Many times at operation or necropsy, cysts containing gas under pressure have been found unexpectedly in the intestinal walls, in the mesentery or elsewhere about the peritoneal cavity. They are thin walled, single or in clusters, of different sizes, and sometimes contain blood or lymph. Similar cysts have also been observed in the vaginal wall during pregnancy. The more or less complete endothelial lining varies from a nearly normal to a greatly thickened plasmodial layer on a loose, fibrous, proliferative connective tissue, rather vascular and containing plasma cells, round cells, polymorphonuclear leukocytes and often mast cells and eosinophils. The physiologic relations are unknown.
Discovered by chance at laparotomy to relieve certain gastro-intestinal symptoms, the cysts have sometimes been resected and the patient apparently cured thereby, while in other cases, although left untouched, they have been found at a later laparotomy or at necropsy to have disappeared. Cysts which seemingly are