564 BA CTER IOLOG Y. 



amples, the toxicity of the invading bacteria appar- 

 ently depends upon the existence of intracellular sub- 

 stances of a poisonous nature that have thus far eluded 

 all efforts to satisfactorily separate them from the 

 bodies of the bacteria in which they develop. The 

 mechanism by which this group of bacteria acts is as yet 

 far from clear. We only know that the presence of 

 members of this group in the bodies of susceptible ani- 

 mals is accompanied by the death of the tissues in which 

 they are located. Whether the poisons are eliminated 

 by the bacteria as secretions, or whether they are set free 

 through the disintegration of bacteria in the tissues can- 

 not be said. The main point is, however, that, both 

 clinically and anatomically, diseases due to this group 

 of bacteria are characterized by marked evidence of 

 intoxication. 



BACTERIAL TOXINS. Through special investigations 

 that have been made upon the products of growth of 

 certain pathogenic bacteria the opinion that infection is 

 a chemical process receives further confirmation. It 

 has been found possible by the use of appropriate methods 

 to isolate from among the mass of material in which 

 certain of these organisms have been artificially culti- 

 vated substances which, when separated from the 

 bacteria by which they were produced, possess the 

 power of causing in animals all the constitutional 

 symptoms and pathological tissue-changes that occur 

 in the course of infection by the organisms themselves. 

 In some instances these poisons toxins, 1 as they are 



1 The term "toxins " is commonly applied to amorphous, nitrogenous 

 poisons produced by bacteria in both living tissues ami dead substances ; 

 while, on the other hand, the term " ptomains " relates to crystallizable, 

 nitrogenous poisons that are formed in dead tissue, and " leucomains " 

 to poisonous and non-poisonous alkaloidal bodies that occur in living 

 tissues as a result of physiological metabolism. 



