CHORDA TYMPANI. 235 



tatory apparatus and to have somewliat different functions. 

 The chorda tympani has already been referred to as one of 

 the branches of the facial ; 1 the glosso-pharyngeal, one of the 

 nerves of the eighth pair, has not yet been described. 



Chorda Tympani. In the description we have given of 

 the facial, the chorda tympani is spoken of as the fourth 

 branch. It passes through the tympanum, between the ossicles 

 of the ear, and joins the inferior maxillary division of the 

 fifth, at an acute angle, between the two pterygoid muscles, 

 becoming so closely united with it that it cannot be followed 

 farther by ordinary dissection. It is impossible to determine 

 with certainty from what root the filaments of this branch 

 derive their origin, whether from the main trunk or the in- 

 termediary nerve of "Wrisberg ; but experiments have shown 

 that it possesses functions entirely distinct from those of the 

 other branches of the facial. The lingual branch of the in- 

 ferior maxillary division of the fifth has been called the gus- 

 tatory branch ; but this is an error ; for, as we shall see, the 

 fifth has nothing to do with gustation, except that it is joined 

 with filaments of the chorda tympani, which reach the tongue 

 through the lingual branch. 



As regards the course of the filaments of the chorda tym- 

 pani after this nerve has joined the fifth, there can be no 

 doubt, both from the effect upon taste following its division, 2 

 and the alteration of the nerve-fibres. Yulpian and Prevost, 8 

 by the so-called "Wallerian method, after dividing the chorda 

 tympani, found degenerated fibres at the terminations of the 

 lingual branch of the fifth in the mucous membrane of the 

 tongue, the fibres being examined ten days or more after the 

 section. It is well known that, a number of days after the 

 section of a nerve, its fibres of distribution undergo change, 



1 See vol. iv., Nervous System, p. 149, et seq. 



2 VULPIAN, Etudes sur Vappareil vaso-moteur. Revue sdentifique, Paris, 1873, 

 2 serie, tome iii., p. 179. 



3 PREVOST, Nouvelles experiences relatives aux fonctions gustatives du nerf lin- 

 gual, Archives de physiologic, Paris, 1873, tome v., p. 388. 



