Physiology Class-Book 
Walters Physiology Class-Book 
BY 
F. M. WALTERS, A. M., 
Instructor in Physiology, Physics, and Chemistry, in State Normal 
School, Warrensburg, Mo. 
C. D. MIDDLETON, 
PUBLISHED BY 
WARRENSBURG, MO. 
PRESS OF 
Sedalia Printing Company, 
SEDALIA, MO. COPYRIGHT 1895, 
BY 
F. M. WALTERS. PREFACE. 
The Physiology Class-Book is the outgrowth of an attempt to 
combine the “text-book” and “lecture” methods of teaching Physi- 
ology. It was published first in 1895 for the use of students in the 
YVarrensburg, Mo., State Normal School. The cordial endorsement 
of the plan of the book by those not associated with the Normal 
School suggested a broader field of usefulness than was at first con- 
templated. In revising the former edition the quantity of subject 
matter has been increased, the original plan of note taking modified, 
and references, by page numbers, to other books supplied. These 
changes have been made with a view of adapting it to the needs of 
those schools where there is a desire to study Physiology from the 
standpoint of a science, but where the school equipment, or the time 
of the teacher, does not permit of individual laboratory practice. 
The following statements, taken from the preface of the Class-Book 
as first published, explain its plan and purpose: 
“ Recognizing the pedagogical principle that to tell a pupil 
what he can easily find out for himself deprives him of an opportu- 
nity to think, while withholding from him what he cannot find out, 
wastes his time in useless endeavor, the aim has been to state in 
clear, concise English what the pupil must be told about the subject. 
This information is intended to serve as a basis for the recitation, 
and is to be supplemented by text-book references, lectures, experi- 
ments, observations, and illustrative drawings. The blank spaces 
are for the recording of experiments, observations, etc., by the pupil, 
so that the completed book may contain his own work as well as the 
subject matter furnished him. 
“ Throughout, the subject has been treated from the standpoint of 
a natural science. Enough has been said and written of late upon vi 
this view of Physiology to make a restatement of argument unneces- 
sary here. Such a treatment, however, necessitates a clear state- 
ment of the principles underlying the science, and a logical arrange- 
ment of the parts, based, if possible, upon some central underlying 
truth. The central idea in the science of Physiology is Nature's 
plan of maintaining life. For this one purpose all the different 
parts of the human organism are made, directly or indirectly, to 
serve. The aim has been to arrange the parts of the subject in such 
an order that each successive step in the study will reveal more and 
more of this plan to the pupil. 
“Further, in teaching a subject as a science, the appeal must be 
made to the pupil’s reasoning powers rather than to his memory, 
and sufficient experimental and observational work must be done to 
furnish clear conceptions—the necessary basis for correct thinking. 
Physiology work should be supplemented by laboratory practice. 
Where this cannot be arranged for, class experiments and observa- 
tions should be furnished by the teacher. The experiments and 
observations given in this book are intended for class purposes. The 
list is suggestive, rather than exhaustive, and contains such as require 
little apparatus.” 
The texts* to which references are made by page numbers, with 
the exception of Stowell’s Essentials of Health ( Missouri’s State Text 
in current use) have an experimental basis, though they differ 
widely in the plan of presenting the subject. F'or the purposes of the 
school room it was thought best to make exhaustive reference to a 
few reliable texts, rather than occasional reference to a larger 
number. 
The necessity of keeping such a book small enough for class 
purposes accounts for the omission of considerable material found 
in books of similar nature. Still, it is believed that the principles 
underlying the science of Physiology have been stated and the method 
suggested for mastering them. 
Warrensburg, Mo., Aug. 30, 1898. 
*Foster and Shore’s Physiology for Beginners, McMillan & Co.; Coltons’ 
Experimental and Descriptive Physiology, D. C. Heath & Co.; and Jenkins’ Ad- 
vanced Bessons in Human Physiology, Indiana School Book Co. TABLE OF CONTENTS. 
Chapter. Page. 
I. General Structure and Functions of the Body . I 
II. The Blood ....... 9 
III. Circulation of the Blood ..... 17 
IV. Lymph and Lymphatics .... 27 
V. The Atmosphere ...... 32 
VI. Respiration ....... 37 
VII. Liberation of Energy in the Body ... 49 
VIII. Foods 55 
IX. Digestion ....... 60 
X. Transfer of P'ood Materials .... 73 
XI. The Abdomen and Its Contents .... 77 viii 
TABLE OF CONTENTS 
Chapter. Page. 
XII. Excretion .... ... 81 
XIII. The Skeleton . . . . . . 93 
XIV. The Muscular System ..... 98 
XV. The Skin .... ... 104 
XVl. General Structure and Function of Nervous Tissue 109 
XVII. Divisions of the Nervous System . . . 114 
XVIII. Work of the Nervous System . . . 122 
XIX. Sound and the Sense of Hearing . . . 131 
XX. Light and the Sense of Sight . . . . 138 
XXL Hygiene of Nervous System .... 147 CHAPTER I. 
General Structure and Function of the Body. 
A Study of Tissues. The first step toward understanding our 
bodies will be to find out what materials or tissues form them. This 
can easily be done by dissecting and examining a portion of the body 
of some animal whose tissues are like our own. 
Observation. Procure the leg of some small animal, such as a cat, rabbit, 
frog, or chicken. On the outside observe the epidermal tissue in the form of cuti- 
cle and hair, claws, scales or feathers, according to the specimen. With a sharp 
knife lay open the skin and observe that it is attached to the parts underneath by 
connective tissue. Next observe the amount and arrangement of the muscular 
tissue. With a blunt instrument separate the muscles by tearing apart the con- 
nective tissue sheaths, and find tough strips of connective tissue (the tendons) 
which attach the muscles to the bones. Find near the central part of the leg some 
white glistening cords (nerves) which form one variety of nervous tissue. At the 
ends of the bones (osseous tissue) find a layer of cartilaginous tissue. The adipose 
or fatty tissue is found immediately beneath the skin and in between the other 
tissues. 
Fill in the following blank spaces with notes taken while observing the 
specimen : 
i. Give the posi- 
tion, kind, and uses of 
epidermal tissue. 
2. Position and ap- 
pearance of adipose 
tissue. 2 
A STUDY OF TISSUES. 
3. Arrangement, 
appearance, use, and 
amount of muscular 
tissue. 
4. Position, ap- 
pearance, kinds, and 
uses of connective tis- 
sue. 
5. Position, ap- 
pearance, and uses of 
osseous tissue. 
6. Position, ap- 
pearance. and uses of 
cartilaginous tissue. 
7. Appearance and 
position of nervous 
tissue. 
What are Tissues? Tissues are the different kinds of material 
which form the body. These are to the body what the wood, stone, 
plaster, and other building materials are to a house. As a house is 
constructed from these different building materials, so the body is 
built up from the tissues. Hence tissues may be called the building 
materials of the body. 
Kinds of Tissues. In the observation of the specimen the following tis- 
sues should be found: 
1. Epidermal tissue (three varieties.) 2. Connective tissue (two varieties.) 
3. Adipose or fatty tissue. 4. Muscular tissue (striated variety.) 5. Osseous 
tissue. 6. Cartilaginous tissue. 7. Nervous tissue (fibrous variety.) PROPERTIES AND USES OF TISSUES. 
3 
The above named tissues form the greater portion of the body. Others less 
abundant but of considerable importance are: 8. Nerve cell tissue. 9. Non-striated 
muscular tissue. 10. Epithelial tissue. 
Properties and Uses of Tissues. Each tissue in the body, like 
each kind of material in a house, is made to serve some definite pur- 
pose. It is able to serve this purpose because of its properties. 
By the properties of a substance are meant its distinguishing qualities or char- 
acteristics. We recognize glass by its hardness, brittleness, and transparency. 
Hardness, brittleness, and transparency are therefore properties of glass. In some 
work on Physics, ascertain the distinction between the general and special proper- 
ties of a substance and find a description of the property of elasticity. 
While each tissue in the body has quite a number of properties 
of minor importance, it also has one or more properties of great im- 
portance in adapting it to some particular purpose in the body. 
Important Properties of Tissues. 1 Of osseous tissue, hardness, 
toughness, and stiffness. 2 Of muscular tissue, contractility. 3. Of nervous 
tissue, irritability. 4. Of cartilaginous tissue, stiffness and elasticity. 5. Of 
connective tissue, toughness andpliability. 6. Of epidermal and epithelial tissues, 
toughness and resistance to the action of external agents.—Note that the proper- 
ties named adapt each tissue to some special purpose in the body. 
General Purposes of Tissues, i. Supporting tissues—those 
which preserve the general form of the body and join the different 
parts together. Name them. 
2. Active tissues—those capable of acting on the other tissues 
either to move or to control them. Name these. 
3. Protective tissues—those which protect the more delicate 
parts of the body. What are they? 
4. Storage tissues—those which store away material for future 
use. There is but one storage tissue of importance in the body. 
What is it? 
Composition of Tissues. The tissues are made up principally 
of minute particles called cells. These are, for the most part, too 
small to be seen with the naked eye. In the body they vary in 
size from 1-4000 to 1-500 of an inch in diameter. They also vary in 
shape and general properties to suit their places in the body. A 
tissue is simply a collection of similar ceils joined together, while the 
properties of a tissue are given to it by its cells. In addition to the 
cells peculiar to a given tissue, there is generally found between the 4 
STRUCTURE OF CELLS. 
cells more or less of a substance without apparent structure. This 
is called intercellular material. 
Observation. Examine with a compound microscope (1) some of the 
scrapings made from the inside of the cheek with a dull knife and (2) some thin 
slices cut from cartilage with a razor. 
Plant cells may be seen by examining thin slices of elder pith, potato, and 
the stems of growing plants. Make drawings of the cells thus observed. 
The Parts of a Typical Cell are known as the cell wall, the pro- 
toplasm, and the nucleus. 
Draw a typical cell, 
naming the parts. 
Draw different forms 
of cells. See S., 12. 
Properties and Uses of Parts. The cell wall is supposed to 
be formed by the hardening of the outside of the protoplasm. It 
covers and protects the more delicate parts of the cell. T\\z proto- 
plasm resembles in appearance the white of a raw egg. It is capable 
of slight motion and is sensitive. It is able to absorb and appropri- 
ate liquid food, and to grow. It is the living, active portion of- the 
cell and is the one part which is absolutely essential. The other 
parts may be absent from the cell but never the protoplasm. Through 
the protoplasm of many cells is scattered more or less of granular 
matter, the function of which is unknown. The nucleus differs from 
the protoplasm in being denser and clearer. Its function is not fully 
understood, but it is supposed to give the cell the power of forming 
new cells. Cells from which the nuclei are absent are unable to form 
new ones. 
Conditions Surrounding1 the Cells. Although the cells are 
packed very closely together in the tissues, there is still room for a CELL ACTIVITIES. 
5 
quiet, colorless liquid to find its way freely among them. This liquid 
is called the lymph. It contains such food materials as the cells need 
for their growth and repair which it exchanges for materials thrown 
off from the cells as waste. The lymph in turn is supplied with 
necessary materials and relieved of waste by a second liquid, the 
blood, which flows through a system of tubes which penetrate the tis- 
sues in all directions. 
Activities Within the Cells. In order that the cell may live, 
grow, and carry on its work in the tissue, it is necessary that certain 
activities be kept up within it. From the surrounding liquids the 
cell absorbs an active element called oxygen and a number of sub- 
stances dissolved in water, making a kind of liquid food. Within 
the cell the oxygen unites with certain portions of the liquid food and 
with the protoplasm of the cell. As a result of these unions, heat 
and force are liberated, waste matter formed, and new material pro- 
duced. The heat keeps up the necessary warmth of the cell; the 
force enables it to carry on its work; the new material is added to 
the protoplasm; and the waste matter flows out into the lymph. 
These activities are therefore of four distinct kinds: 
i. Absorption, whereby new materials are taken into the cell 
from the outside. 2. Chemical change, caused by the uniting of 
oxygen with substances in the cell and resulting in the production of 
heat, new material, and waste material. 3. Addition of the new 
material to the protoplasm of the cell, causing it to grow. 4. Ex- 
cretion, or the throwing off of waste material. 
Formation of New Cells. In all the tissues there occurs, at 
some stage of the growth of the body, the process of cell formation, 
or reproduction. In a few tissues, the epidermal for example, this 
process takes place continuously during life in order to supply new 
cells for replacing old and worn out ones. New cells are always 
formed from old ones. The most common plan by which this is ac- 
complished is called cell division. By this plan a single cell will, 
after attaining its growth, separate into two or more new cells. The 
new cells thus formed begin at once to grow, absorbing liquid food 
and oxygen and may, upon attaining their full size, divide to form 
other new cells. 6 
PLAN OF THE BODY. 
1. 
2. 
Make drawings to show different stages in cell division. 
Importance Of the Cells. A knowledge of the structure, 
growth, and work of cells is the first step toward a clear understand- 
ing of the body. The body grows by the growth and reproduction 
of its cells. All of its work is done by them. It is nourished and 
kept alive by nourishing and keeping alive the cells which compose 
it. The cell is thus the unit of structure and of function. 
Organs and Systems. Any part of the body which has some 
special work to perform is called an organ. The eye is the organ of 
sight.'' The hand is an organ for grasping. 
Name other examples. What different 
tissues are found in the hand? What pur- 
pose does each tissue in the hand serve? 
A collection of organs working to 
accomplish the same end or purpose in the 
body is called a system. The heart, art- 
eries, veins, and capillaries, for example, 
have for their common purpose the circula- 
tion of blood and together they form the 
circulatory system. Name the organs 
which form the digestive system. 
The Plan of the Body. Viewed ex- 
ternally,the body is seen to be made 
up of a central portion, the trunk, to 
which is attached the head, the upper ex- 
tremities (arms and hands), and lower ex- 
tremities (legs and feet). 
The internal structure is adapted in 
Various ways to the peculiar needs of the 
body. The plan here provides for: (i.) 
A framework or skeleton to which the other 
Complete the sketch, 
showing and naming 
the important cavities 
of the body. THE MAINTENANCE OF LIFE. 
7 
parts are attached. (2 ) The motion of the body as a whole and 
of its parts. (3.) Cavities for holding important organs. (4.) A 
continuous supply of liquid food and oxygen and the removal of 
waste material from all parts of the body. (5.) A supply of heat 
for warming the body and of force for carrying on its work. (6.) 
The intelligent oversight and general management of the body and 
the control of each part (7.) Protection of the body as a whole 
and of its parts. 
The Maintenance of Life. Notwithstanding the great variety 
of work carried on by the different portions of the body, all parts of 
it must be regarded as working for one purpose, which is the main- 
tenance of life. In one sense the body may be regarded as a 
mechanism whose purpose is the maintenance of life. The relation 
of the different organs and systems to each other, and to the body, as 
a whole, is therefore such that each is made to contribute something 
directly or indirectly toward this end. 
While the nature of life is, as yet, a great mystery, the plan of 
maintaining it in the bodies of animals is fairly well understood. 
Physiologically speaking, the life of the body may be regarded as the 
sum of the lives of the cells which compose it. Hence all effort 
toward maintaining life must be directed toward the cells. 
Anatomy, Physiology, and Hygiene are terms which desig- 
nate the different standpoints from which the body may be studied. 
Anatomy treats of the construction of the body—the parts which 
compose it, what they are like, and where they are located. It is of 
two kinds, known as Gross Anatomy and Histology. Gross Anat- 
omy is the study of rough, coarse structures—those parts which can 
be seen readily by the naked eye. Histology is the study of the 
minute structures—those parts which are too small to be seen by the 
naked eye and which can be known only by the use of the micro- 
scope. 
Physiology treats of the function or use of the different parts of 
the body, the work which these parts do, and how they do it, and 
the relation they sustain to each other in the maintenance of life. 
Hygiene treats of the ways of taking care of the body and keep- 8 
PRACTICAL QUESTIONS. 
ing its parts in good working order. The conditions which must be 
observed in doing this are termed the “laws of health.’’ All the 
laws of health may be summed up in one fundamental law, which is 
this: 
Habits of living must be in harmony with the plan of the body. 
References. * On cells, S., 11-16; J., 29-34; C., 6. On tissues, J., 23-27; F. 
and S., 1. On systems, J. 28. 
» 
Practical Questions. 1. Compare the tissues of the body to the build- 
ing materials of a house. 2. Show that the use made of building materials in 
both house and body must depend upon their properties. 3. If a tissue be com- 
pared to a brick wall, to what do the separate bricks correspond? To what, the 
mortar between the bricks ? 4. What relation do cells, tissues, organs, and sys- 
tems sustain to each other in the construction of the body? 5. Compare the 
conditions surrounding a one-celled animal living in water to the conditions sur- 
rounding the cells within a tissue. 6. Describe the different activities taking 
place within the cell. 7. What results are brought about by the uniting of oxy- 
gen with material in the cells ? 8. Why is protoplasm regarded as the most 
important part of the cell? 9. Define and illustrate general use of the terms, 
structure, function, composition, and property. 
*In references the initial of the author’s name only is given. J. indicates Jenkins’ 
Advanced Lessons in Human Physiology; S. Stowell’s Essentials of Health; C. Colton’s Ex- 
perimental and Descriptive Physiology; and F. and S. Foster and Shore’s Physiology for 
Beginners. CHAPTER II. 
The Blood. 
Two Liquids of similar nature are found in the body, known as 
the blood, and the lymph. The former is kept moving rapidly 
through a system of tubes called the blood vessels, while the latter is 
allowed to lie in minute spaces in the intercellular material and to 
flow slowly through a second system of tubes called the lymphatics. 
Both liquids minister to the wants of the cells. The study of the 
lymph will be deferred to a later period. 
A Study of Blood. 
Secure through the assistance of a butcher (See Appendix) a bottle of 
blood which has been allowed to coagulate without shaking or stirring; a bottle 
of defibrinated blood; and a bottle of blood which has been kept from coagulating 
by mixing with Epsom salts. 
Experiment. Let some of the defibrinated blood flow (not fall) on the 
surface of water in a glass vessel. Does it remain on the surface or sink to the bot- 
tom cf the vessel ? 
Result. 
Inference. 
Experiment. Place a small amount of the dark, defibrinated blood in a 
large test tube or bottle and thin it by adding an equal amount of water. Then 
place the hand over the mouth of the tube and shake until the blood is thoroughly 
mixed with the oxygen of the air in the vessel. Compare with a portion of the 
blood not mixed with oxygen and notice any difference in color. IO 
PHYSICAL PROPERTIES OF BLOOD. 
Result. 
Inference. 
Experiment in Coagulation. Fill four tumblers each two-thirds full of 
water. At intervals of one-half hour pour into each, and, thoroughly mix with the 
water, two tablespoonfuls of the blood containing the Epsom salts. The water 
dilutes the salts so that coagulation is no longer prevented. Jar the vessels occa- 
sionally as coagulation proceeds. After blood has been added to the tumbler make 
a comparative study of all. Sketch the tumblers showing the appearance of the 
blood in the different stages of coagulation. 
1234 
Observation. Examine the coagulated blood in the bottle obtained from 
the butcher. Observe the dark central mass 
(the clot') surrounded by a clear liquid (the 
serum). Sketch the vessel and its contents, 
showing and naming the two parts into which 
the blood separates by coagulation. 
Collection of Fibrin. Place the clot from 
one of the tumblers in which blood was al- 
lowed to coagulate into a large vessel of 
water. Thoroughly wash, adding fresh water 
until a clear, white, stringy solid remains. 
This substance is called fibrin. 
Physical Properties of Blood. 
The foregoing and other experiments 
show the blood to be heavier and denser than water; to have 
a faint odor and a slightly sweetish taste; to have a bright red 
color when it contains oxygen and a dark red color when oxygen is 
absent; and, when exposed to certain conditions, to undergo a 
change called coagulation. 
The cause of coagulation is the fibrin. This substance does not 
exist in blood in its natural condition, but forms as coagulation takes 
place. It is formed from liquid substances, which are always present COMPOSITION OF BLOOD. 
11 
in the blood, known as fibrin factors. Coagulation is therefore 
brought about by the changing of fibrin factors to fibrin. This gen- 
erally occurs on the exposure of the blood to some unnatural condi- 
tion, such as its escape from the blood vessels. 
The Purpose of Coagulation is to check the flow of blood 
from wounds. Clots forming in the mouths of small blood vessels, 
when they are cut or broken, close them up and stop the flow of 
blood which would otherwise go on indefinitely. 
Composition of the Blood. The blood is made up of two dis- 
tinct portions, the plasma and the corpuscles. The plasma is a 
liquid. The corpuscles are small, round bodies, which float in the 
plasma. The corpuscles are of two kinds, the red and the white. 
Observation. Examine with a compound microscope a small drop of 
human blood. (See Appendix.) This should be diluted with a little water or saliva, 
else the corpuscles will be too numerous to be dis- 
tinguishable. Generally the only corpuscles to be 
seen are the red ones. Sometimes, however, the 
white ones may be found. They are easily distin- 
guished from the red ones by their greater size and the 
peculiar wTay that light shines through them. On ac- 
count of the small amount of coloring matter in a red 
corpuscle it does not appear red under the microscope. 
Make a sketch of the corpuscles as they appear 
under the microscope. 
Structure and Function of Red Corpuscles. The red corpus- 
cle may be regarded as a single cell, though it has no nucleus and 
is supposed to be without a cell wall. It consists of a little mass of 
elastic and somewhat spongy protoplasm called the stroma which is 
saturated with a reddish coloring matter called haemoglobin. 
In shape the red corpuscles are thin, circular disks with concave 
sides. In size they are about 1-3300 of an inch through the long 
diameter and 1-6500 of an inch through the short diameter. They 
are exceedingly numerous, there being estimated to be as many as 
five million in a small drop of healthy blood. In poor health, 
however, the number is greatly diminished. 
The function of the red corpuscles is to act as oxygen carriers. 
They absorb oxygen from the air at the lungs and give it up to the 12 
BLOOD CORPUSCLES. 
different tissues of the body. They owe this power entirely to the 
presence of the 
Haemoglobin. This substance has the remarkable property of 
forming a weak chemical union with oxygen and, after being united 
with it for awhile, of giving it up to tissues which need oxygen. It 
forms about 9-10 of the solid portion of the red corpuscles and gives 
them their color. The stroma seems to be a contrivance for holding 
the haemoglobin. 
Experiment. Procure a strong magnet, a weak magnet (a knife blade 
magnetized on strong magnet will serve), and some iron filings. Lay the strong 
magnet on a table a foot or two from a small pile of the iron filings. Pass 
the weak magnet first to the filings and then near the strong magnet, noting the 
effect. Repeat until convinced that all the filings may be transferred to the large 
magnet by the weak magnet acting as a carrier. 
Apply to the action of the haemoglobin of the red corpuscle. 
Origin of Red Corpuscles. As the red corpuscles are con- 
stantly being destroyed in various ways, new ones have to be regu- 
larly supplied from some source to take their place. Their origin is 
not definitely known, though the best authorities now agree that a 
portion of them, at least, is formed in the red marrow of the bones. 
There is also evidence to the effect that some of them may be formed 
in the spleen. 
The White Corpuscles are irregular in shape and about three 
times as large as the red ones. They are much less numerous, there 
being in healthy blood only one white corpuscle for about every 300 
red corpuscles. They are, for that reason, not easily observed in the 
blood. They may be obtained in large quantities from lymphatic 
glands. 
Observation. Obtain from a butcher shop a 
small piece of the neck sweetbread of a calf. Press 
it between the fingers to squeeze out a whitish, 
semi-liquid substance. Dilute this with w'ater on a 
glass slide and examine with compound microscope. 
Numerous white corpuscles, of different kinds, will 
be found. Make sketches of them. If a little dilute 
acetic acid be allowed to flow under the coverglass, 
the corpuscles will be rendered more transparent 
and the nuclei will become more distinct. 
Sketch of white corpuscles. THE PLASMA. 
13 
The white corpuscles are endowed to some extent with the 
power of motion and are able to change their shape. For these 
reasons they are migratory in the body, be- 
ing able to penetrate the thin walls of small 
blood vessels and to pass in between the 
cells. They collect in large numbers at 
parts of the body that may be inflamed and 
form a considerable portion of the white 
matter found in sores, called pus. They orig- 
inate in lymphatic glands. 
The Function of White Corpuscles is 
not understood. Since there are different 
kinds of them in the blood, it is supposed 
that they serve different purposes. The two following uses are as- 
cribed to them by most physiologists: 
1. They help to keep the blood pure. They do this by de- 
stroying minute living bodies known as bacteria or disease germs 
which find their way into the blood. 
2. They furnish a kind of ferment which causes the fibrin fac- 
tors to change into fibrin in the coagulation of the blood. The fer- 
ment is given up on account of the injury which the corpuscles sustain 
by the escape of blood from the body. 
The Plasma is the liquid portion of the blood. It consists of 
water with a great number of different substances dissolved in it and 
is prepared for the blood by the digestive organs. It is a very com- 
plex liquid. The following important constituents may be named: 
i. The fibrin factors which, by changing into fibrin, cause the 
blood to coagulate. 2. Substances which serve as food for the cells. 
Chief among these are serum albumen, fatty substances, sugary sub- 
stances, and salts. 3. Impurities from the cells, most important of 
which, are carbon dioxid and urea. 
The serum is that portion of the plasma which remains, after 
the separation of the fibrin factors. When does this separation 
occuri 
Sketch, showing the 
changes which a single 
white corpuscle may un- 
dergo in a few minutes. 14 
CHANGES IN THE BLOOD. 
Functions of the Plasma. The plasma serves three main pur- 
poses : i. It floats the corpuscles through the different blood ves- 
sels. 2. It supplies liquid food to the cells. 3. It serves as a 
carrier of impurities from the cells to the organs of excretion. 
Changes in the Blood. In performing its work in the body, 
the blood must of necessity undergo rapid and continuous change. 
The following table indicates some of these changes and shows in a 
general way how they are accomplished: 
Supplied by. 
Removed by. 
Food substances. 
The Digestive Organs. 
The Cells. 
Oxygen. 
The Dungs. 
The Cells. 
Water. 
The'Digestive Organs. 
The Organs of Excretion. 
The Cells. 
The Cells. 
Impurities. 
The Cells. 
The Organs of Excretion. 
In health there is such an adequate control of the supply of ma- 
terials to the blood and of the removal of materials from the blood 
that its general composition and density do not change from time to 
time. An excess of certain impurities prompts a greater activity of 
the organs of excretion. If the blood becomes too dense, a feeling 
of thirst prompts one to drink water to thin the blood. Likewise a 
scarcity of food material causes a feeling of hunger, and a lack of HYGIENE OF THE BLOOD. 
15 
oxygen in the blood induces a desire for a deep breath of air. In 
time of fasting the blood obtains food materials from the tissues. 
Even the quantity of blood, which is about 1-13 of the entire weight 
of the body, remains nearly constant during the varying conditions 
of food and water supply and activity of the body. 
Hygiene of the Blood. The condition of the blood is a most 
important factor in the general health of the body. An adequate 
supply of healthy blood is not only a safeguard against disease, but is 
a most important agent in the recovery of the body from the effects 
of disease. Moreover, the condition of the blood is largely depend- 
ent on one’s habits of living. From a health standpoint, the most 
important constituents of the blood are the red corpuscles. These 
are generally sufficient in number and vigor in the blood of those who 
take plenty of physical exercise, expose the body freely to outdoor 
air and sunlight, and indulge in plenty of sleep. On the other hand 
they are always deficient in quantity and of inferior quality in those 
who pursue the opposite course. Impurities frequently find their 
way into the blood through the digestive organs. One should eat 
wholesome, well-cooked food, drink pure water, and limit the quan- 
tity of his food to what he can properly digest. The natural puri- 
fiers of the blood are the organs of excretion. The skin is one of 
these and its power to throw off impurities is proportional to its 
cleanliness, and the activity of the circulation of the blood through it 
Alcoholic drinks have an injurious effect on the blood and interfere 
with its work in the body. 
Patent medicines for purifying the blood, as a rule, do more harm than good. 
One may safely rely on wholesome food, pure water, outdoor exercise, sunlight, 
plenty of sleep, and a clean skin for keeping his blood in a good condition. When 
these natural remedies fail, let him consult a physician. 
References. On description ofblood, S., 93-99; J., 81-88; C., 94-98; F. and S., 
26-31. On blood of lower animals, S., 100-101; J., 87; C., 51. On effect of alcohol on 
the blood, S , 102; C., 94. 
Practical Questions, i. State the necessity for a liquid like the blood 
in the body. 2. Show how its physical properties and composition adapt it to its 
different purposes. 3. Compare blood and water with reference to weight, density, 
complexity of composition, color, and odor. 4. Show how the blood, though 
a liquid constantly changing, is kept about the same in quantity, density, 
and composition. 5. Compare the red and white corpuscles with reference to 16 
PRACTICAL QUESTIONS. 
size, shape, number, origin, and function. 6. After coagulation, what portions of 
the blood are found in the clot? What portions in the serum? 7. What purposes 
are served by the water in the blood? 8. As a rule the blood of small animals co- 
agulates more quickly than that of large animals. What is the necessity for this 
difference? 9. Account for the change of blood from a dark red to a light red 
color as it flows through the lungs. 10. If haemoglobin had a strong attraction 
for oxygen could it serve as a carrier of oxygen in the blood? Why? n. What 
habits of living favor the development of red corpuscles? 12. Why will keeping 
the skin clean and active improve the quality of one’s blood? CHAPTER III. 
Circulation of the Blood. 
The blood is a moving liquid. Its regular movement through 
the body—starting at one place, flowing out to the different parts 
and returning to that place—is termed its circulation. 
The Discovery of the Circulation of the Blood was made in 1616 by 
an English physician named Harvey. In 1619 he taught it in his public lectures 
and in 1628 published the proofs. No single discovery with reference to the human 
body has proved of so great importance. A knowledge of the nature and purpose of 
the circulation was the necessary first step in understanding the plan of the body 
and the method of maintaining life. Hence, Physiology as a science dates from the 
time of Harvey’s discovery. 
The Necessity for the Circulation lies in the fact that the 
blood acts as a carrier for the cells. Oxygen from the lungs, and 
liquid food from the digestive organs, reach the cells through the 
blood. Likewise, the blood must convey the impurities from the 
cells to the organs of excretion. To accomplish these results, the 
blood must move. So great is the necessity for the circulation that 
its stoppage, for only a brief interval of time, results in death. 
The Organs of Circulation consist of a central force pump con- 
nected with a system of tubes which penetrate to all parts of the body. 
The force pump is called the heart, the tubes are called blood 
vessels. The blood vessels are of three kinds known as the arteries, 
the veins, and the capillaries. 
The different organs of circulation are so connected that the 
blood flows through them in regular order. From the heart it flows 18 
DISSECTION OF HEART. 
into the arteries; from the arteries into the capillaries; from the cap- 
illaries into the veins; and from the veins back into the heart. 
Observation on the Heart. Procure, by the assistance of a butcher, the 
heart of a sheep, calf, or hog. To insure the specimen against mutilation, the 
lungs and diaphragm must be left attached to the heart. In studying the different 
parts, good results will be obtained by observing the following order: 
1. Observe the connection of the heart to the lungs, diaphragm, and large 
blood vessels. Inflate the lungs and observe the position of the heart with refer- 
ence to them. 
2. Examine the sack surrounding the heart. It is called the pericardium.. 
Pierce its lower portion and collect the pericardial fluid. Increase the opening 
thus made until it is large enough to slip the heart out through it. Slide back the 
pericardium until its attachment to the large blood vessels above the heart is 
found? Observe that a thin layer of it continues down from this attachment, 
making the outer covering of the heart. 
3. Trace out for a short distance and study the veins and arteries connected 
with the heart. The arteries are to be distinguished by their thick walls. Care- 
fully remove and save for later study a section each of an artery and. vein, three 
or four inches in length. The heart may now be severed from the lungs by 
cutting the large blood vessels, care being taken to leave a considerable length of 
each one attached to the heart. 
4. Observe the outer portion of heart. The thick lower portion contains 
the cavities called ventricles; the thin upper ear-shaped portions are the auricles. 
The thicker and denser side lies toward the left of the animal’s body and is called 
the left side of the heart; the other is the right side. Locate the right auricle and 
the right ventricle; the left auricle and the left ventricle. 
5. Make an incision into the right auricle large enough to see the inner por- 
tion. Observe the muscular arrangement and inner surface. At the entrance into 
right ventricle find the tricuspid valve. 
6. Lay open the right ventricle. Study the tricuspid valve from the under 
side, noting its parts and the slender strips of connective tissue which attach the 
edges of the valves to muscular pillars in the ventricle. Study muscular arrange- 
ment and lining of the ventricle. Compare thickness of walls with those of right 
auricle. Find the opening into pulmonary artery. 
7. Split open this artery to where it enters the ventricle and find the right 
semi-lunar valve. Of how many parts is it composed? 
8. In like manner dissect the left side of heart. Compare the auricle, 
ventricle, and valves, on this side, with similar parts on the right side of heart. 
9. Separate the aorta from the other blood vessels and cut it entirely free 
from the heart, care being taken to leave enough of the heart attached to the 
artery to insure the semi-lunar valves being left in good condition. After closing 
up the openings in the sides of the aorta, pour water into the small end and observe 
the closing of the semi-lunar valve. Repeat the experiment until the action of the 
valve is understood. Sketch the artery showing the valve in a closed condition. NOTES ON TIIE HEART. 
19 
Observations on the Heart of a 
Position with refer- 
ence to lungs. 
Attachments. 
Description of peri- 
cardium. 
Size, shape, and col- 
or of heart. 
Blood vessels at- 
tached to the heart. 
Inner surface and 
lining. 
Cavities; position 
and names. 
Valves; location, 
names, divisions. 
Walls ; comparison 
as to thickness. 
Sketch of aorta, 
showing left semi- 
lunar valve. 20 
WORK OF THE HEART. 
The Human Heart does not differ materially in structure from 
the heart which has been studied. It is about the size of the clinched 
fist of the owner, and is situ- 
ated very near the center of 
the thoracic cavity. It is pear- 
shaped and is so placed that 
the small end extends down- 
ward and to the left. The 
student should consult some 
text on Physiology for infor- 
mation on the structure of 
the heart not revealed by the 
dissection. Make a sectional 
drawing of heart, showing 
cavities, valves, and large 
blood vessels connected with 
Complete this sectional view of heart. jt Indicate by arrows the 
passage of blood through the two sides of the heart. 
How the Heart Does Its Work. The heart is a hollow muscle 
and does its work by contracting and relaxing. When it contracts 
its cavities" are closed and the blood is forced from them. When it 
relaxes the cavities open and the blood flows in to refill them. 
Valves prevent the backward flow of blood. How? The heart’s 
action may be readily illustrated in the following manner: 
Procure a syringe bulb with an opening in each 
end. Attach a rubber tube to each end of bulb, letting 
the tubes reach into two tumblers containing water. 
By alternately compressing and releasing the bulb, 
water is pumped from one vessel into the other. The 
bulb may be taken to represent one of the ventricles. 
What action of the ventricle is represented by com- 
pressing the bulb ? What by releasing the pressure ? 
By making the proper connections with a greater 
length of tubing and filling the whole with water the 
entire circulation may be represented. Make a sketch 
showing the arrangement of the valves in the syringe 
bulb. 
Section of syringe bulb 
showing valves. ARTERIES AND VEINS. 
21 
Arteries and Veins. These are cylindrical tubes, connected 
with the heart, through which the blood passes. The arteries re- 
ceive the blood from the ventricles and permit it to pass through 
them and their branches to capillaries in all parts of the body. In 
its return to the heart from the capillaries the blood passes through 
the veins. 
Arteries and Veins Compared. 
Observation. Examine carefully the artery and vein saved from the dis- 
section of the heart. Compare with reference to thickness of walls, elasticity, and 
toughness. Which stand open without pressure from within? Separate each into 
its layers or coats. 
Both arteries and veins have three coats. The inner coat con- 
sists of flat, thin cells, united at their edges, and is called the en- 
dothelium. It is continuous with the lining membrane of the heart. 
The middle coat consists mainly of non-striated muscular tissue. In 
the veins it is very thin. The otiter coat is connective tissue. In 
arteries it is thick and highly elastic. 
Other differences between arteries and veins are as follows: 1. 
Veins contain valves; arteries do not. .2. Arteries carry blood rich 
in oxygen toward the tissues; veins carry blood deficient in oxygen 
from the tissues. (Pulmonary arteries and veins are exceptions.) 3. 
In the arteries the blood is under greater pressure and moves faster 
than in the veins. 4. The veins taken together hold more blood 
than the arteries. 
Advantage of Elasticity of Arteries, i. To prevent bursting 
of arteries when an excess of blood is emptied into them from the 
ventricles. 2. To keep the blood under pressure while the ventri- 
cles are relaxing.—By the contraction of the ventricles the arteries 
are filled over full and have to swell out to make room for the excess 
of blood. While the ventricles are relaxing, the arteries exert their 
elastic force to keep the blood flowing steadily into the capillaries. 
Experiment. Close up one end of a piece of artery six or eight inches long 
(the aorta of a calf or sheep) and fit a stopper, having a pointed glass tube through 
its center, in the other end. With a force pump or syringe bulb force water into 
the artery. Observe (i) that the artery swells and may be filled over full and (2) 
that water is forced out through the little opening in the artery when there is 
no pressure from the pump. 22 
IMPORTANT ARTERIES. 
The Pulse, felt by placing the finger over an artery near the 
surface of the body, Is due to the swelling of the elastic artery at each 
contraction of the left ventricle. 
The Purpose of Valves in the Veins is to enable the contrac- 
tion of muscles over the body to assist in propelling the blood. When 
muscles contract they press against the sides of the veins and tend to 
empty them. Since the valves open in the direction of the flow of 
the blood, they are closed by any backward motion. The force of mus- 
cular contraction is thus made to push the blood forward. 
Observation. Exercise the arm a few minutes to increase the circulation. 
With the finger stroke one of the veins upward toward the shoulder. Much of the 
blood can be forced out of it. Now stroke the vein toward the hand - The blood is 
not forced backward but the vein swells instead, the swelling being greatest at one 
or two places resembling “knots.” These knots mark the position of valves which 
prevent the return of blood to the hand. 
In structure the valves in the veins are like the semi-lunar valves 
of the heart. They are formed by a folding of the inner coat of the 
vein. 
Important Arteries. The two main arteries are the pulmonary 
and the aorta. The first receives blood from the right ventricle and 
through its divisions, distributes it to all parts of the lungs. The 
second by its branches distributes the blood through the entire body. 
To obtain a practical knowledge of the arterial system, the aorta and 
its branches should be traced out in some small animal, as a cat or 
rabbit. To secure the best results, the arteries should be injected 
with coloring matter. (See Appendix.) The following description will 
serve as a guide to the main arteries: 
The aorta connects with the left ventricle, leaving the heart at its upper por- 
tion. From here it passes over as an arch and descends nearly in front of the spinal 
column. It passes through the diaphram and down to the lower portion of 
the abdomen, where it divides. The portion in the thorax is called the thoracic 
aorta; that in the abdomen, the abdominal aorta. 
The first branch to leave the aorta consists of two parts which go to the heart, 
called the coronary arteries. These leave just above the semi-lunar valves. 
The second leaves at the right upper part of the arch and is called the innom- 
inate artery. It is very short, and divides into the right commo7i carotid and the 
right subclavian artery. The right subclavian artery passes into the right arm. 
In the arm pit it is called the axillary, and in the arm, the brachial artery. In 
the forearm it divides into the ulnar and radial arteries, which lie along the bones THE AORTA AND ITS BRANCHES. 
23 
of the same name. These unite in the palm of the hand, forming the palmar 
arch. The right common carotid ascends the right side of the neck and divides in- 
to the internal carotid, supplying the right side of the brain, and the external 
carotid supplying the right side of the 
face and outer right side of the skull. 
The third branch leaves the aorta near 
the top of the arch and is called the left 
common carotid. It branches in an ex- 
actly similar waj' to the right common 
carotid. 
The fourth branch leaves at the left 
upper portion of the arch and is called 
the left subclavian artery. It passes to 
the left arm and forms divisions corres- 
ponding to those of the right subclavian 
artery. 
Other branches from the thoracic aorta 
are the intercostal arteries. One follows 
each rib, running in a groove on the under 
side. 
The branches from the abdominal aorta, 
of importance are: The phrenic, going 
to the diaphragm; the coelic axis which 
divides at once into the hepatic (to the 
liver), the gastric (to the stomach), and 
the splenic (to the spleen); the superior 
and inferior mesenteric going to the in- 
testines; and the renal arteries going to 
the kidneys. 
The two divisions of the lower end of 
the aorta are called the right and left com- 
mon iliac arteries. Each of these divides, 
first into an internal and an external 
branch. The internal goes to the organs 
of the pelvic region, while the external 
(the larger) passes into the leg. It extends 
down by the side of the femur bone where 
it is called the femoral, and back of the 
knee where it is the popliteal artery. 
Below the knee it divides into the anterior and posterior tibeal arteries and 
these unite in the foot in an arch similar to the palmar arch. 
All the arteries named divide and subdivide until their minute portions reach 
all parts of the body. Trace in the cut the general course of the aorta and its 
branches through the body. 
Important Veins. The large veins lie alongside of the large arter- 
ies and have corresponding names. Those from the arms, head, and 
Sketch an outline of the aorta 
and its branches. 24 
THE CAPILLARIES. 
upper part of the trunk unite to form the descending vena cava which 
connects with the right auricle from above. The veins from the 
lower extremities, viscera, and lower part of the trunk unite to form 
the ascending vena cava which connects with the right auricle from 
below. The pulmonary veins (four in number) and their branches 
pass the blood from the capillaries of the lungs to the left auricle. 
The portal vein, the large vein of the abdomen, receives blood from 
stomach and intestines and conveys it to the liver. 
The Capillaries consist of a network of very fine blood vessels 
which connect the terminations of the smallest arteries with the be- 
ginning of the smallest veins. With a few exceptions, they penetrate 
and permeate all parts of the body. They differ from both arteries 
and veins in being very small and in having very thin walls. Their 
only coat consists of a very thin layer of endothelial cells placed edge 
to edge. 
Observation. Study with a compound microscope the circulation of 
blood through the capillaries in the web of a frog’s foot. For an extended obser- 
vation it is best to remove the frog’s brain. (See Appen- 
dix. ) The frog may be attached to a thin board which 
has an opening in one end over which the web of the 
foot may be stretched. Threads should extend from 
two of the toes to pins driven in the board to secure 
the necessary tension ot the web. The appearance is 
truly wonderful, but allowance must be made for the 
fact that the motion of the blood is also magnified and 
that it really moves much more slowly than it appears 
to move under the microscope. 
The Function of the Capillaries is 
to distribute the blood among the tissues. On capilJaries in 
account of the extent to which they penetrate 
the tissues, the blood is brought very near the individual cells. Then 
the thinness of their walls permits of an easy exchange of materials 
between the blood within the capillaries and liquids on the outside. 
The Circulation Traced. The blood passes through the 
circulatory organs in the following order: Right auricle, tricuspid 
valve, right ventricle, right semi-lunar valve, pulmonary artery and 
its branches, capillaries of lungs, pulmonary veins, left auricle, biscus- 
pid valve, left ventricle, left semi-lunar valve, aorta and branches, HYGIENE OE THE CIRCULATION. 
25 
systemic capillaries, veins, vena cava ascending and descending, and 
then again into right auricle. At the lungs the blood gives up carbon 
dioxid and receives oxygen. In the 
systemic capillaries it gives up its 
oxygen and receives carbon dioxid 
and other impurities. 
The circulation of the blood through 
the lungs is called the pulmonary 
circulation; through the body, the 
systemic; through the liver, the 
portal; through the kidneys, the re- 
nal; and through the heart itself, the 
coronary circulation. 
Health Suggestions. The vigor 
of the circulatory system is largely 
dependent upon one’s habits of living. 
As a rule those conditions which are 
favorable to the general health are 
beneficial to the organs of circu- 
lation Regular physical exercise 
is one of these conditions and 
its importance with reference to the 
circulation cannot be overestimated. 
The presence of valves in the veins 
shows that part of the force to move 
the blood must come from the con- 
traction of muscles surrounding the 
veins. It is also known that moderate 
physical exercise aids indirectly in 
keeping up the vigor of the heart’s 
action. On the other hand, violent 
and prolonged physical exertion over- 
taxes the heart and endangers the 
walls of the blood vessels. 
The organs of circulation are under the control of the nervous 
system. Hence it frequently happens that a weakness in this system 
results in a disturbance of the circulation. Many of the so-called 
Construct a diagram showing the 
course of the blood through the or- 
gans of circulation. 26 
PRACTICAL QUESTIONS. 
“heart troubles” are due to an overtaxed or weakened condition of 
the nervous system and disappear when it recovers its normal con- 
dition. 
Stimulants and narcotics, mainly through their effect on the 
nervous system interfere with the healthy action of circulatory 
organs. They should be carefully avoided. 
Tight fitting clothing, on any part of the body, interferes with 
the free circulation and for this reason should not be worn. 
The blood should circulate uniformly through the different parts 
of the body. A continued excess of blood in certain parts, especially 
the brain, may lead to serious results. Congestion in any part is 
generally relieved by activity of other parts of the body or by irritat- 
ing them in some way. We have an example of this in the relief of 
blood pressure on the brain which follows placing the feet in hot 
water. 
Suggested Topies for Further Study, i. Quantity of work 
performed by the heart. 2. Sounds of the heart. 3. Effect of 
bodily exercise on the activity of the heart. — Count the number of 
pulsations per minute (a) when lying down, (b) when in a sitting 
posture, (c) when standing, (d) after walking, and (e) after running. 
4. Circulatory systems of other animals. Compare systems of the 
insect, fish, reptile, and warm-blooded animal. 5. Effect of alco- 
hol and tobacco on the organs of circulation. 6. Checking the 
flow of blood from wounded arteries and veins. 
References. On structure of heart, S., 103-109; F. and S., 78-86; J., 94-95. 
On amount of work done by the heart, S., no, J , 107. On structure of blood ves- 
sels, C., 75-78; S., ii2-ii4;J., 90-93; F. andS., 95-100. On effect of muscular contrac- 
tion on circulation, S., 117; C., 83, 84. How the heart does its work, C., 72-75; F. and 
S., 87-90. Effect of alcohol on the circulation, S., 118-121. Effect of tobacco on the 
heart, S., 122. 
Practical Questions, i. Of what special value to science was the dis- 
covery of the circulation? 2. State the necessity for a circulating liquid in the 
body. 3. Show how the heart does its work. 4. Of what use are the valves in 
the heart? In the veins? 5. State the necessity for the difference in structure 
between the right and left ventricles. 6. Of what advantage is the elasticity of 
the arteries? 7. How is blood forced from the capillaries back to the heart? 8. 
Show how the heart is able to rest about six hours out of every twenty-four. 9. 
What is the special work of the capillaries? 10. Why should severe mental or 
physical labor be avoided fora time after taking a full meal? 11. Trace the blood 
through a complete circulation, beginning with the left auricle. CHAPTER IV. 
Lymph and the Lymphatics. 
Necessity of the Lymph. The blood, it will be remembered, 
moves everywhere through the body in a system of closed tubes. It 
does not come in direct contact with any of the cells of the body ex- 
cept those which float in it and those which line the interior of the 
blood vessels. There is need of a quiet liquid between the blood and 
the cells to convey materials from one to the 
other. The lymph occupies this position 
and does this work. Make a sketch showing 
the relative positions occupied by the blood, 
the lymph, and the cells. 
The Chief Source of the Lymph is the 
plasma of the blood. As before described, 
the walls of the capillaries consist of a single 
layer of endothelial cells placed edge to 
edge. Partly on account of the pressure on 
the blood in the capillaries and partly on account of the natural tend- 
ency of liquids to pass through animal membranes, a considerable 
portion of the plasma penetrates the thin walls and enters the spaces 
occupied by the lymph. 
Other sources of the lymph, of less importance, are the outward 
flow of liquids from the cells and the absorption of liquids from the 
alimentary canal. Liquids absorbed through the skin on the outside 
of the body also become a part of the lymph. 
Relative position of blood, 
lymph, and cells. 28 
LYMPH VESSELS. 
The Composition of the Lymph, as would be expected, is 
quite similar to that of the blood. In fact, nearly all the important 
constituents of the blood are found in the lymph, but in different 
proportions. Food materials for the cells and fibrin factors, exist in 
smaller proportions than in the blood, while impurities from the cells 
exist in larger proportions. The number of white corpuscles is slightly 
greater than in the blood, while there is an absence of ted corpus- 
cles. 
Physical Properties. The lymph is a colorless liquid slightly 
heavier and denser than water, though not so dense as the blood. It 
has no well defined odor or taste. It has the power of coagulating, 
but coagulates more slowly than the blood. 
Kinds of Lymph Vessels. Most of the lymph of the body lies 
in the minute cavities surrounding the cells. These are called lymph 
spaces and correspond, in a way, to the capillaries. Connected with 
these are great numbers of slender tubes, with thin walls, called 
lymphatics. They may be likened to the veins and, like the veins, 
contain valves. The lymphatics from different parts of the body 
gradually converge toward two main tubes. One of these, the right 
lymphatic duct, empties into the right subclavian vein, where it is 
joined by the right jugular vein. The other, the thoracic duct, 
empties into the left subclavian vein, where it is joined by the left 
jugular vein. 
The lymphatic tubes which join the thoracic duct from the small 
intestine are called the lacteals. These differ somewhat in structure 
from those found in other parts of the body, their special function 
being to absorb digested fats from the small intestine. 
Movements of the Lymph. Though the lymph may be re- 
garded as a comparatively quiet liquid, it has three well defined 
movements as follows: i. A current passing through it from the 
the capillaries toward the cells. 2. A current from the cells toward 
the capillaries. 3. A movement of the entire body of lymph 
along the lymph channels, toward the larger lymph vessels. RETURN OF LYMPH TO THE BLOOD. 
29 
Return of Lymph to the Blood. From the lymph spaces, 
lymph enters the lymphatics. It passes through these tubes until it 
enters either the thoracic duct or 
the right lymphatic duct. From 
these it passes into the subclavian 
veins. Show by a sketch the con- 
nection of the lymph vessels in the 
different parts of the body with 
the blood vessels. 
Lymph from the right side of 
the head, right arm, and right side 
of chest, passes into the blood 
through the right lymphatic duct. 
Lymph from the lower extremities, 
abdomen, left side of chest and 
head, and left arm, passes into the 
blood through the thoracic duct. 
Causes of Flow of Lymph. 
There is no force pump, like the 
heart, connected with the lym- 
phatics and the causes of the flow of 
lymph are somewhat obscure. The 
following seem to be the chief 
causes: 
1. Blood pressure in the cap- 
illaries. The plasma which is forced 
through the capillaries makes room 
for itself by pushing a portion of 
the lymph out of the lymph spaces. 
This in turn pushes on the lymph 
in the tubes which it enters. In 
this way the pressure is passed on to the whole body of lymph. 
2. By the contraction of muscles against the walls of the lymph 
tubes. Any pressure on the sides of the lymph tubes tends to close 
them up and push the lymph past the valves which, by closing, pre- 
vent its return. It is thus seen that the effect of contracting muscles 
is the same on the lymph as on the blood in the veins. 
Complete the sketch showing 
the connection of the lymph ves- 
sels with the blood vessels. 30 
OSMOSIS. 
The Lymphatic Glands are small, solid bodies situated along 
the course of the lymphatics. They vary in size, some of the largest 
being an inch or more in length. The lymphatic tubes generally 
open into them on one side and leave them on the other. Each 
gland is made up of a mesh-work of connective tissue fibers, within 
which is found large numbers of white blood corpuscles. State the 
function of these glands. 
Interchange of Materials at the Cells. 
Liquid food and oxygen in passing from the blood through the 
lymph into the cell must penetrate both the wall of the capillary and 
the wall of the cell. These are likewise penetrated by the impuri- 
ties which flow from the cell back to the blood. The passage of 
materials between liquids separated by animal membranes, takes place 
according to the principle known in Physics as osmosis or dialysis. 
Osmosis Illustrated. If a vessel with an upright membranous 
partition be filled on one side with water containing salt, and on the 
other side with water containing sugar, an 
interchange of material will take place 
through the membrane until the same pro- 
portion of salt and sugar exists in the sepa- 
rated liquids. 
Experiment. Separate the shell from the lin- 
ing membrane, at one end of an egg, over an area an 
inch in diameter. To do this without injuring the 
membrane, the shell must be broken into small pieces 
and be picked off with a pair of forceps or a small 
knife blade. Fit a small glass tube, 8 inches long, in- 
to the other end, so that it shall penetrate the mem- 
brane and pass down into the yolk. Securely fasten 
the tube to the shell with beeswax, and set the egg in a small tumbler partly filled 
with water. Examine in the course of half an hour. What evidence now exists 
to prove that water has passed through the membrane into the egg? Has any of 
the egg substance passed into the water? Make a sketch of the tumbler and the 
egg, showing by arrows the passage of material. 
The Conditions Under Which Osmosis Occurs are as follows: 
i. The liquids on the two sides of the membrane must be unlike 
either in composition or density. In case of a difference in density EXCHANGES AT THE CELLS. 
3i 
the greater flow of liquid is toward the denser substance. 2. Both 
liquids must be capable of wetting or penetrating the membrane. If 
but one liquid wets the membrane, the flow will take place in but 
one direction. 3. The liquids must have enough attraction for 
each other to mix readily. 
Give two reasons for the greater flow of the water into the egg in the previous 
experiment. 
Osmosis at the Cells. Oxygen and food materials which are 
found in great abundance in the blood, are less abundant in the lymph 
and still less abundant in the cells. According to the principle of 
osmosis the flow of oxygen and food material will be from the capil- 
laries toward the cells. On the other hand the impurities are most 
abundant in the cells where they are formed, less abundant in the 
lymph, and least abundant in the blood. Hence the impurities will 
flow from the cells toward the capillaries. 
The Work of Water in these exchanges should not be over- 
looked. The materials to be exchanged are dissolved in water. 
Water then, by keeping them in a liquid condition, supplies the con- 
ditions necessary for osmosis to take place. 
Massage. Too great an accumulation of lymph in any part of the body 
causes swelling. This may frequently be reduced by a process of rubbing, press- 
ing, and kneading, known as massage. The force applied in this way on the 
outside of the body has the same effect on the veins and lymph tubes as muscular 
contraction from within. Where one is too weak for exercise or is disabled in any 
part of the body this passive exercise may be substituted with good results for 
active exercise taken in the usual way. 
References. On the lymph, F. and S., 104; J., 86; C., 98; S., 88. On the 
lymph vessels, S., 88, 89; F. and S., 104, 105; J., 100; C., 98 On flow of lymph, C., 
99. On massage, C., 103. 
Practical Questions. 1. Compare lymph and water with reference to 
density, color, and composition. 2. Compare blood and lymph with reference to 
composition, physical properties, and movement through the body. 3. Compare 
the lymph tubes with the blood vessels with reference to general structure and the 
different kinds. 4. Show how blood pressure at the capilliaries causes a flow of 
the lymph. 5. Trace the lymph in its flow from the right hand to where it enters 
the blood. From the feet to where it enters the blood. 6. What conditions pre- 
vail at the cells to keep the oxygen continually flowing in one direction and impur- 
ities in the opposite direction ? 7. What part does water play in the exchanges 
at the cells? , CHAPTER V. 
The Atmosphere. 
As before stated, one purpose of the blood is to carry oxygen 
to the cells. This supply of oxygen is obtained from the atmos- 
phere. In this and other respects the atmosphere sustains a most 
important relation to the plan of the body. It is necessary therefore 
that we study briefly its important constituents and properties. 
Composition of the Atmosphere. The atmosphere com- 
pletely surrounds the earth, forming an envelope at least fifty miles 
in depth. It is composed of colorless gases, the greater amount of 
it being made up of oxygen and nitrogen. The former comprises 
about one-fifth and the latter nearly four-fifths of the entire atmos- 
phere. Mingled with the oxygen and the nitrogen, but in small 
quantities, are a number of other substances. Of these, carbon 
dioxid and watery vapor, are of greatest importance. 
Properties of Oxygen. 
(Four large mouthed bottles of oxygen are needed for the following experi- 
ments. For methods of collecting see Appendix.) 
Experiment 1. Examine a bottle of oxygen, noting if it has color. Insert a 
small burning splinter in the upper part of the bottle and observe the change in 
the burning. Remove quickly and extinguish the flame, leaving only a spark on 
the end of the splinter. Rower the spark into the oxygen and observe the result. 
Repeat until the oxygen in the bottle is exhausted. 
Exp. 2. Hollow out the end of a short piece of crayon, fasten a wire holder 
to it, and fill the cavity with powdered sulphur. Ignite the sulphur in the flame 
of an alcohol lamp and lower it into a bottle of oxygen. Observe the effect on the 
burning, the color of the flame, and the material formed in the bottle by the burning. 
Exp. 3. Bend a small loop on the end of a piece of picture wire. Heat the 
loop in a flame and then insert in some powdered sulphur. Ignite the melted 
sulphur which adheres and insert it quickly in a bottle of oxygen. Observe the 
dark brittle material which is formed by the burning of the iron. It is a com- 
pound of oxygen and iron, similar to iron rust and has been formed by their uniting. PROPERTIES OF OXYGEN. 
33 
State effect of oxygen on the 
burning of things which also burn 
in air. 
Describe burning of the iron. 
What proof is furnished by these 
experiments that matter in burn- 
ing is not destroyed? 
Oxygen causes substances to burn by uniting with them. The 
new substances formed are different from both the oxygen and the 
things with which it unites. Heat and light result from the rapidity 
of the uniting. Oxygen is able to unite in this rapid manner on ac- 
count of the intense affinity or attraction which it has for certain sub- 
stances. It is only the free or uncombined oxygen that is capable of 
uniting with substances. For this reason that which is already united 
with substances is unable to support combustion. 
Properties of Nitrogen. 
Experiment. I. Insert a long, burning splinter in a large mouthed bottle or 
jar, filled one-fourth full of lime water. (See Appendix.) Keep the top closely covered 
with a piece of cardboard while the splinter is burning. The carbon and hydro- 
gen of the splinter unite with the oxygen of the air, leaving the nitrogen and such 
impurities as are formed by the burning. Keeping the top tightly closed, shake 
the jar to bring the lime water in contact with the enclosed gases. If fresh air 
gets into the jar the burning and shaking should be repeated. The lime water 
unites with most of the impurities, leaving only the nitrogen. 
2. Note that the nitrogen in the jar is colorless. Test its ability to support 
combustion. 
Compare with oxy- 
gen with reference to 
ability to support com- 
bustion. 
The affinity of nitrogen for other substances is very slight. 
Hence it is unable to support combustion as oxygen does. In the 
atmosphere it serves the purpose of diluting or weakening the 
oxygen. 
Carbon Dioxid is a compound of carbon and oxygen and is 
formed whenever these substances unite. Its chemical symbol co2, 
indicates one part of carbon and two parts of oxygen. The test for 
CO is lime water, with which it unites to form carbonate of lime. 34 
CARBON DIOXII). 
When this occurs the lime water, which is colorless, becomes milky- 
white in appearance. 
Experiment, i. (a.) Attach a piece of charcoal (carbon) no larger than 
the end of the thumb to a piece of wire. Ignite the charcoal and lower it into a 
vessel of oxygen. Observe its combustion. Eet it remain until it ceases to burn. 
Note that in burning the piece of carbon has diminished in size and the oxygen 
has disappeared. Has anything been formed in their stead? 
(b) Remove the charcoal and add a small amount of lime water to the 
bottle. Cover the bottle and bring the gas and lime water in contact by shaking. 
Note change in color of the lime water. What does it indicate? 
2. Burn a splinter in a large vessel of air, keeping the top covered. Add 
lime water and shake. Note and account for the result. 
3. Place several small pieces of limestone (marble) in a fruit or candy jar 
holding at least one-half gallon. Barely cover the limestone with water and then 
add hydrochloric acid until a gas is rapidly evolved. This gas is carbon dioxid. 
(a) Examine it to see if it possesses color. 
(b) Insert a burning splinter and notice the result. 
(c) Blow a small soap bubble on the end of a tube and disengage it in the 
jar. (A tube -Ms inch in diameter is best for this purpose.) 
(d) Tip the jar over the mouth of the tumbler, as you would to empty it of 
water, though not far enough to spill the acid. Then insert a burning splinter in 
the tumbler. Result? 
State concl u s i o n s 
with reference to 
weight and color of 
and its effect on 
combustion. 
Removal of Carbon Dioxid from the Atmosphere. It is 
readily seen that, if the combustion of carbon removes oxygen from the 
atmosphere and replaces it with carbon dioxid, the whole atmosphere 
would in time become deficient in the one and contain too much of 
the other. This condition is prevented through the agency of vege- 
tation. Plants absorb the carbon dioxid from the air, decompose 
it, build the carbon into compounds that become a part of the plant, 
and return the oxygen to the air. In doing this, they not only pre- 
serve the necessary proportion of oxygen and carbon dioxid in the 
atmosphere, but also put the carbon and oxygen in such a condition 
that they may again unite. This process which takes place in the 
leaves, goes on only while sunlight is acting on the plant. 
Watery Vapor is water in the form of a gas. Water, whether 
it occurs as a solid (ice), liquid, or gas, is a compound of hydrogen ATMOSPHERIC PRESSURE. 
35 
and oxygen. Its chemical symbol, H°, indicates two parts of 
hydrogen and one of oxygen in its composition. Watery vapor is 
always present in the atmosphere, but in varying proportions. It 
gets into the air by evaporation from the surface of water, by its es- 
cape from the bodies of plants and animals, and by its formation in 
the combustion of substances containing hydrogen. 
It is removed from the air principally by condensation, which 
results from a portion of the atmosphere becoming cooled. When 
this occurs the watery vapor may fall as rain or snow (depending on 
the temperature), or be deposited as dew. 
Account for the collection of moisture on the outside of a pitcher of cold 
water. 
Account for the formation of the water which collects on the inside of a cold 
lamp chimney, when placed on a lighted lamp. 
Atmospheric Pressure. 
Experiment 1. Wet a circular disk of leather, having a strong cord at- 
tached to the center, and press it against the smooth surface of the the blackboard. 
An attempt to jerk it away fails because the pressure of the air holds it tight. 
2. Place a stiff piece of paper over the mouth of a tumbler filled with water. 
Keeping the paper in position invert the tumbler. Atmospheric pressure holds 
the water in the tumbler. 
3. Suck the air from the mouth of a small bottle, letting it come in contact 
with the end of the tongue. Atmospheric pressure will cause it to adhere to the 
end of the tongue. 
4. Stretch a thin sheet of rubber (the kind used by dentists) over the mouth. 
By lowering the jaw, make a partial vacuum in the mouth. Atmospheric pressure 
pushes in the rubber. 
Where an air pump can be obtained many other interesting experiments, illus- 
trating the pressure of the air, may be performed. 
Atmospheric pressure is due to the weight of the air. It is greater 
at low places than on high elevations because there is more air above 
the low places to press down. At the sea level it averages nearly 
fifteen pounds to the square inch. This pressure is not felt on the 
body because the air which penetrates the tissues exerts an outward 
pressure which balances it. 
Inequality of atmospheric pressure causes motion. The motion 
may be confined to the air itself or communicated to other bodies. 
The direction of the motion is from the place of greater to the place of 
less pressure. 36 
RELATION OF ATMOSPHERE TO THE BODY. 
Experiment. Suck tlie air from one end of a glass tube, which has the 
other end in water. Water rises in the tube, because the pressure of the air on the 
inside of the tube is less than the pressure on the surface of the water outside of 
the tube. 
Other Properties of the Atmosphere of importance in our 
study are elasticity, mobility, and diffusibility. 
Its elasticity is shown by its power to regain its former volume 
after having been compressed, and is well illustrated by the boy’s pop- 
gun. Since air returns exactly to its former volume, after the re- 
moval of pressure, it is said to be perfectly elastic. The pressure 
which it exerts in returning to its former volume is called its elastic 
force. 
Mobility may be described as freedom of motion. On account 
of the degree to which air possesses this property it flows easily from 
a place of greater to a place of less pressure. For the same reason 
it offers little resistance to the movement of bodies through it. 
Diffjisibility refers to the mixing of gases regardless of their weight. 
If a tumblerful of carbon dioxid, a heavy gas, were exposed to the 
air it would soon leave the tumbler and mix with the surrounding air. 
This will happen even when a porous covering separates the carbon 
dioxid from the air. Diffusion is due to the rapid motion of the 
molecules of the gases. In the atmosphere it serves the purpose of 
keeping the different gases mixed. 
What the Atmosphere Does for the Body. i. It supplies 
the body with oxygen and receives the gaseous impurities which es- 
cape from it. 
2. It supplies the pressure which makes it possible to take air 
into and expel it from the lungs. 
3. It serves as a carrier of sound waves, by means of which, 
hearing is made possible. 
Practical Questions. 1. Why will not the oxygen in water support 
combustion? 2. State the objections to an atmosphere of pure oxygen. 3. If 
substances which burn are not destroyed, what becomes of them? 4. Would lite be 
possible without an atmosphere? Why? 5. In what different ways does carbon 
dioxid get into the atmosphere? How is it removed? 6. In what different ways 
does watery vapor get into the atmosphere? How is it removed? 7. Define these 
terms: chemical affinity, combustion, element, molecule, compound, combustible, 
and supporter of combustion. CHAPTER VI. 
Respiration. 
Respiration, or breathing, is carried on by alternately taking air 
into and expelling it from special contrivances in the body called the 
lungs. The act of taking air into the lungs is known as inspiration; 
that of expelling it, expiration. 
The Purpose of Respiration is indicated by the changes which 
air undergoes while in the lungs. 
Experiment, i. Fill a quart jar even full of water. Place a heavy piece of 
cardboard over its mouth and invert it, without spilling, in a pan of water. Insert- 
ing a tube under the jar, blow air that has been held as long as possible in the 
lungs, into it. When filled with air, remove the jar from the pan, but keep the 
top well covered. Insert a burning splinter and observe the result. This proves 
the absence of what? Pour in a little lime water and shake to mix with the air. 
Account for the result. 
2. Blow the breath against a cold window pane. Note and account for the 
result. 
State results and 
conclusions. 
Air taken into the lungs in ordinary breathing, parts with about 
five per cent, of itself in the form of oxygen and it receives about four 
per cent, of carbon dioxid, considerable watery vapor, and a small 
amount of other impurities. These changes suggest a two-fold pur- 
pose of respiration: 38 
ORGANS OF RESPIRATION. 
i. To obtain from the atmosphere the supply of oxygen needed 
in the body. 2. To transfer to the atmosphere certain materials 
(impurities) which must be removed from the body. 
The Respiratory Organs, taken together, form an apparatus 
for dealing with matter in the gaseous state and are constructed with 
special reference to the properties of the atmosphere. They provide 
for four different things: 
1. For bringing the air very near a large surface of blood. 
The special contrivances for doing this are called the air vesicles. 
2. Fora continuous passage way between the air vesicles and 
the outside atmosphere. The tubes which provide this passage way 
are called the air passages. 
3. For a cavity for holding the main organs of respiration. 
This cavity is enclosed by the walls of the thorax or chest and is 
called the thoracic cavity. 
4. For the necessary pressure for forcing the air through the 
air passages. This is furnished by muscles situated for the most part 
within the walls of the thorax. 
The Lungs are two sack-like organs suspended in the thoracic 
cavity. They consist chiefly of the walls of the air vesicles, smaller 
air passages, and blood vessels, and occupy most of the space not 
taken up by the heart. 
Observation. Secure from a butcher the lungs of a sheep, calf, or hog. 
The windpipe and heart should be left attached and the specimen kept in a moist 
condition until used. Study in the following order: 
1. Examine the large open tube (the trachea) and the closed tube lying back 
of it (the oesophagus). Observe the cartilaginous rings in the trachea. What 
purpose do they serve ? Remove one and make a drawing of it. 
2. Insert a tube in the trachea and inflate the lungs. About how many 
times is their volume thus increased ? 
3. Examine the thin membrane (the pleura) enclosing the lungs. Strip off 
a piece and test its elasticity. 
4. Sever the small upper lobe from the remainder by cutting the bronchial 
tube. Split this tube a short distance into the lung, observing its smooth lining 
and the openings of smaller tubes branching off from it. Are the rings in these 
tubes circular or like those in the trachea ? Make cross sections of this portion of 
the lung and find the openings of the lesser bronchial tubes. 
5. Follow the trachea down to where it branches to form the bronchi. Find 
a branch of the pulmonary artery which approaches one of the bronchi and cut A STUDY OF THE LUNGS. 
39 
both artery and bronchus from their connections. Now trace bronchus and 
artery into the lung. Observe that as one branches, the other branches, until the 
smallest divisions are reached. The pulmonary veins also lie alongside the bron- 
chial tubes, but are not so easily traced as the arteries. 
6. Place a piece of lung upon water. In floating, what proportion of it is 
submerged ? Inference. 
7. Beginning with one of the bronchi, strip all the outer material from the 
tube and its branches. Make a drawing of it in this condition. 
1. Comparison of 
trachea and oesoph- 
agus. 
2. Description of 
cartilaginous ring 
with drawing, giving 
use. 
3. Effect of blow- 
ing air into lungs. 
4. Description of 
pleura. 
5. Relation of blood 
vessels to the bron- 
chial tubes. 
6. Describ e the 
branching of the 
trachea. Make a draw- 
ing, showing the 
branches. 40 
THE AIR PASSAGES. 
7. Weight of lung 
compared with weight 
of water. 
8. Name trie differ- 
ent tissues found in 
lungs. 
The Air Passages, named in the order that air goes through 
them as it enters the lungs, are the nostrils,(pharynx), larynx, trachea, 
bronchi, bronchial tubes, and lesser bronchial tubes. As the air 
passes through the nostrils it comes in contact with a large surface of 
moist mucous membrane and is warmed, moistened, and freed from 
particles of dirt. Only the upper part of the pharynx can properly 
be classed as an air passage. The lower portion is a part of the food 
canal, while the middle part provides a suitable cross-roads for the 
air tract and the passage way for the food. 
Air may also enter the pharynx through 
the mouth. This is necessary in many in- 
stances, but in ordinary breathing the air 
should pass through the nostrils. The larynx 
will receive special study as the instrument of 
the voice. 
Leaving the lungs the air goes through 
the same passages, but in the reverse order. 
To enable the air to move easily through the 
different passages, it is necessary that they 
be kept open and clean. 
1 he air passages are kept open by special 
contrivances found in their walls. In trachea, 
bronchi, and larger bronchial tubes these con- 
sist of imperfect rings of cartilage. In the 
smaller tubes the cartilage disappears, its place being taken by stiff 
connective tissue. The walls of the larynx contain strips and plates 
of cartilage, while the nostrils and pharynx are kept sufficiently open 
by their bony surroundings. 
Show by a drawing the 
position of the pharynx 
with reference to mouth, 
nostrils, trachea, arid oe- 
sophagus. THE AIR VESICLES. 
41 
The air passages are kept clean by certain cells designed 
especially for that purpose, known as the ciliated epithelial cells. The 
peculiarity of these cells is their small, hair- 
like projections, called cilia. Ciliated epithe- 
lial cells line the mucous membrane in most 
of the air passages and are so placed that the 
cilia extend into the open space in the tubes. 
The cilia keep up an inward and outward 
wave-like motion which has greater force in 
the outward direction. The effect of this 
motion is to carry any foreign matter to where 
it may be easily expelled from the lungs. 
The Air Vesicles are the small mem- 
branous sacs found at the ends of the smallest bronchial tubes. They 
measure about i-ioo of an inch in diameter and a cluster of them is 
found at the end of each tube. Each is composed of a lining of thin, 
flat cells, resting upon a delicate support of connective tissue which 
is very elastic. Within the walls of the vesi- 
cle is a net work of capillaries through which 
the blood flows. This arrangement brings 
the air very near a large surface of blood and 
renders possible the exchange of gases. It 
is thus seen that the air and blood do not 
come in direct contact but that the exchanges 
take place through the capillary walls and 
the lining of the air vesicles. 
The Supply of Blood to the Lung’s is 
provided for through the pulmonary blood 
vessels. The pulmonary artery coming from 
the right ventricle, sends branches to all parts 
of the lungs. A division of this artery fol- 
lows each bronchial tube down into the lungs 
and finally terminates in the capillaries which surround the air vesicles 
with which the tube connects. From the capillaries the blood is re- 
turned to the heart by the pulmonary veins. These lie alongside the 
Drawing to show form 
of ciliated epithelial cells 
and their position in a 
bronchial tube. 
I. 
2. 
Drawings to show the 
structure of the air vesi- 
cles and their connection 
with the smallest bron- 
chial tubes. 42 
THE THORAX. 
arteries and bronchial tubes and unite to form four veins, two from 
each lung, which enter the right auricle. 
The lungs also receive blood through branches from the aorta which supply 
nourishment to the different tubes and also to the tissues of the lungs. 
The Thorax, or chest, is that part of the trunk between the neck 
and the abdomen which encloses a space, known as the thoracic 
cavity. The framework of the thorax is furnished by the ribs, the 
portion of the spinal column with which they connect in the back, and 
the sternum or breast bone with which they connect in front The 
ribs do not encircle the cavity in a horizontal direction but slant down- 
ward toward the front. The thoracic cavity is separated from the 
cavity below by a partition called 
The Diaphragm. At its edges the diaphragm is attached to 
the walls of the thorax where they join the abdominal walls. At the 
outer margin is a layer of muscles which pass from the walls on the 
outside to a strong layer of connective tissue in the center. The 
diaphragm is naturally in an arched condition, being kept in this 
form by pressure from the organs below. 
The Muscles of the Thorax, called into play in ordinary breath- 
ing, are chiefly of two kinds, known as the elevators of the ribs and 
the intercostal muscles. The first 
pass from the back portion of the 
ribs to the vertebrae above. The 
second form oblique bands between 
the ribs, which are arranged in two 
sets, known as the external and in- 
ternal intercostal muscles. 
The Pleura is a thin, elastic 
membrane, which covers the outside 
of the lungs and lines the inside of 
the chest walls. The part covering 
the lungs joins v ith the part lining 
the walls, so as to form a closed sac. 
In this sac'is secreted a liquid which diminishes friction between the 
lungs and their surroundings. 
Drawing to show position 
of pluera in thoracic cavity. MECHANICS OF RESPIRATION. 
43 
An extension of the pleura, passing from the lungs to the 
diaphragm below and the chest walls in front, divides the thorax ver- 
tically into two halves, each distinct from the other. The left lung 
is suspended in one of these divisions; the right lung in the other. 
How Air Is Brought Into and Expelled From the Lungs. 
The principle involved in breathing is that air flows from a place of 
greater to a place of less pressure. The construction of the thorax 
adapts it to the application of this principle. Its walls are air tight 
and it is able, by changing the size of the cavity within it, to produce 
alternately a place of less and a place of greater pressure than that of 
the atmosphere on the outside of the body. 
The lungs are suspended from the upper portion of the thoracic 
cavity and are always sufficiently filled with air to keep their outer 
surface pressed against the chest walls. The trachea and the upper 
air passages provide the only opening to the outside atmosphere. 
When the thorax is enlarged, making an area of less pressure within, 
the greater pressure of the atmosphere on the outside, forces the air 
into the lungs, causing them to expand and fill the extra space 
within the cavity. When the thorax is diminished in size the air 
within the lungs is compressed, causing it to exert greater pressure 
by its elastic force than the atmosphere exerts on the outside. This 
causes air to flow out until the equality of pressure is again restored. 
In this connection a hand bellows, such as used in kindling fires, may be 
studied with profit, its action being similar to that of the thorax. Observe that when 
ths eides are spread apart air flows into the bellows. When they are pressed together 
the air flows out. If a sac were hung in the bellows with its mouth attached to 
the projecting tube and the valve in the side of the bellows closed it would repre- 
sent almost exactly the plan of the breathing organs. 
Experiment. With a tape line take the circumference of the chest of a boy, 
when he has expelled from the lungs all the air possible. Take it again when he 
has them inflated to their utmost capacity. The difference in the measurements 
represents his relative chest capacity. What does this experiment show with ref- 
erence to the cause of breathing ? 
How the Thorax Changes its Capacity. The space within 
the thorax is increased by the elevation of the ribs and the depression 
of the diaphragm. The former process increases the transverse 
diameter; the latter the longitudinal. The ribs are raised mainly 
by the action of the elevators of the ribs, and by the outer set of inter- 44 
CHANGES IN THE THORACIC CAVITY. 
costal muscles. The diaphragm, being naturally in an arched posi- 
tion, is depressed by the contraction of the muscles within it. As it 
lowers, it pushes down the contents of the abdomen. 
Experiment. With five narrow strips of cardboard, one 8 inches long and 
the others 6 inches, construct a figure to represent the thorax. Let the long strip 
serve as the spinal column and one of the short ones as the breast bone. Fasten 
the others between them for ribs. The fastenings, which must admit of motion, 
may be made by simply pushing pins through the strips where they join. 
Holding the piece representing the spinal column in a vertical position, raise 
and lower the piece representing the breast bone. When is the space between the 
upright pieces the greatest ? Apply to the action of the ribs in increasing the 
thoracic cavity. 
The capacity of the thorax is dimin- 
ished by lowering the ribs and elevating 
the diaphragm. Ordinarily the ribs are 
lowered by their own weight. In forced 
expiration the internal intercostal muscles 
are brought into play. The diaphragm is 
pushed up by the contents of the abdomen, 
which are pressed upon by the contraction 
of the abdominal walls. 
To Estimate the Quantity of Air 
Breathed. 
Experiment, (a) Fill a half gallon fruit 
jar even full of water, cover the top with a stiff 
piece of paper, and invert, without spilling, in a 
pan of water. Insert a tube under the jar and blow 
the air expelled from the lungs in ordinary breath- 
ing into the jar. Count the number of expirations 
required to fill the jar and then calculate the quan- 
tity breathed out during a single expiration. This 
equals the amount breathed in at an average in- 
spiration, and is called the tidal air. 
(b) Fill and invert the jar as before. This 
time, after an ordinary inspiration, empty the 
lungs as completely as possible. (A second vessel 
should be ready to receive the excess of air in case 
the jar should prove too small.) This air, less the 
tidal air, is called the reserve air. 
The air that is left in the lungs after the 
forced expiration is called the residual air. In quantity it nearly equals the sum 
of the tidal and reserve air. Record results of experiment. 
Tidal air Reserve air Residual air 
Insert diaphragm 
and indicate by dotted 
lines the changes 
which the cavities un- 
dergo during inspira- 
tion. CARE OF THE LUNGS. 
45 
The sum of these quantities gives the volume of the lungs, 
which in the average individual, is about one gallon. In forced in- 
spiration the quantity may be increased about one-third. 
The Interchange of Gases at the Lungs, though not fully un- 
derstood, is supposed to result largely from the natural tendency of 
gases to diffuse. (See p.36.) Diffusion not only causes the mixing 
of the air entering the lungs with that already in the vesicles, but 
experiments prove that diffusion takes place between gases in a 
liquid, as the blood, and the air, even when an animal membrane en- 
closes the liquid. 
It is highly probable that the attraction between the haemoglobin of the 
blood and the oxygen of the air also plays an important part in the interchange of 
gases at the lungs. 
Hygiene of Respiratory Organs. The liability of the lungs 
to attack from such a dread disease as consumption, makes ques- 
tions touching their hygiene of first importance. Consumption never 
attacks sound lung tissue, but always has its beginning at some weak 
or enfeebled part of the lungs, which has lost its “power of resist- 
ance.” Neither is consumption inherited as many suppose. Weak 
lung tissue, however, may be transmitted from parents to children 
and this accounts for the frequent appearance of consumption in the 
same family. Consumption, as well as the other respiratory affec- 
tions, can in the majority of cases be prevented by an intelligent ob- 
servation of well established laws of health. 
Respiratory Health Rules. (Selected from various sources.) 
:. Breathe through the nostrils. 
2. Maintain an erect position both in sitting and standing. 
3. Practice deep breathing sufficiently to insure the easy access of air to all 
parts of the lungs. 
4. Wear clothing loose enough around the chest and waist to permit of per- 
fect freedom in the respiratory movements. 
5. Never permit a cold to settle on the lungs. If it cannot be relieved by 
counter irritation a physician should be consulted. 
6. Take active exercise in the open air. Bxercise which causes a notable 
increase in the respiratory acts are of especial value in strengthening the lungs. 
7. Avoid smoking and the use of alcoholic drinks. Tobacco smoke irritates 
the upper air passages, causing in some instances what is called “the smoker’s sore 
throat.” “Alcohol weakens the power of lung tissue to resist disease.” 46 
VENTILATION. 
Ventilation. The health of the respiratory organs and of the 
entire body as well, demands that we breathe pure air. By pure air 
is meant that which contains the same proportion of oxygen as the 
general atmosphere. (How does breathing render air impure?) 
Ventilation is the process of bringing pure air into a room, and 
of getting rid of the air which is unfit for breathing purposes. Since 
warm air is lighter £han cold air, suitable openings in the walls of 
dwellings enable currents of air to pass between the rooms and the 
outside atmosphere. Care must be taken to prevent drafts and too 
great a loss of heat from the rooms. The plan of ventilating must 
be adapted to the construction of the building, plan of heating, and 
the general condition of the weather. No specific directions can be 
given. 
The following general rules may be followed with good results 
in ventilating crowded rooms where the air is not heated before it is 
brought into the rooms: 
1. Introduce air into the room through many small openings instead of a 
few large ones. 
2. Introduce the air at the warmest portions of the room. 
3. Provide openings both at the upper and lower parts of the room. 
4. If a wind is blowing ventilate principally from the sheltered side of the 
building. 
Additional Observations. 
1. Separate the thorax of a small animal (a kitten will answer) from the 
remainder of the body, leaving uninjured the trachea and diaphragm. Remove 
skin and examine the intercostal muscles. Note shape and arrangement of 
diaphragm. Inflate the lungs through trachea and observe change in thorax. Cut 
through chest wall and note collapse of lung when air enters. Study the pleura 
finding the partition between the two sides of the thorax. 
2. Remove the lungs from a frog. Inflate them and then tie the windpipe to 
prevent escape of air. Ret dry and examine. The human lung is made up of a 
number of parts, each similar to the entire lung of the frog. 
3. Examine the scrapings from the roof of the mouth of a live frog, in a little 
water, with a compound miscroscope, for cilia. 
4. Observe the respirations of the human body. Determine the number 
made per minute by the different members of the class, and then find the average. OXIDATION IN TIIE BODY. 
47 
The Passing of Oxygen Through the Body. 
The purpose for which oxygen is introduced in the body is 
accomplished at the cells.. From what has been learned by the 
study of the blood and lymph, the organs of circulation, and the 
organs of respiration, the pupil should be able to trace the passage of 
the oxygen from the outside atmosphere to the cells. 
What Oxygen Does at the Cells. At the cells the oxygen 
unites with the carbon and hydrogen of the compounds in the liquid 
food and with the cell protoplasm. This uniting goes on all the time, 
keeping up what has been called, a continuous series of chemical 
changes. Since these changes are brought about by the uniting of 
oxygen with cell substances the term oxidation has been applied to them. 
The Chief Results of Oxidation are as follows: 
1. The liberation of energy in the body, to be used as heat, 
muscular motion, and nervous action. 
2. The formation of useful substances which are added to the 
cell protoplasm, either to take the place of other material or to en- 
able it to grow. 
3. The formation of waste materials. 
The setting free of energy in the body and the formation of mater- 
ials which may be added to the protoplasm are results of vast import- 
ance to the body. They are the conditions necessary to the maintenance 
of life. Hence oxygen is frequently called the supporter of life. Is it 
any more a supporter of life than the food materials with which it unites ? 
Passage of Oxygen From the Body. In serving its purpose 
in the cells, oxygen ceases to exist as a free, or uncombined, element 
and becomes a part of the substances which it helps to form. Since 
the great majority of these are finally reduced to waste material, the 
oxygen finds its way out of the body as a constituent of the waste 
products. The carbon dioxid, which leaves the body at the lungs, 
contains a part of it. The waste materials thrown off by kidneys, 
skin, and liver contain the remainder. 
A Comparison. The oxygen which passes through a stove during com- 
bustion serves a purpose similar to that which passes through the body. The 
oxygen in the stove, by uniting with the carbon and hydrogen of the wood or coal, 
causes the chemical change (oxidation) which is called combustion. The results 
of the oxidation are the liberation of energy in the form of heat and light and the 48 
PRACTICAL QUESTIONS. 
formation of compounds, all of which are waste materials. The oxygen enters the 
stove as a free element and leaves it as a part of the gaseous compounds which 
pass out through the chimney. 
References. On description of respiratory organs, F. and S., 112-117; S., 
128-131; C., 104-110; J., 162-166. On respiratory movements, F. and S., 117-123; 
S., 131-135; C., 113-117; J., 166-169. Interchange of gases at the lungs, F. and 
S., 108-112; J., 175-179. Quantity of air breathed, F. and S., 124; J., 180. On 
ventilation, F. and S., 127; S., 140-150; C., 137-142; J., 179-183. On effect of 
alcohol and tobacco on air passages, S., 137-138. On hygiene of respiratory organs, 
C., 120. On dangers of breathing-dust, C.. 142-150. 
Practical Questions. 1. What properties of the atmosphere are taken 
advantage of in the different processes of respiration ? 2. Of what advantage is 
the elasticity of the pleura ? 3. How does the air entering the lungs differ in com- 
position from that leaving the lungs ? Account for the difference. 4. Trace the 
passage of the oxygen from the outside atmosphere to the cells. Trace it from the 
cells to the outside atmosphere. 5. Give three reasons for breathing through 
the nostrils. 6. What is the special work of the diaphragm in breathing ? 
7. Why are you unable to expand the chest when the mouth and nostrils are 
closed? Try it. 8. What effect would an opening in the chest wall have on one’s 
ability to inflate the lungs? 9. . Show how active exercise, as running and bicycle 
riding, tends to develop the lungs. 10. How does compressing the waist inter- 
fere with breathing? 11. If 30 cubic inches of air pass into the lungs at each in- 
spiration and .04 of this enters the blood as oxygen, calculate the number of cubic 
feet of oxygen consumed each day, the number of inspirations being 18 per min- 
ute. 12. Find the weight of a day’s supply of oxygen as found in the above 
problem, allowing 1.3 oz. as the weight of a cubic foot of oxygen. 13. In what 
sense is oxygen a supporter of life? 14. In what different ways is the oxygen of 
the atmosphere adapted to bringing about the chemical changes in the body? 
15. Make a study of the school room with reference to its hygienic ventilation. CHAPTER VII. 
Liberation of Energy in the Body. 
What is Energy ? Energy is the power which certain bodies 
have of acting on other bodies. Although there is a great variety of 
ways in which bodies may act on each other, all such actions are 
alike in this: There is a transfer of motion from the acting body to 
the body acted upon. This motion may cause a change in the posi- 
tion of the body. It may set into vibration the molecules which 
compose the body. Or it may agitate the ether which surrounds 
and penetrates all bodies and fills all space. In any event the trans- 
ference of motion is known to take place and is the chief evidence of 
action between bodies. Hence, we may say that bodies possess energy 
when they are able to give motion to other bodies. 
Types of Energy. All moving bodies, without exception, are 
able to communicate motion to bodies against which they strike. 
Hence, all moving bodies have energy. Do bodies at rest possess 
energy ? We know that a stone held above the earth, a stretched 
piece of rubber, the powder in a rifle have the capability of causing 
motion within themselves and then of communicating this motion to 
other bodies. Certainly these bodies possess energy. 
Physicists recognize two types of energy. One is that possessed 
by a body on account of its motion and is called kinetic energy. The 
other is that possessed by a body on account of its position or the 
condition of its molecules and is called potential energy. The first is 
described as energy in action; the second as energy at rest. 50 
POTENTIAL ENERGY. 
How Energy Becomes Potential. Much of the potential 
energy about us is due to the attraction which different portions of 
matter have for each other. If bodies, having an attraction for each 
other, are separated, their attraction tends to make them move 
toward each other. This gives them the capability of motion and 
accounts for their energy. If we raise a stone above the earth, we 
give it potential energy, because we place it where gravitation can 
cause it to move. Stretching a piece of rubber gives it potential 
energy because it separates the molecules, giving cohesion an oppor- 
tunity to draw them closer together. Other attractive forces may be 
taken advantage of in the same way. The following statements are 
easily proven: 
1. Potential energy exists where portions of matter, which at- 
tract each other, are separated. 
2. Potential energy may be given to bodies by separating them 
from bodies for which they have an attraction. 
Chemical Potential Energy is that which bodies have because 
of chemism, or chemical affinity. Chemism is the attraction be- 
tween atoms, the smallest particles found in matter. A body 
possesses chemical potential energy when its atoms are separated 
from the atoms of other bodies for which they have an attraction. 
Gun powder, for example, has chemical potential energy. It is 
prepared by mixing (not uniting) in correct proportions, sulphur, 
carbon, and potassium nitrate, or nitre, which is rich in oxygen. 
The atoms of the sulphur and carbon have a strong attraction for the 
atoms of oxygen. When the temperature of the powder is raised 
sufficiently the atoms fly toward each other and unite to form new 
compounds, causing the explosion. 
In the atmosphere is a large supply of free, or uncombined oxy- 
gen. (Recall its properties.) On the earth are many substances 
which contain elements, the atoms of which have a strong affinity for 
the atoms of oxygen. By complying with certain known condi- 
tions a union between these elements and oxygen is readily brought 
about. Combustion is a result of such a union. It thus happens 
that the oxygen of the air on the one hand, and the products of 
plant life, wood, coal, etc., on the other hand, on account of the HOW PLANTS STORE ENERGY. 
5i 
mutual attraction of their atoms and their condition of separation, 
hold in reserve the earth’s largest supply of potential energy. 
Transformation of Energy. When the separated bodies, in 
obedience to their attraction, move toward each other, their potential 
energy is transformed into kinetic. The energy of position or con- 
dition becomes energy of motion. The falling of a stone and the 
burning of wood are alike illustrations of such a transformation. 
On the other hand, if kinetic energy is employed to separate 
bodies which have an attraction for each other, the reverse of this 
occurs. Kinetic energy is transformed into potential energy. The 
lifting of a weight, the bending of a bow, and the separation of water 
into oxygen and hydrogen by electricity, are familiar examples. 
This process has been called the “ storing of energy.” 
The Work of Plants. Plants transform kinetic into potential 
energy on a large scale by the separation of carbon dioxid into 
carbon and oxygen, (See p. 34.) The kinetic energy in this case 
is the sunlight, and the potential energy which carbon and oxygen 
have on account of being separated, represents the kinetic energy of 
the sunlight which the plant used in separating them. In doing this, 
plants store up the energy of the sun for future use. 
Forms of Kinetic Energy. In the transformation of energy 
which takes place when wood burns, two forms of kinetic energy are 
readily recognized as heat and light. We are sometimes made 
aware of a third form through the sense of hearing. If the heat is 
applied to water, steam is produced which, in passing through the 
cylinder of a steam engine, causes motion of the machinery, and this 
in turn may cause electrical energy. We have thus suggested the 
chief forms of kinetic energy, which are heat, light, mechanical 
motion, sound, and electrical energy. An extended study of energy 
reveals: — 
1. That the different forms of kinetic energy are related to each 
other in the sense that each is a form of motion, 
2. That one form of kinetic energy is readily changed into an- 
other form. 52 
ENERGY OF THE BODY. 
3. can neither be created nor destroyed. It can 
be transferred from one body to another, and changed from one form 
into another form. It may pass from kinetic into potential, or the re- 
verse, and may become so diffused that it cannot be used by man. 
Still there is neither loss nor gain of energy—the sum total in the 
universe remaining always a constant quantity. 
The Energy of the Body. The body can communicate motion 
to its surroundings and can move itself from place to place. These 
are unmistakable evidences of its energy. Even when the body is 
perfectly quiet, as regards external things, we have proofs of its 
energy in the work done in carrying on the vital processes and in the 
production of heat. 
To supply the energy needed by the body is one of the most 
difficult problems of animal life. The animal cannot create energy; 
neither can it, like the plant, use the kinetic energy which may come 
to it from the outside. The energy needed by the body must be 
taken from the supply of potential energy possessed by the oxygen 
of the air and the products of vegetation. Accordingly we have 
introduced into the body through the oxygen which we breathe and 
the food which we eat, energy in the potential form. This when 
liberated, or transformed into kinetic energy, is used in doing the 
work of the body. 
Energy is Liberated in the Body through the uniting of oxygen 
with food substances in the cells. The potential energy, which they 
have, by virtue of their separation, becomes kinetic energy by their 
union and as heat, motion, or nervous energy is used by the body. 
The energy must be liberated just as it is needed. Hence the 
oxidations in the cells must be so controlled that their rapidity shall 
correspond to the demands of the body. The quantity of energy 
liberated by a certain organ is also under control and is made to cor- 
respond to the work which that organ is called upon to perform. 
Animal Heat. It is estimated that as much as 5-6 of the 
energy liberated in the body is in the form of heat, the remainder 
being used in doing work. The proportion varies with different in- 
dividuals and in the same person during different seasons of the year. ANIMAL HEAT. 
53 
The heat is used in keeping the body at that temperature which is 
best suited to carrying on the vital processes. This is about 98° F. 
and is called the normal temperature. To maintain this temperature 
uniformly through all the varying conditions within, and on the outside 
of, the body requires a very delicate adjustment of the heat-producing 
and regulating processes. All parts of the body through the oxida- 
tions taking place within them, furnish heat. Active organs, how- 
ever, such as the muscles, brain, and large glands furnish propor- 
tionally a larger share. The blood in its passage through the body 
serves as a heat distributer and keeps the temperature about the same 
in all parts of the body. 
One’s Capacity for Producing Heat sustains a very important relation 
to the general health, inasmuch as a sudden chill to the body may result in a num- 
ber of derangements, the best known of which is that condition called a “cold.” 
In some individuals the capacity for producing heat is so low that the body is un- 
able to respond to a sudden demand for heat, as happens when one goes from a 
warm into a cold room, and, as a consequence, is unable to protect itself against un- 
avoidable exposures to cold. 
Impairment of the Heat Producing Capacity is brought about in 
many ways. Many of the diseases which attack the body do this directly or in- 
directly to quite an extent. In health excessive care in protecting the body from 
cold is perhaps the most potent cause of its impairment. Staying in rooms heated 
above a temperature of 70° F., wearing clothing unnecessarily heavy, and sleeping 
under an excess of bed clothes, diminish the power to produce heat, because 
they accustom the body to producing only a small amount, hack of physical 
exercise in the open air as well as too much time spent in poorly lighted and ven- 
tilated rooms tend also to diminish it. Since most of the heat of the body comes 
by the union of oxygen with food materials in the cells, a limited supply of either 
will interfere with the production of heat. 
A knowledge of the ways by which the heat producing power of the body is 
impaired will suggest the proper methods for preserving and increasing it. 
References. On forms of energy, J., T23; F. and S., 8; C., 251, 252. On 
the source of energy in the body, J., 124. On production of heat in the body, J., 
208-210; F. and S., 179-182; C., 132; S., 224-232. 
Practical Questions. 1. What is the proof that a body possesses 
energy? 2. Show that a stone lying against the earth has no energy, while the 
same stone above the earth has energy. 3. Water is composed of hydrogen and 
oxygen, which have an attraction for each other. Why then does not water con- 
tain potential energy ? 4. What kind of energy has a bent bow, a revolving 
wheel, a coiled spring, the wind ? 5. Why is it necessary to separate bodies hav- 
ing an attraction for each other, in order to give them energy ? 6. Account for 
the energy possessed by the oxygen of the air and food substances ? 7. How do 54 
SIMPLE EXPERIMENTS. 
plants store the sun’s energy ? 8. In what different ways does the body expend 
energy ? 9. What is the source of the body’s energy ? 10. Give directions for 
increasing one’s ability to produce heat. 
Simple Experiments. 1. The change of kinetic into potential energy 
(the storing of energy) may be shown by stretching a piece of rubber, lifting a 
body, separating the armature from a magnet, and by decomposing water with an 
electric current. 
2. The change of potential into kinetic energy may be shown by letting bodies 
fall, releasing the end of a stretched piece of rubber, causing the magnet to attract 
the armature, and by burning wood. 
3. The change of one form of kinetic energy into another form may be shown 
by rubbing two pieces of wood together until they become heated, by ringing a 
bell by striking it, and by causing motion in air and water by heating them. If suit- 
able electrical apparatus is at hand the transformation of electrical energy into 
heat, light, sound, or mechanical motion can easily be shown. 
Notes on Energy. CHAPTER VIII. 
Foods. 
How Chemical Changes in the Body Differ From Those in a 
Stove. Much of the material taken into the body is not oxidized at 
once, but is formed into material which becomes a part of the cell. 
On the other hand, the protoplasm of the cell unites with oxygen as 
well as material not a part of the protoplasm. Thus in addition to 
simple oxidations, like those which take place in a stove, there goes 
on all the time in the body the double process oi building up and tear- 
ing down of tissues. 
Purposes of Food. Food serves two distinct purposes in the 
body. First of all, it supplies material for the rebuilding of the 
tissues. In the second place, by uniting with the oxygen, it liberates 
energy. Any substance which does not serve one or both of these 
purposes is not food in the true sense. Perhaps the best definition 
yet offered for food is this: “Food is that which, introduced into 
the body, builds tissue or yields energy.’’ 
Substances Suitable for Food. All substances which contain 
materials needed for rebuilding tissues cannot be used as food. It 
is also true that many substances which yield energy outside of the 
body, are unsuited to supplying energy within the body. In general,- 
materials to serve as food, must conform to the following conditions: 
i. They must be capable of reduction to a liquid state or to a 
finely divided condition, which makes it possible for them to be taken 
into the body and distributed by the blood to the cells. 56 
CLASSES OF FOODS. 
2. They must consist of compounds, the affinity of whose ele- 
ments is weak enough to permit oxygen to unite with those parts for 
which it has an attraction. In other words, they must be capable of 
oxidation. This is necessary, both to liberate energy and to prepare 
material for the tissues. 
3. They must be of such a nature that they will not injure the 
body in their passage through it. 
Kinds of Foods. All substances which may be properly classed 
as foods are obtained from the vegetable and animal kingdoms. The 
following table shows the more important classes of foods and their 
sources: 
Found in lean meat and the white of 
eggs. 
i. Proteids, or 
Nitrogenous substances 
' Albumen. 
Casein 
Found in milk and cheese. 
Gluten .... 
Found in grains. 
[ Legumen 
Found in beans and peas. 
Solid fat 
Found in animals. 
2. Non-nitrogenous 
substances 
Fats .. 
Oil 
Found in nuts, olives, grain, etc. 
" Starch.. 
Found in potatoes, 
rice, grain, etc. 
Carbo-hydrates 
Sugar... 
Cane.. 
r Sugar cane, 
L beets, etc. 
Grape 
' Certain 
L fruits.- 
These are called organic foods, because they have been prepared 
by organized bodies—plants and animals. They are alike in that 
they contain carbon, hydrogen, and oxygen. The nitrogenous sub- 
stances, however, contain nitrogen in addition to these. The four 
elements named form, by far, the greater bulk of all food substances. 
Other elements, as sulphur, iron, phosphorus, potassium, calcium, 
and sodium which occur in various foods, are found in minute quan- 
tities. 
Inorganic Substances, supplied by the mineral kingdom, also 
find their way into the body, though they are not properly classed 
as foods. The most important of these are water and common salt. TABLE OF FOODS. 
57 
COMPOSITION OF FOOD MATERIALS. The following table condensed from Atwa- 
ter’s “Foods: Nutritive Value and Cost,” published by the U. S. Department of Agriculture 
shows the percentage of proteids, fat, carbohydrates and mineral matter in the edible por- 
tions of the more common substances taken as food: 
Food Materials. 
Water. 
Solids. 
Pro- 
teid. 
Fat. 
Carbo- 
hydrates 
Mineral 
1 value 
tors’ 1 of 1 
ters- .pound. 
Animal foods, edible portion. 
Beef; 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Cal. 
Neck 
62 
38 
19.5 
17.5 
1 
1 100 
Shoulder ... 
63.9 
36.1 
19.5 
15 6 
1 
1.020 
Chuck rib 
58 
42 
17 6 
23.5 
.9 
1.320 
Rib 
48.1 
51.9 
15.4 
35.6 
.9 
1 790 
Sirloin 
60. 
40 
18.5 
20.5 
i 
1,210 
68.2 
31.8 
20 5 
10.1 
1 % 
Side, without kidney fat 
54.8 
45.2 
17.2 
27.1 
.9 
1,465 
58.1 
41.9 
13 3 
26.6 
2 
1,370 
Flank,corned 
49.8 
50.2 
14.2 
33 
3 
68.8 
31.2 
20.2 
9.8 
1 2 
790 
Mutton: 
Shoulder 
41 4 
18.1 
22.4 
.9 
1,280 
Leg 
61.8 
38.2 
18.3 
19 
.9 
1.140 
49.3 
50.7 
35 
.7 
Side, without kidney fat 
53.5 
16.9 
28.7 
.9 
1,525 
Pork: 
50.3 
49.7 
16 
32.8 
.9 
1.680 
Ham, salted, smoked 
41 5 
58.5 
16.7 
39.1 
2.7' 
1.960 
Fat, salted 
12.1 
87.9 
.9 
82.8 
422 
3.510 
Sausage: 
41.5 
58.8 
13.8 
42.8 
2 2 
2.065 
Bologna 
62.4 
18.8 
15 8 
3 
1.015 
72.2 
27.8 
24.4 
2 
1.4 
540 
Turkey 
33.8 
23.9 
8.7 
1.2 
810 
73.8 
26.2 
14 9 
10.5 
.8 
721 
Milk 
87 
13 
3.6 
4 
4.7 
.7 
325 
Butter 
10.5 
89 
1 
85 
.5 
.3 
3,615 
Oleomargarine 
11 
89.5 
.6 
85 
.4 
3 
3.605 
Cheese 
Full cream 
30.2 
69.8 
28.3 
35.5 
1.8 
4 2 
2,070 
Skim milk 
41.3 
58 7 
38.4 
6.8 
8.9 
4.6 
1.165 
Fish: 
82.6 
17.4 
15.8 
.4 
1 2 
310 
73.4 
26.6 
18.2 
7.1 
13 
640 
63.6 
36 4 
21.6 
13.4 
1.4 
965 
43.4 
17.3 
26.4 
2.5 
1,860 
Oysters 
87.1 
12.9 
6 
1.2 
3.7 
2 
230 
Vegetable foods. 
Wheat flour 
12.5 
87.5 
11 
1.1 
74.9 
.5 
1,645 
Graham flour (wheat; 
13.1 
86 9 
11.7 
1.7 
71.7 
1.8 
1,625 
Rye flour 
13.1 
86.9 
6.7 
.8 
78.7 
.7 
1,625 
Buckwheat flour 
14.6 
85.4 
6.9 
1.4 
76.1 
i 
1,605 
Oatmeal 
7 6 
92.4 
15.1 
7.1 
68.2 
2 
1,850 
Corn meal 
15 
85 
9.2 
3.8 
70.6 
1.4 
1,645 
Rice 
12.4 
87.6 
7.4 
.4 
79.4 
.4 
1,630 
Peas 
12.3 
87.7 
26.7 
1.7 
56.4 
2.9 
1,565 
Beans 
12.6 
87.4 
23.1 
2 
59.2 
3 1 
1.615 
Potatoes 
78 9 
21.1 
2 1 
.1 
17.9 
1 
375 
Sweet potatoes 
71.1 
28.9 
1.5 
.4 
20 
1 
530 
Turnips 
89.4 
10.6 
1.2 
.2 
8.2 
1 
185 
('amits .... 
88.6 
11.4 
1.1 
.4 
8.9 
1 
200 
< inions 
87.6 
12 4 
1.4 
.3 
10.1 
.6 
225 
String beans 
78.2 
12.8 
2.2 
.4 
9.4 
.8 
235 
Green peas 
78.1 
21.9 
4.4 
.6 
16 
.9 
405 
Green corn 
81.3 
18.7 
2.8 
1.1 
13.2 
.6 
345 
Tomatoes 
96 
4 
.8 
.4 
2.5 
.3 
80 
Cabbage 
91.9 
8.1 
2.1 
.3 
5.5 
1.1 
155 
Apples 
83.2 
16.8 
.2 
.4 
15.9 
.3 
315 
*> 
98 
97.8 
22 
1.820 
24.6 
73.1 
2.3 
1,360 
White bread (wheat) 
32.3 
67.7 
8.8 
1.7 
56.3 
.9 
1,280 
Boston crackers 
8.3 
91.7 
10.7 
9.9 
68.7 
2.4 
1,895 58 
USES OF WATER. 
Special Uses of Nitrogenous and Non-Nitrogenous Foods. 
Both of these classes, on account of their ability to unite with 
oxygen, are capable of yielding energy. But since all the tissues 
contain nitrogen, only the nitrogenous foods are suitable for tissue 
building purposes. 
On the other hand, the non-nitrogenous foods unite more readily 
with oxygen, and produce fewer waste materials when they do unite. 
For these reasons they are especially adapted to liberating energy. 
In a general way then we may speak of nitrogenous substances as 
tissue foods, and the non-nitrogenous as energy foods. 
A well balanced diet is one in which these two classes of food 
are eaten in the proportion in which the body needs them. This 
proportion varies with the individual and his occupation. In general 
it may be stated that the body needs about four parts of energy food 
to one part of tissue food. 
Importance Of Water. Since water, in passing through the 
body undergoes no chemical change and yields no energy, it cannot 
be classed as a food. Yet, next to oxygen, it is probably the most 
important substance taken into the body. It is present in all the 
tissues, and forms about two-thirds of the total weight of the body. 
Its main uses are: 
1. To keep the tissues of the body soft and pliable. 
2. To dissolve food materials so that they may enter the body 
and be distributed in the blood to different parts. 
3. To dissolve waste materials so that they may be removed 
from the body by the organs of excretion. 
4. To serve as a means of transfer of substances according to 
the principle of osmosis. (See p. 30.) 
The Purpose of Common Salt in the body is not understood. 
By some it is claimed that it assists in digestion and in the assimila- 
tion of material at the tissues. Others have advanced the theory 
that its wide-spread use is the result of habit. The fact that animals 
deprived of salt lose in health and general vitality, indicates that it 
serves some important purpose. PRACTICAL QUESTIONS 
59 
References. On uses of food, S., 17; J., 119. On classes of food, S., 23-40; 
J., 120; C., 167-170; F. and S., 152-155. On purposes of water, J., 125; S., 19-22; C., 
I7°'I73- On purposes of salts, C., 173; S., 18; J., 125. 
Practical Questions, i. Give two differences between the chemical 
changes in a stove and those in the body. 2. Wood and coal contain energy; why 
cannot they be used as food ? 3 Why are non-nitrogenous foods unsuited to re- 
building tissue ? 4. What advantages have the non-nitrogenous over the nitro- 
genous foods in the liberation of energy ? 5. Show that life cannot be carried on 
in the body without water. 6. Consulting the table on page 57, select four foods 
which, if eaten at a single meal, will furnishhe proportion of tissue aud energy 
material needed by the body. CHAPTER IX. 
Digestion. 
Purpose and Nature of Digestion. Digestion is the process 
by which food material is prepared for the blood. Since nothing but 
liquids can enter the blood vessels, digestion must consist, to a large 
extent, of the reduction of solids to the liquid state. This is accom- 
plished by dissolving them in certain liquids which are prepared for 
this purpose by organs called glands. 
The condition of the materials acted on and the changes which 
they undergo are suggested by the following 
Experiment: Label three tumblers. In the first, place some water ; in 
the second, a teaspoonful of fine salt; and in the third, some pulverized limestone. 
Note that the contents of the first tumbler is already in a liquid condition. To the 
second add water and note the result. To the third add water also. If no result 
follows, add hydrochloric acid, noting what happens. State the changes, if any, 
which were necessary to reduce the contents of the different tumblers to a liquid 
state. 
1. 
2. 
3- 
The limestone, being insoluble in water, is changed by the acid to calcium 
chlorid, a substance soluble in water. DIGESTIVE ORGANS. 
61 
Digestibility of Foods. With reference to the changes they 
undergo during digestion, foods may be divided into three classes: 
1. Substances already in the liquid state. Name one. These 
require no digestion, but are ready, at once, to be taken into the 
blood vessels. Oils and milk are exceptions to this class. 
2. Foods which are soluble in water. Give examples. These 
require only to be dissolved. 
3. Substances insoluble in water. The first step in the diges- 
tion of these is to change them into substances which are soluble in 
water. This class contains the greater number of our solid foods and 
includes proteids, starches, and fats. 
The Organs Of Digestion are of three kinds. 1. Those for 
crushing and grinding the food. These consist of the teeth, jaws, 
and muscles of mastication. 
2. Glands, to secrete the liquids which act upon the food to 
change it chemically and to dissolve it. 
3. Cavities, in which the different processes of digestion take 
place and tubes connecting them. 
The different cavities and tubes are connected to form one con- 
tinuous tube which begins at the mouth and extends entirely through 
the body, called the alimentary canal. The parts of this canal and 
the glands which empty their liquids into it, are shown by the follow- 
ing table: 
Salivary 
Gastric 
Diver 
Pancreas 
Intestinal 
Parotid 
Submaxillary 
Sublingual 
Digestive Glands. 
Digestive 
Organs. 
Mouth containing 
Teeth and 
Tongue 
Parts of 
Alimentary 
Canal. 
Pharynx 
Oesophagus 
Stomach 
Intestines 
Small 
Duodenum 
Jejunum 
Ileum 
Ccecum and Verm- 
iform Appendix. 
Large 
Colon... 
_ Rectum 
Ascending 
Transverse 
Descending 62 
MUCOUS MEMBRANE. 
The Alimentary Canal in different individuals varies in length 
from 25 to 30 feet. The greater portion of it 
is made up of three distinct layers of sub- 
stance, called coats. (The oesophagus and 
the pharynx have only two coats.) The 
inner coat consists of mucous membrane, the 
middje coat is muscular; the outer coat is a 
serous membrane, being a continuation of 
the lining of the abdominal cavity called 
the peritoneum. Another coat 
is sometimes described, called 
the submucous, which lies be- 
tween the mucous and the mus- 
cular. 
The Mucous Membrane of 
the alimentary canal is similar to 
that found in other parts of the 
body. This membrane is some- 
times spoken of as the inner skin. 
It is like the outer skin in being 
made up of two distinct layers. 
The under layer is the thicker 
and contains blood vessels, 
nerves, and glands. The upper 
layer consists principally of 
tough, non-sensitive epithelial 
cells. Mucous membrane lines 
all the inner cavities that have 
connection with the outside of 
the body. It is named from 
a liquid it secretes called mucus, 
which keeps it soft and pliable. 
The mucous membrane pre- 
sents different appearances in 
different parts of the alimen- 
Make a sketch showing 
coats of the canal. 
Complete the sketch showing the dif- 
ferent parts of the canal and large glands 
attached to it. TIIE ALIMENTARY MUSCLES. 
63 
tary canal. That of the mouth, pharynx, and oesophagus is 
smooth. In the stomach it contains a number of longitudinal 
folds which greatly increase its surface and furnish additional 
room for the gastric glands embedded within it. In the small intestine 
it has a soft, velvety appearance due to the presence of large numbers 
of absorbent vessels called the villi', and its surface is much increased 
by transverse folds or ridges. These folds retard the motion of the 
food through the small intestine and provide more surface- for the 
villi. The mucous membrane of the large intestine resembles that of 
the stomach, but the folds are smaller. 
The Muscular Coat is continuous throughout the entire length 
of the canal, except the mouth, where its place is taken by the strong 
muscles of mastication. It presents variations at different places as 
follows: 
i. In the pharynx it is made up of a series of thin overlapping 
muscles, one above the other. 2. In 
the stomach it consists of three layers 
which surround that organ in differ- 
ent directions. 3. In the oesopha- 
gus, the small intestine, and the large 
intestine, the coat consists of two 
layers, one encircling the canal, the 
other covering it longitudinally. 
(The longitudinal layer in the large 
intestine converges into three narrow 
bands which, being shorter than the rest of the tube, cause it to be 
thrown into pouches between them.) 
Work of the Alimentary Muscles. The mechanical part of 
digestion is accomplished by the muscles which encircle the alimen- 
tary canal. Their chief uses are: 
1. To push the food through the canal. This seems to be the 
main use of the muscles of the pharynx, oesophagus, small intestine, 
and large intestine. 
Sketch the stomach, showing 
the muscles. 64 
USES OF THE MUSCULAR COAT. 
2. To supply the necessary force for grinding the food. What 
muscles do this work? 
•3. To mix the food with different juices. Supply illustrations. 
4. To close up the passage at certain places until the digestive 
processes at those places are completed. This is the function of the 
muscular bands at the two openings of the stomach. 
The regular movements of the stomach and small intestines caused 
by their muscles, are called the peristaltic movements. 
Parts of the Alimentary Canal. 
Since information concerning the structure and function of the parts of the 
canal is easily obtained trom the usual school text-books on Physiology, only the 
plan of their study is here indicated. 
The Mouth is an irregular cavity at the beginning of the canal. 
Give three of its uses. Name its boundaries. How is it separated 
from the pharynx? How may its size be varied to suit its contents? 
Most of the space within the mouth is usually taken up by the tongue 
and 
The Teeth. The parts of a tooth are the crown, the neck, and 
the fang. A tooth is made up of enamel, dentine, pulp, and cement. 
Give properties and uses of each substance. 
Represent a section 
of a tooth showing its 
parts and the position 
of the different mate- 
rials composing it. 
Show by a diagram 
the position of the dif- 
ferent kinds of teeth in 
the jaw. DIVISIONS OF THE ALIMENTARY CANAL. 
65 
Name, locate, describe, and give use of the different kinds of 
teeth. What set of teeth is called 
permanent? What temporary? How 
many in each set? State two func- 
tions of the teeth. Give directions 
for care of teeth. When should the 
dentist be consulted? 
The Tongue is a muscular organ 
which has its fibers running in all di- 
rections. It is thus able to assume 
a great variety of shapes. At its 
base it is connected with the hyoid 
and submaxillary bones. Name two uses of the tongue. 
Pharynx. This cavity is the cross roads of the air tract, and 
the food canal. It lies back of the mouth and has seven different 
openings. Name them. (See drawing on p. 40.) How is it 
separated from the mouth? What is its work in swallowing? Are 
its muscles voluntary or involuntary? 
Oesophagus. What is its length? With what is it connected 
at upper and lower ends? Describe its coats. Does the food fall 
from mouth into stomach, or is it forced down? Give proofs. 
Stomach. Give its shape, size, location, openings, and coats. 
Describe its two orifices. Compare with other digestive cavities 
with reference to size. What glands does it contain? Where do 
they lie? Describe muscles of stomach? What is their function? 
Small Intestine. Name and locate its parts. Give its length 
and diameter. What coats has it? Describe its mucous membrane. 
How is so long a tube able to accommodate itself to the cavity in 
which it lies? What is the mesentery? What are its uses? 
Large Intestine. Give its length and name its parts. At its 
beginning there is a sort of pouch, or sac, called the coecum, into 
which the small intestine empties by the ileo-coecal valve. At the 
lower portion the coecum connects with a very narrow tube, called the 
vermiform appendix, which is not only an organ without a function, 
but is often a source of disease. 
Represent a longitudinal 
section of the tongue show- 
ing direction of some of its 
muscular fibers. 66 
STRUCTURE OF GLANDS 
Glands. 
Glands are found in many parts of the body, their function 
being to secrete liquids. These liquids serve different purposes, 
those of the digestive organs being to dissolve the food. The 
materials which form the liquids are obtained by the glands from the 
blood, but they are supposed to undergo a change as they pass 
through the glands. Water is the chief constituent of all gland 
secretions. 
General Structure of Glands. All glands have the same 
essential parts. These are: 1. A layer of gland or secreting cells. 
2. A thin layer of connective tissue, called the basement mem- 
brane. 3. A network of capillaries very near the cells. 4. A 
system of nerve fibres. 
The gland cells are the active agents in secreting, the basement 
membrane furnishes a support for the cells, the capillaries bring a 
supply of blood near the cells, while the nerve fibers connect the 
cells with the nervous system which controls their activity. 
Kinds of Glands. The parts common to all glands are arranged 
in different ways, as follows: 
1. The gland cells are spread over a smooth surface. This is 
the simplest arrangement possible and is called a plain secreting sur- 
face. This arrangement is seen where only a small amount of liquid 
is needed and there is a large amount of surface to furnish it. As a 
rule it is found in serous membranes like the pleura and peritoneum. 
It cannot be employed where a large amount of liquid is needed. 
2. The gland cells line simple tube-shaped, or sac-shaped, 
cavities. This greatly increases the secreting surface and forms two 
kinds of glands. These, from their shapes, are called simple tubular 
and simple sacidar glands. 
3. The gland cells line tube and sac-shaped cavities which con- 
tain two or more divisions. This arrangement still further increases 
the secreting surface and forms the compound tubular and compound 
sacular glands. 
4. lhe gland cells are made to line tube and sac-shaped cavi- 
ties having a great number of divisions, but all communicating with a EVOLUTION OF GLANDS. 
67 
single duct or outlet. This arrangement forms a true compound gland 
and is the most efficient contrivance for removing liquids from the 
blood. 
Show by drawings the structure of the different kinds of glands. 
i. 2. 3. 4. 5. 
6. 
Digestive Glands. The differ- 
ent kinds of glands which secrete 
liquids to act on the food are the sim- 
ple and compound tubular and sacu- 
lar glands and the true compound 
glands. The sacular and tubular 
glands lie in the mucous membrane 
of the canal, while the true compound 
glands are situated a short distance 
from the canal and connect with it 
by means of ducts. Within the canal 
the liquids come in direct contact with, 
and act upon, the food. 
Information concerning the location, structure, and secretions of these glands 
is easily obtained from the usual texts on Physiology. Only the plan of study is 
here indicated. 
Salivary Glands. Locate and describe the different kinds. Are 
they simple or compound? Compare them with reference to size. 
When are they most active? How much saliva is secreted daily by 
them? Locate the ducts which convey the saliva to the mouth. 
Make drawings, showing 
evolution of glands. 68 
THE LIVER. 
Gastric Glands. Where located ? Number ? Size ? How 
much liquid do they secrete daily? What is it called? To what 
class of glands do they belong? 
Liver. Give its location, size, color, and general structure. 
How much bile is secreted daily? Where does it enter the canal? 
The liver, unlike the other glands, is more or less active at all times 
and for this reason has a reservoir called the gall bladder which re- 
tains the bile until it is needed for digestive purposes. 
Functions of the Liver. The work of the liver is not thoroughly under- 
stood. However, most physiologists agree that it has at least three functions: 
1. It secretes a liquid, which aids in digestion. 
2. It removes impurities from the blood. 
3. It acts as a storage organ. It stores material by preparing from the sub- 
stances which come to it through the portal vein, a sweetish solid called glycogen. 
“This is formed during digestion and is stored in the liver, to be gradually trans- 
formed, in the intervals of digestion, into grape sugar.” 
Blood Supply of the Liver. More blood passes through the liver than 
through any other single organ of the body, excepting the heart and lungs. It 
receives blood from two sources : 
1. From the stomach, intestines, and spleen. Blood is passed from these 
organs to the liver through the portal vein. This blood is loaded with food 
material recently digested, but it contains no oxygen. 
2. From the aorta. This contains oxygen and reaches the liver through the 
hepatic artery. 
In the liver the portal vein and hepatic artery divide and subdivide until they 
empty into capillaries surrounding the liver cells. The capillaries in turn empty 
into a single system of veins which unite to form the large hepatic vein. This vein 
empties into the vena cava ascending. 
Pancreas. Give its location, size, shape, and general struc- 
ture. What is its secretion called? How much of this liquid is 
daily secreted ? Where do the ducts from the liver and pancreas 
enter the intestine? 
Intestinal Glands. These are embedded in the mucous mem- 
brane of both the small and large intestines and are, for the most 
part, simple tubular glands. What is their secretion called? How 
much is there of it? 
The Quantity of Digestive Fluids. Calculate the total number of 
pounds secreted daily by all the glands. This equals pounds. How does 
this compare with the quantity of solid food taken daily ? What becomes of these 
liquids after they have served their purpose in the canal? DIGESTIVE PROCESSES. 
69 
Digestive Processes. 
The General Plan of Digestion is to act on the food in differ- 
ent ways, as it passes through the canal, with the final purpose of 
reducing it to a liquid state. The different processes through which 
it passes are mastication, insalivation, deglutition, stomach digestion, 
and intestinal digestion. Any portion of food not reduced to a 
liquid by these processes, passes from the canal as waste. 
Mastication. Of what does this process consist? By what 
organs is it accomplished? Why should it be performed slowly and 
thoroughly? One purpose of mastication is illustrated by the 
following 
Experiment. Pulverize a teaspoonful of salt and place it in one of two 
tumblers. In the other, place the same amount of coarse salt. Add water until 
each tumbler is half full and observe in which the salt first dissolves. In which 
does the water come in contact with the greater surface of salt ? 
State 
results 
Since mastication helps reduce the food to a proper condition 
for swallowing and for the rapid action of the digestive fluids, it is to 
be regarded as a preparatory process. 
Insalivation. This process consists in the mixing of the food 
with the saliva. How does it prepare the food for swallowing? 
How does it enable us to taste substances? Name two substances 
which are dissolved by the saliva. The effect of saliva on starch is 
shown by the following 
Experiment. Make a starch paste by boiling a small lump of starch in a 
half dozen tablespoonfuls of water, (a) Place a few drops of this in a test tube 
half full of water and thoroughly mix. Add to this three or four drops of a solu- 
tion of caustic potash and the same amount of a dilute solution of blue vitriol. Boil 
the mixture and watch for results. (6) Collect a teaspoonful of saliva from the 
mouth, thin it with a little water, and add two or three drops of the starch paste, 
thoroughly mixing. . Keep in a warm place for five minutes, then add caustic pot- 
ash and blue vitriol, as in previous experiment, and heat until the mixture boils. 
If it turns an orange-red color it indicates the presence of grape sugar. 
State results and 
conclusions. 70 
ACTION OF THE GASTRIC JUICE. 
The change of starch into grape sugar is brought about by an 
active agent in the saliva called ptyalin. What is the advantage of 
such a change? This action, however, continues but a short time, 
as it is checked in the stomach by the gastric juice. 
Deglutition, or swallowing, is the process by which food is 
transferred from the mouth to the stomach. How is it transferred 
from the mouth to the pharynx? From the pharynx to the stom- 
ach? Locate the muscles which do this work. How much of the 
swallowing process is voluntary? 
Stomach Digestion is accomplished by the gastric juice. The 
most important active agents in this liquid are hydrochloric acid and 
pepsin. Three results follow the action of the gastric juice: — 
1. The action of the saliva on the starch is checked. 
2. The globules of fat are released from the cell walls which 
enclose them. Fat, however, is not acted upon. 
3. The insoluble nitrogenous food substances, the proteids, are 
changed into soluble substances called peptones. This is by far 
the most important work of the gastric juice. It may be illustrated 
by the following * 
Experiment. Prepare artificial gastric juice as follows: To a half tumbler- 
ful of water add 15 or 20 drops of hydrochloric acid. In this dissolve twice as 
much pepsin as will lay on the point of a pen knife. (Both the pepsin and the 
acid are obtained from the drug store.) Place in the mixture (he white of a hard- 
boiled egg, broken into very small pieces. Allow the w'hole to stand for 24 hours 
in a place where the temperature is about 98° F. During this time portions of 
the egg will be dissolved. 
Intestinal Digestion is accomplished mainly by the action of 
the bile and pancreatic juice. 
The bile has only a feeble action upon any of the food sub- 
stances, but it helps along digestion, indirectly, in different ways. 
1. It counteracts the acid of the stomach, giving the food an 
alkaline reaction which is necessary for the action of the pancreatic 
juice. 
2. It increases the peristaltic action of the intestines by acting 
as a stimulus to the muscular coat. 
3. It retards the decomposition of food in the intestines. ACTION OF PANCREATIC JUICE. 
71 
4. It furnishes a large bulk of liquid which serves to move the 
contents of the intestines readily along. 
The pancreatic juice is the most important of the digestive fluids 
and acts with vigor on all classes of foods. 
1. It changes starch into grape sugar, completing the work 
begun by the saliva. 
2. It changes proteids into peptones, finishing the work of the 
stomach. 
3. It emulsifies the fats; that is, it breaks them up into very 
fine particles so that they can be absorbed. 
4. It changes a portion of the fats into two soluble substances 
called glycerine and fatty acid. 
Experiment. 1. Mix a few drops of starch paste with half a test tube full 
of a solution obtained by soaking a pig’s pancreas, chopped fine, in water. Ret 
the mixture stand in a warm place for ten minutes. Then test for grape sugar as 
in previous experiment. (Pancreatin, obtained from drug store and dissolved in 
water may be substituted for the solution from the pancreas.) 
2. To a little sweet oil in a test tube or small bottle add water and attempt 
to mix by shaking. Result? Then add a little baking soda and shake again. 
The oil is broken into very fine particles, forming what may be called an emulsion. 
Results and 
inferences. 
Health Suggestions. Different physiologists have suggested 
the following rules for the care of the digestive organs. Find some 
reason for obeying each one: i. Eat slowly and masticate the 
food thoroughly. 2. Avoid eating between meals. 3. Avoid 
use of all stimulants, such as alcoholic drinks, tea, and coffee. 4. 
Take active exercise daily, in the open air. 5. Drink little water 
during meals, but plenty of water between meals. 6. Boil impure 
water before drinking it. 7. Eat only wholesome, well-cooked 
food. 8. Never swallow anything which is not thoroughly masti- 
cated. 9. Obey your appetite and do not think too much about 
what you eat and how you eat it. 72 
PRACTICAL QUESTIONS. 
Oare of the Bowels. The undigested contents of the alimentary canal 
should be regularly evacuated. When this is neglected a condition known as 
constipation or costiveness ensues. This is not only a source of great annoyance 
but is injurious to the health. In most instances it can be avoided by observing 
the following habits : i. Have a regular time each day for evacuating the 
bowels. 2. Drink plenty of water between meals. 3. Eat generously of fruit 
and such coarse foods as oatmeal, corn bread, etc. 4. Practice such exercises as 
bring the abdominal muscles into play and knead the abdomen with the hands.— 
The importance of this recommendation lies in the fact that weakness of the mus- 
cular coat is frequently the cause of the trouble. It is only through such indirect 
exercises as those suggested that the tone of the alimentary muscles can be restored. 
Do not rely upon patent medicines, pills, etc., as they usually leave the canal 
in a weakened condition. When necessary consult a physician. 
References. On parts of alimentary canal, S., 59-78 ; J., 131-146 ; F. and 
S., 132-151. On the structure of glands, J., 132-134 ; C., 155; F. and S., 134-136. 
On the teeth, S., 61-66 ; J., 135-139 ; C., 199-202. On functions of liver, S., 76, 77 ; 
F. and S., 162. On digestive processes, J., 150-155 ; C., 206 214. On the effect 
of alcohol on digestive organs, S., 79-82. On cooking, C., 193 ; S., 37-39. 
Practical Questions. 1. State the purpose of digestion. How does 
digested food differ from that not digested ? 2. Name the different kinds of foods 
which must be reduced to soluble substances, before being dissolved. 3. What 
is gained through masticating the food ? Why should this process come first ? 
4. What are the uses of the muscular coat of the alimentary canal? Why should 
their weakness, through insufficient exercise, interfere with the digestive processes? 
5. Describe the arrangement whereby the liquids, secreted by the glands, are 
brought in contact with the food. 6. Distinguish in structure and location 
between compound tubular glands and true compound glands. 7. Name organs 
which are attacked by each of the following diseases: Appendicitis, gastritis, 
parotitis, and peritonitis. 8. Why should the liver be supplied with blood from 
two sources? Why is the liver the only gland with a reservoir for its fluid? 
9. Where, by what juices, and in what manner are the fat of meats, the white of 
eggs, the starch of potatoes, salt, and sugar digested ? CHAPTER X. 
Transfer of Food Materials. 
By digestion the different food materials are reduced to a liquid 
state—a condition adapted to the needs of the cells. Before they 
can reach the cells, however, they must be taken in charge by the 
organs of circulation and become a part of the blood stream. The 
transfer of liquids from the alimentary canal to the circulation includes 
two processes, as follows: 
1. The absorption of the liquids by minute vessels in the walls 
of the canal. 
2. Their passage along regular channels to the general circu- 
lation. 
Absorption. In general, absorption means the penetration of a 
liquid into the small spaces in the body of a solid and is due to the 
attraction between the solid and the liquid. The conditions under 
which it takes place along the alimentary canal, bring into play 
other forces whose action is not fully understood In the walls of the 
canal the absorbing vessels are of two kinds, capillaries and 
lymphatic tubes. 
The Capillaries throughout the entire length of the canal take 
in liquids, but the greater amount of their absorbing is done at the 
small intestine. The capillaries absorb all kinds of liquid material, 
except the emulsified fats. 
The Lymphatic Vessels are also capable of absorbing, to a 
small extent, from all parts of the canal, but all of their important 
work of this kind is confined to the small intestine. Here they have 74 
ABSORPTION AT SMALL INTESTINE. 
a remarkable development, forming a system of tubes peculiar to 
themselves, called 
The Lacteals. The lacteals are special absorbent vessels for the 
emulsified fats. The different tubes comprising the lacteals run 
together, to form larger and larger ones in the mesentery, until they 
reach the thoracic duct. While they have for their principal function 
the absorption of fats, they also, to a small extent, absorb other sub- 
stances. 
Absorption at the Small Intestine. By far the greater amount 
Make a sketch showing the villi and 
their absorbing vessels. 
of material absorbed from the al- 
imentary canal is taken up at the 
small intestine. Its great length, 
small diameter, and the condition 
of its mucous membrane all com- 
bine to adapt it in a remarkable 
way for the absorption of liquids. 
Linin g the small intestine 
throughout the entire length are 
minute elevations, called 
The Villi. Each villus is 
about 1-50 of an inch in length, 
has a diameter 1-4 as great, and 
is covered with a layer of epi- 
thelial cells. 
Beneath this covering is a fine 
kind of connective tissue, through 
Finish the drawing showing the two 
routes from the alimentary canal to the 
circulation. THE VILLI. 
75 
which passes a net work of capillaries. Within the center of the villus 
is a long, narrow and sometimes branched space which forms the 
beginning of a lacteal. The capillaries join small veins which connect 
with the branches of the portal vein. The small lacteals unite to 
form larger ones which finally connect with the thoracic duct. The 
villi are so numerous that they give the mucous membrane of the 
small intestine a velvety appearance. 
Two Routes to the Circulation. There are two distinct routes 
from the alimentary canal to the general circulation. If substances 
are absorbed by the blood vessels they pass through the portal vein 
to the liver. From there they go through the hepatic vein to the 
vena cava ascending, and then to the right auricle. 
If they are absorbed by the lacteals they pass to the thoracic 
duct and through it to the left subclavian vein, then into the vena 
cava descending, and into the right auricle. Make a drawing show- 
ing these routes. 
Fill out the blank spaces in Table I, indicating the passage of materials into 
the circulation. 
References. On absorption, F. and S., 132, 149; S., 84-92; C., 217-221; J., 
i55,i56. On the villi, F. and S., 148; S., 86; C., 224. On the lacteals, F. and S., 148; 
C., 222. O11 absorption from the small intestine, S., 87; F. and S., 149. Absorp- 
tion from the stomach, C., 215. 76 
TRANSFER OF FOOD MATERIALS. 
TABLE I. THE PASSAGE OF MATERIAL INTO THE CIRCULATION. 
(TO BE COMPLETED BY THE PUPIL.) 
Digested ? By what juices ? How Changed? Absorbed by ? Route to the Circulation. 
Classes of 
Foods. 
Proteids 
Fat 
Starch 
Soluble 
Substances... 
Liquids CHAPTER XI. 
The Abdomen and Its Contents. 
The Abdominal Cavity lies immediately below the thorax from 
which it is separated by the diaphragm. Its surrounding walls are 
continuous with those of the thorax, but are less resisting and admit 
of greater freedom of motion. The spinal column and muscles cf the 
loins form a heavy, supporting structure at the back, while the side 
and front walls are made up mainly of connective tissue and sheets of 
muscle. The cavity terminates below in the hollowed out portion of 
the pelvic bones, which join firmly with the spinal column behind 
and provide suitable projections for the attachment of the muscular 
walls in front and at the sides. The abdominal cavity is the largest 
cavity in the body and contains organs of great importance. 
Dissection of the Abdomen. If the class is not too large, a half grown 
cat is perhaps the best specimen available. It may be killed with chloroform in 
the following manner: Warm a small, tight box, or jar, having a close-fitting lid, 
by placing it near a stove or fire-place. Put in the cat and place on the lid, but 
leave a small opening, through which pour 3 or 4 tablespoonfuls of chloroform. 
Then close the opening and fasten down the lid. In about 12 minutes the cat will 
be dead. , 
Before the cat stiffens stretch it on a board and drive a small nail through each 
foot. The teacher should make a preliminary examination of the abdomen to see 
that it is in a fit condition for class study. If the bladder is unnaturally distended, its 
contents may be forced out by slight pressure. 
The following materials will be needed during the dissection and should be 
near at hand. A sharp knife with a good point, a pair of heavy scissors, a vessel 
of water, some cotton batting, or a sponge, some fine cord, a few tacks, and a 
hammer. 
During dissection, the specimen should be kept as clean as possible. The 
escaping blood should be mopped up with cotton or a damp sponge. The teacher 78 
DISSECTION OF ABDOMEN. 
should make at least one dissection privately before attempting a class demon- 
stration. 
Order of Observations, i. Cut through the abdominal wall in the 
center of the triangular space where the ribs converge. From here cut a slit down- 
ward to the lower portion of the abdomen and sideward, each way, as far as con- 
venient. Tack the loosened abdominal walls to the board and proceed to study 
the exposed parts. Observe the muscles in the abdominal walls and the fold of 
th& peritoneum which forms an apron-like covering over the intestines. 
2. Observe the position of the stomach, intestines, liver, and spleen, and 
then, by pushing the intestines to one side, find the kidneys and the bladder. 
3. Study the liver with reference to location, size, shape, and color. On the 
underside, find the gall bladder from which a small tube leads to the small intes- 
tine. Observe the portal vein as it passes into the liver. As the liver is surcharged 
with blood, care must be taken to prevent cutting it, or its connecting blood 
vessels. 
4. Within the first coil of the small intestine as it leaves the stomach find 
the pancreas. Note its color, size, and branches. Find where it connects with the 
small intestine. 
5. Tie the canal tightly in two places, half an inch apart above the stomach 
and cut it in two between these places. Likewise tie and cut the rectum. The 
stomach and intestines may now be removed from the abdominal cavity and 
studied to better advantage. Examine the mesentery and its connections with the 
intestines. Notice the divisions of the portal vein and the lacteals passing through 
it. Sketch a coil of the intestine and the mesentery attached to it. 
6. Find in the center of the coils of the small intestine an elongated, gland- 
like body. This is the beginning of the thoracic duct and is called the receptacle of 
the chyle. From this the thoracic duct rapidly narrows until it becomes difficult to 
trace in a small animal. 
7. Cut away about two inches of small intestine from the remainder. Split it 
open for a part of its length and wash out its contents. Observe its coats. Place in 
water and examine the mucous membrane with a lens to find the villi. 
8. Study the connection of the small intestine with the large; split it open at 
this place, wash out contents, and examine the ileo-coecal valve. 
9. Observe the size, shape, and position of the kidneys. Do they lie in front 
of or back of the peritoneum ? Do they lie exactly opposite each other ? 
10. Note the connection of each kidney with the aorta and vena cava ascend- 
ing by the renal artery and renal vein. Find a slender tube, the ureter, running 
from each kidney to the bladder. Do the ureters connect with the top or base of 
the bladder ? Show by a sketch the connection of the kidneys with the large 
blood vessels and the bladder. 
11. Separate a kidney from its connections. With a sharp knife split the 
kidney like a bean. Examine the cavity on the hollow side and note its connection 
with the ureter. This is called thepelvis of the kidney. 
12. Note the differences in color between the outer and inner margins of the 
kidney. Find the little elevations within the pelvis known as the urinary 
pyramids. CONTENTS OF THE ABDOMEN. 
79 
1. Draw a curved line to 
represent the general shape 
of the abdominal cavity, and 
indicate the position of the 
stomach, liver, intestines, 
spleen, kidneys and bladder. 
2. Show by a drawing 
the shape of the pancreas 
and its connection with the 
small intestine. 
3. Make a drawing of a 
coil of the small intestine 
showing the mesentery and 
the branches of the portal 
vein. 
4. Show by a drawing the 
iwaion of the small, with the 
large intestine. 
5. Make a sketch show- 
ing the connection of the 
kidneys with the large blood 
vessels and the bladder. 
Organs of the Abdomen. As shown by the dissection, most 
of the abdominal cavity is taken up by the organs of digestion—the 
stomach, large and small intestines, the liver, and the pancreas. 
Next to these in the amount of space occupied, are the organs for 
separating and retaining, temporarily, liquid impurities from the 
blood — the kidneys and the bladder. 80 
THE PERITONEUM. 
The Spleen occupies a ' position below and to the left of the 
stomach. The function of this organ is not understood. Its only 
connection is with blood vessels, and it is spoken of as a blood gland. 
Since life continues after its removal from the body, its work, what- 
ever it is, is not regarded as of great importance. 
The Peritoneum, already referred to as forming the outer coat 
of the greater part of the alimentary canal, is to the abdominal cavity 
what the pleura is to the thoracic cavity. It consists of a double 
membrane, one layer of which lines the walls of the abdomen, while 
the other folds over the outside of the 
organs of the abdominal cavity. It se- 
cretes a liquid which prevents friction. 
An extension of the peritoneum which 
holds the intestines in position is called 
the mesentery. 
A Question of Hygiene. The plan 
of the body demands freedom of motion 
on the part of the abdominal walls. This 
is necessary both in bending the trunk 
and in breathing. Clothing should not 
interfere with the abdominal movements. Tight lacing prevents 
natural breathing and robs the trunk of its freedom of motion. More- 
over, it breaks down the lower thoracic arch, compresses the liver, 
and disturbs the natural location of the abdominal organs. Its con- 
tinued practice leads to serious results. 
References. On dissection of the abdomen, C., 195-197; J., 146; F. and S., 
13-19. On the peritoneum, F. and S., 20; C., 197. On the spleen, J., 167; F. and 
S., 163; C., 102. 
Practical Questions. 1. What cavities are found in the trunk? Name 
the important organs found in each. 2. Compare the pleura and peritoneum with 
reference to structure, general arrangement, and function. 3. Give functions of 
the abdominal muscles and the diaphragm. 4. How are the abdominal walls held 
in position? 5. What changes in the shape of the abdomen take place during 
respiration? Why are these changes necessary? 
Represent a cross section of the 
abdomen showing extent of peri- 
toneum. CHAPTER XII. 
Excretion. 
Necessity for Excretion. Organs Employed. Excretion is 
the process of removing waste material from the body. Much of the 
material, formed by the chemical changes in the cells, is of no use in 
the body and is produced only that energy may be liberated. Waste 
material, if left in the body, interferes with its work and in a short 
time causes death. Its removal is as necessary as the introduction of 
oxygen and food into the body. 
From the cells the waste materials pass through the lymph into 
the blood. The blood conveys them to the organs of excretion, 
where they are separated and then passed to the exterior of the body. 
The organs of excretion, named in the order of their importance, are 
the kidneys, lungs, skin, and liver. 
The Different Kinds of Waste Materials resulting from the 
union of oxygen with food substances in the cells and with the cell 
protoplasm are mainly the following: 
1. Carbon Dioxid. The natural state of this compound is a 
gas, but in the body it is found dissolved in different liquids. 
(Review its properties. See p. 33.) 
2. Water. Only a small amount of the water discharged from 
the body is formed in it. Its discharge in large quantities is neces- 
sary to the removal of substances dissolved in it. 
3. Urea. This is a solid, soluble in water, and found in the 
body dissolved in liquids. 82 
THE KIDNEYS. 
4. Salts. These comprise a number of different materials 
some of which are formed in the body while others, like common 
salt, enter as.a part of the food. They are solids, but must leave 
the body dissolved in water. 
Relation of Waste Materials to Foods. The non-nitrogenous 
foods, such as sugar, starch, and fat, by uniting with oxygen, form 
carbon dioxid and water. 
Nitrogeneous foods, such as albumen, gluten, etc., by uniting 
with oxygen form carbon dioxid, water, and urea. 
The salts are derived, to some extent, from all classes of foods. 
Quantity of Material Removed From the Body. After growth 
has been attained the weight of the adult varies only slightly from 
time to time. The tissues are torn down as fast as they are built up, 
and only minute portions of materials entering the body stay there 
permanently. The quantity of material leaving the body must 
therefore balance the quantity entering it; and the work done by the 
organs of excretion must offset the results of absorption at the 
organs of digestion and respiration. 
This is estimated for the average indi- 
vidual to be about five pounds daily. 
The Kidneys. 
The Kidneys are two bean-shaped 
organs situated in the back and upper 
portion of the abdominal cavity, one 
on each side of the spinal column. 
They weigh from 4 to 6 ounces each 
and lie between the abdominal wall 
and the peritoneum. Two large ar- 
teries from the aorta, called the renal 
arteries, supply them with blood, 
while they are connected with the 
vena cava ascending by the renal 
veins. They remove from the blood 
an exceedingly complex liquid called 
Show by a drawing the connec- 
tion of the kidneys with the large 
blood vessels and the bladder. STRUCTURE OF THE KIDNEYS. 
83 
the urine, the principal constituents of which are water, salts of differ- 
ent kinds, and urea. The kidneys pass their secretion to the bladder 
by two slender tubes, called the ureters. 
Review notes on the dissection of the abdomen. 
Minute structure of the Kidneys. The structure of a kid- 
ney is the same as that of a true compound gland. Its inner sub- 
stance is made up chiefly of blood vessels and a system of small tubes, 
called the 
Uriniferous tubes. Each tube starts from the outer margin of 
the kidney in a globular enlargement called the capsule which encloses 
a cluster of capillaries. From here the tube passes toward the open 
space on the concave side, known as the pelvis of the kidney. Be- 
fore reaching this place, however, it makes several loops or turns, and 
connects with other tubes to form 
larger ones. It is lined throughout 
its entire length by secreting epithelial 
cells and is surrounded by a network 
of capillaries. The materials, re- 
moved from the blood as it passes 
through the kidneys, enter the urin- 
iferous tubes and by them are carried 
to the pelvis of the kidney. 
The Work of the Kidneys is di- 
vided between the clusters of capilla- 
ries, at the beginning of the tubes, 
and the secreting cells lining them. 
The former separate water and the 
salts dissolved in it, from the blood, 
while the latter separate the dissolved 
urea. 
Hygiene of the Kidneys. The work which devolves upon the 
kidneys may be lessened in two ways: 
1. By keeping the skin clean and active. (See excretory 
work done by the skin.) 
2. By avoiding an excess of nitrogenous foods.—What waste 
materials are formed by the union of oxygen with nitrogenous foods? 
Show by a drawing the general 
arrangement of theuriniferous tubes. 84 
OTHER EXCRETORY ORGANS. 
Other Organs of Excretion. 
The Lung'S have already been studied. They are the principal 
organs for removing carbon dioxid. They also remove small quan- 
tities of water and “ animal matter.” It is the last named impurity 
that gives air in poorly ventilated rooms its peculiar odor. How 
prove the presence of carbon dioxid in the breath? How show the 
presence of watery vapor? (See p. 37.) 
The Skin is an organ with many functions and it will be more 
fully described at another place. Its excretory product is the per- 
spiration, or sweat, which consists of water with a small amount of 
urea, common salt, and other substances dissolved in it. It is sepa- 
rated from the blood by the sweat glands. Find a description of 
these in some physiology. The perspiration comes from the skin 
either as a liquid or in the form of an invisible vapor. When a liquid 
it is called sensible perspiration; when a vapor, insensible. 
Experiment. Lay the palm of the hand against a cold window pane for a 
short time. Account for the collection of moisture on the pane. Does this experi- 
ment illustrate sensible or insensible perspiration ? 
The work of the skin is quite similar to that of the kidneys. In 
reality it does on a small scale what the kidneys do on a large scale. 
When the kidneys are diseased the skin becomes more active. Why 
should it? Why should one bathe frequently? 
The Liver discharges its impurities in the bile. This liquid has 
not been studied sufficiently to determine what portions of it are ex- 
crementitious and what portions assist in digestion. 
Show by filling out the blank spaces in Table II, how the more important 
waste materials are formed and what organs of excretion remove them. THROWING OFF OF WASTE. 
85 
Carbon Dioxid 
Urea 
Water 
Common Salt 
TABLE II. THE PASSAGE OF THE WASTE FROM THE BODY. 
State to which it Form in which it How Formed at c „ . „ T, 
Belongs. Leaves the Body. the Cells? The Chief Organs to Remove It. 
(TO BE COMPLETED BY THE PUPIL. ) 
Common salt is 
not found at the 
cells. 86 
GENERAL SUMMARY. 
Combined Work of Different Systems. 
General Summary. We have seen that the body is an aggre- 
gation of different kinds of cells; that it grows by the growth and 
reproduction of these cells; and that the life of the body, as a whole, 
is maintained by keeping these cells alive. For ministering to the 
wants of the cells two liquids (the lymph and the blood) are em- 
ployed. To keep these liquids in the proper condition for their work 
in the body, requires the combined action of all the systems which 
we have studied. The results of their combined work are both direct 
and indirect. 
The Direct Result of the combined action of the systems is to 
keep up two general movements of materials in the body as follows: 
1. An inward movement which carries material from the out- 
side of the body toward the cells. 
2. An outward movement which carries material from the cells 
to the outside of the body. 
Passing inward we have the oxygen and food materials in a con- 
dition to unite with each other and thereby change their potential 
into kinetic energy. Passing outward we have the oxygen and food 
material after they have united at the cells and liberated their energy. 
The Indirect Result, of supreme importance, is the keeping 
up of a continuous series of chemical changes in the cells. These lib- 
erate energy, provide material for the growth and repair of the tis- 
sues, and preserve the life of the body. 
Relation of the Systems Illustrated. The relation of the systems to 
each other and to the cells may be illustrated in the following manner : 
With a common center, and with radii of y2, and inches, draw 
four concentric circles. Let the space represented by the first, or inner, circle RELATION OF SYSTEMS ILLUSTRATED. 
87 
represent the cells ; that between the first and second, the lymph ; between the 
second and third, the 
blood; and that between 
the third and fourth, the 
systems which have been 
studied. Write the names 
in the different circles and 
indicate by arrows, (i) the 
flow of material from the 
digestive and respiratory 
systems to the cells and 
(2) the flow of material 
from the cells to the 
organs of excretion. 
Indicate by filling out 
the blank spaces in Table 
III, the passage of the 
more important materials 
through the body - 
References. On struc- 
ture of kidneys, J., 203- 
205; C., 163-165; F. and S., 
166-172 ; S., 151-154. On materials removed by kidneys, S., 153 ; F. and S., 169- 
172 ; C., 162. On care of the kidneys. S., 154, 155. 
Practical Questions. 1 What is the necessity for the production of 
impurities at the cells ? 2. Name other functions which certain of the organs 
of excretion perform. 3. How do impurities get from the cells to the organs of 
excretion? 4. In what do the uriniferous tubes have their beginning? In what 
do they terminate ? With what are they lined? 5. Bright’s disease of the kid- 
neys affects the uriniferous tubes and interferes with their work. What impurity 
is then left in the blood ? 6. Trace urea, water, and salts from where they are 
removed from the blood through the different tubes to the bladder. 7. Trace 
carbon dioxid from the cells to the outside atmosphere. 
Draw a diagram illustrating the relation of the 
systems. « 88 
PASSAGE OF MATERIAL. 
PurP°ses- Qrgans which Remove U aS Waste' 
TABLE III. PASSAGE OF MATERIAL THROUGH THE BODY. 
(TO BE COMPLETED BY THE PUPIL.) 
Materials. 
Proteids 
Fat 
Starch 
Oxygen 
Water CHAPTER XIII. 
The Skeleton. 
The Tissues Employed in the construction of the skeleton, or 
framework of the body, are the osseous, cartilaginous, and connec- 
tive tissues. These form the bones, supply elastic pads fortheendsof 
the bones, and furnish strong bands, or ligaments, for fastening the 
bones together. Note that the properties of these tissues adapt them 
to the purposes which they serve in the skeleton. (See p. 3.) 
The Composition Of a Bone is indicated to some extent by the 
following 
Experiments: 1. Soak a slender bone, like that in the leg of a chicken, 
over night in a mixture of one part of hydrochloric acid with four parts of water. 
Ascertain by bending, stretching, and twisting what properties the bone has lost. 
2. Burn a small piece of bone in a clear gas flame or on a bed of coals until 
it ceases to blaze. By testing, find what properties the bone has lost by the 
burning. 
State 
I. 
results. 
2. 
The acid dissolved out the material which gives the bone its 
property of stiffness. This is called the mineral matter and consists 
chiefly of carbonate and phosphate of lime. 
Burning destroys the material which gives the bone its proper- 
ties of toughness and elasticity. This is called the animal matter. It 90 
STRUCTURE OK BONE. 
consists of connective tissue, walls of blood vessels, nerves, and the 
protoplasm of the bone cells. About one-third of the bone is animal 
matter. The other two-thirds is mineral matter. 
Gross Structure of Bones. 
Observations, i. Procure a long, dry bone. One that has lain out in a 
field until it has bleached will answer the purpose excellently. Test its hardness, 
strength, and stiffness. Saw it in two, a third of the distance from one end and 
saw the short piece in two, lengthwise. Compare the structure at different places. 
Find rough elevations on the outside for the attachment of muscles and small open- 
ings into the bone for the entrance of blood vessels and nerves. Make drawings 
to represent the sections. 
2. Procure a fresh bone from the butcher shop. Note differences between it 
and the dry bone. Examine the material covering ends and that which surrounds 
it. Look for the red and yellow marrow. 
x. Drawings ol sec- 
tions of bone. 
2. Description of 
the fresh bone. 
The ends of the bone are capped by a layer of elastic cartilage 
while its entire surface is covered by a sheath of connective tissue, 
called the periosteum. In the central part is 
a long hollow portion, called the marrow 
cavity. This is lined with an inner sheath, 
the endosteum, and is filled with a fatty sub- 
stance called the yellow marrow. Around the 
marrow cavity, the bone is very dense and 
compact. At the ends the bone substance is 
coarse and spongy, containing a great num- 
ber of small cavities which are filled with the 
red marrow. What is the supposed function 
of the red marrow? 
Minute Structure of Bones. A micro- 
scopic study of bone shows two kinds of small 
canals which penetrate all portions of it. 
These are known as the Haversian canals and 
Drawing to show the 
gross structure of a bone. NOURISHMENT OF BONES. 
9i 
the canaliculi. The Haversian canals are the larger of the two kinds 
and, as a rule, run the long way of the bone. Surrounding each canal 
are several thin, circular layers of hard, bony substance. (Shown by 
a transverse section of bone prepared for microscopic study.) The 
canaliculi pass out from the Haversian canals, at right angles, to a 
great number of irregular clusters in'the layers of bone, called the 
lacunae. 
Under the micro- 
scope the lacunae pre- 
sent an appearance 
similar to that of a 
number of large burrs 
fastened together by 
their projecting 
spines. The walls of 
the lacunae contain 
the mineral matter of 
the bone and are, 
therefore, hard and dense. Within each lacuna is an open space 
in which lies a soft body, having a nucleus. This is the bone cell, 
or bone corpuscle as it is sometimes called. The work of this cell is 
to provide for the hardness and stiffness of the bones by depositing 
mineral matter in the walls surrounding it. 
How the Bone Cells Are Nourished. They, like all the other 
cells of the body, are nourished by the lymph which escapes from 
the blood. This reaches the cells in different parts of the bone in two 
ways, as follows: 
1. The cells at the surface of the bone receive lymph from blood 
vessels in the periosteum. It reaches them through canaliculi passing 
from the outside of the bone to the lacunae near the surface. 
2. The cells within the bone receive nourishment through the 
channels penetrating the bone. Many of these are large enough to 
be seen with the naked eye and enclose small veins and arteries. The 
Haversian canals probably contain capillaries, while the canaliculi 
convey the lymph. 
I. 
Drawings of sections of bone. 
2. 92 
PLAN OF SKELETON. 
The Names of the Principal Bones and their grouping in the body are 
shown by the following table : 
I. Axial Skeleton. 
A. Skull, 28. 
1. Cranium, 8. 
a. Frontal, forehead 1 
b. Parietal 2 
c. Temporals, temples 2 
d. Occipital. 1 
e. Sphenoid 1 
f. Ethmoid 1 
2. Face, 14. 
a. Inferior Maxillary 1 
b. Superior Maxillaries . 2 
c. Palatine, palate 2 
d. Nasal bones 2 
e. Vomer :. 1 
f. Inferior Turbinated 2 
g. Lachrymals 2 
h. Malars, cheek bones 2 
3. Bones of the Ear, 6. 
a. Malleus 2 
b. Incus 2 
c. Stapes 2 
B. Spinal Column, 26. 
1. Cervical, or neck vertebrae 7 
2. Dorsal, or thoracic vertebrae 12 
3. Lumbar vertebrae 5 
4. Sacrum 1 
5. Coccyx 1 
C. Thorax, 25. 
1. Ribs 24 
2. Sternum 1 
D. Hyoid, 1 1 
II. Appendicular Skeleton. 
A. Shoulder Girdle, 4. 
1. Clavicle, collar bone .....2 
2, Scapula, shoulder blade 2 
B. Upper Extremities, 60. 
1. Humerus 2 
2. Radius 2 
3. Ulna 2 
4. Carpals, wrist bones 16 
5. Metacarpals 10 
6. Phalanges 28 
C. Pelvic girdle, 2. 
1. Os innominatum 2 
D. Dower Extremities, 60. 
1. Femur, thigh bone 2 
2. Tibia 2 
3. Fibula 2 
4. Patella, knee cap 2 
5. Tarsals, ankle bones .14 
6. Metatarsals, bones ot the instep .10 
7. Phalanges, bones of the toes 28 
If a skeleton can be obtained, it 
should be studied sufficiently to enable 
the pupil to locate the different bones 
and understand the plan and purpose of 
each group of bones. 
The Plan of the Skeleton must be such as 
to provide a framework for a moving structure. 
Stationary structures are built onto founda- 
tions. A moving structure, as a wagon or a 
bicycle, must have within it some strong, cen- 
tral part to which the remainder is joined. The 
part of the skeleton to which the other parts 
are attached is a bony axis made of a num- 
ber of bones firmly bound together, called the 
spinal column. The head, the ribs, and the 
pelvic girdle are attached directly to the 
spinal column, while the other parts are 
attached indirectly. 
Drawing to show plan 
of the skeleton. IMPORTANT GROUPS OF BONES. 
93 
Important Groups of Bones. 
Only the plan of study is here indicated. In getting information consult, first 
of all, the skeleton. After this consult the cuts and descriptions in text books. 
Spinal Column. Give its purposes, plan of construction, length, 
general shape, and position with reference to the other parts of 
the body. Study the construction of a single vertebra and the plan 
of joining it to others. How is the spinal cavity formed? What is 
its purpose? Where is the cartilage placed? What purpose does it 
serve? Locate and describe vertebrae, known as the axis and the atlas. 
Locate and give number of the cervical vertebrae, the dorsal 
vertebrae, and the lumbar vertebrae. Locate and describe the sacrum. 
The Head- Locate and name the bones of the cranium and the 
bones of the face. What is the general shape of the bones of the 
cranium? What important cavity do they enclose? What different 
purposes are served by the bones of the face? Describe and give 
function of the temporal, sphenoid, inferior maxillary, and itiferior 
turbinated bones. 
Ribs. Give number, shape, and functions of the ribs. Describe 
plan of attachment to spinal column and to the sternum. Distinguish 
between the true, false, and floating ribs. Why are the ribs placed in a 
slanting position? What is the main purpose of the ribs? 
Pelvic and Shoulder Girdles. Give general purposes of each 
and describe the bones which form them. Compare them with refer- 
ence to the number and size of their bones, connection with spinal 
column, strength of parts, and their uses. (The pelvic arch is the 
strongest arch in the body.) 
The Humerus and the Femur. Locate them and name the 
bones with which they join. Study the joints formed by their artic- 
ulation with other bones. Compare them with reference to length, 
shape, strength, and purpose in the body. 
Bones of the Forearm and Lower Leg1. Name and locate 
these bones. Study the joints formed by their articulations with 
other bones. Compare the two groups with reference to size, shape, 
and strength of bones. What bone in the lower leg, has no corres- 
ponding bone in the forearm? What joint in the forearm has no 
corresponding joint in the lower leg? 94 
ARTICULATIONS. 
Carpal and Tarsal Bones. Locate and give general use of 
these groups. Compare with reference to position, number, and 
shape of bones and strength. 
Metacarpal and Metatarsal Bones. Locate and give general 
use of the groups. Compare them with reference to the size, shape, 
strength, and number of their bones. 
Upper and Lower Phalanges. Locate and give general use of 
these groups. Compare them with reference to the number, size, 
and shape of their bones. Account for the superior development of 
one group over the other. 
Size and Shape of Bones. The bones vary in shape and size 
to suit their position and use in the body. Some bones, like the 
humerus, are adapted to giving form, strength, and stiffness to parts 
of the body. Others, like the pelvic bones, are fitted for supporting 
and protecting. Others still, as the wrist and ear bones, are adapted, 
by their size and shape, to giving a peculiar kind of motion. Where 
is the smallest bone in the body? Where is the largest? Why 
should the skull bones and the ribs be flat? Why should the femur, 
and the humerus, be long and cylindrical? Why should the bones 
of the wrist be short and rounded? 
Articulations. 
Any place in the body where two 
or more bones are joined together 
is called an articulation. Articula- 
tions are of two kinds, known 
as the movable and the immov- 
able. A great number of the latter 
are to be found in the skull where 
projections from one bone interlock 
with those of another, the tissue be- 
tween being very thin. This kind of 
an articulation is called a suture. (Ex- 
amine bones of a skull.) 
A joint is a movable articulation. It 
must be so constructed that the bones 
glide over each other easily and with- 
Show by a drawing the plan of 
a joint, naming parts. DIFFERENT KINDS OF JOINTS. 
95 
out friction. The parts of the bones which help to form joints are 
smooth and are covered with a thick layer of cartilaginous tissue. This 
serves as an elastic cushion to deaden shocks. The cartilage is cov- 
ered with the synovial membrane, the inner surface of which secretes 
the synovial fluid. What is the purpose of this fluid? It is retained in 
the joint by the synovial membrane, which surrounds the ends of 
the bones and extends from one to the other so as to form a closed 
sac. Strong ligaments join the bones together. The fibers of the 
ligaments are interwoven with the periosteum, making a very secure 
attachment. In some cases the ligaments form one continuous sheath 
around the joint, making what is called a capsular ligament. Give 
an example. 
Observation. Procure from the butcher shop the joint of some small ani- 
mal (hog or sheep). Cut it open and locate the cartilage, synovial membrane and 
ligaments. Observe the smoothness of the rubbing parts and the strength of the 
ligaments. 
The Different Kinds of Joints are the ball and socket, the hinge, 
the pivot) and the combination joint. The ball and socket joint con- 
sists of a ball-shaped end of bone which fits into a cup-shaped cavity, 
called a socket. Name examples. This joint admits of motion in 
what directions? In the hinge joint the bones are grooved and fit 
together something after the plan of a hinge. Name examples. Of 
what motion is it capable? The pivot joint is formed by one bone 
rotating or turning against another. Give examples. This joint 
admits of motion around a given axis. Where a joint combines the 
motion and structure of some of the above joints it may be called a 
combination joint. Give examples. 
The Bones as Instruments of Motion. 
In many different ways the bones are valuable aids to the 
muscles in the production of motion. They do their most important 
work in this respect by acting as levers. 
A Lever may be described as a stiff bar which is used in lifting 
weights. It is made to turn on a fixed point- of support called the 
fulcrum. The force applied to the bar is called the power, and that 
which is lifted is termed the weight. Levers are of three kinds, 96 
USES OF THE LEVER. 
known as the first class, second class, and third class. The only 
difference between them is in the position of the power, weight, and 
fulcrum. In the first class the fulcrum is between the power and 
weight. In the second class the weight is between the fulcrum and 
the power. In the third class the power is between the fulcrum and 
weight. 
The distance between the fulcrum and the power is called the 
arm of the power and the distance between the fulcrum and the 
weight is called the arm of the weight. This applies to all the classes 
of levers. 
Represent by drawings the different classes of levers, naming the parts, and 
showing in each the arm of the power and the arm of the weight. 
Uses of the Lever. In a mechanical sense the lever has two 
important uses: 
1. To enable a small power acting through a long distance to 
move a great weight through a short distance. 
2. To enable a great power acting through a short distance to 
move a small weight through a long distance. 
Whether it does the one or the other, depends upon the relative 
lengths of the lever arms. The weight will be as many times greater 
than the power as the power's arm is times longer than the weight's arm, 
and the distance moved by the weight will be as many times greater than 
the distance moved by the power as the weight's arm is times longer than 
the power's arm. 
Experiment. With a stiff, wooden rod, a small weight, a hand scale, and 
a suitable fulcrum illustrate the foregoing uses of levers. By placing the power and 
weight at suitable distances from the fulcrum, prove the relation which the power 
and weight sustain to the lever arms. 
A third use of the lever is to enable a power acting in one direc- 
tion to cause the'weight to move in an opposite direction. PRACTICAL QUESTIONS. 
97 
Levers in the Body. In the body the muscles furnish the power ; 
a part of the body itself, or some object to be lifted, serves for the 
weight, and the fulcrum is generally at a joint. Find in the body a 
representative of each of the three classes of levers. To which class 
do most of the levers of the body belong? How does the length of 
the arm of the power compare with the length of the arm of the weight? 
Levers serve two mam purposes in the body: — i. They ena- 
ble muscles acting in one direction to move parts of the body in the 
opposite direction. 2. They enable the muscles acting with great 
force through short distances to move portions of the body through 
long distances. 
The contraction of the longest muscles does not amount to more 
than two or three inches, yet they are able, by the use of levers, to 
make portions of the body move as many feet. Furnish illustrations 
of this fact. 
On the Care of the Bones. What is the danger of having children walk 
at too early an age ? Why should children not sit on seats too high for their feet 
to reach the floor ? Why is moderate exercise beneficial, and violent exercise 
injurious to the bones? How is a broken bone “set?” What is a sprain ? What 
is a dislocation ? Why must a sprain have careful treatment ? 
References. On the structure of bone, F. and S., 59-63; J., 56-58; S., 156- 
163; C., 352-354. On the skeleton, F. and S., 36-46; J., 42-51; S., 164-173; C.. 346- 
352. On joints, F. and S., 47-53; J-, 59-61; S., 173-177; C., 24-27, On levers, F. 
and S., 70-75; J., 72, 73; C., 21-23. On care of the bones, S., 163; C.,355. On dis- 
locations and sprains, J., 61, 62; S., 359; C., 355. 
Practical Questions. 1. How many bones in the body ? What differ- 
ent purposes do they serve ? 2. Show that each bone is adapted by its size, shape, 
and strength, to the use made of it in the body. 3. Locate the bone cells. What 
is their use in the bone ? 4. What is the necessity for the animal matter in a 
bone ? For the mineral matter ? 5. What is the mechanical advantage of hav- 
ing certain bones hollow? 6. Give the use of the periosteum. 7. State the 
purpose of the Haversian canals. Of the canaliculi. 8. What part does the spinal 
column play in the plan of the skeleton ? 9. What purposes are served in the body 
by the use of levers ? 10. Why is it easier to hold a heavy weight straight out from 
the shoulder, if placed at the elbow than if held in the hand? 11. Name the 
different materials used in the construction of a joint, and the purpose served 
by each. CHAPTER XIV. 
The Muscular System. 
Muscular Tissue forms nearly one-half of the entire weight of 
the body. This fact in itself indicates the importance of the problem 
of supplying the body with the power of motion. Muscular tissue is 
able to cause motion through its property of contractility. This 
property enables the tissue, when stimulated, to become shorter and 
thicker (a condition called contraction) and when the stimulus is 
removed, to return to its former condition of relaxation. 
Most of the muscular tissue in the body is organized into work- 
ing groups, called muscles. The muscles are of two general types— 
the striated and the non-striated. 
Note. The reddish muscle found in a piece of beef is a good example of 
striated muscle, while the clear muscle surrounding the intestine of the cat (p. 78) 
represents non-striated muscle. 
Structure of Striated Muscles. The unit of structure of 
striated muscular tissue is the muscle fiber. This is a slender, 
thread-like structure, varying in length from Ys to \Y inches and 
tapering to a point at each end. Its sides are marked by a great 
number of dark, transverse lines, called striations. The outside part 
consists of a thin wall, which encloses a semi-liquid material, known 
as muscle protoplasm, which is the contractile part of the fiber. 
Connected with the muscle fiber near its center is the minute termina- 
tion of a nerve fiber. 
The nature of the muscular fiber is not fully understood. By some physiolo- STRUCTURE OF MUSCLES. 
99 
gists it is regarded as a single cell; by others, as a collection of many small cells. 
The weight of evidence seems to be in favor of regarding it as a single cell. 
In the long muscles a number of fibers may be joined to form 
muscle threads. A number of these threads form a slender bundle, 
around which is placed a thin layer of connective tissue. These 
bundles are again bound into larger ones by bands of connect- 
ive tissue, so that the entire muscle consists of bundles of bundles of 
muscular threads. The whole is surrounded by a single sheath of 
connective tissue called the perimysium. At the ends the muscles 
are attached to tendons which connect them with the bones. 
Observation. Examine the structure of a piece of beef which has been 
boiled for a considerable length of time. Separate into the small bundles which 
make it up. If possible separate one of the smallest bundles into its fibers. 
Structure of Non-Striated Muscle. The cells of non-striated 
muscles differ from the fibers of striated muscles in being shorter, 
and decidedly spin'dle-shaped, and in having a single well-defined 
nucleus. Furthermore, there is a 
lack of striations, the surface being 
smooth, and the connection with 
nerve fibers is less marked. 
In the formation of non-striated 
muscles the cells are interwoven to 
some extent and held in place by a 
cementing material. They form thin 
sheets or bands which surround the 
organs on which they act. 
General Differences Between the 
Types of Muscles, i. The striated 
muscles are under control of the will; 
the non-striated are not. Find exceptions. 2. The striated are 
reddish in color; the non-striated are light and pale. 3. The stri- 
ated are usually attached to the bones of the skeleton which they 
move as levers; the non-striated surround hollow cavities and tubes, 
such as the stomach and arteries. 4. The striated muscles con- 
tract and relax quickly; the non-striated, slowly. 5. In shape the 
striated are inclined to be rounded; the non-striated are thin and 
sheet-like. 
Make drawings representing mus- 
cle fibers and cells. IOO 
MUSCULAR ENERGY. 
Muscular Stimuli. The natural condition of a muscle is that of 
relaxation. It is made to contract by the action of some force upon 
it. That which acts upon a muscle to cause it to contract is called a 
stimulus. All the muscles of the body are controlled by the nervous sys- 
tem which furnishes a stimulus known as the nervous impulse. This 
originates in the nerve centers and reaches the muscles through the 
nerves. It will receive further study in connection with the nervous 
system. 
Experiment. Remove the skin from over the large muscles in the leg of a 
live, brainless frog. (See Appendix.) Wet a piece of rock salt and rub it against 
the muscle, noting what happens. Then pass a weak current of electricity through 
the muscle. Finally, by separating the muscles, find a white cord (a nerve) and 
cut it in two, leaving the end nearest the muscles accessible. Irritate the nerve by 
pinching or by passing a current of electricity through it, noting results. 
State results. 
Hot and cold objects, electricity, many kinds of chemicals, and 
mechanical irritation can all cause muscular contraction and may, 
therefore, be called muscular stimuli. In the body, however, the 
nervous impulse is the only stimulus employed. 
Liberation of Energy in Muscles. The chief evidences of the 
liberation of energy at the muscles are the results which accompany 
their contraction. Careful experiments show that, during the con- 
traction period, oxygen and food material are consumed, waste mater- 
ials such as carbon dioxid and urea are produced, and heat is liberated. 
The blood supply to the muscles is also such as permits of mater- 
ials being carried rapidly to and from the muscles. Blood vessels 
penetrate them in all directions and the capillaries lie very close to the 
individual cells. Provision is also made, through the nervous system, 
whereby the flow of blood in a muscle is increased when it is at work. 
From these things, as well as from the great force with which 
the muscle contracts, we may conclude that the muscle is a trans- 
former to energy—that within its protoplasm the chemical changes 
take place whereby the potential energy of oxygen and food materials 
is converted into the kinetic energy of motion. THE PLACING OF MUSCLES. 
101 
The Plan of Using- Muscular Force in doing the work of the 
body is interesting from a mechanical, as well as physiological 
standpoint. Muscles exert force only when they contract. They can 
pull but not push. Hence in the body each muscle must work 
against some force which produces a result directly opposite to that 
of the muscle when it contracts. Some work against the elasticity 
of certain parts of the body; others, to some extent, against gravity; 
and others, against pressure. But in most instances 
Muscles Work Against Muscles. The muscles of the skeleton 
are arranged after this plan. As a rule, a pair of muscles is so 
placed, with reference to a joint, that one moves a part of the 
body in one direction, while the other moves it in the opposite direc- 
tion. With reference to the work which they do, skeletal muscles 
are classed as follows : 
I. Flexors and extensors. 2. Adductors and abductors. 3. 
Rotators. 4. Radiating and sphincters.—These are arranged in 
pairs, the members of which give the different parts of the body their 
opposing movements. 
The flexors and extensors bend and straighten joints; the 
adductors and abductors draw the limbs toward and away from the 
axis of the body; the rotators (two kinds) twist and untwist joints; 
the radiating and sphincters open and close natural openings. Find 
examples of each of these different classes of muscles. 
Tendons are the strong cords of 
connective tissue which attach the 
muscles to the bones. The white 
fibrous tissue of which they are 
composed is interwoven with the 
perimysium of the muscle at one end 
and the periosteum of the bone at the 
other, making, in this way, a very 
secure attachment. Are tendons elas- 
tic or inelastic? Why? 
Work of the Non-Striated Mus- 
cles. The motions of the body which 
are directly concerned in maintaining 
Show by a drawing the attach- 
ment of the biceps muscle to the 
bone. 102 
IMPORTANT MUSCLES. 
life are brought about by non-striated muscles. The most important 
of these are the motion of the respiratory and digestive organs, and 
the changes in the size of the arteries. Why should such important 
movements be involuntary? 
Important Muscles. There are nearly 500 separate muscles in the body, 
These vary in size, shape, and plan of attachment, to suit their special work in the 
body. Some of those prominent enough 
to be distinguished from the outside of 
the body are as follows: 
1. Of the Head: the temporal, in 
the temple, and masseter, in the cheek. 
These are attached to the lower jaw, and 
are the chief muscles of mastication. Of 
the neck: the sterno-mastoid, which pass 
between the base of the skull and the 
sternum. They assist in turning the head. 
Of the arm: the biceps, on the front side, 
the triceps behind, and the deltoid, above 
and beyond the projection of the shoulder. 
The deltoid lifts the arm. Of theforearm: 
the flexors of the fingers, on the under 
side, and the extensors of the fingers, on 
the upper side. Of the hand: the adductor 
pollicis between the thumb and other part 
of the hand. Of the trunk: the pedoralis 
major, between the upper iront part of 
thorax and the shoulder, the trapezius, 
between the back of the shoulder and 
the spine, the rectus abdominis, passing 
over the front of the abdomen from above 
downward, the erector spinae, found in 
the small of the back. Of the leg: the 
gastrocnemius, the large muscle in the 
calf of the leg. 
This is the largest muscle in the body, 
and connects with the heel bone by the 
tendon of Achilles. 
The Necessity for Exercise. 
The body is designed for motion 
and any perversion of its plan 
means disease. Let the ambitious 
student, and others of sedentary habits, remember that nearly half 
of the entire weight of the body is muscular tissue. If physical 
Indicate in the cut the position 
of large muscles, giving names. NECESSITY OF EXERCISE. 
103 
qxercise is neglected the muscles begin a slow process of degenera- 
tion which results in their becoming weak, soft, and flabby. In this 
condition they contract with little force and tire with slight exertion: 
But the worst effects of neglected exercise are to be observed on 
other portions of the body. The circulation is diminished in force, 
the blood loses large numbers of its red corpuscles, the breathing 
capacity is lessened, the excretion of waste is retarded, appetite fails, 
power to resist disease is diminished, and energy for both mental and 
physical work is lacking. In brief, one may become a helpless inva- 
lid simply by neglecting to take a sufficient amount of physical 
exercise. 
References. On structure of muscles, S., 181-183; F- and S., 64-67; J., 68-70; 
C., 14-16. On muscular contraction, S., 184-186; F. and S., 67-69; J., 70-71; C., 17. 
On the heart muscle, F. and S., 67. On muscle and nerve, C , 12-14; J-> 69; F. and 
S., 69. On muscle fatigue, J., 72. On necessity for exercise, S., 191-197; J., 75-77; 
C., 234-240. On effect of alcohol on muscles, S., 197-201. 
Practical Questions. 1. How does the muscle cause motion in the body? 
2. If muscles could push as well as pull would so many be needed in the body ? 
Why ? 3. Locate a muscle which works against elasticity. One which works 
against pressure. One which works, to some extent, against gravity. 4. How 
does the nervous system control the muscles ? 5. Give differences in structure be- 
tween the striated and the non-striated muscles. 6. Give general uses of the 
striated muscles in the body. Of the non-striated. 7. Show how muscular contraction 
aids in the circulation of the blood and the lymph. 8. What are the proofs of the 
change of potential into kinetic energy during muscular cqntraction? 9. What 
are the peculiarities of the heart muscle ? 10. What results follow a lack of suffi- 
cient exercise ? 11. What precautions should be observed in taking exercise? CHAPTER XV. 
The Skin. 
Protective Covering’s. Three kinds of coverings are employed 
for the protection of the body. These are the skin, the mucous mem- 
brane, and the serous membrane. The mucous membrane has already 
been studied. (See p. 62.) The pleura and peritoneum afford 
good illustrations of serous membrane. (See pp. 42, 80.) 
The skin covers the entire outside of the body, and consists of 
two layers:—the dermis, or true skin, and the epidermis, or cuticle. 
The Dermis is the under and thicker layer of skin and is made 
up mainly of a dense network of connective tissue fibers. This gives 
to the skin its toughness. Interwoven with the connective tissue, are 
numerous blood vessels, lymphatics, oil glands, perspiratory glands, 
and nerves which terminate in small bulb-shaped organs called touch 
corpuscles. 
At its outer surface, the dermis is exceedingly rough and uneven, 
forming numerous elevations called the papillae. Each papilla con- 
tains the loop of a capillary vessel and a nerve fiber, and many of 
them are crowned with touch corpuscles. The inner surface of the 
dermis is attached to the parts beneath by a loose network of con- 
nective tissue. 
The sebaceous, or oil, glands are situated at the roots of hairs. 
The oil which they secrete keeps the outside of the skin soft and pliant. 
A perspiratory gland consists of a single slender tube which 
passes through the epidermis and terminates in a rounded coil in the 
dermis. It is lined with a single layer of cubical cells and is sur- SECTION OF THE SKIN. 
105 
rounded in the dermis by a network ot capillaries. It secretes the 
perspiration, or sweat. The perspiratory glands are exceedingly 
numerous. 
Observation. Examine the palm of the hand with a hand lens. Note the 
small ridges which correspond to the papillae beneath the cuticle. In these 
ridges find small pits, the openings of the sweat glands. By counting the number 
of these on a quarter of an inch of surface, estimate the number on the entire palm 
of the hand. 
Make a sectional drawing illustrating the structure of the skin, naming the 
parts. 
The Epidermis, or cuticle, is much thinner than the dermis. It 
is tough, non-sensitive, and in some places, rough and hard. It 
contains no blood vessels, nerves, or lymphatics. Its purpose is 
purely protective. 
Observation. Examine the cuticle of the hand. Where is it thickest ? 
Account for the difference in thickness at different places. Pick a thick portion of 
it with a pin to see if pain is felt. Inference. 
State 
results. 106 
HAIR AND NAILS. 
The cuticle grows by the multiplication of cells at its under sur- 
face. These receive nourishment through the lymph coming from 
the blood vessels in the dermis. At the inner surface the cells of 
the cuticle are full and round, while at the outer surface they are flat 
and scaly. 
Where the cuticle joins the dermis is a layer of pigment, or color 
cells, which gives the color to the skin. 
The Hair and Nails are modifications of the cuticle. 
A hair is a long, slender cylinder of epidermis. It grows 
from a kind of pit in the dermis, by the addition of cells to its inner 
end. Give uses of the hair. 
The nails are composed of a number of hard, flat, epidermal 
cells. They grow in length by the addition of cells to their roots 
and in thickness, by the addition of cells to their undersurface. That 
part of the dermis from which the nails grow is called the matrix. 
Of what use are the nails? 
Observation. Examine a finger nail. Is the edge or root the thicker ? 
Account for the difference. What is a proof that the nails are not sensitive ? 
Functions of the Skin. The skin has the following functions: 
i Protection. I his is its main function and is provided for 
through the connective tissue in the dermis, the tough, non-sensitive 
cells in the epidermis, and the touch corpuscles and their connecting 
nerve fibers. 
2. It is an organ of excretion. (See p. 84.) 
3. It is an organ of absorption. The small blood vessels and 
lymphatics absorb liquids to a small extent. 
4. It is an organ of touch, or feeling. This function is provided 
for through the touch corpuscles and their nerve fibers. 
5. It assists in regulating the temperature of the body, i. e., 
in keeping the body from getting too hot or too cold. 
How the Skin Regulates Temperature. It assists in keeping 
the body warm by preventing the escape of heat from the body. In REGULATION OF TEMPERATURE. 
107 
the under portion of the dermis there is considerable fat This is a 
poor conductor of heat and acts as would a layer of clothing to keep 
the heat within the body. 
The skin assists in cooling the body in two ways: 
1. By the radiation of heat from its surface as from a stove. 
2. By the evaporation of the perspiration. 
Experiments. 1. Wet the back of the hand with water and move it 
through the air to hasten evaporation. Observe that as the hand dries, a sensation 
of cold is felt. Repeat the experiment, using alcohol or gasoline instead of water 
and noting difference in the effect. Alcohol and gasoline evaporate faster than water. 
2. Wet the bulb of a thermometer with alcohol or water. Move it through 
the air to hasten evaporation. Note and account for the action of the mercury. 
State 
results. 
The above experiments prove the principle that a liquid, in 
changing io a gas, absorbs heat. The perspiration in evaporating, or 
changing from a liquid to a gas, absorbs heat from the body, making 
it cool. 
The Control of the Heat Producing* and Reg’ulating’ Pro- 
cesses is given over to the nervous system. This system controls 
the temperature of the body principally through its control over the 
circulation, the glands in the skin, and the chemical changes in the 
body. By varying the activity of different places and by shifting the 
circulation the temperature of the body is kept always at about 
98° F. 
A fall in temperature in the body is prevented 
1. By diminishing the circulation in the skin and increasing it 
in the internal organs. 
2. By diminishing the secretion of perspiration. 
3. By increasing the chemical changes in the cells, thereby 
increasing the amount of heat generated in the body. (See p. 52.) 
A rise of temperature in the body is prevented 
1. By increasing the circulation of blood in the skin, bringing 
more heat to the surface, where it can be radiated. 108 
CLOTHING. 
2. By increasing the amount of perspiration. 
3. By diminishing the rate of chemical changes at the cells. 
Alcohol, by interfering with the nervous control of the circulation causes 
heat to be wasted at a time when the body should be saving it. If taken on a cold 
day, it increases the circulation in the skin and causes a feeling of warmth. This 
fact has given rise to the erroneous idea that alcohol may act as a heat producer in 
the body. 
The Hygiene Of the Skin is nearly all included in the problems 
of keeping it warm and clean. It is kept warm by clothing. Bath- 
ing is the method of keeping it clean. 
Hygienic clothing should be warm and loose fitting. Woolen 
clothing is generally preferred to cotton because, being a poorer con- 
ductor of heat, it affords better protection from cold. But woolen 
clothing fails to absorb the perspiration rapidly from the skin and 
pass it to the outside where it is evaporated. This, together with its 
tendency to irritate, makes it objectionable for wearing next to the 
skin. If cotton clothing is worn between the woolen clothing and 
the skin, these difficulties are obviated. 
One should bathe often enough to keep the body clean. This will 
depend upon the season, the occupation of the individual, and the 
nature and amount of the perspiration. As to the kind of bath to be 
taken and the precautions to be observed, no general directions can 
be given These must be determined by the health and natural vigor 
of the bather. Care must be exercised at all times, however, in pre- 
venting too great an exposure of the body, during the bath. 
References. On structure of the skin, F. and S., 173-178; S., 202-210; C., 
151-156; J., 194-197. On functions of skin, C., 157; J., 198. On glands of skin, F. 
and S., 1765 s., 207, 214; C., 154-156; J., 197. On the hair and the nails, F. and S., 
178; S., 211-214; J., 2or. On regulation of temperature, C., 157-161; J., 199; F. and 
S., 181. On clothing, S., 219-222; C., 160. On bathing, S., 215-219; C., 233; J., 
203. On effect of alcohol on regulation of temperature, S., 230-232. 
Practical Questions. 1. Compare the dermis and epidermis with refer- 
ence to thickness, composition, and functions. 2. To what is the color of the 
skin due ? How is color affected by sunlight? 3. What different kinds of epider- 
mis are found on our bodies? What kinds on the body of a chicken? 4. Show 
what provision is made for each of the different functions of the skin. 5. How 
does perspiration cool the body ? 6. How does alcohol make one feel warm when 
he is losing heat? 7. What precautions should be observed, by one in poor 
health, in taking a bath ? CHAPTER XVI. 
General Structure and Function of Nervous Tissue. 
Nervous Tissue is of two varieties. These, on account of their 
color, have been designated the “gray matter” and the “white mat- 
ter.” Both are soft, weak, inelastic and, to the naked eye, appear 
as structureless masses. The microscope, however, shows them to 
be organized into cells which have long, thread-like attachments, 
called fibers. 
Important Properties of Nervous Tissue. Nervous tissue pos- 
sesses in a high degree the property of irritability. This property refers 
to the ability of a substance to respond to an external stimulus, and 
is illustrated by the contraction of muscles, following the application 
of electricity. Nervous tissue is so delicately organized that the least 
disturbance from without is sufficient to excite important chemical 
changes within. The result of these chemical changes is to liberate a 
peculiar form of energy which is called nervous force or nervous energy. 
The nervous tissue as organized in the body is also able to transmit 
this energy from the place where it is liberated to where it is to be 
used. Irritability and the power to liberate and transmit nervous 
energy adapt nervous tissue to the different purposes which it serves 
in the body. 
The Nerve Cell has the usual parts of a complete cell (name 
them), but differs from all the other cells of the body in having its 
protoplasm extended, at one or more places, to form the central part 
of the nerve fiber. The nerve cells found in different parts of the 
body, differ greatly in size and shape. I I o 
NERVE CELLS AND FIBERS. 
Nerve cells do not exist singly 
in the body but are found in groups. 
A single group of nerve cells is called 
a ganglion. The brain and the spinal 
cord are great collections of ganglia. 
The function of nerve cells is to 
act as generators of nervous energy. 
If a number of nerve cells act together 
for a common purpose, they form a 
nerve center. 
The Nerve Fiber is a slender 
filament or thread of nervous mat- 
ter, leading off from the nerve cell and connecting it with some part 
of the body. Every fiber contains a central part which is a continua- 
tion of the protoplasm of the nerve cell and is called the axis cylinder. 
In most fibers the axis cylinder is surrounded by two other parts, an 
outside coat, called the primitive sheath, and a middle layer of oily 
substance, called the medullary sheath. These are called medullated 
nerve fibers. Those consisting of only the axis 
cylinder are called non-medullated fibers. 
The function of nerve fibers is to transmit nervous 
energy from one part of the body to another. This 
work is done wholly by the axis cylinder, the purpose 
of the other two coats being to protect the axis cylin- 
der and to prevent the escape of the nervous energy 
from it. In this respect the primitive sheath and 
medullary layer serve a purpose similar to the cover- 
ings around an electrical wire and may be said to 
“insulate” the axis cylinder. 
Make drawings to show the differ- 
ent forms of nerve cells. 
Drawings to show the con- 
nection of the nerve fiber 
with nerve and muscle cells, 
and the structure of a nerve. THE NERVOUS IMPULSE. 
111 
The nerve fibers do not extend singly through the body, but are 
collected into bundles. A bundle of nerve fibers is called a nerve. 
The largest nerve of the body is found in the thigh and is called the 
sciatic nerve. 
Relation of the Nerve Cell and the Nerve Fiber. The nerve 
cell and the nerve fiber may be regarded as two parts of the same 
thing. In their growth, the cell forms first and the fiber grows 
out from it toward that with which it is to make connection. The 
“gray matter’’ appears to be the true nerve substance, being able 
both to originate and to transmit nervous energy. The “white mat- 
ter’’ insulates and protects the “gray matter.’’ In nerve cells the 
gray matter predominates, giving them a grayish color. In the 
medullated fibers the white matter is in excess, causing them to have 
a whitish appearance. 
The Nervous Impulse, or nerve current, is a form of nervous 
energy which passes over the nerve fiber from one part of the body 
to another. Its nature is not understood. Some physiologists look 
upon it as a sort of wave motion which is started in the nerve cell, by 
chemical action, and which travels out, through the protoplasm of 
the fibers, to the different parts of the body. The impulse is 
the means, employed by the nervous system for communicating be- 
tween and controlling different parts of the body. 
Kinds of Nervous Impulses. When sent out over nerve fibers 
to organs in different parts of the body the impulses are able both to 
throw them into action and to check their action. Impulses which 
throw inactive organs into action, or quicken the action of those al- 
ready at work, are called excitant impulses. Those which check 
altogether, or diminish, the action of working organs are said to be 
inhibitory. Supply illustrations. 
Connections of Nerve Fibers. One end of every nerve fiber is, 
of course, connected with its own nerve cell. The other end will be 
connected with that part of the body into which the cell is to dis- 
charge its impulse. This may be some non-striated muscle, such 
as is found in the arteries, or digestive organs. It may be in 
one of the many different kinds of glands or nerve centers. Then, I 12 
KINDS OF NERVE FIBERS. 
again, it may find its way to one of the striated muscles. The dif- 
ferent fibers are named according to their connections and the direc- 
tion and nature of the impulses which they transmit. 
The Different Kinds Of Fibers are shown by the following table : 
Afferent 
Sensory 
Excito-motor 
Nerve Eibers. 
Efferent 
Motor 
Vaso-motor 
Secretory 
Excitant 
Inhibitory 
Intercentral 
Excitant 
Inhibitory 
Those fibers which connect with special sense organs at the 
outside of the body, 
and which convey im- 
pulses inward to cen- 
tral ganglia are called 
afferent fibers. Those 
whose cells are locat- 
ed within the body 
and which carry im- 
pulses outward t o 
muscles and glands 
are efferent fibers. 
Those which connect 
different ganglia with- 
in the body are called 
intercentral ox commis- 
sural fibers. Those 
afferent fibers whose 
• impulses excite sen- 
sations (feeling, pain, sight, etc.) are called sensory; those whose 
impulses stimulate nerve centers to send out efferent impulses to 
muscles are called excito-motor. 
Of the efferent fibers those which go to muscles are called motor; 
those connected with arteries and control the flow of blood are 
the vaso-motor, and those going to glands to regulate the secretion of 
By a suitable drawing illustrate the connections 
of afferent, efferent, and intercentral fibers. PRACTICAL QUESTIONS. 
liquids are secretory fibers. Excitant fibers are those which convey 
excitant impulses; the inhibitory are those which transmit impulses 
by that name. 
113 
References. On functions of nervous matter, C., 29; J., 233-238. On 
structure of nerve cells and fibers, C., 33-36 ; S., 255-256 ; J., 215-217 ; F. and S., 
183-185. On the nervous impulse, C.. 38; S., 267; J., 237; F. and S., 70. On 
the kinds of nerve fibers, S., 256 ; F., 218 ; F. and S., 183. 
Practical Questions. 1. In what sense may nervous tissue be regarded as 
the “ master tissue ” ? 2. How do nerve cells differ in structure from all the other 
cells of the body ? 3. How does a ganglion differ from a nerve center ? 4. Why 
is the “gray matter” supposed to be the true nerve substance? 6. Account for 
the grayish appearance of nerve cells and the whitish appearance of nerve fibers. 
7. What purposes are served in the body by the nervous impulse ? 8. With 
what will one end of a fiber always be connected ? With what different things in 
the body may the other end connect? 9. Name examples of afferent, efferent, 
and intercentral nerve fibers. CHAPTER XVII. 
Divisions of the Nervous System. 
There are two recognized divisions of the nervous system, known 
as the Sympathetic System and the Cerebro-SpinalSystem. Both these 
divisions are made up of cells and fibers and do their work through 
the agency of the nervous impulse. In both, the cells are collected 
into ganglia, and the fibers into nerves. They differ with respect to 
the arrangement and position of their ganglia, the distribution of 
their nerves, and, to some extent, in the nature of the work which 
they perform. 
Dissection of the Nervous System. Chloroform a half grown cat 
(see p. 77), and fasten it to a board, as in dissection of the abdomen. Open 
the abdominal cavity and remove its contents, tying the alimentary canal where it 
is cut, and washing out any blood which may escape. Dissect for the nervous 
system in the following order : 
x. Cut away the front of the chest, exposing the heart and lungs. .Find on 
each side of the heart a nerve which passes by the side of the pericardium to the 
diaphragm. These are nerves which assist in controlling respiration, and are 
called the phrenic nerves. Find other nerves going to the different organs in the 
thorax. 
2. Remove the heart and lungs. Find in the back part of the thoracic 
cavity on each side of the spinal column a number of small “ knots ” of nervous 
matter joined together by a single nerve. These are ganglia of the sympathetic 
system. Where the neck joins the thorax, find two sympathetic ganglia much 
larger than the others. 
3. Cut away the skin from the upper side of the shoulder and fore leg. By 
separating the muscle and connective tissue where the leg joins the thorax find 
several nerves of considerable size. These connect with each other, forming a net 
work called the brachial plexus. From here nerves pass to the thorax and to the 
fore leg. Show by a drawing the main divisions of the brachial plexus. DISSECTION OF THE NERVOUS SYSTEM. 
115 
4- From the brachial plexus trace out the nerves which pass to different 
pirts of the fore leg. In doing this, separate the muscles with the fingers and cut 
only where necessary to expose the nerves. Note that some of the branches pass 
into muscles while others connect with the skin. 
5. Remove the skin from the upper part of one of the hind legs and separate 
the muscles carefully until a large nerve is found. This is one of the divisions of 
the sciatic nerve. Carefully trace it to the spinal cord, cutting away the bone where 
necessary, and find the branches where it joins the cord. Then trace it toward the 
foot discovering its branches to different muscles and to the skin. Make a sketch 
showing the sciatic nerve and its branches. 
6. Unjoint the neck and remove the head. Examine the spinal cord where 
exposed. Cut away the bone sufficiently to show the connection between the cord 
and one of the spinal nerves. On one of the roots of the nerve, find a small gan- 
glion. Make a sketch of the cord and nerve where they join. 
7. Fasten the head to a small board and remove the scalp. Saw through 
the skull bones in several directions. Pry off the small pieces of bone so as to 
show the upper part of the brain. Study its membranes, convolutions, and divis- 
ions. 
8. With a pair of nippers break away the skull until the entire brain can be 
removed from its cavity. Examine the different divisions, and make a “side view” 
drawing, showing the relative position and size of the parts. 
9. With a sharp knife cut sections through the different parts of the brain to 
show the position of the “gray” and the “white matter.” Make drawings repre- 
senting their arrangement in the different parts. 
Make drawings of the sympathetic ganglia, brachial plexus, sciatic nerve, spinal 
cord, and of the brain. 116 
THE SYMPATHETIC SYSTEM. 
The Sympathetic System. 
The Cells of the Sympathetic System are collected into small 
ganglia which range in size, from a pin-head, to half an inch in dia- 
meter. They are situated in various parts of the body. The more 
important ones are to be found in two chains which are in front, and a 
little to each side, of the spinal column. Each of these chains contains 
24 ganglia in addition to one found at their convergence in the lower 
part of the trunk. Besides these ganglia, there are several in the 
heart, a few in the head, and many small ones scattered throughout 
the body. 
The Sympathetic Nerve Fibers are short and belong, for the 
most part, to the non-medullated variety. They form no large 
nerves, but the small sympathetic nerves are sufficiently numerous in 
some places to form complex clusters 
or groups. Such a group is called a 
plexus. 
Of the different plexi of the body 
the cardiac plexus of the heart and 
the solor plexus of the abdomen are 
the most important. 
Connection of Sympathetic Fi- 
bers. Fibers from the sympathetic 
ganglia have been traced to the non- 
striated muscles of the alimentary ca- 
nal, to the walls of arteries, to the 
spinal cord, and to the other sympa- 
thetic ganglia. The heart is also well 
supplied with sympathetic fibers, part 
of which come from ganglia within 
it and part from ganglia situated else- 
where. 
The Function of the Sympa- 
thetic System, as inferred from the 
distribution of its fibers, is to control the action of involuntary 
organs, especially those concerned in the maintenance of life. It can- 
Represent by a drawing the ar- 
rangement of the ganglia and nerves 
of the sympathetic system. DIVISIONS OF CEREBRO-SPINAL SYSTEM. 
ii7 
not be stated definitely, however, that this is its exclusive function, 
as fibers from the cerebro-spinal system also go to these organs. 
From the close connection of the tvyo systems, it is difficult to sepa- 
rate their functions. In many instances it is certain that they together 
control the same organ. 
The Cerebro-Spinal System. 
The Ganglia of the Cerebro Spinal System form a connected 
mass of nervous matter, known as the brain and spinal cord, from 
which nerves pass to all parts of the body. The brain and cord 
form the center of the system, while the nerves provide the means of 
communication between the center and the different paDs of the 
body. The main divisions of the system are shown by the following 
table: 
Cerebrum 
Cerebellum 
Medulla Oblongata 
Brain - 
Cerebro-Spinal 
System 
[ Central ganglia 
Spinal cord 
Nerves 
Cranial 
Spinal 
Importance of the Cerebro-Spinal System. Most of the 
work of the nervous system as a whole is done by the cerebro-spinal 
division. It has entire control of the voluntary organs of the body 
and assists in the control of the involuntary organs. It contains the 
organ of the mind. It also provides the means for communication 
between the organ of the mind and the other parts of the body. 
General Composition and Structure of Brain and Cord. In 
addition to the nerve cells which, from a functional standpoint, 
supply the material of chief importance in these organs, other 
materials are found as follows: 
1. Nerve fibers. Some of these connect different parts of the 
brain and cord together, while others are continuous with the fibers 
which connect parts of the body with the brain and cord. 
2. Connective tissue. This exists in small quantities and gives 
firmness and stability to different parts. 118 
PROTECTION OF BRAIN AND CORD. 
3. Blood vessels and Lymphatics. These tubes are very num- 
erous, supplying the brain and cord with nourishment and removing 
waste. 
The Protection of the Brain and Cord is accomplished in three 
different ways, as follows: 
1. By the bones which 
surround the cavities in which 
they lie. What bones are 
these ? 
2. By three membranes of 
connective tissue which en- 
velop them. Find a descrip- 
tion of the position and struc- 
ture of these membranes in 
some physiology. 
3. By a layer of liquid 
which completely surrounds 
them. This occupies the large 
spaces in the loose arachnoidal 
membrane and serves as a 
“watery cushion” for the 
brain and cord. 
The Brain is that portion of the cerebro-spinal system which lies 
in the cranial cavity. From some physiology ascertain its relative 
size and weight, its general structure, and its divisions. Is it a double 
or single organ? Name its parts. 
The Cerebrum forms about seven-eights of the entire brain. In 
what portion of the cranial cavity does it lie? 
• Locate the “gray matter” of the cerebrum. What portion of it 
is “white matter?” Of what are these “matters” composed? How 
is the surface for “gray matter” increased? What are the hemis- 
pheres? How are they joined? 
Note.—If a pencil be placed over the ear and pressed down, all that portion of the 
brain lying above the pencil is cerebrum. 
Functions of Cerebrum. The cerebrum is the organ of the mind 
and co7itrols voluntary motion. These functions are performed by its 
Make a side view drawing of the brain, 
showing the position and relative size of 
the parts. Indicate on the cerebrum the 
places whose functions are known. DIVISIONS OF THE BRAIN. 
119 
cells which are arranged into nerve centers. The centers which are 
concerned in mind activity are called the psychic centers; those con- 
trolling motion are called the motor centers. 
Location of Cerebral Functions. It has been proven within 
the last few years that each part of the cerebrum, like each part of 
the body, has a particular work of its own. Experiments on the 
brains of lower animals and the study of the effect of injuries to the 
brain of man have both helped to prove this fact. Some of the cen- 
ters which have been definitely located are the centers of vision, of 
hearing, of motion, and of speech. 
Much difficulty, however, is encountered in locating many of 
the most important centers, so that the cerebrum is still, to a large 
extent, “ an unexplored country.” 
The Cerebellum. Ascertain from some physiology its size, 
location, and general structure. Give position of its gray and white 
matter. Describe its convolutions and compare them with those of 
the cerebrum. Numerous fibers connect the cerebellum with the 
cerebrum, medulla oblongata, and the spinal cord. 
The Function of the Cerebellum is not understood, but it 
would seem, from experiments upon lower animals, that it assists the 
cerebrum in controlling voluntary motion. Animals from which it 
has been removed are unable to regulate and co-ordmate their volun- 
tary motions. 
The Medulla Oblongata. Give its location, size, shape, and 
connections. Its gray and white matter have no definite arrange- 
ment, as in other parts of the brain, but the gray is scattered through 
the white in small clusters. 
Functions of the Medulla Oblongata. The medulla is a con- 
ductor of impulses between the brain and cord and contains a number 
of important nerve centers. The most important of these are the 
the centers which control breathing, and are called the respiratory 
centers. 
The Spinal Cord. Ascertain its length and diameter. Does it 
fill the entire spinal cavity? In what does it terminate at the upper 120 
CRANIAL NERVES. 
end? In what at the lower end? Is it double or single? Give ar- 
rangement of its gray and white matter. 
Functions of the Cord. The spinal cord has two distinct 
functions. 
1. It conducts impulses between the brain and the spinal nerves. 
2. It controls a large number of the reflex actions of the body. 
—Which of these functions is performed by the white matter of 
the cord? Which by the gray matter? Upon what do you base 
your conclusion? 
Cerebro-Spinal Nerves. The brain and cord are connected 
with the different parts of the body by forty-three pairs of fiber 
bundles, or nerves. Those which connect with the brain are called 
cranial nerves, and those connected with the cord, spinal nerves. 
The fibers of the cerebro-spinal nerves consist of two important 
classes. One class comes from the special sense-organ cells of the 
skin, nose, eyes, ears, and tongue. They convey impulses toward 
the brain and cord. What are they called? The other class makes 
connection with muscles and glands and conducts impulses away 
from the brain and cord. What are they called? 
The Cranial Nerves are numbered in the order in which they 
leave the brain. The pair that leaves farthest toward the front is 
called the first pair, the next in order is the second pair, and so on. 
The distribution and function of these nerves are shown by the fol- 
lowing table: 
Number. 
Name. 
Distribution. 
Function. 
First Pair 
Olfactory 
Mucous membrane of nose... 
Nerves of smell. 
Second Pair 
Optic 
Retina of the eye 
Nerves of sight. 
3d, 4th, 6th Pairs 
Motores oculi 
Muscles of the eye 
Control motion of eyes. 
| Skin of face, muscles of 
Sensory nerve of face, con- 
Fifth Pair 
Trigeminal 
J jaws, mucous membrane 
; of mouth, and front of 
trols muscles of mastica- 
tion, nerve of taste to 
ttongue 
front of tongue. 
Seventh Pair. 
Facial 
Muscles of the face... 
Control muscles of ex- 
pression. 
Hearing. 
Eighth Pair 
Auditory 
Internal ear 
Ninth Pair 
Glossopharyngeal 
( Back of tongue, muscles 
| of pharynx 
Nerve of taste to back of 
tongue, controls muscles 
of pharynx, 
Tenth Pair 
Pneumogastric 
Larynx, lungs, liver & stom- 
Eleventh Pair.. 
ach 
Sensory and inhibitory. 
Spinal accessory . 
Hypoglossal 
Twelfth Pair 
Muscles of tongue 
Motion. SPINAL NERVES. 
12 1 
Which of the cranial nerves are purely afferent ? Which contain 
only efferent fibers? Which contain both kinds? 
The Spinal Nerves pass from the spinal cord through small 
openings in the spinal column. How many pairs of them? Each 
nerve joins the cord by two roots, the one toward the front being 
called the anterior root and the one 
toward the back, the posterior root. 
The posterior root contains afferent 
fibers while the anterior root contains 
efferent fibers. What will be the di- 
rection of impulses in each of the two 
roots? With what parts of the body 
are the efferent fibers probably con- 
nected? With what the afferent? 
References. On structure of sympathetic system, S., 253 ; F. and S., 199 ; 
J., 226. On structure of cerebro-spinal system, S., 253 ; J., 219-226. Ou the brain, 
S., 257-263 ; F. and S., 193-199 ; J., 223 226. On the cord, S., .262-265 ; F. and S., 
187-191 ; J., 222. Functions of the brain, S., 268-272; C., 259263; F. and S., 
199; J., 243-249. On cranial nerves, C., 260; F. and S., 196 ; J., 221. 
Practical Questions. 1. Of what essential parts are both divisions of 
the nervous system composed? 2. Compare the systems with reference to arrange- 
ment of ganglia and nerves. With reference to function. 3. Why should the 
brain and cord be carefully protected? 4. Why are most of the fibers of the cerebro- 
spinal system medullated while those of the sympathetic system are non-medullated? 
5. Compare the arrangement of “gray and white matter’’ in the cerebrum, cere- 
bellum, medulla oblongata, and spinal cord. 6. What results would follow cut- 
ting the fifth pair of nerves where they emerge from the brain? 7. Why does an 
injury to the medulla oblongata cause almost instant death? 8. What result 
would follow the cutting of the anterior root of a spinal nerve? The posterior 
root ? 
Show by a drawing a cross section 
of the spinal cord with roots of spi- 
nal nerves. CHAPTER XVIII. 
Work of the Nervous System. 
METHODS OF NERVOUS CONTROL. 
The Means Employed by the nervous system in controlling the 
different organs of the body are the nervous impulses which are of 
two kinds. (Distinguish between excitant and inhibitory impulses. 
See p. ill.) Passing between the nerve centers, which originate the 
impulses, and the organs to be controlled by them, are the fibers 
which transmit the impulses. 
Nerve centers cannot of themselves cause action. They are able 
to discharge their impulses only when they are stimulated from some 
source outside of themselves. Accordingly they in turn have nerve 
fibers coming to them from the sources of their stimuli. 
The first step then in causing an organ to act is to stimulate, not 
the organ, but the nerve center which controls it. The center then 
discharges the impulses which act directly on the organ. There are two 
general methods of stimulating and controlling nerve centers. These 
are designated voluntary action and reflex action. 
Voluntary Action refers to all those movements of the body 
which can be brought about by an effort of the will. The voluntary 
centers are located in the motor area of the cerebrum and are proba- 
bly made to discharge their impulses by impulses which they receive 
from the psychic centers. The separate steps leading up to a volun- 
tary action are about as follows: — REFLEX ACTION. 
123 
i. A purely mental action, such as a wish or desire. 2. 
Stimulation of voluntary centers. 3. Sending out of impulses from 
the voluntary centers to the muscles. 4. Contraction of muscles. 
Reflex Action refers to those movements of the body brought 
about by impulses which nerve centers receive from the surface of the 
body. Good examples of these are the involuntary closing of the 
eyelids, dodging on account of some unexpected sight or noise, and 
the movements of one asleep, caused by some external irritation. 
Experiment. Irritate the toe of a brainless frog by pinching it or pricking 
it with a pin. (See Appendix.) Observe and account for the frog’s movements. 
Rub a piece of rock salt against the skin of the abdomen and observe the result. 
What is the positive evidence that the frog’s movements are not voluntary ? 
State results 
and give infer- 
ences. 
Most of the reflex centers are located in the medulla oblongata, 
spinal cord, and the ganglia of the 
sympathetic system. The impulses 
which stimulate them come from sense 
organs. Since the action is in the 
direction from which the exciting im- 
pulses come it is called reflex, which 
means bending back. 
The different steps in the produc- 
tion of a reflex action are as follows: 
I. Strong stimulation of sense or- 
gan cells on the outside’of the body. 
2. Excitation of reflex centers by the 
impulses from the sense-organ cells. 3. Sending out of impulses 
from the reflex centers to the muscles. 4. Contraction of muscles. 
Study the movements of your own body for the purpose of detecting reflex 
actions. Determine the purpose of the different reflex movements which you 
discover. 
Draw a diagram to illustrate re- 
flex action. 
Habit. Any nervous action becomes easier by repetition. If 
the same act be repeated over and over a great many times, the cen- 124 
CONTROL OF THE HEART. 
ters which control it, may become independent of their controlling 
sources. They are then described as automatic, or self-acting. The 
formation of habit is illustrated in learning to walk, and in acquiring 
all kinds of skill. Actions which at first required constant “effort of 
the will, are in time performed with such ease that the will need 
direct them only in a general way. 
Habit is necessary for economy in nervous energy, the greatest 
saving being on the part of the mind. 
Control of Important Processes. 
The Control of the Blood Supply to the different organs of the 
body is effected through the management of the heart’s contractions 
and the muscular tissue in the walls of the arteries. 
Control of the Heart. The heart has a small nervous system 
of its own, composed 
of sympathetic gang- 
lia which act auto- 
matically. Impulses 
from these are able to 
keep up its continued 
contractions, but are 
unable either to in- 
crease or diminish its 
motion. The heart 
is connected with oth- 
er parts of the nerv- 
ous system by three 
kinds of nerve fibers. 
i. A set of sensory 
fibers which connect 
with the medulla ob- 
longata and report 
the condition of the heart to the nerve centers located there. 
2. A set of inhibitory fibers which also connect with the medulla 
oblongata, but these carry impulses to the heart to slow its motion. 
Draw a diagram illustrating control of the heart. CONTROL OF THE ARTERIES. 
125 
3. A set of excitant fibers which connect with the sympathetic 
system and bring impulses to the heart to quicken its motion. 
Impulses from the medulla oblongata and the sympathetic sys- 
tem are thus able to regulate the heart’s action. If there should be 
a greater demand than usual for blood over the body, how will the 
heart be made to beat faster? After the extra demand has ceased, 
how will the heart be made to beat more slowly. 
Control of blood stipply to different orga?is Organs when active 
receive more blood than when inactive. The quantity of blood 
flowing into an organ is determined by the size of the arterial tubes 
which penetrate it and this is subject to variation. 
If the walls of the arteries be examined they are found to contain 
bands of myiscular tissue. These bands are thickest where the arteries 
enter organs and are naturally in a moderate state of contractioyi. Should 
an organ need more than the usual amount of blood, inhibitory im- 
pulses go to the muscular walls of its arteries, causing them to relax. 
How will this increase the amount of blood which enters the organ? 
If it be desirable to decrease the blood supply to a certain organ, 
excitant impulses cause the muscular walls to contract. How will this 
diminish the amount of blood going to that organ? 
Control of Respiration. Afferent fibers extend from all parts of the 
mucous membrane, lining the air passages, to the medulla oblongata. 
These report the condition of the air passages to that part of the 
medulla known as the respiratory centers. From these centers one 
set of excitant fibers go to the diaphragm, another to the intercostal 
muscles, and another set to the abdominal muscles. Impulses from 
these fibers produce the requisite contraction of muscles to cause the 
alternate expansion and contraction of the thorax. 
The usual method of stimulating the respiratory centers is by 
the blood which passes through them. If the blood contain a small 
amowit of oxygen it causes the centers to send out impulses to increase 
the respiratory acts. If it contain a large amount of oxygen, the im- 
pulses are less in strength. This explains how physical exercise may 
increase the force and rapidity of the respiratory acts. The muscles, 
at work, consume large quantities of oxygen and give carbon dioxid 126 
CONTROL OF RESPIRATION. 
to the blood. In this way they get the blood into such a condition 
that it can act strongly upon the respiratory centers. 
The respiratory centers may also be stimulated in other ways. 
Should a foreign substance get into the larynx, violent coughing re- 
sults. This is caused by nerve cells 
in the mucous membrane, discharging 
impulses to the respiratory centers, 
which stimulate them to send out im- 
pulses to the respiratory muscles. In 
like manner an irritation of the mucous 
membrane of the nostrils causes sneez- 
ing. It is thus seen that the respira- 
tory centers may be made to act re- 
flex ively by impulses from sense-organ 
cells. 
Voluntary centers in the brain are 
also able to stimulate the respiratory 
centers and make them act under the direction of the will. Furnish 
illustrations of this fact. 
Control of Digestive Processes. Afferent fibers leave the 
mucous membrane at all points along the alimentary canal and con- 
nect with nerve centers situated in the brain, spinal cord, and sympa- 
thetic ganglia. These make known the condition of the canal at the 
different centers. From these centers, fibers go to the glands which 
supply the digestive fluids, to the muscles which are concerned in 
digestion, and to the walls of the arteries which supply the blood to the 
various digestive organs. 
The food pressing against the mucous membrane, causes a dis- 
charge of impulses to the different nerve centers and these, in turn, 
stimulate the organs with which they are connected. By this arrange- 
ment, the food itself causes that work to be done which is necessary 
for its digestion. Thus it is seen that the method of controlling the 
organs of digestion is through reflex action. 
Make a drawing to illustrate the 
control of salivary glands. GENERAL AND SPECIAL SENSATIONS. 
127 
Sensations. 
What is a Sensation? We have already noticed the existence 
of a large class of nerve fibers which are connected with nerve cells 
at the outside of the body and which conduct impulses inward to 
nerve centers. (What are these fibers called? What effect do their 
impulses have upon reflex centers?) Impulses passing along these 
fibers are able, when they reach the brain, to stimulate certain of the 
psychic centers. This causes a peculiar form of nervous action, called 
a sensation, the nature of which is not understood. For our pur- 
poses we may regard the sensation as an activity of psychic centers 
caused by afferent impulses-. 
The Purpose of Sensations is to give the mind information. 
Intelligent action makes it necessary for the mind to know the con- 
dition of the body itself and also the physical conditions which sur- 
round it. Through the interpretation which the mind gives to these 
effects of afferent impulses it is made aware of these conditions. Sen- 
sations are of two kinds—general and special. 
General Sensations are caused by impulses coming from differ- 
ent parts of the body, but which, so far as known, do not originate 
in nerve terminations designed for that purpose. They seem rather 
to result from a general condition of the nervous system. Good 
examples of general sensations are hunger, thirst, nausea, pain, and 
the feelings of comfort and discomfort. 
Through the general sensations the mind becomes aware of the 
condition of the different organs and can modify the activities of the 
body to suit their condition. Show the value of hunger and thirst, 
of comfort and discomfort in the protection of the body. 
Special Sensations are caused by impulses which come from 
definite places at the surface of the body, called the special sense 
organs. There are at least six different kinds of special sense organs, 
the sensations which they cause being known as the special senses. 
These are sight, hearing, smell, taste, touch, and temperature. 
A Special Sense Apparatus includes all the parts necessary for 
the production of a special sensation. These parts are as follows: 128 
TOUCH AND TEMPERATURE. 
i. Sense-organ cells to originate the impulses. 2. Nerve 
fibers to transmit the impulses. 3. Nerve centers which receive 
the impulses and give rise to the sensation. 
Through the special sensations the mind becomes acquainted 
with the condition of the surroundings of the body. To what extent 
do the senses of sight, hearing, and touch make one acquainted with 
his surroundings? 
Special Sense stimuli. Each sense organ is capable of being 
stimulated by a single form of energy. This is known as the 
stimulus for that sense organ. For example, the sense organ cells 
of sight are made to discharge their impulses by the action of light. 
Light then, is their stimulus. Furnish other illustrations. 
Touch is the simplest of the special senses. Its sense-organ 
cells are located in the touch corpuscles of the skin. Their stimulus 
is pressure. When pressure is applied to the skin impulses are 
started, which, when transmitted to the brain, cause an activity of the 
psychic centers, called the touch sensation. At what places on the 
body is the sense of touch best developed? 
Experiment. Place the points of a pair of dividers on the back of the hand 
of one who has been instructed to look in the opposite direction. Is one point felt 
or two? Repeat several times, changing the distance between the points until it is 
fully determined how near together they must be to be felt as one. In like manner 
test other parts of the body, as tips of fingers and back of neck. From a compari- 
son of results, determine what portion of the body is most sensitive. 
Give results 
and inferences. 
The Temperature Sense. It was at one time supposed that the 
touch corpuscles were also stimulated by heat and cold, but it is now 
known that there are special sense-organ cells for temperature. When 
the temperature of objects near the skin is the same as the skin, no 
sensations are produced. But when their temperature is above or 
below that of the skin, the temperature cells are made to discharge 
impulses. TASTE AND SMELL. 
129 
Recent investigation proves the sense-organ cells of temperature 
to be of two kinds—one kind stimulated by heat, the other by cold. 
If a metal point, lightly weighted, be slowly and evenly moved over the 
skin, it gives rise to sensations of touch at some places and sensations of tempera- 
ture at others. If it be a little warmer than the skin, at certain places it causes a 
sensation of heat. If it be colder than the skin, it gives rise to a sensation of cold 
as it travels over some places. The ‘ cold sensation ’ spots are different from the 
‘ warm sensation ’ spots and are constant in the same individual from day to day.” 
—Martin’s Human Body. 
The Sense of Taste. The sense-organ cells of taste are scattered 
over the upper surface of the tongue and perhaps the lower portion of 
the soft palate. They are found in little bulb-shaped organs 
called the taste buds. The inner ends of these cells connect with 
fibers which join the nerves of taste. The stimulus for the sense- 
organ cells of taste are substances in the liquid state. Solid sub- 
stances, to be tasted, must first be dissolved. 
Little is known of the manner by which the different tastes are 
produced. The different kinds recognized are sweet, sour, bitter, 
salty, and alkaline. Flavors, such as vanilla and lemon, and the 
flavors of meats and fruits are really smelled, not tasted. Of what 
use is the sense of taste? 
The Sense of Smell. The sense-organ cells of smell are located 
in the mucous membrane of the nasal passages. These cells are 
stimulated to discharge their im- 
pulses by the passage of odors 
through the nostrils. The mu- 
cous membrane of the nose also 
contains ciliated cells and touch 
corpuscles. The latter make it 
sensitive to the contact of foreign 
bodies. The olfactory, or smell- 
ing cells, are wedged in between 
the ciliated cells, with one end 
touching the surface of the mem- 
brane and the other end con- 
nected with fibers which transmit 
the impulses to the brain. 
Show by a drawing the branching of the 
olfactory nerve. 130 
PRACTICAL QUESTIONS. 
In order to smell, the odor must be in motion through the nostrils, 
and must come in direct contact with the olfactory cells. Of what 
use is the sense of smell? Describe the nerves of smell. 
Sight and Hearing. The importance of these senses, the com- 
plexity of their sense organs, and the nature of their stimuli make 
necessary their study in separate chapters. 
References. On reflex action, S., 272-273; J., 240-250; F. and S , 191; C-, 36- 
39, 268-269. On habit, C., 281; S., 275. On control of circulation, J., 113. On 
control of respiration, J., 169; C., 122. On control of digestion, J., 153. On the 
sense of touch, S., 323-325; F. and S., 202; J., 255; C., 286. On the sense of taste, 
S., 308-310; F. and S , 203-204; J., 259; C., 296. On the sense of smell, S., 312-314; 
F. and S., 206; J., 257; C., 298. On the sense of temperature, S., 226 230, 325; J., 
257; F. and S., 203; C., 285, 290. 
Practical Questions. 1. How does voluntary action differ from reflex 
action? 2. Are weak or strong impulses required to cause voluntary muscles to 
act reflexively? 3. State the purpose of reflex action. 4. Trace the impulses 
which cause the hand to be jerked away from a hot stove before the owner feels 
pain. 5. How does habit save nervous energy? 6. Why are habits hard to 
change? Show the importance of forming useful habits. 7. Is there a relation 
between “character building” and “habit forming”? 8. Account for the fact that 
violent exercise makes the face first pale and then red. 9. During hard study 
where is the excess of blood needed? How is it obtained? 10. How does running 
cause one to breathe faster? 11. To what class of nervous actions do those of 
digestion belong? 12. How does the presence of food in the mouth cause a flow of 
the saliva? 13. Compare special and general sensations with reference to their cause 
and the purposes which they serve. 14. Of what value is pain in the protection 
of the body? 15. What different things must happen in order to produce the sen- 
sation of touch? 16. What different kinds of sense organs are found in the skin? 
17. How is the mind made aware of the presence of solids, liquids, and gases? CHAPTER XIX. 
Sound and the Sense of Hearing. 
Sound is a form of vibration which is capable of stimulating the 
organ of hearing. It originates in vibrating bodies. 
Experiments. 1. Strike a bell an easy blow and hold against its side 
some light substance, as a pith ball attached to a thread. Account for the move- 
ments of the light substance. 
2. Sound a tuning fork by plucking, or striking it against the table. Its 
vibrations can be felt. If it is a large fork they can be seen. ■ Place the vibrating 
prongs in water. Observe and account for the result. 
Give results 
and inferences. 
All sound producing bodies are known to be in a state of vibra- 
tion at the time of giving out sound. Account for the production of 
sound by the violin, organ, piano, flute, and jews-harp. All vibra- 
tions, however, are not classed as sound, but only those that are more 
rapid than 16 per second and less rapid than 40,000 per second. 
Vibrations whose rate is less than 16, or more than 40,000 per 
second, are not able to cause the sensation of hearing. 
How Sounds Differ. Sounds differ in pitch, inteiisity, and qiiality. 
By pitch is meant the height of a sound. It depends upon the 
rapidity of the vibrations. By intensity is meant the energy of the 
vibrations—their ability to act on bodies and to set them in motion. 132 
SOUND WAVES. 
It is nearly expressed by the word loudness. Intensity depends upon 
the amplitude, or width, of the vibrations. Quality is that peculiarity 
of sound which enables us to distinguish one sound from another 
having the same pitch and intensity. 
Experiments, i. Draw the edge of a visiting card over the teeth of a 
comb. The sound produced from each separate tooth may be considered a vibra- 
tion. Account for the fact that a slow motion produces a tone of low pitch and a 
rapid one, a tone of high pitch. 
2. With a violin or guitar, show how pitch is affected by the length, tension, 
and size of the strings. 
3. Show by plucking a string of a guitar, first lightly and then forcibly, that 
the loudness of the sound depends upon the amplitude of its vibrations. 
Transmission of Sound Vibrations. Sound vibrations may be 
transmitted, or carried, from where they originate to other places by 
all elastic substances. The atmosphere, however, since it presses in 
close against vibrating bodies and is in sufficient abundance to form a 
connecting medium between all things on the earth, is the most 
important transmitter of sound. (See p. 36.) Vibrating bodies set 
the air in contact with them into vibration. These vibrations pass 
through the air in the form of waves, called sound waves. When 
sound waves strike against delicately poised substances they set them 
into vibration. 
Experiment. Wave a flat, stiff body, such as a chart or board, back and 
forth through the air, in front of, and about ten feet away from, a large sheet of 
paper, which is held loosely by its upper corners. The moving object imparts its 
motion to the air and the air transmits it to the' paper, causing it to vibrate. 
Apply the principles involved in this experiment to the origin, transmission and 
effect of sound waves. 
Nature Of Sound Waves. Sound waves are not, like the waves 
on water, made up of crests and troughs, but are composed of con- 
densed and rarefied portions. The condensed portion is formed 
when a given surface of the vibrating body moves toward the air and 
the rarefied portion when it recedes. The length of a sound wave 
is the distance across one condensed portion and one rarefied 
portion. Sound waves vary in length from a few inches to several 
feet. 
Importance of Sound Waves. Sound waves sustain a very 
important relation to the subject of physiology. By means of them, THE LARYNX. 
133 
man, in common with most animals, becomes acquainted with a cer- 
tain condition of surrounding objects and is able to communicate 
with his fellows. Accordingly, the body is supplied with a contriv- 
ance for producing sound vibrations and also a contrivance, by means 
of which, the vibrations are able to stimulate a part of the brain and 
produce the sensation of hearing. Name and locate these contrivances. 
Production of Sound in the Body. 
The Sound Producing1 Mechanism of the body consists essen- 
tially of three parts: 
1. Delicately arranged bodies easily set into vibrations, 
2. Contrivances for acting on the vibrating parts so as to pro- 
duce changes in pitch, quality, and intensity. 
3. An arrangement for supplying the necessary force to cause 
vibrations. 
The first part of this mechanism consists of the vocal cords; the 
second part comprises the muscles of the larynx and throat; while 
the situation of the vocal cords in the air passages enables the mus- 
cles of respiration, acting on the respired air, to supply the necessary 
force for producing the vibrations. 
The Larynx (see p. 40) consists of a short tube, the walls of 
which are made up of nine separate pieces of cartilage, joined to- 
gether by short ligaments. 
Mucous membrane lines the inside of the larynx, while small 
muscles cover a considerable portion of the exterior surface. The 
vocal cords consist of two folds in the mucous membrane on opposite 
sides of the larynx, covering strips of “elastic tissue” which connect 
with pieces of movable cartilage. By the action of muscles upon the 
cartilage the tension of the cords may be changed and differences in 
pitch produced, Above the vocal cords in the larynx, and resem- 
bling them in appearance, are two other folds in the mucous mem- 
brane. These are called the false vocal cords. 
The Voice is Produced by the respired air setting the vocal 
cords into vibration. When the cords are not in use they are in a 
relaxed condition, so that the air moving through the larynx does not 134 
PARTS OF THE EAR. 
strike against them. A contraction of the muscles connected with the 
movable cartilage pulls them out so that they partly close the passage. 
The effect of the vocal cords is greatly increased by reason of their 
situation in the air passages, which together act on the principle of 
an organ pipe. Through the action of the tongue, lips, soft palate, 
and respiratory muscles the sound from the cords is much modified 
and separated into distinct tones of short duration, forming the ele- 
ments of articulate speech. 
Observations. I. Lightly grasp the larynx with the fingers while talking. 
Observe the changes both in the position and shape of the larynx in the production 
of different sounds. 
2. Observe the differences in the action of the muscles of respiration in the 
production of loud and faint sounds. 
3. Pronounce slowly the vowels, A, E, I, and O, and the consonants C, P, 
K, R, S, T, and V, noting the changes in the shape of the mouth, the position of 
the tongue, and the action of the lips. 
Detection of Sound in the Body. 
The Structure 
of the Organ of 
Hearing adapts it 
perfectly to the na- 
ture and properties 
of sound waves. It 
consists of a con- 
trivance for enab- 
ling sound waves to 
stimulate the sense- 
organ cells of hear- 
ing and cause them 
to send impulses to 
the brain. The or- 
gan of hearing con- 
sists of three parts: 
the external ear, 
the middle ear, and 
the internal ear. 
Complete the sketch, showing and naming the divis' 
ions of the ear.' THE MIDDLE EAR. 
i35 
The External Ear consists of the part on the outside of the 
head, called the pinna, or auricle, and the tube leading into the 
internal ear, called the auditory canal. This canal is closed, at its inner 
end, by a thin membrane called the membrana tympani. 
The pinna, by its peculiar shape, is able to reflect sound waves 
into the auditory canal which, in turn, conducts them to the 
Membrana Tympani. This membrane consists of three thin 
layers. The outer layer is a continuation of the membrane lining the 
auditory canal; the inner, is a part of the membrane of the internal 
ear; while the middle is a layer of connective tissue. Being thin and 
delicately poised, the membrana tympani is easily made to vibrate by 
the sound waves which enter the auditory canal. 
The Middle Ear, or Tympanum, is an irregular cavity in the 
temporal bone. It is lined with mucous membrane and is connected 
with the pharynx by a canal, known as the eustachian tube. Extend- 
ing across the middle ear and connecting the membrana tympani, on 
one side, with a membrane closing a small passage to the internal 
ear, on the other side, is a chain of three small bones. (Find 
names of these bones.) 
The eustachian tube admits air into the middle ear and, in this 
way, maintains an equality of atmospheric pressure on the two sides 
of the membrana tympani. 
Experiment. Close the nose and mouth tightly with the hand and 
attempt to exhale air from the lungs. Account for the pressure in the ears. 
Repeat the experiment, attempting to inhale instead of exhale. 
State 
results. 
The purpose of the chain of bones is to transmit vibrations from 
the membrana tympani to the 
Internal Ear, or Labyrinth. This division of the ear consists 
of a group of membranous tubes which lie in corresponding channels 
in the temporal bone. There are three parts to the labyrinth: The 
semicircular canals, the cochlea, and the vestibule. The different parts 
are connected and the cochlea and semi-circular canals may be con- 
sidered as branches of the vestibule. 136 
HOW WE HEAR. 
Of the different parts of the 
labyrinth, the cochlea is perhaps the 
most important, as it contains the 
auditory cells. It is a spiral tube, 
coiled like a snail shell, with three 
internal divisions running its entire 
length. One division connects with 
the vestibule and is called the scala 
vestibula. Another reaches to the tym- 
panum and is called the scala tympani. 
The other lies between these two and 
is called the scala media, or cochlear 
canal. .This is the true organ of 
hearing and contains the 
Auditory Cells. These are spread out over a thin membrane, 
called the basilar membrane. Fibers from the auditory nerve connect 
with the cells and transmit their impulses to the brain. Sound vibra- 
tions are communicated to them by the liquid which fills all three of 
the divisions of the cochlea. 
How we Hear. Sound waves which originate at vibrating bodies 
are transmitted by the air to the external ear. The pinna and audi- 
tory canal direct the vibration against the membrana tympani and 
this is made to vibrate. The vibration of this membrane causes the 
chain of bones to vibrate and it, in turn, communicates the vibration 
to the liquid in the labyrinth. This liquid vibrating against the two 
sides of the scala media, sets the auditory cells into vibration, causing 
them to discharge nervous impulses. These impulses, on reaching the 
brain, cause the sensation of hearing. 
Many things connected with hearing are not fully understood. 
The smallness of the true organ of hearing and its position in the 
temporal bone make its study exceedingly difficult. 
The Fuyiction of the Semi-circular Canals has not, as yet, been 
demonstrated. On account of the directions in which they extend 
through the temporal bone and the effect which their removal has 
upon lower animals, they are supposed to assist in keeping the body 
balanced. 
Represent a section of the coch- 
lea, naming parts. PRACTICAL QUESTIONS. 
137 
Care Of the Ear. The ear being a delicate organ, injury to it 
often results from careless or rough treatment. The ear wax should 
not be “picked” out of the auditory canal. The ear has a way of its 
own for discharging it; besides the practice is attended with consider- 
able danger. Children’s ears should never be pulled or boxed. In 
removing foreign substances which may have accidentally gotten into 
the ear, use only gentle means. In case of serious trouble there 
should be no delay in consulting a physician. 
References. On structure of larynx, J., 162, 186, T92; F. and S., 235; S., 
125; C., 55, 321. On dissection of larynx, F. and S., 235-237; C., 321. On produc- 
tion of voice, C., 320 327; F. and S., 238. On speech, C., 326-327; F. and S., 239. 
On nature of sound, C., 317; F. and S., 233. On structure of the ear, C., 316-318; 
J., 280-283; S., 316 320; F. and S., 226-228. On care of the ears, S., 321, 354; C., 
318. How we hear, F. and S., 234. 
Practical Questions. 1. What is a sound wave ? How does it originate? 
How is it transmitted ? State its effects on delicately poised bodies. 2. How do 
sound waves differ from waves on the surface of water? 3. What are the advan- 
tages of having the body supplied with a sound receiver and a sound producer ? 
4. Describe the plan for the production of sound in the body. 5. Account for 
the production of pitch and intensity by the organ of the voice. 6. How is the 
sound produced by the vocal cords changed into speech ? 7. What parts of the 
organ of hearing are concerned in transmitting sound waves? 8. Give purpose 
of the middle ear. 9. Trace a sound vibration from a bell to the auditory cells, 
and the impulse it causes from the auditory cells to the brain. 10. Why should 
not the ears be picked? CHAPTER XX. 
Light and the Sensation of Sight. 
Light is supposed to be a form of wave-like motion thrown off 
from bodies highly heated. Such bodies are said to be luminous. 
Name examples. Light waves pass from luminous bodies, in straight 
lines in all directions. When they strike other bodies, they may be 
reflected, absorbed, or transmitted. Name a body which reflects light; 
one which absorbs light; one which transmits light. A single line of 
light is called a light ray. A collection of rays is called a beam of 
light. 
Kinds of Reflection. Rays of light striking against the smooth 
surface of a mirror are thrown off in definite directions, depending on 
the angle at which they strike the mirror. (Illustrate by holding a 
mirror in the direct rays of the sun.) This is called regtilar 
reflection. 
Rays of light which strike rough surfaces are reflected in all 
directions, apparently without reference to the angle at which they 
strike. (Illustrate by placing a piece of white paper in the direct 
rays of the sun. It matters not from what direction it is looked at, 
intense rays of light from it strike the eye.) This kind of reflection 
is called diffusion. 
Refraction Of Light. When light passes from one medium into 
another of different density, as for instance, from air into water, it is 
bent out of its course. This bending is called refraction. If different 
light rays are bent so that they meet at a point, they are said to be OPTICAL ILLUSTRATIONS. 
139 
focused, and the point of meeting is called the foctis. If rays which 
are reflected from a given point on a body are focused, they form a 
picture or image of that pomt. A collection of the images of all the 
reflected points of a body forms an image of the whole body. 
Experiments, i. Heat an iron, or platinum wire in a clear gas flame. 
Observe that as it is heated to a high temperature it gives out light rays, or becomes 
luminous. 
2. Cover one hand with a white handkerchief and the other with a piece of 
black cloth and hold both, for a short time, in the direct rays of the sun. Note 
and account for the difference in temperature which is felt. 
3. Stand a book, or block of wood, by the side of an empty pan in the sun- 
light, so that the end of the shadow falls on the bottom of the pan. Mark the place 
where the shadow terminates and fill the pan with water. Account for the 
shadow’s changing in length. 
4. Place a coin in the center of an empty pan and have the members of the 
class stand where the coin is barely out of sight over the edge of the pan. Fill the 
pan with water and account for the coin’s coming into view. 
5. Hold a piece of card-board, about eight inches square and having a 
smooth, round hole in it an eighth of an inch in diameter, in front of a lighted 
candle in a darkened room. Back of the opening place a muslin, or paper screen. 
An image of the candle will be formed on the screen. Account for the fact that it 
is inverted. 
6. Hold a convex spectacle lens between the card-board and screen so that 
the rays of light pass through it. The image should become smaller and more 
distinct. 
Construct a drawing 
to show the formation 
of the image through 
the opening in the 
screen. 
How we See. There is no producer of light in the body. In 
seeing we make use of the rays of light reflected from the surfaces of 
bodies by the process of diffusion. To see an object four things must 
happen: i. Light rays must pass from the object to the eye. 2. 
These rays after being focused, must stimulate the sense-organ cells 
to discharge their impulses. 3. The impulses must be transmitted 
to nerve centers in the brain. 4. The centers, in response to the 
impulses, must become active. This activity is the sensation of sight. 140 
PARTS OF THE EYEBALL. 
The Organ of Sight is adapted by its structure to the nature and 
properties of light waves. It consists of the eyeball, or globe of the 
eye, together with the tissues for its protection and control. 
On dissection of the eyeball see C., 302-305. 
The Globe of the Eye is a contrivance for focusing the rays of 
light from an object, upon the sense-organ cells of sight. Its parts 
are as follows: 
1. The cornea, a clear 
transparent membrane, 
is in the center of the 
front of the eye. It fits 
into the sclerotic coat 
which surrounds it on all 
sides, as the crystal of a 
watch into its case. It 
admits light into the 
globe. 
The sclerotic coat is 
white, dense, and firm. 
It surrounds the remain- 
ing portion of the eye- 
ball, except where the 
optic nerve enters. At 
this place it continues 
back as the sheath of the 
nerve. The portion of 
it seen in front, is called 
the “white of the eye.’’ 
2. The sclerotic coat is lined by a dark colored coat, the 
choroid, which is crowded with the blood vessels that furnish most of 
the nourishment to the eye. On account of its color it is able to 
absorb surplus rays of light. The choroid coat is continued forward 
into the circular curtain back of the cornea called the iris. The iris 
is the colored portion of the eye. In the center of the iris is a cir- 
cular opening called the pupil. 
Complete the drawing, naming the parts. STRUCTURE OF EYEBALL. 
141 
3. Lying next to the choroid coat, in the back portion of the 
eyeball and covering about two-thirds of its inner surface, is the 
retina. Though only about one-fiftieth of an inch in thickness, it 
is very complex in structure and contains the sense-organ cells of sight. 
These cells, on account of their peculiar shapes, are called the rods 
and cones. Fibers from the optic nerve connect with these cells and 
conduct their impulses to the brain. That portion of the retina im- 
mediately back of the pupil, called tho.yellow spot, is the place where 
it is most sensitive. At the place where the optic nerve enters the 
eye, the rods and cones are absent. This is called the blind spot. 
4. The crystalline lens is situated immediately back of the iris. 
It is a transparent solid body, convex on both sides, being about 
one-third of an inch in diameter and one-fourth of an inch thick. It 
is quite elastic. It is surrounded and held in position by a mem- 
branous capsule, the edges of which connect with an extension of 
the supporting connective tissue of the retina, called the suspensory 
ligament. 
Surrounding the lens, and lying at the junction of the iris and 
choroid coat, is a circular band of muscle, called the ciliary muscle. 
Its contraction has the effect of diminishing the long diameter and 
increasing the thickness of the lens. 
The lens, together with its surrounding membranes and the 
ciliary muscle, form a partition across the front of the eyeball. The 
small space in front of this partition is called the anterior chamber; 
that back of it is the posterior chamber. 
5. Two liquids—the aqueous and vitreous humors—occupy the 
two chambers of the eyeball. The aqueous humor is a thin, watery 
liquid and occupies the anterior chamber. The vitreous humor is 
dense and jelly-like, and occupies the posterior chamber. Both 
liquids help to hold the eyeball in shape and assist in focusing light rays. 
Regulation of the Quantity of Light Entering the Eyeball. 
The quantity of light entering the posterior chamber of the eye is 142 
1IOW THE EYEBALL FOCUSES. 
regulated by the size of the pupil. The iris 
contains two sets of involuntary muscles. One 
set encircles the pupil while the other is at- 
tached between the inner and outer margins 
of the iris. (See work of sphincter and radi- 
ating muscles, p. ioi.) By the action of 
these muscles the size of the pupil is modified 
to suit the quantity of light needed. What 
effect does a contraction of the circular mus- 
cles have on the size of the pupil? What, the contraction of the radiat- 
ing muscles? 
To Prove the Presence of the Blind Spot. Close the left eye and 
with the right gaze steadily at the spot on the left side of this page. Starting with 
the book a foot or more from the face, move it slowly 
Make drawing to show 
the arrangement of the 
muscles of the iris. 
toward the eye. One place will be found where the spot on the right entirely 
disappears. On bringing it nearer, however, it is seen again. As the book moves 
forward or backward, the position of the image of this spot on the retina changes. 
Where is it when the spot cannot be seen? 
Structure and Action of the Eyeball Illustrated. In the center of 
one end of a chalk box, having a tight fitting lid, cut a round hole half an inch in 
diameter. Over this hole fasten a small piece of tin which has in its center a 
smooth, round hole three-sixteenths of an inch in diameter. Back of the hole 
fasten by a suitable support a convex lens, such as may be obtained from ati old 
pair of spectacles. At the upper left hand corner of the same end of the box, cut 
another opening, making it one-fourth of an inch in diameter. Fit a stiff piece of 
white paper in the back end of the box and arrange it so that its position may be 
shifted. 
If the lid be placed on the box and the opening in the center turned toward 
a window, by looking in the hole at the corner of the box, an inverted image will 
be seen on the paper screen. Care must be taken that the head does not obstruct 
the rays of light which pass from the window to the hole. The distinctness of the 
image will be increased by a coat of black paint on the inside of the box. Com- 
pare the box to the eyeball, part for part. 
Focusing Power of the Eyeball. It is necessary for distinct 
vision that the light from the surfaces of objects be focused upon the 
retina. This means that the rays of light passing from each of the ACCOMMODATION. 
different points on the object, shall meet at corresponding points on 
the retina. This collection of the images of the surface points of the 
object upon the retina, forms the image of the object as a whole. 
The instruments used in Physics for focusing light rays are called 
lenses. The eye is provided with two of these. The cornea with the 
liquid behind it, forms one of them ; the crystalline lens is the other. 
Show by a drawing the focusing of light rays by the eyeball. 
Accommodation. Rays of light from near objects enter the 
eyeball at a different angle from those of distant objects. Rays from 
distant objects are nearly parallel while those from near objects are 
divergent—the divergence increasing as the object comes nearer 
the eye. To focus rays of light coming from objects at different 
distances requires a change in the curvature of the crystalline lens. 
To overcome the effect of increased divergence on the part of light 
rays, the convexity of the lens is increased; to focus rays of light 
more nearly parallel, the lens becomes flatter and thinner. This 
changing of the lens to suit the distance of the object viewed, is'called 
accom mo da tion. 
The Method Of Accommodation is difficult to determine. The accepted 
explanation is as follows: 
The lens is suspended back of the pupil by its membranous capsule and the 
suspensory ligament. The suspensory ligament is attached to the sides of the eye- 
ball in such a manner that it exerts continuous tension on the membranous capsule 
which, in its turn, exerts pressure on the sides of the lens, tending to flatten it. 
This arrangement brings the elastic force of the eyeball into opposition with 
the elastic force of the lens. The ciliary muscle plays between them in the fol- 
lowing manner: 
i. To thicken the lens, the ciliary muscle contracts, pulling forward the sus- 
pensory ligament and releasing its tension on the membranous capsule. This 
permits the lens to thicken by virtue of its own elastic force. 
3. To fla.tten the lens the ciliary muscle relaxes, the elastic force of the eyeball 
resumes the tension on the suspensory ligament and the membranous capsule 
resumes its pressure against the sides of the lens. 
Experiment. Hold a pencil between the eyes and a window, looking at the 
window. Why does the pencil appear blurred and indistinct ? Keeping the 144 
DEFECTS IN FOCUSING. 
pencil in the same position look at it, instead of the window. Account for the 
appearance of the window, kook from one to the other several times in succes- 
sion. Is it easier to look from the distant to the near object, or vice versa? Why ? 
Results. 
Inference. 
Defects in Focusing1 Power. An eye in a natural, or normal, 
condition is able, when at rest, to focus objects which are 20 feet or 
more away and is able to accommodate itself to objects as near as five 
inches. 
An eye is said to be myopic ox short-sighted when it is unable to 
focus light rays from distant objects. In such an eye, the ball is too 
long for the convexity of the lens, and the image falls in front of the 
retina. 
A longsighted or hypermetropic eye is one which can focus the 
rays from distant objects but not those from near objects. In such 
an eye the ball is too short for the convexity of the lens and the 
image of the object, if formed, would fall behind the retina. These 
defects in focusing are remedied by wearing spectacles whose lenses 
are shaped so as to correct the defect in the eye. Shortsightedness is 
corrected by a concave 
lens and longsighted- 
ness by a convex lens. 
In astigmatism 
all parts of the eye 
fail to focus at the 
same distance. As 
a result one part of 
an object is seen dis- 
tinctly while another 
part is dim. This 
defect is generally 
due to some fault in 
the curvature of the 
cornea. It is reme- 
Make drawing to show the muscles which move 
the eyeball. HYGIENE OF THE EYES. 
145 
died by lenses ground to correct the particular defects which happen 
to be present in a given eye. 
The Movements of the Eyeball are brought about by the action 
of six small muscles attached to its outside. Four of these, the recti 
muscles, are attached between the upper, lower, inner, and outer 
sides of the ball, and the back portion of the socket. These are able 
to turn the eye upward, downward, inward, and outward. The other 
two, the oblique muscles, are attached between the upper and lower 
portions of the ball and the sides of the socket. These rotate the eye. 
Protection of the Eyeball. The delicacy of the organ of vision, as 
well as its importance, requires that it be carefully protected. The 
different things which aid in its protection are as follows: 
i. Its position within an open cavity in the skull bones. 2. 
The cushions of fat which line this cavity. 3. The lids which pro- 
vide a movable covering. 4. The c07ijunctiva, a thin, sensitive mem- 
brane which covers the front of the eyeball and lines the underside 
of the lids. This membrane prevents 
foreign bodies from getting behind the 
eyeball. 5- The tears. (Consult 
some text book with reference to the 
supply of tears to the exposed surface 
of the eyeball.) 6. The eyebrows 
and eyelashes. 7. The general over- 
sight of the nervous system. 
Care of the Eyes. On account 
of their delicacy, the eyes are easily 
injured by careless use. If the 
following precautions are observed, 
many of the common ailments of the 
eyes may be prevented: 
1. Never read where the light is 
very intense or very dim. 2. When 
the eyes hurt quit using them. 3. 
Never hold a book so that the smooth 
page reflects light into the eyes. The best way is to sit or stand so that 
Make a drawing to show the tear 
system. 146 
PRACTICAL QUESTIONS. 
light passes from over the shoulder to the book. 4. Never study by 
a lamp which is not shaded. 5. When the eyes are weak, wash 
them frequently in water containing enough salt to slightly smart them. 
When something serious affects the eyes, consult a physician. 
References. On structure of the eyeball, J., 263-265 ; F. and S., 210-214. 
On muscles of the eye, J., 274 ; F. and S. 208 ; C., 301. On dissection of the eye- 
ball, C., 302. On accommodation, J., 266; F.. and S., 216-219; C., 308, 309 On 
how we see, J., 266 ; F. and S., 214. Care of the eyes, S,, 303; C., 312-314. On 
defects in focusing, J., 273 ; F. and S., 219 ; S., 302. 
Practical Questions. 1. When are light rays reflected ? When 
absorbed ? When transmitted ? When refracted ? 2. Where does the light 
come from which enables us to see objects? 3. How may the light rays reflected 
from an object be made to form an image of that object? 4. What different 
things must happen in order that we may see an object ? 5. What portions of 
the eyeball transmit light? What absorb light? What reflect? What refract 
light ? 6. Show how the iris, the crystalline lens, the retina, the ciliary muscle, 
and the cornea aid in seeing. 7. Trace a ray of light from a visible object, 
through the different media, to the retina. 8. What change in the shape of the 
crystalline lens occurs when we look from a distant to a near object? Why is this 
change necessary? How is it brought about? 9. Show how concave lenses 
remedy short-sightedness. How convex lenses remedy longsightedness. 10. Of 
what importance are the muscles attached to the eyeball? 11. Describe the con- 
junctiva and give its function. Why should it be sensitive? CHAPTER XXI. 
Hygiene of Nervous System. 
Delicacy of Nervous Tissue. No tissue of the entire body is 
so easily injured as the nervous tissue, Its peculiar use in the body 
necessitates an extreme delicacy of structure. For this reason the 
ganglia and nerves occupy those places in the body which afford 
greatest protection from external injuries. There is no provision, 
however, for the protection of the nervous system from the results of 
continued misuse on the part of the individual. 
Since nervous tissue provides for the control and regulation of 
all the organs of the body, its weakness is as frequently manifested 
through the inefficiency of different organs as through well recognized 
symptoms of nervous derangement. Poor digestion, irregularities of 
the heart’s action, troubles with the eyes, etc., are frequently indica- 
tions of an overtaxed nervous system, and disappear when this sys- 
tem regains its normal condition. 
Mental Work is conducive to the health of the nervous system. 
Even severe mental exertion may be undergone without bad effects, 
provided proper hygienic conditions are observed. But “brain work- 
ers” as a class are more or [ess liable to nervous derangements. For 
this reason they should observe at least the more general rules in 
caring for the nervous system and practice economy in the use of 
nervous energy. 
Plenty of Sleep is one of the first requirements of the nervous 
system. This is the time during which the exhausted brain tissues 148 
ECONOMY OF NERVOUS ENERGY. 
are being replenished. To shorten the natural period of sleep is to 
weaken the brain and lessen its working force. No one should at- 
tempt to get along with less than eight hours of sleep each day and 
most people require more. 
Physical Exercise is another requirement of healthy nervous 
action. It is important in a general way because of its beneficial 
effect upon digestion, circulation and excretion, thereby insuring a 
liberal supply of oxygen and food material to all the tissues. (See 
p. 102.) 
It also has a direct effect upon the nervous system, Mental 
work causes an excess of blood to be sent to the brain and a dimin- 
ished amount to other parts of the body. Physical exercise will 
redistribute the blood and equalize the circulation. Light exercise, 
therefore, should follow hard study. The student on retiring at night 
is greatly assisted in getting to sleep, and put in better condition for 
the next day’s work, by i 5 or 20 minutes of light gymnastics. 
Fretting1 and Worrying1 are unhealthful forms of nervous ac- 
tivity which should be carefully avoided. Certainly the vast quantity 
of nervous energy which may be expended in these ways cannot be 
used in doing mental work. A fretting person may be likened to the 
leaking boiler of a steam engine. The escaping steam not only 
lessens the working power of the engine but is disagreeable and dis- 
tracting as well “It is worry not work that causes the mental 
wreck.” 
Cheerfulness. Mental states have much to do with the health- 
fulness of the nervous system. Angry and resentful feelings and 
manifestations of envy and jealousy are known to work positive in- 
jury to the nervous system as well as the disposition, while brooding 
over real or imaginary wrongs has caused many cases of insanity. On 
the other hand, cheerfulness, contentment, patience, and manifes- 
tations of good will and good fellowship are necessary conditions for 
healthful nervous action. 
What We Eat and Drink has an important effect upon the ner- 
vous system. Like other portions of the body, it fares best when 
there is a liberal supply of wholesome, well-cooked food. In addi- ALCOHOL. 
149 
tion to the usual foods there is a large number of substances which, 
because of the delicacy of its structure, have an injurious effect upon 
the nervous system. Some of these act as violent poisons while others 
are more mild in their action. Two classes of these substances 
require special consideration. 
Stimulants and Narcotics. 
Stimulants act upon the nervous system to increase its activity 
while the general effect of narcotics is to lessen its activity. Although 
the use of these drugs in disease may be beneficial and often invalu- 
able, the frequent use of them in health is decidedly injurious. 
Among some of the more common ones may be named alcohol, mor- 
phia, the nicotine of tobacco, the caffeine of coffee, and the theine of 
tea. 
Alcohol is the intoxicating principle in the usual saloon drinks, 
such as whisky, beer, ale, wine, etc. It is formed by the fermenta- 
tion of fruits and grains. When pure it is a colorless liquid, lighter 
than water, with an agreeable odor and a hot, pungent taste. It is 
inflammable, and burns with a clear, hot flame. It is able to dissolve 
many substances not soluble in water, such as oils, gums, and resins. 
It has a strong affinity for water and is able to absorb it from organic 
substances. Its first effect upon the nervous system is that of a stim- 
ulant, though in large doses it acts as a narcotic. 
Experiments, i. Place a tablespoonful of alcohol in a saucer and ignite it 
with a burning match. Observe that the flame contains no soot and gives little 
light but great heat. 
2. Pour some alcohol over the white of a raw egg and observe the effect. 
The coagidation of the albumen is due to the absorption of water from it by the 
alcohol. 
3. Place a drop of blood on a glass slide and place over it a cover glass. 
Examine under a compound microscope. Then add a tiny drop of alcohol to the 
blood on the slide and examine a second time. The shrunken condition of the 
corpuscles is caused by the alcohol coagulating the albumen in them. 
Give results and 
nferences. 150 
TOBACCO. 
Alcohol has some very important uses. It is used as a com- 
bustible for obtaining a hot, smokeless flame. It is used in dissolv- 
ing gums, oils, and resins; for medical purposes; and in the 
arts. It is used by scientists in preventing the decay of animal and 
vegetable substances and, by some physicians, jn the treatment of 
diseases where a stimulant is needed. 
The Evil Effects Of Alcohol lie in its use as a beverage. It has 
been proven to be a poison, whether used in large or small quanti- 
ties, and is in no sense to be regarded as food. Introduced into the 
body, it weakens the nervous system by making it too active; it 
hardens the tissues by absorbing water from them; it interferes with 
digestion and the natural circulation of the blood ; it so disturbs the 
action of the brain as to induce temporary insanity, or drunkenness, 
which, if frequently repeated, leads to permanent insanity; it rapidly 
weakens the stomach, liver, and kidneys, rendering them unfit for 
their important work. But, worst of all, it creates an appetite for 
itself that causes the victim to take it in larger and larger doses until 
death or insanity is the result. As a beverage, alcohol, in all its 
forms, should be carefully avoided. It should never be used as a 
medicine except by the advice of a physician. 
Morphia is perhaps the most powerful and dangerous of the 
narcotics. It is an extract from opium and is a valuable medicine. 
Its use, however, is attended with great danger, as the opium habit 
is easily contracted and is even worse in its effects than the alcohol 
habit. 
Nicotine is an oily, colorless liquid obtained from tobacco. It 
is eminently a poison. Taken in very small quantities it is a mild 
stimulant, and if the doses are repeated a habit is formed which is 
very hard to break. Tobacco is used for the peculiar stimulating 
effects of this drug. The tobacco habit, while not so serious in its 
results as the alcohol and morphine habits, is of no benefit, is a great 
and useless expense, and, in many instances, causes a derangement 
of the healthy actions of the body. Its use by the young is espe- 
cially injurious, as it decidedly interferes with the proper develop- 
ment of both body and mind. To the bad effects of the nicotine COFFEE AND TEA. 
15 1 
may also be added those of questionable substances used either for 
their agreeable flavor or for adulteration. 
The cigarette is as yet the most dangerous of the manufactured 
products of tobacco, as it has its chief consumers among small boys. 
In addition to the dwarfing and stunting effects which it has upon 
the young, it has been the direct cause of a large number of deaths 
in the last few years. The title “ little coffin nail ” is well deserved. 
The Caffeine of coffee and Theine of tea are mild stimulants, 
and it is for the effects of these drugs that tea and coffee are so 
extensively used. Tea and coffee are similar in their action, though 
they affect persons differently. If the system needs a stimulant they 
are preferable to alcohol. Their habitual use, however, interferes 
with the healthy action of the body and for that reason they should 
be avoided. 
The practice of some students of drinking coffee and tea in order 
to study late at night, if persisted in, can only end in nervous 
derangement. 
References. On care of the nervous system, S., 277-281. On the effects 
of alcohol, F. and S , 156 ; S., 283-293 ; C., 274 ; J., 289. On effects of tobacco, 
J., 291 ; C., 191. On effects of tea and coffee, S , 252 ; C., 174. On the cigarette* 
S., 233. On patent medicines, S., 251. 
Practical Questions. 1. Why is nervous tissue more easily injured than 
the other tissues of the body ? 2. Of what value is sleep to the nervous system ? 
3. What is the special value of physical exercise to the brain worker? 4. How 
do fretting and worrying lessen one’s power to work ? 5. What mental states are 
condusive to the healthfulness of the nervous system ? What ones interefere with 
its healthy action ? 6. How do stimulants differ from narcotics ? How do both 
differ from foods? 7. Give the properties and uses of alcohol. 8. What are a 
few of the bad effects which it has upon the body? 9. What bad effects has nico- 
tine upon the body ? xo. Why do brain workers experience worse effects from 
the use of stimulants narcotics than others? 11. Show the folly of acquiring 
a habit injurious to the health. APPENDIX. 
To Prepare Oxygen. Mix thoroughly a heaping of potas- 
sium chlorate with half as much manganese dioxid and place in a test tube six 
inches long. The top of the tube should be tightly closed with a cork through 
which passes the end of a small glass tube 15 inches in length. To secure the 
proper shape for passing the gas into receivers, this tube should be bent nearly at 
right angles about an inch above the cork and again slightly, about one half an 
inch from the other end. 
For collecting the gas a wash basin and several large-mouthed bottles are 
required. Fill each bottle even full of water, place a stiff piece of paper over the 
mouth, and invert without spilling in the pan, which should contain water to the 
depth of tliree-fourtlis of an inch. 
When everything is ready heat the test tube over the flame of an alcohol 
lamp, bringing it near enough for the flame to spread over the end of the tube. 
When the gas begins to pass off insert the end of the tube under one of the bottles. 
Leave the bottles of gas inverted in the pan until ready to use the gas. On remov- 
ing keep the bottles tightly covered. 
Injection of the Arteries. Remove the front portion of the thorax, 
exposing the heart and the lungs. Grasping the heart between two fingers and 
the thumb of the left hand, make an incision in the lower end of the left ventricle. 
Insert the end of a small tube, connected with a syringe already filled with the in- 
jecting mass, and push it well into the entrance of the aorta. Secure in this posi- 
tion by a ligature around the upper portion of the heart. After a good connection 
has been made force the injecting mass by steady pressure into the arteries. (For 
composition of injection masses see J., 102 and C., 66.) 
To Destroy the Brain of a Frog. For certain experiments in which 
live frogs are used the most successful as well as the most humane way of manag- 
ing them is to destroy the brain. This puts the frog under the complete control 
of the operator and at the same time destroys all sensation. 
Make an incision with a sharp knife over the spinal cord where the head 
joins the body. Insert the blunted end of a wire, or a large knitting needle, and 
push it into the cavity occupied by the brain. Probe with the wire in different 
directions until sure that the different ganglia have been disorganized. When the 
frog drops into a relaxed and lifeless condition the operation is complete. APPENDIX. 
153 
Collection of Blood. If only a drop or two is needed it can easily be obtained 
from the finger. Wrap one of the fingers of the left hand with a handkerchief, 
from the hand down to the last joint. Bend this joint, give it a sharp, quick blow 
with the point of a clean pin or needle above the root of the nail. Pressure 
applied to the under side of the finger will force plenty of blood out through a 
very small opening. 
If blood is needed in large quantities it can be obtained from the slaughter 
house. To be sure of securing the specimens of blood needed for the experiments 
in Chapter II, take to the butcher three suitable vessels, upon which paste labels 
like the following: 
I. 2. 3. 
Fill % full. While the 
blood is cooling, stir rap- 
idly with the hand or a 
bunch of switches to re- 
move clot. 
Fill % full and set aside 
without shaking or stir- 
ring. 
Fill % full and thor- 
oughly mix with the liq- 
uid in the bottle. 
Label No. 3 must be pasted on a bottle, having a tight fitting cork, which 
is filled one-fifth full of a saturated solution of Epsom salts. 
Lime Water is prepared by dissolving lime in water. Fill a quart jar 
nearly full of water and add a few small lumps of fresh lime. Mix the two and 
let stand till all the undissolved lime settles to the bottom. This will require a 
day or more. Pour off and use the clear liquid above the lime. (Only fresh lime 
can be used in preparing lime water.) INDEX. 
Abdominal cavity .77, 79 
Absorption 73, 74 
Accommodation 143 
Afferent nerve fibers 112 
Air passages 38, 40, 41 
Air vesicles ... 38-41 
Alcohol 149-150 
Alimentary canal 62 
Anatomy defined 7 
Aorta 22 
Arteries 21 
Articulations 94 
Atmosphere . 32-36 
Composition of 31 
Properties of. 36 
Pressure of 35 
Uses of 36 
Auditory cells 136 
Auricles 18 
Bile 70 
Blind spot 141, 142 
Blood 7-16 
Bone cells 91 
Bones 89-95 
Composition 88 
Names of 92 
Structure of 90 
Brachial plexus 114 
Brain 117-119 
Canaliculi 91 
Capillaries 24 
Capsular ligament 95 
Carbon dioxid 33, 34, 51 
Cardiac plexus 116 
Cells 4-6 
Cell division 5 
Cell walls 4 
Functions of 119 
Cerebro-spinal nerves 120 
Cerebrospinal system 117-121 
Ganglia of. 117 
Cerebrum 118 
Functions of. 118, 119 
Cerebellum 119 
Cheerfulness 148 
Choroid coat.. 140 
Ciliary muscle 141, 143 
Circulation of the blood 17 
Discovery of. .17 
Coagulation 
Cochlea 135, 136 
Coecum 65 
Coffee 151 
Connective tissue 117 
Cornea ...140 
Corpuscles n-13 
Red 1 r, 12 
White 12, 13 
Cranial nerves 120 
Crystalline lens 141, 143 
Cuticle 105 
Deglutition 70 
Dermis 104 
Diaphragm : 42 
Diffusion 138 
Digestibility of foods 61 
Digestion 60-72 
Organs of 6r 
Digestive processes 69 
Dissection of 
Abdomen 77, 78 
Heart 18, 19 
Lungs 38, 39 
Nervous system 114 
Far , 134 
External 135 
Internal 136 
Middle .. 135 156 
INDEX. 
Efferent fibers 112 
Endosteum 90 
Energy 48-54 
Kinetic 49, 51 
Potential 49, 50 
Transformation of 51 
Epidermis 105 
Eustachian tube 136 
Eyeball 140 
Muscles of eyeball 145 
Excretion 81-86 
Organs of 81 
Experiments to illustrate 
Accommodation 143 
Alcohol 149 
Atmospheric pressure 35, 36 
Carbon dioxid 34 
Composition of bones 92 
Digestion 60, 69, 70, 71 
Elasticity of arteries 21 
Energy 54 
Eustachian tube 135 
Insensible perspiration 84 
Levers 96 
Light 139 
Mechanics of respiration 43, 44 
Muscular stimuli 100 
Osmosis 30 
Properties of blood 9, 10 
Properties of nitrogen 33 
Properties of oxygen 31 
Purpose of respiration 37 
Quantity of air breathed 44 
Reflex action 123 
Sound 131, 132 
Structure of eyeball 142 
Working of heart 20 
Femur 93 
Fibrin 10 
Fibrin factors 11 
Focusing 139, 142 
Foods 55-59 
Composition of food materials 57 
Inorganic foods 56 
Kinds of 56 
Nitrogenous 58 
Non-nitrogenous 58 
Purposes of 55 
Fretting 148 
Gall bladder 68 
Gastric glands 68 
Gastric juice ! 70 
Glands 66-68 
Kinds of 66 
Structure of 66 
Gross anatomy .*. 7 
Habit 123, 124 
Haemoglobin 11-12 
Haversian canals 91 
Hearing... 130-136 
Heart 1S-20 
Heat.. 52, 53, 107 
Hepatic vein 68 
Histology defined 7 
Humerus 93 
Hygiene defined 7 
Hygiene of 
Blood i 15 
Bones 97 
Circulation 25 
Digestive organs .70, 71 
Ear 136 
Eye 145 
Kidneys 83 
Muscles 103 
Respiration 45 
Ileo-coeal valve 65 
Images 139, 142 
Insalivation 69 
Intestinal digestion .' 70 
Intestinal glands 68 
Inter-central fibers 112 
Inter-costal muscles. 42, 43 
Iris 140, 141 
Irritability : 109 
Joints 95 
Kidneys 82 
Pelvis of 78 
Structure of 83 
Work of 83 
Labyrinth 136 
Lacteals 28, 74 
Lacunea * 91 
Larynx 133 INDEX. 
157 
Levers .. 96, 97 
Of the body 97 
Light 138, 139 
Liver 58, 84 
Functions of 68 
Longsightedn ess 144 
Lungs ; 38, 84 
Lymph 5, 9, 27 
Flow of 29 
Source of. 27 
Lymphatic ducts .28 
Lymphatic glands 30 
Lymphatic vessels 73 
Maintenance of life 7 
Marrow 90 
Massage 31 
Mastication 69 
Medulla oblongata 119 
Function of 119 
Mesentery 65, 80 
Meta-carpal bones 94 
Meta-tarsal bones 94 
Morphia 150 
Mucous membrane 62 
Mucus 62 
Muscles 98-103 
Names of. 102 
Plan of using 101 
Stimuli 100 
Structure of 98 
Muscular tissue 98 
Nerve cell 109 
Nerve fibers 117 
Kinds of. 112 
Sympathetic 1x1 
Nervous control of 
Arteries 125 
Digestion 126 
Heart 124 
Respiration 125 
Nervous impulses no 
Nervous tissue 109, 112 
Nicotine 150 
Nitrogen 33 
Non-striated muscles 99 
Nucleus 4 
Observations of 
Cells 4 
Arteries and veins 21 
Circulation of blood 24 
Joints 95 
Larynx 134 
Red corpuscles 11 
Skin .. 104 
Structure of bones 90 
Tissues 1 
White corpuscles 12 
Oesophagus 65 
Organ 6 
Osmosis 30, 31 
Oxidation 47 
Oxygen 32, 33, 47 
Pancreatic juice 70, 71 
Pancreas 68 
Passage of waste 85 
Patent medicines 15 
Pelvic girdle 93 
Peptones 70 
Pericardium 18 
Periosteum 90 
Peritoneum 78-80 
Perspiratory glands 105 
Pharynx 65 
Phalanges 94 
Phrenic nerves 114 
Physiology defined 7 
Plants, work of 51 
Plasma 11, 13, 14 
Pleura 38, 42 
Plexus 116 
Portal vein .68 
Protection of brain and cord 118 
Proteids 70 
Protoplasm 4 
Ptyalin.. 70 
Pulmonary artery - 22 
Pulse 22 
Pupil .140 
Receptacle of the chyle 78 
Reflection of light 138 
Reflex action 123 
Refraction 138 
Regulation of temperature 107 
Renal artery 78 
Renal vein 78 
Respiration 37 158 
INDEX. 
Retina 141 
Ribs 93 
Sacrum 93 
Salivary glands 67 
Salt 58 
Salts 82 
Sciatic nerve 115 
Sclerotic coat 140 
Seeing 139 
Semi-circular canals 135, 136 
Sensation 127 
General 127 
Special 127 
Serum 13 
Shortsightedness 144 
Shoulder girdle 93 
Skeleton 93 
Plan of 92 
Skin 84, 104-108 
Sleep 147 
Small intestine 65 
Smell 129 
Special sense stimuli 128 
Spinal column 93 
Spinal cord 119 
Functions of. 120 
Spinal nerves 12 r 
Spleen 80 
Solar plexus 116 
Sound 131, 132 
Sound waves 132 
Stomach 65 
Stroma 11, 12 
Suspensory ligament 141, 143 
Suture 
Sweat glands .84 
Sympathetic system .114-117 
Function of ri6 
Synovial fiuid 95 
Synovial membrane 95 
Tables of 
Absorption 76 
Blood changes 14 
Bones 72 
Cranial nerves 120 
Foods 56, 57 
Nerve fibers 112 
Organs of digestion..... 61 
Passage of material through body..88 
Passage of material into body 85 
Tarsal bones 94 
Taste 129 
Tea 151 
Temperature sense 128 
Tendons 101 
Thoracic cavity 38 
Thoracic duct 24, 78 
Thorax 42 
Tissues 1-3 
Kinds of 2 
Purposes of 3 
Properties of 3 
Tight lacing 80 
Tongue 65 
Touch 128 
Trachea 38 
Transfer of food materials 73-76 
Urea Sr, 83 
Ureters 78, 83 
Urinary pyramids 78 
Urine S3 
Uriniferous tubes 83 
Veins 21, 22 
Vena cava ascending 24 
Vena cava descending. 24 
Ventilation .' 46 
Ventricles 18 
Vermiform appendix 65 
Vestibule 135 
Villi 63, 74 
Vocal cords 133 
Voluntary action 122 
Water, work of 31, 58 
Watery vapor 34 
Yellow spot 141