128 THORAX 



cardiac branch, which goes to the right half of the deep 

 cardiac plexus, and some anterior pulmonary branches to 

 the front of the root of the right lung, where they join 

 with branches of the cardiac plexus to form the anterior pul- 

 monary plexus. As it passes posterior to the root of the lung 

 it gives branches to the bronchi and the lung ; and in the 

 posterior mediastinum it gives branches to the oesophagus, 

 and to the posterior part of the pericardium and pleura. 



The Left Vagus. As the left vagus descends through the 

 superior mediastinum it lies first behind the left common 

 carotid artery, and behind the left phrenic nerve which 

 crosses from left to right in front of it, and it is in front of the 

 left subclavian artery. Then it passes across the left side 

 of the arch of the aorta. In the latter situation it is crossed 

 laterally by the left superior intercostal vein. Below the 

 lower border of the aortic arch it passes posterior to the root 

 of the left lung, where it breaks up into branches which enter 

 into the formation of the posterior pulmonary plexus. At 

 the lower border of the root of the left lung it emerges from 

 the plexus as two trunks, which descend, into the posterior 

 mediastinum, to the oesophagus, where they unite with 

 branches of the right vagus to form the oesophageal plexus. 

 At the lower end of the thorax the left vagus again becomes 

 a single trunk, which passes through the cesophageal orifice 

 of the diaphragm on the anterior aspect of the oesophagus. 



Thoracic Branches of the Left Vagus. In the superior 

 mediastinum, whilst it lies against the left side of the aortic 

 arch, it gives off the left recurrent branch, branches to 

 the upper and anterior part of the pericardium, and branches 

 to the left anterior pulmonary plexus. Posterior to the root of 

 the left lung, it supplies branches to the left bronchus and 

 the left lung; and during its course through the posterior 

 mediastinum, as it takes part in the cesophageal plexus, it 

 gives branches to the oesophagus, to the posterior part of the 

 pericardium, and to the left pleura. 



The Thoracic Part of the Left Recurrent Nerve. 

 The left recurrent nerve springs from the trunk of the 

 left vagus near the lower border of the left side of the 

 aortic arch. It curves round the lower border of the arch, 

 posterior to and to the left of the ligamentum arteriosum, 

 and passes upwards, behind and to the right of the arch, 

 through the superior mediastinum, in the angle between the 



