ORIGIN AND DISTRIBUTION OF THE NERVES. 



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artery, and takes its course along the neck to the chest. Its 

 filaments are — 1. To the cervical ganglion. 2. The pharyn- 

 geal branch, whose filaments pass to the oesophagus and 

 larynx. 3. Two slender branches to the carotid artery, 

 which form a plexus. 4. The laryngeal branch. 



At the back part of the neck the par vagum inclines up- 

 wards, and is found above the carotid artery ; it then passes 

 between the two first ribs, into the chest. Having entered 

 the thoracic cavity, it runs within the superior mediastinum ; 

 the right nerve adheres to the trachea, crosses above the root 

 of the right lung, alongside of the oesophagus, and gains the 

 under side of that tube before it leaves the chest. On the 

 left side the nerve accompanies the anterior aorta, and crosses 

 the root of the posterior aorta, and also reaches the oesopha- 

 gus. Its branches within the chest are filaments to the 

 tracheal and cardiac plexuses ; also, a branch called the recur- 

 rent nerve : branches to the pulmonary plexus, and also two 

 cords that branch out and penetrate the walls of the auricles. 

 The recurrent nerve of the left side originates from the par 

 vagum, by the side of the anterior aorta, and coils round the 

 root of the posterior aorta. 



The recurrent nerve, so denominated from its retrograde 

 course, passes upwardly and outwardly, and is found between 

 the carotid artery and the trachea; having reached the top of 

 the latter, it spreads into fine terminating branches, several 

 of which run to the muscles of the larynx and thyroid carti- 

 lage, and end in ramifications upon the membrane of the 

 glottis. Its branches are filaments to the pulmonary plexus, 

 cardiac plexus, posterior cervical ganglion, and branches to 

 the oesophagus and trachea. 



The par vagum runs to the stomach. The left nerve sends 

 filaments to the heart, and others along the small curvature, 

 which communicates with the ramifications of the right nerve ; 

 the other crosses to the left side, and joins the great semi- 

 lunar ganglion. The right nerve, as soon as it reaches the 

 heart, divides into numerous branches, which join the left, 

 and spread their ramifications upon the under part of the 



