THE majority of gastro-intestinal patients whom we see are referred for study because of functional disturbances. In many instances, it is the colon which presents the most striking departures from normal. These departures may or may not be accompanied by the clinical manifestations of constipation and diarrhea. When there are obvious disturbances of function, our aim should be to explain the underlying cause. When there are no obvious disturbances, the condition of the colon often furnishes information which may be of value to the clinician in his appraisal of the problem. Despite the great amount of study given to the colon and its mechanism, there is still much that is not known, not only of the nervous control but the factors which tend to disturb the delicate balance of that control. Roentgenologic indications of colon dysfunction are by no means always clear-cut, and the correct valuation of the evidence elicited is often as difficult as it is important. In my experience, the fed meal affords a far more satisfactory means for the study of colonic function than does the enema. The ideal procedure is the correlation of both methods, but the time required in many instances precludes such a course. Many of the patients referred to our department for study come from a distance, and frequently circumstances compel us to forego the enema. However, I feel that the enema frequently gives a misleading picture. The advancing solution is seen to fill a more or less uniformly constricted distal gut which, as the filling continues, relaxes and finally assumes normal or approximately normal contours as the result of pressure. I use at times a meal which more nearly simulates the habitual contents of the colon than does the usual contrast meal. For this purpose oatmeal as ordinarily cooked has seemed the most satisfactory vehicle. Other cereals may be used but the oatmeal barium mixture seems to be more palatable than some of the others. This may be taken as part of the ordinary breakfast and observations made in eight and in twenty-four hours and continued as long as indicated. By this means, barium is incorporated with the usual components of cellulose and bulky food material and the behavior of the colon under ordinary conditions is more nearly simulated. A clear appreciation of the normal colon must be in our minds before intelligent appraisal of disturbed function is possible. Not only must the ideal norm be recognized, but also the acceptable variations in colon morphology and tone. The entire picture depends on progress, tone, haustration, and caliber. At the end of five hours, the standard meal should have left the stomach and the head of the barium column should be in the ascending colon. Failure to make this progress implies hypomotility, either gastric or of the small intestinal tract, or an obstructive lesion proximal to the ileocecal valve.