STUDIES ON CULTURAL REQUIREMENTS OF BACTERIA. II

studies, it was intimated that by treating an infusion of beef heart with charcoal, two factors necessary in the growth of hemolytic streptococci were removed, and that these factors could be again supplied by the addition to the charcoal treated infusion of commercial peptone or of a sulphuric acid hydrolysate of casein. The main facts learned up to this time about these two growth determining substances have been already briefly reported (Mueller, 1920), and will be here presented in detail. Work upon these substances has not yet been completed in the sense of chemical isolation and identification, and it is hoped that after further investigation which is now under way, it will be possible to give a more definite report of their nature. TECHNIC The general technic of preparation of media, adjustment of reaction, inoculation and recording of results, together with the method of carrying the test strain of streptococcus in culture, etc., has been fully described in the introductory paper (Mueller, 1922), and need not be repeated here. Removal of certain growth determining factors from beef heart infusion by charcoal, and reactivation of the charcoal treated infu-sion by means of peptone Three hundred cubic centimeters of a beef heart infusion, prepared by mixing chopped heart muscle and water in the pro