Substances Produced in Bacterial Cultures. 55 



various organisms and testing cross protection, have failed because, 

 so far, we have no evidence of antigenic action of these substances. 

 Repeated injection of rabbits with doses too small to produce 

 definite sickness that is, doses of 1 to 2 c.c, have resulted in 

 emaciation, gradual falling out of hair, and eventual death of the 

 animals by apparent chronic injury. In such experiments rabbit 

 protein was used in the media to exclude anaphylactic injury. 

 We have not yet been able to obtain any of these poisons in suffi- 

 cient potency to permit us to draw conclusions from systematic 

 experiments concerning their action after intraperitoneal and sub- 

 cutaneous injection. Although we have obtained some indication 

 of injury after subcutaneous injection this point calls for further 

 study. 



Summary and Conclusions. 



It will be noticed that whatever the organisms used, whatever 

 the medium, and whether the substances used were filtrates of 

 liquid cultures or filtrates of washings of young cultures grown 

 on solid media, the general nature of the toxic effects, incubation 

 time, etc., were always the same. Autopsy findings in all such 

 cases in which acute death was obtained, never showed lesions 

 that might in any way be regarded as characteristically defining 

 the pharmacology of the poisons. These facts, together with our 

 failure to establish specificity by any immunological tests, inclines 

 us to believe that in all cases the poisons were of a similar, perhaps 

 of the same nature. 



The fact that there was a regular incubation time, that the 

 toxic substances seemed to show heat instability, that they had a 

 relatively greater toxicity for rabbits than for guinea pigs, and 

 that they appeared in young cultures with apparent diminution as 

 the cultures grew older, constitute evidence which prevents our 

 dismissing them, peremptorily as split products of constituents of 

 the media. 



We cannot, at the present time, characterize them definitely, 

 but we are safe in asserting that they are neither exotoxins in the 

 ordinary sense, and cannot be regarded as endotoxins or extractive 

 substances from the bacterial bodies. 



We believe that it is these substances which have been regarded 

 by many writers as exotoxins of streptococci. Also, it is not 

 unlikely that they represent the substances which have been 



