THE MENSTRUAL CYCLE 



mere lowering of estrogen dosage below a certain level will 

 produce the bleeding. The word "deprivation," as used in 

 this connection, is therefore to be taken in a relative sense. 



Estrin- deprivation hijpothjesia: 



INTACT ANH^MAL / 



*; ^ >^ 



Teat of the hijpothesia: 



__ est Trm_siyerv2r 

 INTACT ^"^ ^/__ "^ \ no bleeding 



- ^ ^^,5 J- ^ - -^ ^ X Xr-X X X K 



Fio. 25. In the lower figure the natural level of estrogen is shown 

 fluctuating cyclically, not as a proved fact, but to show how the actual 

 results of injecting the ovarian hormone bear on the estrin-deprivation 

 theory. 



The correctness of the estrin-deprivation h3^othesis can 

 be tested in a very simple way. We need only choose a monkey 

 that is menstruating regularly, and keep up her estrogen 

 level by injecting the hormone, for say ten days before the 

 expected menstrual period. This should prevent menstruation. 

 I tried this in a sufficient number of monkeys, giving them 

 doses of estrogen I thought similar to their own natural 

 supply from their ovaries. Later in the experiments these 

 doses were increased several fold. The hormone did not stop 

 the next menstrual period. If the treatment was continued 

 into later cycles, menstruation was often delayed, perhaps 

 because of roundabout action through the pituitary gland. 

 Zondek has found that in women very large doses of estro- 

 genic hormone disturb the menstrual cycle, owing to inhibi- 



{ 163 } 



