uents of the body are, iron, lime, magnesia,
common salt, and the alkalies.

The nutritive process is seen in its simplest form in carnivorous
animals. This class of animals lives on the blood and flesh of the
graminivora; but this blood and flesh are, in all their properties,
identical with their own. Neither chemical nor physiological
differences can be discovered.

The nutriment of carnivorous animals is derived originally from
blood; in their stomach it becomes dissolved, and capable of
reaching all other parts of the body; in its passage it is again
converted into blood, and from this blood are reproduced all those
parts of their organisation which have undergone change or
metamorphosis.

With the exception of hoofs, hair, feathers, and the earth of bones,
every part of the food of carnivorous animals is capable of
assimilation.

In a chemical sense, therefore, it may be said that a carnivorous
animal, in supporting the vital process, consumes itself. That which
serves for its nutrition is identical with those parts of its
organisation which are to be renewed.

The process of nutrition in graminivorous animals appears at first
sight altogether different. Their digestive organs are less simple,
and their food consists of vegetables, the great mass of which
contains but little nitrogen.

From what substances, it may be asked, is the blood formed, by means
of which of their organs are developed? This question may be
answered with certainty.

Chemical researches have shown, that all such parts of vegetables as
can afford nutriment to animals contain certain constituents which
are rich in nitrogen; and the most ordinary experience proves that
animals require for their support and nutrition less of these parts
of plants in proportion as they abound in the nitrogenised
constituents. Animals cannot be fed on matters destitute of these
nitrogenised constituents.

These important products of vegetation are especially abundant in
the seeds of the different kinds of grain, and of peas, beans, and
lentils; in the roots and the juices of what are commonly called
vegetables. They exist, however, in all plants, without exception,
and in every part of plants in larger or smaller quantity.

These nitrogenised forms of nutriment in the vegetable kingdom may
be reduced to three substances, which are easily distinguished by
their external characters. Two of them are soluble in water, the
third is insoluble.

When the ne