_The Cerebrum an Organ giving Adaptation and Readjustment of Motor
Acts._--The exercise of this control and the acquirement of skilled
actions have obviously elements in common. By skilled actions, we
understand actions not innately given, actions acquired by training in
individual experience. The controlling centres pick out from an
ancestral motor action some part, and isolate and enhance that until it
becomes a skilled act. The motor co-ordination ancestrally provided for
the ring finger gives an extending of it only in company with extension
of the fingers on either side of it. The isolated lifting of the ring
finger can, however, soon be acquired by training. In such cases the
higher centre with conscious effort is able to dissociate a part from an
ancestral co-ordination, and in that way to add a skilled adapted act to
the powers of the individual.

The nervous organs of control form, therefore, a special instrument of
adaptation and of readjustment of reaction, for better accommodation to
requirements which may be new. The attainment of more precision and
speed in the use of a tool, or the handling of a weapon, means a process
in which nervous organs of control modify activities of reflex centres
themselves already perfected ancestrally for other though kindred
actions. This process of learning is accompanied by conscious effort.
The effort consists not so much in any course of reasoning but rather in
the acquiring of new sensorimotor experience. To learn swimming or
skating by simple cogitation or mere visual observation is of course
impossible. The new ideas requisite cannot be constructed without motor
experience, and the training must include that motor experience. Hence
the training for a new skilled motor manoeuvre must be simply _ad hoc_,
and is of itself no training for another motor co-ordination.

The more complex an organism the more points of contact does it have
with its environment, and the more does it need readjustment amid an
environment of shifting relationships. Hence the organs of consciousness
and control, being organs of adaptation and readjustment of reaction,
will be more pronounced the farther the animal scale is followed upward
to its crowning species, man. The cerebrum and especially the cerebral
cortex may be regarded as the highest expression of the nervous organ
of individual adaptation of reactions. Its high development in man makes
him the most successful animal on earth's surf