208 NERVOUS SYSTEM. 



lower part of the ganglion of the trunk. Their filaments 

 come from the side opposite to the point of junction of the 

 pneumogastric with the communicating branch from the spi- 

 nal accessory, so that probably the superior laryngeals con- 

 tain few if any motor fibres from this nerve. The superior 

 laryngeal gives off the external laryngeal, a long, delicate 

 branch, which gives a few filaments to the inferior con- 

 strictor of the pharynx, and is distributed to the crico-thy- 

 roid muscle and the mucous membrane of the ventricle of 

 the larynx. The external laryngeal anastomoses with the 

 inferior laryngeal and with the sympathetic. The internal 

 branch is distributed to the mucous membrane of the epi- 

 glottis, the base of the tongue, the aryteno-epiglottidean fold, 

 and the mucous membrane of the larynx as far down as the 

 true vocal cords. A branch from this nerve, in its course 

 to the larynx, penetrates the arytenoid muscle, to which it 

 sends a few filaments, but these are all sensory. This branch 

 also supplies the crico-thyroid muscle. It anastomoses with 

 the inferior laryngeal nerve. An important branch, de- 

 scribed by Cyon and Ludwig, in the rabbit, under the name 

 of the depressor-nerve, arises by two roots, one from the su- 

 perior laryngeal and another from the trunk of the pneumo 

 gastric, passes down the neck by the side of the sympathetic, 

 and, in the chest, joins filaments from the thoracic sympa- 

 thetic, to penetrate the heart between the aorta and the 

 pulmonary artery. 1 This nerve will.be referred to more 

 particularly in connection with the influence of the pneu- 

 mogastrics upon the circulation. 



It is important, from a physiological point of view, to 

 note that the superior laryngeal nerve is the nerve of sensi- 

 bility of the upper part of the larynx, as well as the supra- 

 laryngeal mucous membranes, and that it animates a single 

 muscle of the larynx, the crico-thyroid, and the inferior con- 

 strictor of the pharynx. 



1 CYON ET LUDWIG, Action reflexe d?un des nerfs sensibles du, cceur sur les nerfs 

 vaso-moteur&, Journal de ranatomie, Paris, 1867, tome iv., p. 472, el seq. 



