The reproductive processes of certain mammals. II.—The size of the Graafian follicle at ovulation

Abstract

It is generally recognised that the size of the mature Graafian follicle varies greatly from species to species, and that, roughly speaking, the size of the follicle at ovulation is greater in the larger mammals than in the smaller. So far as can be ascertained, however, no attempt has been made to examine this relationship accurately. The present paper is primarily concerned with the correlation between the size of ripe follicle and the body weight of the species of animal, but a second point is also included. Brambell (1928) has shown that even in an animal such as the mouse, where the ripe follicle is comparatively small, the growth of the ovum is completed at an early stage, and that the subsequent growth of the follicle must, therefore, be concerned with some other function than the nutrition of the ovum. Brambell actually found that the growth of the ovum was completed before the formation of the antrum, i. e. , that the essential characteristic of the mammalian follicle only appears after the nutrition of the ovum has cased to be an urgent function. It seemed of interest, therefore, to ascertain whether a similar state of affairs exists in the follicles of larger mammals, and if so, what relationship the size of the follicle, when the ovum is fully grown, bears in different species to the ultimate size of the follicle at ovulation.