342 THE PHYSIOLOGY OF REPRODUCTION 



without injuring the entire organ. The ovaries during pregnancy 

 consist very largely of corpora lutea, and any attempt in a 

 relatively small animal to discriminate between luteal tissue 

 and stroma, while the ovary was lying in its normal position in 

 the body cavity, seemed in our judgment to be impracticable. 



It will be seen that our experiments on the results of ovari- 

 otomy during pregnancy fully confirm those of Fraenkel. It 

 must be pointed out, however, that there is no evidence that the 

 corpus luteum governs the fixation of the embryo in any other 

 than the indirect sense implied in the supposition that the 

 secretion elaborated by that organ acts as a stimulus which excites 

 the uterine mucosa to undergo the necessary hypertrophy. 

 In this general sense, also, it is probably true that the luteal 

 secretion (or, at any rate, the secretion of the ovary) assists in 

 nourishing the embryo during the first stages of pregnancy, 

 since there is every reason for concluding that it helps to 

 maintain the raised nutrition of the uterus. It has been shown 

 that the presence of the ovaries is not essential for the con- 

 tinuance of pregnancy in the later stages, when the corpora 

 lutea are in process of degeneration. It would seem not un- 

 likely, therefore, that the atrophic changes (fibrosis) which 

 take place in the decidua serotina, or maternal placenta, in the 

 later part of the gestation period are directly correlated with the 

 degeneration of the corpus luteum. 1 



Cases have been recorded by Essen-Moller, 2 Graefe, 3 and 

 Flatau, 4 in which pregnancy was not interrupted by double 

 ovariotomy in women when performed in the early stages of 

 pregnancy. These cases are undoubtedly very exceptional, 

 and it seems legitimate to conclude that a small portion of an 

 ovary, probably containing luteal tissue, was left behind acci- 



1 It has been suggested that the corpus luteum contributes an essential 

 factor in the nourishment of the embryo through the trophoblast, and that 

 it consequently ceases to be functional in the later part of pregnancy when 

 the trophoblast is superseded by the allantoic placenta. See Andrews, 

 loc. cit. 



2 Essen-Moller, " Doppelseitige Ovariotomie im Anfange der Schwanger- 

 schaft," Central./. Oyndk , vol. xxviii., 1904. 



3 Graefe, "Zur Ovariotomie in der Schwangerschaft," Zeitechr.f. Oeb. u. 

 Gyndk., vol. Ivi.. 1905. 



* Flatau, " Ueber Ovariotomie wahrend der Schwangerschaft," Arch. f. 

 Oyndk., vol. l.xxxii., 1907. 



