THE HORMONES IN HUMAN REPRODUCTION 



embryos is a job for a grown-up uterus. Thereafter we used 

 only adult rabbits and never had another failure. Before we 

 published the method one of our laboratory technicians made 

 a lot of the extract unassisted and it worked. 



Meanwhile the Wisconsin workers, Hisaw and his col- 

 leagues, had found that their extracts that relaxed the guinea 

 pig's pelvic bones would not work in infant guinea pigs unless 

 the animal was first "primed" with estrogenic hormone. Fol- 

 lowing up this clue, Allen learned that if we make the infant 

 uterus grow larger by a few days' treatment with an estro- 

 gen, it will then respond fully to progesterone. A very striking 

 experiment illustrating this is shown in Plate XVIII, E, An 

 infant rabbit has, of course, a very small uterus. After 5 days' 

 treatment with estrogenic hormone, the uterus becomes large 

 and well differentiated. If progesterone is then given for 5 

 days, the uterus shows full progestational proliferation like 

 that of an adult in early pregnancy. Meanwhile the rabbit 

 herself remains a baby small enough to hold on the palm of 

 one's hand. 



By what means does progesterone affect the uterus? Just 

 how the various hormones exert their action upon the organs 

 which they control is very obscure. About the action of pro- 

 gesterone we have at present only a very remote idea. We 

 can guess that in some way the hormone alters the general 

 nutritional state of the cells of the uterus by way of a change 

 in their metabolic rate or some other deep-seated effect on 

 cellular physiology. 



What happens to progesterone after it acts? In 1936 a 

 discovery of great importance was made by Ethel H. Venning 

 and J. S. V. Browne of Montreal. This is that in the human 

 body used-up progesterone is converted into another sub- 

 stance called pregnanediol (preg-nane-di-ol). The conversion 

 takes place by the addition of six atoms of hydrogen. I give 

 the chemical formula for those who are interested: 



{ 120 } 



