THE DISTRIBUTION OF RED CELLS AND PLASMA IN LARGE AND MINUTE VESSELS OF THE NORMAL DOG, DETERMINED BY RADIOACTIVE ISOTOPES OF IRON AND IODINE 1

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Abstract
Seventeen % of the total whole blood vol. is within the minute vessels (arterioles, capillaries and venules) of the normal dog under light morphine narcosis. The unit values of whole blood (ml./g. of tissue) of the various tissues range in order of magnitude as follows: spleen 0.4 ml.; liver, lungs and kidneys 0.2 ml.; heart and gastrointestinal tract 0.06 ml.; and skeletal muscle and brain 0.02 ml. The percentage of total whole blood vol. in the various organs is: skeletal muscle, 7%; liver, 5%; spleen, lungs, kidneys, gastrointestinal tract (excluding mesentery), from 1 to 2% each; heart and brain, less than 1% each. The hematocrit of blood in the several organs in animals with an avg. arterial hematocrit of 43. is approx.: spleen, 80; liver, 40; lungs, 35; heart and skeletal muscle, 20 to 25; and kidney, gastrointestinal tract and brain, 15 to 20. The hematocrit of the blood in the large vessels, of all the blood in the body, and of the blood in the minute vessels is always less than that of arterial or venous blood. The ratios of the partition hemato-crits to the arterial hematocrit are approx. 0.9, 0.85 and 0.7, respectively. The ratios of rapidly circulating to total red cells in the several organs is unity. Hence all red cells in the vascular bed are in active circulation, and no reserves of red cells exist in the normal dog.