Studies on the hypophysectomized ferret. IV.—Comparison of the reproductive organs during anœstrus and after hypophysectomy

In Part II (Hill and Parkes, 1932, b) it was shown that hypophysectomy of the male ferret during the breeding season caused the testes to regress to a condition very similar to the found in the normal animal during anœstrus. This result suggested that decreased activity of the anterior pituitary body might be the causative factor in anœstrus. The hypophysectomized ferrets regressed from full activity to the anœstrous condition in about one month, i. e., much more rapidly than the normal animal regresses at the end of the breeding season. This fact showed that hypophyseal activity diminishes gradually at the end of the breeding season and presumably reaches its lowest level when the testes are most atrophic in November. The next problem was to determine whether or not hypophysectomy during November leads to further regression, i. e., whether the pituitary body is wholly or only partially inactivated at the extreme of the anœstrous period. We have now investigated this question, and also carried out similar experiments on the female.