[The single hormone hypothesis. An instructive episode in the history of ovarian endocrinology]

In the mid-twenties of the present century renowned scientists held the opinion that only one female sex hormone is secreted by the ovary. A survey is given how this hypothesis arose, for which reasons it was favoured and why it had to be given up. The importance of the Allen-Doisy test (1923) and the Corner-Allen test (1929) and of the publications by these authors is stressed. Finally, it is shown that Thomas S. Kuhn's theory, explaining how scientific advance is promoted by changing a paradigm, is also applicable to this phase of research in ovarian endocrinology as well.