Description: Papers of Harold H. Mitchell (1886-1966), professor of animal science (1918-54), including an alphabetical subject file (1922-66), correspondence concerning the administration of research for the Saltpeter Investigation in the laboratory of Physiological Chemistry (1906-12), photographs of the apparatus used in the saltpeter experiment and in metabolism, digestion, perspiration and respiration studies (1907-40); 80 unpublished manuscripts (1906-48) and 158 publication reprints (1916-62) relating to protein and mineral nutrition and metabolism, comparative nutrition and climatic stress research.