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organs of sense, which, but for the absorption of the mind, would produce sensation. Another quality that may give to a sensation the power of exclusively occupying the mind is novelty. The cause of this will be explained as we proceed. Another quality in sensations that gives them power to fix the attention upon themselves, is the amount of pleasure or of pain which they occasion. An exquisite pleasure, which may be afforded by a very slight action on the sensory nerves, or a painful sensation, which perhaps is not always occasioned by too strong an action on the nerves of sense, but sometimes by the nature of the action, will irresistibly command the attention of the mind. Still another cause of the absorption of the mind by one sensation, is a desire accompanying it to examine or consider it, which desire may be excited by various motives. But of this, also, more as we proceed.
It has been argued, that the mind is capable of being affected by only one cause of sensation at a time. That, however, cannot be said to have been proved. On the contrary, there are phenomena that seem to militate against it; while, on the other hand, it must be admitted, that many of the phenomena that seem to exhibit the mind, as influenced by several sensations at the same time, are rather to be accounted for by a rapid transition from one sensation to another, than by an absolutely simultaneous attention to different sensations. Whether, indeed, all other sensations are excluded from the mind for the moment by the absorbing sensation, or whether the other sensations exist in the mind, but the mind is rendered insensible to them by the master sensation of the moment, is scarcely an intelligible question, and at all events one which it would be very difficult, if not impossible, to answer. There can be no doubt, however, that the general habit of the mind is to attend to only one sensation at a time.
This tendency of the mind to be wholly occupied with
one sensation at a time has been regarded by someperhaps, by metaphysicians generally-as a distinct power of the mind, and called "attention." But it ought, perhaps, rather to be regarded as a limit to its power than as a distinct power-a limit confining it to one object of thought at a time. The quality or adjunct of a seusation, which causes it to absorb the whole attention of the mind, is usually, we have seen, from without-some quality in the external object of sense. When it is in the mind itself, as when it consists of an accompanying desire to examine it, the motive to that desire is from without, or at least does not originate in any act of the mind itself. But we shall have occasion to return to this subject. We shall therefore retain the word
attention," but not signifying a distinct power of the mind, but as a limit to its capacity of receiving influences from without; or, more generally, a limit to its power of thought, confining it to one object at a time. The cases in which the mind seems to exert a power to command attention to any object of thought will come to be considered in the sequel.
6. Many of our sensations are either agreeable or disagreeable, some pleasurable even to ecstasy, and some painful to overpowering agony. Many which have become indifferent were either agreeable or disagreeable, pleasant or painful, on our first experiencing them. Perhaps, few or none were indifferent when first experienced, but have become so in obedience to a law afterwards to be noticed.
There are two causes which render sensations disagreeable. We do not here allude to. secondary causes, such as the suggestion of painful recollections, but to the effect produced by them on experiencing them for the first time. The first is, too great intensity-too dazzling a light, too loud a sound, too intense a smell or taste, too great excitement of the nerves of touch, as by a wound, or a blow, or a pressure, or burning. The too violent action of any of the nerves of sense, renders
sensations, which would be pleasant if experienced in a slighter degree, disagreeable, painful, agonising, according to the degree of the too violent action on them. And it is to be observed, that too violent action on the nerves of sense does not depend exclusively on the external object acting on them, but partly on the state of the organ itself. The organs of touch are defended by the cuticle, which is itself a horny, insensible substance, sheathing them like a glove. If the cuticle be removed from any part, and the extremity of the nerve laid bare, the touch of the blandest substance becomes like the touch of fire. The nerves of the other senses seem to be protected in a similar manner, so that when any disease lays them bare, or more exposed to be acted on, the slightest excitement of them may become intolerable. The eye may feel the introduction of the faintest light to be torture, the ear be unable to bear the slightest sound; and the taste and smell be painfully affected with the gentlest savour or odour.
The other cause that renders sensations unpleasant, is something in the exciting cause of the sensation which all experience, but which cannot be defined. Some tastes and smells are unpleasant when experienced in the slightest degree. Some sounds also, as the creaking of rusty wheels or hinges, the filing of metals, especially in sharpening saws, and, to some persons, the cutting of coarse paper, create unpleasant sensations. Some tactile sensations, also, are unpleasant, such as that occasioned by a fringe or rag on one of the nails coming into contact with cloth, especially woollen cloth; although in this feeling, and, perhaps, in some others, there may be an admixture of unpleasant suggestions. We have never heard of any modification of light being in itself unpleasant to the nerves of sight. It is reported of a person, who received his sight at a mature age by a surgical operation, that he expressed the greatest horror when any black object was presented to him. But black
is the absence of colour, and his horror might be occasioned by its reminding him of the darkness from which he had been delivered, and in that case would rather prove the delight which the sensation of sight afforded him. We have known a man blind from early infancy, but who still retained the power of distinguishing bright light from darkness, taking great pleasure in going out to the open air on sunny days, and rolling his sightless eyeballs opposite to the sun, and declaring that he would not exchange the sensation which he experienced for any worldly emolument. Sensations unpleasant in their own nature are chiefly confined to the senses of smell and taste; which, having the office assigned to them to judge what is fit or unfit for food, and the substances which are unfit for food far outnumbering the others, one might expect that the disagreeable sensations of smell and taste would far outnumber those that are agreeable. But most substances that are unfit for food are destitute of odour; and if they have an unpleasant savour, they must actually be applied to the tongue before they can produce sensation. The sensations of smell and taste are thus much more within the power of the will than other sensations. But, excluding the sensation of smell and taste, we conceive it highly probable that all other sensations, all sights and tactile feelings, with the few exceptions noticed above, are, when not too intense, originally pleasant, many of them exquisitely so. Bright light, whether white or coloured, if not too intense-all sounds, if not too loud, especially musical sounds—seem always to afford pleasure to an infant. And when an infant, very recently introduced into the world of sounds and sights, and feelings, and tastes, and smells, is awake, and even when it is asleep, its little countenance indicates a constant play of agreeable or disagreeable sensations; the transition from the one to the other, from the smile to the frown, and from the frown back to the smile, being rapid and incessant.
We conclude, therefore, with expressing our conviction that all sensations, when first experienced, are either agreeable or disagreeable, pleasant or painful.
When sensations, whether pleasant or painful, are long continued, the pain or the pleasure gradually subsides; pleasant sensations become indifferent; slightly disagreeable sensations also become indifferent; and very painful sensations, if they do not become indifferent, become much more tolerable. The sweetest sounds, and the most beautiful and brilliant colours, cease, by continuance, to afford the delight which they at first gave; so also the most exquisite perfumes and savours lose their power of affording pleasure. Painful sensations also tend to lose their power of giving pain, and to become indifferent. People who live in the midst of the most offensive smells, or the most discordant and deafening sounds, gradually become insensible to them.
There are two causes which contribute to this effect; but whether they be the only causes we are not prepared to assert. The first is, that the organs of sense seem to become insensible to the pain or pleasure of any sensations. Take a familiar example: put one hand into water hotter than can be borne without great pain, and you cannot keep it in the water for a single second; yet if it be not hot enough to blister the skin, you may by trying it several times, at length be able to keep it immersed in the water without any pain. That this does not arise from the water having cooled, you will find by trying the other hand; and you will find it still too hot for that hand, till, according to the common expression, it has become accustomed to it. In the same manner the palate becomes accustomed to the most pungent tastes-strong pepper, mustard, or ardent spirits, so that they can be swallowed without pain. This is a most merciful provision in a state in which we are exposed to so much pain; and to what extent causes of pain the most excruciating when first experienced,