re so closely allied to it that for convenience they are
usually classified under the general name of "albumen." The chief of
these is _gluten_, which is found in wheat, rye, and barley. _Casein_,
found in peas, beans, and milk, and the _fibrin_ of flesh, are elements
of this class.

_Fats_ are found in both animal and vegetable foods. Of animal fats,
butter and suet are common examples. In vegetable form, fat is abundant
in nuts, peas, beans, in various of the grains, and in a few fruits, as
the olive. As furnished by nature in nuts, legumes, grains, fruits, and
milk, this element is always found in a state of fine subdivision, which
condition is the one best adapted to its digestion. As most commonly
used, in the form of free fats, as butter, lard, etc., it is not only
difficult of digestion itself, but often interferes with the digestion
of the other food elements which are mixed with it. It was doubtless
never intended that fats should be so modified from their natural
condition and separated from other food elements as to be used as a
separate article of food. The same may be said of the other carbonaceous
elements, sugar and starch, neither of which, when used alone, is
capable of sustaining life, although when combined in a proper and
natural manner with other food elements, they perform a most important
part in the nutrition of the body. Most foods contain a percentage of
the _mineral_ elements. Grains and milk furnish these elements in
abundance. The cellulose, or woody tissue, of vegetables, and the bran
of wheat, are examples of _indigestible_ elements, which although they
cannot be converted into blood in tissue, serve an important purpose by
giving bulk to the food.

With the exception of gluten, none of the food elements, when used
alone, are capable of supporting life. A true food substance contains
some of all the food elements, the amount of each varying in different
foods.

USES OF THE FOOD ELEMENTS.--Concerning the purpose which these
different elements serve, it has been demonstrated by the experiments of
eminent physiologists that the carbonaceous elements, which in general
comprise the greater bulk of the food, serve three purposes in the body;

1. They furnish material for the production of heat;

2. They are a source of force when taken in connection with other food
elements;

3. They replenish the fatty tissues of the body. Of the carbonaceous
elements,--starch, sugar, and fats,--fats pro