Influence of Sex and Heredity on the Development of Tar Tumors

Abstract

The influence of heredity on the induction of tar tumors in mice has been studied, according to Woglom (1), by Parodi (2), who concluded as a result of his experiments on a small number of animals, that heredity has no influence. Miss Lynch (3) extended this work, using two strains of mice in which the incidence of spontaneous mammary cancer was 65 per cent and 28 per cent respectively. These animals, 20 in each group, were painted with coal tar. No variation was detected between the two strains. Murray (4), working with mice having spontaneous tumors, endeavored to determine the influence these tumors would have on the artificial induction of tumors with tar. He makes the statement: “If there is a difference, it is in the direction of a more rapid induction of tumors in cancer mice.” For our purposes we have selected two strains of mice in which the incidence of spontaneous cancer is markedly different: a strain of albino mice (strain 3) in which the incidence of mammary cancer is 93 per cent of the bred females, and a hybrid strain resulting from crossing an albino with the common house mouse, having a low or delayed tumor incidence. Ninety-two animals of strain 3 and 32 of the hybrid strain were chosen for the experiment. They were kept in individual cages, and painted twice weekly with tar obtained from the Barrett Company, over an area approximately 1 cm. in diameter, in the interscapular region, from which the hair had previously been removed by sodium sulphide. After two weeks of tarring it was no longer necessary to remove the hair.