CIRCULATION OF THE BLOOD. 



495 



body and transmitting it through an opening, guarded by a valve, to the 

 ventricle, from which the blood is propelled to the bulbus arteriosus, and 

 then through four or five branching vessels supported on the cartilaginous 

 branchial arches to the gills (Figs. 182 and 183). After being subjected to 



Fig. 185.— Circulatory Apparatus in 



the Fish. (Owen.) 



A, bulhus arteriosus; B, branchial arteries; 6, 

 branchial veins; H, veatricle; h, auricle; L L, portal 

 vein ; V V, vena cardinalis ; v*, jugular veins ; I, in- 

 testine; A' A', aorta; K, kidney. 



The lower figure shows an enlarged diagram of a 

 branchial arch, the lettering being the same as above, 

 be being the branchial cavity. 



Fig. 186.— Heart of Tortoise. (Btclard.) 



1, right auricle; 2, single ventricle; 3, left auricle; 

 4, right aorta; 5, left aorta; 6, pulmonary artery dividing 

 into two branches ; 7, venae cava?. 



Fig. 187.— Heart of Frog. (Livon.) 



I, anterior view; II, posterior view. A A, aortaj ; 

 Vc, superior vense cavje ; Or, auricles ; V, ventricle; Ba f 

 aortic bulb ; SV, venous sinus ; Vci, inferior venas cavie ; 

 Vh, hepatic veins; Vp, pulmonary veins. 



aeration in the capillaries of the gills, the blood is then collected by the 

 branchial veins, which, uniting into a single arterial trunk situated on 

 the dorsal aspect of the alimentary canal, and corresponding to the 

 aorta of higher vertebrates, serves by a system of branching vessels to 



