this have to psychical force? The modern view of physiology demands that we shall interpret the beginnings of every activity of the individual in terms of protoplasm. It is difficult at first sight to understand the relation between the muscle cell and the gray cell of the brain. It is not so difficult, however, when we remember that both were originally undifferentiated protoplasm, having common properties: both were able to contract, and both to co-ordinate. Gradually the one cell specialized so that this contracting function superseded and dominated all the others, while in the other case it was the co-ordinating or directing or automatic function that was given the first place. Whatever of vigor there was in the original protoplasm we find in the specialized cell of the adult body. Vigor is at bottom one thing, and we find that vigorous psychical force tends to be found in the same individuals in which vigorous physical force is found. When an undifferentiated bit of protoplasm contracts—as, for example, an amoeba—what happens? This is the simplest term of muscular contraction. All we can now say is that the mass does not change, the total volume remains constant, the ultimate particles rearrange themselves. This may be done so as to overcome resistance, and thus becomes work. That these particles should be able to arrange themselves, in opposition to mechanical force exerted upon them from the outside, indicates that there is something besides mechanical force within the cell, something besides physical force. It can hardly be regarded as mere chemical force, for in the case of many of the lower forms of even single-celled organisms there is a high degree of adaptation of means to ends, indicating psychical activity. To work out this relation of muscular to psychical force would, I think, throw light upon some of the interesting questions as to why some races are fitted to survive and others are not; as to why weak-minded individuals are so often those with flabby muscles; and as to why there is such a close connection between vigorous doing and strong willing. These matters are related not merely to the individual, but to the whole race, and, indeed, to the whole series of which the human race is but a part.
2. Of how much importance is physical exercise in the development of the brain? The modern school of psychologists tell us that from one third to one half of the brain surface has muscular functions; that this great fraction of the brain is concerned with making muscles contract, each little spot being concerned with its own muscle or group of muscles. This does not prevent these parts of the brain being also used in other ways. This we know less about. We do know, however, that it is necessary to have muscular exercise of any group of muscles, if the corresponding nerve center is to be developed. Careful examinations have been made of the brains of those who had
