A Pure Strain of Rous Sarcoma Cells

this work. We are also indebted to the " W. H. Ross Foundation (Scotland) for the Prevention of Blindness," who have defrayed the expenses of this investigation; to Sir Henry Dale, who kindly gave us some of his supply of tyrothricin; to Dr. Trevan, of the Weilcome Research Foundation, who kindly supplied us with penicillin made by Dr. Pope and Miss Stevens; and to Mr. Edwards, of British Schering, Ltd., who kindly supplied us with sodium sulphacetamide (Albucid soluble).