PATHOGENIC BACTERIA 



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rophytic bacteria may be indirectly pathogenic by reason of 

 the fact that they may frequently multiply in various food 

 products, such as meats, milk, cheese, etc., and, by their sap- 

 rogenic processes, produce poisonous protein substances 



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FIG. 48. Trypanosoma bruci of nagana. The trypanosome is carried by the 

 tsetse fly. After Williams. 



called ptomains. These ptomains, when taken into the body 

 and absorbed by the lymphatics and blood, give rise to serious 

 intoxications. These substances will be considered more in 

 detail later. 



The injection of certain species of true saprophytic bacteria 

 under the skin of some of the experimental animals is often 

 attended by the production of abscesses, necrosis, and general 

 gangrene.^ 



