rresponds in it to
the directing will of the animal is, we believe, the direction in which
it bends the energy of the solar radiation when it uses it to break the
connection of the carbon with the oxygen in carbonic acid. What
corresponds in it to the sensibility of the animal is the
impressionability, quite of its kind, of its chlorophyl light. Now, a
nervous system being pre-eminently a mechanism which serves as
intermediary between sensations and volitions, the true "nervous system"
of the plant seems to be the mechanism or rather chemicism _sui generis_
which serves as intermediary between the impressionability of its
chlorophyl to light and the producing of starch: which amounts to saying
that the plant can have no nervous elements, and that _the same impetus
that has led the animal to give itself nerves and nerve centres must
have ended, in the plant, in the chlorophyllian function_.[55]

* * * * *

This first glance over the organized world will enable us to ascertain
more precisely what unites the two kingdoms, and also what separates
them.

Suppose, as we suggested in the preceding chapter, that at the root of
life there is an effort to engraft on to the necessity of physical
forces the largest possible amount of _indetermination_. This effort
cannot result in the creation of energy, or, if it does, the quantity
created does not belong to the order of magnitude apprehended by our
senses and instruments of measurement, our experience and science. All
that the effort can do, then, is to make the best of a pre-existing
energy which it finds at its disposal. Now, it finds only one way of
succeeding in this, namely, to secure such an accumulation of potential
energy from matter, that it can get, at any moment, the amount of work
it needs for its action, simply by pulling a trigger. The effort itself
possesses only that power of releasing. But the work of releasing,
although always the same and always smaller than any given quantity,
will be the more effective the heavier the weight it makes fall and the
greater the height--or, in other words, the greater the sum of potential
energy accumulated and disposable. As a matter of fact, the principal
source of energy usable on the surface of our planet is the sun. So the
problem was this: to obtain from the sun that it should partially and
provisionally suspend, here and there, on the surface of the earth, its
continual outpour of usable e