In this paper, Dr Wardrope states that he has endeavoured to shew, by a series of observations and experiments, that the muscles, besides being the active organs of motion, perform, by their contractions, an important office in the circulation of the arterial as well as venous blood; an office which has not hitherto been described by physiologists, but which appears to be capable of explaining several interesting phenomena in the living body, of which no satisfactory account has yet been given.