that following. Genius as a sport, as well as sudden
degeneration of family stock, the whole problem of mutation, may be
closely connected with this tendency.

It has been noted that the extinction of species has been preceded by
a great increase in their size, for example, the case of the great
reptilia of prehistoric time. That possibly represented pituitary
stabilization, and so an abeyance of the ability to vary, necessary
for fresh adaptation to a changing environment. Indeed, endocrine
instability appears the fundamental condition of the tendency to vary,
endocrine stability the opposite.

Certain endocrine facts in relation to heredity should be mentioned.
The daughters of mothers who menstruated early, themselves menstruate
early. Animals fed upon thyroid during pregnancy, comparable to the
thyrocentric, give birth to offspring with a very large thymus,
comparable to the thymocentric. Women with partial thyroid deficiency,
or myxedema, bear cretins. These are suggestive of what the internal
secretions may do to an individual in inheritance and development.
Inherited endocrine potential is the maximum reaction of which a gland
is capable. This matter of potential is comparable to the factor of
reserve power or margin of safety demonstrated up to the hilt for
such organs as the heart and kidney as varying from individual to
individual. A low potential, like instability of an internal secretion
gland, may be latent, and not made manifest until the proper stimulus,
the maximum amount of stress and strain, like accident, disease, shock
or war, arrives.

When the individual is tested the effects may be purely local because
there is always in the organism a point of least resistance. Physical
changes alone may be prominent. Or because somatic changes are minor,
the psychic will dominate the picture. An attack of the "blues,"
unaccompanied by any demonstrable transformation of the bodily
processes, may be the sole symptom of an endocrine failure somewhere
in the chain due to hereditary weakness or low potential.

So we may account for family trends and streaks, for varieties
and strains among individuals, upon more precise lines based upon
endocrine analysis. Family disturbances of the internal secretions of
the extreme sort denominated disease are well known. Indeed, a number
of family diseases or predispositions to diseases, have been traced
to them. Predisposition in any direction will probably be shown to be
ca