Biological Tests for Carcinogenicity

in which ground glass connections could not be used because of the large size of the flasks, it was found that benzene extracts of rubber stoppers previously washed with ether and methanol still contained blue-green fluorescing substances. These extracts had the ultraviolet absorption spectra of carcinogenic hydrocarbons and other compounds of interest. This discovery seemed of such great possible importance to investigators in cancer re search, to the rubber industry, and to public health that further experiments were made. It was found that extracts of rubber stoppers were car cinogenic for mice. In similar extracts, the pres ence of pyrene, 3,4-benzpyrene, chrysene, and other aromatic hydrocarbons was detected. The same compounds were found in benzene extracts of an automobile tire. Further observations, together with comments on the possible origins and impor tance of these compounds, are here presented.