396 THE CORPUS LUTEUM OF DASYmUS, 



.secretion wliose function vvas to prepare the uterus for the recep- 

 tion of the egg, and to give the impulse to the organismal changes 

 accompanying pregnancy, they performed certain experiments, 

 suggested by the following considerations : — 



(1) That the ovum cannot itself produce the changes in the 



organism, for these iDegin even before the ovum reaches the 

 uterus. 



(2) In ectopic gestation the uterus undergoes the usual changes, 



although the ovum is in the tube. 



(3) If the ovum reaches the uterus, its growth alone does not 



explain the great increase in size of the uterus, and there 

 must be some other factor at work. 



The corpus luteum was thought to be this factor, because it is 

 a large structure whose function is not evident, and w^iich is 

 remarkably constant throughout the manniialian order. These 

 observers then, as an additional reason, say that Aplacentalia, 

 such as Monotremes and Marsupials, whose ova develop outside 

 the uterus (sic) possess only a rudimentary corpus lutem, or none 

 at all. This is erroneous. Both these classes of animals have a 

 large corpus luteum, consequently this reason carries no weight. 



By their experiments they claim to have shown that, in the 

 rabbit, destruction of the corpora lutea prevented the ovum from 

 being retained in the uterus, and that the presence of the corpus 

 luteum has some influence on this retention. Their work is not 

 concluded, but promises to throw some new light on the function 

 of the corpus luteum. 



Some may object that these arguments lose weight in the case 

 of the false corpora lutea and the corpora lutea atretica. But a 

 similar, though modified, explanation may be considered to hold 

 good in these cases. The ovary, in the case of the false corpus 

 luteum, does not concern itself with the fate of the ovum. The 

 absence of fertilisation can be considered to be an accidental 

 failure of Nature's intention. The corpus luteum forms in just 

 the same way, and with the same effect of staying ovulation until 

 it atrophies, and possibly M-ith the intention of preparing the 

 genitalia and the organism generally for the changes which would 



