Detailed evidence has been accumulating that at least one chain reaction occurs during the coagulation of blood. Both the metamorphosis of platelets and the development of thrombokinase appear to be involved. The autocatalytic effect may serve a function in making possible the growth of a hemostatic plug. It also offers advantages in the physiologic control of the clotting mechanism. It is likely that the chain reaction occurs in most instances where a thrombus forms, and plays some part in its propagation.

The chain reaction is a potentially explosive phenomenon which demands an adequate countermechanism. With materials derived from blood, reactions have long since been demonstrated which can reduce thrombokinase activity, inactivate thrombin and liquefy fibrin. These reactions may help to maintain the fluidity of the circulating blood by removing the products of smoldering clotting reactions.

Such effects could help to delimit the growth of a hemostatic plug, or to end the propagation of a thrombus.

While it is now possible to correlate in this way the data on blood coagulation with present knowledge of hemostasis and thrombosis, critical gaps in our understanding still remain.

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