178 Dr. J. O. W. Barratt. The Nature of the 



the nucleo-protein invoked in the earlier hypothesis of C. J. Martin would, 

 in more modern terminology, be called thrombokinase. Mellanby concluded 

 from his observations that viper venoms did not contain fibrin ferment, but 

 that the active blood-coagulating agent contained in these venoms consisted 

 of pure thrombokinase. He based this conclusion upon the circumstance that 

 (1) the coagulant effect of viper venom upon fibrinogen is increased by the 

 addition of calcium chloride, and (2) that when venom is allowed to act upon 

 prothrombin (in the absence of added calcium chloride or in presence of 

 potassium oxalate) fibrin ferment is produced. As regards (1) it may be 

 pointed out that, as shown by Bordet and Delange,* the action of fibrin 

 ferment upon fluid blood plasma is increased in the presence of calcium 

 chloride. 



With a view of throwing additional light upon the problem whether the 

 coagulant action of viper venom is due to thrombin or thrombokinase, it was 

 determined to investigate further the action of heated and unheated venom 

 upon circulating blood plasma. Before proceeding to describe the experiments 

 made with viper venom it will, however, be necessary to consider the action 

 of heat upon thrombin and thrombokinase respectively, and also to refer to the 

 effect, in respect of production of fibrin, of the injection of these substances, 

 into the blood stream. 



In order to obtain a solution of thrombin fibrinogen was coagulated by a 

 small amount of thrombokinase in presence of calcium chloride ; the fluid 

 expressed from the coagulum furnished a supply of thrombin. As source of 

 thrombokinase red-cell stromata were used in most experiments ; less 

 frequently peptone was employed. 



The venom employed was that of the phoorsa, Echis carinatus. For a 

 supply of this venom I am indebted to the great kindness of Dr. C. J. Martin, 

 to whom my best thanks are due for his generous gift. 



Action of Thrombin and Thrombokinase upon Circulating Blood Plasma. 



The coagulant effect of thrombin and thrombokinase is usually tested 

 in vitro. For this purpose a solution of fibrinogen is generally employed ; 

 less frequently fluid blood plasma is used. It has, however, been pointed out 

 in a previous commuiricationf that the action of blood coagulants may be 

 studied more conveniently by intravascular injection, for if, after injection, 

 separation of fibrin occurs, this can be recognised by the presence of masses 



* J. Bordet and L. Delange, " La Coagulation du Sang et la Genese de la Thrombine," 

 'Annales de l'lnstitut Pasteur,' 1912, vol. 26, p. 657. 



t J. 0. Wakelin Barratt, "On Fibrinsemia," 'Journ. Pathol, and Bacterid. ,' 1913, 

 vol. 17, p. 303. 



