[Ill.u.s.tration: 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.

[Ill.u.s.tration: 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.

[Ill.u.s.tration: 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 ca.n.a.l. 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 pa.s.sing 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.

[Ill.u.s.tration: FIG. 35.--Yeast plants growing as in the making of beer and wine. Much enlarged.]

=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.

[Ill.u.s.tration: FIG. 36.--Photograph of sprouted barley grains called malt.]

=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.

[Ill.u.s.tration: FIG. 37.--Photograph of a spray of hops, which are used to flavor beer.]

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.

[Ill.u.s.tration: FIG. 38.--The quant.i.ty of grapes required to make this gla.s.s full of wine.]

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.