166 



cular cells imniediately adjacent to the ectoplacenta. An endo- 

 vascular plasmodium is now formed by the ingrowth of. processes 

 of the ectoplacenta into the raaternal blood vessels. The original 

 endothelium is destroyed, and a new lining formed from the 

 plasmodium. The formation gradually advances into the blood 

 vessels in the deeper layers. During the final stage of placentation 

 the plasmodium covering the allantoic capillaries disappears, and 

 the vesicular cells undergo complete granular degeneration with 

 the exception of those in the 'couche vésiculeuse protectrice'. The 

 thickness of the maternal tissues is thus very considerably reduced, 

 while the foetal tissues in the allantoic region of the placenta 

 have been increasing in inverse ratio. 



Masquelin and Swaen, whose paper is not accompanied by any 

 figures, deal only with the incipient changes in the maternal 

 tissues. They mention the formation of the 'gaines périvasculaires' 

 and the disappearance of the cell-boundaries in the epithelium. 

 They describe further a process of blood formation in the dege- 

 nerating glands; they speak constanfcly of various bodies as being 

 'imprégnés d'hémoglobine', without, however, producingany evidence 

 of the existence of such a substance. 



Masius describes a differentiation of the 'fer-a-cheval placen- 

 taire' into cytoblast and plasmodiblast; he also saw the degene- 

 ration of the uterine epithelium. 



Strahl also saw a placental thickening composed of two layers, 

 a lower clear, and an upper dark; but while he recognised the 

 trophoblastic origin of the former, he believed the latter to be 

 derived from the uterine epithelium. As we shall see, this author 

 entertains similar views with regard to the maternal epithelium 

 in every mammalian placenta which he has investigated. 



Kossmann's short paper is not illustrated by any figures; he 

 too derives the syncytium of the placenta from the epithelium of 

 the uterus. Into his dogmatic generalisations it is unnecessary to 

 folio w him. 



Marchand described the 'gaines périvasculaires' and the dege- 

 neration of the uterine epithelium. He also recognised the exis- 



