Component bases of nucleic acid in photographic gelatins were analyzed by the column chromatography in order to find out restraining substances. The pH dependence of physical retardance of gelatins changed by the ion exchange treatment. It was found that adenine, guanine and other bases were eliminated from gelatins by the deionization. Physical retardance lost by the ion exchange could be partly restored in neutral and alkaline pH's by the addition of adenine and guanine.