MICHAELIS, LEONOR (1875–1949), German biochemist. Born in Berlin, he worked with Paul *Ehrlich at the City Hospital where he directed the bacteriology department from 1906 to 1922. In 1908 he was appointed professor of medicine at the University of Berlin, and from 1920, professor of physical chemistry. From 1922 to 1926 he was professor of biochemistry in Nagoya, Japan. In 1926 he went to the Johns Hopkins University in the U.S. and then to the Rockefeller Institute for Medical Research in New York. He contributed many scientific papers on topics concerned with casein, blood pH in biological systems, the behavior of dyestuffs in biological media, and respiration. His books included Hydrogen Ion Concentration (1926), Praktikum der physikalischen Chemie inbesondere der Kolloidchemie fuer Mediziner und Biologen (19304; Practical, Physical and Colloid Chemistry for Students of Medicine and Biology, 1925), and Oxydations-Reduktion Potential (1929; Oxidation Reduction Potentials, 1930).