V. Contributions to the physiology of mammalian reproduction. Part I.—The œstrous cycle in the dog. Part II.—The ovary as an organ of internal secretion

Abstract
The present paper, which is divided into two parts, deals mainly with the œstrous cycle in the Bitch and with the factors controlling its periodicity. Before describing the changes which the generative organs periodically undergo and the causes which assist in producing these changes, it seemed important to give a brief comparative account of what is known regarding the œstrous cycle and its frequency of recurrence in the order of mammals to which the Bitch belongs. This we do in the present part (Part I).