THE COAGULATION OF THE BLOOD 69 



and solutions of fibrinogen prepared from blood plasma. The 

 thrombins contained in venoms probably act as catalysts, and 

 induce a formation of fibrin from fibrinogen. In this respect 

 the behaviour of thrombo-kinase to birds' plasma, when coagu- 

 lation is induced by the kinase effecting such a change in 

 thrombogen in the presence of calcium that fibrin-ferment is 

 formed, is in no way comparable to the action of venom on 

 blood. For the thrombin of snake venom the rate of clotting 

 varies with the amount of venom employed, so that the time 

 multiplied by quantity of venom is constant. 1 



7. The Intra-vascular Injection of Peptone 



From the fate which has overtaken nearly every theory 

 which has been advanced to explain the coagulation process, 

 it is permissible to predict that the one advanced by 

 Morawitz will eventually prove to be only a provisional 

 working hypothesis. If thrombo-kinase can be derived from 

 any one or all of the morphological bodies in blood, it is 

 difficult to understand why, during life, small quantities of this 

 do not exist in circulating plasma. That the leucocytes at 

 any rate disintegrate while circulating is almost certain. Con- 

 trasted with the duration of the life of the erythrocytes, the 

 polymorphonuclear leucocytes survive only a few days. Any 

 liberated kinase will play a part in the production of thrombin, 

 and this will be rendered inactive by some anti-body or, what 

 is improbable, since it is somewhat stable, changed into another 

 form. It is also conceivable that any liberated kinase may be 

 also neutralised, so that no formation of thrombin is possible. 



The existence of thrombin cannot be demonstrated in many 

 extra-vascular plasmas, though both proteolytic enzymes and 

 anti-enzymes have been described in blood-serum and considered 

 to be existent in plasma. Bordet and Gengou have shown that 

 neutral salts hinder or suppress the formation of thrombin from 

 its precursors, and in stronger concentration entirely abolish 

 the activity of any thrombin which may be present. Similarly, 

 the cooling of plasma acts essentially in the first manner. 

 Arthus arranges the bodies which restrain coagulation into two 

 groups : 



1. Those substances— of which peptone, or rather deutero- 



1 C. J. Martin, Journ. of Phys. xv. 1894 ; xx. 1896; xxxii. 1905. 



