Walpole, Williams, and Roberts (13) observed a high incidence of tumors of the colon in white rats given injections of 4-aminodiphenyl and 3,2dimethyl-4-aminodiphenyl. By feeding radioactive yttrium (Y91)to rats, Lisco et al. (6) also reported that a high proportion of animals developed car cinoma of the colon. With other substances, cancer of the large intestine has been but seldom pro duced. Krebs (4, 5) reported that, of sixteen mice given alcohol by rectum, one developed carcinoma of the

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... on with metastasis to the liver. Spitz, Maguigan, and Dobriner (10) found seven in stances of adenocarcinoma of the rectum at its junction with the colon among 385 white rats in jected with benzidine. AJÕ seven occurred in male rats. Bielchowsky (1) fed acetylaminofluorene to 104 albino rats. Ninety-three of them developed a total of 105 malignant tumors, of which only five were of the intestine. One of these five was a cancer of the cecum with metastasis into the liver. The location of the other four intestinal tumors was not recorded. Among 22 rats which survived totalbody irradiation longer than 6 months, Brecher, Cronkite, and Peers (2) reported that eight devel oped tumors and, of these eight, only one devel oped a lesion in the colon (350 days after irradiation with 1,000 r). Cox, Wilson, and De Eds (3), work ing with acetoaminofluorene in albino rats, found that among 84 animals that developed multiple tumors only two had adenocarcinoma of the colon. Lorenz and Stewart (7, 8, 11, 12) demonstrated precancerous and cancerous lesions of the forestomach and small intestine of mice after feeding methylcholanthrene or after injecting this car cinogenic hydrocarbon directly into the wall of the stomach, but no lesions were observed in the colon.