A solution of crystalline ribonuclease was injected intraperitoneally andintravenously into the blood stream of the mouse. A depletion of the ribonucleicacid together with a decrease of the calcium ash was observed in the corticalportion of the liver cell 12 minutes after the injection until recovery of normaldistribution 122 hours later. The possible association of calcium with ribonucleicacid in the cytoplasm constituents of the liver cell is discussed.