FCETAL NUTRITION: THE PLACENTA 475 



first month they are fewer in number than over the serotina 

 (Kastschenko l ). 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 foetal 



'e.g. 



p.s. 

 -all. 



-Ent. 





FIG. 127. Median longitudinal section of an embryo of 2 mm. (von Spec). 

 (From Quain's Anatomy, Longmans.) 



v., villus ; c.v., core of villus; mes., mesoderm ; c.s., connecting stalk; p.s., 

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

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



part of the placenta, which is essentially a mass of foetal villi 

 between 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). 



1 Kastschenko, " Das menschliche Chorionepithel und desscn Rolle bei 

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



