TASTE. 



859 



On the other hand, it has been maintained 

 by some physiologists (especially Magendie, 

 Mliller, Gurlt, and Kornfeld), that the lin- 

 gual branch of the fifth pair is the special nerve 

 of taste ; although Mliller does not altogether 

 exclude the participation of the glosso-pha- 

 ryngeal as having a share in the transmission 

 of gustative impressions from the posterior 

 part of the tongue and the fauces. The ex- 

 periments of Dr. Alcock and others, however, 

 appear to show that very distinct indications 

 of gustative sensibility are presented by ani- 

 mals in which this nerve has been divided, the 

 sense being merely deficient in the anterior 

 part of the tongue. 



On the whole, then, it may be concluded 

 from experiment, that the glosso-pharyngeal 

 nerve and the lingual branch of the fifth pair 

 minister alike to the sense of taste ; the for- 

 mer being concerned in the transmission of 

 gustative impressions from the fauces and the 

 posterior part of the tongue, and the latter 

 from the anterior portion of the tongue ; and 

 the former being the special recipient of the 

 impressions which produce the sense of nau- 

 sea. This inference is so completely in har- 

 mony with the results of anatomical inquiry, 

 that it may be considered as having a very 

 strong claim to reception as a physiological 

 truth. The branches of the glosso-pharyn- 

 geal appear to constitute the sole nervous 

 supply of that region at the base of the 

 tongue, of which the circumvallate papillae 

 form the centre, and also of the sides of the 

 tongue near the base. As it is universally 

 admitted that these parts are acutely endowed 

 with gustative sensibility, we cannot help re- 

 garding the glosso-pharyngeal nerve as its 

 instrument. On the other hand, the middle 

 and anterior parts of the dorsum of the tongue 

 appear to be solely supplied from the fifth pair, 

 the tip, however, receiving a branch from 

 the glosso-pharyngeal, which runs towards it, 

 along the under surface. It has been denied 

 by some physiologists that the central por- 

 tion of the upper surface possesses the proper 

 gustative sensibility ; but we fully coincide in 

 the statements of those who maintain the 

 affirmative : and although it must be admitted 

 that the sense is not so acute as it is at the 

 base, sides, and apex of the tongue ; yet this 

 may be fairly attributed to the greater thick- 

 ness of the epithelial investment, and to the 

 predominance of the conical papillae over the 

 fungiform in the central region. 



On turning to the pathological evidence 

 which bears upon this question, we find an 

 apparent contradiction in the phenomena re- 

 corded by different observers ; but this is in a 

 great degree removed by a more careful ex- 

 amination ; and the evidence on the whole 

 preponderates in favour of the preceding con- 

 clusions. We shall make use of the excellent 

 summary recently put forth by Dr. J. Reid * : 

 " In the single cases observed and recorded 

 by Mayo, Serres, Romberg, Mr. Bishop, and 

 Todd and Bowman, and in the two cases by 



* Physiological, Pathological, arid Anatomical 

 Researches, p. 268. 



Mr. Dixon, both common sensation and the 

 sense of taste were annihilated in those parts 

 of the tongue supplied by the fifth pair ; while 

 in one case related by Mr. Noble, and ano- 

 ther by Vogt, common sensation was lost in 

 the parts of the tongue supplied by the third 

 branch of the fifth pair, yet the sense of taste 

 remained in these parts ; and in a second case 

 related by Mr. Noble, there was loss of taste 

 with maintenance of feeling." In some of 

 these cases the loss of the sense of taste ap- 

 peared to extend to the base of the tongue ; 

 but there was evidence that in these the 

 glosso-pharyngeal nerve was also involved in 

 the paralysis. " We have no proof," con- 

 tinues Dr. Reid, " that in the cases related by 

 Mr. Noble and Vogt, the whole of the fila- 

 ments of the fifth pair sent to the tongue 

 were affected ; and in the case of Vogt the 

 derangement of the nerve was only tempo- 

 rary, for the patient recovered the sensation 

 of the part paralysed after the end of six 

 weeks. We believe that these cases, when 

 examined more closely, will rather be regard- 

 ed as affording arguments in favour of the 

 opinion, that the same nervous filaments do 

 not convey inwards the impressions which 

 excite pain and touch and the impressions 

 which excite taste ; and that different fila- 

 ments for conveying inwards the impressions 

 that excite these sensations are bound up in 

 the lingual branch of the fifth pair." There 

 is believed to be no case on record, in which 

 the whole of the fifth pair, or of the third 

 branch of it, was found to be diseased after 

 death, and in which, during life, the sense of 

 taste had been retained in the anterior and 

 middle parts of the tongue. The evidence of 

 pathology, therefore, is in favour of that con- 

 clusion, as to the participation of the fifth 

 pair with the glosso-pharyngeal in the sense 

 of taste, at which we had arrived on other 

 grounds. 



The question still remains, however, as to 

 the speciality of the nervous fibres which con- 

 vey the gustative impressions ; that is, whether 

 they are the common sensory fibres, whose 

 peculiarity of function depends on the nature 

 of the papillary apparatus at their peripheral 

 origin ; or whether they are incapable, like 

 the fibres of the olfactive, optic, and auditory 

 nerves, of conveying impressions of the ordi- 

 nary sensorial kind, being adapted exclusively 

 to receive and transmit the peculiar impres- 

 sions made by sapid bodies. Now, in favour 

 of the first view, it may be urged, that the 

 conditions of the sense of taste are so nearly 

 allied to those required for the exercise of 

 touch, that the two can scarcely be dis- 

 tinguished on this ground, and that the fifth 

 pair and the glosso-pharyngeal are both nerves 

 of common as well as of gustative sensibility ; 

 neither of which can be affirmed in regard to 

 the three other senses, or of the nerves which 

 minister to them. But, on the other hand, it 

 must be remarked, that these nerves do not 

 seem to be endowed with gustative and com- 

 mon sensibility in equal proportions ; for the 

 glosso-pharyngeal, which is decidedly more 



