496 



THE PHYSIOLOGY OF REPRODUCTION 



strands of tiophoblast as iiitti the spaces lietM^een them. Latei- still, 

 mesohlastic processes penetrate into the cellular lnuls and comp)lete 

 the vascidar chorionic villi. 



Round the blastodermic \'esicle is a zone of degenerated tissue, 

 the " 1 )etrituszone " (Fig. 151). It is uncertain wliether it is formed 



^ ^ • . « , • 





"4 . "' »■» 



- rh'c 



Fiii. l.jO. — Section of a portion of the wall of tlie human l3lastocy.st. 

 (Bryce and Teacher.) 



ci/t., Cyto-trophoblast ; (fo-., decidua ; e/n/.^ endothelium of maternal capillary 

 p/., Plasmodium ; ?!;., necrotic zone of decidua. 



by the influerice of the trophoblast or maternal elements. At its 

 innei- edge, and within its spaces, are numerous large mononuclear 

 cells \vhieli ai-e " more likely maternal " (Biyce and Teacher). Peters 

 also mentioned the presence of many large cells, and compared them 

 to the deciduofracts of the hedgehog. Y. Heukelom described the 

 cellular laj'er outside the sync}'tium as fcetal, and derived from 

 Langhans' layer.^ Whate^'er their origin, the mononuclear cells in 



' Much uncertainty still exists regarding the origin of these large cells in 

 man and other animals. In the mouse, Duval and Sobotta consider them fcetal, 



