BACILLI OF THE COLON-TYPHOID-DYSENTERY GROUP 635 



For a consideration of the distribution of colon bacilli in the intestines 

 of human beings at various ages and under modified dietary conditions 

 the reader is referred to the section on the normal flora of the intestinal 

 canal. 



Poisonous Products of the Colon Bacillus. The colon bacillus 

 belongs essentially to that group of bacteria whose toxic action is sup- 

 posed to be due to the poisonous substances contained within the 

 bacillary body. Culture filtrates of the colon bacillus show very little 

 toxicity when injected into animals; whereas the injection of dead 

 bacilli produces symptoms almost equal in severity to these induced by 

 injection of the live microorganisms. Corroborative of the assumption 

 of this endotoxic nature of the colon-bacillus poison is the fact that, 

 so far, no antitoxic bodies have been demonstrated in serum as resulting 

 from immunization. 



Dead colon bacilli have a very high toxicity for rabbits and some 

 what less for guinea pigs. 



Immunization with the Colon Bacillus. The injection into animals 

 of gradually increasing doses of living or dead colon bacilli gives rise to 

 specific bacteriolytic, agglutinating, and precipitating substances. 



The bacteriolytic substances may be easily demonstrated by the 

 technique of the Pfeiffer reaction. In vitro bacteriolysis is less marked 

 than in the case of some other microorganisms such as the cholera spiril- 

 lum or the typhoid bacillus. Owing probably to the habitual presence 

 of colon bacilli in the intestinal tracts of animals and man, considerable 

 bacteriolysis may occasionally be demonstrated in the serum of normal 

 individuals. 



Agglutinins for the colon bacillus have often been produced in the 

 sera of immunized animals in concentration sufficient to be active in 

 dilutions of 1 : 5000 and over. The agglutinins are produced equally 

 well by the injection of live cultures and of those killed by heat, if the 

 temperature used for sterilization does not exceed 100 C. It is 17 

 a noticeable fact that the injection of any specific race of colon bacilli 

 produces, in the immunized animal, high agglutination values only for 

 the individual culture used for immunization, while other strains of 

 colon bacilli, although agglutinated by the serum in higher dilution 

 than are paratyphoid or typhoid bacilli, require much higher concen- 

 tration than does the original strain. The subject has been extensively 

 studied by a number of observers and illustrates the extreme individual 

 specificity of the agglutination reaction. Thus a serum which will 



" Wolff, Cent. f. Bakt., xxv, 1899. 



