268 Proceedings of the Royal Irish Academy. 



XLIY. COXTEIBIJTIOK'S TO THE StTJDT OF I^EEVE AcTIOX IN COXIfEXIOH" 



WITH THE SeIs'SE OE TaSTE. II. FimCTIOXS OF THE ChOEDA TyIIPANT. 



By Geoege SiGEEsoif, M.D., Ch. M., F.L.S. 



[Eead, Febniary 9, 1880.] 



In the preceding Paper certain facts have been demonstrated with, 

 respect to the functions of nerves supplying the tongue and buccal 

 cavity. From these facts the following conclusions, amongst others, 

 may be deduced : — 



The so-called gustatory nerve is not exclusively, if at all, a nerve 

 of taste. It exercises, as I have proved, a remarkable influence over 

 the epithelial cells of the tongue. "When its action is annulled by 

 paralysis, there is retardation or ari'est in the elimination of these 

 cells. Hence the conditions necessary for the proper performance of 

 the function of taste are disturbed ; a film of effete matter, which, in 

 other circumstances, would have been shed off, now remains, and 

 interposes between the sapid substance and the taste organ. In this 

 manner, the acuteness of the sense of taste might become dulled or 

 diminished to a considerable extent, after paralysis of the " gustatoiy" 

 nerve, without that diminution going to prove that this nerve is in 

 truth a nerve of taste. Even if we supposed it to be merely a trophic 

 nerve (which I by no means affii'm), there would necessarily be some 

 loss of taste, if paralysis prevented the accomplishment of its trophic 

 work. 



The continuance of the power of tasting in the anterior portion of 

 the tongue after paralysis, and even after section of the gustatory or 

 lingual nerve, compels us to regard the chorda tympani as the 

 principal nerve of taste in this region. The question of its action is 

 involved in considerable obscurity, and it can scarcely be said that 

 its constitution has yet been definitely demonstrated. Berard declared 

 that the chorda tympani was an enigma propounded to the sagacity of 

 physiologists. Eecently Beclard has pointed out that, " whilst many 

 suppositions have been made concerning the role of this singular 

 nerve, it must be confessed that more than one obscurity remains to 

 be cleared up in connexion with it." ^ 



Again, whilst some physiologists consider that it obtains its taste- 

 filaments fi'om the facialis (thus making the latter to be a nerve of 

 taste), others maintain that the fibres so obtained were previously 

 borrowed by the facialis from the glosso-pharyngeus or the trigemi- 

 nus. Against the fijst-mentioned opinion I adduced the fact that, in 

 a case of absolute facialis-paralysis of one side, arising from pontine 



1 Beolard, Tra.itc de Fhysiologie. Paris, 6« edition, p. 1016. 



