Thus, in animal food, carbon predominates in fats, while in vegetable
food it shows itself in sugar, starch, and vegetable oils. Nitrogen
is found in animal food in the albumen, fibrin, and caseine; while in
vegetables it is in gluten, albumen, and caseine.
[Illustration: Fig. 55]
It is also a curious fact that, in all articles of food, the elements
that nourish diverse parts of the body are divided into separable
portions, and also that the proportions correspond in a great degree
to the wants of the body. For example, a kernel of wheat contains all
the articles demanded for every part of the body. Fig. 55 represents,
upon an enlarged scale, the position and proportions of the chief
elements required. The white central part is the largest in quantity,
and is chiefly carbon in the form of starch, which supplies fat and
fuel for the capillaries. The shaded outer portion is chiefly nitrogen,
which nourishes the muscles, and the dark spot at the bottom is
principally phosphorus, which nourishes the brain and nerves. And these
elements are in due proportion to the demands of the body. A portion
of the outer covering of a wheat-kernel holds lime, silica, and iron,
which are needed by the body, and which are found in no other part of
the grain.
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