will remain as a sediment. Scrape the starch out on a piece of newspaper, and let it dry.

191. What are the Minerals in Foods? The minerals found in some foods and water are often called the body regulators. Our table salt is a mineral without which we cannot exist. One of the most cruel methods the ancients had of inflicting punishment upon prisoners

FIG. 111.

The cheesecloth

bag contains wheat-flour dough. When this is kneaded under

water, the starch of the flour

passes through the cloth, leaving the gluten inside.

was to kill them by leaving salt out of their food. They died a slow, painful death.

Some foods, such as spinach, lettuce, onions, and different greens, consist almost entirely of water and minerals. Fruits and vegetables are rich in mineral matter. The elements which are required by the body are sulphur (found in great amounts in eggs), calcium (best source is in milk), potassium, phosphorus, chlorine, iron, and others. Our bones are made largely of calcium compounds. If we do not have enough of these compounds, we are likely to be weakboned or undersized. At what ages do we need the most calcium? Experts say that young children should have a quart of milk a day and that older boys and girls should have at least a pint in order to be sure to get enough calcium compounds.

When iron is lacking in the diet, the disease anemia lays hold upon the person. Many pale children who seem dull and lifeless are suffering because there is not enough iron in the blood. The body cannot digest nails

or a bar of iron, so we must get our iron by eating those foods which are rich in it. Spinach is especially rich in iron; so are eggs. Raisins, dates, figs, and prunes give it in quantities we can measure, and many vegetables contain a small per cent of iron.

Many people believe that a diet of meat, potatoes, and bread is sufficient to keep them in health. This is a mistake. If we wish to have splendid health and the perfect kind of body which has no weak points and so can resist disease, we must be careful to add milk to the list and to eat plenty of fresh fruits and vegetables. Only thus can we get the precious minerals we need.

When any food is burned completely, the ashes which remain are the minerals contained in that food.

Experiment. Set the cover of a baking-powder can upon some hot coals, or over a gas flame, and in it heat a small piece of bread until all the charcoal has burned away and only grayish ashes remain. Is the amount great or small? Put the ashes in a glass dish and add a drop of some acid. What happens? What gas is probably given off (cf. § 38)?

192. Why Do We Need Water in the Diet? - Every food contains some water, and some foods, such as milk, are mostly water. Water is the most important thing in the diet. Man can live without food for days and days, but water is absolutely necessary if life is preserved for long. Water is used in building up the tissues, in carrying them supplies, and in carrying away wastes. Drinking water at meal time is not harmful, if we do not "wash down" half-chewed portions of food with it. A drink of water a little while before eating is of great benefit in preparing the digestive organs for receiving food. Some physicians advise the drinking of eight glasses of water

every day; others say more or less. It is well for us to cultivate the habit of drinking a great deal of water; we shall have better health if we do.

193. How Do We Depend upon Plants? Could we live without plants? No, we could not. Can we take a pinch of sulphur, a bit of carbon from coal, and a quart of nitrogen from the air? The question is ridicu

complex compounds, such as sugars, oils, and nitrogenous substances. Then animals eat the plants and get the food materials from them in a useful form. The animal food which we eat, such as meat, eggs, and milk, was formed by an animal from plant food eaten by that animal or by smaller animals upon which it feeds. What do sheep feed upon? Chickens?

To make a carbohydrate, carbon dioxide is taken from the air and by a process which goes on in the plant is joined with water to form sugar or starch. These are oxidized in the animal body to give water and carbon dioxide again. Thus plant life and animal life help each other and a delicate balance is kept between the two.

The plant stores food to nourish its young. Examine a kernel of corn (Fig. 112). You will find there is a small dark spot at the tip. This is the germ, or living part, which will start growing if put into water. The greater part of the kernel is a white substance, starch (Fig. 113). This starch is stored around the germ so that the little plant when it starts growing will have some food close at hand in a form

easy to use.

It is these plant storehouses that we usually eat.

Sometimes we eat the leaves (spinach), sometimes the stalk (celery), but more often it is the seed (peas, beans, rice, wheat) or the fruit (grapes

and oranges). Roots and under- FIG. 113.-Grains of starch, ground stems are often the storing

much magnified.

places (potatoes, radishes, onions). Name some other plant seeds that we use as a food.

194. Exercises.

1. Name the five classes of nutrients.

2. What are the chief nutrients in milk, meat, potatoes, bread, sugar, olive oil?

3. What is the value of a vegetable salad in a dinner?

4. What nutrients are not abundant enough in a meal of bread, boiled potatoes, and rice pudding?

5. What do you think of this as a balanced or proper kind of meal: meat, baked potatoes, celery and baked apples?

6. Why can a dog digest bone, while we cannot?

7. The body temperature of some Arctic explorers was found to be about 97° F. instead of 98.6°; why? What kinds of food did they need most?

8. Show that the energy of your body comes originally from the sun.

CHAPTER XXI

THE COOKING AND BAKING OF FOODS

195. Why Do We Cook Food? - When in his history do you suppose man invented cooking? No wild animal cooks its food; very early savage man doubtless ate flesh and other foods raw,

бас

FIG. 114.

as some savage races still do.

No doubt the reason why man began to cook food was because he found that cooking improved the flavor; but he has found, as his knowledge has grown,

A cross section of potato that the most important

cells, showing the cellulose walls and the starch grains inside.

digest better.

reason for the cooking of food is to make it Cooking softens and breaks up the walls which surround the real food. These walls are of cellulose in vegetables and of a tough material called connective tissue in meat. If you examine a slice of potato under the microscope (Fig. 114), you will find that it is composed of many irregular cells; the cell walls are of cellulose, the grains within are grains of starch. Starch