SiGERSON — On ihe Studi/ of Nerve-Action. 263 



the tongue. Such, an opportunity was desirable, because of certain 

 inferences drawn from disturbances of taste observed occasionally 

 in cases of hemi-facial paralysis, which would attribute gustatory 

 power to the facialis. It was of considerable interest, likewise, in 

 connexion with the much-debated question of the physiological func- 

 tion of the chorda tympani ; which I reserve for discussion to another 

 occasion. 



Now, the result of the paralysis of the inferior maxillary nerve, 

 and consequently of its lingual branch, was that the right anterior 

 two-thirds of the tongue were distinctly less sensitive to touch and 

 taste than the left. Tet as there was complete facialis paralysis on 

 the left side, and as the lesion was not only intra-cranial but intra- 

 pontine, there is every probability that whatever fibres the facialis 

 gives to the chorda tympani were paralysed. It appears to follow 

 from this, that whatever connexion the latter nerve may have with 

 the sense of taste is not attributable to any filaments it may 

 receive from the facialis. This goes to support the conclusion of 

 Professor Schiff, who holds that the chorda tympani represents loan- 

 fibres which had been previously borrowed by the facialis from the 

 trigeminus. 



Another question is suggested here, namely, the relationships of 

 the lingual and chorda tympani, respectively, to the senses of touch, 

 pain, and taste. Lussana and Inzani, in 1869, report a case where, 

 after section of the chorda tympani, in the middle ear, the anterior 

 two-thirds of the tongue lost their sensibility to sapid impressions, 

 whilst still sensitive to touch and pain. A complementary fact is 

 found in the result of an experiment by Professor Schiff, who, on 

 dividing the lingual nerve above its junction with the chorda tympani, 

 observed that the anterior two-thirds of the corresponding side of the 

 tongue became insensible to touch and pain, whilst some sensibility to 

 taste-impressions were preserved. 



In the case to which I have referred, there was impairment alike 

 of sensibility to touch and to taste. An incident occurred which served 

 to explain the reason of this double impairment, and to furnish a 

 revelation of physiological mechanism of great interest. Owing to a 

 certain want of care on his part, the patient got an attack of tonsil- 

 litis; and as a consequence his tongue became "loaded," covered with 

 white fur. In due time, the disorder gave way to treatment, and then 

 a phenomenon was remarked which I will state in the words of a note 

 made at the period : — 



" Nov. 24. Tongue completely loaded, white all over. 



" Nov. 25. This morning, tongue presented nearly the same ap- 

 pearance. During the course of the day, the left half became clean 

 and red, whilst the right (trigeminal-paralysed) half remained loaded. 

 The right half was quite loaded from tip to back, when I saw him in 

 the evening, whilst the left half was quite clean. 



" Nov. 26. Tongue has cleaned still more, but the cleaning has 

 gone on, from left to right, — about a quarter of an inch has now 



