502 PAR VAGUM. 



muscles and to the membrane which lines the larynx and 

 covers the epiglottis. It is said that fine twigs can be traced 

 into the foramina, which are to be seen in the cartilage of 

 the epiglottis ; some ramifications can be traced to the pha- 

 rynx ; others communicate with the branches of the recurrent 

 nerve. 



The External Branch sends twigs to the pharynx, to the 

 lower and inner part of the larynx, and to the thyroid gland. 



In its course downwards, the great nerve sometimes sends off 

 a twig, which unites with one from the ninth pair that passes to 

 the sterno-hyoidei and sterno-thyroidei muscles. 



It uniformly sends off one or more twigs called cardiac, 

 which pass into the thorax and combine with small branches 

 from the sympathetic or intercostal nerve, to form the Cardiac 

 plexus, which sends nerves to the heart. 



After entering the thorax, the right trunk of the Par Va- 

 gum passes before the subclavian artery ; and the left trunk 

 before the arch of the aorta ; and immediately after passing 

 these arteries, each of the nerves divides into an anterior and 

 posterior branch. The anterior is the continuation of the Par 

 Vagum ; the posterior is a nerve of the Larynx ; which from its 

 retrograde course, is called the Recurrent or Inferior Laryngeal 

 Nerve. 



On the left side the Recurrent Nerve winds backwards round 

 the aorta, and, on the right side, round the subclavian artery, 

 and proceeds upwards, deeply seated, on the side of the tra- 

 chea, to the Larynx. Soon after its origin it sends filaments 

 to a ganglion of the sympathetic, to the cardiac plexus, and to 

 a pulmonary plexus, soon to be mentioned. In its course 

 upwards, it sends twigs to the trachea and the oesophagus. It 

 proceeds behind the thyroid gland, and sends twigs to that 

 organ. At the lower part of the larynx it sends off a branch 

 which communicates with branches of the superior laryngeal 

 nerve. It also divides into branches which are spread upon 

 the posterior crico-arytenoid and the arytenoid muscles ; 

 and also upon the lateral crico-arytenoid and the thyro-aryte- 

 noid muscles, as well as upon the membrane which lines the 



