326 PULMONARY ARTERY. 



of the arch by a ligamentous cord, the remains of the ductus arte- 

 riosus. 



Relations. It is enclosed for one half of its extent by the pericar- 

 dium, and receives the attachment of the fibrous portion of the peri- 

 cardium by its upper portion. Behind, it rests against the ascend- 

 ing aorta ; on either side is the appendix of the corresponding 

 auricle and a coronary artery ; and above, the cardiac ganglion 

 and the remains of the ductus arteriosus. 



The Right pulmonary artery passes beneath the arch and behind 

 the ascending aorta, and in the root of the lungs divides into three 

 branches for the three lobes. 



The Left pulmonary artery, rather larger than the right, passes in 

 front of the descending aorta, to the root of the left lung to which it 

 is distributed. These arteries divide and subdivide in the structure 

 of the lungs, and terminate in capillary vessels which form a net- 

 work around the bronchial cells, and become continuous with the 

 radicles of the pulmonary veins. 



Relations. In the root of the right lung examined irom above 

 downwards, the pulmonary artery is situated between the bronchus, 

 arid pulmonary veins; the former being above, the latter below; 

 while in the left lung the artery is the highest, next the bronchus, 

 and then the veins. On both sides, from before backwards, the 

 artery is situated between the veins and bronchi, the former being 

 in front, and the latter behind. 



