The time course and magnitude of delayed compliance in a typical large vein, the external jugular vein of the dog, were studied in an effort to determine whether or not delayed compliance in the large veins is an important factor in allowing the circulatory system to accommodate to large changes in blood volume. These studies showed that essentially all delayed compliance is complete within approximately 20 min and that its magnitude was only one-third to one-fifth as great as the immediate elastic compliance of the vessel. Therefore, it was concluded that delayed compliance in the large veins plays little role in allowing the circulatory system to accommodate itself to large changes in blood volume, and that most of this accommodation must occur in other vascular beds.

The effect of circulatory hypotension on the small intestine was studied in 42 dogs. The small intestine was clamped at the gastric and ileocecal ends, and the dogs were subjected to control studies or to hypotension of 30 or 40 mm Hg, with and without Dibenzylene, atropine, or vagotomy. The dry gut weight, the wet gut weight, the lumen contents, and the survival time were measured. The increase in gut weight was related entirely to the accumulation of fluid in the lumen of the gut. Vagotomy did not reduce the quantity of fluid in the gut lumen, but Dibenzylene reduced the amount and atropine abolished the accumulation of fluid. It is suggested that local irritation of the gut by anoxia causes secretion of fluid and hypermotility of the gut.

No abstract