Lung Tumors Following Intraperitoneal Injection of 1:2:5:6-Dibenzan-thracene into Young Mice of Three Strains

Data have already been published 1 demonstrating inherited differences in degree of susceptibility to spontaneous and to tar-induced lung tumors in two inbred strains of mice when the criteria for susceptibility included not only the percentage of tumor-bearing animals per group but also the number of tumor nodules per individual. The same criteria revealed constitutional differences in susceptibility among 3 strains of mice observed after intraperitoneal injections of 1:2:5:6-dibenzanthracene into very young animals. 2 The present paper reports further data obtained after intraperitoneal injections, combined with the original observations made following this technic.

The three strains used, the Swiss, our branch of Bagg albinos, and No. 1194,∗ differ in susceptibility to spontaneous neoplasms. The Swiss have the highest lung tumor incidence. In a sample of 448 mice (Table I), about one-half, or 46.1%, and tumor. This figure is based upon mice of all ages. However, tumor incidence increases with age, and, in groups of mice of this strain that have reached a year and a half of more, 80% have tumor. Tumors occur early in this strain, a growth having been observed in a mouse only 3 months of age. One of the characteristics of lung tumor is that the nodules may be multiple.