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 i860 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 0.00015 g^i- P^^ ^^o 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 



1 Brainard. Smithsonian Report. 1854. 



2 Weir Mitchell. Smithsonian Contributions to Knowledge. 1861. 



' Feoktistow. Ueber die Wirkung des Schlangengiftes auf den thierischen Organismus. Mem. d. 

 I'Acad. Imp. d. Sc. d. St.-Petersbourg. 1888, XXXVI. 



* Heidenschild. Untersuchungen iiber die Wirkung des Giftes der Brillen- und der Klapperschlange. 



Inaug. Dissert. Dorpat, 1886. 



* C. 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. 

 « 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. 



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