lation, secretion, etc., whose function it is to repair, cleanse
and protect it, to create an unvarying internal environment for it, and
above all to pass it potential energy to convert into locomotive
movement.[58] It is true that the more the nervous function is
perfected, the more must the functions required to maintain it develop,
and the more exacting, consequently, they become for themselves. As the
nervous activity has emerged from the protoplasmic mass in which it was
almost drowned, it has had to summon around itself activities of all
kinds for its support. These could only be developed on other
activities, which again implied others, and so on indefinitely. Thus it
is that the complexity of functioning of the higher organisms goes on to
infinity. The study of one of these organisms therefore takes us round
in a circle, as if everything was a means to everything else. But the
circle has a centre, none the less, and that is the system of nervous
elements stretching between the sensory organs and the motor apparatus.

We will not dwell here on a point we have treated at length in a former
work. Let us merely recall that the progress of the nervous system has
been effected both in the direction of a more precise adaptation of
movements and in that of a greater latitude left to the living being to
choose between them. These two tendencies may appear antagonistic, and
indeed they are so; but a nervous chain, even in its most rudimentary
form, successfully reconciles them. On the one hand, it marks a
well-defined track between one point of the periphery and another, the
one sensory, the other motor. It has therefore canalized an activity
which was originally diffused in the protoplasmic mass. But, on the
other hand, the elements that compose it are probably discontinuous; at
any rate, even supposing they anastomose, they exhibit a _functional_
discontinuity, for each of them ends in a kind of cross-road where
probably the nervous current may choose its course. From the humblest
Monera to the best endowed insects, and up to the most intelligent
vertebrates, the progress realized has been above all a progress of the
nervous system, coupled at every stage with all the new constructions
and complications of mechanism that this progress required. As we
foreshadowed in the beginning of this work, the role of life is to
insert some _indetermination_ into matter. Indeterminate, _i.e._
unforeseeable, are the forms it creates i