Considerable evidence supports the view that the reactions of the hemostatic mechanism are in a balanced state of activity. This balance is the result of opposing tendencies originating, on the one hand, from the forward reactions tending toward blood coagulation and, on the other hand, from terminating reactions tending toward dissolution of the clot and inactivation of active products such as thrombin. The balanced state normally results in physiological fluidity of the blood. Hypocoagulability and hypercoagulability are states of imbalance in one direction or the other; they may result from perturbations in any of the contributing component forces.
Consistent with this view, it seems likely, though by no means yet certain, that the hemostatic process is regulated either by changing the rate of certain key forward or by terminating reactions. Moreover, this probably involves variations between slow and fast, rather than between off and on. Support for this concept comes