ke to
regard the mind as having before it the cerebral machinery, all nicely
laid out, together with the acquired art of selecting and touching the
right nervous elements in order to produce the desired motion, as a
skilful player of the piano handles his keyboard."

How then are the muscles informed of the service required of them? Or
more precisely, how does the central nervous mechanism know what
distribution of nerve impulses to make among the different nerve centers
governing the muscles? As Prof. Ladd says, our ignorance on this point
is almost complete. There resides in the central nervous mechanism
governing the muscles something which for lack of a better name may be
called an instinct. When a purposeful movement of any part of the body
is willed, the mental picture of the movement is translated by the
central nervous mechanism into a succession of nerve impulses; these
impulses are transmitted through the lower centers to the muscles. The
instinct informing the central nervous mechanism how to apportion the
discharges of nerve impulse among the various muscular centers is to a
high degree mysterious. The present purpose will not be served by
carrying the analysis of this instinct further.[7]

[Note 7: The evolutionary development of this instinct is not
altogether mysterious. Science can fairly well trace the successive
steps in the development of the central nervous mechanism, from the
amoeba to the highest type of vertebrate. "Nerve channels" are worn by
the repeated transmission of impulses over the same tracts.
Coordinations become in successive generations more complex and more
perfect. As consciousness develops further, in each succeeding type,
actions originally reflex tend to take on a more consciously purposeful
character. But all we are concerned with now is the problem of
tone-production. Our purpose is best served by accepting the faculty of
muscular adaptation as an instinct, pure and simple.]

There is therefore no direct conscious guidance of the muscles, in any
movement, simple or complex. So far as the command of voluntary muscular
actions is concerned, the first simple statement of the process sums up
all that for practical purposes need be determined;--we know what we
want to do, and we do it. The mind forms the idea of an action and the
muscles instinctively respond.

But the fact remains that the muscles need to be guided in some way. We
do not perform instinctively many complex action