376 



The deeper layer of the chorionic epithelium consists of distinct cells 

 with round nuclei and clear protoplasm. Although this is a single layer 

 at the base of young villi, it produces great masses of cells at their tips. 

 These columns or caps of cells in which the villi terminate fuse with one 



-Syncytium. 



Cuboidal cells of the 

 basal layer. 



Connective tissue. 



Blood vessel containing 

 nucleated red cor- 

 puscles. 



Oblique section of the epithelium. 

 FIG. 376. CROSS SECTION OF A HUMAN CHORIONIC VILLUS OF THE FOURTH WEEK OF PREGNANCY. 



Epithelium. 



Epithelial nucleus- 



Capillaries ? - - - - 



Sy ncy tial knot. -. 



Small artery. 



Syncytial knot 



-Epithelium. 



Syncytial knot. 



FIG. 377. CROSS SECTION THROUGH A SMALLER (A) AND A LARGER (B) CHORIONIC VILLUS OF A HUMAN 

 PLACENTA AT THE END OF PREGNANCY. Xaso. (Schaper.) 



another next the decidua, and the uterine tissue seems to be dissolved as 

 this mass of epithelium proliferates. All the superficial epithelium of the 

 decidua basalis degenerates and disappears, and the underlying parts of 

 the blood vessels in the tunica propria are destroyed. The uterine blood 



