12. To that sensible changes are not necessarily accompanied with con sciousness, we observe, that the diminu tion of consciousness can be traced in its various stages, from the state of active attention, to cases where we have no rea son to believe that consciousness is ex cited, where yet we have abundant rea son to believe that there were sensible changes ; because those effects are pro duced, which we know are produced by sensations (that is, by sensible changes of which we are conscious), and, as far as we know, in no other way. We can not, consistently with our requisite limits, advance so many facts as may appear M some to be necessary to prove our state ments, but the following will at least illustrate them.—Persons, much accus tomed to employ notes in singing, some times feel so deeply interested in the thoughts and feelings excited by the words they are singing, that, though the notes continue to regulate their tones of voice, the sensible changes are altogether unnoticed by them; they do not excite the consciousness. Again, many who have been long accustomed to perform upon a musical instrument, and can play with ease at first sight, while playing a piece of music which they have not seen before, can converse and carry on a train of reasoning, and yet play correctly : the appropriate sensible changes must in such cases be produced ; for otherwise the proper motions of the lingers could not ; but they are not accompanied with as soon as they are, at tention to the conversation, or train of reasoning, is interrupted. In the same manner, persons accustomed to read aloud, can continue to read aloud, even what they never read before, with at least correctness, and at the same time have their thoughts closely employed on other objects. The following case, stated by Dr. Percival, will by most be admitted as a strong corroboration of our princi ples. " Several years ago the Countess of fell into an apoplexy about seven o'clock in the morning : among other stimulating applications, I directed a feather, dipped in hartshorn, to be fre quently introduced into her nostrils. Her ladyship, when in health, was much addicted to the taking of snuff, and the present irritation of the olfactory nerves produced a junction of the fore-finger and thumb of the right-hand; the eleva tion of them to the nose, and the action of snuffing in the nostrils. When the snuffing ceased, the hand and and drop ped down in a torpid state. A fresh ap plication of the stimulus renewed these successive efforts ; and I was Witness to their repetition till the hartshorn lost its power of irritation, probably by destroy ing the sensibility of the olfactory nerves. The Countess recovered from the fit about six o'clock in the evening; but though it was neither long nor severe, her memory never afterwards furnished the least trace of consciousness during its continuance." Now here the impres sions produced by the hartshorn on the external organ, produced (by means of the nerves) sensible changes; and these, either through the medium of ideal changes, or, more probably, directly, pro duced motory changes, which (by means of the nerves) produced muscular action; and the whole without exciting conscious ness. The gradual diminution of atten tion to, or the consciousness of, external objects of sensation, (the beat of a clock for instance), when the mind is becom ing closely engaged upon some object of reflection, must he every one who thinks on what passes within him ; and it cannot be requisite to enlarge on that point.—Those who admit what we have stated respecting sensible changes will feel little hesitation in admitting the Same positions respecting ideal changes ; because the latter are merely relicts of the former. Besides, there is another point of agreement. Sensible changes, are produced without any effort of the mind, without any volition ; so also are ideal changes. These latter, when not interrupted by sensations, follow one ano other isn a train, without an effort, and often contrary to effort, regulated by the modes of connexion to which the indivi dual is most prone. We believe that the position advanced respecting sensible changes, at the beginning of this para graph, is equally applicable to ideal changes, Inutatis mutandis. We shall give only one instance of that case in which consciousness entirely disappears, where yet we are certain, that there must have been ideal changes. Every one who can add up a column of figures, knows the nature of the operation, because it is learnt after the memory has acquir ed considerable power. The sum of two or three figures is first ascertained : the ideal change of that sum must of course be in the mind, and with that sum is com bined the next figure, which forms a new sum, and so on. Now then there is the
act of adding a number, the ideal change of which is in the mind, to another number of which there is a sensible change, and there is the ideal change of the sum, and so on, continually recurring s this we per ceive when we are trying to add up slow ly. But persons who are very familiar with such additions, will tell the result or final sum, apparently without an ef fort, apparently without the intervention of the mind, and certainly without any consciousness of the operations and ideal changes which must have passed in the mind before the result could have been obtained. It will not unriequently be found, that persons very much habituated tothese operations,can add up much more correctly while they leave themselves nn conscious of the operations and ideal changes, than when they are conscious of them : and, what appears to us to settle the point, as far as consciousness is con cerned, persons who; by constant custom, have become familiar with all possible combinations of small numbers, can go through a series of additions, and at the same time closely engage the attention upon another object ; for instance, can dictate one or more letters.—As to mo tory changes, the fact is so obvious, that muscular actions, which must have their origin in the mind, as being regulated by impressions upon the external organs of sense, go on in long succession, and with frequent variation, while at the same time the attention is fully occupied by some object of thought, that we should be ready to suppose nothing but opposi tion to a pre-formed hypothesis could lead a person to doubt, whether in such cases the muscular action excited the con sciousness. Such an immense variety of muscular actions are continually taking place, in cases in will& volition was once concerned, without in any way whatever attracting the notice of the mind, and this is so obvious a fact, and so satisfactorily accounted for by Hartley, that, however plausible the counter-considerations of the great northern philosopher, Dugald Stewart, (see Elements, chap. ii.) we can not suppose that they can gain admission where the principle of association is tho roughly understood.
13. If this distinction between sensible and ideal changes, and sensations and ideas, be just ; or rather, if the existence of sensorial changes, without conscious ness, be admitted, (and we more and more feel satisfied that it is a fact, and if so, a very important one in our mental frame), then the four preceding faculties, or ca pacities of the mind, are to be referred to the sensorium, and are, in reality, the properties or powers of the mental or gans. We feel disposed to admit, that the sensorinm is the medullary substance of the brain ; but we beg our readers to bear in mind, that what we have ad vanced is entirely independent of this opinion, and that indeed it is rather clogged by it. We use the terms sen sorium and mental organs, because, in our opinion, they tend to give greater dis tinctness to our reflections on what pass es within us; but it is with no view to decide whether they are material or im material.—Consciousness, or the perci pient faculty, we consider as a distinct faculty from those already mentioned ; it is the faculty or capacity by which the mind is affected by sensorial changes, whether sensible, ideal, or motory. Con sciousness is in fact the notice of the mind itself; and the term is appl ied to that state, with which every sensorial change which excites the notice of the mind is at tended.—When the consciousness is con firmed, either on a particular object, or on a particular succession of obje ct s, whether or not that continuance is caused by voli tion, the state of the mind is called at tention.—It is by consciousness alone that we have any knowledge of the other powers of the mind ; and when directed to their operations, the appella tion is peculiarly appropriate. When it is excited by sensible changes, it is usu ally called perception : consciousness re ferring to the operations of the mind, as such; perception to them, as produced by external objects. (For an account of per ceptions, as distinct from sensations, see SENSATION.) We are conscious of al