Further Observations on the Organs of Mice Painted with Carcinogenic Agents

The study of the effect on the internal organs of mice of the application of carcinogenic agents to the skin has occupied our attention during recent years, a preliminary analysis of findings in several thousand animals having already been published (1). Most of these earlier experiments were performed with the primary object of testing the reaction of the skin to various carcinogenic agents. More recently a number of experiments have been carried out specifically for the purpose of correlating any changes observed 'in the skin with differences in the morphology of the internal organs. This paper will be devoted for the most part to a description of our findings in these special experiments. Having found that the general health of the animal has an important bearing on tumour incidence, we were led to believe that the " balance " of certain organs might play some part in the cancerous process. We therefore from time to time weighed or measured certain of the internal organs of large batches of animals, and from the results obtained have been able to compile correlation values for the various organs one with another, and to compare the organs as to actual size or weight. By this means we have been able to compare (1) tumour and tumourless animals; ( 2 ) animals bearing malignant tumours and those without such tumours; ( 3 ) painted and control animals; (4) males and females in the different groups. The following organs were weighed: spleen, brain, and pituitary gland of certain groups. The following organs were measured: pituitary gland, thyroid, and parathyroid of certain groups. The body weight of each animal was recorded. The pituitary glands were measured in the fresh state, under a low power of the microscope, while stained sections of the thyroid and parathyroid were projected and measured with a planimeter. Correlation values for all animals were obtained for: brain and body weight, brain and spleen, brain and superficial area of pituitary, body weight and spleen, body weight and superficial area of pituitary, spleen and superficial area of pituitary.