Fig. 16 —Bacteria or microbes found in water, dust, and waste. They help change straw and other dead matter into food for plants. Much enlarged.
There are hundreds of different kinds of germs. Some are round like little balls and others are the shape of tiny rods. Many of them which look just alike act very different in growing. There are more than twenty different kinds that grow in our bodies and cause diphtheria, tuberculosis, and other diseases. We have measles and scarlet fever because we have gotten these disease germs from some one else in whom they were growing.
Fig. 17 —Mold which grew on moist bread in two days. 5, seed bodies breaking out of the sack; 1, 2, and 4, one of the seed bodies after one, two, and four hours' growth. Much enlarged.
Most germs feed on dead matter instead of our living bodies and make it melt away or change into another form. An apple or a piece of meat thrown out on the ground will soon change and become like the earth on which it lies. The change, called decay, is caused by millions of germs. The farmer's best friends are certain germs which help make the ground rich, so that the crops will grow.
Mold.—The dust raised in sweeping contains tiny living seedlike bodies. If these fall on bread, cheese, or fruit, and this food is afterward kept moist in a warm room for a day or two, they will grow into grayish fluffy spots. These spots are mold. The greenish white growth on the top of some canned fruit and on berries left in the warm kitchen over night is also mold.
Mold is a plant which grows from tiny round bodies acting like seeds (Fig. 17). These seed bodies of mold are common in all dust and often fly through the air. On this account food should be kept covered when possible and especially when one is sweeping. Some mold gives bread, cheese, and other food a bad taste, but it will not make one sick.
How Germs Grow.—Germs will not grow where it is very cold, but freezing the germs does not kill them. Boiling one minute kills most germs. Drying will stop the germs from growing, but will not kill all of them. Sunlight kills many of them.
Moisture and warmth make germs grow rapidly. A germ in growing lengthens out a little and then divides in the middle. It does this so quickly that one germ may become two in fifteen minutes. Each of these will then divide. In this way one germ can make many million germs in a single day (Fig. 18).
The Spoiling of Meat.—Fresh meat will not remain good even one day if left in a warm place. A large greenish blue fly seen buzzing about in warm weather will sometimes lay its eggs on meat. These will hatch the next day into little worms, called maggots. They grow rapidly and a few days later change into flies.
Fig. 18 —Drawing of the germ at the top every ten minutes, showing how it grew into two germs in a half hour. Much enlarged.
Germs will also spoil meat not kept cold. They feed on the meat and give off a poison, making it unfit to eat. The bad odor tells when the germs are at work. Every home should have a cold cellar or an ice box to keep food from spoiling.
Saving Food from Souring.—The souring of milk and of cooked food of any kind is due to the germs always present in the air and clinging by the thousands to unwashed dishes and hands. If meat or fruit is cooked and kept tightly covered, it will remain good for years. Many persons save fruit and vegetables for use in winter by putting them in jars, which are heated to kill the germs, and sealed tight to keep out other germs.
Fig. 19 —Yeast plants used in making bread and beer. Those on the right are growing new plants. Much enlarged.
Yeast or the Alcohol Plant.—Sweet cider and other fruit juices are sometimes spoiled by a plant named yeast. This plant has the form of a football and is so small that a million of its kind together would not make a mass as large as the head of a pin. It floats about in the air and is present on the skins of fruits.
Yeast is also called the alcohol plant because whenever it grows in a sweet substance like fruit juice it changes part of it into a biting substance called alcohol. At the same time it gives off a gas. It is this gas which forms the bubbling or frothing in beer.
The millions of yeast plants in the yeast cake bought at the store, when put into the dough for bread, grow and form gas. This pushes the bits of dough apart and makes it light. The little alcohol formed is all driven off in the baking.
The alcohol which yeast forms by growing in sweet cider is in a few weeks changed to vinegar by other germs called the vinegar plants. Sour cider may make those who use it sick and drunk because it contains alcohol. Yeast makes wine out of grape juice.
PRACTICAL QUESTIONS
1. Where are germs found?
2. What is the form of microbes?
3. Name some diseases caused by germs.
4. What is mold?
5. Why should food be kept covered when not in use?
6. What causes meat to spoil?
7. How may fruit be kept from spoiling?
8. Where is yeast found?
9. What effect has yeast on fruit juice?
10. Why should you not drink sour cider?
CHAPTER VI
MILK MAY BE A FOOD OR A POISON
Of what Milk is Made.—Milk is the most perfect food known. It contains everything needed to build and strengthen the body. In one gallon of milk there is about one teacupful of pure fat, nearly the same amount of sugar, one teacupful of body-building food needed to make muscle and blood. There is also some lime and other mineral matter to make the bones of the young grow strong. The remaining seven pints are water.
Kinds of Milk.—When milk is left standing in a jar for several hours, much of the fat, which is present in the form of tiny balls, rises to the upper part. This upper layer of milk full of fat is called cream. If this is removed, the rest is called skim milk.
Milk after standing in a warm place one or two days becomes sour. It is then sometimes put into a tight box or barrel and beat in such a way as to break up the little balls of fat. These are then pressed together into a mass called butter. It requires a whole gallon of milk to make one teacupful of butter. The milk remaining after the butter is taken out is called buttermilk. Cheese is made from milk.
Milk as a Food.—Milk is a healthful drink for nearly every one and especially useful for those with weak bodies. During sickness it is sometimes the only food the patient can take. It is well for children to use two or three glasses of milk daily with their meals. It should be sipped slowly so it will mix with the fluid in the mouth and not form lumps called curds in the stomach.
A quart of milk contains more food for the body than a half pound of good beefsteak. A pint of milk will supply the body with about as much food as a pint of oysters. A bowl of milk and a half loaf of bread is a healthful supper for a boy or girl. Skim milk and buttermilk are healthful drinks which furnish much food for building bone, blood, and muscle.
When Milk is a Poison.—In New York, Cincinnati, and Chicago it has been noticed for many years that large numbers of babies become sick in warm weather and many of them die. The doctors learned that most of the babies taken sick were being fed on cows' milk because their own mothers did not have enough for them. It was then found that the sick babies had been using milk from dairies where the stables were dirty, the cows soiled, and the hands of the milkers unclean. On this account much dirt got into the milk.
Babies fed on clean milk from clean cows kept in clean stables remained strong and well. By much study the doctors learned that dirty milk is poisonous milk. The poison is made by the germs or bacteria living by the millions in unclean stables and in milk buckets not well washed in boiling water. Dirty milk becomes most poisonous in hot weather because warmth makes the germs grow very fast and become so numerous that millions are present in a teaspoonful of milk.
Keeping Milk Clean.—During one week of hot weather in Cincinnati, over a hundred babies were poisoned with dirty milk. In the same week twice this number were made sick by unclean milk in Philadelphia. During the hot part of the year in our country bad milk kills more than a half dozen babies every hour of the day and night.
The only way to have milk clean is to have clean stables with clean cows, milked by clean hands, and the milk handled in clean pails, cans, and bottles which have been scalded after being washed. The milk must then be kept cold until used, so that the germs will not grow in it.
Saving the Baby from Bad Milk.—If possible, milk should be bought for the baby in bottles sealed with a pasteboard lid. If milk turns sour the same day it is delivered, it is not fit for the baby to take. Heating it makes most milk safer for use. The heating of milk to kill most of the germs is pasteurizing it. It should be kept very hot for about fifteen minutes, but should not be allowed to boil. It should be cooled by placing the vessel on ice or in cold water.
The baby's bottle and nipple should be washed in cold water and then well scalded immediately after being used. The bottle, the nipple, and the milk should be kept away from flies and dust. One fly has been known to carry on its body more germs than there are leaves on a large tree.
Fig. 22 —Plan of the prison at Easton, Pa. The crosses show into which cells the flies brought typhoid germs from the sewer and made the prisoners sick with fever.
Flies and Fever in a Prison.—In August, 1908, thirteen prisoners in the jail at Easton, Pennsylvania, were taken ill with typhoid fever. They had not been near any sick persons and their food and water were found to be pure. All those sick were in cells in one end of the prison. About twenty feet from this end a sewer had been uncovered two weeks before and left open. This sewer carried the waste from the hospital where several patients were sick with the fever. Flies fed on the waste in the sewer and then with the germs sticking to their feet flew into the cells of the prisoners and walked over their cups, spoons, and food. A little girl who played near this open sewer and shared her lunch with the flies had a severe attack of fever two weeks later because the germs scraped from the flies' feet on her food got into her body and grew.
Milk and Disease.—We must be very careful to get not only clean milk but milk from healthy cows milked by persons who have no typhoid fever, scarlet fever, or diphtheria in their homes. If only one or two disease germs get into the milk from the hands of those who have nursed the sick, these will grow into immense numbers in a single day. Many of those who use the milk will then become ill. Hundreds are made sick in this way every year.
PRACTICAL QUESTIONS
1. Why is milk a good food?
2. What does a gallon of milk contain?
3. What is cream?
4. How is butter made?
5. For whom is milk specially good?
6. How does milk become poisonous?
7. Why is dirty milk more poisonous in hot weather?
8. Tell what harm unclean milk does.
9. How may milk be kept clean?
10. Explain how milk is heated to make it safe for use.
11. Show how flies may cause fever.
12. Tell how milk may carry diphtheria into our homes.
CHAPTER VII
HOW THE BODY USES FOOD
Organs for making ready the Food.—Before the food can get into the blood and be carried over the body to feed the muscles and the brain, it must be made into a fluid. This changing of the solid food into a liquid by the stomach and other organs is called digestion. The organs which do this work are known as digestive organs. They consist of a food tube and several bodies called glands.
The Food Tube.—The food canal is about thirty feet long. Its first part, the mouth, opens back of the tongue into the throat, named the pharynx. This leads into a tube, the gullet, passing down through the back part of the chest into the stomach below the diaphragm. The stomach is a bent sac opening into a tube over twenty-five feet long called the bowels or intestines. This tube is folded into a bunch which fills a large part of the cavity of the abdomen.
Fig. 23 —The plan of a gland. a carries blood to the gland and v takes it away after the gland has taken out what it needs. On the right side the top of the gland has been cut off.
The Glands or Juice Makers.—A gland is a little tube closed at one end, or a bunch of such tubes, which can take something out of the blood and make it into a juice. A gland under each ear and four others near the tongue make the juice called saliva which flows into the mouth through tubes.
A long, flat, pink gland back of the stomach is called the sweetbread or pancreas. This and a large brown gland, the liver, empty their juices into the intestines. The whole inner surface of the stomach and intestines is lined with tiny tubes, the glands. The juice of these with that of the other glands softens the food and makes it into a liquid.
The Work of the Mouth.—The mouth has three things to do: It should break the lumps of food into fine bits so it can be well wet with the slippery fluid called saliva and also easily swallowed. It must roll the food about so that it gets soaked with saliva. It must hold the food long enough to get much taste from it because this starts the juices to flowing into the stomach. Food gives out its taste only after it is changed to a liquid. It should not be washed down with water, as this weakens the juices in the stomach.
No food should be swallowed until it is broken into bits nearly as small as the head of a pin. Some foods, such as cheese, bananas, and nuts, should be made even finer than this. There is nothing in the stomach to crush to pieces large lumps of food. The juices of the stomach can do their full work only when the food is well chewed in the mouth.
Fig. 25 —Photograph of a chestnut chewed a half minute by a boy who had poor teeth because he had not taken care of them. The lumps are so large that the juices of the stomach could not dissolve them.
The Chewing of Food keeps away Sickness.—Bread, meat, and potatoes should be cut into pieces no larger than half the size of your thumb and each piece put separately into your mouth with a fork. It should then be chewed from twenty to thirty times before another piece is put into the mouth. Food treated in this way will not cause headache or a sickness in the stomach called indigestion or dyspepsia. It is said that there are so many persons with this kind of sickness that more than $5,000,000 are spent every year for medicine to help them.
Too little chewing of the food while you are young may not cause many aches or pains, but if you form the habit of rapid eating it is hard to learn to eat slowly. No one who chews his food poorly can avoid sickness long or grow well and strong.
The Work of the Stomach.—When the food is swallowed, it passes through the gullet into the stomach. This is a sac holding more than a quart (Fig. 27). It is made of an outer wall of muscle and an inner skinlike coat full of tiny tubes called gastric glands. Millions of these give out drop by drop a watery fluid named gastric juice. This juice begins to flow as soon as we smell or taste food and continues to drop out as long as there is any food in the stomach.
The use of the gastric juice is to help change part of the food into a more watery fluid. To do this it must be well mixed with the food. This mixing is done by the muscles in the outer wall of the stomach (Fig. 29). They squeeze together and then loosen up in such a way as to move the food about and turn it over until every particle is wet again and again with the gastric juice.
How long Food stays in the Stomach.—A ring of muscle around the end of the stomach keeps the food from escaping until it has become a thin grayish liquid. The stomach can finish its work on some kinds of food in one or two hours. With other foods it must work four or five hours.
The stomach can finish its work on soft boiled eggs, milk, roasted potatoes, and broiled lamb within two hours. With pork, veal, cabbage, and fried potatoes it must work four or five hours. When a person is sick the stomach is weak, and he should have only the food which causes the stomach the least work.
The Work of the Intestines.—The last part of the work in getting the food ready for the blood is done in the long folded tube known as the intestine (Fig. 27). Here juices coming from the pancreas and liver mix with the food and change into a liquid those parts not acted on in the stomach.
The intestine does quite as much work as the stomach. Sometimes when the stomach is sick, too much work is put off on the intestines and then they become sick and give much pain.
The pint of watery fluid from the pancreas and the quart of greenish yellow fluid called bile given out by the liver are carried through two tubes into the intestine (Fig. 27). To mix these juices with the food the intestine is being swung gently back and forth and the walls squeezed together by muscles forming its outer coat. As soon as the intestine has finished its work the food begins to enter the blood.
Fig. 28 —Showing how the food in the dog is carried from the intestine to the liver and heart. The white tubes carry the fats up to the vein in the neck, and the dark tubes which are veins carry the other part of the food to the liver.
How Food gets into the Blood.—An hour or two after food has entered the intestine it is almost as thin a fluid as milk. Millions of tiny fingerlike growths stick out from the inner side of the intestines and drink in the watery food. These little fingers for drinking up the food are scarcely one fourth as large as the point of a pencil. They are called villi.
The villi are filled with blood tubes having thin walls. The food passes through these walls into the blood stream. Much of it then goes to the liver, but the fatty parts flow up a tube along the backbone and empty into a blood tube in the neck. From the neck and the liver the food goes with the blood to the heart which sends it to all parts of the body.
What the Liver does.—The liver is a dark red body nearly as large as the upper half of your head. It lies just below the diaphragm. It works night and day helping to keep the inner parts of the body clean and at the same time deal out food.
The liver takes some waste out of the blood and sends it out into the intestine with the bile. When there is no food in the intestine, the bile is stored up in the gall bladder under the liver. The liver changes certain waste matter in the blood into such form that other organs can cast it out of the body. It also stores up certain parts of the food coming from the intestines and gives it out to the body little by little as it is needed.
When and How much to Eat.—When the food organs do not do their work rightly, the whole body becomes sick. Eating too much overworks the stomach. It becomes so full that the food cannot be moved about and well mixed with the juices. Germs then work on the food and make it sour. In fact the germs may change part of the food into a poison. This poison will cause headache and a bad feeling.
Do not form a habit of taking powders to cure headache. They are likely to hurt the heart. Take less food, eat it more slowly, and do not wash it down with drink. Stop eating before your stomach feels full.
Each meal gives the stomach about four hours of work to do. It then needs one hour of rest. This shows that the time from one meal to the next should be about five hours. Very young children and sick persons need food oftener. Boys and girls should not eat candies, cake, or other food between meals. It spoils the appetite and is likely to get the stomach out of working order.
Danger Signals.—A white or yellowish coat on the tongue, a bad breath, pain in the bowels, or a headache is a danger signal. It tells that the food organs are not doing their work as they should and unless help is given sickness is likely to occur. Medicine may help, but using foods easy to digest, eating less, chewing more, and getting plenty of exercise in the fresh air are likely to be the greatest aids to health.
The Chewing of Tobacco and Digestion.—Some men chew tobacco as much as ten hours every day. The taste of the tobacco makes the saliva flow from the glands into the mouth. This dissolves the poison out of the tobacco and it is then spit out. If the tobacco-soaked saliva were all swallowed, the man would be poisoned.
The chewing of tobacco causes the loss of much saliva which is needed to help digest the food. Anyone who tires his jaw by chewing tobacco is not likely to chew his food well. Some of the poison in the tobacco is taken into the body through the blood vessels in the lining of the mouth. This is shown by the fact that a boy not used to tobacco becomes very sick after he has chewed a mouthful for only ten minutes.
Smoking and Digestion.—Some persons think that the smoking of a cigar after a meal helps digestion. It may do so in some cases. If a lawyer is much excited about a case he is trying, or a business man is in trouble about his losses, the thinking causes the blood to flow to the head when it is needed in the stomach to give out digestive juices.
The taste of the tobacco smoke may cause some gastric juice to run out into the stomach, but at the same time it is likely to hurt the nerves of taste so that food cannot give so much enjoyment as when the nerves are unharmed. Although smoking may at the time help digestion a little, the poison in the tobacco may afterward injure the body. This poison is especially harmful to growing bodies, and boys who are wise will refuse to smoke on all occasions.
Beer and Digestion.—Some people drink beer with their meals because they think it makes the food taste better. It really prevents them from getting the full taste of the food because they wash it down before it is well soaked with the saliva.
Fig. 29 —The stomach, showing the arrangement of the muscular fibers which alcohol may hinder from doing good work. At the right a piece is cut out of the top layer of muscle.
The flavor of beer may sometimes cause an extra flow of gastric juice into the stomach, but the alcohol in the beer is likely to make the movements of the stomach slower. This prevents the food from being well and quickly mixed with the juices. Several glasses of beer used at one meal will make the stomach do its work very slowly, and it will not do it well.
Wine and Digestion.—Wine is taken by some people to give more appetite for food. It is likely, however, to do more harm than good because the alcohol in it makes the muscles which mix the food in the stomach act more slowly. Some of the food may sour before it gets wet with the juice. Much wine used at a meal is always harmful.
Natural Appetite.—If one is in health, he should feel a desire for his food at every meal. This desire for a reasonable amount of food is a natural appetite. Fresh air and exercise will do much to give one the right kind of an appetite. The eating of much sweets and the breathing of bad air are likely to spoil the appetite.
The use of some things, such as opium, tobacco, beer, wine, and whisky, creates an unnatural appetite. That is, after one has used these articles a few months he cannot stop their use without great suffering. The younger the person, the sooner the appetite becomes fixed. For this reason young persons should never use tobacco or alcoholic drinks of any kind.
PRACTICAL QUESTIONS
1. What is digestion?
2. Name the parts of the food tube.
3. Where does saliva come from?
4. Explain how the food is acted on in the mouth.
5. Why should food be well chewed?
6. What forms the gastric juice?
7. Of what use is the gastric juice?
8. How long does food stay in the stomach?
9. Name some foods easily digested.
10. What does the intestine do?
11. What are villi?
12. Tell how the food gets into the blood.
13. Of what use is the liver?
14. Why should we not eat too much?
15. Should we eat between meals?
16. Give three reasons why you should not use tobacco.
CHAPTER VIII
THE CARE OF THE MOUTH
Sickness often begins in the Mouth.—A clean mouth and sound teeth have much to do in keeping one well. The germs which cause nearly a half million deaths in the United States every year enter the body through the mouth. If the mouth is unclean, only one or two disease germs entering it may remain there and grow.
It is just as important to wash the mouth two or three times each day as it is to wash the hands and face. A few germs of diphtheria, sore throat, or tuberculosis are likely to get into the mouth any day, but if the mouth and teeth are well washed with a brush morning and night, the germs will not have time to grow and cause sickness.
The Teeth.—The first twenty teeth that appear are called the milk set. The eight front teeth grow out during the first year of life and back of these twelve others appear during the second year. Between the seventh and the tenth year all of the milk teeth are lost because others grow beneath them and push them out.
Fig. 31 —The full set of teeth on the right side at twelve years of age. The numbers show at what year of age each one grows out of the gum.
The first four teeth of the second set appear in the sixth year, just behind the last milk teeth (Fig. 30). These teeth should be watched very closely and at the first sign of decay you should go to the dentist. As the milk teeth get loose and come out, the second set of teeth take their places.
If you are ten or eleven years old, you should have twelve good teeth in the upper jaw and the same number below. The last ones to break through the gums are the four wisdom teeth at the back of the mouth. They appear after the seventeenth year.
The front teeth are called incisors because they are used to cut the food. The back teeth are named molars because they are used in grinding the food.
Fig. 32 —Photograph of teeth not kept clean, showing how germs and a sour substance called acid eat holes in them and thus cause decay and toothache.
Toothache.—Toothache is a common ailment, and yet it can be entirely prevented. A tooth does not ache until it has a hole in it. The tender nerve within gives us warning that it is being hurt. The dentist can stop the ache and mend the tooth so that it will not ache again. Look at your teeth every month and feel about them with a wooden tooth-pick to know when the decay begins. If the little holes are mended as soon as found, you will never have toothache, and you can keep your teeth as long as you live.
Fig. 33 —Slice down through a tooth showing f, the enamel, and d, the soft pulp with nerves and blood tubes from the root at h.
How to keep the Teeth Sound.—Every tooth is covered with a layer of hard shining substance called enamel (Fig. 33). So long as this is unbroken the softer bony part of the tooth cannot decay. At the base of the tooth where the gum joins it the enamel is very thin, so that the scratch of a pin or other instrument may break it.
Never pick the teeth with a pin or needle. The biting off of thread, finger nails, and other hard material may crack the enamel. It may also be softened and eaten away by acid formed where food remains about a tooth. For this reason a quill or wooden pick or piece of tough thread, called dental floss, should be used to clear the teeth of food after each meal. Slimy matter collects over the whole surface of the teeth, and is likely to cause decay in spots unless it is cleaned off night and morning with brush and water. The chewing of dry crusts of bread or crackers strengthens the teeth and keeps off decay.
Why Candy and other Sweets cause the Teeth to Decay.—A sour substance called acid usually starts the decay of a tooth by eating through the enamel. Germs change sugar and other sweets into an acid. The acid is not made at once. An hour or more is needed for the germs to grow to form the acid. If, after eating sweet foods, the mouth is well cleaned, no acid will be formed. Sugar and candy do not, therefore, spoil the teeth unless it is left sticking about them.
How to brush the Teeth.—Every boy and girl should own a toothbrush. The teeth should be brushed every night and morning and kept white. Yellow or gray slimy teeth are very ugly. The teeth should be brushed on the inside as well as on the outside. It is best to brush the teeth crosswise for two minutes and then spend another two minutes brushing the upper teeth downwards and the lower teeth upwards. This prevents pushing the gum away from the teeth. Plenty of water should be used with the brush, and a little good powder is helpful once a day.
How the Dentist can Help.—Sometimes the milk teeth do not get loose so that they can be pulled with the fingers at the right time. The second teeth then come in at one side and may never get straight in place. They then spoil the appearance of the face and do poor work in chewing. The dentist should be asked to help straighten the teeth as soon as they appear crooked.
Fig. 34 —Exact drawing of the teeth of two persons. Those in the lower picture began to decay over twenty-five years ago and they were then filled so as to remain perfect. The teeth in the upper picture began to decay less than ten years ago but were not filled.
It is wise to have the dentist examine the teeth once or twice every year and remove a limy substance called tartar collecting at their base. The dentist can stop the decay in a tooth by cleaning out the little hole and filling it with gold or some other material. It may cause a little pain and expense to have the teeth filled, but it will save a hundred times as much pain and expense later. The six year molars need special care as they are likely to decay early. Even the milk teeth often need filling so that they will not be lost too soon.
Bad Teeth cause Sickness.—When anything decays, it is full of germs, and they are always giving off some poison. The poison may hurt the body and is likely to make parts of the mouth sore and tender so that other germs of disease can break through into the flesh. Disease germs can easily lodge in the holes of decaying teeth, grow in numbers, and finally cause diphtheria, sore throat, or other ailments.
Four out of every five children suffering from diphtheria or other throat or ear troubles are found to have from one to ten bad teeth. You must keep good teeth if you wish to be well and strong.
The Value of Sound Teeth.—Sound teeth which will do good work in chewing food are worth more than a foot or an arm. If the foot or arm is lost, the body is likely to get well and be as healthy as ever. The health of the whole body depends upon the work done by the teeth. Unless they do their part the stomach cannot get the food ready for the blood.
A part of badly chewed food is turned into a poison farther down in the food canal. This is what makes many people feel so tired and miserable much of the time. Hundreds of men have been refused admission to our army because they have poor teeth. Soldiers must be strong and well to take long marches and fight battles. Sound teeth give strength and health.
PRACTICAL QUESTIONS
1. Why should the mouth be washed out every day?
2. When do the milk teeth appear?
3. When are the milk teeth lost?
4. How many teeth have you?
5. How many show signs of decay?
6. How may toothache be prevented?
7. How may the teeth be kept sound?
8. Why do sweets cause the teeth to decay?
9. How should you brush your teeth?
10. Why should the dentist examine your teeth every year?
11. Why are sound teeth of great worth?
CHAPTER IX
ALCOHOLIC DRINKS
Drink needed for Health.—Water in the form of sweat and in other ways is constantly passing off from the body. This water carries with it the waste matter which, if it remained, would poison the body. There is some water in the food we eat, but not enough to supply the wants of the body.
Some persons think that the body needs beer or wine to keep it in good order. These liquids, as well as whisky, brandy, and rum, are called alcoholic drinks. The latest experiments and studies show that the body never needs alcoholic drinks to keep it in the best of health. These drinks sometimes make the body sick, and if much alcohol is taken at one time, the person becomes dizzy, staggers, and may fall down and go to sleep.
The Desire for Drink.—When parts of the body have too little water, there is a longing for drink. This is called thirst. As soon as a cup of water is drunk the desire is satisfied. There is no danger of drinking too much pure water.
Persons who have been accustomed to use alcoholic drink have a thirst which water does not satisfy. It is an unnatural thirst. Even beer or wine will not satisfy such a thirst except for a few minutes. Very often a person's thirst is not satisfied until he has used so much wine or whisky that he becomes dull and unsteady in his walk. He is then said to be drunk.
How the Yeast Plant makes Alcohol.—In the cake of yeast bought at the grocery there are millions of tiny plants, each shaped somewhat like a potato. This strange little plant will grow very rapidly when put into any sweet watery substance. It sends out a bud which grows larger and larger until in a half hour the bud is as large as the old plant. It may then break loose and grow other buds, just like the mother plant.
When yeast grows, it changes the sugar or sweet part of the water into alcohol and a gas called carbon dioxide. It is this gas which makes beer foam and bubble when opened. All alcohol used in beer, porter, ale, wine, brandy, rum, gin, and whisky is made by yeast plants.