GREAT VESSELS OF THE HEART. 515 



the pulmonary artery, and immediately proceeds to the right, 

 covered by that vessel, until it mounts up between it and the 

 right auricle : it then forms a great curve, or arch, which/ turns 

 backward and to the left, to a considerable distance beyond the 

 pulmonary artery. In this course, it crosses the right branch of 

 the pulmonary artery ; and, turning down in the angle between 

 it and the left branch, takes a position on the left side of the 

 spine. 



Fig. 128.* 



The course of this artery, from its commencement at the ven- 

 tricle, to the end of the great curve or arch, is extremely varied. 

 The uppermost part of the curve is in the bottom of the 



* a, Left ventricle, b, Right ventricle, c, Right auricle. The left auricle 

 is seen above the left ventricle of the same side, d, Vena cava inferior, e, 

 Subclavian and jugular veins j those of the left side unite to form the vena 

 transversa ; those of the right, to form the vena innominata ; the junction of 

 these larger trunks, constitutes the vena cava superior or descendens. /, Left 

 carotid, g, Left subclavian artery, arising from the arch of the aorta, h, De- 

 scending aorta, z, k, Right subclavian, and right carotid, given off from the 

 arteria innominata, which is seen arising from the arch of the aorta. I, Pul- 

 monary artery, dividing into two branches, one for each lung the left passing 

 in front of the descending aorta, the right, behind the aorta, where it begins to 

 form the curve, m, Vena cava superior, n, Aorta, o, Left pulmonary veins, 

 entering auricle of same side. The right pulmonary veins, are seen on the 

 opposite side, p, p, Lungs, t, Trachea. p. 



