1. Men use tobacco for the sake of its nicotine. Nicotine is a very strong poison.2. Tobacco causes a man to waste his saliva.3. Tobacco makes the mouth dry.4. Tobacco hinders digestion.5. Tobacco stains the teeth, and makes the breath smell bad.6. Tobacco makes a person sick at the stomach.7. Tobacco weakens the muscles.8. Tobacco is more harmful to the young than to grown persons.9. Chewing is the worst form of using tobacco.10. Smoking cigarettes is the worst form of smoking.
1. Men use tobacco for the sake of its nicotine. Nicotine is a very strong poison.
2. Tobacco causes a man to waste his saliva.
3. Tobacco makes the mouth dry.
4. Tobacco hinders digestion.
5. Tobacco stains the teeth, and makes the breath smell bad.
6. Tobacco makes a person sick at the stomach.
7. Tobacco weakens the muscles.
8. Tobacco is more harmful to the young than to grown persons.
9. Chewing is the worst form of using tobacco.
10. Smoking cigarettes is the worst form of smoking.
58. Souring of fruit.—When a little fruit is set away in a warm place for a day or two it sours or ferments. Anything sweet will do the same thing. Little bubbles rise up through the juice and a foam comes on top. Then the juice has a sharp taste or is sour. Canned and preserved fruit becomes sour soon after the jar is opened, and cider soon turns to vinegar. All fruit juice does this even in cold weather. But in cold weather it keeps for a longer time.
FermentationFermentation in a jar ofcherries.
Fermentation in a jar ofcherries.
59. Preserving fruit.—If your mother wishes to keep fruit all winter she boils it and at once puts it into tight jars. This shuts out the air and then the fruit keeps good all winter. Boiling kills all living things, and no more can get in through the tight jars. Does a living thinghave anything to do with making the fruit juice turn sour?
60. Yeast.—Yeast will make all sweet things ferment. Bakers make yeast grow in bread sponge. Yeast is alive. It is made of millions of tiny round cells. New cells sprout out from the side of the old cells like young lilies on an old lily bulb. Soon each new cell breaks off and lives all by itself. In a single night enough new cells will form to fill the whole loaf of bread.
YeastYeast plant cells (×500).
Yeast plant cells (×500).
61. How yeast makes alcohol.—Yeast will grow only where sugar is. When it has grown for some time there is no more sugar, and instead of a sweet taste there is a sharp or sour taste. The yeast has changed the sugar to alcohol. All alcohol is made from sugar by yeast.
The seeds of the yeast plant are everywhere in the air. Some are on the skins of fruit and so are found in the juice when it is squeezed out. There they begin to grow at once and soon change the sugar to alcohol. They do this by taking a gas away from the sugar. The gas rises in little bubbles, and makes a froth upon the top of the juice.Boiling kills the yeast plant. If the juice is at once put into tight jars no new yeast plants can get in, and so the juice keeps.
62. Vinegar.—Sometimes fruit juice turns sour. The sourness is due to vinegar. Besides yeast, other little living plants fall into the juice and turn the sugar to vinegar. But if there is much alcohol in the juice, the vinegar plants will not grow.
63. Yeast in bread.—Growing yeast plants always make alcohol. They change some of the sugar of bread dough to alcohol and a gas. The gas bubbles through the bread and makes it light. When bread is baked, the heat of the oven drives off the alcohol, and so we do not eat any in bread.
64. Alcohol.—Alcohol is a clear liquid and looks like water. It has a sharp taste and smell. It burns very easily and makes a very hot flame. Its smoke cannot be seen, and its flame will not make anything black, as a match flame will do.
65. Use of alcohol.—Alcohol will dissolve more things than water will dissolve. It is used to dissolve drugs, varnishes, perfumery, and many other things. It will dissolve even oil and fat. Tailors clean grease spots from clothes with it. It takes water away from flesh and makes it dry, hard, and tough. It will keep anything from rotting. In museums we pour alcohol over pieces of flesh orplants in glass jars. Then they will keep and we can look at them at any time. Thus alcohol is a very useful thing, and we could hardly do without it.
66. Strong drink.—Some men use alcohol in a wrong way. They swallow it as a drink. But men cannot drink pure alcohol, for it would burn their mouths. They always drink it mixed with some water. Alcohol in water is calledstrong drink.
67. Why men use strong drink.—Some men take strong drink to make themselves warm, and some to make themselves cool. Some drink to keep themselves awake, and some to make themselves sleep. Some drink to keep themselves still, and some to make themselves stir around faster. Men use strong drink really because it seems to make them feel strong for a while. It does not make them stronger, but it harms the body and the mind. Its alcohol does the harm.
1. Sugar in fruit or in water turns to alcohol or vinegar, and a gas.2. The change to alcohol is caused by the cells of the yeast plant.3. The change to vinegar is caused by another small plant.4. Boiling fruit juice kills the yeast plants and then the juice will keep without change.5. Alcohol looks like water. It has a sharp and burning taste.6. Alcohol takes water from flesh and hardens it.7. Alcohol burns with a great heat and no smoke.8. Alcohol is used to dissolve things, and to keep things from spoiling.9. Alcohol in water formsstrong drink.
1. Sugar in fruit or in water turns to alcohol or vinegar, and a gas.
2. The change to alcohol is caused by the cells of the yeast plant.
3. The change to vinegar is caused by another small plant.
4. Boiling fruit juice kills the yeast plants and then the juice will keep without change.
5. Alcohol looks like water. It has a sharp and burning taste.
6. Alcohol takes water from flesh and hardens it.
7. Alcohol burns with a great heat and no smoke.
8. Alcohol is used to dissolve things, and to keep things from spoiling.
9. Alcohol in water formsstrong drink.
68. Wine.—All strong drink is alcohol and water. There may be other things to give it taste, but alcohol and water are always in it. No strong drink is over one half alcohol.
WineA glass of wine contains so,much alcohol.
A glass of wine contains so,much alcohol.
In olden times wine was the only strong drink. Men used to crush out the juice of grapes and let it ferment. This made wine. But very often they used the juice before it fermented. Then it had no alcohol and could do no harm, but was a good food. We read of wine in the Bible. Some of it was fresh fruit juice.
In wine, the sugar is changed to alcohol. The rest of the juice stays the same. All wine is made by the yeast plant growing in fruit juice. No yeast is put in, for there is always enough on the outside of the fruit. Wine is about one tenth alcohol.
69. Homemade wine.—Cider is a kind of wine. It is made from apple juice. It has alcohol a day or two after it is made. All homemade wines havealcohol. Any of them can make a person drunk. Using weak homemade wine and cider often makes an appetite for stronger drinks. The alcohol in any of them is enough to harm the body.
BeerA glass of beer contains somuch alcohol.
A glass of beer contains somuch alcohol.
70. Beer.—After man had made wine for a long time, some one found out how to cultivate yeast. Then men could make sugar and water ferment whenever they wanted to. So men boiled grain to take out its sugar. Then they poured off the liquor and added yeast and let it ferment. This made beer and ale. Now millions of bushels of grain are used every year in making beer. Men call beer alightdrink. But it has alcohol and is a strong drink, and can make men drunk.
71. Root beer.—Some persons boil roots and herbs, and add molasses and yeast. Then the liquid ferments and becomesroot beer. They say "it has no alcohol, for we made it." But it does have alcohol, for yeast always makes alcohol. Some ginger ale is made by putting yeast in sweetened ginger water. It has alcohol, too.
72. Distillation.—Boiling water turns to vapor or steam and goes off in the air. When the vapor is cooled, you can see the water again. It often cools on the window and makes little streams ofwater. You can catch the steam in a tube. If you keep the tube cool, the steam will turn to water in the tube. This process is calleddistillation.
WhiskyA glass of whisky contains somuch alcohol.
A glass of whisky contains somuch alcohol.
Boiling alcohol also passes off into the air as vapor. When the vapor is cooled, it becomes liquid again. Alcohol boils with less heat than water. When alcohol in water is heated, the alcohol boils first. So the vapor has more alcohol than the water. When the vapor is cooled, the liquid has more alcohol than it had at first. When the liquid is distilled again it has more alcohol yet. Pure alcohol can be made in this way.
73. Whisky.—Distilling wine or strong beer makeswhiskyandbrandy. Whisky is one half alcohol. It is more harmful than wine or beer.
74. Habit.—Some strong drinks have only a little alcohol and some have a great deal. No one begins to drink the strong liquors. He begins with wine or beer. When he has once learned, he has a hard time to stop drinking. It is dangerous to drink even weak drinks.
75. Strong drink and thirst.—When a man is thirsty, water will satisfy him but strong drink will not. Sometimes the mouth is dry and dirty and then a man feels thirsty. Rinsing the mouthwith water, and rubbing the tongue and teeth clean will help the dryness and stop the thirst. At any rate, strong drink will only make the mouth dryer.
Some men drink only when they are tired. Then a cup of strong and hot tea or coffee will make them feel much better than a glass of strong drink, and will not harm them so much.
When strong drink is swallowed, its alcohol takes water from the mouth. When your mouth is dry, you feel thirsty. Strong drink makes the mouth dry, and so a drink makes a man more thirsty. The alcohol also makes the mouth smart. Men need another drink to cool the mouth after the first one. So one drink leads to another. All the while a person drinks water with the alcohol until he has too much water. But his mouth is dry and he feels as thirsty as ever.
76. Effect of alcohol upon the stomach.—When strong drink is swallowed it makes the stomach smart just as it does the mouth. So the stomach feels warm, but it is really no warmer. This harms the stomach and keeps it from working well.
Alcohol also keeps the gastric juice from changing albumin to a liquid. Alcohol keeps flesh from decaying in a museum. In the same way it may hinder the digestion of food in the stomach.
When alcohol is used for only a short time, the stomach can get well; but if it is used for months and years, the stomach will stay weak. Then the drinker can hardly eat at all.
77. What becomes of alcohol.—In the stomach a great deal of gastric juice is mixed with the alcohol. So it is very weak when it reaches the intestine. Alcohol needs only a little digesting. It soon soaks into the blood from the intestine along with the other food. The blood flows fast and washes the alcohol away as soon as it leaves the intestine. Too little gets into the blood at once to harm it much.
Alcohol goes to the liver, and is there destroyed; but it still does great harm. The liver has to attend to the alcohol, and so it does not change the food to good blood, and it does not take all the poisons out of the blood. Then the whole body becomes weak and sick. Alcohol hurts the liver first, and more than other parts of the body. On this account, drinkers often have bilious attacks and stomach troubles.
78. Bitters.—Many medicines are made by dissolving drugs in alcohol. In taking a strong medicine, we use only a few drops, and so do not get much alcohol. Some kinds of medicines must be taken in large doses. Bitters are weak medicines,and must be taken by the tablespoonful. A tablespoonful of the medicine has more alcohol than a large drink of whisky. The bitters seem to make a person feel well, but it is because he is taking a large amount of strong drink.
Jamaica Ginger is only common ginger dissolved in alcohol. It, too, is a form of strong drink.
79. Strong drink as medicine.—People sometimes keep whisky or brandy in the house to give for colds or other slight forms of sickness. A drink of hot coffee does more good than the strong drink, and has none of its dangers.
By using whisky or brandy for medicine, children learn to believe in strong drink, and so they will be likely to use it when they grow up. This reason alone ought to keep any one from giving it to a child.
80. Alcohol in cooking.—In making bread, alcohol is formed in the dough by the yeast. When the bread is baked, all the alcohol is driven off by the heat, and so we do not eat any.
Sometimes brandy or wine is put into desserts. If it is put in after the dessert is cooked, we shall get as much alcohol as if we had drunk it. If the liquor is put in before cooking, the heat will drive off the alcohol but the flavor of the liquor will remain. The flavor will do no harm in itself, butpeople will learn its taste, and from it may learn to like the strong drink itself. The alcohol in bread has no special flavor and does not leave any taste behind. So we cannot learn to like strong drink by eating bread.
1. Fruit juice makes wine or cider.2. All kinds of wine contain alcohol.3. When the liquid from boiled grain has fermented, it becomes beer, or ale.4. By boiling wine or beer, and cooling the vapor, distilled drinks like whisky are made. They are one half alcohol.5. Water will satisfy a real thirst. Strong drink will not.6. Alcohol keeps the stomach from digesting food.7. Alcohol soaks into the blood tubes and goes to the liver.8. The liver destroys the alcohol, but is hurt in doing it.
1. Fruit juice makes wine or cider.
2. All kinds of wine contain alcohol.
3. When the liquid from boiled grain has fermented, it becomes beer, or ale.
4. By boiling wine or beer, and cooling the vapor, distilled drinks like whisky are made. They are one half alcohol.
5. Water will satisfy a real thirst. Strong drink will not.
6. Alcohol keeps the stomach from digesting food.
7. Alcohol soaks into the blood tubes and goes to the liver.
8. The liver destroys the alcohol, but is hurt in doing it.
81. Blood.—After food becomes blood, it goes to every part of the body to feed the cells. Even a pin prick anywhere in the body draws blood. The blood makes the skin pink. There are five or six quarts of blood in a man's body. This is about 1/13 of his body.
Blood cellsBlood corpuscles (×400).aa pile of red blood cells.bred blood cells seen flatwise.cred blood cells seen edgewise.dwhite blood cells.
Blood corpuscles (×400).aa pile of red blood cells.bred blood cells seen flatwise.cred blood cells seen edgewise.dwhite blood cells.
Blood looks like a red liquid. But if you look at it through a strong microscope, it looks like water, and millions of little red cells. These cells carry air through the body. They make the blood look red. There are also a smaller number of white cells. Blood is made of red cells, white cells, and a liquid.
82. The liquid in blood.—The liquid part of the blood is albumin, and water, with a little fat, sugar, and minerals. It is food and drink for the cells of the body. When blood is drawn from the body it soon becomes like jelly. We call the jelly aclot. When you cut your finger, a clot forms inthe cut and plugs up the bleeding place. If it did not, the blood would all run out of the body and we should die.
The heartDiagram of the heart while it is beating.avein entering the auricle.bauricle.cclosed valve to keep blood from flowingback into the auricle.dventricle.eartery.fvalve to keep blood from returning to theventricle.
Diagram of the heart while it is beating.avein entering the auricle.bauricle.cclosed valve to keep blood from flowingback into the auricle.dventricle.eartery.fvalve to keep blood from returning to theventricle.
83. The heart.—The blood is held in tubes. A pump inside the body keeps it always moving. This pump is called theheart. The heart is a bag of muscle with thick sides. It is about as large as your fist. When it is full, it has the power to make itself smaller, and so it squeezes the blood out through a tube. We can feel each squeeze as a heart-beat. You can find the heart-beat just to the left of the middle of the body about two hand-breadths below the neck.
84. The heart-beat.—A man's heart beats about seventy times each minute. Boys' and girls' hearts beat much faster. Running or hard work of any kind makes the heart beat faster yet. Your heart will keep on beating until you die. It does notseem to rest at all, yet it works only while you feel it beat. Between each beat it rests while the blood is filling it again. So it really rests one half of the time.
85. Arteries.—The heart pumps the blood through a single tube. This tube opens into smaller tubes. These open into still smaller ones. You must use a strong microscope to see the finest blood tubes. The tubes reach every part of the body, and carry blood to its cells. They are calledarteries. At each heart-beat a wave of blood can be felt in an artery. This wave is thepulse. It can be felt in the wrist, temples, and other places. By the pulse we can tell how often and how strongly the heart is beating.
CapillariesArrangement of capillaries.asmallest artery.bsmallest vein.cnetwork of capillaries.
Arrangement of capillaries.asmallest artery.bsmallest vein.cnetwork of capillaries.
86. Capillaries.—The smallest arteries divide into a fine network of small tubes. These tubes are thecapillaries. They lie around every cell of the body. Their sides are very thin. As the blood flows through them, some of it soaks through the sidesof the tubes. Blood contains all kinds of food for the cells. Each cell is always wet with food and can eat it at any time. The cells are like the tiny animal, the ameba, and can take in the food by any part of their bodies. The cells are better off than the ameba, for their food is brought to them. They pay the body for their food by working for it.
87. Veins.—The capillaries come together again to form large tubes. These tubes are calledveins. Only a little of the blood goes through the sides of a capillary. The rest flows on into the veins. The veins unite to form two large tubes. These two tubes open into the heart.
88. How the blood flows.—The blood is pumped out of the heart, through the arteries to the capillaries. There some goes out to the cells. The rest flows into the veins and goes back to the heart. All the blood in the body passes through the heart every two minutes. It takes only twenty seconds for a drop of blood to go from the heart to the toes and back again. The arteries are deep in the flesh, but some of the large veins can be seen upon the back of the hands.
89. Bleeding.—If a large artery or vein is cut there is a great deal of bleeding. You can always stop a cut from bleeding by holding it fast betweenthe hands. Do not be afraid of the blood when you see any one bleeding, but hold the sides of the cut tightly with both of your hands. This will stop any bleeding until help comes. You may keep a person from bleeding to death by doing this when other persons are afraid of the blood.
90. Healing cuts.—When your flesh is cut it soon grows together again. The work of the little white cells in the blood is to help heal cuts and wounds and bruises. These cells are like little amebas in the blood. They keep moving around with the blood, and now and then burrow outside the capillaries to see if all is well. If they find a cut, hundreds and thousands rush to the spot at once. Some eat up any specks of dirt on the cut. Others fit themselves into the sides of the cut and grow long and slender, like strings, and so bind the two edges of the cut together. In this way all cuts are healed.
BacteriaBacteria growing in a kidney and producing an abscess (×300).akidney tube.bwhite blood cell attacking bacteria.cbacteria.dblood vessel of the kidney.
Bacteria growing in a kidney and producing an abscess (×300).akidney tube.bwhite blood cell attacking bacteria.cbacteria.dblood vessel of the kidney.
91. The white blood cells kill disease germs.—There are tiny living beings everywhere in the air, and soil, and water. Some of them can grow inside a man and make him sick. These tiny things are calleddisease germs. One kind gives a man typhoid fever, and another diphtheria. Another kind grows on cuts, and sometimes makes them very sore. The white cells of the blood are alwayswatching for these enemies, like a cat hunting mice, and when they find them they at once try to kill them. But sometimes the white blood cells get killed. Then they look like cream in the cut. We call this creamy liquidmatterorpus, and say "We have caught cold in the cut." In most pricks and cuts the white cells of the blood can kill all these enemies and also heal the cut.
92. Catching cold.—Sometimes the cold air blows on our head and hurts the cells of the nose. If there are disease germs in the air, they may grow in the injured part of the nose and make us have a "cold in the head." Then the white blood cells gather at the spot so as to kill the disease germs. Also the arteries bring a great deal of blood to the nose so as to heal the injured parts. Some of the white blood cells and the liquid from the blood run out, and we have to blow the nose. The white blood cells help to make us well whenever we catch a cold or other kind of sickness.
93. Red blood cells.—The red blood cells are like tiny flat plates. They float in the liquid part of the blood and make the blood look red. They carry air from the lungs to the cells of every part of the body, and thus help all the cells to breathe.
94. Why the heart beats hard when we run.—When we work hard, the cells of our bodies need a great deal of food. So the heart beats much harder, and sends them much more blood. We can feel our heart beat when we run hard.
When the cells work they get more blood in another way. The arteries become larger and hold more blood. Then the part looks red and feels warm. Thus your face gets red when you run hard. This is because your heart and arteries bring more blood to feed the working cells.
95. Need of a strong heart.—The heart must keep sending blood to feed the cells. If it should stop for only a little while, the cells would starve to death and we should die. We need strong hearts. When we work very hard for a long time, the heart gets tired. Then the cells do not get enough food and we feel weak all over. Boys ought not to run and lift till they are tired out, for this hurts their hearts.
96. What alcohol does to the blood.—Alcohol hinders the digestion of food. Then too little foodwill reach the blood, and so the cells of the body will get too little. Alcohol does not add strength to the body, but it takes it away. It seems to make men stronger, for it takes away their tired feelings. But it makes them really weaker, for it harms the blood.
97. How alcohol affects the heart.—Alcohol at first makes the heart beat more strongly and quickly, but it tires it out and makes it weaker. Then the heart pumps too little blood to the rest of the body, and a man is weaker all over.
If a drinker tries to run or work hard, his heart may not pump enough food to the working cells of his arms and legs. Strong drink takes away a man's strength and makes him less able to endure a long strain.
98. How alcohol harms the arteries.—Alcohol causes the arteries to become larger and to carry more blood. Then the face will be red and the skin will become warm. This makes a person feel well, and he seems to be helped. His blood seems to be flowing faster because his face is red. But really it is flowing slower.
When the arteries have been made large very often, they stay large all the time. A drinker's nose is often red from this cause.
Alcohol sometimes causes the arteries to becomehard, and even to change to a kind of bone. Then they cannot change their size to carry just so much blood as each part needs.
99. How tobacco affects the heart.—Tobacco weakens all the body, but it harms the heart more than the rest. It often makes the heart beat slowly at one time and fast at another. It weakens the heart and keeps it from working harder when the working cells need more food. A smoker gets out of breath quickly. He cannot run far or work very hard. Chewing is a still more harmful form of using tobacco. When men train for a game or a race they never use tobacco.
Boys are not so strong as men, and so tobacco is more hurtful to them. Boys are harmed by tobacco far more than men. Cigarette smoke harms their stomachs and keeps food from their blood. If boys smoke, they become pale and weak. The poisonous smoke weakens the heart, and they cannot run or work so hard as they should. Even if a father uses tobacco, he should not allow his boys to use it.
1. Blood is a liquid. It contains many round red cells and a few white cells.2. Blood contains all kinds of food for the cells of the body.3. The blood is kept moving by the heart.4. The heart pumps or beats about seventy times a minute.5. The blood flows through arteries to all parts of the body.6. The arteries open into the capillaries. Capillaries make a network around each cell of the body.7. Some of the liquid parts of the blood go out through the sides of the capillaries and become food for the cells of the body.8. From the capillaries the blood flows into the veins and back to the heart.9. Bleeding can be stopped by holding the cut tightly between the hands.10. The white blood cells grow into the sides of cuts, and so heal them. They also guard the body against the seeds of many diseases.11. The red blood cells carry air to the cells of the body.12. Alcohol weakens the heart and arteries.13. Tobacco harms the heart.
1. Blood is a liquid. It contains many round red cells and a few white cells.
2. Blood contains all kinds of food for the cells of the body.
3. The blood is kept moving by the heart.
4. The heart pumps or beats about seventy times a minute.
5. The blood flows through arteries to all parts of the body.
6. The arteries open into the capillaries. Capillaries make a network around each cell of the body.
7. Some of the liquid parts of the blood go out through the sides of the capillaries and become food for the cells of the body.
8. From the capillaries the blood flows into the veins and back to the heart.
9. Bleeding can be stopped by holding the cut tightly between the hands.
10. The white blood cells grow into the sides of cuts, and so heal them. They also guard the body against the seeds of many diseases.
11. The red blood cells carry air to the cells of the body.
12. Alcohol weakens the heart and arteries.
13. Tobacco harms the heart.
100. The lungs.—Our food becomes blood and feeds the cells of our body, but we grow only a little heavier. What becomes of the food?
The lungThe air tubes and lung.alarynx or voice box.btrachea or windpipe.dair sacs, each like a tiny frog's lung.
The air tubes and lung.alarynx or voice box.btrachea or windpipe.dair sacs, each like a tiny frog's lung.
Besides food, air is always getting into our bodies. In breathing, air passes through the nose into a tube in the neck. This tube is called thewindpipe. You can feel it as a pile of hard rings in the front part of the neck. The windpipe divides into many branches. At the end of its smallest branches are littlebags or sacs. The branches and the sacs make the two lungs. So a lung is a soft and spongy piece of flesh, and can be blown up like a rubber bag. A frog's lung is a single, thin bag, about half an inch across it. Each little sac of a man's lung is like a tiny frog's lung.
LungA frog's lung (×4).
A frog's lung (×4).
101. The diaphragm.—The lungs fill the upper part of the body just below the neck. They are covered by the bony ribs, and rest upon a broad muscle. This muscle is called thediaphragm. It divides the inside of the body into two parts. The upper part is thechest, and holds the heart and lungs. The lower part is theabdomen, and holds the stomach, intestine, and liver, and a few other parts.
Internal partsThe parts inside the body.alungs.dstomach.bheart.eliver.cdiaphragm.fintestine.
The parts inside the body.
102. Breathing.—When the diaphragm lowers itself, or the ribs are raised, the chest is made larger. Then the air rushes through thenose and swells out the lungs to the size of the chest. This is taking a breath. Then the chest becomes smaller again, and blows the air out. A man breathes about eighteen times a minute. He does not seem to rest in breathing, but as he works only when he takes in breath, he rests one half of the time.
103. How air gets into the blood.—After the blood has been around the body through the arteries and capillaries and veins, the heart sends every drop to the lungs before it sends it out to feed the cells again. The blood flows through little capillaries upon the sides of the air sacs. There the red blood cells take up some of the air, and carry it with them. When they have a load of air, they become of a brighter red color. The blood in the arteries on its way to the cells is bright red.
104. How the cells get air.—When the blood reaches the capillaries around the cells of the body, the red blood cells give up some of the air to the cells. Thus each cell of the body gets some air, and so it breathes. The cells cannot reach the air themselves, and so the red blood cells bring it to them. We breathe so as to supply the cells with air.
105. What burning is.—When meat is put into ahot stove it quickly burns, and passes off in smoke, and leaves only a little ashes. The ashes are the mineral parts of the meat. If the fire is very hot, you cannot see the smoke. The burning of the meat makes heat. Heat in a steam engine makes the machine do work.
Every fire must have plenty of air. If air is shut off, the fire goes out. When meat burns, the air unites with the meat and makes smoke, and ashes, and gives out heat. Air unites with something in every fire.
106. Burning inside the body.—In every part of a man's body a very slow fire is always burning. The blood brings to the cells food from the intestine, and air from the lungs. The food and air join in a burning. The smoke goes back to the blood and is carried to the lungs, and breathed out with the breath. The ashes, also, go back to the blood, and are carried away by the skin and kidneys. The burning makes no flame or light for it goes on very slowly. You cannot see the smoke, but you can feel the warmth of the burning. Some of the heat is turned to power, and gives the body strength to do work. The body is like a steam engine. It burns up all its food.
107. How the body is warmed.—The body is warmed by the slow burning in the cells. Thisburning keeps the body always at the same warmth. On a hot summer's day you feel warmer than on a cold snowy morning. But your body is no warmer. Only your skin is warmer.
If the skin is warm, the whole body feels warm, but if the skin is cold, the whole body feels cold. On a hot summer's day the heat is kept in the skin, and we feel warm. On a cold winter's day a great deal of heat passes off from the skin, and we feel cold. Yet our bodies have the same warmth in winter as in summer.
108. How the sweat keeps us cool.—When your hands or feet are wet, they are cold. On a hot summer's day, your body becomes wet with sweat. This cools the body as if water were poured over it. So sweating keeps you from getting too warm, and from being sunstruck.
We are sweating all the time, but the sweat usually dries as fast as it forms. When we are too warm it comes out faster than it dries. On a winter's day we sweat only a little, and so we save the heat. But more heat passes off from the skin into the cold air, and we do not grow warmer.
109. Clothes.—We wear clothes to keep the heat in the body. They do not make heat, but they keep it from going off. Wool and flannel clothes keep the heat in better than cotton. We wearwoolen in the winter, and cotton in the summer.
Fur keeps in heat the best of all. In very cold lands only fur is worn.
Linen lets heat out easily. It makes good summer clothes.
110. Where to wear the most clothes.—The face and hands are kept warm by the blood and we do not cover them except in the coldest weather. Our feet are more tender and need to be covered enough to keep them warm. We ought to wear thick-soled shoes or rubbers in damp weather so as to keep the feet dry and warm. We ought to dry the stockings every night, for they will get wet with sweat.
The trunk of the body needs the most clothes. The legs ought to be kept warm, too. If the dress reaches only to the knee, thick underclothing is needed for the lower part of the leg.
Do not keep one part of the body warm while another part remains cold. It is wrong to bundle the neck or wear too much clothing over any part of the body. It is also wrong to wear too little and be cold.
When you are moving about, you need less clothing than when you are sitting still. When you have worked until you are very warm, it is wrong to stop to cool off. When you stop, you ought toput on a thick coat or else go into the house. If you do not, you may be chilled and made weak so that you can easily catch cold or some other disease.
111. Heating houses.—In winter our bodies cannot make heat fast enough to keep us warm unless we put on a great deal of clothing. So we warm our houses. Our grandfathers used fireplaces, but these did not give out much heat. People now use stoves, but some use a furnace in the cellar, or heat the rooms by steam. Some use kerosene stoves, but they are not so good, for they make the air bad. A room should feel neither too warm nor too cold. It is of the right warmth when we do not notice either heat or cold.
112. Change of air.—After air has been breathed it is no longer fit for use. In an hour or two you would breathe all the air of a small room once if it were not changed. When the air is partly used, you feel dull and short of breath, and your head aches. As soon as you get out of doors, you feel better. Foul air of houses and meeting places often contains disease germs. It is necessary to change the air of all rooms often. You can do this by opening a door or window. It is a good plan to sleep with your bedroom window open, so as to get good air all night.
Air passes in and out of every crack in the windowsand doors. If only one person is in a room, this may make enough change of air. If many persons are in a room, you will need to change the air in other ways. You can do this by opening a door or window. Do not let the cold air blow upon any one, for it may help to make him catch cold, if the air of the room is impure. If we lower a window from the top, warm impure air may pass out above it without making a draft.
Room ventilationDiagram of the natural ventilation of a room.The arrows show the direction of the air currents.
Diagram of the natural ventilation of a room.The arrows show the direction of the air currents.
You need fresh air at night as much as in the daytime. You need not be afraid of the night air, for it is good and pure like the day air. You ought to sleep with your window open a little. You ought to open the windows wide every morning and air your bed well. At night you ought to take off all your clothes and put on a night-dress. Then hang your clothes up to air and dry.
113. When to air a room.—When you first enter a room full of bad air it smells musty and unpleasant. But after you have been in the room a while, you get used to it. If, however, you go out of doors a minute and then come back, you will smell the bad air again. If the air smells bad, open a door or window until it is sweet again.
114. How to breathe.—When you run hard, the cells of your body use up all the air, and then you feel short of breath. While you run, burning goes on faster, and you feel warmer. You can work harder and longer if you can breathe in a great deal of air. You will also feel better and stronger for it. Then if you are sick, you will be able to get well more quickly. You ought to know how to breathe right.
First, you ought to breathe through your nose. Even when you run, you ought to keep your mouth closed.
Second, you should try to breathe deeply. You should take a very deep breath often, and hold it as long as you can. By practice you can learn to hold it a full minute.
Third, you ought to run, or do some hard work, every day. When you get short of breath, you will have to breathe more deeply. After a while you may be able to run a half mile, or even a mile, without getting out of breath. But do not get tired out in your run, for this will harm you.
Fourth, you must sit and stand with your shoulders back, and your chest thrown forward. A round-shouldered boy cannot have large lungs or be long winded.
By breathing right, you can make your lungs very much larger and stronger.
115. The voice.—We talk by means of the breath. At the upper part of the windpipe is a small box. Its front corner can be felt in the neck, just under the chin, and is called theAdam's apple. Two thin, strong covers slide across the top of the box, and can be made to meet in the middle. The covers have sharp edges. When they are near together, and air is breathed out between them, a sound is made. This sound is thevoice. The tongue and lips change it to formwords.
116. Care of the voice.—The voice shows ourfeelings, even if we do not tell them in words. We can form a habit of speaking in a loud and harsh tone, as if we were always angry, or we can speak gently and kindly. We shall be more pleasant company to others if we are careful always to speak in gentle but distinct tones.
Larynx viewsTop view of the larynx, with thevocal cords closed, as in speaking.Top view of the larynx, with thevocal cords open, as in breathing.aepiglottis.bvocal cords.aepiglottis.bvocal cords.
Shouting strains the voice and spoils its tone for singing. Reading until the throat is tired makes the voice weak. Singing or shouting in a cold or damp air is also bad for the voice. Breathing through the mouth is the worst of all for the voice.
117. What becomes of alcohol in the body.—When alcohol is taken up by the blood, it is carried to the liver. The liver tries to get rid of it by taking some air from the blood and burning it up, just as it burns the real food of the body. But this takes some air from the cells of the body. Then they do not burn as they should.
When a stove gets too little air through its draft, it makes an unpleasant smoke, and cools off. Just so, when the cells of the body do not burn as they should, they produce the wrong kind of smoke and ashes. This poisons the body and makes men sick. The most of the poisoning of alcohol is due to these new poisons.
When alcohol takes air from the cells of the body, they do not get enough air. Then they are like a short-winded boy, and do not do their work well. In this way alcohol makes the body weak.
Alcohol does not cease to be harmful because it is burned up in the body. It is harmful just because it burns so quickly. Using alcohol in the body is like trying to burn kerosene in a coal stove. The body is not made to burn alcohol any more than a coal stove is made to burn kerosene. You can burn a little kerosene in a coal stove if you are very careful. Just so, men can burn alcohol in their bodies. But kerosene will always smoke and clog up the stove, and may explode and kill some one. So alcohol in the body burns quickly and forms poisons. It always harms the body and may destroy life at once.
118. Alcohol and the lungs.—If you run a long race, your lungs will need a great deal of air. If you take strong drink, the alcohol will use upmuch of the air, and you will not have enough to use on your run. So you will feel short of breath, and will surely lose the race. You cannot drink and be long-winded.
Two drinks of whisky will use up as much air as the body uses in an hour. It would be easy to smother a person with strong drink. Drunken persons are really smothered; they often die because of the failure of their breathing, even while their heart is able to beat well.
Alcohol often causes the lungs to become thickened. Then air cannot easily pass through their sides, and a person suffers from shortness of breath. Sometimes these persons cannot lie down at all, but must sit up to catch their breath.
119. Drinking and taking cold.—A strong, healthy man can stand a great deal of cold and wet. If he breathes deeply in his work, all the cells of his body get plenty of air, and if he eats good food, the cells get plenty to eat. Then it will take a great deal to harm them. But alcohol hinders the digestion of their food, and also takes away their air. So the cells are both starved and smothered, and are easily hurt. Then a little cold and wet may do great harm to his body, for a drinker cannot stand bad weather or hard work so well as he could if he should leave drink alone.
Men often drink to keep themselves from taking cold. The alcohol really makes them more liable to take cold. It causes the blood to flow near the surface of the skin; there it is easily cooled, and the drinker soon becomes chilled; then he feels colder than ever. The cold harms the cells of his body, and then the white blood cells cannot easily fight disease germs. For this reason a drinker easily takes cold and other diseases.
120. Alcohol lessens the warmth of the body.—Alcohol causes the blood tubes in the skin to become larger. Then more blood will touch the cool air, and the body will become cooler. But because more warm blood flows through the skin, a man feels warmer. But he is really colder. Alcohol makes men less able to stand the cold. Travelers in cold lands know this and do not use it.
121. How tobacco affects breathing.—We would not live in a room with a smoking stove. But tobacco smoke is more harmful than smoke from a stove, for it has nicotine in it. Tobacco smoke in a room may make a child sick.
Cigarette smoking is very harmful to the lungs, for the smoke is drawn deeply into them, and more of the poison is likely to stay in the body. The smoke of tobacco burns the throat and causes a cough. This harms the voice.