result. A bud is formed; this bud reaches the surface,
where it is exposed to the sun's rays, which are also to be regarded as a
kind of vibratory motion. And as the motion of common heat, with which the
grain and the substances surrounding it were first endowed, enabled the
grain and these substances to exercise their attractions and repulsions,
and thus to coalesce in definite forms, so the specific motion of the
sun's rays now enables the green bud to feed upon the carbonic acid and
the aqueous vapor of the air. The bud appropriates those constituents of
both for which it has an elective attraction, and permits the other
constituent to resume its place in the air. Thus the architecture is
carried on. Forces are active at the root, forces are active in the blade,
the matter of the earth and the matter of the atmosphere are drawn toward
both, and the plant augments in size. We have in succession the bud, the
stalk, the ear, the full corn in the ear; the cycle of molecular action
being completed by the production of grains similar to that with which the
process began.

Now there is nothing in this process which necessarily eludes the
conceptive or imagining power of the purely human mind. An intellect the
same in kind as our own would, if only sufficiently expanded, be able to
follow the whole process from beginning to end. It would see every
molecule placed in its position by the specific attractions and repulsions
exerted between it and other molecules, the whole process and its
consummation being an instance of the play of molecular force. Given the
grain and its environment, the purely human intellect might, if
sufficiently expanded, trace out _a priori_ every step of the process of
growth, and by the application of purely mechanical principles demonstrate
that the cycle must end, as it is seen to end, in the reproduction of
forms like that with which it began. A similar necessity rules here to
that which rules the planets in their circuits round the sun.

You will notice that I am stating my truth strongly, as at the beginning
we agreed it should be stated. But I must go still further, and affirm
that in the eye of science _the animal body_ is just as much a product of
molecular force as the stalk and ear of corn, or as the crystal of salt or
sugar. Many of the parts of the body are obviously mechanical. Take the
human heart, for example, with its system of valves; or take the exquisite
mechanism of the eye or han