Nitrogen equivalent to about 35 per cent of the nitrogen intake, though not necessarily derived directly from it, is daily secreted in the succus entericus in dogs on a mixed diet; about 10 per cent is excreted in the feces. and about 25 per cent is reabsorbed. The amount of reabsorbed nitrogen-containing material is considerably larger if the bile and pancreatic secretion are included. The metabolic significance of this reabsorption can only be surmised. That it is probably of great importance is indicated by the fact that in the experiments here recorded the amount of nitrogen reabsorbed equaled approximately 25 per cent of the nitrogen intake.