CHAPTER XIII. 
EFFECTS OF SNAKE VENOM UPON THE COAGULABILITY 
OF THE BLOOD. 
The fluidity of the blood after the bite of certain snakes has been long 
known. In 1787 Fontana stated that the blood of animals dying of viper 
bite remained fluid. Brainard! mentions that when death occurred imme- 
diately in animals bitten by rattlesnakes, the blood was found at the autopsies 
to be coagulated, but if some time elapsed before the animal succumbed, 
the blood remained fluid in the vessels. In 1860 Weir Mitchell? confirmed 
Brainard’s observations. Halford observed that the same continued fluidity 
of the blood followed the injection of some venom of Australian species. 
Feoktistow * confirmed Fontana’s observation on the condition of the blood 
after injection of the venoms of Vipera ammodytes and Vipera berus. 
The continued fluidity of the blood after the bite of the Indian viperine 
snakes has been frequently noted in past years. Mitchell and Reichert 
demonstrated the anticoagulating property of the rattlesnake and moccasin 
venoms directly in vitro. 
The increased coagulability of the blood in animals injected with a large 
amount of viper venom was noticed by Fontana, and nearly one hundred 
years later also by Heidenschild ‘ on the crotalus venom and by C. J. Martin 
on the pseudechis venom independently. 
In 1893 C. J. Martin ® found that o.oco15 gm. per kilo or upwards of the 
venoms of two Australian snakes, Pseudechis porphyriacus and Notechis 
scutatus, when introduced into the circulation of dogs, cats, and rabbits, 
caused intravascular clotting. This action also occurs when the snake dis- 
charges a relatively large amount of venom into small animals, as when seiz- 
ing frogs or mice as prey, but it is not a usual phenomenon of poisoning by 
these snakes in man. When the quantity of the venom fails to effect an 
intravascular coagulation there is always a phase of increased coagulability 
which lasts but a few minutes, only to be followed by another phase of 
abnormally diminished coagulability. An intermediate quantity produces 
thrombosis only in the portal vein, but the blood in the vessels elsewhere 
pean rae pee crpeweee ti Se ies eS See 
1 Brainard. Smithsonian Report. 1854. 
2 Weir Mitchell. Smithsonian Contributions to Knowledge. 1861. 
3 Feoktistow. Ueber die Wirkung des Schlangengiftes auf den thierischen Organismus. Mém. d. 
__ PAcad. Imp. d. Sc. d. St.-Pétersbourg. 1888, XXXVI. 
4 Heidenschild. Untersuchungen iiber die Wirkung des Giftes der Brillen- und der Klapperschlange. 
Inaug. Dissert. Dorpat, 1886. 
5C. J. Martin. On some effects upon the blood produced by the injection of the venom of the Aus- 
tralian black snake (Pseudechis porphyriacus). Jour. of Physiol., 1893, XV, 380. 
6 An explanation of the marked difference in the effects produced by subcutaneous and intravenous 
injection of the venom of Australian snakes. Proc. Roy. Soc. N. S. W., 1896. 
133 
