THORACIC CAVITY 37 



bodies of the vertebrae, lie the right aortic intercostal arteries, 

 the accompanying veins, and the splanchnic nerves. Still 

 more laterally, on the line of the heads of the ribs, runs the 

 sympathetic trunk, and beyond the sympathetic trunk are the 

 intercostal spaces and their contents (Fig. 13). 



The phrenic nerve still covered by the strip of pleura left 

 in situ descends along the right innominate vein, the superior 

 vena cava, the pericardium, and the inferior vena cava. 



Contents of the Mediastinum and the Structures of the 

 Posterior Wall of the Thorax seen from the Left Side. 

 After the removal of the four pleural flaps, described on p. 33, 

 and the extra-pleural areolar tissue, the following structures 

 are visible in the thorax on the left side (see Fig. 14). 

 Below and anterior to the root of the lung is the 

 pericardium, covering the left atrium, the left ventricle, the 

 conus arteriosus of the right ventricle and the pulmonary 

 artery. Above the root of the lung is the arch of the 

 aorta. The arch of the aorta terminates posteriorly in the 

 descending aorta, which passes downwards behind the root 

 of the lung and the pericardium, but it is separated from 

 the lower part of the posterior wall of the pericardium by 

 the oesophagus, which, at that level, is inclining towards 

 the left side. On the left and anterior aspect of the aortic 

 arch, from behind forwards, lie the left vagus nerve, the 

 superior cervical cardiac branch of the left sympathetic 

 trunk, the inferior cervical cardiac branch of the left vagus, 

 and the left phrenic nerve, with its accompanying vessels. 

 Crossing the arch obliquely, from behind forwards and 

 upwards, is the left superior intercostal vein, which passes 

 lateral to the vagus and medial to the phrenic nerve. Above 

 the arch of the aorta are the lower parts of the left common 

 carotid and left subclavian arteries, and posterior to the latter 

 lies the oesophagus, with the thoracic duct running along its 

 left border on a posterior plane, and the left recurrent nerve 

 ascending along its anterior margin. 



Posterior to the descending aorta are the left aortic inter- 

 costal arteries, the accompanying veins, and the splanchnic 

 nerves ; and still more posteriorly and laterally lie the 

 sympathetic trunk of the left side and the left intercostal 

 spaces and their contents. 



After the relative positions of the structures exposed by 

 the removal of the mediastinal pleura have been examined 



