wly-expressed juices of vegetables are allowed to stand,
a separation takes place in a few minutes. A gelatinous precipitate,
commonly of a green tinge, is deposited, and this, when acted on by
liquids which remove the colouring matter, leaves a grayish white
substance, well known to druggists as the deposite from vegetable
juices. This is one of the nitrogenised compounds which serves for
the nutrition of animals, and has been named vegetable fibrine. The
juice of grapes is especially rich in this constituent, but it is
most abundant in the seeds of wheat, and of the cerealia generally.
It may be obtained from wheat flour by a mechanical operation, and
in a state of tolerable purity; it is then called gluten, but the
glutinous property belongs, not to vegetable fibrine, but to a
foreign substance, present in small quantity, which is not found in
the other cerealia.

The method by which it is obtained sufficiently proves that it is
insoluble in water; although we cannot doubt that it was originally
dissolved in the vegetable juice, from which it afterwards
separated, exactly as fibrine does from blood.

The second nitrogenised compound remains dissolved in the juice
after the separation of the fibrine. It does not separate from the
juice at the ordinary temperature, but is instantly coagulated when
the liquid containing it is heated to the boiling point.

When the clarified juice of nutritious vegetables, such as
cauliflower, asparagus, mangelwurzel, or turnips, is made to boil, a
coagulum is formed, which it is absolutely impossible to distinguish
from the substance which separates as a coagulum, when the serum of
blood, or the white of an egg, diluted with water, are heated to the
boiling point. This is vegetable albumen. It is found in the
greatest abundance in certain seeds, in nuts, almonds, and others,
in which the starch of the gramineae is replaced by oil.

The third nitrogenised constituent of the vegetable food of animals
is vegetable caseine. It is chiefly found in the seeds of peas,
beans, lentils, and similar leguminous seeds. Like vegetable
albumen, it is soluble in water, but differs from it in this, that
its solution is not coagulated by heat. When the solution is heated
or evaporated, a skin forms on its surface, and the addition of an
acid causes a coagulum, just as in animal milk.

These three nitrogenised compounds, vegetable fibrine, albumen, and
caseine, are the true nitrogenised constituents