52 



HUMAN ANATOMY. 



penetrate the placental septa as spirally directed channels of enlarged calibre bounded 

 by endothelial walls. After a shorter or longer course within the septa, the arterial 



Fig. 6i. 



Amnion 

 ^^5g^ — Chorion 



f^;i=^:— Stalk of villus 



Intervillous blood-spaces 



Section of larger villus 



Intervillous blood-spaces 



Maternal blood-vessel 



Maternal blood-space 



Maternal blood-vessel 



?',>|^ — Basal plate 



Torn surface at line of 

 separation 



Section r>f human placenta at end of pre.^ancy. X 12. The foetal blood-vessels have been injected ; the maternal 

 blood-spaces appear as clear areas surrounding the sections of the foetal villi. 



trunks open directly into the intervillous or intraplacental blood-spaces which are 

 limited by the chorion and the villi on the one side and by the septa and basal plate 



