ing to observe
that in respect to this question of caring for the body, making it grow
and work and think, many come to grief, having breakdowns which are
called by various big-sounding names. Indeed, to the student of
dietetics, the surprise is that the body is so well able to withstand
the abuse it receives.

It has already been explained in the previous essay how essential it is
if we live in an artificial environment and depart from primitive
habits, thereby losing natural instincts such as guide the wild animals,
that we should study diet. No more need be said on this point. It may
not be necessary that we should have some general knowledge of
fundamental principles, and learn how to apply them with reasonable
precision.

The chemical constitution of the human body is made up of a large
variety of elements and compounds. From fifteen to twenty elements are
found in it, chief among which are oxygen, hydrogen, carbon, nitrogen,
calcium, phosphorus, sodium, and sulphur. The most important compounds
are protein, hydrocarbons, carbohydrates, organic mineral matter, and
water. The food which nourishes the body is composed of the same
elements and compounds.

Food serves two purposes,--it builds and repairs the body tissues, and
it generates vital heat and energy, burning food as fuel. Protein and
mineral matter serve the first purpose, and hydrocarbons (fats) and
carbohydrates (sugars and starches) the second, although, if too much
protein be assimilated it will be burnt as fuel, (but it is bad fuel as
will be mentioned later), and if too much fat is consumed it will be
stored away in the body as reserve supply. Most food contains some
protein, fat, carbohydrates, mineral matter, and water, but the
proportion varies very considerably in different foods.

Water is the most abundant compound in the body, forming on an average,
over sixty per cent. of the body by weight. It cannot be burnt, but is a
component part of all the tissues and is therefore an exceedingly,
important food. Mineral matter forms approximately five or six per cent.
of the body by weight. Phosphate of lime (calcium phosphate), builds
bone; and many compounds of potassium, sodium, magnesium and iron are
present in the body and are necessary nutrients. Under the term protein
are included the principal nitrogenous compounds which make bone, muscle
and other material. It forms about 15 per cent. of the body by weight,
and, as mentioned above, is burnt