Croonian Lecture, 1906.—On nerve endings and on special excitable substances in cells

Abstract Amongst the fundamental problems of physiology is the determination of the actual seat of the changes which accompany or are the cause of physiological activity. The earliest step was the attribution of the more obvious functions of the body to the several organs which compose it. This has been followed by more or less successful attempts to ascertain the separate function of each tissue of an organ, and of each constituent of a tissue. And in recent years investigation has been largely concerned with the endeavour to localise functions long known, and those which from time to time are discovered, in the several parts, and in the several chemical constitutents of the ultimate unit, the cell. I propose to-day to consider what is the actual seat of certain physiological activities in cells, and chiefly in those of muscular and nervous tissues. About 50 years ago Claude Bernard investigated the action of various poisons on the properties of the nervous and muscular systems. The most important observations were those on the action of curari. It had long been known that a muscle contracted when it was stimulated, but it was a question of interminable arguments whether it responded to the stimulus in virtue of its own intrinsic properties, or in consequence of the presence of nerve-fibres in its substance.