_Carbohydrates._--A third class of food-stuffs required by the body is
known as the carbohydrates, or sugars and starches. This class of foods
is used as fuel, for the production of heat and energy in the body.
Excess of carbohydrates may be stored in the body as fatty tissue.
_Potatoes._--Potatoes are a cheap source of carbohydrates. They are also
valuable for their mineral matter and for the large quantity of water
which they contain. Three fourths of the potato is water. The framework
of the potato is cellulose, which is an indigestible carbohydrate
material. Potatoes have only a small amount of cellulose, however, and
they are comparatively easy of digestion. When dry and mealy, they are
most digestible. When used for a meal, potatoes should be supplemented
by some muscle-building food, such as milk, cheese, eggs, fish, or meat.