Molecular Orientation in Living Matter

Living matter offers many examples of what appears to be action exerted at a distance. I am not attempting to renew the discussion of the classical problem of physics because the action at a distance which I have in mind is not exerted through vacuous space but through matter, and its peculiarity lies in the fact that the intervening matter seems to act in a purely passive way. The example which has been present in my mind for more decades than I feel happy in contemplating is furnished by the neuro-muscular system. The muscle fibres are controlled by the nervous system with respect to three things: (1) those contractions which move the several parts of the body, (2) their elastic properties which maintain the several parts of the body in their normal posture and (3) the production of heat by the muscles of warm blooded animals in which the skeletal muscles are the chief thermogenic tissues. Of these the second is commonly called by physiologists muscular tone. The agent, the middle man that is, between a particular cell in the central nervous system and the group of muscle fibres which it controls, is a delicate fibril no more than say 4t~ in diameter which consists mainly of protein, and which is enclosed in an insulating sheath of fat ty matter. The way this agent acts in controlling the contraction of the muscle fibres is well known. Waves of short length, called nervous impulses, pass down the fibril to discharge some of the stored energy of the muscle fibres, the muscle fibre being an internal combustion engine. Each nervous impulse viewed in one aspect is a wave of molecular displacement involving chemical change, and in another aspect a wave of electrical displacement. The mode of action of the nerve fibre, however, in the other two cases is, so far as I am aware, completely unknown. It is of course possible that muscular tone and 641