tions of our mind are directly followed by certain states of our bodily organs. The nerve of sight, for example, is affected in a certain manner; vision, which is an affection or state of the mind, is its consequence. I will to move my hand; the hand obeys my will, so rapidly, that the motion, though truly subsequent, seems almost to accompany my volition, rather than to follow it. In conformity with the definitions before given of power and susceptibility, the one as implying a reference to something consequent, the other a reference to something antecedent, I should be inclined to consider the sensation which follows the presence of an external object as indicating a mental susceptibility of being so af fected; the production of muscular motion by the will, as indicating a mental power. But the terms are of less consequence, if you understand fully the distinction that is implied in them; and you may be allowed still, in compliance with the general language, to speak of the power or faculty of sensation or perception, if you mean nothing more, as often as you use these terms, than that the mind is affected in a certain manner, and, therefore, must have had a previous susceptibility of being thus affected whenever certain changes have previously taken place, in that nervous system, with which it is connected.

In considering the susceptibilities of the mind, I comprehend, under its external affections, all those phenomena or states of the mind, which are commonly termed sensations; together with all our internal organic feelings of pleasure or pain, that arise from states of the nervous system, as much as our other sensations. Many of these are commonly ranked under another head, that of appetites, such as hunger, thirst, the desire of repose, or of change of muscular position, which arises from long-continued exertion; the oppressive anxiety, which arises from impeded respiration, and various other diseases, arising from bodily uneasiness. But these appetites evidently admit of being analysed into two distinct elements,—a pain of a peculiar species, and a subsequent desire of that which is to relieve the pain,-states of mind, of which one may immediately succeed the other; but which are, unquestionably, as different in themselves, as if no such succession took place, -as different as the pleasure of music is from the mere desire of enjoying it again, or as the pain of excessive heat, in burning, from the subsequent desire of coolness. The pain, which is one

element of the appetite, is an external affection of the mind, to be classed with our other sensations,-the succeeding desire, which is another element of it, is an internal affection of the mind, to be classed with our other emotions of desire. We might have felt the same pain of hunger, though we had not been aware, that it arose from want of food, and consequently could not have felt any desire of food, but merely the general desire of relief which attends every disagreeable sensation. We might have felt the same uneasiness, which we term thirst, though we had not been aware, that it would be relieved by a draught of any beverage, and the same pain of impeded respiration or fatigue, though nature had not led us instinctively, in the one case to perform the muscular actions necessary for expiration and inspiration; in the other, to change our posture, and thus give repose to the wearied limbs. Whatever be the organic states, which occasion these painful feelings, that are elementary in our appetites, there can be no doubt, that some organic affections precede them, as truly as some affection of an external organ precedes the pain of a burn, or the painful temporary blindness, when we are dazzled with excessive light. And though, in the case of the appetite, we may give the same name to the pain, and to the desire of that which is to relieve the pain; or rather, may give one name to the combination of the two feelings, which is not to be wondered at, where the two feelings are so universally and so immediately successive, this error, or rather this mere abbreviation of language, is no reason that we should consider the elementary pain itself, as different, in kind, from our other pains, that have not merely half a term to express them, but a whole undivided word of their own. The pain, of which the appetite desires the relief, is a sensation, as much as any other internal bodily pain which we feel,—a state or affection of the mind, arising, immediately and solely, from a state or affection of the body, which is the only definition that can be given of a

sensation.

The pain of hunger and thirst, then, and, in general, every internal pain arising from a state of the bodily organs,-and distinct from the subsequent desires which they occasion,-are as truly sensations, as any other sensations; and the desires that follow these particular sensations, are as truly desires, as any other desires of which we have the consciousness. We may, indeed, if

we resolve to invent a new name, for those particular desires, that terminate immediately in the relief of bodily pain, or the production of bodily pleasure, give to such desires the name of appetites; but it is surely a very simple analysis only, that is necessary to separate, from the desire of relief, the feeling of the pain which we wish to be relieved; since it is very evident, that the pain must have existed primarily before any such desire could be felt.

That the various species of uneasiness, which are elementary parts of our appetites, recur, at intervals, in which there is some degree of regularity, does not alter their nature, when they do recur, so as to render a peculiar arrangement necessary for includ ing them. The mental states, which constitute the uneasiness that is felt, recur thus at intervals, not from any thing peculiar in the mind itself, the phenomena of which alone we are considering, but because the body is only at intervals in the state, which precedes or induces those peculiar mental affections. If, instead of the two or three periods, at which the appetite of hunger recurs, the nervous system were, one hundred times in the day, at intervals the most irregular, in that state, which is immediately followed by the feeling of hunger, the painful feeling,-and the consequent desire of food, which has been found to relieve it, would of course, be felt one hundred times in the day. The regularity, therefore, of the recurrence of this state of the nerves, is a phenomenon, which belongs to the consideration of the physiologist of the body, not of the physioligist of the mind, whose immediate office is finished, when he can trace any particular feeling of the mind to some affection of our organic frame, as its invariable antecedent; and who knowing, therefore, that the feeling of pain in any of our appetites, is the effect or result of some organic affection, is not surprised that it should not recur, when that organic affection has not previously taken place,—any more than he is surprised that we do not enjoy the fragrance of roses or violets, when there are no particles of odour to be inhaled by us; or do not listen to songs and choral harmonies, when there is no vibration to be transmitted to the auditory nerve. It is at certain regular periods, that the full light of day, and the twilight of morning and evening, are perceived by us. But we do not think it necessary, on this account, to give any peculiar name to these visual perceptions, to distinguish them from others less

regular, because we know, that the reason of the periodic recurrence of these perceptions, is that the various degrees of sunshine, which produce them, exist only at such intervals. We are hungry, when the nerves of the stomach are in a certain state; we perceive the sun, when the organ of vision is in a certain state. It is as little wonderful, that we should not have the feeling of hunger, except when the nerves of the stomach are in this state, as that we should not have the perception of the meridian sun, when the sun itself is beneath our horizon.

Since the mere pains of appetite, however, most important as they truly are, for the ends which they immediately answer, are yet of little importance in relation to our general knowledge, it is unnecessary to dwell on them at length. But I cannot quit the consideration of them, without remarking that admirable provision which the gracious Author of Nature has made by them, for the preservation not of our being merely, but of our well-beingof that health and vigour, without which, a frail and feverish existence, at least in its relation to this earthly scene, would be of little value. The daily waste of the body requires daily supply to compensate it; and if this supply be neglected, or be inadequate—or, on the other hand, if it be inordinately great, disease is the necessary consequence. To preserve the medium, therefore, or at least to prevent any very great deviation from it, He, who planned our feelings and faculties as well as our bodily frame, has made it painful for us to omit what is so important to life; and painful also to prolong the supply in any great proportion, after the demands of nature have been adequately satisfied. If food had afforded gratification only as relieving the pain of hunger, these natural boundaries of appetite would have required no aid from moral or physical lessons of temperance. But the indulgence of nature, in conferring on us the sense of taste, and making food a luxury as well as a relief, we abuse, as we abuse her other kindnesses. The pleasures of this most intemperate of senses, may lead, in some degree, beyond the due point of supply, the greater number of mankind; and may drive, to excesses more injurious, all those herds of unthinking sensualists who prefer the sickly enjoyment of an hour, to the health and virtue, and intellectual as well as physical comfort, of more frugal repasts. Yet even to them, nature points out in the feeling of satiety, where intemperance begins, or where

it has already begun; and if they persist, notwithstanding this feeling, how much more would they be in danger of over-loading the powers of life, if there had been no such feeling of growing uneasiness, to suppress the avidity of insatiable indulgence.

"Though a man knew," says Dr Reid, "that his life must be supported by eating, reason could not direct him when to eat, or what; how much, or how often. In all these things, appetite is a much better guide than reason. Were reason only to direct us in this matter, its calm voice would often be drowned in the hurry of business, or the charms of amusement. But the voice of appetite rises gradually, and, at last, becomes loud enough to call off our attention from any other employment."*

If indeed, the necessary supply were long neglected, the mor bid state of the body which would ensue, though no pain of actual hunger were to be felt, would convince, at last, the sufferer of his folly. But the providence of our gracious Creator, has not trusted the existence of man to the dangerous admonition of so rough a monitor, which might, perhaps, bring his folly before him only when it was too late to be wise. The pain of hungerthat short disease, if it may be so termed, which it is in our pow er so speedily to cure, prevents diseases that more truly deserve the name. Between satiety on one side, and want on the other, the stream of health flows tranquilly along, which, but for these boundaries, would speedily waste itself and disappear; as the most magnificent river, which, if dispersed over a boundless plain, would flow almost into nothing, owes its abundance and majestic beauty to the very banks that seem to confine its waters within too narrow a channel.

Besides those particular feelings of bodily uneasiness, which, as attended with desire, constitute our appetites, there are other affections of the same class, which, though not usually ranked with our external sensations or perceptions, because we find it difficult to ascribe them to any local organ, are unquestionably to be arranged under the same head; since they are feelings which arise, as immediately and directly from a certain state of a part of the nervous system, as any of the feelings which we more commonly ascribe to external sense. Of this kind is that muscular pleasure of alacrity and action, which forms so great a part of the * On the Active Powers, Essay III. c. 1.