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.! 
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 3 xx. 18963; xxxii. 1905. 
