A method of producing in inbred albino rats a high percentage of immunity from tumors native in their strain.

During our studies on the extraction of substances from induced primary and transplanted rat sarcomata, we obtained a fat soluble fraction that in some instances brought about a sarcoma when injected into rats (Aptekman, King and Lewis '43) and also an alcohol-soluble fraction that inhibited the growth of grafts of tumors and conferred immunity from further growth of grafts of the same tumor in a large percentage of the treated rats. It, therefore, seemed of moment to expand our studies in regard to the tumor-inhibiting fraction in the hope of reaching a clearer understanding of this complicated biological process. Material and Method. As was shown by King and Lewis ('45), an injection of a carcinogenic agent (1:2:5:6-dibenzanthracene, 2:3 benzypyrene or methylcholanthrene dissolved in olive oil) into the right axilla of rats resulted in the development of a malignant tumor at the site of the injection in every one of the injected rats.