These anatomic curiosities, due to defect of development or subsequent alteration in structure, seem to attract little attention; nevertheless, they are of scientific interest. Holes in the mesentery are apparently of great infrequency and with few exceptions no references to them are found in the literature nor attempts to explain their origin. In the mesogastrium (the omentum) they are not infrequent. It is probable that the same conditions which cause them in the omentum lead to their formation in the mesentery. They are seldom found in the upper part; the nearer the cecum the more numerous and the larger they become. Traumatism with laceration, the breaking down of caseous glands, and emptying of serous or chylous cysts may give origin to them, but the most frequent situation for their location being proximal to the cecum, suggests defective arterial supply and gradual absorption as the more logical explanation for their existence.