THE MENSTRUAL CYCLE 



way of proving that the ovarian hormones are the sole factors 

 involved is to exclude all other possible factors, but when 

 we cut off the estrogenic hormone, how can we know we are 

 not thereby putting some other factor into action? If some- 

 body could show us how to keep a coiled artery alive and 

 working outside the body where we could deal with it alone, 

 we could soon test this hypothesis, but the infant art of tissue 

 culture has by no means reached the point of keeping an 

 artery alive all by itself, and moreover these arteries are 

 so tiny that they would have to be handled under the micro- 

 scope — a truly difficult project! 



Hypothesis 2. This admits the possibility, mentioned 

 above, that withdrawal of estrogen permits something else 

 to go into action. We know that even in the non-menstruating 

 animals, withdrawal of the ovarian hormone causes a certain 

 amount of deterioration of some of the cells of the surface 

 epithelium and of the glands of the uterus. Under the micro- 

 scope we see fragmentation of the nuclei and the accumula- 

 tion of protoplasmic debris in the cell bodies. Is it possible 

 that some chemical substance produced in the course of 

 cellular breakdown (as histamine, for instance, is produced 

 in burned tissues) diffuses through the endometrium to the 

 arteries and causes them to contract? This hypothesis has 

 interested me very much and I have made many experiments 

 to test it, but always with negative results. 



Hypothesis S. Another conjecture, a variation upon the 

 foregoing, is that the uterine coiled arteries are sensitive, 

 when not protected by the ovarian hormones, to some sub- 

 stance that is normally present in the blood stream. We must 

 suppose that withdrawal of the hormone allows this substance 

 to act upon the arteries. One of the possible constrictor sub- 

 stances would be pituitrin, the secretion of the posterior lobe 

 of the pituitary gland, a hormone which is highly potent in 

 promoting contraction of smooth muscle. Carl G. Hartman 

 tried this with negative results, and moreover P. E. Smith 



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