Page:Observations on Man 1834.djvu/131

 heat in the organ, which remains after the peculiar taste ceases. Now this connexion of certain tastes with heat is some presumption, that they arise from vibrations, provided we allow heat to arise from them, according to the common opinion.

Secondly, Since disagreeable tastes must, according to the account of pain given above, arise from such a violence in the vibrations excited, as produce the solution of continuity, and pleasant tastes, from more moderate degrees of vibrations, which, though they approach to the solution of continuity, yet fall short of it; the pains of taste must proceed from stronger vibrations than the pleasures. And, agreeably to this, bodies which impress very active and disagreeable tastes, manifest great activity in other trials for the most part.

Thirdly, It is very difficult to give any plausible account of the great variety of pleasant and unpleasant tastes from the doctrine of vibrations. However, the different frequency of vibrations, which belongs to the small particles of different sapid bodies, may be, in a good measure, the source of this great variety. For if the particles of the body A oscillate twice, while those of the body B oscillate only once, the sensations excited by them may be different, though both fall within the limits of pleasure, or both pass into those of pain. The differences of degree may also contribute; for it is observable, that different disagreeable tastes, in declining, leave agreeable ones, which approach to each other. This I have experienced in aloes, lime, and green tea not sweetened. It may therefore be, that the different disagreeable tastes were such rather on account of degree than kind. And, upon the whole, it may be, that the several combinations of the differences of kind with those of degree may be sufficient in number to account for all the varieties and specific differences of tastes.

Fourthly, Tastes appear to be more different than they are from the odours which accompany some of them. And this observation, by reducing the number of tastes properly so called, does somewhat lessen the difficulty of accounting for their number. But then it is also to be observed, that part of this difficulty is to be transferred to the head of odours.

Fifthly, The power of distinguishing tastes seems to depend upon sight, to a certain degree. And this consideration also lessens the number of tastes properly so called.

Sixthly, If we suppose the sapid body to consist of particles, that excite vibrations of different frequencies, which may be the case of many bodies in their natural state, and probably must be with such as are compounded by art, compound medicines for instance, a great variety of tastes may arise, some resembling the tastes of simple bodies, others totally unlike these: just as some of the colours reflected by natural and artificial bodies resemble one or other of the simple primary ones, whilst others are colours that can scarce be referred to any of these. And we may