194 VENOMS 
as that of the Lachesis, with anticoagulant venoms such as that of 
the Cobra or of Ancistrodon, it is found that these mixtures, when 
properly effected, become neutral, so that the respective effects of 
the component venoms are entirely destroyed. Assuming, for 
instance, that 1 milligramme of Lachesis-venom coagulates in two 
nunutes 1 c.c. of 1 per cent. citrate rabbit-plasma, if we add to the 
plasma firstly 1 milligramme of Ancistrodon-, or 1 milligramme of 
Cobra-venom, and then 1 miulligramme of Lachesis-venom, the 
plasma remains non-coagulated, yet coagulates perfectly on the 
subsequent addition of 1 c.c. of a 4 per cent. solution of chloride 
of calcium. 
There is, therefore, a real antagonism between the actively 
coagulant substance contained in certain VIPERINE venoms and 
the anticoagulant substance comprised in the venoms of certain 
other Vipkribæ (Ancistrodon), belonging to the subfamily Cro- 
TALINÆ, and in those of all the COLUBRIDÆ. 
The conclusion to be deduced from the foregoing facts is that 
the venoms of COLUBRIDÆ and those of certain VIPERIDÆ are 
decidedly anticoagulant, while the majority of the venoms of 
VIPERIDÆ, on the contrary, possess strong coagulant properties, 
even when mixed with blood in infinitesimal doses. 
The question therefore arises why these coagulant VIPERINE 
venoms suppress the coagulability of the blood when mixed with it 
in vitro in strong doses (for example, in doses beginning from 
4 milligrammes of Lachesis-venom, or 7 milligrammes of the venom 
of Vipera russellit for 1 c.c. of 1 per cent. citrate rabbit-plasma). 
The explanation of this apparently contradictory phenomenon 
is furnished by the intense proteolysis that these VIPERINE venoms 
exert upon fibrin, in solution or coagulated. This. proteolysis 
actually manifests itself with weak coagulant doses, for the compact 
clots formed at the outset soon become soft and then dissolve, 
like a cube of egg-albumen in an experiment in artificial digestion 
by trypsin. We shall revert to the subject later on. 
