A year ago we believed we had isolated the organism responsible for at least a prominent part in the cause of chronic ulcerative colitis of the so-called idiopathic type.1 The organism was obtained with sterile swabs through the proctoscope from the depths of an ulcer of the colon, after the latter had been thoroughly cleansed by repeated washings and the top of the ulcer had been carefully wiped with a preliminary swab. Cultures of stools failed to yield the organism but in cultures of the rectal discharge of mucus, pus and blood it was often found as the vastly predominating bacterium. The material obtained was cultured immediately in warm dextrose brain broth,2 blood agar and lactose agar and incubated for twenty-four hours. All mediums were titrated to a pH 7.4. The organism isolated in this way as the predominating bacterium and often in pure cultures is a gram-positive, lancet shaped