VII.] THE VEINS OF THE LIVER. 227 



Fig. 74. 



^f 1^ 





DiAGRAJI OF THE VeNOUS CIRCULATION AT THE COMMENCE- 

 MENT OF THE Fifth Day. 



M. heart, d.c. ductus Cuvieri. Into the ductus Cuvieri of each 

 side fall J. the jugular vein or superior cardinal vein, 

 W. the vein from the wing, and c. the inferior cardinal vein. 

 S. V. sinus venosus. Of. vitelline vein. U. allantoic vein, 

 which at this stage gives off branches to the body-walls. 

 V.C.I, vena cava inferior. I. liver. 



The hepatic circulation, which was commenced on 



7j the third day, becomes completely established. Those 



branches which come off from the ductus venosus soon 



after its entrance between the liver lobes carry blood 



into the substance of the liver and are called vence 



advehentes, while those which join the ductus venosus 



shortly before it leaves the liver (i.e. nearer the heart) 



I carry blood away from the hepatic substance in.to the 



ductus and are called ven(B revehentes. As a result of 



Ithis arrangement there is a choice of paths for the 



j blood in passing from the vitelline vein to the sinus 



venosus ; it may pass through the capillary net-work 



of the liver, going in by the venaB advehentes and 



152 



