116 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOMS 



The inflammatory haemorrhagic focus becomes necrotic and may form a 

 crust and be cast off or may be absorbed. 



The intravenous administration of the habu venom into rabbit and dog 

 brings about rapid reduction of blood pressure with the frequence and size of 

 pulse almost unaltered. Ishizaka believes that the vasomotor nerve is not 

 paralyzed, as the blood pressure can increase in a later stage of toxication 

 when the artificial respiration is suspended. The irritability of the splanchnic 

 nerve is greatly diminished, but never abolished completely. He also points 

 out that the peripheric vessels are not markedly relaxed. Respiratory fre- 

 quency is not affected at the beginning, but it lessens gradually and finally 

 disappears. Judging from the presence of the irritability of the phrenic and 

 sciatic nerves after death, the failure of respiration is ascribed to the central 

 paralysis. 



By intravenous injection in rabbits and dogs haemorrhages are produced 

 in internal organs, especially in the pericardium, endocardium, and gastric 

 mucous membrane. In dogs the internal haemorrhages appear to be more 

 frequent and also present in the lungs, mesenterial membrane, and intestinal 

 tract. On the other hand, administration of the venom per anum did not 

 kill the rabbit when 3.25 gm. were given in divided doses, but killed it when 

 a single dose of 0.34 gm. was given. In this case there was no haemorrhage 

 in the mucous membrane, but the histological examination of the kidney 

 showed parenchymatous nephritis. 



Under no conditions was Ishizaka able to produce bloody urine or haemor- 

 rhages in the brain, spinal cord, and their membranes, or in the bone marrow. 



VIPERA. 



Vipera russellii or Daboia is one of the most dreaded snakes in India and 

 its venom is known to cause death with a lightning rapidity when sufficiently 

 injected into the victim. The cause of this quick death has since been dis- 

 covered to be due to its large content of fibrin ferment capable of producing 

 instantaneous intravascular thrombosis. As to this property of daboia venom 

 and venom in general I will give fuller details in a later chapter. Fayrer and 

 Brunton studied the action of this venom very carefully and the former gives 

 many interesting experiments of the effects of the daboia bite on various 

 kinds of animals. Dogs, cats, and fowls succumbed to a single bite, with the 

 symptoms of pain, swelling, and paralysis of respiratory center. Convulsions 

 were almost constant before death. The blood was found to have lost its 

 coagulability. Horses were allowed to be bitten by Daboia, and these were 

 always killed. Respiration was affected most and seemed to be the cause 

 of death, although always accompanied by general weakness. The blood 

 remained fluid. One experiment with an ox showed that the bite of Daboia 

 fails to kill even if its fangs take effect. There was, however, great swelling 

 and general weakness lasting for a few days. 



A more accurate study of this venom has been made by Lamb, who mostly 

 employed monkeys, rabbits, rats, and pigeons. 



