SNAKE-BITES AND POISONOUS FISHES. 119 



The action of venom on the blood has been shown by Martin and 

 Halford to cause a rapid destruction of the red corpuscles, the leucocytes 

 beicg relatively increased in numbers, these very quickly degenerating, their 

 vital activity being destroyed. Martin placed two small pieces of sponge 

 antiseptically in the abdominal wall of a guinea-pig, one having been soaked 

 in a neutral saline solution containing 1 per cent, of venom, the other in the 

 solution free from venom ; oedema occurred around the sponge containing 

 the venom. After five hours the animal was killed. Both sponges were 

 withdrawn, hardened, and sections made from them. In the first, healthy 

 leucocytes were only found at the periphery, broken down ones filling the in- 

 terior ; in the second, the whole was permeated with healthy phagocytes. 



Calmette, from his experiments, finds that the venom does not act directly 

 on the nerve-cells of the brain, but on the leucocytes, and that it is carried 

 by them to the bulbo-medullary centre. 



The rapidity with which venom acts depends on 



(1) The quantity injected. 



(2) The rapidity of absorption. 



(3) The condition of the snake at the time of the bite. 



(4) The susceptibility of the animal ; the personal factor, as pointed out 

 by Elliot, being very important. 



A minimum lethal dose always takes a considerable time to produce its 

 results, and, as the amount injected is generally small, there is frequently 

 time to apply remedial measures. 



Calmette gives the toxicity of venoms according to their virulence, based 

 on the number of grammes of an animal killed by one gramme of poison, as 



Cobra, 4,000,000. 



Hoplocephalus, 3,450,000 (4,000,000 Martin). 



Pseudechis, 800,000(2,000,000 „ ). 



Common Viper, 280,000. 



Sir J. Fayrer believes that a full dose of venom from a cobra, hamadryad, 

 krait, or Daboia is necessarily fatal. It is only in cases where an amount 

 little above the minimum lethal dose has been injected that remedial 

 measures are of any use. 



The effects of Heat and Chemical Agents. — A temperature of 100° C., if 

 prolonged, will modify or destroy any snake venom, even after the removal 

 of the coagulable proteid. 



A 10 per cent. sol. of caustic potash or soda, after being in contact five or 

 ten minutes, diminishes the poisonous properties of the virus. 



A 1 per cent. sol. of pot. permang. destroys one part of venom when in 

 contact, but its action is unreliable. 



Hypochlorite of lime, 1 in 60 of water freshly made up, destroys the 

 venoms completely, as also does 1 per cent, of chloride of gold. The latter 

 two are the only ones recommended by Calmette, and are generally accepted 

 now as being the best 



