The nature of the researches? They would be infinite in their variety and significance. Their practical by-products, dropped in the pursuit of knowledge by the scientist, as Atalanta's lover the golden apples in his race, to assuage the scent of the hard-headed business man, would be profitable enough for any country in peace or war, to pay for itself ten times over and at compound interest. A volume could be filled with suggestions for interesting and promising investigations. But we may glance at some of the immediately useful aspects that might exercise those concerned with the everyday life of men, women and children. THE ENDOCRINE EPOCHS OF LIFE There is no more famous classifications of the epochs of life that mark off the milestones of the individual's evolution than Shakespeare's Seven Ages. So different is he at those different stages of his development, so changed his body and mind that it has become a part of popular physiology that we are entirely made over every seven years, and that no cell in the organism lasts longer than that. The tradition certainly does not apply to the brain and nervous system, for the number of brain cells is fixed at birth, and cannot be increased, only decreased, because they are too highly specialized to reproduce themselves. What transfigures the individual as the years go by is no simple wear and tear of the tissues, nor the replacement of old cells by new. It is the rearrangement of relationships among the ductless glands, the shifting of influences from the predominant to the subordinate, and vice versa, in the constellation of the internal secretions, that determines the unfolding of the personality. The transformations raise doubt sometimes as to the reality of personal identity. What actually happens in the changes from childhood to adolescence, from adolescence to maturity, and so on, is the sloughing of one internal glandular dominance for another. Growth, as a general name for the mutations, the ensemble of somatic and psychic differentiation, from year to year, passes through five epochs that are standard for the normal. The normal is the being who harmonizes with his environment, and yet reacts with it because of recurring needs within him. His endocrine equation settles what is unique and different in him. But the gland which flourishes during the epoch as its time of triumph, when it has its day, determines what makes him like his fellows. From this point of view it becomes permissible to speak of the five Endocrine Epochs. Similarities and resemblances of mind and body between people at a given period of life, childhood, youth, maturity must be put down to their common government by the salient endocrine of the epoch. So one may list: