478 



MANUAL OF ZOOLOGY 



. The right auricle receives the right and left pre-cavals 

 {r. pre, I. pre) and the post-caval (pte), the left, four large 

 pulmonary veins (p. v). The left ventricle (Fig. 288, /. vn), 

 as in the crocodile, gives origin to the right aortic arch 

 {a. ao), but the right ventricle (;-. vn) gives off only one 

 trunk, the pulmonary artery, which soon divides into two 



Fig. 288. — A, heart of the pigeon, dorsal aspect. a. ao, arch of aorta; b-r. a, 

 brachial artery; br. v, brachial vein; c. c, common carotid; pi, jugular; I. an, 

 left auricle; /. p. a, left pulmonary artery; /. vn, left ventricle; pc. v, left pre- 

 caval; pic, post-caval; p v, pulmonary veins; r. an. r. are', right auricle; r p a, 

 right pulmonary artery; r. pre, right pre-caval ; r. vn, right ventricle. B, heart 

 of a bird with the right ventricle opened L. V, septum ventriculorum; R. V, 

 right ventricle; V, right aurrculo-ventricular valve. (A, from Parker's Zootomy; 

 B, from Headley's Birds.) 



(r.p. a., I. p. a). The left aortic arch is absent in the adult, 

 and it is the right alone which is continued into the dorsal 

 aorta. The result of this is that the systemic arteries re- 

 ceive pure arterial blood from the left side of the heart, and 

 the only mingling of aerated and non-aerated blood is in the 



