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Evans (1947) has reported that treatment of sea water with X-radiation deleteriously affects the survival and activity of Arbacia eggs and sperm. This effect can be duplicated by H202 and can be completely negated by the addition of catalase. Such biological effects of irradiations have been studied in a number of laboratories (Barron et al., 1947; Giese, 1947). Stone et al. (1947, 1948) increased the mutation rate of Staphylococcus aureus to penicillin and streptomycin resistance by ultraviolet irradiation of the substrate prior to inoculation of the organisms. They suggest that the mutant individuals arise as a result of the assimilation of modified substrate molecules. A similar enhancement of the mutation rate results when the organisms are grown in a nutrient broth that has been treated with hydrogen peroxide prior to inoculation (Wyss, Stone, and Clark, 1947). Since very sensitive chemical methods failed to show any residual hydrogen peroxide at the time of inoculation of the treated broth, the mechanism appears analogous to the irradiation experiments. The similarity of the effects produced on proteins and peptones by H202 and radiations has been reviewed by Anow (1937). Fernau (1923) concluded that the results of a treatment with Roentgen rays, ultraviolet, and alpha particles on albumin solutions were identical with those produced by peroxide. Lieben (1927) states that the disappearance of the color reaction for tyrosine and tryptophan in proteinaceous solutions exposed to ultraviolet can be duplicated with H202. After the solutions stand for several days, the color reactions reappear. This process can be hastened by the addition of spongy platinum to decompose traces of peroxide in the solutions. However, Taylor, Greenstein, and Hollaender (1948) showed that the changes in viscosity of sodium thymus nucleate solutions that occurred following X-radiation could not be duplicated by H120 at 10-2 to 10-' M.

The preparation designated "EDC" is that sold by Nutritional Biochemicals Corporation as "Casein hydrolysate-enzymatic." 10 The nature of the growth stimulation by the nucleic acid derivatives has not been further investigated, nor have impurities been ruled out as a contributing factor to their activity. The favorable effects of ascorbic acid on growth of L. casei in media of this type were observed by E. L.