Coagulant of the Venom of Echis carinatus. 



183 



to the thrombin injected * little or no fibrinogen is removed, the amount of 

 fibrin subsequently obtainable from the blood not being markedly diminished, 

 so that it may be doubted whether the exceedingly limited separation of 

 fibrin occasionally observed after injection of red cell stromata is more than 

 a subsidiary and perhaps relatively unimportant process attending the action 

 of thrombokinase ; the difference, in respect of fibrin formation, between the 

 injection of thrombin and thrombokinase cannot be attributed to the latter 

 being introduced in a relatively insufficient amount. 



The effect of thrombokinase upon circulating blood plasma is thus seen to 

 be strikingly different from its action upon a solution of fibrinogen in vitro 

 in presence of calcium chloride. In the latter case coagulation occurs ; in 

 the former no coagulant action is observed or at most only an insignificant 



. * 



quantity of fibrinogen is converted into fibrin. The two experiments are, 

 however, essentially different. When thrombokinase acts in vitro its action 

 is directed to the conversion of prothrombin into thrombin in presence of 

 calcium chloride. "When on the other hand thrombokinase acts upon 

 circulating blood plasma in presence of the free calcium salt contained in 

 the plasma (and the same is true if the calcium content of the plasma is 

 increased by injection of calcium chloride) the non-production of thrombin 

 proves that prothrombin is not present in the circulating blood plasma. By 

 a similar mode of reasoning based upon experiments in vitro, Bordet and 

 Delanget have shown that prothrombin does not at first exist in fluid plasma 

 {plasma limpide), whence these observers conclude that in this fluid it is 

 represented by an antecedent body which bears the same relation to pro- 

 thrombin (serozyme of Bordet) that prothrombin bears to thrombin : and as 

 the term fibrin-ferment is applied to thrombin, which reacts with fibrinogen 

 to form fibrin, so, using the same mode of nomenclature, the substance which 

 takes part in the conversion of proserozyme into serozyme may be termed 

 serozyme-ferment, though the exact mode in which the latter substance is 

 concerned in the coagulation of shed blood has still to be determined. The 

 explanation of the failure of thrombokinase when injected into the blood 

 stream to cause fibrin formation lies, therefore, in the fact that it is unable 

 of itself to change proserozyme into serozyme. In those experiments in 

 which, after the injection of red-cell stromata, a small amount of fibrin is 

 recognisable in the blood-vessels of the lungs, it would appear that either 



* If the amounts injected per kilogramme of body -weight in Experiments 1, 2, and 3 

 had been such as would coagulate in vitro equal quantities of fibrinogen solution, 

 according to the data given in the next section, then the amount of stromata injected in 

 Experiment 2 would have been increased two and a half times, while the amount of 

 peptone injected in Experiment 3 would have been reduced to one-twelfth. 



t J. Bordet and L. Delange, loc. cit. 



