CYCLICAL CHANGES IN THE VAGINA AND VULVA OF THE FERRET

Abstract

The vagina and vulva of the ferret undergo well‐marked cyclical changes in correlation with those of the ovaries and uterus.During the anœstrum the vulva is small and the connective tissue of which it is mainly composed is compact. The vagina during this period is lined by a low columnar epithelium consisting of only two or three rows of cells and without a cornified layer.During the pro‐œstrum and œstrus the vulva swells up to about fifty times its anœstrous size, the submucous connective tissue becoming spongy and the nuclei of the cells widely separated. The vaginal epithelium is several layers in thickness, and in the deeper part the cells become high and squamous. There is a pronounced cornified layer. Later, during cestrus, the cornified layer begins to slough, the process being continued over some time. The entire period represents the “follicular stage” of LOEB and other authors, and is presumably brought about by the action of œstrin. The vulval swelling serves the purpose of facilitating effective copulation which in the ferret is very prolonged.During pregnancy and pseudo‐pregnancy (the latter condition in the ferret only occurring under experimental conditions as after copulation with a vasectomised male) the vulva is reduced to its ancestrous size. The reduction is accompanied by lymphoid degeneration and an invasion of leucocytes. The vaginal epithelium becomes reduced to a low columnar or cubical structure. There is no cornified layer, this being completely shed during œstrus. This period clearly represents the “luteal phase” in the ovarian cycle.It is to be noted that the vulval swelling and other characteristics of the follicular stage terminate with ovulation just as does the swelling of the sexual skin in the Primate, as described by ZUCKERMAN and PARKES.The description of the changes here recorded are in general agreeument with the observations by PARKES (1930) on the vaginal smear at different stages of the cycle in the ferret.The vaginal cycle in the ferret is in a general way similar to that of the dog, as described by EVANS and COLE. It may be again remarked, however, that pseudo‐pregnancy only occurs under experimental conditions in the ferret, yet under the influence of pro‐gestin secreted by the corpus luteum the vagina and vulva undergo similar changes during both pregnancy and pseudo‐pregnancy.