The effect of tobacco tar on the bronchial mucosa of dogs

HE IMPRESSIVE evidence for the relationT ship between cigarette smoking and lung cancer is based for the most part on epidemiological data.2 Although the carcinogenicity of tobacco tar for the skin of mice has been demonstrated,' it has seemed desirable to seek experimental support for the epidemiological evidence in attempts to induce lung tumors comparable to human bronchogenic carcinoma. The bronchial epithelium, with its protective watery mucous coat and its ability to rapidly clear inhaled materials, is a unique tissue, and materials carcinogenic at other sites could well be ineffectual when applied to the respiratory tract. The induction of experimental bronchogenic carcinoma would permit a detailed study of the pathogenesis of this lesion and of those factors that influence its production. The following is a report on the early effects of the application of tobacco tar to the bronchial mucosa of dogs over a period of 11 months.