480 VEINS. 



separately into the left auricle. Occasionally they remain separate ; there are then 

 three veins on the right side. Not unfrequently, the two left pulmonary veins 

 terminate by a common opening. 



Within the lung, the branches of the pulmonary artery are in front, the veins 

 behind, and the bronchi between the two. 



At the root of the lung, the veins are in front, the artery in the middle, and the 

 bronchus behind. 



Within the pericardium, their anterior surface is invested by the serous layer 

 of this membrane, the right pulmonary veins pass behind the right auricle and 

 ascending aorta, the left pass in front of the thoracic aorta, with the left pul- 

 monary artery. 





