DEVELOPMENT OF AUTOMATIC ACTIVITY.
THE automatic activity of the nervous elements awakes at variable epochs, according to the precocity of mor phological development of these elements. Thus, the spinal axis being more rapidly developed than the brain, in the regular evolution of the nervous system, automatic manifestations may take place in it, even while they are very imperfectly developed in the cerebral grey substance.
The manifestations of automatic activity in the brain follow by degrees the progress of physical develop ment, and this in a very rapid fashion. When the arrival of external excitations calls its sensibility into play in the different foci in which it is concentrated, the child begins to benefit by the automatic develop ment of the activity of his cerebral instrument, and it is by this process of continual absorption of impres sions, which incessantly reverberate in all the regions of the that the external world penetrates into him, and that by the silent evolution of the specific energies of the cerebral cells, his mental development goes on with that prodigious rapidity which excites our astonishment.
We have all witnessed and wondered at the incest sant mobility of these young creatures, and their insatiable appetite for knowledge of the external world. They want to embrace it with their little hands, to touch all that surrounds them, and take cognizance of everything that comes within their ken. We have been struck by their deep reflections, of which the scope, the logic, and the subtlety, surprise us all the more from -their being exempt from all reserve, and their coming to light simply from the natural play of the cerebral activity abandoned to its frankest mani festations.
Moreover, while the physical world penetrates into him and leaves its traces upon him, the child begins to feel emotions, and have developed in him the primordial elements of common sensibility. He feels very distinctly, of his own accord and by the mere energies of the vitality of his own sensorium, what things and persons are agreeable or disagreeable to him.
It is through the action of the same unconscious vital forces that his first sentiments arise, and are developed and perpetuated ; by means of a blind original force, without the direct intervention of the personality.
Childhood and youth are the two phases of life during which the automatic activity of the cerebral elements reveals itself with the greatest energy. It is the period when memory has the greatest vigour, when the sensibility of the cerebral cell is most exquisite, either to feel the excitations which thrill through it, or to retain them. It is also that at which its reactionary faculties are most intense.
It is indeed the period when ideas are associated with the greatest rapidity, when the conjunction of new with old ideas takes place instantaneously, when individual spontaneity and personal originality burst forth in the most pronounced manner, and when, in fact, the man appears with the cerebral temperament which specifi cally characterizes him.
As maturity approaches, the automatic energies of the cells become gradually less intense. Their sensibility is already dulled in consequence of the multitude of impressions which have affected them in turn ; their appetite for unknown things is less intense ; it is their period of beginning saturation. The thirst for know ing and registering new facts calms down by degrees, and the mental forces then concentrate themselves for the regular classification of acquired riches, the methodic grouping of facts belonging to the past, and the calling into activity of the materials long ago accumulated, which serve for the building up of our judgments, the formation of our thoughts, the maturation of our re flections—so that if the human brain has already lost something of its freshness, and the juvenility of its manner of feeling, it has gained, per contra, the fruits of acquired experience. It knows and automatically expresses what it knows ; and these different modes in which the human personality reveals itself as regards its external manifestations, represent the true synthesis of all the mental activities in their full expansion:* The effects of progressive senility are marked by in sensible gradations in human brains, by a slow and gradual enfeebling of the automatic activity of their elements.