158 Regeneration 



the fertilized ovum comes in contact with the wall of 

 the uterus it calls forth a growth there, namely the 

 formation of the maternal placenta (decidua). This 

 author showed that the corpus luteum of the ovary gives 

 off a substance to the blood which alters the tissues in 

 the uterus in such a way that contact with any foreign 

 body induces this deciduoma formation. The case is of 

 interest since it indicates that the substance given off 

 by the corpus luteum does not induce growth directly, 

 but that it allows mechanical contact with a foreign body 

 to do so while without the intervention of the corpus 

 luteum substance no such effect of the mechanical stim- 

 ulus would be observable. The action of the substance 

 of the corpus luteum is independent of the nervous 

 system, since in a uterus which has been cut out and 

 retransplanted the same phenomenon can be observed. 

 Bouin and Ancel 1 have shown that the corpus luteum, 

 which in the case of pregnancy continues to exist for a 

 long time, is responsible for the changes in the mammary 

 gland in the first half of pregnancy, when an active 

 cell proliferation takes place in the gland. This process 

 can be interrupted by destroying the corpus luteum 

 artificially. During the second half of gravidity no 

 further cell proliferation takes place, but the cells begin 

 to secrete milk while during the period of cell prolifera- 

 tion such secretions do not occur. 



1 Quoted from M. Caullery, Les Probl&mes de la Sexualite, Paris, 1913, 

 p. 126. 



