Wassermann, August von (1866–1925), a German bacteriologist. In 1906 he devised the Wassermann blood test for diagnosing syphilis. A positive reaction to the test shows the presence of antibodies formed as a result of infection with the disease. Wassermann practiced medicine in Strasbourg, then in 1906 became director of the department of experimental therapy and serum research at the Robert Koch Institute for Infectious Diseases in Berlin. He was director of the department of experimental therapy at the Kaiser Wilhelm Institute, 1913–25.