Anatomy and Physiology 
for Nurses AMY ELIZABETH POPE 
ESSENTIALS OF DIETETICS 
A QUIZ BOOK FOR NURSES 
ANATOMY AND PHYSIOLOGY FOR NURSES 
MEDICAL DICTIONARY FOR NURSES 
(With Anna Caroline Maxwell) 
PRACTICAL NURSING Text-Book 
of 
Anatomy and Physiology 
For Nurses 
By 
Amy E. Pope 
Graduate of the School of Nursing of the Presbyterian Hospital 
in the City of New York; Special Diploma in Education from 
Teachers College, Columbia University, New York; Form- 
erly Instructor in the School of Nursing, Presbyterian 
Hospital; Formerly Superintendent of the Insular School 
of Nursing, San Juan, Porto Rico; Instructor in 
School of Nursing, St. Luke's Hospital, San Fran- 
cisco, Cal. Author of " A Medical Dictionary 
for Nurses." Joint Author of " Practical 
Nursing," " A Quiz Book of Nursing," 
" Essentials of Dietetics " 
With 155 Illustrations 
Second Edition, Revised'and Erilar^d 
G. P. Putnam's Solns 
New York and London 
Ube Iknfckerbocker " press' 
1915 Copyright, 1913 by 
AMY E. POPE 
Copyright, 1915 by 
AMY E. POPE 
(For Revised Edition) 
'Ebe Iknfckcrbockcr Jprcse, Iftcw Korb PREFACE TO SECOND EDITION 
The material of the first edition of Anatomy 
and Physiology for Nurses has been thoroughly 
revised for this new edition and a number of 
questions for each chapter have been inserted at 
the end of the book. My thanks are due to Dr. 
F. G. Inman, of San Francisco, for helping me 
with the revision. 
Amy Elizabeth Pope. PREFACE 
If nurses are to render intelligent and interested 
assistance in the research work that is becoming 
an ever increasingly large item of hospital routine, 
and to do the teaching of hygiene and sanitation 
expected of them in connection with social-service 
work, it is necessary that they be well grounded in 
the principles of physiology. In the hope of help- 
ing in this instruction, I have sought to collect from 
the latest authorities on physiology the facts re- 
lating to this subject that seemed to me to be of 
importance for nurses to know, and to put these 
facts into as concise and simple language as possible. 
In order not to make the book too large, I have 
omitted some of the details of anatomy given in 
many of the text-books of anatomy and physiology 
for nurses, but nothing, I think, that it is of 
importance for nurses to remember or that it is 
necessary for them to know in order to understand 
the functioning of the body. 
My thanks are due to the W. B. Saunders Com- 
pany for their courtesy in allowing me to use 
illustrations and to quote from A Text-Book of 
Physiology by William H. Howell, Ph.D., M.D.; 
to William Wood & Company for allowing me to 
V VI 
Preface 
use illustrations and quote from Kirk's Handbook 
of Physiology ; and to Lea & Febiger for allowing 
me to do the same from A Text-Book of Anatomy 
by American Authors, edited by Frederic Henry 
Gerrish, M.D. 
Amy Elizabeth Pope. CONTENTS 
CHAPTER PAGE 
I.-Nature of the Composition of the 
Body ...... i 
II.-Divisions of the Body ... 12 
III.-Tissues ...... 20 
IV.-Bone or Osseous Tissue . . 36 
V.-The Joints or Articulations . . 86 
VI.-Muscular Tissue .... 99 
VII.-Nerve Tissue and the Nervous 
System ..... 140 
VIII.-Nervous System (Continued) . .163 
IX.-Nervous System (Continued) . .187 
X.-Membranes ..... 204 
XI.-Circulating Fluids of the Vascular 
System ..... 215 
XII.-The Vascular System (Continued) . 238 
XIII.-The Vascular System (Continued) . 258 
XIV.-The Vascular System (Continued) . 279 
VII VIII 
Contents 
CHAPTER PAGE 
XV.-The Respiratory Organs and 
Respiration .... 297 
XVI.-The Glands ..... 327 
XVII.-The Digestive System . . . 340 
XVIII.-Food, Digestion, Absorption . 370 
XIX.-Metabolism, Heat Regulation . 395 
XX.-Elimination . . . . .416 
XXI.-The Skin and its Appendages . 438 
XXII.-Sensations ..... 452 
XXIII.-The Eye and the Sense of Vision 459 
XXIV.-The Ear and the Sense of Hearing 478 
XXV.-The Organs of Generation . 489 
XXVI.-Development. Senescence. Physi- 
ology of Sleep . . .518 
Glossary ..... 527 
Questions ..... 543 
Food Values of Food Materials 
and Prepared Foods . . 586 
Index ...... 589 T ext-Book 
of 
Anatomy and Physiology 
For Nurses Text-Book of 
Anatomy and Physiology 
CHAPTER I 
NATURE OF THE COMPOSITION OF THE BODY 
The Principal Branches Relating to the Study of the Structure 
and Functioning of the Body. Relation of Chemistry and Physics 
to Physiology. Nature of the Phenomena of Life. Chemical 
Composition of the Animal Body. Nature of Proteins, Carbo- 
hydrates, Fats. Inorganic Constituents of the Body. Nature of 
Plant and Animal Cells. Unicellular Animals and Plants. Cell 
Division. Life-Cycle of Cells. Difference in Cells. 
I. The chemical nature and the life processes 
of man, the lower animals, and plants are much 
more similar than might be expected from their 
outward appearance, and much of the knowledge 
of the structure and functioning of the human 
body has been obtained from the study of the 
so-called lower forms of life. For these reasons the 
names of many of the branches into which such 
study has been divided are similar for both plants 
and animals, including the human animal, as can 
be seen by the following names and definitions: 
1 2 
Anatomy and Physiology 
2. Biology1 is the science which treats of life 
and all living things. Its two principal divisions 
are Zoology,2 the science treating of animal life, 
and Botany,3 the science treating of plant life. 
The main subdivisions of these sciences are Ana- 
tomy, 4 Physiology,5 Embryology,6 and Histology.7 
3. Anatomy, literally, means the act or process 
of dissecting an organized body, either animal or 
vegetable, with a view to ascertaining its internal 
organization. Technically, the word stands for 
the knowledge of the structure of organized bodies 
obtained by their dissection. Anatomy is divided 
into Animal Anatomy and Vegetable Anatomy; 
and Animal Anatomy is again divided into Human 
Anatomy and Comparative Anatomy, the latter 
being that branch of the science which compares 
the structure of the human with that of the lower 
animals. 
4. Physiology is the science which treats of 
the various functions of animal and vegetable 
organisms and of the changes which take place in 
such bodies, as the result of the performance of 
their functions. The subdivisions of physiology 
are the same as those of anatomy. 
1 From the Greek bios-course of life, and logos-a discourse. 
3 From the Greek zoon-a living creature, and logos-a dis- 
course. 
3 From the Greek botane-grass. 
4 From the Greek ana-up, and temno-to cut. 
s From the Greek physiologia-an enquiry into the nature of 
things. 
6 From the Greek embryon-an embryo, and logos-a discourse. 
7 From the Greek histos-a web or tissue, and logos. The Composition of the Body 
3 
5. Embryology is the science which treats of 
the formation and growth of living organisms, from 
the moment of their coming into being until they 
are fully developed. 
6. Histology is sometimes called microscopic 
anatomy. It is the science which deals with the 
minute or microscopical structure of organic 
bodies. 
7. Relation of Physiology to Chemistry 
and Physics.-The sciences of Chemistry and 
Physics are intimately connected with the science 
of Physiology. In fact, the animal body might 
well be likened to a chemical laboratory, for, from 
the moment of conception until long after death, 
chemical processes are incessantly taking place 
within it. 
8. Nature of the Phenomena of Life.- 
Until very recently it was thought that many of 
the more complicated life processes were due to a 
so-called vital principle-i. e., an unknown and 
undiscoverable phenomenon, quite distinct from 
any ordinary physical or chemical force. But 
increased knowledge and the improved facilities 
and equipment of modern laboratories have en- 
abled the chemist and the physiologist to under- 
stand enough of the processes occurring within 
the animal body to lead them to believe that the 
phenomena of life are dependent upon the working 
of much the same physical and chemical forces as 
are active in the rest of the world. 
9. Chemical Composition of the Animal Anatomy and Physiology 
4 
Body.-Analytical study of the animal body has 
shown that not only are the life processes taking 
place within it similar to those occurring in other liv- 
ing processes of nature, but that the body is made up 
of elements that are very common in nature, viz.: 
(chemical symbol of elements) 
Oxygen 0 
Carbon C 
Hydrogen H 
Nitrogen N 
Calcium Ca 
Phosphorus P 
Sulphur S 
Sodium Na 
Chlorine Cl 
Fluorine Fl 
Potassium K 
Iron Fe 
Magnesium Mg 
Silicon Si 
Copper Cu 
Lead Pb 
Aluminium Al 
io. The elements present in the animal body in 
greatest abundance are oxygen, carbon, hydrogen, 
and nitrogen. These constitute about 97 per cent, 
of the body. The most abundant of the metallic 
elements are calcium, sodium, and potassium. 
11. With the exception of O, H, and N, these 
elements are never found in a free or uncombined 
state in the animal body. O and H have been 
found in the blood, and N, as well as 0 and H, in The Composition of the Body 
5 
the intestines, but the bulk of these elements, as 
well as all of the others that enter into the composi- 
tion of the body or are present therein in any way, 
are found in the form of compounds. 
12. Nature of Compounds Composing the 
Animal Body.-The compounds constituting the 
animal body are of two kinds, namely: organic and 
inorganic.1 The organic compounds have been 
classified according to their chemical composition 
as nitrogenous or protein compounds and non- 
nitrogenous compounds. 
13. Nitrogenous Compounds.-The compo- 
sition of the nitrogenous or protein substances is 
very complex, and that of the majority of them is 
not known further than that they contain O H C N 
S and, generally, P and Fe. The principal protein 
compounds found in the animal body are various 
forms of albumin, globulin, gelatinoids, and what 
are known as derived proteins, viz.: the products 
of katabolism (breaking down) of the other pro- 
teins. The nature of these substances will be more 
fully discussed in the chapters on metabolism and 
nutrition, and in the glossary. 
1 Organic substances are those possessing life or those produced 
by living organisms and the term now includes also matter re- 
sembling the latter made by man, for the chemist has discovered 
means of making many compounds that it was once thought 
could be produced only as the result of living processes. As all 
such matter contains carbon, organic matter is often defined as 
" compounds containing carbon." There are, however, a few 
substances containing carbon (e. g., sodium carbonate) that re- 
semble and are classed with mineral matter and other com- 
pounds not endowed with life, as inorganic matter. 6 
Anatomy and Physiology 
14. Non-Nitrogenous Substances.-The 
non-nitrogenous organic substances are divided 
into two classes, viz.: Carbohydrates and Fats. 
15. Carbohydrates.-The principal carbo- 
hydrates found in plants are sugars, starch, cellu- 
lose, and gums. Of these only glucose (a simple 
sugar) and glycogen, also termed animal starch, 
are usually found in animal tissue. Glucose and 
glycogen are composed of C H O. The chemical 
formula for glucose is C6 HI2 O6, showing that 
each molecule1 of glucose is composed of six atoms 
of carbon, twelve atoms2 of hydrogen, and six atoms 
of oxygen. The chemical formula for glycogen is 
C6 HI0 05n. 
16. Fats.-Human fat is made up of three 
simple fats named stearin, olein, and palmitin; and 
each molecule of these simple fats consists of three 
molecules of a fatty acid and one molecule of 
glycerine.- The acid from which stearin is derived 
is known as stearic acid; the foundation of olein is 
oleic acid; and that of palmitin, palmitic acid. 
17. Fats are composed of the same elements as 
the carbohydrates, viz.: C O H, but the elements 
are present in different proportions from those in 
the carbohydrates, and the relative amounts vary 
in the different forms of fat. 
18. Inorganic Matter.-The inorganic 
matter present in the animal body consists of 
water, mineral salts, and gases. 
1 A molecule is the smallest part of a compound that can 
exist alone. 
2 An atom is the smallest part of an clement that can exist. The Composition of the Body 
7 
19. Water.-Water constitutes about 70 per 
cent, of the body weight, and it enters into the 
composition of both the fluids and the solid tissues 
of the body. Bone, which is one of the hardest 
tissues, contains approximately 50 per cent, of 
water. The chemical formula for water is H 2 0. 
20. Mineral Salts.--A salt is formed by the 
union of an alkali or base and an acid, and is 
named after the alkali and acid composing it.1 
Thus, calcium carbonate is a salt formed by the 
union of the base calcium (lime) and carbonic acid; 
sodium chloride is derived from the base sodium 
and hydrochloric acid; magnesium phosphate 
from the base magnesium and phosphoric acid; 
sodium sulphate from sodium and sulphuric acid, 
etc. 
21. The most important salts in the animal 
body are: 
Sodium 
n , 
Potassium 
Chlorides 
Calcium 
Potassium 
Sodium 
Carbonates 
Calcium 
Potassium 
Sodium 
Magnesium 
Calcium 
Potassium 
Sodium 
Phosphates 
Sulphates 
22. To recapitulate: The substance of the body 
is composed of some seventeen elements, which are 
formed by chemical union into certain organic and 
inorganic compounds that are classified as: 
1 See Glossary, for chemical definition and description of 
alkalies, acids, and salts. 8 
Anatomy and Physiology 
Organic 
Proteins 
Fats 
Carbohydrates 
Inorganic 
Mineral matter 
Water 
Gases 
As will be seen later, both animal and vegetable 
foods contain similar substances and from these 
man obtains the matter necessary for growth. 
Cells. 
23. From the chemist's standpoint the elements 
named in paragraph 9 are the units or fundamental 
parts of organic life. From the anatomist's point 
of view the cell is the unit. 
24. Nature of Plant and Animal Cells.- 
The term cell, from the Latin cella-a cavity-was 
used first by botanists who described1 the plant cell 
as " a more or less spherical body surrounded by a 
membrane wall and containing a smaller body 
termed a nucleus,2 which, in turn, encloses one or 
more still smaller bodies or nucleoli." This de- 
scription is partly true of many plant cells, but it 
has been found that the majority of animal cells 
have no wall and are, therefore, not cavities, but 
minute masses of what has been called protoplasm. 
Another erroneous idea formerly held was that the 
wall was the essential feature of cells, but, in reality, 
the wall is secreted by the protoplasm and serves 
merely for support. 
25. Nature of Protoplasm.-The protoplasm 
1 Handbook of Physiology, page 2, Kirke. Revised by 
Frederick C. Busch, B.S., M.D. William Wood & Company. 
2 See next paragraph. The Composition of the Body 
9 
of animal cells is a semi-fluid, usually colorless, 
substance which is not miscible with water. It 
consists principally of water, proteins, lecithin- 
a phosphorized nitrogenous fat,-cholesterin-a 
form of alcohol, and inorganic salts, such as the 
phosphates and cholorides of calcium, sodium, and 
potassium. When examined under the micro- 
scope the protoplasm of the majority of animal 
cells is seen to consist of an outer mass of granular 
substance which has been named cytoplasm, and, 
somewhere near the center of the mass, a dot of 
more solid substance, consisting largely of a net- 
work of fine fibers called the nucleus, in which are 
minute spherical bodies termed nucleoli. Also, 
there is near the nucleus a small body named the 
centrosome or attraction sphere, which plays an im- 
portant part in nuclear division. See paragraph 28. 
The protoplasm of the nucleus is called karyoplasm. 
26. Size of Cells.-The majority of animal 
cells are from 1 /3000 to 1 /300 of an inch in diameter. 
27. Unicellular Animals and Plants.-• 
Some exceedingly small animals and plants consist 
of but one cell. The amoeba is an example of the 
former, and bacteria of the latter. 
28. Cell Division. All the higher forms of 
life consist of many, many millions of cells, all of 
which have originated from a single cell called the 
ovum,1 that has become fecundated by a cell from 
1 From the Latin ovum-an egg. The germ from which off- 
spring are formed, which develops in the ovary of the female 
animal. 10 
Anatomy and Physiology 
the male animal, called the spermatozoon. Cells 
multiply by dividing in half and thus forming two 
cells which, likewise, divide, and so on. They do 
Fig. i. - Indirect division of cell 
(karyokinesis). (i) Resting cell. (2) Cell 
preparing to divide - two centrosomes. 
(3) Filaments of the fibers of the nucleus 
have been formed into what is known as 
the spindle. (4) Spindle has separated. 
(5) Nuclear material has separated. (6) 
Cell has divided. 
this in two ways, one of which is known variously 
as simple or direct division, and akinesis--from a 
Greek word meaning movement. The other 
method is known as indirect division or mitosis- 
from a Greek word meaning a thread,-or karyo- 
kinesis-from the Greek, movement of a kernel. 
In direct division the nucleus and cytoplasm be- The Composition of the Body 
11 
come constricted in the center and then split in 
half. In indirect division, which is the almost 
universal method, a series of changes is undergone 
in the fibers of the nucleus before division of 
either nucleus or cytoplasm takes place. Some- 
thing of the nature of these changes can be seen 
in Figure I. 
29. Life-Cycle of Cells.-Cells are not only 
constantly multiplying; they are as constantly 
dying. Every cell grows, produces other cells, 
and dies, going through the same, though briefer, 
cycle, as does the whole living organism, either 
vegetable or animal. It is this fact that gave rise 
to the saying: "The human body undergoes a com- 
plete change in the course of every seven years. " 
The breaking down-katabolism1-and building 
up-anabolism2-of cells will be further discussed 
in the chapters on metabolism3 and the skin. 
30. Difference in Cells.-Cells are not all 
exactly alike, either in shape, chemical constitu- 
ents, or function, and the higher the animal is in 
the scale of life the greater will be the variety of 
the cells composing it, and the more complex and 
highly specialized some of these cells will be. Cer- 
tain of the important points of difference will be re- 
ferred to in the chapters describing the various kinds 
of tissue of which the human body is composed. 
1 From the Greek katabole-a throwing down. 
3 From the Greek anabole-a throwing up. 
3 From the Greek metabole-a change. The chemical changes 
of katabolism and anabolism are constantly going on in the body. CHAPTER II 
DIVISIONS OF THE BODY 
Organs. Systems. Anatomical Position. Surfaces of the 
Body. Main Divisions of the Body. Cavities and Organs in 
Each Cavity. Regions of the Abdomen. Words Used in De- 
scribing the Location of Different Parts of the Body. 
3i. Organs.-As stated in the preceding chap- 
ter, the animal body consists of an aggregation of 
cells formed into tissues of varying nature. . Many 
of these tissues are in turn moulded into organs, 
i. e., parts capable of performing some special 
function-as the heart, stomach, lungs, etc. 
32. Systems.-Each individual organ of the 
body has its own work to perform, but in no case 
is one organ sufficient for the carrying on of any 
one complete function of the body, and the organs 
that are dependent upon each other for the per- 
fecting of their functions are in* description grouped 
together in what are called systems, e. g., the cir- 
culatory system, the respiratory system, etc. 
Even the systems of the body are dependent upon 
each other for the carrying on of their work, e. g., 
all the organs are dependent upon the circulatory 
system for their existence, and the functioning of 
12 Divisions of the Body 
13 
the various systems would be useless to the body 
as a whole were it not for the nervous system, 
which affords a species of telegraphic communica- 
tion between the different parts of the body, so 
that all can work in harmony. 
In several instances one organ forms a part of 
more than one system; thus, the pharynx is an 
adjunct of the organs of speech, of the respiratory 
system, and of the digestive system. 
33. On account of this interdependence of the 
different organs and systems it is important for 
the student, before taking up their study in detail, 
to gain a general idea of the comparative location of 
the several parts of the body, and this can be best 
done by a careful inspection of the skeleton and of 
the manikin, or, if such are not to be had, of the 
various plates in this book. Also, it is necessary 
to know the names that anatomists have given to 
the surfaces and cavities of the body in order to 
facilitate description and the localizing of organs. 
These are as follows: 
34. The Anatomical Position.-Those de- 
scribing the various surfaces and regions of the body 
always consider the figure as standing with the 
face toward the observer, the palms of the hands 
turned forward. This constitutes what is known 
as the anatomical position. 
35. Surfaces of the Body.-With the figure 
in the anatomical position, the front surface-i. e., 
the surface facing the observer-is called the 
anterior or the ventral surface; and the back, the Fig. 2.-Front view of a man in the anatomical position. On 
one lateral half the parts are labelled in English, on the other in 
Latin. The right upper limb is drawn away from the trunk in 
order to show the arm more fully than is possible when it hangs 
perpendicularly. 
14 Divisions of the Body 
15 
posterior or the 
dorsal surface. 
36. Divisions 
of the Body.- 
The main divisions 
of the body are the 
head, the neck, the 
trunk or torso, and 
the upper and lower 
extremities. The 
trunk is divided 
into the chest or 
thorax, abdomen, 
pelvis. Each up- 
per extremity or 
limb is divided into 
the arm-the part 
between the shoul- 
der and the elbow 
-the forearm, and 
the hand. Each 
lower extremity is 
divided into the 
thigh-the portion 
between the hip- 
bone and the knee 
-the leg, and the 
foot. For the lo- 
cation of these and 
minor divisions see 
Figs. 2 and 3. 
Fig. 3.-Back view of a man. On 
one lateral half the names of the parts 
are given in English, on the other in 
Latin. 16 
Anatomy and Physiology 
yj. Body Cavities.-The cavities of the body 
and the organs in each cavity are as follows: 
Body Cavities. 
Organs in Cavity. 
Dorsal 
cavity 
Cranial cavity 
Spinal cavity 
Brain 
Spinal cord 
Tongue 
Teeth 
Salivary glands 
Tonsils 
Buccal cavity 
Nasal cavity 
Esophagus 
Trachea 
Lungs 
Heart 
Blood and 
lymph vessels 
Thoracic cavity 
V entral 
cavity 
Stomach 
Spleen 
Pancreas 
Liver 
Gall-bladder 
Kidneys 
Large and small 
intestines 
Abdominal cavity 
Urinary bladder 
Rectum 
(Female) Generative organs 
Pelvic cavity 
38.-Regions of the Abdomen.-For the pur- 
pose of description, the abdomen is considered as 
being divided into nine regions, namely: the right Divisions of the Body 
17 
hypochondriac,1 the epigastric,2 the l$ft hypochon- 
driac, the right lumbar,3 the umbilical4 the left 
lumbar, the right inguinal,5 the hypogastric, and 
the left inguinal. The relative position of these 
regions can be seen in Fig. 4. The regions will be 
further discussed in connection with the organs of 
digestion, Chapter XVII. 
Words Used in Describing the Location of 
Different Parts of the Body. 
39. Medial and Lateral.-By medial is 
meant the part nearest what is known as the median 
line, i. e., an imaginary line drawn through the 
middle of the head and trunk to the floor between 
the feet; and by lateral, the part farthest from the 
line. 
40. Internal and External.--These words 
are often used instead of medial and lateral, but 
are also employed to designate within and without 
the body. 
41. Proximal and Distal.-The former word 
is used in referring to position near the head or 
source of any part, and the latter to position 
farthest from the head or source. 
1 Hypochondriac, from the Greek hypo-under, and chondr os- 
a cartilage. The hypochondriac regions are under the cartilage 
of the ninth rib. 
2 Gastric, from the Greek gastro-the belly, and epi-over. 
3 Lumbar, from the Latin lumbaris-the loin. 
Umbilical, from the Latin umbilicus-the navel. 
s Inguinal, from the Latin inguinalis-the groin. Fig. 4.-Diagram of Thoracic and Abdominal Regions. 
A. Aortic valve. 
M. Mitral valve. 
P. Pulmonary valve 
T. Tricuspid valve. 
Heart 
Heart 
18 Divisions of the Body 
19 
42. Periphery.1-This means the outer cir- 
cumference, the part farthest from the center. 
43. Afferent 2 and Efferent. 3-These two 
words are used more especially in connection with 
the nerves and blood-vessels; afferent means to 
carry to, and efferent to carry from. 
44. Centripetal 4 and Centrifugal. 5-The 
former means traveling toward the center; the 
latter, receding from the center, i. e., toward the 
periphery. 
1 From the Greek periphereia-the circumference of a circle. 
2 From the Latin ad-to, and ferre--to carry. 
3 From the Latin ef-out, and ferre-to carry. 
From the Latin centrum-center, and petere-to seek. 
5 From the Latin centrum-center, and fugere-to flee. CHAPTER III 
TISSUES 
Origin of Tissue. Nature and Definition. Classification. 
Epithelial Tissues: Nature, Varieties, Location, Function. 
Connective Tissues: Varieties, Reason for Classification, Dis- 
tribution. Fibrous Tissue: Varieties, Nature, Distribution, and 
Purpose of Each Variety. Tendons. Ligaments. Fascia. Apo- 
neuroses. Adipose Tissue: Distribution, Structure, Uses. 
Lymphoid, Retiform, or Adenoid Tissue: Structure, Purpose. 
Cartilage: Varieties, Nature, Use, and Location of Each Variety. 
45. Origin of Tissue.-Every cell of the ani- 
mal body is descended from one cell, the female 
germ cell or ovum, that has been made fertile1 by 
the entrance of a male cell-the spermatozoon. 
A human ovum measures about 0.2 mm.-tIk 
of an inch-in diameter. It is surrounded by a 
transparent membrane. Its cytoplasm contains 
numerous yolk or vitellus granules intended for 
food for the embryo in the very early stages of 
development. In the midst of the cytoplasm is 
the nucleus or germ vesicle and within this is the 
nucleolus and a substance called chromatin. The 
male cell also contains chromatin. The chromatin 
develops into threads called chromosomes and these 
1 See Chapter XXV. 
20 Tissues 
21 
contain the principle that transfers hereditary 
traits from parents to offspring. After impregna- 
tion takes place the ovum divides and subdivides 
until the number of cells increases to many mil- 
lions. At first these cells appear to be all alike, but 
after a few days they become arranged into three 
distinct layers, see Fig. 135, and the nature and 
purpose of each layer are different from those of 
the others. From the outermost layer-called the 
epiblast 1-the skin and nervous tissue are derived. 
The innermost layer-the hypoblast2-is the source 
of the greater part of the alimentary and respira- 
tory tracts, the liver, pancreas, and other glands. 
From the middle layer-the mesoblast 3-the circu- 
latory and urino-genital systems, also the muscles, 
bones, and other connective tissues of the body are 
developed. 
46. Thus it can be see that the structure of the 
body consists for the most part of masses of cells 
derived from a single cell,4 and that these cells 
have various shapes and special characteristics 
which enable them to perform their functions. 
47. Nature and Definition of Tissue.- 
The cells are held together either by a cement-like 
substance derived from the cells and called inter- 
cellular substance, or else by anastomosing pro- 
1 From the Greek epi-upon, and blastos-a sprout germ. 
2 From the Greek hypo-below, and blastos-a sprout germ. 
J From the Greek mesos-middle. 
4 The ovum and spermatozoon combined are usually considered 
as one cell, because neither one alone contains all the essentials 
necessary for cell division and growth. 22 
Anatomy and Physiology 
cesses on the surface of the cells. The substance 
formed by these aggregations of cells is called 
tissue. Literally tissue means a web-like structure 
or a woven fabric, but as the word is used in 
anatomy it stands for any organized1 substance in 
the body. 
48. Classifications of Tissues.-According 
to the purpose which the various kinds of tissue 
serve in the body, they have been classified as: 
(1) Epithelial tissues: tissues covering the free 
surfaces of the body; 
(2) Sustentacular or connective tissues: tissues 
passively supporting and connecting other parts as: 
Fibrous tissue 
Adipose tissue 
Lymphoid, retiform, or adenoid tissue 
Cartilage 
Bone and dentine; 
(3) Liquid tissues: tissues performing a nutri- 
tive function, viz: blood and lymph; 
(4) Muscular tissues: tissues devoted to move- 
ment; 
(5) Nervous tissues: tissues essential to sen- 
sation. 
Epithelial Tissues 
49. Location.-Epithelial tissues are those 
which cover the surfaces of the body, e. g., the 
'The words organized and organic must not be confused. 
Organized tissue is that with a definite structure: it may consist 
of either organic or inorganic substances, or both. Tissues 
23 
outer or scarf skin; the covering of the mucous 
membrane, i. e., the membrane which lines those 
passages and cavities that communicate with the 
exterior of the body, as the alimentary canal, the 
respiratory and urinary organs; the covering of the 
serous membrane, i. e., the membranes lining the 
closed cavities of the body, as the thoracic cavity 
and the abdominal cavity. Epithelial tissue also 
lines the glandular organs. 
50. Nature.-Epithelial tissues consist of cells 
placed in close contact with each other and spread 
out so as to form a thin sheet of tissue known as 
epitheti/um. The cells composing this variety of 
tissue are of different shapes, and the 
tissue often receives its distinctive name 
from the shape of its cells. The only 
name of particular importance for nurses 
to remember is ciliated epithelium. 
51. Ciliated Epithelium. - The 
cells composing this form of epithel- 
ium are columnar in shape; they are 
packed closely together and have a 
number of small hair-like processes call- 
ed cilia extending from their free edge. 
The cilia have a constant vibrating mo- 
tion with a strong stroke in one direc- 
tion and a weak one in the other; this 
serves to protect the orifices and cav- 
ities which they line against the entrance of for- 
eign substances. This form of epithelium, in the 
adult, is found mainly in some of the respiratory 
Fig. 5. 
Two conoid- 
al epithelial 
cells, their 
free ends fur- 
nished with 
cilia. 24 
Anatomy and Physiology 
organs and in some of the organs of generation. 
In children it is found also in the central canal of 
the spinal cord and the ventricles of the brain. 
52. Functions of Epithelial Tissue.-The 
more common functions of epithelial tissue are 
protection, secretion, and sensation. 
Protection.-Epithelial tissue protects the body 
in several ways: (1) it affords an almost imper- 
meable covering for the body; (2) the vibratory 
movement of the cilia brush away foreign sub- 
stances from the cavities lined by that form of 
epithelium; (3) the epithelial cells covering the 
serous and mucous membranes take an active 
part in secreting the fluid which moistens, lubri- 
cates, and thus protects those membranes. 
Secretion- The cells of the epithelial lining of 
the glandular organs and, as stated in the preceding 
paragraph, those of the covering of the mucous and 
serous membranes are the active agents in the pro- 
cess of secretion that is characteristic of such organs 
and membranes. The process of secretion and the 
secretory organs will be described in Chapter XVI. 
Sensation.-In parts of the nose, mouth, eyes, 
and ears, in close connection with the terminal 
filaments of the nerves devoted to smell, taste, 
hearing, and sight, are cells called, by virtue of 
their office, sensory or neuro-epithelial cells. Such 
a cell is attached at one end to the peripheral 
ending of a sensitive nerve, and its free end, which 
is generally prolonged into a stiff, hair-like process, 
projects beyond the surrounding surface. Any Tissues 
25 
agitation in the media around these projections 
causes a vibratory movement in the cells which 
agitates the nerve endings and causes the nerves 
to carry impressions to the brain. 
The Sustentacular or Connective Tissues 
53. Tissues Belonging to Sustentacular 
or Connective-Tissue Group.-The tissues 
classified under this heading are: 
Areolar 
White 
Yellow or elastic 
Fibrous tissue 
Adipose or fatty tissue 
Retiform, adenoid, or lymphoid tissue 
Cartilage 
Bone, and dentine 
54. Reason for Classification.-Though 
some of these tissues vary considerably in their 
composition, they are all classed under the same 
heading: because (1) they are (as stated in para- 
graph 45) all developed from the same embryonal 
element; (2) they serve the same purpose in the 
body, namely: they act as a framework, as a 
support, and as a connecting link between the 
various parts and organs of the body; (3) they are 
all passive, i. e., they originate no action, they do 
nothing of themselves, but are active only when 
influenced by other tissues. 
55. Distribution.-Connective tissues are very 
widely distributed in the body; in fact, they Anatomy and Physiology 
26 
are so closely interwoven with its substance that 
if all other tissues were removed the connective 
tissues left would give a very exact though porous- 
looking model of every tissue and organ of the body. 
Fibrous Connective Tissue 
56. Varieties.-There are three main varieties 
of fibrous tissue: viz., areolar tissue, white fibrous 
tissue, and yellow or elastic tissue. 
Areolar Tissue 
57- Nature and Distribution.-If the skin of a 
Fig. 6.-Areolar tissue, com- 
posed of bundles of white 
fibrous tissue and branched 
strands of yellow fibrous tis- 
sue loosely intertwined. 
Fig. 7.---A portion of areolar 
tissue inflated and dried, show- 
ing areolse. 
dead animal is cut and raised in any part where 
there is not much fat, a filmy, tenacious, slightly Tissues 
27 
elastic mesh work of tissue will be seen holding the 
skin to the flesh beneath it. This is areolar tissue. 
It will be found also under mucous membrane, and 
investing the muscles, nerves, blood-vessels, and 
internal organs, and penetrating into the substance 
of the latter, holding their tissues together. 
58. Structure.-Examined under the micro- 
scope, areolar tissue appears to be composed of 
innumerable fine, wavy fibers or threads and 
bundles of such fibers interlacing each other in all 
directions, with open spaces between the fibers and 
various kinds of tissue cells in some of these spaces. 
59. Nature of White Fibrous Tissue.- 
White fibrous tissue' is a white, shiny, tough, pli- 
ant, but not elastic, 
tissue. Seen through 
the microscope it 
appears to consist of 
long, generally parallel 
bundles of fibers, with 
chains of cells separ- 
ating the bundles. 
60. Nature of 
Yellow Fibrous or 
Elastic Tissue.- 
The general structure 
of this form of fibrous 
tissue is very similar to that of the white, but it 
is usually of a yellowish color and is elastic. 
61. Elasticity of Tissue.-Both yellow and 
white fibers often enter into the composition of the 
Fig. 9.-Cells 
of white fibrous 
tissue, often 
called connec- 
tive-tissue cells. 
Fig. 8.-White 
fibrous tissue. Anatomy and Physiology 
28 
same tissue, and the degree of elasticity of the part 
will depend upon the proportion in which the two 
varieties of fibers are present. 
62. Function of Fibrous Tissue.-Fibrous 
tissue serves several purposes in the body: (1) It 
holds the bones together at their places of juncture 
or articulations; (2) It attaches muscles to the 
bones; (3) It connects the muscles to each other; 
(4) It envelops muscles and holds them, as well as 
other tissues, in place; (5) It serves as a support 
for blood-vessels, nerves, etc.; (6) It forms part of 
the substance of many of the body organs and 
membranes; (7) It forms the foundation for certain 
of the other tissues, as fat and bone. 
63. Different Shapes and Names of Fib- 
rous Tissue Holding Bones and Other Tissues 
Together.-The fibrous tissues which serve to 
connect bones, muscles, etc., are usually in the 
form of either broad sheets, bands, or cords, and 
are known as ligaments, 1 tendons2 or sinews, 
fasciae,3 aponeuroses,4 sheaths, or membranes. 
64. Ligaments-Nature and Purpose. -Liga- 
ments are strong, flexible bands of fibrous tissue, 
which serve chiefly to hold bones together at 
their places of joining or articulations. The liga- 
ments holding bones together at the freely mov- 
able articulations, as the shoulder and hip joints, 
1 Ligament. From the Latin ligamentum-a band. 
2 Tendons. From the Latin tendo-to stretch. 
3 Fascia. From the Latin fascia-a band. 
4Aponeuroses (sing, aponeurosis). From the Greek apo- 
from and neuron-a sinew or tendon. Tissues 
29 
where free movement but no extension is desired, 
are composed of the white variety of tissue. 
Those connected with joints where limited motion 
combined with extensibility is desired, as between 
the arches of the vertebras, consist of both yellow- 
elastic and white fibers. 
65. Tendons or Sinews-Nature.-Tendons 
are white, glistening, fibrous cords, some of which 
are flat and some round. The majority of them 
are composed chiefly of white fibers, but many of 
them contain a varying quantity of yellow fibers 
and are thus slightly elastic. Tendons are very 
sparingly supplied with nerves and blood-vessels. 
66. Function.-Tendons serve to attach muscles 
to bone, their fibers blending with fibers of the 
periosteum. The muscle, to the contraction of 
which the movement of the bones is due, is often 
"compared to an engine in which force is gener- 
ated; the tendons to the ropes by which the power 
is applied to distant objects.'' 1 
67. Fascia-Nature and Purpose.-Fasciae are 
sheets or broad bands of fibrous tissue. They are 
classified as superficial and deep. The former 
consists of the areolar tissue that holds the skin to 
the underlying tissue. The deep fasciae comprise 
the sheets of fibrous tissue which envelop the mus- 
cles and both separate them and hold them to- 
gether. The fascia covering the palms of the 
hands is known as palmar fascia, and that cover- 
1 Text-Book of Anatomy, page 259, Frederic Henry Gerrish, 
M.D. Lea Bros. Co. Anatomy and Physiology 
30 
ing the soles of the feet as plantar fascia. The 
palmar and plantar fasciae arc much thicker and 
stronger than the fasciae in other parts of the 
body. The more important of the other deep fasciae 
have been named either after the muscle they 
cover or the part of the body in which they are 
located. 
68. Aponeuroses-Nature and Piirpose.- 
Aponeuroses are virtually flat, wide tendons, and 
they serve very much the same purpose as the 
latter, but they connect the ends of muscles to 
each other, instead of to bones. 
69. Aponeuroses are destitute of nerves, and 
only the thicker ones are supplied with blood- 
vessels. 
Adipose Tissue 
70. Distribution.-Adipose or fatty tissue is 
Fig. io.-Fat-cells: a,filled 
with oil; b, exhausted of oil, 
the cell-wall shriveled. 
Fig. ii.-Fat-cells packed 
closely together, and thus be- 
coming polyhedral. 
found in nearly all parts of the body; exceptions are 
the substance of the lungs and liver, the subcutane- Tissues 
31 
ous tissue of the eyelids, penis,1 and scrotum.1 
71. Structure.-Adipose or fatty tissue con- 
sists of a number of closely packed vesicles, the 
walls of which are formed of an exceedingly deli- 
cate structureless membrane derived from areolar 
tissue. These vesicles which average about 1/500 
of an inch in diameter, are filled with fatty2 matter, 
which is liquid during life but becomes solidified 
after death. 
72. Uses.-Adipose tissue serves several pur- 
poses in the body: (1) It acts as a store of energy 
material for the body, for when the system requires 
matter for the production of heat and energy3 the 
fatty substance can be oxidized; (2) The fat under 
the skin, being a non-conductor of heat, prevents 
the too rapid loss of heat through the skin; (3) 
It fills spaces in the tissues and thus affords support 
for, and prevents pressure on, delicate structures 
such as blood-vessels and nerves; (4) Fat is col- 
lected in large masses around the kidneys and 
helps to retain them in place. 
Lymphoid, Adenoid, or Retiform Tissue 
73. Structure.-Lymphoid tissue, known also 
as adenoid and retiform tissue, consists chiefly of 
'See Chapter XXV., Organs of Generation. 
2 The nature of this fatty matter is discussed in paragraphs 16 
and I/. 
3 The production of heat and energy and oxidation are de- 
scribed in the chapters dealing with food, metabolism, and heat 
regulation. Anatomy and Physiology 
32 
a delicate mesh work1 of white fibers covered with 
flat cells. The interstices of the network are filled 
with lymph cells and the tissue is cemented to- 
gether with an almost fluid intercellular substance. 
Purpose.-Lymphoid tissue forms the stroma- 
i. e., the bed or principal part of the substance- 
of the spleen and lymphatic glands; also it enters 
into the composition of the thymus gland, the 
tonsils, some of the intestinal glands, and the 
mucous membranes. 
74. In childhood an abnormally large amount 
of this tissue often develops in the naso-pharynx2 
and the child is then said to have adenoids. Com- 
mon causes are colds and the sucking of pacifiers. 
Cartilage3 
75. Nature and Where Found.-Cartilage, 
commonly known as gristle, is an exceedingly 
tough, strong, and, except the white variety, 
elastic tissue. In the adult the cartilage is found 
chiefly in the joints, in the walls of the thorax- 
chest,-and in various tubes such as the air- 
passages, nostrils, and ears, which are to be kept 
permanently open. In the fetus the greater part 
of the skeleton is at first cartilaginous, and' this 
cartilage, as it is afterward replaced by bone, is 
called temporary cartilage, in contradistinction to 
1 The meshwork is sometimes called retiform tissue and the 
combined meshwork, cells, and intercellular substance, lymphoid 
or adenoid tissue. 
2 Described in paragraph 602. 
3 From from the Latin cartilago-gristle. Tissues 
33 
that which remains unossified during life, which is 
called permanent cartilage. 
76. Structure and Classification.-Carti- 
lage is composed chiefly of a substance known as 
collagen, which is resolved into gelatin by boiling. 
It consists of cells imbedded in an intercellular 
substance called the matrix.1 The matrix varies 
somewhat in composition, and according to this 
variation cartilage is known as: 
Hyaline2 cartilage 
Yellow-elastic carti- 
lage 
White fibro-cartilage 
77. Blood Sup- 
ply-Perichon- 
drium. 3-Cartilage 
is not supplied with 
either blood-vessels 
or nerves; the hyal- 
ine variety usually 
obtains its nutrient 
from the bones which it covers; the yellow and 
white cartilages from the vascular fibrous mem- 
brane called the perichondrium, which envelops 
them. 
Fig. 12.-White fibro-cartilage. 
Hyaline Cartilage 
78. Appearance of Matrix.-In appearance 
1 From the Latin mater-mother. 
2 From the Greek hyalos-glass. 
s From peri, a prefix used with words of Greek origin, meaning 
about, around; and chondrin-a cartilage. 34 
Anatomy and Physiology 
the matrix of hyaline cartilage resembles ground- 
glass, being slightly transparent but somewhat 
granular. 
79. Uses and Distribution.-(1) Hyaline carti- 
lage covers the articulating surfaces of bones for 
the purpose of preventing friction between the 
moving parts. Cartilage serving this purpose is 
called articular cartilage. (2) The hyaline variety 
of cartilage forms the costal cartilages1 which 
serve to prolong the ribs forward to the sternum. 
Costal cartilage being very strong and elastic, 
though more yielding than bone, helps very con- 
siderably in the respiratory movements of the 
chest walls. (3) Hyaline cartilage forms also an 
important part of the structure of the nasal 
passages, the larynx,1 trachea,1 and bronchi,1 and 
being tough, hard, and firm it serves to maintain 
their shape and to afford an attachment for their 
muscles. 
Yellow-Elastic Cartilage 
8o. Structure.-The matrix of elastic cartilage 
consists chiefly of a network of fine elastic fibers, 
and is very similar to elastic fibrous tissue. 
81. Where Found.-Elastic cartilage enters 
into the structure of the external ear, the Eusta- 
chian tubes,2 the epiglottis, and parts of the 
larynx. 
1 Described in Chapter XV. 
2 The fine tubes extending from the middle cavity of the ear 
to the pharynx, i. e., the space behind the mouth. Tissues 
35 
White Fibro-Cartilage 
82. Structure.-White fibro-cartilage resembles 
the yellow in its structure, but the fibers of its 
matrix are white and non-elastic. They resemble 
those of white fibrous tissue, but are tougher and 
firmer. 
83. Distribution and Purpose.-White carti- 
lage is found connecting, or helping to connect, 
articulating bones, in places where great strength 
is required, as the knee joint, the pubic bones, and 
the vertebrae of the spinal column. In the last 
named location the cartilage is in the form of 
thick disk-shaped pads, and these are placed 
between the vertebrae, where they serve not only 
to hold the bones together, but also to prevent 
concussion between them. 
Another purpose of white cartilage is that it 
forms sheaths for the tendons, and sometimes 
enters into their substance, and being even stronger 
than the fibrous tissue of which the tendons are 
mainly composed, the cartilage serves to increase 
their strength. CHAPTER IV 
BONE OR OSSEOUS1 TISSUE 
Tissue of which the Skeleton is Composed. Function of the 
Bones. Composition of Bone. Nature of Organic and In- 
organic Matter in Bone. Comparative Proportion of Each in 
Bone. Difference in Fractures in Children and Adults. Cause 
of Rickets. How the Composition of Bone can be Studied. 
Classification of Bones. Structure of Bone. Markings of Bones. 
Purpose of Prominence and Depressions of Bones. Nature and 
Purpose of Parts Composing Haversian System. Marrow7, 
Nature and Purpose. Periosteum. Endosteum. Repair of 
Bone. Number of Bones Comprising the Skeleton, their Nature, 
Names, and Location. 
84. The bones of which the hard framework or 
skeleton2 of the body is composed consist of bone 
or osseous tissue. 
85. Function of the Bones.-The purposes 
which the bones serve are: (1) to give support and 
shape to the body; (2) to act as a foundation and 
afford places of attachment for the soft parts; 
(3) to support the weight of the trunk; (4) to act 
as levers for locomotion and other movements of 
the body; (5) to form cavities to hold the vital 
1 From the Latin os-a bone. Plural ossa. The branch of 
anatomy treating of the structure, arrangement, and uses of bone 
is called osteology, from the Greek osteon-a bone and logos 
•-a discourse. 2 Skeleton. Greek, a dried body. 
36 Bone or Osseous Tissue 
37 
organs; (6) to afford protection for those organs. 
86. Composition of Bone.-Bone consists of 
about 50% water and 50% solid matter. The 
solid matter comprises both organic and inorganic 
substances. 
87. Nature of Organic Matter.-The or- 
ganic matter consists chiefly of cartilage and blood- 
vessels. The cartilage, it will be remembered, is 
composed principally of a substance known as 
collagen, which is transformed into gelatin by 
boiling. 
88. Nature of Inorganic Matter.-The 
inorganic matter, known also as mineral and 
earthy matter, consists almost entirely of phos- 
phate of calcium and carbonate of calcium. 
89. Comparative Proportion of Organic 
and Inorganic Matter.-The comparative pro- 
portion of organic and inorganic substance in 
bones varies with age; thus in the fetus the tissues 
that later, by taking mineral1 and other matter 
from the blood and incorporating it into their 
substance,become bone, are largely cartilaginous or 
fibrous. In young children the animal matter is 
still in excess of the mineral; in the bones of adults, 
on the other hand, there are about two parts of 
inorganic substance to one of organic, and in the 
bones of old persons the per cent, of inorganic 
matter is even larger.2 
1 Lime. 
2 With a few exceptions the bones of the head and face are 
preformed in membrane and those of the trunk and limbs in a Anatomy and Physiology 
38 
90. Difference in Nature of Fractures 
Due to Variation in Composition of Bone.- 
As the result of this preponderance of mineral 
material, the bones of the aged are very brittle 
and, therefore, easily broken. On the contrary, 
the bones of children, owing to the large amount of 
gelatinous substance therein, are very flexible, so 
that they bend, but do not break readily. In 
consequence of this difference in composition, 
accidents that in adults will cause a complete 
severance of a bone will in children merely bend 
it or cause an incomplete or partial break, such as 
that likely to occur in bending a green tree twig. 
This kind of fracture is therefore known as a 
green-stick fracture. 
91. Cause of Rickets.-Children who do not 
get food containing sufficient mineral matter will 
have an even smaller proportion of this substance 
than usual in their bones, in consequence of which 
the latter are likely to become bent, even without 
the intervention of an accident. This condition 
is known as rickets or rachitis. 
92. How the Composition of Bone can be 
Studied.-(1) Put a piece of bone, about four 
inches in length, in a bottle containing sufficient 
dilute hydrochloric acid to cover the bone, and let 
cartilage that is covered with a vascular membrane. Bone form- 
ing cells, called osteoblasts, and lime salts are gradually deposited 
in the membrane forming the skull, and in the cartilage fore-plan 
of the trunk and limbs, and as the bone tissue develops the carti- 
lage is broken down, absorbed, and carried away by the blood. 
The process of bone formation is spoken of as ossification. Bone or Osseous Tissue 
39 
it stand for a few days. The hydrochloric acid 
will dissolve the mineral matter, and the bone 
(which is now more like cartilage) 
can be easily bent and knotted, 
as in Fig. 13. 
(2) Burn a small piece of bone. 
The remaining ash is the mineral 
matter which, on chemical anal- 
ysis, has been found to consist 
chiefly of phosphate and carbon- 
ate of calcium or lime. The or- 
ganic matter has been destroyed 
by the heat; that is, it has been 
broken down into its elements- 
CHO N-which have passed off 
into the air. 
93. Classification of Bones. 
-Bones are classified according 
to their shape as long, short, flat, 
and irregular. The most typical 
long bones are those of the arms 
and legs; examples of the short 
bones are those of the wrist and ankle; of the flat 
bones, the shoulder-blades, pelvis, and larger bones 
of the skull; of the irregular bones, the vertebras 
of the spine and the temporal and ethmoid of the 
skull. 
Also, there are what is known as the sesmoid1 
and Wormian2 bones. 
Fig. 13.-Human 
bone which has been 
deprived of its 
earthy matter and 
tied in a knot. 
'From the Latin sesame-bones resembling the seeds of the 
sesame. 2 Called after a famous Dutch naturalist. Anatomy and Physiology 
40 
94- The sesmoid bones are small, osseous masses 
developed in tendons at points where they are 
stretched over joints and exposed 
to pressure. A patella or knee-cap 
is an example of a sesmoid bone. 
95. The Wormian bones are 
small, irregular ossicles found on 
the edges of the cranial bones where 
the latter come together. 
96. Structure of Bone.-On 
examining pieces of bone from dif- 
ferent parts of the skeleton it will 
be seen that the substance of the 
majority of them is much more 
dense on the outside. Also it will 
be noticed that the relative propor- 
tion of dense or compact tissue- 
as the outer substance is called- 
and spongy or cancellous1 tissue 
-the more porous substance-var- 
ies in the different kinds of bones. 
Thus, it will be seen that in the 
long bones of the arms and legs, 
where great strength is required, 
there is no cancellous tissue except at the extremi- 
ties, and in hopes, as some of those of the skull, 
where lightness and not strength is required, there 
Fig. 14.-The 
longitudinal sec- 
tion of a long 
bone. 
1 Def.: having an open or porous structure. From the Latin 
cancellus-a lattice-work. The composition of compact and 
cancellous tissue is the same, the difference in their appearance 
being due to the larger size of the spaces between the lamellae or 
framework. Bone or Osseous Tissue 
41 
is less compact substance. Other points to be 
observed are: (i) the canal or cavity extending 
through the center of the shaft of each long bone, 
called the medullary1 canal because it contains the 
medulla or marrow; and (2) the markings of the 
bones. 
97. Markings of the Bones.-Many of the 
bones show certain irregularities on their surface 
known as markings. These markings are of 
various characters and each variety is distinguished 
by a special name. Thus, projections are called 
processes, and rounded processes which do not 
articulate with other bones are called tuberosities,2 
and smaller ones tubercles,3 and rounded processes 
which do articulate with other bones are called 
condyles4 and heads; long, sharp, slender processes 
are known as spines; prominent borders are called 
crests. Holes through a bone are termed fora- 
mina (sing, foramens); non-articular depressions 
are known variously as fossa, grooves, fissures, 
notches; articular depressions are called cavities. A 
constricted portion of bone beneath a head is 
called a neck, and the long straight portion of the 
long bones, shafts. See Figs. 41, 42, 43. 
98. Purpose of Prominences and Depres- 
sions of Bones.-Articular processes fit into 
articular depressions and thus the strength of a 
1 Latin medulla-marrow. 
3 Tuberosities 
3 Tubercles 
-> Greek kondulos-a knob. 
Latin tuber-a swelling. 
s Latin foramen-an aperture, a hole. Plural foramina. Anatomy and Physiology 
42 
joint and evenness of movement are secured. 
Non-articular eminences and depressions serve 
to increase the extent of surface for the at- 
tachment of ligaments and muscles. 
99. Haver- 
sian System. - 
After examining 
the gross struc- 
ture of the bones 
it is well, if pos- 
sible, for the stu- 
dent to examine 
a few thin slices 
of bone under the 
microscope. 11 
will be then seen 
that even in the 
dense tissues of 
the shafts of the 
long bones there 
are (1) several 
apertures that in 
the bone as a 
whole would con- 
stitute longitudinal canals; (2) that each of these 
canals has smaller canals radiating from it, some- 
what like the spoke of a wheel, and communicat- 
ing with small, irregular, open spaces; (3) that 
these open spaces, of which there are several rings 
(see Fig. 16) communicate with each other by 
means of small canals similar to the ones connect- 
Fig. 15.-Longitudinal section of 
compact osseous tissue, greatly mag- 
nified. The Haversian canals are cut 
lengthwise. The dots in the canals 
are openings of canaliculi. (Gerrish.) Bone or Osseous Tissue 
43 
ing them with a longitudinal canal, so that there 
is free communication between the latter and the 
spaces. The longitudinal canals are called Ha- 
versian canals-after Havers, a famous anatom- 
ist; the smaller ones are called canaliculi1; the 
spaces are termed lacunce2; the bony fibers com- 
prising the framework between the open parts 
and constituting the solid portions of the bone 
are known as the lamella,3 and the whole arrange- 
ment combined is called an Haversian system. 
100. Purpose and Distribution of Haver- 
sian Canals, etc.-Lacunae and canaliculi serve 
as pathways for the lymph4 through the bone; they 
are present in all true bones; but Haversian canals, 
which serve as tubes to hold the blood and lymph 
vessels, and nerves are not found in bones which 
are so thin that they can obtain nourishment from 
blood-vessels on their surface. 
101. Marrow-Nature and Purpose.-In 
the living bone the medullary canal of the shafts 
of the long bones and the open spaces of the 
cancellous tissue are filled with a substance known 
as marrow. This consists chiefly of a small 
amount of fibrous tissue with blood-vessels, fat- 
cells, marrow-cells, and red blood-cells. The 
marrow in the medullary canals contains a larger 
per cent, of fat than that in the cancellous sub- 
stance, and is yellow in color. That in the 
1 From the Latin canaliculus, dimin. of canalis-a channel. 
2 Latin lacuna-a hollow. Pl. lacuna. 
3 Latin-a thin plate. Pl. lamella. 
4 Described in paragraph 494. Anatomy and Physiology 
44 
cancellous substance is highly vascular and, conse- 
quently, has a reddish hue. The chief uses of 
marrow are: (i) to serve as a source of nourishment 
for the bone; (2) to support blood- and lymph- 
vessels and nerves; (3) as a location for the for- 
mation of blood corpuscles (see paragraph 461). 
102. Periosteum-Blood and Nerve Supply 
of Bone.-The outer surface of bones, except at 
their joints, where they are protected with car- 
tilage, are covered with an exceedingly vascular 
membrane called the periosteum.1 The blood- 
vessels running through the canals of the bones are 
for the most part branches of those of the perios- 
teum; therefore destruction of the periosteum of a 
bone will interfere with the nutrition of the latter 
and may result in necrosis-i. e., death of the bone. 
The marrow in the medullary canal of the shaft 
of the long bones is supplied with blood also by a 
medullary artery, which penetrates the compact 
tissue obliquely and then divides into two main 
branches, one of which ascends and the other 
descends in the canal. 
103. The periosteum and bone are supplied 
also with nerves. These run in the same channels 
as the blood-vessels. 
104. Endosteum.- The medullary and can- 
cellous cavities of the bones are lined with a 
membrane similar to the periosteum, known as 
the endosteum.2 
1 From the Greek peri-about, and osteon-a bone. 
2 From the Greek endon-within, and osteon-a bone. Fig. i6.-Diagram of the structure of osseous tissue. A small part of a 
transverse section of the shaft of a long bone is shown. At the uppermost 
part is the periosteum covering the outside of the bone; at the lowermost 
part is the endosteum lining the marrow-cavity. Between these is the 
compact tissue, consisting largely of a series of Haversian systems, each 
being circular in outline and perforated by a central canal. In the first 
one is shown only the area occupied by a system; in the second is seen the 
concentric arrangement of the lamellae; and in the others, respectively, 
canaliculi; lacunae; lacunae and canaliculi; the contents of the canal, artery, 
vein, lymphatic, and areolar tissue; lamellae, lacunae, and canaliculi; and, 
finally, all of the structures composing a complete system. Between the 
systems are circumferential and intermediate lamellae, only a few of which are 
represented as lodging lacunae, though it is to be understood that lacunae 
are in all parts. The periosteum is seen to be made' up of a fibrous layer 
and a vascular layer, and to have upon its attached surface a stratum of 
cells. From the fibrous layer project inward the rivet-like fibres of Sharpey. 
(Gerrish.) Bone or Osseous Tissue 
45 
105. Repair of Bone.-Fracture of a bone is 
always complicated with more or less injury to the 
periosteum and other tissues, and with inflamma- 
tion in the affected area. When tissue is inflamed 
there is an unusual amount of blood sent to the 
part, and a consequent exudation of plasma and 
white corpuscles1 from the blood into the tissue. 
When this occurs in bone, a viscid, fibrous tissue 
called callus2 is formed from substances taken 
from the plasma which sticks the ends of the bone 
together. Usually, bone cells-osteoblasts-and 
lime salts are gradually deposited in this callus, 
which, consequently, becomes hardened, forming 
new bone. Excess callus around the point of 
fracture may be felt, and sometimes seen, as a 
prominent lump, for some time after the bone has 
united, but, usually, this is gradually absorbed by 
the blood, and so removed. Occasionally (es- 
pecially if the individual's health is poor at the time 
the fracture occurs) the callus does not ossify. 
This condition is spoken of as fibrous union. 
106. Should the periosteum at the point of 
injury be completely destroyed, the blood supply 
to the interior of the bone will be so limited that 
the bone may not be repaired or regenerated. 
107. Number and Names of the Bones of 
the Skeleton.-There are two hundred bones in 
the adult human skeleton, exclusive of the three 
ossicles (small bones) contained in each ear and 
x Described in paragraphs 462, 463. 
2 Latin callus-a hard or thickened skin. 46 
Anatomy and Physiology 
the sesmoid bones embedded in the tendons 
covering the bones of the hands, knees, and feet. 
The two hundred bones are situated as follows. 
In the skull 22 
" " spinal column 24 
" " pelvis 4 
" " upper extremities 64 
" " lower extremities 60 
Ribs 24 
Os hyoid I 
Sternum 1 
200 
108. The Bones of the Skull.-The skull, 
which consists of the head and face, contains 
twenty-two bones-eight in the head or cranium1 
and fourteen in the face. 
109. Nature of Bones of the Skull.-With 
a few exceptions (to be discussed later) the bones 
of the skull belong to the class known as the flat 
bones. The majority of these consist of an outer 
layer of compact tissue and an inner one of can- 
cellous, which in some parts of the skull is so 
fragile that a blow, too weak to injure the outer 
case, may break off a fragment, and this, by making 
pressure on the brain, may induce paralysis or 
convulsions. Certain of these bones, as will be 
seen in their detailed description, contain hollow 
spaces-antra 2 and sinuses 3--which serve two 
purposes: (1) they make the bones lighter; (2) they 
1 Latin cranium-the skull. 
3 Latin antrum-a cave, ' Latin sinus-a bend, a hollow. Bone or Osseous Tissue 
47 
act as air chambers. Also, in some of the bones 
there are foramina for the passage of nerves and 
blood, and lymphatic vessels to and from the brain. 
pig. 17.-Skull, viewed from the left side, showing the prin- 
cipal craniometric points. 
no. Names of the Bones of the Head or 
Cranium.-The names of the eight bones forming 
the cranium are:, 
Occipital1 Frontal4 
2 Parietal2 Sphenoid5 
2 Temporal3 Ethmoid6 
1 Latin occiput-back of the head. 2 Latin paries-a wall. 
3 Latin tempus-time. So called because, usually, it is the hair 
covering the scalp of this part that turns gray first, as the result 
of age or time. 4 Latin frons-the forehead. 
5. Greek sphen-a wedge, and eidos-form. 
6 Greek ethmos-a sieve, and eidos-form. 48 
Anatomy and Physiology 
in. The Occipital Bone.-This bone forms 
the back of the skull. It consists of two portions: 
one, called the squamous (scale-shaped), articulates 
with the two parietal bones; and the other, the 
basal portion, extends inward, forming what are 
known a s the 
base of the 
skull and the 
roof of the 
throat. 
112. In the 
posterior por- 
tion of the oc- 
cipital bone is 
a large opening 
known as the 
foramen mag- 
num (the great 
hole) through 
which nerve- 
fibers extend 
between the brain and the spinal canal. On either 
side of the foramen magnum is a prominent 
process known ' as the occipital condyle. These 
condyles articulate with the first bone of the 
spinal vertebrae and permit of the nodding move- 
ments of the head. 
113. The Parietal Bones.-The parietal 
bones, two in number, are situated one on either 
side at the top of the head. The outer surface of 
these bones is convex and smooth; the inner, con- 
Fig. i8.-The occipital bone, viewed 
from above. Bone or Osseous Tissue 
49 
cave and marked by deep depressions and grooves. 
The former provide space for the convolutions of 
the brain; the latter form channels for some of the 
larger vessels in which the blood flows to and from 
the brain. 
114. The Temporal Bones.-The two tem- 
poral bones are situated one on either side of the 
skull. They each 
consist of three 
parts, namely, the 
squamous,1 the 
mastoid,2 and the 
petrous.3 The 
squamous is the 
portion which ex- 
tends from the 
front of the ear to 
the cheek. In its 
lower edge is a de- 
pression known as 
the glenoid4 or mandibular5 fossa, into which a 
condyloid process of the lower jawbone or man- 
dible fits. The mastoid portion is the promi- 
nence behind the ear. The lower part of the 
mastoid is composed largely of cancellous tissue 
and contains many honeycomb-shaped cavities, 
Fig. 19.-The right temporal bone, 
outer surface. The dotted lines in- 
dicate the lines of suture between 
squamous, mastoid, and tympanic 
portions. 
1 Latin squamosus from squama-a scale. 
2 From the Greek mastos-the breast, and eidos-form. 
s From the Greek petra-a rock. 
4 From the Greek glene-a cavity, and eidos-form. 
s From the Latin mandere-to chew, masticate. 50 
Anatomy and Physiology 
which communicate with the middle ear. These 
are called the mastoid cells. They are some- 
times the seat of a disease known as mastoidi- 
tis, which usually occurs as the result of infection 
from the middle ear. As the bone at this point is 
very porous, any suppurative process is exceedingly 
dangerous, for the infection is likely to travel 
inward and involve the brain. The petrous 
portion of the temporal bone is, as the name implies, 
exceedingly hard. It is situated between the 
mastoid and the squamous parts at their lower 
extremity. The inner part of the ears, in which 
are situated the most essential parts of the organs 
of hearing, is contained in the petrous portions of 
the temporal bone. 
115. The Frontal Bone.-At birth there are 
two frontal bones, the bone being divided by a 
vertical fissure into two lateral halves, but usually 
the two bones unite in the course of a few years. 
The single bone thus formed consists of two parts, 
(1) a vertical or frontal, which forms the forehead, 
(2) a horizontal portion, which enters into the 
formation of the roof of the orbits (the cavities 
which contain the eyes) and the back of the nasal 
cavity. The vertical portion of the bone articu- 
lates at its upper extremity with the two parietal 
bones, and is bounded at the lower edge by the 
prominent ridges known as the supraorbital1 mar- 
gin, over which are the eyebrows. Within the 
1 From the Latin super-above, and orbita-a tract, and orb-a 
ball. Bone or Osseous Tissue 
51 
substance of the frontal bone, just above each 
supraorbital margin, is a hollow space which opens 
into the nose. These 
spaces are known as 
the frontal sinuses. 
They are often the 
seat of a troublesome 
infection. In the 
horizontal part of the 
bone, in the upper 
angle of each orbit, 
is a small depression 
termed the lachrymal 
fossa, which contains 
the lachrymal1 gland, where tears are formed. 
116. The 
Ethmoid.- 
This is a small, 
exceedingl y 
light, cancel- 
lous bone. 
It is situated 
between the 
two orbits, 
at the upper 
part of the 
posterior wall 
of the nose, 
and is joined at the back to the base of the 
skull. It thus enters into the formation of 
Fig. 20.-The frontal bone, seen 
from in front. 
Fig. 21.-The ethmoid bone, seen from 
above. 
1 From the Latin lacrima-tear. 52 
Anatomy and Physiology 
the orbital and nasal cavities and of the base 
of the skull. Protruding from the ethmoid, on 
either side of the nasal cavity, are two masses 
of thin, sponge-like projections of bone known as 
the superior and middle turbinated1 bone. In the 
middle plane of the ethmoid are a number of small 
foramina through which fibers of the olfactory 
Fig. 22.-The sphenoid bone, viewed from above. 
nerve pass to the tissues covering the superior 
turbinated process and the septum-the division 
between the two sides of the nose. 
117. The Sphenoid.-The shape of the sphe- 
noid bone is that of a bat with extended wings. 
It is situated immediately behind the ethmoid, to 
which it is joined, and it articulates also with all 
the other bones of the skull and with five of those 
1 From the Latin turbo-a top. So called because of their 
twisted shape. Bone or Osseous Tissue 
53 
of the face, viz: the two molar, the two palate, 
and the vomer. It contains several small fora- 
mina for the passage of nerves and blood-vessels. 
118. The Fontanelles and Sutures.- 
Before birth, and for some time afterward, the 
Fig. 23.-Fetal skull, side view. Half size. The 
coronal suture extends from the top of the head down- 
ward on either side to the point E; the lambdoidal suture 
from the back forward, on either side to the point F. 
The sagittal suture is not shown, but is indicated by the 
upper margin of the illustration, beginning at the base 
of the nose, passing backward across the coronal suture 
(anterior fontanelle), and ending at the lambdoidal 
suture (posterior fontanelle.) 
bones of the skull are united by membrane only, 
and the membranous spaces between the bones are 
quite perceptible at the angles formed at the junc- 
tion of (i) the two parietal and the frontal bones, 
(2) of the two parietal and the occipital bones, 
(3) of the lower corners of the parietal bones with 
the upper corners of the temporal bones. These 54 
Anatomy and Physiology 
spaces are called fontanelles,1 because, especially in 
the anterior fontanelle-the angle at the junction 
of the parietal and frontal bones (see Fig. 23)-the 
pulsations of thebrain are visible and were thought, 
by the early anatomists who named them, to re- 
semble the rise and fall of a fountain. The 
lateral fontanelles-the four small ones at the 
side of the head (see Fig. 23)-close soon after birth, 
and the posterior-that at the junction of the 
parietal and occipital bones-closes a few months 
after birth; but the largest one, the anterior, is 
usually not completely closed until the second year 
after birth, and sometimes later; occasionally it 
never closes. The remainder of the membrane 
between the edges of the bones becomes ossified 
very soon after birth and the bones firmly united; 
but, owing to the peculiar formation of their edges, 
there is a distinct marking along the surface of 
their articulation, which the early anatomists 
thought resembled stitches, and therefore named 
sutures.2 
119. This division of the bones of the fetal 
skull is of great importance in labor, for it permits 
of the overlapping of the bones at that time and so 
diminishes the size of the head, thus facilitating 
its passage through the mother's pelvis. This 
process of overlapping is known as moulding. 
120. Bones of the Face.-The names of the 
fourteen facial bones are: 
1 French fontanelle-a little fountain. 
3 From Latin sutus, pf. part, of suo-to sew. Bone or Osseous Tissue 
55 
Nasal 2 
Vomer I 
Inferior turbinated 2 
Lachrimal ' 2 
Malar 2 
Palate 2 
Superior maxillary or maxilla 2 
Inferior maxillary or mandible 1 
I2i. The Nasal Bones.-The nasal bones are 
the two small oblong bones which 
form the bridge of the nose. 
122. The Vomer.1-The vomer 
is situated at the lower and back 
part of the nasal cavity and forms 
part of the septum2 which consti- 
tutes the central wall of that cavity. 
The septum is frequently curved to 
one side, making the nasal cham- 
bers of unequal size. This is due to the fragility 
of the vomer, which, especially in childhood, when 
it is largely cartilaginous, allows of it being so 
easily bent that even congestion, due to a cold 
in the head, can do the bending. 
123. The Turbinated3 Bones.-These are 
two thin, scroll-shaped, cancellous bones which 
extend horizontally, one on either side, along the 
outer wall of the nasal fossa.4 They are below the 
Fig. 24.-Na- 
sal bone viewed 
from before. 
1 Latin -vomer-a ploughshare. 
3 The front part of the septum consists of cartilage. 
s From the Latin turbo-a top. 
4 The nasal fossae are two irregular cavities situated one on 56 
Anatomy and Physiology 
superior and middle turbinated bones, which, it 
will be remembered, are processes of the ethmoid. 
The inferior 
turbinated 
bones articu- 
late with the 
ethmoid, the 
superior maxil- 
lary, the lach- 
rymal, and the 
palate bones. 
Hypertrophy 
and other ab- 
normal condi- 
tions of the 
turbinated 
bones and the membrane covering them consti- 
tute some of the more common nasal diseases. 
124. The Lachry- 
mal1 Bones. - These 
are two small, exceed- 
ingly thin bones, situ- 
ated one on either side 
of the nose, between it 
and the orbital cavities. 
They are so-called be- 
Fig. 25.-Sagittal section of face, a 
little to the left of the middle line, show- 
ing the vomer and its relations. 
Fig. 26.-Right inferior tur- 
binate bone, external surface. 
either side of the face, at the back of the nose. Their anterior 
margins, the openings into the nose, are spoken of as the anterior 
nares, and the posterior, which open into the pharynx-part of 
the throat-as the posterior nares. 
1 From the Latin lacrima-a tear. Bone or Osseous Tissue 
57 
cause they contain part of the canal through 
which the lachrymal tear-duct runs. 
125. The Malar1 Bones.-The 
malar bones form the prominences 
of the cheeks and part of the floor 
and outer wall of each orbital cavity. 
They articulate at their posterior 
border with a process of the tem- 
poral bones and by so doing form 
what is known as the zygomatic2 arch. 
126. The Palate3 Bones. - 
These two bones are each shaped 
like an L. They constitute the back part of the 
roof of the mouth, part of the floor and outer 
walls of the nasal 
fossa, and of the 
floor of the orbits. 
127. The Su- 
perior Maxil- 
lary4 Bones.- 
These bones us- 
ually unite before 
birth forming prac- 
tically one bone 
known as the 
maxilla or upper 
jawbone,5 which constitutes the greater part of 
Pig. 27.- 
Right lachry- 
mal bone inner 
surface. 
Fig. 28.-Right malar bone. 
1 From the Latin mala-the cheek. 
3 From the Greek zygos-yoke. 
3 From the Latin palatum-palate. 
4 From the Latin maxilla-jaw. 
s When it fails to do so, the condition is known as cleft palate 58 
Anatomy and Physiology 
the roof of the mouth, part of the floor and outer 
wall of the na- 
sal fossa, and 
part of the floor 
of the orbits. 
The lower an- 
terior process of 
the bone is call- 
ed the alveolar1 
process and in 
it are the de- 
pressions into 
which the roots 
of the upper 
teeth fit. The 
two upper anterior extremities of the bone are 
hollow and the cavities, called the antra of 
Fig. 29.-The two palate bones in 
their natural position, dorsal view. 
Fig. 30.-Superior Maxillary bone and the bony sinuses of 
the head. (Gerrish.) 
Highmore, open one on either side into the nasal 
chambers. These antra are very frequently the 
1 Alveolar. From the Latin alveolus-a little hollow. Bone or Osseous Tissue 
59 
seat of a troublesome infection, the usual source 
of which is abnormal conditions of either the nose 
or teeth. 
Fig. 31.-The right half of the mandible, inner surface. (Gerrish.) 
128. The Inferior Maxillary or Mandible 
Bone.-This is the only movable bone in the skull. 
It consists of 
a curved 
horizontal 
body with a 
thick e n ed 
border called 
the alveolus, 
which con- 
tains the 
lower teeth, and an upright branch on each side, 
the ramus,1 which is attached by means of ligaments 
to a temporal bone. On the upper end of each 
Fig. 32.-The Hyoid bone. Viewed from the 
left and in front. (Gerrish.) 
1 Latin ramus-a branch. Plural rami. 60 
Anatomy and Physiology 
ramus is a condyloid process which enters into 
articulation with the temporal bone. 
129. The Hyoid.1-Bone of the Neck.-The 
hyoid is a U-shaped bone situated in the neck just 
above the cartilaginous prominence known as 
Adam's apple. It does not articulate with any 
other bones, but is suspended from a process of 
each temporal bone by ligaments and muscles. 
It serves to support the tongue, which is attached 
to it by muscles. 
130. The Trunk or Torso.-The trunk con- 
sists of the thoracic, abdominal, and pelvic cavities. 
The bones which form its framework are those of 
the spine, the ribs, the sternum, and the pelvis. 
The Spinal or Vertebral Column 
131. Number of Bones Constituting the 
Column.-In youth the spine consists of thirty- 
three irregular bones called vertebrae. Early in life, 
however, the nine bones at the lower end of the 
column become ossified so that they form but two 
bones, the upper five uniting to form what is 
known as the sacrum, and the remaining four, the 
coccyx. Thus, for the greater part of life the spine 
consists of: 
24 vertebras proper 
1 sacrum 
1 coccyx 
1 Greek hyoeidos-the hyoid bone, so called from its shape. Fig. 33.-The spinal column, right lateral 
view and dorsal view. (Gerrish.) 
61 62 
Anatomy and Physiology 
The vertebrae are called according to their location: 
Cervical (neck) vertebrae, of which there are 7 
Thoracic (chest) " " " " " 12 
Lumbar (groin) " " " " " 5 
132. General Nature of Vertebral-Each 
vertebra consists of a solid portion called the body, 
which constitutes the anterior and more compact 
portion of the spinal column, and an arch. The 
two united form a ring of bone. On each arch are 
seven processes, two of which, situated one on 
either side of the arch near its junction with the 
body, are called the transverse processes-they serve 
for the attachment of muscles; the next four, 
situated two on each side of the arch, one projecting 
upward and the other downward, are called the 
articular processes, because they articulate with the 
vertebrae above and below them; the seventh 
process, called the spinous, projects backward and 
can be felt by drawing a finger down the center 
of the back; it serves for the attachment of 
muscles. 
133. Nature of the Vertebral Column.- 
The bodies of the vertebrae are piled one upon 
another with thick disks of fibro-cartilage between 
them. They are held together by the articulation 
of (1) their articular processes, (2) by the cartilagi- 
nous disks between them, and (3) by semi-elastic 
ligaments, and form a strong but flexible column. 
The interior of the column is hollow and is termed 
the spinal canal. It contains the spinal cord. Be- Bone or Osseous Tissue 
63 
tween each pair of vertebrae are apertures through 
which the spinal nerves pass from the cord. 
134. Curves of the Spinal Column.-A 
glance at the vertebral column shows that it is not a 
straight vertical pillar, but that it has four decided 
curves: one at the neck, rounding convexly slightly 
forward; a second in the thorax curving convexly 
slightly backward; a third in the lumbar region, in 
which the convexity of the curve is very decidedly 
forward-this forms the hollow known as the 
small of the back; the fourth is that of the sacrum 
and coccyx, and, as its convexity is backward, it 
serves to increase the size of the pelvic cavity very 
considerably. 
135. Purpose of Curves and the Cartilage 
Pads.-The curves of the spinal column add to its 
strength and elasticity and thus increase its re- 
sistance to injury, and prevent jarring of the 
spinal cord and brain. The pads of fibro-cartilage 
between the bodies of the vertebrae serve the same 
purpose; these also, as previously stated, serve to 
hold the vertebra; together. 
136. Abnormal Curves.-Pathological exag- 
gerations of the spinal curves may exist, either 
as the result of injury or disease. Exaggerated 
curves are often spoken of as curvatures of the spine; 
and if the curve is lateral, i. e., toward one side, it 
is called scoliosis1; if dorsal, kyphosis (humpback); 
and if ventral, i. e. forward, lordosis.2 
1 From the Greek scolios-crooked. 
3 From the Greek lordos-bent supinely. 64 
Anatomy and Physiology 
137. Spina Bifida.-Another abnormal con- 
dition that occasionally occurs in the structure of 
the spinal column is a lack of proper development 
of the arch of some of the vertebrae, in consequence 
of which there will be at birth a protrusion of the 
spinal meninges1 through the resulting aperture. 
This condition is known as spina bifida. 
Fig. 34.-A thoracic vertebra, upper surface. (Gerrish.) 
138. Variation in the Shape of the Verte- 
brae in Different Parts of the Spine.--The 
vertebras are not all exactly the same size or shape. 
The bodies of the five lumbar vertebrae are larger 
and stronger than those of the thoracic and cervical. 
Those of the thoracic are larger than the cervical, 
and they contain depressions which receive the 
vertebral ends of the ribs. The arches of the 
cervical vertebrae are larger than those of the other 
1 The membranes covering the spinal cord and brain. Bone or Osseous Tissue 
65 
two regions, but their spinous processes are 
shorter and some of them are bifid, i. e., split in 
two. The two upper cervical vertebras, known as 
the atlas1 and axis,2 differ from all others. The 
atlas-the uppermost one-has a depression on 
either side into which the condyloid processes of 
the occipital bone fit; thus it supports the head. 
The atlas has neither a body nor spinous processes 
and is prac- 
t i c a 11 y a 
bony ring. 
A strong lig- 
ament is 
stretched 
transversely 
across the 
interior of 
this ring, di- 
v i d i n g it 
into two sec- 
tions, a posterior and an anterior. The former 
serves as a passage for the spinal cord, and the 
latter receives a process which projects upward 
from the axis. This process, called on account 
of its shape, the odontoid,3 acts as a pivot 
around which the atlas and with it the skull can 
rotate. It is retained in position and prevented 
Fig. 35.-Cervical vertebra, viewed from 
above. (Gerrish.) 
1 So called because it supports the head, after a giant of myth- 
ology who was supposed to support the world on his shoulders. 
2 Latin axis-an axle. The pin on which a body turns. 
3 From the Greek odontos-a tooth, and eidos-form. 66 
Anatomy and Physiology 
from pressing on the spinal cord by the trans- 
verse ligament of the atlas. A hard fall on the 
head is likely, either by dislocating the atlas on 
the axis or by fracture of the odontoid process, 
to cause the latter to press upon the spinal cord 
and result in instant death. Such an injury is 
commonly known as a broken neck. 
Fig. 36.-The atlas, viewed from above. (Gerrish) 
The Thoracic Cavity 
139. The bony framework of the thoracic1 
cavity is formed by the sternum,2 the ribs, and the 
thoracic vertebrae of the spine. 
140. The Sternum.-The sternum or breast- 
bone is a thin, flat, narrow bone, about, in the adult, 
six inches long, situated in the median line of the 
anterior chest wall. It consists of three parts, 
named the manubrium or handle, the gladiolus or 
blade, and the ensiform or sword.3 In youth these 
1 From the Greek thorax-a breastplate. 
2 Latin sternum-the breast bone. 
3 These names were given to the different parts of the sternum 
because it was thought to be shaped like a sword. Bone or Osseous Tissue 
67 
three parts are 
united by cartilage 
and ligaments only, 
and the ensiform is 
entirely cartilagin- 
ous, but later ossifi- 
cation takes place 
and the three parts 
are firmly united as 
one bone; the lower 
end of the ensiform, 
however, remains 
cartilage. On either 
side of the handle 
and blade are notch- 
es for articulation 
with the sternal 
ends of the ribs. 
The ensiform has no 
articulation with 
the ribs, but it af- 
fords attachment 
for the abdominal 
muscles. 
141. The Ribs. 
-The ribs, twenty- 
four in number, are 
situated twelve on 
each side of the 
thoracic cavity. The upper seven, called tne true 
ribs, articulate with the upper seven thoracic 
Fig. 37.-The sternum, ventral 
aspect. 68 
Anatomy and Physiology 
vertebrae at the back and, by means of the costal 
cartilages, with the sternum in front. The lower 
five, called the false ribs, are attached to the ver- 
tebrae in the back, but they are not connected with 
the sternum. The upper three pairs, viz: the 
eighth, ninth, 
and tenth, are 
each attached to 
the costal carti- 
lage of the rib 
next above it. 
The two remain- 
ing ribs are unat- 
tached in front, 
and are therefore 
called floating 
ribs. The spaces 
between the ribs 
are called inter- 
costal spaces. 
142. It will be 
noticed that the front attachments of the ribs are 
all cartilaginous, and, the costal cartilages being 
somewhat elastic, this helps in the expansion of the 
chest when certain of the muscles covering the ribs 
contract, and in the relaxing of the chest walls, as 
the muscles relax. This action will be again re- 
ferred to in the chapter devoted to the respiration. 
143. The Bones of the Upper Extremities 
-Number.-There are thirty-two bones in each 
of the upper extremities, thus: 
Fig. 38.-The skeleton of the thorax, 
front view. Bone or Osseous Tissue 
69 
In the shoulder girdle 
clavicle 1 
scapula 1 
" " arm humerus 1 
" " forearm 
ulna 1 
radius 1 
" " wrist carpus 8 
" " hand 
metacarpus 5 
phalanges 14 
32 
144. The Shoulder Girdle.-The two clavi- 
cles, or collar-bones, and the two scapulas, or 
Fig. 39.-The right clavicle, upper surface. 
shoulder-blades, together form what is known as 
the shoulder girdle, which serves to connect the 
upper extremities with the trunk. 
145. The Clavicle1 or Collar-Bone.-The 
clavicle is a long bone, but, unlike the typical 
long bones, it has no medullary canal. It is 
slightly curved, the curve being more pronounced 
and the bone thicker in men than in women. It 
is placed horizontally across the upper part of 
the thorax, articulating at its inner extremity 
1 From the Latin clavis-a key. Anatomy and Physiology 
70 
with the sternum-to which it is held in appo- 
sition with strong anterior and posterior liga- 
ments-and at its outer end with the acromion1 
process of the scapula. 
146. The Scap- 
ula2 or Shoulder- 
Blade.-The scapula 
is an irregular triang- 
alar-shaped bone, 
placed on the dorsal 
surface of the thorax 
between the first and 
eighth ribs. The up- 
per third of the pos- 
terior surface of the 
bone is crossed by a 
sharp ridge called the 
spine of the scapula, 
which terminates in 
a prominent projection called (because it forms the 
summit of the bone) the acromion1 process. Be- 
low and in front of the acromion process is the 
coracoid* process, and under these two processes, 
which serve for the attachment of some of the mus- 
cles holding the arm in place, is the glenoid4 cavity, 
into which the head of the humerus-arm-bone- 
fits. 
Fig. 40.-The right scapula, ven- 
tral view. 
1 From the Greek akron-the summit. 
2 Latin scapula-the shoulder-bone. 
3 From the Greek korakos-a crow, and eidos-form. The 
process was so named because it was thought to be the shape of a 
crow's beak. * From the Greek glene-a cavity, and eidos-form. Bone or Osseous Tissue 
71 
147- The Humerus. 1-The humerus, which is 
the arm-bone, may be said to consist, like all long 
bones, of a shaft and two extremities; the shaft 
being the straight, central portion and the ex- 
tremities the broader, irregular portions at either 
end. The upper extremity of 
the humerus consists of a hemi- 
spherical prominence called the 
head, which fits into the glenoid 
cavity; a constricted portion 
known as the anatomical neck, 
and two prominences, one on 
either side of the bone, called 
the greater and the lesser tuber- 
osities. Below the tuberosities, 
at the beginning of the shaft, 
is a slight constriction known 
as the surgical neck because it 
is so frequently fractured. At 
its lower extremity the humerus 
becomes flattened from before 
backward and is divided in the center by a 
small indenture, so that it ends in two rounded 
prominences known as the inner or medial condyle 
and the outer condyle. These help to form the 
elbow joint. Between the two condyles is what is 
known as the articular surface, the medial part of 
which, called the trochlea, fits into a depression in 
the upper end of the ulna, and the smaller, outer 
part, called the capitellum, fits into a depression in 
Fig. 41. - The 
humerus, or arm- 
bone. 
1 Latin humerus-the shoulder. Anatomy and Physiology 
72 
the radius. Just above the trochlea are two 
small depressions which receive the front articu- 
lating processes of the ulna and radius when the 
forearm is bent. 
148. The Ulna.-The ulna1 or elbow-bone is- 
with the figure in the anatomical position (para- 
graph 34)-the inner bone of the forearm. It is 
thicker and longer than the radius. On the end 
of its upper extremity are two rather flat, curved 
processes; the one on the back of the bone, which 
is the larger of the two, is called the olecranon2; the 
one on the front surface is termed the coronoid3; 
between the two is a depression into which the 
trochlea of the humerus fits. On the outer side 
of the coronoid3 process is a depression-the 
lesser sigmoid cavity-into which the head of the 
radius fits. The lower extremity of the ulna ends 
in two prominences; the outer one, called the head, 
articulates with the radius; the inner one, known as 
the styloid * process, serves for the attachment of 
ligaments from the wrist; but the ulna does not 
articulate with any of the wrist bones. 
149. The Radius.-The radius is on the outer 
or thumb side of the forearm, parallel with the 
ulna. On its upper extremity is a cylindrical 
prominence-the head-in the top of which is a 
shallow depression to receive the capitellum of the 
1 From the Greek olene-elbow. 
2 From the Greek olene-the elbow, and kranon-the head. 
3 From the Greek korone, meaning anything hooked or curved. 
4 From the Greek stylos-a pillar, and eidos-form. Bone or Osseous Tissue 
73 
humerus, and around which is a ridge that moves 
in the lesser sigmoid cavity of the ulna when the 
radius, and with it the hand, is rotated-turned. 
Below the head is a constricted portion-the neck 
Fig. 42. - The 
bones of the right 
forearm, dorsal 
view. 
Fig. 43.-The 
bones of the right 
forearm, ventral 
view. 
-and a tuberosity for the attachment of muscles. 
The lower extremity of the radius is wider than the 
upper. On its inner surface is a shallow depres- 
sion into which the head of the ulna fits. Its 
lower edge is concave and articulates with two of 
the bones of the wrist. At its outer edge is a 
process called (like that of the ulna) the styloid. 
150. Carpus1 or Wrist.-The wrist is com- 
1 From the Greek karpos-the wrist. Anatomy and Physiology 
74 
posed of eight small, short bones, arranged in two 
rows, one below the other, and held together with 
Fig. 44.-The bones of the right hand, palmar aspect. (Gerrish.) 
ligaments. They are named from their shape as 
follows: Bone or Osseous Tissue 
75 
First row: 
Scaphoid. Greek, skaphe-boat, and eidos-form. 
Semilunar. Latin, semi-half, and luna, moon. 
Cuneiform. Latin, cuneus-wedge. 
Pisiform. Latin-posum-pea, anA forma-likeness. 
Second row: 
Trapezium. Greek, trapezion-a table. 
Trapezoid. Greek, trapezion-a table, and eidos- 
form. 
Os magnum. Latin, os-bone, andmagwum-large. 
Unciform. Latin, uncus-a hook, and forma- 
likeness. 
151. The Metacarpus or Bones of the 
Palm of the Hand.-The skeleton of the palm 
of the hand consists of five cylindrical bones. 
Like the long bones, the metacarpal bones have a 
shaft and two extremities, but they have no 
medullary canal. They are slightly convex on 
their back surface and concave on their inner. 
They articulate at their base with the lower row 
of carpal1 bones and with each other, and at their 
heads with the first row of phalanges.2 
152. The Phalanges.-The phalanges are the 
bones of the fingers and thumb. There are three 
in each finger and two in the thumb, making 
fourteen in each hand. The first row articulates 
with the metacarpal bones; the second with the 
first row of phalanges, and the third with the 
second row. 
1 Same as carpus. 
2 From the Latin phalanx-a line of soldiers. 76 
Anatomy and Physiology 
The Pelvis 
153. Bones of the Pelvis.-The pelvis,1 so 
called from its supposed resemblance to a basin, is 
composed of four bones, viz: 
2 ossa innominata2; these constitute the two hip 
bones; 
1 sacrum of the vertebral column; 
1 coccyx " " " " 
In youth each 
os innomina- 
t u m c o n - 
sists of three 
bones, and 
though in the 
adult the 
three are 
welded into 
one, the bone 
is, for conven- 
ience in description, usually spoken of as consisting 
of: 
Fig. 45.-Female Pelvis. 
The ilium3 (plural ilia) 
The ischium (plural ischia) 
The pubis4 (plural pubes) 
1 Latin pelvis-a basin. 
. 2 From the Latin ossa-bones, and innominata-unnamed. 
These bones were so called because their shape did not resemble 
that of any known object. 3 Greek ilium-a citadel. 
4 From the Latin, pubes-hair. So called because the skin 
covering these bones, at the time of puberty, becomes covered 
with hair. Bone or Osseous Tissue 
77 
154. The Ilia.-The ilia are the two large 
bones which, with the sacrum (with which they 
articulate at the back), form the back and sides 
of the pelvis. The upper expanded portion of 
each ilium, called the wing, constitutes the side 
wall of what is known as the false pelvis, and also 
the prominence of the hip. The ridge, or upper 
border of the wing, is called the crest of the ilium, 
and the anterior extremity of the crest is known as 
the anterior superior spine of the ilium. 
155. The Pubes.-The two pubic bones form 
the front wall of the pelvis. They are held to- 
gether in the front median line with strong car- 
tilage, the point of articulation being known as the 
symphysis1 pubis. They are connected with the 
ilia at their posterior end, and with the ischia at 
their lower border. At the place of union of the 
three bones is a deep cup-shaped depression, called 
the acetabzilum,2 into which the head of the femur- 
the thigh-bone-fits. Between the central por- 
tion of the ischium and pubic bone is a large hole 
called the obturator foramen. 
156. False and True Pelvis.-As can be 
seen by looking at Fig. 45, the upper part of the 
pelvis flares and is larger in every way than the 
more constricted lower portion, and the change 
in shape takes place so suddenly that there is 
a decided marking line between the two parts. 
The upper flaring portion is known as the false 
1 Greek symphysis-growing together. 
2 Latin acetabulum- concave, depressed. 78 
Anatomy and Physiology 
pelvis, and it constitutes the posterior support of 
the abdominal cavity. The dividing line is known 
as the brim of the true pelvis, and also as the supe- 
rior strait of the pelvis. The constricted portion 
below the brim is termed the true pelvis. It 
contains the internal organs of generation, the 
rectum, and the urinary bladder. The upper 
opening of the true pelvis, i. e., the space between 
the brim, is called the inlet of the pelvis, and the 
opening at the bottom of the pelvis is known as the 
inferior strait and outlet (see Fig. 45). 
157. Differences between the Female 
and Male Pelvis.-Comparing the female with 
the male pelvis, we find that the former is so modi- 
fied that it is especially adapted for pregnancy and 
parturition. It is more shallow than the male 
pelvis, but wider and more capacious, the coccyx 
is more movable, the inlet and outlet larger, and 
the bones lighter and smoother. 
Bones of the Lower Extremities 
158. Number of Bones.-In addition to the 
ossa innominata, which enter into the formation of 
the hip-joint, as well as that of the wall of the 
pelvic cavity, there are thirty bones in each of the 
lower extremities. 
159. The Pelvic Girdle.-The bones of the 
pelvis, especially when spoken of in connection 
with the lower extremities, are often referred to as 
the pelvic girdle, and they are to the lower extremi- Bone or Osseous Tissue 
79 
ties what the bones of the shoulder girdle are to 
the upper, viz., the connecting link between the 
extremities and the trunk. 
160. Names of Bones.-The names of the 
bones in each of the two lower extremities are: 
In the thigh the femur I 
" " knee the patella I 
u n . j the tibia I 
1 the fibula I 
" " ankle the tarsus 7 
" " foot the metatarsus 5 
" " toes the phalanges 14 
30 
161. In their shape, markings, and articula- 
tions, the bones of the lower extremities are very 
similar to those of the upper, but they are much 
stronger and larger. The thigh bone and the 
bones of the leg comprise, like those of the arm 
and forearm, an upper and lower extremity and 
a shaft, with prominences and depressions for 
articulation, and prominences and grooves for the 
attachment of muscles. 
162. The Femur 1.-This is the longest, largest, 
and strongest bone in the body. When a person 
is in the erect posture the femur is not vertical, 
being separated from its fellow above by the whole 
breadth of the pelvis, but inclining gradually 
1 Latin femur-the thigh. 80 
Anatomy and Physiology 
downward and inwara, 
so as to approach its 
fellow toward its lower 
part, for the purpose 
of bringing the knee- 
joint near the line of 
gravity of the body. 
The degree of this 
inclination varies 
in different individuals, 
and is greater in 
women than in men, on 
account of the greater 
width of the pelvis in 
the former. The 
upper extremity of the 
femur consists of (1) 
a large spherical tuber- 
osity called the head, 
which fits intothe 
acetabulum of the in- 
nominate bone of the 
pelvis, (2) a constricted 
portion called the 
neck, which connects 
the head with the shaft, 
and (3) two large tu- 
berosities, one at each 
side, at the junction of 
the neck and shaft, 
called the greater and 
Fig. 46.-The right femur, 
rear view. (Gerrish.) Bone or Osseous Tissue 
81 
lesser trochanter.1 These trochanters afford at- 
tachment for the muscles which allow of the 
rotation of the thigh. At its lower extremity the 
femur is flattened from before backward, and di- 
vided into two processes called the internal and 
external condyles. The condyles are continuous 
in front and present a smooth concave surface 
which articulates with the patella. 
163. The Pa- 
T E L L A 2 OR 
Knee-Cap. - 
This is a flat, 
triangular bone 
situated in front 
of the knee-joint 
which it serves 
to protect. It 
articulates, a s 
stated in the 
preceding paragraph, with the two condyles of 
the femur. It is developed in tendon and, on 
account of this and its shape is called a sesmoid 
bone (paragraph 94). 
164. The Tibia or Shin Bone.-Next to the 
femur, the tibia3 is the largest bone in the body. 
It is situated in the front and inner side of the 
leg. The upper extremity or head is large and 
expanded into two tuberosities, in each of which is 
Fig. 47.-The right patella, dorsal sur- 
face. (Gerrish.) 
1 From the Greek trochao-to turn. 
2 From the Latin patera-a dish, a pan. 
J Latin tibia-a pipe, the shin bone. 82 
Anatomy and Physiology 
a concave 
depression for 
articulation 
with the con- 
dyles of the 
femur. The 
lower extrem- 
ity is much 
smaller than 
the upper, 
and is pro- 
longed down- 
ward on its 
inner side in- 
to a strong 
process, the 
inner or med- 
ial malleolus, 
which serves 
for the a t - 
tachment o f 
ligaments o f 
the ankle and, 
being concave 
on its inner 
surface, en- 
ters into the 
articulation 
with the as- 
tragalus, one 
of the large 
Fig. 48.-The right tibia and fibula in their 
normal relations, rear view. (Gerrish.) Bone or Osseous Tissue 
83 
bones of the ankle. The tibia articulates also 
with the fibula. 
165. The Fi- 
bula or Calf 
Bone.-The fib- 
ula, 1 a much more 
slender bone than 
the tibia, extends 
parallel with it, 
but on the outer 
side of the leg. On 
its upper extremity 
is a slight depres- 
sion which articu- 
1 a t e s with the 
external tuberos- 
ity of the tibia, 
and a pointed pro- 
cess- the styloid. 
The lower extrem- 
ity of the fibula 
ends in a promi- 
nent process, con- 
vex on its outer 
surface and con- 
cave on its inner, 
the external mal- 
leolus, which af- 
fords attachment for ligaments of the ankle and 
articulates with the outer surface of the astragalus. 
Fig. 49.-The bones of the right 
foot, viewed from above. 
1 Latin fibula-a buckle, a clasp. 84 
Anatomy and Physiology 
166. Tarsus Bones.-There are seven tarsus1 
bones, viz: 
Fig. 50.-The Human Skeleton. 
Calcaneum or os calcis. Latin calx-the heel; 
Astragalus. Greek astragalos-the ball of the 
ankle; 
1 Tarsus. From the Latin tarsos-the instep. Bone or Osseous Tissue 
85 
Cuboid. Greek kubos-a cube, and eidos-shape; 
Scaphoid. Greek skaphe--a boat, and eidos- 
form; 
Internal cuneiform. Latin cuneus-a wedge, and 
forma-form; 
Middle cuneiform. Latin cuneus-a wedge, and 
forma-form; 
External cuneiform. Latin cuneus-a wedge, and 
forma-form. 
167. Of these the calcaneum and the astragalus 
are the two largest; the former constitutes the 
heel bone, and the latter, as it supports the tibia 
and articulates with both tibia and fibula, is an 
important factor in the movements of the ankle. 
168. The Metatarsus Bones.-There are 
five metatarsus bones. Their shape and mode of 
attachment are similar to those of the metacarpus 
of the hand. 
169. The Phalanges.-The phalanges of the 
toes, both in number and general arrangement, 
resemble those of the hand, there being two in the 
large toe, and three in each of the others. CHAPTER V 
THE JOINTS OR ARTICULATIONS-THE TEETH 
Different Kinds of Joints. Names and Nature of Each 
Variety. Synovitis. Bursitis. Sprains. Dislocations. 
The Teeth: Location. Names of Various Parts. Nature of 
Tooth Substance. Structure. Different Kinds of Teeth. Tem- 
porary and Permanent Teeth: Their Number, Nature, and Time 
of Eruption. Development of the Teeth. 
The Joints 
Each of the bones constituting the skeleton, ex- 
cept the hyoid, is connected to one or more of the 
other bones, and the connected surfaces are spoken 
of as joints or articulations. 
170. Different Kinds of Joints.-The ar- 
ticulations are classified according to the amount 
of movement of which they are capable, as: 
1. Immovable j oints.1 
2. Slightly movable joints.2 
3. Freely movable joints.3 
171. Immovable Joints.-The surfaces of ar- 
1 Also called synarthrosis. 2 Known also as amphiarthrosis, 
a Or diarthrosis. 
86 Joints or Articulations-The Teeth 
87 
ticulation of the bones of the head and of the face, 
except the lower jaw, are of this type. 
172. Nature of the Immovable Joints of 
the Skull.-The articulating surfaces of the 
bones are applied in almost close contact, being 
separated only by the interposition of a thin 
layer of fibrous membrane, the sutural ligament, 
and, in certain situations at the base of the skull, 
a thin layer of cartilage. The bones are held 
together as well as separated by cartilage and 
fibrous tissue, and the majority of the bones of the 
head are held in apposition also by the tooth-like 
processes along their edges, the. processes of each 
bone interlocking with those of the one with which 
it articulates. 
173. Sutures.-The surfaces of the joints 
formed by this interlocking of processes have 
somewhat the appearance of sewed seams and 
were therefore named sutures. 
174. Slightly Movable Joints.-The prin- 
cipal examples of the slightly movable joints are 
the articulations (1) between the bodies of the 
vertebrae of the spinal column; (2) between the 
two pubic bones-the symphysis pubis; (3) 
between the ilia and the sacrum-the sacro-iliac 
articulation. 
175. Nature of Articulation in the 
Slightly Movable Joints.-In this form of 
articulation the surfaces of the contiguous bones 
are either connected by pads of fibro-cartilage 
which adhere to the end of each bone, as in the 88 
Anatomy and Physiology 
articulation between the bodies of the vertebrae, 
or else the articulating surfaces are covered with 
fibro-cartilage, partially lined with synovial mem- 
brane and connected by external ligaments, as in 
the sacro-iliac articulation and symphysis pubis. 
Both these forms are capable of limited motion. 
The motion between the pubic articulations is, in 
women, very much increased during parturition, 
certain of the ligaments holding the bones together 
becoming considerably softened during pregnancy. 
This increased power of movement facilitates, in 
fact is essential for, the normal birth of a child. 
176. Nature of the Articulation of the 
Vertebral Column.-All of the articulations in 
the vertebral column do not belong to the type 
just described; as will be seen later, the articula- 
tions between the articulating processes of the 
arches are of the freely movable gliding-joint type 
and, as can be seen by examining the skeleton, the 
arches of the vertebrae are not superimposed upon 
each other in the same compact manner as the 
bodies. This arrangement, as well as the elastic 
nature of the intervertebral pads of cartilage and 
of the ligaments of the spine, allow of the bending 
and other free movements of the spine. Also, the 
arrangement of the ligaments is particularly 
adapted to free motion. It is as follows: On the 
anterior and posterior surfaces of the bodies-the 
latter being of course within the spinal canal- 
the ligaments extend as long, strong, but elastic 
bands, from the axis to the sacrum; and the short, Joints or Articulations-The Teeth 
89 
thin, elastic ligaments holding the arches together, 
extend but from arch to arch. As age advances, 
the ligaments lose their elasticity and movement 
of the spine is much more limited. 
177. Nature of the Freely 
Movable Joints.-In the freely 
movable joints the bones form- 
ing the articulation are generally, 
for the greater convenience of 
their mutual connection, expand- 
ed at their surfaces of apposition, 
and the articulating part of the 
extremity of one bone is concave 
and that of the other convex, 
so that they fit into each other. 
The articulating surfaces are 
covered with smooth hyaline 
cartilage and held together by 
strong ligaments or capsules of 
fibrous tissues, and lined with a 
membrane called the synovial 
membrane, which secretes a fluid to lubricate the 
various parts of the joint and thus prevent fric- 
tion between the moving surfaces. This mem- 
brane, which will be further described in Chapter 
X, connects with the cartilage between the articu- 
lating surfaces and lines the ligaments holding 
the bones in apposition, so that with the cartilage 
it completely encloses, or encapsulates, the joint. 
See Fig. 51. 
178. Bursae.-In addition to the synovial 
Fig. 51.-Diagram 
of articular synovial 
membrane. The 
cartilages are repre- 
sented as drawn 
apart for the sake of 
clearness. The syno- 
vial membrane is 
shown by a broken 
line. (F. H. G.) 90 
Anatomy and Physiology 
membrane lining the joint, as described in the 
last paragraph, there are flat sacs of similar 
membrane placed over such prominent parts of 
joints as the patellas, the malleoli, the olecranons, 
the knuckles, etc. These sacs are called bursa.1 
The membrane composing them secretes a fluid, 
so that normally they always contain a slight 
amount of fluid, which serves to prevent friction 
between the bone and the ligament, tendon, or 
skin moving over it. Bursae will be further de- 
scribed in Chapter X. 
179. Different Kinds of Freely Movable 
Joints.-Though the foregoing description is true 
in the main of all the freely movable joints, 
there is considerable difference in the character of 
the joints placed under this heading; therefore the 
class has been subdivided and, according to the 
nature of their structure or of their movement, 
the joints belonging to this variety have been 
classed as: 
I. Ball-and-socket joints. 
2. Condyloid joints. 
3. Hinge joints. 
4. Pivot joints. 
5. Saddle joints. 
6. Gliding joints. 
180. Ball-and-Socket Joints.-The hip and 
shoulder joints are of this type. They consist of 
a large rounded head which fits into a cap-shaped 
1 Bursa. Latin, a bag. Joints or Articulations-The Teeth 
91 
depression and is held in place with strong non- 
elastic ligaments, the surrounding muscles, and, 
especially in the case of the shoulder joints, at- 
mospheric pressure. Such joints are freely mov- 
able in all directions, the shoulder joint being the 
most freely movable articulation in the body. 
181. Condyloid Joints.-In this form of 
joint an ovoid articular head, or condyle, is re- 
ceived into an elliptical cavity in such a manner as 
to permit of the movements known as flexion and 
extension, abduction and adduction, and cir- 
cumduction, but not rotation. Examples of 
condyloid joints are the wrists and the articula- 
tions of the metacarpal and the metatarsal bones 
with the phalanges. 
182. Hinge Joints.-In hinge joints the bones 
are held in apposition chiefly by strong lateral- 
side-ligaments which permit of motion in two 
directions only, viz. backward and forward, i. e., 
flexion and extension. The most perfect examples 
of hinge joints are the elbows and the articulations 
between the phalanges; the knee and ankle joints 
are also of this type, but in some positions they 
allow of other movements than flexion and ex- 
tension. The rotary movements of the forearm 
which appear to take place in the elbow occur, in 
reality, in the articulation between the radius and 
ulna. 
183. Pivot Joints.-Pivot joints are those 
in which one bone rotates around another, the 
latter remaining stationary. Examples of this Anatomy and Physiology 
92 
form of joint are: (i) that between the axis and 
atlas, in which the atlas, and with it the skull to 
which it is attached, turns around the odontoid 
process of the axis; (2) the articulation between 
the head of the radius and lesser sigmoid cavity 
of the ulna. By virtue of this articulation, when 
the hand is turned, the radius, which articulates 
with certain of the carpal bones, rotates around the 
ulna, the latter remaining stationary. 
184. Saddle Joints.-The best example of this 
form of joint is that between a metacarpus of the 
hand and the first phalanges of the thumb. This 
kind of joint was so named because when one bone 
is extended from the other, as the thumb from the 
hand, the shape of the angle formed is somewhat 
that of the position which a man assumes when 
sitting on a saddle. Saddle joints, like the con- 
dyloid, allow of all kinds of movements, except 
rotation. 
185. Gliding Joints.-This is a form of 
articulation in which the surfaces of the connecting 
bones are nearly flat and the amount of motion 
between them limited by the ligaments or osseous 
processes surrounding the joint. There is less 
motion in this form of joint than in any of the 
other freely movable joints. Examples of this 
type are the articulation between the individual 
carpal and tarsal bones and between the articular 
processes of the vertebras of the spinal column. 
186. The Kinds of Movements Admitted 
in Joints.-The types of movements admissible Joints or Articulations--The Teeth 
93 
in joints are gliding, angular, circumduction, and 
rotation. 
187. Gliding Movement.-In this form of 
motion one surface moves or glides upon another 
without any angular or rotary movement. It is 
common to all joints, but it is the only movement 
of which the gliding joints are capable. 
188. Angular Movements.-Angular move- 
ments are those in which the angle between two 
bones is increased or diminished. The movements 
included under this heading are abduction and 
adduction, flexion and extension. 
In adduction, the part is brought toward the 
central line of the body; in abduction, it is drawn 
away. In the hands and feet the middle phalanx 
is considered the middle line, hence the thumb is 
abducted when it is drawn toward the middle 
finger, and adducted when it is extended. Flexion 
is the bending or flexing of a part, and extension 
the opposite. 
189. Circumduction.-In circumduction, a 
part is so moved that it describes a cone-shaped 
figure, the joint being considered the apex of the 
cone, and its base the circle described by the distal 
end of the moving limb. 
190. Rotation.-In this form of motion a 
limb is turned on its own axis. Rotation of the 
forearm results in the supination and pronation 
of the hand, by supination being meant the turning 
of the palm forwards, and by pronation, the turn- 
ing of the palm backwards. Anatomy and Physiology 
94 
191. Sprains and Dislocations.-Too forcible 
movement of a joint, such as occurs in slipping or 
falling, is likely to cause stretching or tearing of 
some of the ligaments holding the bones in apposi- 
tion. If this injury to the ligaments is not compli- 
cated by displacement of the articulating bones, 
it is known as a sprain; if a bone is displaced, the 
injury is called a dislocation. 
The Teeth 
As dentine, the chief substance of the teeth, is 
similar to bone, and as the teeth, like the bones, 
remain as a part of the skeleton after the softer 
tissues of the dead body have become disintegrated 
and dissociated, it seems well to consider the 
teeth in connection with the bones. 
192. Location of Teeth.-The teeth are 
contained in the cavities of the alveolar1 processes 
of the upper and lower maxillary bones. 
193. The Gums.-The alveolar processes are 
covered with the gums. These consist of dense 
fibrous tissue covered with mucous membrane. 
The gums of each jaw are connected with the 
periosteum lining the alveolar cavities or tooth 
sockets. This dental periosteum serves as a 
means of attachment of the teeth to their sockets, 
and, being very vascular, as a source of nourish- 
ment for them. 
194. Parts of a Tooth.-Each tooth consists 
1 From the Latin alveoli-sockets for the teeth. Joints or Articulations-The Teeth 
95 
of three parts: (i) a crown or body which projects 
beyond the level of the gums; (2) a root or roots 
contained within the alveolar cavity; (3) a neck, the 
constricted portion between the root and the 
crown, which is normally encircled by the free 
margin of the gums. 
195. Nature of Tooth Substance.-The 
substance of the teeth may be said to consist of 
three kinds of material: dentine, enamel, and 
dental pulp. 
196. Dentine,1 which constitutes the general 
framework of the teeth, closely resembles bone in 
its chemical composition, but it contains a larger 
per cent, of mineral matter and is much harder. 
It is, next to enamel, the hardest tissue in the body. 
Enamel, which forms a thin covering over the 
crown of teeth, resembles bone and dentine in its 
composition, but is harder and more compact. 
197. Dental pulp. The pulp consists of a 
loose connective tissue and cells, and a number of 
blood-vessels and nerves which enter a tooth 
through a small aperture in the point of its root. 
198. Structure of Teeth.-On making a 
vertical section of a tooth, a hollow cavity will be 
found in the interior. This cavity is situated in 
the base of the crown and is continuous with a 
canal that traverses the center of each root and 
opens by a minute orifice at its extremity. The 
shape of the cavity resembles the general outline of 
the teeth. Its wall is composed of dentine, and 
1 From the Latin dens-a tooth. 96 
Anatomy and Physiology 
the part constituting the crown is covered with 
enamel. The cavity is filled with dental pulp and 
is, therefore, generally called the pulp cavity. 
199. Temporary and Permanent Teeth.- 
During the course of his life, man is provided with 
two sets of teeth, which make their appearance at 
different times. The teeth comprising the first 
set are known variously as the temporary, milk, 
and deciduous teeth. They are twenty in number, 
ten in each jaw, and appear gradually, as shown 
in the table, paragraph 204, between the ages of 
six months and two and a half years. Usually, at 
about six years of age they begin to drop out and 
leave space for their successors. The teeth re- 
placing the temporary set are known as the 
permanent teeth. They number thirty-two, sixteen 
in each jaw. The order in which they appear can 
be seen in the table, paragraph 205. 
200. Names of Teeth.-Teeth are not all the 
same shape, and according to their form they 
are classified as: incisors, canines, bicuspids, and 
molars. 
201. The incisors or cutting teeth, so called from 
their broad, sharp edge, which especially adapts 
them for cutting the food, are the front teeth; they 
are eight in number, four in each jaw. 
The canine or eye teeth are larger and stronger 
than the incisors and have a sharp-pointed edge. 
In the human animal they serve the same purpose 
as the incisors. They are four in number, two in 
each jaw, one on either side of the incisors. Joints or Articulations-The Teeth 
97 
202. The bicuspid teeth receive their name from 
the two dents or cusps in the lower surface of their 
crown, which is broad and flat. There are eight 
bicuspid teeth in the permanent set, four in each 
jaw, two being placed immediately behind each 
of the canine teeth; but there are none in the 
temporary set of teeth. The root of the bicuspids 
generally contains a deep groove which divides it 
almost in two. 
203. The molars are the largest of the teeth. 
They have broad, fiat crowns which adapt them 
for their purpose of grinding and pounding the 
food. There are eight molars in the temporary 
set and twelve in the permanent. The root of the 
molars is divided into from two to five fangs. 
204. Number of Each Variety of Tooth 
in the Temporary and Permanent Sets and 
their Order of Appearance.-In the temporary 
set of teeth there are four incisors, two canines, 
and four molars in each jaw. The figures given 
in the following table indicate in months the age 
at which each tooth appears: 
Lower Central | 
Upper Incisors 
' i st Molars and 1 
Canines 
1 Second Molars 
Incisors 
6-9 
s.„ 
Lateral Incisors 
12-15 J 
18-24 
1 24-30 
In nearly all cases the teeth of the lower jaw are 
cut shortly before the corresponding ones of the 
upper jaw. 
205. In the permanent set of teeth there are 
four incisors, two canines, four bicuspids, and 
twelve molars in each jaw. The figures in the 98 
Anatomy and Physiology 
table represent the year of life in which each tooth 
is cut. 
First 
( Incisors 
| Biscuspids 
1 Canines 1 
Second 
I Third Molars 
Molars 
6 
Central 1 Lateral 
1 7 1 8 | 
| First 1 second 
9 | io 
1 12-14 | 
Molars 
12-15 
or Wisdom 
1 17-25 
206. The ages given in these tables for the 
eruption of the teeth are the average, but there is 
considerable variation even in healthy children, 
some cutting their first teeth before six months and 
others not until nearly twelve months. Diseases 
such as rickets and marasmus retard the eruption 
period very considerably. The molars of the 
permanent teeth do not replace temporary teeth 
but are added gradually as the jaws develop. The 
third molars, commonly known as the wisdom 
teeth because of their late appearance, are some- 
times unerupted through life from want of suffi- 
cient jaw space. 
207. Development of Teeth.-Teeth are 
developed from the downward growth of epithelial 
cells of the mucous membrane, the alveolar pro- 
cesses, and the maxillary bones, the enamel being 
derived from the outer cells and the dentine and 
pulp from the deeper structures. The develop- 
ment of the temporary teeth commences about the 
sixth week of intra-uterine life and that of the 
permanent (except the second and third molars) 
about the sixteenth week. The second permanent 
molars are thought to originate about the third 
month after birth, and the third molars or wisdom 
teeth about the third year. CHAPTER VI 
MUSCULAR1 TISSUE 
Where Found. Chemical Composition. Different Kinds. 
Names and Nature of Each Variety. Special Characteristics of 
Muscular Tissue. Nature of Irritability and Stimuli. Nature of 
Contraction. Chemical Changes that Take Place in Muscle as 
the Result of Contraction. Cause and Result of Muscle Fatigue. 
Tetanus. Nature, Cause, and Purpose of Muscle Tone. Con- 
ditions that Cause Variation in Muscle Tone. Difference in the 
Contraction of Voluntary and Involuntary Muscle. Exten- 
sibility and Elasticity of Muscle. Nature of Skeletal Muscles. 
Method of Attachment, Size, Shape, Number of Skeletal Muscles. 
Names, Situation, Origin, and Insertion of Some of the.More 
Important Skeletal Muscles. 
HAVING finished the study of the osseous tissue 
and the bony framework of the body, we will 
take up that of the tissue which forms the bulk of 
the substance covering the framework; viz. the 
muscular tissue. This tissue constitutes more 
than a third of the body weight and in addition to 
forming the main substance of the fleshy parts of 
the body, it enters very largely into the structure 
of the majority of the internal organs. 
1 From the Latin musculus-a muscle. 
The branch of anatomy concerned with the muscles is known as 
myology, from the Greek myos-a muscle, and logos-a discourse. 
99 Anatomy and Physiology 
100 
208. Chemical Composition of Muscular 
Tissue.-The substances known to be constituents 
of muscular tissue are: (1) proteins-chiefly sub- 
stances known as myogen and myosin1-, (2) fats; 
(3) carbohydrates-chiefly glycogen and glucose; 
(4) inorganic salts; (5) pigments-i. e. coloring 
matter; (6) ferments2; (7) waste substances-i. e. 
simple substances resulting from the breaking 
down of the more complex compounds. 
209. Different Kinds of Muscular Tissue. 
-There are three varieties of muscular tissue, viz.: 
(1) Plain muscular tissue, known also as unstriped, 
non-striated, visceral, and involuntary. 
(2) Striped muscular tissue, called also striated, 
skeletal, and voluntary. 
(3) Striped or striated, involuntary cardiac tissue. 
Plain Muscular Tissue 
210. Meaning of Names.-This form of 
muscular tissue received the names of plain, un- 
striped, and non-striated, because its fibrils are not 
striped or striated, as are those of the second type. 
It was called visceral, because it constitutes a 
large portion of the substance of many of the 
viscera-i. e., internal organs-and involuntary, 
because it receives its nerve supply from what is 
known as the sympathetic nervous system,3 and its 
1 See Glossary. 
2 Described in connection with metabolism and heat produc- 
tion, Chapters XXVIII and XXIX. 3 gee Chapter VII. Muscular Tissue 
101 
working is therefore not under the control of the 
will. 
211. Structure.-Plain muscle is made up of 
elongated cells, varying from vov to k? of an 
inch in length, and consisting of a delicate elastic 
outer membrane or sheath filled with muscle 
plasma and a nucleus. These cells are placed side 
by side and end to end, and cemented together in 
variously shaped bundles. These bundles are 
both separated and held together and to other 
tissues and membranes by connective tissue. 
212. Nature of Plasma of Muscle Cell.- 
When, after the death of an animal, the plasma of 
muscle is examined under a microscope it appears 
to consist of minute fibrils and a granular, struc- 
tureless substance known as sarcoplasm. The 
plasma of the cell is known as the contractile sub- 
stance, because the power of contraction which 
characterizes muscular tissue is due to the con- 
tractility of the plasma fibrils. 
Striated Muscular Tissue 
213- Meaning of Names.-This form of 
muscular tissue is, as previously stated, known 
also as striped, skeletal, and voluntary muscular 
tissue. It is called striped and striated because the 
fibrils of its protoplasm consist of alternate light 
and dark parallel transverse stripes which give 
the muscles a striped or striated appearance. It is 
called skeletal because it forms the muscles which Anatomy and Physiology 
102 
cover and are attached to the skeleton, and volun- 
tary, because its movements are under the control 
of the central nervous system and, 
to a great extent, of the will. 
214. Structure.-Striped mus- 
cle is composed of slender tube-like 
fibers about an inch or more in 
length and yvo of an inch in di- 
ameter. The walls of 
the fibers are com- 
posed of an exceeding- 
ly thin, transparent, 
elastic membrane 
called thesarco- 
lemma.1 The fibers 
are filled, as in the 
case of the plain mus- 
cular tissue, with 
muscle plasma, which is appar- 
ently similar to that in the cells 
except for the shading 
of the fibrils, which is 
responsible for the 
striped appearance 
of skeletal tissue, and the presence 
of several nuclei instead of one in 
each fiber. These muscle fibers, 
together with numerous blood-ves- 
sels and nerves are held in bundles 
with an exceedingly delicate connective tissue. 
Fig. 52.- 
Fragment of a 
fiber of cross- 
striped muscu- 
lar tissue show- 
i n g fibrils 
separated at one 
end by teasing. 
(Gerrish.) 
Fig. 53 - 
Fragment of a 
fiber of cross- 
striped muscular 
tissue, hardened, 
showing trans- 
verse cleavage. 
(Gerrish.) 
Fig. 54.- 
Transverse sec- 
tion of muscle- 
fiber, showing 
nuclei. (Ger- 
rish.) 
1 From the Greek sarkos-fleshy, and lemma-a husk. Muscular Tissue 
103 
The bundles, in turn, are bound with similar, but 
stronger, tissue to 
form muscles of 
varying length, 
breadth, thick- 
ness, and shape. 
Cardiac1 Tissue 
215. Meaning 
of Name.-Car- 
diac tissue is so 
called because it 
is found only in 
the heart sub- 
stance. It is 
striped like the 
Fig. 55.-Part of a fiber of cross- 
striped muscular tissue, showing the 
alternating bands. (Gerrish.) 
skeletal muscle, but there are sev- 
eral points of difference between 
the two, the more marked of which 
are: (i) Its action is involuntary; 
(2) its fibers are shorter; (3) the 
bundles into which the fibers are 
bound are nearly square, and (4) 
are held together with branches or 
offsets of the fibers; (5) no sarco- 
lemma has been proved to exist. 
Fig. 56. - Cell 
of cardiac mus- 
cular tissue. 
(Gerrish). 
1 From the Greek kardia-the heart 104 
Anatomy and Physiology 
These differences in structure are thought to be 
of great importance in the action of the heart 
muscle, which is different from that of other mus- 
cular tissue. The characteristics of cardiac muscle 
will be considered in the chapter concerned with 
the circulation. 
216. Blood and Nerve Supply.-All types 
of muscular tissue are plentifully supplied with 
blood, which they receive from capillaries arranged 
in networks around the fibers or cells, outside the 
sarcolemma or membranous wall. The capil- 
laries do not enter the membrane, and interchange 
of substance between the blood and the cell 
contents takes place by osmosis.1 Muscular tis- 
sue is provided also with innumerable nerves. 
Those supplying the skeletal muscles belong prin- 
cipally to the central nervous system, but the 
majority of those supplying the cardiac and 
involuntary tissue belong to the sympathetic 
system. 
217. Special Characteristics of Muscular 
Tissue.-These are irritability,2 contractibility,3 
extensibility, and elasticity. 
218. Irritability and Stimuli.-By irrita- 
bility of tissue is meant its power of responding 
to stimulation, and the manner in which a tissue 
1 The diffusion-passage-of fluid through membrane. 
2 Irritability is peculiar to nervous and muscular tissue and 
certain epithelial cells, as those of glandular organs. 
3 Contractibility is peculiar to muscular tissue, white blood 
corpuscles, and ciliated epithelium. Muscular Tissue 
105 
responds to stimulation is by performing its special 
function; thus, a gland when stimulated will 
secrete, and a muscle will contract. In the living 
muscle the most common source of stimulation is 
the nervous system1; the nerve impulse2 being 
sent from the brain, spinal cord, or sympathetic 
ganglia3 along the motor nerves to the muscles 
where it causes, in some unknown way, certain 
chemical changes to take place4 in the cell, which 
result in contraction of the tissue. 
219. Muscular Contraction.-By contrac- 
tion is meant shortening. As previously stated 
in paragraphs 217 and 218, the cells and fibers of 
muscles are long and slender, but when the tissue is 
stimulated they become shorter and broader, which 
results in the muscle becoming contracted or 
shortened so that its two ends, and whatever is at- 
tached to these ends, are brought nearer together; 
e. g., the contraction of certain muscles of the arm 
will flex the forearm, and contraction of certain 
muscles of the forearm will flex the wrist, etc. 
Thus it can be seen that muscular contraction is 
the active agent in the causation of all the move- 
ments of the body, and, as stated in the preceding 
paragraph, muscular contraction in the living 
body is usually the result of nerve stimulation. 
1 Though in the living animal nerve impulse is the usual source 
of stimulation, muscular tissue can be stimulated by electricity 
and by chemical and physical agents. 
2 See paragraph 321. 3 See paragraph 307. 
4 See paragraph 220. 106 
Anatomy and Physiology 
220. Chemical Changes that Take Place 
in Muscle as the Result of Contraction.- 
Muscular contraction, as stated in paragraph 218, 
is due to chemical changes which take place in the 
muscle as the result of nerve stimulation, and 
muscular contraction, or, in other words, work or 
activity causes similar changes. The exact nature 
of these changes is not known beyond that they 
consist of splitting and oxidation, in consequence 
of which the complex compounds in the substance 
of muscle, primarily the glucose and glycogen, are 
broken into smaller and more simple ones as lactic 
acid, water, carbon-dioxide, and other waste pro- 
ducts with the production of heat1 and the libera- 
tion of the energy2 that held the atoms of the 
complex compounds together. The energy thus 
liberated is utilized both for the carrying on of 
external work-that done by the activity of the 
skeletal muscles-and internal work-respiration, 
circulation, digestion, etc. 
221. Cause of Muscle Fatigue.-Continued 
activity of voluntary muscle results in a sense of 
fatigue and a slowness on the part of the muscle to 
respond to stimulation. The reason for this fatigue 
is twofold: (1) to a loss of nutrient material, that 
in the muscle having been oxidized; (2) to an 
accumulation of acids and other waste products 
in the muscles. These waste products are often 
spoken of as fatigue poisons. 
1 Heat. See paragraph 801. 
2 Energy. See Glossary. Muscular Tissue 
107 
222. Recovery from Fatigue.1-The sense 
of fatigue disappears after the fatigue poisons have 
been eliminated from the system, in the respira- 
tion, urine, etc., and fresh nutrient material has 
been brought to the tissues by the blood; the 
blood getting the supply from the food that has 
been digested and absorbed. Rest is, of course, 
necessary for recovery, because as long as the 
body is in motion more waste products are being 
formed. Massage gives relief in severe fatigue 
because it hastens the passage of the poisons into 
the blood stream, improves the circulation of the 
blood and lymph, and thus accelerates the elimina- 
tion of the poisons. 
223. Tetanus.-If a muscle is very much 
overworked there may be such an accumulation of 
irritating fatigue poisons as to cause the muscle 
to become more or less over-contracted, and for 
the time being to remain so, causing temporary 
stiffness and perhaps pain. This condition is 
sometimes spoken of as tetanus of the muscle. If 
fatigue is often carried to this point, permanent 
impairment of the overworked muscle is likely 
to result. Tetanus of muscle must not be con- 
fused with the disease of the same name. 
224. Nature and Cause of Muscle Tone 
or Tonus.-In the living body the muscles are 
normally in a state of continuous contraction, 
slight in extent but varying in degree from time 
1 Sleep is thought to be due, at least in part, to the effect 
of these fatigue poisons on the system; see Chapter XXVI. 108 
Anatomy and Physiology 
to time. This state of slight, constant contraction 
is known as miiscle tone or tonus. It is due to the 
fact that the nerves are constantly sending light 
nerve impulses into the muscles and thereby caus- 
ing slight chemical changes in the tissues, with the 
result that the muscles remain in a state of slight 
contraction. 
225. Causes of Nerve Impulse-In order 
to discharge impulses, the nerves must first be 
stimulated, and this they are continuously: dur- 
ing waking hours through impressions received 
by the sensory nerves 1 connected with the senses 
of sight and hearing, through those of the skin 
which are affected by variations in temperature, 
contact of clothing, etc.; and at all times through 
the sensory nerves from the muscles. 
226. Value of Muscle Tone.--Muscle tone 
is thought to be of importance to the body in 
several ways, viz., it, together with the extension 
of muscle-see paragraph 232--permits of a 
quicker response of muscle tissue to stimulation; 
(2).it assists in maintaining the circulation of the 
blood and lymph; (3) in controlling the regulation 
of body heat and nutrition. These two last uses 
of muscle tone will be referred to again in the 
chapters dealing with the circulation of the blood 
and metabolism. 
227. Conditions that Cause Variation in 
Muscle Tone.-As stated in paragraph 224, the 
1 The nerves which carry impressions from the periphery to 
the brain. Muscular Tissue 
109 
degree of tonus in muscle is somewhat variable. 
The most common causes of increased tonus in the 
living organism are: (i) muscular activity; (2) 
mental activity; (3) lowering of the surrounding 
temperature. 
228. Exercise as a Cause of Muscular 
Tone.-Exercise means muscular contraction, 
and is therefore, of course, attended with the pro- 
duction of the products of disintegrated tissue 
substance. The bad result of over-exercise has 
been already discussed, but a normal amount of 
exercise is not attended with a greater produc- 
tion of waste substances than the system can 
easily get rid of, and when present in moderation 
these improve muscular tone, and consequently 
the circulation of the blood and lymph, nutrition, 
etc. 
229. Mental Activity as a Cause of In- 
creased Muscular Contraction.-An example 
of increased muscular contraction as the result of 
mental activity is the tension that often accom- 
panies excitement of any kind, or intense mental 
concentration-as when listening to eloquent 
oratory, a very exciting tale, etc. This accounts 
for the feeling of relaxation that follows such 
concentration, the fatigue that follows protracted 
excitement or concentration, and the unusual 
strength that results from extreme excitement. 
230. Lowering of Temperature as a Cause 
of Increased Muscular Tone.-When the skin 
becomes chilled certain of the sensory nerves 110 
Anatomy and Physiology 
therein become stimulated and act upon the nerve 
centers1 in the brain or spinal cord, in consequence 
of which there will be an increase in the impulses 
sent along the motor nerves to the muscles, which 
will cause an increase in the degree of muscle con- 
traction. If the chilling is severe the increase in 
muscle contraction may be so intense that shivering 
will result. As stated in paragraph 220, muscular 
contraction produces heat and the increased tonus 
following chilling is one of nature's methods of 
heat regulation. 
231. Differences in the Contraction of 
Involuntary and Voluntary Muscle.-Con- 
traction of the involuntary muscle of the viscera 
takes place more slowly and regularly and lasts 
longer than that of voluntary muscle. If, for any 
reason, such as excessive nervous irritation, con- 
traction takes place more quickly than usual in 
involuntary muscle, pain will result. A familiar 
example of this is the gastric or intestinal cramp 
that often follows the taking of indigestible food 
or of drastic cathartic medicines, etc. 
232. Extensibility and Elasticity of Mus- 
cle.-It was said in paragraph 217 that muscle 
is extensible-i. e., it can be stretched-and 
elastic-i. e., it can return to its original shape 
after it has been stretched. In our bodies the 
skeletal muscles are, normally, always in a con- 
dition of slight tension, being stretched from bone 
to bone. This condition is of great importance 
1 See paragraph 329. Muscular Tissue 
111 
in the functioning of the muscles, because (l) 
a stretched muscle will contract more quickly 
than one which is relaxed; (2) smoothness of 
movement is in many parts of the body de- 
pendent upon it. To understand how the latter 
fact can be true it is necessary to know that 
the majority of the skeletal muscles are so 
arranged that certain muscles or groups of 
muscles oppose or are antagonistic to the ac- 
tion of others. For instance, on the anterior 
surface of the forearm are muscles called flexors, 
because their contraction flexes the wrist, hand, 
or fingers; and on the posterior surface are mus- 
cles, called extensors, that cause extension. Now, 
as these extensor muscles are in a state of tension, 
the flexors when stimulated must overcome the 
resistance of the extensors, and therefore contrac- 
tion takes place more slowly and evenly; this 
prevents jerking, such as takes place when a 
muscle is very strongly stimulated, as by an electric 
shock. 
The Skeletal Muscles 
233- Nature of a Muscle.-"A muscle is an 
organ whose essential part is a mass of striated 
muscular tissue, prolonged at its opposite ends or 
margins by cords, bands, or sheets of white fibrous 
tissue which are fastened to ether structures, 
usually bones. The muscular tissue is contractile, 
and is the active portion of the organ; the fibrous 112 
Anatomy and Physiology 
is strong and flexible, but is only passive. The 
contractile portion is called the muscle proper, the 
belly or the body of the muscle; the fibrous ex- 
tensions are called tendons, and sometimes when 
greatly expanded, aponeuroses. The muscle proper 
may be compared to an engine in which force is 
generated; its tendons to the ropes by which the 
power is applied to distant objects. "T 
234. Origin and Insertion of Muscles.- 
A muscle is attached to two objects. The part 
fastened to the more fixed of these objects is 
spoken of as the origin of the muscle, and the part 
attached to the body which the muscle moves the 
most easily is called the insertion of the muscle. 
235. Methods of Attachment.-Muscles have 
several different kinds of attachment. (1) They 
are usually connected with bones by means 
of tendons and ligaments, the contractile muscle 
fibers gradually blending with the non-contractile, 
tough tendon, or ligament fibers, which in turn 
become gradually blended into the substance 
of the periosteum to which they hold the mus- 
cle, and thus when the muscle contracts, the 
tendons and ligaments, being unable to do so, 
pull on the two bones, bringing them nearer 
together. (2) In several parts of the body 
one muscle is attached to another by means 
of a broad, flat band of fibrous tissue, termed 
an aponezirosis. (3) Groups of muscles are held 
1 Text-Book of Anatomy by American Authors, page 259. 
Gerrish. Lea Bros. Co. Muscular Tissue 
113 
together and muscles are connected with the skin 
and with other tissues by thin sheets and bands 
of fibrous tissue known as fascias. 
236. Size and Shape.-Muscles vary in size 
from the fraction of an inch to nearly two feet in 
length. Their shape, also, is very diverse, some 
muscles being thick, others thin and sheet-like 
some broad, others slender, etc. 
237. Nomenclature and Number.-The vol- 
untary muscles are nearly always called by their 
Latin names, which are usually descriptive either 
of their action, their situation, their shape, or some 
special characteristic in their structure. Their 
number is generally estimated as 405. With a 
few exceptions they occur in pairs. As a knowl- 
edge of the names of the muscles is not of much 
importance to nurses, only the larger muscles and 
those likely to be referred to in describing different 
parts or functions of the body will be mentioned 
here. The ones which are so constantly referred 
to that it is well to remember their names and 
situations are starred. In reading the following 
description of the muscles it is to be remembered 
that though, as a rule, only one muscle or group of 
muscles is mentioned, those spoken of here occur 
in pairs, with the exception of the occipito-fronta- 
lis and the diaphragm. 
Muscles of the Head and Face 
238. The names of the principal muscles of the 
head and face are: 114 
Anatomy and Physiology 
Occipito-frontalis 
Recti, 4 for each eye 
Oblique, 2 for each eye 
Levator palpebrce superioris 
Masseter 
Temp oralis 
Pterygoid extermis 
Pterygoid internus 
Buccinator 
Orbicularis oris 
Geniohyo gios sus 
Styloglossus 
Lingualis 
of the 
tongue 
*239. Occipito-Frontalis.-This consists prac- 
tically of two muscles: the occipital, which covers the 
back or occiput of the head, and the frontal, which 
covers the front of the skull and is inserted in the 
skin and muscles of the root of the nose and eyebrows. 
The two muscles are held together by an aponevtrosis, 
which covers the top of the head. The frontalis is the 
more active muscle. Action: it elevates the brows, 
catising transverse wrinkling of the forehead. 
*240. Muscles of Eyeball.-These are the 
superior, inferior, internal, and external recti, and 
the superior and inferior oblique. The four recti1 
muscles have their origin in the long structure of 
the orbital cavity. At the apex of the eye they 
pass forward and are inserted in the sclerotic2 coat 
of the eye, near the margin of the cornea3; the 
superior at the upper part of the eye; the inferior 
opposite it at the lower margin; the external on the 
outer side; and the internal on the inner side. 
*241. Action.-Contraction of the superior 
rectus rolls the eyeball upward; contraction of 
1 Recti, singular rectus, Latin-straight. 
2 Described in paragraph 948. 3 Ibid., 949. Muscular Tissue 
115 
the inferior, rolls it downward. The right external 
rectus of one eye and the left internal of the other 
Fig. 57.-Superficial muscles of head and neck. (Gerrish.) 
act together, when a person is looking toward the 
right, to turn the eyes to the right; and the left 
external rectus and right internal act together to 
turn the eyes toward the left. Both internal recti 116 
Anatomy and Physiology 
act together to turn both eyes toward the middle 
line, as is done when directing the vision toward a 
near object in front of the eyes. The superior 
oblique has its origin in the inner side of the orbital 
cavity, and is in- 
serted in the 
outer surface of 
the eyeball, in the 
sclerotic coat, be- 
tween the superior 
and the external 
recti. The in- 
ferior oblique 
arises from a de- 
pression in the orbital articulation of the superior 
maxillary, near the nasal duct. It passes around 
to the outer side of the eye and is inserted 
near the tendon of insertion of the superior oblique. 
Action: the oblique muscles rotate the eyeball 
on its antero-posterior axis. This kind of move- 
ment is particularly required for the correct viewing 
of an object when the head is moved laterally, as 
from shoulder to shoulder. 
242. Levator Palpebr^e Superioris.-The 
name of this muscle-lifter of the upper lid-denotes 
its action. It arises from the bony structure at the 
back of the eye and is inserted in the upper lid. 
243. Masseter. -Origin: superior maxilla and 
zygomatic arch. Insertion: angle of lower jaw. 
Action: assists in mastication. 
Fig. 58.-Muscles of eyeball. (Gerrish.) 
1 From the Greek massaomai- to chew. Muscular Tissue 
117 
*244. Temporal.-Origin: fossa and fascia of 
the temporal bone. Insertion: coronoid process of 
the lower jaw bone. Action: assists in mastication. 
245. Internal Pterygoid. 1-Origin, insertion, 
and action similar to the temporal. 
246. External Pterygoid. 1-Origin: sphenoid, 
ethmoid, palate, and superior maxillary bones. In- 
sertion: lower jaw. Action: assists in mastication. 
247. Buccinator.2-Origin: alveolar processes 
of the upper and lower jaw bones. Insertion: 
muscles of the lips. Action: compresses the cheeks, 
so that food is kept in immediate contact with the 
teeth, and assists in such motion as blowing a 
trumpet, etc., hence its name. 
248. Orbicularis Oris.3-This is a sphincter* 
muscle, elliptic in form, which surrounds the mozith 
and extends from the nostrils to the chin. Action: 
it closes the lips. 
Chief Muscles of the Tongue 
249. Geniohyoglossus. 5-Origin: superior tu- 
bercle of lower jaw. Insertion: body of the hyoid 
bone and under surface of the tongue from base to 
1 From the Greek pier on-a wing, and eidos-form. These 
muscles were so named from their shape. 
2 Buccinator. From the Latin bucinare-blow a trumpet. 
s Orbicularis Oris. Latin, pertaining to an orb, and oris-the 
mouth. 
4 Sphincter. From the Greek sphiggo-to close. 
5 Genio-hyo-glossus. From the Greek geneion-the jaw, 
huoeides-the hyoid, and glossa-the tongue. 118 
Anatomy and Physiology 
point. Action: it protrudes as well as retracts the 
tongue, and also depresses it, as in the act of sucking. 
250. Styloglossus.-Origin: the styloid proces- 
ses of the temporal bone. Insertion: side and lender 
surface of the tongue. Action: draws the tongue 
backward. 
251. Lingualis.-This muscle forms the bulk 
of the tongue. The fibers of the lingualis blend with 
the other muscles of the tongue and some of them are 
inserted in the hyoid bone. Action: it draws the 
center and apex of the tongue downward.1 
Muscles of the Neck 
The principal muscles of the neck are: 
Platysma2 Myoides3 
Sternocleidomastoid 
Sternothyroid 
252. Platysma Myoides.-A thin, broad muscle 
covering the upper part of the shoulder and side of 
the neck. Origin: the deep-fascice over the pectoral, 
deltoid, and trapezius muscles. Insertion: the lower 
jaw. Action: depresses the jaw and angle of the 
mouth, and wrinkles the skin of the neck. 
1 Anaesthetics, as ether and chloroform, when given to an in- 
dividual in sufficient quantity to produce general anaesthesia, 
depress the nervous system and, consequently, lessen muscular 
tonus. This loss of tone, or relaxation of the muscle in the 
tongue, makes that organ likely to fall back over the trachea-air 
passage to the lungs-unless the head is kept turned on one side 
and the jaw pressed forward and upward. 
2 Platysma. From the Greek platus-broad. 
3 Myoides. From the Greek myo-muscle, and oides-likeness. Fig. 59.--Muscles in the superficial layer of the back 
(Gerrish.) 
119 Anatomy and Physiology 
120 
*253. Sternocleidomastoid.1-Origin: the up- 
per part of the sternum and the inner border of the 
clavicle. Insertion: mastoid process of the temporal 
bone. Action: flexes the head on the neck and chest 
and rotates the chin. 
254. Sternothyroid.1-Origin: sternum. In- 
sertion: thyroid cartilage of the larynx. Action: 
depresses the larynx. 
Muscles of the Back 
The largest superficial muscles of the back are: 
The trapezius 
The latissimus dor si 
*255. The Trapezius.-Origin: the occipital 
bone, the processes of the seven cervical and the twelve 
dorsal vertebrce. Insertion: in the clavicle and 
scapula. This muscle covers the back of the neck 
and the zipper part of the back. Action: draws the 
shoulder upward, backward, and laterally, and moves 
the scapula. 
*256. Latissimus Dorsi.-Origin: the six lower 
dorsal vertebrce and the crest of the ilium. Insertion: 
in the front of the humerus. This muscle covers the 
lower part of the back and converges {see Fig. 59) into 
a narrow band which passes upward and around 
towards the front of the chest where it merges into a 
tendon that is inserted in the humerus. Action: it 
draws the humerus downward and backward, while 
1 These muscles are named from the bones and cartilages of 
their origin and insertion, cleido meaning clavicle. Muscular Tissue 
121 
rotating it inward; it helps raise the lower ribs in 
forcible inspiration, and it helps in the movements of 
climbing and pulling. 
Muscles of the Thorax 
257- The principal muscles of the thorax are the 
internal and external intercostal muscles, the leva- 
tores costarum, the triangularis sterni. 
*258. The External and Internal Inter- 
costal Muscles.-These two sets of muscles, as 
their names imply, are situated between the ribs, the 
internal behind the external. Each external muscle 
arises from the lower border of a rib, runs downward 
and forward and is inserted in the ripper border of 
the rib next below. Action of external intercostals: 
they raise the ribs. Each of the internal intercostals 
arises from the inner surface of a rib and its cartilage, 
just above their lower border, runs down and back- 
ward, and is inserted in the inner surface of the rib 
next beneath. Their action is not agreed upon. 
259. Levatores Costarum.-They are twelve 
in number. Each one arises from the tip of the 
transverse process of a vertebra and is inserted into 
the outer surface of the rib next below. Action: it 
was thought formerly that these muscles elevated the 
ribs, hence their name; but it is now considered that 
they only assist in the extension and lateral flexion 
of the dorsal part of the thorax. 
260. The Triangularis Sterni. 1-Origin: the 
1 Triangular muscle of the sternum, so called from the shape 
and attachment of the sternum. Anatomy and Physiology 
122 
lower part of the sternum and the cartilages oj the 
lower two or three true ribs. Insertion: the outer 
extremities of the costal cartilages, from the second to 
the sixth. Action: depression of those ribs to the 
cartilages of which it is attached. 
*261. The Diaphragm.-The diaphragm is a 
Fig. 6o.--Diaphragm, viewed from in front. (Gerrish.) 
thin musculo-fibrous septum placed obliquely 
between the thoracic and the abdominal cavities, 
forming the floor of the former cavity and the roof 
of the latter. It consists of a tendon which forms 
its central portion, and a muscle which surrounds 
and is inserted in the tendon. The muscle has its 
origin in the lower boundaries of the thoracic 
framework-the sternum, some costal cartilages, Muscular Tissue 
123 
several vertebrae, and fibrous bands connected 
with the last rib. The shape of the diaphragm 
is that of a flattened dome, its highest point being 
the central tendon. While passive, its lower part 
is in apposition with the chest walls. On contrac- 
tion of the muscular portion, the tendon, being 
non-contractile, is pulled upon and drawn down so 
that the dome is flattened and the capacity of the 
thoracic cavity thus greatly increased. There are 
three large foramina in the diaphragm for the 
passage of the esophagus,1 the aorta,2 and the 
inferior vena cava,3 also several smaller ones for 
the entrance and exit of blood-vessels, lymphatics, 
and nerves to and from the lower half of the body. 
Action: the diaphragm is the principal muscle of 
respiration and at times it assists the abdominal 
muscles in their function. 
262. Abdominal Muscles.-The chief muscles 
of the abdomen are: 
External oblique 
Internal oblique 
Transversalis abdominis 
Rectus abdominis 
263. Abdominal Aponeuroses, Linea Alba, 4 
and Poupart's Ligament.-The oblique and trans- 
versalis muscles of the two sides of the abdomen are 
1 Esophagus. The tubes connecting the mouth with the 
stomach. 2 Aorta. The main artery. 
J Vena Cava. One of the largest veins of the body. 
4 Linea Alba. Latin, white line. Anatomy and Physiology 
124 
united by means of their aponeuroses, which interlace 
in the median line of the abdomen, forming a heavy 
white cord which extends from the ensiform cartilage 
to the symphysis pubis and is known as the tinea alba. 
The aponeuroses cover a considerable portion of the 
front of the abdomen, and at their lower extremity 
extend in a heavy band from the spine of the pubis 
to the anterior superior spine of the ilium. This 
ligament was named Pollpart's ligament, after the 
surgeon who first described it; also, it is called, from 
its location, the inguinal ligament. 
264. External Oblique Muscle.-Situation: 
in the superficial surface of the side and front wall of 
the abdomen. Origin: the order surface of the lower 
eight ribs. Principal points of insertion: the an- 
terior half of the iliac crest, the tinea alba, Poupart's 
ligament. 
265. Internal Oblique.-Situation: behind 
the external oblique. Origin: order half of Poupart's 
ligament, the center of the crest of the ilium and 
the lumbar fasciae. Insertion: the lower borders of the 
six lower costal cartilages, the ensiform process, the 
linea alba, and the pubic bone. 
266. Transversalis. 1-Situation: beneath the 
internal oblique. Origin: the inner surface of the 
lower six costal cartilages, the transverse processes 
of the lumbar vertebrae, the crest of the iluim, and the 
older third of the inguinal ligament. Insertion: the 
linea alba and the crest of the pubic bone. 
1 So called because the greater part of the fibers have a 
transverse-horizontal-direction. Muscular Tissue 
125 
267. Rectus1 Abdominis.-Nature and situa- 
tion; a long slender, flat muscle which extends along 
the whole length of the front of the abdomen. The 
aponeuroses of the oblique and transversalis muscles, 
which are all blended into one, separate at the outer 
border of the rectus, forming two sheets, which pass 
one under and the other over the muscle, and unite 
again at the medial border, forming, with the aponeii- 
roses of the opposite side, the linea alba. Origin of 
the rectus: the pubic bone. Insertion: the fifth, sixth, 
and seventh costal cartilages. 
*268. Action of the Abdominal Muscles.- 
These muscles, by constricting the cavity of the 
abdomen, compress the abdominal viscera in 
which action they are materially assisted by the 
descent of the diaphragm. This action helps in 
the expulsion of feces from the rectum, urine from 
the bladder, the contents of the stomach in vomit- 
ing, and, in parturition, the fetus from the uterus. 
The abdominal muscles also assist in respiration2 
and in various movements, such as climbing, flex- 
ing the thorax upon the pelvis, rotation of the 
trunk, etc. 
*269. The Inguinal Canal.-In the groin or 
inguinal region, between the abdominal muscles, 
is a small crevice called the inguinal canal, through 
which, in the female, the round ligament of the 
uterus passes and, in the male, the spermatic cord. 
1 Rectus. So called because its fibers run directly perpen- 
dicularly. From the Latin rectus-straight. 
2 See Chapter XV. Respiration. 126 
Anatomy and Physiology 
This canal is about an inch and a half long and 
extends obliquely downward and toward the 
median line, from an aperture in the fasciae of the 
transversalis muscle, called the internal abdominal 
ring. This ring is on a line midway between the 
anterior superior iliac spine and the symphysis 
pubis, and about an inch above Poupart's ligament. 
The canal ends at the external abdominal ring 
which is in the aponeurosis of the external oblique 
muscle. As these rings are the frequent seat of 
hernia they have a special interest for nurses. 
270. Hernia.-A hernia, or rupture, is a 
protrusion of a portion of intestine through one of 
the weak points of the abdominal wall, such as the 
umbilicus, the rings described above, and another 
ring situated below Poupart's ligament, called the 
femoral ring. Hernia in the umbilicus is called 
umbilical hernia; in the inguinal rings, inguinal 
hernia, and in the femoral ring, femoral hernia. 
271. Chief Muscles of the Upper Ex- 
tremity.-These are named ': 
Pectoralis major 
Pectoralis minor 
Deltoid 
Shoulder 
Brachialis 
Biceps flexor cubiti 
Triceps extensor cubiti 
Arm Muscular Tissue 
127 
Pronators 
Supinators 
Flexors 
Extensors 
Abductors 
Adductors 
Forearm 
Hand 
*272. Movements Caused by the Contrac- 
tion of the Majority of Muscles of the Upper 
and Lower Extremities and Arrangement of 
Muscles.-The movements of which the extremi- 
ties of the body are capable are: flexion and exten- 
sion, abduction and adduction, supination and pro- 
nation, circumduction and rotation. The nature of 
these movements was described in the preceding 
chapter. As has been already stated, muscles and 
groups of muscles causing antagonistic movements, 
as flexion and extension, etc., are so arranged that 
the antagonistic ones oppose the action of each 
other, as, owing to the normal extension of the 
muscles, this secures evenness of movement. 
Muscles of the Shoulder 
*273. Pectoralis1 Major.-Situation: front 
and upper part of the chest. Origin: the clavicle, 
sternum, and sixth costal cartilage. Insertion: in 
the humerus. Action: draws the arm downward 
and forward. 
1 Latin pectoralis-pertaining to the breast. On account of 
their location, the pectoral muscles are often classed with the 
muscles of the thorax, but as their action is concerned with 
the arm they are as frequently classed with those of the upper 
extremities or shoulder girdle. 128 
Anatomy and Physiology 
*274. Pectoralis Minor.-Situation: the chest 
Fig. 61.-Front of chest and shoulder of right side, superficial 
muscles. (Gerrish.) 
(see Fig. 61}. Origin: third, fourth, and fifth ribs. 
Insertion: in the coracoid process of the scapula. Muscular Tissue 
129 
Action: depresses the shoulder and assists in the 
elevation of the ribs during inspiration. 
275. Deltoid.1-Situation: covering the most 
prominent part of the shoulder and the middle of the 
outside of the arm. Origin: outer third of the clavicle, 
outer border of the acromion process, lower border of 
the spine of the scapula. Insertion: on the outer 
side of the humerus. Action: it abducts-raises-- 
the arm to a right angle with the trunk, draws the arm 
forward, if the portion attached to the clavicle works 
alone, or backward, if only the portion attached to the 
scapula contracts.2 
Muscles of the Arm 
276. Brachialis.3-Situation: on the front of 
the arm. Origin: the humerus. Insertion: the ulna. 
Action: flexion of the forearm. 
*277. Biceps. 4-Situation: in the front of the 
arm. Origin: the biceps, as its name implies, has 
two heads; they both have their origin in the scapula 
but in different parts. Insertion: in the radius. 
Action: flexes the forearm. 
278. Triceps. 5-Situation: in the back of the 
1 Delta-like muscle. Delta being the name of the Greek letter, 
the form of which the deltoid is thought to resemble. 
2 The latissimus dorsi, described with the muscles of the back, 
and some small muscles around the shoulder, oppose the action of 
the deltoid and adduct the arm-draw it down toward the trunk. 
3 From the Latin brachium-the arm. 
4 From the Latin, bis--twice, and caput-a head. 
5 From the Latin, tris-three, and caput-a head. 130 
Anatomy and Physiology 
arm. Origin: the triceps 
has three heads, two of 
which have their origin 
in the scapula and one 
in the humerus. Inser- 
tion: back of the olecra- 
non process of the ulna. 
Action: extension of the 
forearm. 
Muscles of the 
Forearm and Hand 
*279- Pronators. 
-There are two. Situ- 
ation: the front of the 
forearm. Origin: (No. 
i), both humerus and 
ulna; (No. 2), ulna 
only. Insertion: both 
in the radius. Action: 
they pronate the radius 
and, consequently, the 
hand.1 
*280. Supinator. 
-Situation: outer part 
of the forearm. Origin: 
1 It will be remembered 
that pronation and supina- 
tion of the radius are obtain- 
ed by the rotation of the 
radius on the ulna. 
Fig. 62.-Superficial muscles of 
front of right forearm. (Gerrish.) Fig. 63.-Muscles of the right palm. The abductors of the 
thumb and little finger have been removed. (Gerrish.) 
131 132 
Anatomy and Physiology 
back and lower part of the humerus. Insertion: 
radius. Action: supinates the radius and, conse- 
quently, the hand.1 
*281. Flexors.-Situation: principally in the 
front and inner border of the forearm; a few in the 
palm of the hand. Origin: front stirface of the hu- 
merus; a few in the ulna. Insertion: front surface 
of the carpal and metacarpal bones and the fingers. 
Action: flexion of the hand and fingers. The flex- 
ors of the forearm concerned with the fingers are 
attached to them by means of long tendons, and deep 
wounds around the wrist or in the palm of the hand 
are likely to sever some of these tendons, and, unless 
the severed parts are sewed together, cause loss of 
power to flex the fingers to which the injured tendons 
belong. The tendons are held to the wrist by the 
annular ligaments. See Fig. 63. 
*282. Extensors.-Situation: principally on 
the back and outer surface of the forearm; a few on 
the back of the hand. Origin: principally the 
humerus. Insertion: dorsal aspect of carpal and 
metacarpal bones and the fingers. As in the case of 
the flexors, the extensors of the forearm concerned 
with the fingers are connected with them by means of 
long tendons. Action: extension of the hand and 
fingers. 
*283. Abductors and Adductors.-Abduc- 
tion and adduction of the forearm takes place only in 
connection with the arm and by the action of the same 
1 It will be remembered that pronation and supination of the 
radius are obtained by the rotation of the radius on the ulna. Muscular Tissue 
133 
muscle causing those movements in the arm, but the 
thumb and each of the fingers have two muscles 
attached to the base of its first phalanx, one on the 
radial and one on the ulnar side, by means of which 
they are abducted and adducted; the abductor being 
sihiated, except in the case of the middle finger, on the 
side farthest from the median line, and the adductor 
on the side nearest to it. In the middle finger both 
muscles are abductors, but when the finger is dis- 
placed laterally by one of these muscles, it is restored 
to the middle line by the contraction of the other. 
These muscles arise from the carpal bones and extend 
over the palm of the hand. 
Chief Muscles of the Lower Extremities 
284. Names : 
Gluteal- 
Region 
(Bzittocks) 
Gluteus maximus (largest) 
Gluteus medius (middle) 
Gluteus minimus (smallest) 
Loin Psoas magnus 
Femoral 
Region 
(Thigh) 
A nterior 
Region 
Sartorius 
Quadriceps 
Adductor gracilis (slender) 
magnus (great) 
longus (long) 
brevis (short) 
Internal 
Region 
Posterior 
Region 
Biceps 
Semitendinosus (half tendon) 
Semimembranosus (half mem- 
brane) 134 
Anatomy and Physiology 
Anterior 
Region 
Tibialis anticus or anterior 
Extensors 
Posterior 
Region 
Popliteus 
Gastrocnemius 
Soleus 
Flexors 
Tibialis posticus or posterior 
Leg 
Fibular 
Region 
Peroneus1 longtts (long) 
Peroneus brevis (short) 
Dorsal 
Region 
Extensors 
Foot 
Plantar 
Region 
Flexors 
Abductors 
Addvictors 
Muscles of the Buttocks and Loin 
*285. Glutei2 Muscles.-These muscles form 
the principal part of the substance of the nates or 
buttocks. The gluteus maximus is the most super- 
ficial and the largest. Origin: ilium, sacrum, 
coccyx. Insertion: great trochanter. Action: ex- 
tends, abducts, and rotates the thigh outward, and 
has greater power than any other muscle to maintain 
the body in the erect position. The gluteus medius 
and gluteus minimus arise from the outer surface of 
the ilium and are inserted in the great trochanter. 
Action: help slipport the trunk, flex and rotate the 
trunk inward, and the gluteus minimus also abducts 
the thigh. 
1 Peroneus. From the Greek per one-fibula. 
2 Glutei. From the Greek gloutoi-the buttocks. Fig. 64.-Muscles in the outer side of right leg and dorsum 
ot foot. (Gerrish.) 
135 136 
Anatomy and Physiology 
286. Psoas Magnus.1-Situation: in the lum- 
bar region, on the side of the spine and margin of the 
pelvis. Origin: the processes of the last thoracic and 
all the lumbar vertebrce. Insertion: in the lesser 
trochanter of the femur. Action: flexes the thigh on 
the pelvis, or vice versa, and rotates the femur outward. 
Muscles of the Thigh 
287. Sartorius. 2-Situation: crossing obliquely 
from the front to the inner side. It helps in pro- 
ducing the cross-legged position sometimes assrimed 
by tailors in sitting on their bench, hence its name. 
Also it helps in rotation and abduction of the thigh. 
288. Quadriceps.3-Situation: the front and 
inner part of the thigh. The quadriceps has four 
heads and is often described as four separate muscles 
called the (z) rectus femoris; (2) vastus4 externus; 
(3) vastus internus; {4} vastus intermedins. Origin: 
the rectus femoris from the spine of the ilium, the 
others from the femur. Insertion: all four are in- 
serted in a tendon which is attached to the tibia. 
The lowest part of this tendon is called the ligamentum 
patella. Action: extension of the leg. 
289. Adductors: Gracilis, Magnus, Longus, 
Brevis.-Situation: inner side of the thigh. Origin: 
1 Psoas magnus. From the Greek psoa-loin and Latin 
magnus-great, large. 
2 Sartorius. From the Latin sartor-a tailor. 
3 Quadriceps. From the Latin, quatuoi-four and caput-head. 
4 Vastus. From the Latin vastitas-vastness. (The vast 
external, internal, and middle muscle.) Muscular Tissue 
137 
each of the four muscles arises from some part of the 
os pubis. Insertion'of gracilis: the inner shaft of the 
tibia; of the other three: the inner side of the femur. 
Action: the gracilis adducts the thigh, flexes the leg 
and rotates it inward; the other three adduct, rotate, 
and flex the thigh. The gracilis is a slender muscle, 
but it is the longest in the body. 
290. Biceps.-Situation: in the back of the thigh. 
Origin: one head arises from the ischial tuberosity, 
the other from the posterior surface of the femur. 
Insertion: the head of the fibula and, slightly, the 
outer tuberosity of the tibia. 
291. SEMITENDINOSUS AND SEMIMEMBRANOSUS. 
-Situation: the back part of the thigh, toward the 
inner side. Origin: the ischium. Insertion: tipper 
and inner part of the tibia. Action: they flex the 
leg on the thigh-i. e., bend the knee, rotate the leg 
inward, and extend the thigh. 
Muscles of the Leg 
292. Tibialis Anticus.-Situation: outer side 
of the tibia. Origin: tuberosity and shaft of the 
tibia. Insertion: underside of the great toe. Action: 
flexes the ankle-joint, rotates the foot inward, abducts 
the foot. 
*293. Extensors.-There are two so named. 
Situation: front surface of the leg. Origin: one from 
the fibula, one from the tibia and fibula. Insertion: 
the phalanges of the toes. Action: they extend the 
toes, flex the ankle, and abduct the foot. 138 
Anatomy and Physiology 
294. Popliteus.-Called also the ham muscle. 
Situation: behind the knee-joint and upper part of 
the leg. Origin: external condyle of the femur. 
Insertion: the tibia. Action: flexion and inward 
rotation of the leg. 
*295. Gastrocnemius. 1-The calf muscle of the 
leg. Situation: back of the leg. Origin: outer side 
of external condyle of the femiLr. Insertion: in the 
tendon Achillis, which attaches it to the heel. Action: 
extension of the foot and, when the ankle joint is 
fixed, extension of the leg. 
296. Soleus. 2-Situation in the back part of the 
leg, in front of the gastrocnemius. Origin: upper 
part of the fibula. Insertion and action: the same as 
the gastrocnemius. 
*297. Flexors.-There are seven. Situation: 
back part of the leg or sole of the foot. Origin: one 
in the fibula, two in the tibia, two in the heel, two in 
the under surface of the metatarsal bones. Insertion: 
in the toes by means of long tendons. Action: 
flexion of the toes. 
298. Peroneus3 or Peroneal Muscles.- 
Situation: one on the anterior and two on the outer 
surface of the leg and sole of the foot. Action: ex- 
tension and abduction of the foot and elevation of 
its oziter edge. 
1 From the Greek gaster-the belly and kneme-the leg. The 
muscle was so named because of its shape. 
2 Pertaining to the sole. 
s From the Greek perone-fibula; so called because they cover 
the fibula. Muscular Tissue 
139 
Muscles of the Foot 
*299- Extensors.-The extensor muscle of the 
toes situated on the dorsum or top of the foot. Origin: 
os calcis and anterior annular ligament. Insertion: 
the phalanges or toes. Action: extension of the toes. 
*300. Abductors and Adductors.-Situation: 
sole of the foot. Origin: tarsal or metatarsal bones. 
Insertion: about the same as the abductors and 
adductors of the fingers. Action: abduction or 
adduction of the toes. 
301. Annular1 Ligaments.-There are three 
important ligaments on the front and sides of the 
ankle, known as the anterior, interior, and external 
annular ligaments, which bind down and act as a 
stay to the tendons passing to the foot and toes. These 
ligaments are of great importance to the proper action 
of the tendons. 
1 Annular. From the Latin annulus-a ring. CHAPTER VII 
NERVE TISSUE AND THE NERVOUS SYSTEM1 
Characteristics of Nerve Tissue. Parts Composing the 
Nervous System. Division of the Nervous System into Cerebro- 
Spinal and Sympathetic Systems. Nature and Parts of Nerve- 
Cells. Nature and Function of Dendrites, Axons, Collaterals, 
and Nerve-Fibers. Medullated and Non-Medullated Nerve- 
Fibers. Sensory and Motor Fibers. Reason for Difference in 
Impulse Carried by Sensory and Motor Fibers. Nature and 
Function of Nerve-Endings. Reaction of the Sensory Nerve- 
Endings to Different Kinds of Stimuli. Nature and Function of 
Neuralgia. Arrangement and Distribution of Nervous Tissue. 
Plexuses. Nature of Respiratory and Other Centers. Central 
Connections of the Nerves. Origin and Nature of Nerve Impulse. 
Function of the Cell-Body. Reflex Action. Automatism. Ori- 
gin of Voluntary Impulses. Degeneration and Regeneration of 
Nerves. Effect of Fatigue, etc., on Cell Bodies. Knee-Jerk. 
THE next tissue to be considered is that which 
forms the main substance of the organs compris- 
ing the nervous system, viz.: nervous tissue. 
1 In the study of anatomy and physiology it is impossible to 
go into the detail of any one system without constantly referring 
to some of the others. This is more especially true of the nervous 
system, the functioning of all the organs of the body being de- 
pendent upon it. As it must be referred to so constantly, and as 
some knowledge of its nature is necessary in order to understand 
the references, it seems well to take up its study, with the 
exception of the organs of special sense, before that of the other 
systems and not, as is generally done, afterward. 
140 Nerve Tissue and Nervous System 
141 
302. This tissue is more highly specialized 
and its action is more wonderful than that of any 
other tissue in the body, for it controls human 
thought and conduct, it gives us the power to 
perceive and appreciate the world about us; to 
hear, to see, to move, to talk; the ability to react 
to our surroundings; also it controls and ensures 
co-ordination in the working of both the viscera 
and the skeletal muscles. 
303. Characteristics of Nerve Tissue.- 
These are irritability and conductivity. By irri- 
tability is meant, as in the case of muscular tissue, 
the power to respond to stimulation; by conduc- 
tivity, the power to transmit the stimulus or, as 
it is often called, nerve impulse, to muscles, glands, 
etc. The nature of this impulse will be discussed 
later. 
304. Parts Composing the Nervous System. 
-The nervous system consists of the following 
parts: (1) Large masses of nerve tissue situated 
within the skull and the spinal column and con- 
stituting the brain and spinal cord; (2) smaller 
masses of ganglionic tissue, situated for the most 
part in the abdominal and thoracic cavities, but 
also in the neck and head, and-constituting what 
are known as sympathetic ganglia; (3) nerve- 
fibers which connect the brain, cord, and sym- 
pathetic ganglia with each other, the periphery 1 
and the viscera; (4) modifications of the periph- 
eral terminations of the nerves which constitute 
1 Periphery, the outside or superficial portions of a body. 142 
Anatomy and Physiology 
the organs of the external senses, as the eye, ear, 
tactile corpuscles, etc. 
305. Division of Nervous System into 
Cerebro-Spinal and Sympathetic Systems.- 
For convenience in description the nervous system 
is divided into two parts, which are usually spoken 
of as the cerebrospinal system and the sympathetic 
system. These two parts, do not, as the names 
might imply, constitute two different systems, for, 
both anatomically and functionally, they are very 
dependent upon each other and, with a few differ- 
ences to be discussed in this and the following 
chapter, very similar. 
306. The so-called cerebro-spinal system con- 
sists of the brain, the spinal cord, and their nerves, 
which are known as (1) the cerebro-spinal nerves, 
(2) the cranial nerves; (3) the spinal nerves. The 
first set of nerves are those connecting the brain 
and the spinal cord; the second, those passing 
to and from the brain through openings in 
or between the bones of the skull, but not be- 
coming part of the spinal cord; the third, those 
nerves extending between the spinal cord and the 
periphery. 
307. The sympathetic system consists of masses 
of nerve cell-bodies known as ganglia, situated for 
the most part, as previously stated, in the abdomi- 
nal and thoracic cavities, and the nerves connected 
with these ganglia. 
To understand the structure and working of the 
nervous system, it is necessary to know something Nerve Tissue and Nervous System 
143 
of the nature of nervous tissue. We will therefore 
take up the study of the tissue first. 
308. Nerve Tissue.-The tissue composing 
the nervous system is different in some respects 
from that of any other tissue of the body. Like 
other tissues, however, its unit is a cell, and the 
cell, like other animal cells, consists of cytoplasm 
with nucleus, nucleolus, and centrosome; but the 
structure of the cell and the nature of its cytoplasm 
is somewhat different from that of the cells of 
other tissues, as can be seen by the following 
description: 
309. Nerve Cells.-Names of different parts: 
Nerve cells, or, as they are also called, neurones, 
may be said to consist of: 
1. A cell-body. 
2. Cell-processes. 
310. The names of processes and their different 
parts are: 
(1) Dendrites or dendritic processes. 
(2) Axis-cylinder processes known also as 
neuraxons, or axons. 
(3) Collaterals (branches of axons). 
(4) Nerve-fibers (continuations of axons). 
(5) Nerve-endings. 
3ii. Number of Processes of a Cell.-The 
number of processes or poles extending from the 
cell-bodies varies, and when there is but one the 144 
Anatomy and Physiology 
cell is said to be unipolar; when there are two it is 
known as a bipolar cell; when there are more than 
Fig. 66.-A neurone from the 
cerebral cortex. The axis-cylin- 
der process, dendrites and col- 
laterals are marked i, 2, and 3, 
respectively. The neuraxon is 
shown in the drawing only for a 
short distance. If the entire 
length were pictured it would run 
a long way below the bottom of 
the page. Very greatly magnified. 
Fig. 65.-A neurone, 
two, as a multipolar cell. One process is airways 
an axon. 
312. Dendrites.1-The dendritic processes, 
1 From the Greek dendrone-a tree. Nerve Tissue and Nervous System 
145 
almost immediately upon emerging from the cell- 
body, break up into a series of fine branched fila- 
ments that divide and subdivide and spread out in 
various directions, like the branches of a tree. 
Some dendrites are long, but the majority are 
short and thick. They do not anastomose, but 
the branches of the dendrites of one cell are in 
very near proximity to those, or other processes, 
of other cells. The function of the dendrites is to 
collect nerve impulses from the processes of other 
cells and carry them to their own cell-body. 
313. The Axis-Cylinder.-The axis-cylinder, 
or as it is also called, the neuraxon or axon, is a 
process, usually of some length, that diminishes in 
diameter slowly in its course, gives off side branches 
at intervals, and terminates either in an arboriza- 
tion like that of the dendrites, or else merges into 
what is known as a nerve-fiber. Along some fibers, 
nerve impulses pass from the cell-bodies to the 
periphery, and along others, impulses pass from 
the periphery to the cell-bodies. It is thought 
that no fibers carry impulses in both directions. 
314. The Collaterals.-The side branches 
of the axons are called collaterals. They end in 
fine brush-like terminations or in little bulbous 
swellings which come in close contact with the 
processes of other neurones. The collaterals are 
found chiefly in the nerve-centers, i. e., the brain, 
spinal cord, and sympathetic ganglia. 
315. Nerve-Fibers.-Nerve-fibers, as stated 
in the preceding paragraph are continuations of 146 
Anatomy and Physiology 
the neuraxons. They are of two kinds: medullated 
or white fibers and non-medullated or gray fibers. 
316. A medullated fiber is composed of three 
parts: (1) an external sheath called the sheath of 
Schwann or the neurilemma1; (2) a white, semi- 
solid substance known as the medullary2 or myelin 
sheath or the white substance of Schwann, to which 
the peculiar opaque, white appearance of the 
medullated nerves is due; (3) the axis-cylinder, a 
continuation of the axis-cylinder process. 
317. Nature of Neurilemma and Nodes of 
Ranvier.-The neurilemma is a delicate, struc- 
tureless membrane in which nuclei are placed at 
intervals. It corresponds to the sarcolemma in- 
vesting muscle fibers. In most medullated fibers 
the neurilemma has ring-like constrictions at 
regular intervals which divide the fibers into a 
series of links. These constrictions are due to 
interruption in the continuity of the white medul- 
lary substance, in consequence of which the neuri- 
lemma sinks inward and comes in contact with the 
axis-cylinder. These constrictions are called the 
nodes of Ranvier. The interval between the nodes 
are known as the internodes. As the nerve-fibers 
approach their terminations, they lose first their 
medullary sheath and then their neurilemma, 
leaving the bare axis-cylinder. 
318. Function of Medullary Sheath.- 
The myelin or white substance of the medullated 
1 From the Greek neuron-a nerve and lemma-a coat. 
2 From the Latin medulla-marrow. Resembling marrow. Nerve Tissue and Nervous System 
147 
nerves serves as a protection to the axis-cylinder, 
and some physiologists think that it may possibly 
act as a non-conducting medium to prevent nerve 
impulses being deflected from their intended 
course before they reach their terminations.1 
319. Function of Nodes of Ranvier.- 
The nodes of Ranvier are supposed to exist for the 
purpose of permitting the passage of blood-plasma2 
into the axis-cylinder in order to supply it with 
nutriment. 
320. Non-Medullated Nerve-Fibers.-The 
non-medullated fibers, which are also known as the 
fibers of Remak, differ from medullated fibers in 
not possessing a medullary sheath, and therefore 
having a grayish color, and in being smaller, being 
only about X to X as large in their course within 
the trunks and branches of the nerves. Non- 
medullated nerve-fibers constitute the principal 
part of the branches and trunks of the sympathetic 
nerves, the whole of the olfactory nerve,3 and they 
are mingled in various proportions in the cerebro- 
spinal nerves. In the fetus, during the early 
stages of development, all the nerve-fibers are 
non-medullated. 
321. Functions of Nerve-Fibers.-The office 
of nerve-fibers is to conduct nerve impulses. 
Normally, within the body, nerve impulses pass 
in two directions only: (1) from the periphery to 
the cell-body, and (2) from the cell-body to the 
1 See paragraph 321. 2 See paragraph 454. 
3 The nerve connected with the sense of smell. 148 
Anatomy and Physiology 
periphery. Fibers carrying impulses in the first 
direction are spoken of as sensory, or afferent,1 or 
centripetal2 fibers. They are called sensory because 
stimuli they carry cause sensation; afferent and 
centripetal because the impulse travelling over 
them is going toward the center. Fibers carrying 
impulses from the cell-body to the periphery or 
viscera are known as motor, efferent,3 and centri- 
fugal* fibers. They are called motor, because the 
impulses which they convey cause functional 
activity-e. g., a muscle contracts, a gland secretes; 
and efferent and centrifugal, because they carry 
impulses out from the center. 
322. Reason for Difference in the Im- 
pulse Carried by Afferent and Efferent 
Fibers.-The nature of the sensory and motor 
nerve-fibers seems to be the same, and the 
difference in the character of the impulse carried 
by them is thought to depend upon the part that 
receives the stimulus; thus, the impulses passing 
over the optic nerves and those passing over motor 
nerves are the same, but, because the optic nerves 
stimulate a certain portion of the cerebral cortex, 
(paragraph 356), we see, and because motor nerves 
stimulate muscle, muscular contraction results. 
It is the peripheral endings of the sensory fibers 
that are adapted for stimulation, and the central 5 
1 From the Latin affero-to bear to. 
' From the Latin centrum-the center, and petere-to seek. 
3 From the Latin effero-to bear out. 
4 From the Latin centrum-the center, and fugere- to flee. 
s In the nerve centers, the brain, spinal cord, or ganglia. Nerve Tissue and Nervous System 
149 
endings of the motor fibers; the motor fibers being 
stimulated by impulses transmitted from the 
sensory fibers. The arrangement of the nerves 
whereby this transmission is made possible is 
shown in paragraph 333. 
323. Nerve Endings.-Towards their ter- 
mination, the medullated nerve-fibers lose their 
neurilemma and their myelin sheath, leaving the 
bare axis-cylinder, which ends in different ways. 
Thus, at the periphery, the sensory nerve-fibers end 
in three different ways: (1) they divide and sub- 
divide into minute branches called inter epithelial 
arborizations,1 which pass among the epithelial cells 
of the skin, mucous membrane, secretory glands, 
etc.; (2) they end in small, variously shaped bodies 
called tactile corpuscles2; the nerve-fibers connected 
with the sense of touch all end in this way; (3) in 
the organs of special senses-e.g.,the eyes, ears, etc.; 
the axis-cylinders, after dividing and subdividing 
into fibrils, enter and terminate in highly special- 
ized epithelial cells. These cells will be further de- 
scribed in the chapters devoted to the sense organs. 
324. The axis-cylinders' of the motor nerve- 
fibers break up into minute fibrils which form a 
network in the sarcolemma, and each fibril ends 
as a flattened granular mass, which is known either 
as a muscle, or a motor, plate. 
1 Arborization. From the Latin arbor-a tree. 
2 It is thought that the different-shaped corpuscles are of a 
somewhat different nature, and that possibly they may react to 
different kinds of stimuli. 150 
Anatomy and Physiology 
325. The non-medullated nerve-fibers which, 
it will be remembered, supply the involuntary 
muscles-i. e., the muscles of the viscera, near their 
termination, divide into a number of branches 
which communicate and form intimate plexuses.1 
From these plexuses minute branches are given off, 
which divide and break up into fibrils, which 
terminate on the surface of the muscle cell. 
The terminations of the dendrites and collaterals 
have been already described in paragraphs 312 and 
314- 
326. Reaction of Sensory Nerve-Endings 
and Centers to Different Kinds of Stimuli.- 
All sensory nerve-endings are not affected by the 
same kind of stimulus, nor do they react to stimuli 
in the same way. Thus, some nerve-endings in the 
skin are affected by heat, others by cold, others by 
pain, etc., the auditory 2 nerve-endings are affected 
only by sound. Nerve centers that are stimulated 
in more than one way usually respond in a similar 
manner to the different stimuli, e. g., the vision 
center is stimulated by the action of light on the 
optic nerve, but a blow on the head may stimu- 
late it and produce a sensation of light. 
327. Possible Result of Afferent Im- 
pulses on Different Sets of Motor Fibers.- 
An afferent impulse received by one kind of 
sensory nerve-endings may influence several 
1 Latin, a plait. The word is used in anatomy as a name for 
networks of nerve-fibers and blood-vessels. 
2 The nerve connected with the sense of hearing. Nerve Tissue and Nervous System 
151 
sets of motor fibers; thus, when the nerve-end- 
ings in the skin that are affected by cold are 
stimulated, the impulse passes to the motor 
centers which cause contraction of the skeletal 
muscles, to those which cause constriction of 
the superficial blood-vessels called vaso-con- 
strictors, and sometimes to those which pro- 
duce contraction of the muscles concerned in 
respiration. 
328. Nature and Function of Neuroglia.- 
Though neuroglia is not considered a form of 
nerve tissue, it is so closely mingled with it and 
forms' such an important constituent of the nervous 
system that it seems well to describe it here. It 
consists of cells that give off numerous fine proces- 
ses which extend in every direction and intertwine 
among the nerve cells and fibers. It is distributed 
to some extent in all parts of the brain and spinal 
cord, and serves the purpose of a connective tissue, 
i. e., it supports and holds together the nerves, 
blood-vessels, etc. 
329. Arrangement and Distribution of 
Nervous Tissue.-The cell-bodies, dendrites, 
commencement of the axis-cylinders and their 
collaterals form the so-called gray matter of the 
brain, spinal cord, and ganglia. The nerve-fibers 
are gathered into bundles and held together with 
their blood-vessels and nerves by connective tissue. 
These bundles are known as nerves or nerve- 
trunks. They extend from the nerve-centers, i. e., 
the brain, spinal cord, and ganglia, to the periphery 152 
Anatomy and Physiology 
and between cells in different parts of the nerve 
centers, thus affording a channel of communication 
between (i) the nerve-centers and the periphery; 
(2) the nerve-centers and the viscera; (3) the 
viscera and the surface of the body; (4) the differ- 
ent parts of the nerve-centers, The majority of 
nerves contain both sensory and motor fibers, but 
as an impulse is discharged only at the nerve- 
ending of a fiber, the impulse travelling over one 
fiber never interferes with that passing over 
another. 
330. Plexuses.-At certain parts of their 
course many of the nerves form plexuses or networks 
in which they anastomose with each other, the 
fibers of one nerve passing into another nerve 
and continuing with its fibers. The objects 
of such interchange of fibers are: (1) to give 
to each nerve passing off from the plexus a 
wider connection with the nerve-centers than 
it would have if it proceeded to its destination 
without such communication with other nerves; 
(2) each nerve is less dependent on the integrity of 
any single portion of a nerve-center or nerve-trunk, 
(3) any given part, say a limb, is less dependent 
upon the integrity of any one nerve. 
331. Branching of Nerves.-In a great 
many cases the fibers of a nerve branch off from 
the main bundle and go to supply muscles and 
viscera quite distant from each other. 
332. Nature of Respiratory and Other 
Centers.-The cell-bodies of the nerves inner- Nerve Tissue and Nervous System 
153 
vating many of the systems of the body are massed 
together in different parts of the brain and spinal 
cord. These masses are called centers; examples 
are the respiratory center which controls res- 
piration, the vaso-motor centers which help in 
regulating the caliber of the blood-vessels and, 
consequently, the circulation of the blood. 
The location of these and other centers and the 
distribution of the nerves will be considered in 
Chapters VIII and IX. 
333. Central Connection of the Nerves. 
-The nerves are so arranged at their terminations 
in the nerve-centers that the terminal processes of 
sensory neurones come almost in contact with the 
dendrites of motor neurones or those of what are 
called intracentral or connecting neurones (see 
Fig. 68), by means of which a sensory neurone can 
be linked to several motor neurones. The proces- 
ses of different neurones do not, it is thought, come 
in direct contact one with another; but the gap, 
which is known as a synapsis, is microscopically 
small and does not interfere with the transmission 
of impulse from one neurone to another. 
334. Origin and Nature of Nerve Impulse. 
-Nerve impulse results from the action of a 
stimulus which causes chemical changes in the 
protoplasm of the nerve cell-body whereby energy 
is liberated, just as energy is liberated in the muscle 
substance by changes in the protoplasm. Of the 
nature of this energy or impulse very little is 
known. Before the discovery of electricity it was 154 
Anatomy and Physiology 
thought that the nerves were tubes and that the 
activating property or impulse flowed through 
these tubes, some physiologists thought in the 
form of air or gas, which they named animal 
spirits, and others thought it was a liquid sub- 
stance and called it nerve juice. After the dis- 
covery of electricity the almost universal opinion 
was that the nerve impulse was of the same nature 
as electricity; but investigation and further 
knowledge of the action of the two have led to the 
discovery of several points of difference between 
them, notably the rate at which they travel-a 
nerve impulse passing at the rate of about 27 
meters per second, and an electric wave at about 
186,000 miles per second-wherefore physiologists 
have decided that although nerve impulse may be 
similar to electricity in some respects, it is not 
identical. 
335. Function of the Cell-Body.-As can 
be seen in the preceding paragraph, the cell-body is 
to the nervous system very much what the battery 
is to many kinds of electrical apparatus, viz.: the 
center in which the action occurs that gives rise 
to the nerve impulse or, in the battery, electric 
current. Also (1) the cell-bodies afford nutriment 
for their processes throughout the length of their 
course. One proof of this is that if a nerve is cut the 
part separated from the cell-bodies degenerates.1 
(2) The cells can modify the impulses brought 
1 Degeneration and regeneration of nerves are described in 
paragraph 347. Nerve Tissue and Nervous System 
155 
to them by their sensory processes-e. g., they may 
collect weak impulses and combine them into one 
effective impulse before transmission to the motor 
nerves; this action is spoken of as summation. (3) 
They may partially or completely block impulses; 
this action is known as inhibition; it will be referred 
to again in connection with reflex action and the 
action of the heart and lungs. 
336. Parts of the Nervous System in 
Which Interchange and Regulation of Nerve 
Impulse Take Place.-The cell-bodies being- 
contained in the brain, spinal cord, and ganglia, it 
is in these parts of the neural system that the 
activities described in the preceding paragraph 
take place, and also the passage of nerve impulse 
from the sensory to the motor neurones. Impulses 
causing reflex actions (see next paragraph) are 
transmitted from one set of fibers to the other in 
the spinal cord or that part of the brain known as 
the medulla oblongata. 
337. Reflex Action.-Definition: By reflex 
action is meant the involuntary contraction of a 
muscle as the result of stimulation by motor nerve- 
fibers that have been activated by impulses 
transmitted by sensory fibers. 
338. Examples of Reflex Actions.-The 
majority of the movements of our bodies, whether 
due to the action of the voluntary or involuntary 
muscles, are reflex-e. g.,when food is taken into the 
mouth the sensory nerves are stimulated, and they 
carry impulses to the nerve-centers controlling 156 
Anatomy and Physiology 
the secretion of the saliva, of mastication, of 
deglutition; consequently impulses are sent along 
the motor nerves of the muscles and glands con- 
cerned in these activities. Likewise, the food, 
either directly or in- 
directly, is the source 
of the stimuli promot- 
ing the activity of the 
stomach, pancreas, 
liver, and intestines. 
Irritating food or poi- 
son in the stomach may 
send impulses along 
certain sensory nerves 
to the center in a part 
of the brain known as 
the medulla oblongata, 
from which impulses 
are sent along motor 
fibers back to the 
stomach, abdominal 
muscles, etc., which 
produce vomiting. An 
example of reflex action due to stimulation of 
peripheral sensory nerves is: If a person is plunged 
into a cold bath, such nerve-endings in the skin as 
react to cold are stimulated, and the impulse re- 
sulting from this stimulus will be transmitted: 
(i) to motor nerves which cause contraction of 
the skeletal muscles; (2) to one of the sets of 
nerves supplying the walls of the peripheral blood- 
Fig. 67.-Moto rial end-plate, 
the termination of a nerve in a 
fiber of cross-striped muscle. Nerve Tissue and Nervous System 
157 
vessels, called from their action the vaso-constric- 
tors1; (3) to the nerves supplying the muscles of 
respiration. The colder the water and the more 
sudden its application, the quicker and stronger 
will be the reflex response. 
339. Reflex actions may or may not be associ- 
ated with consciousness.---When a reflex action is 
associated with consciousness, the sensory fibers 
transmit their stimuli, not only to motor fibers in the 
spinal cord, but also to sensory fibers, which carry 
them to those parts of the brain concerned with 
consciousness. An example of this is the quick 
withdrawal of the hand if it comes in contact with 
a hot stove. But, even when associated with con- 
sciousness, the action is involuntary, and is, in 
fact, performed before the impulse has had time to 
reach the brain. 
340. Some movements that are at first voli- 
tional later become reflex-e. g., walking, dancing 
riding, etc. 11 In learning such movements one must, 
as the saying goes, establish his reflexes, and the result 
can hardly be understood otherwise than by suppos- 
ing that the continual adjustment of certain sensory 
impidses to certain co-ordinated movements results in 
the formation of a more or less complex reflex arc."2 
341. Nature of Reflex Arc.-By reflex arc 
is meant the pathway over which the impulse 
travels-over the sensory nerve-fibers from the 
periphery to the nerve-centers and thence over the 
1 From the Latin vas-a vessel. 
3 Text-Book of Physiology, page 152. Howell, Saunders, & Co. Anatomy and Physiology 
158 
motor nerve-fibers to the muscles, etc. Move- 
ments, such as walking, which after infancy are 
normally the result of reflex action due, in the case 
of walking, to stimulation of certain sensory nerves 
in the soles of the feet and others which have to do 
with muscle-sense,1 are much less perfect when 
performed voluntarily. This can be seen in 
patients suffering with 
the disease known as 
locomotor ataxia, in 
which, due to disease 
of the part of the spinal 
cord containing the 
nerves over which the 
impulses of muscle-sense 
travel, the impulses can- 
not reach the parts of 
the central system 
where the reflexes con- 
cerned in walking are 
adjusted, and consequently each step becomes a 
voluntary or considered action, and though there 
is absolutely no paralysis of the muscles concerned 
in walking, the gait is staggering and uncertain. 
The same thing is true of infants until the parts of 
their central nervous systems connected with the 
regulation of the walking reflexes and maintenance 
of equilibrium have been trained to send impulses 
Fig. 68.-Schema to show 
the connection between the 
neoron of the posterior root 
and the neuron of the anterior 
root,-the reflex arc. 
1 By the term muscle-sense is meant the sensations arising 
from stimulation of sensory nerves ccncerned with feelings of 
pressure, touch, weight, etc. (See Chapter XXII.) Nerve Tissue and Nervous System 
159 
to the proper muscles, i. e., until their reflex arcs 
have become established. 
342. Modification of Impulses.-As stated 
in paragraph 335, the nerve cell-bodies may con- 
siderably modify impulses passing along their 
processes. This is of particular importance to 
reflex actions, and one very important example of 
this is that the reflex response to a stimulus does 
not always cease immediately after the stimulus 
has ceased to act, but may persist for some time 
and one single reflex may start a succession of co- 
ordinated movements,-11 e. g., if the sole of the foot 
of a sleeping person be tickled, the leg is drawn 
zip, and after an interval is -again straightened 
out. The return to the straight position is not merely 
a passive falling back of the limb, but is an orderly 
movement, showing that the first reflex has initiated 
a second reflex producing an opposite effect. A 
similar phenomenon occurs in the reflex movements 
of ordinary walking^'1 
343. Inhibition of Reflexes by the Brain. 
-Certain reflex actions may be inhibited by the 
brain; for instance, in the reflex from tickling the 
muscular movement can often be repressed by 
voluntary act, so also to a limited extent can the 
respiratory movements, the action of micturition, 
etc. 
344. Diffusion of Impulses.-Very strong 
stimulation of certain nerve-centers may cause 
1 The Nervous System, page 18. J. D. Lickley, M.D. Long- 
mans, Green, & Co. 160 
Anatomy and Physiology 
diffusion of impulses-1. e., the impulses are passed 
over more reflex pathways than are usually in- 
volved in any one variety of stimulation. This is 
what happens in convulsions. 
345. Automatism.-Another function possessed 
by certain nerve-centers and also by the tissue 
of the heart is that which is known as automatic 
action or automatism. By this is meant that such 
a center or tissue is not dependent for its activity 
upon any afferent stimuli from the outside, 
but that the stimuli which excite it to activity 
arise within itself. This action differs from reflex 
movements in that it is rhythmical; it will be 
referred to again in connection with the heart and 
the respiratory movements. 
346. Origin of Voluntary Impulses.-What 
actually originates a voluntary action-one per- 
formed by an effort of the will-physiologists have 
not yet determined. Dr. Busch says: 
11 No doubt impulses from the periphery conducted to 
the cerebral cortex* along all kinds of different channels 
must have something to do with it, directly or indirectly, 
sooner or later. In the hitman cortex2 it would seem that 
the apparatus for performing all manner of possible 
co-ordinated movements which may result in speech or 
action are stored. This apparatus is capable of being 
set in action either in the absence of consciousness by 
afferent stimuli of some kind directly, or, it may be, in- 
directly or remotely, in some way the result of afferent 
stimuli, viz., the will. It is also probable that the will 
1 See paragraph 356. 2 Ibid., 356. Nerve Tissue and Nervous System 
161 
of another may take the place of a man's own will, and 
may call for the movements, action, and speech, all of 
which are, as it were, ready to be called forth by a stimulus 
of some kind."1 
347- Degeneration and Regeneration of 
Nerves.-As stated in paragraph 335, the pro- 
cesses for a nerve cell are dependent upon the cell- 
body of their nutrition; therefore, if a nerve is cut, 
the portion which is no longer in communication 
with the cell-body degenerates, is broken up, and 
then absorbed. The part still connected with the 
cell, except for a small distance from the cut sur- 
face, preserves its vitality during the life of the 
cell. If measures be taken to bring the cut ends of 
a nerve into apposition, even after a considerable 
period has elapsed, the nerve will regenerate by the 
growth of new fibers from the central stump, these 
fibers using the old pathways and growing down 
to the original terminations. 
348. Effect of Fatigue, Disease, and In- 
jury on Cell-Bodies.-Experiments in which 
animals have been kept constantly in motion and 
then anesthetized, killed, and their nerve-cells 
examined, have shown that after excessive bodily 
fatigue the cell-bodies are often congested or, as 
a further stage of exhaustion, atrophied. The 
effect of fatigue on human beings is thought to be 
the same as that on animals when the conditions 
inducing it, whether they be physical or mental 
1 Hand-Book of Physiology, page 651. Kirk. Wm. Wood & Co. 162 
Anatomy and Physiology 
work, or disease, are long continued. Rest, men- 
tal and physical, and proper medical treatment will 
usually restore the cell-bodies to their original 
condition. If, however, any group of cell-bodies, 
either by injury or local disease, have become 
absolutely destroyed they will not be regenerated, 
but if they are only temporarily injured they are 
likely, with proper treatment, to recover. 
349. Use of Knee-Jerk in Diagnosis.-A 
common means used by doctors to ascertain if a 
patient's nerve-centers are intact is the so-called 
knee-jerk. This consists in flexing one of the 
patient's legs so that the quadriceps muscle will 
be under tension, and then tapping lightly below 
the knee-cap. If the patient's nervous system is 
normal the foot usually gives a light jerk, due to 
contraction of the quadriceps muscle; but if there 
are lesions in certain parts of the spinal cord there 
will not be any response, as the passage of either 
the sensory or motor impulses are interfered with- 
which ones depending upon the location of the 
trouble. On the other hand, abnormal conditions 
in other parts of the cord or some parts of the 
brain may allow of an increase in the force of the 
jerk by cutting off or weakening the inhibitory 
influence that certain parts of the brain have on 
spinal reflexes. CHAPTER VIII 
nervous system-Continued 
The Brain 
Location, Weight, Ventricles, Main Divisions of Brain. The 
Cerebrum: Arrangement of Gray and White Matter, Tissues, 
Convolutions or Gyres, Lobes, Function, Localization of Func- 
tion. Nature, Location, and Function of Motor Area, Sensory 
and Association Areas. The Mesencephalon or Midbrain: 
Location, Structure, and Function. The Cei%bellum: Location, 
Divisions, Arrangement of Gray and White Matter, Function. 
The Pons Varolii: Location, Appearance, Structure, and Function. 
The Medulla Oblongata: Location, Divisions, Decussation of 
Nerves in Medulla, Function, Reflex and Automatic Centers. 
Membranes Covering the Brain: Names and Nature. 
HAVING considered the nature and function 
of nerve tissue we shall proceed to study the 
structure of the system of which the tissue forms 
the principal substance and shall begin with the 
brain. 
350. Location of the Brain.-The brain1 or 
encephalon2 is that portion of the cerebro-spinal 
1 From the Greek bregma-the upper part of the head. 
9 From the Greek, engkephalus-within the head. 
Note. In describing the brain and spinal cord it is almost 
impossible to avoid mentioning names which are not necessary 
for nurses to remember. Those that are will, therefore, be starred. 
163 164 
Anatomy and Physiology 
nervous system which is contained in the cranial 
cavity. 
351. Weight of the Brain.-The human 
brain is heavier than that of any of the lower 
animals excepting the elephant and the whale. 
The prevailing weight of the brain in the human 
adult male ranges from 46 to 53 ounces, the aver- 
age being about 49X ounces, or a little more than 
three pounds. That of the female ranges between 
41 and 47 ounces, the average being 44 ounces. 
The brain increases in weight rapidly up to the 
seventh year, more slowly to between sixteen and 
twenty, and still more slowly to between thirty 
and forty, when it reaches its maximum weight. 
Beyond this age the weight decreases slowly, about 
an ounce each ten years. 
352. Formerly it was thought that the size 
of the brain corresponded to the intellectual 
capacity of the individual, but this is certainly not 
always the case, for some individuals who have 
never shown any remarkable capacity have had 
very large brains. 
353. Ventricles of the Brain.-The brain 
is not a solid mass, for, as can be seen in Fig. 69, 
there are in its interior a series of connected cavi- 
ties called ventricles* The two known as the 
lateral ventricles are the largest. These, as can 
be seen in Fig. 69, are situated one in each half or 
hemisphere (see paragraph 360) of the brain. 
They are connected with one another and with the 
third ventricle by a small opening called the Nervous System-Continued 
165 
foramen of Monro.1 In the septum, or wall divid- 
ing the two ventricles, is a cavity which does not 
connect with the other ventricles, that is known 
as the fifth ventricle. The third ventricle is con- 
nected, as can be seen in Fig. 69, with the fourth 
ventricle by the small tube-like canal known as 
the aqueduct of Sylvius.2 The fourth ventricle 
is the space between the posterior surface of the 
medulla ob- 
longata3 and 
pons3 in front, 
and the cere- 
bellum3 be- 
hind. It is 
continuous 
with the canal, 
known as the 
central canal, 
which trav- 
erses the en- 
tire length of 
the spinal cord. 
354. The ventricles and central canal are lined 
with a serous membrane which secretes a serous 
fluid. In health the amount of fluid is small, but 
in certain diseases of the brain, as meningitis, the 
amount is much increased, and is present not only 
in the ventricles but all through the substance of 
Fig. 69.-Scheme showing relations of the 
ventricles to the surface of the brain. 
1 Name of a famous anatomist. 
2 Ibid. 
3 See paragraphs 389, 385, 380. 166 
Anatomy and Physiology 
the brain, and the symptoms of the disease are 
partly due to pressure by this fluid on the nerve 
tissue. The cause of this increased quantity of 
fluid is the same as that of the exudation of fluid 
into the tissues in inflammatory conditions of other 
parts of the body. This is discussed in paragraph 
469. 
355. Main Divisions of the Brain or 
Encephalon.-The brain is divided into five 
principal parts, viz: the cerebrum1-the mesen- 
cephalon or mid-brain-the cerebellum,2 the pons 
Varolii, and the medulla oblongata. The relative 
location of these various parts can be seen in Figs. 
70 and 71. 
The Cerebrum 
356. Arrangement of the White and Gray 
Matter.3-The entire surface of the cerebrum, 
both upper and under, is composed of layers of 
gray nervous tissue which is of variable thickness 
in different parts. This is called the cortex,4 
because like the cortex-bark-of a tree it forms a 
covering. There are also four masses of gray 
matter, two on either side, at the base of the cere- 
brum. These are the two thalami (sing, thalamus5') 
1 Latin cerebrum-the brain. 
2 Latin cerebellum, a little brain. 
3 It will be remembered that the gray matter consists of all 
bodies, dendrites, axons, and non-medullated nerve-fibers. 
4 Latin cortex-the bark. 
s From the Greek thalamas-a bed-chamber. In anatomy 
the word means the place where a nerve originates. Nervous System-Continued 
167 
and the corpus striatum.1 Between the layers of 
gray matter and between the cells of each layer are 
gray and white nerve-fibers running in all directions 
and supported by 
neuroglia. The bulk 
of the white matter, 
however, is in the 
interior of the cere- 
brum. It consists 
of a close network 
of medullated fibers 
which link the dif- 
ferent parts of the 
brain together and 
connect the brain 
with the spinal cord. 
357. Fissures 
and Convolutions 
of the Cerebrum. 
-In the young fetus 
the cortex is smooth 
and uncreased, but 
as months go by it 
becomes wrinkled, 
narrow depressions 
occurring all over it 
and getting deeper 
and more numerous with its development both 
Fig. 70.-Sem i di a g ramma t ic 
view of the cerebro-spinal axis, left 
side. (Gerrish.) 
1 From the Latin corpus-a body and stria-a streak. So 
called because of its striated-striped-appearance, due to the 
intermingling of numerous white fibers with the gray matter. 168 
Anatomy and Physiology 
during intra-uterine life and after birth. On 
the other hand, as old age advances the ridges, 
known as convolutions or gyri,1 between the 
depressions undergo atrophic changes, and the 
depressions, consequently, grow less marked. 
Their size and number vary greatly in different 
brains. 
358. These creases are infoldings of the cortex, 
and, consequently, the more numerous and deeper 
they are the greater is the amount of the peripheral 
gray substance and the larger the extent of surface 
for the termination of the white fibers. The deeper 
depressions are called fissures and the more shallow 
ones sulci.2 
359. Total Fissures.-Some fissures are much 
deeper than others, and those in which the de- 
pression extends almost through the entire thick- 
ness of the brain wall are called total fissures. The 
principal ones are: 
(1) The Great Longitudinal Fissure.-This ex- 
tends from the back to the front of the cerebrum 
and divides it into two hemispheres which are held 
together by a wide band consisting of white or 
medullated nerve-fibers. This band is known as 
the corpus callosum. 
(2) The Transverse Fissure which is between 
the cerebrum and the cerebellum. It is half in one 
hemisphere and half in the other. 
(3) The Sylvian Fissure; for location see Fig. 
1 From the Greek gyres-a ring. 
2 Latin Sulcus (pl. sulci)-a furrow. Fig. 71.-Under surface of the brain, showing the superficial origins of 
the cranial nerves. The Roman numerals indicate the nerves. (Gerrish.) Nervous System-Continued 
169 
72. There is one in each hemisphere, as are also 
the two following ones. 
(4) The Rolandic* or Central Fissure; see Fig. 
72 for location. 
(5) The Parieto-Occipital Fissure; see Fig. 72. 
360. Lobes of the Cerebrum.-As already 
stated, the great longitudinal fissure divides the 
cerebrum into two hemispheres, and the transverse 
fissure di- 
vides the 
cerebrum 
from the cer- 
e b e 11 u m 
The othei 
fissures di- 
vide the twc 
hemi spheres 
into lobes. 
The lobes, 
with one exception, were named from the bones of 
the cranium under which they lie; therefore, they 
are known as the frontal, parietal, temporal, occip- 
ital, and-the exception-the central lobes. The 
location of the first four can be seen in Fig. 72. 
The central lobe, also called the island of Reil, 
is not seen because it is covered by the lower 
ends of the frontal and parietal lobes. The lobes 
are the same in both hemispheres. 
361. Function of the Cerebrum.-In the 
cerebrum are situated the nerve centers which 
govern the phenomena of the mind and co-ordina- 
Fig. 72.-The lobes of the convex surface of 
the hemisphere, left side. 170 
Anatomy and Physiology 
tion of movements. These centers are the seat of 
intelligence, reason, and will, the means of retaining 
impressions of things and of reproducing them in 
ideas. They are the medium of all the higher 
emotions and. feelings and of the faculties of judg- 
ment, imagination, memories, etc. 
362. Localization of Function.-As the 
result of experiments on anesthetized animals and 
observation of individuals suffering from cerebral 
wounds or diseases, physiologists have been able to 
localize the special parts of the brain which control 
the various movements of the body and some of 
those concerned with sensation. Also, they have 
been able to gain some idea of the portions of 
the cerebrum concerned with the higher mental 
attributes. 
363. Names of Areas.-The portion of the 
cerebrum governing the muscular movements of 
the body is known as the motor area*; those parts 
controlling sensation, as the sensory areas*; and 
those connected with such mental properties as 
reason, will, imagination, etc., as association areas* 
364. The Motor Area.-The motor area is 
known also as the Rolandic* area, because, as can 
be seen in Fig. 73, it adjoins the fissure of Rolando. 
The various parts of the body of which the move- 
ments are controlled by nerves arising in this area, 
and the special portions of the area in which the 
nerves supplying the various parts arise, can be 
seen in the same figure. 
365. Decussation of the Nerves.-It must Nervous System-Continued 
171 
be remembered, however, that the nerves arising 
in the cortex of the right side of the brain govern 
the movements of the left side of the body, and 
vice versa. The reason of this is that in the lower 
Fig. 73.-Location of motor areas in brain of chimpanzee 
(Sherrington and Greenbaum); The extent of the motor 
areas is indicated by stippling; it lies entirely in front of the 
fissure of Rolando (sulcus centralis). Much of the motor 
area is hidden in the sulci. The regions marked eyes in- 
dicate the areas whose stimulation gives conjugate move- 
ments of the eyeballs. It is doubtful, however, whether 
these represent motor areas proper. 
end of the medulla the nerves extending into and 
from the spinal cord decussate or cross. Because 
of this, injury to the right side of the brain will 
interfere with movement of the left side of the 
body, and vice versa. 
366. Value of Knowledge of Areas.-The 
knowledge of the location of these motor areas is of Anatomy and Physiology 
172 
great value to physicians and surgeons when 
treating patients who are subject to convulsions, or 
who are paralyzed as the result of pressure on some 
part of the cerebrum, for by observing the parts of 
the body involved in the convulsive movements, or 
in which there is loss of function, they can usually 
locate the exact portion of the brain that is affected. 
Nurses caring for patients who have convulsions 
must note every detail of the nature of an attack, 
viz: which parts of the body are involved, which 
are affected first and in what manner, how long 
an attack lasts, and the after-effect upon the 
patient. 
367. Difference in the Functioning of 
the Motor Area in the Lower Animals and 
Man.-In birds and many of the lower animals, 
extirpation of the cortex of the cerebrum does not 
interfere with their power of movement, but only 
with such intelligent and connected movements as 
are outgrowths of past or inherited experiences. 
Consequently, the movements they do make are 
simple reflex responses. For example, a cerebrum- 
less pigeon, if placed on a hot plate, will lift first 
one foot and then the other, the ordinary reflex re- 
sponse to such a stimulus; but it will not fly away. 
Such a pigeon will be kept alive only if it is fed, for 
even when hungry (having forgotten the connec- 
tion between hunger and feeding) it will not look 
for food. 
368. In man, on the contrary, even the power 
of movement is controlled by the motor area of the Nervous System--Continued 
173 
cerebrum, and disease of or injury to any portion of 
this area will interfere with the functioning of the 
part of the body supplied with nerves that have 
their origin in the affected part. 
369. The Sense Areas.-By the sense areas 
is understood those parts of the brain to which 
sensation is due and which control vision, hearing, 
taste, smell, and, to some extent, speech, etc. 
With the exception of the speech center, the dis- 
cussion of this part of the nervous system will be 
taken up in the chapters devoted to the sense 
organs-viz., the skin, eyes, nose, mouth, and ears. 
As the speech center is an excellent example of a 
memory center, it seems well to give a short de- 
scription of its functioning here. 
370. Speech Center.-The speech center is, 
as just stated, an example of a distinctly memory 
center. It does not contain the centers for the 
nerves supplying the muscles of speech, and the 
power of speech may be partly or entirely lost 
without any paralysis of those muscles, simply as a 
result of loss of memory of the definite words by 
which the individual was taught in childhood to 
express his ideas. 
371. Motor Aphasia.-Such loss of memory is 
termed motor aphasia. It is usually due to injury 
or disease of the part of the brain in which the 
memory of words was stored. There are several 
forms of aphasia and the nature of the trouble will 
depend upon the extent and location of the brain 
injury. Thus, the loss of memory of words may 174 
Anatomy and Physiology 
be complete or it may be only partial, and it may 
affect the patient in different ways. For instance, 
he may forget only certain things, as names; he 
may be able to express himself in writing, though 
not in speaking; or he may lose only the power 
of expressing himself in writing. This latter con- 
dition is known as agraphia. 
372. Sensory Aphasia.-In this form of 
aphasia the individual, though his hearing and 
vision are not impaired, fails to understand either 
spoken or written language or even both, because 
he has lost all association between the verbal or 
written symbols and the ideas he formerly con- 
nected with them. 
373. Location of Speech Centers.-The 
parts of the cerebrum affected in these various 
forms of aphasia may be seen in Fig. 74. The 
speech centers, unlike the centers in the motor area 
of the cerebrum and those connected with vision, 
hearing, etc., are not developed in both hemispheres. 
In right-handed individuals the speech center is 
fully developed only in the left hemisphere, and in 
left-handed persons, in the right hemisphere. 
374. Association Areas.-Inspection of Figs. 
73 and 74 will show that the motor and sense 
areas occupy only a small portion of the cortex 
of the cerebrum. The remaining parts of the 
cortex have been termed the association areas, and 
it is thought that it is these areas which control 
the higher and more complex mental activities. 
375. Of the manner in which the cerebrum Nervous System-Continued 
175 
discharges its functions with regard to the higher 
senses very little is known. Dr. Howell says: 
11 In the association areas our memory records of 
past experience and their connections are laid down 
Fig. 74.-Lateral view of a human hemisphere; 
cortical area V, damage to which produces " mind- 
blindness " (wo rd-blindness); cortical area H, dam- 
age to which produces "mind-deafness" (word- 
deafness) ; corticle area S, damage to which causes 
the loss of audible speech; corticle area W, damage 
to which abolishes the power of writing. (Howell.) 
in some, as yet unknown, material change in the 
network of nerve cells and fibers."1 
376. It is thought that the various faculties, 
such as music, painting, literature, oratory, each 
has its special center in these association areas, 
and that these centers differ in different individuals 
both in their nature at birth and as the result of 
1 Text-Book of Physiology, page 220. Howell, Saunders, & Co. 176 
Anatomy and Physiology 
after-development by use. This is the opposite 
of the view entertained by the majority of physi- 
ologists in the early part of the nineteenth cen- 
tury. At that time the general belief was that a 
talented person could develop a particular aptitude 
for any art or science that he chose. Thus, if a 
man were a brilliant mathematician it was thought 
that with a different training he would have made 
an equally good doctor or general. Also, it was 
then thought that children's minds could be so well 
trained by a study of mathematics, Latin, Greek, 
and a few similar studies that they could later, if 
they were sufficiently gifted, take up any science 
or art they desired and excel in it quite as well as 
though they had studied that special subject from 
childhood. This idea also has been proven errone- 
ous by a better knowledge of the localization of 
function, and it is now generally believed that it is 
only when subjects are similar to each other that 
the study of one helps to any extent in the master- 
ing of another. 
377. Localization of Function in the 
Association Areas.-Physiologists and psycholo- 
gists have not yet been able to determine the 
special parts of the association areas devoted to 
the various faculties further than basing their 
views upon the connections existing between the 
sense areas and the association areas. They think 
that the posterior portion of the cerebrum may 
be particularly concerned in the organization of 
the experiences founded upon visual and auditory Nervous System-Continued 
177 
sensations, and the anterior portion in the organi- 
zation of experiences based upon the internal 
associations such as bodily appetites and desires. 
Howell says: 11 In this part of the brain possibly 
arises the conception of individuality, the idea of the 
self as distingicished from the external world. And 
in alterations or defective development of this portion 
of the brain may lie possibly the physical explana- 
tion of mental and moral degeneracy."1 This latter 
view developed from the fact that, in autopsies 
performed on those who in life had always been 
mentally deficient, the frontal association area 
was found undeveloped, and in autopsies on those 
who suffered from certain forms of insanity the 
cortex in this area was frequently found to be more 
or less atrophied. 
378. Unilateral Action of the Association 
Areas.-In discharge of its mental function "it 
appears that for all but its highest intellectual acts 
one of the cerebral hemispheres is sufficient; for 
numerous cases are recorded in which no mental 
defect was observed, although one cerebral hemisphere 
was so disorganized or atrophied that it could not be 
supposed capable of discharging its functions. The 
remaining hemisphere was, in these cases, adequate 
to the functions generally discharged by both. But 
the mind does not seem in any of these cases to have 
been tested by very high intellectual exercises, so that 
it is not certain that one hemisphere will suffice for 
these. In general the brain combines as one sensa- 
1 Text-Book of Physiology, page 222. Howell, Saunders, & Co. 178 
Anatomy and Physiology 
tion the impressions which it derives from one object 
through both hemispheres, and the ideas to which two 
such impressions give rise are single. "1 
The Mesencephalon or Mid-Brain* 
379. Location and Structure.-The mesencepha- 
lon, often called the isthmus of the brain, is the 
narrow neck which connects the cerebrum with 
the structures below. Its ventral part is shaped 
like two pillars which converge toward the pons. 
It is called the crura cerebri. On the dorsal surface 
are four rounded prominences called the corpora 
guadrigemina. The mid-brain is hollow, the 
aqueduct of Sylvius traversing its length. 
The Cerebellum* 
380. Location, Size, and Divisions.-The cere- 
bellum is the great solid mass of nervous tissue 
lying back of, but on the same plane as, the pons 
Varolii. It is oblong in shape and measures about 
three and a half to four inches transversely and 
two to two and a half from before backward. It 
is divided by fissures into three lobes, one medial, 
known as the vermis or worm, and two lateral, 
called the cerebellar hemispheres. 
381. Connections.-The cerebellum is connected 
with the rest of the brain by six bands of white 
nerve-fibers, three on either side, called the su- 
perior or anterior, middle, and inferior or posterior 
1 Hand-Book of Physiology, page 652. Kirk. Wm. Wood & Co. Nervous System-Continued 
179 
peduncles. The nerve-fibers of the peduncles, 
some of which are continuous with those of other 
parts of the brain and some with those of the 
spinal cord, terminate in fine networks of fibrils 
about cells in the gray matter, and an impulse 
that comes into the cerebellum from one of the 
higher centers in the cerebrum may be subdivided 
into a great number of currents that, passing to 
and down the cord, and thence to the periphery, 
will produce co-ordinate action in a whole group or 
groups of muscles. The cerebellum has no cavity. 
382. Arrangement of Gray and White 
Matter.-The bulk of the gray matter of the 
cerebellum, like that of the cerebrum, is on the 
exterior, and the white in the interior. Also like 
that of the cerebrum, the gray matter dips into the 
white matter in order that a larger amount may be 
contained in a given space. Beside the gray 
matter on the surface there is a small mass near 
the center of the white matter called the corpus 
dentatum.1 
383. Functions of the Cerebellum.-It is 
thought that co-ordination of ordinary movements 
and maintenance of equilibrium are the principal, 
if not the only, functions of the cerebellum. The 
chief reason for this belief is that injury to, or 
disease of, this part of the brain does not seem to 
interfere with the intellect nor with the power of 
actual movement, but only with the power of co- 
1 From the Latin corpus-a body and dentatus-toothed, 
tooth-shaped body. 180 
Anatomy and Physiology 
ordinating muscular movements, especially those 
connected with locomotion and equilibrium, which 
results in a loss of ability to stand, walk, etc. 
384. In reference to the reason for this loss of 
co-ordination Dr. Howell says1: 
" We may assume that the cerebellum exerts its co- 
ordinating influence by virtue of the definite nervous 
mechanisms contained in it-that is, by nervous com- 
plexes which, on the afferent side, are connected with the 
peripheral sensory nerves to the vestibule of the ear,2 the 
muscles, joints, etc., and on the efferent side are in direct 
or indirect relations with the motor areas of the brain as 
well as the motor centers in the cord. These mechanisms 
are inherited structures, but, like other nervous mechan- 
isms, they are developed by rise. The many muscular 
contractions made in our ordinary movements of equi- 
librium are learned by experience, and the effects of this 
training are felt mainly upon those cerebellar paths or 
mechanisms. We regard the speech center in the cere- 
brum as a collection of nervous mechanisms in which are 
stored or preserved the connections necessary to the motor 
presentation of thoughts, a memory for the spoken 
symbols of orir concepts. It is possible that in the same 
way we may regard the cerebellum as a memory center of 
the muscular movements concerned in eqttilibrium." 
The Pons Varolii3 
385. Location.-The pons Varolii* (bridge of 
1 Text-Book of Physiology, page 237. Howell, Saunders, & Co. 
2 A portion of the inner ear is also concerned in maintaining 
equilibrium. (Described in paragraphs 987 and 992.) 
3 Latin, a bridge. Varolius same of the anatomist who dis- 
covered the pons. Nervous System-Continued 
181 
Varolius) is situated below the crura cerebri 
above the medulla oblongata and between the 
two hemispheres of the cerebellum. 
386. Structure.-The pons presents the 
appearance of a prominence composed of 
strands of white nerve-fibers some of which 
run transversely and some longitudinally. The 
transverse strands narrow towards either side 
and are continued into the cerebellum. Some 
of the longitudinal fibers are those motor fibers 
passing down from the motor centers in the 
cortex of the cerebrum to the cord where they 
are known as the pyramids. Others, which 
pass upward, are the sensory tracts and lead 
upward from the sensory nuclei in the upper 
part of the posterior columns of the spinal cord 
and lower part of the oblongata to the optic 
thalami, two small oval bodies which rest upon 
the cruri cerebri and contain nuclei that form im- 
portant auxiliary centers for several of the body 
movements. 
387.-Arrangement of Gray Matter in the 
Pons.-The gray matter of the pons no longer 
forms a cortex, as in the cerebrum, nor a con- 
tinuous column, as it does in the spinal cord, but 
it is cut up into small masses which are scattered 
among the interlacing fibers. 
388. The fifth, sixth, seventh, and eighth 
cranial nerves pass from the brain either through 
the pons or between the pons and medulla 
oblongata. See Fig. 71. 182 
Anatomy and Physiology 
The Medulla Oblongata 
389. Location.-The medulla oblongata, 
known also as the spinal bulb, is situated under 
the mid-brain and pons and above the spinal 
cord. In fact, the medulla is simply a widening 
out or expansion of the cord. The medulla 
rests in a groove in the lower part of the oc- 
cipital bone, directly above the foramen mag- 
num (paragraph 112) through which the spinal 
cord enters the cranial cavity. The medulla 
is directed (from above) obliquely downward 
and backward. 
390. Form.-In shape, the medulla resembles 
a truncated cone with its base upward and at- 
tached to the pons. 
391. Structure.-Like other parts of the 
brain, the medulla consists of masses of gray 
matter and bundles of nerve-fibers. Some of the 
fibers are on the exterior and some in the interior. 
The anterior surface of the medulla and the lower 
part of the posterior are marked by a deep fis- 
sure, but the posterior fissure is soon replaced by 
the fourth ventricle which is formed by the ex- 
pansion of the central canal of the spinal cord. 
The posterior surface of the medulla is largely 
occupied by the nuclei of origin of the cranial 
nerves, from the sixth to the twelfth inclusive. 
Distributed throughout the substance of the 
medulla are masses of gray matter which consti- 
tute- the automatic centers for the heart and Nervous System-Continued 
183 
respiration, vaso-moter centers and many others 
that govern important functions of the body. 
Also there are two convoluted masses of gray 
matter, lying one on each side of the middle line, 
known as the olivary bodies. Their function is 
unknown, but it is thought that they may help 
us to maintain the upright position. The nerve- 
fibers composing the sensory tracts-those pass- 
ing from the spinal cord to the brain-change 
their position considerably on entering the brain, 
some passing to the sides while others cling to the 
middle line. The motor fibers-those going from 
the brain to the cord-now come to lie in two 
composite groups, one on each side of the middle 
line, on the anterior surface. They are known as 
the pyramids. 
392. Decussation of the Pyramids.-Toward 
the lower end of the medulla, some of the fibers 
of each pyramid change their course, passing over 
to the opposite side to occupy a position in the 
lateral columns of the cord (page 190). This cross- 
ing of fibers is known as the decussation of the 
pyramids. This decussation accounts for the fact 
that injury involving the motor cortex of one side 
of the cerebrum causes a paralysis on the opposite 
side of the body. 
393. Cavities of the Oblongata.-Like the 
other parts of the brain, excepting the cerebellum, 
which, it will be remembered, is solid, the medulla 
oblongata is hollow; the cavities which make it so 
are the upper end of the central canal of the spine 184 
Anatomy and Physiology 
and the expansion of the latter, which is known as 
the fourth ventricle (see Fig. 69). 
394. Functions of the Medulla Oblongata. 
-The functions of the oblongata are those of 
conduction, reflex action, automatism. 
395. Conduction.-As a conductor of nerve 
impulse the oblongata has a wider extent of func- 
tion than any other part of the nervous system, 
since all impressions passing between the brain 
and spinal cord must be transmitted through it. 
396. Reflex and Automatic Action.-The 
most vital reflex and automatic centers of the body 
are situated in the oblongata, e. g., the respiratory 
center, the accelerator centers for the heart, the 
vaso-motor centers, the center controlling the 
impulses which enable the muscles of the palate, 
pharynx, and esophagus to produce the successive 
co-ordinate movements necessary to the act of 
swallowing, and many others. So important are 
the functions of the medulla oblongata that injury 
to it is likely to result in instant death. 
397. Unity of the Nervous System.- 
Though the manner in which the nerve-fibers and 
the gray matter are arranged in the brain makes 
it convenient to study certain portions as though 
they were separate parts, it is to be remembered 
that all parts of the brain and also the spinal cord 
and sympathetic ganglia are intimately connected 
with one another; for, as already stated, nerve- 
fibers extend between the outer surface and organs 
of the body and the nerve-centers and from cer- Nervous System-Continued 
185 
tain nerve-centers to others. Another point to be 
appreciated is that centers in several parts of the 
brain and cord must be stimulated and transmit 
the stimuli to motor nerves that will carry im- 
pulses to the muscles in order that we may accom- 
plish such simple actions as walking, maintaining 
balance, and the like. Probably it is only very 
simple reflexes that involve but one group of sen- 
sory and motor centers; therefore, learning to do 
anything involves the establishment of proper 
communication between various nerve-centers. 
398. The Membranes Covering the Brain. 
-The brain and spinal cord are enveloped in three 
membranes or meninges,1 the outer one of which is 
known as the dura mater, the middle as the arach- 
noid, and the innermost one as the pia mater. 
399. The Dura Mater.* 2-The dura is a 
strong tough, inelastic fibrous membrane containing 
a great number of blood-vessels. It is arranged in 
two layers which are attached to each other except 
in a few parts. The external surface is adherent to 
the bones of the skull, thus forming its internal 
periosteum. In some places the inner layer of 
dura separates from the outer and projects inward. 
These projections form supports for the lobes of 
the brain, nerves, and blood-vessels, and in some 
places form sinuses for the veins that return the 
blood from the brain; also it forms sheaths for the 
nerves as they pass from the skull. 
1 Meninges. From the Greek meninggos-a membrane. 
3 Dura mater. Latin, hard mother. 186 
Anatomy and Physiology 
400. The Pia. *-The pia, or pia mater,1 consists 
of blood-vessels held together by areolar tissue. 
It is the nourishing tunic of the brain and lies close 
to its surface, dipping into and extending to the 
bottom of every fissure. It covers the roots of the 
nerves and becomes merged with their connective- 
tissue sheath, and branches of its arteries extend 
into the substance of the brain. 
401. The Arachnoid.*2-The arachnoid is a 
thin, delicate membrane situated between the 
dura and the pia, but nearer the former, as, except 
in the case of the longitudinal fissure, it does not 
follow the pia into the fissures. It is connected 
with the dura by means of small, oblique bundles 
of fibers. It resembles serous membranes in its 
nature and function-i. e., it secretes a serous fluid 
which lubricates the other membranes and so pre- 
vents friction. Like the serous membrane lining 
the ventricles, the arachnoid when inflamed-men- 
ingitis-secretes an excessive amount of fluid. 
402. The Cerebro-Spinal Fluid.-The ven- 
tricles of the brain, the central canal of the spinal 
cord, and the space between the arachnoid and 
the pia are filled with a clear fluid called the 
cerebro-spinal fluid. This acts as a water bed for 
the brain and cord and minimizes the danger of ill 
effects from blows on the head and spinal column. 
In meningitis, the quantity of fluid becomes in- 
creased, and the symptoms occurring during the dis- 
ease are partly due to its pressure upon the brain. 
1 Latin, tender mother. 
2 From the Greek arachne-a spider's web, and eidos-form. CHAPTER IX 
the nervous system-Continued 
THE SPINAL CORD. THE SYMPATHETIC SYSTEM. 
THE NERVES 
The Spinal Cord: Location, Membranes, Structure, Function. 
Different Sets of Nerves. Number, Origin, Nature, and Names 
of the Cranial and of the Spinal Nerves. Roots and Ganglia of 
Spinal Nerves. Distribution of the Peripheral Branches of the 
Spinal Nerves. The Sciatic Nerve. The Sympathetic System: 
Constituents, Nature of Ganglia, Distribution of Nerves. Con- 
nections between the Spinal and Cerebro-spinal Systems. Func- 
tion. Influence of Cerebro-spinal System on the Sympathetic, 
Vaso-motor Centers and Nerves. 
The Spinal Cord 
403. Location.-The spinal cord is the ter- 
minal portion of the cerebro-spinal axis. It is 
contained within the canal formed by the union 
of the vertebra and the intervertebral disks of 
cartilage, and extends from the foramen magnum1 
to the body of the second lumbar vertebra, where 
it terminates in a fine non-nervous strand called 
the filum terminale. The collected nerves arising 
1 Described in paragraph 112. 
187 188 
Anatomy and Physiology 
from the lower end of the spinal cord are called 
the cauda equina.1 
404. Differences be- 
tween the Membranes of 
the Cord and Those of the 
Brain.-Like the brain, the 
cord is surrounded by the 
three membranes known as 
the dura mater, pia mater, and 
arachnoid. Though these 
membranes are direct con- 
tinuations of the ones cover- 
ing the brain they differ 
slightly from the latter in 
their structure; thus, the dura 
does not form the periosteum 
of the vertebral bones, as it 
does of the skull, but it hangs 
like a long tube within the 
canal, and this prevents it in- 
terfering with movement be- 
tween the vertebra. 
405. The pia of the cord 
is more fibrous and less vas- 
cular than is that of the brain, 
and it has on each side a long band of connective 
tissue, on the outer edge of which are sharp 
projections which extend and are attached to the 
dura between the places where the spinal nerves 
perforate that membrane. 
Fig. 75.-Lower end 
of the spinal cord and 
the cauda equina, dor- 
sal aspect. The dorsal 
roots of the right side 
have been removed. 
1 Latin, a horse's tail. Nervous System-Continued 
189 
There are also some slight points of difference 
in the arachnoid, but these need not be mentioned 
here. 
406. Structure of the Cord.-The substance 
of the cord is made up of gray and white nervous 
matter supported by neuroglia. The gray matter 
which, it will be remembered, consists of the cell- 
bodies with their dendrites, the beginning of the 
axis cylinder processes, and collaterals, is massed 
together in something the shape of the letter H, 
around the canal which runs through the center 
of the cord. The white matter, which consists of 
medullated nerve-fibers, is grouped in bundles 
known as tracts or columns, on the outside of the 
gray matter. Some of these tracts have their 
origin in the gray matter of the cord, and their 
terminations in the gray matter of the brain. 
These are termed ascending or sensory tracts 
because they carry impulses to the brain. Others 
arise from cell-bodies in the gray matter of the 
brain and terminate in arborizations around cells 
in the gray matter of the cord; these are termed 
descending or motor tracts and they convey im- 
pulses downwards. The names of the more import- 
ant tracts are: 
j- 
escen wg 
Direct pyramidal tracts 
Crossed pyramidal tracts 
Columns of Goll 
Columns of Burdach 
Direct cerebellar tracts 
A scending 190 
Anatomy and Physiology 
In addition to these long tracts there are 
columns which consist of bundles of fibers, no 
one of which is continuous throughout the cord. 
These columns, which are known as the lateral 
columns, serve to connect centers in different 
Fig. 76.-Transverse section of the spinal cord at the middle 
of the thoracic region. The neuroglia septum has been re- 
moved from between the dorsal columns. (Gerrish.) 
parts of the cord. They contain both sensory and 
motor nerve-fibers. 
407. Names of Different Parts of Gray 
Matter.-The transverse bar uniting the two 
lateral masses of gray matter is spoken of as the 
gray commissure; the points of the side masses 
are named the horns, the two in front being called 
the anterior horns and the two in the back the 
posterior. 
408. Fissures and Canal of the Cord.- Nervous System-Continued 
191 
The substance of the cord is almost completely- 
divided into two lateral halves by two fissures, 
one in front-the ventral or anterior fissure, and 
one in the back-the dorsal or posterior fissure, 
and by the central canal which extends through 
the entire length of the center of the cord. 
409. Function of the Cord.-Within the 
gray matter of the cord, the impulses entering 
from the sensory peripheral or visceral nerves are 
transmitted to motor fibers going to the periph- 
ery, or to sensory cell-bodies from which fibers 
pass to the brain-the ascending columns-or to 
both; and impulses coming from the brain are 
transmitted to motor fibers passing outward from 
the cord. Thus the spinal cord serves as a center 
for the transmission of impulses and as a conduc- 
tion path to and from the brain; also it, with the 
medulla oblongata, is the center for reflex actions. 
The Nerves 
4io. There may be said to be four sets of 
nerves in the human body: (i) The cranial nerves 
which pass to and from the brain through open- 
ings in or between the bones forming the base 
of the skull and do not become a part of the 
spinal cord; (2) the cerebro-spinal nerve-fibers 
extending between the brain and the cord and 
forming the tracts or columns (white matter) of 
the cord; (3) the spinal nerves and their periph- 
eral branches, those connecting the spinal cord 192 
Anatomy and Physiology 
with the periphery and with the sympathetic 
system; (4) the nerves of the sympathetic system. 
The Cranial Nerves 
4ii. Number and Origin.-In man there are 
twelve pairs of cranial nerves. They appear to 
arise, in a double series, from the under surface 
of the anterior surface of the cerebrum and the 
medulla oblongata (see Fig. 71) and this is called 
their superficial origin; but they can be traced 
back to various masses of gray matter in the 
higher parts of the brain. These parts are called 
their deep or real origin. 
412. Nature.-Some of the cranial nerves are 
purely sensory; others are entirely motor, and 
some are mixed, i. e., both sensory and motor. 
Most of the cranial nerves arise from several 
roots, i. e., groups of cell-bodies, and consist of 
many bundles of nerve-fibers which in some 
cases, after the nerve emerges from the cranium, 
become split up and branch to various parts of 
the body. 
413. Names.-The cranial nerves were named 
by numbers corresponding to the order of their 
superficial origin in the brain, beginning at the 
top, and also by names descriptive of their nature, 
function, or distribution. Their names, distribu- 
tion, and function can be seen in the following 
table. In the section on the right is a doggerel 
used by students of anatomy as a help to connect 
the numerical and ordinary name of the nerves. Nervous System-Continued 
193 
Table of the Cranial Nerves 
Names. 
Distribution. 
Function. 
Doggerel. 
i. Olfactory.1 
Upper third of nasal cav- 
ity. 
S.2 Smell. 
On. 
2. Optic.3 
Retina (Inner membrane 
of the eye). 
S.2 Sight. 
old. 
3. Oculomotor. 
Muscles of eyeball, ex- 
cept external rectus and su- 
perior oblique. 
M.4 
Olympus. 
4. Pathetic or 
Trochlear. 
Superior oblique of eye- 
ball. 
M.4 
piney. 
5. Trifacial or 
Trigeminal. 
Sensory part of face and 
tongue, motor, to muscles 
of mastication. 
S. and M.S 
tops. 
6. Abducent. 
External rectus of eye- 
ball. 
M.4 
a. 
7. Facial. 
Sensory part to tongue, 
motor to those muscles of 
the face concerned in ex- 
pression. 
S. and M.S 
Finn. 
8. Auditory. 
Membranous labyrinth 
of ear (described in para- 
graph 984J. 
S. Hearing 
and 
equilibrium. 
and. 
9. Glosso- 
pharyngeal.6 
Pharynx (see paragraph 
602) and back part of 
tongue. 
S. Taste. A 
few motor 
fibers. 
German. 
10. Pneumo- 
gastric? or 
Vagus.8 
Sensory to external ear. 
Motor and sensory to 
pharynx, trachea, lungs, 
esophagus, stomach, heart, 
liver. 
S. and M. 
picked. 
11. Spinal, 
accessory. 
A portion of the spinal 
accessory joins and is dis- 
tributed with the vagus. 
The other portion supplies 
the sternomastoid and the 
trapezius muscles. 
M. 
some. 
12. Hypoglossal. 
Muscles of the tongue. 
M. 
hops. 
1 From the Latin olfacio-to smell. 2 Sensory. 
3 From the Greek optikos-belonging to the sight. 
4 Motor. s Sensory and Motor. 
6 From the Greek glossa-the tongue and pharynggos-the 
pharynx. 
7 From the Greek pneumon-the lung and gaster-the belly. 
8 Latin wandering. The nerve is so called from its wandering 
course. 194 
Anatomy and Physiology 
414. Cerebro-Spinal Nerves.-The cerebro- 
spinal nerves are those which form the white 
matter of the cord and, except for the cranial 
nerves, the white matter of the brain. Their 
arrangement has been already discussed. 
Spinal Nerves 
415. Number and Names.-In man there are 
thirty-one pairs of spinal nerves. They wTere 
named for the regions of the vertebral column 
where they emerge; thus there are: 
8 Cervical-region of the neck 
12 Thoracic-region of the chest 
5 Lumbar-region of the loins 
5 Sacral 
1 Coccygeal-terminal portion of the spinal column. 
416. Origin.-The spinal nerves, with the 
exception of the first cervical, spring from both 
sides of the spinal cord and emerge, with the excep- 
tion of the first cervical and the coccygeal, through 
the intervertebral foramina-openings. The first 
cervical nerve arises from the medulla oblongata 
and leaves the neural canal between the occipital 
bone and the atlas; the coccygeal passes from the 
lower end of the canal. 
417. Nature of Spinal Nerves.-The spinal 
nerves consist almost entirely of medullated nerve- 
fibers ; they contain both motor and sensory fibers, 
and are therefore called mixed nerves. 
418. Roots of Spinal Nerves.-Each nerve Nervous System-Continued 
195 
is attached to the cord by two roots. One, called 
the anterior root, springs from the ventral horn of 
gray matter in the cord. It consists of bundles of 
motor fibers. The other, known as the posterior 
root, arises from the dorsal horn. It is composed 
of sensory fibers, and it differs somewhat in 
appearance from the motor root, the principal 
difference being the presence of 
a ganglion (see Fig. 77). The 
two roots join, i. e., they come 
together, and the fibers compos- 
ing them are held in contact by an 
investment of connective tissue 
--immediately beyond the gan- 
glion, that is, just as they are 
passing through the interverte- 
bral foramen. 
419. Spinal Ganglia.-The 
ganglia on the sensory or pos- 
terior roots of the spinal nerves consist of small 
ovoid masses of gray matter. They are placed 
in the intervertebral foramina.1 The cell-bodies 
of these ganglia are bipolar, and one pole of each 
cell passes into the spinal cord via the posterior 
root, and the other passes outward. The pro- 
cesses passing outward are the fibers which, unit- 
ing with the fibers from the anterior root, form a 
spinal nerve. 
420. Distribution of the Peripheral 
Fig. 77. - For- 
mation of a spinal 
nerve. 
1 Openings between the vertebrae, through which the roots 
pass. Anatomy and Physiology 
196 
Branches of the Spinal Nerves.-Almost 
immediately after emerging from the vertebral 
column each spinal nerve divides into two main 
trunks known as the anterior and posterior divi- 
sions. Each division contains both sensory and 
motor fibers. The posterior divisions pass back- 
ward and give off branches which supply the 
muscles and skin of the back of the head, neck, 
and trunk. The branches of the anterior divisions 
supply the parts of the body in front of the spine 
and the extremities. Each anterior division gives 
off fibers to, and receives fibers from, the sym- 
pathetic system. In the cervical, lumbar, and 
sacral regions, the branches of this division form 
plexuses, previous to their distribution. These 
are known as the cervical, lumbar, and sacral 
plexuses. The nerves in passing to their destina- 
tion in the peripheral muscles, skin, etc., usually 
follow the same pathways as the blood-vessels. 
The various natures of their endings were de- 
scribed in paragraph 323. 
421. Names of Peripheral Nerves.-The 
Great Sciatic Nerve. The majority of the larger 
nerves bear the name either of the blood-vessels 
with which they are continuous or else of the 
locality which they supply. An exception to this 
are the two great sciatic nerves which pass down, 
one on either side of the body, near the center of 
each buttock and back of each thigh to the 
popliteal region.1 Motor branches pass from 
1 Region back of the knee. Nervous System-Continued 
197 
these nerves to all of the muscles of the legs 
and feet, and they receive sensory branches from 
nearly all parts of the skin of the lower extremi- 
ties. This nerve is of particular interest to nurses, 
as it is sometimes the seat of a troublesome form 
of neuritis-inflammation of a nerve-known as 
sciatica. 
The Sympathetic System 
422. Constituents.-The sympathetic system 
may be said to consist of: (i) Two chains of ganglia 
and fibers, variously known as the lateral or 
vertebral ganglia and the gangliated cord, which 
extends from the cranium to the pelvis along each 
side of the spinal column, within the thoracic and 
abdominal cavities, and from which branches are 
distributed both to other parts of the sympathetic 
system and to the cerebro-spinal system; (2) 
irregular groups of ganglia called collateral or 
prevertebral ganglia and plexuses of nerve-fibers 
which give off branches to the thoracic and 
abdominal viscera; (3) various ganglia known as 
the terminal ganglia, and plexuses in the substance 
of some of the viscera; (4) sympathetic nerve 
cells in the brain and spinal cord. 
423. Number of Lateral Ganglia.-In the 
thorax the number of sympathetic lateral ganglia 
corresponds with the number of spinal nerves, 
but in the cervical and lumbar region some of the 
ganglia are fused together so that while there are 
thirty-one spinal nerves passing from each side of 198 
Anatomy and Physiology 
the cord there are only twenty or twenty-three 
ganglionic masses. 
424. Nature of and Connections between 
the Sympathetic Ganglia.-The ganglia lying 
on either side of the spinal column-the lateral 
ganglia-consist of small masses of gray matter 
linked to each other by bundles of nerve-fibers 
Fig. 78.-Plan of the constitution of a spinal nerve. 
(Gerrish.) 
called the ganglia cords (see Fig. 78). They are 
connected to the spinal nerves by branches called 
the rami communicantes (these will be described 
in the next paragraph), and to the viscera, includ- 
ing the blood-vessels, by branches which reach 
their destination in several ways: (1) they pass 
directly to the viscera; (2) they join the collateral 
ganglia and plexuses; (3) they first converge to 
form three main trunks known as the great 
splanchnic* (visceral nerve), the small splanchnic 
nerve, and the least splanchnic nerve, and then 
1 From the Greek splangchnon-a bowel. Nervous System-Continued 
199 
branch off and pass to different viscera; (4) they 
join the spinal nerves by way of the gray rami 
communicantes (see next paragraph) and in them 
reach the vessels, fascia, bones, etc., for which they 
were destined. The collateral or pre vertebral 
ganglia consist of aggregations of nerves and 
ganglia which, as stated in paragraph 420, form 
plexuses that give off branches to the thoracic and 
abdominal viscera. The chief of these plexuses 
are: the cardiac plexus, situated above the heart 
and supplying it; the solar plexus lying in the 
abdomen behind the stomach and supplying most 
of the abdominal viscera and their vessels; and 
the hypogastric* plexus, which is placed in the 
center of the lower part of the abdomen and 
Supplies the pelvic viscera. In many of the in- 
ternal organs the nerve branches derived from 
the prevertebral plexuses form a secondary plexus 
called the terminal plexus, and from these plexuses 
branches pass in between the individual muscles 
of the organs and send off fine fibrils which 
terminate on the walls of the muscle cells. 
425. Rami Communicantes. 2-As stated in 
the preceding paragraph, the lateral ganglia of 
the sympathetic system are connected with the 
spinal nerves by branches called the rami com- 
municantes. Usually two rami communicantes 
connect a sympathetic ganglia with a spinal nerve. 
The two rami differ from each other in color, one 
consisting of medullated and the other of non- 
1 Described in paragraph 702. 2 Communicating branches. Anatomy and Physiology 
200 
medullated fibers. The former is therefore called 
the white ramus and the latter the gray ramus. 
The white ramus consists of fibers which emerge 
from the spinal cord and pass to the sympathetic 
ganglion; the gray consists of axons of cells con- 
tained in the sympathetic ganglion which pass out 
and join the spinal nerve (see Fig. 78), and so 
reach the vessels, etc., which they are to supply. 
They then branch off and enter the substance of 
the organ. 
426. Function of the Sympathetic Portion 
of the Nervous System.-(1) The sympathetic 
portion of the nervous system sends nerve-fibers 
to the muscles of the vascular system-i. e., the 
heart and the blood and lymph-vessels, to the 
visceral muscles, and to the secretory gland-cells. 
(2) Owing to the manner of distribution of the 
branches of the sympathetic nerves, especially 
the interchange of nerve-fibers of the different 
nerves that takes place in the collateral plexuses, 
the organs constituting a system (as for instance 
the digestive system) are brought, as it were, 
into direct telegraphic communication with each 
other and coordination of action in all the organs 
of the system thus effected. 
427. Influence of the Cerebro-Spinal Sys- 
tem on the Sympathetic and on the Viscera.- 
It has been shown that the spinal nerves both give 
fibers to and receive fibers from the sympathetic 
ganglia, so that there is a direct pathway for 
impulses between the thoracic, abdominal, and Nervous System-Continued 
201 
pelvic viscera and the spinal cord and brain. 
Also, many of these viscera are brought into 
relationship with the brain by means of certain 
of the cranial nerves. The action of these cranial 
nerves is in some instances antagonistic to that 
of the sympathetic system. For instance, the 
action of the tenth cranial nerve-the pneumogas- 
tric or vagus-on the heart is to inhibit or slow its 
beat, and that of the nerve-fibers received from 
the sympathetic cardiac plexus is the acceleration 
or quickening of its beat. This antagonistic 
action of the vagus and the sympathetic system 
will be referred to again in connection with the 
circulation and respiration. 
428. The Vasot-Motor Centers and Nerves. 
-The vaso-motor nerves are those which supply 
and control the caliber of the blood-vessels; they 
are thus an important factor in regulating many 
of the life processes of the animal body, such as 
the circulation of the blood, metabolism, heat 
regulation, etc. The nerves are divided into two 
classes called, according to their action on the 
blood-vessels, vaso-constrictors and vaso-dilators. 
Impulses from the former cause contraction of the 
muscular tissue in the walls of the arteries, and 
consequently a diminution in the size of the 
vessels; impulses from the latter result in relaxa- 
tion and dilation of the vessels. 
429. Location of Vaso-Constrictor Centers 
and Distribution of Vaso-Constrictor Nerves. 
1 From the Latin vas-a vessel. Anatomy and Physiology 
202 
-It has been found that the main vaso-constrictor 
center is in the medulla oblongata and that the 
cell-bodies composing it give off neuraxons which 
descend to various levels in the cord where they 
terminate in cells contained in the anterior horns 
of gray matter. These cells form what are known 
as the spinal waso-motor centers, and they give off 
axons which pass to cells in the sympathetic 
ganglia, whence fibers are continued to the blood- 
vessels, more especially those of the skin and of 
the abdominal viscera. Under normal conditions 
the vaso-constrictor centers in the cord do not 
work independently of those in the medulla ob- 
longata, but when action of the latter has been 
lost by injury, vessel tone has been shortly estab- 
lished by the influence of the centers in the spinal 
cord and sympathetic ganglia. The center in the 
oblongata is in constant action, in consequence of 
which the arteries it supplies are kept in a condi- 
tion of tone or slight contraction. This has been 
proven by experiments On animals in which the 
fibers that transmit impulses from this center have 
been cut, such experiments resulting in dilation 
of the blood-vessels. The ordinary normal degree 
of tonicity may be either increased or decreased 
by reflex stimulation of the center through the 
sensory nerves. Thus, there are certain afferent 
nerves which, when stimulated, cause reflexly an 
excitation of the vaso-constrictor center, and conse- 
quent constriction of the peripheral arteries. Other 
sensory nerves when stimulated cause a lessening Nervous System-Continued 
203 
of the tone of the vaso-constrictor center and 
consequent dilation of the blood-vessels. Thus, 
dilation of the blood-vessels may take place as the 
result of depression or inhibition of the action of 
the vaso-constrictor centers as well as by stimula- 
tion of the vaso-dilator fibers. 
430. Vaso-Dilator Center and Distribution 
of Nerves.-The vaso-dilator nerve-fibers arise, 
it is thought, from separate cells in the medulla 
oblongata, no definite general center having been 
found. The parts of the body the blood-vessels 
of which are supplied with these fibers seem to be 
the erectile tissue,1 secretory glands,2 the bucco- 
facial region, and the muscles. The vaso-dilator 
fibers seem to end in the muscular tissues of the 
walls of the arteries supplying those parts, and it 
is thought that they act, when stimulated, by 
inhibiting or depressing the usual tonic contrac- 
tion of this tissue. The vaso-dilator fibers, unlike 
the vaso-constrictor fibers, are not in constant 
activity, but become active only in response 
to stimuli transmitted from sensory nerves. Ex- 
amples of vaso-dilation are the flushing of the face 
known as blushing-the usual stimuli in such 
cases being of psychic origin, e. g., embarrassment, 
anger, etc.,-and the congestion of the vessels in 
the salivary glands, the secretory glands of the 
stomach, etc., during mastication and digestion. 
1 Described in the chapter dealing with the organs of genera- 
tion. 
3 Described in Chapter XVI. CHAPTER X 
MEMBRANES 1 
Nature. Classification. Function. Secretion. Serous Mem- 
branes: Structure, where Found. Synovial Membranes: Struc- 
ture, Nature of Secretion, Classification, Nature and Location of 
Different Kinds of Membrane. Synovitis and Bursitis. Mucous 
Membranes, where Found, Structure, Nature of Secretion. 
431. Nature of Membrane.-The free sur- 
faces of the body and its organs, both internal and 
external, are covered with membrane, i. e., a thin, 
Fig. 79.-A typical membrane in vertical section. (Ger- 
rish.) 
sheet-like expansion of tissue. In the widest 
sense of the meaning of the word membrane it can 
be, and often is, used for any thin, expanded sheet 
of tissue, as, for instance, the periosteum covering 
the bones, and the thin layer of cells beneath the 
epithelium of certain surfaces, commonly known 
as basement membrane; but, in its more restricted 
sense, the word is applied to sheets of tissue 
1 From the Latin membrana-a skin. 
204 Membranes 
205 
covering parts or lining cavities which have a free 
unattached surface. 
432. Classification of Membranes.-There 
are four different classes of membranes answering 
the foregoing description. They are called: 
1. Serous membranes 
2. Synovial membranes 
3. Mucous membranes 
4. Cutaneous membrane 
433. Function of Membranes.-With the 
exception of the cutaneous membrane or, as it is 
usually called, the skin, which has many func- 
tions, the chief purpose of these membranes is the 
protection of the parts they cover. Some of the 
serous membranes also serve to connect and 
support the organs they invest, as, for instance, 
the folds of peritoneum1 known as the mesentery2 
and the omentum,2 and some of the mucous mem- 
branes, which are very vascular,3 afford nutrient3 
for non-vascular parts which they cover. 
434. Method of Protection.-These mem- 
branes afford protection in two ways: (1) by acting 
as a covering; (2) by secreting a lubricating fluid 
which keeps their surfaces moist and thus pre- 
vents friction between the contiguous organs of 
which the membranes form the covering. Also, 
in the case of mucous membrane, the .secretion is 
1 The membrane lining the abdomen and covering its organs. 
2 Described in paragraph 703. 
3 Having a large number of blood-vessels. The blood is the 
conveyer of nutrient to the tissues. 206 
Anatomy and Physiology 
somewhat thick and viscid, and thus prevents 
injury of the surface by substances entering the 
cavities and passages which it lines. 
435. Secretion.-By secretion is meant the 
taking, by secretory cells, of certain substances 
from the blood and changing them so that they 
are adapted to the purpose for which they are 
required. Also, the word is used to designate the 
substances so prepared. The secretions of the 
serous, synovial, and mucous membranes are 
simple in composition and, unlike the secretions 
to be discussed later in connection with the secre- 
tory glands, there is not much change made in the 
substance extracted from the blood. 
Serous Membranes 
436. Structure.-Serous membranes are thin, 
transparent, and somewhat elastic. They consist 
of two layers of tissue (1) the corium,1 (2) the epi- 
thelium. The corium is a thin layer of tissue 
substance constructed of white and yellow fibrous 
and lymphoid tissues, and containing blood and 
lymph vessels and nerves. It is held to the un- 
derlying parts by areolar tissue, which in such 
locations is often called subserous tissue. The 
epithelium which forms the free surface of the 
membrane consists of closely fitted endothelial2 
cells. These cells secrete a thin serous3 fluid which 
1 Latin corium-leather. 
2 From the Greek endon-within and thele-a nipple. 
3 This fluid resembles the serum of the blood, hence its name 
and that of the membrane. Membranes 
207 
keeps the membrane moist. Normally this fluid 
is present in very small amounts, for just as fast 
as it is secreted it is withdrawn by the lymphatics 
in the corium, but in certain diseased conditions 
affecting the membrane, equilibrium between the 
rate of secretion and absorption is disturbed and 
there is an accumulation of fluid in the part. 
437. Where Found.-(1) Serous membrane 
lines the cavities and passages of the body which 
do not communicate with its exterior. These are: 
the thoracic and abdominal cavities, the cavity of 
the heart, of the blood and lymph vessels, of the 
brain and spinal cord, of the inner ears, and a 
small cavity at the back of each eyeball. (2) 
Serous membrane covers the lungs, the heart, the 
abdominal viscera, and the upper surface of some 
of the pelvic viscera. 
438. Serous Membranes Proper.-The serous 
membranes covering the lungs and lining the thor- 
acic cavity, the membrane covering the heart 
and that lining the abdominal cavity and invest- 
ing and supporting its organs, differ in some 
respects from the membrane lining the other cavi- 
ties, and they are often termed serous membranes 
proper. They will be further described in con- 
nection with the organs with which they are 
respectively related. 
Synovial1 Membranes 
439. Structure and Secretion.-Synovial 
1 From the Greek syn-with and the Latin ovum-an egg. 208 
Anatomy and Physiology 
membrane is composed of fibrous tissue that has 
on its free surface an imperfect covering of irregu- 
larly shaped cells which secrete a glairy, viscid 
fluid resembling the white of egg, and is therefore 
called synovial fluid. 
440. Classification.-Synovial membranes 
are divided into three groups, viz.: 
Articular synovial membranes 
Bursal synovial membranes 
Vaginal synovial membranes 
44i. Articular Synovial Membranes.- 
These are found in articulations of the skeleton 
where two bones run upon each other when mov- 
ing. It will be remembered that in the description 
of the joints it was said that the articular surfaces 
of such joints are covered with smooth hyaline 
cartilage and held together with strong ligaments 
that are lined with a synovial membrane, which 
turns inward and is connected with the cartilage, 
thus forming with the cartilage a closed sac 
between the two bones. 
442. Bursal Synovial Membranes.-A syn- 
ovial bursa is a small sac of fibrous tissue lined 
with synovial membrane and placed between 
parts which move upon each other, as two muscles, 
twro tendons, a muscle or tendon and a bone, the 
skin and a bone. The sac is connected with the 
surrounding parts by areolar tissue, and the two 
surfaces facing each other are kept moist with 
synovial fluid, and friction thus prevented. Some Membranes 
209 
of the larger bursa are found over the patella, the 
olecranon, the malleoli, between the glutei muscles, 
and on the surface of the great trochanters. 
443. Vaginal Synovial Membranes.-These 
are also called synovial sheaths. They are found 
in parts where the tendons or muscles run over 
bones, as do those of the flexor and extensor 
muscle of the fingers and toes. In these cases the 
bone is grooved and the membrane is in the form 
of a tube, and is attached at its outer under surface 
to the bone, and encloses the tendon in its cavity. 
The secreting surface forms the inside of the tube, 
and thus friction is prevented in the movements 
of the tendon. 
444. Synovitis and Bursitis.-As in the case 
of the serous membranes, the synovial normally 
secretes only a small amount of fluid, and that is 
constantly being absorbed; but inflammatory con- 
ditions, which occur most frequently as the result 
of injury, are likely to cause disturbance between 
the rate of secretion and absorption, and result, as 
in other inflammations, in an accumulation of fluid 
and consequent distension of the tissues and pain. 
This condition is known as synovitis, or, if a bursa 
is affected, as bursitis; the suffix itis meaning 
inflammation. 
Mucous Membranes 
44 5- Where Found.-Mucous membranes line 
the cavities and passages which communicate 210 
Anatomy and Physiology 
with the exterior of the body. There are two 
separate sets of mucous membranes, each of which 
lines a continued series of organs. They are called 
the gastro-pulmonary and the genito-urinary. The 
Fig. 8o.-Diagram of mucous membrane in vertical section 
(Gerrish.) 
former, as the name denotes, lines the alimentary 
and respiratory tracts. The alimentary portion 
begins at the lips and is continued over the mouth, 
the middle and lowest part of the pharynx, the 
esophagus, stomach, small and large intestine, and 
at the orifice of the rectum it becomes continuous 
with the skin. In its course it sends offsets to the 
ducts of the salivary glands, the pancreas, the Membranes 
211 
liver, the gall-blad- 
der, and the vermi- 
form appendix. The 
respiratory portion 
begins in the nos- 
trils and passes 
through the upper 
pharynx, the larynx, 
trachea, bronchi, 
bronchial tubes, and 
ends in the air vesi- 
cles of the lungs. 
The genito - urinary 
mucous membrane, 
as the name implies, 
lines the genital and 
urinary tracts. In 
both sexes the urin- 
ary mucous mem- 
branes line the 
urethra, bladder, 
ureters, and end at 
the papillae of the 
kidneys. In the fe- 
male that lining the 
genital tract begins 
at the vulva and is 
continued through 
the vagina, uterus, 
and two Fallopian 
tubes at the free ex- 
Fig. 8i.-Diagram of the gastro- 
pulmonary mucous membrane, 
showing the continuity of all its 
parts. (Gerrish.) 212 
Anatomy and Physiology 
tremity of which it blends with the serous mem- 
brane lining the abdominal cavity. 
446. Structure.-Usually the foundation of 
mucous membrane-4he part attached to the 
Fig. 82.-Diagram of female genito-urinary mucous mem 
brane, showing continuity of all its parts. (Gerrish.) 
underlying tissues-consists of a thin layer of 
plain muscular tissue, termed the muscularis 
mucosa. On top of this is the corium which is 
similar to that of the serous membrane, but is 
thicker, contains less elastic and more lymphoid 
tissue, and is very vascular. The corium is in 
most cases covered with a single layer of cells 
called basement membrane, and covering this are 
the epithelial cells. Mucous membranes, however, Membranes 
213 
vary considerably in their structure and the epi- 
thelium is the only element in the membrane that 
is never lacking. Other variations in mucous 
membranes are: (i) it is much thicker in some 
parts of the body than in others; (2) in certain 
locations it contains minute glands,1 or its surface 
is covered with papillae,2 villi,2 hairs,3 or cilia4; 
(3) it is attached to the underlying tissues in 
different ways; for instance, in parts where there 
is no distention, as the interior of the nose, the 
membrane is attached directly to the bone; in 
other parts it is held to the under surface by areolar 
tissue, and the amount of tissue varies greatly in. 
different parts of the body, there being very little 
in some locations and a great deal in others. In 
the stomach, for example, which is distended 
when full and collapsed when empty, there is 
such a large amount of areolar tissue holding the 
membrane to the elastic muscular wall of the organ 
that when the latter is empty and consequently 
collapsed, the mucous membrane is thrown into 
folds. This arrangement prevents the numerous 
small glands contained in the gastric5 membrane 
becoming injured, as they would be if the mem- 
brane were stretched when the stomach became 
distended, as would happen if the membrane were 
elastic like the serous membrane, and applied 
1 Examples, the stomach and intestines. 
2 Examples, the intestines. 
3 Example, entrance to nasal cavities. 
4 Examples, the larynx, bronchi. $ Stomach. Anatomy and Physiology 
214 
tightly to the walls of the organ. The nature of 
the special forms of mucous membrane will be 
further described in connection with the organs 
which they line. 
447. Secretion of the Mucous1 Membrane. 
-The secretion of the mucous membrane is 
called mucus. It is thicker and more viscid 
than the secretions of the other two membranes; 
this is necessary because the mucous membrane is 
more exposed to irritating substances than the 
others. 
'Latin mucus-the fluid within the nose. CHAPTER XI 
THE CIRCULATING FLUIDS OF THE VASCULAR 
SYSTEM 
Divisions of the Vascular System. The Blood: Functions, 
Quantity, Characteristics, Color, Composition. Nature, Func- 
tion, etc., of Corpuscles, Blood-plates, Plasma, Gases, Internal 
Secretion, and Antibodies Contained in the Blood. Clotting of 
Blood. Lymph: Nature, Derivation, and Function. 
448. Divisions of the Vascular System.- 
The vascular system of the body is classed under 
two headings: 
(i) The blood-vascular system 
(2) The lymph-vascular system 
The former consists of the heart, arteries, capil- 
laries, and veins; the latter of the lymph spaces, 
the lymphatic vessels including the lacteals and 
ducts, and the lymphatic nodes or glands. 
Before taking up the study of the organs of 
these systems we will consider the nature of the 
fluids for the conveyance of which the organs are 
required; the fluids being the essential feature and 
the organs only of use inasmuch as they serve to 
convey the fluids to and from the tissues. 
215 Anatomy and Physiology 
216 
The Blood 
449- Functions.-The blood serves several 
purposes in the body: (i) It carries to the tissues: 
(a) the material, including water, which they 
require for their growth and repair-this it gets 
from the alimentary canal; (5) oxygen-this the 
blood absorbs from the air while passing through 
the lungs-oxygen is necessary for the process of 
oxidation which must go on within the tissues in 
order to provide the heat and energy necessary 
to maintain the body mechanism at work; (c) 
certain glandular secretions which are necessary 
to promote oxidation and other important meta- 
bolic processes. 
(2) The blood takes away from the tissues the 
waste products of the materials which have been 
broken down by oxidation and are not only of no 
use to the body but poisonous, and must therefore 
be eliminated by the kidneys, lungs, and skin, 
whither the blood carries them. 
(3) The blood distributes and equalizes the heat 
produced in the tissues by oxidation. 
(4) The blood contains certain constituents 
which aid in protecting the body from bacteria 
and other foreign substances. 
450. Quantity.-The quantity of blood in the 
human body is generally estimated at from y^to 
of the total body weight. 
451. Characteristics.-Blood is a red, vis- 
cid, heavy, opaque liquid with a normal specific The Vascular System 
217 
gravity of between 1.041 to 1.067, of an approxi- 
mately neutral reaction and a normal temperature 
of about ioo°F. 
452. Color.-The red color of the blood is 
due to the presence of colored bodies called the 
red corpuscles or erythrocytes. The shade is vari- 
able and depends upon the amount of oxygen 
contained in the corpuscles. The blood in the 
arteries and pulmonary veins has the largest 
supply of oxygen and is of a bright scarlet hue. 
That in the veins, other than the pulmonary, has 
lost much of its oxygen and is therefore of a 
darker shade with a purplish tinge. 
453. Composition of Blood.-Blood consists 
of: 
(1) Water 
Corpuscles 
Red 
White 
Blood-plates 
Fibrinogen 
Albumin 
Globulin 
Nucleo- 
proteins 
Proteins 
such as: 
(2) Solids 
Fatty substances 
Sugar 
Inorganic salts 
Extractives 
which represent 
waste products 
such as: 
' Urea 
Creatin 
Lactic and 
other acids 
(3) Gases 
Oxygen 
Carbon dioxide 
Nitrogen 218 
Anatomy and Physiology 
(4) Enzymes 
(5) Immune 
bodies such 
as: 
Opsonins 
Antitoxins 
Antibacterial substances 
454. The Plasma.-The fluid portion of the 
blood is known as the plasma. So long as the 
blood is circulating in the blood-vessels, the solids 
and gases are held in suspension in the plasma, 
but if the blood escapes from the vessels, as in 
hemorrhage, the greater part of the solids will, under 
favorable circumstances, become formed into a 
firm mass which is known as a clot. Clotting of the 
blood will be further described in paragraph 483. 
455. What the Solid Substances in the 
Blood Represent.-The solids of the blood, 
with the exception of the corpuscles and, perhaps, 
the fibrinogen, represent: (1) the nutritive sub- 
stances that are being carried from the alimentary 
canal to the tissues, and (2) the waste matter that 
is being carried away from the tissues. 
456. Red Corpuscles or Erythrocytes.1- 
Chemical Composition. The red blood-corpuscles 
consist of: 
Water 
Hemoglobin 
Protein substance 
Fats 
Cholesterin 
Lecithin 
Inorganic salts 
Oxygen, which is in loose combination with the 
hemoglobin. 
1 From the Greek erythros-red, and kytos-a hollow vessel. The Vascular System 
219 
457- Structure.-The red corpuscles1 are flat, 
circular, biconcave disks. They consist of a color- 
less, transparent, extensible, spongy framework 
infiltrated in all parts by a red coloring matter 
termed hemoglobin, which contains a small amount 
of iron. Those in the blood have no nuclei. 
458. Purpose.-By virtue of their hemoglobin, 
which combines readily with oxygen, the red 
corpuscles are able, while the blood is passing 
through the lungs, to get oxygen from the air and 
carry it to the tissues. The physical forces which 
control the taking in and giving up of oxygen by 
the blood will be discussed in connection with 
respiration. Hemoglobin, when holding oxygen 
in combination, is called oxyhemoglobin and is of 
a red color. After it parts with its oxygen, the 
hemoglobin and, consequently, the blood are of a 
bluish hue. x 
459. Size of Erythrocytes.-The red cor- 
puscles vary in size from yoVo to of an inch 
in diameter and T20 of of an inch in thickness. 
460. Number.-The average number of ery- 
throcytes in a cubic millimeter of blood is about 
5,000,000 in men and 4,500,000 m women, but the 
number varies, even in health, and it sometimes 
becomes very greatly reduced either as the result 
of (1) loss of blood, as by hemorrhage; (2) ab- 
normally rapid destruction of the cells as the re- 
sult of disease of the spleen, the absorption of 
1 The red corpuscles were formerly thought to consist of a cell 
membrane enclosing a fluid substance. Anatomy and Physiology 
220 
bacterial toxins, certain drugs, or other substances 
that cause hemolysis; (3) a deficient production 
of new cells-this is often due to disease of the bone 
marrow. The-condition produced by a deficiency 
of erythrocytes is known as anemia. Anemia will 
be present also if the cells have not their normal 
quantity of hemoglobin, even if there is no defi- 
ciency in number. This often happens when, due 
to loss of cells, new ones are produced at a rapid 
rate and when the bone marrow is diseased. 
461. Life History of the Erythrocytes.- 
The red corpuscles are constantly undergoing 
disintegration in different parts of the circulatory 
system, particularly in the spleen. The pigment 
which gives color to the bile is derived from worn- 
out cells which the liver takes from the blood and 
discards after splitting off the iron to save for 
further use. New cells are formed, in intrauterine 
life, in the liver and spleen and, later, in the red 
marrow of the bones. After birth, the latter is 
usually the only seat of their production. They 
are formed, by cell division, from large nucleated 
red cells called erythroblasts, but, before entering 
the circulation, cells lose their nuclei. Iron is 
necessary for the production, as well as for the 
functioning, of hemoglobin. 
White Corpuscles 
462. Various Names. The so-called white 
corpuscles are really colorless rather than white, The Vascular System 
221 
and are now often termed colorless. They are 
known also as leucocytes,1 and small, newly formed 
ones are called lymphocytes.2 
463. Structure.-The leucocytes of human 
blood consist of almost spherical masses of proto- 
plasm containing one or more nuclei. They have no 
cell wall. There are at least five different varieties. 
464. Size.-The colorless corpuscles vary in 
size, but are all larger than the red. 
465. Number.--In the blood of a healthy adult 
the average number of leucocytes in each cubic 
millimeter of blood is between 7000 and 9000, 
which means about 4 to every 666 of the red. 
This number, however, varies considerably in the 
course of the same day, even in health; for in- 
stance, shortly after a full meal the number may 
be increased one-third and then fall again to 
normal in the course of two or three hours. In 
many abnormal conditions the number of leuco- 
cytes becomes very greatly increased, and in some 
diseases a knowledge of change in their number is 
of great assistance in judging the progress of the 
disease and in diagnosis. An increase in number 
is spoken of as leucocytosis. 
466. Where Formed.-Like the red corpuscles, 
leucocytes are constantly coming into being and 
as constantly being destroyed. They are thought 
to be formed in the lymphatic glands, the spleen, 
1 From the Greek leukos-white, and kytos-a hollow vessel. 
2 From the Latin lympha-clear, and Greek kytos-a hollow 
vessel. 222 
Anatomy and Physiology 
and the bone marrow. They are formed, like other 
cells, by the dividing of existing cells. It is not 
known where they are destroyed. 
467. Principal Differences between Ery- 
throcytes and Leucocytes.-(1) The leucocytes 
have no pigment nor hemoglobin and, therefore, 
are colorless and cannot carry oxygen to the 
tissues as do the red corpuscles. (2) Under nor- 
mal conditions the leucocytes are present in the 
blood in far smaller num- 
bers than the erythrocytes, 
but they are larger than 
the latter. (3) The ery- 
throcytes are peculiar to 
the blood, and under nor- 
mal conditions are seldom 
found in other parts of 
the body. They have no power of spontaneous 
movement, but are carried along in the blood 
stream. The white cells, on the other hand, by 
virtue of their amoeboid motion1 can pass through 
the walls of the capillaries, and are found in the 
lymph, chyle, the spaces of the connective tissues, 
and in pus, when this substance forms as the result 
of suppurative processes. (4) The functions of 
Fig. 83.-A moeboid 
movements. 
1 Amoeboid Motion. The white cells move as does the micro- 
scopically small animal known as the amoeba, hence the name of 
their movement If a drop of blood be examined under the 
microscope the white cells will be seen to be constantly changing 
their shape, as in Figure 83. In this way they can become elon- 
gated and pass through the walls of the blood-vessels or send 
out processes and surround bacteria, etc. The Vascular System 
223 
the leucocytes are quite different from those of 
the erythrocytes. 
468. Functions of the Leucocytes.1-(1) 
Leucocytes protect the body from pathogenic 
bacteria and other foreign organisms by (o') in- 
gesting them, (b} by the formation of substances 
that destroy the bacteria. (2) Leucocytes aid in 
the absorption of fats and proteids from the 
intestines. (3) They assist in the coagulation of 
blood. 
469. Phagocytes.2 Inflammation.3 Pus.- 
When bacteria or other foreign cells or organisms 
enter the tissues irritation ensues, the first effect 
of which will be an increased flow of blood to the 
part. If the irritation continues, or if it was origin- 
ally severe, the flow of blood in the part soon 
begins to slacken, and a condition known as 
inflammatory stasis is produced. The leucocytes 
then adhere in large numbers to the walls of the 
capillaries and small veins, and by amoeboid 
movements migrate into the tissues; also, plasma 
and a small number of red blood-cells pass out of 
the blood-vessels. The resulting collection of fluid 
in the tissues is spoken of as inflammatory exuda- 
1 The substance of all the leucocytes is not exactly the same, 
and it is thought that each special kind may have its particular 
part to take in the work relegated to these cells. 
2 From the Greek, phagein-to eat, and kytos-a hollow vessel. 
s The symptoms of inflammation are redness, heat, swelling, 
pain, and loss of motion. The two first symptoms are due to the 
increased supply of blood in the part; the three last, principally, 
to the engorged vessels and the presence of the exudation. 224 
Anatomy and Physiology 
lion, and the general condition as inflammation. 
In the tissues certain of the leucocytes known as 
phagocytes change the shape of their substance, 
as in Figure 83 and endeavor to engulf or eat zip 
the invaders. If the phagocytes succeed, the 
exudation and all the debris of the struggle-dead 
tissue cells, bacteria, and blood-cells-will be 
absorbed and carried away by the blood and 
lymph. If the phagocytes do not overcome the 
bacteria, destruction of the former and of body 
tissue, with production of pus, will ensue. Thus 
pus consists of blood plasma, a few red cells, 
many colorless cells, disintegrated tissue, dead and 
living bacteria, and poisonous substances or toxins 
produced by the bacteria. 
470. Opsonins. 1-The victory or defeat of the 
phagocytes is largely dependent upon substances 
contained in the blood, called opsonins. These 
substances, the nature of which is as yet little 
understood, enter into more or less close union 
with the bacteria, and acting upon them, in some 
unknown manner, prepare them for digestion by 
the phagocytes. 
471. Blood-Plates.-Very little is known 
about the third variety of blood-corpuscle, the 
blood-plates; in fact, it has not even been decided 
whether they are independent cells or fragments 
of disintegrated cells. This lack of knowledge is 
due to two causes: (1) the cells are exceedingly 
minute, being even smaller than the red corpuscles; 
1 From the Latin opsono-I cater for, or prepare food for. The Vascular System 
225 
(2) they disintegrate so rapidly after removal from 
the circulating blood that it has been impossible 
to study them under the microscope. 
472. Function.-The blood-plates are thought 
to take an active part in the initiation of coagula- 
tion. It is supposed that in the process of disin- 
tegration they give rise to a substance known as 
thrombokinase which, with the aid of the calcium 
salts in the blood, changes a substance called pro- 
thrombin, that is attached to the fibrinogen-see 
paragraph 476-into thrombin-see paragraph 484. 
473. Proteins of the Blood Plasma.-The 
principal proteins of the plasma are: serum al- 
bumin, 1 serum globulin (also known as para- 
globulin), and fibrinogen. 
474. Serum-Albumin.-This protein belongs 
to the same class of albumins as that found in the 
white of egg. It is thought to be derived from the 
digested proteins of food, and to be the main 
source of protein building material for the tissues.2 
475. Serum-Globulin.-There are many 
theories advanced as to the nature of serum- 
globulin. One of the most common is that it is 
derived from broken-down body tissue, disinte- 
grated leucocytes, and other formed elements of 
the blood. 
476. Fibrinogen.-This is a protein of the 
globulin type. Its origin is uncertain, but the 
1 The nature of albumins and globulins is explained in the 
Glossary. 
2 This will be referred to again in the chapter on metabolism. 
15 226 
Anatomy and Physiology 
results of numerous experiments seem to indicate 
that at least part of it may be formed in the liver. 
When blood is shed under favorable conditions,1 
fibrinogen is changed to an insoluble and there- 
fore solid protein known as fibrin, a substance 
which is essential to the clotting of blood. 
477. Extractives Contained in the Blood 
Plasma.-The so-called extractives of blood are sub- 
stances other than the proteins already described 
which may be extracted from dried blood by water, 
alcohol, or ether. The most important ones are: 
1. Fats, which, except after a meal, are present 
only in very small quantities. 
2. Glucose, present in the blood under normal 
conditions in the amount of 0.1 to 0.15 per cent. 
The quantity is often increased temporarily after 
eating a large amount of sugar and, unless relieved 
by dietetic treatment, permanently in the disease 
known as diabetes. 
3. Nitrogenous Extractives-these are chiefly 
protein waste matter. The most important are 
urea, creatin, uric, and other acids,. 
478. The Mineral Matter of the Blood 
Plasma.-The mineral substances of the blood 
consist chiefly of: 
Chlorides 
Carbonates 
Sulphates 
Phosphates 
Sodium 
Potassium 
Calcium 
Magnesium 
Iron 
of 
1 Described in paragraph 486. The Vascular System 
227 
These are derived: (i) from food, (2) as the 
result of certain chemical reactions that are 
continually going on in the body.1 
479. Gases-The gases contained in the blood 
are: carbonic acid, oxygen, and nitrogen. Arterial 
blood contains relatively more oxygen and less 
carbonic acid2 than venous blood; but even in 
the arteries there is more carbonic acid than 
oxygen, as can be seen by the following figures: 
Oxygen. 
Carbonic Acid. 
Nitrogen. 
Arterial blood 
20 vol. per cent. 
8-12 " " " 
39 vol. per cent. 
46 
1 to 2 vols. 
Venous blood 
" " " " 3 
480. Internal Secretions, Enzymes, Im- 
mune Bodies, etc.-There are in the body a 
number of substances that were quite unknown 
until recent years, and of which even yet know- 
ledge is limited beyond the fact that some of them 
play an important part in the processes of diges- 
tion and metabolism, and others in guarding the 
body against pathogenic bacteria. These sub- 
stances are: (1) Internal secretions-these will be 
described in the chapter devoted to the ductless 
glands-and (2) enzymes-for description see the 
chapters on digestion and metabolism. 
481. Antibodies.-In addition to the phago- 
cytes and opsonins, which have been already 
1 Described in paragraph 796. 
2 Carbon dioxide-H2O. 
3 Handbook of Physiology, page 162, Kirk. Wm. Wood & Co. 228 
Anatomy and Physiology 
described, the blood contains various other defen- 
sive substances known collectively as antibodies. 
The majority of these antibodies, unlike the 
phagocytes, are specific in their action; i. e., each 
variety will protect the body against only one 
special form of bacteria or toxin; e. g., the anti- 
body for typhoid will not give protection against 
diphtheria. It is not yet known positively whether 
these antibodies are a natural constituent of the 
blood or if they are developed only during an 
attack of the disease; but they certainly are 
greatly increased by this cause, which accounts 
for the immunity against certain diseases of bac- 
terial origin afforded by one attack. Just how 
these antibodies come into existence is not posi- 
tively known. The most generally accepted theory 
of the present day is that advanced by Prof. 
Ehrlich1 called the receptor theory. It assumes 
that in all the cells of the animal body there are 
certain chemical substances that he calls cell- 
receptors which have the power of taking from the 
blood or lymph the material which they require 
for their nourishment, and that these receptors 
will combine with the bacterial substances just as 
they do with the food molecules; but the former, 
unlike the food material, destroy the receptors.2 
1 Director of the Royal Prussian Institute for Experimental 
Therapy at Frankfort-on-the-Main. 
2 It is thought that when a certain limit of anchoring of recep- 
tors by toxins has taken place the cell perishes, and if a sufficient 
number of cells with vital functions to perform are destroyed, 
death of the individual follows. The Vascular System 
229 
Unless injury to the cell is carried too far, however, 
not only will regeneration of the substance known 
as receptors take place, but a supply in excess1 of 
the cells' needs will be formed, and the surplus 
will be discharged into the blood-stream. These 
free receptors constitute the antibodies known as 
antitoxins,2 antibacterial3 substances, etc. The 
anti-bodies thus formed vary both in their composi- 
tion and in their action on toxins, etc., but the 
primary means by which they protect the body 
is by uniting with the toxic substances, thus pre- 
venting their union with tissue cells. The power 
of the body thus to defend itself from disease is 
spoken of as immunity.4 
1 Over-production of cells is very common in the process of 
tissue repair; e. g., the over-abundant growth of cells in granulat- 
ing wounds. 
2 Antitoxin substances act upon the poison secreted by bacteria 
and neutralize its toxic property. 
3 Antibacterial substances affect the bacteria themselves and 
destroy them or paralyse their action. 
4 Immunity against certain diseases may be acquired also by 
receiving injections of blood-serum containing antibodies taken 
from an animal that has had the disease against which the 
individual wishes to be protected, or by being inoculated by 
preparations containing either dead bacteria or bacteria that 
have by some means been rendered less virulent, as for instance 
the vaccine of small-pox, in which the organism to which small- 
pox is due is weakened by passage through another species of 
animal. Immunity gained by the first method is termed passive 
immunity, because the recipient's body has taken no active part 
in the preparation of the antibody, it having been formed in the 
body of another animal. Immunity obtained by the second 
method is called active immunity, since the individual's body 
itself forms the antibody as the result of the invasion of the 230 
Anatomy and Physiology 
Clotting or Coagulation of Blood 
482. Nature of Phenomena.-One of the 
most characteristic properties which the blood 
possesses is that of clotting or coagulation. The 
phenomena may be observed under the most 
favorable conditions in blood which has been 
drawn into an open vessel. They are as follows: 
In about two or three minutes at the ordinary 
temperature of the air the fluid is seen to become 
semi-solid or jelly-like on the surface and at the 
sides of the vessel in which it is contained, and 
the change gradually extends throughout the 
entire mass. This solid mass so formed is called 
the clot. If the clot be wratched for a few minutes 
a light, straw-colored fluid may be seen appearing 
on the surface; this fluid is known as the serum. 
It gradually increases in quantity and soon begins 
to exude from the sides and under surface of the 
clot, while the clot as gradually shrinks and 
grows harder. This exuding of the serum from the 
clot continues for from thirty-six to forty-eight 
hours. 
483. Physiology of Clotting.-The blood 
circulating in the blood-vessels consists, it will be 
remembered, of: (1) plasma, which is water hold- 
bacteria; though owing to the attenuated condition of the 
bacteria the recipient's health is little affected. Further informa- 
tion regarding the nature, action, and preparation of antitoxins 
can be obtained from almost any recently published bacteriology 
or materia medica. General Bacteriology. Jordan. W. B. 
Saunders Co. is particularly recommended. The Vascular System 
231 
ing in solution a number of soluble substances, 
and (2) corpuscles held in suspension in the plasma. 
One of the soluble substances of the plasma is 
fibrinogen and this, when blood is shed, is changed 
to an insoluble substance called fibrin, which, 
being insoluble, is precipitated. The precipitate 
consists of a meshwork of fine threads which 
gathers into its substance the corpuscles and a 
large portion of the solid substances of the plasma. 
Thus, the serum represents the plasma, minus 
the majority of its solids and corpuscles. It will, 
however, contain a considerable number of white 
corpuscles, because these, by virtue of their amoe- 
boid motion, pass out of the clot during its contrac- 
tion. The contraction of the clot is due to the 
shrinking of the threads of the fibrin mesh work. 
484. Origin of Fibrin.-It is now the gen- 
erally accepted belief that fibrin, the essential 
agent in the clotting of blood, is derived 
from the soluble fibrinogen by the action of a 
ferment known as thrombin, that, as stated in 
paragraph 472, is formed from prothrombin by 
the action of thrombokinase, a substance set 
free from leucocytes and blood-platelets on their 
disintegration. 
485. Advantage of the Clotting Property 
of Blood.-The clotting property of blood is of 
great value, for upon it depends very largely 
the arrest of hemorrhage, and nearly all the pro- 
cedures used to prevent the escape of blood from 
severed vessels are directed toward hastening the 232 
Anatomy and Physiology 
formation of a clot. There are abnormal condi- 
tions of the blood which prevent its clotting 
readily, and an individual whose blood is so 
constituted may bleed to death from a very 
slight wround. A lack of calcium salts in the 
blood is thought to be one of the most common 
causes of this condition. 
486. Conditions which Promote and Re- 
tard Clotting.-Clotting of the blood is assisted 
by: 
(i) Injury to the walls of the blood-vessels; 
(2) Contact with foreign substances; thus, clotting 
will be accelerated if gauze or like substance 
is put into a wound, and a clot may form in 
a blood-vessel if air is introduced; 
(3) Contact with a rough surface; 
(4) Heat-about 1160 to 1200 F. 
(5) Rest. 
487. The reason these conditions accelerate 
clotting is thought to be that, with the exception 
of rest, they hasten the disintegration of leuco- 
cytes and blood-platelets, and, consequently, the 
formation of thrombin. 
488. Clotting May be Prevented or Re- 
tarded by; 
(1) Contact with the living tissue-as the 
interior of the blood-vessels; 
(2) The absence of calcium salts; 
(3) Cold retards coagulation; nevertheless, cold 
is often used to arrest hemorrhage because it 
contracts the blood-vessels; The Vascular System 
233 
(4) The addition to the blood of neutral salts, 
of strong acid or alkalies, oil or other viscid sub- 
stances, certain organic ferments as trypsin and 
pepsin, snake venom, leech extracts, a large 
quantity of water; 
(5) Removal of the fibrin. If normal, fresh 
blood is stirred for a few minutes after its 
removal from the body, the fibrin will collect on 
the stirring utensil in a shredded mass. The re- 
maining liquid, which looks like unaltered fresh 
blood, will not clot. It is called the defibrinated 
blood. 
489. Why Blood Does not Clot within 
the Living Blood-Vessels.-Blood seldom clots 
within the living blood-vessels. Why it does not 
is still a matter of conjecture. Some of the theories 
advanced are: 
1. That in the living blood-vessels the leuco- 
cytes and blood-plates do not disintegrate in 
sufficient numbers at a time to allow of thrombin 
being formed, so that circulating blood does not 
contain thrombin. 
2. That the circulating blood does contain at 
least a small amount of thrombin, but that the 
body has safeguards which diminish its activity. 
Some investigators think that the thrombin is 
destroyed in the liver; others, that the lining of 
the walls of the heart and blood-vessels secrete an 
anti-thrombin substance. 
490. Why Intravascular Clotting Does 
Sometimes Occur.-Occasionally the blood does 234 
Anatomy and Physiology 
clot within the vessels. Some of the causes for 
this are: 
i. Entrance of air into a blood-vessel. The 
air, if not absorbed, will act as a foreign substance 
and cause disintegration of the blood-plates and 
leucocytes, and consequent formation of thrombin 
and clotting. 
2. Injury to the internal wall of a blood-vessel, 
as, for instance, by a ligature, or as the result of 
disease, as in phlebitis. 
491. Thrombus 1 and Embolus 2.-A clot form- 
ed in a blood-vessel is called a thrombus. It is a 
source of great danger to the individual in whose 
veins it forms, because, though it may be broken 
up and disappear, it is likely to be carried to some 
point in a main vessel where its presence may 
cause instant death. A thrombus that is moved 
from the place of its formation is termed an 
embolus. 
492. Regeneration of Blood after Hemor- 
rhage.-A large portion of the entire blood of the 
body may be lost suddenly by hemorrhage with- 
out producing a fatal result. Recovery has been 
known to occur after the loss of a quantity of 
blood amounting to as much as three per cent, of 
the body weight, especially when the lost blood 
has been at once replaced by some solution such 
1 From the Greek thrombus-a lump, a piece. 
2 From the Greek embolus--a wedge. The word is often used 
to designate one thing that is inserted in another and moves 
therein; hence its connection in the present sense. The Vascular System 
235 
as physiological salt solution,1 i. e., sodium chloride 
0.7 to 0.9 per cent. When given to replace lost 
blood the solution is usually injected into a vein, 
and the operation is called intravenous infusion. 
The benefits derived from such an injection are: (1) 
prevention of injury to the tissue cells by loss of 
water; (2) the circulating blood is brought to a 
sufficient quantity to maintain normal conditions 
of pressure and velocity of the heart-beat; (3) it 
acts as a stimulus to the heart action, by forcing 
it to take stronger contractions in order to propel 
the extra fluid so provided into the blood-vessels; 
(4) the red corpuscles that remain in the vessels 
are kept in circulation, and complete loss of 
oxygen to the tissues is thus prevented. The 
corpuscles lost in the hemorrhage are gradually 
replaced. The manner in which this is done was 
described in paragraph 461 of this chapter. 
493. Blood Transfusion.-Occasionally in- 
stead of injecting physiological salt solution into 
1 A solution used for this purpose must contain one or more of 
the important salts of the blood, and it must be isotonic with 
the blood-serum; i. e., it must have the same degree of concentra- 
tion and thereby exert the same degree of osmotic pressure 
(see Glossary). A less concentrated solution would, by reason of 
its low osmotic pressure, enter the red blood-corpuscles and 
cause hemolysis; i. e., breaking down of the cells. Blood thus 
acted upon is said to be laked, and a solution that will cause 
such a condition is said to be hypotonic to blood-serum. On the 
other hand a more concentrated solution, e. g., one containing a 
larger per cent, of salt than 0.7 or 0.9 per cent, would, by reason 
of its high osmotic pressure, extract water from the corpuscles 
and cause them to shrivel. Solutions which exert a higher 
osmotic pressure than blood-serum are termed hypertonic. 236 
Anatomy and Physiology 
a patient's vein, blood from the vein of another 
individual is allowed to flow into one of the 
patient's veins. This operation is called blood 
transfusion. For several reasons this operation is 
not often done; one reason is that it is attended 
with considerable danger; e. g., the injected blood 
is likely to form sufficient thrombin to cause 
clotting; also, the blood of one individual is often 
hemolytic to that of another. At one time it was 
thought that the blood of the lower animals could 
be transfused into the veins of human beings; 
but experiments soon proved that the blood of one 
species of animal is nearly always hemolytic to 
that of another species. 
Lymph 
494- Nature.-Lymph is a colorless or slightly 
yellow-colored fluid that, with a few exceptions, 
resembles blood in its composition, the essential 
differences being: 
(l) An absence of erythocytes and blood- 
plates ; 
(2) A lower specific gravity, or, in other words, 
a lower content of solid matter. This lower specific 
gravity1 is of great importance in regulating the 
passage of lymph to and from the blood and 
lymph-vessels and the tissues. 
(3) Especially in the lymph contained in the 
1 The specific gravity of blood varies from 1041 to 1067; that 
of lymph from 1012 to 1022. The Vascular System 
237 
lacteals1 there is a higher per cent, of fat than in 
the blood; 
(4) Lymph coagulates more slowly and less 
firmly than blood. 
495- Where Found.-Lymph is found in the 
lymphatic vessels, and in practically all spaces in 
the subcutaneous tissues. 
496. Derivation.-Lymph is derived directly 
from the blood. It is, in fact, blood plasma plus 
some white corpuscles and minus some solid sub- 
stances, which have passed through the walls of 
the capillaries into the tissues. The forces which 
cause it to do so and later to return to the blood 
will be described in Chapter XIV. 
497. Functions.-(1) Lymph diffuses widely 
through all the tissues of the body, and the latter 
take from it the nutrient they need. (2) It collects 
and carries to the heart, via the lymphatic vessels 
and veins, the waste material formed in the tissues 
as the result of the perpetual chemical activities 
occurring there. Some of this waste matter can 
be used again, and is carried by the blood to parts 
of the body for this purpose. Some of it is of no 
further use to the body, and is carried to the 
kidneys, skin, or lungs, to be excreted. 
1 Latin lacteus, from Zac-milk. The lymphatic vessels con- 
tained in the walls of the intestines which absorb the fat. So 
called because their contents, especially after a meal, are milky 
looking. CHAPTER XII 
the vascular system-Continued 
Structure, Location, and Function of the Organs of the Blood- 
and Lymph-Vascular Systems. 
498. Organs Constituting the Blood-Vas- 
cular System.-As stated in the preceding chap- 
ter, the blood-vascular system consists of the 
heart, arteries, capillaries, and veins. 
499. Function.-The heart pumps the blood 
into the arteries; the arteries carry the blood to the 
capillaries; the veins carry it from the capillaries 
back to the heart. The capillaries are, in a way, 
the main factor in the whole vascular system as it 
is, due to conditions to be discussed later, while 
passing through these vessels that the blood per- 
forms its ultimate function, namely, the giving 
off to the tissues of the substances they require 
for their nourishment, etc., and the collection of 
waste matter. Also, it is while flowing through 
the capillaries of the excretory organs that the 
waste substances are eliminated. 
Anatomy of the Heart 
5oo. Shape and Position.-The heart is a hol- 
low muscular organ of conical shape. It is situated 
238 The Vascular System-Continued 
239 
in the thoracic cavity, between the right and 
left lungs, and behind the lower two-thirds of the 
sternum, with 
its lower edge 
resting upon 
the diaphragm. 
It lies obliquely 
and extends 
farther to the 
left than to the 
right of the me- 
dian line. Its 
broad part, or 
base, points 
upward, back- 
ward, and to 
the right; its 
pointed por- 
tion, or apex, is 
directed down- 
ward, forward, 
and to the left. 
The low'er end 
of the apex 
comes in contact with the chest wall, and its beat 
can be felt in the fifth intercostal space,1 about 
one and a half inches to the left of the mid-sternal 
line. 
501. Attachments.-The heart is, as it were, 
Fig. 84.- Front view of the heart. 
1 Between the fifth and sixth ribs. A little below and to the 
inner side of the nipple of the left breast. 240 
Anatomy and Physiology 
suspended in the chest by the large blood-vessels 
which proceed from it. It has no other attach- 
ments and, excepting for this connection, it lies 
free within the membranous sac known as the 
pericardium. 
502. Size.-The heart is generally estimated 
as being about the size of the owner's closed 
fist. 
503. Substance of the Heart: Myocard- 
ium.-Myocardium is the name given to the main 
substance of the heart. It is composed very 
largely of striated, but involuntary, muscular tis- 
sue (described in paragraph 215), of blood-vessels, 
lymphatics, and nerves. It has a small amount of 
fatty tissue, especially at its base, and of fibrous 
tissue which is disposed in rings around the orifices 
that exist between the auricles and the ventricles, 
and at the origin of the aorta and the pulmonary 
artery. It is covered by the pericardium and 
lined with a serous membrane known as the 
endocardium. 
504. The Pericardium1: Structure and 
Position.-The conical-shaped membranous sac 
enclosing the heart and known as the pericardium 
consists of two distinct parts: (1) an outer external 
membrane which is attached by its lower border 
to the diaphragm, by its upper posterior surface 
to the large blood-vessels emerging from the heart, 
and by its front surface, by means of two fibrous 
bands, to the sternum; (2) an inner serous mem- 
1 From the Greek perikardion-about the heart. Fig. 85.-Arrangement of pericardial sac. The Vascular System-Continued 
242 
brane which lines the fibrous layer, but at the 
parts where the latter is attached to the large 
blood-vessels, passes forward and down over the 
heart, thus forming as it were a closed sac around 
that organ, as shown in Fig. 85; the red lines 
indicating the walls of the heart and blood-vessels; 
the black, the outer layer of the pericardium; the 
blue, the inner serous layer. The portion of the 
serous membrane lining the fibrous coat of the peri- 
cardium is called the parietal layer; and that 
covering the heart, the visceral or epicardium 
layer. 
505. Functions of the Pericardium.-The 
sac-like character of the pericardium makes an 
interstice between the heart and the lungs and dia- 
phragm, and prevents the movements of these 
organs interfering with the heart movements. The 
serous layer secretes a viscid fluid which lubricates 
the two surfaces and thus enables them to glide 
smoothly over each other during the movements 
of the heart. 
506. Endocardium.-The endocardium is a 
smooth, simple form of serous membrane which 
lines the heart and enters into the formation of its 
valves. It is directly continuous with the lining 
of the blood-vessels. 
507. Chambers or Cavities of the Heart.- 
The interior of the heart is divided longitudinally, 
by a muscular partition, into two chambers or 
cavities-a right and a left, and each of these 
cavities is subdivided into an upper and a lower 242 
Anatomy and Physiology 
chamber. The two upper cavities are known as 
the auricles and the two lower ones as the ventricles. 
508. Orifices of the Heart.-Normally after 
birth there are ten orifices in the heart, not includ- 
ing the small openings in the right auricle to 
receive the blood returning from the myocardium. 
There is one between each auricle and ventricle; 
one in the left ventricle which connects writh the 
aorta1; one in the right ventricle which opens into 
the pulmonary2 artery; four in the left auricle- 
one for each of the four pulmonary veins; two in 
the right auricle-one for the superior and the 
other for the inferior vena cava3; also as previously 
stated there are in the right auricle a varying 
number of small openings connected with the 
veins returning the blood from the myocardium 
or heart substance. In the fetus there is an orifice 
between the two auricles, but unless this closes at 
birth the infant usually dies in a short time. 
There is, normally, no opening between the two 
sides of the heart after birth. 
509. Purpose of the Blood-Vessels Open- 
ing into the Heart.-The aorta receives the 
blood that is to go to all the tissues of the body 
for their nutrition, etc.; the pulmonary artery, 
that which must go to the lungs to exchange its 
excess carbon dioxide for oxygen. The pulmonary 
1 From the Greek aorte-to carry. 
3 From the Latin pulmono-lung (relating to the lungs). 
s Latin, hollow veins. 
This will be further discussed in connection with the circulation. Fig. 86.-Left auricle and ventricle, the back wall of each has been 
removed. The Vascular System-Continued 
243 
veins bring back the blood from the lungs-two 
from the right and two from the left lung. The su- 
perior vena cava returns the blood from the upper 
part of the body, and the inferior vena cava, that 
from the lower portion. Thus it will be seen 
that the left side of the heart contains the blood 
that has been aerated and is ready to go through 
the system; and the right side, the blood that must 
go to the lungs to exchange some of its carbon 
dioxide for oxygen. 
510. Names and Location of the Valves of 
the Heart.-Each of the auriculo-ventricular ori- 
fices is guarded by a valve, as are also the openings 
into the aorta and the pulmonary artery. The 
valve between the left auricle and ventricle is 
called the bicuspid1 or mitral2 valve; that between 
the right auricle and ventricle is known as the 
tricuspid3; the one protecting the opening to the 
aorta and the one guarding the pulmonary artery 
bear the same name and are known as the semi- 
lunar4 valves. The opening into the inferior vena 
cava is partly covered by a membrane known as 
the Eustachian5 valve, but the other veins at their 
connection with the heart have no valves. 
511. Structure of the Valves.-The valves 
1 Latin prefix bi-two and cuspis-a point, so called because 
it has two points. 
2 So called because it was thought to be the shape of a bishop's 
miter. 
J Latin prefix tri-three and cuspis-a point. 
4 From the Latin semis-half and luna-the moon. 
s Called after Eustachius, a famous anatomist. Anatomy and Physiology 
244 
of the heart are composed mainly of fibrous and 
elastic tissue enveloped by the endocardium. The 
tricuspid, as its name signifies, has three cusps or 
flaps, and the bicuspid has two. The flaps of each 
of these valves are attached at their base to a 
fibrous ring which encircles the auriculo-ventri- 
cular orifices so that they form an annular mem- 
brane around the orifice. The free end of each 
flap falls downward into the ventricle when the 
valve is not in action, i. e., while the blood is flowing, 
through into the ventricle. The ventricular sur- 
face1 of each flap is attached by slender tendinous 
fibers called the chordae tendinece to small muscular 
projections called the muscidi papillares2 which 
cover a portion of the inner surface of the ven- 
tricles. These musculi papillares are elastic and 
pliable, and prevent the contractions of the heart 
interfering with the action of the valves, as they 
would if the chordoe were attached directly to the 
walls of the ventricles. The semilunar valves 
each consist of three flaps of semilunar-i. e., half- 
moon-shape. The convex border of each flap is 
attached to a fibrous ring which encircles the open- 
ings between the heart and arteries, and the free 
border, which is slightly concave, projects into 
the artery. On the edge of this border is a fine 
fibrous cord, and in the center of the cord a small 
nodule known as the corpus Aranti.3 
1 The surface of the flap facing the ventricle. 
2 From the Latin papilla-a nipple. 
3 Body of Arantius. Fig. 87.-Valves of the heart and great arteries viewed from above, the 
auricles have been removed. The Vascular System-Continued 
245 
5i2. Purpose and Mechanism of the 
Valves.-The valves serve to prevent the re- 
gurgitation of blood after it has passed from the 
auricles into the ventricles, and from the ventri- 
cles into the arteries. While the blood is flowing 
through a valve the free edges of its flaps are 
pointed in the direction of the blood current. 
When the cavity or vessel into which the blood is 
flowing is filled, the blood gets behind the flaps 
and they float up and close the orifice. The 
chordoe tendineas prevent the flaps of the bicuspid 
and tricuspid valves floating up too far into the 
auricles which, as they are comparatively large, 
they would be likely to do were it not for this 
restraint. The corpus Aranti on the edges of the 
flaps of the semilunar valves secure firm closure 
of those valves. 
513. Blood Supply of the Heart.-The 
blood contained within the chambers of the heart 
does not nourish the heart substance further than 
the endocardium. It is, therefore, supplied with 
blood-vessels derived from the right and left 
coronary arteries. These arteries were so named 
because they encircle the heart like the band of a 
crown. 
514. Nerve Supply.-The heart receives its 
nerve supply from the cardiac plexuses which are 
distributed freely both on its surface and in its 
substance. The plexuses are formed partly from 
nerves derived from the sympathetic system, and 
partly from branches of the two cranial nerves Anatomy and Physiology 
246 
known as the vagi. Stimulation of the sym- 
pathetic fibers accelerates and increases the force 
of the heart-beat. They are therefore called 
cardiac accelerators or augmentors. Stimulation of 
the vagi, on the contrary, inhibits the rate of the 
heart-beat, therefore these are known as cardiac 
inhibitors. The heart is supplied also with sensory 
fibers, the function of which is not clearly under- 
stood, but it is thought that the pain which occurs 
in certain pathological conditions is due to their 
stimulation. 
The Arteries 
515- Derivation of Name.-The arteries were 
so named from two Greek words, aer-air, and 
tereo-to watch over; because, owing to their 
elastic nature, they force their contents into the 
veins at the time of death, but nevertheless retain 
their shape; and the ancient anatomists, finding 
that in the dead bodies they examined the arteries 
were empty of blood, conceived the erroneous 
notion that they were designed for the circulation 
of air through the system. 
516. Structure of the Arteries.-The walls 
of the arteries are composed of three coats termed 
the external, middle, and internal. The external 
coat consists mainly of white and yellow-elastic- 
fibrous tissue, the fibers of which run longitudi- 
nally. This coat serves to give strength to the 
vessels and, being only slightly elastic, prevents The Vascular System-Continued 
247 
their undue dilatation. The middle coat is con- 
structed of muscular and elastic fibrous tissue, 
the fibers of which, being arranged transversely, 
encircle the vessels. This coat, which is much 
thicker in the larger than in the smaller arteries, 
gives the vessels the elastic property that is so 
essential to their proper functioning. In old age, 
and sometimes as the result of disease, the arteries 
lose much of their elasticity and a condition 
known as arteriosclerosis ensues.1 This interferes 
with the proper circulation of blood in the tissues 
and, consequently, the tissue changes character- 
istic of old age are produced. The inner coat, or 
lining of the arteries, which is continuous with the 
endocardium lining the heart, consists of a layer 
of elastic tissue covered with a delicate simple 
form of serous membrane. This coat provides a 
smooth polished surface over which the blood can 
flow without interference or friction, which is 
most essential, friction being one of the causes of 
the clotting of blood. , 
517. Size of the Arteries.-The largest 
arteries of the body are those connected with the 
heart, the aorta and the pulmonary artery. They 
measure in the adult about 30 mm. in diameter 
at their largest part, that is, at their connection 
with the heart. Every branch arising from these 
two arteries and every sub-branch of the main 
branches is smaller than the artery from which it 
springs, and all arteries grow smaller toward their 
1 Hardening of the arteries. 248 
Anatomy and Physiology 
distal end, and gradually losing the characteristic 
artery structure merge into the capillaries. Small 
arteries are called arterioles. 
518. Blood Supply of the Arteries.-The 
walls of the arteries, with the exception of the inter- 
nal coat, are not nourished by the blood flowing 
through the vessels, but are supplied with minute 
arteries, capillaries, and veins. These vessels are 
called vaso vasorum, i. e., the vessels of the vessels. 
519. Nerve Supply.-Arteries are also sup- 
plied with nerves which are derived chiefly from 
the sympathetic, but also from the cerebro-spinal 
system. They form intricate plexuses upon the 
surface of the larger vessels, and from these 
plexuses branches enter to the muscular coat of 
the vessels, and others pass onwrard to supply 
some of the smaller arteries. These nerves are 
called the vaso-motor nerves. They regulate the 
caliber of the blood-vessels and consequently, the 
blood supply to the tissues. 
520. Nature and Purpose of Sheaths.-The 
majority of the large arteries are with an accom- 
panying vein, and sometimes a nerve, enclosed in 
firm connective tissue. The vessels are attached 
to this membrane, which is called a sheath, by 
delicate areolar fibers. A sheath helps to support 
and to hold vessels and nerves in position. 
The Veins 
52i. Structure.-The structure of the veins 
is very similar to that of the arteries, the main The Vascular System-Continued 
249 
differences being: (i) the walls of the veins have 
less elastic tissue and are thinner; (2) the majority 
of the larger veins have valves in their interior, 
and the arteries, except the aorta 
and the pulmonary artery at their 
connection with the heart, have 
not. 
522. Nature and Mechanism 
of the Valves of the Veins.- 
The flaps of the valves of the 
veins are semilunar in shape, and 
they consist of a reduplication of 
the inner coat of the vein strength- 
ened by connective tissue and elas- 
tic fibers. They are generally placed 
in pairs, but in some of the larger 
veins there are as many as three 
or four flaps. They are attached to 
the walls of the veins in much the 
same manner as the semilunar 
valves of the heart are attached 
to that organ, viz., by their con- 
vex border; their free end, while 
the blood is flowing through, being 
flattened against the wall of the 
vein, but pointing toward, instead of away from 
the heart like the flaps of the valves between 
the heart and the arteries. As the space be- 
tween two valves is filled the flaps float up and 
coming together form a wall which prevents the 
regurgitation of the blood and thus keeps it 
Fig. 8 8.- 
Valves of veins 
A shows a vein 
cut open be- 
tween the seg- 
ments of two 
valves. B shows 
appearance of 
valves closed 
and open. 250 
Anatomy and Physiology 
flowing in the right direction, i. e., toward the 
heart. 
523. Veins in which the Valves Are Most 
Numerous or Absent.-Valves are most numer- 
ous in the veins of the extremities, and more so in 
those of the legs than in those of the arms. They 
are absent in the majority of very small veins, in 
the superior and inferior vena cava, in the portal, 
renal, hepatic, and pulmonary veins, and in those 
veins not subjected to muscular pressure as those 
in the interior of the cranium, vertebral column, 
and bones. 
The Capillaries 
524. Size.-The capillaries1 are exceedingly 
minute vessels, varying in size from fooo to rsVo 
of an inch in diameter. Unlike the arteries and 
veins the capillaries do not increase or decrease in 
diameter toward their termination. 
525. Structure.-The walls of the capillaries 
are much more simple in structure than those of 
the arteries and veins. They are very thin and 
consist of but one coat which is continuous with, 
and similar to, the inner one of the arteries and 
veins. 
526. Distribution.-The capillaries arise 
from the innumerable small branches of the arter- 
ies and they, like the arteries, give off branches 
in all directions. They anastomose in such a 
manner that they form delicate networks in all 
1 From the Latin capillus-a. hair. Fig. 89.-The lymph-nodes of the upper part of the thorax and neck. 252 
Anatomy and Physiology 
lymph. Another similarity between lymphatic 
vessels and veins is that they both begin as 
minute capillary-like vessels that gradually in- 
crease in size and unite to form larger vessels. 
The smaller vessels resemble the capillaries of the 
blood-vascular system and are called lymph-capil- 
laries. The two larger vessels resulting from the 
converging of all the smaller ones are called 
respectively the right and left lymphatic ducts; the 
latter is known also as the thoracic dzict. The 
lymph-vessels that have their origin in the walls 
of the small intestine are called the lacteals,1 
because of the milky-looking substance known as 
chyle which they absorb from the small intestine 
during the intestinal digestion of food; but their 
structure is the same as that of the other lymph- 
vessels. 
530. Origin and Distribution of Lymph- 
Vessels.-The lymph-vessels begin as exceed- 
ingly minute capillary-like vessels in the lymph 
spaces. They are distributed in two distinct sets- 
a deep and a superficial. The deep lymphatics2 
accompany the large blood-vessels; the superficial 
are distributed through the subcutaneous areolar 
tissue. There is no communication between the 
two sets, but the vessels of each set anastomose 
freely with each other, and those of the superficial 
1 From the Latin lactezis-milky. 
2 Formerly it was thought that the lymphatics at their origin 
in the lymph-spaces were open vessels; but many physiologists 
now doubt if this be the case. Fig. 90.-The regions whose lymph flows into the 
right lymphatic duct are suggested by the lighter area; 
those which are tributary to the thoracic duct by the 
darker area. 
253 Anatomy and Physiology 
254 
set form frequent intricate plexuses in the sub- 
cutaneous tissues. 
531. The Ducts.-The contents of both sets 
of vessels are poured into one or other of the two 
ducts mentioned in paragraph 529. That from 
the right side of the head, neck, and chest, the 
right lung, the right side of the heart, the right 
upper limb, and the upper surface of the liver 
flows into the right lymphatic duct; that from the 
rest of the body enters the left lymphatic or 
thoracic duct. The right lymphatic duct is about 
an inch or'less in length and opens into the right 
innominate vein at the junction of the right 
internal jugular and right subclavian1 vein (see 
Fig. 89). The thoracic duct is a much larger 
vessel, being in the adult from fifteen to eighteen 
inches long and about the diameter of a goose- 
quill. It begins as a pear-shaped dilatation in front 
of the second lumbar vertebra and ascends up- 
ward at the right side of the aorta to the level of 
the fourth thoracic vertebra, where it passes be- 
hind that vessel, and arching downward and out- 
ward opens into the left innominate vein between 
the left subclavian and the left internal jugular 
veins. The lymph flowing from the ducts into 
the innominate veins becomes mixed with the 
blood in those veins and with it enters the superior 
vena cava and thence the right auricle of the 
heart. 
532. Functions of the Lymphatic Vessels.- 
1 Known also as the brachio-cephalic. The Vascular System-Continued 
255 
The lymphatic vessels serve to absorb the lymph 
and carry it to the heart. The lacteals help in 
the absorption of diges- 
ted food products, espe- 
cially fats, from the 
intestine. 
533. Nature and 
Location of Lymph- 
Nodes or Glands.- 
These are small round 
or oval bodies situated 
in the course of lacteal 
and other lymphatic 
vessels, through which 
the chyle and lymph 
pass on their way to 
the blood. The nodes 
consist of a covering or 
capsule of fibrous tissue 
from which fibers pass 
to the interior of the 
gland and divide it into 
hollow spaces which 
communicate freely 
with each other. These spaces, or alveoli, con- 
tain the special glandular substance which con- 
sists principally of adenoid tissue and leucocytes, 
and is known as gland- or lymph-pulp. The pulp 
does not completely fill the alveoli, and the va- 
cant spaces communicate with each other, form- 
ing a tortuous channel through the gland that is 
Fig. 91.-A lymph-node 
with its afferent and efferent 
vessels. (Gerrish.) 256 
Anatomy and Physiology 
named a lymph-path or a lymph-sinus. The major- 
ity of the nodes have a depression on one side 
called the hihcmp through which the blood-vessels 
enter and leave its interior, and from which 
the efferent lymphatic vessels emerge. Afferent 
lymph-vessels enter a node at different parts of its 
surface and in its interior branch out and form 
plexuses through the substance. These vessels 
lose their coats, except the endothelial2 lining 
which is continuous with the lining of the lymph- 
path into which they empty, and from which the 
efferent vessels arise. The lymph entering the 
gland by the afferent vessels is thus poured into 
the sinus which winds through the gland substance, 
before it enters the efferent vessels. 
534. Function of the Lymph-Nodes.- 
Lymph leaving a node has a larger number of 
leucocytes than that entering; therefore it has 
been decided that the formation of leucocytes is 
one of the functions of these glands; another 
seems to be that they protect the body from 
infection by acting as sieves, catching and detain- 
ing in meshes of tissue that cross the sinus foreign 
substances absorbed with the lymph from the 
lymph-spaces in the tissues. When the foreign 
matter consists of bacteria, an inflammatory pro- 
cess often ensues, but owing to the large number 
1 From the Latin hilum-a depression. 
2 From the Greek endon-within and thele-a nipple. The 
name given to the thin layer of secretory cells lining the blood- and 
lymph-vessels, etc. The Vascular System-Continued 
257 
of leucocytes present, the bacteria are more likely 
to be destroyed here than in the tissue, and they 
do less harm than if they entered the general 
circulation, as they would were they not detained 
in the nodes.1 
535. Number and Location of Nodes.-The 
number of nodes has been estimated at about 700 
of which the greater part are in the abdomen and 
thorax. The face and neck have a considerable 
number, the limbs a few, especially in the groin 
and axilla, the brain case none. They vary con- 
siderably in size; the larger ones are about the 
size of a bean. Some of the nodes frequently 
referred to are the solitary glands and Peyers 
patches of the intestine and the tonsils in the 
pharynx, described in Chapter XVII. 
1 When glands are enlarged or inflamed, they often fail to destroy 
bacteria and, for this reason, abnormal conditions of the masses of 
lymphoid tissue known as the tonsils make them a source of danger, 
rather than a protection, to the body. It is thought that the germs 
producing rheumatism, endocarditis, chorea, and other infectious 
diseases often gain entrance to the body through diseased tonsils. CHAPTER XIII 
vascular system-Continued 
Names of the Divisions of the Blood-Vascular System. Nature 
of the Distribution of the Blood-Vessels. Names and Location 
of the More Important Arteries and Veins. 
536. Divisions of the Circulatory System. 
-The blood-vessels of the body are arranged into 
two distinct main systems and an accessory sys- 
tem. The largest of the main systems is that 
intended for the general or systemic circulation. 
It provides passage for the blood from the left 
ventricle of the heart through, practically, all the 
tissues of the body to the right auricle of the 
heart. Its purpose is to provide the tissues with 
the nutrient material, oxygen, etc., that they 
require and to help gather up the waste matter. 
The second main system, called the lesser or pul- 
monary system, contains the blood flowing from 
the right ventricle of the heart to the lungs and 
thence back to the heart, to the left auricle. This 
blood, having been through the system giving 
up its oxygen and collecting carbon dioxide, 
passes to the lungs that it may exchange its excess 
carbon dioxide for oxygen. The accessory system, 
258 Fig. 92.-Diagram showing plan of distribution of arteries and veins. ? Fig. 93.-The pulmonary artery and aorta. The front part of the 
right lung has been removed, in order to expose the pulmonary vessels 
and the bronchial tubes. The Vascular System-Continued 
259 
known also as the portal system, forms a kind of 
loop on the general system. Its purpose is to pro- 
vide passage for the blood 
from the stomach, intes- 
tines, spleen, and pancreas 
through the liver, so that 
certain of its constituents 
(especially those derived 
from digested food-stuffs) 
may undergo necessary 
chemical changes in that 
organ before being emp- 
tied into the general cir- 
culation. 
537. General Plan of 
Distribution of Blood- 
Vessels.-All the arteries 
of the body originate, di- 
rectly or indirectly, from 
the two main trunks, the 
aorta and the pulmonary 
artery. Those springing 
from the aorta constitute 
the main trunk of the ar- 
terial portion of the sys- 
temic system. From these 
branches arteries pass to 
nearly all the tissues of the body, and the arterioles 
and capillaries arising from them form fretworks 
or plexuses in the tissues as described in paragraph 
527. The capillaries gradually merge into veins 
Fig. 94.-Diagram show- 
ing the formation of large 
veins by convergence of 
small, and the branching of 
veins. (Gerrish.) 260 
Anatomy and Physiology 
which as gradually become larger and run to- 
gether, so that finally all those from the lower 
part of the body have united to form the 
inferior vena cava, and those from the upper 
part of the body, except the ones belonging 
to the pulmonary system, unite to form the 
superior vena cava. The main trunk of the 
pulmonary system is the pulmonary artery. 
This artery bifurcates, i. e., divides into two 
branches, one of which passes to the right and 
the other to the left lung. Arteries arise 
from these main branches which divide and 
subdivide and dwindle in size, and finally 
merge into capillaries. The latter gradually 
assume the characteristics of veins and the 
veins as gradually grow larger and unite to 
form, usually, two large veins in each lung 
which pass to the left auricle of the heart. 
The distribution of the vessels of the por- 
tal system will be described in paragraph 
5$4- 
538. The larger blood-vessels are usually 
deeply seated, or else placed in situations where 
they are protected from pressure and other 
dangers. Usually the main artery convey- 
ing blood to a part, and at least one of the 
veins returning it, follow the same course and 
are often held together in the same investing 
sheath. 
539. Anastomoses of the Blood-Vessels.- 
Many of the branch arteries and a still greater The Vascular System-Continued 
261 
number of the veins anastomose1 or inosculate; 
that is, they unite at their distal ends. This 
anastomoses of the vessels is of great importance, 
Fig. 95.-Diagram showing the branchings, anas- 
tomoses, and confluence of arteries. (Gerrish.) 
as it allows of the ligating of veins and arteries in 
operations and after injuries in which they have 
been severed, without interfering to any extent 
with the circulation in the part-the blood 
being able to flow through the anastomosing 
vessels. 
1 From the Greek anastomoo-to stop the mouth of. 262 
Anatomy and Physiology 
Names and Location of the Larger Systemic 
Arteries 
540. The Aorta.-The aorta arises from the 
upper part of the left ventricle, ascends for a short 
distance, arches backward and to the left side 
over the root of the left lung, descends within the 
thorax on the left side of the vertebral column, 
passes through the aortic opening of the diaphragm 
into the abdomen, and terminates on a level with 
the fourth lumbar vertebra by bifurcating and so 
forming the right and left common iliac arteries. 
For convenience in description the aorta is com- 
monly spoken of as consisting of the ascending 
aorta, the arch of the aorta, the descending thoracic 
aorta, the abdominal aorta. The branches arising 
from the aorta are as follows: 
Portion of 
Aorta 
Branches 
Ascending 
aorta 
Coronary arteries 
Innominate or brachio-cephalic 
Left common carotid 
Left subclavian 
Arch 
Pericardial 
Bronchial 
Esophageal 
Posterior mediastinal 
Intercostal 
Descending 
thoracic Fig. 96.-Superficial arteries of the head. The Vascular System-Continued 
263 
Celiac axis 
Inferior phrenic 
Superior mesenteric 
Inferior mesenteric 
Middle suprarenal 
Renal 
Spermatic in male, ovarian in female 
Lumbar 
Dorsal 
Middle sacral 
Abdominal 
aorta 
541. The Coronary Arteries.-The right 
and the left coronary arteries arise from the aorta 
immediately above the margin of the semilunar 
valves. They anastomose with each other and 
encircle the heart, giving off numerous small 
branches for the supply of the heart's substance. 
542. The Innominate Artery.-The innomi- 
nate, known also as the brachio1-cephalic artery, is 
about one and a half inches in length. It ascends 
obliquely from the arch of the aorta to the upper 
edge of the right clavicle, near the articulation of 
the latter with the sternum. There the innomi- 
nate divides, forming the right common carotid 
and right subclavian. 
543. Carotid Arteries and their Branches. 
-The right common carotid springs from the 
innominate artery, the left from the arch of the 
aorta. They ascend, one on either side the trachea, 
to the upper level of the laryngeal prominence 
1 From the Latin brachium-the arm and cephalicus-■ 
pertaining to the head. 264 
Anatomy and Physiology 
known as Adam's Apple, where they divide, each 
one forming two branches called the external and 
internal carotids. The two external carotids give 
off branches for the supply of the throat, skull, 
face, ears, and tongue. Two very important 
branches are the superficial temporal and the 
facial. Each temporal artery is directly continu- 
ous with an external carotid. It commences in 
the substance of the parotid1 gland in the inter- 
space between the neck of the condyle of the 
lower jaw and the external meatus of the ear; it 
passes up the side of the face in front of the ear, 
giving off in its course several branches to help 
supply the parotid gland, ear, and face, and it 
ends on the forehead a little above the outer angle 
of the eye, in several branches which anastomose 
with other arteries, and gives off branches for the 
supply of the scalp and skull. Each of the two 
facial arteries arises from an external carotid near 
the base of the tongue, passes through a sub- 
maxillary gland, and curves upward over the 
border of the lower jaw about one-half inch to the 
inner side of the angle of the jaw.2 It then 
passes up to the outer angle of the mouth and 
thence to the inner angle of the eye, giving off in 
its course numerous branches for the supply of 
the throat and face. The course of this vessel, 
both in the throat and around the mouth, is very 
1 The parotid and submiliary glands secrete saliva. 
2 Its pulsation can be felt here and especially in etherizing the 
pulse is often counted at this point. Fig. 97.-Subclavian and axillary arteries. The Vascular System-Continued 
265 
tortuous-in the former situation to accommodate 
itself to the movements of the pharynx in deglu- 
tition, and in the latter to the movements of the 
jaw. As can be seen in Fig. 96, the arteries of 
the face and skull anastomose very freely. Each 
internal carotid passes upward and outward 
from its connection with a common carotid to 
the carotid foramen1 in the petrous portion of 
the temporal bone, where it passes inward, 
pierces the dura mater, and divides into num- 
erous branches for the supply of the brain and 
eye. 
544. Other Source of Brain Blood Supply 
and Circle of Willis.-In addition to the inter- 
nal carotids, some parts of the brain are supplied 
with blood from branches of the basilar2 artery 
which is formed at the base of the skull by the 
union of the two vertebral arteries. Branches of 
the internal carotids and of the basilar arteries 
anatomose at the base of the brain forming what 
is known as the circle of Willis. 
545. The Subclavian, 3 Axillary, and 
Brachial Arteries.-The right subclavian 
springs from the innominate artery; the left from 
the arch of the aorta. Each vessel passes upward 
and outward and then arches downward and 
outward to the border of the first rib. Thence it 
passes into the axilla and is known as the axillary 
1 Situated directly in front of the ear at its lower edge. 
2 So called from its situation at the base of the brain. 
3 Under the clavicle. 266 
Anatomy and Physiology 
artery, and thence down the inside of the arm1 
to below the bend of the elbow under the name 
of the brachial artery; there it bifurcates forming 
the radial and the ulnar arteries. The subclavian 
artery gives off numerous branches for the supply 
of the neck, back, and chest. The axillary sends 
branches to the chest, shoulder, and arm, and the 
brachial to the muscles, bones, and other tissues 
of the arm. 
546. The Ulnar and Radial Arteries and 
their Branches.-These two terminal branches 
of the brachial artery extend down the arm, the 
ulnar on the inner and the radial on the outer or 
thumb side. At the wrist the ulnar terminates in 
two branches, one of which passes in the form of 
an arch to the radial side of the hand where it 
unites with a branch from the radial and so forms 
what is known as the superficial palmar arch; 
the second penetrates into the deeper tissues of 
the hand and anastomoses with a branch from the 
radial, which forms an arch in the deeper tissues 
of the hand, called the deep palmar arch. The 
superficial arch, formed principally by the ulnar, 
helps supply the tissues of the palm of the hand, 
and the deep arch, which is formed chiefly by the 
radial, supplies the back of the hand. The ulnar 
1A depression in the muscles of the arm can be felt along the 
inner border of the biceps, about the center of the inner surface 
of the arm, and by pressing the fingers in deeply at this part 
from before backward, or by the application of a tourniquet, the 
brachial artery can be pressed against the humerus, and hemor- 
rhage in the arm or hand can be thus controlled. Fig. 98.-Superficial palmar arch and its branches. The Vascular System-Continued 
267 
and radial arteries both give off numerous branches 
to supply the tissues of the arms and hand. 
547. Arteries Arising from the Thoracic 
Aorta.-These are the pericardiac, bronchial, 
esophageal, posterior mediastinal, and the 
intercostal. 
The pericardial arteries are vessels of small size 
which pass to and supply the pericardium. 
The bronchial arteries, three in number, pass, one 
to the right and two to the left lung. Branches 
from these arteries are distributed through the 
lung tissue to supply it with nutrition, and to the 
bronchial tubes, esophagus, and pericardium. 
The esophageal arteries, of which there are five 
or six, supply the esophagus. 
The posterior mediastinal1 arteries are small arter- 
ies which pass backward to the thoracic vertebra 
to supply the lymph-nodes in that locality. 
The intercostal arteries, varying in number from 
nine to eleven pairs, have their origin from both 
lateral (side) surfaces of the thoracic aorta. They 
extend outward to the intercostal spaces and then 
pass forward in those spaces to the anterior chest 
wall. They give off branches to supply the muscles 
and other tissues of chest and back, the mammary 
gland, the pleura, the spinal cord and its mem- 
branes, and the vertebral column. 
548. Branches of the Abdominal Aorta.- 
These, for convenience in description, are divided 
1 Pertaining to the mediastinum, i. e., the central division of the 
thoracic cavity. 268 
Anatomy and Physiology 
into three groups: the visceral, those which supply 
the viscera; the parietal, those distributed to the 
walls of the abdomen; the terminal, the branches 
formed by the bifurcation of the aorta. The 
visceral group comprises the celiac1 axis, the supra- 
renal, the superior mesenteric, the renal, the sper- 
matic (ovarian), and the inferior mesenteric. The 
parietal group consists of the phrenic, lumbar, 
and the middle sacral arteries, and the terminal 
branches are the right and left common ilia 
arteries. 
The celiac axis is a short, -stout trunk, about 
one half-inch in length, which arises from the 
aorta just below the aortic foramen in the dia- 
phragm. It divides into three arteries called the 
gastric, hepatic, and splenic. 
The gastric artery passes to the stomach and 
gives off branches for the supply of that organ 
and the esophagus. 
The hepatic artery extends to the liver, and its 
branches are distributed to the tissues of that 
organ and to those of the gall-bladder, omentum,2 
part of the stomach, pancreas, and upper part of 
the duodenum. 
The splenic artery passes along the upper sur- 
face of the pancreas to the spleen. Its branches 
are distributed to the pancreas, spleen, and parts 
of the stomach. 
The superior mesenteric arises from the aorta 
1 From the Greek koilos-hollow. 
2 Described in paragraph 703. The Vascular System-Continued 
269 
about one-quarter of an inch below the celiac axis. 
It is distributed to the small intestine, except the 
part of the duodenum supplied by the hepatic, 
and to part of the large intestine. 
The inferior mesenteric is given off from the 
aorta a little above its bifurcation. It supplies 
the lower part of the large intestine and, under 
the name of the hemorrhoidal artery, the rectum. 
The renal arteries arise from the aorta a little 
below the superior mesenteric and pass one to 
each kidney. The nature of the distribution of 
their branches will be described in connection 
with the structure of the kidneys. 
The suprarenal arteries, known also as the ad- 
renal, extend to and supply the suprarenal bodies. 
The spermatic arteries (in the male) are given 
off from the front of the aorta. They supply 
the testes. 
The ovarian arteries (in the female) take the 
place of the spermatic arteries of the male. They 
send branches to the Fallopian tubes, ovaries, and 
uterus. 
The two phrenic arteries arise from the aorta, 
just below the diaphragm, the under surface of 
which they supply. 
The lumbar arteries, four or five in number on 
each side, pass from the sides of the upper portion 
of the abdominal aorta. Their branches are 
distributed to the muscles of the back and abdo- 
men, the lumbar vertebra, and the spinal cord. 
The sacra media arises from the lower end of Anatomy and Physiology 
270 
the aorta and its branches are distributed to the 
sacrum and coccyx. 
The right and left common iliac arteries originate 
as the result of the bifurcation of the abdominal 
aorta These two arteries bifurcate in turn, each 
one giving rise to an internal and external iliac 
artery. 
The branches of the internal iliac arteries are 
distributed to the pelvic organs, pelvic walls, 
the external genitals, the buttocks and structures 
about the hip joint. One very important branch 
of this artery, in the female, is the uterine artery, 
the branches of which supply the tissue of the 
uterus. The course of these vessels in the uterine 
tissue is very tortuous in order to prevent them 
being stretched and injured when the uterus 
enlarges during pregnancy. 
The branches of the different arteries supplying 
any one of the abdominal or pelvic organs anas- 
tomose freely with each other; thus, even some of 
the large branches can be ligated in operation 
without cutting off the nutrition from the organ. 
549. The External Iliac and its Branches. 
-The two external iliac arteries pass from their 
bifurcation from the right and left common iliac 
down through the abdomen, over the brim of the 
pelvis, down and around the thigh, on the inner 
side to the lower end of the popliteal space- 
behind the knee. The portion of the artery 
extending from the pelvic brim to the upper part 
of the popliteal space is called the femoral artery, The Vascular System-Continued 
271 
the portion in the back of the knee joint is called 
the popliteal artery. Both the femoral and popli- 
teal arteries give off several branches for the supply 
of the soft tissues and bones of the thigh and 
knee joint. The popliteal artery ends by dividing 
into two arteries called the anterior tibial artery 
and the posterior tibial artery. 
The anterior tibial artery passes around from 
the popliteal space to the front or anterior surface, 
down which it extends to the ankle; there it 
receives the name of the dorsalis pedis.1 It gives 
off several branches for the supply of the struc- 
tures in the anterior part of the leg. 
The posterior tibial extends down the back of 
the leg on the tibial side to the heel, where it 
divides into the internal and external plantar 
arteries. It gives off several branches which sup- 
ply all the tissues of the leg excepting those in 
front. One of the largest branches is called the 
peroneal.2 This branches off from the posterior 
tibial about half an inch below the bifurcation of 
the latter from the popliteal, and extends down the 
outer or fibula side of the leg. 
550. The Dorsalis Pedis and Plantar 
Arches.-The dorsalis pedis is the continuation 
of the anterior tibial. • It extends from the ankle 
over the dorsum3 of the foot on the tibial side to 
1 From the Latin dorsum or dorsalis-the back and pedis-a 
foot. 
2 From the Greek per one-the fibula. 
3 From the Latin dor stem-the back. 272 
Anatomy and Physiology 
the great toe. It then passes through the interos- 
seous1 muscles to the sole of the foot. It gives off 
branches which help supply the dorsum and sole 
of the foot and the toes, and help the external and 
internal plantar arteries form the external and 
internal plantar arches. These arches give cff 
branches which are distributed to the digital end 
of the foot and the toes. 
The Veins 
551. The Pulmonary Veins.-The veins be- 
longing to the pulmonary system originate from 
the capillary network in the air cells of the lungs. 
The innumerable small veins of each lung unite to 
form two large veins, and, as such, leave the lung 
and pass to the left auricle of the heart. They 
hold arterial blood. 
The Systemic Veins 
552- Classification.-There are a great many- 
more large veins than there are arteries. They 
have been classified according to their location 
and nature as superficial veins, deep veins, and 
sinuses. 
553. Distribution.-The superficial veins are 
found between the layers of superficial fascia. 
They connect with the deep veins by means of 
branches extending inward. The deep set usually 
accompany the arteries and are generally enclosed 
1 Between the bones. Fig. 99.-Sinuses of the dura, left lateral view. The Vascular System-Continued 
273 
in the same sheath with those vessels. The 
smaller of the main arteries, as the brachial, 
radial, ulnar, tibial, and peroneal are accompanied 
by two veins, one lying on each side of them. Veins 
so arranged are called vence comites, i. e., compan- 
ion veins. The larger of the main arteries as the 
axillary subclavian, popliteal, and femoral, have 
usually only one accompanying vein, and in some 
cases the deep veins do not accompany the arter- 
ies; e. g., the veins of the skull and spinal canal and 
the hepatic veins in the liver. The veins anasto- 
mose even more freely than the arteries. ■ 
554. Sinuses.-Sinuses are venous channels 
found in the interior of the skull. They are 
formed by a separation of the layers of the dura 
mater, their outer wall consisting of the fibrous 
coat of that membrane and their inner one of its 
internal or endothelial layer. This layer is con- 
tinuous with the walls of the vessels which empty 
their contents into the sinuses. The location of 
these sinuses can be seen in Fig. 99. 
Names and Location of the More Important Veins 
555- The Coronary Veins.-These veins re- 
turn the blood from the heart substance-the 
myocardium. They empty directly into the right 
auricle of the heart, and not, as do the other sys- 
temic veins returning blood from the upper part 
of the body, into the superior vena cava. 
556. The Superior Vena Cava and its 274 
Anatomy and Physiology 
Tributaries.-The superior (known also as the 
descending) vena cava, is a short trunk varying 
from two and a half to three inches in length and 
formed by the union of the right and left brachio- 
cephalic or innominate veins, behind the lower 
part of the junction of the first right costal carti- 
lage with the sternum. From this point it ex- 
tends downward and opens into the right auricle. 
It receives the blood returning from the head, 
neck, upper extremities, and thoracic walls. 
557. The Right and Left Brachio-Ce- 
phalic1 or Innominate1 Veins.-The right in- 
nominate vein is about an inch and a half in 
length, and the left two and a half to three inches. 
They are formed by the union of the subclavian 
and internal jugular veins, behind the sternum 
end of each clavicle, and descend to just below 
the cartilage of the first rib, close to the right 
border of the sternum, where they unite to form 
the superior vena cava. 
558. The Internal Jugular Veins.-These 
veins receive the blood from the numerous veins 
and the sinuses of the cranial cavity. They com- 
mence in the base of the skull and descend, one 
on either side, through the neck on the outer 
side of, first, the internal, and then the common 
carotids to behind the sternal end of the clavicle 
where they unite with the subclavians to form the 
brachio-cephalic veins. 
1 There is only one innominate or brachio-cephalic artery, but 
two veins. The Vascular System-Continued 
275 
559- External Jugular Veins.-These two 
veins receive the blood from the face and exterior 
of the cranium. They commence, one on either side 
of the neck, in the substance of the parotid glands, 
on a level with the angles of the lower jaw, being 
formed by the union of two of the larger veins of 
the face. They terminate in the subclavian veins, 
opposite the middle of the clavicles. 
560. Veins of the Upper Extremities.-The 
deep veins are the vense comites (companion 
veins) which accompany the arteries of the fore- 
arm and arm, the axillary and the subclavian 
vein; the last two follow pretty much the same 
course as the arteries of the same name. The 
principal superficial veins are (1) the radial, which 
communicates in the hand with the deep palmar 
arch and runs up the radial side of the forearm 
to a little above the bend of the elbow where it 
joins the median cephalic vein; (2) the posterior 
ulnar, which runs up the dorsal aspect of the 
ulnar side of the forearm; (3) the anterior ulnar 
which extends up the front surface; (4) the com- 
mon ulnar, formed by the union of the posterior 
and anterior, which after a short course joins the 
median basilic; (5) the median, extending alcng 
the front of the arm, from the wrist to the bend of 
the elbow, where it bifurcates, forming (6) the 
median basilic and (7) the median cephalic veins. 
The first of these, the median basilic,1 which is 
1 This is the vein commonly chosen when performing phlebot- 
omy, intravenous infusion, etc. 276 
Anatomy and Physiology 
the larger of the two, runs upward to about the 
center of the arm where it joins the common 
ulnar to form (8) the basilic. The median ce- 
phalic runs a short course upward and joins the 
radial to form (9) the cephalic. The basilic vein 
as it approaches the axilla unites with the inner 
vena conTes1 of the brachial artery to form the 
axillary vein. The cephalic ascends the arm and 
ends in the axillary vein. 
561. Veins of the Thorax.-The majority 
of the principal veins of the thoracic walls, the 
spinal canal and cord, the abdominal and pelvic 
walls and viscera bear the same name and follow 
the same course as the arteries. Some exceptions 
are: 
562. The Inferior Vena Cava.-This large trunk 
vein which receives and carries to the heart the 
blood from the lower extremities, the pelvis, and 
the greater part of that from the abdomen, is 
formed by the union of the two common iliac 
veins at a level with the fifth lumbar vertebra. 
It extends upward through the abdomen and 
pierces the diaphragm near the aorta, enters the 
pericardium, and opens into the lower and back 
part of the right auricle. 
563. The Azygos Veins.-These are three veins 
called the right or great azygos vein, the left 
lower azygos, and the left upper azygos. The 
great azygos commences in the abdomen as an 
upward continuation of the lumbar vein, which 
1 Singular of venee comites. Fig. ioo.-Azygos and intercostal veins. The Vascular System-Continued 
277 
communicates with the common iliac vein and 
frequently with the inferior vena cava. It ascends 
on the right side of the vertebral column through 
the abdominal and thoracic cavities to the level 
of the fourth thoracic vertebra, where it empties 
into the superior vena cava. The lower left 
azygos commences on the left side of the abdomen 
in the same manner as the right. It ascends on the 
left side of the vertebral column and connects 
with the right azygos at about the level of the 
eighth thoracic vertebra. The left upper azygos 
branches from one of the large intercostal veins 
and opens into the left lower azygos. These veins 
receive the venous blood from the greater part of 
the dorsal and lateral thoracic walls. They are 
often called the supplementary channel because by 
virtue of their anastomoses with the common iliac 
and the superior vena cava they could, if an 
obstruction occurred in the inferior vena cava, 
return the blood from the lower part of the body. 
564. The Portal Vein-Portal System.-The 
portal vein has its origin behind the pancreas and 
in front of the inferior vena cava, on a level with 
the first lumbar vertebra. It is formed by the 
junction of the splenic and superior mesenteric 
veins and receives branches from the stomach 
and pancreas. It extends upward and to the right 
for about three inches and enters the liver where it 
divides into smaller veins which end in plexuses 
of capillaries. These unite, and with the capil- 
laries arising from the hepatic artery (which 278 
Anatomy and Physiology 
supply the substance of the liver with nutrient 
material) they form the hepatic vein through 
which the blood from the liver reaches the inferior 
vena cava. The two veins from which the portal 
vein originates carry the blood from the small 
intestine and spleen, and those connecting with it 
carry the blood from the stomach, pancreas, and 
gall-bladder. Therefore, the portal vein serves to 
carry the blood from those organs to the liver 
where it undergoes certain necessary chemical 
changes before flowing onward through the hepatic 
vein to enter the inferior vena cava. 
565. The Principal Veins of the Lower 
Extremity.-The principal deep veins returning 
the blood from the lower extremities are: belowT 
the knee, the venae comites accompanying the 
arteries; behind the knee, the popliteal; in the 
thigh, the femoral. The principal superficial ones 
are: the internal or long saphenous and the exter- 
nal or short saphenous. The internal saphenous 
vein arises from the inner side of the plexus of 
veins situated on the dorsum and instep of the 
foot called the dorsal plexus, and, ascending the 
inner aspect of the leg and thigh, ends in the femoral 
vein about an inch and a half below where the 
latter passes over the pubic bone and becomes 
the external iliac vein. The external saphenous 
arises at the outer side of the dorsal plexus, passes 
up the back of the leg, and terminates in the 
popliteal vein. CHAPTER XIV 
the vascular system-Continued 
Course Followed by the Blood in its Circulation through the 
Body. Nature of the Heart Action. Meaning of Systole, Dias- 
tole, and Cardiac Cycle. Relative Time Required for the Systole 
and Diastole of the Auricles and of the Ventricles. Heart Sounds 
and Murmurs. Cause of the Heartbeat. Function of Na, Ca, and 
K in Connection with the Heart Action and Osmotic Pres- 
sure. Influence of the Vagi and the Sympathetic Nerves on the 
Heart Action. Factors Maintaining Arterial and Venous Circu- 
lation. Velocity of the Circulation. Blood Pressure: Nature, 
Average Degree in Health, Causes of Changes, Means of Ascer- 
taining Degree of Pressure. The Pulse: Cause of Pulsation, 
Locations Where Felt, What Can Be Determined by Palpitation, 
Normal Frequency. Lymph: Forces Controlling Circulation. 
Cause of Edema. 
566. Course Followed by the Blood in its 
Circulation through the Body.-As has been 
already stated, the blood flows from the auricles 
of the heart into the ventricles, from the right 
ventricle into the pulmonary artery, and from the 
left ventricle into the aorta. From the pulmonary 
artery the blood passes to the right and left 
pulmonary arteries and through these to the in- 
numerable capillaries surrounding the air sacs or 
alveoli of the lungs, from these into the pulmonary 
veins, and thence back to the heart, but to the left 
279 280 
Anatomy and Physiology 
instead of the right auricle. The blood forced 
into the aorta passes to the many branches and 
sub-branches of this great trunk and thus reaches 
the capillaries and thereby, practically, all the 
tissues of the body, both the skeletal and the 
visceral. From the capillaries it enters the small 
veins and then the blood in the upper part of the 
body, except that in the myocardium, goes by 
way of the superior vena cava to the right auricle 
of the heart. That from the myocardium reaches 
the same destination by way of the coronary veins, 
and that from the abdominal and pelvic cavities, 
their organs, and the lower extremities, reaches it 
via the inferior vena cava. The blood is kept 
flowing in the right direction by the valves which 
are placed wherever their presence is necessary to 
prevent regurgitation of the blood. Their locations 
were given in the preceding chapter. 
567. Nature of the Heart Action.-At the 
moment that the ventricles eject the blood from 
their cavities they are in a state of contraction; 
the tricuspid and the bicuspid valves are closed^ 
and the blood is flowing into the emptied auricles. 
This condition lasts but the fraction of a second, 
then the ventricles relax, and as soon as this 
happens the pressure of blood in the auricles 
causes the auriculo-ventricular valves to open and 
the blood from the large veins pours into both 
the auricles and the ventricles-the heart during 
this time being in a passive state or at rest, the 
auriculo-ventricular valves open, but the semi- The Vascular System-Continued 
281 
lunar valves of the pulmonary artery closed. The 
auricles being partially filled before the blood 
begins to flow into the ventricles, and holding 
rather less than the latter,1 very shortly become 
distended; then the large veins contract and a 
sharp wave of contraction passes first over the 
auricles and then the ventricles. The contraction 
of the auricles forces their contents into the ven- 
tricles, and the auricles then relax. The ventricles 
dilate very rapidly on receiving the blood from the 
auricles and the auriculo-ventricular valves are 
floated up and closed. The ventricles then con- 
tract and at the same time the semilunar valves 
are forced open and the blood propelled into the 
pulmonary artery and aorta. The contraction of 
the ventricles is followed by their sudden relaxa- 
tion and the blood attempts to regurgitate, but 
as it does so it pushes up the flaps of the semilunar 
valves which slap together shutting off the two 
arteries from the heart. Then follows the pause 
described at the beginning of this paragraph, in 
which both the auricles and the ventricles are 
relaxed and inactive, and the blood is poured into 
the chambers. The auricles, it will be remembered, 
relaxed as soon as they had emptied their contents 
1 During life each ventricle is capable of containing about four 
ounces of blood. The auricles are a little less capacious, but 
owing to the much thicker walls of the ventricles the difference 
in the capacity of the chambers is not as great as might be 
expected from a casual examination of a heart. The walls of the 
left ventricle are thicker than those of the right, because it has 
to start the blood on a longer journey than the right. 282 
Anatomy and Physiology 
into the ventricles, and immediately upon their 
relaxation the blood from the veins poured in; 
thus the flow from the veins is only retarded for 
the exceedingly short space of time that the 
auricles are in contraction. 
568. Meaning of Systole, Diastole, and 
Cardiac Cycle.-The contraction of any part of 
the heart is spoken of as its systole; its relaxation 
and period of rest as its diastole. The systole and 
diastole of the auricles and of the ventricles are 
known as a cardiac cycle. Each cardiac cycle 
corresponds to one beat or pulsation of the heart. 
569. Relative Time Required for the Sys- 
tole and Diastole of the Auricles and Ven- 
tricles.-The length of time that the heart takes 
to complete a cycle depends upon the rate at which 
it is working. When the pulse-beat is 72 per 
minute, the time required will be about 0.8 of a 
second, and the time occupied by each part of the 
cycle will be about as follows: 
Auricular systole 0.1 of a second 
Auricular diastole 0.7 of a second 
Ventricular systole 0.3 of a second 
Ventricular diastole 0.5 of a second 
As can be seen by the above figures, there are 0.4 
of a second during which both auricles and ventri- 
cles are in diastole, or, in other words, during 
which the heart is at rest. Therefore when there 
are 72 cycles per minute the heart gets about 28.8 
seconds rest during that time, but if the speed of The Vascular System-Continued 
283 
the heart be increased it is the time of diastole 
and not that of the systole which is diminished, 
and the heart's rest is thus interfered with. 
570. Heart Sounds and Murmurs.-If the 
ear is placed over the region of the heart two 
sounds will be heard with every beat of that 
organ. These sounds are usually described by the 
syllables lubb-diib. The first sound, which is dull 
and comparatively prolonged, is thought to be 
due to the vibrations caused by the closure of the 
auriculo-ventricular valves and the contraction 
of the ventricles; the second, which is short and 
sharp, is attributed to vibrations set up by the 
sudden closure of the semilunar valves. Changes 
in the nature of these sounds occur in certain 
diseased conditions of the heart, due very often 
to failure of the valves to close properly and 
consequent regurgitation of the blood. Such 
sounds are called murmurs. 
571. Cause of the Heartbeat.-Though the 
cause of the heartbeat has been the subject of 
inquiry from very early times, it is still but im- 
perfectly understood. Formerly it was thought to 
be dependent upon stimulation from the central 
nervous system, but it has been demonstrated by 
numerous experiments that, though the central 
and sympathetic nervous systems help to regulate 
the heartbeat, the actual action of the heart is 
not dependent upon stimulation from outside 
nerves; for the heart will continue to beat after 
connection with the nervous system is severed; 284 
Anatomy and Physiology 
in fact, it has been found that a frog's heart will 
continue to do so for hours after removal from the 
body, if its substance is kept moist with what is 
known as Dr. Ringer's solution, which contains 
small amounts of chlorides of sodium, potassium, 
and calcium. The most generally accepted theory 
of the present day is, therefore, that the heart 
muscle itself possesses the property of being 
stimulated, and that this property is most highly 
developed in the area of the wall of the right 
auricle between the openings of the two venae 
cavae; for contractions seem to start here and pass 
first over the walls of the auricles and thence of 
the ventricles. The nature of the stimulus which 
affects the heart muscle is not known, but it is 
thought that the chlorides of sodium, potassium' 
and calcium contained in the blood have a powerful 
influence. 
572. Function of Sodium, Calcium, and 
Potassium in Connection with the Heart 
Action and Osmotic Pressure.-The blood 
plasma contains about 0.5 to 0.6 per cent, sodium 
chloride and smaller amounts of calcium and 
potassium. These salts, though present in such 
small quantities, are exceedingly necessary in 
maintaining the heart action, the calcium pro- 
moting contraction and the sodium and potassium 
promoting relaxation. Also, the sodium chloride 
seems to be the principal factor in maintaining 
the normal osmotic pressure1 of the blood. 
1 See Glossary. The Vascular System-Continued 
285 
573- Influence of the Vagi and the Sym- 
pathetic Nerves on the Heart Action.-The 
heart, as previously stated, is innervated by nerve 
fibers extending from the two cranial nerves 
known as the vagi (singular, vagus) and from 
fibers from the sympathetic system. It has been 
found by experiments on anesthetized animals 
that if the vagi are cut the speed of the heart is 
accelerated. This and various other experiments 
have led to the decision that the vagi inhibit the 
rate of the heart action and the sympathetic nerve 
supply accelerates it. Both the accelerator and 
the inhibitory centers are in a state of constant 
slight activity; therefore under normal conditions 
the heart muscle is kept in a state of tone and is 
constantly under the influence of the two antago- 
nistic forces. This enables it to respond quickly 
to reflex impulses. Unusual stimulation of the 
vagi may cause marked slowing of the heart rate, 
and either depression of the vagi or stimulation 
of the sympathetic or accelerator nerve supply 
may cause acceleration of the heart action. Such 
stimulation or depression may be caused by various 
things; for example: (i) Abnormal substances in 
the blood, such as the toxins produced in disease; 
(2) drugs, certain of which stimulate the vagi 
while others depress them, some drugs acting on 
the origin of these nerves in the medulla, and 
others on their endings in the heart muscle; (3) 
injury or disease of the parts of the brain in which 
the vagi have their origin is likely to stimulate 284 
Anatomy and Physiology 
in fact, it has been found that a frog's heart will 
continue to do so for hours after removal from the 
body, if its substance is kept moist with what is 
known as Dr. Ringer's solution, which contains 
small amounts of chlorides of sodium, potassium, 
and calcium. The most generally accepted theory 
of the present day is, therefore, that the heart 
muscle itself possesses the property of being 
stimulated, and that this property is most highly 
developed in the area of the wall of the right 
auricle between the openings of the two venae 
cavae; for contractions seem to start here and pass 
first over the walls of the auricles and thence of 
the ventricles. The nature of the stimulus which 
affects the heart muscle is not known, but it is 
thought that the chlorides of sodium, potassium' 
and calcium contained in the blood have a powerful 
influence. 
572. Function of Sodium, Calcium, and 
Potassium in Connection with the Heart 
Action and Osmotic Pressure.-The blood 
plasma contains about 0.5 to 0.6 per cent, sodium 
chloride and smaller amounts of calcium and 
potassium. These salts, though present in such 
small quantities, are exceedingly necessary in 
maintaining the heart action, the calcium pro- 
moting contraction and the sodium and potassium 
promoting relaxation. Also, the sodium chloride 
seems to be the principal factor in maintaining 
the normal osmotic pressure1 of the blood. 
1 See Glossary. The Vascular System-Continued 
285 
573- Influence of the Vagi and the Sym- 
pathetic Nerves on the Heart Action.-The 
heart, as previously stated, is innervated by nerve 
fibers extending from the two cranial nerves 
known as the vagi (singular, vagus) and from 
fibers from the sympathetic system. It has been 
found by experiments on anesthetized animals 
that if the vagi are cut the speed of the heart is 
accelerated. This and various other experiments 
have led to the decision that the vagi inhibit the 
rate of the heart action and the sympathetic nerve 
supply accelerates it. Both the accelerator and 
the inhibitory centers are in a state of constant 
slight activity; therefore under normal conditions 
the heart muscle is kept in a state of tone and is 
constantly under the influence of the two antago- 
nistic forces. This enables it to respond quickly 
to reflex impulses. Unusual stimulation of the 
vagi may cause marked slowing of the heart rate, 
and either depression of the vagi or stimulation 
of the sympathetic or accelerator nerve supply 
may cause acceleration of the heart action. Such 
stimulation or depression may be caused by various 
things; for example: (i) Abnormal substances in 
the blood, such as the toxins produced in disease; 
(2) drugs, certain of which stimulate the vagi 
while others depress them, some drugs acting on 
the origin of these nerves in the medulla, and 
others on their endings in the heart muscle; (3) 
injury or disease of the parts of the brain in which 
the vagi have their origin is likely to stimulate 286 
Anatomy and Physiology 
these centers and cause slowing of the heart rate; 
(4) reflex action, e. g., some of the abdominal 
organs get part of their nerve supply, both sen- 
sory and motor, from the vagi, and injury or 
disease of such an organ may, by stimulating the 
sensory nerve endings therein, send impulses to 
the vagi centers; thus a blow on the abdomen may 
cause very alarming slowing of the heart. Also, 
the sympathetic nerve supply may be stimulated 
reflexly; common examples are: the acceleration 
of the heart rate as the result of fear or other 
emotional disturbances, or by the stimulation of 
the sensory nerves of the limbs as the result of 
exercise, etc. 
574. Factors Maintaining Arterial Circu- 
lation.-The three most important factors in 
maintaining arterial circulation are, the pumping 
action of the heart, the elasticity of the arterial 
walls, and the resistance offered to the flow of 
blood by the arterioles and capillaries on account 
of their small diameter. Also, it is assisted by 
muscular contractions and by the movements of 
respiration, but the arterial flow is not nearly as 
dependent upon these last two forces as is the 
venous. 
575. Factors Maintaining Venous Circu- 
lation.-The pumping action of the heart has 
much less effect upon the venous than upon the 
arterial circulation, owing to the small caliber and 
frequent branching of the capillary vessels divid- 
ing the arteries and veins; therefore, the blood The Vascular System-Continued 
287 
flowing through the veins, especially in parts 
below the heart where it must flow uphill, is 
dependent upon other influences to keep it in 
circulation. Some of the more important of these 
influences are: (i) the suction action of the heart 
caused by the emptying of the auricles; (2) the 
respiratory movements which are continually al- 
tering the pressure relations in the thorax and 
abdomen; (3) the pressure of the muscles, both 
skeletal and visceral, upon the vessels-the greater 
the amount of muscular contraction taking place 
the greater the degree of pressure upon the vessels; 
this is one reason why bodily exercise improves 
the circulation of the blood; (4) the valves in the 
veins, which keep the blood flowing in the right 
direction, i. e., toward the heart. 
576. Velocity of the Circulation.-It has 
been estimated, as the result of numerous experi- 
ments,1 that under normal conditions it takes the 
portion of blood pumped from the heart by a 
ventricular contraction about twenty-three sec- 
onds to complete its circulation through the sys- 
tem; this would correspond to about twenty-six 
or twenty-eight beats of the heart. 
577. Difference of the Rate of Flow in 
the Various Vessels.-The rate at which the 
blood flows varies in the different sets of vessels 
1 Many of these experiments are described in Text-Book of 
Physiology, Howell, page 253, W. B. Saunders & Co., and 
Handbook of Physiology, Kirk, pages 237-240, Wm. Wood & 
Co. 288 
Anatomy and Physiology 
and also in different sized vessels of the same set. 
The speed is greatest in the large arteries and 
least in the capillaries. In the veins the flow is 
quicker than in the capillaries, but slower than 
in the arteries. 
578. Variations in the Quantity of Blood 
in Different Parts of the Body.--Activity of 
any part of the body causes a greater amount of 
blood to flow to that part and, as the quantity 
of blood in the body is always about the same, 
an influx to one part will deplete the quantity in 
another; e. g., after a hearty meal there will be 
an increased supply of blood in the stomach and 
intestines and less in the brain, but violent exer- 
cise or a warm bath will increase the amount of 
blood in the superficial parts of the body and 
lessen that in the stomach and intestines. 
Blood Pressure 
579- Difference in Degree of Pressure 
in Different Vessels.-The degree of pressure 
exercised by the blood on the walls of the blood- 
vessels varies, as does the speed at which it flows 
through the vessels, according to the nature and 
size of the vessels; thus, it is greatest in the 
largest arteries and least in the capillaries. The 
proof of this is seen when a blood-vessel is punc- 
tured: if the vessel be an artery the blood is ejected 
with great force, and the larger the vessel the 
greater the force and the higher the stream is The Vascular System-Continued 
289 
projected. The spurt from a vein is not nearly 
so forceful, and the smaller the vein the less force- 
ful the spurt. Another difference between arterial 
and venous or capillary flow is that the blood from 
an artery is projected in spurts, each spurt cor- 
responding to the contraction of the ventricles, 
and the flow of blood from veins and capillaries 
is steady and continuous. The reason for this 
difference can be seen in paragraph 575. 
580. Why the Blood Exercises Pressure 
on the Walls of the Arteries.-The reasons 
that the blood exercises so much pressure upon 
the walls of the arteries are: (1) the heart at each 
systole forces four to six ounces of blood into the 
arteries; (2) the arteries are full of blood when 
they receive the extra supply from the heart, 
because there is not sufficient time between the 
heartbeats for the blood to pass into the capil- 
laries; (3) the arteries, being capable of consider- 
able distention, dilate to accommodate themselves 
to the extra supply of blood forced into them; (4) 
the resistance offered to the flow of blood by the 
arterioles, capillaries, and small veins. 
581. Normal Degree of Blood-Pressure 
and Causes of Variation.-The pressure exerted 
by the blood on the walls of the arteries varies 
with the systole and diastole of the heart, being 
of course greater during systole and less during 
diastole. Thus, in adults of from twenty to 
thirty-five years the average normal pressure 
exerted by the blood on the walls of the brachial Anatomy and Physiology 
290 
artery is, during systole, about no mms. to 120 
mms., and, during diastole, 75 mms. to 85 mms.1 
Pressure varies with age, being less in the young 
and greater in old age when the arteries have 
lost much of their elasticity. Pressure is, however, 
not constantly the same in any individual even in 
health, for factors that increase the force of the 
heartbeat increase the degree of pressure. Also, 
certain drugs, as adrenalin, by causing constriction 
of the arteries will raise the blood-pressure. 
Others, as nitroglycerine, by causing dilation of 
the arteries will lower the blood-pressure. In 
diseases characterized by over-constricted or scler- 
otic arteries the blood-pressure may be very high. 
On the contrary, when arteries have lost their 
normal tone,2 as in shock, or when the heartbeat 
loses its force, the blood-pressure is very low. 
Two important causes for loss of force of the heart- 
beat are loss of normal muscular tone and con- 
tinued high speed of the heart action. 
582. Means of Ascertaining the Degree 
of Blood-Pressure.-Some idea of the degree of 
blood-pressure can be gained by holding the 
fingers over those parts of the body where a large 
1 See end of following paragraph. 
2 The muscular walls of the arteries are normally in the same 
state of slight contraction or tone as the skeletal muscles, and 
for the same reason. This tonicity of the arteries is very im- 
portant to the proper functioning of the heart, as, in order to 
contract properly it needs the slight resistance offered by the 
contracted vessels. An abnormal degree of contraction, however, 
compels the heart to work too hard. The Vascular System-Continued 
291 
artery approaches the surface and in which its 
pulsation can be felt. If the pulsation feels tense 
and hard to compress it is known that the blood- 
pressure is high. If, on the other hand, the pulsa- 
tion can be easily obliterated by pressure of the 
fingers, the blood-pressure is low. The knowledge 
Fig. ioi.-Sphygmomanometer. 
gained in this way is, however, very indefinite, 
and several forms of apparatus have been devised 
of late years by different doctors by which a 
much more accurate knowledge can be obtained by 
means of an apparatus called a sphygmomano- 
meter. Of these there are many varieties, but they 
have the same essential parts, viz: (i) an elastic bag 
(see Fig. ioi) outside of which is a leather cuff; (2) 
a mercury manometer which is connected with the 
elastic .bag by means of rubber tubing and also 292 
Anatomy and Physiology 
with (3) an air-pump. The way in which this 
works is as follows: The elastic bag, covered with 
the cuff, is strapped around the arm and then 
inflated by means of the pump until no pulsation 
can be felt in the radial artery at the wrist. The 
height at which the mercury stands is then read. 
This gives the maximum or systolic pressure. The 
pressure on the arm is then reduced until the wid- 
est oscillations of the mercury column are obtained, 
and the lowest position of the mercury meniscus 
gives the minimum or diastolic blood-pressure. 
The systolic pressure-when the subject is about 
30 or 35 years of age-raises the mercury in the 
manometer about 120 millimeters, and this is 
why it is said to exert a pressure of 120 mms. 
The Pulse 
583. Cause.-As each ventricular systole forces 
the blood into the arteries the walls of these 
vessels expand in order to accommodate the extra 
supply of fluid, and as the blood passes into the 
capillaries the arterial walls gradually recoil. This 
intermittent distention of the arterial walls can 
be felt on palpation wherever a large artery 
approaches the surface, and is known as the pulse. 
584. Locations where the Pulse is Most 
Easily Felt.-These are: the radial artery on the 
thumb side of the wrist; the facial artery where it 
passes over the lower jawbone (see Fig. 96); the 
temporal artery a little above and to the outer 
side of the outer angle of the eye (see Fig. 96); The Vascular System-Continued 
293 
the femoral artery where it passes over the pelvic 
bone (see Fig. 92); the dorsalis pedis on the dor- 
sum of the foot (see Fig. 92). 
585. What Can be Determined by Feeling 
the Pulse.-By placing her fingers over one of 
the locations mentioned in the preceding para- 
graph, a nurse can determine (1) the frequency of 
the pulse, and, therefore, the frequency of the 
heartbeat; (2) the force of the heart action- 
whether strong or weak; (3) whether the pulsation 
is regular in frequency, i.e., the same number of 
beats each minute, and force, i. e., each pulsation 
having the same force, and not some strong and 
some weaker; (4) the strength of the blood- 
pressure-how this can be told has been already 
described; (5) if the pulse is intermittent--i. e., if a 
beat is dropped; when this happens it means that 
a heartbeat is so weak that its impulse fails to 
distend the more distant arteries; (6) if the pulse 
is dicrotic-i. e., if some pulsations are divided, 
the second part of the beat being weaker than the 
first. A dicrotic pulse occurs when there is a lack 
of tone in the arterial walls, in consequence of 
which the aorta becomes over-distended during 
systole, when the blood is injected into it, but, 
as systole ends, the aorta tends to recover 
itself and contract, and drives the blood back 
against the semilunar valves, closing them, but, 
on account of the suddenness of its contraction, 
giving rise to a wave-the dicrotic wave-which 
passes onward toward the periphery. Anatomy and Physiology 
294 
586. Normal Frequency of the Pulse.-• 
The normal number of heartbeats per minute 
varies considerably with age. The average rate 
at different ages is as follows: 
At birth about 130 to 160 per minute 
During the first year about 120 
" " second " " no " " 
" " third " " 95 
After the third " " 72 to 90 " 
Adults, women " 65 to 80 " 
" men " 60 to 70 " 11 
The rate of the pulse may vary very considerably, 
however, even in health, e. g., it is more rapid 
when an individual is in the erect posture than 
when recumbent, also, its rate is increased some- 
what after a meal, and usually very considerably 
by muscular exercise and excitement. 
Lymph 
587. Forces Controlling the Flow of 
Lymph into the Tissues.-The principal factors 
inducing the flow of blood-plasma-which is the 
origin of the lymph-from the capillaries into 
the tissues are: (1) the pressure under which the 
blood is in the capillaries, owing to the very much 
smaller size of these vessels than the arteries and 
veins; (2) the force of diffusion,1 due to differences 
in the chemical composition of the blood-plasma 
1 Described in Glossary. The Vascular System-Continued 
295 
in the capillaries and the lymph in the tissues; (3) 
the difference in the osmotic pressure1 in the capil- 
laries and the tissues; (4) the permeable nature 
of the endothelial cells forming the .walls of the 
capillaries. 
588. Factors Controlling the Flow of 
Lymph from the Tissues to the Lymphatic 
Ducts.-The direction of the circulation of the 
lymph is from the tissues to the thoracic and 
right lymphatic ducts. The principal causes for 
the maintenance of this direction are: (l) There 
is a greater pressure of lymph in the lymph-spaces 
than in the lymph-capillaries, and a lower pressure 
in the large vessels near the ducts than in the 
smaller vessels, so that there is, as it were, a 
suction force drawing the lymph onward; (2) the 
movements of respiration; (3) the contraction of 
the skeletal and visceral muscles; (4) the action 
of the heart inasmuch as it affects the venous 
circulation influences to some extent the flow of 
the lymph. 
589. Causes of Edema.-In health the amount 
of lymph in the lymph-spaces varies from time to 
time, and in different parts of the body; all in- 
crease in capillary pressure causing a temporary 
increase in the amount of exudation of plasma 
into the tissues; but normally this increase is 
never excessive and soon passes off. In certain 
diseases, however, there may be a very great 
accumulation of lymph in the tissues, either in 
1 See Glossary. 296 
Anatomy and Physiology 
restricted areas or throughout the body. Such a 
condition is known as edema. It may be due to (i) 
the excessive formation of lymph; (2) to interrup- 
tion in its circulation. The former is much the 
more common cause. And it may be due (1) to 
changes in blood-pressure; (2) changes in the com- 
position of the blood; (3) pathological conditions 
in the walls of the blood-vessels. The reason and 
nature of a local excessive exudation of plasma 
into the tissue, as the result of irritation, were 
described in paragraph 469. CHAPTER XV 
THE RESPIRATORY ORGANS AND RESPIRATION 
Purpose of Respiration. Name, Location, Structure, and 
Function of Each of the Various Organs Concerned in External 
Respiration. Nature of External Respiration. Mechanism and 
Causes of Inspiration and Expiration. Influence of Sensory 
Nerves and of the Vagi on Respiration. Cause of the First 
Respiratory Movement. Causes of the Interchange of Gases 
Taking Place in Respiration. Nature of Internal Respiration. 
Changes in the Blood Due to Respiration. Normal Rate of 
Respiration. Terms Used in Describing the Quantity of Air 
Inhaled and Exhaled in Respiration. Capacity of the Lungs. 
Forces Causing Movement of Air in the Lungs. Changes in the 
Air as the Result of Respiration. Bad Effects of Poor Ventila- 
tion. Required Amount of Ventilation and Air-Space. Abnor- 
mal Types of Respiration. Modified Respiratory Movements. 
590. Purpose.-The purpose of respiration is 
(i) to supply the body with the oxygen that it 
requires for tissue building, and to maintain the 
continual oxidation necessary to provide the heat 
that is essential to keep the body warm and to 
supply the energy required to maintain the mechan- 
ism of the body at work; (2) to rid the body of the 
excess carbon-dioxide resulting from this oxida- 
tion; (3) to help equalize the temperature of the 
body; (4) to rid the body of excess water. 
297 298 
Anatomy and Physiology 
59i- External and Internal Respiration. 
-In order that respiration may accomplish all 
the purposes mentioned in the preceding para- 
graph, two distinct processes are necessary, viz.: 
external and internal respiration. The former 
process takes place in the lungs and consists in the 
elimination of some of the carbon-dioxide that 
the blood has brought from the tissues, and of the 
absorption of oxygen from the air. Internal res- 
piration, which is taking place unceasingly in the 
tissues, consists of (i) the diffusion of oxygen 
from the blood-vessels into the tissues, (2) its 
union there with substances in and of the tissues 
and their consequent breaking down into simpler 
substances, such as carbon-dioxide and water, and 
(4) the passage of these substances into the blood 
and lymph-vessels. 
Organs Concerned in External Respiration 
592. Names of Organs.-The organs concerned 
in external respiration are the nose, mouth, phar- 
ynx, larynx, trachea, bronchial tubes, and lungs, 
with certain of the muscles of the thorax and the 
diaphragm and, sometimes, the abdominal muscles. 
The Nose 
593- Function.--The nose serves several pur- 
poses: (i) it is the special organ of the sense of 
smell; (2) it filters, moistens, and warms air passing 
through it, and should therefore be the principal Respiratory Organs and Respiration 
299 
port for the entrance of air to the internal re- 
spiratory organs; (3) it helps in phonation and in 
the sense of taste. 
594. Main Divisions.-The nose consists of 
two parts: an external, which constitutes w'hat is 
generally known as the nose, and an internal, 
called the nasal fosses. 
595. Structure of the External Nose.- 
The external nose is composed of a framework of 
bones and cartilage covered externally with skin 
and internally with mucous membrane. At the 
lower end of the vestibules are the two openings 
known as the nostrils, around the inner edge of 
which are a number of stiff hairs which help to 
prevent the entrance of foreign substances to the 
internal respiratory organs. 
596. Nasal Fossae.-The internal portion of 
the nose is divided into two somewhat triangular- 
shaped cavities called the nasal fosses. The 
upper portion of the septum dividing the two 
cavities is formed by the perpendicular plate of 
the ethmoid bone, the lower part of the posterior 
portion, by the vomer, and the anterior, by carti- 
lage. The cavities of the nose are seldom of equal 
size,1 because, during childhood, the septum is so 
pliable that even congestion, such as may result 
from a cold in the head, may bend it. The fossse, 
1 It is important to remember the fact when feeding a patient 
through the nose. If any difficulty is experienced in passing 
the tube used for the purpose in one nasal cavity, withdraw it 
and insert it through the other. Anatomy and Physiology 
300 
at their anterior extremity, are continuous with the 
anterior nares or nostrils and at their upper end 
Fig. 102.-Sagittal section of face and neck, showing external 
wall of right nasal fossa. (Gerrish.) 
with the posterior nares which open into the naso- 
pharynx. 
597. Why it is Better to Breath through 
the Nose than the Mouth.-That the nose 
is a better passageway for the air than the 
mouth is due to two reasons: (1) the presence Respiratory Organs and Respiration 
301 
of the hairs inside the nostrils, these acting as 
filters; (2) the arrangement of the turbinated 
bones which makes the upper part of the nasal 
space very narrow and thus forces the air to 
pass exceedingly slowly over the moist and very 
vascular mucous membrane, thus moistening and 
warming it before it gains the internal respiratory 
organs. 
598. Pituitary Membrane.-The mucous 
membrane lining the fossae is called the pituitary1 
membrane from the nature of its secretion, or 
Schneiderian membrane, from Schneider, the anato- 
mist who first showed that the secretion proceeded 
from this mucous membrane and not, as was 
formerly supposed, from the brain. 
599. Nerve Supply.-The nose gets its nerve 
supply from the olfactory nerve and from the 
fifth or trifacial nerve. The olfactory nerve, 
which is the special nerve for the sense of smell, 
passes forward from its origin in the brain to the 
ethmoid bone, where it expands into an oblong 
mass of gray matter called the olfactory bulb. 
From this bulb are given off numerous nerve 
filaments which enter the nose through the fora- 
mina in the ethmoid bone and are distributed to 
the mucous membrane covering the ethmoid and 
the superior and middle turbinated bone. When 
a person is suffering with a cold in the head the 
mucous membrane lining the lower portion of the 
nose becomes congested and so interferes with 
1 From the Latin pituita-phlegm. 302 
Anatomy and Physiology 
the passage of odorous substances to the olfactory 
nerve endings, and thus there is a loss of the sense 
of smell. The branches derived from the trifacial 
nerve are distributed to the mucous membrane in 
the lower part of the nose. These fibers, when 
stimulated, give rise to such sensations as pain, 
cold, pressure, etc. 
600. Communication between the Nose and 
the Frontal Sinuses, etc.-There are in the bones 
at the back of the nose openings to minute channels 
which lead to the frontal sinuses-paragraph 115- 
and to the antra of highmore-paragraph 127- 
and inflammatory conditions in the nose frequently 
extend through the channels into these cavities. 
601. The Mouth.-As the anatomy of the 
mouth is more especially adapted to the processes 
connected with digestion rather than respiration 
it will be described with the organs of digestion. 
602. The Pharynx.-Form and Position.-The 
pharynx forms a part of both the respiratory and 
digestive systems. It is a musculo-membranous 
sac, somewhat conical in form, with its base 
upward and its apex downward. It extends from 
the under surface of the skull to the esophagus, 
behind the nose, mouth, and larynx. Its upper 
portion, which opens into the nose, is called the 
naso-pharynx. The part seen when looking into 
the mouth when the tongue is depressed is known 
as the oraT-pharynx, and the lowest portion is 
known as the laryngo-pharynx. 
1 From the Latin oro-to speak. Respiratory Organs and Respiration 
303 
603. Adenoid Tissue of the Pharynx.-In 
the mucous membrane of the pharynx there is a 
considerable amount of adenoid or lymphoid tis- 
sue. This sometimes, especially in the naso- 
pharynx, during infancy and childhood, increases 
to such an extent that it interferes with respiration, 
and the child is then said to have adenoids. Other 
masses of lymphoid tissue in this part of the body 
are the tonsils. These will be described in para- 
graph 691. 
604. Apertures of the Pharynx.-There are 
seven openings in the pharynx, viz.: the two pos- 
terior nares communicating with the nose; the 
two Eustachian1 tubes leading to the ears; the 
esophagus, the tube leading from the pharynx to 
the stomach; the larynx, the tube leading to the 
bronchi and thence to the lungs; the mouth. 
The Larynx 
605. Position.-The larynx is situated at the 
upper and fore end of the neck, between the 
trachea and the base of the tongue, below and in 
front of the pharynx. 
606. Shape.-At its juncture with the trachea 
the larynx is narrow and of a cylindrical form, but 
its upper portion is broader and is shaped some- 
thing like a triangular box flattened behind and 
at the sides, but slightly rounded in front. 
607. Cartilages of the Larynx.-The lar- 
1 Named after a famous anatomist. 304 
Anatomy and Physiology 
ynx is composed of nine bands of fibro-cartilage 
held together with elastic ligaments and muscles 
and covered with mu- 
cous membrane. The 
five most important 
pieces of cartilage are: 
The epiglottis 
The cricoid 
The thyroid 
The two arytenoids 
6o8. The Epiglot- 
tis. 1- The epiglottis 
is a thin, leaf-shaped 
piece of cartilage that 
is attached to the up- 
per edge of the thyroid 
by its smaller extrem- 
ity, between the base 
of the tongue and the 
larynx. During respiration its free end is directed 
upward and thus does not interfere with the 
passage of air into the larynx; but when the larynx 
is drawn beneath the tongue in the movements 
incidental to deglutition-swallowing-the epiglot- 
tis is carried downward and backward so that it 
completely covers the opening of the larynx and 
thus prevents food or liquids entering the larynx. 
609. The Thyroid2 Cartilage.-Shape and 
Fig. 103.-Laryngeal cartilages 
and ligaments from in front. 
1 From the Greek epi-upon and glossa-the tongue. 
2 From the Greek thyro-a shield and eidos-form. Respiratory Organs and Respiration 
305 
Location. The thyroid is the largest cartilage of 
the larynx. It is shaped something like a shield, 
and is situated in the upper part of the larynx, in 
the front of the neck, where it forms a projection 
known as Adam's Apple. 
6io. The Cricoid1 and Arytenoids.2-The 
cricoid cartilage is situated below the thyroid. 
In shape it resembles a seal ring, the seal portion 
forming the back and the circular part the front. 
Attached to this at the back are two pyramid- 
shaped cartilages, the arytenoids. 
611. The Vocal Cords.-Attached to the 
thyroid cartilage in front and to the arytenoids at 
the back, and thus stretched across the larynx, 
are the two fibrous elastic bands that are known 
as the vocal cords, because they are the principal 
factor in the production of the voice. Their action 
will be described in the paragraph devoted to the 
description of the voice. 
612. The Glottis.-Between the two cords 
is a narrow fissure that is known as the glottis or 
rima glottidis. The shape of the glottis changes 
continually, the change being controlled by the 
laryngeal muscles. During quiet breathing it is 
V-shaped, becoming a little wider during inspira- 
tion. During forced inspiration it becomes almost 
round, and in singing, when taking a high note, 
the glottis is almost completely closed. 
613. The False Vocal Cords.-Above the 
1 From the Greek krikos-a ring and eidos-form. 
2 From the Greek arytaina-a cup (cup-shaped.) 306 
Anatomy and Physiology 
true vocal cords are two bands of mucous mem- 
brane, each enclosing a thin elastic band. These 
are the false vocal cords, so called because they are 
not concerned in the production of the voice. 
The Trachea1 
614. Size and Location.-The trachea, or 
windpipe, is a straight, flexible tube about four 
and a half inches in length and three quarters to 
one inch from side to side. It lies in.front of the 
esophagus and extends from the larynx on a 
level with the sixth cervical vertebra to opposite 
the fourth dorsal vertebra, where it divides into 
two tubes known as the bronchi. 
615. Structure.-The trachea is composed 
of muscular, fibrous, and elastic tissue, stiffened, 
except at the back, with rounded bands of fibro- 
cartilage and lined with mucous membrane that 
is covered with ciliated epithelium; the purpose of 
the ciliated epithelium being to protect the air 
passages from the entrance of dust and other 
deleterious substances. 
The Bronchi2 
616. Position.-The bronchi are two tubes 
which branch off on either side from the termina- 
tion of the trachea. The one on the right side 
1 From the Latin trachia-the windpipe. Derived from the 
Greek trachys-rough. So called on account of the marked 
inequalities felt on its surface. 
3 From the Greek bronchos-the windpipe. Fig. 104.-Bronchi and bronchioles. The lungs have been widely 
separated, and tissue cut away to expose the air-tubes. (Gerrish.) Respiratory Organs and Respiration 
307 
goes to the right lung, that on the left to the left 
lung. 
617. Branches of the Bronchi and their 
Subdivisions.-As soon as a bronchus enters a 
lung numerous branches are given off. These 
branches in turn give rise to numerous smaller 
branches called bronchioles. Each bronchiole 
terminates in small funnel-shaped enlargements 
known as infundibular and from the outer edge 
of each infundibulum extend innumerable small 
finger-shaped sacs called the alveoli2 or air-cells. 
618. Structure of the Bronchi. Like the 
trachea, the bronchi are constructed of muscular, 
fibrous, and elastic tissue, stiffened, so that they 
will remain constantly as rounded, open canals, 
with bands of fibro-cartilage, and lined with mu- 
cous membrane covered with ciliated epithelium. 
619. Structure of the Bronchioles, In- 
fundibula, and Alveoli.-The structure of the 
larger bronchioles is similar to that of the bronchi, 
but the smaller ones have no fibro-cartilage and 
less fibrous tissue. The walls of the infundibula 
are about the same as the smaller bronchioles, but 
those of the alveoli are composed of an exceedingly 
thin film of muscular and elastic tissue lined with 
mucous membrane. 
The Lungs 
620. Position and Shape.-The lungs are the 
1 Latin infundibulum-a funnel (plural infundibula.) 
3 Sing., alveolus. Latin, a little trough. 308 
Anatomy and Physiology 
two large organs which fill the thoracic cavity, 
except for the space occupied by the air-passages, 
the heart, the large blood-vessels, lymphatics and 
esophagus. In shape they resemble cones with 
concave bases. The bottom or base of each cone 
rests upon the diaphragm, and the top or apex 
extends to about an inch above the first rib. 
621. Structure.-The lung substance, which 
is soft and sponge-like, consists of the bronchioles 
and their terminations-the infundibula and al- 
veoli-innumerable blood-vessels, lymphatics, and 
nerves, held together by elastic connective-tissue 
and covered by a serous coat which is derived 
from the pleura, as described in paragraph 627. 
622. Lobes and Lobules.-The substance of the 
lungs is divided by deep fissures into lobes-the right 
into three and the left into two. The lobes are again 
divided by smaller depressions into lobules. 
623. Difference in the Size of the Lungs. 
-The right lung is broader and heavier than the 
left, but it is somewhat shorter on account of the 
position of the liver, which extends higher in 
the abdomen than do any of the other abdominal 
organs. The left lung is not only narrower but is 
more deeply indented than the right, in order to 
provide space for the heart, which, it will be 
remembered, extends much farther to the left 
than to the right side. 
624. The Hilum.1-On the inner surface of 
1 Latin hilum-a little thing. The word is used in anatomy 
to designate a small fissure or depression. Respiratory Organs and Respiration 
309 
each lung, very near the center, is a depression 
known as the hilum, through which the bronchus, 
blood and lymphatic-vessels, and nerves enter and 
leave the lung. 
625. Nerve Supply.-The nerve supply of 
the substance of the lungs is derived from the 
sympathetic system and from branches of the 
tenth cranial nerves known as the pneumogastric 
or vagi. The part which these nerves take in 
respiration will be discussed in paragraphs 638 
and 639. 
626. Blood Supply.-Blood is brought to the 
lungs from the heart through branches of the 
bronchial and pulmonary arteries. The former 
contain the blood needed for the nourishment of 
the heart, and on entering the hilum give off 
branches, from which capillary extensions go to all 
parts of the lung substance-the connective tissues, 
the walls of the blood-vessels, etc. The pulmon- 
ary arteries1 carry from the right ventricle to the 
lungs the blood which has been through the sys- 
tem, giving up its oxygen and gathering carbon- 
dioxide. On entering the lungs the pulmonary 
arteries give off numerous branches which gradu- 
ally pass into capillaries that form a plexus or 
network around the infundibula and alveoli. 
The walls of both the capillaries and the air sacs 
1 It will be remembered that there is but one pulmonary 
artery opening from the heart, but that about two inches from 
its origin this artery divides into two branches, one of which 
goes to the right and the other to the left lung. Anatomy and Physiology 
310 
oeing exceedingly thin and of such a nature that 
gases can readily diffuse through their membrane, 
an interchange of carbon-dioxide and oxygen read- 
ily takes place. The forces which further this 
diffusion of gases will be considered in connection 
with the respiration. 
The Pleura1 
627. Nature.-Each lung is invested upon its 
external surface with an exceedingly delicate serous 
membrane named the pleura, which encloses the 
organ as far as its root and is then reflected upon 
the inner surface of the thoracic wall, thus forming 
a closed sac. The portion of the sac covering the 
lung is called the visceral layer, and that covering 
the chest wall is called the parietal layer. The 
space between the two layers is called the cavity 
of the pleura. The space, however, is very minute, 
the lung and the chest wall being almost in contact. 
628. Function.-The function of the pleura 
is to secrete a lubricating liquid which prevents 
friction between the lungs and the chest walls 
during the movements of respiration. 
629. Pleurisy.-This is the name given to an 
inflamed or irritated condition of the pleura which 
sometimes occurs. There are two types of the 
disease; in one there is a lack of the lubricating 
secretion and when, at each inspiration, the two 
roughened layers of pleura come in contact, great 
1 From the Greek pleura-a rib. Fig. 105.-Diagram of a lobule of the lung. A bronchiole is seen dividing 
into two branches, one of which runs upward and ends in the lobule. In 
the lobule are four groups of infundibula. At the left are two infundibula, 
the alveoli of which present their outer surfaces. Next are three infundi- 
bula in vertical section, the alveoli of each opening into the common 
passageway. Upon the ultimate bronchiole of this group are alveoli. In the 
next group the first infundibulum shows a pulmonary arteriole surround- 
ing the opening of each alveolus, and the second gives the same with the 
addition of the close capillary network in the wall of each alveolus. The 
same arrangement of vessels is seen in the alveolus upon the bronchiole 
of this group. Around the fourth group is a deep deposit of pigment, such 
as occurs in old age, and in the lungs of those who inhale coal dust and the 
like. On the bronchiole lies a branch of the pulmonary arteries (blue), 
bringing blood to the infundibula for aeration. It also supplies nourishing 
blood to the tubes and other structures within the lobule. Beginning be- 
tween the infundibula are the radicles of the pulmonary vein (red), a root 
of which lies upon the bronchiole. The bronchial artery is shown as a 
small vessel bringing nutrient blood to the bronchiole (outside of the lobule), 
the artery and vein, and all of the structures between and around the lobule. 
No attempt is made to show the sustentacular tissue which occupies the 
spaces within and around the lobule. (Gerrish.) Respiratory Organs and Respiration 
311 
pain is produced. This type is called dry pleurisy. 
In the second form, known as pleurisy with effusion, 
there is an over-abundant secretion of fluid. There 
is usually less actual pain with this type of the 
disease, but it interferes very seriously with 
respiration. 
630. Mediastial Space.-The space left in the 
median line of the chest by the non-approximation 
of the two pleurse is known as the mediastial space. 
It extends from the sternum in front to the spine 
behind. 
External Respiration 
631. Of What it Consists.-External respira- 
tion consists of the alternate expansion and con- 
traction of the chest walls and the lungs by means 
of which air is drawn into and expelled from the 
lungs. The first action is known as inspiration; 
the second is known as expiration. 
632. Mechanism of Inspiration.-During in- 
spiration the diaphragm1 contracts, its dome be- 
comes flattened and is pulled downward, its sides 
are drawn away from the chest walls. At the same 
time the contraction of certain of the muscles of 
the thorax (see next paragraph) elevates the ribs 
in front and at the sides; the size of the thorax is 
thus considerably enlarged, and as the lung sub- 
stance expands in keeping with the sides and floor 
1 The action of the diaphragm is much more pronounced in men 
and children than in women. This is thought to be due to a 
difference in clothing rather than to physiological differences. 312 
Anatomy and Physiology 
of the thorax a vacuum is created in the air-cells, 
which the outside air is sucked in to fill. 
633. Muscles Concerned in Inspiration.- 
These are the diaphragm, the external intercostals, 
part of the internal intercostals, the scaleni, the 
levatore costarum, the muscles of the glottis, and, 
in hurried or forced breathing, those around the 
nostrils. 
634. Mechanism of Expiration.-In expira- 
tion the lungs and the thorax return to the position 
and size they occupied before the act of inspiration, 
and air is thus expelled from the lungs. Quiet 
expiration is an almost passive act, due in part to 
the elastic recoil of the muscles and tissues in- 
volved in inspiration. In forced expiration, howT- 
ever, many of the abdominal muscles are involved. 
These act (1) by pressing the abdominal vis- 
cera against the diaphragm and thereby forcing 
it up; (2) by drawing down the ribs and costal 
cartilages.1 
635. Nature of Respiratory Movements.- 
Respiration is both a voluntary and an involuntary 
act; that is to say, it can be controlled to a cer- 
tain extent by the will, but, except on occasion, it 
proceeds without any voluntary effort. In fact, 
any attempt to modify the respiratory rhythm 
will soon cease from one or other of two causes, 
viz.: (1) conscious effort wall be followed by such a 
sense of fatigue that it will soon be discontin- 
1 It will be remembered that the abdominal muscles are 
attached to the ribs and costal cartilages. Respiratory Organs and Respiration 
313 
ued; (2) continued suppression of respiration will 
produce an abnormal increase in the amount 
of carbon-dioxide in the blood, which, by stimu- 
lating that part of the medulla oblongata known 
as the respiratory center, will eventually cause 
inspiration. 
636. Cause of Inspiration.-Unlike the beat 
of the heart, the respiratory movements are en- 
tirely dependent on the nervous system, especially 
that part known as the respiratory center. Ana- 
tomically the respiratory center has not been 
sharply localized further than that it is in the 
medulla oblongata and below the center which 
controls the vasomotor system. It is brought 
into relation with the muscles of respiration by 
efferent nerves which, arising in the center (1) 
pass down the cord and end in the gray matter 
there at the different levels at which the motor 
nuclei of the respiratory nerves are situated, and 
(2) which pass on to such of the motor centers of 
the vagus and facial nerves as are connected with 
any of the muscles of respiration. The impulses 
arising in the respiratory centers are thus trans- 
mitted to the nerves which cause action in the 
muscles concerned in the act of inspiration. 
637. Causes of the Activity of the Res- 
piratory Center.-Numerous experiments have 
shown conclusively that the respiratory center, 
like the heart, works automatically-i. e., the 
stimuli discharged from it are produced within its 
own cells-but that it is also very easily affected 314 
Anatomy and Physiology 
by afferent impulses. The stimulus causing the 
automatic action of the respiratory center is, 
however, different from that affecting the heart. 
It has been found that an excess of oxygen in the 
blood will cause the respiratory center to cease 
acting, in other wrords to become apneic,1 and that 
the same effect will follow the quick removal of 
carbon-dioxide. Therefore, it is now the generally 
accepted theory that the usual stimulus activating 
the respiratory center is the carbon-dioxide which 
the blood gathers from the tissues in its voyage 
through the body. This accounts for the increased 
rate of respiration in fever-the excessive oxida- 
tion that is going on wThen the temperature is high 
being naturally associated with an increased pro- 
duction of carbon-dioxide. 
638. Influence of the Sensory Nerves on 
the Respiratory Center.-Though the respira- 
tory center works automatically, it is also influenced 
by sensory nerves passing to and from the brain. 
This is shown by the changes caused in respiration 
by any strong stimulation of such nerves, as by 
sudden pain, strong emotion, cold, etc. Hence 
one reason for inducing pain in the treatment for 
opium poisoning, this drug causing death by de- 
pression of the respiratory center. 
639. Effect of the Vagi on Respiration.- 
If the branch of a vagus nerve which supplies 
fibers to the respiratory organs is cut, the rate of 
respiration is much increased. If the branches 
1 From the Greek apnoia-want of wind. Respiratory Organs and Respiration 
315 
from both the vagi are cut the acceleration is even 
more marked. It has therefore been concluded 
that the vagi regulate the speed of the respiratory 
movements. Experiments seem to prove also 
that the fibers from the vagi which supply the 
lungs are of two kinds: (i) inspiratory fibers, which 
tend to increase the rate of respiration, and (2) ex- 
piratory fibers, which inhibit the action of the 
inspiratory set. The inspiratory fibers are stimu- 
lated to action by the collapse of the lung, and the 
expiratory by the expansion of the lung. 
640. Causes of Expiration.-It is now 
thought by many physiologists that the respira- 
tory center would have been more correctly named 
the inspiratory center; normal respiration actually 
consisting of an active inspiratory act followed by 
a passive expiratory movement due, as stated in 
paragraph 634, to the elastic recoil of the muscles 
engaged in inspiration; and in forced respiration, 
as in dyspnea, coughing, etc., when expiration does 
become an active movement, it is not known what 
activates the nerves supplying the muscles en- 
gaged in the action. Some authorities consider 
that the nerve stimulation comes from the respira- 
tory center as the result of extra stimulation arising 
in dyspnea, from an excessive amount of carbon- 
dioxide in the blood, or in coughing, etc., from 
increased nerve impulses from the sensory nerves. 
But other physiologists think that the nerve 
impulses which activate the muscles causing 
active expiratory movements are derived from 316 
Anatomy and Physiology 
a different center as yet undiscovered-an ex- 
piratory center. 
641. Cause of the First Respiratory Move- 
ment.-The fetus, during intra-uterine life, re- 
ceives its necessary supply of oxygen and gives off 
carbon-dioxide by means of the blood-vessels of 
the umbilical cord, which connects its circulatory 
system with that of the mother. Its lungs are 
therefore unnecessary during that time, and re- 
main in a collapsed condition until the first breath 
is taken at birth, when the lungs become filled 
with air and the respiratory center starts the 
automatic action that continues until death. The 
causes of the starting of activity are supposed to 
be: (1) the increased venosity of the blood due to 
the cutting of the umbilical cord; (2) stimulation 
from the sensory nerves due to cooler1 air on the 
skin, handling, etc. 
642. Causes of Interchange of Gases that 
Takes Place in Respiration.- It has been 
stated repeatedly in the preceding pages that 
carbon-dioxide passes from the blood and oxygen 
into the blood while it is flowing through the pul- 
monary capillaries. The reason the carbon-dioxide 
leaves the blood is that the latter is passing 
through a region in which there is less carbon- 
dioxide than in itself, and the tendency of gases is 
always to mix in uniform proportion.2 Following 
1 The child while in utero has been in an atmosphere with a 
temperature of about ioo° F. 
2 See Diffusion of Gases-Glossary. Respiratory Organs and Respiration 
317 
this same tendency, the oxygen, being pres- 
ent in larger amounts in the air-cells than 
in the blood, passes from the alveoli into the 
capillaries. 
643. Internal Respiration.-By internal 
respiration is meant the interchange of gases- 
oxygen and carbon-dioxide-that takes place be- 
tween the blood and the tissues, as the blood flows 
through the capillaries in all parts of the body. 
The reasons for this interchange are the same as 
those causing the exchange in the lungs: (1) there 
is always a larger amount of carbon-dioxide in 
the tissues than in the blood, because it is con- 
stantly being formed in the former as the result 
of metabolism; (2) there is less oxygen in the 
tissues than in the blood-in fact, there is practi- 
cally no free oxygen in the tissues, for on entering 
them it at once combines with substances therein. 
Therefore, the carbon-dioxide passes from the 
tissues to the blood, and the oxygen from the blood 
to the tissues. 
644. Changes in the Blood Due to Res- 
piration.-The principal changes that take 
place in the blood due to respiration are: (1) 
it gains oxygen; (2) it loses carbon-dioxide; 
(3) in consequence of these changes, it assumes 
a redder color; (4) it becomes slightly cooler. 
The comparative degree of pressure due to 
carbon-dioxide and oxygen in the alveoli, ar- 
terial and venous blood, and the tissues is as 
follows: 318 
Anatomy and Physiology 
OXYGEN 
CARBON-DIOXIDE 
Alveoli 
Venous Blood... 
Arterial Blood. . 
Tissues 
ioo mms 
37-6 " 
IOO " 
o 
35-40 mms 
42.6 
35 
50 to 70 " 
645. Normal Rate of Respiration.-The 
average rate of respiration for a healthy adult is 
about 18 respirations per minute, but it is quicker 
in childhood and infancy, and somewhat slower 
in the aged. It may vary, however, very consider- 
ably, even in health, for it becomes accelerated as 
the result of muscular exercise, etc.-in fact, any- 
thing that influences the heart-beat will, ordinarily, 
have a like effect upon the respirations, and, 
except in diseased conditions, the ratio of the 
respiration and heart-beat remains about 1 to 4 or 
1 to 5. 
Terms Used in Describing the Quantity of Air 
Breathed and the Capacity of the Lungs 
646. Tidal Air.-At each inspiration an aver- 
age-sized man inspires and expires about 500 c.cm. 
(30 cubic inches) of air. This amount of air 
exchanged is called breathing or tidal air. 
647. Complemental Air.- By taking a deep 
inspiration, 1600 c.cm. (100 cubic inches) over and 
above that inhaled in tidal air can be taken into the 
lungs. This is called complemental air. 
648. Reserve Air.-All the air contained in Respiratory Organs and Respiration 
319 
the lungs is not expelled with each expiration, 
and the amount remaining that could be expelled 
with a forced expiration is called the reserve air. 
The average amount of reserve air in the adult is 
about 1600 c.cm. (100 cubic inches.) 
649. Vital Capacity.-The vital capacity or, 
as it is sometimes termed, the respiratory capacity 
of the lungs constitutes the quantity of air which 
a person can expel from his lungs after a forcible 
expiration following the deepest inspiration possi- 
ble. The average capacity in the adult is about 
3500 c.cm. (225 cubic inches). The vital capacity 
is the sum total of the tidal, complemental, and 
reserve air. 
650. Residual Air.--The lungs cannot be 
completely emptied, even by forcible expiration, 
and the amount which remains after the reserve 
air has been expelled is termed residual air. The 
quantity of residual air varies considerably, as it 
depends upon the size of the chest, but it has 
been estimated at averaging about 1600 c.cm. 
651. Forces Causing Movement of Air in 
the Lungs.-It is not to be understood from the 
foregoing paragraph that any definite part of air 
in the lungs is residual air, for the air is being 
constantly moved in the lungs and therefore in 
the course of time renewed. The forces which 
cause the mixing and movement of the air in the 
lungs are1: (1) the alternate expansion and shrink- 
ing of the lungs in the movements of respiration; 
1 See Glossary. 320 
Anatomy and Physiology 
(2) the pulsation of the arteries; (3) the convection 
currents due to the inequalities in temperature 
between the air in the lungs and the freshly 
inspired air; (4) the difference in the proportion of 
carbon-dioxide and oxygen in the inspired air and 
the residual air. 
652. Changes in the Air as the Result of 
Respiration.-The air as it is taken into the 
lungs-inspired air-consists of nitrogen, oxygen, 
and carbon-dioxide in the following proportions: 
NITROGEN 
OXYGEN 
CARBON-DIOXIDE 
79 per cent. 
20.96 per cent. 
0.04 per cent. 
The comparative proportion of these gases in 
expired air is: 
NITROGEN 
OXYGEN 
CARBON-DIOXIDE 
79 per cent. 
16.02 per cent. 
4.38 per cent. 
Thus the air loses 4.94 volumes of oxygen and 
gains 4.34 volumes of carbon-dioxide. Other 
changes in the expired air are an increase of 
temperature and of moisture, expired air being, 
regardless of the temperature of the inhaled air, 
about the temperature of the blood, and almost, if 
not quite, saturated with moisture. Some authori- 
ties consider that there is also some form of toxic 
matter present in expired air, but this has never 
been proved. 
653. Bad Effects of Poor Ventilation.- 
The usual consequences of remaining in a badly Respiratory Organs and Respiration 
321 
ventilated room are a feeling of general discomfort, 
headache, languor, and a sense of oppression. It 
is a well-known fact, however, that people can 
become so accustomed to a lack of fresh air that 
its absence causes them little discomfort; but they 
are, nevertheless, affected by it, as is constantly 
demonstrated by the lack of vitality shown by 
those who live in poorly ventilated quarters. The 
exact reason for the ill effects of poor ventilation 
is not known. Formerly they were thought to 
be due to the volatile organic matter and C02 
given off in the respiration, but experiments have 
tended to prove that in average ill-ventilated 
buildings there is not sufficient CO2 to produce 
poisoning and that the organic matter, which 
comes principally from the stomach and particles 
of food left in the mouth, is not poisonous, and 
many authorities consider that the injurious effects 
are due solely to the interference in heat regula- 
tion1 by the increased moisture and temperature, 
and to the lack of oxygen. 
654. Amount of Ventilation and Air Space 
Necessary to Prevent Vitiation of the Air.- 
In order to prevent the air indoors becoming 
vitiated two things are necessary: (1) the air must 
be changed constantly; (2) the size of rooms must 
be in proportion (a) to the number of people who 
are to inhabit them; (6) the quality of the facilities 
for ventilation; (c) the degree of air contamination 
likely to occur. Calculations based upon the 
1 Described in Chapter XIX. 322 
Anatomy and Physiology 
amount of air taken into the lungs at each inspira- 
tion, and the changes caused in it during its stay 
in those organs, show that each individual re- 
quires as a minimum 1000 cubic feet of air space,1 
and this size space is only adequate when there is 
sufficient ventilation to change the whole air of 
the room in the course of every twenty minutes. 
In hospitals, factories, and other places where air 
is likely to become vitiated more quickly than in 
dwelling houses, a greater air space should be 
allowed for each individual. The following table 
gives the amount of air space required per capita 
in different institutions, when the air can be com- 
pletely renewed in the course of every 30 minutes: 
"Hospitals 30-5° cubic meters" 1 
Prisons 25 " 
Factories 30-50 " 
Barracks 15-23 " 
Theaters 20-25 " 
Halls and Assembly Rooms.. 15-30 " 
Schools 7-5~10 " 
Classrooms for Adults 12-15 " 
Abnormal Types of Respiration 
655. Dyspnea.-By dyspnea is meant difficult 
or labored breathing. The more common causes 
of the condition are: (1) over-stimulation of sensory 
nerves, especially those causing pain in the lungs; 
1 Text-Book of Physiology, page 648. Howell. W. B. Saunders 
Co. Respiratory Organs and Respiration 
323 
(2) an increased venosity of the blood-i. e., an 
abnormal increase in the per cent, of carbon- 
dioxide; (3) a marked decrease of oxygen in the 
blood. Dyspnea, as the result of an increased per 
cent, of carbon-dioxide and lack of oxygen in the 
blood, is likely to occur in any condition in which 
the normal rate of respiration and of the heart- 
beat is seriously interfered with, and where there 
is any interference with the passage of air to and 
from the lungs. 
656. Cheyne-Stokes Respiration.-This form 
of respiration was so called because of the two 
doctors who first discovered it. Its actual cause 
is unknown. It is frequently associated with 
advanced brain, heart, and kidney diseases, and 
has been observed in perfectly healthy children 
during profound sleep. It appears in two forms: 
In one, the respirations gradually increase in 
force and frequency up to a certain point and then 
as gradually decrease until they entirely cease; a 
short pause then ensues and the respirations begin 
as before. In the other form, - the respirations 
gradually increase in force and frequency, as in 
the former case, but they cease suddenly, instead 
of decreasing gradually. The phenomena may con- 
tinue for some time and then cease, or it may 
continue and cause marked dyspnea. 
657. Edematous Respiration.-The so-called 
edematous respiration or breathing is the result of 
the infiltration of fluid from the lung capillaries 
into the air-cells. It is recognized by the moist Anatomy and Physiology 
324 
rattling sounds-rales-that follow each inspira- 
tion. It is a very serious condition, for, unless 
relieved, asphyxia will follow. 
658. Asphyxia.-Asphyxia may be produced 
by any continual interference with the aeration of 
the blood, either by direct obstruction to the 
entrance of air to the lungs, or by any condition 
that prevents a due interchange of gases between 
the air and the blood. The condition is associated 
with severe dyspnea, the expiratory efforts become 
very forced and convulsive, and, unless the con- 
dition is relieved, the convulsive movements may 
become general and be followed by exhaustion and 
death. The convulsions are the result of stimula- 
tion of motor nerves from impulses due to the 
over-stimulated respiratory center, the stimula- 
tion of the respiratory center being the outcome 
of the extreme venosity of the blood. 
659. Modified Respiratory Movements.- 
There are several actions, such as laughing, sobbing, 
sighing, hiccoughing, coughing, sneezing, speak- 
ing, singing, etc.-, that are classed as modified res- 
piratory movements because in their performance 
some of the same muscles are brought into action 
as are used in respiration, but further than this 
they have nothing to do with the process of 
respiration. The differences in the sounds pro- 
duced in these actions is largely dependent upon 
the relative force and rate of inspiration and 
expiration and the degree of dilatation of the rima 
glottidis at the time of these actions, thus: Respiratory Organs and Respiration 
325 
Laughing consists of a series of short and rapid 
expirations, during which the glottis is open. 
Sobbing consists of a series of convulsive inspira- 
tions during which the glottis is closed. 
Sighing consists of a prolonged inspiration fol- 
lowed by a sudden expiration. 
Hiccough resembles sighing, but the inspiration 
is sudden instead of gradual, and is followed by a 
spasmodic contraction of the diaphragm which 
forces the air back toward the rima glottidis while 
the latter is still closed-hence the peculiar sound. 
Common causes of it are irritation of the phrenic 
nerve, or of sensory nerves of the stomach or 
intestines. 
Speaking is a more complicated action than any 
of those already mentioned. During speaking, the 
glottis is more or less closed and the vocal cords in 
a state of tension, so that when there is a volun- 
tary expulsion of air from the lungs by means of 
the expiratory muscles it forces its way through 
the glottis and as it does so sets the vocal cords in 
vibration; this produces sound. Language is made 
up of the elementary sounds known as vowels and 
consonants. The difference between the two sets 
of sounds and of the various sounds belonging to 
both sets is obtained principally by changing the 
shape of the resonance cavities1-the pharynx, 
1 These cavities are called the resonance cavities because by 
alteration of their size and shape they pitch out and emphasize 
certain component parts of the fundamental tones produced in 
the larynx. 326 
Anatomy and Physiology 
mouth, and nasal passages, and the tongue, lips, 
and palate. In making consonant sounds the air 
or voice is more or less obstructed by means of the 
lips, teeth, tongue, and palate. 
Whispering is performed with the glottis par- 
tially open and the air passing through so gently 
that the vocal cords are not set in motion. 
Singing resembles speaking in the manner of its 
production, but it entails more frequent alteration 
in the shape of the resonance chambers, in the 
shape of the glottis, and consequently the tension 
of the vocal cords, and in the force of the expira- 
tory movements which set the cords in vibration. CHAPTER XVI 
THE GLANDS 
Glands: Their Nature, Function, and Classification. Nature 
of Secretions. Names of the Secretory Glands. Names, of the 
Ductless Glands and Other Organs Furnishing Internal Secre- 
tions. Location and Function of the Thyroid, Parathyroids, 
Thymus, Suprarenal Capsules, and Pituitary Body. The 
Function of the Internal Secretion of the Pancreas, Ovaries, 
Kidneys, Liver. .Names of the Excretory Glands. The Spleen: 
Function, Location and Structure. 
660. Definition.-A gland is an organ which 
has the power of abstracting specific material from 
Fig. 106.-Diagram showing development of glands: A, a 
mere dimple in the surface; B, enlargement by division; C, en- 
largement by dilatation; D, a combination of B and C; E, a 
racemose gland; F, development of method of E; G, a single 
tube intricately coiled. (Gerrish.) 
the blood flowing through its substance, and, in 
some cases, of transforming this material into 
matter of a different nature. 
327 Anatomy and Physiology 
328 
661. Characteristics.-Glands vary consid- 
erably in their size and structure, some being mere 
depressions in a membrane or tissue, and others, 
as the liver, large and 
complex organs. 
They all have, how- 
ever, certain charac- 
teristics in common, 
viz.: they contain 
secretory cells, a lib- 
eral blood supply, 
and their action is 
controlled by the ner- 
vous system. The 
usual arrangement of 
the secretory cells and 
blood-vessels is for 
the former to cover 
the free side of 
a thin basement 
membrane and the 
capillaries to be 
spread in a dense 
network upon its 
under surface. This 
membrane with its cells and capillaries is found 
arranged in several different shapes (see Fig. 106), 
and according to the form it assumes the gland is 
known as (I) a simple tubular or saccular gland, or 
if one end of the tube is coiled, as in the sweat 
glands (see Fig. 106), a simple convoluted tubular 
Fig. 107.-Compound tubular 
gland. The upper part is the 
duct; the lower is the secreting 
portion. (Gerrish.) The Glands 
329 
gland-, (2) a compound tubular gland (see Fig. 
107); (3) a compound saccular or racemose1 gland 
(see Fig. 108). 
662. The simple glands are formed by a secret- 
ing membrane dipping down into the substance 
beneath it in such a manner as to form innumerable 
minute tubes, each one having an opening or duct 
at the free sur- 
face. The tubu- 
lar glands in the 
stomach and 
some of those in 
the intestine are 
of this type. 
663. In a com- 
pound tubular 
gland there are 
a number of 
branching tubes 
all opening into 
one duct. In some glands the free ends of the 
branching tubes are convoluted; the glands of the 
kidneys and pancreas are of this type. 
664. A racemose gland is composed of groups 
of small sacs which open into a common duct. 
The salivary glands are examples of this type. 
665. Ductless Glands.-The glands thus far 
described all have ducts through which the secre- 
tions they manufacture reach the surface of the 
membrane or the interior of the cavity in which 
Fig. 108.-Compound racemose 
gland. The resemblance to a bunch 
of fruit is very marked. (Gerrish.) 
1 From the Latin racemus-a cluster of grapes. Anatomy and Physiology 
330 
they are contained. There are, however, some 
glandular organs in the body which have no such 
ducts, the secretions they form being taken up by 
the blood either directly or indirectly by way of 
the lymphatics-i. e., the secretions are absorbed 
by the lymphatic vessels in the glands and carried 
to the superior vena cava. 
666. Secretory and Excretory Glands.- 
It is the office of certain glands to extract material 
from the blood and change this so that it can be 
used for special purposes in the body; such glands 
are called secretory1 glands, and the substances 
they manufacture are called secretions. Other 
glands take from the blood only such matter as is 
to be discarded or eliminated, and are therefore 
designated excretory2 glands, and the substances 
they eliminate are called excretions; but, in the 
preparation of most of the excretions, secretion is 
necessary; therefore the majority of excretory 
glands are provided with secretory cells. Also, 
some of the excretions are made use of in the 
process of their elimination from the body. Thus, 
the perspiration which is excreted by the swTeat 
glands of the skin helps to regulate the body 
temperature, and the bile, an excretory product 
of the liver, helps in the digestion of fats, and is of 
use in other ways that will be described later. 
In fact, the bile is of use in so many ways that it is 
called a secretion as often as an excretion. 
1 From the Latin se-aside and cerno-separate. 
2 From the Latin ex-out and cerno-separate. The Glands 
331 
667. Nature of Secretions.-Secretions may 
be divided into four classes, viz.: (1) Simple 
secretions, the purpose of which is to lubricate 
or moisten the surface upon which they are 
discharged, and which differ very little from the 
substance extracted from the blood for their 
manufacture. Of this nature are the secretions 
of the membranes described in Chapter X, and the 
secretion of the lachrymal glands; (2) secretions 
containing substances very different from anything 
that pre-existed in the blood, among other things 
one or more organic substances known as ferments 
or enzymes, which aid in causing the chemical 
changes that take place in food during digestion; 
(3) the secretion of the mammary or milk glands, 
the nature and purpose of which differ from that 
of all other secretions; (4) the secretions of the 
ductless glands and of certain other glands and 
organs which are known as internal secretions. 
Very little is known of the composition of these 
internal secretions or of the precise nature of 
their function beyond that they are in some way 
or other indispensable to metabolism and that 
certain of them contain chemical substances which 
produce activity in other organs. These latter 
substances are named hormones.1 
668. Names of the Secretory Giands 
which Furnish External Secretions : 
The lachrymal glands, which secrete the tears for 
1 From the Greek hormos-a chain. Anatomy and Physiology 
332 
the purpose of moistening and keeping the con- 
junctiva of the eye free from foreign matter. 
The sebaceous glands of the skin, that secrete an 
oily substance which lubricates the skin and serves 
other purposes that will be described in'Chapter 
XXI. 
The glands which manufacture the fluids or 
juices required for the process of digestion, viz.: 
the salivary, gastric, and intestinal glands, the 
pancreas, and liver. These will be described with 
the organs of digestion. 
The mammary glands, which after parturition 
supply milk for the nourishment of the infant. 
669. Names of the Ductless Glands and 
of Other Glands and Organs which Furnish 
Internal Secretions.-The principal ductless 
glands are: the thyroid, parathyroids, thymus, supra- 
renal capsules, and hypophysis. The other glands 
and organs that furnish secretions which reach 
their destination by way of the blood are: the 
pancreas, liver, kidneys, and ovaries. 
670. The Thyroid.-This organ consists of 
two small oval masses of glandular tissue, situated 
one on either side of the trachea just below the 
thyroid cartilage. The two masses, or lobes, are 
connected at their lower end by a small mass of 
similar tissue named the isthmus. Little is known 
of the nature and specific action of the secretion 
of the thyroid, but if the gland be removed or 
destroyed a condition known as myxoedema results, 
and the individual's whole system, physical and Fig. 109.-Diagram showing the thyroid body and contiguous blood- 
essels. The Glands 
333 
mental, so deteriorates that unless he receives 
proper treatment he frequently becomes a hope- 
less idiot. The treatment consists of 'giving ex- 
tracts of the thyroid gland of animals. When 
atrophy or destruction of the thyroid occurs dur- 
ing childhood, growth and mental development 
are arrested. This condition is known as cretin- 
ism. If, on the other hand, the thyroid gland 
becomes over-active so that there is a super- 
abundant production of thyroid secretion, a con- 
dition known as exophthalmic goitre1 results, 
prominent symptoms of which are extreme nerv- 
ousness, accelerated heart action, protrusion of the 
eyes. 
671. In addition to the main thyroid body a 
number of small masses of thyroid tissue are 
sometimes found along the trachea as far down as 
the heart; they are called accessory thyroids. Their 
function is probably the same as the thyroid. 
672. The Parathyroids.-These are small 
bodies, usually four in number, situated, as a rule, 
behind or at the side of the thyroids, but some- 
times in the substance of those bodies. Their 
function seems to be to destroy toxic material 
formed elsewhere in the body. 
673. The Thymus.2-This is a two-lobed, 
1 This is not the same as the condition known as goitre, in 
which the gland is enlarged. In goitre the secretion is not 
necessarily interfered with. 
2 From the Greek thymo-thyme, so called because the shape 
of the gland was thought to resemble the flowers of thyme. Anatomy and Physiology 
334 
elongated glandular body situated below the thy- 
roid. It is called a temporary organ because it is 
largest during intra-uterine life and infancy, and 
gradually disappears. Formerly it was said that 
it gave place to fat and lymphoid tissue during 
early childhood, but now many authorities think 
that true thymus tissue persists until puberty. 
The function of this gland is not known, but it is 
thought that it may have some relationship to the 
reproductive organs. 
674. The Suprarenal1 Capsules or Ad- 
renal Bodies.- These are two flat or cocked- 
hat-shaped bodies which rest one upon either 
kidney (see Fig. 120). They produce a secre- 
tion that has been named adrenalin, the prin- 
cipal purpose of which seems to be connected with 
the maintenance of the tone of the blood-vessels 
and heart, since extirpation of these glands 
is followed by such a loss of tone that death 
ensues. It is not known if the maintenance of 
tone is affected by the direct action of the se- 
cretion on the tissues, or if it is obtained in- 
directly by influencing the nerve-centers. An 
extract made from the suprarenal capsules of 
animals is often used in hemorrhage to pro- 
duce constriction of the blood-vessels and, when 
the heart action is weak, to improve the tone 
of the heart and vessels and thereby act as a 
heart stimulant. 
TFrom supra, a Latin preposition used as prefix with the mean- 
ing of over or above, and Latin ran-the kidney. The Glands 
335 
675. The Pituitary Body or Hypophysis. 
-This is a small, reddish-gray colored glandular 
organ situated in a depression in the central 
portion of the sphenoid bone. Judging from the 
results of injections of extracts of this gland into 
animals, it has been decided that the secretion it 
produces has a specific effect upon the organs of 
circulation and the kidneys whereby blood pres- 
sure is raised and the excretion of the kidneys 
increased, and that it has a very decided effect 
upon the metabolism of carbohydrate. Under- 
development (as in dwarfs) and excessive growth 
(as in giants), it is thought, may be due to ab- 
normalities in this gland. 
676. The Carotids, the Coccygeal, and 
Pineal Glands.-The carotids are situated near 
the bifurcation of the carotid arteries and the 
coccygeal near the tip of the coccyx. Their 
function is unknown. The pineal body or epiphysis 
is in the third ventricle of the brain. Its nature 
changes after puberty and it is thought that it 
may in some way influence the development of 
the organs of generation. 
677. The Internal Secretions of the Pan- 
creas.-In addition to the secretion which the 
pancreas expels through its duct into the intestine 
during intestinal digestion, it also secretes an 
internal secretion that is carried by the blood to the 
tissues. This secretion seems to be one of the 
important factors in the oxidation of glucose, 
diseases of the pancreas which interfere with the 336 
Anatomy and Physiology 
production of this secretion resulting in diabetes 
mellitus-a disease characterized by a lack of 
oxidation of glucose in the tissues and its conse- 
quent appearance in the urine. 
678. Internal Secretion of the Ovaries.- 
Complete extirpation of the ovaries is followed by 
a cessation of menstruation, hypertrophy of the 
uterus, and often by distressing mental conditions, 
also a faulty metabolism that results in an in- 
crease of adipose tissue such as often follows the 
normal menopause. It has therefore been thought 
that the ovaries may produce a secretion which is 
responsible for menstruation and that influences 
metabolism. 
679. Internal Secretion of the Kidneys.- 
It is thought that the kidneys secrete a substance 
that is of importance to metabolic processes. 
680. Internal Secretion of the Liver.- 
The glycogen,1 which is made in the liver from the 
glucose, brought from the intestines by the portal 
vein, is by many authorities classed as an internal 
secretion. 
681. Names of the Excretory Glands.- 
The names of the excretory glands are: the sudor- 
iferous or sweat glands of the skin, the kidneys, 
and the liver. These glands will be described in 
other chapters. 
The Spleen 
The spleen was formerly classed with the duct- 
1 For description of glycogen, see paragraphs 15 and 799. Fig. no.-The thymus, the sternum and costal cartilages having been 
removed. The Glands 
337 
less glands, but as it apparently furnishes no in- 
ternal secretion this classification is thought not 
to be correct. 
682. Functions.-The functions of the spleen 
are as yet imperfectly understood, but the pur- 
poses usually attributed to it are: (1) that it serves 
as a location for the formation of leucocytes-the 
reason for this supposition is that the blood in the 
splenic vein contains a larger number of white 
corpuscles than that in the arteries; (2) the forma- 
tion of red corpuscles during fetal life and for a 
short time after birth; (3) the preparation of new 
hemoglobin, or the preservation of the iron set 
free by the disintegration of red corpuscles, it is 
thought, may be one of the functions of the spleen 
because there is a larger amount of iron present 
in the spleen than in other parts of the body, 
except the blood; formerly the presence of this 
iron was taken as a proof that the red cells were 
destroyed in the spleen, but now this is not 
thought, to be the case; (4) it is thought that the 
spleen may be concerned in the metabolism of 
absorbed protein food-products-the principal 
reason for this theory being that uric acid and 
other waste products of the metabolism of pro- 
teins are found therein; (5) it is considered that 
the spleen may be concerned with digestion or 
metabolism, in some way as yet unknown, because 
after a meal the organ gradually enlarges and 
then as gradually resumes its ordinary size; (6) 
some physiologists consider that the spleen may 338 
Anatomy and Physiology 
serve to modify the character of abnormal material 
in the blood, their reason for the supposition being 
the enlargement of the organ in certain diseases, as 
malaria and typhoid. 
683. Size, Shape, and Location.-The spleen 
is an oblong, bean-shaped body. Normally it 
measures from six to eight inches in length and 
weighs about six ounces, but it becomes enlarged 
in certain diseases, as malaria and typhoid. Usu- 
ally it resumes its normal size at the termination 
of the disease, but sometimes it remains perma- 
nently enlarged. It is situated directly below the 
diaphragm, behind the cardiac extremity of the 
stomach. About the center of its inner concave 
side is a depression known as the hilum, through 
which the blood and lymphatic vessels and nerves 
pass to and from the organ. 
684. Outer Coat.-The spleen is covered 
with a serous coat from which folds pass to the 
membrane covering the stomach, the peritoneum, 
kidneys, and diaphragm. These folds help to 
hold the organ in place. 
685. Structure.- If a spleen is cut open it is 
seen to consist of a dark red or violet-colored, 
spongy mass, dotted with numerous white spots. 
These spots are called the Malpighian1 or spleen 
corpztscles. They consist of a collection of minute 
bodies resembling the white corpuscles of the 
blood and are traversed by a capillary network 
derived from small branches of the splenic artery. 
1 So named from the anatomist who first described them. The Glands 
339 
The red substance of the spleen is composed of a 
spongy framework of white fibrous and elastic 
tissue, the spaces of which are filled with a pulpy 
mass called spleen pulp. This pulp consists of 
blood thickened by the addition of a large number 
of leucocytes and of a variety of corpuscles 
peculiar to the spleen called splenic cells. 
686. Blood Supply.-The circulation of the 
blood in the spleen differs from that in any other 
organ. It receives its supply from the splenic 
artery, which, just before entering the hilum, 
divides into several branches. These branches 
subdivide within the spleen, and, after the usual 
manner of arteries, the branches grow smaller 
in size, forming arterioles, but these, instead of 
merging into capillaries, end abruptly and pour 
their contents into the spleen pulp. The blood is 
collected from the pulp by small veins that, by 
gradually uniting, form the splenic vein, through 
which the blood flows to the portal vein and thence 
to the liver. CHAPTER XVII 
THE DIGESTIVE SYSTEM 
Names of the Organs of Digestion. Description of the Mouth, 
Tonsils, Tongue, etc. Location of the Salivary Glands. Loca- 
tion and Structure of the Esophagus. Divisions or Regions of 
the Abdomen. Nature and Function of the Peritoneum. Pur- 
pose, Structure, etc. of the Stomach, Small and Large Intestine, 
Pancreas, Liver, and Gall Bladder. Collection of Bile. 
687. If food is to be of use to the body it must 
pass into the blood and be carried by it to the 
tissues. In order for organic food to do this it is 
necessary for it to undergo certain changes in 
which the complex molecules of the food material 
are broken into smaller and simpler molecules and 
thus rendered of such a nature that they can be 
absorbed by the blood-vessels and the lacteals. 
These changes are spoken of as digestion, and the 
organs in which the food is contained while under- 
going these changes, as well as the organs which 
contribute in other ways to the process, are 
classed as the digestive system or apparatus. 
688. The digestive apparatus thus consists of 
the alimentary canal and the accessory organs. 
The alimentary canal, which extends from the 
mouth to the opening leading from the rectum- 
the anus - includes the 
340 The Digestive System 
341 
Mouth 
Pharynx 
Esophagus 
Stomach 
Small intestine 
Large intestine 
The accessory 
organs are: 
Teeth 
Tongue 
Salivary glands 
Pancreas 
Liver and gall 
bladder 
Anatomy of the 
Digestive Ap- 
paratus 
689. The 
Mouth or 
Buccal Cav- 
1 t y . - The 
mouth is an 
almost oval-shaped cavity which is bounded in 
front by the lips, on the sides by the cheeks, be- 
low by the larynx, above by the hard palate, and 
at the back by the pharynx. 
690. The Hard and Soft Palates and Uvula. 
-The hard palate is the bone which forms the 
Fig. hi.-Diagram of the alimentary 
tube and its appendages. (Gerrish.) Anatomy and Physiology 
342 
roof of the mouth and serves to divide it from the 
nasal cavities. It is covered with mucous mem- 
brane. The soft palate is the movable fold of soft 
tissue which is suspended from the posterior 
border of the hard palate and forms an incomplete 
septum between the mouth and the pharynx. Its 
central point- 
ed portion is 
termed the 
uvula.1 See 
Fig. 102 and 
112. 
691. The 
Fauces, 2 
Palatine 
Arches, and 
Ton sils.- 
The fauces is 
the name 
given to the 
aperture between the mouth and the pharynx. 
On either side of the fauces is an arched fold of 
muscular tissue, covered like the rest of the mouth 
with mucous membrane. These are the arches or 
pillars of the soft palate, commonly known as the 
palatine arches. The top of each arch is at 
the base of the uvula. One of its pillars, called the 
anterior pillar, extends downward and forward to 
the base of the tongue, and the other pillar, 
Fig. i 12.-The soft palate and tonsillar 
regions. 
1 From the Latin uva-a grape. 
2 From the Latin faucis-the throat.' The Digestive System 
343 
named the posterior pillar, extends downward and 
backward to the sides of the pharynx. Lying 
between the anterior and posterior pillars of each 
of the palatine arches is an almond-shaped body 
called a tonsil. These are really lymph glands. 
During childhood there are many similar but 
smaller glands around the base of the tongue and 
extending up into the naso-pharynx. When large 
they are spoken of as adenoids. See page 257. 
692. Accessory Organs Found in the 
Mouth.-The accessory organs found in the 
mouth are: the teeth, tongue, and openings to the 
ducts of the salivary glands. The teeth were 
described in Chapter V. 
The Tongue 
693- Why Classed with Digestive Organs. 
-The tongue is classed as an accessory organ of 
digestion for the following reasons: (i) it assists in 
swallowing; (2) the sense of taste, of which it is 
the principal seat, is one of the sources of the 
nerve impulses which start the secretion of the 
digestive juices; (3) the follicles at the back of 
the tongue secrete mucus which lubricates the 
food and aids in its passage to the stomach. 
694. Nature and Connections.-The tongue 
is a freely movable muscular organ, or, rather, 
double organ, for its two sides, though united, are 
quite distinct, so that the function of one side 
need not necessarily be impaired because of dis- 344 
Anatomy and Physiology 
ease or injury of the other. Its base or root is 
directed backward and connected to the hyoid 
bone by means of numerous muscle. It is con- 
nected with the epiglottis by folds of mucous 
membrane and with the soft palate of the anterior 
pillars of the palatine arches. 
695. The Papillae of the Tongue.-The 
mucous membrane lining the under surface of 
the tongue is the same as that lining the rest of the 
buccal cavity, but that covering its upper surface 
differs in several respects, one point of difference 
being that it is studded by small projections called 
papillae. These papillae are of three varieties: (1) 
those called the circumvallate,1 which are situated 
at the base of the tongue. These are larger than 
the other varieties and are circular in shape. 
They serve to secrete the mucus which lubricates 
the food and so helps in its deglutition; also they 
contain small structures known as gustatory buds 
or taste goblets containing filaments of the nerve of 
taste. (2) The papillae next in size are the fungi- 
form,2 so called because their shape somewhat 
resembles that of mushrooms. They are situated 
principally on the tip and sides of the tongue. 
In each papilla there is a loop of capillaries and 
a nerve fiber derived from the glosso-pharyngeal 
-the special nerve of the sense of taste. The 
third and smallest set of papillae are the filiform, 
1 From the Latin circum-around and vallum-a wall. So 
called because they are surrounded by a kind of wall. 
2 From the Latin fungus-a mushroom. Fig. i 13.-Dorsal surface of the tongue. (Gerrish.) 
345 346 
Anatomy and Physiology 
which, in man, are delicate, hair-like processes. 
They are the most numerous, being scattered all 
over the surface of the tongue. From their pecul- 
iar structure it is thought that these papillae are 
concerned with the sense of touch, rather than 
that of taste. 
696. Nerve Supply.-The nerve-fibers which 
supply the papillae and other parts of the tongue 
are: (1) filaments of the lingual nerve, w'hich is 
derived from branches of the fifth or trifacial 
nerve, and the seventh or facial nerve. These are 
thought to give rise to the senses of touch and taste. 
(2) The ninth or glosso-pharyngeal nerve, which 
is concerned with the sense of taste. (3) The 
twelfth or hypoglossal nerve, which is distributed 
to the muscles of the tongue and is the motor 
nerve of the organ. 
697. Functions of the Tongue.-In addition 
to assisting in deglutition, the tongue is the special 
organ of the sense of taste and assists in articulation. 
698. The Salivary Glands.-The principal 
salivary glands are: (1) the parotid1 glands, situ- 
ated one at each side of the face below and in front 
of the external ear. Each one communicates with 
the mouth by means of a duct about two and a 
half inches long and the diameter of a crow-quill, 
which has its openings on the inner surface of the 
cheek opposite the second molar tooth of the 
upper jaw. (2) The submaxillary2 glands, situated 
1 From the Greek para-beside and otos-the ear. 
2 From the Latin prefix sub below and maxilla-a. jaw. Fig. i 14.-The salivary glands. The right half of the body of the 
mandible has been removed. GL. W., gland of Weber. GL. B., gland of 
Blandin. (Gerrish.) The Digestive System 
347 
below the jaw and opening into the floor of the 
mouth by means of ducts somewhat smaller than 
those of the parotid gland. (3) The sublingual1 
glands situated one on each side beneath the 
mucous membrane of the floor of the mouth, 
under the tongue, and opening into the mouth by 
numerous small ducts. (4) The mucous membrane 
of the mouth is studded with small glands which, 
like the larger glands, discharge their secretion 
into the mouth. The secretion from each set of 
glands differs slightly in composition; the whole 
combined is known as the saliva. Its function 
will be discussed in the next chapter. 
Pharynx.-The pharynx was described in con- 
nection with respiration in Chapter XV. 
The Esophagus2 
699- Location.-The esophagus is a muscu- 
lar canal from about nine to ten inches in length, 
which has its origin at the lower end of the phar- 
ynx, behind the trachea. It descends in front of 
the spine, passes through the diaphragm and 
connects with the stomach just below the dia- 
phragm, slightly to the left of the median line. 
700. Structure.-The walls of the stomach are 
composed of three coats: (1) an external or muscu- 
lar, (2) a middle or areolar, and (3) an internal or 
mucous coat. The fibers of the muscular coat are 
1 From the Latin sub-below and lingua-the tongue. 
2 From the Greek oiso-to carry and phagein-to eat. 348 
Anatomy and Physiology 
arranged in two different planes; those of the 
outer plane run longitudinally and those of the 
inner plane run circularly. This arrangement is 
of importance in the peristaltic1 movements which 
carry the food from the pharynx to the stomach. 
The areolar coat serves to connect the muscular 
and the mucous coats. The mucous coat is dis- 
posed in longitudinal folds that disappear on the 
distention of the tube. It is studded with minute 
papillae and small glands which secrete a fluid to 
lubricate the canal. 
The Abdomen 
Before describing the organs of digestion situ- 
ated in the abdomen it seems well to say some- 
thing of the cavity in which they are contained. 
701. Location.-The abdominal cavity is situ- 
ated between the diaphragm and the pelvic cavity. 
There is no partition between the two cavities, 
but the brim of the pelvis is considered the dividing 
line. 
702. Regions of the Abdomen.-For con- 
venience in the description of the location of the 
viscera, the abdomen is artificially divided into 
nine regions. The divisioning is as follows: two 
circular lines are supposed to be drawn around the 
abdomen, the one parallel with the cartilages of 
the ninth rib and the other with the highest joint 
of the crest of the ilia; this divides the abdomen 
1 From the Greek peristello-to compress. The Digestive System 
349 
into three zones-an upper, a middle, and a lower. 
Each of these three zones is supposedly sub- 
divided into three parts by two parallel lines, one 
on each side of the abdomen, extending from the 
eighth rib to the center of Poupart's ligament. 
See Fig. 4. 
The names of the nine regions and of the 
viscera contained in each region are as follows: 
Right Hypochondriac 
Epigastric. 
Left Hypochondriac 
The right lobe of the 
liver and the gall-blad- 
der; hepatic flexure of 
the colon and part of 
the right kidney. 
The middle and py- 
loric end of the stom- 
ach; left lobe of the 
liver; the pancreas; the 
duodenum; parts of the 
kidneys; and the su- 
prarenal capsules. 
The splenic end of 
the stomach; the 
spleen; extremity of 
the pancreas; the splen- 
ic flexure of the colon; 
and part of the right 
kidney. 
Right Lumbar. 
Umbilical Region. 
Left Lumbar 
Ascending colon; part 
of the right kidney and 
some convolutions of 
the small intestines. 
The transverse col- 
on; part of the great 
omentum and mesen- 
tery; transverse part of 
the duodenum, and 
part of the jejunum 
and ileum; part of 
both kidneys. 
Descending colon; 
part of the omentum; 
part of the left kidney, 
and some convolutions 
of the small'intestine. 
Right Inguinal 
Hypogastric Region. 
Left Inguinal. 
The cecum and ver- 
Convolutions of the 
Sigmoid flexure of 
miform appendix; the 
right ureter. 
small intestine; the 
bladder in children, 
and in adults if dis- 
tended; and the uterus 
during pregnancy. 
the colon; the left 
ureter. 
703. The Peritoneum.1-The abdomen is 
lined with a serous membrane known as the peri- 
1 From the Greek peri-about and teino-I stretch. Anatomy and Physiology 
350 
toneum. This is a double membrane forming, in 
the male, a shut sac,1 the outer or parietal layer 
of which lines the inner surface of the abdominal 
and pelvic cavities, and the inner or visceral 
layer is reflected back over the viscera.2 In this 
respect the peritoneum resembles the pleura and 
pericardium, but the arrangement is much more 
complex than that of those membranes, for it has 
several elongated sacs or double folds extending 
from it which pass in between and either wholly 
or partially surround the various organs in the 
abdominal and pelvic cavities. One large fold, 
known as the mesentery,3 invests the greater part 
of the small intestine, and its posterior portion 
extends backward and is gathered into folds which 
are attached to the spine; thus it serves to hold 
the intestines in place. Another important fold is 
the omentum.4 This hangs like a curtain in front 
of the stomach and intestines, and as it contains 
considerable fat it serves, in addition to the usual 
functions of the peritoneum, to keep the organs it 
covers warm. 
704. Functions of the Peritoneum.-This 
membrane serves to hold the abdominal and pelvic 
organs in position, to unite contiguous organs, and 
1 In the female, the peritoneum is not an absolutely closed sac, 
because the Fallopian tubes open into it at their extremities. 
2 The dorsal surface of the kidneys, the lower part of the 
rectum, bladder, and uterus, as well as small areas of some of the 
other organs, are not invested with peritoneum. 
3 From the Greek mesos-middle and enter on-intestine. 
< Latin omentum-coverlet. The Digestive System 
351 
also to separate and prevent friction1 between 
them; also it serves as a support for the numerous 
blood and lymphatic vessels and nerves passing to 
and from the viscera. 
The Stomach 
705. Purpose.-The stomach serves (1) to 
connect the esophagus with the small intestine; 
(2) to hold the food while it undergoes that part 
of the process of digestion known as chymification; 
(3) to secrete the fluids necessary for that process. 
706. Shape, Names of Parts.-The stomach 
is the most distended portion of the alimentary 
canal. Its shape is that of a cone with its base 
placed upward and its apex downward, but bent 
sidewise, to the right. There is an opening in the 
base which connects with the esophagus and one 
in the apex that opens into the small intestine. 
The former is called the cardiac orifice and the 
latter the pylorus2 or pyloric orifice. The bending 
of the stomach causes its lower border to be much 
longer than its upper one; the lower border there- 
fore is spoken of as the greater curvature and the 
upper as the lesser curvature. The rounded por- 
tion to the left of the esophagus is called the body 
or fundus;3 the central portion is called the inter- 
mediate or prepyloric region; and the right extrem- 
1 The peritoneum, like all other serous membranes, prevents 
friction between adjacent parts by secreting a lubricating fluid. 
2 From the Greek pzilotiros-a gate-keeper. 
3 From the Latin fundus-the base of a cone-shaped organ. 352 
Anatomy and Physiology 
ity, which is much constricted, is called the pyloric 
Fig. i 15.-The stomach and intestine, front 
view, the great omentum having been removed 
and the liver turned up and to the right. The 
dotted line shows the normal position of the an- 
terior border of the liver. 
Joy. Size.-The size of the stomach depends 
upon the size of the individual and the quantity of The Digestive System 
353 
its contents. When moderately full the average 
transverse diameter of an adult's stomach is about 
twelve inches and its vertical four. When empty, 
the stomach is in a collapsed condition. The size 
of an infant's stomach at different ages is of 
importance for nurses to know. The average is as 
follows: 
AGE. 
3d to 7th day 
7th day to 3d week 
4th to 5th week 
6th week to 3d month 
3d month to 5th month 
5th month to 9th month 
9th month to 12th month 
capacity of stomach. 
1 to iX ounces 
iX to 2X ounces 
2X to 3 ounces 
3 to 4X ounces 
4 to 5X ounces 
5X to 8 ounces 
8 to 12 ounces 
708. Position.-The stomach is situated in 
the left hypochondriac and epigastric regions of 
the abdomen, directly under the diaphragm. The 
fundus is behind the lower ribs and in contact 
with the spleen to which it is attached by folds of 
the omentum. The smaller or pyloric end extends 
slightly back of the liver. 
709. Coats of the Stomach Walls.-The 
walls of the stomach are composed of four coats: 
(1) the outer or serous coat, which is a continua- 
tion of the peritoneum and entirely invests the 
organ except at the points of attachment of the 
omentum; (2) the muscular coat. This consists of 
three sets of fibers, the outer of which run longi- 
tudinally, the middle circularly, and the inner Anatomy and Physiology 
354 
obliquely-the oblique fibers are limited to the 
cardiac end of the stomach. This arrangement of 
the muscular fibers facilitates the peristaltic action 
of the stomach, because the longitudinal fibers 
contract as the circular ones dilate, and vice versa. 
(3) The areolar or submucous coat, which serves 
to connect the muscular and the (4) coat, which is 
the inner or mucous coat. This last has a thick, 
soft, velvety surface which when the organ is 
contracted is thrown into folds or rugce. When 
examined under the microscope, this coat has a 
honeycomb appearance, due to the presence of 
numerous tubular glands or follicles which during 
digestion secrete the gastric juice, and certain 
of those in the prepyloric region secrete the hydro- 
chloric acid. This will be further referred to in 
connection with digestion. 
710. Blood and Nerve Supply.-The arteries 
supplying the stomach are the gastric and branches 
of the hepatic and splenic. The nerve supply is 
received from the sympathetic system and from 
branches of the pneumogastric or vagi. 
The Small Intestine 
7ii- Purpose.-The small intestine secretes 
the succus entericus, one of the juices that digests 
food, and it is in the small intestine that the 
greatest amount of digestion and absorption of 
food products takes place. 
712. Size and Situation.-The tube known Fig. 116.-Stomach and duodenum. The liver and most of the intes- 
tines have been removed. The Digestive System 
355 
as the small intestine is about twenty feet in length 
and two inches in diameter at its commencement, 
i: e., at the pyloric end of the stomach, but not 
more than one inch at its termination-the en- 
trance to the large intestine. It is coiled up in the 
central and the lower part of the abdominal cavity 
and in the upper part of the pelvic cavity, and is 
held in position, as described in paragraph 703, 
by the mesentery. 
713. Divisions of the Small Intestine.- 
For convenience of description, the small intestine 
is divided into three portions, known as the 
duodenum, the jejunum, and the ileum. 
The duodenum1 is the broadest and shortest 
portion of the small intestine, being, as the name 
implies, only twelve inches in length. It com- 
mences at the pylorus, curves obliquely slightly 
upward and backward to the under surface of the 
liver and then descends perpendicularly in front 
of the kidney and passes transversely across the 
lower portion of the spinal column, behind the 
colon, and terminates in the jejunum. 
The jejunum,2 so called because it is usually 
found empty after death, includes the upper two 
fifths of the rest of the small intestine. 
The ileum,3 so called from its numerous coils 
or convolutions, includes the remaining three 
fifths of the small intestine. 
1 From the Latin duodeni-twelve each. 
2 From the Latin jejunus-empty. 
J From the Greek etied- to twist. 356 
Anatomy and Physiology 
7i4- Structure of the Wall of the Small 
Intestine.-The wall of the small intestine, like 
that of the stomach, consists of four coats: the 
serous, muscular, areolar, and mucous. ■ The se- 
rous, which is the outer coat, is derived from the 
peritoneum. This invests the whole of the small 
intestine, except a small portion of the duodenum, 
and is continuous at the back with the mesentery 
folds which, it will be remembered, are attached 
to the spine. The muscular coat is arranged in 
two layers of fibers, one-the outer layer-ar- 
ranged longitudinally, the other circularly. This 
arrangement is necessary for the peristaltic action 
of the intestine. The areolar or submucous coat 
serves to connect the muscular coat with the 
inner or mucous coat. The mucous coat is thick 
and highly vascular in the duodenum and jejunum, 
but becomes thinner and paler in the ileum. This 
and other conditions to be described later serve to 
make the upper portion of the intestine the most 
active part in digestion. 
715. Valvula Conniventes.-From about 
two inches beyond the connection of the duodenum 
with the pylorus to the middle of the ileum, the 
mucous and submucous tissues are arranged in 
folds which extend around the cylinder of the 
intestine. Unlike the folds of the stomach, these 
do not disappear when the intestine is distended. 
They are called the valvulas conniventes. Their 
purpose is twofold: (1) to prevent the food passing 
through the intestine too quickly; (2),to present a The Digestive System 
357 
greater surface for the absorption of the digested 
food. 
716. Villi.1-Through the whole length of 
the small intestine there are minute finger-like 
processes projecting from the mucous membrane; 
these are the villi. Each villus consists of a net- 
Fig. 117.-Free surface of the mucous membrane of the small intes- 
tine, showing villi, solitary glands, and openings of the intestinal glands. 
Semidiagrammatic. 
work of capillaries and a lacteal lymphatic vessel 
held together and supported by lymphoid tissue 
and covered by the mucous lining of the intestine. 
It is into the capillaries and lacteals of these villi 
that the food passes after it has been digested. 
717. Glands.-There are also in the mucous 
membrane of the small intestine innumerable 
minute glands of four different varieties. These 
are known as: 
1 Villi, plural of villus, Latin-shaggy hair. 358 
Anatomy and Physiology 
Simple follicles, or crypts of Lieberkuhn1 
Duodenal or Brunner's1 glands 
Solitary glands 
Peyer's glands or patches 
The simple follicles and duodenal glands serve 
to secrete the succus entericus,2 i. e., the intestinal 
digestive juice. The former are scattered all 
through the small intestine; the latter are con- 
tained only in the duodenum and commencement 
of the jejunum. 
The solitary glands and Peyer's patches are 
lymph follicles. The former are scattered through- 
out the small intestine, but are more numerous in 
the lower part of the ileum. The latter are simply 
aggregations or patches of solitary glands. The 
patches are largest and most numerous in the 
ileum, hence the tenderness in the right iliac 
region in typhoid fever, in which disease these 
patches are inflamed and ulcerated. 
The Large Intestine 
718. Purposes.-(1) The continuation of the 
process of digestion. That digestion is carried on 
in the large intestine is due to the presence of 
bacteria and to the succus entericus with which 
the food became mixed in the small intestine. 
The fluid of the large intestine does not contain 
the enzymes necessary to activate the chemical 
1 So called from the men who described them. 
2 From the Latin succus-juice and enter on-the intestine. The Digestive System 
359 
processes of digestion. (2) Absorption. (3) The 
removal of waste products from the body. 
719. Size and Position.-The large intestine 
begins at the termination of the ileum in the right 
iliac region, and extends to the anus. It is, in the 
adult, about five feet in length. 
720. Divisions.-For convenience in descrip- 
tion the large intestine is divided into the 
Cecum1 
Ascending 
Transverse 
Descending 
Sigmoid flexure 
Colon 
Rectum 
The cecum is the dilated, pouch-like portion of 
the large intestine at its point of communication 
with the ileum. In order to prevent the passage 
of material back into the small intestine after it 
has once passed into the cecum, there is at the 
junction of these two parts a valve and sphincter 
known as the ileo cecal valve and sphincter. 
The vermiform appendix2 is a narrow, worm- 
like tube attached to the cecum. In man it is 
about three to six inches in length and about the 
diameter of a goose quill, but in lower mammalia 
it is much larger and is an important part of the 
intestine. 
The colon, though one continuous tube, for 
1 From the Latin caecus-blind. 
2 From the Latin vermis-a worm and forma-shape. 360 
Anatomy and Physiology 
convenience of description is divided into four 
parts, named: the ascending, transverse, descend- 
ing colon, the sigmoid flexure, and the rectum. 
The ascending colon, which is continuous with the 
cecum, ascends to the under surface of the liver, 
where it bends abruptly to the left and becomes 
the transverse colon; this crosses the abdomen 
into the left hypochondriac region, curves beneath 
the lower end of the spleen, and then passes-as 
the descending colon-vertically downward to 
the upper part of the left iliac fossa; there it curves 
inward, forming the sigmoid flexure.1 From this 
bend the intestine, under the name of rectum, 
extends obliquely downward and, after a slight 
curve forward, backward. The rectum measures 
from six to eight inches. 
721. Structure.-The walls of the large in- 
testine consist in some parts of four coats, but in 
others of three only, for the serous coat is lacking, 
or only partially covers some parts. The muscular 
coat, like that of the small intestine, consists of 
two layers of fibers, one arranged longitudinally 
and the other circularly. The third coat, as in the 
small intestine and stomach, consists of areolar 
tissue, and the fourth or inner coat consists of 
mucous membrane. The mucous coat of the large 
intestine contains numerous small follicles and 
solitary glands, but they are largely lymph glands 
1 This bend is called the sigmoid flexure because it curves like 
the letter S and sigma is the Greek word used to express the 
letter S, and from eidos-shape-S-shape. Fig. 118.-Relative position of the duodenum and pancreas. The liv er 
has been lifted up and the greater part of the stomach removed; the 
dotted lines indicate the usual position of the latter. The Digestive System 
361 
and do not secrete digestive juice. There are 
no villi nor valvulas conniventes in the large 
intestine, but there are a few circular folds above 
the rectum which prevent the too rapid urging of 
fecal matter toward the anus where its presence 
excites a desire for defecation. When the rectum 
is contracted the inner surface is thrown into 
longitudinal folds, but these disappear when the 
tube becomes distended. 
722. The Anus.-This is the aperture leading 
from the large intestine to the exterior of the body. 
Except during defecation this orifice is kept closed 
by the contraction of the involuntary circular 
muscle known as the external sphincter. 
The Pancreas1 
723. Purpose.-Two secretions are formed in 
the pancreas: one, which is poured into the duo- 
denum during intestinal digestion, constitutes 
about the most important of the digestive juices; 
the other, which is known as the internal secretion 
of the pancreas, is absorbed by the blood and 
carried to the tissues. Its use was discussed in 
paragraph 677. 
724. Shape and Position.-The shape of the 
pancreas is generally likened to a dog's tongue. 
The gland lies transversely in the abdomen, behind 
the stomach, and extends from the duodenum to 
the spleen. 
1 From the Greek pan-all and kreas-flesh. 362 
Anatomy and Physiology 
725. Size.-The length of the pancreas varies 
from six to eight inches; its breadth is about one 
and a half inches, and it is from half an inch to 
one inch thick. 
726. Structure.-The substance of the pan- 
creas is composed of minute masses called lobules 
bound together with connective tissue into larger 
masses called lobes. Each lobule consists of a 
gland of the racemose type (see paragraphs 663 and 
664). The small ducts from the glands of each 
lobe unite to form larger ducts, and these empty 
the secretion that has passed into them from the 
glands into the pancreatic duct. This duct ex- 
tends through the center of the pancreas-from 
tip to base-and, uniting with the common bile 
duct (described in paragraph 738) opens into the 
duodenum. 
727. Islands of Langerhans.-Scattered ir- 
regularly through the substance of the pancreas 
are collections of cells known as the Islands of 
Langerhans. It is thought that the internal secre- 
tion of the pancreas is formed in these cells. 
728. Blood Supply.-The numerous blood- 
vessels are derived from branches of the gastric, 
splenic, and hepatic arteries. 
The Liver 
729. Function.-The functions of the liver are 
more complex and numerous than those of any 
other gland in the body. It secretes the bile; it Fig. 119.-The liver, lower surface. (Gerrish.) 
363 364 
Anatomy and Physiology 
changes the glucose, brought to it from the 
intestine by the portal vein, into glycogen, and 
reconverts the glycogen into glucose when the 
latter substance is needed in the tissues; it acts 
as a storehouse for the glycogen; it forms the urea, 
which is then taken up by the blood and excreted 
by the kidneys; and it changes the nature of many 
toxic substances that arise from the putrefaction 
of protein food in the intestines into less harmful 
substances. These, like the urea, are excreted by 
the kidneys. 
730. Location.-The liver is situated directly 
below the diaphragm and in front of the right 
kidney, the upper part of the ascending colon and 
of the pyloric end of the stomach. It is held in 
position by five ligaments, four of which are 
derived from the peritoneum and connected to the 
diaphragm; the fifth is a round, fibrous cord 
resulting from the obliteration of the umbilical 
vein (described in paragraph 1036 which extends 
to the inferior vena cava. 
731. Size.-The liver is the largest gland in 
the body; it weighs from fifty to sixty ounces, 
measures ten to twelve inches in the transverse 
diameter, from six to seven in its antero-posterior 
-i. e., from front to back-and it is about three 
inches thick at its broadest part. 
732. Lobes and Fissures.-The liver is di- 
vided by fissures into five lobes. These fissures 
serve also as channels to hold the large blood and 
lymphatic vessels and nerves, and the gall-bladder The Digestive System 
365 
fissure-in the under surface of the liver-supports 
the gall-bladder. 
733. Structure.-The substance of the liver 
consists of an aggregation of lobules, blood and 
lymphatic vessels, and nerves, held together with 
delicate areolar tissue. The lobules measure from 
To to A of an inch in diameter. Each one con- 
sists of a mass of hepatic secretory cells that is 
surrounded and penetrated by capillaries, and of 
small ducts which arise from between the cells. 
Thus each lobule has all the essentials of a secre- 
tory gland; viz.: (1) cells by which the secretion is 
formed; (2) blood-vessels in close connection with 
the cells, containing the blood from which the 
secretion is derived; (3) ducts, by which the secre- 
tion is carried away. The outer surface of the 
liver is covered with an areolar coat called the 
capsule of Glisson, and this, except at the attach- 
ments of the ligaments and bottom of the fissures, 
is covered by a serous coat derived from the 
peritoneum. 
734. Blood-Vessels of the Liver.-The he- 
patic artery and portal vein hold the blood flowing 
to the liver and the hepatic veins hold the blood 
which is leaving it. The hepatic artery and portal 
vein enter the liver at the same point-the portal 
fissure-and run together through the substance 
of the organ in small grooves called the portal 
canals. In their course through the liver they give 
off branches which divide and subdivide, and 
finally break up into capillary plexuses which 366 
Anatomy and Physiology 
are distributed between the lobules. From these 
plexuses capillaries extend into the lobules con- 
verging toward the center and giving off branches 
which surround the liver cells. In the center of 
each lobule all the capillaries of the portal vein 
connect with a small vein-the intralobular1 vein- 
that extends through the length of the lobule. 
At the base of the lobule the intralobular vein opens 
into what is known as a sublobular2 vein. The 
sublobular veins unite to form the hepatic veins, 
and these in turn unite to form the three large 
hepatic trunks which empty into the inferior vena 
cava where it passes upward at the back of the 
liver. The branches from the hepatic artery 
follow those from the portal vein into the lobules 
and end in the capillary network surrounding the 
hepatic cells; thus the blood from the hepatic artery 
leaves the liver with that from the portal vein. 
735. Lymphatics.-The lymphatic vessels of 
the liver are large and numerous. They assist in 
absorbing and carrying away some of the sub- 
stances that collect as the result of activity of the 
liver and absorption from the blood. 
736. Nerves.-The nerve supply of the liver 
is derived from branches of the pneumogastric or 
vagi and from the sympathetic system. 
The Biliary Ducts of the Liver 
737. Purpose.-The biliary ducts serve to col- 
lect the bile after it is secreted by the cells, and 
1 Within the lobule. 2 Under the lobule. The Digestive System 
367 
carry it during digestion to the duodenum, or, 
during the intervals when digestion is not going 
on, to the gall-bladder. 
738. Names and Locations of the Ducts.- 
The names of the principal biliary ducts are: the 
hepatic ducts, the cystic duct, and the common duct. 
The hepatic ducts, those which collect the bile 
as it is secreted by the liver cells, have their origin 
in the minute interspaces that exist between the 
hepatic cells. From these spaces numerous small 
capillary-like ducts arise in each lobule, and these 
uniting form an intralobular duct. The numerous 
intralobular ducts thus formed unite in turn to 
form larger ducts, and these converge to form two 
main ducts, one in the right and one in the left 
side of the liver. These two ducts join also, and 
by so doing form the chief hepatic duct. The 
large hepatic ducts pass from the liver in the 
same channel as the hepatic artery and portal 
vein, viz.: the portal canal. 
The cystic duct, which is the passage-way for 
the bile to and from the gall-bladder, extends from 
the neck of the gall-bladder (see Fig. 119) to the 
hepatic duct and joins with it to form the common 
duct. 
The common duct formed, as just stated, by the 
union of the hepatic and cystic ducts, serves to 
carry the bile from the other two ducts to the 
duodenum. It is about three inches in length and 
the diameter of a goose-quill. The orifice of the 
duct is situated about four inches below the 368 
Anatomy and Physiology 
pylorus. It is very small and appears to be pro- 
vided with a sphincter muscle, which keeps it 
closed when bile is not passing through. This, as 
has been previously said, is only during digestion. 
739. Secretion and Collection of Bile.- 
The secretion of bile is continually going on, but 
is retarded in fasting and accelerated during 
digestion. It is formed in the hepatic cells-from 
substances brought to them by the blood-vessels- 
and discharged into the interspaces, whence it 
flows into the small ducts and thence to the hepatic 
duct. During intestinal digestion it passes through 
the common duct into the duodenum, but at 
other times it enters the cystic duct and some of 
it is stored in the gall-bladder until required. 
It does this because the sphincter at the orifice 
between the duct and duodenum is closed when 
the duodenum is empty. When food enters the 
intestine the stimulus of the food excites contrac- 
tions which relax the sphincter and allows the 
passage of bile from the gall-bladder and liver. 
The Gall-Bladder 
740. Shape and Size.-The gall-bladder, 
which is the reservoir for the bile, is a pear-shaped 
organ, about four inches in length and one inch 
in breadth at its widest part. It holds about 
eight to ten drams. 
741. Location.-It is situated in the gall- 
bladder fissure, on the under surface of the liver, Fig. 120.-Abdominal aorta and inferior vena cava. The Digestive System 
369 
and is held in position by folds of peritoneum 
which are attached to the liver. 
742. Structure.-The walls of the gall-blad- 
der are composed of three coats: the outer one is 
of serous membrane; the middle of muscular and 
fibrous tissue; and the internal of mucous mem- 
brane. CHAPTER XVIII 
FOOD. DIGESTION. ABSORPTION 
Classification of Food. Chemical Composition of Food. 
Uses of Organic and Inorganic Food Substances. Reasons for 
Digestion. Nature and Action of Enzymes. Nature of Diges- 
tive Juices. Mechanism of the Secretion of Digestive Fluids. 
Organs in which the Digestion of the Various Foodstuffs Takes 
Place. Influence of Bacteria on Digestion. Mechanical Proc- 
esses of Digestion. Defecation. Nature of Feces. Where 
Absorption Takes Place. Nature of Absorption. 
743- Definition of Digestion.-By diges- 
tion is meant the process which takes place in the 
alimentary canal whereby food is made soluble 
and of such a nature that it can pass through the 
walls of the intestinal blood-vessels, be absorbed 
by the blood, and be utilized by the body for the 
building and repair of tissue and the production 
of heat and energy. 
In order to understand the changes which take 
place in food during digestion and the purposes 
for which it is used after it has been digested and 
absorbed, it is necessary to know something of 
the chemical nature of the substances used as 
food. Therefore, the next few pages will be 
devoted to their description. 
370 Food. Digestion. Absorption. 
371 
744. Classification of Food.-Foods may 
be divided into two classes: 
1. Organic 
2. Inorganic 
Organic foods are subdivided into: 
Proteins 
Carbohydrates 
Fats 
Inorganic foods are subdivided into 
Mineral matter 
Water 
745. Proteins.-Examples of the protein sub- 
stances are: (1) Albumin, e. g., the white substance 
seen when egg is heated; the scum that forms on 
the top of milk when its temperature is raised 
above 1700 F.; the white coating that forms on 
meat when it has been in a hot oven for a short 
time. (2) Caseinogen,T e. g., the substance that is 
formed into a curd when acid or rennet is added to 
milk, or when milk sours.2 (3) Gluten, e. g., the 
gummy substance in wheat. (4) Legumin, a pro- 
tein substance contained in the class of vegetables 
known as the legumes, e. g., beans, peas, lentils. 
(5) Gelatin. (6) Extractives, e. g., simple protein 
substances which are formed in both animal and 
1 From the Latin caseus-cheese. 
2 Milk becomes sour because the sugar it contains-lactose- 
is, under the influence of bacteria, changed to lactic acid. 372 
Anatomy and Physiology 
plant bodies as the result of metabolism. Meats 
and many plants owe their flavor to extractives. 
746. Chemical Elements of Organic Food. 
-The elements of which proteins are formed are: 
carbon, hydrogen, oxygen, nitrogen, sulphur, and, 
usually, phosphorus and iron. The proteins are 
often called the nitrogenous foodstuffs, because 
they contain nitrogen and the carbohydrates and 
fats do not. The carbohydrates and fats contain 
only carbon, hydrogen, and oxygen; the fats hav- 
ing much less oxygen than the carbohydrates. 
747. Varieties of Carbohydrates.-The 
foodstuffs classed as carbohydrates are the amy- 
loses1 or polysaccharids2 and the sugars. 
748. The Amyloses.-The group of substances 
known as amyloses are: starch, dextrine,3 cellu- 
lose, 4 glycogen,5 and gums. These are of a much 
more complex structure than the sugars. Each 
molecule of an amylose consists of a number of 
molecules, each one of which is made up of 6 
atoms of carbon, 10 atoms of hydrogen, 5 atoms 
of oxygen (C6 H10 Os). 
749. Classification and Nature of Sugars. 
1 From the Latin amylum-starch. 
2 From the Greek polus-many, and Latin saccharum-sugar. 
3 Dextrine is formed from starch in the process of digestion 
and by the action of heat; the browned part of toasted bread is 
an example. 
4 Examples: the rind and fibrous parts of vegetables and other 
plants. 
5 Called also animal starch. This will be described in para- 
graph 799. Food. Digestion. Absorption. 
373 
-Sugars, according to their chemical composition, 
are divided into two classes: (i) the disaccharids1 
or sucroses; (2) the monosaccharids or glucoses. 
The sucroses are: cane sugar, beet sugar, maple 
sugar, maltose (sugar of malt), and lactose (sugar 
of milk). Each molecule of these sugars consists 
of 12 atoms of carbon, 22 atoms of hydrogen, 11 
atoms of oxygen (CI2 H22 O„). 
The glucoses are: glucose or dextrose2; fruit 
sugar or levulose3; invert sugar. Glucose and 
levulose are both found in fruit. Invert sugar, of 
which honey is a familiar example, consists of a 
mixture of the two. Glucose can be made by boil- 
ing polysaccharids or disaccharids in dilute acids, 
and in the animal body it is formed as the result of 
the digestion of polysaccharids and disaccharids. 
The monosaccharids consist of 6 atoms of carbon, 
12 atoms of hydrogen, and 6 atoms of oxygen. 
Thus, it will be seen, one molecule of a disaccharid 
(CI2 H22 Ou) plus one molecule of H 2 O will yield 
two molecules of a monosaccharid, C6 HI2 O6. 
750. Fats.-Fats and oils are practically the 
same, oils being fats that are liquid at ordinary 
temperature. Like the carbohydrates, they con- 
sist of carbon, hydrogen, and oxygen; but the last- 
named element is present only in small quantities. 
1 From the Greek dis-twice, and Latin saccharum-sugar. 
2 From the Latin dexter-the right. 
3 From the Latin Icevus-the left. 
The sugars were so named because dextrose deflects polarized 
light to the right and levulose causes it to deviate to the left. Anatomy and Physiology 
374 
The ordinary fats and oils of animal and vegetable 
foods are not simple fats, but consist of a mixture 
of simple fats, the principal ones of which are 
known as stearin, olein, and palmitin. These 
simple fats also are compound substances, and 
each molecule of a simple fat is made up of three 
molecules of a fatty acid and one molecule of 
glycerine. The fatty acids of which the above 
simple fats are composed are called stearic, oleic, 
and palmitic acids. 
751. Solubility and Decomposition of Fats. 
-Fats are insoluble in water and in cold alcohols, 
but are soluble in hot alcohol, ether, chloroform, 
and similar substances. They are easily decom- 
posed or saponified by alkalies or super-heated 
steam into their constituent parts-fatty acids 
and glycerine. 
752. Lecithin.-This is a substance that is 
usually classed with the fats, because the manner 
of its digestion is similar to that of the latter, and 
it somewhat resembles them in its composition; 
but it contains only two molecules of fatty acid, 
the third one being replaced by a protein molecule. 
This protein molecule contains phosphorus and, 
of course, nitrogen; therefore, lecithin is often 
spoken of as a phosphorized fat, or as a nitrogenous 
fat. It is found in small quantities in many sub- 
stances, but is contained chiefly in the yolk of egg 
and nerve tissue. It is an important constituent 
of the latter. 
753. Cholesterine.-This is a fat-like sub- Food. 
Digestion. 
Absorption. 
375 
stance, but it is not a true fat. Its chemical com- 
position is similar to an alcohol. It is contained 
in many of the body tissues and also in plants. 
754. Uses of Organic Food-Substances.- 
These are: (1) To build the body tissues and to 
repair the constant waste that is going on in the 
body as the result of muscular activity. (2) To 
supply heat to keep the body warm. (3) To pro- 
vide the energy necessary to maintain the func- 
tional activities of the body. The different parts 
of the body machinery-the heart, lungs, nervous 
system, etc.-can no more keep active unless they 
are supplied with power or energy than can ma- 
chinery constructed by man. 
Inorganic Foods 
755. As previously stated, the inorganic food 
principles are: inorganic salts and water. 
The principal inorganic salts contained in food 
are: 
Carbonate 
Chloride 
Phosphate 
and 
Sulphate 
of 
Sodium 
and 
Potassium 
of 
Calcium 
and 
Magnesium 
Carbonate 
and 
Phosphate 
756. Uses of Inorganic Salts.-The inor- 
ganic salts taken into the body in food are not 
oxidized and, therefore, have no fuel value; never- 
theless they are absolutely indispensable to the 
life of the body. Some of their more important 376 
Anatomy and Physiology 
uses are as follows: They form an essential part 
of the tissues of the body. They maintain the 
normal osmotic pressure in the liquids and tissues 
of the body, and in this way help in regulating the 
flow of fluids to and from the tissues. The calcium 
salts are of importance in maintaining the irri- 
tability of nerve and muscle and the firm consist- 
ency of bone; also, they are necessary for the 
clotting of the blood. The chlorides of sodium, 
potassium, and calcium are necessary to maintain 
the rhythmical contraction and relaxing of the 
heart muscle. Sodium chloride is necessary for 
the manufacture of the hydrochloric acid of the 
gastric juice, and iron for the production of 
hemoglobin and for oxidative processes. 
Water 
757. Function.-Water, like mineral matter, 
does not give rise to heat and energy, but is never- 
theless essential to life. It enters into the compo- 
sition of even the hardest tissues, such as cartilage 
and bone; it supplies fluid for the body; it acts as a 
solvent for food; and is necessary for the removal 
of waste matter. 
Digestion 
758- Why Necessary.-Water and salts are 
absorbed into the system unchanged, the salts 
being soluble in water, but all organic foods 
except the sugars must undergo certain chemical 
changes before they are capable of passing through Food. Digestion. Absorption. 
377 
the walls of the stomach and intestines, and 
thence into the blood-vessels and lacteals. One 
reason for this is that with the exception of the 
sugars the organic foods are not soluble-i. e., 
they cannot be dissolved-in water. The sugars 
are soluble in water, but the disaccharids-i. e., 
cane sugar, etc.-cannot be utilized in the system 
unless they are changed to glucose in the alimen- 
tary canal. If they are introduced into the blood 
in their natural state they will be excreted at once 
through the kidneys. The body cannot use them, 
and therefore it gets rid of them as quickly as 
possible, just as it does poisons. 
759. Types of Digestive Processes.-Diges- 
tion comprises two distinct kinds of processes; 
one mechanical and the other chemical. 
760. Mechanical Processes.-The mechani- 
cal processes consist of: 
i. Mastication 
2. Deglutition or swallowing 
3. Peristaltic action of the esophagus, stomach, and 
intestines 
4. Defecation 
761. Nature of Chemical Digestion.- 
Chemical digestion consists of what is known as 
hydrolysis,1 i. e., the absorption of water and 
splitting of the complex molecules of the food 
substances into more simple ones. For example, 
each molecule of cane sugar consists of Ci2 H22 
1 See Glossary. 378 
Anatomy and Physiology 
0„. When this has undergone hydrolysis and 
thereby been changed to glucose, it consists of 2 
molecules of C6 H12 Oe- Thus each molecule of 
glucose represents half the molecule of cane-sugar 
plus a molecule of water, H20. In the disaccha- 
rids only one splitting is necessary, therefore they 
are quickly and easily digested, but the molecules 
of starch1 must undergo several divisionings before 
they are changed to glucose. Each splitting of the 
molecules causes certain changes in the nature of 
the starch, and the substance produced by each 
divisioning is known by different names. Thus, 
as the result of the first splitting we have dextrin, 
of which there are three varieties, each one being 
produced as a result of a further splitting of the 
molecules; then maltose is yielded, and, finally, 
glucose. Protein substances being of a still more 
complex nature must undergo an even greater 
number of divisionings than starches. 
The names of the principal classes of substances 
so formed are: acid-proteins, proteoses, peptones, 
polypeptids, and amino-acids. Peptones are solu- 
ble and can be absorbed, and some physiologists 
think that a considerable proportion of the pro- 
teins may not go beyond this stage in digestion. 
Fats, as a result of chemical digestion, are first 
split into fatty acids and glycerine; the fatty acids 
then unite with alkaline substances of the bile and 
pancreatic juice and form soap. 
1 It will be remembered that starch consists of a number of 
molecules of CJ2 H10 0a. Food. Digestion. Absorption. 
379 
762. Cause of Chemical Changes.-Outside 
the body, the carbohydrates and proteins can be 
made to undergo the same changes as those which 
occur in digestion by boiling them with acid, or 
by the addition of specific ferments,1 and fats will 
be saponified if boiled with alkalies. Within the 
body the changes take place at a comparatively 
low temperature, 990 to ioo° F., and that they do 
so is now universally attributed to the presence 
of organic catalyzers2 called ferments or enzymes 
in the digestive juices of the stomach, small 
intestine, and pancreas. 
763. Nature of Enzymes.-The exact compo- 
sition of enzymes is not known. Professor Howell 
defines them as "organic substances derived from 
proteins and of a colloidal nature."3 They are 
called catalyzers because, like the inorganic cata- 
lyzers, they hasten reactions but do not initiate 
them, and are not used up in the reaction. En- 
zymes are specific in their action, i. e., the enzyme 
that aids in the digestion of one food-stuff will 
have no effect upon the others. Enzymes are 
affected by temperature, the body temperature 
is the optimum; a high degree of heat will destroy 
them, a low temperature will retard their action. 
Their activity is altered also by the reaction of 
1 The ferments used to digest starches are made from the 
glutin of wheat; those used for protein from the pancreas or 
stomach of animals. 
2 See Glossary. 
3 Text-Book of Physiology, page 717. William H. Howell. 
W. B. Saunders Co. 380 
Anatomy and Physiology 
their surroundings. The enzyme of the saliva 
requires a neutral or slightly alkaline medium; 
those of the gastric juice require an acid; those of 
the pancreatic and intestinal juices require an 
alkaline. 
764. Nature of the Digestive Juices.-The 
digestive juices consist principally of water, mucin1 
salts, specific enzymes, and, in the case of the 
gastric juice, hydrochloric acid. 
765. Function of the Hydrochloric Acid.- 
Hydrochloric acid, which during digestion is se- 
creted by special gastric cells at the expense of the 
chlorides of the blood in sufficient quantity to be 
present in the gastric juice in the proportion of 
0.2 to 0.4 per cent., is a most important adjunct 
in gastric digestion. It activates the pepsin; 
helps in the inversion of sugar; acts as a disinfec- 
tant, killing many bacteria that gain entrance to 
the stomach; and regulates the passing of food 
from the stomach into the intestine. How this 
last action is produced will be described in para- 
graph 787. 
766. Mechanism of the Secretion of the 
Digestive Fluids.-Saliva.-The flow of saliva 
from the salivary glands is the result of reflex 
stimulation of the secretory nerves connected wflth 
those glands. For instance, certain sensory nerves 
are stimulated by the movements of the mouth, 
the taste and odor of food, etc. The impulses thus 
started are carried to a nerve-center-thought to 
1 An albuminoid constituent of mucus. Food. Digestion. Absorption. 
381 
be in the medulla oblongata-and from thence 
motor impulses are transmitted through the effer- 
ent nerves to the gland, and the gland is stimu- 
lated to activity. The secretion of saliva may be 
influenced also by psychical acts, e. g., it may be 
excited by the thought of savory food, feeling of 
nausea, etc., and inhibited by such sensations as 
anger, fear, and worry. 
766. Gastric Juice.-When the stomach is 
inactive, i.e., when there is no food in it, no gastric 
fluid is secreted, and its inner surface is covered 
with mucus of a neutral or alkaline reaction, but 
immediately upon the entrance of food into the 
stomach the gastric glands commence secreting 
and an acid fluid is poured out over the walls of 
the organ. The factors causing this secretion are: 
(1) the sensations of eating, and the taste and odor 
of the food; the sensory nerves producing this 
stimulation are situated in the mouth and nose, 
and the motor impulses are carried to the stomach 
by the vagus nerve; (2) the action of substances 
known as secretogogues contained in certain foods; 
meat juices and extracts are particularly rich in 
these substances, but milk, bread, white of egg, 
and similar substances do not appear to have any. 
How these secretogogues act is not known, but it 
has been suggested1 that "they act upon the 
pyloric mucous membrane and form a substance 
which Edkins designates as gastrin or gastric 
1 Text-Book of Physiology, pages 748-749. William H. Howell. 
W. B. Saunders Co. 382 
Anatomy and Physiology 
secretin, and this substance, after absorption into 
the blood, is carried to the gastric glands and 
stimulates them to secretion. " 
The secretion of gastric juice, like that of the 
saliva, is greatly affected by psychical influences, 
thus pleasant flavors, odors, etc., will induce 
secretion, and distaste of the food, anger, 
worry, etc., will inhibit secretion. Secretion 
is retarded also if the blood supply to the 
stomach is interfered with, as by active exercise 
soon after a meal. 
768. Pancreatic Secretion.-The principal 
agent influencing pancreatic secretion is the gas- 
tric juice. When the acid chyme enters the 
intestine it acts upon a substance called prosecretin 
present in the mucous membrane of the intestine, 
thereby producing secretin which is carried by the 
blood to the pancreas and stimulates the action 
of that gland. 
769. Succus Entericus--Intestinal Secretion. 
-The succus entericus or intestinal juice flows 
from the glands of Lieberkuhn in the small in- 
testine. The mechanism of its secretion is very 
imperfectly known. 
770. The Bile.-This consists of waste sub- 
stances derived from the blood and arising in the 
liver. It contains water, mucin, pigment, bile, and 
inorganic salts, fat, lecithin, and cholesterin. 
771. The names of the enzymes contained in 
the various digestive juices and their action on 
the food can be seen in the following table: Food. Digestion 
Absorption. 
383 
Digestive Juices. 
Enzymes. 
Action on Food. 
Saliva 
Ptyalin 
Maltase 
Turns starch to dextrin and 
maltose 
Turns maltose to dextrose 
'Rennin 
Coagulates milk 
Gastric juice 
Pepsin 
Hydrochloric! acid 
Splits proteins to proteoses and 
peptones 
Slight inversion of sugar by HC1 
.Gastric lipase 
Commences the digestion of 
emulsified fats, as cream 
Pancreatic juice ■ 
'Amylopsin 
Trypsinogen2 
Continues work of ptyalin 
Continues work of pepsin, split- 
ting proteoses into peptones and 
amino-acids 
Lipase or steap- 
sin 
Decomposes fats into fatty 
acids and glycerin 
' Erepsin 
Continues work of pepsin and 
trypsin, splitting peptones to 
amino-acids 
Intestinal juice 
Sucrase 
Maltase 
Inverts sucroses to dextrose- 
glucose-and levulose 
Changes maltose to dextrose 
Lactase 
Changes lactose to dextrose 
Bile No known en- 
zyme 
Aids lipase in splitting fats to 
fatty acids and glycerin. Assists 
the alkalies of the intestinal_ and 
pancreatic juices in the saponifica- 
tion of the fatty acids and aids in 
their absorption 
Organs in which Digestion of the Various Food- 
Stuffs Takes Place 
772. Changes Occurring in the Mouth.- 
As can be seen by the foregoing table, though all 
food is acted upon mechanically while in the 
mouth-i. e., broken by the teeth, moistened with 
saliva, and made into a bolus that can be easily 
swallowed-it is only, starch in which any chemical 
change takes place. 
1 Hydrochloric acid is not an enzyme. 
2 Trypsinogen is a zymogen or antecedent of an enzyme. It 
is inactive until it comes in contact with an activating enzyme- 
or hormones-called enterokimase, secreted by the intestinal 
cells, which activates it, changing it into trypsin. 384 
Anatomy and Physiology 
Starch.-The starch is changed partially 
to dextrine and maltose by the ptyalin and to 
dextrose by the maltase of the saliva, but diges- 
tion is not completed because the food remains 
in the mouth such a short time, and though the 
action of these enzymes is continued for a short 
time after the food enters the stomach, they are 
destroyed as soon as the food becomes acidulated. 
The amylopsin of the pancreatic juice is therefore 
necessary to complete the change to maltose and 
the maltose of the intestinal juice to invert the 
maltose to dextrose. The pancreatic and intesti- 
nal juices become mixed with the food while it is 
in the duodenum. 
774. Protein.-The chemical digestion of the 
protein foods begins in the stomach, by the action 
of the pepsin plus the hydrochloric acid; it is 
continued in the duodenum by the trypsin of the 
pancreatic juice and the erepsin of the intestinal 
juice. 
775. Fats.-Emulsified fats, such as cream, 
are split into fatty acids and glycerin by the 
gastric lipase, but other fats undergo no change 
in the stomach. In the duodenum, the steapsin 
or, as it is now often called, lipase1 splits them to 
fatty acids and glycerin, and the alkalies of the 
bile, pancreatic, and intestinal juices saponify them. 
776. Sugars.-Sugars, like fats, undergo little 
change until they reach the duodenum. The acid 
1 The chemical name for fats is lepins, from the Greek lipose- 
fat. Food. Digestion. Absorption. 
385 
of the gastric juice may cause some slight change, 
but it is the ferments-sucrase, lactase, and mal- 
tase-that invert the sucrose, lactose, and maltose, 
respectively, to glucose. 
777- Chyme and Chyle.-The thick liquid 
substance resulting at the end of gastric digestion 
is called chyme. The milky-colored emulsion 
occurring as the result of the digestion of fats 
in the duodenum is termed chyle. 
778. Influence of Bacteria on Digestion. 
-Bacteria are always present in the intestine and 
take an active, though not indispensable, part in 
the breaking-up of food substances. Normally, 
only bacteria capable of producing fermentation 
of carbohydrates are active in the small intestine, 
but, in the large intestine, those producing putre- 
faction of proteins are the most common. Bac- 
teria which cause fermentation and those that 
produce putrefaction do not seem to thrive to- 
gether ; some authorities think that this is because 
the bacteria are antagonistic to each other; others 
think that the acids produced in the process of 
fermentation destroy, or render inert, the putre- 
faction-producing bacteria. If excessive fermenta- 
tion takes place, gases will be formed and flatulence 
result. If much putrefaction occurs, protein 
digestion is carried beyond the amino-acid 
stage and substances such as indol, skatol, and 
various gases as carbon-dioxide, sulphurated hy- 
drogen, etc., result. When not in excess these sub- 
stances pass off in the feces, and it is to such 386 
Anatomy and Physiology 
matter as indol and skatol that the odor of the 
feces is due. When these substances are formed 
in abnormal amounts, or when their elimination 
is retarded, they are absorbed, carried to the liver 
where they undergo certain changes, and are then 
carried to the kidneys and excreted in the urine. 
The indol is changed to indican in the liver. The 
amount of this substance present in the urine is 
therefore an indication of the extent of putrefac- 
tion going on in the large intestine. The products 
of putrefaction are more or less poisonous, and 
when formed in sufficient quantities to be absorbed 
they are likely to give rise to such symptoms as 
headache, general lassitude, etc. Also, it is 
thought that when they are frequently present 
in the system they induce premature sclerosis or 
hardening of the arteries and, consequently, the 
conditions of old age. 
779. Mechanical Process of Digestion.- 
As stated in paragraph 760, the mechanical 
process of digestion consists of: 
Mastication 
Deglutition 
Peristaltic1 action of the stomach 
Peristaltic1 action of the intestine 
Defecation 
1 From the Greek perist ello-to compress. 
The waves of contraction that pass slowly over the stomach 
and along the intestine resemble in appearance the movements of 
a worm. The nature of the movement is due to the arrangement 
of the muscular fibers in the walls of the esophagus, stomach, Food. Digestion. Absorption. 
387 
780. Nature of Mastication.-Mastication 
is a voluntary act which takes place in the mouth. 
The teeth grind the food into small pieces, while 
the movements of the tongue and of the muscles 
of the cheeks and lips help to hold it in place 
between the teeth and to gather it into such a 
position that it can be swallowed. During the 
process of mastication the food becomes mixed 
with saliva. 
781. Necessity for Mastication.-Unless 
food is properly masticated it enters the stomach 
in pieces that are too large, and gives that organ 
more mechanical work than it is fitted for. Also, 
the food does not become properly mixed with 
saliva, and in the case of starches it is very impor- 
tant that it should be so mixed. 
782. Deglutition.-The act of swallowing is 
at first a voluntary action, but after the bolus of 
food passes the orifice of the esophagus the act is 
involuntary, and is assisted by the peristaltic 
action of the esophagus. This action is the result 
of reflex nervous stimulation caused by the pres- 
ence of the food. Liquid or very soft food is shot 
through the canal by the initial act of swallowing 
and reaches the cardiac opening of the stomach 
0.1 second after it has been swallowed, but solid 
food takes almost 4.6 to 8.6 seconds to pass 
through the esophagus. The orifice to the stomach 
and intestines, which, it will be remembered, are in two layers, 
those in one layer being arranged longitudinally and those of the 
other transversely, so that they encircle the organs. 388 
Anatomy and Physiology 
is guarded by a valve which does not open until 
the worm-like wave which passes slowly down the 
esophagus reaches the stomach, and the fluid food 
which passed through the canal quicker than the 
wave will have to wait until the wave started by its 
deglutition reaches the stomach, unless the valve 
has been previously opened for the passage of 
food. 
783. Vomiting.-The valve between the esopha- 
gus and stomach prevents the regurgitation of 
food under ordinary circumstances, but if for any 
reason strong contractions are started in the 
stomach, it may open and the food return through 
the esophagus. This is called vomiting. 
784. Peristaltic Action of the Stomach.- 
In order to understand how the mechanical action 
of the stomach can perform its function it is 
necessary to remember that the cavity of the 
stomach is always the size of its contents. When 
it is empty, the stomach is uniformly constricted; 
as food enters, the stomach expands sufficiently to 
hold it; as the food passes into the intestine the 
stomach contracts so that its walls continue to 
press upon its contents. This condition enables 
the worm-like wave of contraction (which passes 
at regular intervals over the intermediary and 
pyloric portions of the stomach from the moment 
food enters it) to press upon the food, macerating 
it, mixing it with gastric juice, and from time to 
time ejecting a small portion of it into the intestine. 
785. Function of the Fundus.-There seems Food. Digestion. Absorption. 
389 
to be little or no movement in that part of the 
stomach known as the fundus, but so long as it 
contains food its muscles are in a state of tone. 
Both these facts are of importance to gastric diges- 
tion: (i) On account of the lack of movement, a 
large part of the food entering the stomach re- 
mains undisturbed for some time and does not 
become saturated with the gastric juice, and so 
long as this is rhe case the ptyalin that became 
mixed with the food while it was in the mouth 
can continue its action on the starch, but the 
ptyalin is rendered inactive as soon as the food 
becomes moistened with the acid gastric juice. 
(2) The special value of the tonicity of the fundus 
muscle is the pressure that it exerts on the food 
lying beneath it, because this pushes the food 
forward as the contents of the pyloric end of the 
stomach are gradually ejected into the duodenum. 
786. Time Required for Gastric Digestion. 
-It requires about five hours to complete the 
gastric digestion of an average meal of mixed food, 
i. e., meat, vegetables, etc. 
787. Factors Regulating the Passage of 
Food into the Duodenum.-Since the invention 
of the X-ray apparatus, the theories regarding the 
discharge of the chyme into the intestine have 
been very much changed. Formerly it was thought 
that the greater part of the food taken at a time 
remained in the stomach until gastric digestion 
was completed, but by means of the X-rays it has 
been found that small quantities of chyme are Anatomy and Physiology 
390 
ejected from the stomach through the pyloric 
orifice at more or less regular intervals. The fac- 
tors which are thought to regulate the relaxing and 
contraction of the sphincter muscle controlling the 
pyloric orifice and, consequently, the passage of 
the chyme are: (i) the consistency and (2) the 
acidity of the chyme. Solid particles against the 
pylorus tend to keep the sphincter closed. The 
way in which the acid is produced and acts is as 
follows: When the stomach is empty the inner 
surface of that organ is covered with mucus that 
is either neutral or slightly alkaline in reaction, 
but immediately upon the entrance of food the 
secretory cells contained in the mucous lining of 
the stomach begin to secrete the gastric juice, and 
certain of them the hydrochloric acid. The latter 
unites with the protein substances, for which it 
has a strong affinity, but after the proteins become 
saturated there is free hydrochloric acid in the 
gastric fluid, and when this occurs the pyloric 
sphincter relaxes and some of the chyme passes 
into the intestine. As soon, however, as a sufficient 
amount of the acid chyme has entered the intes- 
tine to render the alkaline contents of the pyloric 
end of the duodenum acid, the orifice closes, and 
remains closed until an alkaline reaction is once 
more regained.1 
788. Movements of the Small Intestine.-■ 
1 A description of the experiments by which these facts were 
ascertained will be found in Text-Book of Physiology, Chapter 
XXXIX. William H. Howell. W. B. Saunders Co. Food. Digestion. Absorption. 
391 
The movements of the small intestine are of two 
kinds: (i) a peristaltic action, which passes the 
substance received from the stomach slowly on- 
ward; (2) a series of local constrictions, which 
forces it into the folds and against the surface of 
the valvulae conniventes, thus assisting in mixing 
it with the digestive juices as well as aiding in 
its absorption. Also, the movements of the intes- 
tine, by causing an intermittent pressure on the 
blood-vessels and lacteals in the walls of the 
bowel, assist in the carrying away of the digested 
food substances after they have been absorbed. 
789. Passage of Food Material through 
the Large Intestine.-The food substance not 
absorbed in the small intestine passes through 
the ileo-cecal valve into the cecum and, under 
normal conditions,1 its regurgitation is prevented 
by the closure of the valve. When the cecum 
becomes filled, strong constriction waves press the 
walls of the cecum upon the food and force it 
onward into the ascending colon and, also, induce 
absorption. The peristaltic waves which pass 
over the walls of the ascending and transverse 
colon are different from those in other parts of the 
organ in that they pass both from and toward 
the small intestine. This, keeps the food moving 
backward and forward and thus prevents its too 
rapid expulsion from the bowel, and facilitates 
1 Obstruction in the large intestine will cause fecal matter to 
regurgitate into the small intestine, and-thence it may pass into 
the stomach and be vomited. Anatomy and Physiology 
392 
absorption-food requires six or seven hours to 
pass through the colon. Also, it is due to this back- 
ward movement in the intestine that fluid injected 
into the rectum is carried high into the colon. 
790. Defecation.-The sphincter muscles, 
whereby the relaxing and contraction of the anus 
are controlled, are involuntary muscles, but they 
are supplied with nerves from the cerebro-spinal 
system; therefore their action and, consequently, 
defecation can be controlled by the will. The 
voluntary action in defecation consists mainly in 
the contraction of the abdominal muscles, which, 
by causing pressure upon the intestines, forces 
their contents into the rectum. The desire for 
defecation arises from irritation of sensory nerve 
endings by an accumulation of feces in the lower 
part of the intestine. The sense of irritation often 
becomes diminished by failure to evacuate the 
irritating material, and by constantly allowing 
the irritation to continue indefinitely the sense 
may become so blunted that the condition known 
as chronic constipation results. 
791. Nature of Feces.-Feces consists 
mainly of: (1) the undigested and indigestible parts 
of the food; (2) substances resulting from the 
decomposition of food., as indol, skatol, fatty 
acids, etc.; (3) salts; (4) bile and other secretions; 
(5) enzymes; and (6) bacteria. The normal color 
of the feces is due largely to the bile, and when 
any obstruction in the liver ducts occur and the 
bile is absorbed instead of being poured into the Food. Digestion. Absorption. 
393 
intestine, the stools are clay-colored. Abnormal 
conditions in any part of the digestive apparatus 
may be often determined by the nature of the 
feces. 
Absorption 
792. Where Absorption Takes Place.-It 
is thought that perhaps a small amount of such 
substances as water, salts, and glucose may be 
absorbed from the stomach, but absorption takes 
place almost entirely from the intestines. The 
protein substances, glucose, etc., pass into the 
capillaries, and the fats into the lacteals of the 
villi that are contained in the mucous membrane 
of the intestine. Formerly it was thought that 
very little absorption took place in the large 
intestine, but experiments conducted with the help 
of the X-rays have shown this not to be the case. 
However, to be absorbed from the large intestine, 
food must be digested, and when food is intro- 
duced into the colon via the rectum, by means of 
a rubber tube (as it often is when it cannot be 
taken by the mouth) it must be digested before it 
is administered, the large intestine not having the 
enzymes necessary for the process of digestion. 
See paragraph 718. 
793. Nature of Absorption.-Absorption is 
not, as was thought formerly, a simple physical 
process whereby the digested food material passes 
by osmosis and diffusion from the intestine into 394 
Anatomy and Physiology 
the blood, but it consists in addition of very com- 
plex physiological processes, due to which, in some 
way as yet unknown, the split products of pro- 
teins and fats are reconstructed. For instance, 
proteins are, in the course of digestion, split into 
peptones, proteoses, etc., but these substances are 
not normally found in the blood; therefore it is 
thought that during their passage through the 
walls of the intestines they are changed to the 
characteristic blood proteins-serum albumin and 
serum globulin. Likewise, the fats which are 
broken up and saponified in the intestine must, it 
is thought, be reconstructed in their passage' 
through the intestinal walls, since fats, and not 
soaps, are found in the lacteals and blood after 
absorption. CHAPTER XIX 
METABOLISM; HEAT REGULATION 
Definition of Metabolism. Factors to which Metabolism is 
Due. Nature of Metabolic Changes. Object of Metabolism. 
Nature of Oxidation. Nature of Metabolism of the Various 
Food Substances. Food Requirement. Bad Effects that may 
be Caused by Ill-Regulated Diet. Where and how Heat is 
Produced in the Body. Distribution of Heat. Where and how 
Heat is Lost from the Body. Factors Regulating Involuntary 
Heat Regulation. Voluntary Methods of Regulating Heat. 
Effects of Cold, Tepid, and Hot Baths in Heat Regulation. 
Nature and Causes of Fever. 
Metabolism1 
794- Definition.-By metabolism is meant 
the changes that occur in the products of digested 
food from the time they are absorbed until they 
are eliminated in the excretions. 
795. Factors to which Metabolism is Due. 
-The more important factors in promoting the 
metabolic changes are: (1) the oxygen absorbed 
from the lungs; (2) the enzymes that are present 
in nearly all the more active tissues of the body; 
(3) the internal secretions. 
796. Nature of Metabolic Changes.-The 
1 From the Greek metabole.-a change. 
395 396 
Anatomy and Physiology 
chemical changes that occur in metabolism are 
many and various. Some of the more important 
are: (i) oxidation, i. e., the union of oxygen with 
material in or of the cells and their breaking down 
into simpler substances with the production of 
heat and energy1; (2) the formation of acids and 
salts--some of the substances resulting from oxi- 
dation are acids, and many of these combine with 
the alkalies present in the tissues to form salts2; 
e. g., protein substances contain sulphur, and when 
the sulphur is set free, as a result of the oxidation 
of the protein, it unites with water and oxygen, 
thereby being converted into sulphuric acid (H2 
SO4). This is a corrosive poison, and did it not 
at once unite with alkalies present in the tissues 
and thus become a salt,2 it would destroy the 
tissue cells with which it came in contact. (3) 
Glucose is changed to glycogen, a substance hav- 
ing the same chemical composition as dextrin. 
(4) Glycogen is reconverted into glucose, when 
the latter substance is needed in the tissues. (5) 
Glucose is changed to fat. (6) The cells select 
from the blood the special substances which they 
require for their growth and repair. (7) The 
1 See Glossary. 
2 All acids, however, are not neutralized-changed to salts- 
some are oxidized to C O2 and H2 O; others are excreted in the 
urine, which gives human urine its characteristic acid reaction. 
In certain diseases, as diabetes, in which metabolism is defective, 
the organism may become so surcharged with acid that acid 
intoxication or poisoning results and, unless the condition is 
relieved, death ensues. Metabolism ; Heat Regulation 
397 
material thus selected is synthesized or built up. 
It will be noticed that these changes are of two 
kinds-breaking and building. The splitting pro- 
cesses are termed katabolism,1 the building pro- 
cesses are termed anabolism.2 
797. Object of Metabolism.-The two fun- 
damental objects of metabolism are: (1) the 
building of the body tissues; (2) the production of 
heat and energy. 
798. Nature of Oxidation.-Formerly it was 
thought that oxygen alone was the cause of the 
decomposition continually going on in the body, 
but increased knowledge of the nature and results 
of the oxidation occurring within the body has 
caused this idea to be abandoned. The present 
most generally accepted theory is that the inciting 
cause consists of ferments or enzymes contained 
within the tissues. These, it is thought, cause a 
gradual cleavage of the complex material in the 
tissues into simpler substances, which under the 
influence of other enzymes-termed oxidases- 
undergo a still further breaking down with the 
intake of oxygen. 
Metabolism of the Various Food Substances 
799. Carbohydrates.-The carbohydrates, it 
will be remembered, are changed to glucose by the 
process of digestion, and absorbed by the capil- 
1 From the Greek kata-down and balto-to throw. 
2 From the Greek ana-up and balto-to build or throw. 398 
Anatomy and Physiology 
laries in the villi of the small intestine. After 
absorption the glucose is carried to the portal vein 
and thence to the liver, where the glucose mole- 
cules are put together with a loss of water, and so 
made into glycogen and as such stored in the liver,1 
or, if there is much, taken to the tissues and stored 
there. The reason for the change from glucose to 
glycogen is that glucose is a soluble substance and 
so could not be stored, but would remain con- 
stantly in the blood. This would be injurious, for 
the presence of glucose in the blood in abnormally 
large amounts is very irritating to the tissues. The 
normal quantity of glucose for the blood is about 
0.1 to 0.15 per cent., and this amount, in health, 
it maintains constantly,2 though it is continually 
giving glucose to the tissues to replace that oxi- 
dized there. That the blood can thus maintain a 
constant per cent, of glucose is due to the fact 
that as it parts with its supply the glycogen in the 
liver and tissues is reconverted into glucose. 
800. Factors Governing the Metabolism 
of Glucose.-The conversion of glucose into 
glycogen and glycogen into glucose, and the oxida- 
tion of glucose in the tissues is thought to be con- 
1 This process is known as dehydration. It is exactly the 
opposite of hydrolysis, the process by which starch and sugars 
are changed to glucose in digestion. 
2 The eating of large amounts of sugar, by providing more 
glucose than the liver can at the time change to glycogen, may 
temporarily surcharge the blood with glucose, but this will be 
eliminated in the urine. This is further described in paragraph 
892. Metabolism ; Heat Regulation 
399 
trolled by the nervous system1 and to be influenced 
by certain enzymes contained in the liver and the 
tissues. For the oxidation of the glucose in the 
tissues the internal secretion of the pancreas also 
is necessary. 
8oi. Products of Carbohydrate Metabo- 
lism.-The final products resulting from the oxida- 
tion of glucose are carbon-dioxide and water. It is 
thought that glucose is first split to lactic acid and 
then oxidized and that at least a portion goes 
through the same stages that occur in the fermen- 
tation of glucose outside the body.2 
802. Results of Metabolism of Carbohy- 
drates.-The oxidation of glucose3 in the body 
has the following results: The heat necessary to 
keep the body warm is supplied, also the energy 
required to maintain muscular work and metabo- 
lism; undue oxidation of the body tissues is pre- 
vented (in starvation, or when oxidation is taking 
1 One reason for this supposition is that if a puncture is made 
in a certain part of the medulla oblongata, the metabolism of 
glucose is interfered with and glucose appears in the urine. 
2 Wines are made from the juice of grapes by the fermentation 
of their glucose, the glucose being converted by fermentation 
into alcohol. If wine is exposed to the air for some time it under- 
goes further fermentation or oxidation and becomes sour, the 
alcohol being changed to an acid. If the acid is still further 
fermented it will be broken down into carbon-dioxide and water. 
3 Disease of the pancreas which interferes with the formation 
of the internal secretion results in the defective oxidation of 
glucose, thus the blood is surcharged with glucose which gives 
rise to many constitutional disturbances. The condition is 
known as diabetes. The changes caused in the constituents of 
the urine by the disease will be discussed in Chapter XX. 400 
Anatomy and Physiology 
place more rapidly than food can be assimilated, 
as in fever, the body tissues are oxidized and 
emaciation results). If more carbohydrate food 
is taken than can be oxidized or stored in the liver 
and tissues as glycogen, the excess glucose will 
be changed to fatty tissue. 
803. Metabolism of Fats.-It will be remem- 
bered that the greater part of the digested fat is 
absorbed by the lacteals in the form of chyle, 
and is then carried to the thoracic duct and thence 
emptied into the left innominate vein, and thus 
enters the blood. The fat remains circulating in 
the blood for a considerable time, being slowly 
picked out as required by tissues' which can use 
it in their metabolic processes. Within these 
tissues it ;s oxidized to C 02 and H20, thereby 
supplying heat and energy, and that not required 
for these purposes is stored up as body fat in 
certain parts of the organism. 
804. Function of Fats.-(1) By their oxida- 
tion they yield heat and energy; (2) when stored 
in the tissues (a) they supply substance for oxida- 
tion when there is a lack of food, either because 
of deficiency of food or in disease, and thus pro- 
tect the protein parts of the body from oxidation. 
The reason why this is of special value will be 
discussed under protein metabolism, paragraph 
807. (Z>) The fat under the skin prevents the too 
rapid radiation of heat, and thus helps to keep 
the body warm. 
805. Source of Body Fat.-The main sources Metabolism; Heat Regulation 
401 
of body fat are the fat and the carbohydrate 
foods. 
806. Cause of Excess Storage of Fats- 
Obesity.-A common cause of obesity is eating a 
larger amount of food than is necessary for the 
body requirements (paragraph 811) especially fat 
and carbohydrate foods. Other causes are: the 
leading of a sedentary life, lack of muscular exer- 
cise, absence of worry, and all other conditions not 
calling for muscular or nervous energy. Some 
individuals store fat much more easily than others. 
This is thought to be due to a difference in the 
capacity to oxidize food-products. This capacity 
is greater in youth than in old age, and at all 
times some people possess it to a much greater 
extent than others. 
807. Metabolism of Proteins.-As stated 
in the last chapter, the proteins are broken into 
peptones, polypeptids, and amino-acids in the 
course of digestion. As these substances normally 
are not found to any extent in the blood, it is 
thought that they must be synthesized into blood 
proteins-e. g., serum albumin and serum globulin, 
in the act of absorption, as they pass through the 
epithelial cells of the intestinal wall. The tissues 
take these substances from the blood as they 
require to replace the body tissue that is being 
continually disintegrated, and in some way, as 
yet unknown, build them up into a more complex 
body tissue. The protein substances absorbed, 
but not utilized for tissue building or repair, are 402 
Anatomy and Physiology 
oxidized, it is thought, in the liver, and thereby 
split into: (i) what is known as an ammonia mole- 
cule and (2) molecules consisting of carbon, oxygen 
and hydrogen, the same elements of which the 
carbohydrates and fats are composed. The latter 
are used for the same purposes in the body as the 
carbohydrates and fats. The ammonia molecule 
contains the nitrogen of the protein. When it is 
further oxidized it is transformed into urea and 
similar substances and carried by the blood to the 
kidneys, and excreted in the urine. Other waste 
products of the oxidation of proteins found in 
the urine are: uric acid, creatinin, xanthin, etc. 
These are derived partly from protein foods, 
but largely from the katabolism of the body tissue. 
808. Nitrogen Equilibrium.-The body is 
said to be in nitrogen equilibrium when the amount 
of nitrogen in the urine is the same as that taken 
in food. Protein molecules contain 16 per cent. 
nitrogen.1 
809. Function of Protein.-The principal 
purpose of the food proteins, except certain simple 
ones such as gelatin and the extractives, is to build 
muscular tissue, and the body is entirely depend- 
ent upon proteins for this purpose, for as the fats 
and the carbohydrates do not contain nitrogen, 
they are unable to do so. The proteins also, by 
virtue of their C O H molecules, perform the same 
offices as the carbohydrates and fats and yield 
1 Students who wish to know more about nitrogen equilibrium 
are referred to Text-Book of Physiology, Chapter XLVII. Howell. Metabolism; Heat Regulation 
403 
heat and energy, and may even be built into adi- 
pose tissue. Gelatin and extractives, though they 
contain nitrogen, are lacking in some of the essen- 
tials for tissue building, and therefore serve only 
for the same purposes as carbohydrates. The 
nitrogen is split off, as in the case of the other 
proteins, in the liver and excreted in the urine. 
8io. Heat Value1 of the Food-Stuffs.-As 
the result of many experiments, it has been found 
that every gram of protein yields to the body about 
four calories of heat; every gram of carbohydrate 
four calories; every gram of fat nine calories. 
8ii. Food Requirement.-The amount of 
food actually required to provide sufficient heat to 
maintain the normal body temperature, to yield 
the necessary amount of energy, and build and 
repair body tissue, will depend upon the indi- 
vidual's occupation, size, sex, and the climate. 
The more muscular force an individual's occupa- 
tion entails, the greater amount of food he will 
require; a large person requires more food than a 
1 The intensity of heat is measured by the clinical thermometer 
and recorded in degrees; the amount of heat is measured with the 
calorimeter and recorded in calories. There are two kinds of 
calories. A small calory is the amount of heat required to raise 
the temperature of one gram of water i degree C; a large calory 
is that required to raise the temperature of i kilogram (1000 
grams) of water i degree C. It is the large calory that is referred 
to in physiology. The difference between the intensity and the 
amount of heat can be illustrated as follows: if boiling water is 
poured into a cup and a quart pitcher, the temperature in both 
vessels is, for the time being, the same; but there is a larger 
amount of heat in the pitcher. 404 
Anatomy and Physiology 
small one, the greater amount of tissue resulting 
in more internal work; a tall, thin person will need 
more than a short, stout person of equal weight, 
on account of the larger skin surface exposed for 
the radiation of heat. Women, being as a rule 
smaller than men and expending less energy in 
their movements, require less food than men- 
about four-fifths of a man's rations. Children 
need food for growth as well as for the repair of 
tissue, and expend comparatively more energy 
than adults, and therefore require more food in 
proportion to their weight than the latter. The 
average comparative amount of food required by 
children can be seen in the following table: 
A child 14 to 16 years requires 0.8 the food of a man doing moderate work 
" " 10 " 13 " " 0.6 " " " " " " " " 
" " 6 " 9 " " 0.5 " " " " " 
" " 3 " 5 " " 0.4 " " 
" .< 2 « « 0 3 .< .< << « <■ <. .. 
By investigating the quantity of food eaten by a 
large number of people in good health and em- 
ployed in various occupations, and by careful 
quantitative analysis of all the excreta, thus deter- 
mining the amount of metabolism going on in the 
body, it has been estimated that a man weighing 
about 140 lbs. needs sufficient food during twenty- 
four hours to yield: 
Calories. 
" When not doing muscular work 2450 
" doing light muscular work {sedentary) 2700 
" " " to moderate muscular work 3050 
" " moderate muscular work 3400 
" " very hard " " 5500 " 1 
1 Circular No. 46. 1906. United States Department of 
Agriculture, Office of Experiment Station. Metabolism; Heat Regulation 
405 
812. Comparative Average Proportion of 
Proteids, Fats, etc., Used.-The comparative 
proportion in which the food principles are used is 
about as follows: sufficient protein food is used to 
give one-fifth the number of calories required; 
sufficient fat to yield a like number of calories; 
sufficient carbohydrates to make up the remaining 
three-fifths of the calories. Thus, to get 2450 cal- 
ories sufficient protein food is used to give 490 
calories, and as each gram of protein yields 4 
calories this would mean 122.27 grams of protein. 
Sufficient fat is used to yield 490 calories, and as 
each gram of fat gives 9 calories, this would mean 
about 54 grams of fat. Enough carbohydrate is 
used to yield 1470 calories, and as each gram of 
carbohydrate gives 4 calories this would mean 
367.2 grams of carbohydrates. A table giving the 
relative amount of protein fats and carbohydrate 
in a few typical foods will be found at the end of 
the glossary. 
813. Bad Effects of too Much and too 
Little Food.-The continual indulging in food 
much in excess of the body requirements favors 
the formation of excessive adipose tissue and is 
conducive to disease because it overworks the 
secretory and excretory organs, and, in the case of 
proteins, overloads the system with the products 
of intestinal putrefaction. Excessive quantities 
of carbohydrates are the source of flatulence due 
to the fermentation of these food-stuffs; also too 
much fat is thought to retard the secretion of the Anatomy and Physiology 
406 
gastric juice and so interfere with digestion. On 
the other hand, a lack of nutritious food weakens 
the body's natural power of resistance to disease. 
Heat Production 
As has been stated repeatedly in the preceding 
pages, one of the most important uses of food is 
the production of heat. 
814. How Heat is Produced.-The heat pro- 
duced in the body arises principally from such of 
the chemical changes going on in the tissues as are 
associated with oxidation. Some of the minor 
sources of heat are friction, e. g., that caused by 
the movements of the muscles, circulation of the 
blood, etc., and the ingestion of warm food. 
815. Where Heat is Produced.-After the 
circulation of the blood was described by Harvey 
in 1628, physiologists taught that the body heat 
was the result of friction due to the circulation of 
the blood and the action of the heart and blood- 
vessels. Later, when the signification of respira- 
tion became better understood, it was taught that 
heat was created in the lungs and distributed 
through the system by means of the blood. But 
modern physiologists have proven conclusively 
that heat is developed in all the living tissues 
of the body, but is produced to a greater extent in 
those tissues in which metabolism is most active, 
as the muscles and the secreting glands, especially 
the liver. Metabolism ; Heat Regulation 
407 
816. Distribution of Heat.-Though a 
greater amount of heat is formed in some tissues 
than in others, the temperature of all the internal 
parts of the body is about alike. This is due to 
the uniform temperature which the blood main- 
tains by circulating rapidly from vessels situated 
in tissues where oxidation is greatest to parts 
exposed to radiation and evaporation, thus bal- 
ancing its gain and loss of heat. 
817. Loss of Heat.-In health the human 
body maintains a constant temperature between 
98° and 990 F. In order to do this, as heat is 
being continually created within the body, there 
must be an equally constant loss of heat. This 
loss is effected in several ways: (1) by radiation 
and conduction from the external surface of the 
body; (2) by constant evaporation of water from 
the same part1; (3) by taking into the lungs colder 
air than that given out; (4) by the loss of warm 
substances from the body, as the urine and feces; 
(5) by the ingestion of cold food and drink. The 
effectiveness of these different channels for the 
loss of heat varies greatly, as can be seen by the 
following table: 
By radiation and conduction from skin 73-0% 
By evaporation from skin 14-5% 
By expired air (vaporization of water from lungs) 7-2% 
" " " (warming of air) 3-5% 
" urine and feces 1.8% 
1 In order that water may evaporate, heat is required-about 
0.5 calories for each gram of water that is evaporated. The heat 
necessary for the evaporation of sweat is taken from the body. 408 
Anatomy and Physiology 
The loss of heat due to the ingestion of cold food 
and drink is so small that it need hardly be 
counted. 
Certain conditions, such as the external tempera- 
ture, may cause considerable difference in the per 
cents, given above, especially in the radiation and 
evaporation; e. g., a high external temperature 
will diminish the loss of heat by radiation and 
increase that by evaporation, owing to the greater 
production of sweat. 
From the figures in the above table it will be 
seen that the skin is the principal factor in getting 
rid of body heat. That it is so is due: (1) to the 
large surface offered for radiation, conduction, 
and evaporation; (2) to the large amount of blood 
which it contains. 
Heat Regulation 
Heat regulation may be said to be effected by 
involuntary and voluntary means. 
818. Influence of the Nervous System on 
Involuntary Heat Regulation.-In health the 
loss and production of heat are so evenly balanced 
that the temperature of the body, as previously 
stated, remains almost constantly between 98° 
and 990 F. This is largely due to the control 
exerted by the nervous system, which is one of the 
principal factors in regulating the amount of heat 
lost through the skin and lungs, and of the degree 
of metabolism taking place in the tissues. Metabolism; Heat Regulation 
409 
819. Influence of the Nervous System in 
Heat Regulation by the Skin.-The regulation 
of body heat by the skin is effected by means of 
the sensory nerves of the skin, the sweat nerves, 
and the vaso-motor nerves. Thus, when the 
external temperature is warmer than usual, the 
nerve-endings in the skin which respond to heat 
are stimulated, and impulses passing from these 
sensory nerves to the centers controlling the motor 
nerves of the sweat glands, the production of 
sweat is increased, and the greater the amount of 
perspiration the greater the amount of heat that 
will be taken from the body to vaporize the water. 
If there is much humidity in the air, however, the 
evaporation of water is hindered and the produc- 
tion of h@at in the body may become excessive. 
This is one of the most common causes of the 
condition known as heat prostration or sunstroke. 
In addition to stimulating the sweat nerves, the 
stimulus from the sensory nerves affected by heat 
causes depression of the vaso-constrictors of the 
skin arterioles, in consequence of which these 
vessels become dilated and an increased supply of 
blood comes to the surface, where it loses some of 
its heat by radiation. On the other hand, when 
the external temperature is cold, the nerve-end- 
ings in the skin which react to cold are stimulated 
and carry impulses to the vaso-motor centers, in 
consequence of which the vaso-constrictors are 
stimulated, and consequently the skin blood- 
vessels become contracted and the blood is driven Anatomy and Physiology 
410 
from the skin, thus lessening the amount of heat 
lost by radiation. 
820. Influence of the Nervous System in 
Heat Regulation by the Respiration.-The 
stimulation of the cold nerves of the skin influences 
the respiratory centers, thereby causing an increase 
in the rate of respiration, and consequently aug- 
menting the loss of heat to some extent. In man, 
however, the respiration plays only a small part 
in heat regulation, but in animals covered with a 
coat of hair, which interferes with the loss of heat 
through the skin, respiration is a very important 
factor. 
821. Influence of the Nervous System in 
Controlling Heat Regulation by Metabolism. 
-How the nervous system influences metabolism 
has not yet been decided. Some physiologists 
consider that there are special nerves and heat 
centers which, influenced by the temperature of 
the blood, augment or inhibit the rate of metabo- 
lism; but many others do not believe in the exist- 
ence of special heat centers and think that the 
variations in heat production occur simply as the 
result of reflex excitation of the motor nerve- 
fibers supplying the muscles which, when 
stimulated by cold, cause a condition of greater 
contraction in those organs and, in consequence, 
an intensification of the oxidation taking place in 
them. The vaso-motor system also influences 
metabolism to some extent, for the process is 
accelerated when, under the influence of cold, Metabolism; Heat Regulation 
411 
the blood is driven, as described in the preceding 
paragraph, to the interior of the body and in- 
hibited when, under the influence of heat, a 
greater amount of heat goes to the surface of the 
body. 
822. Voluntary Methods of Controlling 
Heat Regulation.-The usual voluntary means 
taken to control heat production and elimination 
are: the use of suitable clothing; regulation of mus- 
cular exercise and diet; use of cold and hot baths. 
823. Clothing.-Clothing serves to protect 
the body against cold by diminishing the loss of 
heat from the skin by radiation and evaporation. 
The properties to be considered in clothing with 
regard to heat regulation are: whether it is loosely 
or tightly woven, its thickness, and to a slight 
extent whether it is of light or dark color. A fairly 
loosely woven fabric will be warmer than a tightly 
woven one, because the loosely woven one is 
capable of holding considerable air in its meshes, 
and air, being a poor conductor of heat, will 
prevent heat radiation. Wool, silk, linen, and 
cotton will have about the same heat value if they 
are equally thick and equally porous. Wool, the 
texture of the materials being the same, may have 
a slight advantage over the silk, linen, etc., in 
retaining heat, in that evaporation of moisture 
takes place more slowly from wool than from the 
other fabrics. Thin, very porous material used as 
clothing helps to keep the body cool, because it 
allows the air to penetrate to the skin, and thus Anatomy and Physiology 
412 
facilitates the evaporation of sweat. Evaporation 
of absorbed perspiration takes place more quickly 
from cotton and linen than from woolen material, 
and they are usually of lighter weight, therefore 
they provide a cooler form of clothing. Dark- 
colored clothing absorbs heat to some extent, and 
therefore is somewhat warmer than white or light 
fabrics. 
824. Regulation of Heat by Muscular 
Movement.-Muscular contractions are attended 
by a marked liberation of heat, therefore muscular 
activity is a frequently used means of counteract- 
ing the effect of external cold. On the other hand, 
in hot weather the tendency is to move slowly and 
as little as possible. That the body temperature 
does not rise to any marked extent as the result 
of muscular activity in hot weather is due to the 
other phenomena attendant upon activity, viz., 
the dilation of the cutanepus blood-vessels and 
consequent flow of blood to the surface, and to the 
increased amount of perspiration. 
825. Effect of Baths in Heat Regulation 
-Cold Baths.-The primary physiological action 
of a cold bath is to contract the cutaneous blood- 
vessels and thus drive the blood to the internal 
organs and increase heat production; but if the 
individual remains only a few minutes in the 
bath, when he leaves it the hot blood comes to the 
surface and there is an accelerated circulation of 
blood through the skin whereby an increased 
quantity of blood is exposed to the cooling in- Metabolism; Heat Regulation 
413 
fluences that act upon the surface of the body, 
thus increasing heat elimination. This constitutes 
the so-called reaction. A cold bath continued for 
some time will, if it does not produce shivering, 
lower the temperature of the muscles lying beneath 
the skin as well as that of the skin itself, and thus 
check the heat-producing processes that are active 
in the muscles. If shivering is produced the con- 
sequent muscular contraction and constriction of 
blood-vessels induce a very decided increase in 
metabolism and heat-production. It is to avert 
this condition that friction is applied during cold 
baths given in fever. The friction by irritating 
the sensory nerves of the skin causes dilation of 
the superficial blood-vessels and the flow of hot 
blood to the surface of the body, thus minimizing 
the sensation of cold and preventing shivering. 
Cold baths, when properly administered, stimu- 
late the nervous system and thus improve muscu- 
lar tonicity, including the muscle of the heart and 
blood-vessels; in this way the circulation is im- 
proved and heat elimination favored. 
826. A Tepid Bath.-A bath of about 950 F., 
by dilating the arterioles of the skin thus causing 
the blood to come to the surface, and increasing 
loss of heat by radiation, will lower the body 
temperature, and the reduction will be greater if 
the tepid bath is followed by a cold one. 
827. A Hot Bath.-A bath above the tempera- 
ture of the body, by preventing radiation of heat 
from the surface of the body, will induce a rise of 414 
Anatomy and Physiology 
temperature. If, however, the individual remains 
in the bath only a short time this effect may be 
counteracted by the increased perspiration and 
loss of heat by radiation that will follow. 
Fever or Pyrexia 
828. Characteristics.-Fever is an abnor- 
mal condition, characterized by elevated tempera- 
ture, quickened respiration and circulation, faulty 
secretions, and increased tissue waste. It is de- 
pendent upon a perversion of the physiological 
processes whereby the generation and loss of heat 
are so balanced as to maintain a uniform tempera- 
ture. 
829. Cause.-The exact cause of fever is un- 
known. As has been previously stated, some 
physiologists believe that there is a heat-regulat- 
ing center which controls the production and 
elimination of heat, and those who believe in such 
a center think that fever may be due to disturb- 
ance of this center by toxic substances circulating 
in the blood, or other abnormal conditions. 
830. Origin of Toxins.-The toxic substances 
producing the thermogenic disturbances may owe 
their origin to bacteria, as in the infectious dis- 
eases; to faulty metabolism, as in gout, diabetes, 
etc.; or to mechanic, thermic, or chemical injury 
to the tissues. 
831. Fever a Protective Measure.- 
Though fever is an abnormal condition it is now Metabolism; Heat Regulation 
415 
thought to be one of nature's protective measures, 
for the body, especially when pyrexia is due to bac- 
terial invasion, seems to be able to fight the poison 
better when its temperature is somewhat elevated. 
This is one reason why antipyretics are not used, 
unless the temperature remains persistently high, 
or the elevation is extreme. Of course, in either 
of the above instances measures must be taken to 
reduce the temperature, or changes will be pro- 
duced in the tissues of the body that may cause 
death. 
832. Baths in Pyrexia.-The use of baths in 
febrile conditions is usually not so much to lower 
the temperature as for their effect on the circula- 
tory, respiratory, and nervous systems. If these 
are favorably affected the temperature, probably, 
will be somewhat reduced. CHAPTER XX 
ELIMINATION 
The Urinary System 
Names of the Excretory Organs. Nature of the Excreta 
Eliminated through these Organs. Name, Location, Structure, 
and Function of Each of the Organs comprising the Urinary 
System. Nature of the Processes of Secretion and Elimina- 
tion of Urine. Quantity of Urine Voided in Twenty-four Hours. 
Physical Properties of Urine. Normal and Abnormal Con- 
stituents of Urine. 
833. It has been stated repeatedly in the pre- 
ceding chapters that the life processes of the body 
are attended with the formation of waste products, 
which must be removed from the system, many 
of them being of a toxic nature. This waste 
matter is spoken of as excreta, the process by which 
it is discharged from the body as excretion or 
elimination, and the organs through which the 
elimination takes place as the excretory organs. 
834. The names of the excretory organs are: 
2 kidneys 
2 ureters 
i bladder 
i urethra 
i. The organs of the urinary system 
416 Elimination 
417 
2. Lungs 
3. Intestines 
4. Liver 
5. Skin 
The waste matter discharged through each of 
these organs is as follows: 
835. (1) By the urinary organs: practically all 
of the protein waste1-both that of metabolized 
food protein and body tissue, nearly all the salts,2 
about four-fifths of the water that is excreted,3 
and a small amount of carbon-dioxide. 
•836. (2) By the lungs: water and nearly all 
the carbon-dioxide formed by oxidation. In dis- 
eased conditions of the kidneys a small amount of 
urea is sometimes removed by the lungs, and is 
easily detected by the odor it imparts to the 
breath. 
837. (3) The liver eliminates the bile which 
contains waste products secreted from the blood 
and those formed in the liver. 
838. (4) The intestines eliminate not only 
1 This consists principally of such substances as urea, uric acid, 
creatinin, xanthin, etc. 
2 The salts excreted represent those taken in food and not 
utilized; those liberated in the breaking down of body tissue; 
those formed by the neutralization of the acids resulting from 
the metabolism of food products and body tissue, as described 
in paragraph 796. 
3 When the skin is very active less water is excreted by the 
kidneys. The water eliminated from the system consists of that 
ingested in both liquid and solid food, and that formed in the 
body as the result of chemical reactions. 418 
Anatomy and Physiology 
undigested and unabsorbed food material, as de- 
scribed in paragraph 790, but some salts, and, 
when the kidneys are diseased, some of the waste 
of protein metabolism. These last-named sub- 
stances pass from the blood as it flows through 
the capillaries in the intestinal walls. 
839- (5) The skin eliminates water, ordina- 
rily about one quart1 in twenty-four hours; a small 
amount of salts and protein waste. The amount of 
protein excreted by the skin is increased when free 
perspiration is induced, especially when the kid- 
neys are not functioning properly. 
Of these organs, those comprising the urinary 
system are the only ones concerned solely in ridding 
the body of waste products. 
Anatomy and Function of the Urinary System 
The urinary system consists, as previously 
stated, of the two kidneys, the two ureters, the 
bladder, and the urethra. 
The Kidneys 
840. Nature and Location.-The kidneys 
are two compound tubular glands situated in the 
posterior part of the lumbar region of the abdo- 
men, one on either side of the spinal column, 
behind the peritoneum. They correspond in posi- 
tion to the two last dorsal and two upper lumbar 
1 This quantity is greatly increased when the body becomes 
over-heated, and the amount then eliminated by the kidneys is 
correspondingly diminished. Elimination 
419 
vertebrae. The right kidney is slightly below the 
left in consequence of the position of the liver. 
841. How Retained in Place.-The kidneys 
are retained in place by the fat in which they are 
imbedded, by the peritoneum which covers their 
anterior surface, and by their ureters and large 
blood-vessels. A diminution of the fat surround- 
ing the kidneys is sometimes the cause of their 
becoming loosened from their position, a condi- 
tion that is known as floating kidney. 
842. Shape.-The kidneys are bean-shaped 
and lie with their concave side toward the spine 
and their convex side directed outward. Near 
the center of the concave side is a notch or 
depression called the hilum, which is the passage- 
way for the ureter and for the blood and lymph- 
vessels, and for the nerves going to and from the 
kidneys. 
843. Size.-The kidneys are about 4 inches 
long, 2^2 inches broad, and iX inches thick, and 
each one weighs about 4X ounces (135 grams). 
844. Names of the Various Parts of Each 
Kidney.-Each kidney may be said to consist of: 
(i) A capsule 
(2) A cortex 
(3) A medullary 
portion 
(4) A pelvis 
Malpighian capsule 
Glomerulus 2 
Malpighian 1 bodies 
' Pyramids of collect- 
ing tubes 
Calyces or cups 
1 Named after Malpighi, a celebrated anatomist. 
2 From the Latin glomerulus-a ball. Anatomy and Physiology 
420 
845. Structure.-Each kidney may be said 
to consist of a central cavity surrounded, except 
at the hilum, by kidney substance. The cavity 
which is called the pelvis is in reality the expanded 
portion of the ureter-the tube connecting the 
kidney with the bladder. The kidney substance 
consists principally of a vast number of minute 
tubes known as the urinary or uriniferous tubes 
or tubules and blood-vessels held together with 
areolar tissue. The outer portion of this sub- 
stance is more compact than that immediately 
surrounding the pelvis and is known as the cor- 
tex1; the less dense portion is called the medulla.2 
846. The Uriniferous Tubes.- The urinifer- 
ous tubes3 commence at the cortical portion of the 
kidney as hollow globes, dented in the center, as 
in Fig. 121, called the Malpighian capsules. The 
tubes at their connection with the capsules are 
very convoluted (see Fig. 121), but they finally 
pass as straight tubes through the medullary 
portion of the kidney and terminate by open 
mouths in the cup-like processes of the pelvis 
known as the calyces. The tubes are bound to- 
gether in cone-shaped bundles called pyramids. 
There are about a dozen such pyramids in a 
human kidney, each one comprising innumerable 
tubes. 
1 From the Latin cortex-bark. 
1 See foot-note page 166. 
s "It has been estimated that each kidney contains about half 
a million capsules and fifteen miles of tubing."-Gerrish. Fig. 12 i.-Diagram of the structure of a lobe of the kidney. The lobe 
is seen in vertical section, the cortex being marked off from the medulla. 
Four medullary rays encroach upon the cortex. At the left is shown the 
course of a single, continuous series of tubes-the straight and spiral tubes 
appearing in the medullary ray, the straight, looped, and excretory in the 
medulla proper, the capsule, neck, convoluted, irregular, and arched in 
the cortex proper. Next is seen the labyrinth, composed of a mass of 
tubes in the cortex, with a medullary ray for a centre. Equidistant 
from the ray on each side is a broken red line, marking the position 
of an interlobular artery. The parts between these lines constitute a 
lobule. Farther to the right is an interlobular artery, giving off lateral 
branches (afferent vessels), each of which ends in a tuft of capillaries, from 
which the blood is collected by an efferent vessel. The uppermost of the 
tufts is shown enclosed in a capsule. On the right of the interlobular artery 
the efferent vessels break up into a capillary network which surrounds the 
(unrepresented) tubes in the cortex and ray. The lowest efferent sends 
vertical vessels also into the medulla. On the right the interlobular vein 
is seen gathering the blood from all the parts supplied by the interlobular 
artery. A branch of the venal artery courses upward between cortex and 
medulla, and forms an arch (here broken) over the base of the medulla. 
From it the interlobular arteries pass upward into the cortex, and straight 
branches go downward into the medulla, supplying its structure, and ending 
at the apex in the capillaries. From the last the radicles of the venal vein 
arise, and accompany the straight arteries to the base of the medulla, 
where a venous arch is formed, continuous with which is the vena comes of 
the entering artery. The calyx embraces the apex of the medullary 
pyramid. It is lined with epithelium, which continues from it over the 
apex, the latter being perforated with the many apertures of excretory 
tubes. (Gerrish.) Elimination 
421 
847- Malpighian Bodies.-In the dented por- 
tion of each Malpighian capsule there is a tuft of 
capillary blood-vessels called a glomerulus. The 
capsule and blood-vessel combined are known as 
a Malpighian body. Each body is about of 
an inch in diameter. The walls of the Malpighian 
capsule as well as those of the glomerulus are 
exceedingly thin and closely adherent, thus facili- 
tating the passage of substances from the blood 
into the tubes. 
848. The Kidney Capsule.-Each kidney is 
covered by a tough fibrous membrane termed the 
capsule. The inner surface of which is slightly 
attached, by means of fine fibers of areolar tissue 
and minute blood-vessels, to the substance of the 
kidney. At the hilum of the kidney this capsule 
becomes continuous with the external coat of the 
ureter. 
849. Blood Supply of the Kidney.-The 
kidney is plentifully supplied with blood by the 
renal artery which, entering through the hilum, 
divides into several branches. These branches 
give off subdivisions that penetrate the kidney 
substance and carry nutriment to the tissues. 
The branches passing to the cortex give off small 
side-twigs which pass to the Malpighian bodies. 
One of these small afferent (carrying-to) vessels 
enters the dented portion of each capsule, and 
breaks up into a dense convoluted capillary plexus 
-the glomerulus-which is ultimately gathered 
up again into an efferent (carrying-from) vessel, 422 
Anatomy and Physiology 
that leaves the capsule near the point at which 
the afferent vessel entered. After leaving the 
capsule the efferent vessel breaks up once more 
into capillaries and forms a plexus over the sur- 
face of the tubules. Finally the capillaries unite 
to form small veins, and these joining the veins 
which hold the blood returning from the substance 
of the kidneys unite to form the renal vein which, 
leaving the kidney at the hilum, passes to the 
inferior vena cava. 
850. Purposes of the Different Sets of 
Capillaries.-It is from the capillaries of the 
glomeruli and those around the convoluted por- 
tion of the tubules that the passage of waste 
matter from the blood to the tubes takes place 
(see paragraphs 847 and 849); the other branches 
of the renal artery serving to hold the blood that 
carries the necessary nutriment to the substance 
of the kidney. 
851. Nerves and Lymphatics.-The kidneys 
are liberally supplied with nerves and with lym- 
phatics. The nerves are derived from both the 
cerebro-spinal and the sympathetic systems, many 
of them are vaso-motor nerves, and as these regu- 
late the contraction and relaxation of the blood- 
vessels the blood pressure in the kidneys is much 
influenced by their action. 
852. Function of the Kidneys.-The func- 
tion of the kidneys is to excrete waste matter 
resulting from metabolism, more especially the 
protein waste, water, and salts, and foreign mat- Elimination 
423 
ter such as poisons, either those taken into the 
body or those formed within the body-auto- 
intoxicants. 
853. Nature of Process.-The exact nature 
of the process by which the kidneys rid the body 
of these substances is not known beyond that 
it is not entirely a matter of simple filtration and 
diffusion, as was thought formerly, but due also 
to the part played by the epithelial cells lining the 
convoluted portion of the tubules which seem to 
make selection of the matter that is to pass into 
the tubules. This activity of the cells is spoken 
of as secretion, and can be compared to the secre- 
tory processes carried on by the secretory cells 
of the stomach, pancreas, and intestines, by 
which they pick out from the blood the substances 
they require for the manufacture of the digestive 
juices. 
854. Excretion of Water and Salts.-The 
diffusion of water and the salts which are in solu- 
tion in the water, takes place chiefly, it is thought, 
in the Malpighian bodies. These, it will be re- 
membered, each consist of a knot- of minute 
capillaries called a glomerulus, surrounded by a 
portion of a urinary tube. The blood in the 
glomeruli, owing largely to the small caliber of 
the vessels and their convoluted arrangement, is 
under considerable pressure1; in the urinary 
1 The degree of pressure is dependent chiefly upon, (i) the 
amount of blood passing through the vessels, (2) the nature of 
the heart-beat, (3) the action of the vaso-rnotor apparatus. Anatomy and Physiology 
424 
tubules, on the other hand, as the urine never 
remains therein but passes at once into the pelvis 
of the kidney and thence into the ureter, the 
pressure is at zero.1 It is therefore only natural, 
the walls of blood-vessels and tubules being very 
thin, that osmosis from the vessels into the tubes 
should take place. 
855. To recapitulate: the water and salts are 
thought to pass into the urinary tubules from the 
glomeruli by osmosis, and the protein waste from 
the capillary plexus on the walls of the convoluted 
portion of the tubules by secretion. 
856. Secretion of Protein Substances.- 
The epithelial cells lining the convoluted portion 
of the urinary tubules are different in structure 
from those of any other part of the tubes and 
similar to many of the secretion cells in the 
glandular organs. For this and other reasons 
which need not be entered into here, it is thought 
that the separation of the protein waste sub- 
stances from the blood is the special function of 
these cells. The manner in which the plexus of 
capillaries arising from the efferent vessels of the 
glomeruli adhere to the walls of the convoluted 
portion of the tubules (see paragraph 849) brings 
these cells into close relation with the blood which, 
owing to the small caliber and tortuous arrange- 
ment of the capillaries, flows, as in the glomeruli, 
very slowly and under considerable pressure. 
1 Pressure is said to be at zero when no pressure is exerted, 
which is of course the case if the tubes are empty. Elimination 
425 
The Ureters 
857. Function.-The ureters serve to connect 
the kidneys with the urinary bladder; they thus 
afford a channel for the urine from the former 
organs to the latter. 
858. Size.-Each u'reter consists of a distended 
portion called the pelvis, which is contained within 
the kidney, and a duct. The duct is about the 
diameter of a goose-quill and from 12 to 18 inches 
(300 to 400 mm.} long. 
859. Structure.-The walls of the ureters 
consist of three coats-an outer elastic coat, a 
middle muscular, and an inner niucous lining. 
The Urinary Bladder 
86o. Function.-The urinary bladder is a 
musculo-membranous sac which forms a reservoir 
for the urine in the intervals of its expulsion from 
the body. 
861. Location.-The bladder is situated in 
the pelvic cavity behind the pubes, in front of (in 
the female) the anterior wall of the vagina and 
neck of the uterus; in front of the rectum, in the 
male. In infancy the bladder extends into the 
hypogastric region of the abdomen; in the adult, 
when empty, it is contracted and lies low in the 
pelvis, and it never rises above the pelvis unless 
over-distended. In the latter case it may extend 
nearly as high as the umbilicus. It is freely 
movable but is retained in position by several 426 
Anatomy and Physiology 
ligaments, some of which are formed by folds of 
peritoneum and some of fascia extending from the 
walls of the rectum, uterus, etc. 
862. Divisions-Size.-The bladder is, for 
purposes of description, usually divided into the 
fundus or body and the cervix or neck, the latter 
being the constricted portion which is continuous 
with the urethra. When moderately distended 
the fundus measures about five inches in length 
and three inches across, and holds about one pint. 
863. Structure.-The wall of the upper part 
of the bladder consists of four coats, and that of 
the lower portion of three; the outer serous coat, 
which is derived from the peritoneum, being pres- 
ent only on the upper extremity of the fundus. 
The other coats are: (1) the muscular, (2) the 
areolar or submucous, (3) the mucous. The mus- 
cular coat is arranged in three layers, the fibers 
of the outer and inner layer having a longitudinal 
direction, and those of the middle a circular. 
The circular layer is especially developed in the 
cervix of the bladder and thus forms a sphincter 
which serves to control the passage of urine. 
864. Blood-Vessels and Nerves.-The blad- 
der is well provided with blood- and lymph-vessels 
and with nerves. The latter are derived from both 
the sympathetic and cerebro-spinal systems. 
The Urethra 
865. Nature and Size.-The urethra is a 
narrow membranous canal about one and one- Elimination 
427 
half inches in length in the female and eight or 
nine in the male. Its normal diameter is about 
one-quarter of an inch, but it is capable of con- 
siderable dilatation. 
866. Location.-The urethra extends from 
the neck of the bladder to the external orifice, 
which is known as the meatus urinarius. In the 
female it is situated beneath the symphysis pubis, 
and embedded in the anterior wall of the vagina. 
Its direction is obliquely downward and forward, 
its course being slightly curved, with the concav- 
ity directed forward and upward. It is important 
to remember the direction of the urethra, as it 
must be followed when introducing a catheter 
into the bladder. The external orifice of the 
urethra, the meatus urinarius, is situated between 
the clitoris and the opening of the vagina (see Fig. 
134, page 497). 
867. Structure.-The wall of the urethra con- 
sists of three coats: an outer muscular coat, a 
submucous, and a mucous. The last named is 
continuous with that of the bladder. The sub- 
mucous coat contains a network of large veins. 
Micturition 
868. Micturition is the act by which the urine 
is expelled from the bladder. It occurs, normally, 
as the result of irritation, due to the accumulation 
of urine, which stimulates the muscular walls of 
the bladder to contraction. This contraction 428 
Anatomy and Physiology 
causes the dilatation of the sphincter muscle and 
ejection of the urine. The action itself is involun- 
tary, but it can be controlled by voluntary effort. 
869. Causes of Involuntary Micturition. 
-Involuntary micturition may occur as the result 
of lack of consciousness; as the result of spinal 
injury involving the nerve-centers that send im- 
pulses to the bladder; in consequence of lack of 
"tone" in the muscular walls; or as the result of 
abnormal irritation. 
870. Retention.-Retention, or failure to pass 
urine from the bladder, may be due to: (1) some 
obstruction in the urethra or neck of the bladder, 
(2) nervous contraction of the urethra, (3) dulling 
of the senses so that there is no desire to pass 
urine. 
871. Retention with Overflow. - The 
bladder may become so fully distended that there 
is a more or less constant overflow or voiding of 
small amounts of urine, but the walls of the bladder 
are temporarily paralyzed and therefore do not 
contract sufficiently to empty the organ. 
The Urine 
872. Quantity.-The average amount of urine 
voided in 24 hours by a healthy adult is about 
40 to 50 ounces; by a child of 
2 to 5 years, 15 to 25 ounces 
5 to 9 years, 25 to 35 ounces 
9 to 14 years, 35 to 40 ounces Elimination 
429 
Causes likely to diminish the quantity of urine 
are: the consumption of a small amount of liquids, 
free perspiration, high fever, diarrhea, vomiting, 
and some disease of the kidneys. 
Causes likely to increase the quantity of urine are: 
the ingestion of a large amount of liquids; nervous- 
ness ; the action of diuretics; certain diseases, more 
especially diabetes mellitus, diabetes insipidus, 
and hysteria. 
873. Physical Properties.-Normal urine is 
a transparent, yellowish or light amber-colored 
liquid, with a characteristic odor, a slightly acid 
reaction, and a specific gravity of 1012 to 1030, 
1020 being the average. 
874. Specific Gravity.-By specific gravity 
is meant the weight of the urine as compared with 
that of distilled water at 6o° F., the weight of the 
water being 1000. The specific gravity indicates 
the relative proportion of solid matter in the urine, 
and when it is much increased the presence of 
abnormal constituents is often suspected; but an 
increase or decrease in the amount of urine, even 
from normal causes, will influence the specific 
gravity, since it will be lower if a large amount 
of water is secreted by the kidneys and higher if 
the urine is less dilute. 
875. Causes of Change of Color in Urine. 
-The conditions causing variations in the quan- 
tity of urine are also likely to change its color. 
When its secretion is diminished it is generally 
highly colored, the amount of solids present being Anatomy and Physiology 
430 
comparatively large. When its secretion is abnor- 
mally increased it is more dilute and is usually of 
a pale straw color, except when the increase is due 
to diabetes mellitus, in which case the color is 
darker, owing to the presence of sugar. Other 
causes of changes of color are: decomposition of 
the solid constituents of the urine; the presence 
of abnormal substances; large doses of certain 
drugs, such as iodoform, salol, guaiacol, and car- 
bolic, which make the urine olive green; logwood, 
which makes it blood-red; rhubarb and senna, 
which cause a bright orange color; methylene 
blue, which makes it a bluish-green shade. 
876. Reaction.-The acid reaction character- 
istic of the urine of the majority of human beings 
is due to the quantity of foods they eat of which 
the waste products are acid. After a diet consist- 
ing solely of carbohydrates the urine will be alka- 
line, as is the urine of herbivorous animals, because 
of the presence of ashes of plant foods which con- 
tain a large amount of alkaline matter. If human 
urine is allowed to stand for any length of time 
after being voided, it will become alkaline, unless 
it be kept sterile, because bacteria will break up 
its protein constituents into ammonia and other 
alkaline substances. This same kind of decompo- 
sition may take place within the body in certain 
diseased conditions of the urinary organs, espe- 
cially cystitis, and under such circumstances the 
urine will be alkaline when voided. 
877. Composition of Urine.-The urine nor- Elimination 
431 
mally consists principally of water, holding in 
solution certain organic substances, such as 
urea, urates, creatinin, xanthin, etc.-which are 
products of the oxidation of protein substances,- 
saline substances, and pigments. Also there may 
be, even in health, various other matters present 
derived from unusual articles of food, or from 
drugs that have been taken into the system. In 
diseased conditions, especially in disturbances of 
metabolism or of kidneys, other substances, which 
will be described later, may be present. Therefore 
the condition of the urine is often of value in 
determining the nature and progress of a disease, 
even when it does not affect the urinary system. 
878. Urea.-Urea, which constitutes nearly 
one-half of the solid constituents of urine, is 
formed in the body, largely in the liver, by the 
oxidation of protein substances derived from food, 
and, to some extent, from body tissue. Normally, 
an adult voids between 20 and 30 grams (about 
one ounce) daily, but the quantity will be increased, 
by a diet containing a large amount of protein 
food, by strenuous exercise, hot baths, fever in its 
early stages, and a few diseases. It will be di- 
minished, when only a small amount of protein 
food is eaten, by^free perspiration, excessive vomi- 
ting, and a few diseases, especially those which 
affect the kidneys and interfere with elimination. 
879. Uric Acid.-Uric acid, next to urea, is 
the medium by which the largest quantity of 
nitrogen is excreted from the body. It is thought 432 
Anatomy and Physiology 
that it is formed in the tissues, especially in the 
liver, from the nuclei of cells. Uric acid when 
pure is colorless, but it is not usually found in its 
free state in normal urine, but in combination 
with potassium, sodium, etc. Such combinations 
are known as urates. In gout its excretion is 
diminished and it accumulates in the blood and 
tissues. 
880. Creatinin, Xanthin, etc.-These sub- 
stances represent the so-called extractives of meat, 
and are therefore taken into the body with the 
food as well as formed in the tissues by the oxida- 
tion of protein substances. 
881. Salts.-The salts eliminated in the urine 
are derived both from food and as products of 
metabolism, as described in paragraph 796. The 
chlorides, next to urea, constitute the chief solid 
component of the urine. In certain diseases, 
especially those associated with serous exudation, 
as in edema, the amount of chlorides excreted is 
very much diminished. 
882. Abnormal Constituents of Urine.- 
Some of the more important abnormal substances 
found in urine are: albumin, glucose, acetone, 
indican, casts, calculi, pus, mucus, blood. 
883. Albumin.-As a rule, the normal renal 
cells do not allow albumin to pass through, but 
occasionally, as after extreme muscular exertion 
or overeating, they will. Albumin in the urine 
from such causes is spoken of as temporary or 
functional albziminuria. Albumin is frequently Elimination 
433 
present in the urine of persons suffering from 
heart disease in consequence of • the abnormal 
pressure changes in the renal blood-vessels, as the 
result of the damaged pump-the heart. It is 
usually, but not always, found in the urine of 
those suffering with nephritis, and it is very fre- 
quently present in the urine in cases of acute fever 
in consequence of an abnormal condition of the 
kidneys due to the disease. 
884. Glucose.-The blood, in health, main- 
tains a constant per cent, of glucose, about 0.1 
to 0.15%. More than this would be injurious to 
the tissues; therefore, when a larger quantity of 
sugar is eaten-e. g., candy-than the system can 
at the time change to glycogen or fat, the kidneys 
secrete and excrete it as quickly as possible. 
When glucose is found in the urine from the above 
cause it is called temporary glycosuria. Temporary 
glycosuria sometimes occurs also after injury to 
the head, during convalescence from febrile dis- 
eases, etc. In such cases the abnormal amount of 
sugar in the urine may be due to an inability of the 
system to oxidize the glucose; but the condition is 
usually relieved as convalescence is established. 
When glucose persists in the urine, the patient is 
said to have diabetes mellitus. One cause of this 
is disease of the pancreas which interferes with the 
secreting of the internal pancreatic secretion, one 
of the activating causes of the oxidation of the 
glucose in the tissues. In mild cases of diabetes 
the condition can be controlled by lessening the 434 
Anatomy and Physiology 
amount of carbohydrate food. In very severe 
cases glucose will appear in the urine when the 
diet is entirely free from carbohydrates, even in 
starvation, because the body tissues will be oxi- 
dized and glucose can be formed from protein 
substances. 
885. Acetone.-Acetone is a volatile com- 
pound sometimes found in the urine of individuals 
suffering from diseases associated with defective 
metabolism, and in normal persons during con- 
tinued fasting. It is thought to be the result of 
the incomplete oxidation of fats and, some authori- 
ties consider, of proteins. 
886. Indican.-The putrefaction of protein 
material in the large intestine gives rise to a sub- 
stance known as indol\ which, after absorption, is 
changed, it is thought, in the liver, into indican, a 
less poisonous substance than the former. Traces 
of indican are found in normal urine, but abnor- 
mal conditions are indicated if it is present in any 
amount. The more common causes of an in- 
creased quantity are: (1) Excessive putrefaction 
of protein substances in the intestine. This is 
usually due either to a diseased condition of the 
intestine which interferes with absorption of the 
normal products of digestion, to constipation, or 
to a diet containing too much protein food. (2) 
Diseases of the stomach, as the result of which food 
lies in that organ a long time and undergoes 
fermentative changes. 
887. Casts.-In certain abnormal conditions Elimination 
435 
of the kidneys the renal tubules become partially 
filled with substances which harden, thus forming 
moulds or casts of the tube. The casts are named 
either from their appearance or from the nature 
of the substances forming them. Thus, there are 
(i) hyaline1 casts-these are pale, translucent casts 
formed from coagulable elements of the blood 
which have transuded into the tubules; (2) pus 
casts; (3) blood casts-these need no explanation; 
(4) epithelial casts-these are composed of cells 
of the walls of the renal tubes which have become 
disintegrated and detached. If the cells have be- 
come decomposed, they are found in the urine as 
masses of granules and are known as granular casts. 
If, as sometimes occurs, they become fatty, they 
are known as fatty casts. The casts, whatever 
their nature, are washed out of the tubes by the 
urine and can be found therein with the aid of a 
microscope. 
888. Urinary Calculi or Stone.-Urinary 
calculi consist of deposits of solid matter that have 
been precipitated from the urine. They may 
form in any part of the urinary tract, from the 
tubules of the kidneys to the meatus urinarius. 
The most frequent causes of their formation are: 
(1) changes in the reaction of the urine, abnor- 
mally acid and abnormally alkaline urine tending 
alike to produce calculi; (2) the excretion of a 
smaller amount of water; (3) an increase in the 
less soluble constituents of the urine. Calculi vary 
1 From the Greek hyalos-glass. 436 
Anatomy and Physiology 
in size, shape, and composition; the size and shape 
depending largely upon their composition and 
location. 
889. Pus.-Pus cells are often present in the 
urine in nephritis and other inflammatory condi- 
tions either of the kidneys or other organs of the 
urinary system. 
890. Mucus.-Mucus may be present in nor- 
mal urine in small quantities; it consists principally 
of the epithelial debris from the mucous surface 
of the urinary organs. In inflammatory condi- 
tions of these organs, especially of the bladder, 
mucus is poured out over their surface and appears 
in large quantities in the urine. 
891. Blood.-Red blood-corpuscles are often 
found in the urine in cases of acute inflammation 
of any of the urinary organs, of tuberculosis, of 
cancer, and of renal stone or calculi. When there 
are many corpuscles present, the color of the urine 
is affected; it may even look like blood. When 
this is the case the condition is known as hema- 
turia. 
892. Toxicity of Urine.-Urine is a toxic sub- 
stance; unless it is secreted the condition known 
as uremia will occur; but the nature of the toxin 
has not been definitely determined. Formerly it 
was thought that the urea was the poisonous 
principle-hence the name uremia,-but numerous 
experiments have shown that this is not the case. 
However, whatever the source of its toxicity, 
urine is poisonous and must not be retained within Elimination 
437 
the body. This is especially the case in illness, 
because the renal cells, in order to protect the 
body, secrete any poisonous substances that find 
their way into the blood, and therefore in illness 
the urine frequently contains a larger amount 
than usual of toxic material, derived in some cases 
from defective metabolism, in others from bacterial 
activity. 
893. Suppression and Retention of Urine. 
-When the kidneys fail to secrete urine the 
condition is spoken of as suppression. It is usually 
due to disease of the kidneys. When the urine is 
secreted by the kidneys but retained within the 
bladder, the term retention is used. The causes of 
retention were given in paragraph 870. CHAPTER XXI 
THE SKIN AND ITS APPENDAGES 
Functions of the Skin. Different Parts. Structure and Mark- 
ings of the Cuticle. Cause of Blisters. Structure, Blood-vessels, 
Nerves, and Papillae of the Derma. Structure of the Sudoriferous 
Glands. Nature, Causes, and Function of Sweat. Ceruminous 
Glands. Structure of Sebaceous Glands. Nature and Function 
of Sebaceous Secretion. The Skin as an Absorbing Organ. 
Inunction. The Appendages of the Skin. Structure and Growth 
of Hair. Cause of Goose-Flesh. Structure and Growth of Nails. 
894- Functions.-The skin serves: (i) as an 
external integument for the protection of the 
softer and more delicate internal tissues; (2) as an 
important factor in heat regulation; (3) as a sense 
organ; (4) as an excretory organ; (5) as an absorb- 
ing organ; (6) as a respiratory organ. In some 
animals, as frogs and reptiles and earthworms, the 
skin serves as an important respiratory organ, 
but in man this action is very slight, only about 
one-half per cent, of the total amount of oxygen 
taken into the body being received, and an even 
smaller proportion of carbon-dioxide passing off, 
through the skin. 
895. Different Parts.-The skin consists of 
two main parts: (1) the epidermis,1 known also as 
1 From the Greek epi-upon and derma-the skin. 
438 The Skin and its Appendages 
439 
the scarf skin or cuticle1; (2) the derma, called 
also the cutis vera or true skin, and the corium.2 
896. Structure of the Epidermis.-The epi- 
dermis or cuticle varies in thickness from 24'0 to 
Fig. 122.-Vertical section of the skin, showing sebaceous 
glands, sweat-glands, hair, and follicle, also arrector muscle. 
(Gerrish). 
2k of an inch, being thickest on the palms of the 
hands and soles of the feet, and thinnest on the 
ventral surface of the trunk and inner surfaces of 
the limbs and large joints. It consists of several 
layers of cells which may be considered as divided 
into two main strata: (i) an upper or horny 
1 From the Latin cutis-the skin. 
3 From the Latin conum-the skin. 440 
Anatomy and Physiology 
stratum, the cells of which have become gradually 
flattened on their external surface and lost their 
nuclei. These are practically dead cells and are 
being constantly shed1 and renewed from the cells 
of the deeper stratum; (2) a germinative or Mal- 
pighian layer, which consists of soft protoplasmic 
cells that multiply by cell-division and, pushing 
toward the surface, become dry, hard, and flat, 
and replace the cells that are being constantly 
brushed off. The pigment in the skin of the negro, 
as well as that of the nipple and elsewhere in white 
races, is formed in the deepest cells of the Mal- 
pighian layer. Many of the end processes of the 
cutaneous nerves enter the Malpighian stratum, 
but the epidermis has no blood-vessels. 
897. Markings of the Cuticle.-The cuticle 
is closely adherent to the true skin and is accu- 
rately moulded over it so that the ridges and 
grooves which mark the surface of the latter are 
plainly discernible. Over most of the body these 
grooves are shallow and not very marked, but on 
the palms of the hands and soles of the feet they 
form definite patterns, peculiar to each individual, 
which never change throughout life, regardless of 
other changes in the hands due to change and toil. 
Hence the value of hand impressions in wax as a 
means of identification. 
898. Cause of Blisters.-Though the cuticle 
is so blended with the derma, it is easily separated 
1 When the body temperature is high these cells are shed very 
quickly. The Skin and its Appendages 
441 
from the latter by strong or long-continued irrita- 
tion, and fluid collects between the two, due to the 
increased blood supply in the part subjected to 
the irritation. The separated cuticle is called a 
bleb or blister. 
899. Structure of the Derma.-The true 
skin or derma consists of white fibrous and elastic 
connective tissue containing innumerable blood 
and lymphatic vessels, nerves, glands, hair-follicles, 
and papillae. The upper surface is connected, as 
previously described, with the epidermis, and its 
upper surface is held to the superficial fascia lying 
beneath it by loose areolar tissue in which (with 
the exception of that in the eyelids, labia minora,1 
and scrotum1) there is a varying quantity of fat 
cells. This subcutaneous layer of tissue enables 
the skin to move freely on the underlying fascia. 
900. Papillae of the Derma.-The upper sur- 
face of the derma is covered with small ridges or 
grooves, as described in paragraph 897, and on the 
summit of the ridges are small papillae, which are 
received into pits that are in the under surface of 
the epidermis. The average length of papillae 
is about 10 0 of an inch, and at their base the 
diameter is about 250 of an inch. Some of these 
papillae have loops of blood-vessels prolonged into 
them, and some have touch corpuscles. They are 
most numerous where sensation is most acute, 
as the cushions of the fingers, palms of the hands, 
and soles of the feet. 
1 Described in Chapter XXV. Anatomy and Physiology 
442 
9oi. Blood-Vessels.-The blood-vessels of 
the skin are found in the cutis vera only. There 
they form a capillary network in which the vessels 
are so close to each other that in many parts the 
point of a pin could not find space between them. 
From this plexus, branches pass to the skin glands 
and papillae. The vessels of the skin are capable 
of holding from half to two-thirds of the entire 
blood supply of the body. Their caliber, and 
consequently the amount of blood they contain, 
is regulated largely by the vaso-motor nerves with 
which they are supplied. 
902. Cutaneous Nerves.-The skin is pro- 
vided with a greater variety of nerves than any 
other portion of the body. They have been 
classified as follows: 
(1) The nerves concerned in the touch or 
pressure sense; 
(2) The two sets of nerves concerned in the 
temperature sense which terminate in the skin 
in the so-called hot and cold spots; 
(3) Nerves which are stimulated by pain; 
(4) Vasomotor nerves; these are distributed in 
the walls of the blood-vessels; 
(5) Motor nerves, derived principally from the 
sympathetic system and distributed chiefly to the 
glands and the arrector muscles. 
As the skin contains so many sensory nerve 
endings from which afferent nerves pass into the 
spinal cord and brain, nearly every nerve-center 
in the body may be more or less affected by sensa- The Skin and its Appendages 
443 
tions arising in the skin. It is for this reason that 
heat and cold, counter-irritants and hydrothera- 
peutic applications can excite so many and various 
reflexes. 
903. Glands of the Skin.-There are two 
kinds of glands in the skin: (1) sudoriferous or 
sweat-glands; (2) sebaceous glands. 
904. Sudoriferous Glands.-The sweat- 
glands are, in man, present almost everywhere in 
the skin, but are largest and most numerous in 
the axilla, the palm of the hand, sole of the foot, 
and forehead. Each of these glands consists of a 
coil of tubing lined with epithelial secretory cells 
and surrounded by blood-vessels and a number of 
nerve filaments, and has a duct through which its 
product is discharged upon the skin. The secre- 
tory portion of the gland, i. e. the coiled tube is 
embedded in the derma and subcutaneous tissue, 
and the duct opens upon the surface of the 
skin. 
905. Perspiration and Sweat.-These are 
the names given the secretion of the sudoriferous 
glands. The average amount of perspiration dis- 
charged in the skin during twenty-four hours is 
about two pints, but it may be increased to such 
an extent that this much or more may be thrown 
off in one hour. When the quantity is not much 
in excess of two pints in twenty-four hours it is 
evaporated as quickly as discharged, and is there- 
fore called insensible perspiration. When the 
secretion is so rapid that it appears in drops Anatomy and Physiology 
444 
on the surface of the skin it is called sensible per- 
spiration. 
906. Conditions that Control the Secre- 
tion of Sweat.--The secretion of sweat is de- 
creased by (1) cold; (2) the voiding of a large 
amount of urine1; (3) diarrhea; (4) certain drugs; 
(5) certain diseases, as in some cases of paralysis, 
diabetes, and diseases associated with fever. 
The secretion of sweat is increased by (1) in- 
creased temperature of the surrounding medium; 
(2) a diluted condition of the blood, such as re- 
sults from the copious drinking of water; (3) 
exercise; (4) dyspnea; (5) mental excitement or 
nervousness; (6) pain; (7) the class of drugs known 
as diaphoretics; (8) massage; (9) stimulation of 
the secretory nerves by electricity; (10) certain 
diseases, as phthisis, acute rheumatism, inter- 
mittent malarial fever. 
907. Causes of Activity of Sweat Glands. 
-Formerly the activity of the sweat glands was 
supposed to be controlled by variations in the 
blood-flow. But that this is not always the case 
is demonstrated by the fact that profuse perspira- 
tion may often accompany a pallid skin, as in 
terror or nausea, and a decrease in the amount of 
perspiration is characteristic of fever, even when 
the skin is flushed. It is therefore supposed that 
the activity of the glands is regulated by stimula- 
tion of the special secretory nerve-fibers supply- 
1 The skin and kidneys seem to act reciprocally: when the 
secretion of one organ is increased that of the other is decreased. The Skin and its Appendages 
445 
ing the sweat glands, either by direct stimulation 
of the nerve endings in the glands or indirect stimu- 
lation through their cells of origin in the central 
nervous system. For instance, it is supposed 
that though increase of perspiration following a 
rise in the temperature of the surrounding medium 
is partly due to stimulation of the peripheral nerve- 
endings in the sweat glands, it is more largely due 
to reflex stimulation of the nerve-centers control- 
ling perspiration, by impulses transmitted from 
such sensory nerves as are stimulated by heat. 
The stimulus thus originated then passes from the 
sweat center along motor nerves to the glands and 
renders them active. 
908. Chemical Composition of Sweat.-The 
chemical composition of sweat is as follows: 
Water 995 parts 
Solids: 5 
Organic acids 9 
Salts 1.8 
Neutral fats and cholesterin 7 
Extractives (including urea) with epithelium 1.6 
1000 parts 1 
909. Value of the Excretory Function of 
the Skin.-The value of the skin as an excretory 
organ lies not so much in ridding the body of 
waste matter, as in the loss of heat from the body 
1 Kirke's Hand-Book of Physiology, page 511. William Wood 
and Co. 446 
Anatomy and Physiology 
by the evaporation of the water; this loss of heat 
being necessary to balance the production of heat 
that is constantly taking place. Formerly it was 
thought that accidents, as burns, or diseases which 
interfered with the excretory function of the skin, 
were likely to cause nephritis or even death, by 
failure of the skin to eliminate its share of waste 
matter, but investigations and experiments have 
shown that when such bad results are traceable 
to the skin they are usually due either to excessive 
rise of temperature due to lack of radiation and 
evaporation, or to irritation of the kidneys by 
toxic substances, or, in the case of burns, absorp- 
tion from the surface of the derma of the poisonous 
substances due to suppuration. 
910. Ceruminous Glands.-The glands con- 
tained in the skin lining the external auditory 
passage, called the ceruminous glands, are very 
similar in structure to the ordinary sudoriferous 
glands. The yellowish, waxy substance which 
they secrete is called the cerumen. The object of 
this secretion will be described in the chapter 
concerned with the ear. 
911. Sebaceous Glands.-The sebaceous 
glands are found in all parts of the cutaneous sur- 
face except the palms of the hands and the soles 
of the feet. Each gland consists of an aggregation 
of small tubes overspread with minute capillaries 
from which a duct ascends and opens either upon 
the surface of the skin or, as is more common, 
into a hair follicle. In the latter case the secretion The Skin and its Appendages 
447 
from the gland passes out to the skin along the 
hair. At times, some of the ducts, especially those 
of the face, do not discharge their contents and the 
secretion sets to a semi-solid mass which, when the 
skin is squeezed, exudes like a short piece of coarse 
thread. 
912. Nature of Sebaceous Secretion.-The 
exact composition of the secretion is not known 
beyond that it contains fats, soaps, cholesterine, 
cast-off epithelium cells, albuminous matter, and 
inorganic salts. A sebaceous substance, similar 
in composition but of thicker consistency than the 
usual secretion of the sebaceous glands, generally 
coats the skin of the newly born; it is called the 
ver nix caseosa.1 
913. Function of Sebaceous Secretion.- 
The sebaceous secretion may be classed with 
the excreta, for it serves to remove waste matter 
from the body, but its more important purposes 
are to keep the skin and hair soft and pliable, 
and to form a thin protective layer on the surface 
of the skin, which prevents undue loss of heat by 
radiation. 
914. The Skin as an Absorbing Organ.- 
Soluble substances are very readily absorbed by 
the derma, but even when in solution they are 
very sparingly absorbed, if at all, by the unbroken 
cuticle. There are, however, some substances, as 
mercury, that when mixed with fat will be fairly 
1 From the Latin ver nix-varnish and caseosa-cheesy (cheesy 
varnish). 448 
Anatomy and Physiology 
readily absorbed by the cuticle, especially in those 
parts of the body where the epidermis is thinnest 
(see paragraph 896). It is not known whether 
water is absorbed by the skin to any extent. 
Thirst has been relieved, when water could not be 
given by mouth, by immersing the individual in 
warm water, but some authorities consider this 
effect due to the hindrance of evaporation of 
water from the skin rather than to its absorption. 
915. Inunction.-As stated in the preceding 
paragraph, substances dissolved in oil are fairly 
readily absorbed by the skin. The amount ab- 
sorbed will be greatly increased if the material is 
rubbed in, and still further if the sebaceous matter 
covering the skin is removed, this matter being 
one of the causes for the non-absorptive proper- 
ties of the cuticle. This is most easily removed 
by washing the skin with hot alcohol, ether, or 
benzine. 
The Appendages of the Skin 
916. The appendages of the skin are the hair 
and nails. 
917. Hair-Location.-With a few excep- 
tional areas the whole skin is studded with hair, 
some of which is exceedingly fine and extends but 
little beyond the hair follicle; but some, as that 
of the scalp, is long and coarse. 
918. Names and Nature of the Various 
Parts of a Hair.-The portion of a hair project- The Skin and its Appendages 
449 
ing beyond the surface of the skin is called the 
shaft or stem; the part embedded in the derma or 
subcutaneous tissue is called the root. This is 
contained in a tube-like depression which extends 
downward from the surface of the skin, called the 
follicle. The root ends in a minute bulbous en- 
largement, in the under surface of which is a cup- 
like depression into which a papilla derived from 
the follicle extends. This papilla consists of con- 
nective tissue, blood-vessels, and pigment. The 
external part of a hair shaft is called the cuticle. 
When viewed through a microscope it is seen to 
consist of a layer of fine scales closely overlapping 
each other. Beneath this is a layer of closely 
packed cells called the cortical layer. These cells 
and the intercellular spaces contain a varying 
amount of pigment, and the color of the hair 
depends upon the quantity. In colored hair of 
the scalp the cortical layer occupies the whole 
inside of the hair, but in white hair of the scalp, 
in the hair of the pubes, and in that of the beard, 
there is another substance called the medulla or 
pith. This is composed of irregular cells and many 
air spaces, and in white hair there are numerous 
air spaces in the cortical portion as well as in the 
medulla. 
919. Blood Supply and Growth of Hair.- 
Hair has no blood-vessels but receives its necessary 
nutrient from the blood-vessels of the papilla in 
the under surface of the root. 
920. Growth of Hair.-The growth of hair 450 
Anatomy and Physiology 
takes place by multiplication of the soft cells in 
the root which, becoming elongated and pushing 
upwards, go to form the cortical layer of the hair. 
The cuticle is derived from the corticle, the cells 
becoming harder and changing their shape as they 
are pushed to the surface. A scalp which is 
favorable to the growth of hair is thick and pliable 
and moves freely over the bones of the skull. If 
the scalp is thin and drawn tightly over the skull 
it will tend to constrict the blood-vessels, lessen 
the supply of blood to the scalp,and cause atrophy 
of the roots of the hair by pressure. In such cases 
massage of the head, by loosening the scalp and 
improving the circulation of blood in it, may be of 
great benefit. 
921. Cause of Goose-Flesh.-The rough 
appearance that the skin often assumes as the 
result of cold or fright is known as goose-flesh. It 
is due to the action of small muscles termed the 
arrector or the erector muscles. These are attached 
to the base of the follicles on the side toward 
which the hairs lie. The follicles naturally slant 
obliquely, but when the arrector muscles contract 
they are pulled upward; this gives the skin a 
rough appearance and makes the hair stand some- 
what erect. 
The Nails 
922. Nature.-The nails consist of flattened, 
horny cells produced, like the outer layer of the The Skin and its Appendages 
451 
cuticle of the skin and hair, by a peculiar growth 
and modification of the underlying cells. Each 
nail is convex on its outer surface and concave on 
its inner side. It is adherent to, and accurately 
moulded upon, the underlying derma, just as the 
epidermis is in other parts of the body. The part 
of the cutis beneath the nail is termed the matrix,1 
because it is the part from which the nail is 
derived. The lower edge of the nail, which is held 
in a shallow crescentic fold of the matrix, is termed 
the root; the exposed portion is known as the body, 
and the part projecting beyond the finger as the 
free edge. The tissue of the matrix, except near 
the root of the nail, is highly vascular. Near the 
root it is more opaque and less vascular; hence the 
nail, the substance of which is somewhat trans- 
parent, has a pinkish hue, except immediately 
above the root, where it is white. The white 
portion, on account of its cresentic shape, is called 
the lunula. 
923. Growth.-The growth of the nail is 
accomplished by the continual dividing of the 
cells of the matrix at the root and under surface 
of the nail, and if a nail is lost through accident 
or disease a new one will form, provided the 
surface of the matrix has not been too badly 
injured. 
1 Latin matrix, from mater-a mother. CHAPTER XXII 
SENSATIONS 
Origin of Sensation. Essentials of a Sense Organ. Where 
Sensations are Perceived. Classification of Sensations. Nature 
of the Sensations of Pain, Hunger, Thirst, Muscular Sense, 
Fatigue, Pressure Sense, Temperature Sense, Smell, and Taste. 
924. Origin of Sensation.-Every sensation 
arises from the stimulation of a special form of 
nervous mechanism known as a sense organ. 
925. Nature of Sense Organs.-The essen- 
tial parts of a sense organ are: (1) a peripheral 
organ for the reception of the stimulus; (2) a nerve 
for conducting it; (3) a nerve center in the brain 
for the perception and interpretation of the 
stimulus. 
926. Where Sensations are Perceived.- 
In all cases sensations are felt and interpreted in 
the brain. This fact is not generally appreciated, 
for we are accustomed to projecting our sensations 
from the brain to the part stimulated. We say 
that we see with our eyes and hear with our ears; 
in reality we do no such thing. The eye and the 
ear contain the nerve-endings which receive the 
stimuli, and they pass the impulse to the brain 
452 Sensations 
453 
where it is interpreted. We, therefore, both see 
and hear with our brains. If a person cuts his 
finger he feels the pain in his brain, but he uncon- 
sciously projects the sensation to the part that he 
knows to be injured. Many individuals who have 
had a limb amputated, if they have pain in the 
stump, will complain of pain in the amputated 
part because they continue to project sensation 
to the part to which they have been accustomed 
to project it. 
927. Classifications of Sensations.-Sen- 
sations have been classed as common and special 
sensations, or, the more modern terms, internal 
and external sensations. Common or internal 
sensations embrace those which we project to the 
interior of the body. They were called common 
because it is very difficult to distinctly localize 
some of the sensations of this class. Examples of 
internal sensations are: pain, hunger, thirst, 
muscle-sense, fatigue, sexual sense, sensations aris- 
ing in the viscera, as the desire for defecation or 
urination. 
928. External sensations include all those 
which we project to the exterior of the body. 
They were named special senses because it is easy 
to locate the special organ in which the nerve 
impulse that gave rise to the sensation was 
started. This class includes: touch, which com- 
prises pressure and temperature sense; taste, smell, 
sight, hearing. A few sensations may be either 
internal or external, e. g., in temperature sense, 454 
Anatomy and Physiology 
when we touch a cold or hot object we project the 
sensation to the exterior; but if the sensation of 
heat or cold is due, for instance, to the weather we 
project the sensation to the interior; we say, "I 
am hot, " or "cold. " Pain is another example of a 
sensation that may be projected to either the 
exterior or interior of the body. 
929. Pain.-It is not yet known definitely if 
there are special nerves that give rise to the 
sense of pain, or if it is caused by over-stimula- 
tion of other sensory nerves, as, for instance, 
the nerves connected with the senses of pressure 
and temperature. 
930. Hunger.-The sense of hunger, it is 
thought, may arise from two different sources: (1) 
a special set of nerves distributed to the mucous 
membrane of the stomach which, in the healthy 
individual, are stimulated when the organ becomes 
empty; (2) nerves that are affected by metabolism. 
One of the many reasons advanced for this latter 
supposition is that the appetite-hunger-is in- 
creased by such conditions as increase the degree 
of oxidation going on in the body, as muscular 
exercise, cold weather, etc. 
931. Thirst.-The sensation of thirst is usu- 
ally projected to the pharynx. The reason for this 
is unknown, but it is thought that when the water 
content in the tissues falls below a certain amount, 
special sensory nerves of the pharynx which give 
rise to the sense of thirst are stimulated. 
932. Muscular Sense.-To the so-called Sensations 
455 
muscular sense is due our knowledge of the condi- 
tion and position of our muscles, and of the joints 
and limbs moved by them. This knowledge en- 
ables us to control our movements and to maintain 
our balance when in the erect position. Muscle- 
sense arising in those muscles of the eyeballs con- 
cerned with focusing, together with the sense of 
vision, helps us in forming our judgments of dis- 
tance and of the size of objects. It is to muscle- 
sense also that our idea of the degree of resistance 
offered us by objects is due, and, in connection 
with the sense of pressure, our idea of their weight. 
This sense is due to stimulation of special sensory 
nerves distributed in the muscles. 
933. Fatigue.-In excessive muscular exercise 
chemical changes take place in the muscles, as 
described in Chapter VI, which changes the qual- 
ity of the stimulation of the nerves connected 
with muscular sense, and the resulting sensation 
is known as fatigue. 
934. Vomiting, Coughing, etc.-Sensations 
which give rise to these actions, as well as to those 
of defecation, urination, etc., are due to stimula- 
tion of sensory nerves contained in the organ or 
part concerned in the action. 
935. Pressure or Tactile Sense.-The 
nerves connected with the pressure sense are 
widely distributed through the skin and certain 
mucous membranes. These nerves end either in 
the hair follicles or, in locations where there are no 
hairs, in the so-called touch or tactile corpuscles 456 
Anatomy and Physiology 
referred to in Chapter XXI. The nerves ending 
in the hair follicles are stimulated by pressure 
upon the hairs. Pressure nerves are not dis- 
tributed evenly, but are much more abundant 
in some parts of the skin than in others, as can be 
seen by the following table, which gives the dis- 
tance between the points at which experiments 
have shown pressure can be felt: 
Tip of tongue I mm. 
Tip of finger {front) 2 mm. 
Middle of palm 8-9 mm. 
Lip 9 mm. 
Forehead 22 mm. 
Back of hand mm. 
Back of neck 60-70 mmF 
The pressure sense can be rendered much more 
acute by practice, as is demonstrated in the blind. 
936. The Temperature Sense.-Certain 
nerve-endings are stimulated by cold and others by 
heat, and the points on the epidermis over these 
endings are called respectively the cold and hot 
spots.2 These endings can be stimulated also by 
1 The Nervous System, page 119. By James Dunlop Lickley, 
M.D. Longmans, Green & Co. 
2 The existence of these spots may be ascertained by moving a 
metallic point gently over the skin. If the point has a tempera- 
ture below that of the skin it will be noticed that at certain points 
it arouses a feeling of contact or pressure and in others one of 
cold. If, on the other hand, the instrument has a higher tempera- 
ture than the skin, the sensation aroused will be either pressure 
or heat. Sensations 
457 
certain substances and the same sensation pro- 
duced as when the stimulus is heat or cold; e. g., 
Q&z excites the warm spots and gives rise to a 
sensation of heat; menthol excites the cold spots 
and causes a sensation of cold. 
937. Smell.-The olfactory nerves arise from 
the olfactory bulb, a mass of gray matter situated 
in the cribriform plate of the ethmoid bone, and 
their filaments are distributed to the mucous mem- 
brane lining the upper part of the nasal cavities. 
These filaments end in elongated epithelial cells, 
the free ends of which terminate in minute* hair- 
like processes. The primary step in producing the 
sensation of smell is the stimulation of these 
processes. This can be done only by substances 
with certain characteristics, viz., (1) they must be 
odoriferous, which property is thought to be de- 
pendent upon some peculiarity of structure; (2) 
they must be in either a gaseous or finely divided 
form. Another important factor in stimulating 
these processes is the presence of moisture; when 
the mucous membrane is dry, the sense of smell is 
much impaired. 
938. Taste.-The so-called taste-buds, the end 
organs of nerve-filaments derived from branches 
of the fifth, seventh, and ninth cranial nerves to 
which the sense of taste is thought to be due, are 
situated chiefly in the tongue, especially in its 
upper surface, but they are found also in and 
around the soft palate. The sense of taste is very 
closely allied to the sense of smell; in fact the two Anatomy and Physiology 
458 
senses are often confused and what we designate as 
the taste of some foods, especially those that owe 
their flavor to volatile substances, is very often 
largely their odor, the substances to which the 
odor is due being liberated during mastication and 
ascending through the pharynx. This accounts 
for the loss of taste that so frequently complicates 
a cold in the head or any other condition causing a 
loss of smell. 
The senses of sight and hearing will be discussed 
in the two following chapters. CHAPTER XXIII 
THE EYE AND THE SENSE OF VISION 
Names of the Main Divisions of the Organ of Vision. Names, 
Location, Structure, and Function of the Appendages of the Eye. 
Structure of the Orbit. Size, Shape, and Divisions of the Eye- 
ball. Structure and Function of the Different Parts of the Eyeball. 
Location and Function of the Optic Nerve. Nature of Accom- 
modation of the Refractory Apparatus of the Eyeball. Common 
Defects of Accommodation. Physiology of Vision. Judgments 
of Size, Motion, and Solidity of Objects. Origin of Color. Color 
Vision. Color Blindness. 
939- The Organ of Vision and Appendages. 
-The organ of vision may be said to consist of the 
eyeballs, the optic nerves, and the optic nerve- 
centers in the brain. In addition to these principal 
parts there are also various appendages which are 
necessary for the protection and functioning of the 
eyeball; these are: the eyebrows, eyelids, eyelashes, 
the lachrymal apparatus, the conjunctiva, and for 
each eye four recti-straight-and two oblique 
muscles. 
940. The Eyebrows.-The eyebrows are two 
thickened ridges of skin covered with short hairs. 
They are situated on the upper border of the orbits 
and serve to protect the eyes from too vivid light, 
dirt, and perspiration. 
459 460 
Anatomy and Physiology 
941. The Eyelids.-These are two movable 
curtains which when closed cover the eyeball. 
The upper lid is larger and moves more freely than 
the lower lid. The main substance of the lids con- 
sists of a dense fibrous tissue known as the tarsal 
cartilage and the small muscles which are con- 
cerned in the movements of the lids. The outer 
surface of each lid is covered with a thin skin and 
its inner surface is lined with a delicate membrane 
-the conjunctiva. The free edges of the lids are 
covered with a line of short hairs-the eyelashes- 
which help to protect the eyes from too strong 
light and dirt. Embedded in the substance of the 
lids is a row of small glands called the meibomian 
glands, the ducts of which open on the under sur- 
face of the lids, just above the eyelashes. These 
glands secrete an oily fluid which tends to keep the 
tears from flowing over onto the face and prevents 
adhesion of the lids. The opening between the 
free margin of the lids is called the palpebral1 fis- 
sure. It is the width of this space that gives to the 
eyes the appearance of largeness and smallness. 
There is very little difference in the size of the eye 
in different individuals of the same age. The 
angle at the outer end of the fissure is called the 
outer canthus, and that on the nasal side the inner 
canthus.2 
942. The Lachrymal3 Apparatus.-This con- 
1 From the Latin palpebra-the eyelid. 
2 From the Greek kanthos-the angle of the eye. 
s From the Latin lachryma-a tear. The Eye and the Sense of Vision 
461 
sists of a secreting portion-the lachrymal gland 
and conjunctiva-and a conducting portion-the 
lachrymal canals, lachrymal sac, and nasal duct. 
The gland is situated just within the orbit, at the 
upper and outer side. It is about the size of a small 
almond and its structure is very similar to that of 
Fig. 123.-The lachrymal apparatus of the 
right eye. 
the salivary glands. At the inner end of each 
upper and lower lid is a small opening-the puncta 
lachrymale-the lachrymal point-from which a 
small canal leads to the lachrymal sac. The lachry- 
mal sac is the upper enlarged end of the nasal duct; 
the latter is a short canal-about three-quarters of 
an inch in length-which opens into the nose. The 
function of the lachrymal gland is the secretion of 
tears. These are necessary to keep the anterior 
surface of the eyeball moist and free from dirt. 
They reach their destination by means of numerous 462 
Anatomy and Physiology 
small ducts which open from the secreting portion 
of the gland and are spread over the front surface 
of the eyeball by the movements of the lids. 
Ordinarily all excess secretion flows through the 
lachrymal puncta, canals, sac, and nasal duct into 
the nose. Excessive secretion or obstruction in the 
canals or duct will, however, result in an overflow 
of tears over the cheek. 
943. The Conjunctiva.1-The conjunctiva is 
a delicate mucous membrane which lines the inner 
surface of the eyelids and is reflected over the 
front of the eyeball. The portion of the membrane 
of the eyeball known as the cornea is exceedingly 
thin and transparent. The conjunctiva secretes a 
fluid like that of the lachrymal gland. This secre- 
tion prevents the moving lids causing friction on 
the eyeball. 
944. The Ocular Muscles.-The muscles of 
the eye are, in description, divided into two 
groups: (1) the intrinsic2 muscles, which include 
the ciliary muscle and the muscles of the iris (these 
will be described later), and (2) the extrinsic3 
muscles, which include the four recti or straight 
and the two oblique muscles. As stated in Chap- 
ter VI, these muscles have their origin at the back 
of the orbit and are inserted in the outer tunic or 
coat of the eyeball. They serve to move the eye- 
ball. Normally the extrinsic muscles of the two 
eyes work in unison; thus, to view an object near 
1 From the Latin con-together and junctum-to join. 
3 Internal. ' External. Fig. 124.-Diagram of the right eye in horizontal section, showing the 
upper surface of the lower segment. The Eye and the Sense of Vision 
463 
and in front of the eyes both eyes will converge; 
to view an object at the right both eyes will turn 
toward the right, etc. This concord in movement 
is necessary in order that the image of the object 
may fall upon corresponding spots of the retina 
of each eye. If it fail to do so double vision will 
result, i. e., the individual will see two objects 
where there is only one. This happens sometimes 
as the result of weakness or paralysis of some of 
the muscles in alcoholic and some other forms of 
poisoning and in certain diseases of the eye. 
945. The Orbit.-The orbits are the two bony 
cavities in which the eyeballs are contained. Each 
orbit is formed by the union of seven of the bones 
of the skull, viz.: the sphenoid, ethmoid, frontal, 
lachrymal, malar, superior maxillary, and palate. 
The orbits are funnel-shaped, the large end being 
directed forward and the small end backward. 
The latter terminates in an opening known as the 
optic foramen, through which the optic nerve and 
the ophthalmic artery pass from the brain to the 
eye. There is another opening in the posterior 
part of each orbit which provides a passage for the 
ophthalmic vein and the nerves, the purpose of 
which is to carry impulses to and from the muscles. 
The optic nerve is concerned with vision only. 
The orbits are lined with fibrous tissue and con- 
tain a pad of fat at the back which supports the 
eyeball. In diseases which cause emaciation this 
fat is absorbed, and the eyes sink deeper into the 
orbits. The outer surface of the connective tissue 464 
Anatomy and Physiology 
and fat is covered with one side of a thin serous 
sac, the other side of which is attached by means of 
delicate strands of areolar tissue to the posterior 
surface of the eyeball. This sac, which is called 
the capsule of Tenon, like all serous membranes 
secretes a lubricating fluid, and this prevents 
friction as the eyeball moves in the orbit. 
946. Size, Shape, and Divisions of the Eye- 
ball.-The human eyeball is a hollow, somewhat 
spherical body. It is made up of the segments of 
two spheres, one placed in front of the other. The 
posterior sphere, which is the larger of the two, 
constitutes about five sixths of the eyeball; and 
the anterior, which fits into the posterior sphere 
much as a watch-crystal fits into its case, forms 
the other one sixth. In the interior, the two 
spheres are divided by a transparent, fibrous sub- 
stance called the lens. This will be described later. 
947. Coats of the Wall of the Eyeball.- 
The wall of the eyeball consists of three coats or 
tunics. The tissue forming the two outer ones 
differs in the posterior and anterior spheres, and 
the parts are therefore known by different names, 
but they are directly continuous with each other. 
The names of the coats are: (1) the sclera and 
cornea, (2)1 the choroid, ciliary zone, and iris; (3) 
the retina. 
1 The second or middle coat of the eyeball is known also, on 
account of the abundant blood supply, as the vascular coat, and, 
on account of its dark color, as the uveal tract, the word uveal 
being derived from the Latin uva-grape. Fig. 125.-Vessels and nerves of the choroid and iris, seen from above. 
The sclerotic and cornea have been removed. (Gerrish.) The Eye and the Sense of Vision 
466 
948. The sclera1 or sclerotic coat, often called 
white of the eye, is a strong, opaque, fibrous 
membrane. It is the strongest coat and the one 
upon which the maintenance of the shape of the 
eyeball depends. The sclera varies in thickness from 
one half of a millimeter to one sixth of a millimeter. 
It is thinner in children than in adults, which is 
why the white of children's eyes is so much clearer 
and bluer than that of adults, the blue color being 
due to the showing through of the darker coat 
underneath. 
949. The cornea, which is continuous with the 
sclera, consists of layers of exceedingly thin trans- 
parent connective tissue held to each other by 
fine fibers. It contains numerous lymph-spaces 
and nerves, but no blood-vessels; it is therefore 
dependent on the lymph contained in the lymph- 
spaces for its supply of nutrient and thus on the 
blood supply of the surrounding tissues, from 
which the lymph is derived. 
950. The choroid2 coat, which is attached to 
the under surface of the sclera, consists almost 
entirely of an interlacement of small blood- 
vessels, held together with a delicate connective 
tissue in which are many pigment cells. The 
numerous blood-vessels and pigment cells of the 
choroid make the membrane so dark and opaque 
that it serves to darken the chamber of the eye, 
which, like the dark chamber of the photo- 
1 From the Greek skier os-hard. 
2 From the Greek chorion-a skin and eidos-form. 466 
Anatomy and Physiology 
grapher's camera, prevents the reflection of 
light. 
951. The ciliary1 zone differs from the choroid 
in containing considerable muscular tissue called 
the ciliary muscle, and, on its under surface, a 
series of fine ridges called the ciliary processes. 
952. The iris,2 which is continuous with the 
ciliary zone, is the colored membrane that hangs 
like a round screen behind the transparent cornea. 
It consists of exceedingly delicate connective and 
muscular tissue with numerous small blood-vessels, 
nerve fibers, and a varying amount of pigment 
cells. The color of the iris depends upon the 
amount of pigment cells. When they are abun- 
dant the iris will be either black, brown, or gray; 
when they are scanty the iris will be blue, because 
the blue shade of the retinal cells will show through 
the membrane of the iris. 
953. The pupil is the aperture in the center of 
the iris through which the light enters the eye. 
954. The retina3 is the inner and nervous 
tunic of the eye. It results from the spreading out 
or expansion of the optic nerve, and extends from 
the optic nerve entrance forward to the margin 
of the pupil. At the posterior border of the ciliary 
processes it loses the nervous element, characteris- 
tic of the portion lining the choroid, and consists 
1 From the Latin cilia-eyelashes. The word is used in 
anatomy for hair-like processes. 
2 From the Latin iris-a rainbow. 
s From the Latin rete-a net. Fig. 126.-Iris, front view. (Gerrish.) The Eye and the Sense of Vision 
467 
chiefly of a thin layer of connective tissue and 
pigment cells. The part of the retina underneath 
the choroid has a very complicated structure. It 
consists principally of several layers of specialized 
nerve tissue held together with delicate connec- 
tive tissue. The only layers that need be men- 
tioned here are those more particularly affected 
by light, viz.: the pigment layer which lies next 
the choroid coat, and the nervous layer inside of 
this, called, from the shape of its parts, the rods 
and cones. It is this layer which is sensitive to 
light and receives the image of external objects. 
It may be likened to the sensitized plate of a 
camera. 
955. The Yellow Spot, Fovea Centralis, 
and Blind Spot.-Near the center of the retina 
is a yellow spot called the macula lutea,1 in the 
center of which is a depression known as the fovea 
centralis.2 This is the part of the retina that is 
most sensitive to light. The optic nerve enters the 
eye a little to the nasal side of the yellow spot. 
There are no rods and cones at this point and it is 
therefore insensible to light and is called the 
blind spot. To prove the presence of the blind 
spot, close the left eye and gaze steadily at the 
cross below with the right eye; move the book 
Fig. 127 
1 From the Latin macula-spot and lutea-yellow. 
3 From the Latin fovea-depression and centralis-central. Anatomy and Physiology 
468 
slowly to and from the eye. In one position the 
circular spot will apparently disappear. 
956. The Optic Nerve.-The optic nerve 
from each eye passes backward through an open- 
ing-the optic foramen-near the apex of the orbit. 
The two nerves come together a short distance 
back of the orbits and form what is known as the 
optic chiasma, and fibers coming from the inner 
or nasal side of each retina cross to the optic nerve, 
or, as it is called, the optic tract, of the opposite 
side. The fibers from the outer side of the retina 
are continued on in the optic tract of the same 
side. The nerves end finally in the cortex of the 
occipital lobes. 
957. The Humors of the Eye.-The poste- 
rior sphere or chamber of the eye is filled with a 
transparent, jelly-like substance termed the vitre- 
ous1 humor, and the anterior chamber contains a 
clear, watery fluid known as the aqueous2 humor. 
958. The Crystalline Lens.3-Between the 
aqueous humor and the vitreous is a transparent 
biconvex-i. e., convex on both its anterior and 
posterior surfaces-fibrous substance called, from 
its exceeding transparency, the crystalline lens. 
This is enclosed in a thin, transparent membrane 
termed the capsule. The lens is supported in place 
by the counterbalancing pressure of the aqueous 
and vitreous humors and by the suspensory liga- 
1 From the Latin vitrum-glass and humor-fluid. 
2 From the Latin aqua-water. 
3 A description of lenses will be found in the Glossary. The Eye and the Sense of Vision 
469 
ment, a strong, elastic membrane which is fused 
to the anterior surface of the capsule and, at 
either side, to the ciliary processes between the 
choroid and the iris. 
959. Function of the Crystalline Lens, 
Humors, etc.-The cornea, the crystalline lens, 
the aqueous and vitreous humors, the ciliary 
muscle, and the suspensory ligament constitute 
what is known as the refractive apparatus. This 
is so called because it is to the cornea, lens, and 
humors that the refraction of the rays of light 
entering the eye is due. By this is meant that as 
the rays of light pass through these media they 
are bent and so converge, as they will when passing 
through any convex lens, and they are thus 
brought to a focus on the retina. When, for any 
reason, rays of light are not focused properly on 
the retina, the vision of objects is blurred and 
indistinct. The part that the ciliary muscle and 
suspensory ligament take in refraction1 will be 
described in paragraph 962. 
960. Why Opaque Objects are Visible.- 
Rays of light which strike the surface of an opaque 
object are partly absorbed and partly reflected. 
It is through the agency of the reflected light that 
objects are visible-i. e., we see an object because 
light from that object enters the eye. 
961. Accommodation for Far and Near Ob- 
jects.-In order that divergent rays of light com- 
1 For further description of the nature of refraction and light, 
see Glossary. 470 
Anatomy and Physiology 
ing from an object nearer than twenty feet may 
be focused on the retina and not behind it, it is 
necessary that the lens should become more con- 
vex than it is when the eye is at rest or when 
looking at distant objects, and the nearer the 
object the greater must be the degree of convexity. 
This increase in the convexity of the lens and, 
consequently, its refractive power, is spoken of as 
accommodation. 
962. Mechanism of Accommodation.-The 
ciliary muscle is thought to be the active agent in 
accommodation, but its exact influence on the 
refractory apparatus is as yet imperfectly under- 
stood. The more generally accepted theory is 
that when the eye is at rest or fixed upon distant 
objects the suspensory ligament exerts a tension 
upon the lens which keeps it flattened, particularly 
along the anterior surface to which it is attached, 
but when the eye becomes fixed on near objects- 
especially in such acts as reading and in doing fine 
work-the ciliary muscle contracts and in doing 
so draws forward the choroid coat and thus relaxes 
the tension of the suspensory ligament, in conse- 
quence of which the anterior surface of the lens 
becomes more convex. 
963. Some of the More Common Conditions 
that Affect Accommodation.-As age advances 
the lens becomes harder and the suspensory liga- 
ment and capsule less elastic, in consequence of 
which the shape of the lens is less easily adjusted 
and it therefore becomes difficult to see small The Eye and the Sense of Vision 
471 
objects-as printed or written letters-near at 
hand. This condition of the eyes is known as 
presbyopia or old sight. Normally this should not 
occur until an individual is about forty-five, but 
weakness of the eyes, ill health, overuse of the 
eyes-e. g., reading or doing fine work in a poor 
light-will weaken the ciliary muscle and bring 
on the other conditions of old sight much earlier. 
To obviate the ill effects of this condition it is nec- 
essary to wear convex glasses which will shorten 
the focus for near objects. 
964. Hypermetropia or farsightedness is a 
condition in which parallel rays of light from near 
objects are brought to a focus behind the retina. 
The defect is usually caused by either a lessened 
curvature of the lens and cornea or a too shallow 
eyeball, and convex glasses are necessary to bring 
the rays of light to a focus on the retina. 
965. In myopia or nearsightedness the condi- 
tions are just the opposite from those in hyperme- 
tropia, i. e., parallel rays are focused before reaching 
the retina, either because there is a too great 
curvature of the cornea and lens or the eyeball is 
too deep. To remedy the condition concave glasses 
are worn; these, by causing a divergence of the 
rays entering the eye, prevent their being focused 
too soon. 
966. Astigmatism.-In the normal eye the 
curvature of the cornea and lens is the same; 
when they differ the condition is known as astig- 
matism. This interferes with the formation of 472 
Anatomy and Physiology 
clear images on the retina. The condition can be 
corrected by wearing cylindrical glasses. 
All of these defects may be congenital or they 
may be acquired, even at a very early age, by the 
same conditions that cause presbyopia. 
967. Function of the Iris.-The power of 
the iris to contract and relax and so lessen or 
increase the size of the pupil and thereby regulate 
the amount of light entering the eye, is of great 
assistance in the obtaining of clear images. That 
the iris is able to do this is due to the presence of 
two bands of muscle tissue, one of which is ar- 
ranged like a sphincter with its fibers encircling the 
pupil; the other with its fibers radiating from the 
pupil to the outer circumference of the iris. These 
muscles are each supplied with nerve fibers from a 
different source and act in opposition to each other. 
When the sphincter muscle contracts, as it does 
when the eye is accommodated for a near object, 
by the contraction of the ciliary muscle, or under 
the stimulation of a bright light, the size of the 
pupil is diminished. When, on the other hand, 
the dilator muscle contracts the pupil is pulled 
open. 
968. Action of the Retina.-The light waves 
emanating from an object and focused on the 
retina form a stimulus that evokes a visual sensa- 
tion. Just how they do this is not known, but a 
common theory is that the waves entering the 
eye cause chemical changes in the rods or cones 
which give rise to the impulses that when trans- The Eye and the Sense of Vision 
473 
mitted to the brain result in sight. In the rods a 
peculiar kind of red pigment, termed visual purple, 
has been found, and it is thought that this and the 
pigment of the retina layer next the choroid play 
an important part in these changes. 
969. Inversion of Images.-Owing to the 
nature of the refraction or bending of the light 
rays as they enter the eye, which causes them to 
cross each other as shown in Fig. 139,1 the figure 
of objects is inverted on the retina. That we see 
them erect is because "experience has taught us 
to project the visual sensation arising from the 
stimulation of any given point on the retina to 
that part of the external world from which the 
stimulus arises-that is, to the luminous point 
giving origin to the light rays. "2 
970. Estimation of the Size of Objects.- 
The apparent size of objects depends upon their 
nearness, and if the eye were a mere machine a 
man at the distance of ten feet would be taken to 
be ten times as large as one at one hundred feet. 
But the eye being backed by the reason, by expe- 
rience, and by muscular sense arising from the 
degree of accommodation necessary to focus the 
eye, it is possible to form a correct estimate of 
the comparative size of the two figures. 
971. Estimation of Movement.-We judge 
of the movement of an object partly from the 
1 See Glossary. 
2 Text-Book of Physiology, page 303. Howell. W. B. Saunders 
Co. Anatomy and Physiology 
474 
motion of its image over the surface of the retina, 
and partly from the motion of our eyes following 
it. 
972. Estimation of Solidity of Objects.- 
The images of objects are portrayed 011 the retina 
as flat figures and our judgment of their solidity is 
due chiefly to the following conditions: (1) In bin- 
ocular vision the images of the two retinas are not 
exactly alike, the retina of the right eye getting 
more of the right side of the object, and the 
retina of the left eye more of the left side, and 
the fusion of the two different aspects is the 
principal factor in giving rise to judgments of 
solidity; (2) the effect of light and shade; (3) 
knowledge gained through pressure and muscle 
sense. 
973. Summary.-The parts of the eye more 
particularly concerned in vision are: (1) the dark 
chamber formed by the dark colored choroid and 
iris; (2) the iris which answers to the diaphragm 
of the photographer's camera and regulates the 
amount of light admitted to the chamber through 
the pupil; (3) the transparent surfaces-the cornea 
and lens-and humors by means of which the rays 
of light emitted by external objects are brought 
to a focus on the retina-these take the place of 
the lens of the camera; (4) the accommodation 
apparatus-the ciliary muscle and ligament- 
which regulates the convexity of the cornea, lens, 
and humors, and thereby the degree of refraction 
in the rays of light entering the eye-this answers The Eye and the Sense of Vision 
475 
to the focusing arrangements of the camera; (5) 
the retina upon which the rays of light emitted by 
external objects are brought to a focus and the 
inverted images of the objects imprinted, just as a 
picture is formed on the sensitized plate of the 
camera; (6) the optic nerve which carries the 
impulses caused by the stimulation of the rods and 
cones of the retina of the brain. Also, there may 
be mentioned the recti and oblique muscle by 
means of which the coordinate movements of the 
eyeballs are attained. 
Color Vision 
974- Nature of Color.-It is the accepted be- 
lief (i) that all space is filled with a medium named 
ether that is so transparent and subtle that it 
cannot be perceived by any of our senses; (2) that 
light is the result of transverse vibrations or waves 
of this ether, and (3) that the color of light is de- 
pendent upon the length of the waves; by length of 
the waves being meant the distance between waves, 
e. g., when there are about 34,000 waves to the 
inch they produce the sensation of red light; 
when they are still shorter-i. e., closer together-■ 
they produce the sensation of orange color; when 
still shorter, yellow, then green, blue, indigo, and 
when they have become so short that there are 
about 60,000 to the inch, violet. Between these 
decided colors there are a great many tones, pro- 
duced by difference in the length of ether waves. 476 
Anatomy and Physiology 
White is simply a totality of effect produced by the 
simultaneous effects of many colors falling upon 
the retina. 
975. The Color of Bodies.-The color of 
light must be distinguished from the color of a 
body. The color of light, as we have seen, depends 
upon the length of its wave, but the color of a 
body depends upon the light it reflects, or, if it is 
transparent, upon the light which passes through 
it; e. g., an opaque body that gives rise to a sensa- 
tion of red does so because it reflects red light and 
absorbs the light of other colors incident upon it. 
An object appears black when it neither reflects 
nor emits light. Some artificial lights do not con- 
tain all the variety of wave lengths contained in 
sunlight-daylight-and objects that would reflect 
these colors, if present, fail to do so. This is why 
the color of some things is different by daylight 
than by artificial light. 
976. Theories of Color Vision.-In order 
that color can be perceived by the brain it is 
necessary that the retina be stimulated in some 
special manner by the color rays entering the eye. 
How it is so stimulated is not known. It is 
thought, however, that there is in the retina some 
compound chemical substance which is acted upon 
by the incoming color waves so that chemical 
changes are brought about which produce the 
nerve impulses that give rise to those color sensa- 
tions which we experience. There are many 
theories regarding the nature of the chemical sub- The Eye and the Sense of Vision 
477 
stance and of the changes caused in it, but nothing 
has been proved.1 
977. Color Blindness.-Some people cannot 
distinguish certain colors, especially red or green. 
This inability is known as color blindness. One 
explanation of the condition is about as follows: 
It is thought that different parts of the retina 
respond to different color sensations and that in 
individuals who are unable to perceive a certain 
color the cones in the part of the retina that should 
respond to that color have not been properly 
developed. Another explanation is that the chemi- 
cal substance concerned in color vision is deficient 
in the parts that should respond to the red or 
green, as the case may be, color wave. 
1 A description of some of the theories will be found in Text- 
Book of Physiology, page 352. Howell. Scientific Ideas of To-day, 
page 204. Charles R. Gibson. J. B. Lippincott Co. Hand- 
Book of Physiology, page 752. Kirk. CHAPTER XXIV 
THE EAR AND THE SENSE OF HEARING 
Main Divisions of the Ear. Structure, Anatomy, and Function 
of the External, Middle, and Inner Ear. Divisions of the Auditory 
Nerve. Physiology of Hearing. Function and Mechanism of 
the Semicircular Canals. 
The Ear 
978. Main Divisions.-The ear consists of 
three main parts termed the external, middle, and 
internal ear. 
979. The External Ear.-This consists of 
the auricle1 or pinna2 and the auditory canal. 
980. The auricle, except the lower portion or 
lobe, consists of a cartilaginous framework con- 
taining a small amount of fatty tissue and a few 
small muscles. In the lobe, the cartilage is re- 
placed by connective tissue. The whole auricle 
is covered with skin. 
981. The exterior portion of the wall of the 
auditory canal is cartilaginous'-the cartilage being 
continuous with that of the pinna. The posterior 
1 From the Latin auris-the ear. Auricula-the external ear. 
2 From the Latin pinna-a wing. 
478 The Ear and the Sense of Hearing 
479 
part is hollowed out of the temporal bone. In 
adults the canal is about inches long. Its 
direction is forward and inward and it is slightly 
curved, so that its central portion is the highest. 
For this reason, in order to see the drum, or 
when giving irri- 
gations, it is ne- 
cessary to raise 
the outer cartil- 
aginous portion of 
the canal by pull- 
ing the auricle 
upward and back- 
ward. In small 
children, owing to 
lack of develop- 
ment of its bony 
portion, the shape 
of the canal is dif- 
erent and it is best 
straightened b y 
drawing the auri- 
cle downward and 
backward. The 
canal is covered with skin that contains a number 
of small glands called the ceruminous glands, which 
secrete a sticky substance known as cerumen or ear 
wax. Near the external meatus or opening are sev- 
eral stiff hairs. These and the cerumen serve to 
protect the ear from the entrance of foreign sub- 
stances. The inner end of the canal is shut off 
Fig. 128.-Vertical section through 
the external auditory meatus and 
tympanum, passing in front of the 
fenestra ovalis. 480 
Anatomy and Physiology 
from the inner ear by a membrane known as the 
tympanic or drum membrane which is stretched 
across the opening between the two cavities. 
982. The Middle Ear or Tympanum.1-The 
middle ear is an irregular bony cavity situated in 
the temporal bone of the skull. It measures about 
half an inch in height and in width, and five- 
eighths of an inch in length. Its upper wall, which 
separates it from the brain, is exceedingly thin- 
about one twenty-fourth of an inch in thickness. 
In the inner wall of the tympanum-opposite the 
drum membrane-are two openings communicat- 
ing with the inner ear, both of which are covered 
with a fibrous membrane. One is called the fenes- 
tra rotunda or round window and the other the fen- 
estra ovalis or oval window. In the posterior wall 
is an opening into the mastoid antrum, and through 
this opening inflammation often extends from the 
middle ear into the mastoid cells, causing a very 
serious condition known as mastoiditis. In the an- 
terior wall also there is an opening into a small 
tube-the Eustachian tube-which extends into 
the throat. The function of this tube is to ventil- 
ate the middle ear and to equalize the air pressure 
on both sides of the drum membrane between the 
external and middle ear. If the tube becomes 
blocked, as it often does in inflammatory condi- 
tions of the nose and throat, the air in the inner 
ear becomes heated and consequently expands 
and either pushes up the tympanic membrane in 
1 From the Greek tympanon-a drum. The Ear and the Sense of Hearing 
481 
the center, or else some of this rarefied air escapes 
through the Eustachian tube and causes a partial 
vacuum within the cavity, which creates a suction 
that pulls down the central portion of the mem- 
brane and also causes congestion of the mucous 
membrane lining the cavity. Unless the obstruc- 
tion is relieved and 
the pressure on either 
side the drum equal- 
ized, the conditions 
just described will be- 
come permanent and 
dullness of hearing 
follow. 
983. The Bones 
of the Middle Ear. 
-Stretching across 
the cavity of the mid- 
dle ear, from the tym- 
panic membrane to 
the oval window, is a 
chain of three small 
bones called from their shape: the malleus - 
hammer; incus - anvil; and stapes - stirrup. 
These ossicles are held in position and attached 
to each other and to the drum membrane 
and the membrane of the oval window by 
minute ligaments and muscles. The handle of 
the hammer is attached to the drum membrane; 
the base of the anvil is connected with the head 
of the hammer; one side of the stirrup is held to 
Fig. 129.-Chain of small bones 
and their ligaments, seen from 
the front in a vertical, transverse 
section of the tympanum. 482 
Anatomy and Physiology 
the long process of the anvil, and its foot-piece 
is attached to the fibrous membrane stretched 
across the oval window. 
984. The Inner Ear or Labyrinth.-The 
inner ear is contained in a very intricate series of 
cavities hollowed out of the temporal bone called 
the bony labyrinth. Within the bony labyrinth 
is a membranous sac of somewhat similar shape, 
known as the membranous labyrinth. It is held to 
the bone in places by bands of fibrous tissue. The 
space between the bone and membrane is filled with 
a watery fluid called perilymph,1 and the cavities 
within the membrane are filled with a similar fluid 
called endolymph.2 The inner ear is divided into 
three distinct, though connected, parts known as 
the vestibule, the cochlea, and the semicircular canals. 
985. The vestibule is the central cavity of the 
labyrinth; it communicates with the cochlea in 
front, with the semicircular canals behind, and in 
its outer wall is the oval window which communi- 
cates with the middle ear, and to which, within 
the latter, the foot of the stapes is connected. The 
membrane within the vestibule is somewhat con- 
stricted in the center so that it appears like two 
small sacs connected with a Y-shaped tube; the 
two sacs are called respectively the saccule3 and 
the utricle,4 and the connecting tube is called the 
1 From the Greek peri-around and lympha-clear water. 
2 From the Greek endo-within. 
3 From the Latin sacculus-a little sac. 
4 From the Latin utricle-a small skin. The Ear and the Sense of Hearing 
483 
ductus endolymphaticus. On the inner wall of 
these sacs are numerous hair-like cells projecting 
into the endolymph, round which terminal fila- 
ments of the vestibular branch of the auditory 
nerve are twined. Lying among the hair cells are 
numerous minute crystals of carbonate of lime 
called otoliths.1 
986. The cochlea2 opens from the saccule or 
front end of the vestibule. It is a spiral tube 
shaped like a snail shell, coiled two and one half 
Fig. 130.-Constituent parts of the osseus cochlea-the 
modiolus, the coiled tube, the spiral lamina-isolated in the 
first three pictures, and combined in the fourth. Diagrammatic. 
times round a small pillar called the modiolus p 
from which a thin spiral lamina4 of bone projects 
that helps to divide the interior of the canal into 
two passages or scala.5 There are numerous 
openings in the modiolus and lamina for the pas- 
sage of nerve fibers which arise from ganglia of 
nerve cells contained within the modiolus. From 
1 From the Greek ous-the ear and lithos-stone (the ear 
stones). 
2 From the Latin cochlea-a snail shell. 
J From the Latin modiolus-the nave of a wheel. 
4 From the Latin lamina-a thin plate or scale. 
s From the Latin scala--a staircase. Anatomy and Physiology 
484 
the lamina, a thin membrane extends to the outer 
wall of the cochlea. The lower part of this, called 
the basilar membrane, consists of fine fibers which, 
though held together, are sufficiently independent 
to be considered as strings. It forms the founda- 
tion for a structure consisting of thousands of 
hairlike cells supported by minute rods. These 
constitute what is known as the organ of Corti.1 
It is to these hair 
cells that the prin- 
cipal part of the 
nerve-endings of 
the nerve of hear- 
ing are distributed. 
987. The semi- 
circular canals are 
three tubes which 
communicate with 
the vestibule by 
five openings. They extend arch-like above and 
behind the vestibule, and their position is such that 
each one is at right angles to the other two. They 
are known as the posterior, vertical, and horizontal 
canals. One end of each tube is dilated, forming 
what is known as an ampulla.2 Two of the arches 
join before entering the vestibule, which is why 
there are five, instead of six, openings into the 
vestibule. The membrane of the ampulla is 
Fig. 131.-Membranous labyrinth 
of the right ear, viewed from the 
outer side. Semidiagrammatic. 
1 Called after the anatomist who first described this part of 
the ear. 
2 From the Latin ampulla-a globular vessel. The Ear and the Sense of Hearing 
485 
covered with hair-like cells similar to those of the 
utricle and saccule, to which are distributed nerve- 
endings of the vestibular branch of the auditory 
nerve. As will be seen later, the semicircular 
canals, and probably the vestibule, are not con- 
cerned in the sense of hearing. 
988. The Auditory Nerve.-The auditory 
nerve trunk contains two distinct sets of nerve 
fibers, the origin, destination, and function of 
which are entirely different. One set of fibers is 
known as the cochlear branch and the other as the 
vestibular. The cells from which the principal 
fibers of the cochlear branch arise are situated in 
the modiolus of the cochlea. These cells are 
bipolar,1 and one axon from each cell passes 
through the walls of the' modiolus and the lamina 
and is distributed around the hair-like cells of the 
cochlea. The other axon passes through an open- 
ing in the internal ear-the internal auditory 
meatus-which leads to the brain and passes to 
what is known as the cochlear root of the auditory 
nerve at the lower edge of the pons Varolii.2 Thence 
fibers pass to the center of hearing in the cortex of 
the temporal lobe of the cerebrum. 
989. The peripheral termination of the vestibu- 
1 Described in paragraphs 309-311. 
2 Nerve fibers leaving the ear do not pass to their destination 
in the pons or from the pons to the cerebrum as continuous 
strands, but there are as it were several relay stations of gray 
matter in which the fibers end and transmit their impulses to 
fibers arising from the cell bodies constituting this gray matter. 
See paragraphs 335-342. Anatomy and Physiology 
486 
lar branch of the auditory nerve is around the hair 
cells of the saccule, utricle, and the ampulla of the 
semicircular canals. The central termination is 
in masses of gray matter in the pons from which 
fibers extend to the cerebellum and to motor 
centers of the spinal nerves. No fibers have been 
traced into the cerebral hemispheres. 
990. Physiology of the Ear.-The external 
ear serves to protect the internal ear from the 
entrance of foreign substances and to conduct 
wave sounds1 to the tympanum. When the sound 
waves strike the tympanic membrane they set 
it in vibration; this moves the hammer; from the 
hammer the motion is transmitted over the anvil 
and stirrup to the membrane covering the oval 
window and starts the membrane vibrating. These 
vibrations set up movement in the perilymph by 
which it is thought some of the strings of the 
basilar membrane are set in motion, and each 
string that vibrates in some unknown way com- 
municates its movement to the hair cells and 
through these to the nerve fibers at their base, 
through which the stimulus is conveyed to the 
brain, where it is interpreted. The nature of the 
stimulus, of course, depends primarily upon the 
nature of the sound causing it. It is generally 
believed that the cochlea is able to analyse sounds 
and to modify the nature of the impulse, but how 
it does this and how the different sounds affect the 
mechanism of the cochlea is not known. 
'For description of the nature and origin of sound, see Glossary. The Ear and the Sense of Hearing 
487 
991- Auditory judgment, i. e., the appreciation 
of the distance and position of a sounding body, is 
less accurate than visual judgment. The apparent 
distance of the sounding body is usually judged 
by the intensity of the sound; but, for this and for 
judgments of position, from whence the sound 
comes, the sense of vision is employed. 
992. Function of the Semicircular Canals 
and the Vestibule.-The semicircular canals and 
the vestibule, though occupying part of the space 
of the inner ear and in direct communication with 
the cochlea, are not, it is thought, connected in 
any way with the sense of hearing. As the result 
of experiments on animals and observation of 
persons in whom this part of the ear has been de- 
stroyed it is assumed that it is connected with the 
maintenance of equilibrium. A man whose semi- 
circular canals have been destroyed loses the 
power to rise from a recumbent position without 
falling. The exact nature of the action by which 
this part of the nervous mechanism performs its 
function is unknown, but the view that has found 
widest acceptance is that stimulation of the nerve- 
endings around the hair-cells results from move- 
ments of the head which set up movement in the 
endolymph of the canals. Movements of the head, 
it is thought, increase the pressure of the endo- 
lymph in the canal in the plane of which the head 
is moved. This pressure moves the hair-cells 
in the ampulla of that canal, the movements 
being furthered by the dragging action of the 488 
Anatomy and Physiology 
otoliths. The movement of the hairs stimulates 
the nerve-endings distributed about their base and 
thus starts impulses that pass along the vestibular 
branch of the auditory nerve to the pons and 
thence to the cerebellum, and thus arouse con- 
sciousness of the position of the body. The cere- 
bellum, it will be remembered, is thought to be 
the center in the brain which is concerned with the 
interpretation and adjustment of impulses arising 
from stimulation of the nerves concerned with 
muscle sense, as well as those due to stimulation 
of the vestibular nerve-endings, and is, therefore, 
the brain center controlling the equilibrium and 
balance of the body.1 
1 The functions of the cerebellum were described in paragraph 
383- CHAPTER XXV 
THE ORGANS OF GENERATION 
Name, Location, Structure, and Purpose of the Female Repro- 
ductive Organs and the Uterine Ligaments. Nature, Purpose, 
and Causes of Ovulation and Menstruation. Nature and Time 
of Puberty and the Menopause. Nature of the Ova and the 
Spermatozoa. Disposal of the Ova. The Decidua. Develop- 
ment of the Impregnated Ovum. Nature and Purpose of the 
Amnion, Chorion, Placenta, Umbilical Cord. Nutrition of the 
Fetus. Fetal Circulation. Function, Situation, Structure, and 
Development of the Breasts. Factors Influencing the Develop- 
ment of the Breasts and the Secretion of Milk. Mechanism of 
the Secretion of Milk. Composition of Colostrum and Milk. 
993. Anatomy of the Female Organs of 
Generation-Names.-The female organs of 
generation are divided into an internal and an 
external group. The internal organs comprise the 
ovaries, the Fallopian tubes, the uterus, and the 
vagina. The external structures include the mons 
Veneris, the labia majora, the labia minora, the 
clitoris, the hymen, the vulvo-vaginal and urethral 
glands. Collectively, the external structures are 
known as the vulva or pudendum. 
The Ovaries 
994- Shape, Location, Attachments.-The 
ovaries are two almond-shaped glandular bodies, 
489 490 
Anatomy and Physiology 
situated one on each side of the uterus-but a 
slight distance from it-in the posterior fold of the 
broad ligament, behind and below the Fallopian 
tubes. Each ovary is attached by its anterior 
margin to the posterior layer of the broad liga- 
ment, by its outer extremity to a fimbria of a 
Fallopian tube, by its inner extremity to a short 
ligament-the ligament of the ovary-which con- 
nects it with the uterus. 
Size. Each ovary is about iX inches in length, 
X of an inch in width, of an inch thick, and it 
weighs from I to 3 drams. 
995. Structure.-The substance of the ovary 
consists of (1) a stroma or bed, comprised of white 
and yellow fibrous tissue, muscular tissue, blood- 
vessels, lymphatics and nerves; (2) Graafian folli- 
cles; (3) a covering of serous membrane that is 
continuous with the peritoneum. 
996. Graafian Follicles.-These are the 
sacs or vesicles which contain the ova or cells from 
which, when fecundated, a new being may be 
developed. The follicles, known also as vesicles 
and ovisacs, consist of (1) an outer transparent 
coat of fibrous tissue that is connected to the 
stroma of the ovary by a plexus of blood-vessels, 
and (2) an inner layer of nucleated cells. The 
vesicles, except the smaller ones, are filled with 
fluid in which an ovum is suspended. In each 
ovary of a young child there are about 36,000 
vesicles of about 8oo to iJ0 of an inch in dia- 
meter, but very few of these ever develop, the Fig. 132.-Vessels of the uterus and its appendages, rear view. (Gerrish.) The Organs of Generation 
491 
majority of them shrinking and disappearing. At 
the time of puberty the ovaries enlarge, become 
very vascular, and a number of follicles gradually 
increase in size, and approach the exterior of the 
ovary and project from its surface in the form of 
clear vesicles, 2Jb to I of an inch in diameter, 
being covered only by an exceedingly thin layer 
of the outer tissue of the ovary. When a vesicle is 
fully matured, it and the restraining tissue rupture 
and the contents of the vesicle-the fluid and ovum 
--are discharged. This gradual development, ma- 
turation and rupture of a follicle, continues at 
regular intervals from puberty until the climac- 
teric. The process is known as ovulation; it will be 
further discussed in paragraphs 1018 and 1023. 
997. The Corpus Luteum.1-After the rup- 
ture of an ovisac and the escape of the fluid and 
ovum, there is an exudation of bloody fluid into 
the emptied sac. This fluid gradually clots and if 
the woman becomes pregnant the clot persists for 
some time, and as it disappears its place is taken 
by a peculiar yellowish connective tissue called 
the corpus luteum, which usually exists until the 
end of pregnancy. When pregnancy does not 
occur, the clot is quickly absorbed and if the 
corpus luteum forms at all it is very small. The 
function of the corpus luteum is unknown. Some 
physiologists think its purpose is to fill the cavity 
resulting from the rupture of the follicle with a 
substance, which can be easily absorbed, and so 
1 From the Latin corpora-body and lutea-yellow. 492 
Anatomy and Physiology 
prevent the formation of scar tissue. Others think 
that the corpus luteum is concerned in the forma- 
tion of the internal secretion of the ovaries. This 
will be further discussed in connection with men- 
struation and the attachment of the ovum to the 
uterine wall. 
The Fallopian Tubes or Oviducts 
998- Number, Location.-The Fallopian tubes, 
two in number, are situated in the free or upper 
margin of the broad ligament and extend between 
the ovaries and the upper angles of the uterus. 
999. Structure.-The walls of the Fallopian 
tubes consist of three coats: (l) an external or 
serous coat, derived from the peritoneum; (2) a 
middle or muscular coat, which consists of a layer 
of longitudinal fibers and a layer of circular fibers; 
(3) an internal mucous coat which is arranged in 
longitudinous folds and covered with ciliated epi- 
thelium. It is continuous at its inner end with the 
lining of the uterus, and at the outer extremity 
with the serous lining of the abdominal cavity. 
This is the only place in the body where a serous 
and mucous membrane connect. 
1000. Size, Shape, Fimbriae.1-Each tube is 
about four inches long. At its point of attach- 
ment at the uterus it is exceedingly narrow, but it 
gradually increases in size so that at its distal end 
it is about of an inch in thickness. At its dis- 
1 From the Latin fimbria-a fringe. The Organs of Generation 
493 
tai end each tube opens into the cavity of the 
abdomen and is surrounded by a series of fringe- 
like processes termed fimbria, one of which, longer 
than the rest, is attached to the ovary. 
1001. Pzirpose.-The Fallopian tubes serve to 
convey the ova from the ovaries to the uterus. 
Just how the ovum when discharged from an 
ovary reaches the Fallopian tube is not known, 
but it is thought that the movements of the cilia 
on the fimbrias and in the tubes set up a current 
that draws the ovum into a tube. It is considered 
probable that many ova discharged from the 
ovaries are not caught up by the fimbrise, but 
remain, and become disintegrated, in the abdom- 
inal cavity, the products of disintegration being 
absorbed and carried away by the blood. Such a 
view explains the occurrence of ectopic gestation. 
After the ovum enters an oviduct it is carried to 
the uterus by the peristaltic action of the tube and 
the movement of the cilia covering its lining mem- 
brane. The nature and disposal of the ovum will 
be discussed in paragraph 1027. 
The Uterus 
1002. Purpose.-The uterus receives the ovum 
from the oviducts and, if the ovum becomes 
fecundated, retains it during its development. 
Later, when the fetus into which the ovum 
develops, is matured, it is expelled chiefly by the 
contraction of the uterine walls. 494 
Anatomy and Physiology 
1003. Shape, Size, Location.-The uterus is a 
hollow, somewhat pear-shaped organ. In the 
virgin state it measures about three inches in 
length, two inches in width at its upper part, and 
one inch in thickness, and is situated in the pelvic 
pavity between the urinary bladder and the rec- 
tum. During pregnancy the uterus becomes enor- 
mously enlarged, measuring twelve inches or more 
in length, and eight to ten inches in width, and it 
extends into the hypogastric and lower part of the 
umbilical region. After parturition the uterus 
returns to almost its original size, but it is slightly 
larger than before pregnancy. In old age it 
becomes much smaller and atrophied. 
1004. Divisions.-For convenience in descrip- 
tion the uterus is considered as being divided into 
three parts, called the fundus, body, and neck. 
The fundus is the upper rounded portion, the body 
the central portion, and the cervix or neck the 
lower constricted part. At its juncture with the 
cavity of the body, the cavity of the cervix is so 
constricted that its sides are in apposition, as they 
are also at its external opening into the vagina. 
The upper constriction is called the os1 uteri inter- 
num, and the lower one os uteri externum. 
1005. Structure.-The walls of the uterus are 
thick and consist of three coats: (1) an external 
serous coat derived from the peritoneum (this 
coat is lacking on the anterior surface of the cer- 
vix) ; (2) a muscular coat; this forms the bulk of 
1 From the Latin os-an opening (plural ora). Fig. 133.-Female pelvic viscera, from above. The ovary and tube of 
the left side have been lifted out of place. (Gerrish.) The Organs of Generation 
495 
the uterine walls. It consists of layers of unstriped 
muscular tissue intermixed with areolar tissue, 
blood-vessels, lymphatic vessels, and nerves. The 
arrangement of the muscle fibers is very complex, 
and the vessels and nerves take a very tortuous 
course through the substance of the organ in 
order to prevent their' being stretched as the 
uterus enlarges during pregnancy. 
1006. The Ligaments.-The uterus is main- 
tained in position by three pairs of ligaments 
named the broad, the round, and the utero-sacral 
ligaments. 
The broad ligaments consist of two opposed 
serous sheets which are continuous with the peri- 
toneum. They cover the anterior and posterior 
surfaces of the uterus and extend from the lateral 
border of that organ and the upper part of the 
vagina outward to the side walls of the pelvis 
where they merge into the parietal peritoneum. 
Between these two sheets of tissue constituting 
the broad ligaments the following structures are 
found: the ovaries and their ligaments, the Fallop- 
ian tubes, the round ligaments, also blood and 
lymphatic vessels, nerves and areolar and fatty 
tissue. 
The round ligaments are two round cords com- 
posed of fibrous muscle and' areolar tissue, blood- 
vessels and nerves. Each one is about five inches 
in length and extends from the upper angle of the 
uterus-a little belovz the attachment of the 
Fallopian tube-forward and outward through the 496 
Anatomy and Physiology 
inguinal canal to the mons Veneris and labia 
majora, in the tissues of which it is lost. 
The utero-sacral ligaments consist of smooth 
muscular fibers and serous membrane. They 
extend between the cervix and rectum and serve 
to hold the cervix and vagina to the sacrum. 
1007. Peritoneal Pouches.-The perito- 
neum dips into a recess between the bladder and 
uterus and thus forms a small pouch which, when 
the bladder is empty, is occupied by coils of small 
intestine. This is called the utero-vesical sac. 
A similar though deeper sac is formed in like man- 
ner between the rectum and the upper part of the 
vagina and the cervix; it is called the recto uterine 
or cul-de-sac of Douglas. 
The Vagina 
ioo8. Nature, Location, Size.-The vagina is a 
membranous sac which encircles the lower por- 
tion of the cervix of the uterus and extends down- 
ward and forward to the vulva, behind the bladder 
and in front of the rectum. The length of its 
anterior wall is about 2 to 2% inches and that of 
its posterior 2^2 to 4 inches. It is constricted at 
its opening into the vulva, but becomes more 
dilated at its uterine extremity. 
1009. Structure.-The vaginal wall is about % 
of an inch in thickness and consists of three coats: 
the outer one is of fibrous tissue; the middle one of 
muscular tissue, and the inner one of mucous The Organs of Generation 
497 
membrane. The mucous coat is disposed in 
transverse folds; this allows of the dilation of the 
vagina during parturition. 
The External Organs 
As previously stated, the external structures 
classed with the organs of generation in the female 
Fig. 134.-Vulva of a virgin. The labia have been 
widely separated to show parts situated between 
them. Foss. Nav., fossa navicularis; Int. Vag., in- 
troitus vaginse; Lab. Min., labium minus; Vestib., 
vestibule. 
are: the mons Veneris, labia majora, labia minora, 
clitoris, hymen, and the vulvo-vaginal and urethral 
glands. 498 
Anatomy and Physiology 
low. Mons Veneris.-The mons Veneris is 
an eminence situated in front of the pubes, con- 
sisting of areolar, adipose, and fibrous tissue 
covered with skin and, after puberty, with hair. 
ion. Labia Majora.-These are two longi- 
tudinal folds of skin containing adipose and con- 
nective tissue. They extend from the mons 
Veneris in front to within an inch of the anus of 
the rectum behind. 
1012. Labia Minora.-These are two longi- 
tudinal folds of modified epithelium. They are 
smaller than the labia majora, between which they 
are situated. They extend from the clitoris (see 
Fig. 134) downward and backward for about iX 
inches 
1013. The Clitoris.-This is a small structure 
situated at the apex of the triangle formed by the 
junction of the labia minora. 
1014. The Hymen.-This is a fold of mucous 
membrane which surrounds the lower part of the 
orifice of the vagina. Occasionally it completely 
covers the vulvo-vaginal opening. This condition 
is spoken of as an imperforate hymen. 
1015. The Glands of the Vulva.-These 
consist of the vulvo-vaginal glands or glands of 
Bartholin and the urethral glands. The former 
are two small glands situated one on either side 
the vagina. Their secretion lubricates the vulval 
canal. The urethral glands are found chiefly in 
the walls and floor of the urethra. They secrete 
mucus. The Organs of Generation 
499 
1016. The Perineum.-The perifieum is not 
usually classed with the organs of generation, but 
it is so closely connected with them, both anatomi- 
cally and functionally, that it seems well to 
describe it here. It consists of bands of muscle 
held together with fasciae and covered with skin. 
It bounds the external outlet of the pelvis and 
constitutes the floor of the genital canal. An 
important part of the perineum is the triangular 
portion which separates the vagina and rectum. 
This, though quite extensible, is frequently torn 
during parturition, and when the tear is of any 
extent and is not repaired, the vagina and uterus 
lose a support, and various abnormal conditions 
may follow. 
Physiology of the Female Reproductive Organs 
1017. Proposes.-The purposes of the female 
reproductive organs are: (i) the formation and 
development of the ovum, the cell which, if it 
becomes united with a spermatozoon-the fecund- 
ating cell developed in the testis of the male-will 
develop into a new individual; (2) the harboring 
and affording sustenance to the fetus-into which 
a fecundated ovum develops-until it is sufficiently 
grown to live outside the body. 
1018. Ovulation.-As stated in paragraph 
996 the ovaries contain in their substance at 
birth a great number of undeveloped Graafian 
follicles, some of which at the time of puberty 
enlarge and come to the surface of the ovary, and 500 
Anatomy and Physiology 
from that 'time at regular intervals of about a 
month a follicle ruptures and discharges its ovum. 
This process of development and maturation of 
the follicle and its ovum and the rupture of the 
follicle is known as ovulation. 
1019. Puberty.-Puberty consists in the mat- 
uration of the testis in the male and of the ovary 
in the female. The boy, at the time of puberty 
and for a short time before, grows rapidly, and 
owing to the rapid growth of the larynx and vocal 
cords marked changes occur in his voice. In the 
girl the time of puberty is marked by increased 
growth, development of the breasts and the appear- 
ance of the menstrual flow. In temperate climates 
the age at which boys usually attain puberty is 
about 15 years and girls 14 to 15 years. In warmer 
countries the age is somewhat younger and in cold 
countries older. The physical changes incidental 
to puberty are not developed suddenly, but take 
place gradually, during the course of several 
months, and the time in which they are occurring 
is known as the period of adolescence. 
1020. The Menopause or Climacteric.-By 
the menopause or climacteric is meant the end of 
the period during which the Graafian follicles 
continue to develop in the ovaries, and, conse- 
quently, the time during which a woman is 
capable of bearing children. It is marked by the 
gradually lessening and, finally, the cessation of 
the menstrual flow, and the atrophy of the ovaries, 
tubes, uterus, and breasts. The Organs of Generation 
501 
io2i. Menstruation.-Menstruation is the 
periodical discharge of bloody fluid from the cavity 
of the uterus. Normally, it occurs at regular inter- 
vals of about 28 to 30 days, except during preg- 
nancy and the period of lactation, from the time of 
puberty until the climacteric or menopause. The 
usual duration of the flow is from four to five days 
and the amount of blood lost is normally from four 
to six ounces. The fluid discharged consists of 
blood which does not clot, epithelium, and mucus. 
There is great difference of opinion as to whether 
or not any of the mucous membrane of the uterus 
is normally shed during the process of menstrua- 
tion; the more common opinion at present is that 
it is not. 
1022. Changes in the Uterus, etc., in Con- 
nection with Menstruation.-Preceding the 
menstrual flow, the pelvic organs and the breasts 
are congested, and there is a more or less marked 
sense of general ill-being. The condition of the 
mucous membrane of the uterus undergoes changes 
preceding, during, and after menstruation as fol- 
lows: five days before the process there is a rapid 
hypertrophy of the membrane; during menstrua- 
tion there is a capillary hemorrhage and the epi- 
thelium undergoes degeneration and is cast off; 
during the seven days following menstruation, 
regeneration of epithelium takes place and the 
membrane returns to its normal size. 
1023. Relation of Ovulation and Men- 
struation.-There have been many theories ad- Anatomy and Physiology 
502 
vanced regarding the relationship of ovulation 
and menstruation. Formerly many physiologists 
thought that menstruation was the result of a 
nervous reflex action occurring in connection with 
the development of a Graafian follicle. Others were 
of the opinion that the two phenomena were not 
at all dependent upon each other, owing to the 
fact that it was found that conception occasionally 
occurred before menstruation was established and 
after it ceased at the time of the menopause. At 
the present day the common view is that the 
menstruation is dependent upon the ovaries, but 
that the influence of the latter is exerted through 
the medium of the blood rather than through the 
nervous system. It is thought that an internal 
secretion is formed in the ovaries-some physiolo- 
gists think by the yellow cells of the corpus luteum 
-which is carried by the blood to the uterus and 
that this secretion is responsible for the hypertro- 
phy and congestion that precedes menstruation. 
It is not known, however, if the secretion of the 
ovary is entirely responsible for the menstrual 
flow or if this is in part induced by some inherent 
property in the uterine tissue. The supposition 
that the ovaries are responsible for menstruation 
arose from the fact that following operations in 
which the ovaries are removed menstruation 
ceases and the uterus becomes atrophied. The 
ovum, it is now thought, is discharged from the 
Graafian follicle some days before menstruation 
occurs. The Organs of Generation 
503 
1024. Reason for Menstruation.-The gen- 
eral view of the present day is that the congestion 
and hypertrophy of the uterine tissue preceding 
the menstrual flow is nature's preparation of the 
wall of the uterus for the reception of the ovum, 
should it become fertilized. 
Physiology of Reproduction 
1025. Nature of the Ovum.1-The ovum is a 
cell measuring about tvo of an inch in diameter. 
It consists of cytoplasm and a nucleus containing 
a nucleolus or germinal spot, and the whole is 
surrounded by a membrane. The cytoplasm con- 
tains the yolk or food material, and the nucleus, 
contains chromatin material. It is thought that it 
is through this chromatin material that hereditary 
characteristics are transmitted from the maternal 
parent to her child. 
1026. Nature of Spermatozoa. 2-The sper- 
matozoon is the male cell of generation; its func- 
tion is to produce impregnation or fertilization of 
the ovum. It consists of a head, a rod-shaped 
middle piece, and a hair-like tail. It measures 
about rio of an inch in length. The head con- 
tains nuclear material including chromatin. Sper- 
matozoa are capable of independent movement, 
and therefore when the seminal fluid, in which 
1 From the Latin ovum-an egg. 
2 From the Greek spermato-a seed and zdon-an animal. 
Plural spermatozoa. 504 
Anatomy and Physiology 
they are contained, is discharged into the vagina 
of the female in the act of coitus, they can travel 
upward, into and through the uterus, and enter 
an ovum. Normally only one spermatozoon enters 
an ovum. 
1027. Disposal of the Ovum.-As stated in 
paragraph 1001, it is thought that when an ovum 
escapes from a ruptured Graafian follicle it is 
usually caught by the fimbriae of a Fallopian tube, 
and then slowly forced through its channel by the 
motion of the cilia covering the membrane by 
which it is lined. If the ovum does not become 
impregnated it enters the uterus and is cast off, 
probably, in the menstrual flow. If, however, as 
it passes through the tube it comes in contact with 
the male element-the spermatozoon-segmenta- 
tion or the process of cell division at once begins, 
and when the ovum reaches the uterus it becomes 
attached to the mucous membrane of that organ, 
usually in the upper part near the openings of the 
Fallopian tubes. 
1028. The Decidua.1-The membrane lining 
the uterus is prepared for the reception of an 
impregnated ovum by the softening and conges- 
tion that precedes the menstrual flow. When 
in this condition it is known as the decidua, or 
decidua vera, and the point to which the ovum 
becomes attached is known as the decidua serotina2 
-this, later, develops into the placenta. A fold 
1 From the Latin deciduus--falling off and vera-true. 
3 From the Latin serotina-latest. The Organs of Generation 
505 
of the decidua vera gradually encapsulates the 
ovum, and this is known as the decidua reflexa.1 
1029. Development of the Ovum.-The 
union of the spermatozoon and ovum2 takes place 
in one of the Fallopian tubes, and it is thought 
that it requires about eight days for the impreg- 
nated ovum to reach the uterus. During this time 
segmentation or cell division is going on, so that 
by the time the ovum reaches the uterus many 
thousands of cells have been formed, and also the 
sac enclosing them. The sac is known as the 
amnion. At first there is little apparent difference 
in the nature of the cells, but they soon divide 
into three distinct layers, and the cells of each 
layer gradually present marked distinctions and 
serve different purposes. Thus, from the outer 
layer called the ectoderm3 or epiblast4 are derived 
the ectodermic layer of the chorion and amnion 
(described in paragraph 1031), the epidermis, 
derma, nails, hair, the enamel of the teeth, the 
mammary and salivary glands, portions of the 
alimentary canal, the mouth, nasal passages, the 
nervous system and sense organs. From the 
middle layer-known as the mesoderm or mesoblast5 
-arise the bones, the muscular and connective 
1 From the Latin reflexa-turned back. 
2 The ovum and spermatozoon combined are usually considered 
as one cell, since neither one alone contains all the essentials 
necessary for cell division and growth. 
3 From the Greek ektos-outside and derma-the skin. 
■* From the Greek epi-upon and blastos-a germ. 
5 From the Greek mesos-middle, etc. 506 
Anatomy and Physiology 
tissues, the urinary and genital organs-except 
the lining of the bladder and urethra-the epi- 
thelium of the vascular and lymphatic systems and 
of the serous cavities, and the blood and lymph 
vessels. From the inner layer-the entoderm or 
entoblast-are derived the epithelium of the ali- 
Fig. 135.-Sectional views of ovum, after segmentation 
(Gerrish.) 
mentary canal, bladder and urethra, and the 
majority of the secretory glands. 
Note of Growth During Intra-Uterine Life 
1030.-Growth takes place more rapidly dur- 
ing intra-uterine life than at any other time. The 
ovum, when it becomes impregnated, is only about 
vko of an inch in diameter; two weeks after 
conception the embryo-as the fecundated ovum 
is called-is the size of a Lima bean; in four weeks 
it is the size of a walnut; in four months it is about 
eight inches in length and has assumed the char- 
acteristic appearance of a human being-its fingers 
and toes are separated, its eyes are well developed, The Organs of Generation 
507 
and the external genitals are sufficiently formed to 
show the sex. It is known now as a fetus. At the 
completion of twenty-six weeks' development it is 
possible for the fetus to live outside the mother's 
body, but if it is born before term, i. e., nine lunar 
Fig. 136.-Diagram of gravid uterus, showing for- 
mation of deciduse and placenta. 
months after conception, it is likely to be very 
fragile. 
1031. The Amnion.-While in the uterus, the 
fetus is surrounded by a membranous sac known 
as the amnion or amniotic sac.1 Except at the 
point of attachment to the uterine wall, the 
amniotic sac consists of three layers: an inner 
1 From the Greek amnion-a bowl. Anatomy and Physiology 
508 
serous layer, a middle layer called the chorion,1 
and an outer layer made up of the decidua reflexa. 
The inner layer secretes a fluid known as the 
amniotic fluid or liquor amnii. The outer surface 
of the chorion is covered with small, shaggy pro- 
jections, like fringes of moss, called chorion villi, 
which, especially at the point of attachment to the 
uterus, become very vascular by the development 
in them of loops of capillaries. The function of the 
chorion is to hold the embryo to the uterus and 
to absorb nutrient matter for the fetus from the 
mother's blood until the placenta is formed; also, 
at its point of attachment to the uterus it enters 
into the formation of the placenta. The other 
purposes of the amniotic sac and its contained 
fluid are: To protect the fetus from injury by jars 
due to the mother's falling or receiving a blow on 
the abdomen, etc.; to allow the fetus freedom of 
movement; to distend the cervix of the uterus 
during labor, and when the sac ruptures setting 
free the liquor amnii, as normally it does shortly 
before the child is forced from the uterus, by the 
contraction of its walls, the discharged fluid lubri- 
cates and washes out the vaginal canal. 
1032. The Placenta.-The placenta is formed 
during the second and third month of gestation. 
It is fully developed by the fourth month, but it 
increases in size as pregnancy advances, and at 
1 From the Greek chorion-skin, leather. 
It will be remembered that the amnion and chorion are derived 
from the outer layer of cells arising from the impregnated ovum. The Organs of Generation 
509 
the end of a normal pregnancy it measures about 
eight inches in diameter and one inch in depth at 
its thickest part, the center, and weighs one to one 
and a half pounds. The placenta consists almost 
entirely of blood-vessels held together with con- 
nective tissue. The vessels form loops that pro- 
ject into the uterine tissue and interlock with 
uterine blood-vessels, there is, however, no anasto- 
moses between the uterine and placental vessels. 
1033. The Umbilical Cord.-There develops 
at the same time as the placenta, a cord-like struc- 
ture known as the umbilical cord. It consists princi- 
pally of two arteries and one vein surrounded by a 
gelatinous substance known as Wharton's jelly. The 
average length of a cord is about twenty inches. 
It is continuous at one end with the placenta and 
at the other end with the fetus, entering the 
abdomen of the latter at a point called the um- 
bilicus or navel. Its purpose will be discussed in 
the next paragraph. The placenta, cord, mem- 
branes and part of the decidua are, normally, 
expelled from the uterus shortly after the birth of 
the fetus. The remaining portion of the decidua 
is cast off gradually during the days following 
parturition, in what is known as the lochia, and a 
new mucous membrane gradually replaces it. 
1034. Nutrition of the Fetus.-At the time 
of fertilization, the ovum contains a small amount 
of nutrient material in its cytoplasm, but only 
about sufficient to last until it becomes attached 
to the decidua of the uterus. After that time the Anatomy and Physiology 
510 
embryo gets its nutrition from the mother's blood. 
That it can do so is due, during the first four 
months of its development, to the presence of the 
chorion, and afterwards to that of the placenta 
and umbilical cord. 
1035. Respiration.-During intra-uterine life, 
the lungs are in a collapsed condition and do not 
function, and the fetus gets its oxygen supply and 
gives up its waste matter through the same chan- 
nels as it receives its nutrition. The blood flowing 
from the fetus to the uterus-consequently the 
blood carrying waste matter from the fetus-is 
contained in the arteries of the cord. The blood 
conveying nutritive material and oxygen from the 
mother to the fetus is contained in the veins. As 
stated in the preceding paragraph, there is no 
anastomosis between the uterine and placental 
vessels, the interchange of material between the 
blood of the two sets of vessels being the result of 
osmosis and diffusion. 
1036. Differences in the Organs of Circu- 
lation in the Fetus and after Birth.-In the 
fetus there are certain structures necessary to the 
performance of its circulation that are of no use 
after respiration is established and the blood no 
longer flows through the vessels of the umbilical 
cord and placenta. These are as follows: (1) an 
opening between the right and left auricles of the 
heart, known as the foramen ovale, which permits 
of the passage of blood from one auricle to the 
other. This, normally, closes at birth; failure to The Organs of Generation 
511 
do so results in what is known as a blue baby, and 
the infant rarely lives many months; (2) a duct 
between the aorta and the pulmonary artery 
called the ductus arteriosus, which closes as soon 
as the child breathes; (3) a short vessel connecting 
the umbilical vein with the ascending vena cava, 
called the ductus venosus-, (4) two arteries, called 
the hypogastric arteries, which, arising from the 
internal iliacs, pass from the abdomen through the 
navel and run into the umbilical cord where they 
are known as the umbilical arteries. The hypogas- 
tric arteries and the ductus venosus close as soon 
as the cord is cut, and gradually atrophy, so that 
they are simply fibrous cords between ten and 
fifteen days after birth. 
1037. Fetal Circulation.-The blood con- 
taining oxygen and nutrition for the fetus is 
carried to it by the umbilical vein and passes 
into the ascending vena cava partly through the 
liver, but chiefly through the ductus venosus, 
which, as stated in the preceding paragraph, con- 
nects the umbilical vein with the vena cava. 
From the ascending vena cava the blood flows 
into the right auricle and thence through the 
foramen ovale into the left auricle, and on into the 
left ventricle, and onward into the aorta. From 
the aorta some of the blood, following the course 
normal after birth, goes to the head and upper 
extremities, and some to the lower extremities. 
The blood which goes to the upper part of the 
body returns through the descending vena cava Anatomy and Physiology 
512 
to the right auricle again, but instead of passing 
into the left auricle as before, it flows into the 
pulmonary artery and some of it passes to the 
lungs-to supply them with nutrition only-and 
some into the aorta through the ductus arteriosus. 
Thence it passes to the lower extremities and 
abdominal viscera. In going to and from the 
lower part of the body the blood follows the same 
course as it does after birth until it reaches the 
internal iliac arteries. From these arteries the 
greater part of the blood passes to the hypogastric 
arteries and so into the umbilical arteries and 
onward to the placenta; but a small amount 
passes back into the ascending vena cava, and, 
mingling with the vitalized blood returning from 
the placenta, again makes the circuit of the body. 
Accessory Organs of Generation 
The two mammary glands or breasts are classed 
as accessory organs of generation. 
1038. Purpose.-The mammary glands serve 
to secrete the milk which the young infant needs 
for its sustenance. 
1039. Situation.-The breasts are situated, one 
on either side, on the anterior wall of the chest 
between the third and seventh ribs. They are 
attached to the pectoral muscles by a meshwork 
of fibrous tissue. 
1040. External surface.-The external surface 
of each breast consists of: (1) an area covered with The Organs of Generation 
513 
skin; (2) an areola, the small circular area of 
tinted skin on which are small projections formed 
Fig. 137.-Right breast in sagittal section, inner surface of 
outer segment. (Gerrish.) 
by minute secreting glands; (3) a nipple, a papilla 
projecting from the center of the areola and having 514 
Anatomy and Physiology 
at its summit the openings of the milk ducts. 
It consists of areolar tissue with some unstriped 
muscular fibers and numerous blood-vessels. 
1041. Structure.-Each breast consists of some 
fifteen or twenty main glands formed by the union 
of smaller (lobular) glands. The main glands or 
lobes are separated from each other by walls of 
fibrous and fatty tissue. Each one is provided 
with an excretory duct which, as it approaches the 
top of the breast, dilates and forms a small reser- 
voir in which, when the gland is active-i. e., 
during the months of lactation-milk can be 
stored. The breasts are supplied with a large 
number of blood and lymphatic vessels and nerves. 
1042. Development.-At the time of puberty 
the mammary glands increase in size, but this 
enlargement is due chiefly to the development of 
their connective tissues, the glandular tissue re- 
maining undeveloped and functionless unless con- 
ception takes place. When conception occurs the 
glandular tissue gradually develops; the breasts 
become enlarged; the areola assumes a deeper hue, 
and toward the end of pregnancy a small amount 
of a fluid known as colostrum is secreted. After 
delivery the secretion of colostrum is increased and 
its composition gradually changes to that of milk. 
1043. Factors Influencing the Develop- 
ment of the Glands and the Secretion of 
Milk.-Formerly it was thought that the develop- 
ment of the mammary glands was influenced by 
some nerve connection between the glands and the The Organs of Generation 
515 
ovaries and uterus. The present theory is that 
their primary development is influenced by the 
internal secretion of the ovaries, for if the ovaries 
are removed the glands do not develop, or, if they 
are developed before the ovaries are removed they 
become atrophied, as they do after the menopause. 
The development of the glandular tissue, it is 
thought, is due to some chemical substance, the 
nature of which is as yet unknown, that is pro- 
duced as the result of the metabolism of the fetus, 
and absorbed by the blood and carried to the 
glands. This substance, it is thought, though 
promoting the development of the glandular tissue 
interferes with its secreting, as it is not until the 
fetus has been expelled from the uterus that 
active secretion commences, and if a new concep- 
tion occurs during the months of lactation the 
character of the milk changes and its secretion 
soon ceases. The stimulus causing the secretion 
of milk arises, it is thought, from the emptying 
of the ducts; one reason for this supposition being 
that when a woman does not nurse her infant the 
secretion of milk soon ceases and the breasts 
return to the size they were before pregnancy. 
The nature of the stimulus is as yet unknown. 
Also, the secretion of milk is to some extent 
influenced by the nervous system, strong emotion 
from any cause interfering with its secretion; but 
this is supposed to be due chiefly to changes in the 
vaso-motor system which interfere with the blood 
supply to the glands. Anatomy and Physiology 
516 
1044. Mechanism of the Secretion of Milk. 
-The secretory portion of the glands composing 
the breasts are, like all other secretory glands, 
lined with secretory cells, and some of the constitu- 
ents of the milk, the water, salts, and probably 
sugar are secreted by these cells from the blood; 
but the proteids and fats, it is thought, are derived 
as the result of the disintegration of the cells 
themselves. The sugar in the blood is glucose and 
that in the milk lactose; therefore if the latter is 
derived from the former it must undergo some 
slight chemical changes, either during or after 
secretion. 
1045. Composition of Colostrum and Milk. 
-Colostrum is a thin, yellowish liquid composed 
of: 
Proteids 5.71 per cent. 
Fat 2.04 " " 
Sugar 3.74 " 
Salts 0.28 " " 
Water 88.23 " " 
100.00 " " 
The milk of every animal is adapted to suit the 
requirements of its young, and human milk differs 
in some respects from that of all other animals. 
The relative proportion of its fluid arid solids 
varies according to the time of lactation-the 
milk being more dilute at the first. The compara- 
tive proporton of the constituents of human and 
cow's milk can be seen in the following table: The Organs of Generation 
517 
Human Milk. 
Average Cow's 
Milk. 
Proteids 
i- 2% 
4% 
Fat 
3- 4% 
3- 4% 
Lactose 
6- 7% 
4-5% 
Mineral 
i- 2% 
•7% 
Water 
87-88% 
86-87% 
1046. Other differences in the two milks that 
must be considered when cow's milk is used for 
young infants are: (1) the proteid of human milk 
is two-thirds lactalbumin and one-third caseinogen 
and that of cow's milk is five-sixths caseinogen 
and one-sixth lactalbumin; (2) human milk coagu- 
lates in small flocculent curds and cow's milk in 
large firm masses. This difference in curding is 
partly due to the smaller amount of caseinogen 
in human milk and partly to the difference in the 
reaction of the two milks-cow's milk being more 
nearly acid than human milk. CHAPTER XXVI 
DEVELOPMENT. SENESCENCE. PHYSIOLOGY OF 
SLEEP 
Normal Rate of Development-Weight, Height, Muscular 
Strength, Bones, Glands, Skull, Brain, Special Senses, Mental 
Development, Speech. Changes Occurring in the System During 
Senescence. Supposed Causes of Senescence. Why Sleep is 
Necessary. Theories for Causation of Sleep. 
Normal Rate of Development 
1047- Weight.-The average weight of male 
infants at birth is from about 6 to 8 pounds, and 
the average weight of female infants from 5X to 
7 pounds. During the first week after birth there 
is usually a slight loss in weight, but from that 
time there should be a steady and fairly regular 
daily increase of /d of an ounce to an ounce during 
the first five months of life, and in the seven 
following months }d to /d of an ounce. Thus an 
infant should have doubled its birth weight by 
the end of five or six months and trebled it at 
between twelve or fifteen months. 
1048. Height.-The average length of male 
infants at birth is about 19.6 to 20 inches, and that 
of female infants 19.1 inches. The average in- 
518 Rate of Development 
519 
crease of growth during the first month of life is 
about iX inches; during the second month iX 
inches; from the third to fifteenth month X to X 
of an inch per month. Thus during the first year 
there is, normally, an increase of about 8 inches in 
height; during the second year about 3X inches, 
and during the third year 3 inches. From the 
above figures it can be seen that the most rapid 
increase in growth takes place during the first 
months following birth. After the third year a 
steady decrease in the rate of growth takes place 
until the time of the second dentitionT-between 
the sixth and ninth years-when there is, for a 
time, a slight acceleration, and again in the period 
of adolescence when, as stated in the preceding 
chapter, there is a rapid increase in stature and 
general physical development. After puberty, 
growth takes place slowly, and gradually ceases. 
1049. Muscular Strength.-At birth, the mus- 
cles of the hands and arms seem to have the 
greatest strength. The muscles of the neck are, 
usually, not sufficiently developed to allow the 
infant to hold up its head until three months after 
birth, and, generally, it is six or seven months 
before those of the back are strong enough to 
allow of an infant's sitting up. The muscles of the 
viscera, also, only become strengthened gradually, 
consequently, the peristaltic action of the stomach 
and intestines is weak, especially during the first 
two years of life. For this reason the former can 
1 The development of the teeth was described in Chapter V. 520 
Anatomy and Physiology 
do little toward the breaking up of food material, 
and defective digestion or constipation quickly 
results in an accumulation of gas in the stomach 
and intestines. 
1050. The Bones.-At the time of birth the 
bones contain, a large amount of cartilaginous 
material and are easily bent. This condition is of 
special importance to the bones of the leg. These, 
at birth, are usually crooked, owing to the fact 
that while in the uterus the fetus generally has its 
legs drawn up and turned inward. In order to 
correct this condition, free play of the legs, which 
will improve the circulation and strengthen the 
muscles, is imperative, but the average child must 
not be encouraged to walk until about twelve 
months of age, the proportion of mineral matter in 
the bones being, until that time, too small to allow 
of their being sufficiently strong to bear the weight 
of the body for any length of time without bending. 
1051. Glands.-The action of the glands 
which manufacture the digestive juices, especially 
the salivary glands and pancreas, is very feeble 
during the first two or three months after birth, 
and the saliva contains little or no ptyalin--.the 
ferment which digests starch-until the eighth 
month. The lachrymal glands are not sufficiently 
developed to shed tears until the third or fourth 
month. The sebaceous glands are active even 
before birth, as is shown by the thick coating of 
sebaceous matter-the vernix caseosa^-that covers 
'Described in Chapter XXV. Rate of Development 
521 
the skin of the infant at birth. The thymus gland 
-see Chapter XVI-is large at birth and in- 
creases slightly in growth until the end of the 
second year, when it attains its maximum size 
and remains the same, it is thought, until puberty, 
when it becomes atrophied. The liver is pro- 
portionately large in the new-born baby. This is 
believed to be due to its receiving more freshly 
vitalized blood than the other glands and organs 
during intra-uterine life. The kidneys are de- 
veloped and function before birth, as is shown by 
the presence of urine in the bladder at the time of 
birth, and the finding of traces of urine in the 
liquor amnii.1 
1052. The Skull, Brain, and Mental De- 
velopment.-At birth the skull is proportionately 
large and it increases in size considerably during 
the first year of life, and then more slowly up to 
the seventh year, when it has attained nearly its 
full growth. The size of the brain does not in- 
crease as rapidly as the skull, for it only reaches 
its maximum of physical development about the 
thirtieth year. The rate and degree of the func- 
tional development of the brain is as little in 
keeping with its physical development as is the 
latter with the growth of the skull, and it depends 
upon such factors as heredity, environment, study, 
health. In some individuals intellectual develop- 
ment continues long after physical growth has 
ceased; in others mental growth is arrested long 
1 Described in Chapter XXV. 522 
Anatomy and Physiology 
before physical. At first the brain and other nerve 
centers work automatically and by reflex action 
only, and usually the first sign of anything like 
intelligence does not occur until between the third 
and fourth months, when a normal infant begins 
to recognize and remember people and things that 
it sees frequently. It is not, however, until the 
third year that the memory centers begin to be at 
all well developed. The emotions, imagination, 
and imitative faculties are developed long before 
the powers of reasoning and judgment, so that 
until a child is at least seven years of age he can 
be more readily taught by example, than by 
reasoning, and more easily controlled by ap- 
peal to his sympathy and affection, than by 
reasoning. 
1053. Special Senses: Speech.-The senses of 
touch and taste are present at birth, but hearing 
does not seem to be developed until a few days 
later, and the sense of vision is apparently not 
very acute until about the third week. Many 
children learn to say short words about the end of 
the first year, but usually they do not begin to 
try to express their wants in speech until between 
the second and third years, and many perfectly 
normal children are even older before they begin 
to talk. 
1054. Senescence.1-After puberty, physical 
development goes on slowly for a few years until 
maturity is reached, the time varying in different 
1 From the Latin senescens, pr. par. of senesco-to become old. Senescence 
523 
individuals, and then very, very gradually at first, 
but nevertheless surely, retrogressive changes be- 
gin. The bones become brittle from an increased 
deposit of inorganic salts; cartilage, ligaments, 
muscles lose their elasticity. The glandular tu- 
bules of the stomach and intestines become dimin- 
ished in number; the glandular tissue of the 
ductless glands is decreased and the fibrillar tissue 
increased, and consequently the secretion of diges- 
tive and internal secretions become diminished. 
The walls of the arteries lose their elasticity and 
become hardened. The hair loses its pigment and 
becomes white, and the skin in some parts of the 
body grows wrinkled. The special senses of taste, 
smell, hearing, and vision lose their acuity. In 
women at about the age of forty-five, and some- 
what later in men, the organs of generation become 
atrophied and lose their power of functioning, and 
the progress of the retrogressive changes there- 
after become more marked. This condition of 
retrogression is known as senescence. Two com- 
mon reasons advanced for the defective metabo- 
lism characteristic of the senescence are (i) lack 
of nutrition of the tissues due to the hardening of 
the arteries-arterio-sclerosis-and (2) the lack of 
internal secretions resulting from the degeneration 
of the ductless glands and other organs furnishing 
such secretions. These beliefs have given rise to 
the sayings: "A man is as old as his arteries, " and 
"A man is only as old as his ductless glands." 
Arterio-sclerosis and degeneration of the glands 524 
Anatomy and Physiology 
take place comparatively early in some individuals, 
and some of the more common causes for this are: 
certain diseases-especially syphilis, rheumatism, 
heart, and kidney diseases; chronic poisoning by 
the continued overuse of alcohol and other drugs, 
as morphine, cocaine, etc., or the products of 
putrefaction resulting from over-feeding; under- 
feeding; exposure tu extremes of temperature; 
over-work; continued mental strain; heredity. 
The Physiology of Sleep 
1055- Why Sleep is Necessary.-All parts 
of the body that are the seat of active work require 
periods of rest. Some parts, as the heart, lungs, 
and muscles concerned in respiration, cannot stop 
work for any length of time, therefore short 
regular intervals of rest have been provided for 
them in the midst of their activity. Such alternate 
periods of rest and work would be impossible, 
however, for the brain, and though the voluntary 
muscles and the viscera are less active at some 
times than at others, the period of activity, and 
consequently their metabolism with the produc- 
tion of waste, is far in excess of their intervals of 
rest and repair. Hence the necessity for the 
period of unconsciousness and repose known as 
sleep, during which muscular tension is relaxed, 
and even those organs which must continue their 
action do so at a slower rate. 
1056. Cause of Sleep.-The cause, or causes, Physiology of Sleep 
525 
of sleep are as yet unknown. Two of the theories 
advanced are as follows: 
(i) That it is the result of an accumulation of 
fatigue poisons within the system. As stated in 
Chapter VI, muscular contraction results in the 
formation of acids and other waste products 
known as fatigue poisons which, after being further 
oxidized, are eliminated from the system in the 
form of CO 2, H2O and urea (CON2H4), etc. 
During waking hours, however, especially when 
an individual is very active, the fatigue poisons 
are formed quicker than the further oxidation 
necessary to transform them to C02, etc., and 
their removal can take place; consequently they 
accumulate in the system, and by their action 
cause a loss of irritability of the central nervous 
system. This lack of nervous irritability, it is 
thought, induces sleep, especially when the sur- 
roundings are dark and quiet so that stimulation 
of the sensory nerves is lessened. 
(2) Sleep is said to be due to anemia of the brain. 
As the result of experiments it has been found that 
during sleep there is a lessened flow of blood 
through the brain; in other words the brain is 
anemic. Many authorities, however, consider this 
condition the result, and not the cause, of sleep. 
Those who consider it the cause of sleep believe 
that it is due to changes in the activity of the 
vaso-motor system. Thus, they think that the 
continual exposure to sensory stimuli, to which 
the body during waking hours is subjected, and 526 
Anatomy and Physiology 
the constant activity of the brain keep the vaso- 
constrictor center constantly active, in conse- 
quence of which the vessels of the skin are more or 
less constricted and those of the brain relaxed. 
As ■ the result of this constant, though varying 
activity, the center becomes fatigued and its 
activity lessened; consequently, the peripheral ves- 
sels lose their tone and accommodate a greater 
supply of blood, thus leaving so little for circula- 
tion in the brain that it cannot easily remain 
functioning. The drowsiness that follows efforts 
to study or to do other mental work after eating a 
heavy meal is an example of the result of anemia 
of the brain on the functioning power of that 
organ. The cause of the anemia was explained in 
paragraph 578. 
1057. Dreams.-The unconsciousness which 
we term sleep, it is thought, often exists in different 
degrees in different parts of the brain, and dreams, 
it is believed, are due to certain memory centers 
in the brain remaining partially active while the 
rest of the brain is asleep. GLOSSARY 
Abduction, drawing or leading away; movement from the 
median line. 
Acid, as adjective: sour; as substantive: an acid is a substance, 
having the following properties: All acids contain hydrogen; 
if they lose this element they cease to be acids. They will 
combine with bases to form salts, and in doing so part with 
their H. They turn blue litmus1 and methyl2 orange red. 
Acids may be gases, liquids, or solids; e. g., carbonic acid is 
a gas; sulphuric acid, a liquid; salicylic acid, a solid. 
Adduction, drawing to; the drawing of one part of the body to 
another. 
Aerate, to subject to the action of air; to oxygenate. 
Afferent, bringing or conducting to. 
Aggregation, the act of collecting together, or the state of 
being so collected or massed. 
Albumins, certain substances containing nitrogen that are 
soluble in water, in dilute saline solutions, and in concen- 
trated solutions of sodium chloride and magnesium sulphate. 
They are precipitated by saturating their solutions with 
ammonia sulphate. They are coagulated by heat and acid. 
Examples are: serum albumin of blood; egg albumin; the 
lactalbumin of milk. 
Aliment, to furnish with food. 
Alimentary, pertaining to aliment or food. 
Alkali, a substance that is capable of neutralizing acids. Alka- 
lies turn red litmus blue; turmeric brown; and most purple 
dyes of vegetable origin green. When combined with fats 
they form soaps. They have a salty taste. 
1 Litmus is a liquid substance obtained from a species of lichen. 
2 Methyl orange is a yellowish coal-tar product. 
527 528 
Anatomy and Physiology 
Anabolism, a putting together; constructive metabolism; the 
opposite of katabolism. 
Analysis, the separation of anything into its constituent elements 
for the purpose of investigation. 
Anastomose, to join or blend together mouth to mouth. 
Anesthetize, to produce anesthesia, i. e., a state of insensibility. 
Antipyretic, a medicine given to reduce fever. 
Aphasia, a loss or impairment of the power of speech. When 
due to loss of memory of how to say some words, it is 
known as motor aphasia. When due to disturbance of the 
parts of the brain concerned with the memory of written or 
spoken words it is known as sensory aphasia. 
Arborization. Tree-like branches. 
Arterio-sclerosis, hardening of the arteries. 
Articular, pertaining to a joint. 
Ash, the residuum left after the burning of anything com- 
bustible. 
Assimilation, to convert into a substance similar to that operat- 
ing upon it; thus, the animal cells have the power of convert- 
ing the material they take from the blood into substances 
like themselves. 
Atom, the usual definition of an atom is "the smallest particle 
into which an element can be divided." But recent re- 
searches have led to the supposition that atoms are not the 
smallest bodies, but that they can be broken up into still 
smaller particles, to which some authorities have given the 
name of electrons, and describe as "an electric charge in 
motion-a unit or atom of negative electricity."1 
Atrophy, a wasting of the body or any of its organs as the result 
of disease or old age. 
Augmentation, the act of augmenting or increasing. 
Auto-intoxication, poisoned by toxic-poisonous-substances 
produced within the system. 
Automatic (as used in physiology), carried on unconsciously. 
Autopsy, examination of the body after death. 
Axial Rotation, rotation of the body around its axis-i. e., a 
straight line, real or imaginary, around which a body 
revolves. 
1 Scientific Ideas of To-day, page 51. Charles R. Gibson. 
T. B. Lippincott Co. Glossary 
529 
Base (chemistry), a substance which unites with an acid to form 
a salt; the alkalies are bases. 
Biconcave, concave, i. e., hollowed out on both sides. 
Biconvex, convex, i. e., rounded outward on both sides. 
Bicuspid, having two points or flaps. 
Bolus, lump. 
Brackish, salty. 
Calculi, plural of calculus, a stone. 
Caliber, the diameter. 
Capsule, a small case or receptacle. 
Catalyzer, a substance which hastens chemical reactions but 
does not itself enter into the reaction. 
Cellulose, the fibrous and woody part of plants. Its chemical 
composition is similar to starch. 
Centrifugal, spreading outward. 
Centripetal, having a tendency to, or causing to, approach the 
center. The opposite of centrifugal. 
Chemical Affinity, the agency which causes substances to 
combine, and which holds them together when combined. 
Chemical Reaction, when a substance undergoes a chemical 
change there is said to be a chemical reaction. By a chemi- 
cal change is meant a change that involves an alteration in 
the nature of the substance. A chemical change is the 
opposite of a physical change, which does not involve a 
change in the composition of the matter. For instance, if 
cane sugar is dissolved in water it is a physical change, 
because the chemical composition of the sugar is not changed, 
as can be proven by allowing the water to evaporate, when 
the sugar will be seen again just as it was before being 
dissolved. If, however, the sugar solution is boiled with 
acid, the sugar will be changed to glucose, a substance 
somewhat different to cane sugar, and in this case a chemical 
change or reaction has taken place. 
Cholesterin, a crystallizable, monatomic alcohol found in small 
quantities in the protoplasm of all cells, and more especially 
in nervous tissue, blood corpuscles, and bile. Its origin and 
function in the animal body are not known, but it is thought 
it may be concerned in tissue formation. 
Coalesce, to grow together. 
Colloid, a non-crystallizable organic substance. 
Colloidal, of the nature of colloids. 530 
Anatomy and Physiology 
Combustion, burning. (See Oxidation.) 
Commissure, a joining together. 
Component, part of a compound body. 
Concussion, the act or state of being dashed violently against 
another body. Concussion of the brain-shock or agitation 
of the brain. 
Conduction, the transfer of force from one part to another. 
Conduction of heat, the transmission of heat in matter by 
invisible molecular motion, the molecules passing their 
motion along from one to another within the body (see 
Molecular Motion). Metals are the best heat conductors; 
organic substances, such as wood, paper, and cloth, are poor 
conductors; glass, also, is a poor conductor. Solids are 
better heat conductors than liquids, and liquids than gases. 
Congenital, existing from birth. 
Constriction, a narrowing or drawing together, a stricture. 
Contiguous, adjacent, near. 
Convection, the act or process of conveying from one part to 
another. 
Convection Currents: when any portion of air is heated it 
expands and becomes less dense than the cooler parts, which, 
acted on by gravity, sink and crowd the warmer parts 
upward. The currents of air established in this way are 
called convection currents. Distribution of heat and ventila- 
tion are accomplished mainly through the agency of convec- 
tion currents. 
Converge, to join at a point. 
Convex, curved outward. 
Convoluted, twisted. 
Counter-irritants, agents, such as irritating drugs that, by 
producing irritation and consequent vascular dilatation in a 
part, will relieve congestion in another part; e. g., a mustard 
foot-bath will relieve congestion in the throat. 
Deciduous, not permanent, shedding. 
Deciduous Teeth, the temporary teeth. 
Decussate, to cross in the form of the letter X. 
Deplete, to empty; to deprive of strength. 
Diagnosis, determination of a disease by its symptoms. 
Dialysis, the separation of crystallizable from non-crystallizable 
or colloid substance by means of a porous membrane. The Glossary 
531 
Dialysis-Continued 
former will pass through a permeable membrane quicker 
than the latter, and, also, crystallizable substances will 
pass through membranes that colloidal substances cannot 
penetrate. 
Diapedesis, the passage of the blood-corpuscles through the 
capillary walls without rupture of the latter. 
Diffuse, to spread out on every side. 
Diffusion of Gases: if a vessel, room, etc., is filled with two or 
more gases, the gases, even if they are of different densities, 
will diffuse and intermingle, so that in time each gas will be 
distributed uniformly through the whole space. 
Disintegration, a breaking apart. 
Distal, distant from the center; e. g., the extremity of a bone 
farthest away from the point of attachment, or an organ 
comparatively distant from the center of the body. 
Dorsal, the back. 
Ectopic, out of place. 
Ectopic Gestation, the name given to pregnancy when the 
fecundated ovum, instead of entering the uterus, either 
remains in a Fallopian tube or falls into the abdominal 
cavity. 
Efferent, to carry outward. 
Emaciation, a wasting away; thin. 
Embryonal, pertaining to an embryo. 
Emulsion, a milk-like preparation of oil and water. 
Energy, operative power; the capacity for doing work. 
Energy-Kinetic, energy engaged in producing motion, etc. 
Energy-Potential, latent energy; stored energy; e.g., plants put 
CO2 and H20 together, forming other more complex com- 
pounds which are poorer in O and with a great affinity, 
especially the fats, for that element. To do this, energy 
is required, and this energy plants get from the sun, which is 
either directly or indirectly the source of all energy. The 
energy thus derived is stored up within the plant and is 
called potential or latent energy. When the products of 
digested food are oxidized in the body, this energy is liberated 
and becomes once more kinetic or work energy that pro- 
duces heat, and the power that keeps all the internal organs 
and metabolism active, as well as the power to perform 532 
Anatomy and Physiology 
Energy-Potential-Continued 
external work. And the sum of the kinetic energy thus 
evolved will be equivalent to that derived from the sun. 
Evaporation, the act or process of resolving into vapor. Evapora- 
tion may be visible to the eye; e. g., the steam issuing from 
the spout of a kettle; the fog rising from the surface of a lake. 
Or it may be invisible, as the evaporation of sweat from the 
surface of the body. For the production of evaporation 
heat is necessary. It requires about 0.5 calory of heat for 
the vaporization of one gram of water, and unless heat is 
supplied, as, for instance, the fire which causes the water in 
the kettle to vaporize, it will be taken from near objects. 
Thus, the heat necessary to vaporize the sweat is taken from 
the body. 
Extirpation, excision; rooting out. 
Exude, to discharge through pores or a membrane. 
Exudation (v), the oozing of fluids through a membrane, etc. (s) 
material that has exuded or oozed from a vessel, etc. 
Facet, a small, flat, articulating surface. 
Fecundation, fertilization, impregnation. 
Fecundity, the power or property of producing young. 
Fermentation, the process by which certain substances are 
broken into their constituent parts by the influence of fer- 
ments. There are several kinds of fermentation, and each 
is thought to be due to the presence of a definite substance 
known as an enzyme. Some of the common forms of fermen- 
tation are: (1) alcohol or vinous fermentation, which is 
caused by a vegetable fermentation contained in yeast and 
which acts upon glucose, breaking it apart into alcohol 
and carbon-dioxide; (2) lactic acid fermentation due to lactic 
acid bacteria in which the sugar of milk-lactose-is broken 
down to lactic acid. Acetic acid fermentation, due to a 
peculiar vegetable ferment which acts upon alcohol, trans- 
forming it into acetic acid. 
Fibrils, small fibers. 
Filament, a thread; a slender thread-like process. 
Focus, a point at which the rays of light refracted from a convex 
lens or reflected from a concave mirror tend to meet. 
Foramen, an opening. 
Fossa, a depression; a groove. Glossary 
533 
Gestation, pregnancy. 
Globulins, protein substances, somewhat similar to the albu- 
mins, but distinguished from them in that they are insoluble 
in water, saturated solutions of sodium chloride, and also 
in solutions of other salts in which albumins are soluble. 
Examples are: the serum globulin and fibrinogen of the 
blood. 
Granular, containing grains or granules. 
Granulate, to form in granules or small masses. 
Granulations, small granular-like fleshy bodies that form on 
the surface of suppurating wounds and ulcers. 
Hemolysis, disintegration or breaking up of red blood-corpuscles. 
Hemolytic, the property of, or a substance causing, hemolysis. 
Hemorrhage, the escape of blood from its containing vessels. 
Hilum or Hilus, a depression; a small aperture. Many of the 
glands and other organs of the animal body have such a 
depression through which the vessels and nerves pass to and 
from their interior. 
Homogenous, of a like structure; consisting of the same 
elements. 
Hormones, chemical substances which stimulate certain of the 
organs of the body to activity; e. g., the gastric secretion 
which stimulates the gastric glands to secrete the gastric 
juice. 
Hydration, the act or process of moistening with water. 
Hydrolysis, the breaking down of complex molecules into 
simpler ones with absorption of water. 
Hydrotherapeutics, Hydrotherapy, the use of water for the 
cure of disease. 
Hydroxide, a base or alkali. 
Hypertrophy, excessive increase in the size of an organ or part. 
Impermeable, not admitting of passage. 
Influx, flowing in. 
Ingest, taking in; e. g., the introduction of food into the stomach. 
Inhibited, to check; to interfere. 
Innervation, to supply with nervous force; the distribution of 
nerves to a part. 
Inoculate, the insertion of virus into a wound or abrasion in the 
skin for the purpose of communicating a disease. Anatomy and Physiology 
534 
Insulate, to isolate; to separate. 
Interpose, to place between. 
Interstice, very narrow spaces between parts. 
Invaginated, to enclose in a sheath. 
Investure, to clothe. 
Katabolism, Catabolism, destructive metabolism. The break- 
ing down of complex substances into more simple ones or 
their elements. Katabolism is the opposite of anabolism or 
building up. 
Lamella, a thin plate; a scale, e. g., the small plates of bone in 
the cochlea of the ear; the bony divisions of the Haversian 
system. 
Lateral, to the side. 
Lens, a transparent substance, usually glass, bounded by two 
curved surfaces or by one curved and one plain surface. 
There are two general classes of lenses: (i) convex lenses, 
which are thicker at the center than at the edges; and (2) 
concave lenses, which are thinner at the center than at the 
edges. Convex lenses are termed converging lenses because 
they cause light to converge to a focus. Concave lenses are 
said to be diverging because they diverge rays of light. (See 
Refraction.) 
Macerate, to soften by steeping. 
Mammalia, belonging to the class of mammals; i. e., the class of 
animals that suckle their young. 
Matrix, a part of the body where new substance can be produced 
-e. g., the uterus; the matrix of the nails. 
Matter, anything which occupies space and possesses weight; 
that of which the universe is composed. 
Medial, the middle. 
Median, situated in or near the center; passing through or 
along the center. 
Meniscus (optics), a lens convex on one side and concave on 
the other. (Physics), the surface of a liquid column-as 
mercury-rendered convex or concave by capillarity. 
Menses, menstruation. 
Metabolic, pertaining to change. Glossary 
535 
Metabolism, the changes that occur in food from the time it is 
absorbed until it is eliminated. This includes the breaking 
down and building up of body tissues, since they are con- 
structed from the substances obtained from food. 
Miscible, capable of being mixed. 
Molecular Motion, movement of the molecules composing 
matter. In gases the molecules are farther apart than they 
are in liquids, and therefore greater and more rapid motion 
goes on, and gases become diffused more rapidly than 
liquids. For the same reason there is more molecular motion 
in liquids than in solids, but even in solids there is movement 
of the molecules, as is shown by the fact that when two 
metals are placed one upon the other-e. g., if gold is overlaid 
with lead, the presence of gold throughout the lead may in 
time be detected. But in solids the force of cohesion has its 
greatest intensity, and the molecules, although in constant 
motion, do not move from point to point within a body with 
freedom as they do in gases and liquids. 
Molecule, the smallest particle of a compound that can exist. 
Mydriasis, abnormal dilatation of the pupil. 
Myogen, a form of albumin contained in muscle. 
Myosin, a globulin contained in muscle (see Albumin and 
Globulin). 
Neurosis, a nervous disease not associated with any discoverable 
lesion; e. g., occupation neurosis, due to over-use or irritation 
of a part of the body in the performance of one's occupation. 
Neutral, neither acid nor basic. 
Neutralize, to render neutral. When an acid and a base-■ 
alkali-are combined, the molecules of the acid minus their 
H atoms and the molecules of the base minus their OH 
atoms combine and form a salt; the H and OH unite to 
form water, H20. Thus: NaOH + HC1 = NaCl + H2O 
NaOH is the chemical formula for sodium hydroxide, a 
corrosive, poisonous alkali. HC1 for hydrochloric acid, a 
corrosive poisonous acid. NaCl, sodium chloride-common 
salt-is a neutral non-poisonous salt used with food. 
Normal, according to the usual rule or type. 
Orifice, an opening. 
Oscillation., vibration; swinging backward and forward. 536 
Anatomy and Physiology 
Osmosis: when two different liquids or solutions are separated 
by a porous partition or permeable membrane, they will pass 
through the dividing wall and intermingle. This diffusion 
of the two liquids is called osmosis. 
Osmotic Pressure: if the liquids on either side of a membrane 
are of different specific gravities, e. g., if one is water and the 
other salt solution, the liquid containing the greater amount 
of solid matter-i. e., the salt solution-will exert a greater 
degree of pressure than the water, in consequence of which 
the water will pass through the membrane much more 
rapidly than the salt solution until the pressure on both 
sides the partition is equal. The pressure exerted in this 
way is spoken of as osmotic pressure. 
Osseous, bone-like. 
Ossicle, a small bone. 
Oxidation, the addition of oxygen to a substance. There are 
several forms of oxidation, e. g., (i) the union of oxygen with 
elements as iron, zinc, copper, etc., with the production of an 
oxide of the element, e. g., oxide of iron, which is commonly 
known as iron rust; oxide of zinc, etc.; (2) the decay of dead 
animal and vegetable matter is a form of oxidation, brought 
about by the action of bacteria; (3) the oxidation that takes 
place in the living animal body; (4) the oxidation of sub- 
stances known as burning or combustion. Oxidation is 
always accompanied by the liberation of heat. If the oxygen 
unites very slowly with a substance, the amount of heat 
liberated is very small and hard to detect. If, however, the 
union with oxygen takes place rapidly, the heat generated 
is very perceptible, and if the union is sufficiently rapid the 
substance will burst into flame. It is then known as com- 
bustion. Unless a substance has a very strong affinity for 
oxygen, the use of a catalyzer is usually necessary in order to 
promote oxidation. Examples of common catalyzers operat- 
ing in the forms of oxidation just mentioned are: heat, 
enzymes, bacteria. Except in the case of elements, the union 
of oxygen with a substance is usually followed by its disinte- 
gration (as has been already said), with the generation of 
heat and also the liberation of the energy that is stored up 
within it. / 
Oxidizing Agents, substances containing a large amount of oxy- 
gen that is easily set free-i. e., which is in loose combination. Glossary 
537 
Palpation, making pressure on the surface of the body with the 
hand for the purpose of ascertaining the consistency of 
underlying parts. 
Peroneal, pertaining to the fibula. 
Peristaltic, the worm-like movement by which the alimentary 
canal propels its contents. 
Permeable, that allows the passage of fluids. 
Phenomenon (plural phenomena), an observed result; an 
unusual appearance. 
Phonation, utterance of vocal sounds. 
Pigment, coloring matter. 
Pigment Cells, cells which produce pigment. 
Plane, a flat surface. 
Plexus, a network. 
Polarized Light: light is due to vibrations in the ether occurring 
in all planes transversely to the direction of the propagation 
of the wave. When the vibrations are made to take place 
all in one plane, the light is said to be plane polarized. The 
result is similar to regularly reflected light {see Reflection). 
Polarizer, an apparatus for polarizing light. 
Propagation, production. 
Punctiform, in the form of a point. 
Psychical, pertaining to the mind. 
Psychologist, one versed in psychology-the science pertaining 
to the nature and functioning of the mind. 
Radiation, the diffusion of rays of light or heat. 
Reduce (surgery), to restore a part to its normal position, as a 
fractured bone; (chemistry), to take away oxygen from a 
substance. 
Reducing Agents, substances that having a strong affinity for 
oxygen extract it from other substances and thus reduce 
them. 
Reduplication, a doubling back. 
Reflect, to bend back. (Physics), the turning back of a ray of 
light, heat, or sound from a surface that it strikes, but does 
not penetrate. 
Reflection-Regular and Diffuse: when a beam of light enters 
a darkened room through a small opening- and strikes a 
mirror, a reflected stream of light will be seen traveling 
along a definite path; this is an example of regular reflection. 538 
Anatomy and Physiology 
Reflection-Regular and Diffuse-Continued 
If, however, the light strikes a rougher surface than the mir- 
ror,-for example, a sheet of white paper,-it will be reflected 
in a diffuse or scattered manner. This is diffuse reflection. 
It is caused by the inequalities of the reflecting surface. All 
rough surfaces, as well as inequalities in the atmosphere, 
such as dust or moisture, serve to diffuse light; were this 
not the case, it would be dark everywhere except in the direct 
path of light from some luminous body. It is because 
opaque objects reflect, or send back, the light which strikes 
them that they are visible. 
Refraction, the deviation of light from its course. A straight 
stick placed at an angle, partly in water and partly in the 
air, looks like a bent stick. This is an example of the bending 
or refraction of light. The cause of refraction is that light 
travels with different velocity in different media; e. g., the 
velocity of light in water is only % of its velocity in air, 
therefore when a beam of light enters water its rate is 
Fig. i. 
retarded; if the beam strike the water obliquely, all portions 
of the wave front will not enter the water at the same time; 
e. g., in Fig. I, let the short parallel lines represent the wave 
front of a beam of light entering obliquely from air into 
water, one part (a) reaches the water before (b), and, as it 
travels more slowly than before, it can go only as far as (c) Glossary 
539 
Refraction-Continued 
while (b) is going to (d). Thus all the waves as they enter the 
water are given a new direction and the beam is bent. When 
Fig. 2.-Normal eye. 
Fig. 3.-Hymertropic eye. The dotted line re- 
presents the refraction that the rays of light undergo 
in passing through the convex lens which brings 
them to a focus on the retina. 
a beam of light strikes the water vertically, it is not refracted 
because the whole front of a light wave strikes and enters the 
Fig. 4.-Myopic eye. Anatomy and Physiology 
540 
Refr acti on-Co nti nued 
water at the same time, consequently the whole wave front 
is retarded. Light is, of course, also refracted when it 
passes through glass and the refractive apparatus of the eye, 
and the degree and nature of the refraction is altered when 
the glass consists of a convex or concave lens. Thus, when 
the lens is convex-i. e., thicker in the center than at the 
edges, the rays of light are bent as in Fig. 3, and the greater 
the degree of convexity the greater the degree of refraction 
of the rays and the more quickly will they be brought to a 
point or focus. Rays of light entering a concave lens {see 
Lens) will be bent as in Fig. 4 and their focussing thus pre- 
vented. For this reason concave glasses are worn in myopia 
(described in paragraph 965), as the rays of light, being 
slightly diverged before entering the eyes, are thus prevented 
focussing too quickly, i. e., before they reach the retina. 
Regurgitation, passing backward. 
Reticular, net-like. 
Retiform, a network. 
Salivation, an excessive secretion of saliva. 
Salts, substances resulting from the chemical union of a base and 
an acid. {See Neutralization.) 
Saponified, converted into soap. 
Sclerosis, hardness. 
Scrotum, part of the male organs of generation; it contains the 
testicles and their accessory organs. 
Segment, a part. 
Septum, a division; a wall. 
Specific Gravity, the weight of a solution as compared with that 
of distilled water. 
Sphincter, a ring-like muscle encircling an orifice. 
Stasis, stoppage; stagnation of the blood-current. 
Stroma, the tissue which forms the foundation substance of an 
organ. 
Sound, the form of vibratory motion in an elastic medium that 
can be perceived by the auditory nerves. Sound always 
originates in a vibrating body which starts trains of waves 
in the surrounding medium. Air is the usual medium for the 
transmission of sound waves, but any uninterrupted series Glossary 
541 
Sound-Continued 
of elastic bodies will answer the purpose, whether they be 
gases, liquids, or solids. Water is a particularly good 
transmitter: when the ear is under water the vibrations 
started by a steamer a mile away can be heard. Sound is 
perceived because the waves set in motion by the vibrating 
body enter the ear and set the drum membrane in motion 
as described in Chapter XXIV. The pitch of a sound de- 
pends on its vibrating frequency; the greater the frequency, 
the higher the pitch. The pitch of notes given forth by men 
is lower than those formed by women, since in men the 
larynx is larger and the vocal cords longer and thicker; 
wherefore they vibrate more slowly and produce a lower note. 
Some sounds have no definite pitch and are called noises. 
A noise generally consists of a mixture of unrelated sounds. 
A musical sound, on the other hand, is one which has a 
definite pitch and which is pleasing to the ear. 
Suction, the act or process of sucking or drawing out. 
Synthesis, building; putting together. 
Tactile, pertaining to the sense of touch. 
Thermic, pertaining to heat. 
Thermogenic, pertaining to the production of heat. 
Toxic, poisonous. 
Transfusion, the transfer of blood from one person to another; 
the introduction of such substance as saline solution into 
the blood-vessels. 
Translucent, slightly transparent. 
Truncated, deprived of limbs. 
Unilateral, one-sided. 
Unossified, devoid of bone formation. 
Vascular, containing a large number of blood-vessels. 
Venosity, excess of venous blood. 
Ventral, pertaining to the abdomen; the front surface of the 
body. 
Ventricle, a small cavity. 
Vermiform, worm-like. 
Vertical, perpendicular. 542 
Anatomy and Physiology 
Vesicle, a small bladder or sac; a blister. 
Vibration, the act of moving rapidly to and fro. 
Viscera, the internal organs. 
Zymogen, a substance that gives rise to an enzyme. QUESTIONS 
For answers see Chapter I 
Define biology, anatomy, physiology. 
Upon what forces do the phenomena of life depend? 
What is an element ? 
Name the elements composing the animal body. 
How are the compounds composing the animal body 
classified? 
What is meant by organic and inorganic substances ? 
Give some examples of nitrogenous compounds and 
mention the elements that generally enter into their 
composition. 
Name the two classes of non-nitrogenous organic 
food-stuffs. 
Name the principal carbohydrates found in plants 
and in animals, and state the elements that enter into 
their composition. 
Of what elements is human fat composed? 
What is a salt? 
Mention the more important salts found in the 
human body. 
What is the unit of the animal body from the 
chemist's and from the anatomist's standpoint? 
Mention an important difference between the 
majority of cells of animal and of plant tissues. 
Describe protoplasm. 
Give an example of a one-celled animal. 
How do cells multiply? ■ 
543 Anatomy and Physiology 
544 
For answers see Chapter II 
What are organs? Give examples 
What is meant by a system? 
Mention some examples of the dependence of 
organs and systems upon each other. 
What is meant by the anatomical position? 
Name the surfaces of the body and state their 
location. 
Mention, and show on the skeleton, the main 
divisions of the body. 
What is meant by medial? 
What is meant by lateral ? 
What is the opposite of distal? 
What is meant by the periphery? 
What is understood by the terms "internal" and 
' ' external ? ' ' 
What is meant by the terms "afferent," "centri- 
petal," " efferent," " centrifugal "? 
For answers see Chapter III 
From what and how are the tissues of the body- 
developed? 
Name the substance that transmits characteristics 
from parents to their offspring. 
State the meaning of the word ' ' tissue " as it is used 
in anatomy. 
How are the cells composing tissue held together ? 
How are the various tissues of the human body 
classified? 
What is meant by organized matter ? 
Where are epithelial tissues found? 
State some of the important functions of epithelial 
tissues. Questions 
545 
Name the different tissues classified as connective 
tissues. 
Why are they thus classified? 
Where are connective tissues found? 
What is areolar tissue and where is it found? 
What is the most essential difference between white 
and yellow fibrous tissue? 
Of what value is this difference? 
Mention the different forms in which fibrous tissue 
is found in the body. 
Describe ligaments and state their purpose. 
What is the nature and what the purpose of tendons ? 
What are fasciae and what is their function? 
Where are the plantar and palmar fasciae and what 
is their purpose? 
What is the nature and the purpose of aponeuroses? 
What is adipose tissue and in what parts of the 
body is it found? 
Mention the uses of adipose tissue. 
Describe lymphoid tissue and state where it is 
found. 
What is cartilage like and where is it found? 
Name the different varieties of cartilage? 
What is the perichondrium? 
How do the costal cartilages assist in respiration? 
Where is cartilage found in the spinal column and 
what purpose does it serve there? 
is their purpose? 
For answers see Chapter IV 
What are the functions of the bones? 
Of what does bone consist? 
How does the relative proportion of organic and 
inorganic matter in bone vary during life? 546 
Anatomy and Physiology 
How does this difference in composition influence 
the strength of bone and the nature of fractures? 
What is the cause of rickets? 
How are the bones of the body classified? 
What is the more porous portion of bone called? 
Mention the names of some of the more important 
markings of bones and state their purpose. 
What constitutes an Haversian System ? 
What is the purpose of the Haversian canals? 
Where are the medullary canals and what purposes 
do they serve? 
State the nature and purpose of marrow. 
What is the periosteum? 
Why is injury to the periosteum likely to result in 
necrosis of the bone? 
Describe the process that occurs in the repair of 
bone after fracture. * 
How many bones are there in the human skeleton? 
Name the bones of the skull. 
What bones enter into the formation of the base of 
the skull? 
Where are the mastoid bones ? 
What is there in the structure of these bones 
that renders mastoiditis a particularly dangerous 
disease ? 
What and where are the frontal sinuses? 
Where is the ethmoid bone? 
What are the fontanelles? 
Where are the turbinated bones? 
Where and what are the antra of Highmore? 
How many vertebrae are there in the spinal col- 
umn? 
How are the vertebrae classified? Questions 
547 
Of what use are the curves of the spinal column and 
the pads of cartilage between the vertebras? 
Mention the names given certain abnormal curves 
of the spinal column. 
Give the names of the two uppermost vertebras. 
What peculiarity is there in the arrangement of 
these two vertebrae that makes fracture of this part of 
the spinal column (broken neck) particularly likely to 
be fatal ? 
Describe the sternum and state its position. 
How many ribs are there? 
How are they classed and why? 
What is meant by the shoulder girdle? 
What is the technical name for the collar bone ? 
Where is it situated? 
Where is the glenoid cavity? 
Describe the humerus. 
Name the bones of the forearm. 
What and where is the olecranon process? 
How are the bones of the wrist classed ? 
What name is given to those of the fingers ? 
Describe the phalanges. 
Name the bones of the pelvis and state their 
location. 
What is meant by the false and the true pelvis. 
What is the prominent line between these two parts 
of the pelvis called? 
What is the upper ridge of the ilium called? 
Name the bones of the lower extremity and state 
their relative position. 
Describe the femur. 
Describe the patella. 
Where are the inner and the outer malleolus ? 548 
Anatomy and Physiology 
For answers see Chapter V 
How are joints classified with respect to the amount 
of movement that they are capable of? 
Give examples of immovable and slightly movable 
joints. 
Describe the articulations of the spinal column. 
Mention the principal features of the freely mov- 
able joints. 
What are bursae? 
What is synovitis? 
What is bursitis? 
Name the different kinds of movements of which 
joints are capable. 
Describe abduction and adduction. 
Describe circumduction. 
Describe flexion and extension. 
Describe rotation. 
What is meant by gliding movements? 
Name the ball and socket joints and state the 
movements they are capable of. 
Give examples of hinge joints and state the move- 
ments that they are capable of. 
Give examples of condyloid joints. 
Give examples of pivot joints. 
Give examples of gliding joints. 
Give examples of saddle joints. 
Describe the gums. 
Name the different parts of a tooth. 
Describe the structure of the teeth. 
Name the temporary teeth and state the ages at 
which they appear. 
Name the permanent teeth. 
How are the teeth developed ? Questions 
549 
For answers see Chapter VI 
Mention some of the constituents of muscle tissue. 
Name the different kinds of muscle tissue and give 
reasons for the names. 
Of what nature is the plasma of muscle cells? 
Describe the structure of plain muscle tissue. 
Describe the structure of striated muscle tissue. 
Mention some points of difference between cardiac 
muscle tissue and plain and striated muscle tissue. 
What are the special characteristics of muscle 
tissue? 
What is meant by irritability? 
By stimuli? 
By contractibility and extensibility? 
By elasticity? 
Mention some chemical changes that occur in 
muscle as the result of contraction. 
Of what importance are these chemical changes to 
the body? 
What is the cause of muscle fatigue? 
When and how will the muscle recover from fatigue ? 
What is meant by tetanus of muscle ? 
What is meant by muscle tone? 
How is it produced? 
What is the origin of the nerve impulses that give 
rise to muscle tone? 
Give examples showing that mental activity affects 
muscle tone. 
What is the result of cold on muscle tone ? Give an 
example. 
Mention some differences between the contraction 
of voluntary and involuntary muscle tissue. 
What is meant by the skeletal muscles? 
tissue? 550 
Anatomy and Physiology 
What is meant by the origin and insertion of 
muscles ? 
How are muscles attached to the bones ? 
Of what value to the movements of the body is the 
tension that, normally, the muscles are under? 
Name the muscles that control the movements of 
the eyeball. 
Of what special use are the muscles which form the 
cheeks and have their insertions in the lips or jaws? 
Why is the tongue likely to fall back over the 
trachea after the taking of a general anesthetic? 
Name some of the principal muscles of the back. 
Of the chest. 
Where is the diaphragm? State its functions. 
Mention the actions of the abdominal muscles. 
What is meant by the inguinal canal ? 
What is a hernia? 
Name some of the more common forms of hernia 
of the intestines and state where they occur. 
Name the large muscle covering the prominent part 
of the shoulder and state its action. 
Name the large muscles of the upper part of the 
arm. 
State how the abductors and adductors, flexors and 
extensors, pronators and supinators of the forearms 
and legs are placed with relation to each other. 
What are the annular ligaments? 
What may be the result of cutting any of the ten- 
dons that hold muscles to the fingers ? 
For answers see Chapter VII 
Name some of the special characteristics of nerve 
tissue. Questions 
551 
Name the principal parts of the nervous system. 
Which of these parts constitutes the cerebro-spinal 
portion of the nervous system and which the sym- 
pathetic portion? 
Mention a point of similarity between the structure 
of nerve tissue and other tissues. 
Name the different parts of a nerve-cell. 
Describe the dendrites. 
What is the axis-cylinder of a nerve-cell ? 
What are collaterals? 
Mention the different kinds of nerve-fibers. 
What is the neurilemma? 
What are the nodes of Ranvier? 
What is the difference between a medullated and a 
non-medullated nerve-fiber ? 
What is thought to be the function of the medullary 
sheath ? 
What is the function of the nerve-fibers ? 
What are the nerve-endings? 
How are nerve-fibers classified with regard to the 
way in which they are stimulated and the result of 
their stimulation? 
Give reasons for the names used? 
How do sensory nerve-endings and nerve-centers 
react to different kinds of stimuli? 
What may be the result of afferent impulses upon 
different sets of nerve-centers? 
What are nerve-centers? 
What is the neuroglia? 
What is the difference between the gray matter and 
the white matter of the nervous system? 
How are the gray matter and the white matter 
distributed in the body? 552 
Anatomy and Physiology 
What are ganglia? 
What are plexuses? 
Of what value are plexuses? 
What is meant by the respiratory center? 
What is meant by vaso-motor centers? 
Describe the arrangement in the nerve-centers by 
means of which impulses can pass from afferent to 
efferent nerve-fibers. 
Mention some of the theories that have existed 
regarding the nature of nerve impulses. 
What are the functions of the cell bodies? 
What is meant by reflex action? 
Mention some activities that are at first volitional 
but later become reflex. 
What is meant by the reflex arc? 
What is meant by the modification of impulses? 
What is meant by the inhibition of reflexes? Give 
an example. 
What is meant by diffusion of impulses? Give an 
example. 
What is meant by automatism? 
What is said of the origin of voluntary impulses? 
Upon what does the repair of injured nerve-fibers 
depend ? 
What is thought to be the effect of excessive fatigue 
upon the cell bodies? 
For answers see Chapter VIII 
What is the average weight of the brain? 
What are the ventricles of the brain? 
Name the ventricles. 
Name the main divisions of the brain. 
Where is the cerebrum? Questions 
553 
What is the relative position of the gray matter 
•and the white matter in the cerebrum? 
Of what is the gray matter of the cerebrum com- 
posed? 
What is meant by the fissures of the cerebrum? 
What are the gyres? 
State the functions of the cerebrum. 
What is meant by the motor area of the cerebrum? 
How have the portions of the cerebrum that control 
movements in different parts of the body been 
localized? 
How is it that injury to parts of the brain on the 
right side will result in loss of function in some part 
of the left side of the body? 
What is meant by the sense areas? 
What is aphasia? 
What is the difference between sensory and motor 
aphasia ? 
What and where are the association areas? 
How do the association areas vary in different 
individuals ? 
Mention two things that are necessary for the 
development of any special talent. 
Where is the mesencephalon? 
Where is the cerebellum? 
What are the functions of the cerebellum? 
Where is the pons Varolii? 
Where is the medulla oblongata? 
What is meant by the decussation of the pyramids ? 
Why is injury to the medulla oblongata likely to 
result in death? 
Name the membranes covering the brain and state 
their relative position. 554 
Anatomy and Physiology 
Describe the dura mater. 
Describe the pia mater. 
Describe the arachnoid. 
What is the cerebro-spinal fluid and what is its 
purpose. 
For answers see Chapter IX 
Where and what is the spinal cord? 
Name the membranes surrounding the spinal cord. 
Describe the structure of the cord. 
Mention the functions of the spinal cord. 
How many cranial nerves are there? 
Why are these nerves called the cranial nerves? 
With what sense is the olfactory nerve concerned? 
With what sense is the optic nerve connected? 
What is the name of the nerve concerned with 
hearing? 
What function is dependent upon some of the fibers 
of this nerve? 
To what organs do fibers of the vagus nerve extend? 
How many spinal nerves are there? 
How do they get through the vertebral column? 
Why are the spinal nerves said to be mixed nerves ? 
What is meant by the spinal ganglia? 
What is meant by the rami communicantes ? 
What constitutes the sympathetic portion of the 
nervous system? 
What and where are the lateral ganglia ? 
Describe the distribution of the sympathetic nerves. 
Name some of the important plexuses of the 
sympathetic system. 
What is the function of the sympathetic portion of 
the nervous system? Questions 
555 
Mention some instances in which the action of the 
nerves of the sympathetic and the cerebro-spinal 
portions of the nervous system are antagonistic to 
each other. 
Describe the action of the vaso-constrictor nerves. 
Describe the action of the vaso-dilator nerves. 
Where is the great sciatic nerve ? 
For answers see Chapter X 
Of what nature are the membranes of the body ? 
How are the membranes classified? 
What is the chief function of the membranes ? 
How do the membranes protect the body? 
Where are the serous membranes found ? 
Give the names of some important serous mem- 
branes. 
Where are the synovial membranes found ? 
How are synovial membranes classified? 
What are bursae and where are they found ? 
What is bursitis? 
What is synovitis? 
Where are the mucous membranes? 
Mention some differences in the structure of mucous 
membranes in different organs, and state why these 
differences are of importance. 
In what ways do mucous membranes differ from 
serous membranes? 
Why does the condition of the tongue give a clue 
to conditions in the stomach and intestine ? 
Mention an important point of difference between 
the secretion of a mucous membrane and that of a 
serous membrane, and state why this difference is 
necessary. 556 
Anatomy and Physiology 
For answers see Chapter XI 
Mention the main divisions of the vascular 
system. 
What organs constitute the blood-vascular system? 
Name the parts constituting the lymph-vascular 
system. 
Mention the principal functions of the blood. 
What characteristics of the blood-vessels and the 
circulation enable the blood to perform its function? 
How much blood is there in the human body ? 
Mention the special characteristics of the blood. 
To what is the color of the blood due and why is its 
color variable? 
Of what is the blood composed? 
What is meant by blood plasma ? 
What is blood serum? 
What do the solid substances in the blood represent? 
What are the red corpuscles called and why ? 
Describe the erythrocytes. 
What is their purpose? 
What constituent of the erythrocytes enables them 
to perform their function ? 
What is hemoglobin? 
What is oxyhemoglobin? 
What is the normal per cent, of hemoglobin in the 
body? 
What is meant by 100 per cent.? 
What is meant by anemia? 
Why are foods containing iron given in the treat- 
ment of anemia? 
Why is anemia likely to complicate bacterial 
diseases ? 
Why is anemia a serious condition? Questions 
557 
About how many erythrocytes are there in a cubic 
millimeter of blood? 
Mention some causes for a reduction in the number 
of red cells. 
Can an individual be anemic if he has the normal 
number of red cells in his blood? 
In what part of the body are the red cells formed ? 
Mention some of the names by which the white 
corpuscles are distinguished. 
Describe the white corpuscles. 
Where are they found? 
What is the comparative number of white to red 
cells? 
Where are the white corpuscles thought to be 
formed ? 
Mention some important points of difference 
between the white and the red cells. 
State the function of the white corpuscles. 
What are the phagocytes? 
Describe the process that occurs in inflammation. 
What are opsonins? 
What are blood-plates? 
What is their function? 
What is fibrinogen? 
For what is it essential? 
What is meant by antibodies? 
What is meant by immunity? 
What are antitoxins? 
Describe the process that occurs in the clotting of 
blood. 
To what is clotting due? 
Of what advantage to the body is the clotting of 
blood? 558 
Anatomy and Physiology 
Mention conditions that promote, and conditions 
that retard, the clotting of blood. 
Why does the blood not often clot within the living 
blood-vessels ? 
What conditions sometimes cause it to clot in the 
vessels during life? 
What is a clot thus formed called? 
What name is given to the clot if it moves from the 
place where it formed ? 
Why is a thrombus dangerous ? 
How is the blood regenerated after hemorrhage? 
Of what benefit are saline infusions after hemor- 
rhage ? 
What is physiological salt solution and why is it 
used for intravenous infusions? 
Why is it exceedingly important to have the right 
amount of salt in saline solutions that are used for this 
purpose ? 
What is meant by blood transfusion? 
Why can not the blood of one of the lower animals 
be used for transfusion into man ? 
What is meant by hemolysis? 
What is meant by laked blood? 
What is meant by defibrinated blood? 
From what is the lymph derived ? 
What are the essential differences between lymph 
and blood? 
Where is the lymph found? 
What are its functions? 
For answers see Chapter XII 
Name the organs composing the blood-vascular 
system. Questions 
559 
State the functions of these organs. 
Where will you put an ice-cap that is to be placed 
over the heart? 
How is the heart held in place ? 
Of what are the walls composed? 
What is the membrane covering the heart called? 
What is the name of the membrane lining the heart ? 
How is the pericardium arranged? 
What is its purpose? 
How many chambers are there in the heart ? 
Which ones communicate with each other ? 
How many orifices has each chamber and into what 
do they open? 
Which of the orifices have valves and what are the 
names of the valves? 
Name the blood-vessels opening into the heart and 
state their purpose. 
Describe the structure of the bicuspid and tricuspid 
valves. 
What is the purpose of these valves ? 
What keeps them from floating into the auricles? 
Why will endocarditis interfere with the closing of 
valves? (See Endocarditis in Practical Nursing or 
other text-book.) 
What is likely to be the result of such interference? 
What arteries supply the walls of the heart with 
blood? 
From what part of the nervous system are the 
nerves that supply the walls of the heart derived ? 
What does the word " artery " mean and why were 
the arteries so called? 
Describe the structure of the arteries. 
What is arteriosclerosis ? 560 
Anatomy and Physiology 
In what ways do the veins differ from the arteries? 
Describe the capillaries. 
How are the capillaries distributed through the 
body? 
What constitutes the lymphatic system? 
What is meant by the lymph spaces ? 
What are the nature and the purpose of the lymph 
vessels ? 
Name and state the location of the two largest 
lymph vessels. 
Describe the lymph nodes or glands. 
What is their purpose? 
Where are they situated? 
Name some important ones. 
Why are abnormal conditions of the tonsils a source 
of danger? 
For answers see Chapter XIII 
What are the three main divisions of the blood- 
vascular system? 
State the function of each of these systems. 
Mention some of the main features in the method of 
the distribution of the blood-vessels. 
What is meant by anastomosis? 
Of what use are the anatomoses of blood-vessels ? 
What names are given to various parts of the aorta ? 
With what part of the heart does the aorta connect? 
Name the large blood-vessels that branch off from 
the thoracic aorta and state the organs that they 
supply with blood. 
Mention the branches of the abdominal aorta. 
How does the brain get its blood supply ? Questions 
561 
How does the blood return from the brain to the 
heart ? 
Trace the course of the blood from the heart to the 
fingers of the right hand and back to the left side of the 
heart. 
On what artery, and where, would you make in- 
direct pressure to stop hemorrhage from a wound 
in the arm? 
What difference is there in the number of blood- 
vessels through which the blood must flow to the right 
and to the left hand? 
Name the principal vessels through which the blood 
flows from the heart to the toes and back to the left 
side of the heart. 
How will the blood get from the right side of the 
heart to the right hand ? 
What artery will you compress, and where, to 
arrest hemorrhage from a wound in the thigh ? 
Trace the blood from the right auricle to the lungs 
and back? 
Through what arteries does the blood intended for 
the nourishment of the lungs travel ? 
Of what does the portal system consist? 
What blood passes through it? 
Why is it necessary that the blood from the intes- 
tines should go to the liver before entering the general 
circulation ? 
For answers see Chapter XIV 
Describe the nature of the heart action. 
What is the meaning of the heart's systole and 
diastole and the cardiac cycle? 
State the time required for the systole and diastole 562 
Anatomy and Physiology 
of the auricles and ventricles when the pulse beat is 
72 per second. 
How much complete rest per minute does the heart 
get when it is working at the rate of 72 cycles per 
minute ? 
Why should the recumbent position be maintained 
whenever possible when the pulse rate is much 
increased ? 
What is meant by heart murmurs ? 
What causes the heart to beat ? 
What influence have the vagi nerves and what 
those of the sympathetic system upon the heart ? 
What are the main factors in maintaining arterial 
circulation ? 
What are the principal factors in maintaining venous 
circulation? 
What is meant by the suction action of the heart ? 
How long does it take blood to go from the heart, 
through the system and back to the heart ? 
In what way does the rate of the blood-flow differ 
in the different vessels and why does it differ? 
What are the main causes of differences in the 
quantity of blood in different parts of the body ? 
Why is it hard to study after eating a large meal ? 
Why is it not well to take a bath immediately after 
dinner ? 
What is meant by blood-pressure ? 
What causes differences in the degree of pressure in 
different vessels? 
How can the degree of blood-pressure be ascer- 
tained ? 
What is the cause of the pulse? 
Where can the pulse be most easily counted? Questions 
563 
What can you tell about the heart action and the 
condition of the blood-vessels by feeling the pulse? 
What is meant by a dicrotic pulse ? 
What is meant by an irregular pulse ? 
Mention the principal forces that control the flow 
of lymph. 
What is meant by edema? 
Mention some causes of edema. 
For answers see Chapter XV 
Mention the purposes of respiration. 
What is meant by internal and what by external 
respiration? 
Name the organs concerned in respiration. 
• What are the functions of the nose? 
Name the divisions of the nose. 
Describe the structure of the nose. 
State some reasons why mouth breathing is 
harmful ? 
Why does a cold in the head interfere with the 
sense of smell? 
Where are the frontal sinuses and the antra of 
Highmore and why do they frequently become 
infected ? 
Describe the pharynx. 
How many openings are there into the pharynx? 
Why will lack of care of the mouth easily result in 
infection of the inner ear ? 
Where and what is the larynx? 
Name some of the important cartilages of the 
larynx and state their purpose. 
What and where is the epiglottis? 
What is its function? Anatomy and Physiology 
564 
What are the vocal cords? 
What and where is the glottis? 
What and where is the trachea? 
Describe the structure of the trachea. 
What is the purpose of its ciliated epithelium ? 
What and where are the bronchi ? 
What are the branches of the bronchi called ? 
What are the alveoli? 
What is their purpose? 
Where are the lungs? 
Describe them. 
In what way does the right lung differ from the left? 
What vessels hold the blood flowing from the heart 
to the lungs ? 
How are the blood-vessels distributed in the lungs? 
Name the membrane that invests the lungs and 
describe its arrangement. 
What is its function? 
What name is given to inflammatory conditions of 
this membrane? 
What constitutes external respiration? 
Describe the mechanism of inspiration. 
Name the principal muscles concerned in inspiration. 
Describe the mechanism of expiration. 
Why are the respiratory movements only very 
slightly under the control of the will? 
What are the causes of respiration? 
In what ways do certain of the sensory nerves 
influence respiration? 
What is the condition of the lungs in the fetus? 
Why? 
What causes the first respiratory movement at 
birth ? Questions 
565 
What physical forces are involved in the inter- 
change of gases that takes place in the lungs? 
What interchange of gases takes place in the tissues ? 
From what is the carbon dioxid that is present in 
the tissues derived? 
State the changes that take place in the blood as the 
result of respiration. 
What is the normal rate of respiration ? 
Why is the rate of the respiration increased in 
fever ? 
What is meant by tidal air? Complemental air? 
Reserve air? Residual air? 
What is the average amount of air exchanged during 
quiet respiration? 
What is meant by the vital capacity of the lungs ? 
What are the forces causing movement of air in the 
lungs ? 
What is the value of this movement? 
State the usual composition of air as it is inspired. 
State the composition of that expired. 
What, therefore, are the differences between air as 
it is inspired and expired ? 
What bad effects may result from being in a badly 
ventilated room? 
To what are these effects due? 
Why is oxygen necessary for life ? 
Upon what are estimates of the amount of air space 
required per capita based? 
In reckoning the necessary size of rooms that are 
to be inhabited by many people, what conditions 
must be considered? 
What is meant by dyspnea? 
What is the cause of dyspnea? 566 
Anatomy and Physiology 
What is the nature of Cheyne-Stokes respiration? 
What is the nature of the respiration in edema of 
the lungs? 
Why is edema of the lungs a dangerous condition? 
What is asphyxia? 
Why are convulsions a common accompaniment 
of asphyxia? 
Mention common causes of hiccough. 
What is meant by the resonance cavities and why 
are they so called? 
How is the action of speaking accomplished ? 
For answers see Chapter X VI 
What is a gland? 
Mention some general characteristics in the struc- 
ture of glands. 
How are glands classified? 
What is meant by a secretion ? 
What by an excretion? 
Mention some excretions that are used by the body. 
How are secretions classified? 
What is meant by an internal secretion? 
Name some of the more important internal 
secretions. 
Name the ductless glands. 
What is the purpose of the secretion of the supra- 
renal capsules? 
Where is the thyroid gland? 
What is the purpose of the secretion of the thyroid 
gland ? 
What is the purpose of the secretion of the pituitary 
body? 
What is the purpose of the thymus gland? Questions 
567 
Of what use are the parathyroid glands? Where 
are they? 
What is thought to be the purpose of the internal 
secretion of the ovaries? 
Where is the spleen situated ? 
How large is it? 
Mention some of the important features of its 
structure. 
State some of the purposes that the spleen is thought 
to serve and give the reasons for the supposition. 
For answers see Chapter XVII 
Name the organs that are concerned with the 
digestion of food. 
Describe the mouth. 
Where and what are the hard and soft palates and 
the uvula? 
What are the palatine arches ? 
Where and what are the tonsils ? 
What is the function of the tonsils? (See page 257.) 
Under what conditions do the tonsils become a 
source of danger to the body and why? (See page 257.) 
Perform the action of swallowing and decide how 
the soft parts at the back of the throat prevent food 
entering the naso-pharynx. 
What part does the tongue take in digestion ? 
What is the nature of the various papillae of the 
tongue ? 
Name, and give the location of, the salivary glands. 
Where is the esophagus? 
What is it like? 
Name the regions of the abdomen. 568 
Anatomy and Physiology 
On what part of the abdomen will you place an 
application that is to be put over the stomach? 
Where would you put one that was to be over the 
liver? 
Where would you place one to be over the right 
kidney? 
How would you know if the bladder was distended ? 
What is the peritoneum? 
What and where is the omentum? 
What and where is the mesentery ? 
Mention the important purposes of the peritoneum. 
What are the names of the different parts of the 
stomach ? 
Name the organs that come in contact with the 
stomach. 
What is the size of the stomach ? 
Name the different kinds of tissue that enter into 
the structure of the walls of the stomach and 
describe their arrangement. 
In what way does this arrangement help the func- 
tioning of the stomach? 
Where are the glands which secrete the gastric 
juice and the hydrochloric acid situated? 
Name the openings of the stomach and state where 
they are situated. 
Where is the small intestine situated ? 
What is its purpose? 
State the names and location of the different parts 
of the small intestine. 
How long is the small intestine? 
Describe the walls of the small intestine. 
What are the valvulas conniventes? 
Describe the villi of the small intestine. Questions 
569 
What is their purpose? 
Name the glands that are situated in the walls of 
the small intestine and state their purposes. 
State the length and position of the large intestine. 
What names are applied to different parts of it? 
How do its walls compare with those of the small 
intestine ? 
What is the purpose of the large intestine ? 
How long is the rectum ? 
How far is it possible to insert a rectal tube without 
having it bend upon itself? 
By means of bismuth injections it has been found 
that fluid is carried much higher into the intestine 
than this, what feature in the action of the intestine 
makes this possible? 
Where is the vermiform appendix? 
Where and what is the cecum? 
What guards the opening between the large and 
the small intestine? 
What is the purpose of this sphincter and valve? 
What and where is the pancreas? 
What is its purpose? 
How does the pancreatic digestive juice enter the 
intestine? 
What is the purpose of the internal secretion of the 
pancreas ? 
What and where is the liver ? 
Describe the liver. 
Name the large veins that enter and leave the liver 
and state their origin. 
In what way does the blood coming to the liver by 
the portal vein differ from that flowing through the 
hepatic artery? Anatomy and Physiology 
570 
What is the purpose of the liver? 
Name the ducts of the liver. 
What and where is the gall-bladder? 
Through what duct does the bile enter the intestine? 
Into what part of the intestine does this duct open ? 
For answers see Chapter X VIII 
How are foods classified? 
What classes of food-stuffs constitute the organic 
foods and what the inorganic? 
Give examples of the protein or nitrogenous food- 
stuffs and state in what foods they are found. 
What elements enter into the composition of 
proteins ? 
Of what elements are fats and carbohydrates 
composed? 
Name the different kinds of carbohydrates. 
Why are these foods called carbohydrates? 
How are sugars classified? 
What is the main difference between the composi- 
tion of these two classes of sugars ? 
Of what are fats composed ? 
Name some substances in which fat is soluble. 
What is meant by saponification? 
What substances will saponify fat? 
What is lecithin and where is it found? 
What is cholesterin? 
Mention the purposes of the organic foods in the 
body. 
What purpose do the proteins serve in the body that 
carbohydrates and fats do not? 
What are some of the important uses of inorganic 
food substances in the body? Questions 
571 
Give a definition of digestion. 
Why is digestion of food necessa y ? 
Under what two heads are the digestive processes 
classified ? 
What constitutes the mechanical processes of 
digestion ? 
What is the nature of chemical digestion ? 
How can the same changes that occur in food as 
the result of digestion be accomplished outside the 
body? 
How is it possible for the chemical changes that 
occur in digestion to take place at body temperature? 
Of what do the digestive juices consist? 
Where is the saliva secreted? 
Mention factors that influence its secretion. 
Name the enzymes it contains. 
Where is the gastric juice secreted? 
Name the enzymes it contains. 
Mention factors that influence its secretion. 
What are the purposes of the hydrochloric acid? 
From what is the hydrochloric acid made? 
What is a zymogen? 
Where is the pancreatic juice secreted and what 
factors influence its secretion? 
Name its enzymes. 
Where is the succus entericus secreted ? 
Name its enzymes. 
What is the action of the enterokinase? 
Name the various stages through which starch 
passes and the enzymes that cause the changes. 
Through what changes do the proteins pass and 
what enzymes produce the changes? 
Where does the digestion of proteins take place? Anatomy and Physiology 
572 
What foods are affected while in the stomach ? 
What changes take place in sugars during digestion 
and what enzymes cause the changes ? 
In what part of the digestive apparatus is the food 
while it is undergoing pancreatic digestion ? 
Where are fats digested and what substances are 
responsible for their digestion ? 
What is the bile? Where is it secreted? 
To what are the changes that occur in food in the 
large intestine due? 
Of what is intestinal putrefaction the result? 
Why is this to be avoided ? 
How long does it take food to pass through the 
intestines ? 
Where does absorption take place? 
Name the various substances into which the differ- 
ent foods are changed before they are absorbed. 
Which of these substances are found in the blood ? 
What is supposed to be the reason that the others 
are not found? 
What is chyme? 
What is chyle? 
For answers see Chapter XIX 
When does the food first begin to be of use to the 
body? 
What is meant by metabolism? 
What is the nature of the metabolic changes that 
occur in the food products? 
Mention factors that influence metabolism. 
How are salts formed in the body? 
What is the result of metabolism? Questions 
573 
What is meant by oxidation ? 
State the various changes through which glucose 
passes after it has been absorbed. 
What are the final products of the metabolism of 
glucose? 
What will be the result if the metabolism of glucose 
is interfered with, as it is in diabetes? 
What happens to fats after they have been absorbed ? 
What is the function of fats ? 
Mention some causes of obesity. 
What is meant by nitrogen equilibrium ? 
What is the special function of proteins in the body? 
State some of the changes caused in proteins as the 
result of metabolism. 
What is the heat value of proteins, carbohydrates, 
and fats? 
Upon what does the amount of food required 
depend ? 
How much food does an averaged-sized man at 
light labor require per day? 
How does the amount of food required by a woman 
compare with a man's requirement? 
What proportion of a man's ration does a child of 
six require? 
Why do children need more food in proportion to 
their size than adults? 
Mention some of the bad effects likely to result 
from eating too much food. 
How is heat produced in the body? 
Where is it produced ? 
If heat is produced to a greater extent in some parts 
of the body than others, how is it that all the interior 
of. the body has about the same temperature? Anatomy and Physiology 
574 
Through what channels is excess heat eliminated 
from the body? 
How is the greatest amount of heat eliminated? 
How is the formation and loss of heat in the body 
regulated ? 
Mention some external conditions that influence 
the loss of heat. 
Why does heat prostration occur more frequently 
on hot days when the humidity is high than when 
there is not much moisture in the air? 
Why does shivering increase heat formation and 
prevent loss of heat? 
How and why do cold baths affect the temperature ? 
Mention some of the supposed causes of fever. 
Why is the respiration increased in fever ? 
In what way is fever thought to be of use to the 
body? 
For answers see Chapter XX 
Name the excretory organs. 
What waste matter is eliminated through the 
urinary organs? 
What through the respiratory organs? 
What through the skin? 
Name the excretion eliminated by the liver. 
From what is the matter eliminated through the 
excretory organs derived? 
What organs constitute the urinary system? 
Where are the kidneys situated? 
How are they retained in place? 
What is a common cause of loosening of the kidneys 
from their position and what is the condition called? 
Of what shape are the kidneys? Questions 
575 
What is meant by the hilum of the kidney? 
Name the different parts of the kidneys and the 
structures forming each part. 
What are the uriniferous tubules? 
What are the Malpighian capsules? 
What are the Malpighian bodies? 
What is a glomerulus? 
What are the calyces of the kidneys ? 
What and where is the pelvis of a kidney? 
Of what do the pyramids consist? 
What arteries supply the kidneys with blood? 
What is meant by the capsule of a kidney ? 
What is the nature of the process by which urine is 
excreted ? 
Where and what are the ureters? 
Where is the urinary bladder situated? 
What is meant by retention of urine? 
What are the usual causes of retention of urine? 
What is meant by retention with overflow? 
What symptoms should lead you to think that 
the passage of urine involuntarily was the result of 
retention ? 
Mention some bad results that might follow reten- 
tion of urine after an abdominal operation? 
How much urine does an adult pass, normally, 
during the twenty-four hours? 
How much do children of about two, five, and nine 
years of age pass? 
Mention some causes likely to diminish the secre- 
tion of urine. 
Mention causes that are likely to increase it. 
Mention some causes for changes in the color of 
urine and state the nature of the change in each case. 576 
Anatomy and Physiology 
What is the normal reaction of urine and to what is 
this reaction due ? 
State the composition of urine. 
What is urea? 
State the average amount of urea passed by an adult 
in twenty-four hours and some causes for changes in 
the amount. 
From what is uric acid derived? 
In what form is it usually found in the urine? 
From what are the salts that are found in urine 
derived ? 
Under what circumstances is albumin likely to be 
found in the urine? 
Mention some causes for the appearance of glucose 
in the urine. 
From what is aceton derived and when is it likely 
to be found in the urine ? 
What is the source of indican and what does its 
presence in the urine indicate? 
What are casts? 
What may be the origin of urinary calculi ? 
What does the presence of pus in the urine indicate ? 
Of mucus? 
Of blood? 
What is the difference between retention and 
suppression of urine? 
What will be the result if the kidneys fail to secrete 
the urine and why will there be such a result ? 
For answers see Chapter XXI 
Mention the functions of the skin. 
What are the two main parts of the skin? Questions 
577 
Mention some of the main features in the structure 
of the epidermis. 
Why can imprints of the hands be used for identifi- 
cation purposes? 
How can blisters be caused and why? 
Describe the principal features in the structure of 
the derma. 
Name the different kinds of nerves that have their 
peripheral terminations in the skin. 
Name the glands of the skin and state their purposes. 
How much perspiration is secreted in twenty-four 
hours at ordinary temperatures? 
What is meant by insensible perspiration? Why is 
it so called? 
Mention causes for increase in the degree of perspira- 
tion. 
Mention common causes for decrease in the amount 
of perspiration excreted. 
How is the activity of the sweat glands controlled? 
Give examples. 
Of what is sweat composed? 
What is the principal value of the excretion of 
sweat ? 
Where are the ceruminous glands situated ? 
What is the secretion of the ceruminous glands 
called and what is its purpose? 
Where are the sebaceous glands found? 
What is the secretion of the sebaceous glands called 
and what is its purpose? 
Discuss the value of the skin as an absorbing organ. 
How must inunctions be given if the substance used 
for the purpose is to be absorbed, and what must be 
the nature of the substance? 578 
Anatomy and Physiology 
What are meant by the appendages of the skin? 
Name the different parts of a hair. 
Upon what does the growth of hair depend? 
What causes the appearance known as goose-flesh ? 
Name the different parts of a nail. 
How does the growth of the nails take place ? 
For answers see Chapter XXII 
What causes sensation? 
What are the essential parts of a sense organ? 
Where are sensations perceived? 
How are sensations classified ? 
Give reasons for the classification. 
How is the sensation of pain perceived? 
What gives rise to the sense of hunger? 
What causes the sense of thirst ? 
What is meant by muscular sense? Give examples. 
What causes the sense of fatigue? 
How are the sensations produced that cause vomit- 
ing, micturition, coughing, and the like? 
What is meant by the pressure or tactile sense ? 
How are the nerve endings connected with this 
sense stimulated? 
In what parts of the body are pressure nerve- 
endings most abundant? 
What is meant by the temperature sense ? 
What name is given to the nerve endings connected 
with this sense, where are they situated, and how are 
they stimulated? 
Mention some of the results of stimulation of the 
cold spots. 
Mention conditions necessary for the stimulation of 
the olfactory nerve-endings. Questions 
579 
Where are the nerve endings of the nerves connected 
with the sense of taste contained and what are they 
called? 
How are they stimulated? 
For answers see Chapter XXIII 
What constitute the essential parts of the organ of 
vision? 
What are meant by the appendages of the eye? 
What are the eyebrows ? 
Describe the eyelids. 
What are the Meibomian glands and where are they 
situated? 
What constitutes the lachrymal apparatus of the 
eye? 
Where is the lachrymal gland situated ? 
Where is the lachrymal sac? Into what does it 
open? 
Where is the nasal duct? 
What is the purpose of the lachrymal gland? 
What is the purpose of the tears ? 
How do they reach, and how are they removed from, 
the surface of the eye? 
Where and what is the conjunctiva? 
Under what two headings are the muscles concerned 
with the eye considered? 
Which of the eye muscles are classed as the intrinsic 
muscles ? 
Name the muscles classed as the extrinsic muscles 
and state their purpose. 
Describe the orbits. 
Why are people's eyes likely to look sunken after 
illness ? 580 
Anatomy and Physiology 
Name the coats of the eye. 
Describe and locate the sclera. 
With what is it continuous? 
Describe the cornea. 
Point out and describe the choroid. 
Where and what is the ciliary zone ? 
Describe the position and. nature of the iris. 
Where and what is the pupil? 
Describe the location and the nature of the 
retina. 
What and where is the fovea centralis ? 
What and where is the blind spot? 
What is meant by the humors of the eye? 
What and where is the crystalline lens ? 
Describe the manner in which the crystalline lens 
is held in position. 
Why do we see objects? 
What is meant by the refractive apparatus of the 
eye and what parts of the eye compose it ? 
Describe the action of the refractive apparatus. 
What is meant by hypermetropia ? 
What is meant by myopia? 
What is meant by astigmatism? 
What is the function of the iris ? 
Describe the manner in which its function is per- 
formed. 
What is the function of the retina? 
How do we judge of the size of objects? 
How do we know that objects are moving? 
How do we estimate the solidity of objects? 
In what ways do the eyes resemble the photog- 
rapher's camera? 
To what is the color of light due? Questions 
581 
Why is sunlight of a white hue if it contains so many 
colors ? 
To what is the color of objects due? 
What makes objects look white? 
What makes them look black ? 
Why are objects not always the same color under 
artificial lights as by daylight? 
Mention one theory regarding the reason why color 
can be perceived. 
Mention one theory regarding the reason for color 
blindness. 
For answers see Chapter XXIV 
Mention the main divisions of the ear. 
Of what does the external ear consist? 
Describe the auricle. 
What is the purpose of the ceruminous glands ? 
Describe the auditory canal. 
How are the external and middle portions of the ear 
separated ? 
Name the bones found in the middle ear and state 
their relative location. 
How many, and what, openings are there in the 
middle ear and with what do they communicate? 
Why can inflammation in the middle ear give rise 
to mastoiditis? 
What is the function of the Eustachian tube ? 
Why is obstruction of this tube a serious matter? 
Name the different parts of the inner ear and state 
their relative position. 
What is the membrane lining the inner ear called? 
Describe the structure of the cochlea. 
What is its purpose? 582 
Anatomy and Physiology 
What is the organ of Corti ? 
Describe the structure of the vestibule. 
Describe the structure of the semicircular canals. 
What is their purpose? 
What will be the result of disease of this part of the 
ear? 
With what part of the brain do the nerve-fibers 
from this part of the ear communicate? 
Describe the process that gives rise to hearing. 
For answers see Chapter XXV 
Under what two headings are the female organs of 
generation divided? 
Name the internal organs of generation. 
Where are the ovaries? 
Describe their structure. 
What are the Graffian follicles? 
What is their purpose? 
About how many follicles are there usually in an 
ovary? 
What is meant by ovulation? 
What is the corpus lutcum? 
What and where are the Fallopian tubes? 
What are the fimbriae of the tubes ? 
What is their purpose? 
What is the purpose of the tubes ? 
What name is given to the condition that arises 
when a fecundated ovum remains in a Fallopian tube ? 
What and where is the uterus? 
How large is the uterus? 
Name the different parts of the uterus. 
Describe the structure of the uterine walls. 
How is the uterus held in position ? Questions 
583 
What and where are the broad ligaments? 
What and where is the vagina? 
Describe the structure of the vagina. 
Name the external organs of generation. 
What and where is the mons Veneris? The labia 
majora? The labia minora? The clitoris? The 
hymen? The perineum? 
What is meant by puberty? 
What is meant by the menopause or climacteric? 
What changes occur in the uterus in connection 
with menstruation? 
In what way are the ovaries thought to influence 
menstruation ? 
Describe the ova. 
Describe the spermatozoa. 
What happens to the ova after they are discharged 
from the ovaries? 
What is meant by the decidua? 
What is the decidua vera? The decidua serotina? 
The decidua reflexa? 
Describe the first stages in the development of 
an ovum after fecundation. 
What is the amnion? 
What are its purposes? 
Describe the placenta and state its purpose. 
Describe the umbilical cord and state its purpose. 
What is the condition of the lungs during intra- 
uterine life? 
How does the fetus get oxygen and part with carbon 
dioxide and other waste matter? 
Mention some points of difference in the circulation 
of the blood before and after birth. 
Describe the structure of the mammary glands. 584 
Anatomy and Physiology 
Mention some factors which influence the develop- 
ment of the mammary glands. 
How is the milk formed in these glands ? 
Compare the composition of human colostrum and 
milk. 
Compare the composition of human milk and cow's 
milk. 
For answers see Chapter XXVI 
What is the normal rate of increase in weight during 
infancy ? 
What is the average normal rate of' increase in 
height during infancy and childhood? 
What should be the rate in increase of muscular 
strength during infancy? 
What is the state of the bones at birth and during 
early infancy? 
What care is necessary to insure their proper 
development ? 
What is the condition of the glands at birth ? 
Why must starch foods, unless they are very thor- 
oughly cooked, not be given infants? 
State the rate at which the skull and brain de- 
velop. 
Discuss the normal rate at which a child's mental 
capacities develop. 
Why is it necessary for those who have charge of 
the training of children to know something about the 
rate of development of a child's capacities? 
What is meant by the senescence? 
To what are the conditions characteristic of the 
senescence due? Questions 
585 
What is meant by arteriosclerosis? 
What is the consequence of arteriosclerosis ? 
Mention some causes of premature arteriosclerosis. 
Why is sleep necessary? 
Mention some theories regarding the cause of sleep. 
To what are dreams thought to be due? FOOD VALUES OF A FEW FOOD MATERIALS AND 
PREPARED FOODS 
Food Material 
Amount 
Weight 
(gms.) 
Protein 
(gms.) 
Fat 
(gms.) 
Carbo- 
hydrate 
(gms.) 
Fuel 
Value 
(calories) 
Cereals, etc.: 
Arrowroot Gruel 
I cup 
240 
7-52 
9-04 
25.08 
211.76 
arrowroot i tbsp, 
milk i cup 
Farina 
I serving 
IOO 
1.65 
0.21 
n-45 
71-30 
Hominy 
I serving 
IOO 
2. 2 
0.20 
17.80 
81.80 
Oatmeal 
I serving 
IOO 
2.42 
i-45 
11.76 
69.77 
Rice 
I serving 
IOO 
2.80 
0.10 
24.40 
IO9.7 
Wheat Germ 
i serving 
IOO 
1-79 
o-34 
12.92 
81.90 
Desserts: 
Baked Custard 
i serving 
245 
12-34 
12.03 
8.61 
192.07 
egg I 
milk 54 cup 
sugar 2 tbsp. 
Bread Pudding 
i serving 
105 
5-52 
4-79 
38-48 
219.II 
bread i cup 
egg i 
milk i cup 
sugar 54 cup 
raisins 54 cup 
Ice Cream, plain 
I serving 
195 
3-90 
21.69 
19-23 
287.73 
cream 54 cup 
milk 54 cup 
sugar I tbsp. 
Orange Jelly 
I serving 
175 
2.6 
44-2 
187.2 
gelatin i tsp. 
lemon juice I tbsp, 
orange juice 54 cup 
sugar 2 tbsp. 
Fluids: 
Beef Soup 
54 cup 
120 
5-28 
0.48 
i-32 
3O-72 
Cocoa 
i cup 
240 
7-64 
9-50 
21.98 
204.98 
cocoa 2 tsp. 
milk 54 cup 
sugar 2 tsp. 
| 
586 Food Values of a Few Food Materials 
587 
Food Material 
Amount 
Weight 
(gms). 
Protein 
(gms.) 
Fat 
(gms.) 
Carbo- 
hydrate 
(gms.) 
Fuel 
Value 
(caiories) 
Fluids: 
Cream, medium 
2+tbsp. 
40 
1.48 
10.28 
I.41 
104.1 
Cream of Pea Soup 
I serving 
8.20 
14-99 
16.46 
236-55 
Butter 2 tsp. 
Flour 2 tsp. 
milk % cup 
peas | cup 
Egg Nog 
1 glass 
12.34 
12.03 
2346 
302.07 
egg i 
milk % cup 
sugar i tbsp, 
whiskey 15 cc. 
Milk 
1 cup 
240 
7-52 
9-04 
11.28 
156.8 
Orange Albumin 
1 glass 
240 
348 
0.06 
22.78 
105-5 
egg white 1 
sugar 1 tbsp. 
orange juice cup 
lemon juice 1 tbsp. 
Fish, etc.: 
Bluefish 
1 serving 
100 
25-90 
4-50 
I44.IO 
Mackerel 
1 serving 
70 
n-73 
4-84 
2.62 
IOO.96 
Salmon 
1 serving 
IOO 
I9-65 
10.21 
5-36 
191-93 
Trout-brook 
1 serving 
50 
10.57 
1.17 
.62 
55-29 
Clams, long 
6 
150 
12.90 
i-5 
3-oo 
77.1 
Oysters 
6 
«5 
5-27 
1.02 
3-i5 
42.86 
Fruits: 
Apple 
1 average 
150 
o-45 
0-45 
16.20 
70.65 
Banana 
1 average 
194 
i-55 
0.78 
27-74 
124.18 
Grapes 
1 bunch 
150 
1-50 
1.80 
21.60 
109.60 
Orange 
1 average 
250 
1.50 
0.25 
21.25 
93-25 
Strawberries 
I serving 
IOO 
1.00 
.60 
7-40 
39-oo 
Prunes, with juice 
4 large 
200 
1.00 
0.20 
44.60 
184.20 
Meats: 
Bacon 
1 serving 
30 
2.98 
18.37 
177-2 
Beef Steak-porterhouse 
1 serving 
120 
21.64 
20.28 
269.08 
Chicken 
1 slice 
IOO 
32.10 
4-40 
2.10 
176.40 
Lamb Chop 
1 
IOO 
21.70 
29.90 
345-9 
Miscellaneous: 
Bread, white-baker's 
1 slice 
30 
2.76 
o-39 
15-93 
78.27 
Bread, graham 
1 slice 
37 
3-29 
•67 
19.28 
96.31 
Butter 
1 ball 
15 
0.15 
12.75 
H5-35 
Cheese, American 
1 cu. in. 
20 
5-70 
7.18 
.06 
87.66 
Cheese, cream 
1 cu. in. 
20 
5.18 
6-74 
.48 
83-3° 
Egg 
1 
50 
6.70 
3-3 
5-25 
74-°5 
Egg, white 
I 
25 
13-2 588 
Anatomy and Physiology 
Food Material 
Amount 
Weight 
(gms.) 
Protein 
(gms.) 
Fat 
(gms.) 
1 0 
is 8 
Fuel 
Value 
(calories) 
Miscellaneous-continued: 
Egg, yolk 
I 
13 
2.1 
4-5 
46.9 
Lactose 
tbsp. 
30 
150 
60.0 
Sugar 
i tbsp. 
30 
i5-o 
60.0 
Whiskey 
15 co. 
50-6 
Vegetables: 
Asparagus, fresh 
1 serving 
120 
2.04 
0.24 
3-72 
25-2 
Beans, lima 
1 serving 
120 
4.08 
0. 8 
25-04 
139-2 
Beans, string 
I serving 
60 
O.48 
0.66 
1.14 
I2.42 
Cauliflower 
1 serving 
120 
I.O8 
0.12 
.48 
7-32 
Celery, raw 
4 stalks 
60 
0.62 
0.06 
1.86 
10.4 
Peas, green 
1 serving 
90 
5-94 
0.42 
14-37 
84.9 
Potatoes, baked 
1 
13° 
3-77 
0.20 
32-07 
I45-i6 
Spinach 
1 serving 
IOO 
2.10 
4.10 
2.60 
55-70 
Tomatoes, raw 
1 average 
200 
2.40 
0.40 
8.00 
45-2 
Note: This Table of Food Values was compiled by Miss Alice C. Keith. INDEX 
A 
Abdomen, regions of, 16,18,348 
Absorption of food, 393, 394 
through skin, 447 
Adenoids, 32 
Air, changes caused in, as the 
result of respiration, 320 
forces causing movement 
of, in lungs, 319 
terms used in describing 
quantity breathed, 318, 
319 
Amnion, the, 507 
Anatomical position, 13 
Antibodies, 227 
Aorta, location and branches, 
262 
Aphasia, motor, 173 
sensory, 174 
Aponeuroses, nature and pur- 
pose, 30 
Arachnoid, 186, 189 
Arteries, anatomy of, 246 to 
248 
names and location of 
larger systemic, 262 to 
272 
pulmonary, 242, 260, 279 
Axis-cylinder, 143, 145 
B 
Bacteria, influence of, in diges- 
tion, 385 
Bladder, the urinary, location 
and structure, 425 
Blood, characteristics, 216 
clotting or coagulation 
of, 225, 230 to 234 
color, 217 
composition, 217 
function of, 216 
plasma, 218, 225 to 227 
plates, 225 
pressure, 288 to 292 
quantity, 216 
regeneration after hemor- 
rhage, 234 
variations in the quantity 
in different parts of the 
body, 288 
Blood-vessels, anastomoses of, 
260 
function of, 238 
general plan of distribu- 
tion, 254 
Body-cavities, 16 
divisions of, 15 
surfaces of, 13 
Bones, blood and nerve supply 
of, 44 
classification, 39 
composition, 37 
fracture of, 38 
function of, 36 
Haversian system of, 42, 
43 
of lower extremities, 77, 85 
of pelvis, 76 
of skull, 46 to 59 
of spine, 60 to 66 
of thoracic wall, 66 to 68 
of upper extremities, 68 to 
75 . 
markings of, 41 
number of, 45 to 46 
prominences and depres- 
sions, 41 
repair of, 45 
589 590 
Index 
B ones- Continued 
sesmoid, 40 
structure of, 40 
Wormian, 40 
Brain, location of, 163 
main divisions of, 166 
membranes of, 185, 186 
ventricles of, 164 
weight of, 164 
Breasts, 512 to 516 
Bronchi, structure and posi- 
tion, 306 to 307 
Bursae, 89 
C 
Canal, inguinal, 125 
Capillaries, anatomy of, 250, 
.25i 
distribution of, 250 
Carbohydrates, digestion of, 
• 383> 384 
function of, 399 
metabolism of, -397 to 400 
nature of, 372 
Cardiac cycle, 282 
Cartilage,-nature of, 32 to 35 
Cells, difference in, 11 
how they multiply, 10 
life cycle of, 11 
Cerebellum, connections, 178 
functions, 179 
location, 178 
structure, 179 
Cerebrum, arrangement of 
white and gray matter, 
166 
association areas, 174 to 
178 
fissures and convolutions 
of, 167 
function of, 169, 170 
motor area, 170 to 172 
sense areas, 173 
speech center, 173, 174 
Cholesterine, 374 
Chromatin, 503 
Circulation, factors maintain- 
- ing, 286 
fetal, 509, 510 
portal, 260, 365 
pulmonary, 279 
systemic, 280 
velocity of, 287, 288 
Climacteric, the, 500 
Cochlea, 483 
Collaterals, 145 
Color vision, 475 to 477 
Colostrum, 516 
Conjunctiva, 462 
Cord, umbilical, 509 
Corpuscles, difference between 
red and white, 222 
red, 218 to 220 
white, 220 to 224 
Corpus luteum, 491 
D 
Decidua, the, 504 
Dendrites, 143, 144 
Development, rate of, after 
birth, 518 to 522 
rate of, during intra-uter- 
ine life, 506, 507 
Diaphragm, 122 
Digestion, definition of, 370 
chemical, nature of, 377 
mechanical, 386 to 393 
organs in which digestion 
of each of the various 
food-stuffs takes place, 
383 to 386 
why necessary, 376 to 377 
Digestive juices, action of, on 
food,383 
mechanism of the secre- 
tion of, 380 
nature of, 380 
system, divisions of, 341 
Dislocations, nature of, 94 
Ducts, biliary, 366 to 368 
Dura mater, 185, 188 
E 
Ear, anatomy of, 478 to 486 
bones of middle, 481 
Edema, causes of, 295 
Elimination, 416, 417 
Embolus, 234 
Endocardium, 241 Index 
591 
Endosteum, 44 
Enzymes, action of, 379 
nature of, 227 
Epiglottis, 304 
Epithelium, ciliated, 23 
Erythrocytes, 219, 220 
Esophagus, location and struc- 
ture, 347, 348 
Expiration, mechanism and 
causes, 311, 312, 315, 316 
Extractives in blood, 226 
Eye, accommodation of, 469, 
472 
Eyeball, 464 
Eyebrows, 459 
Eye, coats of, 464 to 466 
humors of, 468 
Eyelids, 460 
F 
Fallopian tubes, 492, 493 
Fascia, nature and purpose, 29 
Fatigue, 106, 455 
Fats, digestion of, 383, 384 
function of, 400 
metabolism of, 400 
nature of, 373, 374 
Feces, nature of, 392 
Fetal circulation, 509, 510 
Fetus, nutrition of, 509 
Fever, nature, cause, and 
treatment, 414 
Fibrin, 231 
Fontanelles, 53 
Food, absorption of, 393, 394 
chemical elements of or- 
ganic, 372 
classification of, 37 
factors regulating passage 
from stomach into intes- 
tine, 389 
heat value of, 403 
inorganic, 375 
requirement, 403 to 406 
Fovea centralis, 467 
G 
Gall-bladder, location, size, 
structure, 368, 369 
Ganglia, lateral, 197, 199 
spinal, 195 
sympathetic, 198, 199 
terminal, 197, 199 
Gases in blood, 227 
Generation, accessory organs 
of, 512 to 516 
anatomy of external or- 
gans, 497, 498 
anatomy of internal or- 
gans, 489 to 496 
physiology of organs, 499 
Glands, classification of, 329 to 
33i 
ductless, 329, 332 to 336 
mammary, 512, 516 
nature and characteristics, 
327, 330 
of small intestine, 357, 
358 
salivary, 346 
sebaceous, 446, 447 
sweat, 443 
thymus, 333 
thyroid, 332 
Glomerulus, 419, 421 
Graffian follicles, 490 
H 
Hair, the, 448 to 450 
Hearing, physiology of, 486 
Heart, anatomy of, 238 to 
246 
distribution of, 407 
function of, 238 
loss of, 407 
nature of action of, 280, 
281 
production of, 406, 407 
regulation of, 408 to 414 
sounds and murmurs, 283 
Heart-beat, cause of, 283 to 
286 
Hernia, 126 
Hunger, sense of, 454 
Hydrochloric acid, functions 
of, 380 
I 
Immune bodies, 227 to 229 
Inflammation, cause of, 223 592 
Index 
Inspiration, causes of, 313 
Intestine, large, divisions, pur- 
poses, size, structure, 
358, 359 
small, 354 to 357 
Inunction, 448 
Iris, 466, 472 
Islands of Langerhans, 362 
J 
Joints, ball and socket, 90 
condyloid, 91 
different kinds of, 86 
freely movable, 89, 93 
hinge, 91 
immovable, 86, 87 
pivot, 91 
saddle, 92 
slightly movable, 87, 88 
K 
Kidney, anatomy, function, 
location, 418 to 424 
Knee-jerk, 162 
L 
Lachrymal apparatus, 460 to 
462 
Larynx, anatomy of, 303 to 305 
Lecithin, 374 
Lens, crystalline, 468, 469 
Leucocytes, 221 to 224 
Ligaments, annular, 131, 132, 
135. 139 
broad, 495 
nature and purpose, 28 
Poupart's, 123 
round, 495 
Liver, function, location, size, 
structure, 362 to 366 
Lungs, capacity of, 318, 319 
position and shape, 307 
structure, 308, 309 
Lymph-ducts, 254 
factors controlling flow of, 
294. 295 
Lymph-glands, nature and 
location, 255 
Lymph-spaces, nature and 
location, 251 
Lymph vascular-system, ana- 
tomy of, 250 to 257 
Lymph-vessels, function of, 
254 
nature and names, 251 
origin and distribution, 252 
M 
Malpighian bodies, 420, 421 
Marrow, 43 
Mediastinum space, 311 
Medulla oblongata, cavities 
of, 184 
form of, 182 
functions of, 184 
gray matter of, 183 
location of, 182 
pyramids of, 183 
structure of, 182 
Membranes, classification of, 
205 
functions of, 205 
mucous, 209 to 214 
nature of, 204 
pituitary, 301 
secretion of, 206 
serous, 206, 207 
synovial, 208, 209 
Menopause, the, 500 
Menstruation, 501 to 503 
Mesencephalon, 178 
Mesentery, 350 
Metabolism, nature and object 
of, 395 to 403 
Milk, composition of, 516, 517 
secretion of, 516 
Mineral matter, in blood, 226 
of food, 375 
Mouth, anatomy of, 341 
Movements, different kinds of 
which joints are capable, 92 
Muscles, extensibility and 
elasticity of, no 
fatigue, 106, 107 
methods of attachment, 
112 
nomenclature and num- 
ber, 113 Index 
593 
M uscles- Continued 
ocular, 462 
of abdomen, 122 to 125 
back, 120 to 121 
buttocks, 134 
face, 114 to 117 
head, 113 to 114 
lower extremities, 133 to 
139 
neck, 118 to 120 
thorax, 121 to 122 
tongue, 117 to 118 
upper extremities, 126 
to 133 
origin and insertion, 112 
size and shape, 113 
, skeletal, nature of, in 
Muscle tone, 108, 109 
Muscular sense, 454, 455 
Muscular tissue, see under 
Tissue. 
N 
Nails, the, 450 
Nasal fossae, 300 
Nerve action, automatism, 160 
auditory, 485 
Nerve cell-bodies, effect of 
fatigue on, 161 
function of, 154 
names of different parts, 
143 
number of processes, 143, 
144 
Nerve centers, nature of, 152, 
201, 202 
Nerve endings, how they react 
to stimuli, 150 
nature of, 149, 150 
Nerve fibers, functions of, 147 
kinds of, 146 
medullary sheath, 146 
medulla ted, 146 
non-medullated, 147 
Nerve impulse, causes of, 108 
diffusion of, 159 
how carried, 147, 148 
modification of, 159 
origin and nature of, 153 
origin of voluntary, 160 
reason for difference in 
impulse carried by affer- 
ent and efferent, 148 
where transmission of im- 
pulse takes place, 155 
Nerve, optic, 468 
Nerve reflex action, definition 
of, 155 
different kinds of, 157 
examples of, 155 
inhibition of, 159 
Nerve reflex arc, nature of, 157 
Nerve tissue, arrangement and 
distribution of, 151 
nature of, 143 
Nerves, branching of, 152 
central connection of, 152 
classification of, 191 
cranial, names of, 192, 
193 
decussation of, 170, 390 
degeneration of, 161 
peripheral, 195, 196 
plexuses, 152 
regeneration of, 161 
spinal, branches of, 196 
names of, 194 
nature of, 194 
number of, 194 
origin of, 194 
roots of, 194 
Nervous system, sympathetic 
connection between 
parts of, 198 
function of, 200 
parts of, 197 
Neurilemma, 146 
Neuroglia, nature and function 
of, 151 
Nodes of Ranvier, 146, 147 
Nose, anatomy and function 
of, 298 to 302 
0 
Omentum, 350 
Opsonins, 224 
Orbit, 463 
Organs, what they are, 12 
Ovaries, anatomy of, 489, 491 594 
Index 
Ovulation, 499 
Ovum, development of, 505 
disposal of, 504 
nature of, 503 
P 
Pain, cause of, 454 
Palates, hard and soft, 341 
Palatine arches, 342 
Pancreas, internal secretion of, 
335 
position, purposes, shape, 
structure, 361, 362 
Pelvis, bones of, 76 
Pericardium, 241 
Periosteum, 44 
Peritoneum, structure and 
functions, 349, 350 
Perspiration, 443 to 445 
Phagocytes, 223 
Pharynx, 302, 303 
Pia mater, 186, 188 
Placenta, the, 508 
Pleura, nature and function of, 
310 
Pleurisy, 310 
Plexuses of nerves, 152, 198, 
199 
Pons Varolii, 180 to 181 
Portal circulation, 277 
Position, anatomical, 13 
Pressure sense, 455 
Proteins, digestion of, 383, 384 
function of, 402 
metabolism of, 401, 402 
nature of, 371 
Puberty, 500 
Pulse, cause of, 292 
frequency of, 294 
what can be determined by 
feeling the, 293 
Pus, 224 
Q 
Questions, 543 
R 
Rami communicantes, 199 
Reflex actions, 155-159. 
Reproduction, anatomy of or- 
gans of, 489 to 499 
organs of, 499 to 503 
physiology of, 503 to 512 
Respiration, abnormal types 
of, 322 to 324 
capacity of lungs, 318, 319 
during intra-uterine life, 
5io 
external, nature of, 298, 
3™ 
internal, nature of, 298, 
317 
nature of movements of, 
312 
purpose of, 297 
Respiratory center, 313 
Retina, 466, 472 
Ribs, 67 
S 
Salts, as the result of chemical 
reaction, 396 
in blood, 226, 232, 284 
food, 375, 376 
urine, 432 
uses of, 375, 376 
Secretions, internal, 227 
of membranes, 206 
Semicircular canals, 484, 487 
Senescence, 522 
Sensations, external or special, 
452, 453 
internal or common, 452, 
454 
nature and classification, 
452, 453 
Sense organs, nature of, 452 
Skin, function of, 483 
glands of, 443, 446 
nerves of, 412 
structure of, 438 to 442 
value of excretory func- 
tion of, 445 
Sinuses, venous, 273 
Sleep, physiology of, 524 to 
526 
Smell, sense of, 457 
Speaking, mechanism of, 325 
Spermatozoa, nature of, 503 Index 
595 
Spina bifida, 64 
Spinal column, 60 to 66 
nature of articulations of, 
88 
Spinal cord, 188 to 189 
Spleen, 338, 339 
Sprains, nature of, 94 
Sternum, 66 
Stomach, 351 to 354 
Sugars, classification of, 372, 
373 
Suprarenal capsules, 333 
Sutures, 53, 87 
System, nervous, divisions, 
141, 142 
Systems, nature of, 12 
T 
Taste, sense of, 457 
Teeth, 94 to 97 
Temperature sense, 456 
Tendons, 29 
Tetanus, 107 
Thirst, location of sensation, 454 
Thrombus, 234 
Thymus gland, 333 
Thyroid gland, 332 
Tissue, adenoid, 31, 303 
adipose, 30, 31 
areolar, 26, 27 
bone, 36 
cardiac muscular, 103 
classification, 22 
connective, classification 
and distribution, 25 
epithelial, 22, 23 
fibrous, 22, 27 
lymphoid, 31 
muscular, characteristics, 
104 
chemical changes that 
take place in, 106 
composition and varie- 
ties, 99, 100 
contraction of, 105, 109, 
no 
irritability of, 105 
nature of, 21 
nervous, nature and char- 
acteristics, 140, 141 
origin of, 20 
plain muscular, 100, 101 
retiform, 31 
striped muscular, 101, 102 
white fibrous, 27 
yellow fibrous, 27 
Tongue, 343, 344 
Tonsils, 257, 342 
Trachea, anatomy of, 306 
U 
Umbilical cord, 509 
Urea, 431 
Ureters, 425 
Uric acid, 431 
Urinary system, organs of, 
416 
Urine, abnormal constituents 
of, 432 to 436 
composition of, 430 
excretion of, 423 
physical properties, 429, 
430. 
quantity, 428, 429 
retention of, 428, 437 
secretion of, 424 
suppression of, 437 
toxicity of, 436 
Uterus, 493 to 495 
ligaments of, 495, 496 
Uvula, 341 
V 
Vagina, 496, 497 
Valves of the heart, 243 to 245 
veins, 249 
Vascular system, divisions of, 
215 
organs constituting, 238 
Vaso-motor centers and nerves, 
201 to 203 
Veins, anatomy of, 248 to 250 
names and location of 
more important, 273 to 
278 
pulmonary, 272 
Ventilation, 320, 321 
Vertebras, 60 to 66 596 
Index 
Vision, color, 475 to 477 
size and movement of 
objects, 473, 475 
Vital capacity in respiration, 
319 
Vocal cords, 305 
Vomiting, 388, 455 
w 
Water, function of, 376 
Words used in describing the 
location of different parts 
of the body, 17 J? Selection from the 
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is, in large part, a quiz book, offering in the form of terse ques- 
tion and answer essential information on a wide range of subjects 
-the information that is essential from the nurse's standpoint. 
Those who teach will find these questions of assistance when the 
time they have to devote to preparation for their class work is 
limited; and those who are taking courses will find the book a 
great help ; especially when studying for examinations. 
G. P, PUTNAM'S SONS 
New York London A History of Nursing 
Vols. I. and II. The Evolution of the 
Methods of Care for the Sick from the 
Earliest Times to the Foundation of the 
First English and American Training 
School for Nurses. 
By 
LAVINIA L. DOCK, R.N. 
and 
M. ADELAIDE NUTTING, R.N. 
dvc. 2 vols . With 80 Illustrations. $5,00 net 
By mail, $5,50 
Vols. HI. and IV. The Story of Modern 
Nursing 
Presenting an Account of the Development in Various Countries 
of the Science of Trained Nursing, with Special Reference to the 
Work of the Past Thirty Years. 
By LAVINIA L. DOCK, R.N. 
6vo, 2 vols, With 75 Illustrations $5.00 net 
By mail, $5,50 
Beginning with the earliest available records of sanitary codes 
which were built up into health religions, and coming down through 
the ages wherever the care and rescue of the sick can be traced, 
through the pagan civilizations, the early Christian works of mercy, 
the long and glorious history of the religious nursing orders, military 
nursing orders of the crusades, the secular communities of the later 
Middle Ages, and the revival of the Deaconess order which cul- 
minated in the modern revival under Miss Nightingale, this history 
is the most serious attempt yet made to collect the scattered records 
of the care of the sick and bring them all into one unified and sym- 
pathetic presentation. 
The story is not told in a dry, technical fashion, but presents its 
pictures from the standpoint of general human interest in a subject 
which has always appealed to the sympathies of men. 
The history is amply illustrated, and contains a copious bibliog- 
raphy of nursing and hospital history. 
G. P. Putnam's Sons 
New York London