worst feature of the problem, however, is not so much the disproportion
in the numbers born to the normal and the abnormal respectively, but the
fact that the defectives propagate their kind.

The defectives, whose existence and whose liberty constitute the
greatest danger to the State, are the intermittent inhabitants of our
lunatic asylums, prisons, and reformatories.

There is one defect common to all these, and that is defective
inhibition.

All human activity is the result of two forces, motor impulses tending
to action, and inhibition tending to inertia.

The lower animals have strong motor impulses constantly exploding and
expressing themselves in great activity, offensive, defensive,
self-preservative, and procreative, being restrained only by the
inhibitive forces of their conditions and environment.

Children have strong motor impulses, which are at first little
controlled. Inhibition is a late development and is largely a result of
education.

If the motor impulses remain strong, or become stronger in the presence
of development with exercise, while inhibition remains weak, we have a
criminal.

Inhibition is the function performed by the highest and last-formed
brain-cells. These brain cells may be undeveloped either from want of
exercise, that is, education, or from hereditary weakness, or, having