THH PHYSIOLOGY OF POISONING 195 
IIL—MECHANISM OF THE ANTICOAGULANT ACTION OF VENOMS ON 
THE BLOOD. 
The anticoagulant action of the venoms of COoLUBRIDÆ and of 
Ancistrodon upon the blood appears to take effect in the first place 
upon the fibrin-ferment, and afterwards upon the fibrin by proteo- 
lysis. The action on the fibrin-ferment seems manifest when we 
experiment with anticoagulant venoms which are feebly proteolytic, 
like the venom of the Cobra. 
I have already stated that a mixture of fresh blood with a suffi- 
cient dose of Cobra-venom is non-coagulable, as though the blood 
on issuing from the animal had been mixed with peptone or leech- 
extract. But, while blood when peptonised or mixed with leech- 
extract coagulates readily on the subsequent addition of fibrin- 
ferment, blood mixed with venom remains positively non-coagulable. 
It is the same with citrate- or oxalate-plasmas, which no longer 
coagulate when chloride of calcium is added to them, and with 
4 per cent. saline plasma on the addition of distilled water. 
The anticoagulant substance in the venoms of COLUBRIDÆ and 
Ancistrodon is precipitable by alcohol, like the coagulant substance 
in the venoms of VIPERID and like the neurotoxins, from which 
it is difficult to separate them. The separation can nevertheless 
be effected by the aid of heat, if we make use of certain venoms 
that are particularly resistant to high temperatures, such as those 
of the Cobra or the Krait. These latter venoms, when heated for 
one hour at 70° C., cease to be anticoagulant, and preserve their 
toxicity unimpaired. It is, however, impossible to suppress the 
toxicity without at the same time destroying the anticoagulant 
substance. 
Antivenomous serum completely protects citrate- or chloridate- 
plasmas against the anticoagulant action of venoms. It is 
sufficient to mix + c.c. of 4 per cent. saline antivenomous serum 
with 1 c.c. of 4 per cent. saline plasma to ensure that the subse- 
quent addition of 1 milligramme of Cobra-venom to this mixture 
remains without effect upon the coagulability of the latter. If, 
