['e', '60', 'and', '60%', 'of', 'the', '3-MC', 'tumored', 'old', 'mice', '(average', 'weight', '0.61', 'gm).', 'Enlarged', 'spleens', 'were', 'found', 'in', '8%', 'of', 'the', 'trioctanoin', 'imjected', 'control', 'mice', '(average', 'weight', '0.33', 'gm)', 'and', 'markedly', 'enlarged', 'spleens', 'were', 'found', 'in', 'those', 'few', 'aging', 'wild', 'mice', 'with', 'spontaneous', 'or', 'induced', 'lymphomas', '(average', 'weight', '0.95', 'gm).', "An'", 'increasing', 'incidence', 'of', 'lymphoma', 'in', 'aging', 'wild', 'mice', 'containing', 'CF', 'gs', 'antigeu', '(almost', '100%)', 'and', 'C-type', 'particles', '(almost', '100%)', 'in', 'tumor', 'or', 'spleen', 'and', 'an', 'increased,prevaienee', 'of', 'C=type', 'particles', 'in', 'old', 'vs.', 'young', 'mouse', '3-MC', 'tumors', '(25%)', 'and', 'in', 'normal', 'spleens', 'with', 'aging', 'alone', '(25%)', 'are', 'all', 'consistent', 'with', 'a', 'lesser', 'suppression', 'of', 'viral', 'activity', 'in', 'aging', 'mice.', 'Although', 'infectious', 'virus', 'was', 'not', 'isolated', 'from', 'any', 'of', 'the', 'wild', 'mouse', 'tumors', 'or', 'from', 'normal', 'tissues', 'in', 'aging', 'mice,', 'it', 'appears', 'that', 'a', 'wild', 'mouse', 'C-type', 'virus', 'has', 'been', 'isolated', 'from', 'wild', 'mouse', 'embryo', 'tissuves', '(sce', 'Virology', 'Program),', '|', "'", 'The', 'lymphomas', 'in', 'aging', 'wild', 'mice', 'were', 'primarily', 'lymphoblastic', 'and', 'characterized', 'by', 'splenomegaly', 'and', 'generalized', 'lymphadeno-', 'pathy', 'without', 'thymic', 'involvement.', 'One', '1lymphoma', 'arose', '26', 'months', 'after', '3-MC', 'inoculation.', 'Two', 'arose', '19', 'and', '24', 'months', 'following', 'abortive', '3-MC', 'tumor', "trans'plant", 'attempts', 'and', 'seven', 'arose', 'spontaneously', 'after', '20-25', 'months', 'in', 'captivity.', 'In', 'addition,', 'six', 'spontaneous', 'pulmonary', 'adenomas,', 'several', 'quite', 'large,', 'and', 'four', 'spontaneous', 'fibrosarcomas', 'have', 'occﬁrred.', 'Four', 'out', 'of', 'four', 'pulmonary', 'adenomas', 'and', '3/4', 'fibrosarcomas', 'were', 'positive', 'for', 'CF', 'gs', 'antigen', 'but', 'all', 'were', 'free', 'of', 'detectable', 'C-type', 'particles.', 'B13', 'N', 'I', 'INROT', 'ANOD', 'BLOSRMNINW', 'NOIIDSILIT', 'OSOu20L']