THE HORMONES IN HUMAN REPRODUCTION 



rally there is no corpus luteum and therefore no premenstrual 

 change in the uterus. Menstruation occurs anyway, and the 

 breakdown takes place in an endometrium which is still in 

 the unaltered state. The corpus luteum is necessary for the 

 premenstrual state, but not necessary for the breakdown. 



This analysis of the situation has been confirmed by 

 Markee through watching menstruation in endometrium 

 grafted in the eye. Markee tells us that when he applies the 

 microscope to the grafts he sees only one difference between 

 ovulatory and anovulatory menstruation, namely the oc- 

 currence of the progestational phase in the former and its 

 absence in the latter. The shutting off of the blood supply, 

 the subsequent reflux of blood through the coiled arteries, 

 the rupture of the small vessels and the hemorrhage are the 

 same in both instances. With all this evidence it can hardly 

 be doubted that anovulatory bleeding is also menstruation. 



It is not possible to distinguish between ovulatory and 

 anovulatory menstruation by ordinary observation of the 

 living animals. The cycles are of similar length, the bleeding 

 is similar in appearance and duration. Recent studies by 

 Ines de Allende and Ephraim Shorr suggest that it may be 

 possible in the future to detect anovulatory cycles by study- 

 ing the vaginal cells. 



My description of menstrual cycles without ovulation was 

 at first rather generally mistrusted, but it has been confirmed 

 by everyone who has studied the Rhesus monkey.^ We know 

 that anovulatory cycles are likely to occur in young animals 

 in the first months after the establishment of menstruation, 

 and in fully mature females in the early fall and late spring, 

 that is to say at the beginning and end of the active breeding 

 season of the winter months. Rhesus monkeys do not men- 

 struate regularly in summer. The anovulatory cycles tend 



7 Carl G. Hartman, "Studies in the reproduction of the monkey, 

 Macacus (Pithecus) rhesus." Carnegie Institution of Washington, Pub- 

 lication No. 433 {Contributions to Embryology, vol. 23), pp. 1-161, 1932. 



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