It is not for us to take a side in the dispute. After all, the question with which we have to deal is not whether the feeling of effort comes from the centre or the periphery, but in what does our perception of its intensity exactly consist? Now, it is sufficient to observe oneself attentively to reach a conclusion on this point which Professor James has not formulated, but which seems to us quite in accord with the spirit of his teaching. We maintain that the more a given effort seems to us to increase, the greater is the number of muscles which contract in sympathy with it, and that the apparent consciousness of a greater intensity of effort at a given point of the organism is reducible, in reality, to the perception of a larger surface of the body being affected. [Sidenote: Our consciousness of an increase of muscular effort consists in the perception of (1) a greater number of peripheral sensations (2) a qualitative change in some of them.] Try, for example, to clench the fist with increasing force. You will have the impression of a sensation of effort entirely localized in your hand and running up a scale of magnitudes. In reality, what you experience in your hand remains the same, but the sensation which was at first localized there has affected your arm and ascended to the shoulder; finally, the other arm stiffens, both legs do the same, the respiration is checked; it is the whole body which is at work. But you fail to notice distinctly all these concomitant movements unless you are warned of them: till then you thought you were dealing with a single state of consciousness which changed in magnitude. When you press your lips more and more tightly against one another, you believe that you are experiencing in your lips one and the same sensation which is continually increasing in strength: here again further reflection will show you that this sensation remains identical, but that certain muscles of the face and the head and then of all the rest of the body have taken part in the operation. You felt this gradual encroachment, this increase of the surface affected, which is in truth a change of quantity; but, as your attention was concentrated on your closed lips, you localized the increase there and you made the psychic force there expended into a magnitude, although it possessed no extensity. Examine carefully somebody who is lifting heavier and heavier weights: the muscular contraction gradually spreads over his whole body. As for the special sensation which he experiences in the arm which is at work, it remains constant for a very long time and hardly changes except in quality, the weight becoming at a certain moment fatigue, and the fatigue pain. Yet the subject will imagine that he is conscious of a continual increase in the psychic force flowing into his arm. He will not recognize his mistake unless he is warned of it, so inclined is he to measure a given psychic state by the conscious movements which