SANGUIFEROUS SYSTEM. 



493 



The three great arterial trunks which arise by distinct 

 orifices from a fossa on the right side of the base of the 

 ventricle, are provided each with a pair of semilunar valves 

 at their origin, and are compactly united together for a short 

 distance by cellular substance and pericardium on leaving the 

 cavity of the heart, as seen in the annexed figure (Fio. 141. 

 A. B.) from Bojanus, representing the ventral and dorsal 

 aspect of the heart and blood vessels of testudo europ&a. 

 The elongated right (A. a. B. a.) and left (A. b. B. b.) auricles 

 rest on the broad base of the ventricle (A. c. B. c.), and the 

 great arterial systemic trunks (A. d. e. f. g.} soon separate 

 for their several destinations. A strong muscular band (A. v.) 

 with circular fibres, embraces the origin of the great arterial 

 trunks (A. d. e.f. g.}, and the trunks of the coronary arteries 



FIG. 141. 



and veins wind round the same part of the ventricle (A. c.), 

 extending their ramifications towards the posterior margins 

 and the apex. The right systemic artery, after giving off the 

 right arch (A././. B./.) of the descending aorta (A. B.w. n.), 

 advances a little forwards, and divides into the right and left 

 arterise innominatse, each of which again bifurcates to form 

 a small ascending common carotid and a large subclavian 

 artery (A. B. d. e.) The common carotid, on each side, sup- 

 plies the parts of the neck, and is continued, ramifying like 



