A series of about two hundred and fifty cases, including normal individuals, a large number of patients representing a variety of pathological conditions, and a group of patients suffering from symptoms supposedly due to intestinal disorders such as constipation, autointoxication, colitis, arthritis, eczema and urticaria, have been treated by dietary restrictions affecting the protein foods. About six hundred and fifty quantitative determinations of the indican, phenols, total nitrogen and creatinine excreted in the twenty-four hour urines have been made. It has been found that a decrease in the total nitrogen intake (meat and eggs) results in a corresponding decrease in the putrefactive products excreted by the same patients when on a higher protein diet. The phenols, as determined by the method of Folin and Denis1, however, showed much less tendency toward significant changes due to diet than did indican. In as much as Tisdall2 has suggested the non-specificity of this method for determining phenols, ou...