Abstract
Materials sedimentable at high speed (approximately 27,000 R.P.M.) were found in all normal and neoplastic tissues studied. They are carriers of the Forssman antigen and of the Wassermann hapten. These heavy materials exhibit species, organ, and individual specificity and produce several antibodies which can be demonstrated by absorption tests. Heavy materials from chicken sarcoma and chicken spleen could not be distinguished by complement fixation tests.