A simple, rapid, and quantitative procedure which determines the amount of pontamine sky blue infiltrated into animal tissue, was described for the assay of the degree of liver damage in mice. From pathological aspect, pontamine sky blue injected intravenously was found only in metamorphic cells of poisoned mouse liver. Apparent infiltration of the dye into liver was initially observed, similarly to that of the carbon tetrachloride or thioacetamide injury, but in the time-courses, the dye infiltration became different from these two injuries. When mouse liver was injured by ethionine, no infiltration of the dye was observed. The infiltration of the dye into liver was completely protected simultaneously by the aminoacetonitrile administeration against the poisons, not only in carbon tetrachloride but also in thioacetamide injury. However, the protection of liver injury was not observed even by the injection of aminoacetonitrile if the liver was previously treated with either carbon tetrachloride or thioacetamide before 8 hours.
