The simplest aspect, that of the mere repetition of the movement, has frequently been examined by psychophysicists. The real founder of experimental psychology, Fechner, showed the way; he performed fatiguing experiments with lifted dumb-bells. Then came the time in which the laboratories began to make a record of the muscular activities with the help of the ergograph, an instrument with which the movements of the arm and the fingers can easily be registered on the smoked surface of a revolving drum. The subtlest variations of the activity, the increase and decrease of the psychomotor impulse, the mental fatigue, can be traced exactly in such graphic records. This psychomotor side of the process, and not the mere muscle activity as such, is indeed the essential factor which should interest us. The results of exercise are a training of the central apparatus of the brain and not of the muscular periphery. The further development of those experiments soon led to complex questions, which referred not only to the mere change in the motor efficiency, but to the learning of particular groups of movements and to the influences on the exactitude and reliability of the movements. The purely mental factors of the will-impulse, especially the consciousness of the task, came into the foreground. These experiences of the scientists concerning the influences of training, the mechanization of repetition, and the automatization of movements have been thoroughly discussed by a brilliant political economist[19] as an explanation of certain industrial facts, but they have not yet practically influenced life in the factory.