As differentiation and bulk thus appear antagonistic, at least at the beginning of growth, the function of the thymus, at a maximum during infancy, seems then to be to restrain the differentiating endocrines, until sufficient material has been accumulated by the organism upon which the differentiating process may work.

If the thymus retrogresses after the second year, what takes its place as a brake upon the forward driving impulses of the other endocrines?

But life episodes and crises, diseases, accidents, and struggles, experiences of pleasure and pain, as well as climatic factors, settle finally which endocrine or endocrines are left in control as a consequence of the series of reactions the period of maturity may be analyzed into.

This fact, together with a number of others, make clear that while the gonads may be the jeune premier of the drama, the vitality of the plot depends upon the other endocrines.

It is difficult, indeed, to avoid becoming merely enthusiastic upon the possibilities of the applications of the endocrines to the educational domain.

The study of the endocrines will by no means supply a panacea.

Just what fatigue is, why different individuals tire at different rates, why some are constructed for monotonous routine while others must have constant variety and change, the relation to accidents and to quantity output, are a few of the major lines of inquiry upon which the endocrines obviously have a large bearing.

By their effects upon the endocrines, public health influences like food, clothing, sleep and overpressure and last but not least, disease, the so-called diseases of childhood, possess a tremendous importance in limiting the output of the educable.

But personality and its reactions, normal and abnormal, are determined by the endocrines.

The endocrines will assist him in the great body of diseases for which no immunity test is at hand.

For better or for worse, we possess now in the endocrines new instruments for swaying the individual as individual, and as related to other individuals, as a member of a type, family, nation, species and genus.

That the proportion of the endocrines determines variation and resemblance, heredity and evolution is a hypothesis advanced, supported by a large amount of facts, and capable of the most interesting experimental verification and observation.

Contemplated from the angle of the effect of environment upon the endocrines, and a reflected action upon the germ cells, we may outline a mechanism of the inheritance of acquired characters at certain times and consequent adaptation.

The endocrines are truly the matter of breeding as they are of growth.

As architects of human qualities the endocrines must be involved in the Mendelian unit factors.

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.

Certainly, whether or no we learn how to change the nature of germplasm within a short time, we have in the endocrines the means at hand for affecting the whole individual that is born and sees the light of day.

The information furnished by the study of the endocrines concerning the genesis of personality provides the foundations for a positive eugenics, a eugenics of the encouragement of desirable matings, with the proper legal and social procedures.

It may be another example of the curious coincidences that have been called the Fitness of the Environment that the investigation of the endocrines promises to put into our hands the instruments of the control of the future of the nervous system.

For while the nonliving act upon the endocrines directly, the living act upon the vegetative system, as a whole.

Alcohol and the endocrines remain to be studied.

All these, and many more could be cited, are instances of the direct influence of environmental factors upon one or more of the endocrines, and so upon the organism as a whole.

So national resemblances, traceable to climatic influences being repeated from generation to generation upon the endocrines, may be explained physiologically.

Upon the basis of these structural, functional and mental differences, the qualitative and quantitative evolution of which in the race as in the individual is guided by the glands of internal secretion, Keith presents a very good case for the view that the white man is an example of relative excess of the pituitary, thyroid, adrenal and gonad endocrines.

And since these endocrines control not only physique and physiognomy, anatomic and functional minutiae, but also mind and behaviour, we are justified in putting down the white man's predominance on the planet to a greater all-around concentration in his blood of the omnipotent hormones.