therefore, to our brain a substance does actually communicate what is, as far as we are concerned, a portion of itself.  Our perception of a thing and its attendant feeling are symbols attaching to an introduction within our brain of a feeble state of the thing itself.  Our recollection of it is occasioned by a feeble continuance of this feeble state in our brains, becoming less feeble through the accession of fresh but similar vibrations from without.  The molecular vibrations which make the thing an idea of which is conveyed to our minds, put within our brain a little feeble emanation from the thing itself—­if we come within their reach.  This being once put there, will remain as it were dust, till dusted out, or till it decay, or till it receive accession of new vibrations.

The vibrations from a pat of butter do, then, actually put butter into a man’s head.  This is one of the commonest of expressions, and would hardly be so common if it were not felt to have some foundation in fact.  At first the man does not know what feeling or complex of feelings to employ so as to docket the vibrations, any more than he knows what word to employ so as to docket the feelings, or with what written characters to docket his word; but he gets over this, and henceforward the vibrations of the exterior object (that is to say, the thing) never set up their characteristic disturbances, or, in other words, never come into his head, without the associated feeling presenting itself as readily as word and characters present themselves, on the presence of the feeling.  The more butter a man sees and handles, the more he gets butter on the brain—­till, though he can never get anything like enough to be strictly called butter, it only requires the slightest molecular disturbance with characteristics like those of butter to bring up a vivid and highly sympathetic idea of butter in the man’s mind.

If this view is adopted, our memory of a thing is our retention within the brain of a small leaven of the actual thing itself, or of what qua us is the thing that is remembered, and the ease with which habitual actions come to be performed is due to the power of the vibrations having been increased and modified by continual accession from without till they modify the molecular disturbances of the nervous system, and therefore its material substance, which we have already settled to be only our way of docketing molecular disturbances.  The same vibrations, therefore, form the substance remembered, introduce an infinitesimal dose of it within the brain, modify the substance remembering, and, in the course of time, create and further modify the mechanism of both the sensory and motor nerves.  Thought and thing are one.

I commend these two last speculations to the reader’s charitable consideration, as feeling that I am here travelling beyond the ground on which I can safely venture; nevertheless, as it may be some time before I have another opportunity of coming before the public, I have thought it, on the whole, better not to omit them, but to give them thus provisionally.  I believe they are both substantially true, but am by no means sure that I have expressed them either clearly or accurately; I cannot, however, further delay the issue of my book.