The intravenous injection of Shiga toxin into dogs causes a rise in hemoglobin, red blood cell count, hematocrit reading, and specific gravity of the whole blood. There is thus a decrease in circulating blood volume. The specific gravity of the blood plasma does not change. These findings indicate that the toxin of B. shigae produces a shock-like circulatory state. As a result there occurs a compensatory vasoconstriction in the duodenum of the dog and in the cecum of the rabbit. It has been shown that the toxin of B. shigae has no direct effect upon the intestinal mucosa when brought into contact therewith, but that its absorption through the mucosa leads to the appearance of a lesion in the duodenum of the dog. Therefore we interpret the pathological alterations in the intestinal tract, following the injection of Shiga toxin, as the anatornic end result of a pronounced and prolonged homeostatic vasoconstriction.

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