558 THE NERYOUS SYSTEM. 



nerve are as follows : by its pharyngeal branches, which, 

 enter the pharyngeal plexus, a large portion of the mucous 

 membrane, and, probably, all the muscles of the pharynx ; 

 by the superior laryngeal nerve, the mucous membrane of 

 the under surface of the epiglottis, the glottis, and the 

 greater part of the larynx, and the crico-thyroid muscle ; 

 by the inferior laryngeal nerve, the mucous membrane 

 and muscular fibres of the trachea, the lower part of the 

 pharynx and larynx, and all the muscles of the larynx 

 except the crico-thyroid; by oesophageal branches, the 

 mucous membrane and muscular coats of the oesophagus. 

 Moreover, the branches of the pneumogastric nerve form 

 a large portion of the supply of nerves to the heart and 

 the great arteries through the cardiac nerves, derived from 

 both the trunk and the recurrent nerve; to the lungs, 

 through both the anterior and the posterior pulmonary 

 plexuses ; and to the stomach, by its terminal branches 

 passing over the walls of that organ. 



From the parts thus enumerated as receiving nerves from 

 the pneumogastric, it might be assumed that this latter is a 

 nerve of mixed function, both sensitive and motor. Expe- 

 riments prove that it is so from its origin, for the irritation 

 of its roots, even within the cranial cavity, produces both 

 pain and convulsive movements of the larynx and pharynx ; 

 and when it is divided within the skull, the same move- 

 ments follow the irritation of the distal portion, showing 

 that they are not due to reflex action. Similar experiments 

 prove that, through its whole course, it contains both 

 sensitive and motor fibres, but after it has emerged from 

 the skull, and, in some instances even sooner, it enters 

 into so many anastomoses that it is hard to say whether 

 the filaments it contains are, from their origin, its own, or 

 whether they are derived from other nerves combining 

 with it. This is particularly the case with the filaments of 

 the sympathetic nerve, which are abundantly added to 

 nearly all the branches of the pneumogastric. The likeness 



