

THE THORAX. 359 



cardium and heart and mediastinum ; a root, at which 

 point the visceral and parietal pleurae become continuous, 

 and where the bronchial tube, vessels, nerves, and lymphatics 

 pass to (or from) the lungs ; an anterior border, thin, 

 notched on the left side for the heart (for its relation to 

 the anterior of the chest see page 263) ; a posterior border, 

 thick, rounded, lying alongside of the spinal column ; and a 

 lower border, which resembles the anterior. For its rela- 

 tions to the chest wall, see page 262. 



The main fissure which divides each lung into two lobes 

 passes from the posterior border, three inches from the 

 apex, downward around the outer surface of the lung to 

 end at the lower portion of the anterior border. 



Besides this main fissure the right lung has a secondary 

 one that passes from the centre of the main fissure to the 

 anterior border, dividing the upper lobe into two portions. 



The structures constituting- the root of the lung- 

 (Fig. 73), are the bronchus, pulmonary artery and vein, 

 the bronchial vessels, nerves, lymphatic glands, the con- 

 necting tissue, and all surrounded by the pleura. 



The relations of the pulmonary artery, vein, and bronchus 

 are from before backward, bronchus, artery, and vein. 

 On the right side, from above downward; the relation is 

 the same, but on the left side it is artery, bronchus, and 

 vein. 



The lungs weigh about forty-two ounces, the right being 

 a little heavier than the left. 



Relations of the Roots of the Lungs. Figs. 71,72. Diag. 

 22. The right : In front, the phrenic nerve, anterior 

 pulmonary plexus, superior vena cava, the right auricle 

 of the heart ; above, the azygos major ; below, broad 

 ligament of the lung ; and behind, the pneumogastric 

 nerve and the posterior pulmonary plexus. 



