Croone accumulated a large fortune from his practice; with it his widow endowed the Croonian Lectures at the Royal College of Physicians, London. He believed muscular contraction to be brought about by the action of a “spirituous liquor” passing from the nerves and interacting with substances in the muscle. Translation of an extract in J. F. Fulton’s Selected readings in the history of physiology, 2nd ed., 1966, pp. 207-9. Complete translation by P. Maquet as On the reason of the movement of the muscles. Philadelphia: American Philosophical Society, 2000.