It is common practice to cover perforated ulcers of the stomach with tabs of omentum, especially when the adjacent gastric wall is too indurated and friable for satisfactory closure of the hole with sutures alone. Free omental transplants, or grafts, have been recommended for that purpose, and illustrations of such an operation may be found in current surgical textbooks. On theoretic grounds it may be questioned whether this procedure is sound surgical practice. One might expect the free transplants, deprived temporarily of a blood supply, to be susceptible both to the digestive action of gastric juice and to infection, which is sure to be present, at least part of the time. In that case the safer procedure would be to cover the defects only with living omentum, which presumably would offer greater resistance to both digestion and infection. EXPERIMENTAL PROCEDURE We have studied this problem experimentally by means of operations