CHAP. XV.] PRECISE SEAT OF TASTE. 443 



distinguished; though, when placed on the middle of the dorsal region, 

 they make little or no impression till pressed against the roof of the 

 mouth. In the latter case, however, the taste of sugar is sufficiently 

 distinct, and referred definitely to the spot on which it is laid ; 

 so that its being tasted does not depend on its diffusion or removal 

 from the central to the circumferential parts, as some imagine. The 

 region now spoken of is supplied almost solely by the lingual branch 

 of the fifth nerve, though Valentin has described a twig of the glosso- 

 pharyngeal running on the under surface towards the tip. 



We conclude generally, with regard to the tongue, that the whole 

 dorsal surface possesses taste, but especially the circumferential parts, 

 viz. the base, sides, and apex. These latter regions are most favour- 

 ably situated for testing the sapid qualities of food ; while they are 

 much less exposed than the central part, to the pressure and friction 

 occasioned by the muscles of the tongue during mastication. The 

 central region, as a whole, is more strongly protected by its dense 

 epithelium, and is rougher, to aid in the comminution and disper- 

 sion of the food. 



Thirdly, the soft palate and its arches, with the surface of the 

 tonsils, appear to be endowed with taste in various degrees in different 

 individuals. Admirault and Guyat affirm that the sense is acute in 

 a spot about the centre, above the uvula; and in some individuals it 

 has so appeared to us. We have also found evidence of the existence 

 of taste on the sides and arches of the soft palate in some individuals, 

 but not on the pharynx, gums, or elsewhere. The soft palate and its 

 arches are supplied by the posterior palatine branches of Meckel's 

 ganglion, and sparingly by the glosso-pharyngeal nerves. 



Of the Nerves of Taste. Taste having been shewn to exist inde- 

 pendently in parts supplied, on the one hand solely by the glosso- 

 pharyngeal nerves, on the other solely by the lingual branches of 

 the fifth pair, it follows, as a direct consequence, that these nerves 

 must respectively participate in the sense; and there is besides 

 reason to attribute a share to the palatal branches of the fifth. 

 Amid many conflicting, and some quite irreconcileable statements 

 on this disputed point, with which it would be needless to distract 

 the reader's attention, the weight of evidence derived from other 

 sources seems to be much in favour of the above conclusion. 



The origin and connexions of the glosso-pharyngeal nerves, which 

 will be described at a future page, may be referred to in connexion 

 with this question. Rapp found no lingual branch of the fifth in the 

 tongue of the swan or parrot, both of which have acute taste. The 

 glosso-pharyngeal and par vagum supplied the organ. 



