these observations lend further support to the thesis that , in the course of physiological coagulation , ( a ) calcium plus platelets ( or tissue derivative ) constitute an enzyme system which reacts with prothrombin to form thrombin , and which is thus analogous to trypsin and to several of the proteolytic venoms here discussed , and ( b ) the thrombin so formed is itself a proteolytic enzyme which , like papain and the majority of the coagulant and proteolytic snake venoms here studied , reacts with fibrinogen to form a fibrillar gel , fibrin .
C0042479
venoms
C0037380
snake venoms