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[Transcriber's Note: Figures 162-167 have been renumbered. In the
original, Figure 162 was labeled as 161; 163 as 162; etc.]




A Practical Physiology

A Text-Book for Higher Schools

By

Albert F. Blaisdell, M.D.

Author of "Child's Book of Health," "How to Keep Well,"
"Our Bodies and How We Live," Etc., Etc.




Preface.



The author has aimed to prepare a text-book on human physiology for use in
higher schools. The design of the book is to furnish a practical manual of
the more important facts and principles of physiology and hygiene, which
will be adapted to the needs of students in high schools, normal schools,
and academies.

Teachers know, and students soon learn to recognize the fact, that it is
impossible to obtain a clear understanding of the functions of the various
parts of the body without first mastering a few elementary facts about
their structure. The course adopted, therefore, in this book, is to devote
a certain amount of space to the anatomy of the several organs before
describing their functions.

A mere knowledge of the facts which can be gained in secondary schools,
concerning the anatomy and physiology of the human body, is of little real
value or interest in itself. Such facts are important and of practical
worth to young students only so far as to enable them to understand the
relation of these facts to the great laws of health and to apply them to
daily living. Hence, it has been the earnest effort of the author in this
book, as in his other physiologies for schools, to lay special emphasis
upon such points as bear upon personal health.

Physiology cannot be learned as it should be by mere book study. The
result will be meagre in comparison with the capabilities of the subject.
The study of the text should always be supplemented by a series of
practical experiments. Actual observations and actual experiments are as
necessary to illuminate the text and to illustrate important principles in
physiology as they are in botany, chemistry, or physics. Hence, as
supplementary to the text proper, and throughout the several chapters, a
series of carefully arranged and practical experiments has been added. For
the most part, they are simple and can be performed with inexpensive and
easily obtained apparatus. They are so arranged that some may be omitted
and others added as circumstances may allow.

If it becomes necessary to shorten the course in physiology, the various
sections printed in smaller type may be omitted or used for home study.

The laws of most of the states now require in our public schools the study
of the effects of alcoholic drinks, tobacco, and other narcotics upon the
bodily life. This book will be found to comply fully with all such laws.

The author has aimed to embody in simple and concise language the latest
and most trustworthy information which can be obtained from the standard
authorities on modern physiology, in regard to the several topics.

In the preparation of this text-book the author has had the editorial help
of his esteemed friend, Dr. J. E. Sanborn, of Melrose, Mass., and is also
indebted to the courtesy of Thomas E. Major, of Boston, for assistance in
revising the proofs.

Albert F. Blaisdell.

Boston, August, 1897.




Contents.



Chapter I.    Introduction
Chapter II.   The Bones
Chapter III.  The Muscles
Chapter IV.   Physical Exercise
Chapter V.    Food and Drink
Chapter VI.   Digestion
Chapter VII.  The Blood and Its Circulation
Chapter VIII. Respiration
Chapter IX.   The Skin and the Kidneys
Chapter X.    The Nervous System
Chapter XI.   The Special Sense
Chapter XII.  The Throat and the Voice
Chapter XIII. Accidents and Emergencies
Chapter XIV.  In Sickness and in Health
  Care of the Sick-Room; Poisons and their Antidotes; Bacteria;
  Disinfectants; Management of Contagious Diseases.
Chapter XV. Experimental Work in Physiology
  Practical Experiments; Use of the Microscope; Additional Experiments;
  Surface Anatomy and Landmarks.

Glossary

Index




Chapter I.

Introduction.



1. The Study of Physiology. We are now to take up a new study, and in
a field quite different from any we have thus far entered. Of all our
other studies,--mathematics, physics, history, language,--not one comes
home to us with such peculiar interest as does physiology, because
this is the study of ourselves.

Every thoughtful young person must have asked himself a hundred questions
about the problems of human life: how it can be that the few articles of
our daily food--milk, bread, meats, and similar things--build up our
complex bodies, and by what strange magic they are transformed into hair,
skin, teeth, bones, muscles, and blood.

How is it that we can lift these curtains of our eyes and behold all the
wonders of the world around us, then drop the lids, and though at noonday,
are instantly in total darkness? How does the minute structure of the ear
report to us with equal accuracy the thunder of the tempest, and the hum
of the passing bee? Why is breathing so essential to our life, and why
cannot we stop breathing when we try? Where within us, and how, burns the
mysterious fire whose subtle heat warms us from the first breath of
infancy till the last hour of life?

These and scores of similar questions it is the province of this deeply
interesting study of physiology to answer.

2. What Physiology should Teach us. The study of physiology is not
only interesting, but it is also extremely useful. Every reasonable person
should not only wish to acquire the knowledge how best to protect and
preserve his body, but should feel a certain profound respect for an
organism so wonderful and so perfect as his physical frame. For our bodies
are indeed not ourselves, but the frames that contain us,--the ships in
which we, the real selves, are borne over the sea of life. He must be
indeed a poor navigator who is not zealous to adorn and strengthen his
ship, that it may escape the rocks of disease and premature decay, and
that the voyage of his life may be long, pleasant, and successful.

But above these thoughts there rises another,--that in studying physiology
we are tracing the myriad lines of marvelous ingenuity and forethought, as
they appear at every glimpse of the work of the Divine Builder. However
closely we study our bodily structure, we are, at our best, but imperfect
observers of the handiwork of Him who made us as we are.

3. Distinctive Characters of Living Bodies. Even a very meagre
knowledge of the structure and action of our bodies is enough to reveal
the following distinctive characters: our bodies are continually
breathing, that is, they take in oxygen from the surrounding air; they
take in certain substances known as food, similar to those composing the
body, which are capable through a process called oxidation, or through
other chemical changes, of setting free a certain amount of energy.

Again, our bodies are continually making heat and giving it out to
surrounding objects, the production and the loss of heat being so adjusted
that the whole body is warm, that is, of a temperature higher than that of
surrounding objects. Our bodies, also, move themselves, either one part
on another, or the whole body from place to place. The motive power is not
from the outside world, but the energy of their movements exists in the
bodies themselves, influenced by changes in their surroundings. Finally,
our bodies are continually getting rid of so-called waste matters, which
may be considered products of the oxidation of the material used as food,
or of the substances which make up the organism.

4. The Main Problems of Physiology briefly Stated. We shall learn in
a subsequent chapter that the living body is continually losing energy,
but by means of food is continually restoring its substance and
replenishing its stock of energy. A great deal of energy thus stored up is
utilized as mechanical work, the result of physical movements. We shall
learn later on that much of the energy which at last leaves the body as
heat, exists for a time within the organism in other forms than heat,
though eventually transformed into heat. Even a slight change in the
surroundings of the living body may rapidly, profoundly, and in special
ways affect not only the amount, but the kind of energy set free. Thus the
mere touch of a hair may lead to such a discharge of energy, that a body
previously at rest may be suddenly thrown into violent convulsions. This
is especially true in the case of tetanus, or lockjaw.

The main problem we have to solve in the succeeding pages is to ascertain
how it is that our bodies can renew their substance and replenish the
energy which they are continually losing, and can, according to the nature
of their surroundings, vary not only the amount, but the kind of energy
which they set free.

5. Technical Terms Defined. All living organisms are studied usually
from two points of view: first, as to their form and structure; second, as
to the