A HORMONE FOR GESTATION 



In these everything was done as before, except the ovaries 

 were not removed. Parts of them were removed, or they were 

 cut in two, leaving their blood supply intact; in short, as 

 much interference and damage was produced as in the first 

 group, but in each case several corpora lutea were left in 

 place. In these rabbits, progestational proliferation of the 

 uterus occurred normally; and in six of the seven, normal 

 embryos were found when the rabbits were killed for study 

 on the 5th to the 8th day. 



To sharpen the results, and pin them directly to the 

 corpus luteum, I was luckily able to find seven rabbits in 

 which, when I explored them, the corpora lutea were found 

 to be grouped all together in one end of an ovary. When 

 this chanced to be the case, in either the right or the left 

 ovary, I could take out one ovary entirely and all the 

 grouped corpora lutea from the other, still leaving a large 

 amount of ovarian tissue. In all these, progestational pro- 

 liferation failed to occur and the embryos died. 



We have proved two points. First, we have shown that 

 successful care of the embryos in utero depends upon a chain 

 of events. The corpora lutea prepare the uterus, the uterus 

 then cares for the embryos. The reason, unknown to Fraenkel, 

 that his embryos died was that he had prevented Ancel and 

 Bouin's progestational proliferation, by removing the cor- 

 pora lutea. 



Second, we have found that the corpora lutea are necessary 

 not only for implantation (as indicated by Loeb's experi- 

 ment), but also still earlier, for the nutrition and protection 

 of the embryos during the time when they are lying free in 

 the uterus. How they do this is another question which will 

 be considered later; obviously it is a matter of chemical 

 substances secreted by the glands of the uterine lining under 

 the influence of the corpus luteum (Appendix II, note 4). 



If the corpus luteum can do these remarkable things by 

 hormone action, we ought to be able to get the hormone out 



{ in } 



