THE CLASS BIRDS. 



331 



al 



Fig. 316. Arterial System of a Bird.* The Grebe, Colymbus a Diver. 



* Arteries of the Grebe : a, aorta ; am, one of its large branches : it gives 

 off the carotid (ac) and subclavian, is ultimately distributed to the muscles 

 of the chest, and corresponds to the mammary arteries of mammals ; av, one 

 of the branches of the vertebral artery supplying the muscles of the shoulder; 

 ee, arterial loops formed by the branches of the external carotid ; al, lingual 

 artery; t, trachea or windpipe j; ar, renal arteries ; az, ischiatic artery, pro- 

 ceeding to the lower extremities ; as, sacral artery, forming a c o ntinuation 

 of the aorta, and giving origin to the inferior mesenteric artery, &c. j cl, the 

 cloaca. 



