THE MENSTRUAL CYCLE 



Progesterone preventa 

 eetrin-deprivaLLion bleeding: 



ovAT?ie0 present /pros-e^lLn ^ 

 eslriti^iven ic ^iven V 



-^ — X X. X X 



withcLrdLWTn. — ^ , , t ^ 

 \ "nobleedm^ 



I NTACT CA5^RATE 



\ 



o bleeding N \^ 



v^7^ r JS^ 



CA5TRATE V^^ >^ 



Fio. 26. The upper figure illustrates the experiments of Smith and 

 Engle, 1932, and Engle, Smith and Shelesnyak, 1935. The lower figure 

 represents the results of Hisaw, 1935, and Corner, 1938. Estrin-depriva- 

 tion bleeding is postponed by progesterone; discontinuance of proges- 

 terone is then followed by bleeding. 



the hormone was purposely stopped at a time which would 

 have been midway between two periods (had the latter been 

 occurring on their original schedule) progesterone-depriva- 

 tion bleeding then occurred within a few days. The monkey 

 next menstruated spontaneously about 4 weeks after the 

 experimental period. This tells us that the monkey's time- 

 piece mechanism accepts progesterone-deprivation bleeding 

 as if it were actual menstruation, and takes a fresh start 

 from the induced period. 



The diagram (Fig. 26) illustrates these facts. 



At this point Dr. Markee may be called again as a witness. 

 He tells us that when bleeding is produced in one of his 



i 165 } 



