152 Anatomy Applied to Medicine and Surgery. 



reaches about the upper border of the fifth dorsal verte- 

 bra. Continuing its course downwards in front of the 

 thoracic vertebrae, it again inclines to the left, about two 

 inches above the aortic opening in the diaphragm, and. 

 passing in front of the aorta, pierces the diaphragm on a 

 level with the upper border of the tenth dorsal vertebra. 

 The oesophagus is situated in the superior mediastinum, 

 above, and in the posterior mediastinum, below, and has in 

 front of it : The trachea, the left common carotid and left, 

 subclavian arteries, the arch of the aorta, the left bron- 

 chus, the pericardium and the left pneumogastric nerve, 

 which forms a plexus on its surface. Behind, it rests on 

 the longus colli muscles in front of the vertebral column ; 

 on the intercostal vessels and the thoracic duct, and on the 

 aorta, just above the diaphragm, and has the pneumogas- 

 tric forming a plexus on its posterior wall ; laterally, it 

 has the pleura and the azygos vein on the right, and the 

 aorta and the pleura on the left. Having the same func- 

 tion as the intestine, viz., the involuntary passage of the 

 food, it has a somewhat similar structure, and is, to some 

 extent, steadied in its passage through the posterior media- 

 stinum by accessory slips, which extend from the longi- 

 tudinal muscular coat, to the pleurae, to the left bronchus 

 and to the pericardium. On examining the relations of 

 the structures in the vicinity of the left end of the trans- 

 verse aorta we notice, that the aorta and the left bronchus 

 cross in front of the oesophagus, and that the pneumogas- 

 tric nerve passes down in front of the left end of the aorta 

 and then between the aorta and the left bronchus, so as to 

 reach the anterior surface of the oesophagus. At the low- 

 er border of the aorta, the pneumogastric gives off the 

 recurrent laryngeal branch, which is distributed to the 

 larnyx. So that, at the left end of the transverse part of 

 the aorta, these important structures, viz., the oesophagus, 



