THE PNEUMOGASTEIC KERVE. 557 



the posterior palatine arches down to the epiglottis; the 

 tonsils and upper part of the pharynx over the root of the 

 tongue. These are the seats of the distribution of the 

 glosso-pharyngeal nerve. The anterior dorsal surface, and 

 a portion of the anterior and inferior surface of the tongue, 

 in which the lingual branch of the fifth is alone distributed, 

 conveyed no sense of taste in the majority of the subjects 

 of Valentin's experiments ; but even if this were generally 

 the case, it would not invalidate the conclusion that, in 

 those who have the sense of taste in the anterior and upper 

 part of the tongue, the lingual branch, of the fifth is the 

 nerve by which it is exercised. 



Physiology of the Pneumogastric Nerve. 



The pneumogastric nerve, nervus vagus, or par vagum (l, 

 fig. 151), has, of all the cranial and spinal nerves, the most 

 various distribution, and influences the most various func- 

 tions, either through its own filaments, or those which, 

 derived from other nerves, are mingled in its branches. 



The parts supplied by the branches of the pneumogastric 

 nerve are as follows : by its pharj r ngeal 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 cesophageal 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, 



