How Beer is Made.—There is more beer used than any other alcoholic drink. It is cheap and is much weaker in alcohol than wine or whisky. Only about one twentieth part of beer is alcohol.
In making beer, a sweet watery mixture is first prepared by mashing sprouted barley grains in water. Barley or any other grain forms sugar as soon as it begins to grow. Yeast plants are added to the sweet mixture. By growing they change some of the sugar into alcohol. Hops are also put in to give the beer a fine flavor. After a time the clear liquid is separated from the barley grains and hops and put into tight casks and bottles.
The Making of Wine.—Wine contains from two to four times as much alcohol as beer. Most of the wine is made in California, France, and Germany because grapes grow better in these countries than elsewhere. Wine may be made from the juice of any fruit, but the grape is generally used.
The grapes after being picked are thrown into large tubs and crushed so that the juice runs out. The wild yeast always present on the grape skins begins to grow in the juice and change some of the sugar into alcohol. This work of the yeast lasts from one to eight weeks. At the end of that time, the grape juice has become a kind of poor wine, consisting of alcohol, water, grape flavor, and some acid. To make the wine good it must be drawn off into casks, where the yeast causes further changes during several weeks. It is then put into bottles, where it should remain about five years to get the right flavor.
Sherry is a strong wine used in flavoring food, such as puddings and sauces. A few teaspoonfuls of this wine will make a child drunk. The wines made at home from elderberries, blackberries, and cherries contain alcohol which will do just as much harm as that in the purchased wines.
How Brandy is Made.—Brandy contains more alcohol than wine and almost as much as whisky. In fact brandy is only very strong wine. After the yeast plants have formed as much alcohol as they can in grape juice it becomes so strong that it kills them. This wine is then heated in such a way as to separate some of the water from it. The taking away of the water leaves the wine stronger in alcohol and it then forms brandy.
Fig. 40 —A still used in making whisky or brandy. The heat makes the alcohol fumes or vapor rise and pass over through the pipe coiled in a vessel of cold water. The cold changes the vapor to a liquid which is whisky.
Whisky and Rum.—These two drinks are strong in alcohol. Nearly one half of each is pure alcohol. Whisky is usually made from rye, corn, or wheat, or all three together. They furnish the food in which the yeast grows and makes alcohol. This watery mixture of grain and alcohol is then heated and the vapor or steam forms whisky after it goes off through a pipe into another vessel. This kind of heating is distillation. Rum is formed in somewhat the same way from molasses or cane juice.
PRACTICAL QUESTIONS
1. Name some alcoholic drinks.
2. What is an unnatural thirst?
3. Explain how the yeast plant forms alcohol.
4. Tell how beer is made.
5. Tell how wine is made.
6. What is brandy?
7. Which drinks contain most alcohol?
CHAPTER X
ALCOHOL AND HEALTH
The Money spent for Alcoholic Drinks.—If the money spent for alcoholic drinks were all collected together in silver dollars, it would more than fill ten schoolrooms of average size. Not only rich men spend large sums yearly for fine wines and brandies, but also the poor give their money for beer and other drinks which the body does not need.
When parents waste their money on drink, they cannot buy the food and clothes needed to keep their families strong and well. In this way strong drink causes much sickness and suffering and sometimes even death.
Alcohol injures the Body.—Some persons drink very little beer or wine, so they seem to have but little effect on the health. Others use strong drink every day and for a few years they may remain quite well. Later ill health often comes on, and they then find that some of the organs have been so much hurt that they will never be quite well again.
A few years ago a group of fifty well-known men in the United States spent much time and thousands of dollars to learn how much alcohol was harming our country. After much study among many people they announced that there were about one million men and boys whose health had been injured by strong drink, such as beer, wine, and whisky. Because strong drink causes so much sorrow and sickness several states have passed laws forbidding its sale, and saloons have been closed by laws in parts of many other states.
How Alcohol affects Kittens.—The body of a kitten is made very much like the body of a child. It has just the same organs that a child has, and they do the same kind of work. Doctor Hodge, a well-known scientist of Massachusetts, therefore concluded that alcohol would act on kittens in the same way as it would on a man or boy.
The doctor got two healthy kittens and fed them a little alcohol every day for nearly two weeks. In a few days they stopped being playful, did not grow, and did not keep their fur clean and smooth as healthy kittens do. After using alcohol several days they became very ill. This experiment showed that alcohol stops kittens from growing and robs them of good health.
How Alcohol hurts Dogs.—Doctor Hodge fed a little alcohol to two dogs nearly every day for three years. He also kept the brother and sister of these dogs, but gave them no alcohol. All the dogs had the same kind of food and were treated alike except that one pair got alcohol and the other pair did not.
The two drinking dogs got sick more easily and staid sick much longer than the temperance dogs. The drinking dogs became lazy, and timid, while the others were strong, full of fun, and brave.
Within four years the drinking dogs had born to them twenty-seven puppies, but only four of them lived to grow up. The others were too weak or sickly to live. During the same time the temperance dogs had forty-five puppies and forty-one of these lived. This shows that strong drink will not only injure the bodies of those who take it, but will make their children weak and sickly.
The Use of Strong Drink causes Disease.—Many persons who take beer or wine every day become fat. They think this is a sign of health. It is really a sign of disease. They become short of breath. They can no longer run so fast or do so much work because the heart is covered with fat and even some of its wall is changed to fat. For this reason the heart cannot do its work easily or well.
The kidneys which take the waste out of the blood often become injured by alcohol and a disease causing death follows. Sometimes the stomach becomes diseased so that it cannot do its work. This makes the whole body sick.
The hardening of parts of the liver is nearly always caused by the use of beer. The liver is sure to suffer if one uses much alcoholic drink because the alcohol goes direct from the food tube to the liver. Long use of strong drink may bring on disease in the brain and nerves.
Alcoholic Drinks may cause Death.—Every ten years the government appoints persons to visit each home in our land to take the census. A part of this census report consists of a table showing the disease of which people died. It is from the census report that we know that hundreds of people die every year from the use of alcohol.
Danger to Health in beginning the Use of Strong Drink.—A large number of people take a drink of beer or wine occasionally because they do not see that it hurts the body. No one expects to become a steady drinker or a drunkard when he begins to drink. Reports show that every drunkard begins his downward course by taking a few drinks occasionally. Thousands of persons begin a drunkard's life every year because the appetite leads them on gently until they become slaves and cannot let drink alone.
CHAPTER XI
TOBACCO AND OTHER DRUGS WHICH INJURE THE
HEALTH
How Tobacco is Made.—Tobacco is made from the leaves of the tobacco plant. The plant may grow as tall as a man and bear more than a dozen leaves. Each leaf is two or three times as large as your hand. The seeds are planted in the springtime, and the plants are ready to be cut in the autumn. Most of our tobacco is raised in the Southern states and Cuba.
After cutting, the tobacco must be dried and cared for in a special way to give it the right flavor. It is then sent to factories and made into cigars, smoking tobacco, or chewing tobacco.
How Tobacco is Used.—Many million dollars are spent every year by the people of our country for tobacco. Most of the tobacco is used in smoking. Some men smoke it in pipes, while others smoke it in the form of cigars or cigarettes.
Many men chew tobacco. When used in this way, something like licorice is generally mixed with the tobacco to give it a more pleasant taste. Sometimes the dry tobacco is ground into a fine powder called snuff. This is used by both men and women.
Tobacco contains a Poison.—When boys chew or smoke tobacco for the first time, it always makes them sick. Chewing or smoking for fifteen minutes will make them grow dizzy and weak and feel so sick that they must lie down for a long time.
The sickness is caused by a poison called nicotine which is present in all tobacco. Much of this poison may be soaked out by boiling the tobacco in water. A cup of water in which a pipeful of tobacco has been boiled will kill goldfish in an hour when poured into a gallon jar of water with the fish. There is enough poison in a handful of tobacco to kill a boy who is not in the habit of using it.
Why Men can use Tobacco without becoming Sick.—Experiments upon animals have shown that the body can learn to use a poison and not become sick from it. The poison of a rattlesnake is deadly to most animals; but if a tiny bit of the poison is put under the skin of the rabbit one day and then on each succeeding day a little larger dose of the poison is given the rabbit for a long time, the animal will become so accustomed to the poison that the bite of a rattlesnake will not harm it. It is the same way with tobacco. Little by little the body learns to overcome the effects of the poison, but much use of tobacco is likely to hurt certain parts of the body.
Tobacco is Harmful to the Young.—A dose of poison which will kill a child may do but little harm to a man. Tobacco is certain to hurt boys more than it does men. The poison makes the body grow slower.
A large number of measurements made by Doctor Seaver showed that the boys who did not use tobacco gained in four years one twentieth more in weight and one fourth more in girth and height than the users of tobacco. These boys were between sixteen and twenty-two years of age. It is likely that tobacco will have a more harmful effect on younger boys.
Laws to keep the Young Healthy.—Boys ought to be wise and brave enough to let alone what keeps their bodies from growing and hurts their health, but some will not do it. For this reason some countries are trying to save the health of their boys by making laws against the use of tobacco.
The Germans a few years ago passed a law in their land forbidding all boys and girls under sixteen years of age to use tobacco in any form. Seeing the good results of this law in Germany and the harm that tobacco was doing the boys in the United States, the Emperor of Japan on the 6th of March, 1900, proclaimed this law: "The smoking of tobacco by minors under the age of twenty is prohibited."
In our own country several states have passed laws against the use of cigarettes by boys. One country after another is learning that if they want strong men, to fight, to work, and to win, tobacco must not be allowed to weaken the bodies of the young.
How the White Man becomes a Slave.—Before the Civil War the black men of the South were slaves. They could not do as they pleased because they belonged to their masters whom they must obey or else they would suffer punishment. No boy can begin the use of tobacco without the danger of becoming a slave to it.
The use of tobacco either by chewing or smoking gradually causes in any one the growth of an appetite which makes him feel miserable and unhappy unless it is kept satisfied. It can be satisfied only by the use of more and more tobacco.
Many men would like to quit the use of tobacco if they could do so without suffering. They are slaves, and tobacco is their master.
Cigarettes and Health.—A cigarette is a tube of paper filled with tobacco. The tobacco is usually not so strong as that used in cigars and pipes. For this reason, boys like it better, and because it is so mild they draw the smoke down into the lungs. This gives the poison a better chance to be taken up by the blood. On this account, and because one is likely to smoke oftener when he smokes a small piece of tobacco, cigarettes are thought by some to be more harmful than the use of tobacco in pipes and cigars.
Tea and Coffee.—Tea is made from the dried leaves of the tea plant. Tea plants are raised in North Carolina, China, and Japan. The drink called tea used at the table is made by pouring boiling water on the tea leaves. The leaves should not be boiled as this draws out a substance which keeps the stomach from doing its work in the right way.
Coffee is the seed of a plant growing in South America and Asia. It is roasted, then ground, and boiled in water to make the drink called coffee.
Fig. 43/44 —Branch of a tea plant.—Branch of a coffee plant with bunches of coffee berries near the bottom.
Children should not use either tea or coffee as they are likely to hurt the stomach and may injure the heart. One or two cups of tea or coffee daily seem to have little or no bad effect on the health of most grown persons. Coffee taken at supper may keep one awake by sending too much blood to the brain.
Opium and Morphine.—Opium is a dangerous drug which is got from the heads of the white poppy plant grown mostly in the far East. From gashes cut in the poppy heads a juice runs out and hardens into a gum from which the pure drug is made.
Some persons smoke opium for the drowsy and pleasant feeling it gives. Its use is very hurtful and ruins both body and mind. Morphine is a pure form of opium. Persons take it to kill pain and make them sleep. You should never take it except when given by the doctor, as a habit is quickly formed which will make you miserable through life.
Patent Medicines.—These are medicines advertised to cure ailments which generally cannot be cured by drugs. They are the medicines much advertised in the newspapers and magazines. Never use them unless your doctor tells you to do so. Many of them contain harmful drugs, such as morphine and alcohol. When you are sick, go to your doctor for advice.
PRACTICAL QUESTIONS
1. Explain how tobacco is raised.
2. How is tobacco used?
3. How does tobacco affect a boy using it for the first time?
4. What is the name of the poison in tobacco?
5. Tell how tobacco keeps boys from growing.
6. What countries do not allow boys to use tobacco?
7. What is meant by being a slave to tobacco?
8. What is tea?
9. What is coffee?
10. Why should you not use opium or morphine?
CHAPTER XII
THE SKIN AND BATHING
Parts of the Skin.—The skin is about as thick as the leather of your shoe. It is fastened to the muscles beneath with fine white threads like spider webs. This is called connective tissue because it connects the skin to the lean meat.
The skin is made of two layers (Fig. 45). The upper layer is formed of cells. This is named epidermis or scarfskin. The deeper layer is made largely of fine threads woven together. It is the true skin or derma. There is no blood in the scarfskin, but there is a network of blood tubes in the true skin. It is the crowding of these with blood that makes the skin look so red when we get hot or excited.
The Use of the Skin.—The skin has three chief uses. It protects the softer parts of the body from being hurt by rough or hard things which might touch it. It contains the organs of feeling. It helps keep the right amount of heat in the body.
Fig. 45 —A thin slice through the skin, showing sweat glands, a nerve, and blood-tubes. Much enlarged.
The top part of the skin is dry and dead. This gives better protection than if it were moist and tender. Particles of it are wearing out and dropping off while other bits are growing beneath to take the place of the worn-out parts. The more this top skin is pressed on and rubbed, the thicker it becomes. For this reason it is twice as thick in the palms of the hand and on the soles of the feet.
Scattered through the true skin are millions of tiny organs fastened to the ends of the nerve threads leading to the spinal cord and brain. These organs tell us when the skin is touched or when it is hot or cold or is being hurt.
The Pores and the Sweat Glands.—On a warm day the skin becomes wet with a salty fluid called sweat or perspiration. This flows from the tiny holes or pores in the skin. A good magnifying glass will show these pores arranged in rows on the ridges in the palm of the hand.
From each pore a tube leads down into the true skin to a coiled tube forming the sweat gland (Fig. 45). Sweat glands are present by the thousands in the skin of all parts of the body. They give out from one pint to a gallon of sweat daily. The more we work and the warmer the weather, the more the sweat flows.
There is a little waste matter carried out of the body by the sweat, but its chief use is to cool the body. It does this by passing off in the air and carrying the heat with it. In this way the body is kept from getting too hot in summer.
The Color of the Skin.—In the African race the color of the skin is black, in the Chinese it is yellowish, while in our race it is nearly white. The different hues are due to a coloring matter called pigment. This lies in the deep part of the scarfskin. Going out in the wind and sun causes more pigment to collect, and we say we are tanned. If the pigment collects in spots, it makes freckles.
There is no way of removing at once freckles or tan. They usually disappear in the winter. No powders nor any other kind of medicine should be taken to make the skin white and smooth. Such medicines may contain poison and are likely in time to hurt the body. The skin may usually be kept soft and smooth by washing well with soft water and good soap. If it becomes harsh or cracked, a little glycerine rubbed on after each washing may help it.
The Nails and their Care.—The nails are hardened parts of the epidermis. They are intended to prevent the ends of the fingers from being hurt and to give a neat appearance to the hand.
The ends of the nails should never be chewed or torn off, as this makes the fingers blunt and the flesh sore. They should be filed or cut neatly with the scissors so that they do not stick out beyond the ends of the fingers.
Fig. 46 —Photograph of hands showing at the right how the nails should appear, and at the left how biting off the nails makes the fingers blunt and sore.
Many boys and some girls spoil the appearance of their nails by letting a line of black dirt remain beneath them. A piece of a stick or a nail cleaner should be passed beneath the nails every time the hands are washed. If the fingers are much soiled, a stiff brush is useful in removing the dirt under the nails.
The Hair.—Some hair grows on nearly all parts of the body. It is much thicker on the head than elsewhere. Each hair grows from a little knob at the bottom of a tiny tube in the skin called the hair sac (Fig. 47). If hair is pulled out, another one will grow in its place if the knob at the bottom of the sac is not hurt.
One or two oil glands open into each hair sac and give out an oil to keep the scalp and hair soft. No other hair dressing is needed.
After thirty or forty years of age the hair begins to turn gray. No medicine will prevent the hair from turning gray, and it is generally unwise to color the hair with a dye. There is poison in some of the mixtures sold to color the hair.
The Care of the Hair.—When the hair is uncombed, the whole person looks untidy. The hair should be combed carefully every morning and again made tidy before each meal. You should use as little water as possible to moisten the hair. The glands can be made to give out their hair oil by squeezing parts of the scalp between the fingers.
The scalp should be well cleansed with soap and warm water every three or four weeks. The hair should be dried quickly with a soft towel and by sitting in the sun or near a stove. One is likely to catch cold by going out of doors when the hair is wet. Hair oils and dandruff cures should not be used unless advised by a physician. Pinching and wrinkling the scalp twice weekly with the fingers makes the blood tubes grow larger and bring more food to the hair. It will also in many persons stop the hair from falling out and prevent dandruff and itching.
Do not use the hair brush of another person or exchange hats with your companions. Unclean persons and those living or playing much with them often have among their hairs little creatures called head lice. They suck blood and cause constant itching. The doctor will tell any one how to get rid of them easily.
Keeping the Skin Clean.—The amount of dead matter carried out by the sweat on to the skin every day is equal to a mass as large as your thumb. Dust also works through the clothing and sticks fast to the moist skin. For this reason every one should wash the whole body once or twice each week. The feet should be washed oftener as they become more soiled.
Many persons take a bath every day. A cold bath taken just after rising in the morning wakes up the nerves, makes the heart work better, and gives health and strength to the whole body. Afterward, the body should be well rubbed with a coarse towel. The bath may be taken by lying in a tub of water or by rubbing the body over quickly with a wet sponge. A hot bath is best for cleansing the skin. A warm bath makes one sleepy and should, therefore, be taken only at bedtime.
The hands should always be well washed before handling food. Persons neglecting to do this have caused much sickness because of the disease germs on their hands. One hundred and fifty persons were given typhoid fever in one city in Massachusetts by a man who handled milk without washing his hands. Dirt and disease are companions. You must be clean if you would be healthy.
The Kidneys.—The sweat glands do not take out of the blood one quarter as much waste matter as the kidneys. These are two bodies longer than the finger and more than twice as wide, and having the shape of a bean. One lies on either side of the backbone below the liver.
The blood coming to the kidneys is full of waste and dead matter picked up from all parts of the body. This is passed out through the thin walls of the thousands of little blood tubes into the many tiny tubes of the kidneys.
Water is required to keep the body clean within as well as without. For this reason you should drink more than a quart of water daily. A glass or two of water drunk a half hour before meals cleanses and rouses to action the digestive organs.
Alcohol and the Skin.—The skin of those who use much beer or whisky often becomes rough, red, and pimply. Any alcoholic drink is likely to injure the skin because it may hinder good digestion. The drunkard has a red nose and a dark-colored skin. This is because alcohol weakens the walls of the blood tubes and lets them become gorged with blood.
If a person takes a drink only once in a while, his face becomes red after each drink, and an hour or two later the effect of the alcohol passes off. The blood tubes have squeezed up to their natural size.
Alcohol and the Kidneys.—Taking several glasses daily of even such weak alcoholic drink as beer often causes the kidneys to become sick. Some of their working parts become changed to fat and some parts become hard. The cells which let the waste matter pass out of the blood get hurt by the poison of the alcohol so that they let some of the food also pass out of the blood.
PRACTICAL QUESTIONS
1. Name the two parts of the skin.
2. Give the three uses of the skin.
3. What is a sweat gland?
4. How much sweat is formed daily?
5. Of what use is the sweat?
6. How should the nails be cared for?
7. Tell what care should be given the hair.
8. Why should you not use another person's hair brush?
9. Why should the skin be washed often?
10. Of what use is a cold bath?
11. Why should the hands be well washed before handling
food?
12. Why does the drunkard have a red nose?
CHAPTER XIII
CLOTHING AND HOW TO USE IT
Kinds of Clothing.—People are beginning to learn that the wearing of the right kind of clothing has much to do with keeping them well. Many persons wear too heavy clothing in winter. Keeping the body too hot makes it weak.
Some kinds of clothing are much warmer than others. Some are expensive and others are cheap. Cheap clothes will often serve the same purpose as the more costly ones. If you look at your handkerchief or stockings, you will see that they are made of threads running crosswise to each other. All clothing is made from threads. Some of these are wool, some are linen, a few are silk, and many are cotton.
Woolen Clothing.—Woolen clothing, such as overcoats and fine cloth dresses and suits, is made from the wool cut from sheep. Enough wool can be sheared from two sheep in one year to make an entire suit of clothes. The raw wool is first twisted into threads and then woven by machines into cloth.
Fig. 50 —At the left is a bunch of flax gathered from the field, and on the right is a spool of thread made from the flax and ready to be woven into linen.
Linen.—Linen is used in making collars, cuffs, and handkerchiefs. It is made from fine threads taken from the flax plant. On a piece of ground as large as a schoolroom enough flax can be raised to make a half dozen collars. Garments to be worn in warm weather are sometimes made of linen.
Silk.—Silk is used in making neckties, gloves, ribbons, and dresses. Silk cloth is woven from the cocoons made by silkworms. A silkworm is about as big as your largest finger. It grows to this size from the egg in one month. In three or four days it spins a shell of silk thread completely surrounding itself. This shell is called a cocoon. Within this it changes to a moth.
When the cocoons are to be used for silk, the worm is killed by heat as soon as it has woven its home so that it may not change to a moth and eat off some of the silk in getting out. Many thousand worms are needed to get enough silk for a dress. The worms are raised largely in China, Japan, Italy, and France.
Cotton.—All calico, muslin, and most cheap clothing are made from cotton thread. This is made from the cotton fibers surrounding the seeds of the cotton plant (Fig. 52). The cotton used in this country is raised in the Southern states.
Cotton clothing is stronger and wears much longer than silk or wool, but it does not look so well and is not nearly so warm.
The Use of Wraps and Overcoats.—Outer wraps and overcoats should never be worn in a warm room or while working hard. They cause much sweat to form on the body, and as soon as one goes out of doors the sweat begins to pass off. This makes the body feel cold and in some cases leads to a long sickness.
When riding in cold weather, extra wraps should be worn. Scarfs and furs should not be worn about the throat except in extreme cold weather. Bundling up the neck and chin is likely to cause sore throat.
Danger from Wet Clothing.—Many children have caught severe colds leading to serious sickness by wearing wet or damp clothing. Wet clothing causes the heat to pass off from the body quickly, so that it is chilled before we know it. This may be shown by wrapping two bottles of warm water in cloths. Wet one cloth and let the other remain dry. In twenty minutes the bottle with the wet cloth will be cool, but the other one will still be warm. If your wet clothing cannot be changed at once, keep exercising or throw a heavy coat about you.
Untidy and Soiled Clothing.—All boys and girls should learn to keep their clothing as clean as possible. Do not wipe the hands on the clothing, or sit down in the dirt, or let food smear the front of the coat or dress.
The sweat is constantly bringing waste matter out of the body. This soils the clothing next to it. On this account clothing to be washed every week or oftener should be worn next to the skin. Very thin cotton underclothing should be worn in summer. Woolen clothes give more warmth for winter.
Fig. 53 —Showing how to prevent the shoe from pressing on corns caused by wearing tight shoes or socks roughly darned.
Shoes.—Badly fitting shoes cause sore feet and much pain. A shoe that is tight across the toes is sure to cause corns. A corn is a thickened part of the top skin which presses on the more tender part beneath. Soaking the feet in hot water and filing off the top of the corn or using a corn plaster will help it. Shoes should always be a half inch longer than the foot. Waterproof shoes or rubbers should be worn in wet weather. Rubbers should not be worn in the house.
Alcohol and Clothing.—Many persons think that a drink of whisky will make them warm when taken on a cold day. For this reason whisky is sometimes used when clothing is really needed. The use of whisky or any other alcoholic drink will not make the body warm. It may make one feel warm because it loosens the muscles in the blood tubes of the skin and so lets more blood come to the surface. In this way the body becomes colder because too much blood gets into the skin and is then chilled by the cold air. As alcohol deadens the feeling it may prevent one from feeling cold when the body is really very cold. Too little clothing and too much alcohol have been known to cause men to freeze to death.
Experience in using Alcohol to keep the Body Warm.—Doctor Hayes, who went as physician with Doctor Kane to explore in the Arctic regions, said that he would never again take alcoholic drink with him on such a trip. He declared alcohol was of no use in helping men to keep warm. He found from actual experience that those who use alcohol cannot endure cold so well as other people.
Doctor Carpenter, a well-known physician, tells of a crew of sixty-six men who tried to stay in Hudson Bay all winter. They used some alcoholic drink. Only two of the party lived through the winter. Later another party of twenty-two men passed the winter in the same place. They used no strong drink at any time and as a consequence all but two of them were reported well and strong in the following spring.
CHAPTER XIV
BREATHING
The Lungs.—The lungs are two light spongy bodies filling up the greater part of the chest. The heart lies between the lungs. The lungs are formed largely of thousands of thin-walled sacs and two sets of tubes. One set of tubes carries air into and out of the lungs, and the other set is filled with blood. These sacs and tubes are held in place by a loose meshwork of tissue.
Fig. 54 —The ribs and front wall of the chest cut away to show the lungs. A piece of one lung is cut off to show the heart. A and E, parts of the breastbone; F, diaphragm.
Why we Breathe.—Breathing means taking air into the lungs and forcing it out. The air is made to go into the lungs in order that a part of it called oxygen may get into the blood. The blood then carries the oxygen to all parts of the body where it can help the organs do their work.
Fig. 55 —Photograph of a salamander, showing the gills on either side of the head, which are used in breathing.
The air which comes out of the lungs is not the same as that which goes in. Some of the oxygen has been used up and in its place is a heavier gas named carbon dioxide, which has been given out by the body. This carbon dioxide is part of the waste formed in every part of the body from the used-up food and dying parts of the body. We breathe therefore to get oxygen into the body and to take out some of the waste matter.
All animals must breathe. If our breath is shut off only four or five minutes, death results. In the earthworm the oxygen goes right through the skin into the blood. Bugs and flies have several little openings along the sides of the body which lead into tubes branching throughout the body to carry air. A fish gets air through its gills lying under a bony flap on each side of the head.
Fig. 56 —The windpipe and lungs viewed from in front. On the right, the tissue is removed to show the air tubes.
How the Air passes into the Lungs.—The outer openings of the nose are called nostrils. From here two channels lead back through the nose to the throat. The cavity of the throat behind the nose and tongue is the pharynx. At the bottom of the pharynx is a tube made mostly of gristle. This tube is larger than your thumb and is named the larynx, or voice box. The bump on its front part forms the lump in the throat called the Adam's Apple.
From the voice box extends the windpipe called trachea, down to the lungs. The windpipe divides at its lower end between the lungs into two branches. One of these enters each lung.
The Air Tubes in the Lungs.—As the branch of the windpipe enters each lung it divides into smaller branches just like the limbs of a tree. These divide into still smaller tubes, which branch again and again until they are as small as a hair. These hairlike tubes have swollen ends called air sacs. The walls of the air sacs are much thinner than tissue paper.
Fig. 57 —A bunch of air cells at the end of an air tube in the lungs, showing the blood vessels which receive the oxygen and give out the carbon dioxide.
How the Blood trades Waste for Oxygen in the Lungs.—The blood, which is constantly running from all parts of the body to the lungs, collects waste formed from the burnt food and dying parts of the organs. When the blood comes to the lungs, it is full of this waste, called carbon dioxide. The blood tubes divide into fine branches with very thin walls and form a rich network over the air sacs. This allows the carbon dioxide and water to pass out of the blood tubes into the air sacs, while the oxygen at the same time goes through into the blood. More than a pint of water is given off in the breath daily.
How we Breathe.—The bottom of the chest cavity is formed by an upward arching sheet of muscle called the diaphragm. This is fastened to the lower ribs. The ribs at rest slant downward and inward. When the ribs are pulled up or the arch of the diaphragm down, the cavity of the chest becomes larger. The air then runs into the lungs and swells them out. When the ribs are let drop or the arch of the diaphragm goes up, the air is pushed out of the lungs.
Without thinking, we work the muscles to draw up the ribs about eighteen times every minute, because all parts of the body are calling for oxygen. The harder we work the oftener we breathe because the muscles need more oxygen to make them go.
Why we should breathe through the Nose.—Most persons find it easy to breathe through the nose. In some, however, the passages in the nose are too small to carry the air without effort. On this account they let the mouth hang open and breathe through it.