Ileus or acute intestinal obstruction may be divided for our purposes into intussusception, volvulus, strangulation and paralysis from interruption of mesenteric circulation. Examples of all these varieties have been encountered and illustrative cases will be cited. In so far as incidence is concerned, the Ungulata and Carnivora greatly outnumber all other orders, showing seven cases each; the sum total in all other orders is but eight. Upon re-reading some of the protocols I have, however, excluded three invaginations in the carnivores, one each in the ungulates and rodents, as probably being postmortem or shortly antemortem occurrences; two had very early peritonitis but other things, sufficient to account for death, were present. These deductions bring the total cases of ileus in mammals to seventeen. Five cases in birds will be discussed briefly. Primates present one case of volvulus, one of intussusception and one of internal strangulation. The first displayed the entrance of four inches of ileum into the colon with such swelling of the wall as to prevent reduction. The exciting cause seemed to be an enteritis, the cause of death a peritonitis. A white-collared mangabey (_Cercocebus collaris_) was the victim of volvulus probably favored by an anomalous position of the transverse and descending colon which lay to the right, the latter traversing the abdomen obliquely from right to left to reach the pelvis. The volvulus occurred in the ileum just above the cecum, the twisted part being found adherent by the peritonitis. The third case is a strangulation due to peritonitis from filaria and adhesions between stomach and colon from a colitis and pericolitis due to cestodes, one of which was found deeply implanted in the colonic wall. Two cases of intussusception are noted (after deductions above) for the Carnivora. They both occurred in the ileum, one restricted thereto, the other extending into the colon. In both a vague history of being “off their feed” or giving evidence of intestinal trouble could be obtained from the keeper. The three excluded cases had invaginations in the middle and lower small intestines but not at the cecal valve. Volvulus did not occur in the Carnivora. A paradoxure (_Paradoxurus hermophroditus_) died as the result of a strangulation of a six-inch knuckle of gut which had passed through a hole in the omentum. The animal had not been eating well for a month but gave no signs by which this ileus could have been diagnosed. Perhaps it had existed for sometime but only shortly before death had swollen sufficiently to cause obstruction.