FIGS. 4, 5, and 6. Foods furnish the body with building material, heat, and strength.

WHEN a person goes without food for more than a few hours, he feels hungry. This means that his body needs food and is calling for it. If the person cannot get food, he will soon become weak and his body will waste away. Without food we cannot keep our health and strength. Without food we cannot even live.

Do you ever wonder why it is that you want to eat? Why one food is sometimes better for us than another food? Why a proper amount of food will give strength to the body, but too much food will make the body ill? Why physicians are continually telling us to be careful about what we eat and insisting that a great part of our sickness comes from improper food? These questions are most important to us, and we shall therefore study foods and the uses that the body makes of them.

Foods necessary for building materials. Scrape the skin of your arm with a knife. Do you not find

dead, dry scales on the knife? This dead material is all the time falling away from the skin, as particles of bark drop from the outside of a tree. The inner parts of your body also are wasting away. Yet your body does not become lighter and thinner. On the other hand, in young persons the body grows larger and becomes heavier year by year. This is because every particle of substance that wastes away in heart or muscle or brain or skin is replaced by new materials, and at the same time new substance is built up for making the body larger. This new material is formed from the food that we eat. One great use of food is to furnish building material to the body.

The building foods. Among the more important building foods are lean meats, milk, and eggs. Bread and grains also contain large amounts of building materials, as do peas, beans, cheese, and nuts. These foods give the body warmth and strength, but their main use is to furnish material for growth and repair. They can do this because they are composed of materials like those which make up our bodies. Only such materials can build up our bodies. It would be just as sensible to try to mend a broken window with bricks or to repair a wornout engine with lumps of coal as to try to repair the body with materials different from those of which it is made. Every day we must eat some building food, for night and day, whether

we are asleep or awake, our bodies are wearing

away.

Foods necessary to give heat to the body. The body is warmer than most of the objects around it. It is kept warm by the food that we eat just as a stove is kept warm by the wood or coal that is burned in it. A second use of food is to furnish heat for warming the body.

Foods necessary to give strength to the body. You have seen a great engine driving hundreds of machines, or you have watched a locomotive as it sped along the rails pulling a train behind it. An engine gets its power to work from the coal that is burned in it. In the same way, when you lift something or when you run, your body gets its strength and its power from the food that it uses. A third use of food is to give the body strength and power to work.

The heating and strengthening foods. The second class of foods is the heating and strengthening foods. These are the foods that contain the starches and sugars, the fats and the oils. We take sugar into the body mainly in fruits and in the foods to which we add it to improve the taste. Molasses, honey, syrups, and other sweet foods also contain large amounts of sugar.

Starch forms more than three fifths of our food. We eat it mainly in potatoes and in the foods made from grains - wheat bread, corn bread, macaroni,

rice, and breakfast foods. Some starch is found also in such vegetables as turnips and cabbages.

The fats we get chiefly in meats and in butter and milk. We also get fat in food cooked with lard or cotton-seed oil and a little fat in fruits and

FIG. 7. We should eat plain, substantial foods that will supply the body's needs and keep it in health. We should learn in youth to eat these foods, for to a great extent we carry through life the habits of eating that we form when we are young.

vegetables. From a pound of fat or oil the body gets twice as much heat and strength as it gets from a pound of any other kind of food.

Selecting foods that will supply all the body needs. We should eat some building foods and some heating and strengthening foods, so that all the needs of the body may be supplied. Some persons eat so much meat that their bodies have more building material than they can use, while at the same time they have very little starch and sugar. Some

persons dislike fat meats and butter and take only a little fat in their food. It is believed that these persons are more liable to certain diseases, especially to consumption, than are persons who eat a reasonable amount of fat. A few persons seem able to live and keep in health on nuts and fruits, but these foods do not contain enough building material for most persons. Eating too much meat, not eating enough fat or building material, and failing to eat sufficient vegetables to supply the body with minerals, are common mistakes in selecting foods.

Learning to eat many different kinds of foods. Nearly all of us like the things that we eat as children, and to a large extent we keep through life the habits of eating formed when we are young. You should therefore eat many different kinds of foods and learn to like them, and guard against falling into the habit of eating only a few things and refusing to taste anything else. This is an important point; for it is only by eating a variety of foods that one can be sure of giving the body all the materials necessary for health.

Questions: 1. Name the first use of foods to the body. 2. Why must the body have building materials? 3. Name the more important building foods. 4. Give two other uses of foods in the body. 5. What materials do these foods contain? 6. Name some foods that contain starch. 7. Name some foods that contain sugar. 8. Name the foods from which we obtain fat. 9. For what is fat especially