IN AN EXPERIMENTAL study of strangulation obstruction, we found a previously undescribed and, as yet, unidentified pigment in the peritoneal fluid.1This has stimulated a search for the pigment in clinical cases of comparable nature, and for the two years of our study, seven of the largest hospitals in Philadelphia have been attempting to supply us with peritoneal fluid from all patients operated on for intestinal obstruction with suspected strangulation.2Two personally observed cases of mesenteric arterial thrombosis requiring resection of all but 16 and 32 cm. of small bowel failed to show any significant spectrophotometric changes in the peritoneal fluid. Thus the demonstration of this pigment in a case with compromised blood supply to the small bowel seemed of sufficient interest to warrant a brief report of its occurrence. Since there are many reasons to indicate that the interference with the blood supply in the obstruction experiments