330 



PULMONARY VESSELS. 



manner that it proceeds downwards between the two branches 

 and behind the angle formed by their bifurcation. From this 

 place of bifurcation a short ligament proceeds to the lower part 

 of the curve of the aorta, which is almost in contact with it. 



Fig. 181.* 



This ligament was originally the canal that formed the com- 

 munication between the pulmonary artery and the aorta of the 

 foetus. Each of the great branches of the pulmonary artery 

 takes a direction backwards, and to its respective side. It soon 

 joins the corresponding branch of the trachea and the two pul- 

 monary veins, being anterior to the branch of the trachea, and 



* Fig. 181. a, Left ventricle, b, Right ventricle, e, Right auricle. The 

 left auricle is seen above the left ventricle of the same side, d, Vena cava in- 

 ferior. 6, Subclavian and jugular veins ; 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, constitute the vena cava superior or descen- 

 dens. /, Left carotid, g, Left subclavian artery, arising from the arch of the 

 aorta, h, Descending aorta, i. Jc, Right subclavian, and right carotid, given 

 off from the arteria innominata, which is seen arising from the arch of the 

 aorta. Z, Pulmonary 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. 0, Left 

 pulmonary veins, entering auricle of same side. The right pulmonary veins, 

 are seen on the opposite side. p,p, Lungs. t t Trachea. 



