A Practical Physiology - Albert F. Blaisdell
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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 processes which go on within them. The science which treats of all
living organisms is called biology. It has naturally two
divisions,--morphology, which treats of the form and structure of
living beings, and physiology, which investigates their functions, or
the special work done in their vital processes.
The word anatomy, however, is usually employed instead of morphology.
It is derived from two Greek words, and means the science of dissection.
Human anatomy then deals with the form and structure of the human
body, and describes how the different parts and organs are arranged, as
revealed by observation, by dissection, and by the microscope.
Histology is that part of anatomy which treats of the minute
structure of any part of the body, as shown by the microscope.
Human physiology describes the various processes that go on in the
human body in health. It treats of the work done by the various parts of
the body, and of the results of the harmonious action of the several
organs. Broadly speaking, physiology is the science which treats of
functions. By the word function is meant the special work which an
organ has to do. An organ is a part of the body which does a special
work. Thus the eye is the organ of sight, the stomach of digestion, and
the lungs of breathing.
It is plain that we cannot understand the physiology of our bodies without
a knowledge of their anatomy. An engineer could not understand the working
of his engine unless well acquainted with all its parts, and the manner in
which they were fitted together. So, if we are to understand the
principles of elementary physiology, we must master the main anatomical
facts concerning the organs of the body before considering their special
functions.
As a branch of study in our schools, physiology aims to make clear certain
laws which are necessary to health, so that by a proper knowledge of them,
and their practical application, we may hope to spend happier and more
useful, because healthier, lives. In brief, the study of hygiene, or
the science of health, in the school curriculum, is usually associated
with that of physiology.[1]
6. Chemical Elements in the Body. All of the various complex
substances found in nature can be reduced by chemical analysis to about 70
elements, which cannot be further divided. By various combinations of
these 70 elements all the substances known to exist in the world of nature
are built up. When the inanimate body, like any other substance, is
submitted to chemical analysis, it is found that the bone, muscle, teeth,
blood, etc., may be reduced to a few chemical elements.
In fact, the human body is built up with 13 of the 70 elements, namely:
oxygen, hydrogen, nitrogen, chlorine, fluorine, carbon, phosphorus,
sulphur, calcium, potassium, sodium, magnesium, and iron. Besides
these, a few of the other elements, as silicon, have been found; but they
exist in extremely minute quantities.
The following table gives the proportion in which these various elements
are present:
Oxygen 62.430 per cent
Carbon 21.150 " "
Hydrogen 9.865 " "
Nitrogen 3.100 " "
Calcium 1.900 " "
Phosphorus 0.946 " "
Potassium 0.230 " "
Sulphur 0.162 " "
Chlorine 0.081 " "
Sodium 0.081 " "
Magnesium 0.027 " "
Iron 0.014 " "
Fluorine 0.014 " "
-----
100.000
As will be seen from this table, oxygen, hydrogen, and nitrogen, which are
gases in their uncombined form, make up 3/4 of the weight of the whole
human body. Carbon, which exists in an impure state in charcoal, forms
more than 1/5 of the weight of the body. Thus carbon and the three gases
named, make up about 96 per cent of the total weight of the body.
7. Chemical Compounds in the Body. We must keep in mind that, with
slight exceptions, none of these 13 elements exist in their elementary
form in the animal economy. They are combined in various proportions, the
results differing widely from the elements of which they consist. Oxygen
and hydrogen unite to form water, and water forms more than 2/3 of the
weight of the whole body. In all the fluids of the body, water acts as a
solvent, and by this means alone the circulation of nutrient material is
possible. All the various processes of secretion and nutrition depend on
the presence of water for their activities.
8. Inorganic Salts. A large number of the elements of the body unite
one with another by chemical affinity and form inorganic salts. Thus
sodium and chlorine unite and form chloride of sodium, or common salt.
This is found in all the tissues and fluids, and is one of the most
important inorganic salts the body contains. It is absolutely necessary
for continued existence. By a combination of phosphorus with sodium,
potassium, calcium, and magnesium, the various phosphates are formed.
The phosphates of lime and soda are the most abundant of the salts of the
body. They form more than half the material of the bones, are found in the
teeth and in other solids and in the fluids of the body. The special place
of iron is in the coloring matter of the blood. Its various salts are
traced in the ash of bones, in muscles, and in many other tissues and
fluids. These compounds, forming salts or mineral matters that exist in
the body, are estimated to amount to about 6 per cent of the entire
weight.
9. Organic Compounds. Besides the inorganic materials, there exists
in the human body a series of compound substances formed of the union of
the elements just described, but which require the agency of living
structures. They are built up from the elements by plants, and are called
organic. Human beings and the lower animals take the organized
materials they require, and build them up in their own bodies into still
more highly organized forms.
The organic compounds found in the body are usually divided into three
great classes:
1. Proteids, or albuminous substances.
2. Carbohydrates (starches, sugars, and gums).
3. Fats.
The extent to which these three great classes of organic materials of the
body exist in the animal and vegetable kingdoms, and are utilized for the
food of man, will be discussed in the chapter on food (Chapter V.). The
Proteids, because they contain the element nitrogen and the others do
not, are frequently called nitrogenous, and the other two are known
as non-nitrogenous substances. The proteids, the type of which is egg
albumen, or the white of egg, are found in muscle and nerve, in glands, in
blood, and in nearly all the fluids of the body. A human body is estimated
to yield on an average about 18 per cent of albuminous substances. In the
succeeding chapters we shall have occasion to refer to various and allied
forms of proteids as they exist in muscle (myosin), coagulated blood
(fibrin), and bones (gelatin).
The Carbohydrates are formed of carbon, hydrogen, and oxygen, the
last two in the proportion to form water. Thus we have animal starch, or
glycogen, stored up in the liver. Sugar, as grape sugar, is also found in
the liver. The body of an average man contains about 10 per cent of
Fats. These are formed of carbon, hydrogen, and oxygen, in which the
latter two are not in the proportion to form water. The fat of the body
consists of a mixture which is liquid at the ordinary temperature.
Now it must not for one moment be supposed that the various chemical
elements, as the proteids, the salts, the fats, etc., exist in the body in
a condition to be easily separated one from another. Thus a piece of
muscle contains all the various organic compounds just mentioned, but they
are combined, and in different cases the amount will vary. Again, fat may
exist in the muscles even though it is not visible to the naked eye, and a
microscope is required to show the minute fat cells.
10. Protoplasm. The ultimate elements of which the body is composed
consist of "masses of living matter," microscopic in size, of a material
commonly called protoplasm.[2] In its simplest form protoplasm
appears to be a homogeneous, structureless material, somewhat resembling
the raw white of an egg. It is a mixture of several chemical substances
and differs in appearance and composition in different parts of the body.
Protoplasm has the power of appropriating nutrient material, of dividing
and subdividing, so as to form new masses like itself. When not built into
a tissue, it has the power of changing its shape and of moving from place
to place, by means of the delicate processes which it puts forth. Now,
while there are found in the lowest realm of animal life, organisms like
the amoeba of stagnant pools, consisting of nothing more than minute
masses of protoplasm, there are others like them which possess a small
central body called a nucleus. This is known as nucleated protoplasm.
[Illustration: Fig. 1.--Diagram of a Cell.
A, nucleus;
B, nucleolus;
C, protoplasm. (Highly magnified)
]
11. Cells. When we carry back the analysis of an organized body as
far as we can, we find every part of it made up of masses of nucleated
protoplasm of various sizes and shapes. In all essential features these
masses conform to the type of protoplasmic matter just described. Such
bodies are called cells. In many cells the nucleus is finely granular or
reticulated in appearance, and on the threads of the meshwork may be one
or more enlargements, called nucleoli. In some cases the protoplasm at the
circumference is so modified as to give the appearance of a limiting
membrane called the cell wall. In brief, then, a cell is a mass of
nucleated protoplasm; the nucleus may have a nucleolus, and the cell
may be limited by a cell wall. Every tissue of the human body is formed
through the agency of protoplasmic cells, although in most cases the
changes they undergo are so great that little evidence remains of their
existence.
There are some organisms lower down in the scale, whose whole activity is
confined within the narrow limits of a single cell. Thus, the amoeba
begins its life as a cell split off from its parent. This divides in its
turn, and each half is a complete amoeba. When we come a little higher
than the amoeba, we find organisms which consist of several cells, and a
specialization of function begins to appear. As we ascend in the animal
scale, specialization of structure and of function is found continually
advancing, and the various kinds of cells are grouped together into
colonies or organs.
12. Cells and the Human Organism. If the body be studied in its
development, it is found to originate from a single mass of nucleated
protoplasm, a single cell with a nucleus and nucleolus. From this
original cell, by growth and development, the body, with all its various
tissues, is built up. Many fully formed organs, like the liver, consist
chiefly of cells. Again, the cells are modified to form fibers, such as
tendon, muscle, and nerve. Later on, we shall see the white blood
corpuscles exhibit all the characters of the amoeba (Fig. 2). Even such
dense structures as bone, cartilage, and the teeth are formed from cells.
[Illustration: Fig. 2.--Amoeboid Movement of a Human White Blood
Corpuscle. (Showing various phases of movement.)]
In short, cells may be regarded as the histological units of animal
structures; by the combination, association, and modification of these
the body is built up. Of the real nature of the changes going on within
the living protoplasm, the process of building up lifeless material into
living structures, and the process of breaking down by which waste is
produced, we know absolutely nothing. Could we learn that, perhaps we
should know the secret of life.
13. Kinds of Cells. Cells vary greatly in size, some of the smallest
being only 1/3500 an inch or less in diameter. They also vary greatly in
form, as may be seen in Figs. 3 and 5. The typical cell is usually
_globular_ in form, other shapes being the result of pressure or of
similar modifying influences. The globular, as well as the large, flat
cells, are well shown in a drop of saliva. Then there are the _columnar_
cells, found in various parts of the intestines, in which they are closely
arranged side by side. These cells sometimes have on the free surface
delicate prolongations called cilia. Under the microscope they resemble a
wave, as when the wind blows over a field of grain (Fig. 5). There are
besides cells known as _spindle, stellate, squamous_ or pavement, and
various other names suggested by their shapes. Cells are also described as
to their contents. Thus _fat_ and _pigment_ cells are alluded to in
succeeding sections. Again, they may be described as to their functions or
location or the tissue in which they are found, as _epithelial_ cells,
_blood_ cells (corpuscles, Figs. 2 and 66), _nerve_ cells (Fig. 4), and
_connective-tissue_ cells.
14. Vital Properties of Cells. Each cell has a life of its own. It
manifests its vital properties in that it is born, grows, multiplies,
decays, and at last dies.[3] During its life it assimilates food, works,
rests, and is capable of spontaneous motion and frequently of locomotion.
The cell can secrete and excrete substance, and, in brief, presents nearly
all the phenomena of a human being.
Cells are produced only from cells by a process of self-division,
consisting of a cleavage of the whole cell into parts, each of which
becomes a separate and independent organism. Cells rapidly increase in
size up to a certain definite point which they maintain during adult life.
A most interesting quality of cell life is motion, a beautiful form of
which is found in ciliated epithelium. Cells may move actively and
passively. In the blood the cells are swept along by the current, but the
white corpuscles, seem able to make their way actively through the
tissues, as if guided by some sort of instinct.
[Illustration: Fig. 3.--Various Forms of Cells.
A, columnar cells found lining various parts of the intestines (called
_columnar epithelium_);
B, cells of a fusiform or spindle shape found in the loose tissue under
the skin and in other parts (called _connective-tissue cells_);
C, cell having many processes or projections--such are found in
connective tissue, D, primitive cells composed of protoplasm with
nucleus, and having no cell wall. All are represented about 400 times
their real size.
]
Some cells live a brief life of 12 to 24 hours, as is probably the case
with many of the cells lining the alimentary canal; others may live for
years, as do the cells of cartilage and bone. In fact each cell goes
through the same cycle of changes as the whole organism, though doubtless
in a much shorter time. The work of cells is of the most varied kind, and
embraces the formation of every tissue and product,--solid, liquid, or
gaseous. Thus we shall learn that the cells of the liver form bile, those
of the salivary glands and of the glands of the stomach and pancreas form
juices which aid in the digestion of food.
15. The Process of Life. All living structures are subject to
constant decay. Life is a condition of incessant changes, dependent upon
two opposite processes, repair and decay. Thus our bodies are not
composed of exactly the same particles from day to day, or even from one
moment to another, although to all appearance we remain the same
individuals. The change is so gradual, and the renewal of that which is
lost may be so exact, that no difference can be noticed except at long
intervals of time.[4] (See under "Bacteria," Chapter XIV.)
The entire series of chemical changes that take place in the living body,
beginning with assimilation and ending with excretion, is included in one
word, metabolism. The process of building up living material, or the
change by which complex substances (including the living matter itself)
are built up from simpler materials, is called anabolism. The
breaking down of material into simple products, or the changes in which
complex materials (including the living substance) are broken down into
comparatively simple products, is known as katabolism. This reduction
of complex substances to simple, results in the production of animal force
and energy. Thus a complex substance, like a piece of beef-steak, is built
up of a large number of molecules which required the expenditure of force
or energy to store up. Now when this material is reduced by the process of
digestion to simpler bodies with fewer molecules, such as carbon dioxid,
urea, and water, the force stored up in the meat as potential energy
becomes manifest and is used as active life-force known as _kinetic
energy_.