For normally, with feminine puberty, there is an increased activity of the thyroid, the posterior pituitary and the adrenal medulla. These changes indeed constitute the formula of normal feminization. In the male, the ripening of the testes is accompanied or perhaps preceded by augmented function of the adrenal cortex and the anterior pituitary. This difference in biochemistry accounts for the contrast between the sexes in the skin, hair, fat, cartilage (voice) and bone changes. Ovary and adrenal medulla and posterior pituitary and thyroid predominance constitute the feminine formula. Testis and adrenal cortex and anterior pituitary predominance comprise the masculine endocrine directorate. THE REACTIONS OF THE OTHER GLANDS As in so many other aspects, the facts about the various influences exerted by the endocrine glands upon the reproductive system are complicated and disjointed. A chink of light has been let in upon a dark cave, and slowly the chink will widen. But the gross effects are clear. Around the ovary and the uterus, the endocrines gyrate as the planets around the sun. The ovary is the organ for the preservation and maturation of the germ plasm, that treasure which the body is built but to cherish and hand on as a sacred heirloom. The ova, the female egg cells, are the fundamental concern of the ovary. Secondarily, it secretes its messengers to keep the rest of the body, and particularly the other endocrines, in touch with the necessities of the adventures of these ova. It is thus enabled to bend every force and power at its command to the service of the reproductive instinct. In learning their rôle so well in the course of evolution, the thyroid, the pituitary and the suprarenal have become indispensable stimulants (in various degrees peculiar to the individual), to the primary function of the ovary. As a consequence, to hold the sex stimulating glands in check, there had to appear others, restraining them and so preventing sex precocity. These are the thymus and pineal. So closely are they all related that insufficient action of the thyroid, pituitary or adrenals may cause atrophy of the ovaries and uterus, with abolition of genital function. If the sex glands themselves fail, as occurs usually in most women sometime in the forties, the thyroid-pituitary-adrenal association must readjust itself to the new development. The adaptation evokes the phenomena of the transition to a new life, the climacteric. THE SIGNIFICANCE OF PUBERTY