is largely made up of soda, but is found with potash in many vegetables.
This last element is also in meat, fish, milk, vegetables, and fruits.
Iron abounds in flesh and vegetables; and sulphur enters into albumen,
caseine, and fibrine.

The simplest division of food is into _flesh-formers_ and
_heat-producers_; the former being as often called nitrogenous food, or
albumenoids; the latter, heat-giving or carbonaceous foods. Much minuter
divisions could be made, but these two cover the ground sufficiently well.
For a healthy body both are necessary, but climate and constitution will
always make a difference in the amounts required. Thus, in a keen and
long-continued winter, the most condensed forms of carbonaceous foods will
be needed; while in summer a small portion of nitrogenous food to nourish
muscle, and a large amount of cooling fruits and vegetables, are
indicated; both of these, though more or less carbonaceous in character,
containing so much water as to neutralize any heat-producing effects.

Muscle being the first consideration in building up a strong body, we need
first to find out the values of different foods as flesh-formers, healthy
flesh being muscle in its most perfect condition. Flesh and fat are never
to be confounded, fat being really a species of disease,--the overloading
of muscle and tissue with what has no rightful place there. There should
be only enough fat to round over the muscle, but never hide its play. The
table given is the one in use in the food-gallery of the South Kensington
Museum, and includes not only the nutritive value, but the cost also, of
each article; taking beef as the standard with which other animal foods
are to be compared, beef being the best-known of all meats. Among
vegetables, lentils really contain most nourishment; but wheat is chosen
as being much more familiar, lentils being very little used in this
country save by the German part of the population, and having so strong