262 



PHYSIOLOGY 



CHAP. 



work extending over the surface of the umbilical vesicle (omphalo- 

 mesenteric circulation (Fig. 114)); the second circulation occurs 



FIG. 114. Omphalo-mesenteric circulation. 1, omphalo-mesenteric artery ; 2, embryo ; 

 3, omphalo-mesenteric vein ; 4, umbilical vesicle. 



Fio. 115. Allantoid or chorionic circulation. (Schematic.) 1, aorta; 2, allantois (abdominal 

 peduncle) ; 3, chorionic villi ; 4, embryo ; 5, heart ; 6, umbilical vesicle with impervious 

 vessels. 



between the heart of the foetus and its vessels, which have 

 almost acquired their final form, and extends to the great vascular 

 network which supplies the placenta (car dio-pla cental circulation 

 or allantoid vesicular circulation (Fig. 115)). 



