252 Vertebrate Embryology 



liver has now two courses open to it ; most of 

 it passes directly through the large meatus 

 venosus to the heart ; but a part passes, by- 

 way of the afferent hepatic vessels, into the 

 substance of the liver, to be collected and 



Fig. 77. — Diagram of the venous circula- 

 tion AT THE COMMENCEMENT OF THE FIFTH DAY. 

 (After Foster and Balfour.) 



yy, heart, d,r.^ ductus Cuvieri ; into the ductus Cuvieri of 

 each side fall y, the jugular vein, W^ the wing vein, and 

 c, the inferior cardinal vein. .?. K., sinus venosus. Cy", vitel- 

 line vein. U^ allantoic vein, which, at this stage, gives off 

 branches to the body-walls. y.C.I,^ inferior vena cava. /, 

 liver. 



brought back to the meatus venosus again by 

 the efferent hepatic vessels (Fig. ^f). 



The part of the meatus venosus in the liver 

 between the openings of the afferent and effer- 

 ent hepatic vessels is generally called the 

 ductus venosus. 



By the fourth day, the allantois has reached 

 a considerable size, and in it are developed 



