It has been repeatedly found in my laboratory that, when normal oxalated blood is placed in an ordinary refrigerator, a reduction of the prothrombin, occasionally as much as 50 per cent, may occur in twenty-four hours. Rhoads and Panzer,1 using my method, have noted that even when blood is carefully preserved at 4 C. the prothrombin rapidly decreases. Lord and Pastore,2 employing the method of Warner, Brinkhous and Smith,3 found on the contrary that the prothrombin was relatively little diminished in stored blood. Obviously a marked discrepancy exists between the two methods for determining prothrombin and this presents a problem which is not only of academic but of practical clinical importance as well.
Without entering into the question of the merits and defects of the two methods, it must be pointed out that both tests are based on unproved assumption; therefore the validity of the results which