that
receives all the food needed.

Both food and the force produced by it result from the activity of
plants. By means of sunlight and moisture a sprouting seed, taking out
of the air and soil different elements, grows into a plant. Then, just
as the plant feeds on the air and soil to get its growth, so the animal
feeds on the plant, to get its growth. Hence, since our animals feed
upon plants, we must find out what is in plants in order to know what
animal food consists of.

Plants contain protein, carbohydrates, fat, mineral matter, water, and
vitamins. You have seen protein compounds like the white of an egg, lean
meat, or the gluten of wheat. The bodies of plants do not contain very
much protein. On the other hand, all plant seeds contain a good deal of
this substance. Animals make use of protein to form new blood, muscles,
and organs. Because of the quality of protein, milk is the best food for
children and young animals.

The protein in some foods is of poor quality. To insure a well-balanced
supply of protein a variety in foods is desirable. Do not rely on a
single kind of mill feed, but combine several kinds, such as cotton-seed
meal, linseed meal, wheat bran and middlings, gluten, and similar grain
by-products. Tankage for young pigs and meat scraps for chickens are
high-grade proteins and are of animal origin.

It is no less important to get the necessary vitamins--those mysterious
substances that keep the body healthy and promote growth and well-being.
Scientists claim that many diseases are food-deficiency diseases--the
body gets out of order because these peculiar vitamins are lacking in
the food. Children require about one or two quarts of milk a day, fresh
fruits, cereal breakfast foods, leafy vegetables as salads, and cooked
vegetables.

Farm animals require the vitamins also. The legume pasture or hay, milk,
grain concentrates when supplied in variety, pasture grass, and green
forage crops are basic foods for farm animals. Very young animals should
have milk also.

Let us next consider the carbohydrates. Sometimes the words _starchy
foods_ are used to describe the carbohydrates. You have long known
forms of these in the white material of corn and of potatoes. The
carbohydrates are formed of three elements--carbon, oxygen, and
hydrogen. The use of these carbohydrates is to furnish to animal bodies
either heat or energy or to enable them to store fat.

In the next place, let us look at the fat