The foregoing articles are only imperfect conjectures, and do not even approach to a satisfactory solution. They may just serve to shew, that the doctrine of vibrations is as suitable to the phænomena of tastes, as any other hypothesis yet proposed. The following methods may perhaps be of some use for the analysis of tastes.
First, To make trials upon bodies whose particles seem similar to each other. Such are perhaps distilled spirits, acid, alkaline, and fermented; also salts and oils; but they must all be sufficiently purified by repeated distillations, solutions, and such-like chemical operations; else we are sure, that their component particles are heterogeneous.
Secondly, To note the changes of taste in chemical operations, and compare them with the changes of colour; which last, by discovering the sizes of the particles, may determine many things relating to their mutual actions. The solutions of metals in acids, by affording many singular and vivid tastes, and sometimes colours, seem to deserve especial notice here.
Thirdly, There are many regular changes in natural bodies, which, by comparison with other phænomena, may be of use. Thus it is remarkable, that the juice of many or most fruits is first acid, i.e. whilst unripe, then sweet, then vinous, after the first fermentation, then acid again, after the second fermentation.
This inquiry is of great importance in medicine and philosophy. And the theory of tastes appears capable of becoming a principal guide in discovering the mutual actions of the small particles of bodies. The difficulty is to make a beginning. This theory may not perhaps be more complex than that of colours; one may, at least, affirm, that the theory of colours appeared as complex and intricate before Sir Isaac Newton’s time, as that of tastes does now; which is some encouragement to make an attempt.
It will easily be conceived, that if tastes, properly so called, (of which under the last proposition) favour, or suit with, the doctrine of vibrations, the sensations of the stomach and bowels may likewise. But a particular examination of these sensations, and comparison of them with tastes, will make this more evident.
First, then, we may observe, that the stomach is less sensible than the tongue, the bowels in general than the stomach, and the inferior bowels than the superior. Thus opium, and bitters, and sometimes spirituous liquors, are disagreeable to the tongue, but fall within the limits of pleasure in the stomach. Thus bile is extremely nauseous in the mouth, and offends even the stomach; but it cannot be disagreeable to the duodenum, which it first enters, or the bowels, through which it passes. Thus also the
