Vertehrata. 



347 



Pig. 286. Diagrams of the arterial arches of various Vertehrata. A emhryonic 

 condition, B Fish, C Urodele, D Eeptile (Lizard) , M Bird, F Mammal. 

 The atrophied vessels are represented by dotted hnes. Ic and li the two first embryonic 

 arches which almost entirely atrophy. 1 — 4 the four posterior arches. 1' and 3' the first 

 and third afferent branchial arteries, 1" and 3" efferent branchial arteries. 2 in D and F 

 second left arches, 2' in D, .B and F second right arches, a, b, r, vessels into which the 

 ventral aorta is divided in Eeptiles, Birds, and Mammals, ao aorta, ca carotid, j) pulmonary 

 artery, s (in F) artery of left limb, s (in B) and si ventral aorta. — Orig. 



