258 Proceedings of the Royal Irish Academy. 



gxiisL. properly, for instance, between degrees of impairment in the 

 taste- sensations of diiierent sapid substances. 



Disease is tbe most skilful vivisector. It can stimulate to excess 

 a given nerve, and enable us to observe the result; or, by paralysing it, 

 disease can render the nerve wholly inactive, and thus withdraw a fac- 

 tor, leaving us to determine its function by observing the consequences 

 of its absence. In presence of so complex a problem as that before us, 

 it is obvious that the sources of possible error of observation are many. 

 Hence, unless where the attention of the observer has been specially 

 directed to determining the topography of taste, it is impossible to 

 accept the recorded results as satisfactory. Thus, frequently, if not 

 generally, in ordinary practice the patient is allowed to withdraw the 

 tongue before signifying whether or not he perceives a taste. In such 

 cases, we can come to no conclusion against a localised abolition of 

 the sense, inasmuch as the withdrawal of the tongue, and its subse- 

 quent motion within the buccal cavity, will bring the sapid substance 

 in contact with regions where the taste sensation is still preserved. 

 "Where precautions have not been taken, with special reference to 

 such dangers, the statement of a positive result cannot be taken as 

 really excluding the presence of a localised paralysis of taste — say, 

 for instance, in the anterior border of the tongue. Or, if the sub- 

 stance be aromatic, its presence may be recognised (ex hypothesi) by 

 the olfactory sense alone, and yet the patient's declaration that he 

 tastes it may be recorded as an instance of the conservation of the 

 gustatory sense. jSTon-attention to these sources of error has been the 

 cause of the reception of many of the contradictory results which help 

 to obscirre the study of this subject. 



Hence, a simple enumeration of recorded results does not, of 

 necessity, increase the weight of evidence, with reference to disputed 

 points, unless it be manifest that the observers who recorded them 

 had their attention particularly directed to the elements of the prob- 

 lem. Such examples have an exceptional interest, and are of great 

 utility, when employed to control and verify the results of a physio- 

 logical experimentation on animals. 



"With the desire of adding something to the exact study of this 

 important question, I venture to submit the following observations 

 which have a direct bearing upon the action of some nerves, and 

 indirectly serve to elucidate the function of others. 



I. 



1. Function of Palatine Nerves. — The facts which I have observed 

 relate to the soft palate. The innervation of this region is somewhat 

 complex. The anatomical investigations of M. Debrou, and the phy- 

 siological experiments of Dr. Yolkmann, go to prove that it receives 

 branches from the glosso-pharyngeus, which supplies the levatores 

 palati and the azygos uvulae. This is a mixed nerve, and its galvani- 

 zation demonstrated, by inducing contraction of these muscles, that 



