THE PNEUMOGASTRIC NERVE. 557 



but retained both, in all the rest of the tongue. M. Lisfranc 

 and others have noted similar cases ; and the phenomena 

 in them are so simple and clear, that there can scarcely be 

 any fallacy in the conclusion that the lingual branches of 

 both the fifth and the glosso-pharyngeal nerves are gus- 

 tatory nerves in the parts of the tongue which they 

 severally supply. 



This conclusion is confirmed by some experiments on 

 animals, and, perhaps, more satisfactorily as concerns the 

 sense of taste in man, by observation of the parts of the 

 tongue and fauces, in which the sense is most acute. 

 According to Valentin's experiments made on thirty 

 students, the parts of the tongue from which the clearest 

 sensations of taste are derived, are the base, as far as the 

 foramen caecum and lines diverging forwards on each side 

 from it ; the posterior palatine arches down to the epi- 

 glottis ; the tonsils and upper part of the pharynx over the 

 root of the tongue. These are the seats of the distribu- 

 tion 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 ma- 

 jority 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 (i, 

 fig. 144), 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 



