What do we require from the fire in our homes? We require heat. The
fires in our bodies give us heat also. Any fire gives off both heat and
energy. State another use of food to the body. _Food produces heat and
energy in the body._

But food does more for the body; it contains substances to keep our
bodies in order. Suppose the clock gets out of order and does not keep
good time, what does the watchmaker do to it? He regulates it. That is
what certain kinds of food do for us. What then is another use of food?
_Food regulates the body._

Name the uses of food to the body.

1. It builds the tissues.

2. It repairs the tissues.

3. It produces heat and energy.

4. It regulates the body.

How then can we judge if a substance be a food? By deciding that it
performs one of these duties in the body.

LESSON II

NECESSARY SUBSTANCES IN FOOD

The names of the substances in food which supply the material for the
different uses of the body should be taken next.

1. _For building and repairing._--(1) Mineral matter--used largely in
hard tissues. (2) Nitrogenous matter, or protein--used largely for
flesh. (3) Water--used in all tissues.

2. _For fuel._--Carbonaceous matter (starch, sugar, fat).

3. _For regulating._--Mineral matter, water.

NOTE.--The teacher should call attention to the
fact that few foods contain all these
substances, some have nearly all, some have
only one, some two or more. In order to get
all, we must eat a variety of foods. The class
is now ready to consider the well-known foods,
in order to find out which of these necessary
substances each food contains, and to obtain a
general idea of their comparative food values.

SOURCES OF FOOD

All nature supplies us with food. The three great divisions of nature
are animal, vegetable, and mineral, and from each we obtain food, though
most largely from the animal and vegetable kingdoms.

Animal food is some part of an animal's body or some product of an
animal: examples--meat or fish, milk, eggs.

Vegetable food is some part of a plant: examples--vegetables, fruit,
seeds.

Mineral food is some constituent of the earth's crust used as food. This
mineral food is obtained by drinking water which in coursing through the
earth has absorbed certain minerals, by eating plants which have
absorbed the minerals from the soil, or by eating animal food which was
built from plan