FCETAL NUTRITION: THE PLACENTA 475 



first montli they are fewer in number than over the serotina 

 (Kastschenko ^). When the blood-supply to the reflexa is re- 

 duced, the villi in relation to it degenerate, and are compressed 

 between the chorion and the apposed decidua reflexa and vera. 

 Over the serotina they continue to branch and form the fcetal 



Fig. 127. — Median longitudinal section of an embryo of 2 mm. (von Spee). 

 (From Quain's Anatomy, Longmans.) 



f., viUus ; C.V., core of villus; me«., mesoderm ; c.«., connecting stalk; p.s., 

 primitive streak; all., allantois ; y.a., yolk-sac; Ent., entoderm; ves., 

 vessels; h., heart ; n.p., notochordal plate ; a., amnion. 



part of the placenta, which is essentially a mass of fcetal viUi 



hetween which maternal blood circulates. By the " Haftzotten " 



the spongy mass is attached to the decidual surface. The 



attached ends may excavate the decidua to some extent, but 



there is no great degree of penetration (Fig. 128). 



' Kastschenko, " Das menschliche Chorionepithel nnd dessen Eolle bei 

 der Histogenese des Placenta," Arch. f. Anat. u. Phys., anat. Abth., 1885. 



