niacal salts, and other matters which are of no
importance. Thus, between them, the soil and the atmosphere contain
all the elementary bodies which we find in the plant; but the plant
has to separate them and join them together afresh.

Moreover, the new matter, by the addition of which the plant grows, is
not applied to its outer surface, but is manufactured in its interior;
and the new molecules are diffused among the old ones.

The grain of wheat is a part of the flower of the wheat plant, which,
when it becomes ripe, is easily separated. It contains a minute and
rudimentary plant; and, when it is sown, this gradually grows, or
becomes developed into, the perfect plant, with its stem, roots,
leaves, and flowers, which again give rise to similar seeds. No
mineral body runs through a regular series of changes of form and
size, and then gives off parts of its substance which take the same
course. Mineral bodies present no such development, and give off no
seeds or germs. They do not reproduce their kind.

The fowl in the farmyard is incessantly pecking about and swallowing
now a grain of corn, and now a fly or a worm. In fact, it is feeding,
and, as every one knows, would soon die if not supplied with food. It
is also a matter of every-day knowledge that it would not be of much
use to give a fowl the soil of a cornfield, with plenty of air and
water, to eat.

In this respect, the fowl is like all other animals; it cannot
manufacture the proteid materials of its body, but it has to take them
ready made, or in a condition which requires but very slight
modification by devouring the bodies either of other animals or of
plants. The animal or vegetable substances devoured are taken into the
animal's stomach; they are there digested or dissolved; and thus they
are fitted to be distributed to all parts of the fowl's own body, and
applied to its maintenance and growth.

The fowl's egg is formed in the body of the hen, and is, in fact, part
of her body inclosed in a shell and detached. It contains a minute
rudiment of a fowl; and when it is kept at a proper temperature by the
hen's sitting upon it, or otherwise for three weeks, this rudiment
grows, or develops, at the expense of the materials contained in the
yolk and the white, into a small bird, the chick, which is then
hatched and grows into a fowl. The animal, therefore, is produced by
the development of a germ in the same way as the plant; and, in this
respect, all pl