But
even when the stimulation received is not at once prolonged into
movement, it appears merely to await its occasion; and the same
impression which makes the organism aware of changes in the environment,
determines it or prepares it to adapt itself to them. No doubt there is
in the higher vertebrates a radical distinction between pure automatism,
of which the seat is mainly in the spinal cord, and voluntary activity
which requires the intervention of the brain. It might be imagined that
the impression received, instead of expanding into more movements
spiritualizes itself into consciousness. But as soon as we compare the
structure of the spinal cord with that of the brain, we are bound to
infer that there is merely a difference of complication, and not a
difference in kind, between the functions of the brain and the reflex
activity of the medullary system."[Footnote: Matter and Memory, pp. 17-
18 (Fr. p. 15).] The brain is no more than a kind of central telephone
exchange, its office is to allow communication or to delay it. It adds
nothing to what it receives, it is simply a centre where perceptions get
into touch with motor mechanisms. Sometimes the function of the brain is
to conduct the movement received to a chosen organ of reaction, while at
other times it opens to the movement the totality of the motor tracks.
The brain appears as an instrument of analysis in regard to movements
received by it, but an instrument of selection in regard to the
movements executed.
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