\ 

 VII.] THE VEINS OF THE LIVER. 227 



DIAGRAM OF THE VENOUS CIRCULATION AT THE COMMENCE- 

 MENT OF THE FIFTH DAY. 



H. heart, d.c. ductus CuvierL 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. 

 &. 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. L liver. 



The hepatic circulation, which was commenced on 

 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) 

 carry blood away from the hepatic substance into the 

 ductus and are called vence revehentes. As a result of 

 this arrangement there is a choice of paths for the 

 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 venae advehentes and 



152 



