THE INHIBITION OF (ESTRUS BY CORPUS LUTEUM EXTRACTS

¹ Animal Breeding Research Department, University of Edinburgh

Kythin inhibits strus by producing pseudo-pregnancy conditions in the injected mice. The inhibition of strin can be obtained for a long period (40 days in some cases) without causing any permanent injury to the ovaries. Preliminary experiments show that the strus is prevented by the inhibition of strin-secretion from the ovary, whose reactivity to the strogenic stimulus of the pituitary is reduced (but not removed). The response of the vagina to strin is also slightly reduced. There is no "neutralisation" of strin by kythin. It is probable that the kythin also acts on the pituitary, inhibiting the secretion of the strogenic substance of the pituitary—a condition similar to that found during pregnancy.

The writer desires to acknowledge his indebtedness to Professor F. A. E. Crew and to Dr B. P. Wiesner for their kind criticism and help.