BACTERIA IN DAILY LIFE 



be handed on by means of an animal's serum, yet 

 the natural immunity from a given poison enjoyed 

 by one species of animal cannot be similarly trans- 

 ferred to less-favoured varieties. 



This fact has long been recognised in the case 

 of poisons of bacterial origin. Thus, white rats are 

 absolutely immune from diphtheria, but Wasser- 

 mann showed some years ago that the serum of 

 these animals has no power whatever to counter- 

 act the action of diphtheria-toxin in other animals. 

 Guinea-pigs were inoculated with fatal doses of 

 diphtheria toxin along with white-rat serum ; but 

 although other guinea-pigs treated with the same 

 toxin mixed with the ordinary artificially elabo- 

 rated anti-diphtheritic serum survived, those which 

 received the rat serum died in every case. 



Now very similar results have been obtained 

 by Calmette in respect to the serum of animals 

 naturally immune from serpent t venom. The 

 serum of the refractory little mongoose, as well 

 as that of the hedgehog, is wholly unable to save 

 other animals from the lethal effect of venom 

 poison, and similar results have been noted in 

 respect to swine serum. But a very curious fact 

 has also been discovered by Calmette i.e. that 

 these so-called naturally immune animals very 

 frequently are quite incapable of being artificially 

 trained to elaborate a serum possessing protec- 



