FCETAL NUTRITION: THE PLACENTA 409 



chorion, and fit into vascular crypts in the uterine mucosa 

 from which they are easily retracted at birth. The epithehum 



■§3 



^ 



+3 n-5 



-a & 



f-i o 



-^ pi 





2 ^ 



o .i3 



^ Q ;3 



.O ■ o 



■a ^ » 



f .2 



:a -5 



- O 

 in 



n =« 



'a a 



o ^ 



to 5 



II 



.- p< 



of the crypts persists as in the cow, and the " osmotic inter- 

 change takes place through two cell-layers of difierent origin, 

 and of different physiological significance (phylogeneticaUy). 



