~Phosphorus.~--This mineral salt is found to be present as an
essential constituent of certain proteins, fats and carbohydrates. It
also enters the body in the form of inorganic phosphates. During the
digestion and metabolism of the organic foodstuffs the phosphoric acid
radical is split off and eventually nearly all of the phosphorus
leaves the body in inorganic form (inorganic phosphates).

~Calcium.~--Being the chief constituent of the bones, large quantities
of calcium salts are stored in the skeleton of the child both before
and after birth. The functions of calcium have already been discussed.
That part not stored, which has finished its work in the body is
excreted through the intestinal wall and leaves the body by way of the
feces, only a small part of the calcium concerned in metabolism being
excreted in the urine.

~The Process of Osmosis in the Body.~--The influence exerted upon the
process of osmosis in the body is one of the most important parts
played by the mineral salts in metabolism. The fact that these
chemical substances are indispensable to the metabolic processes makes
it necessary for the nurse to know where they can be found in food and
how best to use them.

~Metabolism of Body Tissues.~--The constant breaking down and building
up of the tissues of the body and the evolution of heat as a
by-product of the energy expended may be summed up in the term
"metabolism." The metabolism of the body is normally supported by the
food ingested. However, it is a known fact that were no food eaten the
processes would continue just the same, the difference only being the
use of the body structure instead of food materials. According to
Sherman, the chemical changes and energy transformations are of course
inseparable. It has become customary to speak of the metabolism of
matter and the metabolism of energy, and to regard the extent of the
metabolism of any material substance as measured by the amount of its
end products eliminated, and the extent of the energy metabolism as
measured by the amount of heat or of heat and external muscular work
which the body gives off.

* * * * *

In summarizing the important factors in the utilization of food by the
body several distinct points are made evident:

1. The composition of the body, and the composition of food, are
practically the same.

2. Food must make good the losses resulting from metabolic processes
and physical activi