398 SPECIAL ANATOMY. 



Plexus pharyngeus, lying on the lateral walls of the 

 pharynx, entwining around the art.pharyng. ascendens t 

 and terminating in the muscles and the mucous membrane. 

 At the superior part fibres generally come from glossophar., 

 in the middle from n. vagus, below from vagus and sym- 

 pathicus. 



2. N. laryngeus superior. The superior laryngeal nerve (prin- 

 cipally a sensitive nerve) arises on the inner side, and passes 

 along it close to the pharynx, obliquely behind the carotis 

 inierna forwards and inwards, and divides into : 



1. N. laryngeus externus, the smaller inferior branch arising 

 sometimes from the trunk of the vagus itself, passes downwards 

 and inwards, and at the side of the larynx forwards, between 

 m. constrictor infer, and thyroid, cartilage, and is lost in the 

 m. crico-thyreoideus and upon the internal surface of the 

 larynx in the m. crico-arytcenoid. It receives two filaments 

 of sympathetic, and gives some to n. cardiacus behind carotis 

 interna (this is, plex. laryngeus) ; farther, to m. constrictor 

 infer, and thyroid, gland. 



2, N. laryngeus internus, continuation of the trunk, passes 

 between os. hyoid. and larynx, enters into the last with art. 

 laryngea super., and divides beneath the mucous membrane 

 in a radiating form into anterior and posterior branches. It 

 supplies the mucous membrane of the epiglottis, the thyroid 

 cartilage, membr. hyo-thyreoid., of the vocal cords, of the mm. 

 arytcBnoidei [merely perforating them in order to reach the 

 mucous membrane], and anastomoses upon the posterior sur- 

 face of the cricoid cartilage with nerv. recurrens. 



c. Several vascular branches pass over and under the point of bi- 

 furcation of carotis, forming plexuses about these vessels. 



d. Rami cardiaci, from two to four, arise below the region of the 

 point of bifurcation of the carotis, pass downwards upon it, 

 anastomosing with one another, and passing into the plexus 

 cardiacus (of sympathicus). To these also belongs the ram. 

 descendens, which passes from the posterior part of the vagus, in 

 the inferior part of the neck above the carotis, partly to the 

 cardiac plexus, partly to the oesophagus, and anastomoses with 

 n. sympathicus. 



645. (III.) The thoracic portion of the Vagus. 



Upon the right side of the trunk passes between ven. and art. 

 subclavia ; upon the left, between carotis communis and art. sub- 



