minds, is not this also an act of recollection or memory? We have a perfect right to extend our conception of memory so as to make it embrace involuntary reproductions of sensations, ideas, perceptions, and efforts; but we find, on having done so, that we have so far enlarged her boundaries that she proves to be an ultimate and original power, the source, and at the same time the unifying bond, of our whole conscious life.

We know that when an impression, or a series of impressions, has been made upon our senses for a long time, and always in the same way, it may come to impress itself in such a manner upon the so-called sensememory that hours afterwards, and though a hundred other things have occupied our attention meanwhile, it will yet return suddenly to our consciousness with all the force and freshness of the original sensation. whole group of sensations is sometimes reproduced in its due sequence as regards time and space, with so much reality that it illudes us, as though things were actually present which have long ceased to be so. We have here a striking proof of the fact that after both conscious sensation and perception have been extinguished, their material vestiges yet

A

remain in our nervous system by way of a change in its molecular or atomic disposition,1 that enables the nerve substance to reproduce all the physical processes of the original sensation, and with these the corresponding psychical processes of sensation and perception.

Every hour the phenomena of sense-memory are present with each one of us, but in a less degree than this. We are all at times aware of a host of more or less faded recollections of earlier impressions, which we either summon intentionally or which come upon us involuntarily. Visions of absent people come and go before us as faint and fleeting shadows, and the notes of long-forgotten melodies float around us, not actually heard, but yet perceptible.

Some things and occurrences, especially if they have happened to us only once and hurriedly, will be reproducible by the memory in respect only of a few conspicuous qualities; in other cases those details alone will recur to us which we have met with elsewhere, and for the reception of which the brain is, so to speak, attuned. These last recollections find themselves in fuller accord with our consciousness, and enter upon it more easily and energetically ; hence also their aptitude for reproduction is

1 See quotation from Bonnet, p. 84 of this volume.

enhanced; so that what is common to many things, and is therefore felt and perceived with exceptional frequency, becomes reproduced so easily that eventually the actual presence of the corresponding external stimuli is no longer necessary, and it will recur on the vibrations set up by faint stimuli from within.' Sensations arising in this way from within, as, for example, an idea of whiteness, are not, indeed, perceived with the full freshness of those raised by the actual presence of white light without us, but they are of the same kind; they are feeble repetitions of one and the same material brain process-of one and the same conscious sensation. Thus the idea of whiteness arises in our mind as a faint, almost extinct, sensation.

In this way those qualities which are common to many things become separated, as it were,

1 Professor Hering is not clear here. Vibrations (if I understand his theory rightly) should not be set up by faint stimuli from within. Whence and what are these stimuli? The vibrations within are already existing, and it is they which are the stimuli to action. On having been once set up, they either continue in sufficient force to maintain action, or they die down, and become too weak to cause further action, and perhaps even to be perceived within the mind, until they receive an accession of vibration from without. The only "stimulus from within" that should be able to generate action is that which may follow when a vibration already established in the body runs into another similar vibration already so established. On this consciousness, and even action, might be supposed to follow without the presence of an external stimulus.-ED.

in our memory from the objects with which they were originally associated, and attain an independent existence in our consciousness as ideas and conceptions, and thus the whole rich superstructure of our ideas and conceptions is built up from materials supplied by

memory.

On examining more closely, we see plainly that memory is a faculty not only of our conscious states, but also, and much more so, of our unconscious ones. I was conscious of this or that yesterday, and am again conscious of it to-day. Where has it been meanwhile? It does not remain continuously within my consciousness, nevertheless it returns after having quitted it. Our ideas tread but for a moment upon the stage of consciousness, and then go back again behind the scenes, to make way for others in their place. As the player is only a king when he is on the stage, so they too exist as ideas so long only as they are recognised. How do they live when they are off the stage? For we know that they are living somewhere; give them their cue and they reappear immediately. They do not exist continuously as ideas; what is continuous is the special disposition of nerve substance in virtue of which this substance gives out to-day the same sound

which it gave yesterday if it is rightly struck.' Countless reproductions of organic processes of our brain connect themselves orderly together, so that one acts as a stimulus to the next, but a phenomenon of consciousness is not necessarily attached to every link in the chain. From this it arises that a series of ideas may appear to disregard the order that would be observed in purely material processes of brain substance unaccompanied by consciousness; but on the other hand it becomes possible for a long chain of recollections to have its due development without each link in the chain being necessarily perceived by ourselves.

One may

emerge from the bosom of our unconscious thoughts without fully entering upon the stage of conscious perception; another dies away in unconsciousness, leaving no successor to take its place. Between the "me" of to-day and the "me" of yesterday lie night and sleep, abysses of unconsciousness; nor is there any bridge but memory with which to span them. Who can hope after this to disentangle the infinite intricacy of our inner life? For we can

1 This expression seems hardly applicable to the overtaking of an internal by an external vibration, but it is not inconsistent with it. Here, however, as frequently elsewhere, I doubt how far Professor Hering has fully realised his conception, beyond being, like myself, convinced that the phenomena of memory and of heredity have common source..—ED.