Summary
Calcium ions accelerated all three basic reactions of blood coagulation at an optimum concentration of 0.01 M. Strontium ions were practically ineffective as substitutes for calcium ions in the formation of autoprothrombin C (factor Xa), but functioned just as effectively as calcium ions in the formation of thrombin. Inhibition was the primary effect of strontium ions in fibrin formation. It is suggested that calcium ions function differently in each reaction. Echis carinatus venom was found to form thrombin directly from its precursor and, likewise, formed autoprothrombin C from its precursor.