ted and driven by an incessant, instinctive craving for
intellectual work." "They ... work ... to satisfy a natural craving
for brain work." "It is very unlikely that any conjunction of
circumstances should supply a stimulus to brain work commensurate with
what these men carry in their own constitutions."

What is this inherent craving for brain work? What is this zeal? And
what is power of endurance and perseverance, the quality of stamina?
How are they to be interpreted in terms of the internal secretions?

In view of what has been said of the ante-pituitary as the gland of
intellectuality, studies of intellectually gifted people having shown
well functioning large pituitaries, and of mental defectives in a
certain number of cases a small limited pituitary, it is justifiable
to regard the factor of inherent capacity as a function of the
ante-pituitary. The factor of zeal or enthusiasm points to the
thyroid. Markedly enthusiastic types are thyroid dominant types. Vigor
as a third factor, the ability to stand stress and strain of continued
effort is dependent upon good adrenal and interstitial cell function.
So we may say that craving and capacity for brain work plus ardor plus
perseverance in its pursuit, the triplicate of natural ability, are
the reflections in conduct and character of balanced and sufficient
ante-pituitary, thyroid, and adrenal-interstitial contributions in
the chemical formula of the personality. In the chapter on historic
personages analyzed from the endocrine viewpoint, we shall see that
some of the most eminent and illustrious people of history have been
pituitary-centered.

MENTAL DEFICIENCY

Natural ability grows in an endocrine soil of a particular kind,
perhaps affected by the internal secretions much as natural soil is by
fertilizers like phosphates or nitrates. Increased production follows
increased fertilization. Natural disability must vary similarly with a
perversion or improper mixture, deficiency or absence of the hormones
that combine in natural ability.

It is assumed as a matter of course that the brain itself is there,
which, to carry out our analogy, means that the crude soil or earth is
there. Sufficient quantity and adequate quality of nerve tissue must
be regarded as prerequisite. If the brain has been damaged in any way
during development or birth, if it has been smashed up in any way, or
if it has failed to evolve the minimum number of healthy nerve cells,
the endocrine