes present.
The lymphatics of the thjTeoid gland begin as abundant plexuses arovmd the vesicles of the
gland lobules. These connect with the interlobular branches which empty into radicles
accompanying the blood-vessels through the septa to the surface of the gland where they
join a considerable plexus placed between the two layers of the capsule. From the cephalic
portion of the isthmus and lobes efferent vessels extend cephalo-medially to one or two small
i
1318 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
pre-laryngeal glands and cephalo-laterally along with the superior thyreoid artery to the deep
cervical glands. From the caudal part of the lateral lobes and isthmus efferent vessels pass
caudally to some small pre-tracheal glands and caudolaterally to the deep cervical glands.
The nerves of the thyreoid gland are probablj' all derived from the sympathetic and arise
from the middle and inferior cervical ganglia and accompany the arteries to the gland.
Development. — The thyreoid gland is first seen in very young embryos as a prominence on
the ventral wall of the pharynx. This becomes a stalked vesicle and divides into lateral lobes.
The stalk elongates forming the thyreoglossal duct of His. Later the lumen is obliterated and
the duct is then represented by an epithehal cord which soon loses its connection with the
pharynx. It opens at first cephalic to the regular second branchial arch on the summit of the
tuberculum impar but later shifts to its caudal boundary (Grosser). It is represented in the
adult only by a short blind pouch, the foramen csecum but very rarely a considerable duct may
be present. The bilobed mass appears to shift caudally, increasing m size and spreading
laterally and dorsally. The median cord of cells formed from the stalk becomes the isthmus
and the p3rramidal lobe, when this is present, the lateral portions form the lateral lobes. The
gland is now composed of irregular, in general transversely disposed cords of cells. More rapid
growth later occurs in the centres of the lateral lobes and the cell cords become closely packed
with,Jittle connective tissue between. Lumina appear in different places in the cell cords and
the cell cords are broken up into groups of cells; in these the lumina continue to appear even
up into early childhood. On each side, diverticula from the more caudal pharyngeal pouches,
the ultimobranchial bodies, come into contact with the dorsal and lateral parts of the anlage
of the thyreoid gland and become partly enclosed in the neighbourhood of the transversely
running cell cords. This core of cells becomes either a compact body or an irregular group of
cells and is probably not transformed into thyreoid tissue.
THE PARATHYREOID GLANDS
The parathyreoid glands are small masses of epithelial cells found in the neigh-
bourhood of the dorsal surface of the thyreoid gland but quite distinct from it and
Fig. 1073. — Parathteeoid Glands, Viewed Fkom Behind (Natural Size).
H — Pharynz
Common carotid ort.
i_ Branch of sup.
thyreoid art.
I — Internal jugular V.
Superior parathyreoid
p- Vagus nerve
— Lateral lobe of thyreoid
— Inferior parathyreoid
i
I
' — Inferior thyreoid art.
Recurrent (inferior
'laryngeal) nerve
I — Trachea
^(Esophagus
of different structure. They are ductless glands and although very small they are
essential to life.
The usual number is four, two on each side, in relation with the lateral lobes
of the thyreoid gland (fig. 1073) . In colour they are yellowish with more or less of
a reddish or brownish tint but lighter than the thyreoid gland. Their consistency
varies somewhat but usually it is softer than that of the thyreoid gland. The
shape of the majority of the glands is a flattened ovoid, sometimes tapering at one
or both ends, rarely a flattened circular disc. At some place on the surface there
is usually a depressed hilum where the artery enters and the vein leaves. The
average size of the glands is 6 to 7 mm. in length; 3 to 4 mm. in width and 1 to 2
mm. in thickness. Occasionally they may be found 15 mm. in length. They
THE THYMUS 1319
weigh from .01 to .1 gm. with an average of .035 gm. From their situation they
have been divided into a superior, or internal, derived from the fourth branchial
pouch, and an inferior, or external, derived from the third branchial pouch.
The superior parathyreoid glands (fig. 1073) are found, as a rule, on the dorsal surfaces of
the lateral lobes of the thyreoid gland at about the junction of the cephalic and middle thirds
Occasionally they may be situated in the areolar tissue at the level of the apex of the thyreoid
gland or cephalic to it. They may be ventral to the prevertebral layer of the cervical fascia, on
the dorsal wall of the oesophagus or pharynx and close to the dorsomedial margin of the thy-
reoid gland. They may also be placed at the level of the caudal border of the cricoid cartilagel
rarely as high as the inferior cornu of the thyreoid cartilage or as low as the sixth trachea,
ring. Sometimes they are imbedded completely in the thyreoid gland. As a rule, they are
tightly attached to the capsule of the thyreoid gland or situated between its layers.
The inferior parathyreoid glands (fig. 1073) are less constant in their situation than the
superior. They usually are found in relation with the dorsal surface of the lateral lobes of the
thyreoid glands, not far from their bases. They may be quite outside the region of the thy-
reoid gland along the carotid arteries or tlie sides of the trachea, or they may be placed more
cephalically than usual or extend caudal to the gland as far as the tenth tracheal ring, even into
the thorax. They are imbedded, when caudally placed, in fatty areolar tissue in relation with
the apex of the thymus gland and the inferior thyreoid veins or applied against the oesophagus.
The parathyreoids are intimately related to branches of the inferior thyreoid artery, a
separate branch of which supplies each of them. When there is a large branch of the inferior
thyreoid artery anastomosing with the superior they are more or less in line with this.
Each parathyreoid gland is surrounded by a fibrous capsule from which extremely vascular
septa and trabecula; penetrate into the gland separating and binding together the masses of
polyhedral cells which are arranged in solid groups or intercommunicating cords of varying
sizes and shapes.
The cell cords, as a rule, are not arranged like the thyreoid vesicles. At times the secretion
may accumulate and produce a vesicular appearance and the secretion then closely resembles
colloid. Two kinds of cells, oxyphile and principal cells, have been described; but the inter-
mediate forms suggest that these are the same sort of cells in different stages of functional
activity. The blood-vessels are distributed m the connective tissue of the trabeculae and thus
their sinusoids are brought into close connection with the cells of the gland. The nerves are
also distributed along the septa. In the highly vascular connective tissue ^between the cell
cords fat cells are found separate or in groups.
The number of parathyreoid glands found by different investigators varies. The average
number in a series of cases is less than four. Whether this is due to a real absence of the
glands or to failure to find them due to their aberrant location, their inclusion in the thyreoid
gland, or the fusion of two glands, is not clear. In some cases it is the superior glands, in
other cases the inferior glands, which appear to be missing. On the other hand various com-
petent observers have reported finding more than four parathyreoid glands. Five or six are
occasionally found; as many as eight have been recorded in one instance. In these cases the
number on a side may not be symmetrical. The increased number may be due to the separation
of buds in the course of development. The parathyreoid glands are liable to be associated with
accessory thymus masses, with small lymphatic glands, and with fat lobules; and as they may
somewhat resemble each of these, they may be mistaken unless a microscopic examination is
made.
Blood-supply. — Each parath3Teoid gland is supplied by a single separate artery derived, as
a rule, from one of the glandular, muscular, or oesophageal branches of the inferior thyreoid
artery or from the anastomosing branch between the superior and inferior thyreoid arteries.
When the glands are in aberrant positions their arteries may be derived from the nearest source.
The arteries are distributed along the trabeculae and septa. The veins returnmg the blood
either follow the arteries or they pass to the surface of the gland where they break up into a
plexus of thin-walled vessels. Upon leaving the gland the veins empty into some one of the
branches of the thyreoid veins.
Development. — The parathyreoids (epithelial bodies) begin as proliferations of the epi-
thelium on the oral and lateral walls of the dorsal diverticulum of the third and fourth pharyn-
geal pouches. The cells show early a histological differentiation with vacuolated and
reticulated plasma. The common pharyngo-branchial ducts diminish in size and become
constricted off and separated from the pharynx. The parathyreoid glands later become
independent and separated from the thymus anlages. The epithelial cells grow out in the
form of cords separated by connective tissue and in intimate relation to the blood-vessels.
Different kinds of cells are not distinguishable until postfcetal life when evidence of secretion
begins.
THYMUS
The thymus is a transitory organ of epithelial origin, but in structure resem-
bling the lymphoid tissue. Its function is not clearly understood but it seems to be
intimately associated with the growth and nutrition of the individual, and it is
classed with the ductless glands of internal secretion.
It is situated in the ventro-cephalic part of the thorax and extends into the
caudal part of the neck (fig. 1074). It lies between the two pleural sacs ventral to
the heart and great vessels, dorsal to the sternum and the sterno-thyreoid and
sterno-cleido-mastoid muscles.
1320 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
Although arising from the branchial clefts one on each side of the neck, the
two portions become so closely associated that they are usually spoken of as one.
Each of these parts is ordinarily regarded as a lobe of the thymus [lobus, dexter
et sinister].
In colour the thymus is pinkish or reddish grey in the foetus and newborn,
becoming greyish white in the adult or yellowish as it undergoes involution. It
is composed of soft, yielding tissue more friable than the thyreoid or spleen.
In size the thymus varies greatly. Under normal conditions it appears to
attain its maximum size at about the age of puberty, and to continue large as
long as the body continues to grow and then to undergo a gradual involution.
Fig. 1074. — Thymus Gland in a Child at Birth.
Thyreoid cartilage./^
Sterno - thyre oi d e u s
Crico-thyreoid
membrane
Crico-thyreoid muscle
Thyreoid gland
Right common carotid
artery
Right vagus
Right internal jugu-
lar vein
Level of sternum
Section of clavicle
Section of first rib
Section of sternum
Thyreo-hyoideus
-hyoideus
Cricoid cartilage
First ring of trachea
Trachea
Left suspensory
ligament
Left recurrent nerve
(Esophagus
Left innominate vein
Left lobe of thymus
Left internal mam-
mary artery
Left lung
Section of fifth rib
cartilage
Xiphoid process
It is, however, very sensitive to any nutritive changes of the individual and becomes very
small, even in the infant, under the influence of wasting diseases. It not infrequently exists in
the adult only as a vestige but in some cases it may remain large until middle age or later. At
birth it is usually from 50 to 60 mm. long cephalo-caudally and about half as broad.
The weight varies with the size. It is given by Hammar as over 13 gm. at birth, increasing
to double this between the sixth and the tenth years and gaining its maximum of between 37
and 38 gm. between the eleventh and fifteenth years. From this time the weight decreases
until between the ages of fifty-six and sixty-five it weighs between 25 and 26 gm. and at seventy-
five years may be as light as 6 gm. The involution of the gland is not accompanied by a cor-
responding reduction in size and weight as the thymic tissue is gradually invaded by fatty tissue
which maintains to some extent the form of the organ.
In shape the thymus is an elongated, spindle-shaped mass consisting of the
central portion or body and two extremities (figs. 1074, 1075). The body is the
THE THYMUS
1321
widest and largest part of the organ and has no distinct separation from the
extremities. The inferior extremity is also broad and is known as the base. It
rests on the pericardium, ordinarily extending as far caudal at birth as the atrio-
ventricular furrow but rarely it may extend as far as the diaphragm. The
superior extremity is much elongated and extends into the neck. It is represented
by two horns nearly always unequal in size the left being usually the larger.
It extends nearly to the thyreoid gland, in some cases reaching it.
Relations. — Topographically the thymus when well developed is divided into
cervical and thoracic parts.
The cervical portion presents for examination an anterior surface and a posterior surface.
The anterior surface is convex and is in relation with the sterno-thyreoid and sterno-cleido-
mastoid muscle. The posterior surface is concave and rests medially upon the anterior surface
of the trachea, laterally upon the common carotid artery and sometimes on the left side upon the
oesophagus.
The thoracic portion of the thymus is much more important representing four-fifths of the
organ (fig. 1075). It presents for examination an anterior, a posterior, and two lateral surfaces.
The anterior surface is dorsal to the sternum from which it is separated cephalically by the
origin of the sterno-thyreoid muscle. To a less extent it is in relation with the sterno-clavicular
articulation and comes into contact laterally with three or four of the cephalic sterno-costal
articulations and lateral to this with the internal mammary artery. The posterior surface is
largely concave and is in relation caudally with the pericardium which separates it from the
Fig. 1075.- — Thymus in an Adult
Superior mediastinum"
Cupula pleurae...
Right lung, __ I
superior lobe ")
(From Toldt's Atlas.)
A^l^'^^
U ^'K\ — sternal end of clavicle
Mediastinal
■ pleura
Mediastinal.
pleura
-— Left lung
Pleural
cavity
•vmsi.'\\.,^-:-\.k'l,t:: iiaiitiKv.s.'.
^Asi
Anterior
* mediastinal
space
right atrium and ventricular portion of the aorta and pulmonary artery. The middle part is in
relation with the aorta and to the right of this with the superior vena cava. The cephaUc part
is in relation with the branches of the aorta and superior vena cava. The lateral surfaces are
somewhat flattened and are separated from the lungs by the mediastinal pleura. The phrenic
nerve on the right side runs in the pleura near the dorsal border of this surface, on the left it is,
as a rule, not in direct contact with the thymus.
Structure. — The two lateral lobes of which the thymus is composed are rarely of the same
size; the right is usually the more strongly developed. They are joined at an oblique plane so
that the ventral surface of the right is narrow and its dorsal surface broader and the reverse
condition is found in the left lobe. The two lobes are separated from one another by connective
tissue. Rarely the two are joined by a medial portion, isthmus, near the middle or toward the
caudal end (fig. 1076).
Each lobe of the thymus is completely surrounded by a thin dehcate connective-tissue
capsule from which numerous septa extend through the gland accompanied by the blood-vessels
and nerves. The capsule is composed mainly of white fibrous connective tissue with some
elastic fibres. It rarely contains much fat in the newborn but the amount of fat increases as
development and involution proceed. Fibrous prolongations from the capsule may extend
from the apices of the lobes to be attached to the cervical fascia in the region of the lateral
lobes of the thyreoid gland, acting as suspensory ligaments for the gland.
The lobes of thymus are divided into numerous small lobules [lobuli thymi] 4 to 11 mm. in
diameter. These are of roundish or polyhedral shape with bases toward the surface where they
show as polygonal areas. The lobules are separated and also bound together by the loose
fibrous tissue septa which extend from the capsule.
Each of the primary lobules of the thymus is divided into a number of secondary lobules or
follicles 1 to 2 mm. in diameter. These lymphoid-like masses of tissue are composed of a
reticulum containing in its meshes lymphocytes or thymus corpuscles. The tissue is denser
near the surface, forming a cortex and passes gradually into a tissue with looser meshed reticulum
near the centre, medulla. In the medulla there are nests of concentrically arranged de-
generated epitheKal cells enclosing a central mass of granular cells containing colloid. These
1322 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
nests are termed the concentric corpuscles of Hassall. The cortex is subdivided by secondary
connective-tissue septa extending in from the septa between the lobules.
t,The arteries of the thymus are somewhat varied in their origin, usually derived from the
internal mammary and inferior thyreoid of each side; branches are sometimes received from the
innominate, subclavian, and superior thyreoid arteries. They reach the gland in various places
and spreading out in the capsule pass with the trabeculae through the gland to form a plexus
around each small lobule. From this capillaries pass through the cortex to the medulla.
The veins issue from the thj'mus in various places and are seen as numerous branches on its
surface. The efferent vessels drain into various veins, mostly into the left innominate vein,
also smaller branches into the internal mammary and inferior thyreoid veins.
The lymphatics arise around the small lobules and pass through the interlobular septa to
the sm-face from which they are drained into small lymph nodes near the cephalic extremity,
into glands ventrally between the thymus and the sternum, and into other glands dorsally be-
tween the thymus and the pericardium.
The nerves of the thymus are very minute. They are derived from the cervical sympa-
thetic and from the vagus and reach the thymus for the most part along with the blood-
vessels which they accompany through the septa.
Fig. 1076. — Thymus in a Child of Two Years.
Thyreoid cartilage
Seventh ring of trachea
Right carotid artery
Right subclavian artery j].
Right innominate vein
Thymus
Vena cava superior
Arch of aorta
Central portion of crico-thyreoid
membrane
Crico-thyreoideus
First ring of trachea
Thyreoid gland
Ligament connecting thyreoid and
thymus gland
Left carotid artery
Left subclavian artery
Arch of aorta
Development. — The thymus arises from the endodermal portion of the third pharyngeal
pouch on each side, as a thickening due to an increase in the epitheUal cells, followed by the
production of a diverticulum. At about the sixth week the connections of the pouches with the
branchial clefts are cut off but a strand of tissue may persist to represent the stalk. These
thick-walled cylinders become sohd cords, elongate so as to extend caudally into the thorax,
and enlarge by a series of secondary buddings. The glands of the two sides come into contact
and become intimately associated. The cephahc portion, as a rule, later atrophies and disap-
pears. Occasionally a small part of it remains near the thyreoid cut off from the rest of the
gland as an accessory thymus. From the fourth pharyngeal pouch rarely a thymus bud may
be developed which produces in the adult also an accessory thymus. The epithelial character
of the cells remains plainly evident for a time, then the characteristic differentiation into
lymphoid structure, cortex and medulla appears. The reticulum and concentric corpuscles
are undoubtedly of epithelial origin; but the thymus lymphocytes are considered by Hammar
and others as leucocytes which have migrated to the thymus, while they are regarded by
THE SUPRARENAL GLANDS
1323
Stohr and his followers as modified epithelial elements, not true blood cells. Maurer, Bruant,
and Bell regard them as modified epithelial cells which become true functional leucocytes.
THE CHROMAFFIN SYSTEM
It has recently been shown that in connection with the ganglia of the sympa-
thetic nervous system, special cells, other than the nerve cells, are found. These
differ from the nerve cells in that when subjected to the action of chromic acid
salts there can be demonstrated in their protoplasm small granules which take on
a darker stain. These cells are therefore known as chromaffin cells. They, with
the cells of the sympathetic system, are derived from the ectoderm. They ap-
pear first as indifferent cells, the sympatho-chromaffin cells. Some of these later
develop into sympathetic ganglion cells, others into chromaffin cells. Some of
these latter cells remain, isolated or in groups, permanently associated with the
sympathetic ganglia, the paraganglia; others become separated and form the
medullary portion of the suprarenal glands, the aortic paraganglia, and the
glomus caroticum.
THE SUPRARENAL GLANDS
The suprarenal glands [glandulae suprarenales] or adrenal glands are small
irregularly shaped glandular bodies composed of two quite different organs.
In the lower vertebrates these two parts are entirely separated from one another
Fig. 1077. — The Suprarenal Glands, Ventral View.
but in man and the mammals they have become joined together one within the
other. The external cortical portion, of unknown function, is developed from the
mesoderm. The internal medullary portion is derived from the sympatho-
FiG. 1078. — The Suprarenal Glands, Dorsal .View.
Marga superior
Apex
suprarenalis
Facies posterior,
'Facies posterior — t—
Basis gl. suprarenalis
chromaffin tissues and thus from the ectoderm in common with the sympathetic
nervous system. This part of the suprarenal glands is known to produce an
internal secretion which reaches the general circulation through the veins and
1324 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
whose principal function seems to be to aid in keeping up the tone and activity of
the muscle and other tissues innervated by the sympathetic system.
Situation. — The glands are deeply placed in the epigastric region (fig. 1080)
lying in the dorsal and cephalic part of the abdominal cavity, one on either side of
the vertebral column in variable relation with the upper extremity of the kidney
of the corresponding side.
Rarely they retain the fcetal relation, capping the superior extremity of the kidney and
extending a little upon both medial and lateral borders. More frequently (especially on the
left) they are placed more upon the medial borders of the kidneys, extending (on the left) as
far caudal as the hilus, sometimes coming in contact with the renal vessels. Aii intermediate
position is often found, especially on the right. In the high positions the suprarenals may be
on a level with the tenth intercostal space or eleventh rib. In the low positions they may
extend as far caudally as the first lumbar vertebra. The left is usually, but not always, a
little higher than the right, corresponding to the position of the kidneys.
Fixation. — The suprarenals, enclosed in the renal adipose capsules, are attached
to the renal fascia by connective-tissue strands and are loosely bound by connect-
ive tissue to the kidneys. The attachment to the kidneys is, however, so loose
that the suprarenals are not dislocated when the kidneys are displaced. In
addition to the attachments common to them and to the kidneys, they are joined
by connective-tissue bands to the diaphragm, vena cava, and liver on the right
side and to the diaphragm, aorta, pancreas and spleen on the left. They have also
additional means of fixation through the arteries, veins, and nerve fibres which
enter and leave them, and through the parietal peritoneum which in places
covers their ventral surfaces.
Fig. 1079. — Diagrammatic Section op the Suprarenal Gland.
Size and weight. — The size of the suprarenals is subject to considerable
variation within physiological limits, in some cases being relatively twice as large
as in others. The two glands are rarely of the same size, the right being more
often the smaller.
Proportionately they are much larger in the foetus and embryo than in the adult, but they
do not decrease in size in old age. They appear to be slightly lighter in women than in men.
The average weight in the adult is from 4 to 54 grams. As a rule, they measure about 30 mm.
in height; 7 or 8 mm. in thickness; and have a breadth at the base of about 45 mm. They
augment in volume during digestion and also increase in size during the acute infectious
diseases and in intoxications such as uremia.
Colour and consistency. — The suprarenal glands as seen from the surface
have a yellowish or brownish-yellow colour. Upon section the colour of the
surface layer appears a little darker while the central part of the gland appears
greyish or, if it contains much blood, of a reddish colour. If some httle time has
elapsed since death, the central part of the suprarenal may be almost black in
colour.
The glands are very fragile and softer in consistency than the thyroid or thymus. As a
rule, they are harder and more resistant than the fat of the adipose capsule and may be thus
readily detected in it.
Form. — The suprarenal glands are markedly flattened dorso-ventrally. Their
surfaces are roughened by irregular tubercles and furrows. They vary consider-
ably in shape (figs. 1077, 1078). The right gland is usually somewhat triangular
in outline while the left is, as a rule, semilunar. Each gland has an anterior and a
posterior surface, a base and an apex, a medial and a superior margin.
The anterior surface [facies anterior] may be either convex or concave, and
THE SUPRARENAL GLANDS
1325
look ventro-laterally. It is marked by a distinct transverse, oblique, or nearly
vertical fissure, the hilus suprarenalis. At this point a small artery enters and the
principal suprarenal vein takes exit from the gland. These surfaces are in
relation with different organs on the right and left sides.
The anterior surface of the right gland is in the greatest part of its extent in contact with the
posterior surface of the hver, upon which it produces the suprarenal impression. The medial
edge of -this surface is overlapped, cephalioally by the inferior vena cava and caudally by the
duodenum. The gland is situated between the two layers of the coronary hgament, in most
cases, in direct contact with the liver to which it is bound by loose connective tissue; but, at
times, the peritoneum which covers the ventral surface of the kidney extends for a greater or less
distance between the suprarenal and the liver.
The anterior surface of the left gland, in some cases, may be in contact in its cephalic part
with the left lobe of the liver and also, at times, with the spleen. The middle and major part
lies against the fundus and cardiac end of the stomach, while caudally the suprarenal is often
Fig. 1080. — Ventral View of the Supbarenal Glands, in Situ. X 3. (From Toldt's
Atlas.)
Hepatic veins Diaphragm, pars lumbalis
Left suprarenal
crossed by the tail of the pancreas and the splenic artery and vein. The whole or a large part of
the anterior surface of the left suprarenal is covered by the parietal peritoneum of the omental
bursa.
The posterior surface [facies posterior] of both the suprarenals is distinctly
smaller than the anterior surface. It is flat or convex and looks dorso-medially.
It is in relation with the lumbar part of the diaphragm, to which it is bound by connective
tissue, but from which it is separated by an extension of the renal adipose capsule.
The base [basis gl. suprarenalis] is a narrow elongated surface distinctly
hollowed out, which lies in contact with the superior extremity of the kidney or its
medial margin, cephalic to the hilus.
This surface looks dorsally, laterally, and somewhat caudally with the result that it extends
farther on the anterior surface than on the posterior surface of the kidney.
The medial border [margo medialis] is sharp, thin, and irregularly convex. It
extends more or less vertically to meet the superior border.
On the right it hes dorsal to the inferior vena cava cephalically and to the duodenum caudally
and is close to, if not in contact with, the sympathetic cceliac ganglion. On the left the medial
border lies dorsal to the stomach and caudally may be crossed by the pancreas and splenic
vessels. It is in close proximity to the aorta and the coeliac sympathetic ganghon.
The superior border [margo superior] is sharp and thin and differs somewhat
on the two sides.
1326 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
On the right it is irregular, straight or convex, and extends, dorsal to the liver, obliquely
cephalo-medially to meet the medial border in a more or less acute point, apex suprarenalis,
which is directed cephaUcally and somewhat medially. On the left the superior border is
irregularly convex in shape and nearly horizontal in direction. It passes gradually over into
the medial border without the intervention of any distinct apex. It is dorsal to the stomach
and in some cases comes into contact with the spleen.
Accessory suprarenal glands [gl. suprarenales accessoriEe] are often foimd in the connective
tissue in the neighbourhood of the principal organs. They are also sometimes found in the
kidney near the internal spermatic veins and in the region of the sexual glands. The structures
recorded as accessory suprarenal glands may be complete suprarenal glands composed of the
cortex and medulla or they may be composed of the cortex only. Masses of chromaffin tissue
representing the medulla are sometimes spoken of as accessory suprarenals but these more
properly belong with the chromaffin system.
Complete absence of the suprarenal glands has been recorded only in monsters with grave
cranial and cephafic defects. Absence of one gland has been found and the fusion of the two
has also been noted.
Structure. — The suprarenal glands are surrounded by a thin and tough fibrous
capsule composed mainly of white fibrous connective tissue. From the capsule
numerous trabeculse are given off which pervade the gland and form septa between
the groups and rows of cells. Within the capsule the suprarenal is composed of
an external firmer yellowish layer, the cortex [substantia corticalis], and an internal
softer whitish layer, the medulla [substantia meduUaris] (fig. 1079).
On section the cortex is seen to form by far the greater part of the gland and it is marked
radially from the centre toward the surface by darker and lighter streaks. In its deepest
part it is brownish yellow or red and is usually slightly torn where it joins the medulla. As
frequently found at autopsy the cortex is separated from the medulla by a sUt filled with a
soft dark brown or blackish mass caused by the breaking down of the deeper layer of the cortex.
The medulla is a greyish, spongy, vascular mass which often because of its blood content appears
of a reddish or reddish-brown colour.
The cortical portion of the gland is subdivided into a superficial, glomerular portion,
zona glomerulosa; an intermediate, fascicular portion, zona fasciculata; and an internal
reticular portion, zona reticulata, according to the peculiar grouping of the gland cells in these
respective areas.
In the glomerular zone the cells are of irregular columnar shape, and grouped in coiled
columns. In the fascicular zone the cells, which are of polyhedral shape, are arranged in more
or less regular parallel columns, while in the reticular zone the cells form trabecute or groups.
The reticular connective-tissue framework, continuous with the capsule, surrounds the cell
masses and cell columns of the several zones. The cells of the medulla show an affinity for
chromic acid — chromaffin cells — and are grouped in irregular masses separated by septa of the
reticulum and venous spaces. The arteries form a close-meshed plexus in the capsule from
which branches run more or less parallel toward the medulla forming a network around the
cell columns of the glomerular and fascicular zones. This opens into a venous plexus of wide
calibre in the reticular zone, which is connected with the vessels of the medulla. Small medul-
lary arteries pass through the cortex without branching to end in a venous plexus in the medulla.
The abundant wide-meshed venous sinuses in the medulla (sinusoids) join to form small
central veins which converge towai'd the centre of the medulla to form the large central vein.
Vessels and nerves. — The suprarenal glands are richly supplied with vessels.
The arteries are three — superior, middle and inferior.
From the inferior phrenic artery, the superior suprarenal artery arises and passes toward the
superior border of the gland. From the aorta the middle suprarenal artery takes origin between
the coehac and superior mesenteric arteries and passes toward the medial border of the supra-
renal. It is a branch of this artery which is usually found at the hilus along with the central
vein. From the renal artery the inferior suprarenal artery arises and reaches the suprarenal
near its base. These three arteries anastomose with one another and form a plexus in the
capsule of the suprarenal from which the arteries for the interior of the gland are derived.
The large central vein from the medulla passes through the cortex to emerge at the hilus
as the suprarenal vein, vena suprarenalis. The right vein opens usually into the inferior vena
cava, where there is a valve, the left into the left renal vein. There may also be small branches
connecting with the phrenic or the right renal vein.
The lymphatics of the suprarenals are very numerous and are represented by a superficial
plexus in the capsule and a deep plexus in the medulla. These are connected by numerous
anastomoses. They pass medially and converge into a number of trunks on each side which
empty into lymph-glands situated along the aorta near the origin of the renal arteries. On the
left side there is also the communication through the diaphragm with a posterior mediastinal
gland.
The nerves are derived chiefly from the coeliac and renal plexuses but include filaments
from the splanchnics, and according to some authors from the phrenic and vagus nerves also.
These numerous fine twigs connect with the gland in many different places and form a rich
plexus. Branches are distributed to the capsule, to the cortical substance, and to the medullary
substance. Groups of sympathetic ganglion cells are found in the medullary part of the gland.
Development. — The suprarenal glands of mammals have their origin from two sources.
The cortical mesodermic portion of the glands arises in early embryos as buds extending from
THE CAROTID BODY 1327
the mesothelium on both sides of the root of the mesentery into the mesoderm ventral to the
aorta. A little later these become definite organs completely separated from the coelomic
epithelium and are soon vasoularised, but the central vein does not become visible until con-
siderably later. The suprarenal glands after their separation from the peritoneum form a
ridge on either side of the posterior wall of the ca4om medial to the mesonephros. Some little
time after the origin of the cortical portion of the gland has undergone cellular differentiation
and has become surrounded by a delicate capsule, the medullary portion is formed by the
migration of masses of sympatho-chromaffin cells from the medial side toward the centre of the
organ so that they surround the central vein as the anlage of the medullary nucleus. They
penetrate the cortical portion of the gland as development proceeds and become completely
surroimded by it. These migrating masses are entirely or for the most part of chromaffin
formative cells derived from the ectoderm. They are clearly differentiated from the cortical
cells by their small size and darker colour, in stained sections. Migration of these cell masses
into the gland seems to be continued even after birth. The differentiation of the cortex into
three layers occurs late in development. The suprarenal glands are relatively large in foetal
life; and their relation to the kidneys is secondarily acquired.
THE GLOMUS CAROTICUM
The carotid bodies [glomera carotica] are small ovoid or spherical bodies
found at or near the point where the common carotid arteries divide into the inter-
nal and external carotids (fig. 1081). They are usually on the dorsal and medial
side of the angle of bifurcation of the arteries. There is ordinarily one body on
Fig. 1081. — The Glomus Caroticum (Carotid Body). (From Testut, after Prince-
teau.) 1, Carotid body; 2, 3, 4, common, external and internal carotids; 5, int. jugular; 7, inf.
cervical .sympathetic ganglion; 8, vagus.
each side, 5 or 6 mm. in length and 2 or 3 mm. in thickness. It is reddish-yellow
in colour and is attached to the carotid by fibrous tissue and by the vessels and
nerves which enter it. A small special fibrous band may sometimes be recog-
nised binding it to the common, external or internal carotid artery.
The carotid body or gland is composed of two essential parts: (1) round, oval, or polyhedral
epithelial cells which contain chromaffin granules, and are bound together by a mass of fibrous
connective tissue; and (2) a rich plexus of capillaries and sinusoids forming a mesh. Large
lymph-vessels surround the outside of the gland. The carotid gland has a very abundant
nerve supply, mostly from the sympathetic system, and ganglion cells are foimd in it. It may
receive twigs from the superior laryngeal, hypoglossal, or glossopharyngeal nerves, as recorded
by some observers.
The size of the carotid body varies considerably. At times the carotid bodies are absent; in
other cases they are so small that they can be detected only in microscopic sections; occasionally
they are 8 mm. in length by 4 or 5 mm. in thickness. Rarely the carotid bodies may be broken
up into two or more smaller masses boimd together by connective tissue. The carotid body
may be larger in old individuals due to an increase in the connective tissue or vascular elements
with a corresponding decrease in the epithehal cells. The origin is probably from sympatho-
chromaffin cells but some investigators believe that they are derived from the endothehum of the
blood-vessels and others that they arise from the endoderm of a branchial pouch.
1328 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS
Figs. 1082 and 1083. — Aortic Paraganglia. (Zuckerkandl.)
Aorta
Sympathetic trunk-
Aortic paraganglia^
Left renal artery
inferior mesenteric artery
- — Plexus aorticus
\ifc*
Common iliac artery
Vena cava int. Aorta
«*#
Right paraganglion -
■Left renal vein
Ureter
Left paraganglion
Inferior mesenteric artery
Plexus aorticus
'"Common iliac artery
REFERENCES FOR SKIN AND DUCTLESS GLANDS
THE AORTIC PARAGANGLIA
1329
The abdominal chromaffin bodies, the paraganglia aortica, or paraganglia
lumbalia, are situated on each side of the abdominal aorta near the point of origin
of the inferior mesenteric artery (figs. 1082, 1083). They are elongated, flat-
tened, ovoid bodies, softer and greyer than the lymphatic glands and extremely
variable in size.
They measure, as a rule, between 6 and 12 mm. in length, although occasionally as long as
30 mm. or as short as 1 mm. They may be connected by transverse bands in front of the
aorta or occur as scattered nodules in this situation. They are intimately related to the aortic
sympathetic plexus and at least one of them is uniformly found. They consist of a mass of
chromaffin cells surrounded by a rich capillary plexus and contain many nerve fibres and nerve
cells.
THE GLOMUS COCCYGEUM
The coccygeal body [glomus coccygeum] is a small, spherical greyish-red body
consisting of a median unpaired mass 2 to 3 mm. in diameter, single or divided
into three to six connected nodules. It is placed immediately ventral to the tip
FiQ. 1084. — Coccygeal Gland, in Sittt. 1, Sacrum; 2, coccyx; 3, coccygeal gland; 4,
middle sacral artery; 5, 6, sacral sympathetic; 7, ganglion impar.; 8, last sacral; 9, coccygeal
nerve; 10, gluteus maximus; 11, ischio-coccygeus; 12, levator ani; 13, ano-coccygeal raphe.
(Testut.)
of the coccyx, imbedded in fat and in relation with the terminal branch or branches
of the medial sacral artery, with the ischio-coccygeal muscles, and fibres of the
sympathetic nervous system (fig. 1084).
It is composed of groups of epithelial cells bound together by a mass of fibrous tissue and
containing a plexus of sinusoidal capillary vessels in intimate relation with the cells. Numerous
nerve fibres also enter the gland. It is not certain that the cells are chromaffin in character or
that the coccygeal body has an internal secretion.
A. References for the skin and mammary gland. — General and topographic: Quain's
Anatomy, 11th ed., vol. ii, pt. 1; Testut, Traits d'Anatomie Humaine, 4th ed .; Poirier-Charpy,
Traits d'Anatomie, vol. v; Rauber-Kopsch, Lehrbuoh der Anatomie, 9th ed.; Bardeleben,
Handbuch der Anatomie, vol. v, pt. 1; Merkel, Topographische Anatomie; Corning, Lehrbuoh
der topographischen Anatomie. Development: Keibel and Mall, Human Embryology. Skin:
Heidenhain, Anat. Hefte., vol. xxx; Kean (finger prints), Jour. Amer. Med. Assoc, vol. xlvii;
Unna (blood and lymph), Arch. f. mikr. Anat., vol. Lx.xii; Botezat (nerves) Anat. Anz., vol.
xxxiii. Nails: Branca, Annales de Dermat. et SyphQis, 1910; Mammary glands; Kerr, Buck's
Ref. Hand. Med. Sci. (Breast) vol. 4, 1914.
B. References for the ductless glands. — General and topographic: Quain's Anatomy,
11th ed. ; Testut, Trait6 d'Anatomie Humaine, 4th ed., vol. iv; Poirier-Charpy, Traite d'Anatomie
vol. iv.; Rauber-Kopsch, Lehrbuch der Anatomie, 9th ed.; Merkel, Topographische Anatomie;
Corning, Lehrbuch der topographischen Anatomie, 3rd ed. Development: Keibel and Mall,
Human Embryology. Spleen: Shepherd, Jour. Anat. and Physiol., vol. x.xxvii; Mall, Amer.
Jour. Anat., vol. ii. Thyreoid: Marshall, Jour. Ansit. and Physiol., vol. xxix. Parathyreoids:
Forsyth, Brit. Med. Jour., 1907; Rulison, Anat. Rec, vol. iii;Halsted and Evans, Annals of Surg.,
vol. xlvi. Thymus: Hammar, Erbge. d. Anat. u. Entwick., Bd., xix. Suprarenal glands:
Gerard, Georges et Maurice, Bull. Mem. Soc. Anat. Paris, 1911, (6) T. 13; Ferguson, J. S.,
Amer. Jour. Anat., vol. v, 1905. Carotid body: Gomez, .L. P., Am. .tour. Med. Sci., vol. cxxxvi;
Aortic paraganglia; Zuckerkandl, Verhandl. d. Anat. Gesell., 15th Versamm., 1901.
I
SECTION XIII
CLINICAL AND TOPOGRAPHICAL
ANATOMY
Revised for the Fifth Edition
Bt JOHN MORLEY, Ch.M., F.R.C.S.
HONORARY SURGEON, ANCOAT's HOSPITAL, MANCHESTER; LECTURER IN CLINICAL
ANATOMY, MANCHESTER UNIVERSITY
THE HEAD
IN describing the clinical and topographical relations, the divisions of the body-
will be successively considered in the following order: headj neck, thorax,
abdomen, pelvis, back, upper and lower extremities.
The bony landmarks of the head will first be considered, followed by a separate
description of the cranium and the face.
Bony landmarks. — These should be studied with the aid of a skull, as well as
on the hving subject. Beginning in front is the nasion, a depression at the root of
the nose, and immediately above it, the glabella, a slight prominence joining the
two supracihary arches. These points mark the remains of the frontal suture, and
the junction of the frontal, nasal, and superior maxillary bones and one of the sites
of a meningocele. In the middle line, behind, is the external occipital protuber-
ance, or inion, the thickest part of the vault, and corresponding internally with
the meeting-point of six sinuses. A line joining the inion and glabella corresponds
to the sagittal, and occasionally the frontal, suture, the falx cerebri, the superior
sagittal sinus, widening as it runs backward, and the longitudinal fissure of the
brain. From the inion the superior nuchal hues pass laterally toward the upper
and back part of the base of the mastoid processes, and indicate the first or so-
called horizontal part of the transverse (lateral) sinus.
This vessel usually presents a varying curve upward and runs in the tentorium. The second
or sigmoid portion turns downward on the inner surface of the mastoid, then forward, and lastly
downward again to the jugular foramen, thus describing the double curve from which this
part takes its name. In the jugular foramen the vessel occupies the posterior compartment;
its junction with the internal jugular is dilated and forms the bulb. A line curved downward
and forward from the upper and back part of the base of the mastoid, reaching two-thirds of
the way down toward the ape.x, will indicate the second part of the sinus. The spot where it
finally curves inward to the bulb would be about 1.8 cm. (J in.) below and behind the meatus.
The two portions of the transverse sinus meet at the asterion laterally; at the entry of the
superior petrosal sinus medially. The right transverse sinus, the larger, is usually a continua-
tion of the superior sagittal sinus, and, therefore, receives blood chiefly from the cortex of the
brain; the left, arising in the straight sinus, drains the interior of the brain and the basal ganglia.
Each transverse sinus receives blood from the temporal lobe, the cerebellum, diploe, tympanic
antrum, internal ear, and two emissary veins, the mastoid and posterior condylar.
About 6 . 2 cm. (2| in.) above the external occipital protuberance is the lambda,
or meeting of the sagittal and lambdoidal sutures (posterior f ontanelle, small and
triradiate in shape) . It is useful to remember, as guides on the scalp to the above
two important points, that the lambda is on a level with the supraciUary ridges,
and the external occipital protuberance on one with the zygomatic arches.
Below the external occipital protuberance, between it and the foramen magnum, an occip-
ital, the commonest form of cranial meningoceles, makes its appearance. It comes through
the median fissure in the cartilaginous part of the squamous portion of the bone.
1331
I
1332 CLINICAL AND TOPOGRAPHICAL ANATOMY
The point of junction of the occipital, parietal, and mastoid bones, the asterion,
is placed about 3 . 7 cm. (1| in.) behind and 1 . 2 cm. (| in.) above the centre of the
auditory meatus (fig. 1085). It indicates the site of the posterior lateral fon-
tanelle and just below it the superior nuchal line terminates. The bregma, or
junction of the coronal, sagittal, and, in early life, the frontal suture (anterior f on-
tan elle, large and lozenge-shaped), lies just in front of the centre of a line drawn
transversely over the cranial vault from one pre-auricular point to the other (fig.
1090) . The bregmatic f ontanelle normally closes before the end of the second year.
The lambdoid fontanelle is closed at birth. The pterion, or junction of the frontal
and sphenoid in front, parietal and squamous bones behind, lies in the temporal
fossa, 3.7 to 5 cm. (IJ to 2 in.) behind the zygomatic process of the frontal, and
about the same distance above the zygoma (fig. 1085). This spot also gives the
position of the trunk and the anterior and larger division of the middle meningeal
artery (fig. 1090), the Sylvian point and divergence of the limbs of the lateral
(Sylvian) fissure, the insula (island of Reil), and middle cerebral artery. It,
further, corresponds to the anterior lateral fontanelle. On the side of the skull
the zygomatic arch, the temporal ridge, and external auditory meatus need atten-
tion. That important landmark, the zygomatic arch, wide in front where it is
formed by the zygomatic (malar), narrowing behind where it joins the temporal,
gives off here three roots, the most anterior marked by the eminentia articularis,
in front of the mandibular (glenoid) fossa, the middle behind this joint, while the
posterior curves upward and backward to be continuous with the temporal ridge.
Within the zygomatic arch lie two fossae separated by the infra-temporal (ptery-
goid) ridge : above is the temporal, with the muscle and deep temporal vessels and
nerves; below is the infra-temporal or zygomatic fossa, with the lower part of the
temporal muscle, the two pterygoids, the internal maxillary vessels, and the man-
dibular division of the fifth. To the upper border of the zygomatic arch is attached
the temporal fascia, to its lower, the masseter. Its upper border marks the level
of the lower lateral margin of the cerebral hemisphere. A point corresponding to
the middle root of the zygoma, immediately in front of the tragus, and on a level
with the upper border of the bony meatus, is called the pre-auricular point.
Here the superficial temporal vessels and the auriculo-temporal nerve cross the
zygoma, and a patient 's pulse may be taken by the anaesthetist. The lower end of
the central (Rolandic) fissure lies 5 cm. (2 in.) vertically above this point. The
temporal ridge, giving origin to the temporal fascia, starts from the zygomatic proc-
ess of the frontal, and becoming less distinct, curves upward and backward over
the lower part of that bone, crosses the coronal suture, traverses the parietal bone,
curving downward and backward to its posterior inferior angle. Here it passes
on to the temporal, and passing forward over the external auditory meatus, is
continuous with the posterior root of the zygoma. Below the root of the zygoma
will be felt the temporo-mandibular joint, and when the mouth is opened, the con-
dyle will be felt to glide forward on the eminentia articularis, leaving a well-marked
depression behind.
The external auditory meatus, measured from its opening on the concha to the membrane,
is about 2.5 cm. (1 in.) in length; if from the tragus, 3.7 cm. (1^ in.). Its long axis is directed
medially and a little forward with a slight convex curve upward, most marked in its centre.
Between the summit of this curve and the membrane is a sUght recess in which foreign bodies
may lodge. The lumen is widest at its commencement, narrowest internally. To bring the
cartilaginous portion in line with the bony, the pinna should be drawn well upward and back-
ward. In the bony portion the skin and periosteum are intimately blended, thus accounting
for the readiness with which necrosis occui's. The sensibility of the meatus is explained by
the two branches sent by the auriculo-temporal nerve. The fact that the deeper part is supplied
by the auricular branch of the vagus explains the vomiting and cough occasionally met with in
affections of the meatus.
The anterior inferior angle of the parietal bone, and its great importance as a landmark,
have already been noted. The posterior inferior angle of tliis bone (grooved by the transverse
(lateral) sinus) lies a httle above and behind the base of the mastoid, on a level with the roots
of the zygoma (fig. 1085). Just below and in front of the tip of the mastoid the transverse
process of the atlas can be made out in a spare subject.
In front, the circumference of the bony orbit can be traced in its whole extent.
The supraorbital notch lies at the junction of the medial and intermediate thirds of
the supraorbital arch. When this notch is a complete foramen, its detection is
much less easy. To its medial side the supratrochlear nerve and frontal arterd
cross the supraorbital margin; like the supraorbital, this nerve and vessel lie, at
THE CRANIUM
1333
first, in close relation with the periosteum. The frontal artery is one of the chief
blood-supplies to flaps taken from the forehead. Owing to the paper-like thin-
ness of the bones on the medial wall of the orbit, e. g., lacrimal, ethmoid, and
body of sphenoid, and the mobihty of the skin, injuries which are possibly pene-
trating ones, as from a slate-pencil, ferrule, etc., are always to be looked upon with
suspicion. After a period of latency of symptoms, infection of the membranes
and frontal abscess have often followed. Above the supraorbital margin is the
supraciliary arch, and higher still the frontal eminence [tuber frontale].
FiQ. 1085. — The Skull, showing Kronlein's Method of Ckaniocerebral Topography.
THE CRANIUM
Under this heading will be considered the scalp, the bony sinuses, cranio-
cerebral topography and the hypophysis.
The scalp. — The importance of the scalp is best seen from an examination
of its layers (fig. 1086). These are — (1) skin; (2) subcutaneous fat and fibrous
tissue; (3) the epicranius (occipito-frontalis) and aponeurosis; (4) the sub-
aponeurotic layer of connective tissue; (5) the pericranium.
The first three layers are connected and move together. The thick skin
supported by the dense fibrous subcutaneous layer and epicranial aponeurosis, is
well adapted to protect the underlying skull from the effects of trauma, and in
this connection the mobility of the first three layers on the subaponeurotic areolar
tissue is important. A scalp wound does not gape widely unless it involves the
epicranial aponeurosis, in which case it involves the subjacent "dangerous area"
of the scalp, so-called because pus in this laj^er maj^ spread widely underneath
the scalp and even give meningeal infection by spreading through the diploic or
emissary veins. In the process of scalping (whether performed by the knife or
by the hair being caught in machinery), separation takes place at this sub-
aponeurotic layer which is loose, delicate and devoid of fat.
The numerous sebaceous glands frequently give rise to cj'sts in the scalp.
1334
CLINICAL AND TOPOGRAPHICAL ANATOMY
The epicranius and aponeurosis have been described elsewhere (p. 336).
The pericranium differs from periosteum elsewhere in that it gives little
nourishment to the bone beneath, which derives most of its blood-supply from
the meningeal vessels. After necrosis of the skull there is no tendency to the
formation of an involucrum of new subperiosteal bone as in the long bones.
The pericranium is firmly adherent to the sutures of the skull bones, so that any
subpericranial effusion of blood or pus is limited by the sutures.
Of the vessels of the scalp, the arteries, arising in the anterior region from
the internal, in the posterior from the external, carotid, are peculiar in their
position. Thus they he superficial to the deep fascia, which is here represented
by the aponeurosis (fig. 1086). From this position arises the fact that a large
flap of scalp may be separated without perishing, as it carries its own blood-
vessels. From the density of the layer in which the vessels run they cannot
retract and are difficult to seize, haemorrhage thus being free. Finally, from
their position over closely adjacent bone, ill-applied pressure may easily lead to
sloughing. A practical point with regard to the veins is given below. The
lymphatics from the front of the scalp drain into the anterior auricular and
parotid, those behind into the posterior auricular, occipital and deep cervical
nodes. The nerves are derived from all three divisions of the trigeminus, from the
Fig. 1086. — Section through the Scalp, Skull, and Duka Mater. (Tillaux.)
Skin and superficial
fascia with
^ hair bulbs and sebace-
glands
/ Fat pellets
Epicranial aponeu-
Skull: diploic tissue
facial (motor) and also from three branches of the second and third cervical.
The supply from the fifth explains the neuralgia in acute iritis, glaucoma, and
herpes frontahs, and also the pains shooting up from the front of the ear in late
cancer of the tongue.
The emissary veins. — These are communications between the sinuses within,
and the veins outside, the cranium. Most of them are temporary, corresponding
to the chief period of growth of the brain. Thus in early life, when the develop-
ment of the brain has to be very rapid, owing to the approaching closure of its
case, a free escape of blood is most essential, especially in children, with their
sudden explosions of laughter and passionate crying!
The gravity of these emissary veins and their free communications with others
are shown by the readiness Avith which they become the seat of thrombosis, and
thus of blood-poisoning, in cranial injuries, erysipelas, infected wounds of the scalp,
and necrosis of the skull. They include the following:
1. Vein through the foramen OEecum, between the anterior extremity of the superior sagittal
sinus and the nasal mucous membrane. The value of this temporary outlet is well seen in the
timely profuse epistaxis of children. Other more permanent communications between the skuD
cavity arid nasal mucous membrane pass through the ethmoid foramina. The fact that the
nasal mucous membrane is loose and ill-supported on the nasal conchas ( turbinate bones)
allows its vessels to give way readily, and thus forms a salutary safeguard to the brain, warding
off many an attack of apoplexy. 2. Vein thi-ough the mastoid foramen, between the transverse
THE BONY SINUSES 1335
(lateral) sinus and the posterior auricular and occipital veins. This is the largest, the most
constant, and the most superficial of the emissary veins. Hence the old rule of applying
blisters or leeches over it in cerebral congestion. 3. Vein through the posterior superior angle
of the parietal between the superior sagittal sinus and the veins of the scalp. 4. Vein through
the condyloid foramen between the transverse (lateral) sinus and the deep veins of the neck.
5. Vein through the hypoglossal canal between the occipital sinus and the deep veins of the
neck. 6. Ophthalmic veins communicating with the cavernous sinus and the angular vein.
These veins may be the source of fatal blood-poisoning, by conveying out of reach septic
material, in acute periostitis of the orbit, or in osteitis, of dental origin, of the jaws. 7. Minute
veins through the foramen ovale between the cavernous sinus and the pharyngeal and pterygoid
veins. 8. Communications between the frontal diploic and supraorbital veins, between the
anterior temporal diploic and deep temporal veins, and between the posterior temporal and
occipital diploic veins and the transverse sinus. In addition to the veins specially mentioned,
the scalp and sinuses communicate by numerous diploic veins, by those in the inter-sutural
membrane, and thi'ough sutures before their obliteration, as already explained.
Structure of cranium. — Two layers and intervening cancellous tissue. Each
layer has special properties. The outer gives thickness, smoothness, and uni-
formity, and, above all, elasticity. The inner is whiter, thinner, less regular —
e. g. the depressions for vessels. Pacchionian bodies, dura mater, and brain.
The diploe, formed by absorption after the skull has attained a certain thickness,
reduces the weight of the skull without proportionately reducing its strength, and
provides a material which will prevent the transmission of vibrations.
A blow on the head may fracture the internal layer only, the external one and diploe escap-
ing. This is difficult to diagnose, and thus it is impossible to judge of the severity of a fracture
from the state of the external layer. This may be whole, or merely cracked, while the-internal
shows many fragments, which may set up meningitis or other mischief. It is usual to find more
extensive splintering of the inner than of the outer layer (table).
The average thickness of the adult skull-cap is about 5 mm. (\ in.). (Holden.) The
thickest part is at the external occipital protuberance, where the bone is often 1.8 cm. (| in.)
in thickness. The thinnest part of the skull vault is over the temporal part of the squamous.
The extreme fragility of the skull here is partly compensated for the by thickness of the soft
parts; these two facts are always to be remembered in the diagnosis of a fracture of the skull
here, after a slight injury. Other weak spots are the medial wall of the orbit, the cerebellar
fossae, and that part of the middle fossa corresponding to the glenoid cavity.
Anatomical conditions tending to minimise the effects of violence inflicted upon the skull. —
(1) The density and mobility of the scalp. (2) The dome-like shape of the skull. This is cal-
culated to bear relatively hard blows and also to allow them to glide off. (3) The number of
bones tends to break up the force of a blow. (4) The sutures interrupt the transmission of
violence. (5) The inter-sutural membrane (remains of fcetal periosteum) acts, in early life,
as a linear buffer. (6) The elasticity of the outer layer (table). (7) The overlapping of some
bones, e. g. the parietal by the squamous; and the alternate bevelling of adjacent bones, e. g. at
the coronal suture. (8) The presence of ribs, or groins, e. g. (a) from the crista galli to the
internal occipital protuberance; (b) from the root of the nose to the zygoma; (c) the temporal
ridge from orbit to mastoid; (d) from mastoid to mastoid; (e) from external occipital protu-
berance to th? foramen magnum. (9) Buttresses, e. g. zygomatic processes and the greater
wing of the sphenoid. (10) The mobility of the head upon the spine.
THE BONY SINUSES
Frontal. — When well developed, the frontal sinuses may reach 5 cm. (2 in.)
upward and 3.7 cm. (1| in.) laterally, occupying the greater part of the vertical
portion of the frontal bone. When very small, they scarcely e.xtend above the
nasal process. In any case, they are rarely symmetrical. The average dimen-
sions of an adult frontal sinus are 3.7 cm. (IJ in.) in height, 2.5 cm. (1 in.) in
breadth, and 1.8 cm. (f in.) in depth. (Logan Turner.) The sinuses are sep-
arated by a septum. The posterior wall is very thin. Each sinus narrows
downward into the infundibulum. This is 'deeply placed, at the back of the
cavity, behind the frontal (nasal) process of the maxilla and near the medial wall
of the orbit. Its termination in the middle meatus is about on a level -mth the
palpebral fissure.' (Thane and Godlee.) Its direction is backward.
The communication of these sinuses with the nose accounts for the frontal headache, the
persistence of polypi and ozsena, and the fact that a patient with a compound fracture opening
up the sinuses can blow out a flame held close by.
To open the frontal sinus, while the incision which leaves the least scar is one along the
shaved eyebrow, superficial laterally so to avoid the supraorbital nerve and vessels, running a
little downward at the medial end, it is always to be remembered that, where the sinuses are
little developed, this or a median incision may open the cranial cavity. To avoid this compli-
cation the sinus should always be opened at a spot vertically above the medial angle.
The development of these by the twentieth or twenty-fifth year may render a fracture
1336
CLINICAL AND TOPOGRAPHICAL ANATOMY
here much less grave in the adult than would otherwise be the case, the inner layer (table), if now
separated from the outer, protecting the brain. Mr. Hilton showed that the absence of any
external prominence here does not necessarily imply the absence of a sinus, as this may be formed
by retrocession of the internal layer. In old people these sinuses may enlarge by the inner
layer following the shrinking brain. Again, prominence of the supracOiary and frontal
eminences does not necessarily point to the existence of a sinus at all, being due merely to a
heaping up of bone.
The mastoid cells are arranged in two groups, of the utmost importance in that
frequent and fatal disease, inflammation of the middle ear: — (A) The upper, or
'antrum,' present both in early and late life, horizontal in direction, closely adja-
cent to and communicating with the tympanum. (B) The lower, or vertical.
This group is not developed in early life.
A. Tympanic antrum (fig. 1088). — This is a small chamber lying behind the
tympanum, into the upper and back part of which (epitympanic recess) it opens.
Its size varies, especially with age. Almost as large at birth, it reaches its maxi-
mum (that of a pea) about the third or fourth year. After this its size usually
diminishes somewhat, owing to the development of the encroaching bone around
Fig. 1087. — Tempobal Bone, showing Suprambatal Triangle. (Barr.)
The lower part of the transverse sinus is here placed too far back to be relied upon with con-
stant accuracy.
Root of zygoma
Suprameatat
triangle
Position for
~^ perforating
vertical cells
it. Its roof, or tegmen, is merely the backward continuation of the tegmen
tympani. The level of this is indicated by the posterior root of the zygoma.
'The level of the floor of the adult skull at the tegmen antri is, on an average, less
than one-fourth of an inch above the roof of the external osseous meatus; in
children and adolescents, from one-sixteenth to one-eighth of an inch.' (Mac-
ewen.) In early life, when the bony landmarks, e. g. the suprameatal crest (fig.
1087), are little marked, the level of the upper margin of the bony meatus will be
the safest guide to avoid opening the middle fossa.
The lateral wall of the antrum is formed by a plate descending from the
squamous bone. This is very thin in early life, but as it develops by deposit
under the periosteum, the depth of the antrum from the surface increases.
Macewen gives the average of the depth as varying from one-eighth to three-
fourths of an inch. The thinness of the outer wall in early life is of practical
importance. It allows of suppuration making its way externally — subperiosteal
mastoid abscess. This will be facihtated by any delay in the closure of the petro-
and masto-squamosal sutures, by which this thin plate blends with the rest of the
temporal bone. Further, by the path of veins running through these sutures or
THE TYMPANIC ANTRUM
1337
their remnants, infection may reach such sinuses as the inferior petrosal. The
sutures normally close in the second year after birth. Through the floor, the
antrum communicates with the lower or vertical cells of the mastoid. This floor
is on a lower level than the opening into the tympanum, and thus drainage of an
infected antrum is difficult, fluid finding its way more readily into the lower cells.
Behind the mastoid antrum and cells is the bend of the sigmoid part of the trans-
verse (lateral) sinus, with its short descending portion (fig. 1087). The average
distance of the sinus from the superior meatal triangle is 1 cm. (f in.). It may be
further back; on the other hand, it may come within 2 mm. (y\ in.) from the
meatus, and even overlap the outer wall of the antrum.
Fig. 1088. — The Mastoid Antrum and Cells. (Jacobson and Steward.)
1. Posterior root of zygoma forming the supramastoid or suprameatal crest and upper
part of Macewen's triangle. 2. Antrum, and in front of it, the epitympanic recess. 3. Vertical
cells of the mastoid. 4. Ridge on the inner wall of the tympanum, caused by the facial canal.
5. Fenestrse on inner wall of tympanum, indicated in shadow. 6. A deficiency present in the
tegmen tympani, enlarged with a small osteotrite to emphasise the thinness of the roof of the
antrum and tympanum. 7. Cells extending, in this case, even into the root of the zygoma.
The exact position of the antrum, a little above and behind the external auditory meatus
is represented by Macewen's 'suprameatal triangle.' This is a triangle bounded by the posterior
root of the zygoma above, the upper and posterior segment of the bony external meatus below,
and an imaginary line joining the above boundaries (fig. 1087). "Roughly speaking, if the orifice
of the external osseous meatus be bisected horizontally, the upper half would be on the level
of the mastoid antrum. If this segment be again bisected vertically, its posterior half would
again correspond to the junction of the antrum and middle ear, and immediately behind this
lies the suprameatal fossa.' (Macewen.) When opening the antrum through this triangle,
the operator should work forward and medially, so as to avoid the transverse sinus (fig. 1087) ;
while, to avoid the facial nerve (fig. 10S7), he should hug the root of the zygoma and the upper
part of the bony meatus as closely as possible. The level of the base of the brain will be a few
lines above the posterior root of the zygoma (fig. 1089) and about 6 mm. (j in.) above the roof
of the bony meatus. (Macewen.)
1338 CLINICAL AND TOPOGRAPHICAL ANATOMY
B. The lower or vertical cells of the mastoid are developed later than is the
antrum, and vary much in their contents. The condition of the mastoid cells
varies very widely. They may be numerous (fig. 1088) or few. In the latter
case they are replaced by diploe, or by bone which is unusually dense, without
necessarily any pathological change. Hence mastoids have been classified as
pneumatic, diploetic, or sclerosed.
As part of the surgical anatomy of this most important region, the different paths by which
infection of the tympanum and antrum may travel should be glanced at. The most important
are: — (1) Upward: either by advancing caries or by infection of veins going to the superior
petrosal sinus, or through the tegmina to the membranes; an abscess in the overlying temporal
lobe, usually the middle and back part. (2) Backward : the transverse (lateral) sinus and
cerebellum (abscess of the front and outer part of the lateral lobe) are reached in the same ways
as those given above, the mastoid vein being the one chiefly affected here. Macewen has shown
that the bony wall of the sinus, like those of the tegmina and the aqueduct of Fallopius, may be
naturally imperfect. (3) Downward : where the vertical cells are well developed (fig. 929)
mischief may reach the mastoid notch and cause deep-seated inflammation beneath the sterno-
mastoid. (v. Bezold's abscess.) (4) Lateralward: the explanation of this, in early life, has
been given above. (.5) Medialward : the facial nerve, or by the fenestra ovahs; the labyrinth is
now in danger. When the internal ear and auditory nerve are affected, infection finds another
path to the cerebellar fossa.
The sphenoidal sinuses are less important surgically, but these points should be remem-
bered:— (1) Fracture through them may lead to bleeding from the nose, which is thus brought
into communication with the middle fossa; (2) the communication of their mucous membrane
with that of the nose may explain the inveteracy of certain cases of polypi and ozaena; (3) here
and in the frontal sinuses very dense exostoses are sometimes formed. Before any operative
attack on these sinuses is undertaken, their most important relations should be remembered.
Thus above are the olfactory and optic nerves, the pituitary body, and front of the pons.
Externally lie the cavernous sinus and superior orbital (sphenoidal) fissure. Below is the roof
of the nose.
The ethmoidal and maxillary sinuses are considered later in connection with the Nose.
See also the sections on Osteology and Respiratory System.
CRANIO-CEREBRAL TOPOGRAPHY
To make as clear as possible the points of practical importance which have, of
late years, been put on a definite basis, and which the surgeon may have to recall
and act upon at very short notice, cranio-cerebral topography will be spoken of
under the following headings: A. Relation of the brain as a whole to the skull,
B. Relation of the chief sulci and gyri to the skull. C. Localisation of the
chief sulci and gyri. Before alluding to the above, it is necessary to say distinctly
that the following surface-markings and points of guidance are only approxi-
mately reliable, for the following reasons: (1) In two individuals of the same
age and sex the sulci and convolutions are never precisely alike. (2) The rela-
tions of the convolutions and sulci to the surface vary in different individuals.
(3) That as the surface area of the scalp and outer aspect of the skull are greater
than the surface area of the brain, and as the convexities do not tally, lines drawn
on the scalp or skull cannot always correspond precisely to cerebral convolutions
or sulci. It results from the above that when a definite area of the surface is said
to correspond accurately in any individual to a definite area of the brain surface,
this result has been correlated from many examinations; and that as surface-
markings, shape, and processes of skull and arrangement of surface are all liable
to variations in different individuals, the surgeon must allow for these variations
by removing more than that definite area of skull which is said to correspond
exactly to that part of the brain which he desires to expose.
A. Relation of the brain as a whole to the skull (figs. 1089, 1091). — To trace
the lower level of each cerebral hemisphere on the skull, the chalk would start from
the lower part of the glabella; thence the line representing the lower borders of the
frontal lobe pursues a course, slightly curved upward, about 0.8 cm. (^ in.)
above the supraorbital margin; next, crossing the temporal crest about 1.2 cm.
(i in) above the zygomatic (external angular) process, it passes not quite hori-
zontally but descending slightly to a point in the temporal fossa just below the
tip of the great wing of the sphenoid (pterion), 2.5 cm. (1 in.) behind the zygo-
matic process. From this point the line of the level of the brain, now convex
forward and corresponding to the anterior extremity of the temporal lobe,
would dip down, still within the great wing of the sphenoid, to about the centre
of the zygoma. Thence the line of the lower border of the temporal lobe would
CRANIO-CEREBRAL TOPOGRAPHY
1339
travel along the upper border of this process about 6 mm. (J in.) above the roof
of the external auditory meatus (fig. 1089), and thence just above the base of
the mastoid and the posterior inferior angle of the parietal, and so along the
linea nuchse suprema, and corresponding to the tentorium and horizontal part
of the transverse (lateral) sinus, to the external occipital protuberance.
The upper margin of each hemisphere would be represented by a line drawn
from just below the glabella, sufficiently to one side of the middle line to allow for
the falx and superior sagittal sinus, to one immediately above the superior external
occipital protuberance and inion.
B. Relation of the chief fissures and convolutions to the skull. C. Local-
isation of the chief sulci and gyri. These headings will be taken together.
It will be well first to indicate the position of the chief sutures which mark off
the parietal bone, under which lies that part of the brain which is most important
to the surgeon — the motor area. The upper limit of the bone will be indicated by
the line already spoken of as giving the upper margin of the hemisphere — the
sagittal line, or Sagittal suture. The anterior limit of the parietal bone, formed
Fig. 1089. — The Outline of the Brain and its Fissures in Relation to the Sutures
OF THE Skull. (Cunningham.)
s.M. Supraciliary margin of the cerebrum, i.l.m. Infero-lateral margin of the cerebrum.
L.s. Position of highest part of the arch of the transverse sinus. R. Central sulcus (Fissure of
Rolando), s^. Anterior horizontal limb of lateral fissure, s^ Anterior ascending limb of
lateral fissure, s^ Posterior horizontal limb of lateral fissure, p.b. Opercular portion of the
inferior frontal convolution, p.t. Triangular portion of the inferior frontal 'convolution.
P.O. Orbital portion of the inferior frontal convolution.
by the coronal suture, may be traced thus : The point where it leaves the sagittal
suture (the bregma) will be found by drawing a line from a point just in front of
the external auditory meatus (the pre-auricular point) (fig. 1085) straight upward
on to the vertex; from this point a line drawn downward and forward to the
middle of the zygomatic arch would indicate that of the coronal suture. Under
this suture lie the posterior extremities of the three frontal convolutions; for the
frontal lobe lies not only under the frontal bone, but extends backward under the
anterior part of the parietal, the central sulcus (fissure of Rolando) , which separates
the frontal from the parietal lobe, lying from 3.7 to 5 cm. (1| to 2 in.) behind the
coronal suture at its upper extremity and about 2.5 cm. (1 in.) at its lower.
The squamoso-parietal suture, which marks the lower border of the anterior two-thirds
of the parietal bone, is not so easy to define, owing to the irregularity and variations of its curve.
Its highest point is usually 4.3 cm. (If in.) above the zygoma.
The lambdoid suture, which forms the posterior boundary of the parietal bone, will be
marked out by a line which starts from a point (lambda) about 6.2 cm. (2i in.) above the
external occipital protuberance, and runs downward and forward to a point on a level with
the zygoma, 3.7 cm. (IJ in.) behind and 1.2 cm. (J in.) above the centre of the meatus.
1340
CLINICAL AND TOPOGRAPHICAL ANATOMY
The position of the chief sulci will now be given: —
Lateral (Sylvian) fissure (fig. 1089). — The point of appearance of this, on
the outer side of the brain, practically corresponds to the pterion (p. 1332, fig.
1085) — a point which lies in the temporal fossa, about 3.7 cm. (1| in.) behind the
zygomatic process and about the same distance above the zygoma. From this
point the lateral fissure, which here separates the frontal and parietal from the
temporal lobe, runs backward and upward, ascending gently, at first in the line
of the squamo-parietal suture, then crossing this suture about its centre and
thence, ascending more rapidly, it climbs up to the temporal ridge, to end 1.8 cm.
(f in.) below the parietal eminence. Its termination is surrounded by the
supramarginal convolution, to which the parietal eminence corresponds with
sufficient accuracy. Such being the surface-marking of the chief or posterior
horizontal limb of the lateral fissure (s^, fig. 1089), it remains to indicate briefly
the two shorter limbs which bound the inferior frontal convolution, which, on the
left side, contains the centre for speech (Broca's convolution), and corresponds
to a point l3ang three fingers' breadth vertically above the centre of the zygo-
matic arch. (Stiles.) Of these, the anterior horizontal (s^, fig. 1089) runs for-
ward across the termination of the coronal, just above the line of the spheno-
parietal suture. The ascending limb (s^, fig. 1089) runs upward for about
Fig. 1090. — Lateral View op the Skull, Showing the Topogeaphy of the Middle
Meningeal Artery and the Transverse Sinus.
Anterior branch
of middle
meningeal art.
Posterior
branch' of
middle menin-
geal art.
2.5 cm. (1 in.) just behind the termination of the coronal suture, or 5 cm. (2 in.)
behind the zygomatic process.
The central sulcus (fissure of Rolando). — This most important fissure, in
front of which, in the precentral convolution of the frontal lobe, lie the motor
centres for the opposite side of the body, is situated under the parietal bone.
It may be marked out with sufficient precision in the following way (Thane):
The sagittal line, from glabella to external occipital protuberance, is bisected,
and a point 1.2 cm. (Jin.) behind the centre represents the superior Rolandic point.
From this point a line drawn downward and forward 9 cm. (3| in.) long, at an angle
of 67|° with the sagittal line (i. e., | of a right angle) will represent the central
sulcus. The lower extremity of this line is known as the inferior Rolandic point.
This method is open to the objection that it only apphes to the average adult skull, and not
to skulls of all sizes. To obviate this difficulty the method of Kronlein may be employed in
addition (fig. 1085). A base line BL is drawn through the lower border of the orbit and the
upper border of the external acustic meatus. Parallel to this an upper horizontal Une UH is
marked out at the level of the upper margin of the orbit. Three hues vertical to the base line
are now drawn, (1) at the posterior border of the mastoid process MRi (2) through the condyle
of the lower jaw (CR2), and (3) from the mid-point of the zygoma (ZS). The point Ri, where
the first vertical joins the sagittal sutiu'e is the superior Rolandic point. The point S where
the third vertical ZS cuts the line UH marks the junction of the three hmbs of the lateral fissure.
A line joining Ri and S will cut the second vertical CR2 at the inferior Rolandic point, Rj.
CRANIO-CEREBRAL TOPOGRAPHY
1341
The posterior limb of the lateral fissure also may be represented by a line bisecting the angle
RiSH and ending behind at the point S^ where it cuts the vertical MRi.
Some further points in the surgical anatomy of the cranium must be referred to: — The mid-
dle meningeal artery. This vessel, entering the middle fossa by the foramen spinosum, grooves
the great wing of the sphenoid and divides into two branches. The anterior grooves the
anterior inferior angle of the parietal bone, and is then continued upward and slightly back-
ward between the coronal suture and central sulcus (fig. 1090), almost to the vertex; the posterior
branch takes a lower level, running backward under the squ.imous bone to supply the parietal
and anterior part of the occipital bones. If a skull, bisected antero-posteriorly, be held up to
the light, it will be seen how thin are the bones over the chief branches of this vessel, thus
accounting for the slight violence sometimes sufficient to rupture it. The groove it occupies
in the parietal is sometimes converted into a canal. A wounded artery retracting here may be
very difficult to secure. The veins which accompany the artery and which lie lateral to it
Fig. 1091.- — Cerebral Topography and Localization. (Gushing, prom Keen's Surgekt.)
in the groove are thin-walled and sinus-like before they open into the spheno-parietal sinus,
another explanation of the obstinacy of this haemorrhage. According to the point of rupture,
three hsematomata should be remembered (Kronlein), anterior or fronto-temporal; middle,
or temporo-parietal; and posterior, or parieto-occipital. The first two are much the most
frequent, and exposure of the pterion, with free removal of the adjacent bone, will suffice for
dealing with them.
Drainage of the lateral ventricle. — (1) Where the anterior fontanelle is closed, Poirier and
Keen have opened the inferior cornu through the middle temporal convolution, the pin of
the trephine being placed 3.1 cm. (IJ in.) behind the external auditory meatus, and about the
same distance above Reid's base-line which is drawn from the lower margin of the orbit through
the mid-point of the external auditory meatus. The needle should here be directed to a point
1342 CLINICAL AND TOPOGRAPHICAL ANATOMY
about 5 cm. (2 in.) above the opposite ear. (2) Kocher's point for draining the lateral ventricle
is taken over the frontal lobe 2.5 cm. from the median line and 3 cm. in front of the upper
Rolandic point. The needle is passed downward and a little backward to a depth of 4 or 5 cm.
Up to this point the outside of the cranium has been mainly considered; it remains to draw
attention to some of the chir.f points in the sjirgical anatomy of the interior, especially ot the
base. The three fossae are of paramount importance in fracture. In the anterior fossa
the delicacy of parts of the floor, the connection of this with the nose and orbit, and the exact
adaptation of its irregular surface to that of the frontal lobes, no 'water-bed' intervening, are
the chief points. Thus the slightness of a fatal fissure, the frequent presence of bruising after
a blow perhaps on the occiput, which has been considered to have caused only concussion, the
characteristic palpebral hemorrhage, and the infection of a fracture here are all explained,
together with the possibility and gravity of a fracture here from a severe blow on the nose. In
the middle fossa the frequency of fractures is explained by the facts that while here, as in the
other fossae, a fracture often radiates down from the vertex, the overlying vault being a region
often struck, the base is weakened by numerous foramina and fissures. Further, the resisting
power of the petrous bone must be lessened by the cavities for the internal ear, the carotid,
and, to a less degree, by the jugular fossa. For fluids to escape through the external meatus,
the dura, the prolongation of the arachnoid into the internal meatus, the membrani tympani,
and probably the internal ear, must all be injured. The presence of the middle meningeal artery
(fig. 1090) and the cavernous sinus in this fossa must also be remembered, especially in such
operations as that on the Gasserian ganglion. Posterior fossa : It is not sufficiently recognised
that fractures here are, owing to the anatomy of the parts, in some respects the most important
of all. It is here that a small fissure-fracture, ultimately fatal, with severe occipital and frontal
bruising and some intradural hemorrhage, has been so often overlooked, especially in the
drunken. This is explained by the supposed strength of the bone, this being really very thin in
places, by the thickness of the soft parts, and the abundance of hair. Further, there is no very
apparent escape of cerebral contents as in the anterior and middle fosse. Blood, etc., may
trickle into the pharynx far back, or a deep-seated eochymosis coming up after two days, under
the muscles about the mastoid process, may call attention to the damage within.
Dura mater. — The outer layer of this membrane acts as a periosteum, by bringing blood-
vessels to the bone while the inner layer supports the brain. The influence of its partitions and
its damping effect on vibrations is great in blows on the head. Its varying adhesions, according
to site and age, must be remembered. Thus while it is intimately connected over the base
with its adhesions to the different foramina, it is more loosely connected with the vault, as is
shown in middle meningeal hemorrhage. In early and later life the closeness of its connection
with the bones is also more marked. It is united to the inter-sutural membranes.
Finally, the existence of the cerebro-spinal fluid with its power of lessening the evil of
vibrations and its aid in regulating infra-cranial pressure, must be borne in mind. The chief
collections, in which the subarachnoid meshwork is almost absent, are met with in front and
behind the medulla. That in front, also lying under the pons, Hilton's 'water-bed,' sends
a prolongation forward to the optic chiasma, but does not extend under the frontal or temporal
lobes. The collection behind lies between the medulla and under surface of the cerebellum.
Here, by the foramen of Magendie, the intra-ventricular cavities communicate with the sub-
arachnoid space of the spinal cord.
THE HYPOPHYSIS CEREBRI
The hypophysis (pituitary body) which has now become of great clinical
importance, consists of a pars anterior and pars intermedia derived from the
buccal ectoderm, and a posterior pars nervosa formed by a downgrowth from
the floor of the third ventricle. The gland lies in the fossa hypophyseos of the
sphenoid bone, and an enlargement of it, apart from general skeletal and nutri-
tional effect due to anomalies of its internal secretions, will cause pressure on
the cavernous sinus on each side, and on the optic chiasma above. It will also
expand the fossa hypophyseos, pushing down its floor at the expense of the
sphenoidal air sinus. Such enlargements may be detected by lateral radiograms.
The normal size of the adult hypophyseal fossa (fig. 1097) is 10-12 mm. from
before backward and 8 mm. from above downward (Keith).
The hypophysis may be exposed surgically either by turning the nose to one side, and remov-
ing the upper part of the septum and floor of the sphenoidal sinus, or by Cushing's method, in
which a sublabial incision is made in the vestibule of the mouth, and through it the mucosa is
then separated from each side, of the nasal septum back to the sphenoidal sinus. A strip of
septum is removed, and also the floor of the sphenoidal sinus, after which the hypophyseal fossa
is opened and the gland e.xposed (fig. 1097).*
THE FACE
The topics included under this heading are the arteries, parotid region, nerves,
mandible and maxilla, orbit, mouth, palate and nose.
The outhne of the different bones — nasal, upper and lower jaws, zygomatic
■* H. Gushing. The Pituitary Body and its Disorders, 1912.
THE FACE
1343
and zygoma — can be readily traced. The last mentioned and the glabella are
alluded to on pp. 1331 and 1332; and the canine fossa should be identified as one
of the antral routes. The delicacy, laxity, and vascularity of the skin are of great
importance in all operations, while the abundance of large gland orifices accounts
for the frequency of lupus here.
Arteries. — The supraorbital artery can be felt beating just above its notch
(junction of medial with lateral two-thirds of supraorbital margin); the little
frontal artery is of importance, as it nourishes the flap when a new nose is taken
from the forehead; the superficial temporal, accompanied by the auriculo-temporal
nerve, can be felt where it crosses the root of the zygoma just in front of the tragus,
its anterior branch about 3.1 cm. (1| in.) above and behind the zygomatic process
of the frontal; the occipital, accompanied by the great occipital nerve (fig. 450),
pulsates to the medial side of the centre of a line drawn from the occipital protu-
berance to the mastoid process; the posterior auricular, rather deeply, between the
auricle and the mastoid process. The external carotid lies behind the ascending
Fig. 1092. — Surface Relations of Vessels and Nerves in Lateral View op the Face
AND Neck.
Supraorbital n.
Supratrochlear n.
Infratrochlear n.
External nasal n.
Infraorbital n.
Buccal n.
Ext. maxillary art.
Mental n.
Post, belly of
digastric
Ant. belly of
digastric
Thyreoid cartilage
Common carotid
art.
Thyreoid gland
External auditory
meatus
Facial nerve (in red)
Parotid gland (yellow)
Sternomastoid
Accessory nerve
Ext. jugular vein
ramus of the jaw. The external maxillary (fig. 1093) crosses the jaw just in front
of the masseter; if divided, both ends must be secured here. It can be felt again
a little behind the angle of the mouth, just beneath the mucous membrane (it
here gives off the labial branches, which can also be felt, lying deeply, if the lip
is taken between the finger and thumb) ; and again by the side of the nose, as it
runs up to Ithe angulusoculi. The small angular branch is, from its position,
always troublesome to secure. To trace the course of the external maxillary
artery a line should be drawn from a point a little above and lateral to the tip of
the great cornu of the hyoid to the lower part of the anterior border of the masse-
ter, and thence to one lateral to and above the angle of the mouth, and so onward,
lateral to the angle of the nose, up to the medial angle. The anterior facial vein
takes a straight course behind the tortuous external maxillary artery. The
absence of valves and its communication by the angular and ophthalmic veins
with the cavernous sinus, and, by the deep facial, with the pterygoid plexus, are
of grave importance in infective thrombosis. The external jugular vein will be
mentioned later.
Parotid region. — A line drawn from the lower border of the meatus to a point
midway between the nose and upper lip gives the level of the parotid duct, which
1344
CLINICAL AND TOPOGRAPHICAL ANATOMY
opens into the mouth opposite the second molar tooth. The level of the duct,
somewhat inconstant, would be usually about a finger^s breadth below the
zygoma. It is accompanied by the transverse facial artery above, and the
infraorbital branch of the facial nerve below.
The sheath of the parotid, continuous with those of the masseter and sterno-mastoid, is
strong enough to cause most exquisitely painful tension when inflammation of the gland is
present, and, together with the presence of deep processes of the gland in connection with the
Fig. 1093. — Scheme op the External Maxillary (Facial) Artery. (Walsham.)
Orbicularis ocuU muscl
Transverse facial artery
M. quadr. labii sup
(caput zygom.)
Zygoma ticus muscle
Buccinator muscle
Masseteric branch
Masseter muscle
Stylo -phar ynge u i
Stylo-glossus muscle
Ascending palatine
branch
Tonsillar branch
External maxillary
artery
External carotid
artery
Posterior belly of
digastric muscle
Lingual artery
Frontal branch of ophthal-
mic artery
Nasal branch of ophthal-
mic artery
-Angular artery
M. quadr. labii
■ sup. (caput ang.)
Infraorbital artery
Caput infraorb.
■Lat. nasal artery
Caninus muscle
—Artery of septum
Superior labial
artery
Risonus muscle
Infenor labial artery
Mental branch of inferior
alveolar artery
Quadratus labii inferioris
muscle
Inferior labial artery
Triangularis muscle
Submental artery
branches to submaxillary
Anterior belly of digastric
Mylo-hyoid muscle
■Hyo-glossus muscle
'Hypoglossal nerve
mandibular (glenoid) cavity and styloid process, to explain the deep burrowing of pus which
may take place into the pharynx and pterygoid region. The relation of the capsule to growths,
innocent or malignant, of the parotid is also important (See figs. S65, 1092).
The parotid region would be thus mapped out (fig. 1096). Above by the pos-
terior two-thirds of the zygoma; below, by a line corresponding to the posterior
belly of the digastric (fig. 1096) ; behind, are the external auditory meatus, mastoid,
and sterno-mastoid. In front the gland and socia parotidis overlap the posterior
part of the masseter, to a variable degree (fig. 1096).
THE FACE 1345
Sensory nerves. — -The cutaneous nerve areas of the face are shown in fig. 774.
The supraorbital nerve, the main sensory branch of the ophthalmic, emerges from
the orbit with its companion artery through the notch (occasionally a foramen)
at the junction of the medial third and lateral two-thirds of the supraorbital
margin. A line drawn from the supraorbital notch downward across the interval
between the bicuspid teeth will cross the infraorbital foramen from which emerges
the infraorbital nerve, the main terminal division of the maxillarj^, at a point
1 cm. below the orbital margin. The mental foramen, the point of exit of the
mental nerve, a branch of the inferior alveolar, is found on a prolongation of the
same line midway between the upper and lower margins of the mandible in the
adult. In the infant in whom the alveolar element of the jaw is relatively
large, the mental foramen is nearer the lower margin, while in the edentulous
jaw of old age it is found much nearer the upper margin.
In trephining to expose the inferior alveolar (dental) nerve, one of the common
seats of neuralgia and one in which a peripheral operation is justified from the
results, the ascending ramus is opened midway between its anterior and posterior
borders, on a level with the last molar.
The semilunar ganglion lies at a depth of 5.5-6 cm. (2i in.) upder the eminentia articularia
at the base of the zygoma. In exposing it for the purpose of excision for intractable neuralgia
the following structures are encountered: (1) Skin and superficial fascia with branches of the
superficial temporal artery; (2) temporal fascia and muscle with deep temporal vessels; (3)
squamous bone and great wing of sphenoid, which are trephined, the floor of the middle fossa
being gouged away ; (4) middle meningeal vessels and dura mater. By elevating the dura mater
and superimposed temporal lobe, and securing the middle meningeal artery, the ganglion is
exposed, lying in a separate compartment [cavum Meckelii] of the dura, which contains cerebro-
spinal fluid. The motor nerve of the muscles of mastication lies on the lower and medial
aspect of the ganglion, and should not be divided.
Injection of the mandibular nerve with alcohol, by means of a long stout hypodermic needle
is practised in cases of intractable neuralgia as an alternative to excision of the semilunar gang-
lion. A vertical line is drawn on the cheek downward from the junction of the posterior and
middle thirds of the zygomatic arch, and the needle is entered on this line at a point 1.5 cm.
from the lower border of the zygoma. It is directed upward and medially so as to pass through
the lowest part of the mandibular notch. If the mouth is opened the notch is depressed and more
room gained. The needle impinges first against the inferior surface of the great wing of the
sphenoid bone, and when the point is lowered a little it engages in the foramen ovale at a depth
of 4-4,5 cm. In most cases the needle can be passed thi'ough the foramen ovale into the semi-
lunar gangUon. (Harris.)*
The maxillary nerve may be injected by passing a needle along the floor of the orbit from its
infero-lateral angle in a direction backward and sUghtly medially to the foramen rotundum
which lies 4.5 cm. from the surface.
Facial nerve. — In the petrous bone the course of this nerve is first outward
and forward, then, having entered the facial canal, backward and downward
along the medial wall of the tympanum, above the fenestra ovalis. Emerging
from the stylo-mastoid foramen the nerve takes first the line of the posterior
belly of the digastric, running forward and a little downward from the anterior
border of the mastoid where this meets the auricle. (Godlee.) Entering at
once the posterior part of the parotid, it crosses the neck of the mandible at the
level of the lower border of the tragus.
The frequent paralysis of this nerve may thus depend upon — (1) cerebral causes; (2) dis-
ease of or injm-y to the petrous portion; (.3) affections after its exit— BeU's paralysis. A diag-
nosis may be arrived at by attention to the following. In cerebral disease the lower part of the
face is chiefly affected, the eyelids usually escaping. In aU the other forms the whole side of
the face is paralysed. Hemiplegia of the opposite side of the body and paralysis of the sixth
nerve are usually present. In petrous paralysis, owing to involvement of the chorda tympani,
there may be interference with the saliva and taste, affecting especially the anterior part of the
tongue. The auditory nerve may also be affected. Here and in (3) there will be a histor}' of
disease or injury. In complete paralysis the smooth side of the face and forehead, the absence
of power of expression, to frown, to blow, or whistle, the open eyelids and epiphora, and subse-
quent liability to mischief in the cornea, the di-opping of the angle of the mouth and dribbling
of saUva, the interference with mastication from paralysis of the buccinator, are the chief points.
Mandible. — Dislocation of the temporo-mandibular joint is referred to on
p. 217. In the usual dislocation, from muscular action, the jaw is suddenly
brought forward against the anterior part of the capsule, which tends, bj!- the
action of the depressors, to give way; the elevators then pull up the mandible, a
sequence that must be remembered in reduction. In the commonest fracture of
* Lancet, Jan. 23, 1912.
1346 CLINICAL AND TOPOGRAPHICAL ANATOMY
the mandible — unilateral, near the mental foramen — the larger anterior fragment
will be pulled by the depressors downward and medially, the smaller posterior one
upward and usually lateral to the other fragment.
Maxilla. — The boundaries of the maxillary sinus (antrum) are of much im-
portance. The base of this irregularly pyramidal cavity corresponds to the
middle and inferior meatuses on the lateral wall of the nose; toward the upper
and back part is the opening into the middle meatus. The apex runs laterally
toward the zygomatic process. The roof is formed by the orbital plate with the
infraorbital nerve and vessels anteriorly; the floor by the junction of the alveolar
arch, carrying the first molars (and often the bicuspids), with the hard palate.
It may be pierced by the roots of the second bicuspid or first and second molar
teeth. Anteriorly, the antrum is bounded by the canine fossa; posteriorly it is
in relation with the zygomatic fossa. The cavity, present at birth, increases
gradually up to the twelfth year.
The chief paths of infection are through the teeth (especially the first and second molar),
the nose, and frontal sinus. The obstinacy of inflammation here is explained by the site of the
opening, high up on the medial wall, and thus inadequate drainage, by the imperfectly multi-
locular cavity of the interior and its rigid walls. The chief sites for opening the antrum are — (a)
thi'ough the sockets of the first or second molars; (b) through the canine fossa, after the reflec-
tion of mucous membrane has been detached, midway between the roots of the teeth and the
infraorbital foramen (this path gives more room) ; (c) through the inferior meatus of the nose.
THE ORBIT AND EYE
The bony orbit is a pyramidal fossa with its base at the orbital margin and its
apex at the optic foramen. The medial walls of the two orbits are approximately
parallel, but the lateral walls diverge as they are traced forward and lie at right
angles to each other. The thin floor which is formed mainly by the maxilla and
corresponds to the roof of the maxillary sinus, is readily destroyed by growths
extending up from the sinus and in the process pressure on the infraorbital
nerve is apt to cause pain referred to the cheek. The roof formed by the
orbital plate of the frontal bone is also thin, and foreign bodies thrust into the
orbit may perforate it and enter the frontal lobe of the cerebrum. The medial
wall is chiefly constituted by the lacrimal and lamina papyracea of the ethmoid,
both very thin bones. This wall is readily destroyed by malignant growths of the
nose.
Injuries of the medial wall such as may be associated with fractures of the nose bring the
ethmoidal air cells into communication with the cellular tissue of the orbit. The latter may thus
be distended with air on attempting to blow the nose.
The lateral wall is formed in its anterior third by the zygomatic bone, which
separates the or"bit from the zygomatic fossa. The posterior two-thirds formed
by the sphenoid bone separate the orbit from the temporal lobe of the brain in
the middle cranial fossa. The orbit communicates with the cranimn by the
optic foramen, which transmits the optic nerve and ophthalmic artery and the
superior orbital fissure through which pass all the other vessels and nerves of the
orbit.
In cases of fracture of the base of the skuU involving the anterior clinoid process, a traumatic
communication (arterio-venous aneurysm) may be formed between the internal carotid artery
and cavernous sinus, behind the apex of the orbit, giving rise to pulsating exophthalmos.
The orbital margin is larger in the transverse than in the vertical direction,
and consequently there is more space on either side than above and below be-
tween it and the eyeball which is nearly spherical. The eyeball lies nearer to the
medial than to the lateral margin and hence foreign bodies more commonly
penetrate the orbit to the lateral side of the eye.
Behind the fascia bulbi, the eyeball rests on a mass of soft loose orbital fat in
which foreign bodies may be hidden for a considerable time.
The structure of the eyelids. — The different layers are of much practical
importance. (1) The skin is delicate and fatless, and contains pigment, the
object of this being to protect the eye from bright light. It helps to explain the
'dark circles' of later life. (2) Areolar tissue. Owing to its looseness and
delicacy, this is very liable to infiltration, as in oedema and erysipelas. (3)
THE ORBIT AND EYE
1347
Orbicularis. Paralysis of this, tiie palpebral portion, leads to epipiiora, tiie
puncta being no longer kept in their normal baclcward direction against the
conjunctiva. (4) Palpebral fascia, reaching from the orbit to the tarsal cartilage.
This is usually strong enough to prevent haemorrhage, due to fractured base of
skull, becoming subcutaneous. (5) Levator palpebr^e. (6) Tarsal plate; in
reality, densely felted fibrous tissue. (7) Tarsal (Meibomian) glands, lashes,
and sebaceous follicles.
I Localised inflammation starting in any of these last three structures, especially the last, will
cause a 'stye.' The frequency with which the lid-border is the seat of that most troublesome
chronic inflammation, blepharitis, and its result, 'blear eye,' is e.xplained by these anatomical
points. Its circulation is terminal and slow; half skin and half mucous membrane, it is moister
and more liable to local irritation than the skin; while its numerous glands readily partici-
pate in any inflammation.
Fig. 1094. — Sagittal Section Thkough the Uppek Eyelid. (After Waldeyer and Fuchs.)
^ Conjunctiva near fornix
/ Anterior layer of insertion
"~ of levator palpebrffl
superioris
■ Superior tarsal muscle
* Miiller
3 from levator passing
tlirough orbicularis to skin
Cutaneous surface
just above supe-
rior palpebral fold
Orbicularis fibres, r.nt_
across [\
Sweat-gland -\^ —
--Supei
/ of I
/--—Fibre
Fine hair with sebaceous
gland at its base
Ciliary gland of MoU
Cilium
^^— Mucous glands
— Mucous gland
_ Tarsal (Meibomian) gland
- -Musculus ciliaris Riolani
'""Posterior edge of lid-margin
Opening of duct of tarsal gland
(8) The conjunctiva. To trace this important membrane, the lids should be
everted, when the following will be noted. The conjunctiva over the tarsal part
of the lid is closely adherent, and through it a series of nearly straight, parallel,
light yellow lines and granules, the tarsal glands, can be seen. Owing to their
position here (fig. 1094) and to avoid scarring, a tarsal cyst is always opened on its
conjunctival surface.
Beyond the tarsi, the palpebral conjunctiva is thicker and freely movable
owing to the abundant lax submucous tissue. Underlying vessels are visible
here. Leaving the eyelid the conjunctiva is reflected onto the eyeball at the
fornix. Into the lateral part of the upper fornix open the ducts of the lacrimal
gland. The bulbar conjunctiva is continued over the front of the ej^eball to the
corneal margin. It is thin and contains fine vessels which are distinguished from
subjacent episcleral vessels by the fact that they move with the conjunctiva.
1348
CLINICAL AND TOPOGRAPHICAL ANATOMY
These conjunctival vessels, derived from the lacrimal and palpebral arteries, become very-
visible in conjunctivitis. In deep inflammation affecting .the iris and ciliary body, the episcleral
branches of the anterior ciliary arteries (which are derived from the muscular and lacrimal
arteries) become engorged and are visible as a pink circumcorneal zone of congestion, deeply
situated under the conjunctiva. These branches take a large share in the nutrition of the cornea,
and are responsible for the vascularity of pannus and the 'salmon patches' of interstitial
keratitis.
The conjunctival nerves for the upper lid and bulbar part of the membrane, and the nerves
to the cornea, are supplied by the ophthalmic division of the trigeminal. The maxillary divi-
sion of this nerve sUpphes the lower palpebral conjunctiva.
The differing structure of the palpebral and ocular portions has important bearings. Thus
the palpebral conjunctiva is thick, highly vascular and sensitive. To this vasovilarity we owe the
chemosis, or hot, red, tense swelling of purulent ophthalmia. The exquisite suffering of the same
disease, or that caused by a foreign body, is explained by the numerous nerve-papillje and end-
bulbs. To the thickness and abundance of the connective tissue are due the contraction and
permanent thickening which may occur in granular lids. The so-called granulations, met with
in this disease on the palpebral conjunctiva, are really little nodules of hypertrophied lymphoid
follicles, or mucous glands, which abound here.
Immediately under the bulbar conjunctiva, between it and the sclerotic, lies the anterior
part of the fascia bulbi (of Tenon). This fibrous membrane forms a sheath for the posterior
Pig. 1095.-
-The Lacrimal Apparatus and Naso-lacrimal Duct.
(Bristles are introduced into the puncta lacrimalia.)
(Bellamy.)
Medial wall of maxillary sinus
Lacrimal sac
Medial palpebral ligament
Valvular folds in naso-lacrimal duct
Lower ndsiii concha Orifice of naso-lacrimal duct
five-sixths of the eyeball, and is intimately connected with the sheaths of the extrinsic muscles
and through the check ligaments with the orbital walls. Together with the conjunctiva it
must be opened in the operation of tenotomy for strabismus, and after division of a rectus tendon
the muscle retains some control over the eye through its connection with the fascia bulbi. In
enucleation of the eyeball both conjunctiva and fascia bulbi are divided around the cornea,
where they are intimately blended. In removal of the upper jaw the attachment of the sus-
pensory ligament of this fascia must always be left if possible, for otherwise the eyeball will tend
to fall forward and the cornea suffer from its exposure (Lockwood). Finally the cavity between
the two layers of the capsule is continuous with the extensions of the cerebral membranes along
the optic nerve, i. e., with the subarachnoid space.
For an account of the intrinsic and extrinsic muscles of the eye the reader is referred to the
section on the Eye. Reference may be made here, however, to the part played by certain fibres
of the cervical sympathetic system. Emerging from the cord at the fh-st and second thoracic
segments, the communicating fibres pass up the sympathetic chain in the neck to cell stations
in the superior cervical ganglion. Thence continuing onward tltrough the carotid canal and
superior orbital fissure, they supply (1) the dilator muscle of the u'is, (2) the unstriped muscle
element in the eyelids, and (3) smooth muscle fibres, deoribed by Sappey, in the check ligaments
and fascia bulbi. Paralysis of the cervical sympathetic nerve in the neck, usually in its lowest
part, by trauma or the pressure of a malignant growth, causes therefore (1) narrowing of the
pupil, (2) narrowing of the palpebral fissure (pseudo-ptosis), and (3) enophthalmos.
The lacrimal gland lies in a hollow at the supero-lateral angle of the orbit,
protected by the zygomatic process of the frontal bone. It is not palpable nor-
mally. Its lower or palpebral portion rests on the lateral third of the fornix
THE MOUTH
1349
conjunctivse, into which the numerous ducts open, and it may be seen through the
conjunctiva on everting and raising the upper lid.
The position of the lacrimal puncta should be noted; owing to their backward direction,
the lids must be previously everted. The puncta are kept open by a minute fibrous ring.
Each is situated on a minute papilla at the junction of the medial and straight third of
the lid with the lateral curved two-thirds. Close to the medial angle, in addition to the puncta
and papillae, should be noted the caruncula lacrimalis, with its delicate haii's, and the plica
semilunaris, which corresponds to the third eyelid of certain birds.
The lacrimal sac is a most important part of the lacrimal apparatus, from its
disfiguring diseases; it lies in a bony groove, between the nasal process of the
maxilla and the lacrimal bone. The medial palpebral ligament crosses it a little
above its centre (fig. 1095) . Thus two-thirds of the sac are below the ligament,
and in suppuration the opening is made below it also. The angular artery ascends
on the nasal side of the sac.
The manipulation of a probe along the lacrimal passages should thus be practised: — the
lower lid being drawn laterally and downward by the thumb, the probe is passed vertically into
the punctum, then turned horizontally and passed on till it reaches the medial waU of the sac.
It is then rotated somewhat forward, raised vertically, and pushed gently along the duct down-
ward, and a little lateralward and backward, till the floor of the nose is reached, the operator
aiming, as it were, for the site of the first molar tooth. The naso-lacrimal duct extends from
the lower end of the lacrimal sac to the inferior meatus of the nose and is about 1 . 2 cm (J in.)
in length.
If the eyes are opened naturally, the greatest part of the cornea, behind it the iris, with the
pupU in the centre, on either side of the cornea some of the sclerotic, the semilunar fold, and
caruncle can be seen.
THE MOUTH
The lips. — When the whole thickness of the lip is incised the labial artery
will be found lying near the free margin, internal to the orbicularis muscle, and
Fig. 1096.— Side op the Face and Mouth Cmiti, showing the Three Salivakt Glansd.
Accessory parotii
Duct of accessory
parotid
Duct of parotid
Frenulum linguae.
Sublingual gland'
Duct of submaxil
lary gland
Mylo-hyoid muscle.
Masseter muscle
Posterior belly of
digastric muscle
Submaxillary
gland,
drawn backward
■Hyoid bo
Deep portion of submaxillary gland
between it and the mucosa. There is a very free anastomosis between the
arteries of the opposite sides.
If the tongue be raised, the under surface is seen to be smooth and devoid of
papillse. In the middle line is the frenulum. When division of this is really
required in tongue-tie, the scissors should be kept close to the bone, in order to
avoid the ranine vessels.
1350
CLINICAL AND TOPOGRAPHICAL ANATOMY
Of these, the veins can be seen just to one side; the arteries are close by, but deeper. Farther
out are two more or less distinct fringed folds, the plica; l fimbria tse, running from behind forward
and, like the frenulum, disappetiring before the tip. Between these and the frenulum are the
small apical mucous glands of Nuhn or Blandin. Farther back, at the junction of the mucous
membrane and the alveoli, are two other projections of the mucosa, the sublingual; under these
are the sublingual glands, the ranine veins, and, more deeply, Wharton's duct and the termina-
tion of the lingual nerve. The majoritj' of the ducts of the sublingual gland (Rivinian) open on
the sublingual ridges. A single larger one, Bartholin's, opens with that of Wharton, or close to
it, on either side of the frenulum (fig. 1096). Dilatation of one of the Rivinian ducts, more fre-
quently dilatation of a muciparous gland — and, much more rarelj', dilatation of Wharton's duct
— constitutes a 'ranula.'
The submaxillary gland can be felt nearer the angle of the jaw, lying between
its fossa and the mucous membrane, especially if pressure is made from outside.
The attachment of the genio-glossi can be felt behind the symphysis: the division
of the muscles allows the tongue to come well out of the mouth; but when both
have to be divided, the tongue loses much of its steadiness, and may easily fall
Fig. 1097. — Sebtion of the Skull and Brain in thp Median Plane. (Braune.)
Falx cerebri
Superior sagittal sinus
Inferior sagittal sinus
Corpus caUosum
Optic chiasma
Corpus mammillare
Occipital lobe of
Torcular Herophili
Medulla oblongata
Posterior ring of atlas
Body of epistropheus (axis)
Thyreoid gland
Sterno-thyreoid muscle'
, Body of second thoracic
\ vertebra
back over the larynx during the administration of the anaesthetic or, later on, in
sleep. It should therefore be secured forward for a while with silk. For the
same reason, in removal of one-half of the mandible, part of this muscular
attachment should always be left, if possible.
Turning now to the dorsum of the tongue, this shows two distinct parts: one, the anterior
two-thu'ds, the buccal, is rich in papiUic; the other, the posterior, the pharyngeal, contains abun-
dant lymphoid follicles like the tonsil. This part possesses peculiar sensibiUty, as shown by
movements of tongue and palate when a depressor is placed too far back. The two parts
are separated by the v -shaped arrangement of the vallate papillEe, with the apex turned back-
ward. Immediately behind the apical vallate papilla is a small pit, the foramen cEecum
which represents the upper remains of the thyreoglossal tract, and may be the seat of lingual
thyreoid growths. While the tongue is mainly a muscular organ, the fine fatty connective tissue
in the septum and between the muscular bundles is the seat of that dangerous condition acute
glossitis, and of gummatous infiltration. While the mouth is widely open, the pterj^go-man-
dibular ligament can be seen and felt beneath the mucous membrane, behind the last molar
tooth. Just below and in front of the lower attachment of this ligament the lingual nerve can
be felt lying close to the bone below the last molar. The simplest and surest method of dividing
the nerve here, to give relief from pain in incurable carcinoma of the tongue, is to draw the tongue
out of the mouth and expose the nerve where it lies superficially under the mucous membrane
thus made prominent between the side of the tongue and the gums, the centre of the incision
THE TONSILS 1351
being opposite to the last molar tooth. (Roser, L6ti6vant.) In cancer of the tongue pain is
often referred up the aurioulo-temporal nerve to the ear and side of head.
Behind the last molar tooth can be felt the coronoid process, and higher up,
just behind and medial to the tooth, the pterygoid hamulus of the sphenoid.
This process is a landmark to the site of the greater palatine foramen, which lies
just in front of it, and which transmits the greater palatine branch of the descend-
ing palatine artery, together with the anterior palatine nerve. The vessel and
nerve run forward in grooves on the lower surface of the palatine process of the
maxilla, giving off anastomosing branches toward the middle line, and join at
the incisive foramen with the nasopalatine artery.
Their position must be remembered in raising the flaps during the operation for closure of
a cleft in the hard palate. To ensure the vitality of the flaps the incisions must be made lateral
to the vascular arch, close to and pai'allel with the upper alveolus, and should not extend be-
yond a point opposite to and just medial to the last molar tooth, for fear of encroaching upon
the posterior palatine canal.
When the teeth are clenched, there is still a space, communicating between the
mouth and pharynx behind the molar teeth, which admits a medium-sized
catheter. When a patient breathes deeply through the mouth and the head is
thrown back, the soft palate is raised, the pillars (arches) separated; the uvula and
fauces, with the anterior and posterior pillars, with their attachments, the tonsils,
and the back of the pharynx are exposed.
This portion of the pharyngeal mucous membrane would lie over the lower part of the
second and the upper part of the third cervical vertebrae, the anterior arch of the atlas corre-
sponding to the level of the posterior nares, and the body of the epistropheus (?ixis) to the level
of the soft palate (fig. 1097). If a finger be introduced past the soft palate to this part of the
spine and turned upward and downward, it is possible, with the aid of an anfesthetic, to examine
the upper four or five and, in children, six vertebrse, as far as the anterior surfaces of their
bodies. 'The part of the column which is accessible to a straight instrument introduced through
the mouth is very hmited, extending, in the adult, from the lower border of the axis to the middle
or lower part of the fourth cervical vertebra; in the child, owing to the small size of the face, it
comprises the bodies of the axis and of the third cervical vertebra.' (Thane and Godlee, from
Chipault.) The distance from the incisor teeth to the commencement of the oesophagus at
the cricoid cartilage is 15 cm. (6 in.) in the adult, and the distance from the teeth to the cardiac
orifice of the stomach is 48 to 50 cm. (16 or 17 in.).
The lymphatic drainage of the face, mouth, and tongue is given on pp. 712
and 715.
Tonsils. — The relations of the tonsils should be carefully examined. Thus,
they are separated externally by the superior constrictor and pharyngeal aponeuro-
sis from the oscending pharyngeal and internal carotid arteries. The latter vessel
lies about 2.5 cm. (1 in.) behind and to the lateral side of the tonsil. When
serious haemorrhage follows operations here, it usually comes from one of the
numerous tonsillar branches (fig. 448). The extent to which the tonsil is covered
by the anterior pillar, how far it projects upward beneath the soft palate or
downward into the pharynx, have all important bearings on the mode of removal.
Its position corresponds to a point a little above and in front of the angle of the
jaw. The lateral surface, enclosed by an imperfect capsule and separated from
the superior constrictor by connective tissue, explains how an enlarged tonsil
can be dragged medialwarcl by a vulsellum, and enucleated after an incision in the
mucous membrane around. It is in this connective tissue that severe infective
inflammation, e. g., after scarlet fever or an imbedded pipe-stem, may set up
haemorrhage or spreading cellulitis, retro-pharyngeal or otherwise.
The finger introduced downward at the back of the mouth, especially if the parts are ren-
dered in sensitive by local anaesthetics, feels the vallate papilla, the lingual and laryngeal surfaces
of the epiglottis, the arytajno-epiglottidean folds, with the cuneiform and corniculate cartilages.
If the finger be moved upward behind the soft palate and turned upward to the base of the skull,
and then forward, it will feel the choanae (posterior nares), separated by the vomer. Tlie other
boundaries of these are, laterally, the medial pterygoid plate and palate bones; above, the basi-
sphenoid; and below, the horizontal plate of the palate bone and the inferior nasal spine.
Within each nostril would be felt the posterior ends of the two lower nasal conchte (turbinate
bones); above and behind is felt the basilar process of the skull, the vault of the pharynx,
and the bodies of the upper cervical vertebree (fig. 1097).
The size of the choanae, in the bony skull 2.5 cm. (Ijin.) vertically by 1.2 cm. (J in.), and the
presence of anj^ adenoids, are especially to be noted. The richness of the naso-pharynx in
glandular structures, its proneness to inflammation, and of this inflammation to spread to other
parts, — e. g., the tympanum, — ^are well known. The finger should be familiar with the feel of
1352 CLINICAL AND TOPOGRAPHICAL ANATOMY
adenoids — i. e., hypertrophied post-nasal lymphatic nodules — soft bodies of irregular shape
blocking up the naso-pharynx. _ To make out how far this is the case, it is well to take the
nasal septum as the starting-point.
Pharyngeal hypophyseal remnants. — In the naso-pharyngeal mucosa, a few millimetres
behind the posterior border of the vomer, a group of glandular cells may be found on micro-
scopical examination in all cases (Haberfeld), corresponding in histological appearance with the
pars anterior of the hypophysis. These cells are a remnant of the primitive bud that grows
toward the brain in front of the bucco-pharyngeal membrane to form the pars anterior of the
hypophysis. In some cases of pituitary disorder they give rise to a palpable tumour in the naso-
pharynx.
The palate.- — Between the diverging pillars of the soft palate is the isthmus
faucium, bounded above by the free margin of the palate, and below by the
dorsum of the tongue. The space between the arches (pihars), glossopalatine and
pharyngo-palatine, with attachments denoted by their names, shallow above,
widens and deepens below. Of its lateral boundaries, the posterior pillars come
nearer each other than the anterior. The coverings of the hard palate are chiefly
mucous membrane, glands, and periosteum. These are intimately blended by
fibrous septa, as in the superficial layers of scalp and palm of the hand. Hence
the readiness with which necrosis takes place here.
Hare-lip and cleft palate. — Failure of union between the mesial nasal process
and the maxillary process of the embryo gives rise to the deformity known as
hare-lip.
The palate is developed from three primitive processes growing down from the basis cranii,
viz., (1) the mesial nasal process forming the premaxilla which lies in front of the anterior pala-
tine foramen and bears the four incisor teeth, (2) and (3) the maxillary process of either side.
The slighter cases of failure to unite affect only the soft palate which is the last part to fuse.
Complete alveolar cleft palate, which occurs combined with hare-lip and may be unilateral or
bilateral, represents more serious non-union. In this condition the lateral incisor may be found
either on the medial or on the lateral side of the cleft, which is explained by the fact that thi&
tooth is developed in the groove between the two processes (Keith).
In paring the edges of a cleft soft palate, the following structures would be, successively,
cut through: — (1) Oral mucous membrane; (2) submucous tissue, with vessels, nerves, and
glands; (3) glosso-palatine muscle; (4) aponeurosis of tensor palati; (5) anterior fasciculus of
pharyngo-palatine; (6) levator palati and uvular muscles; (7) posterior fasciculus of pharyngo-
palatine; (8) submucous tissue, vessels, nerves, and glands; (9) posterior mucous membrane.
The soft palate is thicker than it seems, the average in an adult being 6 mm. (i in.). The
muscles widening a cleft are the tensor and levator, while the superior constrictor closes it in
swallowing. Of the arteries of the palate, from the external maxillary (facial), ascending pharyn-
geal, and internal maxillary, the largest is the descending palatine branch of the last. This
emerges from the posterior palatine canal close to the inner side of the last molar tooth.
THE NOSE
On the face the outline of the nasal bones can be easily traced, and below them
the lateral nasal cartilages, flat and also somewhat triangular. Below these are
the greater alar cartilages, curved and so folded back that each forms a lateral
and a medial plate. Of these, the medial meet below the septal cartilage to form
the tip of the nose, while the lateral curve backward, and, together with dense
masses of cellular tissue and fat and accessory cartilages, form the alse.
With the speculum, especially if the head be thrown back and the tip of the
nose drawn up, the lower part of the septum, floor of the nose, and greater portion
of the inferior concha (turbinate bone) can be seen. On throwing the head
further back, with a good light the lower margin of the middle concha can also
be made out. This is much higher up and nearly on a level with the root of the
nasal bone. The septum often deviates to one side. The mucous membrane
over it is, in health, dull red in colour; that over the inferior concha is thicker.
The anterior extremity of the latter bone is about 1.8 cm. (| in.) behind the nasal
orifice, while the opening of the naso-lacrimal duct is about 2.5 cm. (1 in.) behind
and about 1.8 cm. (| in.) above the floor, concealed by the anterior extremity of
the inferior concha. The opening into the maxillary sinus (antrum) is situated in
about the centre of the middle meatus and 2.5 cm. (1 in.) above the floor
The olfactory area of the mucous membrane extends over the highest concha
(possibly also somewhat lower) and corresponding portions of the septum. The
respiratory portion is more vascular and thicker, especially over the conchse. It
is firmly adherent to the periosteum and perichondrium. The veins, especially
over the lower conchse, form a dense plexus, closely resembling cavernous tissue.
THE NOSE
1353
This fact explains the severity of epistaxis, and, together with the drainage of
blood into out-of-the-way veins, such as the spheno-palatine and ethmoidal,
Fig. 1098. — Section of the Nose, showing the Conch.*: (Turbinate Bones) and Meatuses
WITH THE Openings in Dotted Outline.
Frontal sinus
Orifice of middle ethmoidal cells ,
Superior concna
Orifice of the posterior ethmoidal cells
Orifice of the sphenoidal smus
Sphenoidal sinus
Orifice of tuba auditiva
Orifice of frontal sinus
Upper orifice of
naso-lacrimal
duct
Middle concha
Inferior co.ncha Orifice of the Orifice of infundibulum
maxillary sinus
Fig. 1099. — Section showing Bony and Cartilaginous Septum.
The dotted line indicates the course of the incisive (anterior palatine) canal.
Nasal bone Frontal sinus
Sphenoidal sinus
ve between sept;
and lateral nasal
cartilage
Thickened border of cartilage
resting upon anterior nasal spine Incisive
papilla Septal cartilage
Orifice of tuba auditiva
Soft palate
accounts for the serious results which may follow on a firmly impacted and in-
fected plug. The boundaries of the posterior nares have been given above.
1354 CLINICAL AND TOPOGRAPHICAL ANATOMY
About 1.2 cm. (| in.) behind tlie posterior extremities of tiie inferior conchse,
just above the level of the hard palate (fig. 1097), on the side of the naso-pharynx,
are the openmgs of the tubce auditivce (Eustachian tubes). Oval in shape, these
are bounded above and behind by the prominence of the cartilage, which is want-
ing below, thus facilitating the entry of a catheter. The lower part of the tube
contains in early life lymphoid tissue; enlargement of this explains the deafness
in certain cases of adenoids. At the upper part of the naso-pharynx, on the
posterior wall, extending down laterally as far as the tubae auditivse, is the col-
lection of lymphoid tissue known as the pharyngeal tonsil, which when hypertro-
phied, plays a large part in 'naso-pharyngeal adenoids.' From the periosteum
of the basi-sphenoid and basi-occipital arise naso-pharyngeal fibromata.
Nasal septum. — The structure of the skeletal element of the septum, which
consists of the septal cartilage, the vertical plate of the ethmoid and the vomer,
is shown in fig. 1099. Slight deviations of the septum to one side are common
in adults, and involve mainly the cartilage and the ethmoid bone, the vomer
being but little affected as a rule.
The convexity is most commonly on the right side, and occlusion of the nares on that side
with unsightly deflection of the whole nose, results in some cases during the transition from the
nfantile to the adult facial conformation. Too extensive removal of the bony septum in the
operation of submucous resection for the relief of this condition may cause sinking in of the
bridge of the nose. More often, however, this is due to the destructive effect of congenital
syphilis.
Accessory sinuses. — The communication of these air sinuses with the nasal
fossae are of great clinical importance. The sphenoidal sinus opens high up into
the spheno-ethmoidal recess. The posterior ethmoidal sinuses open into the
superior meatus under cover of the superior concha. The infundibulum of the
frontal sinus, the anterior and middle ethmoidal and the maxillary sinus all
communicate with the middle meatus under cover of the middle concha. The
orifice of the maxillary sinus lies at the lowest part of the hiatus semilunaris
into the front and upper end of which the frontal sinus opens. Consequently
infected fluid may trickle down from the latter into the maxillary sinus. The
orifice of this sinus is placed high up in its medial wall so that fluid does not
drain away from it readily in case of infection. When the head is held forward
in a stooping position some of the pus or mucus may escape from the nostrils,
since in this position the fluid contents more readily reach the orifice.
The naso-Iacrimal duct which carries the tears into the nose opens into the front and upper
part of the inferior meatus under cover of the inferior concha.
THE NECK
The topics considered in the neck are the landmarks, thyreoid gland, sterno-
mastoid, clavicle, triangles and cervical ribs.
Bony and cartilaginous landmarks. — The body of the hyoid is nearly on a
level with the angles of the jaw, and the interval between the third and fourth
cervical vertebrae (fig. 1097). With the head in the usual erect position it lies
a little higher than the chin. It divides the front of the neck into supra- and
infra-hyoid regions, convenient for remembering the distribution of the deep
fascia. On either side of the body are the great cornua, with the lesser cornua
attached to their upper borders at the junction with the body. The upper borders
of these are the guides to the lingual arteries. The outline and mobility of the
body and the great cornua are easily determined by relaxing the deep fascia and
pushing the bone over to the opposite side. Below the hyoid is the thyreo-hyoid
space, which corresponds with the epiglottis and the upper aperture of the
larynx. Thus, if the throat be cut above the hyoid, the mouth will be opened
and the tongue cut into; if the thyreo-hyoid space be cut, the pharynx would be
opened and the epiglottis wounded near its base. In the former case the lingual
and external maxillary are the most likely vessels to be wounded ; in thyreo-hyoid,
the commonest cut-throat, the superior thyreoid vessels, and the superior laryn-
geal nerve. The projection of the thyreoid notch, about 2.5 cm. (1 in.) below
the hyoid, is much more distinct in men than in women or children. It does
not appear before puberty, and thus flatness of the thyreoid must be expected
^
THE NECK 1355
when the landmarks for tracheotomy are sought for in children with short fat
necks.
The cricoid, on the other hand, is always to be made out. It corresponds in horizontal
plane to the following: — (1) The sixth cervical vertebra. (2) The junction of pharynx and
oesophagus: from the narrowing of the tube here, foreign bodies may lodge at this point and cause
dyspncea by pressing on the air-tube in front. The cricoid is taken as the centre of the incision
in cesophagotomy, and also for ligature of the common carotid. (3) The junction of larynx
and trachea. (4) The crossing of the omo-hyoid over the common carotid. (5) The middle
cervical ganglion. Above the cricoid is the crico-thyreoid rnembrane. In laryngotomy, the
deepest part of the incision should be kept to the middle line for fear of injuring the crico-
thyreoids, and as near the cricoid as possible, so as to avoid the neighbourhood of the vocal
cords and the small crico-thyreoid vessels. The space is always small, and, after middle life,
increasingly rigid.
The distance between the cricoid and the manubrium is only about 3.7 cm.
(1| in.). When the neck is stretched, about 1.8 cm. (f in.) more is gained.
Thus, as a rule, there are not more than seven or eight tracheal rings above the
sternum. Of these, the second, third, and fourth are covered by the thyreoid
isthmus.
The parts met with in the middle line — (a) above, and (6) below, the isthmus — high and
low tracheotomy — should be borne in mind: (o) Skin, superficial fascia, branches of transverse
cervical and infra-mandibular nerves, lymphatics, cutaneous arteries, anterior jugular veins —
with their transverse branches smaller above — deep fascia, sterno-hyoids, cellular tissue, supe-
rior thyreoid vessels, and pre-tracheal layer of deep fascia. The importance of this last is two-
fold, as, first, the tube in tracheotomy may be passed between it and the trachea, and after a
wound in this region this layer, continuous with the pericardium, may conduct discharges into
the mediastina, (6) The surface structures are much the same, but the anterior jugular veins
and their transverse branches are much larger. The inferior thyreoid veins are also larger. A
thyreoidea ima may be present, and the innominate artery, especially in children, may be 1.2
cm. (2 in.) above the sternum. The trachea is also smaller, deeper, and less steadied by muscles.
The thymus, too, in young children, may prove a difficulty. Thus, in children, the high opera-
tion, incising the cricoid and crico-tracheal membrane, if needful, is to be preferred. The cricoid
is, however, not to be incised, if possible; the higher the tube is inserted, the greater the irritation.
The suprasternal notch, between the sternal heads of the sterno-mastoids in on a level with
the disc between the second and third thoracic vertebrae. Just below the level of the cricoid
cartilage, on deep pressure at the anterior border of the sterno-mastoid the transverse process of
the sixth cervical vertebra may be felt. It is known as Chassaignac's carotid tubercle, and the
common carotid may be compressed against it. Compression below it will command the
vertebral artery as well.
The thyreoid gland enclosed in a capsule of deep fascia derived from the pre-
tracheal layer (fig. 1070) is closely connected by this to the upper trachea and
larynx. The upper somewhat pointed extremity of each lateral lobe reaches to
the upper and back part of the thyreoid cartilage; here enter the superior thyreoid
vessels. The lower layer and rounded extremity reaches to the fifth or sixth
tracheal ring; its posterior and lower aspect is in relation to the inferior thyreoid
vessels and the recurrent nerve; the lateral lobe, posteriorly, also overlaps the
carotid sheath, which may be infiltrated in malignant disease of the thyreoid.
The thyreoidea ima has been mentioned above.
The isthmus in the adult is opposite to the second, third, and fourth tracheal rings. At
its upper border is an arterial arch formed by the superior thyreoids; over the anterior surface
of the gland and isthmus the inferior thyreoid veins take origin in a plexus. The upper border
of the thymus (fig. 1100) may be in relation with the lower border of the isthmus. From the
upper border of the latter, the pyramidal lobe, especially on the left side, is often present, reach-
ing by a pedicle to the liyoid. The pyramidal lobe, when present, is the persistent remnant of
the thyreo-glossal duct, and occasionally cystic outgrowths persist obstinately as remnants of
this duct, in the middle line, above, behind, and below (the commonest form) the hyoid bone.
In short-necked people the thyreoid is relatively lower in relation to the sternum, and en-
largements of the gland are apt to become mainly intra-thoraeic. An enlargement of the
thyreoid is liable to give trouble by pressure on (1) the trachea, which is compressed laterally
between the lateral lobes; (2) the oesophagus; (3) the internal jugular vein and carotid artery;
(4) the reciu-rent laryngeal or cervical sympathetic nerves.
Parathyreoids. — These small glands, about the size of a pea, vary somewhat in number and
situation. There are usually four — t^A■o behind each lateral lobe. The upper glands lie im-
bedded in the capsule of the thyreoid about the junction of the middle and upper thirds of the
lateral lobes on the posterior aspect. The lower pair lie nearer the lower poles of the lateral
lobes, sometimes separated from them by a distinct interval. Excision of all the parathyreoids
gives rise to tetany in animals.
The stemo-mastoid is the landmark for several important operations. Its
medial border, the thicker and better marked of the two, overlaps the carotids;
1356
CLINICAL AND TOPOGRAPHICAL ANATOMY
the common carotid corresponding, as far as the upper border of the thyreoid,
with a line drawn from the sterno-clavicular joint to midway between the mastoid
process and the angle of the jaw. The artery can be best compressed above the
level of the cricoid, as here it is less deeply covered. The student should recall
the deep relations of the sterno-mastoid, which he may classify as vessels, nerves,
muscles, glands, and bones; or, according to their position, (1) those above the
level of the angle of the jaw; (2) those between the angle of the jaw and the omo-
hyoid; (3) those below the omo-hyoid.
Of the two heads of the sterno-roastoid, the sternal is the thicker and more prominent, the
clavicular the wider. A stab through the interval wliich lies between tlie two heads might
wound the bifurcation of the innominate on the right side, and the common carotid on the left,
the internal jugular, vagus, and phrenic veins, according to the direction of the wound.
Fig. 1100. — Thymus Gland in a Child at Birth.
r^~.
Hyo-thyreoid membrane
Thyreoid cartilage [~;^^/
Sterno-thyreoid muscle'
Crico-thyreoid ■^^;^- w-
membrane ^^»^*
Crico-thyreoid muscle
Thyreoid gland
Right vagus nerve
Right internal jugular,
vein
Level of sternu
Section of clavicle
Section of first rib
Section of sternum
^ Thyreo-hyoid muscle
I^VL Omo-hyoid muscle
Cricoid cartilage
First ring of trachea
-r — Left suspensory
\ ligament
Left recurrent nerve
(Esophagus
Left innominate vein
Left lobe of thymus
Left internal mammary
artery
Pericardium
Section of fifth costal
cartilage
■Xiphoid process
The anterior jugular, commencing in branches from the submaxillary and
submental regions, descends at first in the superficial fascia between the middle
line and anterior border of sterno-mastoid, perforates the deep fascia just above
the clavicle, here entering Burns's space (p. 1361); it then curves laterally to
pass beneath both origins of the sterno-mastoid a little above the clavicle, to end
usually in the external jugular.
When distended, a large communicating branch between it and the common facial, which
runs along the anterior border of the sterno-mastoid, must always be remembered in operations
for removal of glands, etc. The varying level at which the external jugular crosses the lateral
THE NECK
1357
border of the clavicular origin must be remembered in such operations as tenotomy here. These
veins vary in size inversely to each other; the anterior jugulars are joined by numerous trans-
vesre branches and become larger below. They have no valves.
Of the chief arteries to the sterno-mastoid, that from the superior thjrreoid will be divided
in gature of the common carotid; that from the occipital runs with the spinal accessory nerve.
Behind the stemo -clavicular joint lies the commencement of the innominate
veins, the bifurcation of the innominate artery on the right, and the common
carotid artery on the left; deeper still lie the pleura and lung.
The clavicle. — This bone can be felt beneath the skin in its whole length.
It forms the only bony connection between the upper limbs and the trunk. As
one traces it laterally toward the acromial end, it rises somewhat, particularly
in children and in subjects of good muscular development. The skin over it is
thin but very mobile, and consequently is not often wounded. The most im-
portant posterior relations of this bone are, passing from the medial end laterally,
the subclavian vein, the subclavian artery, and the cords of the brachial plexus
as they He on the first rib.
Fig. 1101. — Anterior and Lateral Cervicai, Muscles.
Stylo-glossus
Hyo-glossus
Mylo-hyoid
Anterior belly of
digastric
Raphe of mylo-
hyoid
Thyreo-hyoid
Inferior constrictor
Anterior belly of omo-
hyoid
Sterno-hyoid
Sterno-thyreoid
The vein occupies the angle between the first rib and the clavicle, and hence is, as a rule,
the first structure compressed in growths of this bone. The artery lies on a deeper plane be-
hind the mid-point of the clavicle, and the nerve cords extend a little further laterally. The
Bubclavius muscle forms a protective cushion between the bone and these important structures,
and this accounts for the rarity of injury to them in fracture of the clavicle. Behind the medial
half of the clavicle the apex of the lung extends upward into the neck toa height of 2. 5-3. 7 cm.
(1-1 2 in.), and consequently is liable to be wounded by a stab in the root of the neck.
Cervical triangles. — In front of the sterno-mastoid is the anterior triangle,
which is subdivided into three smaller triangles by the digastric muscle above,
and the anterior belly of the omo-hyoid below (fig. 1101). These smaller tri-
angles are called, from above, the submaxillary, the superior and inferior carotid
triangles.
The submaxillary or digastric triangle is bounded above by the jaw, and a line
drawn back to the mastoid process; below, by the digastric and stylo-hyoid
muscles; and in front by the middle line of the neck.
1358 CLINICAL AND TOPOGRAPHICAL ANATOMY
This space contains the submaxillary gland, and embedded in the gland is the external
maxillary artery, the facial vein lying superficial to the gland; deeper than the gland are the
submental vessels and the mylo-hyoid vessels and nerve. Posteriorly, and separated from the
above structures by the styro-mandibular ligament, which subdivides the triangle into a sub-
maxillary and parotid part, is the upper part of the external carotid artery running up into the
parotid gland, where it gives off its two terminal and the posterior auricular branches. More
deeply lie the internal jugular vein, internal carotid artery, and the vagus. The floor of the
triangle is formed by the mylo-hyoid, hyo-glossus, and superior constrictor. The lingual
artery may be tied here, or, better, in order to get behind the dorsalis linguae, close to its origin,
by an incision similar to that for exposing the external carotid.
The hypoglossal is a guide to the carotids and the occipital artery at the lower border of the
digastric, and farther forward, to the subjacent lingual, from which it is separated by the
hyo-glossus.
The superior carotid triangle is bounded above by the digastric, below by
the omo-hyoid, and behind by the sterno-mastoid. It contains the upper part of
the common carotid and its branches, the external being at first somewhat
anterior to the internal. All the branches of the external carotid, save the three
just given, are found in this space, together with their veins, the internal jugular
vein, the vagus and sympathetic nerves, and, for a short distance, the accessory,
together with those nerves which lie in front of and behind the carotids.
Ligature of the common carotid is usually performed at the 'seat of election,' where the
vessel is more superficial, above the omo-hyoid. An incision with its centre opposite the cricoid
is made 7.5 cm. (3 in.) long in the line of the carotid artery. The deep fascia along the an-
terior border of the sterno-mastoid having been divided, the cellular tissue beneath is opened up,
the omo-hyoid identified and drawn down or divided. The sterno-mastoid is next drawn well
laterally, and the artery felt for. At this stage, such veins as the communication between
the common facial and the anterior jugular and the superior and middle th}Teoi_ds may give
trouble. The sheath is next opened well to the medial side, opposite to the cricoid cartilage,
the ascending cervical, when seen, being avoided. If the internal jugular be distended, it may
be drawn aside with a blunt hook, or pressure made lightly in the upper angle of the wound.
The needle should be passed from the lateral side in very close proximity to the lateral and back
part of the artery, so as to avoid the vein and vagus. Ligature helow the omo-hyoid is rendered
more difficult by the presence of the anterior jugular, the pretracheal muscles, an overlapping
thyreoid gland, especially if enlarged, the greater depth of the artery, especially pn the left side
and, here also, the closeness of the internal jugular. The collateral circulation is given at p. 1360.
Ligature of the external carotid, otherwise difficult, is rendered very simple by first exposing the
bifurcation of the common carotid artery, the incision similar to the last being prolonged up-
ward. Here the facial and lingual veins and hypoglossal nerve cross the trunk, over which
also lie some of the deep cervical glands. The ligatiue is usually placed between the superior
thyreoid and lingual branches.
Allusion must here be made to the chief structures liable to be met with in operations
on the neck. These are the internal jugular, the accessory, and phrenic nerves, the vagus
and hypoglossal, the thoracic duct, low down and deep on the left side, the oesophagus and
recurrent nerve in difficult operations on the thyreoid gland. Of these, the internal jugular is,
in some ways, the most important. Glands, tuberculous or epitheliomatous, are often adherent
to its sheath, especially those which drain the submaxillary group. When this condition is
present or suspected, it is always well to begin the dissection low down in the inferior carotid
triangle, where the structures are probably normal and the landmarks easy to identify. In
infective thrombosis of the transverse sinus the internal jugular is often tied opposite to the
cricoid cartilage, being either divided between two ligatures, or, if the thrombus has extended
downward, as much of the vein as is possible is removed. This vein contains only a single pair
of valves low down in the neck. In all operations here on it and the other two jugulars, the
risk of entry of air is to be remembered. The accessory and phrenic nerves are alluded
to on p. 1360.
The inferior carotid or tracheal triangle is bounded above by the omo-hyoid,
behind by the sterno-mastoid, and in front by the middle line of the neck. It
contains the lower part of the carotid sheath and its contents, with, behind^ it, the
inferior laryngeal nerve and inferior thyreoid vessels, and to the medial side the
trachea, thyreoid gland, and oesophagus. More deeply are the vertebral vessels;
on the left side is the thoracic duct.
The position of the branches of the external carotid should be remembered.
The great cornu of the hyoid and the ala of the thyreoid are landmarks for the
origin of most of them.
The superior thyreoid, arising just below the level of the great cornu of the hyoid bone,
passes downward and forward to the back part of the thyreoid cartilage and upper part of the
thyreoid body. Many of its branches are important in surgery. The superior laryngeal
perforates the thyreo-hyoid membrane. The sterno-mastoid passes laterally into the middle
of the muscle, across the carotid sheath. The crico-thyreoid crosses the space of the same name
just below the lower border of the thyreoid cartilage. The small hyoid branch runs to the lower
THE NECK 1359
border of the hyoid bone. Anastomosing branches of the superior thyreoid form an arch along
the upper border of the isthmus. The Ungual artery arises from the parent trunk, opposite the
tip of the great cornu of the hyoid, and passes forward just above the great cornu, crossed by
the hypoglossal, and thence to the side of the tongue. In the first part of its course, before it
reaches the hyo-glossus, it is curved, at first ascending, and then, having descended slightly,
before it reaches the hyo-glossus, and while it lies under it, its curve is gentle, with the concavity
upward; beyond the hyo-glossus, as it lies on the muscles of the tongue beneath the mucous
membrane, it is tortuous. The lingual vein, it will be remembered, does not run with its artery,
but lies superficial to the hyo-glossus. It receives the two small venae comitantes which run
with the lingual itself just before it crosses the common carotid. The line of the external
maxillary (facial) artery (fig. 1093), which often arises with the lingual, has been given on p. 1343.
The occipital artery, starting on the same level as the facial (i. e., at a point a little above and
outside the tip of the great cornu of the hyoid bone), follows a line drawn upward and laterally,
first to the interval between the transverse process of the atlas and the mastoid process, the
former bone being felt just below and in front of the tip of the latter; thence, lying in the occipital
groove of the mastoid, the artery ascends gradually, enters the scalp, together with the great
occipital nerve, a little medial to a point midway between the external occipital protuberance
and the mastoid process, to follow, tortuously and superficial to the aponeurosis, the line of the
lambdoid suture.
The surface marking of the digastric and omo-hyoid, which subdivide the anterior triangle
into the three smaller subtriangles above described, should be noted. The line of the posterior
belly of the digastric corresponds to one drawn from the apex of the mastoid process to a point
just above the junction of the great cornu and body of the hyoid bone; and from this spot,
which gives the point of meeting of the two tendons, one slightly curving upward to a point
just behind the symphysis menti, would give that of the anterior belly.
To trace the omo-hyoid, a line should be drawn from the lower margin of the side of the
hyoid bone obliquely downward, so as to cross the common carotid opposite the cricoid carti-
lage and thence curving laterally under the sterno-mastoid at the junction of its middle and
lower thirds, and then onward and still laterally parallel with and a little above the clavicle,
as far as its centre.
Posterior triangle. — This shows in its lower part a wide<depression, the supra-
clavicular fossa. Here the brachial plexus may be felt, and, by pressure down-
ward and backward immediately behind the clavicle, just lateral to and behind the
lateral margin of the sterno-mastoid, the pulsation of the subclavian artery can be
stopped against the first rib.
The supra-clavicular fossa should be opened out by depressing the arm, and parts relaxed
by carrying the shoulder forward and turning the head to the same side. This vessel curves
upward and laterally from behind the sterno-clavioular joint to disappear behind the centre of
the clavicle, the highe.st point of the curve being 1.2 to 2.5 cm. (i to 1 in.) above the bone.
The artery on the left side lies more deeply than the right, and does not rise so high into the neck.
The subclavian vein lies at a lower level, separated by the scalenus anterior, and under cover of
the clavicle. Into the above curve rise the pleura and lung. The pleura must be expected to
rise 2.5 cm. (1 in.) above the clavicle, behind the clavicular head of the sterno-mastoid.
The transverse scapular and transverse cervical vessels run laterally, parallel with the
clavicle. The former lies behind the bone and subclavius ; the latter also runs laterally in a trans-
verse direction, across the root of the neck, but on a slightly higher plane, and thus a little above
the clavicle.
Ligature of the third part of the subclavian is best performed by an angular incision, the
horizontal portion along the centre of the clavicle, and the vertical one along the posterior
border of the sterno-mastoid, with partial division of this and the trapezius when closely ad-
jacent. The chief points to bear in mind are the venous plexus into which the external jugular,
transverse cervical, transverse scapular, and cephalic veins enter; the omo-hyoid and division
of the fascia which ties this to the clavicle; identification of the lateral margin of the scalenus
anterior and the scalene tubercle; care of the transverse scapular artery and the descending
branch of the transverse cervical. The needle is passed from above downward so as not to in-
clude the lowest cord of the brachial plexus, the vein, if distended, being depressed with a blunt
hook. If the nerve to the subclavius be seen, it must be uninjured, as it occasionally forms an
important part of the phrenic. The collateral circulation is given at p. 1360.
Crossing the sterno-mastoid, a little obliquely, in a line drawn from a point
just below and behind the angle of the jaw which marks its origin in the union of
the posterior part of the internal maxillary and the posterior auricular veins to the
centre of the clavicle, runs the external jugular vein. Above, it lies between the
platysma and deep fascia, and is accompanied by the group of superficial cervical
nodes (p. 709). About 3.7 cm. (1| in.) above the clavicle it perforates the deep
cervical fascia, its coats being blended with the opening. Gentle pressure with a
finger at this point renders the vein above clearly visible. The dilated part
between this point and the subclavian vein is called the sinus, and is marked by
two valves, neither of which is usually perfect.
Opening into the external jugular, in the middle or lower third of its course, is the posterior
external jugular, a vessel which begins in the occipital region superficially and runs down in front
of the anterior border of the trapezius, across the posterior triangle.
1360 CLINICAL AND TOPOGRAPHICAL ANATOMY
The accessory nerve, having crossed the transverse process of the atlas at a
point lying a little below and in front of the apex of the mastoid, enters the ante-
rior border of the sterno-mastoid at about the junction of the upper and middle
thirds of the muscle. Having traversed the muscle obliquely, it leaves it usually
at a point a little lower down, pursues a similar course across the posterior triangle
and disappears under the anterior border of the trapezius, to enter into the sub-
trapezial plexus with the third and fourth cervical nerves.
Above it is accompanied by a branch from the occipital, below by the transverse cervical
artery. It is always seen in thorough operations on the upper deep cervical glands. The nerve
is resected in spasmodic torticollis, and in recent years inveterate facial paralysis has been
treated by anastomosing the facial to this nerve or the hypoglossal. A line drawn from midway
between the tip of the mastoid and the angle of the mandible along the above given course of
the nerve would denote its position.
Just above the centre of the sterno-mastoid, the small occipital, great auricular, and cuta-
neous cervical nerves emerge, the first passing upward and backward to the scalp, the second
upward and forward across the upper part of the sterno-mastoid to the ear, and the last turning
straight forward to the front of the neck. The small occipital and great auricular are often
in intimate association with the accessory at its exit from the muscle. At this point also care
must be taken not to injure the nerve in removal of glands from the posterior triangle.
The phrenic nerve, taking its largest root from the fourth cervical, would
begin deeply about the level of the hyoid bone; thence descending under the
sterno-mastoid, and, passing obliquely medially across the scalenus anterior (the
posterior borders of the above two muscles roughly correspond to each other in
the lower part of the neck), it descends under the subclavian vein and clavicle to
enter the thorax.
When the internal j ugular is distended, its lateral border will be liable to overlap this nerve.
The relations of the scalenus anterior should be noted here. In addition to the plurenic, which
runs with a slight obliquity medially and is in close contact with the muscle, the following struc-
tures cross it medio-laterally : the subclavian vein and termination of the external jugular,
the transverse scapular and transverse cervical vessels, and the omo-hyoid. At its medial
margin are the thyreo-cervical trunk and vertebral arteries, and over them, the internal jugular.
Behind it are the subclavian artery, the brachial plexus, and pleura.
The level of the brachial plexus (upper border) would be given by a line drawn
from the cricoid cartilage to the centre of the clavicle. The lowest, medial cord
(eighth cervical and first thoracic, giving off chiefly the ulnar, medial head of
median, and medial antibrachial cutaneous) is just above and behind the sub-
clavian artery. Its importance in ligature of the artery has been referred to
(p. 1359).
In paralys's of the newly born, after some violent manipulation, it is usually the upper and
lateral cord (fifth nerve, and axillary and median chiefly) which suffers, elevation and abduction
at the shoulder and flexion at the elbow-joint being lost.
Collateral circulation after ligature of the common carotid (fig. 1102). — This takes place
by means of (1) the free communication which exists between the opposite carotids, both with-
out and within the craniujm; and (2) by enlargement of the branches of the subclavian artery on
the same side as that on which the carotid has been tied. Thus, outside the cranium, the supe-
rior and inferior thyreoids are the chief vessels employed (fig. 1102). Within the cranium the
vertebral replaces the internal carotid.
Collateral circulation after ligature of the second and third parts of the subclavian (fig. 1102).
— Here the following three sets of vessels are those chiefly employed: —
The transverse scapular, the transverse \ -.r^ / The thoraco-acromial, infra- and sub-
cervical, / 1 scapular, and circumflex scapular.
The superior intercostal, the aortic inter- 1 ■, , ( The lateral thoracic and subscapular
costals, and the internal mammary, J \ arteries.
Numerous unnamed branches passing 1
through the axilla from branches of the > with Branches of the axillary,
subclavian, J
Deep cervical fascia. — The arrangement of this must be remembered — (a)
above, and (5) below, the hyoid bone. The latter is far more important.
(a) Arrangement above the hyoid bone. — Here two chief processes can be made out: — (i)
one, continuous with that in front of the sterno-mastoid, traced upward from the hyoid bone,
-encloses the submaxillary gland, passing over the mylo-hyoid, and, ascending, is connected with
the lower border of the mandible, gives off the masseteric and parotid fascia, and is attached
to the lower border of the zygoma, and, more posteriorly, to the mastoid and linea nuchse
Buprema. (ii) A special process, which forms the stylo-mandibular ligament, is important in
its power of checking over-action of the external pterygoid. By both these processes the ante-
rior border of the sterno-mastoid is tied firmly forward to the mandible about its angle, and more
deeply to the styloid process. This renders all operations under the upper part of the muscle,
•e. g., the removal of glands, extremely difficult.
THE NECK
1361
(6) Below the hyoid bone. — The importance of the fascia here is infinitely
greater. Four layers must be rememhored; (i) Superficial; (ii) pretracheal;
(iii) prevertebral; (iv) carotid, (i) Superficial. This starts from the ligamentum
nuchee, encases the trapezius, forms the roof of the posterior triangle where it is
perforated by branches of the superficial cervical nerves and the external jugular
Fig. 1102. — The Collateral Circulation after Ligature of the Common Carotid and
Subclavian Arteries.
(A ligature is placed on the common carotid and on the third portion of the subclavian artery.)
Right anterior cerebral -fLi'l ^^^* anterior cerebral
J/'^\^ Anterior communicating
Internal carotid -VV^ Post_ communicating
Right posterior cerebral J J ?r^f\^ Left posterior cerebral
Occipital
Descending branch of occipital
External carotid
Superficial branch of descending
occipital
Deep branch" ~
Anterior spinal
External maxillary
Lingual
Superior thyreoid
Transverse
cervical
Descending branch
Acromical branch
Subscapular branch —
Su praspinous k. ..
branch
Anterior circumflex
Infraspini
branch
Post.
circumflex
Lateral thoracic
Subscapular'
Circumfl
Innominate
Superior
intercostal
Left com. carotid
Left subclavian
Sup. thoracic
Internal mammary
Anterior intercostal
vein. Passing on it encloses the sterno-mastoid; and, passing over the anterior
triangle, it meets its fellow in the middle line.
jThin behind, it is thickened anteriorly. Behind this thickened union lie the anterior
jugular veins. Below, at a varying distance below the thyreoid cartilage, this layer divides
into two, attached to the front and back of the manubrium. Between these (Burns*s space)
1362
CLINICAL AND TOPOGRAPHICAL ANATOMY
lie some fat, a small gland, a communicating branch between the anterior jugulars and a small
portion of the veins, and the sternal heads of the sterno-mastoids. The sheath to the depressors
of the hyoid bone is partly derived from this layer, partly from the next. Laterally, this layer
gives a sheath to the posterior belly of the omo-hyoid, is attached to the clavicle, and passing on,
is continuous with the sheath to the subclavius and coraoo-clavioular fascia.
(ii) Pretracheal or middle. This lies under the depressors of the hyoid, over
the trachea, also encasing the thyreoid gland. Farther laterally it helps, to-
gether with the prevertebral, to form the carotid sheath. Traced downward,
the pretracheal layer passes over the trachea into the thorax (middle mediastinum)
As it descends, it encases the left innominate vein, and ends by blending with the fibrous
layer of the pericardium. Hilton suggested that the attachment of this fascia above, and that
of the central tendon of the diaphragm below, to the pericardium served to keep this sac duly
stretched, and so prevented any pressure of the lungs upon the heart.
Fia. 1103. — Section of Neck through the Sixth Cervical Vertebra. (Braune.)
Larynx
Pharynx
Longns colli
Inferior laryngeal
Thyreo-arytaenoid
Cricoarytaenoideus lateralis
Penrertebral layer of deep cervical fascia
FretTacheal layer of deep cervical fascia
Sup. thyreoid art.
DesG hypoglossi
Sterno-mastoid
Vagus
Sym^thetic
Phrenic
Scale
anterior
Brachial plexus
Scalenus
medius
External
jugular
Part of articu-
lar process
Spinal
accessory
Sterno-hyoid, just posterior
are seen the thyreo- and
omo-hyoid muscles
Thyreoid cartilage
Muscular process of
arytaenoid
Cervical fascia
Thyreoid
gland
Common
carotid
Carotid sheath
Internal
jugular
Brachial
plexus
Scalenus medius
External jugular
Ihocostalis
cervicis
Scalenus posterior
Spinal accessory
Splenius
Semispinalis colli and multifidus
Semispinalis capitis
Deep cervical vessels
_rficial layer of deep cervical fascia on
the deep aspect of the trapezius which
it here encloses
Sixth cervical vertebra
(iii) Prevertebral. This layer passes over the longus colli and capitis upward
to the base of the skull, and downward over the longus colli behind the oesophagus
into the posterior mediastinum. Laterally it helps to form the carotid sheath,
and, lower down, gives a sheath to the subclavian artery and so to the axil-
lary, (iv) The carotid sheath. This is formed by septa from i, ii, and iii, meeting
under the sterno-mastoid (fig. 1103).
The following uses and important points with regard to the anatomy of the deep cervical fascia
should be noted: — (A) It forms certain definitely enclosed spaces in which pus or growths
may form, and by the walls of which these morbid structures may be tied down and thus rendered
difficult of diagnosis, while their increasing pressure may embarrass the air-passages, etc.
Thus: (1) In the first space, which lies between No. 1 and the skin, the structures met with,
the platysma and superficial branches of the cervical plexus, are unimportant. Any abscess
here is prone to extend, but superficially. (2) In the second space, between the superficial and
middle layers, lies a narrow space containing loose cellular tissue and lymphatic glands. Sup-
puration here is very common, but usually comes forward. (3) This is the largest and most
important of all. From its contents it has been called the visceral compartment. (Stiles.)
THE THORAX 1363
It is bounded in front by the middle, and behind by the prevertebral layer. Its contents are —
larynx, trachea, cesophagus, thyreoid, carotid sheath, glands; and below, brachial plexus, sub-
clavian artery, and abundant loose cellular tissue for the movements of the neck. Suppuration is
somewhat rarer here; but either pus or growths, if oonfined in this space, may have baneful
effects, from pressure, or from their tendency to travel behind the sternum. (4) This space
between the prevertebral layer in front and muscles behind, is very limited. Retropharyngeal
abscess forms here, and the dyspnoea it causes is thus explained. The origin of such abscesses
is chiefly twofold, either in one of the highest deep cervical nodes, e. g., from infection of the
naso-pharynx (p. 717), or from disease of the upper cervical vertebrae. In the former cases
CStiles, Chiene) the suppuration will be in front of the prevertebral fascia, pointing toward the
pharynx; in the latter behind the above fascia, spreading laterally, behind the carotid sheath.
In making his incision, now along the posterior border of the sterno-mastoid, the surgeon should
keep close to the transverse processes of the vertebrae, to avoid!opening the visceral compartment
and infecting the structures in it. (B) The deep cervical fascia gives sheaths or canals tc>
certain veins which perforate it, e. g., the external jugular. These are thus kept patent, and a.
ready passage of blood ensured from the head and neck. Further, this fact accounts for the
readiness with which air may enter veins, in operations low down in the neck. The carotid
sheath is another and different instance. (C) It helps to resist atmospheric pressure. (D)
Hilton's suggestion as to its action on the pericardium has already been mentioned.
The lymphatic nodes of the head and neck have already been described.
(See Section VI, Lymphatic System.)
THE THORAX
The bony landmarks of the thorax will be discussed first, followed by the
structures of the thoracic wall, the lungs and pleura, and finally the heart and
pericardium.
Bony landmarks. — The top of the sternum corresponds (in inspiration) to the
fibro-cartilage between the second and third thoracic vertebrae, and is distant
about 6.2 cm. (2| in.) from the spine. In the newborn child it corresponds to
the middle of the first thoracic vertebra (Symington). If traced downward, the
subcutaneous sternum presents a ridge (sternal angle of Louis) opposite to the
junction of the manubrium and body, and the second costal cartilages on either
side; this ridge usually corresponds to the disc between the fourth and fifth
thoracic vertebrae. At the lower extremity of the sternum the xiphoid cartilage
usually retires from the surface, presenting the depression of the epigastric angle
or 'pit of the stomach.' This is opposite to the seventh costal cartilages and the
expanded upper end of the recti, and corresponds to the tenth thoracic vertebra
behind.
Parts behind manubrium. — There is little or no lung behind the first bone of
the sternum, the space being occupied by the trachea and large vessels, as follows;
The left innominate vein crosses behind the sternum just below its upper border. Next
come the great primary branches of the aortic arch. Deeper still is the trachea, dividing into
its two bronchi opposite to the junction of the first and second bones of the sternum. Deepest
of all is the cesophagus. About 2.5 cm. (1 in.) below the upper border of the sternum is the high-
est part of the aortic arch, lying on the bifurcation of the trachea. (Holden.) (Fig. 1104).
Sterno-clavicular joint. — The expanded end of the clavicle and the lack of
proportion between this and the sternal facet, on which largely depends the
mobility of this, the only joint that ties the upper extremity closely to the trunk,
can be easily made out through the skin. Its strength, considerable when the
rarity of dislocation compared with fracture of the clavicle is considered, depends
mainly on its ligaments, the buffer-bond meniscus, the costo-clavicular ligament,
which checks excessive upward and backward movements, and the fact that the
elastic support of the first rib comes into play in strong depression of the shoulder
as in carrying a weight. The relative weakness of the anterior ligament deter-
mines the greater frequency of anterior dislocation of the clavicle at this joint.
Behind the joint lie, on the right side, the innominate artery, right innominate vein, and
pleura; on the left, the left innominate vein, the left carotid, and the pleura.
Acromio -clavicular joint. — On tracing the clavicle laterally, it is found to
rise somewhat to its articulation with the acromion. This joint has very little
mobility, and owes its protection to the strong conoid and trapezoid ligaments
hard by. Owing to the way in which the joint-surfaces are bevelled, that of the
clavicle looking obliquely downward, and resting upon the acromion, it is an
upward displacement of the clavicle which usually takes place.
Ribs. — In counting these, the position of the second is denoted by the trans-
1364
CLINICAL AND TOPOGRAPHICAL ANATOMY
verse line at the junction of the manubrium and body of the sternum. It is well
always to count ribs from this point and never from below, as the twelfth rib
varies in size and may be obscured by the sacro-spinalis muscles. The nipple
in the male, lies between the fourth and fifth, nearly an inch lateral to their
cartilages. The lower border of the great pectoral corresponds to the fifth rib.
The seventh, the longest of the ribs, is the last to articulate by its cartilage with
the sternum. When the arm is raised, the first three digitations seen of the
serratus anterior correspond to the fifth, sixth, and seventh ribs. The ninth rib
Fig. 1104. — The Abch of the Aorta, with the Pulmonary Artery and Chief Branches
OF THE Aorta.
(Modified from a dissection in St. Bartholomew's Hospital Museum.)
Int. jugular v.^ Inferior thyreoid veins
Transverse cervical a
Transverse scapular a
Right inf. laryng. n
Right com. carotid a
Subclavian v
Vagus nerve
Innominate a -"^^"^
Left innominate v
Phrenic nerve
Superior vena cava
Arch of aorta
Right bronchus
Branch of right pul-
monary a.
Branch of right pul-
monary V
Right pulmonary a.
Branch of right pul-
monary a.
Branch of right pul-
monary V.
Right atrium
Right coronary a.
Thoracic vertebra
Azygos vein
Intercostal vv.
Intercostal aa.
Thyreoid body
Left int. jugular v.
Vagus nerve
Left com. carotid a.
Left inf. laryng. n.
Left subclavian a.
Lelf subclavian v.
Left int. mammary v.
Left sup. intercostal v.
Phrenic nerve
Vagus nerve
Recurrent n.
Lig. arteriosum
Left pulmonary a.
Left pulmonary v.
Left bronchus
Branch of left pul-
monary a.
Pulmonary a.
Left pulmonary v.
Left coronary a.
Conus arteriosus
(Esophagus
Thoracic duct
Thoracic aorta
is the most oblique. The eleventh and twelfth can be felt lateral to the sacro-
spinalis. Owing to the obliquity of the ribs, their sternal ends are on a much
lower level than their vertebral extremities.
'Thus the first rib in front corresponds to the fourth rib behind, the second to the si.xth,
the thu-d to the seventh, the fourth to the eighth, the fifth to the ninth, the sixth to the tenth,
and the seventh to the eleventh. If a horizontal line be drawn round the body from before back-
ward at the level of the inferior angle of the scapula, while the arms are at the sides, the line would
cut the sternum in front between the fourth and fifth ribs, the fifth rib at the nipple line, and
the ninth rib at the vertebral column.' (Treves.) The most frequently broken are the sixth,
seventh, and eighth. The upper four and the two lowest ribs are best covered by soft parts,
and, in the case of the former, the shoulder and arm take off some of the violence that would
otherwise reach them. The way in which the ribs are embedded in the soft parts (fig. 1106),
and the fact that the fragments are often held in place by the periosteum, account for the diffi-
culty which is often met with in detecting crepitus. The intercostal spaces are wider in front
than behind. The three upper are the widest of all.
THE THORAX 1365
Cervical ribs. — It occasionallj' happens that the rib element of the seventh
cervical vertebra, normally fused with the true transverse process, is segmented off
as a separate, though usually rudimentary, rib. This anomaly is generally
bilateral. It occurred in 3 of 260 subjects (1.16 per cent.) examined by Wingate
Todd.*
The anterior extremity of a cervical rib may, according to the degree of its development
(1) lie free amongst the scalene muscles; (2) be connected with the sternum by a hgameutous
prolongation; (3) articulate with the upper surface of the first thoracic at about its centre by
a synchondrosis, or (4) form a complete rib, articulating by a costal cartilage with the sternum.
The lowest trunk of the brachial plexus formed by the eighth cervical and first thoracic
roots, the subclavian artery and less commonly the subclavian vein, curve over the upper
surface of these ribs. The abnormality owes its clinical importance to the pressure effects
produced on the nerve trunk in a small proportion of the cases. This pressure is manifested
by ( 1) pain, going on to anaesthesia down the medial side of arm, forearm and hand; (2) paralysis
of the intrinsic muscles of the hand, producing the main en griffe, and to a less extent of the mus-
cles of the forearm; (3) vascular effects (anamia, gangrene, etc.), manifested chiefly in the hand.
Todd has shown that these vascular effects are not due to mechanical pressure on the subclavian
artery by the cervical rib as was formerly supposed, but are trophic lesions of the sympathetic
(vasomotor) nerves. The vasomotor nerves to the arm mainly come from the second thoracic
root by the communication it gives to the lowest cord of the brachial plexus, and so are exposed
to pressure from the rib.
Fig. 1105. — Cervical Ribs, Viewed from Above. ( X i.) NN, Impression for Lowest
Trunk op Brachial Plexus. AA, Impression for Subclavian Artery. (T. Wingate
TODD.)
The same investigator has shown that similar symptoms may be produced occasionally by
a first thoracic rib in cases where the brachial plexus has migrated caudad. In the living
patient, unless a radiogram be taken showing all the vertebroe up to the base of the skuU, it is
not possible with precision to ascertain with which vertebra the highest rib present articulates.
Structures found in an intercostal space. — (1) Skin; (2) superficial fascia,
with cutaneous vessels and nerves; (3) deep fascia; (4) external intercostal; (5)
cellular interval between intercostals, containing trunks of intercostal vessels and
nerves; (6) internal intercostals; (7) thin layer of fascia; (8) subpleural connective
tissue; (9) pleura (fig. 1106).
The intercostal arteries are nine aortic and two from the superior intercostal. An aortic
intercostal having given off its dorsal branch, lying beneath the pleura, crosses the space ob-
liquely upward to gain the lower border of the rib above, enters the costal groove at the angle,
and runs forward between the intercostal muscles to anastomose with the anterior intercostals
from the internal mammary or musculo-phrenic. Hence the rule of making the incision in
empyema above the upper margin of the lower rib and in front of the angle. Along the dorsal
branch a vertebral abscess may track backward.
Internal mammary artery.- — This descends behind the clavicle, the costal
cartilages, and the first six spaces, about 1.2 cm. (| in.) from the edge of the ster-
num. In the sixth intercostal space it divides into musculo-phrenic and superior
epigastric acteries. Its vense comitantes uniting join the innominate vein of the
same side. A punctured wound of the artery is most easily secured in the second
and third spaces; below, resection of part of a costal cartilage will be needed.
Structures passing through the upper aperture of the thorax. — If a section
is made passing through the manubrium sterni, upper border of the first rib, and
* Journal of Anatomy and Physiology, Vol. 47, 1913.
1366
CLINICAL AND TOPOGRAPHICAL ANATOMY
upper part of the first thoracic vertebra, the following structures are met with :
— (1) In the middle line. Sterno-hyoid and sterno-thyreoid muscles, with their
sheaths of deep cervical fascia, cellular tissue in which are the remains of the
thymus gland, the inferior thyreoid veins, the trachea and tracheal fascia, the
oesophagus, and longus colli muscles. Between the trachea and oesophagus are
the recurrent nerves. (2) On each side. The apex of the lung, covered by pleura,
deep cervical fascia, and membranous cervical diaphragms ("Sibson's fascia")
derived from the scalenes, rises about 3.7 cm. (1| in.) above the first rib. Between
it and the trachea and oesophagus lie the following : the internal mammary artery,
the phrenic nerve; on the right side, the innominate vein and artery, with the
vagus between the two, the cardiac nerves, and the right lymphatic duct. On
the left side are the common carotid and subclavian arteries, with the left vagus
between them, the cardiac nerves and the thoracic duct. Farthest back and
on each side are the trunk of the sympathetic, the superior intercostal artery, and
the first thoracic nerve.
The mamma. — This lies chiefly on the pectoralis major and slightly on the
rectus abdominis and serratus anterior. It is usually described as reaching from
the second to the sixth rib, and from the sternum to the anterior border of the
axilla. It is most important to remember that the breast is often a much more
extensive structure than would be included in the above very limited description.
Thus — (1) the gland is not encapsuled at its periphery, its tissue branching and
breaking up here to become continuous with the superficial fascia. (Stiles.) (2)
Fig. 1106. — Section op the Sixth Left Intercostal Space, at the Junction of the
Anterior and Posterior Thirds. (Tillaux.)
Intercostal vein
Intercostal artery-
Intercostal nerve -
Serra tus anterior"
Serratus aponeurosis'"
osis covering external inter--.
costal muscle
External intercostal muscle"
— Aponeurosis covering the internal
intercostal muscle
Internal intercostal muscle
— Pleura
The retinacula cutis contain lymphatics and, sometimes, mammary tissue. (3)
There is a lymphatic plexus, and, often, minute lobules of gland tissue, in the
pectoral fascia. (Heidenhain.) Fully one-third of the whole mamma lies
posterior and lateral to the axillary border of the pectoralis major so that it
reaches almost to the mid-axillary line. That part of the upper and lateral
quadrant known as the axillary lobe is of especial importance from its reach-
ing into close vicinity with the anterior pectoral group of axillary nodes (p. 719).
In the male the nipple is usually placed in the fourth space, nearly 2.5 cm. (1 in.)
lateral to the cartilages of the fourth and fifth ribs. On the nipple itself open the
fifteen or twenty ducts which dilate beneath it, and then diverge and break up
for the supply of the lobules. The skin over the areola is very adherent, pig-
mented, and fatless. Here also are groups of little swellings corresponding to
large sebaceous follicles and areolar glands. The skin over the breast is freely
movable, and united to the fascia which encases the organ, and thus to the inter-
lobular connective tissue, by bands of the same structure — the retinacula cutis.
Under the breast, and giving it its mobility, is a cellulo-fatty layer, the seat of
submammary abscess.
' The nerves which supply the breast are the anterior cutaneous branches of the second,
third,' foui'th, and fiftli intercostal nerves, and the lateral branches of the last three. The
connection of tliese trunliS serves to explain the diffusion of the pain often observed in painful
affections of the breast. Thus pain may be referred to the side of the chest and bacli (along the
above intercostal trunks), over the scapula, along the medial side of the arm (along the inter-
costo-brachial nerve), or up into the neck. The gland is supplied by the following arteries : the
aortic intercostals of the second, third, fovirth, and fifth spaces, similar intercostal branches
from the internal mammary, which runs outward, two small branches to each space, perforating
branches from the same vessel, one or two given off opposite to each space, the long thoracic and
external mammary (when present) from the axillary.
THE LUNGS
1367
The lymphatics have aheady been described (p. 721, fig. 566).
In removal of the breast elliptical incisions will usually suffice if employed on wide lines,
and if attention be paid to the following points: — (1) Those details in the surgical anatomy
already referred to, especially those bearing on the extensiveness of this organ, and the propor-
tionate difference between seen and unseen disease. (2) The importance of removing in one
continuous piece the whole breast, all the skin over it, the costo-sternal part of the pectoralis
major, the pectorahs minor, the axillary fat, and lymi^hatics.
Outline of the lungs. Their relation to the chest-wall. — To map out the
lung, a line should be drawn from the apex, a point about 2.5 cm. (1 in.) above the
clavicle, a little lateral to the sterno-mastoid muscle, at the junction of medial
and middle thirds of clavicle, obliquely downward, behind the sterno-clavicular
joint, to near the centre of the junction of the first and second bones of the ster-
num. Thence, on each side, a line should be drawn slightly convex as far as a
similar point on the sternum lying opposite the articulation of the fourth chondro-
sternal joint. On the right side the line may be dropped as low as the sixth chon-
dro-sternal joint; on the left the incisura cardiaca may be shown by drawing a
vertical line along the middle line of the sternum, from the level of the medial
extremities of the fourth costal cartilages to the lower end of the gladiolus, and
Fig. 1107. — Outline op the Heart, its Valves, the Lungs (shaded), and the Pleura.
(Holden.) (Cf. fig. 437.)
by carrying two other lines, from the extremities of the first line, outward so as
to meet at a point over the heart's apex (Cunningham); to mark this gap, a
line should be drawn sloping laterally and downward from the fourth chondro-
sternal articulation across the foui'th and fifth interspaces, to a point about
3.7 cm. (1| in.) below the left nipple (male) and 2.5 cm. (1 in.) to its medial side.
This point, lying in the fifth space, marks the apex of the heart. Thence the line
curves medially to the sixth costal cartilage, a little medial to its chondro-
sternal junction, and in the lateral vertical line. Thus the lower part of the
anterior surface of the right ventricle is not covered by lung. The lower border
of the lung will be marked on the right side by a line drawn from the sixth chondro-
sternal articulation across the side of the chest down to the tenth thoracic spine.
The lower border of the left lung will follow a similar line, starting on a level
with a similar joint (sixth chondro-sternal joint), but much farther laterally
than on the right side, i. e., in the fifth space, about 7.5 cm. (3 in.) to the left
of the middle line, or a point corresponding to the heart's apex. In the nipple-
line the lung crosses the sixth rib, in the mid-axillary line the eighth, and opposite
1368 CLINICAL AND TOPOGRAPHICAL ANATOMY
the angle of the scapula (the arms being close to the sides), the tenth rib. The
position of the great fissure in each lung may be ascertained approximately by
drawing a line curving downward and forward from the second thoracic spine
to the lower border of the lung at the sixth costal cartilage; and the smaller fissure
of the right lung extends from the middle of the foregoing to the junction of the
fourth costal cartilage with the sternum. It will be seen from the above that
there is little lung behind the manubrium. The connective tissue here between
the lung margins contains the thymus, large up to the age of puberty, and, later,
its remains. The hilus (root) of the lung is referred to on p. 1230.
The pleura, following much the same line as the lung above and in front,
reaches lower clown laterally and behind. Thus the two sacs starting from about
2.5 cm. (1 in.) above the medial third of the clavicle converge toward the angle
of Louis (p. 1238) ; meeting here, they descend vertically, the left overlapping the
right slightly, to the fourth chondro-sternal joint. Hence the right sac descends
behind the sternum to the sterno-xiphoid junction and sixth chondro-sternal
joint. Thence, as it curves to the back of the chest, it crosses the eighth rib
close to the lateral vertical line {vide supra), the tenth in the mid-axillary, the
eleventh in the line of the angle of the scapula, and thence toward the twelfth
thoracic vertebra. On the left side the pleura parts company from the right at the
level of the fourth chondro-sternal junction, deviating laterally and downward
across the fourth and fifth interspaces; it then turns again slightly medially to
meet the sixth costal cartilage. Thus, as in the case of the lung, but to a less
extent, there is a small area of the pericardium, and, under it, the right ventricle
uncovered by the pleura. Over the side and back of the chest, along its dia-
phragmatic reflection, the left pleura reaches a little lower than the right.
The deepest part of the pleural sac is where the reflection crosses the tenth rib or tenth space
in the mid-axillary line. From this it ascends slightly as it curves back to the spine. (Cun-
ningham.) The relations of the pleura to the last rib are of much importance to the surgeon in
operations on the kidney. In the case of a twelth rib of ordinary length, the pleural reflection
crosses it at the lateral border of the sacro-spinalis ; when a rudimentary last rib does not reach
the lateral border of this muscle, an incision carried upward into the angle between the eleventh
rib and the sacro-spinalis will open the pleural sac. (Melsome.)
For tapping the pleura there are two chief sites: — (1) The sixth or seventh space in front
of the posterior fold of the axilla. (2) The eighth space behind, in the line of the angle of the
scapula. For the incision of an empyema the first is usually chosen. The overlying soft parts
are not thick, the interspace is wide enough, drainage is sufficient (especially if part of the
seventh or eighth rib be resected), and this site is free from the objection that the angle of the
scapula overlaps the seventh and eighth ribs, unless the arm is raised.
Outline of the heart. Its relation to the chest-wall. — The upper limit of
the heart (base) will be defined by a line crossing the sternum a little above the
upper border of the third costal cartilage, reaching about 1.2 cm. (J in.) to the
right and about 2.5 cm. (1 in.) to the left of the sternum. Its apex point is in the
fifth space, 3.7 cm. (1| in.) below the male left nipple, and 2.5 cm. (1 in.) to the
medial side. This point will be at 7.5 cm. (3 in.) from the left border of the
sternum. The right border (right atrium) will be given by a line, slightly convex
laterally, drawn from the right extremity of the upper border to the right sixth
chondro-sternal joint. If another line, slightly convex upward, be drawn
onward from this point across the last piece of the sternum, just above the
xiphoid cartilage, to the apex, it will give the lower border (margo acutus of right
ventricle), which rests on the central tendon of the diaphragm. The left border
(margo obtusus of left ventricle) will be given by a line, convex to the left, passing
from the left extremity of the upper border to the apex, medial to the nipple-
line. This line should be 7.5 cm. (3 in.) from the middle of the sternum at the
level of the fourth costal cartilage. The base of the heart is opposite four of
the thoracic vertebrae, viz., the sixth, seventh, eighth, and ninth. The apex
and anterior or costo-sternal surface have been mentioned. The inferior or
diaphragmatic surface (chiefly left atrium and left ventricle) rests upon the
diaphragm, mainly the central tendon, to which the intervening pericardium
is connected, and is thus adjacent to the liver and a small portion of the stomach.
If a circle 5 cm. (2 in.) in diameter be described around a point midway between the left
nipple and the lower end of the gladiolus, it will define with sufficient accuracy for practical
purposes that part of the heart which lies immediately behind the chest wall, and which is
uncovered by lung and (in part) by pleura. (Latham.)
THE HEART 1369
The valves. — The pulmonary valves (the highest and most superficial) lie, in
front of the aortic, behind the third left chondro-sternal joint, and opposite to
the upper border of the third costal cartilage. The aortic valves lie behind and a
little below these, opposite to the medial end of the third intercostal space,
and on a level with the lower border of the third left costal cartilage. The
atrio -ventricular openings lie at a somewhat lower level than that of the aortic
and pulmonary. Thus the tricuspid valves lie behind the middle of the sternum
at the level of the fourth intercostal space; and the mitral valves, the most deeply
placed of all, lie a little to the left of these, behind the left edge of the sternum
and the fourth left costal cartilage (fig. 1107; also cf. fig. 437).
'Thus these valves are so situated that the mouth of an ordinary-sized stethoscope will
cover a portion of them all, if placed over the juncture of the third intercostal space, on the left
side, with the sternum. All are covered by a thin layer of lung; therefore we hear their action
better when the breathing is for a moment suspended.' (Holden.)
The pericardium. — This fibro-serous sac, occupying the middle mediastinum,
is triangular in shape, with the apex upward. Here its fibrous layer gives mvest-
ment to the large vessels, except the inferior cava. It is also continuous with the
deep cervical fascia. The base, connected with the diaphragm, has been referred
to above. In front an area of variable size (fig. 1107), owing to the divergence
of the left pleura, is in contact with the left half of the lower part of the sternum,
and more or less of the medial ends of the fourth, fifth, and sixth costal cartilages,
here forming the posterior boundary of the anterior mediastinum. Behind, the
pericardium is the anterior boundary of the posterior mediastinum, and is in
close contact with the oesophagus and aorta.
Paracentesis of pericardium. — While the seat of election must here remain an open question,
each case requiring a decision for itself, the one most suitable on the whole is the fifth left space,
about 2.5 cm. (1 in.) from the sternum, so as to avoid injury to the internal mammary artery
and the pleura, of which the line of reflection has been shown to vary.
In incision of the pericardium to establish free drainage, a portion of the fifth or sixth left
costal cartilage should be carefully resected, the internal mammary artery tied, the trans-
versus thoracis (triangularis sterni) scratched through, and the pleural reflexion pushed aside.
Relation of vessels to the wall of the thorax. — Aortic arch. — The ascending part of the
aorta reaches from a spot behind the sternum, a little to the left of the centre, on a level with the
third left costal cartilage, to the upper border of the second right cartilage; thus it passes up-
ward, backward, and to the right, and is about 5 cm. (2 in.) long. The transverse part then
crosses backward to the left behind the sternum (the highest part of the arch being about 2.5
cm. (1 in.) below the notch), reaching from the second right costal cartilage to the lower border
of the fourth thoracic vertebra on the left side. This part recedes from the surface, and, with
the next, cannot be marked out on the surface. The third, or descending part, the shortest
of the three, reaches from the lower border of the fourth to that of the fifth thoracic vertebra.
Fig. 1104 will remind the reader of many of the pressure symptoms which may accompany
an aneurysm of the aortic arch; e. g., pressure on the left innominate vein, the three large arte-
ries, trachea, and left bronchus, recurrent nerve, oesophagus, and thoracic duct. In aneurysm
of the thoracic aorta, pain, usually unilateral, referred to the corresponding intercostal nerves,
is a common pressure symptom.
The pulmonary artery lies behind the left side of the sternum and its junction with the sec-
ond and third costal cartilages.
Innominate artery. — A line drawn from the top of the arch, about 2 . 5 cm. (1 in.) below
the sternal notch, and close to the centre, to the right sterno-clavicular joint, will give the line
of this vessel.
Left common carotid. — This vessel will be denoted by a line somewhat similar to the above,
passing from the level of the arch a little to the left of the last starting-point to the left sterno-
clavicular joint.
Left subclavian artery. — A line from the end of the transverse arch, behind the left of the
sternum, straight upward to the clavicle, delineates the vertical thoracic course of the long left
subclavian artery; its thoracic portion lies behind the left carotid.
Innominate veins. — The left, 7.5 cm. (3 in.) long, extends very obliquely from the left
sterno-olavicular joint, behind the upper part of the manubrium, to a point 1.2 cm. (| in.) to
the right of the sternum, on the lower border of the first right costal cartilage. The right,
about 2.5 cm. (1 in.) long, descends almost vertically to the above point from the right sterno-
clavicular joint.
Venae cavae. — The superior descends from the point above given for the meeting of the
innominate veins in the first intercostal space, close to the sternum, and perforates the right
atrium on a level with the third costal cartilage. The inferior vena cava. — The opening of this
vein into the right atrium lies under the middle of the fifth right interspace and the adjacent
part of the sternum.
The oesophagus. — The relations of this tube in its cervical and thoracic
portions are most important, e.g., to the trachea and left bronchus; the vagi
and left recurrent nerve; the pleurae, left above and right [below, aorta, and
1370 CLINICAL AND TOPOGRAPHICAL ANATOMY
pericardium. Its lymphatics go below into the posterior mediastinal and superior
gastric nodes; above into the lower deep cervical nodes, a point sometimes diag-
nostic in malignant disease.
The lumen of the oesophagus is narrowed at three points: — (1) and best marked at the cri-
coid cartilage, (2) where it is crossed by the left bronchus, (3) as it passes through the dia-
phragm. The tube, 25 to 27 cm. (10 to 11 in.) long, extends from the sixth cervical to the lower
■ border of the tenth thoracic vertebra. In an adult, the distance from the incisor teeth to the
cricoid is about 15 cm. (6 in.); an additional 7.5 cm. (3 in.) gives the level of the crossing of
the left bronchus, while from the teeth to the opening in the diaphragm would be from 41 to 43
cm. (16 to 17 in.). To expose the tube in the neck an incision is made on the left side, much
as for the higher ligature of the common carotid, but carried lower down. The depressors of
the hyoid being drawn medially or divided, the pretracheal fascia is opened, which allows of
the overlapping thyreoid and trachea being displaced medially, while the carotid sheath is re-
tracted laterally. The tracheal rings are the best guide to the oesophagus. The recurrent
nerve must be avoided.
THE ABDOMEN
The regions and subdivisions will first be considered, the abdominal wall
next, and finally the abdominal cavity, including the peritoneum and the various
organs.
Subdivision of the abdominal cavity. — Certain arbitrary horizontal and
vertical planes, represented by lines drawn on the ventral surface, are used to
subdivide the abdomen for topographical purposes (fig. 898). A. Horizontal
planes. (1) Infracostal through the lower margins of the tenth costal cartilages
(the lowest part of the costal margin). This plane crosses the body of the third
lumbar vertebra. (2) Intertuhercular, passing through the tubercles, prominent
points of the ihac crests, which are situated about 5 cm. (2 in.) behind the anterior
superior spines. This plane crosses the body of the fifth lumbar vertebra.
B. Vertical planes. (1) Median vertical, drawn upward in the middle line
from the symphysis pubis. (2) Lateral vertical, drawn upward on each side
parallel to the former, from a point midway between the anterior superior iliac
spine and the symphysis pubis.
These lateral lines if prolonged upward into the thorax pass rather more than 2.5 cm.
(1 in.) to the medial side of the male nipple and meet the clavicle a little medial to its mid-point.
According to the BNA system, the lateral vertical lines are slightly curved, extending
upward from the pubic tubercle on each side along the lateral margin of the rectus muscle
(corresponding to the linea semilunaris).
The infracostal and intertuhercular planes, with the two lateral vertical
planes that intersect them divide the abdomen into nine regions: — three median,
viz., the epigastric, umbilical, and h3rpogastric and on each side three lateral, viz.,
hypochondriac, lumbar, and iliac (fig. 898).
Another transverse plane of practical importance, though we do not use it as a boundary
of the abdominal subdivisions, is represented by Addison's transpyloric line, drawn horizontally
through a point midway between the umbilicus and the sterno-xiphoid junction (or midway
between the symphysis pubis and supra-sternal notch). It crosses the spine at the level of
the first lumbar vertebra. It must be noted that the pylorus only lies in this plane during
life when the subject is in the horizontal position. On assuming the upright position the pylorus
falls at least one vertebra lower. The sterno-xiphoid plane, drawn horizontally through the
junction of the body of the sternum with the xiphoid, outs the spine at the disc between the
ninth and tenth thoracic vertebrte, and the umbilical plane, passing through the umbilicus,
crosses the disc between the third and fourth lumbar vertebrae (though in corpulent subjects it is
somewhat lower).
The abdominal wall. Bony and muscular landmarks. — The linea alba
forms a perceptible groove in the middle fine from the xiphoid cartilage to below
the umbilicus. It is a band of interlacing fibres, mostly crossing each other at
right angles, that forms the main insertion of the transversus and oblique
muscles, and stretches between the two recti muscles from xiphoid cartilage to
symphysis. It is on the average 1.2 cm. (| in.) wide above the umbilicus. Below
the umbilicus it narrows rapidly and becomes merely a thin fibrous septum
between the two recti, which in this position lie close together.
In its broad supra-umbilical portion, small hernial protrusions of subperitoneal fat often
force their way through interstices in the linea alba, and true peritoneal sacs may be drawn
through after them. The linea alba is not very vascular, and hence was at one time the favour-
THE ABDOMEN 1371
ite site of incisions in opening the abdominal cavity. Since the resulting scar is weak and
yielding, however, it is now more customary to make vertical incisions through the rectus
sheath, to one side of the middle line, where the abdominal wall can be sutured in layers, and
an incisional hernia prevented.
The umbilicus lies in the linea alba rather below its centre. It is somewhat
prone to hernia formation (p. 1402) and is occasionally the site of congenital
fistulas, which may originate in a Meckel's diverticulum (p. 1376) or a patent
urachus.
When the recti are thrown into contraction the linea semilunaris on each side
is made evident as a groove, extending with a slight lateral convexity from
the tip of the ninth costal cartilage, where the lateral vertical line meets the thoracic
margin, to the pubic tubercle.
The contraction of the recti muscles also shows up the three lineae transversae, fibrous
intersections adherent to the anterior layer of the sheath of the rectus, which cros.? the substance
of the muscle (1) at the umbilicus, (2) at the tip of the xiphoid, and (3) midway between the
former two. A tonic contraction of one or both recti localised to one of these segments occa-
sionally gives rise to the "phantom" tumors which occur in some hysterical cases.
The linea semilunaris shares the disadvantages of the linea alba as a site for incisions, and
there is the further danger of injury to the nerve supply of the rectus, which may involve a
diffuse bulge of the atrophied muscle.
In tapping the bladder above the pubes, the trocar should be introduced immediately above
the pubes and driven backward and a little downward. In this operation, and in suprapubic
cystotomy, the retro-pubic space or cavum Retzii is opened. This is bounded in front by the
pubes and superior fascia of the urogenital diaphragm, behind by the anterior surface of the
bladder. Below are the true ligaments of this viscus. The space contains fatty tissue and veins,
increasing in size with the advance of life. If about ten ounces of fluid are injected into the
bladder, the peritoneum will be raised sufficiently to allow of a three-inch incision being made
between the recti and pyramidales immediately above the pubes. The transversalis fascia is
thicker below, and is often separated from the linea alba by fat, which must not be mistaken
for the extra-peritoneal layer. The peritoneal reflexion is loosely connected to the bladder
and can always be peeled upward.
A transverse line drawn from one anterior superior iliac spine to the other crosses at about the
level of the top of the promontory of the sacrum. Such a line will always show whether the
pelvis is horizontal or not. (Holden.)
The inguinal (Poupart's) ligament corresponds to a line drawn with a slight
curve downward between the anterior superior iliac spine and the pubic tubercle.
The first of these bony prominences corresponds to the starting-point of the
above ligament, the attachment of the fascia lata to the ilium, the meeting of the
fleshy and aponeurotic parts of the external oblique (denoted by a line drawn
upward from this spine to the ninth costal cartilage, or often a little anteriorly
to these points), the point of emergence of the lateral cutaneous nerve of the
thigh, and part of the origins of the internal oblique, transversus, and tensor
fasciae latae.
The pubic tubercle marks the lateral pillar (inferior crus) of the subcutaneous
inguinal (external abdominal) ring, the mouth of which corresponds to the crest
of the pubes lying between the tubercle and the symphysis. The neck of an
inguinal hernia is above the tubercle and Poupart's ligament; that of a femoral
hernia below and lateral to the tubercle, and below the same hgament. The ring,
and especially its lateral pillar, can easily be felt by invaginating the scrotal skin
with a finger, and pushing upward and laterally. In a female patient, if the thigh
be abducted, the tense tendon of tlu' adductor longus will lead up to the site of the
ring. The abdominal inguinal (internal abdominal) ring is situated about 1.2 cm.
(J in.) above the centre of Poupart's ligament; oval in shape, and nearly vertical
in direction, it has the arching fibres of the transversus above it, and to its
medial side the inferior epigastric artery, lying behind the spermatic cord. The
pulsations of this vessel here guide the finger in the insertion of the uppermost
deep sutures in radical cure of hernia. The canal runs obliquely downward and
forward between the two rings. In the adult it is about 3.7 cm. (1^ in.) long, but
in early life, and in adults with a large hernia dragging upon the parts, the two
rings are much nearer, and may be one behind the other. For the anatomy of
inguinal hernia see p. 1304.
Vessels in the abdominal wall. — The three superficial branches of the com-
mon femoral, the external pudic, epigastric, and circumfiex iliac, supply the lowest
part of the abdominal wall and the adjacent groin and genitals. The others
that have to be remembered are the inferior epigastrics and the epigastric branch
1372 CLINICAL AND TOPOGRAPHICAL ANATOMY
of the internal mammary, the deep circumflex iliacs, the last two intercostals, and
the abdominal branches of the lumbar arteries.
Of these, the infei'ior epigastric is the most important; its course will be marked out by a
line drawn from a point just medial to the centre of the inguinal ligament, upward and medially
to the medial side of the abdominal ring, and thence to a point about midway between the pubes
and umbilicus, forming the lateral boundary of Hesselbach's triangle (fig. 1121). Here the
vessel, which at first lies between the peritoneum and fascia transversalis, perforates the latter
and, passing over the semicircular line (fold of Douglas) enters the sheath of the rectus. It then
runs upward, closely applied to the back of that muscle, and, a little above the level of the
umbilicus, divides into branches which anastomose with the epigastric branch of the internal
mammary.
One superficial vein in the abdominal wall needs especial mention, the thoraco-epigastric,
joining the veins of the chest, e. g., the long thoracic above with, the superficial epigastric
below. Its valves directing the blood downward below and upward above (Stiles) may be
rendered incompetent when this vessel is enlarged, as in interference with the portal vein, mth
which it communicates by a vein in the round ligament, or in blocking of the inferior vena cava.
Lymphatics. — It is sufficiently correct to say here that those above the umbilical line go
to the axillary, and those below that line to the inguinal nodes.
Nerves. — The lower seven intercostals and the ilio-hypogastric and ilio-
inguinal supply the abdominal wall. The sixth and seventh intercostals supply
the skin over the upper epigastrium; the eighth, the area of the middle linea
transversa; the tenth, that of the imibilicus ; the last thoracic, ilio-inguinal and ilio-
hypogastric, the region above Poupart's ligament, and that of the pubes. The
ilio-hypogastric supplies the skin over the subcutaneous inguinal (external
abdominal) ring; the ilio-inguinal that over the cord and scrotum. The last
thoracic and ilio-hypogastric cross the iHac crest to supply the skin of the buttock.
The diaphragm. — The upper limit of the diaphragm rises to the following
levels in full expiration: Its central tendon to about the lower end of the body of
the sternum, or the seventh chondro-sternal joint; the right half to the fifth rib,
or about 1 cm. (| in.) below the nipple; the left half not rising quite so high, i. e.,
to the fifth space, or 2.5 cm. (1 in.) below the nipple.
Topographical relations of abdominal viscera. — These will include the
peritoneum, liver and bile passages, stomach, spleen, pancreas, intestines,
kidneys and ureters, and large abdominal vessels.
The peritoneal spaces. — The peritoneum presents certain potential spaces,
determined by its various reflections from the parietes and abdominal viscera.
In these spaces collections of fluid such as abscesses or extravasations from hollow
viscera or blood vessels may collect and become shut off by adhesions or overflow
in various directions into neighbouring spaces. The transverse mesocolon and
great omentum together form a shelf transversely placed, which divides the greater
sac into two main divisions — supra-omental and infra-omental.
The supra-omental region, in which the various forms of subphrenic abscess are found, con-
tains the following fossa; (Barnard).* (1) Right subphrenic, between the right lobe of the liver
and right cupola of the diaphi-agm, bounded toward the median line by the falciform ligament,
and behind by the coronary ligament. It communicates below with (2) the subhepatic fossa
or right renal pouch (Morison), which is bounded above by the visceral surface of the liver, and
below by the mesocolio shelf and right kidney. It extends from the right lateral abdominal
wall, its most capacious part, across the median line under the left lobe of the liver, and on its
posterior aspect lie the upper pole of the right kidney, epiploic foramen, and anterior surface of
small omentum. (3) The left subphrenic, also known as the anterior perigastric fossa, lies
between the left dome of the diaphragm above, and the left lobe of liver, stomach, spleen and
omentum below. It is bounded on the right by the falciform ligament which lies somewhat to
the right of the median line. (4) The omental bursa may be regarded as a diverticulum from
the subhepatic fossa with which it communicates by the epiploic foramen. Abscesses in this
sac are rare, but occasionally laceration of the pancreas which is closely related to it behind
gives rise to a collection of pancreatic juice and blood in the lesser sac, known as a pancreatic
pseudo-cyst (Jordan Lloyd).
The infra-omental region is subdivided in its abdominal part into (1) right and (2) left
compartments by the attachment of the root of the mesentery to the spine, descending from the
duodeno-jej unal flexure downward into the right iliac fossa. These fossae communicate with the
supra-omental regions in the neighbourhood of the hepatic and splenic flexm-es of the colon
respectively, and below with (3) the pelvis. The deepest level of the peritoneum lining the pelvis
constitutes in the male the recto-vesioal, and in the female the recto-vaginal fossa (pouch of
Douglas).
It should be noted that with a patient in the supine position, owing to the contour of the
psoas muscles and the anterior convexity of the lumbar spine, any fluid above the pelvic brim
will tend to gravitate into the subphrenic spaces across the flexures of the colon which lie far
back in the loins. This is undesii-able in view of the great absorbing power of the subphrenic
lymphatics, and may be obviated by propping the patient in a half-sitting position.
* Barnard, H. L., Brit. Med. Journal, Feb. 15, 1908.
THE STOMACH 1373
Viscera behind the linea alba. — From above downward there are the follow-
ing:— (Ij Above the umbiUcus — the left lobe of the liver, the stomach, the
transverse colon, part of the great omentum, the pancreas, and cceliac (solar)
plexus. (2) Below the umbilicus — the rest of the great omentum, covering in
the small intestines and their mesentery. In the child, the bladder occupies a
partly abdominal position; and in the adult, the same viscus, if distended, will
rise out of the pelvis and displace the above structures, raising the peritoneum
until, if distended half way to the umbilicus, there is an area of nearly 5 cm.
(2 in.) safe for operations above the symphysis. The gravid uterus also rises
behind the linea alba.
The liver (figs. 914, 941, and 1125). — In the erect position, the anterior thin
margin of the liver projects about 1 cm. (| in.) below the costal cartilages, but
can only be made out with difficulty in this position. It may also be displaced
downward by pleuritic effusion or tight lacing. The liver is also, proportion-
ately, much larger in small children.
Of the three more accessible surfaces, the right lateral is opposite the seventh to the eleventh
intercostal arches, separated from them by the pleura, the thin base of the lung, and the dia-
phragm. The superior surface is accurately fitted with its right and left portions into the hol-
lows of the diaphragm, a slightly depressed area intervening which corresponds to the central
tendon. Its level corresponds to that of the diaphragm given above. On the left side, in the
adult, the limit of the left lobe will be in the fifth interspace, about 7.5 cm. (3 in.) from the ster-
num. The antericr surface is in contact with the diaphragm, costal arches, and, between them,
the xiphoid cartilage, and, below, with the abdominal wall. Both the superior and anterior
siu'faoes are subdivided by the falciform ligament, an important point in subphrenic suppura-
tion. In the right hypochondrium the anterior margin corresponds to the lower margin of
the thorax; but in the epigastric region, running obhquely across from the ninth right to the
eighth left costal cartilage, it crosses the middle line about a hand's breadth below the sterno-
xiphoid articulation (Godlee), or half-way between the sterno-xiphoid j unction and umbiUcus,
i.e., in the transpyloric line (fig. 914). Behind, the anterior margin, following the right lateral
surface within the costal arches, crosses the last rib toward the level of the eleventh thoracic
spine. In the anterior border, a little to the right of the median vertical plane, is the umbilical
notch, where the falciform and round ligaments meet. Still further to the right, and just to the
left of the mid-Poupart plane, is the fundus of the gall-bladder.
Gall-bladder and bile passages. — The fundus of the gall-bladder, situated in a
fossa on the under surface of the right lobe of the liver, and having the quadrate
lobe to its left, lies opposite to the right ninth costal cartilage, close to the lateral
edge of the rectus. This point corresponds to the site of intersection of the lateral
vertical and transpyloric lines. It is in contact with the hepatic flexure of the
colon and the first piece of the duodenum, into either of which, but particularly
the latter, large gall-stones impacted in the neck of the gall-bladder occasionally
ulcerate. A distended gall-bladder as it enlarges tends to take a line obliquely
from the above point where it emerges from under the costal margin toward the
umbilicus.
The long axis of the gall-bladder is directed from the fundus backward and upward. The
cystic duct runs from the neck downward and forward in the gastro-hepatic omentum, and so
forms an acute angle with the gall-bladder. A spiral fold of mucous membrane at the junction
of the two, which fulfils the function of keeping the lumen open for the flow of bile, adds to the
difficulty of passing a bougie from the gall-bladder down into the common duct.
The hepatic and cystic ducts join in the right free margin of the gastro-hepatic omentum
to form the common bile-duct, 7.5 cm. (3 in.) in length, which as it runs down to open into the
duodenum presents four distinct stages. (1) It first lies in the free edge of lesser omentum in
front of the epiploic foramen, with the hepatic artery to the medial side, and the portal vein
behind them both. (2) Behind the first part of the duodenum with the gastro-duodenal artery
accompanying it. (3) In a deep groove in the head of the pancreas, between that gland and
the posterior aspect of the second part of the duodenum. The pancreatic tissue siurounds it
completely in 75 per cent, of cases, (Bunger) hence the jaundice that occurs in chronic inter-
stitial pancreatitis. (4) Piercing the muscular waU of the duodenum obliquely it ends by
joining the main duct of the pancreas at the ampulla of Vater and opening into the second part
of the duodenum by a common orifice. This orifice, situated on the postero-medial aspect of
the gut, rather below the centre of the second portion, is raised on a small papilla and is nar-
rower than the lumen of the common duct.
The stomach. — The study of this organ by rendering its contents opaque with
bismuth salts and projecting its shadow by X-rays on a fluorescent screen, has
greatly modified the conception of its shape and position formed from post-
mortem and operative observations. Examined post-mortem, or at operations
under general ansesthesia it forms a flaccid sac with its long axis directed from the
fundus obliquely downward, forward, and to the right. Seen under X-rays,
1374 CLINICAL AND TOPOGRAPHICAL ANATOMY
with the patient standing upright, the cardiac portion (the fundus and body
together) is vertical, and the smaller pyloric portion is directed backward and to
the right and slightly upward (fig. 1125). The most fixed point is the cardiac
orifice.
The cardiac orifice lies under the seventh left costal cartilage 2 cm. (f in.) from the sterno-
xiphoid junction at a depth of about 10 cm. (4 in.) from the surface. Behind, this point corre-
sponds to the tenth thoracic vertebra.
The pyloric orifice hes in the transpyloric plane when the patient is recumbent,'but when the
patient is standing it falls to the level of the second or third lumbar vertebra, or lower still
Fig. 1108. — Photograph op an Empty Stomach. (J. S. B. Stopford.)
when"any transient faintness or nausea causes loss of muscular tone (Barclay). The pylorus is
slightly to the right of the middle line in the empty stomach. As the stomach fiUs it descends
farther and moves a little farther to the right. The lesser curvature presents a definite notch at
the junction of the cardiac and pyloric portions of the stomach — the incisura angularis.. The
greater curvature reaches the umbihoal plane in the erect posture, even when the stomach is
empty. When the viscus is full tliis curvature lies distinctly below this plane, being lower in
women than in men (Hertz). The ■pyloric portion of the full stomach is directed backward
and a httle upward, as the distended pyloric vestibule moves further to the right than the pyloric
orifice and lies on an anterior plane. In the recumbent posture the greater curvature hes above
the umbihcal plane, even when moderately distended, and the stomach is more obliquely placed.
The fundus invariably contains gas, even when the stomach contains no food, in which case the
organ forms a contracted J-shaped tube (fig. 1108). In extreme distention the left dome of the
diaphragm is so pushed up by the fundus that it lies at a level as high as or even higher than the
THE INTESTINES 1375
right dome (Hertz). The pressure thus exerted on the heart accounts for the dyspnoea and
cardiac pain so often associated with flatulence. The position of the pyloric sphincter is shown
on the outer surface by a very constant venous ring runrling toward both lesser and greater
curvatures in the subserous layer at right angles to the long axis of the pyloric canal (Moynihan).
In connection with the extravasation of contents that results from perforating ujcers of the
stomach, a knowledge of the subphrenic peritoneal fossaj is important (p. 1372). Perforation
is rare on the posterior surface since it is less mobile than the anterior, and protective adhesions
form readily. When it does occur, extravasation into the omental bursa results, and suzih a
perforation is exposed by turning up transverse colon and stomach and incising the transverse
meso-colon. Perforation on the anterior surface usually gives rise to general peritonitis, but in
the less sarious cases an abscess may form localised to (l) the right subphrenic space, (2) the
subhepatic fossa, or (3) the left subphrenic space, according to the situation of the ulcer on the
stomach.
The Spleen (fig. 1127; see also figures in Sections IX and XII). — This lies very
obliquely in the left hypochondrium, its long axis corresponds closely with the line
of the tenth rib. It is placed opposite the ninth, tenth, and eleventh ribs exter-
nally, being separated from these by the diaphragm; and medially it is connected
with the great end of the stomach. Below, it overlaps slightly the lateral border
of the left kidney (fig. 1127). Its highest point is on a level with the spine of
the ninth thoracic, and its lowest with that of the eleventh thoracic vertebra.
Its upper pole is distant about 3.7 (1| in.) from the median plane of the body, and
its lower pole about reaches the mid-axillary line on the same rib. (Godlee.)
In the natural condition it cannot be felt; but if enlarged, its notched anterior
margin extends downward toward the umbilicus, and is both characteristic and
readily felt.
The pancreas. — The head of the pancreas lies in the hollow formed by the
three parts of the duodenum, on the bodies of the second and third lumbar
vertebrae. The inferior vena cava lies behind it. The neck, body, and tail of
the pancreas pass obliquely to the left and slightly upward, crossing respectively
the commencement of the portal vein, the aorta, and the left kidney. The root
of the transverse mesocolon is attached to the anterior margin of the gland, so
that its supero-anterior surface is related to the omental bursa, and its inferior
surface to the greater sac. The importance of this relation in the formation
of pancreatic pseudo-cysts has been referred to above.
Pancreatic ducts. — The main duct, the duct of Wirsung, opens into the common ampulla of
Vater with the bile duct. This ampuUa usually opens into the gut by a narrow orifice raised
on a small papilla. A gaU-stone impacted in the ampulla may cause a flow of bile backward
along the duct of Wirsung, and so give rise to acute pancreatitis (Opie). The small accessory
duct of Santorini opens into the duodenum independently about 2 cm. higher up. It often
anastomoses with the larger duct in the substance of the gland.
Accessory nodules of pancreatic tissue are occasionally met with in the walls of the stomach
or small intestine at diff'erent regions.
A cyst originating in the pancreas may "point" toward the anterior abdominal wall by
three routes: — (1) Above the stomach through the lesser omentum; (2) between stomach and
transverse colon through the great omentum; (3) below the transverse colon through the trans-
verse mesocolon. The posterior aspect of the head of the gland, with the third part of the
common bile duct may be exposed by incising the peritoneum on the lateral margin of the second
part of the duodenum, and turning the gut medially toward the middle line.
Intestines. (A) Small. — The average length of the small intestine is about
6.85 m. (22| ft.), though the length as measured post mortem varies considerably
with the degree of contraction of the longitudinal muscular coat. The duodentma
is about 25 cm. (10 in.) in length. Of the remaining portion the upper two-fifths
constitute the jejunum and the lower three-fifths the ileum, though this division
is quite arbitrary. Cases are recorded in which patients have survived the re-
moval of over 5 m. (16 ft.) of small intestine.
The first part -of the duodenum extends from the pylorus on the first or second lumbar ver-
tebra, backward and to the right. It ends near the upper pole of the right kidney and on the
medial side of the neck of the gaU-bladder, by turning down to form the less mobile second -part,
which descends in front of the hilum of the right kidney to the level of the third lumbar vertebra.
The third part of the duodenum crosses the body of the third lumbar vertebra horizontally in
the infracostal plane, and then turns up obliquely to the left side of the spine and ends at the
level of the upper border of the second lumbar vertebra in the duodeno-jejunal flexure. The
first part is the most mobile, since it is covered back and front by peritoneum in the first half
of its course. The second part has a peritoneal covering in front onlj' and is devoid of it where
it is crossed by the commencing transverse colon. The third part is covered by peritoneum
in front except where the superior mesenteric vessels pass across it to join the commencement of
the mesentery. It is probably the constricting effect of these vessels on the duodenum that
gives rise to the acute dilatation of the stomach which occasionally follows abdominal operations.
1376 CLINICAL AND TOPOGRAPHICAL ANATOMY
The duodeno-jejunal flexure, which hes on the left side of the body of the second lumbar
vertebra, immediately below the body of the pancreas, is held up to the right crus of the dia-
phragm by a band of fibro-muscular tissue known as the suspensory ligament of Treitz. Some of
the fibres of this structui-e are continued onward into the root of the mesentery. It is not found
in pronogxade animals. The duodeno-jejunal flexure is the commonest site of traumatic rup-
ture of the small intestine, since it is the point of union of a fixed and a freely movable portion
of the gut.
In the operation of posterior gastro-enterostomy the duodeno-jejunal flexm'e is readily
found by passing the hand along the under surface of the transverse meso-colon to the left side
of the spine, the omentum and colon being turned upward. The first coil of the jejunum is
anastomosed to the posterior wall of the stomach, which is exposed by making an opening in
the transverse meso-colon.
In some cases the first few centimetres of the jejunum are found to be fused between the
layers of the transverse meso-colon. Certain peritoneal fossas are often found on the left side
of the flexure. They may give rise to retro-peritoneal hernia and strangulation of intestine.
The duodenal fossaj are described on p. 1164.
Jejunum and ileum. — The mesentery contains between its two peritoneal
layers the superior mesenteric vessels and their intestinal branches, the superior
mesenteric plexus, lacteals and many lymph nodes on their course. These
nodes are frequently enlarged in abdominal tuberculosis in children (tabes
mesenterica) . The attached border of the mesentery may be marked out
on the surface by a line drawn from just below the transpyloric plane and a little
to the left of the middle line (the duodeno-jejunal flexure), which curves downward
and to the right to end in the iliac fossa at the junction of the intertubercular
and right lateral vertical lines (the ileo-caecal valve).
Meckel's diverticulum which is present in about 2 per cent, of subjects (Treves) is found in
the free border of the ileum 30 cm. to 1 m. (1 to 3 ft.) above the ileo-caecal valve. It is a remains
of the vitello-intestinal duct. It is usually a blind conical pouch some 6 to 9 cm. long with a
free extremity, but may be attached to the umbihcus by a fibrous cord. This cord may cause
acute intestinal obstruction by strangulating a coil of gut, or the diverticulum may be invag-
inated and form the starting-point of an intussusception.
The presence of aggregated lymph nodules (Peyer's patches) in the lower part of the ileum
accounts for the fact that tuberculous ulcers and perforating typhoid ulcers are almost confined
to this part of the gut.
Intestinal localisation. — It often happens that the surgeon wishes to ascertain
roughly to what part of the small intestine a given coil presenting in a wound
belongs. The variations in length of the small intestine and the considerablf
range of movement of the coils during peristalsis render the problem difficult,
but it may be stated as a general rule that the upper third of the intestine lies
in the left hypochondrium and is not usually encountered in a wound; the
middle third occupies the middle part of the abdomen, and the lower third lies
in the pelvis and right iliac fossa (Monks). The jejunum is thicker walled and
more vascular than the ileum. The lumen steadily diminishes as we pass
downward, hence foreign bodies such as gall-stones that pass through the jeju-
num are apt to become impacted in the lower ileum.
The most reliable indications of the level of a given coil are found, however, on inspection
of the mesentery and its blood-vessels (see fig. 482 in Section V). Opposite the upper part of
the bowel the mesenteric arteries are arranged in a series of large primary anastomosing loops.
From these the vasa recta run to the gut 3 to 5 cm. long, straight and unbranched. Passing
downward toward the lower end, the single large primary loops give place to smaller and more
numerous secondary loops arranged in layers coming nearer and nearer to the bowel. Hence
the vasa recta become shorter. They become also less regular and more branched, and in the
lower third of the small intestine are less than 1 cm. in length. The mesenteric fat in the upper
third never reaches quite to the free edge of the meusentery, so that clear transparent spaces
are left near the bowel. In the lower third the fat usually occupies the whole of the mesentery
right up to the intestine, and makes it thicker and more opaque.*
The average width of the mesentery, from its root at the posterior parietes to the bowel
is 20 cm. (8 in.) and the longest part lies between 2 and 8 m. from the duodenum (Treves).
The ileum is freely movable on a long mesentery down to the ileo-C£ecal region. In some cases
however a congenital fusion of the leit half of the mesentery with the parietal peritoneum near
the pelvic brim binds the bowel down a few inches above the ileo-ca3cal valve, and has been said to
give rise to symptoms of intestinal stasis. (Flint,! Gray, and Anderson.)
(B) Large intestine. Ileo-csecal region. — The position of the ileo-csecal
valve may be marked on the surface by the junction of the intertubercular and
right lateral vertical lines, though it is often found considerably lower. It is
situated on the postero-medial aspect of the caecum. The caecum, which is the
* Monks: Trans. Araer. Surg. Assoc, 1913.
t Bulletin, Johns Hopkins Hospital, Oct., 1912.
i
THE INTESTINES
1377
blind extremity of the colon lying below the horizontal level of the ileo-caecal
valve, is approximately 6.2 cm. (2| in.) in both vertical and transverse diameters,
though its size varies much with the degree of distention. It lies usually in
contact with the anterior abdominal wall above the lateral half of the inguinal
ligament. The orifice of the appendix (vermiform process) lies some 2 cm. below
the ileo-cEecal valve. The caecum is completely covered by peritoneum as a
rule, though exceptionally its posterior surface is bound down in the right iliac
fossa.
The axial rotation of the midgut and descent of the OEeeum that normally take place dui'ing
intra-u,terine life (p. 1168) are occasionally not completed, with the result that the cfficum and
appendix may be found above and to the left of the umbilicus, or less uncommonly just below
Fig. 1109. — -Blood-vessels of the Ileo-c.eal Region. (From Kelly).
the right lobe of the liver (3 per cent., Alglave), when an attack of appendicitis may simulate
inflammation of the gall-bladder. On the other hand certain cases occur in which the CEBCum
descends unusually far, proceeding downward and medially until it becomes a pelvic organ
whenever the bladder and rectum are empty. This pelvic position of the ca;cum is found in
10 per cent, of infants (G. M. Smith).*
In the commonest form of intussusception, the ileo-caecal valve and lower ileum are pro-
lapsed into the colon and carried down by the force of peristalsis toward the anus. The valve
in these cases forms the apex of the intussusceptum, however far it travels.
* Anat. Record, vol. 5, 1911, p. 549.
1378 CLINICAL AND TOPOGRAPHICAL ANATOMY
The vermiform process (appendix) is developed at the apex of the caecum,
and persistence of the apical appendix of foetal type, is not uncommon. The
fact that all three tsenis coli converge at the base of the appendix is an anatomical
reminder of its primitive position. The anterior tsenia is of great service in opera-
tions on the appendix, since by following it down from the colon the base of the
appendix can alwaj^s be found. The adult position of the base of the appendix
on the postero-medial aspect of the caecum is due to the disproportionate growth
of the lateral saccule of the caecum which comes to form the apparent caecal apex.
The appendix averages 10 cm. (4 in.) in length in the adult. The position of its base only
is at all constant. It lies distinctly below MoBurney's point, which is midway between the
umbilicus and the right anterior superior iliac spine. This point is often the seat of greatest
tenderness in appendicitis. The appendix itself may be found (1) pointing upward and to the
left toward the spleen, behind the terminal ileum and mesentery; (2) hanging over the pelvic
brim, in which position tenderness on rectal examination or pain on micturition results when
the organ is inflamed; (3) in the retro-colic fossa; and (4) with its tip projecting to the right of
the csecum in the right lateral paracolic fossa, where it causes tenderness when inflamed close
to the anterior superior ihac spine. The course and to some e.xtent the gravity of abscesses
originating in the appendix will depend upon the position the inflamed organ is occupying at
the time of perforation.
The artery of the appendix derived from the posterior branch of the ileo-eoUo reaches it by
running down behind the end of the ileum. It raises a fold of peritoneum called the mesen-
terioluin or mesoappendix. Very rai-ely the artery comes from the anterior branch of the
ileo-colic.
The tmnice coli referred to above as converging on the base of the appendix contribute its
longitudinal muscular coat. The inner circular coat is thicker, but along the attachment of
the mesenteriole certain gaps for the passage of lymph and blood-vessels occur in the muscular
coats. Through these gaps infection may easily spread from the mucosa to the peritoneum
(Lockwood).
The appendix is essentially a lymph gland and has been called the "abdominal tonsil."
The lymph follicles he in the submucosa. They are poorly developed at birth but reach
their fuU development within the first few weeks of extra-uterine hfe (Berry).* ObUteration
of the lumen is common but is inflammatory in origin, and not, as was once thought, a change
normal in advanced age.
Pericsecal fossa. — In addition to the mesentery of the appendix certain other folds of per-
itoneum are usually present at the ileo-cffical junction: (1) the ileo-colic or anterior vascular
fold (fig. 1109) containing the anterior branch of the ileo-cohc arterj^; (2) the ileo-caecal, or
bloodless fold of Treves, running from the lower border of ileum onto the ciEcum. The appen-
dix may be in a fossa behind either of these folds. It may also be found in the retro-colic fossa
lying behind the cfficum and commencement of ascending colon.
The colon is readily distinguished from the small intestine by its three lon-
gitudinal taeniae and saccules and by the appendices epiploicse, which are devel-
oped before birth.
The ascending colon runs with a slight lateral convexity upward from its
junction with the caecum to the hepatic flexure which lies under the ninth
right costal cartilage at the level of the second lumbar vertebra and in contact
with the anterior surface of the right kidnej^ and the lower surface of the right
lobe of the liver. It lies lateral to the right lateral vertical plane. This de-
scription is only true of an ascending colon examined by X-raj^s in the recumbent
position. When the patient stands up, the flexure sinks to the infracostal
plane (third lumbar vertebra) or even lower. As the colon ascends in the angle
between the quadratus lumborum and psoas, it also passes backward at an angle
of 51° ■ndth the horizontal, as may be seen in a sagittal section through the right
half of the abdomen (Coffey). f The caecum and ascending colon are distended
as a rule with fluid contents and gas, and form the widest part of the colon.
The variations in the peritoneal attachments of the colon, which are of growing clinical
importance, are explained by its mode of development (p. 1179). During intra-uterine Ufe
after rotation of the midgut round an axis formed by the superior mesenteric vessels, there is
a stage in which the colon has almost assumed its permanent position in the abdomen but is
still provided with a free mesocolon for both ascending and descending parts. This represents
the normal condition of quadruped mammals. In the normal human individual this stage is
transient, and before birth the ascending and descending colons lose their mesenteries by
fusion of the posterior layers with the parietal peritoneum. Meanwhile the great omentum,
formed by a bulging out of the primitive dorsal mesogastrium, fuses with the transverse colon
and its mesocolon. The extent of these processes of fusion varies, particularly as far as the
ascending and descending colons are concerned. Thus only 52 per cent, of adults have neither
ascending nor descending mesocolons (the normal condition). A mesocolon is found on the
left side in 36 per cent, of all cases and on the right side in 26 per cent. (Treves). In only a
* Journ. Anat. and Phys., vol. 35, 1900, S3.
t Surgery, Gynecology and Obstetrics, vol. 15, 1912, p. 390.
i
THE KIDNEYS 1379
small proportion (1.8 per cent., however, does the true primitive type of ascending mesocolon
persist, continuous with the mesentery of the small intestine (G. M. Smith). Such an anomaly
renders the patient liable to volvulus of the ileo-0£ecal region. In the common types of in-
complete fusion of its peritoneal attachments the colon is inadequately adapted to the upright
position and is predisposed to ptosis. A layer of peritoneum sometimes found passing down-
ward and medially from the parietes in the right flank onto the front of the ascending colon,
known as Jackson's pericolic membrane, is probably due to persistence of an early stage in the
development of the great omentum, which passes to the right across the ascending colon to
join with the parietal peritoneum before the descent of the cjecum is complete, and so is the most
primitive agent in fixing the proximal colon back in the right loin. This membrane is usually
associated with a congenitaUy mobile ascending colon (Morle}^.*
At the hepatic flexure the colon bends forward and to the left, leaving the front of the kidney
to which it is fixed, and crossing the second part of the duodenum. In the region of the flexure
three inconstant peritoneal folds are met with giving it additional attachment to the neigh-
bouring parts, viz., (1) the phreno-colic and less commonly (2) the hepalo-colic and (3) cysto-
colic hgaments (Testut). Thej' must not be confused with pathological adhesions acquired
after birth.
The transverse colon is freely mobile except at its extremities. It crosses the
abdomen with a convexity downward and forward, being separated from the
anterior abdominal wall in the middle region by the great omentum.
At the mid-line it usuaUy lies near the umbihcal plane in the recumbent posture, consider-
ably lower in the erect, but may be found anywhere from the infra-costal plane to the pubes,
depending on the tonicity of the stomach. Its main artery, the middle colic branch of the
superior mesenteric, must be avoided carefully in the operations of gastro-enterostomy and gas-
trectomy, since hgature of it causes gangrene of the transverse colon.
The splenic flexure lies far back in the left hypochondrium and is considerably
higher than the hepatic flexure. It is in contact with the lower end of the spleen,
and is almost invariably held firmly in position by its -phreno-colic ligament,
derived from the left extremity of the great omentum.
The descending colon is of narrower calibre than the preceding parts and
usually is found firmly contracted and empty. It passes downward and forward
in the angle between the psoas and quadratus lumborum and obliquely across
to the right the iliac fossa to end in the sigmoid or pelvic colon. The lower part
of the descending colon, from the iliac crest to the pelvic brim, is often termed
the iliac colon.
In its upper part it hes in front of the convex lateral margin of the left kidney. The varia-
tions in its peritoneal attachments have been referred to above (p. 1242). The operation of
lumbar colostomy, common in pre-antiseptic days, was performed through an incision in the
back parallel with the last rib. The colon lies 2.5 cm. (1 in.) to the lateral side of the edge of
the sacro-spinalis, between the twelfth rib and ihac crest. The occurrence of a mesocolon here
was a common source of difficulty in gaining access to the bowel without opening the peritoneum.
The pelvic colon (also known as the sigmoid or omega loop (Treves), is almost
as long as the transverse colon, and forms a loop, the two ends of which, at the
pelvic brim and at the front of the third sacral vertebra respectively, are placed
somewhat closely together. The loop is thus anatomicallj^ predisposed to axial
rotation, and is the commonest seat of volvulus in the whole intestinal tract.
On the left and inferior aspect of the pelvic mesocolon near its base, a small peritoneal
fossa {intersigmoid) is usually found in the angle formed by the root of the mesocolon and
the parietal peritoneum. It occasionaUy contains an internal hernia which may become
strangulated.
The upper part of the pelvic colon is frequently brought out and opened tlirough an inci-
sion in the left iliac region to form an artificial anus in cases of inoperable growth of the
rectum.
In advanced life, and in the chronically constipated, certain diverticula of mucous membrane
are occasionally met with which project through the vascular gaps of the muscular coat into
the bases of the appendices epiploicse in this region, and also between the layers of the pelvic
mesocolon. They often contain foecal concretions and may become inflamed or even perforate,
forming an abscess in the left ihac fossa, f
The junction of pelvic colon and rectum opposite the third sacral vertebra forms a more or
less acute angle and constitutes the narrowest part of the colon. It is a frequent site of stricture.
The kidneys. — These lie at the back of the abdominal cavity so deeply in the
hypochondriac and epigastric region as to be beyond palpation in most individuals,
unless enlarged or unduly mobile. The lower end of the right being slightly
lower than its fellow, encroaches in health upon the lumbar and umbilical
regions, and may be palpable on deep inspiration in spare subjects. These
* Lancet. Dec, 1913.
t McGrath: Surgery, Gynecology and Obstetrics, vol. 15, 1912, -129.
1380
CLINICAL AND TOPOGRAPHICAL ANATOMY
organs lie much higher and nearer to the vertebrae than is usually supposed to be
the case, the upper two-thirds of the right and all the left kidney being behind
the ribs. Relatively to the vertebra3, the kidneys lie along the sides of the last
thoracic and the first three lumbar.
To mark them in from the front the following points should be noted: The upper extremity
of the right should reach as high up as the seventh costal cartilage, the left up to the sixth, on
either side close to the costo-chondral and inter-cliondral junctions. This level will corre-
spond to one half way between the sterno-xiphoid and transpyloric lines. The lower end.
Fig. 1110. — Renal Fascia, as seen in Cross-section.
Aorta and vena cava
Anterior layer of renal fascia
Peritoneum
Posterior layer of renal fascia
about 11 cm. (4| in.) below this point, would be opposite to the subcostal line; that of the right
kidney is usually lower, and may encroach upon the umbilical line. For practical piu'poses
the hilus is opposite a point on the anterior abdominal wall, a finger's breadth medial to the tip
of the ninth costal cartilage (Stiles), or the junction of the transpyloric and lateral vertical
lines. The importance of the relation of the last rib has been mentioned at p. 1245. The
lateral vertical line has one-third of the kidney to its lateral side, and two-thirds to its medial
side. The shortest distance between the two kidneys, obliquely placed so as to be closer above,
'at the upper part of their medial borders' (Thane and Godlee), measures about 6.2 cm. (2| in.).
On the posterior surface of the body the ividney's boundaries are indicated by the following:
— (1) A line parallel with, and 2.5 cm. (1 in.) from, the mid-line, between the lower edge of the tip
Fig. 1111. — Renal Fascia, as seen in Sagittal Section.
-Lung
Suprarenal gland
—Kidney
■Anterior layer of renal fascia
Posterior layer of renal fascia
of the spinous process of the eleventh thoracic and the lower edge of the spinous process of the
third lumbar vertebra; (2) and (3) lines drawn from the top and bottom of this line laterally,
at right angles to it, for 7 cm. (2f in.); (4) a line parallel to the first, and connecting the ex-
tremities of (2) and (3). Within this parallelogram the kidney lies (Morris).
The chief relations of the kidneys are: — posteriorly — quadratus lumborum,
psoas, diaphragm, last thoracic, ilio-hypogastric, and ilio-inguinal nerves. The
twelfth rib lies behind both, the right, as a rule, not reaching above the upper
border. The left often reaches the eleventh rib. The pleural reflection usually
crosses the twelfth rib obliquely reaching below its neck. Anteriorly — The
liver, right colic flexure and second part of the duodenum (figs. 956 and 1009), on
THE URETER
1381
the right side. The liver, and stomach above, the body of the pancreas and spleen
over the centre, and the descending; colon over the lower part of the left kidney.
The attachments of the specialised fibrous sheets known as the renal fascia
are shown in figs. 1110 and 1111.
The anterior and posterior layers are seen to be continuous above and laterally. Medially
and below they remain separate and it is in this dii-ection that the abnormally movable kidney
travels. The fatty tissue between the kidney and the renal fascia is known as the perinephric
fat; that outside the fascia is the paranephi'ic fat.
The kidneys are maintained in position by (1) the vascular pedicle; (2) fatty
capsule and fascia; (3) above all by the intra-abdominal pressure.
Failure to ascend during development from its original position near the pelvic brim to
its normal level accounts for certain cases of movable kidney of congenital origin. In these cases
Fig. 1112. — The Abdominal Aorta and Vena Cava Inferior,
Gall-bladder
Hepatic duct
Cystic duct
common bile duct
Portal vein —
Gastro-duodenal br
Right gastric art.
Hepatic artery
Right suprarenal vein
Inferior suprarenal
artery
Renal artery
Renal vem
Inferior vena cava
Kidney ij
Right spermatic vein
Right spermatic artery
Quadratus lumborum
muscle
Lumbar artery
and vein
Uieteric branch of —
spermatic artery
Middle sacral vessels.
Left lobe of Uver
(Esophagus
Left phrenic artery
Right phrenic artery
Superior suprarenal
Left gastric artery
Inferior suprarenal
Splenic artery
Left phrenic vein
Left suprarenal vein
Superior mesenteric
artery
Kidney
Ureteric branch of renal
Left spermatic vein
Ureter
Left spermatic artery
Inferior mesenteric
artery
Ureteric branch of
spermatic
Ureteric branch of
common iliac
iliac artery
External iliac artery
Hypogastric artery
the renal artery may take origin from the common iliac artery. An accessory renal artery
running into the lower end of the kidney from the aorta may cause kinking of the ureter and is
a not uncommon cause of hydronephrosis.
The suprarenal glands are not so firmly attached to the kidneys as to the
diaphragm; hence they are not encountered in operations for movable kidney and
are not removed in nephrectomy.
Brode] has shown that incisions into the kidney should be made rather behind its convex
border (Brodel's bloodless line). Occasionally fusion of the lower poles occurs during develop-
ment across the middle hue of the body, and a single horseshoe kidney results, with double
ureter and vascular supply.
The ixreter. — On an average 30 cm. (12 in), long, this tube descends almost
vertically in its abdominal course on the psoas muscle. It is crossed obUquely
1382 CLINICAL AND TOPOGRAPHICAL ANATOMY
by the spermatic or ovarian vessels. It crosses the brim of the pelvis just in
front of the bifurcation of the common iliac, and descends on the side wall of the
pelvis in front of the hypogastric artery.
The abdominal part of the ureter may be exposed extraperitoneally by an extension for-
ward of the usual lumbar renal incision. It is found lying between peritoneum and psoas
3.7 cm. (IJ in.) from the middle line and when the peritoneum is stripped from the posterior
abdominal wall the ureter is invariably carried with it.
Aorta and iliac arteries. — The aorta enters the abdomen opposite the last
thoracic vertebra, a point 12 to 15 cm. (5 to 6 in.) above the umbilicus, or rather
above the mid-point between the infrasternal depression and the umbilicus
(Thane and Godlee), and thence, lying to the left of the mid-line, divides into the
two common iliacs opposite the disc between the third and fourth lumbar vertebrae,
or opposite the body of the fourth lumbar vertebra. This point is about 2.5
cm. (1 in.) below and to the left of the umbilicus, and on a level with a line
drawn across the highest part of the iliac crest. A line drawn from this point,
with a slight curve laterally, to just medial to the centre of Poupart's ligament,
will give the line of the iliac arteries; the upper third of this line giving the aver-
age length of the common iliac. The relation of the common iliac veins is shown
in fig. 1112. The right, much shorter than its fellow, lies at first behind and
then somewhat lateral to its artery. The left is at first to the medial side of
its artery, and then behind the right. At the upper part of the fifth lumbar
vertebra behind and lateral to the right artery, the vena cava begins.
The site of some of the branches of the aorta may be thus approximately
remembered as follows: The cceliac artery is given off immediately after the aorta
has perforated the diaphragm; directly below this is the superior mesenteric
artery. About 2.5 cm. (1 in.) lower down, or 7.5 cm. (3 in.) above the umbilicus,
the renal arteries are given off. About 2.5 cm. (1 in.) above the umbilicus would
be the level of the inferior mesenteric artery. The relation of the above vessels to
the transpyloric line (p. 1153) is as follows: (Stiles.) The cceliac artery is two
fingers' breadth, the superior mesenteric one, above the line, the renal arteries are
a finger's breadth below it. The origin of the inferior mesenteric is midway be-
tween the transpyloric and intertubercular lines.
Collateral circulation after ligature of the common iliac. — The chief vessels here are: —
ABOVE. BELOW.
Pubic branch of inferior epigastric with Pubic branch of obturator.
Internal mammary and lower intercostals with Inferior epigastric.
Lumbar with Ilio-lumbar and circumflex iUac.
Middle sacral with Lateral sacral and superior gluteal.
Superior haemorrhoidal with Inferior and middle haemorrhoidal.
Ovarian with Uterine
Collateral circulation after ligature of the external iliac : —
Internal mammary, lower intercostals, 1 ■, . t <■ ■ • * •
and lumbar. / "^'^^ Inferior epigastric.
Ilio-lumbar, lumbar, and gluteal with Deep circumflex iUao.
Internal and external circumflex with Superior and inferior gluteal (sciatic).
Perforating branches of profunda with Inferior gluteal (comes nervi ischiadici) .
Circumflex and epigastric with Obturator.
External pudic with Internal pudic.
Collateral circulation after ligature of the internal iliac : —
Branches of profunda with Inferior gluteal (sciatic).
Inferior mesenteric with Hismorrhoidal arteries.
Vessel of opposite side with Pubic branch of obturator.
Branches of opposite side with Branches of pudic.
Superior and inferior gluteal (sciatic) with Circumflex and perforating of profunda.
Middle sacral with Lateral sacral.
lUo-lumbar and superior gluteal with Circumflex iUac.
THE PELVIS
The male pelvis will be considered first, then the female pelvis, and finally a
section on hernia.
The Male Pelvis
The topics under this heading will be considered in the following order:
boundaries and subdivisions, scrotum and testis, ductus deferens and spermatic
THE MALE PELVIS
1383
cord, penis and urethra, prostate, bladder, ischio-rectal fossa, rectum and anal
canal.
Bony boundaries. — These are the same in either sex. Above and in front is
the symphysis pubis, rounded off by the subpubic ligament; diverging downward
and laterally from this point on either side are the rami of the pubes and ischia,
ending at the tuberosities of the latter. In the middle line behind is the apex of
the coccyx, and reaching from this to the tuberosities are the sacro-tuberous (great
sacro-sciatic) ligaments, to be felt by deep pressure, with the lower border of the
gluteus maximus overlapping them.
The depth of the perineum varies greatly — from 5 to 7. .5 cm. (2 to 3 in.) in the posterior
and lateral part to 2.5 cm. (1 in.) or less in front. In the middle hne, extending longitudinally
through the perineum, is the raphe, the guide to the urethra, and 'the line of safety' (on account
of the small size of the vessels here) for operations on it.
Fig.
1113. — ^Thb Male Perineum. (Modified from Hirschfeld and Leveilld.)
Bulbo-cavernosus
Superficial layer of uro-genital trigone
Ischio-cavernosus
Muscles of thigh
Post. fern, cutaneous ni rv
Permeai nerve | i
Inferior haemorrhoidal nerve
Cutaneous branch of fourth sacral
Gluteus maximus
Tuberosity of ischium
Sacro-tuberous ligament
Superficial transversus perinei
Sphincter ani externus
Subdivisions. — An imaginary line drawn transversely across the perineum
from one tuber ischii to its fellow divides the lozenge-shaped space into two
triangles — (1) An anterior, or uro-genital; and 2) a posterior, or rectal. The
pelvic floor includes an upper or pelvic diaphragm (formed by the levator ani and
coccygeus on each side) and a lower incomplete uro-genital diaphragm (or trigone) .
The pelvic diaphragm (figs. 1113, 1114, 1115; see also figs. 397, 399, 400)
isYmade up of the levator ani coccygeus muscles. It is somewhat funnel-
shaped. When viewed from above or below (fig. 395), its fibres are seen to form
horseshoe-like loops, arising on either side anteriorly, and passing posteriorly
backward around the uro-genital apertures to be inserted chiefly in the mid-line
posteriorly. The pelvic diaphragm serves primarily for the support of the
abdominal viscera. For a detailed description of these muscles, as well as those
of the uro-genital diaphragm, see section on the Muscular System.
1384
CLINICAL AND TOPOGRAPHICAL ANATOMY
The xiro-genital diaphragm (or trigone) (fig. 400), the lower diaphragm of the
pelvic floor, is both morphologically and functionally different from the upper.
The uro-genital diaphragm is a sphincter muscular layer, derived (with the sphincter
ani externus) from the primitive sphincter cloacae. The uro-genital diaphragm is
composed of superior and inferior fascial layers, enclosing the membranous urethra,
the sphincter urethrae membranacese and the transversus perinei profundus.
Superficial to the uro-genital diaphragm is the superficial perineal interspace
(fig. 400). This is covered by the superficial perineal (CoUes') fascia, and in-
cludes the crura and bulb of the corpora cavernosa, with associated muscles,
vessels and nerves.
The space in the pelvic floor on each side below the pelvic diaphragm is the
ischio-rectal fossa (figs. 399, 400, 1114). In the posterior or rectal triangle, where
the urogenital diaphragm is absent, the ischio-rectal fossae form large wedge-shaped
spaces. The lowei- wall or base is formed chiefly by the corresponding skin and
superficial fascia, and partly by the external sphincter ani ; the medial wall by the
Fia. 1114. — Coronal Section of the Ischio-rectal Fossa. (G. Elliot Smith.)
Falciform process
muscles (levator ani and coccygeus) and inferior fascia of the pelvic diaphragm;
the lateral wall by the obturator internus muscle, with the corresponding obturator
fascia (with Alcock's canal, incluchng the pudic vessels and nerves) . The apex of
the fossa is above, where medial and lateral walls meet. The narrow fibrous roof
strip joining the medial and lateral walls just above the level of the internal
pudic vessels and nerves has been called the lamina terminalis (Elliot Smith,
fig. 1114). Posteriorly the fossa is bounded by the gluteus maximus and lig.
sacro-tuberosum. Anteriorly on each side the ischio-rectal fossae extend as narrow
spaces between the pelvic diaphragm above, the uro-genital diaphragm below, and
the pelvic wall laterally (figs. 400, 401, 402).
Contents. — The ischio-rectal fossa is filled with loose adipose tissue continuous with the
subcutaneous fat of the buttock. It is traversed by the inferior htemorrhoidal branches of
the internal pudic artery, with the associated veins and nerves, passing to the external anal
sphincter, the skin and the adjacent mucosa. The superficial vessels and nerves, as the)'
run forward to pierce the superficial perineal fascia, lie in this space, as well as the inferior
clunial (perforating cutaneous) branches and branches of the fom'th sacral nerve. The inferior
THE MALE PELVIS 1385
hemorrhoidal veins traverse the fossa obUquely from the lateral wall downward and medially.
They are usually somewhat dilated near the anal orifice, and when morbidly enlarged constitute
the condition known as htemorrhoids ("piles")- The inner opening of an ana! fistula caused
by the bursting of an ischio-rectal abscess into the gut is usually within 2 cm. of the anal margin,
between the internal and external sphincters.
The central point of the perineum is in the adult nearly an inch (2.5 cm.) in
front of the anus, or midway between the centre of the anus and root of the scro-
tum. Here the following structures meet, viz., the levatores ani, the two trans-
verse perineal muscles, the bulbo-cavernosus, and the sphincter ani.
The comparative weakness of the attachment of the sphincter ani in front, i. e., not into a
bony point, is important in the division of it, as in operation for fistula. The sphincter should
never be cut through anteriorly, especially in women, where its attachment here, blending with
the sphincter vaginae, is a very weak one. This point also corresponds to the centre of the
lower margin or base of the uro-genital diaphi'agm (triangular ligament). Its development
varies much in different bodies. A little in front of this point is the bulb, with the corpus
spongiosum passing forward from it. This would also be the level of the artery of the bulb,
so that in lithotomy the incision should always begin below this point. A knife introduced
at the central point, and carried backward and very sUghtly upward, shoiild enter the mem-
branous urethra just in front of the prostate, e. g., iu median lithotomy and Cock's external
urethrotomy. If pushed more deeply, it would enter the neck of the bladder.
In median lithotomy, an incision 3.7 cm. (I5 in.) long is made tlirough the central tendinous
point and raphe, so as to hit the membranous urethra. The following structures are divided: — •
Skin and fasciae; some of the most anterior fibres of the external sphincter ani; raphe and
central tendinous point; minute branches of transverse perineal vessels and nerves; base of
uro-genital diaphragm Ln centre; membranous m'ethra and constrictor urethras.
The attachments and arrangements of the superficial fascia (fig. 1115) must be
traced and remembered. If the two layers of which it consists, the superficial
alone extends over both urethral and rectal triangles alike, and is continuous with
the similar structures in adjacent regions, the only difference being that, if traced
foward into the scrotum and penis, it loses its fat, and contains dartos fibres.
The deeper layer, found only over the urethral triangle, is called the fascia of CoUes
(fig. 1115). Attached at the sides to the rami of the pubes, behind to the base of
the uro-genital trigone or diaphragm, and open in front, it forms the superficial
wall of a somewhat triangular pouch, limited behind by the uro-genital trigone,
and containing the superficial vessels, nerves, and muscles, the bulb, adjacent
part of the urethra, and crura of the penis. Owing to this space being closed behind
and open in front, and to its containing the above structures, fluids extravasated
within this space will obviously tend to make their way forward into the scrotum,
penis, and lower part of the abdominal wall.
The uro-genital triangle is subdivided into two planes by the inferior fascia of
the uro-genital diaphragm and fascia of Colles. The structures in the swperficial
-plane, between the uro-genital diaphragm and the fascia of Colles, have been
given above. Those in the deeper, i. e., between the two layers of fascia of the
diaphragm, are — (1) The membranous urethra; (2) deep transverse perineal
muscle and sphincter of the membranous urethra; (3) the bulbo-urethral (Cow-
per's) glands; (4) and (5) part of the pudic artery and nerve, and branches.
The scrotum. — The skin of the scrotum is thin and delicate so that when
distended, as by a hydrocele in the tunica vaginalis, it is remarkably translucent.
Attached to its deep aspect is a layer of involuntary muscle, the dartos. When
the dartos is contracted, as under the influence of cold, the scrotal skin becomes
rugose.
To this tendency to wrinkling, with consequent irritation from retained dirt, and the
presence of many sweat glands the frequency of epithehoma in this part is due. The dartos is
apt to cause inversion of the skin in wounds of the scrotum, but this difficulty in suturing may
be counteracted by the application of a hot sponge, which relaxes the muscle.
The superficial fascia of the scrotum is continuous with the fascia of Colles and the super-
ficial fascia of the penis. Hence extravasation of urine under the fascia of Colles's balloons the
scrotum and penis. The laxity of the areolar tissue under the dartos accounts for the great
swelling that occurs in cedema of this part.
The lymphatics of the scrotum, important by reason of the e.\ten.sion of
scrotal cancer, drain into the superficial inguinal nodes. Those from the anterior
aspect nearest the median raph6 run to the supero-lateral glands of this group,
within a few cm. of the anterior superior spine.*
* Morley: Lancet, 1911 (ii), p. 1545.
1386
CLINICAL AND TOPOGRAPHICAL ANATOMY
The numerous large sebaceous glands that are found in the skin of the scrotum may give
rise to cysts or adenomata. The deeper layers of the scrotum are derived from the abdom-
inal wall, being brought down by the processus vaginalis in the descent of the testis.
Testis and epididymis. — The left testis, the first to descend, lies somewhat
lower in the scrotum, and this fact is one reason of the frequency with which a
Fig. 1115. — The Arteries of the Perineum.
Perineal vesseli
-cavernosus
Colles's fascia, turned back
Ischio-cavernosus
Transverse perineal vessels
Cut edge of uro-genital
trigone
Perineal nerve giving off
transverse branch
Pudic vessels
Dorsal artery of penis
Deep artery of penis
Artery of bulb
Bulbo-urethral gland
Pudic artery
Sacro -tuberous ligament
Levator ani
External sphincter ani
Gluteus maximus
Fig
Symphysis pub:
Transverse fold
Vesicula seminalis
rJ-Ductus ejaculatorius
L Prostate
^—External sphincter
f- Internal sphincter
.External sphincter
varicose condition of the spermatic veins occurs on the left side. On palpation
the Smooth firm body of the testis, pressure on which causes the characteristic
"testicular sensation" can be felt to lie in front of and rather medially to the
epididymis. The three parts of the latter^ the caput above, the body, and the
Cauda epididymidis below, can also be distinguished. Running upward from the
THE TESTIS 1387
back of the epididymis to the subcutaneous inguinal ring the spermatic cord can
be felt. The bulk of the cord is made up of its coverings, of which the cremaster
muscle is the most considerable, and of the pampiniform plexus of veins. On roll-
ing the cord between the finger and thumb the ductus deferens can be felt like
a piece of whipcord in the posterior part.
The ductus (vas) deferens is thickened and nodular in tuberculous epididymitis. In vari-
cocele the dilated and elongated veins of the pampiniform plexus feel on palpation like a bag
of worms in the scrotum. It is important that the student, before studying diseased con-
ditions, should make himself familiar with the feel of the normal parts as mentioned above and
be able to identify them.
Underneath the visceral layer of the tunica vaginalis, the body of the testis is covered by
a dense fibrous layer, the tunica albuginea, which accounts for the small extent of swelling in
orchitis as compared with epididymitis. The lymphatics of the testis run up in the spermatic
cord through the inguinal canal, and accompanying the spermatic vessels end in the lumbar
lymph nodes, below the level of the renal arteries. These nodes may be reached and removed
along with the vessels by making an incision in the loin above the inguinal (Poupart's)
ligament, and stripping the peritoneum off the posterior abdominal wall.
On the right side of the perineum (left side of this figure) CoUes's fascia has been turned back
to show the superficial vessels. On the left side the superficial vessels have been cut away with
the anterior layer of the uro-genital trigone to show the deep vessels.
The epididymis is the convoluted first part of the duct of the testis, about 6 m. (20 feet)
in length. Its three portions are in differing connection with the testis. Thus the cauda is
held in place by connective tissue, the body by the same medium; the caput by the vasa efferentia.
Thus, when tubercular disease begins here, the testis itself is more likely to be early involved.
Ductus deferens. — -The two extremities and the course of this involve several practical
points. About 4.5 cm. (18 in.) long, it begins, convoluted at first and with a distinct bend
upward, in the cauda epididymidis. It thence passes almost vertically upward at the back of
the testis and cord to the tubercle of the pubes. Entering the canal, it lies on the grooved upper
aspect of the inguinal (Poupart's) ligament, and then under the arching fibres of the internal
oblique and transversus, upon the transversalis fascia. Its position, characteristic feel, and
yellowish aspect are' well-known guides in operations for varicocele and hernia, while it is always
to be isolated and palpated when tubercular disease below is suspected. Leaving the canal
by the abdominal inguinal ring, it hooks round the inferior epigastric artery and then descends
into the pelvis over the external iliac vessels. Continuing its course downward and backward
over the side of the pelvis, it arches backward over the side of the bladder, superficial to the
obliterated hypogastric artery, and then deep to the ureter. The two ducts now help to form
the lateral boundaries of the external trigone, between the base of the bladder and the rectum.
They here become dilated and sacculated and then contract again to empty into the ejaculatory
ducts.
The vesiculae seminales are diverticula growing out from the lower end of the deferential
ducts at an acute angle, one on each side. They lie below and lateral to the deferential ducts
and are related in front to the base of the bladder and posterior surface of the prostate, behind
to the rectum, and above to the reoto-vesical pouch of peritoneum, which also descends to cover
the upper part of their posterior aspect. The normal vesiculae seminales can scarcely be dis-
tinguished from the base of the bladder on rectal palpation, but when diseased, as in tuberculous
or gonorrhoeal vesiculitis, are enlarged and indurated and can be detected readily.
The ejaculatory ducts, formed by the union of the vesicular and deferential duct of each
side, are 2-2. .5 cm. in length. The first few millimeters of their course is extra-prostatic, and
then entering the posterior surface of the prostate they run side by side downward and forward
through the gland, close to the middle line, to open into the urethra on the colliculus seminalis
at either side of the opening of the prostatic sinus. It is by these little ducts that infection
travels from the urethra to the vesiculas and epididymis in gonorrhoea.
Descent of the testis. — -The testis is developed between the tenth and twelfth thoracic
segments of the embryo, and subsequently moves downward. By the third month of intra-
uterine life it descends into the iliac fossa; from the fourth to the seventh month it hes at the
abdominal inguinal ring; during the seventh month it passes obliquely through the abdominal
wall by the inguinal canal; by the eighth month it lies at the subcutaneous inguinal ring, and it
reaches the fundus of the scrotum about the time of birth. The left testis is slightty earlier
than the right in all these stages. The descent referred to is due in part to the common descent
of organs, associated with the descent of the diaphragm, but mainly to the gubernaculum. This
is a mass of fibro-muscular tissue that forms under the inguinal fold (or plica gubernalrix) of
peritoneum below the testis as it lies in the iliac fossa, and in the mesorchium. It grows down
obliquely through the abdominal wall from a point lateral to the inferior epigastric artery, and
tunnels out a passage for the testis. As it travels down into the scrotum it carries in front of
it three layers of investing fascia derived from the abdominal wall, viz., e.xternal spermatic
fascia from the external oblique, cremasteric from internal oblique and transversus muscles,
and infundibuliform fascia from the transversalis fascia. The gubernaculum is attached above
to the peritoneum and the posterior aspect of the testis, and by its subsequent contraction it
draws down into the scrotum first a diverticulum of peritoneum, the processus vaginalis, and
secondly the testis, which projects into the processus from behind just as it did into the
coelom.
Shortly after birth, obliteration of the processus vaginalis should occur, commencing at
the deep abdominal ring and immediately above the testis. The part of the processus between
these two points disappears completely. The lowest part, surrounding the testis, persists as
the tunica vaginalis. Failure of obliteration, if complete, leaves a congenital hernial sac; if
1388
CLINICAL AND TOPOGRAPHICAL ANATOMY
only the upper part perists, and does not communicate with the tunica vaginalis, it is called a
funicular sac. Cysts originating in the processus vaginalis between the upper and lower
points of primary occlusion are known as encysted hydrocele of the cord.
tTndescended testis. — It occasionally happens that descent of the testis fails on one or
both sides, and in these cases the organ may remain, (1) in the iliac fossa, (2) in the inguinal
canal, or (3) at the subcutaneous ring. Deprived of the protection normally afforded against
injury bj^ the scrotum and tunica vaginalis, the misplaced testis is subject to trauma, shows a
tendency to torsion of its pedicle owing to its long mesorohium, and sometimes becomes the
seat of malignant disease. A funicular hernial sac is generally present. Such testes are atro-
phic and functionally deficient, and it is probably owing to their small size at an early stage that
the gubernaculum fails to gain a hold on them. It has been shown by Bevan* that in unde-
scended testis the ductus deferens is usually long enough to allow the organ to be placed in the
bottom of the sci-otum by the surgeon without tension provided that the spermatic artery and
pampiniform plexus of veins are divided. The blood-supply of the organ is then entirely
derived frotn the deferential artery, a branch of the superior vesical. In rare cases the testis
descends in a wrong direction (ectopia testis) and comes to he in the perineum, over Scarpa's
triangle, or on the pubes.
Penis. — The subcutaneous tissue of the penis, as on the scrotum, is devoid
of fat and the delicate skin is very mobile and distensible, hence the ballooning
of these parts in extravasation of urine or cedema. The fascia penis is continuous
with CoUes's fascia.
In radical amputation of the penis for malignant disease the whole organ, including the
crura, is removed through an incision that splits the scrotum, and the stump of the corpus
spongiosum (corpus cavernosum urethras) is brought out into the perineum behind the scrotum.
The preputial orifice varies greatly in size. Normally large enough to allow easy retrac-
FiG. 1117. — Cross-section op Penis.
Dorsal artery y | /Deep dorsal ^
Tunica albuginea
Tunica albuginea-
Corpus cavernosum penis
Fibrous sheatli of penis
Artery
Urethra
Corpus cavernosum urethrse (spongiosum)
tion of the prepuce from off the glans, it is frequently so small that retraction is impossible
and it may even cause difficulty in micturition. The mobility of the skin over the penis must
be borne in mind in the operation of circumcision, and care taken lest too much of the prepuce
be removed, leaving insufficient skin to cover the penis. In this operation the vessels from which
bleeding occurs lie, (1) on the dorsum, (2) in the frenum.
Congenital malformations of penis. — At an early stage of development the urethra opens
on the inferior aspect of the penis behind the glans. After the ingi-owth of epithelium that
forms the glandular urethi-a, this primitive meatus should close. Occasionally, however, it
persists, and the glandular urethra is represented by a groove on the under aspect of the glans.
In these cases of hypospadias the glans is flexed on the penis and the prepuce is deficient IdbIow
and has a pecuhar "hooded" appearance. In epispadias the upper wall of the m-ethra and
corresponding part of the corpora cavernosa are absent. This condition is usually present
in cases of ectopia vesicas.
The male urethra is about 20 cm. (8 in.) in length, consisting of the cavernous
portion, 16 cm, (6| in.), membranous 1 cm. (| in.) and prostatic 3 cm. (IJ in.).
The narrowest part is the external orifice, and next to it the membranous
urethra. The prostatic urethra is the widest and most dilatable. The bulbous
urethra, just in front of the uro-genital diaphragm, is wider than the rest of the
penile portion, but since it forms the most dependent spot in the fixed part of
the urethra (from bladder to suspensory ligament of penis) , it is specially prone
to gonorrhoeal stricture. Behind the bulb, the urethra narrows suddenly as it
passes through the uro-genital diaphragm and contraction of the sphincters of
* Journ. Amer. Med. Assoc, vol. 41, 1903, p. 718.
THE PROSTATE 1389
the membranous urethra may here give additional difficulty in the passage of
a catheter.
False passages most commonly occur through the floor of the bulb on account of this,
difficulty in entering the membranous urethi-a. The point of a small catheter may also be
caught in the following apertm'es: (1) The lacuna magna in the roof of the fossa navicularis
of the glandular urethra; (2) other crypts or lacunae in the penile part, mostly situated in the
upper wall; (3) the prostatic sinus in the floor of the prostatic urethra about its centre. With
the penis raised the urethra presents a simple cm-ve under the symphysis with the proportions
of an ordinary silver catheter.
It is in the region of the uro-genital diaphragm that the urethra is most liable to be damaged
by a fall or blow, and the urine extravasated as a result will be beneath CoUes's fascia. In
rupture of the membranous urethra urine may find its way in front of the inferior fascia of the
uro-genital diaphragm by coexisting injury to this, or tlirough openings in the vessels, etc.;
in a few such cases urine will make its way backward behind the fascia into the space of
Retzius, ascending thence between the peritoneum and transversahs fascia. The attachment
of the deep layer of superficial fascia to the base of the m-o-genital diaphragm accounts for the
fact that urine extravasated from a ruptured m'ethra or thi-ough an opening behind a stricture
passes not backward into the anal triangle, but forward onto the scrotum and abdominal wall.
The prostate consists of a mass of racemose glandular tubules imbedded
in a fibro-muscular stroma, that surrounds the first part of the urethra and lies
below the neck of the bladder. Its base is intimately connected with the bladder
by the continuation of vesical and urethral mucous membrane and by the inser-
tion of the outer longitudinal muscular coat of the bladder into the gland. The
inner circular muscle fibres of the bladder become specialised round the internal
urethral orifice to form the internal sphincter.
Adenomatous enlargements of the gland usually grow upward through this sphincter which
is thus dilated and pushed aside, so that the glandular growth is covered only by vesical mucous
membrane.
The apex of the prostate hes at the level of the lower border of the pubic
symphysis and 1.5 cm. behind it. It is firmly fixed to the superior fascia of the
uro-genital diaphragm (deep layer of the uro-genital trigone) and here the urethra
leaves it to become the membranous part. The anterior surface directed
vertically lies 2 cm. behind the lower part of the pubic symphysis in relation to
the prostatic plexus of veins; and from it the dense pubo-prostatic ligaments
run forward on either side to the pubes. The posterior surface is in contact with
the rectum, through the anterior wall of which it may be palpated 4 cm. (I5 in.)
above the anal margin. It is separated from the rectum by the two layers of
the recto-vesical septum (Elliot Smith).* The lateral surfaces are supported
by the anterior fibres of the levator ani, from which, however, they are separated
on each side by a dense mass of fibrous tissue in which the pudendal (prostatic)
plexus of veins is imbedded.
The prostatic urethra traverses the gland nearer the anterior than the pos-
terior surface, with a slight forward concavity. Its floor is placed posteriorly
and presents an eminence, the colliculus seminalis, about the centre of which is
the orifice of the prostatic sinus, on either side of which open the common ejacu-
latory ducts. The prostate is indefinitely divided into two lateral lobes. The
fissure uniting them across the middle line in front of the urethra (the anterior
commissure) is fibro-muscular and contains no glandular tissue. Behind the
urethra the lateral lobes are continuous and the portion of gland Ijang between
bladder, ejaculatory ducts and urethra has been erroneouslj^ termed the "middle
lobe." Though not a separate lobe anatomically, adenomatous hypertrophy
of this part is common, when it projects up into the bladder, and prevents the
proper emptying of that organ.
Capsule and sheath of the prostate. — In senile enlargement of the prostate removal may be
effected by the suprapubic or by the perineal route. In the former, the bladder is opened
above the pubes, the mucous membrane lying over the gland as it projects into the bladder is
scratched through behind, and with the finger the whole adenomatous mass is enucleated.
This process usually involves tearing out the whole of the prostatic m-ethra, and the ejaculatory
ducts. The parts left behind consist of (1) the "capsule" which is simply the outer part of
the gland proper stretched over the adenomatous mass, and consists of fibro-muscular tissue
with a few flattened glandular tubules (C. Wallace). f Outside this (2) the fibrous "sheath"
is derived from the visceral layer of pelvic fascia, in which is imbedded, on the anterior and
lateral aspects of the gland, the prostatic plexus. Since these veins are not torn there is com-
* Studies in Anatomy of the Pelvis. Journ. Anat. and Physiol., vol. 42, 190S.
t C. Wallace. Prostatic Enlargement, 1907.
1390 CLINICAL AND TOPOGRAPHICAL ANATOMY
paratively little hfemorrhage. In the perineal operation the posterior surface of the gland is
exposed by cutting through the perineum between the bulb and external sphincter ani, and
dividing the attachment of the recto-m-ethi-al muscle to the m-o-genital diaphragm and its in-
ferior fascia. This exposes the back of the recto-vesioal septum (aponeurosis of DenonvilKers)
which is split at its base, opening up the reoto-prostatic space of Proust. By a longitudinal
incision into the prostate on each side the adenomatous lateral lobes may be enucleated sepa-
rately, and it is claimed without injury to the urethra or ejaeulatory ducts (Hugh Young).*
The bladder lies above the pubic symphysis at birth and so is mainly an
abdominal organ. The anterior surface, in contact with the abdominal wall,
has no peritoneal covering, but posteriorly the peritoneal reflection descends to
cover the posterior surface of the prostate, which is relatively lower than in the
adult.
The adult bladder when empty forms a pyriform contracted organ behind the symphysis,
and bounding the retro-pubic space of Retzius posteriorly. Into this space urine is extrava-
sated in extra-peritoneal rupture of the bladder, and may mount up behind the abdominal wall
in the extra-peritoneal tissue. The space is closed below by the pubo-pro.stafic ligaments and
prostatic plexus of veins. In distention, the neck of the bladder and prostate being relatively
fixed and immovable, the free a-pex rises up into the abdomen. As it does so it raises the peri-
toneum off the abdominal wall, so that in moderate distention 5 cm. (2 in.) of abdominal wall
above the pubes are free of peritoneum, and the bladder may be tapped here safely. The upper
surface and a little of the posterior are covered by peritoneum, which is also related to the upper
halves of the vesiculae seminales. Below the recto-vesioal pouch the base of the bladder pre-
sents a small triangular area in contact with rectum, bounded by the peritoneal cul-de-sac above,
the converging deferential ducts on each side and the prostate below. Tlirough this triangle
which is rather expanded in distention of the bladder, puncture per rechmi was formerly prac-
tised. The infero-lateral surfaces are slung up by the levator ani as by a hammock. The inte-
rior of the bladder can be examined by the cystoscope in the living patient. The mucous mem-
brane is loose and ruQ;ose in contraction, except over the trigone at the base, the angles of
which are formed by the ureteric orifices and the internal meatus. The mucosa here is firmly
adherent to the muscular coat and smooth. In hypertrophy of the bladder-muscle from ob-
struction, a fasciculated appearance of the mucosa is seen and possibly diverticula between
the bands of muscle.
Rectum and anal canal. — The rectum proper extends from the end of the
pelvic colon, opposite the third sacral vertebra, to the upper end of the narrow
anal canal, which runs downward and backward almost at right angles to the
rectum and is 3-4 cm. in length. The commencement of the rectum lies 13-14
cm. (5-5| in.) above the anus in the adult. This point is marked internally
by an infolding of the mucosa on the right and anterior wall and to some extent
of the circular muscle fibres, due to the angle at which the free pelvic colon turns
into the fixed rectum. This shelf of mucous membrane is known as the upper
transverse fold (first valve of Houston).
Under normal conditions the rectum does not form a reservoir for faecal material, which
is stored in the lower end of the pelvic colon, above the upper transverse fold, leaving the
rectum empty except in defsecation. The rectum proper is subdivided into two compartments
by the inferior transverse fold on the anterior wall (third or great valve of Houston), situated
8-9 cm. (3-3i in.) above the anus at the level of the anterior cul-de-sac of the peritoneum, and
resulting from the adaptation of the rectum to the hollow of the sacrum. This can usually
be made out on digital examination. The other transverse folds are inconstant and only
present on great distention.
The rectum and anal canal may be divided into three regions: (1) peritoneal
from the third sacral vertebra to the lower transverse fold and anterior reflexion
of peritoneum onto bladder or vagina; (2) infraperitoneal (rectal ampulla)
below this and above the levator ani; (3) anal canal, below the level of the
levator ani, constriction b3r which marks it off from the ampulla and converts
it into an antero-posterior slit.
The mucous membrane of the rectum proper is redundant and mobUe and of a bright pink
colour as seen by the sigmoidoscope. It is dotted over by rectal pits, visible to the naked eye,
containing lymphoid follicles, and by the smaller and more numerous Lieberkhiin's glands.
In the peritoneal chamber the mucosa is transversely plicated. In the rectal ampulla it presents
longitudinal folds in which lie branches of the superior hfemorrhoidal vessels. These longi-
tudinal folds, known as the rectal columns, converge into the anal canal, and end at the level
of the anal valves half way down the canal, each uniting two adjacent valves. The anal valves
probably represent the original cloacal membrane, dividing the proctoda^um (formed from the
epiblast) from the hypoblastic hindgut, and persistence of this membrane gives one form of
imperforate anus (Wood Jonesf). The tearing down of a valve by hard faeces may be a cause
of anal fissure, etc. (Ball). The mucous membrane of the anal canal is more firmly adherent
* Studies on Hypertrophy and Cancer of the Prostate. J. H. H. Reports, vol. 14, 1906.
t Brit. Med. Journal, Dec. 14, 1904.
FEMALE GENITAL ORGANS 1391
to the underlying muscular coat than that of the rectum, hence in prolapse the mucosa of the
rectal ampulla is the first to be extruded.
Peritoneal relations. — The peritoneal chamber of the rectum has no covering of peritoneum
behind, and the peritoneum, at first covering its first aspect and sides, leaves the sides
obliquely and finally is reflected onto the base of the bladder (or the vaginal fornix in the
female), at the level of the inferior rectal fold, 8 cm. from the anus.
Blood-supply. — (1) The superior hsemorrhoidal artery, a continuation of the inferior me-
senteric, reaches the rectum behind, via the pelvic meso-colon and bifurcates at once. The two
branches run round on either side below the peritoneal reflection; giving ofl^ secondary branches
that pierce the muscular coat about the level of the inferior transverse fold, or anterior perit-
oneal reflection. Joining the submucous layer, these arteries run down in the rectal columns
to the anal canal, where they anastomose with (2) the middle hsemorrhoidal arteries, branches
of the hypogastric (internal iliac) and (3) the inferior hasmorrhoidal branches of the internal
pudendal. The veins correspond. Their free anastomosis in the hsemorrhoidal plexus under
the rectal columns, the union afforded here between the portal and systemic veins, the absence
of valves in the superior hsemorrhoidal veins, and the constriction they are subject to in passing
through the muscular coat, are some of the anatomical causes of the frequency of haemorrhoids.
The branches of the superior hremorrhoidal artery to the rectum anastomose but little
with one another, as compared with the sigmoid arteries to the pelvic colon. The main trunk
of the superior hsemorrhoidal usually receives a large anastomotic branch from the lowest
sigmoid artery 1-2 cm. below the sacral promontory, upon which the upper part of the rectum
is dependent for its blood-supply after ligature of the superior haemorrhoidal. Hence in high
excision of the rectum it is important to place the ligature on the superior hsemorrhoidal above
the sacral promontory if sloughing of the gut is to be avoided.*
For lymphatics of the rectum see p. 735.
Supports of the rectum. — The anal canal is fixed by its attachment to the levator ani and
perineal body. After division of the perineal body and recto-urethral muscle in front, the
rectum is readily separable from -the back of the prostate and recto-vesical septum. When
the levator ani has been divided on each side and the peritoneum opened, as in the perineal
operation for excision of the rectum, the gut cannot be pulled down freely. The hand passed
up behind it in the hollow of the sacrum meets on each side with a dense fibrous layer running
from the sacrum opposite the third foramen onto the side of the rectum. This is the rectal
stalk (Elliot Smith) and consists of dense fibrous tissue round the nervi erigentes from second,
third and fourth sacral foramina and the middle haemorrhoidal vessels. It lies about 2.5 cm.
above the levator ani, and after division of it the bowel is easily freed, so that the whole of the
rectum and part of the pelvic colon may be drawn out at the perineum without tension.
Rectal examination. — The following points can be made out by the finger introduced into
rectum: — (1) The thickened, roll-like feel of a contracted external sphincter; (2) the narrower,
more expanded, internal sphincter extending upward for 2.5 cm. (1 in.) from this; (3)
the rectal insertion of the levatores ani, which here narrows somewhat the lumen of the gut;
(4) above the anal canal, with its contrasting capaciousness, is the more or less dilated rectum
proper; (5) the condition of the ischiorectal fossse on either side; (6) the membranous urethra in
front, especially if a staff has been introduced; the instrument now occupies the middle line,
and has the normal amount of tissue between it and the finger, thus differing from one in a
false passage (in a child an instrument is especially distinct); (7) just beyond the sphincters, or
3.7 cm. (1| in.) within the anus, lies the prostate; (8) converging toward the base of the prostate,
and forming the sides of the triangular space, are the vesiculse seminales and ejaculatory ducts.
These can rarely be felt unless diseased and enlarged; any enlargement of the sacculated ends
of the deferential ducts is much more perceptible; (9) it is within this triangular space that the
elasticity of a distended bladder can be felt. (10) Usually the lowest of the transverse folds
(folds of Houston), semilunar in form and about 1.2 cm. (J in.) in width, can be made out (fig.
1116). (11) Behind, the coccyx and its degree of pliability and the lower part of the sacrum.
It may also be possible to feel enlarged sacral nodes and a growth from the other pelvic
bones.
The above examination refers chiefly to the male.^ It remains to refer to rectal examination
in the female. Anteriorly, the soft perinseal body and recto-vaginal septum will be met with,
and, through the latter, the cervix and os uteri, and, higher up, the lower part of the cervix uteri.
More laterally the ovaries may be felt, but the uterine or Fallopian tubes, unless enlarged and
thickened, are not to be made out. The student should be familiar with the feel of a healthy
recto-uterine or recto-vesical pouch, according to the sex, and the coils of intestine which it
may contain, so as to be able to contrast this with any collection of inflammatory or other
fluid or mischief descending from the upper pelvis, e. g., from the vermiform appendix. Pos-
teriorly, certain structures are met with in either sex. After a very short interval (sphincter
and ano-ooccygeal body) the finger reaches the tip of the coccyx and explores the hollow of the
sacrum. On each side are the ischial tuberosity and wall of the true pelvis. The finger
hooked lateralward and upward, comes on the border of the falciform process of the sacro-
tuberous (great sacro-sciatic) ligament, passing between the above-mentioned bones.
FEMALE GENITAL ORGANS
The external organs will be considered first, followed by the internal. Under
the external organs are included, for convenience sake, the labia majora and
minora at the sides; and, in the middle line, from above downward — (1) The
glans clitoridis with its prepuce; (2) the vestibule; (3) the urethral orifice; (4) the
* H. Hartmann. Annals of Surgery, Dec, 1909.
1392 CLINICAL AND TOPOGRAPHICAL ANATOMY
vaginal orifice with the hymen or its remains; (5) the fossa navicularis; (6) the
fourchette; (7) the sldn over the base of the perineal body.
These parts have been described elsewhere, and only those points which are of
importance in a clinical examination will be alluded to here.
The labia majora are two thick folds of skin, covered with hair on their outer
surface, especially above, where they unite {anterior com7nissure) in the mons
Veneris. They contain fat, vessels, and dartos, but become rapidly thinner
below, where they are continuous at the front of the perineum (their posterior
commissure).
When the above folds are drawn aside, the labia minora, or nymphae, appear,
not projecting, in a healthy adult, beyond the labia majora. They are small
folds of skin, which meet above in the prepuce of the clitoris, and below blend
with the labia majora about their centre. Sometimes, especially in nulliparae,
they unite posteriorly to form a slight fold, the fourchette.
The glans clitoridis, covered by its prepuce, occupies the middle line above.
Below it comes the vestibule, a triangular smooth surface of mucous mem-
brane, bounded above by the clitoris, below by the upper margin of the vaginal
orifice, and laterally by the labia minora. In the middle line of the vestibule
and toward its lower part, about 12 mm. (J in.) below the glans clitoridis, and 25
mm. (1 in.) above the fourchette, is the meatus or opening of the urethra (figs.
1034, 1037).
The vaginal orifice lies in the middle line between the base of the vestibule
above, and the fossa navicularis below. Its orifice is partially closed in the virgin
by a fold of mucous membrane, the hymen (fig. 1037). This is usually crescentic
in shape attached below to the posterior margin of the vaginal orifice, and with
a free edge towards the base of the vestibule. In some cases it is diaphragmatic
i. e. attached all around, but perforated in the centre (fig. 1037).
The schrivelled remains of the hymen probably constitute the carunculse
hymenales. On either side of the vaginal orifice, at it lower part, lie the racemose,
muciparous, vestibular glands (glands of Bartholin), situated beneath the super-
ficial perineal fascia and sphincter vaginae. Their ducts run slightly upward and
open, external to the attachment of the hymen, within the labia minora. In
relation to the upper two-thirds of the vaginal orifice, placed between the uro-
genital diaphragm behind and the sphincter vaginae in front, are the vascular
bulbs of the vestibule, rupture of which produces pudendal hfematocele.
Fourchette and fossa navicularis. — The fourchette, as stated above, is the
posterior commissure of the labia minora. Normally the inner aspect of this is
in contact with the lower surface of the hymen. When the fourchette is pulled
down by the finger, a shallow depression is seen, the fossa navicularis, with the
fourchette for its posterior, and the hymen for its anterior, boundary.
Internal organs. — The examinations through the vagina and anus will be
considered first, followed by uterus and appendages, ovary and ureter.
Examination per vaginam. — The finger, introduced past the gluteal cleft,
perineum, and fourchette, comes upon the elliptical orifice of the vagina, and notes
how far it is patulous or narrow; the presence or otherwise of any spasm from the
adjacent muscles; then, passing into the canal itself, the presence or absence of
rugae, a naturally moist or a dry condition are observed. In the anterior wall the
cord-like urethra can be rolled between the finger and the symphysis ; and further
up than this, if a sound be passed, the posterior wall of the bladder. The anterior
wall of the vagina is about 6.7 cm. (2| in.) long. The posterior wall, 7.5 cm. (3
in.) long, forms the recto-vaginal septum, and through it any faeces present in
the bowel are easily felt. The cervix uteri is next felt for in the roof of the vagina,
projecting downward and backward in a line drawn from the umbilicus to the
coccyx. Besides its direction, its size, shape, mobility, and consistence should be
noted. The os uteri should form a dimple or fissure in the centre of the cervix.
Of its two lips, the posterior is the thicker and more fleshy feeling of the two.
The vaginal culs-de-sac or fornices are next explored. These should be soft and
elastic, giving an impression to the finger similar to that when it is introduced
into the angles of the mouth. Any resistance felt here may be due to scars,
swellings connected with the uterus (displacements or myomata), effusions of
blood or inflammatory material, and, in the case of the lateral culs-de-sac, a
displaced or enlarged ovary, or dilatations of the Fallopian tubes. The posterior
cul-de-sac is much deeper than the anterior, and, owing to the peritoneum
THE OVARY
1393
descending upon the posterior wall of the vagina, when the finger is placed here
it is only separated from the peritoneal sac by the vaginal wall and pelvic fascia.
In examination of the pelvic organs the bimanual method, by which one hand
on the hypogastric region, pushes them down and steadies them as well, is always
to be employed to complete an examination.
The uterus and appendages. — The normal non-gravid uterus is usually
anteflexed and anteverted so as to lie with its long axis approximately at right
angles to that of the vagina. Its position varies considerably with the degree
of distention of the bladder in front and of the rectum behind. The distance
from external os to fundus, as estimated by the passage of a sound is in the
adult virgin uterus 5.5 cm. of which 3 cm. belong to the cervix and 2.5 cm. to the
body. In the empty multiparous uterus the total length of the cavity is 6 cm.,
2.5 cm. comprising the neck and 3.5 cm. the body.
Peritoneal relations. — In front the peritoneum is reflected from the uterus to form the
utero-vesical pouch at the level of the isthmus. Behind it covers not only the uterus but the
posterior fornix of the vagina, before turning off onto the front of the rectum. Laterally the
peritoneum leaves the uterus and passes on to the lateral pelvic wall as a large twofold partition
fig. 1118), the broad ligament.
Fig. 1118. — Sagittal Section of the Bhoad Ligament.
Graafian follicles
of ovary
Mesovarium
Mesometrium
Posterior surface
Uterine veins
Base of ligament
The broad ligament, bearing in its upper border the uterine tube, in front the round ligament
and behind the ovary, consists of (1) an upper thin part, the mesosalpinx lying above the
attachment of the mesovarium, and containing the ovarian vessels and the epoophoron, and
below this (2) the thicker mesometrium, between the layers of which is a dense mass of fibrous
tissue surrounding the uterine artery.
The anterior aspect of the cervix below the utero-vesical pouch of peritoneum, is readily
separable from the bladder with which it lies in contact, and the peritoneum may be raised oil
the uterus with ease in the lower part of its attachment both front and back. Over the upper
part of the body and fundus, however, the peritoneal covering is firmly adherent, and cannot
be dissected off.
The ovary, attached by its hilum to the mesovarium, lies in a fossa at the
back of the lateral wall of the pelvis just between the diverging external ihac and
hypogastric vessels. To feel it the finger should be pushed well up in the side of
the vagina toward the lateral wall of the pelvis. On the abdominal surface its
position corresponds to the middle of a line drawn from the anterior superior
ihac spine of that side to the opposite pubic tubercle (Rawlings).
1394 CLINICAL AND TOPOGRAPHICAL ANATOMY
The lymphatics of the ovary follow the ovarian veins (see p. 745).
Supports of the uterus. — The great mobility of the body of the uterus has been referred
to above. The organ derives its support almost entu'ely from the attachments of the cervix
and vaginal fornices. These rest on the pelvic floor, formed by the levator ani and perineal
body which support them the more efficiently since the long axis of the vagina is at right angles
to that of the uterus. Above the pelvic diaphragm the cervix is held up to the pelvic walls by
strong specialised bands of fibro-muscular tissue running in both antero-posterior and trans-
verse directions. The chief of these, lying in the base of the broad ligaments is a fibrous sheath
sm-rounding the uterine artery as it descends medially from the hypogastric. In the antero-
posterior direction the utero-vesical ligaments hold up the cervix to the pubes in front and the
sacro-uterine ligaments bind it to the anterior aspect of the sacrum behiind. While firmly
supporting the uterus these bands are elastic, and so do not fix it rigidly, but allow of the cervix
being drawn downward by traction with vulsellum forceps.
For lymphatics of uterus and vagina see p. 745.
The ureter. — The pelvic portion of this duct is of special importance in opera-
tions on the uterus and upper vagina. It crosses the brim of the pelvis on either
side at the biftu-cation of the common ihac artery, or just in front of it, and
descends on the side waU in front of the hypogastric artery, crossing the ob-
literated umbilical 'and obturator arteries. Curving forward and medially it
passes under the base of the broad ligament, where the uterine artery crosses
above it, and so gains the lateral angle of the bladder by passing across in rela-
tion to the lateral fornix of the vagina. In the base of the broad ligament the
ureter lies about 2 cm. (f in.) from the side of the cervix, and this relation must
be borne in mind in excision of the uterus.
Pelvic floor. — The pelvic floor of the female corresponds in general to that
of the male (see p. 1383). There are, however, important differences, due to the
sexual organs. The urogenital diaphragm is relatively smaller in area, due to per-
foration by the vagina. The pelvic diaphragm is also correspondingly modified,
and the pubo-coccygeus component is more strongly developed (see section on
Musculature.) The ischio-rectal fossa is similar to that of the male (p. 1384).
HERNIA
Three varieties of hernia will be considered, inguinal, femoral, and umbilical
PARTS CONCERNED IN INGUINAL HERNIA
In inguinal hernia, as in femoral and umbilical, there is a weak spot in the ab-
dominal wall — one weakened for the needful passage of the testicle from within
to outside the abdomen (p. 1387). The parts immediately concerned are the two
inguinal rings, subcutaneous (external) and abdominal (internal), and the canal.
Now, it must be remembered at the outset that the rings and canal are only
potential — they do not exist as rings or canal save when opened up by a hernia,
or when so made by the scalpel. The canal is merely an oblique slit or flat-sided
passage. The subcutaneous and abdominal rings are so intimately blended with
the structures that pass through them, and so filled by them, that they are potential
rings only.
The subcutaneous inguinal (external abdominal) ring. — This is usually
described as a ring : it is really only a separation or gap in the aponeurosis of the
external oblique, by which in the male the testicle and cord, and in the female
the round ligament by which the uterus is kept tilted a little foward, pass out
from the abdomen. The size of this opening, the development and strength of its
crura or pillars, the fascia closing the ring — all vary extremely. Formation : by
divergence of two fasciculi of the external oblique aponeurosis. Boundaries : two
crura — (1) Superior, the smaller, attached to the symphysis and blending with the
suspensory ligament of the penis; (2) inferior, stronger, attached to the pubic
tubercle and blending with the inguinal ligament, and so with the fascia lata. On
this inferior, stronger crus rests the cord (and so the weight of the testicle) or
round ligament. Shape : triangular or elliptical, with the base downward and
medially toward the pubic crest.
Intercrural fibres (intercolumnar fascia) (external spermatic fascia). — This, derived from
the lower part of the aponeurosis of the external oblique, ties the two crm'a together, and, being
continued over the cord, prevents there being any ring here, unless made with a scalpel. This
is the rule in the body: when any structure passes through an opening in a fibrous or muscular
INGUINAL HERNIA
1395
layer, it carries with it a coating of tissue froro that layer; e. g., the inferior cava passing through
its foramen in the diaphi-agm, and the membranous uretlu-a thi'ough the uro-genital diaphragm.
Effect of position of the thigh on the ring.— As the lower crus is blended with Poupart's
hgament, and as the fascia lata is connected with this, movements of the thigh will affect the
rmg much, making it tighter or looser. Thus extension and abduction of the thigh stretch
the crura and close the ring. In flexion and adduction of the thigh the crura are relaxed; and
this is the position in which reduction of a hernia is attempted. In flexion and abduction of
the thigh, the rmg is open; and this is the position in which a patient should sit, with thighs
widely apart, to try on a tru.ss, and cough or strain downward, as in rowing. If the hernia is
now kept up, the truss is satisfactory.
_ Helping to protect this most important spot, and preventing its being more than a potential
rmg, are not only the two crura and the intercrural fibres, but also a structure which has been
called a thu-d or posterior pillar, namely, the reflected inguinal ligament. This has its base
above at the lower part of the linea alba, where it joins its fellow and the aponeurosis of the
external oblique, and its apex downward and laterally, where, having passed behind the medial
crus it blends with the lacunar (Gimbernat's) ligament. Again, the falx inguinalis (the con-
FiG. 1119. — The Parts concerned in Inguinal Hernia.
(From a dissection in the Hunterian Museum.)
External oblique, cut and turned back Internal oblique External oblique
Falx inguinalis
Poupart's (inguinal) hgament
Reflected inguinal ligament
joined tendon of the internal oblique and transversahs), curving mediaUy and downward to
be attached to the ilio-pectmeal hne and spine, is a most powerful protection, behind, to what
13 otherwise a weak spot and a potential ring.
Inguinal canal.— This is not a canal in the usual sense, but a chink or flat-
sided passage m the thickness of the abdominal wall. The descriptions of the
canal usually given apply rather to the diseased than to the healthy state. It
was a canal once, and for a time only, i. e., in the later months of fcetal life (p. 1387).
It remains weak for a long time after, but only a vestige of it remains in the well-
made adult.
Length.— In very early life there is no canal; one ring lies directly behind the
other, so as to facilitate the easy passage of the testis. In the adult it measures
about 37 mm. (l^ in.) in length, this lengthening being brought about by the
growth and separation of the alse of the pelvis. This increased obliquity gives
additional safety. On the other hand, a large hernia has not only opened \^^dely
the canal and rings, but it has pulled them close together, and one behind the other
thus not only rendering repair much more difficult, but also the path to the
1396 CLINICAL AND TOPOGRAPHICAL ANATOMY
peritoneal sac shorter and more direct. Direction.— From the abdominal to the
subcutaneous ring, downward, forward, and medially. -^ • in ,
Boundaries.— For convenience sake, certain hmits (largely artifacial) have
been named : — , , , i, i j. iu
(1) Floor. — This is best marked near the outlet, where the cord rests on the
grooved upper margin of the inguinal (Poupart's) and the lacunar (Gimbernat's)
lio-ament. The meeting of the transversalis fascia with this hgament forms the
floor (2) i?oo/.— The apposition of the muscles and the arched border of the
internal oblique and transversus. (3) Anterior wall— Skin, superficial fascia,
external oblique for all the way. Internal oblique, i. e., that part arising from
Poupart's ligament, for the lateral third or so. To a slight extent, the trans-
versus and the cremaster. (4) Posterior wall.—For the whole extent, transversalis
fascia, extraperitoneal tissue, and peritoneum. For the medial two-thirds, con-
joined tendon of internal oblique and transversus, and the lateral edge of the
reflected inguinal hgament, when developed.
Fig. 1120. — Dissection of Inquinai, Canal. (Wood.)
^ %%\W , ^'
External oblique,
(turned down)
11 > Internal oblique
Transversus
Falx inguinalis (con-
VTMW 1 I joined tendon)
\ VWi I I Reflected ligament
^■— ^-^ 1 j (triangular fascia)
Cremaster
The transversalis fascia is thicker and better marked at its attachments below; these are-
fa) laterally, to medial lip of iliac erest; (b) to the ingmnal ligament between the anterior-
superior spine and the femoral vessels, where it joins the fascia ihaca; (c) opposite the femoral
vessels it Tlso joins the fascia iliaca, and forms with it a funnel-shaped sheath; (d) mecbal to the
femoral vessels the fascia transversalis is attached to the terminal (.^'l°-Pe«t>,^^f ) J^^^' ^^^J^f,
the conjoined tendon, with which it blends. The falx ingmnahs {conjoined tendon) needs special
reference It is foriied by the lower fibres of the internal oblique and transversus (arciform
fibres) arching downward over the cord to be inserted into the crest and spme and the termmai
aho-pectineal) line. The fibres of the internal oblique become increasingly tendmous as they
descend, and this, with the fact that below they give off the cremaster, may «ause some difficulty
in theh- identification when it is desked to unite them to the upper surface of Poupart s liga-
ment in the operation of radical cure.
The abdominal inguinal (internal abdominal) ring.— It has already been said
that the term 'ring' is here misapplied except in an artiflcial sense, as when an
opening is made by a scalpel; or in abnormal conditions when a hernial sac is
present. The abdominal ring is not a ring in the least, but merely a tunnel-
shaped expansion of the transversahs fascia, which the cord carries on with it as
it escapes from the abdomen.
INGUINAL HERNIA
1397
Site. — Midway between the anterior superior iliac spine and pubic tubercle.
Shape : oval, with the long diameter vertical. Boundaries : centre of inguinal
(Poupart's) ligament, about 12 mm. (| in.) below. Medially, the inferior
epigastric artery (fig. 1121); the position of this vessel, by its pulsation, is an im-
portant guide to the insertion of the highest sutures between the arciform fibres
and the inguinal ligament. Owing to the artery lying to the medial side, the
incision, in cutting to relieve the deep constriction of an inguinal hernia, should
always be made directly upward, so as to avoid the above vessel. A large ob-
lique hernia may so have altered the relations of the parts, including the artery,
that it is difficult to decide whether the hernia is oblique or direct. The above
incision will be safe, because, iia either case, parallel to the vessel.
Coverings. — There are two chief forms of inguinal hernia : —
A. The cominon form: lateral, or oblique. — Lateral, because it appears
(at the abdominal ring) lateral to the inferior epigastric artery. Oblique,
because it traverses the whole of the inguinal canal, entering it at its inlet and
leaving it at its outlet. This form is usually congenital in origin, and is due to
non-obliteration of the processus vaginalis in infancy.
Fia. 1121. — Dissection of the Lower Part of the Abdominal Wall from within, the
Peritoneum having been removed. (Wood.)
order of the poste-
rior part of the
sheath of the rec-
tus (fold of Doug-
Fascia transversal- -^ ■ — ^
Inferior epigastr:
artery
Ductus (vas) deferens
Spermatic vessels
Obliterated hypo-
gastric artery
"■ Lymphatics in
femoral ring
External iliac artery
B. Rarer form : medial, or direct. — Medial, because it appears medial to the
inferior epigastric artery. Direct, because, instead of making its way down the
whole oblique canal, it comes by a short cut, as it were, only into the lower part
of the canal, and then emerges by the same opening as the other.
A. Oblique inguinal hernia. — This possesses its coverings as follows: —
(1) At the abdominal ring, or inlet, it obtains three: — (a) Peritoneum; (6) extra-peritoneal
fat; (c) iiifuiidibuliform fascia, or the vaginal process of transversalis fascia prolonged at this
spot along the cord.
(2) In the canal it obtains one. As it emerges beneath the lower border of the internal
oblique it gets some fibres from the cremaster.
(3) At the subcutaneous ring, or outlet, the hernia obtains three, viz.: (a) Intercrura
fibres (interoolumnar fascia) ; (b) superficial fascia; and (c) skin.
B. Direct inguinal hernia. — This does not come through the abdominal ring, but,«making
its waj' through the posterior wall of the lower third of the canal, either through the medial or
intermediate inguinal fossa. Its coverings, therefore, vary slightly with its mode of exit (vide
infra).
Hitherto the two forms of inguinal hernia have been considered from the superficial aspect,
that in which they are met with in practice. The inguinal region should also be studied as to
1398 CLINICAL AND TOPOGRAPHICAL ANATOMY
the posterior aspect of its so-called rings and canal, as these have to bear the early stress of a
commencing hernia. It is against this aspect that a piece of omentum or intestine is constantly
and insidiously pressing and endeavoui'ing to make its way out. Furthermore, when either of
the above constituents of hernia have made their way a little farther, and got out into the ab-
dominal ring or into the canal, the patient is no longer sound.
On the posterior wall are certain cords and depressions, marking off regions which corre-
spond to those on the surface. Thus, there are three prominent cords and three fossae
(fig. 1121).
Three cords — (1) Median, or urachus; (2) lateral, or the obliterated hypogastric arteries.
(1) Median, or urachus. This interesting foetal relic, the intra-abdominal part of the
allantois, passes up between the apex of the bladder and the umbilicus.
(2) The obliterated hypogastric arteries. These, the remains of vessels which during
foetal life carry the impure blood of the foetus out to the mother through the umbilicus, run
up and join the urachus at the umbilicus.
In relation to these cords are the following fossae : — (a) A medial one, between the virachus
and the obliterated hypogastric artery. This corresponds, on the anterior surface, to the
subcutaneous inguinal (external abdominal) ring. Through this fossa comes the commonest
form of direct inguinal hernia, (ft) Between the obliterated hypogastric artery and the inferior
epigastric artery, which runs upward and medially to form the lateral boundary of Hessel-
bach's triangle, is an intermediate fossa. This is the smallest of all. The rarer form of direct
hernia comes tlirough here, (c) The lateral fossa is lateral to the inferior epigastric artery. It
is the most distinct of the three, from the way in which the cord or round ligament passes down
within a glove-like vaginal process of the transversalis fascia. This fossa corresponds to the
abdominal ring.
The coverings of a direct hernia may now be considered, together with the two-fold manner
of exit of this hernia. It only traverses the lower part of the canal, making its way through
either the medial or the intermediate inguinal pouch, (i) The commonest form, coming
through the medial inguinal pouch, either pushes its way through or stretches before it the falx
inguinalis. Its coverings are: — (1) Peritoneum; (2) extra-peritoneal fat; (3) transversalis fascia;
(4) falx inguinalis (unless this is suddenly burst through); (5) (6) (7). At the subcutaneous
ring the three coverings are the same as in the oblique variety, (ii) This rarer form of direct
hernia comes through the intermediate inguinal pouch. As a rule, the falx inguinalis does not
reach over this fossa. The coverings will be the same as in the last, with two exceptions —
there is no falx inguinalis, and the cremasteric fascia, if well developed, will be present.
Varieties of inguinal hernia according to the condition of the vaginal process of peritoneum.
— Inguinal herniEe have above been classified according to tlieir relation to the deep epigastric
artery. It remains to allude to the arrangement of these same hernias according to the varying
condition of the processus vaginalis. This pouch of peritoneum, which paves the way for the
passage of the testis before this organ makes its start, eventually becomes the parietal layer
(p. 1387) of the tunica vaginalis below, in this fashion: During the first few weeks after birth
the process becomes obliterated at two spots — one near the abdominal ring, and one just
above the testis. The obliterative process, commencing first above and descending, and then,
ascending from below, the shrivelling continues until nothing is lett save the tunica vaginalis
below. The following are possible hernial results of an imperfect obliteration of the process: —
(1) If the process does not close at all, a descending hernia is called congenital. This may
make its way into the scrotum. The testis is now enveloped and concealed by the hernia.
(2) If the process is closed only above, i. e., near the abdominal ring, two varieties may be
met with, the infantile and the infantile encysted. In the infantile, owing to pressure above, the
weak septum gradually yields and forms a sac behind the unobliterated lower part of the pro-
cessus funiculo-vaginalis. Thus three layers of peritoneum may now be met with in an opera-
tion, the two of the incompletely obliterated tunica vaginalis, and the proper sac of the hernia.
In the encysted infantile variety the hernial pressure causes the septum to yield and form a sac
projecting into, not behind, the incompletely obliterated tunica vaginalis. Here, theoretically,
two layers of peritoneum will be met with. Another variety of such an encysted hernia may
be produced by rupture, not stretching, of the above-mentioned septum.
(3) If the processus vaginalis be closed below and not above, a patent tubular process of
peritoneum will lead down as far as the top of the testis. Any hernia into this process is called
a hernia into the funicular process. All these varieties save the congenital and hernia into the
funicular process are rare in practice. Other practical points are that all hernise in children and
young adults are probably of congenital origin, and, therefore, the weakness is often bilateral,
though it may not be so palpably. This applies to both sexes. Again in hernia of sudden
origin into the funicular process with narrow surroundings, strangulation may be very acute.
Inguinal hernia in the female. — The inguinal canal in women is smaller and narrower than
in men. Inguinal hernia is, therefore, less common in the female sex, and occurs in patients who
happen to be tlie subjects of an unobliterated processus vaginalis, which extends for a varying
distance along the round ligament, and is called the canal of Nuok. Inguinal hernia in the
female is, therefore, always congenital. It is, practically, always of the oblique variety, and
travels along the round ligament toward the labium majus. Its coverings will be the same as
those of the oblique variety in the male, save that the cremaster, as a distinct muscle, is absent,
and any fibres of the internal oblique which may be present are but little developed.
FEMORAL HERNIA
Parts concerned in femoral hernia. — (1) Skin and superficial fascia of groin.
— The latter consists of two layers: (a) Superficial layer of superficial fascia. —
Fatty, met with over the whole groin, and continuous with the superficial fascia
FEMORAL HERNIA
1399
of the rest of the body, (b) Deep layer of superficial fascia. — Thin and mem-
branous, only met with over the lower third of the abdominal wall and to the
medial side of the groin.
It is continuous through the scrotum with the deep layer of the superficial fascia of the
perineum. Just below the inguinal hgament it is joined to the fascia lata. From these two
facts it results that in rupture or giving way of the urethra the extravasated urine may come
forward by way of the genitals (p. 13S5) and from the continuity of the fascia make its way on
to the abdomen, but not down on to the thigh.
Between the two layers of superficial fascia lie the superficial nodes of the groin, the super-
ficial branches of the common femoral artery, one or two cutaneous nerves, and some veins
descending to the fossa ovahs to join the great saphenous vein.
(2) Inguinal (Poupart's) ligament. — This is also known as the crural arch, a
misnomer, as 'crus' means leg. A description of its shape and attachments is
given on p. 1371. Owing to the connection of the fascia lata to its lower border,
the fossa ovalis (saphenous opening), which is situated in the fascia lata, and has
its upper cornu blending with the inguinal ligament, will be affected by movements
of the thigh, much as is the subcutaneous inguinal (external abdominal) ring,
being tightened and stretched when the limb is extended and abducted, relaxed
when it is adducted and flexed.
Fig. 1122. — The LAnrNi? ekneath the Inguinal Ligament. (Lookwood.)
— ■ Inguinal ligament
Muscular lacuna
Ilio-pectineal Hgament^l
1 \ \ \
Vascular lacuna
Hio-pectineal eminenc
Cooper's ligament
Lacunar ligament
Spermatic cord
The parts beneath the ligament which block up the gap between it and the
innominate bone are of the utmost importance in preventing the escape of a
femoral hernia (fig. 1122).
The different structures are arranged in three compartments (fig. 1122),
named latero-medially : — A. lateral, iliac, or muscular; B. central, or vascular;
and C. medial, or pectineal. Of these, the first is the largest; the second or
intermediate one lies slightly nearer to the inguinal ligament than the other two ;
while the medial compartment differs from the other two by not communicating
with the pelvis, being closed above {vide infra).
(A) The lateral, or iliac, compartment is bounded in front by the inguinal ligament and the
iliac fascia, which is here blending with it, behind by the ihum, laterally by this bone and the
sartorius, and medially by the ilio-pectineal septum, which, descending from the blending
of , the iliac fascia and the inguinal ligament above, passes down to the iUo-pectineal eminence,
and thence to the medial aspect of the front of the capsule of the hip-joint. This compartment
transmits the ilio-psoas and femoral (anterior crural) and lateral cutaneous nerves. (B) The
vascular compartment is bounded, in front, by the inguinal ligament and the transversahs
fascia, which here blends with it, forming the so-called deep crui'al arch, and at the same time
1400 CLINICAL AND TOPOGRAPHICAL ANATOMY
descends on to the front of the femoral sheath. The posterior boundary, Cooper's ligament, is
formed by the meeting of the ilio-pectineal septum laterally and the pectineal fascia or sheath —
medially the lacunar (Gimbernat's) ligament, and laterally the ilio-pectineal septum. This
intermediate compartment transmits the ex ernal iliac vessels and the lumbo-inguinal nerve.
This lies to the lateral side of the artery, the vein medially. Between the vein and the base of
the lacunar ligament is the femoral canal (vide infra). (C) The medial or pectineal compart-
ment is bounded by the pectineal fascia, continuous with the pubic part of the fascia lata, and
behind by the pubic ramus. It lodges the upper end of the pectineus muscle, and the handle of
a scalpel passed upward along the muscle would be prevented from passing into the pelvis by the
lacunar ligament and the blending of the pectineal fascia with the upper border of the pubic
ramus.
(3) Lacunar (Gimbernat's) ligament. — This is merely tlie triangular medial
attachment of Poupart's ligament. Its apex is attached to the pubic tubercle;
of its three borders, the base is free toward the vein and the femoral canal.
Its upper border is continuous with Poupart's ligament; its lower is attached to
the terminal (ilio-pectineal) line.
(4) Fascia lata. — Two portions are described over the upper part of the thigh :
■ — (a) An iliac, lateral and stronger, attached to the inguinal ligament in its whole
extent and lying over the sartorius, ilio-psoas, and rectus. (6) A pubic, medial,
weaker, and much less well defined, is attached above to the terminal line and
the tubercle of the pubes. The upper cornu of the fossa ovalis is at the lacunar
ligament, and at the lower cornu the two portions of the fascia blend.
Their relation to the femoral vessels. — The iliac portion, being attached along
Poupart's ligament, passes over these. The pubic portion, fastened down over
the pectineus, which slopes down on to a deeper plane than the adjacent muscles,
passes behind the femoral vessels to end on the capsule of the hip-joint.
(5) Fossa ovaUs (saphenous opening). — This is not an opening, but an oval
depression, situated at the spot where the two parts of the fascia lata diverge on
different levels. Though the fascia lata is wanting here, there is no real opening,
as the deficiency is made up by the deep layer of superficial fascia, or cribriform
fascia, which fills up the opening.
Uses of the fossa ovalis {saphenous opening). — Though a weak spot, it is so on purpose to
transmit the saphenous to the femoral vein, and the superficial to the deep lymphatics. The
depression is present in order to allow the saphenous vein to be protected from pressure in
flexion of the thigh.
Site. — At the medial and upper part of the thigh, with its centre 3.7 cm. (1 J in.) below and
lateral to the tubercle of the pubis.
Diameters. — Vertically, 2.5 cm. (1 in.), by 1.2 or 1.8 cm. (| or f in.). Shape: oval, with
its long axis downward and laterally. Two exlremities or cornua: upper blending with the
lacunar ligament; lower, where the two parts of the fascia lata meet. Two borders: lateral or falci-
form, also known as the ligament of Hey, or femoral ligament. Semilunar in shape, arching
downward and laterally from the lacunar ligament to the inferior cornu. This lies over the
femoral vessels, and is adherent to thezn; to it is fixed superficially the cribriform fascia {vide
infra). The medial border is much less prominent, owing to the weakness of the pubic part
of the fascia lata which forms it.
(6) Femoral sheath. — This is a funnel-shaped sheath, carried out by the
femoral vessels under Poupart's ligament, and continuous above (in front) with
the transversalis fascia as it descends to the ligament, lining the inner surface
of the abdominal wall; and (behind) with the iliac fascia, and below continuous
with the proper sheath of the femoral vessels.
It is not only funnel-shaped, but large and loose, for two reasons: — {a) That there be plenty
of room for the femoral vein and the slowly moving venous current in it to ascend without com-
pression; (b) to allow all the movements of the thigh taking place — flexion and extension —
without undue stretching of the vessels. By two connective-tissue septa the sheath is divided
into three compartments — the lateral for the artery, the intermediate for the vein, and the
medial one for the femoral canal {vide infra). Thus one septum lies between the artery and
vein, and another between the vein and the femoral canal.
(7) Femoral canal. — Definition: the medial division of the femoral sheath.
The fascia transversalis and fascia iliaca meet directly on the lateral side of the
femoral artery, but not so closely on the medial side of the femoral vein. Hence
a space exists here, perhaps to prevent the thin-walled vein, with its sluggish
current, being pressed upon, but it is merely a slight gap — not a canal, unless so
made by a knife or by the dilating influence of a hernia.
Length: about 1.9 cm. (J in.). Limits: below, fossa ovalis; above, femoral ring {vide
infra).
FEMORAL HERNIA
1401
Boundaries. — Laterally, a septum between it and the vein; medially, base of the lacunar
ligament and meeting of fascia iliaca and transversalis; behind, fascia iliaca; in front, fascia
transversalis.
Contents. — Cellular tissue and fat, continuous with extra-peritoneal fatty layer. A lym-
phatic node, which is inconstant.' Lymphatics passing from inguinal nodes to those in the
pelvis.
(8) Femoral ring. — This is mainly an artificial product. It is the upper or
abdominal opening of the femoral canal. Shape: oval, with its long axis trans-
verse. It is larger in women. Boundaries: medially, the lacunar ligament;
laterally, the femoral vein; in front, the inguinal ligament and the thickening
of the transversahs fascia attached to it, and called 'the deep crural arch';
behind the pectineus and Cooper's ligament, a thickened fascial bundle attached
Fig. 1123. — Irregulahities of the Obturator Artery. (After Gray.)
A
External iliac artery
External iliac vein
Obturator foramen
— Inferior epigastric artery
Lymphatic node in femoral ring
The obturator artery, given off
from the external iliac with the
inferior epigastric, descends to
gain the obturator foramen, but
at a safe distance from the
The obturator artery, coming off
from the inferior epigastric,
takes a course so near to the
femoral ring that it would very
likely be divided by the bis-
toury introduced from without
to divide the base of the lacunar
ligament, the cause of the con-
strictioii
to the hnea terminalis (fig. 1122). It is closed by the septum crurale, which
is a barrier of fatty connective tissue, continuous with the extra-peritoneal
fatty layer, perforated by lymphatics passing upward to the pelvic nodes.
Position of vessels around the ring. — Laterally the femoral vein; above, the
epigastric vessels as they ascend from the external iliac vessels, pass close to the
upper and lateral aspect of the ring; immediately in front are the cord and sper-
matic vessels always to be remembered in this hernia in the male; toward the
medial side there may be an unimportant anastomosis between the epigastric
artery above and the obturator below.
If from dilatation of the above anastomosis the obturator artery comes off abnormally
from the inferior epigastric, it will descend, and usually does so, close to the junction of the ex-
ternal iliac and common femoral vein, and thus to the lateral and so the safe, side of the ring
(fig. 1123, A). In a very few cases it curves more mediallj', close to the lacunar ligament, and
thus to the medial side of the ring, and is then in great danger (fig. 1123, B). In two out of
1402 CLINICAL AND TOPOGRAPHICAL ANATOMY
every five cases the obturator arises from the inferior epigastric. In about thirty-seven per
cent, of the eases with such an origin the artery either crosses or courses along the side of the
ring. (Cunningham.)
Course of femoral hernia. — At first this is downward in the femoral canal. A pouch of
peritoneum having been gradually, after repeated straining, coughing, etc., pushed through the
weak spot, the femoral ring, further weakened perhaps, together with all the parts in the fem-
oral arch, by child-bearing, some extra effort will force intestine or omentum into this pouch and
thus form a hernia. Thus formed, femoral hernia passes at first downward in the femoral canal
as far as the fossa ovaUs, but, as a rule, does not go farther downward on the thigh, but mounts
forward and upward, and somewhat laterally, even reaching the level of the inguinal ligament.
The reasons for this change of position are: — (1) The narrowing of the femoral sheath, funnel-
like, i. e., wide above, but narrowed below; (2) the unyielding nature of the lower margin of the
fossa ovalis; (3) the fact that this margin and the lateral border are united to the femoral sheath;
(4) the constant flexion of the thigh; (.5) the fact that vessels (cliiefly veins) and lymphatics
descend to the fossa ovaUs, the veins to join the saphenous vein and the lymphatics to join
the deeper group; these descending vessels serve to loop upward or suspend a femoral hernia,
and thus prevent its further course downward.
Coverings of a femoral hernia. — (A) At the upper or femoral ring it obtains
peritoneum, extra-peritoneal fat, and septum femorale (crurale).
(B) In the canal, a coating of the femoral sheath.
(C) At the external opening, further coverings of cribriform fascia, skin,
and superficial fascia are added.
Some of these may be deficient by the hernia bursting through them, or they may be matted
together. Sir A. Cooper thought this especially likely to occur with the layer of femoral sheath
and septum crurale, to which he gave the name oi fascia propria.
The relations of an inguinal and femoral hernia respectively to the pubic tubercle are of
importance in distinguishing between them clinically. If a finger is placed on the pubic tubercle
a hernia that lies above and medial to it will be inguinal, one below and lateral to it wiU be
femoral.
Radical cure of femoral hernia. — The close proximity of the femoral vein always intro-
duces difficulty in the introduction of the deep sutures for closure of the crural ring. Any clo-
sure below this point is certain to be inefiicient. The safest and simplest method is to feel
for the pulsation of the femoral artery, and make allowance for the vein on its medial side. The
latter vessel is then protected by the finger-tip passed up the femoral canal, so that its dorsum
rests against the vein and its tip upon the linea terminalis. The sutures are then passed so
as to pick up the ilio-peotineal fascia and its thickened part. Cooper's ligament, below, and the
deep crural arch and Poupart's ligament above (fig. 1122). Thus, when tightened, they draw
the anterior and posterior boundaries of the ring together. (Lockwood, Bassini.)
PARTS CONCERNED IN UMBILICAL HERNIA
A hernial protrusion at the umbilicus, or exomphalos, may occur at three
distinct periods of life, according to the anatomy of the part. Any account of
umbilical hernia would be incomplete without an attempt to explain how this
region, originally a most distinct opening, is gradually closed and changed into
a knotty mass of scar, the strongest point in the abdominal wall.
During the first weeks of foetal life, in addition to the urachus, umbilical
arteries, and vein, some of the mesentery and a loop of the intestine pass through
the opening to occupy a portion of the body cavity situated in the umbilical cord,
later on returning to the abdominal cavity. Occasionally this condition persists,
owing to failure of development, and the child is born with a large hernial swell-
ing outside the abdomen, imperfectly covered ^vith skin and peritoneum. To
tlais condition the term congenital umbilical hernia should be applied.
Later on in foetal life it is the umbilical vessels alone which pass through this
opening. At birth there is a distinct ring, which can be felt for some time after
in the flaccid walls of an infant's belly. If this condition persist, a piece of
intestine may find its way through, forming the condition which should be known
as infantile umbilical hernia.
This condition is not uncommon. Why it is not more frequently met with
is explained by the way in which this ring of infancy is closed and gradually
converted into the dense mass of scar tissue so familiar in adult life. This is
brought about — (1) by changes in the ring itself; (2) by changes in the vessels
which pass through it.
(1) Changes in the ring itself. — The umbilical ring is surrounded by a sphincter-like
arrangement of elastic fibres, best seen during the first few days of extra-uterine life, on the
THE BACK 1403
posterior aspect of the belly wall. In older infants these fibres lose their elasticity, become
more tendinous, and then shrink more and more. As they contract they divide, as by a liga-
ture, the vessels passing through the ring, thus accounting for the fact that the cord, wher-
ever divided, drops off at the same spot and without bleeding.
(2) Changes in the vessels themselves. — When blood ceases to traverse these, their lumen
contains clots, their muscular tissue wastes, while the connective tissue of their outer coat
hypertrophies and thickens. Thus, the umbilical vessels and the umbilical ring are, alike,
converted into scar tissue, which blends together. This remains weak for some time, and may
be distended by a hernia (infantile).
Finally, we have to consider the state of the umbilicus in adult life. The very dense,
unyielding, fibrous knot shows two sets of fibres: — (1) Those decussating in the middle line;
and (2) two sets of circular fibrous bundles which interlace at the lateral boundaries of the
ring. The lower part of the ring is stronger than the upper. In other words, umbilical hernia
of adult life, when it comes through the ring itself and not at the side, always comes through
the upper part. In the lower three-fourths of the umbilicus the umbihcal arteries and urachus
are firmly closed by matting in a firm knot of scar tissue; in the upper there is only the umbil-
ical vein and weaker scar. To the lower part run up the umbilical arteries and the urachus.
Owing to the rapid growth of the abdominal wall and pelvis before puberty, and the fact
that the urachus and the umbilical arteries, being of soar tissue, elongate with difficulty, the
latter parts depress the umbilicus by reason of their intimate connection with its lower half.
Owing to the usual exit of an umbilical hernia of adult life being through the upper part of
the ring, the constricting edge in strangulation should be sought below and divided downward.
As pointed out by Mr. Wood, it is here that the dragging weight of the hernial contents and the
weight of the dress tend to produce the chief results of strangulation. An incision here also
gives better drainage if required.
Coverings of an umbilical hernia. — These, more or less matted together, are : —
(1) Skin; (2) superficial fascia, which loses its fat over the hernia; (3) prolonga-
tion of scar tissue of the umbilicus gradually stretched out; (4) transversalis
fascia; (5) extra-peritoneal fatty tissue; (6) peritoneum. If the hernia come
through above the umbilicus, or just to one side, the coverings will be much the
same; but, instead of the layer from the umbilical scar, there will be one from the
linea alba.
Strangulated umbilical hernia of adult life. — In this, the most fatal of the strangulated
hernise ordinarily met with, the following are practical points in the surgical anatomy: — 1. The
coverings, including the sac, are always thin, at times so markedly so that the intra-peritoneal
contents are practically subcutaneous. 2. The sac is multilocular, and one or more of its cham-
bers may he very deep. 3. The contents are numerous, viz., omentum, often voluminous and
adherent, transverse colon, and later in the history, small intestine. 4. The contents are often
adherent to the sac and each other, thus explaining the irreduoibility. 5. The long duration
of the presence of the transverse colon with its stouter walls accounts for the period, often pro-
longed, in which warning evidence of incarceration precedes that of strangulation. 6. The
communication with the peritoneal sac is direct, short, and during a prolonged operation, free.
Infection is thus readily brought about.
THE BACK
The surface form and landmarks of the back will be considered first, followed
by the relations of skeleton, muscles, viscera and nervous system.
Median furrow. — This is more or less marked according to the muscular
development, lying between the trapezii and semispinales capitis, in the cervical
region, and the sacro-spinales lower down. The lower end of the furrow corre-
sponds to the interval between the spines of the last lumbar and the first sacral
vertebra. (Holden.)
Vertebral spines. — Those of the upper cervical region are scarcely to be made
out even by deep pressure. That of the axis may be detected in a thin subject.
Over the spines of the middle three cervical vertebrae is normally a hollow, owing
to these spines receding from the surface to allow of free extension of the neck.
The seventh cervical is prominent, as its name denotes. Between the skull and
atlas, or between the atlas and epistropheus, a pointed instrument might pene-
trate, especially in flexion of the neck.
Of the thoracic spines, the first is the most prominent, more marked than that of the last
cervical; the tliird should iDe noted as on a level with the medial end of the scapular spine, and
in some cases with the bifurcation of the trachea; that of the seventh with the lower angle of
the scapula; that of the twelfth with the lowest part of the trapezius and the head of the twelfth
rib. The obliquity and overlapping_ of the thoracic spines are to be remembered.
Of the lumbar spines, the most important are the second, which corresponds to the termi-
nation of the cord, and the fourth, which marks the highest part of the iliac crests and the
bifurcation of the abdominal aorta. The lumbar spines project horizontally, and correspond
with the vertebral bodies. The third is a little above the umbilicus.
1404
CLINICAL AND TOPOGRAPHICAL ANATOMY
Owing to the obliquity of the thoracic spines, most of them do not tally with the heads of
the correspondino; ribs. Thus, the spine of the second corresponds with the head of the third
rib ; the spine of the third with the head of the fourth rib ; and so on till we come to the eleventh
and twelfth vertebrae, which do tally with then* corresponding ribs. (Holden.)
The lower ribs may be felt lateral to the sacro-spinalis but in counting them
from below it must be remembered, as pointed out by Holl, that in quite a
Fig. 1124. — Diagram and Table showing the Approximate Relation to the Spinal
Nerves of the various Motor, Sensory, and Reflex Functions of the Spinal Cord.
(Arranged by Dr. Gowers from anatomical and pathological data.)
.,\^ i MOTOR SENSORY REFLEX
St erno -mastoid
Trapezius
\ Serratus
j Shoulder
Arm \ muse.
Flexors, Mp
Extensors, knee
Adductors
Muscles of leg mov-
ing foot
I7eck and scalp
Neck and shoulder
I Shoulder
Arm
Front of thorax
I Buttock, upper
part
[• Groin and scrotum
(front)
Lateral side
Medial side
Leg, medial side
Buttock, lower
Back of thigh
Leg )
and > except medial
[foot J part
1 Perineum and anus
[Scapular
■ Cremasteric
I 1
J I Knee-joint
Foot-clonus
Plantar
considerable percentage the last rib is so abnormally short that it does not reach
as far as the lateral border of the sacro-spinalis; or is so rudimentary as to re-
semble a transverse process (consequently the only safe method of counting ribs
is from above). In these cases the lower end of the pleura maj^ pass from the
lower part of the twelfth thoracic vertebra, almost horizontally to the lower edge
of the eleventh, rib.
THE BACK
1405
Muscles. — The student will remember the greater number and complexity and the numerous
tendons of the muscles which run up on either side of the spines; the firmness and inextensibility
of their sheaths; the large amount of cellular tissue between them; and the fact that toward the
nape of the neclc these muscles lie exposed instead of being protected in gutters, as is the case
below: all these anatomical points explain the extreme painfulness and obstinacy of sprains
here.
Trapezius. — To map out this muscle, the arm should be raised to a right angle with the
trunk. The external occipital protuberance should be dotted in, and the superior nuchal line
passing out from this; below, the twelfth thoracic spine should be marked; and laterally, the
lateral third of the clavicle and the commencement of the scapular spine. Then a line should
be drawn from the protuberance vertically downward to the twelfth thoracic spine; a second
from about the middle of the superior nuchal line to the posterior and lateral third of the
clavicle; and a third from the last thoracic spine upward and laterally to the root of the spine
of the scapula.
Fig. 1125. — Relations of the Abdominal Visceba to the Antbbiob Body Wall.
Lateral yertical (mid-
clavicular) line
Sterno-xiphoid line
Addison*s "trans-
pyloric" line
Infracostal line
Hiac colon
Intertubercular line
Cfficum and vermiform process
Latissimus dorsi. — The arm being raised above a right angle, the spines of the sLxth thoracic
and the third sacral vertebra should be marked; then the outer Up of the crest of the Uium, the
lower two or three ribs, the lower angle of the scapula, and the posterior fold of the axiUa, and
finally the intertubercular (bicipital) gi-oove should all be marked.
A vertical line from the sixth thoracic to the thu-d sacral spine will give the spinal origin of
the muscle. Another from the thu-d sacral spine to a point on the iliac crest, 2.5 cm. (1 in.) or
more lateral to the edge of the sacro-spinalis, will give the origin of the muscle from the sheath
of the sacro-spinalis and the ilium. A line from the sixth thoracic spine, almost transversely
at first, with increasing slight obliquity over the inferior angle of the scapula to the axilla and
intertubercular groove, will mark the upper border of the muscle. Another very oblique line
from the point of the iliac crest upward and laterally to the axilla will give the lower border
and the tapering triangular apex of the insertion. The muscle may be attached to the angle
of the scaptila, or separated from it by a bursa.
1406
CLINICAL AND TOPOGRAPHICAL ANATOMY
Triangle of Petit. — This small space lies above the crest of the ihum, at about
its centre, bounded by the anterior edge of the latissimus behind and the posterior
border of the external obhque, in front. Through this gap, when the muscles
are weak, a lumbar abscess occasionally, and very rarely, a lumbar hernia, may
appear.
Origin of spinal nerves. — It is very important to remember the relations of
these to the vertebral spines, in determining the results of disease or injury of the
cord and the parts thereby affected. The above relations may be given briefly
as follows: —
The origins of the eight cervical nerves correspond to the cord between the
occiput and the sixth cervical spine. The upper six thoracic come off between
Fig. 1126. — Chief Arterial Anastomoses on the Scapula.
(From a dissection in the Hunterian Museum.)
Supra-spinatus Transverse scapular artery
Descending branch of transversa colli artery
Rhomboideus minor
Levator scapulae
Infra-spinatus
Triceps, cut
Deltoid, insertion
Deltoid
Trapezius
Rhomboideus major
Teres major I
[Teres major, insertion
Circumflex scapular artery Posterior circumflex artery
the above spine and that of the fifth thoracic vertebra. The origins of the
lower six thoracic nerves correspond to the interval between the fourth and the
tenth thoracic spines. The five lumbar arise opposite the eleventh and twelfth
thoracic spines; and the origins of the five sacral correspond to the first lumbar
spines. The diagram and table (fig. 1124), arranged by Dr. Gowers from
anatomical and pathological data, show the relations of the origins of the nerves
to their exits from the vertebral canal, and the regions supplied by each.
Scapula, its muscles and arterial anastomoses. — Amongst the landmarks
in the back, the student should be careful to trace the angles and borders of the
scapula as far as these are accessible. The upper border is the one most thickly
covered. With the hands hanging down, the upper (medial) angle corresponds
to the upper border of the second rib; the lower angle to the seventh intercostal
space; and the root of the spine of the scapula to the interval between the third
and fourth thoracic spines.
THE BACK
1407
The axillary border of the scapula, covered by the latissimus dorsi and teres major, may
best be palpated with the arm hanging to the side. The vertebral border is brought into
prominence by placing the hand on the opposite shoulder. This border is held in apposition
with the thorax by the serratus anterior; consequently in paralysis of that muscle, supplied by
the long thoracic nerve (5, 6, and 7 C), it becomes unduly prominent, giving rise to "winged
scapula." Fig. 1126 shows the chief arteries around the scapula. The anastomoses on the
acromial process between the transverse scapular (supra-scapular) thoraoo-acromial, and
circumflex humeral arteries are not shown. The numerous points of ossification, primary and
secondary, by which this bone is developed explain, in part, the frequency of cartilaginous and
other growths here.
The anatomy of the loin behind, the ilio-costal region, is of prime importance, owing to the
numerous operations here. The lateral border of the sacro-spinalis and quadratus lumborum
may be indicated on the surface thus. (Stiles.) That of the sacro-spinalis by drawing a line
from a point on the Oiac crest 8.2 cm. (Sj in.) (four fingers'-breadth) from the middle line up-
ward and slightly laterally to the angles of the ribs. That of the quadratus passing upward
and sUghtly medially Ues a little lateral to that of the sacro-spinahs (erector) at the crest,
Fig. 1127. — Relations of the Abdominal Viscera to the Posterior Body Wall.
and a little medial to it at the twelfth rib. The ascending and descending colon lie in the
slightly depressed angle between the two muscles. The iho-costal region varies greatly in
space according to the length of the lower ribs, shape of the chest, and development of the ihac
crest. An incision here — that for exploration of the kidney may be taken as the type — would be
an oblique one, about 10 cm. (4 in.) long, starting in the angle'between the twelfth rib and the
sacro-spinahs muscle and passing forward and downward toward the anterior extremity of
the iliac crest. In its upper part the incision should lie 1.2 cm. (J in.) below the tweltfh rib.
The anterior fibres of the latissimus dorsi are divided behind, the posterior ones of the external
oblique in front. The yellowish-white lumbar fascia now comes into view, and is the first
important landmark. It and the fibres of the internal oblique and transversus which arise
from it are next carefully divided. The last thoracic nerve and lowest intercostal artery may
also require division. If the latter is cut close to the rib, the htemorrhage is troublesome. The
transversalis fascia remains to be divided. To avoid the peritoneum, the deeper part of the
1408 CLINICAL AND TOPOGRAPHICAL ANATOMY
incisions should always be made from behind forward. If more room is required, as in large
growths or in exploration of the ureter, the incision must be prolonged beyond the iliac crest,
the lumbo-ilio-inguinal incision of Morris.
Viscera. — Several of these, which can be mapped in behind — viz., the kidneys,
spleen, etc. — have been already mentioned (pp. 1375, 1379).
The commencement of the trachea and oesophagus has been given in front as
corresponding to the sixth cervical vertebra. If examined from behind, this
point, o-sving to the obliquity of the spines, would be a httle lower down. The
trachea, about 12.5 cm. (5 in.) long, descending in the middle line, bifurcates
opposite to the interval between the third and fourth thoracic spines (or fourth
and fifth bodies). The bronchi enter the lungs at about the level of the fifth
thoracic spine, the right being the shorter, wider, and more horizontal. The
root of the lung is opposite to the fourth, fifth, and sixth dorsal spines, midway
between these and the vertebral border of the scapula. The structures in it are
the bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, lymph-
atics, and nerves. The phrenic nerve is in front, the posterior pulmonary plexus
behind. On the right side the superior vena cava is in front, the vena azygos
(major) arching over the root at the level of the fourth thoracic vertebra. On
the left side the aorta arches over the root, and the thoracic aorta descends
behind it. The oesophagus, about 25 cm. (10 in.) in length, starting in the
middle line, curves twice to the left, at first gradually at the root of the neck;
from this point it tends to regain the middle line up to the fifth thoracic vertebra;
thence finally turns again, and more markedly to the left, and passes through the
diaphragm opposite to the tenth, entering the stomach here or at the eleventh
thoracic vertebra (ninth or tenth thoracic spine). In the thorax this tube tra-
verses first the superior, then the posterior, mediastinum. At three spots, i. e.,
its commencement, where it is crossed by the left bronchus, and at the cardiac
orifice, it presents narrowings. The relations of this tube to the pleura, peri-
cardium, aorta, vagi, and thoracic duct are important in the ulceration of
malignant disease and infected bodies, and in the passage of instruments.
The aorta reaches the left side of the vertebral column, with its arch just above
the fourth thoracic spine, and thence descends on the front of the column, with a
shght tendency to the left, to bifurcate opposite the fourth lumbar spine.
The spinal cord. — This, about 45 cm. (18 in.) long, extends from the foramen
magnum to the junction between the first and second lumbar vertebrae. Up to
the third month of foetal life it reaches to the sacral end of the vertebral canal ;
later, owing to the more rapid growth of the bony wall, its lower limit is at birth
opposite the third lumbar vertebra. The dura mater is continued, as a sheath,
as low as the second sacral vertebra. It is anchored above to the upper cervical
vertebrae and the foramen magnum, and below, as the filum terminale, to the peri-
osteum of the coccyx. The deficiency of the spinous processes and laminae of the
fourth and fifth pieces of the sacrum allows of infection, e. g., of a bed-sore reach-
ing the membranes, and so the cord. The arachnoid and pia of the cord are
continuous above with those of the brain.
The parts of the column most exposed to injury are the thoraco-lumbar and cervico-thoraoic
partly because here more mobile parts are joined to those which are more fixed, and also from
the amount of leverage exerted on the thoraco-lumbar region, and, in the case of the upper
region, because this is affected by violence exerted on the head. The chief provisions for pro-
tection of the cord are the number of bones and joints which allow of movement without serious
weakening, the thi'ee om-ves and columns, cervical, thoracic, and lumbar, ensuring bending
before breaking; the large amount of cancellous tissue and the number and structure of the
intervertebral discs all tending to damp vibrations; the large size of the theca vertebrahs and the
way in which the cord, anchored and slung by the thirty-one pairs of nerves and the Ugamenta
denticulata, about twenty in number, occupies neutral ground in the centre of the canal as
regards injury directly and indirectly applied.
In lumbar puncture (Quincke) as a means of diagnosis or of relieving pressure
advantage is taken of the fact mentioned above that the theca extends below the
cord.
A line drawn joining the highest points of the iliac crests crosses the fourth lumbar spine.
The needle is inserted in the median line between the third and fom-th or the fourth and fifth
spines, and directed forward and slightly upward. The back must be flexed as fully as possible
in order to widen the interspinous spaces. The needle is passed to a depth of about 5 cm. (2 in.)
in an adult, or 1.8 cm. (f in.) in an infant. In the supine position the lowest part of the sub-
arachnoid space ia in the mid-thoracic region, and an anaesthetic fluid, non-diffusible and of a
THE SHOULDER AND ARM 1409
higher specific gravity than the cerebro-spina) fluid, will tend to gravitate there (Barker).
The level of the anaesthesia can be varied by raising the pelvis or the shoulders to diiferent
levels.
The following table, from Holden and Windle, with additions, will be found very useful in
determining the relation of numerous viscera and other structiires to the bodies of the vertebrse.
VERTEBRAL LEVELS
Cervical
First. Level of hard palate.
Second. Level of free edge of upper teeth.
Second and third. Superior cervical ganglion of sympathetic.
Fourth. Hyoid bone. Upper aperture of larynx.
Fifth. Thyreoid cartilage and rima glottidis. Between this and the last would be the
bifurcation of the common carotid.
Sixth. Cricoid cartilage. Ending of pharynx and larynx. Consisting of the fused fifth
and sixth ganglia, the middle cervical ganglion is usually opposite this vertebra. Here the
omo-hyoid crosses the common carotid, and at this spot, the seat of election, the centre of the
incision for tying this vessel is placed. At this level the inferior thyreoid passes behind the
carotid trunk.
Seventh. Inferior cervical ganglion. Apex of lung. Arch of thoracic duct oyer apex of
lung, outward and downward to termination.
Thoracic
First. Summit of arch of subclavian. (Godlee.) The height of this varies. Usually
it is from 1.2 to 2.5 cm. (J to 1 in.) above the clavicle. It is always in close relation with the
cervical pleura.
Second. Level of episternal notch. This is usually opposite the fibro-cartilage between
the second and third. Bifurcation of innominate. (Godlee.)
Third. Beginning of superior cava, at junction of first right costal cartilage with sternum.
Highest part of aortic arch, about 2.5 cm. (1 in.) below notch.
Fourth. Bifurcation of trachea. Second piece of aortic arch, extending from upper border
of second right costal cartilage, reaches spine. Arch of vena azygos. The superior medias-
tinum is bounded behind by the upper four thoracic vertebrae. Louis' angle, junction of manu-
brium and gladiolus. Thoracic aorta begins.
Fifth to ninth. Base of heart.
Sixth. Pulmonary and aortic valves, opposite third left costal cartilage at its sternal junc-
tion, in front. Commencement of aorta and pulmonary artery. End of superior cava, third
right chondro-sternal junction in front.
Seventh. Mitral orifice.
i Eighth. Tricuspid orifice.
Ninth. Lower level of manubrium and sterno-xiphoid fine (at lower border). Opening
in 'diaphragm for inferior vena cava (lower border).
Tenth. Level of tip of xiphoid cartilage. Lower limit of lung posteriorly. Upper limit
of Uver comes to the surface posteriorly. QDsophagus passes through diaphragm. Cardiac
orifice of stomach (sometimes). Upper limit of spleen. .
Eleventh. Lower border of spleen. Suprarenal gland. Cardia (sometimes).
Twelfth. Lowest part of pleura. Aorta passes through diaphragm (lower border).
Coeliac artery (lower border), tipper end of kidney.
Lumbar
First. Superior mesenteric arteries. Pancreas. Pelvis of kidney. Renal arteries.
Transpyloric Line. (Addison.)
Second. Spinal cord ends at junction of first and second. Duodeno-jejunal flexure. Re-
ceptaculum (cisterna) chyli. Lower end of left kidney.
Third. Umbilicus, opposite disc between third and fourth. Lower end of right kidney.
Fourth. Bifurcation of aortic arch. Highest part of iliac crest.
Fifth. Commencement of superior vena cava.
Sacral
Third. End of pelvic colon and beginning of first piece of rectum proper. Lower Umit
of spinal membranes.
Fifth. Reflexion of recto-vesical pouch of peritoneum 2.5 cm. (1 in.) above base of prostate.
Coccyx (tip). 2.5 cm. (1 in.) below this commencement of anal canal. Termination of
filum terminale.
THE UPPER EXTREMITY
THE SHOULDER AND ARM
The surface form and landmarks of the upper extremity will first be considered
followed by the various regions of the shoulder, arm, forearm and hand.
1410
CLINICAL AND TOPOGRAPHICAL ANATOMY
General surface form. Landmarks. — The following surface -marks, of the
greatest importance in determining the nature of shoulder injuries, can be made
out here: — The clavicle in its whole extent, the acromion process, the great
tuberosity, and upper part of the shaft of the humerus. Much less distinctly,
the position of the coracoid process in the infraclavicular fossa and the head of
the humerus through the axilla can be made out. The anterior margin of the
clavicle, convex medially and concave laterally, can be made out in its whole
extent, the bone, if traced laterally, being found not to be horizontal, but rising
somewhat to its junction with the acromion. The stemo- and acromio-clavicu-
lar joints have been referred to at p. 1363.
The frequency of fracture of the clavicle is explained chiefly by its exposure to shocks of varied
kinds from the upper extremity, inseparable from the out-rigger-like action of the bone and its
early ossification. On the other hand, the main safeguards are the elasticity and curves of the
bone, the way in which it is embedded in muscles which will damp vibrations, and the buffer-
bond fibro-cartilages at either extremity. The looseness and toughness of the overlying skin
explain the rarity of compound fracture here. The junction of the two curves is the weakest
spot and the usual site of fracture. The weight of the limb acting through the coraco-olavicular
ligaments and overcoming the trapezius is the chief factor in the downward displacement; the
pectoralis minor and serratus anterior acting on the scapula draw the acromial fragment for-
ward. The tip of the acromion, when the arm hangs by the side with the hand supinated, is in
the same Mne as the lateral condyle and the styloid process of the radius. On the medial side,
the head and medial condyle of the humerus and the styloid process of the ulna are in the same
line. Thus the great tuberosity looks laterally, the head medially, and the lesser tuberosity some-
what forward. Between the two tuberosities runs the intertubercular (bicipital) groove, which,
Fig. 1128. — Transverse Section THRoncH the Right Shoulder-joint, showing the
Stkucturbs in contact with it. (Braune.)
Acromion-
Supra-spinatus
Trapezius
Teres minor
Teres major'
Latissimus dorsi'
Deltoid
Pectoralis major
ji of subscapularis blended
with the scapular ligament
Coraco-brachialis and short head of biceps
with the arm in the above position, looks directly forward. In thin subjects its lower part
can be defined. Its position can be marked with sufficient accuracy by a Hne running down-
ward from the acromion in the long axis of the humerus. Besides the tendon and its synovial
sheath, the insertion of the latissimus dorsi, the humeral branch of the thoraco-acromial artery,
and the anterior circumflex artery run in the groove. When the fingers are placed on the acro-
mion and the thumb in the axilla, the lower edge of the glenoid cavity can be felt; and if the
humerus be rotated (the elbow-joint being flexed), the head of the humerus can be felt also.
The characteristic roundness of the shoulder is due to the great tuberosity
lying under the deltoid (fig. 1130). In dislocation the loss of this roundness is
due to the absence of the head and tuberosity and consequent projection of the
acromion.
This normal projection of the deltoid renders it impossible to place a flat straight body in
contact with both the acromion and the lateral epicondyle at the same time (Hamilton's dis-
location test). Below the junction of the lateral and middle thirds of the clavicle, between
the contiguous origins of the pectoralis major and deltoid, is the infraclavicular fossa, in which
lie the cephalic vein, the deltoid branch of the thoraco-acromial artery, and a lymphatic node
which may be involved in obstinate tuberculosis of the cervical groups. On pressing deeply
here, the coracoid process can be made out if the muscles are relaxed, and the axillary artery
compressed against the second rib.
On raising the arm and abducting it, the different parts of the deltoid can often be made out
— viz., fibres from the lower border of the spine of the scapula, the lateral edge of the acromion,
and the lateral third or more of the front of the clavicle; the characteristic knitting of the surface
THE AXILLARY FOSSA
1411
owing to the presence of fibrous septa continuous, alike, with the skin and the sheath of the
muscle and the tendinous septa which separate the muscular bundles, will also be seen. The
muscle will be marked out by a base-line reaching along the above bony points, and two sides
converging from its extremities to the apex, a point on the lateral surface of the humerus, about
its centre. In paralysis of the deltoid, the humerus being no longer braced up against the
scapula, the finger-tips can be placed between it and the acromion.
To map out the pectoralis major, a line should be drawn down the lateral aspect of the
sternum as far as the sixth costal cartilage, and then two others marking the borders of the
muscle — the upper corresponding to the medial border of the deltoid, the lower starting from
the sixth cartilage, and the two converging to the folded tendon, which is inserted as a double
Fig. 1129. — The Shoulder- joint, as shown by the Rontgen-bays.
layer into the lateral tubercular (bicipital) ridge. The pectoralis minor will be marked out by
two lines, from the upper border of the third and the lower border of the fifth rib, just lateral
to their cartilages, and meeting at the coracoid process. The lower line gives the level of the
long thoracic artery; the upper, where it meets the line of the axillary artery, that of the thoraco-
acromial.
When the arm is abducted and the humerus rotated a httle laterally, the prominence of a
well-developed coraco-brachialis comes into view; a Une drawn from the centre of the clavicle
along the medial border of this muscle to its insertion into the humerus gives the Une of the
axillary artery.
Axillary fossa. — The boundaries of this space anterior, posterior, medial, or
thoracic, lateral or humeral, apex and base, with the structures forming them and
1412
CLINICAL AND TOPOGRAPHICAL ANATOMY
the vessels and nerves in relation to them, must be remembered. The chief vessels
are the axillary on the lateral wall, brought into prominence when the arm is
abducted, as in removal of the mamma, and the subscapular on the posterior wall.
The apex is felt, when the finger is pushed upward in an operation here, to be
bounded by the clavicle in front, the first rib behind, and the coracoid some-
what laterally. The base is concave, owing to the coraco-clavicular (costo-
coracoid) membrane as it descends to blend with the sheath of the pectoralis
minor, giving also a process to the axillary fascia which unites the anterior
and posterior boundaries. This process also sends septa to the skin.
An axillary abscess, always to be opened early to avoid subsequent interference with the
movements of the shoulder, is reached by an incision on the medial wall, midway between the an-
terior and posterior boundaries, so as to avoid the long thoracic and subscapular vessels, respec-
tively, the back of the knife being directed toward the lateral wall. The only vessel on this wall
is the superior thoracic, which lies high up. Additional safety is given by the use of Hilton's
method. For exploration of the axilla the best incision is an angular one, the two limbs being
placed in a line with the anterior margin of the great pectoral, and in the line of the axillary
vessels. This runs from a point on the centre of the clavicle (the limb being at a right angle
to the trunk) to the medial margin of the coraco-brachialis. If this be obliterated by swelling,
the above line should be prolonged to the middle of the bend of the elbow, which will give the
guide to the brachial also. Collateral circulation. If the first part of the artery be tied, the
channels are the same as in ligature of the third part of the subclavian {q.v.). In ligature
of the third part of the axillary, if the ligature be above the circumflex arteries, the chief vessels
concerned are the transverse scapular (suprascapular) and thoraco-acromial above and the
Fig. 1130. — Diagrammatic Section op Shoulder through the Intertuberculab
(Bicipital) Groove. (Anderson.)
Deltoid
Subacromial bursa
Capsule of shoulder-joint
Long tendon of bicepE
Synovial membrane lining cap-
sule and biceps tendon
Glenoid lip (ligament)
Glenoid cavity
Glenoid lip (ligament)
Inner fold of capsule and
synovial membrane
— Humerus
posterior circumflex below. If the ligature be below the circumflex, the anastomoses will be
those concerned in ligature of the brachial above the profunda (p. 1414). The lymphatic
nodes in the axilla have been mentioned at p. 719, (fig. 566).
The depression of the axillary fossa is best marked when the arm is raised from the side
to an angle of about 45°, and when the muscles bounding it in front and behind are contracted.
. In proportion as the arm is raised, the hollow becomes less, the head of the humerus now pro-
jecting into it. When the folds are relaxed by bringing the arm to the side, the fingers can be
pushed into the space so as to examine it.
The axiUary (circumflex) nerve and posterior circumflex vessels wind around the humerus
under the deltoid; a hne drawn at a right angle to the humerus and a little above the centre
of this muscle marks their position on the surface.
To trace the synovial membrane of the shoulder -joint is a comparatively
simple matter (fig. 11.30). Covering both aspects of the free edge of the glenoid
ligament, it lines the inner aspect of the capsule, whereb.y it reaches the articular
margin of the head of the humerus; there is a distinct reflection, below, from the
capsule on to the humeral neck before the rim of the cartilage is reached.
An extensive protrusion of synovial membrane takes place in the form of a synovial bursa,
at the medial and anterior part of the capsule, near the root of the coracoid process under the
tendon of the subscapularis. Another protrusion takes place between the two tuberosities
along the intertubercular groove, as low as the insertion of the pectoralis major. A third
synovial protrusion may be seen, but not frequently, at the lateral or posterior aspect, in the
form of a bursa, under the infra-spinatus tendon. Thus the continuity of the capsule is inter-
rupted by two and sometimes three synovial protrusions.
THE SHOULDER-JOINT
1413
Shoulder-joint. — The frequency of dislocations here, nearly equal to those of
all the other joints put together, calls attention to the points contributing to make
the joint alike insecure and safe. Strength is given by (1) the intimate blending
of the short scapular muscles, especially the subscapularis with the capsule; (2)
the coraco-acromial vault; (3) atmospheric pressure; (4) the long tendon of the
biceps; (5) the elasticity of the clavicle; (6) the mobility of the scapula. The
weakness of the joint is readily explained by its free mobility, the want of corre-
spondence between the articular surfaces, its exposure to injury, and the length of
the humeral lever. The rent in the capsule is usually anterior and below, and to
this spot the head of the humerus must be made to return. While dislocations are
usually primarily subglenoid, owing to the above part of the capsule being the
thinnest and least protected, they take usually a secondarily forward direction,
Fig. 1131. — Posterior View of the Scapular Muscles and Triceps.
Supraspinatus
The X mark indicates
where the radial
nerve leaves the long
head of the triceps
and passes under the
outer head to gain
the groove.
as the triceps prevents the head passing backward. In addition to the above
features of the lower part of the capsule, laxity is here also a marked feature, to
allow of free abduction and elevation. This movement wall be accordingly much
checked by any inflammatory matting of this part of the capsule.
The best incision for exploring the joint is one commencing midway between the coracoid
and acromion processes and carried downward parallel with the anterior fibres of the deltoid.
The cephaUc vein and biceps tendon are to be avoided. If drainage is needed, it must be
BuppUed by a counter-incision behind. This may be made along the posterior border of the
deltoid, part of its humeral attachment being detached if necessary. The axillary (circumflex)
nerve must be avoided in the upper part of the incision.
1414
CLINICAL AND TOPOGRAPHICAL ANATOMY
The shaft of the humerus is well covered by muscles in the greater part of its
extent, especially above. Below the insertion of the deltoid, the lateral border of
the bone can be traced downward into the lateral supracondyloid ridge. The
medial border and ridge are less prominent.
Attached to these ridges and borders are the intermuscular septa, each lying between the
triceps and brachiaUs (anterior), and the lateral one giving origin to the brachio-radialis (supi-
nator longus) and extensor carpi radialis longus as well. The medial extends up to the insertion
of the coraco-braohialis, the lateral to that of the deltoid. The lateral septum is perforated by
the anterior part of the profunda vessels and the radial (musculo-spiral) nerve, the medial by the
superior and posterior branch of the inferior ulnar collateral (anastomotica magna) artery and
the ulnar nerve.
The biceps has a two-fold attachment above and below. The former is of much importance
in steadying the various movements, especially the upward one, and in harmonising the simul-
taneous flexion and extension of the shoulder- and elbow-joints. (Cleland.) The lacertus
fibrosus curving downward and medially with its semilunar edge upward, across the termina-
tion of the brachial artery, strengthens the deep fascia and the origin of the flexors of the fore-
arm. The two heads unite in the lower third of the arm. The tendon, before its insertion,
becomes twisted, the lateral border becoming anterior.
Fig. 1132. — Cross-Section through the Middle of the Right Arm. (Heath.)
Musculo-cutaneous nerve
Brachialis
Hadial nerve
Profunda vessels
Biceps
Brachial vessels
Triceps, with fibrous intersection
Superior ulnar collateral vessels
On either side of the well-known prominence of the biceps is a furrow. Along
the lateral ascends the cephahc vein. The medial corresponds to the line of the
basilic vein which lies superficial to the deep fascia below the middle of the arm,
and superficial and medial to the brachial vessels and median nerve.
The strength of such muscles as the deltoid, and their intimate connection with the peri-
osteum of the humerus, account for fracture of this bone by muscular action being more common
than elsewhere. The presence of muscular tissue between the fragments, together with de-
ficient immobiUzation, explains the fact that ununited fractures are also most common in the
humerus. The best incisions for exploring the humerus, e. g., in acute necrosis, etc., are (a)
for the upper portion, the two already mentioned along the anterior and posterior borders of the
deltoid. In the latter case the presence of the radial (musculo-spiral) nerve in the deeper part
of the wound must be remembered; (6) for the lower end one parallel with the lateral inter-
muscular septum, deepened between the brachialis and brachio-radialis.
A line drawn along the medial edge of the biceps from the insertion of the teres
major to the middle of the bend of the elbow corresponds to the brachial artery.
In the upper two-thirds, this artery can be compressed against the bone by pres-
sure laterally; in its lower third the humerus is behind it, and pressure should be
made backward. The presence of the median nerve will interfere with any pro-
longed digital pressure applied in the middle of the arm.
THE ARM
1415
In ligature of the artery here the line extends from the mid-axillary region above, prolonged
to the centre of the front of the elbow. The only structures seen should be the medial
edge of the biceps, the basilic vein, and the median nerve. The profunda comes off 2.5 cm.
(1 in.) below the teres major, having the same relation to the heads of the triceps; thus, it first
lies on the long head, behind the axillary and brachial arteries, then between the long and
medial heads, and next, in the groove, between the medial and lateral heads, and courses with
the radial (musculo-spiral) nerve (fig. 1132); the nutrient artery arises opposite the middle
of the humerus; in many cases it arises, on the back of the arm, from the profunda; the superior
ulnar collateral (inferior profunda) below the middle, and courses with the ulnar nerve through
the intermuscular septum to the back of the medial condyle. The inferior ulnar collateral
(anastomotica magna) is given off from 2.5 to 5 cm. (1 to 2 in.) above the bend of the elbow.
Fig. 1138 will show the collateral circulation after ligature of the brachial, according as the
vessel is tied above or below the superior profunda, or below the superior ulnar collateral.
The centre of the arm is a landmark for many anatomical structures. On the
lateral side is the insertion of the deltoid; on the medial, that of the coraco-
brachialis. The basilic vein and the medial brachial cutaneous nerve (nerve of
Wrisberg) here perforate the deep fascia, going in reverse directions. The supe-
rior ulnar collateral is here given off from the brachial and joins the ulnar nerve;
the median nerve also crosses the artery, and the ulnar nerve leaves the medial
side of the vessel to pass to the medial aspect of the limb.
The brachialis can be mapped out by two pointed processes which surround the insertion
of the deltoid, pass downward into lines corresponding to the two intermuscular septa, and then
converge over the front of the elbow to their insertion into the coronoid process.
The median nerve (lateral head, 5th. 6th, 7th C; medial head, Sth C. and 1st T.) can be
traced by a line drawn from the lateral side of the third part of the axillary and first part of the
brachial artery, across this latter vessel about its centre, and then along its medial border to
the forearm, where it passes between the two heads of the pronator teres.
Fia. 1133. — Cross-Section through the Elbow. ( X 1/2). (After Braune.)
Tendon of biceps.- _, '^^ ;::^^^\'ff^ -Pronator teres
Brachio-radiahs / [-i. ^^ \^<r _ Median nerve
Extensor carpi radialis longus - ^Mf^^^^' '*''*t^' - *''* Vv
-Ulnar collateral ligament
'ff^ -Ulnar nerve
^ — Olecranon
Anconeus ^^N5v""^3 ^~~^~^^^^
-Tendon of triceps
Radial ;
Brachialis -
"Flexor carpi radialis
The ulnar nerve (Sth C. and 1st T.) lies to the medial side of the above arteries as far as
the middle of the arm, where it leaves the brachial to course more medially and perforate the
medial intermuscular septum together with the superior and posterior branch of the inferior
ulnar collateral and so get to the back of the medial condyle. A line drawn from the medial
border of the coraco-brachialis, where, in the upper part of its course, the nerve is in close rela-
tion with the medial side of the axillary and brachial arteries, to the back of the medial condyle,
will indicate its course. Low down, the nerve is in the medial head of the triceps, and may be
injured in operations here.
The radial (musculo-spiral) nerve (5th, 6th, 7th, and Sth C.) can be traced by a line begin-
ning behind the third part of the axillary artery, then carried vertically down behind the upper-
most part of the brachial, and then, just below the posterior border of the axilla, curving back-
ward behind the humerus and slightly downward just below the insertion of the deltoid. Thus,
passing from laterally and from before backward in its groove, accompanied by the profunda
vessels, first the trunk, and then the smaller anterior division, it again comes to the front by
perforating the lateral intermuscular septum at a point about opposite to the junction of the
middle and lower thirds of the arm, and passes down in front of the lateral supracondyloid
ridge, lying here between the brachio-radialis and brachialis anterior, to the level of the lateral
condyle, in front of which it divides into the superficial (radial) and deep (posterior interos-
seous) radials. The former of these accompanies the radial artery to the front of the arm, the
latter travels backward to the back of the forearm. A line from the lateral condyle to the
insertion of the deltoid indicates the lateral intermuscular septum.
In addition to injuries caused by fracture, the nerve may be injured in crutch pressure,
the sleep of intoxication, use of an Esmaroh's bandage, or the careless reduction of a dislocated
shoulder with the foot in the axilla. To expose the nerve the incision begins below, over the
lateral intermuscular septum, where it lies between the brachio-radialis and brachialis (anterior).
Hence the incision is prolonged freely upward and backward toward the posterior border of the
deltoid.
On the back of the arm is the triceps muscle, with its three heads and tendon
of insertion, all brought into relief in a muscular subject when the forearm is
strongly extended. Of the three heads, the medial is the least distinct, arising
1416
CLINICAL AND TOPOGRAPHICAL ANATOMY
below the groove (musculo-spiral) for the radial (musculo-spiral) nerve, reaching
to each intermuscular septum, and tapering away above as high as the teres major.
Most of the fibres of this head lie deeply. The lateral head, arising above the
groove as high as the great tuberosity, appears in strong relief just below the
deltoid; while the middle or long head, arising from the scapula just below the
glenoid cavity, appears between the teres muscles. The tendon of insertion,
passing into the upper and back part of the olecranon over a deep bursa, is shown
by a somewhat depressed area. On the lateral side, an important expansion to
the fascia over the anconeus is given off.
Fig. 1134, — The Elbow-Joint, as Shown by the Rontgen-hats.
)
In the ossification of the humerus the epiphyses are of first importance. The upper,
consisting of those for tlie head and two tuberosities, wliich form one about the seventh year,
blends with the shaft between the twentieth and twentj'-fittli years. Separation usually takes
place at an earlier date, this being explained by the fact that the cone-like arrangement by which
the diaphysis fits into the cap of the epiphysis becomes more marked toward the date of union,
and thus tends to prevent displacement. (Thomson.) The lower epiphysis. The condition
of this varies with the degree of coalescence of its four centres. The first and chief, that for the
capitulum (second or third year), unites with those for the trochlea and lateral epicondyle soon
after puberty, and forms an epiphysis which joins with the shaft at about sixteen. The epi-
physis for the medial epicondyle appears at the fifth year and unites with the shaft at the
eighteenth. Injury to this epiphysis may damage the ulnar nerve and open the elbow-joint.
Thus, at and after puberty, there are two chief epiphyses to remember here: — (a) the larger,
consisting of capitular, trochlear, and lateral epicondyle centres. This is almost entirely intra-
articular; (6) the smaller, that for the medial epicondyle; the extent to which this is intra-artic-
ular varies. The structures that would be divided in an amputation at the centre of the arm
THE ELBOW
1417
are shown in fig. 1132. The chief points needing attention are: — (1) To leave as much of
the lever of the humerus as possible; (2) clean section of the large nerves, the radial (musoulo-
spiral) in its groove being especially liable to be frayed by the saw; (3) the difference between the
amount of retraction of the free biceps in front, and the triceps behind, fixed to the bone and
septa.
THE ELBOW
The bony points, epicondyles, olecranon, and head of radius, andtheir relation
to one another, should be carefully studied. The medial epicondyle is the more
prominent of the two, is directed backward as well as medially, and lies a little
above its fellow. Above it can be traced upward the supracondyloid ridge and
corresponding intermuscular septum. The lateral epicondyle is more rounded, and
thus less prominent; below, and a little behind it, the head of the radius can be felt
moving under the capitulum when the forearm is supinated and flexed. A depres-
sion marks this spot and corresponds to the interval between the anconeus and
brachio-radialis and extensor carpi radialis longus; at the back, the upper part
of the olecranon is covered by the triceps. The lower part is subcutaneous, and
separated from the skin by a bursa. If the thumb and second finger be placed on
the epicondyles and the index on the tip of the olecranon, and the forearm com-
pletely extended, the tip of the olecranon rises so as to be on the line joining the
two epicondyles. In flexion at a right angle, the olecranon is below the line of the
Fig. 1135. — Longitudinal Section of the Elbow-joint. (One-half.) (Braune.)
Extensor carpi ulnaris
Radial nerve
inr \ \ 'Brachio-radialis
— Supinator
■Extensor carpi radialis longus
epicondyles, and in complete flexion quite in front of them. Between the medial
epicondyle and olecranon is a pit, in which lie the ulnar nerve and the anastomosis
between the inferior ulnar collateral and the posterior ulnar recurrent arteries.
The coronoid process is so well covered by muscles, vessels, and nerves that its
position cannot be distinctly made out.
The synovial membrane of the elbow-joint communicates with that of the superior radio-
ulnar. Hence the facility with which tuberculous disease may be set up after neglected falls
on the hand, in early life. At this time the weakness of the annular (orbicular) ligament leads
to its being easily injured. Swelling, due to effusion into the joint, appears on either side of the
triceps tendon, and soon obliterates the depression below the lateral epicondyle. The simplest
incision for an infected elbow-joint is a vertical one, on the lateral side of the olecranon. A
superficial swelling over the tip of the olecranon is due to effusion into the bursa between the
soft parts and that bone. A deeper, less easily defined swelling in the same region is due to
inflammation of the bursa between the olecranon and the triceps. A swelling on the medial
side of the elbow-joint, if painful and accompanied by inflammation of the skin, may be due
to mischief in the epitrochlear lymphatic node situated just above the medial epicondyle, and
receiving lymphatics from the medial border of the forearm and the two medial fingers.
The hollow in front of the elbow. — The delicacy of the skin here must always be borne in
mind in the application of splints. Owing to the insidious rapidity with which pressure may set
up ischaemic paralysis, anterior angular splints are always to be used with caution. The M-like
1418
CLINICAL AXD TOPOGRAPHICAL AX ATOMY
arrangement of the superficial veins as usually described is by no means constant (fig. 1136),
The median basilic is the vein usually chosen for venesection, owing to its larger size and its
being firmly supported by the subjacent bicipital fascia which separates it from the brachial
artery; but the median cephalic is the safer. The median basilic is crossed by branches of
the medial antibrachial (internal) cutaneous nerve, while those of the musculo-cutaneous lie
under the median cephalic. In the semiflexed position, the fold of the elbow is seen, a little
above the level of the joint. This forms the base of the triangular fossa below the elbow, the
lateral side corresponding to the brachio-radialis, the medial to the pronator teres, and the
apex to the meeting of these muscles. The tendon of the biceps can be easih' made out in the
centre of the fossa, giving off above the lacertus fibrosus from its medial side to fasten down the
flexors of the forearm. Under the tendon on its medial side lie the bracliial artery and the
median nerve, a little medial to it, for a short distance. The radial nerve (musculo-spiral) lies
outside the fossa, between the brachio-radialis and the brachialis (anterior), and gives off its two
Fig. 1136. — The Bend of the Ei^ow with the Superficial Veins.
(From a dissection by Dr. Alder Smith in the Museum of St. Bartholomew's Hospital.)
Median nerve
Posterior branch, of in-
ferior ulnar collateral
Branches of medial
anti-brachial
cutaneous nerve ■
Posterior ulnar vein
Brachialis
Anterior branch of in-
ferior ulnar collateral
Anterior ulnar vein
Median basilic vein
Tendon of biceps
Lacertus fibrosus
Deep median vein
Ulnar artery
Pronator teres
Biceps
Vena comitans of
brachial artery
Basilic vein
Brachialis
Cephalic vein
Brachial artery
Lateral anti-
brachial cuta-
neous nerve
Radial n. and as-
, cending branch
of radial recur-
rent artery
Radial vein
Median cephalic
Ascending br. of
radial recurrent
Superficial radial
nerve
Radial recurrent
artery
Bra chio -ra diali s
Median vein
Superficial
radial
nerve
terminal branches in front of the lateral epicond^'le. The brachial usually bifurcates oppo-
site to the neck of the radius.
The arterial anastomoses about the elbow-joint are as follows: The radial recurrent runs up
unaer cover of the brachio-radialis to anastomose with the anterior branch of the profunda
on the front of the lateral condyle. The posterior interosseous recurrent ascends, between the
supinator and the anconeus, to anastomose on the back of the lateral condyle with the posterior
branch of the profunda. It further joins, by a large anastomotic arch across the back of the
joint, with the inferior ulnar collateral (anastomofic magna) and posterior ulnar recurrent.
The anterior ulnar recurrent passes upward on the brachialis to join the anterior part of the
inferior ulnar collateral under the pronator teres, on the front of the medial epicondyle. The
posterior ulnar recin-rent makes for the interval between the back of the medial epicondyle
and the olecranon, to join with the superior and the posterior branch of the inferior ulnar
collateral.
It will be seen that the inferior ulnar collateral (anastomotica magna) is the artery most
largely employed, distributing branches everywhere, save to the front of the lateral epicondyle.
THE FOREARM
1419
THE FOREARM
Bony landmarks. — The -posterior border of the ulna can be easily traced down
from the olecranon to the back of the styloid process; the bone becomes somewhat
rounded below, and lies between the flexor and extensor carpi ulnaris. The tip of
the styloid process corresponds to the medial end of the line of the wrist-joint. The
radius is covered above by the brachio-radialis and radial extensors of the carpus,
and the outline of the bone is less easily followed. Its styloid process is readily
made out below a finger 's breadth above the thenar eminence. It is placed about
1.2 cm. (I in.) lower than that of the styloid process of the ulna.
Thus, a line drawn straight between the two processes would fall a little below that of the
wrist-joint, this being shown by a line drawn between the two processes forming a slight curve,
with its conoa\'ity downward (corresponding to the concavity of the lower surface of the radius
and fibro-cartilage) about 1.2 cm. (5 in.) above the straight Une given above.
The radial styloid process is covered by the abductor longus and extensor brevis polhcis,
while farther out Ues the extensor pollicis longus. Between the styloid process of the ulna and
Fig. 1137. — The Brachial Artery at the Bend of the Elbow.
(From a mounted specimen in the Anatomical Department of Trinity College, Dubhn.)
Posterior branch of medial
antibrachial cutaneous
nerve
Anterior branch of medial
antibrachial cutaneous
nerve
Biceps muscle
Brachial artery
Branch to pronator teres
Lacertus fibrosus, cut
Pronator teres muscle
Median nerve
Ulnar artery
Branch of radial nerve J
supinator longus
Superficial radial nerve
Radial recurrent artery an
deep radial nerve
Tendon of biceps
Musculo-cutaneous nerve
Brachio-radialis muscle
Radial artery
the rounded head is the groove for the extensor carpi ulnaris. The bones are nearest to each
other in complete pronation, and farthest apart in complete supination. On section, the bones
are found at every point nearer to the back than to the front of the limb, but increasingly so
above. 'The lower the section proceeds down the Umb, the less will the bones be covered at the
sides, and the more equally wUl the soft parts be distributed about the anterior and posterior
aspects of the Umb. It will be noticed that where one bone is the more substantial, the other
is the more slender, as near the elbow and wrist; and that it is about the centre of the limb
that the two are most nearly of equal strength.' (Treves.) When the Hmb is pronated, the
interosseous space is narrowed; in supination and the mid-position it is widened out. In
pronation, both styloid processes can be distinctly made out; in supination, that of the radius
is the more distinct, as now the skin and soft parts are stretched and raised over that of the ulna.
about
, — ..w .. ^.-^. ^ „...^ ..„.., j^..,. to aie oLicLuiicu iiuu lai&eu uvei mat oi tuc Luua.
Joints. — The position of the superior radio-ulnar joint is marked by a dimple
)ut 12 mm. (I in.) below the lateral epicondyle. The inferior can just be felt,
1420
CLINICAL AND TOPOGRAPHICAL ANATOMY
when the forearm is pronated, between the head of the ulna and lower end of the
radius. The recessus sacciformis here may be enlarged in rheumatic and other
affections. The interosseous membrane not only ties the bones together and
gives attachment to muscles, but in falls on the hand it enables the ulna to partici-
pate in the shock.
The following are important points with regard to the bones. Common fractures. Ole-
cranon.— This usually takes place at the constricted centre of the semilunar (greater sigmoid)
notch or the junction of the olecranon with the shaft. A fall is here the usual cause, and
the heavier the fall, the more frequently is the fracture nearer the shaft, though displacement is
now likely to be slight, owing to the abundance of fibrous and muscular structures on both sides
Fig 1138. — Diagram of the Anastomoses op the Beachial Artery.
(MacCormac and Anderson.)
Thoraco-acromial
Long thoracic
Anterior curcumfl'
Posterior circumflex'
Superior radial collateral (i
sively large)
Middle collateral
Radial collateral-
Superior ulnar collateral
Radial recurrent-
Subscapular
Circumflex scapular
ulnar collateral
Transverse branch of inferior
ulnar collateral
Anastomosis of anterior ulnar recurrent
th inferior ulnar collateral
Anterior ulnar recurrent
Posterior ulnar recurrent
Posterior interosseous from common interosseous of ulnar
of the fracture. The shaft of one or both hones. Usual site, about the middle or a little below it,
fracture of the radius being more frequent from its connection with the hand. In these fractures
the chief muscular agencies are — (1) the extensors and flexors in drawing the lower fragment or
fragments upward, forward, or backward, according to the direction of the fracture; (2) the
biceps in drawing the upper fragment of the radius upward; (3) the influence of the pronator
teres, if the fracture is, as usual, below it, and (4) that of the quadratus in drawing the lower
fragments together. Thus the chief practical points are — (a) the reduction of displacement,
whether antero-posterior or lateral; (6) the greater the number of fragments, the greater the
tendency to union across the interosseous space, with its embarrassing results, and the greater
the need of a supinated position in the setting; (c) the risk of gangrene here from the faciUty
with which the vessels are compressed against the contiguous bones, especially in flexion of
the forearm; and the consequent need of attention to the width of the splints and the bandaging;
(d) the readiness with which ischsemic paralysis may rapidly and insidiously be caused. Colles'
fracture. Here, after a fall on the hand, the radius gives way usually at its weakest part, about
THE FOREARM
1421
Fig. 1139. — The Arteries of the Forearm with the Superficial Volar Arch.
Tendon of biceps
Lacertus fibrosus of biceps
Radial recurrent artery
Brachio-radialis
Superficial radial nerve
Radial artery
Flexor pollicis longus
Pronator quadrati
Radial artery winding to back
of wrist under extensors of
thumb
Superficial volar br.
Superficial volar arch
Brachial artery
Basilic vein
Median nerve
Inferior ulnar collateral
Brachial artery
Medial epicondyle
Ulnar artery
Pronator teres
Flexor carpi ulnaris
Flexor digitorum sublimis
Flexor carpi radialis
Palmaris longus
Median nerve
Flexor digitorum sublimis
Ulnar artery
Pisiform bone
Transverse carpal ligament
Palmaris brevis
1422
CLINICAL AND TOPOGRAPHICAL ANATOMY
18 mm. (f in.) above its extremity, where the narrow compact tissue is suddenly expanding
into cancellous. There is frequently impaction of the upper into the lower fragment. There
is a three-fold displacement of the lower fragment: — (1) It is driven and drawn upward and
backward. (2) It is rotated so that its articular surface looks somewhat backward. (3) It
is drawn to the radial side. The chief causes of the discreditable stiffness often allowed to result
are non-reduction of the deformity, adhesions in the opened wrist-joint, teno-synovitis, and
prolonged immobilisation.
Separation of epiphysis. — This may take place in the radius up to about the age of eighteen:
it is commoner before. Its possible importance in interfering with the symmetry of the growth
of the bones is obvious. Here, as in CoUes' fracture, the level of the styloid processes of the
radius and ulna, and the correspondence of the two styloid processes of the radii, are important
in diagnosis. Exposure of the bones. In the case of ununited fracture or necrosis the radius
may be reached — (o) Behind, by an incision in a line drawn from the lateral epicondyle to the
back of the radius. The field opened here lies between the brachio-radialis and the radial
extensors on the one side, and the common extensor on the other. Care must be taken of the
Fig. 1140. — Distribution of CuTANEOtrs Nerves on the Anterior and Posterior Aspects
OP the StrpERiOR Extremity.
Supra-acromial
Medial anti-
brachial
cutaneous
osto-
brachial
Twig of medial
antibrachial
cutaneous
Dorsal
antibrachial
cutaneous
Musculo-
cutaneous
(lateral anti-
brachial
cutaneous)
Lateral
brachial
cutaneous
Dorsal anti-
brachial
cutaneous
Musculo
cutaneous II
(lateral anti- |
brachial I
cutaneous)
deep radial (posterior interosseous) nerve. (6) In front. The incision here lies in the sulcus
between the brachio-radialis and the flexors. The pronator teres and the flexor subUmis must,
in part, be detached from the radius. If more room is required to reach an injured upper
extremity of the radius, the incision will descend from above the lateral epicondyle in the groove
between the anconeus and common extensors. In the detachment of the supinator the deep
radial nerve will again need attention. The ulna is more easily reached by an incision between
the flexor and extensor carpi ulnaris. In removal of the lower part of the bones for myeloid
sarcoma or osteitis, the ulna is reached in the interval last mentioned. The radius is best
exposed by an incision between the brachio-radialis and extensor carpi radialis longus, the super-
ficial radial nerve being the guide. (Morris.) Finally, the so-called 'carrying angle' of the
forearm deserves mention. In extension the bones of the forearm are not in a straight line with
the humerus, but directed sUghtly laterally, the angle at the elbow-joint being obtuse, and open
laterally. This angle is so named from its facilitating carrying objects during walking. In
flexion the forearm is deflected somewhat toward the middle line, mouth, etc. These properties
are liable to be lost under many and widely different conditions, of wliich injuries to the epiphyses
of the humerus, badly united fractures of the forearm, and osteoarthritis of the elbow-joint are
instances.
THE FOREARM
1423
Soft, parts. — Along the lateral border, of the forearm descend the brachio-
radialis and radial extensors of the carpus, fleshy above, tendinous below. About
3.7 cm. (I5 in.) above the styloid process of the radius, a fleshy swelling directed
obliquely downward and forward from behind, across this lateral border of the
forearm, denotes the extensors of the thumb crossing those of the carpus.
Along the medial border is the fleshy mass of the pronator teres and flexors, the
ulna being covered by the flexor carpi ulnaris and flexor profundus. The tendon
of the pronator is inserted into the radius a little below its centre — a point of im-
portance in the treatment of fractures and in amputation. The flexor carpi ul-
naris tendon can be felt just above the wrist making for the pisiform bone; and
just lateral to it lies the ulnar artery, about to pass over the transverse carpal (ante-
rior annular) ligament.
The course of the artery is denoted by the lower two-thirds of a hne drawn from the
front of the medial epicondyle to the lateral edge of the pisiform bone. From the bifurcation
of the brachial, a line drawn to meet the former at the junction of its middle and upper third
marks the upper part of the artery, here thickly covered by muscles. In ligature of the artery
in the middle of the forearm, the white line and sulcus between the flexor carpi ulnaris and sub-
limis must be identified. A small muscular branch will often lead down to the artery. The
line of the ulnar nerve is one drawn from the interval between the medial epicondyle and the
Fig. 1141. — Section through the Middle of the Right Forearm. (Heath.)
Brachio-radialis
Supinator
Extensor carpi radialis longus _^
and brevis W
Abductor pollicis longus
l|pf- Flexor digitorum sublimis
Flexor carpi ulnaris
Extensor digitorum
Extensor carpi ulnar
Posterior interosseous vessels and deep radial nerve | Median nerv
Extensor pollicis longus
Ulnar vessels and nerve
Flexor digitorum profundus
olecranon to the medial side of the ulnar artery just above the wrist. The nerve joins the artery
at the junction of the upper and middle thirds of the forearm. The median nerve runs in a
hne drawn from the medial side of the brachial artery, in the elbow triangle, to a point beneath,
or just to the medial side of, the palmaris longus at the mid-point of the front of the wrist. The
radial artery will be marked by a line drawn from the centre of the bend of the elbow (where the
brachial artery divides opposite to the neck of the radius) to a point just medial to the radial
styloid process descending along the medial edge of the brachio-radialis. The muscular interval
is that between the brachio-radialis and pronator teres above, and the flexor carpi radialis below.
The superficial radial nerve will be marked by the same line (it lies just lateral to the artery) for
its upper two-thirds; it then leaves the artery about 7.5 cm. (3 in.) above the wrist-joint, and
passes to tiie back of the forearm under the tendon of the brachio-radialis. The volar inter-
osseous artery runs down on the interosseous membrane and passes to the back of the fore-
arm by perforating it below, having passed behind the pronator quadratus. The dorsal
interosseous lies between the superficial and deep extensors. These small arteries reinforce
the palmar through' the carpal arches, and thus bring down blood after ligature of the trunks
above.
The front of the forearm is supplied by the miiscido-cutaneous on the lateral,
and the medial aniibrachial (internal) cutaneous on the medial, side; just above
the wrist the palmar cutaneous branches of the median and ulnar perforate the
deep fascia (fig. 1140). The back of the forearm is supplied by the radial (mus-
1424 CLINICAL AND TOPOGRAPHICAL ANATOMY
culo-spiral) and posterior branches of the musculo-cutaneous laterally, and the
posterior branches of the medial antibrachial cutaneous medially (fig. 1140).
The lymphatics of the upper extremity are superficial and deep; the former
run with the superficial veins, the latter with the deep vessels. Occasionally a
few small nodes occur below the elbow. The epitrochlear nodes lie upon
the basilic vein, a little above the medial epicondyle and draining the fourth and
fifth digits. The majority of the lymphatics open into the axillary nodes, and
terminate, on the left side in the thoracic duct, on the right in the lymphatic duct.
A few, accompanying the cephahc vein, reach the subclavian or infraclavicular
nodes, and thus communicate with the lymphatics of the neck.
It will be well briefly to consider here the chief results of paralysis of the main
nerves of the upper extremity.
Paralysis of the median nerve. — (a) In forearm: Loss of pronation, (fe) At ivrisl: Dimin-
ished flexion 1111(1 tciidciicy toward ulnar adduction, (c) In the hand: Power of grasp is lessened
especially in the tliunili and lateral two fingers. Owing to the loss of flexion in the phalanges
of these fingers the phalanges are liable to become overextended by the action of the extensors
and interossei. The thumb remains extended, adducted, and closely applied to the index, the
human characteristic being thus lost, and the ' ape's hand' of Duchenne being produced. Sensa-
tion will be lost over the palmar aspect of the thumb and lateral two and one-half fingers and
over the distal ends of the same fingers, to a varying degree, according to the sensory distribution
of the median and other cutaneous nerves. The above apphes to lesions of the trunk. If the
nerve be injured at the wrist, flexion of the wrist and fingers is less interfered with.
Paralysis of the ulnar nerve. — (a) At wrist: Power of flexion is diminished and that of ulnar
adduction lost. (&) In the hand: Power of grasp will be lessened in the ring and little fingers.
The interossei will be powerless to abduct or adduct the fingers, and there will be marked wasting
of the interosseous spaces and hypothenar eminence. The thumb cannot be adducted. After
a time, from paralysis of the lumbricals and interossei, the hand becomes 'clawed' — the first
phalanges overextended, and the second and third flexed (main en griff e). Sensation will be
lessened over the area supplied by the nerve.
Paralysis of the radial (musculo-spiral) nerve. — (a) In the forearm This is flexed, ex-
tension being impossible. The forearm is pronated, supination being impossible save by biceps,
which acts now most strongly on a flexed elbow-joint, (b) In the wrist: This is dropped, owing
to the loss of extension, (c) hi the hand: The thumb is flexed and adducted. Some slight
power of extension of the second and third phalanges of the fingers remains by means of the
lumbricales and interossei. Sensation is impaired over the posterior and lateral aspect of the
forearm and lost to a varying extent over the distribution of the radial on the back of the hand.
Paralysis of the deep radial (posterior interosseous) nerve. — The evidence here is somewhat
similar to that just given, but with the following differences, (o) In the forearm: There is no
loss of extension, and the loss of supination is less as the brachio-radialis is not paralysed, (b)
At the wrist: The 'drop' and loss of extension are not so marked, as the extensor carpi radiahs
longus escapes. Sensation : There is no loss.
Paralysis of the musculo-cutaneous nerve. — Forearm: Power of flexion is impaired, owing
to complete paralysis of the biceps and partial of the brachialis (anterior). Sensation: This is
impaired over the lateral aspect of the forearm, both back and front.
Amputation of forearm. — The 'mixed' method by skin-flaps roundly arched and circular
division of the soft parts, the dorsal flap being the longer, is the most generally applicable. The
bones should always be sawn below the pronator teres, when possible. In sawing them they
must be kept parallel, the limb being in the supinated position. As the radius is the less securely
held above, it is well to complete the section of this bone first. The relative position of the ves-
sels has been indicated above (p. 1423, and figs. 1139 and 1141).
THE WRIST AND HAND
Bony points. — On the medial side the styloid pi'ocess and, further laterally, the
head of the ulna can be made out. On the lateral side, the radial styloid process
descends about 1.2 cm. (| in.) lower than that of the radius, and is somewhat ante-
rior to it. Abduction of the hand is thus less free than adduction. Between the
apex of the styloid process and the ball of tlie thumb a bony ridge can be felt, with
some difficulty, formed by the tubercle of the navicular and the ridge of the greater
multangular (trapezium). At the base of the hypothenar eminence the pisiform
can be more readily distinguished. The hook of the hamatum (unciform) lies below
and to the radial side of the pisiform. On the front of the metacarpo-phalangeal
joint of the thumb, the sesamoid bones can be distinguished.
At the back of the wrist and hand the triquetrum (cuneiform) bone can be felt
below the head of the ulna; and more toward the middle line tlie prominence of
the capitatum (os magnum), which supports the third or longest digit.
A line drawn from the base of the fifth metacarpal bone to the radio-carpal joint, slightly
curved downward, will give the line of the carpo-metacarpal joints. (Windle.) When the
fingers are flexed, it will be seen that in each case it is the proximal bone which forms the prom-
THE WRIST AND HAND
1425
inence ; thus, the knuckle is formed by the head of the metacarpal, the interphalangeal prominence
by the head of the first phalanx, and the distal one by the head of the second. _ Thus, the joint
in each case lies below the prominence, the distal joint being 2 mm. {^t in.), the interphalangeal
4 mm. (i in.), and the metacarpo-phalangeal 8 mm. (3 in.) below its prominence.
Skin and skin-folds. — The skin over the palm is thickened over the heads of
the metacarpal bones and hypothenar eminence, thinner over the thenar. It is
peculiar in its absence of sebaceous glands and hair-follicles; hence the absence of
boils and sebaceous cysts. It is intimately connected with the palmar fascia,
hence the chief difficulty in operations when this is contracted. Over the pulp
of the digits the skin is closely connected with the periosteum of each ungual
phalanx. The importance of this is alluded to under the heading of whitlow
(vide infra).
Skin -folds : two or three of these are seen on the palmar surface of the wrist : two lower down,
and usually close together, and one less well marked, a little higher up upon the forearm. None
of these corresponds exactly to the wrist-joint (fig. 1142). The lowest 'precisely crosses the arch
of the OS magnum in the line of the third metacarpal bone' (Tillaux), and is not quite l.S cm.
(f in.) below the arch of the wrist-joint. It is about 1.2 cm. (5 in.) above the carpo-metacarpal
joint line, and indicates very fairly the upper border of the transverse carpal (anterior annular)
ligament.
'Of the many creases in the skin of the palm, three require especial notice. The first starts
at the wrist, between the thenar and hypothenar eminences, and, marking off the former emi-
FiG. 1142.
-Relation of the Volar Arches to the Folds op the Palm.
Tillaux.)
(Modified from
nence from the palm, ends at the lateral border of the hand and at the base of the index-finger.
The second fold is slightly marked. It starts from the lateral border of the hand, where the
first fold ends. It runs obliquely medially across the palm, with a marked inclination toward
the wrist, and ends at the lateral Hmit of the hypothenar eminence. The third, lowest, and best
marked of the folds starts from the little elevation opposite the cleft between the index and
middle fingers, and runs nearly transversely to the ulnar border of the hand, crossing the hypo-
thenar eminence at the upper end of its lower fourth. The first fold is produced by the adduc-
tion of the thumb; the second, mainly by the bending simultaneously of the metacarpo-phalan-
geal joints of the first and second fingers; and the third by the flexion of the three medial fingers.
The second fold, as it crosses the third metacarpal bone, about corresponds to the lowest part
of the superficial volar arch. The third fold crosses the necks of the metacarpal bones, and
indicates pretty nearly the upper limits of the synovial sheaths for the flexor tendons of the
three lateral fingers. A httle way below this fold, the palmar aponeurosis breaks up into its
four slips, and midway between the fold and the webs of the fingers lie the metacarpo-phalan-
geal joints. Of the transverse folds across the fronts of the fingers, corresponding to the meta-
carpo-phalangeal and interphalangeal joints, the highest is placed nearly IS mm. (f in.) below
its corresponding joint. The middle folds are multiple for all the fingers, and are exactly
opposite to the first interphalangeal joints. The distal creases are single, and are placed a little
above the corresponding joints. There are two single creases on the thumb cori-esponding
to the two joints, the higher crossing the metacarpo-phalangeal joint obhquely. The free edge
of the web of the fingers, measured from the palmar surface, is about 1.8 cm. (f in.) from the
metacarpo-phalangeal joints. (Treves.)
_ The superficial volar arch, formed by the ulnar anastomosing with the super-
ficial volar, or radialis indicis, will be shown by a line descending to the radial side
1426
CLINICAL AND TOPOGRAPHICAL ANATOMY
of the pisiform bone, and then, a Httle lower, curving across the palm on a line with
the thumb when outstretched at right angles with the index-finger. The four
common digital arteries, the main branches of the superficial arch, run downward
along the interosseous spaces, and bifurcate 12 mm. (J in.) above the webs of the
fingers; the most medial digital does not bifurcate.
The digital arteries then descend along the sides of the fingers under the digital nerves,
giving ofi twigs to the sheath of the tendons, which enter by apertures in it, and run in the
vincula vasculosa. It is owing to the readiness with which these tiny twigs are strangled by
inflammation that sloughing of the tendon takes place so readily and irreparably. Throughout
its course the superficial volar arch deserves its name. It is only covered by the palmaris
Fig. 1143. — Anastomoses and Distribution op the Arteries of the Hand.
Volar interosseous -
Radial artery -
Volar radial carpal
Superficial vola
Dorsal radial carpal
Radial artery at wrist
First dorsal
metacarpal
Second d
metacarpal
Princeps polli
First dorsal meta-
carpal (branch to
index)
Radialis indicis , , ,, ,, ,, ,, ^^ , ^^r , i^ i*x ^— .c^ ^» .
Common volar
digitals
Dorsal meta-
carpals
Common volar
digital
Dorsal digital
Volar digital
First dorsal branch of volar digital
Second dorsal branch of volar digital
Anastomosis of volar digital arteries
about matrix of nail and pulp of
brevis and central part of the palmar fascia. Beneath it, medio-laterally are the flexor brevis
and opponens digiti quinti, the digital branches of the ulnar and median nerves, and the flexor
tendons and lumbricales.
The deep volar arch, formed by the radial and communicating branch of the
ulnar, lies about 1 . 2 cm. (| in.) nearer to the wrist than the superficial. It is not
so curved as the superficial arch, and rests upon the interossei and metacarpal
bones just below their bases. The structures separating it from the superficial
arch have been already given.
Owing to the frequency of wounds here, the relation of the structures in front of
the wrist is most important. The radial artery lies between the tendon of the
THE WRIST AND HAND
1427
brachio-radialis and flexor carpi radialis. Next to this tendon is the palmaris
longus, when present. At the mid-point of the front of the wrist and usually
under the palmaris longus is the median nerve. To the medial side of the palmaris
longus is the flexor sublimis, the tendons for the middle and ring-finger being in
front. The tendon of the flexor carpi ulnaris is most medial and between this and
the superficial flexor of the finger the ulnar nerve and vessels have come up into a
superficial position.
Fig. 1144. — The Superficial Muscles op the Palm of the Hand.
Flexor carpi radialis
Abductor pollicis longus
Opponens pollicis
Abductor pollicis brevis
Flexor pollicis brevis
Flexor digitorum
profundus
Fasciae and sheaths. — The transverse and dorsal carpal (annular) ligaments
bind down and hold in place the numerous tendons about the wrist. The trans-
verse carpal (anterior annular) , when healthy, cannot be detected. It is attached
to the pisiform and triquetral (cuneiform) bones on the medial, and to the na-
vicular and greater multangular (trapezium) on the lateral, side.
1428
CLINICAL AND TOPOGRAPHICAL ANATOMY
The ulnar nerve and vessels, the superficial volar, and palmar cutaneous branches of the
median and ulnar pass over it. The ulnar artery and nerve are especially protected by
their position between the pisiform and hook of the hamate (unciform), and also by a
process of the flexor carpi ulnaris, which passes to the transverse ligament, thus forming a
kind of tunnel. The flexor carpi radialis passes through a separate sheath formed by the liga-
ments and the groove in the greater multangular; while beneath the Hgaments lie the flexor
tendons, the median nerve, and accompanying artery. Attached to its upper border is the
deep fascia of the forearm, and to its lower the palmar fascia and the palmaris longus tendon,
while from the lateral and medial parts arise some of the thenar and hypothenar muscles. The
upper border of the transverse carpal ligament corresponds to the lower of the two lines which
Fig 1145. — The Deeper Muscles of the Palm of the Hand.
— Abductor poUicis longus
Flexor carpi radialis
Extensor poUicis brevis
Abductor pollicis brevis
Opponens pollicis
Abductor pollicis
brevis
.Flexor pollicis
brevis
Adductor pollicis
cross the wrist just above the thenar and hypothenar eminences. The large synovial sheath,
for all the flexors of the fingers, reaches beneath and below the transverse ligaments as far as
the middle of the palm, and above the wrist for 3.7 to 5 cm. (1 J to 2 in.).
The dorsal carpal (posterior annular) ligament is attached to the back of the
lateral margin of the radius above the styloid process, and medially to the back of
the styloid process of the ulna, the triquetrum and pisiform. Its direction is
obhque, being higher on the radial side. It contains six tendon-compartments, of
which four are on the radius.
The most lateral contains the long abductor and short extensor of the thumb; the second
the two radial extensors of the carpus; the third, the extensor pollicis longus; this deep and narrow
groove can be identified when the hand is extended, by its prominent lateral margin; the fourth
transmits the extensor communis and extensor indicis proprius; the fifth, lying between the
THE WRIST AND HAND
1429
Fig. 1146. — Section throttgh Region of Wrist, a Little above the Joint. Kight Side,
Upper Half of the Section. (Tillaux.)
Flexor carpi radialis Flexor pollicis longus
Flexor sublimis
Radial artery
Brachio -radialis
Flexor profundus
Pronator quadratus
Superficial radial nerve
Abductor pollicis longus
Extensor brevis pollicis
Extensor carpi radialis
longus
Extensor carpi radialis
brevis
Extensor pollicis longus
Ulnar artery, and nerve
Volar interosseous artery
Flexor carpi ulnaris
Extensor com'
- munis and indicis
Radius Extensor digiti quinti
Extensor carpi ulnaris
Fig. 1147. — Region of the Wrist, as Shown by the ROntgen-rays.
1430
CLINICAL AND TOPOGRAPHICAL ANATOMY
radius and ulna, the extensor digiti quinti; and the sixth, lying just lateral to the styloid process
of the ulna, the extensor carpi ulnaris. The sheaths for the last two extensors are the only ones
which follow the tendons of their insertion, the others ending at a varying distance below the
carpal ligament. The lower border of the dorsal carpal corresponds to the upper margin of the
transverse carpal ligament.
Fig. 1148. — Thansverse Section of the Wrist through the Middle op the Pisifohm Bone.
Sheath of flexores sublimis and profundus digitorum and flexor pollicis longus
enclosed by the transverse carpal ligament
Cut tendon of palmaris longus Ulnar nerve
Lunate bone | I Ulnar vessels
Sheath for flexor carpi radialis
Radial origin of transverse
carpal ligament ^
Sheath for abductor longus and J, "
Sheath of extensor carpi ulnaris
Sheath of extensores carpi radialis, longus and brevis
Sheath of extensor communis and indicis
Lunatu
Sheath of extensor digiti quinti
Triquetn
Hamatum
Fig. 1149. — Diagram of the Great Palmar Bursa.
Ulnar portion of palmar bursa
Radial portion of palmar bursa
Transverse carpal ligament
Deep transverse
ligament
The palmar aponeurosis, by its strength, toughness, numerous attachments,
and intimate connection with the superficial fascia and skin is well adapted to pro-
tect the parts beneath from pressure.
The thenar and hypothenar muscles are enclosed in two processes, which are thinner so as
not to interfere with the contraction of the subjacent muscles. The central part, pointed above
THE WRIST AND HAND
1431
at its attachment to the carpal ligament, spreads out fan-like below, and gives off four sKps,
each of which bifurcates into two processes, which are attached to the sides of the first phalanx
of each finger and into the superficial transverse ligament of the web and the deeper one which
ties the heads of the metacarpal bones together. Transverse fibres pass between the processes
into which each of the four slips bifurcates, and thus form the beginning of the theca, which is
continued down the finger to the base of the last phalanx. It is the contraction of the palmar
aponeurosis, especially of the slip to the two medial fingers, which gives rise to Dupuytren's
contraction. The theca is strong opposite the first two phalanges (hgamentum vaginale),
weak and loose opposite the joints (ligamentum annulare). The density of this osseo-fibrous
tunnel and its close proximity to the digital nerves explain the pain in thecal inflammation.
Its tendency to gape widely after section is to be remembered in amputations through infected
parts.
Sjraovial membranes. — Beneath the transverse carpal ligament lie two
synovial sacs, one for the flexor pollicis longus, and one for the superficial and
deep flexors of the fingers. They extend above the transverse ligament for rather
more than 2.5 cm. (1 in.). The two sacs may communicate. A compound
palmar ganglion has an hour-glass outline, the transverse carpal ligament forming
the constriction.
The creaking sensation in teno-synovitis and that of 'melon-seed' bodies often present in
tuberculosis here is well known. The sheath for the long flexor of the thumb reaches to the
base of the last phalanx. That for the finger-flexors gives off four processes. The one for the
little finger also reaches to the base of the last phalanx. Those for the index-, middle, and third
fingers end about the middle of the metacarpal bones. Traced from the insertions of the flexor
sublimis and profundus
Ulnar vessels and nerve
Palmaris brevis
iHypothenar muscles
Fig. 1150. — Section op Cabpus through the Hamate Bone
(BeUamy, after Henle.)
Median nerve
Flexor pollicis longus Flex'
Flexor carpi radialis
Thenar muscles
Base of first metacarpal bone
Abductor pollicis longus-
Greater multangular-
Extensor pollicis brevi
Radial vessel
Extensor carpi radialis longus —
(Two-thirds.)
Lesser multangulai
Extensor carpi radialis brevis
Capita turn
Extensor indicis
Extensor carpi ulnaris
Extensor digiti quinti
Hamatum
Extensor digitorun
proprius
profundus, the digital synovial sheaths extend upward into the palm as far as the bifurcation
of the palmar fascia (p. 1430), i. e., into a point about opposite to the necks of the metacarpal
bones, denoted on the surface by the crease which corresponds to the flexion of the fingers.
Thus, about 1 - 2 cm. (|in.) separates the sheaths of the lateral three fingers from the large syno-
vial sac beneath the transverse carpal ligament. There is no synovial sheath beneath the pulp
of the fingers or thumb, this part lying on the periosteum of the last phalanx.
This has an important bearing on whitlow. Infection here may be merely subcuticular,
or deeper, in the latter case from the connection of the skin with the periosteum here existing
the bone is soon affected, and necrosis keeps up a tedious ulcer. As the two centres of the pha-
lanx do not unite till about the twentieth year, the distal one only requires removal; as the
flexor sheath only reaches to the insertion of the flexor, i. e., into the proximal, part of the bone,
both sheath and tendon may escape implication. Higher up along the fingers whitlow may be
cellulo-cutaneous or thecal. While the continuity of the synovial sheath in the httle finger and
thumb (fig. 1149) renders infection here more dangerous, the short gap between the digital
and the palmar sacs is readily traversed by acute infection, with all the grave results of
thecal suppuration.
Suppuration in the hand owes much of its gravity to the possibility of infection of the syno-
vial tendon sheaths and consequent sloughing of the tendons. At the same time it is now
recognised that unless these sheaths are primarily infected pus collects at first in certain jioten-
tial spaces, more or less well defined, in the looser connective tissue of the hand. One of these,
known as the middle palmar space (Kanavel*) is situated on the front of the metacarpals of
the middle and ring fingers, and lies deeply between the flexor tendons and the interosseous
muscles. Continuations of this potential space extend downward along the lumbrical muscles
* Kanavel, A. B.: Infections of the Hand, 1912.
(
1432
CLINICAL AND TOPOGRAPHICAL ANATOMY
on the radial side of the three medial fingers, and may lead pus from the palm to the subcutane-
ous tissue of these fingers or vice versa. A second potential compartment, the thenar space
(Kanavel) lies in front of the index metacarpal, between the flexors of the index-finger and the
adductor transversus poUicis. As in the former space, the corresponding lumbrical muscle pro-
longs it down to the radial side of the index -finger.
Distention of the middle pahnar space with pus leads to obliteration of the hollow of the
palm and a variable extension of the swelling along the radial side of the three medial fingers.
Distention of the thenar space follows the thenar eminence, obliterates the adduction crease of
Fig. 1151. — Tendons trpoN the Doksum of the Hand.
(The dorsal expansion or aponeuiotic sheath has not been removed.)
Abductor polUcis longus
Extensor pollicis brevis
Dorsal carpal ligament
Extensor carpi ulnaris
Extensor digitorum communis
Extensor digiti quinti
Extensor indicis proprius
Attachment of extensor
digitorum communis
to third phalanx
the thumb, and may extend down the radial side of the index-finger. There is not in either case
the extreme tenderness and pain on passive extension of the fingers that is characteristic of
infection of the synovial sheaths. The pus is best evacuated by an incision on the radial side
of the finger most affected, a little beliind the web, sinus forceps being passed along the lumbrical
muscle into the palm, so as to avoid opening and infecting the synovial sheaths.
It must be remembered also that infection of the above fascial spaces may take place
secondarily, by the bursting into them of pus from the synovial tendon sheaths.
THE WRIST AND HAND
1433
Deeper are the articular synovial sacs, five in number: — (1) Between the
interarticular cartilage and the head of the ulna; (2) between the radius and the
interarticular cartilage above, and the navicular and lunate and triquetrum
below; (3) between the greater multangular and first metacarpal bone; (4) be-
tween the pisiform and the triquetral bone; (5) between the two rows of carpal
bones, sending two processes upward between the three bones of the upper row,
and three downward between the four of the lower row; these three processes being
also continued below into the medial four carpo-metacarpal and three inter-
metacarpal joints.
Beneath the palmar aponeurosis covering the thenar eminence are the following structures: —
Superficial volar artery, abductor pollicis brevis, opponens pollicis, radial head of short flexor,
tendon of long flexor, ulnar head of short flexor, first volar metacarpal arteries, metacarpal bone
of the thumb, with the tendon of the flexor carpi radialis and greater multangular.
Beneath the central part of the palmar aponeurosis are the superficial arch and its digital
branches; the ulnar and median nerves, with their branches; the lle.xors, superficial and deep,
with their synovial sheath; and the lumbricales; then a layer of connective tissue (the only
Fig. 1152. — Diagrams Illustrating the Insertions of the Extensor, Litmbrical and
Interosseous Muscles op the Right Hand. A, Index finger. B, Middle finger. C, Ring
finger. D, Little finger. IL, 2L, 3L, 4L, Lumbricales. 1D9, 2D9, 3E)9, 4D9, dorsal interossei.
1P9, 2P9, 3P9, palmar (volar) interossei. EC, Extensor communis digitorum. E9, Extensor
indicis proprius. EMD, Extensor digiti quinti proprius. AMD, abductor digiti quinti (Willan :
Anat. Anz. Bd. 42, 1912.)
Riont
structure, together with the deep layer of fascia over the interossei, which prevents matter pent
in by the palmar aponeurosis from making its way back out through the dorsum), the deep
arch, the interossei, and the metacarpal bones.
In the hypothenar eminence under the fascia are part of the ulnar artery and nerve, the ab-
ductor and flexor brevis digiti quinti, the opponens, the deep branch of the ulnar artery and
nerve, and the fifth metacarpal bone.
The back of the wrist and hand. — The dorsal carpal (posterior annular) liga-
ment has already been described. On the lateral side is the so-called 'snuff-box
space' (tabatiere anatomique of Cloquet), a triangular hollow, bounded toward the
radius by the long abductor and short extensor of the thumb, and toward the
ulna by the long extensor. The navicular and greater multangular, ^dth their
dorsal ligaments, form the floor. In the roof lie the radial vein and branches of the
radial nerve. More deeply is the artery, following a line from the apex of the
styloid process to the back of the interosseous space.
The different tendons have already been given. Between the first two metacarpal bones is
the first dorsal interosseous muscle, wliich forms a fleshy projection against the radial side of
the index metacarpal, when the thumb and index are pressed together. On its palmar aspect
is the adductor polUcis. Wasting of the former muscle is a ready indication of injury or disease
of the ulnar nerve.
1434 CLINICAL AND TOPOGRAPHICAL ANATOMY
The skin on the dorsum, by its laxity, readily allows of cedema, this being sometimes evi-
dence of pressure on the axillary vein by carcinomatous deposits. The dorsal venous arch
receives the digital plexuses, and from it the radial and posterior ulnar veins ascend. The me-
dian vein begins in plexuses at the root of the thumb and the front of the wrist.
Ganglia are common on the dorsum, in connection with the extensors of the fingers and the
thumb. While usually due to a weakening of the sheath and protrusion of this and the synovial
membrane, such swellings may be due to a projection of the articular synovial membrane.
Owing to the laxity of the skin, the slight vascularity, the size of the tendons, their connection
with joint-capsules and with each other, which fixes them, the dorsum of the wrist is the 'seat
of election,' for tendon-anastomosis and other operations. Metacarpo-phalangeal dislocation.
This ocom's in the thumb and the index-finger especially. The chief cause in the difficulty in
reduction is the glenoid ligament. This, in reality a fibro-cartilaginous plate, is blended with
the lateral ligaments on the palmar aspect of the joint, and is firmly attached to the phalanx,
but more loosely to the metacarpal. Thus when dislocation occurs in violent hyperextension,
the metacarpal attachment of the glenoid ligament gives way and it is carried by the phalanx
over the head of the metacarpal bone. In the case of the thumb, the buttonhole-like slit with
which the two heads of the flexor brevis, now displaced, embrace the head of the metacarpal,
the contraction of the other short muscles, and, occasionally, a displaced long flexor, are addi-
tional causes. In the case both of the thumb and finger, tilting the phalanx well back on the
dorsum of the metacarpal and then combined pressure with the thumbs forward against the
base of the phalanx, when this is sharply flexed, will with an anaesthetic, be usually successful.
The thumb should he, first, adduoted into the palm.
THE LOWER EXTREMITY
HIP AND THIGH
The various segments of the lower extremity will be successively considered as
follows: hip and thigh, knee and leg, ankle and foot.
Bony landmarks. — Many of these, such as the anterior superior iliac spine and
crest of the ilium and the tubercle of the pubis, have already been mentioned.
The relative length of the limbs is obtained by carrying the measure from the an-
terior superior spine to the tip of the corresponding medial malleolus. The pelvis
must be horizontal and the limbs parallel. The share taken by the femur and
tibia respectively is estimated by finding the transverse sulcus which marks their
meeting-point.
The head and shaft of the femur are well covered in, save in the emaciated. The head
lies just below Poupart's ligament, under the ilio-psoas, and a little to the outer side of the centre
of that ligament. A line drawn horizontally laterally from the pubic tubercle will cross the lower
part of the head. All the head and the front of the neck, but only two-thirds of the back, are
within the capsule; this intra-capsular position of the upper epiphysis, which, appearing at the
first year, does not unite till eighteen or twenty, accounts largely for the extreme gravity of
acute epiphysitis here. The structure of the neck, i. e., the two sets of lamellae, vertical to sup-
port the weight, transverse and intersecting in order to meet the puU of the muscles, and the wast-
ing of these after middle life, has an important influence on injuries. The strong process,
femoral spur or calcar (Merkel) which, arising from the compact tissue on the medial and under
side of the neck, just above the lesser trochanter, spreads laterally toward the trochanteric
(digital) fossa, also affords strength, and its degeneration probably plays an important part in
the fractures of the neck.
Hip-joint. — The chief points of surgical importance are the following: — The
capsule shows fibres chiefly longitudinal in front, circular behind. Of the former,
the ilio-femoral or inverted Y-shaped hgament descends fi-om the anterior inferior
spine to the two extremities of the anterior intertrochanteric line. It not only
checks extension and strengthens the front of the joint, but it keeps the pelvis and
trunk propped forward on the heads of the femurs, thus preventing waste of mus-
cular action. It is joined on the medial side by the pubo-capsular ligament,
which checks abduction. Between the two is the medial part of the front cap-
sule, and here the ilio-psoas bursa may communicate with the joint. This fact
must be remembered in tuberculous disease of the psoas, and the presence of this
bursa explains certain deep-seated swellings in the front of the joint in adults.
Behind, the ischio-femoral is the strongest part of the capsule, its fibres blending
with the circular and weaker part of the capsule here. Dislocation usually
occurs at the posterior, lower and medial part of the joint. It is to be noted that
in full extension and flexion the head of the femur is in contact with the weakest
spot in the capsule, in front and behind, respectively. From the deep aspect of
the capsule fibres pass up at the line of reflection of the synovial membrane on to
the neck- — the cervica,! Hgaments of Stanley. In intracapsular fracture these
THE HIP AND THIGH
1435
fibres keep the fragments together; hence one need of gentle handling; their
softening may explain, a little later, an increase in the shortening.
Exploration of the joint. — This is usually effected by an oblique incision downward and
slightly medially between the sartorius and rectus medially and the gluteus medius and minimus
laterally. A branch of the ascending division of the lateral cu-oumflex is the only artery met
with. In tapping the joint the puncture is made in the same line, 2 or 3 inches below the
anterior-superior spine. 'If the instrument is pushed upward, medially, and backward beneath
the rectus, it will pass into the joint a little above the anterior intertrochanteric Kne. (Stiles.)
Fig. 1153. — Region of the Hip-joint, as Shown by the Rontgen-rays.
Trochanter major. — This valuable landmark is most prominent when the limb
is rotated medially or adducted; it lies at the bottom of a depression when the
femur is everted.
The chief structure of importance between it and the skin is the upper part of the insertion
of the gluteus maxim us, that going to the fascia lata, and the bursa beneath the muscle. Tliis is
often multilocular. It is, not very uncommonly, the seat of tubercular inflammation which
readily invades the cancellous tissue of the trochanter. The top of the great trochanter is
about 1.8 cm. (f in.) below the level of the femoral head, and, when the femur is extended is a
little below the centre of the hip-joint. This part of the bone is covered by the gluteus medius.
1436
CLINICAL AND TOPOGRAPHICAL ANATOMY
The slightness of the prominence of the great trochanter in the living subject compared with that
in the skeleton is explained by fig. 1154, which shows how the descending gluteus medius and
minimus fill up the space between the ilium and trochanter. To examine the great trochanter,
the thigh should be abducted, so as to relax the strong fascia lata passing upward over the tensor
and glutei to the iliac crest.
Nelaton's line. — This useful guide is a line drawn from the anterior superior
spine of the ilium to the most prominent part of the tuberositj^ of the ischium. In
normal limbs, the top of the great trochanter just touches this line. In dislocation,
fractures of the neck, and in wasting of the neck, as in osteo-arthritis, the relation
of the trochanter to Nelaton's line becomes altered.
The top of the gi'eat trochanter is a guide in Adams's operation for division of the neck of an
ankylosed femur, the puncture being made and the saw entered 2.5 cm. (1 in.) above and about
the same distance in front of this point. Owing to the fact that in many cases of ankylosis
the neck is destroyed, the above operation has been largely replaced by the simpler and more
widely applicable Gant's osteotomy just below the great trochanter, from the lateral side.
Fig. 1154.-
-Transverse Section op the Hip-Joint and its Relations.
(One-third.) (Braune.)
External iliac artery
Gluteus minimus
Gluteus medius
; Obturator internus'
Adductor magnus
Obturator externus — -^
Adductor longus-^
'Adductor brevis ■
Bryant's triangle. — Bryant makes use of the following in deciding the position of the great
trochanter. The patient being flat on his back (1) a line is dropped vertically on to the couch
from the anterior superior spine; (2) from the top of the great trochanter a straight Hne in the
long axis of the thigh is drawn to meet the first; (3) to complete the triangle, a line is drawn from
the anterior superior spine to the top of the trochanter. This line is practically Nelaton's.
The second line will be found diminished on the damaged or diseased side.
Muscular prominences. — The tensor fasciw latoe forms a prominence beginning just lateral
to the sartorius and reaching downward and somewhat backward to the strong fascia lata,
7.5 to 10 cm. (3 to 4 in.) below the great trochanter. Below this point, as far as the lateral con-
dyle of the tibia, the strong ilio-libial band can be felt. Like the inverted Y-shaped Ugament,
this band is a powerful saving of muscular action in maintaining the erect position. At the in-
sertion of the tensor fascis lata3 it bifurcates into two layers, which enclose the muscle. The
superficial is attached to the iliac crest and the sheath of the gluteus medius; the deep blends with
the capsule and the reflected head of the rectus. This deeper layer is perforated by the ascend-
ing branch of the lateral circumflex. The ilio-tibial band is a guide for reaching the femur
(p. 1334). The sartorius, the chief landmark of the thigh, forming a boundary of the femoral
trigone (Scarpa's triangle), the adductor (Hunter's) canal, and the popUteal space, can be readily
brought into view by the patient's raising his limb slightly rotated laterally. In the middle line
the rectus muscle stands out in bold relief, with its tendon of insertion and the patella, when the
THE HIP AND THIGH
1437
leg is extended. On either side of this muscle is a furrow, and on either side, again, of this
furrow the vasti become prominent. Between the vastus medialis and adductor muscles is a
depression indicating the adductor canal. At the upper and medial third of the thigh, if the
limb be abducted, the upper part of the adductor longiis comes into strong reUef . On the medial
side below, above the knee-joint, the vertical fibres of the adductor magnus end in a powerfxil
tendon coming down to the adductor tubercle (fig. 1159). This replaces here the medial inter-
muscular septum, and the insertion of the tendon marks the level of the lower epiphysial Hne
of the femur. At the lateral and back part of the thigh the vastus lateralis is separated from the
biceps by a groove which indicates the lateral intermuscular septum. Of these septa, prolonga-
tions inward from the fascia lata to the linea aspera, the lateral lies between the vastus lateraUs
and the biceps. It reaches from the lateral tuberosity of the femur to the insertion of the gluteus
maximus. Just above the condyle it is perforated by the superior lateral articular vessel and
nerve. The medial septum extends from the adductor tubercle to the trochanter. It is weak in
Fig. 1155. — The Muscles attached to the Pdbes.
(From a dissection in the Hunterian Museum.)
External oblique--
Rectus abdominis'
Rectus abdominis
Pectineus
Adductor longus
Adductor brevis
Adductor longus
Corpora cavernosa — \A ^
Adductor brevis ;
adductor magnus
and obturator
externus
Corpus spongiosum
(cavernosum
urethrse)
Transversus
perinei prof.
Bulb-cavernosus
Obturator
externus
Adductor magnus
Gracilis
Ischio-cavernosus
Transversus perinaei
Central tendinous point
Sphincter ani
comparison, and separates the adductor from the vastus mediaUs. A third, the weakest of all,
separates the adductor and the hamstrings. The fascia lata has the same effect as that in the
neck in causing pus to burrow, especially downward, and in rendering the diagnosis of swellings
beneath it difficult. Thickest above and on the lateral aspect, and again about the bony promi-
nences at the knee-joint, at both of which sites it receives accessions from muscles, it is divided
into iliac and pubic portions. The former is attached behind to sacrum and coccyx, iliac crest
and the inguinal hgament, terminal Una and pubic tubercle. Here it blends with the pubic
portion, which is connected with the pubic arch. At the fossa ovaUs (saphenous opening) the
two may be said to separate, the iliac forming the upper cornu and lateral falciform margin,
and descending over the femoral vessels and extensors. The pubic, much thinner, forms the
medial margin of the fossa, and descends obliquely over the pectineus and adductor longus
behind the vessels, to blend with the sheath of the ilio-psoas and capsule of the hip-joint.
(
1438
CLINICAL AND TOPOGRAPHICAL ANATOMY
The inguinal (Poupart's) ligament. — The abdomen is separated from the
thigh by a fold, best marked in flexion — the inguinal furrow. In this, pressure
detects the meeting of the aponeurosis of the external oblique and the fascia lata,
i. e., Poupart's ligament, extending between the anterior superior spine of the ilium
and the tubercle (spine) of the pubes. The line representing it should be drawn
slightly convex downward, o^ving to the attachment of the deep fascia. It forms
the base of the femoral trigone; its medial attachment blends with the triangular
lacunar (Gimbernat's) ligament. The parts passing under the inguinal ligament
and their arrangement have been given at p. 1399, fig. 1122.
-Diagram of Arteries of Thigh.
Ilio-lumbar artery
Common femoral
Deep femoral (profunda)
Descending branch of lateral circumflex
Inferior lateral articular
Posterior tibial recurrent (from
anterior tibial)
Anterior tibial recurrent
Superior fibular
Anterior tibial,
Common iliac artery
Inferior epigastric
Hypogastric, dividing into anterior
and posterior trunks
External iliac
Obturator
Inferior gluteal
Internal pudic
Lower terminal branch of medial
circumflex
Superficial femoral (muscular
branches omitted)
Perforating branches of deep femoral,
forming anastomotic loops and sup-
plying posterior muscles
Superior medial articular
Inferior medial articular (sural arteries
arising below this omitted)
Posterior tibial
The femoral trigone (Scarpa's triangle) (fig. 1159). — Immediately below the
inguinal ligament a hollow is seen corresponding to this region, the lateral and
medial boundaries of which are brought into view when the limb is raised, the
adductor longus especially when the limb is abducted, and the sartorius when the
thigh is flexed and the limb extended and rotated laterally. The floor of the
femoral trigone is not horizontal, the plane of the medial part being very oblique.
It is formed latero-medially by the ilio-psoas, pectineus, adductor brevis (slightly),
and adductor longus.
A psoas abscess descending below the inguinal ligament usually does so on the lateral aspect
of the femoral vessels; if the sheath gives way, or if the abscess follows the profunda artery, it
will pass beneath the adductor longus and point toward the medial side of the thigh. (Taylor.)
THE HIP AND THIGH
1439
Fig. 1157. — Section of the Right Thigh at the Apex of the Femoral^Trigone. (Heath.)
Femoral vessels
Sartorius
Lateral cutaneous nerve
Profunda vessels
Adductor longus
Superficial part of obturator nerve
Rectus femoris
Femoral nerve
Lateral circumflex-
vessels \ii
Tensor fa
Vastus laterali
Gracilis
^\.f Pectineus
C^ld Adductor brevis
^\'^1| Deep part of obturator
-f-^H nerve
""Vv Adductor magnus
Semi-membranosus
:nii-tendinosus
Posterior cutaneous nerve
Sciatic nerve
Fig. ,1158. — Superficial Dissection of the front of the Thigh.
(Hirschield and Leveill6.)
Inguinal ligament
Anterior cutaneous nerve
Anterior cutaneous nerve
Branch to sartorius
Lateral cutaneous nerve —
Anterior cutaneous nerve
Superficial branches of
femoral artery
Femoral artery
Femoral vein
Anterior cutaneous nerve
Great saphenous vein
Anterior cutaneous nerve
■Anterior cutaneous nerve
Anterior cutaneous nerve
Patellar branch of
saphenous nerve
Saphenous nerve
(
1440
CLINICAL AND TOPOGRAPHICAL ANATOMY
If it simulate a femoral hernia, examination of the back and the fact that the sweUing is below
the fossa ovahs will prevent mistakes. Three nerves come into the thigh between the pelvis
and Poupart's ligament, i. e., the lumbo-inguinal (genito-crural) in the femoral sheath, the
femoral (anterior crural) between the iliacus and psoas and the lateral cutaneous close to the
lateral attachment of the inguinal ligament.
The obturator nerve divides into two in the obturator foramen, the two divi-
sions being separated by some fibres of the obturator externus, and lower down by
the adductor brevis. The relations, course, and distribution of this nerve, in the
medial fibres of the psoas, over the sacro-iliac joint and under the ilio-pelvic or
sigmoid colon (Hilton), through the obturator foramen with its branches (from
the superficial division) through the cotyloid notch to the hip, and (from the deep)
Fig. 1159. — Femoral and Obtubator Nerves.
Femoral vein Femoral artery
(Ellis.)
Pectineus
Obturator (anterior div.)
Obturator (posterior
division) \.\ >' i 1
Adductor longus — r — f
Adductor brevis
Saphenous
— Nerve to vastus medialis
Adductor magnus
'Geniculate branch of obturator
Semi-membranosus
Adductor longus
Femoral artery
Genu suprema artery
Patellar branch of saphenous
along the popliteal artery to the knee, and others to the lower third of the thigh,
and sometimes the upper and medial aspect of the leg (Hilton), may be of much
surgical importance, e. g., in carcinoma of the bowel, disease of the sacro-iliac and
hip-joints, growths of the pelvis, and the rare obturator hernia. The distribution
of the cutaneous nerves is shown in fig. 1158. Lying superficially in the base of
the trigone, the inguinal lymphatic nodes can be detected in a thin person (fig.
1172).
The fossa ovalis (saphenous opening). — The depression corresponding to this
Is placed just below the lacunar (Gimbernat's) ligament, with which its upper ex-
tremity blends. Its centre is about 3.7 cm. (11 in.) below and also lateral to a
THE THIGH
1441
line dropped vertically from the pubic tubercle. This and the other structures
concerned in femoral hernia are fully described under this section (vide supra,
p. 1398). The course of the great saphenous vein is given below, p. 1456.
Line of femoral artery. — A line drawn from the mid-point between the anterior
superior spine and the symphysis pubis to the adductor tubercle will correspond
with the course of this vessel. The sartorius usually crosses it 10 cm. ( 3 to 4 in.)
below the inguinal (Poupart's) ligament. The profunda artery arises usually
3.7-5 cm. (1| to 2 in.) below Poupart's ligament.
The incision for tying tiie femoral in the femoral trigone should be about 7.5 cm. (3 in.)
long, in the Kne of the artery, and begins about 7.5 cm. (3 in.) below the inguinal ligament, and
runs over the apex of the triangle. The femur is flexed slightly, abducted and rotated laterally.
The fascia lata being divided, the sartorius, readily recognised by its direction, is drawn later-
ally. The closely subjacent sheath must be opened on its lateral side. Structures that may
be seen are a vein joining the great saphenous, the anterior cutaneous, saphenous nerve, and
that to the vastus medialis. The collateral circulation (fig. 1156) is mainly through the following
Fig. 1160. — Section of Thigh through upper Part of Hunter's Canal. (W. A.)
Saphenous nerve.
Femoral artery, with
small venee comit-
antes (femoral vein
deeper)
Sheath of vessels
Great saphenousvein
Superficial fascia
Deep fascia contin-
ued over back of
thigh as superficial
layer of deep fascia
Deep layer of deep
fascia (muscular
aponeurosis)
Vein
channels: — (1) The lateral and medial circumflex above, with the genu suprema and lower
muscular branches of the femoral, and the articular of the popliteal. (2) The perforating
branches of the profunda above, with the vessels below first given. (3) The comes nervi iscliia-
dici with the articular of the popKteal.
The femoral vein Ues, below the inguinal ligament, immediately to the medial side of the
artery. From this point on the vein gets to a somewhat deeper plane, though stOl very close to
the artery, and gradually inclining backward, lies behind its companion at the apex of the tri-
angle, and below lies somewhat laterally to it.
From the apex of the femoral trigone (Scarpa's triangle) a depression runs
down along the medial aspect of the thigh, corresponding to the groove already
mentioned between the vastus medialis muscle and the adductors. Along this
groove lies the sartorius, and beneath it the adductor (Hunter's) canal, a triangu-
lar inter-muscular gap with its apex toward the linea aspera, and its base or roof
formed by the fibrous expansion which ties together its boundaries, viz., the adduc-
tor longus and magnus and the vastus medialis.
The vein, which in the upper part of the canal lies behind the artery, separating it from
the three adductors, lower down inclines more and more to the lateral side. The saphenous nerve
lies also in the canal, but not in the sheath. The above-mentioned space terminates at about
the junction of the middle and lower thirds of the thigh, in the opening in the adductor magnua
(
1442 CLINICAL AND TOPOGRAPHICAL ANATOMY
by which the artery enters the upper and medial part of the pophteal space. The saphenous,
the largest branch of the femoral nerve, having crossed the femoral vessels latero-mediaUy,
accompanies them as far as the opening in the adductor magnus. Here it perforates the aponeu-
rotic roof, and is prolonged under the sartorius, accompanied by the superficial part of the genu
suprema artery, to perforate the fascia lata between the sartorius and gracilis, and run with the
great saphenous vein at the upper and medial part of the leg.
Pressure may be applied to the femoral artery — (1) Immediately below the inguinal liga-
ment: it should here be directed backward so as to compress the vessel against the brim of the
pelvis and the capsule of the hip-joint; (2) at the apex of the femoral trigone the pressure here
being directed laterally and a little backward, so as to command the vessel against the bone;
(3) in the adductor canal the pressure should be directed laterally with the same object. Care
must be taken, especially above, to avoid the vein, which lies very close to the artery, and also
the femoral nerve, which enters the thigh about 1.2 cm. (J in.) outside the artery, and at once
breaks up into its branches, superficial and deep.
In ligature of the femoral artery in Hunter's canal, the line of the incision, in the middle
third of the thigh, must exactly follow that of the vessel. It is frequently made too lateral,
exposing the vastus medialis. Branches of the saphenous vein being removed, the fascia lata
is slit up and the sartorius identified by its fibres descending medially. Those of the vastus
medialis are less oblique and are directed downward and laterally. The sartorius having been
drawn to the medial side, usually, the aponeurotic roof of the canal is opened, and the femoral
sheath identified. The vein, here posterior and to the lateral side, is closely coimected to the
artery.
The close contiguity of the femoral artery and vein accounts for the comparative frequency
of arterio-venous aneurysms especially in the upper part, where the vessels are easily wounded.
Their superficial position here further accounts for the facility with which mahgnant disease,
e. g., epitheKomatous glands, may cause fatal ha;morrhage. Access to the femur. This is best
attained on the lateral side of the shaft along the line of the lateral intermuscular septum
(fig. 1160), the biceps being pulled backward, and the vastus lateralis detached anteriorly. On
the medial side the bone may be exposed by an incision starting from a point midway between
the inner margin of the patella and the adductor tubercle and passing obliquely upward and
laterally, but the parts here are more vascular. Fractures of the shaft usually occur about the
centre. The main tendency to displacement is of the lower fragment upward by the ham-
strings. The upper fragment is anterior; this is especially marked in the upper third, owing to
the action of the iho-psoas, which also rotates the upper fragment laterally. In the lower third
the forward curve of the femur and its more superficial position explain the fact that it is here that
compound fractures of the femur may, occasionally, occur. Ossification. The unstable
nature of the tissues about the upper epiphysis, which appears at the end of the first year and
unites about eighteen, and the frequency of tuberculous disease in early life are well known.
In the lower epiphysis ossification begins before birth, a point of medico-legal importance in
deciding whether a newly born child has reached the full period of uterine gestation. From this
epiphysis, the level of which is denoted by a line drawn horizontally laterally from the adductor
tubercle, and the vascular growing tendon of the adductor magnus — the origin of an exostosis
is not uncommon. Displacement of this epiphysis (it unites about twenty) in boj'hood and adol-
escence is a grave injury from the immediate risk of the popliteal vessels. The mischief is
usually done by overextension of the leg, as when this is caught in a rapidly moving carriage-
wheel; the epiphysis is carried forward in front of the diaphysis, the lower end of which is directed
backward, endangering the vessels which are posterior and closely adjacent.
Amputation through the thigh. — This is usuaUj' performed in the lower third, by anterior
and posterior flaps, the former being the longer, so as to ensure a scar free from pressure, and
circular division of the muscles, vessels, and nerves. The vessels requiring attention are the
femoral, which lie at the medial side, and the more posteriorly, the lower the amputation; the
descending branch of the lateral circumflex, and the termination of the profunda near the
linea aspera. The femoral artery has a marked tendency to retract in the adductor canal.
Care should be taken not to include the saphenous nerve when the femoral vessels are tied, and
to cut the sciatic cleanly and high up. When amputation has to be performed in the upper
third of the thigh, the tendency of the ilio-psoas to flex the shortened limb and thus bring the
sawn femur against the end of the stump must be remembered, and met by keeping the patient
propped up and the stump as horizontal as possible. Some of the structures now divided are
shown in fig. 1160.
The buttocks. Bony landmarks. — The finger readily traces the whole outline
of the iliac crest. Behind, it terminates in the posterior superior iliac spine,
which corresponds in level to the second sacral spine and the centre of the sacro-
iliac joint. (Holden.)
The third sacral spine marks the lowest limit of the spinal membranes and the cerebro-
spinal fluid; it also corresponds to the upper border of the great sacro-sciatic notch. The first
piece of the coccyx corresponds to the spine of the ischium. (Windle.) Its apex is in the furrow
just behind the last piece of the rectum.
The tuberosities of the ischium are readily felt by deep pressure on either side
of the anus. In the erect position they are covered by the lower margin of the
gluteus maximus. In sitting they are protected by tough skin, fasciae, with coarse
fibrous fat, and often by a bursa known, according to the patients in whom it be-
comes enlarged, as weaver's, coachman's, lighterman's, drayman's bursa. The
THE THIGH
1443
skin of the buttock is coarse and difficult to cleanse satisfactorily. The abun-
dance of sebaceous glands accounts for the frequency of boils here.
Gluteus maximus. — The 'fold of the buttock' neither corresponds accurately
to, nor is caused by, the lower margin of this muscle. Thus, medially, it lies below
the lower margin of the muscle, as it runs laterally it crosses it, and comes to lie
on the muscle. The fold is really due to creasing of the skin adherent here to the
coarsely fibro-fatty tissue over the tuber ischii during extension. But in early hip
disease, in which flexion of the joint is, with wasting of the muscle, almost unvary-
ingly present, the fold disappears with well-known rapidity. The prominence of
the buttock is mainly due to the gluteus maximus, especially behind and below,
and in less degree to the other two glutei in front. Under the lower edge of the
gluteus maximus the edge of the sacro-tuberous (great sacro-sciatic) ligament can
be felt on deep pressure.
To mark out the upper border of the gluteus maximus a line is drawn from a point on the
ihac crest 5 cm. (2 in.) in front of the posterior superior spine, downward and laterally to the
back of the great trochanter. The lower border is marked out by a second hne drawn from the
side of the coccyx parallel with the former, and ending over the linea aspera at the junction of
the upper and middle thirds of the thigh. It must be remembered that only the lower and inter-
nal fibres of the muscle are inserted into the gluteal ridge on the femur. The greater part of
Fig. 1161. — Section through the Hip and Gluteal Region. (One-third.)
SartoriuE
Reflected tendon
of rectus \
Psoas and iliacus
and bursa v
Femoral nerve^.
Common femoral.^
artery
Common femoral vein^
Profunda vessels^' y'^
Se
Gracili
membranosus
Adductor brevls
Semi-tendinosus
Obturator externus
Adductor magnu^-f- —
Adductor longus
Gluteus maximu:
Gluteus medius
Gluteus minimus
Sciatic nerve and infe-
rior gluteal vessels
Biceps
Quadratus femoris
it is inserted into the fascia lata and ilio-tibial band and so Into the lateral condyle of the tibia.
Weakness of the gluteus maximus and tensor fasciae lata;, with consequent laxity of the ilio-
tibial band, gives rise to abnormal side-to-side passive mobility at the knee-joint in full extension.
-The following superficial nerves can be marked in over
Nerves and vessels,
the buttock (fig. 1182).
Behind the great trochanter, branches of the lateral cutaneous; coming down over the crest,
the lateral cutaneous branch of the last thoracic (about in a line with the great trochanter),
and behind this the lateral branch of the ilio-hypogastric. Two or three oiTsets of the posterior
primary branches of the lumbar nerves cross the hinder part of the ihac crest at the lateral
margin of the sacro-spinahs. Two or three twigs from the posterior divisions of the sacral
nerves pierce the gluteus maximus close to the coccyx and sacrum, and ramify laterally. Fi-
nally, over the lower border of the gluteus maximus, turn upward branches of the posterior
cutaneous (small sciatic) and its perineal branch (inferior pudendal), and the fourth sacral
nerve.
Sciatic nerve (figs. 1162, 1163). — The point of emergence below the gluteus
maximus and the track of this nerve (fourth and fifth lumbar and first three sacral
nerves) will be given by a line drawn from a spot a little medial to the middle of
the space between the great trochanter and the tuber ischii to the lower part of
the back of the thigh, where it usualty divides into the tibial and common peroneal
(internal and external popliteal) nerves.
{
1444
CLINICAL AND TOPOGRAPHICAL ANATOMY
To stretch the nerve, an incision about tliree inches long is made in the line of the nerve,
beginning about 3.7 cm. (IJ in.) below the gluteus maximus. The long head of the biceps which
covers the nerve trunk and which is descending mediolaterally, is drawn medially. If the
nerve is exposed lower down, the interval between the hamstrings is identified and these muscles
drawn aside. The perineal branch of the posterior cutaneous (inferior pudenal) perforates
the deep fascia about 2.5 cm. (1 in.) in front of the tuber ischii, and turns forward to supply the
genitals.
Superior gluteal artery. — If a line be drawn from the posterior superior spine to the apex
of the great trochanter, the limb being slightly flexed and rotated medially, the point of emer-
gence of the artery from the upper part of the great sacro-sciatic notch will correspond with the
junction of the upper and middle third of this line. (MacCormao.) The gluteal nerve emerges
immediately below the artery, and sends branches into the deeper portion.
Inferior gluteal (sciatic) and pudic arteries. — The limb being rotated medially, a line is
drawn from the posterior superior spine to the lateral part of the tuber ischii. The point of exit
of the above arteries will correspond to the junction of the middle and lower thirds of this line.
(MacCormac.)
THE KNEE
Bony landmarks. — The patella, the condyles of the femur, the condyles and
tuberosity of the tibia, the head of the fibula, are all easily examined.
Fig. 1162. — The Gluteal Region, with the Superior and Inferior Gluteal and Pudic
Arteries.
Gluteus medius, turned up
■ gluteal nerve
Gluteus maximus, cut
Medial circumflex artery
Obturator externus ,
Insertion of gluteus medius
Lateral circumflex artery
Gluteus minimus
Muscular branches of inferior gluteal artery
Deep branch of superior gluteal artery
Superior gluteal nerve
Piriformis perforated by peroneal
portion of sciatic nerve
Cut edge of gluteus
Insertion of
gluteus maximus
First perforating artery
Quadratus femoris
Branch of internal circumflex artery
Obturator internus with the two gemelli
Pudic artery and nerve
Inferior gluteal artery
Biceps
Semi-tendinosus
Semi-membranosus
Posterior cutaneous nerve
comitans nervi ischiadic!
Tibial portion of sciatic nerve
Perineal branch of posterior cutaneous
Perineal portion of sciatic
(From a dissection by W. J. Walsham in St. Bartholomew's Hospital Museum.)
The muscular branch of the inferior gluteal (sciatic) artery has been drawn inward over the
tuber ischii with the reflected origin of the gluteus maximus muscle.
The patella. — ^The limb being supported in the straight position, and the exten-
sor muscles relaxed, the natural range of mobility laterally of the patella can be
estimated. This is interfered with by muscular action in inflammatory conditions.
J
THE KNEE
1445
or by early tuberculous ulceration of the contiguous cartilages. The niunerous
longitudinal strise or sulci on the anterior surface of this bone can now also be
detected. In these are embedded tendinous bundles of the rectus, so as to give
firmer leverage. The fact that these fibres, thus tied down, are liable after stretch-
ing and tearing to fold in between the ends of the bone after fracture, is a ready
explanation of the difficulty of ensuring bony union here. (Macewen.) The
patella is separated from the tibia by a pad of fat and a deep bursa, save at its
insertion. Owing to the lowest part of the patella being thus separated from the
joint by fat, fracture here does not, necessarily, open the joint.
The bone has the following relation to the femur in different positions: — (1) In extension, the
patella rises over the condyles, and in full extension only the lower third of its articular surface
rests upon that of the condyles; its upper two-thirds lies upon the bed of fat which covers the
Fig.
1163. — Deep Dissection of the Gluteal Region.
Hunterian Museum.)
(From a preparation in the
Gluteus medms
Gluteus minimus
Piriformis, divided
into two by the,
sciatic
Great trochanter
Obturator externus
Quadratus femons
Fascial insertion of
gluteus
Horizontal fibres of
adductor magnus
Sciatic foramen
(notch)
Gluteal nerve sup-
plying portions of
gluteus medius
Gluteus ]
Obturator internus.
Below is the infe-
rior gemellus. The
superior gemellus
is absent
Sciatic nerve. Under it,
oblique fibres of adduc-
tor magnus are seen
lower and front part of the femur. (2) In extreme flexion, as the prominent anterior surface
of the condyles affords leverage to the quadriceps, the patella needs to project very httle; thus,
only its upper third is in contact with the femur, its lower two-thu-ds now resting on the pad of
fat between it and the tibia. (3) In semiflexion the middle third of the patella rests upon the
most prominent part of the condyles. (Humphry.) While the bone now affords the greatest
amount of leverage to the quadriceps, it is also submitted to the greatest amount of strain from
this muscle, which is acting almost at a right angle to the long axis of the patella. This position
may therefore be called the 'area of danger,' as, in a sudden and violent contraction, the patella
may be snapped across by muscular action, aided by the resistance given by the condyles, in
the same way as a stick is snapped across the knee. The amount of separation of the fragments
i
1446
CLINICAL AND TOPOGRAPHICAL ANATOMY
in a fracture of the patella is due chiefly to the extent to which the lateral tendinous expansions
of the vasti are torn; to a less degree to the haemorrhage from the numerous articular vessels
(p. 1452) and synovial effusion. The lower fragment is usually the smaller, and its fractured
surface tilted forward; that of the upper one usually looks backward.
The patella, the largest of the sesamoid bones, ossifies by a centre which appears from the
third to the fifth year. The process is completed about puberty. The rareness with which
necrosis and caries occur here, when the exposed situation of the bone is remembered, is partly
Fig. 1164. — Knee-joint as Shown by the ROntgen-rays, Antero-posterior View.
explained by the density of its tissue, especially in front, and the intimate blending of the rectus
fibres with its periosteum. When the knee-joint is bent, the trochlear surface of the femur can
be made out, with some difficulty, underneath the quadriceps expansion. The upper and lateral
angle of this surface forms a useful landmark (Godlee) as a line drawn from it to the adductor
tubercle marks the level of the lower epiphysis of the femur.
Dislocation of the patella. — The following anatomical facts account for this taking place
much more frequently laterally: — (1) The medial edge of the patella is more prominent, and
thus more exposed to injury; it is also well supported, as is seen when, the parts being relaxed, the
THE KNEE
1447
fingers are insinuated beneath each border. (2) The pull of the extensor upon the patella,
ligamentum patella;, and tibia is somewhat laterally, as the tibia is directed a little laterally
to the femur, to meet the medial direction of this bone; the femora being directed medially here,
to bring the knee-joints nearer the centre of gravity, and, so, counterbalance their wide separa-
tion above at the pelvis. The lateral pull of the quadriceps upon the patella is, in all normal
action of the muscle, counteracted by the space taken in the trochlear surface by the lateral
condyle, this being wider and creeping up higher, and having a more prominent and thus pro-
tective lip. In violent contraction, however, these counteracting points may be overcome.
The condyles of the femur and tibia. — It should be noted that on the medial
side the prominence of the medial epicondyle of the femur is well marked, and that
Fig. 1165. — Knee-joint as shown by the Rontgen-rats, Lateral View.
of the tibia is less so, while on the lateral side this condition is reversed. Descend-
ing to the lateral condyle of the tibia, the ilio-tibial band of the fascia lata can be
traced. The more distinct lateral condyle is a good landmark for opening the
joint in amputation and excision. It also indicates the lower level of the synovial
membrane of the knee-joint.
Farther back are the biceps and fibular collateral (long external lateral) Ugament. The gap
onjthe medial side between the femoral and tibial condyles is the place for feeling for a displaced
medial fibro-oartilage in 'internal derangement' of the knee, and also for 'lipping' in suspected
osteoartliritis. On each femoral epicondyle, posteriorly, in a thin subject, can be felt its tubercle,
which gives attachment to the collateral ligament. Owing to their being placed behind the
■ centre of the bone, these ligaments become tight in extension. On the upper and posterior
{
1448
CLINICAL AND TOPOGRAPHICAL ANATOMY
part of the medial femoral epicondyle the adductor tubercle and the vertical tendon of the ad-
ductor magnus can be felt during flexion. This bony point is a guide to the lower epiphysis,
the ossification of which and its occasional exostosis have been mentioned at p. 1442. The
medial aspect of this epicondyle faces practically in the same direction as the head of the femur.
Ligamentum patellae and tuberosity of tibia. — These, in a well-formed leg,
should, with the centre of the ankle-joint, be all in the same straight line, a useful
point in the adjustment of fractures. (Holden.) Behind the upper half of the
ligament is the infrapatellar pad of fat; below, the lower half is separated from the
tibia by a deep bursa. The tuberosity (tubercle) of the tibia is on a level with the
head of the fibula.
[Prepatellar bursa. — This usually protects the lower part of the patella and upper part of
the ligamentum pateUaj. It is liable to be enlarged in those who habitually kneel much, the
enlargement being either fluid or solid, and occasionally, in tertiary syphilis. Its close connec-
tion with the patella and, at the sides, with the joint itself, is to be remembered in infective
inflammations of the bursa. Usually the deep fascia, passing off from the sides of the patella
upward to the thigh and downward to the leg, serves to conduct inflammation away from the
joint.
Synovial membrane (fig. 1167). — This, the largest of the synovial membranes,
forms a short cul-de-sac above the patella, between the quadriceps extensor and the
front of the femur, this process reaching about 2.5 cm. (1 in.) above the trochlear
surface of the femur. At its highest point this cul-de-sac communicates with an-
FiG. 1166. — Horizontal Section of the Knee-joint.
Prepatellar bursa
(One-half.) (Braune.)
Fibular collateral lig.
Lateral condyle of femur
Tibial n. '
Semimembranosus
Tibial collateral lig.
Medial condyle of femur
M. sartorius
Great saphenous vein
f!^^' ^Gastrocnemius, medial head
Tendon of gracilis
Tendon of semitendlnosus
other synovial, bursa-like sac lying between the quadriceps and front of the femur.
Thus, synovial membrane will usually be met with 6.2 cm. (2| in.) or more above
the trochlear surface or the upper border of the patella when the limb is extended.
Flexing the joint draws the membrane down very slightly. During extension, the
above pouch is supported by the articularis genu (subcrureus) . Traced down-
ward, the membrane reaches the level of the head of the tibia, being separated in
the middle line from the upper part of the ligamentum patellae by fat. It here
gives off to the intercondyloid notch the patellar synovial fold (ligamentum mu-
cosum), with its free lateral prolongations, the alar folds (ligamenta alaria).
These three so-called ligaments contain fat, the processes not only padding gaps,
but also meeting concussions.
The enlargement of these processes, under conditions not yet understood, may certainly
be a cause of 'internal derangement,' and simulate a loosened meniscus. But the synovial
membrane of this joint is not only the largest: it is also the most complicated, a fact accounting
for the grave peril of infective arthritis, and the well-known difficulty of effective drainage and
cleansing this joint. Thus 'it passes over the gi-eater portion of the crucial ligaments, but the
posterior surface of the posterior crucial, which is connected by means of fibro-areolar tissue
to the front of the ligamentum postioum, and the lower portions of both crucial ligaments, where
they are united together, of course cannot receive a complete covering from the membrane.,
(Morris.)
From the above ligaments the membrane is conducted, lining the lower part
of the capsule and other ligaments, to the semilunar cartilages, first over their
THE KNEE 1449
upper surfaces to their free borders, and then along their under surfaces to the
tibia. Between the lateral of these and the upper and back part of the tibia is a
prolongation of the synovial membrane to facilitate the play of the popliteus
tendon.
Finally, amid the complications of this synovial membrane, its communication with some
of the bursae mentioned below, and occasionally with the superior tibio-fibular joint, is to be
borne in mind. In effusion the bony prominences are obliterated, and the patella 'floats.'
The knee-joint is easUy opened by free lateral incisions lying midway between the margins of
the patella and the tuberosities of the condyles, drainage-tubes being passed so as to meet above
the patella. The above-mentioned complications of the synovial membrane show that such
drainage wiU be often inadequate. By passing a director to the back of the joint and cutting
down upon it carefully from the popliteal space, better drainage will be given, but opening the
joint by an anterior flap is needed where the above fail, and, even then, cleansing of the numerous
deep recesses is obviously difficult.
Structures on the head of the tibia. — From before backward these are: —
(1) Transverse ligament. (2) Anterior end of medial meniscus (fibro-cartilage).
(3) Lower attachment of anterior crucial. (4) Anterior end of lateral meniscus
blending with (3). (5) Posterior extremity of lateral meniscus giving off a strong
process to posterior crucial. (6) Posterior extremity of medial meniscus. (7)
Posterior crucial ligament. Menisci. — These serve as buffer-bonds and cushions
between the contiguous bones. The more frequent displacement of the medial is
explained by — (a) its greater fixity, and, therefore, its feeling strains more. Thus,
in addition to weaker attachments to the coronary and transverse ligaments, it is
connected all along its convex border with the inside of the capsule, and strongly
with the tibial collateral ligament. The lateral meniscus, on the other hand, is
more weakly attached to the capsule, especially opposite to the popliteus tendon,
and has no tie to the fibular collateral ligament. (&) When, in the erect position,
the knee-joint is rotated laterally and slightly flexed, a common position, an
especial strain is thrown upon the very important tibial collateral ligament, and
from the above-mentioned connection, on the medial meniscus also.
Position of knee-joint in disease. — In inflammatory effusion, the position which best
accommodates the collection of fluid is one of moderate flexion, the ligaments being now mainly
relaxed. Later on, when the ligaments are softened, the hamstrings obstinately displace the
leg backward, the tibia being rotated laterally by the biceps. The antero-posterior displacement
is always more marked than the lateral. In straightening an anchylosed joint, the resistance of
the shortened lateral, crucial, and posterior ligaments, and the facility with which a softened
upper epiph.ysial line of tlie tibia may give way, must never be forgotten. Erasion and excision.
— The extent and comphcations of the synovial membrane render attention to the following
points imperative: — (1) Free exposure of the joint usuaUy by an anterior curved incision, the
medial extremity of which must not damage the great saphenous vein. (2) The extent of the
pouch under the quadriceps, it may be for 5 cm. (2 in.) above the patella, and the lateral recesses
under the vasti. The pouches at the back of the joint are far more difficult to deal with, viz.,
the partial covering of the posterior crucial ligament, the proximity of the popliteal artery,
the pouches in relation to the popUteus, gastrocnemii, and back of the femoral condyles. In
erasion, the cartilage and bone, where diseased, are removed with a gouge. Owing to the
removal, in addition to the synovial membrane, of the fibro-cartilages, and crucial ligaments,
and the damage to lateral and patellar ligaments, there is a most obstinate tendency to flexion
afterward. In excision, to avoid injury to the epiphysis, the section of the femur should not
pass higher than through the upper third of the trochlear surface. Of the tibia, only 12 mm.
(J in.) should be removed.
Genu valgum. — Here the natural angle at which the femur inclines medially to the tibia
is increased. As shown by the late v. Mikulicz, this is due to an abnormal growth downward
of the medial part of the femoral diaphysis, the epiphysial line being gradually altered from
one at right angles to the shaft to one which runs obliquely from without downward and medially.
The femur is not only elongated on its medial side, but bent at its lower end, the concavity of
the curve being lateral. Other changes have to be remembered. Pes valgus very commonly
coexists, and in the tibia there may be a compensatory curve, the concavity being medial,
in the lower third, or an analogous alteration in the line of the upper epiphysis may be present,
its direction being no longer at a right angle with the shaft, but obhque. In Sir W. Macewen's
supra-condyloid osteotomy, a longitudinal incision, about 3.7 cm. (IJ in.) long is made where
the following lines meet, viz., one transverse, a finger's breadth above the upper margin of the
lateral condyle, and one longitudinal, 1.2 cm. (J in.) in front of the adductor magnus tendon.
The bone is divided in front of the genu suprema and above the superior medial articular artery,
above the epiphysial line and behind the upward extension of the synovial membrane under the
quadriceps.
The following bursae about the knee-joint must be remembered. Some, it
will be seen, are much more constant than others : —
(
1450
CLINICAL AND TOPOGRAPHICAL ANATOMY
A. In front. — (1) One between the patella and skin, the bursa prepatellaris subcutanea
(fig. 1167); (2) a deeper one between the ligamentum patellse and the upper part of the tibia;
(3) between the skin and the lower part of the tuberosity of the tibia. This is not constant.
B. On the medial side. — (1) One between the medial head of the gastrocnemius and medial
condyle, often extending between the above muscle and the semi-membranosus. This is the
largest of the burs^ about the knee-joint, and, after adult life, usually communicates with the
knee-joint. But, owing to the narrow communication, it is rarely possible, when the parts are
relaxed by flexion of the joint, to empty the cyst. For its removal a straight incision is made
over the most prominent part of the swelling, its neck found by drawing aside the tendons. A
ligature is then pushed high up around the neck, and the cyst cut away. (2) One superficial
to the tibial (collateral) ligament, between it and the tendon of the sartorius, gracilis, and semi
Fig. 1167. — Vertical Section op the Knee-joint in the Anteeo-posterior Direction.
(The synovial bursa usually present above the upper synovial cul-de-sac is not shown.)
(The bones are somewhat drawn apart.) (After Braune.)
M. vastus lateralis
M. vastus inter-
medius
Synovial cavity
Prepatellar bursa
Anterior crucial lig,
Lig. patella
M. gastrocnemius
M. tibialis post
tendinosus (3) One beneath the ligament, between it and the tendon of the semi-membrano-
sus. (4) One between the medial condyle of the tibia and the semi-membranosus. (5) One
between the semi-membranosus and semi-tendinosus. Of the above bursae, the first two alone
are constant. The second and third are often one bursa prolonged.
C. On the lateral side. — (1) One between the lateral head of the gastrocnemius and the
condyle; (2) one superficial to the fibular collateral ligament between it and the biceps tendon;
(3) one under the ligament between it and the popliteus tendon; (4) one between the popHteua
tendon and the lateral condyle of the femur. This is usually a diverticulum from the synovial
membrane.
The following explanations may be given of an inflamed knee-joint usually taking the
flexed position: — -(1) By experimental injections, Braune found that the capacity of the synovial
sac reaches its maximum with a definite degree of flexion, i. e., at an angle of twenty-five degrees.
THE POPLITEAL SPACE
1451
(2) As the same nei-ves supply the synovial membrane and the muscles which act upon the
joint, reflex spasm of the flexors will help to explain the flexed position. (HQton.)
Anastomoses around the front and sides of the knee-joint. — The most impor-
tant of these take the form of three transverse arches. (1) The highest passes
through the quadriceps fibres just above the upper edge of the patella. It is
formed by a branch from the deep division of the genu suprema (anastomotica
magna) and one from the lateral circumflex and superior lateral articular. The
middle and lowest arches lie under the ligamentum patellte. (2) The middle arch,
formed by branches from the genu suprema and superior medial articular on the
medial side, and the inferior lateral articular, on the lateral, runs in the fatty tissue
Fig. 1168. — Side View of the Popliteal Artebt.
(From a dissection in the Hunterian Museum.)
Femoral artery and
Branches of the med
cutaneous
Sartoriu
Genu suprema artery
Vertical fibres of the
adductor magnus —
Popliteal artery
Vastus medialis
Cut edg.^ of fascia lata
close to the apex of the patella. (3) The lowest arch lies on the tibia just above
its tuberosity, and results from the anastomosis of the recurrent tibial and
the inferior medial articular. Seven arteries thus take place in this series of
anastomoses.
POPLITEAL SPACE
In flexion, the hollow of this space appears; in extension it is obliterated and
its boundaries are ill-defined the only ones now to be made out being the semi-
tendinosus and the biceps.
Popliteal tendons. — When the knee is a little bent and the foot rests on the ground, the
following can be made out:— on the lateral aspect, behind the ilio-tibial band, and descending to
the prominence on the lateral side of the head of the fibula, is the tendon of the biceps. This
i
1452
CLINICAL AND TOPOGRAPHICAL ANATOMY
prominence also gives attachment to the fibular collateral ligament, which splits the tendon
into two parts. IJehind is the apex (styloid process) from which the posterior part of the
fibular collateral ligament arises. Parallel and close to the medial border of the tendon, the
peroneal nerve descends, as a rounded cord, to cross the neck of the fibula and enter the peroneus
iongus. In tenotomy of the biceps an open incision should be employed to avoid injiary to
the nerve and insure the division of any contracted fascial bands. On the medial side the ten-
dons are thus arranged: Nearest to the middle of the popliteal space is the long and more slender
tendon of the semi-tendinosus; next, the thicker tendon of the semi-membranosus; this and the
gracilis, which comes next, appear as one tendon, but by a little manipulation the finger can be
made to sink into the interval between the semi-membranosus, with its thick rounded border
laterally and the gracilis medially. The sartorius can easily be thrown into relief on the medial
side of the joint by telling the patient to raise the leg extended, the limb being rotated laterally
and one leg crosses over the other.
Popliteal vessels. — The artery traverses this space from above downward,
appearing beneath the semi-membranosus, a little to the medial side of the middle
line, and then passing down in the centre of the space to the interval between the
gastrocnemii. Its course corresponds with a line drawn from the medial side of the
Fig. 1169. — Deep View of the Popliteal Space. (Hirsohfeld and LeveiM.)
Adductor magnus
Popliteal vein
Popliteal artery
Tibial nerve
Vastus medialis
Superior medial articular artery
Tendon of semi-membranosuE
Medial h.
Inferior r
ad of gastrocnenuus
ledial articular artery
Popliteal vein
Popliteus
Tendon of plantaris
Vastus lateralis
Sciatic nerve
Short head of biceps
Peroneal nerve
Long head of biceps, cut
Lateral head of gastrocnemius
Lateral cutaneous crural nerve
Gastrocnemius
Small saphenous vein and
hamstrings to the centre of the lower part of the space. The artery bifurcates on
the level of a line corresponding to the tuberosity of the tibia. It lies on the pop-
liteal surface of the femur, the oblique popliteal ligament and the popliteus. It
is the second of these structures which usually prevents popliteal aneurism and
abscess from making their way into the joint.
The popliteal vein, intimately adherent to the artery, lies to the lateral side above, but
crosses to its medial side below. The popliteal sheath is also unusually strong. The tibial
nerve crosses the artery in the same direction as the vein, by which it is separated from the
artery. This nerve is the direct continuation of the sciatic nerve (fig. 1 169), and enters more into
the space than its fellow branch. The close relation of the vein and nerve explains the early
stiffness of the knee, the pains below, often called 'rheumatic,' and the oedema, in popliteal
aneurism; also the pulsation of swelUngs not aneurismal.
The superior articular arteries (fig. 1169) course laterally and medially immediately above
the femoral condyles; the way in which they cUng closely to the bone here is one provision to pre
vent overstretching of the artery; the inferior ones lie j ust above the head of the fibula and below
the medial condyle of the tibia (fig. 1169). The deep part of the genu suprema artery runs in
front of the tendon of the adductor magnus; the superficial with the saphenous nerve.
The popliteal artery may be ligatured — (A) Behind, in the upper part of the popHteal
space, just after its emergence from under the semi-membranosus. Here, for a short space
THE LEG 1453
of about 2.5 cm. (1 in.), the vessel is comparatively superficial after division of the fasciae. The
nerve is generally seen first, and, with the vein, must be drawn laterally. The needle should be
passed from the vein. (B) From the front, at the medial side. The thigh being flexed, ab-
ducted, and rotated laterally, a free incision is made parallel and just behind the adductor
magnus tendon, commencing at the junction of the middle and lower third of the thigh. The
sartorius and the hamstrings are drawn backward, and the adductor magnus forward. Care
must be taken of the genu suprema (fig. 1168). The space between the hamstrings and the
adductor magnus being carefully opened up, the artery will be found in fatty areolar tissue.
The vein and tibial nerve are on the lateral side of the vessel. The needle is passed in latero-
medially. The collateral circulation (fig. 1156) depends chiefly on the genu suprema.
The small saphenous vein perforates the roof of the popliteal space in its lower part. As
a rule, it is not visible, unless enlarged.
The popliteal nodes are not to be felt unless enlarged.
Bursse in the popliteal space. — These have been already spoken of (p. 1449).
THE LEG
The skin. — The proneness of the skin to dermatitis in the lower third of the
medial and front aspect of the leg as a result of varicose veins is well known. The
close contiguity of the periosteum to the skin here accounts for the difficulty in
healing chronic ulcers whose callous base has become fixed to the periosteum, and
the frequency with which the upper fragment of a fractured tibia perforates the
skin.
Bony landmarks. — From the tuberosity (tubercle) of the tibia descends the
anterior border or 'shin. ' This soon becomes sharp, and continues so for its upper
two-thirds ; in the lower third it disappears, to be overlaid by the extensor tendons.
It is curved somewhat laterally above and medially below. The medial border can
also be felt from the medial condyle to the medial malleolus. Between these two
borders lies the medial surface, subcutaneous save above, where it is covered by
the three tendons of insertion of the gracilis and semi-tendinosus, and, overlying
them, that of the sartorius. The tibia is narrowest and weakest at the junction of
the middle and lower thirds, the most common site of fracture. Behind the
medial malleolus, part of the groove for and the tendon of the tibialis posterior can
be felt.
The head of the fibula can be felt distinctly, but the shaft soon becomes buried
amongst muscles till about 7.5 cm. (3 in.) above the lateral malleolus, where the
bone expands into a large triangular subcutaneous surface.
This lies between the peroneus tertius and the other two peronei. The peroneus longus
overlaps the brevis, especially in the upper two-thirds of the leg. In the lower thii'd the brevis
tends to become anterior (fig. 1173). Behind the lateral malleolus these tendons descend to the
foot in a groove on its posterior border. The shaft of the fibula is placed on a plane posterior
to that of the tibia, and curves backward in a du-ection reverse to that of the tibia.
Muscular compartments and prominences. — When the muscles of the leg are
thrown into action by dorsi-flexion and plantar flexion of the foot or by standing
on the toes, several groups of muscles stand out on the surface, owing to certain
compartments, and the origin of certain muscles from, and their separation by, the
deep fascia, which knits the surface into corresponding elevations and depressions.
The bones and the two peroneal septa divide the leg into four compartments.
These are, medio-laterally : — (1) A medial, corresponding to the medial sm-face of the tibia.
(2) An anterior, between the crest of the tibia and the anterior peroneal septum, attached
to the antero-lateral border of the fibula, and separating the extensors from the peronei. Its
surface-marking would be a line from the front of the head of the fibula to the front of the
lateral malleolus. In this anterior compartment lie the extensor muscles and origin of the
peroneus tertius, and the anterior tibial vessels and nerves. (3) A lateral or peroneal com-
partment, lying between the anterior and posterior peroneal septum, the latter being attached
to the postero-lateral border of the fibula, and separating the peronei from the calf and deep
flexors. This peroneal compartment, a narrow one, contains the two chief peronei and the
peroneal (external popUteal) nerve and its three divisions. (4) Much the largest, this, the
posterior, lies between the posterior peroneal septum and the medial border of the tibia, and
contains the calf and deep flexor muscles, the' posterior tibial vessels and nerves, and the
peroneal artery and its posterior branch.
The space between the tibia and fibula in front is mainly occupied by the fleshy belly of the
tibialis anterior; lateral to this, and much less prominent, is the narrower extensor digitorum
longus; lateral to this, again, are the peronei longus and brevis. Lower down, in an
interval between the tibialis and the extensor of the toes, the extensor hallucis, here almost
entirely tendinous, comes to the surface. Behind, the prominence of the calf is mainl}' formed
by the gastrocnemius. On the patient's rising on tip-toe, the tendo Achillis starts into relief
{
1454
CLINICAL AND TOPOGRAPHICAL ANATOMY
from about the middle of the leg. Of the two heads of the gastrocnemius, the medial is seen
to be the larger. On either side of the tendon, but more distinctly on the lateral side, where it is
less overlapped by the gastrocnemius, the soleus comes into view. Its muscular fibres are
continued on the deep surface of the tendon to within a short distance of the heel. Between
the tendon and the upper part of the os calois is a bursa, oocasionaUy the seat of effusion, as
in gonorrhoea.
The bones. — Their relative position and curves have been mentioned (p. 1453). Access. —
That to the tibia is easy along the medial aspect. The fibula is best explored by a free incision
along the line of the posterior peroneal septum, which lies between the peronei and the muscles
at the back (p. 1453). The presence of the superficial peroneal (musculo-cutaneous) nerve per-
forating the deep fascia in the lower third below and that of the common peroneal (external
popliteal) in relation to the neck of the fibula above, must be remembered. Fractures. — When,
Fig. 1170. — Anastomoses op Tibial Arteries.
J
Anterior tibial recurren
Posterior tibial, giving off muscular and
medullary branches
Anastomosis of medial malleolar of — (l_\
anterior tibial with posterior medial
malleolar
Medial calcanean
Medial and lateral plantar
Popliteal
Anterior tibial, giving off posterior tibial
recurrent and superior fibular before
piercing interosseous membrane and
anterior tibial afterward
Lateral malleolar of anterior tibial
joining posterior peroneal
as is most frequent, the tibia gives way from indirect violence, the fracture is usually at the
weakest spot, or the junction of the middle and lower thirds. The line of obliquity is generally
marked, and from above downward and forward. The lower fragment, pulled upward by the
powerful calf muscles, rides behind the upper, which projects forward under the skin. The
fibula, bending more than the tibia, snaps at a higher level. Tenderness on pressure is the best
guide here, as it is in suspected fractures of the upper tibia, transverse from direct violence.
The most common variety of fracture of the fibula is that called after Pott, complicated with
displacement of the foot. Here, from abduction of the foot, a severe strain is thrown upon the
deltoid ligament, which gives way; the talus (astragalus) is pressed against the lateral malleolus,
and the inferior tibio-fibular ligaments resisting, the fibula yields 5 to 7 cm. (2 to 3 in.) above the
anlde, the upper end of the lower fragment being usually displaced toward the tibia. If the
deltoid ligament is strong, the strain often tears off the medial malleolus. The medial margin
of the foot is turned toward the ground, the lateral raised. The foot is also displaced backward.
On the medial side of the ankle there is a marked projection of the lower end of the tibia; higher
THE LEG
1455
up, on the lateral side, a depression where the fibula is broken. The need of replacing the^foot
and the weight-bearing talus (astragalus) accurately, the fact that the ankle-joint is opened and
the numerous tendons iikety to be matted are the chief points to bear in mind. In Dupuytren^s
fracture there is not only fracture of the lower end of the fibula, but the inferior tibio-fibular
ligaments are now torn. The foot is displaced upward and laterally, together with the lower
Fig. 1171. — The Anterior Tibial Artery, Dorsal Artery of the Foot, and Perforating
Branch of the Peroneal Artery, and Their Bbanches.
Superior medial articular artery
Inferior medial articular artery
Anterior tibial recurrent artery
Anterior tibial artery
Tibialis anterior muscle
Deep peroneal nerve
Extensor hallucis longus
Medial malleolar artery
Crucial ligament-
Dorsalis pedis artery.
Innermost tendon of extensor digi-
torum brevis
Deep plantar branch
First dorsal metatarsal artery
Superior lateral articular artery
Inferior lateral articular artery
—Extensor digitorum longus
Perforating peroneal artery
Lateral malleolar artery
Peroneus brevis muscle
Extensor digitorum brevis, cut
Arcuate branch
Dorsal metatarsal artery
end of the fibula. Epiphyses.—The upper one of the tibia appears shortly before birth and
includes the condyle and tuberosity. It does not fuse with the shaft till the age of twenty or
later. This fact and the powerful strain of the rectus on this epiphysis explain the obscure
pain sometimes complained of in young adults much given to atliletics, over the tibial tuberosity.
The lower epiphysis, including the medial malleolus, appears in the second and joins about the
eighteenth year. Separation here is not very uncommon up to puberty. In osteotomy of the
i
1456
CLINICAL AND TOPOGRAPHICAL ANATOMY
tibia, simple or cuneiform, when the curve is antero-posterior as well as lateral, the close vicinity
of the tibiaUs anterior tendon to the lateral border of the crest must be remembered, and when
the fibula does not yield to careful force, it, also, must be divided, or damage may be done to
the superior and inferior tibio-fibular Ugaments, or to the epiphyses of the bones.
Fig. 1172. — The Superficial Veins and Lymphatics of the Left Lower Limb.
Superficial lymphatics from
lateral wall of abdomen
Superficial lymphatics from
lower and anterior walls
of abdomen
Superficial epigastric vein'
Common femoral vein
Superficial subinguinal lym-
phatic nodes
External pudendal veir
Accessory saphenous vein
Great saphenous vein
>
Medial malleolus
Dorsal venous arch
Superficial inguinal lym-
phatic glands
Superficial circumflex
iliac vein
Vessels. — The saphenous veins should be carefully traced, owing to the tend-
ency of these and their branches to become varicose. The great saphenous
THE LEG
1457
(figs. 1158, 1172), having passed from the arch on the dorsum over the medial
malleolusjf'runs up close to the medial border of the tibia, where it is to be avoided
*in ligature of the posterior tibial, to the back of the medial condyle; here this ves-
sel is to be remembered in operations on the knee-joint; then upward along the
thigh, over the roof of the adductor (Hunter's) canal, to the fossa ovalis (saphe-
FiG. 1173. — Relations of the Popliteal Artery to Bones and Muscles.
Superior lateral articular artery •
Tibial nerve -
Fibular lateral ligament -
Inferior lateral articular artery .
Popliteus -
Muscular branch to soleus "
Soleu
Anterior tibial artery
Peroneus longus •
Peroneal artery ■
Branch of tibial nerve to flexor
hallucis longus
Flexor hallucis longus —^
Cutaneous branch of peroneal artery
Peroneus brevis .
Continuation of peroneal artery -
Superior medial articular artery
■ Popliteal artery
■ Posterior ligament of knee
Azygos articular artery
Semi -membrano SUB
- Inferior medial articular artery
- Muscular branch
. Tibialis posterior
■ Tibial nerve
Muscular branch of tibial nerve to
flexor digitorum longus
. Flexor digitorum longus
Posterior tibial artery
Tibialis posterior
Communicating branch
Laciniate ligament
Calcaneus ,
Internal calcaneal artery
nous opening) (p. 1440 and fig. 1172), where it joins the femoral by perforating
the cribriform fascia and the femoral sheath. Four to six valves are present
chieily in the upper part.
rpntJi'nf'?hrfh^°ul^''?u'' °''-f^^ ^? T^^'^'^ thrombosis is most Hkely to occm-, reaches from the
h»?„ ,f fi I ^u *° t'^l^i'ldle of the leg. (Bemiett.) The saphenous nerve joins the vein
below the knee, having been under the sartorius above this point (fig. 1159 and 1160) The
i
1458
CLINICAL AND TOPOGRAPHICAL ANATOMY
surface-marking of the upper part of the vein is a line drawn from the posterior border of the
sartorius or the adductor tubercle to the lower part of the fossa ovalis. The small saphenous
vein passes behind the lateral malleolus, runs upward over the middle of the calf, and joins the
popliteal by perforating the deep fascia in the lower part of the popliteal space. This vein is
accompained by the medial sural cutaneous (external saphenous) nerve throughout its course.
The popliteal artery bifurcates at the lower border of the popliteus, about on
a level with the tuberosity of the tibia. About 5 cm. (2 in.) lower down the pero-
neal artery comes off from the posterior tibial (fig. 1173).
The course of the posterior tibial corresponds with a line drawn from the centre
of the lower part of the popliteal space to a point midway between the tip of the
medial malleolus and the medial edge of the calcaneus.
In the lower third, the artery becomes more superficial, passing from beneath the calf
muscles, lying between the tendo Achillis and medial border of the tibia, and covered only by
the skin, deep fascia, and, lower down, by the laciniate (internal annular) ligament. It is here,
in its close relation to the tendons of the tibialis posterior and flexor digitorum longiis, that it
is liable to be injured in the older methods of tenotomy. The nerve is medial above, lateral
below (fig. 1173).
Ligature of the posterior tibial in the middle of the leg. — The following are the chief points
in the technique. An incision, 7.5 to 10 cm. (3 to 4 in.) long, is made 1.2 em. (J in.) behind the
Fig. 1174. — Upper Segment of a Section of the Right Leg in the Upper Third. (Heath.)
Tibialis anterior
Extensor digitorum longus
AAnterior tibial vessels and
deep peroneal nerve
Peroneus longus
Flexor hallucis longus
Soleus with fibrous intersection.
Gastrocnemius
Tibialis posterior
Flexor digitorum longus
Lateral sural cutaneous nerve
Small saphenous
Posterior tibial vessesls and tibial nerve
medial_border of the tibia, to avoid the trunk of the great saphenous. The deep fascia being
freely opened, the medial head of the gastrocnemius is drawn backward. The tibial attachment
of the soleus, thus exposed, is out through carefully, so as to allow of identification of its central
membranous tendon, which must not be confused with the deep intermuscular septum over
the flexor. Any sural vessels are now tied. The above-mentioned special septum is next
made out, passing between the bones (vertical Une descending from oblique hne of tibia and
oblique line of fibula). On division of this septum the nerve usually comes into view, the artery
lying more laterally. The needle is passed from the nerve; the vense comitantes may be in-
cluded. The muscles should now be fully relaxed by flexion of knee and plantar flexion of foot.
The ligature will be placed below the peroneal artery.
The course of the anterior tibial artery corresponds with a line drawn from a
point midway between the lateral condyle of the head of the tibia and the head of
the fibula to one on the centre of the ankle-joint.
This line corresponds to the lateral border of the tibialis anterior and the interval between it
and the extensor digitorum longus (figs. 1170 and 1171). This is shown when the first of these
muscles is thrown into action. The accompanying nerve is in front in the middle third of the
leg, lateral above and below.
Ligature of the anterior tibial artery at the junction of the upper and middle thirds of the
leg. The limb being flexed and rotated medially, an incision is made, 7.5 to 10 cm. (3 to 4 in.)
long, in the line of the artery, distant 2.5 cm. (1 in.) or more (according to the size of the leg)
from the crest, and beginning about 5 cm. (2 in.) below the head of the tibia. If, on exposure
of the deep fascia, the intermuscular septum between the tibialis and long extensor of the toes
THE ANKLE 1459
is not well defined, the fascia must be freely slit up in the line of the artery, and the sulcus felt
for. A small muscular artery may lead down to the trunk. The foot is now dorsiflexed and the
artery sought for deep on the interosseous membrane. The nerve should be drawn to the
outer side. The venas comitantes may be included in the ligature.
In senile gangrene the liabiUty of the tibial arteries to disease and consequent thrombosis
and interference with the collateral cu-eulation accounts both for the extension of the disease
and the difficulty in detecting pulsation.
The peroneal artery, given off from the posterior tibial about an inch below
the popliteus, or two inches below the head of the fibula, runs deeply along the
medial border of this bone, covered by the flexor hallucis longus, the nerve to
which accompanies the vessel.
It gives off the anterior peroneal, through the interosseous membrane, to the front of the
lateral malleolus about an inch above the level of the ankle-joint. Its continuation, as the pos-
terior peroneal, runs behind the malleolus, to join the anastomosis about the ankle-joint.
Tlie nutrient artery of the tibia arises from the posterior tibial near its commencement. It
is the largest of all the nutrient arteries to the shafts of long bones; that for the fibula comes from
the peroneal.
As a general rule, in amputation 2.5 cm. (1 in.) below the head of the fibula, only one main
artery — the popliteal — is divided. In amputations 5 cm. (2 in.) below the head of the fibula,
two main arteries — the anterior and posterior tibials — are divided. In amputations 7.5 cm.
(3 in.) below the head, three main arteries — the two tibials and the peroneal — are divided.
(Holden.)
In an amputation through the middle of the leg, the anterior tibial artery would be found
cut on the interosseous membrane between the tibialis anterior and the extensor hallucis longus,
the deep peroneal nerve here lying in front of the vessel. The posterior tibial would be between
the superficial and deep muscles at the back of the leg lying on the tibialis posterior, its nerve
being to the lateral side. The peroneal would be close to the fibula in the flexor hallucis longus.
The superficial peroneal (musculo-cutaneous) nerve, having passed through
the peroneus longus and then between the peroneus longus and peroneus brevis,
perforates the deep fascia in the lower third of the leg in the line of the septum
between the peronei and extensors. Directly after, it divides into its two terminal
branches.
Amputation of the leg. — To give one instance only, amputation 'at the seat of election,
or a hand's-breadth below the knee-joint, will be alluded to. Lateral skin-flaps and circular
division of the muscles give an excellent result in hospital practice where the various conditions
which call for such a step are usually met with. The above name was given because the pressure
of the body is well carried on the prominences about the knee-joint, especially the tuberosity
of the tibia, when the patient walks with the knee flexed on a 'bucket' artificial limb. Thus the
scar, being central, is here not of importance. Two broadly oval lateral flaps of skin and fasciae
are raised, and the remaining soft parts severed down to the bones with circular sweeps of the
knife. In sawing the bone, the smaller size of the fibula and its position behind the tibia must
be remembered. It is well, in order to ensure complete division of the fibula first, to roll the
limb well over on its medial side, and place the saw well down on the lateral side. The parts
cut thi'ough are shown in fig. 1174.
THE ANKLE
Bony landmarks. — The following are the differences between the two malleoli :
The medial is the more prominent, shorter, and is placed more anteriorly than the
lateral, being a little in front of the centre of the joint. The lateral descends
lower by about 1.2 cm. (| in.), and thus securely locks in the joint on this side;
it is opposite to the centre of the ankle-joint, being placed about 1.2 cm. (| in.)
behind its fellow.
Owing to the lateral malleolus descending lower than the medial, in Syme's and Pirogoff's
amputations the plantar incision should run between the tip of the lateral malleolus and a point
1.2 cm. (J in.) below that of the medial one. When a fracture is set, or a dislocation adjusted,
the medial edge of the patella, the medial malleolus, and the medial side of the great toe are
useful landmarks and should be in the same vertical plane, regard being paid at the same time
to the corresponding points in the opposite limb. (Holden.)
On the posterior aspect of the medial malleolus is a groove for the tibialis pos-
terior and flexor digitorum longus, the first named being next the bone. The tip
and borders of the process give attachment to the deltoid ligament. The anterior
border and tip of the lateral malleolus give attachment to the anterior talo-fibular
and calcaneo-fibular ligaments respectively, the posterior talo-fibular arising from
a pit behind and below the articular facet. The posterior border is grooved for
the two peronei. The line of the ankle-joint corresponds to one about 1.2 cm.
(I in.) below the tip of the medial malleolus drawn across the anterior aspect.
{
1460
CLINICAL AND TOPOGRAPHICAL ANATOMY
Effusion or tuberculous thickening shows itself first in front, between the medial malleolus
and tibialis anterior and between the peroneus tertius and lateral malleolus and then behind,
where it fills up the hollow between the tendo Achillis and the two malleoli. Owing to the thin-
ness of the transverse crural (anterior) ligament, the extensor sheaths are easOy affected in
neglected tuberculous disease. Owing to the way in which the joint is locked in, it is not easy
to open and drain an infected ankle-joint satisfactorily. Removal of a portion of the lateral
Fig. 1175. — Branches of the Common Peroneal Nerve.
Common peroneal nerve'
Recurrent articular'
Superficial peroneal
Branch to peroneus longus-
Branch to extensor,
digitorum longus
Branch to peroneus brevis
Superficial peroneal-
Intermediate dorsal cutaneous-
Lateral dorsal cutaneous"
Deep peroneal nerve
Anterior tibial artery
Tibialis anterior
Deep peroneal nerve
Medial dorsal cutaneous
Deep peroneal (lateral division)
— Deep peroneal (medial division)
malleolus subperiosteally, leaving the tip and calcaneo-fibular, will admit of the insertion of a
tube and good drainage if the foot is so slung as to keep its lateral aspect dependent.
Tendons. — (A) In front of ankle. — ^Latero-medially are — (1) The tibialis
anterior, the largest and most medial. This tendon appears in the lower third of
the leg, lying just under the deep fascia, close to the tibia; then, crossing over the
THE ANKLE
1461
lower end of this and the ankle-joint, it passes over the medial side of the tarsus,
to be inserted into the medial and lower part of the first cuneiform and the ad-
jacent part of the first metatarsal. (2) The extensor hallucis longus. This ten-
don, concealed above, appears low down in a line just lateral to the last, and then,
crossing over the termination of the anterior tibial vessels and nerves (to which
its muscular part lies lateral), it descends along the medial part of the dorsum to
be inserted into the base of the last phalanx of the great toe. (3) and (4) The
extensor digitorum longus and peroneus tertius enter a common sheath in the
transverse crural ligament. The former then divides into four tendons, which
Fig. 1176. — Lateral View op the Ankle Region, as Shown by the ROntgbn-rats
run to the four lateral toes. The peroneus tertius is inserted into the upper
surface of the base of the fifth (often also the fourth) metatarsal bone.
(B) Behind. — The tendo Achillis, the thickest of all tendons, begins near the
middle of the leg, in the junction of the tendons of the gastrocnemii and, a little
lower, (p. 1453) the soleus. Very broad at its commencement, it gradually nar-
rows and becomes very thick. About 3 . 7 cm. (1| in.) from the heel, or about the
level of the medial malleolus, is its narrowest point. After this it again expands
sHghtly, to be inserted into the middle of the back part of the calcaneus. The
long tendon of the plantaris runs along its medial side, to blend with it or to be at-
tached to the calcaneus. On either side of the tendo Achillis are well-marked
{
1462
CLINICAL AND TOPOGRAPHICAL ANATOMY
furrows below. Along the medial, the tendon of the tibialis posterior and the
posterior tibial vessels and nerve come nearer the surface. Along the lateral,
the small saphenous vein (more superficially) ascends from behind the lateral
malleolus.
(C) On the medial side. — The tendon of the tibialis posterior, which has pre-
viously crossed from the interspace between the bones of the leg to the medial side,
lies behind the inner edge of the tibia above the medial malleolus, then behind this,
being here under the flexor digitorum longus, the two tendons having become super-
ficial on the medial side of the ten do Achillis. It then passes forward over the
deltoid and under the laciniate (internal annular) ligament between the medial
malleolus and the sustentaculum tali, and then below and close to the plantar cal-
FiG. 1177. — Horizontal Section through the Lower Part of the leg. (After Braune.)
Deep peroneal n.
Ant. tibial vessels
M. extensor digitorum com.
Tendon of peroneus longus
M. peroneus brevis
M. flexor hailucis longus — \
Sural nerv
Tendon of ant. tibial
M extensor hailucis longus
Tendon of post, tibial
Tendon of flexor longus digitorum
Tendo calcaneus (Achillis)
caneo-navicular ligament {vide infra) , and so to its insertion, by numerous slips,
into the tarsus and metatarsus, especially the tuberosity of the navicular. The
tendon of the flexor hailucis longus cannot be felt. Having passed medially from
the fibula, it crosses the lower end of the tibia in a separate furrow, then grooves
the backof the talus, and passes under the sustentaculum tali on its way to its
insertion.
The arrangement of the structures at the medial ankle from above downward, and medio-
laterally, is as follows (fig. 1177): — tibialis posterior, flexor digitorum longus, companion vein,
posterior tibial artery, companion vein, tibial nerve, flexor hailucis longus. The tibiales pos-
terior and anterior turn the sole mediaUy, antagonising the peronei. They also bear a large
THE ANKLE 1463
share in maintaining the longitudinal arch of the foot. The flexors not only act upon the toes,
but aid the calf muscles in straightening the foot upon the leg in walking or standing upon tip-
toe; hence the value of educating them in cases of flat-foot.
(D) Tendons on the lateral aspect. — The tendons of the two peronei, which
arise from the fibula between the extensor digitorum longus and flexor hallucis
longus, pass behind the lateral malleolus, the brevis being nearer to the bone (fig.
1177). They then pass forward over the lateral surface of the calcaneus, sepa-
rated by the peroneal tubercle when present, and diverge.
The brevis — the upper one — passes to the projection at the base of the fifth metatarsal;
the longus, lying below the brevis on the calcaneus, winds round the lateral border of the foot,
grooving the lateral border and under surface of the cuboid. Finally, crossing the sole obliquely
forward and medially, it is inserted into the adjacent parts of the first cuneiform and the back
part and under surface of the first metatarsal. While in connection with the under surface of
the cuboid, this tendon is covered in by a sheath from the long plantar ligament, and often
contains a sesamoid bone. The two peronei evert the foot, as is seen in talipes valgus and in
fracture of the lower end of the fibula; the peroneus longus aids in the support of the arch of the
foot (p. 1466), and, by keeping the great toe on the ground, is important in the third stage of
walking, skating, etc.
Annular ligaments and synovial membranes of tendons. — These strap-like
bands of deep fascia, which serve to keep the above tendons in position, are three
in number, viz.: —
(A) Lateral. — This, the superior peroneal retinaculum, extends from the tip
of the lateral malleolus to the lateral surface of the calcaneus. It keeps the two
Fig. 1178. — Relations op Parts behind the Medial Malleolus. (Heath.)
Tendo Achillis
Tibialis posterior
Flexor digitorum longus
Cruciate Ugament 7^-i^ ' li'-f'CJ' ■ Posterior tibial artery
Tibialis posterior
Tibialis anterior
Tibial nerve
Fezor digitorum longus
peronei in place, and surrounds them behind the fibula in one sheath with a single
synovial sac, which extends upward into the leg for 3 . 7 cm. (1| in.), and sends two
processes into the two sheaths in which the tendons lie on the calcaneus. Farther
on, while in relation with the cuboid, the peroneus longus has a second synovial
sheath.
(B) Medial. — This, the laciniate ligament, crosses from the medial malleolus
to the medial surface of the calcaneus. Beneath it are the following canals : — (1)
For the tibialis posterior. This tendon-sheath is lined by a sj^novial membrane
extending from a point 3.7 cm. (1| in.) above the malleolus to the navicular. (2)
For the flexor digitorum longus. The synovial sheath of this tendon is separate
from that of the closely contiguous tibialis posterior. It extends upward into the
leg about as high as the sheath just given. It reaches down into the sole of the
foot; but where the tendon subdivides to enter the thecse, each of these is lined by
a separate synovial sheath. Next comes (3) a wide space for the posterior tibial
vessels and nerve; and, lastly, (4) a canal, like the other two, with a separate
synovial sheath, for the tendon of the flexor hallucis longus. The lower margin of
this annular ligament gives an attachment to the abductor hallucis and blends
with the plantar fascia. The medial calcaneal vessels and nerve perforate the
ligament.
\
1464 CLINICAL AND TOPOGRAPHICAL ANATOMY
(C) Anterior annular ligament. — This is a double structure. (1) Upper
(transverse crural ligament), above the level of the ankle-joint, and tying the
tendons down to the lower third of the leg, passes transversely between the ante-
rior crest of the tibia and fibula. Here is one sheath only, with a synovial mem-
brane for the tibialis anterior. (2) Lower, over the ankle-joint. This band, the
cruciate ligament, is arranged like the letter -<, placed thus. It is attached by its
root to the calcaneus, and by its bifurcations to the medial malleolus and plantar
fascia.
This arrangement of the branches of this ligament is not constant. In this, the lower
annular ligament, there are usually three sheaths with separate synovial membranes — the
most medial (the strongest in each) for the tibialis anterior, the next for the extensor halluois
longus, and the third common to the extensor communis and peroneus tertius. The extensor
digitorum brevis has a partial origin from this ligament.
Points in tenotomy and guides to the tendons. — The tendo Achillis should be divided
about 3.7 cm. (If in.) above its insertion, its narrowest point, which is about on a level with the
medial malleolus. The knife should be introduced on the medial side and close to the tendon,
so as to avoid the posterior tibial artery (fig. 1178).
The tibialis anterior may be divided about 25 mm. (1 in.) above its insertion into the first
cuneiform, a point which is below the level of its synovial sheath. The tendon has here the
dorsalis pedis on its lateral side, but separated by the tendon of the extensor hallucis longus.
The knife is introduced on this side.
The tibialis posterior. — The usual rule for dividing this tendon is to take a spot 5 cm.
(2 in.) above the medial malleolus, and as accurately as possible midway between the anterior
and medial borders of the leg. This point will give the medial margin of the tibia, in close ap-
position to which the tendon is lying, and is a point at which the tendon is rather farther from
the artery than it is below, and is also above the commencement of its synovial sheath. A
sharp-pointed knife is used first to open the sheath freely, and then a blunt-pointed one to
divide the tendon. The flexor digitorum longus is usually cut at the same time.
Owing to the risk of injury to the posterior tibial vessels, the difficulty of ensuring division
of the tendons, the following open method is, nowadays, superior, being more certain, and ad-
mitting of division of ligaments, e. g., talo-navicular and anterior part of deltoid (syndesmotomy
of Parker), which are always contracted in advanced talipes equino-varus. A V-shaped flap
with its apex over the first metatarsal bone, and its two limbs starting, the lower below the
margin of the plantar fascia on a line with the medial malleolus, the upper from a point over
the head of the talus, is turned backward. The plantar fascia is divided, the tibiaUs anterior is
found, near its insertion, under the upper hp of the wound, the tibialis posterior and the flexor
digitorum longus in the lower, the former close to the navicular. If necessary, the calcaneo-
and talo-navicular and anterior part of the deltoid ligaments can be divided also.
Peronei. — The peronei longus and brevis may be divided 5 cm. (2 in.) above the lateral
malleolus, so as to be above the level of their synovial sheath. The knife should be inserted
very close to the bone, so as to pass between the fibula and the tendons. Division below the
ateral malleolus by a small flap is easier.
THE FOOT
Bony landmarks. — The following are of the greatest practical importance
owing to the operations which are performed upon the foot.
(A) Along the medial aspect of the foot are the following :■ —
(1) Medial tuberosity of the calcaneus; (2) medial malleolus; (3) 2.5 cm.
(1 in.) below the malleolus, the sustentaculum tali; (4) about 2.5 cm. (1 in.) in
front of the medial malleolus, and a little lower, is the tuberosity of the navicular,
the medial guide in Chopart's amputation, the gap between it and the susten-
taculum being filled by the calcaneo-navicular ligament and the tendon of the
tibialis posterior, in which there is often a sesamoid bone; (5) the first cuneiform;
(6) the base of the first metatarsal; and (7) the head of the same bone, with its
sesamoid bones below. (Holden).
(B) Along the lateral aspect are : — (1) The lateral tuberosity of the calcaneus;
(2) the lateral malleolus; (3) the peroneal tubercle of the calcaneus (when pres-
ent), 2.5 cm. (1 in.) below the malleolus, with the long peroneal tendon below it,
and the short one above; (4) the projection of the anterior end of the calcaneus,
and the calcaneo-cuboid joint, midway between the tip of the lateral malleolus and
the base of the fifth metatarsal bone; (5) the base of the fifth metatarsal bone; (6)
the head of this bone. The greater process of the calcaneus and the muscular
origin of the short extensor lie between the peroneus brevis and tertius.
Levels of joints and lines of operations. — The line of the ankle-joint has been given at
p. 1459. That of the talo-calcaneal joint — the limited lateral movements of the foot take
place here and at the medio-tarsal joint — corresponds, on the lateral side, to a point a little in
front of the lateral malleolus and midway between it and the peroneal tubercle; on the medial
THE FOOT
1465
side, to one just above the sustentaculum tali. In Syme's amputation through the ankle-joint,
the incision starts from the tip of the lateral malleolus, and is then carried, pointing a little back-
ward toward the heel, across the sole to a point 1.2 em. (i in.) below the medial malleolus.
The chief supply to the heel-flap is from the medial calcaneal. Care should be taken to divide
the posterior tibial below its bifurcation and not to prick this vessel afterward.
In Pirogoff's amputation the incision begins and ends at the same points, but is carried
straight across the sole. In each amputation the extremities of the above incision are joined
by one going directly across the ankle-joint, which lies about 1.2 cm. (5 in.) above the tip of the
internal malleolus.
In Chopart's medio-tarsal amputation, which passes between the talus and the navicular
on the medial side, and the calcaneus and the cuboid on the lateral, the line of the joints to be
opened would be one drawn across the dorsum from a point just behind the tuberosity of the
navicular to a point corresponding to the calcaneo-cuboid joint, just midway between the tip
of the lateral malleolus and the base of the fifth metatarsal bone. The convexity of the plantar
flap should reach to a point 2.5 cm. (1 in.) behind the heads of the metatarsal bones. Owing
to the tendency of the unbalanced action of the calf muscles to tilt up the calcaneus and thus
thi'ow the scar down into the line of pressure, the powerful tibialis anterior tendon and those of
the extensors should be carefully stitched into the tissues of the sole flap.
In Lisfranc's, or Hey's, or the tarso -metatarsal amputation, the bases of the fifth and first
metatarsals must be defined. The first of these can always be detected, even in a stout 'or
swollen foot; on the medial side the joint between the first cuneiform and the first metatarsal
Fig. 1179. — Vektical Section through the Cuneiform and Cuboid Bones. (One-half.)
Dorsalis pedis vessels and nerve
Extensor hallucis longus
First cuneiform
Tibialis anterior
Second cuneiform
I Third cuneiform
, Extensor digitorum brevis
, Dorsal aponeurosis
I Cuboid
I Peroneus tertius
Abductor ballucus
Medial plantar vessels and nerve
Abductor hallucis
Flexor hallucis longus
Plantar fascia
Flexor digitorum longus
Abductor digiti quinti
Lateral plantar vessels and nerve
Tendon of peroneus longus
Flexor digitorum brevis
bone lies 3.7 cm. (IJ in.) in front of the navicular tuberosity. In opening the joint between the
second metatarsal and the middle cuneiform, its position (the base of the former bone projecting
upward on to a level 6 or 8 mm. (| or 5 in.) above the others), and the way in which it is locked
in between its fellows and the cuneiform bones, must be remembered. The convexity of the
plantar flap here reaches the heads of the metatarsal bones.
In marking out the flaps for the amputation of the great toe, the large size of the head of
the first metatarsal, and the importance of leaving this so as not to diminish its supporting
power and the treading width of the foot, and thus of marking out flaps sufficiently long and
large, must be borne in mind. The dorsal incision should begin 3.7 cm. (1| in.) above the web.
The line of the joint is a httle distal to the centre of the ball of the toe (fig. 1181). The sesa-
moid bones should be left, so as not to endanger the vitaUty of the flaps. In amputation of
the other toes, the line of their metatarso-phalangeal joints lies a full inch above the web.
Bursse and synovial membranes. — The synovial sheath of the extensor hal-
lucis longus extends from the front of the ankle, over the instep, as far as the meta-
tarsal bone of the great toe. There is generally a bursa over the instep, above, or
it may be below, the tendon.
There is often an irregular bursa between the tendons of the extensor digitorum longus
and the projecting end of the talus over which the tendons play. There is much friction here.
It is well to be aware that this bursa sometimes communicates with the joint of the head of the
talus. (Holden.) There is a deep synovial bursa between the tendo Achillis and the cal-
caneus. Numerous other bursie may appear over any of the bony points in the foot, especially
when they are rendered over-prominent by morbid conditions.
Synovial membranes. — In addition to that of the ankle-joint, there are six
synovial membranes in the tarsus, viz.: — (1) Talo-calcaneal, peculiar to these
i
1466
CLINICAL AND TOPOGRAPHICAL ANATOMY
bones; (2) talo-calcaneo-navicular, common to these bones and the navicular;
(3) between the calcaneus and the cuboid; (4) between the cuboid and the lateral
two metatarsals; (5) between the first cuneiform and the first metatarsal; (6) a
comphcated and extensive one, which branches out between the navicular and
cuneiform bones; between the cuneiforms; between the third cuneiform and the
cuboid ; between the second and third cuneiform and the second and third meta-
tarsal bones; and between the second and third and the third and fourth meta-
tarsal bones.
Fig. 1180. — Superficial Nerves in the Sole of the Foot. (Ellis.)
Abductor hallucis-
Flexor digitorum brevis'
Medial plantar nerva
Medial plantar artery.
Proper plantar digital
nerve to medial side
of hallux
Abductor minimi digiti
Lateral plantar artery
Lateral plantar nerve
Proper plantar digital
branches of the
lateral plantar
Proper plantar digital
branches of the
medial plantar
Dorsal artery. — The line of this is from the centre of the ankle-joint to the
upper part of the first interosseous space.
On its medial side is the tendon of the extensor hallucis longus ; on its lateral, the most medial
tendon of the extensor digitorum longus. It is crossed by the most medial tendon of the extensor
brevis. The origin of this muscle should be noted on the lateral and fore part of the calcaneus.
Cutaneous nerves (fig. 1182). — The sites of these, numerous on the dorsum
of the foot, are as follows: — The superficial peroneal (musculo -cutaneous) nerve,
having perforated the fascia in the lower third of the leg, divides into two chief
branches, medial and lateral, which supply all the toes save the lateral part of the
little, and the adjacent sides of the first and second. The deep peroneal becomes
cutaneous in the first space, and is distributed to the contiguous sides of the above-
THE FOOT
1467
mentioned toes. The sural nerve runs with the small saphenous vein below the
malleolus, and supphes all the lateral border of the foot and the lateral side of
the little toe. The saphenous nerve, coursing with the great saphenous vein in
front of the medial malleolus, supplies the medial border of the foot as far as the
middle of the instep. The cutaneous nerves to the sole (from the medial calcaneal,
medial, and lateral plantar) are shown in fig. 1180.
Plantar arteries. — The line of the medial would be one drawn from the bifur-
cation of the posterior tibial, or about midway between the tip of the medial mal-
leolus and the medial border of the heel, to the middle of the plantar surface of the
great toe. The course of the lateral plantar runs in a line drawn from the bifur-
cation, first obhquely across the foot to a point a little medial to the medial side of
the base of the fifth metatarsal, and thence obliquely across the foot till it reaches
the first space and joins with a communicating branch from the dorsal artery. It
thus crosses the foot twice. In the first part, it is more superficial, in the second
Fig. 1181. — Longitudinal Section of Foot. (One-third.) (Braune.)
Tendo AchiUis
Posterior tibial vessels ,
Talus and nerve
Kavicular
First cuneiform
Extensor hallucis longi
Flexor hallucis longus
Flexor hallucis brevis
Lumbricalis
Calcaneus
Abductor digiti (juinti
Lateral plantar vessels and nerve
Quadratus plantse
Flexor digitorum brevis Flexor digitorum communis
Medial plantar nerve
very deep ; it here forms the plantar arch, and is only separated from the bases of
the metatarsals by the interossei.
The anastomosing branches about the ankle-joint are shown in figs. 1170
and 1171.
Tarsal bones. — The chief surgical points about these is the frequency with which they are
diseased and their changes in taHpes. Frequency of disease. — This is explained, chiefly,
by their delicate structure and the fact that on the aspect in which they are most exposed to
injury the soft parts are scanty. Disease once started, often by slight injury, finds in the ter-
minal circulation of the parts, and the frequent want of rest, other contributing causes. The
numerous and complicated synovial membranes mentioned above explain the extension of the
disease. The calcaneus is the only bone in which mischief is likely to remain limited. The
presence of an epiphysis to this bone appearing about the age of ten and joining at puberty
is to be remembered as a starting-point of disease here. Talipes. — To take one instance, a case
of talipes equino-varus, of congenital origin and confirmed degree, the following are the chief
structural changes which should have been obviated and now have to be met, given briefly.
Calcaneus. — This is elevated posteriorly, and rotated so that its long axis is du"ected obliquely
medially. Talus. — The inclination of the neck medially is much increased, and the whole bone
protruded from the ankle-joint. According to some, the neck is increased in length. Navicular.
— This is displaced medially so that it articulates with the medial side of the head of the talus,
and its tuberosity may form a facet on the medial malleolus. Cuboid. — The dorsal surface of
this is displaced downward, and bears much of the pressure in wall^ing. Tendons. — Those
chiefly shortened are the tendo AchiUis and those of the tibials and flexor digitorum longus.
The tendo AchiUis is displaced medially. Ligaments. — Those on the lateral side are stretched,
those on the medial, especially the anterior part of the deltoid, the dorsal talo-navicular and the
plantar calcaneo-navicular ligaments are shortened. The plantar fascia is also shortened,
together with the abductor hallucis, which arises from it.
i
1468 CLINICAL AND TOPOGRAPHICAL ANATOMY ■
ARCHES OF THE FOOT
These are two — the longitudinal and the transverse.
(A) Longitudinal arch (fig. 1181). — This is by far the most important. Ex-
tent : From the heel to the heads of the metatarsal bones. The toes do not add
much to the strength and elasticity of the foot. (Humphry.) They enlarge its
area and adapt it to inequalities of the ground, are useful in climbing, and in
giving an impulse to the step before the foot is taken from the ground, in the third
stage of walking. Two pillars. — The late Professor Humphry laid stress on the
important differences between these two: — (1) Posterior pillar: This consists of
the calcaneus and hinder part of the talus, viz., only two bones in order to secure
solidity, and to enable the calf-muscles to act directly upon the heel, without any
of that loss of power which would be brought about by many moving joint-sur-
faces. (2) Anterior pillar: Here there are many bones and joints to provide (a)
elastic springiness, and (6) width. This anterior pillar may again be divided into
two: (a) A medial pillar, very elastic, consisting of the talus, navicular, three
cuneiforms, and three medial metatarsals. (6) A lateral, formed by the cuboids
and two lateral metatarsals. This is stronger and less elastic, and tends to but-
tress up the medial pillar. Keystone : This is represented by the summit of the
trochlear surface of the talus.
It differs from the keystones in ordinary arches in the following important particulars
(Humphry) : (a) in not being wedge-shaped; (6) in not being so placed as to support and receive
support from the two halves of the arch: in front the talus does fulfil this condition by fitting
into the navicular; behind, it overlaps the calcaneus without at all supporting it; (c) this arch
and the support of its keystone largely depend on ligaments and tendons; (d) it is a mobile
keystone : to give it chances of shifting its pressure, and so obtaining rest, its equilibrium is not
always maintained in one position.
(B) Transverse arch (fig. 1179). — This is best marked about the centre of the
foot, at the instep, along the tarso-metatarsal joints. This, as well as the longitu-
dinal arch, yields in walking, and so gives elasticity and spring.
Uses of the arches. — (1) They give combined elasticity and strength to the tread. Thus
they give firmness, free quickness, and dignity, both in standing and walking, instead of what
we see in their absence, viz., the lameness of an artificial limb, and the shufHing or hobbhng
which goes with tight boots, deformed toes, flat-foot, bunions, corns, etc.; (2) they protect the
plantar vessels, nerves, and muscles; (3) they add to man's height; (4) they make his gait a per-
fect combination of plantigrade and digitigrade, as is seen in man's walking, when he uses first
the heel, then all the foot, and then the toes. (Hiimphry.)
Maintenance of the arch. — (1) Plantar fascia. — -This is (a) a binding tie between the pillars
of the longitudinal arch; (6) it protects the structures beneath; (c) it is a self-regulating ligament
and protection. Thus, having a quantity of muscular tissue attached to its upper and back
part, is constantly responds by the contraction of this, to the amount of any pressure made upon
the foot. (2) Plantar calcaneo-navicular ligament. — This is a thick tie-plate of fibro-cartil-
aginous tissue, partly elastic, hence called the 'spring-ligament,' attached to the anterior margin
of the sustentaculum tali and under surface of navicular. It is thickest at its medial side, where
it blends with the anterior part of the deltoid ligament, and below, where the tibialis posterior,
passing into the sole, is in contact with the ligament and gives much support to the head of the
talus and the navicular, while it assists the power and spring of this ligament {vide infra). The
dropping of the talus and navicular and their projection on the medial side in flat-foot are largely
due to the giving way of the above ligament. (3) Calcaneo-cuboid ligaments, (o) Long;
(b) short. — 'These ligaments are the main support of the lateral, firm, and less elastic part of the
longitudinal arch. (4) Tibialis posterior. — The reason of this muscle having so many insertions
below is to brace together the tarsal bones, and to prevent their separation when, in treading,
the elastic anterior pillar tends to widen out. Of these numerous offsets, that to the navicular
is the most important. Thus it strengthens the calcaneo-navicular ligament by blending with
it, and thus supports the arch at a trying time. By coming into action when the heel is raised,
this tendon helps the calcaneo-navicular ligament to support the head of the talus, and to main-
tain the arch of the foot when the weight of the body is thrown forward on^to the instep. In
other words, the tibialis posterior comes into play just when the heaviest of its duties is devolving
upon this ligament, viz., when the heel is being raised, and the body-weight is being thrown
over the instep on to the opposite foot. (5) Peroneus longus. — This raises the lateral pillar,
and steadies the lateral side of the arch. Further, by its strong process attached to the first
metatarsal bone, it keeps the great toe strapped down firmly against the ground; thus, keeping
down the anterior pillar of the longitudinal arch, it aids the firmness of the tread. (Humphry.)
(6) Tibialis anterior. — This braces up the keystone of the arch. Thus, by keeping up the first
cuneiform, it maintains the navicular, and so indirectly the talus in situ.
Fig. 1172 will remind the reader of the arrangement of the superficial lym-
phatics of the lower extremity. These follow chiefly the saphenous veins, and
enter the inguinal nodes, except those from the lateral aspect of the heel which
THE LOWER LIMB
1469
drain into the popliteal lymph-nodes . The superficial lymphatics of the buttock
enter the lateral, and those over the adductor muscles the most medial group of
the inguinal glands.
The deep lymphatics of the lower limb, comparatively few in number, follow
the course of the deeper vessels. After passing through some four or five glands
deeply placed about the popliteal vessels (these glands also receive the lymphatics
along the small saphenous vein), the lymph is carried up by lymphatics along the
femoral artery to the deep inguinal nodes; one very often occupies the femoral
canal.
Fig. 1182 shows the distribution of the superficial nerves on both aspects of the
limb.
Fig. 1182.-
-DlSTRIBUTION OF CuTANEOUS NerVES ON THE POSTERIOR AND AnTEEIOB ASPECTS
OF THE Inferior Extremity.
Posterior
branches
of lumbar
nerves
Posterior
branclies
of sacral
nerves
Perforating
cutaneous of
fourth sacral
Perineal
branch of
posterior
cutaneous
Branch of
posterior
cutaneous
Obturator
Branch of
femoral
nerve
Twigs from
saphenous
Cutaneous
branch of
peroneal
Superficial
peroneal
Deep
peroneal
Paralysis of the nerves of the lower extremity. — Ttie student sliould take this opportunity
of considering from the surgical anatomy the results of paralysis of the nerve chiefly affected,
viz., the great sciatic and its branches. Sciatic: The limb hangs flail-like, much in the position
of one affected with advanced infantile paralysis. In addition to the results of paralysis of its
two divisions, flexion at the knee will be lost, owing to paralysis of the hamstrings. Peroneal
(external popliteal) nerve: The extensors and psronei being paralysed the foot drops, it cannot be
dorsiflexed at the ankle nor abducted at the medio-tarsal joint. Adduction at the latter joint
is impaired owing to paralysis of the tibialis anterior. The arch of the foot is largely lost owing
to paralj'sis of the peroneus longus. Slight extension of the two distal phalanges of the four
lateral toes is still possible by means of the interossei. Sensation is impaired over the distribu-
tion of the medial sural cutaneous deep, and superficial peroneal nerves. Tibial (internal
popliteal) nerve: Here the calf muscles, the flexors, and the muscles of the' sole of the foot are
paralysed. The ankle cannot be plantar-flexed.
i
INDEX
Bold-face type indicates the more complete descriptions
Abdomen, 1142
clinical anatomy of, 1370
landmarks of, 1370
lymphatic nodes of, 730
lymphatics of, 730
morphology of, 1144
muscles acting on, 503
regions, 1142, 1370
Abdominal aorta, 690, 1382, 1408
branches, 591
aortic plexus of nerves, 1045
branches of vagus, 958
fossaj, 430
(inguinal) rings, 429, 430, 1371, 1394, 1396
portion of ureter, 1248
wall, lymphatics in^ 733
superficial veins m, 683
Abducens, 934
nucleus of, 826
Abduction, 321
Abductor acoessorius digiti quinti, 499
digiti quinti (foot), 454, 498
(hand), 404
hallucis, 496
longus, 482
ossis metatarsi quinti, 499
pollicis brevis, 406, 407
longus (extensor ossis metacarpi pollicis),
392, 393
Aberrant artery of aorta, 590
spinal ganglia, 965
Abnormalities (see individual organs).
Aocessorius ad fiexorem digitorem profundum,
402
of gluteus minimus, 462
(ilio-costalis dorsi), 416
Accessory (spinal accessory) nerve, 958
Acervulus cerebri, 846
Acetabular artery, 608
foramen, 174
notch, 174
Acetabulum, 169, 173
Acoustic area, 814
(auditory) nerve, 949, 1096
nuclei of, 823
meatus (see "Auditory Meatus"),
(medullary) strix, 814, 824
Acromial branches of posterior circumflex hu-
meral artery, 573
of thoraco-acromial artery, 571
of transverse scapular artery, 565
(scapular) e.xtremity of clavicle, 141
Aoromio-clavicular joint, 251, 1363
Acromion angle, 144
process, 144
Acromio-thoracio axis, 671
Action of muscles (see corresponding muscle).
Adam's apple, 1211
Addison's transpyloric line, 1153, 1370
Adduction, 321
Adductor brevis, 453, 471, 474
(Hunter's) canal, 468, 618, 1441
digiti secundi, 498
hallucis, 454, 496, 498
longus, 453, 471, 472, 1437
Adductor magnus, 453, 471, 474, 1437
(medial) group of thigh muscles, 453
minimus, 474
pollicis, 407, 408
tubercle of femur, 181
Adenoids, naso-pharyngeal, 1130, 1354
Adipose body, pararenal, 1243
capsule of kidney, 1242
folds of pleura, 1237
Aditus of larynx, 1222, 1223
Adminiculum lineae albse, 427
Adrenals (see "Suprarenal glands").
Aeby's division of bronchial branches, 1232
Agger nasi, 88, 1206
Aggregated follicles (Peyer's patches), 704
Air-cells, mastoid, 72
Air-sacs, 1232
Ala of central lobule of cerebellum, 806
cinerea (trigonum vagi), 814
nucleus of, 820
Alse of frontal bone, 60
nasi, 1201
Alar folds, 291
(lateral occipito-odontoid or check) liga-
ments, 223
(lower lateral) nasal cartilages, greater, 1201
lesser, 1202
processes of ethmoid, 81
Alcock's canal, 441, 445, 1384
Alimentary tract, lymphatics of, 699, 733,
1168
Ali-sphenoid centre, 67, 119
AUantois, 13, 1253
Alopecia, 1293
Alveolar (dental) artery, inferior, 548
posterior superior, 549
anterior superior, 549
canals, 87
ducts, 1232
(dental) nerves, 938
inferior, 941
superior, 938
periosteum, 1119
point, 109
part of mandible, 96
maxilla, 87, 90
saccules (air-sacs), 1153
veins, 646
Alveoli (air-cells), 1232
Alveus, 877
of limbic lobe, 868, 869
Amastia, 1301
Amnion, 9, 10
Ampulla, of ductus (vas) deferens, 1257
lactiferous, 1302
phrenica, 1142
recti, 1176
of semicircular canals, 80
of tubs uterinse (Fallopian tubes), 1270
of Vater, 1188
Ampullae, membranous, 1095
of splenic arterioles, 1312
Ampullar branches of vestibular ganglion, 950
Anipullary crista, 1095
sulcus, 1095
Amputation at centre of the arm, 1416
Chopart's medio-tarsal, 1465
I
1472
INDEX
Amputation of foot, 1465
of forearm, 1424
of great toe, 1465
of leg, 1459
Pirogoff's, 1465
Syme's, 1465
tarso-metatarsal (Hey's or Lisfranc's), 1465
through thigh, 1442
Amygdala (tonsil) of cerebellum, 807
Amygdaloid nucleus, 881
of lateral ventricle, 877
Amyloid tubercle of lateral ventricle, 877
Anal canal, 1177
surgical anatomy of, 1390
valves, 1177, 1390
Anapophysis, 38
Anastomosis of arteries (see corresponding
artery). ,
Anastomotic branch of facial nerve, 944
(perforating) of middle meningeal arterj',
548
ulnar, of superficial radial nerve, 987
Anastomotica magna artery (genu suprema),
621
Anatomical neck of humerus, 147
Anatomy, definition of, 1
of fourth ventricle, 812
Anconeus, 374, 377, 379
internus, 402
Andersch, ganglion of, 951
Angle (s), acromion, 144
cephalo-auricular, 1084
of fissure of Rolando, 860
infrasternal, 139
of Louis, 139
lumbo-saoral, 43
of mandible, 86
of maxilla, 88
of occipital bone, 53
of parietal bone, 57, 1332
of rib, 127
sacro-vertebral, 39, 43
of scapula, 143
of sternum, 133, 139
subscapular, 145
Angular artery, 540
gyrus, 863
motion of joints, 214
process, lateral (zygomatic), 60
medial, 60
vein, 643
Angulus Ludovici, 139
Ankle, annular ligaments, 1463
bony landmarks of, 1459
clinical anatomy of, 1459
synovial membranes of tendons at, 1463
tendons at, 1460
Ankle-joint, 297
arterial supply, 300
ligaments of, 298
movements, 300
muscles acting upon, 301
nerve-supply, 299
synovial membrane of, 299
Annular ligaments of ankle, 1463
of superior radio-ulnar joint, 262
of trachea and bronchi, 1227
of wrist, 387
Annulus(i) fibrosi of heart, 518
fibrosus, 318
inguinalis abdominalis, 430
subcutaneous, 430
iridis major, 1054
minor, 1054
tendineus communis, 1067
of tympanic membrane, 1087
urethral, 1253
Ano-coccygeal nerves, 1018
Anomalous (muscle of nose), 335
Ano-rectal lymphatic nodes, 735
Ansa hypoglossi, 953, 974, 979
lenticularis, 880
subclavia (ansa Vieussenii), 1036
Antagonists (muscles), 322
Anthelix, 1082
Antibrachial cutaneous branch (external), dor-
sal, of radial nerve, 985
cutaneous nerve, lateral, 987
(internal) medial, 984
interosseous nerve, dorsal, 986
fascia, 384
vein, median, 667
Anti-tragicus, 1084
Antitrago-helicine fissure, 1084
Antitragus, 1082
Antrum cardiacum, 1142
of Highmore (maxillary), 87, 90, 111, 1346
maxOlary, 77, 79, 1274
pyloric, of stomach, 1151
tympanic (mastoid), 72, 73, 78, 1092, 1336
Anus, 1177
clinical anatomy of, 1390
development of, 1179
lymphatics of, 735
sphincters of, 448
Aorta, 529, 586, 590
abdominal, 690, 1382, 1408
branches, 591
arch of, 530
ascending, 529
descending, 586
development, 633
relations of, 1369, 1382
semilunar valves of, 517
thoracic, 586, 1369
variations, 637, 638
Aortic arch, 530
intercostal arteries, 588
isthmus, 531
paraganglia, 1329
septum, 527
sinuses (of Valsalva), 518, 530
spindle, 531
Aortico-renal ganglion, 1043
Apertura pyriformis, 108, 112
Aperturae cutis, 1282
Apertures, anterior nasal (nares), 108, 1200
of larynx, 1222
palpebral, 1052
of pelvis, 175, 176
posterior nasal (choanae), 1206
superior thoracic, 138, 1365
Apex of arytsenoid cartilage, 124
of fibula, 190
of heart, 508
linguaj, 1106
of lung, 1230, 1233
of nose, 1200
of patella, 185
of prostate, 1264, 1389
of thyreoid lobes, 1315
of suprarenal gland, 1326
Apical dental (suspensory) ligament, 223
Aphasia, motor, 894
sensory, 894
Aponeuroses, 314, 317
Aponeurosis of epicranius (occipito-frontalis),
337
palmar, 387, 1430
pharyngeal, 1130
plantar, 492
Apophysis of femur, 184
Apparatus, lacrimal, 1078
olfactory, 1049
J
INDEX
1473
Appendages of skin, 1290
cutaneous glands, 1296
hair (pili), 1290
mammary glands, 1299
nails (ungues), 1293
Appendices epiploicae, 1170
vesiculosi (hydatids of Morgagni), 1269
Appendicular artery, 598, 1378
skeleton, 139
Appendix epididymidis, 1257
testis (hydatid of Morgagni), 1257
ventricular, of larynx, 1223
vermiform, 1173, 1378
Aquaeductus cerebri (Sylvii), 834
vestibuli, 72, 80, 117
Aqueduct of Fallopius (facial canal), 72
Aqueous chambers, 1064
humor, 1052
Arachnoid granulations (Pacchionian bodies),
649, 919
membrane, 771, 917
cranial, 918
spinal, 919
vessels and nerves of, 920
Arantius, ventricle of, 813
Arbor vitK of cerebellum, 809
Arch of aorta, 530
branches of, 532
costal, 139
of cricoid cartilage, 1210
deep volar, 586, 639, 1426
venous, 671
dental, 1123
digital venous, 667
dorsal venous (foot), 684
jugular venous, 648
lateral lumbo-costal, 437
medial lumbo-costal, 437
parieto-occipital, 863
plantar, 627
pubic, 176
superciliary, 59, 108
superficial volar, 582, 639, 1425
venous, 671
tarsal, inferior, 554
superior, 554
venous, plantar, 687
of vertebrse, 30
zygomatic, 1332
Arches, of atlas, 32, 33
branchial, 17
of the foot, 1468
palatine, 1132
Architecture of heart, 518
Archoplasm, 5
Arciform process, 466
Arcs, reflex, 768
Arcuate (metatarsal) artery), 632
crest of arytajnoid cartilage, 1212
fibres of medulla oblongata,
external, 800, 818
internal, 815, 817
ligament, external, 437
internal, 437
of symphysis pubis, 239
renal arteries, 1247
Arcus tendineus, 317, 440
fascise pelvis (white line), 440
Area(s) acustica, 814
association, of cerebral cortex, 894
auditory (cochlear), of cerebral cortex, 893
of Broca (area parolfactoria), 858, 865
cortical, of speech, 894
dangerous, of the leg, 1457
of scalp, 1333
gustatory, of cerebral cortex, 894
olfactory, of cerebral cortex, 893
Area(s), olfactory, of nasal cavity, 1049
plumiformis (of Retzius), 814
postrema of Retzius, 814
somsesthetic, of cerebral cortex, 893
surface, of telencephalon, 853
visual, of cerebral cortex, 893
Areas, cutaneous, of face, 1018
of lower extremity, 1024
of neck, 1019
of scalp, 1018
of trunk, 1020
of upper limb, 1022
of distribution of spinal nerves, 970
functional, of cerebral cortex, 893
Areola of mammary gland, 1300, 1304
secondary, 1304
Areolar glands (of Montgomery), 1304
Arm, centre of, as a surgical landmark, 1414
fasciaj of, 377
musculature of, 362, 374
veins of, 667
Arnold's bundle, 832, 889
ganglion, 963
nerve, 956
Arrectores pilorum, 1293
Arteria aberrans of aorta, 590
of superior intercostal, 568
centralis retinae, 553, 1065
princeps pollicis, 586
radialis indicis, 586
septi nasi, 541
Arterial supply of bones and joints (see corre-
sponding bone or articulation),
system, morphogenesis and variations of,
633
ArterioliE rectae of kidney, 1247
Artery (see also "Blood-vessels").
Artery (ies), 527
aberrant, 568, 590
accessory (small) meningeal, 548
pudendal, 610, 639
renal, 638
acetabular, 608
acromio-thoracic (thoraco-acromial), 571
angular, 540, 541
anterior central of medulla, 908
cerebral, 554, 562
ciliary, 553, 1065
circumflex humeral, 572
communicating, 555, 562
conjunctival, 553
deep temporal, 548
ethomidal, 554
inferior cerebellar, 561
intercostal, 588
interosseous, of forearm, 1423
mediastinal, 567
perforating, 620
peroneal, 626, 640, 1459
scrotal (or labial), 620
spinal, 561, 792, 638
superior alveolar (dental), 549
tibial, 629, 640, 1458
recurrent, 632
tympanic, 547
aorta, 529, 586, 637, 638
aortic intercostals, 588
appendicular, 598, 1378
arcuate (metatarsal), 632
articular, of knee-joint, 622, 1452
ascending cervical, 564
pharyngeal, 537
palatine, 540
of auricle (of ear), 1084
axillary, 569, 1412
azygos, of vagina, 610
basilar, 561
1474
INDEX
Artery(ies), brachial, 573, 640, 1414
of brain, 555, 905
bronchial, 588, 638, 1234
buccal, 548
of bulb of urethra, 613
caroticotympanic, 552
central or ganglionic, 906
of pons, 908
of cerebellum, 907
of cerebral hemorrhage (Charcot), 562, 906
peduncles, 907
chorioid, 554, 908
ciliary, 553, 1065
circumflex (dorsal) scapular, 572
of the clitoris, 613
deep, 614
dorsal, 614
casliao, 593, 638
common carotid, 533
digital, 582
iliac, 603
interosseous, of forearm, 577
coronary, 519
cortical cerebral, 906
costo-cervical trunk, 568
cystic, 595
deep auricular, 547
cervical, 568
circumflex iliac, 616
lingual, 540
plantar (communicating), 633
deferential, 610
descending palatine, 549
dorsal of foot, line of, 1466
digital (foot), 633
(hand), 586
interosseous (metatarsal),^633
of forearm, 579
lingual, 539
metacarpal, 586
metatarsal (interosseous), 633
nasal, 554
perforating, of palm, 586
radial carpal, 585
thoracic (thoraco-dorsal), 572
ulnar carpal, 580
recurrent, 577
dorsalis hallucis, 633
pedis, 632
episcleral, 553
of external acoustic (auditory) meatus, 1086
carotid, 536, 1343
iliac, 614
maxillary (facial), 540, 638, 1343;]
pudendal (pudic), 619
spermatic, 615
striate, 906 'I
femoral, 616, 1441
common, 616
superficial, 616
fibular nutrient, 626
of the fraenum, 540
frontal, 554, 1343
gastro-duodenal, 594
genu suprema (anastomotica magna), 621,
640
gluteal, 608
hepatic, 594
of humerus, nutrient, 576
hypogastric (internal iliac), 605, 639
ilio-colic, 598
ilio-lumbar, 606
inferior alveolar (dental), 548
(deep) epigastric, 614, 639
gluteal, 609, 639, 1444
haimorrhoidal, 613
labial (coronary), 541
Artery(ies), inferior laryngeal, 564
lateral articular, 623
medial articular, 622
mesenteric, 602, 638
pancreatico-duodenal, 596
phrenic, 592, 638
quadrigeminate, 907
suprarenal, 598
thyreoid, 564
tympanic, 537
ulnar collateral, 576
vesical, 609
infraorbital, 549, 1075
innominate, 532, 1369
internal auditory, 561
carotid, 549
mammary, 566
maxillary, 645, 638
pudendal (pudic), 610,!639
spermatic, 598, 638, 1259
striate, 906
intercostals, 588, 638
interosseous recurrent, 580
intestinal, 596
jejunal and iliac, 598
lacrimal, 552
lateral circumflex, 620,^640
malleolar, 632
palpebral, 552
plantar, 627, 640
posterior malleolar, 626
sacral, 607
tarsal, 632
thoracic, 571
left colic, 603
common carotid, 533
iliac, 605
coronary, 520
gastric, 593
gastro-epiploic, 595
pulmonary, 529
subclavian, 556
superior suprarenal,*592,il326
lenticulo-optic, 562
lenticulo-striate, 562
of lig. teres uteri, 615
lingual, 539
long posterior ciliary ,""553, 1065 ,
lowest lumbar (ima), 603
lumbar, 593, 638
major palatine, 549
masseteric, 548
medial circumflex, 620, 640
malleolar, 632
palpebral, 554
plantar, 629
tarsal, 632
median, of forearm, 578, 639
of medulla oblongata, 908
meningeal, 917
middle or azygos, 623
cerebral, 555, 562
colic, 598
collateral, 576
hsemorrhoidal, 610
meningeal, 547, 1341
quadrigeminate, 907
sacral, 603
suprarenal, 598, 638
temporal, 545
vesical, 609
minor palatine, 649
musoulo-phrenic, 567
nutrient of femur, 621
of humerus, 576
of radius and ulna, 579
of tibia, 626, 1459
INDEX
1475
Artery (ies), obturator, 608, 639
occipital, 642, 638, 1343
oesophageal, 588
omphalo-mesenterio, 638
ophthalmic, 552, 638, 1074
ovarian, 602
parietal, 543
peduncular, 907
of penis, 613
deep, 614
dorsal, 614
perforating, of the profunda, 620
pericardiac (of aorta), 588
pericardio-phrenic, 567
perineal, 613, 639
peroneal, 626, 640, 1459
plantar digital, 628
metatarsal, 628
popUteal, 621, 640, 1452
posterior auricular, 543, 1343
central of medulla, 908
cerebral, 561
circumflex humeral, 573
communicating, 554
conjunctival, 554
deep temporal, 548
ethmoidal, 553
inferior cerebellar, 561
meningeal, 537
peroneal, 626
scapular, 565
scrotal (labial), 613
spinal, 561, 792
superior alveolar (dental), 549
tibial, 624, 640,1458
recurrent, 632
princeps cervicis, 543
poUicis, 586
profunda or deep femoral, 620, 640
(superior) profunda of arm, 576
axillaris, 640
proper digital, 582
heptaic, 595
of pterygoid canal (Vidian), 549
pulmonary, 528, 1234
of quadrigeminate bodies, 907
radial, 582, 1423
collateral, 576
recurrent, 583
at wrist, 584
radialis indicis, 586
renal, 598, 638
of retina, central, 1065
right cohc, 598
common iliac, 605
coronary, 519
gastric, 594
gastro-epiploic, 595
pulmonary, 529
subclavian, 557
superior suprarenal, 592
saphenous, 621
sciatic, 609, 640
short posterior ciliary, 553, 1066
sigmoid, 603
spheno-palatine, 549
spinal, 590
splenic, 595
stapedial, 638
sternocleidomastoid, 542
stylo-mastoid, 544
subclavian, 556, 638
subcostal, 588
subungual, 540
submental, 541
subscapular, 571
superficial cervical, 566
Artery(ies), superficial circumflex iliac, 618 '
epigastric, 618
temporal, 545, 1343
superior cerebellar, 561
epigastric, 567
gluteal, 608, 1444
hajmorrhoidal, 603
intercostal, 568
labial (coronary), 641
laryngeal, 538
lateral articular, 622
medial articular, 622
mesenteric, 696, 638
pancreatico-duodenal, 595
phrenic, 590
quadrigeminate, 907
thoracic, 570
thyreoid, 638, 638
tympanic, 548
ulnar collateral, 576
vesical, 609
supraorbital, 552, 1343
suprarenal, 1326
suprascapular (transverse scapular), 564
sural, 622
systemic, 529
temporal, 545, 548, 1343
testicular, 601
thoraco-aoromial, 571
of thymus, 567
thyroidea ima, 533
transverse cervical (transversa colli), 565.
638 '' '
facial, 545
scapular, 564, 638 '
of tympanic cavity, 1091
ulnar, 576, 1423
umbilical, 609
urethral, 613
uterine, 610
vaginal, 610
variations of, 637, 639
vertebral, 559, 638
of vertebral canal, 590
vesical, 609
Vidian, 549
volar interosseous of forearm, 677, 639
metacarpal, 586
radial carpal, 584
ulnar carpal, 580
recurrent, 577
zygomatico-orbital, 545
Arthrodial diarthroses, 212
Articular arteries of knee-joint, 622, 1452
branches of auriculo-temporal nerve, 941
of common peroneal (external popliteal)
nerve, 1013
of deep peroneal (anterior tibial) nerve
1015
of genu suprema artery, 621
of obturator nerve, 1004
of popliteal artery, 623
of posterior circumflex humeral arterv
573 ^'
of profunda artery, 621
of tibial (internal popliteal) nerve, 1010
of transverse scapular artery, 565
capsules of acromio-olavicular joint, 251
of articulation of atlas with occiput, 218
of atlanto-dental joint, 222
of capitular articulation, 241
of carpo-metacarpal joint of thumb, 273
of costo-transverse articulation, 243
of hip-joint, 277
of inferior radio-ulnar joint, 264
of knee-joint, 287
of lateral atlanto-epistrophic joint, 231
1476
INDEX
Articular capsules of mandibular articulation,
215
of medial tarso-metatarsal articulation,
308 ^ ,
of metacarpo-phalangeal joint of thumb,
275
of shoulder-joint, 254
of sterno-costo-olavicular joint, 248
of tibio-fibular union, 295
of vertebral joints, 228
cartilage, 211
of shoulder-joint, 255
disc of aoromio-olavicular joint, 251
of inferior radio-ulnar joint, 264
of mandibular articulation, 216
of sterno-costo-clavicular joint, 249
furrows of skin, 1284
nerve, recurrent, of leg, 1013
process of vertebrae, 31
processes of vertebrae, ligaments conneotmg,
228
rete, of knee, 622
Articular tubercle of temporal bone, 71
veins of mandibular joint, 646
Articularis genu (subcrureus), 470
Articulation (s) , 2 1 1
acromio-clavicular, 250
ankle, 297
of anterior parts of tarsus, 303
arycorniculate, 1215
atlanto-epistrophic, 220, 221
of atlas with occiput, 218
of auditory ossicles, 1090
of bodies of vertebrse, 225
calcaneo-cuboid, 306
carpal, 268
carpo-metacarpal, 272
classification of, 212
constituents of, 211
costo-capitular, 241
costo-chondral, 245
costo-transverse, 243
costo-vertebral, 241
crico-arytaenoid, 1214
crico-thyreoid, 1213
cuboideo-navicular, 303
oubo-metatarsal, 308
ouneo-cuboid, 304
cuneo-navicular, 304
elbow, 258
front of thorax, 244
hip, 276, 1434
incudo-malleolar, 1090
incudo-stapedial, 1090
interchondral, 246
intercoccygeal, 238
intercuneiform, 304
intermetacarpal, 273
intermetatarsal, 309
interphalangeal, of fingers, 276
of toes, 310
intersternal, 244
knee, 284
mandibular, 215
of lower limb, 276
medio-carpal, 270
medio-tarsal (transverse tarsal) 305
metacarpo-phalangeal, 274
of thumb, 275
metatarso-phalangeal, 310
movements of, 213
occipito-epistrophic, 223
of ossicles of ear, 1090
of i)elvis, 234
radio-carpal (wrist-joint), 265
radio-ulnar, 261, 1419
sacro-coccygeal, 237
Articulation (s), sacro-vertebral, 232
shoulder, 253, 1413
of the skull, 215
between skull and vertebral column, 218
sterno-costal, 245
sterno-costo-clavicular, 248,
1363
synarthrosis, 212
talo-navicular, 305
tarsal, 301
tarso-metatarsal, 307
tibio-fibular, 295
transverse tarsal, 305
of the trunk, 224
of upper extremity, 248
of vertebral column, 225
Ary-oorniculate articulation (synchondrosis),
1215
Ary-epiglottic fold, 1221
muscle, 1220
Ary-membranosus muscle, 1220
Arytaenoid cartilages, 1211
Arytaenoideus obliquus, 1220
transversus, 1219
Ary-vocalis muscle of Ludwig, 1220
Ascending aorta, 529
cervical artery, 564
colon, 1173, 1379
lumbar veins, 662, 663
palatine artery, 541
pharyngeal artery, 537
Association areas of cerebral cortex, 894
frontal, 894
occipito-temporal, 894
parietal, 894
fibres of spinal cord, 789
system of cerebral hemisphere, 890
Asterion, 101, 1332
Asternal ribs, 127
Astragalus (talus), 192
Athelia, 1301
Atlanto-dental articular capsule, 222
articulation, 220
Atlanto-epistrophic articulation, 220
central, 221
lateral, 221
ligaments, anterior, 221
posterior, 221
Atlanto-mastoid muscle, 422
Atlanto-occipital articular capsule, 218
articulation, 218
ligaments, anterior, 218
posterior, 218
Atlas and epistropheus, joints between, 220
description, 32
development of, 46
with occiput, articulation of, 218
Atria of heart, 508, 511
of lungs, 1232
Atrial musculature, 518
Atrial plexus, 1041
Atrio-vetnricular bundle (of His), 517, 519,
627
orifice (ostium venosum) of left side, 514
of right side, 513
Atrium of heart, 612, 514
of middle nasal meatus, 1206
Attachments and origin of cranial nerves, 929
of spinal nerves, 964
topography of, 966
Attic of middle ear, 77
AttoUens aurem, 337
Attrahens aurem, 337
Auditory (cochlear) area of cerebral cortex,
893
artery, internal, 661
conduction paths, 900
INDEX
1477
Auditory foramen, 125
meatus, external, 75, 108, 1084, 1332
internal, 72, 117
(cochlear) nen^e, 949, 950
(Eustachian) tube, 1092
pharyngeal aperture of, 1130
veins, internal, 652, 657
Auerbach, plexus of, 1030, 1046, 1168
Auricle (pinna) of ear, 1082
cutaneous areas of, 1019
lymphatics of, 714
vessels and nerves, 1084
of heart, 508
Auricular artery, deep, 547
posterior, 543, 1343
branches, anterior, of auriculo-temporal
nerve, 941
of great auricular nerve, 973
of occipital artery, 543
of posterior auricular artery, 544
of small occipital nerve, 977
of superficial temporal artery, 545
of vagus, 956
cartilage, 1084
fissure, 75, 108
lymph-nodes, anterior, 709
posterior, 709
muscles, 337
nerve, great, 978
posterior, 944
point, 101
sulcus, posterior, 1083
tubercle (tubercle of Darwin), 1083
veins, anterior, 646
posterior, 647
Auricularis anterior (attrahens aurem), 337
posterior (retrahens aurem), 337
superior (attoUens aurem), 337
Auriculo-frontalis muscle, 337
Auriculo-temporal nerve, 941
Axial set of bones, 27
skeleton, 27, 29
Axillary arch, 374
artery, 569
collateral circulation, 1412
parts, 569, 570
fascia, 370, 371
fossa, clinical anatomy of, 1411
lymphatic nodes, 719
(circumflex) nerve, 984
vein, 671
Axis (epistropheus), 33, 47
cceliac, 593
of eyeball, 1055
of heart, 509
of pelvis, 176
of scapula, 145
th}'reoid (thyreocervical trunk), 564
Axones, 762
motor (efferent), 764
sensory (afferent), 762
sheaths of, 766
of spinal cord, 777
terminations of, 762
Azygos artery of vagina, 610
(major) vein, 662
minor (hemiazygos) vein, 662
tertia (accessory hemiazygos) vein, 663
B
Back of hand, 1433
clinical anatomy of, 1403
muscles (spinal), 410
Baillarger, stripes of, 879
Band, diagonal, of Broca, 866
ilio-tibial, 457, 458
Band, ilio-trochanteric, 280
moderator, of heart, 516
tendino-trochanteric, 280
Barba, 1290
Bars, hyoid, 119
mandibular, 119
metamorphosis of branchial or visceral, 119
thyreoid, 119
Barthohn, duct of, 1278, 1892
glands of, 1278, 1392
Basal ganglia, 878
vein, 657
Base of arytsenoid cartilage, 1211
of cranium, 103, 113
of encephalon, 794
of heart, 508
line, Reid's, 1341
of lungs, 1229, 1233
of nose, 1200
of prostate, 1264, 1389
of skull, external, 103
of suprarenal gland, 1325
of thyreoid lobes, 1315
Basi-bregmatic axis, 112
Basi-cranial axis, 112
Basi-facial axis, 112
Basi-hyal, 100, 119
Basilar artery, 561
groove, 54
plexus of veins, 651
sulcus of pons, 804
Basilic vein, 667
median (median cubital), 667
Basion, 108, 112
Basi-occipital, 119
Basi-pharyngeal canal, 63, 67
Basis (pes) pedunculi, 840
cranii, interna, 113
Basi-sphenoid centre, 67, 119
Basivertebral veins, 666
Bechterew's bundle, 784
nucleus of vestibular nerve, 823
• Bell, external respiratory nerve of, 982
Belly of muscle, 314
Bertin, bones of, 67
columns of, 1246
Biceps brachii, 374, 379, 382
relations, 1414
femoris, 453, 475
Bicipital groove, 148
muscles, 314
Bicuspid teeth, 1121
(mitral) valve, 515, 516
Bifurcation of trachea, 1225
Bile-duct, common, 1188, 1373
Bile-passages, 1186
Bipenniform muscles, 315
Birth, bones of skull at, 120
Biventer cervicis, 418
Biventral lobe of cerebellum, 807
Bladder (urinary), 1249
surgical anatomy of ,f 1390
Blandin, glands of, 1110
Blood-vascular system, 507
of small intestine, 1166
of spinal cord, 792
of stomach, 1155
Blood-vessels (see also "Arteries" and
"Veins").
of abdominal wall, 1371
of brain, 905
of cerebellum, 907
ciliary, 1065
of conjunctiva, 1348
of ductus deferens, 1259
around elbow, 1418
of eyeball, 1065
1478
INDEX
Blood-vessels of eyelids, 1078
of face, 1343
of Fallopian tube, 1270
of female external genitals, 1278
of heart, 519
of kidney, 1247
of large intestine, 1179
of larynx, 1224
of lips and cheeks, 1104
of liver, 1185
of lungs, 1234
of lymph-glands, 706
of mammary glands, 1305
of nose, 1203, 1208
of oesophagus, 1141
of orbit 1074
of ovary, 1269
of palate, 1106
of parathyreoids, 1319
of parotid, 1115
of penis, 1262
of pericardium, 523
of pharynx, 1138
of pleura, 1239
of prostate 1265
of rectum, 1391
retinal, 1065
of scalp, 1334
of scrotum, 1255
of skin, 1288
of spleen, 1312
of sublingual gland, 1117
of submaxillary gland, 1116
of suprarenal glands, 1326
of teeth, 1124
of testis and appendages, 1256
of thymus, 1322
of thyreoid gland, 1316
of tongue, 1111
of trachea and bronchi, 1228
of ureter, 1249
of urinary bladder, 1253
of uterus, 1274
of vagina, 1276
of vulva, 1192
Bochdalek, ganglion of, 939
Body(ies) of axis (epistropheus), 33
carotid, 1327
ciliary, 1060
coccygeal, 1329
of corpus callosum, 852
of epididymis, 1256
of femur," 178
of fornix, 869
of gall-bladder, 1187
geniculate, 834, 845
of hyoid bone, 99
inferior quadrigeminate, 839
of ischium, 171
(central portion) of lateral ventricles, 875
of Luys, 884
mammillary, 871
of nails, 1294
Nissl, 766
Pacchionian, 919
of pancreas, 1195
pararenal adipose, 1243
of penis, 1260
pineal, 845
pituitary, 848, 1352
of pubis, 172
of radius, 153
restiform, 810
of medulla oblongata, 800
of rib, 127
of scapula, 141
of sphenoid, 62
Body(ies) of sternum, 133
of stomach, 1151
superior quadrigeminate, 825, 841
• of sweat gland, 1297
of thymus, 1320
of tongue, 1106
of ulna, 157
of urinary bladder, 1250
of uterus, 1271
of vertebra, 30
vitreous, 1064
Wolffian, 1278
Bone(s), astragalus (talus), 191, 192
of Bertin (sphenoidal conchce), 67
calcaneus, 191, 195
capitate (os magnum), 159, 163
carpal, 159
clavicle, 139
cotyloid, 173
coxal (os innominatum), 169
cuboid, 191, 199
cuneiform, 161, 191, 197
epipteric, 68, 101
ethmoid, 81
of the face, 51
femur, 198
fibula, 189
fifth metacarpal, 167
fifth metatarsal, 203
first metacarpal, 165
first metatarsal, 201
of foot as a whole, 205
fourth metacarpal, 167
fourth metatarsal, 203
frontal, 59
greater multangular (trapezium), 159, 162
hamate (unciform), 159, 163
humerus, 146
hyoid, 99
incus, 79, 119
innominate, 169
inferior nasal concha, 84
interparietal (inca bone), 57
lacrimal, 85
lesser multangular (trapezoid), 159, 162
of limbs, homology of, 206
of the lower extremity, 169
lunate (semilunar), 159, 161
malar, 93
malleus, 79, 119
mandible, 95
maxilla, 87
metacarpal, 164
metatarsal, 200
of middle ear, 79
nasal, 86
navicular (scaphoid), 159, 160, 191, 196
occipital, 51
of orbit, 109
palate, 91
parietal, 57
patella, 184
phalanges, 167, 203
pisiform, 159, 162
pre-maxilla, 89
radius, 152
ribs, 126
scapula, 141
second metacarpal, 166
second metatarsal, 202
sesamoid, 168, 204, 275, 317
of the skull, 51
at birth, 120
morphology of, 117
sphenoid, 62
stapes, 80, 119
styloid, 168
INDEX
1479
Bone(s), suprasternal, 133
talus (astragalus), 191, 192
tarsal, 191
temporal, 68
at birth, 122
mastoid portion, 68, 71
petrous portion, 68, 72
squamous portion, 68, 70
tympanic portion, 69, 70, 75
third metacarpal, 166
third metatarsal, 202
of thorax, 126
tibia, 185
triquetral (cuneiform), 159, 161
turbinate, 67, 83, 84
of tympanum, 79
ulna, 155
of upper extremity, 139
vomer, 85
Wormian, 68
zygomatic, 93
Bony boundaries of perineum, 1383
landmarks of abdomen, 1370
of the ankle, 1459
of the buttocks, 1442
of elbow, 1417
of the foot, 1464
of forearm, 1419
of head, 1331
of the knee, 1447
of the leg, 1453
of the hip and thigh, 1434
ot thorax, 1363
of wrist and hand, 1424
sinuses of skull, 1335
Borders (see individual organs).
Boundaries (see individual parts).
Bowman's membrane, 1060
Brachia conjunctiva (superior cerebellar pe-
duncles), 831, 840
Brachial artery, 573, 640, 1414
branches, 575
collateral circulation, 1414
(internal) cutaneous branch, posterior, of
radial nerve, 985
cutaneous nerve, lateral, 985
medial, 983
fascia, 377
group of axillary Ivmphatic nodes, 719
plexus, 980
branches, 982
cords of, 981
relations of, 981, 1360
terminal branches of, 985
venae comitantes, 671
Brachialis, 374, 380, 382
surface markings of, 1415
Brachio-cephalic (innominate) veins, 641
Brachio-radialis (supinator radii longus), 387,
388
Brachium conjunctivum, 812
inferior, 834
superior, 834
pontis, 811
Brain (encephalon), 792
blood-supply of, 905
cerebral hemispheres, 850
cerebrum, 833
cerebellum, 804
diencephalon (inter-brain), 843
isthmus rhombencephali, 832
medulla oblongata, 799
meninges of, 908
mesencephalon (mid-brain), 833
pons (Varoli), 804
prosencephalon (fore-brain), 843
rhombencephalon, 799
Brain, telencephalon (end-brain), 847
topography of, 903, 1338
Branches (see corresponding vessel or nerve).
Branchial arches, 17
bars, metamorphosis of, 119
grooves, 17
Branchiomerism, 16, 17
Breast, female (mammary gland), 1299
male, 1305
Bregma, 101, 112, 1332
Brim of pelvis, 175
Broad (lateral) ligaments of uterus (alse ves-
pertilionis), 1267, 1393
Broca's area, 858, 865
convolution, 858
diagonal band, 866
Bronchi, 1226, 1231, 1408
Bronchial arteries, 588, 638, 1234
branches, Aeby's division of, 1232
of internal mammary artery, 567
(pulmonary) branches of vagus, 957
glands, 1231
lymphatic nodes, 725, 1225
tubes, branching of, 1231
veins, 664, 666, 1234
Bronchioles, 1232
Broncho-oesophageal muscle, 1141, 1228
Bronchus, eparterial, 1232
hyparterial, 1232
Brunner's glands, 1166
Bryant's triangle, 1436
Buccal branches of cervico-facial nerve, 945
artery, 548
nerve, long, 939
veins, 646
Buccinator, 334
(long buccal) nerve, 939
set of facial lymph-nodes, 711
Bulb(s) , artery of, 613
of hair, 1292
of internal jugular vein, 659
olfactory, 758, 865
of posterior cornu of lateral ventricle, 876
of urethra, 1262
Bulbar plexus, 1041
Bulbi vestibuh, 1277
Bulbo-cavernosus 443, 450
in female (sphincter vaginae), 451
Bulbo-urethral (Cowper's) glands, 1265
Bulbous corpuscles (end-bulbs of Krause),
1290
Bulbus aortae, 530
Bulla, ethmoidal, 84. Ill, 1205
Bundle, Arnold's, 832, 889
atrio-ventricular (of His), 517, 519, 527
commissural, 788
Helweg's (Bechterew's), 784
posterior longitudinal, 817
Tiirk's, 832, 890
of Vicq d'Azyr, 871
Burdach's column of spinal cord, 781
Bursa(Ee) anguli mandibuli, 1288
anserina, 474
of anterior ilio-femoral musculature, 456
thigh muscles, 471
of the arm, subcutaneous, 377
muscular, 379, 383
of back of leg, 486, 491
bicipito-radialis, 383
cubitalis interossea, 383
of dorsal arm muscles, 379
epicondyli medialis dorsalis, 379
of facialis musculature, 330
of foot, 500, 1465
of forearm and hand, 384, 395, 403
of front muscles of leg, 483
gluteofemorales, 462
1480
INDEX
Bursa(ae), hyoid, 1217
iliaca subtendinea, 457
iliopeotinea, 456
of infra-hyoid muscles, 353
infrapatellaris profunda, 471
subcutanea, 466
intermetacarpophalangese, 395
intermetatarsophalangeae, 500
intratendinea olecrani, 379
ischiadiea musculi glutei maximi, 462
of ischio-pubo-femoral musculature, 464
of medial thigh muscles, 474
mucosEe, 313, 318
subcutaneous, 1288
subfascial, 318
submuscular, 318
subtendinous, 318
musculi abductoris pollicis longi, 395
anconei, 379
bicipitis femoris inferior, 476
superior, 476
gastrocnemiahs, 476
coraco-brachialis, 383
extensoris carpi radialis brevis, 395
ulnaris, 395
pollicis longi, 395
flexoris carpi radialis, 403
ulnaris, 403
gastroenemii lateralis, 486
medialis, 486
infraspinati, 370
latissimi dorsi, 370
obturatoris externi, 464
interni, 464
pectinei, 474
peetoralis majoris, 374
piriformis, 462
quadrati femoris, 464
recti femoris (inferior), 471
(superior), 471
sartorii propria, 471
semimembranosus, 476
sterno-hyoidei, 353
subscapularis, 370
supinatoris, 395
teretis majoris, 370
thyreo-hyoidei, 353
omentalis (lesser sac) 1146, 1372
of pectoral muscles, 374
pharyngeal, 1130
of posterior iho-femoral musculature, 476
praepatellaris subcutanea, 466
subfascialis, 466
subtendinea, 471
prepatellar, 1288, 1448
of shoulder musculature, 369
sinus tarsi, 483
subacromialis, 369
subcutanea acromialis, 365
caloanea, 477
digitorum dorsales, 384, 1288
epicondyli lateralis, 377
medialis, 377
infrapatellaris, 1288
malleoli medialis et lateralis, 477
metacarpo-phalangea dorsalis, 384, 1288
olecrani, 377, 384
prementalis, 330
prominentiiB laryngse, 330
sacralis, 1288
troohanterioa, 1288
tuberositatis tibiae, 477
submammary (retromammary), 1303
subtendinea musculi extensoris hallucis
longi, 483
olecrani, 379
supracoracoidea, 370
Bursa(ae), suprapatellaris, 471
synovial, 313, 318
tendinis calcanei, 486
musculi tibialis anterioris, 483
of ventral arm muscles, 383
Bursa tendinum musculi extensoris digitorum
communis, 395
of trapezius, 350
trochanterica musculi glutei maximi, 462
medii anterior, 462
posterior, 462
minimi, 462
subcutanea, 457
Buttocks, bony landmarks of, 1442
clinical anatomy of, 1442
nerves of, 1443
Caecum (caput coH), 1170
cupular, 1096
topography of, 1376
variations of, 1171
vestibular, 1096
Calamus scriptorius, 812
Calcaneal pillar, 205
Caleanean branches, lateral, of sural nerve,
1013
of peroneal artery, lateral, 626
of posterior tibial artery, medial, 626
nerves, medial, 1010
Caloaneo-cuboid articulation, 306
ligaments, 306, 307
Calcaneo-fibular ligament, 299
Calcaneo-metatarsal ligament 492,
Calcaneo-navicular ligament, lateral, 302, 305
plantar (spring), 305
Calcaneo-plantar cutaneous nerves, 1010
Calcaneus (os calcis), 191, 195
Calcar avis (hippocampus minor), 864, 868
femorale, 184
Calcarine fissure, 864
Calcification of bones, 27
of teeth, 1126
Callosal convolutions, 868
Calloso-marginal fissure, 857, 859
Calyces of kidney, 1246
of ureter, 1248
Camper's fascia, 425
Canal(s), accessory palatine, 103
adductor (Hunter's), 468, 618, 1441
Alcock's, 441, 445
alveolar, 87
anal, 1177
basi-pharvngeal, 63
carotid, 73, 108
central, of spinal cord, 775
of cervix, 1272
ethmoidal, 61, 83, 110, 113, 126
facial (Fallopian), 72, 73, 77, 78
femoral (crural), 468
gubernacular, l06
of Huguier, 75, 77, 108
hyaloid, 1064
hypoglossal, 117
inferior dental, 96
infra-orbital, 87, 126
inguinal, 424, 430
clinical anatomy of, 1395
lateral semicircular, 78
mandibular (inferior dental), 96, 126
palatine, 92
of Petit, 1064
pharyngeal, 66, 92, 103
posterior palatine, 126
pterygoid (Vidian) canal, 103, 107, 108, 126
pterygo-palatine, 88, 92, 103
INDEX
1481
Canal (s), pyloric, 1152
sacral, 42
of Schlemm, 1059
semicircular, 80, 1092
zygomatico-facial, 126
zygomatico-orbital, 94
Canaliculi, carotico-tympanic, 74
Canaliculus coohlese (ductus perilvmphaticus),
73, 81, 108
innominatus, 65
mastoid, 73
tympanic, 73, 108
Canalis musculo-tubarius, 73, 77,'[108
facialis, hiatus of, 116
Canine fossa, 87
teeth, 1120
Caninus (levator anguli oris), 332
Capillaries, lymphatic, 697
Capilh, 1290
Capitate (os magnum) bone, 159, 163
Capitular (oosto-central) articulation, 241
ligaments of tibio-fibular union, 295
Capitulum of humerus, 150
Capsular ligament of elbow-joint, 258
(perirenal) branches of renal arteries, 598
Capsule, articular, acromio-clavicular, 251
atlanto-dental, 222
atlanto-epistrophic, 221
atlanto-occipital, 218
of capitular articulation, 241
carpo-metacarpal of thumb, 273
costo-transverse, 243
crico-thyreoid, 1213
of hip-joint, 277
of knee-joint, 287
of mandibular articulation, 215
of medial tarso-metatarsal joint, 308
of metacarpo-phalangeal joint of thumb,
275
of shoulder-joint, 254
of sterno-costo-clavicular joint, 248
of tibio-fibular union, 295
of vertebral joints, 228
external (telencephalon), 881, 888
Glisson's, 675, 1186
glomerular, 1246
internal (telencephalon), 878, 886
of kidney, 1242, 1303
of prostate, 1265, 1389
of suprarenal gland, 1326
Tenon's, 1073
surgical importance of, 1348
of thyreoid gland, 1316
Caput angulare (levator labii superioris alseque
nasi), 332
infraorbitale (levator labii superioris), 332
zygomatioum (zygomaticus minor), 332
Cardia of stomach, 1151
Cardiac branches of vagus, 957
fossa of lungs, 1229
ganglion (of Wrisberg), 1041
nerve, inferior, 1037
middle, 1036
superior cervical, 1036
notch of left lung, 1229
portion of stomach, 1151, 1374
plexus, 1041
vein, anterior, 521
great, 520
middle, 520
small cardiac, 521
smallest cardiac, 521
Carina tracheae, 1225
urethral, 1275, 1278
Carotico-clinoid foramen, 65
Carotico-tympanic artery, 552
canaliculi, 74
Carotieo branches from tympanic plexus,
951, 961
Carotid arteries, common, 533
collateral circulation, 536, 1360
external, 533, 536, 1343
branches, 536
relations, 536
internal, 533, 549
variations, 637
canal, 73, 108
gland (body), 550, 1327
groove, 64
nerves, external, 1036
internal, 960, 1033
plexus of nerves, common, 1036 \\
external, 1036
internal, 1033
ridge, 73
sheath, 1362 _
triangle, inferior (tracheal), 1358
superior, 1358
(anterior) wall of tympanic cavity, 1054
Carpal arch (rete), volar, 581
artery, dorsal radial, 585
dorsal ulnar, 580
volar radial, 584
volar ulnar, 581
bones, ossification of, 164
head of adductor pollicis, 408
joints, 268, 269
(annular) ligaments of wrist, 1427
rete, dorsal, 579, 586
Carpo-metacarpal joints, 272
of the thumb, 273
Carpus, description of, 159, 270
ligaments, 384, 387
Cartilage (s), 211
alar, 1201, 1202
articular, of shoulder-joint, 255
arytenoid, 1211
auricular, 1084
corniculate (Santorini), 1212
costal, 130
cricoid, 1210
cuneiform (Wrisberg), 1213
epiglottic, 1212
interarytasnoid (procricoid), 1213, 1218
of larynx, 1209
lateral nasal, 1201
Meckel's, 98, 119
nasal, 120
periotic, 117
septal nasal, 1202
sesamoid nasal, 1202
laryngeal, 1213
sphenotic, 117
thyreoid, 1210
tracheal, 1227
varieties, 211
vomero-nasal, 1203
Cartilaginous plate (pelvic joints), ear-shaped,
235
CartUago triticea, 1217
Caruncle, lacrimal, 1052, 1055
sublingual, 1117
Carunculte hymenales (myrtiformes), 1275,
1392
Cauda equina, 772
helicis, 1084
Caudate branch of middle cerebral artery, 562
(Spigelian) lobe of liver, 1184
nucleus, 877, 879
process of liver, 1184
Cavernous nerves of clitoris, 1047
of penis, 1047
plexus of nasal conchse, 1208
of nerves, 1033
1482
INDEX
Cavernous (spongy) portion of male urethra,
1264, 1388
sinus, 652, 691
Caves, Meckel's, 916
Cavity, body, 14
epidural, 911
glenoid, of scapula, 143
of larynx, 1220
lesser sigmoid, of ulna, 157
mediastinal, 1239
nasal, 1203
oral, 1100
of orbit, 1066
pelvic, 175
pericardial, 522
pleural, 1236
of radius, sigmoid, 154
subarachnoid, 918
subdural, 912
thoracic, 1235
of tooth, 1118
tympanic, 77, 1088
of ulna, greater sigmoid, 156
of uterus, 1271
Cavum conchas, 1082
pelvis subperitoneale, 448
Retzii, 1250, 1371
Cellifugal processes of neurone, 762
Cellipetal processes of neurone, 762
Cells, 4
chromaffin, 1323
ependymal, 768
ethmoidal, 83, 84, 111, 1207
Golgi, in cerebellum, 809
gustatory, 1050
olfactory, 1051
mastoid, 1092, 1336
of Purkinje, 809
stellate, 809
Cementum of teeth, 1119
Central (ganglionic) arteries of cerebrum, 906
of medulla oblongata, 908
branches of cerebral arteries, 562, 563
canal of spinal cord, 775
connections of cranial nerves, 818
of abducens, 934
of cochlear, 824
of facial nerve, 825, 946
of glosso-palatine, 825, 947
of glosso-phar\ns<"il, 820, 952
of hypoglossal, 820, '.).") 4
of masticator, 829, 94-_'
of oculo-motor, 838, 933
of olfactory, 873, 929
of optic, 848, 931
of spinal accessory, 820, 959
of trigeminus, 826, 935
of trochlear, 837, 934
of vagus, 820, 958
of vestibular, 823, 950
gyrus, anterior (ascending frontal convolu-
tion), 857
posterior (ascending parietal), 861
lobe or insula, 856
lobule of cerebellum, 806
nervous system, 751
point of perineum, 1385
sulcus (fissure of Rolando), 859, 1340
angle of, 860
inferior genu. 860
in foetus, 860
of insula, 857
superior genu, 860
tendon of perineum, 449
veins of retina, 659
Centres, association, of cerebral cortex, 894
Centrum semiovale, 886
Centrum (body) of vertebrse, 30
Cephalic index, 117
plexus, gangliated, 959
portion of sympathetic trunk, 1033
vein, 667, 671
Cephalo-auricular angle, 1084
Cerato-cricoid ligaments, 1213
muscle, 1218
Cerato-hyal center, 100
segment, 119
Cerebellar artery, anterior inferior, 561, 907
posterior inferior, 561, 907
superior, 561, 907
notches, 805, 915
peduncle, inferior, 810
superior, 812, 831
tract, direct, of Flechsig, 784
veins, 657
Cerebello-olivary fibres, 817
Cerebellum (hind brain), 804
ala of central lobule, 806
anterior medullary velum of, 812
arbor vitse of, 809
biventral lobe, 807
blood-vessels of, 907
brachium pontis, 811
conjunctivum, 812
central lobule of, 806
conduction paths of, 899
cortex of, 809
culmen of, 806
declive (clivus), 806
dentate nucleus of, 810
external features, 808
fissures, 805
flocculus, 807
peduncle of, 807
folium vermis (cacuminis), 806
fourth ventricle, anatomy of, 812
functions of, 832
gross divisions of, 805
hemispheres of, 805
inferior vermis, 808
internal structure of, 808
lingula of, 806
lobes and lobules, 805
montioulus, 806
nodule of inferior vermis, 808
notch of, 805
nuclei of, 809, 810
peduncles of, 810
posterior medullary velum, 808
pyramid of vermis, 808
sulci of, 805
superior vermis of, 806
tentorium of, 804
tonsil (amygdala) of, 807
tuber vermis, 808
uvula of vermis, 808
vallecula of, 807
veins of, 908
vermis of, 805, 807
Cerebral arteries, anterior, 554, 562
branches, 562
middle, 556, 562
posterior, 561, 562
commissure, anterior, 871
inferior, 842, 890
cortex, 879
cornu ammonis, 879
functional areas of, 893
structure of, 879
hemispheres, 850
caudate nucleus, 877
corpus striatum, 868, 879
cortex of, 852, 879, 893
gyri of, 852
INDEX
1483
Cerebral hemispheres, lateral ventricle, 873
lobes of, 853
central (insula), 856
frontal, 857
occipital, 863
parietal, 860
temporal, 854
rhinencephalon, 864
sulci of, 852
path for cranial nerves, 895
peduncles (crura), 833, 835
arteries of, 907
veins, 644, 657
central or deep (ganglionic), 655
great (of Galen), 657
inferior, 655
internal, 657
middle, 655
superior, 654
Cerebro-spinal fasciculus, lateral, 783
ventral, 788
fluid, 920, 1342
path, 895
Cerebrum, 833
mesencephalon (mid-brain), 833
prosencephalon (fore-brain), 843
diencephalon (inter-brain), 843
telencephalon (end-brain), 847
Cerumen, 1085, 1298
Ceruminous glands, 1085, 1297
Cervical artery, ascending, 564
deep, 668
superficial, 566
transverse, 565
branches of uterine artery, 610
chains of lymphatic nodes, deep, 714
enlargement of spinal cord, 772
fascia, external, 347
middle, 350
ganglion of sympathetic, inferior, 1036
middle, 1036
superior, 960, 1035
loop (ansa hypoglossi), 953, 974
muscle, 330
nerves, 971, 974
anterior primary divisions, 974
posterior primary divisions, 971
plexus, 974
ascending branches of, 977
deep branches of, 978
descending branches of, 978
posterior, of Cruveilhier, 971
superficial branches of, 977
supra-clavicular branches of, 978
transverse branch, 978
portion of external maxillary artery, 540
of internal carotid artery, 550
of sympathetic trunk, 1033
construction of, 1037
of vertebral artery, 559
ribs, 131, 1365
triangles, 1357
vein, deep, 661
veins, transverse, 672
vertebra;, description of, 31
development of, 47
Cervicalis ascendens, 416
Cervico-facial nerve, 945
Cervix of uterus, 1271
Chains of nerurones, 768
Chambers of the eye, 1064
Charcot's artery of cerebral hemorrhage, 562,
906
Check (alar) ligaments, 223
of eyeball, 1072
Cheek, 1103
Chiasma, optic, 848, 849
Choanaj (posterior nares), 107, 112, 1130,
1206, 1351
Chondro-cranium, 117
Chondro-humeralis (epitrochlearis), 374
Chondro-glossus, 346
Chopart's medio-tarsal amputation, 1465
Chorda tympani nerve, 826, 946, 948
Chorda tendinse, 515
Chords of Willis, 649
Chorio-capillaris, 1055
Chorioid, 1057, 1060
artery, 554, 908
branches of posterior cerebral artery, 563
fissure, 868
glomus, 876
plexus of fourth ventricle, 922
of lateral ventricle, 875, 877, 924
tela of fourth ventricle, 758, 812
of third ventricle, 923
vein, 657
Chorioidal arteries of medulla oblongata, 908
fissure, 1080
lamina, epithelial, 876, 924
membrane, 1052
Chorion, 10
Chromaffin bodies, 1329
cells, 1323
system, 1323
Chromatin, 5
Cilia, 1290
Ciliary arteries, anterior, 1065
long posterior, 1065
short posterior, 1065
body, 1060
ganglion, 961, 1076
branches, 961
roots, 932, 937, 961, 1033
glands (glands of Moll), 1078, 1297
muscle, 1057, 1060
nerves of eyeball, 1064, 1076
long, 937
short, 961, 1076
processes, 1057
veins, 658
Cingulum, 867, 890
of teeth, 1120, 1121
Circle of Willis (circulus arteriosus), 555
Circular sinus, 651
sulcus (limiting sulcus of Reil), 857
Circulation, collateral, of axillary artery, 1412
of brachial artery, 1414
of common carotid artery, 1360
iliac arteries, 1382
of external iliac artery, 1382
of femoral artery, 1441
of internal iliac artery, 1382
of popliteal artery, 1453
of subclavian artery, 1360
fcEtal, 695
pulmonary, 507
systemic, 507
Circulus arteriosus major, 1065
minor, 1065
tonsillaris, 952
Circumanal glands, 1297
Circumduction, 215
Circumferential cartilage, 211
Circumflex artery, lateral, 620, 640
medial, 620," 640
femora! veins, 690
humeral artery, anterior, 572
posterior, 573
iliac arterj', deep, 616
superficial, 618
vein, deep, 683
superficial, 684
nerve, 985
1484
INDEX
Circumflex (dorsal) scapular artery, 572
veins, 671
Circumvallate papillae of tongue, 1106
Cisterna basalis, 918
cerebello-medullaris (cisterna magna), 919
chyli, 726
pontis, 918
subarachnoid, 918
superior, 919
Clarke's column of spinal cord, 776
Classification of articulations, 212
of muscles, 319
Claustrum, 880
Clava, 801
Clavicle, 139, 1357, 1410
ossification of, 141
structure of, 141
Clavicular branch of thoraco-aoromial artery,
571
Cleft, middle ear, 77
palate, 1106, 1352
Clinical and topographical anatomy, 1331
of abdomen, 1370
of back, 1403
of head, 1331
of lower extremity, 1434
of neck, 1354
of pelvis, 1382
of thorax, 1363
of upper extremity, 1409
Clinoid process, anterior, 65, 116
middle, 65, 116
posterior, 63, 116
Clitoris, 1277
artery of, 613
cavernous nerves of, 1047
deep artery of, 614
dorsal artery of, 614
vein of, 1018
lymphatics of, 745
Clivus, 117
Cloaca, 1179, 1253, 1278
Clunial (gluteal) branches, inferior, of poste-
rior femoral cutaneous nerve, 1007
nerve, inferior medial (perforating cutan-
eous), 1007
middle, 973
superior, 973
Coats of the eyeball, 1058
Coccygeal body, 1329
cornua, 43
foveola, 1284
ganglion, 1040
ligament, 911
nerves, 973
posterior primary division of, 973
rudimentary, 964
plexus, 1018
vertebras, 42
development of, 49
Coccygeus, 440, 448
Coccyx, 30, 42
muscles of, 448
Cochlea, 81, 1092
Cochlear area of cerebral cortex, 893
duct (membranous cochlea, or scala media),
1090
fenestra, 1089
nerve, 824
nuclei of, 824
Cochleariform process, 1089
Coeliac artery (axis), 593, 638
branches of vagus, 958
(semilunar) ganglia, 1043
lymphatic nodes, 730
plexus of nerves, 1043
Coelom, 14
Colic, artery, left, 603
middle', 598
right, 598
flexures, 1173, 1379
(basal) surface of spleen, 1310
veins, 677, 678
Collateral artery, inferior ulnar, 576
middle, 576
radial, 576
superior ulnar, 576
branch of intercostal arteries, 588
circulation of axillary artery, 1412
of brachial artery, 1414
of common carotid artery, 536, 1360
iliac arteries, 605, 1382
of external iliac artery, 1382
of femoral artery, 1441
of internal iliac artery, 1382
of popliteal artery, 1453
of subclavian artery, 1360
eminence, 868, 877
fissure, 864
trigone of lateral ventricle, 876
Collecting renal tubule, 1246
Colles' fascia, 445
fracture, 1420
CoUiouli, inferior, 834, 839
superior, 841
Colliculus of arytaenoid, 1212
facialis, 815
seminalis (verumontanum), 1263, 1389
Colloid of thvreoid gland, 1316
Colon, ascending, 1173, 1378
descending, 1174, 1379
iliac, 1174
pelvic, 1174, 1379
sigmoid, 1174, 1379
transverse, 1174, 1379
Colostrum, 1303
Column anterior of spinal cord, 786
Burdach's, 781
Clarke's, 776
GoU's, 781
lateral of spinal cord, 782.
posterior of spinal cord, 780
vertebral, 29, 43
Columna rugarum, 1275
Columns, anterior, of fornix, 870
rectal (of Morgagni), 1177, 1390
renal (of Bertin), 1246
Comedo, 1298
Comma-shaped fasciculus, 782
Commissural branches of sympathetic, 1032
bundle, 788
fibres of white substance of spinal cord, 779
system of fibres, of telencephalon, 890
Commissure, 769
anterior cerebral, 848, 871, 890
grey, of spinal cord, 775
habenular, 872, 885, 890
hippocampal, 869, 890
inferior cerebral (Gudden's), 842, 850, 890
middle cerebral, 844
optic, 849
posterior, of cerebrum, 835, 890
of vulva, 1276
supramammillary, 871, '890
white, of spinal cord, 776
Common bile-duct (ductus choledochus), 1188
carotid artery, 533
branches, 536
collateral circulation, 536, 1360
in the neck, 533
relations, 533, 534, 1369
thoracic portion of left, 533
digital arteries, 582
veins (foot), 684
INDEX
1485
Common digital veins, volar, 671
facial vein, 644, 646
femoral artery, 616
iliac arteries, 603, 605
collateral circulation, 605
veins, 679
interosseous artery of forearm, 570
Communicans cervicalis, 974
fibularis, 1013
Communicating artery, anterior, 555, 562
posterior, 554
Comparative anatomy of large intestine, 1180
of lips and cheeks, 1104
of liver and gall-bladder, 1 192
of palate, 1106
of pancreas, 1197
of peritoneum, 1151
of salivary glands, 1117
of stomach, 1160
of teeth, 1127
of tongue, 1112
of tonsOs, 1138
Compartments under inguinal ligament, 1399
Complexus, 412, 417
Compound bones, 27
Compressor bulbi proprius, 450
hemisphserium bulbi, 451
venae dorsalis, 451
Conarium, 845
Concha, 1082
eminence of, 1083
Concha;, nasal, 83, 84, 1205
sphenoidal, 64, 67
Conchal (inferior tiarbinate) crest, 88, 92
Conduction paths, auditory, 900
involving cerebellum, 899
of nervous system, summary of, 895
methods of determining, 779
of olfactory apparatus, 902
of optic apparatus, 900
vestibular, 899
Condylar foramen (canal), 54
fossa, 54, 108
process of mandible, 96, 97
tubercle of mandible, 97
Condylarthroses, 213
Condyles, 29
of femur, 182
of femur and tibia, 1447
of mandible, 97
of occipital bone, 54, 108
third occipital, 56
of tibia, 185
Condyloid emissary veins, 652
Cone, elastic, of larynx, 1215
Conical papillte of tongue, 1106
Conjoined tendon of internal oblique and
transversalis, 435
Conjugate diameter of pelvic inlet, 175
Conjunctiva, 1054, 1347
lymphatics of, 698, 712
ocular, 1054
palpebral, 1054
Conjunctival arteries, anterior, 553
posterior, 554
sac, 1054
semilunar fold of, 1055
veins, 658
Connecting fibro-cartilage, 211
Connections, central, of cranial nerves, 818
(for individual nerves, see "Central con-
nections"),
cortical, of thalamus, 883
of nuclei of corpus striatum, 880
Conoid ligament, 251
tubercle, 140
Constituents of articulations, 211
Constrictor laryngis, 1218
radicis penis, 450
vaginEe, 449
Constrictors of pharynx, 1137
Construction of nervous system, 762
Conus arteriosus, 516
meduUaris, 771
Convoluted renal tubules, 1246
Convolutions, cerebral, 852
Cooper's ligament, 1400
Coraco-acromial hgament, 252
Coraco-brachialis, 374, 379, 381
Coraco-clavicular union, 251
arterial supply, 251
ligaments, 251
movements, 252
nerve-supply, 251
(costo-coracoid) fascia, 371
Coraco-humeral ligament, 255
Coracoid (suprascapular or superior trans-
verse) ligament, 253
process of scapula, 144
(conoid) tubercle, 140
Cord, oblique, 262
spermatic, 1259, 1387
spinal, 751, 771
clinical anatomy, 1408
external morphology of, 771
internal structure of, 775
Cords of brachial plexus, 917
ganghated, neurones of, 755
vocal (gee "Vocal folds").
Corium, 1286
Cornea, 1052, 1054, 1056, 1069, 1065
Comiculate cartilages (of Santorini), 1212
tubercle (of Santorini) of larynx, 1221
Corniculo-pharyngeal ligament, 1218
Cornu ammonis, 868, 879
Cornua of fascia lata, 467
of fossa ovalis (saphenous opening), 467
of hyoid bone, 99, 100
of lateral ventricles, 873, 874, 876
of sacrum, 40
of thyreoid cartilage, 1211
Cornucopise, 923
Corona cilaris, 1060
glandis, 1260
iridis, 1054
radiata, 887
ocoipito-thalamic (optic) radiation of, 888
Coronal suture, 57, 101, 1339
Coronary arteries, 519
ligaments of knee-joint, 290
of liver, 1184
plexuses of nerves, 1041
sinus, 521
valve (of Thebesius) of, 512
sulcus of heart, 510
(gastric) vein, 675
veins, 520
Coronoid fossa of humerus, 150
process of mandible, 97, 1351
of ulna, 156
Corpora albicantia, 844, 1269
cavernosa of clitoris, 1277
penis, 1260
mammillaria (albicantia), 844
quadrigemina, 834
quadrigemina-thalamus path, 786
Corpus adiposum buocse, 1103, 1104
callosum, 851
body of, 852
forceps major, 890
minor, 890
genu, 851
peduncle of, 866
radiation of, 851, 890
1486
INDEX
Corpus callosum, rostral lamina of, 852
rostrum of, 852
spleuium of, 852
striffi of, 851
sulcus of, 867
cavernosum urethras (corpus spongiosum),
1261
Highmori, 1256
mammae, 1302
papillare of skin, 1286
spongiosum (cavernosum urethrae), 1261
striatum, 879
caudate nucleus of, 879
connections of nuclei of, 880
internal capsule of, 886
lenticular nucleus of, 879
trapezoideum, 824
Corpuscles, bulbous (of Krause), 1290
genital, 1290
colostrum, 1303
concentric (Hassal's) of thymus, 1321, 1322
Golgi-Mazzoni, 1290
lamellous (Vater-Paoinian), 1290
renal (Malpighian), 1246
Ruffini, 1290
salivary, 1132
splenic (Malpighian), 1311
tactile (Meissner), 1290
Corrugator cutis ani, 445
muscle, 336
Cortex, cerebellar, 809
cerebral, 879
functional areas of, 893
of kidney, 1246
of lens of eye, 1062
of suprarenal gland, 1326
of thymus, 1321
Corti, organ of, 1096
Cortical branches of cerebral arteries, 562, 563
(superficial) cerebral veins, 654
connections of thalamus, 883
Cortico-pontine fibres, 811
Costal arch, 139
branch, lateral, of internal mammary ar-
tery, 567
cartilages, 130
Costal groove, 127
pleura, 1237
processes, 38
tuberosity of clavicle, 140
Costo-axUlary veins, 671
Costo-central (capitular) articulation, 241
ligaments, 241
Costo-cervical arterial trunk, 568
Costo-ohondral joints, 245
Costo-clavicular (rhomboid) ligament, 249
Costo-eoracoid fascia, 371
ligament, 371
Costo-coracoideus, 374
Costo-mediastinal sinus, 1238
Costo-transverse articulations, 243
arterial supply, 244
ligaments of, 243
middle (neck), 243
posterior (tubercular), 243
superior, 243
movements, 244
nerve-supply, 244
foramen, 32, 127
of atlas, 33
Costo-xiphoid ligament, 244, 245
Costo-vertebral articulations, 241
groove, 138
Cotunnius, nerve of, 962
Cotyloid bone, 173
fibro-cartilage, 281
fossa, 169
Cowper's (cremasteric) fascia, 426, 434, 1254
glands, 1265
Coxal bone (os innominatum), 169
ossification of, 174
Cranial arachnoid, 918
cavity, floor of, 112
relations of brain to walls of, 903
dura mater, 913
fossa, anterior, 113
middle, 116
posterior, 116
surgical anatomy of, 1342
nerves, 927
abducens, 934
central connections of, 818
cochlear, 950
facial, 943
glosso-palatine, 946
glosso-pharyngeal, 951
hypoglossal, 952
masticator, 942
oculo-motor, 931
olfactory, 929
optic, 930
paths of, cerebral, 895
short reflex, 898
spinal accessory, 958
superficial attachments of, 929
terminal, 929
trigeminus, 934
trochlear, 933
vagus, 954
vestibular, 949
pia mater, 922
subdural cavity, 917
venous lacunae, 649
sinuses, 649, 692, 916
Cranio-cerebral topography, 903, 1338
Cranio-mandibular musculature, 325, 338,
341
Cranium, 51
clinical anatomy of, 1333
measurements of, 117
remnants of cartilaginous, 124
Cremaster, 423, 434, 1254
external, 1259
internal, 1254, 1259
Cremasteric branches of internal spermatic
arteries, 501
fascia (external spermatic, or Cowper's
fascia), 426, 434, 1254
Crest(s), 29
arcuate, of arytaenoid cartilage, 1212
conchal, 88, 92
ethmoidal, 92
external occipital, 52
of fibula, 190
frontal, 60
of greater tuberosity of humerus, 148
of Uium, 169
incisor, 90
inferior turbinate, 92
internal occipital, 53
interosseous, of radius, 153
of ulna, 157
intertrochanteric, 178
lacrimal, posterior, 85
nasal, 90
neural, 754
obturator, 173
of scapula, 144
sphenoidal, 63
superior turbinate, 92
of tibia, anterior, 188
transverse, 72
Cribriform lamina, 119
plate of ethmoid, 81
INDEX
1487
Crico-arytaenoid articulation, 1214
ligament, 1214
Crico-arytaenoideus lateralis, 1219
posterior, 1218
Cricoid cartilage, 1210
Crico-pharyngeal ligament, 1218
Crico-thyreoid articulation, 1213
ligament, 1215
muscles, 1218
Crico-tracheal ligament, 1218
Crista, ampullary, 950, 1095
galli, 81, 113
supraventricularis, 516, 527
terminalis, 513
urethralis, 1263
vestibuli, 80
Crista} of matrix unguis, 1295
of skin, 1284
Crossed pyramidal tract, 783
Crown of tooth, 1117
Crucial anastomosis, 620
ligament of atlanto-epistrophic joint, 222
ligaments of knee-joint, 288
Cruciate ligament of leg (lower part of anterior
annular ligament), 479
of fingers, 387
Crura of anthelix, 1083,
of cerebrum, 833, 835
clitoridis, 1277
of diaphragm, 437
of fornix, 868
of greater alar nasal cartilages, 1202
of penis, 1261
of stapes, 80
Crural canal, 468
fascia, 477
nerve, anterior, 1001
interosseous 1010
Crureus, 468, 470
Cruro-pedal muscles, 486
Crus of helix, 1082, 1083
Cruveilhier, posterior cervical plexus of, 971
Cryptorohism, 1257
Crypts of iris, 1054
of Lieberktihn, 1166, 1177, 1390
of lingual tonsil, 1107
of palatine tonsil, 1132
Crystalline lens of eye, 1052, 1057, 1061
Cubital lymphatic node, superficial (supra-
trochlear), 719
Cuboid, 191, 199
Cuboideo-navicular ligaments, 303 '
union, 303
Cubo-metatarsal joint, 309
ligaments, 309
Culmen of cerebellum, 806
Cuneiform bones, 159, 161, 191, 197
first (medial, 197
third (lateral,) 198
second or middle, 197
cartilages (of Wrisberg), 1213
tubercle (of Wrisberg) of larynx, 1221
Cuneo-cuboid articulation 304
Cuneo-lingual gyrus, anterior, 864
posterior, 864
Cuneo-navicular articulation, 304
Cuneus, 864
Cupola of pleura, 1237
Cupular CEecum, 1096
portion of epitympanic recess, 1090
Curvatures of spinal column, 43
of stomach, 1152, 1374
greater, 1152
lesser, 1152
Cusps of atrio-ventricular valves, 516
Cutaneous areas of face, 1018
of lower extremity, 1024
Cutaneous areas of neck, 1019
of pinna (auricle), 1019
of scalp, 1018
of trunk, 1020
of upper limb, 1022
branches of anterior ethmoidal artery, 554
of intercostal arteries, 589, 590
(communicans fibularis) of common pero-
neal nerve, 1013
of deep circumflex iliac artery, 616
dorsal antibrachial (external) of radial
nerve, 987
of ilio-hypogastric nerve, 995
lateral, of thoracic nerves, 995
of median nerve, 992
plantar, of medial plantar nerve, 1010
posterior brachial (internal), of radial
nerve, 985
femoral cutaneous nerve, 1007
of sacral plexus, 1007
of superficial peroneal (musculo-cutane-
ous) nerve, 1015
of superior epigastric artery, 567
(medial sural cutaneous or tibial com-
municating) of tibial nerve, 1010
of ulnar nerve, 990
glands, 1296
glomiform, 1296
sebaceous, 1298
nerves, anterior of abdomen, 996
of femoral nerve, 1003
calcaneo-plantar, 1010
of foot, lateral dorsal, 1013
surface markings, 1466
intermediate dorsal, of leg, 1015
lateral, 1000
of abdomen, 995
sural, 1013
medial antibrachial (internal), 934
brachial, 983
dorsal, of leg, 1015
sural, 1010
posterior femoral (small sciatic), 1007
superficial cervical, 978
rete arteriosum, 1289
veins, 1289
Cuticle (epidermis), 1285
Cutis, 1285, 1286
Cymba conchse, 1082
Cystic artery, 595
duct, 1187
vein, 677
Cysto-colic ligament, 1379
Cytomorphosis, 7
Cytoplasm, 5
"Dangerous area" of leg, 1457
of scalp, 1333
Dartos, 1254, 1260
Darwin, tubercle of, 1083
Deciduous (milk) teeth, 1126
times of eruption, 1127
Declive of cerebellum, 806
Decussation, fountain, 842
of lemnisci, 815
of pyramids, 799, 815
of superior cerebellar peduncles (brachia
conjunctiva), 840
Deferential artery, 610
plexus of nerves, 1047
Deiters' nucleus, 823
Deltoid branch of profunda artery, 576
of thoraco-acromial artery, 571
(internal lateral) ligament of ankle-
joint, 298
surface markings, 1410
1488
INDEX
Deltoideus, 365
Delto-peotoral lymphatic nodes, 719
Dendrites, 762
Dens (odontoid process), 33
Dental arches, 1123
branches, inferior, of inferior dental plexus,
941
superior, of superior dental plexus, 938
canal, inferior, 96, 126
nerves, 938, 941
inferior, 941
superior, 938
Dentary centre, 98
Dentate fascia, 868
gyrus, 868
nucleus of cerebellum, 810
sutures, 212
Dentine, 1118
Denticulate ligament, 920, 921
Depressor alfe nasi, 334
anguli oris, 333
labii inferioris, 332
septi nasi, 334
Derma (oorium), 1286
Descemet, membrane of, 1060
Descendens cervicalis (hypoglossi), 953, 974,
979
Descending aorta, 586
brandies of cervical plexus, 978
of lateral circumflex artery, 543
(princeps cervicis) of occipital artery, 543
of spheno-palatine (Meckel's) ganglion,
963
of transverse cervical artery, 565
colon, 1174, 1379
palatine artery, 549
Descent of the testis, 1257, 1387
Development of anus, 1179
of arteries, 633
of articulations (joints), 213
of bones, 27 (see also the individual bones)
of brain, 754
of central sulcus (fissure of Rolando), 860
of oorium, 1290
of diaphragm, 120
of ear, 1096
of epidermis, 1286
of eye, lOSO
of face, 18
of hairs, 1293
of heart, 523
of hypophysis cerebri, 848
of kidney, 1248
of large intestine, 1179
of larynx, 1225
of limbs, 20
of lips and cheeks, 1104
of liver, 1189
of lungs, 1235
of lymphatic system, 706
of lymph-nodes, 707
of mammary gland, 1306
of muscles, 316
of nails, 1296
of nerve fibres, 758
of nervous system, 754
of nose, 18, 1208
of oesophagus, 1141
of oral cavity, 1102
of palate, 1105
of palato-pharyngeal muscles, 1137
of pancreas, 1195
of parathyreoid glands, 1319
of pericardium, 527
of peritoneum, 1144
of pharynx, 1138
of reproductive organs, 1278
Development of salivary glands, 1117
of sebaceous glands, 1298
of skull, 117
of small intestine, 1168
of spleen, 1312
of stomach, 1157
of suprarenal glands, 1326
of sweat glands, 1297
of teeth, 1124
of thymus, 1322
of thyreoid gland, 1318
of tongue, 1112
of tonsils, 1133
of tympanum, 80
of urinary bladder, 1253
of veins, 690
of ventricles of brain, 758
of vermiform process, 1179
of vertebra3, 45
of viscera, 18
Diagonal sulcus, 858
band of Broca, 866
Diameters of the pelvis, 175, 177
Diaphragm, 425, 436, 1372 .
crura, 437
and heart, recession of, 20
lymphatics, 725, 728
pelvic, 440, 1383
urogenital, 440, 1383
Diaphragraa pelvis (Meyer), 440
sella;, 848, 915
Diaphragmatic pleura, 1237
lymph nodes, 725, 736
pelvic fascia, 442, 447
plexuses of nerves, 1044
surface of heart, 509
of lung, 1229
of spleen, 1308
Diaphysis, 28
Diapophyses, 51
Diarthroses, 212
heteromorphic, 283
homomorphic, 212
Diencephalon (interbrain), 758, 843
Digastric fossa, 95
muscles, 314
triangle, 1357
Digastricus, 343, 344
Digestive system, 1099
abdomen, 1142
intestines, 1161
liver, 1180
mouth, 1100
oesophagus, 1138
pancreas, 1192
peritoneum, 1145
pharynx, 1129
stomach, 1151
Digital arteries, common (hand), 582
dorsal (foot), 633
plantar, 628
proper (hand), 582
branches, dorsal, of ulnar nerve, 990
of medial plantar nerve, 1011
volar, of ulnar nerve, 991
fossa of epididymis, 1255
of femur, 178
of fibula, 191
nerves, common plantar, 1011, 1013
common volar, of hand, 991
dorsal, of foot, 1013
of hand, 987, 990
proper plantar, 1011, 1013
volar, of hand, 992
veins (foot), dorsal, 684
plantar, common, 684
volar (hand), 671
INDEX
1489
Digital venous arch (hand), 667
Digitations, hippocampal, 877
Dilator naris anterior, 335
posterior, 335
pupilte, 1061
Dimples of skin, 1285
Diploe, veins of, 648
Direct cerebellar tract of Flechsig, 784
pyramidal tract, 788
Disc, articular, of the aoromio-clavicular
joint, 251
of inferior radio-ulnar articulation, 264
of mandibular articulation, 216
of the sterno-costo-clavicular joint, 249
optic, 1055
Dislocation of mandible, 1345
metaoarpo-phalangeal, 1434
of patella, 1446
Diverticula, intestinal, 1170, 1379
Diverticulum, Meckel's, 1169
Dolichopellie pelvis, 177
Dorsalis hallucis artery, 633
pedis artery, 632
Dorso-epitrochlearis, 379
Dorsum of foot, muscles of, 492
of ilium, 165
of nose, 1200
of penis, 1260
sellte (epihippi), 63, 116
of tongue, 1106
Douglas' fold, 427
(recto-uterine or recto-vaginal) pouch, 1148,
1267
Duct(s), alveolar, 1232
of Bartholin, 1117
cochlear, 1096
common bile, 1188
cystic, 1187
efferent of testis, 1256
ejaculatory, 1257, 1263, 1387
endolymphatic, 1094
of epididymis, 1256
of gall-bladder, 1188, 1373
of Gartner, 1275
hepatic, 1187
of lacrimal gland, excretory, 1047
lactiferous, 1302
of mammary glands, 1302
MilUerian, 1257, 1267, 1279
naso-lacrimal, 1080, 1205, 1349
pancreatic (of Wirsung), 1194, 1375
accessory (of Santorini), 1195
papillary (of Bellini), 1246
paraurethral (of Skene), 1277
of parotid gland (Stenson's), 1115, 1343
right lymphatic, '728
of Rivinus, 1117
semicircular, 1094
of sublingual gland, 1117
of submaxillary gland (Wliarton's), 1116
of sweat glands, 1297
thoracic, 726
thyreo-glossal, 1318
utriculo-saccular, 1094
Wolffian, 1248, 1267, 1278
Ductless glands, 1306
aortic paraganglia, 1329
chromaffin system, ,1323
glomus caroticum, 1325
ooccygeum, 1329
parathyreoid glands, 1318
spleen," 1306
suprarenal glands, 1323
thymus, 1319
thyreoid gland, 1312
Ductuli aberrantes (of epididymis), 1257
Ductus arteriosus (Botalli), 528
Ductus oholedochus (common bile-duct),
1188
(vas) deferens, 1257, 1259, 1387
(canaliculi) lacrimales, 1079
perilymphaticus, 81
reuniens of membranous labyrinth, 1094
venosus, 675, 694
Duodenal fossa;, 1164
papQla;, 1164, 1195
veins, 677
Duodeno-jejunal flexTire, 1152, 1376
Duodenum, 1161, 1375
lymphatics of, 734
parts of, 1161
Dupuytren's fracture, 1455
Dura mater, 771, 910
blood-vessels of, 917
cranial, 913
filum of, 911
nerves of, 917
spinal, 911
surgical anatomy of, 1342
Ear, 1082
development of, 1096
internal, 1092
middle, 1086
muscles of, 337, 1084
ossicles of, 79, 1090
vessels and nerves, 1084, 1086, 1091, 1096
Ectoderm, 10
Ehrenritter, ganglion of, 951
Ejaculatory duct, 1257, 1263, 1387
Elastic cone of larynx, 1215
membrane of larynx (Lauth), 1215
Elbow, clinical anatomy of, 1417
Elbow-joint, 258
arterial anastomoses around, 1418
supply of, 261
ligaments of, 258
movements of, 201
muscles acting upon, 261
nerve-supply of, 261
synovial membrane of, 261
Elevations of skin, 1284
Eleventh thoracic vertebra, 39
Elliptical recess (fovea hemielliptica), 80
Embryonic disc, 9, 10, 11
Eminence of auricle, 1083
collateral, 868, 877
frontal, 59, 108
hypoglossal, 814
ilio-pectineal, 169
medial, of floor of fourth ventricle, 813
parietal, 57
pyramidal, of temporal bone, 77
Eminentia arcuata, 78, 116
Emissary veins, 647, 649, 652, 916
mastoid, 647
parietal, 649
of scalp, 1334
Enamel, 1118 _
Enarthrodial diarthroses, 213
Encephalon, 751, 792
blood-supply of, 905
divisions of, 796
Endocardium, 508
Endoderm, 10
Endognathion centre, 91
Endolymph, 1093
Endolymphatic duct, 1094
sac, 1094
Endometrium, 1274
Endomysium, 315
Endo-pelvic fascia (recto-vesical), 442, 447
1490
INDEX
Endothoracic fascia, 1235
Enlargements of spinal cord, 772
Ensiform process (metasternum), 132, 134
Eparterial bronchus, 1232
Ependymal cells, 768, 846
Ephippial diarthroses, 212
Epicardium, 508
Epicondyles of femur, 183
of humerus, 151
Epicranial aponeurosis, 337
musculature, 336
Epicranio-temporalis, 337
Epicranius (occipito-frontalis), 336
Epidermis, (cuticle), 1285
Epididymal branches of int. spermatic ar-
teries, 601
Epididymis, 1266, 1386
Epidural cavity, 911
Epigastric artery, inferior (deep), 614, 639
superficial, 618
superior, 567
lymphatic nodes, 732, 733
plexus, 1043
region, 1143
veins, inferior, 683
superficial, 684
superior, 666
Epiglottic cartilage, 1212
tubercle, 1212, 1222
vallecula, 1221
Epihyal segment of styloid process, 119
Epimysium, 316
Epiphyseal cartilages, 28
lines, 28
Epiphyses, 28 (see also individual bones).
Epiphysis (pineal body), 758, 834, 845
Epiploic foramen (of Winslow), 1147
or omental branches of epiploic arteries, 595
Epipteric bones, 68, 101, 119
Episcleral arteries, 553
veins, 659
Epispadias, 1388
Epistropheus, description of, 33
Epithalamus, 845
Epithelial chorioid lamina, 924
Epithelium lentis, 1064
Epitrochleo-olecranonis (anconeus internus),
402
Epitym panic recess, 78
Eponychium, 1294, 1296
Epoophoron, 1269
Equator of eyeball, 1055
of lens of eye, 1062
Erector penis (or olitoridis), 451
spinas, 412, 414
Eruption of teeth, 1127
Ethmoid, 81
at birth, 124
cells, 83, 111, 1207
Ethmoidal artery, anterior, 554
posterior, 553
branches of anterior ethmoidal artery, 554
of posterior ethmoidal artery, 553
bulla. 111, 1205
canals, 61, 83, 110, 113, 126
(superior turbinate) crest, 92
fissure, 113
infundibulum, 1205
nerve, anterior, 936, 937
posterior, 937
notch, 61
process, 85
spine, 63, 113
veins, 659
Ethmo-turbinals, 119
Ethmo-vomerine region of skull, 117
Eustachian tube, 74, 1089, 1092
Eustachian tube, openings of, 1130, 1354
valve, 512
Excretory ducts of lacrimal gland, 1079
Exoccipital, 119
Exognathion centre, 91
Expiration, muscles which affect, 248
Extension (of muscles), 321
Extensor carpi radialis acoessorius, 391
brevis, 388, 389
intermedius, 391
longus, 387, 388
ulnaris, 388, 391
communis pollicis et indicis, 394
digiti annularis, 395
quinti proprius (extensor minimi digiti),
388, 391
digitorum brevis (foot), 454, 492
(hand), 395
communis, 388, 391
longus, 453, 480, 481
group of arm muscles, 377
hallucis brevis, 482, 492
longus, 453, 480, 482
indicis proprius, 392, 394
medii digiti, 395
ossis metacarpi pollicis (abductor pollicis
longus), 393
pollicis brevis, 392, 394
longus, 392, 394
Extremity, lower, bones of, 169
clinical and topographical anatomy of,
1434
lymphatics of, 746
upper, bones of, 139
clinical and topographical anatomy of,
1409
lymphatics, 719, 1424
Extrinsic muscles of tongue, 345
Eye, 1051
blood-vessels of, 1031
clinical anatomy of, 1346
crystalline lens, 1052
development of, 1080
eyelids, 1053, 1076
general surface view, 1052
lymphatics of orbit, 715
nerves of, 1064, 1348
Eyeball, (bulbus ocuh), 1-055
blood-vessels of, 1065
equator of, 1055
hemispheres of, 1057
insertions of muscles, 1056
muscles of, 501, 1067
nerves of, 1064
poles of, 1055
Eyelashes (cilia), 1053, 1347
Eyelids, 1053, 1076
blood-vessels of, 1078
clinical anatomy, 1346
glands of, 1078
lymphatics of, 712, 1078
nerves of, 1078
structure of, 1077
Face, bones of, 51
clinical anatomy, 1342
cutaneous areas of, 1018
development of, 18
lymphatic vessels of, 712
muscles of, 324, 329, 501
veins of, 643
Facial (external maxillary) artery, 540, 1343
branches of great auricular nerve, 978
(Fallopian) canal, 72, 77, 78
lymph-nodes, 709, 711
INDEX
1491
Facial nerve, 943, 946, 1345
nucleus of, 825
paralysis of, 1345
portion of external maxillary artery, 540
vein, anterior, 643, 1343
common, 644, 646
posterior (temporo-maxillary), 644
transverse, 646
Facialis, musculature, 324, 329, 501
Falciform ligament of liver, 1185
margin of fascia lata, 467
process of great sacro-soiatic ligament, 236
Fallopian canal, 72, 77, 78
tubes, 1269
Fallopius, aqueduct of (facial canal), 72
Falx cerebelU, 915
cerebri, 914
inguinalis (conjoined tendon of internal ob-
lique and transversalis), 436, 1396
Fascia(8B) antibrachial, 384
of arm, 377
axillary, 370, 371
brachial, 377
bulbi (Tenon's capsule), 1073, 1348
Camper's, 425
Colles', 425
coraco-clavicular (costo-coracoid), 371
cranio-mandibular, 339
cremasteric (Cowper's), 426, 434, 1254
cribrosa, 467
crural, 477
of deep musculature of shoulder girdle, 356
deep cervical, 1360
deep palmar, 387
dentate, 868
diaphragmatic pelvic, 442, 447
endo-pelvic (recto-vesical), 442, 447
endothoracica, 1235
external cervical, 347
spermatic, 1387
of foot, 491
of forearm and hand, 384
of hand, 1427
of head and neck, 329
hypothenar, 387
iliac, 455, 466
of ilio-femoral musculature, 455
ilio-peotineal, 455, 466
of infrahyoid musculature, 350
intercolumnar (external spermatic), 1304
interpterygoid, 339
of ischio-pubo-femoral musculature, 463
lata, 454, 457, 466, 1400, 1436
lateral pharyngeal, 339
of leg, 477
lingual, 346
lumbar, 436
lumbo-dorsal, 414, 428
masseteric, 339
middle cervical, 350
muscle, 313
of musculature of shoulder, 365
nuchae, 414
obturator, 439, 463
of orbit, 1071
palpebral, 1071
parietal (pelvic), 447
parotid, 339, 348, 1114
of pectoral muscles, 371
of pelvis, muscular, 443, 446, 447
subcutaneous, 445
penis, 1260
plantar, 1468
of posterior group of ilio-femoral muscles,
457
of prevertebral musculature, 355
prostatico-perineal, 447
Fascia (ae) psoas, 455
renal, 1242
of scalene musculature, 353
Scarpa's, 425, 445
of scrotum, 1385
semilunar, 382
Sibson's, 129, 356, 1237
of spinal musculature, 413
superficial, 313
permeal (Colles'), 446, 1385
of shoulder girdle, 347
of supra-hyoid musculature, 344
temporal, 339
thenar, 387
of thigh, 466
thoraco-abdominal musculature, 425
subcutaneous, 425
transversalis, 426
triangular, 430
of upper limb musculature, 363
of urogenital diaphragm, 445
of wrist, 1427
transversi of palmar aponeurosis, 387
Fas ci cuius (i), 769
anterior marginal, 786
comma-shaped, 782
cuneatus (Burdach's column), 781
gracilis (Goll's column), 781
inferior longitudinal, 892
intermediate, 784
lateral cerebro-spinal, 783
mammillo-mesen cephalic (tegmento-mam-
millary or mammillo-peduncular), 871
mammilio-thalamic, 871, 883
medial longitudinal, 817, 842
oblique, 804
oooipito-frontal, 892
pedunculo-mammillary, 849
proprii, 769
proprius, dorsal, 782
lateral, 782
ventral, 786
retroflexus of Meynert, 841, 843, 872, 886
rubro-spinal, 786
spino-cerebellar, dorsal, 784
spino-olivary (Helweg's bundle), 784
sulco-marginal, 788
superficial ventro-lateral (spino-cerebellar),
784
superior longitudinal, 892
■uncinate, 891
ventral cerebrospinal, 788
vestibulo-spinal, 786
Fasciola cinerea, 868
Fauces, isthmus of, 1100, 1130, 1131
Female, reproductive organs, 1265
clinical anatomy of, 1391
development of, 1278
external (vulva),- 1276
lymphatics of, 744, 1278
ovaries, 1238
tubffi uterinse (Fallopian tubes), 1269
uterus, 1271
vagina, 1274
vessels and nerves of, 1278
urethra, 1278
Femoral artery, 616, 1441
branches, 618
collateral circulation, 1441
common, 616
profunda or deep, 620, 640
superficial, 616
canal (crural canal), 468, 1400
cutaneous nerve, posterior (small sciatic),
1007
hernia, 1398
(anterior crural) nerve, 1001
1492
INDEX
Femoral plexus of nerves, 1045
ring, 466, 1401
septum, 466
sheath, 1400
trigone (Scarpa's triangle), 467, 1438
vein, 690, 1441
tributaries, 690
Femoro-tibial muscle, 486
Femoro-popliteal vein, 685, 693
Femur, 178
clinical anatomy of, 1434, 1442
condyles of, 1447
ossification of, 184
trochanters of, 178
Fenestra cochleae (rotunda), 73, 1089
vestibuli (ovalis), 73, 1089
Ferrein, pyramid of, 1246
Fibras propriae, 890
Fibres, arcuate, 817
association, of telencephalon, 890, 893
of white substance of spinal cord, 779
of cerebellar cortex, 809
cerebello-olivary, 817
of cerebral cortex, 879
commissural system of, 890
external arcuate, of medulla oblongata, 800
interorural (intercolumnar fascia), 430
internal arcuate, 815
muscles, 315
nerve, 767
development of, 758
projection, of telencephalon, 886
sympathetic, 970, 1029
visceral afferent, 970
efferent, 970
Fibro-cartQages, cotyloid, 281
interosseous, 244
interpubic, 240
intervertebral, 225, 238
semilunar, 289
triangular (articular disc), 264
Fibula, description of, 189, 1454
ossification of, 191
Fibular branch of posterior tibial artery, 626
collateral ligament, 286
nutrient branch of peroneal artery, 626
Fibulo-calcaneus medialis, 491
Fibulo-tibialis, 486
Fifth ventricle (cavity of septum pellucidum),
872
Fila radicularia, 775', 964
Filaments, root, of spinal nerves, 775
of pons, lateral, 804
Filiform, papillae of tongue, 1106
Filum of dura mater, 911
terminale, 771, 721
Fimbria, 868, 877
ovarica, 127
Fimbriae of tubae uterinae (Fallopian tube),
1270
Fimbriate folds of tongue, 1107
Fimbrio-dentate sulcus, 868
Fingers, 4
muscles acting on, 505
Fissura prima, 866
serotina, 865
Fissure(s), anterior median, 772
antitrago-helicine, 1084
auricular, 75, 108
calcarine, 864
calloso-marginal, 857, 859
of cerebellum, 805
of cerebrum, 852
chorioid, 1080
collateral, 855, 864
ethmoidal, 113
external parieto-occipital, 862
Fissure(s), Glaserian, 71, 77
hippocampal or (chorioid), 868
horizontal (of cerebellum), 805
inferior orbital (spheno-maxillary), 102, 109,
126
lateral (Sylvian), 850, 855, 1340
of liver, 1183
longitudinal, of cerebrum, 850
of lung, 1230, 1234
oral, HOC
parieto-occipital, 860, 864
petro-tympanic, 71, 77, 108, 126
portal, 1183
posterior median, of medulla oblongata, 801
postlimbic, 863
pterygo-maxillary, 102
pterygo-palatine, 102
retrotonsillar, of cerebellum, 807
of Rolando, 859, 1340
semilunar (of cerebellum), 805
spheno-maxillary, 102, 109
of spinal cord, 772
superior orbital (sphenoidal), 65, 109, 116'
125
of Sylvius, 850, 855
of telencephalon, 853
transverse, of cerebrum, 850
tympano-mastoid, 71, 75, 108
umbilical, of liver, 1183
Flechsig, direct cerebellar tract of, 784
secondary optic radiation of, 890
Flexion of muscles, 321
Plexor accessorius, 454, 495
longus digitorum, 491
carpi radialis, 396, 398
brevis (radio-carpeus), 403
ulnaris, 396, 398
brevis (ulno-earpeus), 402
digiti quinti brevis (foot), 454, 498, 499
(hand), 404
digitorum brevis, 454, 493
longus, 454, 486, 489
profundus, 401
Flexor digitorum profundus, 401
sublimis, 399
group of arm muscles, 379
haUucis brevis, 454, 496, 497
longus, 454, 486, 490
poUicis brevis, 407, 408
longus, 402
Flexure(s) of duodeno-jejunal, 1376
of duodenum, 1161
left cohe (splenic), 1174, 1379
of rectum, 1176
right colic (hepatic), 1173, 1379
Floating ribs, 127
Floccular fossa, 73
Flocculus of cerebellum, 807
peduncle of, 807
Floor of cranial cavitj', 112
of fourth ventricle, 813
pelvic, 1384
in female, 1394
Fluid, cerebro-spinal, 920 1342
Flumma pilorum, 1291
Fcetal circulation, 695
skull, general characters of, 120
Fold(s), adipose, of pleura, 1237
alar, 291
ary-epiglottic, 1221
of Douglas, 427
of duodenum, 1164
glosso-epiglottic, 1220
inferior palpebral, 1053
neural, 754
patellar, 290
recto-uterine, 1274
INDEX
1493
Fold(s), semilunar, of conjunctiva, 1055
of skm, 1284
sublingual, 1116
superior palpebral, 1053
transverse (Houston's), of rectum, 1177,
1390
of tympanic mucous membrane, 1089
ventricular, of larynx, 1222
vocal, 1223
Foliate papUlse of tongue, 1106
Folium vermis (cacuminis) of cerebellum, 806
Follicles, Graafian, 1269
of hair, 1292
lingual, 1107
lymph, 704
Fontana, spaces of, 1060
Fontanelle(s), sagittal, 59
of skull, 120
Foot, amputations of, 1465
arches of, 1468
arteries of, 627, 631
bones of, 191, 205, 1467
bony landmarks of, 1464
bursae of, 1465
clinical anatomy of, 1464
cutaneous nerves of, 1466
muscles acting on, at ankle-joint, 505
musculature of, 491
synovial membranes of, 1465
talipes, 1467
Foramen(ina), 29
acetabular, 174
apicis dentis, 1118
auditory, 125 ■
caecum, 61, 113, 1318
of ethmoid, 81
of medulla oblongata, 799
(Morgagni) of tongue, 1106
carotico-olinoid, 65
condylar, 54
costo-transverse, 127
of diaphragma sellae, 916
epiploic (foramen of Winslow), 1147
greater palatine, 106
hypoglossal, 54, 108, 125
incisive, 89
inferior dental, 96
infra-orbital, 87, 1345
intervertebral, 30
intraventricular (Monroi), 847, 874
jugular, 74, 108, 117, 125
laoerum, 63, 74, 108, 116
lesser palatine, 106
of Magendie, 813
magnum, 51, 56, 108, 117, 125
mandibular (inferior dental), 96
mastoid, 72, 108, 117
mental, 95
palatine, 106
of Monro, 847, 874
of nerves of skull, 125
of norma facialis, 108
obturator (thyreoid), 174
optic, 63, 64, 110, 116, 125
ovale, 66, 116, 125
of Pacchioni, 116
papillaria, 1246
parietal, 57
petro-sphenoidal, 125
. pharyngeal, 126
rotundum, 65, 103, 116, 125
sacral, 40
scapular, 142
of Scarpa, 89, 106, 126
spheno-palatine, 93, 103, 111, 126
spinosum, 65, 116
of Stenson, 89, 106
roramen(ina), sternal, 133
stylo-mastoid, 73, 108, 126
supra-orbital, 60
supratrochlear, 150
thyreoid (thyreoid cartilage), 1211
trigeminal, 125
venae cavae, 438
venarum minimarum (Thebesii), 514
vertebral, 31
Vesalii, 65, 116
zygomatioo-temporal, 126
Forceps major, 876
Forearm, clinical anatomj- of, 1419
common fractures of bones of, 1420
joints of, 1419
muscles of, 362
musculature of, 383
nerves of, 1423
synovial tendon sheaths of, 395, 403
vessels and nerves of, 1423
Fore-brain, 843
Formation, reticular, 816
Fornix, anterior pillars (columns) of, 870
body of, 869
conjunctival, 1054, 1347
fibres of, 869, 870, 871, 890
of Limbic lobe, 868
pharyngeal, 1130
posterior pillars (crura), 868
transverse, 869, 890
of vagina, 1275
Fossa (e), abdominal, 430
anterior cranial, 113
of anthelix, 1082
axillary, clinical anatomy of, 1411
canine, 87
cardiac, of lung, 1229
condylar, 54, 108
coronoid, 150
cotyloid, 169
digastric, 95
digital, of femur, 178
of fibula, 191
ductus venosi, 1183
duodenal, 1164
of femur, intercondyloid, 182
floocular, 73
of gall-bladder, 1183
glenoid, 29
of humerus, coronoid, 150
olecranon, 150
radial, 151
hypophyseos, 63, 116
iliac, 170
ileo-caecal, 1172
ileo-colic, 1172
ilio-pectineal, 467
incisive, 87
incisor, 95
infraspinous, 142
infra-temporal (zygomatic), 101, 1332
interpeduncular, 835
intersigmoid, 1175
ischio-rectal, 441, 445, 1384
jugular, 73, 108
lacrimal, 61, 109
mandibular, 108
mastoid, 72
middle cranial, 116
nasal, 108, 110
navicularis, 1264, 1277, 1392
olecranon, 150
ovalis (of heart), 512
(saphenous opening), 467, 1400, 1440
ovarica, 1268
paraduodenal (Landzert), 1164
pericardial, 1172, 1378
1494
INDEX
Fossa(e), posterior cranial, 116
pterygoid, 66, 107
pterygo-palatine (spheno-maxillary), 102
radial, 151
rhomboidea, 802
of Rosenmueller, 1130
scaphoid, 54, 55, 66, 95, 107
of skull, surgical anatomy of, 1342
spheno-maxillary (pterygo-palatine), 102
subareuata, 73, 117
subscapular, 141
supraspinous, 141
supratonsillar, 1132
Sylvian, 854
temporal, 101
triangular, of auricle, 1082
of elbow, 1418
trochanteric or digital, 178
trochlear, 61
venee cavEe, 1183
vermiform, 53, 108, 117
zygomatic, 101, 1332
Fossula cochlearis, 72
petrosa, 73
vestibularis, 72
Fountain decussation (Forel), 842
Fourchette, 1276, 1392
Fourth ventricle, 812
anatomy of, 812
chorioid plexus of, 922
floor of, 813
roof of, 812
tela chorioidea of, 922
Fovea of arytaenoid cartilages, 1212
centralis, 1055
of femur, 178
hemielliptica, 80
hemisphserica, 80
inferior, of floor of fourth ventricle, 814
superior of, floor of fourth ventricle, 815
inguinalis, 430
pterygoidea, 97
sublingualis, 95
umbilical, 1284
Foveola palatina, 1104
Fracture or fractures of bones of the leg, 1454
doUes', 1420
common, of bones of forearm, 1420
Dupuytren's, 1455
of mandible, 1345
of olecranon, 1420
Pott's, 1454
Freckles, 1283
Frenulum of anterior medullary velum, 832
clitoridis, 1277
of ileo-caecal valve, 1172
of penis, 1260
of tongue, 1107, 1349
veli, 812, 835
Frenum (duodenal), 1164
Frequency of disease of tarsal bones, 1396
Frontal artery, 554, 1343
association area, 894
bone at birth, 123
description of, 59
branches of anterior ethmoidal artery, 554
of superficial temporal artery, 545
convolution, ascending, 851
crest, 60
eminences, 59, 108
gyrus, inferior, 858
middle, 858
superior, 857
lobe, 857
nerve, 936, 1075
notch, 60
operculum, 856
Frontal pole, 850
pontile path (Arnold's bundle), 832, 840,
889
process of maxilla, 87, 88
sinus, 59, 61, 1207, 1335
spine, (nasal), 60
sulcus, inferior, 858
middle, 858
superior, 858
suture, 59
vein, 644
Frontal vein, 644
diploic, 648
Frontalis, 337
Fronto-ethmoidal cells, 84
Fronto-marginal sulcus, 858
Fronto-nasal plate, 117
process, 119
Fronto-sphenoidal process, 95
Functional areas of cerebral cortex, 893
Functions of cerebellum, 832
of muscle groups, 500
Fundiform hgament of penis, 427
Fundus of gall-bladder, 1187
of stomach, 1151, 1374
uterus, 1271
Fungiform papillse of tongue, 1106
Funiculi of nerves, 769
spinal cord, 774, 780
Funiculus, anterior, 775, 786
cuneatus of medulla oblongata, 801
gracilis of medulla oblongata, 801
lateral, 775, 782
posterior, 774, 780
separans, 814
Furcal nerve, 998
Furrow, 29
Furrows, articular, of skin, 1284
Fusiform gyrus (occipito-temporal convolu-
tion), 855, 864
muscles, 315
Galea aponeurotica (epicranial aponeurosis),
337
Galen, veins of, 923
Gall-bladder, 1187
clinical anatomy of, 1372
ducts of, 1187, 1188, 1372
Ganglion (ia), aberrant spinal, 965
of Andersch, 951
aortico-renal, 1043
basal, 878
of Bochdalek, 939
cardiac (ganglion of Wrisberg), 1041
ciliary, 961, 1033, 1076
ooccygeum impar, 1032, 1040
coeliac (semilunar), 1043
(neural) crest, 754
first thoracic, 1038
geniculate, 826, 947
inferior cervical, 1036
interpeduncular (von Gudden's), 843, 872,
885
jugular (superior), of glosso-pharyngeus,
957
of vagus, 954, 956
of glosso-pharyngeus, 951
middle cervical, 1036
nodosum (ganglion of trunk), 954, 956
otic (Arnold's), 963
petrosal, 951
phrenic, 1044
renal, 1044
of root of vagus, 956
roots of, 959
INDEX
1495
Ganglion (ia), second thoracic, 1038
semilunar (Gasserian), 826, 938, 1345
spheno-palatine (Meckel's), 962
spinal, 964
spiral, of cochlea, 950
splanchnic, 1039
submaxillary, 963
superior cervical, sympathetic, 960, 1035
jugular, or Ehrenritter's, 951
mesenteric, 1043, 1045
sympathetic, 959, 1032
of head, 959
of synovial sheaths, 1434
terminal, 930
of trunk of vagus, 956
of Valentine, 939
vestibular, 823, 950
of Wrisberg, cardiac, 498
Gangliated cephalic plexus, 959
nerve trunks (cords), 755, 1029, 1032
Ganglionic branches of middle meningeal
artery, 548
Gartner, duct of, 1275
Gasserian (semilunar) ganglion, 826, 935,
1345
Gastric artery, left, 593
right, 594
branches of epiploic arteries, 595
of vagus, 958
lymphatic nodes, 730, 734
plexus of nerves, anterior, 958
inferior, 1045
posterior, 958
superior (coronary), 1045
surface of spleen, 1309
Gastrocnemius, 453, 484, 485
Gastro-duodenal artery, 594
Gastro-epiploic artery, left, 595
right, 595
vein, left, 675
right, 675
Gastro-hepatic ligament, 1150
Gastro-phrenic ligament, 1150
Gastro-splenic (gastro-lienal) ligament
(omentum), 1150, 1310
Gastroptosis, 1160
Gemellus inferior, 464
superior, 464
Gemmules, 762
Genial tubercles, 95
Geniculate bodies, 834, 845
ganglion, 826, 949
Geniculo-tympanio branch of glosso-palatine,
951, 961
Genio-glossus, 346
Genio-hyoideus, 343, 344
Genio-pharyngeus, 346
Genital corpuscles, 1290
ridge, 1267, 1278
swellings, 1279
tubercle, 1279
Genitalia, female, external, 1276
clinical anatomy of, 1391
male, 1253
Genito-femoral (genito-crural) nerve, 1000,
1260
Genu of corpus callosum, 851
of facial canal, 78
inferior, of central sulcus (fissure of Rol-
ando), 860
of internal capsule (telencephalon), 887
superior, of central sulcus (fissure of Rol-
ando), 860
suprema artery, 621, 640
valgum, 1449
Germ laj'ers, 9
Gimbernat's hgament, 424, 429, 466, 1400 •
Gingival branches, inferior, of inferior dental
plexus, 941
superior, of superior dental plexus, 939
Ginglymi diarthroses, 213
Girdle, pelvic, 207
shoulder, 207
Glabella, 60, 101, 109, 1331
Gladiolus (mesosternum), 132
Gland(s), 1099
broncliial, 1231
Brunner's, 1166
bulbo-uretliral (Cowper's) 1265
carotid, 550, 1327
ceruminous, 1297
ciliary (of Moll), 1078, 1297
circumanal, 1297
ductless, 1306
of eyeUds, 1078
glomiform, 1296
greater vestibular (of Bartholin), 1278, 1392
Henle's 1078
I&ause's, 1078
lacrimal, 1079, 1348
lingual, 1108
lesser vestibular, 1278
of Lieberkuehn, 1166, 1177, 1390
of lips and cheeks, 1103
lymphatic, 704
intercolated, 706
mammary, 1299
of Montgomery, 1304
mucous, of larynx, 1224
nasal, 1208
of Nuhn or Blandin, 1110,
olfactory, 1208
para-thyreoid, 1318, 1355
parotid, 348, 1113
accessory, 1114
preputial, 1298
prostate, 1264
salivary, 1113
sebaceous, 1298
of skin, 1296
of small intestine, 1166
of palate, 1104
sublingual, 1116
submaxillary, 1116, 1350
sudoriferous (sweat), 1296
suprarenal, 1323
accessory, 1326
tarsal (Meibomian), 1054, 1078
thymus, 1319
thyreoid, 1312
accessory, 1315
clinical anatomy of, 1355
tracheal, 1227
urethral (of Littrg), 1264
Zeiss's, 1078
Glandular branches of external maxiUarj', 541
of inferior thyreoid artery, 564
Glans clitoridis, 1277
of penis, 1260
Glaserian fissure, 71, 77
Gleno-humeral bands, 254
ligament, 255
Glenoid cavity of scapula, 143
fossa, 29
ligament, (lip) 255
of metacarpo-phalangeal joints, 294
lip of shoulder-joint, 255
of hip-joint (cotyloid fibro-cartilage), 281
Gliding motion of joints, 214
Glisson's capsule, 675, 1186
paUidus, 880
Glomerular capsule, 1246
layer of olfactory bulb, 866
Glomeruli of olfactory nerves, 929
1496
INDEX
Glomiform glands, 1296
Glomus caroticum (carotid gland), 1327
choroideum, 876
cocoygeum, 1040, 1329
Glosso-epiglottic folds, 1220
ligament 1218
Glosso-hyal process, 99
Glosso-palatine arches, 1132
nerve, 826, 946
Glosso-palatinus (palato-glossus), lldo
Glosso-pharyngeal nerves, 820, 951
Glottis, 1223
Gluteal arteries, 608, 1444
branches, 609
superior, 608
inferior, 609, 639
branches of internal pudendal artery, 613
of posterior femoral cutaneous nerve, 1007
line, anterior, 170
inferior, 166
posterior, 170
nerve, inferior, 1007
superior, 1007
tuberosity of femur, 178
veins, inferior 680
superior, 680
Gluteus maximus, 453, 457, 459
surface marking, 1443
medius, 453, 457, 461
minimus, 453, 457, 461
Golgi cells in cerebellum, 809
Golgi-Mazzoni corpuscles, 1290
GolUs column, 781
Gomphosis sutures, 212
Gonion, 112, 113
Gower's tract, 784
Graafian follicles, 1269
Gracilis, 453, 471, 472
Granular layer of cerebellar cortex, 809
Granulations, arachnoid, 649, 919
Great auricular nerve, 978
cardiac vein, 520
omentum, 1149
(anterior) palatine nerve, 963
prevertebral plexuses of nerves, 1010
(internal) saphenous vein, 684, 1456
splanchnic nerve, 1038
superficial petrosal nerve, 948
trochanter of femur, 178, 1435
Greater alar (lower lateral) nasal cartilages,
1201
curvature of stomach, 1152
multangular (trapezium) bone, 162
occipital nerve, 971
palatine foramina, 106
canals, 92
tuberosity of humerus, 147 , ,• n
vestibular glands (glands of Bartholm),
1278, 1392
Grey commissure of spinal cord, 775 _ ■
rami communicantes of sympathetic sys-
tem, 1030
substance, central, of niesencephalon, 836
of pons (nuclei pontis), 831
of nervous system, 768
of spinal cord, 775
Groove of atlas, 33
basilar, 54
bony, 29
carotid, 64
costal, 127
costo-vertebral, 138
of cuboid, peroneal, 199
infra-orbital, 87
intertubercular (bicipital), 148
lacrimal, 85, 87, 110
mylo-hyoid, 96
Groove, neural, 754
obturator, 172
occipital, 72
optic, 63, 113
for radial nerve (musoulo-spiral), 149
sacral, 41
sigmoid, 72
Grouping of muscles according to function, 500
Growth, prenatal, 22
of the organs, 25
of the parts, 24
of the systems, 25
Gubernacular canals, 106
Gubernaculum testis, 1257, 1387
Gudden's commissure (inferior cerebral com-
missure), 842, 850, 890
Guftis, 1119
lymphatics of, 715
Gustatory area of cerebral cortex, 894
cells, 1051
organ, 1051
Gynecomastia, 1305
Gyrus (i) Andres Retzii, 868
ambiens, 865
angular, 863
anterior central, 857
cuneo-lingual, 843
orbital, 858
breves (precentral gyri), 857
of cerebellum, 804
of cerebrum, 852
cinguli (cingulum), 867
cunei, 864
cuneo-lingual, 864
deep annectant, 860
dentate, 868
epicallosus, 868
external orbital, 838
fornicatus, 867
cinguli (cingulum), 867
hippocampus, 868
isthmus of, 867
fusiform (occipito-temporal convolution),
855, 864
hippocampal, 868
inferior frontal, 858
temporal, 855
lateral occipital, 863
olfactory, 865
orbital, 859
lingual, 855, 864
longus, 857
marginal, 858
medial olfactory, 866
orbital, 858
middle frontal, 858
temporal, 855
orbital, 858
origin of, 853 ■ ^ in oci
posterior central (ascending parietal), 86 J.
orbital, 858
post-parietal, 863
profundi, 852
rectus, 858
semilunar, 865 ,
subcallosal (peduncle of corpus callosum).
866
submarginal, 858
superior frontal, 857
occipital, 863
parietal, 862
temporal, 854
supracallosal, 868
supramarginal, 863
transitivus, 852
transverse temporal, 855
• uncinatus, 868
INDEX
1497
H
Habenulse, 846
Habenular commissure, 846, 872, 885, 890
nucleus, 872, 885
trigone, 835
Habenulo-peduncular tract, 873
Hajmolymph nodes, 708
Haemorrhoidal artery, inferior, 613, 1391
middle, 610, 1391
superior, 603, 1091
of middle sacral artery, 603
nerves, inferior, 1017
middle, 1017
superior, 1045
plexus of nerves, middle, 1045, 1046
superior, 1045
of veins, 683, 1391
Hairs (pili), 1290
development of, 1293
olfactory, 1050
Hamate (unciform) bone, 159, 163
Hamular process of sphenoid, 66, 106, 1351
Hamulus, 81, 163
Hand, bony points of, 1424
clinical anatomy of, 1424
fascia of, 1427
muscles acting on, at wrist, 504
musculature of, 363, 383, 403
skin-folds of, 1425
synovial membranes of, 1431
Hard palate, 1104
Hare-lip, 1352
Harmonic sutures, 212
Hassal's corpuscles of thymus, 1322
Head of axis, 33
of bone, 29
bony landmarks of, 1331
clinical and topographical anatomy of, 1331
deep lymphatic nodes of, 714
vessels of, 714
of epididymis, 1256
lymphatics of, 709
of muscle, 314
muscles acting on, 502
musculature of, 323
of pancreas, 1192
process, 11
sympathetic ganglia of, 959
Heart, 508
Heart, atria of, 511
development of, 623
foetal, 695
ventricles of, 516
lymphatics of, 701, 730, 522
muscle of, 518
nerves of, 522
relation to chest-wall, 523, 1368
vessels of, 519
Heister, valve of, 1187
Helicis major, 1084
minor, 1084
Helicotrema, 81
Helix, 1083
Helweg's (Bechterew's) bundle, 784
Hemiazygos vein (azygos minor), 662
accessory, 663
Hemispheres of cerebellum, 805
cerebral, 850
Henle, loop of, 1246
Henle's glands, 1078
Hepatic artery, 594
branches of superior epigastric artery, 567
of vagus, 958
duct, 1187
(right coUc) flexure, 1173, 1379
lymphatic nodes, 730, 736, 1186
Hepaticlymphatics, 1186
plexus of nerves, 1045
veins, 675
Hepato-oolic ligament, 1379
Hepato-duodenal ligament, 1150, 1185
Hernia, congenital, 1255, 1387, 1398
femoral, 1394
into the funicular process, 1255, 1398
infantile, 1398
inguinal, 1255, 1394, 1398
scrotal, 1255
surgical anatomy of, 1394
umbilical, adult, 1402
Hesselbach, ligament of, 430
triangle of, 1398
Hey's amputation, 1465
Hiatus, accessory, 116
aorticus of diaphragm, 437
canalis facialis, 73, 116
cesophageus, 437
sacralis, 40
semilunaris of middle nasal meatus, 1205
Highest nuchal line, 52
Highmore, antrum of, 87, 90, 111, 1206, 1346
Hilus of kidney, 1242
of lungs, 1229, 1230
of ovary, 1268
of spleen, 1309
of suprarenal glands, 1325
Hind-brain, 804
Hip, musculature of, 453, 454
Hip-joint, 276
arterial supply, 282
ligaments of, 277
lymphatics of, 750
movements of, 282
muscles acting upon, 283
nerve-supply, 282
relations, 282
surgical anatomy of, 1435
Hippocampal branch of posterior communi-
cating artery, 554
commissure (psalterium or b'ra), 869, 890
digitations, 877
(ohorioid) fissure, 868
gyrus, 868
Hippocampus, 868
gyrus of, 868
major, 868, 877
minor (calcar avis), 864, 868, 876
Hirci, 1290
Homologies of parts in sexes, 1280
Homology of the bones of the limbs, 206
Horizontal fissure of cerebellum, 805
Horner's muscle, 336, 1078
Horns of spinal cord, 776
Houston's folds of rectum, 1177, 1390
Huguier, canal of, 75, 77, 108
Hum.eral artery, anterior circumflex, 572
posterior circumflex, 573
Humerus, description of, 146
clinical anatomy of, 1410, 1414
nutrient artery of, 576
ossification of, 161, 1416
tuberosities of, 147
Humor, aqueous, 1052, 1064
vitreous, of eye, 1052, 1064
Hunter's (adductor) canal, 468, 1441
Hyaloid canal (canal of Cloquet), 1064
membrane, 1064
Hydatid of Morgagni, 1257, 1269
Hymen, 1276, 1392
Hyo-epiglottic ligament, 1218
Hyo-glossal membrane, 346
Hj'o-glossus, 346
Hyoid bars, 119
bone, 99, 119
1498
INDEX
Hyoid bone at birth, 124
cornua of, 99, 100
muscles acting on, 501
branch of lingual artery, 540
of superior thyreoid artery, 538
bursa, 1217
Hyo-mandibular muscles, 325
Hyo-temporal muscles, 325
Hyo-thyreoid ligament, 1217
membrane, 1217
Hyparterial bronchus, 1232
Hypertrichosis, 1290
Hypertrophy of nails, 1296
Hypochondriac region, 1143
Hypochordal bar, 51
Hypogastric (internal iliac) artery, 605, 638
branches, 606, 639
lymphatic nodes, 732
plexuses of nerves, 1045
region, 1143
(internal iliac) vein, 679
tributaries, 680
Hypoglossal eminence (trigonum hypoglossi),
814
foramen (canal), 54, 108, 117, 125
(cervical) loop, 974, 979
nerve, 952
central connections, 820, 954
nucleus of, 820
Hypomalar, 95
Hypophyseal fossa (sella turcica), 63
Hypophysis cerebri, 758, 847, 848, 1342
development of, 848
Hypospadias, 1280, 1388
Hypothalamic nucleus (body of Luys), 884
sulcus, (sulcus of Monro), 847
Hypothalamus, 881
optic portion of, 847
Hypothenar fascia, 387
Hypo-tympanic recess, 77
Ileo-csecal fossa, 1172
(colic) valve, 1172
region, 1376
Ileo-colic artery, 598
fossa, 1172
vein, 677
Ileum, 1165, 1376
Iliac arteries, collateral circulation, 605, 1382
common, 603, 605, 638
deep circumflex, 616
external, 614, 638
superficial circumflex, 618
branch of ilio-lumbar artery, 607
(nutrient) branch of obturator artery, 608
colon, 1174, 1379
fascia, 455, 466
fossa, 170
lymphatic nodes, common, 731
external, 732
plexus of nerves, 1045
spines, 169
vein, external, 683
internal (hypogastric), 679
veins, common, 679
Iliacus, 455
minor, 455
Ilio-cocoygeus, 440, 448
Ilio-costal region, 1407
Ilio-costalis cervicis (cervicalis asoendens),
416
dorsi (accessorius), 416
lumborum, 416
Ilio-femoral ligament, 278
musculature, 454
Ilio-hypogastric nerve, 998
Ilio-inguinal nerve, 1000
Ilio-lumbar artery, 606
ligament, 233
vein, 680
Iho-pectineal eminence, 169
fascia, 455, 466
fossa, 467
line, 173
Ilio-tibial band, 457, 458, 1436
Ilio-trochanteric band, 280
Ilium, 169
crest of, 169
tuberosity of, 171
Inca bone, (interparietal), 57
Incisive branch of inferior alveolar (dental)
artery, 548
foramen, 89
fossa, 87
papilla, 1104
sutures, 106
Incisivus labii inferioris, 332
superioris, 332
Incisor crest, 90
fossa, 95
teeth, 1120
Incisura, 29
apiois cordis, 510
interarytsenoidea, 1222
Incisure, anterior, of auricle, 1082
antitragic, 1082
of Santorini, 1085
terminal (auricle), 1084
Incudo-maUeolar articulation, 1090.
Incudo-stapedial articulation, 1090
Incus, 79, 119
ligaments of, 1091
Index, cephalic, 117
pelvic, 177
thoracic, 139
Induseum griseum, 868
Infra-clavicularis, 374
Infraglenoid tubercle of scapula, 143
Infrahyoid musculature, 327, 350
portion of external cervical fascia, 347
Infra-omental region of peritoneum, 1372
Infra-orbital artery, 549, 1075
branches of cervico-facial nerve, 945 ,
canal, 87, 103, 126
foramen, 87, 1345
groove, 87
nerve, 937, 939
plex-us, 937, 939, 945
process, 95
sulcus, 1284
vein, 646
Infraspinatus, 368
Infraspinous branches of posterior scapular
artery, 566
of transverse scapular artery, 565
fossa, 142
Infra-temporal (zygomatic) fossa, 101, 1332
ridge, 65
Infratrochlear nerve, 936, 937
Infra-vomerine center, 71
Infundibula (ureter), 1248
Infundibular recess, 848
Infundibulo-pelvic ligament, 1267
Infundibulum of cerebrum, 848
of ethmoid, 83
in middle nasal meatus. 111, 1205
of tuba? uterinte (Fallopian tubes), 1270
Inguinal abdominal (internal abdominal)
ring, 430, 1371, 1396
branches of femoral artery, 620
canal, 424, 430, 1371, 1395
hernia, 1255, 1394, 1398
INDEX
1499
Inguinal (Poupart's) ligament, 424, 429, 1371,
1399, 1438
reflected (triangular) fascia, 430, 1395
lymphatic nodes, 746
ring, subcutaneous (external abdominal),
429, 1371, 1394
(iliac) regions, 1143
Inion, 101, 1331
Inlet or brim (superior aperture) of pelvis, 175
Innominate artery, 532, 637, 1369
branches, 532
Innominate canal (canaliculus), 65
bone, 169
(brachio-cephalic) veins, 641, 691, 692
relations to thoracic wall, 1369
Inscriptio tendinea, 317, 430
Insertion of muscles, 314 (see also individual
muscles)
Inspiration, muscles which affect, 247
Insula (island of Reil), 856
Integument, 1281
Interarticular cartilage, 211
ligament (capitular articulation), 241
(sterno-costal joint), 245
menisci (semilunar ftbro-cartilages), 289
Interarytffinoid (procricoid) cartilage, 1213,
1218
Inter-brain, 843
Intercalated lymph-nodes, 706
Intercapitular veins (hand), 667
(foot), 684
Intercarpal ligaments, 269
Interchondral articulation, 246
arterial supply, 247
capsule of, 247
movements, 247
nerves, 247
Interclavicular ligament, 248
notch, 133
Intercoccygeal joints, 238
Intercondyloid fossa of femur, 182
eminence of tibia, 185
fossae of tibia, 185
tubercles, 185
Intercostal branches of internal mammary
artery, 567
arteries, 588
superior, 568
branches of musculo-phrenic artery, 567
ligaments, external, 423, 432
lymphatics, 724, 728
muscles, function of, 422
nerves, thoracic, 995
spaces, 139
veins, 664
Intercostales externi, 423, 432
interni, 423, 433
Intercosto-brachial (interc osto- humeral)
nerve, 995
Intercrural (intercolumnar) fibres of external
obhque, 430, 1394
Intercuneiform articulation, 304
Interfascial (Tenon's) space, 715
Interfoveolar ligament, 430, 435
Interior of skull, 112
Interlobar fissure of lungs, 1230
Intermediate cell mass, 15
crus of diaphragm, 437
fasciculus (mixed lateral zone), 784
plex-us, 1041
Intermetacarpal articulations, 273
Intermetatarsal joints, 309
Intermuscular septa, 314
of foot, 492
of leg, 477
of thigh, 468
septum of arm, lateral, 377
Intermuscular septum of arm, medial, 377
Interossei dorsales (foot), 499
(hand), 410
plantares, 499
volares (hand), 409
Interosseous arteries of foot, 633
of forearm, 577, 579, 1423
artery, of forearm, common, 577
dorsal, 579
volar, 577, 639
crest of fibula, 190
of radius, 153
of tibia, 188
of ulna, 157
crural nerve, 1010
ligaments, anterior talo-calcaneal joint, 302
inferior, tibio-fibular articulation, 297
intercuneiform joints, 304
middle tarso-metatarsal joints, 308
of middle tibio-fibular union, 296
of pelvic, articulations, 235
of posterior talo-calcaneal joint, 301
superior, tibio-fibular joint, 295
membrane of forearm, 263, 264, 1420
muscles of foot, 454, 499
of hand, 409
nerve, posterior, 986
volar (anterior), 992
recurrent artery, 580
Interparietal bone, 119
sulcus (intraparietal), 861
Interpeduncular fossa, 835
nucleus (ganglion), 843, 885
Interphalangeal articulations of fingers, 276
of toes, 310
Interpterygoid fascia, 339
Interpubic fibro-cartilage, 240
Intersigmoid fossa, 1175
Interspinal muscles (interspinals), 412, 419
Interspinous ligaments, 231
Intersternal joints, 244
Intertragic notch, 1082
Intertransversarii, 412, 417
Intertransverse ligaments, 231
muscles, anterior and lateral, 356
dorsal, 412
Intertrochanteric crest, 178
Intertubercular (bicipital), groove, 148
Intervaginal space of optic nerve, 1073
Interventricular foramen (foramen of Monro),
847, 874
septum, 516
Intervertebral articulation, ligaments of, 225
fibro-cartilages, 225, 238
veins, 666
Intestinal arteries, 596
veins, 677
lymphatic trunk, 731
Intestines, clinical anatomy of, 1375
large, 1170, 1376
lymphatics of, 734
small, 1161, 1375
Intracranial portion of internal carotid artery,
550
of vertebral artery, 560
Intralabial muscles, 331
Intraparietal sulcus, 861
Intrinsic muscles of great toe, 495
of larynx, 1218
of httle toe, 498
of tongue, 1110
Introduction, 1
Intumescentia tympanica, 951
Involution of mammary gland, 1303
Iris, 1052, 1054, 1060, 1065.
Ischial spine, 172
Ischio-bulbosus muscle, 451
1500
INDEX
Ischio-capsular ligament, 278
Ischio-cavernosus (erector penis), 443, 451
Iseliio-femoralis, 461
Ischio-pubicus (Vlacovitoh), 450
Ischio-pubo-femoral musculature, 463
Ischio-rectal fossae, 441, 445, 1384
Ischium, 171
Island of Reil (insula or central lobe), 865
Isthmus, aortic, 531
of Fallopian tubes, 1290
of fauces, 1100, 1352
of gyrus fornicatus, 867
pharyngeal (faucium), 1100, 1130, 1131,
1352
of rhombeneophalon, 758, 832
of thymus, 1321
of thyreoid gland, 1313
of tuba auditiva (Eustachian tube), 1092
of uterus, 1271
Iter chordae anterius, 126
posterius, 78, 126
Jacobson, nerve of, 951, 961
organ of, 1057, 1204
Jejunal and Oiac branches of superior mesen-
teric artery, 598
Jejuno-ileum, lymphatics of, 734
Jejunum, 1165, 1376
Joint-furrows, 1284
Joints (see "Articvdations").
Jugular foramen, 74, 108, 117, 125
fossa, 73, 108
ganglion (superior) of glosso-pharyngeal,
951
of vagus, 954, 956
nerve, 960, 1035
(interclavicular) notch, 133
process, 54, 108
vein, anterior, 648
line of, 1356
external, 646, 1359
internal, 659, 691
posterior external, 648
venous arch, 648
Jugum sphenoidale, 67
K
Kidneys, 1241, 1379
clinical anatomy of, 1379
development of, 1247
lymphatics of, 701, 737, 1247
position and relations of, 1243, 1380
structure, 1246
surfaces of, 1243
variations and comparative, 1247
vessels and nerves of, 1247
Knee-joint, 284
anastomoses around, 1457
arterial supply, 291
bursae around, 1449
clinical anatomy of, 1449
ligaments of, 284
lymphatics of, 750
movements of, 292
muscles acting upon, 295
nerve-supply, 292
relations, 292
synovial membrane of, 290, 1448
Krause, end-bulbs of, 1290
glands of, 1078
Kronlein's method for topography of brain,
1340
Labia (see also "Lips").
of cervix uteri, 1272
majora, 1276, 1392
minora (nymphae), 1277, 1392
Labial arteries (of mouth), 541
(or scrotal) arteries, anterior, 620
posterior, 613
branches, inferior, of mental nerve, 941
superior, of maxillary nerve, 939
nerves, anterior, 1000
posterior, 1017
tubercle, 1102
veins (of mouth) 644
(of vulva), 683, 684
Labyrinth of ethmoid, 82
membranous, 1092
osseous, 80
Lacertus fibrosus (semilunar fascia), 382
Lacrimal apparatus, 1079
clinical anatomy of, 1346
artery, 552
bone, 85
at birth, 124
branch of dorsal nasal artery, 554
of middle meningeal artery, 548
canal, 1080
caruncle, 1052, 1055
crest, 85, 110
ductus (canaliculi), 1079
fossa, 61, 109
gland, 1079, 1348
groove, 85, 87, 110
nerve, 936, 1075
papilla, 1054
process, 85
puncta, 1079, 1349
sac, 1080, 1349
tubercle, 88
vein, 659
Lacrimo-ethmoidal cells, 84
Laciniate ligament (internal annular) of leg,
480
Lactiferous duct, 1254
sinus (ampulla), 1254
Lacuna(8e) laterales, 649
magna, 1264
of Morgagni (urethral), 1264
musculorum, 466
vasorum, 466
venous, of dura, 916
Lacunar (Gimbernat's) ligament, 424, 429,
466, 1400
Lalognosis, 894
Lambda, 101, 1331
Lambdoid suture, 57, 101
Lamellous corpuscles of (Vater, or Pacinian),
1290
Lamina(Ee), anterior elastic, of cornea, 1060
basal (vitreous), of chorioid, 1060
basilaris of membranous labyrinth, 1096
of cerebellum, medullary, 808
chorio-capillaris, 1060
cribriform, 119
cribrosa solera, 930, 1055, 1059, 1073
of temporal bone, 92
of cricoid cartilage, 1210
epithelial chorioid, 876, 924
fusca, 1059
mediastinales, 1237
medullary, of lenticular nucleus, 880
of thalamus, 882
papyracea (os planum), 83
posterior elastic, of cornea, 1060
quadrigemina, 833
rostal, of corpus callosum, 852
INDEX
1501
Lamina of septum pellucidum, 812
spiralis, 81
suprachoroidea, 1057, 1060
terminalis, (of brain), 848
(of isohio-rectal fossa), 1384
of thyreoid cartilage, 1210
tragi, 1084
of tuba auditiva, 1092
of vertebrEe, 30
Landmarks of abdomen, 1370
bony of the ankle, 1459
of the buttocks, 1442
of cranium and scalp, 1333
of elbow, 1417
of the foot, 1464
of forearm, 1419
of the knee, 1447
of neck, 1354
of the leg, 1453
of thigh and hip, 1434
of wrist and hand, 1424
Langerhans, islets of, 1195
Lanugo, 1290
Large intestine, 1170
anus, 1177
blood-vessels of, 1179
caecum or caput coli, 1170, 1377
clinical anatomy of, 1376
colon, 1173, 1378
development of, 1179
lymphatics of, 1179
nerves of, 1179
rectum, 1176
variations and comparative, 1130
vermiform process (appendix), 1173, 1378
Laryngeal artery, superior, 538
inferior, 564
nerve, inferior, 957
superior, 956
pharynx, 1134
prominence, 1211
veins, inferior, 659
superior, 659
ventricle, 1222
Larynx, 1209
cartilages of, 1209
cavity of, 1220
development of, 1225
joints of, 1213
lymphatics of, 719, 1224
muscles of, 326, 501, 1218
vessels and nerves of, 1224
vocal folds (cords), 1223
Latissimo-condjdoideus (dorso-epitrochlearis),
379
Latissimus dorsi, 368
clinical anatomy of, 1405
Law of developmental direction, 12
Laxator tympani muscle, 79
Left atrium of heart, 514
colic artery, 603
vein, 678
common carotid artery, 533
iliac artery, 605
coronary artery, 520
gastric artery, 593
gastro-epiploic artery, 595
vein, 677
innominate vein, 641
lower bronchial artery, 588
pulmonary artery, 529
veins, 529
subclavian artery, 556
upper bronchial artery, 588
ventricle of heart, 516, 517
Leg, bony landmarks of, 1453
clinical anatomy of, 1453
Leg, fasciae of, 497
nauscles acting on, 505
muscular compartments, 1453
musculature of, 453, 477
vessels of, 1456
Lemnisci, decussation of, 815
of medulla oblongata, 815
Lemniscus, 831, 839
lateral, 816, 831, 839
medial, 816, 831, 839
nucleus of, 824, 839
Lens, crystalline, 1052, 1057, 1062
Lens-capsule, 1057
Lenticular nucleus, 878, 879
process of incus, 79
papillte of tongue, 1106
Lenticulo-optic artery, 562
Lenticulo-striate arterjf, 562
Lesser alar (sesamoid) nasal cartilages, 1202
curvature of stomach, 1152
multangular (trapezoid) bone, 159, 162
(gastro-hepatio) omentum, 1150, 1185
palatine foramina, 106
sac of peritoneum, 1148
sigmoid cavity of ulna, 157
splanchnic nerve, 1039
tuberositj' of humerus, 147
Levator ani, 440, 448
claviculae, 359
cushion, 1130
epiglottidis, 347
labii superioris, 322
alaeque nasi, 332
menti, 334
palpebrae superioris, 1068
penis, 451
scapulffi 356, 359
of thyreoid gland, 1315
veli palatini, 1137
Levatores costarum, 423, 432
longi, 432
Levels, vertebral, 1409
Lieberkiihn, (crypts) glands of, 1166, 1177,
1390
Lienal plexTis of nerves, 1045
Lieno-renal ligament, 1310
Lieutaud, vesical trigone of, 1252
Ligament (s) (see also "Ligamentum"), 211
alar (occipito-dental or check), 223
of ankle-joint, 298, 1463
annular, at ankle, 1463
of finger, 387 ^
of superior radio-ulnar joint, 262
of trachea and bronchi, 1227
of wrist, 387
anterior, of ankle, 298
annular (wrist), 387
atlanto-epistrophic, 221
atlanto-occipital, 218
crucial, 288
longitudinal, 227
medio-carpal, 270
oblique (lateral occipito-atlantal), 219
sacro-coccygeal, 234
sacro-iliac, 234
of symphysis pubis, 239
talo-calcaneal, 302
talo-fibular, 299
apical dental (suspensory), 223
arcuate (subpubic), 239
connecting articular processes vertebrae, 228
Cooper's, 1400
of articulation of atlas with occiput, 218
of atlanto-epistrophic joint, 221
of auricle (of ear), 1084
uniting bodies of vertebrae, 225
broad (lateral), of uterus, 1267, 1393
1502
INDEX
Ligament(s) of ealcaneo-cuboid joint, 306
calcaneo-fibular, 299
calcaneo-metatarsal, 492
of capitular (oosto-oentral) articulation, 241
capsular, of elbow-joint, 258
carpal (annular), 1427
of carpo-metacarpal joints, 272
of the carpus, dorsal, 384
transverse, 387
volar, 387
cerato-oricoid, 1213
check, of eyeball, 1072
coccygeal, 911
CoUes', 430
conoid, 251
coraco-acromial, 252
coraco-clavioular, 251
coraco-humeral, 255
corniculo-pharyngeal, 1218
coronary, of knee-joint, 290
of liver, 1184
costo-clavicular, (rhomboid), 249
of oosto-transverse articulation, 243
costo-xiphoid, 244,245
crioo-arytaenoid, 1214
crico-pharyngeal, 1218
crico-tracheal, 1218
crucial, of central atlanto-dental joint, 222
of knee-joint, 288
cruciate, of leg, 479
of fingers, 387
of cuboideo-navicular union, 303
of cubo-metatarsal joint, 308
of cuneo-ouboid articulation, 304
of cuneo-navicular articulation, 304
cysto-oolic, 1379
deltoid (of ankle-joint), 298
denticulate, 920, 921
dorsal intercarpal, 269
of elbow-joint, 258
external arcuate, 437
intercostal, 423, 432
lateral, of knee-joint, 286
falciform, of liver, 1185
fibular collateral, 286
of first row of carpal bones, 269
fundiform (superficial suspensory) of penis,
427
gastro-hepatic, 1150, 1185
gastro-phrenic, 1150
gastro-splenic, (gastro-lienal), 1150, 1310
Gimbernat's, 424, 429, 466
gleno-humeral, 255
glenoid (lip), 255
glosso-epiglottic, 1218
hepato-colic, 1379
hepato-duodenal, 1150, 1185
Hesselbach's, 430
of hip-joint, 277
hyo-epiglottic, 1218
hyo-thyreoid, 1217
ilio-lumbar, 238
ilio-femoral, 278
immediate, 225
of incus, 1091
inferior interosseous, (tibio-fibular), 297
of inferior radio-ulnar joint, 264
inferior sacro-iliac, 235
transverse, (spino-glenoid), 253
infundibulo-pelvic, 1267
inguinal (Poupart's), 424, 429, 1371, 1399,
1438
interarticular, 241, 245
interclavicular, 248
of intercuneiform joint, 304
interfoveolar, 430, 435
intermediate, 225
Ligarnent(s) of intermetacarpal joints, 273
of intermetatarsal joints, 309
internal arcuate, 437
lateral, of knee-joint, 286
of mandibular articulation, 215
interosseous, cubo-metatarsal joint, 309
anterior talo-calcaneal, 302
intercuneiform joints, 304
intermediate tarso-metatarsal joint, 308
metacarpal, 269
of pelvic articulations, 235
of posterior talo-calcaneal joint, 301
of interphalangeal joints, fingers, 276
of toes, 311
interspinous, 231
of intersternal joints, 244
intertransverse, 231, 238
of intervertebral articulation, 227
of knee-joint, 284
(internal annular) laciniate, of leg, 480
ischio-capsular, 278
lacunar (Gimbernat's) 424, 429, 466, 1400
of larynx, 1213
lateral, of ankle-joint, 299
calcaneo-navicular, 302, 305
hyo-thyreoid, 1217
malleolar, anterior, 296
posterior, 297
sacro-coccygeal (intertransverse), 238
of left vena cava, 521, 523
of liver, 1184
malleolar (of tympanum), 1091
of mandibular articulation, 215 ,
medial palpebral, 1052
median crico-thyreoid, 1215
hyo-thyreoid, 1217
of medio-carpal joint, 270
of metacarpo-phalangeal joints, 274,;_275
of metatarso-phalangeal joints, 310
of mid radio-ulnar union, 262
middle costo-transverse, 243
tibio-fibular (interosseous), 296
morphology of, 213
neck, 243
oblique, of mid radio-ulnar union, 262
popliteal (hgament of Winslow), 287
occipito-cervical, 223
uniting occiput and epistropheus,' 223
orbito-tarsal, 1071
of ossicles of ear, 1090
ovarian, 1269
patellar, 471
of pelvic articulations, 234
piso-hamate, 269
piso-metacarpal, 269
phreno-cohc or costo-colic, 1150, 1174, 1310,
1379
phrenico-lienal (lieno-renal) ,'1310
plantar, 1468
calcaneo-ouboid, 307
calcaneo-navicular, 302, 305
accessory, 310
long, 307
pulmonary, 1236
posterior, of ankle-joint, 298
annular (wrist), 384
atlanto-epistrophic, 221
atlanto-occipital, 218
costo-transverse, 243
crucial (of knee), 288
longitudinal, 227
(dorsal) medio-carpal,' 270
sacro-iliac, 234
of symphysis pubis, 239
of talo-calcaneal joint, 301
talo-fibular, 299
Poupart's, 424, 429,n371
INDEX
1503
Ligament (s), proper scapular, 252
pubo-prostatic (pubo-vesical), 1252
radial collateral, 261, 267
radiate of anterior costo-central or stellate,
242
of medio-carpal joint, 270
sterno-costal, 245
of radio-carpal joint, 266
of radio-ulnar joints, 261, 264
reflected inguinal (triangular fascia), 430
rhomboid (costo-clavioular), 249
round, of uterus, 1274
of liver, 1185
of sacro-coccygeal articulation, 238
sacro-lumbar, 232
saoro-spinous or small sacro-sciatic, 236
sacro-tuberous, 235
of sacro-vertebral articulations, 232
of second row of carpal bones, 270
of shoulder-joint, 254
between skull and vertebral column, 218
spheno-mandibular, 217
spino-glenoid (inferior transverse), 253
connecting spinous processes of vertebrae,
229
spiral, of cochlea, 1096
spring, 305
sterno-clavicular, 248
of sterno-costal joints, 245
of sterno-costo-clavicular articulation, 248
sterno-pericardial, 522
stylo-hyoid, 99
stylo-mandibular (stylo-maxillary), 217
superficial transverse, 387
superior costo-transverse, 243
interosseous, tibio-fibular joint, 295
sacro-iliac, 234
sterno-costal, 245
transverse (coracoid or suprascapular),
253
supraspinous, 230, 238
suspensory, of Cooper, 1303
of the eyeball, 1072, 1348
of lens of eye, 1057, 1064
of ovary, 1269
of penis, 427, 1260
of Treitz, 1164, 1376
of symphysis pubis, 238
talo-calcaneal, 302
of talo-navicular joint, 305
temporo-mandibular, 215
thyreo-epiglottic, 1215
thyreoid, 1314
tibial collateral, 286
tibio-fibular, 295
transverse, of central atlanto-epistrophic
joint, 222
crural, 479
dorsal (medio-carpal joint), 270
- of heads of metatarsal bones, 309
of hip-joint, 280
humeral, 256
of knee-joint, 289
of pubis, 446
connecting transverse processes of vertebrae,
231
trapezoid, 251
triangular, of liver, 1185
tubercular (posterior costo-transverse), 243
ulnar collateral, 259, 266
umbilical, 1250, 1252
uniting laminae of vertebrae, 229
of urinary bladder, 1252
utero-sacral, 1274
vaginal, 317
vaginal (fingers), 387
ventricular of larynx, 1215
Ligament(s), vocal, 1215
volar accessory (glenoid), 274
intercarpal, 269
radio-carpal, 266
Ligamenta denticulata, 911
flava, 229
Ligamentous branch of ovarian artery ,"[ 602
Ligamentum (a) alaria (knee-joint), 291
ano-coccygeum, 449
arteriosum, 628, 531
breve, 399, 401
dentioulatum, 920, 921
epididymis, 1255
interfoveolare, 430
longum, 399, 401
rauoosum (knee-joint), 290
nuchas, 231, 414
patellae, 285, 1448
pectinatum iridis, 1060
sacro-iliaoa, anteriora, 177, 234
teres, 280
of liver, 675, 1185
(round ligament) of uterus, 1274
venosum of liver, 675, 1185
Winslowii, 287
Ligature of anterior tibial artery, 1458
of brachial artery, 1414
of common carotid artery, 1358
of femoral artery, 1441
in Hunter's canal, 1442
of popUteal artery, 1452
of posterior tibial artery, 1458
of third part of subclavian artery, 1359
of ulnar artery, 1423
Ligula (taenia ventriculi quarti), 813
Limbic lobe, 865, 866
Limbous sutures, 212
Limbs, cutaneous areas of,'1020, 1022,',1024
development of, 20
Limbus of cornea, 1025
fossae ovalis, 511
sphenoidalis, 63
of tympanic membrane, 1087
Limen of insula, 857, 865
nasi, 1204
Limiting sulcus of floor of fourth ventricle, 813
Line(s) (see also "Linea").
(striae) albicantes, 1283, 1384
bony, 29
of femur, intertrochanteric, 178
sph-al, 178
of fibula, oblique, 190
secondary obUque, 190
gluteal, 170
ilio-pectineal, 173
mylo-hyoid, 95
Nflaton's, 1436
oblique, of mandible, 95
of radius, 154
of thyreoid, 124
popliteal, 189
of scapula, oblique, 142
supra-condylar, of femur, 181
temporal (ridges), 57, 60, 1332
transpyloric (Addison's), 1153, 1370
trapezoid (oblique), 140
of ulna, oblique, 157
LLaea alba of abdomen, 427, 1370
viscera behind, 1373
aspera, 178
pectinea of femur, 181
semiciroularis, 427
semilunaris of abdomen, 1371
splendens, 921
suprema (highest nuchal line), 52
Lingual artery, 539
branches, 539
1504
INDEX
Lingual (gustatory) branch of inferior alveolar
(dental) artery, 548
of glosso-pharyngeal nerve, 952
of facial nerve, 944 ^
fascia, 346
follicles, 1107 ■'
gyrus, 864
nerve, 940, 1350
papillae, 1160
plexus of nerves, 1036
tonsil, 1107
veins, 660
Lingula cerebelli (luigula vermis), 806, 831
of left lung, 1229
of mandible, 96
of sphenoid, 64 >
of Wrisberg, 942
Lips, 1102, 1349
of Eustachian aperture, 1130
glenoid, 255
of ileo-c£ecal valve, 1172
lymphatics of, 713
variations and comparative, 1172
vocal, 1223
Lisfranc, amputation of, 1465
Lissauer, marginal zone of, 782
Little finger, muscles of, 404
Littr6, glands of (urethral), 1264
Liver, 1180
blood-vessels of, 1185
clinical anatomy of, 1373
development of, 1189
ductus oholedochus (common bile-duct),
1188
gall-bladder, 1187
ligaments of, 1184
lobes and fissures of, 1180
lymphatics of, 699, 736
topography of, 1373
Liver, surfaces and borders of, 1181
variations and comparative, 1190
Lobe(s), biventral, 807
central, 856
of cerebellum, 805
frontal, 857
inferior semilunar, of cerebellum, 807
limbic, 865, 866
of liver, 1183
of lungs, 1230
of mammary gland, 1302
occipital, 863
olfactory, 865
■parietal, 860
of prostate, 1265
pyramidal, of thyreoid gland, 1314
quadrangular, 806
superior semilunar of cerebellum, 806
of telencephalon, 853
temporal, of cerebrum, 854
of thymus, 1320
of thyreoid gland, 1313
uvular, of cerebellum, 791
Lobule of auricle of ear, 1083
central, of cerebellum, 806
of cerebellum, 805
inferior parietal, 863
paracentral, 857, 863
quadrate, 863
splenic, 1312
superior parietal, 862
of testis, 1256
of thymus, 1321
of thyreoid gland, 1316
Lobulus epididymis (conus vasculosus), 1256
Locus caeruleus of floor of fourth ventricle,
815, 829
Loewenthal's tract, 786
Longissimus capitis (trachelo-mastoid), 416
cervicis (transversalis cervicis), 416
dorsi, 416
Longitudinal arch of foot, 1468
bundle, posterior, 817
fasciculus, inferior, 892
medial, 817, 842
nucleus of, 871
superior, 892
fissure of cerebrum, 850
ligament of intervertebral articulation, 227
(sagittal) sinuses, 649, 650
striEe of corpus callosum, 851, 892
of hippocampus, 871
vertebral veins, 665
Longitudinalis hnguse inferior medius, 347
Longus capitis (rectus capitis anterior major),
355
colli, 355
Loop, cervical (hypoglossal), 953, 979
Henle's, 1246
Louis, angle of, 139
Lower extremity, articulations of, 276
clinical anatomy of, 1434
cutaneous areas of, 1024
fasciie of, 454
lymphatics of, 746, 748
musculature of, 452
Lowest lumbar (lumbalis ima) artery, 603
Lumbar arteries, 593, 638
lowest (ima), 603
branch of ilio-lumbar artery, 607
enlargement of spinal cord, 772
fascia, 436
lymphatic nodes, 730
trunks, 730
muscle, 436
nerves, 973, 996
posterior primary divisions, 973
plexus, 998
branches of, 998
composition of nerves of, 998
situation of, 998
portion of sympathetic system, 1039
puncture (Quinclve), 1408
regions, 1143
ribs, 132
veins, 675
ascending, 662, 663
vertebrse, 37
description, 37
development of, 48
Lumbo-costal arch, lateral, 437
medial, 437
Lumbo-dorsal fascia, 414, 428
Lumbo-inguinal (crural) branch of genito-
femoral nerve, 1000
Lumbo-sacral angle, 43
plexus, 996
trunk, 1005
Lumbricales (foot), 454, 495
(hand), 408, 409
Lunate (semilunar) bone, 159, 161
Lungs (pulmones), 1228
clinical anatomy of, 1367
development of, 1235
form of, 1228
lobes of, 1230
lymphatics of, 729, 1235
surfaces of, 1229
topography of, 1233, 1367
variations of, 1235
vessels and nerves of, 1234
Lunula of nails, 1295
of semilunar valves, 517
Luys, body of, 884
Lymph, movement of, 702
INDEX
1505
Lymphatic capillaries, 697, 698
duct, right (terminal collecting), 728
follicle, 70-1
nodes (glands) of abdomen and pelvis,
730
ano-rectal, 735 -
anterior auricular, 709
mediastinal, 724
axillary, 719
bronchial, 725, 1226
buccinator, 711
coeliac, 730
common iliac, 731
deep cervical chain, 714
delto-pectoral, 719
development of, 707
diaphragmatic, 725, 736
epigastric, 732, 733
external iliac, 732
facial, 709, 711
gastric, 730, 734
of head and neck, 709, 714
hepatic, 730, 736
hypogastric, 732
inferior deep cervical, 714
inguinal, 746
internal mammary, 724
intercostal, 724
of larynx, 1224
of lower extremity, 746
lumbar, 730
mesenteric, 731
meso-colic, 734
occipital, 709
parietal, of thorax, 724
parotid, 709
of pelvis, 730
popliteal, 748
post-aortic, 731
posterior mediastinal, 725
auricular, 709
pre-aortic, 730
pulmonary, 725
sacral, 733
splenic, 730, 736
structure of, 704
subinguinal, 746
submaxillary, 709
submental, 711
superficial cubital (supratrochlear),
719,1
superior deep cervical, 714
supramaxillary, 711
of thorax, deep, 724
visceral, 724
umbilical, 733
of upper extremity, 719
system, 697
general anatomy of, 697
special anatomy of, 709
development of, 706
of eyeball, 1065
of orbit, 1076
vessels, 702, 705
of abdomen and pelvis, 733
of eyelids, 1078
of face, 712
of head, 712, 714
of hip-joint, 750
of knee-joint, 750
of lower extremity, 748
of neck, 712, 714
of CESophagus, 730, 1141
regeneration of, 707
structure of, 702
of thorax, deep, 725
superficial, 723
95
Lymphatic vessels of upper extremity, deep,
721
superficial, 721
Lymphatics of abdomen and pelvis, 730
in abdominal wall, 1372
of alimentary tract, 699, 733
of anus, 735
of auricle (of ear), 714, 1084
of brain, 714
capillaries, 697
of clitoris, 745
of conjunctiva, 698, 712
of diaphragm, 728
of digestive tract in head and neck, 715 '
of ductus deferens and seminal vesicles, 744
of duodenum, 734
of excretory organs, 737
of external auditory meatus, 714, 1086
of the eye, 715, 1065
of eyelids, 712
of Fallopian tube, 745, 1270
of female external genitals, 744, 1278
of gums, 715
of head and neck, 709
of heart, 522, 701, 730
of ileooEeoal region, 734
intercostal, 728
of jejuno-ileum, 734
of kidney, 737, 1247
of large intestine, 734, 1179
of larynx, 719, 1224
of lips, 713
of liver, 736, 1186
of lower extremity, 746, 1468
of lungs, 729, 1235
of mammary gland, 723, 1305
of nasal cavities, 717, 1208
of neck, 709
of nose, 712, 1203, 1208
of ovary, 745, 1269
of palate, 717
of pancreas, 736, 1195
of parotid gland, 1115
of penis, 744, 1262
offpharynx, 717, 1138
of pleura, 1239
of prostate, 739, 1265
of rectum and anus, 735
of reproductive organs, male, 742
of scalp, 712
of scrotum, 742, 1255, 1385
of shoulder-joint, 723
of skin, 698, 1289
of small intestine, 1168
of spleen, 736, 1312
of stomach, 734, 1156
of suprarenal glands, 738, 1326
of teeth, 1124
of testis, 744, 1256, 1387
of thoracic muscles, 723
of thorax, 723
of thj'reoid gland, 719, 1317
of thymus, 729, 1322
of tongue, 715, 1111
of tonsils, 1138
of trachea and bronchi, 699, 1228
of tubae (Fallopian tubes), 1270
of upper extremity, 719, 1424
of ureter, 738, 1249
of urethra, female, 742
male, 744
of urinary bladder, 739, 1253
of uterus, 745, 1274
of vagina, 745, 1276
of vulva, 744, 1278
Lymph-follicles, 704
Lymph-nodes, 704
1506 INDEX
Lymphoglan dulse, 704
Lymphoid organs, 704
Lyra, hippocampal, 869
M
Macewen's suprameatal triangle, 1337
Macula aoustica saoouli, 950, 1094
utriculi, 1093
lutea (yellow spot), 1055, 1057
Magendie, foramen of, 813
Major sublingual duct (of Bartholin), 1117
palatine artery, 549
Malar bone, 93
branches of maxUlary nerve, 938
of temporo-facial nerve, 945
tubercle, 95
tuberosity, 93
Male mammary gland, 1305
pelvis, 1382
reproductive organs, 1263, 1386
Malleolar artery, lateral, 632
medial, 632
posterior lateral artery, 626
folds of tympanic mucous membrane, 1089
ligaments, anterior lateral, 296
posterior lateral, 297
of ossicles of ear, 1091
prominence of tympanic membrane, 1087
recesses of tympanic mucous membrane,
1089
rete, lateral, 626, 632
medial, 626, 632
stria of tympanic membrane, 1087
Malleoli, clinical anatomy of, 1451
lateral, 191
medial, 189
Malleus, 79, 119
Malpighi, pyramids of, 1246
Malpighian corpuscle (renal), 1246
(splenic), 1311
Mammary artery, external, 1305
internal, 566, 1365
cutaneous branches of aortic intercostal
arteries, 590
gland (mamma), 1299
clinical anatomy of, 1366
line (ridge), 1306
lymphatics of, 723, 1305
in male, 1305
vessels and nerves of, 1305
plexiis of nerves, internal, 1037
veins, internal, 666
venous plexus, 671
MammiUary bodies, 843, 871
process, 38
MammUlo-mesencephalic fasciculus, 871
Mammillo-thalamic fasciculus, 871, 883
Mandible (lower jaw), 95
age changes in, 99
at birth, 124
ossification of, 98
surgical anatomy of, 1345
Mandibular bars, 119
branches of cervico-faoial nerve, 946
(inferior dental) canal, 96, 126
foramen, 96
fossa, 108
nerve (third division of trigeminus), 939,
1345
(sigmoid) notch, 96, 97
portion of internal maxillary artery, 546
spine, 96
Manubrium of malleus, 79
sterni (presternum), 132, 133
Margin, falciform, of fascia lata, 467
of lungs, 1229, 1233
Marginal gyrus, 858
sinuses, 650
zone of Lissauer, 782
Marge aoutus of heart, 510
obtusus, 510
Marshall, obhque vein of, 521, 523
Massa intermedia, 844
Masseter muscle, 338, 341
Masseteric branch of external maxillary
artery, 541
artery, 548
fascia, 339
nerve, 943
veins, 644, 646
Mastication, muscles of, 325
Masticator nerve, 829, 942
Mastoid antrum (see "Tympanic antrum"),
branch of great auricular nerve, 978
of occipital artery, 543
of small occipital nerve, 977
of stylo-mastoid artery, 544
canaliculus, 73
cells, 72, 1092, 1336
foramen, 72, 108, 117
(supra-meatal) fossa, 72
notch (digastric fossa), 72
process, 72, 108
development of, 76
Mater, dura, 771
pia, 771
Maxilla, 86, 1346
at birth, 124
ossification of, 91
Maxillary artery, external, 540, 638, 1343
internal, 545, 638
nerve (second division of trigeminus), 937
plexus of nerves, external, 1036
internal, 1036
process of inferior turbinate, 85
of palate bone, 92
sinus (antrum of Highmore), 87, 90, 111,
1206, 1346
vein, internal, 646
Maxillo-ethmoidal cells, 84
Maxillo-turbinates, 119
Meatal branch of stylomastoid artery, 544
Meatus, external auditory (acoustic), 75, 108,
1084, 1332
internal auditory, 72, 117
naso-pharyngeus, 1206
of nose, 83, 111, 1205
Meckel's cartilage, 98, 119
caves, 916
diverticulum, 1169
ganglion, 962
Median antibrachial vein, 667, 668
artery of forearm, 578, 639
basilic (cubital) vein, 667, 669
cephalic vein, 668
crico-thyreoid ligament, 1215
cubital vein, 667
fissure of spinal cord, anterior, 772
hyo-thyreoid ligament, 1217
nerve, 991, 1423
results of paralysis of, 1424
sulcus of floor of fourth ventricle, 813
Mediastinal artery, anterior, 567
branches of aorta, 590
lymphatic nodes, anterior, 724
posterior, 725
pleura, 1237
septum, 1239
surface of lungs, 1229
veins, 664, 667
Mediastinum, 20, 1228, 1239
divisions, 1239
testis (corpus Highmori), 1256
INDEX
1507
Medio-oarpal joint, 270
arterial supply, 270
ligaments, 270
movements of, 271
muscles acting upon, 270
nerve-supply of, 270
Medulla of kidney, 1246
oblongata, 799
blood-vessels of, 908
central connections of cranial nerves in,
818
ventral aspect of, 799
of suprarenal gland, 1321
of thymus, 1326
Medullary cavity, 28
lamina of lenticular nucleus, 880
of thalamus, 882
laminae of cerebellum, 808
ray of kidney, 1246
sheaths, 759
strise, acoustic, 824
velum, anterior (superior), 812
posterior, 808
MeduUated fibres, 760, 767
Medullation of fasciculi of spinal cord, order
of, 791
Meibomian glands, 1054, 1078
Meissner, tactile corpuscles of, 1290
plexus of, 1030, 1045
Membrana sacciformis, 265
Membrane (s). Bowman's, 1060
choroidal, 1052
of Descemet, 1060
elastic, of larynx, 1215
hyaloid, 1064
hyo-glossal, 346
hyo-thyreoid, 1217
interosseous, of forearm, 1420
of mid-radio-uLnar union, 263, 264
of middle tibio-fibular union, 295
pharyngeal, 1102
quadrangular of larynx, 1215
secondary tympanic, 1089, 1096
Shrapnell's, 1087
synovial, 211; (see also the individual ar-
ticulations)
Membrane, tectorial, 223
tympanic, 1086
vestibular (membrane of Reissner), 1096
Membranous ampullae, 1095
cochlea, 1095
cranium, 117
labyrinth, 1092
nasal septum, 511
semicircular canals, 1094
urethra, 1264, 1388
Meningeal artery, accessory (small), 548
arteries, 917
middle, 547
surgical anatomy of, 1341
posterior, 537
branches of anterior ethmoidal artery, 554
of maxillary nerve, middle (recurrent)
937
of occipital artery, 543
of ophthalmic nerve, recurrent, 935
of posterior ethmoidal artery, 553
of spinal nerve-trunks (recurrent), 970
of vagus, 956
of vertebral artery, 560
plexus of nerves, 1036
veins, 646, 917
Meninges, 908
arachnoid, 917
dura mater, 910
pia mater, 920
relation to spinal nerves, 965
Meningoceles, 1331
Menisci, interarticular, 289
Mental branch of inferior alveolar (dental)
artery, 548
foramen, 95
muscle, 334
nerve, 941
protuberance, 95
spine, 95
tubercle, 95
Mentalis (levator menti), 334
Mento-labial sulci, 1284
Meridians of eyeball, 1055
Mesatipellio pelvis, 177
Mesencephalon, 758, 833
blood-vessels of, 907
external features of, 834
internal structure of, 836, 843
Mesencephalic root of masticator nerve, 836,
942
nucleus of, 829
Mesencephalo- or tecto-spinal tract, 786, 842
Mesenteric artery, inferior, 602, 638
superior, 596, 638
ganglion, superior, 1043, 1045
lymphatic nodes, 731
plexus of nerves, inferior, 1045
superior, 1045
vein, inferior, 678
superior, 677
Mesenteriolum, of appendix, 1173
Mesentery, 1165, 1376
development of, 19
Mesethmoid, 119
Meso-colic lymphatic nodes, 734
Meso-colon, 1174, 1175
Mesoderm, 10, 14
Mesognathion centre, 91
Meso-metrium, 1267
Meso-nephros (Wolffian body), 16, 1256, 1278
Meso-palatine suture, 89, 106
Meso-salpinx, 1267
Meso-scapula, 145
Meso-sternum, 132
Mesotendons, 318
Mesovarium, 1267
Metacarpal arteries, dorsal, 586
volar, 586
bones, 164
union of heads of, 274
head of adductor polUcis, 408
veins, dorsal, 667
volar, 671
Metacarpo-phalangeal joints, 274
of thumb, 275
Metacarpus, ossification of, 168
Metamerism, 15
of cranial musculature, 327
Metamorphosis of branchial (visceral) bars,
119
Metanephros, 1278
Metasternum, 132
Metatarsal artery, dorsal, 633
plantar, 628
bones, 200
union of heads of, 309
piUar, 205
veins, plantar, 687
Metatarso-phalangeal articulations, 310
Metatarsus, 200
Metathalamus (geniculate bodies), 845
Metopic suture, 69, 101
Meynert, fasciculus retroflexus, 843," 885
Micromastia, 1301
Mid-brain, 833
Middle alveolar canal, 87
(azygos) articular artery, 623
1508
INDEX
Middle cardiac nerve, 1036
vein, 520
cerebral artery, 555, 562
vein, 655
clinoid process, 65
coat of eye, 1060
colic artery, 598
collateral (branch, of profunda) artery, 576
constrictor of pharynx, 1137
costo-transverse (neck or interosseous) liga-
ment, 243
cranial fossa, 116
Middle ear, 77, 1086
ethmoidal cells. 111
hsemorrhoidal artery, 610
meatus of nose. 111
meningeal artery, 547, 1341
veins, 646
nasal conchae, 83
palatine foramina, 106
peduncle of cerebellum, 811
sacral artery, 603
vein, 679
suprarenal arteries, 598
temporal artery, 545
thalamic branch of posterior communicating
artery, 554
thyreoid vein, 661
umbilical ligament, 1250
Mid-radio-ulnar union, 262
Milk, 1303
teeth, 1126
Minor palatine arteries, 549
sublingual ducts (of Rivini), 1117
Mitral cells of olfactory bulb, 866
(bicuspid) valve, 515, 516
Moderator band of heart, 516
Modiolus, 81
Molars, 1121
Molecular layer of cerebellar cortex, 809
Moll, glands of, 1078
Monro, foramen of, 847, 874
sulcus of, 847
Mons pubis (veneris), 1276
Montgomery, glands of, 1304
Monticulus of cerebellum, 806
Morgagni, columns of, 1177
hydatid of, 1257, 1269
lacunse of, 1264
sinus of, 1137
ventricle of, 1222
Morphogenesis, 7 (see also "Development")
Morphological axis of scapula, 145
Morphology (see also "Comparative
Anatomy")
of alimentary canal, 1099
of joints, 213
of musculature of head and neck, 323
of pelvic outlet, 444
of skull, 117
of spinal cord, external, 771
of the testis, 1256
of the vertebrEe, serial, 50
Morula, 9
Motor aphasia, 894
area of speech, 894
roots (see individual nerves)
TMouth, 1100
clinical anatomy of, 1349
muscles of, 332
Movements of joints, 214 (see also individual
articulations)
Mullerian duct, 1257, 1267, 1279
Multangular bone (trapezium) greater, 159,
162
(trapezoid) lesser, 159, 162
Multifidus, 412, 419
Multipenniform muscle, 315
Muscle(s) (see also "Musculature")
abductor aocessorius digiti quinti (foot), 499
digiti quinti (foot), 454, 498
(hand), 404
hallucis, 454, 496
longus, 482
ossis metatarsi quinti, 499
poUicis brevis, 406, 407
longus (extensor ossi metaoarpi polli-
cis), 392, 393
abnormal, of front of leg, 482
of back of leg, 491
of volar side of forearm and wrist, 392
accessorius ad flexorem digitorum profun-
dum (forearm), 402
of gluteus minimus, 462
of spinal musculature, 416
accessory peroneal, 484
acting upon joints (see individual articula-
tion)
adductor brevis, 453, 471, 474
digiti secundi, 498
hallucis, 454, 496, 498
longus, 453, 471, 472, 1437
magnus, 453, 471, 474, 1437
minimus, 474
poUicis, 407, 408
anconeus, 374, 377, 379
internus, 402
of the angle of the mouth, 332
anomalus, 335
antagonists, 322
anterior and lateral intertransverse, 356
antitragus, 1084
articularis genu, 470
atlanto-mastoid, 422
attached to the tendons of flexor digitorum,
longus, 495
attachments of bones (see individual bones)
of auricle (of ear), 337, 1084
auricularis anterior (attrahens aurem), 337
posterior (retrahens aurem), 337
superior (attollens aurem), 337
auriculo-frontalis, 337
ary-epiglottic, 1220
ary-membranosus, 1220
arytaenoideus obliquus, 1220
transversus, 1218
ary-vocalis, of Ludwig, 1220
belly of, 314
biceps brachii, 374, 379, 382, 1414
biceps femoris, 453, 475
bicipital, 314
bipenniform, 315
biventer cervicis, 418
brachialis, 374, 380, 382
braohio-radialis (supinator radii longus),
387, 388
broncho-oesophageal, 1141, 1248
buccinator, 334
bulbo-cavernosus, 443, 450
in female, (sphincter vaginae), 450, 1278
oaninus, 332
caput angulare, 332
infraorbitale, 332
zygomaticum, 332
cerato-cricoid, 1218
cervical, 330
cervicalis ascendens, 416
chondro-humeralis (epitrochlearis), 374
chondro-glossus, 346
ciliaris Riolani, 1077
ciliary, 1057, 1060
classification of, 319
coooygeus, 440, 448
complexus, 412, 417
INDEX
1509
Musole(s), compressor bulbi proprius, 450
hemisphseriura bulbi, 451
venae dorsalis, 451
constrictor laryngis, 1218
radicis clitoridis, 451
penis, 450
vaginae, 449, 451
ooraco-brachialis, 374, 379, 381
corrugator, 336
cutis ani, 445
costo-coraooideus, 374
cremaster, 423, 434, 1254, 1259
crico-arytEenoideus lateralis, 1219
posterior, 1218
crico-thyreoid, 1218
crureus, 468, 470
cruro-pedal, 486
deltoideus, 364, 365, 1410
depressor alae nasi, 334
anguli oris, 333
labii inferioris, 332
septi nasi, 334
diaphragm, 425, 436
digastric variety of, 314
digastricus, 343, 344
dilator naris anterior, 335
posterior, 335
pupilte, 1061
divisions of, 316
of dorsum of foot, 492
epicranio-temporalis, 337
epicranius, 336
epitrochleo-olecranonis (anconeus internus),
402
erector spinas, 414
extensor carpi radialis accessorius, 391
brevis, 388, 399
intermedius, 391
longus, 387, 388
ulnaris, 388, 391
communis pollicis et indicis, 394
digiti annularis, 395
quinti proprius, 388, 391
digitorum brevis (foot), 454, 492
(hand), 395
communis, 388, 391
longus, 453, 480, 481
hallucis brevis, 482, 492
longus, 453, 480, 482
indicis proprius, 392, 394
medii digiti, 395
minimi digiti, 388, 391
ossis metacarpi pollicis, 392, 393
poDicis brevis, 392, 394
longus, 392, 394
erector penis (clitoridis), 443, 451
fascite, 313
femoro-tibial, 486
fibulo-calcaneus medialis, 491
fibulo-tibialis (peroneo-tibialis), 486
finer structure of, 315
flexor accessorius (digitorum longus), 491
(quadratus plantae), 495
carpi radialis, 396, 398
brevis (radio-carpeus), 403
ulnaris, 396, 398
brevis (ulno-carpeus), 402
digiti quinti brevis (foot), 454, 498, 499
(hand), 404
digitorum brevis (foot), 454, 493
longus (leg), 454, 486, 489
profundus, 401
sublimis, 399
hallucis brevis, 454, 496, 497
longus, 454, 486, 490
pollicis brevis, 407, 408
longus, 402
Muscle (s), of front of leg, 480
frontalis, 337
fusiform, 315
gastrocnemius, 453, 484, 485
gemellus inferior, 464
superior, 464
genio-glossus, 346
genio-hyoideus, 343, 345
genio-pharyngeus, 347
glosso-palatinus (palato-glossus), 1135
gluteus maximus, 443, 457, 459
medius, 457, 461
minimus, 457, 461
gracilis, 453, 471, 472
gross structure of, 314
grouped according to function, 500
head of, 314
helicis major, 1084
minor, 1084
Horner's, 336
hyo-glossus, 346
iliacus, 455
minor, 456
ilio-coccygeus, 440, 448
ilio-costalis cervicis (cervicalis ascendens),
416
dorsi (accessorius), 416
lumborum, 416
incisivus labii inferioris, 332
superioris, 332
incisure helicis (Santorini), 1084
inferior constrictor of pharynx, 1136
oblique, 1068
infra-clavicularis, 374
infraspinatus, 364, 368
insertion of, 314
intercostales externi, 423, 432
interni, 423, 433
internal cremaster, 1254, 1259
interossei dorsales (foot), 454, 499
(hand), 410
plantares, 454, 499
volares (hand), 409
interspinal, 412, 419
intertransversarii, 417
intralabial, 331
ischio-bulbosus, 451
ischio-cavernosus (erector penis or clitoris)
443, 451
isohio-femoraUs, 461
isohio-pubicus (Vlacovitch), 450
of larynx, 1218
latissimo-condyloideus (dorso-epitrochle-
aris), 379
laxator tympani, 79
latissimus dorsi, 364, 368, 1405
levator anguli oris, 332
ani, 440, 448
clavioulae, 359
epiglottidis, 347
labii superioris, 332
alaeque nasi, 332
menti, 334
palpebrae superioris, 1068
scapulae, 356, 369
veli palatini, 1137
levatores costarum, 423, 432
longi, 432
of little finger, 404
longissimus capitis (trachelo-mastoid), 416
cervicis (transversalis cervicis), 416
dorsi, 416
longitudinalis superior and inferior, 1110
linguae inferior medius, 347
longus capitis, 355
colli, 355
lumbar, 436
1510
INDEX
Muscle (s), lumbricales (foot), 454, 495
(hand), 408
masseter, 341
meatalis, 334
middle constrictor of pharynx, 1137
multifidus, 412, 419
multipenniform, 315
mylo-hyoideus, 343, 344
nasalis, 334
pars alaris (depressor alse nasi), 334
pars transversa (compressor naris), 334
nerves of, 318
nomenclature of, 319
number of, 315
obliquus abdominis externus, 423, 432
interaus, 423, 434
auriculae, 1084
capitis inferior, 412, 420
superior, 412, 420
obturator externus, 453, 463, 464
internus, 453, 463
occipitalis, 337
minor, 337
occipito-frontalis, 336
occipito-scapularis, 359
ocular, 1068
action, 1068
omo-hyoideus, 351
opponens digiti quinti (foot), 454, 498, 499
(hand), 404, 405
hallucis, 498
poUicis, 407, 408
oral, 331
orbicularis oculi, 336, 1077
oris, 331
of orbit, 324, 325,''1067
orbital (of Mueller), 1071
origin of, 314
of ossicles of ear, 1091
palmaris brevis, 404
longus, 396, 398
papillary, 515, 516, 517
pectineus, 453, 471, 472
pectoral group, 362, 370, 372
abnormal, 374
pectoralis major, 370, 372, 1411
minimus, 374
minor, 370, 373, 1411
pectoro-dorsalis (axillary arch), 374
periorbital, 335
peroneo-calcaneus internus, 491
peroneo-tibialis, 486
peroneus brevis, 453, 483
digiti quinti, 484
longus, 453, 483
tertius, 453, 480, 482
pharyngo-palatinus (palato-pharyngeus),
1136
of pharynx, 1134
physiology of, 320
piriformis, 467, 461
plantaris, 454, 484, 485
platysma, 330
pleuro-cesophageal, 1141
polygastric, 314
popliteus, 454, 486
procerus, 336
pronator quadratus, 402
teres, 395, 396
psoas major, 455
minor, 455, 456
pterygoideus externus, 342
internus, 342
pubo-cavernosus (levator penis), 452
pubo-coccygeus, 440, 448
pubo-peritonealis, 436
pubo-rectalis, 440, 448
Muscle (s), pubo-transversaUs, 436
pyramidalis, 424, 431
auriculae (Jungi), 1084
nasi, 336
quadrate, 332
quadratus femoris, 453, 463, 464
labii inferioris, 332
superioris, 332
lumborum, 425, 436
plantse (flexor accessorius), 454, 495
quadriceps femoris, 453, 468, 470
radio-carpeus, 403
recti, of eye, 1068
recto-cocoygeus, 449, 1177
recto-uterine, 1252
recto-vesical, 1252
rectus abdominis, 422, 424, 430
acessorius, 471
capitis anterior (minor), 356
major, 355
lateralis, 356
posterior major, 417, 419
minor, 412, 419
femoris, 468, 470, 1436
relation to the skin, 313
retrahens aurem, 337
rhomboideus major, 356, 358
minor, 356, 358
risorius, 333
rotatores, 412, 419
sacro-coccygeus anterior, 448
posterior, 448
sacro-spinalis (erector spinae), 412, 414
sartorius, 453, 468, 1436
scalenus anterior, 353
medius, 354
minimus, 355
posterius, 354
scansorius, 462
scapulo-clavicularis, 374
semimembranosus, 453, 475, 476
semispinalis capitis (complexus), 412, 417
cervicis, 419
dorsi, 419
semitendinosus, 453, 475, 476
serratus anterior, 356, 359
posterior inferior, 423, 431
superior, 423, 431
of shoulder musculature, 362, 365
of soft palate, 1134
of sole of foot, 493
soleus, 454, 484, 485
accessorius, 485, 491
sphincter ani, externus, 441, 449
internus, 1177
of bladder, 1253
pupdlae, 1061
urethrae (membranaceae), 449
urogenitalis, 442, 449
vagina;, 451, 1278
spinalis capitis (biventer cervicis), 418
cervicis, 412, 417
dorsi, 412, 417
splenius capitis, 414
cervicis, 414
accessorius, 414
stapedius, 1091
sternalis, 374
sterno-chondro-scapularis, 374
sterno-clavioularis, 374
sterno-cleido-mastoid, 347, 349
sterno-hyoideus, 351
sterno-thyroideus, 351
stylo-glossus, 346
stylo-hyoideus, 343, 344
stylo-pharyngeus, 1137
subanconeus, 378
INDEX
1511
Muscle (s), subclavius, 370, 373
subcostales, 423, 434
suborureus, 470
subcutaneous, 313
suboccipital, 328, 412, 419
subscapularis, 364, 369
minor, 369
superior constrictor of pharynx, 1137
obUque, 1068
tarsal (Mueller's), 1068
supinator (brevis), 392
radii longus, 388
supracostales, 432, 433
supraspinatus, 364, 368
synergists, 322
tail of, 314
tarsal, 1072, 1078
temporalis, 341
superficialis, 337
tensor capsularis artioulationis metacarpo-
phalangei digiti quinti, 406
fascise dorsalis pedis, 482
lata; 457, 459, 1436
suralis, 476
lamina; posterioris vaginae musculi recti
abdominis, 436
laminae posterioris vagina; musculi recti
et fasciae transversalis abdominis, 436
ligamenti annularis anterior, 393
posterior, 393
tarsi (Horner's), 336
tympani, 1089, 1091
veil palatini, 1137
tenuissimus, 475
teres major, 364, 369
minor, 364, 367
of thigh, 453, 464
of the thumb, 406
thyreo-arytaenoideus (externus), 1219
internus (m. vooalis), 1220
obliquus, 1220
superior, 1220
thyreo-epiglottic, 1220
thyreo-hyoideus, 351
tibialis anterior, 453, 480, 1468
posterior, 453, 486, 490, 1468
secundus (tensor of capsule of anlde-
_ joint), 491
tibio-astragalus anticus, 482
of tongue, 345, 346, 1110
trachelo-mastoid, 416
tragicus, 1084
transversalis cervicis, 416
transverso-spinal, 412, 419
transversus abdominis, 424, 435
auriculae, 1084
linguae, 1110
menti, 333
nuoh^, 337
perinei profundus, 442, 449, 1278
superficialis, 444, 452, 1278
thoracis (triangularis sterni), 424, 434
vaginae (Fiihrer), 449
trapezius, 347, 349, 1405
triangularis, (depressor anguli oris), 333
sterni, 424, 434
triceps brachii, 374, 377, 378, 1416
surae, 484
ulnaris digiti quinti, 392
ulno-carpeus, 402
unci-pisiformis, 403
unipenniform, 315
uvula;, 1137
variation in, 320
vastus intermedins (crureus), 468, 470
lateralis (vastus externus), 468, 470
medialis (vastus internus), 468, 470
Muscle(s), ventricular, of larynx, 1220
vertebro-ocoipital, 417
verticahs linguae, 1111
vessels of, 319
vocaUs, 1220
zygomaticus, 333
minor, 332
Muscular process of arytaenoid, 1211
veins (of orbit), 658
Musculature (see also "Muscles"), 313
of the arm, 362, 374, 377, 379
cranio-mandibular, 338, 341
epicranial, 336
of expiration, 248
external genital, 450
facialis, 324, 329, 380, 501
of forearm and hand, 362, 383, 387
of foot, 454, 492
functional groups, 600
of hand, 363, 403
of head, neck, and shoulder girdle, 323
of heart, 518
of the hip, 453, 454
of inspiration, 247
of leg, 453, 477, 480
of lower limb, 452
of mastication and swallowing, 325
of neck, 327
of pelvic outlet, 439, 448
prevertebral, 328, 355
of respiration, 503
of shoulder girdle, 327, 347, 363
spinal, 410, 412
of thigh, 453, 468
thoracic-abdominal, 422, 430
of the upper limb, 360
Musculi papillares, 515, 516, 517
pectinati (heart), 513
Musculo-cutaneous nerve, 987, 1014, 1459
results of paralysis, 1424
Musculo-phrenic artery, 567
Musculo-spiral groove, 149
(radial) nerve, 985
results of paralysis of, 1424
Musculus ciliaris Riolani, 1077
interfoveolaris, 435
uvulae, 1137
vocalis, 1220
Myelencephalon, 799
Mylo-hyoid branch of inferior alveolar (dental)
artery, 548
nerve, 943
groove, 96
line 95
Mylo-'hyoideus, 343, 344
Myocardium, 508, 518
Myometrium, 1274
N
Nail-bed, 1295
Nails (ungues), 1293
Nail-wall, 1294
Nares, 1200
posterior (choana;), 107, 112, 1206
Nasal aperture, anterior, 108
bones at birth, 124
description of, 86
branches of anterior ethmoidal artery, 554
nerve, 937
of infra-orbital artery, 549
of maxillary nerve, 939
of posterior ethmoidal artery, 553
of spheno-palatine artery, 549
(Meckel's) ganghon, 962
cartilages, 1201
cavity, 1203
1512
INDEX
Nasal conchae (turbinate bones), 83, 84, 1205
crest, 90
fossa?, IDS, 110
glands, 1208
meatuses, 1205
muscles, 324, 334, 501
notch, 60, 87
pharynx, 1130
septum, cartilaginous, 1204, 1354
membranous, 1204
osseous. 111, 1354
sinuses, accessory, 1354
spine, anterior, 60, 87, 90, 112
posterior, 91
vein, external, 644
Nasalis, muscle, 334
pars transversa (compressor naris), 334
pars alaris (depressor alse nasi), 334
Nasion, 109, 1331
Naso-ciliary (nasal) nerve, 936
Naso-frontal vein, 658
Naso-lacrimal duct. 111, 1080, 1205, 1349
Naso-palatine nerve (of Cotunnius), 962
Naso-pharyngeal adenoids, 1130, 1354
meatus, 1206
Navicular (scaphoid) bone, 159, 160, 191, 196
Neck af axis, 33
cutaneous areas of, 1019
deep, lymphatic nodes of, 714
vessels of, 714
fascia; of, 347, 1360
of gall-bladder, 1187
landmarks, 1354
ligament, 243
lymphatics of, 709
musculature of, 323, 327
of penis, 1260
superficial lymph-nodes of, 709
surgical anatomy of, 1354
of teeth, 1117i
triangles of, 1357
NiSlaton's line, 1436
Nephrotome, 16
Nerve (s), 769
in abdominal wall, 1372
accessory (spinal), 958, 1360
abducens, 934, 1075
accessory obturator, 1005
acoustic (auditory), 949,'?1096
to adductor magnus, 1009
ano-coccygeal, 1018
anterior crural, 1001
cutaneous of abdomen, 995
of thigh, 1003
ethmoidal, 936, 937
interosseus, 992
labial, 1000
palatine, 963
scrotal, 1000
superior alveolar (dental) ,'^938
tibial, 1015
of Arnold, 956
to artioularis genu (suborureus),^1003
of auricle of ear, 1084
auriculo-temporal, 941
axillary (circumflex), 984
to biceps femoris, 1009
bronchial (pulmonary), 957
buccinator (long buccal), 939
cardiac, 522
cavernous, of penis, 1047
of clitoris, 1047
cervical, 971, 974
cervico-faoial, 945
chorda tympani, 826, 946, 948
ciliary, of eyeball, 937, 1064, 1076
circumflex, 984
Nerve(s), coccygeal, 973
cochlear or auditory, 950
nucleus of, 624
common peroneal (external popliteal), 1013
plantar digital, 1011
communicans cervicalis, 974
fibularis, 1013
of conjunctiva, 1348
of Cotunnivis, 962
cranial, 927
nuclei in medulla oblongata, 818
of cranial dura mater, 917
cranio-spinal, 926
cutaneous, of face, 1345
of foot, 1466
of forearm, 1423
of lower extremity, distribution of, 1024,
1469
of thigh, 1025
perforating, 1007
deep peroneal (anterior tibial), 1015, 1466
radial (posterior interosseous), 985, 986
temporal, 943
descendens cervicalis, 953, 974
dorsal antibrachial interosseus, 986
digital, of foot, 1013
of hand, 986, 990
of ductus deferens, 1259
of penis (or clitoris), 1018
scapular (nerve to rhomboids), 982
thoracic, 984
of external acoustic (auditory) meatus, 1086
carotid, 1036
popliteal, 1013
to external pterygoid muscle, 943
external respiratory, of Bell, 982
superficial petrosal, 1036
of eyeball, 1064
of evelids, 1078
facial, 943, 1345
nucleus of, 825
of female external genitalia, 1278
femoral (anterior crural), ICJOl
fibres, development of, 758
fifth cervical, 971
cranial (trigeminus), 934
first cervical, 971, 974
thoracic, 994
to flexor carpi radialis, 992
ulnaris, 990
digitorum longus, 1010
profundus, 990
sublimis, 992
hallucis longus, 1010
foramina of skull, 125
fourth cervical, 971, 975
frontal, 935, 1075
furcal, 998
geniculo-tympanic, 948
to genio-glossus, 954
to genio-hyoid, 954, 976
genito-femoral (genito-crural), 1000
glosso-palatine, 946
nucleus of, 825
glosso-pharyngeal, 951
nucleus of, 820
great auricular, 978
(anterior) palatine, 963
splanchnic, 1038
superficial petrosal, 948
greater occipital, 971
of heart, 522
to hyo-glossus, 954
hypoglossal, 952, 1111
nucleus of, 820
ilio-hypogastric, 998
ilio-inguinal, 1000
INDEX
1513
Nerve(s), inferior alveolar (dental), 941
cardiac, 957, 1037
clunial (gluteal), 1007
hsemorrhoidal, 1017
(or recurrent) laryngeal, 957
medial clunial (perforating cutaneous),
1007
vesical, 1017, 1047
infra-orbital, 937, 939, 1345
infratroohlear, 936, 937
intercosto-brachial (intercosto-humeral),
995
intermediate dorsal cutaneous, of leg, 1015
intermedius, 825
internal carotid, 960, 1033
pterygoid muscle, 939, 943
interosseous crural, 1010
ischiadicus, 1008
of Jacobson, 951, 961
jugular, 960, 1035
of kidney, 1247
lacrimal, 936, 1075
of large intestine, 1178
of larynx, 1225
last thoracic, 995
lateral anterior thoracic, 983
antibrachial cutaneous, 987
cutaneous, 1000
of abdomen, 995
brachial, 985
dorsal, 1013
sural, 1013
plantar, 1012
least splanchnic, ,1039
lesser internal cutaneous, 983
splanchnic, 1039
to levator scapula;, 979
lingual, 940,, 1111, 1350
of lips and cheeks, 1104
of liver, 1186
long ciliary', 937
(middle") subscapular, 984
thoracic, 982
to longus capitis, 979
colli, 979
of lower extremity, paralysis of, 1469
lower subscapular, 984
lumbar, 973, 995
of lumbar plexus, composition of, 998
of lungs, 1235
of lymphatic vessels, 702 '
of mammary gland, 1305
mandibular (third division of trigeminus),
939, 1345
masseteric, 943
masticator, 942
nucleus of, 829
maxillary, 937, 1076, 1345
medial anterior thoracic, 983
antibrachial (internal) cutaneous nerve,
984
brachial cutaneous, 983
calcaneal (calcaneo-plantar cutaneous),
1010
dorsal cutaneous, of leg, 1015
plantar, 1010
sural cutaneous, 1010
median, 991, 1415
mental, 941
middle cardiac, 1036
clunial, 973
hajmorrhoidal, 1017 a
(recurrent) meningel, 937
(external) palatine, 948, 963
(long) subscapular, 984
superior alveolar (dental), 938
of muscles, 318
Nerve(s), musculo-cutaneous, 987, 1459
results of paralysis, 1424
musculo-spiral, 985
to mjdo-hyoid, 943
naso-ciliary (nasal), 936, 1076
naso-palatine, 962
of nose, 1203, 1208
obturator, 1003, 1440
accessory, 1005
to obturator internus, 1007
oculomotor, 835, 838, 931, 1075
nucleus of, 837
of oesophagus, 958, 1141
olfactory, 865, 929
to omo-hyoid, 953, 976
ophthalmic, 1075
optic, 848, 930, 1052, 1073
of orbit, 1075
of ovary, 1269
of palate, 1105
to palmaris longus, 992
of pancreas, 1195
of parotid gland, 1115
to peetineus, 1002
of penis, 1262
pericardiac, 957
perineal, 1017
peroneal, 1469
phrenic, 979
relations, 1360
to piriformis, 1007
of pleura, 1239
pneumogastrio (vagus), 954
to popliteus, 1010
posterior auricular, 944
belly of digastric, 944
brachial cutaneous, 985
ethmoidal, 937
femoral cutaneous (small sciatic), 1007
inferior nasal, 963
interosseus, 986
(small) palatine, 963
scrotal (labial) nerves, 1017
superior alveolar (dental), 938
thoracic, 982
to pronator teres, 992
proper plantar digital, 1011
volar digital, 992
of prostate, 1265
pudio (pudendal), 1017
to quadratus femoris, 1007
radial (musculo-spiral), 985, 1415
to rectus capitis anterior (minor), 979
lateralis, 979
femoris, 1003
recurrent articular, of leg, 1013
(inferior laryngeal), 957
to rhomboids, 982
roots, 769
rudimentary coccygeal, 964
sacral, 973, 1006
of sacral plex-us, composition of, 1006
saphenous, 1003, 1467
to sartorius, 1002
to scalene muscles, 978
sciatic (n. ischiadicus), 1008, 1443, 1469
of scrotum, 1255
to semimembranosus, 1009
to semitendinosus, 1009
seventh cranial (facial), 943, 1345
short subscapular, 984
of skin, 1289
of small intestine, 1168
occipital, 977
palatine, 948
sciatic, 1007
superficial petrosal, 951
1514
INDEX
Nerve(s), smallest occipital, 971
to soleus, 1010
spheno-palatine, 938
spinal, 964
accessory, 958
nucleus of, 820
origin of, 1406
spinous (recurrent), 939
of spleen, 1312
to stapedius muscle, 944
to sterno-mastoid, 978
to sterno-thyreoid, 963
of stomach, 1156
to stylo-glossus, 954
to stylo-hyoid, 944
to subclavius, 983
sublingual, 941
gland, 1116
of submaxillary gland, 1117
suboccipital, 971
subscapular, 984
superficial cervical cutaneous, 978
peroneal (musculo-cutaneous), 1014,
1459, 1466
radial (radial), 986
superior alveolar, 938
cardiac,\957
cervical cardiac, 1036
clunial, 973
gluteal, 1007
hsemorrhoidal, 1045
laryngeal, 956
vesical, 1047
supra-acromial, 978
supraclavicular, 978
supra-orbital, 935, 1345
of suprarenal glands, 1326
suprascapular, 982
supratrochlear, 936
sural (external or short saphenous), 1013,
1467
of teeth, 1124
temporo-facial,r945
tenth cranial (vagus or pneumogastric),
954
terminalis, 929
thoracic, 971,' 994
intercostal, 995
thoraco-abdominal, 995
thoraco-dorsal (middle or long) subscapu-
lar, 984
of thymus, 1322
to thyreo-hyoid, 953, 976
of thyreoid gland, 1318
tibial, 1009, 1469
communicating, 1010
to tongue, 1111
of trachea and bronchi, 1228
to trapezius, 979
trigeminus, 934
nuclei of, 826
trochlear, 835, 837, 933, 1075
nucleus of, 837
trunks, gangliated, 1029, 1032
of tubsE uterina3 (Fallopian tubes), 1270
tympanic, 961
of tympanic cavity, 1091
ulnar, 987, 1415
anastomotic, 987
collateral, 985
upper (short) subscapular, 984
of ureter, 1249
of urinary bladder, 1253
of uterus, 1274
of vagina, 1017, 1276
vagus or pneumogastric, 954
nucleus of, 820
Nerve(s), to vastus intermedius (crureus), 1003
lateralis, 1003
mediahs, 1003
vestibular, 949
nuclei, 823
Vidian, 962
volar digital, of hand, 992
(anterior) interosseous, 992
of Wrisberg, 946, 983
zygomatic, 938, 1076
zygomatico-facial (malar), 938
zygomatioo-temporal, 938
Nerve-foramina of the skull, 125
Nerve-supply of muscles (see "Nerves;" also
corresponding muscles, articulations, etc.)
Nerve-trunks, gangliated, 1029, 1032
mixed, 965
spinal, primary divisions of, 944, 967, 970
Nervous system, 751
central, 751, 770
construction of, 762
development of, 754
general summary of some of principal
paths of the nervous system, 895
peripheral, 754, 924
sympathetic, 1026
Nervus intermedius, 825
Neural branches of spinal arteries, 590
crest, 754
folds, 754
groove, 10, 11, 754
plate, 11, 754
tube, 14, 754
Neuraxis, 762
Neurenteric canal, 11
Neurilemma, 761
Neuroblasts, 755
Neuro-central suture, 45
Neuro-fibrillfe, 765
Neuroglia, 759, 767
Neuroglia, 759, 767
Neuro-muscular spindle, 764
Neurone, 755, 762
chains, 768
structure of, 765
systems of spinal cord, 777
Neurones of cerebral path for cranial nerves,
895
of cerebro-spinal path, 895
Nipple of mammary gland, 1300, 1304
Nissl bodies, 766
Node(s), atrio-ventricular, 519
haemolymph, 708
lymph(atic) (see "Lymphatic nodes")
Nodulus Arantii, 517
of cerebellum, 808
Nomenclature, anatomical, 1
of muscles, 319
Non-medullated fibres, 767
Norma basilaris, skull, 103
facialis of skull, 108
lateralis, skull, 101
occipitalis, skull, 101
verticalis, skull, 100
Nose, 1200
cartilages of, 1201
clinical anatomy of, 1352
development of, 1208
lymphatics of, 712
meatuses of, 1205
muscles of, 334
nostril (nares), 1200
olfactory area (region), 1050
sinuses connecting with, 1206
vessels and nerves, 1203, 1208
Notch, 29
acetabular, 174
INDEX
1515
Notch, cardiac, of left lung, 1229
of cerebellum, 805
ethmoidal, 61
frontal, 60
great scapular, 137
sciatic, 172
intertragic, 1082
jugular (interclavicular), 133
mandibular (sigmoid), 96, 97
mastoid, 72
nasal, 60, 87
pancreatic, 1194
posterior cerebellar, 915
preoccipital, 861
pterygoid, 66
radial (lesser sigmoid cavity) of ulna, 157
of Rivinus, 77
scapular, 142
semilunar (greater sigmoid cavity) of ulna,
156
small sciatic, 172
spheno-palatine, 91, 93
of spleen, 1311
supra-orbital, 60
temporal, 868
tentorial, 915
thyreoid, 1210, 1211
of tibia, popliteal, 185
tympanic, 77
ulnar (sigmoid cavity) of radius, 154
Notochord, 11
Notochordal region of skull, 117
Nuchal line, highest, 52
inferior, 52
superior, 52
Nuck, canal of, 1398
Nucleus(i), abducens nerve, 826
accessory olivary, 817
of the ala cinerea, 820
ambiguus, 822
amygdalae, 881
amygdaloid, of lateral ventricle, 877
arcuatus, 818
Bechterew's, 823
caudate, 877, 879
of cerebellum, 809
of cochlear nerve, 824 ■
of cranial nerves in meduUa oblongata, 818
Deiters's, 823
dentate, of cerebellum, 810
dorsal efferent, of cochlear nerve, 824
of vagus, 822
dorsalis (Clarke's column), 776
of Edinger and Westphal, 838
emboliformis of cerebellum, 810
of facial nerve, 825
fastigii (roof nucleus) of cerebellum, 810
funiculi cuneati (of Burdach's column),
801, 815
gracihs;(of GoU's column), 801, 815
globosus of cerebellum, 810
of glosso-palatine nerve, 825
of glosso-pharyngeus, 820
habenular, 872, 885
of hypoglossal nerve, 820
hypothalmio, 884
incertus of floor of fourth ventricle, 815
of inferior colliculus, 839
inferior olivary, of medulla oblongata, 817
intercalatus, 814
interpeduncular (Von Gudden), 843, 872,
885
of lateral lemniscus, 824, 839
of thalamus, 845
of lens of eye, 1062
lenticular, 878, 879
lentiformis, 857
Nucleus of masticator nerve, 829
of medial longitudinal fasciculus, 843, 871
medial thalamic, 845
of mesencephalic root of trigeminus nerve,
829
of oculomotor (or third) nerve, 837
pontis, 831
pulpy, 226
red, 840
respiratory, 822
salivatorius, 826, 947
of scapula, 139
Schwalbe's, 823
of solitary-tract, 820
of spinal accessory nerve, 820
tract, 826
spinahs, 823
Stilling's, 776
of superior colliculus, 842
superior olivary, 824
of termination, 770
of thalamus, 871, 882
trapezoidei, 824
of trigeminus nerve, 826
of trochlear (or fourth) nerve, 837
of vagus or pneumogastric, 820
vasomotor, 822
ventral cochlear, 824
vestibularis, 823
Number of muscles, 315
Nutrient arteries of femur, 621
of fibula, 626
of humerus, 576
of radius and ulna, 679
tibial, 626, 1459
branch of obturator artery, 608
of posterior circumflex humeral artery,
573
of transverse scapular artery, 565
Nymphaj (labia minora), 1277, 1392
O
ObeUon, 101
Obex, 802, 813
Obhque diameter of pelvic inlet, 175
fasciculus, 804
head of adductor hallucis, 498
of adductor poUicis, 408
ligament (mid-radio-ulnar union), 262
line of clavicle, 140
of fibula, 190
of mandible, 95
of radius, 154
posterior, 154
of scapula, 142
of thyreoid cartilage, 1211
of ulna, 157
muscle of eye, inferior, 1068
superior, 1068
popliteal ligament (hgamentum Winslowii),
287
sinus of pericardium, 523
vein of left atrium (of Marshall), 521, 623,
691
Obliquus abdominis externus, 423, 432
internus, 423, 434
capitis inferior, 412, 420
superior, 412, 420
Oblong fovea of aryta;noid, 1212
Obturator artery, 608, 639
crest 173
externus, 453, 463, 464
fascia, 439, 463
(thyreoid) foramen, 174
groove, 172
internus, 453, 463
1516
INDEX
Obturator nerve, 1003, 1440
accessory, 1005
vein, 680
Occipital artery, 542, 638, 1343
bone, 51
articulations of, 56
at birth, 121
ossification of, 56
branches of occipital artery, 543
of posterior auricular artery, 545
nerve, 944
of small occipital nerve, 977
condyle, third, 56
condyles, 108
crest, external, 52
internal, 53, 117
groove, 72
gyri, 863
lobe, 863
lymph-nodes, 709
nerve, greater, 971
small, 977
smallest, 971
point, 101, 112
pole, 850
pontile fibres, 840
portion of vertebral artery, 560
protuberance, external, 52, 101
internal, 53
sinus, 650
sulci, 862, 863
suture, 101
vein, 647
diploic, 648
Occipitalis, 337
minor, 337
Occipito-atlantal articulation, 218
ligaments, 219
Occipito-cervioal ligament, 223
Occipito-epistrophic articulation, 223
Occipito-frontal fasciculus, 892
Occipito-frontalis, 336
Ocoipito-mastoid suture, 101
Occipito-mesencephalic path (Flechsig's sec-
ondary optic radiation), 890
Occipito-pontile path, 832
Occipito-scapularis, 359
Occipito-temporal association area, 894
convolution, 864
Oocipito-thalamic (optic) radiation, 888
Occiput and atlas, ligaments uniting, 218
Ocular conjunctiva, 1054
muscles, 325, 1067
Oculomotor nerves, 835, 838, 931
nucleus of, 837
sulcus, 835
Odontoid process (dens) of axis, 33
(Esophageal arteries, 588
branches of inferior thyreoid artery, 564
of left gastric artery, 594
of vagus, 958
plexuses, 954, 955
veins, 661, 664
(Esophagus, 1138
clinical anatomy of, 1369, 1408
development of, 1141
lymphatic vessels of, 730, 1141
variations and comparative, 1141
vessels and nerves of, 1141
Olecranon fossa of humerus, 150
process of ulna, 156
Olfacto-mammillary tract, 873
Olfacto-mesencephalic tract, 873
Olfactory apparatus, 1049
area of cerebral cortex, 893
(region) of nasal mucous membrane, 1049,
1352
Olfactory brain, 864
bulb, 758, 865, 1050
cells, 1050
conduction path, 902
glands, 1208
groove, 1206
gyrus, lateral, 865
medial, 866
layer of olfactory bulb, 866
lobe, 865
nerve, 865, 929
central connections, 929
organ, 1049, 1208
region of nasal cavity, 1208
strias (gyri), 865, 866
sulcus, 858
tract, 758, 865, 893
development of, 758
trigone (tubercle), 865
ventricle, 866
Olivary, nuclei, accessory, 817
inferior, 817
superior, 824
Olives of medulla oblongata, 800
Omental branches of epiploic arteries, 595
bursa (lesser sac), 1146, 1372
Omentum, great, 1149
lesser (gastro-hepatic), 1160, 1185
Omo-hyoideus, 351
Omphalo-mesenteric artery, 638
Opercula of insula, 856
Operculum proper, 854, 856
temporal, 854, 866 ■
Ophryon, 109, 112
Ophthalmic artery, 552, 638, 1074
branches, 552
division of trigeminus (fifth nerve), 936, 1075
veins, 658, 659, 1075
Ophthalmo-meningeal vein, 655
Opisthion, 107, 108
Opponens digiti quinti (foot), 454, 498, 499
(hand), 404, 405
hallucis, 498
pollicis, 407, 408
Optic-acoustic reflex path, 840, 842
Optic apparatus, conduction paths of, 900
chiasma, 847, 848, 849
cup, 1080
disc, 1055
foramen, 63, 64, 110, 116, 125
groove, 63, 116
nerve, 848, 930, 1052, 1073
sheaths of, 931, 1073
papilla of, 1055
portion of hypothalamus, 847
radiation, 888
Flechsig's secondary, 890
recess, 848
tracts, 849
vesicle, 758, 1080
Ora serrata, 1057
Oral cavity, 1100
development of, 1102
fissure, (rima oris), 1100
fossa, 1102
muscles, 331
orifice, muscles of, 501
pharynx, 1130
vestibule, 1100
Orbicular tubercle of incus, 79
Orbicularis ciliaris, 1060
ocuU, 336, 1097
oris, 331
Orbit, 108, 109, 1332, 1346
fascije of^ 107l
lymphatic system of, 1076
muscles of, 325, 1067
INDEX
1517
Orbital branch of middle meningeal artery, 548
branches of maxillary nerve, 938
of spheno-palatine (Meckel's) ganglion,
963
fissure, inferior, 109, 126
superior, 65, 109, 116, 125
gyri, 858
muscle of Muller, 1071
periosteum, 1071
plates, 61
process of malar bone, 94
of palate bone, 91, 93
sulci, 858
wings of sphenoid, 64
Orbito-sphenoid centre, 67, 119
Organ (s), 4
of Giraldes, 1257
of Jacobson, 951, 961, 1051, 1204
lymphoid, 704
olfactory, 1049, 1208
reproductive, male, 1253
female, 1265
of special sense, 1049
spiral (organ of Corti), 1096
of taste, 1051
urinary, 1241
Orifice, atrio-ventricular, of heart, 513, 514
external urethral, 1264
of stomach, 1151, 1374
(os) of uterus, 1271
Origin of muscles, 314 (see also individual
muscles)
of spinal nerves, 964
Os calcis (calcaneus), 191, 195
centrale, 164, 208
innominatum, 169
Japonicum, 95
linguae, 99
planum, 83
trigonum, 194, 199
uteri, 1271
Vesalianum, 199
Osseous labyrinth, 80
part of tuba auditiva (Eustachian tube) , 1092
portion of external acoustic (auditory)
meatus, 1085
Ossicles of ear, 79, 1090
articulations, 1090
ligaments, 1090
muscles, 1091
Ossification of bones, 27 (see also the in-
dividual bones")
Osteogenesis, 27
Osteology, 27
Ostium abdominale of tuba? uterinae (Fallo-
pian tubes), 1270
venosum (atrio-ventrioular orifice), 513, 514
Otic (Arnold's) ganglion, 963
Otoconia (otoliths), 1095
Outlet (interior aperture) of pelvis, 176
Ovarian arteries, 602
branches, 602
branches of uterine artery, 610
ligaments, 1269
plexuses of nerves, 1045
veins, 674
Ovaries, 1268
clinical anatomy of, 1393
lymphatics of, 701, 745, 1269
vessels and nerves of, 1269
Ovula Nabothi, 1274
Ovum, segmentation of, 9
Pacchionian bodies (arachnoid granulations),
649, 919
Pacchionius, foramen ovale of, 116
Pacinian corpuscles, 1290
Palate, 1104
bone, 91
at birth, 124
development of, 1106
hard, 1104
lymphatics of, 717
muscles acting on, 502
soft, 326, 1104
surgical anatomy of, 1352
Palatine arches, 1132
branch of ascending pharyngeal artery, 537
artery, ascending, 541
descending, 549
major, 549
canals, 92, 103, 126
accessory, 103
foramina, 106
nerve, great (anterior), 963
middle (external), 948, 963
posterior (small), 948, 963
process of maxilla, 87, 88
tonsil, 1132
variations and comparative, 1106
vein, 644
superior, 646
Palato-ethmoidal cells, 84
Palm, muscles acting on, 504
Palmar aponeurosis, 387, 1430
arch, (see "Volar arch")
cutaneous branch of median nerve, 992
of ulnar nerve, 990
fascia, deep, 387
Palmaris brevis, 404
longus, 398
Palpebra, inferior, 1053
superior, 1053
Palpebral aperture, 1052
arteries, lateral, 552
branches of infratrochlear nerve, 937
of maxillary nerve, inferior, 939
of ophthalmic artery, palpebral, 552
of supra-orbital artery, 553
conjunctiva, 1054, 1078
fascia, 1071
folds, 1053
ligament, medial, 1052, 1078
raphe, lateral, 1078
veins, 644, 658
Pampiniform plexus, 674, 1259
Pancreas, 1192
blood-supply of, 1195
development of, 1195
lymphatics of, 699, 736, 1195
topographic, 1375
variations and comparative, 1197
Pancreatic branches of splenic artery, 595
duct (canal of Wirsung), 1194, 1375
accessory (of Santorini), 1195
Pancreatico-duodenal artery, inferior, 596
superior, 595
vein, 675, 677
Panniculus adiposus, 313, 1287
carnosus, 313
Papilla, duodenal, 1164, 1195
hair, 1292
incisive, 1104
of kidney, 1246
lacrimal, 1054
(nipple) of mammary glands, 1300, 1304
optic, 1055
Papillae of skin, 1286
of tongue, 1106
Papillary ducts (of Bellini), 1246
muscles of heart, 515, 516, 517
process of liver, 1184
Paracentral lobule, 857, 858, 863
1518
INDEX
Paradidymis (organ of Giraldes), 1257
Paraduodenal fossa, 1164
Paraganglia, 1323
aortic (lumbalia), 1329
Paralysis of deep radial (posterior interos-
seous) nerve, results of, 1424
of facial nerve, 1345
of median nerve, results of, 1424
of musculo-cutaneous nerve, 1424
of nerves of lower extremity, 1469
of radial (musculo-spiral) nerve, 1424
of ulnar nerve, results of, 1424
Paramedial sulcus, 858
Parametrium, 1274
Paranasal sinuses, 1206
Parapophysis, 51
Pararenal adipose body, 1243
Parasinoidal sinuses, 919
Para-thyreoid glands, 1318
Paraurethral ducts, 1277
Parietal association area, 894
bones, 57
at birth, 123
branches of abdominal aorta, 592
of hypogastric artery, 606
(posterior temporal) of superficial tem-
poral artery, 545
of thoracic aorta, 588
eminence, 57
emissary vein, 649
fascia of pelvis, 447
foramen, 57
lobe, 860
lobule, inferior, 863
(gyrus) superior, 862
lymphatic nodes of thorax, 724
peduncle of thalamus, 8 S3
pleura, 1237
Parieto-mastoid suture, 101
Parieto-ocoipital arch, 863
fissure, 860, 864
Parolfactory area (Broca's area), 858, 865
sulci, 865, 866
Paroophoron, 1269
Parotid branches of auriculo-temporal nerve,
941, 961
of superficial temporal artery, 545
fascia, 339, 348, 1114
gland, 348, 1113
accessory, 1114
duct (Stenson's), 1115, 1343
lymph-nodes, 709
veins, 644, 646
vessels and nerves, 1115
plexus (pes anserinus), 945
region, 1343
Pars alaris (depressor alee nasi), 334
ciliaris retinae, 1061
fixa of penis, 1260, 1264
flaccida (Shrapnell's membrane), 1087
glabra of Ups, 1104
intercartilaginea, 1223
intermedia of facial nerve, 946
(of Kobelt), 1278
intermembranacea, 1223
Ubera of penis, 1260, 1264
tensa, 1087
transversa (compressor naris), 334
villosa of lips, 1104
Parumbilical veins, 678
Patches, Peyer's, 704, 1166
Patella, 184
clinical anatomy of, 1444
Patellar fold (ligamentum mucosum), 290
ligament, 47l
plexus, 1001
rete, 622
Paths, auditory conduction, 900
cerebral, for cranial nerves, 895
cerebro-spinal, 895
conduction, involving cerebellum, 899
of olfactory apparatus, 902
of optic apparatus, 900
summary of, 895
frontal pontile (Arnold's bundle), 832, 889
occipito-mesencephalic, 890
occipito-pontile, 832
optic, 900
optic-acoustic reflex, 840
short reflex, of cranial nerves, 898
spino-cerebral, 895
of spinal cord, short reflex, 895
temporal pontile (Turk's bundle), 832, 840,
890
vestibular, 899
Pecten of pubis, 173
Pectineo-femoral band, 278
Pectineus, 453, 471, 472
Pectoral (descending) branch of anterior
circumflex humeral artery, 573
branch of thoraco-acromial artery, 571
group, of muscles, 362, 370
of axillary lymphatic nodes, 720
Pectoralis major, 372
surface markings, 1411
minor, 373
surface markings, 1410
minimus, 374
Pectoro-dorsalis (axillary arch), 374
Pedicles of axis, 34
of lumbar vertebrae, 37
of vertebrae, 30
Peduncles of cerebellum, 810, 831
of cerebrum, 833, 835
of corpus callosum, 866
of flocculus, 807
of superior olive, 825
of thalamus, 880, 883
Peduncular tract, transverse, 835
Pedunculi conarii, 846
Pelvic articulations, 234
ligaments of, 234
diaphragm, 440, 448, 1383
fasciae, 446
clinical anatomy of, 1385
floor in female, 1394
in male, 1383
girdle, 207
index, 177
inlet, diameters of, 175
measurements, 177
outlet, 176
muscles of, 439
colon, 1174, 1379
plexuses of nerves, 1046
portion of ureter, 1248
splanchnics, 1017, 1040, 1046
Pelvis, articulations of, 234
axis of, 176
description of, 175, 1382
differences according to sex, 177
inlet (superior aperature) of, 175
lymphatics of 730, 733
major (false), 175
measurements, 177
minor (true), 175
muscles acting on, 505
outlet (inferior aperature) , 176
renal, 1248
of ureter, 1247
visceral lymphatic vessels of, 733
Penis, 1260
artery of, 613
cavernous plexus of, 1047
INDEX
1519
Penis, deep artery of, 614
dorsal artery of, 614
nerves of, 1018
lymphatics of, 744, 1262
surgical anatomy of, 1388
vessels and nerves of, 1262
Perforated substance, anterior, 847, 866
posterior, 835, 844
Perforating branches of deep volar arch,
586
of lateral plantar artery, 628
of the profunda, 620
of internal mammary artery, 567
maxillary artery, 529
of peroneal artery, 626
veins, 690
Pericsecal fossa;, 1172, 1378
Pericardiac branches of aorta, 588
of internal mammary artery, 567
of phrenic nerve, 979
Pericardial branches of vagus, 956
cavity, 522
development of, 527
lymph-capillaries of, 702
pleura, 1237
Pericardio-phrenic artery, 567
Pericardium, 522
development, 20, 525
surgical anatomy, 1369
vessels of, 523
Perichondrium, 28
Pericranium, 1334
Perilymph, 1092
Perilymphatic space of membranous labyrinth,
1095
Perimetrium, 1274
Perimysium internum (endomysium), 315
externum (epimysium,) 316
Perineal artery, 613, 639
fascia, superficial, 445
nerve, 1017
Perineum, 1383
central tendon of, 449
muscles acting on, 503
surgical anatomy of, 1385
triangles of, 1383
Periorbita, 1071
Periorbital muscles, 335
Periosteal branches of supra-orbital artery,
553
Periosteum, 28
lymph-capOlaries of, 701
Periotic capsule, 69, 117
cartilages, 117
Peripheral, nervous system, 754, 924
cranio-spinal system, 926
sympathetic system, 926, 1026
Peritoneal branches of superior epigastri-c
artery, 567
cavity, lymphatic capillaries of, 702
Peritoneum, 1141
clinical and topographical anatomy of, 1372
development of, 1144, 1151
of rectum, 1177
spaces of, 1372
sections, 1146
variations and comparative, 1151
vessels and nerves, 1151
Permanent teeth, times of eruption of, 1127
Peroneal artery, 626, 640, 1459
anterior (perforating), 626, 1459
posterior, 626
groove of cuboid, 199
muscles, accessory, 484
nerve, common (external popliteal), 1013
results of paralysis of, 1469
deep, (anterior tibial), 1015, 1466
Peroneal nerve, superficial (musculo-cutane-
ous), 1014, 1459, 1466
retinacula, 480
vein, 688
Peronei muscles, tenotomy of, 1464
accessory, 484
Peroneo-caloaneus internus(of Macalister), 491
Peroneo-tibialis, 486
Peroneus brevis, 453, 483
digiti quinti, 484
longus, 453, 483, 1468
tertius, 453, 480, 482
Perpendicular plate (mesethmoid) of ethmoid,
82
Pes anserinus, 945
hippocampi, 877
pedunculi, 840
Petiole of epiglottic cartilage, 1212
Petit, canal of, 1064
triangle of, 434, 1406
Petrosal branch of middle meningeal artery,
548
ganglion, 951
nerve, external superficial, 1036
great superficial, 948
small superficial, 951
portion of internal carotid artery, 550
process, posterior, 63
sinuses,''652
Petro-mastoid, 119
Petro-sphenoidal foramen, 125
Petro-squamous sinus, 653
(squamo-mastoid) suture, 71
Petro-tympanic (Glaserian), fissure 71, 77,
108, 126
Petrous portion of temporal bone, 68, 72
Peyer's patches, 704, 1166
Phalanges of fingers, 167
ossification of, 168, 204
third, terminal, or ungual, 168, 204
of toes, 203
Pharyngeal aponeurosis, 1130
arterj', ascending, 537, 638
branches of ascending pharyngeal artery,
537
of inferior thyreoid artery, 564
of glosso-pharyngeal nerves, 951
of spheno-palatine (Meckel's) ganglion,
963
of vagus, 956
bursa, 1130
(pterygo-palatine) canal, 66, 92, 103
foramen, 126
hypophyseal remnants, 1352
sthmus (faucial), 1130, 1131
membrane, 1102
ostium of tuba auditiva, 1092
plexus of nerves, 956, 1036
of veins, 659
recess, 1130
tonsil, 1130, 1354
tubercle, 54, 108
veins, 659
Pharyngo-palatine arches, 1132
Pharyngo-palatinus (palato-pharjmgeus),
1136
Pharynx, 1128
development, 1138
laryngeal, 1134
lymphatics of, 717, 113S
muscles of, 325, 502, 1134
nasal, 1130
oral, 1130
variations and comparative, 1138
vessels and nerves, 113S
Philtrum, 1102, 1284
Phrenic arteries, inferior, 692, 638
1520
INDEX
Phrenic arteries, superior, 590
branches of musculo-phrenic artery, 567
of superior epigastric artery, 567
ganglion, 1044
nerve, 979
relations of, 1360
(diaphragmatic) plexuses of nerves, 1044
veins, inferior, 675
superior, 667
Phrenico-oostal sinus, 1237
Phreno-colic ligament, 1150, 1174, 1310, 1379
Phrenicohenal (lienorenal) ligament, 1310
Physiology of muscles, 320, 323
Pia mater, 771, 920
cranial, 922
spinal, 921
Pigment of iris, 1061
retinal, 1062
of skin, 1286
Pillars of the foot, 205, 1468
of fornix, anterior, 870
posterior, 868
Pineal body, 845
Pinna (see Auricle)
Piriformis, 453, 457, 461
Pirogoff's amputation, 1465
Pisiform bone, 159, 162
Pits, olfactory, 1050
rectal, 1390
Pituitary body, 848, 1342
Plane or arthrodial diarthroses, 212
Plantar aponeurosis, 492
arch, 627
arteries, lines of, 1467
artery, deep (communicating), 633
lateral, 627, 640
medial, 629
calcaneo-cuboid (short plantar) ligament,
307, 1468
calcaneo-navicular ligament, 1468
digital (collateral) arteries, 628
branches, proper, of medial plantar nerve,
1011
nerves, common, 1011, 1013
proper, 1011, 1013
veins, 684
fascia, 492, 1468
ligaments, 307, 1468
accessory, 310
metatarsal arteries, 628
veins, 687
nerve, lateral, 1009, 1012
medial, 1009, 1010
venous arch, 687
rete, 684
Plantaris, 454, 484, 485
Planum popliteum, 181
Plate, cribriform, of ethmoid, 81
fronto-nasal, 117
neural, 754
olfactory, 1050
orbital, 61
perpendicular, of ethmoid, 82
pterygoid, 66
tympanic, 108
Platypelhc pelvis, 177
Platysma, 330
Pleura, 1236
blood-vessels of, 1239
clinical anatomy of, 1368
development of, 20
lymphatics of, 701, 1239
nerves of, 1239
Pleural cavity, 1236
reflection, lines of, 1237
sinuses, 1237
vilh, 1237
Pleurapophysis, 51
Plexuses of nerves, abdominal aortic, 1045
anterior pulmonary, 957
atrial, 1041
of Auerbach, 757, 1030
brachial, 980
line of, 1360
bulbar, 1041
cardiac, 1041
cavernous, 1033
of penis (or clitoris), 1047
of cephalic ganglia, 960
cervical, 974
coccygeal, 1018
coeliac, 1043
common carotid, 1036
coronary, 1041
deferential, 1047
external carotid, 1036
maxillary (facial), 1036
femoral, 1045
gangliated cephalic, 959
hepatic, 1045
hypogastric, 1045
iliac, 1045
inferior dental, 941
gastric, 1045
mesenteric, 1045
infra-orbital, 937, 939, 945
internal carotid, 1033
mammary, 1037
maxillary 1036
intermediate, 1041
lingual, 1036
lumbar, 998
lumbo-sacral; 996
of Meissner, 757, 1030
meningeal, 1036
middle hajmorrhoidal, 1046
myentericus (plexus of Auerbach), 1045
cesophageal, 954, 955
ovarian, 1045
parotid, 945
patellar, 1001
pelvic, 1046
pharyngeal, 956, 1036
phrenic (diaphragmatic), 1044
popliteal, 1045
posterior cervical, of Cruveilhier, 971
oesophageal, 954
pulmonary, 954, 955, 957
pulmonary, 1043
prevertebral, 755, 1029, 1032, 1040
prostatic, 1047
pudendal, 1016
renal, 1044
sacral, 1006
spermatic, 1045, 1260
splenic (lienal), 1045
submucosus (plexus of Meissner), 1045
subsartorial, 1003
subtrapezial, 979
superior dental, 939
gastric (coronary), 1045
haemorrhoidal, 1045
mesenteric, 1045
thyreoid, 1036
thoracic aortic, 1038
suprarenal, 1044
tympanic, 951, 961, 1033, 1089
utero-vaginal, 1047
vertebral, 1037
vesical, 1047
of veins, anterior sacral, 679
basilar. 651
chorioid, of fourtli ventricle, 922
of lateral ventricle, 924
INDEX
1521
Plexuses choroid of third ventricle, 924
chorioidea, 875, 877
hsemorrhoidal, 683
of internal carotid, 653
mammary, 671
pampiniform, 674, 1259
pharyngeal, 659
pterygoid, 682
thyreoideus impar, 660
utero-vaginal, 683
vertebral, 664
vesical, 683
Plica(86) ciliares, 1057
ciroulares, 1165
epigastrioa, 430
fimbriata, 430
incudis, 1090
lacrimalis (Hasneri), 1080, 1205
longitudinalis duodeni, 1189
palatinsB transversa;, 1104, 1106
palmataa, 1272
salpingo-pharyngea, 1130
salpingo-palatina, 1130
semilunaris, 1053, 1170
triangularis, 1132, 1133
of tympanic membrane, 1087
umbilicalis lateratis, 430
ureterioa, 1252
Pneumogastrie nerve, 954
Point(s), alveolar, 109
auricular, 101
central, of perineum, 1385
occipital, 101
pre-auricular, 1332
Bolandic, 1340
subnasal, 109
Poles, of cerebral hemispheres, 850
of eyeball, 1055
of lens of eye, 1062
Polygastric muscles, 314
Polymastia, 1301
Polytheha, 1301
Pons (Varoli), 804
basilar sulcus of, 804
blood-vessels of, 90S
brachia conjunctiva (superior cerebellar
peduncles), 831
grey substance of, 831
internal structure of, 815, 829
lemniscus (fillet) in, 831
Pontile path, frontal, 832, 840, 889
temporal (Turk's bundle), 832, 890
Pontine branches of basilar artery, 561
sulci, 804
Popliteal artery, 621, 640, 1452
collateral circulation, 1453
ligament, oblique, 287
line, 189
lymphatic nodes, 748
nerve, external, 1013
internal, 1009
nerves, paralysis of, 1469
plexus of nerves, 1045
space, clinical anatomy of, 1451
vem, 688, 1452
accessory, 689
Pophteus, 454, 486
Pore, canal, 1051
of skin, 1285
sudoriferous, 1297
taste, 1051
Porta hepatis, 1183
Portal fissure of liver, 1183
vein, 528, 675
development, 694
tributaries, 675
veins, accessory, 678
Position of organs (see corresponding Or-
gan)
Post-aortic lymphatic nodes, 731
Post-auditory process, 122
Post-central branches of spinal arteries, 590
sulcus, inferior, 861, 862
superior, 861, 862
Post-glenoid process, 71
Post-limbic fissure, 863
Post-malar, 95
Post-nodular sulcus of cerebellum, 808
Post-parietal gyrus, 863
Post-scapula, 145
Post-sphenoid centre, 67
Pott's fracture, 1454
Pouch of Douglas, 1148, 1267, 1274
of Prussak, 1089
recto-uterine (recto-vaginal), 1148, 1267,
1274
recto-vesical, 1148
of Troltsch, 1089
Poupart's ligament, 424, 429, 1371, 1399, 1438
Precuneus (quadrate lobe), 863
Prjeputium clitoridis, 1277
penis, 1260
Praevesical space (cavum Retzii), 1250
Pre-aortic lymphatic nodes, 730
Pre-auricular point, 1332
Precentral sulcus, 807, 857
Preglenoid tubercle, 71
Pre-laminar branches of spinal arteries, 590
Premalar, 95
Premaxilla, 89, 91, 119
Premolars, 1121
Preoccipital notch, 861
Pre-palatine centre, 91
Prepatellar bursa, 1448
Prepuce, 1260
Pre-scapula, 145
Pre-sphenoid centre, 67, 119
Presternum, 132
Prevertebral musculature, 328, 355
plexuses, 755, 1029, 1032, 1040
Primary curvatures of spinal column, 43
divisions of spinal nerve-trunk, 967
anterior, 968
posterior, 967
Primitive groove, 10
node, 11
pit, 10
streak, 10
Princeps cervicis artery, 543
pollicis artery, 586
Procerus (pyramidalis nasi), 336
Process (es), accessory (of vertebra), 38
acromion, 144
alar, of ethmoid, 81
alveolar, 87, 90
anterior clinoid, 65, 116
arciform, 466
caudate, of liver, 1184
cihary, 1057
cochleariform, 1089
condylar, of mandible, 96
coracoid, of scapula, 144
coronoid of mandible, 96, 1351
ensiform, 132, 134
ethmoidal, 85
external auditory, 75
frontal, of maxilla, 87, 88
fronto-nasal, 119
fronto-sphenoidal, 95
glosso-hyal, 99
hamular, 66, 106
infra-orbital, 95
jugular, 54, 108
lacrimal, 85
1522
INDEX
Process(es), lenticular, of incus, 79
mastoid, 72, 108
maxillary of inferior nasal concha, 84
of palate bone, 92
middle cHnoid, 65, 116
muscular, of arytEenoid cartilage, 1211
orbital, of malar bone, 94
of palate bone, 91, 93
palatine, 87, 88
posterior clinoid, 63, 116
petrosal, 63
post-glenoid, 71
pterygoid, 62, 66
pyramidal, of palate bone, 91, 92
sphenoidal, of palate bone, 91, 92
styloid, 70, 73, 75, 108
of fibula, 190
of radius, 155
of third metacarpal bone, 166
of ulna, 158
supracondylar, 149
temporal, of malar bone, 95
trochlear, 195
unciform, 163
uncinate, of ethmoid, 83
vaginal of sphenoid, 63, 66
of temporal, 75
vermiform, 1378
vocal, of arytenoid cartilage, 1212
xiphoid, 132, 134
zygomatic, 70, 87, 88
Processus cochleariformis, 77
Folii, 79
globulares, 119
gracilis, 79
marginalis, 95
tubarius, 66
uncinatus (of Winslow), 1194
vaginalis, 1387
Profunda (superior) artery, 576
axillaris artery, 640
(deep) femoral artery, 620, 640
branches, 620
vein, 690
Projection fibres of white substance of telen-
cephalon, 886, 889
Prominence, laryngeal, 1211
Promontory in cochlea, 81, 1089
of temporal bone, 73
Pronation, 321
Pronator quadratus, 402
ridge of ulna, 157
teres, 395, 396
Proper digital arteries, 582
plantar digital nerves, 1011
scapular ligaments, 252
volar digital nerves of hand, 992
veins, 671
Prosencephalon (fore-brain), 843
external features of 843
internal structure of, 878
Prostate, 1264
lymphatics of, 700, 739
surgical anatomy of, 1389
vessels and nerves of, 1265
Prostatic branches of inferior vesical artery,
608
plexus of nerves, 1047
portion of urethra, 1263, 1265, 1388
Prostatic utriculus (sinus pocularis, uterus
masoulinus), 1263
Prostatico-perineal fascia, 447
Protoplasm, 5
Protuberance, external occipital, 52
internal occipital, 52
mental, 95
Prussak, pouch of, 1089
Psalterium, hippocampal, 869
Psuedo-hermaphroditism, 1230
Psoas abscess, 1438
fascia, 455
major, 455
minor, 455
Pterion, 101, 1332
Pterygoid, accessory, 342
branches of internal maxillary artery, 548
(Vidian) canal, 103, 107, 108, 126
fossa, 66, 107
hamulus (of sphenoid), 66, 1351
muscles, 338, 342
notch, 66
plate, lateral 66
medial, 66
plexus of veins, 646
portion of internal maxillary artery, 546
processes, 62, 66
tubercle, 66
veins, 646
Pterygoideus externus, 338, 342
internus, 338, 342
Pterygo-maxillary fissure, 102
Pterygo-palatine (pharyngeal) canal, 88, 92,
103
fissure, 102
(spheno-m axillary) fossa, 102
portion of internal maxillary artery, 546
Pubes, 1290
Pubic arch, 176
branch of inferior epigastric artery, 615
of obturator artery, 608
Pubis, 172
symphysis, 238
tubercle (spine) of, 172
Pubo-capsular (pectineo-femoral) band, 278
Pubo-cavernosus (levator penis), 451
Pubo-coccygeus, 440, 448
Pubo-peritonealis, 436
Pubo-prostatic hgaments, middle, 1252
Pubo-rectalis, 440, 448
Pubo-transversalis, 436
Pubo-vesical ligaments, 1252
Pudendal (pudic) artery, 610, 639
accessory, 638
(superficial) external, 619
internal, 610, 639
nerve, 1017
long, 1007
vein, external, 684
internal, 681
plexus of nerves, 1016
of veins, 682, 683
Pulmonary artery, 528, 1234
circulation, 507
left, 529
relations, 1369
right, 529
variations, 637
branches of vagus, 957
ligament, 1236
lymphatic nodes, 725
(visceral) pleura, 1236
plexus, anterior, 957, 1043
posterior, 954, 955, 957, 1043
(semilunar) valves, 517
veins, 529, 1234
Pulp of tooth, 1118
Pulpa lienis, 1311
Pulpy nucleus of intervertebral fibro-cartU-
ages, 226
Pulvinar of thalamus, 845, 889
Puncta lacrimalia, 1054, 1079, 1349
PupO, 1054
Purkinje cells, 809
fibres of heart, 516
INDEX
1523
Putamen, 880
Pyloric antrum of stomach, 1151
canal, 1152
portion of stomach, 1151
vein, 675
Pylorus, 1152, 1374
Pyramidal eminence of temporal bone, 77
fasciculi of pons, 830
fibres, 840, 889
lobe of thyreoid gland, 1314
process of palate bone, 91, 92
tract, anterior or direct, 788
crossed, 783
Pyramidalis, 424, 431
nasi, 336
Pyramids of Ferrein, 1246
of Malpighi (renal), 1246
of medulla oblongata, 783, 799
decussation of, 815
structure of, 815
of vermis, 808
vertebral, 43
Quadrangular lobe of cerebellum, 806
membrane of larynx, 1215
Quadrate lobe, of liver, 1184
muscles, 332
Quadratus femoris, 453, 463, 464
. labii inferioris (depressor labii
inferioris), 332
superioris, 332
lumborum, 425, 436, 1407
plantae (flexor accessorius), 454, 495
Quadriceps femoris, 453, 468, 470
Quadrigeminate arteries, 907
body, inferior, 834, 839
superior, 825, 834, 841
Quadrigemino-pontile fibres, 841
R
Radial artery, 582
in palm (deep volar arch), 586
at the wrist, 584
carpal artery, dorsal, 585
volar, 584
collateral ligament, 261, 267
fossa of humerus, 151
(musculo-spiral) nerve, 985
hne of, 1415, 1423
results of paralysis of, 1424
deep (posterior interosseous), 985
results of paralysis of, 1424
superficial (radial), 987
notch (lesser sigmoid cavity) of ulna, 157
recurrent artery, 583
vena) comitantes, 671
Radialis indicis artery, 586
Radiate (anterior costo-central or stellate)
ligament, 242
sterno-oostal ligament, anterior, 245
Radiation of corpus eollosum, 851
Flechsig's secondary optic, 890
occipito-thalamic (optic), 888
Radicular veins, 792, 908
Radio-carpal or wrist-joint, 265
arterial supply of, 267
ligaments of, 266
movements of, 267
muscles acting upon, 268
nerve-supply, 267
relations of, 267
Radio-carpeus muscle, 403
Radio-ulnar joint, inferior, 263, 419
mid, 262
superior, 262, 1419
ligaments, 262, 264
Radius, 152
clinical anatomy of, 1419, 1422
Ramus(i) bronchial, 1231
colli (infra-mandibular branch), of cervico
facial nerve, 946
communicantes, 969, 1030, 1037
of fissure of Sylvius, 856
of ischium, 172
isthmi faucium, 940
Knguales, 954
of mandible, 95
of pubis, 172
Ranvier, nodes of, 761, 767
Raphe of palate, 1104
lateral palpebral, 1078
scrotal, 1254
Receptaeulum (cisterna) chyli, 726
Recess(es), elUptical, 80
epitympanic, 78
hypo-tympanie, 78
infundibular, 848
optic, 848
pharyngeal, 1130
spheno-ethmoidal, 1206
spherical, 80
supra-pineal, 847
of tumpanic mucous membrane, 1089
Recessus ellipticus (fovea hemielliptioa), 80
sphajricus (fovea hemisphaerica), 80
Rectal branches of lateral sacral arteries, 608
(hsemorrhoidal) of middle sacral arteries,
columns (of Morgagni), 1177, 1390
examination, 1391
pits, 1390
sinuses, 1177
stalk, 1391
triangle, 440, 1383
Recto-uterine folds, 1274
pouch (of Douglas), 1267, 1274
Recto-vaginal pouch of peritoneum, 1148
Recto-veslcal pouch of peritoneum, 1148
Rectum, 1176
clinical anatomy of, 1390
lymphatics of, 735
supports of, 1391
Rectus abdominis, 422, 424, 430
accessorius, 471
capitis anterior (minor), 356
lateralis, 356
major, 355
posterior major, 412, 419
minor, 412, 419
femoris, 468, 470, 1436
Recurrent artery, anterior tibial, 632
dorsal ulnar, 577
interosseous, 580
posterior tibial, 632
radial, 583
volar ulnar, 577
articular nerve of leg, 1013
branches of deep volar arch, 586
of lacrimal, 552
of spinal nerve-trunks, 970
of vagus nerve, 956
meningeal branch of maxillary nei-ve, 937
of ophthalmic nerve, 935
(inferior laryngeal) nerve, 957
Red nuclei, 840
References for articulations, 311
blood-vascular system ,''696
digestive system, 1197"
ductless glands, 1329
lymphatic system, 750
morphogenesis, 25
musculature, 506
nervous system, 1047
1524
INDEX
References for osteology, 209
respiratory system, 1240
skin and mammary glands, 1329
special sense organs, 1098
urogenital system, 1280
Reflected inguinal ligament (CoUes' ligament,
triangular fascia), 1395
Reflex paths of cranial nerves, 898
of spinal cord, 895
optic acoustic, 840
Regeneration of lymphatics, 707
Region, ilio-costal, 1406
parotid, 1343
of skull, anterior, 108
inferior, 103
lateral, 101
posterior, 101
superior, 100
Regions of abdomen, 1142, 1370
Reil, island of (insula), 856
Reissner, membrane of, 1096
Relations of organs (see correspondmg
organs)
Renal arteries, 598, 638
accessory, 638
branches of lumbar arteries, 693
of vagus, 958
columns (of Bertin), 1246
(Malpighian) corpuscles, 1246
fascia, 1242
ganglia, 1044
pelvis, 1248
plexuses of nerves, 1044
pyramids (of Malpighi), 1246
surface of spleen, 1309
tubules, 1246
veins, 673
Reproductive organs, development of, 1278
female, 1265
male, 1253
lymphatics of, 742, 744
Respiration, 1199
musculature, 247, 248, 503
Respiratory nerve of Bell, external, 982
nucleus, 822
system, 1196
larynx, 1209
lungs, 1228
mediastinal septum, 1239
nose, 1200
pleura}, 1236
thoracic cavity, 1235
trachea and bronchi, 1225
region of nose, 1208, 1352
Restiform body, 800, 810
fibres of, 830
in pons, 830
Rate arteriosum, cutaneous, 1289
sub-papillary, 1289
articular of knee, 622
canalis hypoglossi, 650, 665
dorsal carpal, 579, 585
venous (foot), 684
(hand), 667
foraminis ovalis, 646
lateral malleolar, 626, 632
medial malleolar, 626, 632
patellar, 622
plantar venous, 684
testis, 1256
volar carpal, 579, 581
Retia venosa vertebrarum, 665
Reticular formation of medulla oblongati
816
layer of thalamus, 882
of pons, 816
of spinal cord, 776
Retina, 1051, 1057, 1061
Retinacula, 1287
mammaj, 1303
pateUse laterale, 471
mediale, 471
peroneal, 480
tendinum, 317
Retinal arteries, 1065
pigment layer, 1057
veins, 1065
Retractors of the lips, 332
Retrahens aurem, 337
Retro-pubic space (of Retzius), 1371
Retrotonsillar fissure of cerebellum, 807
Rhinencephalon, 864
Rhombencephalon, 758
isthmus of, 832
summary of principal structures in, 833
Rhomboid fossa, 802
ligament (costo-clavioular), 249
muscles, nerve to, 982
Rhomboideus major, 356, 358
minor, 356, 358
Ribs, 120
asternal or false, 127
bicipital, 132
cervical, 131, 1365
clinical anatomy of, 1363, 1404
eleventh, 130
first, 128
floating, 127
lumbar, 132
ossification of, 130
pecuUar, 128
second, 129
sternal (true), 127
tenth, 129
twelfth, 130
typical characters of, 127
variations of, 131
vertebral, 127
vertebro-chondral, 127
vertebro-sternal, 127
Ridge (s), carotid, 73
genital, 1267, 1278
nfra-temporal, 65
lateral supracondylar, 149
medial supracondylar, 149
pronator, of ulna, 157
transverse, of palate, 1104, 1106
temporal, 71
Right atrium (auricle) of heart, 512
branch of hepatic artery, 595
bronchial artery, 588
colic artery, 598
common iliac artery, 605
coronary artery, 519
branches, 519
gastric artery, 594
gastro-epiploic artery, 595
vein, 677
innominate vein, 641
lymphatic duct, 728
pulmonary artery, 529
veins, 529
superior intercostal vein, 664
terminal branch of hepatic artery, 589
collecting lymphatic duct, 728
ventricle of heart, 516
Rima glottidis, 1223
oris, 1100
palpebrarum, 1052
pudendi, 1276
vestibuli, 1222 . , ,. , , , ,
RinK(s), abdominal ingumal (mternal abdom-
inal), 430, 1371, 1396
femoral, 466, 1401
INDEX
1525
Rings, subcutaneous inguinal (external abdom-
inal), 429, 1371, 1394
tonsillar (Waldeyer's), 1133
Risorius, 333
Rivinus, notch of, 77
Rolandic angle, 860
points, 1340
Rolando, fissure of, 859, 1340
gelatinous substance of, 776
Root(s) of Arnold's or otic ganglion, 963
canal of tooth, 1118 '
of ciliary ganglion, long, 937
short, 932
filaments of spinal nerves, 775, 964
of hair, 1292
of lungs, 1229, 1230, 1234, 1408
of nails, 1294
of nose, 1200
of optic tracts, 849
of penis, 1260
of spheno-palatine (Meckel's) ganglion, 962
of spinal nerves, 771, 964
of teeth, 1117
of tongue, 1107
Rosenmtiller, fossa of, 1130
Rostral lamina of corpus calloum, 852
sulci, 858
Rostrum of corpus callosum, 852
of sphenoid, 63
Rotation, 215, 321
-Rotatores, breves, 412, 419
longi, 412, 419
Round ligament liver, 1185
of uterus, 1274
Rubro-spinal fasciculus, 786
Ruffini, corpuscles of, 1290
RugsB of vagina, 1275
Sac, conjunctival, 1054
endolymphatic, 1094
lacrimal, 1080, 1349
lesser, 1148
synovial, 313
Saccular branch of vestibular ganghon, 950
Saccule of membranous labyrinth, 1093
Sacculo-ampullar division of vestibular nerve,
950
Sacral arteries, lateral, 607
middle, 603
branches, lateral of middle sacral artery, 603
canal, 42
cornua, 40
foramina, 40
groove, 41
hiatus, 40
lymphatic nodes, 733
nerves, 973, 1006
plexus, 1006
composition of nerves of, 1006
of veins, anterior, 679
portion of sympathetic system, 1040
veins, lateral, 680
middle, 679
vertebrae, development of, 48
Sacro-coccygeal articulation, 237
ligament, anterior, 238
deep posterior, 238
superficial posterior, 238
Sacro-coccygeus, anterior, 448
posterior, 448
Sacro-iliac articulation, 234
ligaments, anterior, 234
inferior, 235
posterior, 234
superior, 234
Sacro-lumbar ligament, 232
Sacro-spinaUs (erector spinas), 412, 414, 1407
Sacro-spinous or small sacro-sciatic ligament,
236
Sacro-tuberous (great or posterior sacro-sciatic)
ligament, 235
Sacro-vertebral angle, 39, 43
articulations, 232
Sacrum, description of, 30, 39
sex and racial differences of, 42
Sagittal fontaneUe, 59
sinus, inferior, 650
superior, 649
sulcus, 60
suture, 57, 101
Salivary corpuscles, 1132
glands, 1113
development of, 1117
variations and comparative, 1117
Salivatory nucleus, 826, 947
Santorini, cartilages of, 1212
duct of, 1195
incisures of, 1085
Saphenous artery, 621
nerve, 1003, 1467
external or short, 1010, 1013
opening (fossa ovaUs), 467, 1400, 1440
vein, accessory, 684
great (internal), 684, 1456
small (ex-ternal), 684, 1458
Sarcolemma, 315
Sartorius, 453^ 468, 1436
Scala media, 1096
tympani, 81, 1096
vestibuli, 81, 1096
Scalene musculature, 328, 353
tubercle, 129
Scalenus anterior, 353
medius, 354
minimus, 355
posterior, 354
Scalp, 1333
cutaneous areas of, 1018
lymphatics of, 712
Scansorius, 462
Soapha of auricle of ear, 1083
Scaphoid bone, 159, 160
fossa, 55, 66, 107
Scapula, 141
clinical anatomy of, 1406
Scapular artery, circumflex (dorsal), 572
posterior, 565
transverse (suprascapular), 564 •
foramen, 142
nerve, dorsal, 982
notch, 142
veins, transverse, 648
Seapulo-clavicular union, 250
Scapulo-clavicularis, 374
Scarf-skin (epidermis), 1285
Scarpa, fascia of, 425, 445
foramina of, 89, 106, 126
triangle of, 467, 1438
Schindylesis sutures, 212
Schlemm, canal of, 1059
Schwalbe, nucleus of, 823
Sciatic artery, 609, 640
nerve (N. ischiadious), 1008, 1443
results of paralysis of, 1469
small, 1007
notch, great, 172
small, 172
Scleral sulcus, 1054
Sclera, 1052, 1056, 1058
Sclerotome, 15
Scrotal (or labial) arteries, anterior, 620
posterior, 613
1526
INDEX
Scrotal nerves, anterior, 1000
posterior, 1017
veins, 684
Scrotum, 12ol
lymphatics of, 698, 742, 1255
surgical anatomy of, 1385
vessels and nerves of, 1255
Scutum, 1089
Sebaceous glands, 1298
Sebum cutaneum, 1298
palpebrale, 1054
Secondary tympanic membrane, 1089, 1096
Sections of peritoneum, 1146
Segmentation of the ovum, 9
Sella turcica, 63, 113
Seraioanalis m. tensoris tympani, 74
Semicircular canals, 78, 80
ducts (membranous semicircular canals),
3094
Semilunar bone, 159, 161
fascia, 382
fibro-cartilages, 289
fissures of cerebellum, 805
fold of conjunctiva, 1055
of large intestine, 1170
ganglia, 1043
(Gasserian) ganglion, 826, 936, 1345
gyrus, 865
lobe, inferior, of cerebellum, 807
superior, of cerebellum, 806
notch (greater sigmoid cavity), 156
valves, aortic, 517
pulmonary, 517
Semimembranosus, 453, 475, 476
Seminal vesicles, 1257
Seminiferous tubules, 1256
SemispinaUs capitis (complexus), 412, 417
cervicis, 412, 419
dorsi, 412, 419
Semitendinosus, 453, 475, 476
Sense, organs of special, 1049
Sensory aphasia, 894
axones, 762
Sensory-motor area of cerebral cortex, 893
Septa, intermuscular, 314
of thigh, 468
Septal branches of spheno-palatine artery, 549
nasal cartilage, 1202
Septulse of mediastinum testis, 1256
Septum aortic, 527
of arm, intermuscular, 377
atriorum, 511
canalis musculotubarii, 73
femoral, 466
of foot, intermuscular, 492
of heart, membranous, 511, 527
interventricular, 516
of leg, intermuscular, 477
linguae, 346
mediastinal, 1239
nasal. 111, 1204, 1354
Septum pellucidum, 872
cavity of, 872
laminaj of, 872
of penis, 1261
posticum of Schwalbe (subarachnoid sep-
tum), 919
sigmoid, 341
sphenoidal, 62
transversum, 20
Serial morphology of vertebrae, 50
Serrate sutures, 212
Serratus anterior (magnus), 356, 359
posterior inferior, 423, 431
superior, 423, 431
Sesamoid bones, 68, 205, 275, 317
cartilages of larynx, 1213
Sesamoid nasal cartilages, 1202
plate, plantar, 310
tibial and fibular, 209
ulnar and radial, 209
Seventh cervical vertebra?, 34
cranial nerve (facial), 943, 1345
Shaft of bones, 29 (see also the individual
bones)
of hair, 1292
Sheath (s), carotid, 1362
femoral, 1400
medullary, 759
of optic nerve, 931
of parotid gland, 1344
primitive, 761
of prostate, 1389
of rectus muscle, 427
of hair roots, 1292
synovial tendon, 317, 318, 403, 483, 484, 491
Shoulder, clinical anatomy of, 1409
musculature of, 323, 363, 503
Shoulder-blade (scapula), 141
Shoulder-girdle, 207
Shoulder-joint, 253
arterial supply, 257
clinical anatomy of, 1413
ligaments of, 254
lymphatics of, 723
movements of, 257
muscles acting upon, 258
nerve-supply of, 357
synovial membrane, 255, 1412
Shrapnell's membrane, 1087
Sibson's fascia, 129, 355, 1237
Sigmoid artery, 603
cavity of radius, 154
of ulna, greater, 156
lesser, 157
colon, 1174, 1379
groove, 72
notch, 96, 97
septum, 341
sinus, 652
vein, 678
Sinuses, accessory nasal, 1354
aortic (of Valsalva), 518
bony, of skull, 1335
cavernous, 652, 691
cervical, 17
circular, 651
connecting with nose, 1354
coronary, 521
costo-mediastinal, 1238
cranial venous, 649, 692, 916
of dura mater, 649
epididymidis (digital fossa), 1255
frontal, 59, 61, 1207, 1335
inferior petrosal, 652
sagittal (longitudinal), 650
interoavernosus, 651
of kidney, 1242
lactiferous, 1302
longitudinal vertebral, 665
mammarum, 1299
marginal, 650 v ■ o-r
maxillaris (antrum of Highmore), 87, 90,
111, 1206, 1354
of Morgagni, 1137 _
oblique, of pericardium, 523
occipital, 650
paranasal, 1206
parasinoidal, 919
of pericardium, transverse, 523, 527
petro-squamous, 653
phrenico-costal, 1237
pleural, 1237
of portal vein, 675
INDEX
1527
Sinuses, rectal, 1177
sigmoid, 652
sphenoidal, 62, 1207, 1338
spheno-parietal, 653
straight, 650
superior petrosal, 652
sagittal (longitudinal), 649
tarsi, 195
transverse (lateral), 651
tympanic, 1089
uro-genital, 1279
of Valsalva, 518, 530
venarum, 513
venosus, of heart, 525
of sclera (Sohlemn), 1059
Sinusoids, 672, 675
Skeleton, 27
appendicular, 139
axial, 29
Skene, ducts of, 1277
Skin, 1281
appendages of, 129
cerium, 1286
development of, 1286, 1290
epidermis, 1285
lymphatics of, 698, 1289
muscle-fibres of, 1288
tela subcutanea (superficial fascia), 1287
vessels and nerves, 1288
Skin-folds of wrist and hand, 1425
Skull, appendicular elements of, 117
articulations of, 215
at birth, 120
bones of, 51
bony landmarks, 1331
sinuses of, 1335
fcetal, general characters, 120
interior of, 112
morphology of, 117
nerve-foramina of, 125
regions of, anterior (norma facialis), 108
inferior (norma basalis), 103
lateral (norma lateralis), 101
posterior (norma occipitalis), 101
superior (norma verticalis), 100
topography of, 1338
as a whole, 160
Small cardiac vein, 521
intestine, 1161, 1375
blood-supply, 1166
clinical anatomy of, 1375
development of, 1168
duodenum, 1161
ileum and jejunum, 1165
lymphatics of, 1168
nerves of, 1168
(accessory) meningeal artery, 548
occipital nerve, 977
palatine nerve, 948
(external) saphenous vein, 684, 1458
sciatic nerve, 1007
superficial petrosal nerve, 951
Smaller palatine canals, 92
Smallest cardiac vein, 521
occipital nerve, 971
Snuff-box space (tabati^re anatomique), 1433
Soft palate, 1104
muscles of, 326
Solar plex-us, 1043
Sole of foot, muscles of, 493
Soleus, 454, 484, 485
accessorius, 491
Solitary follicles, 704
glands of small intestine, 1166
tract, 820
Somresthetic (sensory-motor) area of cerebral
cortex, 893
Somites, mesodermic, 14, 15
Space(s), Burns', 1356
of Fontana, 1060
intercostal, 139
interfascial (Tenon's), 715, 1073
popliteal, 1451
praevesical, 1250
snuff-box, 1433
subarachnoid, 771
subdural, 771
Special sense, organs of, 1049
Speech, cortical areas of, 894
Spermatic artery, external, 615
internal, 698, 638, 1259
branch, external, of genito-femoral nerve,
1000
cord, 1254, 1269, 1387
fascia, external, 1387
plexus of nerves, 1045
veins, 674, 1259
Spermatozoa, 1256
Spheno-ethmoidal branch of naso-ciliary
(nasal) nerve, 937
cells, 84
recess, 1206
Sphenoid, 62
at birth, 122
Sphenoidal conchas (turbinate bones), 64, 67
at birth, 124
development of, 119
crest, 63
(superior orbital) fissure, 65, 109, 116, 126
process of palate bone, 91, 92
of septal cartilage, 1203
septum, 62
sinuses, 62, 1207
Spheno-mandibular ligament, 217
Spheno-maxillary fissure, 102, 109, 126
fossa, 102
Spheno-palatine artery, 549
nerve, 938
foramen, 93, 103, 111, 126
(Meckel's) ganglion, 962
branches, 962
roots, 962
notch, 91, 93
vein, 646
Spheno-parietal sinus, 653
Sphenotic cartilage, 117
Spherical recess, 80
Sphincter ani externus, 441, 449
internus, 1 177
tertius, 1177
internal, of urinary bladder, 1253, 1389
pupillae (iridis), 1061
urethras (in female), 449
membranaceae, 449
urogenitalis, 442, 449
vaginaj, 1276, 1278
Spigelian lobe of liver, 1184
Spinal accessory nerve, 958
nucleus of, 820
arachnoid, 919
artery, anterior, 561, 638, 792
posterior, 561, 792
branches of aortic intercostal arteries, 590
of deep cervical artery, 568
of Uio-lumbar artery, 607
of lateral sacral arteries, 60S
of superior intercostal arteries, 568
of vertebral artery, 560
cord, 751, 771
blood supply of, 792
central canal of, 775
clinical anatomy of, 1408
external morphology of, 771
internal structure of, 775
1528
INDEX
Spinal cord, meninges of, 908
summary of, 788
surface of, 772
systems of neurones in, 777
terminal ventricle, 775
dura mater, 911
ganglia, 964
aberrant, 965
neurones of, 755
musculature, 410
nerves, 964
aberrant ganglia, 965
areas of distribution of, 970
attachment of, 964
Cauda equina, 966
course of, 965
filia radicularia, 965
ganglion of, 964
origm of, 964
roots of, 964
topography of attachment of, 966, 1406
nerve-trunks, anterior primary divisions, 968
meningeal (recurrent) branch of, 970
posterior primary divisions, 967, 970
rami communicantes, 969
pia mater, 921
(inferior) portion of (spinal) accessory
nerve, 958
tract, of trigeminus nerve, 828
veins, anterior, 665
posterior, 665
Spinalis capitis (biventer cerviois), 418
cervicis, 412, 417
dorsi, 412, 417
Spindle, aortic, 531
neuromuscular, 764
Spine (s), 29
anterior nasal, 87, 90, 112
ethmoidal, 63, 113
frontal (nasal), 60
of helix, 1084
of ilium, 169
ischial, 172
mandibular, 96
mental, 95
nasal (frontal), 60
posterior, 91
of pubis, 172
of scapula, 141, 144
of sphenoid, 65, 108
suprameatal, 72
of tibia (iatercondyloid eminence), 185
vertebral, 1403
Spino-cerebellar fasciculi, 784
path, 985
Spino-mesencephalic (spLno-tectal) tract, 786,
842
Spino-olivary fasciculus, 784
Spino-thalamic tract, 786
Spinous process of epistropheus, 34
of seventh cervical vertebra, 34
of vertebra:, 31
ligaments connecting, 229
Spiral canal of cochlea, 81
ganglion of cochlea, 950
ligament of cochlea, 1096
line of femur, 178
organ (organ of Corti), 1096
valve (of Heister), 1187
Splanchnic ganglion, 1039
nerve, great, 1038
least, 1039
lesser, 1039
pelvic, 1017, 1040, 1046
Spleen (lien), 1306
development, 1312
lymphatics, 736, 1312
Spleen, topography of, 1310, 1375
variations, 1310
vessels and nerves, 1312
Splenic artery, 595
branches of vagus, 958
(left colic) flexure, 1174, 1379
lobules, 1312
lymphatic nodes, 730, 736
(lienal) plexus of nerves, 1045
pulp, 1311
vein, 677
Splenium of corpus callosum, 852
Splenius, 412, 414
capitis, 414
cervicis, 414
accessorius, 414
Spongioblasts, 755
Spot, yellow, of fundus oculi, 1055
of larynx, 1223
Spring ligament, 305
Squamous portion of temporal bone, 68
sutures, 212
Stapedial fold, 1090
artery, 638
Stapedic branch of stylo-mastoid artery, 544
Stapedius, 1091
nerve to, 944
Stapes, 80, 119
Stellate cells of cerebellar cortex, 809
figures of lens of ej'e, 1063
ligament, 242
Stem of fissure of Sylvius, 855
Stenson's duct, 1115, 1343
foramina, 89, 106
Stephanion, 101
Sternal branches of internal mammary artery,
567
foramen, 133
synchondrosis, 133
Sternalis, 374
Sternebras, 132
Sterno-chondro-scapularis, 374
Sterno-clavicular joint, surgical anatomy of,
1363
ligaments, 248
Sterno-clavicularis, 374
Sterno-cleido-mastoid artery, 542
Sterno-cleido-mastoideus, 347, 349
Sterno-costal articulations, 245
ligaments, 245
surface of heart, 510
Sterno-oosto-clavicular articulation, 248
ligaments of, 248
movements of, 250
Sterno-hj'oideus, 3i51
Sterno-mastoid branch of superior thyreoid
artery, 538
as a landmark, 1355
vein, 660
Sterno-pericardial ligaments, 522
Sterno-thyreoideus, 351
Sterno-xiphoid plane, 1370
Sternum, 132
abnormaUties of, 138
angle of, 133, 139
body of, 133
development of, 135
StUling's nucleus, 776
Stomach, 1151
blood-vessels of, 1151
clinical anatomy of, 1373
comparative, 1160
development of, 1157
lymphatics of, 734, 1156
nerves of, 1156
peristalsis of, 1159
position and relations, 1153
INDEX
1529
Stro/ight (collecting), renal tubule, 1167
sinus, 450
Stratum album medium, 842
profundum, 842
cinereum, 842
corneum, 1286
unguis, 1295
germinativum (Malpighii), 1286, 1295
granulosum, 1286
lemnisci, 825, 839, 842
lucidum, 1286
opticum (stratum album medium), 842
zonale, 839, 842, 845, 881
Streeter, nucleus incertus of, 815
Strias acustica(ae), 814
(linete) albicantes, 1283, 1304
intermediate olfactory, 865
Lancisii, 851, 871
lateral longitudinal, of corpus callosum, 851
longitudinal, of corpus callosum, 851, 892
of hippocampus 871
medial longitudinal, of corpus callosum, 851
medullares acustici, 824
(pineales) of thalami, 846, 872
olfactory, 865, 866
terminalis thalami (ttenia semicircularis),
845, 892
of thalamus, 873, 881, 892
transverse, of corpus callosum, 852
Striate arteries, external, 906
internal, 906
Stripes of Baillarger, 879
Structure of organs (see corresponding organ)
Stylo-glossus, 346-
Stylo-hyal portion of styloid process, 75, 119
Stylo-hyoid ligaments, 99
Stylo-hyoideus, 343, 344
Styloid bone, 168
process, 70, 73, 75, 77, 108
of fibula, 190
of radius, 155
of third metacarpal bone, 166
of ulna, 158
Stvlo-mandibular (stylo-maxillary) ligament,
217
Stylo-mastoid branch of posterior auricular
artery, 544
foramen, 73, 108, 126
vein, 646
Stylo-pharyngeus, 1137
Subanconeus, 378
Sub-arachnoid cavity or space, 771, 919
cisternas, 918
Subcallosal gyrus (peduncle of corpus callo-
sum), 866
sulcus, 866
Subclavian artery, 556
collateral circulation, 1360
left, 556
relations, 556, 558, 1369
right, 557
variations, 638
group of axillary lymphatic nodes, 719
sulcus, of lung, 1229
vein, 671
Subclavius, 373
Subcostal artery, 588
Subcostales, 423, 434
Subcrureus, 470
Subcutaneous dorsal veins of penis, 684
inguinal (external abdominal) ring, 429,
1371, 1394
muscles, 313
of hand, 404
Subdural cavity, 912, 917
space of spinal cord, 771
Subfascial bursse mucosae, 318
Subiculum of the promontory, 1089
Sublingual artery, 540
caruncle, 1116, 1117
fold, 1116
gland, 1116
ducts of, 1117
vessels and nerves, 1117
lymphatic nodes, 746
nerve, 941
vein, 660
Submammary (retromammary) bursa;, 1303
Submarginal gyrus, 858
Submaxillary ganglion, 963
roots, 963, 1036
gland, 1115, 1350
duct of (Wharton's) 1116
vessels and nerves, 1116
lymph-nodes, 709
portion of external cervical fascia, 347
(digastric) triangle, 1357
Submental artery, 541
set of facial lymph-nodes, 711
vein, 644
Submuscular bursa; mucosae, 318
Subnasal point, 109, 112
Suboccipital muscles, 412, 419
nerve, 971
Subparietal sulcus (postlimbic fissure), 863
Subphrenic area of peritoneum, 1372
Subsartorial plexus, 1003
Subscapular angle, 145
artery, 571
branches of posterior scapular artery, 566
of transverse scapular arterj', 565
fossa, 141
group of axillary lymphatic nodes, 720
nerves, 984
vein, 671
Subscapularis, 369
minor, 369
Substance, anterior perforated, 847, 866
central grey, of mesencephalon, 836
of medulla, 818
gelatinous, central, of spinal cord, 776
of Rolando, 776
grey, of pons, 831
of nervous system, 768
of spinal cord, 775
of telencephalon, 879
posterior perforated, 835, 844
white, nervous system, 768
of spinal cord, 775, 777
of telencephalon, 885
Substantia alba, 768
corticalis, 1293
grisea, 768, 818
medullaris, 1293
nigra, 836, 840
reticularis alba (Ai'noldi), 868
Subtendinous bursa; mucosse, 318
Subtrapezial plexus, 979
Sudoriferous glands (sweat-glands), 1296
pore, 1297
Sulco-marginal fasciculus, 788
Sulcus(i), 29
ampullary, 1095
antero-inferior, 807
antero-intermediate, 774
antero-lateral, 773
auricular, 1082
basilar, of pons, 804
breves, 857
central (fissure of Rolando), 859, 1340
of cerebellum, 805
of cerebrum, 852
cinguli (calloso-marginal fissure), 857, 858,
869
1530
INDEX
Sulcus(i), circular, 857
coronarius, 510
of corpus callosum, 867
of crus of helix, 1084
cunei, 864
diagonal, 858
fimbrio-dentate, 868
of floor of fourth ventricle, 813
fronto-marginal, 858
of heart, 510, 511
hypothalamic, 847
inferior frontal, 858
postcentral, 861, 862
temporal, 855
infra-orbital, 1284
interparietal (intraparietal), 861
lateral occipital, 863
matricis unguis, 1294
median subcallosal, 866
mento-labial, 1284
middle frontal, 858
temporal, 855
of Monro, 847
oculomotor, 835
olfactory, 858
orbital, 858
parallel, 855
para-medial, 858
parolfactory, 865
pontine, 804
postcentral of cerebellum, 806, 861, 862
posterior median, 772
postero-inferior, 807
postero-intermediate, 773
postero-lateral, 773
post-nodular, 808
pre-auricularis, 177
precentral, 807, 857
rostral, 858
sagittal, 60
scleral, 1054
of skin, 1284
of spinal cord, 772
subclavian, of lung, 1229
subparietal, 863
superior frontal, 858
postcentral, 861, 862
temporal 855
supra-orbital, 1284
of telencephalon, 853
terminalis of tongue, 1106
of heart, 511
transverse occipital, 862, 863
temporal, 855
transversus, 69, 108
of anthelix, 1083
tympanicus, 75
Supercilia, 1290
Superciliary arch, 59, 108
Supination, 321
Supinator (brevis), 392
radii longus, 388
Supracallosal gyrus, 868
Supra-clavicular branches of cervical plexus,
978
nerves, 978
portion of brachial plexus, branches of,
982
Supra-condylar lines, 181
process, 149
ridge, lateral, 149
medial, 149
Supracostales, anterior, 433
posterior, 432
Supraglenoid tubercle of scapula, 144
Supra-hyoid musculature, 325, 344
Supramammillary commissure, 871, 890
Supra-mandibular branch of cervico-facial
nerve, 946
Supramarginal gyrus, 863
Supra-maxillary set of facial lymph-nodes,
711
Supra-meatal fossa, 72
spine, 72
triangle, Macewen's, 1337
Supra-occipital, 119
Supra-omental region of peritoneum, 1372
Supra-orbital artery, 552, 1343
branches, 553
border, 60
nerve, 935
notch, 60
sulcus, 1284
vein, 644
Suprapineal recess, 847
Suprarenal artery, inferior, 598
middle, 598"
superior, 592
glands, 1323, 1381
accessory (of Marchand), 1326
development, 1326
lymphatics, 701, 738
vessels and nerves of, 1326
plexuses of nerves, 1044
veins, 673
Suprascapular (transverse cervical) artery,
564
(coracoid or superior transverse) ligament,
253
nerve, 982
Supraspinatus, 368
Supraspinous branches of posterior scapular
artery, 566
of transverse scapular artery, 565
fossa, 141
ligament, 230, 238
Suprasternal bones, 133
Supratonsilar fossa, 1132
Supratragic tubercle, 1082
Supratrochlear branch of frontal nerve, 936
foramen, 150
lymphatic node, 719
Sural branches of popliteal artery, 622
(ex-ternal or short saphenous) nerve, 1010,
1013, 1467
Surfaces of organs (see corresponding organ).
Surgical anatomy of organs (see corresponding
organ).
Suspensorius duodeni, 1164, 1376
Suspensory ligament of Cooper, 1303
of the eyeball, 1072, 1348
of lens of eye, 1057, 1064
(apical dental) of occipito-epistrophic
articulation, 223
of ovary, 1269
of penis, 427, 1260
of Treitz, 1164, 1376
Sustentaculum hepatis, 1174
lienis, 1174
tali, 195
Suture(s), 212
of anterior cranial fossa, 113
coronal, 57, 101, 1339
frontal, 59
incisive, 106
lambdoid, 57, 101, 1339
meso-palatine, 89, 106
metopic, 59, 101
neuro-central, 45
of norma facialis, 108
occipital, 101
occipito-mastoid, 101
parieto-mastoid, 101
petro-squamous, 71
INDEX
1531
Suture(s), sagittal, 57, 101, 1339
squamoso-parietal, 1339
transverse, 108
palatine, 106
of vertex of skull, 101
Swallowing, muscles of, 325
process of, 1137
Sweat-glands, 1296
Swellings, genital, 1279
Sylvian fossa, 854
point, 856
Sylvius, aqueduct of, 834
fissure of, 850, 855, 134,0
Syme's amputation, 1465
Sympathetic fibres, 970, 1029
nerves of orbit, 1076, 1348
relations of spinal cord, 789
system, 959, 1026
construction of, 1030
ganglia of, 959
origin of, 1029
prevertebral plexuses of, 1029
trunks, 1032, 1033
Symphysis of mandible, 95
pubis, 238
ligaments of, 238
Synapses, 762, 765
Synarthroses, 212
Synchondroses, 212
sternal, 133
Syncytium, 759
Syndesmoses (synarthroses), 212
tympano-stapedial, 1090
Synergists, 322
Synovial bursse, 313, 318
membrane, 211 (see also corresponding
articulations)
sheaths (vaginae mucosae tendinum), 378
tendon-sheaths, 317
of forearm muscles, 395, 403
of leg muscles, 483, 484, 491
System, association, of hemisphere, 890
blood-vascular, 507
chromaffin, 1333
digestive, 1099
of fibres, commissural, 890
lymphatic, 697
nervous, 751
central, 751, 770
peripheral, 754, 924
sympathetic, 1026
neurone, 777, 895
respiratory, 1199
urogenital, 1241
Systemic arteries, 529
circulation, 507
veins, 640
Tabatifere anatomique (of Cloquet), 1433
Table showing relations of cervical and thora-
cic nerves to branches of brachial
plex-us, 993
of lumbar and sacral nerves to branches
of lumbar and sacral plexuses and to
pudic nerve, 1016
of muscles of lower extremity to nerves
of lumbar and sacral plexuses, 1016
of muscles of upper extremity to cervi-
cal nerves, 993
of vertebral levels, 1409
of distribution of spinal nerves (Cow-
ers'), 969
Tactile corpuscles (Meissner), 1290
Tsenia chorioidea, 844
fimbria, 868, 877
Taenia fornicis, 868
pontis, 855
semicircularis, 845, 873
thalami, 846, 872
Tail of caudate nucleus, 877
of epididymis, 1256
of muscle, 314
of pancreas, 1194
Talipes, 1467
Talo-calcaneal union, 301
Talo-fibular ligament, anterior, 299
posterior, 299
Talo-navicular articulation, 305
ligament, 306
Talus or astragalus, 191, 192
Tan, 1283
Tangential layer of fibres of cortex, 879
Tapetum of posterior cornu of lateral ventricle,
876
Tarsal arch, inferior, 554
superior, 554
arteries, medial, 632
bones, 191
clinical anatomy of, 1467
branches of dorsalis pedis artery, 632
elements, accessory, 199
(Meibomian) glands, 1054, 1298
joints, 301
transverse, 305
muscles, 1072, 1078
Tarso-metatarsal articulation, 308
Tarsus, 191
anterior articulations of, 303
of eyelids, 1053, 1077
Taste, organ of, 1051
Taste-buds, 1051
Taste-pores, 1051
Tectorial membrane, 223
Teeth, 1117
canine, 1120
deciduous or milk, 1126
incisor, 1119
molars, 1121
premolar or bicuspid, 1121
times of eruption, 1127
variations and comparative, 1127
vessels and nerves, 1124
Tegmen tympani, 77
Tegmento-mammUlary fasciculus, 871
Tegmentum of pons, 830
Tela chorioidea, 758
of fourth ventricle, 922
subcutanea (superficial fascia), 313, 1287
of the abdomen, 425
of the arm, 377
of the back, 413
of the forearm and hand, 384
of the foot, 491
of gluteal region, 457
of head and neck, 347
of leg, 477
of pectoral region, 371
of the perineum, 445
of shoulder, 365
of thigh, 466
of thoracic-abdominal musculature, 425
Telencephalon, 758, 847
gyri, fissures and sulci, 852
lobes, 853
central (insula), 856
frontal, 857
occipital, 863
parietal, 860
rhinencephalon, 864
temporal, 854
projection fibres of, 886
Telodendria of axones, 762
1532
INDEX
Temporal artery, anterior deep, 54S
middle, 545
posterior deep, 548
superficial, 545, 1343
bone, 68
at birth, 122
mastoid portion of, 68, 71
petrous portion of, 68, 72
squamous portion of, 68, 70
tympanic portion of, 69, 70, 75
branches, superficial, of auriculo-temporal
nerve, 942
of maxillary nerve, 938
of temporo-facial nerve, 945
fascia, 339
fossa, 101
gyrus, inferior, 855
middle, 855
superior, 854
lines (ridges), 57, 60, 71, 1332
lobe of cerebrum, 854
operoula of, 854
nerves, deep, 943
notch, 868
pole, 850
pontile path (Ttirk's path), 832, 840, 890
process of malar bone, 95
sulcus, middle, 855
superior, 855
vein, deep, 646
diploic, 648
middle, 646
superficial, 646
wings of sphenoid, 65
Temporalis muscle, 338, 341
superficialis, 337
Temporo-facial nerve, 945
Temporo-malar branch of maxillary nerve,
938 .
Tempo ro-maxillary (posterior facial) vein, 644
Tendino-trochanteric band, 280
Tendo Achillis, 485 ■
Tendon(s), 314, 317
at the ankle, 1460
conjoined, 435
of the conus, 518
popliteal,11451
of the quadriceps, 471
Tendon-sheaths, 317
of forearm muscles, 395, 403
of leg muscles, 483, 484, 491
Tenon's capsule, 1073, 1348
space, 715
Tensor capsularis articulationis metacarpo-
phalangei digiti quinti, 406
of the capsule of the ankle-joint, 491
fasciae dorsalis pedis, 482
latffi, 457, 459 ,1436
suralis, 476
laminas posterioris vaginas musculi recti
abdominis, 436
posterioris vaginae musculi recti et fasciae
transversalis abdominis, 436
ligamenti annularis anterior, 393
posterior, 393
tarsi, (Horner's muscle), 336
tympani, 1089, 1091
vaginae femoris (tensor fasciae latae), 457,
459, 1436
veli palatini, 1137
Tentorial (recurrent meningeal) branch of
ophthalmic nerve, 935
notch, 915
Tentorium cerebelli, 914
Tenuissimus, 475
Teres major, 369
minor, 369
Terminal branches (see corresponding artery
or nerve)
incisure (auricle), 1084
nerve, 929
stria, of thalamus, 873
sulcus, 1106
vein (of corpus striatum), 657
ventricle of spinal cord, 775
Testes, 1255, 1386
descent of, 1257, 1387
lymphatics of, 700, 744, 1256, 1387
Testicular arteries, 601
Tetrahedral-shaped spleen, 1310
Thalamencephalon, 844
Thalami, 758, 844
Thalamo-olivary tract, 817, 830
Thalamo-spinal tract, 786
Thalamus, 881
anterior tubercle (nucleus) of, 845, 882
cortical connections of, 883
medullary lamina of, 882
nuclei of, 871, 882, 883
peduncles of, 880, 883
pulvinar of, 882
stratum zonale, 881
stria terminahs of, 845, 881, 892
stria; meduUares, 872
Thebesius foramina of, 514
valvula of, 512
Theoa folhouli, 1292
Thenar fascia, 387
Thigh, bony landmarks of, 1434
fasciae of, 466
muscles, 453, 464
acting on, 505
muscular prominences of, 1436
Third occipital condyle, 56
part of axillary artery, 570
of subclavian artery, 558
ventricle of brain, 846
chorioid plexuses of, 924
Thoracic aorta, 586, 1369
aortic plexus, 1038
aperture, superior, 138
artery, dorsal, (thoraco-dorsal) , 572
lateral, 571
superior, 570
cavity, 1235
duct, 726
ganglia, 1038
intercostal nerves, 995
muscles, lymphatics, 923
nerves, 971, 994
lateral anterior, 983
medial anterior, 983
long, 982
posterior, 982
portion of left subclavian artery, 556
of sympathetic system, 1037
of thymus, 1321
vein, lateral, 671
vertebrae, description of, 30, 36
peculiar, 36
Thoracic-abdominal musculature, 422
fasciae of, 425
muscles of, 430
nerves, 995
Thoraco-acromial (acromio-thoracic axis),
artery, 571
vein, 671
Thoraco-dorsal (middle or long) subscapular
nerve, 984
Thoraco-epigastric vein, 671, 1372
Thorax, 126
articulations at front of, 244
bony landmarks, 1363
clinical anatomy of, 1363
INDEX
1533
Thorax, deep veins of, 665
lymphatics of, 723, 724, 725
movements of, 247
as a whole, 138
Thumb, muscles of, 406
acting on, 504
Thymic arteries, 567
veins, 661
Thymus, 1319
corpuscles of, 1321
cortex of, 1321
development of, 1322
lymphatics of, 729, 1322
medulla of, 1321
vessels (and nerves) of, 1322
Thyreo-arytsenoideus externus, 1219
internus (m. vocalis), 1220
obhquus, 1220
superior, 1220
Thyreocervical trunk (thyreoid axis), 564
Thyreo-epiglottic ligament, 1215
muscle, 1220
Thyreo-glossal duct, 1318
Thyreo-hyal centre, 100
segment, 119
Thyreo-hyoideus, 351
Thyreoid artery, inferior, 564
superior, 538, 638
bars, 119
cartilage, 1210
gland, 1312
accessory, 1315
clinical anatomy of, 1355
development of , 1318
lymphatics of, 699, 719, 1317
laminae, 1210
hgament, 1314
vessels, 1316
notch, inferior, 1211
superior, 1210
plexus of nerves, inferior, 1036
superior, 1Q36
tubercle, inferior, 1211
superior, 1211
veins, 660, 661, 1317
Thyreoidea ima artery, 533
vein, 661
Tibia, 185, 1454
condyles of femur and, 1447
epiphyses of, 1435
structures on head of, 1449
tuberosity of, and ligamentum patellaj, 1448
Tibial artery, anterior, 629, 640, 1458
posterior, 624, 640, 1458
collateral ligament, 286
communicating nerve, 1010
nerve (internal popliteal), 1009
paralysis of, 1469
anterior, 1015
posterior, 1009
nutrient artery, 626, 1459
recurrent artery, anterior, 632
posterior, 632
veins, anterior, 688
posterior, 688
Tibialis anterior, 453, 480, 1468
tenotomy, 1464
posterior, 454, 486, 490, 1468
secundus (tensor of capsule of ankle-joint),
491
Tibio-astragalus anticus, 482
Tibio-fibular ligaments, 295
union, 295
Tigroid masses, 766
Tissues, 4
Toes, muscles acting on, 506
Tomes' fibrils and sheath, 1118
Tongue, 1106
development of, 1112
glands of, 1108
lymphatics of, 715
muscles of, 325, 345, 346, 502, 1110
papillaj, 1106
surgical anatomy of, 1350
variations and comparative, 1112
vessels and nerves, 1111
Tonsil (amygdala) of cerebellum, 807
Tonsillar branch of external maxillary artery,
541
of ascending palatine, 541
of glosso-pharyngeal nerve, 952
fossEe, 1131, 1132
ring (Waldeyer's), 1133
TonsUs, lingual, 1107
lymphatics of, 1132
palatine, 1132, 1351
pharyngeal, 1130, 1354
variations and comparative, 1138
vessels of, 1132
Topography of attachment of spinal nerves,
966
of brain, general, 793, 1338
of organs (see corresponding organ)
Torcular Herophili, 650
Torus tubarius, 1130
Trabecute (carnese) cordis, 516
lienis, 1311
Trabecular region of skull, 117
Trachea, 1225, 1408
lymphatics of, 699, 1228
vessels and nerves, of 1228
Tracheal branches of inferior thyreoid artery,
564
cartilages, 1227
glands, 1227
veins, 661
Trachelo-mastoid, 416
Tract, anterior or direct pyramidal, 788
crossed pyramidal, 7S3
direct cerebellar (Flechsig), 784
Gower's, 784
habenulo-peduncular, 873
Loewenthal's, 786
mesencephalo-(tecto-) spinal, 786, 842
olfacto-mammillary, 873
olfacto-mesencephalic, 873
olfactory, 758, 865, 893
optic, 849
solitary, 820
spinal, nucleus of, 826
of trigeminus nerve, 828
spino-mesencephalic (spino-teotal), 786,
842
spino-thalamic, 786
thalamo-olivary, 817, 830
thalamo-spinal, 786
transverse peduncular, 835
ventral vestibulo-spinal, 786
Tractus ilio-pubicus, 430
ilio-tibialis, 457, 458
spino-teotalis, 786
Tragi, 1290
Tragus, 1082
Trans-pyloric line (Addison), 1153, 1370
Transyersalis cervicis, 416
fascia, 426
Transverse arch of foot, 1468
carpal (anterior annular) ligaments, 1427
cervical (transversa coUi) artery, 565, 638
veins, 672
colon, 1174
crest, 72
crural ligament of leg (upper part of anterior
annular ligament), 479
1534
INDEX
Transverse diameter of pelvic inlet, 175
facial artery, 545
vein, 646
fissure of cerebrum, 850
(Houston's) folds of rectum, 1177, 1390
fornix, 869, 890
humeral ligament, 256
ligament of central atlanto-epistrophic, 222
of heads of metatarsal bones, 309
hip-joint, 280
inferior (spino-glenoid), 253
of knee-joint, 289
of pubis, 446
superior (coracoid, or suprascapular), 253
nasal branch of dorsal nasal artery, 554
palatine suture, 106
processes of atlas, 33
of vertebrte, 31
ligaments connecting, 231
scapular (suprascapular) artery, 664, 638
veins, 648
(lateral) sinus, 651, 1331
of pericardium, 523, 527
strise of corpus callosum, 851
sulci, 108
suture, 108
Transverso-spinal muscles, 412, 419
Transversus abdominis, 424, 435
group of lateral division of thoraco-abdomi-
nal muscles, 434
menti, 333
nuchae (occipitalis minor), 337
•perinei profundus, 442, 449
superficialis, 444, 452
thoracis (triangularis sterni), 424, 434
vaginae (Fvihrer), 449
Trapezium, 159, 162
Trapezius, 347, 349
clinical anatomy, 1405
Trapezoid bone, 159, 162
ligament, 251
(obhque) line, 140
Treitz, suspensory ligament of, 1164, 1376
Triangle, Bryant's, 1436
Hesselbach's, 1398
inferior carotid (tracheal), 1358
Macewen's suprameatal, 1337
of neck, posterior, 1359
of Petit, 434, 1406
rectal, 440, 1383
Scarpa's 467, 1438
submaxillary (digastric), 1357
superior carotid, 1358
urogenital, 440, 1383, 1385
Triangles, cervical, 1357
of perineum, 1383
Triangular fascia, 430
fibro-cartilage, 264
fossa of auricle, 1082
fovea of aryta^noid, 1212
ligament, urogenital diaphragm, 442, 1384
(lateral) ligaments of liver, 1185
Triangularis (depressor anguli oris), 333
sterni, 424, 434
Tributaries of veins (see corresponding vein)
Triceps brachii, 374, 377, 378
surface markings, 1416
surse, 484
Tricuspid valve, 515, 516
Trigeminal foramen, 125
impression, 73
Trigeminus nerve, 934
nuclei of, 826
spinal tract of, 828
Trigona fibrosa, 518
Trigone, collateral, of lateral ventricle, 876
femoral, Scarpa's triangle, 467, 1438
Trigone of lemniscus, 832, 835
of Lieutaud, 1252
olfactory, 865
urogenital, 442, 446, 1384
vesical (of Lieutaud), 1252
Trigonum lumbale (triangle of Petit), 434
Triquetral (cuneiform), bone, 159, 161
Trochanter, great, 178
third, 181
Trochanteric of digital fossa, 178
Trochanters of femur, 178
clinical anatoiny of, 1435
Trochlea, 318, 1068
of humerus, 150
of talus, 193
Trochlear branches of supra-orbital artery,
553
fossa, 61
nerve, 835, 837, 933
process, 195
Troltsch, pouches of, 1089
True ligaments of bladder and prostate,
1252
synchondroses, 212
Trunk, articulations of, 224
costo-cervical arterial, 568
cutaneous areas of, 1020
lumbo-sacral, 1005
lymphatic, intestinal, 731
lumbar, 730
sympathetic, gangliated, 1029, 1032
thyreocervical, 564
Tuba auditiva (Eustachian tube) 74, 1089,
1092, 1354
Tubae uteriuEe (Fallopian tubes), 1269
lymphatics of, 700, 745, 1270
vessels and nerves, 1270
Tubal branch of ovarian artery, 602
branches of uterine artery, 610
Tube, auditory, (Eustachian), 74, 1089, 1092,
1354
neural, 754
Tuber caloanei, 196
einereum, 847, 848
omentale, 1184
vermis, 808
Tubercle(s), 29
adductor, of femur, 181
amygdaloid, of lateral ventricle, 877
anterior of thalamus, 845, 882
articular, of temporal bone, 71
of atlas, 32
auricular (tubercle of Darwin), 1083
of calcaneus, anterior, 195
condylar, of mandible, 97
coracoid (conoid) of clavicle, 140
cornioulate, of larynx, 1221
cuneiform, of larynx, 1221
of epiglottis, 1212, 1222
of femur, cervical, 178
genial, 95
genital, 1279
inferior thyreoid, 1211
intervenosum (of Lower), 513
labial, 1102
lacrimal, 88
malar, 95
mental, 95
olfactory, 865
pharyngeal, 54, 108
preglenoid, 71
pterygoid, 66
(spine) of pubis, 172
for the quadratus, 178
of rib, 127
scalene, 129
of scapula, infraglenoid, 143
INDEX
1535
Tubercles, of scapula, supraglenoid, 144
superior thyreoid, 1211
supratragic, 1082
of thoracic vertebrse, 37
Tubercular (posterior costo-transverse) liga-
ment, 243
Tuberculum aeustioum, 815
cuneatum, 801
intervenosum (of Lower), 513
jugulare, 54
sella;, 63, 116
Tuberosity, 29
of calcaneus, 196
of clavicle, costal, 140
of cuboid, 199
of femur, gluteal, 178
of fifth metatarsal bone, 203
of first metatarsal bone, 201
of humerus, greater, 147
lesser, 147
of ilium, 171
of ischium, 172
malar, 93
of maxilla, 87, 92, 106
of navicular (scaphoid), 161, 196
of radius, 152
of tibia, 185
of ulna, 156
ungual (of third phalanx), 168
Tubes, Fallopian, 1269
Tubules, renal, 1246
seminiferous, 1256
Tubuli recti, 1256
Tunica albuguiea of testis, 1256
of penis, 1260
of spleen, 1311
propria of corium, 1286
serosa of spleen, 1310
vaginalis communis (internal spermatic or
infundibuliform fascia), 1254, 1259
propria, 1254
vasculosa (of testis), 1256
Turbinate bones (conchse) 83, 84, 1205
sphenoidal, 64, 67
Turk's bundle, 832, 890
Tympanic antrum, 72, 73, 78, 1092, 1336
artery, anterior, 547
inferior, 537
superior, 548
bone, at birth, 123
branch of petrosal ganglion, 951
of stylo-mastoid artery, 544
canaheulus, 73, 108
cavity, 77, 1088
vessels and nerves, 1091
walls of, 1088
membrane, 1086
secondary, 1089, 1096
mucous membrane, 1089
nerve, 961
notch, 77
ostium of tuba auditiva, 1092
plate, 108
plexus, 951, 961, 1033, 1089
portion of temporal bone, 69, 75
sinus, 1089
sulcus, 75
veins, 696
Tympano-hyal portion of styloid process, 75,
119
Tympano-mastoid (auricular) fissure, 71, 75,
Tympano-petrosal branch of tympanic plexus,
961
Tympano-stapedial syndosmosis, 1090
Tympanum, 77
bones of, 79
development of, 80
U
IHna, 155
clinical anatomy of, 1419, 1422
Ulnar anastomotic branch of superficial radial
nerve, 987
arterj^ 576, 640, 1423
vena3 comitantes, 671
collateral artery, inferior, 576
superior, 576
nerve, 985
collateral ligament, 259, 266
nerve, 987
line of, 1415, 1423
results of paralysis, 1424
notch (sigmoid cavity) of radius, 154
recurrent artery, volar, 577
Ulno-carpeus, 492
Ultimobranchial bodies, 1318
Umbilical artery, 609
fissure of liver, 1183
fovea, 1284
hernia, 1402
hgaments, 1250, 1252
lymphatic nodes, 733
notch, 1182
plane, 1370
recess, 675
region, 1143
vein, 675, 680
Umbilicus, clinical anatomy of, 1371
Umbo of tympanic membrane, 1087
Unciform bone, 159
process, 163
Uncinate fasciculus, 891
process of ethmoid, 83
Unci-pisiformis, 403
Uncus, 868
Ungual phalanges, 168
process of third phalanx, 168
Ungues (nails), 1293
Union, coraco-clavicular, 251
cuboideo-navicular, 303
of heads of metacarpal bones, 274
of metatarsal bones, 309
of radius with ulna, 261
scapulo-clavicular, 250
talo-oalcaneal, 301
tibio-fibular, 295
Unipenniform muscle, 315
Urachal branch of superior vesical artery, 609
Urachus, 1250, 1252, 1253, 1398
Ureter, 1248
clinical anatomy of, 1381, 1394
lymphatics of, 738, 1249
portions of, 1248
vessels and nerves of, 1249
variations and development of, 1249
Ureteral branches of renal arteries, 598
of internal spermatic artery, 601
of ovarian arteries, 602
Ureteric branches of superior vesical artery,
609
Urethra, female, 1277, 1278
lymphatics of, 742
male, 1262, 1388
lymphatics of, 740
surgical anatomy of, 1389
Urethral annulus, 1253
artery, 613
bulb, artery of, 613
carina, 1276, 1278
glands (of Littr6), 1264
lacuna3 (of Morgagni), 1264
orifice of bladder, 1263
Urinary bladder, 1249
development of, 1253
1536
INDEX
Urinary bladder, parts of, 1250
lymphatics of, 700, 739, 1249
vessels and nerves of, 1253
organs, 1241
bladder, 1249
kidneys, 1241
ureters, 1249
Urogenital diaphragm, 440, 449
sinus, 1279
system, 1241
triangle, 440, 1383, 1385
trigone (triangular ligament), 442, 1384
Uterine artery, 610
branch of ovarian artery, 602
veins, 683
Utero-sacral ligaments, 1274
Utero-vaginal plexus of nerves, 1047
of veins, 683
Uterus (womb), 1271
clinical anatomy of, 1393
lymphatics of, 700, 745, 1274
masculinus, 1263
vessels and nerves of, 1274
Utricle, 1093
Utricular branch of vestibular ganglion, 950
Utriculo-ampullar division of vestibular nerve,
950
Utriculo-sacoular duct, 1094
Utriculus, prostatic, 1263
Uvula of palate, 1104, 1106, 1137
of urinary bladder, 1252
of vermis, 808
Vagina, 1274, 1277
clinical anatomy of, 1392
lymphatics of, 745, 1276
vessels and nerves of, 1276
Vagina fibrosa tendinis, 317
musculi flexoris hallucis longi, 491
flexorum digitorum longi, 491
tibialis posterior, 491
tendinis musculi extensoris carpi ulnaris,
395
digiti quinti, 395
hallucis longi, 483
pollicis longi, 395
flexoris carpi radialis, 403
pollicis longi, 403
peronsei longi plantaris, 484
tibialis anterioris, 483
tendinum musculorum abductoris pollicis
longi et extensoris pollicis brevis, 395
extensoris digitorum communis et ex-
tensoris indicis, 395
longi, 483 . ' . .
extensorum carpi radialium, 395
flexorum communium, 403
peroneorum communis, 484
VaginEE mucosa} tendinum, 318
tendinum digitales, 491
musculorum flexorum digitorum, 403
Vaginal artery, 610
ligaments, 317
of finger, 387
nerves, 1017
of sphenoid, 63, 66
of temporal bone, 76
Vagus (pneumogastric), 954
nucleus of, 820, 822
Valentine, ganglion of, 939
Vallate (circumvallate) papillis of tongue,
1106
Vallecula cerebelli, 807
epiglottic, 1107, 1221
Sylvii, 856
Valsalva, sinus of, 518, 530
Valve (s), anal, 1177, 1390
of aorta, semilunar, 517
atrio-ventricular, 515
bicuspid (mitral), 515
of fossa navicularis, 612
of Heister, 1187
(folds) of Houston, 1390
ileo-caical (colic), 1172
mitral, 515
pulmonary semilunar, 517
sinus coronarii, 512
(of Thebesius), 612
tricuspid, 515
of veins, 528
venfe cavaj (Eustachian), 512
Valvula foraminis ovalis, 512
Variability, 25
Variations of blood-vessels, 508
arteries, 637, 639
veins, 69
of organs (see corresponding organ)
Vas aberrans, 640
(ductus) deferens, 1257
Vasa aberrantia hepatis, 1184
brevia, 696
vasorum, 628
Vascular coat of eye, 1060
Vaso-motor nuclei, 822
Vastus intermedins (crureus), 468, 470
lateralis (vastus externus), 468, 470
medialis (vastus internus), 468, 470
Vater, ampulla of, 1188
corpuscles of, 1290
Vein(s) (see also "Vena"), 528
of abdominal wall, superficial, 683
accessory cephalic, 667
hemiazygos (azygos tertia), 663
popliteal, 689
portal, 678
• saphenous, 684
angular, 643
anterior auricular, 646
bronchial, 666
cardiac, 521
external spinal, 792
facial, 643, 1343
jugular, 648, 693
mediastinal, 667
parotid, 644
tibial, 688
articular of mandible, 646
ascending lumbar, 662, 663
of auricle (of ear), 1084
axillary, 671
azygos (major), 662, 693
basal, 657
basilic, 667
basivertebral, 666
brachial vense comitantes, 671
of brain, 663
bronchial, 1234
buccal, 646
cardiac (coronary), 620
central (ganglionic), 666
of retina, 659
cephalic, 667, 671
accessory, 667
cerebellar, 657, 908
cerebral, 654
chorioid, 657
ciliary, 658
circumflex, 671
of cochlear canaliculus, 652, 658
common facial, 644, 646, 693
iliac, 699
volar digital, 671
INDEX
1537
Vein(s), condyloid emissary, 652
conjunctival, 658
coronary (gastric), 675
of corpus striatum, 657
cortical or superficial cerebral, 654
costo-axillary, 671
cutaneous, 1289
cystic, 677
deep (ganglionic), 655
cervical, 661
circumflex iliac, 683
of clitoris, 683
temporal, 646
of the diploe, 648
dorsal digital (foot), 684
of clitoris; 683
lingual, 660
metacarpal, 667
metatarsal, 684
of penis, 681
duodenal, 677
of the ear, 667
emissary, 647, 649, 652, 916, 1334
episcleral, 659
ethmoidal, 659
of external acoustic (auditory) meatus, 1086
iliac, 683
jugular, 646, 693
nasal, 644
pudendal, 684
femoral, 690
vena3 comitantes, 690
femoro-popliteal, 685, 693
frontal, 644
diploic, 648
great cerebral (of Galen), 657, 923
cardiac, 520
(internal) saphenous, 684, 693
hajmorrhoidal plexus of, 683
of head and neck, 642, 693
superficial, 643
deep, 648
of heart, 520
hemiazygos (azygos minor), 662
accessory, 663
hepatic, 675
hypogastric (internal iliac), 679
ileo-colic, 677
ilio-lumbar, 680
inferior alveolar (dental), 646
cerebellar, 657
cerebral, 655
epigastric, 683
gluteal (sciatic), 680
hemorrhoidal, 683
labial, 644
laryngeal, 659
mesenteric, 678
ophthalmic, 646, 659
palpebral, 644
phrenic, 675
thyreoid, 661
infra-orbital, 646
innominate (brachio-cephalic), 641, 691, 692
intercapitular (hand), 667
of foot, 684
intercostal, 664
internal auditorj', 652, 657
cerebral, 657
jugular, 659, 691, 693
mammary, 666
maxillary, 646
pudendal; 681
spinal, 792
intervertebral, 666
Intestinal, 677
labial (of mouth), 644
Vein(s), labial (of vulva), 683, 684
lacrimal, 659
lateral circumflex, 690
sacral, 680
thoracic, 671
left colic, 678
gastro-epiploio, 677
superior intercostal, 664
lingual, 660
of lower extremity, 683, 693
lumbar, 675
of Marshall, oblique, 521, 523
masseteric, 644, 645
mastoid emissary, 647, 652
medial perforating, 690
median antibrachial, 667, 668
basilic, 669
cephalic, 668
cubital, 667
of medulla, 908
of medulla oblongata, 657, 908
meningeal, 917
middle cardiac, 520
cerebral, 655
colic, 677
hajmorrhoidal, 683
meningeal, 646
sacral, 679
temporal, 646
morphogenesis and variations, 690
muscular (of orbit), 658
of nasal cavities, 657
naso-frontal, 658
oblique (of Marshall), of left atrium. 521,
623
obturator, 680
occipital, 647
oesophageal, 661, 662
ophthalmic, 658, 659, 1075 .
ophthalmo-meningeal, 655
of orbit, 658
ovarian, 674
palatine, 644
palpebral, 658
pancreatic, 677
pancreatico-duodenal, 677
parietal emissary, 649
parumbilioal, 678
pericardiac, 666
of pharynx, 659
plantar, digital, 684
metatarsal, 687
of pons, 657, 908
popliteal, 688
portal, 528, 675
development of, 694
posterior auricular, 647
bronchial, 664
external jugular, 648
spinal, 792
facial (temporo-maxillary ) , 644
labial, 683
of left ventricle, 521
mediastinal, 664
parotid, 646
superior alveolar (dental), 646
tibial, 688
profunda or deep femoral, 690
proper volar digital (hand), 671
pterygoid plexiis of, 646
pulmonary, 529, 1235
pyloric, 675
radial vena; comitantes, 671
radicular, 792, 908
renal, 673, 693
right colic, 677
gastro-epiploic, 677
1538
INDEX
Vein(s), right colic, superior intercostal, 664
sigmoid, 678
scrotal, 684
small cardiac, 521
(external) saphenous, 684, 693
smallest cardiac, 521
spermatic, 674, 1259
spheno-palatine, 646
spinal, 665
splenic, 677, 1312
sterno-mastoid, 660
stylo-mastoid, 646
subclavian, 671
subcutaneous dorsal of penis, 684
sublingual, 660
submental, 644
subscapular, 671
superficial, in abdominal wall, 683
circumflex iliac, 684
epigastric, 684
of lower extremity, 683
temporal, 646
of upper extremity, 667
superior cerebellar, 657
cerebral, 654
epigastric, 666
gluteal, 680
hsemorrhoidal, 683
labial, 644
laryngeal, 659
mesenteric, 677
ophthalmic, 658
palatine, 646
palpebral, 644
phrenic, 667
thyreoid, 660
supra-orbital, 644
suprarenal, 673
systemic, 640
temporal (of diploe), 648
temporo-maxillary (posterior facial), 644
terminal (of corpus striatum), 657
thoraoo-acromial, 671
thoraoo-epigastric, 671, 1372
of thorax, 662
thymic, 661
thyreoid, 660, 1317
thyreoidea ima, 661
tracheal, 661
transverse cervical, 672
facial, 646
scapular (suprascapular), 648
tympanic, 646
cavity, 1091
ulnar venae comitantes, 671
umbilical, 675, 680
of upper extremity, 667
development of, 692
uterine, 683
vermian, 908
vertebral, 661, 664
Vesalian, 646
volar metacarpal, 671
Velum, anterior (superior) medullary, 812
interpositum, 847, 923
of palate, 1104
posterior medullary, 808
Vena canaliculi cochleae, 652, 658
cava, inferior, 672
development of, 693
superior, 641
development, 690
centralis retinae, 1065
cerebri magna (Galeni), 657
comitans n. hypoglossi, 660
septi pellucidi, 657
Venae cava?, relation to thoracic wall, 1369
Venae cavffi comitantes, 528
vorticosa;, 659, 1057, 1065
Venous arch, digital (hand), 667
lacunae of dura, 916
plexuses, vertebral, 664
sinus of sclera, 1059
sinuses, cranial, 528, 649, 916
Ventricle(s) of Arantius, 813
of brain, development of, 758
fifth, 872
fourth, 812
of heart, left, 516, 517
right, 516
of larynx (ventricle of Morgagni), 1222
lateral, of cerebral hemisphere, 873
drainage of, 1341
olfactory, 866
terminal, of spinal cord, 775
third, of brain, 846
Verga's, 869
Ventricular appendix (laryngeal saccule), 1223
folds (false vocal cords), 1222
ligament of larynx, 1215
musculature, 518
muscle of larynx, 1220
Ventro-lateral fasciculus, superficial, 770
Verga's ventricle, 869
Vermiform process (appendix), 1173, 1378
fossa, 53, 117
Vermis of cerebellum, 805
furrowed bands of uvula of, 808
inferior, 807, 808
pyramid of, 808
superior, 806
tubes, 808
uvula of, 808
Vernix caseosa, 1299
Vertebra prominens, 35
structure of, 45
Vertebra(a3), 29
articulations of bodies of, 225
cervical, 30, 31
coccygeal, 30, 42
lumbar, 30, 39
ossification of, 45
thoracic (dorsal), 30, 36
Vertebral artery, 559, 638
articulations, 225
branches of lumbar arteries, 593
canal (spinal), 31
arteries of, 590
venous plexuses of, 664
column, 29
as a whole, 43
foramen, 31
groove, 43
levels, 1409
ligaments, 228
notches, 30
plexus of nerves, 1037
portion of vertebral artery, 560
spines, 1403
Vertebro-occipital muscle, 412, 417
Vertex of urinary bladder, 1250
Vesalian vein, 646
Vesahus, foramen of, 66, 116
Vesical arteries, inferior, 609
middle, 609
superior, 609
branch of obturator artery, 608
nerves, inferior, 1017, 1047
superior, 1047
plexus of nerves, 1047
of veins, 683
portion of ureter, 1249
vein, 661
Vesicle(s), brain, 755
INDEX
1539
Vesicles, optic, 758
of thyreoid gland, 1316
Vesicula; seminales, 1257, 1387
lymphatics, 744
Vessels (see "Blood-vessels," "arteries,"
"veins," "lymphatic vessels").
Vestibular branch of stylo-mastoid artery, 544
csecum, 1096
conduction paths, 899
fenestra, 73, 1089
ganglion (gangUon of Scarpa), 823, 950
glands, 1278
membrane (membrane of Reissner), 1096
nerve, 949
nuclei of, 823
slit, 1222
Vestibule (of temporal bone), 80
of larynx, 1221
of nose, 1204
oral, 1100
of vagina, 1277, 1392
Vestibulo-spinal fasciculus, 786
VibrisssB, 1204, 1290
Vicq d'Azyr, bundle of, 871
Vidian artery, 549
canal, 103, 107, 108, 126
nerve (n. canalis pterygoidei), 962
Villi, pleural, 1237
of small intestine, 1166
Vincula tendinum, 399, 401
Visceral bars, metamorphosis of, 119
lymphatic nodes of thorax, 724
vessels of abdomen, and pelvis, 733
Visual area of cerebral cortex, 893
Vitreous body or humor of eye, 1052, IO64
lamina of chorioid, 1026
Vocal folds (cords), false, 1222
true, 1223
ligaments, 1215
lip, 1223
muscle, 1220
process of arytenoid cartilage, 1212
Volar arch, deep, 586, 639, 1426
venous, 671
superficial, 682, 639, 1425
venous, 671
artery, superficial, 584
carpal rete (arch), 579, 581
digital veins, 671
interosseous artery of forearm, 577
(anterior) interosseous nerve, 992
ligament, accessory (or glenoid), 274
metacarpal arteries, 586
veins, 671
musculature, 363
perforating branches of radial artery, 586
radial carpal artery, 584
(anterior) radio-carpal ligament, 266
ulnar carpal artery, 580
Vomer, 85
Vomero-nasal organ (of Jaoobson), 1051, 1204
Vortices of hair, 1291
Vulva (external female genitalia), 1276
W
Waldeyer's tonsillar ring, 1133
Wallerian degeneration, 780
Wharton's duct, 1116
White commissures of spinal cord, 776
ramus communicans, 1030
substance of nervous system, 768
of spinal cord, 775, 777
of telencephalon, 885
Whitlow, 1431
Willis, circle of (circulus arteriosus), 555
chords of, 649
Wings of sphenoid, 62
great or temporal, 65
small or orbital, 64
Winslow, foramen of, 1147
Wirsung, duct of, 1194
Wisdom teeth, 1122
Wolffian body, 1278
duct, 1248, 1267, 1278
Word-blindness, 895
Wormian bone, 68
Wrinkles of skin, 1284
Wrisberg, cardiac ganglion of, 1041
cartilages of, 1213
lingula of, 942
nerve of, 946, 983
Wrist, bony points of, 1424
clinical anatomy of, 1424
Wrist-joint, 265
Xiphoid branch of superior epigastric artery,
567
process, 132, 134
Yellovc spot (macula lutea), 1055
of larvnx, 1223
Yolk-sac, 10, 13
Zeiss's glands, 1078
Zinn, ligament of, 1067
Zona fasoiculata, 1326
glomerulosa, 1326
reticulata, 1326
Zone(s), marginal, of Lissauer, 782
mixed lateral, 784
Zonula oiliaris, 1064
Zonular spaces, 1064
Zygapophysis, 57
Zygomatic arch, 1332
bone (malar), 93
at birth, 124
branches of lacrimal artery, 552
(orbital or temporo-malar) of maxillary
nerve, 938
(malar) of temporo-facial nerve, 945
fossa, 101, 1332
process, 70, 87, 88
Zygomatico-facial (malar) branch of maxillary
nerve, 938
canals, 126
Zygomatioo-orbital artery, 545
canals, 94
Zygomatico-temporal (temporal) branch of
maxillary nerve, 938
foramen, 126
Zygomaticus (zygomaticus major), 333
minor, 332
COLUMBIA UNIVERSITY LIBRARIES (hsLstx)
QM 23 IV183 1914 C.1
Morris's human anatomy
2002191202
QM27j
Hvunan anatomy
UBz
1914
MAR 2 0 1944 '=i^' <> (^-^J^^<^ T)r
'\
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11