ON THE COMPOSITE NATURE OF THE ESTRUS PHENOMENON1

Abstract

It has become increasingly evident that the total estrus phenomenon cannot be regarded as a unity, but is composed of a number of integrated reactions in the various organs, and even in the different component tissues of a single organ. This is of more than theoretic significance, since we have recently shown that different estrogenic substances, in comparable doses based on their ability to cause vaginal cornification in the rat, differ markedly in the degree to which they suppress the pituitary in the same animal (1). We have also induced partial or incomplete estrus at certain stages of immaturity in the rat; an estrus reaction in which the vagina and uterine musculature were fully affected, without any signs of endometrial stimulation (2). These experimental separations of the different phases of the estrus phenomenon suggest the possibility that normally occurring complete estrus may not be due to a single ovarian hormone, but to a number of hormones each of which is especially concerned with a parti...