WHEN A careful search is made, about one-third of people past 45 years of age will be found to have some diverticula of the colon. These lesions are found most commonly in the sigmoid, next in frequency in the descending colon, but may be scattered throughout the large bowel. We have never seen them below the peritoneal reflection. It is our feeling that these are pulsion diverticula. Figure 1 is a section of the sigmoid done post mortem in an 80-year-old patient who had no symptoms referable to the colon. The only barrier between the lumen of the bowel and the peritoneal cavity is the mucosa, some subperitoneal fat, and the peritoneum. In this section we also see that in one area the mucosa is beginning to herniate through the muscularis as if a new diverticulum is forming near the main one. However, even the completely formed diverticula are still