The Period of Induction in Blood Clotting.

Abstract

What are the changes taking place in blood plasma from the time it is drawn until the first fibrin appears? Although this period of apparent inactivity occupies the major portion of the so called “clotting time,” it has received very little attention from students of the problem of blood clotting. Our recent work establishes certain facts concerning this latent period, or period of induction. First, fibrin production is not a continuous process, beginning when blood is drawn, but occurs with sudden onset and rapid completion in only a final small part of the “clotting time.” If one oxalates plasma only a few seconds before the first signs of fibrin appear, the clotting is completely inhibited. Under such conditions we find the blood fibrinogen unchanged, so that the final appearance of fibrin as a clot represents its actual time of production. Second, since thrombin acts well in the presence of oxalate, we must conclude that, up to the time of oxalation a few seconds before clotting occurs, there has also been no thrombin formed. Third, preformed thrombin takes over twice as long to clot citrated plasma as it does to clot this same plasma immediately after recalcification, although calcium has no influence on the action of such preformed thrombin. From this we must conclude that the more rapid clotting in the recalcified plasma is due to the formation of new thrombin to aid the old in the fibrin production, We have shown that such formation of new thrombin in plasma may take place in 10 to 20 seconds, when some agent, such as preformed thrombin or tissue fibrinogen, is acting to start a removal of the blood fibrinogen from the plasma.