THE HORMONES IN HUMAN REPRODUCTION 



vagina undergo rapid reduction in size. In the rabbit, in which 

 the phenomenon has been quite fully studied, the uterus loses 

 half its weight in two or three weeks and its tissues become thin 

 and flabby (Plate XIV). This atrophy of the uterus produced 

 by castration of the adult female is obviously just the reverse 

 of what happens at the time of puberty, when the ovaries first 

 become mature. The uterus and the other accessory repro- 

 ductive organs (oviducts, vagina and mammary glands) 

 which in infancy are small and undeveloped, grow to adult size 

 when the ovaries begin to function. Both pubertal growth and 

 castrate atrophy indicate clearly that the adult uterus is 

 dependent upon the ovary. 



It is difliicult to realize that less than fifty years ago nobody 

 could guess how this action of the ovary upon the uterus is 

 produced. Some thought that castrate atrophy was due to 

 interference with the blood supply of the uterus when the 

 ovaries were removed, others thought the nerve connections 

 were upset. 



A Hormone of the Ovary? 



The first step toward demonstrating the endocrine function 

 of the ovary was taken in 1896 by Emil Knauer of Vienna, 

 who took out the ovaries of guinea pigs and grafted pieces 

 of them back into the same animals, at new sites. He demon- 

 strated that such grafted ovaries prevent the occurrence of 

 castrate atrophy. It must be, then, that the ovary makes some 

 sort of chemical substance which acts upon the uterus. This 

 is lost when the ovaries are removed, but again becomes avail- 

 able if the ovary is successfully regrafted, no matter where, 

 in the animal's body. 



In 1900 Knauer definitely suggested this idea of an internal 

 secretion of the ovary. In the same year Josef Halban, also 

 of Vienna, took three infantile guinea pigs, grafted bits of 

 adult ovaries of the same species under their skin, and found 

 that their uteri promptly grew to adult size. On the basis of 



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