394 PATHOGENIC BACTERIA. 



possess this property, and unless trypsin is present it must 

 be dependent upon the proteolytic activity of other bac- 

 teria for a suitable form of proteid food. Perhaps these 

 bacteria form an albuminate molecule, which like leucin 

 and tyrosin cannot be broken up into indol, and thus 

 there might be caused an important modification of the 

 metabolism of the colon bacillus, which might have 

 either an immediate or remote influence upon its acquisi- 

 tion of disease-producing properties, for our own experi- 

 ments indicate that the power to form indol, and the 

 actual forming of it, are to some extent an indication of 

 the possession of pathogenesis." 



To the laboratory animals the colon bacillus is patho- 

 genic in varying degree. Intraperitoneal injections into 

 mice cause their death in from one to eight days if the 

 culture is virulent. Guinea-pigs and rabbits also suc- 

 cumb to intraperitoneal and intravenous injection. Sub- 

 cutaneous injections are of less effect, and in rabbits seem 

 to produce abscesses only. 



When the bacilli are injected into the abdominal cavity 

 a sero-fibrinous or purulent peritonitis occurs, the bacilli 

 being very numerous in the abdominal fluids. 



The pathogeny of the colon bacillus is due to irritating, 

 chemotactic substances in its protoplasm. The experi- 

 ments of Pfeiffer and Kolle and Loffler and Abel have 

 proved very conclusively that the poisonous principle is 

 in, and cannot by any means be separated from the bodies 

 of the bacteria. 



Frequent transplantation lessens the virulence, passage 

 through animals increases it. 



Numerous observers have found that cultures of the 

 bacillus obtained from cholera, cholera nostras, and other 

 intestinal diseases are much more pathogenic than those 

 obtained from normal feces or from pus. 



Cumston, 1 from a careful study of thirteen cases of sum- 

 mer infantile diarrheas, comes to the following conclu- 

 sions: 



1 International Medical Magazine, Feb., 1897. 



