276 THE CIRCULATORY SYSTEM. 
appendage, presents externally is due to the muscular thicken- 
ings of the wall (musculi pectinati). 
Fic. 115.— HEART, VENTRAL VIEW. Fic. 116.—Hzart, Dorsat VIEW. 
Fig. 115.—a, right ventricle; 4, left ventricle; ¢, right auricular appendage; ¢, 
left auricular appendage; ¢, conus arteriosus; 7, pulmonary artery; g, aortic arch; 
A, thoracic aorta; 2, vena cava superior; 7, innominate artery; 4, left subclavian 
artery; 7, left common carotid; m, right common carotid; , right subclavian; », 
azygos vein; Z, the two innominate veins; g, coronary artery. . 
Fig. 116.—a, right ventricle; 4, left auricle; ¢, right auricle; d@, vena cava in- 
ferior; ¢, vena cava superior; /, aorta; g, 2, 7, groups of pulmonary veins (g, dorsal 
group; 4, sinistral group; 7, dextral group); 7, pulmonary artery (division into two); 
%, innominate artery; /, left subclavian; m, left common carotid; ~, right common 
carotid; v, right subclavian; , azygos vein. 
The cavity (including that of the auricular appendage) is 
somewhat egg-shaped, with its long axis transverse. The 
