THE CIRCULATORY SYSTEM 81 



cavity and has semilunar valves similar to 

 those in the pulmonary artery. Tendinous 

 cords (chordce tendinece) are attached to the 

 bicuspid valve on the one hand and to papillary 

 muscular elevations of the ventricular wall 

 {musculi papillares) on the other. 



The Arteries (Fig. 47) 



The single pulmonary artery, arising from 

 the right ventricle, soon divides into right and 

 left branches, each entering one of the lungs. 



The aorta leaves the base of the left ventricle 

 and immediately supplies two coronary arteries 

 to the substance of the wall of the heart itself. 

 After a very short course, the aorta appears 

 to divide into two almost equal branches. The 

 right of these, however, is the true continuation 

 of the aorta, as will be evident if it is followed 

 as it curves round the right bronchus to pursue 

 an approximately median course through the 

 thorax and abdomen. The aorta, therefore, 

 before bending round the bronchus, gives off 

 two large branches : — first the left brachio- 

 cephalic artery, and later the right brachio- 

 cephalic artery. Each of these divides into a 

 common carotid and a subclavian artery. 

 The common carotid artery supplies blood to 



