General and professional correspondence (ca. 8000 items), family correspondence (ca. 1500 items), biographical data, speeches, awards, photos, and other material. Loeb's scientific writings include drafts of his books, Forced Movements, Tropisms, and Animal Conduct, 1918, Proteins and the Theory of Colloidal Behavior, 1922, and Regeneration From a Physico-chemical Viewpoint, 1924; laboratory notebooks relating principally to his research on bryophytes, gelatin, and frogs, which led to his development of the tropism theory; and scientific articles (in English and German) on such topics as colloid chemistry, genetics, osmosis, and proteins. Correspondents include Svante Arrhenius, Bernard Berenson, James B. Conant, Paul De Kruif, Paul Ehrlich, Albert Einstein, Sigmund Freud, Julian Huxley, Ivan Pavlov, and Harlow Shapley.