It is almost certain that in a human pathological service of fifty-five hundred autopsies, one or more diverticula of the Meckel variety would be encountered and perhaps several of other kinds. In our material only pouchings or false diverticula of the colonic wall are recorded, and our personnel has often spoken of the absence of these gross abnormalities of the alimentary tract. The two cases, notes of which are given, are instances of hernial pouchings of the colonic mucosa and serosa, a condition which is well known in human medicine. It may be said to occur in two varieties, one in which the pouchings have heavy walls formed by a thickened mucosa, muscularis and peritoneum and one in which the bulgings have delicate walls, then being small herniæ of the inner coats through rifts in the outer. Such a division is probably unnecessary or misleading since the latter may be only a forerunner of the former. However the clinical evidence of the simple variety is scanty and may be little more than constipation while the peritonitic variety gives a clinical picture of pain, constipation and a mass in the left abdominal area, then known as diverticulitis or pericolitis sinistra. In these cases the colon is much distorted by the irregularity of its mucosa and by inflammatory thickening of the muscularis and serosa. Diverticula arise from defects of the muscular coat, or secondarily after inflammation or prolonged constipation, by weakness of muscle, or as hernial protrusions around the entrance of blood vessels where the muscle is thin. Such sacculations permit feces to collect and continue the inflammation, thus further weakening the gut and producing constipation, the whole vicious cycle being favorable to the formation of more sacculations; coproliths may form in the diverticula. The two monkeys now reported seem to have varying grades of the same condition, a long standing colitis with diverticula, constipation and the collection of inspissated feces in the sacculations. These animals did not have hemorrhoids. Black Ape ♀ (_Cynopithecus niger_). Coprostasis. Coproliths in diverticulum. Chronic colitis. Cor bifida. The large intestine is of the same calibre as the small intestine should be when not distended. The sacculations as seen before opening the organ are salient, forming distinct pouches. In one or two cases they are so pronounced as to constitute diverticula 7 cm. long. In two instances the serosa at the fundi of these diverticula is markedly hyperemic and very thin. In many cases the sacculations contain coproliths. The wall of the organ is distinctly thickened, puckered, inelastic and opaque. Mucosa is thrown up into coarse rugæ.