So, again, we often observe in illness that an alteration in the physical conditions of the system so far affects the sense of taste, as to produce a great alteration in the usual appe tencies. These alterations may probably be due in some instances to the depravation of the buccal secretions, so that the gustative papillae are constantly surrounded with a sub stance possessing a certain taste of its own, which of course affects their impressibility by other savours. But there can be little doubt that they are more commonly occasioned by alterations in the condition of the gustative apparatus itself, which becomes the exponent (so to speak) of the wants of the system, and which may be trusted, to a very considerable extent, as indicating what is really most de sirable for it. Thus Dr. Holland remarks *: —" In the majority of instances of actual illness, provided the real feelings of the pa tient can be safely ascertained, his desires as to food and drink may be safely complied with. But undoubtedly much care is need ful that we be not deceived as to the state of the appetites by what is merely habit or wrong impression on the part of the patient, or the effect of the solicitation of others. This class of sensations is more nurtured out of the course of nature than are those which relate to the temperature of the body. The mind becomes much more deeply engaged with them ; and though in acute illness they are generally submitted again to the natural law, there are many lesser cases where enough remains of the leaven of habit to render every precaution needful. With such precautions, however, which every physician who can take schooling from experience will employ, the stomach of the patient becomes a valuable guide ; whether it dictate abstinence from a recurrence to food ; whether much or little in quantity; whether what is solid or liquid ; whether much drink or little; whe ther things warm or cold ; whether sweet, acid, or saline ; whether bland or stimulating to the taste." Further, Dr. Holland remarks : " It is not wholly paradoxical to say that we are authorised to give greatest heed to the stomach when it suggests some seeming ex travagance of diet. It may be that this is a mere depravation of the sense of taste ; but frequently it expresses an actual need of the stomach either in aid of its own functions or indirectly (under the mysterious law just re ferred to) for the effecting of changes in the whole mass of blood. It is a good practical rule in such cases to withhold assent till we find after a certain lapse of time that the same desire continues or strongly recurs ; in which case it may generally be taken as the index of the fitness of the thing desired for the actual state of the organs. In the early stage of recovery from long gastric fevers, I recollect many curious instances of such contrariety to all rule being acquiesced in, with manifest good to the patient. Dietetics must become a much more exact branch of knowledge, before we can be justified in opposing its maxims to the natural and repeated sugges tions of the stomach, in the state either of health or disease." In regard to the use of wine in fever, it is universally admitted by prac tical physicians that very important indica tions may frequently be drawn from the appe tency or dislike manifested towards it by the patient ; this being often exhibited when there is an almost entire obtuseness of the mind in regard to all other external impressions. In such circumstances these dormant instincts seem to manifest themselves, which are kept under by the intelligence in the normal con dition; instincts akin to those which guide the lower animals in their choice of food. There is probably not a plant, however poisonous to most, which has not one or more species of animal specially adapted to derive from it wholesome nutriment, and which is obviously drawn to it by its odour or savour ; whilst the most omnivorous feeders, such as the monkey, are usually restrained by dislikes, excited through these same senses, from touching fruits which would be noxious to them.
It cannot be doubted that, in all persons of ordinary aptitude for the discrimination of flavours, there are certain natural harmonies and discords among these, as among colours • nd sounds ; so that particular substances of ery different flavours taste agreeably in corn 'nation, whilst others are mutually repug ant. Thus every body likes sugar in combi ation with the acid of fruits ; and the sugar s popularly believed to neutralise the acid, which (as we need scarcely say) is not at all the case. On the other hand, sugar and oysters are said to form one of the most nauseous combinations possible. So, again,
the flavour of many wines is improved by being tasted simultaneously with cheese, whilst it is injured by fruits.—The art of cookery is founded upon a knowledge of these facts, which have not yet perhaps received from the scientific physiologist the systematic atten tion they deserve. Attempts have been made by Linnmus, Boerhaave, and others, to form a classification of savours ; but no such clas sification has come into general use, although there are certain savours which all agree to consider primary ; such as the aromatic, the sweet, the acid, the bitter, the saline, the astringent, and the pungent. By the first of these the sense of taste is connected with that of smell ; by the last two with that of touch.
The impressions made upon the sense of taste seem to remain longer after the with drawal of the body that excited them, than those which are received through most of our other senses. This is not surprising, when it is considered that particles of the sapid sub stance, which have once penetrated the pa may linger there in contact with the sentient extremities of the nerves, for some little time after they have passed away from the external surface. In many cases, how ever, the substance leaves an after-taste which is different from that which it first excited. It is difficult to say how much of this may be due to the difference of the impression which is made upon the sensory papillm at the front of the tongue and upon those at its base, and also to the admixture of the olfactive sense, which will be most actively called into play as the sapid body is passing the fauces; and how much to the exhaustion of the nerves conse quent upon their previous stimulation, so that the after-taste is complementary to that first received. It certainly appears to confirm the former explanation, that the after-taste is generally of that bitterish character which we have seen to be produced by the mere me chanical stimulation of the papillm at the base of the tongue. On the other hand, the fact that tannin, one of the bitterest substances known, has a sweetish after-taste, seems to favour the latter view. Probably both causes may participate in the production of the re sult.
It is not very common to find the sense of taste excited in a purely subjective manner ; since many of the tastes which are experienced in disease are probably due, as already re marked, to the depravation of the buccal secretions. Nevertheless, we occasionally meet with instances in which some peculiar gustative sensation, usually of a disagreeable nature, is constantly experienced without being traceable to any such cause ; and in which, therefore, we must seek for its occasion in some disordered functional condition of the sensorium.
The purpose of the sense of taste is obviously to serve as the guide and attraction towards wholesome food, and to afford pleasure in the reception of it, whilst it deters from the use of such as would be deleterious. This is more obvious in the lower animals than it is in man, who is frequently led by habit and fashion to a preference for substances which are high flavoured over those which are most whole some, and who is still more frequently induced to gratify his gustative sense by the reception of an amount of food which appetite alone would not incite him to take in. Of the pernicious results of such excess, this is not the place to speak.
The only ulterior purposes which ',.he sense of taste appears to perform in the economy, are to aid in exciting the flow of saliva, and in certain cases to excite the act of vomiting. Although the secretion of saliva is greatly affected by other causes,—as, for example, by the movement of the jaws, tongue, &c.,—yet it is much influenced by the sapid qualities of the food introduced into the mouth, being greatly increased by the taste of savoury food. It is also augmented by the sight or odour of such food ; but it is probable that the latter sensations influence it not so much directly as indirectly, namely, through the ideas which they call up, for the idea alone, if called up with sufficient vividness, is sufficient to make "the mouth water." The sense of nausea, as already remarked, seems intermediate between taste and touch ; but it is connected most closely with the former. We experience more or less of difficulty in swallowing all substances whose taste is peculiarly repugnant to us, and we find ourselves compelled to regurgitate them when the impression becomes of a certain intensity. This is one of the auto matic actions in which it appears requisite that a sensation, not a mere impression, should participate.
(William B. Carpenter.)