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Scientific Proceedings (132) 



Two phases can be distinguished in the sexual cycle; the first 

 phase is dominated by an ovarian factor other than the corpus 

 luteum, in all probability by the maturing follicles the wall of 

 which secretes a substance which causes various kinds of circu- 

 latory changes and growth processes and in addition certain 

 psychical alterations. Proliferation, under the influence of this 

 substance, occurs in the mammary gland, in the vagina and also 

 in the uterine wall; this substance calls forth changes in the 

 ovary which culminate in ovulation. 



These growth processes usually cease in the vagina suddenly 

 with the appearance of oestrus, while in the mammary gland they 

 may continue for a short time longer. 



Ovulation leads to the formation of the corpus luteum. The 

 second phase of the sexual cycle is dominated by a substance 

 or substances given off by the corpus luteum. This substance or 

 these substances sensitize the uterus, making possible the pro- 

 duction of decidua or of placentomata, or the normal predecidual 

 proliferation and facilitating the fixation and development of 

 the fertilized ovum; they cause growth processes in the mam- 

 mary gland and prevent procestrus, oestrus and ovulation; the 

 corpus luteum on the other hand does not prevent the maturation 

 of follicles, at least in rodents. The corpus luteum substance 

 is without a direct effect on vagina, tube or other connective tis- 

 sue or epithelial structures of the guinea pig. This substance 

 or these substances act on different tissues at different periods 

 of the sexual cycle. The sensitization of the uterine wall is 

 limited to the first half of the life of the corpus luteum. The 

 growth of the mammary gland occurs in the rabbit during the 

 whole period of the life of the corpus luteum; in the guinea pig 

 it begins about on the sixteenth day of the cycle. The substance 

 inhibiting the effects of the maturing follicle acts throughout the 

 whole period of the preservation of the corpus luteum. When 

 degenerative changes occur in the corpus luteum, this function 

 ceases. 



Between these two phases, the first phase probably dominated 

 by the maturing follicle and the second, the lutein phase, there 

 may be a short intermission during which the first substance has 

 ceased to act and the second substance has not yet been pro- 

 duced in sufficient quantity to be effective. Certain degenerative 

 processes may occur during this intermission, caused probably 



