312 



SYSTEMATIC ZOOLOGY. 



purplish red. In its passage through the gills it rids itself 

 of one kind of waste (carbon dioxide) and absorbs oxygen 

 from the water. This exchange is accompanied by a 

 A BCD 



_ EC 



i 



H 



FIG. 117. Diagram of the arterial arches and their modifications in various 

 vertebrates (after Boas). The primitive arches are outlined; those which 

 are functional in the adult are black. A, embryonic condition; B, Ceratodus 

 (fish); C, Salamandra; D, Triton; E, frog; F, lizard; G, bird; H, mammal; 

 C, carotid artery ; DB, ductus Botallii ; DO, dorsal aorta ; EC, external carotid ; 

 1C, internal carotid; P, pulmonary artery ; SC, subclavian artery ; VO, ven- 

 tral aorta; 1-6, primitive arches. 



change of color to bright red. The other w r aste is gotten 

 rid of in the kidneys. In the capillaries of the body it 

 gives up its oxygen and nourishment to the surrounding 



