Summary
The fibrinogen, plasma antithrombin, and thrombin activity curves of twenty-four normal
individuals were determined under carefully controlled conditions of analysis. From
these determinations plasma prothrombin and thromboplastic activities were calculated.
These activities were defined in kinetic terminology and a theoretical rate of fibrination
in plasma was calculated and used as a basis for comparing plasmas. Compensatory relationships
were found among the various activities. Thus, low values of thromboplastic activity
were associated with increased concentrations of prothrombin and fibrinogen; the effect
of the latter activities in increasing the potential of plasma for fibrination was
moderated by an increase in antithrombin activity.
The fibrin-forming potential of each plasma was calculated relative to the mean value
for all plasmas, to furnish a fibrinotic index. The latter was relatively constant
in spite of wide variations in discrete activities, indicating that a physiological
balance is maintained among those coagulation factors responsible for fibrination.
