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Carl Friedrich Wilhelm Ludwig (1816-1895) was a German physician and physiologist. Ludwig researched several topics such as the physiology of blood pressure, urinary excretion and anesthesia. He received the Copley Medal in 1884 for his research. In 1869, he was elected a foreign member of the Royal Swedish Academy of Sciences. He is credited for inventing the stromuhr, an instrument for measuring the quantity of blood that flows per unit of time through a blood vessel.