he form of uric acid is
especially significant in certain pathological conditions, gout, for
example, in which the body has difficulty in eliminating these
compounds.

The purin bodies are both endogenous and exogenous--that is, they may
be brought into the body in food as such, or they may be formed as a
result of the metabolism of the body tissues. For this reason the
damage wrought by these substances may to a certain extent be
controlled by eliminating the purin-bearing foods from the diet.
Flesh-foods are high in purins, especially the highly nucleated
glandular organs, liver, thymus (sweetbreads), etc., kidney, beef,
mutton, veal, pork, chicken, turkey, goose, sardines, anchovies, all
kinds of fish except cod. Among the vegetable foods asparagus, beans,
peas, and spinach are highest in purins. Boiling extracts much of the
purins from food. Meat especially should be prepared by this method,
if used in the diet of individuals suffering from gout. Eggs and milk
are purin free, and may be used freely. Certain substances increase
the difficulty of eliminating uric acid. Alcoholic beverages for
example are especially deleterious.

~Creatinin.~--This end-product of protein metabolism is, like uric
acid, endogenous and exogenous. It is one of the normal constituents
of the urine. The quantity is fairly constant for the individual,
averaging about 0.02 gram per kilogram of body weight per day.

~Mineral Metabolism.~--A study of the organic foodstuffs reveals the
fact that many of the mineral salts concerned in nutrition enter the
body in organic combination with those constituents. Certain of the
mineral salts, however, enter, exist in and leave the body in the
same organic form in which they occur in the food materials. This is
true of chlorine, which for the most part, functions in and leaves the
body in the form of chlorides (chiefly sodium chloride). A small part
of the chlorine is used in the production of the hydrochloric acid of
the gastric juice.

Sulphur and iron, both enter the body as essential constituents of
proteins, and their metabolism occurs with that of these foodstuffs;
the sulphur being converted largely into sulphuric acid must be
neutralized at once, and it leaves the body by way of the urine as
inorganic sulphates. Part of the sulphates are excreted as ethereal
(conjugated) sulphates; the amount excreted in this form depending
largely upon the extent of purification in the intestinal tract.[62]