THE HORMONES IN HUMAN REPRODUCTION 



corpora lutea, then he got no placenta-like tumors. In short, 

 when the corpora lutea are present, the uterus is in a special 

 state in which it can respond to the need of the embryos for 

 maternal protection. 



Reviewing the story, we see that Fraenkel demonstrated 

 that the implantation of the embryos depends upon the 

 corpus luteum, while Ancel and Bouin had shown by one 

 experiment, and Loeb by another, that the functional state 

 of the uterus depends upon this same gland. We cannot 

 escape the conclusion that these two facts are connected; 

 in other words, that the corpus luteum fosters the embryos 

 by setting up progestational proliferation. No doubt this 

 would have been proved very promptly had not the World 

 War of 1914-1918 interfered with such investigation. 



It fell to my own lot (in 1928) to conduct the experiments 

 which tied together the discoveries of Fraenkel and of Bouin 

 and Ancel, by showing exactly what happens, and when, 

 to embryos deprived of the support normally afforded them 

 by the corpus luteum. In the first of my experiments I mated 

 seven female rabbits to fertile males. Fourteen to eighteen 

 hours thereafter the ovaries were removed by surgical opera- 

 tion under complete anesthesia. At this time, as we know 

 from previous studies by embryologists, the eggs were in 

 the 2-cell stage and were in the oviducts. Five, six, or seven 

 days thereafter the animals were killed and examined. Proges- 

 tational proliferation had of course not occurred, because 

 the corpora lutea had been removed. When the embryos were 

 recovered, by washing them out of the uterus, it was found 

 that they had died in utero. From their measurements and 

 stage of development, as compared with normal embryos 

 (Plate XVIII, B, A), it could be ascertained that they had 

 ceased to grow on the fourth day, i.e. as soon as they had 

 entered the uterus. These embryos died because the uterus 

 was unprepared to receive them. 



A control experiment was done with seven more rabbits. 



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