e are the pungent, like
pepper, cayenne and mustard; the astringent, like borax and alum; the
alkaline, like soda and potash; the acid, like vinegar and green fruit;
and the saline, like salt and ammonia. Almost all the bodies likely to
give rise to such tastes (or, more correctly, sensations of touch in
the tongue) are obviously unwholesome and destructive in their
character, at least when taken in large quantities. Nobody wishes to
drink nitric acid by the quart. The first business of this part of the
tongue is, therefore, to warn us emphatically against caustic substances
and corrosive acids, against vitriol and kerosene, spirits of wine and
ether, capsicums and burning leaves or roots, such as those of the
common English lords-and-ladies. Things of this sort are immediately
destructive to the very tissues of the tongue and palate; if taken
incautiously in too large doses, they burn the skin off the roof of the
mouth; and when swallowed they play havoc, of course, with our internal
arrangements. It is highly advisable, therefore, to have an immediate
warning of these extremely dangerous substances, at the very outset of
our feeding apparatus.

This kind of taste hardly differs from touch or burning. The sensibility
of the tip of the tongue is only a very slight modification of the
sensibility possessed by the skin generally, and especially by the inner
folds over all delicate parts of the body. We all know that common
caustic burns us wherever it touches; and it burns the tongue only in a
somewhat more marked manner. Nitric or sulphuric acid attacks the
fingers each after its own kind. A mustard plaster makes us tingle
almost immediately; and the action of mustard on the tongue hardly
differs, except in being more instantaneous and more discriminative.
Cantharides work in just the same way. If you cut a red pepper in two
and rub it on your neck, it will sting just as it does when put into
soup (this experiment, however, is best tried upon one's younger
brother; if made personally, it hardly repays the trouble and
annoyance). Even vinegar and other acids, rubbed into the skin, are
followed by a slight tingling; while the effect of brandy, applied,
say, to the arms, is gently stimulating and pleasurable, somewhat in the
same way as when normally swallowed in conjunction with the habitual
seltzer. In short, most things which give rise to distinct tastes when
applied to the tip of the tongue give rise to fainter sensatio