146 HAND-BOOK OF PHYSIOLOGY. 



of the pharynx, the Eustachian tube, the arches of the palate, the tonsils 

 and their mucous membrane, and the tongue as far forward as the foramen 

 caecum in the middle line, and to near the tip at the sides and inferior 

 part. 



Functions. The glosso-pharyngeal nerve contains some motor fibres, 

 together with those of common sensation and the sense of taste. 1. The 

 muscles which receive filaments from the glosso-pharyngeal are the stylo- 

 pharyngei, palato-glossi, and constrictors of the pharynx. 



Besides being (2) a nerve of common sensation in the parts which it 

 supplies, and a centripetal nerve through which impressions are conveyed 

 to be reflected to the adjacent muscles, the glosso-pharyngeal is also a 

 nerve of special sensation; being the nerve of taste, in all the parts of 

 the tongue and palate to which it is distributed. After many discussions, 

 the question, Which is the nerve of taste? the lingual branch of the fifth, 

 or the glosso-pharyngeal? may be most probably answered by stating 

 that they are both nerves of this special function. For very numerous 

 experiments and cases have shown that when the trunk of the fifth nerve 

 or its lingual branch is paralyzed or divided, the sense of taste is completely 

 lost in the superior surface of the anterior and lateral parts of the tongue. 

 The loss is instantaneous after division of the nerve; and, therefore, cannot 

 be ascribed to the defective nutrition of the part, though to this, perhaps, 

 may be ascribed the more complete and general loss of the sense of taste 

 when the whole of the fifth nerve has been paralyzed. 



But, on the other hand, while the loss of taste in the part of the tongue 

 to which the lingual branch of the fifth nerve is distributed proves that to 

 be a gustatory nerve, the fact that the sense of taste is at the same time 

 retained in the posterior and postero -lateral parts of the tongue, and in the 

 soft palate and its anterior arch, to which (and to some parts of which 

 exclusively) the glosso-pharyngeal is distributed, proves that this also 

 must be a nerve of taste. 



PNEUMOGASTRIC OR VAGUS NERVE. 



Distribution. The pneumogastric nerve, nervus vagus, or par vagum 

 (1, Fig. 347), has, of all the cranial and spinal nerves, the most various 

 distribution, and influences the most various functions, 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 vagus 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 mem- 

 brane of the under surface of the Epiglottis, the Glottis, and the greater 

 part of the Larynx, and the crico-thyroid muscle; by the inferior laryn- 

 geal nerve, the mucous membrane and muscular fibres of the Trachea, 



