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 caused by them, within limits.  Research here has its opportunity.

THE IMPROVEMENT OF RACIAL STOCK

A vast new territory of inquiry and achievement, as yet totally unexplored, is opened by the endocrines to the eugenists, and those idealists whose most earnest aspiration is the improvement of racial stock as a necessary preliminary to improvement of racial life.  Beginning with Galton, they have brought to light a great collection of data to prove that human traits and faculties, good and bad, are inherited.  Ability has been shown to run in certain families and degeneracy in others.  Yet all of the practical net result has been summed up in the term “negative eugenics,” the eugenics of prohibition and warning.