70 LEO LOEB. 



Our observations are also of interest from another point of 

 view. We know that under ordinary circumstances the corpus 

 luteum remains longer preserved in pregnancy than in the non 

 pregnant animal. Pregnancy prolongs the sexual cycle. We 

 may now inquire into the cause of the prolongation of the life 

 of the corpus luteum during pregnancy. Several years ago I 

 pointed out, that the growth of the embryo might perhaps directly 

 or indirectly prolong the life of the corpus luteum during preg- 

 nancy.^ 



Now we find in our case a small embryo as well as an embryonal 

 placenta developing outside the uterus. Notwithstanding this 

 fact a new ovulation had taken place about three days pre- 

 viously and accordingly the corpora lutea of the preceding 

 sexual cycle which had been terminated at the time of the last 

 ovulation were degenerated. 



This observation proves that a developing embryo including 

 embryonal placenta is in itself, not sufficient to protect the corpus 

 luteum from degeneration, and to prevent a new ovulation. It 

 is possible that the maternal placenta is concerned in the pro- 

 longation of the life of the corpus luteum either alone or in con- 

 nection with the embryo, which latter as our further experiments 

 have shown, prolongs noticeably the life of the experimental 

 placentomata (deciduomata). Indeed experiments which I 

 carried out some time ago have shown that the development of 

 deciduomata without the development of an embryo is able to 

 prolong the sexual period ; while normally the sexual cycle in the 

 guinea pig has a duration of from 15 to 18 days, it lasts from 20-30 

 days after production of deciduomata. ^ Whether as a result of 

 these experimental interferences also the life of the corpus luteum 

 is prolonged will have to be still further investigated. 



Our observations are furthermore of significance for the inter- 

 pretation of certain structures, which I found in about 5 per cent, 

 of the ovaries of young guinea pigs.^ 



In as much as these structures become absorbed after a certain 

 time and are substituted by connective tissue, these structures 



1 Zentralblatt f. Physiol., Bd. XXIV., Nr. 6; Medical Record, June 25, 1910. 



2 Leo Loeb, Biological Bulletin, Vol. XXVIL, July, 1914. 



^ Arch. f. mikrosk. Anatomie, Bd. 65, 1905; Roux's Archiv, Bd. XXXIL, p. 662, 

 1911; Zeitschrifl f. Krehsforschung, 11. Band; 2. Heft, 1912. 



