First Book in Physiology and Hygiene
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4. If we wish to keep our digestive organs in good order, we must take care to eat at regular hours. We ought not to eat when we are very tired. The stomach cannot digest well when we are very much fatigued.
5. Sweet Foods.—We ought not to eat too much sugar or sweet foods, as they are likely to sour or ferment in the stomach, and so make us sick. Candies often contain a great many things which are not good for us, and which may make us sick. The colors used in candies are sometimes poisonous. The flavors used in them are also sometimes very harmful.
6. Fatty Foods Hurtful.—Too much butter, fat meats, and other greasy foods are hurtful. Cream is the most digestible form of fat, because it readily dissolves in the fluids of the stomach, and mixes with the other foods without preventing their digestion. Melted fats are especially harmful. Cheese, fried foods, and rich pastry are very poor foods, and likely to cause sickness.
7. Eating too many Kinds of Foods.—Children should avoid eating freely of flesh meats. They ought also to avoid eating all highly-seasoned dishes, and taking too many kinds of food at a meal. A simple diet is much the more healthful. Milk and grain foods, as oatmeal, cracked wheat, graham bread, with such delicious fruits as apples, pears, and grapes, are much the best food for children.
8. Avoid Use of Cold Foods.—We ought not to take very cold foods or liquids with our meals. Cold foods, ice-water, and other iced drinks make the stomach so cold that it cannot digest the food. For this reason it is very harmful to drink iced water or iced tea, or to eat ice-cream at meals. These things are injurious to us at any time, but they do the greatest amount of harm when taken with the food.
9. Things sometimes Eaten which are not Foods.—Things which are not foods are often used as foods, such as mustard, pepper, and the various kinds of seasonings. Soda, saleratus, and baking-powders also belong to this class. All of these substances are more or less harmful, particularly mustard, pepper, and hot sauces.
10. Common Salt.—The only apparent exception to the general rule that all condiments and other substances which are not foods are harmful is in the case of common salt. This is very commonly used among civilized nations, although there are many barbarous tribes that never taste it. It is quite certain that much more salt is used than is needed. When much salt is added to the food, the action of the digestive fluids is greatly hindered. Salt meats, and other foods which have much salt added to them, are hard to digest because the salt hardens the fibres of the meat, so that they are not easily dissolved by the digestive fluids.
11. Care of the Teeth.—The teeth are the first organs employed in the work of digestion. It is of great importance that they should be kept in health. Many persons neglect their teeth, and treat them so badly that they begin to decay at a very early age.
12. The mouth and teeth should be carefully cleansed immediately on rising in the morning, and after each meal. All particles of food should be removed from between the teeth by carefully rubbing both the inner and the outer surfaces of the teeth with a soft brush, and rinsing very thoroughly with water. A little soap may be used in cleansing the teeth, but clear water is sufficient, if used frequently and thoroughly. The teeth should not be used in breaking nuts or other hard substances. The teeth are brittle, and are often broken in this way. The use of candy and too much sweet food is also likely to injure the teeth.
13. Some people think that it is not necessary to take care of the first set of teeth. This is a great mistake. If the first set are lost or are unhealthy, the second set will not be as perfect as they should be. It is plain that we should not neglect our teeth at any time of life.
14. Tobacco.—When a person first uses tobacco, it is apt to make him very sick at the stomach. After he has used tobacco a few times it does not make him sick, but it continues to do his stomach and other organs harm, and after a time may injure him very seriously. Smokers sometimes suffer from a horrible disease of the mouth or throat known as cancer.
15. Effects of Alcohol upon the Stomach.—If you should put a little alcohol into your eye, the eye would become very red. When men take strong liquors into their stomachs, the delicate membrane lining the stomach becomes red in the same way. Perhaps you will ask how do we know that alcohol has such an effect upon the stomach. More than sixty years ago there lived in Michigan a man named Alexis St. Martin. One day he was, by accident, shot in such a way that a large opening was made right through the skin and flesh and into the stomach. The good doctor who attended him took such excellent care of him that he got well. But when he recovered, the hole in his stomach remained, so that the doctor could look in and see just what was going on. St. Martin sometimes drank whiskey, and when he did, the doctor often looked into his stomach to see what the effect was, and he noticed that the inside of the stomach looked very red and inflamed.
16. If St. Martin continued to drink whiskey for several days, the lining of the stomach looked very red and raw like a sore eye. A sore stomach cannot digest food well, and so the whole body becomes sick and weak. What would you think of a man who should keep his eyes always sore and inflamed and finally destroy his eyesight by putting pepper or alcohol or some other irritating substance into them every day? Is it not equally foolish and wicked to injure the stomach and destroy one's digestion by the use of alcoholic drinks? Alcohol, even when it is not very strong, not only hurts the lining of the stomach, but injures the gastric juice, so that it cannot digest the food well.
17. Effects of Alcohol upon the Liver.—The liver, as well as the stomach, is greatly damaged by the use of alcohol. You will recollect that nearly all the food digested and absorbed is filtered through the liver before it goes to the heart to be distributed to the rest of the body. In trying to save the rest of the body from the bad effects of alcohol, the liver is badly burned by the fiery liquid, and sometimes becomes so shrivelled up that it can no longer produce bile and perform its other duties. Even beer, ale, and wine, which do not contain so much alcohol as do rum, gin, and whiskey, have enough of the poison in them to do the liver a great deal of harm, and to injure many other organs of the body as well.
SUMMARY
2. Irritating substances and things which are not foods should not be eaten.
3. The teeth must be carefully used and kept clean.
4. Tobacco-using does the stomach harm, and sometimes causes cancer of the mouth.
5. Alcohol injures the gastric juice, and causes disease of the stomach and the liver.
CHAPTER X
A DROP OF BLOOD1. The Blood.—Did you ever cut or prick your finger so as to make it bleed? Probably you have more than once met with an accident of this sort. All parts of the body contain blood. If the skin is broken in any place the blood flows out.
2. How many of you know what a microscope is? It is an instrument which magnifies objects, or makes them look a great deal larger than they really are. Some microscopes are so powerful that they will make a little speck of dust look as large as a great rock.
3. The Blood Corpuscles.—If you should look at a tiny drop of blood through such a microscope, you would find it to be full of very small, round objects called blood corpuscles.
4. You would notice also that these corpuscles are of two kinds. Most of them are slightly reddish, and give to the blood its red color. A very few are white.
5. Use of the Corpuscles.—Do you wonder what these peculiar little corpuscles do in the body? They are very necessary. We could not live a moment without them. We need to take into our bodies oxygen from the air. It is the business of the red corpuscles to take up the oxygen in the lungs and carry it round through the body in a wonderful way, of which we shall learn more in a future lesson.
6. The white corpuscles have something to do with keeping the body in good repair. They are carried by the blood into all parts of the body and stop where they are needed to do any kind of work. They may be compared to the men who go around to mend old umbrellas, and to do other kinds of tinkering. It is thought that the white corpuscles turn into red ones when they become old.
7. The corpuscles float in a clear, almost colorless fluid which contains the digested food and other elements by which the body is nourished.
SUMMARY1. The blood contains very small objects called blood corpuscles.
2. There are two kinds of corpuscles, red and white.
3. The red corpuscles carry oxygen.
4. The white corpuscles repair parts that are worn.
5. The corpuscles float in a clear, almost colorless fluid, which nourishes the body.
CHAPTER XI
WHY THE HEART BEATS1. If you place your hand on the left side of your chest, you will feel something beating. If you cannot feel the beats easily, you may run up and down stairs two or three times, and then you can feel them very distinctly. How many of you know the name of this curious machine inside the chest, that beats so steadily? You say at once that it is the heart.
THE HEART.
2. The Heart.—The heart may be called a live pump, which keeps pumping away during our whole lives. If it should stop, even for a minute or two, we would die. If you will place your hand over your heart and count the beats for exactly one minute, you will find that it beats about seventy-five or eighty times. When you are older, your heart will beat a little more slowly. If you count the beats while you are lying down, you will find that the heart beats more slowly than when you are sitting or standing. When we run or jump, the heart beats much harder and faster.
3. Why the Heart Beats.—We have learned in preceding lessons that the digested food is taken into the blood. We have also learned that both water and oxygen are taken into the blood. Thus the blood contains all the materials that are needed by the various parts of the body to make good the wastes that are constantly taking place. But if the blood were all in one place it could do little good, as the new materials are needed in every part of the body. There has been provided a wonderful system of tubes running through every part of the body. By means of these tubes the blood is carried into every part where it is required. These tubes are connected with the heart. When the heart beats, it forces the blood through the tubes just as water is forced through a pipe by a pump or by a fire-engine.
4. The Heart Chambers.—The heart has four chambers, two upper and two lower chambers. The blood is received into the upper chambers, and is then passed down into the lower chambers. From the lower chambers it is sent out to various parts of the body.
THE INSIDE OF THE HEART.
5. The Blood-Vessels.—The tubes through which the blood is carried are called blood-vessels. There are three kinds of blood-vessels. One set carry the blood away from the heart, and are called arteries (ar'-te-ries). Another set return the blood to the heart, and are called veins. The arteries and veins are connected at the ends farthest from the heart by many very small vessels. These minute, hairlike vessels are called capillaries (cap'-il-la-ries).
6. The Arteries.—An artery leads out from the lower chamber of each side of the heart. The one from the right side of the heart carries the blood only to the lungs. The one from the left side of the heart carries blood to every part of the body. It is the largest artery in the body, and is called the aorta. Soon after it leaves the heart the aorta begins to send out branches to various organs. These divide in the tissues again and again until they become so small that only one corpuscle can pass through at a time, as shown in the colored plate. (Frontispiece.)
7. The Veins.—These very small vessels now begin to unite and form larger ones, the veins. The small veins join to form larger ones, until finally all are gathered into two large veins which empty into the upper chamber of the right side of the heart. The veins which carry blood from the lungs to the heart empty into the upper chamber of the left side of the heart.
8. What is Done in the Blood-Vessels.—While the blood is passing through the small blood-vessels in the various parts of the body, each part takes out just what it needs to build up its own tissues. At the same time, the tissues give in exchange their worn-out or waste matters. The red blood corpuscles in the capillaries give up their oxygen, and the blood receives in its stead a poisonous substance called carbonic-acid gas.
9. Red and Blue Blood.—While in the arteries the blood is of a bright red color; but while it is passing through the capillaries the color changes to a bluish red or purple color. The red blood is called arterial blood, because it is found in the arteries. The purple blood is called venous blood, because it is found in the veins. The loss of oxygen in the corpuscles causes the change of color.
10. Change of Blood in the Lungs.—Exactly the opposite change occurs in the blood when it passes through the lungs. The blood which has been gathered up from the various parts of the body is dark, impure blood. In the lungs this dark blood is spread out in very minute capillaries and exposed to the air. While passing through the capillaries of the lungs, the blood gives up some of its impurities in exchange for oxygen from the air. The red corpuscles absorb the oxygen and the color of the blood changes from dark purple to bright red again. The purified blood is then carried back to the upper chamber of the left side of the heart through four large veins. The blood is now ready to begin another journey around the body.
11. The Pulse.—If you place your finger on your wrist at just the right spot, you can feel a slight beating. This beating is called the pulse. It is caused by the movement of the blood in the artery of the wrist at each beat of the heart. The pulse can be felt at the neck and in other parts of the body where an artery comes near to the surface.
12. How much Work the Heart Does.—The heart is a small organ, only about as large as your fist, and yet it does an amount of work which is almost beyond belief. Each time it beats, it does as much work as your arm would do in lifting a large apple from the ground to your mouth. It beats when we are asleep as well as when we are awake. When we run we know by the way in which it beats that it is working very fast. Do you know how much a ton is? Well, in twenty-four hours the heart does as much work as a man would do in lifting stones enough to weigh more than one hundred and twenty tons.
13. The Lymphatics.—While the blood is passing through the capillaries, some of the white corpuscles escape from the blood-vessels. What do you suppose becomes of these runaway corpuscles? Nature has provided a way by which they can get back to the heart. In the little spaces among the tissues outside of the blood-vessels very minute channels called lymph channels or lymphatics (lym—phat'-ics) begin. The whole body is filled with these small channels, which run together much like the meshes of a net. In the centre of the body the small lymphatics run into large ones, which empty into the veins near the heart. This is the way the stray white blood corpuscles get back into the blood.
LYMPH GLAND AND VESSELS.
14. The Lymph.—In the lymph channels the white corpuscles float in a colorless fluid called lymph. The lymph is composed of the fluid portion of the blood which has soaked through the walls of the small vessels. The chief purpose of the lymphatics is to carry the lymph from the tissues back to the heart.
15. Lymphatic Glands.—Here and there, scattered through the body, are oval structures into each of which many lymphatic vessels are found to run, as shown in the illustration. These are called lymphatic glands.
16. The heart and blood-vessels are among the most wonderful structures in the body. It is no wonder, then, that alcohol, tobacco, and other narcotics and stimulants produce their most deadly effects upon these delicate organs. What these effects are we shall learn more fully in the next chapter.
SUMMARY1. The heart beats to circulate the blood.
2. The heart has four chambers, two upper and two lower.
3. There are tubes called blood-vessels which carry the blood to all parts of the body.
4. These tubes are connected with the heart.
5. The vessels which carry blood away from the heart are called arteries, and those which carry blood back to the heart are called veins.
6. The arteries and veins are connected by small tubes called capillaries.
7. The blood found in the arteries is red; that in the veins is dark blue or purple.
8. The color of the blood changes from red to blue in going through the capillaries. The change is due to the loss of oxygen.
9. In the circulation of the lungs, the blood in the arteries is blue, that in the veins, red.
10. The change from blue to red takes place while the blood is passing through the capillaries of the lungs. The change is due to the oxygen which the corpuscles of the blood take up in the lungs.
11. The pulse is caused by the beating of the heart.
12. The heart does a great deal of work every day in forcing the blood into different parts of the body.
13. Some of the white blood corpuscles escape from the blood-vessels through the thin walls of the capillaries.
14. These corpuscles return to the heart through small vessels called lymph channels or lymphatics.
15. The lymphatics in many parts of the body run into small roundish bodies called lymphatic glands.
16. The object of the lymphatics is to remove from the tissues and return to the general circulation the lymph and white blood corpuscles which escape through the walls of the capillaries.
CHAPTER XII
HOW TO KEEP THE HEART AND THE BLOOD HEALTHY1. The heart is one of the most important of all the organs of the body. If we take good care of it, it will do good service for us during a long life. Let us notice some ways in which the heart is likely to be injured.
2. Violent Exercise.—Did you ever run so hard that you were out of breath? Do you know why you had to breathe so fast? It was because the violent exercise made your heart beat so rapidly that the blood could not get out of the lungs as fast as the heart forced it in. The lungs became so filled with blood that they could not do their work well. Sometimes, when a person runs very fast or takes any kind of violent exercise, the lungs become so filled with blood that a blood-vessel is broken. The person may then bleed to death. It is very unwise to overtax the heart in any way, for it may be strained or otherwise injured, so that it can never again do its work properly.
3. Effects of Bad Air.—Bad air is very harmful to the heart and to the blood also. We should always remember that the blood of the body while passing through the lungs is exposed to the air which we breathe. If the air is impure, the blood will be poisoned. In churches and in other places where the air becomes foul, people often faint from the effects of the impure air upon the heart. It is important that the air of the rooms in which we live and sleep should be kept very pure by good ventilation.
4. Effects of Bad Food.—The blood is made from what we eat, and if we eat impure and unwholesome food, the blood becomes impure. We ought to avoid the use of rich or highly-seasoned foods, candies, and all foods which are not nutritious. They not only injure the blood by making it impure, but they cause poor digestion.
5. Plenty of Sleep Necessary.—If we should take a drop of blood from the finger of a person who had not had as much sleep as he needed, and examine it with a microscope, we should find that there were too few of the little red-blood corpuscles. This is one reason why a person who has not had sufficient sleep looks pale.
6. Proper Clothing.—We should be properly clothed, according to the weather. In cold weather we need very warm clothing. In warm weather we should wear lighter clothing. Our clothing should be so arranged that it will keep all parts of the body equally warm, and thus allow the blood to circulate properly. The feet are apt to be cold, being so far away from the heart, and we should take extra pains to keep them warm and dry.
7. Effects of Excessive Heat.—In very hot weather, many persons are injured by exposing themselves to the sun too long at a time. Persons who drink intoxicating liquors are very often injured in this way, and sometimes die of sunstroke.
8. Effects of Anger.—When a person gets very angry, the heart sometimes almost stops beating. Indeed, persons have died instantly in a fit of passion. So you see it is dangerous for a person to allow himself to become very angry.
9. Effects of Alcohol upon the Blood.—If you should take a drop of blood upon your finger, and put it under the microscope, and then add a little alcohol to it, you would see that the corpuscles would be quickly destroyed. In a few seconds they would be so shrivelled up that no one could tell that they had ever been the beautiful little corpuscles which are so necessary to health. When alcohol is taken as a drink, it does not destroy the corpuscles so quickly, but it injures them so that they are not able to do their work of absorbing and carrying oxygen well. This is one reason why the faces of men who use alcoholic drinks often look so blue.
10. Alcohol Overworks the Heart.—Dr. Parkes, a very learned English physician, took the pains to observe carefully the effects of alcohol upon the heart of a soldier who was addicted to the use of liquor. He counted the beats of the soldier's pulse when he was sober; and then counted them again when he was using alcohol, and found that when the soldier took a pint of gin a day his heart was obliged to do one fourth more work than it ought to do.
11. Effects of Alcohol upon the Blood-Vessels.—If you put your hands into warm water, they soon become red. This is because the blood-vessels of the skin become enlarged by the heat, so that they hold more blood. Alcohol causes the blood to come to the surface in the same way. It is this that causes the flushed cheeks and the red eyes of the drunkard. Sometimes, after a man has been using alcohol a long time, the blood-vessels of his face remain enlarged all the time. This makes his nose grow too fast, and so in time it gets too large, and then he has a rum-blossom.
12. Effects of Tobacco on the Heart and the Blood.—When a boy first tries to use tobacco, it makes him feel very sick. If you should feel his pulse just then, you would find it very weak. This means that the heart is almost paralyzed by the powerful poison of the tobacco. Tobacco also injures the blood corpuscles.