THE HORMONES IN HUMAN REPRODUCTION 



of cycles and unpredictable variations make it much less 

 than certain.* 



Role of the blood vessels of the uterus in menstruation. 

 Within the past few years a good deal has been learned 

 about what actually happens to produce the menstrual break- 

 down. Much of this advance we owe to G. W. Bartelmez of 

 the University of Chicago, and to his former associate, 

 J. E. Markee, now of Duke University. To make it clear we 

 must first understand the arterial blood circulation of the 

 lining of the uterus. The endometrium is fed by arteries which 

 come up into it from the underlying muscle (Fig. 23). These 

 have branches of two kinds. Those of one kind are very 

 pecuhar, for they are wound into coils, making their ex- 

 tremely tortuous way toward the surface, where they break 



Fig. 23. Diagram of the arteries of the uterus, from the description of 

 Daron. Enlarged about 20 times. 



* Carl G. Hartman, Time of Ovulation in Women. Baltimore, 1936. 



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