430 THE FEMALE REPRODUCTIVE ORGANS 



term) the syncytium is found to have undergone a peculiar altera- 

 tion, having become much thinner, and having even completely 

 disappeared from considerable portions of the villi, it being re- 

 placed by canalized fibrin; at other points the syncytial cyto- 



FIG. 347. CHORIONIC VILLI FKOM THE HUMAN PLACENTA AT FULL TERM. 

 Heraatein and eosin. Photo, x 114. 



plasm is much thickened and the nuclei appear to be bunched or 

 grouped within the thickened portions; these areas are known 

 as cell-knots or 'proliferation islands. Here and there the degen- 

 erated cell-knots have been replaced by canalized fibrin. Wherever 

 the main stems are inserted into the decidua the epithelium which 

 formerly covered their tips appears to have also degenerated into 

 a peculiar hyaline border zone. 



Within its syncytium the substance of the villus consists of the 

 superficial cells of Langerhans with their large ovoid nuclei, and a 



