FIFTY years ago the science of physiology, as now 1 understood, was scarcely recognised. It began in England when the early anatomists added an account of the uses or actions of the several muscles, glands, aiid viscera to the account of their form and structure. So in the sixteenth and seventeenth centuries each anatomical description was followed by the word Usus. True, experiments were practised from the time of Vesalius downward, by Harvey himself, by Redi, and by the Rev. Stephen Hales, and often with brilliant success. The problems of the circulation, of spontaneous generation, and of blood-pressure in the arteries were solved by these admirable experimenters; but their efforts were isolated: Fifty years ago we had in England excellent observers with the microscope, particularly Sharpey and Bowman; but there was no systematic study of the working of the human machine by masters like Johannes Müller, Ludwig and Claude Bernard, and “practical physiology” consisted in little more than examining the tissues under the microscope and exhibiting a few chemical reactions of animal fluids.