THE THORAX AND ITS CONTENTS 99 



circulation and respiration become established. The walls of 

 the pulmonary artery are supplied by a branch of the left 

 coronary artery, and probably also by branches of other 

 vessels. 



34. Aorta: Left ventricle; to entire system. The divisions 

 of the aorta usually recognized are the arch (arcus aortae), 

 thoracic, and abdominal aorta. The arch gives off two, 

 rarely three, important branches, the innominate and the 

 left subclavian as wxll as some smaller branches. 



35. Coronary a.: Aorta, just distad to the right and left 

 aortic semilunar valves; to the walls of the heart and probably 

 other structures near the auricles. In general the left coronary 

 supplies the left and ventral sides of the ventricular portion 

 of the heart while the right coronary passes along the opposite 

 region. The coronary arteries and coronary veins comprise the 

 coronary system. Method: Remove the remaining fat from the 

 auricles and transect the pulmonary artery near the right ven- 

 tricle. If the auricles contain an unusual quantity of blood 

 clot a portion of one or both may have to be removed in order 

 to gain access to the base of the coronary arteries. 



36. Innominate (brachio-cephalic) a.: Arch of aorta; by two 

 branches (common carotids, 30) to neck and head and one 

 (right subclavian, cf. a. 37) to the right superior limb. The 

 left common carotid arises from various points on the innomi- 

 nate and occasionally from the aortic arch, as in man. 



37. Left subclavian a.: Arch of aorta; to left superior 

 limb principally (cf. right subclavian artery, Fig. 26). 



38. Vertebral a.: Subclavian arteries, rarely aortic arch, 

 commonly near the base of the left subclavian; to cranium via 

 the vertebrarterial (costo-transverse) foramina (Fig. 5, V). In- 

 side the skull the two vertebrals flow together to form the basilic 

 (Fig. 33). Method: Because of the amount of labor involved, 

 this artery is not often dissected out by the class. Determine 

 which of the vertebrae it enters. 



39. Internal mammary (sternal) a.: Subclavian, near or 

 with costocervical axis; to sternal, intercostal, phrenic, and 



