161 



duits destinés au sang maternal, les deux ou trois plus volu- 

 miueux qui occupeut Ie ceutre du placenta sont les voies de la 

 circulation eu retour'. This assertion is all the more surprising, 

 cousidering that he has described in other Rodents, and in Car- 

 nivora, an arrangement of placental arteries and veins which 

 corresponds precisely with what I have observed in the mouse. 

 I can only suppose that he has been misled by the union of the 

 venous channels at the root of the mesometrium. 



These disagreements are, however, slight in comparison with 

 the divergence of opinion which I am sorry to say exists between 

 us respecting the complicated changes which take place on the 

 maternal side of the placenta, during the second and third periods. 



My own view, as put forward in the first part of this paper, 

 is that the subepithelial tissue in the placental region, consisting 

 very largely of glycogenic cells, undergoes complete degeneration, 

 and is replaced by a tissue, also glycogenic, but of trophoblastic 

 origin which gradually encroaches on the space once occupied by 

 the former, and engulfs the maternal blood vessels situated there; 

 and I have called attention to the great complexity of the tissue 

 which results, a complexity due to the facts that processes of the 

 glycogenic trophoblast dip down into the lower allantoic portion 

 of the placenta, that certain patches of trophoblast never become 

 glycogenic, and that, on the extreme upper side, there is a most 

 perplexing intermingling of this glycogenic tissue with the débris 

 of maternal cells. 



Now in the first place Duval has not explicitly described the 

 maternal glycogen cells at all. His figures (Figs. 133, 135) of 

 the subepithelial tissue show only fusiform and stellate cells 

 scattered in a homogeneous matrix, and are certainly very unlike 

 what my preparations show. It is true that he says they tend 

 to become vesicular and figures (Fig. 138) a few somewhat rounded 

 cells attached to the upper border of the trophoblast and to the 

 endothelium of a maternal blood vessel. 



In the second place he has not described or figured any dege- 

 neration of these cells, but apparently believes them to become 



