200 Vertebrate Embryology 



large veins on each side of the body (Fig. 66, 

 J, C) \ these are the anterior and posterior 

 cardinal veins ; the anterior cardinals, as the 

 name would suggest, bringing the blood back 



LCA E.CA. 



I-JLX 





Fig. 6g. — Diagram of the arterial circula- 

 tion ON the third day. (After Foster and Bal- 

 four.) 



1, 2, 3, the first three pairs of aortic arches. A^ the vessel 

 formed by the junction of the three pairs of arches. A.O.^ 

 dorsal aorta, formed by the junction of the two branches, A . 

 it quickly divides into two branches, which pass down one on 

 each side of the notochord. 0/,A.^ vitelline artery. E.CA.^ 

 I.CA ., external and internal carotid arteries 



to the heart from head region, and the pos- 

 terior cardinals bringing it back from the 

 posterior end of the body. The anterior and 

 posterior cardinal veins of each side unite to 

 form a common vein that empties, at right 

 angles, into the sinus venosus (Figs. 66, dc, 



