THE LUNGS 409 



The Surfaces. The base (facies diaphragmatis) is concave, 

 broad, and surrounded by the sharp inferior border. It lies 

 in relation with the superior surface of the diaphragm, which 

 separates the right lung from "the convex surface of the right 

 lobe of the liver, and the left lung from the superior surface 

 of the left lobe of the liver, the fundus of the stomach, and 

 the spleen. Laterally and behind the thin sharp margin of 

 the lung projects for some distance into the costophrenic sinus 

 of the pleura, found between the lower ribs and the diaphragm. 

 The costal or thoracic surface is convex and smooth. The 

 right lung presents a Y-shaped fissure, which divides it into 

 three lobes; the left lung is crossed by a single fissure, dividing 

 it into two lobes. 



The Inner or Mediastinal Surface. The left surface pre- 

 sents the cardiac depression, which receives the left ventricle, 

 covered by the pericardium; above this is the hilum (root of 

 the lung), and passing down around the margins of the latter, 

 two layers of pleura fuse and form the ligamentum pulmonale, 

 extending from the lower aspect of the hilum to the inferior 

 border, one to two inches posterior to the interlobar fissure. 

 Immediately above the hilum is seen a large furrow for the 

 transverse portion of the arch of the aorta, and extending 

 upward from this toward the apex is a groove for the left 

 subclavian artery; a slight impression anterior to the latter 

 and approaching the margin of the lung lodges the left innomi- 

 nate vein. Behind the hilum and extending downward and 

 slightly backward is the groove for the descending portion 

 of the thoracic aorta, and in front of this is a slight impres- 

 sion for the esophagus, near the base of the lung, showing 

 that the esophagus is anterior and to the left of the aorta, 

 just before the former pierces the diaphragm. The right 

 surface shows, anterior to the hilum, the cardiac depression, 

 which receives the right ventricle of the heart, covered by the 

 pericardium. Immediately above the hilum is an arched 

 furrow for the vena azygos major vein; as it arches forward 

 above the right branches to empty into the superior vena 

 cava, then running upward and outward below the apex is 

 a wide groove for the superior vena cava and right innominate 

 vein; and nearer the apex and behind the vein is a second 

 depression for the innominate artery. Sometimes a slight 



