86 



THORAX 



Relations. Above, the left innominate vein runs along its 

 upper border immediately anterior to the origins of the in- 

 nominate artery, the left common carotid artery and the left 

 subclavian artery, which spring from its upper border ; the first 

 arises from the apex of the convexity, posterior to the centre 



Phrenic nerve 

 Aortic arch 



Vagus nerve 



Recurrent 

 nerve 



Left superior 

 intercostal vein 



(Esophagus 

 Thoracic duct 



Sympathetic 

 trunk 



Internal 



FIG. 43. Transverse section through the Superior Mediastinum 

 at the level of the fourth dorsal vertebra. 



of the manubrium sterni ; the second arises close to, and some- 

 times in common with the first, whilst the origin of the 

 subclavian is a little more posterior and to the left, separated 

 by a distinct interval from the left common carotid (Figs. 20 and 

 24). Below the arch lie (i) the bifurcation of the pulmonary 

 artery and portions of its right and left branches; (2) the liga- 



