EFFECTS OF SNAKE VENOM ON COAGULABILITY OF THE BLOOD 139 
ANTICOAGULATING PROPERTY OF SNAKE VENOMS. 
From Fontana’s time to the present it has been one of the most remarkable 
features of venom poisoning that the blood of animals bitten by certain snakes, 
or of those injected with the venoms of certain species of snakes, tempo- 
rarily loses its coagulability totally or partially. As has been briefly mentioned 
in the beginning of this chapter, Fontana determined the fluidity of the blood 
of animals which died of viper poison; Weir Mitchell and Brainard observed 
the same fluidity in subacute crotalus poisoning, Fayrer in daboia poisoning, 
Wall in cobra venom toxication in case of man, and Halford found the same 
with animals which had received an injection of some Australian snake 
venoms. ‘The occurrence of the fluidity of the blood of the animals accident- 
ally or experimentally toxicated with these different venoms was nevertheless 
so inconstant that its nature had been a great puzzle to most of these observers. 
Weir Mitchell has shown by a direct test-tube experiment that the venom of 
rattlesnake exerts an anticoagulating effect upon blood shed and allowed to 
flow into a flask containing rather a large amount of the venom. Martin 
demonstrated im vivo that an amount of the venoms of Notechis and Pseu- 
dechis, insufficient to produce instantaneous thrombosis (positive phase), 
diminishes or destroys coagulability of the blood for some time to follow 
(negative phase). Martin’s work as a whole received confirmation in the 
careful investigations of Lamb with daboia venom, but the latter author 
went into a deeper inquiry as to the nature of the negative phase produced 
by these Australian as well as Indian snake venoms. ‘The primary question 
was to ascertain whether the incoagulability brought about by a small amount 
of daboia venom in the animal body is identical in its mechanism with the 
diminution of coagulability occasioned by the cobra-venom poisoning. 
Cunningham ! found that if a sufficient quantity of cobra venom is mixed, 
outside of the body, with shed blood, coagulation of the latter may be greatly 
diminished or eventually suppressed i toto. 
Kanthack ? followed and enlarged Cunningham’s observations by his experi- 
ments with the normal and immunized bloods. With the latter Kanthack 
found no inhibitory action of cobra venom on coagulation with the dose 
which just suffices to suppress clotting of the normal blood. It may be 
added that the addition of sufficient quantity of antivenomous serum neu- 
tralized the discoloring and anticoagulating effects of cobra venom upon 
the blood in vitro. 
Stephens and Myers,’ working under Kanthack, confirmed the anticoagu- 
lating property of cobra venom on the blood, although they conducted the 
blood direct from the artery to the test solution, and the results were observed 
at intervals of varying lengths of time. ‘Their results show that when more 
than o.or gm. of cobra venom is contained in 1 c.c. and mixed with 1 c.c. of 



1D. D. Cunningham. Sci. Mem. by Medical Officers in the Army of India, 1895, part 9, 1. 
2 Kanthack. System of Medicine, edited by T. Clifford Allbutt, London, 1896, I, 570. 
8 Stephens and Myers. The action of cobra poison on the blood; a contribution to the study of passive 
immunity. Jour. of Pathology and Bacteriology, 1898, V, 279. 
