Rearing rats on low-and high-protein diets yielded no difference in the level of hepatic ammonia while urea production was assessed at a higher level in the high-protein diet group. The appearance of a large number of ammonia-producing nonsporeforming anaerobic bacteria in the jejunum of the rats reared on a high-protein diet seems to imply that the hepatic urea cycle was stimulated by the bacteria enhancing the generative reaction from ammonia to urea. These results are significant when viewed

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... as the probable indication of the integral ecological function of intestinal flora in the homeostatic regulation mechanism, taking the regulation of the urea cycle as one example.