CEREBRAL ACTIVITY.
have already se.-:n that sensorial impressions, once received into the different regions of the cortical peri phery, become dispersed in the plexuses of the sensorium, which constitutes for them a vast field of projection, and that, pursuing their course from this point onwards, they enter into particular relations, some with the sphere of psychical, others with that of purely intel lectual, activity. In these cerebral regions they find the last stage of their long migrations through the organism. There they are concentrated and trans formed, and, under new forms, having become intellec tualiz,cd excitations of the psycho-intellectual sphere, they constitute the fundamental elements of all the phenomena of cerebral life.
There, in fact, these same sensorial excitations, incarnated in the living cell, become perpetuated as persistent excitations ; to become, as it were, durable memorials of the first impression that gave birth to them. There they repose, in those infinite labyrinths of the psycho-intellectual sphere where they live, a!ways alert, always brilliant, like faithfully-kept ar chives of the past of our intellect and emotions. There they form that common fund of ancient memories, accumulated from our earliest years, which gives birth to those fundamental-ideas which we always carry within us, and which are but radiations from the external world, that have previously been impressed upon us. They have lived with us for long years, and have assumed in a manner an independent existence, like foreign grafts implanted in our substance. The ideas and emotions which are nearest to us are, then, only direct reflexions and prolonged repercussions of the external world that have impressed us during our course through life ; and this subtle operation, which commences with the earliest phases of our existence, is perpetuated, and perpetuates itself incessantly, by an incessant participation of the brain's own activity.
Each sensorial impression that affects us leaves a record, a specific memory ; and it is this posthumous memory of the absent object that continues to vibrate, that perpetuates, vivifies, reinforces itself by means of excitations of the same pitch, which communicate to it a new freshness when it begins to grow feeble. The
origin and permanence of our ideas, as of our emotions, depend upon this daily maintenance of persistent im pressions.
If, indeed, we inquire profoundly into the genalogy of each of these in particular—if we submit each to a series of elementary analyses, decomposing it into its primary elements, we shall always find as the ultimate result, at the bottom of the crucible, that our ideas, like all our emotions, are reducible to a sensorial impression, as the fundamental condition of their occurrence. This sensorial impression is at the bottom of all our ideas, all our conceptions, though it may at first conceal in the form of a binary, ternary, quaternary compound ; and, on our methodically pursuing the inquiry, it is easily recognizable—just as a simple substance in organic chemistry may always be sum moned to appear, if we sit down with the resolution to disengage it from all the artificial combinations which hold it imprisoned.* All our ideas and emotions originate then, physiologi cally, in an external phenomenon which is incarnated in us, and perpetuates itself as a remembrance ; and it is thus that our ideas, like our remembrances, live in the life of the organic substratum that supports them, and with it undergo all the oscillations that may affect it.
Thus by means of the calling into activity of the nerve-cell with all its intrinsic and extrinsic attributes, the sensorial impression imprinted upon it becomes an idea, that is to say, a remembrance of the absent object. It is propagated to a distance by means of anastomotic plexuses, and is thus transformed, by cell after cell, into a progressive and radiating impression.