270 Proceedings of the Royal Irish Academy. 



follows : Some of them, I may mention, are confirmatory of those 

 mentioned by Dr. Duchenne (de Boulogne), whilst others are addi- 

 tional, and pertain solely to my own obserration. 



The functions of the chorda tympani, then, as far as can be 

 determined by the results of faradaic stimulation of that nerve on its 

 passage in the ear, may be described as follows : — 



1°. The sensation of a peculiar taste is produced, which can only 

 be described as " metallic," to use the term employed by Dr. Duchenne. 

 This taste is not always perceived immediately on excitation of the 

 nerve ; occasionally, repeated stimulation is necessary before this sen- 

 sation is experienced. Some persons, on the contrary, notice it early 

 and constantly, even with a moderate intensity of excitation. Thus 

 different degrees of stimulation are required to cause its production in 

 different individuals. 



2°. A sensation of astringency is occasionally experienced. This 

 has been perceived several times by persons on whom I have experi- 

 mented. When experimenting on myself I observed the same sensa- 

 tion, and recognised that it was due to a pecidiar thrill caused by the 

 stimulated nerve. 



This fact has not hitherto been described. 



3°. A sensation of dryness and roughness over the corresponding 

 region of the tongue is frequently noticed. Here I have to confirm 

 the observation of Dr. Duchenne, with this addition, that I believe we 

 may attribute the production of this roughness on the tongue to the 

 same mechanism which, on similar stimulation, produce roughness on. 

 the cutaneous surface (commonly known as " goose-skin"). I found 

 that the power of setting this mechanism at work was lost to a 

 surface-region affected by paralysis of the ulnar nerve. Here, 

 especially in the outer portion of the hand, the skin was smooth and 

 somewhat parchment-like. 



4°. A sensation of prickling and numbness, as where a nerve of 

 general sensibility is excited, is a usual consequence of the stimula- 

 tion. Dr. Duchenne has remarked it. In my experience I have ob- 

 served that this sensation, although generally affecting the anterior 

 two-thirds of the tongue on the same side with the operation, may, 

 nevertheless, vary in extent and position within certain limits. Some- 

 times, for instance, but a small area may be first affected, and a 

 gradual enlargement of area may go on untU the entire of the corre- 

 sponding region be included. In most cases, this may requii'e only a 

 few minutes ; but, in some, repeated stimulations may be necessary. 

 In one -case I observed that, whilst on one side the anterior two-thirds 

 were affected by this sensation, on the other only a circumscribed 

 region (say, the middle thii'd on that side) was affected : the area 

 increased, under the influence of repeated stimulations, but never 

 quite advanced to the tip of the tongue. Lastly, in another instance, 

 the result of the stimulation was invariably to produce, amongst other 

 things, a tickling irritation in the throat, which was followed by a 

 short dry cough. 



Can we explain the diversities of effect described by supposing a 



