DEVELOPMENT OF THE PHENOMENA OF MEMORY.
general faculty of memory, the organic phos phorescence of the nervous elements, is liable to present great modifications, according as it is considered at the different periods of the development of the human being. It goes through successive phases, which are merely more or less direct reflexes of the histological properties of the cells, by means of which it reveals itself.
In young children the cerebral cells are endowed with special histological characters ; they are flabby, greyish, flexible in a manner ; they are, moreover, from the dynamic point of view, virgin to any anterior impres sion. The sensorial excitation that affects them at that age must therefore imprint itself upon them more readily, since it finds them in a state of vacuity, their power of retention not being as yet put to the test.
On the other hand, in the first years of life the cere bral substance is in perpetual exercise and organic development. New elements are perpetually being added to the old ones, and as the new are most pro bably derived from their predecessors, we are led to conclude that the daughter-cells which appear, borrow from the mother-cells which give them birth an inevit able bond of relationship, a species of hereditary trans mission of the different states of the mother-cells from whence they spring. It is, then, probable that the primordial cells, which give birth to all the generations of daughter-cells that appear in the course of cerebral development, transmit to their descendants the special sensitive properties, the specific degrees of phosphores cence, with which they were animated at the moment of their origin ; and that it is in these intimate connections between cell and cell, in these mysterious bonds of relationship, that we must look for the secret of the perennial character of certain memories. Thus it is that certain impressions received in our early childhood become the common patrimony of certain families of cells, which maintain them in a state of freshness, cessantly vivifying them by a sort of permanent co-opera ton.
In the young child the impressionability of the cerebral substance is such that it retains, molu proprio, all the impressions that assail it, as passively as a sentized photographic plate that we expose to the light retains all the images that are reflected on its surface.
Visual and sensitive impressions are the first to he inscribed upon the sensoriim.
The child sees objects and persons that interest him, within a restricted circle. These first impressions captivate him, and he keeps the remembrance of them, individually recognizing each person or thing. Little by little, auditory impressions coming into play, he hears sounds, which are vague at first, without comprehending or interpreting them ; and insensibly, by the effect of the activity of the brain, from the persistence of the impressions and the notion of them that he acquires, he comes to recognize that these determinate sounds answer to precise objects, which are always the same, and which in some way interest his personality.
Little by little, this work of cerebral culture being pursued without cessation, new acquisitions are inces santly registered in the sensorium. The different modes of sensibility awakened bring with them new ideas and new remembrances, and at the same time excite appro priate reactions. The regions of intellectual activity begin to make more and more use of the excitations which come from the surrounding world to erethise them.
At this happy age the child retains what he sees, hears, tastes, without trouble. The strangest words, complete phrases that he does not comprehend, abstract proper substantives, pieces of poetry, the operations of mental calculation, leave in him persistent impressions which are perpetuated and registered in a stable manner. It is this special period of complete absorption, which we might call the age of substantives, that represents in the history of the development of the human being the first rudiments of intellectual activity, as, in the history of the development of humanity in general, the stone age represents the first outlines of human labour.* In the adult the elements of cerebral activity in a condition of complete development are endowed with all the energies they are capable of assuming. They do not now behave as they did in the young child during the period of his evolution, as far as regards the preser vation and storing up of external excitations.