Allen and D oisy (1) induced a prolonged cestrus by continuing to inject liquor folliculi for several consecutive days. They made similar experiments with extracts of follicular fluid; the characteristic cornification of the vaginal mucosa continued for 41 days. Frank, Kingery and Gustavson(2) record having maintained a positive vaginal smear in immature rats for from 8 to 9 days, by continuing the injections.The statements of Allen and Doisy are of a great theoretical interest in connection with the problem of the mechanism of the sexual rhythm. If it can be demonstrated that the somatic substratum of the cestral phenomena is capable of reacting continuously to a continuous injection of ovarian hormones, then it is clear that the sexual rhythm repeats an ovarian rhythm; if, on the contrary, the somatic substratum reacts discontinuously though ovarian hormones are continuously present, then one must conclude that the sexual rhythm depends upon changes in the sensitiveness of the tissues. Brouha and S imonnet(3 repeated the experiments of Allen and D oisy with special reference to the question here discussed. According to them, rats injected during 30 days with follicular extracts reveal indeed a prolonged cestrus; but the latter lasts only 4 to 5 days and then a dicestral phase of 1 to 2 days takes place. Allen and D oisy(1) also stated that in several experiments in which by repeated injections the cestrus was extended, a leucocytic infiltration was present in the smears. But they interpreted this as caused by a "discontinuous action of the hormones due to difficulty in making the injections serve continuously as does the secretion of the normal follicles during the growth phase of the cycle." Further observations by others corroborate the view taken by Allen and D oisy. These authorities drew a parallel between their experiments and the condition in which a cystically degenerate follicle maintains the cestrus, probably by continuous secretion of the follicular hormone. The cases of " nymphomania" in the cow are well known; similar conditions were observed by