A further abnormality attributed to deficiency of fat-soluble A in the diet was reported by Osborne and Mendel (22). They found in the urinary tract, calculi of calcium phosphate. In 857 autopsies they found calculi in 91 animals. Forty-three per cent of these had not had a satisfactory supply of fat-soluble A. Mendel (23) calls attention to the fact that urinary calculi are exceptionally common among peoples of the Tropics, and of the Far East, who live on diets quite unlike the mixed diets common among Europeans and Americans. He suggests a correlation of his experience with the well-known fact that these calculi are deposited from neutral or alkaline urines, which frequently owe their reaction to the formation of ammonia as a result of bacterial decomposition. The possibility that the invasion of the urinary tract by microorganisms results from the lowered vitality due to partial or complete starvation for fat-soluble A is suggested by their findings at necropsy. I am not greatly impressed with the view that there is any specific relation between starvation for fat-soluble A and the occurrence of calculi. Fifty-seven per cent of the animals found in the autopsies of Osborne and Mendel to contain calculi of the urinary tract had had a satisfactory supply of this dietary factor. In our own experience calculi have occurred so frequently in animals whose diets contained an abundance of this factor, but were faulty in other respects, that it would seem to be the result of general debility rather than lowered vitality brought about by specific cause.