34 



ANIMAL BIOLOGY. 



[Parti. 



the stomach and intestines. The dorsal aorta passes back- 

 wards beneath the back-bone, and becomes posteriorly the 

 caudal artery. The circulus cephalicus formed by the epi- 

 branchials and transverse vessel is shown very diagram atically 

 in Fig. 14, which must be taken to indicate the principle of the 

 arrangement of the vessels. 



The sinus venosus receives the blood that has circulated 

 through the body. At its posterior end it receives the two 



f.W ac v , 



FIG. 14. DIAGRAM OF HEART AND GREAT VESSELS : COD. 



hepatic veins (he. v.) from the liver. Dorsal to these, there enter 

 two large veins running downwards on either side of the gullet. 

 They are the ductus Cuvieri (d. c. ). Each results from the union at 

 its dorsal end of two factors ; an anterior factor (anterior cardinal, 

 a. c. v.) bringing blood from the head, and a posterior factor 

 (posterior cardinal) p. c. v.) bringing blood from the posterior 

 regions. The right posterior cardinal is continuous through the 

 substance of the kidney, but the left is aborted for some dis- 

 tance. Posteriorly the two cardinals unite in the caudal vein, 

 which, with the caudal artery, runs in a canal (the hcemal arch) 

 protected by bony (haemal) processes of the vertebrae. The right 

 ductus Cuvieri, slightly above the sinus venosus, receives a vein 



