THE FUNDAMENTALS OF HUMAN ANATOMY THE FUNDAMENTALS OF 
HUMAN ANATOMY 
INCLUDING ITS BORDERLAND DISTRICTS 
From the Viewpoint of a Practitioner 
BY /. 
MARSH PITZMAN, A.B., M.D. 
»•« 
PROFESSOR OF ANATOMY IN THE DENTAL DEPARTMENT OF WASHINGTON UNIVERSITY, 
ST. LOUIS 
WITH ONE TIEN DRED ONE ILLUSTRATIONS 
ST. LOUIS 
C. V. MOSBY COMPANY 
1920 Copyright, 1920, by C. V. Mosby Company 
{All rights reserved) 
Press of 
C. V. Mosby Company 
St. Louis TO THOSE 
WHOSE ESSENTIAL AIM IT IS TO 
ADVANCE THE BOUNDS OF OUR 
ANATOMIC KNOWLEDGE, 
THIS BOOK IS 
DEDICATED PREFACE 
The following discussion might, perhaps, be more fittingly entitled 
"One point of view as to the teaching and learning of anatomy." 
With this general disclaimer, and the statement that the usual 
preface data may be found on pages 6 to 7, I offer the following as 
the theory and aim of this effort. That anatomy is taught to the 
students of medicine by two groups of men with varying antecedents 
and aims; those who are essentially anatomists and those who are 
essentially practitioners. The extremists of these groups naturally 
have many grave disagreements, but surely no exponent of either 
extreme seriously questions the value of the other element. Both 
these groups have as their aim the advancement of the science and 
the practice of anatomy, even though emphasis is differently placed. 
These forces should be considered therefore not as opposing but as 
complementary forces. 
However much these groups of teachers may disagree among 
themselves, every posted observer of either side will agree that the 
rank and file of practitioners of medicine show an unfortunate lack 
of knowledge of and interest in anatomy. The importance and 
practical value of anatomy as an aid to the practitioner in any or all 
of the subdivisions of medicine deserves emphasis. In so unstable a 
field as medicine the value of a stock of relatively fixed facts as a 
foundation for the practitioner can scarcely be overestimated. True, 
a knowledge of anatomy will not in itself make a diagnostician or a 
surgeon, but on the other hand a lack of such knowledge is a fatal 
shortcoming. After making due allowance for the exaggerated 
importance any group of men necessarily attach to their particular 
work, the fact remains that any serious attempt to improve the 
anatomic knowledge of practitioners is worthy of the consideration 
of all those interested in the advancement of medical education. 
Let us counsel together. Admittedly under the present system 
many or even most medical students get a fairly satisfactory knowl- 
edge of anatomy, but the question is-Is the present method of 
teaching the best that can be evolved, other factors remaining 
3 4 
PREFACE 
unchanged ? It is very natural for us, as teachers, to ignore the 
shortcomings, or to point out the weaknesses in our present or 
former students in extenuation, but are we blameless? Anatomy is 
taught in the medical school because it is of value to the practitioner 
and the embryo-practitioner is justly interested in anatomic facts 
in direct proportion to their practical usefulness. These axiomatic 
principles are all too often lost sight of in the preparation of books 
and at times perhaps even in the actual teaching of students. Let 
me emphasize that this is not a discussion of how to advance the 
science of anatomy, but how to teach students and practitioners of 
medicine. To the scientist the demonstration of a new fact with its 
full detail is a matter of the greatest interest. Common experience 
has abundantly justified this point of view even from the utilitarian 
standpoint, for what is today an isolated bit of knowledge without 
practical importance, tomorrow often becomes an element of our 
foundation. Before a body of medical men the importance of the 
study of anatomy as a pure science certainly should require no 
defense, for practitioners must recognize that most of our advances 
in anatomy-and in later years there have been many-are neces- 
sarily based on abstract scientific effort. But to maintain such a 
point of view in the teaching of students or practitioners of medicine, 
as is sometimes unconsciously done, is in the opinion of most prac- 
titioners a serious pedagogical error. 
A stock tendency of the reactionaries is the attempt to restrict the 
teaching to pure or straight anatomy, meaning thereby such anatomy 
as can be seen by the unaided eye. But the progressives maintain 
that anatomy never has been taught strictly from this point of view, 
and that if it should be so taught it would necessarily yield an 
artificially narrow conception of the subject. They point out that 
the action of muscles, which is technically function or physiology, 
that the question of rupture, which is technically disease or path- 
ology, that the subject of development, which is technically embry- 
ology, and so forth indefinitely, have long been treated as intrinsic 
parts of anatomy. The progressives maintain that the great modern 
advance in our conceptions of anatomy is due to an attack on the 
subject from all available points of view; they point out that the 
sidelights from microscopic anatomy, zoology, embryology, physi- 
ology, Pathology, and the practice of medicine and surgery, are 
vitalizing anatomy by breaking down what are in reality artificial PREFACE 
5 
barriers. In practice many of these important borderland discus- 
sions, belonging distinctly neither to one chair of the medical school 
nor the other, are omitted from the students' course. Perhaps the 
most striking example of this is the serious omission of references 
to practical anatomy from books on general medicine. To cite a 
concrete illustration at random, the otherwise very detailed articles 
on cerebrospinal meningitis and tetanus in Osler's Modern Medicine, 
make no mention of the normal relative strengths of the muscle 
groups in connection with the contractures so characteristic of these 
diseases. The practical importance of these borderland interrela- 
tionships of anatomy must be conceded by all, hence the argument 
resolves itself into the question of who shall teach this field. The 
practitioner, whose knowledge of anatomy is necessarily limited, or 
the anatomist, whose knowledge of practice is limited, or both? 
Most of the newer anatomies and the newer editions of the 
standard works recognize the force of this reasoning and by bringing 
in borderland discussions make a radical departure from former 
standards. But as these sidelights have been progressively added 
to the already large books on anatomy, and nothing subtracted, 
these enlarged volumes have gradually grown into encyclopedias of 
our entire anatomical knowledge of the human body. They unques- 
tionably fill a most useful place, for the advanced student as a 
reference work and for the beginner on account of their summaries 
and wonderful illustrations. But as textbooks, their very complete- 
ness and scientific detail makes them almost impossible. No intelli- 
gent individual ever literally read one of these books through, 
except perhaps the author, and he usually divides the burden by 
means of sectional authorship. Every posted observer recognizes 
that the amount of detail a student can absorb without losing his 
bearings varies markedly with the individual, and that the attempt 
on the part of the ambitious students to master too much detail only 
too often results in confusion. The time-honored rule of teaching 
the fundamentals of a subject before attempting to fill in the detail 
demands recognition, if we are to avoid "mental indigestion" of our 
average and even of our best students. The dissector group of books 
on account of their lesser size furnish a text, much more readable 
and understandable for the student. The shortcomings of those in 
widespread use, according to the practitioner's point of view, lie in 
too great an insistence on detail and too little recognition of the 6 
PREFACE 
borderland interrelationship of anatomy. To give a concrete illus- 
tration of a tone, which in my opinion runs throughout these books, 
the dissector in most widespread use devotes approximately one- 
fifteenth of its consideration of the upper and lower extremities to 
the cutaneous nerves, a topic of almost negligible practical value. 
The compend class of books are too often simply abridged catalogues 
of anatomic facts without explanation. 
After frankly stating my views, I set to work to write what I 
consider a modern textbook of human anatomy. This book will be 
written on a progressive system; that is, the essential facts will 
first be emphasized and then later on details and sidelights will be 
gradually added. Every term will be explained at its first appear- 
ance so that any student without previous special education should 
be able to follow the text, always provided the preceding parts have 
been understood and retained. As the title suggests, the rather 
old-fashioned pedagogical rule of "teaching more by not attempting 
to teach too much" will receive recognition. For the sake of 
brevity and clearness a dogmatic style will be adopted, leaving 
detailed argument and varying opinion for more complete works. 
A conscious attempt has been made to pay more regard than has 
been customary to the modern pedagogical emphasis on the corre- 
lation of ideas. Logic will be introduced so far as possible to take 
the place of memorizing, of which there is at best in anatomy 
necessarily a great amount. The advantage of this method is that 
in practice a fact held by understanding is retained much longer 
and more effectively than one entrusted to memory. The text will 
follow the Basle revision of anatomical nomenclature, such minor 
variations as are used having been discussed elsewhere.* As this 
book makes no pretense except as an auxiliary to more complete 
works, only such diagrammatic illustrations will be used as seem 
absolutely indispensable. 
To the student I should like to emphasize the fact that very many 
anatomic points can be made out on his or her own body, which has 
the obvious advantage of being ever present. The drawings and 
plates of the modern larger anatomic works are of unquestionable 
help while an articulated skeleton is more than worth its trouble 
and expense. But of course no aid approaches in value that of 
* Some Suggested Changes in Nomenclature-Anatomical Record, xiii, No. 3, pp. 165-168. PREFACE 
7 
actual dissection, for the guidance of which I trust sufficient direc- 
tions are to be found in the text. A fair general conception of the 
whole area under consideration should be acquired before any 
attempt is made at dissection. This rule will minimize mistakes and 
reduce the necessity for minute details of dissection rules and for 
expert supervision. 
My confidence in the aims of this book is greater than my faith in 
the performance! It is not written for the extremists, whose criti- 
cisms respectively will surely be that it is altogether too detailed 
and altogether too lacking in detail. But the anatomic point of 
view is of so great practical value in the general practice of medicine 
and surgery that the embryo-practitioner or practitioner must 
surely be repaid for whatever time is devoted to the subject. If this 
volume tends in any degree, directly or indirectly, to bring the 
teacher and student of anatomy into closer sympathy, it will have 
fulfilled its mission. 
Let me here acknowledge thanks to Doctors Tupper, Neilson, 
Sluder, and Dock, of St. Louis, for their helpful criticisms and 
encouragement; to Mr. Wm. H. French for the excellent way in 
which he has fulfilled my simple wants in regard to illustrations; 
and above all, to the publisher, C. V. Mosby Company, for optimis- 
tic faith in the practical value of my conception. CONTENTS 
CHAPTER I 
Introduction 19 
Subdivisions of Anatomy, 19; Cells, 20; Mitosis, or Karyokinesis, 
22; Reproduction, 22; Segmentation, 23; Bilateral Symmetry, 23; 
The Vertebrates, 23; Descriptive Terms, 24; Systemic versus Re- 
gional Anatomy, 25. 
PART I 
SYSTEMIC ANATOMY 
CHAPTER II 
The Skin and Mucous Membrane 27 
The Skin (Cutis), 27; Epidermis, 27; Dermis, or Corium, 28; Varia- 
tions in Thickness, 30; Pigment, 30; Accessories, 30; Mucous Mem- 
branes, Mucosa, 31; Submucosa (Tela Submucosa), 32; Types of 
Epithelium, 33. 
CHAPTER III 
Subcutaneous Fatty Layer and Deep Fascia 34 
Subcutaneous Fatty Layer (Panniculus Adiposus), 34; Variations 
in Thickness, 34; Fat Cells, 34; Heat Radiation, 35; Superficial 
Venous System, 35; Fascia, 36; Intergroupal Septa, 36; Variations, 
37; Practical, 37. 
CHAPTER IV 
Muscles (Musculi) 38 
Types, 38; Development, 39; Attachments, 39; Origin and Insertion, 
40; Lever Principle, 41; Counteraction, 41. 
CHAPTER V 
Bones and Joints 42 
Bones (Ossa), 42; Pliability versus Brittleness, 42; Cartilage, 43; 
Classification, 44; Gross Development, 44; Microscopic Develop- 
ment, 46; Tubular Structure, 47; Projections, 48; Vessels and 
Nerves, 48; Joints (Articulations), 49; Classification, 49; Freely 
Movable Joints, 49; Development, 50; Dislocations, 50. 
9 10 
CONTENTS 
CHAPTER VI 
Blood and Lymph Vessels 52 
Blood Vessels (Vasa Sanguinea), 52; Circulation, 52; Blood (San- 
guis), 52; Capillaries, 53; Large Arteries, 53; Arterioles, 54; Veins, 
54; Rate of Flow, 55; Thickness of Walls, 55; Anastomosis, 56; Sec- 
ondary Position of Vessels, 56; General Locations, 57; Superficial 
Venous System, 58; Vales in Veins, 58; Lymph Vessels (Vasa 
Lymphatica), 59; Lymph Glands (Lympho-glaudulse), 59. 
CHAPTER VII 
Nerves (Nervi) 61 
Microscopic Structure, 61; Systems, 63; Peripheral Nerves Proper 
versus Sympathetic Nerves, 63; Segmentation, 64; Repair, 64. 
PART II 
REGIONAL ANATOMY 
CHAPTER VIII 
The Upper Extremity 65 
Shoulder and Arm, 65; Scapula, 66; Clavicle, 67; Humerus, 68; 
Vertebrae, 68; Dissection, 70; Subcutaneous Fatty Layer, 71; Fas- 
cia, 72; Muscles, 72; Front of Chest, 73; Sternum, 73; Costae, 73; 
Mammary Gland (Mamma), 74; Structure of a Compound Duct 
Gland, 75; Fatty Layer and Fascia, 76; Muscles, 77; Fossa Axillaris, 
77; Brachial Plexus, 77; Sympathetic Nerves, 78; Arteries and 
Veins, 78; Lymphatic Glands, 79; Removal of Upper Extremity 
from Trunk, 80; Rotator Muscles of Arm, 81; Adduction of Arm, 
81; Abduction of Arm, 82; Flexion and Extension of Arm, 82; The 
Arm (Brachium), 83; Superficial Venous System, 83; Deep Fascia, 
84; Anterior or Flexor Compartment, 84; Posterior or Extensor 
Compartment, 86; Vessels, 86; Brachial Plexus, 87; Shoulder Joint 
(Articulatio Humeri), 88; General Rule of Nerve Supply, 89; Dis- 
location, 89; Acromioclavicular Joint, 90; Forearm and Hand (Anti- 
brachium et Manus), 90; Ulna, 90; Radius, 92; Car pals, 92; Meta- 
carpals, 92; Phalanges, 93; The Skin, 94; Subcutaneous Fatty 
Layer, 94; Deep Fascia, 94; Muscles, 95; Flexors and Pronators, 
96; Short Muscles of Hand, 97; Blood Supply, 98; Nerves, 99; 
Practical, 101; Extensors and Supinators, 101; Vessels and Nerves, 
102; Radio-Ulnar Joints, 103; Elbow Joint (Articulatio Cubiti), 
103; The Wrist, 104; Phalangeal Joints, 105; Bone Section, 105; 
Practical, 105. CONTENTS 
11 
CHAPTER IX 
The Lower Extremity 108 
Hip and Thigh, 108; Hip Bone (Os Coxae), 108; Pelvis, 108; Bony 
Landmarks, 109; Ligaments, 110; Obturator Foramen, 111; The 
Femur, 111; Gluteal Region, 113; Gluteus Maximus Muscle, 113; 
Ischiatic, or Sciatic, Nerve, 113; Internal Rotator Muscles, 114; 
Special External Rotators, 114'; Thigh Region (Regio Femoralis), 
115; Subcutaneous Fatty Layer, 115; Deep Fascia, 116; Adductors 
of Thigh, 116; Nerve Supply, 117; Flexors and Extensors of Thigh, 
118; Extensors of Leg, 118; Nerve Supply, 119; Flexors of Leg, 
119; Fossa Poplitea, 120; Blood Supply of Thigh, 120; Hip Joint 
(Articulatio Coxae), 121; Dislocation, 122; Practical, 122; Leg and 
Foot (Crus et Pes), Tibia and Fibula, 123; Tarsal, Metatarsal, and 
Phalangeal Bones, 125; Developmental Rotation, 125; Skin, 127; 
Subcutaneous Fatty Layer, 127; Deep Fascia, 127; Anterior Tibiofib- 
ular Compartment and Dorsum of Foot, 129; Tibial Compartment, 
129; Fibular Compartment, 130; Posterior Tibiofibular Compart- 
ment, 130; Sole of the Foot, 131; Vessel Supply, 131; Nerve Supply, 
133; Knee Joint (Articulatio Genu), 134; Ankle Joint (Articulatio 
Talocruralis), 135; Tarsal Joints, 136; Other Joints, 137. 
CHAPTER X 
The Abdomen 138 
Perineum, 138; Cloaca, 138; Pelvic Diaphragm (Diaphragma Pel- 
vis), 138; Anal Region, 139; Vessels and Nerves, 141; Male Uro- 
genital Region, 142; Penis, 142; Skin and Fatty Layer, 144; Deep 
Fascia, 145; Female Anal Region, 146; Female Urogenital Region, 
146; Urogenital Diaphragm, 146; Clitoris, 146; Vaginorectal Space, 
148; Hermaphroditism, 149; The Abdominal Wall, Divisions, 149; 
Superficial Layers, 150; Muscles and Aponeuroses, 150; Anterior 
Portion, 151; Lateral Portion, 151; Posterior Portion, 153; Nerve 
Supply, 153; Vessels, 154; Deep Layers, 154; Hernia, 155; Surgical 
Incisions Through Abdominal Wall, 159; Superior Abdominal Wall, 
160; The Gastrointestinal Tract, Peritoneal Cavity (Cavum Peri- 
tonsei), 160; Contents of Abdomen, 162; Walls of Gastrointestinal 
Tract, 162; General Principles, 163; Muscle Layers (Tunica Mus- 
cularis), 163; Examination of Abdominal Cavity, 164; Arrangement 
of the Peritoneum, 167; Practical, 168; Stomach (Ventriculus or 
Gaster), 168; Practical, 168; Small or Thin Intestine (Intestinum 
Tenue), 170; Practical, 170; Large or Thick Intestine (Intestinum 
Crassum), 171; Practical, 172; Vessels, 172; Nerves, 173; Practical, 
174; Dissection, 174; Mucosa (Tunica Mucosa), 175; Embryologic 
Blood Supply of Abdomen, 178; Vitelline and Allantoic Sacs and 
Ducts, 178; Umbilical Arteries and Vein, 179; Vena Porta, 180; 12 
CONTENTS 
Liver (Hepar), 181; Blood Supply, 181; Bile Passageways, 183; 
Practical, 185; Pancreas, 186; Practical, 186; Other Abdominal 
Organs, 188; Spleen (Lien), 188; Blood Supply of Abdomen, 189; 
Development of Kidneys, 193; Kidney (Ren), 194'; Microscopic 
Structure, 194; Gross Structure, 195; Suprarenal Gland (Glandula 
Suprarenalis), 197; Urinary Bladder (Vesica Urinaria), 197; Male 
Internal Genitalia, 198; Testicle (Testis), 199; Female Internal 
Genitalia, 201; Origin of Iliopsoas Muscle, 203; Nerves, 203; Prac- 
tical, 204. 
CHAPTER XI 
The Thorax 205 
Bony Framework, 205; Muscles, 205; Vessels and Nerves, 207; 
Respiration, 207; Types of Chest, 208; Relation to General Physique, 
209; Relation to Abdomen, 209; Contents of Mediastinum (Cavum 
Mediastinale), 210; Pleural Cavities (Cavum Pleurae), 211; Lungs 
versus Abdomen, 212; Diaphragm (Diaphragma), 212; Lung 
(Pulmo), 213; Vessels and Nerves, 214; Lobes, 215; Practical, 215; 
Heart (Cor or Cardia), 216; Simplest Type, 216; Valves, 217; 
Chambers, 217; Flow Through Heart, 217; Fetal Circulation, 219; 
Pericardium, 221; Gross Anatomy, 221; Atria, 222; Valves (Val- 
vulae), 223; Ventricles (Ventriculi), 223; Vagus Nerves, 225; Sym- 
pathetic Nerves, 226; Thoracic Arteries, 226; Thoracic Veins, 227; 
Thoracic Lymph Duct (Ductus Thoracicus), 228; Esophagus and 
Trachea, 229; Gangliated Sympathetic Trunks, 229; Thymus, 231; 
Vertebral Column (Columna Vertebralis), 231; Extensor Vertebrae 
Muscle Group, 234; Curves, 235; Spinal Cord (Medulla Spinalis), 
235; Dura Mater, Arachnoidea, and Pia Mater, 237. 
CHAPTER XII 
The Neck 240 
Bony Framework and Landmarks, 240; Superficial Layers, 241; 
Deep Fascia, 242; Extensor Vertebrae Muscle Group in Neck Region, 
243; Flexors of Neck and Head, 244; Sternomastoid (Sternocleido- 
mastoideus), 244; Depressors of Hyoid Bone, 245; Elevators of 
Hyoid, 245; Minor Triangles, 246; Deep Venous System, 247; 
Scalene Muscles, 248; Arteries, 248; Branches of Subclavian, 249; 
Branches of External Carotid, 249; Nerves of Neck, 250; Thyroid 
Gland (Glandula Thyreoidea), 252; Pharynx, 253; Gills and Gill- 
Clefts, 254; Larynx, 255; Aperture of Larynx (Aditus Laryngis), 
257; Vocal Folds (Plicae Vocales), 258; Practical, 259; Cranio- 
vertebral Joints, 260; Occipital Bone, 260; Atlas, 261; Epistro- 
pheus, 262; Muscles, 262. CONTENTS 
13 
CHAPTER XIII 
The Head 264 
Skull Proper, 264; Cranium Cerebrale, 264; Landmarks, 265; De- 
velopment of Skull, 265; Suturse et Fonticuli, 267; Scalp, 268; 
Vessels and Nerves, 268; Skull Section, 269; Meningeal Vessels, 
270; Dura Mater (Dura Mater Encephali), 270; Partitions, 271; 
Venous Sinuses, 272; Fossae, 273; Bony Floor of Skull (Basis 
Cranii Interna), 274; Cranial Nerves (Nervi Cerebrales), 276; 
Cranial Arteries, 276; Veins, 277; Foramina, 277; Middle Cran- 
ial Fossa, 278; Cavernous Sinus, 278; Hypophysis, 279; Fractures 
of the Skull, 279; Clinical Signs of Fracture, 280; Central Nervous 
System, 280; Development, 281; Nerve Cell (Neuron), 282; Gang- 
lia, 282; Efferent versus Afferent Neurons, 283; Spinal Cord 
(Medulla Spinalis), 283; Cross-Sections of Spinal Cord, 284; Periph- 
eral Neurons, 285; Central Neurons, 286; Tracts of Spinal Cord 
(Fasciculi Medullm Spinalis), 287; Development of Encephalon, 
289; Vesicles, or Ventricles, 291; Encephalon, 292; Tracts of Brain 
Stem, 292; Gray Substance of Brain Stem, 294; Lateral View of 
Encephalon, 295; Cerebellum, 296; Base of Encephalon, 297; Arter- 
ies, 299; Midsection of Encephalon, 299; Cerebrospinal Fluid, 
301; Horizontal Section, 303; Half Inch Below Top of Corpus Cal- 
losum, 303; Three-Quarter Inch Below Top of Corpus Callosum, 
305; Dissection of Fresh Encephalon, 305; Meningitis, 307; Hemor- 
rhage, 307; General Encephalon Pressure, 308; Local Encephalon 
Pressure, 308; Face, 309; Face Bones (Ossa Faciei), 309; Divisions, 
311; Skin, 311; Subcutaneous Fatty Layer, 311; Muscles of Eye 
Group, 312; Muscles of Nasal Group, 312; Muscles of Oral Group, 
312; Blood Supply, 313; Motor Nerve Supply, 313; Sensory Nerve 
Supply, 314; Orbital Cavity (Orbita), 314; Eyelids (Palpebrae), 
315; Conjunctiva, 315; Orbital Fascias, 316; Muscles (Musculi 
Oculi), 317; Sensory Nerve Supply, 317; Vessels, 317; Optic Nerve 
(Nervus Opticus), 318; Fibrous Coat of Eye (Tunica Fibrosa 
Oculi), 319; Chorioidea and Retina, 319; Crystalline Lens, 321; 
Iris, 321; Humors, 322; Mandible Region (Mandibula), 323; Teeth, 
(Dentes), 324; Parotid Gland (Glandulse Parotis), 325; Muscles of 
Mastication, 325; MandibulaT, 326; Vessels and Nerves, 327; 
Submaxillary Region, 327; Interior of Mouth (Cavum Oris), 328; 
Roof of Mouth, 329; Soft Palate (Palatum Molle), 329; Tongue 
(Lingua), 330; The Nose (Nasus), 331; Bony Boundaries, 332; 
Lining of Nasal Cavities, 333; Air Sinuses, 333; Practical, 334; 
Vessels and Nerves, 334; Nasopharynx (Pharynx, Pars Nasalis), 
335; Elevator Palate Muscle, 336; Lymphatic Ring, 336; Practical, 
336; Peritonsillar Abscess, 338; Ear;, 338; External Acoustic 
Meatus (B.N.A. Acustic), 339; Middle Ear Cavity (Cavum Tym- 
pani), 339; Internal Ear (Auris Interna), 340; Facial Nerve, 342; 
Nerve and Blood Supply of Temporal Bone, 342. ILLUSTRATIONS 
MG. PAGE 
1. Illustrating variations in the size of characteristic body cells as 
contrasted with the bacteria and the one-cell animals ... 21 
2. Stratified squamous epithelium 28 
3. Young connective tissue cells 29 
4. Fully developed connective tissue 29 
5. Simple cylindrical epithelium 32 
6. Muscle cells and fibers 39 
7. Diagram of lever action 40 
8. Cartilage 43 
9. Bone development 4'5 
10. Compact bone ? . . 46 
11. Anastomosis of blood vessel 56 
12. Primary versus secondary positions of arteries and veins .... 57 
13. Diagram of a neuron 62 
14. Right scapula, dorsal surface 66 
15. Right clavicle, superior surface 67 
16. Right humerus, anterior surface 69 
17. Typical thoracic vertebra, superior surface 70 
18. Sternum and costal cartilages 74 
19. Diagrammatic lobule 76 
20. Diagram of superficial veins, from in front, left arm 84 
21. Fascial compartments at middle of arm 85 
22. Diagram of brachial plexus 88 
23. Left ulna (A) and radius (B), anterior surface (C), medial view of 
upper extremity of ulna 91 
24. Left hand (manus), dorsal surface 93 
25. Fascial compartments at middle of forearm 95 
26. Diagram of arteries of upper extremity 99 
27. Diagram of nerves of upper extremity 100 
28. Longitudinal section of long bone (femur) 106 
29. Female pelvis, front view, tilted slightly forward 109 
30. Left femur, posterior surface 112 
31. Fascial compartments at middle of thigh 117 
32. Left tibia and fibula, anterior surface 124 
33. Right foot (pes) superior or dorsal surface 126 
34. Fascial compartments at middle of leg (crus) 128 
35. Diagram of arteries of lower extremity 132 
36. Diagram of nerves of lower extremity 133 
15 16 
ILLUSTRATIONS 
F10- PAGE 
37. Bony-ligamentous boundaries of perineum 139 
38. Diagram of pelvic diaphragm 140 
39. Diagram of penis, skin and subcutaneous fatty layer removed . . 143 
40. Female external genitalia, skin and subcutaneous fatty layer re- 
moved 
41. Muscles and aponeuroses of abdominal wall, umbilical level . . . 152 
42. Diagram of inguinal hernia 155 
43. Femoral canal and its relationship 157 
44. Peritoneal relationships 161 
45. Arrangement of peritoneum, diagrammatic median section . . . 165 
46. Arrangement of peritoneum, diagrammatic transverse section . . 167 
47. Stomach (ventriculus) 169 
48. Diagrammatic cross section of intestines 171 
49. Diagram of mucosa of gastrointestinal tract 176 
50. Diagram of mucosa of gastrointestinal tract 176 
51. Diagram of mucosa of gastrointestinal tract 177 
52. Diagram of placenta 179 
53. Diagram of portal vein circulation 180 
54. Lobules of liver, diagrammatic 182 
55. Diagram of bile ducts 184 
56. Pancreas and duodenum 187 
57. Diagram of arteries of abdominal cavity 190 
58. Diagram of veins of abdominal cavity 191 
59. Kidney tubule, diagrammatic 195 
60. Longitudinal section of kidney 196 
61. Diagram of testicle and its ducts 200 
62. Uterus and associated organs, posterior view, right side sectioned 202 
63. Bony-cartilaginous thorax 206 
64. Transverse section of thorax, level of fifth thoracic vertebra . . 211 
65. Diagram of pulmonary lobule 214 
66. Heart, single chamber type, no valves 217 
67. Heart, double chamber type, with valves 217 
68. Heart, four chamber type, with valves 218 
69. Diagram of fetal circulation 220 
70. Diagram of thoracic arteries 227 
71. Diagram of thoracic veins 228 
72. Diagram of sympathetic trunks 230 
73. Tenth thoracic vertebra 232 
74. Spinal Cord 236 
75. Spinal Cord 236 
76. Diagrammatic fascial compartments of neck 242 
77. Minor triangles of neck 246 
78. Diagram of arteries of neck 250 
79. Diagram of human gill arterial arches 255 
80. Posterior view of larynx, showing arytenoid and cricoid cartilages 
projected to surface 256 ILLUSTRATIONS 
17 
FIG. PAGE 
81. Superior surface of atlas, the first cervical vertebra 261 
82. Skull (cranium) at birth, superior view 266 
83. Skull (cranium) at birth, lateral view 266 
84. Diagram of dura mater, frontal section, posterior portion of skull 272 
85. Bony floor of skull 274 
86. Development of spinal cord 281 
87. Diagrammatic transverse section of spinal cord 284 
88. Diagram of tracts (fasciculi) of spinal cord 288 
89. Showing junction of white and gray substances 288 
90. Developmental stages of encephalon 290 
91. Diagram of tracts (fasciculi) of brain stem 293 
92. Lateral surface of encephalon 295 
93. Basal surface of encephalon 298 
94. Medial surface of encephalon, .shaded parts sectioned 300 
95. Interior of cerebrum 304 
96. Interior of cerebrum 306 
97. Front view of skull (cranium) 310 
98. Diagrammatic horizontal section of eye 320 
99. Lateral view of mandible 324 
100. Frontal section at middle of ethmoid bone 332 
101. Internal ear 341 FUNDAMENTALS 
OF 
HUMAN ANATOMY 
CHAPTER I 
INTRODUCTION 
Subdivisions of Anatomy 
Anatomy, derived from old roots meaning dissection, refers now- 
adays to our so-obtained knowledge of structure. The term anatomy 
is commonly used in the consideration of the structure of plants or 
animals, though figuratively it has been applied to almost any 
knowledge of structure. Dissections such as can be seen by the 
unaided eye are known as macroscopic or Gross Anatomy, in con- 
tradistinction to microscopic anatomy or Histology (macro = large; 
micro = small). Purely as a matter of teaching convenience the gross 
and the microscopic anatomy are ordinarily considered in separate 
texts and courses, though it is obvious they are mutually strongly 
dependent. 
Historically gross dissection was practically the only fruitful 
method by which knowledge of the human body's structure was 
obtained. The gradual improvements in the microscope and its 
application to the study of anatomy resulted in the discovery of 
cells in plants by Schleiden, in 1837; of cells in animals by Schwann, 
in 1838. This was a revolutionary step forward in our understanding 
of anatomy. Cells gradually became recognized as the essential 
element of all life. Embryology, the study of development, became 
intelligible under the new discoveries and began to shed great light 
on many of the previously darkest spots of our knowledge. Com- 
parative Anatomy, the study of the corresponding parts in various 
19 20 
FUNDAMENTALS OF HUMAN ANATOMY 
animals, has added materially to our understanding of human 
anatomy. 
Aside from these direct methods the science of anatomy has 
received valuable contributions from the sidelights of other studies. 
Thus, as anatomy has aided in our conception of physiology, the 
study of function, so physiology has in turn keyed up our apprecia- 
tion of practical points in anatomy. The same statement applies 
with equal force to pathology, the study of disease. The science of 
medicine in all its branches owes a great debt to anatomy, which 
nowadays is beginning to be repaid. A modern emphasis on the 
close interrelation of all divisions of our medical knowledge is 
making headway against the historically established system, the 
so-called pure anatomy as learned simply from gross dissection. 
The modern anatomic text tends more and more to consider struc- 
ture from all the available sidelights and points of view. 
Cells 
The essential building stones of all life are the cells. Cells, varying 
in size in the various animals and plants and parts thereof, are all 
microscopic in size and therefore were unknown before the perfec- 
tion of the compound microscope. An average cell when magnified 
one hundred times, appearing to the eye the size of an ordinary 
pinhead, yields a rough working conception of their size. Cells are 
made up of a more or less centrally placed core or nucleus and a 
white-of-an-egg-like surrounding zone known as the cytoplasm. 
With the amount of light of the microscope cut down, the nucleus 
appears as a granular dark mass, and when stained, commonly takes 
on a much deeper color than the cytoplasm. The cytoplasm under 
ordinary circumstances appears homogeneous, but often with special 
stains various types of granules and finer markings can be made out. 
Very simple animals and plants are made up of a single cell, 
characteristically having a nucleus surrounded by cytoplasm. Some 
of the very smallest of organisms do not have a definite nucleus, 
such for example are the bacteria groups. It has long been a heated 
subject of debate as to whether bacteria belonged to the animal or 
vegetable division of living things, and the argument is still 
open. The larger one-celled organisms with a distinct nucleus are 
readily classified either as animals or as plants. Ascending the INTRODUCTION 
21 
scale from the lowest animals and plants are the higher animals and 
plants, made up of a number of cells, and with this anatomic change 
conies the beginnings of the division of labor. All the 'cells con- 
tribute their share towards the life of the individual plant or animal, 
Fig. 1.-Illustrating variations in the size of characteristic body Cells as contrasted with 
the bacteria and the one-cell animals. 
A. Bacteria of various types and sizes. 
B. Human white blood cells of various types and sizes. 
C. Ameba, as example of one-celled animal. 
D. Human surface-covering cell. 
E. Human young connective tissue cell. 
SCALE: 
A large white blood celI = 10 micromillimeters = .01 millimeter. 
% inch plus as in diagram = 1 centimeters 10 millimeters. 
10.00 
- = 1000 magnification. 
.01 
but groups of cells are set aside, specialized in structure and func- 
tion. One of the early groups of specialized cells are those set aside 
for the function of reproduction. 
In the one-celled plants and animals, there is a simple type of 
reproduction by which the parent cell divides into two; each of 22 
FUNDAMENTALS OF HUMAN ANATOMY 
these in turn may divide into two, and provided conditions are 
favorable, this process, so far as we have been able to check it up, 
may continue ad infinitum. In the more highly specialized animals 
and plants, when once a group of cells is set aside for reproduction, 
then these cells, and these only, retain the power of producing a 
new individual. But most of the other body cells retain the power 
of reproducing themselves until the death of the individual. But 
even further, it has been demonstrated that cancerous breast cells, 
after the death of the mouse of which they were originally part, 
can be transplanted artificially from one mouse to another, repro- 
ducing themselves ad infinitum. 
Mitosis, or Karyokinesis 
The division of an animal or plant cell into two is ordinarily a 
mathematically exact process known as mitosis (thread-splitting). 
The nuclear granular material becomes arranged as a thick coiled 
thread, which then breaks up into a number of equal-sized sections 
or segments. The number of segments varies in different plants and 
animals, but is a fixed number for any particular kind of plant or 
animal. Each of these segments then splits longitudinally and is 
drawn off to its side of the nucleus. Thereupon the remainder of 
the cytoplasm divides equally, and two new cells are the result. 
Wherever in animal or plant life cells are reproducing themselves 
rapidly, provided special precautions are taken for the rapid killing 
and special staining, these figures can be seen abundantly. The 
division of cells without these careful procedures occurs in animals 
and plants, but it is questionable whether it is ever truly a normal 
process. It is known as amitosis (a = without). 
Reproduction 
A special group of sexual cells take care of the production of new 
individuals in the more complex plants and animals. Reproduction 
depends upon the union of the male cell, the spermatozoon, and the 
female cell, the ovum. The ovum contains sufficient nourishment to 
care for the embryo after fertilization until other sources of nutri- 
ment are established. Spermatozoa are ordinarily actively motile 
and normally a single one makes its way into the ovum. The two 
nuclei mingle and then the characteristic mitotic division follows. INTRODUCTION 
23 
The resulting two cells divide into four, the four into eight, and so 
on until the individual plant or animal is fully developed. When 
the animal has reached its adult size, the cells stop further growth 
and only reproduce what is lost through wear and tear. The control 
of this occurrence is still one of the unsolved mysteries of life. 
During early development the irregular mass of cells is spoken of as 
the morula (mulberry-like). As development proceeds the morula 
becomes hollowed out and becomes known as the gastrula (stomach- 
like). Then the three important primary layers of the embryo 
develop: the outer layer or ectoderm, the middle layer or mesoderm, 
and the inner layer or endoderm. These layers maintain their rela- 
tive positions and are guides in the study of the development of the 
higher animals. 
Segmentation 
The principle of segmentation runs through the animal kingdom. 
In the more complicated animals it is Nature's provision to make the 
different sections or segments firm and to allow freer motion between 
the divisions. This underlying phenomenon has necessarily a great 
influence on the structure of all the higher animals in the scale, 
including man. 
Bilateral Symmetry 
The principle of bilateral symmetry, the two sides alike, is based 
on the problem of locomotion and is the rule among the animals. 
Exceptionally, on account of method and mode of life, some animals, 
such as the flounder fish, or the attached animals, fail to show this 
common attribute. Naturally this bilateral symmetry has a great 
influence on the anatomy of most animals, including man. 
The Vertebrates 
Animals are classified into two great divisions according to the 
presence or the absence of a backbone, the vertebrates and the non- 
vertebrates or invertebrates. The vertebrates have a bony support- 
ing framework inside their bodies and are the higher animals in the 
scale. The vertebrates are divided into five classes, as follows: 
(1) Pisces, or fish, such vertebrates as breath in water; (2) Am- 
phibia, as frogs, such vertebrates as breathe during one part of their 
life in water and during the other part on land; (3) Reptilia, as 
snakes, such vertebrates as have a scaly skin, lay eggs, and breathe 24 
FUNDAMENTALS OF HUMAN ANATOMY 
in air throughout life; (4) Aves, or birds, such vertebrates as have 
feathers, are warm-blooded, and brood their eggs; (5) Mammalia, 
such vertebrates as have a mammary gland. The mammalia give 
birth to their young living and well developed, and suckle them at 
the breast. Man, as a matter of common knowledge, belongs to the 
mammalia. 
Descriptive Terms 
Universal usage has fixed the standard of naming anatomic rela- 
tionship of man according to the upright position, with the arms at 
the sides and the thumbs turned outward. This arbitrary anatomic 
rule should be universally adhered to, no matter what secondary 
position the body or parts thereof may happen to assume. Thus we 
speak of the front or anterior surface of the body, and the back or 
posterior surface. In relation to the midline of the trunk anatomists 
in the past have made use of the terms, outer, or external, and inner, 
or internal. Further, we speak of a part as being above, or superior 
to, another when it is nearer the top of the head, in contradistinction 
to below, or inferior, when it is nearer the soles of the feet. This 
resume gives the three dimensions of space in both English and 
Latin, so it would appear that all possible requirements of anatomy 
must be satisfied. 
But most animals go with their bellies paralleling the ground and 
are named anatomically according to this position. This different 
relation to space causes great confusion in comparing the anatomy 
of the lower animals with man, and in order to remedy this condition, 
other terms have been more or less successfully introduced into 
human anatomy. Thus the terms belly, or ventral surface, and back, 
or dorsal surface, have gained considerable usage in place of anterior 
and posterior. On the other hand, the terms cranial, or towards the 
head, and caudal, or towards the tail, have made but little progress 
in human anatomy against superior and inferior. The relative 
values of external and internal do not change, whether the animal 
be in the upright or in the belly parallel to the ground position; 
hence in this case it was not found necessary to introduce new terms. 
The descriptive terms ventral, dorsal, cranial, and caudal have the 
advantage of being unchanged, no matter what be the relation of 
the animal to space, and hence have great value in comparative 
anatomy. 
The adjective superficial, or toward the surface, is of great de- INTRODUCTION 
25 
scriptive value in contradistinction to deep. As a matter of fact, the 
term external has been very commonly used in the sense of super- 
ficial, and internal in the sense of deep. This double usage of the 
terms external and internal is obviously a very possible source of 
confusion. In order to obviate this danger, modern anatomists have 
advocated and practiced substituting the terms lateral for "to the 
outer side," and medial for "to the inner side," and now use the 
terms external and internal only in their secondary sense. As this 
book follows the usage of the B. N. A.,* the terms lateral and medial 
will be adopted instead of external and internal. 
Systemic versus Regional Anatomy 
Experience has evolved two main lines of attack in the pursuit of 
the study of anatomy. Either a single tissue, a collection of cells of 
similar structure and function, such as the skin, or muscles, or bones 
for example, may be considered as a unit and traced through the 
body. This is known as the systemic plan. Or a part of the body 
may be studied in detail, considering all the tissues taking part, 
which is known as the regional, relational, or topographic plan. 
Each method has its obvious advantages and its equally obvious dis- 
advantages. From neither system alone would it be possible to gain 
a practical knowledge of anatomy. Therefore this book will first 
take up an outline of the main points in systemic anatomy, leaving 
the modifications and greater detail for the regional division. 
* The last revision of anatomical names, completed in 1895, was the end result of a discussion 
by a congress at Basle, Switzerland. The revised list of anatomical names has become known as 
the Basle Nomina Anatomica or, abbreviated, the B. N. A. PART I 
SYSTEMIC ANATOMY 
CHAPTER II 
THE SKIN AND MUCOUS MEMBRANES 
THE SKIN (CUTIS) 
The word skin means the protective surface covering of the 
exterior of the human body primarily, although it is also used to 
name the corresponding layer in some of the lower animals. A 
protective external layer is found variously developed and modified 
throughout the animal kingdom. Some lower animals have a rela- 
tively soft covering, such as worms or caterpillars, while very tough 
coverings are represented by the shell-fish and lobster groups. A 
very common expedient of many incased animals, to allow for an 
increase in size, is to throw off their outer covering in one piece, for 
a while being soft-shelled, but shortly reforming a new and larger 
covering. This phenomenon -is popularly known, for instance, in 
regard to insects, crawfish, and snakes. 
Epidermis 
Human skin is made up of two structurally and developmentally 
distinct layers, the dermis and the epidermis (epi = upon). These 
layers are normally firmly fixed to each other, there being elevations 
and depressions on the outer surface of the dermis fitting into 
corresponding depressions and elevations of the inner surface of the 
epidermis. A water blister following a superficial burn or injury is 
a commonly known phenomenon, and is a collection of fluid between 
these two layers. On account of the relatively poor preservation of 
dissecting room bodies, the epidermis over great parts of the body 
can commonly be peeled off from the dermis in large sheets. On 
microscopic section the epidermis may be noted to be made up of a 
stratified squamous epithelium (layered flat surface-covering). The 
27 28 
SYSTEMIC ANATOMY 
deeper cells are roundish and are continually undergoing reproduc- 
tion via the mitotic process. As the older cells are shoved up from 
the deeper layer they gradually lose their finer anatomic markings, 
flatten out, die, and eventually are cast off from the surface. The 
epidermis is derived from the ectoderm, the outer layer of the 
embryo. 
Fig. 2.-Stratified squamous epithelium (x 300). 
Dermis, or Corium 
The dermis on microscopic examination is found to be macle up 
essentially of white fibrous connective tissue. Young white con- 
nective-tissue cells are roundish and possess the usual power of 
mitotic division. As development proceeds they lengthen out and 
eventually form strong, long fibers, which when grouped with similar 
strands appear to the unaided eye as a white bundle. These fibers 
are not living structures, but are simply the product of living cells, 
not being any more alive than the lime salts of the bones of the body 
or the shell of an oyster. But living connective-tissue cells are 
found amidst these strands, lying dormant unless called into activity 
by injury, when they assume the task of producing new fibers. 
Rather similar fibers, known on account of color and consistency as 
yellow elastic fibers, are admixed in a variable proportion. These 
primary bundles are interlaced and woven in all directions, which 
equalizes the strength against any stress and strain. The strength 
of the dermis layer among animals is popularly recognized in its 
commercial form of leather, the B. N. A. term corium, meaning THE SKIN AND MUCOUS MEMBRANES 
29 
Fig. 3.- Young connective tissue cells (x 600). 
nucleus- 
-matted 
arrangement 
fiber- 
< loose 
arrangement 
- paralleling 
arrangement 
Fig. 4-Fully developed connective tissue (x 250), 30 
SYSTEMIC ANATOMY 
leather. The dermis is derived from the mesoderm, the middle layer 
of the embryo. 
Variations in Thickness 
The skin forms a complete covering for the exterior of the body. 
It is a matter of common knowledge that it varies in thickness and 
strength according to age, vigor, and localization. The lateral sur- 
faces of the thigh and arm, for example, have much thicker skin 
than the medial surfaces. The scalp, palm of the hand and sole of 
the foot have extraordinarily thick skin, whereas the eyelids have 
an extremely delicate covering. The dermis and epidermis take 
ordinarily an approximately proportional part in these changes in 
thickness. The epidermis varies from a tissue-paper thinness over 
the eyelids of a young child to a layer perhaps an eighth of an inch 
thick over the palm of a manual laborer. Except for the deeper 
layers, there is obviously no need for vessels or nerves in the epi- 
dermis and none exist. The dermis averages about ten times the 
thickness of the epidermis, though in regions especially exposed to 
much pressure, as for example the palm of the hand and the sole of 
the foot, the epidermis may be even thicker than the dermis. It is 
obvious that the dermis on account of its strength would resist for 
a considerable time the escape of pus, hence the knife is often 
justly used to hasten the process. 
Pigment 
All normal human beings have a certain amount of pigment in the 
deeper layers of the epidermis, which serves to prevent the penetra- 
tion of the sun's rays. This pigment serves to protect the living 
cells against the injurious effect of bright sunlight, the amount of 
pigment increasing on exposure to the sun's rays. The term 
"albinos" is used to designate those human and lower animals 
which absolutely lack this normal pigment (albus = white). The 
dermis is a dense white even in the colored races, so the popular 
saying that a negro's color is only skin-deep is not scientifically 
true, the pigmentation being only epidermis-deep. 
Accessories 
The hair (pili) and the nails (ungues) are special structures 
formed through the activity of the epidermal cells. In health the 
hair and nails are continually added to at the root and broken or THE SKIN AND MUCOUS MEMBRANES 
31 
cut off at the end. Hair, as a matter of common knowledge, varies 
according to age and sex, and according to the different parts of the 
body. The scalp, eyebrows, and in the male, the beard area are 
examples of luxuriant growth, while the palms and soles have none. 
Further where parts of the body would tend to chafe by friction, 
as in the armpits, for example, a heavy growth of hair tends to keep 
the surfaces apart and thus prevents irritation. Two small sacs 
lined by a single layer of modified epidermal cells pour their oily 
secretion into the root cavity of each hair. These sacs with their 
collecting ducts are known as sebaceous glands. Another general 
system of glands, also derived from the epidermis, are the sweat, 
or sudiferous, glands. These sweat glands are scattered over the 
whole surface of the body and are the mechanism for the evapora- 
tion of water with loss of heat from the body surfaces. The nails 
and the sebaceous glands lie outside of the deep layers of the dermis, 
while the hair roots and the sweat glands go through the dermis into 
the underlying tissues. 
MUCOUS MEMBRANES 
Mucosa 
Wherever the skin turns in at the various external openings of 
the body, it becomes modified into a mucous membrane. Some of 
these openings are the nose, mouth, anus, penis, and in the female, 
the vagina. The characteristic feature which gives these surfaces 
their name is the secretion by special cells of a thick, viscid, trans- 
parent semifluid known as mucus. At these openings of the body 
the surface covering is developmentally and structurally a continua- 
tion of the epidermis, and is made up like it of stratified squamous 
epithelium. As the interior of the body is not so exposed to injury, 
the dermis connective tissue layer is not represented. The absence 
of a dermis layer explains why the small blood vessels can be seen 
through a mucous membrane, yielding the characteristic pink color. 
Under the epithelial covering lies a loosely woven connective-tissue 
layer, containing fat in its meshes and very small vessels and 
nerves. The mucous glands lie in this layer and pour their secre- 
tions via a small duct on to the surface. This fatty tissue layer 
together with its epithelial covering is known as the mucosa. On SYSTEMIC ANATOMY 
32 
the deep surface of the mucosa lies a firm layer of matted white 
fibrous tissue known as the submucosa (sub = under). 
Submucosa (Tela Submucosa) 
The submucosa, the layer lying under the mucosa, is made up 
essentially of strong white fibrous tissue woven in many directions. 
It is this layer that gives the strength to the parts and which must 
crypt 
"goblet cell 
cylindrical cell 
_ submucosa 
Fig. 5.-Simple cylindrical epithelium (xlOO). 
be carefully sewed up in various surgical procedures. So-called cat- 
gut is made from this fibrous layer of the intestinal tract of sheep. 
It is further this layer which is utilized as a container for the 
chopped meat in the various types of sausages. The larger vessels 
and nerves of the part lie deep to the submucosa and send branches 
through into the mucosa. ' Under the submucosa lie the muscles, 
which will be considered under a special heading. THE SKIN AND MUCOUS MEMBRANES 
33 
Types of Epithelium 
But this stratified squamous epithelium, occurring near the body- 
openings and for a varying distance inward, is not the only or even 
the commonest type of covering for the mucosa. The stomach, in- 
testines, and womb, for example, are lined by simple columnar epi- 
thelium, i. e., a single layer of column-shaped cells as a surface cov- 
ering. The stratified squamous epithelium is used essentially as a 
protective covering, whereas the simple columnar lines such sur- 
faces as have to do with secretion or absorption. The simple 
columnar cells are not commonly arranged in a straight surface line, 
but usually dip down into deep pockets known as crypts (crypt = 
hidden). Roughly speaking, about every tenth cell is modified in 
structure to what is known on account of its shape as a goblet cell, 
which specializes in the secretions of mucus, taking the place of 
special mucous glands. As individual cells die or are destroyed, the 
neighboring cell divides and takes its place. The presence of crypts 
obviously greatly increases the epithelial surface without adding to 
the bulk. 
The smaller collecting ducts of the various glands of the body are 
lined by simple columnar epithelium without crypts. Presumably 
due to the extra wear and tear, the larger collecting ducts of the 
compound glands are lined by a stratified columnar epithelium. As 
this stratified epithelial type contains no goblet cells, mucous glands 
in the underlying tissues pour their secretion via small ducts on to 
the surface. This stratified columnar epithelium differs from the 
stratified squamous epithelium in the fact that the uppermost cells 
are still living and are columnar in shape. The other minor modi- 
fications of the epithelial types will be taken up in the regional 
considerations. 
Such parts of the digestive, respiratory and genital tracts as are 
lined by a columnar epithelium are ' generally speaking developed 
from the endoderm, the lining of the primitive body cavity of the 
embryo. CHAPTER III 
SUBCUTANEOUS FATTY LAYER AND DEEP FASCIA 
SUBCUTANEOUS FATTY LAYER (PANNICULUS ADIPOSUS) 
The subcutaneous fatty layer is the loose fatty layer, which 
throughout the body lies just under the skin (sub = under; cutaneous 
= skin). A loose connective-tissue layer holding fat-containing 
cells richly in its meshes is also known under the term of areolar 
tissue. Instead of subcutaneous fatty or areolar layer, the term 
superficial fascia has become fairly established, but this unfortunate 
term should be corrected, inasmuch as fascia plays anatomically 
and functionally a minor part. 
Variations in Thickness 
This subcutaneous fatty layer, or superficial fascia, is obviously 
continuous under the skin covering of the entire body. It is a mat- 
ter of common knowledge that the amount of fat in its meshes 
varies greatly in different individuals and in different parts of the 
same individual. It is relatively thick over the buttocks and belly 
wall, and thicker over the lateral surfaces of the thigh and arm 
than over the medial surfaces. It is so thin over the eyelids even in 
excessively stout individuals as to be almost nonexistent. It varies 
also in consistency in different parts of the body, due to a propor- 
tional change in its constituent tissues. For example, over the palm 
and soles and over the scalp the amount of the fibrous tissue element 
is greatly increased. 
Fat Cells 
Fat cells specialize in the power of gathering a ball of fat within 
themselves. Young fat cells are noncharacteristic, roundish cells, 
which possess the power of mitotic division, replacing those lost by 
wear and tear and also under certain circumstances increasing in 
number. The adult form of functionating fat cell is characterized by 
gathering a large ball of fat within its outer cell wall, which forces 
the nucleus to the side and makes it assume a crescent shape. The 
stored-up fat serves as a reserve food supply, but has other recog- 
34 SUBCUTANEOUS FATTY LAYER AND DEEP FASCIA 
35 
nized functions. These cells loaded with fat are held in the meshes 
of a delicate connective-tissue framework, which can be seen by the 
unaided eye, or readily under the microscope whenever, as in the 
usual preparations, the fat is dissolved out. 
Heat Radiation 
This subcutaneous fatty layer contains a great number of small 
arteries, veins and nerves. The larger nerves are the cutaneous 
branches, which serve to supply sensation to the skin. The arteries 
with their corresponding veins serve to nourish and care for the skin 
and the subcutaneous fatty layer, but also subserve an entirely 
different function. The vessels are in reality larger and more 
numerous than would be required were it not for the necessities of 
heat radiation. The activities of the body constantly develop heat, 
and the excess is thrown off by a nervous heat regulating center, 
which causes more blood to flow in the surface vessels. By throwing 
the overheated blood into small vessels near the surface and with the 
aid of sweat gland evaporation, the body in health keeps the tem- 
perature in normal range, and in disease keeps it from mounting too 
high. The flushed appearance of the skin after viole'nt exercise or 
during high fever represent Nature's effort to get rid of extra heat. 
During high fever, except during a chill when heat is being rapidly 
produced and not radiated, it is a serious condition if the skin and 
subcutaneous layers are not engorged with blood, for that condition 
represents a loss of control by the heat-regulating center. 
The amount of fat in the subcutaneous fatty layer varies directly 
with the total fat of the body. As a matter of common knowledge 
the heat regulation of the body is markedly affected by the thick- 
ness or thinness of this fatty layer. Very stout people to all practical 
intents and purposes have an inside overcoat under their skin, and 
at all times have difficulty in getting rid of excess heat. Very thin 
people and especially very old people, who have lost their fat, 
properly take extra precautions to prevent undue loss of body heat. 
Superficial Venous System 
Another structure found throughout the subcutaneous fatty layer 
is the superficial venous system. This system of veins has absolutely 
nothing whatever to do with the nourishment of the layer nor with 36 
SYSTEMIC ANATOMY 
the system of heat radiation. Veins are vessels which return the 
blood to the heart. These veins are, as it were, accidentally located 
in this anatomic layer and will therefore be considered under the 
general topic of vessels. 
An occasional structure is the cutaneous muscle, but this discus- 
sion will be postponed until reached in the regional considerations. 
FASCIA 
The fascia is a matted layer of white fibrous connective tissue, 
which encases the muscles and special organs (fascia = wrapper). 
A main function of this layer is to form a firm compartment for the 
various muscles and muscle groups. It is in the proper sense of the 
words a fascia made up of white connective-tissue fibers, its con- 
stituent fiber bundles being woven in at least two directions and 
being without any other tissue admixture. As described in connec- 
tion with the dermis, a few white connective cells are to be found 
lying semidormant among the white fibers. The dermis differs from 
the fascia in the character of its weaving and in the presence of 
yellow elastic fibers. The descriptive "deep" has been added to 
distinguish the fascia layer covering the muscles from the improp- 
erly named superficial fascia, which is in reality the subcutaneous 
fatty layer. 
Intergroupal Septa 
The fascia not only surrounds all muscles on all surfaces, but is 
continued as a double thickness mat bridging the spaces between 
neighboring muscles. If the skin and subcutaneous fatty layer 
were absolutely removed from a dissecting room body, the whole 
body would be found covered by a layer of deep fascia, varying, 
however, greatly in strength in the various parts. Not only is the 
external surface covered, but partitions are sent in between the 
various muscles and muscle groups down to the bones. These parti- 
tions between muscle groups are known as intermuscular septa, but 
more accurately phrased, they are intergroupal septa. These strong 
fascias attached to the bones very commonly serve as surfaces from 
which muscle fibers arise. SUBCUTANEOUS FATTY LAYER AND DEEP FASCIA 
37 
Variations 
The thickness and strength of this fascia layer varies according to 
age, physical vigor and part of the body. The strongest deep fascia 
is found on the lateral surface of the thigh, and modified in the 
palms of the hands and soles of the feet, while the weakest deep 
fascia is found over the eyelids and the back of the hands and feet. 
A direct proportion exists in general between the power of a muscle 
group and the strength of the fascia. Usually the fascia is not so 
well developed over the fleshy part of the muscles as it is over the 
sinew or tendon running off from the muscle, the fascia forming a 
sheath around the tendon and holding it in its proper position during 
contraction of the muscle. At the wrist and ankle, for example, the 
fascia layer is specially modified and strengthened in order to hold 
these tendons down to the bone when the parts are moved. 
But fascia has other similar important functions. It surrounds 
all the organs of the body and together with other factors to be 
considered in the special sections holds them normally in their 
proper position. It further forms sheaths or compartments around 
the vessels and nerves and thereby tends to hold them in their place. 
Practical 
The anatomy of these fascial layers has great practical interest, 
both from the diagnostic and the treatment point of view, whenever 
pus collects down deep in the tissues. On account of the physical 
toughness of the fascia one would expect pus to have great difficulty 
in working through, at any rate over all parts where the fascia is 
thick. If pus is not given an artificial point of least resistance by 
an incision, it travels along the natural lines of least resistance, at 
times causing a serious spreading of the infection. To be sure cer- 
tain cold abscesses should not be opened, but this discussion would 
carry us too far afield. Suffice it to state that the anatomy of the 
fascia is a problem of real practical importance. CHAPTER IV 
MUSCLES (MUSCULI) 
Muscular tissue is made up of specialized cells or groups of cells, 
which possess the power of contracting in one direction only. This 
action is normally brought about through a nervous impulse, but it 
may be caused by many other types of stimulants.. Muscle is 
developed from the mesoderm, the middle layer of the embryo. 
Types 
The simplest type of muscle is the involuntary, nonstriated cell, 
which is made up of an elongated cell with a centrally placed 
nucleus. The adjective involuntary says these cells are not under 
the control of the will, while nonstriated is used because there are 
no cross-markings. These simple muscle cells are found in the walls 
of the gastrointestinal tract, bronchial tubes, urinary passages, 
womb with its tubes, smaller arteries and veins, tubes leading from 
the various glands, attached to the shaft of the hair, and so forth, as 
will be noted in the various special sections. 
The next type of muscle is the involuntary striated cell, as found 
in the heart. These cells are differentiated from the ordinary invol- 
untary muscle cell essentially by the fact that cross-striations are 
demonstrable when the light under the microscope is cut down or 
with the ordinary stains. 
The most highly developed type of muscle is the voluntary 
striated fiber, as found in the bulk of the muscles of the body. 
These are collections of muscle cells held in a strong fibrous sheath, 
the number of cells varying with the length of the particular muscle 
fiber. The characteristic feature of these muscle fibers is that the 
cytoplasm of one cell is not marked off from the cytoplasm of the 
next. These muscle fibers in man may reach a length of three to 
four inches, terminating by attaching to the white connective tissue 
in the interior of the muscle. In the embryonic fibers the nuclei lie 
in the center, but in the fully developed fibers they lie near the 
38 MUSCLES 
39 
sheath covering. These fibers show the characteristic cross-stria- 
tions under the microscope, on decreasing the illumination or with 
the ordinary stains. Each muscle fiber tapers to a point at its ends 
and connects with the white fibrous tissue framework of the muscle. 
The individual muscle fibers are wrapped with others into primary 
bundles, the primary into secondary, and so forth. 
When any muscle fiber or cell contracts, the individual fiber or 
cell becomes shorter and thicker just as the muscle as a whole. 
Plain muscle cells (x 150). 
Heart muscle cells (xl»O). 
Striated muscle fiber (xl50). 
Fig. 6. 
Development 
Muscle cells of the various types are formed early in embryonic 
life and increase in size and power as growth proceeds. No new 
muscle cells or fibers are formed normally after the birth of the 
embryo, although if called upon to perform extra work, the individ- 
ual cells may increase in size and power. If destroyed by accident 
or disease, muscle cells are replaced by the less highly specialized 
white fibrous tissue, resulting in the formation of a scar. The 
increase in size of an individual cell is known technically as hyper- 
trophy, whereas if the extra work causes an increase in the number 
of the cells, as, for example, in the epithelium or fibrous tissue, it is 
known as hyperplasia. 
Attachments 
The involuntary muscle cells may attach at both ends to white 
fibrous tissue, which, however, is not attached to the bones. The 
voluntary muscle fibers are ordinarily attached via white fibrous 
tissue to the bones of the body at both ends, hence are often known 
as skeletal muscles. These strands of white fibrous tissue may be 40 
SYSTEMIC ANATOMY 
long or short. When these strands are long and running parallel, 
are compacted into a rounded or flattened cord, they are spoken of 
as tendons, or popularly sinews. When the muscle ends in a broad 
flat sheet with the white fibers paralleling each other, this flattened 
out tendon is known as an aponeurosis. The word aponeurosis 
states that it is derived from a nerve and is historically interesting 
as it shows the confusion existing before the introduction of the 
microscope between nerves and tendons. This confusion was due to 
the fact that both are white in color and tough in texture. The 
gross appearance and the microscopic construction of aponeurosis 
and fascia are very similar, but the distinction between the two 
must be kept clear. 
Origin and Insertion 
The fixed point on the bone from which a muscle arises is known 
as the origin, while the part of another bone on which it pulls is 
known as the insertion. When a muscle contracts, the point from 
Fig. 7.-Diagram of lever action. 
which it acts, or origin, is held firm, while the point on which it acts, 
or insertion, is drawn closer to the origin. Logic demonstrates that 
a muscle never arises and inserts on the same bone, for if so it could 
produce movement only by breaking the bone. Muscles arise on one 
bone and frequently pass over the next bone or bones to their inser- 
tion. Under certain extraordinary circumstances, for instance, a 
man walking on his hands, the origins and insertions of the muscles 
may be temporarily reversed. The terms origin and insertion are 
applied anatomically to the ordinary fixed and moving points. MUSCLES 
41 
Lever Principle 
A simple principle of mechanics may justly be referred to here 
on account of its application to the origin and insertion of muscles. 
The diagram shows bones at a right-angle and brings out the short 
versus the long lever principle. 
In diagram A. C. = long lever = great strength but speed no greater 
than muscle contraction. 
A. D. = short lever = less strength, but greatly increased speed. 
The muscular attachments of the body make use of the short or 
long lever principles according to their various needs. 
Counter Action 
Normally when a part of the body is moved by muscular action 
not only the active group contracts, but an opposing group contracts 
also, only in a much lesser degree. The object of this phenomenon is 
to steady the part so that it may move evenly. As a result it follows 
that if any group of muscles is injured or otherwise rendered in- 
capable, not only is their action hampered or destroyed as the case 
may be, but the action of the opposing group is materially interfered 
with. CHAPTER V 
BONES AND JOINTS 
BONES (OSSA) 
Bones form the supporting, and in case of the skull, chest and 
vertebra] column, the protecting framework of the body. The 
presence of a bony endo-skeleton separates the higher from the lower 
animals, the vertebrates from the invertebrates (endo = inside). A 
bone properly prepared for museum purposes is materially lighter 
in weight than one of equal size freshly removed from a cadaver. 
This is due to the fact that living bone in addition to its lime salts 
contains white connective-tissue fibers, marrow, body fluids and the 
bone cells. Such substances as a matter of common knowledge 
would spoil unless protected by an antiseptic of some kind. For 
the purposes of dissecting room models, these structures are encour- 
aged to decay and then the bones are boiled in strong soaps to 
remove the last traces of organic matter. The white fibrous tissue 
framework remains, but even this can be destroyed by prolonged 
baking in dry heat. If these fibers are destroyed, bone becomes very 
brittle. 
Pliability versus Brittleness 
A bone so prepared is the product of formerly living bone cells, 
but it itself, strictly speaking, never was alive. The salts which 
were deposited in a connective tissue framework to give the hardness 
to the bone are chiefly calcium phosphate, with a minor admixture 
of other earthy salts. So our conception of the body being made 
up of cells is to be modified on account of the occurrence of various 
types of intercellular substances (inter = between). These deposited 
salts may be dissolved out by acids and then we have the absolute 
reverse of the above picture, a perfectly pliable bone made up of 
connective tissues and containing bone cells. 
It is a matter of common knowledge that the consistency of bone 
varies normally according to the age of the individual. In youth 
the bones are relatively very pliable', as is borne out by the occur- 
rence of green stick fractures and the fact that the average child 
42 BONES AND JOINTS 
43 
grows up without breaking all the bones in his or her body. Ana- 
tomically this pliability is due to the relatively greater proportion of 
the connective tissue elements. In the adult bones reach their 
maximum strength, which is due to the full deposit of lime with the 
retention of vigor in the connective tissue elements. In old age 
the bones are characteristically brittle, probably due to a lessening 
of the strength of the white fibrous connective tissue elements. 
Two diseases, or possibly the same process at different periods of 
life, due to an inefficient, one-sided nourishment of the body, cause a 
reabsorption of the deposited lime out of the bones. Under such 
circumstances the bones become excessively pliable and if weight is 
Fig. 8.-Cartilage (x 200). 
put on such bones various types of bending deformities result, such 
for example as bowlegs. During the first few years of life this 
condition is known as rickets (rachitis), whereas the nowadays rare 
disease of adult life is known as osteomalacia (bone-softening). 
Cartilage 
The portions of the embryo, which will eventually become the 
bony skeleton, are first differentiated by the formation of cartilage. 
Cartilage is a connective tissue, and like the other connective tissues 
is derived from the mesoderm. Cartilage is popularly known as the 
covering over the ends of the bones of the higher animals at the 
joints. As to its physical characteristics, it is bluish white in color, 44 
SYSTEMIC ANATOMY 
semitranslucent, possesses considerable elasticity, and while it offers 
resistance is readily cut by a sharp knife. Cartilage has a very 
complicated chemical structure, and is not strictly a living structure, 
but is deposited and controlled by living cartilage cells. During the 
period of active growth the cartilage cells actively undergo mitotic 
division, but in adult life lie dormant unless called into activity by 
injury of some kind. Fine passageways, which can only be brought 
out by special staining methods, allow the body fluids to circulate 
about these cells. These passageways are known as canaliculi, the 
word meaning diminutive canals. Cartilage in the embryo is char- 
acterized by the great number of cells as compared with the hyaline 
cartilage of the adult (hyaline = glassy). Very commonly white 
connective tissue fibers are woven in the cartilage, which gives 
greatly increased strength, known as white fibro cartilage. At other 
places yellow elastic fibers are also added and the resultant type 
is known as yellow elastic fibrocartilage. 
Classification 
Bones are classified as long, short, flat or hollow according to 
their preponderant characteristics. The development of a typical 
long bone will be followed through in detail, bearing in mind that 
the same principles, although not so readily diagrammed, control the 
formation of the other bones of the body. 
Gross Development 
A long bone is first laid down in an embryonic form of nonfibrous 
or hyaline cartilage. About the eighth week of embryonic life the 
calcium salts begin to be deposited at the center of the bone, which 
then becomes known as the primary center of ossification or bone- 
making. This process gradually progresses from the center, until 
at the time of birth a small shaft exists running nearly the whole 
length of the bone. This shaft is continuously added to at its outer 
circumference by the deposit of bone, while at each end the cartilage 
remains unaltered until just about the time of birth. Then varying 
somewhat with the different bones, the secondary centers of ossifica- 
tion appear in these end pieces. These two end parts are known as 
the epiphyses, while the shaft is known as the diaphysis (epi = upon; 
di = between). Cartilage exists therefore at birth between the BONES AND JOINTS 
45 
diaphysis and the epiphyses and remains throughout the period of 
bony growth, roughly twenty-odd years. New bone is being con- 
stantly formed at the diaphysis-epiphyseal junction throughout the 
period of growth and it is by this process that increase in the length 
of a bone is brought about. The cartilage disappears and the junc- 
tion of the shaft with the two end pieces becomes solid bone at the 
end of the growth period. If the cartilage persists throughout life, 
the pieces are considered separate bones with a semijoint between 
them. If disease destroys the epiphyseal cartilage during youth, 
Secondary center of ossification 
epiphysis 
diaphysis 
Secondary center of ossification 
ipiphysis 
Fig. 9.-Bone development 
the increase in length of the bone involved is irretrievably lost. 
These facts of development have a marked influence on the character 
of bone injuries during childhood. 
Very commonly the epiphysis is not one piece, but is eventually 
made up by the coalescence of smaller pieces. Other marked pro- 
jections on the adult bone are commonly formed in the same manner 
as the epiphyses, developing later and fusing earlier than the main 
end pieces. As a rule the later in life the appearance of a tertiary 
center the earlier it coalesces with the main shaft. 46 
SYSTEMIC ANATOMY 
Microscopic Development 
The preceding discussion should have made clear that bone is 
made up of two essential constituents, to-wit, a white fibrous con- 
nective tissue framework in which lime salts are deposited. Cartilage 
is only a preliminary structure in bone and is invariably absorbed 
before or during the time that bone is being developed. The cells 
that make the connective-tissue framework are known as fibroblasts, 
while those controlling the deposit of lime are osteoblasts (blast = 
makers of). During the period of normal growth and eventually 
during the repair of fractures or following other bone injuries, these 
two classes of cells can be distinguished microscopically. During 
the growth process these cells are constantly producing new fibers 
Haversian canal 
cell space 
canaliculus 
Fig. 10.-Compact Bone (x 200). 
and new bone, adding it to the outer circumference of the shaft or 
at the diaphysis-epiphyseal junction as the case may be. From time 
to time blood vessels, fibroblasts and osteoblasts are covered over 
from the outer side and consequently built into the substance of the 
bone. These blood vessels are therefore open tubes of microscopic 
size running the long axis of the bone and are named the Haversian 
canals. Blood vessels are also built in at the diaphysis-epiphyseal 
junction, but in this area without regularity of arrangement. The 
fibroblasts and osteoblasts carry on the process of bone building BONES AND JOINTS 
47 
inside of these large primary canals and gradually fill in the space 
from the outer surface inwards until there is only space left for the 
vessels. During this process the osteoblasts, about equally spaced, 
are caught in the bone and then become known as the bone cells. 
Very small canal spaces are left open in the bone, known as cana- 
liculi, which allow body fluids to nourish and carry off waste from 
the bone cells. These bone cells lie semidormant unless called into 
activity by injury or disease. After the period of growth a stronger 
inner and outer layer of bone, with bone cells but no Haversian 
canals, is laid down, known in connection with the shaft as the 
inner and outer circumferential lamella (thin flat plate). The main 
bundles of white fibers of the shaft run the long axis of the bone, but 
other bundles cross at right angles. The growth process is essen- 
tially the same at the circumference of the shaft and at the diaphysis- 
epiphyseal junction, although the process, being more regular, is 
easier to follow in connection with the shaft. 
The skull bones covering the brain develop a distinct fibrous 
framework in their cartilage a considerable time before the osteo- 
blasts begin to deposit the lime. As a white fibrous framework is 
always laid down before lime is deposited, the only peculiarity of 
this occurrence is the time element. It is known as intramembranous 
bone development. 
Tubular Structure 
During the process of growth the body makes use of a well- 
recognized principle of mechanics. If the bones were simply added 
to at its circumference, it would become a solid rod. But weight 
for weight physics has demonstrated that a round tube is very mate- 
rially stronger than a solid rod. The body produces the tubular 
structure of bones by a type of cells known as osteoclasts (clast = to 
break down). These osteoclasts live inside the bone and during the 
process of growth eat away the innermost layers of the shaft as new 
outer layers are formed. Through the agency of these same cells 
the broad ends and projections of bones are hollowed out, so as to 
produce lightness with the preservation of the requisite amount of 
strength. The architecture of these porous textured parts of the 
bone is well adapted to withstand probable injuries, while at the 
same time weight is minimized. The porous textured portions are 
known as spongy bone, while the large cavity extending throughout 48 
SYSTEMIC ANATOMY 
the length of the bone in its interior is known as the medullary or 
marrow cavity. The solid appearing portions of the bone, which, 
however, possess the microscopic Haversian canals, etc., are known 
as the compact bone. 
Projections 
Bones have various projections which are caused by and serve to 
give firm attachment to the muscle tendons. The more powerful the 
muscle, other things being equal, the more marked the bony pro- 
tuberance. If these projections are sharp they are generally known 
as spines; if blunt and knotted, as tuberosities (tuber = root). Large 
rounded prominences in the neighborhood of joints, which serve to 
make larger opposing surfaces, are generally known as condyles. 
The sharp projections raised up from the condyles by muscle 
attachments are generally known as epicondyles. The term ridges, 
grooves, lines, and so forth, used in description are self-explanatory, 
while variations in naming will be considered in the regional 
divisions. 
Vessels and Nerves 
Bone has throughout life a system of arteries and veins. During 
the period of growth the necessity for a liberal supply is very 
obvious, but after the bone is once completed to its adult condition 
the vessels have comparatively little to do except in case of injury 
or disease. The main vessels of a long bone enter about the middle 
of the bone through a round opening known as the nutrient foramen 
(nourishment window). The two main subdivisions go in opposite 
directions towards the epiphyses, where they join with other small 
vessels entering near the ends of the bone. The blood circulates 
through the Haversian canals and the irregular spaces of the spongy 
end portions. Sensory nerves follow along with the vessels for the 
supply of the bone. 
Cross-sections of a living shaft bone show the cancellous ends 
filled with a soft material known as red bone marrow (medulla 
ossium rubra). The red bone marrow has to do with the production 
of blood and, as it is only accidentally, as it were, in the bone, will 
be considered with the blood system. Yellow bone marrow, a loose 
fatty layer which fills up the medullary cavity, has no special func- 
tional importance (medulla ossium flava). BONES AND JOINTS 
49 
JOINTS (ARTICULATIONES) 
Classification 
Joints, or articulations, are specialized anatomic structures devel- 
oped for the purpose of allowing motion between the bones. As a 
matter of common knowledge the range and character of the motion 
allowed at the different joints varies materially. The diarthroses 
are the freely movable type, the commonest and most important in 
the body (di = between, referring to the space between the bones). 
The synarthroses is the term applied to those joints which can take 
up the shock of blows but have no real motion (syn = together). 
This type of joint is found essentially in the suture lines of the skull, 
as will be detailed in the regional consideration. The amphiar- 
throses is the term applied to those joints which possess a very 
limited range of sliding motion (amphi = partaking of the character 
of both). In the B. N. A. these amphiarthrodial joints are not given 
a separate grouping, but are considered a subdivision of the diar- 
throses. In this case, however, this book will follow the many 
anatomists of standing who refuse to accept the change from the 
older classification. 
Freely Movable Joints 
In the class of freely movable joints, three distinct types occur: 
The ball and socket, the hinge, and the gliding. The shoulder and 
hip-joints are of the freely movable ball and socket type (enar- 
throsis). The hinge type (ginglymus) is best represented by the 
elbow and ankle joints, which possess a wide range of motion but 
only in one plane. Very many joints of all parts of the body allow 
a limited range of motion in all directions, and these are of the 
gliding type (arthrodia). Innumerable modifications of these types 
of freely movable joints occur, as will be detailed in the regional 
considerations. < 
The amphiarthrodial type is not popularly recognized, but makes 
up a group midway between the gliding type of diarthrodial joints 
and the synarthrodial joints. 50 
SYSTEMIC ANATOMY 
Development 
The cartilages of the bones are joined together in early embryonic 
life by white fibrous tissue. Early in embryonic life the joint cavity 
(cavum articulare) forms in this connective tissue layer, at no stage 
of its development being connected with the surface of the body. 
The interior of the joint cavity is lined by a layer of endothelial 
cells, which are derived from the mesoderm (endo = inside; thelium = 
covering). These cells form a single flat pavement layer and, being 
perfectly smooth, functionate by reducing friction to a minimum. 
During developmental stages this endothelium is said to line the 
whole of the interior of the joint cavity, but after birth the endo- 
thelial layer disappears from the opposing bearing surfaces. A layer 
of hyalin cartilage persists over the ends of the bone at the joint, 
which serves to give a perfectly smooth surface and also, to a certain 
extent, to take up shocks. Surrounding the joint cavity and attached 
firmly to both bones around the circumference are bundles of white 
connective tissue, which make the capsular lig'ament (capsule = 
surround). The thickness and strength of this capsular ligament 
varies according to the vigor of the individual and the joint in 
question, but is everywhere strong. At various points, as required 
by the exigencies of the special case, the capsular ligament becomes 
thickened, these thickened portions of the capsule being known as 
the ligaments of the joint. In the recesses of the interior of the 
joint cavity lie groups of synovial glands, which pour into the joint 
a thick, clear lubricating fluid. Following accident or disease this 
synovial fluid may be increased or decreased in amount. Judging 
by analogy with other internal body cavity secretions, synovial fluid 
is probably being continually secreted and reabsorbed. 
The synarthroses do not possess joint cavities, while most amphiar- 
throses have cavities but usually of a poorly developed type. 
Dislocations 
The bones are held together at the joints by various factors. In 
the first place the strength of the capsular ligament is a very obvious 
and important factor. Great support is given to the joints by the 
muscles, which pass over the joint and tend to hold the bones in 
apposition. Still another factor is the occurrence of a vacuum in BONES AND JOINTS 
51 
the interior of the capsular ligament. This suction resistance hold- 
ing the bone together varies with the size of the joint cavity, but 
may be demonstrated to be considerable in the larger ball and socket 
joints. These three factors offer great resistance to the tearing 
apart of the bones, known as dislocation or luxation. Where these 
resistance factors, as a matter of practical experience, most often fail 
to prevent dislocations will be noted in the regional considerations. CHAPTER VI 
BLOOD AND LYMPH VESSELS 
BLOOD VESSELS (VASA SANGUINEA) 
The vessels which carry blood away from the heart are known 
as arteries (arteriae), while those carrying blood back to the heart 
are known as veins (venae). While arteries ordinarily carry red 
oxygenated blood and veins blue nonoxygenated blood, there are 
exceptions, which will be detailed in connection with the study of 
the heart. A system of very small vessels, known as capillaries, 
connect up the smallest arteries with the smallest veins. That the 
medical profession until the discovery of Harvey, in 1628, had not 
known of the circulation of the blood seems extraordinary to a 
present-day student. This lack of knowledge was in great part due 
to the fact that capillaries are microscopic in size and therefore are 
not visible to the unaided eye. 
Circulation 
The circulation of fluids exists in all animals and plants through- 
out life. It is by means of this circulation system of distribution 
that nourishment in its broadest sense is carried to distant parts of 
the body and waste products of life are gathered up to be thrown off. 
To accomplish this result the circulating fluids must therefore reach 
every living cell of the body. The absolute stopping of the circu- 
lation of animals, persisting for a variable length of time, determines 
the death of the individual. Many of these body cells, however, if 
brought into contact with the circulation of another individual of 
the same kind are still viable. After a short time, varying with the 
character of the cells, all cells cut off from the circulation die. 
Blood (Sanguis) 
All the higher, more complex animals have some type of muscular 
pump to keep up the circulation, which is known as the heart. Its 
52 BLOOD AND LYMPH VESSELS 
53 
general plan, similarities, and dissimilarities in the various animals 
and man will be noted in the special division devoted to that organ. 
The blood is made up of water in which are dissolved certain 
elements of nourishment and waste products, the plasma, and certain 
formed elements, the corpuscles. The relatively high percentage of 
albumins gives plasma its familiar viscid, sticky consistency. The 
plasma in man is approximately half filled by very highly specialized 
corpuscles, the red blood corpuscles, or erythrocytes (erythro = red). 
These are biconcave, round discs and are not cells in the ordinary 
sense, inasmuch as normally in the circulating blood after birth they 
have no nuclei. These corpuscles specialize on the functions of 
carrying oxygen to the tissues, giving it up to the cells, and return 
as blue blood carrying back carbon dioxide. This carbon dioxide is 
thrown off in the lungs and oxygen again taken up. These red 
blood corpuscles are being constantly destroyed in the body and are 
replaced by new corpuscles formed by nucleated cells in the red 
marrow of the bones. Besides these erythrocytes, white blood cells, 
or leucocytes, exist normally in the blood in a small percentage, 
averaging during health about one to every seven hundred erythro- 
cytes. These cells have nuclei and are being constantly produced 
and destroyed, as will be detailed later on. They not only exist in 
the blood but possess the power of working through the capillary 
walls into the tissue spaces and therefore are often called the 
wandering cells. They functionate as protectors and scavengers of 
the body. 
Capillaries 
The inner lining of the entire heart, artery, vein, and capillary 
system is made up of a single layer of endothelial cells. Just as in 
the interior of the joints and in all other parts where they are found 
these cells form a perfectly smooth, shiny surface, which serves to 
reduce the friction to a minimum. Capillaries are made up simply 
of this layer without any other coat. 
Large Arteries 
The heart forces the blood at great speed and under high pressure 
into the main arterial trunks. This pressure is held by a thick, very 
firmly woven coat of yellow elastic fibers, which coat gives the 
yellowish tinge to the interior of a freshly sectional larger artery. 
Capillaries 
Large Arteries 54 
SYSTEMIC ANATOMY 
Spaces are left open in this layer, which allows the body fluid to care 
for the dormant lying cells existing among the elastic fibers. The 
elasticity of this layer causes the vessels to contract down on the 
column of blood, producing a more continuous flow. If for any 
reason the pressure of the blood mounts extra high and this condition 
is maintained over long periods of time, this elastic coat becomes 
irreparably injured. This condition is known as arteriosclerosis 
(sclerosis = hardening). Later on lime salts may become deposited 
in this coat, as is very common in degenerated tissues, and on account 
of the movements of the body semijoints are formed, causing the 
bead-like feel of a calcified artery. The inner endothelial coat of 
the blood vessels is known technically as the intima, the important 
middle coat as the media, and there is an outer coat of white connec- 
tive tissue known as adventitia. 
Arterioles 
This anatomic structure is maintained along the arterial system, 
decreasing quantitatively down to the very smallest arteries, which 
are known as arterioles (oles = diminutive ending). These arte- 
rioles have little connective tissue in their walls, but its place is 
taken by circular plain muscle fibers, which are under the control 
of the involuntary nervous system. When any part of the body on 
account of activity requires a more liberal supply of blood, the 
muscles of the arteriole wall relax and more.blood flows to the part. 
Conversely, when the circular muscles of the arteriole wall contract 
strongly, less blood flows to the part supplied by the narrowed 
vessels. When the muscles of the arteriole wall are tightly con- 
tracted the blood in the interior of these vessels can not be seen, but 
when the muscular walls are relaxed the red color of the arterial 
blood shows distinctly through the thinned-out wall. 
Veins 
After its passage through the capillaries the blood is gathered into 
venules, which, like the arterioles, have circular muscle fibers in their 
walls. The venules run together into larger veins, the larger veins 
into others still larger, and by progressive junction all the blood of 
the body pours into two large veins, which empty into the heart. 
The walls of the veins, having much less pressure to sustain, are BLOOD AND LYMPH VESSELS 
55 
materially thinner than the corresponding arteries. They possess 
practically no elastic tissue, but are made strong by woven, white 
fibrous connective tissues. The walls of veins are white, but when 
distended the characteristic dark blue color of venous blood is trans- 
mitted through the wall. Veins, on account of their thinner walls, 
are much more easily torn than arteries, the walls of even the largest 
veins being so thin that the color of the dark venous blood shows 
distinctly through. 
Rate of Flow 
The same amount of blood during any prolonged fixed time must 
flow through the main artery, the capillaries, and the main veins. 
For if this condition were not fulfilled, all the blood of the body 
must eventually accumulate in one division. The combined cross- 
section of all the capillaries is several hundred times that of the 
main artery and veins at their connection with the heart. There- 
fore the blood flows very slowly through the capillaries, allowing 
ample time for the interchange between the blood and the tissue cells. 
The flow of blood through the main artery and veins, on the other 
hand, is very rapid. For example, whereas the blood flows in the 
main arteries at the rate of at least a foot per second, in the capil- 
laries red blood corpuscles may be noted to wander leisurely across 
the microscopic field. 
Thickness of Walls 
It may be accepted as a universal proposition in anatomy that the 
strength of any portion of the body is no greater than the ordinary 
requirements of the part, plus a fair factor of safety. The blood in 
the capillaries is under a high unit pressure, but due to the extremely 
small bore of the individual capillary the actual total pressure on 
the walls is easily cared for by the single layer of endothelial cells. 
Fact is, under abnormal conditions the pressure in the capillaries 
may rise six times as high as normal without rupture of the vessel. 
Following this same principle, with equal unit pressure, the larger 
the caliber of a vessel the thicker must the walls be in order to insure 
proportionately equal strength. This law of physics explains the 
anatomic finding, which is that the larger the artery or vein the 
thicker and stronger are its walls. 56 
SYSTEMIC ANATOMY 
Anastomosis 
It is obviously important that the circulation be maintained under 
all circumstances. The big safety factor in the vascular system, by 
which with the main vessels blocked circulation is nevertheless 
maintained, is known as anastomosis (ana = again; stoma = mouth). 
If a direct route is blocked by accident or disease, the blood flows 
out of one of the branches before the blockade, through smaller 
connecting arteries and into the main vessel beyond the blockade. 
At first this makeshift, collateral circulation, although amply suffi- 
cient to maintain life, is not really efficient. If the blockade is main- 
blockade 
anastomosis 
Fig. 11.-Anastomosis of blood vessels. 
tained over a longer period of time, the anastomosing vessel becomes 
larger and fully equal to the maximum requirements. Anatomists 
formerly believed that parts of the body, the brain and heart for 
example, did not possess anastomoses, but the newer researches have 
apparently proved this to be an error of observation. Our present 
knowledge leads us to believe that anastomosis is everywhere present 
throughout the vascular system, both on the arterial and venous side. 
Secondary Position of Vessels 
In embryonic life the main arteries accompany the main nerves, 
the segmental artery, vein, and nerve being wrapped up in one con- BLOOD AND LYMPH VESSELS 
57 
nective tissue bundle. The nerves maintain their position unchanged 
throughout life. But the arteries and veins, by a process through 
which the anastomosis becomes large while the main vessel becomes 
the anastomosis, can readily and do often change their positions. 
That certain vessels in some individuals do and in others do not 
change from their embryonal position is the reason back of the 
frequently found variations from the normal found in actual dis- 
section. Some examples and details of this occurrence will be noted 
in the regional considerations. 
Primary arrangement 
Secondary condition 
- anterior median line of body 
Fig. 12.-Primary versus secondary positions of arteries and veins. Solid lines in diagrams 
are arteries, veins and nerves. Dotted lines in diagrams are anastomosing arteries and veins. 
General Location 
The main arteries and veins ordinarily accompany each other and 
are ordinarily named according to the region they are traversing. 
These vessels are always under the deep fascia, usually in the most 
protected region and very commonly down deep in close proximity 
to the bone. With but a single exception the vein does not lie 
directly between the artery and the bone. It is obvious that such a 
relation would tend to obstruct the return of venous blood. Smaller 
arteries are accompanied by a pair of veins on opposite sides, which 
are known as the venae comitantes (comitans = accompanying). 
Where a part is fleshy the artery and vein ordinarily lie deep down 58 
SYSTEMIC ANATOMY 
from the surface, whereas when the muscle gives way to tendon, as, 
for example, at the elbow, wrist, knee, or ankle, the artery lies nearer 
the surface, or, more accurately phrased, the surface lies nearer to 
the artery. 
Superficial Venous System 
Aside from the system of veins just discussed, an entirely distinct 
system is found in the subcutaneous fatty layer over the whole body. 
This venous system lies outside of the deep fascia and is known as 
the superficial venous system in contradistinction to the deep venous 
system inside of the deep fascia, the two systems anastomosing 
freely. The superficial venous system has no analogous arterial 
system. The cause for the existence of this superficial venous sys- 
tem is that when the muscles and fascias are drawn tense the resist- 
ance within the deep fascia increases. This pressure does not mate- 
rially influence the flow of blood in the arteries, but proves a great 
handicap to the return flow of blood in the veins. The venous blood 
then escapes into the superficial venous system, is carried around 
the obstruction and is consequently enabled to return unobstructed 
towards the heart. Inasmuch as the blood in these superficial veins 
is in thick-walled vessels with limited surface, the heat radiation 
factor is practically negligible. 
Vales in Veins 
Most veins of both the superficial and deep venous systems possess 
valves, which are arranged so as to prevent the reflux of blood when 
the vein is compressed. The valves are made up of white fibrous 
tissue covered by endothelium, and blend around their outer circum- 
ference with the connective tissue walls of the veins. When the 
venous blood is flowing towards the heart these valves are open, but 
if the flow be reversed the valves close and prevent backflow. 
Movements of the body tend therefore to drive the blood on towards 
the heart. The only veins lacking valves completely are the two 
largest veins of the body (vena cavas superior and inferior), which 
empty directly into the heart. This peculiarity of the largest veins 
presumably has a functional reason for its existence, even though 
none has been established. BLOOD AND LYMPH VESSELS 
59 
LYMPH VESSELS (VASA LYMPHATICA) 
A superficial cut through the epidermis of a living individual is 
rapidly filled up with bright red blood. This comes from the capil- 
laries and soon stops as the cut ends of the capillaries become filled 
with a blod clot. If the blood clot be wiped off with a moist cloth, 
taking care not to reopen the vessels, the surface becomes covered 
with a yellowish tinged sticky fluid, which is lymph. Lymph is very 
similar to the plasma of the blood with all its red corpuscles removed, 
but is not exactly the same thing. The capillaries in health do not 
allow red blood cells to escape into the tissue spaces, but allow water 
containing certain salts and foodstuffs, including albumins, to escape 
through their walls. White blood cells also normally work their 
way out of the capillaries into the tissue spaces and hence receive 
their name of wandering cells. A striking and popularly known 
illustration of this fact is in the formation of pus. This lymph is 
being constantly secreted by the capillaries and constantly makes 
its way back into the veins. It flows through the tissue spaces, then 
through small collecting vessels, and eventually into one large trunk, 
which empties into a large vein at the base of the neck. The lym- 
phatic vessels anastomose freely and the main trunks accompany the 
veins of the part. All the living cells of the body must be bathed 
in lymph, as it carries nourishment to them and takes away their 
waste products. It is therefore an extremely important element in 
the circulation. 
If a vein is blockaded so that the pressure in the capillaries rises 
high, so much lymph is formed that the vessels can not carry it off 
with sufficient rapidity and the part becomes overfilled with lymph, 
giving a white color and a doughy feel. This condition is known as 
circulatory dropsy. 
Lymph Glands (Lympho-glandulae) 
The lymph vessels are fitted with valves, so arranged that all the 
movements of the body tend to drive the lymph onward towards the 
veins. Every lymph vessel pours its lymph through a type of filter, 
known as a lymph gland or node. These lymph glands check or 
attempt to check the entrance of foreign bodies, or of bacteria, or of 60 
SYSTEMIC ANATOMY 
cancer cells, into the general circulation. Lymph glands are nor- 
mally only slightly firmer than fat in consistency, are bean-shaped 
and about one-eighth of an inch in their greatest diameter. These 
lymphatic glands are found sometimes solitary, more often grouped 
around the main veins in convenient localizations. But the action 
of the lymph glands is more than a mechanical filter, for if called 
upon to resist invasion of the general blood they increase in size and 
functional ability. It is only when this lymphatic defense is broken 
down that bacteria or cancer cells can enter the general circulation 
via the lymph. CHAPTER VII 
NERVES (NERVI) 
Microscopic Structure 
Nerves are highly specialized body cells, whose function is to carry 
messages from the brain or spinal cord out to the various parts of 
the body, or vice versa. Nerve cells are derived developmentally 
from the ectoderm, as will be detailed in connection with the con- 
sideration of the central nervous system. Most of them are rela- 
tively large cells, being commonly twenty times in diameter the size 
of a red blood corpuscle. They are characterized by sending out an 
axis-cylinder process and one or more dentritic processes (dentrite = 
small root.) The extraordinary feature of these axis-cylinder proc- 
esses is the fact that they may be three feet or more in length, 
extending, for example, from the spinal cord down to the sole of the 
foot. All the other body cells previously studied, it may be well to 
emphasize, have been microscopic not only in width but also in 
length. A nerve cell, together with all its processes, is known as a 
neuron. Most all these nerve processes are enclosed in a very thin 
translucent sheath known as the neurilemma. Further, most axis- 
cylinder processes are surrounded by a thick covering known as the 
medullary or myelin sheath, which lies between the neurilemma and 
the nerve process, and presumably functionates as an insulator. 
The medullary layer is an intercellular substance, deposited prob- 
ably through the activity of the nerve processes. 
This medullary sheath is very delicate and is glistening white in 
color, which helps to give the characteristic white, shiny appearance 
to the ordinary nerve. The gross physical appearance accounts for 
the confusion between tendons and nerves which is so commonly 
found in old anatomic texts. A few nerves appear gray in color, 
due to the absence of a medullary sheath, nerve substance proper 
being gray. The axis cylinder processes covered by their medullary 
sheaths are wrapped together by liberal amounts of white connective 
tissue into bundles, which, on account of the connective tissue 
elements, possess very considerable tensile strength. A nerve of 
61 62 
SYSTEMIC ANATOMY 
one-eighth of an inch in diameter containing several hundred thou- 
sand axis-cylinder processes yields a fair working conception of 
their average size in cross-section. The axis-cylinder process termi- 
dendritic process 
cell body 
cylinder process 
medullary sheath 
end plates 
(nuclei terminates) 
Fig. 13.-Diagram of a Neuron (x 300). 
nates in some special type of end-plate in the skin or on a muscle 
fiber, or at some other terminal point. Each axis-cylinder process 
near its terminus commonly branches to a dozen or more of these 
bulbous end plates (nuclei terminales). NERVES 
63 
Systems 
The Central Nervous System is made up of the brain and spinal 
cord, while the Peripheral Nervous System consists of the nerve 
processes leading from the brain and spinal cord to various parts of 
the body (peri = around ; pherro = carry). The peripheral nervous 
system is divided into the peripheral nerves proper and the sym- 
pathetic nerves. 
Peripheral Nerves Proper versus Sympathetic Nerves 
The peripheral nerves proper control the voluntary activities of 
the body, while the sympathetic nerves control the involuntary 
activities, although minor exceptions to this rule will be noted in the 
regional considerations. Thus the sensory processes to the skin, 
fascias, muscles and bones, and the motor processes to the voluntary 
musculature belong to the peripheral nerves proper. On the other 
hand, the nerve processes to the various glands, all involuntary plain 
muscles, and the automatically regulating thoracic and abdominal 
organs belong to the sympathetic nerves. 
The peripheral nerves proper are characterized anatomically by 
the fact that all cell bodies lie in the brain or spinal cord; that all 
processes are medullated after birth; and, further, that their pro- 
cesses make up the great bulk of the nerves, except those running 
to the various thoracic or abdominal or other special organs. The 
sympathetic nerves are characterized anatomically by the fact that 
many of their groups of cell bodies lie outside of the central nervous 
system; that many of their processes are nonmedullated throughout 
life; and that, although many of their processes follow along in the 
peripheral nerves proper, others run a separate course along with 
the fascial compartments of the blood vessels. The sympathetic 
nerve processes commonly stop several times or more en route to 
their terminations in a way-station of nerve cells, known as a 
ganglion (swelling). A ganglion is a collection of nerve cell bodies, 
hence gray, held together by connective tissue. Many more proc- 
esses commonly leave these peripheral sympathetic ganglia than 
enter from the spinal cord side. Thus a multiplication of sympa- 
thetic nerves takes place, commonly a very great multiplication just 
before their termination, which does not occur in connection with 
the peripheral nerves proper. 64 
SYSTEMIC ANATOMY 
Segmentation 
The nerve supply of the body is very distinctly segmental in type 
and remains strictly in its embryologic relations throughout life, 
variations being extremely uncommon. Primarily these nerves were 
accompanied by an artery and vein, although, as was noted in the 
section on vessels, the artery and vein very commonly leave their 
primary positions. All the main nerve trunks lie under the deep 
fascia and ordinarily in the most protected positions. No segmental 
nerve ever completely supplies the corresponding body segment 
among the higher animals, some nerve processes from the segmental 
nerve above and some from the nerve below invariably joining the 
nerve trunk. This arrangement provides a safety factor against 
injury at the vertebral column exits and is known as the plexus, or 
weaving, of the nerves. 
Repair 
Nerves are very highly specialized cells and are not produced 
after birth. If an axis-cylinder process or dentrite is cut, the cell 
possesses the power of growing a new process. But if after a certain 
stage of embryonic life the nerve cell itself is destroyed, the damage 
is permanent, as no new cell can be produced. PART II 
REGIONAL ANATOMY 
CHAPTER VIII 
THE UPPER EXTREMITY 
SHOULDER AND ARM 
The part of the body composed of the shoulder, arm, forearm, and 
hand is known collectively as the upper extremity. The upper 
extremities obviously possess bilateral symmetry, one upper extrem- 
ity being the accurate mirror reverse of the other. The upper 
extremities are further characterized by segmentation, as they are 
controlled, as will be detailed later, by the paired fifth, sixth, sev- 
enth, and eighth cervical and the first thoracic segmental nerves. 
In any regional consideration of anatomy the bones are justly 
considered first, as they make up the supporting framework. 
Wherever the bones are not covered by muscles, or the muscle cover- 
ing is thin, the projecting parts can be felt as landmarks under the 
skin and subcutaneous fatty layer. The relative position of other 
anatomic structures can then be estimated or even accurately deter- 
mined. Bones vary in different individuals in regard to size, 
strength, and relative position, but by an examination of the corre- 
sponding opposite bone a fair estimate of the normal for the bone 
under consideration may be drawn. 
In most cpiadrupeds, to whom anatomically, at any rate, man is 
closely related, three developmentally distinct bones are joined 
together to form the socket for the ball of the armbone. In man 
two of these bones of the shoulder girdle fuse into one, so that in the 
adult we have only two bones forming the shoulder socket, the 
scapula and the clavicle. The original coracoid bone becomes the 
coracoid process of the scapula (coracoid = like a raven's beak). 
The bone descriptions should be supplemented by reference to the 
65 66 
REGIONAL ANATOMY 
drawings in the anatomic atlases or reference books, or preferably 
to the actual dried specimens. Much help can also be gained by 
outlining the bones in the student's own body. 
--coracoid 
process 
medial 
angle - 
tacromion 
- glenoid 
cavity 
spine-Afe 
vertebral 
margin. 
-axillary or 
armpit 
margin 
inferior 
angle _ 
Fig. 14.-Kight Scapula, dorsal surface. 
Scapula 
The scapula is a flat, triangular-shaped bone spread out over the 
upper part of the back of the trunk (scapula = spade). The back or 
posterior surface is generally known as the dorsal surface, whereas THE UPPER EXTREMITY 
67 
the front or anterior surface is known either as the ventral or costal 
surface (costa = rib). A heavy ridge runs horizontally across the 
dorsal surface about three-quarters of the way up. The free edge 
of this ridge, not being covered by muscles, is subcutaneous and 
therefore readily palpable. This ridge has been given the misnomer 
spine of the scapula, whereas logically it should be known as the 
ridge of the scapula. This ridge continues beyond the scapula, 
making a right-angled turn forward over the shoulder joint, and in 
this region becomes known as the acromion or acromial process 
(summit of the shoulder). The socket lying under the acromial proc- 
ess, known as the glenoid cavity, is the receptacle for the ball of 
the arm bone. Projecting forward and above the glenoid cavity is 
anterior border 
acromial 
extremity 
posterior 
border 
sternal 
extremity 
Fig. 15.-Left Clavicle, superior surface. 
the irregular strong coracoid process, which, like the acromial proc- 
ess, makes an arch over the scapular socket. The other names of 
the parts of the bone are explained on the diagram sufficiently for 
our present purposes. 
Clavicle 
The clavicle or, popularly, the collar bone, has a subcutaneous 
surface throughout, and consequently is readily palpable (clavicle = 
key). At its medial end it is attached to the sternum or breast bone, 
and at its lateral to the acromial process of the scapula. It is an 
irregularly rounded and, in its lateral third, flattened bone. Its 
middle third is materially smaller in circumference than its sternal 
and its acromial thirds. Its curves vary somewhat in different indi- 
viduals, but can readily be followed just under the skin. 68 
REGIONAL ANATOMY 
Humerus 
The humerus is the strong, long bone of the arm (humerus = 
funny). It is characteristically like the general description of a 
typical long bone, being made up developmentally of a diaphysis 
and two epiphyses, and in the adult of a body or shaft and two 
extremities. The ball of the upper extremity of the humerus is 
known as the head, just below which lies the neck, the groove in 
which the capsular ligament of the joint attaches. The greater, or 
lateral, and the lesser, or medial, tuberosities are raised up by muscle 
attachments. The B. N. A. peculiarly uses the diminutive form 
tubercle instead of tuberosity, but this usage has not been followed, 
as it is not in keeping with the facts. The intertubercular sulcus or 
groove, containing one tendon of the biceps or two-headed muscle, 
runs between the greater and lesser tuberosities and continues sev- 
eral inches down the front surface of the humerus. The lips of the 
intertubercular groove are raised up by the aponeurotic insertions 
of strong muscles. The epicondyles are the inferior portion of the 
bone, widened out for articulation with the bones of the forearm. 
Vertebrae 
The vertebrae are the series of bones making up the vertebral 
column or backbone (vertebra = turn). The upper seven are called 
the cervical or neck vertebrae. The next twelve are named the 
thoracic or chest vertebrae, or sometimes improperly, because not 
distinctive, the dorsal vertebrae. These vertebrae are characterized 
by each having a pair of ribs, with notches where the ribs attach. 
Then follow the five lumbar, or loin, vertebrae. The next five origi- 
nal vertebrae in the adult are fused into one piece, which is held 
between the hip bones and is known as the sacrum (sacrum = sacred). 
Below the sacrum follows the coccyx, representative of the tail bones 
of the lower animals and made up until middle life of two separate 
tapering pieces (coccyx - cuckoo's beak). The larger upper bone 
of the coccyx is developed from one original piece, the lower of three 
or four parts fused into one. 
Vertebrae are typically made up of a body (corpus vertebrae) and 
an arch which surrounds the spinal cord (arcus vertebrae). Extend- 
ing back in the midline from the arch is a more or less sharp process, 
known as the spine of the vertebra. The tips of these spinous proc- THE UPPER EXTREMITY 
69 
head 
greater tuberosity 
lesser tuberosity 
intertubercular groove 
anatomical neck 
nutrient foramen 
lateral epicondyle, 
medial epicondyle 
surface for radius 
surface for ulna 
Fig. 16.-Right Humerus, anterior surface. 70 
REGIONAL ANATOMY 
esses from the sixth cervical vertebra down to the coccyx are 
subcutaneous and therefore readily palpable. These spines should 
theoretically follow each other in a perfectly straight line, but as 
a matter of practice there is always some side-to-side deviation. 
By gentle manipulation of the spines it is ordinarily possible to 
determine the presence or absence of fracture of the arch of the 
vertebra. The characteristic signs of fracture are : Abnormal range 
- body 
foramen for 
spinal cord 
transverse 
process 
spinous 
process 
Fig. 17.-Typical thoracic Vertebra, superior surface. 
of motion, grating and severe pain on movement of the part, and 
hemorrhage at site. The other features of the vertebrae are explained 
sufficiently in the diagram for our present purposes. 
Dissection.-The body is to be laid on the table with the back 
region up, and preferably fixed by blocks under the body so that 
the whole area is stretched. The tips of the vertebral spines, the 
spine of the scapula with its continuation, the acromial process, and 
the clavicle are to be located under the skin. Also the ridge of the 
hip bone, which is technically known as the crest of the ilium. Then THE UPPER EXTREMITY 
71 
in spots the epidermis is to be scraped off in order to note its thinness 
and the pigment in the deeper layers. A cut is then to be made 
through the tough dermis in the middle line from the lower part of 
the skull to the sacrum. A two-inch long incision is then to be 
carried lateralward across the back part of the neck at its junction 
with the skull and a lower incision of about four inches length fol- 
lowing the crest of the ilium. The dermis layer should be dissected 
off from the subcutaneous fatty layer. This is rather difficult for 
the beginner, at least, and can best be accomplished by holding the 
dermis evenly tense and shoving against the under surface with a 
sharp round-bellied knife. The dermis tends to slip out of the grip 
of even-teethed forceps, so that after a start has been made it is 
often very helpful to perforate the loosened part of the dermis for 
finger grips. Actual experience with, if possible, the aid of an 
experienced demonstrator is the only efficient teacher. If the under 
surface of the dermis is strictly adhered to, the surface will show 
evenly distributed pits. A very obvious advantage of sticking close 
to the under surface of the dermis is that the danger of destroying 
deeper parts is absolutely done away with. 
During the progress of dissection the body should be prevented 
from drying out by wrapping it in cheese cloth, which should be kept 
soaked with water. An outer covering of oil cloth tends to keep the 
water from evaporating and consequently minimizes labor. If parts 
of the body should become too dry during the progress of dissection, 
they should immediately be immersed in a prolonged bath. If the 
drying has not progressed beyond a certain stage, this bath will 
restore conditions to the normal; but if the part has been allowed 
to mummify, it has become useless for dissecting purposes. 
Subcutaneous Fatty Layer 
Due to the evaporation of water out of the body the subcutaneous 
fatty layer is frequently found to be thinner than during life, while 
the action of the preservatives commonly used makes the fatty layer 
appear pale in color. If the body has lain on its back for a long 
time, however, the preserving fluids may gravitate in extra quantity 
into this loose layer. The fatty layer covers the whole back in 
average thickness, varying with the general stoutness. The larger 
fibrous tissue framework is microscopically visible surrounding the 72 
REGIONAL ANATOMY 
globules of fat, but in spite of this connective tissue the layer is not 
strong. This fatty layer contains the segmentally arranged poste- 
rior series of cutaneous arteries, veins, and nerves, and, in addition, a 
superficial venous system. 
This arrangement should be noted in a general way as the subcu- 
taneous fatty layer is dissected off from the deep fascia. 
Fascia 
The deep fascia over this region is moderately strong and should 
be noted to give a complete covering to the muscles, and to be con- 
tinued between the neighboring muscles. 
Muscles 
The first layer is made up of two muscles, extending practically 
over the whole back. 
The trapezius arises from the base of the skull and from the spines 
of all the cervical and thoracic vertebras (trapezius - pair make a 
trapeze-shaped figure). The upper fibers run downward and for- 
ward to their insertion into the posterior surface of the acromial 
third of the clavicle, the middle fibers run straight to the medial 
surface of the acromion, while the lower fibers run upwards into the 
superior edge of the spine of the scapula. It acts as a raiser and 
also as a rotator of the shoulder. 
The latissimus aorsi arises through an aponeurosis, extending 
from the lower six thoracic spines, all the lumbar spines, from the 
sacrum and the posterior third of the crest of the ilium (latissimus = 
broadest). Its fibers run with varying degrees of obliquity, pass the 
lower angle of the scapula as a contracted, much thicker mass, and 
continue through the posterior fold of the arm-pit to the humerus. 
Dissection.-These two muscles must be cleared of their outer 
layer of deep fascia, in order that their constituent muscle bundles 
may be clearly seen. The aponeurosis origins, which look just like 
a deep fascia, should not be disturbed. 
By dividing the trapezius muscle half-way between its origin and 
insertion, and turning the divided ends back, the deeper layer of 
muscles is brought into view. 
The rhomboids arise from the lower four cervical and upper four 
thoracic spines of the vertebrae and run diagonally lateralward and THE UPPER EXTREMITY 
73 
downward to their insertion along the whole vertebral border of the 
scapula, (rhomboid = parallel-sided figure). 
The levator scapulae runs from the transverse processes of the 
upper four cervical vertebrae and inserts as a rounded mass into the 
superior vertebral angle of the scapula (levator =to raise up). 
Front of Chest 
The body is next to be turned upon the back, and the front of the 
chest is to be considered. The subcutaneous border of the clavicle 
is readily felt, making a convenient surface separation between the 
front of the chest and the lower part of the neck. The coracoid 
process, although covered by muscle, can be felt by pressing just in 
front of and below the clavicle at the junction of its middle and 
acromial thirds. The ribs can be felt as bony landmarks, although 
covered throughout by muscles, while in the middle line the sternum 
or breastbone can be palpated. 
Sternum 
The sternum is a rather porous bone made up of three distinct 
parts, which are named according to their alleged resemblance to a 
dagger. These parts are the manubrium, or handle, the corpus, or 
body, and the xiphoid or ensiform process, or tip. A cartilaginous 
insert between the manubrium and corpus sections of the sternum 
allows a limited range of motion. 
Costae 
Seven pairs of ribs are directly attached to the sternum by means 
of costal cartilages, and are therefore known as the true ribs (costae 
verae). The remaining lower five pairs of ribs are functionally inde- 
pendent of their attachment to the sternum and are therefore known 
as false ribs (costae spuriae). The costal cartilages of the eighth, 
ninth, and tenth ribs do join with the costal cartilages of the ribs 
above, but this slight connection is of distinctly minor practical 
importance. The costal cartilages of the eleventh and twelfth ribs 
end absolutely free and hence these are popularly known as the 
floating ribs. The costal cartilaginous inserts obviously serve to 
increase the elasticity of the chest. 
The ribs, considered from above downwards, form segments of 74 
REGIONAL ANATOMY 
progressively larger circles. The little head of a rib forms a joint 
with the vertebrae, then follows a constricted portion known as the 
neck, while the great bulk of a rib is known as the body. The Latin 
word for head is caput, for little head is capitulum, for neck collum, 
and for body corpus. The bodies of the ribs are materially wider 
superiorly-inferiorly than externally-internally. The ribs can be felt 
- manubrium 
corpus (body) 
-xiphoid 
process 
Fig. 18.-Sternum and costal cartilages. 
best in the midaxillary line, as in this area they are only covered by 
a thin sheet of muscle. 
Mammary Gland (Mamma) 
The skin is of average strength and is only remarkable on account 
of the presence of the mammary or breast gland (mammary = adjec- 
tive of mamma). These glands are paired and the nipple lies nor- 
mally over the fourth interspace between the ribs, a relatively con- 
stant distance from the midline. Normally only one pair of these THE UPPER EXTREMITY 
75 
glands develop from the skin, but as an abnormality one or more 
extra pairs may occur in series as in the lower animals. They reach 
the height of their development during the child-bearing period of a 
woman's life and after that normally involute, that is, undergo 
retrogade changes. During pregnancy the gland lobules increase 
in size in conformity with the functional demand. The gland is 
divided by radially arranged fascial septa into compartments, which 
fact should always be taken into consideration in planning a sur- 
gical incision. The gland is embedded in the subcutaneous fatty 
layer and is held in position by strands of connective tissue attach- 
ing it to the deep fascia and to the skin. These attachments nor- 
mally allow a certain range of motion in all directions to the breast. 
A unilateral, localized decrease in this range of mobility demon- 
strates a shrinkage of the connective tissues. When other causes 
of this shrinkage can be excluded, the presence of this sign is most 
suspicious of the contracting, scar-tissue forming type of cancer. 
The blood and lymph supply of the large female mammary gland 
comes in great part from the arm-pit region, but also as will be 
noted later from branches from inside of the chest wall. The 
lymphatic drainage assumes great practical importance in the tem- 
porary localization of the secondary cancer nodules in the lymphatic 
glands. 
Structure of a Compound Duct Gland 
The typical structure of a large compound duct gland, such as 
the mamma, will be outlined. The smallest subdivision of such a 
gland is known as an acinus, which is made up of a group of large 
secreting cells arranged around the termination of the smallest 
duct. The Greek word acinus means grape, and is here used fig- 
uratively to imply that each acinus has the same relation to the 
entire compound gland that each grape has to the bunch of which 
it is a part. In the case of some compound glands the smallest 
subdivision is known as an alveolus, this word stating that the 
smallest subdivision is hollowed out or saccular. The walls of these 
acini or alveoli are made up by a single layer of large cubical cells, 
which vary somewhat in structure and markedly in function in the 
various compound glands. A number of acini or alveoli are grouped 
together in a delicate connective-tissue capsule, making up a lobule, 
which is visible to the unaided eye (lobule = diminutive of lobe). 
Very commonly a great number of these lobules, which empty into a 76 
REGIONAL ANATOMY 
common duct, are grouped together in a fibrous covering to form a 
lobe of the gland. The lobule ducts are lined by a cubical epithelium, 
the smaller lobe ducts by a columnar epithelium, while the larger 
lobe ducts are lined by a stratified columnar epithelium. 
During resting periods of the mammary gland, the smallest sub- 
divisions are known as acini, but during functional activity they 
develop an alveolar form. About twenty large lobe ducts empty 
onto the surface of the nipple, these lobes being radially arranged 
and partly separated by connective-tissue septa. It is interesting to 
note as a variation from the general rule that each mamma is made 
up of about twenty separate compound duct glands. 
•lobule duct 
acinus 
alveolus 
Fig. 19.-Diagrammatic Lobule (xl50). 
Dissection.-The skin should be incised along the clavicle, the mid- 
line of the sternum and the lower margins of the ribs, and dissected 
off. The male mammary gland is a rudimentary organ, but if a fe- 
male gland is available many of the points noted may be made out. 
Fatty Layer and Fascia 
The subcutaneous fatty layer has no special characteristics. It 
is supplied by segmentally arranged series of lateral and of anterior 
arteries, veins, and nerves. The area also contains, as would be 
expected, branches of the superficial venous system. The deep 
fascia has over the powerful muscles of the area rather more than 
average strength. 
The fattv layer should be dissected off. THE UPPER EXTREMITY 
77 
Muscles 
The pectoralis major arises from the sternal third of the anterior 
border of the clavicle, from the front of the sternum and from the 
upper six costal cartilages (pectus = breast; major = greater). Its 
fibers converge and crossing in front of the arm-pit insert into the 
crest of the greater tuberosity, i. e., the lateral lip of the inter- 
tubercular groove of the humerus. 
The pectoralis minor arises by fleshy strands from the third, fourth 
and fifth ribs under the pectoralis major and converging inserts into 
the tip of the coracoid process of the scapula. 
The deep fascia should be cleared from off the muscles. 
Fossa Axillaris t 
The axillary fossa or arm-pit is the cavity between the lateral sur- 
face of the chest and the medial surface of the arm. The pectoralis 
major muscle forms the anterior fold, while the latissimus dorsi 
with an associated teres major muscle forms the posterior fold. The 
skin over this region is thin and further characterized by a luxuriant 
growth of hair. The subcutaneous fatty layer is thin, but otherwise 
as elsewhere. The deep fascia is strong, is bound down by its con- 
nections, and is continuous with the deep fascia over the anterior 
and posterior folds. 
Brachial Plexus 
Five pairs of segmental nerves run through the axillary spaces; 
these are the fifth, sixth, seventh, and eighth cervical and the first 
thoracic. The five nerves and the five fingers are the permanent 
reminders of the fact that the upper extremity is made up of five 
vertebral segments. These nerves come out of their respective in- 
tervertebral foramina and approaching each other go through below 
the clavicle and above the first rib (foramen = window). The eight 
pairs of cervical segmental nerves are accounted for by one pair 
coming out under the skull and one pair under each of the cervical 
vertebrae. These nerves eventually take up a position deep down 
near the humerus on the medial side, as would be anticipated, for 
this is the most protected region. The nerves mutually interchange 
branches, which is the reason for the name brachial plexus (brachium 
= arm; plexus = weaving). In the middle of their passage through 78 
REGIONAL ANATOMY 
the axillary space the nerves become grouped about the axillary 
artery and are arranged in three cords, which on account of their 
relation to the artery are known as the lateral, medial and posterior 
cords (fasciculi). The lateral and medial are the anterior cords, 
which will later be demonstrated to gather all processes of supply 
to the front of the shoulder, arm, forearm and hand. The posterior 
cord carries the supply to the back of the shoulder, arm, forearm, and 
hand. The nerve trunks have little or no slack, so following a 
severe unexpected jerk of the arm, the nerve cords may be torn 
without serious injury to the bones or other parts. 
Sympathetic Nerves 
Axis cylinder processes of the sympathetic nervous system run 
into the upper extremity for the control of involuntary musculature, 
making the same segmental connections with the spinal cord as the 
peripheral nerves proper. All involuntary activities of the upper 
extremity are controlled by sympathetic processes, as for example 
sweating, contraction of the hair muscles and control of the blood 
supply. Messages also travel from the peripheral terminations of 
these sympathetic nerves to the spinal cord. Many of these sympa- 
thetic processes travel along with the connective-tissue sheath of the 
artery, while the bulk travel along in the brachial nerves proper en 
route to their terminations. 
Arteries and Veins 
Developmentally at an early stage of the embryo five segmental 
arteries and veins accompanied the brachial nerves. By the proc- 
ess as described under anastomosis, four of the primitive vessels 
disappear entirely, while the remaining vessel enlarges. The artery 
comes out from inside the chest and until it passes beyond the 
clavicle is known as the subclavian; through the axilla the artery 
is known as the axillary, while beyond the space it continues as the 
brachial. The corresponding vein receives corresponding names. 
As would be anticipated, the vein lies superficial to the artery, in 
fact in this instance just under the deep fascia. Two rather con- 
stant branches are given off from the artery to the anterior fold of 
the axilla, the one just beyond the clavicle being known as the 
thoracoacromial, while the branch near the lower border of the pec- THE UPPER EXTREMITY 
79 
toralis major is known as the lateral thoracic. The branch arising 
towards the lower part of the space and running into the posterior 
fold is known as the subscapular. It is, as would be anticipated 
from an examination of the parts, very materially larger than the 
anterior axillary branches. A branch which conies off from the 
axillary artery near the lower border of the axillary space encircles 
the upper part of the humerus and is therefore known as the cir- 
cumflex. The veins correspond to the arteries, while the lymphatic 
vessels follow the veins accurately. 
Lymphatic Glands 
The main group of lymphatic glands for the whole upper extremity 
and the neighboring trunk areas is to be found in the axillary fossa. 
Normal glands can not be distinguished in a dissecting room body 
on account of their small size, and fat-like consistency and color. 
In acute infections the lymph glands become enlarged, soft and 
painful, and eventually may be overcome by the bacteria, breaking- 
down into a pocket of pus. This pus would lie under the deep fascia, 
consequently the progress of escape can be hastened by incising the 
fascia layer. If the surgeon simply stabbed a knife through the skin, 
subcutaneous fatty layer and deep fascia, it is obvious that the 
brachial vessels and nerves and their branches might be seriously 
endangered. The external layers are commonly raised up by the 
pressure of the enclosed pus, but a sudden move might result in a 
serious catastrophe. Consequently the established surgical rule is 
to lay open the skin and subcutaneous fatty layer freely and then 
if necessary nick the deep fascia with a knife. Through this open- 
ing in the deep fascia a pair of blunt forceps may be introduced and 
opened without any danger. The tearing of the deep fascia, if the 
surgeon avoids putting extra pressure on the enclosed pus, does not 
cause any great amount of pain. A split piece of rubber tubing is 
commonly introduced through the deep fascia and sewed in place in 
order to make sure the fascia does not close before the drainage is 
completed. This is the generally accepted surgical rule for the 
opening of lymphatic gland abscesses in the neighborhood of their 
large veins and other important structures. 
The enlarged glands secondary to cancer of the breast are char- 
acterized by their hardness and their tendency to remain separate 
and distinct. 80 
REGIONAL ANATOMY 
Dissection.-The skin, the subcutaneous fatty layer and the deep 
fascia should be dissected off layer by layer from over the axillary 
fossa. In order to get a clean dissection of the area, it is then ad- 
visable to cut through the pectoralis major and minor muscles at a 
convenient midpoint and turn the divided parts back towards their 
origins and insertions. After noting that the axillary vein lies 
nearer the surface than the artery, the vein may be disregarded in 
the further cleaning up of the arteries and nerves. The lymphatic 
glands, unless diseased, will be hard to identify from the fat. When 
the fat and fascia is removed the points noted in the preceding dis- 
cussion are ready to be made out. 
Removal of Upper Extremity from Trunk 
The only bony connection of the upper extremity to the trunk is 
through the clavicle, which acts as a radius rod holding the shoulder 
joint a fixed distance out from the sternum. It is especially exposed 
to fracture since either direct blows or falls on the lateral surface 
of the shoulder are liable to break it, usually in its middle third. In 
severe machinery accidents when the whole upper extremity is torn 
from the trunk, this slight clavicle is the only bony resistance to be 
overcome. As the muscles play a great part in the attachment of 
the upper extremity to the trunk, an unexpected jerk may find them 
off guard so that the strain falls on the clavicle and the brachial 
plexus nerve trunks. With or without a fracture of the clavicle the 
nerve trunks may be torn, very commonly inside of the vertebral 
column, which accident yields a complete permanent paralysis of 
the extremity. 
The serratus anterior (O.T. magnus) muscle arises by slips from 
the first to the ninth rib along the front lateral chest wall and runs 
backward to its insertion in the costal surface of the scapula along 
the whole vertebral border (serratus = saw-shaped). The other 
muscles holding the upper extremity to the trunk have been pre- 
viously considered, and after a review they may be cut across 
midway between their origins and insertions. The trapezius, rhom- 
boids, levator scapulae, pectoralis minor and the serratus anterior 
are the muscles holding the scapula to the trunk. In addition to 
these muscles the pectoralis major and the latissimus dorsi must be 
divided in order to complete the removal of the upper extremity 
from the trunk. THE UPPER EXTREMITY 
81 
At this stage of the work it is advisable to remove only one upper 
extremity from the trunk. The removed extremity will allow a 
better demonstration of certain facts, whereas the attached ex- 
tremity will yield a better understanding of the continuity of 
various structures. The clavicle of the upper extremity to be 
removed should be sawed across at its midpoint, and the axillary 
vessels and nerves sectioned just below the clavicle. 
Rotator Muscles of Arm 
Four muscles hold the head of the humerus against the glenoid 
cavity and attach to the tuberosities just below the anatomic neck 
of the humerus. The muscle arising from the greater part of the 
costal surface of the scapula is known as the subscapularis. It runs 
in front of the shoulder joint to its insertion into the lesser tuberos- 
ity, which lies medially to the intertubercular groove. The muscle 
arising on the dorsum of the scapula above the ridge is the supra- 
spinatus. It runs over the top of the shoulder joint and attaches to 
the upper facet of the greater tuberosity. The muscle arising on the 
dorsum of the scapula below the ridge or spine is the infraspinatus. 
It converges and runs across the back part of the shoulder joint 
to its attachment to the second facet of the greater tuberosity. 
Arising somewhat lower down along the axillary border of the 
scapula is a smaller muscle closely associated with the infraspinatus, 
which is known as the teres minor (teres = round). The teres minor 
inserts into the lowest facet of the greater tuberosity. The origins 
and insertions of these muscles explain their respective internal and 
external rotary powers, the subscapularis being an internal rotator, 
whereas the infraspinatus and teres minor are external rotators. If 
they all act powerfully at the same time they tend to hold the head 
of the humerus firmly in the glenoid cavity. 
These muscles should be cleared of their fascia coverings and 
traced out to their origins and insertions. 
Adduction of Arm 
Adduction refers ordinarily to the midline of the body (ad = 
towards; duco = lead). The pectoralis major muscle converges on a 
tendon, turning on itself so as to yield a rounded lower border. It 
forms the anterior fold of the axillary fossa and inserts into the 82 
REGIONAL ANATOMY 
crest of the greater tuberosity, i. e., the lateral lip of the intertuber- 
cular groove. The latissimus dorsi tendon passes the inferior angle 
of the scapula, turns around the teres major muscle in the posterior 
fold of the axilla, and inserts into the bottom of the intertubercular 
groove. The teres major muscle is closely associated with the latissi- 
mus dorsi. It arises from the axillary border of the scapula near 
the inferior angle and inserts into the crest of the lesser tuberosity, 
i. e., the medial lip of the intertubercular groove. These muscles 
would obviously draw the arm in towards the midline of the body, 
and so justify their classification as adductors. Inasmuch as the 
intertubercular groove is on the anterior surface of the humerus, 
they would also produce a limited internal rotation. 
Abduction of Arm 
Abduction (ab= away from) is produced mainly by the action of 
the deltoid muscle (delta = triangular Greek letter). Arising from 
the anterior surface of the acromial third of the clavicle, the lateral 
margin of the acromial process and the inferior margin of the spine 
of the scapula, this muscle converges onto a tendon, which inserts 
into the middle of the lateral surface of the shaft of the humerus. 
This muscle has the power of raising the arm only to a right-angle 
with the body, whereas the carrying of the arm to full elevation is 
accomplished through rotation of the scapula. The supraspinatus 
muscle, described as a matter of convenience in connection with the 
rotators, is an abductor. 
The skin should be dissected off to the middle of the arm, and the 
abductor and adductor muscles cleared of their fascias and traced 
out. 
Flexion and Extension of Arm 
The word flexion means bending, while the word extension is 
applied to the opposing action or straightening. The muscle which 
has the power of drawing the arm forward as its essential function 
is known as the coracobrachialis. This small muscle arises in com- 
mon with the short head of the biceps from the tip of the coracoid 
process and inserts near the middle of the humerus on its medial 
surface. The biceps muscle is also a flexor of the arm at the 
shoulder, this action being only a subsidiary power of this compli- 
cated muscle (biceps = two-headed). THE UPPER EXTREMITY 
83 
The long' head of the triceps or three-headed muscle arises from 
just under the glenoid cavity of the scapula and joins the other 
heads of this muscle in the lower posterior part of the arm. This 
long head of the triceps is the main extensor muscle of the arm al 
the shoulder. 
The coracobrachialis and the long head of the triceps muscle 
should be cleared of their fascias and traced out. The consideration 
of the muscle groups controlling the shoulder, now completed, gives 
the simple components of the very wide range of motion. To sum- 
marize, these movements are flexion and extension, abduction and 
adduction, and internal and external rotation. 
The Arm (Brachium) 
Most of the humerus is heavily covered by muscles, but the lateral 
and medial epicondyles at the elbow region are readily palpable as 
bony prominences. The skin over the lateral surface of the arm 
being more exposed to injury, is tougher than over the medial sur- 
face. 
The skin should be dissected off the remainder of the arm and the 
upper half of the forearm. 
Superficial Venous System 
In the superficial fatty layer are to be found the routine cutaneous 
arteries, veins and nerves, and the superficial venous system. This 
part of the superficial venous system deserves more careful consid- 
eration than usual, as it has been historically and is today the site 
of election for blood-letting. It lies in the subcutaneous fatty layer, 
but anastomoses with and eventually joins the deep venous system. 
The median vein courses up to the middle of the front of the fore- 
arm and divides just below the elbow into a mediancephalic and a 
medianbasilic. A profunda branch runs from about the junction of 
these three vessels through the deep fascia to join the deep venous 
system. The median cephalic is joined by a radial vein, while the 
median basilic is joined usually by two ulnar branches (the radius is 
the lateral bone of the forearm, the ulna the medial). In the de- 
scription of the veins after they have received these branches the 
term median is dropped. The cephalic vein runs upward along the 
posterior lateral border of the biceps muscle, follows along between 84 
REGIONAL ANATOMY 
the pectoralis major and deltoid muscles, and eventually dips down 
to join the subclavian vein just below the clavicle (cephalic = to- 
wards head). The basilic vein follows along the posterior medial 
border of the biceps and dips down to join the brachial vein just 
below the axillary space. The name basilic is said to mean base, and 
was due to an historical misconception and exaggeration of its im- 
portance. The median basilic being the larger is commonly chosen 
for blood-letting, but it should be noted that it crosses directly over 
the main vessels, separated only by a layer of deep fascia. 
The superficial venous system should be dissected out, and then 
the subcutaneous fatty layer should be removed. 
basilic 
cephalic 
median basilic 
median cephalic 
profunda 
radial 
ulnar 
median 
Fig. 20.-Diagram of Superficial Veins, from in front, left arm. 
Deep Fascia 
The deep fascia should be noted to be stronger on the lateral side 
of the arm, and much stronger in the region of the. elbow where the 
big muscle bellies join their tendons. The fascia sends in intermus- 
cular septa between the muscles and extra strong partitions, the 
intergroupal septa, down to the bone between the front and back 
compartments of the arms. The front compartment contains the 
flexor muscle group, while the back contains the extensor group. In 
the lower half of the arm these intergroupal septa help raise up the 
medial and lateral margins of the humerus. 
Anterior or Flexor Compartment 
The short tendon of the biceps brachii muscle arises from the tip 
of the coracoid process, while the long tendon arises from the top THE UPPER EXTREMITY 
85 
of the glenoid cavity of the scapula. The long tendon traverses the 
shoulder joint, then emerges and helps to form the intertubercular 
groove on the anterior surface of the humerus. The intertubercular 
groove was known in the old terminology as the bicipital. These 
tendons swell out into the popularly known bellies of this muscle, 
which converge onto another tendon of insertion, running to the 
radius just below the elbow joint. 
In the early developmental stage of embryonic life the muscle 
flexor muscle group 
intermuscular 
septa 
intergroupal 
septa 
extensor 
muscle 
group 
deep fascia 
Fig. 21.-Fascial compartments at middle of Arm. 
arrangement is much simpler than in so complicated a muscle as the 
biceps. When muscles are first developed they run from a region 
past a joint into the next bone, as for example from the shoulder 
to the arm, or from the arm to the forearm. By fusion of two 
separate embryonic muscles, such complicated muscles as the biceps 86 
REGIONAL ANATOMY 
are developed. The biceps has the double power of flexing the arm 
at the shoulder and the forearm at the elbow. 
The brachialis (O.T. brachialis anterior) muscle arises from the 
front lower half of the humerus, lies deep to the biceps, and inserts 
into the ulna just below the elbow. The biceps and brachialis mus- 
cles act on a short lever speed principle and are mainly flexors of 
the forearm, although the biceps as will be noted later has still 
another important action. 
The deep fascia should be split in the midline and dissected back 
on each side to the intergroupal septa in order to clear these muscles. 
Posterior or Extensor Compartment 
The triceps brachii muscle arises from a lateral or upper head 
and a medial or lower head from the back of the humerus. Between 
these two heads lies the radial nerve, accompanied by an artery and 
vein. The old terminology for the radial nerve was musculospiral. 
The long head of the triceps muscle arises from the scapula just 
below the glenoid cavity of the scapula, as noted in connection with 
extension at the shoulder. All three heads join onto a common ten- 
don, which attaches to the elbow point or olecranon of the ulna. 
Fracture of the humerus in its middle third may result in catching 
the radial nerve between its rough ends with resultant complete 
destruction of nerve function below the point. This accident com- 
monly calls for surgical relief. 
The anconeus muscle arises from the lateral epicondyle of the 
humerus and inserts along the posterior margin of the ulna through- 
out its upper third. It therefore acts as an extensor of the forearm 
and is an accessory to the triceps. Although the anconeus lies 
regionally in the forearm, on account of similar function it is fittingly 
considered with the triceps. 
These muscles should be cleared of their fascias and traced out. 
Vessels 
The brachial artery and vein run down well protected under the 
medial border of the biceps muscle to a midline position in front of 
the elbow. As the muscle belly gives way to tendon, the skin 
approaches nearer to the artery, which during life can be felt 
pulsating in front of the elbow, just medially to the biceps tendon. THE UPPER EXTREMITY 
87 
Instead of giving off a great number of small branches the general 
tendency of larger arteries is to give off a main branch, which in 
turn gives off the smaller branches. The main branch from the 
brachial conies off in the upper part of the arm, and on account of 
its relations is known as the profunda, or deep. This profunda 
brachialis stem gives off numerous branches to the muscles, and 
also branches accompanying the main nerves. Just above the elbow 
the brachial artery gives off superior articular branches, which 
anastomose with the inferior articular branches below the joint. 
This arrangement, although names may vary in different areas, is 
practically universal at all the really freely movable joints. The 
deep venous system is made up of paired veins (venae comitantes), 
but otherwise corresponds to the arteries. 
The vessels should be cleared and traced out. 
Brachial Plexus 
The brachial plexus is formed by the union of the fifth, sixth, sev- 
enth, and eighth cervical and first thoracic segmental nerves. These 
become known in the mid-axilla as the lateral, medial, and posterior 
cords on account of their relation to the axillary artery (cord = B.N. 
A. fasciculus). The lateral cord divides into the musculocutaneous 
branch and the lateral head of the median nerve. The musculo- 
cutaneous supplies the biceps and brachialis muscles, and continues 
as a small cutaneous branch down the lateral anterior surface of the 
forearm. The medial head of the median nerve is supplied by the 
medial cord. The large median nerve then continues down in com- 
pany with the brachial vessels, and eventually will be noted to take 
a midline position in the forearm. The continuation of the medial 
cord is known as the ulnar, which runs contrary to what would be 
expected in back of the medial epicondyle of the humerus in its 
course into the forearm. The ulnar nerve can be easily palpated 
just posterior to the median epicondyle, and it is the impinging 
of this nerve against the bone which yields the name humerus or 
funny bone. The posterior cord sends off a large circumflex branch 
to the shoulder region, and then continues through the posterior 
compartment of the arm as the radial. The radial nerve forms a 
groove between the lateral and medial heads of the triceps muscle 
and passes contrary to what would be expected in front of the 
lateral epicondyle of the humerus. It supplies both the muscular 88 
REGIONAL ANATOMY 
and cutaneous branches to the posterior compartment of the arm, 
and eventually of the corresponding compartments of the forearm 
and hand. It peculiarly does not supply sensation to the back of 
the fingers. 
The nerves should be traced through the arm. 
5th-6th-7th-8th cervical 
1st thoracic 
segmental 
nerves 
lateral cord (fasciculus) 
medial cord 
posterior cord 
ulnar 
musculo-cutaneous 
median 
radial (musculo-spiral) 
Fig. 22.-Diagram of Brachial Plexus. (Dotted lines are parts in posterior compartments). 
Shoulder Joint (Articulatio Humeri) 
The shoulder joint is a diarthrodial articulation of the ball and 
socket type. It is the joint between the head of the humerus and 
the glenoid cavity of the scapula. It possesses a very wide range 
of motion, which may be classified as abduction and adduction, 
flexion and extension, and internal and external rotation. After 
resection of all the muscles and an incision into the capsule so as to THE UPPER EXTREMITY 
89 
obviate suction, the great strength of the capsular ligament may be 
tested by trying to pull the humerus from the scapula. The cap- 
sular ligament runs from around the glenoid cavity to the anatomic 
neck of the humerus, and may be noted to be composed of fibers 
running mainly in parallel bundles. The capsular ligament is then 
to be cut across midway between the humerus and scapula, when the 
long tendon of the biceps running to its insertion at the upper part 
of the glenoid cavity will come into view. This is a characteristic, 
unique feature of this joint. This tendon must be cut across in 
order to separate the bones. The cartilage covering of the bones is 
to be noted, and the very smooth synovially lubricated interior of 
the joint. Above the joint the overprojecting acromion and coracoid 
processes are joined by a strong ligament, logically named the 
coracoacromial ligament. This arch is an important element in in- 
creasing the size of the socket. Between the upper surface of the 
capsular ligament and the under surface of this coracoacromial arch 
lies a bursa, an endothelial sac lubricated by synovial glands. 
General Rule of Nerve Supply 
The same segmental nerves that supply the muscles controlling a 
joint, send cutaneous branches to the skin of the area, and also 
sensory branches into the interior. This gives an anatomic basis to 
two well-established clinical facts; the influence of surface applica- 
tions on joint pains and the muscular protective rigidity of a joint 
in case of inflammation in its interior. The arteries, veins, and lym- 
phatics are from the neighboring smaller vessels. 
Dislocation 
The coracoacromial arch prevents the head of the humerus from 
jumping out of the socket in any direction except inferiorly. With 
the arm fully abducted a fall on the palm of the hand may and not 
infrequently does, cause the head of the humerus to tear its way 
through the inferior portion of the capsular ligament. After it has 
escaped from the capsule, the head may take any one of a number 
of secondary positions. The separation of opposing bones is known 
as dislocation or luxation. The importance of muscular resistance 
in holding the bones together has been emphasized, therefore if the 
muscles are caught off guard the probability of dislocation is 90 
REGIONAL ANATOMY 
greater. In order to reduce a dislocation the rigidity of the muscles 
is often advisedly lessened by an anesthetic before reduction is 
attempted. 
Acromioclavicular Joint 
The acromioclavicular joint allows only a limited degree of glid- 
ing motion in all directions. The interior of this joint cavity differs 
from the usual type in the presence of a complete partition", an 
interarticular disc of fibrocartilage. The clavicle is bound down 
firmly to the root of the coracoid process by a strong ligament, 
named logically the coracoclavicular ligament. Fractures of the 
clavicle usually occur medially to this connection with the coracoid 
process. 
FOREARM AND HAND (ANTIBRACHIUM ET MANUS) 
The forearm, hand and fingers are considered together for the 
reason that several muscles from the forearm continue down to the 
fingers. As usual in taking up the consideration of a region, the 
bones will first be described, with special stress laid on the more 
important landmarks. 
Ulna 
The ulna is the medial bone of the forearm. It is a long bone with 
usual type of development, that is, a diaphysis and two epiphyses, 
or in the adult a body, or shaft, and two extremities. The ulna has 
the characteristic elbow point or olecranon process, which serves to 
grasp the lower end of the humerus. The front portion of this 
grasping curve is the coronoid process, whereas the curved surface 
between these two processes is known as the semilunar notch (luna 
= moon). The lower extremity has a small rounded head, with a 
projection from its medial surface known as the styloid process 
(stylus = quill pen). The dorsal margin of the ulna is not covered 
by muscles and consequently is a most important landmark of the 
forearm. Running between the opposing surfaces of the radius 
and ulna is a woven white fibrous layer, the interosseus membrane. 
This layer raises up a sharp ridge on the lateral surface of the ulna 
and also on the medial surface of the radius. THE UPPER EXTREMITY 
91 
olecranon (process) 
surface for humerus 
coronoid process 
head 
(capitulum) 
neck 
radial 
tuberosity 
semilunar 
notch"- 
olecranon 
coronoid 
process - 
interosseous 
membrane 
styloid 
process 
styloid process 
Fig. 23.-Left Ulna (A) and Radius (B), anterior surface. (C) medial view of upper 
extremity of ulna, 92 
REGIONAL ANATOMY 
Radius 
The radius, the bone that turns or radiates about the ulna, is a 
typical long bone. With the thumb side of the hand held outward, 
the radius parallels the ulna, whereas with the thumb turned inwards 
it crosses over the ulna. External rotation of the forearm, that is 
with the thumb held out, is known as the supine position, whereas, 
internal rotation of the forearm, that is with the thumb held in, is 
the prone position. At least two bones are required in the forearm 
in order to allow for these changes in position. The radius has a 
small disc-shaped head, the upper surface of which is slightly con- 
caved to fit over the rounded lower surface of the humerus. The 
constricted neck is surrounded by a firm encircling ligament, which 
holds the radius steady during rotation. The radial tuberosity just 
below the neck and on the medial side is raised up by the attach- 
ment of the biceps muscle. At its lower extremity the radius widens 
out to meet the bones of the wrist, while projecting from its lateral 
surface is a styloid process. The head of the radius can be felt 
about one-half inch below the lateral epicondyle of the humerus, and 
its position verified by rotating the forearm. Due to the muscle 
bellies giving way to tendon the lower third of the radius is readily 
palpable. 
Carpals 
The wrist has a number of small very irregular bones, two rows 
of four each, known as the carpal bones. Their dorsal surfaces are 
readily palpable, while on the ventral surface a lateral and a medial 
ridge is not covered by muscle. A logical identification system for 
these bones would be to number them from the thumb side inwards, 
one, two, three, and four of the first and second carpal rows. Their 
names, hard to remember and of minor importance, in the same 
sequence are: os naviculare manus, os lunatum, os triquetrum, os 
pisiforme and os multangulum ma jus, os multangulum minus, os 
capitatum, os hamatum. 
Metacarpals 
The hand has as its framework five metacarpal bones, which are 
readily palpable from the dorsal surface. The rounded heads of the 
metacarpals fit into shallow sockets at the bases of the first 
phalanges. THE UPPER EXTREMITY 
93 
Phalanges 
The phalanges are three in number to each finger except the 
thumb, which has only two. Their dorsal and lateral surfaces are 
especially superficial. The accepted system of numbering the meta- 
carp a Is 
metacarpals 
► phalanges 
Fig. 24.-Left Hand (manus), dorsal surface. 
carpal and phalangeal bones is noted on the diagram. The words 
proximal and distal are widely used in the consideration of the 
forearm and hand, proximal meaning nearer to the trunk, distal 
further away. 94 
REGIONAL ANATOMY 
The Skin 
The skin has relatively greater thickness over the radial parts 
of the forearm in conformity with its greater exposure. On the 
palmar surface of the hand and fingers the skin is very thick, the 
epidermis becoming extraordinarily thick in the calloused hand of a 
laborer. The line creases in the palm and across the fingers are thin 
areas of the skin to allow for the closing of the hand, and are more 
noticeable in the hands of strong people. It is to be specially noted 
that the creases do not lie over the metacarpophalangeal series of 
joints. The finger-nails are special structures developed from the 
epidermis. Neither hair nor sebaceous glands are present in the 
palm. 
The skin should next be dissected off and even though extra diffi- 
cult, care should be exercised to stick as closely to the under surface 
as possible. 
Subcutaneous Fatty Layer 
The subcutaneous fatty layer contains the cutaneous arteries, 
veins and nerves, and branches of the superficial venous system. 
The cutaneous nerves on the back of the forearm and hand are gen- 
erally speaking derived from the posterior cord, whereas all in 
front are from branches of the lateral and medial cords. The palmar 
surfaces of the fingers and thumb over the distal phalanges have an 
extraordinarily liberal nerve supply, and here the sense of touch is 
highly developed. The large size of the cutaneous nerves in com- 
parison with the small area for supply is especially to be noted. In 
the central compartment of the palm and over the fingers the sub- 
cutaneous fatty layer is characterized by the great amount of the 
fibrous tissue element, which makes this layer extremely tough and 
resistant. 
The fatty layer should be dissected off. 
Deep Fascia 
The deep fascia surrounds and encloses all the muscles of the fore- 
arm and hand in a firm sheath. Over the central compartment of 
the palm the deep fascia is very strong and in the case of a manual 
laborer very materially stronger. This deep fascia is reinforced by 
the aponeurosis of the palmaris longus muscle. This combination THE UPPER EXTREMITY 
95 
deep fascia and aponeurosis serves as a protection to the deeper 
structures. The portion of the deep fascia across the back of the 
wrist is extra heavy and receives the special name of dorsal carpal 
ligament. The transverse carpal ligament in front of the wrist is 
even stronger, due to the more powerful group of muscle tendons it 
has to hold down. The old terminology was anterior and posterior 
annular or ring ligaments. This transverse carpal ligament raises 
up a ridge on the lateral and medial sides of the front surfaces of the 
carpal bones, which projections are readily palpable. Across the 
front surfaces of the fingers the deep fascia is strengthened and 
deep fascia 
intergroupal septa 
flexor pronator 
group . 
ntermuscular 
septa 
ulna _ 
sxtensor- 
supinator 
group 
intergroupal septa 
radius 
nterosseous 
membrane 
Fig. 25.-Fascial compartments at middle of Forearm. 
attached to the junction of the front and collateral surfaces of the 
phalanges in order to hold down the tendons. These flexor tendon 
sheaths (ligamenta vaginalia) possess synovially lubricated in- 
teriors. 
Muscles 
The flexor group of muscles of the forearm has the power of bend- 
ing the fingers on the hand and the hand on the forearm. The 
pronator group of muscles has the power of turning the radius over 
the ulna, that is internal rotation. The flexor muscles of the fingers 
are as popularly known much more powerful than the opposing 
extensors. The flexor-pronator group arises in the main from a 
common tendon on the medial epicondyle of the humerus, as may 
be noted by contracting the muscles. These muscles should also be 96 
REGIONAL ANATOMY 
noted to arise from the deep fascia and intermuscular septa of the 
upper part of the forearm, thus obtaining a secondary indirect 
attachment to the bones. The extensor-supinator group arises in 
the main from a common tendon on the lateral epicondyle of the 
humerus. These two muscle groups are separated by the subcu- 
taneous dorsal margin of the ulna, whereas in front the two groups 
are not well marked off. 
Flexors and Pronators 
The pronator teres runs from the common tendon and an accessory 
ulnar head deeply across the forearm to the middle of the radius, 
wrapping itself half way around the bone. It is to be specially 
noted that as a matter of logic all pronators and supinators must 
insert into and act on the radius. 
The flexor carpi radialis runs superficially across the transverse 
carpal ligament to its spread-out insertion on the carpal and base 
of the metacarpal bones of the radial side. Its tendon is readily seen 
above the wrist. 
The palmaris longus runs over the transverse carpal ligament 
about its middle to the deep fascia of the palm. 
The flexor carpi ulnaris, arising from the common tendon and also 
from the ulna, runs over the transverse carpal ligament to its inser- 
tion in the carpal and base of the metacarpal bones on the ulnar 
side. 
The flexor digitorum sublimis (superficialis) arises from the com- 
mon origin and an accessory radial head, and divides up into four 
tendons, which run under the transverse carpal ligament. These 
tendons separate in the palm and enter their respective flexor 
sheaths. Each tendon in this synovial sheath divides into two parts, 
which insert on the sides of the second phalanx. 
The deep group of muscles does not arise from the common ten- 
don. 
The flexor digitorum profundus arises underneath the superficial 
flexor from the interosseous membrane and the ulna, and follows 
the same division and course into the flexor sheaths. Each tendon 
then runs through the divided superficial tendon to its attachment 
at the base of the third phalanx. The four lumbricle muscles, run- 
ning from these tendons in the palm to the deep fascia on the back THE UPPER EXTREMITY 
97 
of the fingers, act by taking up slack and straightening out the line 
of pull (lumbricle = earthworm). 
The flexor pollicis longus arises from the radius and the interos- 
seous membrane, runs under the transverse carpal ligament to the 
flexor sheath of the thumb, and inserts into the base of the terminal 
phalanx (pollex = thumb). 
The pronator quadratus is a thin square sheet, arising from the 
lower part of the ulna and inserting into the lower part of the 
radius. 
Short Muscles of Hand 
The intrinsic muscles of the hand arise from the carpal or meta- 
carpal bones and insert into the base of the first phalanges. An 
exception is the small opponens muscle of the thumb and of the 
little finger, which arise from a carpal bone, and lie next to and 
insert into the metacarpal bone. The comparative anatomy of the 
short muscles of the hand is complicated in its detail because some 
of the muscles found well developed in the lower animals have 
become greatly modified or have disappeared from the human hand. 
Although the muscles belong to various comparative groups, muscles 
which functionate as abductors, adductors and short flexors exist 
for all five digits. The terms abduction and adduction are used with 
reference to the midline of the hand. The metacarpal bone of the 
thumb has a free range of motion, contrasting sharply with the 
condition of the other metacarpals. The proximal end of the medial 
four metacarpal bones have only a slight range of motion, which, 
however, is magnified in amount at the distal end of these bones. 
The relatively large muscles making up the muscular mass ove? 
the thumb metacarpal are named from the radial side medially, the 
abductor pollicis brevis, the flexor pollicis brevis, the adductor pol- 
licis and on a deep plane the opponens pollicis. Covering the ulnar 
side of the fifth metacarpal lies the relatively large abductor digiti 
quinti, along the lateral side of which lies the flexor digiti quinti 
brevis, the opponens digiti quinti lying deep between these two 
muscles. The muscles lying between the metacarpal bones, known 
as the interossei, are divided into a volar, or palmar, and a dorsal 
group. The volar group of interossei muscles are three in number 
and are arranged so as to act as adductors of the first phalanges. 
The dorsal group of interossei muscles are four in number and are 98 
REGIONAL ANATOMY 
arranged so as to act as abductors of the first phalanges. Both of 
these groups of interossei muscles act also as functionally unim- 
portant flexors of the first phalanges. Comparative anatomy and 
the nerve supply from the anterior cords in the human hand both 
demonstrate that the dorsal group of interossei muscles belong to 
the palmar musculature and only secondarily take a semidorsal 
position between the metacarpal bones. 
Blood Supply 
The brachial artery and vein dip down into the forearm between 
the flexorpronator and the extensorsupinator muscle groups. The 
radial branch continues down between these two muscle groups 
and becomes superficial near the wrist, which is the routine point of 
selection for palpation of the pulse wave. The ulnar branch runs 
deeply under the pronatorflexor group of muscles, but is palpable 
above the wrist. The continuation of the brachial artery is known 
as the common interosseous, which almost immediately breaks up 
into ventral and dorsal interosseous divisions, so called on account 
of their relation to the interosseous membrane. Recurrent branches 
from all these vessels are given off for the elbow region, large mus- 
cular branches at intervals, and eventually smaller anastomosing 
branches above the wrist. 
The ulnar artery proceeds through a compartment of the trans- 
verse carpal ligament into the hand, remaining beneath the deep 
fascia. The radial artery turns laterally at the carpal bones, goes 
around the metacarpal bone of the thumb and then turns back into 
the deep part of the palm. The connecting vessel between the ulnar 
and radial arteries lying superficial to the flexor tendons is known 
as the superficial volar or palmar arch, which lies on a level with 
the base of the outstretched thumb. The branches of the superficial 
volar arch run forward between the metacarpal bones to the web 
of the fingers, sending digital branches along both protected sides 
of the fingers. The deep volar or palmar arch is materially smaller, 
lies up much nearer to the carpal bones, and besides supplying the 
area sends branches between the metacarpals to the back of the 
hand. The superficial volar arch is normally made up chiefly by the 
ulnar, the deep volar arch chiefly by the radial. These volar arches 
are both beneath the deep fascia as is the rule for larger arteries. THE UPPER EXTREMITY 
99 
and receive the adjective superficial and deep solely on account of 
their relation to the flexor tendons. 
Main Vessels 
Branches 
subclavian 
scapular 
thoraco-acromial 
lateral thoracic 
axillary 
subscapular 
circumflex of humerus 
profunda brachialis 
brachial 
superior articular 
inferior articular 
radial- 
common interosseou: 
ulnar- 
ventral interosseous 
dorsal interosseous 
deep volar arch 
superficial volar arch 
digital -► 
Fig. 26.-Diagram of Arteries of upper extremity. (Dotted lines are parts in 
posterior compartments.) 
Nerves 
The ulnar nerve enters the foramen between the medial epicondyle 
and the olecranon, runs deep through the muscle group supplying 
the flexor carpi ulnaris, and then follows the ulnar artery in its 100 
REGIONAL ANATOMY 
further course. In general it tends to supply the medial half of the 
hand and fingers. The large size of the branches for the palmar 
surface of the distal phalanges of the medial two and one-half fingers 
should be noted. The median nerve follows the brachial artery and 
Main Nerves 
Branches 
cervical 
thoracic 
lateral cord _ 
medial cord 
anterior axillary 
posterior axillary 
posterior cord - 
ulnar _ 
median _ 
i flexor muscles of arm 
musculo-cutaneou 
extensor muscles of arm 
radial (musculo-spiral) 
extensor-supinator muscles 
of forearm 
ulna: _ 
flexorpronator muscles 
of forearm 
musculo-cutaneou 
median 
radia - 
ulnar - 
median 
lateral part of hand 
medial part of hand 
digital ~ 
Fig 27.-Diagram of Nerves of upper extremity. (Dotted lines are parts in 
posterior compartments.) 
vein into the mid-upper part of the forearm, sends off branches 
supplying the flexorpronator muscle group, and eventually goes 
through under the transverse carpal ligament into the palm. In 
general it supplies the lateral side of the hand, and sends large THE UPPER EXTREMITY 
101 
cutaneous branches to the finger tips of the thumb, index, and lateral 
half of the middle finger. 
Dissection.-The deep fascia should be opened up over the flexor- 
pronator muscle group and should be dissected off from the palm of 
the hand. After the various structures noted in the preceding dis- 
cussion have been traced out, the flexor tendon sheaths and event- 
ually the transverse carpal ligament may be opened up. 
Practical 
Pus under the tough fascias of the palm would obviously have 
an extremely difficult task in working to the surface. The great 
associated swelling of the loose tissues of the back of the hand often 
leads the inexperienced to an erroneous diagnosis and treatment. 
Pus in the palm on account of the tough layers does not produce 
much swelling, but may be recognized by local tenderness on pres- 
sure. It should be evacuated early in order to stop the pain and to 
minimize the danger of spreading. The incision should be in a line 
over the metacarpal bone and should not commence nearer the 
wrist than the base of the outstretched thumb, on account of the 
danger to the superficial volar arch. The fairly common bone infec- 
tions of the distal phalanges are popularly known as bone felon or 
whitlow, and are extremely painful so long as the pus is enclosed in 
the bone. An incision into the flexor tendon sheaths may cause the 
infection to spread into the palm, or in the case of the thumb or 
little finger even to the synovial sheath of the wrist region. 
Extensors and Supinators 
The extensor and supinator muscle group arises in the main from 
a common tendon from the lateral epicondyle of the humerus, 
although minor secondary origins are present. This group is marked 
off on the back of the forearm by the dorsal margin of the ulna, 
whereas on the front surface the dividing line is not well marked. 
The extensors of the fingers are much weaker than the flexors, but 
the extensors of the wrist are approximately equal to the flexors in 
strength. 
The biceps muscle wraps around the medial side of the radius, 
as a result of which it is not only a flexor, but also a strong supin- 
ator of the forearm. The supinator group is on this account ma- 102 
REGIONAL ANATOMY 
terially stronger than the pronator group. The threads on screws 
are commonly set so as to utilize this power in driving the screw 
inward. 
The brachioradialis (O.T. supinator longus) arises from the lateral 
margin of the humerus and runs down to a tendon attachment to 
the lateral surface of the lower part of the radius. This muscle is a 
flexor of the forearm at the elbow and also to a minor degree a 
supinator. Between the brachioradialis and the flexor carpi radialis, 
an intergroupal fibrous septa runs from the deep fascia down to the 
bone. 
The extensor carpi radialis arises from the common tendon and 
inserts by two separate tendons into the carpal and base of the 
metacarpal bones on the radial side. This muscle, in fact all these 
muscles which pass the wrist, run through separate compartments 
in the dorsal carpal ligaments. 
The extensor digitorum communis arises from the common ten- 
don and spreads out over the back of the hand into four tendons for 
the respective fingers. These tendons attach partly to the sides of 
the second phalanges and terminate at their attachment to the base 
of the distal phalanges. 
The extensor carpi ulnaris arises from the common tendon and the 
dorsal margin of the ulna throughout and inserts into the base of 
the fifth metacarpal. 
The thumb has two special extensors, which arise in the lower 
back part of the forearm, and insert into the bases of the first and 
second phalanges. The muscle which inserts into the base of the 
thumb metacarpal is known as the abductor pollicis longus. The 
index finger and little finger have extra separate extensor muscles. 
The supinator (brevis) arises by a short tendon from the upper 
lateral surface of the ulna and wraps around the lateral side of the 
upper half of the radius, more markedly so when the forearm is 
pronated. It lies next to the bone, hence deeply under the other 
muscles. 
Vessels and Nerves 
The posterior cord continues as the radial nerve through the 
back of the arm, runs contrary to what would be expected in front 
of the lateral epicondyle, and terminates in the extensorsupinator 
group of muscles. This nerve also supplies the skin over the back 
of the forearm and hand. Theoretically it should also supply the THE UPPER EXTREMITY 
103 
skin over the back of the fingers, bnt as a matter of fact the supply 
for this area comes mainly via the anterior cords of the brachial 
plexus. Branches from the dorsal interosseous arteries and veins 
furnish the main blood supply. 
Dissection.-The extensor-supinator group of muscles should be 
cleared and traced out. The vessels and nerves should also be fol- 
lowed out. 
Radio-Ulnar Joints 
Near the proximal extremity a strong collar arises from the lateral 
surface of the ulna, and encircling the neck of the radius attaches 
again to the ulna. This is known as the annular ligament (0. T. 
orbicular) of the radius, which, while holding the radius in position, 
allows free rotation. The depression on the lateral surface of the 
ulna made by the head of the radius is known as the radial notch. 
At the distal end a powerful ligament arises from a point at the base 
of the styloid process of the ulna and, widening out, attaches to the 
lowest ulnar surface of the radius. This ligament is the discus 
articularis, which, while allowing free rotation, prevents the radius 
from spreading away from the ulna. The discus articularis was 
formerly well named the triangular fibrocartilage. 
Elbow Joint (Articulatio Cubiti) 
The elbow joint is a diarthrodial articulation of the hinge type, 
being the junction of the humerus with the radius and ulna. It is 
to be especially noted that the forearm in full extension does not 
continue straight down in line with the axis of the arm, but distinctly 
deviates laterally, forming the so-called carrying angle. When the 
joint is fully extended the anterior part of the capsular ligament is 
tense, whereas in full flexion the posterior portion becomes taut. 
As no muscles directly resist side-to-side strain, the lateral 
and medial parts of the capsular ligament are especially thickened, 
and are known as the radial and ulnar collateral ligaments. The 
capsular ligament should be cut around about its midpoint. The 
semilunar notch of the ulna fits over the rounded ulnar surface of 
the humerus, and on close inspection a tongue-like projection of the 
ulna will be noted to fit into a corresponding groove of the humerus. 
This is a typical arrangement for hinge joints. The disc-shaped 
head of the radius shows a depression, which fits over the radial 104 
REGIONAL ANATOMY 
ball-shaped surface of the humerus. The olecranon process, the 
coronoid process, and the radial head all fit into pits in the lower 
part of the humerus, which arrangement allows for free flexion and 
extension at the elbow. The interior of the joint is otherwise not 
characteristic, but it should be noted that the proximal radioulnar 
joint is continuous with the elbow joint proper. 
Backward dislocation of the ulna on the humerus occurs quite 
frequently in childhood. It rarely occurs in adult life, and then 
ordinarily in association with fractures of the coronoid process. 
A bursa is present in the fatty layer over the olecranon process, 
with the obvious purpose of allowing the skin to slide and conse- 
quently reducing the liability to injury. 
The elbow joint should be dissected. 
The Wrist 
What is popularly known as the wrist is composed in reality of 
three joints: The radiocarpal, the intercarpal, and the carpometa- 
carpal. After removal of the muscles the strong anterior and 
posterior portions of the capsular ligament are exposed to view. 
The cord-like radial and ulnar collateral ligaments of the carpus, 
being unsupported by muscles, are specially strong, and their attach- 
ments to the lower ends of the radius and ulna raise up the styloid 
processes. The interior of the radiocarpal joint has a separate 
synovial membrane, while the intercarpal and carpometacarpal 
synovial cavities are generally distinct, sometimes, however, con- 
tinuous. Strong interosseous ligaments run between the different 
carpal bones and are a large factor in the strength of the wrist. 
The motion at each joint is small, but the full range is brought out 
by the summation of the radiocarpal, intercarpal, and carpometa- 
carpal movements. The lower end of the radius is widened out to 
meet all the first row of carpal bones, as must be so in order that the 
hand follow the movements of the radius. The articular disc, which 
connects the distal extremity of the ulna to the radius, shuts out the 
head of the ulna from meeting the carpal bones. 
A fall on the outstretched palm, breaking through the lower part 
of the radius with backward displacement of the hand, is known as 
Colles' fracture. This injury is almost always accompanied by a 
rupture of the ulnar collateral ligament or a fracture of the styloid 
process of the ulna. Chronic inflammation in the wrist joint may THE UPPER EXTREMITY 
105 
produce an increase in joint secretion, bulge out the capsular liga- 
ment, and cause rounded fixed swellings on the back of the wrist. 
The wrist joint should be dissected. 
Phalangeal Joints 
The metacarpal-phalangeal joints have a rounded metacarpal ball 
and shallow phalangeal socket, allowing limited collateral motion 
but free flexion and extension. The two interphalangeal series of 
joints show a slight tongue and groove arrangement, as in all hinge 
joints. The extensor digitorum tendons become intimately blended 
with the posterior portion of the capsule of these joints. 
These joints should be dissected. 
Bone Section 
One or more of the long bones of the upper extremity should be 
sawed longitudinally. This dissection will allow an examination of 
the interior of the body or shaft and the two extremities, or, if the 
body is of youthful age, of the diaphysis and the two epiphyses. 
The varying resistance to the cutting action of the saw will in itself 
demonstrate the inequality of the strength of the bone. A cursory 
examination of the cut halves will demonstrate that there is no ratio 
between the outward size and the real strength. Clinically, gener- 
ally speaking, there is no greater liability of fracture at the large 
weak end portions than at the solid smaller shaft. The bones are 
so arranged architecturally as to yield throughout the ordinarily 
required strength plus a factor of safety, while at the same time 
minimizing weight. 
The tubular shaft is made up practically of solid bone, known as 
the compact substance. The end portions have a narrow, compact 
inner and outer shSll, between which lies the porous spongy sub- 
stance. The spongy portions of the bone are filled with red bone 
marrow, while the large medullary cavity is filled by the fatty yellow 
bone marrow throughout its length. 
Practical 
The spongy portions of the bones are more commonly attacked by 
the various bacterial infections. The special localization of the 
infection is generally attributable to a neglected minor injury of 106 
REGIONAL ANATOMY 
the bone, while the individual is suffering from some infection with 
living bacteria circulating in the blood stream. The infection once 
- spongy substance 
- compact substance 
medullary cavity 
-spongy substance 
Fig. 28.-Longitudinal section of long bone (femur). 
localized causes swelling, and due to the anatomic limitations of this 
process the blood supply is seriously interfered with. This causes THE UPPER EXTREMITY 
107 
local death or necrosis of the bone area. The diagnosis of these 
infections of the bone is to be made by the general symptoms of 
severe illness plus the localizing tenderness. The bone abscess, if 
neglected, may work its way into the neighboring joint, into the 
medullary cavity or onto the external surface of the bone. The 
obvious surgical procedure calls for the immediate free opening of 
the outer shell of the bone, eventually of the medullary cavity, in 
order to determine the most favorable line of least resistance. 
Although certain types of joint infection are unquestionably pri- 
mary, many joint infections are secondary to diseases of the spongy 
substance of the bones. CHAPTER IX 
THE LOWER EXTREMITY 
HIP AND THIGH 
The part of the body composed of the hip, thigh, leg, and foot is 
known collectively as the lower extremity. The lower extremities 
possess bilateral symmetry, while the five pair of spinal nerves are 
the lasting evidence of their segmental origin. The lower extrem- 
ity, as in the quadruped animals, is firmly attached by bones to the 
trunk, but the upright position of man has resulted in anatomic 
modifications 
Hip Bone (Os Coxse) 
The bones of the hip girdle are developmentally made up of three 
distinct parts, but with the disappearance of the epiphyseal lines 
these three parts fuse into one solid piece. This fused hip bone was 
formerly known as the innominate, or nameless, for, on account of 
its irregularity, the imagination of former-time anatomists played 
out. The three original parts, known as the ilium, ischium, and 
pubis, join at the socket for the thigh bone, which is known as the 
acetabulum, or vinegar cup. The presence of cartilaginous lines in 
the bone allows for growth of the acetabulum, hence we would 
expect these lines, as in fact occurs, to disappear at the end of the 
growth period. 
Pelvis 
The two hip bones are held together in the midfront line by a 
very slightly movable joint known as the symphysis pubis. In back 
the hip bones are held apart by the presence of the sacrum, which 
is fastened to the iliac portions of the hip bones by very powerful 
interosseous ligaments. The combination of the two hip bones plus 
the sacrum and coccyx make up the pelvis or basin. This is subdi- 
vided into the part which has the shape of a basin, hence known as 
the lesser or true pelvis, and the flared-out iliac portions of the hip 
bones making the greater or false pelvis. It is to be especially noted 
108 THE LOWER EXTREMITY 
109 
that this true pelvis is not on a horizontal plane in the upright posi- 
tion of man, but that the plane of its brim is on over a fifty degree 
forward-downward slant. Or, in other words, the top of the sym- 
physis pubis is about four inches lower than the top of the sacrum. 
The brim of the pelvis is known technically as the apertura pelvis 
minoris superior. These points can only be made out satisfactorily 
by the examination of an articulated bony pelvis, or by outlining the 
pelvis in the student's own body. 
sacrum sacro-iliac joint 
posterior 
superior 
spine 
crest of 
ilium _ 
anterior 
superior 
spine 
iliac part 
lesser 
pelvis 
crest of 
pubis 
obturator 
foramen 
tuber of 
ischium 
acetabulum 
- pubic part 
ischial 
part 
Fig. 29. - Female Pelvis, front view, tilted slightly forward. 
symphysis pubis 
Bony Landmarks 
The bold, curving, irregular ridge of the hip bone above the hip 
joint is subcutaneous throughout and is known as the crest of the 
ilium or, more accurately, the crest of the iliac portion of the hip 
bone (ilium = flank). The terminations of the subcutaneous crest 
of the ilium are named the anterior and posterior superior iliac 
spines, which terminology naturally means that there are also ante- 
rior and posterior inferior spines. These will be more appropriately 
considered later. This iliac crest makes the surface separation 
between the abdominal region and the gluteal or buttocks region. 
The ridge at the upper part of the symphysis pubis runs subcu- 110 
REGIONAL ANATOMY 
taneously lateralwards for about one inch and is known as the crest 
of the pubis-that is, the pubic portion of the hip bone (pubis = 
covered by hair, as in the word puberty). This crest separates the 
front of the abdomen from the perineum, or region around the birth 
canal (peri = around; neum=new, hence birth). This seems like a 
reasonable explanation of the "neum," but the researches say the 
origin is uncertain or unknown. The bold, rough projection ex- 
tending down below the hip joint on the medial side of the thigh is 
known as the tuber of the ischium-that is, ischial portion of the 
hip bone. This tuber or tuberosity separates the perineum from the 
lower part of the gluteal region. 
The spines on the posterior surface of the sacrum are subcutaneous, 
while the lower part of the sacrum is covered only by a thick aponeu- 
rosis. The posterior surface of the coccyx is subcutaneous. 
Ligaments 
A narrow ligament runs from the anterior superior spine of the 
crest of the ilium to the nearest point of the crest of the pubis, 
raising up the pubis tubercle at its attachment. This is known as 
the inguinal or as Poupart's ligament (inguen = groin). The ingui- 
nal ligament separates the lower part of the abdominal wall from 
the front of the thigh. 
A wide ligament starts from the lateral margin of the sacrum, 
converges in its midportion, and widens out again near its attach- 
ment to the tuber of the ischium. This is known as the sacro- 
tuberous or greater sacrosciatic ligament. The word sciatic is used 
practically as a synonym of ischiadic, though ischiadic is preferred 
in the B. N. A. A fairly wide ligament starts from the lateral mar- 
gins of the sacrum and converges at its attachment to the ischium, 
about one and one-half inches above the tuber of the ischium, raising 
up the spine of the ischium. This is known as the sacrospinous or 
lesser sacrosciatic ligament. The large open space between the 
sacrum and the ischium is converted by these ligaments into the 
greater and lesser sciatic foramina. The greater sciatic foramen 
forms a passageway between the lesser or true pelvis and the gluteal 
region. The lesser sciatic foramen serves as a passageway between 
the gluteal region and the perineum, as will be detailed later. THE LOWER EXTREMITY 
111 
Obturator Foramen 
The obturator foramen is a large, oval opening between the true 
pelvis and the medial portion of the upper part of the thigh (obtu- 
rator = closed). This window exists at the expense of the pubic and 
ischial portions of the hip bone, an interosseous membrane stretching 
across this space during life. The narrowed portions of the pubic 
and ischial bones are known as the rami or branches, which for 
obvious reasons were formerly differentiated into an ascending and 
descending ramus of the pubis and an ascending ramus of the 
ischium. In the revised nomenclature the ascending ramus of the 
pubis is known as the superior, the descending as the inferior, while 
the ascending ramus of the ischium is known as the inferior. Frac- 
tures of the pelvis commonly pass through these rami on account of 
their relative weakness. The symphysis pubis and the two sacro- 
iliac amphiarthrodial joints give elasticity to the pelvis and conse- 
quently minimize the frequency of fractures. 
The Femur 
The femur or thigh bone is a typical long bone. It has a rounded 
head, which fits into the acetabulum, forming a ball and socket joint. 
A relatively long neck runs off on a downward lateralward slant, 
carrying the shaft well away from the hip bone. The large rough- 
ened projection on the lateral side of the upper end of the shaft is 
known as the greater trochanter. The use of the word ' ' trochanter ' ' 
instead of tuberosity in connection with the femur is historically 
established, but, is in my opinion, unnecessary, being a distinction 
without a difference. The greater trochanter is many faceted on 
account of muscle insertions, whereas the lesser trochanter on the 
medial posterior surface serves for the attachment of a single tendon. 
Down the posterior surface of the femur run a series of parallel sharp 
lines or linea aspera, which are raised up by muscle aponeurosis and 
fascia sheets. The widened-out lower end of the femur has a lateral 
and medial condyle, which articulate with the tibial bone of the leg 
to form the knee joint. The projections from the condyles raised up 
by tendons are known as the lateral and medial epicondyles. 112 
REGIONAL ANATOMY 
head 
neck 
greater trochanter 
lesser trochanter 
_ linea aspera 
body of shaft 
medial condyle 
-lateral condyle 
Fig. 30.-Left Femur, posterior surface. THE LOWER EXTREMITY 
113 
Gluteal Region 
The body is to be turned upon its belly in order to examine the 
gluteal region. The main bony landmarks are the crest of the ilium, 
the tuber of the ischium and, somewhat covered by muscle aponeu- 
rosis, the greater trochanter of the femur. The sacrum and the 
coccyx are also landmarks, but the sacrotuberous ligament is so 
heavily covered by muscle that it can only be made out by deep 
palpation. 
The skin is thick and tough, while the subcutaneous fatty layer, 
except for its thickness, is as routine. A bursal sac should be noted 
between the skin and the tuber of the ischium. After removing the 
skin and fatty layers the powerful muscles, covered by their strong 
deep fascia, may be outlined. 
Gluteus Maximus Muscle 
The gluteus maximus muscle arises from the posterior fifth of the 
crest of the ilium and from the sides of the sacrum and coccyx. 
Running in parallel strands downward and lateralward, its upper 
fibers insert into the lateral deep fascia of the thigh and its lower 
fibers into the lateral crest of the linea aspera, upper fifth. It is a 
thick, powerful muscle, its lower fibers covering the sacrotuberous 
ligament, thereby extending into the perineum. The aponeurosis 
runs over the greater trochanter of the femur, a bursa lying between 
these two structures. This muscle acts as an external rotator and 
also as an extensor of the thigh. 
The gluteus maximus should be cut across about its middle and its 
fibers turned back towards their origin and insertion. By this dis- 
section the great majority of gluteal structures are exposed to view. 
Ischiatic, or Sciatic, Nerve 
The large flat nerve cord just lateral to the tuber of the ischium is 
the ischiatic, or sciatic, nerve, which is the main continuation of the 
lower extremity nerve plexus. The lower extremity plexus is com- 
posed of spinal segmental nerves from the fourth and fifth lumbar, 
and the first, second, and third sacral intervertebral foramina. 
Processes of the sympathetic nervous system join the lower ex- 114 
REGIONAL ANATOMY 
tremity plexus, just as has been previously detailed in connection 
with the upper extremity nerve plexus. These sympathetic nerves 
control the involuntary activities of the lower extremity and make 
the same segmental connections as the peripheral nerves proper. 
Many of the sympathetic processes travel along the fascial compart- 
ments of the arteries, while the bulk join the lower extremity plexus 
en route towards their terminations. 
In the sitting posture, in spite of its depth, the sciatic nerve is 
subject to pressure, as is popularly recognized in the " gone-to-sleep " 
feeling of the lower extremity. At one stage of development it is 
accompanied by the main artery and vein of the lower extremity, 
but presumably due to this exposed position these original vessels 
disappear, while the anastomosis in front becomes the main trunk. 
This sciatic nerve comes out of the lesser or true pelvis through the 
greater sciatic foramen. 
Internal Rotator Muscles 
The powerful gluteus medius muscle arises just below the crest of 
the ilium over the anterior four-fifths of the outer surface of the 
bone, and converges onto a tendon running downwards and back- 
wards to its insertion onto the greater trochanter of the femur. The 
gluteus minimus arises from the outer surface of the hip bone under 
the gluteus medius and, following approximately the same course, 
inserts into a separate facet of the greater trochanter. The anterior 
fibers of these muscles have a special function as internal rotators of 
the thigh. The action of the three gluteal muscles acting together 
would be negative as regards rotation, but on account of their 
origins being above their insertions they would cause abduction of 
the thigh. 
These muscles should be cleared and examined. 
Special External Rotators 
The pyriformis arises from the ventral surface of the sacrum, 
enters the gluteal space through the greater sciatic foramen, and in 
common with the other muscles of this group runs in back of the hip 
joint to its attachment to the greater trochanter of the femur (pyri- 
formis - pyramid-shaped). 
The smaller vessels and nerves for the regional supply coming out THE LOWER EXTREMITY 
115 
above the pyriformis are known as the gluteal, whereas those below 
are the sciatic. 
The obturator internus arises on the inside of the obturator fora- 
men, leaves the perineum through the lesser sciatic foramen, and 
crosses deep to the sciatic nerve to its attachment to the femur. Two 
little muscle bellies attaching to the upper and lower border of this 
tendon are known as the gemelli, or twin muscles. 
The obturator externus arises on the outside of the obturator fora- 
men and runs closely applied to the back of the hip joint-capsule to 
its insertion. 
The quadratus femoris arises from the lateral surface of the tuber 
of the ischium, is approximately square, as its name implies, and 
inserts onto the femur. These four muscles running in back of the 
hip joint to their insertion into the femur necessarily act as external 
rotators. 
These muscles should be cleared and examined. 
Thigh Region (Regio Femoralis) 
The femur is heavily covered by muscles, not quite so thick, to be 
sure, over its anterior and lateral surfaces, but still liberally covered. 
At the upper end the greater trochanter of the femur is covered only 
by the aponeurosis of the gluteus maximus muscle and hence is prac- 
tically subcutaneous. At the lower end of the femur, where the 
muscle bellies give way to tendon, the lateral and medial condyles 
are readily palpable. The skin follows the general rule of being 
thicker over the lateral exposed sides and thinner over the medial 
more protected parts. It is especially thin over the popliteal or back 
of the knee region. 
The skin is to be dissected off to below the knee. 
Subcutaneous Fatty Layer 
The subcutaneous areolar layer is of average thickness and con- 
tains the routine cutaneous arteries, veins, and nerves. The super- 
ficial venous system is represented by one main trunk, which runs up 
the medial side of the leg and thigh to a point about one inch below 
the inguinal ligament, and about one inch lateral to the pubic spine. 
This large saphenous vein receives smaller branches from various 
directions, and dips down through the saphenous opening in the deep 116 
REGIONAL ANATOMY 
fascia to join the femoral vein. The corresponding small saphenous 
vein will later on be noted to dip through the deep fascia in back of 
the knee. A series of lymph vessels, as is usual, run in close associa- 
tion with the large saphenous vein. The lymphatic glands of these 
vessels are practically all grouped about the saphenous opening, 
which explains the enlargement of this region found in association 
with infection or malignant growths of the lower extremity. Over 
the region in the neighborhood of the inguinal ligament lie a group 
of lymphatic glands, which belong more directly to the lymphatic 
vessels of the external genitalia. Anatomically the characteristic 
unusual feature of these groups is the fact that they lie chiefly in 
the subcutaneous fatty layer. As a result, when they are unable to 
handle the infection and break down, the pus pocket lies much nearer 
the surface than is usual in lymphatic gland abscesses of other parts 
of the body. 
This layer should be dissected and then removed. 
Deep Fascia 
The deep fascia, as is usual, encircles the thigh and eventually 
attaches above around the pelvic bones and below to the bones in 
the neighborhood of the knee. It is, as would be anticipated, very 
much more powerful over the lateral side of the thigh than over the 
medial side. Fact is, on the lateral side it is the strongest deep 
fascia of the body and receives the special name of fascia lata (lata = 
broad). This fascia lata may be considered in part as an aponeu- 
rosis, inasmuch as part of the gluteus maximus muscle attaches to it. 
A muscle known as the tensor fascia latse arises near the anterior 
superior spine of the iliac crest and, running straight down between 
two folds, inserts this fascia. The deep fascia further sends in inter- 
groupal septa between the muscle groups which attach to the linea 
aspera, marking off the compartments of the thigh. 
Adductors of Thigh 
The adductor muscle group arises from the body of the pubic bone 
and the rami of the pubis and ischium, and runs downward and 
lateralward to its insertion into the linea aspera of the femur. 
Owing to the fact that the linea aspera is on the back surface of the 
femur, this group also possesses some power as external rotators. THE LOWER EXTREMITY 
117 
The pectineus arises from the top of the superior ramus of the 
pubis and, following a downward and lateral course, inserts into the 
upper sixth of the linea aspera (pectineus = comb-like). 
The adductor longus arises from the body of the pubis and, paral- 
lelling the pectineus, inserts into the linea aspera below this muscle, 
extending somewhat below the middle of the thigh. 
The adductor brevis arises from the body of the pubis and, running 
on a deeper plane, inserts into the linea aspera behind the mid- 
sections of the two preceding muscles. 
The adductor magnus arises over a large area of the rami of the 
deep fascia 
intergroupal 
septa- 
extensor of 
leg group 
adductor of 
thigh group- 
intergroupal 
septa - 
intergroupal 
septa 
intermuscular 
septa - 
flexor of 
leg group 
Fig. 31.-Fascial compartments at middle of Thigh. 
pubis and ischial bones, lies on a deeper plane, and is a large, power- 
ful muscle. It follows the same general course and inserts into the 
linea aspera throughout the lower two-thirds, extending down to the 
medial condyle. 
The gracilis is a strap-like muscle, arises from the subcutaneous 
edge of the rami of the pubis and ischium, and inserts into the medial 
front surface of the tibia just below the knee. 
Nerve Supply 
The nerve supply of this group comes from the lower extremity 
plexus, but does not join the sciatic trunk. The nerve takes a 118 
REGIONAL ANATOMY 
separate divergent course through the obturator foramen, hence is 
called the obturator nerve. The arterial supply is from branches 
of the profunda femoris, as will be detailed later on. 
This group of muscles and their nerve supply should be cleared. 
Flexors and Extensors of Thigh 
The large- tendon of the powerful iliopsoas muscle comes out of 
the abdominal cavity over the iliac part of the hip bone, medial to 
its anterior superior spine, runs in front of the capsule of the hip 
joint and inserts into the lesser trochanter of the femur. This point 
lies to the back and medial side of the upper part of the femur, so 
that when this tendon is pulled upon, flexion of the thigh will be 
produced, plus a certain amount of external rotation. The psoas 
portion arises from the sides of the bodies of the lumbar vertebrae, 
whereas the iliac portion arises from the inside of the ilium and joins 
the psoas tendon, the iliac muscle belly being readily demonstrable 
in the upper part of the thigh. This is a strong, powerful muscle, 
but its origin can not be seen until after the abdominal cavity has 
been opened. Other muscles of the front compartment, arising from 
the pelvis and running into the thigh, incidentally act as accessory 
flexors of the thigh. 
The main extensor of the thigh is the gluteus maximus muscle, as 
previously noted. Other muscles of the back compartment incident- 
ally act as accessory extensers. 
Extensors of Leg 
The muscles of the group in the front compartment of the thigh 
are chiefly extensors of the leg. The main muscle, considered as a 
whole, is known as the quadriceps or four-headed extensor. The 
straight central portion, the rectus femoris, arises from the anterior 
inferior spine of the ilium and joins the common tendon. On each 
side, arising from ridges of the linea aspera, are large muscle bellies, 
the vastus lateralis and medialis. The vastus intermedins division 
arises from the greater part of the front of the femur and inserts 
into the common tendon. These four bellies come together into a 
common tendon, which, passing in front of the knee, eventually is 
continued onto the tibia, raising up the tibial tuberosity. A piece 
of porous bone, the patella, or knee-cap, is developed in this tendon. THE LOWER EXTREMITY 
119 
Bones developed in tendons are technically known as sesamoid bones 
(sesamoid = like a seed). The patella serves to hold the tendon 
away from the joint and allows the tendon to work at less mechani- 
cal disadvantage. Some of the quadriceps tendon passes over the 
patella, but the bulk inserts into the patella, and a new portion, 
known as the ligamentum patella, runs to the tibial tuberosity. The 
main function of this group is to extend the leg, which, as a matter 
of common knowledge, works on a short-lever, rapid-action principle. 
Inasmuch as the rectus division arises from the pelvis, this muscle 
group has also some power as a flexor of the thigh. 
The sartorius is a narrow strap-like muscle running from the ante- 
rior superior spine of the ilium diagonally, medially, and downwards 
to its insertion on the medial front surface of the upper part of the 
tibia (sartor = tailor). Inasmuch as it runs from the pelvis through 
the femur to the leg, its action is complicated and varies with the 
circumstances. 
Nerve Supply 
This group of muscles, with the overlying skin and underlying 
bone, receives its nerve supply from the lower extremity nerve 
plexus. The nerve takes a separate divergent short cut over the 
iliopsoas muscle to the area. It was formerly named the anterior 
crural, a misnomer, as crural means leg, in contradistinction to 
thigh. It is now known as the femoral nerve. The blood supply 
from the profunda femoris will be considered in a special paragraph. 
The extensor group of muscles and its nerve supply should be 
cleared. 
Flexors of Leg 
The muscles of the group in the posterior compartment of the 
thigh are chiefly flexors of the leg. The three muscles arise from a 
common tendon on the ischial tuber and, running past the knee, 
insert into the tibia and fibula. The biceps femoris diverges to the 
lateral side and the lower end, reinforced by a short head arising 
from the linea aspera, inserts into the head of the fibula. The semi- 
membranosus runs to the medial side and attaches in back of the 
tibia just below the knee. The semitendinosus runs in close proxim- 
ity to the semimembranosus, but continues to the front medial sur- 
face of the tibia. The insertions of the sartorius, gracilis, and semi- 
tendinosus are grouped on the surface of the tibia. Inasmuch as 
these muscles pass the knee along its posterior medial surface, they 120 
REGIONAL ANATOMY 
act as flexors and also as accessory rotators of the leg. While the 
biceps, semitendinosus, and semimembranosus are flexors of the 
leg, it should be noted that they are also extensors of the thigh. 
Further, inasmuch as they arise from the pelvis, they have the power 
of moving the pelvis on the thigh or the thigh on the pelvis, as the 
special requirements may call for. The sciatic nerve runs deep 
under these muscles and, incidentally, sends off the branches for 
the area. 
Just as in the case of the biceps muscle of the arm, there are many 
complicated muscles in the thigh which pass from the pelvis through 
the thigh to the leg. Embryologically, the muscles are much sim- 
pler, passing only from the pelvis to the thigh and from the thigh to 
the leg. The complicated muscles are the rectus femoris, sartorius, 
gracilis, semitendinosus, semimembranosus, and the biceps. 
This flexor muscle group and its nerve supply should be cleared. 
Fossa Poplitea 
The popliteal pit is the name given to the area in back of the knee. 
It is an important region, because the main vessels and nerves of the 
leg take this protected channel in their course past the knee. The 
small saphenous vein of the superficial venous system pierces the 
deep fascia about the center of the region en route to the popliteal 
vein. The divergent tendons of the biceps on the lateral side and 
the semimembranosus and semitendinosus on the medial side form an 
upper triangle. The converging heads of the gastrocnemius muscle 
of the leg form a lower triangle (gastro = belly; nemius = calf). 
These two triangles considered together make up a diamond-shaped 
space, which is covered over by strong, deep fascia. Just under the 
fascia lie the two terminal subdivisions of the sciatic nerve. The 
popliteal artery lies against the bone, while the popliteal vein lies 
on its superficial surface. The further details of this area will be 
considered in connection with the vessels and with the leg area. 
The deep fascia should be split longitudinally, and the major struc- 
tures cleared and identified. 
Blood Supply of Thigh 
Originally there were five pairs of segmental arteries, veins, and 
nerves, corresponding to the five segments of the lower extremity THE LOWER EXTREMITY 
121 
as represented in the adult by the five toes. In the next stage of 
embryonic development the main artery and vein accompany the 
sciatic nerve. Presumably due to their exposure to pressure, the 
main arterial and venous trunks become an anastomosis, while the 
original anastomosis down the front protected area of the thigh 
become the main trunk. This vessel, after it passes under the 
inguinal ligament of Poupart, is known as the femoral artery, the 
femoral vein lying along its medial side. In this area the vessels 
lie close to the surface in Scarpa's triangle. Scarpa's triangle is 
bounded by the inguinal ligament and by the sartorius and adductor 
longus muscles. The vessels next dip under the sartorius muscle, 
following it as a guide. At about the middle of Scarpa's triangle 
the branch is given off which is to subdivide to supply the whole 
thigh region, the profunda femoris. The femoral artery continues 
through Hunter's canal, under the sartorius muscle, into the pro- 
tected popliteal space. As per routine, lateral and medial articular 
anastomosing branches are given off above and below the knee, while 
a single branch enters the knee joint. 
The profunda femoris, as the name implies, works down close to 
the medial side of the femur. It sends off at progressively lower 
levels four paired branches, which encircle the femur, hence known 
as the circumflex or, inasmuch as they perforate the intergroupal 
fascial septa, as the perforating arteries. These vessels supply the 
whole thigh, and anastomose above with the sciatic and gluteal 
vessels. The deep venous system corresponds to the arterial, with 
the usual exception that all the smaller arteries have paired venae 
comitantes. The great saphenous vein of the superficial venous sys- 
tem has been considered with the fatty layer dissection. 
The vessels should be cleared. 
Hip Joint (Articulatio Coxae) 
Dissect off all the muscles holding the femur to the trunk, taking 
care not to open the capsule of the hip-joint. The head of the femur 
will remain firmly in the acetabulum, and in this large joint will even 
resist considerable traction. This is a typical factor in every joint 
and is due to the suction action of the vacuum. In a midrange posi- 
tion the capsular ligament is necessarily nowhere really tense, so that 
in such a position the capsular ligament does not hold the bones 
together. The muscles, however, more especially if they were 122 
REGIONAL ANATOMY 
slightly or markedly contracted, would hold the bones in firm 
apposition. 
The extra thickened, powerful front portion of the capsular liga- 
ment may be brought into relief by manipulation. The thickened 
portion arises from the anterior inferior spine of the ilium and inserts 
into the anterior intertrochanteric line. This iliofemoral ligament, 
on account of its shape, was formerly known as the inverted Y liga- 
ment. When the normal body is erect the center of gravity falls just 
behind the center of the hip joint, and consequently this ligament 
takes the strain off the muscles of the thigh in standing. 
The capsular ligament may then be cut, encircling the neck of the 
femur. A ligamentum teres will be noted, attaching the head of the 
femur to the acetabulum (teres = round). This usually contains 
fibrous tissue of considerable strength, which resists excessive range 
of motion, perhaps the most important of which is its resistance to 
extreme abduction. Another function consists in carrying an anas- 
tomosing blood supply to the head of the femur. This ligament 
should be cut across and the limb removed. The acetabular socket 
should be noted to be built out by a cartilaginous rim and to have 
a depressed area for the ligamentum teres. Towards the obturator 
foramen a small opening for vessels to the ligamentum teres should 
be noted. 
Dislocation 
The depth of the socket would make dislocation accidents seem 
very unusual. The so-called congenital dislocations of the hip are 
explicable on the ground of relative shallowness of the acetabulum 
in early childhood. It is probable that some of these dislocations 
occur during the process of birth. The iliofemoral ligament is prac- 
tically never torn in dislocations and hence is used as a lever to pry 
the head back into the socket. Dislocation, just as in the case of 
the shoulder joint, is more readily produced in extreme abduction. 
On account of the strength of the muscles and ligaments a pull on 
the leg, no matter how strong or sudden, would never put a serious 
strain on the lower extremity nerve plexus. "Pulling the leg" is 
anatomically, at any rate, less dangerous than pulling the arm. 
Practical 
An infection of the hip joint, unless the pain sense is destroyed, 
results in contraction of all the muscles controlling the hip, the THE LOWER EXTREMITY 
123 
position assumed by the thigh depending upon the relative strength 
of the muscle groups. The characteristic position assumed under 
these circumstances is flexion, external rotation, and adduction, due 
to the fact that those groups are markedly stronger than their oppo- 
nents. Fractures of the neck of the femur are more common in the 
brittle bone of old age. They usually occur following a fall on the 
greater trochanter of the femur. The position assumed by the leg 
is very similar to the picture of infection of the hip, with the addi- 
tional symptom of shortening, as the muscle contraction causes an 
overriding of the fragments. The seriousness of this injury is due 
more to the general lack of resistance and bone-building power than 
to the accident itself. 
LEG AND FOOT (CRUS ET PES) 
Tibia and Fibula 
The leg is, anatomically speaking, that part of the lower extremity 
which extends from the knee to the ankle. The large medial bone 
has a broad subcutaneous surface, carries the bulk of the weight of 
the body, and is known as the tibia or, popularly, the shin bone. 
The fibula, as the diminutive "ula" ending indicates, is the smaller 
lateral bone, which, except for its upper and lower portions, is cov- 
ered by muscles. At the lower end on each side of the ankle joint 
the rounded projections extending down are known as the malleoli, 
medial and lateral. Although given the special name malleoli, they 
are of the type of projections generally known as condyles. Inas- 
much as the term condyles, medial and lateral, is applied to the 
widened-out upper part of the tibia at the knee joint, a repetition of 
the same term at the lower end would lead to confusion. Between 
the opposing surfaces of the tibia and fibula runs an interosseous 
membrane, which, as would be anticipated, raises up ridges of attach- 
ment. The intergroupal muscular septa raise up two additional 
ridges on the fibula, as will be detailed in the consideration of the 
fascias of the leg. These bones are typical long bones, both in devel- 
opment and structure. 124 
REGIONAL ANATOMY 
medial condyle- 
lateral condyle 
tibial tuberosity 
interosseous membrane 
medial malleolus. 
■lateral malleolus 
Fig, 32.-Left Tibia and Fibula, anterior surface THE LOWER EXTREMITY 
125 
Tarsal, Metatarsal, and Phalangeal Bones 
Inasmuch as most of the muscles of the leg extend into the foot, 
the tarsal, metatarsal, and phalangeal bones may well be considered 
at this time. The tarsal bones are held firmly together by dorsal, 
interosseous, and plantar ligaments. The bone held between the 
malleoli of the tibia and fibula, and with them making up the ankle 
joint, is known as the talus or astragalus. The bone extending back 
from the under surface of the talus into the heel is known as the 
calcaneus or o.s calcis. Continuing the medial column of the foot 
forwards from the talus are found the navicular (0. T. scaphoid) and 
the three cuneiform or wedge-shaped bones. Continuing the lateral 
column of the foot forward from the calcaneus is found the cuboid 
bone. Running forward from the cubocuneiform irregular line are 
the five metatarsal bones. Then follow the phalanges, three in num- 
ber for every toe, except the great toe, which has only two. The 
tarsal, metatarsal, and phalangeal bones can be readily palpated, 
except on the surface-that is, the sole of the foot. 
Developmental Rotation 
The sole of the foot obviously corresponds to the palm of the 
hand, while the top of the foot corresponds to the back of the hand. 
In this fully developed anatomic position the big toe side lies 
medially, while the corresponding thumb side lies laterally. During 
one stage of development both the big toe side of the foot and the 
thumb side of the hand are the ventral surfaces. A secondary rota- 
tion inwardly of ninety degrees carries the big toe side of the foot, 
leg and thigh towards the midline of the body, while a rotation 
outwardly of ninety degrees carries the thumb side of the hand, 
forearm and arm away from the midline to its adult position. 
Anatomically the hand is always considered in the supine position, 
that is with the thumb lateralward. The top of the foot has been 
given the misnomer dorsum, whereas it is in reality the superior or 
even the ventral surface of the foot. This anatomic nomenclature 
variation, however, is worthy of being retained as it emphasizes the 
developmental changes and brings out the comparisons. The ven- 
tral compartments of the arm, forearm, and hand in the fully devel- 
oped status contain the flexor muscles, while as a result of rotation, 126 
REGIONAL ANATOMY 
_ calcaneus 
__ talus 
tarsals 
^navicular 
cuboid 
-cuneiforms 
metatarsals - 
phalanges . 
Fig. 33.-Right Foot (pes) superior or dorsal surface. THE LOWER EXTREMITY 
127 
the ventral compartments of the thigh, leg, and foot contain the 
extensor muscles. 
Skin 
The skin is fairly equally exposed and consequently of approxi- 
mately equally tough texture on all sides of the leg. On the dorsum 
of the foot the skin is delicate, while at the ends of the toes the nails 
are to be noted. On the plantar surface of the foot the skin is as 
would be anticipated especially thick and tough. The epidermis 
of the plantar surface is especially thickened, more markedly so 
over the bony prominences. Callous forms in this layer over the 
bony projections, and if the pressure is kept up more or less con- 
tinuously, the resulting painful calluses are popularly known as 
corns. Neither hair nor sebaceous glands are present over the sole 
of the foot. 
The skin should be dissected off from the leg and foot. 
Subcutaneous Fatty Layer 
The subcutaneous fatty layer is not characteristic over the leg or 
dorsal surface of the foot, but is greatly toughened over the central 
compartment of the sole, as would be expected from analogy with 
the palm. Cutaneous arteries, veins, and nerves branch from the 
regional trunks. Considerable tactile sense, although ordinarily 
not trained, lies latent in the pulp of the toes, as the relatively large 
size of the nerves bear witness. The superficial venous system on 
the top or dorsum of the foot runs off into two main trunks, the 
great and the small saphenous. The greater crosses the lower end 
of the tibia and takes the posterior edge of the tibia as its guide to 
beyond the knee. The lesser saphenous runs in back of the fibular 
malleolus, progresses towards the midline of the leg, and terminates 
in the popliteal vein. 
This layer should be dissected off. 
Deep Fascia 
The deep fascia arising at one subcutaneous border of the tibia, 
encircles the leg, and attaches to the other border of the same bone. 
Over the fibula the fascia sends two intergroupal septa down to the 
bone, separating off a small fibular or peroneal compartment. The 
leg is therefore considered as having four compartments, a tibial 128 
REGIONAL ANATOMY 
and a fibular, and, separated by the interosseous membrane, an 
anterior and a posterior tibio-fibular compartment. Over the lower 
part of the front compartment of the leg, where the muscle bellies 
give way to tendon, the thickened portion of the deep fascia is 
called the transverse crural ligament. The thickened portion across 
the dorsum of the foot is known as the cruciate or cross ligament. 
On each side bridging from the malleoli to the calcaneus the thick- 
tibial 
compartment 
anterior tibio- 
fibular 
compartment 
intergroupal 
septa 
flbular 
compartment 
intermuscular 
sept 
deep fascia 
posterior tibio- 
fibular 
compartment 
Fig. 34.-Fascial compartments at middle of Leg (crus) 
ened portions of the deep fascia might be identified as the lateral 
and medial crural ligaments. (B. N. A. retinaculum musculorum 
peroneorum sup. et inf.-ligamentum laciniatum.) Over the cen- 
tral compartment of the sole of the foot the deep fascia or plantar 
aponeurosis is especially thick and tough. When pus gathers in the 
sole of the foot the strong fascias prevent much swelling of the 
region, while the loose tissues on the back of the foot swell markedly. 
Tenderness on deep pressure makes clear the diagnosis and calls 
for an incision through the deep fascia. The deep fascia serves to 
protect the more vulnerable deeper structure. The flexor tendons 
are held down by the specialized deep fascia tubes, which make up 
the synovially lined flexor tendon sheaths (ligamenta vaginalia). THE LOWER EXTREMITY 
129 
Anterior Tibiofibular Compartment and Dorsum of Foot 
In the anterior tibiofibular compartment lie three main muscles, 
named the extensor digitorum longus, the extensor hallucis longus 
and the tibialis anterior. The front of the leg corresponds anatomic- 
ally to the back of the forearm, as during development, as previously 
detailed, a rotation of a half-circle takes place. The extensor hal- 
lucis longns arises from the lateral surface of the tibia in front of 
the interosseous membrane and inserts into the second or terminal 
phalanx of the big toe (hallux = great toe). The extensor digitorum 
longus arises mainly from the fibula, separates into four tendons 
near the ankle, terminating on the second and eventually third 
phalanges of the toes. A small slip from this muscle, known as the 
peroneus tertius inserts into the base of the fifth metatarsal. The 
tibialis anterior arises mainly from the tibia and inserts into the 
medial side of the first cuneiform. This muscle, therefore, inverts 
the foot across the tarsal joints. These muscles should be noted to 
arise not only from the bone and interosseous membrane, but also 
from the deep fascias of the area as is a widespread occurrence in 
muscle origins. 
The small muscle arising over an area just in front of the mal- 
leolus of the fibula is the extensor digitorum brevis. This muscle 
sends a tendon to all the toes except ordinarily the little toe. The 
part of this muscle running to the dorsum of the great toe is called 
the extensor hallucis brevis. 
The deep fascia should be split open in order to dissect out these 
muscles, noting particularly the thickened portion in front of the 
ankle region. These ligaments consist of a transverse portion be- 
tween the tibia and fibula, and a diagonal portion over the dorsum 
of the foot. 
Tibial Compartment 
The tibial compartment is subcutaneous, except in its uppermost 
part, where the tendons of the cpiadriceps and of the sartorius, 
gracilis and semitendinosus insert. Various bone diseases tend to 
localize in the tibia following minor traumata on account of its ex- 
pt sed position without muscle covering. 130 
REGIONAL ANATOMY 
Fibular Compartment 
The fibular compartment contains two muscles, which arise from 
the fibula and septal fascias. They run in back of the fibular mal- 
leolus under the lateral crural ligament, then go forward and down- 
ward to the lateral margin of the foot. The peroneus brevis attaches 
to the lateral side of the base of the fifth metatarsal. The peroneus 
longus runs around the lateral border of the foot into the sole and 
spreads out at its insertion into the first cuneiform and base of the 
metatarsal bones. These peroneus muscles act as everters of the 
foot. 
These muscles should be cleared to the lateral margin of the 
foot. 
Posterior Tibiofibular Compartment 
The posterior tibiofibular compartment contains two groups of 
muscles, well separated by an intergroupal fascial septum. The 
superficial group is really a triceps muscle, for the muscleheads 
come together into the common Achilles or calcanean tendon. The 
lateral and medial gastrocnemii heads arise from the back surfaces 
of the lateral and medial condyles of the femur respectively. The 
soleus head lies underneath the gastrocnemii, arises from the pos- 
terior surface of the tibia and fibula throughout their upper halves, 
and joins the common tendon in the lower third of the leg. The 
Achilles common tendon inserts into the posterior upper surface of 
the calcaneus, therefore, the essential action of the muscle is flexion 
of the foot. 
The deep group is made up of a flexor digitorum longus and a 
flexor hallucis longus, arising from the tibia and fibula, respectively, 
and running under the medial crural ligament into the sole of the 
foot. In the sole of the foot the flexor hallucis longus tendon sends 
a slip to join the flexor digitorum longus tendon, consequently the 
flexor hallucis longus acts a flexor of all the toes. The course of 
these muscles to the terminal phalanges of the toes in special flexor 
sheaths is the same as the deep flexors in the palm of the hand. 
The tibialis posterior arises from both bones and the interosseous 
membrane, and runs to a tubercle at the medial inferior surface of 
the navicular bone. It, therefore, acts as an inverter of the foot. 
These muscles should be cleared to the sole of the foot. THE LOWER EXTREMITY 
131 
Sole of the Foot 
Three muscles arise near the heel and run forward in the super- 
ficial layer in special fascial compartments. In the center compart- 
ment lies the flexor digitorum brevis, which, dividing for the four 
toes, enters the flexor tendon sheaths. Just as in the palm, each 
superficial tendon splits to allow the deep flexor to pass through 
and inserts into the sides of the second phalanx. The lateral com- 
partment contains the abductor digiti quinti, which runs to the base 
of the first phalanx of the little toe. The medial compartment con- 
tains the abductor hallucis, which runs to the base of the first 
phalanx of the big toe. 
The second layer of the sole is made up of the flexor tendons in 
their course to the toes. The flexor longus digitorum tendon is 
joined by the quadratus plantse muscle from the calcaneus and by 
lumbricle muscles arising from the first phalanx of the four outer 
toes. These muscles tend to steady the main tendon in its move- 
ments and to keep it pulling in a proper line. 
The third layer is composed of intrinsic small muscles of the first 
and fifth toes. These small muscles are an adductor hallucis, a 
flexor hallucis brevis, and a flexor digiti quinti brevis. Between the 
metacarpals lie the interossei muscles, the dorsal group acting as 
abductors in relation to the midline of the foot, the plantar group 
as adductors. 
The muscles in the sole of the foot should be dissected out, layer 
by layer. The tendon of the peroneus longus muscle should be 
traced through its synovial sheath to its spread out insertion under 
the cuneiform and base of the first metatarsal bone. 
Vessel Supply 
The popliteal artery divides just below the knee into the anterior 
and posterior tibial branches. The anterior tibial artery runs for- 
ward through the interosseous membrane, goes deep through the 
anterior tibiofibular compartment, and when the muscle bellies give 
way to tendon, becomes superficial over the dorsum of the foot, 
where it receives the regional name dorsalis pedis. The posterior 
tibial artery sends off a large peroneal or fibular branch, and con- 
tinues down with the deep muscle group, eventually following the 
muscle tendons into the sole of the foot. It is, as would be antici- 132 
REGIONAL ANATOMY 
pated on account of the muscle bulk to be supplied, much larger 
than the anterior tibial. In the sole of the foot the posterior tibial 
artery divides into medial and lateral plantar branches, which ves- 
sels run along the intergroupal septa of the first layer of the sole. 
Main vessels 
gluteal- 
Branches 
sciatic - 
profunda femoris 
femoral - 
circumflex and 
perforating 
popliteal 
superior articular 
inferior articular 
anterior tibial 
posterior tibial 
peroneal 
dorsalis pedis 
medial plantar 
lateral plantar 
plantar arches 
digital A 
digital 
Fig. 35.-Diagram of Arteries of lower extremity. (Dotted lines are parts in 
posterior compartments.) 
These plantar arteries make small superficial and deep plantar 
arches with digital branches, superficial and deep to the flexor ten- 
dons. As usual about a joint, a free anastomosis is found at the 
ankle, in simplest terminology to be known as the superior and in- 
ferior articular anastomosing branches. THE LOWER EXTREMITY 
133 
Nerve Supply 
The entire nerve supply below the knee is carried by the sciatic 
nerve, with the exception of some minor cutaneous branches follow- 
ing the course of the great saphenous vein. The common peroneal 
Main Trunks 
Branches 
lumbar 
sacral 
gluteal muscles 
adductor muscles 
extensor muscles 
sciatic - 
flexor muscles 
common peroneal 
- flexor muscles in leg 
- peroneal muscles 
extensor muscles in leg 
dorsalis pedis 
lateral plantar 
medial plantar 
digital 
digital 
Fig. 36.-Diagram of Nerves of lower extremity. (Dotted lines are parts in 
posterior compartments.) 
nerve turns around the upper end of the fibula and, after supplying 
the peroneal muscles, enters the anterior tibiofibular compartment. 
It then joins the anterior tibial artery in its further course, and REGIONAL ANATOMY 
134 
receives corresponding names. The anterior tibial vessels in their 
original embryonic position followed the course of this nerve, but 
later develop a more direct route through the interosseous mem- 
brane. The larger tibial nerve supplies the muscles in the posterior 
tibiofibular compartment, and in its further course follows the pos- 
terior tibial artery. Its main divisions in the foot are known as the 
lateral and medial plantar nerves. 
The vessels and nerves should be traced out. 
Knee Joint (Articulatio Genu) 
The knee joint is in general of the hinge type, but is modified 
inasmuch as near the end of the extension of the leg motion a 
limited but distinct internal rotation takes place. This rotation at 
the knee is referred to as the "locking" or "screw-home" device. 
Conversely, the first part of flexion of the leg starts with external 
rotation. The opposing surfaces of the femur and the tibia are 
arranged to accommodate this movement. 
Anatomically the knee is essentially of the hinge type, that is, it 
has a strong capsular ligament connecting tibia and femur, strongly 
reinforced by the extensor muscle groups in front and the flexor 
group in back. Inasmuch as the lateral motion can not be strongly 
resisted by muscular action, we would expect to find thickened 
lateral and medial portions of the capsular ligament, the cord-like 
fibular and tibial collateral ligaments. Two ligaments run from the 
upper posterior surface of the tibia to between the condyles of the 
femur, which are known because they cross each other, as the 
crucial ligaments of the knee. The anterior crucial ligament acts as 
a check against excessive flexion, while the posterior crucial re- 
sists overextension. These ligaments prevent the tongue in the 
middle of the tibia from slipping out of the shallow groove of the 
femur. Attached by their outer circumference to the inside of the 
capsular ligament and to midline bony points on the tibia are the 
lateral and medial menisci (meniscus = crescent) (O.T. semilunar 
cartilages). These menisci taper towards the center and have a 
large central opening. These interarticular fibrocartilages keep the 
bones riding steadier, but still the joint may functionate fairly well 
after their surgical removal. The synovial membrane extends for 
several inches up under the extensor tendon, consequently increased 
amount of fluid can readily be seen to bulge out on both sides of the THE LOWER EXTREMITY 
135 
tendon. The patella may be floated away from its contact with the 
femur by increased joint fluids. On account of its exposed position, 
the reaction to injury or disease can be especially well followed in 
this joint, that is the accumulation of blood, pus or extra amounts 
of synovial fluid. The continuation of the quadriceps extensor ten- 
don from the inferior surface of the patella to the tibial tuberosity 
is known as the ligamentum patellae. 
During about the last fifteen degrees of extension there is a 
slight rotation internally of the leg on the thigh, or if the leg is 
held firm, of external rotation of the thigh on the knee. The 
popliteus muscle arises from the lateral side of the lateral condyle 
of the femur and inserts into the upper half of the posterior surface 
of the tibia. This muscle may cause internal rotation of the leg or 
external rotation of the thigh, and is therefore an important factor 
in locking the knee. 
Pieces of the menisci altered by disease occasionally become de- 
tached, roll up into balls and lie as foreign bodies in the joint. They 
produce symptoms by becoming caught suddenly between the oppos- 
ing bone surfaces and wedging them apart. This is naturally asso- 
ciated with excruciating pain, is followed by increased joint fluid 
and what is popularly known as the symptoms of sprain. These 
bodies should be removed through surgical intervention. 
The exterior of the capsular ligament should be cleared and exam- 
ined with the aid of moving the bones. Then the front of the joint 
may be opened by carrying an incision down on each side of the 
quadriceps tendon. Finally the crucial ligaments and the remainder 
of the capsular ligament should be cut across and the opposing bony 
surfaces examined. 
Ankle Joint (Articulatio Talocruralis) 
The ankle is a typical hinge joint allowing for flexion and exten- 
sion of the foot. The convex upper surface of the talus is held firmly 
between the malleoli of the tibia and fibula. As no muscles directly 
protect the sides of this joint, the side portions of the capsular liga- 
ment are thickened and may be called the tibial and fibular col- 
lateral ligaments of the ankle. The B. N. A. terms are too compli- 
cated for our purposes, inasmuch as they give eight separate names 
for the component parts of these ligaments. Both of these collateral 136 
REGIONAL ANATOMY 
ligaments are triangular in shape, spreading out at their attachment 
to the tarsal bones. 
The distinction should be kept clearly in mind between the tibial 
and fibular collateral ligaments, which protect the joint, and the 
medial and lateral crural ligaments, which hold down the tendons. 
Falls on the foot in forced eversion produce a serious strain on the 
ligaments and bones, resulting in the characteristic Pott's fracture. 
This consists essentially in a tearing loose of the tibial collateral 
ligaments from the malleolus and a slanting fracture through the 
lower end of the fibula. When the everters of the foot, the peroneus 
longus and brevis, and the inverters, the tibialis anterior and pos- 
terior, act together, the net result is to hold the ankle joint steady. 
The ankle joint should be dissected. 
The range of motion between the tibia and fibula is distinctly 
limited, the poorly developed synovial cavities at both ends being 
rudimentary and often connecting with the knee and ankle joints 
respectively. The bones are held together by strong interosseous and 
capsular ligiments, especially powerful at the distal tibiofibular 
articulation (distal=furtherest from body). 
These joints should be cleared, manipulated and dissected. 
Tarsal Joints 
The tarsal bones are held together by very strong interosseous 
and plantar ligaments and by weaker dorsal ligaments. The motion 
between the various bones is limited in extent and of a sliding char- 
acter, but the sum total as brought out in eversion and inversion of 
the foot is large. The shape of the individual bones plus the great 
strength of the interosseous and plantar ligaments are obviously 
important factors in maintaining the arch of the foot. The deep 
fascia of the sole, running from the calcaneus to the ball of the foot, 
acts as a tie-beam and is another important factor. 
But these ligaments and fascias would yield to continuous pres- 
sure unless supported by the muscles of the leg, especially the 
peroneus longus, tibialis posterior, and the flexor digitorum mus- 
cles. So important is the support of these muscles that most ob- 
servers conceive the cause of the fallen arch to be the chronic 
putting of weight on the arch after these muscles are tired. The 
characteristic footprint shows the normal distribution of weight, 
the skin being thickened over the weight-bearing parts. The sag- THE LOWER EXTREMITY 
137 
ging arch is painful and in advanced cases the bony changes cause 
localized pressure, commonly resulting in painful corns. The de- 
struction of the arch causes a loss of spring in walking. The treat- 
ment of fallen arches consists essentially in strengthening the mus- 
cles, plus a properly fitting support under the instep when the 
muscles are unavoidably to be submitted to undue strain. The body 
compensates for the raised heel of modern civilized man's shoeware 
so that removal of the heel from the shoe may actually cause pain. 
No reasonable anatomic ground for this custom is apparent. 
The dorsal and interosseous ligaments should be cut, locating the 
joint interspaces by manipulation of the various bones. The bones 
will be held together and the arch maintained against considerable 
pressure by the very strong plantar ligaments. The tarsus contains 
a number of separate synovial cavities. 
Other Joints 
The tarsometatarsal joint, as in the hand analogy, allows but a 
limited range of motion being firmly held by dorsal, interosseous 
and plantar ligaments. This joint line is irregular, the second meta- 
tarsal being set in deeply between the first and third cuneiforms. 
The metatarsal phalang'eal joint allows free flexion and extension, 
and slight abduction and adduction. It is a shallow ball and socket 
type of joint. The interphalangeal joint of both sets are of the 
typical hinge type, the opposing surfaces having a slight tongue and 
groove arrangement. 
These joints should be dissected. CHAPTER X 
THE ABDOMEN 
PERINEUM 
The inferior wall of the abdominal cavity is known as the 
perineum. The perineum stretches across the inferior aperture of 
the lesser pelvis, often referred to in the female on account of the 
course of the child during the birth process as the outlet of the true 
pelvis. The bony landmarks of the perineum are: the crest of the 
pubic bones in front, the ischial tubers at the side, and the tip of the 
coccyx behind, outlining a somewhat diamond-shaped space. The 
rami of the pubis and ischium connect the tubers of the ischium with 
the body of the pubic bone, while the sacrotuberous ligaments con- 
nect the tubers of the ischium with the sacrum and coccyx. This 
region is divided as a matter of convenience by an imaginary line 
between the opposed tubers of the ischium into an anal and a uro- 
g'enital subdivision. The anus is the terminus of the intestinal tract, 
while the front subdivision surrounds the terminations of the 
urinary and genital tracts. 
Cloaca 
At a very early stage of embryonic development the urogenital 
and intestinal tubes exist through the perineum via a common tube, 
known as the cloaca. The cloaca persists functionally throughout 
life in the lower vertebrates including the birds, but is not found 
normally in the fully developed animals of the higher mammal 
groups. The lower vertebrates have a partial separation of the 
cloaca into an anal and urogenital division, which simply becomes 
complete in all except the lowest orders of the mammalia group. 
Pelvic Diaphragm (Diaphragma Pelvis) 
The pelvic diaphragm forms practically a complete partition 
across the lower part of the lesser or true pelvis, the region .below 
this diaphragm being the perineum, while the region above is the 
138 THE ABDOMEN 
139 
pelvic portion of the abdominal cavity. This diaphragm is made up 
by a thin muscle sheet, which is covered on each surface by fascias, 
known as the superior and inferior fascias of the pelvic diaphragm. 
The pair of muscles, known on account of their chief function as the 
levator ani, arise from the medial bony walls of the lesser pelvis 
along a straight line, which extends from the back of the symphysis 
pubis to the spine of the ischium. These muscles run medially, 
downward and backward, inserting into a median line tendon, which 
symphysis 
pubis 
urogenital 
region 
rami of pubis 
and ischium 
tuber of 
ischium 
anal region 
sacrotuberous 
ligament 
coccyx 
Fig. 37.-Bony-ligamentous boundaries of Perineum 
extends from the back of the symphysis pubis to the tip of the 
coccyx. This median line tendon of the levator ani muscles is per- 
forated in both sexes by the anal tubes, while anteriorly it is per- 
forated in the male by a combination urogenital tube, in the female 
by separate urinary and genital tubes. The part of the muscle sheet 
which arises from the spine of the ischium and inserts into the 
lateral margins of the coccyx is known as the coccygeus. 
This pelvic diaphragm deserves especial attention as an anatomic 
boundary, and further, as will be detailed later, on account of its 
practical importance in the female. 
Anal Region 
The tube leading down from the rectum, that is, the straight ter- 
minal portion of the intestinal tract, to the surface is known as the 140 
REGIONAL ANATOMY 
anal part of the rectum. The area of junction of the mucous mem- 
brane with the skin is the anus, which in both sexes is located about 
the center of the region. The walls of the anal portion of the 
rectum are held in firm apposition physiologically by the contraction 
of the internal sphincter ani muscle (sphincter = encircle). This 
muscle is made up of involuntary muscle tissue, which is, however, 
to a certain extent at least, under the control of the will. This 
sphincter will later be reconsidered in connection with the other 
sphincter muscles of the gastrointestinal canal. 
The skin over the anal region, being in a protected part, is rather 
thin, more especially so in between the folds of the buttocks. The 
fatty layer is especially liberal in amount and extends to the deep 
greater pelvis 
lesser pelvis 
- bony wall 
- fascias 
pelvic diaphragm 
perineum 
fascia of the levator muscle, technically the inferior fascia of the 
pelvic diaphragm. Towards the tubers of the ischium the fat is an 
inch and a quarter or more deep, and fills up a space loosely called 
the ischiorectal fossa. The lower part of the rectum, including its 
anal portion, is swung in the levator muscles, this fact being the 
justification for the name levator ani. 
The ischiorectal fossa is of great practical importance because if 
a skin abscess works down into this ditch it may find either one of 
two methods of exit. The abscess commonly breaks through the 
skin and heals without trouble. If the skin is abnormally resistant, 
however, and is not incised early, the abscess may break through 
the levator muscle with its fascias and through into the anal portion 
of the rectum. Fecal material may then pass from the anal portion 
of the rectum into this ischiorectal fossa, the tortuous passageways 
may become blocked, and a new abscess result. This abscess may 
again break through into the anal portion of the rectum, but 
eventually it tends to work its way out through the skin, producing THE ABDOMEN 
141 
the condition known as fistula in ano. (fistula = diminutive wrong 
tract). These fistula?, when neglected, tend to perpetuate them- 
selves, and even to become worse. The probability of the formation 
of a fistula in ano is said to be greater if the patient has a chronic 
cough, for then the levator ani muscles are semicontinuously in 
action. These fistulse can be cured by running a probe from the 
skin opening through the tract into the anal part of the rectum, 
dilating the sphincter ani muscles so as to minimize the number of 
muscle fibers cut, and dividing down to the probe. If the condition 
is an uncomplicated simple fistula in ano the wound tends to heal 
from the bottom up, the result being a complete cure. Fistulas in 
this region due to disease of the neighboring bones must be carefully 
distinguished from the simple fistula in ano, as these fistulas nat- 
urally differ materially both as to outlook and as to treatment. 
The gluteus maximus muscle arises as low as the tip of the 
coccyx and therefore overlaps the sacrotuberous ligament and this 
anal region considerably. A small muscle runs forward from the 
coccyx, encircles the anus, and inserts into a central tendinous 
point of the perineum. This muscles is known as the external 
sphincter ani, which, being made up of striated muscle fibers, is 
under the control of the will. A pair of superficial transverse 
perinei muscles run from the ischial tubers to the central tendinous 
point of the perineum. 
Vessels and Nerves 
The internal pudendal arteries and veins and pudendal nerves 
run around the posterior border of the pelvic diaphragm in their 
course from the pelvic portion of the abdominal cavity to the 
perineum (pudor = shame). They course from the lesser pelvis 
through the greater sciatic foramen into the gluteal region, and, 
turning around the spine of the ischium, run through the lesser 
sciatic foramen into the perineum. Each pudendal artery, vein, and 
nerve runs forward just below the pelvic diaphragm and along the 
medial surface of the bony wall of the lesser pelvis, eventually ter- 
minating in the external genitalia. Superficial and deep branches 
from the femoral vessels in the upper part of the thigh carry an 
anastomosing blood supply to the external genitalia, known as the 
external pudendal vessels, but no nerves exist corresponding to 142 
REGIONAL ANATOMY 
these secondarily developed vessels. As the internal pudendal ves- 
sels and the pudendal nerves traverse the anal region they send off 
the inferior hemorrhoidal branches to the anal part of the rectum 
(hemorrhoids = running of blood). 
Hemorrhoids, or popularly, piles, are dilated veins of the anal 
region, which will later be considered in their proper place, that is, 
in connection with the venous blood supply of the abdominal cavity. 
The skin is to be dissected off the anal region, cutting through at 
its junction with the anal mucous membrane. After the subcutan- 
eous fatty layer has been dissected out, the points noted in the 
description are readily to be made out. 
Male Urogenital Region 
Some fundamental considerations must first be taken up before 
the detail dissection of this combination urogenital region. In the 
first place the pelvic diaphragm, just as in the anal region, separates 
this part of the perineum from the pelvic portion of the abdominal 
cavity. The testicles, the essential male sexual glands, lie in a loose 
skin, fatty layer and fascial sac of the perineum, known as the 
scrotum. The testicles are developed in the abdominal cavity just 
below the kidneys and descend into the scrotum shortly before the 
birth of the child. The left testicle normally hangs somewhat lower 
than the right, which protects them against constant injury in walk- 
ing. The testicles maintain their original blood, lymph, and nerve 
supply from the abdominal cavity, and consequently may be con- 
sidered as belonging to that region and being only accidentally, as 
it were, in the perineum. The testicles will be considered in con- 
nection with the internal genitalia and also in connection with the 
course of the spermatic cord through the anterior abdominal wall. 
Penis 
The penis is made up of a root, that is the part attached to the 
bones and fascias of the urogenital subdivisions of the perineum, of 
a body, and of a glans. The combination urogenital tube, which 
traverses the penis from the root to the external meatus at the glans 
is known as the urethra. The essential structures of the body of the 
penis are three chambers, thickly walled by fibroelastic connective 
tissue and subdivided by numerous small septa, which are known THE ABDOMEN 
143 
as the corpora cavernosa. The spaces within the corpora cavernosa 
are continuous with the terminal branches of the internal pudendal 
arteries and veins, and, like the vessels, are lined by endothelium. 
An erection of the penis is produced by muscles, which contract down 
upon the outgoing veins, thus causing an increased amount of blood 
under high pressure in the cavernous spaces. The inferior of these 
cavernous bodies of the body of the penis, which is traversed by the 
orifice (meatus) 
glans 
corpus cavernosum 
penis 
body 
corpus cavernosum 
urethrae 
urethra 
. crus 
root 
.bulb 
Fig 39.-Diagram of Penis, skin and subcutaneous fatty layer removed. 
urethra, is known as the corpus cavernosum urethrae; the two supe- 
rior cavernous bodies, incompletely separated from each other in the 
midline, are known as the corpora cavernosa penis. The erectile 
tissue of the glans penis is directly continuous with the corpus caver- 
nosum urethra, the two corpora cavernosa penis ending bluntly at 
the base of the glans. Towards the root of the penis each corpus 
cavernosum penis deviates laterally and, becoming known as the crus 
of the penis, attaches to the rami of the pubis and ischium. The 144 
REGIONAL ANATOMY 
corpus cavernosum urethrae runs straight back in the median line, 
widens out at the root, and becomes known as the bulb of the penis. 
The muscle which has the power of causing an erection and covers 
each crus of the penis is known as the ischiocavernosum; that cover- 
ing the bulb, as the bulbocavernosum. The bulb of the penis attaches 
to the inferior fascia of the urogenital diaphragm, this attachment 
being the essential reason for the existence of this fascial membrane. 
This inferior fascia of the urogenital diaphragm attaches to the 
superior medial margins of the rami of the pubis and ischium, and 
blends at its posterior free border with the superior fascia of the 
urogenital diaphragm. On account of its shape, this fascia was for- 
merly known as the triangular ligament. The muscles between the 
fascias of the urogenital diaphragm are known as the sphincter of 
the membranous urethra and as the deep transverse perineal mus- 
cles. The membranous urethra pierces this inferior fascia of the 
urogenital diaphragm about its middle and enters the bulb of the 
penis. Above the urogenital diaphragm, as previously noted, the 
pelvic diaphragm separates the urogenital subdivision of the peri- 
neum from the pelvic portion of the abdominal cavity. 
Skin and Fatty Layer 
The skin over the symphysis pubis region is of moderate thick- 
ness and well covered by hair. The skin over the scrotum is very 
thin, when relaxed, and has as a characteristic feature, involuntary 
muscle fibers, which, when contracted, cause the skin to be puck- 
ered up into folds. The skin over the penis is extremely delicate, 
the free fold over the glans penis being known as the prepuce, or, 
popularly, foreskin. The opposing surfaces of the glans penis and 
the foreskin are covered by a mucous membrane, which statement 
may be checked up macroscopically by the characteristic pink color 
of these surfaces. 
The subcutaneous fatty layer is characterized by its extreme 
delicacy over the penis and scrotum. It contains the routine 
cutaneous vessels and nerves and a superficial venous system, the 
vessels being derived both from the external and internal pudendals. 
This blood and the corresponding lymph supply is of great practical 
importance in the understanding of infections or cancer of the glans 
penis. THE ABDOMEN 
145 
Whenever the foreskin is so injured by accident or disease as not 
to turn back freely, thus preventing cleansing of the recess, surgical 
intervention is indicated. The foreskin should be split open on its 
dorsal, that is, its upper surface, or for cosmetic reasons a complete 
circumcision should be performed. 
The skin and subcutaneous fatty layer should be dissected off. 
Deep Fascia 
The fairly strong deep fascia blends posteriorly with the base of 
the urogenital diaphragm, while laterally it is attached along the 
rami of the pubis and ischium, and to the sides of the body of the 
pubic bone up to the pubic crest. The part of this deep fascia en- 
closing the testicles and penis is thinner than the remainder. 
When urine with its admixture of pus escapes from the urethra 
in back of a stricture, it undermines this deep fascia and eventually 
follows the line of least resistance onto the anterior abdominal wall 
(stricture = contracted scar). On account of the attachment of this 
deep fascia, urine does not spread back into the anal region or onto 
the thighs, but tends to mount higher and higher over the belly 
wall. The deep fascia, wherever undermined, should be incised to 
allow the escape of the foul, infected urine, while to prevent its 
reaccumulation an opening should be made in back of the stricture 
through the perineum into the urethra and bladder. 
The suspensory and sling-like ligaments of the penis arise from 
the front surface of the pubic bones, giving support to the first part 
of the body of the penis. 
Dissection.-The deep fascia should be split in the median line and 
turned back to its attachments. The testicles with their cords 
should be turned back over the front of the abdominal wall for later 
consideration. Blunt dissection with the handle of the knife will 
readily demonstrate the crura and bulb of the penis, covered by 
their musculature, and on their deep surface the inferior fascia of 
the urogenital diaphragm. On one side this fascia should be split 
anteroposteriorly in order to demonstrate the terminal branches of 
the pudendal arteries, veins and nerves entering the root of the 
penis. Then a series of cross-sections of the penis should be made to 
demonstrate its interior structure. 146 
REGIONAL ANATOMY 
Female Anal Region 
The anal region is practically identical in both sexes. Due to the 
fact that the lesser pelvis is relatively larger in the female than in 
the male on account of the requirements of childbirth, the distance 
between the tubers of the ischium is relatively greater. 
Female Urogenital Region 
The parts of the urogenital region which immediately surround 
the exits of the urinary and genital tubes is known as the pudendum 
or vulva. The two pairs of lips surrounding the urogenital cleft 
are known as the labia majora and minora pudendi. Each major 
labium is covered on its external surface by tough skin with a 
liberal supply of hair, while each minor labium folds inside and is 
covered practically throughout by mucous membrane. Into this 
urogenital cleft, technically the rima pudendi, the urethra empties 
about its midpoint, while just posteriorly lies the entrance to the 
vagina (vagina = narrow canal). The vaginal canal leads upwards 
and backwards to the uterus or womb, which lies in the pelvic por- 
tion of the abdominal cavity. Across the vestibule of the vagina 
lies a septum, known as the hymen or popularly maidenhead, which 
normally has an opening in its center. Occasionally this septum is 
not perforated, which clinically leads to symptoms due to the dam- 
ming up of the menstrual or monthly flow in the upper vagina and 
uterus. 
Urogenital Diaphragm 
The urogenital diaphragm exists in the female, but, besides the 
opening for the urethra, possesses an extra opening for the vagina. 
Both the pelvic and urogenital diaphragms join into the side walls 
of the vagina. The vaginal portion of the levator muscles attach to 
the vagina about one inch inside of the pudendum, keeping above 
the urogenital diaphragm as would be anticipated. 
Clitoris 
The clitoris in the female is made up of erectile tissue, correspond- 
ing to the penis in the male, on a diminutive scale. Besides its 
materially smaller size, it is differentiated from the penis by the 
fact that the urethra does not traverse the clitoris. The body of the 
Clitoris THE ABDOMEN 
147 
clitoris lies between the upper part of the labia majora, is attached 
by ligaments to the symphysis pubis region and hangs downward. 
The two corpora cavernosa of the clitoris separate at the root, be- 
come known as the crura, and attach to the rami of the pubis and 
ischium. Each crus clitoris is covered by an ischiocavernosum mus- 
cle. The clitoris is tipped by a miniature glans, which is covered by 
a free fold of mucous membrane, known as the prepuce. The 
symphysis 
pubis 
clitoris 
ramus of 
pubis 
crus clitoris 
urethra 
vagina 
bulb of 
vestibule 
ramus of 
ischium 
urogenital 
diaphragm 
tuber ischium 
Fig. 40.-Female external genitalia, skin and subcutaneous fatty layer removed. 
divided bulb is separated by the vagina into two halves, which are 
known on account of their position as the bulbs of the vestibule. 
These bulbs are attached to the under surface of the inferior fascia 
of the urogenital diaphragm and are covered by bulbocavernosum 
muscles. This separation of the two halves of the bulb is the original 
status also in the male, although the two halves normally fuse in 
the male, having the urethra between them. The median notch of 
the male bulb and the median scar under the corpus cavernosum 
urethrae are the permanent reminders of this developmental stage 
of the male. 148 
REGIONAL ANATOMY 
The female urethra is a canal about one inch in length and is 
surrounded at the base of the bladder by a sphincter muscle. 
Dissection.-The skin and then the subcutaneous fatty layer 
should be dissected off the urogenital region. Then the deep fascia 
should be split as near the median line as possible, and reflected 
back to the rami of the pubis and ischium and the base of the uro- 
genital diaphragm. The two crura and the two vestibular bulbs of 
the clitoris should then be dissected and traced to their connections 
with the clitoris. By removing the inferior fascia of the urogenital 
diaphragm from one side the terminal branches of the internal 
pudendal artery, vein, and nerve, may be demonstrated. 
Vaginorectal Space 
The obstetricians often use the term perineum in the restricted 
sense of the region between the back of the vagina and the front 
of the rectum. This region is often torn in childbirth. The tear 
through the pelvic diaphragm and the posterior portion of the uro- 
genital diaphragm is of major importance, and may occur with or 
without a tear through the skin. This accident is more apt to occur 
when the first child is born late in the woman's life, or following 
rapid or instrumental delivery. It is questionable how efficacious 
any of the efforts to prevent this accident really are, consequently 
a tear is not to be blamed on the attendant unless some ill-advised 
hastening of the labor process has been used. Immediate suture of 
the tear often results in fairly efficient repair, although never, to 
be sure, anatomically perfect. A severe tear of this type, or a minor 
tear when the muscles are weak, will allow the uterus and eventually 
the urinary bladder and rectum to sag down from their normal 
position in the pelvic portion of the abdominal cavity into the 
vagina. These parts may even, in neglected cases, appear outside 
through the pudendal rima or cleft. The descending uterus drags 
on its veins, partially obstructing them and becomes soggy with 
lymph and venous blood. The uterus, therefore, tends to increase 
in size and weight, which makes it bear down harder, resulting in a 
vicious circle. This vicious circle is best broken by sewing the pelvic 
and the urogenital diaphragms together in the midline. The round 
ligaments of the uterus are commonly shortened at the same time, 
which procedure helps temporarily to hold the uterus in position. 
This operation gives great relief to the sufferer, more especially in THE ABDOMEN 
149 
the severer traumatic cases, and is probably justly supposed to de- 
crease the danger of cancer of the uterus. 
Hermaphroditism 
The term "hermaphrodite" (Hermes = a greek god; Aphrodite = 
a goddess) is applied to the class of human beings originally sup- 
posed to belong to both sexes. True hermaphroditism, that is, an 
individual having both functional ovaries and testicles, has never 
been proved to exist. The doubtful cases belong to the group with 
various genital malformations, for instance, the testicles remain 
in the abdominal cavity, the male urethra does not traverse the 
corpus cavernosum, or the clitoris so much overgrown as to simulate 
a penis. Many of these individuals have neither functional ovaries 
nor testicles, and are in reality sexless. But if functional sex glands 
are present, after puberty the secondary sexual characteristics 
ordinarily serve to determine their sex, that is, the voice, develop- 
ment of breasts, growth of beard, and the other lesser manly or 
womanly attributes. 
THE ABDOMINAL WALL 
Divisions 
The area between the lower border of the ribs and the upper 
border of the bony pelvis is covered by various layers making up 
the abdominal wall. The tips of the lumbar spines are the bony 
landmarks in the posterior midline. Superiorly the lower border 
of the ribs with their cartilages and the xiphoid process are the sur- 
face bony landmarks separating the abdominal from the chest cavi- 
ties. The crest of the ilium and the inguinal ligament separate the 
abdominal wall from the gluteal region and thigh, respectively, 
while nearer the middle line the crest of the pubis marks the division 
from the perineum. 
As a matter of convenience in accurately locating internal organs 
it has become customary to subdivide the large abdominal cavity 
into a number of arbitrarily defined regions. The great number of 
systems proposed and more or less widely accepted is due to the 
fact that all systems have their serious limitations, as will be 
brought out in connection with the detailed consideration of the 150 
REGIONAL ANATOMY 
thoracic wall. In most of the proposed systems, however, the upper 
part of the belly cavity is known as the epigastrium and the lower 
part as the hypogastrium (gastrium = stomach, i. e., abdomen; epi = 
above; hypo = below). The area in the neighborhood of the um- 
bilicus or navel is known as the umbilical region. The epigastric 
portions of the belly cavity under the ribs and costal cartilages is re- 
ferred to in the B. N. A. system as the hypochondrium (chondrium 
= cartilage). In the use of these terms, however, it must always 
be borne in mind that their exact significance varies materially 
with the different systems. 
Superficial Layers 
The skin over the abdominal wall is moderately thick and over 
the less defensible posterior parts appreciably thicker. If the 
abdominal wall has been greatly distended during a prolonged period 
of time by a mass within the abdominal cavity, as, for example, by 
a large tumor, pregnancy or excessive stoutness, the dermis layer 
tends to tear open. These tears heal after the distension is relieved 
with the formation of shiny scars, known as striaa, which are ordi- 
narily curved about the umbilicus as a center. Striae are also to be 
found in other parts of the body wherever the skin has been unduly 
stretched, as in excessive stoutness, for example. 
The subcutaneous fatty layer varies with the general stoutness, 
in stout individuals often becoming excessively thick. The depth 
of the navel gives an accurate estimate of the thickness of this layer, 
for fat never accumulates over this physiologic scar. The fatty 
layer contains the routine segmental cutaneous vessels and nerves, 
and a superficial venous system. 
The deep fascia attaches along the iliac crest and the inguinal 
ligament of Poupart inferiorly, but does not attach to the pubic 
crest; hence the peculiarities of the lines of least resistance for es- 
caped urine, as previously noted in connection with the male uro- 
genital region. This rather weak deep fascia encases the abdominal 
muscles with their aponeuroses. 
These layers should be dissected. 
Muscles and Aponeuroses 
The real strength of the abdominal wall depends upon the muscles 
with their aponeuroses. THE ABDOMEN 
151 
Anterior Portion 
On each side of the middle line lies the rectus abdominis muscle, 
which arises from the xiphoid process and from the costal cartilages 
of the fifth, sixth and seventh ribs. Its fibers, running approxi- 
mately parallel, eventually insert into the crest of the pubis. This 
muscle is enclosed in the strong aponeurosis of the lateral abdominal 
muscles, which cross over and under the muscle in their course to 
the midline. The midline contains no muscle fibers, hence shows up 
white and is known as the linea alba. The umbilicus lies in the linea 
alba and somewhat nearer the pubis than the xiphoid. The blending 
of these aponeuroses at the lateral margin of the rectus muscles is 
white and is known as the linea semilunaris. Throughout the upper 
three-fourths the aponeurosis splits to enclose the rectus, but in the 
lower fourth of the area the whole aponeurosis goes in front of the 
muscle. A minor muscle, the pyrimidalis, arises from the pubic 
crest and inserts into the lower two inches of the linea alba, lying 
superficial to the rectus muscle. 
The individual muscle fibers of the rectus do not traverse the 
whole distance, but after going three to four inches end in an 
irregular tendinous line, which is fastened to the rectus sheath 
(vagina musculi recti abdominis). The fibers end together, three or 
four transverse lines being found in the course from the costal 
cartilages to the pubis. Individual striated muscle fibers as a general 
rule are not more than three to four inches long, inserting into the 
fascias in the interior of the muscle. If a muscle belly is longer 
than four inches, other fibers start and continue their quota of the 
distance. Due to the fact that the individual fibers of this rectus 
muscle begin and stop together, this condition in this instance is 
macroscopically visible. 
Lateral Portion 
The lateral portion of the abdominal wall is made up of three 
muscle layers, which over the greater part of the region cross each 
other on deeper planes in three different directions. This matting 
arrangement obviously gives great strength relative to thickness. 
The outermost of these abdominal muscles is called the external 
oblique, the middle the internal oblique, and the innermost the 
transversus. Anteriorly the aponeuroses of these muscles come to- 
gether at the linea semilunaris and are then continued, as just noted, 152 
REGIONAL ANATOMY 
over and under the rectus muscle to the linea alba. Posteriorly the 
deep fascia of these muscles blends with the posterior abdominal wall 
fascias and thus is connected up with the lumbar vertebrae. At the 
upper and lower areas of the wall the crossing of these muscles be- 
comes less marked and eventually in certain areas the fibers parallel 
sacrospinalis 
quadra tus 
lumborum 
- psoas 
external oblique 
internal oblique 
transversus 
linea 
semilunaris 
rectus 
abdominus 
linea alba 
Fig. 41.-Muscles and Aponeuroses of abdominal wall, umbilical level. 
each other, as will later be noted in detail. The external oblique 
follows a downward and medial direction, arising from the outer 
surface of the lower ribs and the lumbar fascias. The lowermost 
part of the external oblique aponeurosis is thickened to take part in 
the formation of the inguinal or Poupart's ligament. This inguinal 
ligament is a fusion of the lower part of the external oblique THE ABDOMEN 
153 
aponeurosis with the deep fascia of the thigh, reinforced by the ex- 
ternal and internal deep fascias of the abdominal wall. The internal 
oblique arises from the lateral half of the inguinal ligament, from 
the greater part of the iliac crest, and from the lumbar fascia, run- 
ning upward and medially to its aponeurosis. The transversus 
arises from the lower borders of the ribs, from the lumbar fascia, 
and from the crest of the ilium plus the inguinal ligament, running 
in the main transversely forward to its aponeurosis. 
Posterior Portion 
The extensor group of muscles of the vertebral column makes up 
the large fleshy mass on each side of the lumbar vertebrae, the mus- 
cles of the lateral and anterior portion of the abdominal wall being 
the opposing flexors. This extensor vertebrae muscle group is sev- 
eral inches broad and thick over the loin region and extends up the 
back, branching out into various columns, which eventually continue 
up through the cervical region to the skull. The relatively small 
muscle, which extends from the twelfth rib straight down to the 
posterior portion of the ilium is known as the quadratus lumborum. 
These muscles will be taken up in more detail in connection with the 
consideration of the vertebral column. 
Nerve Supply 
The segmental nerves of the lower six thoracic and first lumbar 
intervertebral foramina take a course just below their respective 
ribs, supplying the chest wall. These nerves then continue onto the 
abdominal wall, and, following the same downward and forward 
course, supply the lateral and anterior portions of the abdominal 
wall to the midline. The main trunks of these nerves lie deep under 
the muscles, but send off at appropriate intervals posterior, lateral, 
and anterior cutaneous branches. The posterior portion of the 
abdominal wall, that is, the extensor vertebrae muscle group area, is 
supplied by branches from the lumbar segmental nerves. The same 
segmental nerve which supplies the abdominal wall musculature 
also supplies the skin and the underlying organs. The clinical 
phenomenon that the overlying muscle is rigid during the painful 
affection of an intraabdominal organ is therefore explicable on this 
anatomic basis. If pain is referred to the back, it lies about at the 
point where the nerve makes its exit from the vertebral column. 154 
REGIONAL ANATOMY 
Vessels 
Developmentally a segmental artery and vein accompany each 
nerve to the midline in front, but during later development the 
rectus muscle takes its supply from what was originally the anas- 
tomosis. An epigastric artery is developed, which runs from the 
rib margin half way down the rectus muscle, and a hypogastric 
artery of the abdominal wall, which runs from just in back of the 
middle of the inguinal ligament to half way up the rectus. This 
hypogastric artery of the abdominal wall has become widely known, 
and even accepted in the B. N. A. revision, as the deep or inferior 
epig'astric artery, but this is an obvious misnomer. The name epi- 
gastric instead of hypogastric was originally given to the artery 
by considering the body stretched out on its back, whereas anatomic 
nomenclature is generally and should invariably be governed by the 
upright standing position. The original segmental arteries carry 
the main supply in the adult for the lateral portions of the abdom- 
inal wall. The deep venous system accompanies the arteries, while, 
as elsewhere, an anastomosing superficial venous system lies in the 
subcutaneous fatty layer of the abdominal wall. If the main trunk 
veins inside the abdominal cavity become seriously obstructed, this 
superficial venous system may become enormously distended. 
Deeper Layers 
On the deep surface of the abdominal muscles and aponeuroses 
lies a layer of deep fascia, which is stronger in the lower part of the 
belly wall. This fascia is named according to its location, as trans- 
versus fascia, iliopsoas fascia, pelvic diaphragm fascia, and so forth. 
On the deep surface of this fascia lies a layer of areolar tissue, vary- 
ing in amount with the general stoutness of the individual, known 
as the extraperitoneal fatty layer. The innermost lining of the belly 
wall is the peritoneum, a delicate membrane made up of endothelial 
cells (peri - around ; toneum = stretch). This smooth surface of the 
inside of the belly wall and of the outside of the abdominal organs 
serves to reduce friction to a minimum. 
The muscles and their aponeuroses, and the vessels and nerves 
should be cleared over one-half of the abdominal wall. THE ABDOMEN 
155 
Hernia 
A hernia or rupture is the protrusion or escape of an intra- 
abdominal organ through the abdominal wall, more commonly a 
part of the gut tube. 
Inguinal Type.-The testicles in the male are developed in the 
neighborhood of the kidneys and, about three months before the 
end of the child's intrauterine life, make their escape through the 
peritoneum 
abdominal ring 
(0. T. internal ring) 
transversus fascia 
transversus muscle 
aponeurosis 
inguinal canal - 
internal oblique muscle 
aponeurosis 
subcutaneous ring - 
external oblique 
aponeuross 
deep fascia 
(0. T. external ring) 
hernial sac - 
peritoneum - 
fascias - 
Fig. 42.-Diagram of Inguinal Hernia 
abdominal wall into the scrotum. The testicles do not break through 
the different layers of the abdominal wall, but theoretically at any 
rate carry a prolongation from each layer down into the scrotum. 
For a short period of time the peritoneum is directly continuous 
along the spermatic cord of the testicle into the scrotum, but nor- 
mally this peritoneum soon disappears except where it forms a sac 
for the testicle itself. This double-layered serous sac of the testicle 156 
REGIONAL ANATOMY 
is known, technically as the tunica vaginalis testis. If the peritoneal 
sac does not close, the individual has an open passageway into the 
scrotum, which is a congenital inguinal hernia. The spermatic cord 
passes through the peritoneum about the middle of, and one-quarter 
of an inch above, the inguinal ligament, then through the trans- 
versus fascia and muscle, then through the internal oblique muscle, 
and, finally, passing through the external oblique muscle, enters the 
scrotum. The space through which the spermatic cord passes is 
known as the inguinal canal. The openings in the muscles and fascias 
are normally only sufficiently large to allow the cord to pass through 
and are triangular in shape. "When, however, intraabdominal struc- 
tures work their way out along this avenue of lesser resistance, the 
openings spread and justify the names of the abdominal and sub- 
cutaneous rings of the inguinal canal, given to the openings in the 
transversus and external oblique muscles respectively. The inter- 
nal oblique and transversus muscles arise from the lateral half of 
the inguinal ligament, but in this region deviate from their typical 
course by turning downward as a conjoint tendon into the crest of 
the pubic bone. 
In repairing hernias of this type, the peritoneal sac is resected, 
and the internal oblique and transversus muscles and aponeuroses 
and the transverse fascia* are sewed down to the inguinal ligament. 
The hypogastric artery of the abdominal wall crosses this area deep 
to these muscles and just medially to the abdominal ring. Whereas 
the typical hernia of this region follows the spermatic cord and 
starts lateral to this vessel, some direct forms of hernia in weak old 
people break through medially to this hypogastric artery. Some 
muscle fibers and fascias derived from the internal oblique and 
transversus muscles form a sling about the testicle, known as the 
cremasteric muscle, which has the power of raising the testicle up 
towards the subcutaneous ring. 
The inguinal is by all odds the commonest and therefore the 
most important of the hernias. 
The lower part of the abdominal wall should be dissected on the 
* Peculiarly the anatomic importance of the transversus fascia has been left out of account, 
so far as I could find out, in all herniotomy technics. By some methods and operators it was 
probably sewed, as it were, accidentally. A method of purposefully repairing this fascia has 
been reported by the author in an article entitled "Suggested Step in the Technic of Inguinal 
Herniotomy", Surg., Gynec. and Obst., March, 1919, pp. 329-331. THE ABDOMEN 
157 
undisturbed side, with special reference to the spermatic cord and 
hernia. 
Femoral Type.-Various structures continue from the abdominal 
cavity into the thigh under the inguinal ligament. But the only 
structures from inside of the fascias of the inner lining of the abdom- 
inal wall are the arteries and veins, the iliopsoas muscle and the 
femoral artery 
femoral vein, 
femoral canal 
lleopaoas 
muscle 
inguinal 
ligament 
of 
Poupart 
lacunar 
ligament 
of 
Gimbernat 
Fig. 43.- Femoral Canal and its relationship. 
femoral nerve, for example, being outside of the inner fascias of the 
abdominal walls throughout. Vessels start from inside all of the 
fascias of the abdominal wall, hence it is possible to have a femoral, 
gluteal, sciatic, pudendal or obturator hernia along these respective 
vessels, but ruptures do not follow the nerves or muscles. The 
femoral vessels being the largest making their exit from inside the 
abdominal cavity, hernias in this position are relatively more fre- 
quent. Laterally to the femoral artery and vein, the transversus 
fascia in front and the iliopsoas fascia in back blend with the lower 
border of the external oblique aponeurosis to form the inguinal 158 
REGIONAL ANATOMY 
ligament. Over and under and along the sides of the femoral ves- 
sels, these fascias are continued for some distance into the thigh 
before they close down firmly on the vessels, forming the femoral 
sheath. The medial inch of the inguinal ligament is reinforced by a 
reflected band, which attaches to the superior pubic ramus and is 
known as the lacunar ligament of Gimbernat. Between the lateral 
margin of the lacunar ligament and the medial surface of the 
femoral vein is a small area not well supported. Through this small 
opening, which is known as the femoral canal, abdominal organs 
may under certain circumstances escape down under the fascia lata 
of the thigh. This is the femoral type of hernia, which tends to 
escape eventually through the saphenous opening of the deep fascia 
into the subcutaneous tissue of the thigh. 
The space between the inguinal ligament and the hip bone should 
be dissected with special reference to femoral hernia. 
Umbilical Type.-The umbilicus, or popularly, navel, is a puckered 
scar, its potential weakness causing it to be a rather frequent site 
for the occurrence of hernia. 
Cause.*-The occurrence of five hernias, two inguinal, two femoral 
and one umbilical, in the same individual at one time is so common 
a clinical observation that the probability of a common underlying 
factor in all hernias is forced into our reckoning. This common 
factor is increased intraabdominal pressure, with, on the other hand, 
weakness of the abdominal musculature, or, in other words, a dis- 
proportion between the strength of the musculature and the amount 
of pressure it is called upon to withstand. Weak children with a 
chronic cough or chronic gaseous distension of the abdomen are to 
be relieved of hernia by correcting the underlying cause. Worn- 
out old people with chronic lung or intestinal disturbance often fur- 
nish the same picture in their second childhood. Any chronic ob- 
struction to the outflow of urine, insofar as the patient makes use 
of general abdominal pressure to overcome the obstruction, may 
become a causative factor in the production of hernia. During the 
vigorous period of life, strong people, when chronically subjecting 
themselves to such overstrains as heavy lifting, may develop a 
hernia, more commonly of the inguinal type. 
* This argument has been presented in greater detail by the author in a paper entitled "The 
Cause and Prevention of Hernia," Jour. Am. Med. Assn., Sept. 8, 1917, Ixix, 776-777. THE ABDOMEN 
159 
It is only fair to state here that anatomists of a past generation 
have built up an elaborate theory of congenital developmental mal- 
formations as the cause of hernias. The arguments had considerable 
plausibility as far as infantile hernias are concerned, but never satis- 
factorily explained the primary occurrence of hernia in middle life 
and old age. Many of the collected facts are correct, but in the 
interpretation, causes and effects were confused. The open peri 
toneal tube leading through the belly wall is, according to the mod- 
ern interpretation, not to be considered the cause of hernia, but to 
exist because there is chronic increased intraabdominal pressure. 
On account of the valve-like character of the inguinal canal, a single 
distention or strain, no matter how great, simply closes the walls 
tighter. Of course, if a rupture has started to descend, a single 
strain may cause a rapid increase in size, but this is an entirely dif 
ferent matter from really causing a rupture. 
Hernias during the vigorous period of life should be corrected 
surgically, bearing in mind the probability of a lesser advanced con 
dition on the opposite side. The results are excellent in the hands 
of competent surgeons, but the patient must be somewhat protected 
against a repetition of the original cause of the hernia. Excessively 
stout people of midlife are especially prone to develop the umbilical 
type of hernia. If their stoutness can be kept in bounds by exercise 
and diet, the results of surgical interference are good. 
Complications.-Aside from their great inconvenience, hernias are 
important on account of the danger of strangulation of their con- 
tents, causing obstruction of the bowel. Small hernias with tight 
walls are more dangerous in this respect than medium-sized hernias 
with their larger rings. Early imprisonment or, technically, incar- 
ceration of the intestines may be caused to work its way back into 
the belly by putting the patient to bed with the pelvis raised and the 
limb semiflexed in order to relax the ligaments. If this procedure 
does not yield relief within a short time, the case demands emergency 
surgical intervention. 
Surgical Incisions Through Abdominal Wall 
A surgical incision through the belly wall is generally known as 
a laparotomy, which term originally meant an incision to remove 
stones. If a long incision in the belly wall is necessary, the middle 160 
REGIONAL ANATOMY 
line should be chosen, because no nerves and only anastomosing 
vessels cross this area. This rule is not so important in the upper 
half of the belly on account of the lesser danger of hernia, due to 
the fact that in upright positions of man, pressure in this region is 
not so great. Transverse incisions across the upper half of the 
abdomen have recently received clinical indorsement, the claim 
being that these incisions reduce the liability to postoperative hernia. 
Insofar as this incision preserves the nerves and splits rather than 
cuts across the main bundles of the aponeurosis, this innovation 
rests on a firm anatomic foundation. Over the lateral portions of the 
abdominal wall the muscle-splitting incisions are to be highly com- 
mended on account of the preservation of muscles, aponeuroses, and 
nerves, even in drainage cases minimizing the liability to hernia. 
The incision along the lateral border of the extensor vertebras muscle 
group, if the twelfth thoracic and first lumbar nerves are cut, is 
often followed later by a hernia in the inguinal region. If infection 
of a wound is associated with sloughing of the aponeuroses and 
fascias, a type of postoperative hernia develops which is often very 
difficult to repair. 
Superior Abdominal Wall 
The diaphragm muscle with its aponeurosis and fascia forms the 
superior wall of the abdominal cavity and at the same time the 
inferior wall of the chest. It is attached around the inner surface 
of the lower rib margins and runs to a central aponeurosis, doming- 
well up under the ribs. Hernias, following injuries or develop- 
mental malformations, may work through the diaphragm into the 
chest cavity. As a matter of dissection convenience, the further de- 
tails in regard to the diaphragm will be taken up in connection with 
the chest considerations. 
THE GASTROINTESTINAL TRACT 
Peritoneal Cavity (Cavum Peritonaei) 
The peritoneal cavity is a closed serous sac, lined as such sacs in 
other parts of the body by a single layer of endothelial cells. In the 
strict sense of the word there is no such thing as a peritoneal cavity 
for the vacuum draws the peritoneal surfaces of the abdominal 
organs into contact. If the vacuum -is destroyed by opening the THE ABDOMEN 
161 
belly, or the peritoneal surfaces are forced apart by the presence of 
a fluid or gas, then of course a cavity exists. The peritoneum itself 
is a very delicate membrane, but, if taken up together with its 
extraperitoneal fatty and fascial layers, has considerable strength. 
The uterine tubes in the female carry the ovum from inside of the 
peritoneal cavity into the uterus, but air can not normally enter into 
the cavity via this route. 
Organs inside the belly cavity are classified as intra- in contradis- 
tinction to extraperitoneal. Developmentally at an early stage all 
abdominal organs are extraperitoneal, but many gradually become 
intraperitoneal as illustrated in Fig. 44. No organ ever becomes 
entirely surrounded by peritoneum, but when the great bulk of an 
organ is covered by peritoneum it is considered an intraperitoneal 
extra-peritoneal 
intra-peritoneal 
perito- 
neal 
- gut tube 
mesentery 
* 
Fig. 44.-Peritoneal relationships 
structure. The use of the terms subperitoneal or retroperitoneal in- 
stead of extraperitoneal should be discouraged, inasmuch as these 
terms vary with the direction of approach, whereas extra has an un- 
changing significance. 
It is worthy of special emphasis that fascial layers cover all 
organs of the abdominal cavity, forming compartments to hold them 
in place. Even though the peritoneal and fascial layer are inti- 
mately blended, the anatomic and functional distinction between 
these two layers should be kept clear, as failure to make this dis- 
tinction has been a great source of confusion. A double fold of 
peritoneum and fascia, containing the vessels, nerves, and fatty 
tissue, leading to a part of the intestinal tract is known as a mesen- 
tery (mes = middle; entery- intestinal). Such parts of the intes- 
tinal tract as have a mesentery are movable, whereas those parts 
that lack a mesentery are fixed. The same type of structure with 
the distinction that it leads to the stomach is known as an omentum, 
or apron. Bands of white fibrous tissue, which hold the other 162 
REGIONAL ANATOMY 
abdominal organs in position, are known as ligaments. For con- 
venience of description, the layer of peritoneum covering the 
various organs is known as the visceral, or organ, layer, whereas 
that lining the abdominal walls is known as the parietal, or wall, 
layer. 
Contents of Abdomen 
Developmentally the simplest type of abdominal cavity content is 
a straight extraperitoneal gut tube. As development proceeds, the 
tube lengthens, becomes coiled up, partly intraperitoneal and partly 
extraperitoneal, and becomes later differentiated into functionally 
different subdivisions. Thus we have the development of a stom- 
ach, the receptacle for and preliminary digester of food, of a small, 
or thin intestine, the main digestive segment, and of a large, or 
thick, intestine, which completes the absorption of digestible ma- 
terial, and also acts as a temporary reservoir for waste material. 
Special glands grow out from the first part of the small intestine, 
the liver and the pancreas, which specialize on the formation of 
digestive juices for the rest of the small intestine. The kidneys, 
which throw out of the body certain types of waste products, remain 
extraperitoneal in contact with the twelfth rib and send down 
tubes to the urinary bladder in the pelvic portion of the abdomen. 
Various sexual glands and tubes are found more or less closely 
associated with the urinary organs. And, further, just as though 
for good measure, the abdomen contains some ductless glands, the 
spleen and the suprarenals. 
Walls of Gastrointestinal Tract 
The inner lining of the gastrointestinal tract, or popularly the 
stomach-gut tube, is a mucosa (tunica mucosa). This mucous mem- 
brane varies in the different subdivisions of the tract, as will later 
be taken up in detail. Outside of this mucosa lies a white fibrous 
tissue layer known as the submucosa (tela submucosa), which gives 
the strength to the walls. The use of this layer from the lower ani- 
mals for catgut and for sausage coverings has been previously com- 
mented upon. Outside of the submucosa lie the muscles (tunica 
muscularis), arranged in at least two layers and directions, the cir- 
cular and the longitudinal. Outside of these muscles, wherever the 
tube is covered by peritoneum, is a serous covering of endothelium 
(tunica serosa). THE ABDOMEN 
163 
General Principles 
The contraction or relaxation of the muscle layers makes a tre- 
mendous difference in the appearance of an otherwise perfectly 
normal wall. The muscles are usually found somewhere between 
full relaxation and contraction, but at times both extremes may be 
noted, the surgeon, for example, characteristically finding full 
relaxation of the intestinal walls above a blockade of the tract and 
complete contraction below. A perfectly normal wall is a dozen 
times or more as thick when fully contracted as when fully relaxed, 
which fact must always be borne in mind in the examination of a 
section of the wall. Another important factor in the thickness of the 
intestinal wall is the amount of blood and lymph supply, which in- 
creases materially during functional activity and as a reaction to 
various irritants. The small or thin intestine when its muscles are 
fully relaxed, has a diameter of about three inches, the large or 
thick intestine, of about five inches, whereas both may contract until 
smaller than the little finger. But beyond the limits noted they 
can not distend, for the white fibrous submucosa is fully stretched 
and any further increase must tear this layer. When fully stretched 
a sudden tap, even though slight, may result in the bursting of the 
fibrous submucosa layer. When fully distended, the serous covering 
is made up of a single layer of endothelial cells, the muscle and 
fascias appear extremely thin, and the mucous membrane is smooth 
without any folds. When contracted down, all the layers are 
thicker and the mucous membrane piles up in heavy folds. The 
mucous membrane folds in the upper part of the small intestine, 
known as plicae circulares, run around the inner circumference of 
the tube. It is claimed that these folds do not entirely disappear 
even on the greatest distension, but this alleged exception to the 
general rule requires more positive proof than has as yet been 
brought forward before it can be absolutely accepted. 
These general principles apply not only to the gastrointestinal 
tract, but also to the urinary and gall bladders, and to other similar 
structures. 
Muscle Layers (Tunica Muscularis) 
The stomach possesses muscle layers in three different planes and 
directions, the mechanics of which arrangement has been explained 164 
REGIONAL ANATOMY 
in connection with the lateral abdominal wall. Throughout the in- 
testinal tract there are only two layers, a circular lying next to the 
submucosa, and a longitudinal lying outside of the circular layer. 
At the inlet and outlet of the stomach, of the small intestine, and of 
the large intestine, the circular fibers are increased in amount to 
form sphincter muscles (sphincter = encircle or bind). The longi- 
tudinal muscles are distributed uniformly over the small intestine, 
but over the large intestine the longitudinal muscle is gathered into 
three bands, spaced equidistant about the cross-section of the gut. 
The longitudinal muscle bands are distinctly shorter than the large 
intestine, and, therefore, produce a characteristic puckering or 
frilling of the walls. One of these bands is invariably hidden by the 
attachment of the mesentery to the intestinal coil, but the other 
two are readily to be made out, showing up best when the intestinal 
wall is distended. The large intestine, when fully distended, is 
materially larger in diameter than the small intestine, but on 
account of varying degrees of distension, this is no real guide. The 
presence of the three longitudinal bands with their resultant puck- 
ering is the essential external feature distinguishing the large from 
the small intestine. It is appropriate to note here that the large 
intestine has numerous fatty appendages (appendices epiploicae), 
which hang free from its outer surface and are not found in con- 
nection with the small intestine. 
Dissection.-After these preliminary considerations, the student 
should be in a position to appreciate what is found on opening the 
abdominal cavity. If not already completed, an incision through 
the abdominal wall should be carried along the linea alba from the 
xiphoid process, turning slightly to the left at the umbilicus, and 
then down to the symphysis pubis. A transverse incision should be 
carried from the umbilicus to within a couple of inches of the 
lateral border of the extensor vertebrae muscle group. The four 
quadrants may then be turned back, exposing the interior of the 
belly cavity freely. The opposing parietal and visceral layers of 
peritoneum should be noted. 
Examination of Abdominal Cavity 
The large, solid liver should be noted in the epigastrium, chiefly 
in the right hypochondriac region, but commonly in dissecting room THE ABDOMEN 
165 
liver - 
'lesser omentum 
stomach 
.omental bursa 
-mesentery 
transverse colon 
•greater omentum 
•mesentery small 
intestine 
general peritoneal 
cavity 
rectum 
bladder 
Fig. 45.-Arrangement of Peritoneum^ diagrammatic median section. 166 
REGIONAL ANATOMY 
bodies projecting down below the border of the ribs. If the spleen 
happens to be much enlarged, its rounded tip may be noted to pro- 
ject down from under the ribs in the left epigastrium. If it is not 
enlarged, the spleen can be palpated by following the lower surface 
of the diaphragm as a guide upwards and backwards, and then 
downwards. If the stomach is moderately distended, it will appear 
as a large bag stretched across the epigastrium, but if it is con- 
tracted down, may be withdrawn close up under the ribs and 
diaphragm. A large apron, the great omentum, hangs down from 
the lower margin of the stomach, and normally covers the anterior 
surface of the rest of the intestinal coils. This apron presumably 
has as one of its functions the protection of the intestines against 
chilling, but it also plays an important part in preventing the spread 
of peritoneal infections. If the lower end of this great omentum be 
picked up and, using gentle traction, be turned back over the chest 
wall, a coil of large intestine may be noted crossing in its posterior 
surface, which coil is known as the transverse colon. Then the intra- 
peritoneal coils of small intestine should be traced from the point 
where they come out from under the transverse mesocolon at the left 
of the vertebral column to the point where they enter the large intes- 
tine, which point lies posterior to the midpoint of an imaginary line 
between the umbilicus and the anterior superior spine of the ilium 
on the right side. The mesentery should be examined by palpation 
and by transmitted light for blood vessels, nerves, lymphatic glands, 
and connective tissues. A coil of large intestine ascends towards the 
liver, goes across as the transverse colon, and descends on the left 
side into the pelvis, terminating in the rectum. The urinary bladder, 
even though empty, may be felt in the pelvic portion of the abdom- 
inal cavity, that is above the pelvic diaphragm and just in back of 
the symphysis pubis. The kidneys may be palpated on each side of 
the vertebral column, being extraperitoneal organs on a level with 
the twelfth ribs. If more than one body is being dissected, advan- 
tage should be taken of the opportunity to examine all specimens, on 
account of varying degrees of distention of the parts of the gastro- 
intestinal tract. Unless the coils of large intestine are distended, it 
is often difficult in a dissecting room specimen to make out the 
longitudinal muscle bands, but in a fresh body these bands are 
readily to be made out. THE ABDOMEN 
167 
Arrangement of the Peritoneum 
At this stage of the discussion it is well to note the reflexions of 
the peritoneum. To trace first a vertical median line course, start 
on the front surface of the great omentum, which hangs down from 
the lower margin of the stomach, then conies in order the stomach, 
the lesser omentum over the liver to the diaphragm, along the 
diaphragm to the anterior abdominal wall, along this wall into the 
pelvis, crossing over the bladder, the uterus in the female, and over 
the rectum, up the posterior abdominal wall to the root of the 
visceral layer peritoneum 
parietal layer peritoneum 
mesentery 
small 
intestine 
descending I 
colon-I 
ascending 
colon 
Fig. 46.-Arrangement of Peritoneum, diagrammatic transverse section. 
mesentery of the small intestine, over the intestinal loop, and back 
again to the posterior wall; then down the transverse mesocolon on 
the posterior surface of the great omentum to the starting point. 
Between the anterior omental fold with the stomach and the pos- 
terior omental fold with the transverse colon lies the omental bursa, 
formerly called the lesser peritoneal sac. This subdivision of the 
peritoneal cavity has very thin walls, and therefore only minor prac- 
tical importance. The omental bursa is continuous with the general 
peritoneal cavity through the epiploic foramen of Winslow, on the 
right side posterior to the gastrohepatic or lesser omentum (hepatic 
= liver). 168 
REGIONAL ANATOMY 
A horizontal section would be from the umbilicus around the belly 
wall, across the large intestine, over the mesentery and coil of small 
intestine, across the opposite loop of the large intestine, and back 
along the belly wall to the starting point. 
Practical 
The opposing surfaces of the peritoneum under normal conditions 
move past each other freely and without pain, while in inflammation 
they tend to adhere to each other and to cause pain on movement. 
Peritonitis is now recognized to be a secondary disease, more com- 
monly secondary to some diseased condition of the abdominal organs 
by direct spread (itis = inflammation of). The more common causes 
are appendicitis, inflammation of the uterine tubes, gall bladder 
infections, and perforations of the gastrointestinal tract. 
Stomach (Ventriculus or Gaster) 
The stomach is a muscularly walled sac, in contracted condition 
containing little inside space, while in an averagely relaxed condi- 
tion it may contain from two to three pints. A gallon or even con- 
siderably more may be contained in a normal stomach, however, 
before the submucosa becomes stretched to its capacity. The upper 
opening, known as the cardia because it is nearest the heart, is fixed 
to the end of the gullet at the diaphragm. The lower opening, 
known as the pylorus, or gatekeeper, is, somewhat movable between 
its omenta. Sphincter muscles are found both at the cardia and the 
pylorus, which muscles normally retain the food until the hydro- 
chloric acid-pepsin digestion has changed the food into a thin gruel 
consistency. The stomach has a lesser, or superior, curvature and a 
much longer, greater, or inferior, curvature, and in the adult an 
anterior and posterior surface. During early development the 
stomach is in a more up and down position, its anterior surface being 
then the left lateral whereas its posterior is the right lateral, as the 
nerve supply to be considered later demonstrates. The adult stom- 
ach lies transversely, with the pylorus relatively fixed to the right 
of the median line about opposite the second lumbar vertebra. 
Practical 
Many general abnormal conditions of the body, having nothing 
directly to do with the gastrointestinal tract, may cause the stomach THE ABDOMEN 
169 
symptom of nausea, eventually vomiting. Stomach symptoms due 
to disturbances of the stomach itself are to be distinguished from 
the foregoing owing to the fact that they bear a definite relation to 
the ingestion and character of the food. Diseases of the liver ducts 
and the appendix also bear a relationship to the ingestion of food, 
and must be carefully excluded through time factors, pain localiza- 
tions, and other individualizing symptoms before a diagnosis of 
intrinsic stomach trouble is permissible. 
Chronic hyperexcitability of the inlet or outlet of the stomach 
may eventually cause an overgrowth of the cardiac or pyloric 
cardia 
lesser 
curvature 
duodenum 
pylorus 
greater curvature 
Tig. 47.-Stomach (ventriculus). 
sphincter musculature. Many forms of chronic abuse of the stomach 
result in an excessive secretion of acid and eventually if the abuse 
is kept up this disturbance may be followed by a secondary de- 
crease in acidity. An ulcer in the mucosa of the stomach or first 
part of the small intestine is a common accompaniment or perhaps 
sequel of this hyperacidity. The danger of hemorrhage from these 
ulcers or of perforations through the submucosa into the peritoneal 
cavity is said to be increased by gastric distention. The passing of a 
stomach tube often drains out great quantities of fluid with a 
minimum of disturbance, even though the patient has apparently 
emptied the stomach by vomiting. Modern x-ray work has demon- 
strated that the stomach musculature under an ulcer remains in a 170 
REGIONAL ANATOMY 
state of spasmodic contraction, as would be expected. Cancer of 
the stomach is considered to be a sequel to chronic ulcer by com- 
petent men, who have had large opportunity to study the subject 
from operative specimens. Cancers which involve the pylorus tend 
to cause obstructive symptoms, but cancer of other parts of the 
stomach may be palpable through the abdominal wall before giving 
rise to alarming disturbance. 
Small or Thin Intestine (Intestinum Tenue) 
The first part of the small intestine is known as the duodenum 
on account of the fact that it is about twelve inches long (duo = 
two; denum = ten). The first three inches are somewhat movable 
with the pylorus, but from this point, where the common ducts of 
the liver and pancreas enter, the remainder of the duodenum is 
extraperitoneal and firmly fixed across the vertebral column. 
The remainder of the small intestine when freed from the mesen- 
tery and stretched out is approximately twenty-two feet in length, 
whereas the root of the mesenteric attachment across the vertebral 
'column is only about six inches long. The small intestine as a mat- 
ter of convenience is divided into approximately a first half, or 
jejunum, and a second portion, or ileum (jejunum = empty; ileum = 
twisted). The duodenojejunal junction is fixed to the left of the ver- 
tebral column, while the ileum-large intestinal junction is fixed 
in the lower part of the right lateral abdominal region. The small 
intestine, except for the duodenum, is intraperitoneal and freely 
movable on its long mesentery. The normal mesentery allows parts 
of the small intestinal coils to follow down into hernial sacs without 
being drawn taut, and with the belly opened permits the coils to 
be lifted out freely. 
Practical 
Cancers are so extremely rare in the small intestine that the clin- 
ical importance of this form of contracting stricture is practically 
nil. The common causes of anatomic obstruction of the small in- 
testine are due to extrinsic factors, such as constriction in a hernial 
sac, or bands due to local or general, acute or chronic peritonitis. 
Clinically the higher up in the intestinal tract the obstruction occurs, 
the more severe are the symptoms. The resultant continuous vomit- 
ing of tremendous quantities of fluids will rapidly and certainly THE ABDOMEN 
171 
usher in a fatal termination, unless the water of the body is replaced 
through some other avenue: i. e., either per rectum or subcutane- 
ously. 
Large or Thick Intestine (Intestinum Crassum) 
The large intestine is subdivided for convenience of description 
into a cecum, ascending colon, right colon flexure, transverse colon, 
left colon flexure, descending colon, sigmoid colon, and rectum. 
These parts are altogether about six feet long. 
The cecum (caecum) is the blind-ending portion of the large intes- 
Large Intestine 
Small Intestine 
Luman 
Db-rnan 
longitudinal 
bands 
serosa 
serosa 
fascia _ 
- mesentery. 
fascia 
arteries, veins, nerves, etc. 
Fig. 48.-Diagrammatic cross section of Intestines. 
tine below the entrance of the ileum (caecum = blind). It normally 
has a short mesentery attaching it to the posterior wall in the upper 
part of the right lateral hypogastrium. The cecum is an extremely 
large important part of the large gut of the herbiverous animals and 
in the early stages of human development. Herbiverous animals 
must eat enormous quantities of their food in order to obtain suffi- 
cient nourishment and therefore require a large reservoir for absorp- 
tion and waste. 
The processus vermiformis or appendix is the vestigial remnant of 
this originally large cecum, which fails to reach its usual size in the 
human and in many carniverous animals. The processus vermi- 
formis is a blind-ending tube, which connects at its open end with 
the cecum. 
Whenever fecal material can not pass freely from the appendix 172 
REGIONAL ANATOMY 
into the cecum, the stagnating fecal material may putrefy and result 
in an attack of acute appendicitis. The formation of a circular 
stricture of the appendix, following previous inflammations, inter- 
feres with the normal drainage and predisposes to chronically recur- 
ring attacks. 
The ascending colon is extraperitoneal and therefore fixed in its 
course up to the under surface of the liver, where after making the 
right colon bend, the large intestine continues as the transverse 
colon. 
The transverse colon runs from the fixed right colon flexure across 
the front of the belly cavity to the fixed left colon flexure, but itself 
has a liberal mesentery and is freely movable. The mesentery of 
the transverse colon attaches across the vertebral column in the 
lower part of the epigastrium. 
The descending colon, fixed to the left posterior wall, leads 
straight down to the left side of the brim of the pelvis. 
The sigmoid colon takes a curve with a liberal mesentery over 
the brim of the pelvis, and continues beyond the third sacral ver- 
tebra into the rectum. The rectum rapidly loses its mesentery and 
especially in its lower part is firmly attached to the pelvic dia- 
phragm. 
The cecum, transverse colon, and sigmoid colon are then normally 
the only freely movable portions of the large intestine. As a reac- 
tion to inflammatory processes these normally movable portions of 
the large intestine may become fixed, or on the other hand, as will 
be detailed later, the normally fixed portions of the large intestine 
may acquire an abnormal range of mobility. 
Practical 
Complete obstruction of the large intestine may be caused by 
external bands or by hernial ring compression, but cancer stricture 
is the more common cause. In advanced inoperable cancers the 
making of an artificial anus through the abdominal wall above the 
constriction gives most gratifying relief from the symptoms. 
Vessels 
The arterial supply of the gastrointestinal tract comes from three 
vessels, the celiac axis, the superior, and the inferior mesenteric, THE ABDOMEN 
173 
which arises in this sequence from the front of the abdominal aorta. 
The celiac axis is a short stem artery of the epigastrium, which 
almost immediately breaks up into three radiating branches. These 
are the branch to the lesser curvature of the stomach, the branch to 
the greater curvature of the stomach, which also supplies the pan- 
creas and spleen, and the hepatic branch, which also sends branches 
to the pyloric end of the stomach and first part of the duodenum. 
The superior mesenteric arises about a half inch lower down than 
the celiac axis, and supplies the remainder of the small intestine 
and the first half or more of the large intestine. The inferior mesen- 
teric arises about opposite the umbilicus and supplies the descend- 
ing colon, sigmoid colon, and rectum. The branches of these ves- 
sels communicate with each other freely through very large anas- 
tomosing stems. The smaller veins correspond accurately to the 
arteries, but the large veins corresponding to the celiac axis, superior 
and inferior mesenteric arteries run together into a large vein, 
which empties its blood into the liver. This extraordinary condi- 
tion, for we would expect these veins to empty directly into the 
vein corresponding to the aorta, will be considered in connection 
with the liver. 
The lymphatic vessels as usual accompany the veins and run 
through lymphatic glands in the mesentery. The lymphatic vessels 
empty into a main reservoir, which will later be noted to be drained 
by a lymph duct, which follows the anterior surface of the vertebral 
column up to the base of the neck. 
Nerves 
Very large matted strands of sympathetic nerves follow the arter- 
ies and their branches to their terminations, receiving corresponding 
names. These nerves are not under the control of the will, but 
automatically regulate the blood supply, the movements, and some 
of the other activities of the gastrointestinal tract. They make the 
same segmental connections with the spinal cord as the nerves which 
control the abdominal wall; i. e., the last six thoracic and the first 
lumbar. Eventually the lower four lumbar, the sacral, and coccy- 
geal segmental nerves control the lower portions of the abdominal 
cavity and its contents. 
The very thick matted plexus around the origins of the oeliac 
axis and superior mesenteric arteries was formerly known as the 
Nerves 174 
REGIONAL ANATOMY 
solar prevertebral plexus (solar = comparison to rays of sun). This 
large, matted plexus contains numerous ganglia, which are aggre- 
gations of the bodies of nerve cells held together by connective tis- 
sue. The lower six thoracic segmental nerves send processes down 
on each side of the aorta, known as the splanchnic nerves, which 
connect this plexus with the spinal cord. The branches from this 
and the other minor prevertebral plexuses are named according to 
the arteries they follow. 
Another series of plexuses with ganglia can be located micro- 
scopically in the various organs. These are known as the visceral 
plexuses and are named according to their respective organs. 
The main points in regard to the vessels and nerves should be 
worked out by dissection. 
Practical 
When a coil of gut is to be freed from adhesions and mobilized, 
it is obviously important to separate from the lateral side. For the 
vessels and nerves arising near the midline and running laterally, 
any attempt to separate between the gut and the midline seriously 
endangers the blood and nerve supply. 
Dissection 
The stomach, the small intestine, except the duodenum, and the 
large intestine are to be removed from the body for more detailed 
examination. The stomach should be cut across close to the dia- 
phragm and the duodenum should be divided about one inch beyond 
the pylorus. If part of the gastrointestinal tract to be cut has much 
contents, as a matter of neatness it is advisable to tie cords around 
the intestinal tube and divide between them. The small intestine 
should be sectioned at the duodenojejunal junction and then the 
mesenteric attachment of the jejunum and ileum cut close to the 
coils. Then the large intestine should be similarly removed, starting 
at the cecum and continuing down to the rectum, which should be 
cut across. 
By tearing off the peritoneal and longitudinal muscle coats it is 
usually possible to demonstrate the bundles of circular muscle fibers. 
The stomach, and sections of the small and large intestines should 
be laid open freely by a longitudinal cut in order, to examine the 
mucosa, noting especially the exaggerated mucous folds wherever THE ABDOMEN 
175 
the gastrointestinal circular musculature is contracted. In a fresh 
coil of gut it is relatively easy to scrape the mucosa off the inner 
surface, and the peritoneum plus muscles off the other, thus demon- 
strating the submucosa. Unfortunately the mucosa in dissecting 
room bodies is usually poorly preserved, hence many of the things 
to be made out in a fresh specimen by the naked eye or by hand- 
glass magnification are not demonstrable. However, even if no 
fresh material is available, the attempt should be made to connect 
up the gross appearance of the mucosa with the microscopic findings, 
which will now be summarized. 
Mucosa (Tunica Mucosa) 
The mucosa of the gastrointestinal tract, being of the secretion 
and absorption type, is lined throughout by a simple columnar epi- 
thelium with goblet cells (see mucous membranes, p. 33). Through- 
out the entire gastrointestinal tract crypts extend down into the 
mucosa, which when viewed from the surface under hand-glass 
magnification appear as little round pits. This description unmodi- 
fied describes the mucosa of the large intestine. The mucosa of 
the stomach is on the same general principle as that of the large 
intestine, with the addition of glands which secrete the gastric 
juices and pour it into the bottom of the crypts. The small intestine 
in the higher animals has no glands to pour out the digestive juices 
on the mucous membrane, the place of such glands being taken by 
the specialized glands, the liver and the pancreas. On the other 
hand large, irregular projections known as villi extend above the 
surface of the small intestinal mucosa and serve to increase the 
surface. 
Nodules of lymphatic tissue may be found microscopically in all 
mucous membrane throughout life. Just like the lymphatic glands 
these nodules tend to increase in size and probably also in func- 
tional ability as a reaction to bacterial poisons. These nodules are 
clinically found to average larger in early youth, when the resist- 
ance to bacterial poisons is less developed, in those mucous mem- 
branes particularly exposed to bacterial infection, and in any 
mucosa subject to an acute or chronic infection. The lymphatic 
nodules in the gastrointestinal mucosa conform to these generaliza- 
tions, being relatively large even in perfect health during infancy 
and early childhood throughout the whole gastrointestinal tract. 176 
REGIONAL ANATOMY 
The stomach and the first half of the small intestine are protected 
by the gastric and biliary-pancreatic secretions, respectively, which 
normally keep bacterial growth down to a minimum, the lymphatic 
nodules in these areas being normally insignificant. The lower half 
solitary lymph nodule 
s' crypt 
large 
intestine 
- muscularis 
mucosae 
-- submucosa 
Fig. 49. 
crypt 
stomach 
gastric glands 
- muscularis 
mucosae 
submucosa 
Fig. 50. 
of the small intestine and the large intestine are normally full of 
bacterial life, and it is in this portion of the gastrointestinal tract 
that the lymphatic nodules are best developed. Solitary lymph- 
nodules (noduli lymphatica solitarii) can be found microscopically THE ABDOMEN 
177 
throughout the stomach and small intestine and much more abun- 
dantly throughout the large intestine. In addition to its solitary 
lymphnodules the small intestine has about thirty aggregated lymph- 
nodules of Peyer, which are about equidistantly spaced and are in- 
variably located opposite the mesenteric attachment. These thin 
plaques naturally vary in apparent size with the amount of disten- 
sion of the intestinal coil, but average perhaps one-quarter times one 
and one-half inchest 
Clinically these aggregations of lymphatic tissue become enlarged 
villus 
small 
intestine 
crypt 
- muscularis 
mucosae 
- submucosa 
Fig. 51. 
Figs. 49, 50, and 51.-Diagram of Mucosa of gastrointestinal tract (x 100) 
as a reaction to any bacterial infection of the intestinal tract, the 
typical example being typhoid fever in which each solitary lymph- 
nodule at the height of the attack becomes about split-pea size. If 
the infection persists or reaches great severity, the process may go 
on to ulcer formation of these areas, the pus eventually formed fol- 
lowing the line of least resistance by breaking through the mucosa 
into the lumen of the intestinal tract. Normally these ulcers lie in- 
side the submucosa, which forms their floor. If the submucosa be- 
comes weakened, however, and an intestinal coil becomes greatly 
distended there is acute danger of a perforation through the intes- 
tinal wall into the peritoneal cavity. 178 
REGIONAL ANATOMY 
Embryologic Blood Supply of Abdomen 
In order to obtain a broad conception of the liver, it is necessary 
to consider first the embryologic blood supply of the belly cavity. 
The developing child while in the womb does not take supplies or 
throw off waste by means of its own organs, but effects these re- 
quirements of life by an intercharge between the embryonic or fetal 
and the maternal circulations. After two months of intrauterine 
development, the human embryo is about one inch long and becomes 
known as the fetus (foetus). The circulatory system of the develop- 
maternal vein 
maternal artery 
material blood sinus 
fetal chorionic villus 
fetal artery - 
chorionic = full of capillary vessels 
villus = mhaggy, i. e., a projection 
fetal vein 
Fig. 52.-Diagram of Placenta (x!50). 
ing fetus uses the child's own blood, which does not mix with the 
maternal blood, the red blood cells of these distinct circulations being 
separated by at least two layers of modified endothelial cells, as illus- 
trated in diagram. Whereas theoretically we would expect the 
bloods of the fetus and mother to be separated by a layer of fetal 
and of maternal endothelial cells, the embryologic evidence acquired 
up to date makes it appear more probable that both these layers are 
of fetal origin. The organ in which this interchange takes place is 
known as the placenta (cake-shaped). The placenta is made up of 
a maternal and fetal part, and after birth, being no longer required, 
is expelled. It is, therefore, popularly known as the afterbirth. 
The cord connecting this placenta with the navel of the fetus con- 
tains as its essential constituents fetal vessels together with some 
connective tissue and an outer skin covering. THE ABDOMEN 
179 
Vitelline and Allantoic Sacs and Ducts 
Animals below the mammals do not have a placenta, which state- 
ment also applies to the human embryo in its earliest stages of 
development. The yolk of a developing bird's egg becomes sur- 
rounded by a vitelline sac, which connects by a duct via the navel 
with the intestinal tract of the developing chick. As development 
proceeds the yolk nourishment is absorbed into capillaries of the 
vitelline vessels and the extraabdominal portion of the vitelline sac 
becomes progressively smaller. Waste products are thrown out 
from the cloaca via an allantoic duct, which runs through the navel 
into an allantoic sac, the extraabdominal portion becoming pro- 
gressively larger as development proceeds. Vessels incidentally 
grow out along the allantoic sac to the inner surface of the shell of 
the egg, taking care of the interchange of carbon dioxide and oxygen. 
Now the human embryo develops both vitelline and allantoic sacs 
and ducts, even though it probably never really uses either of them. 
A number of other similar facts will be noted later, all of which 
emphasize our anatomic relationship to the lower animals. If 
abnormally the vitelline duct persists in the fully developed human, 
it runs from the navel to the ileum about two feet above the ileo- 
cecal junction, and is known as the diverticulum ilei of Meckel. It 
may persist in part or in toto. The allantoic duct normally persists 
in the adult as the obliterated urachus running from the navel to the 
nearest medial point of the bladder. In case of obstruction to the 
urinary outflow via the normal route, this normally obliterated 
urachus may remain patent and allow the escape of urine via the 
navel. 
Umbilical Arteries and Vein 
Two umbilicial arteries carry the child's blood to the fetal por- 
tions of the placenta, while one umbilical vein carries the purified 
blood back. Veins, as previously noted, are not named according to 
the character of their contents, but according to the direction of 
flow, that is, whether towards or away from the heart. The umbili- 
cal arteries arise from the hypogastric arteries of the lesser pelvis 
and passing along the sides of the bladder converge at the umbilicus. 
The umbilical vein carries its blood towards the heart, but part of 180 
REGIONAL ANATOMY 
its blood runs through a second set of capillaries in the liver before 
returning to the heart. The bulk of the blood in the umbilical vein, 
when it reaches the inferior surface of the liver, short-circuits 
through the ductus venosus into the inferior vena cava, which 
empties into the heart. The umbilical arteries and the vein and the 
ductus venosus, having no function to perform after birth, bncome 
obliterated and remain as fibrous cords in the adult. The place at 
about the middle of the inferior surface of the liver where the umbili- 
cal vein and other structures enter or exit is known as the porta, or 
gate, of the liver. 
Vena Porta 
The veins returning from the gastrointestinal tract of the adult, 
the veins corresponding to the celiac axis, superior and inferior 
capillaris in 
gastrointestine 
vena porta 
capillaris 
in liver 
L celiac axis 
_ superior mesenteric 
inferior mesenteric 
hepatic veins 
inferior vena 'lava- 
abdominal aorta 
Fig. 53.-Diagram of Portal Vein circulation 
mesenteric arteries, unite to form the vena porta. Now this vena 
porta sends its blood through this same system of capillaries in the 
liver as is used by part of the blood of the fetal umbilical vein. 
This is an extraordinary anatomic fact, which must have some 
functional necessity back of it. The working theory that one func- 
tion of the liver is to protect the general circulation against any 
substances abnormally absorbed from the gastrointestinal tract has 
a sound anatomic basis. It is now a well-established fact of physi- 
ology that certain foodstuffs, notably the albumins, if injected 
subcutaneously without first undergoing digestion, cause profound 
disturbances of the body. The liver stores up certain foodstuffs as a THE ABDOMEN 
181 
reserve supply, and probably changes other absorbed products of 
digestion before they are allowed to enter the general circulation. 
Liver (Hepar) 
The liver is developed as an outgrowth from the duodenum, and 
as noted in connection with the mucosa of the small intestine, takes 
the place of digestive glands throughout this mucosa. It is a large 
solid organ, which fits up under the vault of the diaphragm and 
normally does not extend below the ribs except near the front mid- 
line. About nine-tenths of the liver lies to the right of the median 
line, filling up the whole right hypochondriac region, while only a 
thin tapering projection runs into the left hypochondrium. The 
normal position of the liver under the ribs gives constant protection 
to the organ, whereas when extending further down, the muscle pro- 
tects only if contracted. The liver is firmly attached to the dia- 
phragm by a circular crown ligament, with the right and left lateral 
portions extending to their respective sides. It is surrounded by 
peritoneum, except for the vessel and ligament entrances. The 
obliterated umbilical vein, also known as the round ligament of the 
liver, with its double fold of reflected peritoneum, divides the in- 
ferior surface of the liver into a right and left lobe, the right lobe 
being considerably the larger. The vertebral column causes a deep 
depression in the posterior surface of the liver. 
The essential liver cells are translucent like the white of a fresh 
egg, the normal color of the organ being due to the rich supply of 
blood in capillary vessels plus the presence of bile. The normal 
consistency is rather soft on account of the relatively small propor- 
tion of connective tissue, the whole organ being surrounded by a 
rather weak fibrous coat plus peritoneum. Acute inflammations 
cause the liver to swell, whereas long continued chronic irritations 
lead to an increase of, and eventually a secondary contraction of, 
the fibrous tissue framework. This secondary contraction is known 
technically as cirrhosis or hardening of the liver. 
Blood Supply 
The liver has, as would be anticipated, an arterial and venous 
supply, which, however, take separate courses, and a collecting duct 
system. The vena porta, which collects the blood from the veins 182 
REGIONAL ANATOMY 
corresponding to the celiac axis, superior and inferior mesenteric 
arteries, is therefore the only unexpected feature in the anatomy of 
the liver. The vessels entering the inferior surface of the liver at 
the porta are the vena porta and the hepatic artery, a branch of the 
celiac axis. The vena porta carries venous blood back from the 
gastrointestinal tract, whereas the hepatic artery carries arterial 
bile capillary 
central vein - 
small hepatic 
vena porta, 
hepatic 
artery, and 
bile duct. 
central vein 
bile capillary 
Liver cells 
(x 400) 
bile capillary. 
Fig. 54.-Lobules of Liver, diagrammatic (x 100). 
blood for the care of the tissues. The right and left hepatic ducts, 
carrying the biliary secretions of the liver cells, leave the liver at 
the porta en route to the duodenum. This hepatic artery, vena 
porta, and bile duct, and their subdivisions, are held together by 
connective tissues, known as the fibrous capsule of Glisson. These 
three structures, as they traverse the liver in company, divide pro- 
gressively into smaller and smaller subdivisions, but, on the other THE ABDOMEN 
183 
hand, the smaller branches become more and more numerous. The 
smallest subdivisions of the hepatic artery, vena porta and bile duct 
terminate at a lobule about the size of a pin-head, which lobule is 
itself a miniature of the whole liver. The bloods of the hepatic 
artery and vena porta traverse capillaries from the outer side of the 
lobule to a centrally placed vein. These central venules are non- 
collapsible spaces in the liver substance, which join with others to 
form the smaller hepatic veins. The large hepatic veins are con- 
stantly open tubes, which connect via a variable number of branches 
with the inferior vena cava as it passes along the posterior surface 
of the liver. 
If the vena porta or its branches are semi-obstructed from any 
cause whatsoever, the anastomosing veins of the general circulation 
at the upper end of the stomach and the lower end of the rectum 
will become greatly distended. In the rectal mucosa these distended 
veins are called hemorrhoids on account of their tendency to bleed. 
Some of the specific factors causing hemorrhoids are obstruction of 
the portal circulation in the liver, chronic increased intraabdominal 
pressure, and various local disturbances to the return circulation of 
the rectal veins. If the vena porta or its capillaries in the liver 
become severely obstructed, lymph is secreted from the capillaries of 
the gastrointestinal tract faster than it can be carried off by the 
lymphatic vessels. This lymph then collects in the peritoneal cavity 
and commonly distends the belly wall to the point at which pres- 
sures and counterpressures are equalized. This collection of lymph 
in the peritoneal cavity is known technically as ascites. 
Bile Passageways 
Bile is secreted by the liver cells, which are arranged within the 
lobules in curving strands as illustrated in the diagram. Each of 
these strands is made up of a series of paired liver cells, which en- 
close a passageway, known as the smallest bile ducts. The smallest 
bile ducts empty into the larger interlobular ducts, these inter- 
lobular ducts empty into the hepatic ducts, which progressively 
become larger and less numerous, eventually making their exit from 
the liver as the right and left hepatic ducts. The right and left 
hepatic ducts join to form the common hepatic duct, which is joined 
by the cystic duct from the gall bladder (vesica fellea). Beyond the 184 
REGIONAL ANATOMY 
junction of the common hepatic duct with the cystic duct, the biliary 
passageway becomes known as the common bile duct (ductus chole- 
dochus). The common bile duct travels straight to the posterior 
surface of the duodenum about three inches beyond the pylorus of 
the stomach, a small nipple-like projection or technically papilla 
surrounding the entrance point into the duodenum. The main pan- 
creatic duct empties into the dilatation of the common bile duct, 
technically the ampulla, which is to be found just liverward from 
left hepatic duct 
right hepatic duct 
common hepatic due 
gall bladder 
(vesica fellea) - 
cystic duct 
common bile duct 
(ductus chole- 
dochus) 
pancreatic duct 
Fig. 55.-Diagram of Bile Ducts. 
duodenum 
the papilla. The common bile duct traverses the wall of the 
duodenum one layer at a time for a distance of over an inch, which 
arrangement gives a valve action against backflow in case of duo- 
denal overdistention. The Avails of the larger ducts and gall bladder 
are made up of mucosa, submucosa, and muscle layers, the unat- 
tached surface of the gall bladder having in addition a peritoneal 
coating. The mucosa of the smaller ducts is lined by simple col- 
umnar cells, whereas the larger ducts are, as usual, of the stratified 
columnar type. 
The old anatomic conception of the gall bladder as a reservoir for THE ABDOMEN 
185 
bile has required modification, since it has been found out that three 
or more pints of bile are secreted daily, whereas the gall bladder 
holds only a few ounces. Bile is secreted actively while food is 
passing into the duodenum, so the gall bladder may well functionate 
as a temporary storage reservoir between pumping activities. If 
the gall bladder is destroyed, other parts of the bile duct may func- 
tionally take its place. The gall bladder is attached to the inferior 
surface of the liver, its free surface approaching the abdominal wall 
at the right nipple line. The obliterated umbilical vein running 
about one inch and a half medially to the gall bladder is helpful as 
a guide to its position. 
Practical 
Bacterial inflammations of the mucous membrane of the biliary 
tracts cause a damming up of bile and its absorption into the blood, 
known clinically as jaundice. Inflammatory disturbances, more 
especially of the gall bladder, often lead to the formation of gall 
stones, which themselves tend to keep up a chronic irritation and 
hence grow by accretion. After these stones have reached a certain 
size, it becomes a physical impossibility for them to be moved on 
account of the strict limitations of the normal mucosa as to dilata- 
tion. The pain is excruciating if the muscle coats attempt to force 
the smaller stones through the inflamed ducts. As no medicines as 
yet discovered will dissolve these foreign bodies, the proper relief 
is their complete surgical removal. During acute inflammatory 
stages these foreign bodies may cause complete obstruction of the 
involved tract, which, however, ordinarily subdivides within a com- 
paratively short time after the beginning of dietary restrictions. As 
the inflammatory reaction subsides the pressure in back of the ob- 
struction tends to force the bile past the ball-like valve along the 
passageway. Persistent obstruction usually means that the sub- 
mucosa has become involved in a stricture process, in practice most 
commonly due to the inflammatory reaction around common duct 
stones of long standing or to cancer. 
These general principles apply also to urinary and other examples 
of stone formation. 
If the finger be slipped around the right free border of the gastro- 
duodenal-hepatic omentum, or in other words through the epiploic 
foramen of Winslow, the hepatic artery, vena porta, and common 186 
REGIONAL ANATOMY 
bile duct may be lifted up en masse. Fortunately for the surgeon, 
the common bile duct lies superficially and nearest the free border 
of the omentum, consequently operations can be performed from in 
front. This surgery calls for a keen appreciation of anatomy, for a 
moment's reflection must convince any one how serious a calamity 
it would be to cut the vena porta or hepatic artery or their main 
subdivisions. An error in the surgery of paired organs may result 
in the sacrifice of one, whereas a tear in one of the main vessels of 
the liver must practically always be fatal. 
Pancreas 
The pancreas is developed as two separate outgrowths from the 
duodenum, but these parts externally fuse into one. All pancreases 
have a duct, which empties together with the common bile duct into 
the duodenum, and in about half of the specimens examined an acces- 
sory duct is to be found, which traverses a separate course into the 
duodenum. The pancreas is a whitish gland stretched transversely 
across the epigastrium, lying extraperitoneally opposite the first 
lumbar vertebra?. The celiac axis artery arises above the pancreas, 
and its branches give the main supply, while the superior mesen- 
teric artery running under the pancreas to the mesentery gives an 
anastomosing supply. The pancreas is divided for descriptive pur- 
poses into a head, a hook process or neck, a body and tail, averaging 
roughly one-quarter times one times six inches in diameters. The 
head of the pancreas is encircled by the duodenum, which also re- 
mains in close contact with the lower part of the body of the pan- 
creas. Both the pancreas and'the duodenum are firmly fixed pos- 
teriorly by connective tissue across the vertebral column. The main 
pancreatic duct receives the minor branches and empties into the 
common bile duct just before its entrance into the posterior wall of 
the duodenum. The small pancreatic acini are made up of small 
groups of cells, which empty into little ducts, and together with 
other units wrapped up in connective tissue make the visible lobules. 
In a fresh body the pancreas appears white when in a nonactive 
state, but pink when engorged with blood. 
Practical 
Due to their fixed position in front of the vertebral column, the 
pancreas and duodenum are subject to injuries due to external THE ABDOMEN 
187 
violence, large pancreatic cysts for example being caused by the 
reaction of the peritoneal tissues to extravasated pancreatic juice. 
A gallstone lodged at the duodenal opening of the bile-pancreatic 
duct may cause bile to enter the pancreas, resulting in the serious 
catastrophe of acute pancreatitis. The pancreatic secretion in this 
condition escapes from the ducts and in its spread laterally digests 
common bile duct 
accessory pancreatic duct 
/celiac axis artery 
main pancreatic duct 
■ duodenojejunal juncture 
superior mesenteric artery 
duodenum 
Fig. 56.-Pancreas and Duodenum. 
the tissues. The bile physiologically makes the contents of the small 
intestine alkaline, while the pancreas furnishes the digestive fer- 
ments. 
Dissection.-The liver, pancreas and duodenum should now be 
removed from the abdominal cavity en masse for detailed study. 
The ligaments holding the liver to the diaphragm should be cut, and 
then the segment of the vena cava inferior running through the pos- 
terior surface of the liver cut just above and below this organ. The 
pancreas and duodenum should then be mobilized from the anterior 188 
REGIONAL ANATOMY 
surface of the vertebral column, and the vessels, nerves and con- 
nective tissues holding them to the posterior wall should be cut 
across. These three organs may then be lifted out. 
The anterior surface of the duodenum should be split open in 
order to examine the entrance of the liver-pancreatic duct at the 
papilla. By pressing on the gall bladder fluid, if present, can com- 
monly be forced through this duct entrance. The smaller liver and 
pancreatic ducts should be noted after free sectioning of these 
organs, and the other points described noted. The preservation of 
the liver is commonly so poor and the discoloration of the tissues so 
great that the lobules can not be made out. These lobules are 
readily to be made out by the unaided eye, however, in a fresh nor- 
mal specimen. 
OTHER ABDOMINAL ORGANS 
Spleen (Lien) 
The spleen is one of the group of glands which do not possess 
ducts, and belongs essentially to the blood system. It is the most 
variable organ of the body in size, varying greatly even during 
apparent absolute health. It increases greatly and characteristically 
in size during infections of the body, following interference with its 
venous outflow and in special blood diseases. The spleen is ordin- 
arily smaller than the clenched fist and has a rounded superior sur- 
face in contact with the left diaphragm vault. The hilus, situated 
about the middle of its inferior surface, serves as the passageway 
for the vessels, nerves, and connective tissues. Except for the region 
about the hilus, the fibroelastic coat is covered by peritoneum. When 
the spleen increases greatly in size, it eventually appears below the 
rib margin at the left nipple line, and then is obviously more exposed 
to external violence. Its long axis is held diagonally in the body by 
its ligaments and its edges are notched. 
The fibroelastic coat, technically the tunica albuginea, sends in 
large partitions, which spaces are further subdivided by numerous 
smaller fibrous partitions. These subdivisions contain numerous 
lymph nodules, about equidistantly spaced, while the larger inter- 
vening areas are known as the pulp. The pulp, so called on account 
of its relatively soft consistency, makes up the great bulk of the THE ABDOMEN 
189 
spleen, and is essentially dilated vessel spaces through which the 
blood circulates very slowly. The lymphatic nodules and many pulp 
cells are like the white of an egg in color, but due to the enormous 
quantity of blood in thin-walled vessels, the organ appears a reddish 
blue. The cherry red colors normally mean an extra admixture of 
arterial blood, while the purplish colors are due to an excess of 
venous blood. 
Many cases of surgical removal have proved that the spleen is an 
organ not essential to life, or, so far as has been noted, to the pre- 
servation of health. On the other hand, all anatomic evidence, both 
developmental and comparative, points to it as an actively function- 
ating gland. The increase in size during acute and chronic infec- 
tions of the body is strong presumptive evidence that in some way 
it actively opposes these attacks. The lymphatic nodules develop 
the lymphatic type of white blood cells throughout life (lympho- 
cytes), while the pulp areas produce red blood cells before birth, 
but normally cease this activity shortly thereafter. The spleen 
differs from lymphatic glands anatomically in the intimate contact 
of its essential cells with large quantities of blood traveling at slow 
speed, and possibly functionally in that it reacts to bacterial poisons 
in the blood stream instead of to poisons in the lymph. With the 
qualification that only part of the blood at any time runs through 
the spleen, it has much the same relationship to the blood that lymph 
glands have to the lymph. 
The spleen should be examined in position and then be removed 
from the body for more detailed examination. 
Blood Supply of Abdomen 
After the removal of the gastrointestinal tract and the various 
glands just considered, the vessels are well exposed and may then 
be studied with advantage. Running slightly to the left of the 
median line and in front of the vertebral column is found the main 
artery, the abdominal aorta. This aorta divides at the junction of 
the fourth and fifth lumbar vertebras into the right and left common 
iliacs. The common iliacs divide near the sacroiliac joint into a 
hypogastric, which enters the lesser pelvis, and a larger external 
iliac, which continues under the inguinal ligament into the thigh 
and then becomes known as the femoral. The hypogastric artery 190 
REGIONAL ANATOMY 
of the lesser pelvis was formerly known as the internal iliac. 
Medially directed branches of this hypogastric artery supply the 
bladder in front and the rectum in back, while between them in the 
female lies the uterine artery. The laterally directed branches of 
Main Vessels 
level of 
diaphragm 
Branches 
cceliac (celiac) 
axis 
- superior 
mesenteric 
abdominal aorta 
renal 
• testicular or 
ovarian 
- lumbar 
segmental 
inferior 
mesenteric 
level of 4th 
lumbar vertebra 
midsacral 
common iliac - 
hypogastric 
(internal iliac) 
external iliac 
level inguinal 
ligament of 
Poupart 
Fig. 57.-Diagram of Arteries of abdominal cavity. 
this hypogastric artery, the gluteal, the sciatic and the internal 
pudendal have been considered in connection with their distribution 
in the gluteal and perineal regions. Inasmuch as these branches 
originate inside the musculofascial layers of the abdominal wall and THE ABDOMEN 
191 
pass through the wall to the outside, it is possible for a hernia to 
work its way out along any of these vessels. 
The vein which accompanies the abdominal aorta and lies to its 
right side, instead of the expected designation of abdominal aortic 
Main Vessels 
right atrium 
(auricle) 
level of 
diaphragm 
Branches 
- hepatic • 
azygos 
vena cava inferior - 
- renal 
hemiazygos 
lumbar 
segmental 
common iliac - 
hypogastric 
(internal 
iliae)- 
external iliac 
Fig. 58.-Diagram of Veins of abdominal cavity. 
vein, is known as the vena cava inferior. The veins accompanying 
the common, the hypogastric and the external iliac arteries receive 
the same names and correspond accurately. The general anatomic 
rule that a vein does not lie directly between an artery and a bone 192 
REGIONAL ANATOMY 
is broken in the case of the left common iliac vein. This vein passes 
under the right common iliac artery and directly against the verte- 
bral column in its course to the inferior vena cava. 
The most plausible theory for this exceptional occurrence is that 
the artery tends to support the column of blood and to minimize 
back pressure. Whatever the true explanation, as a practical result, 
clotting of blood in the left common iliac vein is very much more 
frequent than in the right common iliac, no matter from which side 
of the body the infection starts. The increase of pressure in the 
capillaries due to venous obstruction causes an excessive secretion 
of lymph, which collects in the tissues as it can not escape as rapidly 
as it is secreted. The excessive amount of lymph in the lower 
extremity stretches the dermis layer to the point at which pressures 
and counterpressures are equal, when no more lymph will be pro- 
duced than can be carried off by the lymphatic vessels. Improve- 
ment from this condition may take place by reabsorption of the clot, 
or by the development of an efficient collateral anastomosing cir- 
culation. So called "milk leg," following childbirth, is due to an 
obstruction in the common iliac vein, or its component subdivisions, 
commonly of the left side. 
The large single branches of the abdominal aorta are the celiac 
axis, and the superior and inferior mesenteries. These vessels have 
been previously described in connection with the blood supply of 
the gastrointestinal tract and may now be traced to their origins. 
The corresponding veins make up the vena porta, its blood travers- 
ing a second set of capillaries of the liver before entering into the 
vena cava inferior. 
The most important and largest paired branches are the renal 
or kidney arteries. These branches normally follow the routine 
anatomic rule, that is, the left renal vein crosses anteriorly to the 
aorta, whereas the right renal artery passes posteriorly to the vena 
cava, that is, the veins do not lie between the arteries and the bone. 
Just below this pair from the aorta arise the paired testicular or 
ovarian arteries, which maintain the blood supply of these organs 
throughout life, the left testicular or ovarian vein generally entering 
the left renal vein instead of the vena cava. A pair of diaphragmatic 
branches, arising up near the first lumbar vertebra, supply the half 
of the diaphragm nearest the aorta, while coming off just below 
these a pair of suprarenal vessels supply the gland of the same name. THE ABDOMEN 
193 
Besides these vessels, four pairs of segmental lumbar arteries are to 
be noted, and also a midsacral branch continuing the aortic course 
down to the coccyx. 
The aorta comes through a. fixed opening in the diaphragm oppo- 
site the twelfth thoracic vertebra, while the vena cava goes through 
somewhat higher up the dome opposite the tenth thoracic vertebra. 
On each side of the vertebral column lies an anastomosing column 
of large veins, known as the azygos, or single veins. These 
azygos veins connect the inferior vena cava through the diaphragm 
with the superior vena cava. These veins receive as tributaries the 
lumbar segmental veins and make several connections with the in- 
ferior vena cava. 
The arteries and veins should be dissected. 
Development of Kidneys 
The kidneys are paired organs, which specialize in the excretion 
of certain waste products from the body. The kidney in the in- 
vertebrate animals is essentially segmental in character, each seg- 
ment having its own excretory gland and duct. This primitive seg- 
mental type of kidney, technically the pronephros, is developed 
very early in the life of the human embryo. It, however, does not 
functionate in the mammalia group, its function being taken over 
by the placenta, and therefore soon retrogresses and disappears 
entirely. 
The second type of kidney of embryonic life, technically the 
mesonephros, consists of tubules, which empty into a common duct 
running to the cloaca. This kidney type persists throughout life in 
many of the lower vertebrates, but is never really called into action 
in the human embryo, its function being taken over by the placenta. 
The main excretory tube of this kidney is known as the Wolffian 
duct, while a tube formed secondarily alongside is known as the 
Muellerian duct. These ducts persist in the human and functionate, 
not as parts of the urinary apparatus, but as parts of the genital 
structures. The association of genital and urinary structures in 
development is very complex, tubes often subserving combined func- 
tions, as is even true in the fully developed male. The Wolffian duct 
persists as the spermatic duct and utriculus of the male, while the 
Muellerian duct persists as the ovarian duct and uterus of the 194 
REGIONAL ANATOMY 
female. Small vestigial remnants of the Muellerian tube are to be 
found near the testicle of the adult male, while remains of the 
Wolffian tube are located near the ovary. 
The third kidney type, technically the metanephros, is a tube- 
stalk extending up from the bladder portion of the cloaca, at the 
far end of which the permanent kidney develops. 
Kidney (Ren) 
The kidneys have the characteristic popularly known shape and 
are very roughly one times two times four inches in size. The kid- 
neys are enclosed in a firm fibrous and fatty outer capsule, which is 
freely connected with the posterior part of the abdominal wall, and 
holds the kidneys in position with their long axes parallel to the 
vertebral column. The anterior surface of the kidneys is partly 
covered by peritoneum, whereas the aperitoneal posterior surface 
is held firmly against the musculature of the posterior abdominal 
wall. Both kidneys come in contact with the twelfth rib posteriorly, 
but the right kidney is shoved lower down by the mass of the liver 
so that only its upper extremity is protected by the twelfth rib. The 
hilus of the kidney is turned towards the middle line and receives 
the renal vessels and nerves, while posteriorly the kidney duct or 
ureter leaves the hilus and immediately turns straight downward 
towards the pelvis. The widened out upper part of the ureter, 
which attaches to the kidney, is known as the pelvis of the ureter. 
The ureter travels extraperitoneally across the common iliac vessels, 
then along the side walls and eventually across the floor of the pelvis 
to the fundus or base of the bladder. 
Microscopic Structure 
By painstaking studies of serial microscopic sections it was deter- 
mined that each kidney is made up of hundreds of thousands of 
small tubules. Each tubule is a miniature kidney with the following 
microscopic structure: A glomerulus, composed of tufts of capillary 
vessels, which secrete the watery constituents of the urine, emptying 
them into the beginning of the tubule. The portion of the tubule 
leading off from the glomerulus takes a curving course, and is 
therefore known as the first convoluted tubule. The succeeding 
long thin parts of the tubule make up the ascending and descending THE ABDOMEN 
195 
loops of Henle. Then follows a second convoluted part of the tubule, 
similar to the first in structure, which empties into a collecting 
tubule. The larger collecting ducts open onto the papillaa which 
project into the pelvis of the ureter. 
Diseases of the glomeruli interfere with the water and salt secre- 
tion of the kidney, while disturbances of the convoluted cell areas 
interfere with the urea type of excretions. The color of the normal 
kidney cells is translucent, like the white of a fresh egg, but the 
great quantity of blood present gives the organ its varying reddish- 
blue color. 
glomerulus 
1st convoluted 
tubule 
2nd convoluted 
tubule 
artery 
vein 
descending loop of Henle 
ascending 
loop of 
Henle 
collecting 
duct 
Fig. 59.-Kidney Tubule, diagrammatic (x 100) 
Gross Structure 
On sectioning a normal kidney an irregular outer zone, known as 
the cortex or shell, is clearly differentiated from an inner zone, 
known as the medulla. The cortex is about one-quarter of an inch 
average thickness and contains the glomeruli and convoluted tubules, 
the glomeruli being macroscopically visible as round dots in a fresh 
kidney. The medulla contains the ascending and descending loops 
of Henle and the collecting ducts, these structures causing macro- 
*copic radial line markings in a fresh normal kidney. 196 
REGIONAL ANATOMY 
The whole kidney has a connective tissue framework and is sur- 
rounded by a fibrous coat, consequently if the kidney cells are 
swollen by disease they will bulge on a section of this tunica fibrosa. 
Chronic low grade inflammations cause an increase of the connective 
tissue elements of the kidney, with eventually irregular shrinkage 
in the size of the organ. In chronic degenerations, the fibrous coat 
cortex 
pelvis of 
/ ureter 
hilus 
medulla' 
_papilla 
ureter 
Fig. 60.-Longitudinal section of Kidney. 
of the kidney becomes extra firmly attached to the thickened in- 
ternal fibrous framework. Malformations or destruction of one 
kidney usually results in an overgrowth or technically hyperplasia 
of the remaining one. 
Dissection.-The relationships of the artery, vein, and ureter 
should be noted. The kidney should then be lifted out of its bed by 
cutting the fibrous compartment layer holding it in position against THE ABDOMEN 
197 
the posterior wall. The ureter should be traced to the bladder and 
may then be cut at a convenient midpoint. The fibrous coat should 
be laid open freely along the convex lateral margin of the kidney, 
and either turned back over the hilus or dissected off. A single 
long cut, splitting the kidney along its lateral margin and from its 
upper to its lower extremity, should be carried through into the 
pelvis of the ureter. If the kidney is normal, the various points 
noted are readily to be made out. 
Suprarenal Gland (Glandula Suprarenalis) 
The suprarenal glands are of the ductless type, lying over the 
upper extremities of the kidneys. These glands fit over the convex 
surfaces and are very roughly one-quarter times one-half times one 
inch in diameter. They are composed of a cortex or shell and an in- 
ner medullary substance, differing in color and histologic structure. 
These glands have a liberal blood and especially liberal sympathetic 
nerve supply. They are essential to health and even to life itself, 
the secretion being normally absorbed either into the venous capil- 
laries or into the lymphatic vessels. 
This secretion has the power of contracting the muscular coats of 
blood vessels, and consequently this secretion obtained from cattle 
glands finds a utilization in surgery. If both of these glands are 
surgically removed or are destroyed by disease, the patient becomes 
progressively weaker and finally dies as a result of the lack of this 
secretion. 
The suprarenal glands should be removed from the body and 
cross-sectioned. 
Urinary Bladder (Vesica Urinaria) 
The part of the urinary bladder from which the urachus arises is 
known as the vertex, this portion rising or sinking down with the 
distention or emptying (for urachus see page 179). The fundus, or 
base, on the other hand, is firmly fixed by fascias in the anterior pel- 
vic portion of the abdominal cavity, which means, of course, above 
the pelvic diaphragm. The fundus has a continuously stretched trian- 
gular area, technically known as the trigonum vesicae, which has an- 
teriorly the urethral exit and posteriorly the entrance of the two 
ureters. The ureters come through the different layers of the blad- 198 
REGIONAL ANATOMY 
der wall in a valve slant, consequently the greater the bladder dis- 
tention the tighter are the ureteral openings closed. The bladder is 
composed of mucosa, submucosa, and muscle layers, and over its 
superior and posterior surfaces is covered by a reflexion of the peri- 
toneum. The mucosa of the whole urinary tract is lined by a strati- 
fied transitional epithelium, differing only from a stratified squa- 
mous epithelium in the fact that its upper cells become very large 
and distended instead of flat and dried out. This change is pre- 
sumably due to the action of the urine on the superficial cells. The 
submucosa is the strong layer, which, after distention to about one 
pint, can stretch no further without great danger of bursting. The 
muscle layers run in two or, according to some, three directions and 
planes, the circular fibers reinforced forming the sphincter muscle 
around the beginning of the urethra. This same description applied 
to the ureter, with the modification that the distensibility of the 
ureters is normally less than one-quarter of an inch. 
Advantage is taken of distention of the bladder with the raising 
of its peritoneal reflexion to perform suprapubic, extraperitonea] 
operations on the bladder, whereas in routine abdominal sections 
the bladder should be empty. Due to the shortness and distensibility 
of the female urethra, stones are ordinarily passed from the female 
bladder before becoming large. 
Male Internal Genitalia 
The prostate gland is a male sexual organ which, as its name im- 
plies, lies around the beginning of the urethra beyond the bladder 
(pro = before; state = stand). This gland lies in the lower pelvic 
portion of the abdominal cavity-that is, above the pelvic dia- 
phragm-and its capsule is firmly anchored by fascias to the bony 
walls. The structure of the prostate is glandular, and it empties 
its secretion by numerous small ducts into the prostatic portion of 
the urethra. The function of this gland is to pour out a male sexual 
secretion to prepare the route for and be mixed with the testicular 
secretions. The prostate surrounds the urethra posteriorly and lat- 
erally, and is very roughly one times one times one and one-half 
inches in diameter, the side-to-side measurement being the greater. 
The prostate gland may be readily palpated through the intact 
anterior wall of the rectum. Gonorrheal infections attack this gland THE ABDOMEN 
199 
and in the chronic stages may lurk in the stagnating fluids more or 
less indefinitely unless cleared out by massage. Firm tumors are 
formed in this gland, more commonly between the ages of fifty to 
seventy, which is just before the physiologic decline of the prostate. 
These tumors, on account of the firm capsule, tend to shut off the 
urethra, consequently surgical removal of the tumor from inside the 
capsule is ordinarily required in order to give lasting relief. 
Testicle (Testis) 
The testicle is made up of hundreds of fine coiled tubules, held 
together in a very firm fibroelastic coat (tunica albuginea). These 
tubules are microscopic in cross-section, but when uncoiled are about 
six feet in length. Their essential function is the development of 
spermatozoa, which are forced out into a larger coiled duct lying 
over the testicle, known as the epididymis (didymis= testicle). 
The epididymis continues as the ductus deferens of the spermatic 
cord, this duct being distinguishable from the other constituents of 
the cord by the thickness of its walls and its firm consistency. This 
testicular duct, or ductus deferens, traverses the anterior abdominal 
wall, as noted in connection with inguinal hernia, and then runs 
extraperitoneally straight to the prostatic urethra. It traverses the 
prostate between the lateral and, if present, the median lobe, and 
empties on each side of a small pocket in the posterior surface of 
the urethra, known as the utriculus. Just as the ovarian ducts in 
the female empty into the uterus, so the testicular ducts of the male 
empty into the outlet of this corresponding utriculus. The testicular 
secretion travels down towards the urethra, but, controlled by a 
sphincter muscle, is stored temporarily in a convoluted sac, known 
as the seminal vesicle (semen = seed). These seminal vesicles have 
the routine mucosa, submucosa, and muscle layers, and their upper 
posterior surfaces are covered by peritoneum. They are coiled 
ducts about one-quarter times two inches in size when distended, 
which lie laterally to the testicular ducts. The lower part of the 
ductus deferens of the testicle is known technically as the ductus 
ejaculatorius. 
On account of the great strength of the fibroelastic coat, acute 
inflammations do not cause the testicle proper to swell, but may 
cause tremendous enlargement of the epididymis. Tumors and the 200 
REGIONAL ANATOMY 
destructive chronic inflammatory infections, on the other hand, may 
break down the testicular tunica albuginea. The testicular duct 
has a very strong fibrous coat, which distinguishes it from the other 
elements of the spermatic cord. Gonorrheal infections, having in- 
vaded the urethral end of the deferent duct of the testicle, tend to 
work back into the seminal vesicles and into the epididymis. 
Dissection.-The urinary bladder and the prostate gland should 
epididymis 
ductus deferens 
testicle 
seminiferous tubules 
epididymis 
seminal vesicle 
ampulla 
ejaculatory duct 
prostatic urethra 
Fig. 61.-Diagram of Testicle and its Ducts. 
be studied in position. Then the ureter should be traced to the 
bladder and a sound passed into the bladder via the urethra. The 
ductus deferens of the testicle should be traced down to the prostate 
gland and the seminal vesicles cleared. Then the bladder should be 
bluntly dissected loose and the urethra cut across just above the 
pelvic diaphragm, removing the urinary bladder, prostate gland, and 
the various ducts en masse. The student should now review the 
attachments of the pelvic diaphragm, which forms the boundary THE ABDOMEN 
201 
between the pelvic portion of the abdominal cavity and the perineum. 
The bladder should be opened in its anterior portion and the triangle 
at its base noted, the urethra in front and the two ureters posteriorly 
on each side. The prostatic urethra should now be split open ante- 
riorly and the entrance points of the ejaculatory portion of the tes- 
ticular ducts and the utriculus noted. The opening of the utriculus 
and the ejaculatory ducts into the prostatic urethra are surrounded 
by a cratered projection, known as the colliculus seminalis. The 
median bar and the lateral lobes of the prostate gland may now be 
sectioned freely. Serial cross-section through the testicle will reveal 
its gross structure and its firm fibroelastic coat. 
Female Internal Genitalia 
The uterus or, popularly, the womb lies in the pelvic portion of 
the abdominal cavity-that is, above the pelvic diaphragm. It is a 
pear-shaped muscular organ, its upper rounded portion being known 
as the fundus, while its lower end, which projects into the fornix, 
or vault of the vagina, is known as the cervix. The normal infantile 
and senile uteri are distinctly smaller than during the childbearing 
period, when it is approximately one times one and a half times two 
and a half inches in diameter. The walls are made up of mucosa, 
submucosa, very heavy muscle, and, over its upper three-fourths, 
peritoneum. The mucosa is lined by simple columnar epithelium 
with crypts, and is partially cast off at each monthly or technically 
menstrual period. The tremendous increase in the musculature dur- 
ing pregnancy is brought about by a great increase in the size of 
the individual fibers. 
The uterus has a broad ligament running to it from each side of 
the pelvis, which contains between its two layers of peritoneum the 
vessels, nerves, lymphatics, and connective tissues of the organ. 
The vessels from the aorta running in the upper free margin of the 
ligaments are the ovarian, while those from the hypogastric artery 
in the lower part of the ligament are the uterine. The uterine, or 
Fallopian, tubes lie in the upper part of this broad ligament and 
functionate by carrying the ova into the uterus. This movement 
of the ovum is brought about by wave-like motions of the fine cilia 
on the surface of the uterine tube epithelium. The ends of the 
uterine tubes are fringed and curled about the neighborhood of the REGIONAL ANATOMY 
202 
ovaries, which are situated on the upper posterior surfaces of the 
broad ligaments just below the tubes. The ovaries, roughly one- 
quarter times one-half times one inch in size, mature the ova, which 
are cast off and normally are carried via the uterine tubes into the 
uterus. The uterus in its normal position lies anteriorly flexed, and 
this position is aided by the musculofibrous round ligaments, which 
act as guy-ropes. These round ligaments arise outside of the belly 
wall and, passing through the inguinal canal, insert in the front 
upper part of the fundus of the uterus. Relaxation of the perineal 
tube 
ovary 
round 
ligament 
fundus 
ovary 
uterine 
tube 
ovarian 
artery 
broad | ' 
ligament 
cervix -1 
vagina 
uterine 
cavity 
ureter 
uterine 
artery 
Fig. 62.-Uterus and Associated Organs, posterior view, right side sectioned. 
wall from any cause often causes retroflexion and eventually descent 
of the uterus. 
The mucosa of the vagina is lined by a stratified squamous epithe- 
lium and has the usual and also some special extra large compound 
mucous glands. 
Dissection.-The uterus, with its round and broad ligaments, its 
tubes and the ovaries, should be examined in position. The peri- 
toneum should receive attention, noting its reflexions and the ves- 
sels, nerves, and connective tissues in the broad ligaments. The 
uterus should then be removed, cutting across the round and broad THE ABDOMEN 
203 
ligaments and the upper part of the vagina. The uterus should then 
be split open in the median line and its walls, its cavity, and the 
opening of the tubes into the cavity examined. A probe should be 
passed through the uterine tubes and these laid open by a free dis- 
section. The ovaries should be incised freely in order to see their 
interior structure, with the developing ova. The ovaries have a 
delicate connective tissue framework, a fairly firm fibrous coat, and, 
except for the hilus, are covered by peritoneum. 
Origin of Iliopsoas Muscle 
The origin of the psoas muscle from the sides of the bodies of the 
lumbar vertebrae and the origin of the iliac division from the ilium 
can now be made out. The course of the combined iliopsoas tendon 
under the inguinal ligament to its insertion into the lesser trochanter 
of the femur has been previously noted. The psoas origin explains 
the occurrence of apparent hip symptoms in diseases of the lumbar 
vertebrae. 
The iliopsoas muscle should be cleared in order that the nerve 
plexus may be followed out. 
Nerves 
The five lumbar, five sacral, and the coccygeal segmental nerves 
supply the lower part of the abdominal cavity and the lower extrem- 
ity. The nerve supply of the abdominal wall coming from the lower 
six thoracic and first lumbar nerves can not be traced to the verte- 
bral column until the chest cavity has been dissected. The origin 
of the lower extremity plexus from the third, fourth, and fifth lum- 
bar, and the first, second, and third sacral nerves should be made out. 
Inasmuch as the nerves lie extraperitoneal and extrafascial through- 
out, hernias never follow along the nerve exits. The detailed con- 
sideration of the involuntary sympathetic nervous trunks will be 
postponed until the thorax has been opened. But it is worthy of 
emphasis again that the nerve supply is segmental-that is, that the 
same segment of the spinal cord that supplies the skin also supplies 
the underlying muscles and organs and the sympathetic nerves. 
The nerves should be traced out. 204 
REGIONAL ANATOMY 
Practical 
Acute painful infections of the abdominal organs, unless the nerves 
are out of commission, cause a reflex spasm of the overlying musca- 
lature. While this localizing symptom has great value, it is not, as 
unfortunately widely considered, a panacea for abdominal differen- 
tial diagnosis. Painful affections of the serous coverings of the 
heart or lungs, for example, cause epigastric muscular rigidity, as 
the nerve supply would lead one to anticipate. The abdominal 
muscle spasm often fails.to differentiate between bile duct, appen- 
dix, and right literal attacks, and in women between appendix and 
uterine tube infections. All other individualizing symptoms and 
objective findings must be considered in order to arrive at a proper 
diagnosis. The muscles of a highly nervous individual react sharply 
to a minor pain, while people of a stable nervous system may be able 
to relax their muscular rigidity even though suffering severely. 
Chronic inflammatory masses and various tumors, including can- 
cers, are commonly palpable through the abdominal walls. Acute 
inflammatory exudates are soft in consistency and, lying under a 
rigid muscle, are not palpable. Marked tenderness on pressure with 
fever is characteristic for the chronic inflammatory masses, in con- 
tradistinction to the lesser tenderness and afebrile course of the 
tumor-cancer group. The anatomy of the abdominal cavity must 
be kept clearly in mind in order to be able to interpret properly the 
palpatory findings. It is, of course, always necessary to compare 
the anatomic findings with the clinical symptomology, utilizing them 
as mutual checks. CHAPTER XI 
THE THORAX 
The thorax or chest is the rib-supported cavity containing as its 
most important structures the pair of lungs and the heart. Inferi- 
orly the twelfth thoracic vertebra, the lower border of the ribs, and 
the xiphoid process form the bony landmarks separating the chest 
from the abdominal cavity. It is to be especially noted that this is 
only a superficial boundary, as due to the dome-shaped roof of the 
diaphragm the abdominal cavity extends well up under the ribs. 
Superiorly the first thoracic vertebra and the first pair of ribs with 
their junction to the sternum form the true boundary separating the 
chest from the neck region, but this is also only a surface demarca- 
tion, as the lung cavity domes up an inch or more into the base of 
the neck. The clavicle lies over the medial part of the first rib and, 
being superficial, is often arbitrarily selected as a bony landmark 
between the neck and chest regions. 
Bony Framework 
The bony framework of the thoracic cavity has been considered 
in connection with the upper extremity, consequently instead of a 
repetition here the reader is referred to pages 74 and 75. 
Muscles 
Muscles belonging to the neck, to the upper extremity, and to the 
abdominal wall arise by digitations from the outer surfaces of the 
ribs. The muscles belonging to the upper extremity which overlay 
the chest are: The pectoralis, major and minor; the trapezius and 
latissimus dorsi; and the rhomboids, levator scapular, and serratus 
anterior. Those belonging to the abdominal wall are: The rectus 
abdominis, the external and internal oblique, and, over the posterior 
wall, the continuation of the extensor vertebrae group. As none of 
these muscles, except the serratus anterior, cover the midaxillary 
space, the ribs are more readily seen and palpated over this area. 
205 206 
REGIONAL ANATOMY 
When the remains of these muscles just considered have been dis- 
sected off, two thin muscle sheets may be found running between the 
adjacent ribs. The external intercostal muscle runs downward and 
medially, just as the external oblique of the abdominal wall, whereas 
the internal intercostal runs downwards and laterally-that is, at 
right angles to the external. Layers of deep fascia lie on the outer 
surface, between, and on the inner surface of these muscles, as would 
infrasternal (inferior costal) angle 
Fig. 63.-Bony-ciirtilaginous Thorax. 
be anticipated. The inner side of this inner fascia is lined by a 
serous membrane, known as the pleura. 
The external and internal intercostal muscles correspond to the 
external and internal muscles of the abdominal wall, both groups 
at a certain stage of fetal development being distinctly segmental in 
arrangement. The segmental arrangement of the intercostal per- 
sists through life, while in the case of the abdominal muscles this 
original segmentation is obscured by the fact that the neighboring THE THORAX 
207 
muscles are not separated by ribs, but grow together into one solid 
sheet. The fact that the original segmental nerve supply to these 
abdominal muscles and to the rectus abdominis persists throughout 
life gives the clue to the early developmental status. The nerves 
have no method by which they can change from their original posi- 
tion, whereas the vessels supply changes so commonly via the extra 
development of anastomoses that it is practically valueless as an aid 
to the understanding of development. The muscles of the extremi- 
ties are also originally segmentally arranged, but on account of the 
complicated character of the changes and migrations of muscles this 
discussion was, generally speaking, omitted. 
Vessels and Nerves 
The segmental intercostal vessels and nerves run deep and well 
protected under the lower border of the rib above, forming a depres- 
sion on the inner surface of the ribs, which is known as the subcostal 
groove. The vessels do not maintain their original condition, but 
the anastomosis along the lateral margins of the sternum become the 
internal mammary vessels. This internal mammary artery lies deep 
to the costal cartilages and divides at the lower border of the ribs 
into a diaphragmatic branch and an epigastric branch, the epigastric 
artery having been previously traced in the rectus sheath towards 
the umbilicus. The fact should be recalled to mind that the lower 
six thoracic and the first lumbar segmental nerves, after supplying 
the chest wall, continue into the abdominal wall. 
The remains of the abdominal and upper extremity muscles should 
be dissected off, and then the muscles, nerves, and vessels in several 
intercostal spaces should be dissected out. 
Respiration 
The first and second ribs are held by muscles extending from the 
cervical vertebra), and during inspiration are raised up. If these 
muscles and all the intercostal muscles contract simultaneously, each 
rib will be drawn up towards its neighbor and the whole thoracic 
wall raised up, resulting in an increased inside area. The partial 
vacuum suction causes air to rush into the lungs and is known as the 
costal type of respiration. The contraction of the muscles of the 
diaphragm pulls this structure down and increases the vertical 208 
REGIONAL ANATOMY 
diameter of the interior of the thoracic cavity, which is the diaphrag- 
matic type of respiration. Normally both types of breathing go on 
simultaneously, but in women, in so far as the corset interferes with 
movement of the diaphragm, the costal respiration must take up 
extra work. 
While the muscles between the ribs and of the diaphragm are of 
the voluntary type and can be controlled by will, both these types 
of breathing are usually performed automatically. This is the clas- 
sical exception to the general rule in regard to striated muscle fibers. 
Types of Chest 
Since the beginning of observation of the human body two ex- 
tremes of types of the healthy chest have been noted. Physically 
strong people have a well-rounded, relatively deep chest antero- 
posteriorly, whereas weak people have a flat chest. The strong type 
is known as the sthenic, the weak as the asthenic (sthenic = strong). 
Historically the sthenic chest development was noted to be more 
common clinically in the apoplectic type of diseases, whereas the as- 
thenic type was more frequently represented in the consumptive type 
of diseases. The anatomic background for these facts has received 
much study during late years and is becoming well established. The 
sthenic type is due to a strong general musculature, which holds the 
bony framework of the thorax well up, even in full expiration, 
whereas the asthenic type is due to a weak musculature allowing the 
thoracic wall to sag down. As anatomic proof of this theory, the 
relatively short neck of vigorous people is advanced. The cervical 
vertebrae are of normal size, so the shortness must be due to a high 
position of the chest wall, whereas in the case of a relatively long 
neck, conditions are reversed. A further anatomic proof is the wide 
inferior costal angle in vigorous people, demonstrating that the chest 
is well raised up in expiration, whereas the narrow costal angle is 
characteristic for the asthenic type of chest. The inferior costal 
angle (angulus infrasternalis) is formed by the costal cartilages of 
the sixth to the tenth ribs on each side as they progress towards the 
sternum. This angle may be noted to widen out during the raising 
up of the anterior thoracic wall, as, for example, physiologically 
during inspiration. The relative depth anteroposteriorly in the 
sthenic type of people, as contrasted with the relative shallowness in THE THORAX 
209 
the asthenic type, is further anatomic proof of the high standing 
position of the thoracic wall. 
It is to be borne in mind that any condition which keeps the chest 
chronically overdistended from the inside, as, for example, asthma, 
may cause simulation of a sthenic type of chest, even in a weakling. 
The so-called chicken-breast type of deformity is produced during 
childhood by some semipermanent obstruction to the flow of air into 
the lungs. The sternum remains out at its normal position, while 
the ribs and cartilage'tend to be more or less drawn in by a partial 
vacuum suction. 
Relation to General Physique 
The sthenic versus the asthenic type of chest is of fundamental 
importance in any physical examination as a clue to the general 
physical vigor of the individual. The sthenic type of chest is an 
anatomic index of physical vigor of stock, while the asthenic type 
means lack of physical vigor as a heritage. The difference in type 
can be noted early in childhood, checking up anatomically the ordi- 
nary observation that it is to a great extent a hereditary element. 
Illness and lack of physical activity may at times produce the 
asthenic type of chest in individuals of physically vigorous stock, 
while the reverse is equally true. 
The common association of the so-called round shoulder with an 
asthenic type of chest is explained by the fact that both are due to 
the same factor-that is, weak musculature-which in both cases 
allows a sagging of the part. 
Relation to Abdomen 
It is proper to consider in this connection the relation of the type 
of thorax to conditions in the abdominal cavity. The bust of the 
"Venus de Milo" has been universally accepted by art critics as the 
standard model of perfection of figure. This torso has a sthenic 
type of chest, a full upper abdominal cavity, a narrower waist line, 
with a proper widening again over the hips. Any anatomist could 
add to the art critics' statement a guarantee that the abdominal 
organs are all in proper condition. On the other hand, a narrower 
upper abdominal cavity and a protruding lower pot-belly are uni- 
versally associated with an asthenic chest. The narrowed upper 210 
REGIONAL ANATOMY 
abdominal cavity does not allow room for the organs normally 
belonging in this area, consequently they tend to sag down, the 
technical word to describe sagging being ptosis. In a markedly 
asthenic individual, more especially if the general physical strength 
is for any reason below par, all the abdominal organs pull on and 
stretch their ligaments until an advanced degree of ptosis is pro- 
duced. All the intraabdominal organs sag in general asthenia and 
develop abnormally long and lax mesenteries, omenta, or ligaments, 
as the case may be. Clinically most stress has been laid on the sag- 
ging of the stomach, kidneys, and large intestine, perhaps more in 
reality than the anatomic changes justified. As the fundamental 
asthenia must be reckoned with, surgery in this field of endeavor 
has been able to accomplish comparatively little. 
Corsets are worn as a social custom and often to make a woman 
appear to have what heritage or lack of exercise have denied her- 
a good figure. The extremely narrow-waisted corset was an artistic 
and anatomic monstrosity, but the modern corset tends more to fol- 
low the natural figure and consequently is not nearly so objection- 
able. Once women become used to corsets they are uncomfortable 
without the artificial support; but there is in the normal person no 
real reason, save vanity or, perhaps, prudery, for their existence. 
Corsets have earned a place in the treatment of ptoses. The effects 
of corsets on the limitation of diaphragmatic breathing has previ- 
ously been commented upon. 
Contents of Mediastinum (Cavum Mediastinale) 
The mediastinum is the midarea between the two pleural sacs 
extending from the back of the sternum to the front of the vertebral 
column, and from the lower part of the neck to the diaphragm. 
It contains the heart, the largest blood vessels of the body, lymphatic 
vessels and glands, nerves, connective tissues, the trachea, or wind- 
pipe, the esophagus, or gullet, and a special ductless gland, the 
thymus. The mediastinum is very thin just back of the sternum, the 
two pleural sacs almost coming into contact. 
Dissection.-To open up the chest for an anatomic or postmortem 
examination the costal cartilages should be cut with an ordinary 
knife near the end of the bony portion of the rib. Then the dia- 
phragm muscle should be freed from its attachment to the inferior 
deep surface of the sternocartilaginous section. By lifting up the THE THORAX 
211 
sternocartilaginous section the attachment of the pleural sacs to its 
deep surface may be demonstrated. After the pleura is cut from 
the back of the sternum and the sternum cut across below the sterno- 
clavicular joint, this section should be removed. The position and 
size of the internal mammary artery should be noted on the deep 
surface of the costal cartilages. 
Pleural Cavities (Cavum Pleurae) 
The two lungs are developed from the mediastinal end of the 
tracheal tube, being developmentally extrapleural and, in the strict 
esophagus trachea 
- lung 
hilus 
parietal 
pleura 
visceral 
pleura 
pericardial 
sac 
Fig. 64.-Transverse section of Thorax, level of fifth thoracic vertebra. 
mediastinum 
sense of the words, remaining extrapleural. But as the lung devel- 
ops, it bulges in a layer of pleura in front of it and becomes entirely 
surrounded by pleura except at the hilus, the lungs being therefore, 
practically speaking, intrapleural organs. The layer of pleura cov- 
ering the wall is the parietal layer, whereas that covering the lung 
is the visceral layer, these two pleural layers being normally held in 
contact by vacuum suction. The strength of the parietal pleural 
layer is due to extrapleural fascia layer'of the wall. The pleural 
sac is reflected back at about one and one-half inches from the lower 
margins of the ribs all the way around, whereas superiorly the domed 212 
REGIONAL ANATOMY 
roof of the pleural sac rises about an inch above the first rib into the 
base of the neck. 
Pleuritis, or pleurisy, is an inflammation of the pleura, character- 
ized anatomically by thickening and adhesion of the surfaces, clini- 
cally by pain more marked on deep breathing or coughing. This 
condition is ordinarily secondary to disease conditions in the lungs. 
Pleuritis may, in addition, be characterized by a collection of air, 
lymph, blood, or pus in the pleural sacs. 
Lungs versus Abdomen 
The surface line between the resonance on striking over the lung 
and the dullness on striking over the liver on the right side is taken 
roughly as the sixth rib in the nipple line, the eighth rib in the mid- 
axillary line and the tenth rib in the scapular line, marking off a 
horizontal plane. It is obvious that this line would vary with in- 
spiration and expiration, and also that the narrow edge of the lung 
really extends further down, but this rule is sufficient for practical 
purposes. Due to the presence of the heart above the diaphragm on 
the left side, this line is about one-half inch lower on the left side. 
The absence of great contrast in the normal percussion note on the 
left side has an influence on the difficulty of diagnosing lung and 
pleural diseases in this area. 
Diaphragm (Diaphragma) 
This muscle partition is made of voluntary striated muscle fibers, 
which are under the control of the will, but ordinarily work auto- 
matically-that is, sympathetically. On both surfaces the diaphragm 
is covered by a serous membrane, which is known as the pleura 
above and the peritoneum below. These muscle fibers have at least 
an inch wide origin from the inner surface of the lower margins of 
the ribs and costal cartilages, and also from the sides of the bodies 
of the lumbar vertebrae. From all directions these fibers run to a 
central aponeurosis. 
But while these general rules of the diaphragm attachments and 
relationship are reasonably accurate, they are most apt to fail just 
when most required-that is, in pus infections of the pleural cavities. 
These collections of pus in the pleural cavity must be opened at the 
lowest gravity point in order to obtain complete continuous drain- THE THORAX 
213 
age, otherwise there will be retention with overflow and the poison- 
ing will persist. Therefore the surgical rule of taking out a section 
of a higher rib and then, with interior guidance, the section from 
the lower rib, is to be most highly recommended. 
The diaphragmatic, or phrenic nerve arises from the fourth cervi- 
cal segment and can be readily traced along the anterior part of the 
side wall of the mediastinum on its course to the diaphragm. It has 
an accompanying artery and vein, which anastomose with the aortic 
diaphragmatic and the internal mammary diaphragmatic branches. 
The nerve supply is a clue to the development of the diaphragm, 
which is primarily opposite the fourth cervical segment and progres- 
sively sinks during fetal life to its final position. The diaphragm on 
expiration normally rises to the fourth interspace mammary line on 
the right side and about one space lower on the left. The abdominal 
aortic opening in the diaphragm lies opposite the first lumbar verte- 
bra, to the right and about two inches higher lies the inferior vena 
caval opening, and to the left, still further up, nearer the top of the 
dome lies the esophageal opening. Nerves, lymphatic ducts, and the 
azygos veins also take advantage of these passageways. 
The attachments of the diaphragm should be noted in the dissected 
body. 
Lung (Pulmo) 
The trachea divides into two primary bronchial tubes, these pri- 
mary into a number of secondary, the smaller secondary into a num- 
ber of tertiary tubes, which finally lead down to the smallest bron- 
chial tube, or bronchiole. The bronchial tubes are made up of 
mucosa, submucosa, and cartilaginous rings instead of the usual 
muscle layers. The object of the cartilage is to keep the passage- 
ways permanently open, while the connective tissue inserts between 
the rings serve to increase the mobility of the tubes. The bron- 
chioles have no cartilage, but in its place a circular muscle layer, 
which has the power to contract and shut off the air supply. The 
bronchial mucous membrane is covered by a simple columnar epi- 
thelium, while the larger tubes have, as would be expected, the 
stratified columnar type. Each bronchiole leads into an air sac 
known as the lobule, the smaller subdivisions of which are known 
under the term alveoli, on account of their saccular form. These 
lobules, when distended, are visible to the unaided eye. The air sac 
is lined by epithelial cells, which are flat when distended by air, 214 
REGIONAL ANATOMY 
while outside of this air sac lies a network of capillaries, connective 
tissues, and lymphatic vessels. 
Oxygen passes through the essential lung cell and the capillary 
wall into the blood, while carbon dioxide is cast out of the blood 
into the air space. While this is the main function of the lung, it is 
known as a matter of common experience that water and volatile 
substances, such as alcohol, oil of onions, and creosote, for example, 
are also thrown off. During normal resting condition of the body 
less than one-quarter of the air in the lungs is changed with each 
respiration. The lungs are collapsed and functionless at birth, but 
bronchiole 
atrium 
alveolus 
Fig. 65.-Diagram of Pulmonary Lobule (xlOO). 
after the connection with the placenta is broken the child normally 
makes its first inspiratory effort. Spasmodic closure of the bron- 
chiole musculature, more common in individuals of a nervous tem- 
perament or with certain physical ailments, is known as asthma. 
Vessels and Nerves 
The pulmonary arteries travel along the bronchial tubes and divide 
into corresponding branches. This artery carries venous blood, 
which returns as arterial blood via the corresponding pulmonary 
veins to the heart, this being the classical reversal of the usual 
conditions. As this venous blood would obviously be unable to care THE THORAX 
215 
for the lung cells themselves, a very much smaller system, known 
as the bronchial arteries and veins, supply the lung cells. The lym- 
phatic vessels drain into a series of glands in the mediastinum, 
which, in the case of the city dweller, at least, are commonly full of 
coal-dust residue. In the lymph or tissue spaces of the lung itself 
black coal-dust splotches are practically normal for a city dweller. 
Numerous processes of the sympathetic nerves form a plexus at the 
hilus of each lung, controlling the arteriole and bronchiole muscula- 
ture, and for other less obvious functions. At the hilus of the lung 
the trachea lies posteriorly, but inside the lung all regularity of the 
hilus structure grouping is soon lost. 
Lobes 
The right lung is larger than the left in the proportion that ten is 
to nine, this difference being due to the greater bulk of the heart on 
the left side. The lungs are divided into lobes by deep fissures, 
which are so slanted that the upper lobe is continuous with the ante- 
rior portion, the lower lobe with the posterior portion. The blunted 
point of the upper lobe, which extends into the base of the neck, is 
known as the apex, the concaved diaphragmatic portion of the lower 
lobe as the base. The right lung has a small extra lobe between 
its upper and lower lobes. 
Tuberculosis typically attacks the apices of the lungs, while lobar 
pneumonia typically attacks the bases, very possibly due to gravity 
differences in the blood supply. Calcareous nodules in the apex, 
demonstrable during life by the x-ray, are generally to be attributed 
to a healed tuberculosis. In weak individuals, more especially 
among the very young or the very old, a small tube bronchitis may 
eventuate in attacking scattered lobules, called lobular pneumonia. 
The typical pneumonia of vigorous adult life involves all the neigh- 
boring lobules in its spread, and hence is called lobar pneumonia. 
Practical 
If a water barrel is half full and is struck by a stick, the upper 
half will yield a long resonant note, while the lower half will yield 
a short, dull note. This principle is made use of in the percussion 
of the chest wall for diagnostic purposes. But the amount of fat 
and thickness of the chest wall will change the resulting note mate- 216 
REGIONAL ANATOMY 
rially, consequently it is customary to compare the notes of the two 
sides. Percussion must remain always simply an approximation, but 
is perfectly satisfactory in the localization of complete dullness- 
that is, solidified lung or large amounts of fluid in the pleural sac. 
But when both lungs are slightly involved percussion fails, as there 
is no guide of the normal for this particular individual. The main 
reliance must then be placed in auscultation-that is, listening over 
the lung area. If the lung is partially solidified, the rough tracheal 
sounds are transmitted to the ear instead of the rustling-like sound 
of normal respiration. Further, the secretions can be heard to rattle 
back and forth in the various bronchial tubes, these sounds being 
technically known as rales. If the lungs are seriously diseased, the 
characteristic symptom is a general blueness of the body. The 
results of physical examination must always be checked up against 
the clinical course. 
Dissection.-The lungs should be examined in position, and then 
one hilus should be dissected, demonstrating the vessels and bron- 
chial tubes. By pulling the lungs out of their respective cavities 
and cutting across at the hilus, the lungs may be removed from the 
body for detailed examination. If the lung has been attacked by 
acute or chronic diseases, adhesions will have to be separated 
between the parietal and visceral layers of the pleura. 
Heart (Cor or Cardia) 
The heart is the muscular pump, which functionates by starting 
and maintaining the circulation of the blood. Inasmuch as the 
lymph-for practical purposes a diluted blood without the red blood 
corpuscles-is being constantly secreted by the capillaries, the cir- 
culation of the lymph is indirectly dependent upon the heart action 
(for a discussion of lymph see p. 59). These fluids are the medium 
of exchange, allow for specialization of labor in the body, and, of 
course, are essential to life. The circulation in plants depends upon 
other factors, but all animals, except the lowest orders, have some 
type of muscular pump. 
Simplest Type 
A very simple type of heart may be noted among the invertebrate 
animals, which is practically a single vessel with an enlarged extra THE THORAX 
217 
heavily muscled section. This primitive heart contracts rhythmi- 
cally in a wave-like motion from its entrance, the vena cava, to its 
exit, the aorta. The blood is thus forced onward through the capil- 
laries of a series of gill or lung arches and then passes into a dorsal 
aorta. This dorsal aorta gives a segmentally arranged supply to the 
body, the blood eventually returning via veins to the heart. The 
early heart of the human embryo is of this type. 
Fig. 66.-Heart, single chamber type, no valves. 
Valves 
When in the more complicated hearts high pressure must be 
developed to force the viscous blood through the system, dependence 
is no longer placed upon the direction of the contracting wave to 
maintain the direction of flow, but valves are introduced. The 
mechanism of the valve does not interfere with the flow of blood in 
the proper direction, but when pressure is lower in the preceding 
chamber the valve shuts and prevents backflow, technically regurgi- 
tation. 
vena cava 
aorta 
i 
atrio-venticular valve 
aortic valve 
Fig. 67.-Heart, double chamber type, with valves. 218 
REGIONAL ANATOMY 
Chambers 
The more complicated hearts have at least two chambers, the first 
of which acts as a receiving station and the second as a pumping 
station. The receiving subdivisions are known as the atria, this 
word meaning hallway, while the more muscular pumping subdivi- 
sions are known as the ventricles, on account of their stomach-like 
shape. The atria were formerly known as the auricles, on account 
of their alleged resemblance in shape to the external ear, this term 
being still retained, but now being limited to the curled-up tips of 
tricuspid valve 
pulmonary semilunar valve 
superior and 
inferior 
vena cavas - 
- pulmonary 
aorta 
pulmonary 
veins 
- systemic 
aorta 
bicuspid or mitral valve 
aortic semilunar valve 
Fig. 68.-Heart, four chamber type, with valves. 
the atria. Further, all the birds and mammals have the heart par- 
titioned into halves, one half carrying the venous blood through the 
lungs and the other half the arterial blood through the general 
circulation. In the human being after birth the right atrium and 
ventricle pump the venous blood through the lungs, while the left 
atrium and ventricle pump the arterial blood through the general 
circulation. 
Flow Through Heart 
Venous blood enters the right atrium from the superior and infe- 
rior vena cavas. No valves are to be found in the vena cavas or in 
the main subdivisions which make up these veins, being an exception 
to the general rule in regard to veins. The venous blood is forced THE THORAX 
219 
by a contraction wave of the right atrium, which starts at the vena 
cavas and forces the blood over the tricuspid valve into the right 
ventricle. Contraction of the right ventricle then closes the tricus- 
pid valve and forces the blood over the pulmonary semilunar valve 
into the pulmonary aorta. The arterial blood from the lungs enters 
the left atrium through the valveless pulmonary veins and then is 
forced over the bicuspid, or mitral, valve into the left ventricle. 
Contraction of the left ventricle closes the bicuspid valve and forces 
the blood over the aortic semilunar valve into the general circulation. 
In actual practice the two atria contract simultaneously and then 
the two ventricles contract. 
Fetal Circulation 
The circulation during intrauterine life differs from the condition 
after birth, as logically must follow from a consideration of com- 
monly known facts. The fetus develops but does not use its lungs 
until after birth, consequently the pulmonary artery would subserve 
no useful function by pumping a great quantity of blood through 
the lungs. The bulk of the blood is therefore short-circuited through 
a vessel, the ductus arteriosus, from the pulmonary aorta to the 
thoracic-that is, the systemic-aorta. This ductus arteriosus ceases 
to functionate after birth and eventually disappears, practically 
without leaving a trace. Now, inasmuch as little blood returns via 
the pulmonary veins from the lungs during fetal life, the left side of 
the heart would be without a sufficient supply to work with were it 
not for the foramen ovale opening in the atrial partition. This fora- 
men allows the blood from the right atrium to cross over into the left 
atrium. The mixing of the fetal bloods causes the blood in the 
arteries to be of a mixed arteriovenous type, distinctly bluish, but 
still perfectly satisfactory for all requirements of the fetus. The 
fetal heart develops four chambers, but on account of the ductus 
arteriosus and open foramen ovale functionates as a two-chambered 
heart. Part of this mixed blood is being sent out constantly to the 
placenta, where it is oxygenated and then returns to the right 
atrium, mingling with the returning venous blood of the general 
circulation. 
Summarizing the course of the blood from the heart to the pla- 
centa and return: A mixed arteriovenous blood is pumped from the 220 
REGIONAL ANATOMY 
left ventricle into the aorta, or from the right ventricle via ductus 
arteriosus to aorta, then through descending thoracic aorta, abdomi- 
nal aorta, and common iliacs, and then through the umbilical 
arteries to the placenta; here it becomes oxygenated and returns as 
right pulmonary 
veins 
left pulmonary 
veins^- 
superior vena 
cava 
inferior vena cava 
right atrium 
(auricle) 
left atrium _ 
foramen ovale 
left ventricle _ 
right ventricle 
systemic aorta - 
pulmonary aorta 
ductus arteriosus - 
pulmonary veins 
pulmonary artery 
thoracic aorta - 
inferior vena 
cava 
hepatic 
capillaries 
ductus venosus 
ductus venosus 
umbilical vein 
abdominal aorta - 
placenta 
common iliac 
umbilical arteries 
hypogastric 
(internal iliac) - 
external iliac 
Fig. 69.-Diagram of Fetal Circulation. 
pure arterial blood via the umbilical vein, the bulk short-circuits via 
the ductus into the inferior vena cava, while a smaller portion goes 
through portal veins of liver into inferior vena cava, and then into 
right atrium (for umbilical vein see p. 179). The ductus arteriosus, 
the foramen ovale, the ductus venosus, and the umbilical arteries and THE THORAX 
221 
veins are fetal structures, which normally cease functionating after 
birth and disappear or exist only as vestigial remains during later 
life. The umbilical vein carries the only pure arterial blood of the 
embryo or fetus; all the ordinary veins carry venous blood, while 
the arteries carry a mixed arteriovenous blood. 
Due to congenital malformation or disease of the systemic aortic 
orifice, the ductus arteriosus and the foramen ovale may have to 
remain open and so cause the condition known clinically as "blue 
baby." This persistence of the fetal condition after birth is incom- 
patible with a normal expectancy of life. 
Pericardium 
The heart lies in the lower half of the mediastinum, with its lower- 
most part in contact with the central aponeurosis of the diaphragm. 
It lies in a pericardial fibrous sac, which is attached to the diaphragm 
and the various connective-tissue layers of the mediastinum. This 
fibrous sac is lined by an endothelial serous sac, which has parietal 
and visceral opposing layers. 
The pericardial sac should be opened freely. 
Gross Anatomy 
Approximately two-thirds of the heart lies to the left of the median 
line. The heart bears a direct ratio to the size and strength of the 
individual, which is approximately given as equal to the individual's 
clenched fist. However, this estimate is very relative, as the amount 
of distention of the cavities obviously would influence materially the 
apparent size. The left ventricle makes a blunted point known as 
the apex, which is the lowest and farthest to the left part of the 
heart. During life this apex strikes the chest wall with every mus- 
cular contraction of the heart and is found normally in the fifth 
interspace just medially to the nipple line. As the base of the heart 
and its posterior portion are held fixed by their vessel connections, 
any increase in the size of the heart, due either to increase in muscle 
mass or dilatation or both, will result in carrying the apex beat 
farther down and farther to the left side. The left border of the 
heart is overlapped by the lung, but over a small triangular area 
near the sternum the pericardium can be entered without traversing 
the pleural cavity. 222 
REGIONAL ANATOMY 
The pulmonary aorta and the thoracic aorta arise from the base of 
the heart and run upward, the pulmonary arching over the thoracic 
aorta. A pair of coronary arteries arise from the ascending portion 
of the thoracic aorta as it leaves the heart and make an encircling 
crown in the atrioventricular groove. These coronary arteries send 
off branches to supply both atria and ventricles, the corresponding 
veins emptying, as would logically be expected, into the right atrium. 
These vessels are obviously important, and modern research has 
shown, in contradistinction to former beliefs, that their branches 
anastomose freely. The anterior and posterior descending branches 
of these coronary arteries run down over the partition between the 
right and left ventricles, and consequently furnish a surface demar- 
cation. The atria lie mainly in back of the heart, but their irregular 
tips, the auricular portions of the atria, project around the origins 
of the pulmonary and thoracic aortas. 
Dissection.-By lifting the apex of the heart out of the pericardial 
sac and cutting across an inch distant from the heart the veins, the 
vena cavas and the pulmonaries, and the arteries, the thoracic and 
pulmonary aortas, the heart may be removed from the body for 
detailed examination. 
Atria 
The atrioventricular groove with the coronary arteries, also the 
entrance of the superior and inferior vena cayas into the right 
atrium, and the entrance of the four pulmonary veins into the left 
atrium, are all readily demonstrable. The inferior and posterior 
surfaces of the ventricles are molded by the diaphragm, which also, 
due to its doming shape, approaches the atria posteriorly. 
The posterior walls of both atria should be opened freely and, if 
the circulation has chanced to give out slowly, clots formed just before 
death will have to be removed. The walls of the atria are thin and 
internally, are irregular, due to the projection of muscle bundles. 
The inner surfaces of the atria, however, are smooth, due to the endo- 
thelial lining, which is continuous with that of the blood vessels. 
A valve-like, thin area in the middle of the interatrial partition, 
the normal adult reminder of the fetal foramen ovale, is ordinarily 
readily demonstrable. 
The atria should now be dissected off. THE THORAX 
223 
Valves (Valvulae) 
The removal of the atria makes the interior of the ventricles visible 
except in so far as the bicuspid and tricuspid valves interfere. The 
normal bicuspid valve admits two fingers, while the tricuspid is 
slightly larger. The valves are rather thin sheets of white fibrous 
tissue, covered on all surfaces by endothelium, and when closed their 
free margins meet liberally. The bases of the valves are materially 
thicker and blend with the connective tissue of the muscular ven- 
tricular walls (annuli fibrosi). The surfaces of the valves towards 
the atria are perfectly smooth, while the ventricular surfaces are 
made irregular by the attachment of muscle tendons, which func- 
tionate by preventing the valves from being forced back into the 
atria. 
The aortas should be trimmed off to within a half inch of their 
exit from the heart. The systemic aorta has materially thicker walls 
than the pulmonary aorta, in conformity with the relative pressures 
these vessels respectively are called upon to withstand. The blood 
clots should be removed from these vessels, and then the three semi- 
lunar cusps of each vessel will become visible. The free edges of Ihe 
cusps overlap, while their bases blend with the connective tissue ele- 
ments of the arterial walls. These valves differ from the atrioven- 
tricular valves in their materially smaller size and in that they do 
not have musculotendinous support. The two coronary arteries 
should be noted coming off from the beginning of the thoracic aorta, 
the origin of these vessels being partly hidden by the cusps, except 
when the aortic valve is closed. 
Various disease processes may attack and partly destroy these 
valves, almost exclusively in the harder worked left side of the heart. 
A leaky valve would obviously increase greatly the work of the 
heart. The extra work of a leaking valve causes a dilitation of the 
heart, and eventually an increase in the musculature in order to 
keep up the function. The valves may be stuck together, resulting 
in too small an opening, technically known as stenosis, or* they 
may be eaten away, resulting in an overlarge opening, causing 
regurgitation. 
Ventricles (Ventriculi) 
The muscular wall of the left ventricle is normally over twice as 
thick as that of the right ventricle, on account of differences in the 224 
REGIONAL ANATOMY 
power required. The thickness of these walls varies materially 
with the amount of dilatation, consequently relative weights of the 
ventricles are of more importance than relative measurements. 
Whereas the right ventricle wall in health averages less than one- 
eighth of an inch, the left is commonly over one-quarter of an inch 
in thickness. The muscle bundles extending into the ventricular 
cavities and attached via tendons to the valves are known as papil- 
lary muscles (adjective of papilla or nipple). Microscopically the 
heart is made up of a special striated type of involuntary muscle 
cells. The general fact that the muscle fibers interweave and make 
whorls can be made out, but the details of this arrangement can only 
be followed in specially prepared specimens. The partition between 
the two ventricles, marked externally by the anterior and posterior 
descending branches of the coronary arteries, is so situated that the 
bulk of the anterior wall is made up by the right ventricle, while the 
bulk of the posterior wall is made up by the left ventricle. 
The condition of the musculature would obviously be a very im- 
portant element in any heart disturbance. Diseases of the coronary 
vessels, in so far as they interfere with the nutrition of the heart 
musculature, may result in heart collapse or even sudden death. 
Stab wounds of the ventricles do not ordinarily allow blood to escape 
from the interior of the cavity, because the uncut paralleling fibers 
draw tight and close the opening. The patient, however, commonly 
bleeds from cut coronary branches, so as to distend the pericardium. 
This blood, under pressure in the pericardial sac, tends to check the 
flow of blood into the atria, which is under low pressure, and causes 
the heart to become short of blood for pumping. This occurrence 
calls strenuously for surgical interference, as the opening of the 
pericardial sac, with release of blood clots, may give instantaneous 
relief. A collection of air, lymph, or pus in the pericardial sac may 
produce the same symptoms and great relief may follow its removal. 
Greatly increased intraabdominal pressure may press the diaphragm 
against the heart, which diminishes the blood supply of the atria, 
resulting in serious circulatory disturbances and even, in patients 
with diseased hearts, in sudden death. 
The walls of the ventricles should be opened in order to examine 
the muscles and the ventricular cavities. The incision through the 
ventricular wall should parallel the septum, the position of which THE THORAX 
225 
may be determined externally by the anterior and posterior descend- 
ing interventricular branches of the coronary arteries. 
Vagus Nerves 
The pair of vagus or tenth cranial nerves leave the base of the 
skull, traverse the neck and the mediastinum, and give off important 
branches to the heart. These nerves regulate the beat of the heart 
to the requirements of the body, this portion of the vagus belonging 
to the sympathetic or automatic nervous system. If these nerves 
are severely injured or destroyed, the heart may continue to beat, 
but without rhythm or force commensurate with the general needs 
of the body. The impulses down the vagus nerves determine the 
rhythm of the atria, which normally fixes the rate of the ventricles. 
At the end of the atrial beat the message is carried along a muscular 
bundle of His from the atrial septum to the ventricular septum. If 
this bundle of His is destroyed the vagus message can not pass to 
the ventricles, which still contract rhythmically, but at about half 
the normal rate, known clinically as heart block. 
The vagus nerves hold a course between the trachea and the esoph- 
agus and are therefore not visible in an ordinary exposure. The 
esophagus holds a course just in front of the vertebral column, while 
the trachea lies just anterior to the esophagus. The vagus nerves 
should be located on each side of the mediastinum by removing the 
parietal pleura just in back of the hilus of the lungs. The left vagus 
may be readily located, as it crosses the lateral surface of the arch 
of the aorta, while the right vagus should be sought for just in back 
of the main right bronchial tube. The vagus nerves should then be 
traced upwmrds towards the neck, and downwards along the esoph- 
agus to the stomach. The left vagus eventually supplies the anterior 
surface of the stomach, developmentally the left surface, while the 
right vagus supplies the posterior surface, developmentally the right 
surface. The larger branches from the vagus nerves in the upper 
part of the mediastinum join the cardiac plexus, while smaller 
branches are given off to the lungs, to the trachea, and to the esoph- 
agus. As the left vagus crosses the arch of the aorta, the left infe- 
rior laryngeal nerve is given off. This nerve curves around the arch 
of the aorta from the lateral side medially and then progresses up- 
ward to the larynx. The peculiar roundabout course of this nerve 
is due to the descent of the heart and aorta during embryonic and 226 
REGIONAL ANATOMY 
fetal life. The word vagus means wander, as in vagabond, and in 
view of the facts noted above is surely justified. 
The vagus nerves should be identified and traced out. 
Sympathetic Nerves 
The sympathetic nerve supply comes from all the cervical and the 
upper thoracic segmental nerves, the three cords into which these 
fibers join supplying their respective sides of the heart. The fact 
that these nerves rise way up in the neck would lead us to surmise 
that the heart was situated in the neck during the early stage of 
development. The heart, as a matter of fact, is developed in the 
neck and only secondarily sinks down in the mediastinum to its pro- 
tected situation in back of the ribs. These nerves essentially control 
the blood supply of the coronary arteries, regulating it according 
to the requirement of the heart. 
The common reference of cardiac pain to the side of the neck, more 
commonly the left, and radiating down the arm is presumably to be 
explained on this anatomic basis. Pericardial pains are located over 
the heart and, if referred, belong to the fourth to the eighth thoracic 
segmental nerves. Other pains are located by the patient in the 
heart itself, but cardiac pains are not commonly referred along the 
vagus nerves. 
Thoracic Arteries 
The thoracic aorta is divided, for descriptive purposes, into an 
ascending portion, an arch, and a descending portion. The ascend- 
ing aorta at its commencement sends off the right and left coronary 
arteries, while the arch on the right side sends off an innominate 
artery, and on the left side a common carotid and a subclavian. The 
innominate artery (arteria anonyma) will later be demonstrated to 
divide in back of the clavicle into its component right common 
carotid and subclavian subdivisions. The descending thoracic aorta 
sends off the lower nine pair of segmental intercostal branches and 
the pair of bronchial arteries. The aorta arches to the left side of 
the mediastinum, while the descending aorta progresses towards the 
middle line, holding a course just in front of the bodies of the 
thoracic vertebras. THE THORAX 
227 
Thoracic Veins 
The subclavian vein joins the jugular, the head and neck vein, on 
both sides of the body just posterior to the junction of the first rib 
with the sternum. These two so-formed innominate veins (vente 
anonymae) join at the right of the sternum just in back of the second 
rib to form the superior vena cava. The intercostal, bronchial, and 
smaller mediastinal veins empty into the respective right and left 
Main Vessels 
left common carotid 
Branches 
left subclavian 
innominate 
arch of aorta 
- bronchial 
ascending aorta 
-coronary 
- intercostal 
descending aorta 
phrenic (diaphragmatic) 
Fig. 70.-Diagram of thoracic Arteries. 
azygos venous trunks, which form an anastomosis between the 
superior and the inferior vena cavas. The left azygos vein (vena 
hemiazygos) terminates in large cross-branches to the right or 
major azygos vein (vena azygos), which empties into the superior 
vena cava. 
The arteries and veins should be completely exposed in the lower 
part of the mediastinum, but the clearing of those in the upper third 
of the mediastinum should be postponed until the neck dissection 
has reached the proper point. 228 
REGIONAL ANATOMY 
Thoracic Lymph Duct (Ductus Thoracicus) 
The main lymphatic duct of the body is a continuation of the ab- 
dominal lymph duct and is known as the thoracic lymph duct. It 
holds a course just in front of the vertebral column, runs approxi- 
mately in the median line and, when distended, is over one-eighth of 
an inch in diameter. When distended with lymph it appears trans- 
lucent and consequently is readily distinguishable from a vein; but 
right jugular 
right subclavian 
right innominate 
vena azygos 
vena cava superior 
intercostals 
vena hemiazygos 
right atrium 
Fig. 71.--Diagram of thoracic Veins. 
in a dissecting-room body it may be difficult to identify. The tho- 
racic duct turns to the left in the upper part of the mediastinum and 
lower part of the neck, and enters the left subclavian vein near its 
junction with the jugular. Embryologically the thoracic Imyph 
duct is made up of two parallel ducts, one on each side of the median 
line, but as development proceeds, the left duct becomes the main 
one, while the right normally drains only its side of the head, neck, 
arm, and chest. Variations in the adult thoracic duct and anasto- 
mosing connections with other veins are very common findings. 
Blockade of the duct may cause lymphatic fluid to collect in the THE THORAX 
229 
left pleural sac or in the peritoneal cavity. This is the classical 
example of edema due to obstructed outflow, most edemas being due 
to an excessive production of lymph. Inasmuch as the digested fat 
from the intestines is carried through this duct into the circulation, 
this lymphatic fluid becomes milky-like after fat digestion and is 
known as chylous fluid. The widened-out abdominal portion of the 
duct, over the first and second lumbar vertebrae, is known as the 
cisterna chyli. 
The lymph duct should be dissected out. 
Esophagus and Trachea 
The esophagus holds a course just in front of the vertebral column, 
deviating at its lower end to the left en route to the stomach. The 
walls of the esophagus are made up of mucosa, submucosa, and 
muscle layers, with the usual characteristics. The esophagus passes 
posterior to the pericardial sac. The trachea maintains a position 
just in front of the esophagus, and as a result the further down it 
is traced the deeper it lies from the anterior surface of the thoracic 
wall. 
The lower half of the esophagus should be dissected, but the detail 
dissection of the upper half of the esophagus and the trachea had 
better be postponed until the neck region is opened up. 
Gangliated Sympathetic Trunks 
The sympathetic nerves of the abdominal and thoracic regions now 
deserve more detailed study, as the next step in dissection will 
destroy these regions. Although in details the cervical sympathetic 
differs from the thoracic and abdominal sympathetic systems, the 
general underlying principles are the same (for general discussion 
see page 63). 
Each segmental nerve of the body just after it emerges from the 
intervertebral foramen sends a branch to, and receives a branch 
from a ganglion of the sympathetic system. These ganglia are sit- 
uated on the sides of the vertebral bodies, in the thoracic region 
situated well back towards the intervertebral foramina, while in the 
cervical, lumbar, and sacral regions their position is more anterior. 
A pair of ganglia exist for each segment of the body, except in the 
neck region, where the original eight ganglia are fused into three. 230 
REGIONAL ANATOMY 
The neighboring ganglia are connected by large strands of nerve 
processes, hence the phrase gangliated sympathetic trunks. At 
every ganglia there is the possibility of a multiplication of the num- 
ber of nerves-that is, one axis-cylinder process may run to a dozen 
or more ganglia cell bodies. As a matter of fact, a great multi- 
plication of sympathetic nerves commonly does take place at the 
various ganglia. 
These ganglia of the sympathetic trunks send branches to each 
sympathetic trunk 
sympathetic trunk 
segmental spinal 
nerve 
ganglion of 
sympathetic trunk 
white ramus 
communicans 
gray ramus 
communicans 
prevertebral plexus 
prevertebral ganglion 
sympathetic trunk 
sympathetic trunk 
Fig. 72.-Diagram of Sympathetic Trunks. 
segmental nerve en route to the various structures under control of 
this system. Other branches follow the fibrous compartments of the 
arteries and, in the case of the chest and abdomen form the three 
large intermediate prevertebral plexuses, the cardiac, the epigastric, 
and the hypogastric, and other prevertebral plexuses of lesser im- 
portance. The branches from the neck and upper thoracic area to 
the cardiac plexus can only be seen satisfactorily after the neck has 
been dissected. The branches from the lower six thoracic ganglia 
should be noted to form into three cords, known as the splanchnic 
nerves, which join the epigastric plexus. The branches from the THE THORAX 
231 
lumbar and sacral ganglia should be traced to the hypogastric 
plexus. 
These prevertebral plexuses contain ganglia and connect up with 
the microscopic visceral ganglia and plexuses in the various organs. 
The descending thoracic aorta and the abdominal aorta should 
now be removed by cutting the lower thoracic and the abdominal 
segmental arteries. The azygos veins and the inferior vena cava 
should also be removed. Minor clearing will now expose the gangli- 
ated cord of the sympathetic trunks from the upper thoracic region 
down to the coccyx. 
Thymus 
The thymus is a ductless gland held by connective tissue in the 
upper half of the mediastinum and extending anteriorly to the pos- 
terior surface of the sternum. It varies materially as regards size, 
being large during childhood, but characteristically after puberty 
decreases to a small indefinite mass. The thymus is developed from 
the epithelial lining of the throat and, while the gross and micro- 
scopic appearance of the adult degenerated gland is very similar to 
lymphatic tissue, modern research has shown it to be functionally 
and anatomically a distinct structure. Its function is unknown, 
though in the normal adult, judging from its shrunken condition, it 
has but little to do. In certain lymphatic and other ductless gland 
diseases the thymus increases greatly in size and, presumably, in 
function, in such a state being made up of two distinct lobes and 
filling up all the otherwise unoccupied space of the mediastinum 
above the pericardium. Some cases of unexpected sudden death 
during childhood show enlargement of the thymus gland, together 
with general lymphatic enlargement, as the only unusual postmortem 
findings. The theory advanced that the enlarged thymus presses 
on the trachea, mechanically shutting off the air supply, has not 
received convincing anatomic or clinical proof. 
Vertebral Column (Columna Vertebralis) 
As a matter of dissection convenience it is preferable to consider 
this series of bones, which continue throughout the body, at one time 
instead of in connection with the separate cervical, thoracic, and 
abdominal subdivisions. Inasmuch as the abdominal and thoracic 
divisions can be freely dissected and the neck considered sufficiently 232 
REGIONAL ANATOMY 
for our purposes, it is well to consider the whole vertebral column at 
this stage. 
The bony framework consists of seven cervical, twelve thoracic, 
and five lumbar vertebras, also the sacrum and coccyx. As each 
upper vertebra has progressively less superimposed weight to carry, 
we would expect to find each upper vertebra to be smaller and 
weaker than the neighboring lower vertebra. This, a priori expec- 
tation, is in fact, absolutely borne out. It is important to note, 
however, that the size of the spinal cord and the space allowed for 
-corpus 
costal articular 
surface. 
.vertebral foramen 
intervertebral 
foramen - 
transverse 
articular surface' 
-radix 
costal 
articular surface- 
..transverse process 
"'lamina 
-spinous process 
Fig. 73.-Tenth thoracic Vertebra. 
it. does not vary materially at the different levels. This space for 
the spinal cord is known technically as the vertebral foramen. The 
bodies of the twelve thoracic vertebra; are, in addition, characterized 
by the presence of joint surfaces, where the heads of the ribs attach, 
the second to the ninth ribs, inclusive, notching two neighboring 
vertebrae. The vertebras are typically made up of a body (corpus 
vertebra;) and an arch (arcus vertebrae), the bodies of the vertebrae 
forming the anterior surface of the spinal cord foramen, while the 
arches surround the spinal cord laterally and posteriorly. The arch 
of each vertebra is subdivided into a pair of roots (radix), a pair of THE THORAX 
233 
transverse processes, a pair of lamina, and a spinous process, as 
illustrated in diagram (lamina = thin flat plate). The spinous and 
transverse processes serve as points of origin and insertion for vari- 
ous muscles and tendons, the length of these projections giving 
excellent leverage power. 
The bodies of the vertebrae, considered in downward sequence, are 
separated by progressively larger fibrocartilaginous discs, which 
serve as cushions against shocks and allow for segmental flexibility. 
The bodies are held together by strong anterior and posterior longi- 
tudinal ligaments over the respective surfaces, these ligaments plus 
the fibrocartilaginous discs making up a series of amphiarthrodial 
joints without synovial cavities. The transverse processes have 
opposing articular surfaces with strong capsular ligaments-that is, 
two joints with separate synovial cavities for each vertebra. The 
lamina are held together by firm ligaments, which, on account of the 
admixture of yellow elastic fibers, are known as the ligamenta flava 
(flava = yellow). The interspinous and intertransverse ligaments 
are of white fibrous tissue, except for a slight extra admixture of 
yellow elastic fibers throughout the neck region. The intervertebral 
foramina lie between the roots of the vertebral arches, these spaces 
being materially larger than the vessels and nerves making use of 
them. 
With the body extended to its maximum, all these ligaments tend 
to lock the vertebrae in position, whereas with the body bent for- 
ward in flexion the vertebrae have considerable lateral rotary possi- 
bilities. As in the other regions of the body, the muscles play a 
predominating part in maintaining the alignment of the vertebral 
column, the ligaments feeling the strain only after the muscle power 
has been overcome. Therefore patients, after the muscle relaxation 
of an anesthetic, unless the normal curves of the back have been 
supported by cushions, very commonly complain of pain in the liga- 
ments of the vertebral column. Fact is, pain in the vertebral col- 
umn is one of the commonest of all symptoms, being found in most 
acute diseases and whenever weakened muscles are overstrained. 
Bone diseases, commonly due to tuberculosis, may attack the bodies 
of the vertebrae, whereas fractures ordinarily involve only the verte- 
bral arches. Dislocations of the vertebrae are extremely uncommon 
except in the cervical region, where the opposing bony surfaces are 
materially smaller. The destruction of the bodies of the vertebrae 234 
REGIONAL ANATOMY 
causes the condition known popularly as hunchback, technically as 
kyphosis. 
Extensor Vertebrae Muscle Group 
The large, powerful muscle group on each side of the vertebral 
column is essentially one bundle throughout the lumbar region and 
is known as the sacrospinalis (0. T. erector spinae). This muscle 
mass arises from the back of the sacrum, from the posterior portion 
of the iliac crest and from the spines, lamina, and transverse pro- 
cesses of the lumbar vertebra?. The quadratus lumborum, lying deep 
to the sacrospinalis and running from the crest of the ilium and the 
transverse processes of the lumbar vertebra? to the twelfth rib, 
belongs functionally to this muscle group. The term sacrospinalis 
is restricted to the muscle group in the lumbar region, but this 
extensor group continues over the thorax and through the back of 
the neck, terminating eventually at the base of the skull. The 
lateral border of this extensor muscle group in the thoracic region 
can be traced on the ribs by the roughening, the ribs at this point 
changing their direction sharply, which is known as the angle of the 
ribs. The muscle group makes a heavy, fleshy mass over the loin, 
but is spread out and thinner across the back of the thorax. The 
muscle strands tend to terminate at each rib, another musculotendi- 
nous strip arising and carrying the bundle upwards. This muscle 
over the back of the chest is rather artificially considered to be made 
up of three main bundles, a lateral costalis division, an intermediate 
longissimus division, and a median spinalis division. An extraordi- 
nary number of names are given to the component parts of this 
extensor group in the thoracic and neck regions, but these names 
are only of minor practical interest and consequently will be dis- 
regarded. The nerve and blood supply of this muscle group is seg- 
mental, each level having its separate supply, which means that the 
muscle group itself was originally segmental in origin. 
This dorsal extensor vertebra? muscle group is opposed by the 
ventral flexor group of the lateral and anterior surfaces of the neck, 
chest, and abdomen. Due to their intrinsic strength and their 
mechanical advantages, these extensors are very much more power- 
ful than the opposing flexors, as is well demonstrated whenever any 
irritant causes both groups to contract to their utmost. Meningitis, 
lockjaw, or strychnine poisoning, for example, cause the body to bow THE THORAX 
235 
backwards in extension, so that in extreme conditions only the 
sacrum and back of the head touch the bed. 
This muscle group should be dissected throughout the abdominal 
and thoracic regions. 
Curves 
The normal vertebral column is not a straight line, but has liberal 
curves anteroposteriorly. The primary lumbar curve anteriorly is 
compensated for by a thoracic curve posteriorly, which tends to hold 
the body in balance above the midpelvis. In very stout people with 
a large protruding abdomen the upper parts of the body must be 
thrown far back in order to maintain balance, which yields a 
pompous, strutting appearance, characterized anatomically by exag- 
gerated curves. Thin, weak people, on the other hand, tend to have 
the backbone approach nearer a straight line, unless the muscle and 
ligament power gives way. Normally in strong individuals with 
symmetrical general development, the spines, in a standing position 
of the body, tend to approach a medial straight line. With weak 
musculature, however, lateral curvatures primary and compensat- 
ing may become marked during developmental years and may even 
become permanently fixed. 
Spinal Cord (Medulla Spinalis) 
The medulla spinalis, or, popularly, spinal cord, lies in the bony 
vertebral canal, well protected from ordinary injuries. The inter- 
vertebral foramina, which lie between the roots of the vertebral 
arches, serve as passageways for the vessels and nerves connecting 
with the spinal cord. The lamina meet with the body in full exten- 
sion, but with the body bent forward in full flexion a space of a 
quarter inch or more exists between the lamina in the lumbar and 
cervical regions. This anatomic fact should be recognized in at- 
tempting to obtain the fluid from around the spinal cord, technic- 
ally known as spinal puncture. With the body fully flexed, a hol- 
low needle with an obturator is run through the skin just on either 
side of the median line, and directed upwards and medially down to 
the lamina, and then raised or depressed until it pierces the liga- 
mentum flavum. The removal of the obturator, if the end of the 
needle is in proper position inside of the dura mater, will allow the 
escape of cerebrospinal fluid. 236 
REGIONAL ANATOMY 
Unopened dural sheath 
Opened dural sheath 
cervical 
cervical 
upper extremity 
enlargement 
(intumescentia 
cervicalis) 
thoracic 
thoracic 
lower extremity 
enlargement 
(intumescentia 
lumbalis) 
lumbar 
cauda equina 
lumbar 
sacral 
sacral - 
coccygeal 
coccygeal 
Fig. 74. 
Fig. 75. 
Figs. 74 and 75.-Spinal Cord (medulla spinalis) THE THORAX 
237 
The spinal cord proper is very much shorter than the canal, ter- 
minating opposite the first lumbar vertebra, while only nerve 
trunks traverse the lumbar and sacral parts of the canal. The 
upper nerves run straight out to their foramina, while those below 
the ffrst lumbar progressively run further inside the canal before 
emerging through their foramina. The size of the nerves varies 
materially according to the segment of the body, those to the upper 
and lower extremities being much the largest. The cord varies in 
size at different levels, but averages approximately one-quarter 
inch anteroposteriorly by three-eighths of an inch in width. The 
long paralleling nerve trunks below the first lumbar vertebrae have 
been named the cauda equina, a comparison to a horse's tail. 
Dura Mater, Arachnoidea, and Pia Mater. 
The spinal cord is encased in a very tough fibrous membrane 
known as the dura mater (dura = tough; mater = mother). This 
protecting dura mater is separated by a space from the bony walls 
of the vertebrae, but, on the other hand, is firmly anchored by con- 
nective tissue and that part of the dura mater which blends with 
the sheath of each segmental nerve as it emerges through the inter- 
vertebral foramen. The inner surface of this dura mater is coated 
by an endothelial serous lining, while the thin connective tissue of 
the outer surface of the spinal cord receives a similar covering, 
which is known as the pia mater (pia=soft). Between the dural 
and pial endothelial layers lies a very delicate membrane, known as 
the arachnoidea, a comparison to a spider's web. Anatomists are 
agreed that this arachnoidea is a complete membrane throughout 
and that there are normally no spaces through which fluid may pass 
outwards. The pia-arachnoidal endothelial space is filled up during 
life by a thick layer of fluid under pressure, which is known on 
account of its continuity with the brain as the cerebrospinal fluid. 
This fluid tends to evaporate out of dissecting room bodies and con- 
sequently is not ordinarily demonstrable. It will be reconsidered 
later in connection with the detailed study of the brain and spinal 
cord. The dura-arachnoidal endothelial layers are physiologically 
in actual contact, the smoothness of these surfaces serving to re- 
duce friction to a minimum. Whenever the dura mater is punc- 
tured, the exploring needle practically speaking always goes 238 
REGIONAL ANATOMY 
through the arachnoidea as well and cerebrospinal fluid pours out. 
The arachnoidea, together with its minor semipartitions through the 
pia-arachnoid space, presumably serves to limit wave action in the 
cerebrospinal fluid. 
Dissection.-In order to expose the spinal cord, the muscles, the 
spinous processes, and the lamina must be removed down to their 
junction with the transverse processes. The surgeon nowadays gen- 
erally uses some type of bone-biting instrument, but for practical 
dissecting room purposes a strong, sharp chisel and heavy mallet 
are satisfactory. After these parts have been removed, the dura 
should be split open along its posterior medial surface from the 
upper thoracic region down to the lower part of the sacrum. Due 
to the evaporation of the cerebrospinal fluid the dura will be found 
collapsed around the spinal cord, but during life it would appear 
round and distended. The endothelial lining of the dura and pia 
maters should be noted. Then the spinal cord should be sectioned 
in the upper thoracic region and lifted out from inside the dural 
sheath, cutting the segmental nerves successively near the inter- 
vertebral foramina. Variations in size and in intradural lengths 
should be noted. The spinal cord should then be put aside in a 
moist place and kept for detailed study in connection with the con- 
sideration of the brain. 
The articulation of the head of the ribs with the bodies of the 
vertebrae or neighboring vertebrae should be examined. Then some 
of the series of costotransverse joints should be opened up. Several 
of the series of intertransverse articulations should be opened up 
both in the lumbar and in the thoracic regions. In the lumbar 
region these joints are in a vertical plane, while in the thoracic re- 
gion these joints are tilted half-way to the horizontal plane. The 
anterior and posterior longitudinal ligaments should be noted and 
several of the intervertebral discs cut across with an ordinary knife 
in order to note their macroscopic structure. 
The slightly movable symphysis pubis joint has flat opposing sur- 
faces held together by powerful interosseous ligaments, but these 
ligaments may be easily cut by an ordinary knife. By manipulating 
the hip bones the irregular sacroiliac joint surfaces should be noted 
and then these surfaces should be dissected and forced apart. The 
sacrum is suspended by strong interosseous ligaments from the 
iliac portion of the hip bone, being often justly referred to as the THE THORAX 
239 
inverted keystone of the pelvic arch. The opposing surfaces of the 
sacrum and iliac portion of the hip bone show all types of irregulari- 
ties, but in spite of this careful fitting and the great strength of the 
interosseous ligaments, major and minor injuries to this joint are 
now recognized to be far from uncommon. Disturbances in the very 
numerous joints of the vertebral column and pelvis are now receiv- 
ing clinical recognition, and a serious attempt is being made to 
separate true joint cases from under the old-fashioned blanket diag- 
nosis of lumbago or sciatica. 
As a matter of dissection convenience the vertebral column should 
be cut across about the fourth thoracic intervertebral disc, and then 
the lower part of the body may be discarded. CHAPTER Nil 
THE NECK 
Bony Framework and Landmarks 
The bony skeleton of the neck consists essentially of the seven 
cervical vertebrae. The first and second vertebrae are very much 
modified from the type plan as will be detailed towards the end of 
this chapter, the third, fourth and fifth are the typical cervical ver- 
tebrae, while the sixth and seventh are more like the thoracic ver- 
tebras. The spinous processes of the second, sixth, and seventh ver- 
tebrae come to the surface, but the short double-pronged spinous 
processes of the other cervical vertebrae lie deep and are covered by 
a modified continuation of the interspinous ligaments. In the neck 
of a fairly strong individual the transverse processes are too well 
covered by muscles to be palpable from the surface. The anterior 
surface of the bodies of all the cervical vertebrae, however, are cov- 
ered only by the esophagus and its prolongation upward, the 
pharynx, and therefore the upper ones can be readily palpated 
through the mouth. 
Many cervical muscles and ligaments attach to the base of the 
skull and to the lower jaw, technically the mandible. The liga- 
mentum nuchse, the elastic continuation of the interspinous liga- 
ments in the cervical region, raises up a prominence in the midline 
at the back of the base of the skull. This is known as the external 
occipital protuberance, which terminology means that the occipital 
bone also has a protuberance internally. Just in back of and below 
the ear the sternomastoid muscle raises up the mastoid process of the 
temporal bone (mastoid = nipple-like). A curved line running be- 
tween these two points represents the attachment of other neck 
muscles to the base of the skull and forms the demarcation of the 
neck from the scalp, while anteriorly the inferior border of the 
mandible separates the neck from the face region. Inferiorly the 
first thoracic vertebra, the first pair of ribs and the upper part of 
the sternum form the bony separation of the neck from the thorax. 
There is no sharp line of demarcation between the neck and the 
240 THE NECK 
241 
upper extremity, various structures from the neck continuing unin- 
terruptedly into the arm area. 
Connected by muscles and ligaments to the lower jaw and to the 
base of the skull is suspended the horseshoe-shaped hyoid bone. 
This, bone is palpable from the surface just under the mandible, the 
open part being faced towards the vertebral column. Swung below 
the hyoid bone lies the thyroid cartilage, which helps to form the 
larynx or voice-box at the top of the trachea (thyroid = shield- 
shaped). Below the thyroid cartilage lies the cricoid, or signet- 
ring, cartilage, which has its narrow band portion in front and its 
broad signet portion behind. Below the cricoid cartilage follow the 
rings of the trachea, which are, however, so thickly covered as not 
to be readily palpable from the surface. The marked anterior pro- 
jection of the thyroid cartilage, much more prominent in the male, 
is known as the laryngeal prominence or popularly as Adam's 
apple. The hyoid bone and the thyroid and cricoid cartilages, al- 
though movable up and down by muscular action, are important 
localization landmarks of the neck. 
Superficial Layers 
The skin is as would be anticipated very thick over the exposed 
posterior portion of the neck and thin over the protectable anterior 
surface. 
Boils and eventually multiple boils or carbuncles are much more 
common over the thicker posterior skin surface. 
The subcutaneous fatty layer contains the routine cutaneous 
arteries, veins and nerves, and the superficial venous system. The 
segmental nerves of the upper four cervical foramina emerge from 
the deep fascia opposite the transverse processes of their respective 
vertebrae, sending branches forward and backward, and also divi- 
sions up over the posterior portion of the scalp and down over the 
clavicle. The main superficial venous trunk, the external jugular, 
runs straight down from the posterior portion of the jaw to about 
the middle of the clavicle, where it enters the subclavian vein of 
the deep venous system. Other veins of the superficial venous sys- 
tem are located over the anterior and posterior portions of the 
neck, but these are so small and so irregular in their arrangement 
that they scarcely deserve special names. 
The platysma is a special skin muscle, which runs vertically 242 
REGIONAL ANATOMY 
downward from the face over the front half of the neck to ter- 
minate over the upper part of the chest (plat = flat). This type of 
skin muscle is more highly developed in the lower animals, its pop- 
ularly known function being to shake the skin rapidly in order to 
scare off flies. This thin muscle sheet has some surgical importance, 
because if the fibers are cut transversely the pull of the muscle 
eventually tends to widen out the scar. 
The skin and the subcutaneous fatty layer should be dissected. 
Deep Fascia 
The deep fascia completely encircles the neck and is stronger 
over the more muscular posterior portion than over the front. It 
larynx' 
flexors of 
head and 
neck 
pharynx 
sterno- 
mastoid 
third 
cervical 
extensors of 
head and 
neck 
Fig. 76.-Diagrammatic fascial compartments of Neck. 
sends in partitions between the muscles and muscle groups, and 
either stops at the bony limits of the neck, or as in the case of the 
mediastinum and shoulder girdle continues into these areas. Layers 
of deep fascia also form compartments for the main vessels and for 
the special organs. 
A few lymphatic glands lie along the superficial jugular veins, but 
most of them lie along the deep jugular vein. This accounts for 
the relative frequency of deep abscesses of the neck, and emphasizes 
the diagnostic and surgical importance of the fascia. THE NECK 
243 
Extensor Vertebrae Muscle Group in Neck Region 
The extensor vertebrae group of muscles in the back of the neck 
is much more powerful than the opposing flexor group, as is demon- 
strated by the commonly known phenomenon in connection with the 
muscular spasms of spinal meningitis, lock-jaw or strychnine poison- 
ing. A source of some confusion is the presence of various muscles 
in this area, which normally have nothing to do with the move- 
ments of the head and neck, but belong to the upper extremity or to 
the thorax. The popularly known columnar elevations of the back 
of the neck, one on each side of the median line and extending 
from the thoracic region to the base of the skull, are produced by 
these extensor vertebrae muscle groups. Some of these muscles in- 
sert into the base of the skull, and are therefore, strictly speaking, 
extensor capitis muscles. This muscle group is covered by the 
aponeurotic origin of the trapezius muscle, and in the lower half of 
the neck by the origin of the rhomboids, while the levator scapulae is 
intimately embedded in the group. After the remaining parts of 
the trapezius and rhomboids have been dissected off, the splenius 
sheet of muscle is exposed to view. The splenius muscle arises from 
the upper thoracic and lower cervical spines, runs upward and later- 
ally and splits into two divisions, the cervical division inserting into 
the transverse processes of the upper cervical vertebrae, the capitis 
division into the curved line between the external occipital pro- 
tuberance and the mastoid process. After examination in position 
the splenius muscle should be divided at the midpoint and turned 
back towards its origin and its insertion. This dissection will ex- 
pose the large semispinalis muscle, which arises from the transverse 
processes of the upper thoracic and lower cervical vertebrae, and 
divides also into cervical and capitis divisions (O.T. complexus). 
The capitis division lies superficial to the cervical and inserts into 
the base of the skull well in back of the head-neck articulation, 
while the cervical division inserts into the spines of the upper cer- 
vical vertebrae. This semispinalis is obviously the continuation of 
the spinalis division of the thoracic region, and whereas there are 
also continuations of the longissimus and costalis divisions, these are 
of distinctly lesser size and importance. The consideration of a 
deeper group of muscles, which lie just in back of the head-neck 244 
REGIONAL ANATOMY 
articulation will be postponed until the upper vertebrae and their 
articulations are taken up in detail. 
Flexors of Neck and Head 
The flexors of the neck and head lie in the lateral and anterior 
portions of the neck. The scalene muscle group of the lateral part 
of the neck, however, has as its sole function the elevation of the 
first two pairs of ribs, while other muscles of these areas have sub- 
sidiary functions as will be brought out in the detail considerations. 
Sternomastoid (Sternocleidomastoideus) 
This important muscle of the neck arises by its main tendon from 
the upper part of the sternum and by an accessory head from the 
medial third of the clavicle, coursing diagonally across the neck 
backwards and upwards to its insertion into the mastoid process of 
the temporal bone. This muscle is sometimes injured during the 
birth process, resulting in the so-called congenital wry neck, the 
head in this condition being turned to one side and flexed on the 
chest. If both sternomastoids act at the same time flexion of the 
head and neck is produced. The most important vessels and nerves 
of the neck, specifically the internal jugular vein, the carotid 
arteries and the vagus nerve lie under this muscle, as much pro- 
tected as is possible in so exposed an area. The sternomastoid is 
also important as a landmark, as it is used to divide the neck into 
an anterior and a posterior triangle, so named on account of their 
relation to this muscle. The anterior triangle is bounded superiorly 
by the mandible, posteriorly by the anterior border of the sterno- 
mastoid and separated from the opposite anterior triangle by an 
imaginary median line. The posterior triangle is bounded anteriorly 
by the posterior border of the sternomastoid, posteriorly by the 
anterior border of the trapezius and inferiorly by the midsection 
of the clavicle. It should be especially noted that while the upper 
part of the posterior triangle is in the posterior portion of the neck, 
the midpart is in the lateral area and the lower part extends even 
to the anterior portion of the neck. 
The nerve supply enters the deep surface of the upper half of the 
sternomastoid and comes roundabout from the upper cervical seg- THE NECK 
245 
ments. A part of this nerve continues vertically downward across 
the posterior triangle to enter the trapezius muscle. 
The sternomastoid should be cleared by dissecting off the 'muer- 
ficial part of its deep fascia. 
Depressors of Hyoid Bone. 
As a matter of ordinary observation it may be noted that the 
hyoid bone, together with the thyroid and cricoid cartilages, moves 
up and down during the process of swallowing. The muscles having 
the power of pulling down the hyoid bone are known as the depres- 
sors, while those raising it up are known as the elevators. The 
superficial group of the depressors are the sternohyoid and the 
omohyoid (onio = shoulder). The sternohyoid runs vertically up- 
wards from the back of the sternum, while the omohyoid runs from 
the scapular notch of the superior scapular margin diagonally 
upwards and forwards to its insertion into the hyoid bone. The 
deep group is made up of what is practically one sheet, which inserts 
into the thyroid cartilage and then another section arises to run up 
to the hyoid, the sections of this muscle being named the sterno- 
thyroid and the thyrohyoid. All these muscles are flat band-like 
sheets. 
Elevators of Hyoid 
The digastric or two bellied muscle arises anteriorly from the 
deep surface of the mandible near the midline and posteriorly from 
under the mastoid process, running to a common tendon which is 
held by a pulley arrangement to the hyoid bone. The mylohyoid 
arises from the hyoid bone and inserts into a ridge around the 
middle of the inside of the mandible, forming a diaphragm muscle 
across the floor of the mouth. The geniohyoid and the stylohyoid 
are also elevators, but these lie deeper and therefore will not be 
considered until a later stage of the dissection (genio = chin). 
These elevator and depressor muscles receive their nerve supply 
from the cervical plexus, but also receive branches from the twelfth 
cranial or hypoglossal nerve. These muscles have not only the 
power of raising and depressing the hyoid bone, but if they all con- 
tract at the same time, work at mechanical advantage in depressing 
the mandible. Further, if the mandible were held closed by its 
muscles, these muscles would then on contraction flex the head and 
neck. 246 
REGIONAL ANATOMY 
Minor Triangles 
The digastric and the omohyoid muscles are used to subdivide the 
large anterior triangle into three minor triangles. The minor 
triangle, marked off by the bellies of the digastric muscle and the 
mandible, is known as the digastric. The triangle between the omo- 
digastric muscle 
sternomastoid 
muscle 
trapezius muscle 
"digastric 
- carotid 
omohyoid muscle 
-muscular 
-occipital 
clavicle 
-supraclavicular 
Fig. 77.-Minor Triangles of Neck. 
hyoid and the posterior belly of the digastric is known as the 
carotid, because just back of this area the common carotid artery 
terminates in its external and internal branches. The remaining 
triangular area is fairly well covered by the sternohyoid muscle and 
hence is called the muscular triangle. 
The omohyoid subdivides the large posterior triangle into two 
smaller minor triangles. The small area below the omohyoid, pos- THE NECK 
247 
terior to the sternomastoid and above the clavicle should be known 
as the supraclavicular triangle, while the remaining large area of 
the posterior triangle is known as the occipital triangle. 
The elevator and depressor muscles of the hyoid bone should be 
cleared sufficiently to demonstrate the minor triangles. Then the 
sternohyoid and the omohyoid muscles should be divided in order to 
demonstrate the deeper layer, that is, the sternothyroid and the 
thyrohyoid muscles. 
Deep Venous System 
The internal jugular vein lies just under the sternomastoid mus- 
cle, the common carotid artery lying deep to the vein, and the vagus 
nerve between the two. The jugular vein is joined by the sub- 
clavian in the lower part of the neck, slightly above the first costo- 
sternal articulation. On the left side the main lymphatic duct of 
the body empties into the left subclavian near its junction with the 
jugular, while on the right side the corresponding lymphatic duct 
drains only its own thoracic and neck regions. The left lymphatic 
duct, over one-eighth of an inch in diameter when distended, is dis- 
tinguishable from a vein on account of color, but this is as previously 
noted untrustworthy in the dissecting room. The left jugulosub- 
clavian, or innominate, vein runs across under the upper part of the 
sternum to join the right jugulosubclavian or innominate, making up 
the superior vena cava (Innominate =BNA anonyma). Along the 
jugular vein and its branches lie the main group of lymphatic 
glands of the neck. 
Dissection.-In order to demonstrate the deep venous system, the 
origins of the sternomastoid muscle from the upper part of the 
sternum and from the sternal third of the clavicle should be cut 
across. Then the sternomastoid muscle should be dissected out of 
its deep fascia sheath up to its attachment to the mastoid process. 
This step exposes the internal jugular vein practically throughout 
its course. In order to expose the subclavian and innominate veins 
it is necessary to remove the remaining parts of the sternum and 
clavicles, which can best be done by sectioning the first pair of 
costal cartilages near their junction with the sternum. The sterno- 
clavicular joints with their limited range of motion should be noted, 
but the joints should not be opened until later, as it is important to 248 
REGIONAL ANATOMY 
be able to replace this sternoclavicular segment from time to time 
in order to keep clear its relation to the deeper structures. 
Scalene Muscles 
The scalene group of muscles should now be noted running from 
the transverse processes of all the cervical vertebrae to the first and 
second ribs. The scalenus anterior raises up a tubercle on the first 
rib and separates the subclavian vein, which runs in front, from 
the subclavian artery, which runs behind this muscle. Through 
the space between the scalenus anterior and the scalenus medius 
also emerge the cervical nerves, the upper four making up the 
cervical plexus, the lower four and first thoracic the much larger 
brachial plexus. The phrenic nerve arises from the fourth cervical 
nerve and crosses the anterior surface of the scalenus anterior 
from the lateral side medially en route to the mediastinum, from 
which place its further course to the diaphragm has been traced. 
The scalenus medius and posterior insert into the first and second 
ribs at the lateral parts of their circumference. These muscles 
would obviously act as a costal respiratory group and eventually 
determine the height at which the whole thorax stands. It should 
be noted again that the apices of the pleural cavities dome up an 
inch or more into the base of the neck. 
These muscles should be cleared sufficiently to bring out the 
points noted. 
Arteries. 
The subclavian artery through branches supplies the lower part 
of the neck, the upper part of the chest and sends a branch into 
the interior of the skull. The common carotid artery through its 
branches supplies the upper part of the neck and carries the pre- 
ponderant bulk of the supply to the head. On the right side the 
innominate artery runs well up into the base of the neck before 
dividing into its separate common carotid and subclavian subdivi- 
sions, while on the left side the common carotid and subclavian 
enter the base of the neck as separate vessels. 
The innominate (anonyma) and the left common carotid and left 
subclavian arteries should be cleared to their origin from the arch 
of the aorta. THE NECK 
249 
Branches of Subclavian 
The branches of the subclavian artery are subject to many varia- 
tions, coming off sometimes separately, or sometimes several vessels 
sprout out of a short axis stem. It will be more convenient to con- 
sider the branches according to the field they supply and to disre- 
gard their varying origins from the subclavian. The internal mam- 
mary runs downward in back of the costal cartilages near the 
sternum, its diaphragmatic and epigastric branches having been 
previously traced to their terminations. The costocervical trunk 
runs down to supply the upper three intercostal spaces and anasto- 
moses with the aortic intercostal vessels of the fourth space. The 
vertebral runs upward through the foramina in the transverse proc- 
esses of the upper six cervical vertebrae and then enters the interior 
of the skull. The transversa colli runs transversely around the 
neck to supply the various muscles of the lateral lower half of the 
region (collum=official name for neck). The transversa scapulae 
runs on a lower level than the transversa colli, terminating in the 
musculature of the scapula. The inferior thyroid runs medially in 
back of the common carotid artery to its termination in the lower 
half of the thyroid gland. 
The branches of the subclavian artery should be cleared and 
traced out, disregarding the corresponding veins. 
Branches of External Carotid 
The common carotid artery travels up under the sternomastoid 
muscles without giving off branches, to its termination just pos- 
terior to the hyoid bone in the external and internal carotids. The 
external carotid at first lies just in front of the internal and is 
therefore not named on account of its primary relationship, but 
because it supplies the exterior of the skull. The internal carotid 
goes through the base of the skull without giving off branches and 
aided by the vertebral artery supplies the brain. The branches of 
the external carotid are fairly regular and are named according to 
their distribution. The superior thyroid runs down to the upper 
half of the thyroid gland, incidentally supplying the larynx. The 
lingual immediately buries itself in the group of muscles at the base 
of the tongue. The external maxillary or facial runs across the 
external surface of the lower jaw, crossing the face diagonally on 250 
REGIONAL ANATOMY 
its course to the 'medial angle of the eye. The internal maxillary is 
a large vessel, which as its name implies travels inside of the lower 
jaw and supplies this important area. The superficial temporal, or 
anterior auricular, runs up just in front of the ear to supply the 
temple region, while the posterior auricular supplies the scalp in 
back of the ear. The occipital supplies the scalp over the back of 
the skull, that is, the occipital region. The ascending pharyngeal 
superficial temporal 
internal maxillary 
posterior auricular 
ascending pharyngeal 
external carotid - 
internal carotid ~ 
occipital 
external maxillary (facial) 
lingual 
superior thyroid 
common carotid - 
inferior thyroid 
transversa colli 
vertebral 
subclavian 
superior intercostal 
internal mammary 
innominate or left common 
carotid and left subclavian 
Fig. 78.-Diagram of Arteries of Neck. 
is a small inwardly directed branch, which helps to supply the 
pharynx region. 
The branches of the external carotid should be cleared in the 
neck, but the tracing out to their distributions must be postponed 
until a later stage of the dissection. 
Nerves of Neck 
The presence of the ninth, tenth, eleventh and twelfth pairs of 
cranial nerves complicates the supply of the neck (cranium = THE NECK 
251 
skull). These cranial nerves (nervi cerebrales) leave the interior 
of the skull through bony canals very deep in from the surface of 
the neck. The ninth, tenth, and eleventh nerves go through the 
same opening as the internal jugular vein, while the twelfth goes 
through a neighboring separate opening. These nerves, together 
with the cervical sympathetic, form a plexus just after emerging 
from the interior of the skull. In the deep dissection these nerves 
can be identified by their location and directions. The ninth, or 
glossopharyngeal, is the special sensory nerve of taste, which breaks 
up into small branches and goes forward closely applied to the 
pharynx to the root of the tongue. The tenth, or vagus, sends motor 
branches to the pharynx, motor and sensory branches to the larynx, 
and has been considered in its further course through the neck and 
mediastinum. The vagus is extra large in the neck as it carries 
processes from these other cranial nerves en route towards their 
termination. The eleventh, or accessory, runs straight down to 
supply the sternomastoid and continues vertically downward across 
the posterior triangle to the trapezius muscle. The twelfth, or hypo- 
glossal, turns around superficially to the branches of the external 
carotid artery and runs forward to supply the group of muscles 
under the tongue. As has been previously noted, this nerve sends 
part of the supply to the muscles controlling the hyoid bone. 
As noted in connection with the scalene muscles, the upper four 
cervical segmental nerves make up the small cervical plexus, while 
the lower four cervical and the first thoracic make up the very 
large brachial plexus. The phrenic nerve, which arises from the 
fourth cervical segmental, has previously been considered as it 
crosses over the anterior surface of the scalenus anterior muscle en 
route to the mediastinum. Theoretically we would expect to find 
eight ganglia of the sympathetic trunks, as there is commonly a 
sympathetic ganglia for each segment. As a matter of fact the 
upper four ganglia are fused into the superior cervical ganglia, the 
next two into the middle cervical ganglia and the lower two into the 
inferior cervical ganglia. The superior cervical ganglia not only 
controls the involuntary activities of the upper part of the neck, 
but also as will be detailed later, a considerable portion of the in- 
voluntary functions of the head. The sympathetic gangliated trunks 
lie at the junction of the bodies of the vertebra) with the roots of 
the vertebral arches. 252 
REGIONAL ANATOMY 
These nerves should be located and cleared as much as possible 
without disturbing unknown structures. The sternoclavicular seg- 
ment should be replaced in position in order to demonstrate the 
course of the brachial nerve plexus and the subclavian artery under 
the midsection of the clavicle and over the first rib. 
Thyroid Gland (Glandula Thyreoidea) 
The thyroid gland at an early stage of development has a duct 
which leads vertically upwards to the superior surface of the root 
of the tongue (thyroid = shield-shaped). This duct does not func- 
tionate after a certain stage of fetal development, but disappears, 
leaving the thyroid a ductless gland. Abnormally remains of the 
mucous membrane of this thyroglossal duct may lead to the forma- 
tion of cystic tumors in the median line. The thyroid is composed 
of two lateral lobes, which lie closely applied to each side of the 
trachea, and an isthmus which forms a connecting strand between 
the lobes. The isthmus crosses the rings of the trachea normally 
about one-quarter of an inch below the cricoid cartilage, but abnor- 
mally the whole gland may sag down, when enlarged even project- 
ing into the mediastinum. The whole gland is surrounded by a cap- 
sule, which is firmly held by ligaments and fascias to the trachea. 
The lateral lobes are considerably larger than the isthmus, extend- 
ing up alongside the cricoid cartilage and inferiorly being com- 
pletely covered by the sternomastoid muscles. The height of the 
thyroid gland above the sternum varies with the relative standing 
of the chest, but on account of its attachment to the trachea the 
gland is always raised up when the head is fully extended. 
Microscopically the gland is made of acinus nests, which are lined 
by a single layer of flat epithelial cells and filled with a varying 
amount of gelatinous-like, or colloid, secretion. The superior thyroid 
arteries are branches of the external carotid, while the inferior 
thyroid arteries come from the subclavian. A varying number of 
small nodules, commonly about six, which lie in the thyroid gland 
or in the posterior portion of its capsule are called parathyroids. 
While not the same thing, these parathyroids are anatomically and 
probably functionally closely related to the thyroid gland. 
It is definitely known that some secretion from the thyroid gland 
is required to keep the body in health. Clinically certain symptoms 
are recognized as due to too little and others as due to too great THE NECK 
253 
activity of this gland, technically hypo- and hyperthyroidism. Gen- 
eral enlargement of the thyroid gland, involving both lateral lobes 
and the isthmus, is popularly known as goiter. 
The inferior laryngeal nerves ascend to the larynx, coursing about 
at the junction of the trachea with the esophagus. After splitting 
the isthmus and dissecting the thyroid from the trachea these nerves 
should be traced through to the larynx. The thyroid gland should 
be examined in place, and then removed and cross-sectioned. 
Pharynx 
The pharynx is a combination respiratory and alimentary tube, 
which in man persists as such throughout life. Air passes back and 
forth from the nose to the larynx via the pharynx, while food and 
drink are forced from the back of the mouth through the pharynx 
to the esophagus. The respiratory portion of the pharynx is held 
permanently open, while the walls of the part nearest the esoph- 
agus come in contact when not in use. The pharynx as a matter 
of convenience is divided into three parts; a superior nasopharynx, 
a middle oropharynx, and an inferior laryngopharynx. Through 
the mouth the posterior wall of the oropharynx can be seen directly, 
but the naso- and laryngo-pharynx are only indirectly visible via 
mirror reflections. The walls of the pharynx are composed of the 
usual mucosa, submucosa, and muscle layers, which have their 
ordinary characteristics. The mucosa as in the mouth and esoph- 
agus is lined by epithelium of the stratified squamous type and 
later on will be noted to contain aggregations of lymphatic tissue. 
The submucosa is a very tough, fibrous layer, which eventually must 
be incised in order to relieve extrapharyngeal abscesses. The 
superior, middle and inferior constrictor muscles of the pharynx 
are very thin sheets, which arise from the mandible, the hyoid bone 
and the thyroid cartilage, respectively, and encircle the pharynx. 
The middle constrictor overlaps the superior and the inferior con- 
strictor overlaps the middle, so that, practically speaking, the whole 
pharynx is covered by crossing muscle sheets. The stylopharyngeus 
muscle runs from the long tip of the styloid process of the base of 
the skull to its insertion into the lateral pharyngeal wall. The 
nerve supply to the pharanyx comes from the vagus and glosso- 
pharyngeal nerves, and is of the voluntary type. It should be espe- 
cially noted that the common carotid arteries lie just lateral to the 254 
REGIONAL ANATOMY 
lateral pharyngeal wall, while the internal and external carotid 
arteries are separated from the lateral pharyngeal wall by a dis- 
tance not greater than half an inch. This distance, however, is 
ordinarily increased when an abscess bulges into the pharynx. 
The constrictor muscles should be cleared, and then the posterior 
pharyngeal wall separated by blunt dissection from the anterior 
surfaces of the cervical vertebra?. The submucosa layer of the 
pharynx should be incised freely along the midposterior line in 
order to demonstrate its relative strength. 
Gills and Gill-Clefts 
The fish group of vertebrates have commonly six pairs of gills, 
which serve as the respiratory apparatus, or in other words which 
bring about the interchange of carbon dioxide and oxygen. The 
number of clefts between the gills varies among the different types 
of fish, but is commonly either five or seven. These gill clefts run 
through from the external surface of the neck region into the 
pharynx, allowing water to circulate freely about the gills. The 
framework of the gills is made up of cartilage, while the function- 
ally essential part is a rich network of capillary vessels, which are 
covered by a modified mucous membrane. The fish's heart pumps 
venous blood into a ventral aorta, which then passes via the series 
of gill arteries and capillaries into a dorsal aorta. This dorsal 
aorta during the life contains arterial blood, which is distributed 
via segmentally arranged branches throughout the body, and after 
passing through the systemic capillaries returns as venous blood to 
the heart. In the neighborhood of the gill clefts the ventrhl and 
dorsal aortas are represented in some types of fish by a single 
vessel, in most types, however, they are made up of paired vessels. 
The gills and their arterial arches, as a matter of arbitrary con- 
vention, are numbered in sequence from the head toward the tail. 
Now the human embryo develops six pairs of gills and four pairs 
of modified clefts, although it is obvious they are purely vestigial 
structures and never functionate. The modification of the clefts 
consists in the fact that they do not open through from the neck into 
the pharynx, but are represented by opposing grooves in the neck 
and pharynx, separated by a thin septum of mucous membrane. 
The cartilaginous framework of the first gill persists as the basis 
for the mandible, as also occurs in many fishes, while the framework THE NECK 
255 
of the second persists as the hyoid bone. The ascending thoracic 
aorta in the human represents the ventral aorta of the fish, the arch 
of the aorta represents the left fourth gill artery, while the de- 
scending thoracic aorta represents the dorsal aorta. Further the 
pulmonary aorta is a part secondarily separated from the original 
ventral aorta, while the pulmonary arteries represent the sixth gill 
arterial arches. 
The clinical occurrence of various types of cartilaginous and 
mucous membrane tumors in the lateral mandibular and neck 
regions is explained as due to the abnormal persistence of parts of 
these embryonic gills. 
ventral aorta 
dorsal aorta 
first gill cleft 
fourth arterial arch 
Fig. 79.-Diagram of human gill arterial arches. 
Larynx 
The larynx functionates as the beginning of the tracheobronchial 
system and as the special organ of speech. The framework of the 
larynx is made up essentially by the thyroid and the cricoid cartil- 
ages. The thyroid cartilage is suspended from the hyoid bone by 
thyrohyoid muscles, ligaments, and a membrane. The cricoid car- 
tilage is attached to the thyroid by a pair of cricothyroid joints, 
muscles, ligaments, and a membrane. The epiglottis is a thin sheet 
of elastic fibrocartilage, which projects up at the back of the tongue, 
and is attached by ligaments essentially to the thyroid cartilage, but 
has other minor musculoligamentous attachments to the tongue, 
hyoid bone, and arytenoid cartilages (glottis = essential voice appar- 
atus). The pair of arytenoid cartilages ride on the upper part of 
the signet surface of the cricoid and are most important structures 256 
REGIONAL ANATOMY 
inasmuch as the vocal ligaments, that is, the true vocal cords are 
attached to them. 
Two nerves leave the vagus trunk to supply the larynx. The 
superior laryngeal nerves follow the superior thyroid arteries, car- 
rying the supply to the upper half of the larynx. The inferior 
laryngeal nerves have previously been noted to follow down in the 
hyoid- 
epiglottis 
aperture 
(aditus laryngis) 
thyroid - 
"arytenoid 
cricoid - 
trachea 
Fig. 80.-Posterior view of Larynx, showing arytenoid and cricoid cartilages projected to 
surface by dotted lines. 
vagus nerve into the mediastinum, and then holding a course be- 
tween the trachea and esophagus to return to the larynx. As the 
inferior are the main motor nerves to the larynx it follows obviously 
that mediastinal disease may manifest itself by a disturbance of or 
loss of speech. , ■' 
After examining the larynx in position, the thyrohyoid muscles THE NECK 
257 
and ligaments should be sectioned, and the musculoligamentous con- 
nections between the epiglottis and the root of the tongue and 
between the epiglottis and the hyoid bone should be cut across at a 
convenient midpoint. Then the trachea and esophagus should be 
divided about an inch below the cricoid cartilage, which dissection 
frees the larynx so that it may be removed for detailed examination. 
It should be especially noted that the cartilaginous semi-rings of 
the trachea are deficient posteriorly, where the trachea comes in 
contact with the vertebrae. 
When the larynx has been removed from the body, the size and 
shape of the thyroid and cricoid cartilages, and of the epiglottis 
and arytenoid cartilages can be reviewed to great advantage. It 
should now be noted that the cavity of the larynx is materially 
smaller than would appear from an external examination of the 
parts while in position, due to the fact that the thyroid cartilage 
forms not only the lateral walls of the larynx, but also protects the 
lateral walls of the laryngopharynx. 
Aperture of Larynx (Aditus Laryngis) 
The aperture of the larynx is the opening in the anterior wall 
of the laryngopharynx through which air passes from the laryngo- 
pharynx into the larynx. The plane of this opening is not ver- 
tically arranged, but slants distinctly downward-backward from 
the epiglottis to the apices of the arytenoid cartilages. The size of 
this opening varies materially as it is surrounded by what amounts 
to a sphincter muscle. The muscles in the free margins of these 
folds are known as the aryepiglottic, as they run from the arytenoid 
cartilages to the epiglottis. Two little cartilages in each aryepiglot- 
tic fold are of the sesamoid type and are known technically as the 
cartilago cuneiformis and the cartilage corniculata. 
Tn contradistinction to former beliefs, it is now recognized that 
the epiglottis maintains its upright standing position at the back of 
the tongue even during swallowing, that is, it does not bend back 
to close the aperture of the larynx. During swallowing the aryepi- 
glottic muscles draw the arytenoid cartilages up to the posterior 
surface of the base of the epiglottis, thus practically closing the 
aperture, while the epiglottis itself prevents liquids from trickling 
into the less firmly closed anterior portion of the aperture. 
The mucous membrane should be split along the aryepiglottic 258 
REGIONAL ANATOMY 
fold and dissected back, thus exposing the muscles, ligaments and 
miniature cartilages noted in the preceding discussion. 
Vocal Folds (Plicae Vocales) 
If now the aperture of the larynx be spread open, by looking 
through the larynx two pairs of folds can be noted along the side 
walls. These ridges are raised up by muscles and ligaments, the 
upper pair being the plicae ventriculares, or false vocal cords, the 
lower pair the plicae vocales or true vocal cords. The ventricular 
folds are simply low ridges, which are raised up by muscle fibers 
covered by mucous membrane and are not concerned with the pro- 
duction of the voice sound. These folds are used as a line of de- 
marcation between the upper part or vestibule and the middle 
compartment of the larynx. The vocal folds attach to the back 
surface of the thyroid cartilage just below the laryngeal prominence 
and run to the vocal processes of the arytenoid cartilages. These 
vocal folds are made up by the vocal muscle and-ligament, covered 
by a very much thinned out mucous membrane, this combination 
of structures being technically known as the vocal lip (labium 
vocale). This ligament is made up of white fibrous tissue and nor- 
mally during life shows up as dense white against the pink back- 
ground of the normal mucosa. 
The vocal folds during the activity of speaking are drawn tense 
and practically together by muscular action on the arytenoid car- 
tilages, but otherwise the muscles are relaxed and the folds separate 
widely. This tightening of the vocal folds is also aided by crico- 
thyroid muscles, which change the relationship of the cricoid and 
thyroid cartilages. Air forced rapidly through the narrow slit pro- 
duces the voice sound, which is variously modified as will be noted 
in connection with the detailed study of the nose, mouth, tongue, 
and lips. The vocal folds of the female are characteristically about 
one-quarter shorter than those of the male, which anatomical fact 
accounts for the differences in pitch of the voices. Very high notes 
call for extreme muscular exertion, while very low notes call for 
relaxation with control, consequently these extremes are the hard- 
est to acquire and to keep. If one vocal lip is incapacitated or its 
musculature destroyed or nonfunctionating, the laryngeal note can 
not be produced, but whispering, which is brought about by the use 
of the tongue, teeth and lips, is not interfered with. THE NECK 
259 
Dissection.-The cricothyroid membrane, which is partly covered 
by a muscle of the same name, now deserves more detailed atten- 
tion. Then by manipulating the thyroid and cricoid cartilages the 
pair of joints can readily be made out. By removing the mucosa 
and submucosa from over the large posterior surface of the cricoid 
cartilage, the pair of cricoarytenoid posterior muscles may be com- 
pletely exposed. By carrying the dissection of the mucosa and 
submucosa upward, the arytenoid cartilages and the cricoarytenoid 
joints may be exposed. The oblique and transverse arytenoid mus- 
cles, running between the medial posterior surfaces of the arytenoid 
cartilages, steady the pivoting of these cartilages during tightening 
of the vocal ligaments. The insertion of the cricoarytenoid and 
thyroarytenoid muscles raise up a processus muscularis on the lateral 
dorsal point of the arytenoid cartilages. The medial ventral point 
of the arytenoid cartilages is known as the processus vocalis on 
account of the attachment of the vocal ligament. Then the attach- 
ment of the base of the epiglottis to the superior margin of the 
thyroid cartilage should be reviewed. Finally an incision in the 
anterior median line should be carried through the epiglottis and 
the thyroid and cricoid cartilages and trachea. By spreading this 
incision the whole interior of the larynx may be freely exposed to 
view. The epithelial covering of the mucosa of the laryngeal cavity 
above the vocal folds is of the stratified squamous type, while that 
below these folds is like the trachea of a stratified columnar type. 
After the ventricular and vocal folds have been examined, the 
mucosa and submucosa may be removed from the whole interior 
of the larynx. Groups of muscles may be recognized in a general 
way, but the full detail is too complicated for our present purpose. 
Practical 
Spasmodic contraction of the laryngeal muscles, known popularly 
as spasmodic croup, may produce a serious appearing condition, but 
after a certain stage of blueness has been reached, the muscles relax. 
This disease is closely related to asthma. If a foreign body by acci- 
dent slips through the larynx into the trachea, the musculature of 
the vocal folds goes into spasm and commonly prevents expulsion. 
If the patient be held up by the heels, the action of gravity will 
cause the foreign body to rest against the contracted vocal folds, 
and if these folds relax on account of the pressing demand of the 260 
REGIONAL ANATOMY 
body for oxygen, the foreign body may fall out into the pharynx. 
Any great surprise, as for example a sudden slap across the back, 
may cause relaxation of the laryngeal spasm and thus aid in expul- 
sion. If the foreign body remains in the trachea, it commonly lodges 
in the right primary bronchus or one of its lower subdivisions, on 
account of greater size and more favorable directions. These for- 
eign bodies tend to cause irregular attacks of pneumonia in the lower 
lobe of the right lung, and after months or years tend to become 
firmly embedded in their position. If the emergency measures noted 
fail to cause expulsion of the foreign body, a special tube with for- 
ceps arrangement must be passed through the larynx, or a tracheot- 
omy must be performed in order to remove the foreign body. The 
usual tracheotomy is performed above the isthmus of the thyroid 
gland, and may or may not be continued through the ring of the 
cricoid. If the surgeon remains strictly in the middle line, the per- 
formance of a tracheotomy or laryngotomy is a very simple oper- 
ation, comparatively free from operative risk. Diphtheria of the 
larynx, which is popularly known as membranous croup, or any 
severe laryngeal disease, may mechanically shut off the air supply 
and call urgently for a tracheotomy. 
Craniovertebral Joints 
The first cervical vertebra is very much modified from the type 
plan of the other cervical vertebras and is known as the atlas (atlas 
- support). The range of flexion and extension motion between the 
transverse processes of the atlas and the base of the skull is ma- 
terially greater than between any other vertebrae. The second 
cervical vertebra is known as the epistropheus (O.T. axis), due to 
the fact that rotation between this bone and the atlas is materially 
greater than between any other vertebrae (stropheus = turning). 
These vertebrae are modified anatomically so as to be fitted for these 
special functions. The anterior and the posterior longitudinal liga- 
ments and the ligamenta flava are carried up practically unmodi- 
fied to their connections with the base of the skull. 
Occipital Bone 
The atlas articulates with the neck surface of the occipital bone 
of the skull. The large opening in the occipital bone through which THE NECK 
261 
the spinal cord enters the interior of the skull is known as the 
foramen magnum. On each side of the anterior portion of this 
foramen lie the condyles, which are convex rocker surfaces for 
articulation with the concave surfaces of the transverse processes 
of the atlas. The anterior and posterior longitudinal ligaments 
attach to the anterior half of the foramen magnum, while the liga- 
menta flava attach to the posterior half. The coming together of 
the anterior and posterior longitudinal ligaments is due to the fact 
that the first cervical vertebra lacks a body. 
Atlas 
The characteristic feature of the atlas is that it has no body, 
while another feature is that the transverse processes extend out 
space for dens 
anterior arch 
- transverse 
H process 
vertebral 
artery foramen 
space for 
spinal cord 
-posterior arch 
_ spinous process 
Fig. 81.-Superior surface of Atlas, the first cervical vertebra. 
materially further than those of the other cervical vertebrae. A 
process from the epistropheus, known as the dens, projects upward, 
usurping the place of the body of the atlas (dens, O.T. odontoid = 
tooth). This process acts as a pivot around which the greatly in- 
creased rotation between the atlas and epistropheus is permitted. 
An anterior arch of the atlas in front and a transverse ligament 
behind form the socket for this dens process. The ligaments as in 
other joint regions act as checks against excessive range of mobility. 
The vertebral arteries after passing through the transverse foramina 
of the upper six cervical vertebrae pierce the ligamenta flava en 
route to the interior of the skull. 262 
REGIONAL ANATOMY 
Epistropheus 
The epistropheus is an especially strong vertebrae with an extra 
long spinous process. The dens projects upwards from the body 
of the epistropheus into the socket formed for it by the atlas and is 
attached by a ligament to the front of the foramen magnum. The 
transverse process articular surfaces of the epistropheus meet the 
opposing articular surfaces of the atlas on practically a horizontal 
plane. These surfaces are extra large and allow an exceptionally 
wide range of lateral movement, as compared with the transverse 
joint surfaces of the rest of the vertebral column. 
Severe injury to the spinal cord in the region of these joints is 
rapidly fatal because respiration is completely stopped, both of the 
costal and of the diaphragmatic types. Scientific hanging consists 
in breaking or dislocating the upper cervical vertebrae by the sudden 
checking up of the body weight during rapid fall. Amateur hang- 
ing usually is performed without a proper fall and is an inhuman 
system of strangling. 
Muscles 
The motions noted in connection with these joints are obviously 
controlled to a great extent by various muscles of the neck pre- 
viously considered, as for example, by the splenius, semispinalis and 
sternomastoid muscles. But the deep group of muscles, which arise 
from the upper cervical vertebrae and insert into the base of the 
skull around the foramen magnum are specialists in causing these 
movements. Two paired muscles of this group in back of the upper 
cervical vertebrae, belonging to the extensor capitis group, are known 
as the rectus capitis posterior, major and minor. Two paired mus- 
cles in front of the cervical vertebrae, belonging to the flexor capitis 
group, are known as the rectus capitis anterior and the longus 
capitis. Two paired muscles, which arise from the transverse proc- 
esses of the atlas and insert into the occipital bone, thus having a 
varying and complicated action, are known as the rectus lateralis 
and the obliquus capitis superior. 
Dissection.-The flexor and extensor capitis muscles may be 
readily demonstrated and then divided near the base of the skull. 
After dividing these muscles the anterior and posterior longitudinal 
ligaments and the ligamenta Hava may be exposed by blunt dissec- THE NECK 
263 
tion and then divided. The knife should then be plunged in from 
both in front and back, dividing the dura mater and spinal cord. 
On account of the lateral extent of the transverse processes of the 
atlas, and their proximity to the base of the skull, it is very difficult 
to demonstrate the lateral capitis muscles and the occipito-atlas 
joints. By forcing the cervical vertebrae strongly to one side, how- 
ever, it is possible to cut and break through these ligaments and 
joints. The points noted in the discussion should then be reviewed. CHAPTER XIII 
THE HEAD 
SKULL PROPER 
Cranium Cerebrale 
The bony framework of the head is known as the cranium, or 
skull, which is subdivided into a part that forms a box for the pro- 
tection of the brain (cranium eerebrale), and a part that makes the 
bony framework of the face (cranium viscerale). In the fetus and 
until the skull has reached its adult size at about fourteen years of 
age, the bony skeleton is made up of a large number of distinctly 
separate bones. The cartilage lines decrease in width as develop- 
ment proceeds and in the adult the bones of the skull with the 
exception of the mandible, become fused into practically one solid 
piece. Because the cartilage of the suture lines does not disappear 
at the end of the growth period, but persists throughout life, the 
various parts of the skull are considered as separate bones (suture 
= sew). The suture lines are very irregular, the projecting parts 
of one bone being deeply set into depressions of the opposing bone. 
The suture lines make practically immovable joints, technically of 
the synarthroidal type, which functionate by yielding extra elas- 
ticity. A peculiarity of the bony development of the skull is that 
the cartilage about the vault of the skull first turns into fibro- 
cartilage before any bone is deposited. This is known as the intra- 
membranous type of bone development, the only peculiarity being, 
as previously noted, the appearance of the connective-tissue frame- 
work before any lime salts are deposited. The very early appear- 
ance of the fibrous tissue in the cartilage of the vault of the skull 
is probably to be explained as a protection to this important area. 
The cranium cerebrate is described as being made up of a calvaria, 
or vault, and a base, or floor. The calvaria forms the well rounded 
dome-shaped portion which extends up from the base encasing the 
brain. The rounded surfaces of the calvaria take advantage of the 
arch principle, which serves to increase its strength. The base is 
264 THE HEAD 
265 
very irregular due to the cervical muscle attachments, and is further 
characterized by a number of openings, which allow the spinal cord 
and numerous arteries, veins and nerves entrance or exit. The con- 
sideration of the cranium viscerale, which is very irregular on 
account of the requirements of the eyes, nose, and mouth, will be 
postponed until the face is taken up in detail. 
Landmarks 
The muscle-aponeurosis covering of the calvaria is relatively thin, 
consequently the bones are readily palpable throughout as land- 
marks. The prominent supraorbital margins are used to separate 
the forehead region of the calvaria from the eye socket (orbita = 
globular socket). The zygomatic arch, which extends from just in 
front of the ear to the cheekbone, separates the temple region of the 
calvaria from the side of the face. The mastoid process, the external 
occipital protuberance and the curved line between these landmarks 
separate the calvaria from the base of the skull. All these points, 
being superficial, are readily to be made out. 
Development of Skull 
The skull is primarily laid down in cartilage, but by the time of 
birth ossification has spread so far that only spaces of about one- 
quarter of an inch between the neighboring sections are still filled 
by cartilage. The frontal bone forms the forehead and extends back- 
ward over the brain almost two inches beyond the normal hairline 
(frons= forehead). On a level with the supraorbital margin, the 
frontal bone sends a thin plate backward to separate the top of the 
eyes and nose cavities from the interior of the skull. At birth this 
bone is made up of two halves separated by cartilage, but these parts 
unite so early in life that the adult bone shows no trace of this divi- 
sion. The parietal bones form great sections of the calvaria, but do 
not reach laterally down to the base. The two marked projections 
on the posterior portion of these bones, marking the widest measure- 
ment of the skull, are known as the parietal tubers. A portion of 
the greater wings of the sphenoid bone takes part in the formation 
of the lateral skull wall between the frontal, parietal and temporal 
bones. The sphenoid bone also takes part in the formation of the 
base of the skull, separating the brain from the nasopharynx and 266 
REGIONAL ANATOMY 
the internal maxillary regions (sphenoid = wedge). The squamous 
plates of the temporal bones bevel onto the opposing outer surfaces 
of the parietal bones. The temporal bone contains the ear, and 
occipital bone 
occipital fonticulus 
(0. T. fontanelle) 
.parietal bone 
frontal fonticulus 
frontal bone 
Fig. 82.-Skull (Cranium) at birth, superior view. 
frontal 
fonticulus 
frontal bone 
parietal bone 
nasal bone 
occipital 
fonticulus 
zygomatic bone 
maxilla 
occipital bone 
mandible 
sphenoid 
ear 
meatus 
temporal bone 
Fig. 83.--Skull (Cranium) at birth, lateral view. 
aside from its squamous plate, zygomatic process, aud mastoid pro- 
cess already noted, takes part in the formation of the base of the 
skull. The junction of the occipital bone with the parietals leaves a THE HEAD 
267 
permanent irregularity, which can be felt in the middle line about 
two and a half inches above the external occipital protuberance. 
The occipital bone turns forward inferiorly, forming, as previously 
noted, a large section of the base of the skull. 
The skulls of the European races are markedly larger anteropos- 
teriorly than from side to side, whereas the skulls of the Asiatic 
races approach nearer to roundness. 
Suturae et Fonticuli 
The cartilage strips allow the cranial bone to overlap during the 
birth process, normally without injury to the cranial contents. The 
width of these cartilage strips decreases markedly as growth pro- 
gresses, and eventually white fibrous tissue grows through the car- 
tilage, yielding strength to the joint. The opposing bone surfaces 
are markedly irregular, and are tongued and grooved so that in 
spite of a small permanent residue of cartilage the skull is practically 
one solid piece. The suture lines in the adult are fully as strong as 
the other parts of the skull, as may be noted in connection with frac- 
tures. The suture lines, though often given special names, are logic- 
ally named according to the bones or parts of bones separated, as 
for example the left fronto-parietal suture line is between the 
frontal and left parietal bone, and so forth. 
As an exception to this rule the suture line between the two 
parietal bones is known as the sagittal suture, while the line be- 
tween the right and left parietals and the frontal bone is known as 
the coronal suture. The reason for this variation in nomenclature 
is that whereas horizontal planes at a fixed level are always definite, 
vertical planes may vary throughout the whole range of the com- 
pass. The vertical planes, which parallel the interparietal suture 
are therefore known as sagittal planes, whereas those which parallel 
the fronto-parietal suture are known as frontal, or coronal, planes. 
A large space in the newborn child is covered only by cartilage at 
the junction of the midfrontal, midparietal and the right and left 
frontoparietal suture lines. This is known as the frontal or major 
fonticulus, for here during the first year of life the normal pulsa- 
tions of the brain may readily be felt (fonticulus, or O.T. fontanelle = 
diminutive of fountain). This pulsation is produced by the arterial 
pulse wave, exaggerated at this point because the remainder of the 
brain is held in a relatively unyielding box. The right and left 268 
REGIONAL ANATOMY 
occipito-parietal and mid-parietal suture lines at their junction form 
the smaller occipital or minor fonticulus. The large frontal fon- 
ticulus is the last cartilage area to be converted into bone, but even 
that is normally changed by the end of the first year of the child's 
life. 
Scalp 
The skin, subcutaneous fatty layer, deep fascia, and a musculo- 
aponeurotic layer are blended into one sheet over the calvaria, 
which is known as the scalp. The scalp, as a matter of common 
knowledge, is freely movable over the skull to a fixed limit and can 
be controlled by voluntary musculature. The skin is characterized 
by the great abundance of hair, except over the forehead region, 
which, although popularly considered a part of the face, is anatomic- 
ally a part of the scalp. The fatty layer is characterized by its 
extreme toughness, and, further, it is interesting to note that the 
amount of fat in its meshes does not increase in general stoutness of 
the individual. The epicranial muscle and aponeurosis is spread 
out over the whole calvaria, the deep fascias being blended with this 
layer (O.T. occipitofrontalis). The small occipital muscle bellies 
arise from near the curved line posteriorly, while the frontal bellies 
arise from the supraorbital margins. 
Vessels and Nerves 
A notch can be palpated along the eye surface of the supra- 
orbital margin between its intermediate and medial thirds. This 
is known as the supraorbital notch, and exists for the passage of the 
supraorbital branch of the fifth cranial nerve, accompanied by a 
small artery and vein. This nerve supplies the frontal part of the 
scalp, and, as it is exclusively sensory, is at times pressed on by an 
examiner in order to determine the depth of unconsciousness in an 
unconscious person. Crossing over the root of the zygomatic pro- 
cess just in front of the ear, run the superficial temporal or anterior 
auricular artery, vein, and nerve. This largest artery of the scalp is 
a branch of the external carotid, while the nerve comes from the 
interior of the skull and is purely sensory. This artery, vein, and 
nerve supply the lateral or temple part of the scalp. A short dis- 
tance behind the ear run the posterior auricular artery, vein, and 
nerve, while nearer the posterior midline are to be found the larger THE HEAD 
269 
occipital artery, vein, and nerve. These nerves are peculiarly sen- 
sory branches from the cervical plexus, while the arteries are 
branches of the external carotids. 
The vessels of the scalp bleed profusely and persistently when 
cut. The anatomic explanation offered is that the tough connective 
tissues do not allow the vessels, when cut, to retract and curl up as 
in other regions of the body. As no forceps yet devised hold this 
layer really satisfactorily, hemorrhage is ordinarily best controlled 
by pressure. The normal beginnings of baldness at points furthest 
removed from the main vessels points to a nourishment factor in 
this common ailment. 
Dissection.-After locating these various arteries, veins, and 
nerves at their entrance into the scalp and tracing them along their 
course for a limited distance, the scalp should be split from one mas- 
toid process to the other and from the external occipital protuber- 
ance to the root of the nose. The cross section should be studied 
and then the scalp pulled down to the face and neck bony land- 
marks. The epicranial muscle bellies and further detail in regard to 
the blood and nerve supply of the scalp may then readily be made 
out. The subscalp layer should be noted to be made up, exclusively 
of white fibrous tissue, and to allow a limited range of motion. The 
loose texture of this layer allows abscesses to spread out under the 
whole scalp, while the various forms of scalping take place through 
this line of lesser resistance. It should be noted that the scalp flaps 
carry their own vessel and nerve supply, when torn loose from the 
calvaria. Periosteum still covers the cranial bones and should be 
scraped off to examine the suture lines between the various bones. 
Then a saw-cut should be carried through the skull on a horizontal 
plane about one-half inch above the root of the nose, taking care 
not to cut too deeply, thus avoiding injury to the brain. The upper 
part of the calvaria may then be pried up and off with a chisel in 
order to expose the interior of the skull. 
Skull Section 
An examination of the cut surfaces of the skull will show at a 
glance irregularities in thickness, which can also be brought out by 
looking through the skull cap against the light. The thicker por- 
tions should be noted to be made up of a compact inner and outer 
layer and a spongy middle layer, which is often unnecessarily given 270 
REGIONAL ANATOMY 
the special name diploe. The wave-like elevations and depressions 
of the inner surface correspond to the grooves and convolutions of 
the brain. The thinner portions have no spongy layer, so that it is 
obvious that the mere thickness is no index of the strength, for that 
depends primarily upon the thickness of the compact layer. The 
spongy layer contains, as in other parts of the body, red bone mar- 
row. In the adult skull irregularly distributed, roundish depressions 
on the inner surface of the calvaria are caused by the arachnoid gran- 
ulations of Pacchioni. These depressions should be noted to lie 
along the main venous channels of the skull, but further details in 
regard to these granulations will be postponed until taken up in con- 
nection with the cerebrospinal fluid. Skulls differ very materially in 
their thickness, ordinarily varying in direct proportion to physical 
vigor. 
Meningeal Vessels 
The so-called meningeal arteries-in reality the nutrient arteries 
of the calvaria-enter the base of the skull and groove the bone 
deeply in their progress towards the middle line anastomosis. They 
are classified as anterior, middle and posterior meningeal arteries, 
but the large middle vessel is the only one of much practical im- 
portance. The middle meningeal divides into primary anterior and 
posterior branches and spreads out in progressively smaller 
branches over almost the whole of the interior of the skull. The cor- 
responding veins leave the base of the skull close to the arteries, but 
usually through separate foramina. The middle meningeal artery 
grooves the bone deeply and, as will be detailed later, is very often 
the cause of serious complications in fracture of the skull. 
The impress of the middle meningeal arteries on the removed sec- 
tion of the skull should be noted. 
Dura Mater (Dura Mater Encephali) 
The dura mater, which lines the interior of the skull, is exposed 
by the removal of the skull cap. The dura mater lining the interior 
of the skull is made up of three firmly fused layers; an outer perios- 
teal, a middle woven fibrous or dura proper, and an inner serous 
lining. Due to the firm attachment of the periosteum to the inner 
surface of the skull, the dura mater is ordinarily partly cut during 
the removal of the skull-cap. The periosteal surface of the dura THE HEAD 
271 
mater shows smaller and larger strands torn out from the bone, 
while the inner surface of the skull-cap is stripped of periosteum. 
Due to the irregularities and the foramina of the base of the skull 
the attachment of the dura is even firmer than over the calvaria, in 
fact it is almost invariably torn in line fractures of the base. The 
dura is very firmly attached to the numerous foramina of the base 
and continues, becoming semiseparated from the bony walls, into 
the vertebral column. This semiseparation of the dura mater spi- 
nalis from the bony wall is necessary to allow for the movements of 
the vertebral column, while obviously no motion is required in con- 
nection with the dura mater encephali. 
Partitions 
The dura mater sends semipartitions into the interior of the skull. 
These presumably act as stabilizers of the brain, just as, for example, 
semipartitions in a gasoline tank prevent the fluids from rushing 
too rapidly from side to side. The main semipartition runs vertically 
from the inner midline surface of the calvaria, extending from the 
roof of the nose to just beyond the external occipital protuberance. 
It divides the cerebrum or large brain into two hemispheres, and on 
account of its shape is known as the falx cerebri (falx = sickle; 
cerebrum = large brain). The falx cerebri is not a complete parti- 
tion, but leaves a large space open inferiorly through which the two 
hemispheres of the cerebrum connect up with each other. The falx 
cerebri attaches to the upper surface of the tentorium cerebelli, 
which lies on about a horizontal plane and separates the cerebrum 
from the cerebellum (tentorium = tent; cerebellum = small brain). 
An open space in the front part of the tentorium, roughly an inch 
and a half wide by two inches long, allows for the connection of the 
cerebrum with the cerebellum and spinal cord. The attachments of 
the falx cerebri and the tentorium cerebelli to the inner surfaces of 
the skull raise up bony processes and ridges. The attachment of the 
falx just above the roof of the nose raises up the crista galli of the 
ethmoid bone (crista = comb ; gallus = cock). The anterior attach- 
ment of the tentorium cerebelli runs forward into two strands, which 
raise up the anterior and posterior clinoid processes of the sphenoid 
bone (clina=bed, as in recline; a comparison with an old-fashioned 
four-poster bed). 272 
REGIONAL ANATOMY 
Venous Sinuses 
The venous and arterial supplies are, in contradistinction to the 
arrangement in the rest of the body, entirely unassociated within 
the skull. The main venous vessels or sinuses are found at the junc- 
tion of the semipartitions with the lining dura mater. Thus the 
falx cerebri splits before joining the lining dura mater, so as to 
leave open a triangular space, which is known as the superior sagittal 
sinus (O.T. longitudinal). This extends from the crista galli, pro- 
gressively increasing in size as it is joined by cerebral veins, back to 
the internal occipital protuberance. The internal occipital pro- 
■superior sagittal sinus 
(0. T. longitudinal) 
lining dura mater- 
falx cerebri _ 
straight or rectus 
sinus 
tentorium cerebelli- 
falx cerebelli- 
transverse sinus 
(0. T. lateral) 
Fig. 84.--Diagram of Dura Mater, frontal section, posterior portion of skull. 
tuberance is formed by the junction of the falx with the tentorium 
and lies approximately one-half inch nearer the foramen magnum 
than the external occipital protuberance. The position of the 
superior sagittal sinus on the inner surface of the skull is marked 
by a groove with parallel ridges. At the internal occipital pro- 
tuberance the superior sagittal sinus is joined by the rectus sinus, 
which lies in the fold of junction between the falx cerebri and the 
tentorium cerebelli. The inferior sagittal sinus, running in the 
lower free border of the falx cerebri and other veins coming from 
the interior and base of the brain make up this straight sinus. The 
combined superior sagittal-straight sinuses immediately divide into 
two transverse sinuses, which run laterally and forward between THE HEAD 
273 
the tentorium and lining dura. These transverse sinuses (O.T. lateral 
sinuses) progress straight to the petrous portion of the temporal 
bone and then make an S-shaped curve to the jugular foramen. 
After traversing the jugular foramina, these sinuses become the in- 
ternal jugular veins of the neck. A pair of anastomosing veins 
ordinarily connect the superior sagittal sinus through the parietal 
bone with the veins of the scalp. A similar anastomosis occurs 
between the transverse sinuses and the mastoid scalp regions, while 
there are other smaller anastomosing sinuses, which will receive 
consideration in the later dissections. 
The lining dura mater should be incised throughout its whole 
extent on a level with the saw-cut. Then the anterior attachment of 
the falx cerebri to the crista galli should be cut, and the whole lining 
dura turned back. The entrance of the cerebral veins into the 
superior sagittal sinus should be noted. By changing the position 
of the head the main points in regard to the semipartitions, the 
bony prominences, and the venous sinuses may be noted. The 
brain should not be disturbed until a later stage of the dissection. 
Fossae 
The bones taking part in the formation of the floor of the cranium 
cerebrate are the frontal, the ethmoid, the sphenoid, the temporals, 
and the occipital. The floor of the skull is markedly irregular and is 
divided into anterior, middle, and posterior cranial fossae (fossa = 
pit or ditch). These fossae are progressively on a deeper plane, the 
floor of the anterior fossa lying roughly on a level with the supra- 
orbital margin, of the middle fossa on a level with the zygomatic 
arch, and of the posterior fossa on a slightly lower level. These 
landmarks are only approximately true, as the floors of these fossa 
are in reality very irregular. The offset between the anterior and 
middle fossae occurs laterally at the posterior edge of the orbital 
plate of the frontal bone, while medially the posterior edge of the 
lesser wing of the sphenoid forms its half of the boundary. The 
offset between the middle and posterior fossae occurs at the ridge of 
the petrous portion of the temporal bone (petrous = stony, as in 
petrify). The impress of the convolutions of the brain on the bony 
floor is very marked over the anterior and middle cranial fossae, 
while the posterior fossa is not affected by the small convolutions of 274 
REGIONAL ANATOMY 
the cerebellum. The impress of the grooves and convolutions on the 
floor of the skull is, as would be expected, much more marked than 
over the vault areas. 
Bony Floor of Skull (Basis Cranii Interna) 
The floor of the anterior cranial fossa is made up chiefly of the 
orbital part of the frontal bone, which makes the bony separation 
Tro^taL 
cribriform plate 
or ethmoid 
cristi galli of 
ethmoid 
anterior cranial 
fossa 
anterior clinoid 
process 
Sphenoid 
optic foramen 
posterior clinoid 
process 
foramen rotundum 
carotid canal 
middle cranial 
fossa 
foramen ovale 
foramen spinosum 
■TemporaL 
internal acustic 
meatus 
petrous ridge 
jugular foramen 
hypoglossal canal 
posterior cranial 
fossa 
foramen magnum 
transverse sinus 
OccupitaT 
- x r w. 
superior sagittal sinus 
Fig. 85.-Bony Floor of Skull (Basis cranii interna). 
between the brain and the orbital cavity. The ethmoid bone with 
its crista galli is wedged in between the two halves of the frontal 
bone, and sends out a small plate intervening between the brain 
and the top of the nose. This horizontal plate is perforated by many THE HEAD 
275 
small holes for the passage of nerves and is therefore known as the 
cribriform plate of the ethmoid. The cribriform plate (lamina 
cribrosa) gives rise to the name ethmoid-that is, like a sieve. Fit- 
ting against the posterior margin of the ethmoid and joining the 
posterior margin of the frontal orbital plate lie the lesser wings of 
the sphenoid bone. The sphenoid bone is compared in nomenclature 
to a butterfly, having a body and lesser and greater wings (alae 
parvae et magnae). 
The anterior and medial portion of the floor of the middle cranial 
fossa is made by the body and greater wings of the sphenoid bone. 
Between the greater and lesser wings of the sphenoid lies a narrow 
slit known as the superior orbital fissure (O.T. sphenoidal). This 
triangular fissure can be seen when looking into the back of the 
orbital cavity and exists as a passageway between the cranial cavity 
and the orbita. The anterior clinoid processes are projections from 
the lesser wings, while the posterior clinoid processes belong to the 
body of the sphenoid bone. The deep space between the clinoid pro- 
cess is usually called the sella turcica, or turkish saddle. This 
changes the comparison previously used to derive the term clinoid, 
for to maintain the same figure of speech the term clina should be 
used. In the posterior cranial fossa the sphenoid forms a solid bony 
junction with the occipital bone, the cartilage ordinarily disappear- 
ing entirely in the adult. The posterior and lateral portion of the 
middle cranial fossa is formed by a plate of the temporal bone. 
The floor of the posterior cranial fossa is made up essentially by 
the part of the occipital bone, which intervenes between the cere- 
bellum and the muscles of the neck. This is very much the thickest 
and strongest portion of the base of the skull, serving as a protection 
for the most vital region of the body, as will be noted in connection 
with the detailed consideration of the brain. In the anterior portion 
of the occipital bone lies the foramen magnum, the opening between 
the skull and the vertebral column. A strong portion of the tem- 
poral bone joins at a suture line the front edge of the occipital bone. 
In this suture line, just lateral to the anterior portion of the 
foramen magnum, lies the jugular foramen. 
Many of the suture lines in the base of the skull become very 
faint in later life, and some, as, for example, the sphenooccipital, in 
reality disappear entirely. 276 
REGIONAL ANATOMY 
Cranial Nerves (Nervi Cerebrales) 
In order to gain a clear conception of the openings in the floor of 
the skull, it is necessary to consider summarily the arteries, veins, 
and nerves, which enter or leave the skull. 
The twelve pairs of cranial nerves are classified as follows: 
NERVE. 
FUNCTION. 
EXIT FROM SKULL. 
I. or olfactory 
smell 
cribriform plate of ethmoid 
II. or optic 
sight 
foramen in lesser wing of 
sphenoid 
III. or oculo-motor 
motor to eye 
superior orbital fissure 
IV. or trochlear 
motor to eye 
superior orbital fissure 
VI. or abducent 
motor to eye 
superior orbital fissure 
^ophthalmic division - supe- 
rior orbital fissure 
maxillary division-foramen 
V. or trigeminal 
sensory of head « 
rotundum 
mandibular division - fora- 
men ovale 
VII. or facial 
motor of head 
internal acustic meatus 
VIII. or acustic 
hearing 
internal acustic meatus 
IX. or glossopharyngeal 
taste, etc. 
jugular foramen 
X. or vagus 
heart, etc. 
jugular foramen 
XI. or accessory 
joins vagus, etc. 
jugular foramen 
XII. or hypoglossal 
motor to tongue 
hypoglossal canal 
Cranial Arteries 
The internal carotid arteries enter the interior of the skull along 
the sides of the sella turcica of the sphenoid bone. The internal 
carotid artery enters the base of the skull just in front of the jugular 
vein, but whereas the carotid canal curves forward sharply the 
jugular vein turns backward. The vertebral arteries go through 
the foramen magnum, and eventually will be noted to anastomose 
about the base of the brain with the internal carotids. The middle 
meningeal artery, a branch of the internal maxillary, enters at the 
posterior tip of the greater wing of the sphenoid, through the 
foramen spinosum. A minor anastomosis will later be noted between 
the intra- and extracranial arterial systems. THE HEAD 
277 
Veins 
The main venous trunks leaving the skull are the internal jugulars. 
A number of anastomoses between the intra- and extracranial venous 
systems take place as will be noted in the later regional dissections. 
These anastomoses are very important clinically on account of the 
danger of infective clot blockade spreading from diseases of the 
face and scalp. 
Dissection.-In order to obtain a view of the floor of the skull, 
the brain must be removed. With the head tilted back so that 
gravity tends to pull the brain posteriorly, if not previously done, 
the dura should be incised all the way around at the same level as 
the saw-cut. Then the falx cerebri should be cut across from its 
attachment to the crista galli. The cerebrum will tend to fall out, 
but is connected with the cerebellum, which is still firmly held in its 
posterior cranial compartment. The tentorium cerebelli should then 
be cut close to its attachments to the bony walls. The various 
nerves and vessels, which connect with the base of the brain, should 
next be cut across at a convenient midpoint. The entire brain 
should then be removed from the skull, and should be kept moist 
and carefully preserved for future study. The floor of the skull is 
exposed by this dissection for detail examination. 
Foramina 
The only pair of cranial nerves in the anterior fossa are the 
olfactory. A bulbous tract of the brain lies directly over the cribri- 
form plate of the ethmoid and sends numerous fine branches into 
the nasal cavities. 
The second, third and fourth pairs may be noted to pierce the 
dura in the middle cranial fossa. The fifth and sixth pairs pierce 
the dura under the tentorium cerebelli, but run forward on each side 
of the body of the sphenoid under the dura mater into the middle 
cranial fossa. The large optic nerves should be noted to pass 
through a separate foramen in the lesser wing of the sphenoid bone, 
situated just medially to the anterior clinoid process. All the oculo- 
motor nerves and the trigeminal lie under the dura mater for some 
distance and consequently can not be followed to their foramina 
until the dura is dissected off. The middle meningeal artery enters 
through the base of the skull at the foramen spinosum in the pos- 278 
REGIONAL ANATOMY 
terior tip of the greater wing of the sphenoid. The spine which 
gives this foramen its name is raised up on the neck surface of the 
base by a ligament attachment. 
The seventh to the twelfth cranial nerves, inclusive, arise under 
the tentorium and make their exit from the posterior cranial fossa. 
The facial and the acustic both enter the internal acustic meatus on 
the posterior surface of the petrous portion of the temporal bone. 
The glossopharyngeal, vagus, and accessory nerves should be traced 
to the jugular foramen, while the hypoglossal runs lower down 
through its separate canal of the occipital bone. 
Middle Cranial Fossa 
The dura mater should be carefully dissected off one side of the 
sphenoid bone, while the other side remains undisturbed for com- 
parison. The oculomotor nerves, the third, fourth, and sixth, 
should be traced forward under the dura to the superior orbital 
fissure. The trigeminal or fifth nerve enters this space as a single 
trunk, which immediately spreads out to form the semilunar or 
Gasserian ganglion. From this ganglion three trunks are given off; 
the ophthalmic division running straight forward to the superior 
orbital fissure, the maxillary division running forward to the fora- 
men rotundum, and the mandibular division running directly down- 
ward into the foramen ovale. The foramen rotundum is located near 
the junction of the greater wing with the body of the sphenoid bone, 
while the foramen ovale is in the posterior part of the greater wing. 
A branch from the facial nerve centers of the brain stem, traveling 
as a separate strand, follows the mandibular division through the 
foramen ovale. This entire nerve, that is, the root, ganglion, and 
divisions, lies protected within a white fibrous connective-tissue 
sheath in its course under the dura mater to its foramina of exit 
from the skull. 
Cavernous Sinus 
A large cavernous venous sinus drains the ophthalmic or eye vein 
and empties posteriorly into the transverse sinuses. This cavernous 
sinus lies along the sides of the body of the sphenoid and sends 
anastomosing branches through the base of the skull. One branch 
leading back along the ridge of the petrous portion of the temporal 
bone to the transverse sinus is known as the superior petrosal sinus. 279 
THE HEAD 
The other branch runs from the posterior extremity of the cavernous 
sinus practically straight backward to the jugular foramen, and is 
known as the inferior petrosal sinus. The two cavernous sinuses 
are connected by transverse anastomosing branches. Nerves are 
embedded in the walls of the cavernous sinus, while the internal 
carotid artery literally traverses the sinus in its course to the interior 
of the skull. 
Hypophysis 
The hypophysis is a globular gland, which is roughly about a 
quarter of an inch in all diameters, and is held firmly encased by 
dura on the sella turcica (O.T. pituitary gland). It is made up of an 
anterior lobe developed from the pharyngeal mucosa and a posterior 
lobe developed from the brain. The anterior lobe is separated by 
the body of the sphenoid bone from the nasopharynx, while the 
posterior lobe retains via a stalk or infundibulum its connection 
with the brain. This infundibulum was necessarily cut or torn 
across in the removal of the brain. 
The gland is commonly considered to be of the ductless type, and 
is essential to a regulated growth of the body, if not to life itself. 
Its proximity to the optic nerves explains anatomically the liability 
to vision disturbances in overgrowth of this gland. The function of 
the pharyngeal and of the brain lobes is different, consequently 
under- and overactivity of the anterior and of the posterior lobe are. 
theoretically at least recognizable in the clinic. 
Fractures of the Skull 
The rounded surfaces of the calvaria, utilizing the arch construc- 
tion, tend to make ordinary blows glance off the skull without 
serious injury. Severe, sudden impacts centered over a small area 
tend to produce localized depressed fractures, ordinarily without 
linear spreading. The temple region, owing to the anatomic fact 
that it is thin and not arched, offers the least resistance to this form 
of injury. Severe blows striking the skull squarely and spread out 
over a large area tend to produce line fractures. These linear frac- 
tures tend to run through the base of the skull on account of its 
thinness, its foramina and its relative flatness. Any blow sufficiently 
severe to cause a fracture will necessarily cause more or less injury 
to the brain itself, characterized clinically by the symptoms of 280 
REGIONAL ANATOMY 
concussion. Fractures can be located by incising the scalp or can 
often be visualized by the use of the x-ray. 
Clinical Signs of Fracture 
If the fracture runs through the cribriform plate of the ethmoid 
or the petrous portion of the temporal bone, the dura is practically 
always torn open, allowing cerebrospinal fluid to escape into the 
nose or ear. This escape of cerebrospinal fluid fixes the diagnosis, 
and on account of the great danger of meningitis is a most serious 
complication. If the fracture runs through the orbital part of the 
frontal bone a hemorrhagic collection in back of the eye is the char- 
acteristic symptom. If the dura is torn in any fracture of the skull, 
unclotted blood may be found by lumbar puncture diffused through- 
out the cerebrospinal fluid, although obviously this might, on the 
other hand, come from the lacerated brain substance itself. Most 
linear fractures do not tear the dura mater of the calvaria, but 
simply loosen its attachments to the skull. If, then, one of the 
nutrient bone arteries is cut by the jagged edges of the skull, an 
extradural hemorrhage collects. The symptomatology of a middle 
meningeal extradural hemorrhage is a more or less marked paralysis 
of the opposite half of the body, the reason for which will be noted 
in connection with the detailed study of the brain. A tear through 
the venous sinuses of the skull will show practically no clinical symp- 
tom on account of the low pressure in the veins. 
It is obvious that in a case of fracture of the base of the skull some 
of the cranial nerves may be destroyed, either at their foramina or 
along their course from the brain stem to the foramina. The sixth 
or abducent nerve is particularly exposed to injury on account of its 
long course between the dura and skull. The localization will be 
dependent upon the particular nerves destroyed, which can only be 
determined by a consideration of their course, function, and distribu- 
tion. The connection of the cranial nerves with the brain will later 
on be taken up in detail. 
CENTRAL NERVOUS SYSTEM 
All the nerves of the body are connected up with and regulated 
through the central nervous system, which is made up of the spinal 
cord (medulla spinalis) and the brain (encephalon). The spinal THE HEAD 
281 
cord in all the vertebrates is protected in the bony vertebral 
column and the brain by the cranium cerebrate. The word brain is 
often applied to the cerebrum alone and at other times to the whole 
nervous contents of the skull. To avoid this possible source of con- 
fusion, the technical term encephalon is justly gaining in usage and 
will be used throughout this description. An uninjured central 
nervous system is obviously essential for the proper functions of 
the body, and certain parts of it even for life itself. 
Development 
The beginning of nervous tissue in the vertebrate embryo is 
in the formation of a dorsal ectodermal groove. This groove lies in 
the midline, directly back of the cartilaginous notochord, and 
Dorsal ectodermal groove, surface view. 
Developmental stages, cross sections, 
notocord neural tube 
dorsal groove 
notocord 
spinal cord 
vertebra 
Fig. 86.-Development of Spinal Cord (medulla spinalis). 
extends throughout the length of the embryo. The notochord is a 
continuous cartilaginous rod, which serves as the basis for the devel- 
opment of the bodies of the vertebras. The dorsal ectodermal groove 
deepens and finally becomes constricted off from the surface, form- 
ing the primitive neural tube, as illustrated in the diagram. The 
walls of the primitive neural tube are made up of developing nerve 
cells, which are technically known as neuroblasts. These neuro- 
blasts are at first noncharacteristic roundish cells without processes, 
which later develop processes and then become known as neurons- 
that is, nerve cells. The developing verterbrae send back their 
arches, which protect the neural tube laterally and posteriorly, while 
at the head end the cranium cerebrate develops. That some of the 282 
REGIONAL ANATOMY 
connective tissue elements of the central nervous system are devel- 
oped from ingrowths from the mesoderm seems a priori plausible, 
but this proposition has been negated by convincing scientific proof. 
The meninges, the dura, arachnoidea and pia are developed from the 
mesoderm, as are the connective-tissue sheath coverings of the 
peripheral nerves. 
The lamina and spinous processes occasionally fail to grow to- 
gether in back of the spinal cord, so that only the skin, fascia, and 
meninges protect the nervous system. This malformation occurs 
more frequently in the lumbar region and, if it is at all large, the 
dura and skin are commonly bulged out by the pressure of the cere- 
brospinal fluid. 
Nerve Cell (Neuron) 
The bodies and processes of nerve cells are gray in color. The 
ordinary peripheral nerves and a great part of the central nervous 
system appear an ivory white, but this is due to the addition of the 
medullary or myelin insulating sheaths around the small gray axis 
cylinder processes. The special connective tissue cells of the nerv- 
ous system are known as the neurog'lia (glia = spider-like). Some 
nerve cells are about the size of a red blood capsule, but the great 
majority are distinctly large cells, a dozen or more times greater in 
diameter. The axis-cylinder processes are in many cases three feet 
or more long, extending, for example, from the spinal cord to the 
sole of the foot. The dendritic processes terminate in relatively 
short branches, which make connections with similar processes of 
neighboring cells. The neuroblasts, after a certain stage of fetal 
development, change into nerve cells, which do not possess the power 
of reproducing themselves. No new nerve cells are produced after 
birth, but if processes are cut across, it is possible for the body of 
the nerve cell to send out new processes. The growth of the 
encephalon after birth is probably in part to be attributed to increase 
in the size of the individual cells and sheaths, although there may 
well be other factors. 
Ganglia 
Aggregations of the bodies of nerve cells held together by con- 
nective tissue are known as ganglia and are gray in col<fr. As the 
nerve processes of the sympathetic system grow out from the central 
nervous system towards the surface, neuroblasts commonly follow THE HEAD 
283 
along the progressing axis-cylinder processes. The primary set of 
ganglia developed are those of the sympathetic gangliated trunks, 
which lie along the sides of the bodies of the vertebra. The second- 
ary set are the prevertebral ganglia, named according to their posi- 
tion and function, the cardiac, the epigastric, the hypogastric, and 
so forth. A tertiary set of ganglia may be found, microscopically, 
scattered in the various organs of the body-for example, in the 
heart, lungs, and gastrointestinal tract-being known as the visceral 
ganglia. These ganglia belong to the sympathetic nervous system 
and are not found in connection with voluntary segmental nerves 
outside of the skull and vertebral column. Most of the sympathetic 
nerves have a medullary sheath, while a few are nonmedullated and 
consequently appear gray in a fresh body. The sympathetic is often 
referred to as the vegetative nervous system, as it is not under the 
control of the will. 
Efferent versus Afferent Neurons 
Nerve cell processes differ from an ordinary insulated wiring sys- 
tem, inasmuch as nerve messages can only be sent in one direction 
on any given nerve process. The nerve processes, which possess the 
power of carrying messages away from the central nervous system 
are known as the efferent, while those leading to the central ner- 
vous system are known as afferent (ferro = carry; e = away; ad = 
towards). The motor nerves obviously belong to the efferent class, 
while the sensory belong to the afferent class. Most of the periph- 
eral nerves are made up of an admixture of both types of proc- 
esses, though in special cases, for example, in the head, many of 
the nerves are made up exclusively of one class. That most of the 
sympathetic nerves also are made up of mingled efferent and afferent 
fibers seems probable, although the presence of afferent fibers is for 
obvious reasons not so readily susceptible of absolute proof. 
These last three topics are discussed with greater detail in the 
introductory chapter on nerves, pp. 61 to 64. 
Spinal Cord (Medulla Spinalis) 
Both the voluntary and the sympathetic nerves connect up seg- 
mentally through the intervertebral foramina with the spinal cord. 
The dura mater wraps around these segmental nerves as a funnel- 284 
REGIONAL ANATOMY 
shaped protector and continues peripherally, eventually blending 
with their connective-tissue coats. Each segmental nerve bundle 
travels a varying distance inside the dura until within about one- 
half inch of the spinal cord, when it divides into an anterior and a 
posterior root. The anterior root, which runs to the anterolateral 
portion of the spinal cord, is made up exclusively of efferent pro- 
cesses, while the posterior root, which runs to the posterolateral 
portion of the cord, contains only afferent processes. The charac- 
teristic feature of the posterior root is the presence of a ganglion, 
which is enclosed in the dura and located just peripherally to the 
intervertebral foramen. 
anterior root 
anterior Assure 
white substance 
intervertebral 
foramen 
anterior column 
central canal 
gray substance 
ganglion 
posterior 
column 
posterior root 
Fig. 87.-Diagrammatic transverse section of Spinal Cord (x 10) 
posterior groove 
Cross-Sections of Spinal Cord 
The spinal cord varies in different segments, but is roughly one- 
quarter times three-eighth inches in diameters. An H-shaped gray 
substance (substantia grisea) can be readily distinguished in a fresh 
specimen by the unaided eye from the surrounding white portions 
(substantia alba). The white portion is made up in the main of 
processes connecting the encephalon with the various segments of 
the spinal cord, of both the efferent and afferent classes, but also 
contains shorter processes, which interconnect between various 
levels of the cord. Logically the white area must then be largest at 
the upper part of the neck, and progressively smaller down to the 
termination of the spinal cord opposite the first lumbar vertebra. 
For all the processes connecting the spinal cord with the encephalon 
must pass through the neck region, whereas in the lumbar region 
only the white processes interconnecting between the lower part of 
the body and the encephalon are to be found. The gray portion is THE HEAD 
285 
made up essentially by the nerve cell bodies of the segmental nerves, 
but possesses also some neuroglia cells. Logically, therefore, the 
gray substance must be largest where the segmental nerves are the 
largest, that is, where the brachial and lumbosacral plexuses join 
the cord (intumescentia cervicalis et lumbalis). The greater size of 
the anterior column of the H-shaped gray substance is due to the 
fact that all the cell bodies are found in this area, instead of partly 
in the root ganglia, as is the case with the posterior root. 
The anterior or efferent roots are composed chiefly of the motor 
processes, both of the voluntary and involuntary musculature. Very 
probably many other kinds of activity of not so obvious a nature 
are also dependent upon impulses through this anterior root. The 
posterior or afferent roots are composed chiefly of sensory processes, 
which connect mainly with the cutaneous surfaces, but also with 
various other parts of the body. It is known, for example, that the 
fascias and muscles have a rather limited sensory supply, but that 
the bones, joints and endothelial surfaces have very acute sensation. 
On account of the plexus arrangement of the spinal nerves, no one 
segmental nerve ever completely supplies a segment of the body, 
there being always considerable overlapping in the peripheral dis- 
tribution. 
Peripheral Neurons 
The nerves having their cell bodies in the anterior column of the 
spinal cord or in the posterior root ganglia are known as the periph- 
eral neurons (peri = around; phero = carry). Even though their 
bodies lie in or near the spinal cord, these nerves belong to the 
peripheral system of neurons on account of their distribution. The 
nerve processes connecting up these cell bodies of the various levels 
of the spinal cord with the encephalon, making up the white sub- 
stance of the spinal cord, belong to the central system of neurons. 
A reflex muscular action may be brought about in a normal indi- 
vidual by tapping the tendon of a stretched muscle, provided the 
patient's attention is distracted from the procedure. The contrac- 
tion of a muscle thus brought out is known as a spinal cord reflex. 
It should be specially noted that the condition of the encephalon 
and upper portions of the spinal cord have nothing to do with this 
action. The message travels up from the muscle through the pos- 
terior root into the particular segment of the spinal cord, crosses 
over to the motor cells of the anterior column, and travels down the 286 
REGIONAL ANATOMY 
anterior root to the muscle. This reflex takes place even though the 
spinal cord be completely severed above this point. The fact is, in 
time it becomes exaggerated under these abnormal circumstances. 
But if either the anterior or posterior root neurons are destroyed by 
accident or disease, the circuit is interrupted and no spinal cord 
reflex is possible. 
Locomotor ataxia, a late syphilitic nervous degeneration, is typical 
of the diseases characterized by a destruction of the posterior roots. 
When this disease is advanced, the patient has a very marked 
diminution of all sensibility and no spinal cord reflex. Clinically 
the painless, badly injured joints, the lack of muscular balance with 
the eyes shut, and the absent reflexes are readily explicable on the 
anatomic basis. 
Infantile paralysis is produced by a poison, which selectively de- 
stroys the motor cell bodies of the anterior column. The resulting 
paralysis and the absence of spinal cord reflexes characteristic for 
this disease is also readily explained by the anatomic considerations. 
Results similar to these are obtainable experimentally by the sec- 
tioning of the anterior or posterior roots. The presence of a normal 
spinal cord reflex then means that the afferent and efferent periph- 
eral neurons are intact, nothing more and nothing less. 
Central Neurons 
But these peripheral neurons must be connected up with the 
cerebrum, if consciousness of pain or voluntary motion is to be 
obtained. The nerve processes connecting up the peripheral neurons 
with the cerebrum belong to the afferent and efferent central 
neurons. These central processes may connect directly from the 
cerebral cortex to the cell bodies of the anterior or posterior column 
of the various levels of the spinal cord. These processes usually, 
however, stop one or more times en route in some mass of gray 
substance, while a new process travels the remainder of the dis- 
tance. If the motor cells of the cortex of the cerebrum, or their 
processes in any part of their course to the anterior column cell 
bodies are destroyed, no voluntary motion of the part is possible. 
But the spinal cord reflex is not interfered with and after a variable 
period of time even tends to become exaggerated. Similarly if the 
sensory cells of the cerebral cortex, or their processes in any part of THE HEAD 
287 
their course from the cortex of the cerebrum to the cell bodies of the 
posterior root are destroyed, no consciousness of pain is possible. 
But again the spinal cord reflex is not interfered with. 
If an individual can not move a part of the body, the condition is 
called paralysis. This may be due to the disease of the peripheral 
motor neurons or of the central motor neurons. The presence of a 
spinal cord reflex would tend to demonstrate that the peripheral 
motor neurons are intact and that therefore by exclusion the dis- 
turbance must be in the central motor series. The same logic 
obviously applies to the question of absence of sensation. 
Tracts of Spinal Cord (Fasciculi Medullae Spinalis) 
The nerve processes connecting up the cell bodies of the various 
levels of the spinal cord with the encephalon run in group bundles 
through the white substance of the cord. In the normal adult spinal 
cord it is absolutely impossible to find any trace of these bundles. 
These group bundles make up the fasciculi or tracts of the spinal 
cord, and have been demonstrated primarily by a study of their dis- 
appearance in disease. Due to the fact that in fetal life certain of 
these tracts develop their medullary sheaths earlier than others, our 
knowledge derived from a study of diseased spinal cords has been 
corroborated and added to. 
The anterior and lateral cerebrospinal tracts are logically so 
named on account of their function and their position in the white 
substance of the spinal cord. They were formerly known as the 
direct and crossed pyramidal tracts, respectively, because they form 
pyramid-like structures on the anterior surface of the medulla 
oblongata, the connecting portion between the spinal cord and the 
upper portions of the nervous encephalon. These tracts are made 
up of the processes of the central motor neurons, which connect up 
the cortex of the brain with the cell bodies of the anterior column of 
the spinal cord. The lateral cerebrospinal tract crosses over from 
one side to the other in the medulla oblongata, while the anterior 
cerebrospinal tract also eventually crosses, but only when its proc- 
esses have reached their terminating level in the spinal cord. The 
cerebellospinal tract lying in the superficial lateral portion of the 
white substance, will later be traced into the cerebellum, at which 
time its function will be considered. The two main sensory tracts 288 
REGIONAL ANATOMY 
are to be found side by side in the posterior segment of the white 
substance of the spinal cord. The medially situated of these tracts 
is known as the gracilis tract of Goll, while the lateral is known as 
anterior 
cerebrospinal 
white substance 
gray substance 
lateral 
cerebrospinal 
cerebrospinal 
graceful 
(gracilis) 
of Goll 
wedge-shaped 
(cuneatus) 
of Burdach 
Fig. 88.-Diagram of Tracts (fasciculi) of Spinal Cord (xlO). 
the cuneatus tract of Burdach, or if these names are forgotten they 
might be identified simply as the posterior median and posterior 
lateral tracts. Other tracts, anatomically less defined and func- 
tionally less important, make up the remainder of the white sub- 
white substance 
(substantia alba) 
■gray substance 
(substantia grisea) 
Fig. 89.-Showing junction of white and gray substances (x 100) 
stance of the spinal cord. Many of these other tracts are processes 
interconnecting various levels of the spinal cord. 
Dissection.-The coverings and gross appearance of the spinal 
cord were considered with the dissection of the vertebral column, THE HEAD 
289 
page 235. If any of the remaining material contains parts of the 
spinal cord it should prove of great advantage to repeat this dis- 
section. Unfortunately in the dissecting room bodies the spinal cord 
is so altered in color and consistency that gross cross-sections are 
ordinarily practically valueless. In order to obtain a just conception 
of the gross color markings and consistency of the spinal cord, it is 
absolutely essential to obtain a part of a fresh cord from one of our 
domestic animals. The surprising feature of a fresh normal spinal 
cord to the elementary student is its very marked delicacy as con- 
trasted with the peripheral nerves previously considered. This 
difference in strength and consistency is presumably related to their 
relative exposure to injury, the central nervous system being well 
protected, while the peripheral nerves are relatively exposed. The 
strength of the peripheral nerves is due essentially to their thick, 
white fibrous connective-tissue sheaths, which, however, do not 
continue inside of the dura mater. While the pia mater and the 
blood vessels do carry some ordinary white connective tissue into 
the central nervous system, most of the connective-tissue function is 
assumed by the relatively delicate and sparse neuroglia cells. The 
parts of the peripheral nerves which connect with the spinal cord 
and encephalon are so delicate that it does not require much strain 
to tear them or pull them out from their origins. 
The discussion in regard to the tracts and gray substance of 
the spinal cord at various levels can be followed by studying the 
diagrams in the larger atlases, or preferably the actual microscopic 
sections. It is obvious that much of the foregoing discussion can not 
be actually demonstrated, as it is based on a compilation of knowl- 
edge derived from various sources. 
Development of Encephalon 
The encephalon makes its first appearance as an enlargement of 
the cephalic end of the neural tube. In the lower animals the head 
end is obviously the first part of the body to come into relation with 
any new object, and consequently is best fitted to gather special 
information, which may then be transmitted to the rest of the body. 
The primary tubular structure of the cephalic portion of the neural 
tube divides after a short period of development into three vesicles 
(vesicle = bladder). These vesicles are known from in back for- 290 
REGIONAL ANATOMY 
wards as the rhombencephalon, or hindbrain (has rhomboid-shaped 
interior cavity), the mesencephalon, or midbrain, and the prosen- 
cephalon, or forebrain. As development progresses the rhomben- 
cephalon divides into three vesicles, which are known embryological- 
Division 1-medulla oblongata 
" 2-cerebellum 
" 3-isthmus rhombencephali 
" 4-mesencephalon 
" 5-diencephalon 
" 6-cerebral hemispheres 
myelencephalon 
metencephalon 
isthmus rhombencephali 
rhombencephalon 
mesencephalon 
diencephalon 
telencephalon 
-cerebrum 
ly as the myelencephalon, the metencephalon, and the isthmus rhom- 
bencephali, forming in the fully developed status the medulla 
oblongata, the cerebellum with its portion of the brain stem, and the 
isthmus rhombencephali, respectively. The mesencephalon does not 
undergo any marked changes, its interior cavity remaining small and THE HEAD 
291 
in the fully developed status persisting as a narrow duct. The pros- 
encephalon divides into two vesicles, which are known as the 
diencephalon and the telencephalon (di = separate as in divide; 
tel = end or distant as in telephone). Further development of these 
six primary vesicles gives rise to the subdivision of the encephalon 
which will be referred to in this text as the medulla oblongata, the 
cerebellum, the isthmus rhombencephali, the mesencephalon, the 
diencephalon and the cerebral hemispheres. The lateral develop- 
ment in the higher animals is characterized by the great increase in 
the cerebral and cerebellar divisions, while the other parts increase 
relatively little. The cerebral hemispheres keep on increasing in 
size until by birth they are roughly a dozen times as large as the 
combined medulla oblongata, cerebellar, mesencephalon and dien- 
cephalon subdivisions of the encephalon. 
Vesicles, or Ventricles 
The walls of these developing vesicles are made up essentially of 
neuroblasts, the cells which undergo division to form the permanent 
nerve cells of the encephalon. The cavities inside these vesicles 
communicate freely and join the neural tube cavity of the spinal 
cord region. During these developmental changes blood vessels 
from the outside grow into these cavities and commence the secre- 
tion of cerebrospinal fluid. In the literal sense of the words these 
vessels do not enter the vesicles, but carry in before them a fold of 
epithelium, which forms a covering over the network of arteries, 
capillaries and veins. The relationship here is the same as the intes- 
tines have to the peritoneal cavity and the lungs to the pleural 
cavities. This layer of epithelial cells, technically known as the 
lamina chorioidea epithelialis, controls the secretion of the cerebro- 
spinal fluid (chorioid = rich network of small vessels). The name of 
the interior cavities during later development is changed from vesi- 
cles to ventricles, the term ventricle referring to their alleged stom- 
ach-shape. At first there is no connection between the vesicotubular 
interior of the central nervous system and the pia-arachnoid space, 
but later foramina develop secondarily. The cerebrospinal fluid 
then under normal conditions escapes out of the ventricles via 
foramina into the pia-arachnoid endothelial sac, as will be detailed 
later. 292 
REGIONAL ANATOMY 
Encephalon 
The encephalon after birth is made up of gray and white sub- 
stance, with the same significance as in other parts of the nervous 
system. The gray substance of the encephalon is not distributed 
regularly as in the Il-shaped center of the spinal cord, although in 
the medulla oblongata, and in the mes- and diencephalons this condi- 
tion is approximated. The white processes connecting the cerebrum 
with the spinal cord must obviously traverse the medulla oblongata, 
the base of the cerebellum and the mes- and diencephalons in order 
to reach their destination, while the cell bodies of the cranial nerves 
tend to lie inside of these white tracts. But in the case of the cere- 
brum and cerebellum the gray substance is characteristically dis- 
tributed over the outer surface or cortex throughout its whole ex- 
tent, although they both do possess some large internal masses of 
gray substance. This gray cortical area is increased markedly by 
the presence of grooves (sulci), which mark off the convolutions 
(gyri). The convolutions average about one-quarter of an inch in 
width in the human cerebrum, but are only about one-tenth as wide 
in the cerebellum. 
Tracts of Brain Stem 
Our knowledge of the various tracts of the nervous encephalon is 
dependent upon the same basis as in the case of the white substance 
of the spinal cord, that is, the study of the white substance in disease 
and in the stages of development. All the efferent and afferent 
tracts connecting up the spinal cord with the cerebral hemispheres 
run through the medulla oblongata, base of the cerebellum, and the 
mes- and diencephalons. The connecting tracts between the cere- 
bral hemispheres and the spinal cord, plus a considerable amount of 
incidental gray substance, is commonly called, as a matter of con- 
venience, the brain stem. The central motor nerve cell bodies lie 
about the mid-lateral surface of the cortex of the cerebrum and send 
their axis-cylinder processes down through the brain stem to the 
anterior column cell bodies of the various levels of the spinal cord. 
These nerve processes may theoretically traverse the whole distance 
themselves, or, as probably happens more commonly, may relay 
through masses of gray substance and other neurons to their dis- 
tribution. These masses of gray substance within the brain stem THE HEAD 
293 
and cerebral hemispheres are known as nuclei, the term ganglion 
being reserved for the knot-like masses of gray substance to be 
found along the course of the peripheral nerves. 
The majority of the motor nerve processes make up the pyramids 
of the medulla oblongata, which can be noted macroscopically on its 
anterior surface, one on each side of the median line. The greater 
diencephalon 
internal capsule 
mesencephalon 
cerebrospinal tracts 
(motor) 
medial lemniscus 
(sensory) 
cerebellum (peduncles 
sectioned) 
nucleus cuneatus 
nucleus gracilis 
medulla oblongata 
decussation of pyramids 
sensory tracts 
spinal cord - 
lateral cerebrospinal 
tract 
anterior cerebrospinal 
tract 
Fig. 91.-Diagram of Tracts (fasciculi) of Brain Stem. (Posterior-superior view with tracts 
projected to surface and cerebellar hemispheres removed.) 
number of these processes cross in the medulla oblongata and make 
up the lateral cerebrospinal tracts of the medulla spinalis, while the 
remainder, which continue straight down, make up the anterior 
cerebrospinal tracts. The main sensory tracts of the spinal cord, 
the fasciculus gracilis (posteromedian) and the fasciculus cuneatus 
(posterolateral) terminate in nuclei of the same names in the pos- 
terior portion of the medulla oblongata. These tracts, however, do 
not really stop in these masses of gray substance, but processes 294 
REGIONAL ANATOMY 
arising from these nuclei carry the sensory tracts upward through 
the brain stem to terminate eventually in the cortex of the cerebrum 
just posterior to the motor area. These processes form the medial 
lemnisci, which course anteriorly within the medulla oblongata and 
about its middle cross over to the opposite sides. The cerebellar 
tract of the spinal cord carries afferent processes into the cerebellum 
and hence traverses only the oblongata portion of the brain stem. 
The other tracts, which have been located anatomically in the white 
substance of the brain stem, are of lesser functional importance, 
and, therefore, of lesser interest for our purposes. 
Gray Substance of Brain Stem 
In the brain stem as in the spinal cord lies gray substance, but as 
previously noted, it is irregularly scattered. This gray substance is 
made up in the main of the peripheral efferent and afferent nerve 
cells of the cranial nerves. The fifth, or trigeminal, nerve has its 
peripheral nerve cell bodies in the semilunar ganglion, which corre- 
sponds to the ganglia on the posterior roots of the spinal cord nerves. 
This same arrangement and logic holds good in connection with the 
glossopharyngeal and Sensory portion of the vagus, these cell bodies 
forming the ganglia on the nerve trunks near the jugular foramen. 
The peripheral neurons of the olfactory, optic and acoustic nerves 
differ from the previously considered arrangement in being made 
up of a series of neurons with intervening processes and ganglia, 
instead of a single axis-cylinder process extending all the way to the 
brain stem. The peripheral neurons of the cranial motor nerves 
have their cell bodies, as would be anticipated, inside of the brain 
stem. The central neurons connect up this gray substance of the brain 
stem with the cerebral hemispheres, just as occurred in connection 
with the spinal cord. In the case of the head, then, it is possible to 
get a brain stem reflex, which is really the same thing as a spinal 
cord reflex, provided the peripheral afferent and efferent neurons 
are intact. This holds true no matter what the condition of the 
central afferent and efferent neurons be, that is, whether the indi- 
vidual can feel or move, or not. The gray substance of the medulla 
oblongata is peculiarly important on account of the presence of the 
centers for the heart and respiration. THE HEAD 
295 
Lateral View of Encephalon 
The encephalon is made up of a dome and a base portion, corre- 
sponding to the skull structure. The falx cerebri has been noted to 
divide the cerebrum by a deep midline depression into two cerebral 
hemispheres. The irregularities of the floor of the skull necessarily 
affect the contour of the basal portion of the brain. The cerebral 
area fitting into the anterior cranial fossa is known as the frontal 
frontal lobe 
central sulcus (Rolando) 
occipital lobe 
lateral cerebral 
fissure (Sylvius) 
temporal lobe 
medulla oblongata 
medulla spinalis' 
cerebellum 
Fig. 92.-Lateral surface of Encephalon. 
lobe; in the middle cranial fossa, as the temporal lobe; and over the 
tentorium cerebelli, as the occipital lobe. 
The offset between the frontal and temporal lobes of the cerebrum 
is continued as a deep depression between these areas over the lateral 
surface of the cerebrum, gradually becoming shallower as it extends 
backward and upward. This marked and deep depression is known 
as the lateral cerebral fissure of Sylvius, which it might be well to 
note here serves as the route for the lateral cerebral artery. By 296 
REGIONAL ANATOMY 
separating the lips of the lateral cerebral fissure a depressed area 
of the cerebral cortex may be noted, which is known as the insula, 
or, popularly, island of Reil. 
The grooves (sulci) and convolutions (gyri) of the surface of the 
brain are always individualistic, just as the surface markings of 
the thumb, for example. But they are invariably on a fixed plan 
so that the lateral cerebral fissure of Sylvius and the important 
central sulcus can always be made out. The central sulcus of 
Rolando turns around the medial falx cerebri surface of the cere- 
brum slightly in back of the midpoint anteroposteriorly. It runs 
laterally, downward and forward, generally with two angles in its 
course, and ends near the lateral cerebral fissure. The central 
sulcus is a very important localization, for just in front of it lie the 
cell bodies of the central motor neurons, while just in back lie the 
central sensory neurons. The head is controlled by these cells near- 
est the lateral cerebral fissure, while the neck, thorax, abdomen, and 
lower extremities follow in regular sequence towards the median 
line, so that the feet, for example, are controlled by those cells lying 
nearest the middle line. The frontal lobes of the cerebrum are the 
higher intellectual centers, which fact gives an anatomic founda- 
tion for the popular association of the high doming forehead with in- 
telligence. The temporal lobes of the cerebrum is the area for cen- 
tral hearing, which is connected up with the peripheral acoustic 
centers in the brain stem. The occipital lobe of the cerebrum is the 
area for central vision, and is connected up with the peripheral 
optic centers in the mes- and diencephalons. The brain anatomically 
shows no signs of these localizations, which have been made out 
chiefly by a study of the symptoms of brain diseases compared with 
the anatomical changes. 
The lateral surfaces of the cerebral hemispheres should be exam- 
ined. 
Cerebellum 
The cerebellum functionates as that part of the encephalon which 
controls balance. One tract from the spinal cord into the cerebellum 
and another tract between the cerebrum and the cerebellum have 
been made out by the usual methods. By manipulating the hemi- 
spheres o.f the cerebellum these tracts may be noted macroscopically 
as they leave the brain stem to enter the base of the cerebellum. The THE HEAD 
297 
spinal cord-cerebellar tract raises an elevation on the posterior sur- 
face of the medulla oblongata, which is known as the corpus resti- 
form, while the cerebrocerebellar tract raises up a visible bundle on 
the posterior surface of the mesencephalon, which is known as the 
brachium conjunctivum. The white interior area of the cerebellum 
is compared for descriptive purposes to the branches of the tree of 
life, technically arbor vitae. Every section through the cerebellum 
shows this tree-like white structure coated by a thin gray cortex. 
The characteristic symptom of cerebellar disease is a disturbance 
in balance. This symptom, however, may be due to a failure of 
messages to reach the cerebellum and not to disease of the organ it- 
self. For example, if the spinal cord-cerebellar or the cerebrocere- 
bellar tracts were destroyed in any part of their course, the loss of 
balance sense would be marked even though the cerebellum itself 
were intact. Sight, as a matter of common knowledge, is an import- 
ant factor in maintaining balance, more especially so if other afferent 
messages are cut off from the cerebellum, as for example in loco- 
motor ataxia. The semicircular canal nerves, a special organ of 
equilibrium in the petrous portion of the temporal bone, connect up 
with the cerebellum. The detailed consideration of this organ will 
be postponed until reached in connection with the study of the 
internal ear. While a diminution in the sense of balance is an in- 
variable accompaniment of serious cerebellar disease, this symptom 
should only be attributed to cerebellar disease when the other com- 
mon sources of the trouble can be excluded. 
The cerebellar hemispheres and their connection with the brain 
stem should be examined. 
Base of Encephalon 
The main irregularities of the base of the encephalon have been 
commented upon in connection with the floor of the skull. The 
medulla oblongata is over twice as large as the spinal cord, due to an 
increased amount of internal gray substance. The pons or bridge 
connects up the hemispheres of the cerebellum across the brain stem, 
the large cords which enter the cerebellum being known as the 
brachia pontis. The longitudinal tracts of the brain stem and the 
transverse tracts of the pons interweave, producing the characteris- 
tic elevation of this area. Above the pons the tracts of the brain 298 
REGIONAL ANATOMY 
stem continue into the mesencephalon, the short columnar part of 
the encephalon, which extends through the opening in the tentorium 
cerebelli. There is no sharp line of demarcation between the mesen- 
cephalon and the diencephalon, but the upper part which divides 
to enter the cerebral hemispheres, belongs to the diencephalon. The 
dividing portions of the mes- and diencephalons, distinctly visible 
Psychical 
olfactory bulb 
frontal Lobe, 
Heann^ 
- lateral cerebral 
fissure 
(Sylvius) 
TemporaVLobe, 
/Tastej 
optic tract 
- peduncles of 
cerebrum 
- pons cerebelli 
■ medulla oblongata 
(6th to 12th 
cranial nerves) 
Occipital Lobe. 
cerebellum 
Fig. 93.-Basal surface of Encephalon. 
spinal cord (medulla spinalis) 
from below as large cords, are known as the pedunculi cerebri 
(peduncles = little foot) (O.T. crura cerebri). These peduncles are 
somewhat overlapped by the temporal lobe of the cerebrum, but by 
pushing this part aside, they may be freely exposed to view. The 
mes- and diencephalons have on their upper surfaces masses of gray 
substance, 'which belongs mainly to the optic nerves. 
The olfactory bulbs should be located on the inferior surface of THE HEAD 
299 
the frontal lobe and the tracts traced back to their connection with 
the cerebrum. The optic nerves should be noted to form a junction 
(chiasm) in the midline in front of the diencephalon, and the optic 
tracts should be followed towards the upper part of the di- and 
mesencephalons. The third and fourth nerves arise from the mesen- 
cephalon, the fifth from the pons, while the last seven pair take'their 
origin from the medulla oblongata. The cerebral localization of the 
centers for higher intellect, hearing and sight are continued into 
the base from the sides. The centers for taste and smell are con- 
tinued into the base from the falx cerebri surface. 
Arteries 
The two vertebral arteries are peculiar inasmuch as they join into 
one basilar trunk, which grooves the pons in the midline. The 
internal carotid arteries enter the area between the temporal lobes, 
and send the anterior cerebral arteries forward into the falx cerebri 
fissure. The lateral cerebral arteries are practically the continuation 
of the internal carotids and enter the lateral cerebral fissure of 
Sylvius between the temporal and frontal lobes. The basilar artery 
after passing the pons divides into the two posterior cerebral arteries 
which supply the posterior portion of the cerebrum. The vertebral 
and internal carotid connect up freely by large branches, this anas- 
tomosis being known as the arterial circle of Willis. In contradis- 
tinction to former beliefs, modern work has demonstrated that the 
terminal branches of the three cerebral vessels also anastomose. 
Numerous small branches from the circle enter the base of the brain. 
The base of the encephalon should be examined. 
Midsection of Encephalon 
A midline section should be made with one sweep of the knife 
between the cerebral hemispheres, continuing also through the brain 
stem and cerebellum. This dissection not only exposes the medial 
surface of the cerebrum, but also demonstrates much of the interior 
structure of the whole encephalon. The cut surfaces of each lateral 
half should be examined, inasmuch as the section practically never 
lies exactly in the midline. The shaded area of the diagram are the 
portions of the encephalon sectioned. 
The corpus callosum is made up essentially of tracts intercom- 300 
REGIONAL ANATOMY 
municating between the cerebral hemispheres, and in this dissection 
is cut at right angles. It is, therefore, white and to a certain extent 
earns its title of callous portion. Outside of the corpus callosum 
lies the medial surface of the hemispheres of the cerebrum, which 
has around its circumference the overlapping of the localization for 
the higher intellect, central motion and sensation, and sight. The 
callosal segment of this medial surface is the central area for the 
special sense of smell and posteriorly the area for taste. The fornix 
septum pellucidum 
- central 
sulcus 
(Rolando) 
fornix 
callosum 
chorioid 
vessels 
aqueductus 
cerebri 
cerebellum 
pons 
cerebelli 
fourth 
ventricle 
- spinal cord 
foramen 
interventriculare 
lateral 
cerebral 
fissure 
hypophysis 
Fig. 94.-Medial surface of Encephalon, shaded parts sectioned. 
is continuous at both extremities with the corpus callosum, and like 
it contains tracts interconnecting between the cerebral hemispheres 
(fornix = vault). Most of its processes run anteroposteriorly con- 
necting up gray areas of the cerebrum, some of these areas being of 
the same, but others of the opposite, sides. Two other much smaller 
tracts, which interconnect the halves of the diencephalon, are known 
as the anterior and posterior commissures. 
The fornix forms the roof of the third ventricle, while extending 
from the fornix to the corpus callosum in the midline is a septum THE HEAD 
301 
pellucidum. The septum pellucidum, as its name implies, is a thin 
sheet which forms the partition between the lateral, that is, the first 
and second, ventricles. The lateral ventricles lie just under the 
corpus callosum, and should be noted to extend well into the cere- 
bral hemispheres. The third ventricle, which lies in between the 
two halves of the diencephalon, has the fornix for its roof and a 
very thin layer for its flo.or. The infundibulum, or stalk, of the 
hypophysis attaches to the floor of the third ventricle, which is the 
foundation for the opinion of some anatomists that the hypophysis 
is not a ductless gland. The third ventricle on each side anteriorly 
has a round opening known as the foramen interventriculare of 
Monroe, which connects up the third ventricle with the first ven- 
tricle in the right cerebral hemisphere and the second ventricle in 
the left cerebral hemisphere. A narrow passageway known as the 
aqueductus cerebri leads from the third ventricle down through the 
mesencephalon to the fourth ventricle (aqueduct = water duct) (O.T. 
iter of Sylvius). The fourth ventricle lies between the brain stem 
of the medulla oblongata and cerebellum, and the cerebellar hemi- 
spheres proper. Vessels grow into the upper back surface of the 
third and fourth ventricles, but technically never enter as they are 
always covered by an epithelial fold (lamina chorioidea epithelialis). 
The connective tissues surrounding these vessels in their course to 
the ventricles is technically known as the tela chorioidea ventriculi. 
The rich vascular network not only lies in the third ventricle, but 
continuing on each side through a thin portion of the upper part of 
the wall and through the interventricular foramina enters the first 
and second ventricles. These chorioid vessels are unfortunately 
stated to form a plexus instead of anastomosis, which is obviously 
a very probable source of confusion. The fourth ventricle has a 
separate series of chorioid vessels, which enter through its roof. The 
chorioid vessels are branches of the posterior cerebral arteries, while 
the corresponding veins eventually enter the straight sinus, which 
courses back in the fold between the falx cerebri and the tentorium 
cerebelli. 
Cerebrospinal Fluid 
These chorioid vessels are of great practical importance, inasmuch 
as they secrete the cerebrospinal fluid. The cerebrospinal fluid in 
health is perfectly clear and colorless, and normally contains only a 302 
REGIONAL ANATOMY 
few desquamated endothelial cells. It contains practically no nour- 
ishment for the cells and practically no waste products, but does 
contain a sufficient mixture of various salts to raise its specific grav- 
ity to about one thousand and six. Pus, lymph, blood, or an increase 
in endothelial cells in the cerebrospinal fluid are all evidence of an 
abnormal condition of the encephalon or spinal cord. The cerebro- 
spinal fluid is probably continuously secreted by these chorioid ves- 
sels, and probably by no other structures. The fluid passes back 
through the aqueductus cerebri to the fourth ventricle and there 
escapes through the medial and lateral apertures between the cere- 
bellum and medulla oblongata into the pia-araehnoidal sac (O.T. 
foramina of Magendie). Cerebrospinal fluid is normally being con- 
stantly absorbed into the lymphatics or capillary veins throughout 
the whole extent of the pia-arachnoidal sac. The thin-walled, tufted 
projections into the venous sinuses of the skull are known as the 
arachnoidal granulations of Pacchioni. These structures allow the 
cerebrospinal fluid to come into intimate contact with the venous 
blood, the two fluids being separated only by a double layer of endo- 
thelial cells. It is generally believed that these bodies have to do 
with the absorption of cerebrospinal fluid into the blood, but this 
outflow would probably only occur during such periods as the pres- 
sure of the cerebrospinal fluid is higher than that in the veins. 
If the lateral and medial apertures of the fourth ventricle or the 
aqueductus cerebri are blocked, cerebrospinal fluid accumulates in 
great quantity inside the ventricles. While a few ounces of cerebro- 
spinal fluid is the normal amount inside the ventricles, in a blocked 
condition the amount may increase to a pint or more. This clinical 
condition is known as internal hydrocephalus, or water inside the 
encephalon. If such an increase of cerebrospinal fluid within the 
ventricles takes place in early childhood, the cranial bones are forced 
apart and the skull proper becomes bulging and extremely large. 
As yielding of the adult skull is impossible, the pressure in the adult 
is exerted on the encephalon, resulting in disturbed nutrition and 
eventually destruction of the brain cells. Even though the blockade 
of the ventricle passageways be complete and cerebrospinal fluid 
accumulates tremendously in the ventricles, a sufficient amount of 
fluid is formed beyond the blockade or escapes through the weak 
points of the distended ventricles to keep the pia-arachnoidal sac 
distended. In clinical cases of great pressure within the skull, the THE HEAD 
303 
sudden removal of quantities of cerebrospinal fluid via lumbar punc- 
ture may result in forcing the medulla oblongata down into the 
foramen magnum and cause sudden death. 
Cerebrospinal fluid must not be confused with the lymph of the 
nervous tissue, as seems often to be done. Lymph carries nourish- 
ment and waste products, whereas cerebrospinal fluid normally con- 
tains, practically speaking, neither nourishment nor waste products. 
The cerebrospinal fluid acts mechanically as a protection to the 
encephalon and spinal cord, just as the lesser amounts of serous 
secretion in all endothelial lined cavities. Cerebrospinal fluid is 
secreted under pressure, consequently the encephalon and spinal 
cord literally float in the fluid. Lymph is produced by the capil- 
laries in the nervous tissues, and serves its usual function as a car- 
rier of nourishment and waste products. As lymphatic vessels have 
not been demonstrated leaving the encephalon, it is very probable 
that the lymph reenters the venous sinuses of the skull via small 
ducts. 
Horizontal Sections 
The next section should be carried through the cerebrum on a 
horizontal plane about one-half of an inch below the top of the 
corpus callosum. This should be carried through both cerebral 
hemispheres, and after this section has been examined, another hori- 
zontal plane should be sectioned about one-quarter of an inch lower 
down. The lateral halves should be fitted together in order to obtain 
a better picture. 
Half Inch Below Top of Corpus Callosum 
The whole cortex of the cerebrum is covered by a layer of gray 
substance about one-eighth of an inch in thickness, following down 
into the grooves and over the convolutions. The falx fissure can be 
readily made out running down to the corpus callosum both in front 
and in back. The first and second ventricles, separated by the 
septum pellucidum, can be noted well opened up and extending 
well into the occipital and frontal lobes. With the aid of a probe 
the part of these ventricles turning down into the temporal lobes may 
be followed out. The ventricles are separated in the middle line by 
the fornix and the septum pellucidum. Masses of gray substance, 
known as the internal or basal nuclei, lie in the interior of the cere- 304 
REGIONAL ANATOMY 
bral hemispheres separated by tracts of white processes. The func- 
tion of these internal nuclei has not been completely determined, 
although it is known that they serve as way-stations between the 
anterior portion of corpus callosum 
caudate 
nucleus 
lentiform 
nucleus 
lateral 
cerebral 
fissure 
claustrum 
(nucleus) 
septum 
peliucidum 
external 
capsule 
internal 
capsule 
ventricles 
fornix 
Fig. 95.-Interior of Cerebrum. (Horizontal section % inch below top of corpus callosum.) 
posterior portion of corpus callosum 
cerebral cortex and the spinal cord. There are also corresponding 
masses of gray substance in the brain stem, but the question of 
which cerebral nerve processes stop in these nuclei and how often 
this process is repeated in the case of individual nerves is not accur- THE HEAD 
305 
ately known. The mass of gray substance, which bulges in the 
lateral wall of the lateral ventricles is known as the caudate nucleus, 
on account o.f the fact that it terminates in two tail-like projections. 
Just outside of this nucleus, separated by white substance, lies the 
lentiform nucleus, so named on account of its similarity in shape to 
a bean. Still further out, and again separated by white substance, 
lies the thin claustral nucleus, the word claustrum stating that it 
forms a barrier under the sunken island portion of the cerebral cor- 
tex. The white strand between the caudate and. the lentiform 
nucleus is known as the internal capsule, while that between the 
lentiform and the claustral nucleus is known as the external capsule. 
These capsule tracts are continued into the brain stem, and, coming 
together in the mesencephalon, make the prominent pedunculi cere- 
bri, which were noted in the external consideration of the base of the 
encephalon. 
Such processes as intercommunicate between the cerebral cortex 
and the brain stem are known physiologically as projection fibers; 
between the two cerebral hemispheres, as commissural, and between 
neighboring cortical areas, as association fibers. 
Three-quarter Inch Below Top of Corpus Callosum 
The corpus callosum is cut across near its lowest parts. The 
fornix is cut across in the midline, and anteriorly shows a small slit, 
which is now known as the cavity of the septum pellucidum. The 
roof of the third ventricle is opened up, its side walls being mainly 
made up of the gray substance of the diencephalon. This mass of 
cell bodies belongs in the main to the optic nerves and is known as 
the thalamus. The lentiform and claustral nuclei appear in this 
section, while only the tail tips of the caudate nucleus are to be 
seen. The thalamus is made up of the peripheral optic nerve cell 
bodies of the brain stem, which connect up via the optic tracts and 
nerves with the eye. These optic thalami make central connections 
with the occipital lobe of the cerebrum, as will be detailed in connec- 
tion with the detailed study of the eye. 
Dissection of Fresh Encephalon 
Even though the dissection of the encephalon of the dissecting 
room body has proved absolutely satisfactory, it is most advisable 306 
REGIONAL ANATOMY 
to supplement this by a dissection of a fresh encephalon from cattle 
or hogs. The fresh encephalon will show even from the surface 
examination the marked contrast between the white and gray sub- 
anterior portion of corpus callosum 
caudate 
nucleus 
lentiform 
nucleus 
claustrum 
septum 
pellucidum 
external 
capsule 
internal 
capsule 
optic 
thalamus 
caudate 
nucleus 
posterior portion of corpus callosum 
Fig. 96.-Interior of Cerebrum. (Horizontal section % inch below top of corpus callosum.) 
stances, and will give a just conception of the soft consistency, as 
noted in connection with the fresh spinal cord. The strength of the 
peripheral nerves is due essentially to their white, fibrous connective- 
tissue sheaths, which are not to be found inside of the dura mater. THE HEAD 
307 
The chorioid vessels, the corpus callosum, the ventricles and the 
basal nuclei and their so-called capsules are all readily demon- 
strable, the colorings and consistency especially being a great im- 
provement over the conditions in any preserved encephalon. 
Meningitis 
Cerebrospinal meningitis is caused by various types of bacteria 
attacking the surfaces of the encephalon and spinal cord. It not 
only attacks the external surfaces, but spreads into the ventricles as 
well. Meningitis may be secondary to direct spreading infection 
from the nose or ear, or occurs in association with some general 
disease as pneumonia or tuberculosis. The epidemic form is caused 
by a special organism, which some authorities believe spreads from 
the nose through the cribriform plate of the ethmoid bone. Men- 
ingitis is a very possible complication of fracture of the skull, and 
also occurs via a septic vein clot in connection with head infections. 
In this disease the cerebrospinal fluid is full of pus, consequently 
various procedures to drain off the infected cerebrospinal fluid semi- 
continuously are nowadays being advocated. Secondary blockade 
of the ventricular passageways is not at all an uncommon sequela 
of any meningitis. 
Hemorrhage 
The characteristics of hemorrhage in association with fractures of 
the skull, and the minute scattered blood effusions in association 
with severe concussions, have already been discussed. The bursting 
of an artery inside the skull without trauma is due to degeneration 
of the vessel wall, and is known clinically as apoplexy. Some of the 
blood mingles with the cerebrospinal fluid, but the bulk of it forms a 
firm clot. The lodgment or the formation of a clot in a large cere- 
bral vessel may cause a somewhat similar clinical picture, but with- 
out the marked pressure symptoms. There is commonly a partial 
recovery from smaller hemorrhages, while the very large hemor- 
rhages cause death within a few hours. The symptoms of severe 
pressure within the skull are stupor, eventually unconsciousness, 
muscle weakness, eventually paralysis, slow, deep breathing, and a 
slow, strong pulse. Accurate localization of the clot in sudden 
serious cases is commonly impossible, but if small in amount, a later 
examination of the nervous system may allow a fairly good estimate 308 
REGIONAL ANATOMY 
of the pressure position. Inasmuch as the walls of other cerebral 
vessels are also degenerated, operative measures in apoplexy offer 
little hope except for temporary benefit. 
The diagnosis and localization of brain tumor, abscess or hemor- 
rhage depend upon two distinct sets of symptoms; viz., general 
encephalon pressure, and local disturbances of the nerve centers and 
tracts. 
General Encephalon Pressure 
General pressure symptoms upon the encephalon may be caused 
by the size of the tumor, abscess or clot. As the encephalon by 
forcing out cerebrospinal fluid has a decided factor of safety, the 
tumor, abscess or clot must be at least the size of an egg in order to 
cause marked general pressure symptoms. Very commonly the 
general pressure is brought to bear by some form of blockade of the 
ventricle passageways, resulting in an enormous increase in the 
intraventricular cerebrospinal fluid, often a pint or more in amount. 
As noted in connection with hemorrhage, the general symptoms of 
pressure may be so marked as to obscure all localizing symptoms. 
In addition to the profound disturbance of the cerebral centers, 
pressure on the medulla oblongata results in a slow respiration and 
pulse, and a type of vomiting unassociated with the eating or digest- 
ing of food. Further, the pressure on the optic nerves results in a 
swelling at their entrance into the orbit, which, if maintained, 
eventually leads to a permanent loss of sight. 
Local Encephalon Pressure 
Local pressure symptoms can be recognized by a careful examina- 
tion of all the peripheral nerves, more especially of the cranial 
group. A motor or sensory disturbance in any part of the body may 
be referable to an encephalon disturbance. The presence of a nor- 
mal spinal cord or brain stem reflex in the affected area would tend 
to exclude peripheral neuron involvement, so that by exclusion the 
disturbance must be in the central neurons. The earlier in its 
course a brain disease comes under observation, other things being 
equal, the easier and more accurate is the diagnosis, and the more 
favorable the outlook for treatment. It follows, therefore, that the 
proper diagnosis and treatment of physical nervous diseases de- 
pends in great part upon a knowledge of the anatomic structure of 
the nervous system. THE HEAD 
309 
FACE 
The face is anatomically that portion of the head which surrounds 
the e'yes, nose, and mouth. The forehead belongs anatomically to 
the cranium cerebrate, although, popularly, it is considered as a 
part of the face. The external surfaces of the facial bones are, gen- 
erally speaking, palpable under the thin layer of face musculature. 
The face bones developmentally are separated by cartilaginous 
strips, which persist as the suture lines of the adult skull. The 
persistence of these suture lines is the justification for considering 
the facial as separate bones instead of as a single bone. 
Face Bones (Ossa Faciei) 
The frontal bone, and the part it takes in the formation of the 
supraorbital margin and the roof of the orbital cavity, has been 
considered in connection with the calvaria. A pair of nasal bones 
run from the frontal bone to about the midpoint of the nose, forming 
what is popularly known as the bridge, while the remainder of the 
facial part of the nose has only a cartilaginous framework. The 
great size and the forward projection of these bones is the racial 
characteristic of the Jewish peoples. On the lateral and inferior 
sides of the orbita, taking part in the formation of this cavity, are 
the prominent zygomatic bones (O.T. malar). Excessive size and 
prominence of these bones are characteristic of the American In- 
dian and the related (?) Mongolian races. The temporal process 
of the zygomatic bone meets the zygomatic process of the temporal 
bone at about the half-way point to form the zygomatic arch. The 
maxillas, or, in the old terminology, the superior maxillas, take a 
prominent part in the formation of the orbital, nasal and oral cavi- 
ties. The nasal and zygomatic bones have suture line attachments 
to the maxillary bones. The mandible, or inferior maxilla, is the 
freely movable lower jaw bone. The ridges projecting out from the 
bodies of the maxilla and mandible for the insertion of the teeth 
are known as the alveolar processes. Whereas the suture lines can 
only be made out by a detailed examination of a skull, the main 
points noted can be made out by surface palpation. 
The nasal and some of the internal bones of the face region as yet 310 
REGIONAL ANATOMY 
unconsidered are classified on developmental evidence as belonging 
to the cranium cerebrale. The paired maxillas, zygomatic and 
frontal 
parietal 
sphenoid 
supraorbital 
notch 
-nasal 
superior 
orbital 
fissure 
zygomatic 
_ infraorbital 
foramen 
- bony nasal 
septum 
maxilla 
^mental 
foramen 
mandible 
Fig. 97.-Front view of Skull (Cranium). 
palatable bones and the mandible are both developmentally and 
functionally parts of the cranium viscerale. THE HEAD 
311 
Divisions 
The face is made up developmentally of three parts, shown in the 
adult by the persistence of the ophthalmic, maxillary, and mandib- 
ular divisions of the trigeminal nerve. The whole head is probably 
to be considered as one greatly modified segment even though the 
lower jaw has a free range of motion. Segmentation is determined 
by movement, but as the mandible goes only part way back it prob- 
ably should not be considered as of a separate segment. The growing 
together in the midline of the three lateral portions of the face is 
represented by the midline sutures of the frontal, nasal, and maxil- 
lary bones. A midline suture exists early in the development of the 
mandible, but disappears without leaving a trace in the adult. 
Skin 
The skin is fairly thick over the face, though, of course, this 
varies with age, sex, exposure and other secondary factors. At the 
orifices of the eyes, nose and mouth the skin joins the mucous mem- 
brane surfaces. The eyebrows (supercilia) with their exuberant 
growth of hair, are a special shade protection for the eyes. The 
presence of a great amount of hair over the beard area is charac- 
teristic for the adult male, while other portions of the face in both 
sexes normally have only very fine hair. A very characteristic 
feature of the skin of the face is the insertion of many voluntary 
muscles into the deep surface, when in action giving rise to changes 
in expression and dimples. The area of higher color over the cheeks 
is anatomically characterized by a thinner skin. 
The skin should be dissected off. 
Subcutaneous Fatty Layer 
This layer varies in thickness with the general stoutness of the 
individual. On account of the delicate character of the deep fascia 
over the small facial muscles, and the insertion of many of these 
muscles into the skin, the distinction between the subcutaneous 
fatty layer and the deep fascia is not easy to keep clear. Cutaneous 
arteries, veins, nerves, and the superficial venous system are to be 
found in this fatty layer, while the main arteries and veins lie under 
the deep fascia. 312 
REGIONAL ANATOMY 
Muscles of Eye Group 
The orbicularis oculi muscle, as its name indicates, encircles the 
eye. It is a wide, thin sheet arising from the bones opposite the 
medial angle of the eye and inserting opposite the lateral. Part of 
this muscle extends down into the eyelid, which portion of the 
muscle is called the orbicularis palpebrae (palpebra = lid). Con- 
traction of the palpebrie portion closes the lids, while the other por- 
tion of the muscle draws in the surrounding skin areas. 
The procerus muscle arises from the bridge of the nose and 
attaches to the skin between the eyebrows. It helps the frontal 
bellies of the epicranius muscle to draw down the eyebrows and is 
used in the familiar scowling appearance of displeasure. 
Muscles of Nasal Group 
The caput angulare of the quadrate muscle of the upper lip arises 
from the frontal process of the maxilla and inserts into the lateral 
cartilaginous wall of the nose. This is the main dilator muscle of 
the nostrils, which comes markedly into play whenever breathing is 
exaggerated from any cause whatsoever. 
The openings of the nostrils onto the face are normally much the 
narrowest part of the nasal cavities, hence this dilation lessens the 
resistance to the inflow of air. A tinge of blueness of the individual 
and exaggerated action of these dilator muscles is very characteristic 
of the various pneumonias. The cartilage tends to spring back into 
place whenever the muscles relax, but there are in addition some 
constrictor muscles of minor importance. 
Muscles of Oral Group 
The orbicularis oris muscle forms a voluntary sphincter muscle 
of the inlet of the mouth cavity. The following muscles run into it 
and blend with it: 
The quadratus labii superiores muscle arises from the maxilla just 
below the orbital cavity and from the zygomatic bone and inserts 
into the upper lip. 
The canius muscle arises from the maxilla deep to the quadratus 
labii superiores origin and inserts into the angle of the mouth. THE HEAD 
313 
The triangularis muscle arises from the body of the mandible, and, 
converging upwards, inserts into the angle of the mouth. 
The quadratus labii inferiores muscle arises from the mandible 
near the midline, partly underneath the triangularis, and inserts 
into the lower lip. 
The buccinator muscle runs from the ligament extending between 
the posterior parts of the upper and lower jaws to the orbicularis 
muscle, extending between the bases of the alveolar processes of the 
maxilla and mandible. This cheek muscle, which lies close to the 
mucous membrane, is popularly known in connection with whistling 
and the blowing of wind instruments. 
The platysma muscle arises over the lower part of the face and 
extends down across the neck, controlling the skin movements. The 
risorius is a slip of the facial part of the platysma, which inserts 
near the angle of the mouth into the skin, producing a dimple on 
contraction. The zygomaticus runs downward from the temporal 
process of the zygomatic bone into the skin near the angle of the 
mouth. The mentalis arises from the mandible and inserts into the 
skin over the chin. 
The facial muscles should be dissected. 
Blood Supply 
The external maxillary or facial branch of the external carotid 
artery crosses the mandible about its midlateral point. The artery 
runs diagonally upwards and medially past the angle of the mouth, 
sending off inferior and superior labial branches. It passes close to 
the wings of the nose, sending off lateral nasal branches, and ter- 
minates near the medial angle of the eye. The artery is somewhat 
coiled when the mouth is shut, but is straightened out when the 
mouth is fully open. The facial vein and lymphatics in general 
correspond to the artery, and empty into both the superficial and 
deep jugular veins, and corresponding lymphatic glands. The artery 
and vein as usual take as deep and protected a position as possible, 
but in this case they necessarily lie not far from the surface. 
Motor Nerve Supply 
The facial, the seventh cranial nerve, should be located at its point 
of exit from the temporal bone. It appears through a foramen in 314 
REGIONAL ANATOMY 
the base of the skull, half way between the mastoid and styloid proc- 
esses, which is therefore known as the stylomastoid foramen. The 
nerve turns sharply forward under the parotid gland and divides 
into radiating branches, which supply all the muscles of the face. 
Sensory Nerve Supply 
The ophthalmic division of the fifth, or trigeminal nerve, leaves 
the interior of the skull via the superior orbital.fissure, the maxillary 
through the foramen rotundum, and the mandibular through the 
foramen ovale. Most of the branches of these nerves traverse canals 
through the facial bones in their course towards the skin. 
The ophthalmic division sends out as its main trunk the supra- 
orbital nerve, which supplies the frontal portion of the scalp. Small 
palpebral branches run to the lids and a separate small branch sup- 
plies the bridge of the nose. 
The maxillary division sends out as its main branch the infra- 
orbital nerve, which leaves the maxillary bone just below the orbital 
cavity at the junction of its intermediate and medial thirds. This 
large nerve supplies the lower part of the nose, the upper lip, and 
part of the cheeks. A small zygomatic branch goes through a 
separate bony canal and appears over the cheekbone. 
The mandibular division sends a mental branch to the skin 
through a foramen approximately an inch lateral to the midline. 
A small buccinator branch supplies the skin over the lateral man- 
dibular area. 
These vessels and the sensory nerves should be cleared. 
Orbital Cavity (Orbita) 
The bony wall of the orbital cavity is a cone-shaped space with its 
widest part at the facial surface. The depth at which the eyeball is 
set in the socket varies, but the eye is normally well protected by 
the projecting supraorbital margins, zygomatic and nasal bones. At 
the small posterior end of the orbital cone lies the superior orbital 
fissure, through which the ophthalmic vein and most of the nerves 
enter the cavity. The optic nerve runs through a separate foramen in 
the lesser wing of the sphenoid bone. The bony walls of the orbital 
cavity are all thin sheets covered on both surfaces, as would be 
anticipated, by periosteum. The roof of the orbital cavity is the THE HEAD 
315 
orbital part of the frontal bone, while the floor is made up chiefly by 
a plate of the superior maxilla, supplemented in its front lateral 
part by the zygomatic bone. The zygomatic bone forms the anterior 
part of the lateral wall, while posteriorly the greater wing of the 
sphenoid forms its section of the wall. The medial wall is made up 
mainly by the ethmoidal labyrinth (O.T. lateral mass) which inter- 
venes between the orbital and the nasal cavities. The small lacrymal 
bone intervenes between the anterior border of the ethmoidal laby- 
rinth and the posterior border of the frontal process of the maxilla, 
completing this medial bony wall. 
Eyelids (Palpebrae) 
The firm connective tissue framework in the interior of each lid is 
known as the tarsus. The tarsal plates are shaped to conform with 
the globular surface of the eye, and are attached by medial and 
lateral ligaments to the maxillary and zygomatic bones, respectively. 
As the upper lid is much larger than the lower, the upper tarsus is 
also larger than the lower. The medial and lateral tarsal ligaments 
serve as points of origin and insertion for the palpebral portion of 
the orbicularis oculi muscle. The skin over the eyelids is extremely 
delicate. The eyelashes are a protecting mechanism of the eye and 
are arranged in regular order along the lid margins. Pulling the 
eyelid off the eyeball by means of traction on the eyelashes will 
show along the lid contact margin the mouths of a modified type of 
sebaceous glands, which are known as the tarsal glands of Meibo.mi. 
If the lid be everted these glands can be noted as parallel yellow 
streaks extending well into the tarsus. The small round opening 
(puncta lacrymalia) in the upper and lower lids near their medial 
angle is the beginning of the lacrymal, or tear, duct. The lids are 
made up of the skin, subcutaneous fatty layer, deep fascia, orbicu- 
laris palpebrae muscle, then the tarsus, and internally the mucous 
membrane. 
Conjunctiva 
The mucous membrane covers not only the inner surface of the 
lids, but also the outer surface of the eyeball, and is therefore called 
the conjunctiva. The lacrymal glands lie back of the upper lid 
under the lateral third of the orbital plate of the frontal bone. These 
glands are only incompletely separated from each other, the whole 316 
REGIONAL ANATOMY 
structure averaging about one-eighth times one-quarter times one- 
half inches in diameter. They are of typical glandular structure and 
pour their secretion into the upper lateral portion of the con- 
junctival sac through many small ducts. The secretion serves to 
keep the surface of the eye washed and is pumped by movements of 
the lids into the laerymal ducts, which will later be noted to empty 
into the nose. 
When the laerymal ducts are partially blocked or when there is an 
extra quantity of laerymal secretion as in crying, the tears run down 
over the surface of the face. Conjunctivitis may be a primary dis- 
ease, or it may be secondary to infection spreading through the 
laerymal ducts from the nose. 
As some of the finer markings are lost in a dissecting room body, 
the student should examine his own lids by means of a looking 
glass, or examine his fellow-student's lids. Then the lids and the 
laerymal sac should be dissected. 
Orbital Fascias 
The eyeball (bulbus oculi) is held in position by layers of fascia 
as would be expected. The fascias surrounding the eyeball are con- 
nected up with those lining the orbital cavity by many sheets of very 
complicated detail arrangement. For general purposes the state- 
ment suffices that the arrangement is such as to hold the eyeball 
steady against up and down, side to side, or front and back move- 
ments. The fascia bundles running between the medial and lateral 
tarsal ligaments under the eyeball in a hammock-like arrangement 
have to withstand gravity pull and are consequently stronger than 
the rest. This portion is often referred to as the suspensory liga- 
ment, which obviously would have great surgical importance. The 
fibrous capsule of the eyeball is known technically as the fascia 
bulbi of Tenon. This fibrous capsule does not differ essentially from 
the extrinsic capsule of other organs, except that it does not sur- 
round the anterior portion of the glo.be of the eye. A serous sac as a 
friction reducer between this outer fibrous capsule and the outer 
coat of the eyeball would be the logical expectation. But most 
investigators have considered the sac, which encloses the posterior 
half of the eyeball, to be a lymph space. As both a lymph space and 
a serous sac are lined by endothelial cells, so that anatomically there THE HEAD 
317 
is no possible distinction, it seems much more reasonable to consider 
this a serous sac. 
The dissection of this fascia capsule must be postponed until a 
later stage of the work. 
Muscles (Musculi Oculi) 
The four rectus oculi muscles arise about the superior orbital fis- 
sure and run straight forward to their equidistant distribution 
about the equator of the eye. These muscles, named, according to 
their position superior and inferior, medial and lateral, act without 
pulling the eye deeper into the orbita because of the resistance of 
the fascia bulbi of Tenon. The internal rotator muscle of the eye, 
known as the superior oblique, arises in common with these muscles, 
but turns through a pulley in the upper medial part of the orbital 
bony wall. The external rotator muscle of the eye, known as the 
inferior oblique, arises from the medioinferior bony wall opposite 
the equator of the eyeball. A special elevator of the upper eyelids, 
the levator palpebrae superiores, also arises from the common ten- 
don, and, running forward just under the orbital part of the frontal 
bone, spreads out for its insertion into the upper lid. 
The superior oblique is supplied by the fourth, or trochlear nerve 
and the lateral rectus by the sixth, or abducent nerve. All the 
other voluntary muscles of the orbital cavity are supplied by the 
third or oculomotor nerve. 
Sensory Nerve Supply 
The ophthalmic division of the fifth cranial nerve enters the eye- 
ball by many branches, giving a liberal sensory supply to the 
various coats. Other branches of this division of the nerve run in 
grooves or canals of the bony wall, supplying the bone and eventually 
terminating on the face. The supraorbital and palpebral branches 
have previously received sufficient consideration. The nasal branch 
tunnels the ethmoidal labyrinth and supplies the upper part of the 
nasal cavities before emerging from its canal on the anterior sur- 
face of the nasal bones. 
Vessels 
The ophthalmic artery is a branch from the internal carotid, 
which runs directly forward through the optic foramen into the 318 
REGIONAL ANATOMY 
orbital cavity (orbita). This artery supplies the bony walls, the fat, 
and the muscles, and enters the eyeball by a number of branches. Ter- 
minal twigs of the ophthalmic anastomose with the external maxil- 
lary at the medial angle of the eye. The ophthalmic vein is made 
up of corresponding branches and entering the skull through the 
superior orbital fissure becomes the cavernous sinus. 
Obstruction of the cavernous sinus will, and semiobstruction of 
the large veins nearer the heart may, produce an overdistention of 
the ophthalmic veins with a secondary edema. This pressure in 
back of the eye gives the clinical picture of exophthalmos, the bulg- 
ing forward of the eyeball. Exophthalmos might also be produced 
by the growth of tumors, abscesses or arterial hematomas in back of 
the eyeball. The reverse picture of enophthalmos would be pro- 
duced by a decrease in the amount of orbital fat, or acutely when 
the orbital vessels are less distended, as in shock, severe hemorrhage, 
or any severe water abstraction from the body. The lymphatics of 
the orbita follow the ophthalmic vein and eventually connect up 
with the deep lymphatic glands of the neck. Sympathetic nerves 
from the superior cervical ganglia follow the branches of the 
ophthalmic artery into the eyeball, controlling part of its blood 
supply and some of the involuntary musculature. 
Optic Nerve (Nervus Opticus) 
The optic nerves may be traced through the optic foramen of the 
lesser wing of the sphenoid bone to their entrance just medial to the 
posterior pole of the eyeball. The nerve eventually terminates in 
the inner coat of the eye in end processes, which serve to gather up 
the light impulses. If the crossing of the optic nerve processes were 
complete where they come into contact with each other, each cere- 
bral center, mass of brain stem nuclei, and tract would control the 
opposite eye. This point of contact and decussation of the two 
optic nerves is known as the optic chiasm. But the actual arrange- 
ment differs from this theoretical probability, inasmuch as the 
decussation involves only the nasal half of each tract. Each cere- 
bral center, series of brain stem nuclei, and tract, as a matter of fact, 
controls its own side half of both eyes. Thus the right occipital 
cerebral center, for example, controls the right, or temporal, side 
of the right eye, and right, or nasal, side of the left eye. A loss of 
sight due to a disturbance in the eye or optic nerve can therefore THE HEAD 
319 
be readily distinguished from a loss of sight due to disease in the 
optic tract, brain stem nuclei, or cortical center. 
Dissection.-A demonstration of the orbital cavity structures may 
be best obtained by chipping out from above the central part of the 
orbital plate of the frontal bone. The periosteum is ordinarily 
shoved off by this dissection from the under surface of the orbital 
plate and consequently will have to be split in order to get at the 
orbital muscles, vessels, and nerves. The loose fatty tissue should 
be freely removed in order to clear these structures. 
Fibrous Coat of Eye (Tunica Fibrosa Oculi) 
The very tough fibrous outer coat of the eyeball, known as the 
sclera, protects the delicate interior structures of the eye. The 
sclera normally shows as a deep white through the conjunctiva, 
being made up of matted bundles of white fibrous connective tis- 
sue. Around the anterior pole of the eye the sclera is replaced 
by the cornea, which is necessarily transparent on account of the 
function of the eye. The cornea proper is a specially modified con- 
nective tissue layer, somewhat comparable to cartilage in structure, 
as it has corpuscles lying in spaces connected up by canaliculi for 
the lymphatic circulation. After birth the cornea normally has no 
arteriovenous supply, while if a section be removed, it is replaced 
by white fibrous scar tissue and not by transparent corneal tissue. 
The layer of conjunctival epithelium over the cornea is without 
pigment even in its basal cells, which is a striking phenomenon as 
the ordinary living body cells are very susceptible to the injurious 
influences of sunlight, and are protected by pigment. The cornea 
makes the segment of a much smaller circle than the sclera, as is 
shown in the diagram. The sclera is thicker posteriorly and, al- 
though varying somewhat with the physical vigor, is really much 
stronger in all individuals than popularly conceived. 
Chorioidea and Retina 
The interior lining of the eye is the retina, which contains the end 
structures of the optic nerve. This layer is thicker and functionally 
most important at the posterior pole of the eye, gradually thinning 
out towards the equator, eventually disappearing. The retina is a 
very delicate layer and is firmly attached to an extraretinal chorioid 320 
REGIONAL ANATOMY 
coat (tunica vasculosa oculi). The chorioidea is made up essentially 
of the arteries, veins, lymphatics and nerves, which supply the 
retina, plus some incidental connective tissue. A layer of black 
pigment in the deeper layers of the retina serves to prevent false 
reflections in the dark room portion of the eye. The combined 
retina and chorioid layers are thin, delicate sheets, in marked con- 
trast to the strong sclera. The retina itself is of a greyish color due 
to the mass of nerve terminal structures, but has a central, avascular 
cornea 
aqueous humor 
crystalline 
lens. 
iris muscle 
ciliary muscle 
vitreous body 
sclera 
choriodea 
retina 
optic nerve 
- .central retinal artery and vein 
Fig. 98.-Diagrammatic horizontal section of Eye (Oculus). 
yellow spot (malcula lutea), which is the area of sharpest vision. 
The optic nerve enters through a cribriform area of the sclera 
slightly to the medial side of the posterior pole. The central retinal 
artery enters at this point and spreads out in chorioid branches for 
the supply of the retina. The veins of the eye correspond, generally 
speaking, to the arteries. 
Hemorrhages of the chorioidal arteries may force the retina from 
its attachments to the interior of the eyeball, and may break through 
into the fluids of the eye. These hemorrhages may be due to a local 
disease or accident, or to a general arterial wall degeneration. THE HEAD 
321 
Crystalline Lens 
The crystalline lens is a biconvex, transparent, noneellular disc, 
which is held in position by a "capsular ligament and muscles. When 
as a hereditary anomaly, or through disease, this lens becomes 
opaque, the condition is known clinically as cataract. The muscles 
and ligaments of the lens are attached to the internal surface of the 
sclera, at about the sclera-corneal junction. The ciliary muscle 
arises from the sclera and inserts into the capsular ligament of the 
lens, consequently when this muscle contracts, it produces a change 
in the shape of the semielastic lens. The normal lens at rest is 
focused for distant sight, while the ciliary muscle changes the shape 
of the lens for focus on objects closer up. 
Iris 
The iris musculoligamentous diaphragm lies just in front of the 
lens, and serves to regulate the amount of light entering the interior 
of the eye. The pigment normally present in the iris varies with the 
general fairness or darkness of the individual, and serves to make 
the iris curtain lightproof. The pink-white iris of the albinos is due 
to the fact that the muscles and ligaments of the iris are not hidden 
by pigment. The iris has a sphincter muscle, while it is still open to 
question as to whether there is also a radial musculature arising 
from the sclera. These radial strands may well be of elastic fibers, 
for, clinically, when the sphincter muscle relaxes as in shock or just 
before death, for example, the pupil characteristically dilates. The 
sphincter muscle can vary the opening in the center of the iris, 
known popularly as the pupil, from a pinpoint size to an opening 
equal to the full extent of the cornea. The normal iris diaphragm 
contracts when the eye is subjected to a bright light and dilates in 
darkness so as to equalize the amount of light entering the eye. The 
pupil appears black because we are looking from the brighter out- 
side into a relatively dark chamber. If a beam of light is thrown 
through the dilated pupil and the observer's eye looks along the 
center of this beam, then the pupil and the interior of the eye 
appear reddish. This is the principle of the ophthalmoscope. The 
iris and the ciliary musculature are both of the plain involuntary 
type, and are controlled automatically. The afferent nerves of the 
iris run in the optic nerve to the thalamus region of the brain stem, 322 
REGIONAL ANATOMY 
while the efferent are contained in the oculomotor nerve. The iris is 
also connected via branches along the internal carotid and ophthal- 
mic arteries with the superior cervical ganglion. The ciliary muscle 
enervation runs in the oculomotor nerve, but it has no afferent root. 
This is the anatomic explanation as to why the disease locomotor 
ataxia characteristically destroys the iris light reflex, but does not 
affect accommodation. 
The chorioidea continues forward to the ciliary and iris muscles, 
carrying the vascular and a motor and sensory nerve supply to these 
parts. The anterior and posterior ciliary arteries pierce the sclera, 
being regularly arranged around the circumference, and being 
named on account of their relationship to the equator of the eye- 
ball. These ciliary arteries and the corresponding veins are accom- 
panied by small nerve twigs from the ophthalmic division of the 
trigeminal nerve. 
Humors 
The globe of the eye behind the lens and its suspensory ligament 
is kept distended by the transparent semifluid vitreous body, while 
the area in front of the lens and its suspensory ligament is distended 
by the clear watery aqueous humor. An endothelial lining surrounds 
both the vitreous and aqueous humor chambers. 
Not all of the details in regard to the secretion of these fluids are 
known, but clinically if the normal outflow into certain lymph chan- 
nels is obstructed, pressure within the eyeball becomes very high. 
The main humor outflow presumably escapes into the sinus venosus 
scleras (O.T. canal of Schlemm), which makes a circle at the sclero- 
corneal junction. The finer passageways from the anterior chamber 
into this venous sinus are not readily determinable anatomically, 
but clinically following an attack of iritis there is always danger 
that they will be blocked. This disturbance is known as glaucoma, 
and if the intraocular pressure becomes and remains sufficiently 
high, it necessarily interferes so greatly with the blood supply of 
the retina as to cause loss of sight. Therefore, although some of 
the anatomic details are still to be demonstrated, it seems fair to 
assume that these fluids of the eye are being constantly secreted and 
reabsorbed. 
Dissection.-The humors commonly evaporate out of the eyeball in 
a dissecting-room body, consequently the appearance is very abnor- THE HEAD 
323 
mal. However, the eyeball should be dissected, as in spite of appear- 
ances many of the main points are to be made out. The eye should 
be removed from the body by cutting the optic nerve, the extrinsic 
muscles, and the smaller arteries, veins, and nerves. The fascia 
bulbi of Tenon is readily to be seen, and by incising it the smooth 
endothelial sac between this capsule and the eyeball may be made 
out. The muscle tendons should be traced to their attachment to 
the sclera. Then the eyeball should be split open with one sweep 
of the knife from its anterior to its posterior pole. The thickness of 
the sclerocorneal coat should be noted to be in marked contrast to 
the blended retinal and chorioid coats. The size and shape of the 
crystalline lens will be found normal, even though its consistency 
and transparency is altered. The black pigmentation of the deeper 
layers of the retina and of the posterior surface of the iris dia- 
phragm should be noted. 
If a fresh eye from cattle or hogs is available, a simple sectioning 
will demonstrate most of the anatomic points noted very satisfac- 
torily. 
Mandible Region (Mandibula) 
The mandible is the freely movable lower jaw bone. It is through- 
out most of its extent subcutaneous, or submucous, consequently its 
outlines can be made out readily from the surface. The bone is de- 
veloped from two lateral halves which meet in a midline suture, but 
these halves fuse early in life into, one solid piece leaving no trace 
of the original condition. The heavy square type of mandible is 
found in people of great physical vigor, and is with considerable 
justification popularly considered to be associated with mental 
stamina. The mandible is obviously very exposed to injury so that 
even though it is extremely strong, fractures are common. Inas- 
much as the mucosa of the gums is firmly attached to the bone, 
these fractures are practically always open for the passage of infec- 
tious material into the break. 
The horseshoe-shaped portion of the mandible is known as the 
corpus, while the upward extending projections at the posterior 
ends of the body are known as the rami. The large, wide, rounded 
surface for articulation with the temporal bone is the condylar proc- 
ess. The thin sharp projection in the front part of the ramus, 
known as the coronoid process, is raised up by the attachment of the 324 
REGIONAL ANATOMY 
temporal muscle. The mandibular canal is the passageway for the 
vessels, nerves, and lymphatics through the interior of the mandible. 
Small branches from this canal exist for the passage of vessels and 
nerves into the pulp cavity of the teeth. The branches from the 
inferior alveolar vessels and nerves through the mental foramen 
have been considered in connection with the face region. 
coronoid process 
condyloid . 
process f 
ramus 
- alveolar 
process 
angle 
mental 
foramen 
body (corpus) 
Teeth (Dentes) 
Before the teeth erupt and after they are lost, the mandible 
closes further and therefore protrudes the chin. The teeth have a 
very hard bone-like core known as dentin (substantia eburnea), and 
are covered by a still harder ectodermally derived enamel (sub- 
stantia adamantina). The dentin has canalicular spaces connecting 
the cells, and is cared for by the circulation and nerves of the tooth 
pulp, while the enamel rods are held together and in place by a 
small amount of connective tissue material. The teeth are highly 
specialized structures, and if injured or destroyed, neither the 
dentin nor the enamel are replaced. The portion of the teeth nor- 
mally within the gum is covered by a bony layer known as cementum 
(substantia ossea), which is held to the alveolar process of the jaw 
by a cartilaginous suture line. This cartilaginous strip persists 
throughout life and, in so far as it yields, acts as a protection for 
the teeth against fracture. THE HEAD 
325 
The temporary, or so-called milk teeth, are two incisors, a canine 
or cuspid, and two molars for each quadrant of the jaw. Inasmuch 
as these teeth are too small for the requirements of the adult and 
possess no mechanism for growth, they are cast off and the per- 
manent teeth grow into place. The permanent teeth are two in- 
cisors, a canine or cuspid, two premolars or bicuspids, and three 
molars in each quadrant. 
The teeth should be examined in position and may then be ex- 
tracted. 
Parotid Gland (Glandulae Parotis) 
The parotid is the salivary gland, which lies mainly over the 
lateral surface of the ramus of the mandible. The gland is held in 
position by fascias, the main part filling in the space between the 
front of the ear and the back of the mandible. It never extends 
upward above the zygomatic arch, but does extend for about half 
an inch down into the neck region. The parotid gland sends its 
ducts straight forward from its thin anterior edge to empty into the 
buccal mucous membrane opposite the second upper molar tooth. 
The continuation of the external carotid artery runs on the deep 
surface of this gland and divides about opposite the mastoid proc- 
ess into its terminal internal maxillary and superficial temporal 
branches. The facial nerve, en route from the stylomastoid fora- 
men to the face, spreads out in the posterior capsule of the parotid 
into its main subdivisions. 
Epidemic parotitis, or, popularly, mumps, must be carefully dis- 
tinguished from deep abscesses in this region inasmuch as the treat- 
ment varies with the diagnosis. Many so-called parotid tumors 
arise in reality from the remains of the first fetal gill. 
The parotid gland should be cleared and then the vessels and the 
facial nerve should be demonstrated. 
Muscles of Mastication 
The four positive muscles of mastication are the masseter, the 
temporal, and the external and internal pterygoids (pterygoid = 
wing-like process of sphenoid bone). These muscles arise from the 
skull and insert into the mandible. A branch from the facial nerve 
nucleus of the brain stem makes its exit through the foramen ovale 
in company with the mandibular division of the trigeminal, carrying 326 
REGIONAL ANATOMY 
the motor supply to this group of muscles. Branches from the 
internal maxillary artery, vein and lymphatics supply this area. 
The masseter arises from the lower edge of the zygomatic arch and 
inserts onto the lateral surface of the mandible near the angle, that 
is, its posteroinferior portion. It acts as a powerful elevator of the 
mandible. 
The temporal arises from a wide area over the side of the skull 
and converges on a tendon, which passes under the zygomatic arch 
to its attachment to the coronoid process. It is a powerful elevator 
of the mandible. 
The main points in regard to these muscles can be made out from 
the surface, when the lower jaw is in action. 
The external and internal pterygoids can only be seen after the 
masseter muscle has been resected and a portion of the ramus of the 
mandible between the body and the condyloid process has been 
sawed out. The ramus should be sawed across near its junction 
with the body, while the condylar process should be divided about 
one-quarter of an inch below the temporomandibular joint. The 
loose segment of the ramus should be removed, which dissection 
exposes the internal maxillary region. 
The external pterygoid arises from the lateral surface of the 
lateral pterygoid plate of the sphenoid bone and from the maxilla, 
and converges straight backward to its attachment to the mandible 
just below the condyloid process. It, therefore, acts as a protruder 
of the lower jaw. 
The internal pterygoid arises from the medial surface of the 
lateral pterygoid plate of the sphenoid and from the maxilla, and 
runs downward, backward, and lateralwards to its attachment on 
the medial surface of the mandible near the angle. It, therefore, 
acts as a combined elevator and adductor of the mandible. 
When all four of these muscles are acting together, the typical 
grinding movement of the opposed molar teeth is produced. The 
depressor muscles of the lower jaw, previously considered in con- 
nection with the neck dissection, oppose these elevators. 
These muscles should be cleared. 
Mandibular Joint 
The temporomandibular joints are formed by the well-rounded 
heads of the mandible fitting into sockets of the temporal bones THE HEAD 
327 
just in front of the external ear canals. A fibrocartilaginous disc 
attached to the inner surfaces of the capsular ligament separates the 
synovial cavity of this joint into two distinct cavities. The capsular 
ligament is strong but rather lax, consequently dislocation is rela- 
tively common. The strength of the joint depends more upon the 
powerful muscles than upon the ligaments. 
The temporomandibular joint should be dissected, noting espe- 
cially the fibrocartilaginous discus articularis. 
Vessels and Nerves 
The inferior alveolar or dental branch of the mandibular nerve 
passes straight from the foramen ovale to the mandibular canal. 
This inferior alveolar nerve and its accompanying artery and vein 
send a branch into the pulp cavity of each tooth, while the exit of 
the mental branch onto the chin has been detailed in connection with 
the consideration of the face. An anterior auricular or temporal 
branch of this mandibular division accompanies the vessels of the 
same name over the temple region of the scalp. At first glance this 
seems a peculiar distribution for this nerve, but the fact that the 
temporal muscle belongs functionally to the lower jaw brings this 
distribution into accord with the general rule. The other large 
branch of this mandibular division of the trigeminal, known as the 
lingual, turns forward to supply the mucous membrane of the floor 
of the mouth and tongue. 
The external carotid artery just above the angle of the jaw sends 
the large internal maxillary branch forward through the middle of 
the space. The important downwardly directed branch of the in- 
ternal maxillary is the inferior alveolar or dental artery, while the 
important upwardly directed vessel is the middle meningeal. The 
middle meningeal runs straight to the foramen spinosum just in 
back of, and lateral to, the foramen ovale. The internal maxillary 
artery supplies the muscles of the area and then runs forward to 
supply the maxillary bone, including the nose. The veins and lym- 
phatics correspond to the arterial arrangement. 
These vessels and nerves should be cleared. 
Submaxillary Region 
The submaxillary region, down to the depth of the mylohyoid 
'uuscle, has been considered in connection with the neck. The skin, 328 
REGIONAL ANATOMY 
subcutaneous fatty layer with its platysma muscle and the deep 
fascia require no special review. The digastric muscle then comes 
into view, marking off the digastric or submaxillary minor triangle. 
The floor of this triangle is formed by the diaphragm-like mylo- 
hyoid muscle, which runs from the hyoid bone to the inner surface 
of the mandible around its whole body. This mylohyoid muscle may 
act as an elevator of the hyoid bone or as a depressor of the man- 
dible according to requirements. It is supplied by the branch of the 
facial, which also supplies the four large muscles of mastication, 
and certainly acts as an opposing depressor to steady the jaw during 
mastication. 
The submaxillary salivary gland lies in the digastric minor tri- 
angle, held in position by fascial layers. It is roughly one-quarter 
times one-half times one inch in diameter, and, besides the saliva, 
pours out some mucous secretion. The facial vessels run through 
a deep groove in this gland, which fact serves as a guide in determin- 
ing its position. The submaxillary duct of Wharton turns around 
the posterior border of the mylohyoid muscle en route to the fren- 
ulum of the tongue. 
The mylohyoid muscle must be divided and turned aside in order 
to follow out this duct and to obtain a view of the tongue muscles. 
The hyoglossus muscle is a thin, flat sheet arising from the hyoid 
bone and running into the sides of the tongue. On its lateral sur- 
face in order from above downwards lie the lingual nerve, the sub- 
maxillary duct, and the hypoglossal nerve. The lingual artery and 
vein enter the tongue by passing deep to this hyoglossus muscle. 
The small styloglossus muscle runs from the long styloid process of 
the base of the skull to the lateral posterior portion of the tongue. 
The geniohyoid muscle arises from a tubercle near the midline inner 
surface of the mandible and inserts into the hyoid bone. The genio- 
glossus lies on a deeper plane, has practically the same origins and 
insertions, but sends the great bulk of its fibers into the tongue. 
The vessels, nerves, and muscles of this area should be dissected. 
Interior of Mouth (Cavum Oris) 
The mouth is the first portion of the alimentary tract. The lips 
with their musculature form the opening onto the face, while pos- 
teriorly the isthmus of the fauces with its musculature separates 
the mouth from the oropharynx. The mouth is lined by a stratified THE HEAD 
329 
squamous epithelium derived from and continuous with the ecto- 
derm, the pink color of the lips being due to a lack of the dermis 
layer. When the teeth are in position and the jaws closed, the 
mouth is divided into an extradental or buccal cavity, and in intra- 
dental cavity or mouth proper. The muscular tongue projects from 
the floor of the mouth, its tip being held down by connective tissue 
strands covered by mucous membrane known as the frenulum 
(diminutive check-rein). The openings of the submaxillary gland 
on the frenulum should be noted. The almond-shaped sublingual 
glands, which pour out a mucous secretion via many small ducts, 
may be seen spreading out to each side just under the mucous mem- 
brane. 
Roof of Mouth 
The roof of the mouth proper is made up of the hard and soft 
palates. The bony framework of the arching hard palate belongs to 
the maxillary and palatal bones, while the soft palate contains no 
bone. The horizontal parts of the palatal bones form the posterior 
quarter inch of the hard palate, while the perpendicular parts will 
later be noted to form a portion of the lateral wall of the nose, being 
wedged between the maxilla in front and the medial pterygoid plate 
of the sphenoid behind. Developmentally at an early period the 
mouth and nose are one single cavity. The palatal processes of the 
maxillary and palatal bones later grow medially and normally meet 
the lower part of the septum of the nose. When through a con- 
genital defect these bones fail to meet the bones of the nasal septum, 
the resulting deformity is known as cleft palate. The hare or rab- 
bit type of lip deformity is very commonly associated with cleft 
palate. These deformities may be unilateral or bilateral, slight or 
very great. The presence of severe palatal clefts interferes seriously 
with the function of the mouth, inasmuch as food and drink can not 
be forced back properly into the pharynx, but flow outward through 
the nose. The roof of the mouth is supplied by branches of the 
maxillary division of the trigeminal nerve, and branches of the 
internal maxillary arteries, veins, and lymphatics. 
Soft Palate (Palatum Molle) 
F . . 
The soft palate continues the hard palate backwards for about an 
inch and a half, and when raised up by muscular action, separates 330 
REGIONAL ANATOMY 
the nasopharynx from the oropharynx. The elevator muscle of the 
soft palate will be considered in connection with the nasopharynx. 
The depressor muscles of the soft palate raise up two folds, for- 
merly known as the anterior and posterior pillars of the fauces. 
The anterior muscle band is the glossopalatine, while the posterior 
is the pharyngopalatine, therefore these pillars are known in the 
B. N. A. as the arcus glossopalantinus and the arcus pharyngopalan- 
tinus. These muscles form a true constriction, hence the term 
isthmus of the fauces. The median posterior tit-like projection of 
the soft palate is the uvula. A pair of small muscles, which arise 
from the posterior margin of the palatal bone near the midline, con- 
trol the elevation of the uvula. Between the faucial arches lie the 
palatine tonsils, aggregations of lymphatic tissue in the mucosa. 
These tonsils will later receive detailed consideration in connection 
with the nasopharyngeal tonsil. The motor supply of the soft 
palate is from the facial and from branches of the vagus, while the 
sensory supply comes from the maxillary division of the trigeminal. 
The vessel supply is from descending branches from the internal 
maxillary, ascending branches from the pharyngeal, and anastomos- 
ing branches which leave the external maxillary in the neck. 
If the soft palate is paralyzed or destroyed by disease, on attempt- 
ing to swallow, food or water will be forced out through the nostrils. 
If the soft palate is held up in speaking the laryngeal voice sounds 
can not reverberate through the nose chambers and the voice ac- 
quires a so-called nasal twang. 
Tongue (Lingua) 
The mucous membrane over the dorsum, that is, the top surface of 
the tongue, is characterized by being extra rough and having large 
papilla scattered evenly throughout. The foramen cecum, the ter- 
mination of the obliterated thyroglossal duct, is a small round pit at 
the midposterior top surface of the tongue. Extending forward and 
laterally from the foramen cecum on each side lie a series of larger 
papilla?, which are part of the localization of the special sense of 
taste. In the mucosa between these papillae and the epiglottis lie a 
great number of solitary lymph nodules, known collectively as the 
lingual tonsil. The median and two lateral glossoepiglottidean 
musculoligamentous folds have been considered in connection with 
Tongue (Lingua) THE HEAD 
331 
the larynx. The musculature of the tongue is of the voluntary type 
and is divided into an extrinsic and an intrinsic group. The ex- 
trinsic muscle, previously considered, are: the genioglossus, the 
hyoglossus, the styloglossus, and the glossopalatinus. The intrinsic 
muscles are collected into bands running from one part of the tongue 
to another in various planes and directions, and are not directly 
connected to bony origins. The main function of the tongue is an 
aid to mastication, but it has a subsidiary function in modifying the 
voice sounds, characteristically in the production of the linguals. 
Dissection.-As the roof of the mouth forms the floor of the nose, 
it is advisable to postpone the completion of the mouth dissection 
until the nose has been considered. The student, however, can gain 
considerable knowledge of the anatomy of this region by examining 
his own mouth by palpation and by means of a looking glass, and 
by examining the mouth of a fellow-student. The tongue tends to 
rise up and to shut off a view of the isthmus of the fauces, but will 
tend to draw down if the individual pronounces a prolonged "Ah" 
or it may be mechanically depressed. The arches of the isthmus 
of the fauces are readily to be seen in any mouth, but the normal 
palatine tonsil of adult life is commonly so small as to be practically 
hidden between the arches. The extent of the hard palate should 
be made out by palpation. The soft palate and its uvular process 
should be noted to rise up when the individual pronounces "Ah." 
After the completion of the nose dissection, the palate and the 
isthmus of the fauces should be reviewed and dissected. The various 
muscles and nerves noted should be traced well into the substance of 
the tongue. Then the mandibular and hyoid bones should be sawed 
across in the anterior median line and the tongue should be com- 
pletely divided by a midline incision. 
The Nose (Nasus) 
The nose is the normal passageway for air to and from the respira- 
tory tract, but if both nasal cavities are blocked, the respiratory air 
may short-circuit through the mouth into the pharynx. The nareS; 
or, popularly, nostrils, are the narrowest portions of the nasal cavi- 
ties and as has been previously noted possess dilator muscles. The 
septum of the no.se should theoretically be straight in the median 
line, but practically in the adult it commonly varies somewhat 332 
REGIONAL ANATOMY 
either to one side or the other. The nasal cavities are large narrow 
spaces, consequently the light entering through the nares does not 
reach the deeper portions of the interior. Examinations of the 
deeper parts are therefore made by reflected light, with a hole in the 
center of the mirror to get the examiner's eye in the middle of the 
light cone. The posterior apertures into the nasopharynx, which lie 
just about the posterior end of the hard palate, can be examined by 
light reflected from an angularly placed mirror held in back of the 
soft palate. The technical name for these apertures is choame, that 
is funnels. 
crista galli 
cribriform plate 
superior concha 
orbital cavity 
ethmoidal labyrinth 
middle concha 
nasal cavity 
Fig. 100.-Frontal section at middle of Ethmoid bone. 
mesethmoid of nasal septum 
Bony Boundaries 
The front portion of the nose has a cartilaginous framework, w^ile 
the rest of the walls of the nasal cavities are of bone. The septum 
is made up of the thin perpendicular plate of the ethmoid, with an- 
teriorly a plate of cartilage and posteriorly a plate, which projects 
down from the body of the sphenoid, known as the vomer bone 
(vomer = ploughshare). The roof of the nasal cavities is made up of 
the cribriform plate of the ethmoid and the body of the sphenoid. 
The floor of the nasal cavities is made up of the palatal process of 
the maxilla and posteriorly the horizontal part of the palatal bone. 
The lateral wall is made up superiorly of the nasal bone, the frontal 
process of the maxilla, and the ethmoidal labyrinth, inferiorly of the 
maxilla, the perpendicular part of the palatal bone, and the medial 
pterygoid plate of the sphenoid. Along the lateral wall lie three 
curled porous bones known as the superior, middle, and inferior THE HEAD 
333 
nasal conchae (O.T. turbinates) (concha = shell). The superior and 
middle conchae are parts of the lateral masses of the ethmoid. The 
inferior nasal concha is a separate bone of larger size, which is 
attached by a suture line to the maxillary and palatal bones of the 
lateral nasal wall. 
Lining of Nasal Cavities 
The respiratory portions of the mucosa are lined by a columnar 
type of epithelium. The submucosa contains the larger arteries, 
veins, nerves, and lymphatics, which are held firmly in position by 
connective tissue. The submucosa is intimately attached to the 
mucosa and to the periosteal lining of the bony walls. In the mu- 
cosa of the conchae lie large thin-walled blood sinuses, which func- 
tionate by moistening and heating the air in its passage through the 
nose. If the nose can not functionate for any reason at all, the 
inspired air should be well moistened and preferably near body tem- 
perature. If these conchal structures are not functionating properly, 
the remainder of the respiratory tract and mouth tends to become 
dry, parched, and inflamed. 
A saw-cut should be carried through the roof and floor of the nose 
on one side of the septum in order to make a detailed examination 
of the interior of the nasal cavities. It should be especially noted 
that the nasal cavities are in reality much larger than most people 
without special information conceive them to be. 
Air Sinuses 
The three nasal conch® covered by mucous membrane and con- 
taining the blood sinuses are readily to be made out along the 
lateral wall. By prying up the anterior portion of the inferior nasal 
concha the exit of the lacrymal duct into the nose may be noted, or a 
toothpick may be passed from the orbital part of the lacrymal duct 
down into the nasal cavity. The frontal bone is hollowed out under 
the supraorbital margin for a large air space of variable shape, 
which is lined by a mucoperiosteal layer. The body of the maxilla 
is likewise hollowed out for a big cavity, known as the air sinus of 
the maxilla, or, in the old terminology, as the antrum of Highmore. 
These air sinuses drain via ducts into the nose just under the middle 
nasal concha, this opening being technically known as the hiatus 
semilunaris. The ethmoidal labyrinth is hollowed out by air cells, 334 
REGIONAL ANATOMY 
that is a sinus which is partially subdivided by delicate bony parti- 
tions. The anterior ethmoidal cells empty into the frontal sinus 
duct, the posterior cells under the small superior concha. The 
sphenoidal air sinuses hollow out the body of the sphenoid and drain 
into the upper parts of the nasal cavities. These air sinuses are 
commonly so large that these facial bones are materially weaker 
than would be expected from an external examination. 
Practical 
Why those air sinuses exist and their probable function has never 
been definitely settled. The air spaces obviously do away with un- 
necessary weight and strength in the front part of the head. Pre- 
sumably these spaces are less liable to cause serious trouble when 
connected with the nose than if not so connected, being more com- 
monly infected, but on the other hand allowing readier drainage. 
Acute and the earlier stages of chronic nasal infections cause swell- 
ing of the nasal conchas, which may partially block the exit of these 
air sinuses and the lacrymal duct into the nose. Infection then 
spreads into the air sinuses causing local tenderness, which tends to 
disappear with the subsidence of the nasal inflammation. Chronic 
air sinus infections call for surgical intervention in order to estab- 
lish efficient dependent drainage. The operation indicated in a 
minor degree of this disease is commonly a cauterization of the 
inferior concha, while in the serious cases a partial resection of the 
middle concha is required. In the upright standing position of the 
body the air sinuses, with the exception of the maxillary and 
sphenoid have dependent drainage. A deviated septum, if markedly 
out of place, may interfere with the normal nasal drainage. Frac- 
tures of the nose or operations for partial resection of the septum 
have intrinsically a certain element of risk, inasmuch as the cribri- 
form plate of the ethmoid may be broken, which accident commonly 
causes cerebrospinal meningitis. 
The ducts of the air sinuses should be located, and then the sinuses 
should be opened up freely by breaking in the thin partitions be- 
tween the sinuses and the nasal cavity. 
Vessels and Nerves 
The internal maxillary artery sends two large palatal branches 
downward through canals in the palatal bone. Branches of these THE HEAD 
335 
vessels supply the lateral nasal wall including the conchal blood 
sinuses. The terminal part of these vessels continues straight 
through into the mucous membrane of the palate, supplying both the 
hard and soft palate regions. Another branch of the internal maxil- 
lary runs in a canal of the sphenoid bone across the roof of the nose 
and then courses diagonally downward and forward across the 
septum. A small continuation of this vessel goes through a midline 
foramen in the hard palate, supplying the anterior part of the hard 
palate. The veins and lymphatics, generally speaking, correspond 
to the arteries. The maxillary division of the trigeminal joins with 
branches of the sympathetic and other complicated nerves to form 
the sphenopalatine ganglion of Meckel, which lies about at the 
point where the internal maxillary artery enters the palatal bony 
canal. The ganglia sends out sympathetic processes which travel 
along with the arterial branches to the nose and to the palates. The 
olfactory nerves of the special sense of smell are distributed in the 
upper part of the nose, over both the medial and the lateral walls. 
Nasopharynx (Pharynx, Pars Nasalis) 
The nasopharynx is that portion of the pharynx lying above the 
elevated soft palate and below the base of the skull. Anteriorly it 
connects with the apertures of the nasal cavities (choanae), while 
posteriorly lies the vertebral column. The lateral walls are made by 
the fibromuscular walls of the pharynx, the muscle falling consider- 
ably short of the base of the skull as no. constriction action is nor- 
mally required. The characteristic feature of the nasopharynx is 
the openings of the auditory or Eustachian tubes on the lateral wall 
at about the midpoint and just above the level of the hard palate 
(tuba auditiva, Eustachii). These air tubes connect up the naso- 
pharynx with the middle ear, tending to equalize air pressure in the 
two cavities. The auditory tubes run straight backwards, upwards 
and lateralwards into the petrous portion of the temporal bones. 
The extrabony portion of this tube is held open by cartilaginous 
semirings, being widest at its pharyngeal end. The posterior wall 
of the pharynx has a large aggregation of lymphatic tissue in the 
mucosa, known as the pharyngeal tonsil (tonsilla pharangea). 
The nasopharynx should be examined. 336 
REGIONAL ANATOMY 
The two elevator muscles of the soft palate arise from the medial 
pterygoid plate of the sphenoid-bone and run into the upper surface 
of the soft palate. The tensor palatini arises from the medial sur- 
face and runs directly downward to the soft palate. The levator 
palatini arises from the lateral surface and its tendon turns around 
a hook process at the bottom of the medial pterygoid plate en route 
to the soft palate. The medial pterygoid plate of the sphenoid is 
materially smaller than the lateral pterygoid plate, in conformity 
with the relative size of the palatine and pterygoid muscles. 
These elevator, and the glossopalatinus and pharyngopalatinus 
depressor muscles of the soft palate should now be dissected. 
Lymphatic Ring 
The pharyngeal tonsil, the two palatine, or faucial tonsils, and 
the lingual tonsil make up what is known as the lymphatic ring of 
Waldeyer. The pharyngeal and lingual tonsils are normally low, 
irregular masses, and are not sharply defined from the more scattered 
lymphatic nodules of the neighboring areas. The palatine tonsils 
are normally almond-shaped, sharply circumscribed masses, which 
on their medial surfaces have a number of small pits (fossulae) and 
on their lateral surfaces firm, white, fibrous capsules. The pharyn- 
geal tonsil is connected essentially with the mucosa of the nose and 
nasopharynx, when chronically enlarged forming a soft, irregular 
mass known clinically as adenoids. Swelling of this tonsil charac- 
teristically interferes with breathing and may predispose to inflam- 
mations secondarily in the middle ear cavity. The palatine tonsils 
anatomically belong to the mucosa of the mouth and oropharynx, 
and when inflamed, tend to interfere with swallowing. Swelling and 
inflammation of the pharyngeal and palatine tonsils are very com- 
monly associated, due to disease of the whole area or perhaps in 
part to a lymphatic anastomosis. The lymphatic tissue of this ring 
increases in amount in acute nasooropharyngeal infections and tends 
to remain hyperplastic in chronic disease. 
Practical 
The presence of solitary lymphatic nodules has previously been 
noted to be universal throughout all mucous membranes. Increase 
Elevator Palate Muscle THE HEAD 
337 
in the number of these nodules and eventually aggregations of 
nodules has been noted in those mucous membranes grossly more 
exposed to infection, as, for example, in the lower half of the small 
intestine, the appendix, and throughout the large intestine. The 
finding of aggregated masses of lymphatic nodules, in the naso- 
pharynx and throat, known as tonsils, is, therefore, not an unex- 
pected feature, but is in accord with our previous anatomic experi- 
ence. The tonsils are physiologically largest during childhood, and 
during adult life tend to progressively involute, that is, undergo 
retrograde changes. 
The consensus of clinical opinion is that the function of the ton- 
sils is unknown, which interpreted means that clinicians reject the 
argument that the tonsils are a protective defense organ and have 
no substitute hypothesis to offer. If the palatine tonsils are subject 
to recurring acute inflammations or to chronic infections with hyper- 
plasia, the generally accepted opinion is that they together with 
their capsules should be completely removed. The older clinical 
evidence in regard to improvement following tonsillectomy was 
based on incomplete removals, whereas the modern clinical opinion 
concedes that the results of these operations were not fully satisfac- 
tory and demands that the tonsil removal should be absolutely com- 
plete. Irrespective of what is eventually accepted as the normal 
function of the palatine tonsils, the clinical evidence in regard to 
great improvement following partial or co,mplete tonsillectomy in 
cases of hyperplastic tonsils is absolutely conclusive. That the 
greatly hyperplastic palatine tonsils go through a form of vicious 
circle, by which they no longer protect the individual, but definitely 
predispose to frequent and severe tonsillar attacks, seems to be 
proved beyond doubt by prolonged clinical experience. Some con- 
scientious clinicians, while conceding the importance and value of 
tonsillectomy in properly selected cases, stoutly oppose what they 
consider extremists' views as regard both to indications and prog- 
nosis. They point out that historically in any new field only the 
strongest men are not carried to extremes by their enthusiasm; that 
clinically even the radical operation does not prevent fresh oro- 
pharyngeal infections, if the patient repeats previous errors of 
hygiene; and that in case of infection after the complete radical 
removal of the palatine tonsils, the danger of lymphatic enlargement 
and extrapharyngeal abscess may even be actually increased. In 338 
REGIONAL ANATOMY 
presenting this minority view, it is only fair to emphasize that the 
tendency of the specialists and even of the general practitioners is 
rather to widen than to restrict the indications for the operation of 
tonsillectomy. 
Peritonsillar Abscess 
The tonsils lie inside the submucosa of the pharynx, consequently 
when enlarged they follow the line of least resistance by bulging 
into the pharynx. The popular belief that swollen tonsils can be 
palpated from the outside is due to an accompanying swelling of 
the deep lymphatic glands of the neck. A peritonsillar abscess, or, 
popularly, quinzy, may be a diffuse inflammation or may be duetto a 
breaking down of these lymphatic glands, which lie just outside of 
the submucosa. These abscesses in time tend to bulge into the 
pharynx, this being the line of lesser resistance. The common 
carotid arteries lie in very close relationship to the lateral walls of 
the laryngopharynx, while the internal and external carotids and 
the external maxillary arteries are commonly stated to be about 
three-quarters of an inch lateral to the oropharynx. Therefore, 
even when the abscess bulges well inwards, any unexpected move- 
ment of the patient's head during operative intervention with a 
sharp knife may cause a serious accident. The retropharyngeal 
abscesses, between the pharynx and the vertebral column, may be 
freely opened in the midline, practically without risk. 
EAR 
The ear, the special organ of hearing, is situated entirely within 
the temporal bone. The auricle or external ear is freely movable 
among the lower animals and in the human retains a slight range of 
motion as was noted in the consideration of the scalp. The function 
of the auricle is to gather sound waves from a large area, which are 
then transmitted to the drum membrane. The framework of the 
auricle is of yellow elastic fibrocartilage, which is covered by a fatty 
layer and skin. The lobule of the auricle is that portion which 
hangs down without a cartilaginous framework. The spiral curves 
leading down into the external acoustic meatus carry the concen- 
trated sound waves to the drum. THE HEAD 
339 
External Acoustic Meatus (B.N.A. Acustic) 
The external acoustic meatus is made up of a cartilaginous ex- 
ternal half and a bony internal section. The canal runs, approxi- 
mately speaking, straight inward, and is somewhat more than an 
inch in length by one-sixth of an inch in cross-section. The tym- 
panic membrane, or, popularly, drum, shuts off the deep end of the 
external acoustic meatus from the middle ear cavity. The drum is 
not set in at a right angle, but on a distinctly downward-medial - 
ward and forward-medialward slant. On account of the depth and 
curving direction of the narrow canal, the tympanic membrane can 
only be examined satisfactorily by reflected light, with the auricle 
pulled backward in order to straighten out the canal. The tympanic 
membrane is made of white fibrous tissue, which on account of the 
darkness in the middle ear cavity appears as a steel-gray under the 
ordinary reflected light. 
If pus accumulates in the middle ear cavity under pressure, the 
tympanic membrane is bulged lateralward and becomes injected, 
more especially at its upper segment. If a vacuum occurs in the 
middle ear cavity, the tympanic membrane is drawn medialwards 
and presses against the little bones o.f the middle ear. Hair and 
special waxy glands are protective structures of the external acoustic 
meatus. Foreign bodies or masses of dried wax in the canal would 
obviously interfere seriously with the transmission of sound waves. 
The external acoustic meatus should be examined in the dissecting 
body and in a fellow-student's ear. 
Middle Ear Cavity (Cavum Tympani) 
The middle ear cavity or cavum tympani connects anteriorly 
through the auditory tube with the nasopharynx. The tympanic 
membrane forms the main part of the lateral wall of the middle ear 
cavity, being drawn somewhat medialward at its center. The medial 
wall has a promontory projecting lateralward, which is caused by 
the internal ear shell. A series of small bones with mutual articula- 
tion extend across from the tympanic membrane to the fenestra 
vestibuli just posterior to the promontory. These ossicles from 
without inward are the malleus, or hammer, the incus, or anvil, and 
the stapes, or stirrup. The handle of the malleus fits against the 
dnim membrane, while the footpiece of the stirrup fits in the fenes- 340 
REGIONAL ANATOMY 
tra vestibuli. The ossicles are connected to each other and to the 
bony walls by ligaments, the malleus and incus in addition having 
special muscles controlled by branches from the facial nerve. This 
chain of ossicles serves to transmit the vibration of the tympanic 
membrane to the internal ear. The upper part of the middle ear 
cavity is known as the epitympanum, or attic, which is separated 
from the brain by only a thin though firm plate of bone, known as 
the paries tegmental is. The epitympanum contains the heavier parts 
of the' malleus and incus ossicles, and connects up posteriorly with 
the mastoid air cells. 
If pus under pressure in the middle cavity is not promptly re- 
lieved by a free incision of the drum membrane, the tympanic 
cavity and the mastoid cells may become seriously infected. On 
account of the anatomic proximity and the various anastomoses, 
thrombosis of the transverse sinuses and secondary brain abscesses 
are not uncommon complications of middle ear and mastoid infec- 
tions. 
Dissection.-A horizontal saw-cut should be made through one 
temporal bone on a level with the upper margin of the internal 
acoustic meatus. A vertical saw-cut should be made through the 
other temporal bone, carrying the section through the posterior 
parts of the external and internal acoustic meatuses. The middle 
ear cavity should be located and carefully cleared of bone-dust. 
Then the tympanic membrane should be studied in both specimens. 
The ossicles should then be removed by grasping their heavier 
parts, which are located in the epitympanic portion of the middle 
ear cavity, and pulling them out. A small probe should then be 
passed through the nasopharyngeal orifice of the auditory tube into 
the middle ear cavity. The thin roof of the epitympanum and the 
bulging of the promontory should be especially noted. 
Internal Ear (Auris Interna) 
The internal ear bulges the medial wall of the middle ear cavity, 
forming the promontory. The internal ear contains, besides the 
essential organ of hearing, a series of canals which control equi- 
librium. Although anatomically associated, the semicircular canals 
have nothing whatever to do with hearing, the anatomic relation- 
ship being, as it were, accidental. Among the lower animals the THE HEAD 
341 
equilibrium organ is anatomically separate from the organ of hear- 
ing. The combined hearing and equilibrium cavities are small, being 
about one-half inch anteroposteriorly by about one-quarter inch in 
other diameters. These structures are well protected against in- 
jury in the strong petrous portion of the temporal bone. 
The combined hearing and equilibrium cavities are surrounded by 
a bony labyrinth, which is held firmly in the petrous portion of the 
temporal bone. Inside this bony labyrinth lies a membranous laby- 
rinth, which is distended by an endo-fluid. The portion of the 
internal ear connecting the semicircular canals with the cochlea is 
known as the vestibule. The semicircular canals lie posteriorly to 
vestibule 
semicircular canals 
cochlea 
fenestra cochlea 
Fig. 101.-Internal Ear (auris interna). (External view of right osseous labyrinth.) 
fenestra vestibuli 
the vestibule, and the three canals lie in the three planes of space. 
The cochlea is a spiral shell-like structure, which lies anteriorly to 
the vestibule and is the essential internal organ of hearing. The 
fenestra vestibuli lies just in back of the center of the promontory 
and receives impulses via the stirrup from the drum membrane 
(fenestra = window). The fenestra cochlea lies directly below the 
fenestra vestibuli and is considered to functionate as a safety valve 
against excessive vibration. The nerve cells of hearing arise in the 
cochlear membrane, and must carry their messages through the 
brain stem up to the temporal lobe of the cerebrum of the opposite 
side before sound can be interpreted (nervus cochlea). The peri- 
pheral nerves of hearing carry messages to. the nuclei in the medulla 
oblongata portion of the brain stem, while the central nerves carry 
message to the temporal lobe of the cerebrum, chiefly of the opposite 342 
REGIONAL ANATOMY 
side. The nerve cells of equilibrium arise in the semicircular canal 
membrane and carry their messages into the cerebellum (nervus 
vestibuli). The internal ear is so well protected that it is but rarely 
disturbed by accident or infection. 
The detail in regard to the internal ear can only be made out sat- 
isfactorily in decalcified temporal bones, with the aid of microscopic 
sections. The general size and position of the internal ear can be 
verified, however, by the removal of bone dust from the sectioned 
temporal bones. 
Facial Nerve 
The facial nerve enters the internal acoustic meatus in company 
with the acoustic nerve, but inside the temporal bone these nerves 
enter separate canals. The facial nerve runs horizontally lateral- 
wards to the promontory, then turns straight backwards to the pos- 
terior wall of the tympanic cavity, which it follows vertically down- 
wards to the stylomastoid foramen. The facial nerve has many 
complicated communicating branches with other nerves, its largest 
branch, the chorda tympani, going through a separate canal to join 
the lingual branch of the mandibular division of the trigeminal. 
Destruction of the facial nerve is always a possible complication of 
middle ear disease, more especially of operative interference. 
The facial nerve should be traced in its course through the tem- 
poral bone. 
Nerve and Blood Supply of Temporal Bone 
No subject in anatomy is more complicated in its detail than the 
nerve supply of the temporal bone. The anatomy of the combined 
acoustic and equilibrium nerve is comparatively simple and estab- 
lished. The motor supply of the muscles within the temporal bone 
would be expected to come from the facial nerve, the sensory supply 
from the trigeminal nerve, whereas the involuntary supply should in 
theory come from the superior cervical ganglia. As a matter of 
fact the facial, the trigeminal, and the sympathetic nerves form a 
most complicated plexus, the various interconnecting strands of 
which traverse minute bony tunnels through the temporal bone. 
The number, position, and size of the connecting processes of this 
plexus have been definitely established, but the further course and 
significance of these strands is still an unsettled problem. The fact THE HEAD 
343 
that some of the nerve processes belonging to the facial nerve 
ganglia of the brain stem short-circuit and travel along with the 
maxillary and mandibular divisions of the trigeminal, obviously 
complicates the solution. The various ganglia outside of the skull 
in connection with the plexus are generally considered to belong 
to the sympathetic nerves. The common reference of pain originat- 
ing in the tympanic cavity along the various branches of the mandib- 
ular division of the trigeminal yields clinical evidence that the 
sensory supply of the middle ear is derived partly at any rate from 
that source. A sensory branch from the glossopharyngeal tunnels 
the bone and helps to supply the middle ear cavity. 
Arterial branches from the middle meningeal, internal maxillary, 
and posterior auricular vessels supply the interior of the temporal 
bone. The veins, generally speaking, correspond to the arteries. 
The anastomoses between these veins and the cranial sinuses are a 
potential source of danger in middle ear infections. INDEX* 
A 
Abdomen, contents of, 162 
walls of, 138, 149, 160 
Abduction, 82 
Abnormalities, of vessels, 56, 57 
Abscess, 37, 79, 101, 107, 116, 140, 
145, 204, 242, 338 
Acetabulum, 108 
Acinus, 75 
Acromion, 67 
Action of, (see structure) 
Adduction, 81 
Adenoid, 336 
Adrenal, 197 
Afferent, 283 
Air-cells or sinuses, 333 
Albinism, 30 
Allantois, 179 
Alveolus, 75 
Amitosis, 22 
Amphiarthrosis, 49, 223, 238 
Amphibians, 23 
Anastomosis, general, 56, 78, 120, 207 
specific (see particular vessels) 
Anatomy, regional or topographical, 
25, 65 
systemic, 25, 27 
Annulus, femoral, (crural), 158 
inguinal, 156 
Anterior, 24 
Antibrachium, 90 
Antrum, of Highmore, 333 
Anus, 138, 139, 146, 172, 183 
Aorta, 189, 222, 226 
Aperatura, pelvis minoris, 109 
ventriculi quarti, 302 
Apex (apicis), 215 221 
Aponeuroses, general, 40, 72, 94, 116, 
150 
specific (see region) 
Apparatus digestorius, 160 
lacrimalis, 315 
respiratorius, 205 
urogenitalis, 138, 193 
Appendix, 171 
Applied Anatomy (see region) 
Aquaeductus cerebri, 300, 301, 302, 
308 
Arachnoid, cerebral, 291 
spinal, 237 
Arch (arcus), branchial, 254 
of foot, 136 
glossopalatine, 330, 336 
pharyngopalatine, 330, 336 
Arm, 83 
Armpit, 77 
Arteries (arteriae): 
general discussion, 52, 78, 120, 207 
223 
specific, alveolar, 327 
anonyma, 226, 248 
aorta, pulmonary, 222 
systemic, abdominal, 189 
ascending, 222, 226 
arch, 226 
descending, 226 
auricular, posterior, 250, 268 
axillary, 78, 99 
basilar, 299 
brachial, 78, 86, 98 
bronchial, 215, 227 
carotid, common, 226, 244, 248, 
250, 253 
external, 249, 254, 338 
internal, 249, 254, 276, 299, 338 
cerebral, 299 
chorioid, 301 
circle, of Willis, 299 
celiac (coeliac), 172, 190, 192 
coronary, of heart, 222, 224, 226 
dental, 327 
dorsalis pedis. 131 
ductus, arteriosus, 219 
epigastric, 154, 156 
facial, 249, 313, 328, 338 
femoral, 121, 132, 157, 189 
gastric, 173 
gluteal, 115, 132, 190 
hemorrhoidal, 142 
hepatic, 173, 182 
hypogastric, 154, 189 
iliacs, 189 
innominate, 226, 248 
intercostal, 207, 226 
interosseous, 98 
ischiadic, 115, 132, 190 
lienal, 173, 188 
♦Both the older terminology (0. T.) and the Basle Nomina Anatomica (B. N. A.) 
345 346 
INDEX, 
Arteries, specific-Cont'd 
lingual, 249, 328 
lumbar, 190, 193 
mammary, internal, 75, 207, 249 
maxillary, external, 249, 313, 328, 
338 
internal, 250, 327, 334 
meningeal, middle, 270, 276, 280, 
327 
mesenteries, 173, 190, 192 
occipital, 250, 269 
ophthalmic, 317 
ovarian, 190, 192, 201, 202 
palatine, 334 
palmar, 98 
perineal, 144, 148 
peroneal, 131 
plantar, 132 
popliteal, 120, 131, 132 
profunda femoris, 121, 132 
pudendal (pudic), 141, 148, 190 
pulmonary, 214, 218, 219, 222 
radial, 98 
renal, 190, 192, 194 
sciatic, 115, 132, 190 
spermatic, 142, 190, 192 
splenic, 173, 188 
subclavian, 78, 99, 226, 248, 250 
subscapular, 79, 99 
temporal, superficial, 250, 268 
testicular, 142, 190, 192 
thyreoids, 249 
tibial, 131, 132 
transversa colli, 249 
transversa scapulae, 249 
ulnar, 98 
umbilical, 179, 220 
uterine, 190, 201, 202 
vertebral, 249, 276, 299 
vitelline, 179 
volar, arches, 98 
Arterioles, 54, 78, 215, 226, 251 
Articulations (articulationes): 
general discussion, 49, 103, 121, 134 
specific, acromio-clavicular, 90 
ankle, 135 
atlanto-cpistropheo-occipital, 260 
costo-chondral, 73 
costovertebral, 232, 238 
coxae, 121 
cranii, 264, 274, 309, 329, 332 
craniovertebral, 260 
cubiti, 103 
elbow, 103 
foot, 136 
genu,134 
hand, 104 
Articulations, specifis-Cont'd 
hip, 121 
humeri, 88 
knee, 134 
mandibular, 326 
manus, 104 
pedis, 136 
radiocarpal, 104 
radioulnar, 103 
sacroiliac, 108, 238 
shoulder, 88 
sternoclavicular, 247 
symphysis pubis, 108, 238 
talocrural, 135 
tarsal, 136 
tibiofibular, 136 
vertebral column, 233, 238, 260 
wrist, 104 
Arytenoid, 255 
Ascites, 183 
Asthenic, 208 
Astragulus, 125 
Atlas, 260, 261 
Atrium, 217, 218, 220, 222, 224 
Auricle, of ear, 338 
of heart, 217 
Auris, 340 
Aves, 24 
Axilla, 77 
Axis, 260 
Axis cylinder process, 61 
Azygos, 193 
B 
Back, 70, 231 
Bacteria, 20 
Base, 215, 221 
Bladder, gall, 183, 163 
urinary, 197, 163 
Blood, 52 
Body, Pacchionian, 270, 302 
pituitary, 279, 300 
vitreous 320, 322 
Bone (see B. N. A. Os, ossis) 
general discussion, 42 
Brachium, 83 
Brain, 280, 289 
Brain-stem, 292 
Breast, 74 
Bronchus, 213 
Bronchiole, 213 
Bucca, 313, 329 
Bulbus, penis, 144 
vestibuli, 147 
Bursa, general, 89, 104, 113 
Bursa, omentalis, 165, 167 
Buttock, 113 INDEX, 
347 
c 
Caecum, 171 
Calcaneus, 125, 126 
Calvaria, 264 
Canal (canalis): 
adductor, of Hunter, 121 
anal, 138, 146, 172, 183 
femoral (crural), 158 
Haversian, 46, 48 
inguinal, 155, 156 
nasolacrimal, 316, 333 
nerve (see nerves) 
semicircular, 340 
spinal, 232 
urogenital, 138 
vertebral, 232 
Canaliculus, 44, 47 
Capillaries, 52, 53 
Capsule, of brain, 293, 304, 305, 306 
of joints, 50, 103 
of Tenon, 316 
Caput (capitis), 74 
Caracoid, 65 
Cardia (heart), 216 
Cardia, of stomach, 168 
Carpus, 92 
Cartilage (cartilage): 
general discussion, 43, 50, 73, 241 
specific, articular, 50 
arytenoid, 255 
costal, 73 
cricoid, 241, 255 
ear (auricle), 338 
embryonic, 44 
epiglottic, 255, 330 
hyaline, 44, 50 
nasal, 332 
semilunar, 134 
thyreoid, 241, 255 
white fibro, 44, 233 
yellow elastic, 44, 255, 338 
Cauda equina, 236 
Cavity, (cavum): 
abdominal, 160 
articular, 50 
medullary (marrow), 48, 105 
' middle ear, 339 
nasal, 331 
oral, 328 
pelvic, 138, 197 
pericardial, 221 
peritoneal, 160 
pleural, 211 
of septum pellucidum, 305 
tympanic, 339 
Cecum, 171 
Cells, general discussion, 20 
Cells, ethmoid, 333 
mastoid, 340 
Central nervous system, 63, 280 
Cerebellum, 290, 296, 298, 342 
Cerebrospinal fluid, 237, 280, 291, 301 
Cerebrum, 271, 273, 289 
Cervical, 240 
Chambers, of eye, 320, 322 
Chiasm, optic, 299, 318 
Chondrium, 43, 150 
Cheek, 313, 329 
Chest, 65, 205 
Choanse, 332 
Chorioid, of brain, 291, 301 
of eye, 320 
Chorion, 178 
Circulation, fetal, 178, 219 
portal, 180, 183 
pulmonary, 214, 218, 219 
systemic, 52, 217 
Cisterna chyli, 229 
Claustrum, 305 
Clavicle (clavicula), 67 
Clitoris, 146 
Cloaca, 138 
Coccyx (coccygis), 68 
Cochlea, 341 
Collateral, 103, 104, 134 
Collum, 74, 240 
Colon, 166, 172 
Column, vertebral, 68, 231 
Conchae nasalis, 332 
Condyle, general, 48, 111 
specific (see particular bone) 
Conjunctiva, 315 
Cor (cordis), 216, 221 
Cord, gangliated sympathetic, 229, 251 
spermatic, 142, 155, 199 
spinal, 235, 280, 283 
umbilical, 178 
vocal, 258 
Corium, 28 
Cornea, 319 
Coronal, 267 
Corpus, callosum, 299, 303 
cavernosum, 143, 147 
of bones, 73, 74 
vitreum, 322 
Corpuscles, red blood, 53 
Cortex, cerebral, 292 
suprarenal, 197 
renal, 195 
Costa, 73, 206 
Coxa, 108 
Cranium, 264, 269, 274, 309, 314, 329 
332 
Cremaster, 156 
Cribriform, of ethmoid, 275 348 
INDEX, 
Crista galli, 271 
Crus (cruris), 123 
Crura cerebri, 298 
clitoris, 147 
penis, 143 
Crypt, 33, 175 
Cutis, 27 
D 
Decussation, of pyramids, 293 
of lemnisci, 293 
Deep, 25 
Dendrites, 61 
Dentes, 324 
Dermis, 27 
Descriptive terms, 24 
Development, general, 19, 23 
specific (see organ or region) 
Diaphysis, 44 
Diaphragm, 160, 208, 212 
pelvic, 138, 148, 197, 198, 201 
'urogenital, 144, 146, 147 
Diarthrosis, 49 
Diencephalon, 290, 291, 293, 298, 305 
Digestion, 168, 175, 181 
Digitus, 96, 129 
Dipice, 270 
Discs, intervertebral, 233 
Diseases of (see structure) 
Dislocation, general, 50, 89, 122, 327 
specific (see articulation) 
Dissection, general, 70 
specific (see region) 
Distal, 93 
Diverticulum ilei, of Meckel, 179 
Dorsal, 24 
Duct (ductus), general, 75 
specific, arteriosus (Botalli) 219 
biliferri, 183 
choledochus, 184 
common bile, 184 
cystic, 184 
deferens, 199, 200 
ejaculatory, 199, 200 
hepatic, 183 
lacrimal, 316, 333 
lactiferri mammae, 75 
lymphatic, 59, 228 
Muellerian, 193 
nasolacrimal, 316, 333 
pancreatic, of Wirsung, 184, 186 
parotid, of Stenson, 325 
sublingual, 329 
Submaxillary, of Warton, 328 
thoracic, 228 
thyroglossal, 252, 330 
venosus (Arantii), 180, 220 
Wolffian, 193 
Duodenum, 170, 186 
Dura mater, 237, 270 
E 
Ear, 338 
Ectoderm, 23, 28, 61, 281 
Edema, 59, 183, 192, 229 
Efferent, 283 
Elbow, 103 
Embryology, general, 19, 23 
specific (see organ or region) 
Encephalon, 280, 289 
Endoderm, 23, 33 
Endothelium, 50, 53 
Ensiform, 73 
Epicondyle, 68, 95 
Epidermis, 27 
Epididymis, 199 
Epigastrium, 150 
Epiglottis, 255, 330 
Epiphysis, 44 
Epiploic, 164, 167 
Epistropheus, 260, 262 
Epithelium, 27, 33 
Erythrocytes, 53 
Esophagus, 210, 225, 229, 253 
Ethmoid, 274, 280, 315, 332' 
Extension, 82 
External, 24, 25 
Extradural, 280 
Extra-peritoneal, 161 
Extremity, inferior, 108 
superior, 65 
Eversion, 130 
Eye, 319 
Eyeball, 316 
Eyelids, 312, 315 
F 
Face, 309 
Falx cerebri, 271 
Fascia, general, 36, 94, 101, 116, 145, 
161 
specific (see region) 
Fasciculus (Tract) 
of encephalon, 292 
of medulla spinalis, 287 
Fauces, 328, 330 
Female genital organs, 146, 201 
Femur, 111 
Fenestra cochleae, 341 
vestibuli, 339 
Fetus, 178 
Fibroblasts, 46 
Fibrocartilage, 44, 233, 338 
Fibula, 123 
Fingers, 90 INDEX. 
349 
Fissure (fissura): 
branchial, 254 
longitudinal cerebral, 271 
lateral cerebral (Sylvii), 295, 298 
of Rolondo, 295, 296 
sphenoidal, 275, 310, 314 
superior orbital, 275, 310, 314 
urogenital, 146 
Fistula in ano, 141 
Flexion, 82 
Foetus, 178 
Fontanelle, 267 
Fonticulus, 267 
Foot, 123 
Foramen or foramina, general, 48, 
77, 276 
specific, epiploic, of Winslow, 167, 
185 
interventricular, 301 
intervertebral, 77, 233 
ischiadic, 110, 114, 115, 141 
jugular, 273, 275, 276 
magnum, 261, 275 
Magendii, 302 
of Monro, 301 
obturator, 111 
ovale, of heart, 219, 220 
sciatic, 110, 114, 115, 141 
ventriculi quarti, 302 
others considered with nerves 
Forearm, 90 
Fornix cerebri, 300, 303, 304 
Fossa, axillaris, 77 
cranial, 273 
ischiorectal, 140 
poplitea, 120 
Fracture, general, 47, 70, 104, 105, 
123, 136, 262, 279, (see also 
particular bone) 
Frenulum (frenum), lingual, 329 
Frontal plane, 267 
Frontal bone, 265, 266, 267, 274 
Function of (see structure) 
Funiculus (cord), spermatic, 142, 
155, 199 
umbilical, 178 
G 
Gall bladder, 183, 163 
Ganglion or ganglia, 63 
basal, 303 
posterior root, 236, 284 
semilunar (Gasserian), 278, 294 
spinal, 229, 251 
sympathetic, 63, 174, 229, 251, 282 
Caster, 168 
Genitalia, female, 146, 201 
male, 142, 198 
Gills and gill clefts, 254 
Glands (gland'ulse), general, 31, 75 
specific, ductless, 188, 197, 231, 
252, 279 
hypophysis, 279 
lacrimal, 315 
lymph, 59, 79. 116, 173, 210, 242 
mammary, 74 
mucous, 31, 329 
parathyreoid, 252 
parotid, 325 
pituitary, 279 
prostate, 198 
salivary, 325, 328, 329 
sebaceous, 31 
spleen, 188 
submaxillary, 328 
sublingual, 329 
sudiferous, 31 
suprarenal, 197 
sweat, 31 
thyroid, 252 
thymus, 210, 231 
Glans, clitoris, 147 
penis, 143 
Glenoid (cavity), 67 
Glossa, 330 
Glottis, 255 
Glomer'ulus, 194 
Gluteal, 113 
Gray nervous substance, 284, 288 
Granulations, arachnoid, 302 
Gyri cerebri, 292, 296, 270, 273 
H 
Hair, 30 
Hallux (hallucis), 129 
Hand, 90 
Harelip, 329 
Head, 264 
Heart, 216, 221 
Hemorrhoids, 142, 183 
Hepar (hepatic), 181 
Hermaphrodite, 149 
Hernia, 155 
Hilus, 188, 194, 211 
Hip, 108 
His, bundle of, 225 
Histology, general, 19 
specific (see structure) 
Humerus, 68 
Humor, aqueous, 322 
vitreous, 322 
Hydrocephalus, 302 
Hymen, 146 
Hyoid bone, 241, 255, 328 
Hyperplasia, 39, 196 350 
INDEX. 
Hypertrophy, 39, 201 
Hypochondrium, 150 
Hypogastrium, 150 
Hypophysis, 279, 300 
I 
Ileum, 170 
Ilium, 108, 109 
Incisions (see regions) 
Incus, 339 
Inferior, 24 
Infundibulum, 279, 301 
Inguen (inguinal), 110, 155 
Innominate bone, 108 
Insertion, 40 
Inspiration, 207 
Integument, 27 
Intercellular substance, 28, 42 
Internal, 24, 25 
Intestines, 162, 170, 171 
Intraperitoneal, 161 
Inversion, 129 
Invertebrates, 23 
Iris, 321 
Ischium, 108, 110 
Isthmus, of fauces, 328 
rhombencephali, 290 
Iter, of Sylvius, 301 
J 
Jaws, 240, 309, 323, 329 
Jejunum, 170 
Joints (see articulations), 49 
K 
Karyokinesis, 22 
Kidney, 162, 193 
Knee, 134 
L 
Labia, majora (pudendi), 146 
minora (pudendi), 146 
oris, 312, 328 
Labyrinth, of ear, 341 
Lacrimal apparatus, 315 
Lamina, 47, 233 
Landmarks (see region) 
Laryngopharynx, 253, 257 
Larynx, 255 
Lateral, 25 
Leg, 123 
Lemnisci, 293, 294 
Lens, Crystalline, 321 
Leucocytes, 53 
Lien, 188 
Ligaments (ligamenta): 
general discussion, 50, 95, 128, 136 
162, 261 
specific, (see structure) 
-crucial, 134 
inguinal, of Poupart, 110, 152 
lacunare, of Gimbernat, 158 
nuchse, 240 
latum uteri, 201 
teres, 122 
Limb, lower, 108 
upper, 65 
Linea (line), alba, 151, 152 
aspera, 111 
semilunaris, 151, 152 
Lingua, 330 
Lips, 312, 328 
Liver, 162, 181 
Lobe (lobus), general, 76, 215 
specific (see organ) 
Lobule, general, 75, 182, 186 
Lung, 211, 213, 215 
Luxation (dislocation), 51, 89, 122, 
327 
Lymph, 59 
Lymph glands, general, 59, 79, 116, 
173, 210, 242 
specific (see region) 
Lymphnodules, 176, 336 
M 
Male genital organs, 142, 198 
Malleolus, 123 
Malleus, 339 
Mamma, 74 
Mammalia, 24 
Mandible, 323 
Manubrium, 73 
Manus, 90 
Marrow, of bone, 48, 105 
Mastication, 325 
Mastoid, 240, 340 
Mater, dura, 237, 270, 280 
pia, 237, 302 
Maxilla, 309, 329, 332, 333 
Meatus, acustic (auditory), 274, 276, 
278, 338, 342 
urinary, 143 
Medial, 25 
Mediastinum, 210 
Medulla oblongata, 290, 292, 293, 294, 
298 
Medulla ossium flava, 48, 105 
ossium rubra, 48, 105 
renal, 195 
spinalis, 235, 280, 283 INDEX 
351 
Membrana interossea, 90, 123 
tympani 339 
Membranous bone, 47, 264 
Meninges, of medulla spinalis, 237 
of encephalon, 270, 280, 291, 302, 
307 
Meniscus, 134 
Mesencephalon, 290, 298, 301 
Mesentery, 161, 171 
Mesoderm, 23, 30, 38, 43 
Mesonephros, 193 
Metacarpal, 92 
Metanephros, 194 
Metatarsal, 125, 126 
Metencephalon, 290 
Mid-brain, 290, 298, 301 
Mitosis, 22 
Mouth, 328 
Morula, 23 
Movements (see muscles), 38 
Mucosa, general, 31 
of gastrointestines, 162, 175 
of oro-naso-pharynx, 336 
Muscles (Musculi): 
general discussion, 38, 85, 120, 206 
specific: 
adductor brevis, 117 
longus, 117 
magnus, 117 
anconeus, 86 
biceps brachii, 82, 84 
biceps femoris, 119 
brachialis (anticus), 86 
brachio radialis, 102 
bulbo cavernosa, 144 
complexus, 243 
constrictor pharyngis, 253 
coraco brachialis, 82 
cremaster, 156 
deltoid, 82 
diaphragm, 160, 208, 212 
digastric, 245 
epicranial, 268 
erector penis, 144 
erector spinse, 153, 234 
extensor carpi radialis, 102 
carpi ulnaris, 102 
digitorum communis, 102 
longus, 128 
hallucis longus, 128 
pollicis longus, 102 
of face, 312 
flexor carpi radialis, 96 
ulnaris, 96 
digitorum longus, 130 
profundus, 96 
sublimis, 96 
hallucis longus, 130 
Muscles, specific-Cont'd 
pollicis longus, 96 
of foot (short) 131 
gastrocnemius, 120, 130 
gemelli, 115 
genioglossus, 328 
geniohyoid, 328 
glossopalatine, 330 
gluteus, 113, 114 
gracilis, 117 
of hand (short), 97 
hyoglossus, 328 
iliocostalis, 234 
iliopsoas, 118, 157, 203 
infraspinatus, 81 
intercostal, 206 
ischiocavernosus, 144 
of larynx, 255 
latissimus dorsi, 72, 82 
levator ani, 139, 146, 148 
palpebrae, 317 
palatini, 336 
scapulas, 73, 243 
lumbricle, 96 
masseter, 326 
mylohyoid, 245, 328 
obliquus abdominis externus, 151 
internus, 151 
capitis, 262 
oculi, 317 
obturators, 115 
occipitofrontalis, 268 
omohyoid, 245, 246 
orbicularis, 312 
palmaris longus, 94, 96 
pectineus, 117 
pectoralis, 77, 81 
peroneal, 130 
pharyngopalatine, 330 
platysma, 241, 313 
popliteus, 135 
pronator quadratus, 97 
pronator (radii) teres, 96 
psoas, 118, 157, 203 
pterygoid, 326 
pyriformis, 114 
quadratus femoris, 115 
lumborum, 153, 234 
quadriceps femoris, 118 
rectus, abdominis, 151 
capitis, 262 
femoris, 118 
oculi, 317 
rhomboids, 72, 243 
sacrospinalis, 234 
sartorius, 119 
scalene, 248 
semimembranosus, 119 352 
INDEX 
Muscles, specific-Cont'd 
semispinalis, 243 
semitendinosus, 119 
serratus anterior (magnus), 80, 
205 
soleus, 130 
sphincter ani, 140, 141, 164 
vesicae, 144, 148 
spinalis, dorsi, 234 
splenius, 243 
sternomastoid, 242, 244, 246 
sternohyoid, 245 
sternothyroid, 245 
subscapular, 81 
supinators, 102 
supraspinatus, 81, 82 
temporal, 326 
tensor faciae latae, 116 
palatini, 336 
teres, 81, 82 
thyrohyoid, 245 
tibialis, anterior, 129 
posterior, 130 
transversus abdominis, 151 
trapezius, 72, 243 
triceps brachii, 83, 86 
vastus, 118 
Myelencephalon, 290 
Myelin, 61 
Myocardium, 223 
N 
Nails, 30, 94, 127 
Nares, 312, 331 
Nasopharynx, 253, 335 
Nasus, 331 
Navel, 150 
Neck, 240 
Nerves (nervi): 
general discussion, 61, 77, 113, 153, 
207, 251, 276, 282 
specific, abducent, 276, 278, 280, 
294, 299 
accessory, 251, 276, 278, 294, 299 
acusticus, 276, 278, 294, 299, 341 
alveolar, 324, 327 
auditory (see acustic) 
auriculotemporal, 268, 327 
cerebral, 251, 276 
cervical, 251 
cochlear, 341 
cranial, 251, 276 
dental, 327 
facial, 276, 294, 299, 313, 325, 342 
femoral, 119 
glossopharyngeal, 251, 276, 278, 
294, 299 
Nerves, specific-Cont'd 
gluteal, 115 
hemorrhoidal, 142 
hypoglossal, 245, 251, 276, 278 
294, 328 
intercostal, 207 
ischiadic, 113, 133, 203 
laryngeal, 225, 253, 256 
median, 87, 100 
musculocutaneous, 87, 100 
musculospiral, 86, 100 
obdurator, 118 
occipital, 269 
oculomotor, 276, 277, 294, 299 
317 
olfactory, 276, 277, 294, 298, 335 
optic, 276, 277, 299, 318, 320 
peroneal, 133 
phrenic, 213, 248, 251 
plantar, 134 
pneumogastric (see vagus) 
popliteal, 120, 133 
pudendal (pubic), 141 
radial, 87, 100, 102 
sciatic, 113, 133, 203 
spinal, 64, 77, 113, 207, 235, 237, 
251 
spinal accessory (see accessory) 
sympathetic, 63, 77, 113, 173, 229, 
251, 282 
thoracic, 207 
tibial, 133, 134 
trigeminal, 268, 276, 277, 278, 294, 
299, 314, 317, 327, 335, 342 
trochlear, 276, 277, 294, 299, 317 
ulnar, 87, 88, 99 
vagus, 225, 244, 251, 276, 278, 294, 
299 
vestibular, 342 
Nervous systems, central, 63, 280 
peripheral, 63, 285 
sympathetic, 63, 77, 113, 173, 229, 
251, 282 
Neuroblasts, 281 
Neuroglia, 282 
Neuron, 61, 282 
Nose, 312, 331 
Notochord, 281 
Nuclei, of encephalon, 293, 303, 305 
Nucleus, caudate, 305, 306 
of cells, 20 
lentiform, 305, 306 
O 
Oculus, 319 
Oesophagus, 210, 225, 229, 253 
Olecranon, 86, 90 
Omentum, 161, 166 INDEX 
353 
Orbita, 314 
Organon auditus, 338 
olfactus, 331 
visus, 319 
Origin, 40 
Oropharynx, 253, 328, 330 
Os or Ossa: 
general discussion, 42, 105 
specific, astragalus, 125 
atlas, 260 
axis, 260 
calcaneus, 125 
carpal, 92 
clavicle, 67 
coccyx, 68 
conchae (nasal), 333 
costae, 73 
coxae, 108, 109 
cranial, 264, 269, 273, 309, 314, 
329, 332 
cuboid, 125 
cuneiform, 125 
epistropheus, 260, 262 
ethmoid, 274, 277, 332 
femur, 111 
fibula, 123 
frontal, 265, 274, 309, 314 
humerus, 68 
hyoid, 241, 255 
ilium, 108 
innominate, 108 
ischium, 108 
lacrimal, 315 
malar, 309 
mandible, 240, 309, 323 
maxilla, 309, 329, 332, 333 
metacarpals, 92 
metatarsals, 125 
nasal, 309 
navicular, 125 
occipital, 260, 266, 274 
palatine, 329, 332 
parietal, 265, 266, 269 
patella, 118 
phalanges, of foot, 125 
of hand, 93 
pubis, 108 
radius, 92 
ribs, 73 
sacrum, 68, 108 
scaphoid, 125 
scapular, 65 
sesamoid, 119 
sphenoid, 265, 275, 277, 278, 332, 
334 
sternum, 73 
talus, 125 
tarsal, 125 
Os or Ossa, specific-Cont'd 
temporal, 266, 273, 275, 280, 338 
tibia, 123 
turbinates, 333 
ulna, 90 
vertebrae, 68, 231, 240, 260 
vomer, 332 
of wrist region, 92 
zygomatic, 265, 309, 314 
Ossicles, auditory, 339 ' 
Ossification, of bone, 44 
Osteoblasts, 46 
Osteoclasts, 47 
Ovary, 202 
Oviducts, 201 
Ovum, 22, 201 
P 
Pacchionian bodies, 270, 302 
Palate, 329 
Palm, 94, 101 
Palpebrae, 315 
Pancreas, 162, 186 
Panniculus adiposus, 34 
Papilla, 184, 195, 224 
Parathyroids, 252 
Parietal, 162, 211 
Parietal bones, 265, 269 
Parotid, 325 
Patches, Peyer's, 177 
Patella, 118 
Pathology of (see structure) 
Penduncles, of cerebrum, 298 
Pelvis, 108 
Penis, 142 
Pericardium, 221, 224 
Peripheral nervous system, 63, 285 
Perineum, 110, 138, 148 
Periostium, 269, 314, 333 
Peritoneum, 154, 160, 167 
Pes (pedis), 123 
Phalanges, of foot, 125 
of hand, 93 
Pharynx, 253, 257, 328, 330, 335 
Physiology of (see structure) 
Pia mater, 237, 302 
Pigment, 30, 321 
Pili, 30 
Pisces, 23 
Pituitary body, 279, 300 
Placenta, 178, 220 
Plane, frontal (coronal), 267 
sagittal, 267 
transversal (horizontal), 153, 267 
Plantar, 127 
Plasma, 53 
Pleura, 206, 211 354 
INDEX 
s 
Sacrum, 68, 108 
Sagittal, 267 
Salivary glands, 325, 328, 329 
Sanguis, 52 
Saphenous, 115, 158 
Scalp, 268 
Scapula, 65 
Sclera, 319 
Scrotum, 142 
Segmentation, 23 
Sella turcica, 275, 279 
Seminal vesicles, 199 
Septum or septa, general, 36 
specific, of atria (auricles), 218. 
222 
intermuscular, 36 
intergroupal, 36 
nasal, 331 
pellucidum (lucidum), 300, 303 
ventricular, 218, 224 
Serosa, 160, 162 
Sheaths, flexor tendon, 95, 128 
Sinus or sinuses: 
air sinuses, 333 
ethmoidal, 333 
frontal, 333 
mastoid, 340 
maxillary, 333 
sphenoidal, 334 
venous, sinuses, 272, 277, 280, 302, 
307 
cavernous, 278, 318 
petrosal, 278 
sagittal (longitudinal), 272, 302 
transverse (lateral), 273, 340 
rectus (straight), 272, 301 
Skeleton, 23, 42 
Skin, 27 
Skull, 264, 269, 274, 309, 314, 329, 332 
Sole, of foot, 127 
Spermatozoa, 22, 199 
Spinal (vertebral) column, 68, 231 
cord, 235, 280, 283 
nerves, 64, 77, 113, 207, 235, 237, 
251 
Spines general, 48, 67, 68, 70 
specific (see particular bone) 
Sphenoid, 265, 275, 277, 278, 332, 334 
Sphincter muscles, 140, 144, 148, 164, 
168 
Splanchnic nerves, 230 
Spleen, 162, 188 
Stapes, 329 
Sternum, 73 
Sthenic, 208 
Stomach, 162, 168 
Plexus or plexuses: 
general discussion, 64 
specific, brachial, 77, 87, 251 
chorioid, 291, 301 
lumbosacral, 113, 133, 203 
prevertebral, 230 
sympathetic, 230, 231, 251 
visceral, 231 
Plica vocalis, 258 
Pollex (pollicis), 97 
Pons (Varolii), 297 
Popliteum, 120 
Porta, of liver, 180 
Posterior, 24 
Prepuce, 144 
Primitive (see organ) 
Process (processus), general, 48 
specific, (see particular bone) 
clinoid, 271, 275 
mastoid, 240, 340 
Processes vermiformis, 171 
Profundus (deep), 25 
Pronation, 95 
Pronephros, 193 
Proscencephalon, 290 
Prostate, 198 
Protuberance, occipital, 240, 272 
Proximal, 93 
Pterygoid region, 326 
Ptosis, 210 
Pubis, 108 
Pudendum, 146 
Pulmo, 211, 213, 215 
Pupil (pupilla), 321 
Pylorus, 168 
Pyramids, of medulla, 293 
R 
Radius, 92 
Radix (radicis), arcus vertebrae, 232 
nervi, 284 
penis, 142, 143 
Ramus, of pubis and ischium, 111 
Recaptaculum chyli, 229 
Rectum, 139, 172 
Reflex, brain stem, 294 
spinal cord, 285 
Ren (renal), 193 
Reproduction, of cells, 22 
Reproductive organs, female, 146, 201 
male, 142, 198 
Reptilia, 23 
Respiration, 207 
Retina, 320 
Rhombencephalon, 290 
Rib, 73, 206 
Rima, (pudendi), 146 
Rings, abdominal wall, 156, 158 INDEX 
355 
Styloid processes, 104 
Subcutaneous fatty layer, general, 34 
specific (see region) 
Substantia nervosa alba, 284, 288, 292 
grisea, 284, 288, 292 
Submucosa, 32, 162, 163, 177, 184, 185, 
338 
Sulci cerebri, 292, 270, 273, 296 
Sulcus, central, of Rolando, 296, 300 
Superficial, 24 
Superficial venous system, 35, 58, 83, 
115, 150, 241 
Superior, 24 
Supination, 96, 101 
Suprarenal glands, 162, 197 
Shrgical (see region) 
Suture (sutura), 264, 267 
Symmetry, bilateral, 23 
Sympathetic nervous system, 63, 77, 
113, 173, 229, 251, 282 
Symphysis pubis, 108, 238 
Synarthrosis, 49, 264 
Synovia, 50 
T 
Talus, 125 
Tarsal bones, 125 
Tarsus, 315 
Teeth, 324 
Tela choroidea, 291, 301 
submucosa, 32, 162, 163, 177, 184, 
185, 338 
Telencephalon, 291 
Temporal bone, 266, 273, 275, 280, 338 
Tendon, general, 40 
specific (see particular muscle) 
Tentorium, cerebelli, 271, 278, 298 
Testis (testicle), 142, 199 
Thalamus, 305 
Thigh, 115 
Thorax, 205 
Thumb, 97 
Thymus, 210, 231 
Thyreoid, 252 
Tibia, 123 
Tissue, general discussion, 25 
orpolor 34 
white fibrous, 28, 36, 39, 42, 46 
connective, 50, 55, 61, 223 
yellow elastic, 28, 53, 233 
connective, 
Toes, 125 
Tongue, 330 
Tonsils (tonsilla), 330, 335, 336 
Trachea, 210, 213, 225, 229 
Tracts, of brain, 292 
of spinal cord, 287 
Transversus (horizontal), 153 
Triangles, of neck, 244, 246 
Trigone, of bladder, 197 
Trochanter, 111 
Trunk (truncus), sympathetic, 229, 
251 
Tube, auditory (Eustachian) 335, 339 
uterine (Fallopian), 161, 201 
Tuber, tuberosity, tubercle: 
general discussion, 48, 68, 110 
specific (see particular bone) 
Tubules, of kidney, 194 
of testicle, 199 
Tunic (tunica), albuginea, 188, 199 
mucosa, 32, 162, 175, 336 
muscularis, 32, 38, 162, 184, 198, 253 
serosa, 161, 162, 163, 167, 184, 198 
Turbinates, 332 
Tympanum, 339 
U 
Ulna, 90 
Umbilicus, 150 
Ungues, 30, 94, 127 
Urachus, 179, 197 
Ureter, 194, 197 
Urethra, 142, 146, 197, 199 
Urogenital apparatus, 138, 193 
Uterus, 146, 167, 201 
Uvula palatina, 330 
V 
Vagina, 146, 201 
Vaginae tendinis, 95, 101, 128 
Valve (valvula), 58, 217, 218, 223 
aortic semilunar, 219, 223 
bicuspid, 219, 223 
mitral, 219, 223 
pulmonary semilunar, 219, 223 
tricuspid, 219, 223 
of veins, 58, 218 
Vas deferens, 199 
Vasa sanguinea, 52 
Vasa lymphatica, 59 
Vein (vena): 
general discussion, 35, 52, 83 
specific, anonyma, 227, 247 
azygos, 193, 227 
basilic, 84 
cava, inferior, 191, 218 
superior, 218, 227 
cephalic, 83 
comitans (comitantis), 57 
ductus venosus, 180 
emissary, 273, 277, 278, 307, 318, 
340, 343 
hemorrhoidal, 142, 183 
hemiazygos, 193, 227 
innominate, 227, 247 
jugular, 227, 241, 247, 273 356 
INDEX 
Vein, specific-Cont'd 
median, 83 
portal, 180, 183 
pulmonary, 214, 218, 219, 222 
saphenous, 115 
umbilical, 179, 220 
vitelline, 179 
see also sinuses (venous) 
for others, see arteries of same 
name. 
Venules, 54 
Ventral, 24 
Ventriculus, 168 
Ventricles, of brain, 291, 301, 303, 
305 
of heart, 218, 223 
Vertebrae, 68, 231, 240, 260 
Vertebrates, 23 
Vesica fellea, 183, 163 
urinarius, 197, 163 
Vesicles, cerebral, 289 
seminal, 199 
Vestibule, of internal ear, 341 
of larynx, 258 
of vagina, 146 
Villi, of intestines, 175, 177 
of placenta, 178 
Visceral, 162, 211 
Vitelline, 179 
Vitreous body, 322 
Vocal, 255 
Volar, 98 
Vomer, 332 
Vulva, 146 
W 
White fibrocartilage, 44, 233 
White fibrous tissue, 28, 36, 39, 42 
46, 50, 55, 61, 223 
White nervous substance, 284, 288 
292 
Wolffian body, 193 
Womb, 146, 167, 201 
Wrist, 92, 104 
X 
Xiphoid, 73 
Y 
Yolk sac, 179 
Z 
Zygomatic bone, 265, 309, 314