NERVES. 



clavian artery. The right nerve then descends beside the in- 

 nominate artery and trachea, behind the right innominate 

 vein and superior vena cava, to the back of the root of the 

 lung. The left nerve runs between the common carotid and 

 subclavian arteries, behind the left innominate vein and 

 phrenic nerve, and over the aortic arch, to the same place. 

 Behind the root of each lung the nerve breaks up into a large 

 plexus (posterior pulmonary), from whose lower end on each 

 side two trunks descend to the ossophagus, crossing over the 

 vena azygos major on the right side and the thoracic aorta on 

 the left. On the oesophagus these split into a common plexus 

 (cesophageal) , but then gather into two nerves just above the 

 cesophageal opening of the diaphragm and pass through this, 

 the left nerve lying in front of the oesophagus and the right 

 behind it. [690] 



Cervical Cardiac Branches. The superior and inferior arise 

 in the neck; both, on the right side, descend behind the sub- 

 clavian artery and beside the trachea to the deep cardiac 

 plexus. On the left side the superior descends beside the 

 trachea to the deep cardiac plexus, while the inferior crosses 

 over the aortic arch, with the vagus, to the superficial cardiac 

 plexus. Cardiac branches of the right inferior laryngeal arise 

 over the subclavian artery and descend beside the trachea to 

 the deep cardiac plexus. [692] 



Thoracic Cardiac Branches. On the right side they arise 

 from the right vagus in the superior mediastinum and descend 

 beside the trachea to the deep cardiac plexus. On the left side 

 they arise from the left inferior laryngeal below the aortic arch 

 and go to the deep cardiac plexus. [693] 



The left inferior laryngeal arises as the vagus crosses the 

 aortic arch, hooks round this external to the ligamentum 

 arteriosum, and ascends between the trachea and oesophagus 

 to the neck, where it has the same course and branches as on 

 the right side. Its cardiac branches arise below the aortic 

 arch. [693] 



[119] 



