Abstract
THE lecturer began by observing that the proper subject of the lecture being βthe nature or laws of muscular motion,β2 he would discuss the chemical, mechanical and electrical concomitants of this most important function with a view to the elucidation of their mutual causal relations. He would, however, ask the attention of the Society chiefly to the electrical phenomena which are associated with muscular action, as being those which he had himself specially studied. Some points relating to the mechanical effects of muscular action must be referred to by way of introduction, inasmuch as it is by these that a muscle performs its function as an organ of motion. There were two ways of investigating these effects experimentally. We might observe and record either the change of form which a muscle undergoes in response to a stimulus of very short duration when contracting isotonically, i.e. as it does when lifting a weight, or the increase of tension which occurs when it endeavours to overcome a resistance, i.e. when it acts isometrically. It was shown that although, as regards an entire muscle, the isometric method was preferable to the isotonic, the time occupied by a single element of muscular structure when directly excited in developing its maximum tension (i.e. in the transformation of chemical into mechanical energy) could be best estimated under isotonic conditions. He then proceeded to describe his own method of accomplishing this measurement with the aid of photography. It consists in observing the change of form of the surface of a living muscle when a single break induction current is led through it in such a way that the observed surface is at the kathode. A magnified image of the kath-odic electrode, which moves freely with the muscle, is projected on a slit behind which a sensitive plate passes, and in this way a curve is obtained from which the time-relations of the movement can be deduced. It is thus learned that at the kathodic spot, i.e. at the spot immediately excited, the process attains its greatest activity before the end of the first hundredth of a second. The importance of this datum consists in its bearing on the question whether or not the electrical change by which the change of form thus observed is accompanied is coincident with it, follows or precedes it. The answer to this question could not, of course, be given until the time-relations of the electrical change had been considered. These were discussed as follows:β
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References
Journal of Physiology, xxiii. p. 325.
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The Relation of Motion in Animals and Plants to the Electrical Phenomena Associated with it. Nature 60, 343β346 (1899). https://doi.org/10.1038/060343a0
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DOI: https://doi.org/10.1038/060343a0