Ammonia in the large intestine of herbivores.

I. The object was to investigate the importance of urea as a source of ammonia in the large intestine of herbivores. Urea was present in small intestinal contents of slaughtered horses in concentrations similar to those in blood but, in the small intestine of slaughtered sheep, the urea was less than in blood. 2. There was little ammonia in small intestinal contents of slaughtered horses but considerable ammonia was present in small intestinal contents of slaughtered sheep. The ammonia in small intestinal contents of the slaughtered sheep was probably formed from urea, as ileal contents taken from a sheep with an ileal cannula contained considerable urea and little ammonia. 3. The ammonia concentration in caecal contents of sheep was related to the concentration of urea in blood except when ileal contents were prevented from entering the caecum. 4. Ileal digesta of sheep contained more free amino nitrogen than did caecal digesta. 5 . Ammonia was absorbed more rapidly than water from the caecum of sheep. The rate of absorption was related to the concentration of ammonia in the caecum.