The human body and its enemies

Front matter

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COPYRIGHT DEPOSIT

Table Of Contents

CHAPTER PAGE

I. Introduction . v ... 1

II. Bacteria. 4

Preface

An examination of school physiologies published within the last four or five decades discloses the changing viewpoints of teachers of this subject. First anatomy was stressed, then physi¬ ology became prominent, while in recent years leaders in educa¬ tional thought are agreed that hygiene is of paramount impor¬ tance. Within this recent period there has been a shifting of accent from dress and diet to the prevention of germ diseases. The most generally accepted course of today for elementary “ physiology ’ ’ is one that does not minimize any of the phases of the subject mentioned, but one that preserves a correct pro¬ portion among them.

The essential principle of hygiene has ever been cleanliness. The race has developed an instinctive horror for the unclean. Since the discovery of micro-organisms as the causative agents of disease, however, our adherence to cleanliness has become specific and intelligent. There are, for example, many harm¬ less substances far more revolting than human blood containing malarial parasites. But modern hygiene teaches that the blood of a malarial patient, taken in conjunction with a certain species of mosquito, makes a combination which is, from a health stand¬ point, very “unclean/’

There is, therefore, a well-founded demand that children be taught the essentials of germ diseases and their prevention. The authors of the present volume have placed this material first, believing that its importance justifies this order of treatment.

There is in some quarters a timidity in dealing with these topics of health and disease on the ground that increased knowl¬ edge along these lines would lead to a more pessimistic point vi of view. The important role of optimism in the preservation of health is well recognized. Yet, in view of our present knowl¬ edge of the wonderful defenses of the human body, it must be conceded that an understanding of them gives an increased confidence and renewed optimism based on fact and not merely on sentiment.

A discussion of the anatomy of the human body has been reduced to a minimum; likewise, the physiology has been sub¬ ordinated to the principles of hygiene. Such a treatment is be¬ lieved to appeal to the reason of the child, for persuasion is more effective than arbitrary command.

The fact has been borne in mind that “physiology and hygiene” is practically the only natural science that the great bulk of our people ever have an opportunity of studying. The scientific treatment has, therefore, been adhered to as closely as the intellectual advancement of the pupil for whom this work is intended would seem to allow.

Aids to the memory, however, have not been omitted. A summary of the important points together with carefully se¬ lected questions at the end of each chapter will be found of help to the pupil in his study. Frequent review questions and cross references in the text afford ample opportunities for repe¬ tition.

Experience in teaching science soon convinces one that poor thinking is largely due to vague mental concepts of things and relations. The laboratory method of “seeing for one’s self” has been stressed in these pages. The numerous experiments in¬ troduced throughout the book are all simple and can be per¬ formed easily and with very little outlay for apparatus and ma¬ terial.

Illustrations are today considered a necessity in a modern scientific book, particularly in one intended for the young mind.

This book contains more illustrations than any book of its kind that has come under our notice. With several exceptions, they were all drawn expressly for this book. For many of the illus¬ trations a distinct pedagogical value is claimed, particularly the types of illustrations exemplified by the section of the skin (Fig. 176, shown in three dimensions) and by the figures of bone tissue (Figs. 189-191).

The authors’ grateful acknowledgments of thanks and appre¬ ciation are due their many friends of the teaching and medical profession in Texas and other States for kind assistance and suggestions in the preparation of this work.

Carl Hartman.

Lewis Bradley Bibb.

Austin, Texas, Aug. 1, 1912.

CHAPTER T.

Introduction .

If it were your duty to care for and operate some fine piece of machinery, like an automobile, you would first want to know a great deal about the machine, its various parts, how they were put together, and how all parts worked in harmony to make the machine go. No doubt you know boys who would delight in taking an automobile to pieces and putting it to¬ gether again. We al¬ ways take pleasure in observing and tinder¬ standing a beautiful machine, such as a watch, an aeroplane, or an automobile.

The Human Body is a Flg The driver ot an automobile Wonderful Machine.— Should study his machine.

Now, it is the duty of each and every one of us to care for and operate a much finer machine than any of those mentioned, and that is the human body. Did you ever stop to think what a won¬ derful machine your body is? Think of the brain, with which we know and remember things, feel emotions, and control our acts. Consider the eye, which is a little camera with sensitive film and focussing apparatus. How wonderfully all the parts of the body are connected by the nerves, which act as tele¬ graph wires, carrying messages from the various parts to the brain, which is like the central office. Most wonderful of all,

The Human Body and Its Enemies.

consider how the food we eat becomes a part of ourselves. We must conclude then that the human body is the most marvel¬ lous machine in existence. If we are to operate this mar¬ vellous machine we certainly should understand something about it, in order that we may take proper care of it and see that it does its work properly.

. We Must Learn What Dan-

Fig. 2. The aviator’s life depends on his mastery over his machine.

gers Threaten Our Bodies. —The driver of an automobile, however, must know more than the parts of his machine; he must know also what kind of dangers are to be met in the road which he is to travel. He must know the whereabouts of cactus thorns, sharp stones, and deep sands, in order that he may avoid them. Just so, the driver of the human automobile must know what dangers beset him on his life-

journey. The habit of drinking alcohol, for instance, is one danger that besets some of us. Impure foods are very harmful to the body, and they are one of the dangers that may befall any of us. One of the commonest dangers, how¬ ever, that lurks along our life-journey is disease or sickness due to germs.

if]

A Camera.

Disease germs not only cause more than one-third of all deaths that occur in this State, but also cause most of the blindness and a large part of the illness which afflicts our citizens. And yet, we can not be harmed by disease germs unless the germs enter our system. In order, then, to protect

Introduction

ourselves against these little germ-enemies, we must study them, learn where they come from, and how they gain entrance into the human body. We shall then be in a position to avoid them, and thus steer our human automobile clear of this danger. If we understand our bodies, and also understand just what dangers threaten us and how to avoid them, we shall be more likely to suc¬ ceed in keeping ourselves in that pleasant con d i t i o n which we call health.

Fig\ 4. The eye, a human camera.

Important Points.

1, The human body is more complex than any machine or instrument made by man.

2 . We should understand this machine in order to keep its various parts in or¬ der.

3. We should also know how best to avoid certain dangers which threaten us,

A few of our germ enemies. suc h ag typhoid fever, tuber-

' Jwi ^ ^ culosis or consumption and other diseases due to germs.

1. Why should we study the human body? 2. Name some things which can injure the body. 3. Name one important cause of blind¬ ness. 4. What percentage or proportion of all deaths in Texas is due to germs? 5. Name several things we should know about dis¬ ease germs in order to avoid them.

CHAPTER II. Bacteria or Germs

I should hate to have to tell you in a single sentence what germs or bacteria are. Bacteria are such wonderful lit¬ tle beings, and are so different from the creatures that we know, that it is very hard to get an idea of what they really are. All of you have read in the fairy tales about certain fairies that were invisible. The story of bacteria is like a fairy tale, be¬ cause for many centuries we were surrounded by bacteria, and yet they were invisible to us, and in fact we never guessed or dreamed that they existed until long after Columbus dis¬ covered America. And bac¬ teria are invisible to this day, unless we use a microscope to aid the human eye, or unless we take a great many of the bacteria in a clump to look at.

Size of Bacteria. —To be¬ gin with, then, bacteria are very small. If you took a colony of them and picked it out with a needle till you had little pieces that you could barely see with the naked eye, each one of these little pieces would contain hundreds and probably thousands of bacteria. Many of them are so small that it would take twenty-five thousand of them placed side by side to occupy the space of an inch. And as small as they are, each one has a definite shape. There are three varieties of bacteria from a standpoint of shape, the rods, the round ones and the spirals. You can see these in Fig. 6.

Fig. 7. This shows how much smaller bacteria are than the finest cam¬ bric needle.

Bacteria or Germs.

Motion of Bacteria. —Some of them can swim about from one place to another, and others never move unless they are washed about or jostled in the fluid ’they live in. Those that move, either do so by squirm¬ ing along like a snake swim¬ ming, or else they have little tiny hairs growing all over their bodies and whip the wa¬ ter with these hairs. Of course the perfectly round ones can¬ not do any squirming, and unless they have little hairs on them they cannot move.

Food of Bacteria. —The bacterium (for this is the word we use in speaking of a single one) has to have food, and many of them have to have oxygen just as we do. But he is so small that the food can soak in from the outside, and he does not need any mouth. Practically all of his active life is spent in a liquid, and the food simply dissolves in the liquid and passes through his very thin skin into his inside. For you know the entire bacterium isn’t nearly so thick as a sheet of tissue pa¬ per, and his skin must be really so thin that we cannot realize its true thinness. But some bacteria (here we use the plural word again) seem to secrete a juice of some kind that digests meat. The only difference between their digestion and ours however, is that they pour the juice over the meat or other food while it is still outside their bodies. They let the diges¬ tion occur outside their bodies, and then absorb or soak up the food in a liquid form.

Toxins.—The bacterium is so small that he needs no kid¬ neys. Whatever of waste matter there is in his body can soak out, or ooze out, just as his food soaks in. And this is one way

Fig-. 8.—The rod-shaped germs can¬ not move about rapidly like the ones with the little lashes on them.

The Human Body and Its Enemies.

that some bacteria injure us. Some kinds of bacteria live in our bodies and pour out or ooze out their waste material in our bodies. If the waste material they pour out is poisonous to us, they make us sick. The poisonous material is called toxin, which means “poison.” Other bacteria form a waste material is called toxin, which means not make us sick unless they multiply fast enough to stop up some passage way in the body.

Multiplication of Bacteria. —And bacteria can multiply very rapidly indeed. They seem to multiply by simply dividing in two. Each one splits half in two and you have two bacteria where only one bacterium w r as in the first place. Starting with one bac¬ terium, we may have many millions in a day or two.

Fig. 9. This glass tube contains bacteria growing on gelatine.

Ultra-Microscopic Bacteria. —In studying bacteria we must not lose sight of the fact that there are some bacteria too small to be seen even with a good microscope. No one has ever seen these germs. You may well ask how then do we know that they exist. We know only from their effects. For instance, we know that foot and mouth disease in cattle is caused by a germ, and the blood of an animal sick of this dis¬ ease, if injected into another animal, will cause that animal to catch the disease. Even if we filter the blood from the sick animal, so as to remove all particles large enough for us to see with the best microscope, it will still cause foot and mouth disease when injected into an animal. Our filters are fine enough to strain out all germs that are visible, and since the filtered blood still causes the disease, we must conclude that there are invisible germs in it. These germs are so small that

Bacteria or Germs.

i

they pass easily through the filter and set up foot and mouth disease as soon as they reaeli their natural living place, which is the body of the cow. Possibly some intelligent pupil at present busy in one of our schools may some day invent a mi¬ croscope powerful enough to reveal these ultra-microscopic bacteria to our sight.

At this time we tend to look on smallpox, yellow fever, measles and infantile paralysis as being due to small bacteria, which we call ultra-microscopic. Certain diseases which at¬ tack the lower animals have been proven beyond a doubt to be due to the ultra-microscopic germs.

Where Bacteria Live. —We have said nothing yet about where the bacteria live. They live almost everywhere. They live in water, they live in milk, they live in the ground, they live in dust, they live in decaying fruits, and we might say they live everywhere, except where they have been removed in some way. The most important place they live is in certain parts of our bodies. There are some harmless bacteria always present in the mouth. There are a great many harmless bac¬ teria always present in the intestines. Some harmless varie¬ ties are in the skin, especially the outer horny layer, at all times. Certain kinds of bacteria cause milk to sour. Certain other kinds cause milk to curdle into cheese. Still other bac¬ teria live on the roots of clover and peas and enrich the soil.

Harmless Germs and Disease Germs. —There are thousands of different kinds of bacteria, and probably not over a hun¬ dred different kinds that are harmful to man. There are some bacteria that do not multiply anywhere except in the human body, and which make poisons or toxins which make us sick or even kill us. These bacteria are dangerous. Typhoid fever, meningitis, tuberculosis, la grippe and diphtheria are all caused by bacteria. The bacteria are visible with the micro-

The Human Body and Its Enemies.

scope, but are so small that they could not harm us except for the poisons which they make in our bodies.

Disease Germs Multiply Only in the Body. —It is very important to remember that most of the bacteria which cause disease cannot live more than a few weeks or months outside the human body. And these harmful bacteria do not as a rule multiply at all except in the human body. This makes it much easier to avoid them and keep free of them, because all we have to do is to see that none of the bacteria from sick people get near us. Think how hard it would be to avoid typhoid fever, for instance, if the germs were found naturally in the ground. It is hard enough to avoid the germs when we know that they are found only where they have been thrown.

How Bacteria Are Scattered. —The germs do seem to have great success in getting themselves scattered. Take, for example, the germs of diphtheria. They can be carried from one individual to another on such a little thing as a lead pen¬ cil, especially if the users of the pencil place its point in their mouths. Waving a soiled pocket handkerchief in the air may set the germs to floating in the air we breathe. The fingers which have touched such a handkerchief may grasp a door¬ knob and leave many germs behind. The next fingers that grasp the doorknob will take away some of the germs. The wash-woman, handling the linen, is especially likely to get the germs into her system. In a general way, every solid or liquid particle that leaves the body of anyone suffering from a germ disease may carry the germs of that disease. Whether it be saliva, tears, perspiration, bath water, or any other thing of this kind, it is dangerous, because it may have germs in it.

Careless People. —Since we know now the exact germ that causes each one of the diseases mentioned, and since we know

Bacteria or Germs.

just how the germs are carried from one man to another, it is only a question of time till we will get the diseases under control. This knowledge is so new that the majority of people either do not know these things, or cannot realize them. You will see men and women with sweet character who go about spreading disease germs and causing sickness and death. Have you not seen consumptives spit on the floor? It would be kinder if the consumptive would set a steel trap to catch little children by the foot instead of setting this disease trap for them. Boys and girls in school now learn a great deal more about disease germs than their parents did when they were in school. The spitting nuisance is dying out. People must expectorate, but they can expectorate into a cuspidor or spit¬ toon, or else carry several handkerchiefs, paper napkins or rags.

Important Points.

1. Bacteria are too small to be seen with the naked eye, and some of them are so small we have never even seen them with the best microscopes.

2. Bacteria live almost everywhere; especially in decaying food and dirty places.

3. Many bacteria live in our bodies, and a few are harm¬ ful to us. Most of the harmful ones make toxins which make us sick.

4. Many people have never learned the importance of not spitting on the floor.

Questions.

1. How small are bacteria? 2. Can they all move about? 3. How do bacteria multiply? 4. Name some places where bacteria live. 5. are all bacteria harmful to man? 6. How do they injure us? 7. Name some of the ways that disease germs are carried from one person to another.

CHAPTER III. Diseases That Are Catching

Did you ever have measles or mumps? If so, you could possibly' tell just whom you caught the disease from. In other words, you could trace the source of contagion or infec¬ tion. Some diseases, like measles and smallpox, are under¬ stood to be contagious, or catching. A better word to use is 1 ‘ communicable. ” A communicable disease is one that can be comihunicated or given to another.

Communicable Diseases. —There are a great many diseases that are communicable. Some diseases we now know to be communicable, but formerly we did not. For instance, typhoid fever is a communicable disease. We have always known that leprosy, cholera, smallpox, plague, measles, scarlet fever, hy¬ drophobia, diphtheria and others were communicable; but we have learned only in our own generation that consumption, typhoid fever, malarial chills and fever, yellow fever, menin¬ gitis,'granulated lids, infantile paralysis, erysipelas, and den¬ gue, are also communicable. A great many well informed and educated people today do not realize that these diseases are communicable.

Scientists Who Gave Up Their Lives. —There have been many scientists who gave up their lives in an effort to find exactly how the dangerous communicable diseases are spread. In 1900, Dr. Lazear and Dr. Carroll, both United States Army surgeons, willingly contracted yellow fever in order to find the exact method by which it is spread; Dr. Lazear died after a few clays ; Dr. Carroll lived for several years, but finally died as a result of the yellow fever. Dr. Ricketts, a young physician of

Diseases That Are Catching.

DANDRUFF

S E.CRETION FROM E.YE- ECRETION FROM NOSE.

>5PUTUn

WASTE

FROM KIDNEY

AND

ALIMENTARY CANA'

.Mosquitoes.

AIMS OTHER. !N6E.ct6

Fi^. 9. This picture shows almost all the different ways by which germs or "contagion” can leave or enter the body. There is not one solid or liquid particle cast off from the human body which may not, under certain conditions, carry or convey disease. Beginning at the top, you will note that dandruff is cast off from the scalp. “Dandruff” is in all probability a contagious disease spread largely by combs and brushes in barber shops. Pus from the eye conveys sore eyes of sev¬ eral kinds, some of which can cause blindness. Secretion from the nose and mouth is the medium for spreading consumption, diphtheria, men¬ ingitis, paralysis of children, and other diseases. Dead skin from the surface of the body is believed to spread smallpox, scarlet fever, measles, and other diseases. Waste matter from the kidneys and bowels un¬ doubtedly conveys typhoid fever, dysentery, Asiatic cholera, hookworm disease, and others. The mosquito is the only insect pictured, but many other insects carry disease from one person to another. You will learn more about these in Chapter XIV. From this page, learn one lesson: all contagion is due to solid or liquid particles which leave the body of the sick, while absolutely all such particles are capable of carrying some disease.

The Human Body and Its Enemies.

Chicago, went to Mexico in 1909 to study jail fever. During his experiences he became sick with the disease and died.

Diseases Are Conveyed by Solid or Liquid Particles That Leave the Body of the Sick. —By exposing themselves to dan¬ ger, these scientists have found out just how most of these communicable diseases are spread. And yet some people still speak as though we did not know how they are spread. It is very important for us to realize that these diseases are not all spread in the same way; but we do know how most of them are spread. They are always conveyed by solid or fluid particles which leave our bodies. The air cannot spread dis¬ ease except for the dust or little pieces of dried material that came from our bodies and float in the air. Water cannot spread disease except when the particles of solid or liquid material that leave our bodies are in the water. Even the mosquito cannot carry disease except when she has sucked up some of the blood of an individual that is sick. The fly is powerless to carry disease except when he has been walk¬ ing over some of the waste that is cast off from our bodies.

How Disease Germs Leave the Body. —Try to rid your mind of that old, hazy, indefinite idea that “contagion” may be “atmospheric,” or due to filth, or to bad weather, or to an unhealthy climate. Instead, think of contagion as something definite, that you can see and weigh and feel. Let us take note of the different ways in which particles leave the body. We have first the waste materials, which are thrown off by the kidneys, the alimentary canal, and the skin. Then we have the dried skin, which peels off every part of the body; these little particles are believed to carry the germ of small¬ pox. Then we have the hair and nails, and the hair may spread a very troublesome disease called ring-worm of the scalp. Then there is the sputum and saliva from the mouth,

Diseases That are Catching. 13

and the nasal secretion, both of which are concerned in the spread of many different diseases, such as measles, scarlet fever, diphtheria, consumption, meningitis, leprosy, smallpox, and other diseases. The secretion from the eye is responsible for the spread of trachoma or granulated lids, and conjunc¬ tivitis, or sore eyes. All these things leave the body natu rally. In addition, certain insects take away from our bodies blood, which conveys malaria. There are then many different ways by which solid and liquid particles leave our bodies, and there is some disease germ which may be carried by al¬ most every one of these particles. To help us get a clear idea how communicable diseases are spread, let us take certain examples.

The Typhoid Germ Is Thrown Off From the Body in Body Wastes. —Typhoid fever is spread especially by the body wastes, which are thrown out from the sick room on the ground. Flies light on it, dip their feet in it, and fly into the dining room and walk over our food. Or else, the rain washes these body wastes into the well, spring, or river, and we drink the water containing the typhoid germs.

Tuberculosis Is Spread Especially by Dust From Dried Spu¬ tum. —For instance, a consumptive spits on the floor; the spit dries; and when the floor is swept, the dried spit is thrown up in the air in the form of dust, where it is inhaled by all those in the room.

Malaria Spread by the Mosquito. —In malaria, yellow fever, and dengue, the disease is not spread by body waste; but the mosquito gets a drop of blood from a patient suffering from malaria, and then bites a well man; and the malaria or other germs are injected into the well man.

Diphtheria Is Sometimes Spread by the Pocket Handker¬ chief. —The patient soils the handkerchief with secretion from

The Human Body and Its Enemies.

his nose. In handling the handkerchief, his fingers get the secretion and germs on them. He then handles knife and fork, and door knobs, or shakes hands with others. The germs are thus passed on to the hands of others, who, in turn, pick at their noses or eat with their fingers, or possibly use a pocket handkerchief, and thus place the germs in the nose, where they can reach the throat and set up diphtheria.

Granulated Lids or Sore Eyes Are Spread by the Secretion From the Eyes of One Suffering From the Disease. —The secre¬ tion or pus is collected on a handkerchief. At the same time some of it reaches the fingers. From the fingers it contami¬ nates lead pencils, towels, door knobs, etcr

Every case of communicable disease is caused by some se¬ cretion or excretion from the body of some one sick with the disease.

Important Points.

1. All disease germs are carried from the body by some solid or liquid particles thrown off from the body.

2. Sputum and body wastes are especially likely to contain disease germs.

3. No disease can spread if we prevent the solid and liquid

particles from leaving the patient and getting into or on some other person. *

Questions.

1. Name all the solid and liquid particles which leave the body. (For example, body wastes, perspiration, etc.)

2. Name ten communicable diseases.

3. Name three diseases spread by sputum.

4. What is meant by communicable disease?

5. Describe how disease germs from body wastes can get from the ground into a new patient.

CHAPTER IV. Our Protection Against Disease Germs

From the chapters that have gone before, you have learned something of the enemies which attack our bodies from with¬ out, and it now remains for us to learn how wonderfully we are protected against these germ enemies. Let us not think for one instant that the germs have an easy fight even after they get into our bodies. Before any germ can make us sick, it must fight the battle of its life, and the human body wins out in the vast majority of cases. Did you know that the human body has a wonderful system of defense against disease germs ?

The Skin as a Protective Covering. —To

begin with, our skin is thick and horny on the outside and very few bacteria can penetrate it if it is kept healthy and whole. The best way to keep the skin healthy is to keep it clean with soap and water in reasonable amount.

The Gastric Juice Kills Germs.—

The stomach is well protected, too.

It is the first stopping place of every¬ thing we swallow. The stomach is bathed at all times in a good anti¬ septic fluid, the gastric juice. The gastric juice is fatal to germs. It contains hydrochloric acid, and the acid itself will kill most germs. The pepsin will also digest germs, and so if our digestion is good not many germs will pass through the stomach.

Fig. 12. The gastric juice in the stomach is fatal to most germs.

Fig. 11. The skin showing its pro¬ tective horny layer.