The tongue, as an organ of mastication, ia provided with the sense of touch ; the
anterior portion, and especially the sides and tip, possessing this sense in an eminent
degree. Division of the lingual branches of the fifth nerves in animals is attended
with evidence of severe pain, and is immediately followed by loss of sensation in the
front part of the organ ; while cases of disease of the fifth nerve in the human subject
are marked by loss of sensation in the tongue, in common with the other parta
which the nerve supplies. The experiments of Alcock and Eeid further show that
mechanical irritation of the glosso-pharyngeal nerve in animals is accompanied with
manifest pain. Hence there can be no doubt that the lingual branches of the fifth
pair are the chief nerves of touch to the tongue, while the glosso-pharyngeal nerves
furnish the feeble common sensation existing iu its hinder part,



Conditions of Taste.
Taste may be produced by a mechanical or chemical excitation of its nerves.
Dr. Balt has observed that a smart tap with the fingers on the tip of the tongue causes

• BiBHOP, ' Med. Gaz.,' 1833 ; Romberg, ' Miiller'a Arcliiv.,' 1838, Heft iii.
t Noble, 'Med. Gaz.,' vol. iv., p. 120; VooT, ' Miiller'a Archiv.,' 1840, p, ?2.
i NoBLB, ' Med. Gaz.,' vol. zri.
M



LOCALIZATION OP VARIETIES OF TASTE.
