OF THE GENITAL ORGANSOFFEMALE MAMMALS. The evidence grouped

The ovaries, although primarily concerned with the genesis of ova, control the development and function of the female sex organs and the determination of secondary sex characters. That this control is ac-complished by hormonal action has been clearly demonstrated by the preparation of ovarian extracts which upon injection into ovariectom-iced animals induce certain of the physiological reactions normally dependent upon ovarian endocrine function. Certain other aspects of this endocrine control are still obscure, but a basis for further study has been laid by the demonstration of at least one essential ovarian hormone. An identical or very similar substance can be extracted by the same methods from placental tissues of certain species. As yet it has not been possible to distinguish between purified material from these two sources by either chemical or physiological reactions. It is possible that there are other hormones in either the ovary or placenta but this seems still to be an open question. The evidence concerning ovarian and placental hormones has been accumulated by means of several methods which have utilized different viewpoints.