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Abstract

Understanding muscle contraction goes to the heart of one of the fundamental questions posed by classical philosophy, namely the nature of the πνευµα ψνχικoν. The nature of ‘understanding’ has altered greatly during the last two millenia, particularly in response to the development of the concept of energy. Moreover, understanding contraction depends on understanding muscle structure. Galen was the first to make a detailed anatomical examination of the mode of action of muscles and recognized the heart as a muscle, but this line of research was not pursued until Leonardo da Vinci rediscovered it 1400 years later. Vesalius used the phrase Machina Carnis, but it was first Descartes who proposed a neuromuscular machine. However, the level of understanding of the physiology of muscle depends critically on the resolution of the available anatomy. Radical new insight was provided by electron microscopy. But an understanding at a physicochemical level is only possible if the structures of the components are known at atomic resolution. These have become known in the last five years and have led to dramatic progress. The present level of understanding of muscle is a physicochemical explanation of how the hydrolysis of ATP by the component proteins actin and myosin leads to movement.