Morphology of Foci Produced by Standard Preparations of Rous Sarcoma Virus

Abstract
Six preparations of Rous sarcoma virus from 3 different sources were titrated in chick-embryo tissue culture under identical conditions and the morphology of the foci compared. The virus preparations can be divided into 3 groups according to the morphology of the foci and the presence or absence of “giant cells.” Only the preparations CT916 (“high titer strain”) and CT895 produced “giant cells.” The possible origin of the differences in morphology is discussed.