340. There is no part of our purely Psychical activity, the relation of which to Physical conditions is more obvious and more intimate, than that reproduction of past states of consciousness, which, when supplemented by the recognition of them as having been formerly experienced, we call Memory. It is now very generally accepted by Psychologists as (to say the least) a probable doctrine, that any Idea which has once passed through the Mind may be thus reproduced, at however long an interval, through the instrumentality of suggestive action ; the recurrence of any other state of consciousness with which that idea was originally linked by Association, being adequate to awaken it also from its dormant or “latent” condition, and to bring it within the “sphere of consciousness.” And as our ideas are thus linked in “trains” or “series,” which further inosculate with each other like the branch lines of a railway or the ramifications of an artery, so, it is considered, an idea which has been “hidden in the obscure recesses of the mind” for years—perhaps for a lifetime,—and which seems to have completely faded out of the conscious Memory (having never either recurred spontaneously, or been found capable of recall by volitional Recollection), may be reproduced, as by the touching of a spring, through a nexus of suggestions, which we can sometimes trace-out continuously, but of which it does not seem necessary that all the intermediate steps should fall within our cognizance.