CALMETTE 



311 



4< Of course, this estimation of virulence is not 

 absolute ; it varies considerably according to the 

 species of animal tested. Thus the guinea-pig, 

 and still more the rat, are extremely sensitive. For 

 instance, 0.15 mgr. of viper- venom is enough to 

 kill, in less than 12 hours, 500 grammes of guinea- 

 pig ; so that the activity of this venom with a 

 guinea-pig is 3,333,000, but with a rabbit is not 

 more than 650,000. With more resistent animals, 

 the opposite result is obtained ; about 10 mgr. of 

 cobra-venom are necessary to kill a dog of 6.50 

 kilogrm. weight ; but to kill the same weight of 

 rabbit 1.65 mgr. is enough. Thus the virulence 

 of this venom with the rabbit is 4,000,000 ; but 

 with the dog not more than 650,000." 



By experiments in test-tubes, Calmette studied 

 these venoms under the influences of heat and 

 various chemical agents. He found how to 

 attenuate their virulence, and how to diminish the 

 local inflammation round the point of inoculation ; 

 and it was in the course of these test-tube experi- 

 ments and inoculations that he discovered the value 

 of calcium hypochlorite as a local application. 

 Working, by various methods, with attenuated 

 venoms, he was able to immunise animals : — 



" I have come to immunise rabbits against 

 quantities of venom that are truly colossal. I have 

 got several, vaccinated more than a year ago, which 

 take, without the least discomfort, so much as 40 

 mgr. of venom of naja triptidians at a single 

 injection ; that is to say, enough to kill 80 rabbits 

 of 2 kilogr. weight, or 5 dogs. 



" Five drops of serum from these rabbits wholly 



