THE CLASS BIRDS. 



301 



al 



Fig. 250. Arterial System of a Bird.* 



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

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

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

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

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

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

 ceeding to the lower extremities ; as, sacral artery, forming a continuation 

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

 cloaca. 



