Thus, by means of these connections, our ideas are associated, grouping themselves methodically into con temporary reminiscences, appealing one to another, when the first link of the chain has been struck ; pre senting themselves again in an irregular and disconnected manner when, abandoning the direction of our mind, we let it run wild, as it is termed ; when we give audience to our thoughts, that is to say, when we leave the auto matic activities of our cerebral cells to exercise them selves according to their natural propensities and appeal to one another according to their natural affinities.
it is by means of this organic mechanism that move ment and life are incessantly spread through the plexuses of the cerebral cortex ; that excitations of all kinds spring up in their minute structure on the arrival of external impressions ; that the materials of the past become associated with recent ideas and impressions, and that, in a word, those marvellous phenomena, so instantaneous and so varied, presented by the activity of the brain, are developed in presence of the conscious personality, which assists, as a spectator, at their evolu tion, without being able to direct the movement which is accomplished, and, strange to say, with the idea that it is regulating them.
We generally imagine that we ordain the direction of our ideas into any desired channel, and that we can govern their evocation. We do not usually perceive that, while we imagine we are leading our ideas in one direction, we are unconsciously obeying the second phase of a movement of which the first has already taken place.
I imagine that I think of an object by a spontaneous effort of my mind ; it is an illusion—it is because the cell-territory where that object resides has bee a previ ously set vibrating in my brain. I obey when I think I am commanding, merely turning in a direction towards which I am unconsciously drawn. A phenomenon quite analogous to the conjuring trick of forcing a card takes place in this instance ; the conjuror forcing us uncon sciously to take a card, while letting us imagine we have a liberty of choice.
Sensorial excitations, once they are disseminated in the plexuses of the cortical substance, continue, as we have already several times said, the movement com menced by their contact with the external world. The process in evolution pursues its course, and then they are distributed—some to the sphere of psychic activity, others to that of intellectual activity proper. We shall now pursue the study of them into these two regions.*