on reasoning as in perception
and memory. And as in the latter, the thyroid determines the velocity.
Quick thinking, as we call it, means good thyroid action, and slow
thinking deficient thyroid action. The other element in judgment,
accuracy, is influenced by the ante-pituitary. During adolescence
there is physical growth which consumes most of the secretion of the
ante-pituitary. After adolescence, after the early twenties, when
physical growth has ceased, the ante-pituitary secretion sensitizes
the cells of the brain to mental growth. The reaction potential of
the ante-pituitary, that is its inherent, latent ability to supply a
maximum of its endocrine for the nerve cells of the frontal lobes, is
the best-known chemical determinant of intellectual genius. It makes
for the greatest co-ordination of experience, knowledge, information,
tastes and problems into one harmonious whole. And curiously, not only
does it cause a fusion of intellectual material: it creates a desire
for and a love of such material.

We should expect to find extraordinarily well-developed ante-pituitary
action among eminent philosophers and men of science, and we do.
Adequate action of it is present throughout the range of normals who
evidence sufficiently ripened judgment as they progress through
life. The ability to profit by experience, and to make more and more
accurate judgments as one grows older implies at least a maximum
efficiency of it. This maturation is not at all universal. Even after
middle age, after forty and fifty years of reasoning, some individuals
retain the juvenile mind of their youth. Like the Bourbons, they
have learned nothing and forgotten nothing. Their ante-pituitary
insufficiency often coupled with a post-pituitary excess, and other
instabilities and disequilibriums in the endocrine system, render them
immature morons, compared with what might be expected of them for
their years. They are the people who are old enough to know better.
For the same reasons, inhibition and emotional control are poor in
them.

Besides the ante-pituitary, in the evolution of judgment, and the
judgment faculty, due stress must be laid upon the influence of the
internal secretion of the testes or ovaries, the product of the
interstitial cells. Although the probability is that the effects
are indirect, through a stimulation of the ante-pituitary, the fact
remains that, in a child, memory may be marvelous and judgment poor
(such memory is po