Applied Physiology Part 4

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.

CHAPTER VII

FERMENTATION

=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.

[Ill.u.s.tration: =Fermentation in a jar of cherries.=]

=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 thing have 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.

[Ill.u.s.tration: =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 or plants in gla.s.s 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 called _strong 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.

WHAT WE HAVE LEARNED

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 forms _strong drink_.

CHAPTER VIII

KINDS OF STRONG 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.

[Ill.u.s.tration: =A gla.s.s 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 have alcohol. Any of them can make a person drunk. Using weak homemade wine and cider often makes an appet.i.te for stronger drinks.

The alcohol in any of them is enough to harm the body.

[Ill.u.s.tration: =A gla.s.s of beer contains so much alcohol.=]