In a recent discussion of the total amount of blood in living animals, preference is given to the intravenous injection of congo-red or vital-red solution as an inirect method. The author has employed vital-red for this purpose. The essential advantage of this method is that the dye injected is not allowed to become filtered off from the blood vessel. He has found, however, that it has another source of error, i. e., the dye injected being absorbed by the erythrocytes. By estimating the amount of dye absorbed by a certain number of erythrocytes, the result was rectified, making the total amount of blood in the dog 9.16% of the weight of the body.