[Illustration: _Muscular Coordination_
_Weissmuller’s horizontal plunge into a swimming pool._]
POPULAR SCIENCE LIBRARY
EDITOR-IN-CHIEF
GARRETT P. SERVISS
AUTHORS
WILLIAM J. MILLER · HIPPOLYTE GRUENER · A. RUSSELL BOND
D. W. HERING LOOMIS HAVEMEYER · ERNEST G. MARTIN
ARTHUR SELWYN-BROWN · ROBERT CHENAULT GIVLER
ERNEST INGERSOLL · WILFRED MASON BARTON
WILLIAM B. SCOTT · ERNEST J. STREUBEL
NORMAN TAYLOR · DAVID TODD
CHARLES FITZHUGH TALMAN
ROBIN BEACH
ARRANGED IN SIXTEEN VOLUMES
WITH A HISTORY OF SCIENCE, GLOSSARIES
AND A GENERAL INDEX
_ILLUSTRATED_
[Illustration]
VOLUME NINE
P. F. COLLIER & SON COMPANY
NEW YORK
Copyright 1922
BY P. F. COLLIER & SON COMPANY
MANUFACTURED IN U. S. A.
PHYSIOLOGY
THE SCIENCE OF THE BODY
BY
ERNEST G. MARTIN
PROFESSOR OF PHYSIOLOGY, STANFORD UNIVERSITY
[Illustration]
P. F. COLLIER & SON COMPANY
NEW YORK
PREFACE
When Alexander Pope wrote “The proper study of mankind is man,” he was
thinking rather of man as a social being than as the possessor of an
amazingly complex and interesting body. It is nevertheless true that to
one who finds enjoyment in the study of intricate mechanisms or to one
for whom that amazing sequence of events which we call life has appeal
there is no more fascinating study than the study of the living body.
That part of the study of the body which concerns itself primarily with
activity and only secondarily with form and structure, makes up the
science of Physiology. The way the body works is the central theme.
The practical value of Physiology to the general reader lies in the fact
that it forms the basis of all sound rules of hygiene. Life is made up
of bodily activities which may be carried on correctly or incorrectly.
Carried on correctly they mean health, carried on incorrectly, unhealth.
The world is flooded with health-preserving or health-restoring systems,
urged upon the public, for the most part, by promoters in search of
gain. Such of these as have merit are based on definite physiological
principles, and anyone who has a common-sense working knowledge of his
own body can order his life in accordance with them, at little or no
expense. Moreover, a sound appreciation of Physiology drives home the
truth that when the body is really out of order its restoration can be
safely intrusted only to the properly trained physician: the man or
woman who through years of painstaking study has won insight into the
intricacies of the human mechanism and whose honest appreciation of the
difficulties of his profession, and courageous sincerity in grappling
with them, justify to the full the confidence in which he is held by his
community.
ERNEST G. MARTIN.
CONTENTS
CHAPTER PAGE
I. THE SIGNS OF LIFE 9
II. THE MAINTAINING OF LIFE 18
III. THE SOURCES OF FOOD 24
IV. THE USES OF FOOD 31
V. BODY CELLS 41
VI. THE SUPPORTING FRAMEWORK 53
VII. MOTION 73
VIII. SENSATION--INTERNAL AND CONTACT SENSES 86
IX. SENSATION--DISTANCE SENSES 96
X. THE NERVOUS SYSTEM AND SIMPLE NERVOUS
ACTIONS 122
XI. THE BRAIN AND COMPLEX NERVOUS ACTIONS 139
XII. SOME SPECIAL NERVOUS ACTIONS; SMOOTH
MUSCLE AND GLAND CONTROL 155
XIII. THE BODY FLUIDS 173
XIV. THE CONVEYER SYSTEM OF THE BODY 191
XV. THE SERVICE OF SUPPLY OF FOOD 226
XVI. THE SERVICE OF SUPPLY OF OXYGEN 253
XVII. THE SERVICE OF REMOVAL OF WASTE 271
XVIII. MORE ABOUT THE USE OF FOOD BY THE BODY 277
XIX. KEEPING WARM IN WINTER AND COOL IN SUMMER 305
XX. THE PERPETUATION OF THE RACE 324
XXI. CHILD AND MAN 345
LIST OF ILLUSTRATIONS
MUSCULAR COORDINATION--WEISSMULLER’S HORIZONTAL
PLUNGE INTO A SWIMMING POOL _Frontispiece_
FACING PAGE
FACTORY’S COOPERATION IN AIDING PHYSICAL FITNESS,
UNDERWEIGHT EMPLOYES ARE GIVEN A MILK LUNCH 32
WEIGHT TEST IN A CHILD’S PHYSICAL EXAMINATION TO
DETERMINE HOW NEARLY THE CHILD APPROACHES
CORRECT STANDARDS OF PHYSICAL DEVELOPMENT 33
FRENCH METHOD OF MEASURING VERTICAL CONFORMATION,
CONSIDERED VALUABLE IN ADVISING AND
TRAINING ATHLETES 64
CURVE OF THE SPINE MEASURED AND DRAWN FOR STUDY
OF AN ATHLETE’S POSSIBILITIES 65
MUSCULAR DEVELOPMENT OF AN ATHLETE--THE DISCUS
THROWER OF MYRON 80
A MODERN “VICTORY”--MISS SABIE AT PRACTICE 81
HOSPITAL DESIGNED TO SUPPLY THE MAXIMUM OF LIGHT
AND AIR--CHIEF REQUISITES FOR HEALTH--TO EACH
ROOM 96
ARCHITECT’S PLAN MADE WITH THE NEED FOR LIGHT
AND AIR IN MIND 97
SOFT, RESTFUL COLORS OF A HOSPITAL ROOM 112
MAGNET PUT TO THE SERVICE OF REMOVING IRON FILINGS
FROM THE EYE 113
TEST FOR BLOOD PRESSURE 192
INDICAN TEST IN URINALYSIS 193
MICROSCOPIC STUDY OF THE BLOOD 208
MICROPHOTOGRAPH OF BRAIN TISSUE 209
X-RAYING THE TEETH AND JAW--HEALTH OFTEN DEPENDS
ON THEIR GOOD CONDITION 224
THROAT EXAMINATION--IMPORTANT IN DETERMINING
PHYSICAL CONDITION 225
LUNCH HOUR IN FRENCH SCHOOL WHERE EXERCISE,
OUT-OF-DOOR LIFE, SUNSHINE AND FRESH AIR ARE
CONSIDERED ESSENTIALS 288
DIET KITCHEN ON A U. S. HOSPITAL SHIP 289
CARING FOR THE EARS--IMPORTANT FOR ADULTS AND
BABIES ALIKE 336
BABY’S FOOTPRINT--A MEANS OF POSITIVE IDENTIFICATION 336
BABIES, PHYSICALLY AND MENTALLY ACTIVE 337
CHAPTER I
THE SIGNS OF LIFE
Physiology is the study of living things, so the first thing to be asked
when we begin to think about physiology is how we are to know whether
anything is alive or not. It is usually pretty easy to tell whether a
dog or cat is alive or dead, although sometimes when a dog is stretched
out on the road we have to look closely to tell whether he has already
met his end or is merely courting it by sleeping in the public highway.
There are in the world hosts of animals with which we are not familiar,
and to tell whether these are alive or dead is often a puzzle. More than
one picnicker has been thoroughly surprised by seeing what looked like a
bit of dead twig begin to walk away, and recognized the walking stick.
On the whole we will agree that the sign of life which we find most
reliable is motion of some sort on the part of the living animal. If the
stretched-out dog makes breathing movements, we pronounce him alive; if
not, we decide that he is dead. It is because the walking stick moves
off when disturbed that we know it is not a twig. But while motion is
the thing we look for in living animals we know perfectly well that it
would be foolish to assert that anything that moves is alive. When the
wind is blowing the air may be full of dead leaves and butterflies, all
moving, but only part, the butterflies, alive. Unless the motion is
produced by the animal itself it is not good as a sign of life. So
widespread among animals is the making of movements, either on their own
account, or when disturbed, that we shall not often find ourselves
mistaken if we decide that an object which remains quiet indefinitely is
not a living animal. Now how about the other side of the question? Is
anything that moves on its own account or when disturbed to be judged
alive?
Suppose that the inhabitants of Mars have finally succeeded in
perfecting a flying boat that can be hermetically sealed and shot across
space from that planet to our earth. Suppose further, that the first
exploring party has set forth on a voyage of discovery, and has reached
a point high in our sky from which objects on the earth’s surface begin
to be distinguishable. Of course the huge landmarks, cities, lakes, and
rivers, have been in view for a long while, and now the explorers are on
the lookout for signs of living things. They are watching, just as we
would be, for moving objects. The first moving thing that they see will
probably be a train, and we can imagine their speculations as to whether
they are actually looking or not at an inhabitant of the earth. As their
craft sinks toward the surface the make-up of the train becomes
perceptible as also the fact that it runs on rails, showing that it is a
mechanical contrivance and not a living being. As smaller objects come
into view black, shiny specks are seen moving about. These show every
appearance of life; they start and stop; pass each other without
interference; in fact conduct themselves about as animals usually do. If
their apparent great power has the effect of discouraging the exploring
party, so that they give up further investigation and fly away to Mars,
the inhabitants of that planet will always suppose the earth to be
populated by automobiles. We know that automobiles are not alive, yet,
as this little allegory shows, they behave enough like living beings to
deceive distant observers. There must be some sign of life which will
apply to an animal and not to an automobile; what is it? Evidently what
the Martian explorers missed was the fact that the automobile does not
really start or stop itself, or guide itself past obstructions. If it
had been alive, it would have done these things of itself. It is not so
much the power of motion, then, that proves that the thing is alive as
the power of making motions that are under the control of the animal
itself.
The sight of an automobile which is not alive behaving as though it were
because it is under control of a driver who is alive may lead us to ask
whether the animal that we know to be living is actually alive in all
its parts, or is a dead mechanism of some sort which has somewhere
within it a living controller, corresponding to the living driver of the
car. The animals with which we are most familiar are ourselves; how is
it with our own bodies? Are they alive in all their parts, or is the
brain the only part of us which is living? When a patient goes under
ether on the operating table, or even when he is sound asleep, the signs
of life are not conspicuously present; the heart goes on beating, to be
sure, but so does the engine of an automobile go on running when the
driver is away, provided he has not shut it off. A favorite belief among
the Hindus is that when they go into a trance the body actually becomes
lifeless while the living spirit soars among the heights. How are we to
decide whether the Hindus are right or not? Evidently we shall have to
look deeper than we have thus far, and learn something of what is
actually going on in the different parts of our bodies when we are
asleep and when we are awake.
Nearly everyone learns in school the main facts about the construction
of the body; that there is a bony skeleton which supports the softer
parts; that motions are made by muscles; that sense organs inform us as
to what is going on in the world around; that the brain is the seat of
the mind; that heart, lungs, stomach, kidneys, and other organs
contribute in various ways to our well-being. Not so many go into detail
as to the make-up of these organs, or into the way in which they do
their work. This is not a simple matter, for several reasons. The first
is that the construction units are so tiny that they cannot be seen by
the unaided eye, but must be studied under the high magnification of a
first-class microscope. It is much harder to make out the manner of the
working of tiny pieces of machinery than of those that are of convenient
size. When the parts are as small as those that make up our bodies, the
task of finding out how they operate is so difficult that even now,
after years of study, there are many details about which we know very
little.
The construction units have been named cells. In some tiny animals the
whole body consists of but one cell; all higher animals, including
ourselves, have millions of cells making up the body. Undoubtedly some
cells are alive; our question is as to whether all of them are, or
whether there are some that are alive and some that are not. There are
parts of our bodies, and of the bodies of nearly all other kinds of
animals, as well, that are certainly not alive. Examples are the hair,
the nails, the enamel of the teeth, and the hard parts of the bones.
Actual living stuff is very soft and liquid. It is too fragile to hold
its own structure except in the very tiniest animals; those that are
larger need some additional supporting framework. In a body the size of
a man’s the supporting framework amounts to a very considerable
percentage of the entire weight (25 per cent). Not only is there the
large bony skeleton, but between and among the individual cells is a
framework made up of fine fibers and sheets which hold the cells in
place. This latter framework is called connective tissue; we run across
it in the gristly parts of meat. It makes up the stringy mass that
clings to the cutter of the meat grinder when beef is being ground for
Hamburg steak. We shall consider later how all this supporting material
is made and put in place. Just now we are interested in the cells, and
in determining whether all of them are alive or not.
There are many different kinds of cells in the body; some are muscle
cells, others nerve cells, still others gland cells, and so on. Careful
study shows, however, that at bottom all cells are alike. All are
composed of one kind of substance to which has been given the name of
protoplasm, meaning first or primary flesh. It is because some, at
least, of this protoplasm is alive that our bodies are alive, and our
physical life consists of nothing more than the combined life of all the
living protoplasm which our bodies contain. Is there any way by which to
tell whether any particular mass of protoplasm is alive or not? In other
words, what are the signs of life of protoplasm as contrasted with the
signs of life of whole animals?
We shall scarcely expect it to be as simple a matter to tell whether the
tiny mass of protoplasm that we call a cell is alive or not as to decide
whether a dog is dead or alive. For one thing, our most useful test of
life, namely motion, cannot always be applied to single cells. We have
in our bodies a great many cells, those in the brain, that we know are
alive if any part of us is, but aside from the exceedingly gradual
shifts in position that take place during growth the brain cells never
make any motions at all, so far as anyone has ever been able to find
out. Of course in the body of any ordinary animal most of the cells are
hidden from view beneath the skin, but there are enough small
transparent animals whose internal parts can be watched through the
microscope to let us say with certainty that some of the cells which we
know to be alive do not move. Tests of life that can be applied to all
kinds of cells will necessarily be difficult to use, and we shall have
to take the word of experts as to whether they have found particular
cells alive or not, but the principle on which the tests are based is
simple enough so that we can examine it. To do this, it will be
necessary to turn our attention for a little while to some of the very
tiniest of all living animals, those whose whole bodies consist of but
one cell.
When these tiny one-celled animals are watched through the microscope as
they swim about it can be seen that in one important feature they behave
just as we do ourselves; that is in their care not to neglect mealtime.
To be sure, mealtime comes for them whenever they happen to hit against
any tinier particle than themselves, which they can take in and digest.
But for them, as for us, the taking of food from time to time is a
necessity of life. Only a small part of the food thus taken in is added
permanently to the bulk of the animal. In other words, the growth does
not go on as fast as does the taking of food. Of course in ourselves,
after we have reached full size, there is little or no increase in
permanent bulk even though we do keep right on eating. Evidently in the
tiny one-celled animal, and in us as well, food is constantly being used
for something besides growth. It can be proved that this food is used
for precisely the same purpose that gasoline is used in the automobile,
namely to run the machine. In a very real sense every living thing is a
machine, and will no more run without a supply of power than will any
other machine. From the engineering standpoint animals can be classified
along with automobiles and locomotives as “prime movers,” namely, as
machines which develop their power within themselves. There are not many
kinds of power which can be developed by prime movers. By far the
commonest is that seen in locomotives and automobiles, namely the
burning of some kind of fuel. We have always known that the locomotive
operates by the burning of coal or oil in the fire box. A moment’s
thought will show us, if we have not realized it before, that the
explosion of the air-gas mixture in the automobile cylinders is also a
burning. Every steam-driven power plant depends on burning fuel for its
power. Evidently fuel materials contain abundant power, if it can be
extracted, and burning is a good method for doing the extracting. The
word “burning” is the common name for a chemical process known
technically as “oxidation,” meaning the union of oxygen with the fuel.
The air is one-fifth oxygen, so there is plenty available, and fuel will
usually oxidize readily after it is properly started.
Not only do animals correspond with other machines in using fuel as
their source of power; they correspond also in that the power is
extracted through the process of oxidation. To be sure, the oxidation in
animals is not accompanied by flame and smoke as it usually is in power
plants, nor do any parts of the animal get as hot as does the furnace
where fuel is ordinarily burned; but in spite of these differences the
fundamental fact is the same, namely that the extraction of power is by
means of oxidation. What this shows is that great heat, flame, and smoke
are not necessary in oxidation, but only in the kinds of oxidation with
which we are most familiar.
As soon as we have described one more feature of animal power
development, we shall be ready to apply what has been said to the topic
in hand, namely the signs of life in single cells. The point that
remains to be made is that in living cells power development has to go
on all the time whether the cell is active or not. This means that fuel
is constantly being burned, and oxygen is constantly being taken in to
do the burning. There has been, and still is, a great deal of debate as
to how much the oxidation can be reduced in living cells without
destroying life. It is evident that it can be cut down to a very low
level indeed, for seeds remain alive for years without using up, or even
noticeably depleting, the store of fuel material which they contain.
Most botanists of the present time doubt the truth of the tale that
grains of wheat have sprouted after being taken from the wrappings of
mummies, where they had lain for thousands of years. Careful efforts
have been made to preserve wheat under as favorable conditions as
existed in the mummy wrappings, but in every case the power to sprout
was lost within a comparatively few years. So far as experiment enables
us to judge, the complete cessation of power development in cells,
either of plants or animals, means their death.
Here we have our sign of life that is applicable to all kinds of cells
wherever they are located, whether making up the whole of a microscopic
animal or deeply imbedded in the body of a large animal which consists
of millions of them. If power development is going on, the cell is
alive; if no power is being developed, the cell is not alive. When this
test is applied it is found that all the protoplasmic cell masses which
are present in the body of a plant or animal are alive, and since such
masses are everywhere throughout the body, life is present in all parts
of it, and not confined to the brain or to any other single region. We
might admit that the Hindus are correct in assuming that the spirit can
sometimes soar away and leave the lifeless body behind, but we cannot
accept the possibility that it can return and establish life within it
again. When life is resumed after a trance, that fact is proof positive
that life continued throughout the trance itself.