SECTION VIII.

SENSATIONS IN THE ALIMENTARY CANAL.

When the sensations in the alimentary canal become acutely painful, they are precise objects of attention to every body.

There is reason to believe that a perpetual train of sensations is going on in every part of it. The food stimulates the stomach. It undergoes important changes, and, mixed with some very stimulating ingredients, passes into the lower intestines; in every part of which it is still farther changed. The degree, and even the nature, of some of the changes, are different, according as the passage through the canal is slower, or quicker; they are different, according to the state of the organs, and according to the nature of the food.

Of the multitude of sensations, which must attend this process, very few become objects of attention; and, in time, an incapacity is generated, of making them objects of attention. They are not, however, as we shall afterwards perceive, feeble agents, or insignificant elements, in the trains of thought. They are of that class of feelings, to which we have already been under the necessity of alluding; a class, which serve as antecedents, to feelings more interesting than themselves; and from which the attention is so instantaneously drawn, to the more interesting feelings by which they are succeeded, that we are as little sensible of their existence, as we often are of the 46 sound of the clock, which may strike in the room beside us, and of course affect our ear in the usual manner, and yet leave no trace of the sensations behind.

The complicated sensations in the intestinal canal, like those in the muscles, though obscure, and even unknown, as individual sensations, often constitute a general state of feeling, which is sometimes exhilarating, and sometimes depressing. The effects of opium, and of inebriating liquors, in producing exhilaration, are well known; and though much of the pleasure in these states is owing to association, as we shall afterwards explain, yet the agreeable feelings in the stomach, are the origin and cause of the joyous associations.16 The state of feeling in the stomach in seasickness, or under the operation of an emetic, is, on the contrary, one of the most distressing within our experience; though we can neither call it a pain, nor have any more distinct conception of it, than as a state of general uneasiness.

16 The exact mode of operation of opium and alcohol is still unknown; but the part affected is probably the nervous substance and not the stomach. It can hardly be said with propriety that any part of the pleasure of these stimulants is due to association. No doubt the exhilarated tone of the mind is favourable to the flow of joyful ideas, which serve to heighten the pleasure; but that pleasure could not be arrested or subdued through the absence of any supposable associations.—B.

The general effects of indigestion are well known. When the organs of digestion become disordered, and indigestion becomes habitual, a sense of wretchedness is the consequence; a general state of feeling composed of a multitude of minor feelings, none of 47 which individually can be made an object of attention.

In the sense of wretchedness, which accompanies indigestion, and which sometimes proceeds to the dreadful state of melancholy madness, it is difficult to say, how much is sensation, and how much association. One thing is certain; that sensations which are the origin of so much misery are of high importance to us; whether they, or the associations they introduce, are the principal ingredient in the afflicting state which they contribute to create.

The effects of indigestion in producing painful associations, is strikingly exemplified by the horrible dreams which it produces in sleep; not only in those whose organs are diseased; but in the most healthy state of the stomach, when it has received what, in ordinary language, is said, whether from quantity or quality, to have disagreed with it.

The general states of feeling composed of the multitude of obscure and unnoticed feelings in the alimentary canal, though most apt to be noticed when they are of the painful kind, are not less frequently of the pleasurable kind. That particular sorts of foods, as well as liquors, have an exhilarating effect, needs hardly to be stated. And it is only necessary to revive the recollection of the feeling of general comfort, the elasticity, as it seems, of the whole frame, the feeling of strength, the disposition to activity and enjoyment, which every man must have experienced, when his digestion was vigorous and sound.17

17 These effects pass beyond the influence of mere digestion. All the viscera contribute to the condition of high general 48 vigour and comfort here supposed. If one were to venture upon a scale of relative importance of the different organs, one would place the nervous centres first, and the digestion second.

The present section is open to several remarks. Some qualification must be given to the author’s surmise ‘that a perpetual train of sensations is going on in every part of the alimentary canal.’ It is hardly correct to say that there are perpetual sensations in any part of it: during a great part of our time we are in a state of indifference as to stomachic changes; and not merely because we are not disposed to attend to them, but because they scarcely exist. The sensibility of the organ is shown, on anatomical grounds, to be mainly in the stomach, and in the rectum; these parts are supplied by the nervus vagus; and very few nerves, besides those of the sympathetic system, are found in the smaller, or in the larger intestine, so that the sensitiveness of those parts is manifested only in case of violent disorganization, as cramp, stoppage, or inflammation. Hence the feelings are principally attendant on the changes in the stomach, as when food has just been taken, and after long privation, when the state called hunger shows itself.

It is not correct to class the sensations of the alimentary canal, as a whole, with those that lose their hold of the attention, that become unheeded in themselves, and are valued only as the antecedents of other more pleasurable feelings. The remark is inapplicable to the sensations mainly characterized as pleasure or pain; nothing can be more interesting than a pleasure, except a still greater pleasure. It applies only to those slight irritations that are in themselves nothing, but may be the symptoms or precursors of ill health, or of returning good health.

The author’s doctrine as to our acquiring artificially the habit of not attending to alimentary states, demands a fuller explanation. The usual cause of inattention to impressions is unbroken continuance; in accordance with the universal law 49 of Relativity or Change, we are usually insensible to the contact of our clothing with the skin, except at the moments when we put on or take off any part of it. In walking, and in standing, for a length of time, we are insensible to the body’s weight; on rising from the recumbent position we are rendered in some degree conscious of it. Now as the alimentary sensations—Hunger and Repletion—are intermitted and alternated with other states, they fulfil the chief condition of wakeful consciousness.

The example of the striking of the clock, adduced in the text, brings into operation a different power of the mind, which may go far to counteract the influence of change. Under a very engrossing sensation, or occupation, we become insensible to the stimulation of the senses by other agents. The strain of the mind in some one direction causes a sort of incapacity for going out in any other direction while the strain lasts. This is the explanation of the indifference to the striking of the clock. By the farther influence of habit, inattention to a certain class of impressions may become habitual; as in the power of carrying on mental work in the midst of distracting noises.

The same effect may arise in connection with the alimentary feelings. A person very much engrossed with a subject is unconscious of hunger, and does not feel the pleasures of eating. Should any one be absorbed habitually with some occupation or pursuit, such an one may contract a settled indifference to the recurring phases of alimentary sensation; but this is an extreme and unusual case. Any ordinary degree of interest in the avocations and pursuits of business is compatible with full attention to the feelings of hunger, and of repletion, as well as to the occasional pains and discomforts of indigestion. We do not often choose to contract an indifference to pleasures, and we seldom succeed in acquiring an indifference to pains, although we may have moments of such indifference, under some special engrossment of mind by other things.

It is over-rating the influence of association to make it a 50 chief element in the pleasure of intoxicating stimulants, or in the wretched feelings of diseased digestion. These states are direct results of physical agency, and are the same throughout all stages of life, with many or with few opportunities of being associated with other feelings. They are not the cases favourable for illustrating the power of association, in the important department of the feelings.—B.

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