The effect of edema upon the anatomical structure of the small intestine may be the basic mechanism responsible for the development of regional enteritis. Our interest in the influence of edema upon the small intestine was stimulated by a study of histopathologic changes in Whipple's disease as compared with changes experimentally produced in animals by chylous obstruction.1 The predominant intestinal changes in experimentally produced obstructive lymphedema are distortion of the mucosal pattern and an inflammatory reaction of the lamina propria characterized by proliferation of plasmacytes and periodic acid-Schiff positive macrocytes. In reviewing intestinal sections of regional enteritis, it was noted that similar mucosal and inflammatory changes occurred in the proximal, preulcerative segments. Progressing in the examination from preulcerative to ulcerative segments a gradual increase of changes was observed. These alterations were associated with characteristic changes in the configuration of the Kerckring folds. It seemed possible that the changing configuration