204 BACTERIA. 



nal disease warrants so perilous an experiment. The 

 bacillus prodigiosus has also been used in anthrax with 

 success. 



Third, an attenuated or modified virus might be used 

 to check the growth of organisms as vaccine does small 

 pox. This of course is of more value as preventive than 

 as cure, Pasteur succeeded in so modifying the virus of 

 anthrax that while the animals, mostly sheep, which 

 were inoculated failed to have the disease itself they were 

 afterward found immune, even if inoculated with the 

 most virulent cultures. It has been estimated that the 

 work of Pasteur in France in stamping out anthrax and 

 the silkworm disease has been of sufficient value to that 

 country to make good in twenty years the enormous 

 amount lost by the payment of the war indemnity to 

 Germany. 



Fourth, the injection of the blood serum of an im- 

 munized animal. This is the principle of the antitoxin. 

 I use the word immunized instead of immune, since the 

 serum of naturally immune animals seems to produce no 

 effect so far as it has been tried. The theory is that in 

 the course of a disease in the human being or a suscepti- 

 ble animal there is gradually formed in the blood a sub- 

 stance which has not yet been isolated which we may 

 call an antiloxin, and this substance counteracts the effect 

 of the toxin or ptomaine in the system and recovery 

 takes place. There is none of this substance in the blood 

 of naturally immune animals, else we could cure con- 

 sumption, for example, by injecting the serum from such 

 animals, dogs, donkies, &c., into our consumptive 

 patients. The diphtheria antitoxin is produced in horses, 

 which animals are susceptible to the disease. A very 

 virulent culture is filtered so that the bacteria are all out 

 of it and only the toxin remains. A small quantity is 

 injected into the horse, which immediately becomes 

 feverish and shows signs of the disease. After all re- 



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