Metchnikoff, Élie, 1845-1916, Russian biologist. He studied in Russia and Germany, lectured at the Univ. of Odessa, and, after working with Pasteur in Paris, became (1904) deputy director of the Pasteur Institute there. He introduced the theory of phagocytosis, i.e., that certain white blood cells are able to engulf and destroy harmful substances such as bacteria. For his work on immunity he shared with Paul Ehrlich the 1908 Nobel Prize in Physiology or Medicine. He developed a theory that lactic-acid bacteria (B. acidophilus) in the digestive tract could, by preventing putrefaction, prolong life; and with P. P. É. Roux he experimented with calomel ointment as a treatment for syphilis. His writings include Immunity in Infectious Diseases (1905) and The Nature of Man (1938).

See Élie, duc Decazes