TOXINS 49 



pathogenic agents, the group as a whole is of little if any interest 

 from the standpoint of the student of infection and infectious disease. 



In the light of more recent knowledge it is even doubtful whether 

 the serious symptoms which are observed in cases of so-called 

 ptomain poisoning are in reality due to ptomains. Since we know 

 that a specific organism, the bacillus botulinus, may frequently be 

 demonstrated in "tainted' ' animal food and that this organism pro- 

 duces a true toxin not a ptomain which is almost as active as the 

 toxin of the tetanus bacillus, one not unnaturally feels a little dubious 

 about the role which the ptomains proper are supposed to play in 

 such cases. 



The most urgent objection, however, which can be raised against 

 the role of the ptomains as active agents in the causation of the symp- 

 toms and pathological changes of the infectious diseases is, above all, 

 the fact that they can never reach such a concentration in the living 

 body as would suffice to bring about a clinical effect. In the course 

 of Brieger's typhoid studies this became especially manifest, for 

 the yield of his "typhotoxin" in typhoid cultures, after four weeks' 

 incubation, was infinitesimally small and often wanting altogether. 

 Noteworthy, further, is the fact that the toxic effect of the isolated 

 ptomains was always markedly less than that of the original culture, 

 and that pathological changes peculiar to infections with the corre- 

 sponding bacteria have never been produced with ptomains. 



To sum up we may say that while ptomains may possibly cause 

 disease or even death, as in some cases of cheese or meat poisoning, or 

 in cases where active absorption is taking place from an abscess or a 

 gangrenous focus, there is no evidence to show that they play a role 

 in the pathology of the infectious diseases per se, and it is doubtful, 

 to say the least, whether the effect which is commonly attributed to 

 them in the conditions just mentioned is really the outcome of their 

 action. 



Toxins. If, then, the ptomains are eliminated as pathogenic 

 agents the question arises, Are there any other substances derived 

 either directly or indirectly from microorganisms to the action of 

 which the clinical picture of the infectious diseases could be attrib- 

 uted? Three groups of substances are now recognized which are of 

 moment in this connection, namely, the true toxins or exotoxins, the 

 endotoxins and the bacterial proteins. 



Of these the endotoxins, like the proteins, are part and parcel of 

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