THE HORMONES IN HUMAN REPRODUCTION 



are about to rupture, the process of cornification of the 

 vaginal wall is very active, and cornified cells are shed in 

 thousands, yielding thick caseous scrapings that can be iden- 

 tified without a microscope. The next day the leucocytes come 

 back (E), the masses of cornified cells disintegrate, and the 

 interval picture reappears. In sexually mature rats and mice 

 this change repeats itself every 5 days, in guinea pigs every 

 15 days. 



Vaginal cycles in other animals. If such clear-cut vaginal 

 changes occurred in all mammals, it would be of great advan- 

 tage in studying their cycles. If they occurred in women, it 

 would be of priceless value to gynecologists, especially in the 

 serious business of diagnosing the cause of sterility. At pres- 

 ent we have no certain way of finding out whether a woman is 

 ovulating or not, except by operative exploration. Unfor- 

 tunately, the vaginal changes are far less clear than in the 

 small rodents. Extreme differences, such as that between 

 normal activity of the ovary on one hand and total inactivity 

 on the other, can be detected, but such changes as occur from 

 day to day in the cycle are faint. The latest word thus 

 far is in volume 31 of our Carnegie Contributions to 

 Embryology, recounting studies made on human patients by 

 Ephraim Shorr of Cornell Medical College and observations 

 of the Rhesus monkey made in the Department of Embryology 

 of the Carnegie Institution by Ines de AUende in consultation 

 with Carl G. Hartman. Dr. de Allende was generally able to 

 diagnose the occurrence or nonoccurrence of ovulation in 

 monkeys, as confirmed by surgical exploration. It seems not 

 improbable that by refining the study of vaginal cells it may 

 ultimately be possible to diagnose ovulation in humans. 



The cause of the cycle. Some day no doubt we shall under- 

 stand the whole mechanism of the ovarian rhythm, and know 

 why and how the cycle is short or long in various animals and 

 why its manifestations vary in so many ways. At present we 

 can do hardly more than guess. We think the alternations of 



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