David Hartley

“ And from this way of reasoning it may now appear, that a great part of our intellectual pleasures are ultimately deducible from those of taste; and that one principal final cause of the greatness and constant recurrency of these pleasures, from our first infancy to the extremity of old age, is to introduce and keep up pleasurable states in the brain, and to connect them with foreign objects. ”

“ The peristaltic motion of the stomach and bowels remains automatic to the last, depending partly on the vibrations descending from the brain, partly on the impressions made on the villous coat. It cannot depend on associated circumstances in its common state, because, being perpetual, it is equally associated with every thing, i.e. particularly so with nothing. However, as grateful aliments increase it, the sight of them may do the same by association. Could we see our stomachs and bowels, it is probable, that we should get some degree of voluntary power over them. ”

“ Thirst is opposite to hunger, and is a general attendant upon fevers. It follows also, in an evident manner, from all considerable degrees of heat in the fauces. The nerves therefore of the mouth, fauces, œsophagus, and stomach, are, during thirst, preoccupied by disagreeable vibrations, of the inflammatory kind, as above observed. And as the pleasures of taste may be said to resemble those of titillation, so thirst seems allied to itching. ”

“ When young children continue to suck, or masticate a tasteless body put between their lips, or into their mouths, we may conceive, that the actions of suction and mastication begin to pass from their automatic towards their voluntary state. ”

“ The actions of vomiting, and expulsion of the fæces, are very nearly related to one another in their automatic state. However, it seems to me, that an irritation in the stomach produces only a gentle contraction in the sphincter ani, viz. such a one as does not exhaust its power, and which therefore tends to confine the fæces. In like manner, an irritation in the rectum may gently contract the upper orifice of the stomach. ”

“ The same eager appetite will bring up the ideas of various aliments from prior associations; and if a new association of it, when particularly eager, happen to be made with this or that food or liquor, the sympathetic eager appetite will ever after bring in the idea of that food or liquor, and adhere inseparably to it. The same eager appetite may also be transferred upon something that is not properly a food, from its exorbitant nature, prior nauseas in respect of common food, and accidental joint appearance. ”

“ Lastly, The connexion between the sensations of the tongue and stomach, and consequently between the manners of explaining them, may be inferred from the office of the taste, as a guide and guard to the organs of digestion; which is very evident, in general, in all animals, notwithstanding a few exceptions, more especially in men.
Prop. XL.—To examine how far the Phænomena of Hunger are agreeable to the Doctrine of Vibrations.
Natural hunger may be reckoned a pleasure in its first rise, and to pass into a pain only by increase and continuance. ”

“ To which we may add, that the least irritation from fulness or acrimony in the rectum or bladder throws the abdominal muscles into contraction in young children, both on account of the extreme sensibility and irritability of their whole nervous systems, and because they have, as yet, no associated influences over the muscles of the abdomen, whereby to restrain their contractions. ”

“ 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. ”

“ For any great degree of voluntary power over the muscular coat of the bowels would much disturb the digestion of the aliment, as those nervous persons experience, who are so unhappy as to be exceptions to the general rule, through the influence of associated circumstances. ”

“ As the sphincters of the rectum and bladder gain strength, more force is required to expel the fæces and urine. However, it appears, that these muscles usually exhaust themselves, previously to the instant of expulsion, thus giving free scope to their antagonists. For, according to theory, they ought to be contracted sooner and stronger than their antagonists, as being nearer to the seat of irritation. ”

“ And we may farther suppose, in both cases, that where the vibrations approach so near in frequency as to overrule each other, and produce one species only, there results a taste, or a colour, that resembles a primary one; whereas, if the vibrations differ so much in frequency, as that two or more principal species keep their own frequency, the taste, or colour generated from them, cannot be likened to any primary one. ”

“ These dreams and disorders are often forgotten; but the uneasy states of body, which then happen, leave vestiges of themselves, which increase in number and strength every day from the continuance of the cause, till at last they are ready to be called up in crowds upon slight occasions, and the unhappy person is unexpectedly, and at once, as it were, seized with a great degree of the hypochondriac distemper, the obvious cause appearing no ways proportionable to the effect. ”

“ As the pleasures of taste are in general greater than those of feeling, and the pains in general less, it follows that the ideas which are affixed to the several words expressing the several pleasant and unpleasant tastes, will be of a middle nature in respect of the ideas generated by tangible impressions ”

“ 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. ”

“ Fourthly, Since the meats, to which particular persons have an antipathy, and from which they receive violent ill effects, are, in general, highly grateful to others, one may perhaps conjecture, that the vibrations excited by these meats in the stomachs of those who have an antipathy to them, do but just pass the limits of pleasure ”

“ When the face of a child or adult is distorted upon the sight of a nauseous medicine, which has before produced distortions automatically, i.e. from the impressions made on the mouth and fauces, we see an evident instance of the power of associated circumstances ”

“ Thus tobacco, pyrethrum, and other acrids, solicit a profuse discharge from the salival glands, by being barely kept in the mouth, i.e. though the neighbouring muscles do not squeeze the glands by the action of mastication. Thus likewise vomits and purges increase both the secretions of all the glands of the intestines, and those of the liver and pancreas. It may be also, that the vibrations which run up the gall-duct are sometimes so strong as to occasion a spasm there ”

“ The action of deglutition affords manifest evidences of the gradual transition of automatic motions into voluntary ones, as well as of voluntary ones into such as are secondarily automatic. For, in common cases, we swallow without the least express intention. ”

“ If we suppose these vibrations to check themselves all at once, by occasioning a sudden contraction in the affected membrane, they may be propagated over the whole nervous system instantaneously, and give rise to the convulsion-fits, which happen to young children from gripes, and distention of the stomach and bowels, and to adults, from poisons, &c. ”

“ Seventhly, Permanent spasms, and violent motions, in the bowels, arise in consequence of uneasy and painful impressions there from indigested aliment, acrid fæces, irritating purges, poisons, &c. They are generally attended with the fermentation of the contents of the bowels, and the consequent generation of air; which, when confined by a spasm on each hand, distends the intermediate part of the bowel often to an excessive degree, causing a proportional degree of painful vibrations. ”

“ It may serve to shew the analogy of the sensations, and the general nature of active medicines, to observe, that these will often operate in several ways, viz. as vomits, purges, diuretics, diaphoretics, sternutatories, vesicatories, and corrosives, by a change of application and circumstances. ”

“ And that many particular foods and medicines become either extremely pleasant or disgusting, from associations, with fashion, joy, hope of advantage, hunger, the pleasures of cheerful conversation, &c. ”

“ Tenthly, It seems to deserve particular consideration here, that milk, and the flesh of certain domestic animals, yield tastes, which are naturally and originally pleasant, to a considerable degree, and yet not in excess, as sugar, and other very sweet bodies, are. ”