262 Proceedings of the Royal Irish Academy. 



of one or other of the nerves named, a new and considerable difficulty 

 would arise. Several physiologists, amongst them being Yemiere, 

 Admyrauld, Longet, Neumann, and Eosenthal, have made experi- 

 ments with a view to localise the different kinds of sapid impressions. 

 The general result, so far as the tongue itself is concerned, seems to 

 be that the base is sensitive to bitter impressions, and the edges and 

 point to saline, sweet, and acid savours especially.^ Now, if the same 

 nerve supply both regions, it is obvious that this remarkable dif- 

 ference stands in need of an explanation. Of course, such a difficulty 

 as this could not exist if we accept the opinion of HH. Bidder and 

 Wagner that the root of the tongue alone, and not the edge and 

 point also, is sensitive to taste-impressions. But whilst this view 

 is in contradiction to that of most experimenters, and indeed to general 

 experience, it would only displace one difficulty in order to substitute 

 another ; for if it be hard to conceive that the same nerve should not 

 receive a bitter savour in the anterior part of the tongue whilst it 

 does perceive it at the base, it is still harder to understand how it 

 should receive all taste-impressions at the base, and reject them all 

 in front. 



Such being the state of the question, in which almost eveiything 

 is yet under litigation, I venture to offer for consideration the follow- 

 ing facts, which, I hope, will help to elucidate the action of the 

 lingual nerve. Pathology, in this instance as in others, may lend its 

 assistance to experimental physiology, and, by removing a factor, 

 enable us to understand, by the consequences of its absence, the func- 

 tion which it fulfilled when in activity. 



The pathological facts were observed in a case which, owing to 

 the peculiar nature of the lesion, was exceptionally well adapted to 

 present them with clearness, and to permit of comparison and verifi- 

 cation. The lesion occupying a position in the bulbar region of the 

 pons varolii, complete paralysis of the facialis nerve had supervened 

 on the left side of the face, whilst on the other this nerve was un- 

 harmed. Here, however, on the right side, the third or inferior 

 maxillary branch of the trigeminus was paralysed, with result of 

 depriving the cutaneous surface of the corresponding region of its 

 normal sensibility to touch and pain. 



"When the condition of things in the interior of the buccal cavity 

 is considered, it will be remarked that a rare opportunity was pre- 

 sented of ascertaining the functions of the nerve-supply derived from 

 the facialis, and the trigeminus, inasmuch as the former was elimi- 

 nated as a factor from the left, and the latter from the right side of 



- Pathology supplies facts •vrhicli tend to accentuate this difference. Thus, in 

 the case of a patient affected with aphonia, sweet mixtures were rejected and 

 "could not be taken," whilst hitters were readily accepted. This would appear 

 to indicate that there are special fibrils for the conveyance of different sapid im- 

 pressions, and that they may become subject to hyperaesthesia. Numerous 

 instances could be given in which intolerance of certain flavours is found to exist. 



