The consciousness of the ‘Ego’ is not synonymous with consciousness in general. While the latter is probably an attribute of all living matter, the former is the result of the concordant action of a nervous tissue highly differentiated and ‘hierarchized,’ or brought into a relation of mutual dependence. It appears very late in the series of organic evolution, and is, up to the present, the highest vital phenomenon of which we have knowledge. It arises little by little from experiences which the organism acquires in the course of the natural activity of its constituent parts. Every one of our nerve-ganglia, every one of our nerve-fibres, and even every cell, has a subordinate and faint consciousness of what passes in it. As the whole nervous system of our body has numerous communications between all its parts, it perceives in its totality something of all the stimulations of its parts, and the consciousness which accompanies them. In this manner there arises in the centre where all the nerve ducts of the whole body meet, _i.e._, in the brain, a total consciousness composed of innumerable partial consciousnesses, having evidently for its object only the processes of its own organism. In the course of its existence, and that at a very early period, consciousness distinguishes two kinds of wholly different perceptions. Some appear without preparation, others accompanied and preceded by other phenomena. No act of will precedes the stimulation of the senses, but such an act does precede every conscious movement. Before our senses perceive anything, our consciousness has no notion of what they will perceive; before our muscles execute a movement, an image of this movement is elaborated in the brain, or spinal marrow (in the case of a reflex action). There exists then, beforehand, a presentation of the movement which the muscles will execute. We feel clearly that the immediate cause of the movement lies in ourselves. On the other hand, we have no similar feelings in regard to sense-impressions. Again, we learn by the muscular sense the realization of motor images elaborated by our consciousness; on the other hand, we experience nothing similar when we elaborate a motor image not having our own muscles exclusively for its object. We wish, for example, to raise our arm. Our consciousness elaborates this image, the brachial muscles obey, and consciousness receives the communication that the image has been realized by the brachial muscles. Next, we wish to raise or throw a stone with our arm. Our consciousness elaborates a motor image, involving our own muscles and the stone. When we are executing the desired and meditated movement, our consciousness receives sensations from the muscles in activity, but not from the stone. Thus it perceives the movements which are accompanied by muscular sensations, and others which appear without this accompaniment.