hours, but
that it contains only one-fourth of the quantity of carbon required.
About half a pound of fat, or one pound of sugar, will supply the
quantity of carbon necessary. The fat, if properly subdivided, and the
sugar, by reason of its solubility, pass with great ease into the
circulation, the physiological labor, consequently, being reduced to a
minimum.

Several common articles of diet contain in themselves all the necessary
elements. Thus, butchers' meat ordinarily contains from 30 to 50 per
cent. of fat; and bread contains the proteid, gluten, and the amyloids,
starch and sugar, together with minute quantities of fat. However, on
account of the proportion in which these proteid and other components of
the body exist in these substances, neither of them, by itself is such a
physiologically economical food, as it is when combined with the other
in the proportion of three to eight, or three quarters of a pound of
meat to two pounds of bread a day.

It is evident that a variety of food is necessary for health. Animals
fed exclusively upon one class, or upon a single article of diet, droop
and die; and in the human family we know that the constant use of one
kind of diet causes disgust, even when not very long continued.
Consequently, we infer that the welfare of man demands that his food be
of sufficient variety to supply his body with all of its component
parts. If this is not done the appetite is deranged, and often craves
the very article which is necessary to supply the deficiency. After the
component parts of the organism have assimilated the nutritious elements
of particular kinds of food for a certain length of time, they lose the
power of effecting the necessary changes for proper nutrition, and a
supply of other material is imperatively demanded. When the diet has
been long restricted to proteids, consisting largely of salt meats,
fresh vegetables and fruits containing the organic acids, become
indispensable; otherwise, the scorbutic condition, or scurvy, is almost
sure to be developed. Fresh vegetables and fruits should be eaten in
considerable quantities at the proper seasons.

VALUE OF ANIMAL FOOD. The principal animal food used in this country
consists of _Pork, Mutton, Beef_, and _Fish_. Beef and mutton are rich
in muscle-producing material. Although pork is extensively produced in
some portions of this country, and enters largely into the diet of some
classes, yet its use, except in winter, is no