verpowering impulses or uncontrollable conduct. The waves of feeling
which precede them are unquestionably endocrine determined. The wave
of fear a cat experiences upon seeing a dog is accompanied and indeed
preceded by an increase of the amount of adrenalin in the blood. The
picture of fright, as observed in a so-called normal person, staring
eyes, trembling hands, dry lips and mouth, corresponds to the portrait
of the appearance in hyperthyroidism. In persons afflicted with
uncontrollable impulses, the inhibiting hormones may not be present in
sufficient quantity.

Feeble-mindedness, ranging from stupidity to imbecility, may also be
a direct effect of insufficient endocrine supply to the brain cells.
When there is not enough of the thyroid secretion in the blood, the
tissue between the cells in the brain become clogged and thickened, so
that a gross barrier to the passage of the nerve impulses is created.
We have here an illustration of internal secretion lack actually
producing gross changes in the brain. But without a doubt, most
endocrine influences upon the brain, at work every minute and second
of its life, are the subtle ones of molecular chemistry and atomic
energetics. We know that such mental qualities as irritability and
stupidity, fatigability, and the power to recover quickly or slowly
from fatigue, sexual potency and impotence, apathy and enthusiasm are
endocrine qualities. We know also that the thyroid dominant tends to
be irritable and excitable, the pituitary deficient to be placid and
gentle, the adrenal dominant to be assertive and pugnacious, the
thymus-centered to be childish and easy-go-lucky and the gonad
deficient to be secretive and shy. This brings us to the relation of
the internal secretions to the type of personality as a whole.

CHAPTER X

THE TYPES OF PERSONALITY

THE ENDOCRINE PERSONALITY

If a single gland can dominate the life history of an individual it
becomes possible to speak of _endocrine types_, the result of the
_endocrine analysis_ of the individual. Studying endocrine traits of
physique, life reactions, disease tendencies, hereditary history and
blood chemistry, one may gain an insight into the composition or
constitution of an individual. The endocrine type of an individual
is a summary of these, his behaviour in the past, and is also a
prediction of his reactions in the future, much as a chemical formula
outlines what we believe to be the skeleton of a compound