activity in general. Now if this striving is to realise itself, thus to manifest itself as movement, this movement must as such have some direction; but this direction must be determined by something, i.e., it requires a guide, and this is the nervous system. For to the mere irritability, as it lies in the muscular fibres and in itself is pure will, all directions are alike; thus it determines itself in no direction, but behaves like a body which is equally drawn in all directions; it remains at rest. Since the activity of the nerves comes in as motive (in the case of reflex movements as a stimulus), the striving force, i.e., the irritability, receives a definite direction, and now produces the movements. Yet those external acts of will which require no motives, and thus also no working up of mere stimuli into ideas in the brain, from which motives arise, but which follow immediately upon stimuli, for the most part inward stimuli, are the reflex movements, starting only from the spinal cord, as, for example, spasms and cramp, in which the will acts without the brain taking part. In an analogous manner the will carries on the organic life, also by nerve stimulus, which does not proceed from the brain. Thus the will appears in every muscle as irritability, and is consequently of itself in a position to contract them, yet only in general; in order that some definite contraction should take place at a given moment, there is required here, as everywhere, a cause, which in this case must be a stimulus. This is everywhere given by the nerve which goes into the muscle. If this nerve is in connection with the brain, then the contraction is a conscious act of will, i.e., takes place in accordance with motives, which, in consequence of external impressions, have arisen as ideas in the brain. If the nerve is not in connection with the brain, but with the sympathicus maximus, then the contraction is involuntary and unconscious, an act connected with the maintenance of the organic life, and the nerve stimulus which causes it is occasioned by inward impressions; for example, by the pressure upon the stomach of the food
