BACTERIAL INVASION 213 



since they appear only some hours after the injection 

 of the toxin, it seems likely that they are not caused 

 directly by the toxin, but by the action of the toxin on 

 the surrounding tissues, in the same manner as was 

 found to be the case when irritating chemicals, such 

 as chloroform, were injected. Such reactions are by 

 no means limited to the bacterial exotoxins, but fol- 

 low the intradermal injection of living bacteria, dead 

 bacteria, and bacterial extracts. (Simmonds, 1928.) 



In agreement with this concept is the fact that the 

 proteolytic organisms produce such localized reac- 

 tions much more rapidly than do the non-proteolytic. 

 This is especially interesting because, as has been 

 shown earlier, the autolytic process which leads to 

 the liberation of cytost is essentially proteolytic in 

 nature. In agreement with this is the well known fact 

 that infection with highly proteolytic organisms such 

 as the Welch bacillus frequently leads to shock, ap- 

 parently identical with that which results from the 

 liberation of cytost by any other means. 



The shock which sometimes follows such infection 

 is really due to cytost liberated as a result of the activi- 

 ties of the microorganisms upon the tissues of the host; 

 for if the infected tissue is dissected out, extracted with 

 water, sterilized, filtered, and injected into another 

 animal, shock frequently ensues. This result must be 

 due to cytost present in the extract, and not to the 

 bacteria or their exotoxins, since the latter are re- 

 spectively removed and inactivated by the processes 

 of filtration and the temperature incident to steriliza- 

 tion. When a similar experiment is conducted with 

 tissues infected with weakly proteolytic or non- 



