166 



Comparative Morphology of Chordates 



turned to the heart should go to the lungs. In dipnoan fishes and 

 amphibians the two kinds of blood are kept separate in the longi- 

 tudinally divided auricular part of the heart but mingle in the un- 

 divided ventricle. In the reptilian heart, as in the others, the systemic 

 venous blood is received by a right auricle and the blood from the 

 lungs by a left auricle, but the ventricle also is divided into right and 



Fir:. 359. (A) Dorsal view of heart of crocodile 

 (after Rose). (B) Ventral scheme of heart laid open 

 (after Greil). (b) Remnants of Botallo's duct; (c) 

 carotid trunk; (ca) celiac artery; (cv) cardinal vein; 

 (d) dorsal aorta; (fp) foramen Panizzae; (h) 

 coronary arteries; (j) jugular vein; (/) left aortic 

 arch; (la) left auricle; (h) left ventricle; (pa) 

 pulmonary artery; (pc) postcava; (pv) pulmonary 

 vein; (r) right aortic (fourth) arch; (ra) right 

 auricle; (rv) right ventricle; (si, sr) left and right 

 suhclavian arteries ; (v) ventricle. (Courtesy. Kings- 

 ley: "Comparative Anatomy of Vertebrates," 

 Philadelphia, The Blakiston Company.) 



left chambers (Fig. 359). The partition, however, is not complete 

 except in alligators and crocodiles. Because of its deficiency and certain 

 peculiarities in the arrangement of the main arteries that carry blood 

 from the heart, a certain amount of systemic blood, instead of going 

 to the lungs, passes into the general circulation (Fig. 73). In alligators 

 and crocodiles, too, the arterial outlets of the heart are so placed that, 

 in spite of the complete division of the ventricle into right and left 

 chambers, some blood from the right auricle passes into the dorsal 

 aorta. 



