Studies on Fowl Leukosis

Following the observations on high-speed centrifugation of the avian sarcoma agent by various investigators,1' 8,10,11,12 similar studies of the agent of fowl leukosis have been undertaken. Since the neoplastic nature of this disease is now rather generally recognized, observations on the filterable agent of chicken leukosis have assumed new significance for the study of the etiology of fowl neoplasms. It is the purpose of this paper to describe (1) observations on the transfer of fowl leukosis with fractions obtained by ultracentrifugation of leukemic bone-marrow extracts and plasma and (2) observations on host resistance to both the filterable agent and leukemic cells. An account of the physical-chemical properties of sediments obtained from leukemic tissue extracts will appear in a subsequent publication.: Materials and methods