CHAPTER XI. 

 EXPERIMENTAL VENOM POISONING IN ANIMALS. 



The accurate nature of the actions of venom on organisms can best be 

 studied by introducing the known amounts of venom, either modified or 

 unmodified, into the system by various modes of inoculation under variable 

 conditions. The symptoms observed in human cases can thus be approxi- 

 mately reproduced in certain animals and studied by the aid of different 

 physiological and pharmacological methods. In treating this topic it appears 

 to me to be most convenient to describe the symptoms and afterwards analyze 

 them. I will also describe later the effects of venom upon different organs, 

 body-fluids, tissues, and cells. With the exception of the frog, the experi- 

 ments made on cold-blooded animals will be given in a subsequent chapter, 

 and those made on warm-blooded animals will be chiefly considered here. 



THE VIPERIDiE. 



CROTALUS ADAMANTEUS. 



Weir Mitchell found that the effect of the venom of this snake on birds 

 is extremely virulent, and so sudden in some cases that when the dose is 

 large there is hardly time to observe the resulting phenomena. Acute poison- 

 ing of pigeons is very common. When pigeons are bitten by Crotalus the 

 symptoms which immediately follow the bite are feebleness and dyspnoea. 

 Convulsions and gasping are always observed. Respiration may cease in a 

 few minutes or sometimes after half an hour. Convulsions may precede the 

 respiratory cessation. Twitching of the muscle near the bitten spot may be 

 seen. The pupil usually remains unaltered, or perhaps slightly contracted. 

 Coagulabihty of blood seems to be normal. Irritability of the sciatic nerve 

 may continue to exist for nine minutes after death. The heart stops several 

 minutes or longer after the cessation of breathing. The irritability of the 

 muscles is well preserved ten minutes after death. The fang marks are sur- 

 rounded by circles of extravasated blood. In one instance death took place 

 in 30 seconds, during which time the bird became completely paralyzed. 



The chronic form of poisoning was also described by Mitchell. When 

 pigeons are not killed rapidly they may partially recover for some days, 

 during which time local necrosis becomes appalling. Death usually occurs 

 within a few days, or it may result in 12 to 24 hours. The peculiarities of 

 the chronic poisoning are the loss of coagulability of blood, and numerous 

 ecchymoses in internal viscera, serous and mucous membranes, and muscular 

 tissue adjacent to the fang marks. 



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