THORACIC CAVITY 



47 



healthy lung is seen in the dissecting-room, for adhesions 

 betw~een the visceral and parietal portions of the pleura, due 

 to pleurisy, are generally present. Each lung is accurately 

 adapted to the space in which it lies, and, when hardened 

 in situ, it bears, on its surface, impressions and elevations 

 which are an exact counterpart of the inequalities of the 

 structures with which its surfaces are in contact at the 

 moment of fixation. 



Each lung, in the natural condition, resembles half a cone ; 

 and it presents for examination an apex, a base, a costal 

 surface, and a medial surface. An anterior and a posterior border 

 separate the medial from the costal surface ; and an inferior 



Right vagus nerve 



Right 

 subclavian artery 



Righ 

 innominate vein 



Innominate 

 artery 



Trachea 



CEsophagus Left subclavian artery 



Sulcus subclavius 



Left vagus nerve 



Left 



common 



carotid 



Left 

 .-.innominate 



vein 



FIG. 17. Cervical Domes of the Pleural Sacs, and parts in relation to them. 



or basal border separates the base from the medial and costal 

 surfaces. The apex rises into the root of the neck for one 

 and a half inches above the level of the anterior part of the 

 first rib, and it is crossed by the subclavian artery, which 

 makes a groove upon the anterior border, a short distance 

 below the summit, although the artery is separated from the 

 lung by the membranous cervical diaphragm (Sibson's fascia), 

 and by the pleura. 



The base of each lung has a semilunar outline and is 

 adapted to the upper surface of the diaphragm. Consequently 

 it is deeply hollowed out, and, as the right cupola of the 

 diaphragm ascends higher than the left, the basal concavity 

 of the right lung is deeper than that of the left lung. The 

 anterior, lateral, and posterior parts of the inferior margin of 

 the lung are thin and sharp and extend downwards into the 



