e as possible, in directions variable and
unforeseen.

Now, whence comes the energy? From the ingested food, for food is a kind
of explosive, which needs only the spark to discharge the energy it
stores. Who has made this explosive? The food may be the flesh of an
animal nourished on animals and so on; but, in the end it is to the
vegetable we always come back. Vegetables alone gather in the solar
energy, and the animals do but borrow it from them, either directly or
by some passing it on to others. How then has the plant stored up this
energy? Chiefly by the chlorophyllian function, a chemicism _sui
generis_ of which we do not possess the key, and which is probably
unlike that of our laboratories. The process consists in using solar
energy to fix the carbon of carbonic acid, and thereby to store this
energy as we should store that of a water-carrier by employing him to
fill an elevated reservoir: the water, once brought up, can set in
motion a mill or a turbine, as we will and when we will. Each atom of
carbon fixed represents something like the elevation of the weight of
water, or like the stretching of an elastic thread uniting the carbon to
the oxygen in the carbonic acid. The elastic is relaxed, the weight
falls back again, in short the energy held in reserve is restored, when,
by a simple release, the carbon is permitted to rejoin its oxygen.

So that all life, animal and vegetable, seems in its essence like an
effort to accumulate energy and then to let it flow into flexible
channels, changeable in shape, at the end of which it will accomplish
infinitely varied kinds of work. That is what the _vital impetus_,
passing through matter, would fain do all at once. It would succeed, no
doubt, if its power were unlimited, or if some reinforcement could come
to it from without. But the impetus is finite, and it has been given
once for all. It cannot overcome all obstacles. The movement it starts
is sometimes turned aside, sometimes divided, always opposed; and the
evolution of the organized world is the unrolling of this conflict. The
first great scission that had to be effected was that of the two
kingdoms, vegetable and animal, which thus happen to be mutually
complementary, without, however, any agreement having been made between
them. It is not for the animal that the plant accumulates energy, it is
for its own consumption; but its expenditure on itself is less
discontinuous, and less concentrated, and therefore les