IRREVERSIBLE SHOCK in the dog whether due to hemorrhage, endotoxins, epinephrine, or occlusion of the superior mesenteric artery is associated with characteristic visceral pathology of which acute hemorrhagic necrosis of the intestinal mucosa is the principal and most striking pathological finding.1, 2 Although pathological changes are also found in the brain, heart, lungs, liver, and kidneys, these changes are usually mild, frequently variable, and cannot be related directly to mortality. The opposite is true of the small bowel lesion, and measures which ameliorate or prevent the bowel lesions also prevent the death of the dog. This similarity of gross pathological changes in various types of shock suggests that at some stage there are common physiological derangements which cause deleterious effects in the intestine. This common denominator in irreversible shock in the dog is believed by the authors to be a mechanical limitation of blood flow to the intestine of