First Book in Physiology and Hygiene

21. What the Spinal Cord Does.—If you tickle a person's foot when he is asleep, he will pull it up just as he would if he were awake, only not quite so quickly. What do you suppose makes the muscles of the leg contract when the brain is asleep and does not know that the foot is being tickled? And here is another curious fact. When you were coming to school this morning you did not have to think about every step you took. Perhaps you were talking or looking over your lessons; but your legs walked right along all the time, and without your thinking about them. Can you tell how?

22. It would be too much trouble for the large brain to stop to think every time we step, and the little brain has work enough to do in taking care of the heart and lungs and other organs, without keeping watch of the feet when we are asleep, so as to pull them up if some mischievous person tickles them. So Nature puts a few nerve cells in the spinal cord which can do a certain easy kind of thinking. When we do things over and over a great many times, these cells, after a time, learn to do them without the help of the large brain. This is the way a piano-player becomes so expert. He does not have to think all the time where each finger is to go. After the tunes have been played a great many times, the spinal cord knows them so well that it makes the hands play them almost without any effort of the large brain.

SUMMARY

1. The part of the body with which we think is the brain.

2. The brain is found filling the hollow place in the skull.

3. There are two brains, the large brain and the small brain.

4. Each brain is divided into two equal and complete halves, thus making two pairs of brains.

5. The brain is largely made up of very small objects called nerve or brain cells.

6. The nerve cells send out very fine branches which form the nerves.

7. The nerve branches or fibres run to every part of the body. They pass out from the brain to the rest of the body through a number of openings in the skull.

8. Most of the nerve branches pass out through a large opening at the back of the skull, in one large bundle called the spinal cord.

9. The spinal cord runs down through a canal in the backbone, and all along gives off branches to the various parts of the body.

10. It gives us pain to prick or hurt the flesh in any way, because when we do so we injure some of the little nerve branches of the brain cells.

11. When we suffer, we really feel a pain in the brain. We know this because if a nerve is cut in two, we may hurt the part to which it goes without giving any pain.

12. We have different kinds of nerves of feeling.

13. There are other nerves besides those of feeling. These are nerves of work.

14. The nerves of work have charge of the heart, the lungs, the muscles, the liver, the stomach, and every part of the body which can work or act.

15. The brain and nerves control the body and make all the different parts work together in harmony, just as a general controls an army.

16. The brain uses the nerves very much as a man uses the telephone or telegraph wires.

17. With the large brain we remember, think, and reason.

18. The little brain does the simple kind of thinking, by means of which the heart, lungs, and other vital organs are kept at work even when we are asleep.

19. The spinal cord does a still more simple kind of work. It enables us to walk and to do other familiar acts without using the large brain to think every moment just what we are doing.

CHAPTER XXIII

HOW TO KEEP THE BRAIN AND NERVES HEALTHY

1. Uses of the Brain.—What do you think a boy or girl would be good for without any brain or nerves? Such a boy or girl could not see, hear, feel, talk, run about, or play, and would not know any more than a cabbage or a potato knows. If the brain or nerves are sick, they cannot work well, and so are not worth as much as when they are healthy.

2. The Brain Sympathizes with Other Organs.—Did you ever have a headache? Did you feel happy and good-natured when your head ached hard, and could you study and play as well as when you are well? It is very important that we should keep our brain and nerves healthy, and to do this we must take good care of the stomach and all other organs, because the brain sympathizes with them when they are sick.

3. We must have Pure Air.—How do you feel when the school-room is too warm and close? Do you not feel dull and sleepy and so stupid that you can hardly study? This is because the brain needs good, pure blood to enable it to work well. So we must always be careful to have plenty of pure air to breathe.

4. We should Exercise the Brain.—What do we do when we want to strengthen our muscles? We make them work hard every day, do we not? The exercise makes them grow large and strong. It is just the same with our brains. If we study hard and learn our lessons well, then our brains grow strong, and study becomes easy. But if we only half study, and do not learn our lessons perfectly, then the study does not do our brains very much good.

5. We should Take Muscular Exercise.—When you get tired of study, an hour's play, or exercise of some sort, rests you and makes you feel brighter, so that you can learn more easily. This is because exercise is necessary to make the blood circulate well. It will then carry out the worn-out particles and supply the brain and nerves with fresh, pure blood. So the same exercise which makes our muscles strong makes our brains healthier also.

6. We should be Careful of our Diet.—We ought to eat plenty of good, simple food, such as milk, fruits, grains, and vegetables. It is not well for children to eat freely of meat, as it is very stimulating and likely to excite the brain and make the nerves irritable. Mustard, pepper, and all hot sauces and spices have a tendency to injure the brain and nerves.

7. We should Allow the Brain to Rest at the Proper Time.—When we are tired and sleepy we cannot think well, and cannot remember what we learn if we try to study. If we have plenty of sleep, free from bad or exciting dreams, we awake in the morning rested and refreshed, because while we have been asleep Nature has put the brain and nerves in good repair for us. We ought not to stay up late at night. We should not eat late or hearty suppers, as this will prevent our sleeping well.

8. We Ought Not to Allow Ourselves to Become Angry.—When a person flies into a passion he does his brain and nerves great harm. It is really dangerous to get angry. Persons have dropped dead instantly in a fit of anger.

9. We should Shun Bad Habits.—Bad habits are very hard to give up, and hence we should be careful to avoid them. When a child learns to swear, or to use slang phrases, the brain after a while will make him swear or use bad words before he thinks. In a similar manner other bad habits are acquired.

SUMMARY

1. A person without a brain or nerves would be of no more account than a vegetable.

2. When the brain or nerves are sick they cannot perform their duties properly.

3. To keep the brain and nerves in good health, we must take good care of the stomach and all other important organs of the body.

4. There are many things which we may do to keep the brain and nerves strong and well.

5. The brain needs pure blood, and so we must be careful to breathe pure air.

6. The brain gets strength by exercise, just as the muscles do. Hence, study is healthful, and makes the brain strong.

7. A good memory is very necessary, but we should not try to remember everything.

8. It is very important that we learn how to observe things closely.

9. Exercise in the open air rests and clears the brain by helping the blood to circulate.

10. Plenty of wholesome and simple food is necessary to keep the brain and nerves in good health. Spices, condiments, and rich foods in general are stimulating and harmful.

11. Plenty of sleep is needed to rest the brain and nerves.

12. It is dangerous as well as wicked to become very angry.

13. We should be careful to avoid forming bad habits of any sort, as they are hard to break, and often adhere to one through life.

CHAPTER XXIV

BAD EFFECTS OF ALCOHOL UPON THE BRAIN AND NERVES

1. Drunkenness.—Did you ever see a man who was drunk? If you live in a city it is very likely that you have. How did the drunken man behave? Perhaps he was noisy and silly. Perhaps he was angry and tried to pick a quarrel with some one.

2. What made the man drunk? You say whiskey, but it may have been wine, or beer, or hard cider that he drank. Anything that contains alcohol will make a man drunk, for it is the alcohol which does all the mischief.

3. The Whiskey Flush.—You can almost always tell when a man has been drinking, even when he has not taken enough to make him drunk. You know by his flushed face and red eyes. When a man's face blushes from the use of alcohol, his whole body blushes at the same time. His muscles, his lungs, and his liver blush; his brain and spinal cord blush also.

4. When a man has taken just enough alcohol to make his face blush a little, the extra amount of blood in the brain makes him think and talk more lively, and he is very jolly and gay. This makes many people think that alcohol does them good. But if we notice what a man says when he is excited by alcohol, we shall find that his remarks are often silly and reckless. He says very unwise and foolish things, for which he feels sorry when he becomes sober.

5. Alcohol Paralyzes.—How does a drunken man walk? Let us see why he staggers. When a man takes a certain amount of alcohol his small brain and spinal cord become partly paralyzed, so that they cannot do their duty well; and so, when he tries to walk he reels and stumbles along, often falling down, and sometimes hurting himself very much. The fact is that the alcohol has put his spinal cord and small brain to sleep so that he cannot make his legs do what he wants them to do. Now, if still more alcohol is taken the whole brain becomes paralyzed, and then the man is so nearly dead that we say he is "dead drunk." It is exceedingly dangerous to become dead drunk, as the brain may be so completely paralyzed that it will not recover.

6. A small amount of alcohol does not make a man dead drunk, but it poisons and paralyzes his brain and nerves just according to the quantity he takes.

7. If a person holds a little alcohol in his mouth for a few moments, the tongue and cheeks feel numb. This is because the alcohol paralyzes them so that they cannot feel or taste. When taken into the stomach it has much the same kind of effect upon the nerves of the whole body.

8. Alcohol a Deceiver.—A hungry man takes a drink of whiskey and benumbs the nerves of his stomach so that he does not feel hungry. Alcohol puts to sleep the sentinels which Nature has set in the body to warn us of danger. A man who is cold takes alcohol and feels warm, though he is really colder. He lies down in his false comfort and freezes to death. A tired man takes his glass of grog and feels rested and strong, though he is really weaker than before. A poor man gets drunk and feels so rich that he spends what little money he has. The alcohol paralyzes his judgment and steals away his good sense. Thus alcohol is always a deceiver.

9. Delirium Tremens. (De-lir'-i-um Tre'-mens.)—When a man takes strong liquors regularly he very soon injures his brain and nerves so that they do not get quiet, as they should, at night, and he does not sleep well. He has frightful dreams. He sees all sorts of wild animals and horrid shapes in his dreams. Perhaps you have sometimes had such dreams from eating late suppers or indigestible food.

10. Did you ever have a dream when you were awake? If a man drinks a great deal he is likely to have a terrible disease known as delirium tremens, in which he sees the same frightful things when he is wide awake that he dreams about when he is asleep. This is one of the terrible effects of alcohol upon the brain and nerves.

11. Alcohol Paralysis.—You have seen how a drunken man staggers when he walks. Did you ever see a man who walked just as though he were drunk when he was really sober? This is because a part of the brain or spinal cord has been permanently injured or paralyzed. Alcohol is not the only cause of this disease, and so you must not think every person who staggers is or has been a drunkard; but alcohol is a very frequent cause of paralysis.

12. Effects of Alcohol upon the Mind and Character.—When a man is under the influence of alcohol is his character good or bad? Is a man likely to be good, or to be bad, when he is drunk or excited by drink? Most men behave badly when they are drunk, and after they have been drunk a great many times they often behave badly all the time. A great many of the men who are shut up in prisons would not have been sent there if they had never learned to drink.

13. A Legacy.—Do you know what a legacy is? If your father should die and leave to you a fine house or farm, or money in the bank, or books, or horses, or any other kind of property to have for your own, it would be a legacy. When a person gets anything in this way from a parent we say that he inherits it.

14. We inherit a great many things besides houses and lands and other kinds of property. For instance, perhaps you remember hearing some one say that you have eyes and hair the same color as your mother's, and that your nose and chin are like your father's. So you have inherited the color of your hair and eyes from your mother and the shape of your chin and nose from your father.

15. The Alcohol Legacy.—The inside of a boy's head is just as much like his parents' as the outside of it. In other words, we inherit our brains just as we do our faces. So, if a man spoils his brain with alcohol and gets an alcohol appetite, his children will be likely to have unhealthy brains and an appetite for alcohol also, and may become drunkards. Is not that a dreadful kind of legacy to inherit?

16. A child that has no mind is called an idiot. Such a child cannot talk, or read, or sing, and does not know enough to take proper care of itself. This is one of the bad legacies which drunken parents sometimes leave to their children.

17. Effects of Tobacco on the Brain and Nerves.—The effects of tobacco upon the brain and nerves are much the same as those of alcohol. Tobacco, like alcohol, is a narcotic. It benumbs and paralyzes the nerves, and it is by this means that it obtains such an influence over those who use it.

18. The hand of a man or boy who uses tobacco often becomes so unsteady that he can scarcely write. Do you know what makes it so unsteady? It is because the cells which send nerves to the muscles of the hand are diseased. When a person has a trembling hand you say he is nervous. If you feel his pulse you will find that it does not beat steadily and regularly as it ought to do. The heart is nervous and trembles just the same as the muscles do. This shows that the tobacco has poisoned the cells in the brain which regulate the heart.

19. Wise physicians will tell you that one reason why tobacco is bad for boys is that it hurts their brains so that they cannot learn well, and do not become as useful and successful men as they might be.

20. Students in the naval and military schools of this country are not allowed to use tobacco on account of its bad effects upon the mind. In France the use of tobacco is forbidden to all students in the public schools.

21. Tobacco Leads to Vice.—Boys who use tobacco are more liable to get into company with boys who have other bad habits, and so are apt to become bad in many other ways. The use of tobacco often makes men want strong drink, and thus leads to drunkenness. If you wish to grow up with a steady hand, a strong heart, and a good character you will never touch tobacco.

22. Effects of Tea and Coffee on the Nerves.—People who use strong tea and coffee are often inclined to be nervous. This shows that strong tea and coffee, like alcohol and tobacco, are very injurious to the nerves.

23. Opium, Chloral, etc.—There are several drugs which are given by physicians to relieve pain or to produce sleep. They are sometimes helpful, but their use is very dangerous. Opium and chloral belong to this class of medicines. The danger is that, after a person has used the medicine a little while, he will continue to use it. If a person takes a poisonous drug every time he has a little pain, he will soon form the habit of using it, and may never break it off. There are many thousands of people who use opium all the time, and they are very much injured by it in mind and body. The mind becomes dull and stupid and the body weak and feeble. No medicine of this sort should ever be taken unless prescribed by a physician.

SUMMARY

1. In order to be well and useful we must keep the brain and nerves healthy.

2. To keep the brain healthy we need plenty of pure air to breathe; proper exercise of the brain by study; sufficient exercise of the muscles in play and work; plenty of good food to make pure blood; a proper amount of rest and sleep.

3. There are several things we ought not to do. We should not read or study too much. We should not allow ourselves to become excited or angry. We should avoid learning bad habits.

4. Alcohol paralyzes the brain and nerves.

5. Alcohol deceives a person who takes it by making him feel strong when he is weak; warm when he is cold; rich when he is poor; well when he is sick.

6. Alcohol makes men wicked. Most men who commit crimes are men who use liquor.

7. The effects of tobacco upon the brain and nerves are much the same as those of alcohol. Tobacco is very injurious to the mind.

8. Tobacco-using often leads boys to drunkenness and other vices.

9. The use of opium and chloral produces even worse effects than the use of alcohol or tobacco.

CHAPTER XXV

HOW WE HEAR, SEE, SMELL, TASTE, AND FEEL

1. The Senses.—We have five senses—hearing, seeing, smelling, tasting, and feeling. These are called special senses because they are very different from each other. They also differ from the general sense of feeling by means of which we feel pain when any part is hurt.

2. Organs of the Special Senses.—Each of the special senses has a special set of nerves and also special cells in the brain which have charge of them. We say that we see with our eyes, hear with our ears, feel with our fingers, etc.; but, really, we see, hear, taste, and smell in the brain just as we feel in the brain. The eyes, ears, nose, and other organs of the special senses are the instruments by means of which the brain sees, hears, smells, etc.

3. Sound and the Vibrations which it Causes.—All sounds are made by jars or vibrations of objects. Sounds cause objects to vibrate or tremble. A loud sound sometimes jars a whole house, while other sounds are so gentle and soft that we cannot feel them in the same way that we feel loud sounds. But Nature has made for us an ingenious organ by means of which we can feel these very fine vibrations as well as loud ones. We call this organ the ear.

4. The Ear.—The part of the ear which we can see is shaped somewhat like a trumpet. The small opening near the middle of the ear leads into a canal or tube which extends into the head about an inch. At the inner end there is a curious little chamber. This is called the drum of the ear, because between it and the canal of the ear there is stretched a thin membrane like the head of a drum. The ear-drum is also called the middle ear.

THE EAR.

5. Bones of the Ear.—Within the drum of the ear there are three curious little bones which are joined together so as to make a complete chain, reaching from the drum-head to the other side of the drum. The last bone fits into a little hole which leads into another curious chamber. This chamber, which is called the inner ear, is filled with fluid, and in this fluid the nerve of hearing is spread out. A part of the inner ear looks very much like a snail shell.

6. How we Hear.—Scratch with a pin upon one end of a long wooden pole. Have some one listen with the ear placed close against the other end of the pole. He will tell you that he hears the scratching of the pin very plainly. This is because the scratching jars the ear and especially the drum-head, which vibrates just as the head of a drum does when it is beaten with a drum-stick. When the drum-head vibrates it moves the bones of the ear, and these carry the vibration to the nerves of hearing in the inner chamber. We hear all sounds in the same way, only most sounds come to the ear through the air.

THE INSIDE OF THE EAR.

The snail-shell of the inner part of the ear hears musical sounds. The rest of the inner ear hears ordinary sounds or noises.

7. How to Keep the Ears Healthy.—The ears are very delicate organs and must be carefully treated. The following things about the care of the ears should never be forgotten:

(1.) Never use a pin, toothpick, or any other sharp instrument to clean out the ear. There is great danger that the drum-head will be torn, and thus the hearing will be injured. Neither is it ever necessary to use an ear-spoon to remove the wax. Working at the ear causes more wax to form.

(2.) Do not allow cold water to enter the ear or a cold wind to blow directly into it.

(3.) If anything accidentally gets into the ear, do not work at it, but hold the head over to one side while water is made to run in from a syringe. If an insect has gone into the ear, pour in a little oil. This will kill the insect or make it come out.

(4.) Never shout into another person's ear. The ear may be greatly injured in this way.

(5.) Boxing or pulling the ears is likely to produce deafness, and ought never to be done.

8. The Eye.—The eye is one of the most wonderful organs in the whole body. It enables us to know what is going on at some distance from us, and to enjoy many beautiful things which our sense of hearing and other senses can tell us nothing about. It also enables us to read. Let us learn how this wonderful organ is made.

9. The Eyeball.—Looking at the eye, we see first a round part which rolls in different directions. This is the eyeball. We see only the front side of the eyeball as it fits into a hollow in the skull. Being thus in a safe place, it is not likely to get hurt.

THE EYE.

The eyeball is mostly filled with a clear substance very much like jelly. It is so clear that the light can shine through it just as easily as it can shine through water.

10. The Pupil.—If you look sharply at the eyeball you will see a small black hole just in the centre. This is a little window which lets the light into the inside of the eyeball. We call this the pupil. Just around the pupil is a colored ring which gives the eye its color. We say a person has blue or brown or gray eyes according as this ring is blue or brown or gray. This colored ring is a kind of curtain for the window of the eye.

11. If you observe the pupil closely, you will see that it is sometimes larger and sometimes smaller. If you look at the light the pupil is small; if you turn away from the light the pupil grows larger at once. This is because the curtain closes when in a bright light and opens in the darkness. It does this of itself without our thinking about it. In this way the eye is protected from too strong a light, which would do it great harm.