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.) 



ff, heart, */.r., ductus Cuvieri ; into the ductus Cuyieri of 

 each side fall _/, the jugular vein, ]V^ the wing vein, and 

 c, the inferior cardinal vein. S.V., sinus venosus. Of, vitel- 

 line vein. /, allantoic vein, which, at this stage, gives off 

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

 liver. 



brought back to the meatus venosus again by 

 the efferent hepatic vessels (Fig. 77). 



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 



