THE PHYSIOLOGY OF POISONING 195 



III. — Mechanism of the Anticoagulant Action of Venoms on 



THE Blood. 



The anticoagulant action of the venoms of Colubrid.e and of 

 Ancistrodon upon the blood appears to take effect in the first pli^ce 

 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 (7o6ra-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 Colubrid^ and 

 Ancistrodon is precipitable by alcohol, like the coagulant substance 

 in the venoms of ViPBRiDiE 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 ser'um 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 Co6?-a-venom to this mixture 

 remains without effect upon the coagulability of the latter. If, 



