Experiments to produce cutaneous carcinoma by application of tar and, more recently, of the several synthesized carcinogenic compounds and to produce sarcoma by subcutaneous or intramuscular injection of these substances have been repeatedly performed on mice, rats, rabbits and guinea pigs. A significant percentage of pulmonary tumors has been observed as a result of cutaneous application of the compounds. However, relatively fewer observations have been published on the production of "internal cancers" by causing the animals to ingest the various carcinogenic agents in one form or another.
By repeated tarring of the mouths of 50 rats Bonne1 produced benign papillomas in the skin of the face about the mouth and also squamous cell carcinomas in the buccal cavity, the esophagus and the cardiac end of the stomach. Voronoff and Alexandrescu2 administered a mixture of tar, hydrous wool fat, aniline oil and toluylenediamine by mouth to 10 rats and