A basal diet containing 0.06 per cent 3′-methyl-4-dimethylaminoazobenzene was fed to albino rats of the Sprague-Dawley strain, and at intervals of 3 to 18 weeks 3-methylcholanthrene was added to the diet in a concentration of 0.0067 per cent. The animals were sacrificed at regular intervals to detect the sequential changes occurring in the livers.

It was found that 3-methylcholanthrene would prevent carcinoma of the liver if it were added to the diet before the 6th week, and that there was partial inhibition if the 3-methylcholanthrene were added before the 10th week of administration of 3′-methyl-4-dimethylaminoazobenzene. After the 10th week no inhibition resulted.


This investigation has been aided, in part, by Cancer Teaching and Cancer Training Grants, The National Cancer Institute, U.S. Public Health Service, and by the Oregon Division of the American Cancer Society.

With another numbering system 3-methylcholanthrene is referred to as 20-methylcholanthrene.

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