But the truth is that the character of movements which are externally identical is internally different, according as they respond to a visual, an auditory or a tactile impression. Suppose I perceive a multitude of objects in space; each of them, inasmuch as it is a visual form, solicits my activity. Now I suddenly lose my sight. No doubt I still have at my disposal the same quantity and the same quality of movements in space; but these movements can no longer be co-ordinated to visual impressions; they must in future follow tactile impressions, for example, and a new arrangement will take place in the brain. The protoplasmic expansions of the motor nervous elements in the cortex will be in relation, now, with a much smaller number of the nervous elements termed sensory. My activity is then really diminished, in the sense that although I can produce the same movements, the occasion comes more rarely from the external objects. Consequently, the sudden interruption of optical continuity has brought with it, as its essential and profound effect, the suppression of a large part of the queries or demands addressed to my activity. Now such a query or demand is, as we have seen, a perception. Here we put our finger on the mistake of those who maintain that perception springs from the sensory vibration properly so called, and not from a sort of question addressed to motor activity. They sever this motor activity from the perceptive process; and, as
