he blood, etc., while the protein compound, or
those which _do contain nitrogen_, form the muscle, a part of the bones,
the hair, and other portions of the animal.

Animals contain a larger proportion of inorganic matter than plants do.
Bones contain a large quantity of phosphate of lime, and we find other
inorganic materials performing important offices in the system.

In order that animals may be perfectly developed, they must of course
receive as food all of the materials required to form their bodies. They
cannot live if fed entirely on one ingredient. Thus, if _starch_ alone
be eaten by the animal, he might become _fat_, but his strength would
soon fail, because his food contains nothing to keep up the vigor of his
_muscles_. If on the contrary the food of an animal consisted entirely
of _gluten_, he might be very strong from a superior development of
muscle, but would not be fat. Hence we see that in order to keep up the
proper proportion of both fat and muscle in our animals (or in
ourselves), the food must be such as contains a proper proportion of the
two kinds of proximates.

[Why is grain good for food?

On what does the value of flour depend?

Is there any relation between the ashy part of plants and those of
animals?

How may we account for unhealthy bones and teeth?]

It is for this reason that grain, such as wheat for instance, is so good
for food. It contains both classes of proximates, and furnishes material
for the formation of both fat and muscle. The value of _flour_ depends
very much on the manner in which it is manufactured. This will be soon
explained.

[What is a probable cause of consumption?

What is an important use of the first class of proximates?

What may lungs be called?

Explain the production of heat during decomposition.

Why is the heat produced by decay not perceptible?]

Apart from the relations between the _proximate principles_ of plants,
and those of animals, there exists an important relation between their
_ashy_ or _inorganic_ parts; and, food in order to satisfy the demands
of animal life, must contain the mineral matter required for the
purposes of that life. Take bones for instance. If phosphate of lime is
not always supplied in sufficient quantities by food, animals are
prevented from the formation of healthy bones. This is particularly to
be noticed in teeth. Where food is deficient of phosphate of lime, we
see poor teeth as a result. Some physicians have s