of the food of
graminivorous animals; all other nitrogenised compounds occurring in
plants, are either rejected by animals, as in the case of the
characteristic principles of poisonous and medicinal plants, or else
they occur in the food in such very small proportion, that they
cannot possibly contribute to the increase of mass in the animal
body.

The chemical analysis of these three substances has led to the very
interesting result that they contain the same organic elements,
united in the same proportion by weight; and, what is still more
remarkable, that they are identical in composition with the chief
constituents of blood, animal fibrine, and albumen. They all three
dissolve in concentrated muriatic acid with the same deep purple
colour, and even in their physical characters, animal fibrine and
albumen are in no respect different from vegetable fibrine and
albumen. It is especially to be noticed, that by the phrase,
identity of composition, we do not here intend mere similarity, but
that even in regard to the presence and relative amount of sulphur,
phosphorus, and phosphate of lime, no difference can be observed.

How beautifully and admirably simple, with the aid of these
discoveries, appears the process of nutrition in animals, the
formation of their organs, in which vitality chiefly resides! Those
vegetable principles, which in animals are used to form blood,
contain the chief constituents of blood, fibrine and albumen, ready
formed, as far as regards their composition. All plants, besides,
contain a certain quantity of iron, which reappears in the colouring
matter of the blood. Vegetable fibrine and animal fibrine, vegetable
albumen and animal albumen, hardly differ, even in form; if these
principles be wanting in the food, the nutrition of the animal is
arrested; and when they are present, the graminivorous animal
obtains in its food the very same principles on the presence of
which the nutrition of the carnivora entirely depends.

Vegetables produce in their organism the blood of all animals, for
the carnivora, in consuming the blood and flesh of the graminivora,
consume, strictly speaking, only the vegetable principles which have
served for the nutrition of the latter. Vegetable fibrine and
albumen take the form in the stomach of the graminivorous animal as
animal fibrine and albumen do in that of the carnivorous animal.

From what has been said, it follows that the development of the
animal organis